A biologically relevant method for considering patterns of oceanic retention in the Southern Ocean

Science.gov (United States)

Mori, Mao; Corney, Stuart P.; Melbourne-Thomas, Jessica; Klocker, Andreas; Sumner, Michael; Constable, Andrew

2017-12-01

Many marine species have planktonic forms - either during a larval stage or throughout their lifecycle - that move passively or are strongly influenced by ocean currents. Understanding these patterns of movement is important for informing marine ecosystem management and for understanding ecological processes generally. Retention of biological particles in a particular area due to ocean currents has received less attention than transport pathways, particularly for the Southern Ocean. We present a method for modelling retention time, based on the half-life for particles in a particular region, that is relevant for biological processes. This method uses geostrophic velocities at the ocean surface, derived from 23 years of satellite altimetry data (1993-2016), to simulate the advection of passive particles during the Southern Hemisphere summer season (from December to March). We assess spatial patterns in the retention time of passive particles and evaluate the processes affecting these patterns for the Indian sector of the Southern Ocean. Our results indicate that the distribution of retention time is related to bathymetric features and the resulting ocean dynamics. Our analysis also reveals a moderate level of consistency between spatial patterns of retention time and observations of Antarctic krill (Euphausia superba) distribution.

How ocean lateral mixing changes Southern Ocean variability in coupled climate models

Science.gov (United States)

Pradal, M. A. S.; Gnanadesikan, A.; Thomas, J. L.

2016-02-01

The lateral mixing of tracers represents a major uncertainty in the formulation of coupled climate models. The mixing of tracers along density surfaces in the interior and horizontally within the mixed layer is often parameterized using a mixing coefficient ARedi. The models used in the Coupled Model Intercomparison Project 5 exhibit more than an order of magnitude range in the values of this coefficient used within the Southern Ocean. The impacts of such uncertainty on Southern Ocean variability have remained unclear, even as recent work has shown that this variability differs between different models. In this poster, we change the lateral mixing coefficient within GFDL ESM2Mc, a coarse-resolution Earth System model that nonetheless has a reasonable circulation within the Southern Ocean. As the coefficient varies from 400 to 2400 m2/s the amplitude of the variability varies significantly. The low-mixing case shows strong decadal variability with an annual mean RMS temperature variability exceeding 1C in the Circumpolar Current. The highest-mixing case shows a very similar spatial pattern of variability, but with amplitudes only about 60% as large. The suppression of mixing is larger in the Atlantic Sector of the Southern Ocean relatively to the Pacific sector. We examine the salinity budgets of convective regions, paying particular attention to the extent to which high mixing prevents the buildup of low-saline waters that are capable of shutting off deep convection entirely.

Determination of the Prebomb Southern (Antarctic) Ocean Radiocarbon in Organic Matter

International Nuclear Information System (INIS)

Guilderson, T P

2001-01-01

The Southern Hemisphere is an important and unique region of the world's oceans for water-mass formation and mixing, upwelling, nutrient utilization, and carbon export. In fact, one of the primary interests of the oceanographic community is to decipher the climatic record of these processes in the source or sink terms for Southern Ocean surface waters in the CO 2 balance of the atmosphere. Current coupled ocean-atmosphere modeling efforts to trace the input of CO 2 into the ocean imply a strong sink of anthropogenic CO 2 in the southern ocean. However, because of its relative inaccessibility and the difficulty in directly measuring CO 2 fluxes in the Southern Ocean, these results are controversial at best. An accepted diagnostic of the exchange of CO 2 between the atmosphere and ocean is the prebomb distribution of radiocarbon in the ocean and its time-history since atmospheric nuclear testing. Such histories of 14 C in the surface waters of the Southern Ocean do not currently exist, primarily because there are few continuous biological archives (e.g., in corals) such as those that have been used to monitor the 14 C history of the tropics and subtropics. One of the possible long-term archives is the scallop Adamussium collbecki. Although not independently confirmed, relatively crude growth rate estimates of A. collbecki indicate that it has the potential to provide continuous 100 year time-series. We are exploring the suitability of this potential archive

Temperature and upwelling / downwelling irradiance data from drifting buoy in the Southern Oceans as part of the Joint Global Ocean Flux Study/Southern Ocean (JGOFS/Southern Ocean) project, from 1994-12-25 to 1998-06-28 (NODC Accession 9900183)

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — Temperature and upwelling / downwelling irradiance data were collected using drifting buoy in the Southern Oceans from December 25, 1994 to June 28, 1998. Data were...

Atmospheric and Oceanic Response to Southern Ocean Deep Convection Oscillations on Decadal to Centennial Time Scales in Climate Models

Science.gov (United States)

Martin, T.; Reintges, A.; Park, W.; Latif, M.

2014-12-01

Many current coupled global climate models simulate open ocean deep convection in the Southern Ocean as a recurring event with time scales ranging from a few years to centennial (de Lavergne et al., 2014, Nat. Clim. Ch.). The only observation of such event, however, was the occurrence of the Weddell Polynya in the mid-1970s, an open water area of 350 000 km2 within the Antarctic sea ice in three consecutive winters. Both the wide range of modeled frequency of occurrence and the absence of deep convection in the Weddell Sea highlights the lack of understanding concerning the phenomenon. Nevertheless, simulations indicate that atmospheric and oceanic responses to the cessation of deep convection in the Southern Ocean include a strengthening of the low-level atmospheric circulation over the Southern Ocean (increasing SAM index) and a reduction in the export of Antarctic Bottom Water (AABW), potentially masking the regional effects of global warming (Latif et al., 2013, J. Clim.; Martin et al., 2014, Deep Sea Res. II). It is thus of great importance to enhance our understanding of Southern Ocean deep convection and clarify the associated time scales. In two multi-millennial simulations with the Kiel Climate Model (KCM, ECHAM5 T31 atmosphere & NEMO-LIM2 ~2˚ ocean) we showed that the deep convection is driven by strong oceanic warming at mid-depth periodically overriding the stabilizing effects of precipitation and ice melt (Martin et al., 2013, Clim. Dyn.). Sea ice thickness also affects location and duration of the deep convection. A new control simulation, in which, amongst others, the atmosphere grid resolution is changed to T42 (~2.8˚), yields a faster deep convection flip-flop with a period of 80-100 years and a weaker but still significant global climate response similar to CMIP5 simulations. While model physics seem to affect the time scale and intensity of the phenomenon, the driving mechanism is a rather robust feature. Finally, we compare the atmospheric and

Ocean sea-ice modelling in the Southern Ocean around Indian

Indian Academy of Sciences (India)

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 ...

Impacts of Atmosphere-Ocean Coupling on Southern Hemisphere Climate Change

Science.gov (United States)

Li, Feng; Newman, Paul; Pawson, Steven

2013-01-01

Climate in the Southern Hemisphere (SH) has undergone significant changes in recent decades. These changes are closely linked to the shift of the Southern Annular Mode (SAM) towards its positive polarity, which is driven primarily by Antarctic ozone depletion. There is growing evidence that Antarctic ozone depletion has significant impacts on Southern Ocean circulation change. However, it is poorly understood whether and how ocean feedback might impact the SAM and climate change in the SH atmosphere. This outstanding science question is investigated using the Goddard Earth Observing System Coupled Atmosphere-Ocean-Chemistry Climate Model(GEOS-AOCCM).We perform ensemble simulations of the recent past (1960-2010) with and without the interactive ocean. For simulations without the interactive ocean, we use sea surface temperatures and sea ice concentrations produced by the interactive ocean simulations. The differences between these two ensemble simulations quantify the effects of atmosphere-ocean coupling. We will investigate the impacts of atmosphere-ocean coupling on stratospheric processes such as Antarctic ozone depletion and Antarctic polar vortex breakup. We will address whether ocean feedback affects Rossby wave generation in the troposphere and wave propagation into the stratosphere. Another focuson this study is to assess how ocean feedback might affect the tropospheric SAM response to Antarctic ozone depletion

A Stratification Boomerang: Nonlinear Dependence of Deep Southern Ocean Ventilation on PCO2

Science.gov (United States)

Galbraith, E. D.; Merlis, T. M.

2014-12-01

Strong correlations between atmospheric CO2, Antarctic temperatures, and marine proxy records have hinted that ventilation of the deep Southern Ocean may have played a central role in the variations of CO2 over glacial-interglacial cycles. One proposition is that, in general, the Southern Ocean ventilates the deep more strongly under higher CO2, due to a change in winds and/or the dominance of thermal stratification in a warm ocean, which weakens ocean biological carbon storage. Here, we explore this idea with a suite of multi-millennial simulations using the GFDL CM2Mc global coupled model. The results are, indeed, consistent with increasing ventilation of the Southern Ocean as pCO2 increases above modern. However, they reveal a surprising twist under low pCO2: increased salinity of the Southern Ocean, due in part to weakening atmospheric moisture transport, actually increases ventilation rate of the deep ocean under low pCO2 as well. This implies that a nadir of Southern Ocean ventilation occurs at intermediate pCO2, which the model estimates as being close to that of the present-day. This is at odds with the interpretation that weak ventilation of the deep Southern Ocean was the unifying coupled mechanism for the glacial pCO2 cycles. Rather, it suggests that factors other than the ventilation rate of the deep Southern Ocean, such as iron fertilization, ecosystem changes, water mass distributions, and sea ice cover, were key players in the glacial-interglacial CO2 changes.

Tropical teleconnections via the ocean and atmosphere induced by Southern Ocean deep convective events

Science.gov (United States)

Marinov, I.; Cabre, A.; Gunn, A.; Gnanadesikan, A.

2016-12-01

The current generation (CMIP5) of Earth System Models (ESMs) shows a huge variability in their ability to represent Southern Ocean (SO) deep-ocean convection and Antarctic Bottom Water, with a preference for open-sea convection in the Weddell and Ross gyres. A long control simulation in a coarse 3o resolution ESM (the GFDL CM2Mc model) shows a highly regular multi-decadal oscillation between periods of SO open sea convection and non-convective periods. This process also happens naturally, with different frequencies and durations of convection across most CMIP5 models under preindustrial forcing (deLavergne et al, 2014). Here we assess the impact of SO deep convection and resulting sea surface temperature (SST) anomalies on the tropical atmosphere and ocean via teleconnections, with a focus on interannual to multi-decadal timescales. We combine analysis of our low-resolution coupled model with inter-model analysis across historical CMIP5 simulations. SST cooling south of 60S during non-convective decades triggers a stronger, northward shifted SH Hadley cell, which results in intensified northward cross-equatorial moist heat transport and a poleward shift in the ITCZ. Resulting correlations between the cross-equatorial atmospheric heat transport and ITCZ location are in good agreement with recent theories (e.g. Frierson et al. 2013; Donohoe et al. 2014). Lagged correlations between a SO convective index and cross-equatorial heat transports (in the atmosphere and ocean), as well as various tropical (and ENSO) climate indices are analyzed. In the ocean realm, we find that non-convective decades result in weaker AABW formation and weaker ACC but stronger Antarctic Intermediate Water (AAIW) formation, likely as a result of stronger SO westerlies (more positive SAM). The signals of AABW and AAIW are seen in the tropics on short timescales of years to decades in the temperature, heat storage and heat transport anomalies and also in deep and intermediate ocean oxygen. Most

South African southern ocean research programme

CSIR Research Space (South Africa)

SASCAR

1987-01-01

Full Text Available This document describes the South African National Antarctic Research Programme's (SANARP) physical, chemical and biological Southern Ocean research programme. The programme has three main components: ecological studies of the Prince Edward Islands...

Variability in the mechanisms controlling Southern Ocean phytoplankton bloom phenology in an ocean model and satellite observations

Science.gov (United States)

Rohr, Tyler; Long, Matthew C.; Kavanaugh, Maria T.; Lindsay, Keith; Doney, Scott C.

2017-05-01

A coupled global numerical simulation (conducted with the Community Earth System Model) is used in conjunction with satellite remote sensing observations to examine the role of top-down (grazing pressure) and bottom-up (light, nutrients) controls on marine phytoplankton bloom dynamics in the Southern Ocean. Phytoplankton seasonal phenology is evaluated in the context of the recently proposed "disturbance-recovery" hypothesis relative to more traditional, exclusively "bottom-up" frameworks. All blooms occur when phytoplankton division rates exceed loss rates to permit sustained net population growth; however, the nature of this decoupling period varies regionally in Community Earth System Model. Regional case studies illustrate how unique pathways allow blooms to emerge despite very poor division rates or very strong grazing rates. In the Subantarctic, southeast Pacific small spring blooms initiate early cooccurring with deep mixing and low division rates, consistent with the disturbance-recovery hypothesis. Similar systematics are present in the Subantarctic, southwest Atlantic during the spring but are eclipsed by a subsequent, larger summer bloom that is coincident with shallow mixing and the annual maximum in division rates, consistent with a bottom-up, light limited framework. In the model simulation, increased iron stress prevents a similar summer bloom in the southeast Pacific. In the simulated Antarctic zone (70°S-65°S) seasonal sea ice acts as a dominant phytoplankton-zooplankton decoupling agent, triggering a delayed but substantial bloom as ice recedes. Satellite ocean color remote sensing and ocean physical reanalysis products do not precisely match model-predicted phenology, but observed patterns do indicate regional variability in mechanism across the Atlantic and Pacific.

Exploring the link between micro-nutrients and phytoplankton in the Southern Ocean during the 2007 austral summer

Directory of Open Access Journals (Sweden)

Christel eHassler

2012-07-01

Full Text Available Bottle assays and large-scale fertilisation experiments have demonstrated that, in the Southern Ocean, iron often controls the biomass and the biodiversity of primary producers. To grow, phytoplankton need numerous other trace metals (micronutrients required for the activity of key enzymes and other intracellular functions. However, little is known of the potential these other trace elements have to limit the growth of phytoplankton in the Southern Ocean. This study investigates the link between the distribution of several micronutrients (Zn, Co, Cu, Cd, Ni and phytoplankton from samples collected during the SAZ-Sense oceanographic expedition (RV Aurora Australis, Jan.–Feb. 2007. Larger phytoplankton are usually associated with lower diffusive supply and higher micronutrient requirement; for this reason, the delineation between phytoplankton larger than 10 µm and those with a size ranging from 0.8–10 µm was made. In addition, different species of phytoplankton may have different requirements to sustain their growth; the phytoplankton biodiversity here was inferred using biomarker pigments. This study, therefore, attempts to elucidate whether micronutrients other than iron need to be considered as parameters for controlling the phytoplankton growth in the Australian sector of the Southern Ocean. Understanding of the parameters controlling phytoplankton is paramount, as it affects the functioning of the Southern Ocean, its marine resources and ultimately the global carbon cycle.

A Southern Ocean trigger for Northwest Pacific ventilation during the Holocene?

Science.gov (United States)

Rella, S. F.; Uchida, M.

2014-02-01

Holocene ocean circulation is poorly understood due to sparsity of dateable marine archives with submillennial-scale resolution. Here we present a record of mid-depth water radiocarbon contents in the Northwest (NW) Pacific Ocean over the last 12.000 years, which shows remarkable millennial-scale variations relative to changes in atmospheric radiocarbon inventory. Apparent decoupling of these variations from regional ventilation and mixing processes leads us to the suggestion that the mid-depth NW Pacific may have responded to changes in Southern Ocean overturning forced by latitudinal displacements of the southern westerly winds. By inference, a tendency of in-phase related North Atlantic and Southern Ocean overturning would argue against the development of a steady bipolar seesaw regime during the Holocene.

Shallow Carbon Export from an Iron fertilised Plankton Bloom in the Southern Ocean

Science.gov (United States)

Sanders, R.; Pollard, R.; Morris, P.; Statham, P.; Moore, C. M. M.; Lucas, M.

2009-04-01

Some regions of the global ocean, notably the Southern Ocean, have high levels of macronutrients yet low levels of chlorophyll (the high nutrient, low chlorophyll or HNLC condition). Numerous artificial iron fertilization experiments conducted in the Southern Ocean have resulted in enhanced phytoplankton biomass and macronutrient drawdown. However the subsequent long-term biogeochemical consequences of such iron fertilization are unclear due in part to the limited size and duration of such experiments. An alternative way to assess the affect of iron over the Southern Ocean biological carbon pump is to observe the evolution of plankton production in regions of the Southern Ocean where shallow topography and Ocean currents interact to promote to release terrestrial iron into HNLC waters. During 2004-5 RRS Discovery conduced a complex programme of observations in such a region around the Crozet Islands in the SW Indian Ocean. The results of this programme, focussing on a quantitative estimate of carbon export per unit iron addition, will be presented.

Examining the controlling factors on Southern Ocean clouds and their radiative effects in the context of midlatitude weather systems

Science.gov (United States)

Kelleher, M. K.; Grise, K. M.

2017-12-01

Clouds and their associated radiative effects are one of the largest sources of uncertainty in the present generation of global climate models. One region where model biases are especially large is over the Southern Ocean, where many models systematically underestimate the climatological shortwave cloud radiative effects (CRE) and/or misrepresent the relationship between shortwave CRE and atmospheric dynamics. Previous research has shown that two "cloud controlling factors", estimated inversion strength (EIS) and mid-tropospheric vertical velocity, are helpful in explaining the relationship between CRE and atmospheric dynamics on monthly timescales. For example, when the Southern Hemisphere midlatitude jet shifts poleward on monthly timescales, the high clouds and their associated longwave CRE shift poleward with the jet, consistent with a poleward shift of the storm track and the attendant vertical velocity anomalies. However, the observed changes in shortwave CRE with a poleward jet shift are small due to a trade-off between the competing effects of opposing EIS and vertical velocity anomalies. This study extends these previous findings to examine the relationship between Southern Ocean cloud controlling factors and CRE on daily timescales. On a daily timescale, the relationship of EIS and vertical velocity with CRE is more complex, due in part to the presence of transient weather systems. Composites of EIS, vertical velocity, longwave CRE, and shortwave CRE around extratropical cyclones and anticyclones are constructed to examine how the CRE anomalies vary in different sectors of midlatitude weather systems and the role that EIS and vertical velocity play in determining those anomalies. The relationships between the cloud controlling factors and CRE on daily timescales provide key insight into the underlying physical processes responsible for the relationships between midlatitude cloud controlling factors and CRE previously documented on monthly timescales.

Pathways of upwelling deep waters to the surface of the Southern Ocean

Science.gov (United States)

Tamsitt, Veronica; Drake, Henri; Morrison, Adele; Talley, Lynne; Dufour, Carolina; Gray, Alison; Griffies, Stephen; Mazloff, Matthew; Sarmiento, Jorge; Wang, Jinbo; Weijer, Wilbert

2017-04-01

Upwelling of Atlantic, Indian and Pacific deep waters to the sea surface in the Southern Ocean closes the global overturning circulation and is fundamentally important for oceanic uptake of anthropogenic carbon and heat, nutrient resupply for sustaining oceanic biological production, and the melt rate of ice shelves. Here we go beyond the two-dimensional view of Southern Ocean upwelling, to show detailed Southern Ocean upwelling pathways in three dimensions, using hydrographic observations and particle tracking in high-resolution ocean and climate models. The northern deep waters enter the Antarctic Circumpolar Current (ACC) via narrow southward currents along the boundaries of the three ocean basins, before spiraling southeastward and upward through the ACC. Upwelling is greatly enhanced at five major topographic features, associated with vigorous mesoscale eddy activity. Deep water reaches the upper ocean predominantly south of the southern ACC boundary, with a spatially nonuniform distribution, regionalizing warm water supply to Antarctic ice shelves and the delivery of nutrient and carbon-rich water to the sea surface. The timescale for half of the deep water to upwell from 30°S to the mixed layer is on the order of 60-90 years, which has important implications for the timescale for signals to propagate through the deep ocean. In addition, we quantify the diabatic transformation along particle trajectories, to identify where diabatic processes are important along the upwelling pathways.

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

Westerly Winds and the Southern Ocean CO2 Sink Since the Last Glacial-Interglacial Transition

Science.gov (United States)

Hodgson, D. A.; Saunders, K. M.; Roberts, S. J.; Perren, B.; Butz, C.; Sime, L. C.; Davies, S. J.; Grosjean, M.

2017-12-01

The capacity of the Southern Ocean carbon sink is partly controlled by the Southern Hemisphere westerly winds (SHW) and sea ice. These regulate the upwelling of dissolved carbon-rich deep water to Antarctic surface waters, determine the surface area for air-sea gas exchange and therefore modulate the net uptake of atmospheric CO2. Some models have proposed that strengthened SHW will result in a weakening of the Southern Ocean CO2 sink. If these models are correct, then one would expect that reconstructions of changes in SHW intensity on centennial to millennial timescales would show clear links with Antarctic ice core and Southern Ocean marine geological records of atmospheric CO2, temperature and sea ice. Here, we present a 12,300 year reconstruction of past wind strength based on three independent proxies that track the changing inputs of sea salt aerosols and minerogenic particles into lake sediments on sub-Antarctic Macquarie Island. The proxies are consistent in showing that periods of high wind intensity corresponded with the increase in CO2 across the late Last Glacial-Interglacial Transition and in the last 7,000 years, suggesting that the winds have contributed to the long term outgassing of CO2 from the ocean during these periods.

Antarctic contribution to meltwater pulse 1A from reduced Southern Ocean overturning.

Science.gov (United States)

Golledge, N R; Menviel, L; Carter, L; Fogwill, C J; England, M H; Cortese, G; Levy, R H

2014-09-29

During the last glacial termination, the upwelling strength of the southern polar limb of the Atlantic Meridional Overturning Circulation varied, changing the ventilation and stratification of the high-latitude Southern Ocean. During the same period, at least two phases of abrupt global sea-level rise--meltwater pulses--took place. Although the timing and magnitude of these events have become better constrained, a causal link between ocean stratification, the meltwater pulses and accelerated ice loss from Antarctica has not been proven. Here we simulate Antarctic ice sheet evolution over the last 25 kyr using a data-constrained ice-sheet model forced by changes in Southern Ocean temperature from an Earth system model. Results reveal several episodes of accelerated ice-sheet recession, the largest being coincident with meltwater pulse 1A. This resulted from reduced Southern Ocean overturning following Heinrich Event 1, when warmer subsurface water thermally eroded grounded marine-based ice and instigated a positive feedback that further accelerated ice-sheet retreat.

Research Ship Southern Surveyor Underway Meteorological Data, Quality Controlled

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — Research Ship Southern Surveyor Underway Meteorological Data (delayed ~10 days for quality control) are from the Shipboard Automated Meteorological and Oceanographic...

Spiraling pathways of global deep waters to the surface of the Southern Ocean

OpenAIRE

Tamsitt, Veronica; Drake, Henri F.; Morrison, Adele K.; Talley, Lynne D.; Dufour, Carolina O.; Gray, Alison R.; Griffies, Stephen M.; Mazloff, Matthew R.; Sarmiento, Jorge L.; Wang, Jinbo; Weijer, Wilbert

2017-01-01

Upwelling of global deep waters to the sea surface in the Southern Ocean closes the global overturning circulation and is fundamentally important for oceanic uptake of carbon and heat, nutrient resupply for sustaining oceanic biological production, and the melt rate of ice shelves. However, the exact pathways and role of topography in Southern Ocean upwelling remain largely unknown. Here we show detailed upwelling pathways in three dimensions, using hydrographic observations and particle trac...

Interhemispheric gradient of atmospheric radiocarbon reveals natural variability of Southern Ocean winds

Science.gov (United States)

Rodgers, K. B.; Mikaloff-Fletcher, S. E.; Bianchi, D.; Beaulieu, C.; Galbraith, E. D.; Gnanadesikan, A.; Hogg, A. G.; Iudicone, D.; Lintner, B. R.; Naegler, T.; Reimer, P. J.; Sarmiento, J. L.; Slater, R. D.

2011-10-01

Tree ring Δ14C data (Reimer et al., 2004; McCormac et al., 2004) indicate that atmospheric Δ14C varied on multi-decadal to centennial timescales, in both hemispheres, over the period between AD 950 and 1830. The Northern and Southern Hemispheric Δ14C records display similar variability, but from the data alone is it not clear whether these variations are driven by the production of 14C in the stratosphere (Stuiver and Quay, 1980) or by perturbations to exchanges between carbon reservoirs (Siegenthaler et al., 1980). As the sea-air flux of 14CO2 has a clear maximum in the open ocean regions of the Southern Ocean, relatively modest perturbations to the winds over this region drive significant perturbations to the interhemispheric gradient. In this study, model simulations are used to show that Southern Ocean winds are likely a main driver of the observed variability in the interhemispheric gradient over AD 950-1830, and further, that this variability may be larger than the Southern Ocean wind trends that have been reported for recent decades (notably 1980-2004). This interpretation also implies that there may have been a significant weakening of the winds over the Southern Ocean within a few decades of AD 1375, associated with the transition between the Medieval Climate Anomaly and the Little Ice Age. The driving forces that could have produced such a shift in the winds at the Medieval Climate Anomaly to Little Ice Age transition remain unknown. Our process-focused suite of perturbation experiments with models raises the possibility that the current generation of coupled climate and earth system models may underestimate the natural background multi-decadal- to centennial-timescale variations in the winds over the Southern Ocean.

Interhemispheric gradient of atmospheric radiocarbon reveals natural variability of Southern Ocean winds

Directory of Open Access Journals (Sweden)

K. B. Rodgers

2011-10-01

Full Text Available Tree ring Δ¹⁴C data (Reimer et al., 2004; McCormac et al., 2004 indicate that atmospheric Δ¹⁴C varied on multi-decadal to centennial timescales, in both hemispheres, over the period between AD 950 and 1830. The Northern and Southern Hemispheric Δ¹⁴C records display similar variability, but from the data alone is it not clear whether these variations are driven by the production of ¹⁴C in the stratosphere (Stuiver and Quay, 1980 or by perturbations to exchanges between carbon reservoirs (Siegenthaler et al., 1980. As the sea-air flux of ¹⁴CO₂ has a clear maximum in the open ocean regions of the Southern Ocean, relatively modest perturbations to the winds over this region drive significant perturbations to the interhemispheric gradient. In this study, model simulations are used to show that Southern Ocean winds are likely a main driver of the observed variability in the interhemispheric gradient over AD 950–1830, and further, that this variability may be larger than the Southern Ocean wind trends that have been reported for recent decades (notably 1980–2004. This interpretation also implies that there may have been a significant weakening of the winds over the Southern Ocean within a few decades of AD 1375, associated with the transition between the Medieval Climate Anomaly and the Little Ice Age. The driving forces that could have produced such a shift in the winds at the Medieval Climate Anomaly to Little Ice Age transition remain unknown. Our process-focused suite of perturbation experiments with models raises the possibility that the current generation of coupled climate and earth system models may underestimate the natural background multi-decadal- to centennial-timescale variations in the winds over the Southern Ocean.

Bioavailable iron in the Southern Ocean: the significance of the iceberg conveyor belt.

Science.gov (United States)

Raiswell, Rob; Benning, Liane G; Tranter, Martyn; Tulaczyk, Slawek

2008-05-30

Productivity in the Southern Oceans is iron-limited, and the supply of iron dissolved from aeolian dust is believed to be the main source from outside the marine reservoir. Glacial sediment sources of iron have rarely been considered, as the iron has been assumed to be inert and non-bioavailable. This study demonstrates the presence of potentially bioavailable Fe as ferrihydrite and goethite in nanoparticulate clusters, in sediments collected from icebergs in the Southern Ocean and glaciers on the Antarctic landmass. Nanoparticles in ice can be transported by icebergs away from coastal regions in the Southern Ocean, enabling melting to release bioavailable Fe to the open ocean. The abundance of nanoparticulate iron has been measured by an ascorbate extraction. This data indicates that the fluxes of bioavailable iron supplied to the Southern Ocean from aeolian dust (0.01-0.13 Tg yr(-1)) and icebergs (0.06-0.12 Tg yr(-1)) are comparable. Increases in iceberg production thus have the capacity to increase productivity and this newly identified negative feedback may help to mitigate fossil fuel emissions.

Ecology of southern ocean pack ice.

Science.gov (United States)

Brierley, Andrew S; Thomas, David N

2002-01-01

Around Antarctica the annual five-fold growth and decay of sea ice is the most prominent physical process and has a profound impact on marine life there. In winter the pack ice canopy extends to cover almost 20 million square kilometres--some 8% of the southern hemisphere and an area larger than the Antarctic continent itself (13.2 million square kilometres)--and is one of the largest, most dynamic ecosystems on earth. Biological activity is associated with all physical components of the sea-ice system: the sea-ice surface; the internal sea-ice matrix and brine channel system; the underside of sea ice and the waters in the vicinity of sea ice that are modified by the presence of sea ice. Microbial and microalgal communities proliferate on and within sea ice and are grazed by a wide range of proto- and macrozooplankton that inhabit the sea ice in large concentrations. Grazing organisms also exploit biogenic material released from the sea ice at ice break-up or melt. Although rates of primary production in the underlying water column are often low because of shading by sea-ice cover, sea ice itself forms a substratum that provides standing stocks of bacteria, algae and grazers significantly higher than those in ice-free areas. Decay of sea ice in summer releases particulate and dissolved organic matter to the water column, playing a major role in biogeochemical cycling as well as seeding water column phytoplankton blooms. Numerous zooplankton species graze sea-ice algae, benefiting additionally because the overlying sea-ice ceiling provides a refuge from surface predators. Sea ice is an important nursery habitat for Antarctic krill, the pivotal species in the Southern Ocean marine ecosystem. Some deep-water fish migrate to shallow depths beneath sea ice to exploit the elevated concentrations of some zooplankton there. The increased secondary production associated with pack ice and the sea-ice edge is exploited by many higher predators, with seals, seabirds and whales

Phytoplankton community structure at the juncture of the Agulhas return front and subtropical front in the Indian Ocean sector of Southern Ocean: Bottom-up and top-down control

Digital Repository Service at National Institute of Oceanography (India)

Naik, R.K.; George, J.V.; Soares, M.A.; Devi, A.; Anilkumar, N.; Roy, R.; Bhaskar, P.V.; Murukesh, N.; Achuthankutty, C.T.

The juncture of the Agulhas Return Front (ARF) and Subtropical Front (STF) in the Indian Ocean sector of Southern Ocean (SO) is characterized by high mesoscale turbulence, which results in sporadic, short lived phytoplankton proliferation The biota...

Oceans around Southern Africa and regional effects of global change

CSIR Research Space (South Africa)

Lutjeharms, JRE

2001-03-01

Full Text Available In the last few decades, a great deal of work has been carried out on the nature of the oceanic circulation around southern Africa. Attempts have been made to determine regional ocean-atmosphere interactions and the effect of changing sea...

Atmospheric radiocarbon as a Southern Ocean wind proxy over the last 1000 years

Science.gov (United States)

Rodgers, K. B.; Mikaloff Fletcher, S.; Galbraith, E.; Sarmiento, J. L.; Gnanadesikan, A.; Slater, R. D.; Naegler, T.

2009-04-01

Measurements of radiocarbon in tree rings over the last 1000 years indicate that there was a pre-industrial latitudinal gradient of atmospheric radiocarbon of 3.9-4.5 per mail and that this gradient had temporal variability of order 6 per mil. Here we test the idea that the mean gradient as well as variability in he gradient is dominated by the strength of the winds over the Southern Ocean. This is done using an ocean model and an atmospheric transport model. The ocean model is used to derive fluxes of 12CO2 and 14CO2 at the sea surface, and these fluxes are used as a lower boundary condition for the transport model. For the mean state, strong winds in the Southern Ocean drive significant upwelling of radiocarbon-depleted Circumpolar Deep Water (CDW), leading to a net flux of 14CO2 relative to 12CO2 into the ocean. This serves to maintain a hemispheric gradient in pre-anthropogenic atmospheric delta-c14. For perturbations, increased/decreased Southern Ocean winds drive increased/decreased uptake of 14CO2 relative to 12CO2, thus increasing/decreasing the hemispheric gradient in atmospheric delta-c14. The tree ring data is interpreted to reveal a decrease in the strength of the Southern Ocean winds at the transition between the Little Ice Age and the Medieval Warm Period.

Pelagic Iron Recycling in the Southern Ocean: Exploring the Contribution of Marine Animals

Directory of Open Access Journals (Sweden)

Lavenia Ratnarajah

2018-03-01

Full Text Available The availability of iron controls primary productivity in large areas of the Southern Ocean. Iron is largely supplied via atmospheric dust deposition, melting ice, the weathering of shelf sediments, upwelling, sediment resuspension, mixing (deep water, biogenic, and vertical mixing and hydrothermal vents with varying degrees of temporal and spatial importance. However, large areas of the Southern Ocean are remote from these sources, leading to regions of low primary productivity. Recent studies suggest that recycling of iron by animals in the surface layer could enhance primary productivity in the Southern Ocean. The aim of this review is to provide a quantitative and qualitative assessment of the current literature on pelagic iron recycling by marine animals in the Southern Ocean and highlight the next steps forward in quantifying the retention and recycling of iron by higher trophic levels in the Southern Ocean. Phytoplankton utilize the iron in seawater to meet their metabolic demand. Through grazing, pelagic herbivores transfer the iron in phytoplankton cells into their body tissues and organs. Herbivores can recycle iron through inefficient feeding behavior that release iron into the water before ingestion, and through the release of fecal pellets. The iron stored within herbivores is transferred to higher trophic levels when they are consumed. When predators consume iron beyond their metabolic demand it is either excreted or defecated. Waste products from pelagic vertebrates can thus contain high concentrations of iron which may be in a form that is available to phytoplankton. Bioavailability of fecal iron for phytoplankton growth is influenced by a combination of the size of the fecal particle, presence of organic ligands, the oxidation state of the iron, as well as biological (e.g., remineralization, coprochaly, coprorhexy, and coprophagy and physical (e.g., dissolution, fragmentation processes that lead to the degradation and release of

Increased exposure of Southern Ocean phytoplankton to ultraviolet radiation

Science.gov (United States)

Lubin, Dan; Arrigo, Kevin R.; van Dijken, Gert L.

2004-05-01

Satellite remote sensing of both surface solar ultraviolet radiation (UVR) and chlorophyll over two decades shows that biologically significant ultraviolet radiation increases began to occur over the Southern Ocean three years before the ozone ``hole'' was discovered. Beginning in October 1983, the most frequent occurrences of enhanced UVR over phytoplankton-rich waters occurred in the Weddell Sea and Indian Ocean sectors of the Southern Ocean, impacting 60% of the surface biomass by the late 1990s. These results suggest two reasons why more serious impacts to the base of the marine food web may not have been detected by field experiments: (1) the onset of UVR increases several years before dedicated field work began may have impacted the most sensitive organisms long before such damage could be detected, and (2) most biological field work has so far not taken place in Antarctic waters most extensively subjected to enhanced UVR.

The Southern Ocean and South Pacific Region

OpenAIRE

Kelleher, K.; Warnau, Michel; Failler, Pierre; Pecl, Gretta; Turley, Carol; Boeuf, Gilles; Laffoley, Dan; Parker, Laura; Gurney, Leigh

2012-01-01

The Region comprises three sub-regions (FAO Statistical Areas) with very different characteristics. The South Pacific includes the vast and virtually unpopulated Southern Ocean surrounding the Antarctic. It has the world’s largest fisheries off Peru and Chile and some of the world’s best managed fisheries in Australia and New Zealand. The Region has over 27% of the world’s ocean area and over 98% of the Region’s total area of 91 million km2 is ‘open ocean’. The Region contains less than 5% of...

IMOS: How seals are changing the way we monitor the Southern Ocean

Science.gov (United States)

Harcourt, R.; McMahon, C.; Jonsen, I.; Goldsworthy, S.; Hindell, M.; Hoenner, X.; Thums, M.

2016-02-01

IMOS (Integrated Marine Observing System) operates a wide range of ocean observing equipment throughout Australia's coastal waters and also the open oceans. This fully integrated, national system, covers physical, chemical and biological ocean sciences forming the basis for robust and informed study of the worlds oceans. Of particular interest in understanding global climate processes is the Southern Ocean (SO), but studying this remote region is difficult and most observations are collected during the short ice-free summer when the region is accessible. Through Winter and Spring it is extremely difficult to collect biophysical ocean information in the Southern Ocean. The importance of good observations from this region, the home of the Antarctic Circumpolar Current (ACC), the largest current system in the world, which connects water masses from the global ocean basins cannot be over emphasised. IMOS through the Australian Animal Tracking and Monitoring System (AATAMS) has made important inroads into collecting otherwise hard to obtain observations from the SO by using CTD bio-loggers to monitor coastal and oceanic movements of marine animals from the Australian mainland as far south as the Antarctic continent. In particular seals equipped with satellite-linked CTD tags have provided unique temporal and spatial coverage of the Southern Ocean. This includes extensive data from the Antarctic continental slope and shelf regions during the winter months, which is outside the conventional areas of Argo autonomous floats and ship-based studies. Over 75,000 temperature and salinity profiles have been collected from 20-140 °E, between the Kerguelen archipelago and Prydz Bay Antarctica. These data offer invaluable new insights into the water masses, oceanographic processes and provides a vital tool for oceanographers seeking to advance our understanding of this key component of the global ocean climate. Here we present an overview of the IMOS database of hydrographic (i

Plutonium in Southern Hemisphere ocean Waters

DEFF Research Database (Denmark)

Hirose, K.; Aoyama, M.; Gastaud, J.

2013-01-01

Plutonium in seawater collected by the BEAGLE2003 cruise was determined using ICP- SF-MS and alpha spectrometry after Fe co-precipitation and radiochemical purification. Levels and distributions of dissolved plutonium activity concentrations in Southern Hemisphere ocean waters are summarized here......, including historical data. Pu-239 concentrations in surface water----of the central South Pacific (32.5 °S) in 2003 were around 1 mBq/m3. The 239Pu concentrations in the Indian Ocean surface waters (20°S) were similar to that in the South Pacific, whereas the 239Pu concentrations in the South Atlantic...... surface waters (30°S) were markedly lower than those in the South Pacific and Indian Oceans. The 239Pu vertical profile pattern was similar to that in the North Pacific subtropical gyre, although 239Pu concentrations in the deep South Pacific were significantly lower than those in the North Pacific. One...

Understanding variability of the Southern Ocean overturning circulation in CORE-II models

Science.gov (United States)

Downes, S. M.; Spence, P.; Hogg, A. M.

2018-03-01

The current generation of climate models exhibit a large spread in the steady-state and projected Southern Ocean upper and lower overturning circulation, with mechanisms for deep ocean variability remaining less well understood. Here, common Southern Ocean metrics in twelve models from the Coordinated Ocean-ice Reference Experiment Phase II (CORE-II) are assessed over a 60 year period. Specifically, stratification, surface buoyancy fluxes, and eddies are linked to the magnitude of the strengthening trend in the upper overturning circulation, and a decreasing trend in the lower overturning circulation across the CORE-II models. The models evolve similarly in the upper 1 km and the deep ocean, with an almost equivalent poleward intensification trend in the Southern Hemisphere westerly winds. However, the models differ substantially in their eddy parameterisation and surface buoyancy fluxes. In general, models with a larger heat-driven water mass transformation where deep waters upwell at the surface ( ∼ 55°S) transport warmer waters into intermediate depths, thus weakening the stratification in the upper 2 km. Models with a weak eddy induced overturning and a warm bias in the intermediate waters are more likely to exhibit larger increases in the upper overturning circulation, and more significant weakening of the lower overturning circulation. We find the opposite holds for a cool model bias in intermediate depths, combined with a more complex 3D eddy parameterisation that acts to reduce isopycnal slope. In summary, the Southern Ocean overturning circulation decadal trends in the coarse resolution CORE-II models are governed by biases in surface buoyancy fluxes and the ocean density field, and the configuration of the eddy parameterisation.

The Southern Ocean deep sea: first insights into biodiversity and biogeography

DEFF Research Database (Denmark)

Brandt, A.; Brix, S.; Brökeland, W.

2007-01-01

Shallow marine benthic communities around Antarctica show high levels of endemism, gigantism, slow growth, longevity and late maturity, as well as adaptive radiations that have generated considerable biodiversity in some taxa1. The deeper parts of the Southern Ocean exhibit some unique environmen......Shallow marine benthic communities around Antarctica show high levels of endemism, gigantism, slow growth, longevity and late maturity, as well as adaptive radiations that have generated considerable biodiversity in some taxa1. The deeper parts of the Southern Ocean exhibit some unique...

Quantifying export production in the Southern Ocean: Implications for the Baxs proxy

Science.gov (United States)

Hernandez-Sanchez, Maria T.; Mills, Rachel A.; Planquette, HéLèNe; Pancost, Richard D.; Hepburn, Laura; Salter, Ian; Fitzgeorge-Balfour, Tania

2011-12-01

The water column and sedimentary Baxs distribution around the Crozet Plateau is used to decipher the controls and timing of barite formation and to evaluate how export production signals are recorded in sediments underlying a region of natural Fe fertilization within the Fe limited Southern Ocean. Export production estimated from preserved, vertical sedimentary Baxs accumulation rates are compared with published export fluxes assessed from an integrated study of the biological carbon pump to determine the validity of Baxs as a quantitative proxy under different Fe supply conditions typical of the Southern Ocean. Detailed assessment of the geochemical partitioning of Ba in sediments and the lithogenic end-member allows appropriate correction of the bulk Ba content and determination of the Baxs content of sediments and suspended particles. The upper water column distribution of Baxs is extremely heterogeneous spatially and temporally. Organic carbon/Baxs ratios in deep traps from the Fe fertilized region are similar to other oceanic settings allowing quantification of the inferred carbon export based on established algorithms. There appears to be some decoupling of POC and Ba export in the Fe limited region south of the Plateau. The export production across the Crozet Plateau inferred from the Baxs sedimentary proxy indicates that the Fe fertilized area to the north of the Plateau experiences enhanced export relative to equivalent Southern Ocean settings throughout the Holocene and that this influence may also have impacted the site to the south for significant periods. This interpretation is corroborated by alternative productivity proxies (opal accumulation, 231Paxs/230Thxs). Baxs can be used to quantify export production in complex settings such as naturally Fe-fertilized (volcanoclastic) areas, providing appropriate lithogenic correction is undertaken, and sediment focusing is corrected for along with evaluation of barite preservation.

Zooplankton biomass (displacement volume) data collected in Indian Ocean, Southern Pacific and Southern Atlantic Ocean during Discovery Investigations project from 1931-01-02 to 1951-10-18 by Discovery II, data were acquired from the NMFS-COPEPOD database (NODC Accession 0071064)

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — Zooplankton biomass (displacement volume) data collected in Indian Ocean, Southern Pacific and Southern Atlantic Ocean during Discovery Investigations project from...

Spiraling pathways of global deep waters to the surface of the Southern Ocean.

Science.gov (United States)

Tamsitt, Veronica; Drake, Henri F; Morrison, Adele K; Talley, Lynne D; Dufour, Carolina O; Gray, Alison R; Griffies, Stephen M; Mazloff, Matthew R; Sarmiento, Jorge L; Wang, Jinbo; Weijer, Wilbert

2017-08-02

Upwelling of global deep waters to the sea surface in the Southern Ocean closes the global overturning circulation and is fundamentally important for oceanic uptake of carbon and heat, nutrient resupply for sustaining oceanic biological production, and the melt rate of ice shelves. However, the exact pathways and role of topography in Southern Ocean upwelling remain largely unknown. Here we show detailed upwelling pathways in three dimensions, using hydrographic observations and particle tracking in high-resolution models. The analysis reveals that the northern-sourced deep waters enter the Antarctic Circumpolar Current via southward flow along the boundaries of the three ocean basins, before spiraling southeastward and upward through the Antarctic Circumpolar Current. Upwelling is greatly enhanced at five major topographic features, associated with vigorous mesoscale eddy activity. Deep water reaches the upper ocean predominantly south of the Antarctic Circumpolar Current, with a spatially nonuniform distribution. The timescale for half of the deep water to upwell from 30° S to the mixed layer is ~60-90 years.Deep waters of the Atlantic, Pacific and Indian Oceans upwell in the Southern Oceanbut the exact pathways are not fully characterized. Here the authors present a three dimensional view showing a spiralling southward path, with enhanced upwelling by eddy-transport at topographic hotspots.

The role of Southern Ocean mixing and upwelling in glacial-interglacial atmospheric CO2 change

International Nuclear Information System (INIS)

Watson, Andrew J.; Naveira Garabato, Alberto C.

2006-01-01

Decreased ventilation of the Southern Ocean in glacial time is implicated in most explanations of lower glacial atmospheric CO 2 . Today, the deep (>2000 m) ocean south of the Polar Front is rapidly ventilated from below, with the interaction of deep currents with topography driving high mixing rates well up into the water column. We show from a buoyancy budget that mixing rates are high in all the deep waters of the Southern Ocean. Between the surface and 2000 m depth, water is upwelled by a residual meridional overturning that is directly linked to buoyancy fluxes through the ocean surface. Combined with the rapid deep mixing, this upwelling serves to return deep water to the surface on a short time scale. We propose two new mechanisms by which, in glacial time, the deep Southern Ocean may have been more isolated from the surface. Firstly, the deep ocean appears to have been more stratified because of denser bottom water resulting from intense sea ice formation near Antarctica. The greater stratification would have slowed the deep mixing. Secondly, subzero atmospheric temperatures may have meant that the present-day buoyancy flux from the atmosphere to the ocean surface was reduced or reversed. This in turn would have reduced or eliminated the upwelling (contrary to a common assumption, upwelling is not solely a function of the wind stress but is coupled to the air/sea buoyancy flux too). The observed very close link between Antarctic temperatures and atmospheric CO 2 could then be explained as a natural consequence of the connection between the air/sea buoyancy flux and upwelling in the Southern Ocean, if slower ventilation of the Southern Ocean led to lower atmospheric CO 2 . Here we use a box model, similar to those of previous authors, to show that weaker mixing and reduced upwelling in the Southern Ocean can explain the low glacial atmospheric CO 2 in such a formulation

Long-term decline in krill stock and increase in salps within the Southern Ocean.

Science.gov (United States)

Atkinson, Angus; Siegel, Volker; Pakhomov, Evgeny; Rothery, Peter

2004-11-04

Antarctic krill (Euphausia superba) and salps (mainly Salpa thompsoni) are major grazers in the Southern Ocean, and krill support commercial fisheries. Their density distributions have been described in the period 1926-51, while recent localized studies suggest short-term changes. To examine spatial and temporal changes over larger scales, we have combined all available scientific net sampling data from 1926 to 2003. This database shows that the productive southwest Atlantic sector contains >50% of Southern Ocean krill stocks, but here their density has declined since the 1970s. Spatially, within their habitat, summer krill density correlates positively with chlorophyll concentrations. Temporally, within the southwest Atlantic, summer krill densities correlate positively with sea-ice extent the previous winter. Summer food and the extent of winter sea ice are thus key factors in the high krill densities observed in the southwest Atlantic Ocean. Krill need the summer phytoplankton blooms of this sector, where winters of extensive sea ice mean plentiful winter food from ice algae, promoting larval recruitment and replenishing the stock. Salps, by contrast, occupy the extensive lower-productivity regions of the Southern Ocean and tolerate warmer water than krill. As krill densities decreased last century, salps appear to have increased in the southern part of their range. These changes have had profound effects within the Southern Ocean food web.

Stirring Up the Biological Pump: Vertical Mixing and Carbon Export in the Southern Ocean

Science.gov (United States)

Stukel, Michael R.; Ducklow, Hugh W.

2017-09-01

The biological carbon pump (BCP) transports organic carbon from the surface to the ocean's interior via sinking particles, vertically migrating organisms, and passive transport of organic matter by advection and diffusion. While many studies have quantified sinking particles, the magnitude of passive transport remains poorly constrained. In the Southern Ocean weak thermal stratification, strong vertical gradients in particulate organic matter, and weak vertical nitrate gradients suggest that passive transport from the euphotic zone may be particularly important. We compile data from seasonal time series at a coastal site near Palmer Station, annual regional cruises in the Western Antarctic Peninsula (WAP), cruises throughout the broader Southern Ocean, and SOCCOM (Southern Ocean Carbon and Climate Observations and Modeling) autonomous profiling floats to estimate spatial and temporal patterns in vertical gradients of nitrate, particulate nitrogen (PN), and dissolved organic carbon. Under a steady state approximation, the ratio of ∂PN/∂z to ∂NO3-/∂z suggests that passive transport of PN may be responsible for removing 46% (37%-58%) of the nitrate introduced into the surface ocean of the WAP (with dissolved organic matter contributing an additional 3-6%) and for 23% (19%-28%) of the BCP in the broader Southern Ocean. A simple model parameterized with in situ nitrate, PN, and primary production data suggested that passive transport was responsible for 54% of the magnitude of the BCP in the WAP. Our results highlight the potential importance of passive transport (by advection and diffusion) of organic matter in the Southern Ocean but should only be considered indicative of high passive transport (rather than conclusive evidence) due to our steady state assumptions.

