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Sample records for indian ocean exhibit

  1. Indian Ocean margins

    Digital Repository Service at National Institute of Oceanography (India)

    Naqvi, S.W.A.

    The most important biogeochemical transformations and boundary exchanges in the Indian Ocean seem to occur in the northern region, where the processes originating at the land-ocean boundary extend far beyond the continental margins. Exchanges across...

  2. Indian Ocean Rim Cooperation

    DEFF Research Database (Denmark)

    Wippel, Steffen

    Since the mid-1990s, the Indian Ocean has been experiencing increasing economic cooperation among its rim states. Middle Eastern countries, too, participate in the work of the Indian Ocean Rim Association, which received new impetus in the course of the current decade. Notably Oman is a very active...

  3. Indian Ocean Rim Cooperation

    DEFF Research Database (Denmark)

    Wippel, Steffen

    Since the mid-1990s, the Indian Ocean has been experiencing increasing economic cooperation among its rim states. Middle Eastern countries, too, participate in the work of the Indian Ocean Rim Association, which received new impetus in the course of the current decade. Notably Oman is a very active...

  4. Indian Ocean Traffic: Introduction

    Directory of Open Access Journals (Sweden)

    Lola Sharon Davidson

    2012-06-01

    Full Text Available Like the Mediterranean, the Indian Ocean has been a privileged site of cross-cultural contact since ancient times. In this special issue, our contributors track disparate movements of people and ideas around the Indian Ocean region and explore the cultural implications of these contacts and their role in processes that we would come to call transnationalization and globalisation. The nation is a relatively recent phenomenon anywhere on the globe, and in many countries around the Indian Ocean it was a product of colonisation and independence. So the processes of exchange, migration and cultural influence going on there for many centuries were mostly based on the economics of goods and trade routes, rather than on national identity and state policy.

  5. Postglacial Indian Ocean

    Digital Repository Service at National Institute of Oceanography (India)

    Naidu, P.D.

    stream_size 37509 stream_content_type text/plain stream_name Encyclopedia_Quatern_Sci_2006_1831.pdf.txt stream_source_info Encyclopedia_Quatern_Sci_2006_1831.pdf.txt Content-Encoding UTF-8 Content-Type text/plain; charset=UTF-8... Encyclopedia of Quaternary Sciences -. - - -. - -- - PALEOCEANOGRAPHY. RECORDS/Postglacial Indian Ocean 1831 Atlantic Ocean. Paleocea~zography 20, PA1017, (doi:10.1029/ 2004PA001021). Diekmann, B., Fiitterer, D. K., Grobe, H., et al. (2004). Terrigenous...

  6. Zoogeography of the Indian Ocean

    Digital Repository Service at National Institute of Oceanography (India)

    Rao, T.S.S.

    The distribution pattern of zooplankton in the Indian Ocean is briefly reviewed on a within and between ocean patterns and is limited to species within a quite restricted sort of groups namely, Copepoda, Chaetognatha, Pteropoda and Euphausiacea...

  7. Oceanography of the Indian Ocean

    Digital Repository Service at National Institute of Oceanography (India)

    Desai, B.N.

    Indian Ocean, the monsoons, changes in the circulation patterns, chemical processes, its geological history and great biological diversity are some of the aspects reflected in the contents of the volume....

  8. Superficial mineral resources of the Indian Ocean

    Digital Repository Service at National Institute of Oceanography (India)

    Siddiquie, H.N.; Hashimi, N.H.; Gujar, A; Valsangkar, A

    The sea floor of the Indian Ocean and the continental margins bordering the ocean are covered by a wide variety of terrigenous, biogenous and anthigenic mineral deposits. The biogenous deposits in the Indian Ocean comprise the corals on shallow...

  9. Precessional forced evolution of the Indian Ocean Dipole

    Science.gov (United States)

    Wang, Yue; Jian, ZhiMin; Zhao, Ping; Chen, JunMing; Xiao, Dong

    2015-05-01

    In a transient accelerated simulation of a coupled climate model, we identified a zonal dipole-like pattern of sea surface temperature (SST) anomalies in the tropical Indian Ocean, which is forced by precessional insolation changes since 300 ka and named as the paleo-IOD (Indian Ocean Dipole). A positive paleo-IOD mean state at 23 kyr precessional band exhibits warmer and wetter conditions over the western Indian Ocean and cooler and drier conditions over the eastern tropical Indian Ocean from August to October. This zonal thermal seesaw at the sea surface can extend downward to the subsurface ocean between 60 and 80 m and accompanies stronger oceanic upwelling in the eastern tropical Indian Ocean. The associated boreal summer-autumn tropospheric circulation anomalies are characterized by anomalous ascent over the western Indian Ocean and anomalous descent over the southeastern tropical Indian Ocean, with anomalous easterlies at the surface along the equatorial Indian Ocean. The positive paleo-IOD largely originates from local air-sea interactions that are induced by the increased summer insolation, and is also contributed by the reduced boreal winter insolation through an oceanic "heat memory effect." Our simulated dipole mode index (DMI) of SST is qualitatively consistent with the paleoceanographic reconstructed DMI based on the UK37 proxy of SST at precessional band and provides a possible explanation for the in-phase precessional variation between boreal winter insolation and the UK37 proxy of SST in the eastern tropical Indian Ocean.

  10. India in the Indian Ocean

    Science.gov (United States)

    2006-01-01

    still are limited but are expanding. Reminiscent of India’s precolonial relationship with coastal Africa , New Delhi’s key connections today are with some...Central Asia to Japan. Finally, and most of all, the rise of India will have consequences in the broad belt of nations from South Africa to Austra...Hormuz and from the coast of Africa to the western shores of Australia. For some Indians, the emphasis is on the northern Indian Ocean, but for others the

  11. Geochemistry of sediment cores of the western equatorial Indian Ocean

    Digital Repository Service at National Institute of Oceanography (India)

    Murty, P; Cronan, D.S.; Rao, Ch.M.; Paropkari, A.L.; Topgi, R.S.; Guptha, M.V.S.; Colley, N.

    Geochemical investigations including partition analysis have been carried out on nine sediment cores from the western equatorial Indian Ocean. The results show that a core from the Arabian Sea exhibits a greater terrigenous influence than cores from...

  12. Simulation of Coupled Variability in the Tropical Indian Ocean

    Science.gov (United States)

    Zhong, A.; Hendon, H. H.; Alves, O.

    2007-12-01

    The coupled ocean-atmosphere variability in the tropical Indian Ocean is investigated by analysing three 100-year integrations of an Australian Bureau of Meteorology coupled seasonal forecast model. In its fully coupled (control) run, ENSO appears to be the leading mechanism that excites Indian Ocean coupled dipole/zonal mode. This involves a feedback between anomalous equatorial easterlies and zonal gradients in SST and rainfall, and is tightly tied to the seasonal cycle. The Indian Ocean zonal mode exhibits a dominant biennial periodicity, which is an amplification of the biennial ENSO mode in this model. In the second run, the local ocean - atmosphere coupling in the Indian Ocean is purposely suppressed by passing the climatological wind stresses derived from the control run to the ocean in the tropical Indian region. The dominant mechanism of SST variation in the Indian Ocean is investigated. A basin-scale surface warm anomaly is developed after the peak of El Niño in the Pacific. It is found that this warming is driven by surface heat flux anomalies that are remotely driven by SST anomalies in the equatorial Pacific. In this run, the biennial periodicity of Indian Ocean zonal mode is significant reduced. In the third run, the ENSO is artificially suppressed by applying climatological surface stresses to the tropical Pacific Ocean. In that case, the Indian Ocean zonal mode still develops in the absence of ENSO but its amplitude is about 20-30% weaker, supporting the notion that the Indian Ocean coupled mode is an intrinsic mode of the variability in the Indian Ocean. Furthermore, the biennial variation, mainly apparent the subsurface, is not amplified at the surface in the absence of ENSO, suggesting that biennial variation in the thermocline itself can not trigger the Indian Ocean zonal mode. Besides ENSO, the model results also suggest that the Indian Ocean coupled mode can be triggered by an equatorward shift of the extratropical ridge/jet, which is

  13. Biogeochemistry of the North Indian Ocean

    Digital Repository Service at National Institute of Oceanography (India)

    DileepKumar, M.

    result from these processes occurring in hydrosphere, geosphere or atmosphere. Oceans form a major part of the hydrosphere on our planet. The Indian Ocean, unlike the Pacific and Atlantic Oceans, does not connect the two Polar Oceans and is special in its...

  14. On chlorinated hydrocarbons in the Indian Ocean

    Digital Repository Service at National Institute of Oceanography (India)

    Sarkar, A.; SenGupta, R.

    stream_size 11 stream_content_type text/plain stream_name Oceanogr_Indian_Ocean_385.pdf.txt stream_source_info Oceanogr_Indian_Ocean_385.pdf.txt Content-Encoding ISO-8859-1 Content-Type text/plain; charset=ISO-8859-1 ...

  15. The warm pool in the Indian Ocean

    Digital Repository Service at National Institute of Oceanography (India)

    Vinayachandran, P.N.; Shetye, S.R.

    ) a single maximum/minimum (northern and southern part of the Pacific warm pool and the south Indian Ocean), (iii) two maxima/minima (Arabian Sea, western equatorial Indian Ocean and Southern Bay of Bengal), and (iv) a rapid rise, a steady phase and a...

  16. North Indian Ocean variability during the Indian Ocean dipole

    Directory of Open Access Journals (Sweden)

    J. Brown

    2008-06-01

    Full Text Available The circulation in the North Indian Ocean (NIO henceforth is highly seasonally variable. Periodically reversing monsoon winds (southwesterly during summer and northeasterly during winter give rise to seasonally reversing current systems off the coast of Somalia and India. In addition to this annual monsoon cycle, the NIO circulation varies semiannually because of equatorial currents reversing four times each year. These descriptions are typical, but how does the NIO circulation behave during anomalous years, during an Indian Ocean dipole (IOD for instance? Unfortunately, in situ observational data are rather sparse and reliance has to be placed on numerical models to understand this variability. In this paper, we estimate the surface current variability from a 12-year hindcast of the NIO for 1993–2004 using a 1/2° resolution circulation model that assimilates both altimetric sea surface height anomalies and sea surface temperature. Presented in this paper is an examination of surface currents in the NIO basin during the IOD. During the non-IOD period of 2000–2004, the typical equatorial circulation of the NIO reverses four times each year and transports water across the basin preventing a large sea surface temperature difference between the western and eastern NIO. Conversely, IOD years are noted for strong easterly and westerly wind outbursts along the equator. The impact of these outbursts on the NIO circulation is to reverse the direction of the currents – when compared to non-IOD years – during the summer for negative IOD events (1996 and 1998 and during the fall for positive IOD events (1994 and 1997. This reversal of current direction leads to large temperature differences between the western and eastern NIO.

  17. Two flavors of the Indian Ocean Dipole

    Science.gov (United States)

    Endo, Satoru; Tozuka, Tomoki

    2016-06-01

    The Indian Ocean Dipole (IOD) is known as a climate mode in the tropical Indian Ocean accompanied by negative (positive) sea surface temperature (SST) anomalies over the eastern (western) pole during its positive phase. However, the western pole of the IOD is not always covered totally by positive SST anomalies. For this reason, the IOD is further classified into two types in this study based on SST anomalies in the western pole. The first type (hereafter "canonical IOD") is associated with negative (positive) SST anomalies in the eastern (central to western) tropical Indian Ocean. The second type (hereafter "IOD Modoki"), on the other hand, is associated with negative SST anomalies in the eastern and western tropical Indian Ocean and positive SST anomalies in the central tropical Indian Ocean. Based on composite analyses, it is found that easterly wind anomalies cover the whole equatorial Indian Ocean in the canonical IOD, and as a result, positive rainfall anomalies are observed over East Africa. Also, due to the basin-wide easterly wind anomalies, the canonical IOD is accompanied by strong sea surface height (SSH) anomalies. In contrast, zonal wind anomalies converge in the central tropical Indian Ocean in the IOD Modoki, and no significant precipitation anomalies are found over East Africa. Also, only weak SSH anomalies are seen, because equatorial downwelling anomalies induced by westerly wind anomalies in the west are counteracted by equatorial upwelling anomalies caused by easterly wind anomalies in the east.

  18. Swell Propagation over Indian Ocean Region

    Directory of Open Access Journals (Sweden)

    Suchandra A. Bhowmick

    2011-06-01

    Full Text Available Swells are the ocean surface gravity waves that have propagated out of their generating fetch to the distant coasts without significant attenuation. Therefore they contain a clear signature of the nature and intensity of wind at the generation location. This makes them a precursor to various atmospheric phenomena like distant storms, tropical cyclones, or even large scale sea breeze like monsoon. Since they are not affected by wind once they propagate out of their generating region, they cannot be described by regional wave models forced by local winds. However, their prediction is important, in particular, for ship routing and off shore structure designing. In the present work, the propagation of swell waves from the Southern Ocean and southern Indian Ocean to the central and northern Indian Ocean has been studied. For this purpose a spectral ocean Wave Model (WAM has been used to simulate significant wave height for 13 years from 1993–2005 using NCEP blended winds at a horizontal spatial resolution of 1° × 1°. It has been observed that Indian Ocean, with average wave height of approximately 2–3 m during July, is mostly dominated by swell waves generated predominantly under the extreme windy conditions prevailing over the Southern Ocean and southern Indian Ocean. In fact the swell waves reaching the Indian Ocean in early or mid May carry unique signatures of monsoon arriving over the Indian Subcontinent. Pre-monsoon month of April contains low swell waves ranging from 0.5–1 m. The amplitudes subsequently increase to approximately 1.5–2 meters around 7–15 days prior to the arrival of monsoon over the Indian Subcontinent. This embedded signature may be utilized as one of the important oceanographic precursor to the monsoon onset over the Indian Ocean.

  19. Preface to: Indian Ocean biogeochemical processes and ecological variability

    Digital Repository Service at National Institute of Oceanography (India)

    Hood, R.R.; Naqvi, S.W.A.; Wiggert, J.D.

    . This is partly because the Indian Ocean re mains substantially under sampled, in both space and time, compared to the Atlantic and Pacific oceans. The situation is compounded by the Indian Ocean being a dynamically complex and highly variable system under... derstanding of the atmospheric and oceanic variability in the Indian Ocean, the Climate Variability and Predictability pro gram (CL1VAR) and the Global Ocean Observing System (GOOS) are deploying a basin-wide observing system in the Indian Ocean. As well...

  20. Bathymetric techniques and Indian Ocean applications

    Digital Repository Service at National Institute of Oceanography (India)

    Chakraborty, B.; Fernandes, W.A.

    the different steps of processing, backed by the examples as experiences of the authors of their use in the Indian Ocean. It proposes innovative and interesting approaches for data analysis. The article is backed with a short but complete bibliography...

  1. Biological processes of the northern Indian Ocean

    Digital Repository Service at National Institute of Oceanography (India)

    Madhupratap, M.; Parulekar, A.H.

    Physical processes such as wind-driven coastal run-off during the monsoons and convective overturning of surface waters due to winter cooling bring in nutrients into the euphotic zone and enhance primary productivity of the northern Indian Ocean...

  2. Ablated tektite from the central Indian Ocean

    Digital Repository Service at National Institute of Oceanography (India)

    Glass, B.P.; Chapman, D.R.; ShyamPrasad, M.

    ) australites found at Serpentine Lakes and Lake Wilson, Australia, and to some HMg microtektites found in deep-sea sediments from the central Indian Ocean. This discovery supports a previous conclusion that the Australasian tektite strewn field covers most...

  3. History of oceanography of the Indian Ocean

    Digital Repository Service at National Institute of Oceanography (India)

    Sengupta, R.

    This paper highlights history of the oceanography of the Indian Ocean. Oceanographic activities during Ancient period, Medieval period, British period, Post-Independence period are briefly discussed. The role of the IIOE, IOC, UNESCO are also...

  4. Biophysical processes in the Indian Ocean

    Digital Repository Service at National Institute of Oceanography (India)

    McCreary, J.P.; Murtugudde, R.; Vialard, J.; Vinayachandran, P.N.; Wiggert, J.D.; Hood, R.R.; Shankar, D.; Shetye, S.R.

    Basic physical processes that impact biological activity in the Indian Ocean (IO), namely, near-surface processes (upwelling, entrainment, detrainment, and advection) and subsurface circulations (shallow overturning cells and subthermocline currents...

  5. Western Indian Ocean Journal of Marine Science

    African Journals Online (AJOL)

    Western Indian Ocean Journal of Marine Science. ... The journal will, from time to time, consist of special issues on major events or important thematic issues. ... Reproductive biology and body condition of exploited populations of Emperor ...

  6. Polymetallic nodule resources of the Indian Ocean

    Digital Repository Service at National Institute of Oceanography (India)

    Nair, R.R.; Jauhari, P.

    nodules. These contain, beside iron and manganese, copper, nickle and cobalt in economically feasible quantities. India has already got a mine site registered in the Central Indian Ocean Basin. As the land resources of strategic metals are declining...

  7. Investigating the Indian Ocean Geoid Low

    Science.gov (United States)

    Ghosh, A.; Gollapalli, T.; Steinberger, B. M.

    2016-12-01

    The lowest geoid anomaly on Earth lies in the Indian Ocean just south of the Indian peninsula.Several theories have been proposed to explain this geoid low, most of which invoke past subduction. Some recent studies have alsoargued that high velocity anomalies in the lower mantle coupled with low velocity anomalies in the upper mantle are responsible for these negative geoidanomalies. However, there is no general consensus regarding the source of the Indian Ocean negative geoid. We investigate the source of this geoid low by using forward models of density driven mantle convection using CitcomS. We test various tomography models in our flow calculations with different radial and lateral viscosity variations. Many tomography modelsproduce a fairly high correlation to the global geoid, however none could match the precise location of the geoid low in the Indian Ocean. Amerged P-wave model of LLNL-G3DV3 in the Indian Ocean region and S40rts elsewhere yields a good fit to the geoid anomaly, both in pattern and magnitude.The source of this geoid low seems to stem from a low velocity anomaly stretching from a depth of 300 km up to 700 km in the northern Indian Ocean region.This velocity anomaly could potentially arise from material rising along the edge of the African LLSVP and moving towards the northeast, facilitated by the movementof the Indian plate in the same direction.

  8. Lithogenic fluxes to the northern Indian Ocean - An overview

    Digital Repository Service at National Institute of Oceanography (India)

    Ramaswamy, V.

    Lithogenic fluxes to the northern Indian Ocean, measurEd. by time-series sediment traps, exhibit a strong seasonality with the bulk of the material (40 to 80 %) being deposited during the southwest monsoon period. This seasonality is more pronounced...

  9. Bats of the Western Indian Ocean Islands

    Directory of Open Access Journals (Sweden)

    John O’Brien

    2011-08-01

    Full Text Available The natural colonisation of many remote oceanic islands by bats, including those of the western Indian Ocean, has been facilitated by their unique capability among mammals for powered flight. In the western Indian Ocean region, only the Malagasy islands of Madagascar and the Comoros archipelago have been naturally colonised by non-volant mammals. Despite their greater potential for inter-island dispersal, and thus gene transfer, endemicity of Chiroptera in the western Indian Ocean islands is high. Given their vulnerability to stochastic and anthropogenic disturbances, greater focus needs to be placed on investigating the demographic and ecological history of bats on Western Indian Ocean islands to safeguard not only their future, but also the ecosystem functioning on these islands, for which they are undoubtedly such an integral part. Here, I summarise the taxonomic and life history information available on bats from Western Indian Ocean islands and highlight knowledge gaps and conservation issues that threaten the continued persistence of some species.

  10. Intraseasonal Oscillation in the Tropical Indian Ocean

    Institute of Scientific and Technical Information of China (English)

    2005-01-01

    The features of the intraseasonal oscillation (ISO) of the tropical Indian Ocean are studied using several sources of observational data. It is shown that there are intraseasonal oscillations in the tropical Indian Ocean, but their periods vary with latitude: the major period is about 20-30 days in the equatorial region, about 30-50 days at 10°N/10°S latitude and 60-90 days at 20°N/20°S latitude. The intensity of the ISO increases with latitude but the speed of the westward propagation of the ISO decreases with latitude. The intensity and propagation speed of the ISO have clear interannual variation features. The atmospheric intraseasonal oscillation over the tropical Indian Ocean is also analyzed and compared with the oceanic intraseasonal oscillation. It is shown that the major period is in the range 30-60 days and the intensity and period of the atmospheric ISO decrease with latitude slightly. The zonal propagation of the atmospheric ISO also has some differences with the oceanic ISO. It is necessary to study the relationship between the atmospheric ISO and oceanic ISO in the tropical Indian Ocean deeply.

  11. TSUNAMIGENIC SOURCES IN THE INDIAN OCEAN

    Directory of Open Access Journals (Sweden)

    B. K. Rastogi

    2008-01-01

    Full Text Available Based on an assessment of the repeat periods of great earthquakes from past seismicity, convergence rates and paleoseismological results, possible future source zones of tsunami generating earthquakes in the Indian Ocean (possible seismic gap areas are identified along subduction zones and zones of compression. Central Sumatra, Java, Makran coast, Indus Delta, Kutch-Saurashtra, Bangladesh and southern Myanmar are identified as possible source zones of earthquakes in near future which might cause tsunamis in the Indian Ocean, and in particular, that could affect India. The Sunda Arc (covering Sumatra and Java subduction zone, situated on the eastern side of the Indian Ocean, is one of the most active plate margins in the world that generates frequent great earthquakes, volcanic eruptions and tsunamis. The Andaman- Nicobar group of islands is also a seismically active zone that generates frequent earthquakes. However, northern Sumatra and Andaman-Nicobar regions are assessed to be probably free from great earthquakes (M!8.0 for a few decades due to occurrence of 2004 Mw 9.3 and 2005 Mw 8.7 earthquakes. The Krakatau volcanic eruptions have caused large tsunamis in the past. This volcano and a few others situated on the ocean bed can cause large tsunamis in the future. List of past tsunamis generated due to earthquakes/volcanic eruptions that affected the Indian region and vicinity in the Indian Ocean are also presented.

  12. Decadal trends in Indian Ocean ambient sound.

    Science.gov (United States)

    Miksis-Olds, Jennifer L; Bradley, David L; Niu, Xiaoyue Maggie

    2013-11-01

    The increase of ocean noise documented in the North Pacific has sparked concern on whether the observed increases are a global or regional phenomenon. This work provides evidence of low frequency sound increases in the Indian Ocean. A decade (2002-2012) of recordings made off the island of Diego Garcia, UK in the Indian Ocean was parsed into time series according to frequency band and sound level. Quarterly sound level comparisons between the first and last years were also performed. The combination of time series and temporal comparison analyses over multiple measurement parameters produced results beyond those obtainable from a single parameter analysis. The ocean sound floor has increased over the past decade in the Indian Ocean. Increases were most prominent in recordings made south of Diego Garcia in the 85-105 Hz band. The highest sound level trends differed between the two sides of the island; the highest sound levels decreased in the north and increased in the south. Rate, direction, and magnitude of changes among the multiple parameters supported interpretation of source functions driving the trends. The observed sound floor increases are consistent with concurrent increases in shipping, wind speed, wave height, and blue whale abundance in the Indian Ocean.

  13. Nodules of the Central Indian Ocean Basin

    Digital Repository Service at National Institute of Oceanography (India)

    Banakar, V.K.; Kodagali, V.N.

    of calcareous sediments within, and pelagic sediments south of 15 degrees S latitude Prior to the launching of the project, very little data was available on the Indian Ocean nodules compared to those of Pacific This chapter summaries the findings of the project...

  14. Upper ocean physical processes in the Tropical Indian Ocean

    Digital Repository Service at National Institute of Oceanography (India)

    Rao, L.V.G.; Ram, P.S.

    This monograph is the outcome of an attempt by the authors to present a synthesis of the studies on physical processes in the Tropical Indian Ocean (TIO) in relation to air-sea interaction, monsoon/climate variability and biological productivity...

  15. Variations in the eastern Indian Ocean warm pool and its relation to the dipole in the tropical Indian Ocean

    Institute of Scientific and Technical Information of China (English)

    ZHANG Qilong; HOU Yijun; QI Qinghua; BAI Xuezhi

    2009-01-01

    Based on the monthly average SST and 850 hPa monthly average wind data, the seasonal, interannual and long-term variations in the eastern Indian Ocean warm pool (EIWP) and its relationship to the Indian Ocean Dipole (IOD), and its response to the wind over the Indian Ocean are analyzed in this study. The results show that the distribution range, boundary and area of the EIWP exhibited obviously seasonal and interannual variations associated with the ENSO cycles. Further analysis suggests that the EIWP had obvious long-term trend in its bound edge and area, which indicated the EIWP migrated westwards by about 14 longitudes for its west edge, southwards by about 5 latitudes for its south edge and increased by 3.52×106 km2 for its area, respectively, from 1950 to 2002. The correlation and composite analyses show that the anomalous westward and northward displacements of the EIWP caused by the easterly wind anomaly and the southerly wind anomaly over the eastern equatorial Indian Ocean played an important and direct role in the formation of the IOD.

  16. Pyloniid stratigraphy - A new tool to date tropical radiolarian ooze from the central tropical Indian Ocean

    Digital Repository Service at National Institute of Oceanography (India)

    Gupta, S.M.

    of 25 modern radiolarian groups in surface sediments and monsoonal surface salinity from the central Indian Ocean is analyzed. Among them, Pyloniids exhibit the potential to serve in the same way as the C. davisiana stratigraphy. Down-core (temporal...

  17. Atlantic and indian oceans pollution in africa

    Science.gov (United States)

    Abubakar, Babagana

    Africa is the second largest and most populated continent after Asia. Geographically it is located between the Atlantic and Indian Oceans. Most of the Africa's most populated and industrialized cities are located along the coast of the continent facing the Atlantic and Indian Oceans, example of such cities include Casablanca, Dakar, Accra, Lagos, Luanda and Cape town all facing the Atlantic Ocean and cities like East London, Durban, Maputo, Dar-es-salaam and Mogadishu are all facing the Indian Ocean. As a result of the geographical locations of African Coastal Cities plus increase in their population, industries, sea port operations, petroleum exploration activities, trafficking of toxic wastes and improper waste management culture lead to the incessant increase in the pollution of the two oceans. NATURE OF POLLUTION OF THE ATLANTIC OCEAN i. The petroleum exploration activities going on along the coast of "Gulf of Guinea" region and Angola continuously causes oil spillages in the process of drilling, bunkering and discharging of petroleum products in the Atlantic Ocean. ii. The incessant degreasing of the Sea Ports "Quay Aprons" along the Coastal cities of Lagos, Luanda, Cape Town etc are continuously polluting the Atlantic Ocean with chemicals. iii. Local wastes generated from the houses located in the coastal cities are always finding their ways into the Atlantic Ocean. NATURE OF POLLUTION OF THE INDIAN OCEAN i. Unlike the Atlantic ocean where petroleum is the major pollutant, the Indian Ocean is polluted by Toxic / Radioactive waste suspected to have been coming from the developed nations as reported by the United Nations Environmental Programme after the Tsunami disaster in December 2004 especially along the coast of Somalia. ii. The degreasing of the Quay Aprons at Port Elizabeth, Maputo, Dar-es-Salaam and Mongolism Sea Ports are also another major source polluting the Indian Ocean. PROBLEMS GENERATED AS A RESULT OF THE OCEANS POLLUTION i. Recent report

  18. Monsoon regime in the Indian Ocean and zooplankton variability

    Digital Repository Service at National Institute of Oceanography (India)

    Nair, V.R.

    The monsoonal effects on zooplankton lead to characteristic zoogeographic patterns in the open ocean and coastal waters. The evaluation of zooplankton variability in the Indian Ocean is presented in three sections: the open ocean, coastal waters...

  19. Igneous rocks of the Indian ocean floor

    Science.gov (United States)

    Engel, C.G.; Fischer, R.L.; Engel, A.E.J.

    1965-01-01

    Four dredge hauls from near the crest and from the eastern flank of the seismically active Mid-Indian Ocean Ridge at 23?? to 24??S, at depths of 3700 to 4300 meters, produced only low-potassium tholeiitic basalt similar in chemical and mineralogic composition to basalts characteristic of ridges and rises in the Atlantic and Pacific oceansA fifth haul, from a depth of 4000 meters on the lower flank of a seamount on the ocean side of the Indonesian Trench, recovered tholeiitic basalt with higher concentrations of K and Ti and slightly lower amounts of Si and Ca than the typical oceanic tholeiite of the ridgeThe last sample is vesicular, suggesting depression of the area since the basalt was emplacedMany of the rocks dredged are variously decomposed and hydrated, but there is no evidence of important chemical modification toward conversion of the lava flows to spilite during extrusion or solidification.

  20. The positive Indian Ocean Dipole–like response in the tropical Indian Ocean to global warming

    Energy Technology Data Exchange (ETDEWEB)

    Luo, Yiyong; Lu, Jian; Liu, Fukai; Wan, Xiuquan

    2016-02-04

    Climate models project a positive Indian Ocean Dipole (pIOD)-like SST response in the tropical Indian Ocean to global warming. By employing the Community Earth System Model (CESM) and applying an overriding technique to its ocean component Parallel Ocean Program version 2 (POP2), this study investigates the similarity and difference of the formation mechanisms for the changes in the tropical Indian Ocean during the pIOD versus global warming. Results show that their formation processes and related seasonality are quite similar; in particular, the Bjerknes feedback is the leading mechanism in producing the anomalous cooling over the eastern tropics in both cases. Some differences are also found, including that the cooling effect of the vertical advection over the eastern tropical Indian Ocean is dominated by the anomalous vertical velocity during the pIOD while it is dominated by the anomalous upper-ocean stratification under global warming. These findings above are further examined with an analysis of the mixed layer heat budget.

  1. Volcanogenic sediments in the Indian Ocean

    Digital Repository Service at National Institute of Oceanography (India)

    Pattan, J.N.

    ….) and lithic fragments. The secondary component is diagenetic alteration of primary components then transferred to Fe-rich smectite, palagonite and zeolites. Volcanism in different tectonic settings contributes tephra to marine environments. In the Indian... Ocean volcanogenic components are derived from MOR volcanism, hot spot volcanism (ex: Reunion and Kerguelen hot spots) and subduction related volcanism in the Indonesian arc. During IIOE large number of sediment cores was retrieved in the Arabian...

  2. An Indian Ocean precursor for Indian summer monsoon rainfall variability

    Science.gov (United States)

    Sreejith, O. P.; Panickal, S.; Pai, S.; Rajeevan, M.

    2015-11-01

    The Indian summer monsoon rainfall (ISMR) depicts large interannual variability strongly linked with El Niño-Southern Oscillation (ENSO). However, many of the El Niño years were not accompanied by deficient ISMR. The results from the study reveal the significant role of coupled air-sea interaction over the tropical Indian Ocean (IO) in modifying the ENSO-ISMR association. The IO warm water volume (WWV), a measure of heat content variations in the equatorial IO has strong influence on ISMR. A deepening (shoaling) of thermocline in the eastern equatorial IO (EEIO) during late boreal spring (April-May) accompanied by increase (decrease) in WWV anomalies weaken (enhance) the ISMR by enhancing (suppressing) the convection over EEIO resulting in the below (above) normal ISMR. Thus, the changes in the WWV anomalies in the EEIO along with ENSO conditions during boreal spring can be considered as a precursor for the performance of subsequent ISMR.

  3. Inputs from Indian rivers to the ocean: A synthesis

    Digital Repository Service at National Institute of Oceanography (India)

    DileepKumar, M.; George, M.D.; SenGupta, R.

    ). Fluxes of chemical substances to the Indian Ocean from these rivers are computed to a first approximation. The major ion contents are inversely proportional to the river runoff especially for the rivers entering the Arabian Sea. On an average Indian...

  4. Indian Ocean SST Biases in a Flexible Regional Ocean Atmosphere Land System (FROALS) Model

    Institute of Scientific and Technical Information of China (English)

    HAN Zhen-Yu; ZHOU Tian-Jun; ZOU Li-Wei

    2012-01-01

    The authors examine the Indian Ocean sea surface temperature (SST) biases simulated by a Flexible Regional Ocean Atmosphere Land System (FROALS) model. The regional coupled model exhibits pronounced cold SST biases in a large portion of the Indian Ocean warm pool. Negative biases in the net surface heat fluxes are evident in the model, leading to the cold biases of the SST. Further analysis indicates that the negative biases in the net surface heat fluxes are mainly contributed by the biases of sensible heat and latent heat flux. Near-surface meteorological variables that could contribute to the SST biases are also examined. It is found that the biases of sensible heat and latent heat flux are caused by the colder and dryer near-surface air in the model.

  5. Warm Indian Ocean, Weak Asian Monsoon

    Science.gov (United States)

    Koll Roxy, Mathew; Ritika, Kapoor; Terray, Pascal; Murtugudde, Raghu; Ashok, Karumuri; Nath Goswami, Buphendra

    2015-04-01

    There are large uncertainties looming over the status and fate of the South Asian monsoon in a changing climate. Observations and climate models have suggested that anthropogenic warming in the past century has increased the moisture availability and the land-sea thermal contrast in the tropics, favoring an increase in monsoon rainfall. In contrast, we notice that South Asian subcontinent experienced a relatively subdued warming during this period. At the same time, the tropical Indian Ocean experienced a nearly monotonic warming, at a rate faster than the other tropical oceans. Using long-term observations and coupled model experiments, we suggest that the enhanced Indian Ocean warming along with the suppressed warming of the subcontinent weaken the land-sea thermal contrast throughout the troposphere, dampen the monsoon Hadley circulation, and reduce the rainfall over South Asia. As a result, the summer monsoon rainfall during 1901-2012 shows a significant weakening trend over South Asia, extending from Pakistan through central India to Bangladesh.

  6. Indian Ocean heat content changes masked by multi-decadal variability: Is the Indian Ocean warming or not?

    Science.gov (United States)

    Ummenhofer, Caroline; Biastoch, Arne; Böning, Claus

    2015-04-01

    The Indian Ocean has sustained robust surface warming in recent decades, with warming rates exceeding those of other tropical ocean basins. Significant, non-uniform trends in Indian Ocean sea surface temperatures - both in observations and projections for the 21st Century - have the potential to impact regional climate, through variations in the monsoon circulation, characteristics of Indian Ocean Dipole events, and the associated hydroclimate across the wider Indo-Pacific. However, it remains unclear what role decadal to multi-decadal variability in upper-ocean Indian Ocean thermal characteristics play in these trends. Using high-resolution ocean model hindcasts building on the ocean/sea-ice numerical Nucleus for European Modelling of the Ocean (NEMO) framework forced with atmospheric forcing fields of the Coordinated Ocean Reference Experiments (CORE), the characteristics of Indian Ocean temperature changes are explored. Sensitivity experiments, where interannual atmospheric forcing variability is restricted to thermal or wind-stress forcing only, support the interpretation of forcing mechanisms for the evolution of temperature characteristics across the Indian Ocean, focusing on the top 700m. Simulated temperature changes across the Indian Ocean in the hindcasts are consistent with those recorded in observational products, as well as ocean reanalyses. Assessment of Indian Ocean heat content since the 1950s suggests extensive (subsurface) cooling for much of the tropical Indian Ocean. The presence of substantial multi-decadal variability in its heat content further implies caution in interpreting linear trends in thermal properties, as long-term trends can be masked. The sensitivity experiments reveal that cooling trends in Indian Ocean heat content since the mid-1960s to the late 1990s are largely driven by wind-stress forcing, likely due to remote Pacific wind forcing associated with the Pacific Decadal Oscillation (PDO). As such, multi-decadal wind-forcing has

  7. Ocean atmosphere thermal decoupling in the eastern equatorial Indian ocean

    Science.gov (United States)

    Joseph, Sudheer; Ravichandran, M.; Kumar, B. Praveen; Jampana, Raju V.; Han, Weiqing

    2017-07-01

    Eastern equatorial Indian ocean (EEIO) is one of the most climatically sensitive regions in the global ocean, which plays a vital role in modulating Indian ocean dipole (IOD) and El Niño southern oscillation (ENSO). Here we present evidences for a paradoxical and perpetual lower co-variability between sea-surface temperature (SST) and air-temperature (Tair) indicating instantaneous thermal decoupling in the same region, where signals of the strongly coupled variability of SST anomalies and zonal winds associated with IOD originate at inter-annual time scale. The correlation minimum between anomalies of Tair and SST occurs in the eastern equatorial Indian ocean warm pool region (≈70°E-100°E, 5°S-5°N), associated with lower wind speeds and lower sensible heat fluxes. At sub-monthly and Madden-Julian oscillation time scales, correlation of both variables becomes very low. In above frequencies, precipitation positively contributes to the low correlation by dropping Tair considerably while leaving SST without any substantial instant impact. Precipitation is led by positive build up of SST and post-facto drop in it. The strong semi-annual response of SST to mixed layer variability and equatorial waves, with the absence of the same in the Tair, contributes further to the weak correlation at the sub-annual scale. The limited correlation found in the EEIO is mainly related to the annual warming of the region and ENSO which is hard to segregate from the impacts of IOD.

  8. Ocean atmosphere thermal decoupling in the eastern equatorial Indian ocean

    Science.gov (United States)

    Joseph, Sudheer; Ravichandran, M.; Kumar, B. Praveen; Jampana, Raju V.; Han, Weiqing

    2016-09-01

    Eastern equatorial Indian ocean (EEIO) is one of the most climatically sensitive regions in the global ocean, which plays a vital role in modulating Indian ocean dipole (IOD) and El Niño southern oscillation (ENSO). Here we present evidences for a paradoxical and perpetual lower co-variability between sea-surface temperature (SST) and air-temperature (Tair) indicating instantaneous thermal decoupling in the same region, where signals of the strongly coupled variability of SST anomalies and zonal winds associated with IOD originate at inter-annual time scale. The correlation minimum between anomalies of Tair and SST occurs in the eastern equatorial Indian ocean warm pool region (≈70°E-100°E, 5°S-5°N), associated with lower wind speeds and lower sensible heat fluxes. At sub-monthly and Madden-Julian oscillation time scales, correlation of both variables becomes very low. In above frequencies, precipitation positively contributes to the low correlation by dropping Tair considerably while leaving SST without any substantial instant impact. Precipitation is led by positive build up of SST and post-facto drop in it. The strong semi-annual response of SST to mixed layer variability and equatorial waves, with the absence of the same in the Tair, contributes further to the weak correlation at the sub-annual scale. The limited correlation found in the EEIO is mainly related to the annual warming of the region and ENSO which is hard to segregate from the impacts of IOD.

  9. The diversity of Indian Ocean Heterotardigrada

    Directory of Open Access Journals (Sweden)

    Roberto SANDULLI

    2007-09-01

    Full Text Available Information about Indian Ocean tardigrades is quite scarce and in most cases refers to species in coastal coralline sediment and occasionally in abyssal mud. The present data concern species found in the intertidal sand of Coco and La Digue Islands in the Seychelles, previously unsampled for tardigrades, as well as species in subtidal sediment found at depths ranging between 1 and 60 m off the shores of the Maldive Atolls. These sediments are all very similar and consist of heterogeneous coralline sand, moderately or scarcely sorted. Sixteen species (three new to science were found in the Seychelles, belonging to Renaudarctidae, Stygarctidae, Halechiniscidae, Batillipedidae and Echiniscoididae. Diversity and evenness data are also interesting, with maximum values of H' = 2.59 and of J = 0.97. In the Maldives 25 species were found (two new to science belonging to Neostygarctidae, Stygarctidae, Halechiniscidae and Batillipedidae. Such a number of species, despite the low percentage of tardigrade fauna (only 0.6% of the total meiofauna, contributes to the high values of both diversity and evenness, with H' ranging between 1.5 and 2.6 and J between 0.6 and 1. The Indian Ocean tardigrade fauna currently numbers 31 species of Arthrotardigrada and 2 species of Echiniscoidida. In the present study, Arthrotardigrada are the most abundant and all the families are present except Neoarctidae. Halechiniscidae is present with all the sub-families (except Euclavartinae, thus contributing to the high diversity values. Furthermore, 18 species, representing more than 50% of the total marine tardigrade fauna, are new records for the Indian Ocean, including five species new to science.

  10. Effects of Aerosols over the Indian Ocean

    Science.gov (United States)

    2002-01-01

    Aerosols that contain black carbon both absorb and reflect incoming sunlight. Even as these atmospheric particles reduce the amount of sunlight reaching the surface, they increase the amount of solar energy absorbed in the atmosphere, thus making it possible to both cool the surface and warm the atmosphere. The images above show satellite measurements of the region studied during the Indian Ocean Experiment (INDOEX)a vast region spanning the Arabian Sea and Bay of Bengal (west to east), and from the foot of the Himalayan Mountains, across the Indian subcontinent to the southern Indian Ocean (north to south). The Aerosol images show aerosol pollution (brownish pixels) in the lower atmosphere over the INDOEX study area, as measured by the Moderate-resolution Imaging Spectroradiometer (MODIS) aboard Terra. These were composited from March 14-21, 2001. The Albedo images show the total solar energy reflected back to space, as measured by Clouds and Earth's Radiant Energy System (CERES) aboard Terra. White pixels show high values, greens are intermediate values, and blues are low. Note how the aerosols, particularly over the ocean, increase the amount of energy reflected back to space. The Atmospheric Warming images show the absorption of the black carbon aerosols in the atmosphere. Where the aerosols are most dense, the absorption is highest. Red pixels indicate the highest levels of absorption, blues are low. The Surface Cooling images show that the aerosol particles reduce the amount of sunlight reaching the surface. Dark pixels show where the aerosols exert their cooling influence on the surface (or a high magnitude of negative radiative forcing). The bright pixels show where there is much less aerosol pollution and the incoming sunlight is relatively unaffected.

  11. Preface to: Marine micropaleontological studies from the northern Indian Ocean

    Digital Repository Service at National Institute of Oceanography (India)

    Nigam, R.; Saraswat, R.

    Indian Ocean is unique, being land-locked towards the northern margin, and experiences, highest reported oceanic productivity. It is also the locale for the most severe oxygen depleted waters in the coastal and intermediate depth regions...

  12. Deep-sea ecosystems of the Indian Ocean

    Digital Repository Service at National Institute of Oceanography (India)

    Ingole, B.S.; Koslow, J.A.

    macrofaunal biomass decreased away from the shore, the meiofaunal biomass increased with distance. The discovery of 'Kairei' and Edmond hydrothermal field near the Rodriguez Triple Junction suggests that mid-ocean ridge systems in the Indian Ocean...

  13. Carbon dioxide and nitrous oxide in the North Indian Ocean

    Digital Repository Service at National Institute of Oceanography (India)

    DileepKumar, M.; Naqvi, S.W.A.; Jayakumar, D.A.; George, M.D.; Narvekar, P.V.; DeSousa, S.N.

    The understanding of biogeochemical cycling of carbon dioxide and nitrous oxide in the oceans is essential for predicting the fate of anthropogenically emitted components. The North Indian Ocean, with its diverse regimes, provides us with a natural...

  14. Upper ocean variability of the equatorial Indian Ocean and its relation to chlorophyll pigment concentration.

    Digital Repository Service at National Institute of Oceanography (India)

    Narvekar, J.; PrasannaKumar, S.

    Hydrographic data from the upper ocean together with atmospheric data and satellite data are used to understand the variability of upper ocean and its relation to surface chlorophyll in the Equatorial Indian Ocean. The sea surface temperature showed...

  15. Archaeological sites on the Indian Ocean Rim - A growing database

    Digital Repository Service at National Institute of Oceanography (India)

    Gaur, A

    This section is designed to act as a plafform for reporting explored and excavated sites of all periods located along the Indian Ocean rim. The Indian Ocean is broadly defined It Includes the Red Sea, Gulf of Aden, the East Afncan coast from Somalia...

  16. Warming in the Northwestern Indian Ocean Associated with the El Ni(n)o Event

    Institute of Scientific and Technical Information of China (English)

    YUAN Yuan; ZHOU Wen; YANG Hui; LI Chongyin

    2008-01-01

    This paper investigates possible warming effects of an El Ni(n)o event on the sea surface temperature anomaly(SSTA)in the northwestern Indian Ocean.Most pure positive Indian Ocean dipole(IOD)events (without an El Ni(n)o event co-occurring) have a maximum positive SSTA mainly in the central Indian Ocean south of the equator.while most co-occurrences with an El Ni(n)o event exhibit a northwest-southeast typical dipole mode.It is therefore inferred that warming in the northwestern Indian Ocean is closely related to the El Ni(n)o event.Based on the atmospheric bridge theory,warming in the northwestern Indian Ocean during co-occurring cases may be primarily caused by relatively less latent heat loss from the ocean due to reduced wind speed.The deepened thermocline also contributes to the warming along the east coast of Africa through the suppressed upwelling of the cold water.Therefore,the El Ni(n)o event is suggested to have a modulating effect on the structure of the dipole mode in the tropical Indian Ocean.

  17. Decadal and Interannual Variability of the Indian Ocean Dipole

    Institute of Scientific and Technical Information of China (English)

    YUAN Yuan; C.L.Johnny CHAN; ZHOU Wen; LI Chongyin

    2008-01-01

    This study investigates the decadal and interannual variability of the Indian Ocean Dipole(IOD).It is found that the long.term IOD index displays a decadal phase variation.Prior to 1920 negative phase dominates.but after 1960 positive phase prevails.Under the warming background of the tropical ocean,a larger warming trend in the western Indian Ocean is responsible for the decadal phase variation of the IOD mode.Due to reduced latent heat lOSS from the local ocean.the western Indian Ocean warming may be caused by the weakened Indian Ocean westerly summer monsoon. The interannual air-sea coupled IOD mode varies on the background of its decadal variability.During the earlier period(1948-1969),IOD events are characterized by opposing SST anomaly(ssTA)in the western and eastern Indian Ocean.with a single vertical circulation above the equatorial Indian Ocean. But in the later period (1980-2003),with positive IOD dominating,most IOD events have a zonal gradient perturbation on a uniform positive SSTA.However.there are three exceptionally strong positive IOD events (1982,1994,and 1997),with opposite ssTA in the western and eastern Indian Ocean,accompanied by an El Ni(n)o event.Consequently,two anomalous reversed Walker cells are located separately over the Indian Ocean and western.eastern Pacific;the one over the Indian Ocean iS much stronger than that during other positive IOD events.

  18. Indian Ocean sea surface salinity variations in a coupled model

    Energy Technology Data Exchange (ETDEWEB)

    Vinayachandran, P.N.; Nanjundiah, Ravi S. [Indian Institute of Science, Centre for Atmospheric and Oceanic Sciences, Bangalore (India)

    2009-08-15

    The variability of the sea surface salinity (SSS) in the Indian Ocean is studied using a 100-year control simulation of the Community Climate System Model (CCSM 2.0). The monsoon-driven seasonal SSS pattern in the Indian Ocean, marked by low salinity in the east and high salinity in the west, is captured by the model. The model overestimates runoff into the Bay of Bengal due to higher rainfall over the Himalayan-Tibetan regions which drain into the Bay of Bengal through Ganga-Brahmaputra rivers. The outflow of low-salinity water from the Bay of Bengal is too strong in the model. Consequently, the model Indian Ocean SSS is about 1 less than that seen in the climatology. The seasonal Indian Ocean salt balance obtained from the model is consistent with the analysis from climatological data sets. During summer, the large freshwater input into the Bay of Bengal and its redistribution decide the spatial pattern of salinity tendency. During winter, horizontal advection is the dominant contributor to the tendency term. The interannual variability of the SSS in the Indian Ocean is about five times larger than that in coupled model simulations of the North Atlantic Ocean. Regions of large interannual standard deviations are located near river mouths in the Bay of Bengal and in the eastern equatorial Indian Ocean. Both freshwater input into the ocean and advection of this anomalous flux are responsible for the generation of these anomalies. The model simulates 20 significant Indian Ocean Dipole (IOD) events and during IOD years large salinity anomalies appear in the equatorial Indian Ocean. The anomalies exist as two zonal bands: negative salinity anomalies to the north of the equator and positive to the south. The SSS anomalies for the years in which IOD is not present and for ENSO years are much weaker than during IOD years. Significant interannual SSS anomalies appear in the Indian Ocean only during IOD years. (orig.)

  19. Indian Ocean sea surface salinity variations in a coupled model

    Science.gov (United States)

    Vinayachandran, P. N.; Nanjundiah, Ravi S.

    2009-08-01

    The variability of the sea surface salinity (SSS) in the Indian Ocean is studied using a 100-year control simulation of the Community Climate System Model (CCSM 2.0). The monsoon-driven seasonal SSS pattern in the Indian Ocean, marked by low salinity in the east and high salinity in the west, is captured by the model. The model overestimates runoff into the Bay of Bengal due to higher rainfall over the Himalayan-Tibetan regions which drain into the Bay of Bengal through Ganga-Brahmaputra rivers. The outflow of low-salinity water from the Bay of Bengal is too strong in the model. Consequently, the model Indian Ocean SSS is about 1 less than that seen in the climatology. The seasonal Indian Ocean salt balance obtained from the model is consistent with the analysis from climatological data sets. During summer, the large freshwater input into the Bay of Bengal and its redistribution decide the spatial pattern of salinity tendency. During winter, horizontal advection is the dominant contributor to the tendency term. The interannual variability of the SSS in the Indian Ocean is about five times larger than that in coupled model simulations of the North Atlantic Ocean. Regions of large interannual standard deviations are located near river mouths in the Bay of Bengal and in the eastern equatorial Indian Ocean. Both freshwater input into the ocean and advection of this anomalous flux are responsible for the generation of these anomalies. The model simulates 20 significant Indian Ocean Dipole (IOD) events and during IOD years large salinity anomalies appear in the equatorial Indian Ocean. The anomalies exist as two zonal bands: negative salinity anomalies to the north of the equator and positive to the south. The SSS anomalies for the years in which IOD is not present and for ENSO years are much weaker than during IOD years. Significant interannual SSS anomalies appear in the Indian Ocean only during IOD years.

  20. Indian Ocean sources of Agulhas leakage

    Science.gov (United States)

    Durgadoo, Jonathan V.; Rühs, Siren; Biastoch, Arne; Böning, Claus W. B.

    2017-04-01

    We examine the mean pathways, transit timescales, and transformation of waters flowing from the Pacific and the marginal seas through the Indian Ocean (IO) on their way toward the South Atlantic within a high-resolution ocean/sea-ice model. The model fields are analyzed from a Lagrangian perspective where water volumes are tracked as they enter the IO. The IO contributes 12.6 Sv to Agulhas leakage, which within the model is 14.1 ± 2.2 Sv, the rest originates from the South Atlantic. The Indonesian Through-flow constitutes about half of the IO contribution, is surface bound, cools and salinificates as it leaves the basin within 10-30 years. Waters entering the IO south of Australia are at intermediate depths and maintain their temperature-salinity properties as they exit the basin within 15-35 years. Of these waters, the contribution from Tasman leakage is 1.4 Sv. The rest stem from recirculation from the frontal regions of the Southern Ocean. The marginal seas export 1.0 Sv into the Atlantic within 15-40 years, and the waters cool and freshen on-route. However, the model's simulation of waters from the Gulfs of Aden and Oman are too light and hence overly influenced by upper ocean circulations. In the Cape Basin, Agulhas leakage is well mixed. On-route, temperature-salinity transformations occur predominantly in the Arabian Sea and within the greater Agulhas Current region. Overall, the IO exports at least 7.9 Sv from the Pacific to the Atlantic, thereby quantifying the strength of the upper cell of the global conveyor belt.

  1. Hydrographic Features of North Indian Ocean

    Directory of Open Access Journals (Sweden)

    T.C. S. Rao

    1965-07-01

    Full Text Available Vertical distribution of temperature, salinity and density in the first 500 meters of the north Indian ocean water has been discussed here. Vertical sections for each parameter are drawn to identity different types of water masses. Spatial distribution of these water masses in relation to the existing surface currents is also described. Two types of water masses are present to the north of the equator. The water from bay of Bengal with its characteristic low salinity (32.60-34.00% is found upto 5 degree N and is spreading in all directions . To the south of 5 degree N the water mass is found with solinity between 35.00-35.20%. This water is existing upto 300 meters with uniform salinity along the equator. The sub-tropical salinity maximum which occurs in a thin layer just above the thermocline is observed to the north and south of equator, similar to the one encountered by defant in the atlantic ocean. The sub-tropical salinity maximum along the equator has been found to be well defined.

  2. Impact of Indian Ocean Dipole on the salinity budget in the equatorial Indian Ocean

    Science.gov (United States)

    DU, Y.; Zhang, Y.

    2013-12-01

    Based on ocean reanalysis data sets and observations, this study analyzes the variability of salinity and its associated ocean dynamics in the equatorial Indian Ocean (IO). The results show that significant interannual variability of salinity in boreal fall are mainly associated with the Indian Ocean dipole (IOD) events, especially the positive IOD (pIOD) events. During pIOD events, forced by anomalous easterly winds, westward current anomalies strengthen the westward advection in summer and weaken the eastward advection of Wyrtki Jets in fall. Analysis of salinity budget indicates that salinity anomalies are mainly dominated by advection, in which zonal component is the key. As the zonal current anomalies are symmetric off the equator, mean zonal salinity gradients dominate the asymmetric distribution of low-salinity advection. Low-salinity water advects to the west, shoals mixed layer, favoring SST increasing after the mature phase of pIOD. After the decay phase, low-salinity water advects across the equator to the southwestern IO, which associates with the off-equatorial anticyclonic circulations in the southern IO. When pIOD events concur with El Niño, the low-salinity water advection strengthens and advects northward and southward simultaneously after the decay phase, due to the strong off-equatorial influence from El Niño.

  3. Upper ocean circulation modulation by phytoplankton concentration in the Equatorial Pacific and the Indian Ocean

    Digital Repository Service at National Institute of Oceanography (India)

    Nakamoto, S.; PrasannaKumar, S.; Oberhuber, J.M.; Sammarco, P.; Muneyama, K.; Sato, T.; AjoyKumar, A.; Frouin, R.

    in the equatorial Pacific, while the spatial asymetricity of wind pattern along with the north-south coastline of the Indian ocean makes upper ocean circulation more complex than that in the Pacific. We propose a feedback mechanisms between phytoplankton...

  4. Tropical Indian Ocean Variability Driving Southeast Australian Droughts

    Science.gov (United States)

    Ummenhofer, C. C.; England, M. H.; McIntosh, P. C.; Meyers, G. A.; Pook, M. J.; Risbey, J. S.; Sen Gupta, A.; Taschetto, A. S.

    2009-04-01

    Variability in the tropical Indian Ocean has widespread effects on rainfall in surrounding countries, including East Africa, India and Indonesia. The leading mode of tropical Indian Ocean variability, the Indian Ocean Dipole (IOD), is a coupled ocean-atmosphere mode characterized by sea surface temperature (SST) anomalies of opposite sign in the east and west of the basin with an associated large-scale atmospheric re-organisation. Earlier work has often focused on the positive phase of the IOD. However, we show here that the negative IOD phase is an important driver of regional rainfall variability and multi-year droughts. For southeastern Australia, we show that it is actually a lack of the negative IOD phase, rather than the positive IOD phase or Pacific variability, that provides the most robust explanation for recent drought conditions. Since 1995, a large region of Australia has been gripped by the most severe drought in living memory, the so-called "Big Dry". The ramifications for affected regions are dire, with acute water shortages for rural and metropolitan areas, record agricultural losses, the drying-out of two of Australia's major river systems and far-reaching ecosystem damage. Yet the drought's origins have remained elusive. For Southeast Australia, we show that the "Big Dry" and other iconic 20th Century droughts, including the Federation Drought (1895-1902) and World War II drought (1937-1945), are driven by tropical Indian Ocean variability, not Pacific Ocean conditions as traditionally assumed. Specifically, a conspicuous absence of characteristic Indian Ocean temperature conditions that are conducive to enhanced tropical moisture transport has deprived southeastern Australia of its normal rainfall quota. In the case of the "Big Dry", its unprecedented intensity is also related to recent above-average temperatures. Implications of recent non-uniform warming trends in the Indian Ocean and how that might affect ocean characteristics and climate in

  5. Structure and tectonic evolution of the northeastern Indian Ocean

    Digital Repository Service at National Institute of Oceanography (India)

    Ramana, M.V; Krishna, K.S.; Ramprasad, T.; Desa, M.; Subrahmanyam, V; Sarma, K.V.L

    Indian Ocean, the inter-relationship between the Broken Ridge-Kerguelen hotspot and the Ninetyeast Ridge. Analysis of geological and geophysical data acquired by the National Institute of Oceanography revealed new interesting results. They include (1...

  6. Empirical relationships between phytoplankton and zooplankton biomass in Indian Ocean

    Digital Repository Service at National Institute of Oceanography (India)

    Jayalakshmy, K.V.

    Empirical models based on regression analysis are derived using published values of phytoplankton and crustacean zooplankton biomass from Indian Ocean. Three regression models are derived. There is significant correlation between zooplankton...

  7. Opportunities for offshore mineral exploration in the Indian Ocean

    Digital Repository Service at National Institute of Oceanography (India)

    Desa, E.

    The Indian Ocean offers several opportunities for offshore mineral resources in the nearshore and coastal areas, the EEZs of different countries as well as the deep sea regions. The coastal and nearshore resources of heavy mineral placers are being...

  8. Bacteriology of ferromanganese nodules from the Indian Ocean

    Digital Repository Service at National Institute of Oceanography (India)

    Chandramohan, D.; LokaBharathi, P.A.; Nair, S.; Matondkar, S.G.P.

    , namely, amylase, gelatinase, lipase, and phosphatase. The dominance of the gram-positive group is attributed to terrigenous influences. The present study clearly indicates that Indian Ocean nodules also harbor a variety of heterotrophic bacteria capable...

  9. Stratification of zooplankton in the northwestern Indian Ocean

    Digital Repository Service at National Institute of Oceanography (India)

    Paulinose, V.T.; Gopalakrishnan, T.C.; Nair, K.K.C.; Aravindakshan, P.N.

    Study on stratification of zooplankton in the north western Indian Ocean was carried out with special reference to its relative abundance and distribution. Samples were collected using multiple plankton net, during first cruise of ORV Sagar Kanya...

  10. Two layers of Australian impact ejecta in the Indian Ocean

    Digital Repository Service at National Institute of Oceanography (India)

    ShyamPrasad, M.; Gupta, S.M.; Kodagali, V.N.

    Only 2 Australian tektites have been found in the Indian Ocean, and both are associated with surficial sediments. Cores from both locations are collected, where the tektites have been reported. The microtektites in these cores (and both the tekties...

  11. Tectonic reorganization in the Indian Ocean: Evidences from seafloor crenulations

    Digital Repository Service at National Institute of Oceanography (India)

    Kessarkar, P.M.

    Multibeam bathymetric data from seafloor area of 24,568 km constrained between magnetic anomaly 18 and anomaly 25 in the Central Indian Ocean Basin (CIOB) reveal presence of three types of seafloor lineaments. Deformation of seafloor across...

  12. Studies on evaporation from the north Indian Ocean

    Digital Repository Service at National Institute of Oceanography (India)

    Rao, Lakshmana G.R.; VeenaDevi, Y.; Reddy, Gopala K.; Prasad, A.L.N.

    Evaporation from the surface of the North Indian Ocean is estimated following the aerodynamic approach The influence of the southwest monsoon and the northeast monsoon is significant giving rise to maximum evaporation from the sea surface due...

  13. Bothid larvae (Pleuronectiformes-Pisces) of the Indian Ocean

    Digital Repository Service at National Institute of Oceanography (India)

    Devi, C.B.L.

    the Indian Ocean, their regional, seasonal as well as diurnal variations. Engyprosopon grandisquamis dominated contributing to 23.2% of the total larvae. Numerically the incidence of bothid larvae suggested a uniform pattern of distribution during the two...

  14. Planktonic foraminifera from core tops of western equatorial Indian Ocean

    Digital Repository Service at National Institute of Oceanography (India)

    Naidu, P.D.; Guptha, M.V.S.

    A set of seven core tops from western equatorial Indian ocean were analysed for planktonic foraminifera, which has yielded 20 planktonic foraminiferal species. Among them Globorotalia menardii, Globigerinoides sacculifer and G. ruber constitute...

  15. Chemical oceanography of the Indian Ocean, North of the equator

    Digital Repository Service at National Institute of Oceanography (India)

    SenGupta, R.; Naqvi, S.W.A.

    Chemical oceanographic studies in the North Indian Ocean have revealed several interesting and unique features. Dissolved oxygen northern boundary, prevents quick renewal of subsurface reducing conditions prevail at intermediate depths (ca. 150...

  16. Alteration of basaltic glasses from the Central Indian Ocean

    Digital Repository Service at National Institute of Oceanography (India)

    Iyer, S.D.

    Textural, mineralogical and compositional characteristics of basaltic glasses from the Central Indian Ocean show them to be altered to varying extents through their interaction with the seawater, resulting in the formation of palagonite. The major...

  17. Organochlorine pesticide residues in the northern Indian Ocean

    Digital Repository Service at National Institute of Oceanography (India)

    Shailaja, M.S.; Sarkar, A.

    periodic monitoring of the levels of the major pollutants. One on-going exercise has been to evaluate, qualitatively and quantitatively, the persistent organochlorine pesticide residues in the Northern Indian Ocean. The baseline levels of some...

  18. Oceanographic data and information network in the Indian Ocean

    Digital Repository Service at National Institute of Oceanography (India)

    Sarupria, J.S.; Reddy, G.V.

    research work is monitored by two IOC committees for the central and western Indian Ocean (IOCINDIO & IOCINCWIO). Enormous amount of oceanographic data / information have been generated by various research, academic, survey, and defense institutes...

  19. Climate of the northern Indian Ocean and associated productivity

    Digital Repository Service at National Institute of Oceanography (India)

    Sastry, J.S.; Gopinathan, C.K.

    The climatic factors likely to influence the phytoplankton production in the northern Indian Ocean are examined. The major cause for the high productivity of the Arabian Sea is the nutrient enrichment of the euphotic zone by upwelling especially off...

  20. Distribution of pelagic harpacticoid copepods from the Indian ocean

    Digital Repository Service at National Institute of Oceanography (India)

    Haridas, P.; Rao, T.S.S.

    Pelagic harpacticoid copepods have been studied from the International Indian Ocean Expedition collections. Macrosetella gracilis and Miracia efferata were the most common species of harpacticoids with high densities near land masses. Other three...

  1. Interannual variability of the tropical Indian Ocean mixed layer depth

    Digital Repository Service at National Institute of Oceanography (India)

    Keerthi, M.G.; Lengaigne, M.; Vialard, J.; Montegut, C.deB.; Muraleedharan, P.M.

    Interannual fluctuations of the mixed layer depth (MLD) in the tropical Indian Ocean are investigated from a long-term (1960-2007) eddy permitting numerical simulation and a new observational dataset built from hydrographic in situ data including...

  2. India's manganese nodule mine site in the Central Indian Ocean

    Digital Repository Service at National Institute of Oceanography (India)

    Banakar, V.K.

    This commentary highlights the activities of massive exploration programme for manganese nodule deposits in the Central Indian Basin located 5 km below the ocean surface and India's claim for mine site development and registration with UNCLOS...

  3. Mass, heat and freshwater fluxes in the South Indian Ocean

    Science.gov (United States)

    Fu, Lee-Lueng

    1986-01-01

    Six hydrographic sections were used to examine the circulation and property fluxes in the South Indian Ocean from 10 to 32 deg S. The calculations were made by applying an inverse method to the data. In the interior of the South Indian Ocean, the geostrophic flow is generally northward. At 18 deg S, the northward interior mass flux is balanced by the southward Ekman mass flux at the surface, whereas at 32 deg S the northward interior mass flux is balanced by the southward mass flux of the Agulhas Current. There is a weak, southward mass flux of 6 x 10 to the 9th kg/s in the Mozambique Channel. The rate of water exchange between the Pacific Ocean and the Indian Ocean is dependent on the choice of the initial reference level used in the inverse calculation. The choice of 1500 m, the depth of the deep oxygen minimum, has led to a flux of water from the Pacific Ocean to the Indian Ocean at a rate of 6.6 x 10 to the 9th kg/s. Heat flux calculations indicate that the Indian Ocean is exporting heat to the rest of the world's oceans at a rate of -0.69 x 10 to the 15th W at 18 deg S and -0.25 x 10 to the 15th W at 32 deg S (negative values being southward).

  4. The potential hydrothermal systems unexplored in the Southwest Indian Ocean

    Science.gov (United States)

    Suo, Yanhui; Li, Sanzhong; Li, Xiyao; Zhang, Zhen; Ding, Dong

    2017-01-01

    Deep-sea hydrothermal vents possess complex ecosystems and abundant metallic mineral deposits valuable to human being. On-axial vents along tectonic plate boundaries have achieved prominent results and obtained huge resources, while nearly 90% of the global mid-ocean ridge and the majority of the off-axial vents buried by thick oceanic sediments within plates remain as relatively undiscovered domains. Based on previous detailed investigations, hydrothermal vents have been mapped along five sections along the Southwest Indian Ridge (SWIR) with different bathymetry, spreading rates, and gravity features, two at the western end (10°-16°E Section B and 16°-25°E Section C) and three at the eastern end (49°-52°E Section D, 52°-61°E Section E and 61°-70°E Section F). Hydrothermal vents along the Sections B, C, E and F with thin oceanic crust are hosted by ultramafic rocks under tectonic-controlled magmatic-starved settings, and hydrothermal vents along the Section D are associated with exceed magmatism. Limited coverage of investigations is provided along the 35°-47°E SWIR (between Marion and Indomed fracture zones) and a lot of research has been done around the Bouvet Island, while no hydrothermal vents has been reported. Analyzing bathymetry, gravity and geochemical data, magmatism settings are favourable for the occurrence of hydrothermal systems along these two sections. An off-axial hydrothermal system in the southern flank of the SWIR that exhibits ultra-thin oceanic crust associated with an oceanic continental transition is postulated to exist along the 100-Ma slow-spreading isochron in the Enderby Basin. A discrete, denser enriched or less depleted mantle beneath the Antarctic Plate is an alternative explanation for the large scale thin oceanic crust concentrated on the southern flank of the SWIR.

  5. Introduced mammals on Western Indian Ocean islands

    Directory of Open Access Journals (Sweden)

    James C. Russell

    2016-04-01

    Full Text Available The diversity of introduced mammals and their introduction history varies greatly across the Western Indian Ocean (WIO islands, from ancient introductions in the past millennia on islands off the East coast of Africa where extant terrestrial native mammal communities exist, to very recent invasions in the past decades on islands in the Mascarene archipelago. We compile the distribution of 16 introduced mammal taxa on 28 island groups comprising almost 2000 islands. Through an exhaustive literature review and expert consultation process we recorded all mammal eradications, and species recoveries which could be attributed to introduced mammal eradication or control. All island groups have been invaded by mammals, and invasive cats and rats in particular are ubiquitous, but cultural contingency has also led to regional invasions by other mammals such as lemurs, civets and tenrecs. Mammal eradications have been attempted on 45 islands in the WIO, the majority in the Seychelles and Mauritius, and where successful have resulted in spectacular recovery of species and ecosystems. Invasive mammalian predator eradication or control in association with habitat management has led to improved conservation prospects for at least 24 species, and IUCN red-list down-listing of eight species, in the Mascarene Islands. Future island conservation prioritisation in the region will need to take account of global climate change and predicted sea-level rises and coastal inundation. Greater investment and prioritisation in island conservation in the region is warranted, given its high biodiversity values and the extent of invasions.

  6. Heavy metal contamination in the Western Indian Ocean (a review)

    Science.gov (United States)

    Mamboya, F. A.; Pratap, H. B.; Björk, M.

    2003-05-01

    Western Indian Ocean Coast has many potential marine ecosystems such as mangrove, seagrass meadows, macroalgae, and coral reefs. It is largely unspoiled environment however, tourism and population growth in coastal urban centres, industrialization, are presenting a risk of pollutants input to the marine environment of the Western Indian Ocean. Mining, shipping and agricultural activities also input contaminants into the marine environment via runoff, vessel operations and accidental spillage. Heavy metals are among the pollutants that are expected to increase in the marine environment of the Western Indian Ocean. The increase in heavy metal pollution can pose a serious health problem to marine organism and human through food chain. This paper reviews studies on heavy metal contamination in the Western Indian Ocean. It covers heavy metal studies in the sediments, biota, particulates and seawater collected in different sites. In comparison to other regions, only few studies have been conducted in the Western Indian Ocean and are localized in some certain areas. Most of these studies were conducted in Kenyan and Tanzanian coasts while few of them were conducted in Mauritius, Somalia and Reunion. No standard or common method has been reported for the analysis or monitoring of heavy metals in the Western Indian Ocean.

  7. The Pliocene Indian Ocean: A Unique Planktonic Foraminifer Distribution

    Science.gov (United States)

    Robinson, M. M.; Dowsett, H. J.; Stoll, D. K.

    2013-12-01

    The Indian Ocean is complex in its ocean-atmosphere interactions, most notably the Indian Monsoon, and in its circulation regime that is dictated by the surrounding continental configuration. Its relative isolation from other ocean basins and its dynamic tropical processes, ruled by variations in interannual variability, create an environment of rapid response to local climate forcings. The Indian Ocean should, therefore, be among the first regions to record geologic indicators of local responses to global climate change. Despite the wealth of global paleoclimate data available for the mid-Piacenzian, ~3.3 to 3.0 Ma, the Indian Ocean has remained a region of sparse geographic coverage in terms of microfossil analysis. This climatically relevant warm period is of particular importance due to the similarity of mid-Piacenzian climate to what is projected for the near future. In the Indian Ocean, the 3.3 to 3.0 Ma interval sits at the intersection of major regional tectonically-induced oceanic and atmospheric circulation changes and global climate reorganizations including uplift of the Tibetan Plateau, expansion of the Antarctic ice sheet, closure of the Indonesian Seaway, intensification of Northern Hemisphere glaciation, and the development of the modern east-west SST gradient in the equatorial Pacific. This was a period of intense summer monsoon activity in the Indian Ocean, leading to a reorganization of the Indian monsoon ~2.8 Ma. In an effort to characterize the surface Indian Ocean during this complex climate interval, we examined the planktonic foraminifera from ODP Sites 709, 716, 722, 747, 751, 754, 757, 758 and 763, encompassing a wide range of oceanographic conditions. Quantitative analysis of Pliocene faunas highlight the unique nature of some Indian Ocean assemblages, particularly in the Bay of Bengal where a high percentage of Sphaeroidenellopsis and Sphaeroidinella points to a thermally homogenous water column capped by a persistent shallow halocline

  8. The Second International Indian Ocean Expedition (IIOE-2)

    Science.gov (United States)

    Cowie, Greg; Hood, Raleigh

    2015-04-01

    The International Indian Ocean Expedition (IIOE) was one of the greatest international, interdisciplinary oceanographic research efforts of all time. Planning for the IIOE began in 1959 and the project officially continued through 1965, with forty-six research vessels participating under fourteen different flags. The IIOE motivated an unprecedented number of hydrographic surveys (and repeat surveys) over the course of the expedition covering the entire Indian Ocean basin. And it was an interdisciplinary endeavor that embraced physical oceanography, chemical oceanography, meteorology, marine biology, marine geology and geophysics. The end of 2015 will mark the 50th Anniversary of the completion of the IIOE. SCOR and the IOC are working to stimulate a new phase of coordinated international research focused on the Indian Ocean for a 5-year period beginning in late 2015 and continuing through 2020. The goal is to help to organize ongoing research and stimulate new initiatives in the 2015-2020 time frame as part of a larger expedition. Several International programs that have research ongoing or planned in the Indian Ocean during this time period and many countries are planning cruises in this time frame as well. These programs and national cruises will serve as a core for the new Indian Ocean research focus, which has been dubbed "IIOE-2." The overarching goal of the IIOE-2 is to advance our understanding of interactions between geological, oceanic and atmospheric processes that give rise to the complex physical dynamics of the Indian Ocean region, and to determine how those dynamics affect climate, extreme events, marine biogeochemical cycles, ecosystems and human populations. This understanding is required to predict the impacts of climate change, pollution, and increased fish harvesting on the Indian Ocean and its nations, as well as the influence of the Indian Ocean on other components of the Earth System. New understanding is also fundamental to policy makers for

  9. Synthesis of morphotectonics and volcanics of the Central Indian Ocean Basin

    Digital Repository Service at National Institute of Oceanography (India)

    Mukherjee, A.D.; Iyer, S.D.

    The Central Indian Ocean Basin (CIOB) is an enigmatic ocean basin in the young and tectonically complex Indian Ocean. Major tectonic and volcanic forms identified are fracture zones, abyssal hills, seamounts and ridges and a unique zone...

  10. How does the Indian Ocean subtropical dipole trigger the tropical Indian Ocean dipole via the Mascarene high?

    Institute of Scientific and Technical Information of China (English)

    FENG Junqiao; HU Dunxin; YU Lejiang

    2014-01-01

    The variation in the Indian Ocean is investigated using Hadley center sea surface temperature (SST) data during the period 1958-2010. All the first empirical orthogonal function (EOF) modes of the SST anomalies (SSTA) in different domains represent the basin-wide warming and are closely related to the Pacific El Niño-Southern Oscillation (ENSO) phenomenon. Further examination suggests that the impact of ENSO on the tropical Indian Ocean is stronger than that on the southern Indian Ocean. The second EOF modes in dif-ferent domains show different features. It shows a clear east-west SSTA dipole pattern in the tropical Indian Ocean (Indian Ocean dipole, IOD), and a southwest-northeast SSTA dipole in the southern Indian Ocean (Indian Ocean subtropical dipole, IOSD). It is further revealed that the IOSD is also the main structure of the second EOF mode on the whole basin-scale, in which the IOD pattern does not appear. A correlation anal-ysis indicates that an IOSD event observed during the austral summer is highly correlated to the IOD event peaking about 9 months later. One of the possible physical mechanisms underlying this highly significant statistical relationship is proposed. The IOSD and the IOD can occur in sequence with the help of the Mas-carene high. The SSTA in the southwestern Indian Ocean persists for several seasons after the mature phase of the IOSD event, likely due to the positive wind-evaporation-SST feedback mechanism. The Mascarene high will be weakened or intensified by this SSTA, which can affect the atmosphere in the tropical region by teleconnection. The pressure gradient between the Mascarene high and the monsoon trough in the tropical Indian Ocean increases (decreases). Hence, an anticyclone (cyclone) circulation appears over the Arabian Sea-India continent. The easterly or westerly anomalies appear in the equatorial Indian Ocean, inducing the onset stage of the IOD. This study shows that the SSTA associated with the IOSD can lead to the

  11. Environmental controls on the seasonal carbon dioxide fluxes in the northeastern Indian Ocean

    Digital Repository Service at National Institute of Oceanography (India)

    Sardessai, S.; Maya, M.V.; Shetye, S.; PrasannaKumar, S.; Fernandes, V.; Paul, J.; Ramaiah, N.

    Total carbon dioxide (TCO sub(2)) and computations of partial pressure of carbon dioxide (pCO sub(2)) had been examined in Northerneastern region of Indian Ocean. It exhibit seasonal and spatial variability. North-south gradients in the pCO sub(2...

  12. Two modes of dipole events in tropical Indian Ocean

    Institute of Scientific and Technical Information of China (English)

    ZHAO YongPing; CHEN YongLi; WANG Fan; BAI XueZhi; WU AiMing

    2009-01-01

    By analyzing the distributions of subsurface temperature and the surface wind stress anomalies in the tropical Pacific and Indian Oceans during the Indian Ocean Dipole (IOD) events,two major modes of the IOD and their formation mechanisms are revealed.(1) The subsurface temperature anomaly (STA) in the tropical Indian Ocean during the IOD events can be described as a "<" -shaped and west-east-oriented dipole pattern;in the east side of the "<" pattern,a notable tongue-like STA extends westward along the equator in the tropical eastern Indian Ocean;while in the west side of the "<" pattern,the STA has opposite sign with two centers (the southern one is stronger than the northern one in intensity) being of rough symmetry about the equator in the tropical mid-western Indian Ocean.(2) The IOD events are composed of two modes,which have similar spatial pattern but different temporal variabilities due to the large scale air-sea interactions within two independent systems.The first mode of the IOD event originates from the air-sea interaction on a scale of the tropical Pacific-Indian Ocean and coexists with ENSO.The second mode originates from the air-sea interaction on a scale of the tropical Indian Ocean and is closely associated with changes in the position and intensity of the Mascarene high pressure.The strong IOD event occurs when the two modes are in phase,and the IOD event weakens or disappears when the two modes are out of phase.Besides,the IOD events are normally strong when either of the two modes is strong.(3) The IOD event is caused by the abnormal wind stress forcing over the tropical Indian Ocean,which results in vertical transports,leading to the upwelling and pileup of seawater.This is the main dynamic processes resulting in the STA.When the anomalous easterly exists over the equatorial Indian Ocean,the cold waters upwell in the tropical eastern Indian Ocean while the warm waters pileup in the tropical western Indian Ocean,hence the thermocline in

  13. Two modes of dipole events in tropical Indian Ocean

    Institute of Scientific and Technical Information of China (English)

    2009-01-01

    By analyzing the distributions of subsurface temperature and the surface wind stress anomalies in the tropical Pacific and Indian Oceans during the Indian Ocean Dipole (IOD) events, two major modes of the IOD and their formation mechanisms are revealed. (1) The subsurface temperature anomaly (STA) in the tropical Indian Ocean during the IOD events can be described as a "<" -shaped and west-east-oriented dipole pattern; in the east side of the "<" pattern, a notable tongue-like STA extends westward along the equator in the tropical eastern Indian Ocean; while in the west side of the "<" pattern, the STA has op- posite sign with two centers (the southern one is stronger than the northern one in intensity) being of rough symmetry about the equator in the tropical mid-western Indian Ocean. (2) The IOD events are composed of two modes, which have similar spatial pattern but different temporal variabilities due to the large scale air-sea interactions within two independent systems. The first mode of the IOD event originates from the air-sea interaction on a scale of the tropical Pacific-Indian Ocean and coexists with ENSO. The second mode originates from the air-sea interaction on a scale of the tropical Indian Ocean and is closely associated with changes in the position and intensity of the Mascarene high pressure. The strong IOD event occurs when the two modes are in phase, and the IOD event weakens or disap- pears when the two modes are out of phase. Besides, the IOD events are normally strong when either of the two modes is strong. (3) The IOD event is caused by the abnormal wind stress forcing over the tropical Indian Ocean, which results in vertical transports, leading to the upwelling and pileup of sea- water. This is the main dynamic processes resulting in the STA. When the anomalous easterly exists over the equatorial Indian Ocean, the cold waters upwell in the tropical eastern Indian Ocean while the warm waters pileup in the tropical western Indian Ocean, hence

  14. Biodiversity of chaetognaths of the Andaman Sea, Indian Ocean.

    Digital Repository Service at National Institute of Oceanography (India)

    Nair, V.R.; Gireesh, R.

    Andaman Sea is a prominent biodiversity hotspot in the Indian Ocean. Stratified zooplankton collections were taken at 33 locations during 2003-2006. Average density of chaetognaths was 8.5/msup(3) in open ocean and 41.6/m sup(3) in coastal waters...

  15. On some aspects of Indian Ocean warm pool

    Digital Repository Service at National Institute of Oceanography (India)

    Saji, P.K.; Balchand, A.N; RameshKumar, M.R.

    Annual and interannual variation of Indian Ocean Warm Pool (IOWP) was studied using satellite and in situ ocean temperature data IOWP surface area undergoes a strong annual cycle attaining a maximum of 24x106km2 during April...

  16. Intraseasonal meridional current variability in the eastern equatorial Indian Ocean

    Digital Repository Service at National Institute of Oceanography (India)

    Ogata, T.; Sasaki, H.; Murty, V.S.N.; Sarma, M.S.S.; Masumoto, Y.

    for the atmospheric disturbances at this time-scale over the eastern Indian Ocean, which can be considered as the forcing to the oceanic ISV, such as those indicated by Chatterji and Goswami [2004], Shinoda and Han [2005], and Fukutomi and Yasunari [2005]. An air...–2482. Fukutomi, Y., and T. Yasunari (2005), Southerly surges on the submonthly timescales over the eastern Indian Ocean during the Southern Hemisphere winter, Mon. Weather Rev., 133(6), 1637–1654. Han, W., D. Yuan, W. T. Liu, and D. J. Halkides (2007...

  17. Conservation and Management of Tuna Fisheries in the Indian Ocean and Indian EEZ

    Directory of Open Access Journals (Sweden)

    P. Satheeshkumar

    2013-05-01

    Full Text Available The focus of the study is to explore the recent trend and stock status of Indian Ocean and Indian EEZ, and its conservation and sustainable management of tuna fishereis. In the Indian Ocean, tuna catches increased rapidly from about 179 959 t in 1980 to about 832 246 t in 1995. They have continued to increase up to 2005; the catch was 1 318 648 t, forming about 26% of the world catch. However, since 2006 onwards there was a decline in tuna catch and in 2010 the catch was only 1 257 908 t. Tuna production in India which was continued to increase with fluctuations from 63 633 t during 2001-2005, average 78 400 t during 2006-2010, and in 2010 the catch was only 65 863 t. Tuna is an important but not a well managed fishery in the Indian Ocean and Indian EEZ. The Indian Ocean stock is currently overfished and has no proper management regulations aimed at with sustaining the stock. In the present study, sustainable management system is evaluated with information on tuna landings, stock status and major issues on tuna fishery. To address these major issues, appropriate tuna fishing policies are proposed to help sustainable development and management of tuna fishery resource in the Indian Ocean.

  18. Typical Surface Seasonal Circulation in the Indian Ocean Derived from Argos Floats

    Institute of Scientific and Technical Information of China (English)

    ZHENG Shao-Jun; ZHANG Yu-Hong; ZHUANG Wei; LI Jia-Xun; DU Yan

    2012-01-01

    This study investigates the surface circulation in the Indian Ocean using Argos float data over the period 1979--2011. The Argos observations manifest some new phenomena. The climatological annual mean circulation shows that the surface current becomes much stronger after turning around in shore in the western Indian Ocean. In the tropical Indian Ocean, the Great Whirl (GW) to the east of Somalia develops quickly in spring (April-May) as the monsoon reverses to move northward, becoming strongest in summer (June-September) and disappearing in autumn (October-November). The west end of the Agulhas retroflection can reach 18°E, and it exhibits a seasonal variation. At approximately 90°E, the Agulhas Return Current combines with the eastward South Atlantic Current and finally joins the Antarctic Circumpolar Current.

  19. Metagenomic exploration of viruses throughout the Indian Ocean.

    Directory of Open Access Journals (Sweden)

    Shannon J Williamson

    Full Text Available The characterization of global marine microbial taxonomic and functional diversity is a primary goal of the Global Ocean Sampling Expedition. As part of this study, 19 water samples were collected aboard the Sorcerer II sailing vessel from the southern Indian Ocean in an effort to more thoroughly understand the lifestyle strategies of the microbial inhabitants of this ultra-oligotrophic region. No investigations of whole virioplankton assemblages have been conducted on waters collected from the Indian Ocean or across multiple size fractions thus far. Therefore, the goals of this study were to examine the effect of size fractionation on viral consortia structure and function and understand the diversity and functional potential of the Indian Ocean virome. Five samples were selected for comprehensive metagenomic exploration; and sequencing was performed on the microbes captured on 3.0-, 0.8- and 0.1 µm membrane filters as well as the viral fraction (<0.1 µm. Phylogenetic approaches were also used to identify predicted proteins of viral origin in the larger fractions of data from all Indian Ocean samples, which were included in subsequent metagenomic analyses. Taxonomic profiling of viral sequences suggested that size fractionation of marine microbial communities enriches for specific groups of viruses within the different size classes and functional characterization further substantiated this observation. Functional analyses also revealed a relative enrichment for metabolic proteins of viral origin that potentially reflect the physiological condition of host cells in the Indian Ocean including those involved in nitrogen metabolism and oxidative phosphorylation. A novel classification method, MGTAXA, was used to assess virus-host relationships in the Indian Ocean by predicting the taxonomy of putative host genera, with Prochlorococcus, Acanthochlois and members of the SAR86 cluster comprising the most abundant predictions. This is the first study

  20. Sea surface salinity variability during the Indian Ocean Dipole and ENSO events in the tropical Indian Ocean

    Digital Repository Service at National Institute of Oceanography (India)

    Grunseich, G.; Subrahmanyam, B.; Murty, V.S.N.; Giese, B.S.

    . The numerous impacts of salinity on the dipole mode make it an important factor in understanding both the atmospheric and oceanic components of both phases of the IOD. This has motivated us to examine the long-term SODA reanalysis SSS data for the 138 years... SSS variability in the Indian Ocean in response to climate variability. 2. Data Analysis 2.1 Simple Ocean Data Assimilation For this study we use a new ocean reanalysis called SODA (Simple Ocean Data Assimilation) 2.2.4 that spans the period...

  1. Seagrass ecosystems in the Western Indian Ocean.

    Science.gov (United States)

    Gullström, Martin; de la Torre Castro, Maricela; Bandeira, Salomão; Björk, Mats; Dahlberg, Mattis; Kautsky, Nils; Rönnbäck, Patrik; Ohman, Marcus C

    2002-12-01

    Seagrasses are marine angiosperms widely distributed in both tropical and temperate coastal waters creating one of the most productive aquatic ecosystems on earth. In the Western Indian Ocean (WIO) region, with its 13 reported seagrass species, these ecosystems cover wide areas of near-shore soft bottoms through the 12 000 km coastline. Seagrass beds are found intertidally as well as subtidally, sometimes down to about 40 m, and do often occur in close connection to coral reefs and mangroves. Due to the high primary production and a complex habitat structure, seagrass beds support a variety of benthic, demersal and pelagic organisms. Many fish and shellfish species, including those of commercial interest, are attracted to seagrass habitats for foraging and shelter, especially during their juvenile life stages. Examples of abundant and widespread fish species associated to seagrass beds in the WIO belong to the families Apogonidae, Blenniidae, Centriscidae, Gerreidae, Gobiidae, Labridae, Lethrinidae Lutjanidae, Monacanthidae, Scaridae, Scorpaenidae, Siganidae, Syngnathidae and Teraponidae. Consequently, seagrass ecosystems in the WIO are valuable resources for fisheries at both local and regional scales. Still, seagrass research in the WIO is scarce compared to other regions and it is mainly focusing on botanic diversity and ecology. This article reviews the research status of seagrass beds in the WIO with particular emphasis on fish and fisheries. Most research on this topic has been conducted along the East African coast, i.e. in Kenya, Tanzania, Mozambique and eastern South Africa, while less research was carried out in Somalia and the Island States of the WIO (Seychelles, Comoros, Reunion (France), Mauritius and Madagascar). Published papers on seagrass fish ecology in the region are few and mainly descriptive. Hence, there is a need of more scientific knowledge in the form of describing patterns and processes through both field and experimental work

  2. Metallogenesis along the Indian Ocean Ridge System

    Digital Repository Service at National Institute of Oceanography (India)

    Banerjee, R.; Ray, Dwijesh

    active hydrothermal black smoker deposit along this ridge system (Figure 1). The obser - vations summarized here comprise the res ults obtained from the Central Indian Ridge (CIR), Southwest Indian Ridge (SWIR), Southeast Indian Ridge (SEIR), Carlsberg... and appears to be in a tectonic stage of rift development. A hydrothermal plume with maximum concentration of 202 nl/l methane (CH 4 ) and a tempera ture anomaly of + 0.05?C was delineated at 24?03 minuteS (hydro - ther mal plume site). Manganese...

  3. Deglacial intermediate water reorganization: new evidence from the Indian Ocean

    Directory of Open Access Journals (Sweden)

    S. Romahn

    2013-07-01

    Full Text Available The importance of intermediate water masses in climate change and ocean circulation has been emphasized recently. In particular, Antarctic Intermediate Water (AAIW is thought to have acted as an active interhemispheric transmitter of climate anomalies. Here we reconstruct changes in AAIW signature and spatial and temporal evolution based on a 40 kyr time series of oxygen and carbon isotopes as well as planktic Mg/Ca based thermometry from a site in the western Indian Ocean. Our data suggest that AAIW transmitted Antarctic temperature trends to the equatorial Indian Ocean via the "oceanic tunnel" mechanism. Moreover, our results reveal that deglacial AAIW carried a signature of aged Southern Ocean deep water. We find no evidence of increased formation of intermediate waters during the deglaciation.

  4. Indian Ocean Networks and the Transmutations of Servitude

    DEFF Research Database (Denmark)

    Kaarsholm, Preben

    2016-01-01

    Focusing on Durban and its harbour, the article discusses the importation of different kinds of transnational bonded labour into Natal in the last half of the 19th century, and examines the ways in which Southern African and Indian Ocean histories were intertwined in the processes that built...... into Natal of freed slaves from the Indian Ocean coast, of indentured labourers from India, and of ‘Amatonga’ migrant workers from Mozambique. An 1877 murder case is discussed, which led to the forced resignation of a Protector, as it threatened to undermine the respectability of the institution. The article...

  5. Two bathyal hydroids (Hydrozoa: Leptothecata) from the Southwest Indian Ocean.

    Science.gov (United States)

    Watson, Jeanette E

    2017-03-27

    Two species of hydroids were recovered from a mooring rope and experimentally deployed whale bone attached to an underwater transponder buoy at a depth of 732 m on the Coral Seamount on the Southwest Indian Ocean Ridge (41° 22.31'S, 54° 57'E) in the Southern Indian Ocean. The material was collected approximately 1,500 km south south-east of Madagascar during Voyage JC066 of the British Royal Research Ship R.R.S. James Cook on 20/11/2011. Hydroids were collected from the mooring rope and whale bone on board the ship after underwater retrieval by ROV.

  6. Yanai waves in the western equatorial Indian Ocean

    Digital Repository Service at National Institute of Oceanography (India)

    Chatterjee, A.; Shankar, D; McCreary, J.P.; Vinayachandran, P.N.

    of Oceanography, and International Pacific Research Center, University of Hawaii at Manoa, Honolulu, Hawaii, U.S.A. 3Centre for Atmospheric and Oceanic Sciences, Indian Institute of Science, Bangalore. D R A F T February 4, 2013, 2:04am D R A F T Author version: J... are similar; differences are23 D R A F T February 4, 2013, 2:04am D R A F T ABHISEK CHATTERJEE ET AL.: YANAI WAVES IN THE WESTERN INDIAN OCEAN X - 3 traceable to the property that HFYWs have longer wavelengths than LFYWs24 for each baroclinic mode.25 D R A F...

  7. Source regions of stratospheric VSLS in the Indian Ocean

    Science.gov (United States)

    Quack, Birgit; Hepach, Helmke; Atlas, Elliot; Bracher, Astrid; Endres, Sonja; Arevalo-Martinez, Damian; Bange, Hermann; Lennartz, Sinikka; Steinhoff, Tobias; Booge, Dennis; Zarvasky, Alexander; Marandino, Christa; Patey, Matt; Achterberg, Eric; Dengler, Markus; Fiehn, Alina; Tegtmeier, Susann; Krüger, Kirstin

    2016-04-01

    Halogenated very-short-lived substances (VSLS), which are naturally produced in the ocean, play a significant role in present day ozone depletion, in particular in combination with enhanced stratospheric sulfate aerosol, which is also partly derived from oceanic VSLS. The decline of anthropogenic chlorine in the stratosphere within the 21st century will increase the relative importance of the natural emissions on stratospheric ozone destruction. Especially, oceanic sources and source regions of the compounds need to be better constrained, in order to improve the future prediction. During boreal summer the Asian monsoon circulation transports air masses from the Indian Ocean to the stratosphere, while the contribution of VSLS from this ocean to stratospheric halogen and sulfur is unknown. During the research cruises SO 234/2 and SO 235 in July-August 2014 onboard RV SONNE oceanic and atmospheric halogenated VSLS such as bromoform (CHBr3), dibromomethane (CH2Br2) and methyl iodide (CH3I) were measured in the subtropical and tropical West Indian Ocean for the first time. Here we present the oceanic sources of the halogenated compounds and their relation to other biogeochemical parameters (short- and longlived trace gases, phytoplankton and nutrients) along the cruise track, which covered coastal, upwelling and open ocean regimes and the Seychelles-Chagos thermocline ridge as important source region for stratospheric bromine.

  8. Woven Webs: Trading Textiles around the Indian Ocean

    Directory of Open Access Journals (Sweden)

    Lola Sharon Davidson

    2012-06-01

    Full Text Available Throughout its long history, the changing networks of the Indian Ocean textile trade have served as circuits of material communication, transmitting cultural values embodied in cloth, defining and redefining identities and relationships. This paper explores some of the cultural ramifications of this venerable trade. From ancient times, India was a major exporter of textiles, sitting at the centre of a complex regional network of exchanges which inserted Indian cottons and silks as prestige items into the textile regimes of societies all around the Indian Ocean. The balance between indigenous production marking local identity and Indian imports marking elite status and trans-local identity was disrupted by the spread of the competing globalisations of Islam and Christianity. Colonialism expanded networks and forged new connections, redirecting a significant portion of production through metropolitan centres towards a global market and facilitating a dynamic process of cultural exchange. By the late 20th century India was no longer the dominant player in a regional system, but one of several players in a global system. Nevertheless, within this new system particular networks continue to connect the disparate communities of the Indian Ocean and to play a complex role in negotiating identification with and resistance to competing globalisations.

  9. Validation of argo data in the Indian Ocean

    Digital Repository Service at National Institute of Oceanography (India)

    Pankajakshan, T.; Muraleedharan, P.M.; Gopalakrishna, V.V.; Reddy, G.V.; Ratnakaran, L.; Revichandran, C.; Murty, V.S.N.

    -6538 versión on-line Gayana (Concepc.) v.68 n.2 supl.TIIProc Concepción 2004 Como citar este artículo Gayana 68(2): 456-458, 2004 VALIDATION OF ARGO DATA IN THE INDIAN OCEAN Pankajakshan Thadathil, P.M. Muraleedharan, V...

  10. Buried nodules from the central Indian Ocean basin

    Digital Repository Service at National Institute of Oceanography (India)

    Pattan, J.N.; Parthiban, G.

    Indian Ocean. Mar. Geol.92, p. 115- 125. Usui, A. and Ito, T. (1994). Fossil manganese deposits buried within DSDP /ODP cores, Legs 1-126. Mar. geol. 119, p. 111-136. Von Stackelberg, U. (1984). Significance of bentic organisms for the growth...

  11. Sea surface salinity variability in the tropical Indian Ocean

    Digital Repository Service at National Institute of Oceanography (India)

    Subrahmanyam, B.; Murty, V.S.N.; Heffner, D.M.

    to February 2007. The observational period covered one strong negative Indian Ocean Dipole Zonal Mode (IODZM) event in 2005 and a strong positive IODZM event in 2006. The Argo profiles in each box captured the impact of these IODZM events with a larger impact...

  12. Morphometric studies on a part of Central Indian Ocean

    Digital Repository Service at National Institute of Oceanography (India)

    Kodagali, V.N.

    Morphometric and slope angle studies carried out on a part of Indian Ocean Basin have shown that gentle slope angle ranges dominate, 92% of the area represented by 0-3 degrees slopes. Young's hypothesis of log-normal distribution of slope angle...

  13. Mineral resources of the Indian Ocean and related scientific research

    Digital Repository Service at National Institute of Oceanography (India)

    Siddiquie, H.N.; Gujar, A.R.; Hashimi, N.H.; Valsangkar, A.B.; Nath, B.N.

    substantially to some of the essential mineral raw materials for the world economy; i.e. oil, tin iron and manganese ores, mica and chromite. The present paper reviews the surficial mineral resources of the Indian Ocean, excluding those in bedrock (oil, gas...

  14. Cultural Voice from an Island Country on the Indian Ocean

    Institute of Scientific and Technical Information of China (English)

    2004-01-01

    <正>Located on the southwestern Indian Ocean, the Republic of Seychelles with a beautiful scenery attracts a large number of tourists every year, 60 percent of its national revenues coming from tourism. Besides beautiful natural scenery, its perfect tourist facilities, multiple-ethnic cultures and rich and colourful sea sports are the main attractions for tourists.

  15. On the vergence field in the north Indian Ocean

    Digital Repository Service at National Institute of Oceanography (India)

    Varadachari, V.V.R.; Sharma, G.S.

    The paper presents some of the results of investigation on the divergence and convergence of the surface waters in the North Indian Ocean, for different months of the year. The divergence is computed by a graphical method from the data on surface...

  16. Indian Ocean circulation and productivity during the last glacial cycle

    Digital Repository Service at National Institute of Oceanography (India)

    Piotrowski, A.M.; Banakar, V.K.; Scrivner, A.E.; Elderfield, H.; Galy, A.; Dennis, A.

    to the Atlantic. It is also an ideal location to reconstruct the link between thermohaline circulation and deep-water nutrient contents. No mixing occurs between major deep-water masses along flow paths within the Indian Ocean, so changes in water-mass provenance...

  17. Distribution of Bowen ratio over the north Indian Ocean

    Digital Repository Service at National Institute of Oceanography (India)

    Rao, G.R.L.; Rao, M.V.; Prasad, P.H.; Reddy, K.G.

    The monthly averages of Bowen ratio over the north Indian Ocean have been computed Three typical situations in the months of January May and September are taken for the present study Month to month differences in the Bowen ratio over the study...

  18. Redefining Maritime Security Threats in the Eastern Indian Ocean Region.

    Energy Technology Data Exchange (ETDEWEB)

    Banerjee, Arjun [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)

    2017-08-01

    This occasional paper analyzes the general security issues and trends relating to maritime trafficking of radiological and nuclear material using small vessels, minor ports, and unchecked areas of coastline existing in the Eastern Indian Ocean Region today. By the Eastern Indian Ocean Region is meant the area starting from the tip of the Indian peninsula in the west to the Straits of Malacca in the east. It lays focus on the potential sources of nuclear or radiological material that may be trafficked here. It further undertakes a study of the terrorist groups active in the region as well as the multinational or national interdiction organizations that have been created to counter maritime threats. It also seeks to discern the various technologies for detecting materials of concern available in the area. Finally, it ascertains possible methods and technologies to improve the maritime security system in the region.

  19. Sea surface height anomaly and upper ocean temperature over the Indian Ocean during contrasting monsoons

    Science.gov (United States)

    Gera, Anitha; Mitra, A. K.; Mahapatra, D. K.; Momin, I. M.; Rajagopal, E. N.; Basu, Swati

    2016-09-01

    Recent research emphasizes the importance of the oceanic feedback to monsoon rainfall over the Asian landmass. In this study, we investigate the differences in the sea surface height anomaly (SSHA) and upper ocean temperature over the tropical Indian Ocean during multiple strong and weak monsoons. Analysis of satellite derived SSHA, sea surface temperature (SST) and ocean reanalysis data reveals that patterns of SSHA, SST, ocean temperature, upper ocean heat content (UOHC) and propagations of Kelvin and Rossby waves differ during strong and weak monsoon years. During strong monsoons positive SSH, SST and UOHC anomalies develop over large parts of north Indian Ocean whereas during weak monsoons much of the north Indian Ocean is covered with negative anomalies. These patterns can be used as a standard tool for evaluating the performance of coupled and ocean models in simulating & forecasting strong and weak monsoons. The rainfall over central India is found to be significantly correlated with SSHA over the regions (Arabian Sea and West central Indian Ocean and Bay of Bengal) where SSHA is positively large during strong monsoons. The SST-SSHA correlation is also very strong over the same area. The study reveals that much convection takes place over these regions during strong monsoons. In contrast during weak monsoons, convection takes place over eastern equatorial region. These changes in SST are largely influenced by oceanic Kelvin and Rossby waves. The Rossby waves initiated in spring at the eastern boundary propagate sub-surface heat content in the ocean influencing SST in summer. The SST anomalies modulate the Hadley circulation and the moisture transport thereby contributing to rainfall over central India. Therefore oceanic Kelvin and Rossby waves influence the rainfall over central India.

  20. Evaluation of radiative fluxes over the north Indian Ocean

    Science.gov (United States)

    Ramesh Kumar, M. R.; Pinker, Rachel T.; Mathew, Simi; Venkatesan, R.; Chen, W.

    2017-05-01

    Radiative fluxes are a key component of the surface heat budget of the oceans. Yet, observations over oceanic region are sparse due to the complexity of radiation measurements; moreover, certain oceanic regions are substantially under-sampled, such as the north Indian Ocean. The National Institute of Ocean Technology, Chennai, India, under its Ocean Observation Program has deployed an Ocean Moored Network for the Northern Indian Ocean (OMNI) both in the Arabian Sea and the Bay of Bengal. These buoys are equipped with sensors to measure radiation and rainfall, in addition to other basic meteorological parameters. They are also equipped with sensors to measure sub-surface currents, temperature, and conductivity from the surface up to a depth of 500 m. Observations from the Moderate Resolution Imaging Spectroradiometer (MODIS) sensor onboard the National Aeronautics and Space Administration (NASA) AQUA and TERRA satellites have been used to infer surface radiation over the north Indian Ocean. In this study, we focus only on the shortwave (SW↓) fluxes. The evaluations of the MODIS-based SW↓ fluxes against the RAMA observing network have shown a very good agreement between them, and therefore, we use the MODIS-derived fluxes as a reference for the evaluation of the OMNI observations. In an early deployment of the OMNI buoys, the radiation sensors were placed at 2 m above the sea surface; subsequently, the height of the sensors was raised to 3 m. In this study, we show that there was a substantial improvement in the agreement between the buoy observations and the satellite estimates, once the sensors were raised to higher levels. The correlation coefficient increased from 0.87 to 0.93, and both the bias and standard deviations decreased substantially.

  1. Growth constraints of the Indian Ocean seamounts

    Digital Repository Service at National Institute of Oceanography (India)

    Mukhopadhyay, R.; Khadge, N.H.

    parallel orientation, morphology, and lava chemistry between these ancient seamounts in CIOB, and young seamount chains off East Pacific Rise (EPR) in the Pacific Ocean indicate that seamount chains are the fundamental product of fast spreading ridges...

  2. Heavy metals in some parts of Antarctica and the southern Indian Ocean

    Digital Repository Service at National Institute of Oceanography (India)

    Kureishy, T.W.; Sengupta, R.; Mesquita, A.; Sanzgiri, S.

    metals were determined in various samples. Zooplankton and krill were collected from 30°S to the Southern ocean. Lichens and moss were collected from the shores of glacial lakes around the Indian station Maitri in the Schirmacher Oasis. Sediments... and Ni levels also being appreciable (Table 3). The mosses and lichens growing on the shores of these lakes exhibited high Cu concentrations, but levels of Cd, Co and Ni were below detection limits in these samples. Feathers collected from moulting...

  3. Biogeochemical processes in the northern Indian Ocean

    Digital Repository Service at National Institute of Oceanography (India)

    Gaye-Haake, B.; Guptha, M.V.S.; Murty, V.S.N.; Ittekkot, V.

    of dustfromtheArabianPeninsula,SomaliandThar Deep-Sea Research II 52 Editorial Biogeochemical Processes in This DSR II volume presents selected papers froman‘‘InternationalWorkshoponbiogeochem- ical processes in the northern Indian Ocean’’ coorganized...) the southern fan area via active deep-sea channels. The Of the 16 papers contained in this volume 11 erosion and convective overturn. Summer mon- desertstotheArabianSea.ThepaperbySchu¨ssler ARTICLE IN PRESS deal with the Arabian Sea, 2 with the Bay of Bengal...

  4. Abyssal benthos of the Central Indian Ocean

    Digital Repository Service at National Institute of Oceanography (India)

    Parulekar, A.H.; Harkantra, S.N.; Ansari, Z.A.; Matondkar, S.G.P.

    standing crop is uniformly high (0.54 to 13.73 g m-2; chi = 2.70 g m-2) and many times larger than previously reported for comparable depths in other oceans and from the same region. Biomass values are significantly related to distance from shore...

  5. Quaternary carbonate record from the equatorial Indian Ocean and its relationship with productivity changes

    Digital Repository Service at National Institute of Oceanography (India)

    Naidu, P.D.; Malmgren, B.A.

    interglacials in the Atlantic Ocean. It is not yet clear as to whether a Pacific or an Atlantic pattern of CaCO sub(3) fluctuations dominates the Indian Ocean. The Ocean Drilling Program (ODP) Site 709A from the western equatorial Indian Ocean for the last 1370...

  6. A biweekly mode in the equatorial Indian Ocean

    Digital Repository Service at National Institute of Oceanography (India)

    Sengupta, D.; Senan, R.; Murty, V.S.N.; Fernando, V.

    -biweekly) period [Yasunari, 1981; Krishnamurti and Ardunay, 1980; Krishnamurti et al., 1988; Goswamietal., 1998]. The 30- to 60-day eastward propagating Madden-Julian oscillation is the dom- inant mode of intraseasonal variability [Madden and Julian, 1972, 1994... Res., 23, 371–390. Wyrtki, K. (1973), An equatorial jet in the Indian Ocean, Science, 181, 262–264. Yasunari, T. (1981), Structure of an Indian summer monsoon system with around 40-day period, J. Meteorol. Soc. Jpn., 59, 336–354. Zhu, Z. H., A. Kaneko...

  7. Introduction to Indian Ocean biogeochemical processes and ecological variability: Current understanding and emerging perspectives

    Digital Repository Service at National Institute of Oceanography (India)

    Wiggert, J.D.; Hood, R.R.; Naqvi, S.W.A.; Brink, K.H.; Smith, S.L.

    is for such research efforts to be inclusive of the entire Indian Ocean. Indeed, this is a principal tenet of the conceptual framework that underlies the Sustained Indian Ocean Biogeochemical and Ecosystem Research (SIBER) initiative. SIBER’s initial development... of the Indian Ocean’s com- plement of unique dynamical processes, biological measure- ments were also performed. These ultimately led to creation of several plankton and production atlases [e.g., Indian Ocean Biological Center, �968; Panikkar, �970; Krey...

  8. Indian Ocean Dipole and El Niño/Southern Oscillation impacts on regional chlorophyll anomalies in the Indian Ocean

    Directory of Open Access Journals (Sweden)

    J. C. Currie

    2013-10-01

    Full Text Available The Indian Ocean Dipole (IOD and the El Niño/Southern Oscillation (ENSO are independent climate modes, which frequently co-occur, driving significant interannual changes within the Indian Ocean. We use a four-decade hindcast from a coupled biophysical ocean general circulation model, to disentangle patterns of chlorophyll anomalies driven by these two climate modes. Comparisons with remotely sensed records show that the simulation competently reproduces the chlorophyll seasonal cycle, as well as open-ocean anomalies during the 1997/1998 ENSO and IOD event. Results suggest that anomalous surface and euphotic-layer chlorophyll blooms in the eastern equatorial Indian Ocean in fall, and southern Bay of Bengal in winter, are primarily related to IOD forcing. A negative influence of IOD on chlorophyll concentrations is shown in a region around the southern tip of India in fall. IOD also depresses depth-integrated chlorophyll in the 5–10° S thermocline ridge region, yet the signal is negligible in surface chlorophyll. The only investigated region where ENSO has a greater influence on chlorophyll than does IOD, is in the Somalia upwelling region, where it causes a decrease in fall and winter chlorophyll by reducing local upwelling winds. Yet unlike most other regions examined, the combined explanatory power of IOD and ENSO in predicting depth-integrated chlorophyll anomalies is relatively low in this region, suggestive that other drivers are important there. We show that the chlorophyll impact of climate indices is frequently asymmetric, with a general tendency for larger positive than negative chlorophyll anomalies. Our results suggest that ENSO and IOD cause significant and predictable regional re-organisation of chlorophyll via their influence on near-surface oceanography. Resolving the details of these effects should improve our understanding, and eventually gain predictability, of interannual changes in Indian Ocean productivity, fisheries

  9. Trace elements in oceanic pelagic communities in the western Indian Ocean.

    Science.gov (United States)

    Bodin, Nathalie; Lesperance, Dora; Albert, Rona; Hollanda, Stephanie; Michaud, Philippe; Degroote, Maxime; Churlaud, Carine; Bustamante, Paco

    2017-05-01

    The mineral composition of target and non-target pelagic fish caught by purse-seiners and longliners in the western-central Indian Ocean was determined. From the 10 essential elements analysed, selenium and zinc showed the highest concentrations in swordfish and blue marlin while Indian mackerel appeared as a good source of copper, iron and chrome. All catch had levels of lead and cadmium, two toxic elements, below the maximum sanitary limits. Although some concerns were raised regarding mercury concentrations in the largest species (wahoo, swordfish and blue marlin), molar ratios of mercury and selenium indicate that all oceanic pelagic fish from the western-central Indian Ocean are safe for human consumption. This study also gives insights on the relationships between the levels of essential and toxic elements in fish muscle and the size, trophic position and diet sources of the studied pelagic species.

  10. Petrology of ocean floor rocks from Central Indian Ocean basin

    Digital Repository Service at National Institute of Oceanography (India)

    Iyer, S.D.; Karisiddaiah, S.M.

    on the pumice is also a possibility IQ. The influence ofsubmarine volca noes as sources for pumice may be possible for CIOO samples, similar to those reported for the Atlantic Ocean 20 . It is envisaged that the uprising magma was basic and highly fluid...

  11. The Structure of Anomalous Oceanic Circulation In The Indian Ocean Dipole

    Science.gov (United States)

    Zhao, Qigeng

    Using an Indian-Pacific Ocean Circulation Model with high resolution a simulation study on the Indian Ocean dipole (IOD) has been done. Forcing the mdel with monthly observational wind stress in 1990-1999 the main characteristics of sea temperature variations in the two IODs (in 1997 and 1994) have been reproduced well. The pat- terns and center positions of sea temperature anomalies in the tropical Indian Ocean surface and in the section of equator-depth during the IOD from the simulation are basically consistent with that from observation. The physical image of anomalous circulation during IOD is revealed from the simulation. We find that an anomalous easterly current along the equator in the upper layer of the eastern Indian Ocean dur- ing IOD period. It is very strong, narrow band and is divergent from equator to both sides. It represents a Rossby wave propagated westwards. During IOD phase there a significant anomalous current cell in the section of equator-depth: the easterly current in the upper layer; westerly compensated current below it; a strong upwelling to the east of 80 E; a weak downwelling to the west of 55 E. Meanwhile two anomalous meridian cells are in the both sides of equator in the eastern Indian Ocean. The com- mon upwelling of them is near equator. The patterns of anomalous current in the out of IOD phase are basically opposite to that in the IOD phase, besides the absolute value of the anomalous current is weaker. Therefore the anomalous sea temperature in the tropical Indian Ocean during IOD could be interpreted with anomalous horizontal and vertical current, especially large-scale upwelling and downwelling.

  12. Southwest Indian Ocean Bathymetric Compilation (swIOBC)

    Science.gov (United States)

    Jensen, L.; Dorschel, B.; Arndt, J. E.; Jokat, W.

    2014-12-01

    As result of long-term scientific activities in the southwest Indian Ocean, an extensive amount of swath bathymetric data has accumulated in the AWI database. Using this data as a backbone, supplemented by additional bathymetric data sets and predicted bathymetry, we generate a comprehensive regional bathymetric data compilation for the southwest Indian Ocean. A high resolution bathymetric chart of this region will support geological and climate research: Identification of current-induced seabed structures will help modelling oceanic currents and, thus, provide proxy information about the paleo-climate. Analysis of the sediment distribution will contribute to reconstruct the erosional history of Eastern Africa. The aim of swIOBC is to produce a homogeneous and seamless bathymetric grid with an associated meta-database and a corresponding map for the area from 5° to 39° S and 20° to 44° E. Recently, multibeam data with a track length of approximately 86,000 km are held in-house. In combination with external echosounding data this allows for the generation of a regional grid, significantly improving the existing, mostly satellite altimetry derived, bathymetric models. The collected data sets are heterogeneous in terms of age, acquisition system, background data, resolution, accuracy, and documentation. As a consequence, the production of a bathymetric grid requires special techniques and algorithms, which were already developed for the IBCAO (Jakobsson et al., 2012) and further refined for the IBCSO (Arndt et al., 2013). The new regional southwest Indian Ocean chart will be created based on these methods. Arndt, J.E., et al., 2013. The International Bathymetric Chart of the Southern Ocean (IBCSO) Version 1.0—A new bathymetric compilation covering circum-Antarctic waters. GRL 40, 1-7, doi: 10.1002/grl.50413, 2013. Jakobsson, M., et al., 2012. The International Bathymetric Chart of the Arctic Ocean (IBCAO) Version 3.0. GRL 39, L12609, doi: 10.1029/2012GL052219.

  13. GEOFON, GITEWS and the Indian Ocean Tsunami Warning System

    Science.gov (United States)

    Hanka, W.; Saul, J.; Hoffmann, T. L.

    2008-12-01

    After the Mw=9.3 Sumatra earthquake of December 26, 2004, which generated a tsunami that affected the entire Indian Ocean region and caused approximately 230,000 fatalities, the German government funded the German Indian Ocean Tsunami Early Warning System (GITEWS) Project. The GEOFON group of GFZ Potsdam was nominated to develop and implement the seismological component of the GITEWS system. This poster presentation describes the concept of the GITEWS Earthquake Monitoring System (EMS) and reports on its present status and progress of implementation. The major challenge for an EMS within a tsunami warning system is to determine earthquake source parameters in terms of location, size and possibly rupture propagation as quickly as possible, in order to allow counter measures before a potential tsunami may hit coastal areas. Tsunamigenic earthquakes usually occur along subduction zones, which are often close to coastal lines. In the Indian Ocean this is particularly true for the Sunda Trench off the shore of Indonesia and the Macran subduction zone off the shore of Iran. For an Indian Ocean monitoring system where short warning times are a requirement, a dense real-time network of seismic stations in Indonesia is therefore essential. It must be supplemented by a substantial number of stations in other countries surrounding the Indian Ocean. International cooperation and real-time data exchange across political boundaries are essential for successful tsunami warning in the Indian Ocean region. Within the GITEWS project, up to 40 new broadband and strong motion stations are being installed in the Indian Ocean region until 2010. Up to 22 new stations are set up in Indonesia and another 18 stations distributed over Sri Lanka, Maldives, Yemen, Kenya, Tanzania, Madagascar and Israel. Real-time communication is provided by private VSAT communication systems. Another challenging task within the GITEWS project is the design and implementation of efficient and fast acquisition

  14. Dynamics of formation of ferromanganese nodules in the Indian Ocean

    Digital Repository Service at National Institute of Oceanography (India)

    Mukhopadhyay, R.; Ghosh, A.K.

    stream_size 27400 stream_content_type text/plain stream_name J_Asian_Earth_Sci_37_394a.pdf.txt stream_source_info J_Asian_Earth_Sci_37_394a.pdf.txt Content-Encoding UTF-8 Content-Type text/plain; charset=UTF-8 Author..., and the model should bring about a predictive estimate of other nodule bearing areas in the world oceans. Key Words: Ferromanganese nodules, Indian Ocean Nodule Field, influencing parameters, Nodule formation and dynamics, Model of nodule formation...

  15. Marine pollution in the Indian Ocean: problems, prospects and perspectives

    OpenAIRE

    Sen Gupta, R.; Singbal, S.Y.S.

    1988-01-01

    Following a brief outline of the physiography of the Indian Ocean, an examination is made of the current situation regarding contamination of the environment. Prominent marine pollutants and the consequences of the marine disposal are discussed, considering in particular oil pollution, heavy metal pollution, agricultural wastes and domestic wastes. Research activities conducted in the area investigating the levels of marine pollution are detailed, and an evaluation made of future prospects co...

  16. Marine pollution in the Indian Ocean: problems, prospects and perspectives

    OpenAIRE

    Sen Gupta, R.; Singbal, S.Y.S.

    1988-01-01

    Following a brief outline of the physiography of the Indian Ocean, an examination is made of the current situation regarding contamination of the environment. Prominent marine pollutants and the consequences of the marine disposal are discussed, considering in particular oil pollution, heavy metal pollution, agricultural wastes and domestic wastes. Research activities conducted in the area investigating the levels of marine pollution are detailed, and an evaluation made of future prospects co...