Bioavailability of organically bound Fe to model phytoplankton of the Southern Ocean

Directory of Open Access Journals (Sweden)

C. S. Hassler

2009-10-01

Full Text Available Iron (Fe is known to be mostly bound to organic ligands and to limit primary productivity in the Southern Ocean. It is thus important to investigate the bioavailability of organically bound Fe. In this study, we used four phytoplankton species of the Southern Ocean (Phaeocystis sp., Chaetoceros sp., Fragilariopsis kerguelensis and Thalassiosira antarctica Comber to measure the influence of various organic ligands on Fe solubility and bioavailability. Short-term uptake Fe:C ratios were inversely related to the surface area to volume ratios of the phytoplankton. The ratio of extracellular to intracellular Fe is used to discuss the relative importance of diffusive supply and uptake to control Fe bioavailability. The effect of excess organic ligands on Fe bioavailability cannot be solely explained by their effect on Fe solubility. For most strains studied, the bioavailability of Fe can be enhanced relative to inorganic Fe in the presence of porphyrin, catecholate siderophore and saccharides whereas it was decreased in presence of hydroxamate siderophore and organic amine. For Thalassiosira, iron bioavailability was not affected by the presence of porphyrin, catecholate siderophore and saccharides. The enhancement of Fe bioavailability in presence of saccharides is presented as the result from both the formation of bioavailable (or chemically labile organic form of Fe and the stabilisation of Fe within the dissolved phase. Given the ubiquitous presence of saccharides in the ocean, these compounds might represent an important factor to control the basal level of soluble and bioavailable Fe. Results show that the use of model phytoplankton is promising to improve mechanistic understanding of Fe bioavailability and primary productivity in HNLC regions of the ocean.

Southern Ocean CO2 sink: the contribution of the sea ice

DEFF Research Database (Denmark)

Delille, B.; Vancoppenolle, Martin; Geilfus, Nicolas-Xavier

2014-01-01

at the air-sea ice interface. The sea ice changes from a transient source to a sink for atmospheric CO2. We upscale these observations to the whole Antarctic sea ice cover using the NEMO-LIM3 large-scale sea ice-ocean and provide first esti- mates of spring and summer CO2 uptake from the atmosphere...... by Antarctic sea ice. Over the spring- summer period, the Antarctic sea ice cover is a net sink of atmospheric CO2 of 0.029 Pg C, about 58% of the estimated annual uptake from the Southern Ocean. Sea ice then contributes significantly to the sink of CO2 of the Southern Ocean....... undersaturation while the underlying oceanic waters remains slightly oversaturated. The decrease from winter to summer of pCO2 in the brines is driven by dilution with melting ice, dissolution of carbonate crystals, and net primary production. As the ice warms, its permeability increases, allowing CO2 transfer...

The Southern Ocean as a driver of centennial to millenial timescale radiocarbon variations

Science.gov (United States)

Rodgers, K. B.; Bianchi, D.; Galbraith, E.; Gnanadesikan, A.; Iudicone, D.; Mikaloff Fletcher, S.; Sarmiento, J. L.; Slater, R. D.

2009-04-01

Paleo-proxy records reveal large delta-c14 variations for both the atmosphere and the ocean on centennial to millenial timescales. One of the most pronounced examples is the onset phase of the Younger Dryas, when atmospheric delta-c14 rose by 70 per mil in only 200 years. Another is the most recent deglaciation (and the associated "Mystery Interval"). Many of the significant centennial to millenial transients in atmospheric delta-c14 are reflected in ocean interior delta-c14 at intermediate depths in the Pacific over the last 50kyrs. An ocean model has been used to test the idea that only modest perturbations to Southern Ocean winds provides a means to link the oceanic and atmospheric delta-c14 variations. Perturbations to the winds over the Southern Ocean are able to drive sizable decoupling of the fluxes of 14CO2 and 12CO2 over the Southern Ocean, thus modifying atmospheric delta-c14. These same perturbations are able to perturb rapidly the depth of intermediate water horizons in the North Pacific through the passage of baroclinic planetary (Rossby) waves. This sensitivity is significantly stronger than what previous studies have found for perturbations to the Meridional Overturning Circulation (MOC) in the North Atlantic. It is suggested that delta-c14 may provide a powerful tracer for understanding past variations in the climate system.

Lead isotopes in deep-sea coral skeletons: Ground-truthing and a first deglacial Southern Ocean record

Science.gov (United States)

Wilson, David J.; van de Flierdt, Tina; Adkins, Jess F.

2017-05-01

Past changes in seawater lead (Pb) isotopes record the temporal evolution of anthropogenic pollution, continental weathering inputs, and ocean current transport. To advance our ability to reconstruct this signature, we present methodological developments that allow us to make precise and accurate Pb isotope measurements on deep-sea coral aragonite, and apply our approach to generate the first Pb isotope record for the glacial to deglacial mid-depth Southern Ocean. Our refined methodology includes a two-step anion exchange chemistry procedure and measurement using a 207Pb-204Pb double spike on a Thermo Finnigan Triton TIMS instrument. By employing a 1012 Ω resistor (in place of a 1011 Ω resistor) to measure the low-abundance 204Pb ion beam, we improve the internal precision on 206,207,208Pb/204Pb for a 2 ng load of NIST-SRM-981 Pb from typically ∼420 ppm to ∼230 ppm (2 s.e.), and the long term external reproducibility from ∼950 ppm to ∼550 ppm (2 s.d.). Furthermore, for a typical 500 mg coral sample with low Pb concentrations (∼6-10 ppb yielding ∼3-5 ng Pb for analysis), we obtain a comparable internal precision of ∼150-250 ppm for 206,207,208Pb/204Pb, indicating a good sensitivity for tracing natural Pb sources to the oceans. Successful extraction of a seawater signal from deep-sea coral aragonite further relies on careful physical and chemical cleaning steps, which are necessary to remove anthropogenic Pb contaminants and obtain results that are consistent with ferromanganese crusts. Applying our approach to a collection of late glacial and deglacial corals (∼12-40 ka BP) from south of Tasmania at ∼1.4-1.7 km water depth, we generated the first intermediate water Pb isotope record from the Southern Ocean. That record reveals millennial timescale variability, controlled by binary mixing between two Pb sources, but no distinct glacial-interglacial Pb isotope shift. Mixing between natural endmembers is fully consistent with our data and points to

Empirical algorithms to estimate water column pH in the Southern Ocean

Science.gov (United States)

Williams, N. L.; Juranek, L. W.; Johnson, K. S.; Feely, R. A.; Riser, S. C.; Talley, L. D.; Russell, J. L.; Sarmiento, J. L.; Wanninkhof, R.

2016-04-01

Empirical algorithms are developed using high-quality GO-SHIP hydrographic measurements of commonly measured parameters (temperature, salinity, pressure, nitrate, and oxygen) that estimate pH in the Pacific sector of the Southern Ocean. The coefficients of determination, R2, are 0.98 for pH from nitrate (pHN) and 0.97 for pH from oxygen (pHOx) with RMS errors of 0.010 and 0.008, respectively. These algorithms are applied to Southern Ocean Carbon and Climate Observations and Modeling (SOCCOM) biogeochemical profiling floats, which include novel sensors (pH, nitrate, oxygen, fluorescence, and backscatter). These algorithms are used to estimate pH on floats with no pH sensors and to validate and adjust pH sensor data from floats with pH sensors. The adjusted float data provide, for the first time, seasonal cycles in surface pH on weekly resolution that range from 0.05 to 0.08 on weekly resolution for the Pacific sector of the Southern Ocean.

Atmospheric Concentrations of Persistent Organic Pollutants in the Southern Ocean

Science.gov (United States)

Vlahos, P.; Edson, J.; Cifuentes, A.; McGillis, W. R.; Zappa, C.

2008-12-01

Long-range transport of persistent organic pollutant (POPs) is a global concern. Remote regions such as the Southern Ocean are greatly under-sampled though critical components in understanding POPs cycling. Over 20 high-volume air samples were collected in the Southern Ocean aboard the RV Brown during the GASEX III experiment between Mar 05 to April 9 2008. The relatively stationary platform (51S,38W) enabled the collection of a unique atmospheric time series at this open ocean station. Air sampling was also conducted across transects from Punto Arenas, Chile and to Montevideo, Uruguay. Samples were collected using glass sleeves packed with poly-urethane foam plugs and C-18 resin in order to collect target organic pollutants (per-fluorinated compounds, currently and historically used pesticides) in this under-sampled region. Here we present POPs concentrations and trends over the sampled period and compare variations with air parcel back trajectories to establish potential origins of their long-range transport.

Distribution of planktonic biogenic carbonate organisms in the Southern Ocean south of Australia: a baseline for ocean acidification impact assessment

Science.gov (United States)

Trull, Thomas W.; Passmore, Abraham; Davies, Diana M.; Smit, Tim; Berry, Kate; Tilbrook, Bronte

2018-01-01

The Southern Ocean provides a vital service by absorbing about one-sixth of humankind's annual emissions of CO2. This comes with a cost - an increase in ocean acidity that is expected to have negative impacts on ocean ecosystems. The reduced ability of phytoplankton and zooplankton to precipitate carbonate shells is a clearly identified risk. The impact depends on the significance of these organisms in Southern Ocean ecosystems, but there is very little information on their abundance or distribution. To quantify their presence, we used coulometric measurement of particulate inorganic carbonate (PIC) on particles filtered from surface seawater into two size fractions: 50-1000 µm to capture foraminifera (the most important biogenic carbonate-forming zooplankton) and 1-50 µm to capture coccolithophores (the most important biogenic carbonate-forming phytoplankton). Ancillary measurements of biogenic silica (BSi) and particulate organic carbon (POC) provided context, as estimates of the biomass of diatoms (the highest biomass phytoplankton in polar waters) and total microbial biomass, respectively. Results for nine transects from Australia to Antarctica in 2008-2015 showed low levels of PIC compared to Northern Hemisphere polar waters. Coccolithophores slightly exceeded the biomass of diatoms in subantarctic waters, but their abundance decreased more than 30-fold poleward, while diatom abundances increased, so that on a molar basis PIC was only 1 % of BSi in Antarctic waters. This limited importance of coccolithophores in the Southern Ocean is further emphasized in terms of their associated POC, representing less than 1 % of total POC in Antarctic waters and less than 10 % in subantarctic waters. NASA satellite ocean-colour-based PIC estimates were in reasonable agreement with the shipboard results in subantarctic waters but greatly overestimated PIC in Antarctic waters. Contrastingly, the NASA Ocean Biogeochemical Model (NOBM) shows coccolithophores as overly

Distribution of planktonic biogenic carbonate organisms in the Southern Ocean south of Australia: a baseline for ocean acidification impact assessment

Directory of Open Access Journals (Sweden)

T. W. Trull

2018-01-01

Full Text Available The Southern Ocean provides a vital service by absorbing about one-sixth of humankind's annual emissions of CO2. This comes with a cost – an increase in ocean acidity that is expected to have negative impacts on ocean ecosystems. The reduced ability of phytoplankton and zooplankton to precipitate carbonate shells is a clearly identified risk. The impact depends on the significance of these organisms in Southern Ocean ecosystems, but there is very little information on their abundance or distribution. To quantify their presence, we used coulometric measurement of particulate inorganic carbonate (PIC on particles filtered from surface seawater into two size fractions: 50–1000 µm to capture foraminifera (the most important biogenic carbonate-forming zooplankton and 1–50 µm to capture coccolithophores (the most important biogenic carbonate-forming phytoplankton. Ancillary measurements of biogenic silica (BSi and particulate organic carbon (POC provided context, as estimates of the biomass of diatoms (the highest biomass phytoplankton in polar waters and total microbial biomass, respectively. Results for nine transects from Australia to Antarctica in 2008–2015 showed low levels of PIC compared to Northern Hemisphere polar waters. Coccolithophores slightly exceeded the biomass of diatoms in subantarctic waters, but their abundance decreased more than 30-fold poleward, while diatom abundances increased, so that on a molar basis PIC was only 1 % of BSi in Antarctic waters. This limited importance of coccolithophores in the Southern Ocean is further emphasized in terms of their associated POC, representing less than 1 % of total POC in Antarctic waters and less than 10 % in subantarctic waters. NASA satellite ocean-colour-based PIC estimates were in reasonable agreement with the shipboard results in subantarctic waters but greatly overestimated PIC in Antarctic waters. Contrastingly, the NASA Ocean Biogeochemical Model (NOBM shows

3He and chlorofluorocarbons (CFC) in the Southern Ocean

International Nuclear Information System (INIS)

Jean-Baptiste, P.; Jamous, D.; Mantisi, F.; Memery, L.; Universite Paris 6

1991-01-01

The distribution of 3 He across the Southern Ocean is depicted on the basis of a meridional section between Antarctica and South Africa measured during the INDIGO-3 survey (1988). A core of δ 3 He values above 10% is observed south of the Polar Front, associated with very low CFC concentrations. This 3 He enriched layer is documented from the GEOSECS and INDIGO 3 He data in the Southern Ocean. It is found at a density level around θ σ =27.8 in all the waters close to Antarctica (i.e. south of 50 degS). Its zonal distribution suggests that it is likely that it originates from the central/eastern Pacific. Hence, it provides an indication of the deep Pacific waters in the Antarctic Circumpolar Current, which are not easily detectable from the standard hydrographic parameters. (author). 19 refs.; 8 figs

Phytoplankton composition and biomass across the southern Indian Ocean

DEFF Research Database (Denmark)

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

2011-01-01

prochlorophytes dominated at these two stations, but also pelagophytes, haptophytes and cyanobacteria were abundant. Haptophytes Type 6 (sensu Zapata et al., 2004), most likely Emiliania huxleyi, and pelagophytes were the dominating eucaryotes in the southern Indian Ocean. Prochlorophytes dominated...

Modulation of the Southern Ocean cadmium isotope signature by ocean circulation and primary productivity

NARCIS (Netherlands)

Abouchami, W.; Galer, S.J.G.; de Baar, H.J.W.; Alderkamp, A.C.; Middag, R.; Laan, P.; Feldmann, H.; Andreae, M.O.

2011-01-01

The High Nutrient Low Chlorophyll (HNLC) Southern Ocean plays a key role in regulating the biological pump and the global carbon cycle. Here we examine the efficacy of stable cadmium (Cd) isotope fractionation for detecting differences in biological productivity between regions. Our results show

Impacts of marine instability across the East Antarctic Ice Sheet on Southern Ocean dynamics

Directory of Open Access Journals (Sweden)

S. J. Phipps

2016-09-01

Full Text Available Recent observations and modelling studies have demonstrated the potential for rapid and substantial retreat of large sectors of the East Antarctic Ice Sheet (EAIS. This has major implications for ocean circulation and global sea level. Here we examine the effects of increasing meltwater from the Wilkes Basin, one of the major marine-based sectors of the EAIS, on Southern Ocean dynamics. Climate model simulations reveal that the meltwater flux rapidly stratifies surface waters, leading to a dramatic decrease in the rate of Antarctic Bottom Water (AABW formation. The surface ocean cools but, critically, the Southern Ocean warms by more than 1 °C at depth. This warming is accompanied by a Southern Ocean-wide “domino effect”, whereby the warming signal propagates westward with depth. Our results suggest that melting of one sector of the EAIS could result in accelerated warming across other sectors, including the Weddell Sea sector of the West Antarctic Ice Sheet. Thus, localised melting of the EAIS could potentially destabilise the wider Antarctic Ice Sheet.

Lagrangian pathways of upwelling in the Southern Ocean

Science.gov (United States)

Viglione, Giuliana A.; Thompson, Andrew F.

2016-08-01

The spatial and temporal variability of upwelling into the mixed layer in the Southern Ocean is studied using a 1/10° ocean general circulation model. Virtual drifters are released in a regularly spaced pattern across the Southern Ocean at depths of 250, 500, and 1000 m during both summer and winter months. The drifters are advected along isopycnals for a period of 4 years, unless they outcrop into the mixed layer, where lateral advection and a parameterization of vertical mixing are applied. The focus of this study is on the discrete exchange between the model mixed layer and the interior. Localization of interior-mixed layer exchange occurs downstream of major topographic features across the Indian and Pacific basins, creating "hotspots" of outcropping. Minimal outcropping occurs in the Atlantic basin, while 59% of drifters outcrop in the Pacific sector and in Drake Passage (the region from 140° W to 40° W), a disproportionately large amount even when considering the relative basin sizes. Due to spatial and temporal variations in mixed layer depth, the Lagrangian trajectories provide a statistical measure of mixed layer residence times. For each exchange into the mixed layer, the residence time has a Rayleigh distribution with a mean of 30 days; the cumulative residence time of the drifters is 261 ± 194 days, over a period of 4 years. These results suggest that certain oceanic gas concentrations, such as CO2 and 14C, will likely not reach equilibrium with the atmosphere before being resubducted.

Chemically and geographically distinct solid-phase iron pools in the Southern Ocean

CSIR Research Space (South Africa)

Mtshali, TN

2012-11-01

Full Text Available Iron is a limiting nutrient in many parts of the oceans, including the unproductive regions of the Southern Ocean. Although the dominant fraction of the marine iron pool occurs in the form of solid-phase particles, its chemical speciation...

Chemically and geographically distinct solid-phase iron pools in the Southern Ocean.

Science.gov (United States)

von der Heyden, B P; Roychoudhury, A N; Mtshali, T N; Tyliszczak, T; Myneni, S C B

2012-11-30

Iron is a limiting nutrient in many parts of the oceans, including the unproductive regions of the Southern Ocean. Although the dominant fraction of the marine iron pool occurs in the form of solid-phase particles, its chemical speciation and mineralogy are challenging to characterize on a regional scale. We describe a diverse array of iron particles, ranging from 20 to 700 nanometers in diameter, in the waters of the Southern Ocean euphotic zone. Distinct variations in the oxidation state and composition of these iron particles exist between the coasts of South Africa and Antarctica, with different iron pools occurring in different frontal zones. These speciation variations can result in solubility differences that may affect the production of bioavailable dissolved iron.

The influence of historical climate changes on Southern Ocean marine predator populations: a comparative analysis.

Science.gov (United States)

Younger, Jane L; Emmerson, Louise M; Miller, Karen J

2016-02-01

The Southern Ocean ecosystem is undergoing rapid physical and biological changes that are likely to have profound implications for higher-order predators. Here, we compare the long-term, historical responses of Southern Ocean predators to climate change. We examine palaeoecological evidence for changes in the abundance and distribution of seabirds and marine mammals, and place these into context with palaeoclimate records in order to identify key environmental drivers associated with population changes. Our synthesis revealed two key factors underlying Southern Ocean predator population changes; (i) the availability of ice-free ground for breeding and (ii) access to productive foraging grounds. The processes of glaciation and sea ice fluctuation were key; the distributions and abundances of elephant seals, snow petrels, gentoo, chinstrap and Adélie penguins all responded strongly to the emergence of new breeding habitat coincident with deglaciation and reductions in sea ice. Access to productive foraging grounds was another limiting factor, with snow petrels, king and emperor penguins all affected by reduced prey availability in the past. Several species were isolated in glacial refugia and there is evidence that refuge populations were supported by polynyas. While the underlying drivers of population change were similar across most Southern Ocean predators, the individual responses of species to environmental change varied because of species specific factors such as dispersal ability and environmental sensitivity. Such interspecific differences are likely to affect the future climate change responses of Southern Ocean marine predators and should be considered in conservation plans. Comparative palaeoecological studies are a valuable source of long-term data on species' responses to environmental change that can provide important insights into future climate change responses. This synthesis highlights the importance of protecting productive foraging grounds

Zooplankton excretion metabolites stimulate Southern Ocean phytoplankton growth

KAUST Repository

Coello-Camba, A.; Llabré s, M.; Duarte, Carlos M.; Agusti, Susana

2017-01-01

Warming over Antarctica is leading to changes in the zooplankton communities inhabiting the Southern Ocean. It has been observed that zooplankton not only regulates phytoplankton through grazing, but also through the recycling of nutrients that are essential for phytoplankton growth. In this way, the effects of warming on zooplankton populations will change the amount or proportion at which recycled nutrients are restored. To estimate how the recycled nutrients released by zooplankton populations, dominated by krill (Euphausia superba), amphipods or copepods, affect the phytoplankton uptake and communities, we performed four incubation experiments: two close to the Antarctic Peninsula and two at the Southern Atlantic Ocean. Our results showed a stimulating effect of the addition of metabolites on ammonia removal rates and on the net growth of phytoplankton communities, with different responses amongst the different phytoplankton groups. According to our results, phytoplankton net growth and community composition may be altered if this relevant source of nutrients is lost due to projected changes in the abundance or distribution of these zooplankton populations.

Zooplankton excretion metabolites stimulate Southern Ocean phytoplankton growth

KAUST Repository

Coello-Camba, A.

2017-04-24

Warming over Antarctica is leading to changes in the zooplankton communities inhabiting the Southern Ocean. It has been observed that zooplankton not only regulates phytoplankton through grazing, but also through the recycling of nutrients that are essential for phytoplankton growth. In this way, the effects of warming on zooplankton populations will change the amount or proportion at which recycled nutrients are restored. To estimate how the recycled nutrients released by zooplankton populations, dominated by krill (Euphausia superba), amphipods or copepods, affect the phytoplankton uptake and communities, we performed four incubation experiments: two close to the Antarctic Peninsula and two at the Southern Atlantic Ocean. Our results showed a stimulating effect of the addition of metabolites on ammonia removal rates and on the net growth of phytoplankton communities, with different responses amongst the different phytoplankton groups. According to our results, phytoplankton net growth and community composition may be altered if this relevant source of nutrients is lost due to projected changes in the abundance or distribution of these zooplankton populations.

CLOUDS, AEROSOLS, RADIATION AND THE AIR-SEA INTERFACE OF THE SOUTHERN OCEAN: ESTABLISHING DIRECTIONS FOR FUTURE RESEARCH

Energy Technology Data Exchange (ETDEWEB)

Wood, Robert [University of Washington; Bretherton, Chris [University of Washington; McFarquhar, Greg [University of Illinois - Urbana; Protat, Alain [Bureau of Meteorology - Melbourne; Quinn, Patricia [NOAA PMEL; Siems, Steven [Monash Univ., Melbourne, VIC (Australia); Jakob, Christian [Monash Univ., Melbourne, VIC (Australia); Alexander, Simon [Australian Antarctic Division; Weller, Bob [Woods Hole Oceanographic Institute

2014-09-29

A workshop sponsored by the Department of Energy was convened at the University of Washington to discuss the state of knowledge of clouds, aerosols and air-sea interaction over the Southern Ocean and to identify strategies for reducing uncertainties in their representation in global and regional models. The Southern Ocean plays a critical role in the global climate system and is a unique pristine environment, yet other than from satellite, there have been sparse observations of clouds, aerosols, radiation and the air-sea interface in this region. Consequently, much is unknown about atmospheric and oceanographic processes and their linkage in this region. Approximately 60 scientists, including graduate students, postdoctoral fellows and senior researchers working in atmospheric and oceanic sciences at U.S. and foreign universities and government laboratories, attended the Southern Ocean Workshop. It began with a day of scientific talks, partly in plenary and partly in two parallel sessions, discussing the current state of the science for clouds, aerosols and air-sea interaction in the Southern Ocean. After the talks, attendees broke into two working groups; one focused on clouds and meteorology, and one focused on aerosols and their interactions with clouds. This was followed by more plenary discussion to synthesize the two working group discussions and to consider possible plans for organized activities to study clouds, aerosols and the air-sea interface in the Southern Ocean. The agenda and talk slides, including short summaries of the highlights of the parallel session talks developed by the session chars, are available at http://www.atmos.washington.edu/socrates/presentations/SouthernOceanPresentations/.

Two new species of Protomyctophum (Pisces, Teleostei, Myctophidae) from the Southern Ocean

NARCIS (Netherlands)

Prokofiev, Artém M.

2004-01-01

Two new species of the genus Protomyctophum from the Southern Ocean are described. P. mcginnisi n. sp. (from off the Southern Shetland Islands) is most closely related to P. bolini (Fraser-Brunner, 1949), from which it differs in photophore arrangement, in metallic shine of the photophores, and in

Evaluating Southern Ocean Carbon Eddy-Pump From Biogeochemical-Argo Floats

Science.gov (United States)

Llort, Joan; Langlais, C.; Matear, R.; Moreau, S.; Lenton, A.; Strutton, Peter G.

2018-02-01

The vertical transport of surface water and carbon into ocean's interior, known as subduction, is one of the main mechanisms through which the ocean influences Earth's climate. New instrumental approaches have shown the occurrence of localized and intermittent subduction episodes associated with small-scale ocean circulation features. These studies also revealed the importance of such events for the export of organic matter, the so-called eddy-pump. However, the transient and localized nature of episodic subduction hindered its large-scale evaluation to date. In this work, we present an approach to detect subduction events at the scale of the Southern Ocean using measurements collected by biogeochemical autonomous floats (BGCArgo). We show how subduction events can be automatically identified as anomalies of spiciness and Apparent Oxygen Utilization (AOU) below the mixed layer. Using this methodology over more than 4,000 profiles, we detected 40 subduction events unevenly distributed across the Sothern Ocean. Events were more likely found in hot spots of eddy kinetic energy (EKE), downstream major bathymetric features. Moreover, the bio-optical measurements provided by BGCArgo allowed measuring the amount of Particulate Organic Carbon (POC) being subducted and assessing the contribution of these events to the total downward carbon flux at 100 m (EP100). We estimated that the eddy-pump represents less than 19% to the EP100 in the Southern Ocean, although we observed particularly strong events able to locally duplicate the EP100. This approach provides a novel perspective on where episodic subduction occurs that will be naturally improved as BGCArgo observations continue to increase.

Southern Ocean Phytoplankton in a Changing Climate

OpenAIRE

Deppeler, Stacy L.; Davidson, Andrew T.

2017-01-01

Phytoplankton are the base of the Antarctic food web, sustain the wealth and diversity of life for which Antarctica is renowned, and play a critical role in biogeochemical cycles that mediate global climate. Over the vast expanse of the Southern Ocean (SO), the climate is variously predicted to experience increased warming, strengthening wind, acidification, shallowing mixed layer depths, increased light (and UV), changes in upwelling and nutrient replenishment, declining sea ice, reduced sal...

AMOC Variability During the Last 400 ka from Nd Isotopes in a Southern Ocean Core

Science.gov (United States)

Lupien, R.; Pena, L.; Goldstein, S. L.

2014-12-01

Paleoceanographic studies have used Nd isotope ratios to characterize paleo-ocean deep-water mass distributions. The Southern Ocean has nearly homogeneous ɛNd that reflects the relative inputs from the north Atlantic and north Pacific, offering the possibility to quantify the AMOC strength through time. However, obtaining an ɛNd record from the Southern Ocean is a challenge because carbonates are poorly preserved there, hindering stratigraphic control and generally precluding use of this important substrate. Alternatively, studies of deep-sea corals and ferromanganese crusts provide snapshots or poor time resolution. Deep-sea core E33-22 (55°S, 120°W, 2743m) lies in the polar frontal zone of the Pacific sector, above the carbonate compensation depth, where foraminifera are preserved. It spans ~400,000 years (from the Holocene to MIS11) with a sedimentation rate of ~2.5 cm/kyr. We measured its ɛNd record with the purpose of determining the best estimate of the export of NADW out of the Atlantic system, which we suggest is our best measure of the vigor of the global thermohaline circulation system. The record shows expected ɛNd variability during orbital and sub-orbital time-scales, that is lower ɛNd during warm and higher ɛNd during cold climate intervals. Moreover, the record passes a critical test in that ɛNd-values are almost always between South Atlantic and Pacific values. The only exceptions are glacial periods when they coincide with South Atlantic values, indicating extension of Southern Ocean system into the South Atlantic. We conclude that these data represent a conservative record of AMOC variability through the late Pleistocene.

Observations of high droplet number concentrations in Southern Ocean boundary layer clouds

Directory of Open Access Journals (Sweden)

T. Chubb

2016-01-01

Full Text Available Cloud physics data collected during the NSF/NCAR High-performance Instrumented Airborne Platform for Environmental Research (HIAPER Pole-to-Pole Observations (HIPPO campaigns provide a snapshot of unusual wintertime microphysical conditions in the boundary layer over the Southern Ocean. On 29 June 2011, the HIAPER sampled the boundary layer in a region of pre-frontal warm air advection between 58 and 48° S to the south of Tasmania. Cloud droplet number concentrations were consistent with climatological values in the northernmost profiles but were exceptionally high for wintertime in the Southern Ocean at 100–200 cm−3 in the southernmost profiles. Sub-micron (0.06  < D <  1 µm aerosol concentrations for the southern profiles were up to 400 cm−3. Analysis of back trajectories and atmospheric chemistry observations revealed that while conditions in the troposphere were more typical of a clean remote ocean airmass, there was some evidence of continental or anthropogenic influence. However, the hypothesis of long-range transport of continental aerosol fails to explain the magnitude of the aerosol and cloud droplet concentration in the boundary layer. Instead, the gale force surface winds in this case (wind speed at 167 m above sea level was  > 25 m s−1 were most likely responsible for production of sea spray aerosol which influenced the microphysical properties of the boundary layer clouds. The smaller size and higher number concentration of cloud droplets is inferred to increase the albedo of these clouds, and these conditions occur regularly, and are expected to increase in frequency, over windy parts of the Southern Ocean.

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

The Effects of Interactive Stratospheric Chemistry on Antarctic and Southern Ocean Climate Change in an AOGCM

Science.gov (United States)

Li, Feng; Newman, Paul; Pawson, Steven; Waugh, Darryn

2014-01-01

Stratospheric ozone depletion has played a dominant role in driving Antarctic climate change in the last decades. In order to capture the stratospheric ozone forcing, many coupled atmosphere-ocean general circulation models (AOGCMs) prescribe the Antarctic ozone hole using monthly and zonally averaged ozone field. However, the prescribed ozone hole has a high ozone bias and lacks zonal asymmetry. The impacts of these biases on model simulations, particularly on Southern Ocean and the Antarctic sea ice, are not well understood. The purpose of this study is to determine the effects of using interactive stratospheric chemistry instead of prescribed ozone on Antarctic and Southern Ocean climate change in an AOGCM. We compare two sets of ensemble simulations for the 1960-2010 period using different versions of the Goddard Earth Observing System 5 - AOGCM: one with interactive stratospheric chemistry, and the other with prescribed monthly and zonally averaged ozone and 6 other stratospheric radiative species calculated from the interactive chemistry simulations. Consistent with previous studies using prescribed sea surface temperatures and sea ice concentrations, the interactive chemistry runs simulate a deeper Antarctic ozone hole and consistently larger changes in surface pressure and winds than the prescribed ozone runs. The use of a coupled atmosphere-ocean model in this study enables us to determine the impact of these surface changes on Southern Ocean circulation and Antarctic sea ice. The larger surface wind trends in the interactive chemistry case lead to larger Southern Ocean circulation trends with stronger changes in northerly and westerly surface flow near the Antarctica continent and stronger upwelling near 60S. Using interactive chemistry also simulates a larger decrease of sea ice concentrations. Our results highlight the importance of using interactive chemistry in order to correctly capture the influences of stratospheric ozone depletion on climate

Antarctic and Southern Ocean influences on Late Pliocene global cooling

NARCIS (Netherlands)

McKay, R.; Naish, T.; Carter, L.; Riesselman, C.; Dunbar, R.; Sjunneskog, C.; Winter, D.; Sangiorgi, F.; Warren, C.; Pagani, M.; Schouten, S.; Willmott, V.; Levy, R.; DeConto , R.M.; Powell, R.D.

2012-01-01

The influence of Antarctica and the Southern Ocean on Late Pliocene global climate reconstructions has remained ambiguous due to a lack of well-dated Antarctic-proximal, paleoenvironmental records. Here we present ice sheet, sea-surface temperature, and sea ice reconstructions from the ANDRILL

New approaches for air-sea fluxes in the Southern Ocean

CSIR Research Space (South Africa)

Gille, S

2016-05-01

Full Text Available Air-sea exchanges in the Southern Ocean of momentum, heat, freshwater, carbon dioxide, and other gases are not well documented because fluxes are sparsely sampled (see Figure 1) and because high winds, high sea state, and lack of calibration...

Shearwater foraging in the Southern Ocean: the roles of prey availability and winds.

Directory of Open Access Journals (Sweden)

Ben Raymond

Full Text Available BACKGROUND: Sooty (Puffinus griseus and short-tailed (P. tenuirostris shearwaters are abundant seabirds that range widely across global oceans. Understanding the foraging ecology of these species in the Southern Ocean is important for monitoring and ecosystem conservation and management. METHODOLOGY/PRINCIPAL FINDINGS: Tracking data from sooty and short-tailed shearwaters from three regions of New Zealand and Australia were combined with at-sea observations of shearwaters in the Southern Ocean, physical oceanography, near-surface copepod distributions, pelagic trawl data, and synoptic near-surface winds. Shearwaters from all three regions foraged in the Polar Front zone, and showed particular overlap in the region around 140 degrees E. Short-tailed shearwaters from South Australia also foraged in Antarctic waters south of the Polar Front. The spatial distribution of shearwater foraging effort in the Polar Front zone was matched by patterns in large-scale upwelling, primary production, and abundances of copepods and myctophid fish. Oceanic winds were found to be broad determinants of foraging distribution, and of the flight paths taken by the birds on long foraging trips to Antarctic waters. CONCLUSIONS/SIGNIFICANCE: The shearwaters displayed foraging site fidelity and overlap of foraging habitat between species and populations that may enhance their utility as indicators of Southern Ocean ecosystems. The results highlight the importance of upwellings due to interactions of the Antarctic Circumpolar Current with large-scale bottom topography, and the corresponding localised increases in the productivity of the Polar Front ecosystem.

Diatom species abundance and morphologically-based dissolution proxies in coastal Southern Ocean assemblages

Science.gov (United States)

Warnock, Jonathan P.; Scherer, Reed P.

2015-07-01

Taphonomic processes alter diatom assemblages in sediments, thus potentially negatively impacting paleoclimate records at various rates across space, time, and taxa. However, quantitative taphonomic data is rarely included in diatom-based paleoenvironmental reconstructions and no objective standard exists for comparing diatom dissolution in sediments recovered from marine depositional settings, including the Southern Ocean's opal belt. Furthermore, identifying changes to diatom dissolution through time can provide insight into the efficiency of both upper water column nutrient recycling and the biological pump. This is significant in that reactive metal proxies (e.g. Al, Ti) in the sediments only account for post-depositional dissolution, not the water column where the majority of dissolution occurs. In order to assess the range of variability of responses to dissolution in a typical Southern Ocean diatom community and provide a quantitative guideline for assessing taphonomic variability in diatoms recovered from core material, a sediment trap sample was subjected to controlled, serial dissolution. By evaluating dissolution-induced changes to diatom species' relative abundance, three preservational categories of diatoms have been identified: gracile, intermediate, and robust. The relative abundances of these categories can be used to establish a preservation grade for diatom assemblages. However, changes to the relative abundances of diatom species in sediment samples may reflect taphonomic or ecological factors. In order to address this complication, relative abundance changes have been tied to dissolution-induced morphological change to the areolae of Fragilariopsis curta, a significant sea-ice indicator in Southern Ocean sediments. This correlation allows differentiation between gracile species loss to dissolution versus ecological factors or sediment winnowing. These results mirror a similar morphological dissolution index from a parallel study utilizing

Phenotypic plasticity of southern ocean diatoms: key to success in the sea ice habitat?

Directory of Open Access Journals (Sweden)

Olivia Sackett

Full Text Available Diatoms are the primary source of nutrition and energy for the Southern Ocean ecosystem. Microalgae, including diatoms, synthesise biological macromolecules such as lipids, proteins and carbohydrates for growth, reproduction and acclimation to prevailing environmental conditions. Here we show that three key species of Southern Ocean diatom (Fragilariopsis cylindrus, Chaetoceros simplex and Pseudo-nitzschia subcurvata exhibited phenotypic plasticity in response to salinity and temperature regimes experienced during the seasonal formation and decay of sea ice. The degree of phenotypic plasticity, in terms of changes in macromolecular composition, was highly species-specific and consistent with each species' known distribution and abundance throughout sea ice, meltwater and pelagic habitats, suggesting that phenotypic plasticity may have been selected for by the extreme variability of the polar marine environment. We argue that changes in diatom macromolecular composition and shifts in species dominance in response to a changing climate have the potential to alter nutrient and energy fluxes throughout the Southern Ocean ecosystem.

Killer whales ( Orcinus orca ) at Marion Island, Southern Ocean ...

African Journals Online (AJOL)

Killer whales (Orcinus orca) were studied using data obtained on an opportunistic basis between 1973 and 1996 at Marion Island (46°54'S, 37°45'E) in the Southern Indian Ocean. A clear seasonal pattern of occurrence with the main peak between October and December was evident. Most killer whales were observed ...

Southern Ocean frontal structure and sea-ice formation rates revealed by elephant seals

Science.gov (United States)

Charrassin, J.-B.; Hindell, M.; Rintoul, S. R.; Roquet, F.; Sokolov, S.; Biuw, M.; Costa, D.; Boehme, L.; Lovell, P.; Coleman, R.; Timmermann, R.; Meijers, A.; Meredith, M.; Park, Y.-H.; Bailleul, F.; Goebel, M.; Tremblay, Y.; Bost, C.-A.; McMahon, C. R.; Field, I. C.; Fedak, M. A.; Guinet, C.

2008-01-01

Polar regions are particularly sensitive to climate change, with the potential for significant feedbacks between ocean circulation, sea ice, and the ocean carbon cycle. However, the difficulty in obtaining in situ data means that our ability to detect and interpret change is very limited, especially in the Southern Ocean, where the ocean beneath the sea ice remains almost entirely unobserved and the rate of sea-ice formation is poorly known. Here, we show that southern elephant seals (Mirounga leonina) equipped with oceanographic sensors can measure ocean structure and water mass changes in regions and seasons rarely observed with traditional oceanographic platforms. In particular, seals provided a 30-fold increase in hydrographic profiles from the sea-ice zone, allowing the major fronts to be mapped south of 60°S and sea-ice formation rates to be inferred from changes in upper ocean salinity. Sea-ice production rates peaked in early winter (April–May) during the rapid northward expansion of the pack ice and declined by a factor of 2 to 3 between May and August, in agreement with a three-dimensional coupled ocean–sea-ice model. By measuring the high-latitude ocean during winter, elephant seals fill a “blind spot” in our sampling coverage, enabling the establishment of a truly global ocean-observing system. PMID:18695241

Accelerated warming of the Southern Ocean and its impacts on the hydrological cycle and sea ice.

Science.gov (United States)

Liu, Jiping; Curry, Judith A

2010-08-24

The observed sea surface temperature in the Southern Ocean shows a substantial warming trend for the second half of the 20th century. Associated with the warming, there has been an enhanced atmospheric hydrological cycle in the Southern Ocean that results in an increase of the Antarctic sea ice for the past three decades through the reduced upward ocean heat transport and increased snowfall. The simulated sea surface temperature variability from two global coupled climate models for the second half of the 20th century is dominated by natural internal variability associated with the Antarctic Oscillation, suggesting that the models' internal variability is too strong, leading to a response to anthropogenic forcing that is too weak. With increased loading of greenhouse gases in the atmosphere through the 21st century, the models show an accelerated warming in the Southern Ocean, and indicate that anthropogenic forcing exceeds natural internal variability. The increased heating from below (ocean) and above (atmosphere) and increased liquid precipitation associated with the enhanced hydrological cycle results in a projected decline of the Antarctic sea ice.

Evaluation of satellite and reanalysis wind products with in situ wave glider wind observations in the Southern Ocean

CSIR Research Space (South Africa)

Schmidt, KM

2017-12-01

Full Text Available observations in the Southern Ocean 2 3 Kevin M. Schmidta, Sebastiaan Swartb,c,d, Chris Reasonc, Sarah Nicholsonb,c 4 a Marine Research Institute, University of Cape Town, Rondebosch, South Africa 5 b Southern Ocean Carbon & Climate Observatory, Council...

Rapid global ocean-atmosphere response to Southern Ocean freshening during the last glacial.

Science.gov (United States)

Turney, Chris S M; Jones, Richard T; Phipps, Steven J; Thomas, Zoë; Hogg, Alan; Kershaw, A Peter; Fogwill, Christopher J; Palmer, Jonathan; Bronk Ramsey, Christopher; Adolphi, Florian; Muscheler, Raimund; Hughen, Konrad A; Staff, Richard A; Grosvenor, Mark; Golledge, Nicholas R; Rasmussen, Sune Olander; Hutchinson, David K; Haberle, Simon; Lorrey, Andrew; Boswijk, Gretel; Cooper, Alan

2017-09-12

Contrasting Greenland and Antarctic temperatures during the last glacial period (115,000 to 11,650 years ago) are thought to have been driven by imbalances in the rates of formation of North Atlantic and Antarctic Deep Water (the 'bipolar seesaw'). Here we exploit a bidecadally resolved 14 C data set obtained from New Zealand kauri (Agathis australis) to undertake high-precision alignment of key climate data sets spanning iceberg-rafted debris event Heinrich 3 and Greenland Interstadial (GI) 5.1 in the North Atlantic (~30,400 to 28,400 years ago). We observe no divergence between the kauri and Atlantic marine sediment 14 C data sets, implying limited changes in deep water formation. However, a Southern Ocean (Atlantic-sector) iceberg rafted debris event appears to have occurred synchronously with GI-5.1 warming and decreased precipitation over the western equatorial Pacific and Atlantic. An ensemble of transient meltwater simulations shows that Antarctic-sourced salinity anomalies can generate climate changes that are propagated globally via an atmospheric Rossby wave train.A challenge for testing mechanisms of past climate change is the precise correlation of palaeoclimate records. Here, through climate modelling and the alignment of terrestrial, ice and marine 14 C and 10 Be records, the authors show that Southern Ocean freshwater hosing can trigger global change.

Contributions of greenhouse gas forcing and the Southern Annular Mode to historical Southern Ocean surface temperature trends

OpenAIRE

Kostov, Yavor; Ferreira, David; Marshall, John; Armour, Kyle

2018-01-01

We examine the 1979-2014 Southern Ocean (SO) sea surface temperature (SST) trends simulated in an ensemble of coupled general circulation models and evaluate possible causes of the models’ inability to reproduce the observed 1979-2014 SO cooling. For each model we estimate the response of SO SST to step changes in greenhouse gas (GHG) forcing and in the seasonal indices of the Southern Annular Mode (SAM). Using these step-response functions, we skillfully reconstruct the models’ 1979-2014 SO ...

Assessment of Export Efficiency Equations in the Southern Ocean Applied to Satellite-Based Net Primary Production

Science.gov (United States)

Arteaga, Lionel; Haëntjens, Nils; Boss, Emmanuel; Johnson, Kenneth S.; Sarmiento, Jorge L.

2018-04-01

Carbon export efficiency (e-ratio) is defined as the fraction of organic carbon fixed through net primary production (NPP) that is exported out of the surface productive layer of the ocean. Recent observations for the Southern Ocean suggest a negative e-ratio versus NPP relationship, and a reduced dependency of export efficiency on temperature, different than in the global domain. In this study, we complement information from a passive satellite sensor with novel space-based lidar observations of ocean particulate backscattering to infer NPP over the entire annual cycle, and estimate Southern Ocean export rates from five different empirical models of export efficiency. Inferred Southern Ocean NPP falls within the range of previous studies, with a mean estimate of 15.8 (± 3.9) Pg C yr-1 for the region south of 30°S during the 2005-2016 period. We find that an export efficiency model that accounts for silica(Si)-ballasting, which is constrained by observations with a negative e-ratio versus NPP relationship, shows the best agreement with in situ-based estimates of annual net community production (annual export of 2.7 ± 0.6 Pg C yr-1 south of 30°S). By contrast, models based on the analysis of global observations with a positive e-ratio versus NPP relationship predict annually integrated export rates that are ˜ 33% higher than the Si-dependent model. Our results suggest that accounting for Si-induced ballasting is important for the estimation of carbon export in the Southern Ocean.

Sea-ice transport driving Southern Ocean salinity and its recent trends.

Science.gov (United States)

Haumann, F Alexander; Gruber, Nicolas; Münnich, Matthias; Frenger, Ivy; Kern, Stefan

2016-09-01

Recent salinity changes in the Southern Ocean are among the most prominent signals of climate change in the global ocean, yet their underlying causes have not been firmly established. Here we propose that trends in the northward transport of Antarctic sea ice are a major contributor to these changes. Using satellite observations supplemented by sea-ice reconstructions, we estimate that wind-driven northward freshwater transport by sea ice increased by 20 ± 10 per cent between 1982 and 2008. The strongest and most robust increase occurred in the Pacific sector, coinciding with the largest observed salinity changes. We estimate that the additional freshwater for the entire northern sea-ice edge entails a freshening rate of -0.02 ± 0.01 grams per kilogram per decade in the surface and intermediate waters of the open ocean, similar to the observed freshening. The enhanced rejection of salt near the coast of Antarctica associated with stronger sea-ice export counteracts the freshening of both continental shelf and newly formed bottom waters due to increases in glacial meltwater. Although the data sources underlying our results have substantial uncertainties, regional analyses and independent data from an atmospheric reanalysis support our conclusions. Our finding that northward sea-ice freshwater transport is also a key determinant of the mean salinity distribution in the Southern Ocean further underpins the importance of the sea-ice-induced freshwater flux. Through its influence on the density structure of the ocean, this process has critical consequences for the global climate by affecting the exchange of heat, carbon and nutrients between the deep ocean and surface waters.

Decadal climate predictability in the southern Indian Ocean captured by SINTEX-F using a simple SST-nudging scheme.

Science.gov (United States)

Morioka, Yushi; Doi, Takeshi; Behera, Swadhin K

2018-01-26

Decadal climate variability in the southern Indian Ocean has great influences on southern African climate through modulation of atmospheric circulation. Although many efforts have been made to understanding physical mechanisms, predictability of the decadal climate variability, in particular, the internally generated variability independent from external atmospheric forcing, remains poorly understood. This study investigates predictability of the decadal climate variability in the southern Indian Ocean using a coupled general circulation model, called SINTEX-F. The ensemble members of the decadal reforecast experiments were initialized with a simple sea surface temperature (SST) nudging scheme. The observed positive and negative peaks during late 1990s and late 2000s are well reproduced in the reforecast experiments initiated from 1994 and 1999, respectively. The experiments initiated from 1994 successfully capture warm SST and high sea level pressure anomalies propagating from the South Atlantic to the southern Indian Ocean. Also, the other experiments initiated from 1999 skillfully predict phase change from a positive to negative peak. These results suggest that the SST-nudging initialization has the essence to capture the predictability of the internally generated decadal climate variability in the southern Indian Ocean.

More losers than winners in a century of future Southern Ocean seafloor warming

Science.gov (United States)

Griffiths, Huw J.; Meijers, Andrew J. S.; Bracegirdle, Thomas J.

2017-10-01

The waters of the Southern Ocean are projected to warm over the coming century, with potential adverse consequences for native cold-adapted organisms. Warming waters have caused temperate marine species to shift their ranges poleward. The seafloor animals of the Southern Ocean shelf have long been isolated by the deep ocean surrounding Antarctica and the Antarctic Circumpolar Current, with little scope for southward migration. How these largely endemic species will react to future projected warming is unknown. By considering 963 invertebrate species, we show that within the current century, warming temperatures alone are unlikely to result in wholesale extinction or invasion affecting Antarctic seafloor life. However, 79% of Antarctica's endemic species do face a significant reduction in suitable temperature habitat (an average 12% reduction). Our findings highlight the species and regions most likely to respond significantly (negatively and positively) to warming and have important implications for future management of the region.

The seasonal sea-ice zone in the glacial Southern Ocean as a carbon sink.

Science.gov (United States)

Abelmann, Andrea; Gersonde, Rainer; Knorr, Gregor; Zhang, Xu; Chapligin, Bernhard; Maier, Edith; Esper, Oliver; Friedrichsen, Hans; Lohmann, Gerrit; Meyer, Hanno; Tiedemann, Ralf

2015-09-18

Reduced surface-deep ocean exchange and enhanced nutrient consumption by phytoplankton in the Southern Ocean have been linked to lower glacial atmospheric CO2. However, identification of the biological and physical conditions involved and the related processes remains incomplete. Here we specify Southern Ocean surface-subsurface contrasts using a new tool, the combined oxygen and silicon isotope measurement of diatom and radiolarian opal, in combination with numerical simulations. Our data do not indicate a permanent glacial halocline related to melt water from icebergs. Corroborated by numerical simulations, we find that glacial surface stratification was variable and linked to seasonal sea-ice changes. During glacial spring-summer, the mixed layer was relatively shallow, while deeper mixing occurred during fall-winter, allowing for surface-ocean refueling with nutrients from the deep reservoir, which was potentially richer in nutrients than today. This generated specific carbon and opal export regimes turning the glacial seasonal sea-ice zone into a carbon sink.

Linking small-scale circulation dynamics with large-scale seasonal production (phytoplankton) in the Southern Ocean

CSIR Research Space (South Africa)

Nicholson, S

2012-10-01

Full Text Available Understanding the seasonal and intra-seasonal (daily to weekly) changes of the upper ocean and the impact on the primary production in the Southern Ocean is key to better understanding the sensitivities of the global carbon cycle....

Secondary calcification of planktic foraminifera from the Indian sector of Southern ocean

Digital Repository Service at National Institute of Oceanography (India)

Mohan, R.; Shetye, S.; Tiwari, M.; AnilKumar, N.

This study focused on planktic foraminifera in plankton tows and surface sediments from the western Indian sector of Southern Ocean in order to evaluate the potential foraminiferal secondary calcification and/or dissolution in the sediment...