  17. ESTIMATION OF PRIMARY PRODUCTIVITY FOR TUNA IN INDIAN OCEAN

    Directory of Open Access Journals (Sweden)

    Ende Kasma

    2012-11-01

    Full Text Available Indonesia has abundant fisheries potency, one of fisheries potency in Indian Ocean is tuna fish. Primary productivity data used as indicator of tuna fisheries potency in Idian Ocean.Research location is in Indian Ocean 070 - 210 S and 1070 - 1210 E. Weekly satellite data in 2007 used are chlorophyl, sea surface temperature, Photosynthetic Available Radiation (PAR and euphotic zone (Zeu data. Daily fisheries data is from tuna fish catching data 2007 in PT. Perikanan Samudera Besar (PT. PSB. Satellite data is processed by Vertically Generalized Production Model (VGPM formula to obtained primary productivity. Tuna fish catching data correlated to satellite data to know correlation of primary productivity value to fish catching data.Result of this research is there four species of tuna fish catch in Indian Ocean, that are Madidihang or Yellowfin tuna (Thunnus albacores, Bigeye tuna (Thunnus obesus, Southtern Bluefin tuna (Thunnus macoyii, and Albacore (Thunnus alalunga. Where 73% tuna fish is Bigeye tuna. Bigeye, Albacore and Yellowfin tuna are produced annually, while Southern Bluefin tuna in northwest monsoon is no fish production. Chlorophyll-a, sea surface temperature and primary productivity value in research location are from 0,06 mg/m3 to 0,38 mg/m3, from 24,640C to 31,820C, and from 73,22mgC/m2 to 658,57 mgC/m2 respectively. Coefficient correlation in primary productivity and fish catching in fishing ground area is small (r = 0.008, its explained that, fish catching number is not influenced by primary productivity. In high or low primary productivity condition tuna fish catched in Indian Ocean area. Potential fishing ground area of Bigeye tuna, Albacore, Yellowfin and Southern Bluefin tuna in Indian Ocean are in 110 – 160 S and 1060 – 1210 E, the primary productivity value is from 73 mgC/m2day to 732 mgC/m2day and differences of sea surface temperature value of tuna fish are from 240 C to 310 C, 240 C to 300 C, and 250 C to 310 C for

  18. Comparative phylogeography of the western Indian Ocean reef fauna

    Science.gov (United States)

    Borsa, Philippe; Durand, Jean-Dominique; Chen, Wei-Jen; Hubert, Nicolas; Muths, Delphine; Mou-Tham, Gérard; Kulbicki, Michel

    2016-04-01

    Assessing patterns of connectivity at the community and population levels is relevant to marine resource management and conservation. The present study reviews this issue with a focus on the western Indian Ocean (WIO) biogeographic province. This part of the Indian Ocean holds more species than expected from current models of global reef fish species richness. In this study, checklists of reef fish species were examined to determine levels of endemism in each of 10 biogeographic provinces of the Indian Ocean. Results showed that the number of endemic species was higher in the WIO than in any other region of the Indian Ocean. Endemic species from the WIO on the average had a larger body size than elsewhere in the tropical Indian Ocean. This suggests an effect of peripheral speciation, as previously documented in the Hawaiian reef fish fauna, relative to other sites in the tropical western Pacific. To explore evolutionary dynamics of species across biogeographic provinces and infer mechanisms of speciation, we present and compare the results of phylogeographic surveys based on compilations of published and unpublished mitochondrial DNA sequences for 19 Indo-Pacific reef-associated fishes (rainbow grouper Cephalopholis argus, scrawled butterflyfish Chaetodon meyeri, bluespot mullet Crenimugil sp. A, humbug damselfish Dascyllus abudafur/Dascyllus aruanus, areolate grouper Epinephelus areolatus, blacktip grouper Epinephelus fasciatus, honeycomb grouper Epinephelus merra, bluespotted cornetfish Fistularia commersonii, cleaner wrasse Labroides sp. 1, longface emperor Lethrinus sp. A, bluestripe snapper Lutjanus kasmira, unicornfishes Naso brevirosris, Naso unicornis and Naso vlamingii, blue-spotted maskray Neotrygon kuhlii, largescale mullet Planiliza macrolepis, common parrotfish Scarus psicattus, crescent grunter Terapon jarbua, whitetip reef shark Triaenodon obesus) and three coastal Indo-West Pacific invertebrates (blue seastar Linckia laevigata, spiny lobster

  19. Tropical cyclone activity over the Southwest Tropical Indian Ocean

    Science.gov (United States)

    Burns, Jessica M.; Subrahmanyam, Bulusu; Nyadjro, Ebenezer S.; Murty, V. S. N.

    2016-08-01

    The Southwest Tropical Indian Ocean (SWTIO) is a key region for air-sea interaction. Tropical cyclones (TCs) regularly form over the SWTIO and subsurface ocean variability influences the cyclogenesis of this region. Tropical cyclone days for this region span from November through April, and peak in January and February during austral summer. Past research provides evidence for more tropical cyclone days over the SWTIO during austral summer (December-June) with a deep thermocline ridge than in austral summer with a shallow thermocline ridge. We have analyzed the Argo temperature data and HYbrid Coordinate Ocean Model (HYCOM) outputs while focusing on the austral summer of 2012/2013 (a positive Indian Ocean Dipole (IOD) year and neutral El Niño Southern Oscillation (ENSO) year) when seven named tropical cyclones developed over the SWTIO region. This study reveals that the climatic events like the IOD and ENSO influence the cyclonic activity and number of TC days over the SWTIO. We ascertain that the IOD events have linkages with the Barrier Layer Thickness (BLT) in the SWTIO region through propagating Rossby waves, and further show that the BLT variability influences the cyclonic activity in this region.

  20. Interbasin effects of the Indian Ocean on Pacific decadal climate change

    Science.gov (United States)

    Mochizuki, Takashi; Kimoto, Masahide; Watanabe, Masahiro; Chikamoto, Yoshimitsu; Ishii, Masayoshi

    2016-07-01

    We demonstrate the significant impact of the Indian Ocean on the Pacific climate on decadal timescales by comparing two sets of data assimilation experiments (pacemaker experiments) conducted over recent decades. For the Indian Ocean of an atmosphere-ocean coupled global climate model, we assimilate ocean temperature and salinity anomalies defined as deviations from climatology or as anomalies with the area-averaged changes for the Indian Ocean subtracted. When decadal sea surface temperature (SST) trends are observed to be strong over the Indian Ocean, the equatorial thermocline uniformly deepens, and the model simulates the eastward tendencies of surface wind aloft. Surface winds strongly converge around the maritime continent, and the associated strengthening of the Walker circulation suppresses an increasing trend in the equatorial Pacific SST through ocean thermocline shoaling, similar to common changes associated with seasonal Indian Ocean warming.

  1. Seasonal mixed layer heat balance of the southwestern tropical Indian Ocean

    Digital Repository Service at National Institute of Oceanography (India)

    Foltz, G.R.; Vialard, J.; PraveenKumar, B.; McPhaden, M.J.

    Sea surface temperature (SST) in the southwestern tropical Indian Ocean exerts a significant influence on global climate through its influence on the Indian summer monsoon and Northern Hemisphere atmospheric circulation. In this study, measurements...

  2. A sink for atmospheric carbon dioxide in the northeast Indian Ocean

    Digital Repository Service at National Institute of Oceanography (India)

    DileepKumar, M.; Naqvi, S.W.A.; George, M.D.; Jayakumar, D.A.

    Intensive observations in the northeast Indian Ocean (Bay of Bengal) during the pre-southwest and northeast monsoon seasons 1991 reveal that freshwater discharge from rivers of the Indian subcontinent exerts the dominant control over total carbon...

  3. Solubility of iron and other trace elements over the Southern Indian Ocean

    Directory of Open Access Journals (Sweden)

    A. Heimburger

    2013-03-01

    Full Text Available The fraction of soluble aerosols that is deposited on the open ocean is vital for phytoplankton growth. It is believed that a large proportion of this dissolved fraction is bioavailable for marine biota and thus plays an important role in primary production, especially in HNLC oceanic areas where this production is limited by micronutrient supply. There is still much uncertainty surrounding the solubility of atmospheric particles in global biogeochemical cycles and it is not well understood. In this study, we present the solubilities of seven elements (Al, Ce, Fe, La, Mn, Nd, Ti in rainwater on Kerguelen Islands, in the middle of the Southern Indian Ocean. The solubilities exhibit high values, generally greater than 70%, and Ti remains the least soluble element. Because the Southern Indian Ocean is remote from its dust sources, only the fraction of smaller aerosols reaches Kerguelen Islands after undergoing several cloud and chemical processes during their transport resulting in a drastic increase in solubility. Finally, we deduced an average soluble iron deposition flux of 23 μg m−2 d−1 (0.4 μmol m−2 d−1 for the studied oceanic area, taking into account a~median iron solubility of 82% ± 18%.

  4. Southern Indian Ocean SST as a modulator for the progression of Indian summer monsoon

    Science.gov (United States)

    Shahi, Namendra Kumar; Rai, Shailendra; Mishra, Nishant

    2016-11-01

    This study explores the possibility of southern Indian Ocean (SIO) sea surface temperature (SST) as a modulator for the early phase of Indian summer monsoon and its possible physical mechanism. A dipole-like structure is obtained from the empirical orthogonal function (EOF) analysis which is similar to an Indian Ocean subtropical dipole (IOSD) found earlier. A subtropical dipole index (SDI) is defined based on the SST anomaly over the positive and negative poles. The regression map of rainfall over India in the month of June corresponding to the SDI during 1983-2013 shows negative patterns along the Western Ghats and Central India. However, the regression pattern is insignificant during 1952-1982. The multiple linear regression models and partial correlation analysis also indicate that the SDI acts as a dominant factor to influence the rainfall over India in the month of June during 1983-2013. The similar result is also obtained with the help of composite rainfall over the land points of India in the month of June for positive (negative) SDI events. It is also observed that the positive (negative) SDI delays (early) the onset dates of Indian monsoon over Kerala during the time domain of our study. The study is further extended to identify the physical mechanism of this impact, and it is found that the heating (cooling) in the region covering SDI changes the circulation pattern in the SIO and hence impacts the progression of monsoon in India.

  5. Indian Ocean temperature dipole and SSTA in the equatorial Pacific Ocean

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    The observed sea surface temperature (SST) data of recent 100 years are analyzed and the existence of the Indian Ocean temperature dipole in the equatorial region is exposed further. It is very clear that the amplitude of the positive phase (higher SST in the west and lower SST in the east than normal) is larger than that of the negative phase (higher SST in the east and lower SST in the west). The dipole is stronger in September-November and weaker in January-April than in other months and it also appears obviously inter-annual and inter-decadal variations. Although the Indian Ocean dipole in the individual year seems to be independent of ENSO in the equatorial Pacific Ocean, in general, the Indian Ocean dipole has obviously negative correlation with the Pacific Ocean dipole (similar to the inverse phase of ENSO mode). The atmospheric zonal (Walker) circulation over the equator is fundamental to relate the two dipoles to each other.

  6. Winter AO/NAO modifies summer ocean heat content and monsoonal circulation over the western Indian Ocean

    Science.gov (United States)

    Gong, Dao-Yi; Guo, Dong; Li, Sang; Kim, Seong-Joong

    2017-02-01

    This paper analyzes the possible influence of boreal winter Arctic Oscillation/North Atlantic Oscillation (AO/ NAO) on the Indian Ocean upper ocean heat content in summer as well as the summer monsoonal circulation. The strong interannual co-variation between winter 1000-hPa geopotential height in the Northern Hemisphere and summer ocean heat content in the uppermost 120 m over the tropical Indian Ocean was investigated by a singular decomposition analysis for the period 1979-2014. The second paired-modes explain 23.8% of the squared covariance, and reveal an AO/NAO pattern over the North Atlantic and a warming upper ocean in the western tropical Indian Ocean. The positive upper ocean heat content enhances evaporation and convection, and results in an anomalous meridional circulation with ascending motion over 5°S-5°N and descending over 15°-25°N. Correspondingly, in the lower troposphere, significantly anomalous northerly winds appear over the western Indian Ocean north of the equator, implying a weaker summer monsoon circulation. The off-equator oceanic Rossby wave plays a key role in linking the AO/NAO and the summer heat content anomalies. In boreal winter, a positive AO/NAO triggers a down-welling Rossby wave in the central tropical Indian Ocean through the atmospheric teleconnection. As the Rossby wave arrives in the western Indian Ocean in summer, it results in anomalous upper ocean heating near the equator mainly through the meridional advection. The AO/NAO-forced Rossby wave and the resultant upper ocean warming are well reproduced by an ocean circulation model. The winter AO/NAO could be a potential season-lead driver of the summer atmospheric circulation over the northwestern Indian Ocean.

  7. ENSO and Indian Ocean dipole mode in three coupled GCMs

    Institute of Scientific and Technical Information of China (English)

    YU Yongqiang; LIU Xiying

    2004-01-01

    The simulated ENSO and Indian Ocean dipole (IOD) mode events from three coupled GCMs with the same oceanic component model, CPM0, CPM1 and FGCM0, are compared. The only difference between the CPM0 and the CPM1 comes from the coupling scheme at the air-sea interface, e.g., flux anomaly coupling scheme for the former and direct coupling scheme for the latter. The FGCM0 is also a directly coupled GCM, but its atmospheric component model is the NCAR CCM3 rather than the NCC T63AGCM as in the other two coupled GCMs CPM0 and CPM1.All three coupled models show El Nino-like interannual variability in the tropic Pacific, but the FGCM0 shows a bit stronger amplitude of El Nino events and both the CPM0 and the CPM1 show much weaker amplitude than the observed one. In the meanwhile, the quasi-biennial variability dominates in the FGCM0 simulations, and 4 a and longer periods are significant in both the CPM0 and CPM1 models. As the El Nino events simulated by the three coupled GCMs, the simulated Indian Ocean dipole mode events are stronger from the coupled model FGCM0 and weaker from both the CPM0 and CPM1 models than those from observation.

  8. Indian Ocean Research Data: Past, Present and Future

    Science.gov (United States)

    Chandler, Cynthia; Groman, Robert; Allison, Molly; Copley, Nancy; Gegg, Stephen; Kinkade, Danie; Rauch, Shannon; Glover, David; Wiebe, Peter

    2015-04-01

    Open access to well-documented data is essential to enable improved understanding of the key processes and their complex interactions in the Indian Ocean. For decades, marine ecosystem data have been collected by expeditions conducting research in this fascinating region. The data from many of the projects including the International Indian Ocean Expedition of the 1960s, the US Joint Global Ocean flux Study (JGOFS) Arabian Sea Expedition of the 1990s, and several more recent projects have been contributed by the original investigators to the Biological and Chemical Oceanography Data Management Office (BCO-DMO). BCO-DMO is funded by the US National Science Foundation to work with marine scientists to improve access to research data and ensure long term preservation of the data that comprise an important part of a research program's legacy. The data are freely available from the Web-accessible BCO-DMO system that supports data discovery, access, display, user-customizable export, and download. The authors will provide an overview of the BCO-DMO data system including examples of the range of data types and an introduction to system capabilities.

  9. Geochemical implications of gabbro from the slow-spreading Northern Central Indian Ocean Ridge, Indian Ocean

    Digital Repository Service at National Institute of Oceanography (India)

    Ray, Dwijesh; Misra, S.; Banerjee, R.; Weis, D.

    Gabbro samples (c. < 0.4 Ma old) dredged from close to the ‘Vityaz Megamullion’ on the slow-spreading Northern Central Indian Ridge (NCIR, 18-22 mm yr sup(-1)) include mostly olivine gabbro and Fe-Ti oxide gabbro. The cumulate olivine gabbro shows...

  10. Dynamics of dissolved organic carbon in the northwestern Indian Ocean

    Digital Repository Service at National Institute of Oceanography (India)

    DileepKumar, M.; Rajendran, A.; Somasundar, K.; Haake, B.; Jenisch, A.; Shuo, Z.; Ittekkot, V.; Desai, B.N.

    / 6,, ~'F t 101 18 ~16 ~o* sb* ,b* 7'o- 8b. Fig. 1. Station locations in the northwestern Indian Ocean. 0 o 302 M. DILEEP KUMAR ET AL. F filtrate was fixed with HgC12 and analysed for DOC, within a month, by a high-temperature catalytic wet... compounds, by the high-temperature catalytic oxidation method used in this study, compared with the apparently incomplete decom- position by simple wet oxidation of Menzel (1964), should be the reason for large DOC differences between the two studies...

  11. A diffuse plate boundary model for Indian Ocean tectonics

    Science.gov (United States)

    Wiens, D. A.; Demets, C.; Gordon, R. G.; Stein, S.; Argus, D.

    1985-01-01

    It is suggested that motion along the virtually aseismic Owen fracture zone is negligible, so that Arabia and India are contained within a single Indo-Arabian plate divided from the Australian plate by a diffuse boundary. The boundary is a zone of concentrated seismicity and deformation commonly characterized as 'intraplate'. The rotation vector of Australia relative to Indo-Arabia is consistent with the seismologically observed 2 cm/yr of left-lateral strike-slip along the Ninetyeast Ridge, north-south compression in the Central Indian Ocean, and the north-south extension near Chagos.

  12. Macrofaunal diversity in the Central Indian Ocean Basin

    Digital Repository Service at National Institute of Oceanography (India)

    Pavithran, S.; Ingole, B.S.; Nanajkar, M.; Nath, B.N.

    shallow water counterparts, so the sieve mesh sizes used to separate deep- sea macrofauna often varies between 500 μm to 250 μm. The basic food for deep-sea macrofauna is the phytodetritus supplied by the euphotic zone. Only 1-3% of the surface... production is known to reach the abyss. Thus their abundance in the deep-sea is limited by availability of food. They can easily be sampled with the aid of grabs and box corer. Macrofaunal diversity in the Central Indian Ocean Basin S. Pavithran*, B. Ingole...

  13. DISCARDS OF THE INDONESIAN TUNA LONGLINE FISHERY IN INDIAN OCEAN

    Directory of Open Access Journals (Sweden)

    Bram Setyadji

    2013-06-01

    Full Text Available Incidental by-catch and associated discarding are difficult to estimate on the basis of logbook information because they are poorly reported by fishing masters and their importance varies with several interrelated factors. The purpose of this paper is to inform the commonly discarded fishes of the Indonesian tuna longline fishery in the Indian Ocean. The study was carried out during 2010 – 2011 following six commercial tuna longline vessels based in Port of Benoa. Discards composition was dominated by longnose lancetfish and pelagic stingrays which composed almost half of total discards. Almost half of total catch are discards and half of discards are disposed dead or dying.

  14. Equatorial Indian Ocean subsurface current variability in an Ocean General Circulation Model

    Science.gov (United States)

    Gnanaseelan, C.; Deshpande, Aditi

    2017-05-01

    The variability of subsurface currents in the equatorial Indian Ocean is studied using high resolution Ocean General Circulation Model (OGCM) simulations during 1958-2009. February-March eastward equatorial subsurface current (ESC) shows weak variability whereas strong variability is observed in northern summer and fall ESC. An eastward subsurface current with maximum amplitude in the pycnocline is prominent right from summer to winter during strong Indian Ocean Dipole (IOD) years when air-sea coupling is significant. On the other hand during weak IOD years, both the air-sea coupling and the ESC are weak. This strongly suggests the role of ESC on the strength of IOD. The extension of the ESC to the summer months during the strong IOD years strengthens the oceanic response and supports intensification and maintenance of IODs through modulation of air sea coupling. Although the ESC is triggered by equatorial winds, the coupled air-sea interaction associated with IODs strengthens the ESC to persist for several seasons thereby establishing a positive feedback cycle with the surface. This suggests that the ESC plays a significant role in the coupled processes associated with the evolution and intensification of IOD events by cooling the eastern basin and strengthening thermocline-SST (sea surface temperature) interaction. As the impact of IOD events on Indian summer monsoon is significant only during strong IOD years, understanding and monitoring the evolution of ESC during these years is important for summer monsoon forecasting purposes. There is a westward phase propagation of anomalous subsurface currents which persists for a year during strong IOD years, whereas such persistence or phase propagation is not seen during weak IOD years, supporting the close association between ESC and strength of air sea coupling during strong IOD years. In this study we report the processes which strengthen the IOD events and the air sea coupling associated with IOD. It also unravels

  15. The Central Sudetes Rheic Ocean Ophiolites: Quantifying the spatial and temporal extent of the Indian Ocean-Dupal mantle signature

    Science.gov (United States)

    band, Ade R.; Barry, Tiffany; Murphy, Brendan; Saunders, Andrew

    2014-05-01

    The Indian Ocean-Dupal (Dupal herein) mantle signature is documented to be an integral component in the formation of the Carboniferous Palaeo-Tethys ophiolites. Spatially associated with the Palaeo-Tethys Ocean, the Rheic Ocean separated Laurussia and Gondwana after its conception during the latest Cambrian until closure during the Devonian-Carboniferous Variscan-Alleghanian orogeny. The age and location of Rheic Ocean ophiolites preserved within the Variscide belt offers an insight into the spatial and temporal extent, and also the origin of the Dupal mantle signature. The Central Sudetes Ophiolites consist of the low metamorphic grade, partially dismembered Nowa Ruda, Braszowice and Ślęża mafic/ultramafic bodies of Lower Silesia, Poland. Geochemical analysis of extrusive and hypabyssal lithologies indicate that despite the majority of samples exhibiting characteristics compatible with formation within a SSZ setting (Th and LILE enrichment, Ta and Nb depletion), a significant MORB suite is also present. MORB offer an opportunity to isotopically fingerprint the underlying mantle source region, thus offering an insight into the chemistry of the southern hemisphere mantle at c. 420-400 Ma. Utilising the robust Hf-Nd systematics this study has succeeded in documenting the mantle domain from which the eastern Rheic Ocean was sourced whilst simultaneously constraining the timing and nature of a previous melt extraction event.

  16. Oceanographic cruise Indian Ocean and Java Trench June 1969 (NODC Accession 7100908)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This report contains oceanographic data which was obtained aboard H.M.A.S DIAMANTINA during an oceanographic cruise in the Java Trench and the Indian Ocean during...

  17. Third Indian National Conference on Harbour and Ocean Engineering (INCHOE - 2004). Proceedings

    Digital Repository Service at National Institute of Oceanography (India)

    Mandal, S.; SanilKumar, V; Jayakumar, S.

    The two volumes contain 103 scientific papers in the field of harbour and ocean engineering, presented at the Third Indian National Conference on Harbour and Ocean Engineering (INCHOE - 2004), held at National Institute of Oceanography (NIO), Dona...

  18. Simulated seasonal and interannual variability of mixed layer heat budget in the northern Indian Ocean

    Digital Repository Service at National Institute of Oceanography (India)

    DeBoyer Montegut, C.; Vialard, J.; Shenoi, S.S.C.; Shankar, D.; Durand, F.; Ethe, C.; Madec, G.

    A global Ocean General Circulation Model (OGCM) is used to investigate the mixed layer heat budget of the Northern Indian Ocean (NIO). The model is validated against observations and shows a fairly good agreement with mixed layer depth data...

  19. TOGA Sea Level Center: Data from the Indian Ocean (NODC Accession 9000251)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This accession contains a scan of the analog publication 'TOGA Sea Level Center: Data from the Indian Ocean'. Abstract from p. iii of the publication: The TOGA Sea...

  20. Internal constitution of manganese nodules from the Central Indian Ocean basin

    Digital Repository Service at National Institute of Oceanography (India)

    Ghosh, A.K.; Mukhopadhyay, R.

    Morphological, chemical, physical and acoustic properties of Mn-nodules in the the Indian Ocean are inter-linked and depend much on local and regional oceanic environments. These nodules are anisotropic and sound propagation is faster parallel...

  1. Teleconnection between the North Indian Ocean high swell events and meteorological conditions over the Southern Indian Ocean

    Science.gov (United States)

    Remya, P. G.; Vishnu, S.; Praveen Kumar, B.; Balakrishnan Nair, T. M.; Rohith, B.

    2016-10-01

    The link between North Indian Ocean (NIO) high swell events and the meteorological conditions over the Southern Indian Ocean (SIO) is explored in this article, using a combination of in situ measurements and model simulations for the year 2005. High waves, without any sign in the local winds, sometimes cause severe flooding events along the south-west coast of India, locally known as the Kallakkadal events and cause major societal problems along the coasts. In situ observations report 10 high swell events in NIO during 2005. Our study confirms that these events are caused by the swells propagating from south of 30°S. In all cases, 3-5 days prior to the high swell events in NIO, we observed a severe low pressure system, called the Cut-Off Low (COL) in the Southern Ocean. These COLs are quasistationary in nature, providing strong (˜25 ms-1) and long duration (˜3 days) surface winds over a large fetch; essential conditions for the generation of long-period swells. The intense equator ward winds associated with COLs in the SIO trigger the generation of high waves, which propagate to NIO as swells. Furthermore, these swells cause high wave activity and sometimes Kallakkadal events along the NIO coastal regions, depending on the local topography, angle of incidence, and tidal conditions. Our study shows that such natural hazards along the NIO coasts can be forecasted at least 2 days in advance if the meteorological conditions of the SIO are properly monitored.

  2. Phytoplankton composition and biomass across the southern Indian Ocean

    DEFF Research Database (Denmark)

    Schlüter, Louise; Henriksen, Peter; Nielsen, Torkel Gissel

    2011-01-01

    Phytoplankton composition and biomass was investigated across the southern Indian Ocean. Phytoplankton composition was determined from pigment analysis with subsequent calculations of group contributions to total chlorophyll a (Chl a) using CHEMTAX and, in addition, by examination in the microscope....... The different plankton communities detected reflected the different water masses along a transect from Cape Town, South Africa, to Broome, Australia. The first station was influenced by the Agulhas Current with a very deep mixed surface layer. Based on pigment analysis this station was dominated by haptophytes......, pelagophytes, cyanobacteria, and prasinophytes. Sub-Antarctic waters of the Southern Ocean were encountered at the next station, where new nutrients were intruded to the surface layer and the total Chl a concentration reached high concentrations of 1.7 μg Chl a L−1 with increased proportions of diatoms...

  3. Fronts and strong currents of the upper southeast Indian Ocean

    Institute of Scientific and Technical Information of China (English)

    HE Zhigang; DONG Zhaoqian; YUAN Xiaojun

    2006-01-01

    Hydrographic data, ADCP velocity and sea level anomaly derived from the satellite altimeter have been jointly analyzed in the southeast Indian Ocean. Results show the locations and orientations of the major oceanic fronts as well as the characteristics of the currents within these fronts in the area. Double subtropical fronts are observed in the section along 120°E, which conflicts with the frontal structure frequently observed before-the North Subtropical Front (NSTF) and South Subtropical Front (SSTF) merge into a single STF between 110°~115°E. The Subantarctic Front (SAF), influenced by the out-of-phase double eddies, runs across 48°S three times between 120° and 127°E. The surface current within the SAF is strengthened up to 105.4 cm/s by the geostrophic effect of these eddies. Furthermore eddies may cause the strong current to split up into two branches within the SAF. The SAF and the primary polar front (PF1) can be identified individually in the ADCP data with a separation distance of about 0.3° at latitude between 140° and 145°E, although they cannot be identified separately in the low-resolution hydrographic data. The different thermohaline characteristics of Circumpolar Deep Water (CDW) and Modified Circumpolar Deep Water (MCDW) result in the formation of Southern Antarctic Circumpolar Current Front (SACCF) in the southeast Indian Ocean. It consistently turns northward along the east flank of the Kerguelen Plateau after it runs through the Princess Elizabeth Trough and turns southward sharply north of 60°S with a little seasonal variations. It is shown that the locations and orientations of the SAF, the primary PF and SACCF in the ACC of the southeast Indian Ocean can be identified more precisely by the current distribution derived from ADCP data than by hydrographic data, because these fronts are usually accompanied by strong currents. However, the locations and orientations of the STF and the secondary PF are more difficult to be identified

  4. Eastern Indian Ocean microcontinent formation driven by plate motion changes

    Science.gov (United States)

    Whittaker, J. M.; Williams, S. E.; Halpin, J. A.; Wild, T. J.; Stilwell, J. D.; Jourdan, F.; Daczko, N. R.

    2016-11-01

    The roles of plate tectonic or mantle dynamic forces in rupturing continental lithosphere remain controversial. Particularly enigmatic is the rifting of microcontinents from mature continental rifted margins, with plume-driven thermal weakening commonly inferred to facilitate calving. However, a role for plate tectonic reorganisations has also been suggested. Here, we show that a combination of plate tectonic reorganisation and plume-driven thermal weakening were required to calve the Batavia and Gulden Draak microcontinents in the Cretaceous Indian Ocean. We reconstruct the evolution of these two microcontinents using constraints from new paleontological samples, 40Ar/39Ar ages, and geophysical data. Calving from India occurred at 101-104 Ma, coinciding with the onset of a dramatic change in Indian plate motion. Critically, Kerguelen plume volcanism does not appear to have directly triggered calving. Rather, it is likely that plume-related thermal weakening of the Indian passive margin preconditioned it for microcontinent formation but calving was triggered by changes in plate tectonic boundary forces.

  5. Progress in developing an Indian Ocean Tsunami Warning System (IOTWS)

    Science.gov (United States)

    Detweiler, S.; Mooney, W. D.; Kelly, A.; Atwater, B.; Sipkin, S.; Petersen, M.; Hudnut, K.

    2007-12-01

    Nearly three years following the devastating 2004 Indian Ocean tsunami, there is much progress to report on building a new Indian Ocean Tsunami Warning System (IOTWS) which will provide tsunami early warnings and framework for disaster management and response systems. To date, the IOTWS has utilized the leadership and technical expertise of many countries including Indonesia, Thailand, India, Sri Lanka, and the Maldives, together with assistance from international partners. Inter-agency cooperation has combined expertise in a broad range of disciplines to accomplish several goals including: 1) developing infrastructures for both real-time analysis of seismic data and rapid communication and warnings (including the upgrade of several Indonesian seismic and GPS stations), 2) land use planning and community preparation aimed at minimizing damage and loss of life from future disasters, and 3) international support for logistics, communications, training, management and administration. Throughout the implementation of the IOTWS, a primary focus was placed on "in-country capacity building," so that individual nations can be self-sustaining in their efforts. We believe that this has been accomplished through extensive training sessions, workshops and site visits.

  6. Low-frequency sound level in the Southern Indian Ocean.

    Science.gov (United States)

    Tsang-Hin-Sun, Eve; Royer, Jean-Yves; Leroy, Emmanuelle C

    2015-12-01

    This study presents long-term statistics on the ambient sound in the Southern Indian Ocean basin based on 2 years of data collected on six widely distributed autonomous hydrophones from 47°S to 4°S and 53°E to 83°E. Daily mean power spectra (10-100 Hz) were analyzed in order to identify the main sound sources and their space and time variability. Periodic signals are principally associated with the seasonal presence of three types of blue whales and fin whales whose signatures are easily identified at specific frequencies. In the low frequencies, occurrence of winter lows and summer highs in the ambient noise levels are well correlated with iceberg volume variations at the southern latitudes, suggesting that icebergs are a major sound source, seasonally contributing to the ambient noise, even at tropical latitudes (26°S). The anthropogenic contribution to the noise spectrum is limited. Shipping sounds are only present north and west of the study area in the vicinity of major traffic lanes. Acoustic recordings from the southern sites may thus be representative of the pristine ambient noise in the Indian Ocean.

  7. Pelagic ecology of the South West Indian Ocean Ridge seamounts: Introduction and overview

    Science.gov (United States)

    Rogers, A. D.

    2017-02-01

    The Indian Ocean was described by Behrman (1981) as the "Forlorn Ocean", a region neglected by science up to the late-1950s. For example, the Challenger Expedition from 1872 to 1876 largely avoided the Indian Ocean, sailing from Cape Town into Antarctic waters sampling around the Prince Edward Islands, Kerguelen Island and Crozet Islands before heading to Melbourne. From 1876 to the 1950s there were expeditions on several vessels including the Valdivia, Gauss and Planet (Germany), the Snellius (Netherlands), Discovery II, MahaBiss (United Kingdom), Albatross (Sweden), Dana and Galathea (Denmark; Behrman, 1981). There was no coordination between these efforts and overall the Indian Ocean, especially the deep sea remained perhaps the most poorly explored of the world's oceans. This situation was largely behind the multilateral effort represented by the International Indian Ocean Expedition (IIEO), which was coordinated by the Scientific Committee for Ocean Research (SCOR), and which ran from 1959-1965. Work during this expedition focused on the Arabian Sea, the area to the northwest of Australia and the waters over the continental shelves and slopes of coastal states in the region. Subsequently several large-scale international oceanographic programmes have included significant components in the Indian Ocean, including the Joint Global Ocean Flux Study (JGOFS) and the World Ocean Circulation Experiment (WOCE). These studies were focused on physical oceanographic measurements and biogeochemistry and whilst the Indian Ocean is still less understood than other large oceans it is now integrated into the major ocean observation systems (Talley et al., 2011). This cannot be said for many aspects of the biology of the region, despite the fact that the Indian Ocean is one of the places where exploitation of marine living resources is still growing (FAO, 2016). The biology of the deep Indian Ocean outside of the Arabian Sea is particularly poorly understood given the presence

  8. Indian naval development: Power projection in the Indian Ocean. Master's thesis

    Energy Technology Data Exchange (ETDEWEB)

    Haynes, A.M.

    1990-12-01

    This thesis examines the U.S.-India relationship in the context of a world power interacting with the predominant regional power. The growing Indian military's power projection and nuclear weapons capability make the Indian Ocean region a critical area for American foreign policy during the next decade. New Delhi's desire to be a hegemonic power in the region combined with the U.S. military drawdown in reaction to the changing strategic environment could threaten long-term U.S. interests. The United States can no longer afford to remain relatively disinterested in the region and must develop a comprehensive policy to promote regional security and stability.

  9. Spreading of water masses and regeneration of silica and sup(226)Ra in the Indian Ocean

    Digital Repository Service at National Institute of Oceanography (India)

    DileepKumar, M.; Yuan-Hui, Li

    Ra in the Indian Ocean 93 OEOSECS STATION NUYDER V. A40W INDIAN _ ____ 6 I I I ‘6’ I I I I I 0 I 2 I L l&l 0 4 5 6 GEOSECS STATION NUMBER 203 IQ EQ 209 IO. EQ LATITUDE Fig. 6. (b) Spreading of water masses (%) in the central Indian...

  10. IMPACTS OF THE TROPICAL PACIFIC COUPLED PROCESS ON THE INTERANNUAL VARIABILITY IN THE INDIAN OCEAN

    Institute of Scientific and Technical Information of China (English)

    FENG Jun-qiao; BAI Xue-zhi

    2010-01-01

    The basic features of climatology and interannual variations of tropical Pacific and Indian Oceans were analyzed using a coupled general circulation model(CGCM),which was constituted with an intermediate 2.5-layer ocean model and atmosphere model ECHAM4.The CGCM well captures the spatial and temporal structure of the Pacific El Nifio-Southern Oscillation(ENSO)and the variability features in the tropical Indian Ocean.The influence of Pacific air-sea coupled process on the Indian Ocean variability was investigated carefully by conducting numerical experiments.Results show that the occurrence frequency of positive/negative Indian Ocean Dipole(IOD)event will decrease/increase with the presence/absence of the coupled process in the Pacific Ocean.Further analysis demonstrated that the air-sea coupled process in the Pacific Ocean affects the IOD variability mainly by influencing the zonal gradient ofthermocline via modulating the background sea surface wind.

  11. Pearl in Indian Ocean,Mauritius Shines in Cooperation with China

    Institute of Scientific and Technical Information of China (English)

    Yang Wei; Guo Yan

    2007-01-01

    @@ Like pearls scattered in Indian Ocean, this nation is composed of several islands and has the reputation of Heaven Island. That is Mauritius. It covers an area of more than 1,865 square km of surface land with over 1.2 million multi-ethnic people. Situated at the south-western entrance of the Indian Ocean, it is home to multi-national cultures from African, European, Indian and Chinese civilizations.Its unique strategic location and cultural background make Mauritius shine brightly in the Indian Ocean.

  12. The Indian Ocean Experiment : Widespread air pollution from South and Southeast Asia

    NARCIS (Netherlands)

    Lelieveld, J; Crutzen, PJ; Ramanathan, A.; Andreae, MO; Brenninkmeijer, CAM; Campos, T; Cass, GR; Dickerson, RR; Fischer, H; de Gouw, JA; Hansel, A; Jefferson, A; Kley, D; de Laat, ATJ; Lal, S; Lawrence, MG; Lobert, JM; Mayol-Bracero, OL; Mitra, AP; Novakov, T; Oltmans, SJ; Prather, KA; Reiner, T; Rodhe, H; Scheeren, HA; Sikka, D; Williams, J

    2001-01-01

    The Indian Ocean Experiment (INDOEX) was an international, multiplatform field campaign to measure Long-range transport of air pollution from South and Southeast Asia toward the Indian Ocean during the dry monsoon season in January to March 1999. Surprisingly high pollution Levels were observed over

  13. Distribution of Oxycephalidae (Hyperiidea-Amphipoda) in the Indian Ocean- A statistical study

    Digital Repository Service at National Institute of Oceanography (India)

    Nair, K.K.C.; Jayalakshmy, K.V.

    Statistical analysis of oxycephalids on coexistence of the species showed two clusters of high affinity in the Arabian Sea, four in the Bay of Bengal, one in the South East Indian Ocean and three in the South West Indian Ocean. Species occurring...

  14. Retrieval of sea surface air temperature from satellite data over Indian Ocean: An empirical approach

    Digital Repository Service at National Institute of Oceanography (India)

    Sathe, P.V.; Muraleedharan, P.M.

    the surface air temperature and surface humidity is analysed by fitting a polynomial between the two for different regions of the Indian Ocean in different seasons. Taking into account the variation in surface air temperatures, the Indian Ocean is split in 14...

  15. Acoustic propagational characteristics and tomography studies of the northern Indian Ocean

    Digital Repository Service at National Institute of Oceanography (India)

    PrasannaKumar, S.; Somayajulu, Y.K.; Murty, T.V.R.

    The results of the acoustic tomographic studies carried out in five sections of the Northern Indian Ocean is given. The characteristics of the sound speed field of the northern Indian Ocean comprising of the Arabian Sea and the Bay of Bengal...

  16. The Indian Ocean Experiment : Widespread air pollution from South and Southeast Asia

    NARCIS (Netherlands)

    Lelieveld, J; Crutzen, PJ; Ramanathan, A.; Andreae, MO; Brenninkmeijer, CAM; Campos, T; Cass, GR; Dickerson, RR; Fischer, H; de Gouw, JA; Hansel, A; Jefferson, A; Kley, D; de Laat, ATJ; Lal, S; Lawrence, MG; Lobert, JM; Mayol-Bracero, OL; Mitra, AP; Novakov, T; Oltmans, SJ; Prather, KA; Reiner, T; Rodhe, H; Scheeren, HA; Sikka, D; Williams, J

    2001-01-01

    The Indian Ocean Experiment (INDOEX) was an international, multiplatform field campaign to measure Long-range transport of air pollution from South and Southeast Asia toward the Indian Ocean during the dry monsoon season in January to March 1999. Surprisingly high pollution Levels were observed over

  17. Weakening of Spring Wyrtki Jets in the Indian Ocean during 2006-2011

    Science.gov (United States)

    2012-04-05

    Weakening of spring Wyrtki jets in the Indian Ocean during 2006–2011 Sudheer Joseph,1 Alan J. Wallcraft,2 Tommy G. Jensen,2 M. Ravichandran,1 S. S. C...measurements of Indian Ocean equatorial currents near addu atoll., Deep Sea Res Oceanogr Abstr., 23(3), 211–221. Large, W. G., J. C. McWilliams , and S. C. Doney

  18. @iGlobigerina pachyderma@@ (Ehrenberg) in the shelf-slope sediments of northern Indian Ocean

    Digital Repository Service at National Institute of Oceanography (India)

    Setty, M.G

    resulting in the occurrence of this species in the northern Indian Ocean sediments, it is proposed that the forms which occur in the low latitudes (upto 25~'N) in the norhern Indian Ocean be referred to henceforth as (1) (a) @iG. pachyderma@@ (Ehrenberg...

  19. Larval and postlarval stages of Atypopenaeus Alcock (Decapoda, Penaeidae: Penaeinae) from Indian Ocean

    Digital Repository Service at National Institute of Oceanography (India)

    Paulinose, V.T.

    Two of the early mysis stages and an early postlarva of a species of Atypopenaeus are described here for the first time. A total of 15 specimens were obtained from the Indian Ocean during the International Indian Ocean Expedition (IIOE). The species...

  20. The meteorology of the Western Indian Ocean, and the influence of the East African Highlands.

    Science.gov (United States)

    Slingo, Julia; Spencer, Hilary; Hoskins, Brian; Berrisford, Paul; Black, Emily

    2005-01-15

    This paper reviews the meteorology of the Western Indian Ocean and uses a state-of-the-art atmospheric general circulation model to investigate the influence of the East African Highlands on the climate of the Indian Ocean and its surrounding regions. The new 44-year re-analysis produced by the European Centre for Medium range Weather Forecasts (ECMWF) has been used to construct a new climatology of the Western Indian Ocean. A brief overview of the seasonal cycle of the Western Indian Ocean is presented which emphasizes the importance of the geography of the Indian Ocean basin for controlling the meteorology of the Western Indian Ocean. The principal modes of inter-annual variability are described, associated with El Nino and the Indian Ocean Dipole or Zonal Mode, and the basic characteristics of the subseasonal weather over the Western Indian Ocean are presented, including new statistics on cyclone tracks derived from the ECMWF re-analyses. Sensitivity experiments, in which the orographic effects of East Africa are removed, have shown that the East African Highlands, although not very high, play a significant role in the climate of Africa, India and Southeast Asia, and in the heat, salinity and momentum forcing of the Western Indian Ocean. The hydrological cycle over Africa is systematically enhanced in all seasons by the presence of the East African Highlands, and during the Asian summer monsoon there is a major redistribution of the rainfall across India and Southeast Asia. The implied impact of the East African Highlands on the ocean is substantial. The East African Highlands systematically freshen the tropical Indian Ocean, and act to focus the monsoon winds along the coast, leading to greater upwelling and cooler sea-surface temperatures.

  1. Variability of upper ocean characteristics and tropical cyclones in the South West Indian Ocean

    Science.gov (United States)

    Mawren, Daneeja; Reason, Chris

    2017-04-01

    Track and intensity are key aspects of tropical cyclone behaviour. Intensity may be impacted by the upper ocean heat content integrated over a variable mixing length (known as Tdy) and barrier layer thickness (BLT). Here, the variability of Tdy and BLT in the South West Indian Ocean and their relationships with tropical cyclones are investigated. It is shown that rapid cyclone intensification is influenced by large Tdy values, thick barrier layers and the presence of anticyclonic eddies. For TC generation in the South West Indian Ocean, the parameter Tdy was found to be important. Large BLT overlay with large Tdy values during summer (r = 0.47, November-April) and are modulated by Rossby waves propagation. Tdy and BLT are strongly correlated with ENSO. The 1997-1998 El Niño shows a strong signal in Tdy, SST and BLT over the South West Indian Ocean. Thereafter, an increasing trend in Tdy occurred over most of the basin which may be associated with changes in atmospheric circulation. Increasing SST, Power Dissipation Index and frequency of Category-5 tropical cyclones also occurred from 1980 to 2010. To further examine the links between tropical cyclones, Tdy and BLT, an analysis of the ocean response to Category 5 Tropical Cyclone Bansi that developed near Madagascar during January 2015 is performed. Its unusual track was found to be linked with the strengthening of the monsoonal north westerlies while its rapid intensification from Category-2 to Category-4 was linked to a high-Tdy region, associated with a warm core eddy and large BLT.

  2. Exploration for nodules in the Central Indian Ocean Basin: Past present and the future

    Digital Repository Service at National Institute of Oceanography (India)

    ShyamPrasad, M.

    in the Indian Ocean is – 10-18 mil. Sq.km Total Estimated reserves in the Indian Ocean—0.15 trillion tones. Successful exploitation depends on : Technological Development, Geological and Environmental Factors, Metallurgical factors, Legal and political... receive valuable seagoing experience which in turn has been of immense use in developing its Marine Wing. There have been other spin offs as well : such as generation of capability for exploring our EEZ, the Indian Ocean Ridge systems, exploring...

  3. Dynamics of Eddies in the Southeastern Tropical Indian Ocean

    Science.gov (United States)

    Hanifah, F.; Ningsih, N. S.; Sofian, I.

    2016-08-01

    A holistic study was done on eddies in the Southeastern Tropical Indian Ocean (SETIO) using the HYbrid Coordinate Ocean Model (HYCOM) for 64 years (from 1950 to 2013). The results from the model were verified against the current and the Sea Surface Height Anomaly (SSHA) from Ocean Surface Current Analyses - Real time (OSCAR) and Archiving, Validation and Interpretation of Satellite Oceanographic Data (AVISO) respectively. The verification showed that the model simulates the condition in the area of study relatively well. We discovered that the local wind was not the only factor that contributed to the formation of eddies in the area. The difference in South Java Current (SJC) flow compared to the Indonesian Throughflow (ITF) and South Equatorial Current (SEC) flow as well as the difference in the relative velocity between the currents in the area led us to suspect that shear velocity may be responsible for the formation of eddies. The results from our model corroborated our prediction about shear velocity. Therefore, we attempted to explain the appearance of eddies in the SETIO based on the concept of shear velocity. By observing and documenting the occurrences of eddies in the area, we found that there are 8 cyclonic and 7 anticyclonic eddies in the SETIO. The distribution and frequency of the appearance of eddies varies, depending on the season.

  4. The influence of tropical Indian Ocean warming on the Southern Hemispheric stratospheric polar vortex

    Institute of Scientific and Technical Information of China (English)

    2009-01-01

    During the past decades, concurrent with global warming, most of global oceans, particularly the tropical Indian Ocean, have become warmer. Meanwhile, the Southern Hemispheric stratospheric polar vortex (SPV) exhibits a deepening trend. Although previous modeling studies reveal that radiative cooling effect of ozone depletion plays a dominant role in causing the deepening of SPV, the simulated ozone-depletion-induced SPV deepening is stronger than the observed. This suggests that there must be other factors canceling a fraction of the influence of the ozone depletion. Whether the tropical Indian Ocean warming (IOW) is such a factor is unclear. This issue is addressed by conducting ensemble atmospheric general circulation model (AGCM) experiments. And one idealized IOW with the amplitude as the observed is prescribed to force four AGCMs. The results show that the IOW tends to warm the southern polar stratosphere, and thus weakens SPV in austral spring to summer. Hence, it offsets a fraction of the effect of the ozone depletion. This implies that global warming will favor ozone recovery, since a warmer southern polar stratosphere is un-beneficial for the formation of polar stratospheric clouds (PSCs), which is a key factor to ozone depletion chemical reactions.

  5. The influence of tropical Indian Ocean warming on the Southern Hemispheric stratospheric polar vortex

    Institute of Scientific and Technical Information of China (English)

    LI ShuangLin

    2009-01-01

    During the past decades,concurrent with global warming,most of global oceans,particularly the tropical Indian Ocean,have become warmer.Meanwhile,the Southern Hemispheric stratospheric polar vortex (SPV) exhibits a deepening trend.Although previous modeling studies reveal that radiative cooling effect of ozone depletion plays a dominant role in causing the deepening of SPV,the simulated ozone-depletion-induced SPV deepening is stronger than the observed.This suggests that there must be other factors canceling a fraction of the influence of the ozone depletion.Whether the tropical Indian Ocean warming (IOW) is such a factor is unclear.This issue is addressed by conducting ensemble atmospheric general circulation model (AGCM) experiments.And one idealized IOW with the amplitude as the observed is prescribed to force four AGCMs.The results show that the IOW tends to warm the southern polar stratosphere,and thus weakens SPV in austral spring to summer.Hence,it offsets a fraction of the effect of the ozone depletion.This implies that global warming will favor ozone recovery,since a warmer southern polar stratosphere is un-beneficial for the formation of polar stratospheric clouds (PSCs),which is a key factor to ozone depletion chemical reactions.

  6. The Indian Ocean tsunami and private donations to NGOs.

    Science.gov (United States)

    Kim, Youngwan; Nunnenkamp, Peter; Bagchi, Chandreyee

    2016-10-01

    Non-governmental organisations (NGOs) are widely believed to raise their flag in humanitarian hotspots with a strong media presence in order to attract higher private donations. We assess this hypothesis by comparing the changes in donations between US-based NGOs with and without aid operations in the four countries most affected by the tsunami in the Indian Ocean in 2004. Simple before-after comparisons tend to support the hypothesis that 'flying the flag' helps attract higher private donations. However, performing a difference-in-difference-in-differences (DDD) approach, we find only weak indications that private donors systematically and strongly preferred NGOs with operations in the region. Extended specifications of the baseline regressions reveal that our major findings are robust. NGO heterogeneity matters in some respects, but the DDD results hold when accounting for proxies of the NGOs' reputation and experience.

  7. The monsoon currents in the north Indian Ocean

    Digital Repository Service at National Institute of Oceanography (India)

    Shankar, D.; Vinayachandran, P.N.; Unnikrishnan, A.S.

    in these ?snap- 40 E 50 E 60 E 70 E 80 E 90 E 100 E 10 S 0 10 N 20 N 30 N SECC SECEACC SC EICC EC SMC SMC LH SEC SECC EC EACC SC WICC EICC WMC Schematic of circulation in the Indian Ocean GW LL SMC SMC WMC WICC July IndiaOman Somalia Sri Lanka Arabian Sea Bay... of Bengal Andaman Sea Sumatra 40 E 50 E 60 E 70 E 80 E 90 E 100 E 10 S 0 10 N 20 N 30 N January IndiaOman Somalia Sri Lanka Arabian Sea Bay of Bengal Andaman Sea Sumatra Fig. 27. Schematic representation of the circulation, as described in this paper...

  8. Westward propagating twin gyres in the equatorial Indian Ocean

    Science.gov (United States)

    Reddy, P. Rahul Chand; Salvekar, P. S.; Deo, A. A.; Ganer, D. W.

    2004-01-01

    A reduced-gravity (1$\\frac{1}{2-layer) model forced by daily climatological winds simulates twin, anticyclonic gyres, which propagate westward on either side of the equator. The gyres form at the beginning of both the Southwest Monsoon and the Northeast monsoon in the equatorial eastern Indian Ocean, and subsequently propagate across the basin. Their existence is supported by velocity observations taken during WOCE in 1995 and by TOPEX/Poseidon sea-level observations during 1993. They are also present in the ECCO model/data product. They form at the front of a Rossby-wave packet generated by the reflection of the equatorial jet (EJ) from the eastern boundary of the basin. They are likely either Rossby solitons or result from the nonlinear interaction between the EJ and the Rossby-wave front.

  9. Analysis of Tropical Cyclone Tracks in the North Indian Ocean

    Science.gov (United States)

    Patwardhan, A.; Paliwal, M.; Mohapatra, M.

    2011-12-01

    Cyclones are regarded as one of the most dangerous meteorological phenomena of the tropical region. The probability of landfall of a tropical cyclone depends on its movement (trajectory). Analysis of trajectories of tropical cyclones could be useful for identifying potentially predictable characteristics. There is long history of analysis of tropical cyclones tracks. A common approach is using different clustering techniques to group the cyclone tracks on the basis of certain characteristics. Various clustering method have been used to study the tropical cyclones in different ocean basins like western North Pacific ocean (Elsner and Liu, 2003; Camargo et al., 2007), North Atlantic Ocean (Elsner, 2003; Gaffney et al. 2007; Nakamura et al., 2009). In this study, tropical cyclone tracks in the North Indian Ocean basin, for the period 1961-2010 have been analyzed and grouped into clusters based on their spatial characteristics. A tropical cyclone trajectory is approximated as an open curve and described by its first two moments. The resulting clusters have different centroid locations and also differently shaped variance ellipses. These track characteristics are then used in the standard clustering algorithms which allow the whole track shape, length, and location to be incorporated into the clustering methodology. The resulting clusters have different genesis locations and trajectory shapes. We have also examined characteristics such as life span, maximum sustained wind speed, landfall, seasonality, many of which are significantly different across the identified clusters. The clustering approach groups cyclones with higher maximum wind speed and longest life span in to one cluster. Another cluster includes short duration cyclonic events that are mostly deep depressions and significant for rainfall over Eastern and Central India. The clustering approach is likely to prove useful for analysis of events of significance with regard to impacts.

  10. Predictability of the Indian Ocean Dipole in the coupled models

    Science.gov (United States)

    Liu, Huafeng; Tang, Youmin; Chen, Dake; Lian, Tao

    2017-03-01

    In this study, the Indian Ocean Dipole (IOD) predictability, measured by the Indian Dipole Mode Index (DMI), is comprehensively examined at the seasonal time scale, including its actual prediction skill and potential predictability, using the ENSEMBLES multiple model ensembles and the recently developed information-based theoretical framework of predictability. It was found that all model predictions have useful skill, which is normally defined by the anomaly correlation coefficient larger than 0.5, only at around 2-3 month leads. This is mainly because there are more false alarms in predictions as leading time increases. The DMI predictability has significant seasonal variation, and the predictions whose target seasons are boreal summer (JJA) and autumn (SON) are more reliable than that for other seasons. All of models fail to predict the IOD onset before May and suffer from the winter (DJF) predictability barrier. The potential predictability study indicates that, with the model development and initialization improvement, the prediction of IOD onset is likely to be improved but the winter barrier cannot be overcome. The IOD predictability also has decadal variation, with a high skill during the 1960s and the early 1990s, and a low skill during the early 1970s and early 1980s, which is very consistent with the potential predictability. The main factors controlling the IOD predictability, including its seasonal and decadal variations, are also analyzed in this study.

  11. Excitation of Annual Polar Motion by the Pacific, Atlantic and Indian Oceans

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    The global oceans play important roles in exciting the annual polar motion besides the atmosphere. However, it is still unclear about how large the regional oceans contribute to the annual polar motion. We investigate systemically the contributions of the Pacific, Atlantic and Indian Oceans to the excitation of the annual polar motion, based on the output data of ocean current velocity field and ocean bottom pressure field from "Estimating the Circulation and Climate of the Ocean (ECCO)" ocean circulation model over the period 1993-2005. The result shows that due to its particular location and shape, the Atlantic Ocean makes a less significant contribution to the x-component of the annual polar motion excitation than the Pacific and Indian Oceans, while all these three oceans contribute to the y-component of the annual polar motion excitation to some extent.

  12. A tropospheric ozone maximum over the equatorial Southern Indian Ocean

    Directory of Open Access Journals (Sweden)

    L. Zhang

    2012-05-01

    Full Text Available We examine the distribution of tropical tropospheric ozone (O3 from the Microwave Limb Sounder (MLS and the Tropospheric Emission Spectrometer (TES by using a global three-dimensional model of tropospheric chemistry (GEOS-Chem. MLS and TES observations of tropospheric O3 during 2005 to 2009 reveal a distinct, persistent O3 maximum, both in mixing ratio and tropospheric column, in May over the Equatorial Southern Indian Ocean (ESIO. The maximum is most pronounced in 2006 and 2008 and less evident in the other three years. This feature is also consistent with the total column O3 observations from the Ozone Mapping Instrument (OMI and the Atmospheric Infrared Sounder (AIRS. Model results reproduce the observed May O3 maximum and the associated interannual variability. The origin of the maximum reflects a complex interplay of chemical and dynamic factors. The O3 maximum is dominated by the O3 production driven by lightning nitrogen oxides (NOx emissions, which accounts for 62% of the tropospheric column O3 in May 2006. We find the contribution from biomass burning, soil, anthropogenic and biogenic sources to the O3 maximum are rather small. The O3 productions in the lightning outflow from Central Africa and South America both peak in May and are directly responsible for the O3 maximum over the western ESIO. The lightning outflow from Equatorial Asia dominates over the eastern ESIO. The interannual variability of the O3 maximum is driven largely by the anomalous anti-cyclones over the southern Indian Ocean in May 2006 and 2008. The lightning outflow from Central Africa and South America is effectively entrained by the anti-cyclones followed by northward transport to the ESIO.

  13. Effect of riverine freshwater discharge in salinity simulations over the northern Indian Ocean

    Science.gov (United States)

    Kalathupurath Kuttan, Sandeep; Pant, Vimlesh; Devendra Rao, Ambarukhana

    2017-04-01

    Sea surface salinity (SSS) in the north Indian Ocean (NIO) exhibits contrasting spatial distribution, particularly in the two semi-enclosed basins namely the Arabian sea (AS) and Bay of Bengal (BoB). BoB experiences excess amount of freshwater inflow from rivers as well as from the surplus of precipitation over evaporation (E-P) and thus maintains a fresher surface water throughout the year as compared to AS. Major rivers such as Ganges, Brahmaputra, Mahanadi, Godavari, Krishna, and Irrawaddy discharge large amount of freshwater volume to the BoB. The input of relatively less saline waters by the Indonesian Throughflow (ITF) makes the eastern equatorial IO fresher. Substantial change in salinity and temperature due to river runoff results in a change in ambient sea-water density near river mouths in coastal regions. In the present study, we simulate the circulation features of the NIO using a free-surface primitive equation ocean general circulation model 'Regional Ocean Modeling System' (ROMS). The model domain extends from 30°S-30°N, 30°E-120°E with 1/4 x 1/4 degree resolution in the horizontal and 40 vertical terrain following sigma levels. The model is initialized with annual mean climatology of temperature and salinity from World Ocean Atlas 2009 (WOA09) and forced with daily climatological winds from Quikscat and ASCAT and other atmospheric forcing fields from TropFlux. Different numerical experiments were carried out to understand the impact of freshwater forcing on the sea surface salinity (SSS) simulations. Model simulations and available in-situ and satellite observations utilized to understand processes, particularly the contribution of freshwater forcing, controlling the SSS spatial and seasonal variations in various sectors of the Indian Ocean.

  14. Evaluation of OSCAR ocean surface current product in the tropical Indian Ocean using in situ data

    Indian Academy of Sciences (India)

    Rajesh Sikhakolli; Rashmi Sharma; Sujit Basu; B S Gohil; Abhijit Sarkar; K V S R Prasad

    2013-02-01

    The OSCAR (ocean surface current analysis real-time),which is a product derived from various satellite observations,has been evaluated in the tropical Indian Ocean (TIO)in two di fferent ways.First,the OSCAR-derived monthly climatology has been compared with available drifter-derived climatology in the TIO.From the comparison of the two climatologies,one can infer that OSCAR product is able to capture the variabilities of the well-known surface current systems in the TIO reasonably well.Fourier analysis of the major current systems,as reproduced by OSCAR,shows that the dominant annual and semiannual periodicities,known to exist in these systems,have been faithfully picked up by OSCAR. Next,the evaluation has been carried out by comparing the OSCAR currents with currents measured by moored buoys.The zonal component of OSCAR-current is in good agreement with corresponding component of buoy-observed current with a correlation exceeding 0.7,while the match between the meridional components is poorer.The locations of the peaks of the mean and eddy kinetic energies are matching in both the climatologies,although the peak in the drifter climatology is stronger than the same in the OSCAR product.Finally,an important feature of Indian Ocean circulation,namely the reverse Wyrtki jet,occurring during anomalous dipole years,has been well-reproduced by OSCAR currents.

  15. Temperature Data From AUSTRALIA STAR and Other Platforms From Indian Ocean and South Pacific Ocean From 19860929 to 19890106 (NODC Accession 8900196)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Temperature data from Australia Star and other ships from Indian Ocean and South Pacific Ocean from September 29, 1986 to January 6, 1989. The data were collected by...

  16. Mercury content in commercial pelagic fish and its risk assessment in the Western Indian Ocean.

    Science.gov (United States)

    Kojadinovic, Jessica; Potier, Michel; Le Corre, Matthieu; Cosson, Richard P; Bustamante, Paco

    2006-08-01

    As top predators of pelagic food webs, large fish naturally bioaccumulate mercury (Hg). Determining Hg burdens in commercialized fish is essential considering the concern about effects of contaminants on human health and the legal thresholds that are therefore set for local consumption and/or exportation. Total Hg levels were measured in the muscular tissue of 183 fish of five commercially important species from the tropical zone of the Western Indian Ocean. All individuals were measured and sexed in order to study the impregnation of Hg with size and sex within each species. Values of Hg found in this part of the Indian Ocean were comparable to Hg in muscular tissue of the same species studied in other areas. The highest Hg levels were noted in Swordfish (Xiphias gladius) caught in waters surrounding Reunion Island (3.97+/-2.67 microg g(-1) dry weight). Following the Swordfish, in decreasing order of Hg content, were the Yellowfin Tuna (Thunnus albacares) and the Skipjack (Katsuwonus pelamis), then the Common Dolphinfish (Coryphaena hippurus) and the Wahoo (Acanthocybium solandri). In the North of the Mozambique Channel, Swordfish had higher Hg levels than Yellowfin Tunas, and Dolphinfish exhibited intermediate Hg levels. The size of a fish was a determining factor of its Hg burden, as was the species. Differences in size-normalized Hg levels were observed between the two study zones for Swordfish and Common Dolphinfish. Sex, in contrast, did not influence Hg levels suggesting that females and males have similar feeding habits. The muscular Hg levels presented here suggest that consumers of fish originating from the Western Indian Ocean should limit themselves to one Swordfish based meal per week, or one fish meal a day if they choose to eat tuna or Common Dolphinfish.

  17. An Ocean Reanalysis System for the Joining Area of Asia and Indian-Pacific Ocean

    Institute of Scientific and Technical Information of China (English)

    YAN Chang-Xiang; ZHU Jiang; XIE Ji-Ping

    2010-01-01

    An ocean reanalysis system for the joining area of Asia and Indian-Pacific Ocean(AIPO)has been developed and is currently delivering reanalysis data sets for study on the air-sea interaction over AIPO and its climate variation over China in the inter-annual time scale.This system consists of a nested ocean model forced by atmospheric reanalysis,an ensemble-based multivariate ocean data assimilation system and various ocean observations.The following report describes the main components of the data assimilation system in detail.The system adopts an ensemble optimal interpolation scheme that uses a seasonal update from a free running model to estimate the background error covariance matrix.In view of the systematic biases in some observation systems,some treatments were performed on the observations before the assimilation.A coarse resolution reanalysis dataset from the system is preliminarily evaluated to demonstrate the performance of the system for the period 1992 to 2006 by comparing this dataset with other observations or reanalysis data.

  18. Signal propagations and linkages of subsurface temperature anomalies in the tropical Pacific and Indian Ocean

    Institute of Scientific and Technical Information of China (English)

    QIAN Weihong; HU Haoran

    2005-01-01

    The propagation characteristics of signals along different zonal-time profiles are analyzed using surface and subsurface temperature anomalies over the tropical Pacific and Indian oceans. Analyses show that there are intrinsic relationships between El Nino events in the eastern equatorial Pacific and dipole events in the equatorial Indian Ocean. In the region of tropical North Pacific between the equator and 16°N, there is a circle of propagation of subsurface temperature anomalies. El Nino events only happen when the warm subsurface signals reach the eastern equatorial Pacific. Dipole events are characterized when a warm subsurface signal travels along off-equatorial Indian Ocean to the western boundary. From these analyses, we believe that subsurface temperature anomalies can be considered to be the oceanographic early signal to forecast El Nino events in Pacific Ocean and dipole events in Indian Ocean, respectively.

  19. Gravity anomalies over the central Indian ridge between 3 degree S and 11 degree S, Indian Ocean: Segmentation and crustal structure

    Digital Repository Service at National Institute of Oceanography (India)

    Samudrala, K.; KameshRaju, K.A; RamaRao, P.

    High-resolution shipboard geophysical investigations along the Indian Ocean ridge system are sparse especially over the Carlsberg and Central Indian ridges. In the present study, the shipboard gravity and multibeam bathymetry data acquired over a...

  20. The hydromedusae and water masses of the Indian Ocean

    Directory of Open Access Journals (Sweden)

    D. Navas-Pereira

    1991-01-01

    Full Text Available This analysis of distribution and abundance of species of Hydromedusae completes a report (Vannucci & Navas, 1973b on the ecology of Indian Ocean Hydromedusae based on the zooplankton collected during the International Indian Ocean Expedition (IIOE. Distribution and abundance are taken here to be the ecological expression of variability of species in space and time. The aim was to identify the biological signature of below surface water masses that cannot be identified by remote sensing techniques. Selected species were taken as biological units, the oceanic water masses as defined by their T-S and T-O2 diagrammes were taken as the non biological units. Taken together they define different ecosystems of the Indian Ocean. About 45,000 specimens of hydromedusae taken at 480 stations were sorted from 900 plankton samples and all specimens were determined and counted. Several hauls, mostly stratified, were taken with closing nets, but not all contained hydromedusae. The distribution of each species was studied in relation to water salinity, temperature and dissolved oxygen; the limits of ecological tolerance and preference were defined by the environmental characteristics of the layers sampled by the nets and are given for each species. These can be grouped as follows: 1. Deep water species, cold tolerant, often eurytopic; 2. Antarctic species, cold loving, usually stenothermal with preference for low salinity; 3. Indian Ocean Central Water species, with preference for temperature lower than 19ºC and salinity not much higher than 35%o, usually found at sub-surface or intermediate depths, they may spread into the Arabian Sea and Bay of Bengal in surface layers; 4. Indian Ocean Equatorial System species, warm tolerant, usually prefer comparatively low salinity, high temperature and high oxygen content; 5. Bay of Bengal Surface Water species, found in surface layers of the Bay, with preference for low salinity, high temperature and high oxygen content

  1. An initial assessment of Ocean Energy Resources in the Western Indian Ocean

    Energy Technology Data Exchange (ETDEWEB)

    Hammar, Linus; Ehnberg, Jimmy

    2011-07-01

    The demand for modern energy is accelerating in the Western Indian Ocean (coastal East Africa). A mixture of different energy sources will by necessity be the option for the long-term future and the most adequate solutions naturally vary between locations. The vast coastlines and many islands of the region make ocean energy (OE) a relevant field to explore. With an early understanding of the resources strategic planning towards sustainable development is facilitate. Moreover, early awareness facilitates a respectful integration of new technologies in the fragile and for local people invaluable ecosystems. This study provides a first assessment of the frontier OE technologies and corresponding resources in the region. Five renewable Ocean Energy technologies have been reviewed and the physical resource abundance for respective energy source has been screened based on available literature and databases. The Western Indian Ocean is shared between nine African countries and two French departments. The studied countries are the Comoros, Kenya, Madagascar, Mauritius, Mayotte, Mozambique, the Seychelles, Tanzania, and Reunion. The energy situation is insufficient throughout the region, either as consequence of lacking domestic energy sources or rudimentary grid extension. The results indicate that ocean energy resources are abundant in much of the region, but different sources have potential in different areas. Several countries have favourable physical conditions for extracting energy from waves and from the temperature gradient between the surface and deep water. Wave power is a young but currently available technology which can be utilized for both large- and small-scale applications. Ocean Thermal Energy Conversion is a technology under development that, once proven, may be applicable for large-scale power production. The physical conditions for small-scale tidal barrage power, tidal stream power, and ocean current power are less pronounced but may be of interest at

  2. The Early Opening of the Indian Ocean: An African Perspective

    Science.gov (United States)

    Gaina, C.; Labails, C.; Reeves, C.

    2010-12-01

    The timing and causes that led to Gondwana break-up remain controversial to date. An earlier opening of the Central Atlantic (Late Sinemurian, ca. 190 Ma) has been recently suggested, and new published models of the East Gondwana evolution allow for a breakup timing closer to Karoo volcanism (ca. 180 Ma). In this contribution we revise the early evolution of the Indian Ocean with an emphasis on the opening of the West Somali basin. It is generally accepted that the continental breakup of Gondwana in the East African region began with the onset of the southward drift of Madagascar (then connected with Antarctica and India) along the Davie Fracture Zone probably during the Early-Mid Jurassic. This motion led to the opening of the western Somali Basin. Although published kinematic models are able to explain and date some of the broad scale features of the Somali and Mozambique oceanic basins, the exact timing of rifting, the early stages of seafloor spreading and the timing of seafloor cessation in the western Somali Basin remain debatable. Our new study aims to investigate the relationship between the long history of rifting along the East African margins and the breakup structures by constructing a consistent database of structural elements and information about their evolution from updated published literature. A thorough investigation of the potential field data (magnetic and gravity anomalies) and an analysis of multichannel seismic reflection helped to identify deep crustal structure and continent-ocean transition zone in the study area. Magnetic anomaly data is re-analyzed and compared with published results in adjacent basins. The evolution of the East African margin (along Somali and Mozambique basins) is shown in a regional framework where consequences of an independent motion of the Madagascar plate are discussed. In addition, the timing of an Early Jurassic breakup of East Gondwana and possible mechanisms are presented within a regional geological context.

  3. The ocean-atmosphere response to wind-induced thermocline changes in the tropical South Western Indian Ocean

    NARCIS (Netherlands)

    Manola, Iris; Selten, F. M.; De Ruijter, W. P M; Hazeleger, W.

    2014-01-01

    In the Indian Ocean basin the sea surface temperatures (SSTs) are most sensitive to changes in the oceanic depth of the thermocline in the region of the Seychelles Dome. Observational studies have suggested that the strong SST variations in this region influence the atmospheric evolution around the

  4. Oceanic crust formation in the Egeria Fracture Zone Complex (Central Indian Ocean)

    Science.gov (United States)

    Le Minor, Marine; Gaina, Carmen; Sigloch, Karin; Minakov, Alexander

    2016-04-01

    This study aims to analyse in detail the oceanic crust fabric and volcanic features (seamounts) formed for the last 10 million years at the Central Indian Ridge between 19 and 21 latitude south. Multibeam bathymetry and magnetic data has been collected in 2013 as part of the French-German expedition RHUM-RUM (Reunion hotspot and upper mantle - Reunion's unterer mantel). Three long profiles perpendicular on the Central Indian Ridge (CIR), south of the Egeria fracture zone, document the formation of oceanic crust since 10 million years, along with changes in plate kinematics and variations in the magmatic input. We have inspected the abyssal hill geometry and orientation along conjugate oceanic flanks and within one fracture zone segment where we could identify J-shaped features that are indicators of changes in plate kinematics. The magnetic anomaly data shows a slight asymmetry in seafloor spreading rates on conjugate flanks: while a steady increase in spreading rate from 10 Ma to the present is shown by the western flank, the eastern part displays a slowing down from 5 Ma onwards. The deflection of the anti J-shaped abyssal hill lineations suggest that the left-stepping Egeria fracture zone complex (including the Egeria, Flinders and an un-named fracture zone to the southeast) was under transpression from 9 to 6 Ma and under transtension since 3 Ma. The transpressional event was triggered by a clockwise mid-ocean ridge reorientation and a decrease of its offset, whereas the transtensional regime was probably due to a counter-clockwise change in the spreading direction and an increase of the ridge offset. The new multibeam data along the three profiles reveal that crust on the eastern side is smoother (as shown by the abyssal hill number and structure) and hosts several seamounts (with age estimations of 7.67, 6.10 and 0.79 Ma), in contrast to the rougher conjugate western flank. Considering that the western flank was closer to the Reunion plume, and therefore

  5. Importance of the Indian Ocean for simulating rainfall anomalies over eastern and southern Africa

    Science.gov (United States)

    Goddard, Lisa; Graham, Nicholas E.

    1999-08-01

    The relative contributions of the Indian Ocean and Pacific Ocean sea surface temperatures (SSTs) to the rainfall variability over eastern central, and southern Africa during the austral spring-summer are examined. The variability of African rainfall is statistically related to both oceans, but the variability in the two oceans is also related. To separate the effects of the Indian and Pacific Oceans, a suite of numerical model simulations is presented: GOGA, the atmosphere is forced by observed SSTs globally; IOGA, the atmosphere is forced by observed SSTs only in the Indian Ocean basin; and POGA, the atmosphere is forced by observed SSTs only in the tropical Pacific basin. While the SST variability of the tropical Pacific exerts some influence over the African region, it is the atmospheric response to the Indian Ocean variability that is essential for simulating the correct rainfall response over eastern, central, and southern Africa. Analyses of the dynamical response(s) seen in the numerical experiments and in the observations indicate that the Pacific and Indian Oceans have a competing influence over the Indian Ocean/African region. This competition is related to the influence of the two oceans on the Walker circulation and the consequences of that variability on low-level fluxes of moisture over central and southern Africa. Finally, given the high correlation found between SST variability in the Indian and Pacific Oceans with the Pacific leading by ˜3 months, we speculate on an approach to long-lead dynamical climate prediction over central-east and southern Africa.

  6. Rayleigh Wave Phase Velocity in the Upper Mantle Beneath the Indian Ocean

    Science.gov (United States)

    Godfrey, K. E.; Dalton, C. A.; Ritsema, J.

    2016-12-01

    Most of what is currently understood about the seismic properties of oceanic upper mantle is based on either global studies or regional studies of the upper mantle beneath the Pacific Ocean. However, global seismic models and geochemical studies of mid-ocean ridge basalts indicate differences in the properties of the upper mantle beneath the Pacific, Atlantic, and Indian oceans. Though the Indian Ocean is not as well studied seismically, it is host to a number of geologically interesting features including 16,000 km of mid-ocean ridge with a range of spreading rates from 14 mm/yr along the Southwest Indian Ridge to 55-75 mm/yr along the Southeast Indian Ridge. The Indian Ocean also contains multiple volcanic hotspots, the Australian-Antarctic Discordance, and a low geoid anomaly south of India, and it overlies a portion of a large low-shear-velocity province. We are using Rayleigh waves to construct a high-resolution seismic velocity model of the Indian Ocean upper mantle. We utilize a global dataset of phase delays measured at 20 periods, between 37 and 375 seconds; the dataset includes between 700 and 20,000 that traverse our study region exclusively, with a larger number of paths at shorter periods. We explore variations in phase velocity using two separate approaches. One, we allow phase velocity to vary only as a function of seafloor age. Two, we perform a damped least-squares inversion to solve for 2-D phase velocity maps at each period. Preliminary results indicate low velocities along the Southeast Indian Ridge and Central Indian Ridge, but the expected low velocities are less apparent along the slow-spreading Southwest Indian Ridge. We observe a region of fast velocities extending from Antarctica northward between the Kerguelen and Crozet hotspots, and lower than expected velocities beneath the Reunion hotspot. Additionally, we find low velocities associated with a region of extinct seafloor spreading in the Wharton basin.

  7. Future change of the Indian Ocean basin-wide and dipole modes in the CMIP5

    Science.gov (United States)

    Chu, Jung-Eun; Ha, Kyung-Ja; Lee, June-Yi; Wang, Bin; Kim, Byeong-Hee; Chung, Chul Eddy

    2014-07-01

    The Indian Ocean sea surface temperature (SST) variability has been represented with the two dominant variability modes: the Indian Ocean basin-wide (IOBW) and dipole (IOD) modes. Here we investigate future changes of the two modes together with mean state and El Niño and Southern Oscillation (ENSO) relationship under the anthropogenic global warming using 20 coupled models that participated in the phase five of Coupled Model Intercomparison Project by comparing the historical run from 1950 to 2005 and the RCP 4.5 run from 2050 to 2099. The five best models are selected based on the evaluation of the 20 models' performances in simulating the two modes and Indian Ocean basic state for the latest 56 years. They are capable of capturing the IOBW and IOD modes in their spatial distribution, seasonal cycle, major periodicity, and relationship with ENSO to some extent. The five best models project the significant changes in the Indian Ocean mean state and variability including the two dominant modes in the latter part of twenty-first century under the anthropogenic warming scenario. First, the annual mean climatological SST displays an IOD-like pattern change over the Indian Ocean with enhanced warming in the northwestern Indian Ocean and relatively weaker warming off the Sumatra-Java coast. It is also noted that the monthly SST variance is increased over the eastern and southwestern Indian Ocean. Second, the IOBW variability on a quasi-biennial time scale will be enhanced due to the strengthening of the ENSO-IOBW mode relationship although the total variance of the IOBW mode will be significantly reduced particularly during late summer and fall. The enhanced air-sea coupling over the Indian-western Pacific climate in response to El Nino activity in the future projection makes favorable condition for a positive IOD while it tends to derive relatively cold temperature over the eastern Indian Ocean. This positive IOD-like ENSO response weakens the relationship between the

  8. Genome microevolution of chikungunya viruses causing the Indian Ocean outbreak.

    Directory of Open Access Journals (Sweden)

    Isabelle Schuffenecker

    2006-07-01

    Full Text Available BACKGROUND: A chikungunya virus outbreak of unprecedented magnitude is currently ongoing in Indian Ocean territories. In Réunion Island, this alphavirus has already infected about one-third of the human population. The main clinical symptom of the disease is a painful and invalidating poly-arthralgia. Besides the arthralgic form, 123 patients with a confirmed chikungunya infection have developed severe clinical signs, i.e., neurological signs or fulminant hepatitis. METHODS AND FINDINGS: We report the nearly complete genome sequence of six selected viral isolates (isolated from five sera and one cerebrospinal fluid, along with partial sequences of glycoprotein E1 from a total of 127 patients from Réunion, Seychelles, Mauritius, Madagascar, and Mayotte islands. Our results indicate that the outbreak was initiated by a strain related to East-African isolates, from which viral variants have evolved following a traceable microevolution history. Unique molecular features of the outbreak isolates were identified. Notably, in the region coding for the non-structural proteins, ten amino acid changes were found, four of which were located in alphavirus-conserved positions of nsP2 (which contains helicase, protease, and RNA triphosphatase activities and of the polymerase nsP4. The sole isolate obtained from the cerebrospinal fluid showed unique changes in nsP1 (T301I, nsP2 (Y642N, and nsP3 (E460 deletion, not obtained from isolates from sera. In the structural proteins region, two noteworthy changes (A226V and D284E were observed in the membrane fusion glycoprotein E1. Homology 3D modelling allowed mapping of these two changes to regions that are important for membrane fusion and virion assembly. Change E1-A226V was absent in the initial strains but was observed in >90% of subsequent viral sequences from Réunion, denoting evolutionary success possibly due to adaptation to the mosquito vector. CONCLUSIONS: The unique molecular features of the analyzed

  9. Studying the Indian Ocean Ridge System: Agenda for the new century

    Digital Repository Service at National Institute of Oceanography (India)

    Mukhopadhyay, R.; Iyer, S.D.; Banerjee, R.; Drolia, R.K.

    Studies on the Indian Ocean Ridge System, though sporadic, was aimed to map the complete IORS petrologically and tectonically. Three areas are placed for immediate investigation; one in the slow spreading Carlsberg Ridge area, the second, along...

  10. North-south diversity of Scolecithricidae species (Copepoda: Calanoida) in the Indian Ocean

    Digital Repository Service at National Institute of Oceanography (India)

    Gopalakrishnan, T.C.; Balachandran, T.

    The effectiveness of north-south hydrographical barriers in restricting the distributions of Scolecithricidae species (Copepoda:Calanoida) in the euphotic zone of the Indian Ocean was studied. Twenty seven species belonging to 7 genera were...

  11. Low frequency variability of the Indian Ocean from TOPEX/POSEIDON sea surface height anomalies

    Digital Repository Service at National Institute of Oceanography (India)

    Somayajulu, Y.K.; Murty, V.S.N.; Sarma, Y.V.B.

    The sea surface height (SSH) anomalies derived from TOPEX/POSEIDON altimeter have been utilized to study the variability of surface circulation in the Indian Ocean during 1993-1999. The Western Bay, southeastern Arabian Sea, regions off Somalia...

  12. Variable relationships of DOC with oxygen in the northwestern Indian Ocean and their ecological implications

    Digital Repository Service at National Institute of Oceanography (India)

    Rajendran, A.; DileepKumar, M.; Ramaiah, N.; Ittekkot, V.; Desai, B.N.

    The relationships between DOC and AOU in the northwestern Indian Ocean regional variations reflecting the different biological characteristics dominanting the respective zones, resulting in the variable percentages of DOM respiration through nitrate...

  13. Temperature profile data from profiling drifter in the Indian, Southern, and Pacific Ocean (NODC Accession 9700028)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Temperature profile data were collected using the ALACE (Autonomous LAgrangian Circulation Explorer), which is a profiling drifter in the Indian, Southern, and...

  14. Five new species of the genus Dendronephthya Kukenthal, 1905, (Octocorallia: Nephtheidae) from the Indian Ocean

    NARCIS (Netherlands)

    Verseveldt, J.; Ofwegen, van L.P.

    1991-01-01

    Five new species of Dendronephthya from the Indian Ocean are described and figured: Dendronephthya (Morchellana) bruuni, D. (M.) hystricosa, D. (M.) pyriformis, D. (M.?) staphyloidea and D. (Roxasia) vervoorti.

  15. Melithaeidae (Coelenterata: Anthozoa) from the Indian Ocean and the Malay Archipelago

    NARCIS (Netherlands)

    Ofwegen, van L.P.

    1987-01-01

    Melithaeidae from the Indian Ocean and the Malay Archipelago are described and figured, including three new species: Clathraria maldivensis, C. omanensis and Acabaria andamanensis. A lectotype is designated for Acabaria variabilis (Hickson).

  16. Watermass structure in the western Indian Ocean: Part 1. Watermasses and their thermohaline indices

    Digital Repository Service at National Institute of Oceanography (India)

    Sastry, J.S.; Premchand, K.; Murty, C.S.

    The concept of "Indian Ocean Common Watermass" is introduced and its characteristics are defined. The temperature-salinity structures which would result when one, two or more watermasses of different temperature and salinity characteristics...

  17. Impact of global warming on cyclonic storms over north Indian Ocean

    Digital Repository Service at National Institute of Oceanography (India)

    RameshKumar, M.R.; Sankar, S.

    The impact of global warming on the cyclonic storms over the north Indian Ocean have been studied using a suite of multiple datasets that includes the NCEP/NCAR Reanalysis, the extended reconstruction sea surface temperature (ERSST) and tracks...

  18. A reduction in marine primary productivity driven by rapid warming over the tropical Indian Ocean

    Digital Repository Service at National Institute of Oceanography (India)

    Roxy, M.K.; Modi, A; Murtugudde, R.; Valsala, V.; Panickal, S.; PrasannaKumar, S.; Ravichandran, M.; Vichi, M.; Levy, M.

    during the past century-although the contribution of such a large warming to productivity changes has remained ambiguous. Earlier studies had described the western Indian Ocean as a region with the largest increase in phytoplankton during the recent...

  19. New ichthyoliths from ferromanganese crusts and nodules from the Central Indian Ocean Basin

    Digital Repository Service at National Institute of Oceanography (India)

    Gupta, S.M.

    Ferromanganese encrusted hardgrounds, their intraclasts and the nuclei of manganese nodules collected from the Central Indian Ocean basin have yielded plentiful numbers of ichthyoliths. Forty well-knon ichthyoliths, one new type and 35 new subtypes...

  20. Distribution, ecology and polymorphic behaviour of the genus Oxycephalus (Hyperiidea, Oxycephalidae) in the Indian Ocean

    Digital Repository Service at National Institute of Oceanography (India)

    Nair, K.K.C.

    two species. Females of O. latirostris collected from the Bay of Bengal and south-central Indian Ocean show pronounced dimorphic characters. Polymorphic behaviour is mostly restricted to O. piscator, mainly due to post-maturity growth. The geographic...

  1. Thermal structure of the Western Indian Ocean during the southwest monsoon, 1983

    Digital Repository Service at National Institute of Oceanography (India)

    Sarma, Y.V.B.; Sarma, M.S.S.; Rao, L.V.G.

    The thermal structure and the variability of heat content of the upper 400 m of the Western Indian Ocean were examined using the expendable bathythermograph (XBT) data collected onboard RV Sagar Kanya during July-August, 1983. Vertical displacement...

  2. New sea surface salinity product in the tropical Indian Ocean estimated from outgoing longwave radiation

    Digital Repository Service at National Institute of Oceanography (India)

    Subrahmanyam, B.; Murty, V.S.N.; O'Brien, J.J.

    The sea surface salinity (SSS) product as derived from space-borne satellite measurements of Outgoing Longwave Radiation (OLR), based on the algorithms developed by (1), is discussed for the tropical Indian Ocean (TIO) during the period 1995...

  3. Five new species of the genus Dendronephthya Kukenthal, 1905, (Octocorallia: Nephtheidae) from the Indian Ocean

    NARCIS (Netherlands)

    Verseveldt, J.; Ofwegen, van L.P.

    1991-01-01

    Five new species of Dendronephthya from the Indian Ocean are described and figured: Dendronephthya (Morchellana) bruuni, D. (M.) hystricosa, D. (M.) pyriformis, D. (M.?) staphyloidea and D. (Roxasia) vervoorti.

  4. Melithaeidae (Coelenterata: Anthozoa) from the Indian Ocean and the Malay Archipelago

    NARCIS (Netherlands)

    Ofwegen, van L.P.

    1987-01-01

    Melithaeidae from the Indian Ocean and the Malay Archipelago are described and figured, including three new species: Clathraria maldivensis, C. omanensis and Acabaria andamanensis. A lectotype is designated for Acabaria variabilis (Hickson).

  5. Mineralogy of polymetallic nodules and associated sediments from the Central Indian Ocean Basin

    Digital Repository Service at National Institute of Oceanography (India)

    Rao, V.P.

    Todorokite is the dominant mineral phase in the nodules of the northern Central Indian Ocean Basin. These nodules are characterised by a rough surface texture, are relatively rich in Mn, Cu and Ni, and are associated with radiolarian sediments rich...

  6. Underwater geomorphology as a function of the variations in ferromanganese nodule characters in the Indian Ocean

    Digital Repository Service at National Institute of Oceanography (India)

    Mukhopadhyay, R.; Banerjee, G.

    Ferromanganese nodules from three areas in the northern part of the Central Indian Ocean Basin have been studied. Statistical analysis shows significant variations in morphological and physical characters of nodules between the area S sub(5), which...

  7. Determination of vertical velocities in the equatorial part of the western Indian Ocean

    Digital Repository Service at National Institute of Oceanography (India)

    Bahulayan, N.; Varadachari, V.V.R.

    Using steady state two-dimensional turbulent diffusion equations of salt and heat some important characteristics of vertical circulation in the equatorial part of the Indian Ocean have been evaluated and discussed. Upwelling and sinking velocities...

  8. Geophysical and geological surveys along the northeastern flank of Mount error, Northwestern Indian Ocean

    Digital Repository Service at National Institute of Oceanography (India)

    Ramana, M.V.; Rajendraprasad, B.; Hansen, R.D.

    Bathymetry, multichannel continuous seismic reflection, magnetic and gravity surveys and sampling were carried out over Mount Error in the northwestern Indian Ocean and along the northeastern flank of the seamount, to study the nature of its...

  9. A new species of Heterospio (Annelida, longosomatidae) from the Indian Ocean

    Digital Repository Service at National Institute of Oceanography (India)

    Parapar, J.; Vijapure, T.; Moreira, J.; Sukumaran, S.

    the Indian Ocean. Heterospio indica sp. nov. is mainly characterised by the conspicuous flattening of the distal half of capillary chaetae located in anterior elongated segments. Several body characters of high taxonomic relevance in the genus are examined...

  10. Relationships between Indian summer monsoon rainfall and ice cover over selected oceanic regions

    Digital Repository Service at National Institute of Oceanography (India)

    Gopinathan, C.K.

    The variations in oceanic ice cover at selected polar regions during 1973 to 1987 have been analysed in relation to the seasonal Indian summer monsoon rainfall. The ice cover over the Arctic regions in June has negative relationship (correlation...

  11. ENSO modulation of interannual variability of dust aerosols over the northwest Indian ocean

    Digital Repository Service at National Institute of Oceanography (India)

    Banerjee, P.; PrasannaKumar, S.

    Mineral dust is known to affect many aspects of the climate of the north Indian Ocean (IO) However, what controls its interannual variability over this region is largely unknown The authors study the mechanism controlling the interannual variability...

  12. Distribution of luminous bacteria and bacterial luminescence in the equatorial region of the Indian Ocean

    Digital Repository Service at National Institute of Oceanography (India)

    Ramaiah, N.; Chandramohan, D.

    The number and species composition of luminous bacteria in seawater and zooplankton samples collected in the equatorial region of the Indian Ocean (Long. 49 degrees -60 degrees E; Lat. 4 degrees N-6 degrees S) were studied. While luminous bacteria...

  13. Contrasted associations between seabirds and marine mammals across four biomes of the southern Indian Ocean

    National Research Council Canada - National Science Library

    Thiebot, Jean-Baptiste; Weimerskirch, Henri

    2013-01-01

    ... few appropriate data exist. In this study, we aimed at quantifying and qualifying these interactions, based on long-term standardised at-sea observations carried out from 1978 to 2005 in the whole southern Indian Ocean. We (1...

  14. A decade of physical and biogeochemical measurements in the Northern Indian Ocean.

    Digital Repository Service at National Institute of Oceanography (India)

    PrasannaKumar, S.; Sardesai, S.; Ramaiah, N.

    of the coupling between the physical and biogeochemical fields in the northern Indian Ocean over the seasonal scale have enhanced tremendously, a sustained regional observational network including repeat sections, moored arrays and drifters is needed...

  15. New insights into the tectonic evolution of the Andaman basin, northeast Indian Ocean

    Digital Repository Service at National Institute of Oceanography (India)

    KameshRaju, K.A.; Ramprasad, T.; Rao, P.S.; Rao, B.R.; Varghese, J.

    Multibeam swath bathymetry data acquired over an area of about 30 000 km 2 ,together with magnetic and single channel seismic data, have been analyzed to understand the tectonic evolution of the Andaman basin,northeast Indian Ocean. Swath bathymetry...

  16. Differential Heating in the Indian Ocean Differentially Modulates Precipitation in the Ganges and Brahmaputra Basins

    Data.gov (United States)

    U.S. Geological Survey, Department of the Interior — This dataset provides an assessment of the differential heating in the Indian Ocean (IO) and the subsequent modulation of the Ganges and Brahmaputra precipitation....

  17. Thermal structure and flow patterns around Seychelles group of Islands (Indian Ocean) during austral autumn

    Digital Repository Service at National Institute of Oceanography (India)

    Vethamony, P.; RameshBabu, V.; RameshKumar, M.R.

    Properties of thermal structure in the upper 750 m around the Seychelles group of islands in the Indian Ocean, based on Expendable Bathythermograph (XBT) data collected in March 1984, are presented along with the inferred flow patterns...

  18. Carbonate preservation during the 'mystery interval' in the northern Indian Ocean

    Digital Repository Service at National Institute of Oceanography (India)

    Naik, S.S.; Naidu, P.D.

    preservation spike during deglaciation in the northern Indian Ocean documented in this study suggests increased deep-water carbonate ion concentrations during the early deglaciation which in turn favored preservation This study sheds new light...

  19. Annual and interannual variation of precipitation over the tropical Indian Ocean

    Digital Repository Service at National Institute of Oceanography (India)

    RameshKumar, M.R.; Prasad, T.G.

    /month, and the lowest amplitudes are found in the western Indian Ocean, especially off the Arabian and east African coasts. The INSAT and GEOS Precipitation Index (GPI) rainfall estimates correlated reasonably well with the island rainfall data, with correlation...

  20. Benthic disturbance and monitoring experiment in the Central Indian Ocean Basin

    Digital Repository Service at National Institute of Oceanography (India)

    Sharma, R.; Nath, B.N.

    Environmental impact assessment studies for deep-sea manganese nodule mining have been initiated in the Central indian Ocean Basin since 1995. As a part of the first phase for collecting the benthic baseline data, echosounding, subbottom profiling...

  1. Variation in size, morphology and chemical composition of polymetallic nodules from the Central Indian Ocean Basin

    Digital Repository Service at National Institute of Oceanography (India)

    Valsangkar, A.B.; Karisiddaiah, S.M.; Parthiban, G.

    Chemical composition of 613 polymetallic nodules from 150 stations in the Central Indian Ocean Basin (CIOB) are determined and variations in Mn, Fe, Cu, Ni, Co, Zn and moisture content are studied with respect to their size and surface texture...

  2. A new CGMW map: The structural map of the Indian Ocean: An attempt at ocean cartography

    Institute of Scientific and Technical Information of China (English)

    2004-01-01

    The Commission for the Geological Map of the World (CGMW), an IUGS affiliated body, has just issued the first edition of the Structural Map of the Indian Ocean which was presented during the 32nd IGC (Florence). During the 1980's, the Commission published the Geological Atlas of the World, which included the maps of the 5 oceans of the globe. Two decades have elapsed and the knowledge of the sea-floor experienced very significant progress; therefore some 5 years ago, the Commission decided to launch a new type of ocean mapping. The Structural Map of the Indian Ocean is the first of this new series of maps.

  3. The NOW regional coupled model: Application to the tropical Indian Ocean climate and tropical cyclone activity

    OpenAIRE

    Samson, G; Masson, S.; M. Lengaigne; Keerthi, M. G.; Vialard, J; S. Pous; Madec, G.; Jourdain, N. C.; Jullien, S; MENKES, C.; Marchesiello, P.

    2014-01-01

    International audience; This paper presents the NOW regional coupled ocean-atmosphere model built from the NEMO ocean and WRF atmospheric numerical models. This model is applied to the tropical Indian Ocean, with the oceanic and atmospheric components sharing a common 1 =4 horizontal grid. Long experiments are performed over the 1990–2009 period using the Betts-Miller-Janjic (BMJ) and Kain-Fritsch (KF) cumulus parameterizations. Both simulations produce a realistic distribution of seasonal ra...

  4. Tropical climate variability: interactions across the Pacific, Indian, and Atlantic Oceans

    Science.gov (United States)

    Kajtar, Jules B.; Santoso, Agus; England, Matthew H.; Cai, Wenju

    2016-06-01

    Complex interactions manifest between modes of tropical climate variability across the Pacific, Indian, and Atlantic Oceans. For example, the El Niño-Southern Oscillation (ENSO) extends its influence on modes of variability in the tropical Indian and Atlantic Oceans, which in turn feed back onto ENSO. Interactions between pairs of modes can alter their strength, periodicity, seasonality, and ultimately their predictability, yet little is known about the role that a third mode plays. Here we examine the interactions and relative influences between pairs of climate modes using ensembles of 100-year partially coupled experiments in an otherwise fully coupled general circulation model. In these experiments, the air-sea interaction over each tropical ocean basin, as well as pairs of ocean basins, is suppressed in turn. We find that Indian Ocean variability has a net damping effect on ENSO and Atlantic Ocean variability, and conversely they each promote Indian Ocean variability. The connection between the Pacific and the Atlantic is most clearly revealed in the absence of Indian Ocean variability. Our model runs suggest a weak damping influence by Atlantic variability on ENSO, and an enhancing influence by ENSO on Atlantic variability.

  5. Exhibition

    Institute of Scientific and Technical Information of China (English)

    2010-01-01

    China[Guangzheu] International Trade Fair for Home Textiles Date:March 18th- March 21st,2011 Venue:China Import and Export Fair Complex(Guangzhou,China) Organizers:China National Textile&Apparel Council China Foreign Trade Center(Group) China Home Textile Association China Foreign Trade Guangzhou Exhibition Corp.

  6. An observational study of the western boundary currents in the Indian and South Atlantic Oceans

    NARCIS (Netherlands)

    Ponsoni, L.

    2016-01-01

    In this thesis we have investigated different aspects of the WBCs in the Indian and South Atlantic Oceans, based on observational data sampled both in situ and from satellites. In October 2010 an array of five moorings were deployed off eastern Madagascar, nominally at 23S, as part of the “INdian-AT

  7. High-resolution Quantification of Turbulent Mixing in the North Indian Ocean During the Monsoons

    Science.gov (United States)

    2014-09-30

    High-resolution quantification of turbulent mixing in the North Indian Ocean during the monsoons Sutanu Sarkar Department of Mechanical and...COVERED 00-00-2014 to 00-00-2014 4. TITLE AND SUBTITLE High-resolution Quantification of Turbulent Mixing in the North Indian Ocean During the...corresponding horizontal pressure gradient drives a counter gravity current which causes the bore to decelerate. The counter current also causes the

  8. Bycatch in the purse seine tuna fisheries in the western Indian Ocean.

    OpenAIRE

    Romanov, E. V.

    1998-01-01

    The yield of associated and dependent species taken as bycatch by the purse seine tuna fishery from the Indian Ocean pelagic ecosystem is estimated from data collected by scientific observers aboard Soviet purse seiners in the Western Indian Ocean (WIO), 1986-1992. A total of 494 sets on free swimming schools, whale shark associated schools, whale associated schools, and log associated schools were analyzed. More than 40 fish species and other marine animals were registered. Among them onl...

  9. Volcanic ash and its enigma: A case study from the Central Indian Ocean Basin

    Digital Repository Service at National Institute of Oceanography (India)

    Pattan, J.N.

    -1 JOURNAL GEOLOGICAL SOCIETY OF INDIA Vol 60, August 2002, pp.127-130 Volcanic Ash and its Enigma: A Case Study from the Central Indian Ocean Basin J. N. PATTAN National Institute of Oceanography. Dona Paula. 403 004. Goa, India. Email: pattan... is reported. Keywords: Ash layer. Glass shards, Youngest Toba Tuff, Terrigenous influx, Indian Ocean. INTRODUCTION Marine ash layers provide information about cyclicity of volcanism. volcanic production rate and volume, eruption duration, geochemical...

  10. A new atlas of temperature and salinity for the North Indian Ocean

    Indian Academy of Sciences (India)

    A Chatterjee; D Shankar; S S C Shenoi; G V Reddy; G S Michael; M Ravichandran; V V Gopalkrishna; E P Rama Rao; T V S Udaya Bhaskar; V N Sanjeevan

    2012-06-01

    The most used temperature and salinity climatology for the world ocean, including the Indian Ocean, is the World Ocean Atlas (WOA) (Antonov et al 2006, 2010; Locarnini et al 2006, 2010) because of the vast amount of data used in its preparation. The WOA climatology does not, however, include all the available hydrographic data from the Indian Exclusive Economic Zone (EEZ), leading to the potential for improvement if the data from this region are included to prepare a new climatology. We use all the data that went into the preparation of the WOA (Antonov et al 2010; Locarnini et al 2010), but add considerable data from Indian sources, to prepare new annual, seasonal, and monthly climatologies of temperature and salinity for the Indian Ocean. The addition of data improves the climatology considerably in the Indian EEZ, the differences between the new North Indian Ocean Atlas (NIOA) and WOA being most significant in the Bay of Bengal, where the patchiness seen in WOA, an artifact of the sparsity of data, was eliminated in NIOA. The significance of the new climatology is that it presents a more stable climatological value for the temperature and salinity fields in the Indian EEZ.

  11. Equatorial Oceanic Waves and the Evolution of 2007 Positive Indian Ocean Dipole

    Directory of Open Access Journals (Sweden)

    Iskhaq Iskandar

    2014-01-01

    Full Text Available The role of equatorial oceanic waves on the evolution of the 2007 positive Indian Ocean Dipole (pIOD event was evaluated using available observations and output from a quasi-analytical linear wave model. It was found that the 2007 pIOD event was a weak and short-lived event: developed in the mid-summer (July, matured in the early-fall (September, and terminated in the mid-fall (October. The evolution of the 2007 pIOD event was linked to the equatorial wave dynamics. The event development was associated with the generation of upwelling equatorial Kelvin waves (westward current anomalies generated by easterly wind anomalies. The event termination was associated with the occurrence of eastward zonal current anomalies resulting from a complex interplay between the wind-forced down welling Kelvin waves and the eastern-boundary-reflected Rossby waves. Results from a quasi-analytical linear wave model show that during the event development and maturation, the wind-forced Kelvin waves played a dominant role in generating zonal current anomalies along the equatorial Indian Ocean, while the eastern-boundary-reflected Rossby waves tended to weaken the wind-forced Kelvin wave signals. During the event termination our model shows that the initiation of anomalous eastward current resulted from the reflected Rossby waves at the eastern boundary. The wind-forced Kelvin waves associated with the seasonal reversal of the monsoon further strengthened the eastward zonal currents generated by the boundary-generated Rossby waves in late-October/early-November. This highlights the importance of the eastern-boundary-reflected Rossby waves on the IOD event termination.

  12. Positive Indian Ocean Dipole events precondition southeast Australia bushfires

    Science.gov (United States)

    Cai, W.; Cowan, T.; Raupach, M.

    2009-10-01

    The devastating “Black Saturday” bushfire inferno in the southeast Australian state of Victoria in early February 2009 and the “Ash Wednesday” bushfires in February 1983 were both preceded by a positive Indian Ocean Dipole (pIOD) event. Is there a systematic pIOD linkage beyond these two natural disasters? We show that out of 21 significant bushfires seasons since 1950, 11 were preceded by a pIOD. During Victoria's wet season, particularly spring, a pIOD contributes to lower rainfall and higher temperatures exacerbating the dry conditions and increasing the fuel load leading into summer. Consequently, pIODs are effective in preconditioning Victoria for bushfires, more so than El Niño events, as seen in the impact on soil moisture on interannual time scales and in multi-decadal changes since the 1950s. Given that the recent increase in pIOD occurrences is consistent with what is expected from global warming, an increased bushfire risk in the future is likely across southeast Australia.

  13. Composition of macrobenthos from the Central Indian Ocean Basin

    Indian Academy of Sciences (India)

    S Pavithran; B S Ingole; M Nanajkar; C Raghukumar; B N Nath; A B Valsangkar

    2009-12-01

    The deep sea is well known for its high faunal diversity. But the current interest in its abundant polymetallic nodules, poses a threat to the little known benthic organisms surviving in this unique environment. The present study is the first attempt to document the Indian Ocean abyssal benthic diversity of macroinvertebrates and to investigate its relation to the surface primary production (chl-), sediment labile organic matter, organic carbon and texture. The present study is based on 87 individuals. Altogether 39 macroinvertebrate genera were obtained from water depths of 4500–5500m from 23 box cores. Reduction in macrobenthic density was seen towards the southern latitudes. The area was dominated by deposit feeding macrobenthos. Vertically, the fauna was distributed down to 30 cm depth, with the highest faunal density in the top 2–5 cm sediment section. The values for population density were strongly correlated with surface water chl- and sediment protein, indicating supply of fresh organic matter as a critical factor for maintaining the deep sea benthic diversity and abundance.

  14. Multiple ciguatoxins present in Indian Ocean reef fish.

    Science.gov (United States)

    Hamilton, Brett; Hurbungs, Mira; Jones, Alun; Lewis, Richard J

    2002-09-01

    Optimised gradient reversed-phase high-performance liquid chromatography electrospray ionisation mass spectrometry (LC/MS) methods, in combination with a [3H]-brevetoxin binding assay (RLB), revealed multiple ciguatoxins in a partially purified extract of a highly toxic Lutjanus sebae (red emperor) from the Indian Ocean. Two major ciguatoxins of 1140.6 Da (I-CTX-1 and -2) and two minor ciguatoxins of 1156.6 Da (I-CTX-3 and -4) were identified. Accurate mass analysis revealed that I-CTX-1 and -2 and Caribbean C-CTX-1 had indistinguishable masses (1140.6316 Da, at 0.44 ppm resolution). Toxicity estimated from LC/MS/RLB responses indicated that I-CTX-1 and -2 were both approximately 60% the potency of Pacific ciguatoxin-1 (P-CTX-1). In contrast to ciguatoxins of the Pacific where the more oxidised ciguatoxins are more potent, I-CTX-3 and -4 were approximately 20% of P-CTX-1 potency. Interconversion in dilute acid or on storage, typical of spiroketal and hemiketal functionality found in P-CTXs and C-CTXs, respectively, was not observed to occur between I-CTX-1 and -2. The ratio of CTX-1 and -2 varied depending on the fish extract being analysed. These results suggest that I-CTX-1 and -2 may arise from separate dinoflagellate precursors that may be oxidatively biotransformed to I-CTX-3 and -4 in fish.

  15. Medieval forewarning of the 2004 Indian Ocean tsunami in Thailand

    Science.gov (United States)

    Jankaew, K.; Atwater, B.F.; Sawai, Y.; Choowong, M.; Charoentitirat, T.; Martin, M.E.; Prendergast, A.

    2008-01-01

    Recent centuries provide no precedent for the 2004 Indian Ocean tsunami, either on the coasts it devastated or within its source area. The tsunami claimed nearly all of its victims on shores that had gone 200 years or more without a tsunami disaster. The associated earthquake of magnitude 9.2 defied a Sumatra-Andaman catalogue that contains no nineteenth-century or twentieth-century earthquake larger than magnitude 7.9 (ref. 2). The tsunami and the earthquake together resulted from a fault rupture 1,500 km long that expended centuries' worth of plate convergence. Here, using sedimentary evidence for tsunamis, we identify probable precedents for the 2004 tsunami at a grassy beach-ridge plain 125 km north of Phuket. The 2004 tsunami, running 2 km across this plain, coated the ridges and intervening swales with a sheet of sand commonly 5-20 cm thick. The peaty soils of two marshy swales preserve the remains of several earlier sand sheets less than 2,800 years old. If responsible for the youngest of these pre-2004 sand sheets, the most recent full-size predecessor to the 2004 tsunami occurred about 550-700 years ago. ??2008 Macmillan Publishers Limited. All rights reserved.

  16. Non-Reporting Ship Traffic in the Western Indian Ocean

    Science.gov (United States)

    Greidanus, Harm; Santamaria, Carlos; Alvarez, Marlene; Krause, Detmar; Stasolla, Mattia; Vachon, Paris W.

    2016-08-01

    AIS ship position reporting data from up to 17 satellites and several coastal locations covering the Western Indian Ocean were collected during a period of one year, that ended 15 Sep 2015. In addition, 1,361 satellite SAR images that were acquired over the region in the same timeframe, were analysed for ship detection. The major part of these were Sentinel-1 images that were analysed fully automatically, yielding 11,510 ship detections that were deemed reliable. Correlating these detections with the reporting ship traffic indicates that, overall, fully one-third of the ships detected with satellite SAR are not reporting on AIS. Some of the analysed SAR data was subjected to manual verification. This concerned data from TerraSAR-X, RADARSAT-2, COSMO-SkyMed, and ALOS-2- PALSAR of various image modes, plus some of the Sentinel-1 images. This confirmed the quoted average for the fraction of non-reporting ships. However, within the overall average there are large geographical variations, besides variations with image resolution.

  17. Teleconnections due the north Indian Ocean tropical disturbances

    Science.gov (United States)

    Jayanthi, V.; Behera, S. K.; Masumoto, Y.; Yamagata, T.

    2012-12-01

    Teleconnections due to long lasting intense tropical disturbances in the north Indian Ocean are investigated in this study. The analyses is carried out for both the pre-monsoon (April-May) and post-monsoon (Oct-Dec) periods. The OLR distribution of the pre-monsoon tropical storms in the Bay of Bengal shows a dipole like structure. The composite plot reveals strong negative OLR anomalies over the Bay region and strong positive OLR anomalies near the Indonesian region. The composite also shows negative OLR anomalies extending from the north-west Pacific region to the western Japan, which is remote from the origin of the Bay of Bengal disturbances. The associated surface temperature anomalies show positive surface temperature anomalies over the northwestern parts of India, Pakistan and Afghanistan with cold anomalies over the Arabian region which is also remote to the region of the tropical disturbances. Further analyses of the anomalies shows that, the negative OLR anomalies over western Japan are due to the Rossby waves generated by the heating over the Bay besides the enhancement of the Pacific-Japan teleconnection. However, the post-monsoon disturbances in the Bay of Bengal and the disturbances formed in the Arabian Sea in both pre- and post-monsoon seasons do not develop remote teleconnections associated with the above type of Rossby wave mechanism.

  18. Exhibition

    CERN Multimedia

    Staff Association

    2017-01-01

    A Look of Hope Islam Mahmoud Sweity From 19 to 30 June 2017 CERN Meyrin, Main Building Islam Mahmoud Sweity Islam Mahmoud Sweity was born in 1997 at Beit Awwa, Palestine. She is currently following a course to get an Art diploma of Painting at the college of Fine Arts at An-Najah National University under the supervision of Esmat Al As'aad. Her portraits, landscapes and still life paintings are full of life and shining colours. Charged of emotional empathy they catch the attention of the viewer and are reminding us that life is beautiful and worth living in spite of all difficulties we have to go through. She participated in many exhibitions and has exposed her drawings in 2015 at CERN and in France in the framework of the exhibition "The Origin“, and in 2017 in the Former Yugoslav Republic of Macedonia, Palestina and Jordan. In this exhibition the oil paintings made in the past year will be presented. For more information : staff.association@cern.ch | T&eacu...

  19. Phenylquinolinones with antitumor activity from the Indian Ocean-derived fungus Aspergillus versicolor Y31-2

    Science.gov (United States)

    Li, Peihai; Fan, Yaqin; Chen, Hao; Chao, Yaxi; Du, Ning; Chen, Junhui

    2016-09-01

    Two phenylquinolinones, including one new compound ( 1) and a previously isolated compound ( 2), were isolated from the ethyl acetate extracts of the fungus Aspergillus versicolor Y31-2, which was obtained from seawater samples collected from the Indian Ocean. The structures of these compounds were established by spectroscopic analyses. 4-(3-Hydroxyphenyl)-3-methoxyquinolin-2(1H)-one ( 1) exhibited moderate cytotoxicity against MCF-7 (human breast carcinoma cell line) and SMMC-7721 (human liver cancer cell line) cells with IC50 values of 16.6 and 18.2 μmol/L, respectively. To the best of our knowledge, this study represents the first reported account of the isolation of compounds 1 and 2 as the secondary metabolites of the seawater derived fungus Aspergillus versicolor from the Indian Ocean.

  20. Asymmetry of upper ocean salinity response to the Indian Ocean dipole events as seen from ECCO simulation

    Institute of Scientific and Technical Information of China (English)

    ZHANG Ying; DU Yan; ZHANG Yuhong; GAO Shan

    2016-01-01

    The interannual variability of salinity and associated ocean dynamics in the equatorial Indian Ocean is analyzed using observations and numerical simulations by the Estimating the Circulation and Climate of the Ocean (ECCO) model. The results show that salinity anomalies in the upper ocean are asymmetrically associated with the Indian Ocean dipole (IOD) events, with stronger response during their positive phases. Further investigations reveal that zonal currents along the equator, the Wyrtki jets, dominate the salinity transport. During the positive IOD events, the Wyrtki jets have stronger westward anomalies. The positive skewness of the IOD explains that the amplitude of the anomalous Wyrtki jets is stronger in the positive IOD events than that in the negative events.

  1. Low-Frequency Coupled Atmosphere-Ocean Variability in the Southern Indian Ocean

    Institute of Scientific and Technical Information of China (English)

    FENG Junqiao; HU Dunxin; YU Lejiang

    2012-01-01

    The low-frequency atmosphere-ocean coupled variability of the southern Indian Ocean (SIO) was investigated using observation data over 1958-2010.These data were obtained from ECMWF for sea level pressure (SLP) and wind,from NCEP/NCAR for heat fluxes,and from the Hadley Center for SST.To obtain the coupled air-sea variability,we performed SVD analyses on SST and SLP.The primary coupled mode represents 43% of the total square covariance and is featured by weak westerly winds along 45°-30°S.This weakened subtropical anticyclone forces fluctuations in a well-known subtropical dipole structure in the SST via wind-induced processes.The SST changes in response to atmosphere forcing and is predictable with a lead-time of 1-2 months.Atmosphere-ocean coupling of this mode is strongest during the austral summer.Its principle component is characterized by mixed interannual and interdecadal fluctuations.There is a strong relationship between the first mode and Antarctic Oscillation (AAO).The AAO can influence the coupled processes in the SIO by modulating the subtropical high.The second mode,accounting for 30% of the total square covariance,represents a 25-year period interdecadal oscillation in the strength of the subtropical anticyclone that is accompanied by fluctuations of a monopole structure in the SST along the 35° 25°S band.It is caused by subsidence of the atmosphere.The present study also shows that physical processes of both local thermodynamic and ocean circulation in the SIO have a crucial role in the formation of the atmosphere-ocean covariability.

  2. Ocean control of the breeding regime of the sooty tern in the southwest Indian Ocean

    Science.gov (United States)

    Jaquemet, S.; Le Corre, M.; Quartly, G. D.

    2007-01-01

    Food availability, which is often seasonal, is regarded as a key factor in the breeding success of seabirds. In oceanic tropical areas, the resources are mostly patchy and ephemeral at the surface, and the seasonality is less marked than at higher latitudes. Such a situation influences greatly the breeding strategies of the oceanic seabird species. We conducted a comparative study of the breeding phenology of the sooty tern ( Sterna fuscata) in relation to the local and regional oceanographic conditions around the four major colonies (Europa, Juan de Nova, Lys and Bird Islands) of the southwest Indian Ocean. Over the 1997-2003 period, around all the studied locations, the sea-surface temperature (SST) and the chlorophyll concentration in the Mozambique Channel and the Seychelles area showed clear seasonal differences related to the southern climate and the monsoon phenomena. The breeding activity is synchronized at each studied colony, but the timings are very different. Seasonal reproduction occurs in austral winter at Europa and Bird Island and in austral summer at Juan de Nova; at Lys Island the reproduction is non-seasonal. For the seasonal colonies, there is a large monthly change in SST just before the beginning of reproduction, which is a proxy indicating the annual phytoplankton bloom. This variation is accompanied by the development of oceanic features such as fronts that favour aggregation of prey, and may also play an important role in the presence of schools of surface tuna, which are very important for the foraging success of sooty terns. Conversely, around Lys Island the seasonal variations of the marine environment do not lead to pronounced development of oceanic structures, and consequently, the longer-lasting phytoplankton bloom could explain the non-seasonal breeding regime there. Further studies will help discern the advantages and disadvantages of seasonal and non-seasonal reproduction regime in response to unpredictable fluctuations of the

  3. The tropical Pacific-Indian Ocean temperature anomaly mode and its effect

    Institute of Scientific and Technical Information of China (English)

    YANG Hui; JIA Xiaolong; LI Chongyin

    2006-01-01

    Temperature anomaly in the Indian Ocean is closely related to that in the Pacific Ocean because of the Walker circulation and the Indonesian throughflow. So only the El Ni(n)o/Southern Oscillation (ENSO) in the Pacific cannot entirely explain the influence of sea surface temperature anomaly (SSTA)on climate variation. The tropical Pacific-Indian Ocean temperature anomaly mode (PIM) is presented based on the comprehensive research on the pattern and feature of SSTA in both Indian Ocean and Pacific Ocean. The features of PIM and ENSO mode and their influences on the climate in China and the rainfall in India are further compared. For proving the observation results, numerical experiments of the global atmospheric general circulation model are conducted. The results of observation and sensitivity experiments show that presenting PIM and studying its influence are very important for short-range climate prediction.

  4. Exhibition

    CERN Multimedia

    Staff Association

    2016-01-01

    Encounters Hanne Blitz From February 1st to 12th 2016 CERN Meyrin, Main Building What is our reaction to a first encounter with a tourist attraction? Contemporary Dutch painter Hanne Blitz captures visitors' responses to art and architecture, sweeping vistas and symbolic memorials. Encounters, a series of oil paintings curated specially for this CERN exhibition, depicts tourists visiting cultural highlights around the world. A thought-provoking journey not to be missed, and a tip of the hat to CERN's large Hadron Collider.

  5. North Indian Ocean warming and sea level rise in an OGCM

    Indian Academy of Sciences (India)

    Bijoy Thompson; C Gnanaseelan; Anant Parekh; P S Salvekar

    2008-04-01

    The variability in the long-term temperature and sea level over the north Indian Ocean during the period 1958–2000 has been investigated using an Ocean General Circulation Model, Modular Ocean Model version 4. The model simulated fields are compared with the sea level observations from tide-gauges, Topex/Poseidon (T/P) satellite, in situ temperature profile observations from WHOI moored buoy and sea surface temperature (SST) observations from DS1, DS3 and DS4 moored buoys. It is seen that the long (6–8 years) warming episodes in the SST over the north Indian Ocean are followed by short episodes (2–3 years) of cooling. The model temperature and sea level anomaly over the north Indian Ocean show an increasing trend in the study period. The model thermocline heat content per unit area shows a linear increasing trend (from 1958–2000) at the rate of 0.0018 × 1011J/m2 per year for north Indian Ocean. North Indian Ocean sea level anomaly (thermosteric component) also shows a linear increasing trend of 0.31mm/year during 1958–2000.

  6. Connection of sea level height between Western Pacific and South Indian Ocean in recent decades

    Science.gov (United States)

    DU, Y.; Wang, T.; Zhuang, W.; Wang, J.

    2014-12-01

    Based on merged altimetry data and in site observations from tide gauges, we analyzed the fast increasing trend of sea surface height (SSH) in the recent two decades in the tropical Pacific and Indian Ocean. The results of analysis indicated a dynamic connection of SSH between the tropical western Pacific and the southeastern Indian Ocean. The low-frequency variations of SSH propagate westward in the tropical Pacific, enter the Indonesian Seas through the waveguide, and influence the southeastern India Ocean with the Kelvin-Rossby wave transformation. The thermal structure of upper ocean reveals the above adjustment mainly occur in the thermocline. However, the impacts from the Pacific are limited in the southeast Indian Ocean. In the central and west of the south Indian Ocean, local wind dominates the SSH changes in the last two decades. By lead-lag statistic analyses, we identified the cause of interdecadal from the interannual SSH variations. The interannual SSH variations is dominated by ENSO, forced by the anomalous wind along the equatorial Pacific. Whereas, the interdecadal SSH variations results from the off-equatorial wind stress curl, which is closely related to the Pacific Decadal Oscillation. The dynamic connections between the western Pacific and the south Indian Ocean were tested in the baroclinic Rossby wave solution and the numerical experiments based on the nonlinear reduced-gravity dynamics model.