The influence of UV irradiation on the photoreduction of iron in the Southern Ocean

NARCIS (Netherlands)

Rijkenberg, M J A; Fischer, AC; Kroon, JJ; Gerringa, LJA; Timmermans, KR; Wolterbeek, HT; de Baar, H J W

2005-01-01

An iron enrichment experiment, EisenEx, was performed in the Atlantic sector of the Southern Ocean during the Antarctic spring of 2000. Deck incubations of open ocean water were performed to investigate the influence of ultraviolet B (UVB: 280-315 nm) and ultraviolet A (UVA: 315-400 nm) on the

Zooplankton biomass and abundance of Antarctic krill Euphausia superba DANA in Indian Ocean sector of the southern ocean

Digital Repository Service at National Institute of Oceanography (India)

Ingole, B.S.; Parulekar, A.H.

Zooplankton sampling was carried out during the first six Indian Scientific Expeditions to Antarctica (1981-1987) to estimate krill abundance in the Indian sector of the Southern Ocean (between 35 to 70 degrees S and 10 to 52 degrees E). This study...

A simple predictive model for the structure of the oceanic pycnocline

Science.gov (United States)

Gnanadesikan

1999-03-26

A simple theory for the large-scale oceanic circulation is developed, relating pycnocline depth, Northern Hemisphere sinking, and low-latitude upwelling to pycnocline diffusivity and Southern Ocean winds and eddies. The results show that Southern Ocean processes help maintain the global ocean structure and that pycnocline diffusion controls low-latitude upwelling.

The Seasonal Cycle of Carbon in the Southern Pacific Ocean Observed from Biogeochemical Profiling Floats

Science.gov (United States)

Sarmiento, J. L.; Gray, A. R.; Johnson, K. S.; Carter, B.; Riser, S.; Talley, L. D.; Williams, N. L.

2016-02-01

The Southern Ocean is thought to play an important role in the ocean-atmosphere exchange of carbon dioxide and the uptake of anthropogenic carbon dioxide. However, the total number of observations of the carbonate system in this region is small and heavily biased towards the summer. Here we present 1.5 years of biogeochemical measurements, including pH, oxygen, and nitrate, collected by 11 autonomous profiling floats deployed in the Pacific sector of the Southern Ocean in April 2014. These floats sampled a variety of oceanographic regimes ranging from the seasonally ice-covered zone to the subtropical gyre. Using an algorithm trained with bottle measurements, alkalinity is estimated from salinity, temperature, and oxygen and then used together with the measured pH to calculate total carbon dioxide and pCO2 in the upper 1500 dbar. The seasonal cycle in the biogeochemical quantities is examined, and the factors governing pCO2 in the surface waters are analyzed. The mechanisms driving the seasonal cycle of carbon are further investigated by computing budgets of heat, carbon, and nitrogen in the mixed layer. Comparing the different regimes sampled by the floats demonstrates the complex and variable nature of the carbon cycle in the Southern Ocean.

Enrichments in authigenic uranium in glacial sediments of the Southern Ocean; Enrichissement en uranium authigene dans les sediments glaciaires de l'ocean Austral

Energy Technology Data Exchange (ETDEWEB)

Dezileau, L. [Universidad de Conception, Programa Regional de Oceanografia Fisica y Climat PROFC, Y Centro de Investigacion Oceanografica (Chile); Bareille, G. [Pau Univ., Lab. de Chimie Analytique Bio-Inorganique et Environnement, EP-CNRS 132, 64 (France); Reyss, J.L. [CEA Saclay, Direction des Sciences de la Matiere, Lab. des Sciences du Climat et de L' environnement, Lab. Mixte CEA-CNRS, 91 - Gif-sur-Yvette (France)

2002-11-01

Four sediment cores from the Polar frontal zone and the Antarctic zone in the Indian sector of the Southern Ocean present an increase of authigenic uranium during glacial periods. We show that this increase in uranium is due to a combination of (i) an increase in the lateral transport of organic matter, (ii) a decrease in the oxygen in deep waters, and (iii) a process of diagenesis. It appears that uranium concentration cannot be used as a proxy of paleo-productivity in the Southern Ocean, as previously suggested by Kumar et al. in 1995. (authors)

Molecular transformation and degradation of refractory dissolved organic matter in the Atlantic and Southern Ocean

Science.gov (United States)

Lechtenfeld, Oliver J.; Kattner, Gerhard; Flerus, Ruth; McCallister, S. Leigh; Schmitt-Kopplin, Philippe; Koch, Boris P.

2014-02-01

More than 90% of the global ocean dissolved organic carbon (DOC) is refractory, has an average age of 4000-6000 years and a lifespan from months to millennia. The fraction of dissolved organic matter (DOM) that is resistant to degradation is a long-term buffer in the global carbon cycle but its chemical composition, structure, and biochemical formation and degradation mechanisms are still unresolved. We have compiled the most comprehensive molecular dataset of 197 Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) analyses from solid-phase extracted marine DOM covering two major oceans, the Atlantic sector of the Southern Ocean and the East Atlantic Ocean (ranging from 50° N to 70° S). Molecular trends and radiocarbon dating of 34 DOM samples (comprising Δ14C values from -229‰ to -495‰) were combined to model an integrated degradation rate for bulk DOC resulting in a predicted age of >24 ka for the most persistent DOM fraction. First order kinetic degradation rates for 1557 mass peaks indicate that numerous DOM molecules cycle on timescales much longer than the turnover of the bulk DOC pool (estimated residence times of up to ~100 ka) and the range of validity of radiocarbon dating. Changes in elemental composition were determined by assigning molecular formulae to the detected mass peaks. The combination of residence times with molecular information enabled modelling of the average elemental composition of the slowest degrading fraction of the DOM pool. In our dataset, a group of 361 molecular formulae represented the most stable composition in the oceanic environment (“island of stability”). These most persistent compounds encompass only a narrow range of the molecular elemental ratios H/C (average of 1.17 ± 0.13), and O/C (average of 0.52 ± 0.10) and molecular masses (360 ± 28 and 497 ± 51 Da). In the Weddell Sea DOC concentrations in the surface waters were low (46.3 ± 3.3 μM) while the organic radiocarbon was significantly

Environmental forcing and Southern Ocean marine predator populations: effects of climate change and variability.

Science.gov (United States)

Trathan, P N; Forcada, J; Murphy, E J

2007-12-29

The Southern Ocean is a major component within the global ocean and climate system and potentially the location where the most rapid climate change is most likely to happen, particularly in the high-latitude polar regions. In these regions, even small temperature changes can potentially lead to major environmental perturbations. Climate change is likely to be regional and may be expressed in various ways, including alterations to climate and weather patterns across a variety of time-scales that include changes to the long interdecadal background signals such as the development of the El Niño-Southern Oscillation (ENSO). Oscillating climate signals such as ENSO potentially provide a unique opportunity to explore how biological communities respond to change. This approach is based on the premise that biological responses to shorter-term sub-decadal climate variability signals are potentially the best predictor of biological responses over longer time-scales. Around the Southern Ocean, marine predator populations show periodicity in breeding performance and productivity, with relationships with the environment driven by physical forcing from the ENSO region in the Pacific. Wherever examined, these relationships are congruent with mid-trophic-level processes that are also correlated with environmental variability. The short-term changes to ecosystem structure and function observed during ENSO events herald potential long-term changes that may ensue following regional climate change. For example, in the South Atlantic, failure of Antarctic krill recruitment will inevitably foreshadow recruitment failures in a range of higher trophic-level marine predators. Where predator species are not able to accommodate by switching to other prey species, population-level changes will follow. The Southern Ocean, though oceanographically interconnected, is not a single ecosystem and different areas are dominated by different food webs. Where species occupy different positions in

Recent Ship, Satellite and Autonomous Observations of Southern Ocean Eddies

Science.gov (United States)

Strutton, P. G.; Moreau, S.; Llort, J.; Phillips, H. E.; Patel, R.; Della Penna, A.; Langlais, C.; Lenton, A.; Matear, R.; Dawson, H.; Boyd, P. W.

2016-12-01

The Southern Ocean is the area of greatest uncertainty regarding the exchange of CO2 between the ocean and atmosphere. It is also a region of abundant energetic eddies that significantly impact circulation and biogeochemistry. In the Indian sector of the Southern Ocean, cyclonic eddies are unusual in that they are upwelling favorable, as for cyclonic eddies elsewhere, but during summer they are low in silicate and phytoplankton biomass. The reverse is true for anticyclonic eddies in that they have counter-intuitive positive chlorophyll anomalies in summer. Similar but less obvious patterns occur in the Pacific and Atlantic sectors. Using ship, satellite and autonomous observations in the region south of Australia, the physical and biogeochemical signatures of both types of eddies were documented in 2016. A cyclonic eddy that lived for seven weeks exhibited doming isopycnals indicative of upwelling. However, low surface silicate and chlorophyll concentrations appeared to be characteristic of surface waters to the south where the eddy formed. Higher chlorophyll was confined to filaments at the eddy edge. Surface nitrate and phosphate concentrations were more than sufficient for a bloom of non-siliceous phytoplankton to occur. Acoustic observations from a high resolution TRIAXUS transect through the eddy documented high zooplankton biomass in the upper 150m. It is hypothesized that a non-diatom bloom was prevented by grazing pressure, but light may have also been an important limiting resource in late summer (April). Two SOCCOM floats that were deployed in the eddy field continued to monitor the physics, nitrate and bio-optics through the transition to winter. These observations across complementary platforms have identified and then explained the reason for these unexpected biological anomalies in an energetic and globally important region of the global ocean. Understanding the role of eddies in this region will be critical to the representation of mesoscale

Decadal-scale thermohaline variability in the Atlantic sector of the Southern Ocean

CSIR Research Space (South Africa)

Hutchinson, K

2016-05-01

Full Text Available . This AGEM has improved accuracy compared to traditional climatologies and other proxy methods. The AGEM for the Atlantic Southern Ocean offers an ideal technique to investigate the thermohaline variability over the past two decades in a key region for water...

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...

History of oceanic front development in the New Zealand sector of the Southern Ocean during the Cenozoic: a synthesis

International Nuclear Information System (INIS)

Nelson, C.S.; Cooke, P.J.

2001-01-01

The New Zealand sector of the Southern Ocean (NZSSO) has opened about the Indian-Pacific spreading ridge throughout the Cenozoic. Today the NZSSO is characterised by broad zonal belts of antarctic (cold), subantarctic (cool), and subtropical (warm) surface-water masses separated by prominent oceanic fronts: the Subtropical Front (STF) c. 43 degrees S, Subantarctic Front (SAF) c. 50 degrees S, and Antarctic Polar Front (AAPF) c. 60 degrees S. Despite a meagre database, the broad pattern of Cenozoic evolution of these fronts is reviewed from the results of Deep Sea Drilling Project-based studies of sediment facies, microfossil assemblages and diversity, and stable isotope records, as well as from evidence in onland New Zealand Cenozoic sequences. Results are depicted schematically on seven paleogeographic maps covering the NZSSO at 10 m.y. intervals through the Cenozoic. During the Paleocene and most of the Eocene (65-35 Ma), the entire NZSSO was under the influence of warm to cool subtropical waters, with no detectable oceanic fronts. In the latest Eocene (c. 35 Ma), a proto-STF is shown separating subantarctic and subtropical waters offshore from Antarctica, near 65 degrees S paleolatitude. During the earliest Oligocene, this front was displaced northwards by development of an AAPF following major global cooling and biotic turnover associated with ice sheet expansion to sea level on East Antarctica. Early Oligocene full opening (c. 31 Ma) of the Tasmanian gateway initiated vigorous proto-circum-Antarctic flow of cold/cool waters, possibly through a West Antarctic seaway linking the southern Pacific and Atlantic Oceans, including detached northwards 'jetting' onto the New Zealand plateau where condensation and unconformity development was widespread in cool-water carbonate facies. Since this time, a broad tripartite division of antarctic, subantarctic, and subtropical waters has existed in the NZSSO, including possible development of a proto-SAF within the

Transport and scavenging of Pu in surface waters of the Southern Hemisphere Oceans

DEFF Research Database (Denmark)

Gastaud, J.; Povinec, P.P.; Aoyama, M.

2011-01-01

The distribution of 239Pu in Atlantic and Indian Ocean waters about four decades after their main injection from atmospheric nuclear weapons tests is discussed. Recent data obtained in the framework of the SHOTS (Southern Hemisphere Ocean Tracer Studies) projects are evaluated and compared...... with previous investigations. Seawater samples were collected during the round the globe BEAGLE2003 (Blue Ocean Global Expedition) along the 30°S transect in the Atlantic and the 20°S transect in the Indian Ocean. The results indicate transport of surface waters labelled with 239Pu from the western North...... Pacific via the Indonesian Seas to the South Indian Ocean and then to the South Atlantic Ocean. Along the whole BEAGLE2003 sampling route, the Atlantic Ocean has the lowest 239Pu content due to its particle scavenging on the long way from the western North Pacific. On the other hand, concentrations...

Actinobacterial community structure in the Polar Frontal waters of the Southern Ocean of the Antarctica using Geographic Information System (GIS: A novel approach to study Ocean Microbiome

Directory of Open Access Journals (Sweden)

P. Sivasankar

2018-04-01

Full Text Available Integration of microbiological data and geographical locations is necessary to understand the spatiotemporal patterns of the microbial diversity of an ecosystem. The Geographic Information System (GIS to map and catalogue the data on the actinobacterial diversity of the Southern Ocean waters was completed through sampling and analysis. Water samples collected at two sampling stations viz. Polar Front 1 (Station 1 and Polar Front 2 (Station 2 during 7th Indian Scientific Expedition to the Indian Ocean Sector of the Southern Ocean (SOE-2012-13 were used for analysis. At the outset, two different genera of Actinobacteria were recorded at both sampling stations. Streptomyces was the dominanted with the high score (> 60%, followed by Nocardiopsis (< 30% at both the sampling stations-Polar Front 1 and Polar Front 2-along with other invasive genera such as Agrococcus, Arthrobacter, Cryobacterium, Curtobacterium, Microbacterium, Marisediminicola, Rhodococcus and Kocuria. This data will help to discriminate the diversity and distribution pattern of the Actinobacteria in the Polar Frontal Region of the Southern Ocean waters. It is a novel approach useful for geospatial cataloguing of microbial diversity from extreme niches and in various environmental gradations. Furthermore, this research work will act as the milestone for bioprospecting of microbial communities and their products having potential applications in healthcare, agriculture and beneficial to mankind. Hence, this research work would have significance in creating a database on microbial communities of the Antarctic ecosystem. Keywords: Antarctica, Marine actinobacteria, Southern ocean, GIS, Polar Frontal waters, Microbiome

Southern Ocean Carbon Dioxide and Oxygen Fluxes Detected by SOCCOM Biogeochemical Profiling Floats

Science.gov (United States)

Sarmiento, J. L.; Bushinksy, S.; Gray, A. R.

2016-12-01

The Southern Ocean is known to play an important role in the global carbon cycle, yet historically our measurements of this remote region have been sparse and heavily biased towards summer. Here we present new estimates of air-sea fluxes of carbon dioxide and oxygen calculated with measurements from autonomous biogeochemical profiling floats. At high latitudes in and southward of the Antarctic Circumpolar Current, we find a significant flux of CO2 from the ocean to the atmosphere during 2014-2016, which is particularly enhanced during winter months. These results suggest that previous estimates may be biased towards stronger Southern Ocean CO2 uptake due to undersampling in winter. We examine various implications of having a source of CO2 that is higher than previous estimates. We also find that CO2:O2 flux ratios north of the Subtropical Front are positive, consistent with the fluxes being driven by changes in solubility, while south of the Polar Front biological processes and upwelling of deep water combine to produce a negative CO2:O2 flux ratio.

Tropical forcing of increased Southern Ocean climate variability revealed by a 140-year subantarctic temperature reconstruction

NARCIS (Netherlands)

Turney, Chris S.M.; Fogwill, Christopher J.; Palmer, Jonathan G.; Van Sebille, Erik; Thomas, Zoë; McGlone, Matt; Richardson, Sarah; Wilmshurst, Janet M.; Fenwick, Pavla; Zunz, Violette; Goosse, Hugues; Wilson, Kerry Jayne; Carter, Lionel; Lipson, Mathew; Jones, Richard T.; Harsch, Melanie; Clark, Graeme; Marzinelli, Ezequiel; Rogers, Tracey; Rainsley, Eleanor; Ciasto, Laura; Waterman, Stephanie; Thomas, Elizabeth R.; Visbeck, Martin

2017-01-01

Occupying about 14% of the world's surface, the Southern Ocean plays a fundamental role in ocean and atmosphere circulation, carbon cycling and Antarctic ice-sheet dynamics. Unfortunately, high interannual variability and a dearth of instrumental observations before the 1950s limits our

Seasonal evolution of the upper-ocean adjacent to the South Orkney Islands, Southern Ocean: Results from a “lazy biological mooring”

Science.gov (United States)

Meredith, Michael P.; Nicholls, Keith W.; Renfrew, Ian A.; Boehme, Lars; Biuw, Martin; Fedak, Mike

2011-07-01

A serendipitous >8-month time series of hydrographic properties was obtained from the vicinity of the South Orkney Islands, Southern Ocean, by tagging a southern elephant seal ( Mirounga leonina) on Signy Island with a Conductivity-Temperature-Depth/Satellite-Relay Data Logger (CTD-SRDL) in March 2007. Such a time series (including data from the austral autumn and winter) would have been extremely difficult to obtain via other means, and it illustrates with unprecedented temporal resolution the seasonal progression of upper-ocean water mass properties and stratification at this location. Sea ice production values of around 0.15-0.4 m month -1 for April to July were inferred from the progression of salinity, with significant levels still in September (around 0.2 m month -1). However, these values presume that advective processes have negligible effect on the salinity changes observed locally; this presumption is seen to be inappropriate in this case, and it is argued that the ice production rates inferred are better considered as "smeared averages" for the region of the northwestern Weddell Sea upstream from the South Orkneys. The impact of such advective effects is illustrated by contrasting the observed hydrographic series with the output of a one-dimensional model of the upper-ocean forced with local fluxes. It is found that the difference in magnitude between local (modelled) and regional (inferred) ice production is significant, with estimates differing by around a factor of two. A halo of markedly low sea ice concentration around the South Orkneys during the austral winter offers at least a partial explanation for this, since it enabled stronger atmosphere/ocean fluxes to persist and hence stronger ice production to prevail locally compared with the upstream region. The year of data collection was an El Niño year, and it is well-established that this phenomenon can impact strongly on the surface ocean and ice field in this sector of the Southern Ocean, thus

Restricted regions of enhanced growth of Antarctic krill in the circumpolar Southern Ocean.

Science.gov (United States)

Murphy, Eugene J; Thorpe, Sally E; Tarling, Geraint A; Watkins, Jonathan L; Fielding, Sophie; Underwood, Philip

2017-07-31

Food webs in high-latitude oceans are dominated by relatively few species. Future ocean and sea-ice changes affecting the distribution of such species will impact the structure and functioning of whole ecosystems. Antarctic krill (Euphausia superba) is a key species in Southern Ocean food webs, but there is little understanding of the factors influencing its success throughout much of the ocean. The capacity of a habitat to maintain growth will be crucial and here we use an empirical relationship of growth rate to assess seasonal spatial variability. Over much of the ocean, potential for growth is limited, with three restricted oceanic regions where seasonal conditions permit high growth rates, and only a few areas around the Scotia Sea and Antarctic Peninsula suitable for growth of the largest krill (>60 mm). Our study demonstrates that projections of impacts of future change need to account for spatial and seasonal variability of key ecological processes within ocean ecosystems.

Effects of whaling on the structure of the Southern Ocean food web: insights on the "krill surplus" from ecosystem modelling.

Directory of Open Access Journals (Sweden)

Szymon Surma

Full Text Available The aim of this study was to examine the ecological plausibility of the "krill surplus" hypothesis and the effects of whaling on the Southern Ocean food web using mass-balance ecosystem modelling. The depletion trajectory and unexploited biomass of each rorqual population in the Antarctic was reconstructed using yearly catch records and a set of species-specific surplus production models. The resulting estimates of the unexploited biomass of Antarctic rorquals were used to construct an Ecopath model of the Southern Ocean food web existing in 1900. The rorqual depletion trajectory was then used in an Ecosim scenario to drive rorqual biomasses and examine the "krill surplus" phenomenon and whaling effects on the food web in the years 1900-2008. An additional suite of Ecosim scenarios reflecting several hypothetical trends in Southern Ocean primary productivity were employed to examine the effect of bottom-up forcing on the documented krill biomass trend. The output of the Ecosim scenarios indicated that while the "krill surplus" hypothesis is a plausible explanation of the biomass trends observed in some penguin and pinniped species in the mid-20th century, the excess krill biomass was most likely eliminated by a rapid decline in primary productivity in the years 1975-1995. Our findings suggest that changes in physical conditions in the Southern Ocean during this time period could have eliminated the ecological effects of rorqual depletion, although the mechanism responsible is currently unknown. Furthermore, a decline in iron bioavailability due to rorqual depletion may have contributed to the rapid decline in overall Southern Ocean productivity during the last quarter of the 20th century. The results of this study underscore the need for further research on historical changes in the roles of top-down and bottom-up forcing in structuring the Southern Ocean food web.

Monsoon-driven variability in the southern Red Sea and the exchange with the Indian Ocean

Science.gov (United States)

Sofianos, S. S.; Papadopoulos, V. P.; Abualnaja, Y.; Nenes, A.; Hoteit, I.

2016-02-01

Although progress has been achieved in describing and understanding the mean state and seasonal cycle of the Red Sea dynamics, their interannual variability is not yet well evaluated and explained. The thermohaline characteristics and the circulation patterns present strong variability at various time scales and are affected by the strong and variable atmospheric forcing and the exchange with the Indian Ocean and the gulfs located at the northern end of the basin. Sea surface temperature time-series, derived from satellite observations, show considerable trends and interannual variations. The spatial variability pattern is very diverse, especially in the north-south direction. The southern part of the Red Sea is significantly influenced by the Indian Monsoon variability that affects the sea surface temperature through the surface fluxes and the circulation patterns. This variability has also a strong impact on the lateral fluxes and the exchange with the Indian Ocean through the strait of Bab el Mandeb. During summer, there is a reversal of the surface flow and an intermediate intrusion of a relatively cold and fresh water mass. This water originates from the Gulf of Aden (the Gulf of Aden Intermediate Water - GAIW), is identified in the southern part of the basin and spreads northward along the eastern Red Sea boundary to approximately 24°N and carried across the Red Sea by basin-size eddies. The GAIW intrusion plays an important role in the heat and freshwater budget of the southern Red Sea, especially in summer, impacting the thermohaline characteristics of the region. It is a permanent feature of the summer exchange flow but it exhibits significant variation from year to year. The intrusion is controlled by a monsoon-driven pressure gradient in the two ends of the strait and thus monsoon interannual variability can laterally impose its signal to the southern Red Sea thermohaline patterns.

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 (>...

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 (>...

Ecological biogeography of southern ocean islands: species-area relationships, human impacts, and conservation

NARCIS (Netherlands)

Chown, S.L.; Gremmen, N.J.M.; Gaston, K.J.

1998-01-01

Previous studies have concluded that southern ocean islands are anomalous because past glacial extent and current temperature apparently explain most variance in their species richness. Here, the relationships between physical variables and species richness of vascular plants, insects, land and

Surface water iron supplies in the Southern Ocean sustained by deep winter mixing

CSIR Research Space (South Africa)

Tagliabue, A

2014-04-01

Full Text Available Low levels of iron limit primary productivity across much of the Southern Ocean. At the basin scale, most dissolved iron is supplied to surfacewaters from subsurface reservoirs, because land inputs are spatially limited. Deep mixing in winter...

Changes in the C, N, and P cycles by the predicted salps-krill shift in the southern ocean

DEFF Research Database (Denmark)

Alcaraz, Miquel; Almeda, Rodrigo; Duarte, Carlos M.

2014-01-01

zooplankton biomass and their metabolic rates, each metabolic process showing a particular response that lead to different metabolic N:P ratios. The predicted change from krill to salps in the Southern Ocean would encompass not only the substitution of a pivotal group for Antarctic food webs (krill) by one...... and proportion of N and P in the nutrient pool, inducing quantitative and qualitative changes on primary producers that will translate to the whole Southern Ocean ecosystem....

A Roadmap for Antarctic and Southern Ocean Science for the Next Two Decades and Beyond

Science.gov (United States)

Kennicutt, M. C., II

2015-12-01

Abstract: Antarctic and Southern Ocean science is vital to understanding natural variability, the processes that govern global change and the role of humans in the Earth and climate system. The potential for new knowledge to be gained from future Antarctic science is substantial. Therefore, the international Antarctic community came together to 'scan the horizon' to identify the highest priority scientific questions that researchers should aspire to answer in the next two decades and beyond. Wide consultation was a fundamental principle for the development of a collective, international view of the most important future directions in Antarctic science. From the many possibilities, the horizon scan identified 80 key scientific questions through structured debate, discussion, revision and voting. Questions were clustered into seven topics: i) Antarctic atmosphere and global connections, ii) Southern Ocean and sea ice in a warming world, iii) ice sheet and sea level, iv) the dynamic Earth, v) life on the precipice, vi) near-Earth space and beyond, and vii) human presence in Antarctica. Answering the questions identified by the horizon scan will require innovative experimental designs, novel applications of technology, invention of next-generation field and laboratory approaches, and expanded observing systems and networks. Unbiased, non-contaminating procedures will be required to retrieve the requisite air, biota, sediment, rock, ice and water samples. Sustained year-round access to Antarctica and the Southern Ocean will be essential to increase winter-time measurements. Improved models are needed that represent Antarctica and the Southern Ocean in the Earth System, and provide predictions at spatial and temporal resolutions useful for decision making. A co-ordinated portfolio of cross-disciplinary science, based on new models of international collaboration, will be essential as no scientist, programme or nation can realize these aspirations alone.

Biogeneration of chromophoric dissolved organic matter by bacteria and krill in the southern ocean

OpenAIRE

Ortega-Retuerta, E.; Frazer, Thomas K.; Duarte, Carlos M.; Ruiz-Halpern, Sergio; Tovar-Sánchez, Antonio; Arrieta López de Uralde, Jesús M.; Reche, Isabel

2009-01-01

Chromophoric dissolved organic matter (CDOM), the optically active fraction of dissolved organic matter, is primarily generated by pelagic organisms in the open ocean. In this study, we experimentally determined the quantity and spectral quality of CDOM generated by bacterioplankton using two different substrates (with and without photoproducts) and by Antarctic krill Euphausia superba and evaluated their potential contributions to CDOM dynamics in the peninsular region of the Southern Ocean....

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...... stations. Secondary production was low (carbon specific egg production o0.14 d1) but typical for food limited oligotrophic oceans...

First insights into the biodiversity and biogeography of the Southern Ocean deep sea

NARCIS (Netherlands)

Brandt, A.; Gooday, A.J.; Brandao, S.N.; Mesel, de I.G.

2007-01-01

Shallow marine benthic communities around Antarctica show high levels of endemism, gigantism, slow growth, longevity and late maturity, as well as adaptive radiations that have generated considerable biodiversity in some taxa. The deeper parts of the Southern Ocean exhibit some unique environmental

Near-surface eddy dynamics in the Southern Ocean

Directory of Open Access Journals (Sweden)

Marilisa Trani

2011-12-01

Full Text Available The Antarctic Circumpolar Current (ACC is a crucial component of the global ocean conveyor belt, acting as a zonal link among the major ocean basins but, to some extent, limiting meridional exchange and tending to isolate the ocean south of it from momentum and heat income. In this work we investigate one of the most important mechanisms contributing to the poleward transfer of properties in the Southern Ocean, that is the eddy component of the dynamics. For this particular purpose, observations obtained from near-surface drifters have been used: they represent a very useful data set to analyse the eddy field because of their ability to catch a large number of scales of motion while providing a quasi-synoptic coverage of the investigated area. Estimates of the eddy heat and momentum fluxes are carried out using data taken from the Global Drifter Program databank; they refer to Surface Velocity Program drifter trajectories collected in the area south of 35°S between 1995 and 2006. Eddy kinetic energies, variance ellipses, momentum and heat fluxes have been calculated using the pseudo-Eulerian method, showing patterns in good agreement with those present in the literature based on observational and model data, although there are some quantitative differences. The eddy fluxes have been separated into their rotational and divergent portions, the latter being responsible for the meridional transports. The associated zonal and depth-exponentially integrated meridional heat transport exhibits values spanning over a range between -0.4 PW and –1.1 PW in the ACC region, consistent with previous estimates.

Pleistocene atmospheric CO2 change linked to Southern Ocean nutrient utilization

Science.gov (United States)

Ziegler, M.; Diz, P.; Hall, I. R.; Zahn, R.

2011-12-01

Biological uptake of CO2 by the ocean and its subsequent storage in the abyss is intimately linked with the global carbon cycle and constitutes a significant climatic force1. The Southern Ocean is a particularly important region because its wind-driven upwelling regime brings CO2 laden abyssal waters to the surface that exchange CO2 with the atmosphere. The Subantarctic Zone (SAZ) is a CO2 sink and also drives global primary productivity as unutilized nutrients, advected with surface waters from the south, are exported via Subantarctic Mode Water (SAMW) as preformed nutrients to the low latitudes where they fuel the biological pump in upwelling areas. Recent model estimates suggest that up to 40 ppm of the total 100 ppm atmospheric pCO2 reduction during the last ice age were driven by increased nutrient utilization in the SAZ and associated feedbacks on the deep ocean alkalinity. Micro-nutrient fertilization by iron (Fe), contained in the airborne dust flux to the SAZ, is considered to be the prime factor that stimulated this elevated photosynthetic activity thus enhancing nutrient utilization. We present a millennial-scale record of the vertical stable carbon isotope gradient between subsurface and deep water (Δδ13C) in the SAZ spanning the past 350,000 years. The Δδ13C gradient, derived from planktonic and benthic foraminifera, reflects the efficiency of biological pump and is highly correlated (rxy = -0.67 with 95% confidence interval [0.63; 0.71], n=874) with the record of dust flux preserved in Antarctic ice cores6. This strongly suggests that nutrient utilization in the SAZ was dynamically coupled to dust-induced Fe fertilization across both glacial-interglacial and faster millennial timescales. In concert with ventilation changes of the deep Southern Ocean this drove ocean-atmosphere CO2 exchange and, ultimately, atmospheric pCO2 variability during the late Pleistocene.

Temperature, salinity profiles and associated data collected in the Southern Oceans in support of the Global Ocean Ecosystem Dynamics project, 2001-04 to 2001-08 (NODC Accession 0001097)

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — The overall goal of the U.S. Southern Ocean GLOBEC program is to elucidate circulation processes and their effect on sea ice formation and Antarctic krill (Euphausia...

Long range transport of hydrocarbons in the Southern Ocean

International Nuclear Information System (INIS)

Pinturier, L.; Leureillard, J.; Arnold, M.; Tisnerat, N.; Pichon, J.J.; Gireaudau, J.

1999-01-01

We report here the first results for hydrocarbon analyses of deep surface sediments collected in the Indian sector of the Southern Ocean. The samples were taken along a north-south transect ranging from 43 deg. S to 55 deg. S in the southwestern Crozet Basin. In order to identify these compounds and elucidate their origins, various techniques were used: gas chromatography and gas chromatography coupled with mass spectrometry; Accelerator Mass Spectrometry (Tandetron: mass spectrometer coupled with a Tandem accelerator allowing the measure of 14 C/ 12 C ratio)

Meridional distribution and seasonal variation of stable oxygen isotope ratio of precipitation in the Southern Ocean

Directory of Open Access Journals (Sweden)

Kayo Nakamura

2010-07-01

Full Text Available The stable oxygen isotope ratio(δ^O in precipitation is known to have important meridional and seasonal variations, but there are almost no measurements of δ^O in precipitation over polar oceans. The present research took advantage of 4 opportunities for in situ observations in summer and winter at high latitudes in the Southern Ocean. In addition, we analyzed samples of precipitation at Syowa Station in 2008 to obtain year-round data. Based on these data, we consider the meridional and seasonal variations of δ^O in precipitation over the Southern Ocean. In general, δ^O decreases with increasing latitude, and is lower in winter than in summer. The latitude gradient is stronger in winter. At 60°S, δ^O is -5.4‰ and -11.3‰ in summer and winter, respectively, while the corresponding figures at 66°S are -10.5‰ and -20.8‰. These results will help us understand the mechanisms of the salinity distribution and its variation in the Antarctic Ocean.

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.

Lithospheric structure of southern Indian shield and adjoining oceans: integrated modelling of topography, gravity, geoid and heat flow data

Science.gov (United States)

Kumar, Niraj; Zeyen, H.; Singh, A. P.; Singh, B.

2013-07-01

For the present 2-D lithospheric density modelling, we selected three geotransects of more than 1000 km in length each crossing the southern Indian shield, south of 16°N, in N-S and E-W directions. The model is based on the assumption of local isostatic equilibrium and is constrained by the topography, gravity and geoid anomalies, by geothermal data, and where available by seismic data. Our integrated modelling approach reveals a crustal configuration with the Moho depth varying from ˜40 km beneath the Dharwar Craton, and ˜39 km beneath the Southern Granulite Terrane to about 15-20 km beneath the adjoining oceans. The lithospheric thickness varies significantly along the three profiles from ˜70-100 km under the adjoining oceans to ˜130-135 km under the southern block of Southern Granulite Terrane including Sri Lanka and increasing gradually to ˜165-180 km beneath the northern block of Southern Granulite Terrane and the Dharwar Craton. This step-like lithosphere-asthenosphere boundary (LAB) structure indicates a normal lithospheric thickness beneath the adjoining oceans, the northern block of Southern Granulite Terrane and the Dharwar Craton. The thin lithosphere below the southern block of Southern Granulite Terrane including Sri Lanka is, however, atypical considering its age. Our results suggest that the southern Indian shield as a whole cannot be supported isostatically only by thickened crust; a thin and hot lithosphere beneath the southern block of Southern Granulite Terrane including Sri Lanka is required to explain the high topography, gravity, geoid and crustal temperatures. The widespread thermal perturbation during Pan-African (550 Ma) metamorphism and the breakup of Gondwana during late Cretaceous are proposed as twin cause mechanism for the stretching and/or convective removal of the lower part of lithospheric mantle and its replacement by hotter and lighter asthenosphere in the southern block of Southern Granulite Terrane including Sri Lanka

The role of diatom resting spores in pelagic-benthic coupling in the Southern Ocean

Science.gov (United States)

Rembauville, Mathieu; Blain, Stéphane; Manno, Clara; Tarling, Geraint; Thompson, Anu; Wolff, George; Salter, Ian

2018-05-01

Natural iron fertilization downstream of Southern Ocean island plateaus supports large phytoplankton blooms and promotes carbon export from the mixed layer. In addition to sequestering atmospheric CO2, the biological carbon pump also supplies organic matter (OM) to deep-ocean ecosystems. Although the total flux of OM arriving at the seafloor sets the energy input to the system, the chemical nature of OM is also of significance. However, a quantitative framework linking ecological flux vectors to OM composition is currently lacking. In the present study we report the lipid composition of export fluxes collected by five moored sediment traps deployed in contrasting productivity regimes of Southern Ocean island systems (Kerguelen, Crozet and South Georgia) and compile them with quantitative data on diatom and faecal pellet fluxes. At the three naturally iron-fertilized sites, the relative contribution of labile lipids (mono- and polyunsaturated fatty acids, unsaturated fatty alcohols) is 2-4 times higher than at low productivity sites. There is a strong attenuation of labile components as a function of depth, irrespective of productivity. The three island systems also display regional characteristics in lipid export. An enrichment of zooplankton dietary sterols, such as C27Δ5, at South Georgia is consistent with high zooplankton and krill biomass in the region and the importance of faecal pellets to particulate organic carbon (POC) flux. There is a strong association of diatom resting spore fluxes that dominate productive flux regimes with energy-rich unsaturated fatty acids. At the Kerguelen Plateau we provide a statistical framework to link seasonal variation in ecological flux vectors and lipid composition over a complete annual cycle. Our analyses demonstrate that ecological processes in the upper ocean, e.g. resting spore formation and grazing, not only impact the magnitude and stoichiometry of the Southern Ocean biological pump, but also regulate the

Cloud amount/frequency, SALINITY and other data from ORION, FUJI II and other platforms in the Southern Oceans, Indian Ocean and other waters from 1950-01-04 to 1989-03-16 (NODC Accession 9200239)

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — The Ocean Serial data in this accession was collected in Southern Oceans (> 60 degrees South) as part of Global Ocean Data Archeaology and Rescue (GODAR) project...

Bacterial community dynamics during polysaccharide degradation at contrasting sites in the Southern and Atlantic Oceans.

Science.gov (United States)

Wietz, Matthias; Wemheuer, Bernd; Simon, Heike; Giebel, Helge-Ansgar; Seibt, Maren A; Daniel, Rolf; Brinkhoff, Thorsten; Simon, Meinhard

2015-10-01

The bacterial degradation of polysaccharides is central to marine carbon cycling, but little is known about the bacterial taxa that degrade specific marine polysaccharides. Here, bacterial growth and community dynamics were studied during the degradation of the polysaccharides chitin, alginate and agarose in microcosm experiments at four contrasting locations in the Southern and Atlantic Oceans. At the Southern polar front, chitin-supplemented microcosms were characterized by higher fractions of actively growing cells and a community shift from Alphaproteobacteria to Gammaproteobacteria and Bacteroidetes. At the Antarctic ice shelf, chitin degradation was associated with growth of Bacteroidetes, with 24% higher cell numbers compared with the control. At the Patagonian continental shelf, alginate and agarose degradation covaried with growth of different Alteromonadaceae populations, each with specific temporal growth patterns. At the Mauritanian upwelling, only the alginate hydrolysis product guluronate was consumed, coincident with increasing abundances of Alteromonadaceae and possibly cross-feeding SAR11. 16S rRNA gene amplicon libraries indicated that growth of the Bacteroidetes-affiliated genus Reichenbachiella was stimulated by chitin at all cold and temperate water stations, suggesting comparable ecological roles over wide geographical scales. Overall, the predominance of location-specific patterns showed that bacterial communities from contrasting oceanic biomes have members with different potentials to hydrolyse polysaccharides. © 2015 Society for Applied Microbiology and John Wiley & Sons Ltd.

Physical and chemical data collected from bottle casts in the Pacific Ocean and the Southern Oceans from ALBA and other platforms from 18 November 1962 to 04 May 1990 (NODC Accession 0000413)

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — Physical and chemical data were collected using bottle casts in the Pacific Ocean and the Southern Oceans from ALBA, LIRA, TAMGA and other platforms from 18 November...

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...

Dissolved inorganic carbon, alkalinity, temperature, salinity and other variables collected from discrete sample and profile observations using Alkalinity titrator, CTD and other instruments from POLARSTERN in the South Atlantic Ocean, South Pacific Ocean and Southern Oceans from 2010-11-28 to 2011-02-05 (NODC Accession 0108155)

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — NCEI Accession 0108155 includes discrete sample and profile data collected from POLARSTERN in the South Atlantic Ocean, South Pacific Ocean and Southern Oceans (>...

An assessment of the role of the k-e vertical mixing scheme in the simulation of Southern Ocean upper dynamics

CSIR Research Space (South Africa)

Boodhraj, K

2016-11-01

Full Text Available Following the work done by Reffrey, Calone and Bourdalle-Badie (2015) we implemented a one dimensional (1D) ocean physical model in the sub-Antarctic Southern Ocean using the Nucleus for the European Modelling of the Ocean(NEMO) model. The 1D model...

PCDDs, PCDFs, and coplanar PCBs in albatross from the North Pacific and Southern Oceans: levels, patterns, and toxicological implications.

Science.gov (United States)

Tanabe, Shinsuke; Watanabe, Mafumi; Minh, Tu Binh; Kunisue, Tatsuya; Nakanishi, Shigeyuki; Ono, Hitoshi; Tanaka, Hiroyuki

2004-01-15

Concentrations of polychlorinated dibenzo-p-dioxins (PCDDs), polychlorinated dibenzofurans (PCDFs), and coplanar polychlorinated biphenyls (coplanar PCBs) were determined in five albatross species collected from the North Pacific and Southern Oceans to assess the north-south differences in residue levels, accumulation patterns, and toxic potential. Black-footed and Laysan albatrosses from the North Pacific Ocean contained higher levels of PCDD/Fs and coplanar PCBs than albatrosses from the Southern Ocean, indicating that emission sources of these contaminants were predominant in the northern hemisphere. Residue levels in albatrosses from the remote North Pacific Ocean far from the point source of pollution were comparable to or higher than those in terrestrial and coastal birds from contaminated areas in developed nations, suggesting the specific exposure and accumulation of PCDD/Fs and coplanar PCBs in albatross. The long life span and ingestion of plastic resin pellets by albatrosses could be the plausible explanations for the elevated accumulation of persistent and lipophilic contaminants including PCDD/Fs and coplanar PCBs in these birds. Relative proportions of PCDFs and coplanar PCBs in albatross were higher than those observed in birds inhabiting terrestrial and coastal areas, suggesting that these toxic chemicals may have higher transportability by air and water than PCDDs. Congener patterns of PCDD/Fs in albatross showed less variability as compared to those in terrestrial species, indicating that contamination patterns of PCDD/Fs were similar within the open ocean environment. Contributions of PCDD/Fs to total TEQs in albatrosses from the open ocean were generally lower than those in terrestrial birds, suggesting different toxic potency of PCDD/Fs and coplanar PCBs on animals inhabiting open ocean and terrestrial environment. Whereas albatrosses from southern oceans retained lower TEQ concentrations, possible adverse effects of PCDD/Fs and coplanar PCBs

A Two-Timescale Response of the Southern Ocean to Ozone Depletion: Importance of the Background State

Science.gov (United States)

Seviour, W.; Waugh, D.; Gnanadesikan, A.

2016-02-01

It has been recently suggested that the response of Southern Ocean sea-ice extent to stratospheric ozone depletion is time-dependent; that the ocean surface initially cools due to enhanced northward Ekman drift caused by a poleward shift in the eddy-driven jet, and then warms after some time due to upwelling of warm waters from below the mixed layer. It is therefore possible that ozone depletion could act to favor a short-term increase in sea-ice extent. However, many uncertainties remain in understanding this mechanism, with different models showing widely differing time-scales and magnitudes of the response. Here, we analyze an ensemble of coupled model simulations with a step-function ozone perturbation. The two-timescale response is present with an approximately 30 year initial cooling period. The response is further shown to be highly dependent upon the background ocean temperature and salinity stratification, which is influenced by both natural internal variability and the isopycnal eddy mixing parameterization. It is suggested that the majority of inter-model differences in the Southern Ocean response to ozone depletion are caused by differences in stratification.

Oceanic control of Northeast Pacific hurricane activity at interannual timescales

International Nuclear Information System (INIS)

Balaguru, Karthik; Ruby Leung, L; Yoon, Jin-ho

2013-01-01

Sea surface temperature (SST) is not the only oceanic parameter that can play a key role in the interannual variability of Northeast Pacific hurricane activity. Using several observational data sets and the statistical technique of multiple linear regression analysis, we show that, along with SST, the thermocline depth (TD) plays an important role in hurricane activity at interannual timescales in this basin. Based on the parameter that dominates, the ocean basin can be divided into two sub-regions. In the Southern sub-region, which includes the hurricane main development area, interannual variability of the upper-ocean heat content (OHC) is primarily controlled by TD variations. Consequently, the interannual variability in the hurricane power dissipation index (PDI), which is a measure of the intensity of hurricane activity, is driven by that of the TD. On the other hand, in the Northern sub-region, SST exerts the major control over the OHC variability and, in turn, the PDI. Our study suggests that both SST and TD have a significant influence on the Northeast Pacific hurricane activity at interannual timescales and that their respective roles are more clearly delineated when sub-regions along an approximate north–south demarcation are considered rather than the basin as a whole. (letter)

Antarctic lakes suggest millennial reorganizations of Southern Hemisphere atmospheric and oceanic circulation.

Science.gov (United States)

Hall, Brenda L; Denton, George H; Fountain, Andrew G; Hendy, Chris H; Henderson, Gideon M

2010-12-14

The phasing of millennial-scale oscillations in Antarctica relative to those elsewhere in the world is important for discriminating among models for abrupt climate change, particularly those involving the Southern Ocean. However, records of millennial-scale variability from Antarctica dating to the last glacial maximum are rare and rely heavily on data from widely spaced ice cores, some of which show little variability through that time. Here, we present new data from closed-basin lakes in the Dry Valleys region of East Antarctica that show high-magnitude, high-frequency oscillations in surface level during the late Pleistocene synchronous with climate fluctuations elsewhere in the Southern Hemisphere. These data suggest a coherent Southern Hemisphere pattern of climate change on millennial time scales, at least in the Pacific sector, and indicate that any hypothesis concerning the origin of these events must account for synchronous changes in both high and temperate latitudes.

High Biomass Low Export Regimes in the Southern Ocean

Energy Technology Data Exchange (ETDEWEB)

Lam, Phoebe J.; Bishop, James K.B.

2006-01-27

This paper investigates ballasting and remineralization controls of carbon sedimentation in the twilight zone (100-1000 m) of the Southern Ocean. Size-fractionated (<1 {micro}m, 1-51 {micro}m, >51 {micro}m) suspended particulate matter was collected by large volume in-situ filtration from the upper 1000 m in the Subantarctic (55 S, 172 W) and Antarctic (66 S, 172 W) zones of the Southern Ocean during the Southern Ocean Iron Experiment (SOFeX) in January-February 2002. Particles were analyzed for major chemical constituents (POC, P, biogenic Si, CaCO3), and digital and SEM image analyses of particles were used to aid in the interpretation of the chemical profiles. Twilight zone waters at 66 S in the Antarctic had a steeper decrease in POC with depth than at 55 S in the Subantarctic, with lower POC concentrations in all size fractions at 66 S than at 55 S, despite up to an order of magnitude higher POC in surface waters at 66 S. The decay length scale of >51 {micro}m POC was significantly shorter in the upper twilight zone at 66 S ({delta}{sub e}=26 m) compared to 55 S ({delta}{sub e}=81 m). Particles in the carbonate-producing 55 S did not have higher excess densities than particles from the diatom-dominated 66 S, indicating that there was no direct ballast effect that accounted for deeper POC penetration at 55 S. An indirect ballast effect due to differences in particle packaging and porosities cannot be ruled out, however, as aggregate porosities were high ({approx}97%) and variable. Image analyses point to the importance of particle loss rates from zooplankton grazing and remineralization as determining factors for the difference in twilight zone POC concentrations at 55 S and 66 S, with stronger and more focused shallow remineralization at 66 S. At 66 S, an abundance of large (several mm long) fecal pellets from the surface to 150 m, and almost total removal of large aggregates by 200 m, reflected the actions of a single or few zooplankton species capable of

Iron stress in the Pacific region of the Southern Ocean : evidence from enrichment bioassays

NARCIS (Netherlands)

Timmermans, Klaas; van Leeuwe, M.A.; de Jong, J.T.M.; Nolting, R.F.; Witte, H.J; van Ooyen, J; Swagerman, M.J W; Kloosterhuis, H; de Baar, H.J.W.

1998-01-01

The effect of iron on phytoplankton physiology in a scarcely investigated part of the Pacific region of the Southern Ocean was studied during an expedition aboard RV 'Polarstern'. Physiological effects of iron enrichments were studied during short-term bottle experiments (72 h) in high-nutrient,

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...

The biogeochemical role of baleen whales and krill in Southern Ocean nutrient cycling.

Directory of Open Access Journals (Sweden)

Lavenia Ratnarajah

Full Text Available The availability of micronutrients is a key factor that affects primary productivity in High Nutrient Low Chlorophyll (HNLC regions of the Southern Ocean. Nutrient supply is governed by a range of physical, chemical and biological processes, and there are significant feedbacks within the ecosystem. It has been suggested that baleen whales form a crucial part of biogeochemical cycling processes through the consumption of nutrient-rich krill and subsequent defecation, but data on their contribution are scarce. We analysed the concentration of iron, cadmium, manganese, cobalt, copper, zinc, phosphorus and carbon in baleen whale faeces and muscle, and krill tissue using inductively coupled plasma mass spectrometry. Metal concentrations in krill tissue were between 20 thousand and 4.8 million times higher than typical Southern Ocean HNLC seawater concentrations, while whale faecal matter was between 276 thousand and 10 million times higher. These findings suggest that krill act as a mechanism for concentrating and retaining elements in the surface layer, which are subsequently released back into the ocean, once eaten by whales, through defecation. Trace metal to carbon ratios were also higher in whale faeces compared to whale muscle indicating that whales are concentrating carbon and actively defecating trace elements. Consequently, recovery of the great whales may facilitate the recycling of nutrients via defecation, which may affect productivity in HNLC areas.

Water masses as a unifying framework for understanding the Southern Ocean Carbon Cycle

Directory of Open Access Journals (Sweden)

D. Iudicone

2011-05-01

Full Text Available The scientific motivation for this study is to understand the processes in the ocean interior controlling carbon transfer across 30° S. To address this, we have developed a unified framework for understanding the interplay between physical drivers such as buoyancy fluxes and ocean mixing, and carbon-specific processes such as biology, gas exchange and carbon mixing. Given the importance of density in determining the ocean interior structure and circulation, the framework is one that is organized by density and water masses, and it makes combined use of Eulerian and Lagrangian diagnostics. This is achieved through application to a global ice-ocean circulation model and an ocean biogeochemistry model, with both components being part of the widely-used IPSL coupled ocean/atmosphere/carbon cycle model.