  7. Impacts of Indonesian Throughflow on seasonal circulation in the equatorial Indian Ocean

    Science.gov (United States)

    Wang, Jing; Yuan, Dongliang; Zhao, Xia

    2017-03-01

    Impacts of the Indonesian Throughflow (ITF) on seasonal circulation in the equatorial eastern Indian Ocean are investigated using the ocean-only model LICOM by opening and closing ITF passages. LICOM had daily forcing from NCEP reanalysis data during 2000-2011. It can reproduce vertical profiles of mean density and buoyancy frequency of World Ocean Atlas 2013 data. The model also simulates well annual oscillation in the central Indian Ocean and semiannual oscillation in the eastern Indian Ocean of sea level anomalies (SLA) using satellite altimeter data, as well as the semiannual oscillation of surface zonal equatorial currents of Ocean Surface Current Analyses Real Time current data in the equatorial Indian Ocean. The wave decomposition method is used to analyze the propagation and reflection of equatorial long waves based on LICOM output. Wave analysis suggests that ITF blockage mainly influences waves generated from the Indian Ocean but not the Pacific Ocean, and eastern boundary reflections play an important role in semiannual oscillations of SLA and zonal current differences in the equatorial Indian Ocean associated with ITF. Reconstructed ITF-caused SLA using wave decomposition coefficient differences between closed and open ITF-passage experiments suggest both Kelvin and Rossby waves from the first baroclinic mode have comparable contributions to the semiannual oscillations of SLA difference. However, reconstructed ITF-caused surface zonal currents at the equator suggest that the first meridional-mode Rossby wave has much greater contribution than the first baroclinic mode Kelvin wave. Both reconstructed sea level and zonal currents demonstrate that the first baroclinic mode has a greater contribution than other baroclinic modes.

  8. Earthquake source mechanisms from body-waveform inversion and intraplate tectonics in the northern Indian Ocean

    Science.gov (United States)

    Bergman, E. A.; Solomon, S. C.

    1985-01-01

    Double-couple point-source parameters for 11 of the largest intraplate earthquakes in the northern Indian Ocean during the last 20 years were determined from a formal inversion of the long-period P and SH waveforms. Two major intraplate tectonic provinces are distinguished in the northern Indian Ocean. The plate-wide stress pattern found and the high level of intraplate seismicity are probably the results of substantial resistance, along the Himalayan continental collision zone, to the continued northward motion of the western portion of the Indian plate.

  9. Phylogeography of the crown-of-thorns starfish in the Indian Ocean.

    Directory of Open Access Journals (Sweden)

    Catherine Vogler

    Full Text Available BACKGROUND: Understanding the limits and population dynamics of closely related sibling species in the marine realm is particularly relevant in organisms that require management. The crown-of-thorns starfish Acanthaster planci, recently shown to be a species complex of at least four closely related species, is a coral predator infamous for its outbreaks that have devastated reefs throughout much of its Indo-Pacific distribution. METHODOLOGY/PRINCIPAL FINDINGS: In this first Indian Ocean-wide genetic study of a marine organism we investigated the genetic structure and inferred the paleohistory of the two Indian Ocean sister-species of Acanthaster planci using mitochondrial DNA sequence analyses. We suggest that the first of two main diversification events led to the formation of a Southern and Northern Indian Ocean sister-species in the late Pliocene-early Pleistocene. The second led to the formation of two internal clades within each species around the onset of the last interglacial. The subsequent demographic history of the two lineages strongly differed, the Southern Indian Ocean sister-species showing a signature of recent population expansion and hardly any regional structure, whereas the Northern Indian Ocean sister-species apparently maintained a constant size with highly differentiated regional groupings that were asymmetrically connected by gene flow. CONCLUSIONS/SIGNIFICANCE: Past and present surface circulation patterns in conjunction with ocean primary productivity were identified as the processes most likely to have shaped the genetic structure between and within the two Indian Ocean lineages. This knowledge will help to understand the biological or ecological differences of the two sibling species and therefore aid in developing strategies to manage population outbreaks of this coral predator in the Indian Ocean.

  10. Exhibition

    CERN Multimedia

    Staff Association

    2017-01-01

    Sintropie Flavio Pellegrini From 13 to 24 March 2017 CERN Meyrin, Main Building Energia imprigionata - Flavio Pellegrini. The exhibition is composed by eleven wood artworks with the expression of movement as theme. The artworks are the result of harmonics math applied to sculpture. The powerful black colour is dominated by the light source, generating reflexes and modulations. The result is a continuous variation of perspective visions. The works generate, at a first approach, an emotion of mystery and incomprehension, only a deeper contemplation lets one discover entangling and mutative details, evidencing the elegance of the lines and letting the meaning emerge. For more information : staff.association@cern.ch | Tél: 022 766 37 38

  11. Comparison between the Coastal Impacts of Cyclone Nargis and the Indian Ocean Tsunami

    Science.gov (United States)

    Fritz, H. M.; Blount, C.

    2009-12-01

    On 26 December 2004 a great earthquake with a moment magnitude of 9.3 occurred off the North tip of Sumatra, Indonesia. The Indian Ocean tsunami claimed 230,000 lives making it the deadliest in recorded history. Less than 4 years later tropical cyclone Nargis (Cat. 4) made landfall in Myanmar’s Ayeyarwady delta on 2 May 2008 causing the worst natural disaster in Myanmar’s recorded history. Official death toll estimates exceed 138,000 fatalities making it the 7th deadliest cyclone ever recorded worldwide. The Bay of Bengal counts seven tropical cyclones with death tolls in excess of 100,000 striking India and Bangladesh in the past 425 years, which highlights the difference in return periods between extreme cyclones and tsunamis. Damage estimates at over $10 billion made Nargis the most damaging cyclone ever recorded in the Indian Ocean. Although the two natural disasters are completely different in their generation mechanisms they both share massive coastal inundations as primary damage and death cause. While the damage patterns exhibit similarities the forcing differs. The primary tsunami impact is dominated by the runup of a few main waves washing rapidly ashore and inducing high lateral forces. On the contrary the tropical cyclone storm surge damage is the result of numerous storm waves continuously hitting the flooded structures on the elevated storm tide level. While coastal vegetation such as mangroves may be effective at reducing superimposed storm waves they are limited at reducing storm surge. Unfortunately, mangroves have been significantly cut for charcoal and land use as rice paddies in Myanmar due to rapid population growth and economic reasons, thereby increasing coastal vulnerability and land loss due to erosion (Figure 1). The period of a storm surge is typically an order of magnitude longer than the period of a tsunami resulting in significantly larger inundation distances along coastal plains and river deltas. The storm surge of cyclone Nargis

  12. Saline Indian Ocean waters invaded the South Atlantic thermocline during glacial termination II

    NARCIS (Netherlands)

    Scussolini, P.; Scussolini, G.; Brummer, G.-J.A.; Peeters, F.J.C.

    2015-01-01

    Salty and warm Indian Ocean waters enter the South Atlantic via the Agulhas leakage, south of Africa. Model simulations and proxy evidence of Agulhas leakage strengthening during glacial terminations led to the hypothesis that it was an important modulator of the Atlantic Ocean circulation. Yet, the

  13. Trends in the Indian Ocean Climatology due to anthropogenic induced global warming

    CSIR Research Space (South Africa)

    Meyer, AA

    2009-09-01

    Full Text Available clearly show that due to global warming the South West Indian Ocean Climatology has been changing and that this changing trend will continue into the future as global warming continues. The impacts of regional oceanic climate change on the regions coastal...

  14. Metazooplankton distribution across the Southern Indian Ocean with emphasis on the role of Larvaceans

    DEFF Research Database (Denmark)

    Jaspers, Cornelia; Nielsen, Torkel Gissel; Carstensen, Jacob

    2009-01-01

    The abundance and depth distribution of metazoans > 20 mu m were investigated at seven stations across the Southern Indian Ocean (SIO), October-November 2006. Copepod nauplii, copepodites and larvaceans dominated the metazooplankton community. Copepodites were most abundant within Agulhas Current...... and Southern Ocean waters, decreasing toward subtropical/tropical areas, whereas larvaceans showed the inverse pattern. The fraction

  15. Modeling Salinity Exchanges Between the Equatorial Indian Ocean and the Bay of Bengal

    Science.gov (United States)

    2016-06-01

    granted to copy this article for use in teaching and research. Republication, systematic reproduction, or collective redistribution of any portion of...Indian Ocean. The dynamics and thermodynam - ics of the ocean are represented by using primitive equations, and the numerical methods are implemented

  16. Relationship Between Upper-Ocean Heat Content in the Tropical Indian Ocean and Summer Precipitation in China

    Institute of Scientific and Technical Information of China (English)

    HUANG Ke; ZHANG Qi-Long; XIE Qiang; WANG Dong-Xiao

    2012-01-01

    An analysis of the Ishii ocean heat content (OHC) in the tropical Indian Ocean from the surface to 700-m depth shows that the OHC changes dramatically on the interannual timescale in the Indian Ocean. The first mode of empirical orthogonal function (EOF1) of the OHC shows that there is a strong air-sea interaction pat- tern in the Indian Ocean with a positive (negative) loading in the east and a negative (positive) loading in the west. This seesaw oscillation pattern influences the summer precipitation in China with a North-South reversed distri- bution. Composite analysis shows that during a positive (negative) OHC episode, an anomalous cyclonic (anti- cyclonic) circulation over the western Pacific and South China weakens (enhances) the monsoonal northward flow in the lower troposphere; meanwhile, anomalous merid- ional circulation connects the descending (ascending) branch over the Southeast Indian Ocean and the ascending (descending) branch in South China as well as a descend- ing (ascending) branch over North China. Analysis of the mechanism behind these features suggests that (1) the accumulation of OHC-induced vorticity is related to the wave activity over the mid-latitudes and that (2) the me- ridional teleconnection induced by the Indo-Pacific air-OHC interaction appears over East Asia and the west- ern Pacific. Both of these patterns can cause summer pre- cipitation anomalies in China.

  17. Solubility of iron and other trace elements in rainwater collected on the Kerguelen Islands (South Indian Ocean

    Directory of Open Access Journals (Sweden)

    A. Heimburger

    2013-10-01

    Full Text Available The soluble fraction of aerosols that is deposited on the open ocean is vital for phytoplankton growth. It is believed that a large proportion of this dissolved fraction is bioavailable for marine biota and thus plays an important role in primary production, especially in HNLC oceanic areas where this production is limited by micronutrient supply. There is still much uncertainty surrounding the solubility of atmospheric particles in global biogeochemical cycles and it is not well understood. In this study, we present the solubilities of seven elements (Al, Ce, Fe, La, Mn, Nd, Ti in rainwater on the Kerguelen Islands, in the middle of the Southern Indian Ocean. The solubilities of elements exhibit high values, generally greater than 70%, and Ti remains the least soluble element. Because the Southern Indian Ocean is remote from its dust sources, only a fraction of smaller aerosols reaches the Kerguelen Islands after undergoing several cloud and chemical processes during their transport, resulting in a drastic increase in solubility. Finally, we deduced an average soluble iron deposition flux of 27 ± 6 μg m−2 d−1 (~0.5 μmol m−2 d−1 for the studied oceanic area, taking into account a median iron solubility of 82% ± 18%.

  18. NUMERICAL SIMULATION OF INFLUENCE OF INDIAN OCEAN SSTA ON WEATHER AND CLIMATE IN ASIAN MONSOON REGION

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    Sea surface temperature anomaly (SSTA) exerts great influence on the generation of global weather and climate. Much progress has been made with respect to SSTA in the Pacific Ocean region in contrast to the Indian Ocean. The IAP9L model, which is developed at the Institute of Atmospheric Physics of the Chinese Academy of Science, is used to simulate the influence of the Indian Ocean SSTA on the general circulation and weather/climate anomalies in the monsoon region of Asia. It is found that the warm (cool) SSTA in the equatorial low latitudes of the Indian Ocean triggers winter (summer) teleconnection patterns in middle and higher latitudes of the Northern Hemisphere that are similar to PNA or EAP. They play a very important role in the anomaly of circulation or weather and climate in the middle and lower latitudes of the Asian summer monsoon region. With the warm (cool) SSTA forcing in the Indian Ocean, the Asian summer monsoon sets up at a late (early) date and withdraws at a early (late) date, lasting for a short (long) duration at a weak (strong) intensity. The Indian Ocean SSTA is shown to be an indicator for precipitation variation in China.

  19. Historical findings of the Russian physical oceanographers in the Indian Ocean

    Science.gov (United States)

    Koshlyakov, M. N.; Morozov, E. G.; Neiman, V. G.

    2016-12-01

    This is a review paper related to three findings of Russian physical oceanographers in the Indian Ocean. Observations in the Indian Ocean were used to investigate mesoscale eddies, subsurface equatorial undercurrent, and internal tidal waves near the Mascarene Ridge. Two surveys with measurements of temperature and salinity profiles in the Arabian Sea in 1967 made possible mapping of mesoscale eddies. Repeated moored measurements of currents in the equatorial zone between 55°E and 85°E revealed the existence of seasonal subsurface easterly Tareev undercurrent. A moored array of current and temperature recorders near the Mascarene Ridge was deployed as an antenna for internal tides. The displacements of isotherms caused by internal tides were as large as 150 m. The wave propagated to the southeast from the ridge. The review is intended to summarize the phenomena of the ocean dynamics of the Indian Ocean now when the scientific community of oceanography celebrates the 50th anniversary of the Indian Ocean expedition and plans the second Indian Ocean expedition.

  20. El Nino Southern Oscillation (ENSO) impact on tuna fisheries in Indian Ocean.

    Science.gov (United States)

    Kumar, Palanisamy Satheesh; Pillai, Gopalakrishna N; Manjusha, Ushadevi

    2014-01-01

    El Nino Southern Oscillation (ENSO) is an important driver of interannual variations in climate and ecosystem productivity in tropical regions. However, detailed information about this important phenomenon of the Indian Ocean is scarce. Consequently, the objective of this study is to improve understanding of the impact of warm event El Nino and cool event La Nina on annual tuna landings from the Indian Ocean from 1980 to 2010. In this study, maximum tuna landings were recorded during a weak El Nino year (1456054 t in 2006) and during a weak La Nina year (1243562 t in 2000), although the lowest tuna catch was followed during the strong El Nino year (1204119 t in 2009) and during a strong La Nina year (706546 t in 1988). Validation of predicted tuna landings and SST were showing a significant positive correlation (p Nino years; landings in Indian Ocean tend to be optimum SST 25 to 26°C in ENSO event. Our results confirm the ENSO impact on climate, tuna abundance and production in the Indian Ocean. However, among the oceanic variables SST explained the highest deviance in generalized additive models and therefore considered the best habitat predictor in the Indian Ocean followed by sea level pressure and Winds (U, V, W).

  1. Distichopora nitida Verrill (Cnidaria, Hydrozoa) from the Maldives, a new record from the Indian Ocean

    Science.gov (United States)

    Scheer, Georg; Obrist, Kurt

    1986-12-01

    The stylasterid Distichopora nitida was found during dives at four localities in the South Maalhosmadulu Atoll, Maldives, Central Indian Ocean. It occurs at the reef slope in a depth of 22 48 m at the edge of grottoes. All features of the Maldive coral coincide with Boschma's (1959) description of D. nitida from the Pacific Ocean. The most important characteristics and the distribution of D. nitida were compared with those of other shallow water representatives of the genus in the Indo-Pacific. A locality of D. nitida in the western Indian Ocean, thus far anpublished, is mentioned.

  2. Coastal biogeochemical processes in the north Indian Ocean (14, S-W)

    Digital Repository Service at National Institute of Oceanography (India)

    Naqvi, S.W.A.; Narvekar, P.V.; Desa, E.

    by Allan R. Robinson and Kennelh H. Brink ISBN 0-67401527-4 a2005 by the President and Fellows of Harvard College 724 COASTAL BIOGEOCIIEMICAL PROCESSES IN TI-IE NORTH INDIAN OCEAN along all meridians. This discontinuity, called the Ilydrochemical Front... JGOFS, focused on the open-ocean and that too mainly in the Arabian Sea. Con- sequently, some portions of the North Indian Ocean have been studied quite in- tensively; such areas covered adequately in this review, include the Somali and Arabian coasts...

  3. Deciphering detailed plate kinematics of the Indian Ocean and developing a unified model for East Gondwanaland reconstruction: An Indian-Australian-French initiative

    Digital Repository Service at National Institute of Oceanography (India)

    Yatheesh, V.; Dyment, J.; Bhattacharya, G.C.; Muller, R.D.

    2January 2013 DCS-DST NEWS DECIPHERING DETAILED PLATE KINEMATICS OF THE INDIAN OCEAN AND DEVELOPING A UNIFIED MODEL FOR EAST GONDWANALAND RECONSTRUCTION: AN INDIAN- AUSTRALIAN-FRENCH INITIATIVE V. YATHEESH1, J. DYMENT2, G.C. BHATTACHARYA1, R... was proposed by McKenzie and Sclater (1971, Geophys. J. R. Astron. Soc., v. 25, 437-528) mainly based on widely spaced geophysical data acquired during the International Indian Ocean Expedition (IIOE). Many subsequent studies (see Appendix-1) enriched...

  4. Development of an Indian Ocean moored buoy array for climate studies

    Digital Repository Service at National Institute of Oceanography (India)

    McPhaden, M.J.; Kuroda, Y.; Murty, V.S.N.

    , international effort of large magnitude. One or just a few nations cannot carry the full investment of resources. The implementation plan includes a set of principles that is meant to encourage broad international participation and rapid transition... tropical oceans. To remedy this situation, the Indian Ocean Panel, sponsored by the Climate Variability and Predictability Program (CLIVAR) and the Global Ocean Observing System (GOOS), has developed a plan for systematic, sustained, and comprehensive...

  5. Impacts of Indonesian Throughflow on seasonal circulation in the equatorial Indian Ocean

    Science.gov (United States)

    Wang, Jing

    2017-04-01

    Impacts of the Indonesian Throughflow (ITF) on the seasonal circulation of the equatorial eastern Indian Ocean are investigated using the ocean-only model LICOM by opening and closing ITF passages. LICOM is forced by daily forcing from NCEP reanalysis data during 2000-2011. And LICOM is capable of reproducing the vertical profiles of mean density and buoyancy frequency of WOA09 data, and also perform annual oscillation in central Indian Ocean and semiannual oscillation in the eastern Indian Ocean of sea level anomalies (SLA) from satellite altimeter data, and semiannual oscillation of surface zonal equatorial currents of OSCAR current data in the whole Indian Ocean very well. The wave decomposition method is used to analyze the propagation and reflection of equatorial long waves based on the LICOM output. Wave analysis suggests that ITF blockage mainly influence the waves generated from the equatorial Indian Ocean not the Pacific Ocean, and eastern boundary reflections play an important role in semiannual oscillation of SLA and zonal current difference associated with ITF in the equatorial Indian Ocean. Reconstructed ITF-caused SLA using wave decomposition coefficients difference between closed and open ITF passages experiment suggest both the Kelvin wave and Rossby waves from the first baroclinic mode have comparable contribution to the semiannual oscillations of SLA difference. However, reconstructed ITF-caused surface zonal current at the equator suggest the first meridional mode Rossby wave has much larger contribution than the Kelvin wave of the first baroclinic mode. Both reconstructed sea level and zonal currents demonstrate that the first baroclinic mode has larger contribution than other baroclinic modes.

  6. Tracking Cyclones in the Southwest Indian Ocean with an Ocean-Bottom Seismometer Network

    Science.gov (United States)

    Davy, C.; Barruol, G.; Fontaine, F. R.; Sigloch, K.; Stutzmann, E.

    2014-12-01

    The French-German RHUM-RUM project deployed 57 broadband ocean-bottom seismometers (OBS) over an area of 2000 x 2000 km2 between September 2012 and December 2013, spread around La Reunion Island and along the Central and the Southwest Indian Ridges. During this period, seven tropical cyclones propagated over the OBS network, providing the unique opportunity for in situ analysis and spatio-temporal tracking of this source of secondary (i.e twice the frequency of the ocean waves) microseismic noise and pressure fluctuations induced on the seafloor. We performed spectral analysis, seafloor pressure and ground polarization analyses on the continuous OBS data, focusing on cyclone Dumile, which passed directly over the OBS network. We observe that microseisms strongly increase in amplitude in the 0.1-0.45 Hz frequency band as the cyclone approaches and propagates over the instruments, and that this noise amplitude is directly related to the distance and intensity of the cyclone. Analysis of the temporal noise variations across the network permit to locate and track the area of maximum noise amplitude, which points towards the cyclone centre with good accuracy. Polarization analyses show that cyclones generate compressional waves in the water column, which give rise to both compressional and surface waves that propagate through the solid earth. In addition to atmospheric, oceanographic and satellite observations, microseisms recorded on the seafloor may therefore be considered a means for monitoring cyclone evolution and intensity.

  7. Assessment of marine weather forecasts over the Indian sector of Southern Ocean

    Science.gov (United States)

    Gera, Anitha; Mahapatra, D. K.; Sharma, Kuldeep; Prakash, Satya; Mitra, A. K.; Iyengar, G. R.; Rajagopal, E. N.; Anilkumar, N.

    2017-09-01

    The Southern Ocean (SO) is one of the important regions where significant processes and feedbacks of the Earth's climate take place. Expeditions to the SO provide useful data for improving global weather/climate simulations and understanding many processes. Some of the uncertainties in these weather/climate models arise during the first few days of simulation/forecast and do not grow much further. NCMRWF issued real-time five day weather forecasts of mean sea level pressure, surface winds, winds at 500 hPa & 850 hPa and rainfall, daily to NCAOR to provide guidance for their expedition to Indian sector of SO during the austral summer of 2014-2015. Evaluation of the skill of these forecasts indicates possible error growth in the atmospheric model at shorter time scales. The error growth is assessed using the model analysis/reanalysis, satellite data and observations made during the expedition. The observed variability of sub-seasonal rainfall associated with mid-latitude systems is seen to exhibit eastward propagations and are well reproduced in the model forecasts. All cyclonic disturbances including the sub-polar lows and tropical cyclones that occurred during this period were well captured in the model forecasts. Overall, this model performs reasonably well over the Indian sector of the SO in medium range time scale.

  8. Manglicolous fungi from atolls of Maldives, Indian Ocean

    Digital Repository Service at National Institute of Oceanography (India)

    Chinnaraj, S.

    stream_size 2 stream_content_type text/plain stream_name Indian_J_Mar_Sci_22_141.pdf.txt stream_source_info Indian_J_Mar_Sci_22_141.pdf.txt Content-Encoding ISO-8859-1 Content-Type text/plain; charset=ISO-8859-1 ...

  9. A note on new indices for the equatorial Indian Ocean oscillation

    Indian Academy of Sciences (India)

    P A Francis; Sulochana Gadgil

    2013-08-01

    It is now well known that there is a strong association of the extremes of the Indian summer monsoon rainfall (ISMR) with the El Niño and southern oscillation (ENSO) and the Equatorial Indian Ocean Oscillation (EQUINOO), later being an east–west oscillation in convection anomaly over the equatorial Indian Ocean. So far, the index used for EQUINOO is EQWIN, which is based on the surface zonal wind over the central equatorial Indian Ocean. Since the most important attribute of EQUINOO is the oscillation in convection/precipitation, we believe that the indices based on convection or precipitation would be more appropriate. Continuous and reliable data on outgoing longwave radiation (OLR), and satellite derived precipitation are now available from 1979 onwards. Hence, in this paper, we introduce new indices for EQUINOO, based on the difference in the anomaly of OLR/precipitation between eastern and western parts of the equatorial Indian Ocean. We show that the strong association of extremes of the Indian summer monsoon with ENSO and EQUINOO is also seen when the new indices are used to represent EQUINOO.

  10. STOMACH CONTENT OF THREE TUNA SPECIES IN THE EASTERN INDIAN OCEAN

    Directory of Open Access Journals (Sweden)

    Bram Setyadji

    2012-12-01

    Full Text Available Feeding habit of tuna in Indian Ocean has been described around Sri Lanka, Indian Waters, Andaman Sea, western Indian Ocean (Seychelles Islands, western equatorial Indian Ocean whereas the tunas feeding habit study in Eastern Indian Oceanis merely in existence. The purpose of this study is to investigate the stomach content of three tuna species (bigeye tuna, yellowfin tuna, and skipjack tuna, apex predator in the southern part of Eastern Indian Ocean. The study was conducted in March – April, 2010 on the basis of catches of commercial tuna longline vessel based in Port of Benoa. A total of 53 individual fishes were collected, consisting of bigeye tuna (Thunnus obesus, yellowfin tuna (Thunnus albacores, and skipjack tuna (Katsuwonus pelamis. Stomach specimens were collected and analyzed.Analysis was conducted on the basis of index of preponderance method. The diet of the three tuna species showed fishes as the main diet (56–82%, followed by cephalopods (squids as the complementary diet (0–8%, and crustaceans (shrimps as the additional diet (2–4%. Fish prey composed of 6 families i.e. Alepisauridae, Bramidae, Carangidae, Clupeidae, Engraulidae, and Scombridae.

  11. The monitoring of atmospheric mercury species in the Southern Indian Ocean at Amsterdam Island (38°S

    Directory of Open Access Journals (Sweden)

    Barret M.

    2013-04-01

    Full Text Available The role of oceans in the global cycle of mercury is still poorly characterized, mainly because of a lack a long-term data on atmospheric mercury concentrations in the remote Southern Ocean. In the frame of GMOS (Global Mercury Observation System, we present here the first results from a new monitoring station at Amsterdam Island in the Southern Indian Ocean. For the period January to April 2012, we recorded mean concentration of gaseous elemental mercury (GEM, reactive gaseous mercury (RGM and particulate-bounded mercury (PHg of 1.03 ng m−3, 0.37 and 0.34 pg m−3 respectively. While GEM concentrations showed little variations, RGM and PHg exhibited fast variations with alternation of value below the instrumental detection limit and maximum values up to 4 pg m−3.

  12. Extant Rhabdosphaeraceae (coccolithophorids, class Prymnesiophyceae) from the Indian Ocean, Red Sea, Mediterranean Sea and North Atlantic Ocean

    NARCIS (Netherlands)

    Kleijne, A.

    1992-01-01

    Rhabdosphaerids were consistently present as a minor constituent of the 1985 summer coccolithophorid flora in surface waters of the Indian Ocean, Red Sea, Mediterranean Sea and North Atlantic. Sixteen taxa are identified, belonging to seven genera, including the two new combinations Cyrtosphaera acu

  13. VM-ADCP measured upper ocean currents in the southeastern Arabian Sea and Equatorial Indian Ocean during December, 2000

    Digital Repository Service at National Institute of Oceanography (India)

    Murty, V.S.N.; Suryanarayana, A.; Somayajulu, Y.K.; Raikar, V.; Tilvi, V.

    The Vessel-Mounted Acoustic Doppler Current Profiler (VM-ADCP) measured currents in the upper 200 m along the cruise track covering the southeastern Arabian Sea and the Eastern Equatorial Indian Ocean during northern winter monsoon (10-31 December...

  14. Phytoplankton species composition, abundance and distribution in Fishing area 58 of Indian Ocean sector of Southern Ocean

    Digital Repository Service at National Institute of Oceanography (India)

    Rathod, V.

    Indian Ocean (Campagne “Antiprod I” du Marion-Dufresne, mars 1977). Bot Mar, 1979, 22, 183-198. 16 Fryxell, G.A., Kang, S.H., Ashworth, T.K., AMERIEZ 1988 and ODP leg 119 : Antarctic phytoplankton summer and winter stage indicators. Antarct J, US...

  15. Observed Intraseasonal Oceanic Variations in the Eastern Equatorial Indian Ocean and in the Outflow Straits of the Indonesian Throughflow

    Directory of Open Access Journals (Sweden)

    Iskhaq Iskandar

    2010-09-01

    Full Text Available The observed currents in the eastern equatorial Indian Ocean and in the outflow straits of the Indonesian Throughflow (ITF are shown to have significant intraseasonal variations and coherency during January 2004 – November 2006. The wavelet analysis between the eastern equatorial Indian Ocean and the ITF straits demonstrates significant intraseasonal coherency for the observed current at 50m depth. At 150m depth, the intraseasonal coherency only occurs between the observed currents in the eastern equatorial Indian Ocean and in the Lombok and Ombai Straits. On the other hand, at 350m depth the intraseasonal coherency is only found between the eastern equatorial Indian Ocean and the Ombai Strait. This intraseasonal coherency is associated with the wind-forced equatorial Kelvin waves which propagate eastward along the equatorial and coastal wave guides. Near-surface intraseasonal variations are associated with the first baroclinic mode with typical phase speed of 2.91 ± 0.46 m s-1, while the deeper layer intraseasonal variations are associated with the second baroclinic mode with typical phase speed of 1.59 ± 0.18 m s-1. Moreover, the lag correlations between the zonal winds and the observed currents at the ITF straits further demonstrate the source of intraseasonal variations in the ITF.

  16. Size fractionation of trace metals in the Edmond hydrothermal plume, Central Indian Ocean

    Science.gov (United States)

    Sands, C. M.; Connelly, D. P.; Statham, P. J.; German, C. R.

    2012-02-01

    The investigation of the distribution of trace elements between the dissolved, colloidal and particulate phases within a hydrothermal plume is key to understanding plume processes. Particulate and colloidal size fractions of four trace elements (iron, manganese, copper and phosphorus) along with the dissolved size fraction of iron, manganese and copper have been determined in the hydrothermal plume overlying the Edmond vent-site in the Central Indian Ocean. Dissolved iron and manganese are the most heavily enriched metals in hydrothermal fluids emerging from vents and iron plays a significant role in subsequent dissolved-particulate interactions within hydrothermal plumes. Copper and phosphorus are each representative members of discrete groups of tracers (chalcophile elements and oxyanions, respectively) that are known to exhibit distinct patterns of behaviour, relative to iron, within hydrothermal plumes. Here we show that iron is present in all three hydrothermal plume fractions (dissolved, colloidal and particulate), being least abundant in dissolved form. Manganese resides predominantly in the dissolved fraction, copper resides primarily in the particulate phase and phosphorus is abundant in both the colloidal and coarser particulate phases, but not the dissolved fraction. The correlation of phosphorus to iron in the Edmond hydrothermal plume is both (i) constant across the colloidal and coarser particulate phases and (ii) matches well to broader inter-ocean trends reported previously from the Atlantic and Pacific Oceans. These results demonstrate a mechanism whereby plume-height P:Fe ratios are established during the very earliest stages of dissolved Fe(II) oxidation, followed by aggregation into coarser hydrothermal plume particles. This provides a strong argument for the study of P:Fe ratios in hydrothermal sediments as potential paleotracers of deep-water dissolved phosphate distributions and, hence, past deep-ocean circulation patterns.

  17. A ˜25 ka Indian Ocean monsoon variability record from the Andaman Sea

    Science.gov (United States)

    Rashid, H.; Flower, B. P.; Poore, R. Z.; Quinn, T. M.

    2007-10-01

    Recent paleoclimatic work on terrestrial and marine deposits from Asia and the Indian Ocean has indicated abrupt changes in the strength of the Asian monsoon during the last deglaciation. Comparison of marine paleoclimate records that track salinity changes from Asian rivers can help evaluate the coherence of the Indian Ocean monsoon (IOM) with the larger Asian monsoon. Here we present paired Mg/Ca and δ 18O data on the planktic foraminifer Globigerinoides ruber (white) from Andaman Sea core RC12-344 that provide records of sea-surface temperature (SST) and δ 18O of seawater (δ 18O sw) over the past 25,000 years (ka) before present (BP). Age control is based on nine accelerator mass spectrometry (AMS) dates on mixed planktic foraminifera. Mg/Ca-SST data indicate that SST was ˜3 °C cooler during the last glacial maximum (LGM) than the late Holocene. Andaman Sea δ 18O sw exhibited higher than present values during the Lateglacial interval ca 19-15 ka BP and briefly during the Younger Dryas ca 12 ka BP. Lower than present δ 18O sw values during the BØlling/AllerØd ca 14.5-12.6 ka BP and during the early Holocene ca 10.8-5.5 ka BP are interpreted to indicate lower salinity, reflect some combination of decreased evaporation-precipitation (E-P) over the Andaman Sea and increased Irrawaddy River outflow. Our results are consistent with the suggestion that IOM intensity was stronger than present during the BØlling/AllerØd and early Holocene, and weaker during the late glaciation, Younger Dryas, and the late Holocene. These findings support the hypothesis that rapid climate change during the last deglaciation and Holocene included substantial hydrologic changes in the IOM system that were coherent with the larger Asian monsoon.

  18. Seasonality in the relationship between El Nino and Indian Ocean dipole

    Energy Technology Data Exchange (ETDEWEB)

    Roxy, Mathew [Centro-Euro-Mediterraneo per i Cambiamenti Climatici, Bologna (Italy); Indian Institute of Tropical Meteorology, Centre for Climate Change Research, Pune (India); Gualdi, Silvio; Navarra, Antonio [Centro-Euro-Mediterraneo per i Cambiamenti Climatici, Bologna (Italy); Istituto Nazionale di Geofisica e Vulcanologia, Bologna (Italy); Lee Drbohlav, Hae-Kyung [University of Hawaii at Manoa, International Pacific Research Center, Honolulu, HI (United States)

    2011-07-15

    The seasonal change in the relationship between El Nino and Indian Ocean dipole (IOD) is examined using the European Centre for Medium-Range Weather Forecasts (ECMWF) Re-Analysis (ERA-40), and the twentieth century simulations (20c3m) from the Geophysical Fluid Dynamics Laboratory Coupled Model, version 2.1. It is found that, both in ERA-40 and the model simulations, the correlation between El Nino (Nino3 index) and the eastern part of the IOD (90-110 E; 10 S-equator) is predominantly positive from January to June, and then changes to negative from July to December. Correlation maps of atmospheric and oceanic variables with respect to the Nino3 index are constructed for each season in order to examine the spatial structure of their seasonal response to El Nino. The occurrence of El Nino conditions during January to March induces low-level anti-cyclonic circulation anomalies over the southeastern Indian Ocean, which counteracts the climatological cyclonic circulation in that region. As a result, evaporation decreases and the southeastern Indian Ocean warms up as the El Nino proceeds, and weaken the development of a positive phase of an IOD. This warming of the southeastern Indian Ocean associated with the El Nino does not exist past June because the climatological winds there develop into the monsoon-type flow, enhancing the anomalous circulation over the region. Furthermore, the development of El Nino from July to September induces upwelling in the southeastern Indian Ocean, thereby contributing to further cooling of the region during the summer season. This results in the enhancement of a positive phase of an IOD. Once the climatological circulation shifts from the boreal summer to winter mode, the negative correlation between El Nino and SST of the southeastern Indian Ocean changes back to a positive one. (orig.)

  19. Forced and Unforced Changes of Indian Ocean Temperature and Land-Sea Temperature Gradient

    Science.gov (United States)

    Achutarao, K. M.; Thanigachalam, A.

    2015-12-01

    Sea surface temperature (SST) over the Indian Ocean is directly connected with circulation, winds, precipitation, humidity, etc. over India. Increased SSTs are a major consequence of climate change driven largely by anthropogenic factors. Recent literature points to weakening of the Indian Summer Monsoon possibly because of decreased land-sea temperature gradient due to faster rate of warming of the oceans compared to land regions. We examine changes in the SST over the Indian Ocean using two observational datasets; HadISST (v1.1) and ERSST (v3b). Based on trend differences between two time periods (1979-2009 and 1948-1978) we identify four regions in the Indian Ocean with different signatures of change - Bay of Bengal (BOB), Arabian Sea (AS), Southwest Indian Ocean (SWIO), and Southeast Indian Ocean (SEIO). We first quantify the extent to which the SST trends over multiple time-scales (20, 30, 50 and 100-years) are outside of the range expected from internal variability of the climate system. We make use of output data from long control run simulations from the Coupled Model Intercomparison Project Phase-5 (CMIP5) database in order to estimate the contribution of external forcings to the observed trends. Using optimal fingerprint Detection and Attribution methods we quantify the contributions of various natural and anthropogenic forcings by making use of the suite of experiments (piControl, historical, historicalNat, historicalAnt, historicalGHG, and historicalAA) from CMIP5 are used in this study. We will also address the question of what drives the observed weakening of land-ocean temperature gradients.

  20. Sources, fate, and pathways of Leeuwin Current water in the Indian Ocean and Great Australian Bight : A Lagrangian study in an eddy-resolving ocean model

    NARCIS (Netherlands)

    Yit Sen Bull, Christopher; Van Sebille, Erik

    2016-01-01

    The Leeuwin Current is the dominant circulation feature in the eastern Indian Ocean, transporting tropical and subtropical water southward. While it is known that the Leeuwin Current draws its water from a multitude of sources, existing Indian Ocean circulation schematics have never quantified the

  1. Vulnerability of teleosts caught by the pelagic tuna longline fleets in South Atlantic and Western Indian Oceans

    Science.gov (United States)

    Lucena-Frédou, Flávia; Kell, Laurie; Frédou, Thierry; Gaertner, Daniel; Potier, Michel; Bach, Pascal; Travassos, Paulo; Hazin, Fábio; Ménard, Frédéric

    2017-06-01

    Productivity and Susceptibility Analysis (PSA) is a methodology for evaluating the vulnerability of a stock based on its biological productivity and susceptibility to fishing. In this study, we evaluated the vulnerability of 60 stocks of tuna, billfishes and other teleosts caught by the tuna longline fleets operating in the South Atlantic and Indian Ocean using a semi-quantitative PSA. We (a) evaluated the vulnerability of the species in the study areas; (b) compared the vulnerability of target and non-target species and oceans; (c) analyzed the sensitivity of data entry; and (d) compared the results of the PSA to other fully quantitative assessment methods. Istiophoridae exhibited the highest scores for vulnerability. The top 10 species at risk were: Atlantic Istiophorus albicans; Indian Ocean Istiompax indica; Atlantic Makaira nigricans and Thunnus alalunga; Indian Ocean Xiphias gladius; Atlantic T. albacares, Gempylus serpens, Ranzania laevis and X. gladius; and Indian Ocean T. alalunga. All species considered at high risk were targeted or were commercialized bycatch, except for the Atlantic G. serpens and R. laevis which were discarded, and may be considered as a false positive. Those species and others at high risk should be prioritized for further assessment and/or data collection. Most species at moderate risk were bycatch species kept for sale. Conversely, species classified at low risk were mostly discarded. Overall, species at high risk were overfished and/or subjected to overfishing. Moreover, all species considered to be within extinction risk (Critically Endangered, Endangered and Vulnerable) were in the high-risk category. The good concordance between approaches corroborates the results of our analysis. PSA is not a replacement for traditional stock assessments, where a stock is assessed at regular intervals to provide management advice. It is of importance, however, where there is uncertainty about catches and life history parameters, since it can

  2. Forcing of recent decadal variability in the Equatorial and North Indian Ocean

    Science.gov (United States)

    Thompson, P. R.; Piecuch, C. G.; Merrifield, M. A.; McCreary, J. P.; Firing, E.

    2016-09-01

    Recent decadal sea surface height (SSH) variability across the Equatorial and North Indian Ocean (ENIO, north of 5°S) is spatially coherent and related to a reversal in basin-scale, upper-ocean-temperature trends. Analysis of ocean and forcing fields from a data-assimilating ocean synthesis (ECCOv4) suggests that two equally important mechanisms of wind-driven heat redistribution within the Indian Ocean account for a majority of the decadal variability. The first is the Cross-Equatorial Cell (CEC) forced by zonal wind stress curl at the equator. The wind stress curl variability relates to the strength and position of the Mascarene High, which is influenced by the phase of the Indian Ocean Subtropical Dipole. The second mechanism is deep (700 m) upwelling related to zonal wind stress at the equator that causes deep, cross-equatorial overturning due to the unique geometry of the basin. The CEC acts to cool the upper ocean throughout most of the first decade of satellite altimetry, while the deep upwelling delays and then amplifies the effect of the CEC on SSH. During the subsequent decade, reversals in the forcing anomalies drive warming of the upper ocean and increasing SSH, with the effect of the deep upwelling leading the CEC.

  3. Forcing of anthropogenic aerosols on temperature trends of the sub-thermocline southern Indian Ocean.

    Science.gov (United States)

    Cowan, Tim; Cai, Wenju; Purich, Ariaan; Rotstayn, Leon; England, Matthew H

    2013-01-01

    In the late twentieth century, the sub-thermocline waters of the southern tropical and subtropical Indian Ocean experienced a sharp cooling. This cooling has been previously attributed to an anthropogenic aerosol-induced strengthening of the global ocean conveyor, which transfers heat from the subtropical gyre latitudes toward the North Atlantic. From the mid-1990s the sub-thermocline southern Indian Ocean experienced a rapid temperature trend reversal. Here we show, using climate models from phase 5 of the Coupled Model Intercomparison Project, that the late twentieth century sub-thermocline cooling of the southern Indian Ocean was primarily driven by increasing anthropogenic aerosols and greenhouse gases. The models simulate a slow-down in the sub-thermocline cooling followed by a rapid warming towards the mid twenty-first century. The simulated evolution of the Indian Ocean temperature trend is linked with the peak in aerosols and their subsequent decline in the twenty-first century, reinforcing the hypothesis that aerosols influence ocean circulation trends.

  4. Soldiers, Artisans, Cultivators and Revolutionaries: The Movement of Sikhs in the Indian Ocean

    Directory of Open Access Journals (Sweden)

    Anjali Gera Roy

    2012-06-01

    Full Text Available The geography of Punjab, a land-locked region divided between India and Pakistan, makes it an unlikely player in oceanic sojourns. But imperial interventions in Punjab in the middle of the 19th century triggered movements from Punjab that inserted this region in the littoral narrative of the Indian Ocean. Unlike the movements of lascars and traders, who have been central to the revisionist histories of the Indian Ocean, those from Punjab have not featured in oceanic dialogues. The absence of Sikhs in Indian Ocean studies is largely due to the silence of Sikh soldiers, skilled craftsmen and cultivators with largely rural roots who were uprooted to strange lands. The confusion of Sikhs with Hindus, Muslims and, even Afghans, in the colonial era, as well as the classification of Punjabi Muslims as Pakistani in the post-colonial, further problematizes the Sikh migration narrative. Drawing on a wide range of official and unofficial historical sources, this essay argues that twin developments in Punjab, namely the construction of Sikhs as ‘a martial race’ and their integration into the imperial capitalist economy, connects the movements of soldiers and policemen to Shanghai, Hong Kong, the Straits Settlements and Kenya with those of skilled artisans to Mombasa and Uganda. Keywords: Sikhs, Indian Ocean, labour migration, cultural identity

  5. Dissolved strontium and calcium levels in the tropical Indian Ocean

    Science.gov (United States)

    Steiner, Zvi; Sarkar, Amit; Turchyn, Alexandra

    2017-04-01

    Measurements of seawater alkalinity and dissolved calcium concentrations along oceanic transects are often used to calculate calcium carbonate precipitation and dissolution rates. Given that the distribution coefficient of strontium in CaCO3 varies greatly between different groups of organisms, adding precise measurements of dissolved strontium concentrations provides opportunities to also track relative contributions of these different groups to the regional CaCO3 cycle. However, there are several obstacles to this approach. These obstacles include unresolved systematic discrepancies between seawater calcium and alkalinity data, very large analytical noise around the calcium concentration measurements and the unconstrained role of acantharia (radiolarian precipitating SrSO4 skeletons) in the marine strontium cycle. During the first cruise of the second International Indian Ocean Expedition (IIOE-2) water samples were collected along 67°E from 9°N to 5°S to explore the dissolution rate of calcium carbonate in the water. The dissolution rate can be calculated by combining measurements of water column potential alkalinity with calcium and strontium concentrations measured by ICP-OES and calcium concentration measurements using isotope dilution thermal ionization mass spectrometry (ID-TIMS). CaCO3 mineral saturation state calculated using pH and total alkalinity suggests that along 67°E, the aragonite saturation horizon lays at depth of 500 m on both sides of the equator. Across the cruise transect, dissolved strontium concentrations increase by 2-3% along the thermocline suggesting rapid recycling of strontium rich phases. This is particularly evident just below the thermocline at 8-9°N and below 1000 m water depth, south of the equator. The deep, southern enrichment in strontium does not involve a change in the Sr/Ca ratio, suggesting that this strontium enrichment is related to CaCO3 dissolution. In contrast, in the intermediate waters of the northern part of

  6. Altimeter data assimilation in the tropical Indian Ocean using water property conserving scheme

    Indian Academy of Sciences (India)

    Bhasha M Mankad; Rashmi Sharma; Sujit Basu; P K Pal

    2012-02-01

    Altimeter data have been assimilated in an ocean general circulation model using the water property conserving scheme. Two runs of the model have been conducted for the year 2004. In one of the runs, altimeter data have been assimilated sequentially, while in another run, assimilation has been suppressed. Assimilation has been restricted to the tropical Indian Ocean. An assessment of the strength of the scheme has been carried out by comparing the sea surface temperature (SST), simulated in the two runs, with in situ derived as well as remotely sensed observations of the same quantity. It has been found that the assimilation exhibits a significant positive impact on the simulation of SST. The subsurface effect of the assimilation could be judged by comparing the model simulated depth of the 20°C isotherm (hereafter referred to as D20), as a proxy of the thermocline depth, with the same quantity estimated from ARGO observations. In this case also, the impact is noteworthy. Effect on the dynamics has been judged by comparison of simulated surface current with observed current at a moored buoy location, and finally the impact on model sea level forecast in a free run after assimilation has been quantified in a representative example.

  7. Nd isotopic composition and REE pattern in the surface waters of the eastern Indian Ocean and its adjacent seas

    Energy Technology Data Exchange (ETDEWEB)

    Amakawa, Hiroshi; Alibo, D.S.; Nozaki, Yoshiyuki

    2000-05-01

    The Nd isotopic composition and dissolved rare earth elements (REEs) have been measured in the surface waters along the 1996/97 R.V. Hakuho-Maru Expedition route from Tokyo to the Southern Ocean, southwest of Australia, through the Philippine and Indonesian Archipelago, the eastern Indian Ocean, the Bay of Bengal and the South China Sea. The radiogenic {epsilon}{sub Nd} values of {minus}1.3 and {minus}1.4 were found in the Sulu Sea and near the Lombok Strait, indicating the strong influence of surrounding volcanic islands, whereas non-radiogenic {epsilon}{sub Nd} values of less than {minus}10 were found in the Southern Ocean and the Bay of Bengal suggesting Nd of continental origin. The dissolved Nd concentrations also showed a wide range of variation from 2.8 to 19.6 pmol/kg and the trivalent REE patterns exhibited characteristic features that can be grouped into each different oceanic province. The geographical distribution of dissolved Nd is different from that of atmospherically derived {sup 210}Pb, but generally resembles that of coastally derived {sup 228}Ra. This strongly suggests that fluvial and coastal input predominates over eolian input for dissolved Nd in the surface ocean. However, the riverine dissolved Nd flux appears to be relatively minor, and remobilization of Nd from coastal and shelf sediments may play an important role in the total Nd input to the ocean. By modeling the distributions of the isotopic composition and concentration of Nd together with the activity ratio of {sup 228}Ra/{sup 226}Ra in the southeastern Indian Ocean, the authors estimate a mean residence time of Nd in the surface mixed layer to be 1.5--2.6 years. The short mean residence time is comparable with, or slightly longer than that of {sup 210}Pb suggesting similar chemical reactivity.

  8. Living planktonic foraminifera of the Wadge bank, Northern Indian Ocean

    Digital Repository Service at National Institute of Oceanography (India)

    Rao, K.K.; Jayalakshmy, K.V.; Panikkar, B.M.; Kutty, M.K.

    Twenty three species of living planktonic Foraminifera belonging to 11 genera have been studied from the Wadge Bank area off southern tip of the Indian peninsula. The fauna is characterized by species such as Globigerinoides conglobatus, G...

  9. The Indian Ocean experiment: widespread air pollution from South and Southeast Asia.

    Science.gov (United States)

    Lelieveld, J; Crutzen, P J; Ramanathan, V; Andreae, M O; Brenninkmeijer, C M; Campos, T; Cass, G R; Dickerson, R R; Fischer, H; de Gouw, J A; Hansel, A; Jefferson, A; Kley, D; de Laat, A T; Lal, S; Lawrence, M G; Lobert, J M; Mayol-Bracero, O L; Mitra, A P; Novakov, T; Oltmans, S J; Prather, K A; Reiner, T; Rodhe, H; Scheeren, H A; Sikka, D; Williams, J

    2001-02-09

    The Indian Ocean Experiment (INDOEX) was an international, multiplatform field campaign to measure long-range transport of air pollution from South and Southeast Asia toward the Indian Ocean during the dry monsoon season in January to March 1999. Surprisingly high pollution levels were observed over the entire northern Indian Ocean toward the Intertropical Convergence Zone at about 6 degrees S. We show that agricultural burning and especially biofuel use enhance carbon monoxide concentrations. Fossil fuel combustion and biomass burning cause a high aerosol loading. The growing pollution in this region gives rise to extensive air quality degradation with local, regional, and global implications, including a reduction of the oxidizing power of the atmosphere.

  10. A new species of Munidopsis Whiteaves, 1874 (Crustacea: Decapoda: Anomura) from the Northwest Indian Ocean Ridge.

    Science.gov (United States)

    Dong, Dong; Li, Xinzheng; Zhou, Yadong; Wang, Chunsheng

    2016-08-23

    A new species, Munidopsis militaris n. sp., from the Carlsberg Ridge, Northwest Indian Ocean Ridge is described herein. The species belongs to a group of species having a pair of epigastric spines, mesial and lateral eye-spines, abdominal tergites unarmed, five or six spines on the lateral margin of the carapace, and a denticulate carina on the distolateral margin of the P1 fixed finger. It can be distinguished from its relatives by the spinous lateral margin of the palm and dorsal carinae on the P2-4 propodus. The Munidopsis fauna of the Indian Ocean Ridge is seldom reported on; this new species is the sixth member of this genus found inhabiting the Indian Ocean Ridge.

  11. PRELIMINARY RESEARCH OF THE PACIFIC-INDIAN OCEAN SSTA MODE AND DEFINITION OF ITS INDEX

    Institute of Scientific and Technical Information of China (English)

    CHEN Lin-ling; JU Jian-hua; LI Chong-yin

    2005-01-01

    Applying the empirical orthogonal function (EOF) analysis to the sea surface temperature (SST) field of the tropical Pacific and Indian Oceans for determination of the first eigenvector field, the current work reveals that there are significant zonal gradients of SST in all seasons of the year in the northwestern and eastern Indian Ocean and equatorial central and eastern Pacific and western Pacific. It is also found that the variance contribution rates of the first EOF mode of every season is more than 33%. This shows that this kind of spatial distribution of the SST is stable. This pattern is named Pacific-Indian Oceans SSTA mode. Through careful analysis and comparison, an index of the mode was defined.

  12. European Slave Trading, Abolitionism, and “New Systems Of Slavery” in the Indian Ocean

    Directory of Open Access Journals (Sweden)

    Richard B Allen

    2012-06-01

    Full Text Available Recent scholarship on British, Dutch, French, and Portuguese slave trading in the Indian Ocean highlights the need to explore structural connections between pre- and post-emancipation migrant labour systems in the colonial world. Europeans purchased and transported a minimum of 431,000-547,000 slaves of African, Indian, Malagasy, and Southeast Asian origin to destinations in the Indian Ocean world between 1500 and 1850. These data, coupled with recent research on European abolitionist activity in the region and the movement of convict and indentured labourers throughout and beyond this oceanic basin, point to the development of an increasingly integrated global movement of migrant labour during the late eighteenth and early nineteenth centuries.

  13. Differential heating in the Indian Ocean differentially modulates precipitation in the Ganges and Brahmaputra basins

    Science.gov (United States)

    Pervez, Md Shahriar; Henebry, Geoffrey M.

    2016-01-01

    Indo-Pacific sea surface temperature dynamics play a prominent role in Asian summer monsoon variability. Two interactive climate modes of the Indo-Pacific—the El Niño/Southern Oscillation (ENSO) and the Indian Ocean dipole mode—modulate the amount of precipitation over India, in addition to precipitation over Africa, Indonesia, and Australia. However, this modulation is not spatially uniform. The precipitation in southern India is strongly forced by the Indian Ocean dipole mode and ENSO. In contrast, across northern India, encompassing the Ganges and Brahmaputra basins, the climate mode influence on precipitation is much less. Understanding the forcing of precipitation in these river basins is vital for food security and ecosystem services for over half a billion people. Using 28 years of remote sensing observations, we demonstrate that (i) the tropical west-east differential heating in the Indian Ocean influences the Ganges precipitation and (ii) the north-south differential heating in the Indian Ocean influences the Brahmaputra precipitation. The El Niño phase induces warming in the warm pool of the Indian Ocean and exerts more influence on Ganges precipitation than Brahmaputra precipitation. The analyses indicate that both the magnitude and position of the sea surface temperature anomalies in the Indian Ocean are important drivers for precipitation dynamics that can be effectively summarized using two new indices, one tuned for each basin. These new indices have the potential to aid forecasting of drought and flooding, to contextualize land cover and land use change, and to assess the regional impacts of climate change.

  14. Differential Heating in the Indian Ocean Differentially Modulates Precipitation in the Ganges and Brahmaputra Basins

    Directory of Open Access Journals (Sweden)

    Md Shahriar Pervez

    2016-10-01

    Full Text Available Indo-Pacific sea surface temperature dynamics play a prominent role in Asian summer monsoon variability. Two interactive climate modes of the Indo-Pacific—the El Niño/Southern Oscillation (ENSO and the Indian Ocean dipole mode—modulate the amount of precipitation over India, in addition to precipitation over Africa, Indonesia, and Australia. However, this modulation is not spatially uniform. The precipitation in southern India is strongly forced by the Indian Ocean dipole mode and ENSO. In contrast, across northern India, encompassing the Ganges and Brahmaputra basins, the climate mode influence on precipitation is much less. Understanding the forcing of precipitation in these river basins is vital for food security and ecosystem services for over half a billion people. Using 28 years of remote sensing observations, we demonstrate that (i the tropical west-east differential heating in the Indian Ocean influences the Ganges precipitation and (ii the north-south differential heating in the Indian Ocean influences the Brahmaputra precipitation. The El Niño phase induces warming in the warm pool of the Indian Ocean and exerts more influence on Ganges precipitation than Brahmaputra precipitation. The analyses indicate that both the magnitude and position of the sea surface temperature anomalies in the Indian Ocean are important drivers for precipitation dynamics that can be effectively summarized using two new indices, one tuned for each basin. These new indices have the potential to aid forecasting of drought and flooding, to contextualize land cover and land use change, and to assess the regional impacts of climate change.

  15. Indian Ocean Variability and Its Association with ENSO in a Global Coupled Model.

    Science.gov (United States)

    Zhong, Aihong; Hendon, Harry H.; Alves, Oscar

    2005-09-01

    The evolution of the Indian Ocean during El Niño-Southern Oscillation is investigated in a 100-yr integration of an Australian Bureau of Meteorology coupled seasonal forecast model. During El Niño, easterly anomalies are induced across the eastern equatorial Indian Ocean. These act to suppress the equatorial thermocline to the west and elevate it to the east and initially cool (warm) the sea surface temperature (SST) in the east (west). Subsequently, the entire Indian Ocean basin warms, mainly in response to the reduced latent heat flux and enhanced shortwave radiation that is associated with suppressed rainfall. This evolution can be partially explained by the excitation of an intrinsic coupled mode that involves a feedback between anomalous equatorial easterlies and zonal gradients in SST and rainfall. This positive feedback develops in the boreal summer and autumn seasons when the mean thermocline is shallow in the eastern equatorial Indian Ocean in response to trade southeasterlies. This positive feedback diminishes once the climatological surface winds become westerly at the onset of the Australian summer monsoon.ENSO is the leading mechanism that excites this coupled mode, but not all ENSO events are efficient at exciting it. During the typical El Niño (La Niña) event, easterly (westerly) anomalies are not induced until after boreal autumn, which is too late in the annual cycle to instigate strong dynamical coupling. Only those ENSO events that develop early (i.e., before boreal summer) instigate a strong coupled response in the Indian Ocean. The coupled mode can also be initiated in early boreal summer by an equatorward shift of the subtropical ridge in the southern Indian Ocean, which stems from uncoupled extratropical variability.

  16. Ocean sea-ice modelling in the Southern Ocean around Indian Antarctic stations

    Indian Academy of Sciences (India)

    Anurag Kumar; Suneet Dwivedi; D Ram Rajak

    2017-07-01

    An eddy-resolving coupled ocean sea-ice modelling is carried out in the Southern Ocean region (9∘–78∘E; 51∘–71∘S) using the MITgcm. The model domain incorporates the Indian Antarctic stations, Maitri (11.7∘E; 70.7∘S) and Bharati (76.1∘E; 69.4∘S). The realistic simulation of the surface variables, namely, sea surface temperature (SST), sea surface salinity (SSS), surface currents, sea ice concentration (SIC) and sea ice thickness (SIT) is presented for the period of 1997–2012. The horizontal resolution of the model varies between 6 and 10 km. The highest vertical resolution of 5 m is taken near the surface, which gradually increases with increasing depths. The seasonal variability of the SST, SSS, SIC and currents is compared with the available observations in the region of study. It is found that the SIC of the model domain is increasing at a rate of 0.09% per month (nearly 1% per year), whereas, the SIC near Maitri and Bharati regions is increasing at a rate of 0.14 and 0.03% per month, respectively. The variability of the drift of the sea-ice is also estimated over the period of simulation. It is also found that the sea ice volume of the region increases at the rate of 0.0004 km3 per month (nearly 0.005 km3 per year). Further, it is revealed that the accumulation of sea ice around Bharati station is more as compared to Maitri station.

  17. Glimpses of British Guiana at the Colonial and Indian Exhibition, 1886

    Directory of Open Access Journals (Sweden)

    Albuquerque, Sara

    2016-06-01

    Full Text Available This paper uses the example of the British Guiana Court at the Colonial and Indian Exhibition of 1886 as a case study to demonstrate how British Guiana (now Guyana was represented in Britain at the time, by crossreferencing different materials (e.g. objects, correspondence, reports, and newspapers from that period. This exhibition also shows which raw materials from the British Guiana were of interest to Britain and the involvement of Royal Botanic Gardens, Kew in this matter. Nevertheless, the exhibition not only displayed objects and commodities, such as the case of sugar, but also displayed people. Here, particular attention is paid to the Amerindians who were portrayed as living ethnological exhibits at the exhibition. This paper aims to understand how British Guiana was seen and administered by its mother country and also how Everard im Thurn (1852-1932, the explorer, sought to manoeuvre that representation, as well as his relation with RBG, Kew. Taking into consideration that this colony was a neglected area of the British Empire, even in im Thurn’s time, this exhibition was an opportunity not only to display the empire but also for advertising the potential of the neglected colony and to ensure that it would not be forgotten.Este análisis se centra en la Exposición Colonial de 1886; a través del estudio de caso del Pabellón de la Guayana Británica (hoy Guyana, demuestra cómo ésta estaba representada en Gran Bretaña. Para mostrar sus contenidos cruza diferentes fuentes de la época: objetos, correspondencia, informes y periódicos. La exposición en aquel pabellón refleja que las materias primas de la Guayana Británica eran de interés para Gran Bretaña y la implicación en esta materia de los Jardines Reales Botánicos, llamados Kew. La exposición no sólo mostró los objetos y las materias primas, como el caso del azúcar, sino que también llevó habitantes de la Guayana. Aquí se presta especial atención a los amerindios

  18. A multisensor climatological view of double ITCZs over the Indian Ocean

    Digital Repository Service at National Institute of Oceanography (India)

    Rameshkumar, M.R.; Devasthale, A.; Levy, G.; Sankar, S.; Bakan, S.; Grassl, H.