Our main new result is the dominance of the overturning circulation (identified by water masses in setting the vertical distribution of carbon transport from the Southern Ocean towards the global ocean. A net contrast emerges between the role of Subantarctic Mode Water (SAMW, associated with large northward transport and ingassing, and Antarctic Intermediate Water (AAIW, associated with a much smaller export and outgassing. The differences in their export rate reflects differences in their water mass formation processes. For SAMW, two-thirds of the surface waters are provided as a result of the densification of thermocline water (TW, and upon densification this water carries with it a substantial diapycnal flux of dissolved inorganic carbon (DIC. For AAIW, principal formatin processes include buoyancy forcing and mixing, with these serving to lighten CDW. An additional important formation pathway of AAIW is through the effect of interior processing (mixing, including cabelling that serve to densify SAMW.

A quantitative evaluation of the contribution of mixing, biology and gas exchange to the DIC evolution per water mass reveals that

Hydrothermal and Chemosynthetic Ecosystems in the Southern Ocean: Current Knowledge on their Biology Paper 217790

Science.gov (United States)

Linse, K.; Rogers, A. D.; Bohrmann, G.; Copley, J.; Tyler, P. A.

2017-12-01

The existence of hydrothermal and other chemosynthetic ecosystems is not surprising in the Antarctic, with its active volcanoes, mid-ocean ridges and back-arc basins, and abundance of marine mammals. In the last two decades a variety of active chemosynthetic ecosystems have been discovered in the Southern Ocean, including low- and high-temperature hydrothermal vents, methane seeps, and whalefalls. Here a summary of the data from the known chemosynthetic communites will be presented, comparing the faunas of vent sites in the Bransfield Strait with those of the East Scotia Ridge (ESR) and the South Sandwich Arc, assessing the fauna at the South Georgia methane seep sites, and discussing the fauna on Antarctic whale falls. As the faunal assemblages of the ESR vents are the most studied in detail to date, this talk therefore focusses on the diversity and composition of the ESR macrofaunal assemblages, their foodweb structure and microdistributions in relation to fluid chemistry and microbiology, and their phylogenetic and biogeographic relationships. The Southern Ocean drives the global ocean conveyor belt, and is suggested to be the centre of origin for global deep-sea fauna, as well as a region of high deep-sea species diversity. In the context of chemosynthetic environments, it may provide a gateway connecting the global vent and seep systems. The mostly endemic species of Southern Ocean vent macrofauna show links to either one or more oceans (Atlantic, Indian, and Pacific), with some evidence for circum-Antarctic connection. The ESR species Gigantopelta chessoia, Kiwa tyleri and Vulcanolepas scotiaensis have their closest known relatives at the Longqi Vent Field on the Southwest Indian Ridge (SWIR), and one species of polynoid polychaete is known from ESR and SWIR vents. Meanwhile, Lepetdrilus sp. and a vesiocomyid clam are linked with species in the Atlantic vent fields. The stichasterid Paulasterias tyleri, the polychaete Rarricirrus jennae and the anthozoan

The discovery of new deep-sea hydrothermal vent communities in the southern ocean and implications for biogeography.

Directory of Open Access Journals (Sweden)

Alex D Rogers

2012-01-01

Full Text Available Since the first discovery of deep-sea hydrothermal vents along the Galápagos Rift in 1977, numerous vent sites and endemic faunal assemblages have been found along mid-ocean ridges and back-arc basins at low to mid latitudes. These discoveries have suggested the existence of separate biogeographic provinces in the Atlantic and the North West Pacific, the existence of a province including the South West Pacific and Indian Ocean, and a separation of the North East Pacific, North East Pacific Rise, and South East Pacific Rise. The Southern Ocean is known to be a region of high deep-sea species diversity and centre of origin for the global deep-sea fauna. It has also been proposed as a gateway connecting hydrothermal vents in different oceans but is little explored because of extreme conditions. Since 2009 we have explored two segments of the East Scotia Ridge (ESR in the Southern Ocean using a remotely operated vehicle. In each segment we located deep-sea hydrothermal vents hosting high-temperature black smokers up to 382.8°C and diffuse venting. The chemosynthetic ecosystems hosted by these vents are dominated by a new yeti crab (Kiwa n. sp., stalked barnacles, limpets, peltospiroid gastropods, anemones, and a predatory sea star. Taxa abundant in vent ecosystems in other oceans, including polychaete worms (Siboglinidae, bathymodiolid mussels, and alvinocaridid shrimps, are absent from the ESR vents. These groups, except the Siboglinidae, possess planktotrophic larvae, rare in Antarctic marine invertebrates, suggesting that the environmental conditions of the Southern Ocean may act as a dispersal filter for vent taxa. Evidence from the distinctive fauna, the unique community structure, and multivariate analyses suggest that the Antarctic vent ecosystems represent a new vent biogeographic province. However, multivariate analyses of species present at the ESR and at other deep-sea hydrothermal vents globally indicate that vent biogeography is more

Passive tracers in a general circulation model of the Southern Ocean

Directory of Open Access Journals (Sweden)

I. G. Stevens

Full Text Available Passive tracers are used in an off-line version of the United Kingdom Fine Resolution Antarctic Model (FRAM to highlight features of the circulation and provide information on the inter-ocean exchange of water masses. The use of passive tracers allows a picture to be built up of the deep circulation which is not readily apparent from examination of the velocity or density fields. Comparison of observations with FRAM results gives good agreement for many features of the Southern Ocean circulation. Tracer distributions are consistent with the concept of a global "conveyor belt" with a return path via the Agulhas retroflection region for the replenishment of North Atlantic Deep Water.

Key words. Oceanography: general (numerical modeling; water masses · Oceanography: physical (general circulation

The 2010 Southern California Ocean Bottom Seismometer Deployment

Science.gov (United States)

Booth, C. M.; Kohler, M. D.; Weeraratne, D. S.

2010-12-01

Subduction, mid-ocean ridge spreading, and transpressional deformation are all processes that played important roles in the evolution of the diffuse Pacific-North America plate boundary offshore Southern California. Existing seismic data for the boundary typically end at the coastline due to the fact that onshore data collection is easier and more feasible. As a result, current models for plate boundary deformation and mantle flow lack data from nearly half the plate boundary offshore. In August 2010, twenty-four broadband and ten short period ocean bottom seismometers (OBS) were deployed on a research cruise as part of a year-long passive OBS experiment off the coast of Southern California. The Asthenospheric and Lithospheric Broadband Architecture from the California Offshore Region Experiment (ALBACORE) will study local seismicity, and crustal and upper mantle seismic structure. Studies using onshore data have shown a high velocity anomaly that exists in the region of convergence under the Transverse Ranges. The Transverse Ranges belong to a large crustal block that experienced clockwise rotation of at least ninety degrees. Geologic studies indicate that the entire Channel Islands on the western end belongs to the region of convergence and have been a part of this rotation. In anticipation of OBS data analysis, a hypothetical velocity model is being developed for the crust and uppermost mantle for the region under the Channel Islands. P-wave arrival times are predicted by propagating teleseismic waves through the model. Different possible P-wave arrival patterns are explored by varying the lithospheric thickness. The long-term goal for developing this model will be to compare it with the actual OBS travel-time residual data to assess the best-fitting model. In preparation for the ALBACORE cruise, existing gravity data near the Channel Island region were examined for correlations with geologic features. Gravity data collected during the ALBACORE cruise will help

Volcanism, Iron, and Phytoplankton in the Heard and McDonald Islands Region, Southern Indian Ocean

Science.gov (United States)

Coffin, M. F.; Arculus, R. J.; Bowie, A. R.; Chase, Z.; Robertson, R.; Trull, T. W.; Heobi in2016 v01 Shipboard Party, T.

2016-12-01

Phytoplankton supply approximately half of the oxygen in Earth's atmosphere, and iron supply limits the growth of phytoplankton in the anemic Southern Ocean. Situated entirely within the Indian Ocean sector of the Southern Ocean are Australia's only active subaerial volcanoes, Heard and McDonald islands (HIMI) on the central Kerguelen Plateau, a large igneous province. Widespread fields of submarine volcanoes, some of which may be active, extend for distances of up to several hundred kilometers from the islands. The predominantly eastward-flowing Antarctic Circumpolar Current sweeps across the central Kerguelen Plateau, and extensive blooms of phytoplankton are observed on the Plateau down-current of HIMI. The goal of RV Investigator voyage IN2016_V01, conducted in January/February 2016, is to test the hypothesis that hydrothermal fluids, which cool active submarine volcanoes in the HIMI region, ascend from the seafloor and fertilise surface waters with iron, thereby enhancing biological productivity beginning with phytoplankton. Significant initial shipboard results include: Documentation, for the first time, of the role of active HIMI and nearby submarine volcanoes in supplying iron to the Southern Ocean. Nearshore waters had elevated dissolved iron levels. Although biomass was not correspondingly elevated, fluorescence induction data indicated highly productive resident phytoplankton. Discovery of >200 acoustic plumes emanating from the seafloor and ascending up to tens of meters into the water column near HIMI. Deep tow camera footage shows bubbles rising from the seafloor in an acoustic plume field north of Heard Island. Mapping 1,000 km2 of uncharted seafloor around HIMI. Submarine volcanic edifices punctuate the adjacent seafloor, and yielded iron-rich rocks similar to those found on HIMI, respectively. Acoustic plumes emanating from some of these features suggest active seafloor hydrothermal systems.

Present and Past Impact of Glacially Sourced Dust on Iron Fertilization of the Southern Ocean

Science.gov (United States)

Shoenfelt, E. M.; Winckler, G.; Kaplan, M. R.; Sambrotto, R.; Bostick, B. C.

2016-12-01

An increase in iron-containing dust flux and a more efficient biological pump in the Southern Ocean have been associated with the CO2 drawdown and global cooling of the Last Glacial Maximum (LGM). While iron (Fe) mineralogy is known to affect Fe bioavailability through its impact on Fe solubility, there are limited studies investigating the importance of Fe mineralogy in dust fluxes to the Southern Ocean, and no previous studies investigating interactions between eukaryotic phytoplankton and particulate-phase Fe in natural dusts applicable to Southern Ocean environments. Since physically weathered bedrock becomes less soluble as it becomes weathered and oxidized, we hypothesized that glacially sourced dusts would contain more Fe(II)-rich primary minerals and would be more bioavailable than dusts from areas not impacted by glaciers. We used a series of natural dusts from Patagonia as the sole Fe source in incubation experiments with the model diatom Phaeodactylum tricornutum, and evaluated Fe bioavailability using culture growth rates, cell density, and variable fluorescence. Monod curves were also used to evaluate the efficiency of the different particulates as sources of nutrient Fe. Using these Monod curves fit to growth rates plotted against particulate Fe concentrations, we observed that 1) Fe(II)-rich primary silicates were significantly more effective as an Fe source to diatoms than Fe(III)-rich oxides, that 2) Fe(II) content itself was responsible for the difference in Fe bioavailability/efficiency of the Fe nutrient source, and that 3) surface interactions with the particulates were important. In an effort to explore the possibility that Fe mineralogy impacted Fe bioavailability in past oceans, we will present our hypotheses regarding productivity and Fe mineralogy/bioavailability through the last glacial cycle.

Impacts of Interactive Stratospheric Chemistry on Antarctic and Southern Ocean Climate Change in the Goddard Earth Observing System Version 5 (GEOS-5)

Science.gov (United States)

Li, Feng; Vikhliaev, Yury V.; Newman, Paul A.; Pawson, Steven; Perlwitz, Judith; Waugh, Darryn W.; Douglass, Anne R.

2016-01-01

Stratospheric ozone depletion plays a major role in driving climate change in the Southern Hemisphere. To date, many climate models prescribe the stratospheric ozone layer's evolution using monthly and zonally averaged ozone fields. However, the prescribed ozone underestimates Antarctic ozone depletion and lacks zonal asymmetries. In this study we investigate the impact of using interactive stratospheric chemistry instead of prescribed ozone on climate change simulations of the Antarctic and Southern Ocean. Two sets of 1960-2010 ensemble transient simulations are conducted with the coupled ocean version of the Goddard Earth Observing System Model, version 5: one with interactive stratospheric chemistry and the other with prescribed ozone derived from the same interactive simulations. The model's climatology is evaluated using observations and reanalysis. Comparison of the 1979-2010 climate trends between these two simulations reveals that interactive chemistry has important effects on climate change not only in the Antarctic stratosphere, troposphere, and surface, but also in the Southern Ocean and Antarctic sea ice. Interactive chemistry causes stronger Antarctic lower stratosphere cooling and circumpolar westerly acceleration during November-December-January. It enhances stratosphere-troposphere coupling and leads to significantly larger tropospheric and surface westerly changes. The significantly stronger surface wind stress trends cause larger increases of the Southern Ocean Meridional Overturning Circulation, leading to year-round stronger ocean warming near the surface and enhanced Antarctic sea ice decrease.

Dissolved inorganic carbon, alkalinity, temperature, salinity and other variables collected from discrete sample and profile observations using Alkalinity titrator, CTD and other instruments from RRS JAMES COOK in the South Atlantic Ocean, South Pacific Ocean and Southern Oceans from 2009-02-03 to 2009-03-03 (NODC Accession 0110379)

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — NCEI Accession 0110379 includes discrete sample and profile data collected from RRS JAMES COOK in the South Atlantic Ocean, South Pacific Ocean and Southern Oceans...

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 2002-11-24 to 2003-01-23 (NODC Accession 0108068)

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — NCEI Accession 0108068 includes chemical, discrete sample, physical and profile data collected from POLARSTERN in the Indian Ocean, South Atlantic Ocean and Southern...

Effects of iron stress on chromatic adaptation by natural phytoplankton communities in the Southern Ocean

NARCIS (Netherlands)

van Leeuwe, M.A.; Timmermans, K.R.; Witte, H.J.; Kraay, G.W.; Veldhuis, M.J.W.; de Baar, H.J.W.

1998-01-01

Effects of iron stress on chromatic adaptation were studied in natural phytoplankton communities collected in the Pacific region of the Southern Ocean. Iron enrichment experiments (48 to 72 h) were performed, incubating plankton communities under white, green and blue light respectively, with and

Phytoplankton and pigment patterns across frontal zones in the Atlantic sector of the Southern Ocean

NARCIS (Netherlands)

van Leeuwe, Maria A.; Kattner, Gerhard; van Oijen, Tim; de Jong, Jeroen T. M.; de Baar, Hein J.W.

2015-01-01

Phytoplankton distribution and concentrations of macronutrients and iron were studied in the Polar Frontal Zone (PFZ) and the eastern Weddell Gyre of the Southern Ocean, during austral autumn. HPLC analysis of algal pigments was combined with microscopy observations to assess algal distribution.

Distribution, abundance and ecological relevance of pelagic fishes in the Lazarev Sea, Southern Ocean

NARCIS (Netherlands)

Flores, Hauke; de Putte, Anton P. Van; Siegel, Volker; Pakhomov, Evgeny A.; Van Franeker, Jan A.; Meesters, Hugo W. G.; Volckaert, Filip A. M.

2008-01-01

The distribution and abundance of larval and postlarval fishes was investigated in the Lazarev Sea, Southern Ocean, in March and April 2004. The upper 200 m of the water column were sampled with an 8 m(2) rectangular midwater trawl at 93 stations. The larval species community clustered in a diverse

Distribution, abundance and ecological relevance of pelagic fishes in the Lazarev Sea, Southern Ocean

NARCIS (Netherlands)

Florentino De Souza Silva, A.P.; Putte, van de A.P.; Siegel, V.; Pakhomov, E.A.; Franeker, van J.A.; Meesters, H.W.G.; Colckaert, F.A.M.

2008-01-01

The distribution and abundance of larval and postlarval fishes was investigated in the Lazarev Sea, Southern Ocean, in March and April 2004. The upper 200 m of the water column were sampled with an 8 m2 rectangular midwater trawl at 93 stations. The larval species community clustered in a diverse

Dissolved trace metals (Ni, Zn, Co, Cd, Pb, Al, and Mn) around the Crozet Islands, Southern Ocean

Science.gov (United States)

Castrillejo, Maxi; Statham, Peter J.; Fones, Gary R.; Planquette, Hélène; Idrus, Farah; Roberts, Keiron

2013-10-01

A phytoplankton bloom shown to be naturally iron (Fe) induced occurs north of the Crozet Islands (Southern Ocean) every year, providing an ideal opportunity to study dissolved trace metal distributions within an island system located in a high nutrient low chlorophyll (HNLC) region. We present water column profiles of dissolved nickel (Ni), zinc (Zn), cobalt (Co), cadmium (Cd), lead (Pb), aluminium (Al), and manganese (Mn) obtained as part of the NERC CROZEX program during austral summer (2004-2005). Two stations (M3 and M1) were sampled downstream (north) of Crozet in the bloom area and near the islands, along with a control station (M2) in the HNLC zone upstream (south) of the islands. The general range found was for Ni, 4.64-6.31 nM; Zn, 1.59-7.75 nM; Co, 24-49 pM; Cd, 135-673 pM; Pb, 6-22 pM; Al, 0.13-2.15 nM; and Mn, 0.07-0.64 nM. Vertical profiles indicate little island influence to the south with values in the range of other trace metal deprived regions of the Southern Ocean. Significant removal of Ni and Cd was observed in the bloom and Zn was moderately correlated with reactive silicate (Si) indicating diatom control over the internal cycling of this metal. Higher concentrations of Zn and Cd were observed near the islands. Pb, Al, and Mn distributions also suggest small but significant atmospheric dust supply particularly in the northern region.

A data assimilating model for estimating Southern Ocean biogeochemistry

Science.gov (United States)

Verdy, A.; Mazloff, M. R.

2017-09-01

A Biogeochemical Southern Ocean State Estimate (B-SOSE) is introduced that includes carbon and oxygen fields as well as nutrient cycles. The state estimate is constrained with observations while maintaining closed budgets and obeying dynamical and thermodynamic balances. Observations from profiling floats, shipboard data, underway measurements, and satellites are used for assimilation. The years 2008-2012 are chosen due to the relative abundance of oxygen observations from Argo floats during this time. The skill of the state estimate at fitting the data is assessed. The agreement is best for fields that are constrained with the most observations, such as surface pCO2 in Drake Passage (44% of the variance captured) and oxygen profiles (over 60% of the variance captured at 200 and 1000 m). The validity of adjoint method optimization for coupled physical-biogeochemical state estimation is demonstrated with a series of gradient check experiments. The method is shown to be mature and ready to synthesize in situ biogeochemical observations as they become more available. Documenting the B-SOSE configuration and diagnosing the strengths and weaknesses of the solution informs usage of this product as both a climate baseline and as a way to test hypotheses. Transport of Intermediate Waters across 32°S supplies significant amounts of nitrate to the Atlantic Ocean (5.57 ± 2.94 Tmol yr-1) and Indian Ocean (5.09 ± 3.06 Tmol yr-1), but much less nitrate reaches the Pacific Ocean (1.78 ± 1.91 Tmol yr-1). Estimates of air-sea carbon dioxide fluxes south of 50°S suggest a mean uptake of 0.18 Pg C/yr for the time period analyzed.

Characteristics of regional aerosols: Southern Arizona and eastern Pacific Ocean

Science.gov (United States)

Prabhakar, Gouri

Atmospheric aerosols impact the quality of our life in many direct and indirect ways. Inhalation of aerosols can have harmful effects on human health. Aerosols also have climatic impacts by absorbing or scattering solar radiation, or more indirectly through their interactions with clouds. Despite a better understanding of several relevant aerosol properties and processes in the past years, they remain the largest uncertainty in the estimate of global radiative forcing. The uncertainties arise because although aerosols are ubiquitous in the Earth's atmosphere they are highly variable in space, time and their physicochemical properties. This makes in-situ measurements of aerosols vital in our effort towards reducing uncertainties in the estimate of global radiative forcing due to aerosols. This study is an effort to characterize atmospheric aerosols at a regional scale, in southern Arizona and eastern Pacific Ocean, based on ground and airborne observations of aerosols. Metals and metalloids in particles with aerodynamic diameter (Dp) smaller than 2.5 μm are found to be ubiquitous in southern Arizona. The major sources of the elements considered in the study are identified to be crustal dust, smelting/mining activities and fuel combustion. The spatial and temporal variability in the mass concentrations of these elements depend both on the source strength and meteorological conditions. Aircraft measurements of aerosol and cloud properties collected during various field campaigns over the eastern Pacific Ocean are used to study the sources of nitrate in stratocumulus cloud water and the relevant processes. The major sources of nitrate in cloud water in the region are emissions from ships and wildfires. Different pathways for nitrate to enter cloud water and the role of meteorology in these processes are examined. Observations of microphysical properties of ambient aerosols in ship plumes are examined. The study shows that there is an enhancement in the number

Accelerated freshening of Antarctic Bottom Water over the last decade in the Southern Indian Ocean.

Science.gov (United States)

Menezes, Viviane V; Macdonald, Alison M; Schatzman, Courtney

2017-01-01

Southern Ocean abyssal waters, in contact with the atmosphere at their formation sites around Antarctica, not only bring signals of a changing climate with them as they move around the globe but also contribute to that change through heat uptake and sea level rise. A repeat hydrographic line in the Indian sector of the Southern Ocean, occupied three times in the last two decades (1994, 2007, and, most recently, 2016), reveals that Antarctic Bottom Water (AABW) continues to become fresher (0.004 ± 0.001 kg/g decade -1 ), warmer (0.06° ± 0.01°C decade -1 ), and less dense (0.011 ± 0.002 kg/m 3 decade -1 ). The most recent observations in the Australian-Antarctic Basin show a particularly striking acceleration in AABW freshening between 2007 and 2016 (0.008 ± 0.001 kg/g decade -1 ) compared to the 0.002 ± 0.001 kg/g decade -1 seen between 1994 and 2007. Freshening is, in part, responsible for an overall shift of the mean temperature-salinity curve toward lower densities. The marked freshening may be linked to an abrupt iceberg-glacier collision and calving event that occurred in 2010 on the George V/Adélie Land Coast, the main source region of bottom waters for the Australian-Antarctic Basin. Because AABW is a key component of the global overturning circulation, the persistent decrease in bottom water density and the associated increase in steric height that result from continued warming and freshening have important consequences beyond the Southern Indian Ocean.

On the role of atmospheric forcing on upper ocean physics in the Southern Ocean and biological impacts

Science.gov (United States)

Carranza, Magdalena M.

The Southern Ocean (SO) plays a key role in regulating climate by absorbing nearly half of anthropogenic carbon dioxide (CO2). Both physical and biogeochemical processes contribute to the net CO2 sink. As a result of global warming and ozone depletion, westerly winds have increased, with consequences for upper ocean physics but little is known on how primary producers are expected to respond to changes in atmospheric forcing. This thesis addresses the impact of atmospheric forcing on upper ocean dynamics and phytoplankton bloom development in the SO on synoptic storm scales, combining a broad range of observations derived from satellites, reanalysis, profiling floats and Southern elephant seals. On atmospheric synoptic timescales (2-10 days), relevant for phytoplankton growth and accumulation, wind speed has a larger impact on satellite Chl-a variability than surface heat fluxes or wind stress curl. In summer, strong winds are linked to deep mixed layers, cold sea surface temperatures and enhanced satellite chlorophyll-a (Chl-a), which suggest wind-driven entrainment plays a role in sustaining phytoplankton blooms at the surface. Subsurface bio-optical data from floats and seals reveal deep Chl-a fluorescence maxima (DFM) are ubiquitous in summer and tend to sit at the base of the mixed layer, but can occur in all seasons. The fact that wind speed and Chl-a correlations are maximal at zero lag time (from daily data) and incubation experiments indicate phytoplankton growth occurs 3-4 days after iron addition, suggests high winds in summer entrain Chl-a from a subsurface maximum. Vertical profiles also reveal Chl-a fluorescence unevenness within hydrographically defined mixed layers, suggesting the biological timescales of adaptation through the light gradient (i.e. growth and/or photoacclimation) are often faster than mixing timescales, and periods of quiescence between storms are long enough for biological gradients to form within the homogeneous layer in density

Turbidity, SOLAR RADIATION - ATMOSPHERIC and other data from PROFESSOR SIEDLECKI in the Southern Oceans from 1977-01-01 to 1978-12-31 (NODC Accession 9600122)

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — The Ocean Serial data in this accession was collected in Southern Oceans (> 60 degrees South) in Polish Antarctic stations as part of Global Ocean Data...

Ertel Potential Vorticity versus Bernoulli Streamfunction in Earth's Southern Ocean: Comparison with the Atmospheres of Earth, Mars, Jupiter and Saturn

Science.gov (United States)

Dowling, Timothy E.; Stanley, Geoff; Bradley, Mary Elizabeth; Marshall, David P.

2017-10-01

We are working to expand the comparative planetology of vorticity-streamfunction correlations established for the atmospheres of Earth, Mars, Jupiter and Saturn to include Earth’s Antarctic Circumpolar Current (ACC), which is the only oceanic jet that encircles the planet. Interestingly, the ACC and its eddies scale like atmospheric jets and eddies on Jupiter and Saturn---the Southern Ocean is a “giant planet” with a zonal jet stream. Our input is the Southern Ocean State Estimate (SOSE; Mazloff et al 2010, J. Phys. Ocean. 40, 880-899), an optimal combination of observations and primitive-equation model that spans 2005-2010. Two hurdles not encountered in atmospheric work arise from the nonlinear equation of state of ocean water: non-zero helicity, which prevents the existence of truly neutral (analogous to adiabatic) surfaces, and the lack of a geostrophic streamfunction in general. We follow de Szoeke et al (2000, J. Phys. Ocean. 30, 2830-2852) to overcome these hurdles, regionally, by using orthobaric density as the vertical coordinate. In agreement with results for all atmospheres analyzed to date, scatter plots of Ertel potential vorticity, Q, versus Bernoulli streamfunction, B, on orthobaric density surfaces in the Southern Ocean are well correlated. The general shape of the correlation is like a hockey stick, with the “blade” corresponding to a broad horizontal region that spans the ACC, and the “handle” corresponding to shallow water. The same linear-regression Q versus B model employed for Mars is applied to the ACC (“blade”) signal. Results include that the deeper water on the equatorward side of the ACC is most prone to shear instability, and elsewhere the ACC is “supersonic” such that the net propagation of vorticity waves is eastward, not the usual westward. During the 6-year span of the SOSE data, there is a steady drift of the correlation to larger values at the top of the vertical profile, and to smaller values in the middle of

Cloud amount/frequency, SALINITY and other data from EL AUSTRAL in the Southern Oceans from 1977-04-21 to 1977-11-12 (NCEI Accession 9200257)

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — The Ocean Serial data in this accession was collected in Southern Oceans (> 60 degrees South) as part of Global Ocean Data Archeaology and Rescue (GODAR) project...

Southern Ocean Circulation: a High Resolution Examination of the Last Deglaciation from Deep-Sea Corals

Science.gov (United States)

Robinson, L. F.; Li, T.; Chen, T.; Burke, A.; Pegrum Haram, A.; Stewart, J.; Rae, J. W. B.; van de Flierdt, T.; Struve, T.; Wilson, D. J.

2017-12-01

Two decades ago it was first noted that the skeletal remains of deep-sea corals had the potential to provide absolutely dated archives of past ocean conditions. In the intervening twenty years this field has developed to the point where strategic collections and high throughput dating techniques now allow high resolution, well dated records of past deep sea behaviour to be produced. Likewise, efforts to improve understanding of biomineralisation and growth rates are leading to refinements in proxy tools useful for examining circulation, nutrient and carbon cycling, temperature and weathering processes. Deep-sea corals are particularly valuable archives in high latitude regions where radiocarbon-based age models are susceptible to large changes in surface reservoir ages. In this presentation we show new high resolution multiproxy records of the Southern Ocean (Drake Passage) made on U-Th dated corals spanning the last glacial cycle. With more than seventeen hundred reconnaissance ages, and around 200 precise isotope dilution U-Th ages, subtle changes in ocean behaviour can be identified during times of abrupt climate change. The geochemical signature of corals from the deepest sites, closest to modern day Lower Circumpolar Deep Waters, typically show a gradual shift from glacial to Holocene values during deglaciation, likely related to ventilation of the deep ocean. By contrast for the samples collected shallower in the water column (within sites currently bathed by Upper Circumpolar Deep Waters and Antarctic Intermediate and Mode Waters) the evidence points to a more complicated picture. Vertical zonation in the geochemical data suggests that periods of stratification are interspersed with mixing events within the upper 1500m of the water column. At the same time comparison to U-Th dated records from the low latitude Pacific and Atlantic points to an important role for the Southern Ocean in feeding the intermediate waters of both ocean basins throughout the

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 (>...

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...

The sensitivity of dimethyl sulfide production to simulated climate change in the Eastern Antarctic Southern Ocean

International Nuclear Information System (INIS)

Gabric, Albert J.; Cropp, Roger; Marchant, Harvey

2003-01-01

Dimethyl sulfide (DMS) is a radiatively active trace gas produced by enzymatic cleavage of its precursor compound, dimethyl sulfoniopropionate (DMSP), which is released by marine phytoplankton in the upper ocean. Once ventilated to the atmosphere, DMS is oxidised to form non-sea-salt sulfate and methane sulfonate (MSA) aerosols, which are a major source of cloud condensation nuclei (CCN) in remote marine air and may thus play a role in climate regulation. Here we simulate the change in DMS flux in the Eastern Antarctic ocean from 1960-2086, corresponding to equivalent CO 2 tripling relative to pre-industrial levels. Calibration to contemporary climate conditions was carried out using a genetic algorithm to fit the model to surface chlorophyll from the 4-yr SeaWiFs satellite archive and surface DMS from an existing global database. Following the methodology used previously in the Subantarctic Southern Ocean, we then simulated DMS emissions under enhanced greenhouse conditions by forcing the DMS model with output from a coupled atmospheric-ocean general circulation model (GCM). The GCM was run in transient mode under the IPCC/IS92a radiative forcing scenario. By 2086, the change simulated in annual integrated DMS flux is around 20% in ice-free waters, with a greater increase of 45% in the seasonal ice zone (SIZ). Interestingly, the large increase in flux in the SIZ is not due to higher in situ production but mainly because of a loss of ice cover during summer-autumn and an increase in sea-to-air ventilation of DMS. These proportional changes in areal mean flux (25%) are much higher than previously estimated for the Subantarctic Southern Ocean (5%), and point to the possibility of a significant DMS-climate feedback at high Southern latitudes. Due to the nexus between ice cover and food-web structure, the potential for ecological community shifts under enhanced greenhouse conditions is high, and the implications for DMS production are discussed

The seasonal cycle of pCO2 and CO2 fluxes in the Southern Ocean: diagnosing anomalies in CMIP5 Earth system models

Science.gov (United States)

Precious Mongwe, N.; Vichi, Marcello; Monteiro, Pedro M. S.

2018-05-01

The Southern Ocean forms an important component of the Earth system as a major sink of CO2 and heat. Recent studies based on the Coupled Model Intercomparison Project version 5 (CMIP5) Earth system models (ESMs) show that CMIP5 models disagree on the phasing of the seasonal cycle of the CO2 flux (FCO2) and compare poorly with available observation products for the Southern Ocean. Because the seasonal cycle is the dominant mode of CO2 variability in the Southern Ocean, its simulation is a rigorous test for models and their long-term projections. Here we examine the competing roles of temperature and dissolved inorganic carbon (DIC) as drivers of the seasonal cycle of pCO2 in the Southern Ocean to explain the mechanistic basis for the seasonal biases in CMIP5 models. We find that despite significant differences in the spatial characteristics of the mean annual fluxes, the intra-model homogeneity in the seasonal cycle of FCO2 is greater than observational products. FCO2 biases in CMIP5 models can be grouped into two main categories, i.e., group-SST and group-DIC. Group-SST models show an exaggeration of the seasonal rates of change of sea surface temperature (SST) in autumn and spring during the cooling and warming peaks. These higher-than-observed rates of change of SST tip the control of the seasonal cycle of pCO2 and FCO2 towards SST and result in a divergence between the observed and modeled seasonal cycles, particularly in the Sub-Antarctic Zone. While almost all analyzed models (9 out of 10) show these SST-driven biases, 3 out of 10 (namely NorESM1-ME, HadGEM-ES and MPI-ESM, collectively the group-DIC models) compensate for the solubility bias because of their overly exaggerated primary production, such that biologically driven DIC changes mainly regulate the seasonal cycle of FCO2.

Impact of transient freshwater releases in the Southern Ocean on the AMOC and climate

Energy Technology Data Exchange (ETDEWEB)

Swingedouw, Didier [Universite Catholique de Louvain, Institut d' Astronomie et de Geophysique Georges Lemaitre, Louvain-la-Neuve (Belgium); CERFACS/GlobC, Toulouse (France); Fichefet, T.; Goosse, H.; Loutre, M.F. [Universite Catholique de Louvain, Institut d' Astronomie et de Geophysique Georges Lemaitre, Louvain-la-Neuve (Belgium)

2009-08-15

The bipolar ocean seesaw is a process that explains the competition between deep waters formed in the North Atlantic (NA) and in the Southern Ocean (SO). In this picture, an increase in the rate of formation of one of these water masses is made at the expense of the other. However, recent studies have questioned the effectiveness of this process. Namely, they show that adding freshwater in the SO can reduce deep water formation in the SO as well as in the NA. In this study, we explore the mechanisms and time scales excited by such a SO freshwater release by performing sensitivity experiments where a freshwater input is added abruptly in the ocean, south of 60 S, with different rates and durations. For this purpose, we evaluate the separate effects of wind, temperature and salinity changes, and we put the emphasis on the time evolution of the system. We find three main processes that respond to these freshwater inputs and affect the NA Deep Water (NADW) production: (i) the deep water adjustment, which enhances the NADW cell, (ii) the salinity anomaly spread from the SO, which weakens the NADW cell, and (iii) the increase in the Southern Hemisphere wind stress, which enhances the NADW cell. We show that process (i) affects the Atlantic in a few years, due to an adjustment of the pycnocline depth through oceanic waves in response to the buoyancy perturbation in the SO. The salinity anomalies responsible for the NADW production decrease [process (ii)] invades the NA in around 30 years, while the wind stress from process (iii) increases in around 20 years after the beginning of the freshwater perturbation. Finally, by testing the response of the ocean to a large range of freshwater release fluxes, we show that for fluxes larger than 0.2 Sv, process (ii) dominates over the others and limits NADW production after a few centuries, while for fluxes lower than 0.2 Sv, process (ii) hardly affects the NADW production. On the opposite, the NADW export is increased by processes

Distribution pattern of macrozooplankton along the 140°E meridian in the Southern Ocean during austral summer 2002 and 2003

Directory of Open Access Journals (Sweden)

Atsushi Tanimura

2008-03-01

Full Text Available Field surveys were conducted along 140°E in the Southern Ocean north of Terre Adelie during three cruises: the KH cruise by RV Hakuho Maru, and TC1 and TC2 cruises by RV Tangaroa during the austral summers of 2002 and 2003. Macrozooplankton were sampled using a Rectangular Midwater Trawl (RMT 8: mesh size: 4.5mm; effective mouth area: 8m2 along each transect. Macrozooplankton communities were separated by the Southern Boundary of the Antarctic Circumpolar Current (SB-ACC based on cluster analysis. North of the SB-ACC, macrozooplankton assemblages comprised species of the northern oceanic community characterized by Salpa thompsoni, Euphausia frigida and Themisto gaudichaudii, while south of the SB-ACC, macrozooplankton assemblages were numerically dominated by Euphausia superba and/or Euphausia crystallorophias. It is suggested that the SB-ACC functions as the major biogeographic barrier to separate the macrozooplankton communities, and the contributions of macro- and meso-zooplankton to total zooplankton abundance varies seasonally as well as regionally in the Indian sector of the Southern Ocean crossing the SB-ACC.

Extratropical Cyclone in the Southern Ocean

Science.gov (United States)

2002-01-01

These images from the Multi-angle Imaging SpectroRadiometer (MISR) portray an occluded extratropical cyclone situated in the Southern Ocean, about 650 kilometers south of the Eyre Peninsula, South Australia. The left-hand image, a true-color view from MISR's nadir (vertical-viewing) camera, shows clouds just south of the Yorke Peninsula and the Murray-Darling river basin in Australia. Retrieved cloud-tracked wind velocities are indicated by the superimposed arrows. The image on the right displays cloud-top heights. Areas where cloud heights could not be retrieved are shown in black. Both the wind vectors and the cloud heights were derived using data from multiple MISR cameras within automated computer processing algorithms. The stereoscopic algorithms used to generate these results are still being refined, and future versions of these products may show modest changes. Extratropical cyclones are the dominant weather system at midlatitudes, and the term is used generically for regional low-pressure systems in the mid- to high-latitudes. In the southern hemisphere, cyclonic rotation is clockwise. These storms obtain their energy from temperature differences between air masses on either side of warm and cold fronts, and their characteristic pattern is of warm and cold fronts radiating out from a migrating low pressure center which forms, deepens, and dissipates as the fronts fold and collapse on each other. The center of this cyclone has started to decay, with the band of cloud to the south most likely representing the main front that was originally connected with the cyclonic circulation. These views were acquired on October 11, 2001, and the large view represents an area of about 380 kilometers x 1900 kilometers. Image courtesy NASA/GSFC/LaRC/JPL, MISR Team.

Effect of Gravity Waves from Small Islands in the Southern Ocean on the Southern Hemisphere Atmospheric Circulation

Science.gov (United States)

Garfinkel, C. I.; Oman, L. D.

2018-01-01

The effect of small islands in the Southern Ocean on the atmospheric circulation in the Southern Hemisphere is considered with a series of simulations using the NASA Goddard Earth Observing System Chemistry-Climate Model in which the gravity wave stress generated by these islands is increased to resemble observed values. The enhanced gravity wave drag leads to a 2 K warming of the springtime polar stratosphere, partially ameliorating biases in this region. Resolved wave drag declines in the stratospheric region in which the added orographic gravity waves deposit their momentum, such that changes in gravity waves are partially compensated by changes in resolved waves, though resolved wave drag increases further poleward. The orographic drag from these islands has impacts for surface climate, as biases in tropospheric jet position are also partially ameliorated. These results suggest that these small islands are likely contributing to the missing drag near 60 degrees S in the upper stratosphere evident in many data assimilation products.

Contributions of Greenhouse Gas Forcing and the Southern Annular Mode to Historical Southern Ocean Surface Temperature Trends

Science.gov (United States)

Kostov, Yavor; Ferreira, David; Armour, Kyle C.; Marshall, John

2018-01-01

We examine the 1979-2014 Southern Ocean (SO) sea surface temperature (SST) trends simulated in an ensemble of coupled general circulation models and evaluate possible causes of the models' inability to reproduce the observed 1979-2014 SO cooling. For each model we estimate the response of SO SST to step changes in greenhouse gas (GHG) forcing and in the seasonal indices of the Southern Annular Mode (SAM). Using these step-response functions, we skillfully reconstruct the models' 1979-2014 SO SST trends. Consistent with the seasonal signature of the Antarctic ozone hole and the seasonality of SO stratification, the summer and fall SAM exert a large impact on the simulated SO SST trends. We further identify conditions that favor multidecadal SO cooling: (1) a weak SO warming response to GHG forcing, (2) a strong multidecadal SO cooling response to a positive SAM trend, and (3) a historical SAM trend as strong as in observations.

The Southern Kalahari: a potential new dust source in the Southern Hemisphere?

International Nuclear Information System (INIS)

Bhattachan, Abinash; D’Odorico, Paolo; Baddock, Matthew C; Zobeck, Ted M; Okin, Gregory S; Cassar, Nicolas

2012-01-01

Most sources of atmospheric dust on Earth are located in the Northern Hemisphere. The lower dust emissions in the Southern Hemisphere in part limit the supply of micronutrients (primarily soluble iron) to the Southern Ocean, thereby constraining its productivity. Climate and land use change can alter the current distribution of dust source regions on Earth. Can new dust sources be activated in the Southern Hemisphere? Here we show that vegetation loss and dune remobilization in the Southern Kalahari can promote dust emissions comparable to those observed from major contemporary dust sources in the Southern African region. Dust generation experiments support the hypothesis that, in the Southern Kalahari, aeolian deposits that are currently mostly stabilized by savanna vegetation are capable of emitting substantial amounts of dust from interdune areas. We show that dust from these areas is relatively rich in soluble iron, an important micronutrient for ocean productivity. Trajectory analyses show that dust from the Kalahari commonly reaches the Southern Ocean and could therefore enhance its productivity. (letter)

Impacts of El Niño Southern Oscillation and Indian Ocean Dipole on dengue incidence in Bangladesh.

Science.gov (United States)

Banu, Shahera; Guo, Yuming; Hu, Wenbiao; Dale, Pat; Mackenzie, John S; Mengersen, Kerrie; Tong, Shilu

2015-11-05

Dengue dynamics are driven by complex interactions between hosts, vectors and viruses that are influenced by environmental and climatic factors. Several studies examined the role of El Niño Southern Oscillation (ENSO) in dengue incidence. However, the role of Indian Ocean Dipole (IOD), a coupled ocean atmosphere phenomenon in the Indian Ocean, which controls the summer monsoon rainfall in the Indian region, remains unexplored. Here, we examined the effects of ENSO and IOD on dengue incidence in Bangladesh. According to the wavelet coherence analysis, there was a very weak association between ENSO, IOD and dengue incidence, but a highly significant coherence between dengue incidence and local climate variables (temperature and rainfall). However, a distributed lag nonlinear model (DLNM) revealed that the association between dengue incidence and ENSO or IOD were comparatively stronger after adjustment for local climate variables, seasonality and trend. The estimated effects were nonlinear for both ENSO and IOD with higher relative risks at higher ENSO and IOD. The weak association between ENSO, IOD and dengue incidence might be driven by the stronger effects of local climate variables such as temperature and rainfall. Further research is required to disentangle these effects.

Iron from melting glaciers fuels the phytoplankton blooms in Amundsen Sea (Southern Ocean): Iron biogeochemistry

NARCIS (Netherlands)

Gerringa, L.J.A.; Alderkamp, A.C.; Laan, P.; Thuróczy, C.E.; de Baar, H.J.W.; Mills, M.M.; van Dijken, G.L.; van Haren, H.; Arrigo, K.R.

2012-01-01

Dissolved iron (DFe) and total dissolvable Fe (TDFe) were measured in January-February 2009 in Pine Island Bay, as well as in the Pine Island and Amundsen polynyas (Amundsen Sea, Southern Ocean). Iron (Fe) has been shown to be a limiting nutrient for phytoplankton growth, even in the productive

Iron from melting glaciers fuels the phytoplankton blooms in Amundsen Sea (Southern Ocean) : Iron biogeochemistry

NARCIS (Netherlands)

Gerringa, Loes J. A.; Alderkamp, Anne-Carlijn; Laan, Patrick; Thuroczy, Charles-Edouard; De Baar, Hein J. W.; Mills, Matthew M.; van Dijken, Gert L.; van Haren, Hans; Arrigo, Kevin R.

2012-01-01

Dissolved iron (DFe) and total dissolvable Fe (TDFe) were measured in January-February 2009 in Pine Island Bay, as well as in the Pine Island and Amundsen polynyas (Amundsen Sea, Southern Ocean). Iron (Fe) has been shown to be a limiting nutrient for phytoplankton growth, even in the productive

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...

Oxygen in the Southern Ocean From Argo Floats: Determination of Processes Driving Air-Sea Fluxes

Science.gov (United States)

Bushinsky, Seth M.; Gray, Alison R.; Johnson, Kenneth S.; Sarmiento, Jorge L.

2017-11-01

The Southern Ocean is of outsized significance to the global oxygen and carbon cycles with relatively poor measurement coverage due to harsh winters and seasonal ice cover. In this study, we use recent advances in the parameterization of air-sea oxygen fluxes to analyze 9 years of oxygen data from a recalibrated Argo oxygen data set and from air-calibrated oxygen floats deployed as part of the Southern Ocean Carbon and Climate Observations and Modeling (SOCCOM) project. From this combined data set of 150 floats, we find a total Southern Ocean oxygen sink of -183 ± 80 Tmol yr-1 (positive to the atmosphere), greater than prior estimates. The uptake occurs primarily in the Polar-Frontal Antarctic Zone (PAZ, -94 ± 30 Tmol O2 yr-1) and Seasonal Ice Zone (SIZ, -111 ± 9.3 Tmol O2 yr-1). This flux is driven by wintertime ventilation, with a large portion of the flux in the SIZ passing through regions with fractional sea ice. The Subtropical Zone (STZ) is seasonally driven by thermal fluxes and exhibits a net outgassing of 47 ± 29 Tmol O2 yr-1 that is likely driven by biological production. The Subantarctic Zone (SAZ) uptake is -25 ± 12 Tmol O2 yr-1. Total oxygen fluxes were separated into a thermal and nonthermal component. The nonthermal flux is correlated with net primary production and mixed layer depth in the STZ, SAZ, and PAZ, but not in the SIZ where seasonal sea ice slows the air-sea gas flux response to the entrainment of deep, low-oxygen waters.

A hierarchical classification of benthic biodiversity and assessment of protected areas in the Southern Ocean.

Directory of Open Access Journals (Sweden)

Lucinda L Douglass

Full Text Available An international effort is underway to establish a representative system of marine protected areas (MPAs in the Southern Ocean to help provide for the long-term conservation of marine biodiversity in the region. Important to this undertaking is knowledge of the distribution of benthic assemblages. Here, our aim is to identify the areas where benthic marine assemblages are likely to differ from each other in the Southern Ocean including near-shore Antarctica. We achieve this by using a hierarchical spatial classification of ecoregions, bathomes and environmental types. Ecoregions are defined according to available data on biogeographic patterns and environmental drivers on dispersal. Bathomes are identified according to depth strata defined by species distributions. Environmental types are uniquely classified according to the geomorphic features found within the bathomes in each ecoregion. We identified 23 ecoregions and nine bathomes. From a set of 28 types of geomorphic features of the seabed, 562 unique environmental types were classified for the Southern Ocean. We applied the environmental types as surrogates of different assemblages of biodiversity to assess the representativeness of existing MPAs. We found that 12 ecoregions are not represented in MPAs and that no ecoregion has their full range of environmental types represented in MPAs. Current MPA planning processes, if implemented, will substantially increase the representation of environmental types particularly within 8 ecoregions. To meet internationally agreed conservation goals, additional MPAs will be needed. To assist with this process, we identified 107 spatially restricted environmental types, which should be considered for inclusion in future MPAs. Detailed supplementary data including a spatial dataset are provided.

Why Southern Ocean uptake of anthropogenic CO2 may be decreasing

CSIR Research Space (South Africa)

Mongwe, P

2012-10-01

Full Text Available to the warm surface water and its influence on CO2 solubility (Figures 2 and 3). The decline is DIC with depth correlates with the decrease in temperature (Figures 2 and 3), as colder water holds more CO2. The Southern Ocean has particularly high DIC... southwards, upwelling is also expected move more southwards, which may result in more intense CO2 outgassing. The emitted CO2 contributes to green house gases, which alter the heat balance and result in increased average temperatures. REFERENCES Le...

Ocean carbon and heat variability in an Earth System Model

Science.gov (United States)

Thomas, J. L.; Waugh, D.; Gnanadesikan, A.

2016-12-01

Ocean carbon and heat content are very important for regulating global climate. Furthermore, due to lack of observations and dependence on parameterizations, there has been little consensus in the modeling community on the magnitude of realistic ocean carbon and heat content variability, particularly in the Southern Ocean. We assess the differences between global oceanic heat and carbon content variability in GFDL ESM2Mc using a 500-year, pre-industrial control simulation. The global carbon and heat content are directly out of phase with each other; however, in the Southern Ocean the heat and carbon content are in phase. The global heat mutli-decadal variability is primarily explained by variability in the tropics and mid-latitudes, while the variability in global carbon content is primarily explained by Southern Ocean variability. In order to test the robustness of this relationship, we use three additional pre-industrial control simulations using different mesoscale mixing parameterizations. Three pre-industrial control simulations are conducted with the along-isopycnal diffusion coefficient (Aredi) set to constant values of 400, 800 (control) and 2400 m2 s-1. These values for Aredi are within the range of parameter settings commonly used in modeling groups. Finally, one pre-industrial control simulation is conducted where the minimum in the Gent-McWilliams parameterization closure scheme (AGM) increased to 600 m2 s-1. We find that the different simulations have very different multi-decadal variability, especially in the Weddell Sea where the characteristics of deep convection are drastically changed. While the temporal frequency and amplitude global heat and carbon content changes significantly, the overall spatial pattern of variability remains unchanged between the simulations.

Zooplankton data collected by ELTANIN in Southern Oceans from zooplankton net casts; 13 October 1963 to 06 June 1968 (NODC Accession 9500111)

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — Zooplankton data were collected using zooplankton net casts from ELTANIN in the Southern Oceans. Data were collected from 13 October 1963 to 06 June 1968 by National...

Physical and biological data collected with a towed vehicle to support studies in the Southern Oceans, January - February 1998 (NODC Accession 0000947)

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — Physical and biological data were collected using fluorometer and CTD casts from the ROGER REVELLE in the Southern Oceans from 12 January 1998 to 03 February 1998....

Preliminary determination of the energy potential of ocean currents along the southern coast of Brazil

Energy Technology Data Exchange (ETDEWEB)

Fischer, Andrea; Beluco, Alexandre; de Almeida, Luiz Emilio B. [Inst. Pesquisas Hidraulicas, Univ. Fed Rio Grande do Sul, Porto Alegre (Brazil)

2013-07-01

The ocean can be a strategic alternative for obtaining energy supplies, both from ocean waves as from sea currents and tides. Among these features, the power generation projects based on ocean currents are still under development. Generating energy from ocean can have great impact on the Brazilian energy grid, since Brazil has a vast coastline, with more than 9,000 km long, with potential for generating energy from ocean currents not fully estimated. This article presents a preliminary determination of the energy potential for power generation from ocean currents along the coast of Rio Grande do Sul, the southernmost state of Brazil, and also presents notes that contribute to the characterization of the system of ocean currents in the region. The data used were obtained in two areas near Tramandai, allowing the determination of velocities and directions of the currents on a seasonal basis. The maximum speeds obtained rarely exceed 0.750 m/s, while the average speeds do not exceed 0.200 m/s. A relationship with the prevailing winds in the region was identified. Unfortunately, the results do not allow optimism about the power generation from ocean currents on the southern coast of Brazil, at least over the continental shelf.

Temperature, salinity and other variables collected from discrete sample and profile observations using CTD, bottle and other instruments from POLARSTERN in the South Atlantic Ocean and Southern Oceans from 1990-11-17 to 1990-12-30 (NODC Accession 0117676)

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — NCEI Accession 0117676 includes chemical, discrete sample, physical and profile data collected from POLARSTERN in the South Atlantic Ocean and Southern Oceans (>...

Warm mid-Cretaceous high-latitude sea-surface temperatures from the southern Tethys Ocean and cool high-latitude sea-surface temperatures from the Arctic Ocean: asymmetric worldwide distribution of dinoflagellates

Science.gov (United States)

Masure, Edwige; Desmares, Delphine; Vrielynck, Bruno

2014-05-01

Dealing with 87 articles and using a Geographical Information System, Masure and Vrielynck (2009) have mapped worldwide biogeography of 38 Late Albian dinoflagellate cysts and have demonstrated Cretaceous oceanic bioclimatic belts. For comparison 30 Aptian species derived from 49 studies (Masure et al., 2013) and 49 Cenomanian species recorded from 33 articles have been encountered. Tropical, Subtropical, Boreal, Austral, bipolar and cosmopolitan species have been identified and Cretaceous dinoflagellate biomes are introduced. Asymmetric distribution of Aptian and Late Albian/Cenomanian subtropical Tethyan species, from 40°N to 70°S, demonstrates asymmetric Aptian and Late Albian/Cenomanian Sea Surface Temperature (SST) gradients with warm water masses in high latitudes of Southern Ocean. The SST gradients were stronger in the Northern Hemisphere than in the Southern Hemisphere. We note that Aptian and Late Albian/Cenomanian dinoflagellates restricted to subtropical and subpolar latitudes met and mixed at 35-40°N, while they mixed from 30°S to 70°S and from 50°S to 70°S respectively in the Southern Hemisphere. Mixing belts extend on 5° in the Northern Hemisphere and along 40° (Aptian) and 20° (Late Albian/Cenomanian) in the Southern one. The board southern mixing belt of Tethyan and Austral dinoflagellates suggest co-occurrence of warm and cold currents. We record climatic changes such as the Early Aptian cooler period and Late Aptian and Albian warming through the poleward migration of species constrained to cool water masses. These species sensitive to temperature migrated from 35°N to 55°N through the shallow Greenland-Norwergian Seaway connecting the Central Atlantic and the Arctic Ocean. While Tethyan species did not migrate staying at 40°N. We suggest that the Greenland-Norwergian Seaway might has been a barrier until Late Albian/Cenomanian for oceanic Tethyan dinoflagellates stopped either by the shallow water column or temperature and salinity

The role of zooplankton in the pelagic-benthic coupling of the Southern Ocean

Directory of Open Access Journals (Sweden)

Sigrid B. Schnack-Schiel

2005-12-01

depths resuspended aggregates and single particles from shallow environments may constitute a considerable fraction of the “fresh” biogenic flux. Submarine canyons accelerate and cause more efficient transfer of energy to the deep-sea benthos. Both faecal pellets and aggregation increase the original sinking velocity of individual particles and reduce their residence time in the water column, thus creating rich organic mats over the seabed in shallow environments. In the Southern Ocean these rapid organic matter transfers are important since they allow the accumulation of highly nutritive material, which may fuel the benthos during the dark months due to constant resuspension by tidal currents. Several factors control the particle fluxes in the Southern Ocean, such as size and composition of phytoplankton blooms, currents, seasonality, depth, and ice coverage. Due to this complexity, despite many efforts there is still a long way to go before the pathway of this ecologically important link can be fully understood and described. Our knowledge of the pelagic-benthic coupling in the Magellan region is still extremely limited and offers many opportunities for future scientific research. The same holds true for the production of meroplanktonic larvae in the Southern Ocean.

The distribution of the standing crop of zooplankton in the Southern Ocean, 02 January 1932 to 18 October 1951 (NODC Accession 0000842)

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — Zooplankton data were collected using net casts in the Southern Ocean from the DISCOVERY II. Data were collected from 02 January 1932 to 18 October 1951. Data were...

Empirical methods for the estimation of Southern Ocean CO2: support vector and random forest regression

CSIR Research Space (South Africa)

Gregor, Luke

2017-12-01

Full Text Available understanding with spatially integrated air–sea flux estimates (Fay and McKinley, 2014). Conversely, ocean biogeochemical process models are good tools for mechanis- tic understanding, but fail to represent the seasonality of CO2 fluxes in the Southern Ocean... of including coordinate variables as proxies of 1pCO2 in the empirical methods. In the inter- comparison study by Rödenbeck et al. (2015) proxies typi- cally include, but are not limited to, sea surface temperature (SST), chlorophyll a (Chl a), mixed layer...

Wandering whales? : Relationships between baleen whales and the sea ice environment in the Southern Ocean

NARCIS (Netherlands)

Beekmans, Bas

2017-01-01

Each austral summer large baleen whales migrate into the Southern Ocean to feed on krill. The melting of sea ice leads to algal blooms which allow rapid growth and development of krill. In order to predict how baleen whales will respond to long-term changes in the physical environment, we need to

Coastal ocean transport patterns in the central Southern California Bight

Science.gov (United States)

Noble, M.A.; Rosenberger, K.J.; Hamilton, P.; Xu, J. P.

2009-01-01

In the past decade, several large programs that monitor currents and transport patterns for periods from a few months to a few years were conducted by a consortium of university, federal, state, and municipal agencies in the central Southern California Bight, a heavily urbanized section of the coastal ocean off the west coast of the United States encompassing Santa Monica Bay, San Pedro Bay, and the Palos Verdes shelf. These programs were designed in part to determine how alongshelf and cross-shelf currents move sediments, pollutants, and suspended material through the region. Analysis of the data sets showed that the current patterns in this portion of the Bight have distinct changes in frequency and amplitude with location, in part because the topography of the shelf and upper slope varies rapidly over small spatial scales. However, because the mean, subtidal, and tidal-current patterns in any particular location were reasonably stable with time, one could determine a regional pattern for these current fields in the central Southern California Bight even though measurements at the various locations were obtained at different times. In particular, because the mean near-surface flows over the San Pedro and Palos Verdes shelves are divergent, near-surface waters from the upper slope tend to carry suspended material onto the shelf in the northwestern portion of San Pedro Bay. Water and suspended material are also carried off the shelf by the mean and subtidal flow fields in places where the orientation of the shelf break changes abruptly. The barotropic tidal currents in the central Southern California Bight flow primarily alongshore, but they have pronounced amplitude variations over relatively small changes in alongshelf location that are not totally predicted by numerical tidal models. Nonlinear internal tides and internal bores at tidal frequencies are oriented more across the shelf. They do not have a uniform transport direction, since they move fine sediment

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 and Southern Oceans from 1995-07-17 to 1995-09-02 (NCEI Accession 0144339)

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — NCEI Accession 0144339 includes discrete sample and profile data collected from AURORA AUSTRALIS in the Indian Ocean and Southern Oceans (> 60 degrees South) from...

Organophosphorus esters in the oceans and possible relation with ocean gyres

International Nuclear Information System (INIS)

Cheng, Wenhan; Xie, Zhouqing; Blais, Jules M.; Zhang, Pengfei; Li, Ming; Yang, Chengyun; Huang, Wen; Ding, Rui; Sun, Liguang

2013-01-01

Four organophosphorus esters (OPEs) were detected in aerosol samples collected in the West Pacific, the Indian Ocean and the Southern Ocean from 2009 to 2010, suggesting their circumpolar and global distribution. In general, the highest concentrations were detected near populated regions in China, Australia and New Zealand. OPE concentrations in the Southern Ocean were about two orders of magnitude lower than those near major continents. Additionally, relatively high OPE concentrations were detected at the Antarctic Peninsula, where several scientific survey stations are located. The four OPEs investigated here are significantly correlated with each other, suggesting they may derive from the same source. In the circumpolar transect, OPE concentrations were associated with ocean gyres in the open ocean. Their concentrations were positively related with average vorticity in the sampling area suggesting that a major source of OPEs may be found in ocean gyres where plastic debris is known to accumulate. -- Highlights: •We provide OPE concentrations in aerosols in a circumpolar expedition. •We find strong anthropogenic source of OPE pollution. •We suggest potential relationship between ocean gyres and OPE pollution. -- Our work provides a circumpolar investigation on OPEs in the Southern Ocean and we suggest a possibility that ocean currents and gyres may act as important roles in global transport of OPEs

Dynamical and biogeochemical control on the decadal variability of ocean carbon fluxes

Directory of Open Access Journals (Sweden)

R. Séférian

2013-04-01

Full Text Available Several recent observation-based studies suggest that ocean anthropogenic carbon uptake has slowed down due to the impact of anthropogenic forced climate change. However, it remains unclear whether detected changes over the recent time period can be attributed to anthropogenic climate change or rather to natural climate variability (internal plus naturally forced variability alone. One large uncertainty arises from the lack of knowledge on ocean carbon flux natural variability at the decadal time scales. To gain more insights into decadal time scales, we have examined the internal variability of ocean carbon fluxes in a 1000 yr long preindustrial simulation performed with the Earth System Model IPSL-CM5A-LR. Our analysis shows that ocean carbon fluxes exhibit low-frequency oscillations that emerge from their year-to-year variability in the North Atlantic, the North Pacific, and the Southern Ocean. In our model, a 20 yr mode of variability in the North Atlantic air-sea carbon flux is driven by sea surface temperature variability and accounts for ~40% of the interannual regional variance. The North Pacific and the Southern Ocean carbon fluxes are also characterised by decadal to multi-decadal modes of variability (10 to 50 yr that account for 20–40% of the interannual regional variance. These modes are driven by the vertical supply of dissolved inorganic carbon through the variability of Ekman-induced upwelling and deep-mixing events. Differences in drivers of regional modes of variability stem from the coupling between ocean dynamics variability and the ocean carbon distribution, which is set by large-scale secular ocean circulation.

Fe (III) speciation in the high nutrient, low chlorophyll Pacific region of the Southern Ocean

NARCIS (Netherlands)

Nolting, R.F.; Gerringa, L.J.A.; Swagerman, M.J.W.; Timmermans, K.R.; Baar, H.J.W. de

1998-01-01

Fe speciation was measured with competitive ligand equilibration adsorptive cathodic stripping voltammetry in the Pacific part of the Southern Ocean between 58° and 68°30′S along the 90°W meridian. The conditional stability constant (K′ with respect to [Fe3+]) was between 10^20.6 and 10^21.6 when

Southern Ocean Mixed-Layer Seasonal and Interannual Variations From Combined Satellite and In Situ Data

Science.gov (United States)

Buongiorno Nardelli, B.; Guinehut, S.; Verbrugge, N.; Cotroneo, Y.; Zambianchi, E.; Iudicone, D.

2017-12-01

The depth of the upper ocean mixed layer provides fundamental information on the amount of seawater that directly interacts with the atmosphere. Its space-time variability modulates water mass formation and carbon sequestration processes related to both the physical and biological pumps. These processes are particularly relevant in the Southern Ocean, where surface mixed-layer depth estimates are generally obtained either as climatological fields derived from in situ observations or through numerical simulations. Here we demonstrate that weekly observation-based reconstructions can be used to describe the variations of the mixed-layer depth in the upper ocean over a range of space and time scales. We compare and validate four different products obtained by combining satellite measurements of the sea surface temperature, salinity, and dynamic topography and in situ Argo profiles. We also compute an ensemble mean and use the corresponding spread to estimate mixed-layer depth uncertainties and to identify the more reliable products. The analysis points out the advantage of synergistic approaches that include in input the sea surface salinity observations obtained through a multivariate optimal interpolation. Corresponding data allow to assess mixed-layer depth seasonal and interannual variability. Specifically, the maximum correlations between mixed-layer anomalies and the Southern Annular Mode are found at different time lags, related to distinct summer/winter responses in the Antarctic Intermediate Water and Sub-Antarctic Mode Waters main formation areas.

Empirical Algorithms to Predict pH and Aragonite Saturation State on SOCCOM Biogeochemical Argo Floats in the Pacific Sector of the Southern Ocean

Science.gov (United States)

Williams, N. L.; Juranek, L. W.; Feely, R. A.; Johnson, K. S.; Russell, J. L.

2016-02-01

The Southern Ocean plays a major role in the global uptake, transport, and storage of both heat and carbon, yet it remains one of the least-sampled regions of the ocean. The Southern Ocean Carbon and Climate Observations and Modeling (SOCCOM) project aims to fill the observational gaps by deploying over 200 autonomous profiling floats in the Southern Ocean over the next several years. Initial float deployments have greatly expanded our observational capability to include wintertime measurements as well as under-ice measurements, and many of these floats include novel biogeochemical sensors (pH, nitrate, oxygen). Here we present empirical algorithms that can be used to predict pH and ΩAragonite from other float-measured parameters (temperature, salinity, pressure, nitrate, oxygen). These algorithms were trained using bottle measurements from high-quality repeat hydrographic GO-SHIP cruises. We obtained R2 values of 0.98 (pH) and 0.99 (ΩAragonite) and RMS errors of 0.007 (pH) and 0.052 (ΩAragonite) for data between 100-1500 m. These algorithms will allow us to both validate pH data from these sensors, as well as predict ΩAragonite and pH on floats that do not have pH sensors. Here we present estimated pH and ΩAragonite over 20 months of deployment for several SOCCOM floats in the Pacific Sector of the Southern Ocean. The results show seasonal ranges in surface pH and ΩAragonite of 0.05 and 0.1, respectively.

Southern Ocean seaweeds: A resource for exploration in food and drugs

Digital Repository Service at National Institute of Oceanography (India)

Dhargalkar, V.K.; Verlecar, X.N

the land drainage in Barton, Pinitos and Penon de Pesca. In Penon de Pesca the nitrate concentra- tion was even higher at 20 and 30 m depth than near the surface. The phosphate concentrations ranged from 1.23 μM to 3.68 μmol l –1 with higher values only... temperatures and low light 235V.K. Dhargalkar, X.N. Verlecar / Aquaculture 287 (2009) 229–242 conditions in the Southern Oceans (Lamb and Zimmermann, 1977; DeLaca and Lipps,1976; Moe and DeLaca,1976; Wiencke and Clayton, 2002; Neushul, 1965; Amsler et al., 1998...

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 (NO_x 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.

Temperature, salinity and other variables collected from discrete sample and profile observations using CTD, bottle and other instruments from USCGC POLAR SEA in the South Pacific Ocean and Southern Oceans from 1994-02-04 to 1994-02-10 (NODC Accession 0116062)

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — NCEI Accession 0116062 includes chemical, discrete sample, physical and profile data collected from USCGC POLAR SEA in the South Pacific Ocean and Southern Oceans...

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 and Southern Oceans from 2012-01-05 to 2012-02-12 (NCEI Accession 0143949)

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — NCEI Accession 0143949 includes discrete sample and profile data collected from AURORA AUSTRALIS in the Indian Ocean and Southern Oceans (> 60 degrees South) from...

Circulation, retention, and mixing of waters within the Weddell-Scotia Confluence, Southern Ocean: The role of stratified Taylor columns

Science.gov (United States)

Meredith, Michael P.; Meijers, Andrew S.; Naveira Garabato, Alberto C.; Brown, Peter J.; Venables, Hugh J.; Abrahamsen, E. Povl; Jullion, Loïc.; Messias, Marie-José

2015-01-01

The waters of the Weddell-Scotia Confluence (WSC) lie above the rugged topography of the South Scotia Ridge in the Southern Ocean. Meridional exchanges across the WSC transfer water and tracers between the Antarctic Circumpolar Current (ACC) to the north and the subpolar Weddell Gyre to the south. Here, we examine the role of topographic interactions in mediating these exchanges, and in modifying the waters transferred. A case study is presented using data from a free-drifting, intermediate-depth float, which circulated anticyclonically over Discovery Bank on the South Scotia Ridge for close to 4 years. Dimensional analysis indicates that the local conditions are conducive to the formation of Taylor columns. Contemporaneous ship-derived transient tracer data enable estimation of the rate of isopycnal mixing associated with this column, with values of O(1000 m2/s) obtained. Although necessarily coarse, this is of the same order as the rate of isopycnal mixing induced by transient mesoscale eddies within the ACC. A picture emerges of the Taylor column acting as a slow, steady blender, retaining the waters in the vicinity of the WSC for lengthy periods during which they can be subject to significant modification. A full regional float data set, bathymetric data, and a Southern Ocean state estimate are used to identify other potential sites for Taylor column formation. We find that they are likely to be sufficiently widespread to exert a significant influence on water mass modification and meridional fluxes across the southern edge of the ACC in this sector of the Southern Ocean.

Estimating carbonate parameters from hydrographic data for the intermediate and deep waters of the Southern Hemisphere oceans

Science.gov (United States)

Bostock, H. C.; Mikaloff Fletcher, S. E.; Williams, M. J. M.

2013-10-01

Using ocean carbon data from global datasets, we have developed several multiple linear regression (MLR) algorithms to estimate alkalinity and dissolved inorganic carbon (DIC) in the intermediate and deep waters of the Southern Hemisphere (south of 25° S) from only hydrographic data (temperature, salinity and dissolved oxygen). A Monte Carlo experiment was used to identify a potential density (σθ) of 27.5 as an optimal break point between the two regimes with different MLR algorithms. The algorithms provide a good estimate of DIC (R2=0.98) and alkalinity (R2=0.91), and excellent agreement for aragonite and calcite saturation states (R2=0.99). Combining the algorithms with the CSIRO Atlas of Regional Seas (CARS), we have mapped the calcite saturation horizon (CSH) and aragonite saturation horizon (ASH) for the Southern Ocean at a spatial resolution of 0.5°. These maps are more detailed and more consistent with the oceanography than the previously gridded GLODAP data. The high-resolution ASH map reveals a dramatic circumpolar shoaling at the polar front. North of 40° S the CSH is deepest in the Atlantic (~ 4000 m) and shallower in the Pacific Ocean (~ 2750 m), while the CSH sits between 3200 and 3400 m in the Indian Ocean. The uptake of anthropogenic carbon by the ocean will alter the relationships between DIC and hydrographic data in the intermediate and deep waters over time. Thus continued sampling will be required, and the MLR algorithms will need to be adjusted in the future to account for these changes.

Estimating carbonate parameters from hydrographic data for the intermediate and deep waters of the Southern Hemisphere oceans

Directory of Open Access Journals (Sweden)

H. C. Bostock

2013-10-01

Full Text Available Using ocean carbon data from global datasets, we have developed several multiple linear regression (MLR algorithms to estimate alkalinity and dissolved inorganic carbon (DIC in the intermediate and deep waters of the Southern Hemisphere (south of 25° S from only hydrographic data (temperature, salinity and dissolved oxygen. A Monte Carlo experiment was used to identify a potential density (σθ of 27.5 as an optimal break point between the two regimes with different MLR algorithms. The algorithms provide a good estimate of DIC (R2=0.98 and alkalinity (R2=0.91, and excellent agreement for aragonite and calcite saturation states (R2=0.99. Combining the algorithms with the CSIRO Atlas of Regional Seas (CARS, we have mapped the calcite saturation horizon (CSH and aragonite saturation horizon (ASH for the Southern Ocean at a spatial resolution of 0.5°. These maps are more detailed and more consistent with the oceanography than the previously gridded GLODAP data. The high-resolution ASH map reveals a dramatic circumpolar shoaling at the polar front. North of 40° S the CSH is deepest in the Atlantic (~ 4000 m and shallower in the Pacific Ocean (~ 2750 m, while the CSH sits between 3200 and 3400 m in the Indian Ocean. The uptake of anthropogenic carbon by the ocean will alter the relationships between DIC and hydrographic data in the intermediate and deep waters over time. Thus continued sampling will be required, and the MLR algorithms will need to be adjusted in the future to account for these changes.

High-frequency and meso-scale winter sea-ice variability in the Southern Ocean in a high-resolution global ocean model

Science.gov (United States)

Stössel, Achim; von Storch, Jin-Song; Notz, Dirk; Haak, Helmuth; Gerdes, Rüdiger

2018-03-01

This study is on high-frequency temporal variability (HFV) and meso-scale spatial variability (MSV) of winter sea-ice drift in the Southern Ocean simulated with a global high-resolution (0.1°) sea ice-ocean model. Hourly model output is used to distinguish MSV characteristics via patterns of mean kinetic energy (MKE) and turbulent kinetic energy (TKE) of ice drift, surface currents, and wind stress, and HFV characteristics via time series of raw variables and correlations. We find that (1) along the ice edge, the MSV of ice drift coincides with that of surface currents, in particular such due to ocean eddies; (2) along the coast, the MKE of ice drift is substantially larger than its TKE and coincides with the MKE of wind stress; (3) in the interior of the ice pack, the TKE of ice drift is larger than its MKE, mostly following the TKE pattern of wind stress; (4) the HFV of ice drift is dominated by weather events, and, in the absence of tidal currents, locally and to a much smaller degree by inertial oscillations; (5) along the ice edge, the curl of the ice drift is highly correlated with that of surface currents, mostly reflecting the impact of ocean eddies. Where ocean eddies occur and the ice is relatively thin, ice velocity is characterized by enhanced relative vorticity, largely matching that of surface currents. Along the ice edge, ocean eddies produce distinct ice filaments, the realism of which is largely confirmed by high-resolution satellite passive-microwave data.

Effects of long-term exposure to ocean acidification conditions on future southern Tanner crab (Chionoecetes bairdi) fisheries management from model studies (NCEI Accession 0157642)

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — This archival package contains model output data to understand the effect of ocean acidification on southern Tanner Crab. Maximum sustainable yield (MSY), maximum...

Diagnosing the leading mode of interdecadal covariability between the Indian Ocean sea surface temperature and summer precipitation in southern China

Science.gov (United States)

Liu, Jingpeng; Ren, Hong-Li; Li, Weijing; Zuo, Jinqing

2018-03-01

Precipitation in southern China during boreal summer (June to August) shows a substantial interdecadal variability on the timescale longer than 8 years. In this study, based on the analysis of singular value decomposition, we diagnose the leading mode of interdecadal covariability between the observational precipitation in southern China and the sea surface temperature (SST) in the Indian Ocean. Results indicate that there exist a remarkable southern China zonal dipole (SCZD) pattern of interdecadal variability of summer precipitation and an interdecadal Indian Ocean basin mode (ID-IOBM) of SST. It is found that the SCZD is evidently covaried with the ID-IOBM, which may induce anomalous inter-hemispheric vertical circulation and atmospheric Kelvin waves. During the warm phase of the ID-IOBM, an enhanced lower-level convergence and upper-level divergence exist over the tropical Indian Ocean, which is a typical Gill-Matsuno-type response to the SST warming. Meanwhile, the accompanied upper-level outflow anomalies further converge over the Indo-China peninsula, resulting in a lower-level anticyclone that contributes to reduction of the eastward moisture transport from the Bay of Bengal to the west part of southern China. In addition, the Kelvin wave-like pattern, as a response of the warm ID-IOBM phase, further induces the lower-level anticyclonic anomaly over the South China Sea-Philippines. Such an anticyclonic circulation is favorable for more water vapor transport from the East China Sea into the east part of southern China. Therefore, the joint effects of the anomalous inter-hemispheric vertical circulation and the Kelvin wave-like pattern associated with the ID-IOBM may eventually play a key role in generating the SCZD pattern.

Improved Chlorophyll-a Algorithm for the Satellite Ocean Color Data in the Northern Bering Sea and Southern Chukchi Sea

Science.gov (United States)

Lee, Sang Heon; Ryu, Jongseong; Park, Jung-woo; Lee, Dabin; Kwon, Jae-Il; Zhao, Jingping; Son, SeungHyun

2018-03-01

The Bering and Chukchi seas are an important conduit to the Arctic Ocean and are reported to be one of the most productive regions in the world's oceans in terms of high primary productivity that sustains large numbers of fishes, marine mammals, and sea birds as well as benthic animals. Climate-induced changes in primary production and production at higher trophic levels also have been observed in the northern Bering and Chukchi seas. Satellite ocean color observations could enable the monitoring of relatively long term patterns in chlorophyll-a (Chl-a) concentrations that would serve as an indicator of phytoplankton biomass. The performance of existing global and regional Chl-a algorithms for satellite ocean color data was investigated in the northeastern Bering Sea and southern Chukchi Sea using in situ optical measurements from the Healy 2007 cruise. The model-derived Chl-a data using the previous Chl-a algorithms present striking uncertainties regarding Chl-a concentrations-for example, overestimation in lower Chl-a concentrations or systematic overestimation in the northeastern Bering Sea and southern Chukchi Sea. Accordingly, a simple two band ratio (R rs(443)/R rs(555)) algorithm of Chl-a for the satellite ocean color data was devised for the northeastern Bering Sea and southern Chukchi Sea. The MODIS-derived Chl-a data from July 2002 to December 2014 were produced using the new Chl-a algorithm to investigate the seasonal and interannual variations of Chl-a in the northern Bering Sea and the southern Chukchi Sea. The seasonal distribution of Chl-a shows that the highest (spring bloom) Chl-a concentrations are in May and the lowest are in July in the overall area. Chl-a concentrations relatively decreased in June, particularly in the open ocean waters of the Bering Sea. The Chl-a concentrations start to increase again in August and become quite high in September. In October, Chl-a concentrations decreased in the western area of the Study area and the Alaskan

Correlation Lengths for Estimating the Large-Scale Carbon and Heat Content of the Southern Ocean

Science.gov (United States)

Mazloff, M. R.; Cornuelle, B. D.; Gille, S. T.; Verdy, A.

2018-02-01

The spatial correlation scales of oceanic dissolved inorganic carbon, heat content, and carbon and heat exchanges with the atmosphere are estimated from a realistic numerical simulation of the Southern Ocean. Biases in the model are assessed by comparing the simulated sea surface height and temperature scales to those derived from optimally interpolated satellite measurements. While these products do not resolve all ocean scales, they are representative of the climate scale variability we aim to estimate. Results show that constraining the carbon and heat inventory between 35°S and 70°S on time-scales longer than 90 days requires approximately 100 optimally spaced measurement platforms: approximately one platform every 20° longitude by 6° latitude. Carbon flux has slightly longer zonal scales, and requires a coverage of approximately 30° by 6°. Heat flux has much longer scales, and thus a platform distribution of approximately 90° by 10° would be sufficient. Fluxes, however, have significant subseasonal variability. For all fields, and especially fluxes, sustained measurements in time are required to prevent aliasing of the eddy signals into the longer climate scale signals. Our results imply a minimum of 100 biogeochemical-Argo floats are required to monitor the Southern Ocean carbon and heat content and air-sea exchanges on time-scales longer than 90 days. However, an estimate of formal mapping error using the current Argo array implies that in practice even an array of 600 floats (a nominal float density of about 1 every 7° longitude by 3° latitude) will result in nonnegligible uncertainty in estimating climate signals.

Interannual drivers of the seasonal cycle of CO2 in the Southern Ocean

Directory of Open Access Journals (Sweden)

L. Gregor

2018-04-01

Full Text Available Resolving and understanding the drivers of variability of CO2 in the Southern Ocean and its potential climate feedback is one of the major scientific challenges of the ocean-climate community. Here we use a regional approach on empirical estimates of pCO2 to understand the role that seasonal variability has in long-term CO2 changes in the Southern Ocean. Machine learning has become the preferred empirical modelling tool to interpolate time- and location-restricted ship measurements of pCO2. In this study we use an ensemble of three machine-learning products: support vector regression (SVR and random forest regression (RFR from Gregor et al. (2017, and the self-organising-map feed-forward neural network (SOM-FFN method from Landschützer et al. (2016. The interpolated estimates of ΔpCO2 are separated into nine regions in the Southern Ocean defined by basin (Indian, Pacific, and Atlantic and biomes (as defined by Fay and McKinley, 2014a. The regional approach shows that, while there is good agreement in the overall trend of the products, there are periods and regions where the confidence in estimated ΔpCO2 is low due to disagreement between the products. The regional breakdown of the data highlighted the seasonal decoupling of the modes for summer and winter interannual variability. Winter interannual variability had a longer mode of variability compared to summer, which varied on a 4–6-year timescale. We separate the analysis of the ΔpCO2 and its drivers into summer and winter. We find that understanding the variability of ΔpCO2 and its drivers on shorter timescales is critical to resolving the long-term variability of ΔpCO2. Results show that ΔpCO2 is rarely driven by thermodynamics during winter, but rather by mixing and stratification due to the stronger correlation of ΔpCO2 variability with mixed layer depth. Summer pCO2 variability is consistent with chlorophyll a variability, where higher concentrations of chlorophyll

Interannual drivers of the seasonal cycle of CO2 in the Southern Ocean

Science.gov (United States)

Gregor, Luke; Kok, Schalk; Monteiro, Pedro M. S.

2018-04-01

Resolving and understanding the drivers of variability of CO2 in the Southern Ocean and its potential climate feedback is one of the major scientific challenges of the ocean-climate community. Here we use a regional approach on empirical estimates of pCO2 to understand the role that seasonal variability has in long-term CO2 changes in the Southern Ocean. Machine learning has become the preferred empirical modelling tool to interpolate time- and location-restricted ship measurements of pCO2. In this study we use an ensemble of three machine-learning products: support vector regression (SVR) and random forest regression (RFR) from Gregor et al. (2017), and the self-organising-map feed-forward neural network (SOM-FFN) method from Landschützer et al. (2016). The interpolated estimates of ΔpCO2 are separated into nine regions in the Southern Ocean defined by basin (Indian, Pacific, and Atlantic) and biomes (as defined by Fay and McKinley, 2014a). The regional approach shows that, while there is good agreement in the overall trend of the products, there are periods and regions where the confidence in estimated ΔpCO2 is low due to disagreement between the products. The regional breakdown of the data highlighted the seasonal decoupling of the modes for summer and winter interannual variability. Winter interannual variability had a longer mode of variability compared to summer, which varied on a 4-6-year timescale. We separate the analysis of the ΔpCO2 and its drivers into summer and winter. We find that understanding the variability of ΔpCO2 and its drivers on shorter timescales is critical to resolving the long-term variability of ΔpCO2. Results show that ΔpCO2 is rarely driven by thermodynamics during winter, but rather by mixing and stratification due to the stronger correlation of ΔpCO2 variability with mixed layer depth. Summer pCO2 variability is consistent with chlorophyll a variability, where higher concentrations of chlorophyll a correspond with lower pCO2

Penguins as bioindicators of mercury contamination in the Southern Ocean: Birds from the Kerguelen Islands as a case study

International Nuclear Information System (INIS)

Carravieri, Alice; Bustamante, Paco; Churlaud, Carine; Cherel, Yves

2013-01-01

Seabirds have been used extensively as bioindicators of mercury (Hg) contamination in the marine environment, although information on flightless species like penguins remains limited. In order to assess the use of penguins as bioindicators of Hg contamination in subantarctic and Antarctic marine ecosystems, Hg concentrations were evaluated in the feathers of the four species that breed on the Kerguelen Islands in the southern Indian Ocean. Compared to other seabirds, adult Kerguelen penguins had low to moderate feather Hg concentrations, with an average ranging from 1.96 ± 0.41 μg g −1 dry weight in the southern rockhopper penguin to 5.85 ± 3.00 μg g −1 dry weight in the gentoo penguin. The species was a major determinant of Hg contamination, with feather Hg concentrations being lower in the oceanic species (king and crested penguins) than in the coastal one (gentoo penguin). In all species however, feather Hg concentrations were higher in adults than in chicks, reflecting the different periods of Hg bioaccumulation in the internal tissues of the two age classes. The relationship between adult penguin trophic ecology and Hg burdens was investigated using stable isotopes. Feeding habits (reflected by δ 15 N values) had a greater effect on adult feather Hg concentrations when compared to foraging habitats (reflected by δ 13 C values), indicating Hg biomagnification in Kerguelen neritic and oceanic waters. Dietary preferences were crucial in explaining individual feather Hg concentrations, as highlighted by intra-specific variation in Hg levels of gentoo penguins sampled at two different breeding sites of the archipelago. Penguins appear to reflect Hg bioavailability reliably in their foraging environment and could serve as efficient bioindicators of Hg contamination in the Southern Ocean on different spatial and temporal scales. - Highlights: • Hg contamination was evaluated in 4 species of penguins at the Kerguelen Islands. • Adults displayed

Penguins as bioindicators of mercury contamination in the Southern Ocean: Birds from the Kerguelen Islands as a case study

Energy Technology Data Exchange (ETDEWEB)

Carravieri, Alice, E-mail: carravieri@cebc.cnrs.fr [Centre d' Etudes Biologiques de Chizé, UPR 1934 du Centre National de la Recherche Scientifique, BP 14, 79360 Villiers-en-Bois (France); Littoral Environnement et Sociétés (LIENSs), UMRi 7266 CNRS-Université de la Rochelle, 2 rue Olympe de Gouges, 17000 La Rochelle (France); Bustamante, Paco, E-mail: pbustama@univ-lr.fr [Littoral Environnement et Sociétés (LIENSs), UMRi 7266 CNRS-Université de la Rochelle, 2 rue Olympe de Gouges, 17000 La Rochelle (France); Churlaud, Carine [Littoral Environnement et Sociétés (LIENSs), UMRi 7266 CNRS-Université de la Rochelle, 2 rue Olympe de Gouges, 17000 La Rochelle (France); Cherel, Yves [Centre d' Etudes Biologiques de Chizé, UPR 1934 du Centre National de la Recherche Scientifique, BP 14, 79360 Villiers-en-Bois (France)

2013-06-01

Seabirds have been used extensively as bioindicators of mercury (Hg) contamination in the marine environment, although information on flightless species like penguins remains limited. In order to assess the use of penguins as bioindicators of Hg contamination in subantarctic and Antarctic marine ecosystems, Hg concentrations were evaluated in the feathers of the four species that breed on the Kerguelen Islands in the southern Indian Ocean. Compared to other seabirds, adult Kerguelen penguins had low to moderate feather Hg concentrations, with an average ranging from 1.96 ± 0.41 μg g{sup −1} dry weight in the southern rockhopper penguin to 5.85 ± 3.00 μg g{sup −1} dry weight in the gentoo penguin. The species was a major determinant of Hg contamination, with feather Hg concentrations being lower in the oceanic species (king and crested penguins) than in the coastal one (gentoo penguin). In all species however, feather Hg concentrations were higher in adults than in chicks, reflecting the different periods of Hg bioaccumulation in the internal tissues of the two age classes. The relationship between adult penguin trophic ecology and Hg burdens was investigated using stable isotopes. Feeding habits (reflected by δ{sup 15}N values) had a greater effect on adult feather Hg concentrations when compared to foraging habitats (reflected by δ{sup 13}C values), indicating Hg biomagnification in Kerguelen neritic and oceanic waters. Dietary preferences were crucial in explaining individual feather Hg concentrations, as highlighted by intra-specific variation in Hg levels of gentoo penguins sampled at two different breeding sites of the archipelago. Penguins appear to reflect Hg bioavailability reliably in their foraging environment and could serve as efficient bioindicators of Hg contamination in the Southern Ocean on different spatial and temporal scales. - Highlights: • Hg contamination was evaluated in 4 species of penguins at the Kerguelen Islands. • Adults

Latitudinal exposure to DDTs, HCB, PCBs, PBDEs and DP in giant petrels (Macronectes spp.) across the Southern Ocean

Energy Technology Data Exchange (ETDEWEB)

Roscales, Jose L., E-mail: jlroscales@iqog.csic.es [Department of Instrumental Analysis and Environmental Chemistry, Institute of Organic Chemistry, CSIC (IQOG-CSIC), Juan de la Cierva 3, 28006 Madrid (Spain); González-Solís, Jacob; Zango, Laura [Institut de Recerca de la Biodiversitat (IRBio) and Department of Animal Biology, Universitat de Barcelona, Av Diagonal 643, 08028 Barcelona (Spain); Ryan, Peter G. [Percy FitzPatrick Institute, DST-NRF Centre of Excellence, University of Cape Town, Rondebosch 7701 (South Africa); Jiménez, Begoña [Department of Instrumental Analysis and Environmental Chemistry, Institute of Organic Chemistry, CSIC (IQOG-CSIC), Juan de la Cierva 3, 28006 Madrid (Spain)

2016-07-15

Studies on Persistent Organic Pollutants (POPs) in Antarctic wildlife are scarce, and usually limited to a single locality. As a result, wildlife exposure to POPs across the Southern Ocean is poorly understood. In this study, we report the differential exposure of the major southern ocean scavengers, the giant petrels, to POPs across a wide latitudinal gradient. Selected POPs (PCBs, HCB, DDTs, PBDEs) and related compounds, such as Dechlorane Plus (DP), were analyzed in plasma of southern giant petrels (Macronectes giganteus) breeding on Livingston (62°S 61°W, Antarctica), Marion (46°S 37°E, sub-Antarctic), and Gough (40°S 10°W, cool temperate) islands. Northern giant petrels (Macronectes halli) from Marion Island were also studied. Stable isotope ratios of C and N (δ{sup 13}C and δ{sup 15}N) were used as dietary tracers of the marine habitat and trophic level, respectively. Breeding locality was a major factor explaining petrel exposure to POPs compared with species and sex. Significant relationships between δ{sup 13}C values and POP burdens, at both inter- and intra-population levels, support latitudinal variations in feeding grounds as a key factor in explaining petrel pollutant burdens. Overall, pollutant levels in giant petrels decreased significantly with latitude, but the relative abundance (%) of the more volatile POPs increased towards Antarctica. DP was found at negligible levels compared with legacy POPs in Antarctic seabirds. Spatial POP patterns found in giant petrels match those predicted by global distribution models, and reinforce the hypothesis of atmospheric long-range transport as the main source of POPs in Antarctica. Our results confirm that wildlife movements out of the polar region markedly increase their exposure to POPs. Therefore, strategies for Antarctic wildlife conservation should consider spatial heterogeneity in exposure to marine pollution. Of particular relevance is the need to clarify the exposure of Antarctic predators to

Latitudinal exposure to DDTs, HCB, PCBs, PBDEs and DP in giant petrels (Macronectes spp.) across the Southern Ocean

International Nuclear Information System (INIS)

Roscales, Jose L.; González-Solís, Jacob; Zango, Laura; Ryan, Peter G.; Jiménez, Begoña

2016-01-01

Studies on Persistent Organic Pollutants (POPs) in Antarctic wildlife are scarce, and usually limited to a single locality. As a result, wildlife exposure to POPs across the Southern Ocean is poorly understood. In this study, we report the differential exposure of the major southern ocean scavengers, the giant petrels, to POPs across a wide latitudinal gradient. Selected POPs (PCBs, HCB, DDTs, PBDEs) and related compounds, such as Dechlorane Plus (DP), were analyzed in plasma of southern giant petrels (Macronectes giganteus) breeding on Livingston (62°S 61°W, Antarctica), Marion (46°S 37°E, sub-Antarctic), and Gough (40°S 10°W, cool temperate) islands. Northern giant petrels (Macronectes halli) from Marion Island were also studied. Stable isotope ratios of C and N (δ 13 C and δ 15 N) were used as dietary tracers of the marine habitat and trophic level, respectively. Breeding locality was a major factor explaining petrel exposure to POPs compared with species and sex. Significant relationships between δ 13 C values and POP burdens, at both inter- and intra-population levels, support latitudinal variations in feeding grounds as a key factor in explaining petrel pollutant burdens. Overall, pollutant levels in giant petrels decreased significantly with latitude, but the relative abundance (%) of the more volatile POPs increased towards Antarctica. DP was found at negligible levels compared with legacy POPs in Antarctic seabirds. Spatial POP patterns found in giant petrels match those predicted by global distribution models, and reinforce the hypothesis of atmospheric long-range transport as the main source of POPs in Antarctica. Our results confirm that wildlife movements out of the polar region markedly increase their exposure to POPs. Therefore, strategies for Antarctic wildlife conservation should consider spatial heterogeneity in exposure to marine pollution. Of particular relevance is the need to clarify the exposure of Antarctic predators to emerging

Dissolved inorganic carbon, alkalinity, temperature, salinity and other variables collected from discrete sample and profile observations using CTD, bottle and other instruments from POLARSTERN in the South Atlantic Ocean and Southern Oceans from 2007-11-28 to 2008-02-04 (NODC Accession 0108067)

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — NCEI Accession 0108067 includes chemical, discrete sample, physical and profile data collected from POLARSTERN in the South Atlantic Ocean and Southern Oceans (>...

Bioproductivity in the Southern Ocean since the last Interglacial - new high-resolution biogenic opal flux records from the Scotia Sea

Science.gov (United States)

Sprenk, D.; Weber, M. E.; Kuhn, G.; Rosén, P.; Röhling, H.-G.

2012-04-01

The Southern Ocean plays an important role in transferring CO2 via wind-induced upwelling from the deep sea to the atmosphere. It is therefore one of the key areas to study climate change. Bioproductivity in the Southern Ocean is mostly influenced by the extent of sea ice, upwelling of cold nutrient- and silica-rich water, and the availability of light. Biogenic opal (BSi) is a significant nutrient in the Southern Ocean, and according to recent investigations only marginally affected by preservation changes. It can therefore be used as bioproductivity proxy. Here we present several methods to determine BSi, discuss them and put the results into context with respect to regional bioproductivity changes in Southern Ocean during the last glacial cycle. We studied deep-sea sediment core sites MD07-3133 and MD07-3134 from the central Scotia Sea with extraordinary high sedimentation rates of up to 2.1 to 1.2 m/kyr, respectively covering the last 92.5 kyr. BSi leaching according to Müller & Schneider (1993) is very time-consuming and expensive, so we measured only 253 samples from large-amplitude variation core sections. In addition, we determined BSi using non-destructive measurements of sediment colour b*, wet-bulk density, and Ti/Si count ratios. Furthermore, we provide the first attempts to estimate BSi in marine sediment using Fourier transform infrared spectroscopy (FTIRS), a cost-efficient method, which requires only 11 mg of sediment. All estimation methods capture the main BSi trends, however FTIRS seems to be the most promising one. In the central Scotia Sea, south of the modern Antarctic Polar Front, the BSi flux reflects a relatively complicated glacial-to-interglacial pattern with large-amplitude, millennial-scale fluctuations in bioproductivity. During Antarctic Isotopic Maxima, BSi fluxes were generally increased. Lowest bioproductivity occur at the Last Glacial Maximum, while upwelling of mid-depth water was reduced, atmospheric CO2 low, and sea-ice cover

Winter habitat predictions of a key Southern Ocean predator, the Antarctic fur seal (Arctocephalus gazella)

Science.gov (United States)

Arthur, Benjamin; Hindell, Mark; Bester, Marthan; De Bruyn, P. J. Nico; Trathan, Phil; Goebel, Michael; Lea, Mary-Anne

2017-06-01

Quantification of the physical and biological environmental factors that influence the spatial distribution of higher trophic species is central to inform management and develop ecosystem models, particularly in light of ocean changes. We used tracking data from 184 female Antarctic fur seals (Arctocephalus gazella) to develop habitat models for three breeding colonies for the poorly studied Southern Ocean winter period. Models were used to identify and predict the broadly important winter foraging habitat and to elucidate the environmental factors influencing these areas. Model predictions closely matched observations and several core areas of foraging habitat were identified for each colony, with notable areas of inter-colony overlap suggesting shared productive foraging grounds. Seals displayed clear choice of foraging habitat, travelling through areas of presumably poorer quality to access habitats that likely offer an energetic advantage in terms of prey intake. The relationships between environmental predictors and foraging habitat varied between colonies, with the principal predictors being wind speed, sea surface temperature, chlorophyll a concentration, bathymetry and distance to the colony. The availability of core foraging areas was not consistent throughout the winter period. The habitat models developed in this study not only reveal the core foraging habitats of Antarctic fur seals from multiple colonies, but can facilitate the hindcasting of historical foraging habitats as well as novel predictions of important habitat for other major colonies currently lacking information of the at-sea distribution of this major Southern Ocean consumer.

Dissolved inorganic carbon, temperature, salinity and other variables collected from discrete sample and profile observations using CTD, bottle and other instruments from POLARSTERN in the South Atlantic Ocean and Southern Oceans from 1998-03-28 to 1998-05-23 (NODC Accession 0113595)

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — NCEI Accession 0113595 includes discrete sample and profile data collected from POLARSTERN in the South Atlantic Ocean and Southern Oceans (> 60 degrees South)...

Observations of frozen skin of southern ocean from multifrequency scanning microwave radiometer (MSMR) onboard oceansat - 1

Science.gov (United States)

Vyas, N.; Bhandari, S.; Dash, M.; Pandey, P.; Khare, N.

Encircling the Antarctic, Southern Ocean connects all the three oceans of the world with fastest current system found anywhere in the world. The region is thermally very stable and is covered with ice, which has a strong seasonal variability. The sea ice pulsates annually with seasonal migration varying from 4 million square kilometer to 20 million square kilometer during summer and winter respectively. This has strong influence on energy balance of the ocean-ice-atmosphere system, and hence on atmospheric general circulation affecting weather and climate. Sea ice also works as an insulator thus inhibiting the energy flux between ocean and atmosphere. It also influences the ecosystem of the southern ocean, which has rich fish resources with global economic values such as krill and tooth fish. During winter Krill survives on algae found at the under side of the sea ice. The southern ocean is known to have high nutrition but low concentration of chlorophyll-a, which is a proxy of the phytoplankton. It is now understood that iron is the limiting factor as has been shown by various iron fertilization experiments. Passive microwave radiometry from space has been extensively used for the study of sea ice types and concentration in the Arctic and the Antarctic regions. Since late 1970s, data from SMMR and SSM/I have been used to study trends in sea ice extent and area. We have further extended the above studies by using data from OCEANSAT - 1 MSMR. The data, acquired at 18 GHz (H) with 50 kilometer resolution and having a swath of 1360 kilometer and a repeat cycle of 2 days, was processed to generate the brightness temperature maps over the Antarctica for a period of 2 years and the results were analyzed in conjunction with those obtained earlier (since 1978) through the study of SMMR and SSM/I data. Besides strong seasonal variability, our analysis shows an increasing trend in the sea ice extent during the recent years and the rate appears to be accelerating contrary to

Biogeography in Cellana (Patellogastropoda, Nacellidae with Special Emphasis on the Relationships of Southern Hemisphere Oceanic Island Species.

Directory of Open Access Journals (Sweden)

Claudio A González-Wevar

Full Text Available Oceanic islands lacking connections to other land are extremely isolated from sources of potential colonists and have acquired their biota mainly through dispersal from geographically distant areas. Hence, isolated island biota constitutes interesting models to infer biogeographical mechanisms of dispersal, colonization, differentiation, and speciation. Limpets of the genus Cellana (Nacellidae: Patellogastropoda show limited dispersal capacity but are broadly distributed across the Indo-Pacific including many endemic species in isolated oceanic islands. Here, we examined main distributional patterns and geographic boundaries among Cellana lineages with special emphasis in the relationships of Southern Hemisphere oceanic islands species. Phylogenetic reconstructions based on mtDNA (COI recognized three main clades in Cellana including taxa from different provinces of the Indo-Pacific. Clear genetic discontinuities characterize the biogeography of Cellana and several lineages are associated to particular areas of the Indo-Pacific supporting the low dispersal capacity of the genus across recognized biogeographical barriers in the region. However, evolutionary relationships within Cellana suggest that long-distance dispersal processes have been common in the history of the genus and probably associated to the origin of the species in Hawaii and Juan Fernández Archipelago. Therefore, the presence of Cellana species in geographically distant Southern Hemisphere oceanic islands, such as the Juan Fernández Archipelago, suggests that long-distance dispersal mediated by rafting may have played an important role in the biogeography of the genus.