    ). In order to see the evolution of the double ITCZs in the Indian Ocean we have composited the rainfall, freshwater flux, cloud cover and cloud liquid water content for the following four stages. We tried several combinations starting from 5 days (pentad...), 10 days, 15 days (fortnight) and monthly mean to look at the DITCZs over the western equatorial Indian Ocean. Only the 15 day composite brought the various phases of the DITCZs very clearly. Hence we have composited them into these four stages...

  19. Bycatch in the tuna purse-seine fisheries of the western Indian Ocean

    OpenAIRE

    Evgeny V Romanov

    2002-01-01

    Bycatch taken by the tuna purse-seine fishery from the Indian Ocean pelagic ecosystem was estimated from data collected by scientific observers aboard Soviet purse seiners in the western Indian Ocean (WIO) during 1986–92. A total of 494 sets on free-swimming schools, whale-shark-associated schools, whale-associated schools, and log-associated schools were analyzed. More than 40 fish species and other marine animals were recorded. Among them only two species, yellow-fin and skipjack tunas, wer...

  20. Seamounts in the Central Indian Ocean Basin: indicators of the Indian plate movement

    Digital Repository Service at National Institute of Oceanography (India)

    Mukhopadhyay, R.; Khadge, N.H

    stream_size 9 stream_content_type text/plain stream_name Proc_Indian_Acad_Sci_(EPS)_99_357.pdf.txt stream_source_info Proc_Indian_Acad_Sci_(EPS)_99_357.pdf.txt Content-Encoding ISO-8859-1 Content-Type text/plain; charset=ISO-8859-1 ...

  1. Northern Indian Ocean Salt Transport (NIOST): Estimation of Fresh and Salt Water Transports in the Indian Ocean using Remote Sensing, Hydrographic Observations and HYCOM Simulations

    Science.gov (United States)

    2014-09-30

    adjustment in the thermocline brings with it salty waters from below and allows for the entrainment of higher salinity values into the upper 50 m of...This layer of salty water likely originates in the AS. Vinayachandran et al., (2013) showed that salty AS water transported into the BoB tends to sink...Estimation of Fresh and Salt Water Transports in the Indian Ocean using Remote Sensing, Hydrographic Observations and HYCOM Simulations PI: Dr

  2. A simple estimation of equatorial Pacific response from windstress to untangle Indian Ocean dipole and basin influences on El Nino

    Digital Repository Service at National Institute of Oceanography (India)

    Izumo, T.; Vialard, J.; Dayan, H.; Lengaigne, M.; Suresh, I.

    negative feedback associated with wave reflection at both boundaries. This simple approach is then applied to assess the relative influence of the Indian Ocean Dipole (IOD) and of the Indian Ocean Basin-wide warming/cooling (IOB) in favouring the phase...

  3. Key to the identification of larvae and postlarvae of the penaeid prawns (Decapoda: Penaeidea) of the Indian Ocean

    Digital Repository Service at National Institute of Oceanography (India)

    Paulinose, V.T.

    Some of the major criteria for identifying the larvae and early postlarvae of the penaeid prawns of the Indian Ocean are presented based on the study on material collected during the International Indian Ocean Expedition (1960-65). The key also...

  4. Occurrence of @iNeogloboquadrina pachyderma@@ new subspecies in the shelf-slope sediments of northern Indian Ocean

    Digital Repository Service at National Institute of Oceanography (India)

    Setty, M.G.A.P.

    ~'N in the Bay of Bengal. Studies of hydrological conditions in the Indian Ocean reveal that the Subtropical Subsurface Water Mass is traceable as far north as the Gulf of Aden, and the Indian Ocean Deep Bottom Water Mass originating in the deepest...

  5. A Diamond in the String of Pearls :The Strategic Importance of Sri Lanka for Indian Ocean Regional Stability

    Science.gov (United States)

    2011-05-04

    Bajaj, “India Worries as China Builds.” 20 Tarique Niazi , “Gwadar: China’s Naval Outpost on the Indian Ocean,” China Brief, Volume 5, issue 4. http... Niazi , Tarique. “Gwadar: China’s Naval Outpost on the Indian Ocean

  6. A snapshot on spatial and vertical distribution of bacterial communities in the eastern Indian Ocean

    Institute of Scientific and Technical Information of China (English)

    WANG Jing; KAN Jinjun; BORECKI Laura; ZHANG Xiaodong; WANG Dongxiao; SUN Jun

    2016-01-01

    Besides being critical components of marine food web, microorganisms play vital roles in biogeochemical cycling of nutrients and elements in the ocean. Currently little is known about microbial population structure and their distributions in the eastern Indian Ocean. In this study, we applied molecular approaches including polymerase chain reaction-denaturant gradient gel electrophoresis (PCR-DGGE) and High-Throughput next generation sequencing to investigate bacterial 16S rRNA genes from the equatorial regions and the adjacent Bay of Bengal in the eastern Indian Ocean. In general,Bacteroidetes,Proteobacteria (mainlyAlpha, andGamma),Actinobacteria, Cyanobacteria andPlanctomycetes dominated the microbial communities. Horizontally distinct spatial distribution of major microbial groups was observed from PCR-DGGE gel image analyses. However, further detailed characterization of community structures by pyrosequencing suggested a more pronounced stratified distribution pattern:Cyanobacteria andActinobacteria were more predominant at surface water (25 m);Bacteroidetes dominated at 25 m and 150 m whileProteobacteria (mainlyAlphaproteobacteria) occurred more frequently at 75 m water depth. With increasing water depth, the bacterial communities from different locations tended to share high similarity, indicating a niche partitioning for minor groups of bacteria recovered with high throughput sequencing approaches. This study provided the first “snapshot” on biodiversity and spatial distribution ofBacteria in water columns in the eastern Indian Ocean, and the findings further emphasized the potential functional roles of these microbes in energy and resource cycling in the eastern Indian Ocean.

  7. Carnivorous sponges (Porifera, Cladorhizidae) from the Southwest Indian Ocean Ridge seamounts

    Science.gov (United States)

    Hestetun, Jon Thomassen; Rapp, Hans Tore; Xavier, Joana

    2017-03-01

    The family Cladorhizidae (Porifera) comprises a particularly interesting group of sponges that has developed a carnivorous feeding strategy unique within the phylum. Cladorhizids are typically considered deep-sea sponges, are frequently found at oceanic ridges and seamount systems, and new species are continuously discovered as new areas are explored. In this study we describe nine new cladorhizid sponges collected on three seamounts of the Southwest Indian Ocean Ridge (SWIOR) during the RRS ;James Cook; cruise JC066: Abyssocladia boletiphora, Ab. corniculiphora, Ab. hemiradiata, Asbestopluma (Asbestopluma) unguiferata, As. (A.) jamescooki, As. (A.) laminachela, As. (A.) pseudoisochela, As. (A.) ramuscula and Chondrocladia (Meliiderma) rogersi; and re-describe four species, viz. Ab. symmetrica, Ch. (M.) stipitata, Cladorhiza moruliformis and Cl. tridentata collected during the ;Challenger; expedition in the Southwest Indian Ocean. Barcodes and a phylogenetic analysis showing the systematic position of the new species are included as additional information. Our results show that the cladorhizid fauna of the Southwestern Indian Ocean is diverse and seems to be bathymetrically structured with no observed overlap between the newly reported upper bathyal species ( 1000 m) and previously described lower bathyal and abyssal species from the area. While the upper bathyal SWIOR species are unique and represent a regionally endemic cladorhizid fauna, similarities in morphology and spicule characters as well as molecular evidence suggests biogeographical affinities to species from the SW Pacific and SW Atlantic, but no similarities to previously reported Antarctic fauna were found. A table of cladorhizid species from the Southwest Indian Ocean and neighboring areas is provided.

  8. The Response of Snow on Tibetan Plateau in Winter to Indian Ocean Sea Surface Temperature Anomaly

    Science.gov (United States)

    Jia, Lha; Xiao, Tiangui; Wang, Chao; Du, Jun; Zhou, Xiaoli

    2017-04-01

    By using the daily snow depth and snow cover days data at 100 meteorological stations in Tibetan Plateau during 1979-2013, the methods of EOF, REOF and SVD were used to analyze the distribution characteristic and time series variation of snow in Tibetan Plateau. The coupling relationship between snow in Tibetan Plateau in winter and Indian Ocean sea surface temperature in winter, and the lag response of the snow in Tibetan Plateau in winter to Indian Ocean sea surface temperature were also studied. Main conclusions are as follows: 1.Snow depth and snow cover reaches the maximum value in January and reaches the minimum value in July; accumulated snow depth and snow cover days shows an increasing tendency during 1980s to 1990s and has a decreasing tendency since then. The accumulated snow depth and snow cover days decrease in summer and increase in autumn. 2. There were 4 high-frequency centers of snow cover days and accumulated snow depth: the southern Himalayas area, the area between the Tanggula Mountains and the Nyainqentanglha Mountains, the area around Bayankela Mountains and the area around Qilian Mountains. 3. The first pattern of SVD between snow in Tibetan Plateau in winter and Indian Ocean sea surface temperature in winter has the feature that Indian Ocean sea surface temperature increase in the whole area and snow has an opposite trend in the western and southeastern Plateau and the northern and southern Plateau. The second pattern shows that Indian Ocean sea surface temperature has an opposite trend in the western ocean and the eastern ocean and snow has an opposite trend in the western Plateau and the southeastern Plateau. There is a significant negative correlation between Indian Ocean sea surface temperature in June and July and snow in Tibetan Plateau in winter. Key words: Tibetan Plateau; snow; Indian Ocean; SVD Acknowledgements This study was supported by National Natural Science Foundation of China Fund Project (91337215, 41575066),National Key

  9. Réunion (Indian Ocean) Oceanic Island Volcanism: Seismic Structure and Heterogeneity of the Upper Lithosphere

    Science.gov (United States)

    Hirn, A.

    2002-12-01

    Réunion island in the Indian Ocean is commonly considered as the recent and active expression of the hotspot that formed the Deccan traps, although both the hypothesis of recent small hotspots for both Reunion and Mauritius, or of relation with the plate heterogeneity have been proposed. Structural studies by seismic methods, from the scale of the upper cone of the active Fournaise volcano to that of the crust 100 km around, have been carried out. At this scale significant departures appear from the Hawaiian case to which it is traditionally compared, with the seismic signature of active volcanism showing differences too. Refraction-reflection seismics do not see a geometry of the top of the underlying plate towards the island, expected in plate flexure modelling by analogy with other hotspot island. Where it is sampled, doming is suggested instead. There appears to be less magmatic products than if there was a large amount buried in a flexural depression. The velocity structure resolved for the volcanic island, apart from high velocity cores under the volcanoes leads to smaller overall density than usually considered in flexure modelling. The same appears to hold for the material of the cone of about 120 km radius rising above the regional sea-bottom level to the 30 km radius island, from coincident reflection and refraction seismics on several lines radial to the southeastern half of the island. At the crust-mantle level, there is evidence from reflection-refraction line extending 150 km either side of the island for a layer of velocity intermediate between normal crust and mantle values. Two radial reflection line to the SSW, close to each other detect a differences in depth of the oceanic basement. This may coincide with a fracture zone suggested from the reconstruction of the sea-floor spreading history from the magnetic anomaly pattern. The latter has been interpreted previously to indicate that the western part of Réunion developed atop a Paleogene fossil

  10. Zoogeography of intertidal communities in the West Indian Ocean as determined by ocean circulation systems: patterns from the Tetraclita barnacles.

    Science.gov (United States)

    Tsang, Ling Ming; Achituv, Yair; Chu, Ka Hou; Chan, Benny Kwok Kan

    2012-01-01

    The Indian Ocean is the least known ocean in the world with the biogeography of marine species in the West Indian Ocean (WIO) understudied. The hydrography of WIO is characterized by four distinct oceanographic systems and there were few glacial refugia formations in the WIO during the Pleistocene. We used the widely distributed intertidal barnacle Tetraclita to test the hypothesis that the distribution and connectivity of intertidal animals in the WIO are determined by the major oceanographic regime but less influenced by historical events such as Pleistocene glaciations. Tetraclita were studied from 32 locations in the WIO. The diversity and distribution of Tetraclita species in the Indian Ocean were examined based on morphological examination and sequence divergence of two mitochondrial genes (12S rDNA and COI) and one nuclear gene (histone 3, H3). Divergence in DNA sequences revealed the presence of seven evolutionarily significant units (ESUs) of Tetraclita in WIO, with most of them recognized as valid species. The distribution of these ESUs is closely tied to the major oceanographic circulation systems. T. rufotincta is distributed in the Monsoonal Gyre. T. ehsani is present in the Gulf of Oman and NW India. Tetraclita sp. nov. is associated with the Hydrochemical Front at 10°S latitude. T. reni is confined to southern Madagascan and Mauritian waters, influenced by the West Wind Drift. The endemic T. achituvi is restricted to the Red Sea. Tetraclita serrata consists of two ESUs (based on mtDNA analysis) along the east to west coast of South Africa. The two ESUs could not be distinguished from morphological analysis and nuclear H3 sequences. Our results support that intertidal species in the West Indian Ocean are associated with each of the major oceanographic circulation systems which determine gene flow. Geographical distribution is, however, less influenced by the geological history of the region.

  11. Tropical Indian Ocean surface salinity bias in Climate Forecasting System coupled models and the role of upper ocean processes

    Science.gov (United States)

    Parekh, Anant; Chowdary, Jasti S.; Sayantani, Ojha; Fousiya, T. S.; Gnanaseelan, C.

    2016-04-01

    In the present study sea surface salinity (SSS) biases and seasonal tendency over the Tropical Indian Ocean (TIO) in the coupled models [Climate Forecasting System version 1 (CFSv1) and version 2 (CFSv2)] are examined with respect to observations. Both CFSv1 and CFSv2 overestimate SSS over the TIO throughout the year. CFSv1 displays improper SSS seasonal cycle over the Bay of Bengal (BoB), which is due to weaker model precipitation and improper river runoff especially during summer and fall. Over the southeastern Arabian Sea (AS) weak horizontal advection associated with East Indian coastal current during winter limits the formation of spring fresh water pool. On the other hand, weaker Somali jet during summer results for reduced positive salt tendency in the central and eastern AS. Strong positive precipitation bias in CFSv1 over the region off Somalia during winter, weaker vertical mixing and absence of horizontal salt advection lead to unrealistic barrier layer during winter and spring. The weaker stratification and improper spatial distribution of barrier layer thickness (BLT) in CFSv1 indicate that not only horizontal flux distribution but also vertical salt distribution displays large discrepancies. Absence of fall Wyrtki jet and winter equatorial currents in this model limit the advection of horizontal salt flux to the eastern equatorial Indian Ocean. The associated weaker stratification in eastern equatorial Indian Ocean can lead to deeper mixed layer and negative Sea Surface Temperature (SST) bias, which in turn favor positive Indian Ocean Dipole bias in CFSv1. It is important to note that improper spatial distribution of barrier layer and stratification can alter the air-sea interaction and precipitation in the models. On the other hand CFSv2 could produce the seasonal evolution and spatial distribution of SSS, BLT and stratification better than CFSv1. However CFSv2 displays positive bias in evaporation over the whole domain and negative bias in

  12. Research opportunities and challenges in the Indian Ocean

    Digital Repository Service at National Institute of Oceanography (India)

    Hood, R.; Naqvi, S.W.A.; Wiggert, J.; Goes, J.; Coles, V.; McCreary, J.; Bates, N.; Karuppasamy, P.K.; Mahowald, N.; Seitzinger, S.; Meyers, G.

    of the world’s ocean basins. In this article, we defi ne several outstanding research questions that need to be addressed in the IO related to ocean currents and variability, the controls and fate of primary production, global change and anthropogenic impacts...

  13. Surface temperature pattern of the Indian Ocean before summer monsoon

    Digital Repository Service at National Institute of Oceanography (India)

    Gopinathan, C.K.; Rao, D.P.

    , suggests that the position of the warmer areas in the Bay of Bengal in May is an indicator of the subsequent summer rainfall over India. The statistical method adopted for the long range forcasting of the Indian summer monsoon gives very little...

  14. Time Series Observations in the North Indian Ocean

    Digital Repository Service at National Institute of Oceanography (India)

    Shenoy, D.M.; Naik, H.; Kurian, S.; Naqvi, S.W.A.; Khare, N.

    with no particular emphasis on sustained measurements to observe long term trends/changes in parameters related to global change. Here, we briefly review some of the past projects such as the Indo-German collaborative project on sediment trap studies in the Indian...

  15. Anomalous circulation in the eastern equatorial Indian Ocean during southwest monsoon of 1994

    Digital Repository Service at National Institute of Oceanography (India)

    Unnikrishnan, A.S.; Murty, V.S.N.; Babu, M.T.; Gopinathan, C.K.; Charyulu, R.J.K.

    Geostrophic circulation derived from hydrographic data collected during July-August, 1994 along 80, 84 and 88E between 5N and 3S latitudinal belt in the eastern equatorial Indian Ocean is presented. A broad westward flow north of the equator...

  16. RELATIONSHIPS BETWEEN AUTUMN INDIAN OCEAN DIPOLE MODE AND THE STRENGTH OF SCS SUMMER MONSOON

    Institute of Scientific and Technical Information of China (English)

    LI Dong-hui; ZHANG Gui; ZHU Yi-min; TAN Yan-ke; WANG Xue-zhong

    2007-01-01

    Based on 1948 - 2004 monthly Reynolds Sea Surface Temperature (SST) and NCEP/NCAR atmospheric reanalysis data, the relationships between autumn Indian Ocean Dipole Mode (IODM) and the strength of South China Sea (SCS) Summer Monsoon are investigated through the EOF and smooth correlation methods. The results are as the following. (1) There are two dominant modes of autumn SSTA over the tropical Indian Ocean. They are the uniformly signed basin-wide mode (USBM) and Indian Ocean dipole mode (IODM), respectively. The SSTA associated with USBM are prevailing decadal to interdecadal variability characterized by a unanimous pattern, while the IODM mainly represents interannual variability of SSTA. (2) When positive (negative) IODM exists over the tropical Indian Ocean during the preceding fall,the SCS summer monsoon will be weak (strong). The negative correlation between the interannual variability of IODM and that of SCS summer monsoon is significant during the warm phase of long-term trend but insignificant during the cool phase. (3) When the SCS summer monsoon is strong (weak), the IODM will be in its positive (negative) phase during the following fall season. The positive correlation between the interannual variability of SCS summer monsoon and that of IODM is significant during both the warm and cool phase of the long-term trend, but insignificant during the transition between the two phases.

  17. The Kelvin Wave Processes in the Equatorial Indian Ocean during the 2006-2008 IOD Events

    Institute of Scientific and Technical Information of China (English)

    DU Yan; LIU Kai; ZHUANG Wei; YU Wei-Dong

    2012-01-01

    The present study investigates the role of Kelvin wave propagations along the equatorial Indian Ocean during the 2006-2008 Indian Ocean Dipole (IOD). The 2006 IOD lasted for seven months, developing in May and reaching its peak in December, while the 2007 and 2008 IODs were short-lived events, beginning in ear- ly May and ending abruptly in September, with much weaker amplitudes. Associated with the above IODs, the impulses of the sea surface height (SSH) anomalies reflect the forcing from an intraseasonal time scale, which was important to the evolution of IODs in 2007 and 2008. At the thermocline depth, dominated by the propagation of Kelvin waves, the warming/cooling temperature signals could reach the surface at a particular time. When the force is strong and the local thermocline condition is fa- vorable, the incoming Kelvin waves dramatically impact the sea surface temperature (SST) in the eastern equatorial Indian Ocean. In July 2007 and late July 2008, the downwelling Kelvin waves, triggered by the Mad- den-Julian Oscillation (MJO) in the eastern and central equatorial Indian Ocean, suppressed the thermocline in the Sumatra and the Java coast and terminated the IOD, which made those events short-lived and no longer persist into the boreal fall season as the canonical IOD does.

  18. The ENSO Events in the Tropical Pacific and Dipole Events in the Indian Ocean

    Institute of Scientific and Technical Information of China (English)

    CHAO Jiping; CHAO Qingchen; LIU Lin

    2006-01-01

    A depth map (close to that of the thermocline as defined by 20℃) of climatically maximum sea-temperature anomaly was created at the subsurface of the tropical Pacific and Indian Ocean, based on which the evolving sea-temperature anomaly at this depth map from 1960 to 2000 was statistically analyzed. It is noted that the evolving sea temperature anomaly at this depth map can be better analyzed than the evolving sea surface one. For example, during the ENSO event in the tropical Pacific, the sea-temperature anomaly signals travel counter-clockwise within the range of 10°S-10°N, and while moving, the signals change in intensity or even type. If Dipole is used in the tropical Indian. Ocean for analyzing the depth map of maximum sea-temperature anomaly, the sea-temperature anomalies of the eastern and western Indian Oceans would be negatively correlated in statistical sense (Dipole in real physical sense), which is unlike the sea surface temperature anomaly based analysis which demonstrates that the inter-annual positive and negative changes only occur on the gradients of the western and eastern temperature anomalies.Further analysis shows that the development of ENSO and Dipole has a time lag features statistically, with the sea-temperature anomaly in the eastern equatorial Pacific changing earlier (by three months or so). And the linkage between these two changes is a pair of coupled evolving Walker circulations that move reversely in the equatorial Pacific and Indian Oceans.

  19. [New species of tremstodes from Indian Ocean and Red Sea fishes].

    Science.gov (United States)

    Parukhin, A M

    1979-01-01

    On the basis of the material collected in the Red Sea and the Indian Ocean four new species of trematodes are described: Bucephalopsis pseni sp. n., Diploproctodaeum chelonodoni sp. n., Bucephalus neoscombropsi sp. n., Phyllodistomum sobolevi sp. n. Anatomical and morphological characteristics of the above species as well as original figures of the trematodes are given, their taxonomic position is discussed.

  20. What Aims, what Motives? Determining Research Priorities in the International Indian Ocean Expedition, 1960-1965

    Science.gov (United States)

    Doel, R.

    2016-12-01

    Fundamental tensions affected planning for United States involvement in the International Indian Ocean Expedition (IIOE). At the highest levels of the US state, science advisors and State Department officials praised the proposed Indian Ocean research plan—loosely modeled on the recently completed International Geophysical Year of 1957-58—as a way of promoting scientific internationalism, seeing this undertaking as a way to help bring India more firmly within the Western sphere amid Cold War East-West conflicts. Dwight D. Eisenhower's presidential science advisor, George Kistiakowsky, had the IIOE in mind when he advised the National Security Council that a key role science could play in American foreign relations lay "in relation with the neutral and less-developed countries." At the same time, American scientists invited to take part in the Indian Ocean Expedition—while generally sympathetic with U.S. foreign policy aims—prioritized research programs in the physical branches of the environmental sciences. While policy-makers hoped to encourage biological research, with the aim of encouraging fisheries and protein production to aid Indian citizens, earth scientists—better-funded, better-organized, supported by military agencies because their studies were crucial to national security—came to dominate the IIOE. While the IIOE was later judged a success, for it extended long-running research programs in physical and chemical oceanography into a less-explored ocean, hopes to advance biological programs on an equal footing proved premature.

  1. Intraseasonal variability of mixed layer depth in the tropical Indian Ocean

    Digital Repository Service at National Institute of Oceanography (India)

    Keerthi, M.G.; Lengaigne, M.; Drushka, K.; Vialard, J.; de Boyer, M.C.; Pous, S.; Levy, M.; Muraleedharan, P.M.

    of the Findlater jet intensity. During winter, the Madden–Julian Oscillation drives most of the intraseasonal MLD variability in the eastern equatorial Indian Ocean. Large winter MLD signals in northern Arabian Sea can, on the other hand, be related to advection...

  2. Minima of interannual sea-level variability in the Indian Ocean

    Digital Repository Service at National Institute of Oceanography (India)

    Shankar, D.; Aparna, S.G.; McCreary, J.P.; Suresh, I.; Neetu, S.; Durand, F.; Shenoi, S.S.C.; Al Saafani, M.A.

    Wavelet analysis of altimeter sea level in the Indian Ocean shows regions of high variability (maxima) and low variability (minima) at all time scales. At interannual time scales, i.e., at periods of 17 months or more, minima are seen at several...

  3. Seasonal Variation of Diurnal Cycle of Rainfall in the Eastern Equatorial Indian Ocean

    Digital Repository Service at National Institute of Oceanography (India)

    RameshKumar, M.R.; Pednekar, S.; Katsumata, M.; Antony, M.K.; Kuroda, Y.; Unnikrishnan, A.S.

    The diurnal cycle of rainfall over the eastern equatorial Indian Ocean is studied for the period 23rd October 2001 to 31st October 2003 using the hourly data from the Triton buoy positioned at 1.5°S and 90°E. An analysis of the active and weak...

  4. Deep-sea nematodes from the Indian Ocean: new and known species of the family Comesomatidae

    NARCIS (Netherlands)

    Muthumbi, A.; Soetaert, K.E.R.; Vincx, M.

    1997-01-01

    Twelve new and known species of the genera Sabatieria, Cervonema, Paramesonchium, Hopperia and Dorylaimopsis and one new genus, Kenyanema are described from the Indian Ocean and S. pisinna Vitiello, 1970 from the Mediterranean Sea. Sabatieria lucia sp. n. is characterised by short but distinct inner

  5. Annual and seasonal mean buoyancy fluxes for the tropical Indian Ocean

    Digital Repository Service at National Institute of Oceanography (India)

    Prasad, T.G.

    . The fluxes of heat and freshwater across the air-sea interface, and hence the surface buoyancy flux, show strong spatial and temporal variability. The Bay of Bengal and eastern equatorial Indian Ocean are characterized by a net freshwater gain due to heavy...

  6. CO sub(2) and N sub(2) O fluxes from the northern Indian Ocean

    Digital Repository Service at National Institute of Oceanography (India)

    Narvekar, P.V.; Naqvi, S.W.A.; DileepKumar, M.

    The CO sub(2) and N sub(2)O in the north Indian Ocean were measured and their fluxes were evaluated. Samples were collected from the Arabian Sea and the Bay of Bengal. The water samples were analysed for dissolved oxygen, pH, TCO sub(2) and N sub(2...

  7. Seabed topography and distribution of manganese nodules in the Central Indian Ocean

    Digital Repository Service at National Institute of Oceanography (India)

    Pattan, J.N.; Kodagali, V.N.

    in number in all the topographic environments. Mn/Fe ratio was least (2.2) for nodules from hill taps whereas it was maximum for those from the plains (4.4). Cu+Ni+Co compositioin varied antipathetically with nodule abundance in the Central Indian Ocean....

  8. Validity of zooplankton biomass estimates and energy equivalent in the Indian Ocean

    Digital Repository Service at National Institute of Oceanography (India)

    Dalal, S.G.; Parulekar, A.H.

    , as deduced from the data on biochemical composition and energy content, it is evident that zooplankton of the Indian Ocean contains on an average 2.7% organic carbon, rather than the widely quoted value of 6.5%. The biomass production in terms of organic...

  9. Monthly mean wind stress along the coast of the north Indian Ocean

    Digital Repository Service at National Institute of Oceanography (India)

    Shetye, S.R.; Shenoi, S.S.C.; Antony, M.K.; Krishnakumar, V.

    Monthly-mean wind stress and its longshore and offshore components have been computed using the bulk aerodynamic method for each of a string of 36 two-degree-latitude by two-degree-longitude squares along the coast of the north Indian Ocean...

  10. Satellite-tracked drifting buoy observations in the south equatorial current in the Indian Ocean

    Digital Repository Service at National Institute of Oceanography (India)

    Shetye, S.R.; Michael, G.S.

    Three satellite-tracked drifting buoys released in the south equatorial current in the Indian Ocean followed the path of the current moving westward approximately zonally in the vicinity of 10 degrees S latitude. On nearing the east coast of Africa...

  11. Geotechnical properties of deep-sea sediments from central Indian Ocean Basin

    Digital Repository Service at National Institute of Oceanography (India)

    Khadge, N.H.

    Physical and geotechnical properties of 2 sediment cores from the nodule rich area of the Central Indian Ocean Basin are studied to know the sediment characteristics. Average water content of sediment from 2 deep-sea cores is 289% with 151...

  12. Recent studies on wind seas and swells in the Indian Ocean

    Digital Repository Service at National Institute of Oceanography (India)

    Vethamony, P.; Rashmi, R.; Samiksha, S.V.; Aboobacker, V.M.

    , Dec 7 & 8, 2012 Recent studies on wind seas and swells in the Indian ocean non-local upward mixing and local downward mixing (ACM2) (Pleim) scheme (Pleim, 2007) and surface physics by Pleim-Xiu scheme. The simulated wind parameters were validated...

  13. Monsoonal and ENSO impacts on particle fluxes and the biological pump in the Indian Ocean

    Digital Repository Service at National Institute of Oceanography (India)

    Rixen, T.; Ramaswamy, V.; Gaye, B.; Herunadi, B.; Maier-Reimer, E.; Bange, H.W.; Ittekkot, V.

    mediated CO sub(2) uptake, referred to as the biological pump, is low in the Arabian Sea during the high productive upwelling period. The biological pump seems to be strongest along the freshwater-influenced continental margins in the eastern Indian Ocean...

  14. Petrological Characteristics and Genesis of the Central Indian Ocean Basin Basalts

    Digital Repository Service at National Institute of Oceanography (India)

    Das, P.; Iyer, S.D.; Hazra, S.

    The Central Indian Ocean Basin (CIOB) basalts are plagioclase-rich, while olivine and pyroxene are very few. The analyses of 41 samples reveal high FeO sup(T) (approx. 10-18 wt percent) and TiO sub(2) (approx. 1.4-2.7 wt percent) indicating a...

  15. Wave climatology of the Indian Ocean derived from altimetry and wave model

    Digital Repository Service at National Institute of Oceanography (India)

    Vethamony, P.; Rao, L.V.G.; Kumar, R.; Sarkar, A.; Mohan, M.; Sudheesh, K.; Karthikeyan, S.B.

    month. Similar procedure is followed for Geosat data for comparison purpose. The wave model, WAVEIN has been run using ECMWF winds to hindcast waves over the Indian Ocean and to compare with Geosat wave parameters. As altimeter does not provide wave...

  16. Dissolved petroleum hydrocarbon concentrations in some regions of the northern Indian Ocean

    Digital Repository Service at National Institute of Oceanography (India)

    SenGupta, R.; Qasim, S.Z.; Fondekar, S.P.; Topgi, R.S.

    Dissolved petroleum hydrocarbons were measured in some parts of the Northern Indian Ocean using UV bsorbance technique with a clean up step. The concentration of oil ranged from 0.6 to 26.5 mu gl. Higher values were recorded along the oil tanker...

  17. Size, surface texture, chemical composition and mineralogy interrelations in ferromanganese nodules of central Indian Ocean

    Digital Repository Service at National Institute of Oceanography (India)

    Banakar, V.K.; Pattan, J.N.; Jauhari, P.

    Fiftyseven ferromanganese nodules, classified into 3 size class (4,4-6 and 6-8 cm diam.), from the siliceous sediments of central Indian Ocean were analysed for transition metals and representative sample from each size class for mineralogy. Smaller...

  18. Size analyses and geochemistry of ferromanganese nodules from the Central Indian Ocean Basin

    Digital Repository Service at National Institute of Oceanography (India)

    Valsangkar, A.B.; Khadge, N.H.

    Ferromanganese nodules collected during the 13th cruise of the M.V. Skandi Surveyor in 1987 cover a very large area, 71 424 km super(2) in the Central Indian Ocean. The area consists of 13 nodule types, which are grouped into six size classes...

  19. The evolution of the Indian Ocean parrots (Psittaciformes): extinction, adaptive radiation and eustacy.

    Science.gov (United States)

    Kundu, S; Jones, C G; Prys-Jones, R P; Groombridge, J J

    2012-01-01

    Parrots are among the most recognisable and widely distributed of all bird groups occupying major parts of the tropics. The evolution of the genera that are found in and around the Indian Ocean region is particularly interesting as they show a high degree of heterogeneity in distribution and levels of speciation. Here we present a molecular phylogenetic analysis of Indian Ocean parrots, identifying the possible geological and geographical factors that influenced their evolution. We hypothesise that the Indian Ocean islands acted as stepping stones in the radiation of the Old-World parrots, and that sea-level changes may have been an important determinant of current distributions and differences in speciation. A multi-locus phylogeny showing the evolutionary relationships among genera highlights the interesting position of the monotypic Psittrichas, which shares a common ancestor with the geographically distant Coracopsis. An extensive species-level molecular phylogeny indicates a complex pattern of radiation including evidence for colonisation of Africa, Asia and the Indian Ocean islands from Australasia via multiple routes, and of island populations 'seeding' continents. Moreover, comparison of estimated divergence dates and sea-level changes points to the latter as a factor in parrot speciation. This is the first study to include the extinct parrot taxa, Mascarinus mascarinus and Psittacula wardi which, respectively, appear closely related to Coracopsis nigra and Psittacula eupatria.

  20. Early diagenetic processes affecting nutrients in the pore waters of Central Indian Ocean cores

    Digital Repository Service at National Institute of Oceanography (India)

    Nath, B.N.; Mudholkar, A.V.

    Pore-water nutrients, nitrite, nitrate, phosphate, silicate, pH and solid-phase organic carbon were analysed for one core from the Arabian Sea and three cores from the manganese nodule area in the Central Indian Ocean Basin. Possible denitrification...

  1. Sinularia mauritiana, a new species of soft coral (Coelenterata: Octocorallia) from Mauritius, Indian Ocean

    NARCIS (Netherlands)

    Vennam, J.; Parulekar, A.H.

    1994-01-01

    Sinularia mauritiana, a new soft coral (family Alcyoniidae) from shallow subtidal waters off Mauritius (Western Indian ocean) is described. Extremely long clubs in the surface layer of the lobes, the presence of eight-radiates in the surface layer of the base, and the many spindles with simple tuber

  2. Bacterioplankton abundance and production and nanozooplankton abundance in Kenyan coastal waters (Western Indian Ocean)

    NARCIS (Netherlands)

    Goosen, N.K.; Van Rijswijk, P.; De Bie, M.J.M.; Peene, J.; Kromkamp, J.C.

    1997-01-01

    Bacterial abundance, [H-3]thymidine incorporation rate and heterotrophic nanoflagellate abundance were measured in the water column along transects perpendicular to the Kenyan coast (western Indian Ocean) during June-July (SE monsoon) and November-December (intermonsoon) 1992. Bacterial abundance wa

  3. Morphological variations in the polymetallic nodules from selected stations in the Central Indian Ocean

    Digital Repository Service at National Institute of Oceanography (India)

    Mukhopadhyay, R.

    Polymetallic nodules from the Central Indian Ocean largely range in size from 2 to 6 cm. The smaller nodules (4 cm) are subspheroidal to spheroidal in shape and with the increase in size, nodules become more discoidal and elongated. The size...

  4. Cephalopods from the Netherlands Indian Ocean Programme (NIOP)- II. Mastigoteuthid lineage and related forms

    NARCIS (Netherlands)

    Salcedo-Vargas, Mario Alejandro

    1997-01-01

    Seven species of bathypelagic squids from the West Indian Ocean are described. Two species from the chiroteuthid lineage are recorded: Pianktoteuthis sp. and Chiroteuthis mega. The family Mastigoteuthidae is divided in two genera: Idioteuthis and Mastigoteuthis. As members of the former are

  5. Coastal sea level response to the tropical cyclonic forcing in the northern Indian Ocean

    Digital Repository Service at National Institute of Oceanography (India)

    Mehra, P.; Soumya, M.; Vethamony, P.; Vijaykumar, K.; Nair, T.M.B.; Agarvadekar, Y.; Jyoti, K.; Sudheesh, K.; Luis, R.; Lobo; Halmalkar, B.

    . M. Balakrishnan Nair2, Y. Agarvadekar1, K. Jyoti1, K. Sudheesh1, R. Luis1, S. Lobo1, and B. Harmalkar1 1CSIR-National Institute of Oceanography (NIO), Goa, India 2Indian National Centre for Ocean Information Services (INCOIS), Hyderabad, India...

  6. Benthic communities associated with ferromanganese nodules from the Central Indian Ocean

    Digital Repository Service at National Institute of Oceanography (India)

    Ingole, B.S.; Pavithran, S.; Goltekar, R.

    Micro- meio- and macrobenthic associations with Ferromanganese nodules collected from the Central Indian Ocean were evaluated. The area of nodules ranged from 13.58 to 21 cm super (2). The density of abyssal macrobenthos varies from 22-110 no. m...

  7. Macrobenthic standing stock in the nodule areas of Central Indian Ocean Basin

    Digital Repository Service at National Institute of Oceanography (India)

    Pavithran, S.; Ingole, B.S.

    Diversity, distribution and standing stock of macrofauna in the nodule areas of Central Indian Ocean Basin (CIOB) were studied during April 2003. The density ranged between 22 to 132 no.m super(-2) (mean: 55 + or - 37 SD, n=25) and biomass ranged...

  8. Impact of 2004 Tsunami in the Islands of Indian Ocean: Lessons Learned

    Directory of Open Access Journals (Sweden)

    Georges Ramalanjaona

    2011-01-01

    Full Text Available Tsunami of 2004, caused by a 9.0 magnitude earthquake, is the most devastating tsunami in modern times, affecting 18 countries in Southeast Asia and Southern Africa, killing more than 250,000 people in a single day, and leaving more than 1.7 million homeless. However, less reported, albeit real, is its impact in the islands of the Indian Ocean more than 1,000 miles away from its epicenter. This is the first peer-reviewed paper on the 2004 tsunami events specifically in the eleven nations bordering the Indian Ocean, as they constitute a region at risk, due to the presence of tectonic interactive plate, absence of a tsunami warning system in the Indian Ocean, and lack established communication network providing timely information to that region. Our paper has a dual objective: the first objective is to report the 2004 tsunami event in relation to the 11 nations bordering the Indian Ocean. The second one is to elaborate on lessons learned from it from national, regional, and international disaster management programs to prevent such devastating consequences of tsunami from occurring again in the future.

  9. Biological oceanography across the Southern Indian Ocean – basinscale trends in the zooplankton community

    DEFF Research Database (Denmark)

    Jonasdottir, Sigrun; Nielsen, Torkel Gissel; Borg, Christian Marc Andersen

    2013-01-01

    We present a study on the protozooplankton 45 mm and copepods larger than 50 mm at a series of contrasting stations across the Southern Indian Ocean (SIO). Numerically, over 80% of the copepod community across the transect was less than 650 mm in size, dominated by nauplii, and smaller copepods, ...

  10. Oceanography and the base of the pelagic food web in the southern Indian Ocean

    DEFF Research Database (Denmark)

    Visser, Andre; Nielsen, Torkel Gissel; Middelboe, Mathias

    2015-01-01

    Processes governing productivity at the base of the pelagic food web of the southern Indian Ocean are influenced primarily by physical–chemical conditions with implications for the structure and function of the entire pelagic food web. Here, we report observations along a great circle transect fr...

  11. Relationship between morphology and composition of manganese nodules from the Central Indian Ocean

    Digital Repository Service at National Institute of Oceanography (India)

    Jauhari, P.

    of Antarctic Bottom Water and its effects on the floor of the Indian Ocean inferred from bottom-water potential temperature, turbidity and sea floor photography. Mar. Geol., 21:171 189. Mallik, T.K., 1980. Macro- and micromorphology of some manganese...

  12. Historical seismicity near Chagos - A complex deformation zone in the equatorial Indian Ocean

    Science.gov (United States)

    Wiens, D. A.

    1986-01-01

    The historical seismicity of the Chagos region of the Indian Ocean is analyzed, using earthquake relocation methods and a moment variance technique to determine the focal mechanisms of quakes occurring before 1964. Moment variance analysis showed a thrust faulting mechanism associated with the earthquake of 1944 near the Chagos-Laccadive Ridge; a strike-slip mechanism was associated with a smaller 1957 event occurring west of the Chagos Bank. The location of the 1944 event, one of the largest intraplate earthquakes known (1.4 x 10 to the 27th dyne/cm), would imply that the Chagos seismicity is due to a zone of tectonic deformation stretching across the equatorial Indian Ocean. The possibility of a slow diffuse boundary extending west of the Central Indian Ridge is also discussed. This boundary is confirmed by recent plate motion studies which suggest that it separates the Australian plate from a single Indo-Arabian plate.

  13. Tectonic evolution of the Perth Abyssal Plain's Quiet Zone, Southeast Indian Ocean

    Science.gov (United States)

    Ehrlich, Zohar Louis; Granot, Roi; Williams, Simon E.

    2013-04-01

    During the Late Jurassic period, the Greater-Indian plate was torn away from Australia, dissociating East Gondwanaland. The Perth Abyssal Plain (PAP) is the southernmost rift segment along the western Australian margin, and has an onset age of ~136 Ma. New marine magnetic and swath bathymetry data, crossing the entire PAP, were acquired recently on geophysical cruise ss2011v06 aboard the R/V Southern Surveyor. These have lead to the outline of conjugate Indian and Australian M-series isochrons in the east and west PAP, respectively [1]. Yet, most of the PAP was created during the Cretaceous Normal Superchron (CNS, 121-83 Ma), a period of no geomagnetic field reversals, hence no comprehensive tectonic model for the PAP exists . Here we present preliminary findings of an analytic bathymetric and magnetic investigation aimed at elucidating the PAP's quiet zone. Recent discoveries regarding the evolution of the geomagnetic field during the CNS [2] provide new time markers that can be utilized to date the oceanic crust. The magnetic anomaly data exhibit the Q2 anomaly marker (~108 Ma), further constraining the spreading history of the PAP. Together with the ridgelet transform method [3] for automated abyssal hill delineation, we present new constraints on the development of crustal construction processes (spreading location, direction and rates) that took place along the PAP spreading center. References: [1] S.E. Williams, J.M. Whittaker, R. Granot, R.D. Muller (in preparation), New constraints on the seafloor spreading history in the Perth Abyssal Plain. [2] Granot, R., J. Dyment, and Y. Gallet (2012), Geomagnetic field variability during the Cretaceous Normal Superchron, Nature Geoscience, 5(3), 220-223. [3] Downey, N. J. and R. W. Clayton (2007), A ridgelet transform method for constraining tectonic models via abyssal-hill morphology, Geochemistry Geophysics Geosystems, 8, Q03004, doi: 10.1029/2006GC001440.

  14. A Heat Budget Study on the Mechanism of SST Variations in the Indian Ocean Dipole Regions

    Institute of Scientific and Technical Information of China (English)

    HU Ruijin; LIU Qinyu; LI Chongyin

    2005-01-01

    By using a new heat budget equation that is closely related to the sea surface temperature (SST) and a dataset from an ocean general circulation model (MOM2) with 10-a integration (1987-1996), the relative importance of various processes determining SST variations in two regions of the Indian Ocean is compared. These regions are defined by the Indian Ocean Dipole Index and will be referred to hereafter as the eastern (0°-10°S, 90°-110°E) and western regions (10°S-10°N, 50°-70°E), respectively. It is shown that in each region there is a falling of SST in boreal summer and a rising in most months of other seasons, but the phases are quite different. In the eastern region, maximum cooling rate occurs in July,whereas in the western region it occurs in June with much larger magnitude. Maximum heating rate occurs in November in the eastern region, but in March in the western one. The western region exhibits another peak of increasing rate of SST in October, indicating a typical half-year period. Net surface heat flux and entrainment show roughly the same phases as the time-varying term, but the former has much larger contribution in most of a year, whereas the latter is important in the boreal summer. Horizontal advection, however, shows completely different seasonal variations as compared with any other terms in the heat budget equation. In the eastern region, it has a maximum in June/November and a minimum in March/September, manifesting a half-year period; in the western region, it reaches the maximum in August and the minimum in November. Further investigation of the horizontal advection indicates that the zonal advection has almost the opposite sign to the meridional advection. In the eastern region, the zonal advection is negative with a peak in August, whereas the meridional one is positive with two peaks in June and October. In the western region, the zonal advection is negative from March to November with two peaks in June and November, whereas the

  15. Hydrological structure and biological productivity of the tropical Indian Ocean

    Digital Repository Service at National Institute of Oceanography (India)

    Muraleedharan, U.D.; Muraleedharan, P.M.

    Hydrological structure analyses of regions in the tropical Atlantic Ocean have consistently revealed the existence of a typical tropical structure characterized by a nitrate-depleted mixed layer above the thermocline. The important biological...

  16. The Indian Ocean nodule field: Geology and resource potential

    Digital Repository Service at National Institute of Oceanography (India)

    Mukhopadhyay, R.; Ghosh, A.K.; Iyer, S.D.

    This book briefly accounts for the physiography, geology, biology, physics and chemistry of the nodule field, and discusses in detail the aspects of structure, tectonic and volcanism in the field. The role of the ocean floor sediment that hosts...

  17. Temperature profile data from STD/CTD casts from the MELVILLE from the Indian Ocean for the International Decade of Ocean Exploration / Geochemical Ocean Section Study (IDOE/GEOSECS) project, 06 December 1977 to 21 April 1978 (NODC Accession 8200055)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Temperature and salinity profile data were collected using STD/CTD casts from MELVILLE from the Indian Ocean from December 6, 1977 to April 21, 1978. Data were...

  18. Regal phylogeography: Range-wide survey of the marine angelfish Pygoplites diacanthus reveals evolutionary partitions between the Red Sea, Indian Ocean, and Pacific Ocean.

    Science.gov (United States)

    Coleman, Richard R; Eble, Jeffrey A; DiBattista, Joseph D; Rocha, Luiz A; Randall, John E; Berumen, Michael L; Bowen, Brian W

    2016-07-01

    The regal angelfish (Pygoplites diacanthus; family Pomacanthidae) occurs on reefs from the Red Sea to the central Pacific, with an Indian Ocean/Rea Sea color morph distinct from a Pacific Ocean morph. To assess population differentiation and evaluate the possibility of cryptic evolutionary partitions in this monotypic genus, we surveyed mtDNA cytochrome b and two nuclear introns (S7 and RAG2) in 547 individuals from 15 locations. Phylogeographic analyses revealed four mtDNA lineages (d=0.006-0.015) corresponding to the Pacific Ocean, the Red Sea, and two admixed lineages in the Indian Ocean, a pattern consistent with known biogeographic barriers. Christmas Island in the eastern Indian Ocean had both Indian and Pacific lineages. Both S7 and RAG2 showed strong population-level differentiation between the Red Sea, Indian Ocean, and Pacific Ocean (ΦST=0.066-0.512). The only consistent population sub-structure within these three regions was at the Society Islands (French Polynesia), where surrounding oceanographic conditions may reinforce isolation. Coalescence analyses indicate the Pacific (1.7Ma) as the oldest extant lineage followed by the Red Sea lineage (1.4Ma). Results from a median-joining network suggest radiations of two lineages from the Red Sea that currently occupy the Indian Ocean (0.7-0.9Ma). Persistence of a Red Sea lineage through Pleistocene glacial cycles suggests a long-term refuge in this region. The affiliation of Pacific and Red Sea populations, apparent in cytochrome b and S7 (but equivocal in RAG2) raises the hypothesis that the Indian Ocean was recolonized from the Red Sea, possibly more than once. Assessing the genetic architecture of this widespread monotypic genus reveals cryptic evolutionary diversity that merits subspecific recognition. We recommend P.d. diacanthus and P.d. flavescens for the Pacific and Indian Ocean/Red Sea forms.

  19. Constraints on lithospheric thermal structure for the Indian Ocean from depth and heat flow data

    Science.gov (United States)

    Shoberg, Tom; Stein, Carol A.; Stein, Seth

    1993-06-01

    Models for the thermal evolution of oceanic lithosphere are primarily constrained by variations in seafloor depth and heat flow with age. These models have been largely based on data from the Pacific and Atlantic Ocean basins. We construct seafloor age relations for the Indian Ocean which we combine with bathymetric, sediment isopach and heat flow data to derive curves for depth and heat flow versus age. Comparison of these curves with predictions from three thermal models shows that they are better fit by the shallower depths and higher heat flow for the GDH1 model, which is characterized by a thinner and hotter lithosphere than previous models.

  20. Possible factors that control calcite dissolution in the western tropical Indian Ocean

    Digital Repository Service at National Institute of Oceanography (India)

    Naik, S.S.; Naidu, P.D.

    CURRENT SCIENCE, VOL. 95, NO. 1, 10 JULY 2008 22 Possible factors that control calcite dissolution in the western tropical Indian Ocean The oceans act as a major controlling de- vice of atmospheric CO 2 through the chemistry of the oceans... and preservation of calcium carbonate in deep-sea sedi- ments 1 . Carbon dioxide dissolved in sea water is present as CO 2 gas, H 2 CO 3 , HCO – 3 and CO = 3 . All these species together con- stitute the Dissolved Inorganic Carbon (DIC) 2 which controls...

  1. Preface to: Coastal and marine biodiversity of Indian Ocean

    Digital Repository Service at National Institute of Oceanography (India)

    Wafar, M.V.M.

    Institute of Science Communication And Information Resources Dr. K. S. Krishnan Marg [Pusa Campus ] New Delhi – 110012 India INDIAN J. MAR. SCI., VOL. 34, NO. 1, MARCH 2005 7 Preface Theories of biological evolution state that species... able to foretell what would eventually live there in the face of changing oceanscape and its environment that the international program on Census of Marine Life (CoML) was launched in 2000. Nowhere in the history of time has there been a more...

  2. After continents divide: Comparative phylogeography of reef fishes from the Red Sea and Indian Ocean

    KAUST Repository

    Dibattista, Joseph D.

    2013-01-07

    Aim: The Red Sea is a biodiversity hotspot characterized by a unique marine fauna and high endemism. This sea began forming c. 24 million years ago with the separation of the African and Arabian plates, and has been characterized by periods of desiccation, hypersalinity and intermittent connection to the Indian Ocean. We aim to evaluate the impact of these events on the genetic architecture of the Red Sea reef fish fauna. Location: Red Sea and Western Indian Ocean. Methods: We surveyed seven reef fish species from the Red Sea and adjacent Indian Ocean using mitochondrial DNA cytochrome c oxidase subunit I and cytochrome b sequences. To assess genetic variation and evolutionary connectivity within and between these regions, we estimated haplotype diversity (h) and nucleotide diversity (π), reconstructed phylogenetic relationships among haplotypes, and estimated gene flow and time of population separation using Bayesian coalescent-based methodology. Results: Our analyses revealed a range of scenarios from shallow population structure to diagnostic differences that indicate evolutionary partitions and possible cryptic species. Conventional molecular clocks and coalescence analyses indicated time-frames for divergence between these bodies of water ranging from 830,000 years to contemporary exchange or recent range expansion. Colonization routes were bidirectional, with some species moving from the Indian Ocean to the Red Sea compared with expansion out of the Red Sea for other species. Main conclusions: We conclude that: (1) at least some Red Sea reef fauna survived multiple salinity crises; (2) endemism is higher in the Red Sea than previously reported; and (3) the Red Sea is an evolutionary incubator, occasionally contributing species to the adjacent Indian Ocean. The latter two conclusions - elevated endemism and species export - indicate a need for enhanced conservation priorities for the Red Sea. © 2013 Blackwell Publishing Ltd.

  3. Dissolved Zn and its speciation in the northeastern Indian Ocean and the Andaman Sea

    Directory of Open Access Journals (Sweden)

    Taejin eKim

    2015-08-01

    Full Text Available Total dissolved Zn and Zn speciation were investigated by cathodic stripping voltammetry (CSV in the northeastern Indian Ocean and the Andaman Sea. Vertical distributions of total dissolved Zn concentration (CZn in the northeastern Indian Ocean and the Andaman Sea reflect that the deep water from the Andaman Sea was rapidly replaced by incoming waters from the northeastern Indian Ocean across the sills and was homogenized by vertical mixing. In the Andaman Sea, CZn at the near surface, < 50 m in depth, ranged from 0.33 nM to 1.14 nM at the southernmost station, which is an order of magnitude higher than those at the northernmost station, 0.03–0.22 nM, where is in close proximity to the estuaries of the Irrawaddy and Salween rivers. However, the Si concentration in the near surface water, 16.3 μM, was highest at the northernmost station of the Andaman Sea. In the northeastern Indian Ocean, only one sample was applied to estimate total ligand concentrations (CL and conditional stability constants (〖K^'〗_(ZnL,Zn^(2+ for organic complexation of Zn. The CL and 〖K^'〗_(ZnL,Zn^(2+ in the northeastern Indian Ocean were 0.5 nM and 10.0, whereas those of the Andaman Sea were 0.4 nM–0.9 nM and 9.6–11.4, respectively. We observed no clear relationship between chlorophyll a (Chl a and CL in the Andaman Sea. Various sources of Zn complexing ligands might be derived in the Andaman Sea, not only from bacteria and phytoplankton, but also from the Irrawaddy–Salween rivers.

  4. Particulate polycyclic aromatic hydrocarbons in the Atlantic and Indian Ocean atmospheres during the Indian Ocean Experiment and Aerosols99: Continental sources to the marine atmosphere - article no. D05308

    Energy Technology Data Exchange (ETDEWEB)

    Crimmins, B.S.; Dickerson, R.R.; Doddridge, B.G.; Baker, J.E. [University of Maryland, Solomons, MD (USA). Chesapeake Biological Lab.

    2004-03-12

    Polycyclic aromatic hydrocarbons (PAHs), mutagenic compounds predominantly derived from combustion, have been used as markers of combustion sources to the atmosphere. Marine aerosol collected aboard the NOAA R/V Ronald Brown during the Aerosols99 and the Indian Ocean Experiment (INDOEX) projects was analyzed for PAHs to assess the continental impact of combustion-derived particulate matter on the Atlantic and Indian Ocean atmospheres. PAH concentrations in the Atlantic and southern Indian Ocean atmospheres were consistent and low, ranging from {lt}0.45 pg/m{sup 3} for coronene to 30 pg/m{sup 3} for 9,10-dimethylanthracene. PAH concentrations increased ten fold as the ship crossed the Intertropical Convergence Zone (ITCZ) into the northern Indian Ocean, indicating an increased anthropogenic influence. PAH concentrations over the northern Indian Ocean atmosphere were approximately an order of magnitude greater than those in the northern Atlantic Ocean atmosphere. PAH composition profiles over the northern Indian Ocean were specific to wind regimes and influenced by a combination of biomass and fossil fuel combustion. This was supported by significant correlations between select PAHs and organic carbon (OC), elemental carbon (EC), SO{sub 4}{sup -2} and K{sup +} for particular wind regimes. Indeno(1,2,3-cd)pyrene/EC ratios used as a combustion source marker suggest that fossil fuel combustion, rather than biomass burning, is the predominant source of PAHs to the Northern Hemisphere Indian Ocean atmosphere. Interestingly, fossil fuel consumption in the Indian sub-continent is a fraction of that in Europe and the United States but the soot and PAH levels in the adjacent Northern Indian Ocean atmosphere are significantly greater than those in the Northern Atlantic atmosphere.

  5. A sea surface salinity dipole mode in the tropical Indian Ocean

    Science.gov (United States)

    Zhang, Yuhong; Du, Yan; Qu, Tangdong

    2016-10-01

    Based on the 10 years sea surface salinity (SSS) data from Argo, we identified a salinity dipole mode in the tropical Indian Ocean, termed S-IOD: a pattern of interannual SSS variability with anomalously low-salinity in the central equatorial and high-salinity in the southeastern tropical Indian Ocean. The S-IOD matures in November-December, lagging the Indian Ocean dipole (IOD) mode derived from sea surface temperature (SST) by 2 months. For the period of observations, the S-IOD persists longer than the IOD, until the following September-October. Oscillations of the two S-IOD poles are governed by different processes. Ocean advection associated with equatorial current variability dominates the SSS anomalies of the northern pole, while surface freshwater flux variability plays a key role in the SSS anomalies of the southern pole, where anomalous precipitation is sustained by preformed sea surface temperature anomalies. The S-IOD concurs with the strong IOD, reflecting an ocean-atmosphere coupling through the SST-precipitation-SSS feedback.

  6. Tracing the drift of MH370 debris throughout the Indian Ocean

    Science.gov (United States)

    Biastoch, Arne; Durgadoo, Jonathan V.; Rühs, Siren

    2017-04-01

    On 8 March 2014, a missing Boeing 777 of Malaysia Airlines (MH370) disappeared from radar screens. Since then, extensive search efforts aim to find the missing plane in the southeastern Indian Ocean. Starting with a flaperon washed up at La Réunion in July 2015, several pieces of debris were found at different shores at islands and African coasts in the southwestern Indian Ocean. Ocean currents were examined to understand the drift paths of debris throughout the Indian Ocean, and in consequence to identify the location of MH370. Here we present a series of Lagrangian analyses in which we follow particles representing virtual pieces of debris advected in an operational high-resolution ocean model. Of particular importance is the lare-scale influence of surface waves through Stokes drift. Large number of particles are analysed in statistical approaches to provide most likely starting locations. Different pieces of debris are combined to refine probability maps of their joint start positions. Forward vs. backward advection approaches are compared.

  7. Why do oceanic negative cloud-to-ground lightning exhibit larger peak current values?

    Science.gov (United States)

    Chronis, T.; Koshak, W.; McCaul, E.