Biogeography in Cellana (Patellogastropoda, Nacellidae) with Special Emphasis on the Relationships of Southern Hemisphere Oceanic Island Species

Science.gov (United States)

Nakano, Tomoyuki; Palma, Alvaro; Poulin, Elie

2017-01-01

Oceanic islands lacking connections to other land are extremely isolated from sources of potential colonists and have acquired their biota mainly through dispersal from geographically distant areas. Hence, isolated island biota constitutes interesting models to infer biogeographical mechanisms of dispersal, colonization, differentiation, and speciation. Limpets of the genus Cellana (Nacellidae: Patellogastropoda) show limited dispersal capacity but are broadly distributed across the Indo-Pacific including many endemic species in isolated oceanic islands. Here, we examined main distributional patterns and geographic boundaries among Cellana lineages with special emphasis in the relationships of Southern Hemisphere oceanic islands species. Phylogenetic reconstructions based on mtDNA (COI) recognized three main clades in Cellana including taxa from different provinces of the Indo-Pacific. Clear genetic discontinuities characterize the biogeography of Cellana and several lineages are associated to particular areas of the Indo-Pacific supporting the low dispersal capacity of the genus across recognized biogeographical barriers in the region. However, evolutionary relationships within Cellana suggest that long-distance dispersal processes have been common in the history of the genus and probably associated to the origin of the species in Hawaii and Juan Fernández Archipelago. Therefore, the presence of Cellana species in geographically distant Southern Hemisphere oceanic islands, such as the Juan Fernández Archipelago, suggests that long-distance dispersal mediated by rafting may have played an important role in the biogeography of the genus. PMID:28099466

Dissolved inorganic carbon, alkalinity, temperature, salinity and other variables collected from discrete sample and profile observations using CTD, bottle and other instruments from MARION DUFRESNE in the Indian Ocean and Southern Oceans from 1996-02-20 to 1996-03-31 (NODC Accession 0115012)

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — NCEI Accession 0115012 includes discrete sample and profile data collected from MARION DUFRESNE in the Indian Ocean and Southern Oceans (> 60 degrees South) from...

Impact of increasing antarctic glacial freshwater release on regional sea-ice cover in the Southern Ocean

Science.gov (United States)

Merino, Nacho; Jourdain, Nicolas C.; Le Sommer, Julien; Goosse, Hugues; Mathiot, Pierre; Durand, Gael

2018-01-01

The sensitivity of Antarctic sea-ice to increasing glacial freshwater release into the Southern Ocean is studied in a series of 31-year ocean/sea-ice/iceberg model simulations. Glaciological estimates of ice-shelf melting and iceberg calving are used to better constrain the spatial distribution and magnitude of freshwater forcing around Antarctica. Two scenarios of glacial freshwater forcing have been designed to account for a decadal perturbation in glacial freshwater release to the Southern Ocean. For the first time, this perturbation explicitly takes into consideration the spatial distribution of changes in the volume of Antarctic ice shelves, which is found to be a key component of changes in freshwater release. In addition, glacial freshwater-induced changes in sea ice are compared to typical changes induced by the decadal evolution of atmospheric states. Our results show that, in general, the increase in glacial freshwater release increases Antarctic sea ice extent. But the response is opposite in some regions like the coastal Amundsen Sea, implying that distinct physical mechanisms are involved in the response. We also show that changes in freshwater forcing may induce large changes in sea-ice thickness, explaining about one half of the total change due to the combination of atmospheric and freshwater changes. The regional contrasts in our results suggest a need for improving the representation of freshwater sources and their evolution in climate models.

Iron fertilization and the structure of planktonic communities in high nutrient regions of the Southern Ocean

Science.gov (United States)

Quéguiner, Bernard

2013-06-01

In this review article, plankton community structure observations are analyzed both for artificial iron fertilization experiments and also for experiments dedicated to the study of naturally iron-fertilized systems in the Atlantic, Indian and Pacific sectors of the Southern Ocean in the POOZ (Permanently Open Ocean Zone) and the PFZ (Polar Frontal Zone). Observations made in natural systems are combined with those from artificially perturbed systems, in order to evaluate the seasonal evolution of pelagic communities, taking into account controlling factors related to the life cycles and the ecophysiology of dominant organisms. The analysis considers several types of planktonic communities, including both autotrophs and heterotrophs. These communities are spatially segregated owing to different life strategies. A conceptual general scheme is proposed to account for these observations and their variability, regardless of experiment type. Diatoms can be separated into 2 groups: Group 1 has slightly silicified fast growing cells that are homogeneously distributed in the surface mixed layer, and Group 2 has strongly silicified slowly growing cells within discrete layers. During the growth season, Group 1 diatoms show a typical seasonal succession of dominant species, within time windows of development that are conditioned by physical factors (light and temperature) as well as endogenous specific rhythms (internal clock), and biomass accumulation is controlled by the availability of nutrients. Group 1 diatoms are not directly grazed by mesozooplankton which is fed by protozooplankton, linking the microbial food web to higher trophic levels. Instead, successive dominant species of Group 1 are degraded via bacterial activity at the end of their growth season. Organic detritus fragments feed protozooplankton and mesozooplankton. The effective silicon pump leads to the progressive disappearance of silicic acid in surface waters. In contrast, Group 2 is resistant to grazing

CDOM Sources and Photobleaching Control Quantum Yields for Oceanic DMS Photolysis

KAUST Repository

Galí, Martí

2016-11-14

Photolysis is a major removal pathway for the biogenic gas dimethylsulfide (DMS) in the surface ocean. Here we tested the hypothesis that apparent quantum yields (AQY) for DMS photolysis varied according to the quantity and quality of its photosensitizers, chiefly chromophoric dissolved organic matter (CDOM) and nitrate. AQY compiled from the literature and unpublished studies ranged across 3 orders of magnitude at the 330 nm reference wavelength. The smallest AQY(330) were observed in coastal waters receiving major riverine inputs of terrestrial CDOM (0.06-0.5 m3 (mol quanta)-1). In open-ocean waters, AQY(330) generally ranged between 1 and 10 m3 (mol quanta)-1. The largest AQY(330), up to 34 m3 (mol quanta)-1), were seen in the Southern Ocean potentially associated with upwelling. Despite the large AQY variability, daily photolysis rate constants at the sea surface spanned a smaller range (0.04-3.7 d-1), mainly because of the inverse relationship between CDOM absorption and AQY. Comparison of AQY(330) with CDOM spectral signatures suggests there is an interplay between CDOM origin (terrestrial versus marine) and photobleaching that controls variations in AQYs, with a secondary role for nitrate. Our results can be used for regional or large-scale assessment of DMS photolysis rates in future studies.

CDOM Sources and Photobleaching Control Quantum Yields for Oceanic DMS Photolysis.

Science.gov (United States)

Galí, Martí; Kieber, David J; Romera-Castillo, Cristina; Kinsey, Joanna D; Devred, Emmanuel; Pérez, Gonzalo L; Westby, George R; Marrasé, Cèlia; Babin, Marcel; Levasseur, Maurice; Duarte, Carlos M; Agustí, Susana; Simó, Rafel

2016-12-20

Photolysis is a major removal pathway for the biogenic gas dimethylsulfide (DMS) in the surface ocean. Here we tested the hypothesis that apparent quantum yields (AQY) for DMS photolysis varied according to the quantity and quality of its photosensitizers, chiefly chromophoric dissolved organic matter (CDOM) and nitrate. AQY compiled from the literature and unpublished studies ranged across 3 orders of magnitude at the 330 nm reference wavelength. The smallest AQY(330) were observed in coastal waters receiving major riverine inputs of terrestrial CDOM (0.06-0.5 m 3 (mol quanta) -1 ). In open-ocean waters, AQY(330) generally ranged between 1 and 10 m 3 (mol quanta) -1 . The largest AQY(330), up to 34 m 3 (mol quanta) -1 ), were seen in the Southern Ocean potentially associated with upwelling. Despite the large AQY variability, daily photolysis rate constants at the sea surface spanned a smaller range (0.04-3.7 d -1 ), mainly because of the inverse relationship between CDOM absorption and AQY. Comparison of AQY(330) with CDOM spectral signatures suggests there is an interplay between CDOM origin (terrestrial versus marine) and photobleaching that controls variations in AQYs, with a secondary role for nitrate. Our results can be used for regional or large-scale assessment of DMS photolysis rates in future studies.

Saccharides enhance iron bioavailability to Southern Ocean phytoplankton

NARCIS (Netherlands)

Hassler, C.S.; Schoemann, V.; Nichols, C.M.; Butler, E.C.V.; Boyd, P.W.; Nichols, C.M.

2011-01-01

Iron limits primary productivity in vast regions of the ocean. Given that marine phytoplankton contribute up to 40% of global biological carbon fixation, it is important to understand what parameters control the availability of iron (iron bioavailability) to these organisms. Most studies on iron

Low dissolved Fe and the absence of diatom blooms in remote Pacific waters of the Southern Ocean

NARCIS (Netherlands)

de Baar, Hein J.W.; de Jong, Jeroen T.M.; Nolting, Rob F.; Timmermans, Klaas R.; van Leeuwe, Maria A.; Bathmann, U.; Rutgers van der Loeff, Michiel; Sildam, Jüri

The remote waters of the Pacific region of the Southern Ocean are the furthest away from any upstream and upwind continental Fe sources. This prime area for expecting Fe limitation of the plankton ecosystem was studied (March-April 1995) along a north-south transect at similar to 89 degrees W. At

Late Quaternary Deep Stratification-Climate Coupling in the Southern Ocean : Implications for Changes in Abyssal Carbon Storage

NARCIS (Netherlands)

Wu, Li; Wang, Rujian; Xiao, Wenshen; Krijgsman, Wout|info:eu-repo/dai/nl/148529763; Li, Qianyu; Ge, Shulan; Ma, Tong

The Southern Ocean plays an important role in modulating Pleistocene atmospheric CO2 concentrations, but the underlying mechanisms are not yet fully understood. Here, we report the laser grain-size distribution and Mn geochemical data of a 523 kyr-long sediment record (core ANT30/P1-02 off Prydz

Copepod faecal pellet transfer through the meso- and bathypelagic layers in the Southern Ocean in spring

Science.gov (United States)

Belcher, Anna; Manno, Clara; Ward, Peter; Henson, Stephanie A.; Sanders, Richard; Tarling, Geraint A.

2017-03-01

The faecal pellets (FPs) of zooplankton can be important vehicles for the transfer of particulate organic carbon (POC) to the deep ocean, often making large contributions to carbon sequestration. However, the routes by which these FPs reach the deep ocean have yet to be fully resolved. We address this by comparing estimates of copepod FP production to measurements of copepod FP size, shape, and number in the upper mesopelagic (175-205 m) using Marine Snow Catchers, and in the bathypelagic using sediment traps (1500-2000 m). The study is focussed on the Scotia Sea, which contains some of the most productive regions in the Southern Ocean, where epipelagic FP production is likely to be high. We found that, although the size distribution of the copepod community suggests that high numbers of small FPs are produced in the epipelagic, small FPs are rare in the deeper layers, implying that they are not transferred efficiently to depth. Consequently, small FPs make only a minor contribution to FP fluxes in the meso- and bathypelagic, particularly in terms of carbon. The dominant FPs in the upper mesopelagic were cylindrical and elliptical, while ovoid FPs were dominant in the bathypelagic. The change in FP morphology, as well as size distribution, points to the repacking of surface FPs in the mesopelagic and in situ production in the lower meso- and bathypelagic, which may be augmented by inputs of FPs via zooplankton vertical migrations. The flux of carbon to the deeper layers within the Southern Ocean is therefore strongly modulated by meso- and bathypelagic zooplankton, meaning that the community structure in these zones has a major impact on the efficiency of FP transfer to depth.

Partial pressure (or fugacity) of carbon dioxide, dissolved inorganic carbon, pH, alkalinity, temperature, salinity and other variables collected from discrete sample and profile observations using Alkalinity titrator, CTD and other instruments from NATHANIEL B. PALMER in the South Atlantic Ocean, South Pacific Ocean and Southern Oceans from 2011-02-19 to 2011-04-23 (NODC Accession 0109933)

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — NCEI Accession 0109933 includes discrete sample and profile data collected from NATHANIEL B. PALMER in the South Atlantic Ocean, South Pacific Ocean and Southern...

Dissolved inorganic carbon, alkalinity, temperature, salinity and other variables collected from discrete sample and profile observations using Alkalinity titrator, CTD and other instruments from POLARSTERN in the South Atlantic Ocean and Southern Oceans from 2006-08-25 to 2006-10-29 (NODC Accession 0108157)

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — NCEI Accession 0108157 includes chemical, discrete sample, physical and profile data collected from POLARSTERN in the South Atlantic Ocean and Southern Oceans (>...

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...

Surface water carbon dioxide in the southwest Indian sector of the Southern Ocean

International Nuclear Information System (INIS)

Metzl, N.; Brunet, C.; Poisson, A.

1991-01-01

Measurements of partial pressure of carbon dioxide (pCO 2 ), total dissolved inorganic carbon (TCO 2 ), total alkalinity (TA) and chlorophyll a (Chl a) have been made in surface water in the southwestern Indian sector of the Southern Ocean (20-85 degE) in the austral summer (INDIVAT V cruise, January-February 1987). Between Antarctica and Africa, pCO 2 distribution was linked to the oceanic frontal zones and Chl a variations. The pCO 2 spatial structure was very close to that explored in summer 1967 in the same region but the pCO 2 differences between the ocean and the atmosphere were smaller in 1987 than 20 years ago. At all latitudes strongly contrasting surface pCO 2 characteristics were found between eastern (around 80 degE) and western (around 25 degE) regions; CO 2 sources were mainly in the west and CO 2 sinks in the east. South of 60 degS, the contrast could be due to biological activity. Between 60 degS and the Antarctic Polar Front, intensification of upwelling might be responsible for the higher pC) 2 values in the west.37 refs.; 4 figs

Partial pressure (or fugacity) of carbon dioxide, salinity and other variables collected from Surface underway observations using Carbon dioxide (CO2) gas analyzer, Shower head chamber equilibrator for autonomous carbon dioxide (CO2) measurement and other instruments from LAURENCE M. GOULD in the South Atlantic Ocean, South Pacific Ocean and Southern Oceans from 2007-01-02 to 2007-12-20 (NCEI Accession 0148773)

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — NCEI Accession 0148773 includes Surface underway data collected from LAURENCE M. GOULD in the South Atlantic Ocean, South Pacific Ocean and Southern Oceans (> 60...

Partial pressure (or fugacity) of carbon dioxide, salinity and other variables collected from Surface underway observations using Carbon dioxide (CO2) gas analyzer, Shower head chamber equilibrator for autonomous carbon dioxide (CO2) measurement and other instruments from LAURENCE M. GOULD in the South Atlantic Ocean, South Pacific Ocean and Southern Oceans from 2011-12-30 to 2012-12-23 (NCEI Accession 0148774)

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — NCEI Accession 0148774 includes Surface underway data collected from LAURENCE M. GOULD in the South Atlantic Ocean, South Pacific Ocean and Southern Oceans (> 60...

Partial pressure (or fugacity) of carbon dioxide, salinity and other variables collected from Surface underway observations using Carbon dioxide (CO2) gas analyzer, Shower head chamber equilibrator for autonomous carbon dioxide (CO2) measurement and other instruments from LAURENCE M. GOULD in the South Atlantic Ocean, South Pacific Ocean and Southern Oceans from 2007-12-31 to 2008-10-27 (NCEI Accession 0148763)

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — NCEI Accession 0148763 includes Surface underway data collected from LAURENCE M. GOULD in the South Atlantic Ocean, South Pacific Ocean and Southern Oceans (> 60...

Partial pressure (or fugacity) of carbon dioxide, salinity and other variables collected from Surface underway observations using Carbon dioxide (CO2) gas analyzer, Shower head chamber equilibrator for autonomous carbon dioxide (CO2) measurement and other instruments from LAURENCE M. GOULD in the South Atlantic Ocean, South Pacific Ocean and Southern Oceans from 2011-01-02 to 2011-12-18 (NCEI Accession 0148767)

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — NCEI Accession 0148767 includes Surface underway data collected from LAURENCE M. GOULD in the South Atlantic Ocean, South Pacific Ocean and Southern Oceans (> 60...

Partial pressure (or fugacity) of carbon dioxide, salinity and other variables collected from Surface underway observations using Carbon dioxide (CO2) gas analyzer, Shower head chamber equilibrator for autonomous carbon dioxide (CO2) measurement and other instruments from LAURENCE M. GOULD in the South Atlantic Ocean, South Pacific Ocean and Southern Oceans from 2006-01-01 to 2006-12-27 (NCEI Accession 0144535)

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — NCEI Accession 0144535 includes Surface underway data collected from LAURENCE M. GOULD in the South Atlantic Ocean, South Pacific Ocean and Southern Oceans (> 60...

Partial pressure (or fugacity) of carbon dioxide, salinity and other variables collected from Surface underway observations using Carbon dioxide (CO2) gas analyzer, Shower head chamber equilibrator for autonomous carbon dioxide (CO2) measurement and other instruments from LAURENCE M. GOULD in the South Atlantic Ocean, South Pacific Ocean and Southern Oceans from 2014-12-30 to 2015-07-01 (NCEI Accession 0144343)

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — NCEI Accession 0144343 includes Surface underway data collected from LAURENCE M. GOULD in the South Atlantic Ocean, South Pacific Ocean and Southern Oceans (> 60...

Partial pressure (or fugacity) of carbon dioxide, salinity and other variables collected from Surface underway observations using Carbon dioxide (CO2) gas analyzer, Shower head chamber equilibrator for autonomous carbon dioxide (CO2) measurement and other instruments from LAURENCE M. GOULD in the South Atlantic Ocean, South Pacific Ocean and Southern Oceans from 2011-01-02 to 2011-12-19 (NCEI Accession 0144354)

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — NCEI Accession 0144354 includes Surface underway data collected from LAURENCE M. GOULD in the South Atlantic Ocean, South Pacific Ocean and Southern Oceans (> 60...

Partial pressure (or fugacity) of carbon dioxide, salinity and other variables collected from Surface underway observations using Carbon dioxide (CO2) gas analyzer, Shower head chamber equilibrator for autonomous carbon dioxide (CO2) measurement and other instruments from LAURENCE M. GOULD in the South Atlantic Ocean, South Pacific Ocean and Southern Oceans from 2007-12-30 to 2008-10-28 (NCEI Accession 0144348)

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — NCEI Accession 0144348 includes Surface underway data collected from LAURENCE M. GOULD in the South Atlantic Ocean, South Pacific Ocean and Southern Oceans (> 60...

Partial pressure (or fugacity) of carbon dioxide, salinity and other variables collected from Surface underway observations using Carbon dioxide (CO2) gas analyzer, Shower head chamber equilibrator for autonomous carbon dioxide (CO2) measurement and other instruments from LAURENCE M. GOULD in the South Atlantic Ocean, South Pacific Ocean and Southern Oceans from 2007-01-02 to 2007-12-22 (NCEI Accession 0144528)

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — NCEI Accession 0144528 includes Surface underway data collected from LAURENCE M. GOULD in the South Atlantic Ocean, South Pacific Ocean and Southern Oceans (> 60...

Partial pressure (or fugacity) of carbon dioxide, salinity and other variables collected from Surface underway observations using Carbon dioxide (CO2) gas analyzer, Shower head chamber equilibrator for autonomous carbon dioxide (CO2) measurement and other instruments from LAURENCE M. GOULD in the South Atlantic Ocean, South Pacific Ocean and Southern Oceans from 2002-03-07 to 2002-12-23 (NCEI Accession 0144356)

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — NCEI Accession 0144356 includes Surface underway data collected from LAURENCE M. GOULD in the South Atlantic Ocean, South Pacific Ocean and Southern Oceans (> 60...

Partial pressure (or fugacity) of carbon dioxide, salinity and other variables collected from Surface underway observations using Carbon dioxide (CO2) gas analyzer, Shower head chamber equilibrator for autonomous carbon dioxide (CO2) measurement and other instruments from LAURENCE M. GOULD in the South Atlantic Ocean, South Pacific Ocean and Southern Oceans from 2011-12-30 to 2012-12-24 (NCEI Accession 0144349)

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — NCEI Accession 0144349 includes Surface underway data collected from LAURENCE M. GOULD in the South Atlantic Ocean, South Pacific Ocean and Southern Oceans (> 60...

Partial pressure (or fugacity) of carbon dioxide, salinity and other variables collected from Surface underway observations using Carbon dioxide (CO2) gas analyzer, Shower head chamber equilibrator for autonomous carbon dioxide (CO2) measurement and other instruments from LAURENCE M. GOULD in the South Atlantic Ocean, South Pacific Ocean and Southern Oceans from 2013-12-31 to 2014-12-20 (NCEI Accession 0144532)

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — NCEI Accession 0144532 includes Surface underway data collected from LAURENCE M. GOULD in the South Atlantic Ocean, South Pacific Ocean and Southern Oceans (> 60...

Partial pressure (or fugacity) of carbon dioxide, salinity and other variables collected from Surface underway observations using Carbon dioxide (CO2) gas analyzer, Shower head chamber equilibrator for autonomous carbon dioxide (CO2) measurement and other instruments from LAURENCE M. GOULD in the South Atlantic Ocean, South Pacific Ocean and Southern Oceans from 2006-01-02 to 2006-12-26 (NCEI Accession 0148764)

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — NCEI Accession 0148764 includes Surface underway data collected from LAURENCE M. GOULD in the South Atlantic Ocean, South Pacific Ocean and Southern Oceans (> 60...

Partial pressure (or fugacity) of carbon dioxide, salinity and other variables collected from Surface underway observations using Carbon dioxide (CO2) gas analyzer, Shower head chamber equilibrator for autonomous carbon dioxide (CO2) measurement and other instruments from LAURENCE M. GOULD in the South Atlantic Ocean, South Pacific Ocean and Southern Oceans from 2002-12-29 to 2003-11-30 (NCEI Accession 0144351)

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — NCEI Accession 0144351 includes Surface underway data collected from LAURENCE M. GOULD in the South Atlantic Ocean, South Pacific Ocean and Southern Oceans (> 60...

Partial pressure (or fugacity) of carbon dioxide, salinity and other variables collected from Surface underway observations using Carbon dioxide (CO2) gas analyzer, Shower head chamber equilibrator for autonomous carbon dioxide (CO2) measurement and other instruments from LAURENCE M. GOULD in the South Atlantic Ocean, South Pacific Ocean and Southern Oceans from 2012-12-31 to 2013-11-15 (NCEI Accession 0144529)

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — NCEI Accession 0144529 includes Surface underway data collected from LAURENCE M. GOULD in the South Atlantic Ocean, South Pacific Ocean and Southern Oceans (> 60...

Partial pressure (or fugacity) of carbon dioxide, salinity and other variables collected from Surface underway observations using Carbon dioxide (CO2) gas analyzer, Shower head chamber equilibrator for autonomous carbon dioxide (CO2) measurement and other instruments from LAURENCE M. GOULD in the South Atlantic Ocean, South Pacific Ocean and Southern Oceans from 2002-03-23 to 2002-12-23 (NCEI Accession 0148766)

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — NCEI Accession 0148766 includes Surface underway data collected from LAURENCE M. GOULD in the South Atlantic Ocean, South Pacific Ocean and Southern Oceans (> 60...

Partial pressure (or fugacity) of carbon dioxide, salinity and other variables collected from Surface underway observations using Carbon dioxide (CO2) gas analyzer, Shower head chamber equilibrator for autonomous carbon dioxide (CO2) measurement and other instruments from LAURENCE M. GOULD in the South Atlantic Ocean, South Pacific Ocean and Southern Oceans from 2014-01-01 to 2014-12-20 (NCEI Accession 0145200)

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — NCEI Accession 0145200 includes Surface underway data collected from LAURENCE M. GOULD in the South Atlantic Ocean, South Pacific Ocean and Southern Oceans (> 60...

Partial pressure (or fugacity) of carbon dioxide, salinity and other variables collected from Surface underway observations using Carbon dioxide (CO2) gas analyzer, Shower head chamber equilibrator for autonomous carbon dioxide (CO2) measurement and other instruments from LAURENCE M. GOULD in the South Atlantic Ocean, South Pacific Ocean and Southern Oceans from 2003-01-01 to 2003-12-29 (NCEI Accession 0148770)

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — NCEI Accession 0148770 includes Surface underway data collected from LAURENCE M. GOULD in the South Atlantic Ocean, South Pacific Ocean and Southern Oceans (> 60...

Partial pressure (or fugacity) of carbon dioxide, salinity and other variables collected from Surface underway observations using Carbon dioxide (CO2) gas analyzer, Shower head chamber equilibrator for autonomous carbon dioxide (CO2) measurement and other instruments from LAURENCE M. GOULD in the South Atlantic Ocean, South Pacific Ocean and Southern Oceans from 2010-01-01 to 2011-12-19 (NCEI Accession 0148765)

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — NCEI Accession 0148765 includes Surface underway data collected from LAURENCE M. GOULD in the South Atlantic Ocean, South Pacific Ocean and Southern Oceans (> 60...

Reconstructing the Mineralogy and Bioavailability of Dust-Borne Iron Deposited to the Southern Ocean through the Last Glacial Cycle

Science.gov (United States)

Shoenfelt, E. M.; Winckler, G.; Lamy, F.; Bostick, B. C.

2017-12-01

The iron (Fe) in dust deposited to the Fe-limited Southern Ocean plays an important role in ocean biogeochemistry and global climate. For instance, increases in dust-borne Fe deposition in the subantarctic Southern Ocean have been linked to increases in productivity and part of the CO2 drawdown of the last glacial cycle [1]. Notably, bioavailable Fe impacts productivity rather than total Fe. While it has long been understood that Fe mineralogy impacts Fe bioavailability in general, our understanding of the mineralogy of Fe in dust in specific is limited to that in modern dust sources. Reduced mineral Fe in dust has been shown to be more bioavailable than oxidized mineral iron, as it is more readily dissolved [2], and it is more easily utilized directly by a model diatom [3]. Our previous work focusing on South American dust sources shows that glacial activity is associated with higher Fe(II) fractions in dust-borne minerals, due to the physical weathering of Fe(II)-rich silicates in bedrock [3]. Thus, we hypothesize that there were higher Fe(II) fractions in dust deposited during cold glacial periods where ice sheets were more widespread. Using synchrotron-based X-ray absorption spectroscopy, we have reconstructed the mineralogy of Fe deposited to Southern Ocean sediment cores from the subantarctic South Atlantic (TN057-6/ODP Site 1090) and South Pacific (PS7/56-1) through the last glacial cycle, creating the first paleorecord of Fe mineralogy and its associated bioavailability. During cold glacial periods there is a higher fraction of reduced Fe - in the form of Fe(II) silicates - deposited to the sediments compared to warm interglacial periods. Thus, Fe(II) content is directly correlated with dust input. The presence of Fe(II) silicates rather than products of diagenesis such as pyrite suggests that these Fe(II) minerals are physically weathered from bedrock and preserved rather than produced in the sediment. This result suggests that not only was there more dust

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 South Atlantic Ocean and Southern Oceans from 2005-01-22 to 2005-04-06 (NODC Accession 0108100)

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — NCEI Accession 0108100 includes discrete sample and profile data collected from POLARSTERN in the South Atlantic Ocean and Southern Oceans (> 60 degrees South)...

Dissolved inorganic carbon, alkalinity, temperature, salinity and other variables collected from discrete sample and profile observations using Alkalinity titrator, CTD and other instruments from POLARSTERN in the South Atlantic Ocean and Southern Oceans from 2008-02-10 to 2008-04-16 (NODC Accession 0108154)

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — NCEI Accession 0108154 includes discrete sample and profile data collected from POLARSTERN in the South Atlantic Ocean and Southern Oceans (> 60 degrees South)...

Dissolved inorganic carbon, alkalinity, temperature, salinity and other variables collected from discrete sample and profile observations using Alkalinity titrator, CTD and other instruments from AURORA AUSTRALIS in the Indian Ocean and Southern Oceans from 2006-01-02 to 2006-03-12 (NODC Accession 0109922)

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — NCEI Accession 0109922 includes chemical, discrete sample, optical, physical and profile data collected from AURORA AUSTRALIS in the Indian Ocean and Southern Oceans...

Dissolved inorganic carbon, alkalinity, temperature, salinity and other variables collected from discrete sample and profile observations using Alkalinity titrator, CTD and other instruments from unknown platforms in the South Pacific Ocean and Southern Oceans from 2010-12-28 to 2014-02-21 (NCEI Accession 0160574)

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — NCEI Accession 0160574 includes chemical, discrete sample, physical and profile data collected from unknown platforms in the South Pacific Ocean and Southern Oceans...

Dissolved inorganic carbon, alkalinity, temperature, salinity and other variables collected from discrete sample and profile observations using CTD, bottle and other instruments from STENA ARCTICA in the South Atlantic Ocean and Southern Oceans from 1989-02-14 to 1989-03-17 (NODC Accession 0113893)

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — NCEI Accession 0113893 includes chemical, discrete sample, physical and profile data collected from STENA ARCTICA in the South Atlantic Ocean and Southern Oceans...

Penguins as bioindicators of mercury contamination in the Southern Ocean: birds from the Kerguelen Islands as a case study.

Science.gov (United States)

Carravieri, Alice; Bustamante, Paco; Churlaud, Carine; Cherel, Yves

2013-06-01

Seabirds have been used extensively as bioindicators of mercury (Hg) contamination in the marine environment, although information on flightless species like penguins remains limited. In order to assess the use of penguins as bioindicators of Hg contamination in subantarctic and Antarctic marine ecosystems, Hg concentrations were evaluated in the feathers of the four species that breed on the Kerguelen Islands in the southern Indian Ocean. Compared to other seabirds, adult Kerguelen penguins had low to moderate feather Hg concentrations, with an average ranging from 1.96 ± 0.41 μgg(-1) dry weight in the southern rockhopper penguin to 5.85 ± 3.00 μg g(-1) dry weight in the gentoo penguin. The species was a major determinant of Hg contamination, with feather Hg concentrations being lower in the oceanic species (king and crested penguins) than in the coastal one (gentoo penguin). In all species however, feather Hg concentrations were higher in adults than in chicks, reflecting the different periods of Hg bioaccumulation in the internal tissues of the two age classes. The relationship between adult penguin trophic ecology and Hg burdens was investigated using stable isotopes. Feeding habits (reflected by δ(15)N values) had a greater effect on adult feather Hg concentrations when compared to foraging habitats (reflected by δ(13)C values), indicating Hg biomagnification in Kerguelen neritic and oceanic waters. Dietary preferences were crucial in explaining individual feather Hg concentrations, as highlighted by intra-specific variation in Hg levels of gentoo penguins sampled at two different breeding sites of the archipelago. Penguins appear to reflect Hg bioavailability reliably in their foraging environment and could serve as efficient bioindicators of Hg contamination in the Southern Ocean on different spatial and temporal scales. Copyright © 2013 Elsevier B.V. All rights reserved.

Dissolved inorganic carbon, alkalinity, temperature, salinity and other variables collected from discrete sample and profile observations using Alkalinity titrator, CTD and other instruments from AURORA AUSTRALIS in the Indian Ocean and Southern Oceans from 2004-12-23 to 2005-02-17 (NODC Accession 0108076)

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — NCEI Accession 0108076 includes discrete sample and profile data collected from AURORA AUSTRALIS in the Indian Ocean and Southern Oceans (> 60 degrees South) from...

Dissolved inorganic carbon, alkalinity, temperature, salinity and other variables collected from discrete sample and profile observations using Alkalinity titrator, CTD and other instruments from ROGER REVELLE in the Indian Ocean and Southern Oceans from 2007-02-04 to 2007-03-17 (NODC Accession 0108119)

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — NCEI Accession 0108119 includes discrete sample and profile data collected from ROGER REVELLE in the Indian Ocean and Southern Oceans (> 60 degrees South) from...

Dissolved inorganic carbon, alkalinity, temperature, salinity and other variables collected from discrete sample and profile observations using Alkalinity titrator, CTD and other instruments from ROGER REVELLE in the South Pacific Ocean and Southern Oceans from 2005-01-09 to 2005-02-19 (NODC Accession 0108095)

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — NCEI Accession 0108095 includes discrete sample and profile data collected from ROGER REVELLE in the South Pacific Ocean and Southern Oceans (> 60 degrees South)...

The conservative behavior of dissolved organic carbon in surface waters of the southern Chukchi Sea, Arctic Ocean, during early summer.

Science.gov (United States)

Tanaka, Kazuki; Takesue, Nobuyuki; Nishioka, Jun; Kondo, Yoshiko; Ooki, Atsushi; Kuma, Kenshi; Hirawake, Toru; Yamashita, Youhei

2016-09-23

The spatial distribution of dissolved organic carbon (DOC) concentrations and the optical properties of dissolved organic matter (DOM) determined by ultraviolet-visible absorbance and fluorescence spectroscopy were measured in surface waters of the southern Chukchi Sea, western Arctic Ocean, during the early summer of 2013. Neither the DOC concentration nor the optical parameters of the DOM correlated with salinity. Principal component analysis using the DOM optical parameters clearly separated the DOM sources. A significant linear relationship was evident between the DOC and the principal component score for specific water masses, indicating that a high DOC level was related to a terrigenous source, whereas a low DOC level was related to a marine source. Relationships between the DOC and the principal component scores of the surface waters of the southern Chukchi Sea implied that the major factor controlling the distribution of DOC concentrations was the mixing of plural water masses rather than local production and degradation.

Zooplankton studies with special reference to krill Euphausia superba Dana from fishing area 58 of Indian Ocean sector in Southern Ocean

Digital Repository Service at National Institute of Oceanography (India)

Rathod, V.

from 16 stations du r- ing the FIKEX (December 1995 to March 1996) of FORV Sagar Sampada to the Indian sector of the Southern Ocean, covering within the geographical limits of latitude 58 ?00 minute to 61 ?17 minuteS and longitude 30 ?00 minute....22 to 8.03 ml 1 ? 1 ( x ? =7.68 ? 0.24). Zooplankton biomass values fluctuated widely du ring the present investigation. They were generally higher and varied between 9.79 and 303.62 ml 100 m ? 3 ( x ? =143.14 ? 77...

Temperature, salinity and other variables collected from discrete sample and profile observations using CTD, bottle and other instruments from LAURENCE M. GOULD in the Gulf of Guinea, South Atlantic Ocean and Southern Oceans from 2006-03-23 to 2010-11-02 (NCEI Accession 0144979)

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — NCEI Accession 0144979 includes discrete sample and profile data collected from LAURENCE M. GOULD in the Gulf of Guinea, South Atlantic Ocean and Southern Oceans...

Influence of freshwater input on the skill of decadal forecast of sea ice in the Southern Ocean

Directory of Open Access Journals (Sweden)

V. Zunz

2015-03-01

Full Text Available Recent studies have investigated the potential link between the freshwater input derived from the melting of the Antarctic ice sheet and the observed recent increase in sea ice extent in the Southern Ocean. In this study, we assess the impact of an additional freshwater flux on the trend in sea ice extent and concentration in simulations with data assimilation, spanning the period 1850–2009, as well as in retrospective forecasts (hindcasts initialised in 1980. In the simulations with data assimilation, the inclusion of an additional freshwater flux that follows an autoregressive process improves the reconstruction of the trend in ice extent and concentration between 1980 and 2009. This is linked to a better efficiency of the data assimilation procedure but can also be due to a better representation of the freshwater cycle in the Southern Ocean. The results of the hindcast simulations show that an adequate initial state, reconstructed thanks to the data assimilation procedure including an additional freshwater flux, can lead to an increase in the sea ice extent spanning several decades that is in agreement with satellite observations. In our hindcast simulations, an increase in sea ice extent is obtained even in the absence of any major change in the freshwater input over the last decades. Therefore, while the additional freshwater flux appears to play a key role in the reconstruction of the evolution of the sea ice in the simulation with data assimilation, it does not seem to be required in the hindcast simulations. The present work thus provides encouraging results for sea ice predictions in the Southern Ocean, as in our simulation the positive trend in ice extent over the last 30 years is largely determined by the state of the system in the late 1970s.

10Be application to soil development on Marion Island, southern Indian Ocean

International Nuclear Information System (INIS)

Haussmann, N.; Aldahan, A.; Boelhouwers, J.; Possnert, G.

2010-01-01

Marion Island, located in the southern Indian Ocean, constitutes the summit of an active shield volcano. It is a small terrestrial environment where glacially abraded bedrock became exposed c x 10 kyr ago. These conditions provide an interesting possibility for the assessment of 10 Be accumulation rates and their application to soil erosion studies on the island. 10 Be concentrations were measured in precipitation, soil profiles and an Azorella selago cushion plant. The data reveal a 10 Be precipitation flux several times higher than model prediction. Estimation of the 10 Be accumulation based on the soil inventory suggests a span between 2000 and 7000 yr. This time span is not in accordance with the accepted notion that the island was covered with ice about 10,000 yr ago and suggests either removal of 10 Be from the soil profile, an overestimated Holocene 10 Be-flux or a delayed soil development history. Our results provide new data on 10 Be concentrations from the sub-Antarctic islands and contribute towards enlarging the southern-hemisphere 10 Be database.

Using ocean bottom pressure from the gravity recovery and climate experiment (GRACE) to estimate transport variability in the southern Indian Ocean

Science.gov (United States)

Makowski, Jessica K.; Chambers, Don P.; Bonin, Jennifer A.

2015-06-01

Previous studies have suggested that ocean bottom pressure (OBP) from the Gravity Recovery and Climate Experiment (GRACE) can be used to measure the depth-averaged, or barotropic, transport variability of the Antarctic Circumpolar Current (ACC). Here, we use GRACE OBP observations to calculate transport variability in a region of the southern Indian Ocean encompassing the major fronts of the ACC. We use a statistical analysis of a simulated GRACE-like data set to determine the uncertainty of the estimated transport for the 2003.0-2013.0 time period. We find that when the transport is averaged over 60° of longitude, the uncertainty (one standard error) is close to 1 Sv (1 Sv = 106 m3 s-1) for low-pass filtered transport, which is significantly smaller than the signal and lower than previous studies have found. The interannual variability is correlated with the Southern Annual mode (SAM) (0.61), but more highly correlated with circumpolar zonally averaged winds between 45°S and 65°S (0.88). GRACE transport reflects significant changes in transport between 2007 and 2009 that is observed in the zonal wind variations but not in the SAM index. We also find a statistically significant trend in transport (-1.0 ± 0.4 Sv yr-1, 90% confidence) that is correlated with a local deceleration in zonal winds related to an asymmetry in the SAM on multidecadal periods.

Chemical, temperature and other data from MIKHAIL SOMOV and PROFESSOR VIZE in the Southern Oceans from 13 December 1967 to 12 March 1987 (NODC Accession 0000234)

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — Chemical, temperature, and other data were collected from the PROFESSOR VIZE and MIKHAIL SOMOV in the Southern Oceans from December 12, 1967 to March 12, 1987. Data...

The storm tracks and the energy cycle of the Southern Hemisphere: sensitivity to sea-ice boundary conditions

Directory of Open Access Journals (Sweden)

C. G. Menéndez

1999-11-01

Full Text Available The effect of sea-ice on various aspects of the Southern Hemisphere (SH extratropical climate is examined. Two simulations using the LMD GCM are performed: a control run with the observed sea-ice distribution and an anomaly run in which all SH sea-ice is replaced by open ocean. When sea-ice is removed, the mean sea level pressure displays anomalies predominantly negatives near the Antarctic coast. In general, the meridional temperature gradient is reduced over most of the Southern Ocean, the polar jet is weaker and the sea level pressure rises equatorward of the control ice edge. The high frequency filtered standard deviation of both the sea level pressure and the 300-hPa geopotential height decreases over the southern Pacific and southwestern Atlantic oceans, especially to the north of the ice edge (as prescribed in the control. In contrast, over the Indian Ocean the perturbed simulation exhibits less variability equatorward of about 50°S and increased variability to the south. The zonal averages of the zonal and eddy potential and kinetic energies were evaluated. The effect of removing sea-ice is to diminish the available potential energy of the mean zonal flow, the available potential energy of the perturbations, the kinetic energy of the growing disturbances and the kinetic energy of the mean zonal flow over most of the Southern Ocean. The zonally averaged intensity of the subpolar trough and the rate of the baroclinic energy conversions are also weaker.Key words. Air-sea interactions · Meteorology and atmospheric dynamics (climatology; ocean · atmosphere interactions

The storm tracks and the energy cycle of the Southern Hemisphere: sensitivity to sea-ice boundary conditions

Directory of Open Access Journals (Sweden)

C. G. Menéndez

Full Text Available The effect of sea-ice on various aspects of the Southern Hemisphere (SH extratropical climate is examined. Two simulations using the LMD GCM are performed: a control run with the observed sea-ice distribution and an anomaly run in which all SH sea-ice is replaced by open ocean. When sea-ice is removed, the mean sea level pressure displays anomalies predominantly negatives near the Antarctic coast. In general, the meridional temperature gradient is reduced over most of the Southern Ocean, the polar jet is weaker and the sea level pressure rises equatorward of the control ice edge. The high frequency filtered standard deviation of both the sea level pressure and the 300-hPa geopotential height decreases over the southern Pacific and southwestern Atlantic oceans, especially to the north of the ice edge (as prescribed in the control. In contrast, over the Indian Ocean the perturbed simulation exhibits less variability equatorward of about 50°S and increased variability to the south. The zonal averages of the zonal and eddy potential and kinetic energies were evaluated. The effect of removing sea-ice is to diminish the available potential energy of the mean zonal flow, the available potential energy of the perturbations, the kinetic energy of the growing disturbances and the kinetic energy of the mean zonal flow over most of the Southern Ocean. The zonally averaged intensity of the subpolar trough and the rate of the baroclinic energy conversions are also weaker.

Key words. Air-sea interactions · Meteorology and atmospheric dynamics (climatology; ocean · atmosphere interactions

Partial pressure (or fugacity) of carbon dioxide, salinity and other variables collected from Surface underway observations using Carbon dioxide (CO2) gas analyzer and other instruments from ROGER REVELLE in the Indian Ocean and Southern Oceans from 2016-02-08 to 2016-03-15 (NCEI Accession 0157333)

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — NCEI Accession 0157333 includes Surface underway, chemical, meteorological and physical data collected from ROGER REVELLE in the Indian Ocean and Southern Oceans...

Ocean Dumping Control Regulations

International Nuclear Information System (INIS)

1978-01-01

These Regulations were made further to the Ocean Dumping Control Act which provides for restrictions in dumping operations. The Regulations contain model applications for permits to dump or load a series of materials. (NEA)

Influence of intense scavenging on Pa-Th fractionation in the wake of Kerguelen Island (Southern Ocean)

International Nuclear Information System (INIS)

Venchiarutti, C.; Roy-Barman, M.; Freydier, R.; Van Beek, P.; Souhaut, M.; Jeandel, C.

2011-01-01

Dissolved and particulate excess 230 Th and 231 Pa concentrations (noted 230 Th xs and 231 Pa xs respectively) and 231 Pa xs / 230 Th xs activity ratios were investigated on and out of the Kerguelen plateau (Southern Ocean) in the framework of the Kerguelen Ocean and Plateau compared Study project in order to better understand the influence of particle flux and particle chemistry and advection on the scavenging of 231 Pa. In the wake of Kerguelen, particulate 231 Pa xs is relatively abundant compared to its content in the dissolved phase. This, together with the low fractionation observed between 230 Th and 231 Pa (F Th/Pa ranging from 0.06 ± 0.01 to 1.6 ± 0.2) reflects the domination of the biogenic silica in the particle pool. Along the eastern escarpment of the Kerguelen plateau, the strong 231 Pa xs horizontal gradient in the deep waters highlights the intense removal of 231 Pa at depth, as already observed for 230 Th xs . This local boundary scavenging was attributed to re-suspension of opal-rich particles by nepheloid layers, resulting in fractionation factors F Th/Pa ≤ 1 along the Kerguelen plateau slope. Therefore, both the composition (biogenic opal) and the flux (intense along the margin) of particles control the scavenging of the two radionuclides in the Kerguelen wake. The modelling of 231 Pa distribution with an advection-scavenging model demonstrates that lateral advection of open ocean water on the Kerguelen plateau could supply most of the 231 Pa, which is then efficiently scavenged on the highly productive plateau, as previously proposed for 230 Th xs . It stresses that lateral advection can play a significant role in the overall budget of particle reactive trace elements in a coastal-open ocean system. (authors)

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.

Automated ocean color product validation for the Southern California Bight

Science.gov (United States)

Davis, Curtiss O.; Tufillaro, Nicholas; Jones, Burt; Arnone, Robert

2012-06-01

Automated match ups allow us to maintain and improve the products of current satellite ocean color sensors (MODIS, MERIS), and new sensors (VIIRS). As part of the VIIRS mission preparation, we have created a web based automated match up tool that provides access to searchable fields for date, site, and products, and creates match-ups between satellite (MODIS, MERIS, VIIRS), and in-situ measurements (HyperPRO and SeaPRISM). The back end of the system is a 'mySQL' database, and the front end is a `php' web portal with pull down menus for searchable fields. Based on selections, graphics are generated showing match-ups and statistics, and ascii files are created for downloads for the matchup data. Examples are shown for matching the satellite data with the data from Platform Eureka SeaPRISM off L.A. Harbor in the Southern California Bight.

Impact of Parameterized Lateral Mixing on the Circulation of the Southern Ocean

Science.gov (United States)

Ragen, S.; Gnanadesikan, A.

2016-02-01

The Antarctic Circumpolar Current (ACC) is the strongest ocean current in the world, transporting approximately 130 Sv Eastward around Antarctica. This current is often poorly simulated in climate models. It is not clear why this is the case as the Circumpolar Current is affected by both wind and buoyancy. Changes in wind and buoyancy are not independent of each other, however, so determining the effects of both separately has proved difficult. This study was undertaken in order to examine the impact of changing the lateral diffusion coefficient A­redi on ACC transport. A­redi is poorly known and its value ranges across an order of magnitude in the current generation of climate models. To explore these dynamics, a coarse resolution, fully coupled model suite was run with A­redi mixing coefficients of 400 m2/s, 800 m2/s, 1200 m2/s, and 2400 m2/s. Additionally, two models were run with two-dimensional representations of the mixing coefficient based on altimetry. Our initial results indicate that higher values of the lateral mixing coefficient result in the following changes. We see weaker winds over the Southern Ocean as a whole. The high mixing case results in an 8.7% decrease in peak wind stress. We see a 2% weaker transport in the Drake Passage in the highest mixing case compared to the lowest, but an 11% decrease in transport for a zonal average. The change of temperature and salinity with depth with different Redi parameters also shows a significant difference between the Southern Ocean as a whole and the Drake Passage. Our findings seem to suggest that the Drake Passage is not an adequate diagnostic for explaining the differences between different climate models, as processes distant from the passage may play an important role. Observed changes in overturning with an increase in lateral mixing include an increase in northward transport of Antarctic Bottom Water fed by a small diversion of northern deep water inflows. This diversion means that less of the

Impact of hydrothermalism on the ocean iron cycle.

Science.gov (United States)

Tagliabue, Alessandro; Resing, Joseph

2016-11-28

As the iron supplied from hydrothermalism is ultimately ventilated in the iron-limited Southern Ocean, it plays an important role in the ocean biological carbon pump. We deploy a set of focused sensitivity experiments with a state of the art global model of the ocean to examine the processes that regulate the lifetime of hydrothermal iron and the role of different ridge systems in governing the hydrothermal impact on the Southern Ocean biological carbon pump. Using GEOTRACES section data, we find that stabilization of hydrothermal iron is important in some, but not all regions. The impact on the Southern Ocean biological carbon pump is dominated by poorly explored southern ridge systems, highlighting the need for future exploration in this region. We find inter-basin differences in the isopycnal layer onto which hydrothermal Fe is supplied between the Atlantic and Pacific basins, which when combined with the inter-basin contrasts in oxidation kinetics suggests a muted influence of Atlantic ridges on the Southern Ocean biological carbon pump. Ultimately, we present a range of processes, operating at distinct scales, that must be better constrained to improve our understanding of how hydrothermalism affects the ocean cycling of iron and carbon.This article is part of the themed issue 'Biological and climatic impacts of ocean trace element chemistry'. © 2016 The Author(s).

New Hampshire / Southern Maine Ocean Uses Atlas

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — The Ocean Uses Atlas Project is an innovative partnership between the Coastal Response Research Center (CRRC) and NOAA's Office of Ocean and Coastal Resource...

The effects of natural iron fertilisation on deep-sea ecology: the Crozet Plateau, Southern Indian Ocean.

Directory of Open Access Journals (Sweden)

George A Wolff

Full Text Available The addition of iron to high-nutrient low-chlorophyll (HNLC oceanic waters stimulates phytoplankton, leading to greater primary production. Large-scale artificial ocean iron fertilization (OIF has been proposed as a means of mitigating anthropogenic atmospheric CO(2, but its impacts on ocean ecosystems below the photic zone are unknown. Natural OIF, through the addition of iron leached from volcanic islands, has been shown to enhance primary productivity and carbon export and so can be used to study the effects of OIF on life in the ocean. We compared two closely-located deep-sea sites (∼400 km apart and both at ∼4200 m water depth to the East (naturally iron fertilized; +Fe and South (HNLC of the Crozet Islands in the southern Indian Ocean. Our results suggest that long-term geo-engineering of surface oceanic waters via artificial OIF would lead to significant changes in deep-sea ecosystems. We found that the +Fe area had greater supplies of organic matter inputs to the seafloor, including polyunsaturated fatty acid and carotenoid nutrients. The +Fe site also had greater densities and biomasses of large deep-sea animals with lower levels of evenness in community structuring. The species composition was also very different, with the +Fe site showing similarities to eutrophic sites in other ocean basins. Moreover, major differences occurred in the taxa at the +Fe and HNLC sites revealing the crucial role that surface oceanic conditions play in changing and structuring deep-sea benthic communities.

Phytoplankton blooms induced/sustained by cyclonic eddies during the Indian Ocean Dipole event of 1997 along the southern coasts of Java and Sumatra

Science.gov (United States)

Reddy, P. Rahul Chand; Salvekar, P. S.

2008-09-01

The Indonesian archipelago is the gateway in the tropics connecting two oceans (Pacific and the Indian Ocean) and two continents (Asia and Australia). During the Indian Ocean Dipole 1997, record anomalous and unanticipated upwelling had occurred along the southern coasts of Java and Sumatra causing massive phytoplankton blooms. But the method/mode/process for such anomalous upwelling was not known. Using monthly SeaWifs chlorophyll-a anomalies, TOPEX Sea Surface Height (SSH) anomalies, Sea Surface Temperatures (SST) and currents from a state-of-the-art OGCM, we report the presence of a series of cyclonic eddies along southern coasts of Sumatra and Java during November, December 1997 and January 1998. Upwelling caused by these cyclonic eddies, as also supported by the SSH and SST anomalies, has been responsible for the phytoplankton blooms to persist and dissipate during the 3 months (November, December 1997 and January 1998).

A roadmap for Antarctic and Southern Ocean science for the next two decades and beyond

OpenAIRE

Kennicutt, M.C.; Chown, S.L.; Cassano, J.J.; Liggett, D.; Peck, L.S.; Massom, R.; Rintoul, S.R.; Storey, J.; Vaughan, D.G.; Wilson, T.J.; Allison, I.; Ayton, J.; Badhe, R.; Baeseman, J.; Barrett, P.J.

2015-01-01

Antarctic and Southern Ocean science is vital to understanding natural variability, the processes that govern global change and the role of humans in the Earth and climate system. The potential for new knowledge to be gained from future Antarctic science is substantial. Therefore, the international Antarctic community came together to ‘scan the horizon’ to identify the highest priority scientific questions that researchers should aspire to answer in the next two decades and beyond. Wide consu...

Air-sea interaction regimes in the sub-Antarctic Southern Ocean and Antarctic marginal ice zone revealed by icebreaker measurements

Science.gov (United States)

Yu, Lisan; Jin, Xiangze; Schulz, Eric W.; Josey, Simon A.

2017-08-01

This study analyzed shipboard air-sea measurements acquired by the icebreaker Aurora Australis during its off-winter operation in December 2010 to May 2012. Mean conditions over 7 months (October-April) were compiled from a total of 22 ship tracks. The icebreaker traversed the water between Hobart, Tasmania, and the Antarctic continent, providing valuable in situ insight into two dynamically important, yet poorly sampled, regimes: the sub-Antarctic Southern Ocean and the Antarctic marginal ice zone (MIZ) in the Indian Ocean sector. The transition from the open water to the ice-covered surface creates sharp changes in albedo, surface roughness, and air temperature, leading to consequential effects on air-sea variables and fluxes. Major effort was made to estimate the air-sea fluxes in the MIZ using the bulk flux algorithms that are tuned specifically for the sea-ice effects, while computing the fluxes over the sub-Antarctic section using the COARE3.0 algorithm. The study evidenced strong sea-ice modulations on winds, with the southerly airflow showing deceleration (convergence) in the MIZ and acceleration (divergence) when moving away from the MIZ. Marked seasonal variations in heat exchanges between the atmosphere and the ice margin were noted. The monotonic increase in turbulent latent and sensible heat fluxes after summer turned the MIZ quickly into a heat loss regime, while at the same time the sub-Antarctic surface water continued to receive heat from the atmosphere. The drastic increase in turbulent heat loss in the MIZ contrasted sharply to the nonsignificant and seasonally invariant turbulent heat loss over the sub-Antarctic open water.Plain Language SummaryThe icebreaker Aurora Australis is a research and supply vessel that is regularly chartered by the Australian Antarctic Division during the southern summer to operate in waters between Hobart, Tasmania, and Antarctica. The vessel serves as the main lifeline to three permanent research stations on the

Partial pressure (or fugacity) of carbon dioxide, dissolved inorganic carbon, temperature, salinity and other variables collected from discrete sample and profile observations using CTD, bottle and other instruments from POLARSTERN in the South Atlantic Ocean and Southern Oceans from 1986-06-27 to 1986-12-14 (NODC Accession 0116642)

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National Oceanic and Atmospheric Administration, Department of Commerce — NCEI Accession 0116642 includes chemical, discrete sample, physical and profile data collected from POLARSTERN in the South Atlantic Ocean and Southern Oceans (>...

Application of sediment core modelling to interpreting the glacial-interglacial record of Southern Ocean silica cycling

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A. Ridgwell

2007-07-01

Full Text Available Sediments from the Southern Ocean reveal a meridional divide in biogeochemical cycling response to the glacial-interglacial cycles of the late Neogene. South of the present-day position of the Antarctic Polar Front in the Atlantic sector of the Southern Ocean, biogenic opal is generally much more abundant in sediments during interglacials compared to glacials. To the north, an anti-phased relationship is observed, with maximum opal abundance instead occurring during glacials. This antagonistic response of sedimentary properties provides an important model validation target for testing hypotheses of glacial-interglacial change against, particularly for understanding the causes of the concurrent variability in atmospheric CO₂. Here, I illustrate a time-dependent modelling approach to helping understand climates of the past by means of the mechanistic simulation of marine sediment core records. I find that a close match between model-predicted and observed down-core changes in sedimentary opal content can be achieved when changes in seasonal sea-ice extent are imposed, whereas the predicted sedimentary response to iron fertilization on its own is not consistent with sedimentary observations. The results of this sediment record model-data comparison supports previous inferences that the changing cryosphere is the primary driver of the striking features exhibited by the paleoceanographic record of this region.

Major role of microbes in carbon fluxes during Austral winter in the Southern Drake Passage.

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Maura Manganelli

Full Text Available Carbon cycling in Southern Ocean is a major issue in climate change, hence the need to understand the role of biota in the regulation of carbon fixation and cycling. Southern Ocean is a heterogeneous system, characterized by a strong seasonality, due to long dark winter. Yet, currently little is known about biogeochemical dynamics during this season, particularly in the deeper part of the ocean. We studied bacterial communities and processes in summer and winter cruises in the southern Drake Passage. Here we show that in winter, when the primary production is greatly reduced, Bacteria and Archaea become the major producers of biogenic particles, at the expense of dissolved organic carbon drawdown. Heterotrophic production and chemoautotrophic CO(2 fixation rates were substantial, also in deep water, and bacterial populations were controlled by protists and viruses. A dynamic food web is also consistent with the observed temporal and spatial variations in archaeal and bacterial communities that might exploit various niches. Thus, Southern Ocean microbial loop may substantially maintain a wintertime food web and system respiration at the expense of summer produced DOC as well as regenerate nutrients and iron. Our findings have important implications for Southern Ocean ecosystem functioning and carbon cycle and its manipulation by iron enrichment to achieve net sequestration of atmospheric CO(2.

Atlantic Ocean CARINA data: overview and salinity adjustments

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T. Tanhua

2010-02-01

Full Text Available Water column data of carbon and carbon-relevant hydrographic and hydrochemical parameters from 188 previously non-publicly available cruise data sets in the Arctic Mediterranean Seas, Atlantic and Southern Ocean have been retrieved and merged into a new database: CARINA (CARbon dioxide IN the Atlantic Ocean. The data have gone through rigorous quality control procedures to assure the highest possible quality and consistency. The data for the pertinent parameters in the CARINA database were objectively examined in order to quantify systematic differences in the reported values, i.e. secondary quality control. Systematic biases found in the data have been corrected in the three data products: merged data files with measured, calculated and interpolated data for each of the three CARINA regions, i.e. the Arctic Mediterranean Seas, the Atlantic and the Southern Ocean. These products have been corrected to be internally consistent. Ninety-eight of the cruises in the CARINA database were conducted in the Atlantic Ocean, defined here as the region south of the Greenland-Iceland-Scotland Ridge and north of about 30° S. Here we present an overview of the Atlantic Ocean synthesis of the CARINA data and the adjustments that were applied to the data product. We also report the details of the secondary QC (Quality Control for salinity for this data set. Procedures of quality control – including crossover analysis between stations and inversion analysis of all crossover data – are briefly described. Adjustments to salinity measurements were applied to the data from 10 cruises in the Atlantic Ocean region. Based on our analysis we estimate the internal consistency of the CARINA-ATL salinity data to be 4.1 ppm. With these adjustments the CARINA data products are consistent both internally as well as with GLODAP data, an oceanographic data set based on the World Hydrographic Program in the 1990s, and is now suitable for accurate assessments of, for example

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 RRS JAMES COOK in the South Atlantic Ocean and Southern Oceans from 2010-03-19 to 2010-04-24 (NODC Accession 0108069)

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National Oceanic and Atmospheric Administration, Department of Commerce — NCEI Accession 0108069 includes discrete sample and profile data collected from RRS JAMES COOK in the South Atlantic Ocean and Southern Oceans (> 60 degrees...

First insights into genus level diversity and biogeography of deep sea benthopelagic calanoid copepods in the South Atlantic and Southern Ocean

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Renz, Jasmin; Markhaseva, Elena L.

2015-11-01

Calanoid copepods constitute the most numerous organisms not only in the pelagic realm, but also in the benthic boundary layer, which gives them an important role in the turnover of organic matter in the benthopelagic habitat. During seven expeditions to the South Atlantic and Southern Ocean, the diversity and biogeography of deep-sea benthopelagic calanoid copepods were studied. The communities of calanoids living in the vicinity of the seabed were characterized by high diversity comparable to many pelagic habitats, but low abundance of individuals. Members of the taxon Clausocalanoidea dominated the communities, and within this taxon most individuals belonged to detritivore calanoids characterized by sensory setae on the second maxillae or aetideid copepods. 73% of all genera classified as obligate or predominantly benthopelagic copepods detected during these expeditions were new to science and a vast number of genera and species have been described since then. Comparing the communities of calanoid genera between different regions, the assemblages in the Southern Ocean differed significantly from the Southeast and Southwest Atlantic. A latitudinal diversity gradient could be observed, with highest numbers of genera in the Southwest Atlantic and low numbers at stations in the Southern Ocean. Reviewing the literature, endemism for benthopelagic calanoids appeared to be low on a latitudinal range caused by connectivity in benthopelagic habitats through spreading water masses. However, considering the habitats structuring the water column vertically, a high number of genera are endemic in the benthopelagial and specialized to living within the vicinity of the seabed.

Dissolved inorganic carbon, pH, alkalinity, temperature, salinity and other variables collected from discrete sample and profile observations using CTD, PAR Sensor and other instruments from MIRAI in the Indian Ocean and Southern Oceans from 2013-01-06 to 2013-02-15 (NCEI Accession 0156925)

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National Oceanic and Atmospheric Administration, Department of Commerce — NCEI Accession 0156925 includes biological, chemical, discrete sample, optical, physical and profile data collected from MIRAI in the Indian Ocean and Southern...

Response of Southern Ocean circulation to global warming may enhance basal ice shelf melting around Antarctica

Energy Technology Data Exchange (ETDEWEB)

Hattermann, Tore; Levermann, Anders [Potsdam University, Earth System Analysis, Potsdam Institute for Climate Impact Research, Potsdam (Germany)

2010-10-15

We investigate the large-scale oceanic features determining the future ice shelf-ocean interaction by analyzing global warming experiments in a coarse resolution climate model with a comprehensive ocean component. Heat and freshwater fluxes from basal ice shelf melting (ISM) are parameterized following Beckmann and Goosse [Ocean Model 5(2):157-170, 2003]. Melting sensitivities to the oceanic temperature outside of the ice shelf cavities are varied from linear to quadratic (Holland et al. in J Clim 21, 2008). In 1% per year CO{sub 2}-increase experiments the total freshwater flux from ISM triples to 0.09 Sv in the linear case and more than quadruples to 0.15 Sv in the quadratic case after 140 years at which 4 x 280 ppm = 1,120 ppm was reached. Due to the long response time of subsurface temperature anomalies, ISM thereafter increases drastically, if CO{sub 2} concentrations are kept constant at 1,120 ppm. Varying strength of the Antarctic circumpolar current (ACC) is crucial for ISM increase, because southward advection of heat dominates the warming along the Antarctic coast. On centennial timescales the ACC accelerates due to deep ocean warming north of the current, caused by mixing of heat along isopycnals in the Southern Ocean (SO) outcropping regions. In contrast to previous studies we find an initial weakening of the ACC during the first 150 years of warming. This purely baroclinic effect is due to a freshening in the SO which is consistent with present observations. Comparison with simulations with diagnosed ISM but without its influence on the ocean circulation reveal a number of ISM-related feedbacks, of which a negative ISM-feedback, due to the ISM-related local oceanic cooling, is the dominant one. (orig.)

Swell Propagation over Indian Ocean Region

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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.

Toward a Unified Understanding of Mercury and Methylated Mercury from the World's Oceans

Science.gov (United States)

McNutt, M. K.; Krabbenhoft, D. P.; Landing, W. M.; Sunderland, E. M.

2012-12-01

Marine fish and shellfish are the main source of toxic methylmercury exposure for humans. As recently as decade ago, very limited aqueous methylated mercury data were available from marine settings, resulting in a generally poor understanding of the processes controlling mercury in pelagic marine food webs. Recent oceanographic cruises have significantly improved availability of reliable measurements of methylated mercury and total mercury in seawater. This presentation will focus on vertical seawater profiles collected to depths 1000 m from three recent sampling efforts in collaboration with the CLIVAR Repeat Hydrography Program sponsored by NOAA including: 1) the northeastern Pacific (P16N cruise from Honolulu, Hawaii to Kodiak, Alaska); (2) the southern Indian Ocean (I5 cruise from Cape Town, South Africa, to Fremantle, Australia); and, (3) the Southern Ocean cruise (S4P from McMurdo, Antarctica, to Punta Arenas, Chile). Analytical results presented were all derived from the USGS Mercury Research Lab (http://wi.water.usgs.gov/mercury-lab). Supporting data derived from these cruises on water mass ages, nutrients, carbon and dissolved oxygen provide an opportunity to develop a stronger understanding of the biogeochemical factors controlling oceanic distributions of mercury and methylated mercury. Whole-water, median total mercury, and methylated mercury concentrations for the northern Pacific, southern Indian, and Southern Ocean were 1.10, 0.80, and 1.65 pM, , and 0.11, 0.08, and 0.32 pM, respectively. For all three oceans, vertical profiles of total mercury generally show the lowest concentrations in the surface mixed layer, and concentration maxima at the 700-1000 m depths. Surface depletion of total mercury is attributed to photo-chemical reduction and evasion of gaseous elemental mercury as well as scavenging by settling particulate matter, the main vector of transport to the subsurface ocean. Methylated mercury in all the ocean profiles reveal distinct mid

Key role of organic complexation of iron in sustaining phytoplankton blooms in the Pine Island and Amundsen Polynyas (Southern Ocean)

NARCIS (Netherlands)

Thuroczy, Charles-Edouard; Alderkamp, Anne-Carlijn; Laan, Patrick; Gerringa, Loes J. A.; Mills, Matthew M.; Van Dijken, Gert L.; De Baar, Hein J. W.; Arrigo, Kevin R.

2012-01-01

Primary productivity in the Amundsen Sea (Southern Ocean) is among the highest in Antarctica. The summer phytoplankton bloom in 2009 lasted for > 70 days in both the Pine Island and Amundsen Polynyas. Such productive blooms require a large supply of nutrients, including the trace metal iron (Fe).

The past, present and future distribution of a deep-sea shrimp in the Southern Ocean

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Zeenatul Basher

2016-02-01

Full Text Available Shrimps have a widespread distribution across the shelf, slope and seamount regions of the Southern Ocean. Studies of Antarctic organisms have shown that individual species and higher taxa display different degrees of sensitivity and adaptability in response to environmental change. We use species distribution models to predict changes in the geographic range of the deep-sea Antarctic shrimp Nematocarcinus lanceopes under changing climatic conditions from the Last Glacial Maximum to the present and to the year 2100. The present distribution range indicates a pole-ward shift of the shrimp population since the last glaciation. This occurred by colonization of slopes from nearby refugia located around the northern part of Scotia Arc, southern tip of South America, South Georgia, Bouvet Island, southern tip of the Campbell plateau and Kerguelen plateau. By 2100, the shrimp are likely to expand their distribution in east Antarctica but have a continued pole-ward contraction in west Antarctica. The range extension and contraction process followed by the deep-sea shrimp provide a geographic context of how other deep-sea Antarctic species may have survived during the last glaciation and may endure with projected changing climatic conditions in the future.

Partial pressure (or fugacity) of carbon dioxide, dissolved inorganic carbon, alkalinity, 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 and Southern Oceans from 2016-01-11 to 2016-03-15 (NCEI Accession 0163181)

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National Oceanic and Atmospheric Administration, Department of Commerce — NCEI Accession 0163181 includes chemical, discrete sample, optical, physical and profile data collected from AURORA AUSTRALIS in the Indian Ocean and Southern Oceans...

Partial pressure (or fugacity) of carbon dioxide, salinity and other variables collected from Surface underway observations using Barometric pressure sensor, Carbon dioxide (CO2) gas analyzer and other instruments from ROGER REVELLE in the South Pacific Ocean and Southern Oceans from 2005-01-06 to 2005-02-19 (NCEI Accession 0144243)

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National Oceanic and Atmospheric Administration, Department of Commerce — NCEI Accession 0144243 includes Surface underway data collected from ROGER REVELLE in the South Pacific Ocean and Southern Oceans (> 60 degrees South) from...

Isotopic investigation of contemporary and historic changes in penguin trophic niches and carrying capacity of the southern Indian ocean.

Science.gov (United States)

Jaeger, Audrey; Cherel, Yves

2011-02-02

A temperature-defined regime shift occurred in the 1970s in the southern Indian Ocean, with simultaneous severe decreases in many predator populations. We tested a possible biological link between the regime shift and predator declines by measuring historic and contemporary feather isotopic signatures of seven penguin species with contrasted foraging strategies and inhabiting a large latitudinal range. We first showed that contemporary penguin isotopic variations and chlorophyll a concentration were positively correlated, suggesting the usefulness of predator δ¹³C values to track temporal changes in the ecosystem carrying capacity and its associated coupling to consumers. Having controlled for the Suess effect and for increase CO₂ in seawater, δ¹³C values of Antarctic penguins and of king penguins did not change over time, while δ¹³C of other subantarctic and subtropical species were lower in the 1970s. The data therefore suggest a decrease in ecosystem carrying capacity of the southern Indian Ocean during the temperature regime-shift in subtropical and subantarctic waters but not in the vicinity of the Polar Front and in southward high-Antarctic waters. The resulting lower secondary productivity could be the main driving force explaining the decline of subtropical and subantarctic (but not Antarctic) penguins that occurred in the 1970s. Feather δ¹⁵N values did not show a consistent temporal trend among species, suggesting no major change in penguins' diet. This study highlights the usefulness of developing long-term tissue sampling and data bases on isotopic signature of key marine organisms to track potential changes in their isotopic niches and in the carrying capacity of the environment.

Isotopic investigation of contemporary and historic changes in penguin trophic niches and carrying capacity of the southern Indian ocean.

Directory of Open Access Journals (Sweden)

Audrey Jaeger

Full Text Available A temperature-defined regime shift occurred in the 1970s in the southern Indian Ocean, with simultaneous severe decreases in many predator populations. We tested a possible biological link between the regime shift and predator declines by measuring historic and contemporary feather isotopic signatures of seven penguin species with contrasted foraging strategies and inhabiting a large latitudinal range. We first showed that contemporary penguin isotopic variations and chlorophyll a concentration were positively correlated, suggesting the usefulness of predator δ¹³C values to track temporal changes in the ecosystem carrying capacity and its associated coupling to consumers. Having controlled for the Suess effect and for increase CO₂ in seawater, δ¹³C values of Antarctic penguins and of king penguins did not change over time, while δ¹³C of other subantarctic and subtropical species were lower in the 1970s. The data therefore suggest a decrease in ecosystem carrying capacity of the southern Indian Ocean during the temperature regime-shift in subtropical and subantarctic waters but not in the vicinity of the Polar Front and in southward high-Antarctic waters. The resulting lower secondary productivity could be the main driving force explaining the decline of subtropical and subantarctic (but not Antarctic penguins that occurred in the 1970s. Feather δ¹⁵N values did not show a consistent temporal trend among species, suggesting no major change in penguins' diet. This study highlights the usefulness of developing long-term tissue sampling and data bases on isotopic signature of key marine organisms to track potential changes in their isotopic niches and in the carrying capacity of the environment.

Partial pressure (or fugacity) of carbon dioxide, salinity and other variables collected from Surface underway observations using Carbon dioxide (CO2) gas analyzer, thermosalinographs and other instruments from JAMES CLARK ROSS in the South Atlantic Ocean and Southern Oceans from 2009-03-11 to 2009-04-17 (NCEI Accession 0157275)

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National Oceanic and Atmospheric Administration, Department of Commerce — NCEI Accession 0157275 includes Surface underway, chemical and physical data collected from JAMES CLARK ROSS in the South Atlantic Ocean and Southern Oceans (> 60...

Partial pressure (or fugacity) of carbon dioxide, salinity and other variables collected from Surface underway observations using Carbon dioxide (CO2) gas analyzer, thermosalinographs and other instruments from JAMES CLARK ROSS in the South Atlantic Ocean and Southern Oceans from 2008-01-02 to 2008-02-17 (NCEI Accession 0157284)

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — NCEI Accession 0157284 includes Surface underway, chemical and physical data collected from JAMES CLARK ROSS in the South Atlantic Ocean and Southern Oceans (> 60...

Changes in the concentration of iron in different size fractions during an iron enrichment experiment in the open Southern Ocean

NARCIS (Netherlands)

Nishioka, Jun; Takeda, Shigenobu; Baar, Hein J.W. de; Croot, Peter L.; Boye, Marie; Laan, Patrick; Timmermans, Klaas R.

2005-01-01

An in situ iron enrichment experiment was carried out in the Southern Ocean Polar Frontal Zone and fertilized a patch of water within an eddy of the Antarctic Circumpolar Current (EisenEx, Nov. 2000). During the experiment, a physical speciation technique was used for iron analysis in order to

Salp/krill interactions in the Southern Ocean: spatial segregation and implications for the carbon flux

Science.gov (United States)

Pakhomov, E. A.; Froneman, P. W.; Perissinotto, R.

Available data on the spatial distribution and feeding ecophysiology of Antarctic krill, Euphausia superba, and the tunicate, Salpa thompsoni, in the Southern Ocean are summarized in this study. Antarctic krill and salps generally display pronounced spatial segregation at all spatial scales. This appears to be the result of a clear biotopical separation of these key species in the Antarctic pelagic food web. Krill and salps are found in different water masses or water mass modifications, which are separated by primary or secondary frontal features. On the small-scale (salps are usually restricted to the specific water parcels, or are well segregated vertically. Krill and salp grazing rates estimated using the in situ gut fluorescence technique are among the highest recorded in the Antarctic pelagic food web. Although krill and salps at times may remove the entire daily primary production, generally their grazing impact is moderate (⩽50% of primary production). The regional ecological consequences of years of high salp densities may be dramatic. If the warming trend, which is observed around the Antarctic Peninsula and in the Southern Ocean, continues, salps may become a more prominent player in the trophic structure of the Antarctic marine ecosystem. This likely would be coupled with a dramatic decrease in krill productivity, because of a parallel decrease in the spatial extension of the krill biotope. The high Antarctic regions, particularly the Marginal Ice Zone, have, however, effective physiological mechanisms that may provide protection against the salp invasion.

Southern Ocean phytoplankton physiology in a changing climate.

Science.gov (United States)

Petrou, Katherina; Kranz, Sven A; Trimborn, Scarlett; Hassler, Christel S; Ameijeiras, Sonia Blanco; Sackett, Olivia; Ralph, Peter J; Davidson, Andrew T

2016-09-20

The Southern Ocean (SO) is a major sink for anthropogenic atmospheric carbon dioxide (CO 2 ), potentially harbouring even greater potential for additional sequestration of CO 2 through enhanced phytoplankton productivity. In the SO, primary productivity is primarily driven by bottom up processes (physical and chemical conditions) which are spatially and temporally heterogeneous. Due to a paucity of trace metals (such as iron) and high variability in light, much of the SO is characterised by an ecological paradox of high macronutrient concentrations yet uncharacteristically low chlorophyll concentrations. It is expected that with increased anthropogenic CO 2 emissions and the coincident warming, the major physical and chemical process that govern the SO will alter, influencing the biological capacity and functioning of the ecosystem. This review focuses on the SO primary producers and the bottom up processes that underpin their health and productivity. It looks at the major physico-chemical drivers of change in the SO, and based on current physiological knowledge, explores how these changes will likely manifest in phytoplankton, specifically, what are the physiological changes and floristic shifts that are likely to ensue and how this may translate into changes in the carbon sink capacity, net primary productivity and functionality of the SO. Copyright © 2016 Elsevier GmbH. All rights reserved.

Projected poleward shift of king penguins' (Aptenodytes patagonicus) foraging range at the Crozet Islands, southern Indian Ocean.

Science.gov (United States)

Péron, Clara; Weimerskirch, Henri; Bost, Charles-André

2012-07-07

Seabird populations of the Southern Ocean have been responding to climate change for the last three decades and demographic models suggest that projected warming will cause dramatic population changes over the next century. Shift in species distribution is likely to be one of the major possible adaptations to changing environmental conditions. Habitat models based on a unique long-term tracking dataset of king penguin (Aptenodytes patagonicus) breeding on the Crozet Islands (southern Indian Ocean) revealed that despite a significant influence of primary productivity and mesoscale activity, sea surface temperature consistently drove penguins' foraging distribution. According to climate models of the Intergovernmental Panel on Climate Change (IPCC), the projected warming of surface waters would lead to a gradual southward shift of the more profitable foraging zones, ranging from 25 km per decade for the B1 IPCC scenario to 40 km per decade for the A1B and A2 scenarios. As a consequence, distances travelled by incubating and brooding birds to reach optimal foraging zones associated with the polar front would double by 2100. Such a shift is far beyond the usual foraging range of king penguins breeding and would negatively affect the Crozet population on the long term, unless penguins develop alternative foraging strategies.

Dissolved inorganic carbon, alkalinity, temperature, salinity and other variables collected from discrete sample and profile observations using Alkalinity titrator, CTD and other instruments from SOUTHERN SURVEYOR in the North Pacific Ocean and South Pacific Ocean from 2009-02-03 to 2009-03-24 (NODC Accession 0108082)

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — NCEI Accession 0108082 includes chemical, discrete sample, physical and profile data collected from SOUTHERN SURVEYOR in the North Pacific Ocean and South Pacific...

The Southern California Coastal Ocean Observing System (SCCOOS): Developing A Coastal Observation System To Enable Both Science Based Decision Making And Scientific Discovery

Science.gov (United States)

Terrill, E.; John, O.

2005-05-01

The Southern California Coastal Ocean Observing System (SCCOOS) is a consortium that extends from Northern Baja CA in Mexico to Morro Bay at the southern edge of central California, and aims to streamline, coordinate, and further develop individual institutional efforts by creating an integrated, multidisciplinary coastal observatory in the Bight of Southern California for the benefit of society. By leveraging existing infrastructure, partnerships, and private, local, state, and federal resources, SCCOOS is developing a fully operational coastal observation system to address issues related to coastal water quality, marine life resources, and coastal hazards for end user communities spanning local, state, and federal interests. However, to establish a sensible observational approach to address these societal drivers, sound scientific approaches are required in both the system design and the transformation of data to useful products. Since IOOS and coastal components of the NSF Ocean Observatories Initiative (OOI) are not mutually exclusive within this framework, the SCCOOS consortium of observatory implementers have created an organizational structure that encourages dovetailing of OOI into the routine observations provided by the operational components of a regional IOOS. To begin the development, SCCOOS has grant funding from the California Coastal Conservancy as part of a $21M, statewide initiative to establish a Coastal Ocean Currents Monitoring Program, and funding from NOAA's Coastal Observing Technology System (COTS). In addition, SCCOOS is leveraging IT development that has been supported by the NSF Information Technology Research program Real-time observatories, Applications,and Data Manageemnt Network (ROADNET), and anticipates using developments which will result from the NSF Laboratory for Ocean Observatory Knowledge Integration Grid (LOOKING) program. The observational components now funded at SCCOOS include surface current mapping by HF radar; high

Enhanced deep ocean ventilation and oxygenation with global warming

Science.gov (United States)

Froelicher, T. L.; Jaccard, S.; Dunne, J. P.; Paynter, D.; Gruber, N.

2014-12-01

Twenty-first century coupled climate model simulations, observations from the recent past, and theoretical arguments suggest a consistent trend towards warmer ocean temperatures and fresher polar surface oceans in response to increased radiative forcing resulting in increased upper ocean stratification and reduced ventilation and oxygenation of the deep ocean. Paleo-proxy records of the warming at the end of the last ice age, however, suggests a different outcome, namely a better ventilated and oxygenated deep ocean with global warming. Here we use a four thousand year global warming simulation from a comprehensive Earth System Model (GFDL ESM2M) to show that this conundrum is a consequence of different rates of warming and that the deep ocean is actually better ventilated and oxygenated in a future warmer equilibrated climate consistent with paleo-proxy records. The enhanced deep ocean ventilation in the Southern Ocean occurs in spite of increased positive surface buoyancy fluxes and a constancy of the Southern Hemisphere westerly winds - circumstances that would otherwise be expected to lead to a reduction in deep ocean ventilation. This ventilation recovery occurs through a global scale interaction of the Atlantic Meridional Overturning Circulation undergoing a multi-centennial recovery after an initial century of transient decrease and transports salinity-rich waters inform the subtropical surface ocean to the Southern Ocean interior on multi-century timescales. The subsequent upwelling of salinity-rich waters in the Southern Ocean strips away the freshwater cap that maintains vertical stability and increases open ocean convection and the formation of Antarctic Bottom Waters. As a result, the global ocean oxygen content and the nutrient supply from the deep ocean to the surface are higher in a warmer ocean. The implications for past and future changes in ocean heat and carbon storage will be discussed.

Studies on the nutrient distribution in the Southern Ocean waters along the 45 degrees E transect

Digital Repository Service at National Institute of Oceanography (India)

Rajakumar, A.; Alagarsamy, R.; Khare, N.; Saraswat, R.; Subramaniam, M.M.

) is thankful to Dr P C Pandey, Former Director of NCAOR, Dr M Sudhakar, Chief Scientist of PESO, the Captain and Officers of the cruise and the Head, Department of Chemistry, I.I.T., Kharagpur for their various helps and encouragements. Reference 1... of the Southern Ocean with particular emphasis on the North Western Weddell Sea, in: Belgian Scientific Research Programme on Antarctica. Scientific results of Phase 2 (Feb.1989- Dec.1991), edited by S Caschetto, Science Policy Office, Brussels., 1993, pp. 1...

Epimeria of the Southern Ocean with notes on their relatives (Crustacea, Amphipoda, Eusiroidea

Directory of Open Access Journals (Sweden)

Cédric d'Udekem d'Acoz

2017-10-01

Full Text Available The present monograph includes general systematic considerations on the family Epimeriidae, a revision of the genus Epimeria Costa in Hope, 1851 in the Southern Ocean, and a shorter account on putatively related eusiroid taxa occurring in Antarctic and sub-Antarctic seas. The former epimeriid genera Actinacanthus Stebbing, 1888 and Paramphithoe Bruzelius, 1859 are transferred to other families, respectively to the Acanthonotozomellidae Coleman & J.L. Barnard, 1991 and the herein re-established Paramphithoidae G.O. Sars, 1883, so that only Epimeria and Uschakoviella Gurjanova, 1955 are retained within the Epimeriidae Boeck, 1871. The genera Apherusa Walker, 1891 and Halirages Boeck, 1891, which are phylogenetically close to Paramphithoe, are also transferred to the Paramphithoidae. The validity of the suborder Senticaudata Lowry & Myers, 2013, which conflicts with traditional and recent concepts of Eusiroidea Stebbing, 1888, is questioned. Eight subgenera are recognized for Antarctic and sub-Antarctic species of the genus Epimeria: Drakepimeria subgen. nov., Epimeriella K.H. Barnard, 1930, Hoplepimeria subgen. nov., Laevepimeria subgen. nov., Metepimeria Schellenberg, 1931, Pseudepimeria Chevreux, 1912, Subepimeria Bellan-Santini, 1972 and Urepimeria subgen. nov. The type subgenus Epimeria, as currently defined, does not occur in the Southern Ocean. Drakepimeria species are superficially similar to the type species of the genus Epimeria: E. cornigera (Fabricius, 1779, but they are phylogenetically unrelated and substantial morphological differences are obvious at a finer level. Twenty-seven new Antarctic Epimeria species are described herein: Epimeria (Drakepimeria acanthochelon subgen. et sp. nov., E. (D. anguloce subgen. et sp. nov., E. (D. colemani subgen. et sp. nov., E. (D. corbariae subgen. et sp. nov., E. (D. cyrano subgen. et sp. nov., E. (D. havermansiana subgen. et sp. nov., E. (D. leukhoplites subgen. et sp. nov., E. (D. loerzae subgen

Ocean Dumping Control Act

International Nuclear Information System (INIS)

1975-01-01

This Act provides for the control of dumping of wastes and other substances in the ocean in accordance with the London Convention of 1972 on Prevention of Marine Pollution by the Dumping of Wastes and other Matter to which Canada is a Party. Radioactive wastes are included in the prohibited and restricted substances. (NEA)

Modeling UV-B Effects on Primary Production Throughout the Southern Ocean Using Multi-Sensor Satellite Data

Science.gov (United States)

Lubin, Dan

2001-01-01

This study has used a combination of ocean color, backscattered ultraviolet, and passive microwave satellite data to investigate the impact of the springtime Antarctic ozone depletion on the base of the Antarctic marine food web - primary production by phytoplankton. Spectral ultraviolet (UV) radiation fields derived from the satellite data are propagated into the water column where they force physiologically-based numerical models of phytoplankton growth. This large-scale study has been divided into two components: (1) the use of Total Ozone Mapping Spectrometer (TOMS) and Special Sensor Microwave Imager (SSM/I) data in conjunction with radiative transfer theory to derive the surface spectral UV irradiance throughout the Southern Ocean; and (2) the merging of these UV irradiances with the climatology of chlorophyll derived from SeaWiFS data to specify the input data for the physiological models.

Contrasted demographic responses facing future climate change in Southern Ocean seabirds.

Science.gov (United States)

Barbraud, Christophe; Rivalan, Philippe; Inchausti, Pablo; Nevoux, Marie; Rolland, Virginie; Weimerskirch, Henri

2011-01-01

1. Recent climate change has affected a wide range of species, but predicting population responses to projected climate change using population dynamics theory and models remains challenging, and very few attempts have been made. The Southern Ocean sea surface temperature and sea ice extent are projected to warm and shrink as concentrations of atmospheric greenhouse gases increase, and several top predator species are affected by fluctuations in these oceanographic variables. 2. We compared and projected the population responses of three seabird species living in sub-tropical, sub-Antarctic and Antarctic biomes to predicted climate change over the next 50 years. Using stochastic population models we combined long-term demographic datasets and projections of sea surface temperature and sea ice extent for three different IPCC emission scenarios (from most to least severe: A1B, A2, B1) from general circulation models of Earth's climate. 3. We found that climate mostly affected the probability to breed successfully, and in one case adult survival. Interestingly, frequent nonlinear relationships in demographic responses to climate were detected. Models forced by future predicted climatic change provided contrasted population responses depending on the species considered. The northernmost distributed species was predicted to be little affected by a future warming of the Southern Ocean, whereas steep declines were projected for the more southerly distributed species due to sea surface temperature warming and decrease in sea ice extent. For the most southerly distributed species, the A1B and B1 emission scenarios were respectively the most and less damaging. For the two other species, population responses were similar for all emission scenarios. 4. This is among the first attempts to study the demographic responses for several populations with contrasted environmental conditions, which illustrates that investigating the effects of climate change on core population dynamics

The Southern Ocean ecosystem under multiple climate change stresses--an integrated circumpolar assessment.

Science.gov (United States)

Gutt, Julian; Bertler, Nancy; Bracegirdle, Thomas J; Buschmann, Alexander; Comiso, Josefino; Hosie, Graham; Isla, Enrique; Schloss, Irene R; Smith, Craig R; Tournadre, Jean; Xavier, José C

2015-04-01

A quantitative assessment of observed and projected environmental changes in the Southern Ocean (SO) with a potential impact on the marine ecosystem shows: (i) large proportions of the SO are and will be affected by one or more climate change processes; areas projected to be affected in the future are larger than areas that are already under environmental stress, (ii) areas affected by changes in sea-ice in the past and likely in the future are much larger than areas affected by ocean warming. The smallest areas (Changes in iceberg impact resulting from further collapse of ice-shelves can potentially affect large parts of shelf and ephemerally in the off-shore regions. However, aragonite undersaturation (acidification) might become one of the biggest problems for the Antarctic marine ecosystem by affecting almost the entire SO. Direct and indirect impacts of various environmental changes to the three major habitats, sea-ice, pelagic and benthos and their biota are complex. The areas affected by environmental stressors range from 33% of the SO for a single stressor, 11% for two and 2% for three, to changes, and together cover almost 86% of the SO ecosystem. © 2014 John Wiley & Sons Ltd.

Global reanalyses over Antarctica and the Southern Ocean: Can they be used prior to 1979?

Science.gov (United States)

Bromwich, D. H.; Nicolas, J. P.

2017-12-01

High southern latitudes are a notoriously challenging area for global reanalyses, largely due to the scarcity of conventional observations in these regions. This lack of observational constraint not only reduces the reanalysis model forecast skill, but is also responsible for artifacts in their time series tied to changes in the observing system. For example, the introduction of new satellite observations (e.g., AMSU in 1998) is now a well-documented cause of widespread spurious changes in the reanalysis moisture and temperature fields, which are often exacerbated over Antarctica and the Southern Ocean. This lack of temporal consistency has significantly reduced the reliability of some reanalysis products and their suitability for trend analysis. Century-long reanalysis efforts such as 20CR and ERA-20C, which only assimilate surface pressure observations, have provided ways to achieve greater homogeneity in the observing system through time and (potentially) produce more temporally consistent datasets, particularly across 1979 and the onset of the modern satellite era. However, important issues quickly became apparent in these reanalyses, related in particular to the handling by their data assimilation systems of the near-complete absence of observations poleward of 50°S prior to the 1950s, or to the prescription of ocean boundary conditions (sea ice, SST) prior to 1979. Because of the data scarcity, comparing reanalyses with each other is one of the primary means to assess their reliability. As such, the release of the CERA-20C and ERA5 (partially) by ECMWF in 2017 provides an opportunity to reassess the skill of recent global reanalyses in high southern latitudes and take stock of the recent improvements and remaining challenges, particularly with regard to their use for long-term climate change studies. Our comparison will include both satellite-era comprehensive reanalyses (ERA-Interim, CFSR, MERRA2, JRA-55, and ERA5) and century-long limited reanalyses (20CR

Novel Methods for Optically Measuring Whitecaps Under Natural Wave Breaking Conditions in the Southern Ocean

Science.gov (United States)

Randolph, K. L.; Dierssen, H. M.; Cifuentes-Lorenzen, A.; Balch, W. M.; Monahan, E. C.; Zappa, C. J.; Drapeau, D.; Bowler, B.

2016-02-01

Breaking waves on the ocean surface mark areas of significant importance to air-sea flux estimates of gas, aerosols, and heat. Traditional methods of measuring whitecap coverage using digital photography can miss features that are small in size or do not show high enough contrast to the background. The geometry of the images collected captures the near surface, bright manifestations of the whitecap feature and miss a portion of the bubble plume that is responsible for the production of sea salt aerosols and the transfer of lower solubility gases. Here, a novel method for accurately measuring both the fractional coverage of whitecaps and the intensity and decay rate of whitecap events using above water radiometry is presented. The methodology was developed using data collected during the austral summer in the Atlantic sector of the Southern Ocean under a large range of wind (speeds of 1 to 15 m s-1) and wave (significant wave heights 2 to 8 m) conditions as part of the Southern Ocean Gas Exchange experiment. Whitecap metrics were retrieved by employing a magnitude threshold based on the interquartile range of the radiance or reflectance signal for a single channel (411 nm) after a baseline removal, determined using a moving minimum/maximum filter. Breaking intensity and decay rate metrics were produced from the integration of, and the exponential fit to, radiance or reflectance over the lifetime of the whitecap. When compared to fractional whitecap coverage measurements obtained from high resolution digital images, radiometric estimates were consistently higher because they capture more of the decaying bubble plume area that is difficult to detect with photography. Radiometrically-retrieved whitecap measurements are presented in the context of concurrently measured meteorological (e.g., wind speed) and oceanographic (e.g., wave) data. The optimal fit of the radiometrically estimated whitecap coverage to the instantaneous wind speed, determined using ordinary least

Friend or Foe: Variability in How Sea Ice Can Both Hinder and Enhance Phytoplankton Blooms Across the Southern Ocean

Science.gov (United States)

Rohr, T.

2016-02-01

Globally, a suite of physical and biogeochemical controls govern the structure, size, and timing of seasonal phytoplankton blooms. In the Southern Ocean, the introduction of seasonal sea ice provides an additional constraining factor. From a bottom-up perspective, a reduction in sea ice can both enhance bloom development by permitting greater levels of surface PAR uninhibited by ice and suppress a bloom when reduced fresh melt-water inputs and increased vulnerability to wind stress combine to create deeper mixed layers and decrease depth integrated light availability. Regions along the Western Antarctic Peninsula have already seen a contradictory response to reduced ice cover, with enhanced summertime chlorophyll concentrations in the South, and large declines to the North. This dichotomy is thought to arise from differences in the interannual mean sea ice state, with extensively ice covered regions benefiting from reduced coverage and more sparsely covered regions hindered by further reductions. The questions arises: 1) At what threshold does a reduction in sea ice transition from amplifying blooms to suppressing them? 2) How do additional environmental considerations such as nutrient availability and trophic interactions complicate this transition? Here, we combine remote sensing observations and in-situ data (from PAL LTER) with a hierarchy of 1-D water column and global general circulation (CESM) models to access the variability in how regional differences in mean ice state combine with other environmental forcings to dictate how interannual variability (or long term trends) in ice coverage will affect bloom structure, size and dynamics. In doing so we will gain a better understanding of how predicted changes in sea ice will effect Southern Ocean productivity, which of course will have important consequences in the global carbon cycle and sustainability of healthy marine ecosystems.

Gaseous elemental mercury in the marine boundary layer and air-sea flux in the Southern Ocean in austral summer.

Science.gov (United States)

Wang, Jiancheng; Xie, Zhouqing; Wang, Feiyue; Kang, Hui

2017-12-15

Gaseous elemental mercury (GEM) in the marine boundary layer (MBL), and dissolved gaseous mercury (DGM) in surface seawater of the Southern Ocean were measured in the austral summer from December 13, 2014 to February 1, 2015. GEM concentrations in the MBL ranged from 0.4 to 1.9ngm -3 (mean±standard deviation: 0.9±0.2ngm -3 ), whereas DGM concentrations in surface seawater ranged from 7.0 to 75.9pgL -1 (mean±standard deviation: 23.7±13.2pgL -1 ). The occasionally observed low GEM in the MBL suggested either the occurrence of atmospheric mercury depletion in summer, or the transport of GEM-depleted air from the Antarctic Plateau. Elevated GEM concentrations in the MBL and DGM concentrations in surface seawater were consistently observed in the ice-covered region of the Ross Sea implying the influence of the sea ice environment. Diminishing sea ice could cause more mercury evasion from the ocean to the air. Using the thin film gas exchange model, the air-sea fluxes of gaseous mercury in non-ice-covered area during the study period were estimated to range from 0.0 to 6.5ngm -2 h -1 with a mean value of 1.5±1.8ngm -2 h -1 , revealing GEM (re-)emission from the East Southern Ocean in summer. Copyright © 2017 Elsevier B.V. All rights reserved.

Polychaeta Orbiniidae from Antarctica, the Southern Ocean, the Abyssal Pacific Ocean, and off South America.

Science.gov (United States)

Blake, James A

2017-01-12

The orbiniid polychaetes chiefly from Antarctic and subantarctic seas and off South America are described based on collections of the National Museum of Natural History and new material from surveys conducted by the United States Antarctic Program and other federal and privately funded sources as well as participation in international programs. A total of 44 species of Orbiniidae distributed in 10 genera are reported from the Pacific Ocean and waters off South America and Antarctica. Twenty-one species are new to science; one species is renamed. Berkeleyia heroae n. sp., B. abyssala n. sp., B. weddellia n. sp.; B. hadala n. sp., Leitoscoloplos simplex n. sp., L. plataensis n. sp., L. nasus n. sp., L. eltaninae n. sp., L. phyllobranchus n. sp., L. rankini n. sp., Scoloplos bathytatus n. sp., S. suroestense n. sp., Leodamas hyphalos n. sp., L. maciolekae n. sp., L. perissobranchiatus n. sp., Califia bilamellata n. sp., Orbinia orensanzi n. sp., Naineris antarctica n. sp., N. argentiniensis n. sp., Orbiniella spinosa n. sp., and O. landrumae n. sp. are new to science. A new name, Naineris furcillata, replaces N. chilensis Carrasco, 1977, a junior homonym of N. dendtritica chilensis Hartmann‑Schröder, 1965, which is raised to full species status. Leodamas cochleatus (Ehlers, 1900) is removed from synonymy and redescribed. A neotype is established for Leodamas verax Kinberg, 1966, the type species. A general overview of Leodamas species is provided. The Leitoscoloplos kerguelensis (McIntosh, 1885) complex is reviewed and partially revised. Definitions of the genera of the Orbiniidae are updated to conform to recently described taxa. Several new synonymies are proposed following a reexamination of previously described type specimens. The morphological characters used to identify and classify orbiniids are reviewed. The biogeographic and bathymetric distributions of the South American and Southern Ocean orbiniid fauna are reviewed.

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

Temperature profile and nutrients data collected using bottle casts from the POLAR DUKE in the Ross Sea and Southern Oceans from 05 February 1992 to 28 February 1992 (NODC Accession 0000888)

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National Oceanic and Atmospheric Administration, Department of Commerce — Temperature profile and nutrients data were collected using bottle casts in the Ross Sea and Southern Oceans from the POLAR DUKE. Data were collected from 05...

Temperature profile and nutrients data collected using bottle casts from the POLAR DUKE in the Ross Sea and Southern Oceans from 08 October 1996 to 06 November 1996 (NODC Accession 0000894)

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — Temperature profile and nutrients data were collected using bottle casts in the Ross Sea and Southern Oceans from POLAR DUKE. Data were collected from 08 October...

Temperature profile and nutrients data collected using bottle casts from the POLAR DUKE in the Ross Sea and Southern Oceans from 06 September 1996 to 12 September 1996 (NODC Accession 0000890)

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — Temperature profile and nutrients data were collected using bottle casts in the Ross Sea and Southern Oceans from POLAR DUKE. Data were collected from 06 September...

Temperature profile and nutrients data collected using bottle casts from the POLAR DUKE in the Ross Sea and Southern Oceans from 13 November 1996 to 26 November 1996 (NODC Accession 0000895)

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — Temperature profile and nutrients data were collected using bottle casts in the Ross Sea and Southern Oceans from the POLAR DUKE. Data were collected from 13...

Partial pressure (or fugacity) of carbon dioxide, 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 LAURENCE M. GOULD in the South Atlantic Ocean and Southern Oceans from 2009-09-16 to 2009-10-09 (NODC Accession 0112845)

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — NCEI Accession 0112845 includes discrete sample and profile data collected from LAURENCE M. GOULD in the South Atlantic Ocean and Southern Oceans (> 60 degrees...

Partial pressure (or fugacity) of carbon dioxide, dissolved inorganic carbon, pH, alkalinity, temperature, salinity and other variables collected from discrete sample and profile observations using Alkalinity titrator, Barometric pressure sensor and other instruments from ROGER REVELLE in the Indian Ocean and Southern Oceans from 2008-02-04 to 2008-03-17 (NODC Accession 0108118)

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — NCEI Accession 0108118 includes discrete sample and profile data collected from ROGER REVELLE in the Indian Ocean and Southern Oceans (> 60 degrees South) from...

Temperature, salinity, nutrients, and other data from CTD and bottle casts in the Southern Ocean (> 60 South) from the R/V NATHANIEL B. PALMER from 14 September 1994 to 12 October 1994 (NODC Accession 0000481)

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National Oceanic and Atmospheric Administration, Department of Commerce — This report includes the primary ocean station data collected in the Pacific sector of the Southern Ocean during cruise 9405 of the Nathaniel B. Palmer. The cruise...

Application of a nonparametric approach to analyze delta-pCO2 data from the Southern Ocean

CSIR Research Space (South Africa)

Pretorius, WB

2011-11-01

Full Text Available NONPARAMETRIC APPROACH TO ANALYZE ?pCO2 DATA FROM THE SOUTHERN OCEAN Wesley B. Pretorius*1, Sonali Das2 and Paul J. Mostert1 *1 Cell: 0722897595, Department of Statistics and Actuarial Science, University of Stellenbosch, Private Bag X1, Matieland 7602...(9-10):1601-1622. Tans, P.P., Fung, I. Y. & Takahashi, T. 1990 Observational constraints on the global atmospheric CO2-budget. Science, 247:1431-1438. Telszewski, M., Chazottes, A., Schuster, U., Watson, A.J., Moulin, C., Bakker, D.C.E., Gonzalez-Davila, M...