    2016-04-01

    This study examines the temporal (monthly) and spatial climatology (2004-2010) of the first return stroke of the cloud-to-ground (CG) lightning flash peak current (Ip) across various land/water boundaries over the contiguous United States. Four regions are examined: the Gulf of Mexico (region 1), the Florida peninsula (region 2), Lake Michigan (region 3), and part of the U.S. Mid-Atlantic (region 4). The crosss across the coastlines of regions 1, 2, and 4 show a gradual oceanward increase in the mean negative polarity CG peak current values (-Ip). This transition along the respective land/ocean boundaries is not sharp but gradual. In direct contrast with ocean, there is no consistent behavior in -Ip values as we move from land out across the fresh water of Lake Michigan (region 3). Meanwhile, the positive CG flash peak current (+Ip) values do not exhibit a consistent variation across any coastal boundary. For region 1, the -Ip values increase as we move toward the coast (southwards) especially during the wet season (June-October). This finding is in direct contrast with studies that documented winter as the season of maximum -Ip values. The zonal and seasonal variations of -Ip values across region 4 are not quite as pronounced, but the oceanic -Ip values are still larger than over the adjoining landmass. We explore in turn which up to date hypotheses pertinent to the oceanic -Ip enhancement are supported or refuted by our findings. It is concluded that the oceanic -Ip enhancement is not an artifact related to CG detection or Ip retrieval methods, nor is it likely related to the cloud top heights or CG activity. The study cannot refute the role of electrical conductivity and its contribution to CG leader attachment processes. However, given the observed "blurred transition" of the Ip values across the coastlines this paper suggests that likely the main physical mechanism is acting on the thundercloud potential. The recently suggested role of sodium chloride (Na

  8. The role of Equatorial Undercurrent in sustaining the Eastern Indian Ocean upwelling

    Science.gov (United States)

    Chen, Gengxin; Han, Weiqing; Shu, Yeqiang; Li, Yuanlong; Wang, Dongxiao; Xie, Qiang

    2016-06-01

    By combining volume transport and salinity analysis from 1958 to 2014, this paper investigates how the transient Equatorial Undercurrent (EUC) sustains the summer-fall equatorial eastern Indian Ocean (EIO) upwelling. On seasonal time scales, the EIO upwelling is mainly supplied by the salty water from the western basin through a buffering process: The winter-spring EUC carries the salty water from the western basin eastward, induces downwelling in the EIO, and pushes portion of the salty water below the central thermocline, which subsequently upwells to the central thermocline during summer-fall and sustains the EIO upwelling. On interannual time scales, enhanced upwelling occurs during positive Indian Ocean Dipole (+IOD) years. The strong summer-fall EUC associated with the +IOD supplies water for the intensified upwelling. This research provides new knowledge for basin-scale mass and property exchanges associated with the EIO upwelling, contributing to our understanding of three-dimensional ocean circulation and climate variability.

  9. Insolation cycles as a major control of equatorial indian ocean primary production

    Science.gov (United States)

    Beaufort; Lancelot; Camberlin; Cayre; Vincent; Bassinot; Labeyrie

    1997-11-21

    Analysis of a continuous sedimentary record taken in the Maldives indicates that strong primary production fluctuations (70 to 390 grams of carbon per square meter per year) have occurred in the equatorial Indian Ocean during the past 910,000 years. The record of primary production is coherent and in phase with the February equatorial insolation, whereas it shows diverse phase behavior with delta18O, depending on the orbital frequency (eccentricity, obliquity, or precession) examined. These observations imply a direct control of productivity in the equatorial oceanic system by insolation. In the equatorial Indian Ocean, productivity is driven by the wind intensity of westerlies, which is related to the Southern Oscillation; therefore, it is suggested that a precession forcing on the Southern Oscillation is responsible for the observed paleoproductivity dynamics.

  10. Plasticity of trophic interactions among sharks from the oceanic south-western Indian Ocean revealed by stable isotope and mercury analyses

    Science.gov (United States)

    Kiszka, Jeremy J.; Aubail, Aurore; Hussey, Nigel E.; Heithaus, Michael R.; Caurant, Florence; Bustamante, Paco

    2015-02-01

    Sharks are a major component of the top predator guild in oceanic ecosystems, but the trophic relationships of many populations remain poorly understood. We examined chemical tracers of diet and habitat (δ15N and δ13C, respectively) and total mercury (Hg) concentrations in muscle tissue of seven pelagic sharks: blue shark (Prionace glauca), short-fin mako shark (Isurus oxyrinchus), oceanic whitetip shark (Carcharhinus longimanus), scalloped hammerhead shark (Sphyrna lewini), pelagic thresher shark (Alopias pelagicus), crocodile shark (Pseudocarcharias kamoharai) and silky shark (Carcharhinus falciformis), from the data poor south-western tropical Indian Ocean. Minimal interspecific variation in mean δ15N values and a large degree of isotopic niche overlap - driven by high intraspecific variation in δ15N values - was observed among pelagic sharks. Similarly, δ13C values of sharks overlapped considerably for all species with the exception of P. glauca, which had more 13C-depleted values indicating possibly longer residence times in purely pelagic waters. Geographic variation in δ13C, δ15N and Hg were observed for P. glauca and I. oxyrinchus. Mean Hg levels were similar among species with the exception of P. kamoharai which had significantly higher Hg concentrations likely related to mesopelagic feeding. Hg concentrations increased with body size in I. oxyrinchus, P. glauca and C. longimanus. Values of δ15N and δ13C varied with size only in P. glauca, suggesting ontogenetic shifts in diets or habitats. Together, isotopic data indicate that - with few exceptions - variance within species in trophic interactions or foraging habitats is greater than differentiation among pelagic sharks in the south-western Indian Ocean. Therefore, it is possible that this group exhibits some level of trophic redundancy, but further studies of diets and fine-scale habitat use are needed to fully test this hypothesis.

  11. Lessons from the 2004 Indian Ocean and 2011 Tohoku Tsunamis, Developments, and Future Directions

    Science.gov (United States)

    Satake, K.

    2014-12-01

    The 2004 Indian Ocean tsunami, the worst tsunami disaster in history with 230,000 casualties, was generated by the largest earthquake (M 9.1) since the 1960 Chilean and 1964 Alaskan earthquakes, but such a giant earthquake was not anticipated in the Indian Ocean. Besides its size, lack of tsunami warning systems in the Indian Ocean and lack of knowledge about tsunami among the coastal residents enhanced the tsunami disaster, while scientific knowledge and technology for far-field tsunami warning system existed. Developments since 2004 include paleo-tsunami studies, global tsunami observations and tsunami warning and hazard mitigation systems. Tsunami deposits found in Indonesia, Thailand and India show that giant tsunamis similar to the 2004 tsunami occurred in the past. Deep ocean pressure gauges (DART system), GPS buoys and coastal tide gauges have been installed with real-time data-telemetry capability in Indian Ocean as well as the Pacific Ocean. Three regional tsunami warning centers are now in operation in India, Indonesia and Australia. The 2011 Tohoku earthquake was also generated by a giant (M 9.0) earthquake. While such an earthquake was unexpected in Japan, similar tsunamis occurred in the past and caused damage on Sanriku coast and Sendai plain. The tsunami warning, issued 3 min after the earthquake, saved many lives yet caused significant (~19,000) fatalities, partly because of underestimation of earthquake size. The insufficient tsunami hazard assessment caused the significant number of casualties and the Fukushima nuclear power plant accident. Existed coastal sea walls might have given inappropriate belief to coastal residents that they were protected from tsunami disaster. Scientific and technological developments needed for the future include estimation of probable maximum earthquake size for tsunami hazard assessment, and real-time estimation of earthquake and tsunami size based on seismic and sea level measurements. In addition, limitation of

  12. Export of dissolved inorganic nutrients to the northern Indian Ocean from the Indian monsoonal rivers during discharge period

    Science.gov (United States)

    Krishna, M. S.; Prasad, M. H. K.; Rao, D. B.; Viswanadham, R.; Sarma, V. V. S. S.; Reddy, N. P. C.

    2016-01-01

    Coastal regions are highly productive due to the nutrients largely supplied by rivers. To examine the contribution of dissolved inorganic nutrients (DIN) by Indian rivers to coastal waters, data were collected near the freshwater heads of 27 monsoonal rivers of peninsular India during three weeks in late July to mid-August, the middle of the principal runoff period of the southwest monsoon of 2011. Twelve researchers in four groups, equipped with car and portable laboratory equipment, sampled mid-stream of each estuary using mechanized boat, and filtered and partly analyzed the water in the evening. The estimated exports were 0.22 ± 0.05, 0.11 ± 0.03, and 1.03 ± 0.26 Tg yr-1 for dissolved inorganic nitrogen, phosphorus and silicate, respectively. Higher amounts of DIN reach the Bay of Bengal than the Arabian Sea due to the higher volume (∼76%) of discharge to the former. In contrast, the export of dissolved inorganic nitrogen is almost same to the Bay of Bengal (0.12 ± 0.03 Tg yr-1) and Arabian Sea (0.10 ± 0.02 Tg yr-1) principally due to the polluted Narmada and Tapti rivers in the northwest. Including input from the glacial rivers, Ganges, Brahmaputra and Indus, it is estimated that the northern Indian Ocean receives ∼1.84 ± 0.46, 0.28 ± 0.07 and 3.58 ± 0.89 Tg yr-1 of nitrate, phosphate and silicate, respectively, which are significantly lower than the earlier estimates of DIN export from the Indian rivers based on DIN measured in the mid or upstream rivers. Such low fluxes in this study were attributed to efficient retention/elimination of DIN (∼91%) before reaching the coastal ocean. Hence, this study suggests that the importance of sampling locations for estimating nutrient fluxes to the coastal ocean. Riverine DIN export of 1.84 ± 0.46 Tg yr-1 would support 12.2 ± 3.1 Tg C yr-1 of new production in coastal waters of the northern Indian Ocean that results in a removal of 12.2 ± 3.1 Tg atmospheric CO2 yr-1.

  13. Observed correlations between aerosol and cloud properties in an Indian Ocean trade cumulus regime

    Directory of Open Access Journals (Sweden)

    K. Pistone

    2015-10-01

    Full Text Available There are many contributing factors which determine the micro- and macrophysical properties of clouds, including atmospheric structure, dominant meteorological conditions, and aerosol concentration, all of which may be coupled to one another. In the quest to determine aerosol effects on clouds, these potential relationships must be understood, as changes in atmospheric conditions due to aerosol may change the expected magnitude of indirect effects by altering cloud properties in unexpected ways. Here we describe several observed correlations between aerosol conditions and cloud and atmospheric properties in the Indian Ocean winter monsoon season. In the CARDEX (Cloud, Aerosol, Radiative forcing, Dynamics EXperiment field campaign conducted in February and March 2012 in the northern Indian Ocean, continuous measurements of atmospheric precipitable water vapor and the liquid water path (LWP of trade cumulus clouds were made, concurrent with measurements of water vapor flux, cloud and aerosol vertical profiles, meteorological data, and surface and total-column aerosol. Here we present evidence of a positive correlation between aerosol and cloud LWP which becomes clear after the data are filtered to control for the natural meteorological variability in the region. We then use the aircraft and ground observatory measurements to explore the mechanisms behind the observed aerosol–LWP correlation. We determine that increased boundary-layer humidity lowering the cloud base is responsible for the observed increase in cloud liquid water. Large-scale analysis indicates that high pollution cases originate with a highly-polluted boundary layer air mass approaching the observatory from a northwesterly direction. This polluted mass exhibits higher temperatures and humidity than the clean case, the former of which may be attributable to heating due to aerosol absorption of solar radiation over the subcontinent. While high temperature conditions dispersed along

  14. Regional boreal summer intraseasonal oscillation over Indian Ocean and Western Pacific: comparison and predictability study

    Science.gov (United States)

    Lee, Sun-Seon; Wang, Bin

    2016-04-01

    The boreal summer intraseasonal oscillation (BSISO) has two major activity centers, the northern Indian Ocean and tropical Western North Pacific, which dominate the monsoon intraseasonal variability over South Asia and East Asia, respectively. The spatial-temporal structures of BSISO over the Indian Ocean (10°S-30°N, 60°-105°E) (IOISO) and Western Pacific (10°S-30°N, 105°-150°E) (WPISO) are examined by corresponding the leading modes of daily OLR and 850-hPa zonal wind (U850). The IOISO features a northeastward propagation with a 30-45 days energy peak and the first principal component (PC1) has maximum variance in May, while the WPISO propagates northward with a broad spectral peak on 10-60 days and the PC1 has maximum variance in August. Because of the large regional differences, two regional indices, the IOISO index and WPISO index, are defined by their corresponding first two leading PCs. The combined IOISO-WPISO index captures about 30 % (10 %) of U850 (OLR) daily variance over the entire IO-WP region (10°S-30°N, 60°-150°E), which doubles that captured by the Madden-Julian Oscillation (MJO) index (Wheeler and Hendon 2004) and is 50 % higher than that captured by the BSISO index (Lee et al. 2013). The combined index also shows superior performance in representing biweekly and pentad-mean variations in the Asian-Pacific summer monsoon region (north of 10°N). The predictability/prediction skill and simulated principal modes of two regional BSISO indices are explored by using data derived from the Intraseasonal Variability Hindcast Experiment project. The major regional modes are reasonably well captured, but the forecasted fractional variances of the leading modes and variability center's locations exhibit significant deficiencies. The multi-model mean estimate of the predictability is 40-45 days for the IOISO index, whereas 33-37 days for the WPISO index. The less predictable WPISO is likely due to the existence of its significant biweekly component

  15. Contrast between the Climatic States of the Warm Pool in the Indian Ocean and in the Pacific Ocean

    Institute of Scientific and Technical Information of China (English)

    MENG Xiangfeng; WU Dexing

    2002-01-01

    Based on the analysis of Levitus data, the climatic states of the warm pool in the Indian Ocean (WPIO) and in the Pacific Ocean (WPPO) are studied. It is found that WPIO has a relatively smaller area, a shallower bottom and a slightly lower seawater temperature than those of WPPO. The horizontal area at different depths, volumes, central positions, and bottom depths of both WPIO and WPPO show quite apparent signals of seasonal variation. The maximum amplitude of WPIO surface area's seasonal variation is 58% larger over the annual mean value. WPIO's maximum volume variation amplitude is 66% larger ovcr the annual mean value. The maximum variation amplitudes of the surface area and volume of WPPO are 20.9% and 20.6% larger over the annual mean value respectively. WPIO and WPPO show different temporal and spatial characteristics mainly due to the different wind fields and restriction of ocean basin geometry. For instance, seasonal northern displacement of WPIO is, to some extent, constrained by the basin of the Indian Ocean, while WPPO moves relatively freely in the longitudinal direction. The influence of WPIO and WPPO over the atmospheric motion must be quite different.

  16. Geochemical variability of MORBs along slow to intermediate spreading Carlsberg-Central Indian Ridge, Indian Ocean

    Digital Repository Service at National Institute of Oceanography (India)

    Ray, D.; Misra, S.; Banerjee, R.

    vary in composition from the average N- and E-MORBs. Most Carlsberg Ridge- Central Indian Ridge MORBs show significantly less fractionation in FeO sub(t), in the MgO-CaO-FeO sub(t) diagram, compared to those of the Mid Atlantic- and East Pacific Rise...

  17. Ferromanganese oxides from Mid-Indian ridge, seamounts and abyssal plains from the Indian Ocean

    Digital Repository Service at National Institute of Oceanography (India)

    Rao, P.S.; Pattan, J.N.

    Mineralogical and chemical investigations show that todorokite is the only Mn mineral in the Mid-Indian Ridge ferromanganese, coatings, delta MnO2 in the seamount crusts, and well crystallised todorokite and minor amounts of delta MnO2...

  18. The reef-building coral Siderastrea siderea exhibits parabolic responses to ocean acidification and warming.

    Science.gov (United States)

    Castillo, Karl D; Ries, Justin B; Bruno, John F; Westfield, Isaac T

    2014-12-22

    Anthropogenic increases in atmospheric CO2 over this century are predicted to cause global average surface ocean pH to decline by 0.1-0.3 pH units and sea surface temperature to increase by 1-4°C. We conducted controlled laboratory experiments to investigate the impacts of CO2-induced ocean acidification (pCO2 = 324, 477, 604, 2553 µatm) and warming (25, 28, 32°C) on the calcification rate of the zooxanthellate scleractinian coral Siderastrea siderea, a widespread, abundant and keystone reef-builder in the Caribbean Sea. We show that both acidification and warming cause a parabolic response in the calcification rate within this coral species. Moderate increases in pCO2 and warming, relative to near-present-day values, enhanced coral calcification, with calcification rates declining under the highest pCO2 and thermal conditions. Equivalent responses to acidification and warming were exhibited by colonies across reef zones and the parabolic nature of the corals' response to these stressors was evident across all three of the experiment's 30-day observational intervals. Furthermore, the warming projected by the Intergovernmental Panel on Climate Change for the end of the twenty-first century caused a fivefold decrease in the rate of coral calcification, while the acidification projected for the same interval had no statistically significant impact on the calcification rate-suggesting that ocean warming poses a more immediate threat than acidification for this important coral species.

  19. Physical and temperature data from MBT casts in the Indian Ocean and North/South Pacific Ocean from 05 March 1965 to 07 December 1988 (NODC Accession 0000265)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Physical and temperature data were collected from multiple ships from March 5, 1965 to December 7, 1988. These data were collected using MBT casts in the Indian...

  20. An evaluation of XBT depth equations for the Indian Ocean

    Digital Repository Service at National Institute of Oceanography (India)

    Pankajakshan, T.; Ghosh, A.K.; Muraleedharan, P.M.

    Ocean with highly variable physicochemical conditions. It is estimated that the mean depth error to vary from -2 to -27 m in a depth range of 0-750 m, which is comparable to that raported by Hanawa, Rual, Baily, Sy and Szabados; hereafter referred...

  1. Seasonal Variability of Salt Transport During the Indian Ocean Monsoons

    Science.gov (United States)

    2011-08-27

    PJCDW was computed from the Florida State University’s (FSU) Center for Ocean-Atmosphere Prediction Studies ( COAPS ) 1° x 1° gridded pseudostress...Ekman transports using COAPS winds data. The annual mean meridional Ekman volume transport from HYCOM was computed following similar methods of

  2. Sea–air CO2 fluxes in the Indian Ocean between 1990 and 2009

    Digital Repository Service at National Institute of Oceanography (India)

    Sarma, V.V; Lenton, A.; Law, R.M.; Metzl, N.; Patra, P.K.; Doney, S.C.; Lima, I.D.; Dlugokencky, E.; Ramonet, M.; Valsala, V

    ), Global Monitoring Division, Boulder, CO, USA 8Laboratoire des Sciences du Climat et de l’Environnement (LSCE), CEA/CNRS/UVSQ, Gif sur Yvette, France 9Indian Institute of Tropical Meteorology, Dr. Homi Bhabha Road, Pashan, Pune, India Correspondence to: V..., 10, 7035–7052, 2013 www.biogeosciences.net/10/7035/2013/ doi:10.5194/bg-10-7035-2013 © Author(s) 2013. CC Attribution 3.0 License. Biogeosciences O pen A ccess Sea–air CO2 fluxes in the Indian Ocean between 1990 and 2009 V. V. S. S. Sarma1, A. Lenton2...

  3. Air-Sea Interaction Studies of the Indian and Pacific Oceans

    Science.gov (United States)

    2014-09-30

    1 DISTRIBUTION STATEMENT A. Approved for public release; distribution is unlimited. Air-Sea Interaction Studies of the Indian and Pacific...2014 2. REPORT TYPE 3. DATES COVERED 00-00-2014 to 00-00-2014 4. TITLE AND SUBTITLE Air-Sea Interaction Studies of the Indian and Pacific Oceans...applied to ship- generated waves in the 1989 Loch Linnhe experiment, J. Geophys. Res., 98, 10,259-10,269. Wikipedia, 2013: “Crow’s Nest”, http://en.wikipedia.org/wiki/ Crow %27s_nest, Referenced May 30, 2013.

  4. Future projections of Indian Ocean SSTs and its impact on monsoon

    Science.gov (United States)

    Thelliyil Sabeerali, Cherumadanakadan; Ravindran, Ajayamohan

    2016-04-01

    Assessing the future projections of the Indian Ocean (IO) Sea Surface Temperatures (SSTs) under the global warming scenario has a paramount societal impact considering its potential to alter the seasonal mean rainfall over the Indian subcontinent. Observations show a pronounced warming in the western tropical IO compared to other ocean basins. Here, we explore the projections of boreal summer SSTs over the IO using the Representative Concentration Pathways 8.5 (RCP8.5) scenarios of Coupled Model Intercomparison Project Phase5 (CMIP5) simulations. Consistent with observations, most of the CMIP5 models show a faster warming rate over the western tropical IO compared to other ocean basins. Model simulations indicate a shift in the mean Walker circulation with an anomalous ascending motion over the central equatorial Pacific and an anomalous descending motion over the eastern tropical IO. As a consequence of this, a negative SST skewness is evident in the eastern tropical IO which leads to the increased frequency of positive Indian Ocean Dipole (IOD) events. Mechanisms responsible for this pronounced western IO warming is studied by analyzing the changes in the mean thermocline depth and circulation features. The impact of these changes in IO SST on seasonal mean monsoon precipitation and circulation in a warming scenario and its associated mechanisms are also investigated.

  5. MEAN SQUARE DEVIATION ANALYSIS OF INTERANNUAL SST VARIABILITY IN TROPICAL PACIFIC AND INDIAN OCEAN

    Institute of Scientific and Technical Information of China (English)

    严华生; 李艳; 等

    2002-01-01

    Using the SST data series in tropical ocean(20°N-20°S,50°E-80°W)during 1951-1997 to calculate its monthly mean square deviation,the work obtains results showing that interannual SST variability of the Pacific is more significant than that of the Indian Ocean.Especially near the central and eastern equatorial Pacific(165°W-90°W,6°N-6°S)。where it ranges from 2℃ to 4℃.The interannual SST variability is obvious in November and December but small in March and April.The interannual variabiltiy of "warm pool"SST is not so obvious as that of the eastern equatorial Pacific,Howerver,interannual SST variability of the Indian Ocean ranges from 1℃to 2℃ or so,being smaller than that of the Pacific,In the Indian ocean.Interannual SST variability of the Southern Hemisphere is more obvious than that of the Northern Hemisphere,According to above characterstics of interannual SST variability,the key sectors are determined.

  6. A new dipole index of the salinity anomalies of the tropical Indian Ocean

    Science.gov (United States)

    Li, Junde; Liang, Chujin; Tang, Youmin; Dong, Changming; Chen, Dake; Liu, Xiaohui; Jin, Weifang

    2016-01-01

    With the increased interest in studying the sea surface salinity anomaly (SSSA) of the tropical Indian Ocean during the Indian Ocean Dipole (IOD), an index describing the dipole variability of the SSSA has been pursued recently. In this study, we first use a regional ocean model with a high spatial resolution to produce a high-quality salinity simulation during the period from 1982 to 2014, from which the SSSA dipole structure is identified for boreal autumn. On this basis, by further analysing the observed data, we define a dipole index of the SSSA between the central equatorial Indian Ocean (CEIO: 70°E-90°E, 5°S-5°N) and the region off the Sumatra-Java coast (SJC: 100°E-110°E, 13°S-3°S). Compared with previous SSSA dipole indices, this index has advantages in detecting the dipole signals and in characterizing their relationship to the sea surface temperature anomaly (SSTA) dipole variability. Finally, the mechanism of the SSSA dipole is investigated by dynamical diagnosis. It is found that anomalous zonal advection dominates the SSSA in the CEIO region, whereas the SSSA in the SJC region are mainly influenced by the anomalous surface freshwater flux. This SSSA dipole provides a positive feedback to the formation of the IOD events. PMID:27052319

  7. A new dipole index of the salinity anomalies of the tropical Indian Ocean

    Science.gov (United States)

    Li, Junde; Liang, Chujin; Tang, Youmin; Dong, Changming; Chen, Dake; Liu, Xiaohui; Jin, Weifang

    2016-04-01

    With the increased interest in studying the sea surface salinity anomaly (SSSA) of the tropical Indian Ocean during the Indian Ocean Dipole (IOD), an index describing the dipole variability of the SSSA has been pursued recently. In this study, we first use a regional ocean model with a high spatial resolution to produce a high-quality salinity simulation during the period from 1982 to 2014, from which the SSSA dipole structure is identified for boreal autumn. On this basis, by further analysing the observed data, we define a dipole index of the SSSA between the central equatorial Indian Ocean (CEIO: 70°E-90°E, 5°S-5°N) and the region off the Sumatra-Java coast (SJC: 100°E-110°E, 13°S-3°S). Compared with previous SSSA dipole indices, this index has advantages in detecting the dipole signals and in characterizing their relationship to the sea surface temperature anomaly (SSTA) dipole variability. Finally, the mechanism of the SSSA dipole is investigated by dynamical diagnosis. It is found that anomalous zonal advection dominates the SSSA in the CEIO region, whereas the SSSA in the SJC region are mainly influenced by the anomalous surface freshwater flux. This SSSA dipole provides a positive feedback to the formation of the IOD events.

  8. Indian Ocean sea surface temperature variability and change since 1960s: forcing and process

    Science.gov (United States)

    Han, W.; Meehl, G. A.; Hu, A.

    2005-12-01

    Indian Ocean sea surface temperature (SST) variability and change since 1960s are investigated using global coupled models,the Community Climate System Model version 3 (CCSM3) and parallel climate model (PCM). Results from the CCSM3 and a series of PCM experiments are analyzed in order to understand the roles played by internal variability, human-induced warming, and external forcing in causing the SST variations. To consolidate the model results, the simple Ocean model Data Assimilation (SODA) products are also analyzed. The results suggest that the SST in both the south and north Indian Ocean (IO) has an increasing trend. Overlying on this trend is decadal variability. Consistent with previous studies, the warming trend results mainly from the human-induced increased green house gases, which increase downward longwave fluxes. Interestingly, warming of the upper tropical and subtropical basins is accomanied by cooling in higher-latitudes in the Antarctic Circumpolar Current (ACC) region, which results from the reduced southward heat transports by weakened the subtropical cells (STCs). This colder, ACC water can enter the IO via deep layers in the south and then shoals upward to the thermocline layer in the tropical Indian Ocean, causing a distinct vertical structrure: with warming in the near surface and below the thermocline and cooling in the thermocline. The SST decadal variability, however, is caused primarily by external forcing, due to a combined effect of surface heat flux and lateral heat transport. Internal variability of the coupled system also plays a role.

  9. RELATIONSHIP BETWEEN DIPOLE OSCILLATION OF SSTA OF INDIAN OCEAN REGION AND PRECIPITATION AND TEMPERATURE IN CHINA

    Institute of Scientific and Technical Information of China (English)

    肖子牛; 晏红明; 李崇银

    2002-01-01

    The work is a general survey using SSTA data of the Indian Ocean and of precipitation at 160Chinese weather stations over 1951~1997 (47 years). It reveals that the dipole oscillation of SST, especially the dipole index of March~May, in the eastern and western parts of the ocean correlates well with the precipitation during the June~August raining season in China. As shown in analysis of 500-hPa Northern Hemisphere geopotential height height by NCEP for 1958~1995, the Indian Ocean dipole index (IODI) is closely related with geopotential height anomalies in the middle- and higher- latitudes in the Eurasian region. As a negative phase year of IODI corresponds to significant Pacific-Japan (P J) wavetrain, it is highly likely that the SST for the dipole may affect the precipitation in China through the wavetrain. Additionally, correlation analysis of links between SST dipole index of the Indian Ocean region and air temperature in China also shows good correlation between the former and wintertime temperature in southern China.

  10. Dianeutral mixing, transformation and transport of the deep water of the Indian Ocean

    Science.gov (United States)

    You, Yuzhu

    1999-01-01

    The realization of North Atlantic Deep Water (NADW) replacement in the deep northern Indian Ocean is crucial to the "conveyor belt" scheme. This was investigated with the updated 1994 Levitus climatological atlas. The study was performed on four selected neutral surfaces, encompassing the Indian deep water from 2000 to 3500 m. The Indian deep water comprises three major water masses: NADW, Circumpolar Deep Water (CDW) and North Indian Deep Water (NIDW). Since NADW flowing into the southwest Indian Ocean is largely blocked by the ridges (the Madagascar Ridge in the east and Davie Ridge in the north in the Mozambique Channel) and NIDW is the only source in the northern Indian Ocean that cannot provide a large amount of volume transport, CDW has to be a major source for the Indian deep circulation and ventilation in the north. Thus the question of NADW replacement becomes that of how the advective flows of CDW from the south are changed to be upwelled flows in the north—a water-mass transformation scenario. This study considered various processes causing motion across neutral surfaces. It is found that dianeutral mixing is vital to achieve CDW transformation. Basin-wide uniform dianeutral upwelling is detected in the entire Indian deep water north of 32°S, somewhat concentrated in the eastern Indian Ocean on the lowest surface. However, the integrated dianeutral transport is quite low, about a net of 0.2 Sv (1 Sv=10 6 m 3 s -1) across the lowermost neutral surface upward and 0.4 Sv across the uppermost surface upward north of 32°S with an error band of about 10-20% when an uncertainty of half-order change in diffusivities is assumed. Given about 10-15% of rough ridge area where dianeutral diffusivity could be about one order of magnitude higher (10 -4 m 2 s -1) due to internal-wave breaking, the additional amount of increased net dianeutral transport across the lowest neutral surface is still within that error band. The averaged net upward transport in the north

  11. Atmospheric response to Indian Ocean Dipole forcing: changes of Southeast China winter precipitation under global warming

    Science.gov (United States)

    Zhang, Ling; Sielmann, Frank; Fraedrich, Klaus; Zhi, Xiefei

    2017-03-01

    To investigate the relationship between autumn Indian Ocean Dipole (IOD) events and the subsequent winter precipitation in Southeast China (SEC), observed fields of monthly precipitation, sea surface temperature (SST) and atmospheric circulation are subjected to a running and a maximum correlation analysis. The results show a significant change of the relevance of IOD for the early modulation of SEC winter precipitation in the 1980s. After 1980, positive correlations suggest prolonged atmospheric responses to IOD forcing, which are linked to an abnormal moisture supply initiated in autumn and extended into the subsequent winter. Under global warming two modulating factors are relevant: (1) an increase of the static stability has been observed suppressing vertical heat and momentum transports; (2) a positive (mid-level) cloud-radiation feedback jointly with the associated latent heating (apparent moisture sink Q2) explains the prolongation of positive as well as negative SST anomalies by conserving the heating (apparent heat source Q1) in the coupled atmosphere-ocean system. During the positive IOD events in fall (after 1980) the dipole heating anomalies in the middle and lower troposphere over the tropical Indian Ocean are prolonged to winter by a positive mid-level cloud-radiative feedback with latent heat release. Subsequently, thermal adaptation leads to an anticyclonic anomaly over Eastern India overlying the anomalous cooling SST of the tropical Eastern Indian Ocean enhancing the moisture flow from the tropical Indian Ocean through the Bay of Bengal into South China, following the northwestern boundary of the anticyclonic circulation anomaly over east India, thereby favoring abundant precipitation in SEC.

  12. Assessing the internal consistency of the CARINA database in the Indian sector of the Southern Ocean

    Directory of Open Access Journals (Sweden)

    C. Lo Monaco

    2010-02-01

    Full Text Available Carbon and carbon-relevant hydrographic and hydrochemical ancillary data from previously not publicly available cruises were retrieved and recently merged to a new data base, CARINA (CARbon IN the Atlantic. The initial North Atlantic project, an international effort for ocean carbon synthesis, was extended to include the Arctic Mediterranean Seas (Arctic Ocean and Nordic Seas and all three sectors of the Southern Ocean. Of a total of 188 cruises, 37 cruises are part of the Southern Ocean. The present work focuses on data collected in the Indian sector (20° S–70° S; 30° E–150° E. The Southern Indian Ocean dataset covers the period 1992–2004 and includes seasonal repeated observations. Parameters including salinity, dissolved inorganic carbon (TCO2, total alkalinity (TA, oxygen, nitrate, phosphate and silicate were examined for cruise-to-cruise and overall consistency. In addition, data from an existing, quality controlled data base (GLODAP were introduced in the CARINA analysis to improve data coverage in the Southern Ocean. A global inversion was performed to synthesize the information deduced from objective comparisons of deep measurements (>1500 m at nearby stations (generally <220 km. The corrections suggested by the inversion were allowed to vary within a fixed envelope, thus accounting for ocean interior variability. The adjustments applied to CARINA data and those recommended for GLODAP data, in order to obtain a consistent merged dataset, are presented and discussed. The final outcome of this effort is a new quality controlled data base for TCO2 and other properties of the carbon system that can now be used to investigate the natural variability or stability of ocean chemistry and the accumulation of anthropogenic carbon. This data product also offers an important new synthesis of seasonal to decadal observations to validate ocean biogeochemical models in a region where available historical data were very

  13. Assessing the internal consistency of the CARINA database in the Indian sector of the Southern Ocean

    Science.gov (United States)

    Lo Monaco, C.; Álvarez, M.; Key, R. M.; Lin, X.; Tanhua, T.; Tilbrook, B.; Bakker, D. C. E.; van Heuven, S.; Hoppema, M.; Metzl, N.; Ríos, A. F.; Sabine, C. L.; Velo, A.

    2010-02-01

    Carbon and carbon-relevant hydrographic and hydrochemical ancillary data from previously not publicly available cruises were retrieved and recently merged to a new data base, CARINA (CARbon IN the Atlantic). The initial North Atlantic project, an international effort for ocean carbon synthesis, was extended to include the Arctic Mediterranean Seas (Arctic Ocean and Nordic Seas) and all three sectors of the Southern Ocean. Of a total of 188 cruises, 37 cruises are part of the Southern Ocean. The present work focuses on data collected in the Indian sector (20° S-70° S; 30° E-150° E). The Southern Indian Ocean dataset covers the period 1992-2004 and includes seasonal repeated observations. Parameters including salinity, dissolved inorganic carbon (TCO2), total alkalinity (TA), oxygen, nitrate, phosphate and silicate were examined for cruise-to-cruise and overall consistency. In addition, data from an existing, quality controlled data base (GLODAP) were introduced in the CARINA analysis to improve data coverage in the Southern Ocean. A global inversion was performed to synthesize the information deduced from objective comparisons of deep measurements (>1500 m) at nearby stations (generally accounting for ocean interior variability. The adjustments applied to CARINA data and those recommended for GLODAP data, in order to obtain a consistent merged dataset, are presented and discussed. The final outcome of this effort is a new quality controlled data base for TCO2 and other properties of the carbon system that can now be used to investigate the natural variability or stability of ocean chemistry and the accumulation of anthropogenic carbon. This data product also offers an important new synthesis of seasonal to decadal observations to validate ocean biogeochemical models in a region where available historical data were very sparse.

  14. Air-Sea Coupling Over The Equatorial Indian Ocean

    Digital Repository Service at National Institute of Oceanography (India)

    Gopika, N.

    structure produces feedbacks to the overlying atmosphere that affect not only the monsoon circulation and rainfall patterns, but also weather and climate in remote parts of the globe through atmospheric teleconnections. Sea surface temperature (SST... the atmospheric Rossby radius, eddies must modify the ocean-atmosphere heat exchange, thereby affecting the total heat in the mixed layer. SST is the result not only of internal and atmospherically forced variability, but it also reflects positive feedback...

  15. Regal phylogeography: Range-wide survey of the marine angelfish Pygoplites diacanthus reveals evolutionary partitions between the Red Sea, Indian Ocean, and Pacific Ocean

    KAUST Repository

    Coleman, Richard R.

    2016-04-08

    The regal angelfish (Pygoplites diacanthus; family Pomacanthidae) occupies reefs from the Red Sea to the central Pacific, with an Indian Ocean/Rea Sea color morph distinct from a Pacific Ocean morph. To assess population differentiation and evaluate the possibility of cryptic evolutionary partitions in this monotypic genus, we surveyed mtDNA cytochrome b and two nuclear introns (S7 and RAG2) in 547 individuals from 15 locations. Phylogeographic analyses revealed four mtDNA lineages (d = 0.006 – 0.015) corresponding to the Pacific Ocean, the Red Sea, and two admixed lineages in the Indian Ocean, a pattern consistent with known biogeographical barriers. Christmas Island in the eastern Indian Ocean had both Indian and Pacific lineages. Both S7 and RAG2 showed strong population-level differentiation between the Red Sea, Indian Ocean, and Pacific Ocean (ΦST = 0.066 – 0.512). The only consistent population sub-structure within these three regions was at the Society Islands (French Polynesia), where surrounding oceanographic conditions may reinforce isolation. Coalescence analyses indicate the Pacific (1.7 Ma) as the oldest extant lineage followed by the Red Sea lineage (1.4 Ma). Results from a median-joining network suggest radiations of two lineages from the Red Sea that currently occupy the Indian Ocean (0.7 – 0.9 Ma). Persistence of a Red Sea lineage through Pleistocene glacial cycles suggests a long-term refuge in this region. The affiliation of Pacific and Red Sea populations, apparent in cytochrome b and S7 (but equivocal in RAG2) raises the hypthosis that the Indian Ocean was recolonized from the Red Sea, possibly more than once. Assessing the genetic architecture of this widespread monotypic genus reveals cryptic evolutionary diversity that merits subspecific recognition.

  16. Temperature profile and water depth data collected from HARKNESS in the Indian Ocean from 15 December 1986 to 14 January 1987 (NODC Accession 8700087)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Temperature profile and water depth data were collected using BT and XBT casts from the HARKNESS in the Indian Ocean and TOGA Area - India Ocean. Data were collected...

  17. Calls reveal population structure of blue whales across the southeast Indian Ocean and the southwest Pacific Ocean.

    Science.gov (United States)

    Balcazar, Naysa E; Tripovich, Joy S; Klinck, Holger; Nieukirk, Sharon L; Mellinger, David K; Dziak, Robert P; Rogers, Tracey L

    2015-11-24

    For effective species management, understanding population structure and distribution is critical. However, quantifying population structure is not always straightforward. Within the Southern Hemisphere, the blue whale (Balaenoptera musculus) complex is extremely diverse but difficult to study. Using automated detector methods, we identified "acoustic populations" of whales producing region-specific call types. We examined blue whale call types in passive acoustic data at sites spanning over 7,370 km across the southeast Indian Ocean and southwest Pacific Ocean (SWPO) from 2009 to 2012. In the absence of genetic resolution, these acoustic populations offer unique information about the blue whale population complex. We found that the Australian continent acts as a geographic boundary, separating Australia and New Zealand blue whale acoustic populations at the junction of the Indian and Pacific Ocean basins. We located blue whales in previously undocumented locations, including the far SWPO, in the Tasman Sea off the east coast of Australia, and along the Lau Basin near Tonga. Our understanding of population dynamics across this broad scale has significant implications to recovery and conservation management for this endangered species, at a regional and global scale.

  18. Ecosystem studies in the Indian Ocean sector of the Southern Ocean undertaken by the training vessel Umitaka-maru

    Science.gov (United States)

    Moteki, Masato; Odate, Tsuneo; Hosie, Graham W.; Takahashi, Kunio T.; Swadling, Kerrie M.; Tanimura, Atsushi

    2017-06-01

    This special issue provides an overview of the ten voyages undertaken by the Umitaka-maru from the austral summers of 2002/2003 to 2014/2015 to promote the next phase of study of the ecosystems in the Indian Ocean sector of the Southern Ocean. The voyages by the Umitaka-maru have mainly targeted three areas in the Indian Ocean sector: off Dumont d'Urville Base (France, 140°E transect), off Casey Station (Australia, 110°E transect), and off Syowa Station (Japan, north of Lützow Holm Bay). The findings of Umitaka-maru's research on the krill-independent food web, animal assemblages, community structure and distribution patterns from the epipelagic to the deeper waters provide invaluable information for elucidating the material cycle and predicting future ecosystem changes. Further studies on assessing the influence of sea ice on food webs in the water column are required, which will provide crucial information for predicting ecosystem changes as a result of projected sea ice changes in the near future.

  19. Physical and underway data collected aboard the ROGER REVELLE during cruise RR0903 in the Indian Ocean and South Atlantic Ocean from 2009-03-20 to 2009-05-13 (NODC Accession 0089624)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — NODC accession 0089624 includes physical and underway data collected aboard the ROGER REVELLE during cruise RR0903 in the Indian Ocean and South Atlantic Ocean from...

  20. Physical and underway data collected aboard the ROGER REVELLE during cruise KNOX03RR in the Indian Ocean, South Pacific Ocean and others from 2007-02-04 to 2007-03-17 (NCEI Accession 0155647)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — NCEI Accession 0155647 includes physical and underway data collected aboard the ROGER REVELLE during cruise KNOX03RR in the Indian Ocean, South Pacific Ocean and...

  1. Physical, profile and underway data collected aboard the MELVILLE during cruise MV1202 in the Indian Ocean and South Atlantic Ocean from 2012-01-23 to 2012-02-08 (NCEI Accession 0130703)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — NODC Accession 0130703 includes physical, profile and underway data collected aboard the MELVILLE during cruise MV1202 in the Indian Ocean and South Atlantic Ocean...

  2. Temperature profile and other data collected from XBT casts in Indian Ocean and N / S Pacific Ocean from ICEBIRD and other platforms from 02 January 1993 to 01 January 1994 (NODC Accession 9400207)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Temperature profile and other data were collected using XBT casts from ICEBIRD and other platforms in Indian Ocean and North / South Pacific Ocean. Data were...

  3. Temperature, salinity and other variables collected from discrete sample and profile observations using CTD, bottle and other instruments from DISCOVERY in the Indian Ocean and Southern Oceans from 1994-02-19 to 1994-03-30 (NCEI Accession 0144242)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — NCEI Accession 0144242 includes discrete sample and profile data collected from DISCOVERY in the Indian Ocean and Southern Oceans (> 60 degrees South) from...

  4. Report of epibiont Thecacineta calix (Ciliophora: Suctorea) on deep sea Desmodora (Nematoda) from the Andaman Sea, Indian Ocean

    Digital Repository Service at National Institute of Oceanography (India)

    Ingole, B.S.; Singh; Sautya, S.; Dovgal, I.; Chatterjee, T.

    of epibiont Thecacineta calix (Ciliophora: Suctorea) on deep-sea Desmodora (Nematoda) from the Andaman Sea, Indian Ocean baban ingole 1 , ravail singh 1 , sabyasachi sautya 1 , igor dovgal 2 and tapas chatterjee 3 1 National Institute of Oceanography, Dona...

  5. Processes controlling the surface temperature signature of the Madden–Julian Oscillation in the thermocline ridge of the Indian Ocean

    Digital Repository Service at National Institute of Oceanography (India)

    Jayakumar, A.; Vialard, J.; Lengaigne, M.; Gnanaseelan, C.; McCreary, J.P.; PraveenKumar, B.

    During boreal winter, there is a prominent maximum of intraseasonal sea-surface temperature (SST) variability associated with the Madden–Julian Oscillation (MJO) along a Thermocline Ridge located in the southwestern Indian Ocean (5 degrees S–10...

  6. Seasonal variability of the vertical fluxes of Globigerina bulloides (D'Orbigny) in the northern Indian Ocean

    Digital Repository Service at National Institute of Oceanography (India)

    Guptha, M.V.S.; Mohan, R.

    Settling particles intercepted using time-series sediment traps at seven locations in the northern Indian Ocean have been examined for the spatial and temporal variability in the distribution and fluxes of Globigerina bulloides (D...

  7. Inter-annual variability of sea surface temperature, wind speed and sea surface height anomaly over the tropical Indian Ocean

    Digital Repository Service at National Institute of Oceanography (India)

    Muraleedharan, P.M.; Pankajakshan, T.; Sathe, P.V.

    have made an attempt to study the annual and inter-annual variability of certain prominent processes occurring over the tropical Indian Ocean. The monthly mean values of Wind Speed (FSU), Sea Surface Temperature (REYNOLDS) and Sea Surface Height Anomaly...

  8. An atlas of mean distribution of precipitable water vapour over the tropical Indian Ocean for the year 1979

    Digital Repository Service at National Institute of Oceanography (India)

    RameshKumar, M.R.; Sathe, P.V.; Muraleedharan, P.M.; Rao, L.V.G.

    The monthly mean maps of the precipitable water (PW) over the tropical Indian Ocean are prepared using the data derived from the Nimbus 7 Scanning Multichannel Microwave Radiometer (SMMR) sensor for the period January to December, 1979. The PW...

  9. Quaternary radiolarian faunal changes in the tropical Indian Ocean: Inferences to paleomonsoonal oscillation of the 10 degrees S hydrographic front

    Digital Repository Service at National Institute of Oceanography (India)

    Gupta, S.M.; Fernandes, A.A.

    in the tropical Indian Ocean. We refined the earlier radiolarian factor assemblage model by relinquishing the rare groups (less than 2% abundance) that caused noise and suppressed the environmental signals. Refined analysis resulted in an additional factor...

  10. Formation of diapiric structure in the deformation zone, central Indian Ocean: A model from gravity and seismic reflection data

    Digital Repository Service at National Institute of Oceanography (India)

    Krishna, K.S.; Rao, D.G.; Neprochnov, Y.P.

    Analyses of bathymetry, gravity and seismic reflection data of the diffusive plate boundary in the central Indian Ocean reveal a new kind of deformed structure besides the well-reported structures of long-wavelength anticlinal basement rises...

  11. Tropical systems from the southwest Indian Ocean making landfall over the Limpopo River Basin, southern Africa: a historical perspective

    CSIR Research Space (South Africa)

    Malherbe, J

    2011-03-01

    Full Text Available The study provides perspective on the contribution of landfalling tropical systems (cyclones, depressions, storms and lows) from the southwest Indian Ocean (SWIO) towards rainfall over the eastern interior of southern Africa, over the period 1948...

  12. Influence of regional and local topography on the distribution of polymetallic nodules in Central Indian Ocean Basin

    Digital Repository Service at National Institute of Oceanography (India)

    Kodagali, V.N.

    Detailed bathymetric surveys from part of the Central Indian Ocean revealed several bathymetric features such as hills, slopes, valleys, and plains. Areas with a local relief of a few to hundreds of meters generally have a high abundance...

  13. Seasonal variability of the vertical fluxes of @iGlobigerina bulloides@@ (D'Orbigny) in the northern Indian Ocean

    Digital Repository Service at National Institute of Oceanography (India)

    Guptha, M.V.S.; Mohan, R.

    Settling particles intercepted using time-series sediment traps at seven locations in the northern Indian Ocean have been examined for the spatial and temporal variability in the distribution and fluxes of @iGlobigerina bulloides@@ (@i...

  14. Identification of fish populations with particular reference to the pelagic fish stocks of the Indian Ocean region

    Digital Repository Service at National Institute of Oceanography (India)

    Dwivedi, S.N.

    The most essential step in any fishery management is the identification of discrete fish populations. This is particularly important for the development of Indian Ocean pelagic fisheries. The simple signal character analysis of meristic or metric...

  15. First record of the synaptid holothurian Protankyrian protankyra Bidentata (Woodward and Barrett, 1858) from the Indian Ocean

    Digital Repository Service at National Institute of Oceanography (India)

    Deshmukh, A.; Ingole, B.S.; Mukharjee, I.; Sivadas, S.K.

    Sea cucumbers (holothurians) are marine invertebrates that are harvested worldwide, mostly for human consumption in Asian countries To date, only eight species of synaptid holothurians of the genus Protankyra have been reported from the Indian Ocean...

  16. New species of Ciliates (Genus: Strombidium sp.) from hypoxic waters of the Bay of Bengal, Northern Indian Ocean

    Digital Repository Service at National Institute of Oceanography (India)

    Elangovan, S.S.; Gauns, M.

    ., 58 (2011), 43- 48. 16. Wyrtki, K., Oceanographic Atlas of the International Indian Ocean Expedition, Natl. Sci. Found., Washington, D. C., (1971), 531 pp. 17. Morrison, J.M., Codispoti, L.A., Sharon L. Smith., Karen Wishner., Charles Flagg...

  17. New records of Thecacineta cothurnioides and Trematosoma rotunda (Ciliophora, Suctorea) as epibionts on nematodes from the Indian Ocean

    Digital Repository Service at National Institute of Oceanography (India)

    Dovgal, I.; Chatterjee, T.; Ingole, B.S.

    of Th. cothurnioides. Key words: Suctoria, fauna, Indian Ocean, Trematosoma, Thecacineta from type locality for both species are fragmentary, the modes of reproduction were unknown. Rede- scription with distribution and nomenclatural notes are also...

  18. Influence of tropical storms in the Northern Indian Ocean on dust entrainment and long-range transport.

    Digital Repository Service at National Institute of Oceanography (India)

    Ramaswamy, V.

    Ninety five tropical cyclonic events (tropical storms, depressions and cyclones) between 2001 and 2010 were studied to determine their impact on dust outbreaks and long-range transport over the northern Indian Ocean and south Asia. In addition...

  19. Variability of mixed layer depth in the northern Indian Ocean during 1977 and 1979 summer monsoon seasons

    Digital Repository Service at National Institute of Oceanography (India)

    Gopalakrishna, V.V.; Sadhuram, Y.; RameshBabu, V.

    Influences of wind stress (tau) and wind stress curl (Grad Gamma) on the short term variability of the mixed layer depth at different locations in the northern Indian Ocean during different phases of summer monsoon activity were examined...

  20. Observations on phytoplankton pigments, zooplankton and physico-chemical parameters in surface waters from southern Indian Ocean and Antarctic region

    Digital Repository Service at National Institute of Oceanography (India)

    JiyalalRam, M.; Goswami, S.C.

    Observations on distribution of chlorophyll a, phaeopigments, zooplankton and physico-chemical parameters in the Southern Ocean were carried out during 9th Indian Antarctic-Expedition (1989-1990). The results indicated high phytoplankton biomass...

  1. On the suitability of global algorithms for the retrieval of SST from the north Indian Ocean using NOAA/AVHRR

    Digital Repository Service at National Institute of Oceanography (India)

    Shenoi, S.S.C.

    The errors associated with the SST retrievals from the north Indian Ocean, using global multichannel sea surface temperature (MCSST), nonlinear sea surface temperature (NLSST), and Pathfinder sea surface temperature (PFSST) algorithms are analysed...

  2. Depth anomalies in the Arabian Basin, NW Indian Ocean

    Digital Repository Service at National Institute of Oceanography (India)

    Ajay, K.K.; Chaubey, A.K.

    (swell). According to Sleep (1990), the regional domal uplift is a characteristic feature of the presence of mantle plumes. The change from vertical upwelling to horizontal flow along the base of the lithosphere induces an upward force on the plate...) Site 715. In: Backman J, Duncan RA et al. (eds) Proceedings Ocean Drilling Program, College Station, TX, pp 917–946 Sichoix L, Bonneville A, McNutt MK (1998) The seafloor swells and superswell in French Polynesia. J Geophys Res 103:27123– 27133 Sleep NH...

  3. Introduction to "Tsunami Science: Ten Years After the 2004 Indian Ocean Tsunami. Volume I"

    Science.gov (United States)

    Rabinovich, Alexander B.; Geist, Eric L.; Fritz, Hermann M.; Borrero, Jose C.

    2015-03-01

    Twenty-two papers on the study of tsunamis are included in Volume I of the PAGEOPH topical issue "Tsunami Science: Ten Years after the 2004 Indian Ocean Tsunami." Eight papers examine various aspects of past events with an emphasis on case and regional studies. Five papers are on tsunami warning and forecast, including the improvement of existing tsunami warning systems and the development of new warning systems in the northeast Atlantic and Mediterranean region. Three more papers present the results of analytical studies and discuss benchmark problems. Four papers report the impacts of tsunamis, including the detailed calculation of inundation onshore and into rivers and probabilistic analysis for engineering purposes. The final two papers relate to important investigations of the source and tsunami generation. Overall, the volume not only addresses the pivotal 2004 Indian Ocean (Sumatra) and 2011 Japan (Tohoku) tsunamis, but also examines the tsunami hazard posed to other critical coasts in the world.

  4. The Influence of Indian Ocean Atmospheric Circulation on Warm Pool Hydroclimate During the Holocene Epoch

    Science.gov (United States)

    Tierney, J.E.; Oppo, D. W.; LeGrande, A. N.; Huang, Y.; Rosenthal, Y.; Linsley, B. K.

    2012-01-01

    Existing paleoclimate data suggest a complex evolution of hydroclimate within the Indo-Pacific Warm Pool (IPWP) during the Holocene epoch. Here we introduce a new leaf wax isotope record from Sulawesi, Indonesia and compare proxy water isotope data with ocean-atmosphere general circulation model (OAGCM) simulations to identify mechanisms influencing Holocene IPWP hydroclimate. Modeling simulations suggest that orbital forcing causes heterogenous changes in precipitation across the IPWP on a seasonal basis that may account for the differences in time-evolution of the proxy data at respective sites. Both the proxies and simulations suggest that precipitation variability during the September-November (SON) season is important for hydroclimate in Borneo. The preeminence of the SON season suggests that a seasonally lagged relationship between the Indian monsoon and Indian Ocean Walker circulation influences IPWP hydroclimatic variability during the Holocene.

  5. Present-day zonal wind influences projected Indian Ocean Dipole skewness

    Science.gov (United States)

    Ng, Benjamin; Cai, Wenju

    2016-11-01

    A prominent feature of the Indian Ocean Dipole (IOD) is its positive skewness, where positive phases tend to be stronger in amplitude than the negative phase. Positive IOD events are associated with devastating floods over parts of East Africa and India, while Australia and Indonesia experience dry conditions. Under greenhouse warming, climate models project a weakening of the positive IOD skewness, but their simulation of present-day skewness is too weak. Here we show that this bias and the projected skewness change are related to the simulation of the climatological zonal wind in the central equatorial Indian Ocean. In particular, models with overly weak present-day westerlies, which is a common model bias, generate overly weak present-day skewness and a smaller projected reduction in skewness. Improving the ability of models in simulating stronger westerly winds may lead to stronger present-day simulated skewness and a larger skewness reduction in a warmer climate.

  6. Banaras in the Indian Ocean: Circulating, Connecting and Creolizing Island Stories

    Directory of Open Access Journals (Sweden)

    Srilata Ravi

    2012-06-01

    Full Text Available What links Bernardin de Saint Pierre’s 1788 novel about Isle de France, Paul et Virginie, with V.S. Naipaul’s 1972 piece, An overcrowded Barracoon? What is common to Joseph Conrad’s 1910 novella, A Smile of Fortune, and tourist brochures of La Grande Baie? What brings together the story of the ruins of Babylon and the Ghats of the Ganges? Actually, these seemingly disjointed narratives make up a vast library of inter-connecting Indian Ocean island stories. In this study I will use the image of ‘Banaras’ as the locus of an inter-textual reading exercise connecting the literary spaces of Mauritian writer and filmmaker Barlen Pyamootoo with other stories like those mentioned above. Pyamootoo’s literary universe reveals to us the dynamic, multilayered and polyphonic nature of Indian Ocean island cultures.

  7. A hot midmantle anomaly in the area of the Indian Ocean Geoid Low

    Science.gov (United States)

    Reiss, Anne-Sophie; Thomas, Christine; van Driel, Jac; Heyn, Björn

    2017-07-01

    We investigate the upper mantle seismic discontinuities at 410 and 660 km depth beneath the Indian Ocean Geoid Low (IOGL). To map the discontinuities' topography, we use differential travel times of PP and SS waves and their precursors. Our final data set consists of 37 events with Mw ≥ 5.8, which densely cover our investigation area, also with crossing ray paths. We use array methods to detect the low-amplitude precursor signals. The best quality data show a deepened 410 km discontinuity in the center of the IOGL as well as a mostly elevated 660 km discontinuity beneath the northern Indian Ocean, which we interpret as a hot anomaly currently residing in the mantle transition zone. We conclude that the largest negative geoid anomaly might be caused by a combined effect of hot material in the midmantle below the innermost IOGL and cold material below 660 km farther south.

  8. Impact of prolonged La Niña events on the Indian Ocean with a special emphasis on southwest Tropical Indian Ocean SST

    Science.gov (United States)

    Singh, P.; Chowdary, J. S.; Gnanaseelan, C.

    2013-01-01

    This study examines the mechanisms governing the teleconnections associated with the long-lived La Niña variability in the tropical Indian Ocean (TIO) sea surface temperature (SST) anomalies using observational and reanalysis products. Two long-lived La Niña events (1973 to 1976 and 1998 to 2001) are observed in the recent years, one falling before and the other after the mid 1970's climatic shift. The winter (boreal) and spring (November to April) TIO SST is highly influenced by long-lived La Niña forcing. Climatic shift in mid 1970s contributes to the changes in TIO SST pattern during these two long-lived La Niña events. Surface heat flux variations due to long-lived La Niña contribute to the SST changes except in the southwest TIO. The upwelling favorable local surface wind stress curl and upwelling Rossby waves originating from the east are the dominant mechanisms responsible for the La Niña related winter time SST cooling over the southwest TIO. Long-lived La Niña induced surface wind anomalies enhance the fall Wyrtki Jet in the equatorial Indian Ocean resulting large scale anomalous heat transport. Local SST cooling reduces convection and contributes to the low rainfall over southwest TIO and the northern parts of Madagascar Island.

  9. Origins of wind-driven intraseasonal sea level variations in the North Indian Ocean coastal waveguide

    Digital Repository Service at National Institute of Oceanography (India)

    Suresh, I.; Vialard, J.; Lengaigne, M.; Han, W.; McCreary, J.P.; Durand, F.; Muraleedharan, P.M.

    over the 30°S−30°N, 30°E−110°E domain, with a coastline determined from the 200-m isobath. The model is forced by intraseasonal (20−150-day filtered) daily QuikSCAT wind-stresses (available from http://cersat/ifremer.fr/data/) from August, 1999... to October, 2009. Several studies indicate that this wind-stress product yields a realistic intraseasonal oceanic response in the equatorial Indian Ocean [e.g., Sengupta et al., 2007; Nagura and McPhaden, 2012]. We show results obtained using 5 baroclinic...

  10. High Resolution Altimetry Reveals New Characteristics of the December 2004 Indian Ocean Tsunami

    OpenAIRE

    Ablain, Michaël; Dorandeu, Joël; Le Traon, Pierre-Yves; Sladen, Anthony

    2006-01-01

    The Indian Ocean tsunami, which occurred on December 26, 2004, was the first to be clearly observed using satellite altimeters. The wave amplitude observed in deep-ocean by TOPEX and Jason-1 was close to 60 cm about 2 hours after the earthquake. Envisat crossed the tsunami wave 3h15 after the earthquake and measured a 35 cm wave. Even though it flew over the tsunami 7h20 after the earthquake, GFO still observed a wave close to 20 cm. To better extract the tsunami signal from altimeter measure...

  11. Hydroacoustic records of seafloor earthquakes, cryogenic sounds, and cetacean vocalizations in the Indian Ocean

    Science.gov (United States)

    Chateau, R.; Royer, J.; Dziak, R. P.; Bohnenstiehl, D. R.; Brandon, V.; Haxel, J. H.

    2009-12-01

    From October 2006 to January 2008, three hydrophones were deployed in the southern Indian Ocean by the CNRS/University of Brest and the NOAA/Oregon State University. These hydrophones were moored in the SOFAR channel and recorded a total of 1780 discrete acoustic events, mainly earthquakes from the mid-ocean ridges and cryogenic acoustic signals from off Antarctica (due to ice shelf creeping and iceberg breaking). The low attenuation of acoustic waves in the SOFAR channel allows for the long-range detection of low-magnitude earthquakes (body-magnitude cetacean species, including blue, fin, and Milke whales.

  12. PBDEs in the atmosphere over the Asian marginal seas, and the Indian and Atlantic oceans

    Science.gov (United States)

    Li, Jun; Li, Qilu; Gioia, Rosalinda; Zhang, Yanlin; Zhang, Gan; Li, Xiangdong; Spiro, Baruch; Bhatia, Ravinder S.; Jones, Kevin C.

    2011-12-01

    Air samples were collected from Jan 16 to Mar 14, 2008 onboard the Oceanic II- The Scholar Ship which navigated an east-west transect from Shanghai to Cape Verde, and polybrominated diphenyl ethers (PBDEs) were analyzed in these samples. PBDE concentrations in the atmosphere over the open seas were influenced by proximity to source areas and land, and air mass origins. The concentrations of Σ 21PBDEs over the East and South China Seas, the Bay of Bengal and the Andaman Sea, the Indian Ocean, and the Atlantic Ocean were 10.8 ± 6.13, 3.22 ± 1.57, 5.12 ± 3.56, and 2.87 ± 1.81 pg m -3, respectively. BDE-47 and -99 were the dominant congeners in all the samples, suggesting that the widely used commercial penta-BDE products were the original sources. Over some parts of Atlantic and Indian Ocean, daytime concentrations of BDE-47 and BDE-99 were higher than the concentrations at night. The strong atmospheric variability does not always coincide with a diurnal cycle, but the variability in air concentrations in such remote areas of the ocean remains strong. No significant trends were found for each of PBDE congener with latitude.

  13. Relation between tropical cyclone heat potential and cyclone intensity in the North Indian Ocean

    Science.gov (United States)

    Jangir, B.; Swain, D.; Udaya Bhaskar, T. V. S.

    2016-05-01

    Ocean Heat Content (OHC) plays a significant role in modulating the intensity of Tropical Cyclones (TC) in terms of the oceanic energy available to TCs. TC Heat Potential (TCHP), an estimate of OHC, is thus known to be a useful indicator of TC genesis and intensification. In the present study, we analyze the role of TCHP in intensification of TCs in the North Indian Ocean (NIO) through statistical comparisons between TCHP and Cyclone Intensities (CI). A total of 27 TCs (20 in the Bay of Bengal, and 7 in the Arabian Sea) during the period 2005-2012 have been analyzed using TCHP data from Global Ocean Data Assimilation System (GODAS) model of Indian National Center for Ocean Information Services and cyclone best track data from India Meteorological Department. Out of the 27 cyclones analyzed, 58% (86%) in the Bay (Arabian Sea) have negative correlation and 42% (14%) cyclones have positive correlation between CI and TCHP. On the whole, more than 60% cyclones in the NIO show negative correlations between CI and TCHP. The negative percentage further increases for TCHP leading CI by 24 and 48 hours. Similar trend is also seen with satellite derived TCHP data obtained from National Remote Sensing Center and TC best track data from Joint Typhoon Warming Centre. Hence, it is postulated that TCHP alone need not be the only significant oceanographic parameter, apart from sea surface temperature, responsible for intensification and propagation of TCs in the NIO.

  14. Changes in erosion and ocean circulation recorded in the Hf isotopic compositions of North Atlantic and Indian Ocean ferromanganese crusts

    Science.gov (United States)

    Piotrowski, Alexander M.; Lee, Der-Chuen; Christensen, John N.; Burton, Kevin W.; Halliday, Alex N.; Hein, James R.; Günther, Detlef

    2000-01-01

    High-resolution Hf isotopic records are presented for hydrogenetic Fe–Mn crusts from the North Atlantic and Indian Oceans. BM1969 from the western North Atlantic has previously been shown to record systematically decreasing Nd isotopic compositions from about 60 to ∼4 Ma, at which time both show a rapid decrease to unradiogenic Nd composition, thought to be related to the increasing influence of NADW or glaciation in the northern hemisphere. During the Oligocene, North Atlantic Hf became progressively less radiogenic until in the mid-Miocene (∼15 Ma) it reached +1. It then shifted gradually back to an ϵHf value of +3 at 4 Ma, since when it has decreased rapidly to about −1 at the present day. The observed shifts in the Hf isotopic composition were probably caused by variation in intensity of erosion as glaciation progressed in the northern hemisphere. Ferromanganese crusts SS663 and 109D are from about 5500 m depth in the Indian Ocean and are now separated by ∼2300 km across the Mid-Indian Ridge. They display similar trends in Hf isotopic composition from 20 to 5 Ma, with the more northern crust having a composition that is consistently more radiogenic (by ∼2 ϵHf units). Paradoxically, during the last 20 Ma the Hf isotopic compositions of the two crusts have converged despite increased separation and subsidence relative to the ridge. A correlatable negative excursion at ∼5 Ma in the two records may reflect a short-term increase in erosion caused by the activation of the Himalayan main central thrust. Changes to unradiogenic Hf in the central Indian Ocean after 5 Ma may alternatively have been caused by the expanding influence of NADW into the Mid-Indian Basin via circum-Antarctic deep water or a reduction of Pacific flow through the Indonesian gateway. In either case, these results illustrate the utility of the Hf isotope system as a tracer of paleoceanographic changes, capable of responding to subtle changes in erosional regime not readily resolved

  15. Acoustic properties of Indian Ocean manganese nodules in relation to physical constitution and chemical composition

    Digital Repository Service at National Institute of Oceanography (India)

    Mukhopadhyay, R.; Ramana, Y.V.

    , 1984; MA et al., 1986). This paper attempts to study the acoustical properties of nodules from different sediment environments in the Indian Ocean, because the physical constitution of nodules provides information on it's crystallochemical structure..., respectively. The above measurements were carried out following pulse transmit time method (SUBBARAJU and RAMANA, 1986) and verified by the compen- sated ultrasonic timer technique (RAMAt~A and SHARMA, 1984). Physical and acoustic properties were determined...

  16. Recent and rapid radiation of the lichen genus Sticta in the Western Indian Ocean islands

    OpenAIRE

    Simon, Antoine; Magain, Nicolas; Goffinet, Bernard; Sérusiaux, Emmanuël

    2016-01-01

    In the framework of a global project on the phylogeny of the lichen genus Sticta (Lobariaceae), extensive sampling was performed on the islands of Reunion and Mauritius as well as in several parts of Madagascar (mainly in two National Parks : Marojejy and Amber Mountain). The aim of this study is to provide the first comprehensive molecular phylogeny of the genus in the Western Indian Ocean islands (and more specifically of a presumably local endemic lineage), and to date its local radiation....

  17. Evolution of Indian Ocean dipole and its forcing mechanisms in the absence of ENSO

    Science.gov (United States)

    Wang, Hui; Murtugudde, Raghu; Kumar, Arun

    2016-10-01

    The evolution of Indian Ocean dipole (IOD) and its forcing mechanisms are examined based on the analysis of coupled model simulations that allow or suppress the El Niño-Southern Oscillation (ENSO) mode of variability. The model can reproduce the most salient observed features of IOD even without ENSO, including the relationships between the eastern and western poles at both the surface and subsurface, as well as their seasonality. This suggests that ENSO is not fundamental for the existence of IOD. It is demonstrated that cold (warm) sea surface temperature (SST) anomalies in the eastern Indian Ocean associated with IOD can be initiated by springtime Indonesian rainfall deficit (surplus) through local surface wind response. The growth of the SST anomalies depends on the initial local subsurface condition. Both the air-sea interaction and surface-subsurface interaction contribute to the development of IOD. The evolution of IOD can be represented by two leading extended empirical orthogonal function (EEOF) modes of tropical surface-subsurface Indian Ocean temperatures; one stationary and the other non-stationary. The onset, growth, and termination of IOD, as well as the transition to an opposite phase, can be interpreted as alternations between the non-propagating mode (EEOF1) and the eastward-propagating Kelvin wave (EEOF2). The evolution of IOD is also accompanied by a westward-propagating Rossby wave which is captured in the EEOF1 of the subtropical surface-subsurface Indian Ocean temperatures. Therefore, both Bjerknes feedback and a delayed oscillator operate during the evolution of IOD in the absence of ENSO also.

  18. Atmospheric research in Southern Africa and Indian Ocean: a South Africa-France bilateral collaborative programme

    CSIR Research Space (South Africa)

    Sivakumar, V

    2009-09-01

    Full Text Available conference proceeding ATMOSPHERIC RESEARCH IN SOUTHERN AFRICA AND INDIAN OCEAN : A SOUTH AFRICA – FRANCE BILATERAL COLLABORATIVE PROGRAMME V. Sivakumar1,2 and R. Delmas3 1 South Africa Coordinator, Department of Geography, Geoinformatics..., Universite de la Reunion, Saint Denis, La Reunion, France. svenkataraman@csir.co.za 1. INTRODUCTION In the present context of global changes, atmospheric and climatic research should be more organized in the framework of international...

  19. Genetic variability and nitrogenase activity of cyanobacterial communities associated with tropical seagrass meadows (western Indian Ocean)

    OpenAIRE

    Hamisi, Mariam

    2010-01-01

    Tropical seagrass ecosystems are highly productive and important for sustaining marine life and associated coastal societies. In this study, the diversity and role of nitrogen-fixing cyanobacteria associated with five common seagrass genera in coastal regions of the western Indian Ocean (WIO; Tanzania) were examined, as well as the impact of anthropogenic activities. Cyanobacteria were characterized morphologically and genetically (16S rRNA and nifH gene phylogeny), as were diel variations in...

  20. Pakistan’s Security Problems and Opportunities in the Indian Ocean Region

    Science.gov (United States)

    1990-03-01

    with the Mediterranean. Involvement of the superpowers in this region has affected the foreign policy orientations of 7 the regional countries and has...significant. Japan is South Africa’s third biggest export market , and South Africa is the fourth largest importer of Japanese goods. In response to the Soviet...Cheema, p. 25. 19 7. Admiral S. N. Kohli , The Indian Ocean and India’s Maritime Security, New Delhi: Tata Hill Publishing Company, 1978, p. 34. 8

  1. On the diurnal ranges of Sea Surface Temperature (SST) in the north Indian Ocean

    Indian Academy of Sciences (India)

    S S C Shenoi; N Nasnodkar; G Rajesh; K Jossia Joseph; I Suresh; A M Almeida

    2009-10-01

    This paper describes the variability in the diurnal range of SST in the north Indian Ocean using in situ measurements and tests the suitability of simple regression models in estimating the diurnal range.SST measurements obtained from 1556 drifting and 25 moored buoys were used to determine the diurnal range of SSTs.The magnitude of diurnal range of SST was highest in spring and lowest in summer monsoon.Except in spring,nearly 75 –80%of the observations reported diurnal range below 0.5°C.The distributions of the magnitudes of diurnal warming across the three basins of north Indian Ocean (Arabian Sea,Bay of Bengal and Equatorial Indian Ocean)were similar except for the differences between the Arabian Sea and the other two basins during November-February (winter monsoon)and May.The magnitude of diurnal warming that depended on the location of temperature sensor below the water level varied with seasons.In spring,the magnitude of diurnal warming diminished drastically with the increase in the depth of temperature sensor.The diurnal range estimated using the drifting buoy data was higher than the diurnal range estimated using moored buoys fitted with temperature sensors at greater depths. A simple regression model based on the peak solar radiation and average wind speed was good enough to estimate the diurnal range of SST at ∼1.0 m in the north Indian Ocean during most of the seasons except under low wind-high solar radiation conditions that occur mostly during spring. The additional information on the rate of precipitation is found to be redundant for the estimation of the magnitude of diurnal warming at those depths.

  2. Indian Ocean Experiment: An integrated analysis of the climate forcing and effects of the great Indo-Asian haze

    OpenAIRE

    2001-01-01

    Every year, from December to April, anthropogenic haze spreads over most of the North Indian Ocean, and South and Southeast Asia. The Indian Ocean Experiment (INDOEX) documented this Indo-Asian haze at scales ranging from individual particles to its contribution to the regional climate forcing. This study integrates the multiplatform observations (satellites, aircraft, ships, surface stations, and balloons) with one- and four-dimensional models to derive the regional aerosol forcing resulting...

  3. Analysis of Equatorial Currents Observed by Eastern Indian Ocean Cruises in 2010 and 2011

    Institute of Scientific and Technical Information of China (English)

    ZENG Xue-Zhi; LI Yi-Neng; PENG Shi-Qiu

    2012-01-01

    Hydrographic and direct current measurements were made in the Eastern Equatorial Indian Ocean in May 2010 and April 2011 as part of the Eastern Indian Ocean Cruises (EIOC) organized by the South China Sea Institute of Oceanology (SCSIO). Analyses of the shipdrift Acoustic Doppler Current Profiler (ADCP) data in- dicate that the equatorial currents observed in May 2010 are characterized by a strongly eastward surface current (Wyrtki Jets, WJs) with a maximum velocity of 0.9 m s-1, while that observed in April 2011 is weak and without a consistent direction. The strongly eastward WJ transports the surface water eastward, resulting in a deeper upper mixed layer, as shown in the temperature and salinity pro- files. However, it was found that the Equatorial Undercurrent (EUC) in the Eastern Indian Ocean is strong in April 2011 and weak in May 2010. The EUC was located approximately at the position of the thermocline, and it had higher salinity (up to approximately 35.5 psu) than the upper and lower waters.

  4. Maculabatis ambigua sp. nov., a new whipray (Myliobatiformes: Dasyatidae) from the Western Indian Ocean.

    Science.gov (United States)

    Last, Peter R; Bogorodsky, Sergey V; Alpermann, Tilman J

    2016-08-18

    A new whipray, Maculabatis ambigua sp. nov., described from material collected from the Red Sea and off Zanzibar (Tanzania), is probably more widespread in the northwestern Indian Ocean. It has been confused with other Indian Ocean whiprays of the genus Maculabatis (formerly Himantura in part) i.e. M. gerrardi and M. randalli. Maculabatis ambigua sp. nov. was first distinguished from these species by molecular analysis, and subsequently by a combination of morphological characters, i.e. disc shape, coloration, morphometrics and squamation. Molecular data suggest that it is most closely related to the morphologically similar M. gerrardi, which occurs further east in the Indian Ocean (Oman to Indonesia) and North-West Pacific (north to Taiwan). The dorsal disc of M. gerrardi typically has a full or partial coverage of white spots (usually present at least on the posterior disc), whereas M. ambigua sp. nov. is plain coloured. Maculabatis randalli, which occurs in the Persian and Arabian Gulfs, is plain coloured, but has a longer disc relative to its width, more acute and longer snout, longer head and larger intergill width, wider internasal distance, and a narrower secondary denticle band in adults. Maculabatis ambigua sp. nov. is relatively common in the shallow, soft-sedimentary habitats of the southern Red Sea from where it is taken as low-value or discarded bycatch of trawl fisheries. It is a medium-sized whipray with a maximum confirmed size of 840 mm disc width.

  5. [Diversity and bioactivities of culturable marine actinobacteria isolated from mangrove sediment in Indian Ocean].

    Science.gov (United States)

    He, Jie; Zhang, Daofeng; Xu, Ying; Zhang, Xiaomei; Tang, Shukun; Xu, Lihua; Li, Wenjun

    2012-10-04

    In order to explore the diversity, antimicrobial activity and enzyme-producing activity of marine actinobacteria isolated from mangrove sediments in Indian Ocean. Eight sediments collected from mangrove sediments in Indian Ocean were treated by the plate dilution method and spread on 24 isolation media only containing sole carbon source for energy. Marine actinobacteria were isolated and identified by 16S rRNA gene sequence analysis. The antimicrobial activity and enzyme-producing activity of isolated strains were further detected by spot planting method. In total 139 representative strains were selected from 521 isolates, and they were further sequenced and performed phylogenetic analysis based on their 16S rRNA gene sequences. There were 35 strains identified as potential novel species. Antimicrobial activity was detected in Bacillus subtilis, Candida albicans, Escherichia coli, Staphylococcus aureus, Aspergillus niger. Enzyme-producing activity for protease cellulase, amylase and esterase were 36.5%, 26.5%, 22.4% and 15.9%, respectively. Diverse marine actinobacteria were discovered in mangrove sediment in Indian Ocean, which have antimicrobial and enzyme activity.

  6. Assessment Of Sea Surface Salinity Obtain From SMOS And Aquarius Satellites Over Indian Ocean

    Science.gov (United States)

    Calla, O. P. N.; Dadhich, Harendra Kumar; Singhal, Shruti

    2013-12-01

    In this paper, assessment is done of Sea Surface Salinity (SSS) obtained from both SMOS and Aquarius satellites for couple of months over Indian Ocean (IO). The SSS values of the Southern Indian Ocean (SIO) are being investigated as the North Indian Ocean (NIO) is found much corrupted with the Radio Frequency Interference and even due to large variability of SSS in IO; the study area has been divided into different sub regions. The data of both the satellites at same location and of same processing level that is Level-2 have been procured and evaluated. The resolution factor is also being taken care for both onboard sensors. The resolution of SMOS L2 data products [1] is 15 X 15 Km and for Aquarius there are three different resolutions according to the BEAM's. BEAM 1 has a resolution of 76 X 94 Km, BEAM 2 has 84X120Km and BEAM3 has 96X156Km. The data have been averaged of SMOS [2] in the same way so as to match up with Aquarius resolution. By this paper we want to convince the readers that measuring SSS from space is a practical idea. SSS remote sensing now bears no more scientific perils than other remote sensing techniques did in their formative years. Advancing technology with proper resources has significantly reduced the errors.

  7. Indian Moorings: Deep-sea current meter moorings in the Eastern Equatorial Indian Ocean

    Digital Repository Service at National Institute of Oceanography (India)

    Murty, V.S.N.; Sarma, M.S.S.; Suryanarayana, A.; Sengupta, D.; Unnikrishnan, A.S.; Fernando, V.; Almeida, A.; Khalap, S.; Sardar, A.; Somasundar, K.; Ravichandran, M.

    region but also to the atmospheric and oceanic conditions over the world through interactions with the monsoon (e.g., Yasunari 1979), El Niño (e.g., McPhaden 1999), tropical cyclones (e.g., Maloney and Hartmann 2001), and others. Although previous...

  8. Seasonal Environmental Characteristics for the Tropical Cyclone Genesis in the Indian Ocean during the CINDY2011/DYNAMO Field Experiment

    Directory of Open Access Journals (Sweden)

    Aya Tsuboi

    2016-05-01

    Full Text Available This study investigated the seasonal environmental characteristics for tropical cyclone genesis (TCG over the Indian Ocean during the Cooperative Indian Ocean Experiment on Intraseasonal Variability in the Year 2011 and the Dynamics of the Madden–Julian Oscillation (MJO (CINDY2011/DYNAMO field experiment and compare them with long-term climatological features. It was found that the spatial pattern of an empirical environmental index for TCG over the tropical Indian Ocean in 2011 is very similar to the feature composited over the years with high activity of MJO. The analyses of the contributions from each environmental factor indicated that relative humidity, absolute vorticity, and vertical velocity contribute to generate positive influences on the conditions for TCG in 2011. The influences of La Niña appear only through a shear effect over the Indian Ocean in 2011. Under the influences of active MJO events during the CINDY2011/DYNAMO period, the environmental conditions for TCG over the Indian Ocean are determined more strongly by MJO than by La Niña, through modifications of some environmental properties favorable for TCG. The environmental characteristics during CINDY2011/DYNAMO seem to be quite typical of the MJO active years; in such a case, the influences of El Niño/La Niña would not appear in determining the environmental conditions for TCG over the Indian Ocean.

  9. Seasonal and geographic variation of southern blue whale subspecies in the Indian Ocean.

    Science.gov (United States)

    Samaran, Flore; Stafford, Kathleen M; Branch, Trevor A; Gedamke, Jason; Royer, Jean-Yves; Dziak, Robert P; Guinet, Christophe

    2013-01-01

    Understanding the seasonal movements and distribution patterns of migratory species over ocean basin scales is vital for appropriate conservation and management measures. However, assessing populations over remote regions is challenging, particularly if they are rare. Blue whales (Balaenoptera musculus spp) are an endangered species found in the Southern and Indian Oceans. Here two recognized subspecies of blue whales and, based on passive acoustic monitoring, four "acoustic populations" occur. Three of these are pygmy blue whale (B.m. brevicauda) populations while the fourth is the Antarctic blue whale (B.m. intermedia). Past whaling catches have dramatically reduced their numbers but recent acoustic recordings show that these oceans are still important habitat for blue whales. Presently little is known about the seasonal movements and degree of overlap of these four populations, particularly in the central Indian Ocean. We examined the geographic and seasonal occurrence of different blue whale acoustic populations using one year of passive acoustic recording from three sites located at different latitudes in the Indian Ocean. The vocalizations of the different blue whale subspecies and acoustic populations were recorded seasonally in different regions. For some call types and locations, there was spatial and temporal overlap, particularly between Antarctic and different pygmy blue whale acoustic populations. Except on the southernmost hydrophone, all three pygmy blue whale acoustic populations were found at different sites or during different seasons, which further suggests that these populations are generally geographically distinct. This unusual blue whale diversity in sub-Antarctic and sub-tropical waters indicates the importance of the area for blue whales in these former whaling grounds.

  10. Seasonality and Predictability of the Indian Ocean Dipole Mode: ENSO Forcing and Internal Variability

    Science.gov (United States)

    Yang, Y.

    2015-12-01

    This study evaluates the relative contributions to the Indian Ocean Dipole (IOD) mode of interannual variability from the El Niño-Southern Oscillation (ENSO) forcing and ocean-atmosphere feedbacks internal to the Indian Ocean. The ENSO forcing and internal variability is extracted by conducting a 10-member coupled simulation for 1950-2012 where sea surface temperature (SST) is restored to the observed anomalies over the tropical Pacific but interactive with the atmosphere over the rest of the world ocean. In these experiments, the ensemble mean is due to ENSO forcing and the inter-member difference arises from internal variability of the climate system independent of ENSO. These elements contribute one third and two thirds of the total IOD variance, respectively. Both types of IOD variability develop into an east-west dipole pattern due to Bjerknes feedback and peak in September-November. The ENSO forced and internal IOD modes differ in several important ways. The forced IOD mode develops in August with a broad meridional pattern, and eventually evolves into the Indian Ocean Basin mode; while the internal IOD mode grows earlier in June, is more confined to the equator and decays rapidly after October. The internal IOD mode is more skewed than the ENSO forced response. The destructive interference of ENSO forcing and internal variability can explain early-terminating IOD events, referred to IOD-like perturbations that fail to grow during boreal summer. Our results have implications for predictability. Internal variability, as represented by pre-season sea surface height anomalies off Sumatra, contributes to predictability considerably. Including this indicator of internal variability, together with ENSO, improves the predictability of IOD.

  11. Seasonal and geographic variation of southern blue whale subspecies in the Indian Ocean.

    Directory of Open Access Journals (Sweden)

    Flore Samaran

    Full Text Available Understanding the seasonal movements and distribution patterns of migratory species over ocean basin scales is vital for appropriate conservation and management measures. However, assessing populations over remote regions is challenging, particularly if they are rare. Blue whales (Balaenoptera musculus spp are an endangered species found in the Southern and Indian Oceans. Here two recognized subspecies of blue whales and, based on passive acoustic monitoring, four "acoustic populations" occur. Three of these are pygmy blue whale (B.m. brevicauda populations while the fourth is the Antarctic blue whale (B.m. intermedia. Past whaling catches have dramatically reduced their numbers but recent acoustic recordings show that these oceans are still important habitat for blue whales. Presently little is known about the seasonal movements and degree of overlap of these four populations, particularly in the central Indian Ocean. We examined the geographic and seasonal occurrence of different blue whale acoustic populations using one year of passive acoustic recording from three sites located at different latitudes in the Indian Ocean. The vocalizations of the different blue whale subspecies and acoustic populations were recorded seasonally in different regions. For some call types and locations, there was spatial and temporal overlap, particularly between Antarctic and different pygmy blue whale acoustic populations. Except on the southernmost hydrophone, all three pygmy blue whale acoustic populations were found at different sites or during different seasons, which further suggests that these populations are generally geographically distinct. This unusual blue whale diversity in sub-Antarctic and sub-tropical waters indicates the importance of the area for blue whales in these former whaling grounds.

  12. The NOW regional coupled model: Application to the tropical Indian Ocean climate and tropical cyclone activity

    Science.gov (United States)

    Samson, G.; Masson, S.; Lengaigne, M.; Keerthi, M. G.; Vialard, J.; Pous, S.; Madec, G.; Jourdain, N. C.; Jullien, S.; Menkes, C.; Marchesiello, P.

    2014-09-01

    This paper presents the NOW regional coupled ocean-atmosphere model built from the NEMO ocean and WRF atmospheric numerical models. This model is applied to the tropical Indian Ocean, with the oceanic and atmospheric components sharing a common ¼° horizontal grid. Long experiments are performed over the 1990-2009 period using the Betts-Miller-Janjic (BMJ) and Kain-Fritsch (KF) cumulus parameterizations. Both simulations produce a realistic distribution of seasonal rainfall and a realistic northward seasonal migration of monsoon rainfall over the Indian subcontinent. At subseasonal time scales, the model reasonably reproduces summer monsoon active and break phases, although with underestimated rainfall and surface wind signals. Its relatively high resolution results in realistic spatial and seasonal distributions of tropical cyclones, but it fails to reproduce the strongest observed cyclone categories. At interannual time scales, the model reproduces the observed variability associated with the Indian Ocean Dipole (IOD) and the delayed basin-wide warming/cooling induced by the El Niño Southern Oscillation (ENSO). The timing of IOD occurrence in the model generally matches that of the observed events, confirming the influence of ENSO on the IOD development (through the effect of lateral boundary conditions in our simulations). Although the KF and BMJ simulations share a lot in common, KF strongly overestimates rainfall at all time scales. KF also overestimates the number of simulated cyclones by a factor two, while simulating stronger events (up to 55 m s-1) compared to BMJ (up to 40 m s-1). These results could be related to an overly active cumulus parameterization in KF.

  13. Ocean feedback to pulses of the Madden–Julian Oscillation in the equatorial Indian Ocean

    Science.gov (United States)

    Moum, James N.; Pujiana, Kandaga; Lien, Ren-Chieh; Smyth, William D.

    2016-01-01

    Dynamical understanding of the Madden–Julian Oscillation (MJO) has been elusive, and predictive capabilities therefore limited. New measurements of the ocean's response to the intense surface winds and cooling by two successive MJO pulses, separated by several weeks, show persistent ocean currents and subsurface mixing after pulse passage, thereby reducing ocean heat energy available for later pulses by an amount significantly greater than via atmospheric surface cooling alone. This suggests that thermal mixing in the upper ocean from a particular pulse might affect the amplitude of the following pulse. Here we test this hypothesis by comparing 18 pulse pairs, each separated by <55 days, measured over a 33-year period. We find a significant tendency for weak (strong) pulses, associated with low (high) cooling rates, to be followed by stronger (weaker) pulses. We therefore propose that the ocean introduces a memory effect into the MJO, whereby each event is governed in part by the previous event. PMID:27759016

  14. Relationship between chemical composition and magnetic susceptibility in sediment cores from Central Indian Ocean Basin

    Indian Academy of Sciences (India)

    J N Pattan; G Parthiban; V K Banakar; A Tomer; M Kulkarni

    2008-04-01

    Three sediment cores in a north–south transect (3°N to 13°S) from different sediment types of the Central Indian Ocean Basin (CIOB) are studied to understand the possible relationship between magnetic susceptibility () and Al, Fe, Ti and Mn concentrations. The calcareous ooze core exhibit lowest (12.32 × 10-7m3 kg−1), Al (2.84%), Fe (1.63%) and Ti (0.14%), terrigenous clay core with moderate (29.9 × 10-7 m3 kg−1) but highest Al (6.84%), Fe (5.20%) and Ti (0.44%), and siliceous ooze core with highest (38.06 × 10-7 m3 kg−1) but moderate Al (4.49%), Fe (2.80%) and Ti (0.19%) contents. The distribution of and detrital proxy elements (Al, Fe, and Ti) are identical in both calcareous and siliceous ooze. Interestingly, in terrigenous core, the behaviour of is identical to only Ti content but not with Al and Fe suggesting possibility of Al and Fe having a non-detrital source. The occurrence of phillipsite in terrigenous clay is evident by the Al-K scatter plot where trend line intersects K axis at more than 50% of total K suggesting excess K in the form of phillipsite. Therefore, the presence of phillipsite might be responsible for negative correlation between and Al ( = −0.52). In siliceous ooze the strong positive correlations among , Alexc and Feexc suggest the presence of authigenic Fe-rich smectite. High Mn content (0.5%) probably in the form of manganese micronodules is also contributing to in both calcareous and siliceous ooze but not in the terrigenous core where mean Mn content (0.1%) is similar to crustal abundance. Thus, systematically records the terrigenous variation in both the biogenic sediments but in terrigenous clay it indirectly suggests the presence of authigenic minerals.

  15. Characterization of novel extracellular protease produced by marine bacterial isolate from the Indian Ocean

    Directory of Open Access Journals (Sweden)

    Rachana Fulzele

    2011-12-01

    Full Text Available Out of the vast pool of enzymes, proteolytic enzymes from microorganisms are the most widely used in different industries such as detergent, food, peptide production etc. Several marine microorganisms are known to produce proteases with commercially desirable characteristics. We have isolated nine different cultures from marine samples of the Indian Ocean. All of them were i motile ii rod shaped iii non spore forming iv catalase and amylase positive v able to grow in presence of 10 % NaCl. They produced acid from glucose, fructose and maltose and grew optimally at 30 0C temperature and pH 7.0-8.0. None of them could grow above 45 0C and below 15 0C. Only one of them (MBRI 7 exhibited extracellular protease activity on skim milk agar plates. Based on 16S rDNA sequencing, it belonged to the genus Marinobacter (98% sequence similarity, 1201 bp. The cell free extract was used to study effects of temperature and pH on protease activity. The optimum temperature and pH for activity were found to be 40 0C and 7.0 respectively. The crude enzyme was stable at temperature range of 30-80 0C and pH 5.0-9.0. It retained 60 % activity at 80 0C after 4 h and more than 70 % activity at 70 0C after 1 h. D value was found to be 342 minutes and 78 minutes for 40 0C and 80 0C respectively. Interestingly the enzyme remained 50 % active at pH 9.0 after 1 h. Comparison with other proteases from different microbial sources indicated that the neutral protease from the halotolerant marine isolate MBRI 7 is a novel enzyme with high thermostability.

  16. Fish, fishers and fisheries of the Western Indian Ocean: their diversity and status. A preliminary assessment.

    Science.gov (United States)

    van der Elst, Rudy; Everett, Bernadine; Jiddawi, Narriman; Mwatha, Gerald; Afonso, Paula Santana; Boulle, David

    2005-01-15

    The Western Indian Ocean represents ca. 8% of the world's oceans but generates only 4% of the global industrial catch. This region is also home to a great proportion of the world's population, living in developing countries with a high dependence on marine resources. Trends in the declared landings of marine resources from the Western Indian Ocean suggest that this ocean may be approaching its maximum harvest potential of ca. 4 Mt per annum, but underreported artisanal catches complicate more-detailed analyses. There is a growing demand for 'new resources' to make up for declining stocks, while several large fluctuations are linked to changes in market demand and over exploitation. Artisanal fisheries in the region are highly diversified. Preliminary results are presented of a project that evaluates the conservation status and sustainable management practices in 168 different fishery types. It is concluded that the majority of the region's artisanal fisheries are not adequately supported by scientific information and that management strategies need to be improved if the enormous development challenges of East African countries are to be met.

  17. A Hurricane Hits Home: An Interactive Science Museum Exhibit on Ocean Mapping and Marine Debris

    Science.gov (United States)

    Butkiewicz, T.; Vasta, D. J.; Gager, N. C.; Fruth, B. W.; LeClair, J.

    2016-12-01

    As part of the outreach component for a project involving the detection and analysis of marine debris generated by Super Storm Sandy, The Center for Coastal and Ocean Mapping / Joint Hydrographic Center partnered with The Seacoast Science Center to develop an interactive museum exhibit that engages the public with a touchscreen based game revolving around the detection and identification of marine debris. "A Hurricane Hits Home" is a multi-station touchscreen exhibit geared towards children, and integrates a portion of a historical wooden shipwreck into its physical design. The game invites museum guests to examine a number of coastal regions and harbors in Sandy affected areas. It teaches visitors about modern mapping technology by having them control boats with multibeam sonars and airplanes with lidar sensors. They drag these vehicles around maps to reveal the underlying bathymetry below the satellite photos. They learn the applications and limitations of sonar and lidar by where the vehicles can and cannot collect survey data (e.g. lidar doesn't work in deep water, and the boat can't go in shallow areas). As users collect bathymetry data, they occasionally reveal marine debris objects on the seafloor. Once all the debris objects in a level have been located, the game challenges them to identify them based on their appearance in the bathymetry data. They must compare the simulated bathymetry images of the debris targets to photos of possible objects, and choose the correct matches to achieve a high score. The exhibit opened January 2016 at the Seacoast Science Center in Rye, NH.

  18. Changes of the oceanic CO2 sink in the Eastern Indian sector of the Southern Ocean

    OpenAIRE

    Brévière, Emily; Metzl, Nicolas; Poisson, Alain; Tilbrook, Bronte

    2011-01-01

    Changes in the carbon dioxide fugacity (fCO2) and air–sea CO2 flux observed in the Southern Ocean, south of Tasmania were analysed and compared for two different years: 1996/1997 and 2002/2003. The CO2 flux showed large and contrasting interannual changes in the permanent open ocean zone (POOZ, 53–61°S) between the 2 yr where the oceanic CO2 sink increased from about −0.3 mmol m−2 d−1 in February 1997 to −20.6 mmol m−2 d−1 in February 2003. The strong sink in February 2003 was associated with...

  19. Seafloor seismicity, Antarctic ice-sounds, cetacean vocalizations and long-term ambient sound in the Indian Ocean basin

    Science.gov (United States)

    Royer, J.-Y.; Chateau, R.; Dziak, R. P.; Bohnenstiehl, D. R.

    2015-08-01

    This paper presents the results from the Deflo-hydroacoustic experiment in the Southern Indian Ocean using three autonomous underwater hydrophones, complemented by two permanent hydroacoustic stations. The array monitored for 14 months, from November 2006 to December 2007, a 3000 × 3000 km wide area, encompassing large segments of the three Indian spreading ridges that meet at the Indian Triple Junction. A catalogue of 11 105 acoustic events is derived from the recorded data, of which 55 per cent are located from three hydrophones, 38 per cent from 4, 6 per cent from five and less than 1 per cent by six hydrophones. From a comparison with land-based seismic catalogues, the smallest detected earthquakes are mb 2.6 in size, the range of recorded magnitudes is about twice that of land-based networks and the number of detected events is 5-16 times larger. Seismicity patterns vary between the three spreading ridges, with activity mainly focused on transform faults along the fast spreading Southeast Indian Ridge and more evenly distributed along spreading segments and transforms on the slow spreading Central and ultra-slow spreading Southwest Indian ridges; the Central Indian Ridge is the most active of the three with an average of 1.9 events/100 km/month. Along the Sunda Trench, acoustic events mostly radiate from the inner wall of the trench and show a 200-km-long seismic gap between 2 °S and the Equator. The array also detected more than 3600 cryogenic events, with different seasonal trends observed for events from the Antarctic margin, compared to those from drifting icebergs at lower (up to 50°S) latitudes. Vocalizations of five species and subspecies of large baleen whales were also observed and exhibit clear seasonal variability. On the three autonomous hydrophones, whale vocalizations dominate sound levels in the 20-30 and 100 Hz frequency bands, whereas earthquakes and ice tremor are a dominant source of ambient sound at frequencies <20 Hz.

  20. Pleistocene oceanographie changes indicated by deep sea benthic foraminifera in the northern Indian Ocean

    Science.gov (United States)

    Rai, Ajai K.; Srinivasan, M. S.

    1994-12-01

    An attempt has been made to understand the Pleistocene bottom water history in response to the paleoclimatic changes in the northern Indian Ocean employing quantitative analyses of deep sea benthic foraminifera at the DSDP sites 219 and 238. Among the 150 benthic foraminifera recorded a few species show dominance with changing percent frequencies during most of the sequence. The dominant benthic foraminiferal assemblages suggest that most of the Pleistocene bottom waters at site 219 and Early Pleistocene bottom waters at site 238 are of North Indian Deep Water (NIDW) origin. However, Late Pleistocene assemblage at site 238 appears to be closely associated with a water mass intermediate between North Indian Deep Water (NIDW) and Antarctic Bottom Water (AABW). Uvigerina proboscidea is the most dominant benthic foraminiferal species present during the Pleistocene at both the sites. A marked increase in the relative abundance of U. proboscidea along with less diverse and equitable fauna during Early Pleistocene suggests a relative cooling, an intensified oceanic circulation and upwelling of nutrient rich bottom waters resulting in high surface productivity. At the same time, low sediment accumulation rate during Early Pleistocene reveals increased winnowing of the sediments possibly due to more corrosive and cold bottom waters. The Late Pleistocene in general, is marked by relatively warm and stable bottom waters as reflected by low abundance of U. proboscidea and more diverse and equitable benthic fauna. The lower depth range for the occurrence of Bulimina aculeate in the Indian Ocean is around 2300 m, similar to that of many other areas. B. aculeata also shows marked increase in its abundance near the Pliocene/Pleistocene boundary while a sudden decrease in the relative abundance of Stilostomella lepidula occurs close to the Early/Late Pleistocene boundary.

  1. Larvae of Crossorhombus valde-rostratus (Alcock) and C. azureus (Alcock) (Heterostomata: Pisces) collected during the International Indian Ocean Expedition and Naga Expedition

    Digital Repository Service at National Institute of Oceanography (India)

    Devi, C.B.L.

    Indian Ocean Expedition (IIOE) 1960-65) and Naga Expedition (1959-61). In the Indian Ocean the larvae of C. Valde-rostratus appear to prefer open ocean, found in the stratum sampled during day time as well as during SW monsoon period whereas C. azureus...

  2. Submarine structure of Reunion Island (Indian Ocean) inferred from gravity

    Science.gov (United States)

    Gailler, L.; Lénat, J.

    2008-12-01

    La Reunion is a large (diameter: 220 km; height: 7 km), mostly immerged (97%) oceanic volcanic system. New land and marine gravity data are used to study the structure of its submarine part. The gravity models are interpreted jointly with the published geology interpretations and compared with magnetic models. This allows us to derive a new model of the shallow and internal structure of the submarine flanks. Recent cruises have collected high quality gravity, magnetic and multi-beam swath bathymetry data over the submarine flanks of La Réunion and the surrounding oceanic plate. A new Bouguer anomaly map has been computed for a reduction density of 2.67.103 kg m-3. A magnetic anomalies map covering the same area has been also built. Studies based on bathymetric and acoustic data have previously shown the presence of different types of submarine features: a coastal shelf, huge bulges built by debris avalanches and sediment deposits, erosion canyons, volcanic constructions near the coast, isolated seamounts offshore, and elongate volcanic ridges on the Mascarene plate. On the new Bouguer anomaly map, all these features are associated with negative anomalies. They have been modeled using 2 3/4 D modeling techniques. The short wavelength anomalies over the coastal shelf area can be explained by piles of low density layers. This suggests that they are mostly built by hyaloclastites which are generally characterized by lower densities than lava flows. The voluminous debris avalanche deposits which formed the huge Submarine Bulges to the east, north, west, and south of the island have also been modeled as low density formations. Each bulge is modeled with an overall density less than 2.67.103 kg m-3, in order to account for its long wavelength anomaly. Some shorter wavelength features are superimposed on these long wavelength negative anomalies. They probably represent heterogeneities within the bulges. Some shallow ones can be associated with observed surface geological

  3. Wave hindcast experiments in the Indian Ocean using MIKE 21 SW model

    Indian Academy of Sciences (India)

    P G Remya; Raj Kumar; Sujit Basu; Abhijit Sarkar

    2012-04-01

    Wave prediction and hindcast studies are important in ocean engineering, coastal infrastructure development and management. In view of sparse and infrequent in-situ observations, model derived hindcast wave data can be used for the assessment of wave climate in offshore and coastal areas. In the present study, MIKE 21 SW Model has been used to carry out wave hindcast experiments in the Indian Ocean. Model runs have been made for the year 2005 using QuickSCAT scatterometer winds blended with ECMWF model winds. In order to study the impact of southern ocean swells, the model has been run in two different domains, with the southern boundary being shifted far south for the Domain 60S model. The model simulated wave parameters have been validated by comparing with buoy and altimeter data and various statistical yardsticks have been employed to quantify the validation. Possible reason for the poorer performance of the model in the Arabian Sea has also been pointed out.

  4. Composition and Genesis of Zeolitic Claystones from the Central Indian Ocean Basin

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    We examined more than fifty indurated sediments recovered from the Central Indian Ocean Basin (CIOB) during the course of collection for manganese nodules and crusts. The samples occur as slabs either over which ferromanganese oxides are present or over a substrate of altered oceanic basalt in conjunction with palagonite or within the nucleus of manganese nodules.Mineralogically and compositionally, the samples show a mixture of phillipsite, palagonite and montmorillonite. We suggest that the volcanogenic precursors occurring in the CIOB were subjected to varying degrees of alteration under the influence of low temperature conditions, resulting in the formation of zeolitic claystones. The CIOB samples have similarities to those reported from various sites in the world oceans.

  5. The Indigo V Indian Ocean Expedition: a prototype for citizen microbial oceanography

    DEFF Research Database (Denmark)

    Lauro, Frederico; Senstius, Svend Jacob; Cullen, Jay

    2014-01-01

    Microbial Oceanography has long been an extremely expensive discipline, requiring ship time for sample collection and thereby economically constraining the number of samples collected. This is especially true for under-sampled water bodies such as the Indian Ocean. Specialised scientific equipment...... only adds to the costs.Moreover, long term monitoring of microbial communities and large scale modelling of global biogeochemical cycles requires the collection of high-density data both temporally and spatially in a cost-effective way. Thousands of private ocean-going vessels are cruising around...... the world’s oceans every day. We believe that a combination of new technologies, appropriate laboratory protocols and strategic operational partnerships will allow researchers to broaden the scope of participation in basic oceanographic research. This will be achieved by equipping sailing vessels with small...

  6. Seasonal Phase-Locking of Peak Events in the Eastern Indian Ocean

    Institute of Scientific and Technical Information of China (English)

    Qin ZHANG; Song YANG

    2007-01-01

    The sea surface temperature (SST) anomaly of the eastern Indian Ocean (EIO) exhibits cold anomalies in the boreal summer or fall during El Ni(n)o development years and warm anomalies in winter or spring following the El Ni(n)o events. There also tend to be warm anomalies in the boreal summer or fall during La Ni(n)a development years and cold anomalies in winter or spring following the La Ni(n)a events. The seasonal phase-locking of SST change in the EIO associated with El Ni(n)o/Southern Oscillation is linked to the variability of convection over the maritime continent, which induces an atmospheric Rossby wave over the EIO. Local air-sea interaction exerts different effects on SST anomalies, depending on the relationship between the Rossby wave and the mean flow related to the seasonal migration of the buffer zone, which shifts across the equator between summer and winter.The summer cold events start with cooling in the Timor Sea, together with increasing easterly flow along the equator. Negative SST anomalies develop near Sumatra, through the interaction between the atmospheric Rossby wave and the underneath sea surface. These SST anomalies are also contributed to by the increased upwelling of the mixed layer and the equatorward temperature advection in the boreal fall. As the buffer zone shifts across the equator towards boreal winter, the anomalous easterly flow tends to weaken the mean flow near the equator, and the EIO SST increases due to the reduction of latent heat flux from the sea surface. As a result, wintertime SST anomalies appear with a uniform and nearly basin-wide pattern beneath the easterly anomalies. These SST anomalies are also caused by the increase in solar radiation associated with the anticyclonic atmospheric Rossby wave over the EIO. Similarly, the physical processes of the summer warm events, which are followed by wintertime cold SST anomalies, can be explained by the changes in atmospheric and oceanic fields with opposite signs to those

  7. The Distribution and Variability of Simulated Chlorophyll Concentration over the Tropical Indian Ocean from Five CMIP5 Models

    Institute of Scientific and Technical Information of China (English)

    LIU Lin; FENG Lin; YU Weidong; WANG Huiwu; LIU Yanliang; SUN Shuangwen

    2013-01-01

    Performances of 5 models from the Coupled Model Intercomparison Project Phase 5 (CMIP5) in simulating the chlorophyll concentration over the tropical Indian Ocean are evaluated.Results show that these models are able to capture the dominant spatial distribution of observed chlorophyll concentration and reproduce the maximum chlorophyll concentration over the western part of the Arabian Sea,around the tip of the Indian subcontinent,and in the southeast tropical Indian Ocean.The seasonal evolution of chlorophyll concentration over these regions is also reproduced with significant amplitude diversity among models.All of 5 models is able to simulate the interannual variability of chlorophyll concentration.The maximum interannual variation occurs at the same regions where the maximum climatological chlorophyll concentration is located.Further analysis also reveals that the Indian Ocean Dipole events have great impact on chlorophyll concentration in the tropical Indian Ocean.In the general successful simulation of chlorophyll concentration,most of the CMIP5 models present higher than normal chlorophyll concentration in the eastern equatorial Indian Ocean.

  8. Nonlinear Responses of Oceanic Temperature to Wind Stress Anomalies in Tropical Pacific and Indian Oceans:A Study Based on Numerical Experiments with an OGCM

    Institute of Scientific and Technical Information of China (English)

    2015-01-01

    As a highly nonlinear dynamic system, oceanic general circulation models (OGCMs) usually exhibit nonlinear responses to prescribed wind stress forcing. To explore mechanisms for these nonlinear responses, we designed and conducted three idealized numerical experiments with an OGCM with modifi ed wind stress forcing. In the experiments, the climatological mean wind stress was identical, and the only diff erences in external forcing were wind stress anomalies. The wind anomalies were set to zero in a control run, and the observed wind stress anomalies with and without reversed signs were superimposed on the mean climatology in two sensitivity experiments. Forced by the prescribed wind stress anomalies in sensitivity runs, the OGCM well reproduced the El Ni˜no–Southern Oscillation (ENSO) and the Pacifi c and Indian Ocean Dipole (IOD) in the Indian Ocean, as well as the asymmetry between positive and negative phases of these modes. Relative to the control run, the two sensitivity runs exhibited almost identical changes in the mean climate state, although the wind stress anomalies were reversed in these two experiments. Thus, it was concluded that the asymmetry of wind stress anomalies contributes only slightly to the mean state changes and ocean internal dynamics was the main contributor. Further heat budget analysis suggested that nonlinear temperature advection terms, including both mean advection and perturbed advection, favor the ENSO/IOD rectifi ed eff ect on the mean state.

  9. Dissolved inorganic carbon, alkalinity, temperature, salinity and other variables collected from discrete sample and profile observations using CTD, Coulometer for DIC measurement and other instruments from JAMES CLARK ROSS in the Indian Ocean, South Atlantic Ocean and Southern Oceans from 2008-12-26 to 2009-01-30 (NODC Accession 0110254)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — NCEI Accession 0110254 includes discrete sample and profile data collected from JAMES CLARK ROSS in the Indian Ocean, South Atlantic Ocean and Southern Oceans (>...

  10. Dissolved inorganic carbon, temperature, salinity and other variables collected from discrete sample and profile observations using CTD, Coulometer for DIC measurement and other instruments from POLARSTERN in the Indian Ocean, South Atlantic Ocean and Southern Oceans from 1996-03-17 to 1996-05-20 (NODC Accession 0116640)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — NCEI Accession 0116640 includes discrete sample and profile data collected from POLARSTERN in the Indian Ocean, South Atlantic Ocean and Southern Oceans (> 60...

  11. Temperature, salinity and other variables collected from discrete sample and profile observations using CTD, bottle and other instruments from DISCOVERY in the Indian Ocean, South Atlantic Ocean and Southern Oceans from 1993-02-06 to 1993-03-18 (NCEI Accession 0143944)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — NCEI Accession 0143944 includes discrete sample and profile data collected from DISCOVERY in the Indian Ocean, South Atlantic Ocean and Southern Oceans (> 60...

  12. Temperature, salinity and other variables collected from discrete sample and profile observations using CTD, PAR Sensor and other instruments from AURORA AUSTRALIS in the Indian Ocean, South Pacific Ocean and Southern Oceans from 2007-12-16 to 2008-01-27 (NCEI Accession 0143932)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — NCEI Accession 0143932 includes discrete sample and profile data collected from AURORA AUSTRALIS in the Indian Ocean, South Pacific Ocean and Southern Oceans (>...

  13. Temperature, salinity and other variables collected from discrete sample and profile observations using CTD, bottle and other instruments from AURORA AUSTRALIS in the Indian Ocean, South Pacific Ocean and Southern Oceans from 2011-01-04 to 2011-02-06 (NCEI Accession 0143947)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — NCEI Accession 0143947 includes discrete sample and profile data collected from AURORA AUSTRALIS in the Indian Ocean, South Pacific Ocean and Southern Oceans (>...

  14. Dissolved inorganic carbon, pH, alkalinity, temperature, salinity and other variables collected from discrete sample and profile observations using CTD, Coulometer for DIC measurement and other instruments from MIRAI in the Indian Ocean, South Pacific Ocean and Southern Oceans from 2012-11-28 to 2013-01-04 (NCEI Accession 0143950)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — NCEI Accession 0143950 includes discrete sample and profile data collected from MIRAI in the Indian Ocean, South Pacific Ocean and Southern Oceans (> 60 degrees...

  15. A first look at past sea surface temperatures in the equatorial Indian Ocean from Mg/Ca in foraminifera

    Digital Repository Service at National Institute of Oceanography (India)

    Saraswat, R.; Nigam, R.; Weldeab, S.; Mackensen, A.; Naidu, P.D.

    Ocean SST was approx. 2.1 degrees C colder during the last glacial maximum as compared to present times. The data further shows that the surface equatorial Indian Ocean was comparatively warmer during isotopic stage 5e than at present (approx. 29.9 vs...

  16. Geochemistry and mineralogy of REY-rich mud in the eastern Indian Ocean

    Science.gov (United States)

    Yasukawa, Kazutaka; Liu, Hanjie; Fujinaga, Koichiro; Machida, Shiki; Haraguchi, Satoru; Ishii, Teruaki; Nakamura, Kentaro; Kato, Yasuhiro

    2014-10-01

    Deep-sea sediments in parts of the Pacific Ocean were recently found to contain remarkably high concentrations of rare-earth elements and yttrium (REY) of possible economic significance. Here we report similar REY-rich mud in a core section from Deep Sea Drilling Project Site 213 in the eastern Indian Ocean. The sediments consist mainly of siliceous ooze, with subordinate zeolitic clay that contains relatively high REY concentrations. The maximum and average total REY (ΣREY) contents of this material are 1113 and 629 ppm, respectively, which are comparable to those reported from the Pacific Ocean. The REY-rich mud at Site 213 shows enrichment in heavy rare-earth elements, negative Ce anomalies, and relatively low Fe2O3/ΣREY ratios, similar to those in the Pacific Ocean. In addition, the major-element composition of the Indian Ocean REY-rich mud indicates slight enrichment in lithogenic components, which probably reflects a contribution from southern African eolian dust. A volcaniclastic component from neighboring mid-ocean ridges or intraplate volcanoes is also apparent. Elemental compositions and X-ray diffraction patterns for bulk sediment, and microscopic observation and elemental mapping of a polished thin section, demonstrate the presence of phillipsite and biogenic apatite, such as fish debris, in the REY-rich mud. The strong correlation between total REY content and apatite abundance implies that apatite plays an important role as a host phase of REY in the present deep-sea sediment column. However, positive correlations between ΣREY and elements not present in apatite (e.g., Fe2O3, MnO, and TiO2) imply that the REY-rich mud is not formed by a simple mixture of REY-enriched apatite and other components.

  17. Ship emitted NO2 in the Indian Ocean: comparison of model results with satellite data

    Directory of Open Access Journals (Sweden)

    V. Eyring

    2008-08-01

    Full Text Available An inventory of NOx emission from international shipping has been evaluated by comparing NO2 tropospheric columns derived from the satellite instruments SCIAMACHY (January 2003 to February 2008, GOME (January 1996 to June 2003, and GOME-2 (March 2007 to February 2008 to NO2 columns calculated with the atmospheric chemistry general circulation model ECHAM5/MESSy1 (January 2000 to October 2005. The data set from SCIAMACHY yields the first monthly analysis of ship induced NO2 enhancements in the Indian Ocean. For both data and model consistently the tropospheric excess method was used to obtain mean NO2 columns over the shipping lane from India to Indonesia, and over two ship free regions, the Bay of Bengal and the central Indian Ocean. In general, the model simulates the differences between the regions affected by ship pollution and ship free regions reasonably well. Minor discrepancies between model results and satellite data were identified during biomass burning seasons in March to May over India and the Indochinese Peninsula and August to October over Indonesia. We conclude that the NOx ship emission inventory used in this study is a good approximation of NOx ship emissions in the Indian Ocean for the years 2002 to 2007. It assumes that around 6 Tg(N yr−1 are emitted by international shipping globally, resulting in 90 Gg(N yr−1 in the region of interest when using Automated Mutual Assistance Vessel Rescue System (AMVER or 72 Gg(N yr−1 when using the International Comprehensive Ocean-Atmosphere Data Set (ICOADS as spatial proxy. The results do not support some previously published lower ship emissions estimates of 3–4 Tg(N yr−1 globally, making this study the first that evaluates atmospheric response to NOx ship emission estimates from space.

  18. Interannual variability of zonal currents in the equatorial Indian Ocean: respective control of IOD and ENSO

    Science.gov (United States)

    Sachidanandan, Chinnu; Lengaigne, Matthieu; Muraleedharan, Pillathu Moolayil; Mathew, Basil

    2017-07-01

    The observational record is too short to confidently differentiate the relative contributions of Indian Ocean Dipole (IOD) and El Niño-Southern Oscillation (ENSO) on the interannual variability of the equatorial current system in the Indian Ocean because of the strong tendency of these two modes to co-occur. In this study, we analyse a five-decade simulation from an ocean general circulation model forced to describe the main interannual variations of surface and subsurface equatorial zonal currents in the Indian Ocean. This simulation is first shown to accurately capture the surface and subsurface zonal current variations in the equatorial region derived from the available observations. Through an EOF analysis on the model outputs, our results further reveals two main modes of equatorial current interannual variability: a dominant mode with largest amplitude in fall largely describing the variability of the fall Wyrtki jet intensity followed a few months later by a secondary mode maximum in winter largely describing the interannual variability of the subsurface currents in that season. Our analysis further confirms that the IOD is largely responsible for the interannual modulation of fall Wyrtki jet intensity by modulating the equatorial wind intensity during that season. The IOD is also responsible for strong subsurface current variations until December, induced by the delayed effect of the IOD wind signal onto the equatorial thermocline tilt. The equatorial current system response to ENSO is weaker and delayed compared to that of the IOD. The remote and delayed impact of ENSO in the IO indeed induces equatorial wind variations in winter that modulate the winter surface current intensity and the spring equatorial undercurrent intensity through its delayed impact on the thermocline tilt.

  19. Relocation of earthquakes at southwestern Indian Ocean Ridge and its tectonic significance

    Science.gov (United States)

    Luo, W.; Zhao, M.; Haridhi, H.; Lee, C. S.; Qiu, X.; Zhang, J.

    2015-12-01

    The southwest Indian Ridge (SWIR) is a typical ultra-slow spreading ridge (Dick et al., 2003) and further plate boundary where the earthquakes often occurred. Due to the lack of the seismic stations in SWIR, positioning of earthquakes and micro-earthquakes is not accurate. The Ocean Bottom Seismometers (OBS) seismic experiment was carried out for the first time in the SWIR 49 ° 39 'E from Jan. to March, 2010 (Zhao et al., 2013). These deployed OBS also recorded the earthquakes' waveforms during the experiment. Two earthquakes occurred respectively in Feb. 7 and Feb. 9, 2010 with the same magnitude of 4.4 mb. These two earthquakes were relocated using the software HYPOSAT based on the spectrum analysis and band-pass (3-5 Hz) filtering and picking up the travel-times of Pn and Sn. Results of hypocentral determinations show that there location error is decreased significantly by joined OBS's recording data. This study do not only provide the experiences for the next step deploying long-term wide-band OBSs, but also deepen understanding of the structure of SWIR and clarify the nature of plate tectonic motivation. This research was granted by the Natural Science Foundation of China (41176053, 91028002, 91428204). Keywords: southwest Indian Ridge (SWIR), relocation of earthquakes, Ocean Bottom Seismometers (OBS), HYPOSAT References:[1] Dick, H. J. B., Lin J., Schouten H. 2003. An ultraslow-spreading class of ocean ridge. Nature, 426(6965): 405-412. [2] Zhao M. H., et al. 2013. Three-dimensional seismic structure of the Dragon Flag oceanic core complex at the ultraslow spreading Southwest Indian Ridge (49°39' E). Geochemistry Geophysics Geosystems, 14(10): 4544-4563.

  20. Biogeochemical and ecological impacts of boundary currents in the Indian Ocean

    Science.gov (United States)

    Hood, Raleigh R.; Beckley, Lynnath E.; Wiggert, Jerry D.

    2017-08-01

    Monsoon forcing and the unique geomorphology of the Indian Ocean basin result in complex boundary currents, which are unique in many respects. In the northern Indian Ocean, several boundary current systems reverse seasonally. For example, upwelling coincident with northward-flowing currents along the coast of Oman during the Southwest Monsoon gives rise to high productivity which also alters nutrient stoichiometry and therefore, the species composition of the resulting phytoplankton blooms. During the Northeast Monsoon most of the northern Indian Ocean boundary currents reverse and favor downwelling. Higher trophic level species have evolved behavioral responses to these seasonally changing conditions. Examples from the western Arabian Sea include vertical feeding migrations of a copepod (Calanoides carinatus) and the reproductive cycle of a large pelagic fish (Scomberomorus commerson). The impacts of these seasonal current reversals and changes in upwelling and downwelling circulations are also manifested in West Indian coastal waters, where they influence dissolved oxygen concentrations and have been implicated in massive fish kills. The winds and boundary currents reverse seasonally in the Bay of Bengal, though the associated changes in upwelling and productivity are less pronounced. Nonetheless, their effects are observed on the East Indian shelf as, for example, seasonal changes in copepod abundance and zooplankton community structure. In contrast, south of Sri Lanka seasonal reversals in the boundary currents are associated with dramatic changes in the intensity of coastal upwelling, chlorophyll concentration, and catch per unit effort of fishes. Off the coast of Java, monsoon-driven changes in the currents and upwelling strongly impact chlorophyll concentrations, seasonal vertical migrations of zooplankton, and sardine catch in Bali Strait. In the southern hemisphere the Leeuwin is a downwelling-favorable current that flows southward along western Australia