Partial pressure (or fugacity) of carbon dioxide, salinity and other variables collected from Surface underway observations using Barometric pressure sensor, Carbon dioxide (CO2) gas analyzer and other instruments from MARION DUFRESNE in the Indian Ocean and Southern Oceans from 1998-01-21 to 1998-12-28 (NODC Accession 0081003)

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — NCEI Accession 0081003 includes Surface underway, chemical, meteorological, optical and physical data collected from MARION DUFRESNE in the Indian Ocean and Southern...

Partial pressure (or fugacity) of carbon dioxide, salinity and other variables collected from Surface underway observations using Barometric pressure sensor, Carbon dioxide (CO2) gas analyzer and other instruments from MARION DUFRESNE in the Indian Ocean and Southern Oceans from 2000-01-15 to 2000-08-14 (NODC Accession 0081005)

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — NCEI Accession 0081005 includes Surface underway, chemical, meteorological, optical and physical data collected from MARION DUFRESNE in the Indian Ocean and Southern...

Climate change and Southern Ocean ecosystems I: how changes in physical habitats directly affect marine biota.

Science.gov (United States)

Constable, Andrew J; Melbourne-Thomas, Jessica; Corney, Stuart P; Arrigo, Kevin R; Barbraud, Christophe; Barnes, David K A; Bindoff, Nathaniel L; Boyd, Philip W; Brandt, Angelika; Costa, Daniel P; Davidson, Andrew T; Ducklow, Hugh W; Emmerson, Louise; Fukuchi, Mitsuo; Gutt, Julian; Hindell, Mark A; Hofmann, Eileen E; Hosie, Graham W; Iida, Takahiro; Jacob, Sarah; Johnston, Nadine M; Kawaguchi, So; Kokubun, Nobuo; Koubbi, Philippe; Lea, Mary-Anne; Makhado, Azwianewi; Massom, Rob A; Meiners, Klaus; Meredith, Michael P; Murphy, Eugene J; Nicol, Stephen; Reid, Keith; Richerson, Kate; Riddle, Martin J; Rintoul, Stephen R; Smith, Walker O; Southwell, Colin; Stark, Jonathon S; Sumner, Michael; Swadling, Kerrie M; Takahashi, Kunio T; Trathan, Phil N; Welsford, Dirk C; Weimerskirch, Henri; Westwood, Karen J; Wienecke, Barbara C; Wolf-Gladrow, Dieter; Wright, Simon W; Xavier, Jose C; Ziegler, Philippe

2014-10-01

Antarctic and Southern Ocean (ASO) marine ecosystems have been changing for at least the last 30 years, including in response to increasing ocean temperatures and changes in the extent and seasonality of sea ice; the magnitude and direction of these changes differ between regions around Antarctica that could see populations of the same species changing differently in different regions. This article reviews current and expected changes in ASO physical habitats in response to climate change. It then reviews how these changes may impact the autecology of marine biota of this polar region: microbes, zooplankton, salps, Antarctic krill, fish, cephalopods, marine mammals, seabirds, and benthos. The general prognosis for ASO marine habitats is for an overall warming and freshening, strengthening of westerly winds, with a potential pole-ward movement of those winds and the frontal systems, and an increase in ocean eddy activity. Many habitat parameters will have regionally specific changes, particularly relating to sea ice characteristics and seasonal dynamics. Lower trophic levels are expected to move south as the ocean conditions in which they are currently found move pole-ward. For Antarctic krill and finfish, the latitudinal breadth of their range will depend on their tolerance of warming oceans and changes to productivity. Ocean acidification is a concern not only for calcifying organisms but also for crustaceans such as Antarctic krill; it is also likely to be the most important change in benthic habitats over the coming century. For marine mammals and birds, the expected changes primarily relate to their flexibility in moving to alternative locations for food and the energetic cost of longer or more complex foraging trips for those that are bound to breeding colonies. Few species are sufficiently well studied to make comprehensive species-specific vulnerability assessments possible. Priorities for future work are discussed. © 2014 John Wiley & Sons Ltd.

Decadal predictions of Southern Ocean sea ice : testing different initialization methods with an Earth-system Model of Intermediate Complexity

Science.gov (United States)

Zunz, Violette; Goosse, Hugues; Dubinkina, Svetlana

2013-04-01

The sea ice extent in the Southern Ocean has increased since 1979 but the causes of this expansion have not been firmly identified. In particular, the contribution of internal variability and external forcing to this positive trend has not been fully established. In this region, the lack of observations and the overestimation of internal variability of the sea ice by contemporary General Circulation Models (GCMs) make it difficult to understand the behaviour of the sea ice. Nevertheless, if its evolution is governed by the internal variability of the system and if this internal variability is in some way predictable, a suitable initialization method should lead to simulations results that better fit the reality. Current GCMs decadal predictions are generally initialized through a nudging towards some observed fields. This relatively simple method does not seem to be appropriated to the initialization of sea ice in the Southern Ocean. The present study aims at identifying an initialization method that could improve the quality of the predictions of Southern Ocean sea ice at decadal timescales. We use LOVECLIM, an Earth-system Model of Intermediate Complexity that allows us to perform, within a reasonable computational time, the large amount of simulations required to test systematically different initialization procedures. These involve three data assimilation methods: a nudging, a particle filter and an efficient particle filter. In a first step, simulations are performed in an idealized framework, i.e. data from a reference simulation of LOVECLIM are used instead of observations, herein after called pseudo-observations. In this configuration, the internal variability of the model obviously agrees with the one of the pseudo-observations. This allows us to get rid of the issues related to the overestimation of the internal variability by models compared to the observed one. This way, we can work out a suitable methodology to assess the efficiency of the

Gravity Field Atlas of the S. Ocean

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — This Gravity Field Atlas of the Southern Ocean from GEOSAT is MGG Report 7. In many areas of the global ocean, the depth of the seafloor is not well known because...

Indian Ocean and Indian summer monsoon: relationships without ENSO in ocean-atmosphere coupled simulations

Science.gov (United States)

Crétat, Julien; Terray, Pascal; Masson, Sébastien; Sooraj, K. P.; Roxy, Mathew Koll

2017-08-01

The relationship between the Indian Ocean and the Indian summer monsoon (ISM) and their respective influence over the Indo-Western North Pacific (WNP) region are examined in the absence of El Niño Southern Oscillation (ENSO) in two partially decoupled global experiments. ENSO is removed by nudging the tropical Pacific simulated sea surface temperature (SST) toward SST climatology from either observations or a fully coupled control run. The control reasonably captures the observed relationships between ENSO, ISM and the Indian Ocean Dipole (IOD). Despite weaker amplitude, IODs do exist in the absence of ENSO and are triggered by a boreal spring ocean-atmosphere coupled mode over the South-East Indian Ocean similar to that found in the presence of ENSO. These pure IODs significantly affect the tropical Indian Ocean throughout boreal summer, inducing a significant modulation of both the local Walker and Hadley cells. This meridional circulation is masked in the presence of ENSO. However, these pure IODs do not significantly influence the Indian subcontinent rainfall despite overestimated SST variability in the eastern equatorial Indian Ocean compared to observations. On the other hand, they promote a late summer cross-equatorial quadrupole rainfall pattern linking the tropical Indian Ocean with the WNP, inducing important zonal shifts of the Walker circulation despite the absence of ENSO. Surprisingly, the interannual ISM rainfall variability is barely modified and the Indian Ocean does not force the monsoon circulation when ENSO is removed. On the contrary, the monsoon circulation significantly forces the Arabian Sea and Bay of Bengal SSTs, while its connection with the western tropical Indian Ocean is clearly driven by ENSO in our numerical framework. Convection and diabatic heating associated with above-normal ISM induce a strong response over the WNP, even in the absence of ENSO, favoring moisture convergence over India.

Temperature profile and nutrients data collected using bottle casts from the NATHANIEL B. PALMER in the Ross Sea and Southern Oceans from 16 December 1995 to 13 January 1996 (NODC Accession 0000889)

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — Temperature profile and nutrients data were collected using bottle casts in the Ross Sea and Southern Oceans from the NATHANIEL B. PALMER. Data were collected from...

Influence of intense scavenging on Pa-Th fractionation in the wake of Kerguelen Island (Southern Ocean

Directory of Open Access Journals (Sweden)

C. Venchiarutti

2011-11-01

Full Text Available Dissolved and particulate excess ²³⁰Th and ²³¹Pa concentrations (noted ²³⁰Th_xs and ²³¹Pa_xs respectively and ²³¹Pa_xs/²³⁰Th_xs activity ratios were investigated on and out of the Kerguelen plateau (Southern Ocean in the framework of the Kerguelen Ocean and Plateau compared Study project in order to better understand the influence of particle flux and particle chemistry and advection on the scavenging of ²³¹Pa.

In the wake of Kerguelen, particulate ²³¹Pa_xs is relatively abundant compared to its content in the dissolved phase. This, together with the low fractionation observed between ²³⁰Th and ²³¹Pa (F_Th/Pa ranging from 0.06 ± 0.01 to 1.6 ± 0.2 reflects the domination of the biogenic silica in the particle pool.

Along the eastern escarpment of the Kerguelen plateau, the strong ²³¹Pa_xs horizontal gradient in the deep waters highlights the intense removal of ²³¹Pa at depth, as already observed for ²³⁰Th_xs. This local boundary scavenging was attributed to re-suspension of opal-rich particles by nepheloid layers, resulting in fractionation factors F_Th/Pa ≤ 1 along the Kerguelen plateau slope. Therefore, both the composition (biogenic opal and the flux (intense along the margin of particles control the scavenging of the two radionuclides in the Kerguelen wake.

The modelling of ²³¹Pa distribution with an advection-scavenging model demonstrates that lateral advection of open ocean water on the Kerguelen plateau could supply most of the ²³¹Pa, which is then efficiently scavenged on the highly productive plateau, as previously proposed for ²³⁰Th_xs. It stresses that lateral advection can play a significant role in the overall

Partial pressure (or fugacity) of carbon dioxide, dissolved inorganic carbon, pH, alkalinity, temperature, salinity and other variables collected from discrete sample and profile observations using CTD, bottle and other instruments from NOAA Ship DISCOVERER in the South Pacific Ocean, Southern Oceans and Tasman Sea from 1996-01-05 to 1996-03-10 (NODC Accession 0115155)

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — NCEI Accession 0115155 includes chemical, discrete sample, physical and profile data collected from NOAA Ship DISCOVERER in the South Pacific Ocean, Southern Oceans...

Atmospheric concentrations of persistent organic pollutants over the Pacific Ocean near southern Taiwan and the northern Philippines.

Science.gov (United States)

Chao, How-Ran; Lin, Ding-Yan; Chen, Kuang-Yu; Gou, Yan-Yu; Chiou, Tsyr-Huei; Lee, Wen-Jhy; Chen, Shui-Jen; Wang, Lin-Chi

2014-09-01

This study investigates the atmospheric occurrence of persistent organic pollutants (POPs) over the Pacific Ocean near southern Taiwan and the northern Philippines. We determined sixty-six compounds, including polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs), dioxin-like polychlorinated biphenyls (DLPCBs), polybrominated diphenyl ethers (PBDEs), as well as polychlorinated diphenyl ethers (PCDEs), polybrominated dibenzo-p-dioxins and dibenzofurans (PBDD/Fs), and polybrominated biphenyls (PBBs), in air samples simultaneously collected from the offshore oceanic atmosphere (n=6) and over a rural area (n=2). We calculated the atmospheric World Health Organization 2005 toxic equivalency levels (WHO2005-TEQ), for the total dioxin-like POPs, including PCDD/Fs, DLPCBs, and PBDD/Fs, being 0.00612 pg WHO2005-TEQ/m(3) and 0.0138 pg WHO2005-TEQ/m(3) over the ocean and land, respectively. We found unexpected lower averaged atmospheric PBDE concentrations in the rural area (15.9 pg/m(3)) than over the ocean (31.1 pg/m(3)) due to higher levels of the BDE209 congener, although the difference was not statistically significant. We have compared and reported our field results with previously published datasets over the global oceans, which suggest PCBs and PBDEs are the dominant chemical contaminants in the global oceanic atmosphere among these halogenated POPs (e.g. PCBs and Σdi-hepta PBDEs could be found in the range of 0.09-48.7 and 8.07-94.0 pg/m(3), respectively, including our dataset). However, there are still very few investigations on the global atmospheric levels of PBDD/Fs, PCDEs and PBBs and our data sums to these earlier studies. Finally, we point out that the halogenated POPs originated from Taiwan or the continental East Asia which could easily reach remote ocean sites via atmospheric transport. Copyright © 2014 Elsevier B.V. All rights reserved.

Southern Hemisphere Ice Limits, 1973-1978

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — Weekly Southern Ocean ice limits, have been digitized from U.S. Navy Fleet Weather Facility ice charts, at the Max-Planck Institut fur Meteorologie, Hamburg....

Biogeographic partitioning of Southern Ocean microorganisms revealed by metagenomics.

Science.gov (United States)

Wilkins, David; Lauro, Federico M; Williams, Timothy J; Demaere, Matthew Z; Brown, Mark V; Hoffman, Jeffrey M; Andrews-Pfannkoch, Cynthia; McQuaid, Jeffrey B; Riddle, Martin J; Rintoul, Stephen R; Cavicchioli, Ricardo

2013-05-01

We performed a metagenomic survey (6.6 Gbp of 454 sequence data) of Southern Ocean (SO) microorganisms during the austral summer of 2007-2008, examining the genomic signatures of communities across a latitudinal transect from Hobart (44°S) to the Mertz Glacier, Antarctica (67°S). Operational taxonomic units (OTUs) of the SAR11 and SAR116 clades and the cyanobacterial genera Prochlorococcus and Synechococcus were strongly overrepresented north of the Polar Front (PF). Conversely, OTUs of the Gammaproteobacterial Sulfur Oxidizer-EOSA-1 (GSO-EOSA-1) complex, the phyla Bacteroidetes and Verrucomicrobia and order Rhodobacterales were characteristic of waters south of the PF. Functions enriched south of the PF included a range of transporters, sulfur reduction and histidine degradation to glutamate, while branched-chain amino acid transport, nucleic acid biosynthesis and methionine salvage were overrepresented north of the PF. The taxonomic and functional characteristics suggested a shift of primary production from cyanobacteria in the north to eukaryotic phytoplankton in the south, and reflected the different trophic statuses of the two regions. The study provides a new level of understanding about SO microbial communities, describing the contrasting taxonomic and functional characteristics of microbial assemblages either side of the PF. © 2012 Society for Applied Microbiology and Blackwell Publishing Ltd.

Partial pressure (or fugacity) of carbon dioxide, dissolved inorganic carbon, temperature, salinity and other variables collected from discrete sample and profile observations using CTD, Carbon dioxide (CO2) gas analyzer and other instruments from LAURENCE M. GOULD in the South Atlantic Ocean and Southern Oceans from 2006-03-21 to 2006-04-04 (NODC Accession 0108070)

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — NCEI Accession 0108070 includes chemical, discrete sample, physical and profile data collected from LAURENCE M. GOULD in the South Atlantic Ocean and Southern Oceans...

Natural Ocean Carbon Cycle Sensitivity to Parameterizations of the Recycling in a Climate Model

Science.gov (United States)

Romanou, A.; Romanski, J.; Gregg, W. W.

2014-01-01

Sensitivities of the oceanic biological pump within the GISS (Goddard Institute for Space Studies ) climate modeling system are explored here. Results are presented from twin control simulations of the air-sea CO2 gas exchange using two different ocean models coupled to the same atmosphere. The two ocean models (Russell ocean model and Hybrid Coordinate Ocean Model, HYCOM) use different vertical coordinate systems, and therefore different representations of column physics. Both variants of the GISS climate model are coupled to the same ocean biogeochemistry module (the NASA Ocean Biogeochemistry Model, NOBM), which computes prognostic distributions for biotic and abiotic fields that influence the air-sea flux of CO2 and the deep ocean carbon transport and storage. In particular, the model differences due to remineralization rate changes are compared to differences attributed to physical processes modeled differently in the two ocean models such as ventilation, mixing, eddy stirring and vertical advection. GISSEH(GISSER) is found to underestimate mixed layer depth compared to observations by about 55% (10 %) in the Southern Ocean and overestimate it by about 17% (underestimate by 2%) in the northern high latitudes. Everywhere else in the global ocean, the two models underestimate the surface mixing by about 12-34 %, which prevents deep nutrients from reaching the surface and promoting primary production there. Consequently, carbon export is reduced because of reduced production at the surface. Furthermore, carbon export is particularly sensitive to remineralization rate changes in the frontal regions of the subtropical gyres and at the Equator and this sensitivity in the model is much higher than the sensitivity to physical processes such as vertical mixing, vertical advection and mesoscale eddy transport. At depth, GISSER, which has a significant warm bias, remineralizes nutrients and carbon faster thereby producing more nutrients and carbon at depth, which

Consensuses and discrepancies of basin-scale ocean heat content changes in different ocean analyses

Science.gov (United States)

Wang, Gongjie; Cheng, Lijing; Abraham, John; Li, Chongyin

2018-04-01

Inconsistent global/basin ocean heat content (OHC) changes were found in different ocean subsurface temperature analyses, especially in recent studies related to the slowdown in global surface temperature rise. This finding challenges the reliability of the ocean subsurface temperature analyses and motivates a more comprehensive inter-comparison between the analyses. Here we compare the OHC changes in three ocean analyses (Ishii, EN4 and IAP) to investigate the uncertainty in OHC in four major ocean basins from decadal to multi-decadal scales. First, all products show an increase of OHC since 1970 in each ocean basin revealing a robust warming, although the warming rates are not identical. The geographical patterns, the key modes and the vertical structure of OHC changes are consistent among the three datasets, implying that the main OHC variabilities can be robustly represented. However, large discrepancies are found in the percentage of basinal ocean heating related to the global ocean, with the largest differences in the Pacific and Southern Ocean. Meanwhile, we find a large discrepancy of ocean heat storage in different layers, especially within 300-700 m in the Pacific and Southern Oceans. Furthermore, the near surface analysis of Ishii and IAP are consistent with sea surface temperature (SST) products, but EN4 is found to underestimate the long-term trend. Compared with ocean heat storage derived from the atmospheric budget equation, all products show consistent seasonal cycles of OHC in the upper 1500 m especially during 2008 to 2012. Overall, our analyses further the understanding of the observed OHC variations, and we recommend a careful quantification of errors in the ocean analyses.

New Hampshire / Southern Maine Ocean Uses Atlas: Industrial sector

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — The Ocean Uses Atlas Project is an innovative partnership between the Coastal Response Research Center (CRRC) and NOAA's Office of Ocean and Coastal Resource...

New Hampshire / Southern Maine Ocean Uses Atlas: Fishing sector

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — The Ocean Uses Atlas Project is an innovative partnership between the Coastal Response Research Center (CRRC) and NOAA's Office of Ocean and Coastal Resource...

CARINA TCO2 data in the Atlantic Ocean

Directory of Open Access Journals (Sweden)

R. Wanninkhof

2010-07-01

Full Text Available Water column data of carbon and carbon-relevant hydrographic and hydrochemical parameters from 188 cruises in the Arctic Mediterranean Seas, Atlantic and Southern Ocean have been retrieved and merged in a new data base: the CARINA (CARbon IN the Atlantic Project. These data have gone through rigorous quality control (QC procedures so as to improve the quality and consistency of the data as much as possible. Secondary quality control, which involved objective study of data in order to quantify systematic differences in the reported values, was performed for the pertinent parameters in the CARINA data base. Systematic biases in the data have been tentatively corrected in the data products. The products are three merged data files with measured, adjusted and interpolated data of all cruises for each of the three CARINA regions (Arctic Mediterranean Seas, Atlantic and Southern Ocean. Ninety-eight cruises were conducted in the "Atlantic" defined as the region south of the Greenland-Iceland-Scotland Ridge and north of about 30° S. Here we report the details of the secondary QC which was done on the total dissolved inorganic carbon (TCO2 data and the adjustments that were applied to yield the final data product in the Atlantic. Procedures of quality control – including crossover analysis between stations and inversion analysis of all crossover data – are briefly described. Adjustments were applied to TCO2 measurements for 17 of the cruises in the Atlantic Ocean region. With these adjustments, the CARINA data base is consistent both internally as well as with GLODAP data, an oceanographic data set based on the WOCE Hydrographic Program in the 1990s, and is now suitable for accurate assessments of, for example, regional oceanic carbon inventories, uptake rates and model validation.

Ocean Robotic Networks

Energy Technology Data Exchange (ETDEWEB)

Schofield, Oscar [Rutgers University

2012-05-23

We live on an ocean planet which is central to regulating the Earth’s climate and human society. Despite the importance of understanding the processes operating in the ocean, it remains chronically undersampled due to the harsh operating conditions. This is problematic given the limited long term information available about how the ocean is changing. The changes include rising sea level, declining sea ice, ocean acidification, and the decline of mega fauna. While the changes are daunting, oceanography is in the midst of a technical revolution with the expansion of numerical modeling techniques, combined with ocean robotics. Operating together, these systems represent a new generation of ocean observatories. I will review the evolution of these ocean observatories and provide a few case examples of the science that they enable, spanning from the waters offshore New Jersey to the remote waters of the Southern Ocean.

Eddy dynamics in the Southern Ocean: How does the interaction of the Antarctic Circumpolar Current with sea-bed topography influence the surface mixed layer and hence the carbon-climate feedback processes?

CSIR Research Space (South Africa)

Kobo, N

2012-10-01

Full Text Available The Southern Ocean is an important sink for heat and CO2 and is one of the world’s most productive regions. The unique absence of blocking continents allows the Antarctic Circumpolar Current (ACC) to connect all ocean basins (Atlantic, Pacific...

Potential climate change effects on the habitat of antarctic krill in the weddell quadrant of the southern ocean.

Science.gov (United States)

Hill, Simeon L; Phillips, Tony; Atkinson, Angus

2013-01-01

Antarctic krill is a cold water species, an increasingly important fishery resource and a major prey item for many fish, birds and mammals in the Southern Ocean. The fishery and the summer foraging sites of many of these predators are concentrated between 0° and 90°W. Parts of this quadrant have experienced recent localised sea surface warming of up to 0.2°C per decade, and projections suggest that further widespread warming of 0.27° to 1.08°C will occur by the late 21(st) century. We assessed the potential influence of this projected warming on Antarctic krill habitat with a statistical model that links growth to temperature and chlorophyll concentration. The results divide the quadrant into two zones: a band around the Antarctic Circumpolar Current in which habitat quality is particularly vulnerable to warming, and a southern area which is relatively insensitive. Our analysis suggests that the direct effects of warming could reduce the area of growth habitat by up to 20%. The reduction in growth habitat within the range of predators, such as Antarctic fur seals, that forage from breeding sites on South Georgia could be up to 55%, and the habitat's ability to support Antarctic krill biomass production within this range could be reduced by up to 68%. Sensitivity analysis suggests that the effects of a 50% change in summer chlorophyll concentration could be more significant than the direct effects of warming. A reduction in primary production could lead to further habitat degradation but, even if chlorophyll increased by 50%, projected warming would still cause some degradation of the habitat accessible to predators. While there is considerable uncertainty in these projections, they suggest that future climate change could have a significant negative effect on Antarctic krill growth habitat and, consequently, on Southern Ocean biodiversity and ecosystem services.

An inter-comparison of six latent and sensible heat flux products over the Southern Ocean

Directory of Open Access Journals (Sweden)

Lejiang Yu

2011-11-01

Full Text Available The latent heat fluxes (LHF and sensible heat fluxes (SHF over the Southern Ocean from six different data sets are inter-compared for the period 1988–2000. The six data sets include three satellite-based products, namely, the second version of the Goddard Satellite-Based Surface Turbulent Fluxes data set (GSSTF-2, the third version of the Hamburg Ocean Atmosphere Parameters and Fluxes from Satellite Data (HOAPS-3 and the Japanese Ocean Fluxes Data Sets with Use of Remote Sensing Observations (J-OFURO; two global reanalysis products, namely, the National Centers for Environmental Prediction–Department of Energy Reanalysis 2 data set (NCEP-2 and the European Centre for Medium-Range Weather Forecasts 40 Year Re-analysis data set (ERA-40; and the Objectively Analyzed Air–Sea Fluxes for the Global Oceans data set (OAFlux. All these products reveal a similar pattern in the averaged flux fields. The zonal mean LHF fields all exhibit a continuous increase equatorward. With an exception of HOAPS-3, the zonal mean SHF fields display a minimum value near 50°S, increasing both pole- and equatorward. The differences in the standard deviation for LHF are larger among the six data products than the differences for SHF. Over the regions where the surface fluxes are significantly influenced by the Antarctic Oscillation and the Pacific–South American teleconnection, the values and distributions of both LHF and SHF are consistent among the six products. It was found that the spatial patterns of the standard deviations and trends of LHF and SHF can be explained primarily by sea–air specific humidity and temperature differences; wind speed plays a minor role.

Millennial-scale changes in atmospheric CO2 levels linked to the Southern Ocean carbon isotope gradient and dust flux

Science.gov (United States)

Ziegler, Martin; Diz, Paula; Hall, Ian R.; Zahn, Rainer

2013-06-01

The rise in atmospheric CO2 concentrations observed at the end of glacial periods has, at least in part, been attributed to the upwelling of carbon-rich deep water in the Southern Ocean. The magnitude of outgassing of dissolved CO2, however, is influenced by the biological fixation of upwelled inorganic carbon and its transfer back to the deep sea as organic carbon. The efficiency of this biological pump is controlled by the extent of nutrient utilization, which can be stimulated by the delivery of iron by atmospheric dust particles. Changes in nutrient utilization should be reflected in the δ13C gradient between intermediate and deep waters. Here we use the δ13C values of intermediate- and bottom-dwelling foraminifera to reconstruct the carbon isotope gradient between thermocline and abyssal water in the subantarctic zone of the South Atlantic Ocean over the past 360,000 years. We find millennial-scale oscillations of the carbon isotope gradient that correspond to changes in dust flux and atmospheric CO2 concentrations as reported from Antarctic ice cores. We interpret this correlation as a relationship between the efficiency of the biological pump and fertilization by dust-borne iron. As the correlation is exponential, we suggest that the sensitivity of the biological pump to dust-borne iron fertilization may be increased when the background dust flux is low.

Partial pressure (or fugacity) of carbon dioxide, salinity and other variables collected from Surface underway observations using Carbon dioxide (CO2) gas analyzer, Shower head chamber equilibrator for autonomous carbon dioxide (CO2) measurement and other instruments from TANGAROA in the South Pacific Ocean, Southern Oceans and Tasman Sea from 2015-01-05 to 2015-12-23 (NCEI Accession 0157326)

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — NCEI Accession 0157326 includes Surface underway, chemical, meteorological and physical data collected from TANGAROA in the South Pacific Ocean, Southern Oceans...

Impact of the initialisation on the predictability of the Southern Ocean sea ice at interannual to multi-decadal timescales

Science.gov (United States)

Zunz, Violette; Goosse, Hugues; Dubinkina, Svetlana

2015-04-01

In this study, we assess systematically the impact of different initialisation procedures on the predictability of the sea ice in the Southern Ocean. These initialisation strategies are based on three data assimilation methods: the nudging, the particle filter with sequential importance resampling and the nudging proposal particle filter. An Earth system model of intermediate complexity is used to perform hindcast simulations in a perfect model approach. The predictability of the Antarctic sea ice at interannual to multi-decadal timescales is estimated through two aspects: the spread of the hindcast ensemble, indicating the uncertainty of the ensemble, and the correlation between the ensemble mean and the pseudo-observations, used to assess the accuracy of the prediction. Our results show that at decadal timescales more sophisticated data assimilation methods as well as denser pseudo-observations used to initialise the hindcasts decrease the spread of the ensemble. However, our experiments did not clearly demonstrate that one of the initialisation methods systematically provides with a more accurate prediction of the sea ice in the Southern Ocean than the others. Overall, the predictability at interannual timescales is limited to 3 years ahead at most. At multi-decadal timescales, the trends in sea ice extent computed over the time period just after the initialisation are clearly better correlated between the hindcasts and the pseudo-observations if the initialisation takes into account the pseudo-observations. The correlation reaches values larger than 0.5 in winter. This high correlation has likely its origin in the slow evolution of the ocean ensured by its strong thermal inertia, showing the importance of the quality of the initialisation below the sea ice.

Marked phylogeographic structure of Gentoo penguin reveals an ongoing diversification process along the Southern Ocean.

Science.gov (United States)

Vianna, Juliana A; Noll, Daly; Dantas, Gisele P M; Petry, Maria Virginia; Barbosa, Andrés; González-Acuña, Daniel; Le Bohec, Céline; Bonadonna, Francesco; Poulin, Elie

2017-02-01

Two main hypotheses have been debated about the biogeography of the Southern Ocean: (1) the Antarctic Polar Front (APF), acting as a barrier between Antarctic and sub-Antarctic provinces, and (2) the Antarctic Circumpolar Current (ACC), promoting gene flow among sub-Antarctic areas. The Gentoo penguin is distributed throughout these two provinces, separated by the APF. We analyzed mtDNA (HVR1) and 12 microsatellite loci of 264 Gentoo penguins, Pygoscelis papua, from 12 colonies spanning from the Western Antarctic Peninsula and the South Shetland Islands (WAP) to the sub-Antarctic Islands (SAI). While low genetic structure was detected among WAP colonies (mtDNA Ф ST =0.037-0.133; microsatellite F ST =0.009-0.063), high differentiation was found between all SAI and WAP populations (mtDNA Ф ST =0.678-0.930; microsatellite F ST =0.110-0.290). These results suggest that contemporary dispersal around the Southern Ocean is very limited or absent. As predicted, the APF appears to be a significant biogeographical boundary for Gentoo penguin populations; however, the ACC does not promote connectivity in this species. Our data suggest demographic expansion in the WAP during the last glacial maximum (LGM, about 20kya), but stability in SAI. Phylogenetic analyses showed a deep divergence between populations from the WAP and those from the SAI. Therefore, taxonomy should be further revised. The Crozet Islands resulted as a basal clade (3.57Mya), followed by the Kerguelen Islands (2.32Mya) as well as a more recent divergence between the Falkland/Malvinas Islands and the WAP (1.27Mya). Historical isolation, local adaptation, and past climate scenarios of those Evolutionarily Significant Units may have led to different potentials to respond to climate changes. Copyright © 2016 Elsevier Inc. All rights reserved.

Distribution and recurrence of phytoplankton blooms around South Georgia, Southern Ocean

Directory of Open Access Journals (Sweden)

I. Borrione

2013-01-01

Full Text Available South Georgia phytoplankton blooms are amongst the largest of the Southern Ocean and are associated with a rich ecosystem and strong atmospheric carbon drawdown. Both aspects depend on the intensity of blooms, but also on their regularity. Here we use data from 12 yr of SeaWiFS (Sea-viewing Wide Field-of-view Sensor ocean colour imagery and calculate the frequency of bloom occurrence (FBO to re-examine spatial and temporal bloom distributions. We find that upstream of the island and outside the borders of the Georgia Basin, blooms occurred in less than 4 out of the 12 yr (FBO < 4. In contrast, FBO was mostly greater than 8 downstream of the island, i.e., to the north and northwest, and in places equal to 12, indicating that blooms occurred every year. The typical bloom area, defined as the region where blooms occurred in at least 8 out of the 12 yr, covers the entire Georgia Basin and the northern shelf of the island. The time series of surface chlorophyll a (Chl a concentrations averaged over the typical bloom area shows that phytoplankton blooms occurred in every year between September 1997 and September 2010, and that Chl a values followed a clear seasonal cycle, with concentration peaks around December followed in many years by a second peak during late austral summer or early autumn, suggesting a bi-modal bloom pattern. The bloom regularity we describe here is in contrast with results of Park et al. (2010 who used a significantly different study area including regions that almost never exhibit bloom conditions.

The effect of sea-ice on the transient atmospheric eddies of the Southern Hemisphere

Energy Technology Data Exchange (ETDEWEB)

Menendez, C.G. [Centro de Investigaciones del Mar y la Atmosfera/CONICET-UBA, Buenos Aires (Argentina); Serafini, V.; Le Treut, H. [Laboratoire de Meteorologie Dynamique/CNRS, Universite P. et M. Curie, Tour 15-25, 4 place Jussieu, 75252 Paris Cedex 05 (France)

1999-09-01

Two 10 y simulations with a full seasonal cycle and 96 x 72 x 19 resolution were carried out with a version of the LMD GCM to diagnose the role of sea-ice on the extratropical climatology of the Southern Hemisphere. The control integration used the usual observed sea-ice distribution, while the anomaly simulation imposed a scenario in which all sea-ice was entirely replaced by open ocean. The simulated control climate was compared with available observational-based analyses. Relevant diagnostics of the time mean and indicators of the transient eddy activity have been evaluated for both integrations. The impact was shown throughout the troposphere and was larger and more organised in winter. We found reduced westerly flow and both falls and rises in sea level pressure in the region from which sea-ice was removed. The removal of ice in the Southern Ocean affects the baroclinic structure of the atmosphere. Changes in baroclinicity and eddy activity are consistent with changes in the mean climate. In general, the meridional wind variance, the poleward transient temperature flux and the eddy flux convergence of westerly momentum were weaker over the Southern Ocean. However, a strengthening of the variance downstream of the subtropical jet was found. The position of the main storm track tends to be slightly displaced equatorward in the anomaly case. (orig.) With 15 figs., 53 refs.

Independence of nutrient limitation and carbon dioxide impacts on the Southern Ocean coccolithophore Emiliania huxleyi.

Science.gov (United States)

Müller, Marius N; Trull, Thomas W; Hallegraeff, Gustaaf M

2017-08-01

Future oceanic conditions induced by anthropogenic greenhouse gas emissions include warming, acidification and reduced nutrient supply due to increased stratification. Some parts of the Southern Ocean are expected to show rapid changes, especially for carbonate mineral saturation. Here we compare the physiological response of the model coccolithophore Emiliania huxleyi (strain EHSO 5.14, originating from 50 o S, 149 o E) with pH/CO 2 gradients (mimicking ocean acidification ranging from 1 to 4 × current pCO 2 levels) under nutrient-limited (nitrogen and phosphorus) and -replete conditions. Both nutrient limitations decreased per cell photosynthesis (particulate organic carbon (POC) production) and calcification (particulate inorganic carbon (PIC) production) rates for all pCO 2 levels, with more than 50% reductions under nitrogen limitation. These impacts, however, became indistinguishable from nutrient-replete conditions when normalized to cell volume. Calcification decreased three-fold and linearly with increasing pCO 2 under all nutrient conditions, and was accompanied by a smaller ~30% nonlinear reduction in POC production, manifested mainly above 3 × current pCO 2 . Our results suggest that normalization to cell volume allows the major impacts of nutrient limitation (changed cell sizes and reduced PIC and POC production rates) to be treated independently of the major impacts of increasing pCO 2 and, additionally, stresses the importance of including cell volume measurements to the toolbox of standard physiological analysis of coccolithophores in field and laboratory studies.

Southern Ocean Predicted Seafloor Topography Poster - MGG9

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — This 36 by 48 inch full color poster is MGG Report 9. In many areas of the global ocean, the depth of the seafloor is not well known because survey lines by ships...

Effect of varying frontal systems on stable oxygen and carbon isotopic compositions of modern planktic foraminifera of Southern Ocean

Digital Repository Service at National Institute of Oceanography (India)

Tiwari, M.; Mohan, R.; Meloth, T.; Naik, S.S.; Sudhakar, M.

, sediment cores and other physi- cal oceanographic parameters were collected. Here, we present the isotopic results obtained from planktic foraminifera from the plankton net samples and sur- face sediments. We find that, in this region too, plank- tic... characteristics in the Indian sector of the Southern Ocean. The δ 18 O value of planktic foraminifera is mainly governed by SST fluctuations: the samples be- come isotopically heavier polewards. Further, the plank- tic foraminifera appear to secrete...

Carbon dioxide, temperature, salinity, and other variables collected via surface underway survey from Volunteer Observing Ship AURORA AUSTRALIS in the Southern Oceans (> 60 degrees South) from 1992-10-19 to 2001-12-12 (NODC Accession 0081031)

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — Surface and Atmospheric fCO2 measurements in the Southern Ocean during the VOS Project line onboard the oceanographic ship Aurora Australis.

Climate Prediction Center (CPC)Oceanic Nino Index

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — The Oceanic Nino Index (ONI) is one of the primary indices used to monitor the El Nino-Southern Oscillation (ENSO). The ONI is calculated by averaging sea surface...

Southern Hemisphere extratropical circulation: Recent trends and natural variability

Science.gov (United States)

Thomas, Jordan L.; Waugh, Darryn W.; Gnanadesikan, Anand

2015-07-01

Changes in the Southern Annular Mode (SAM), Southern Hemisphere (SH) westerly jet location, and magnitude are linked with changes in ocean circulation along with ocean heat and carbon uptake. Recent trends have been observed in these fields but not much is known about the natural variability. Here we aim to quantify the natural variability of the SH extratropical circulation by using Coupled Model Intercomparison Project Phase 5 (CMIP5) preindustrial control model runs and compare with the observed trends in SAM, jet magnitude, and jet location. We show that trends in SAM are due partly to external forcing but are not outside the natural variability as described by these models. Trends in jet location and magnitude, however, lie outside the unforced natural variability but can be explained by a combination of natural variability and the ensemble mean forced trend. These results indicate that trends in these three diagnostics cannot be used interchangeably.

Temperature profile and nutrients data collected using bottle casts from the POLAR DUKE and NATHANIEL B. PALMER in the Ross Sea and Southern Oceans from 08 April 1997 to 05 May 1997 (NODC Accession 0000897)

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — Temperature profile and nutrients data were collected using bottle casts in the Ross Sea and Southern Oceans from the POLAR DUKE and NATHANIEL B. PALMER. Data were...

Temperature profile and nutrients data collected using bottle casts from the POLAR DUKE and NATHANIEL B. PALMER in the Ross Sea and Southern Oceans from 10 November 1997 to 12 December 1997 (NODC Accession 0000898)

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — Temperature profile and nutrients data were collected using bottle casts in the Ross Sea and Southern Oceans from the POLAR DUKE and NATHANIEL B. PALMER. Data were...

Multi-model analysis of expected future trends in the landfall of tropical systems from the Southwest Indian Ocean over the eastern parts of southern Africa

CSIR Research Space (South Africa)

Malherbe, J

2010-09-01

Full Text Available the southwest Indian Ocean (SWIO) over southern Africa as well as the simulated change in the frequencies, tracks and intensities of landfalling low-pressure systems in the context of climate change. The main finding in this regard is that there exists general...

Ocean heat content variability and change in an ensemble of ocean reanalyses

Science.gov (United States)

Palmer, M. D.; Roberts, C. D.; Balmaseda, M.; Chang, Y.-S.; Chepurin, G.; Ferry, N.; Fujii, Y.; Good, S. A.; Guinehut, S.; Haines, K.; Hernandez, F.; Köhl, A.; Lee, T.; Martin, M. J.; Masina, S.; Masuda, S.; Peterson, K. A.; Storto, A.; Toyoda, T.; Valdivieso, M.; Vernieres, G.; Wang, O.; Xue, Y.

2017-08-01

Accurate knowledge of the location and magnitude of ocean heat content (OHC) variability and change is essential for understanding the processes that govern decadal variations in surface temperature, quantifying changes in the planetary energy budget, and developing constraints on the transient climate response to external forcings. We present an overview of the temporal and spatial characteristics of OHC variability and change as represented by an ensemble of dynamical and statistical ocean reanalyses (ORAs). Spatial maps of the 0-300 m layer show large regions of the Pacific and Indian Oceans where the interannual variability of the ensemble mean exceeds ensemble spread, indicating that OHC variations are well-constrained by the available observations over the period 1993-2009. At deeper levels, the ORAs are less well-constrained by observations with the largest differences across the ensemble mostly associated with areas of high eddy kinetic energy, such as the Southern Ocean and boundary current regions. Spatial patterns of OHC change for the period 1997-2009 show good agreement in the upper 300 m and are characterized by a strong dipole pattern in the Pacific Ocean. There is less agreement in the patterns of change at deeper levels, potentially linked to differences in the representation of ocean dynamics, such as water mass formation processes. However, the Atlantic and Southern Oceans are regions in which many ORAs show widespread warming below 700 m over the period 1997-2009. Annual time series of global and hemispheric OHC change for 0-700 m show the largest spread for the data sparse Southern Hemisphere and a number of ORAs seem to be subject to large initialization `shock' over the first few years. In agreement with previous studies, a number of ORAs exhibit enhanced ocean heat uptake below 300 and 700 m during the mid-1990s or early 2000s. The ORA ensemble mean (±1 standard deviation) of rolling 5-year trends in full-depth OHC shows a relatively steady

Silicon pool dynamics and biogenic silica export in the Southern Ocean inferred from Si-isotopes

Directory of Open Access Journals (Sweden)

F. Fripiat

2011-09-01

Full Text Available Silicon isotopic signatures (δ³⁰Si of water column silicic acid (Si(OH₄ were measured in the Southern Ocean, along a meridional transect from South Africa (Subtropical Zone down to 57° S (northern Weddell Gyre. This provides the first reported data of a summer transect across the whole Antarctic Circumpolar Current (ACC. δ³⁰Si variations are large in the upper 1000 m, reflecting the effect of the silica pump superimposed upon meridional water transfer across the ACC: the transport of Antarctic surface waters northward by a net Ekman drift and their convergence and mixing with warmer upper-ocean Si-depleted waters to the north. Using Si isotopic signatures, we determine different mixing interfaces: the Antarctic Surface Water (AASW, the Antarctic Intermediate Water (AAIW, and thermoclines in the low latitude areas. The residual silicic acid concentrations of end-members control the δ³⁰Si alteration of the mixing products and with the exception of AASW, all mixing interfaces have a highly Si-depleted mixed layer end-member. These processes deplete the silicic acid AASW concentration northward, across the different interfaces, without significantly changing the AASW δ³⁰Si composition. By comparing our new results with a previous study in the Australian sector we show that during the circumpolar transport of the ACC eastward, the δ³⁰Si composition of the silicic acid pools is getting slightly, but significantly lighter from the Atlantic to the Australian sectors. This results either from the dissolution of biogenic silica in the deeper layers and/or from an isopycnal mixing with the deep water masses in the different oceanic basins: North Atlantic Deep Water in the Atlantic, and Indian Ocean deep water in the Indo-Australian sector. This isotopic trend is further transmitted to the subsurface waters, representing mixing interfaces between the surface and deeper layers.

Basin-scale transport of hydrothermal dissolved metals across the South Pacific Ocean.

Science.gov (United States)

Resing, Joseph A; Sedwick, Peter N; German, Christopher R; Jenkins, William J; Moffett, James W; Sohst, Bettina M; Tagliabue, Alessandro

2015-07-09

Hydrothermal venting along mid-ocean ridges exerts an important control on the chemical composition of sea water by serving as a major source or sink for a number of trace elements in the ocean. Of these, iron has received considerable attention because of its role as an essential and often limiting nutrient for primary production in regions of the ocean that are of critical importance for the global carbon cycle. It has been thought that most of the dissolved iron discharged by hydrothermal vents is lost from solution close to ridge-axis sources and is thus of limited importance for ocean biogeochemistry. This long-standing view is challenged by recent studies which suggest that stabilization of hydrothermal dissolved iron may facilitate its long-range oceanic transport. Such transport has been subsequently inferred from spatially limited oceanographic observations. Here we report data from the US GEOTRACES Eastern Pacific Zonal Transect (EPZT) that demonstrate lateral transport of hydrothermal dissolved iron, manganese, and aluminium from the southern East Pacific Rise (SEPR) several thousand kilometres westward across the South Pacific Ocean. Dissolved iron exhibits nearly conservative (that is, no loss from solution during transport and mixing) behaviour in this hydrothermal plume, implying a greater longevity in the deep ocean than previously assumed. Based on our observations, we estimate a global hydrothermal dissolved iron input of three to four gigamoles per year to the ocean interior, which is more than fourfold higher than previous estimates. Complementary simulations with a global-scale ocean biogeochemical model suggest that the observed transport of hydrothermal dissolved iron requires some means of physicochemical stabilization and indicate that hydrothermally derived iron sustains a large fraction of Southern Ocean export production.

Marine aerosol distribution and variability over the pristine Southern Indian Ocean

Science.gov (United States)

Mallet, Paul-Étienne; Pujol, Olivier; Brioude, Jérôme; Evan, Stéphanie; Jensen, Andrew

2018-06-01

This paper presents an 8-year (2005-2012 inclusive) study of the marine aerosol distribution and variability over the Southern Indian Ocean, precisely in the area { 10 °S - 40 °S ; 50 °E - 110 °E } which has been identified as one of the most pristine regions of the globe. A large dataset consisting of satellite data (POLDER, CALIOP), AERONET measurements at Saint-Denis (French Réunion Island) and model reanalysis (MACC), has been used. In spite of a positive bias of about 0.05 between the AOD (aerosol optical depth) given by POLDER and MACC on one hand and the AOD measured by AERONET on the other, consistent results for aerosol distribution and variability over the area considered have been obtained. First, aerosols are mainly confined below 2km asl (above sea level) and are dominated by sea salt, especially in the center of the area of interest, with AOD ≤ 0 . 1. This zone is the most pristine and is associated with the position of the Mascarene anticyclone. There, the direct radiative effect is assessed around - 9 Wm-2 at the top of the atmosphere and probability density functions of the AOD s are leptokurtic lognormal functions without any significant seasonal variation. It is also suggested that the Madden-Jullian oscillation impacts sea salt emissions in the northern part of the area considered by modifying the state of the ocean surface. Finally, this area is surrounded in the northeast and the southwest by seasonal Australian and South African intrusions (AOD > 0.1) ; throughout the year, the ITCZ seems to limit continental contaminations from Asia. Due to the long period of time considered (almost a decade), this paper completes and strengthens results of studies based on observations performed during previous specific field campaigns.

Impact of ocean model resolution on CCSM climate simulations

Energy Technology Data Exchange (ETDEWEB)

Kirtman, Ben P.; Rousset, Clement; Siqueira, Leo [University of Miami, Rosenstiel School for Marine and Atmospheric Science, Coral Gables, FL (United States); Bitz, Cecilia [University of Washington, Department of Atmospheric Science, Seattle, WA (United States); Bryan, Frank; Dennis, John; Hearn, Nathan; Loft, Richard; Tomas, Robert; Vertenstein, Mariana [National Center for Atmospheric Research, Boulder, CO (United States); Collins, William [University of California, Berkeley, Berkeley, CA (United States); Kinter, James L.; Stan, Cristiana [Center for Ocean-Land-Atmosphere Studies, Calverton, MD (United States); George Mason University, Fairfax, VA (United States)

2012-09-15

The current literature provides compelling evidence suggesting that an eddy-resolving (as opposed to eddy-permitting or eddy-parameterized) ocean component model will significantly impact the simulation of the large-scale climate, although this has not been fully tested to date in multi-decadal global coupled climate simulations. The purpose of this paper is to examine how resolved ocean fronts and eddies impact the simulation of large-scale climate. The model used for this study is the NCAR Community Climate System Model version 3.5 (CCSM3.5) - the forerunner to CCSM4. Two experiments are reported here. The control experiment is a 155-year present-day climate simulation using a 0.5 atmosphere component (zonal resolution 0.625 meridional resolution 0.5 ; land surface component at the same resolution) coupled to ocean and sea-ice components with zonal resolution of 1.2 and meridional resolution varying from 0.27 at the equator to 0.54 in the mid-latitudes. The second simulation uses the same atmospheric and land-surface models coupled to eddy-resolving 0.1 ocean and sea-ice component models. The simulations are compared in terms of how the representation of smaller scale features in the time mean ocean circulation and ocean eddies impact the mean and variable climate. In terms of the global mean surface temperature, the enhanced ocean resolution leads to a ubiquitous surface warming with a global mean surface temperature increase of about 0.2 C relative to the control. The warming is largest in the Arctic and regions of strong ocean fronts and ocean eddy activity (i.e., Southern Ocean, western boundary currents). The Arctic warming is associated with significant losses of sea-ice in the high-resolution simulation. The sea surface temperature gradients in the North Atlantic, in particular, are better resolved in the high-resolution model leading to significantly sharper temperature gradients and associated large-scale shifts in the rainfall. In the extra-tropics, the

Warming of the Indian Ocean Threatens Eastern and Southern Africa, but could be Mitigated by Agricultural Development

Science.gov (United States)

Funk, Chris; Dettinger, Michael D.; Brown, Molly E.; Michaelsen, Joel C.; Verdin, James P.; Barlow, Mathew; Howell, Andrew

2008-01-01

Since 1980, the number of undernourished people in eastern and southern Africa has more than doubled. Rural development stalled and rural poverty expanded during the 1990s. Population growth remains very high and declining per capita agricultural capacity retards progress towards Millennium Development goals. Analyses of in situ station data and satellite observations of precipitation identify another problematic trend. Main growing season rainfall receipts have diminished by approximately 15% in food insecure countries clustered along the western rim of the Indian Ocean. Occurring during the main growing seasons in poor countries dependent on rain fed agriculture, these declines are societally dangerous. Will they persist or intensify? Tracing moisture deficits upstream to an anthropogenically warming Indian Ocean leads us to conclude that further rainfall declines are likely. We present analyses suggesting that warming in the central Indian Ocean disrupts onshore moisture transports, reducing continental rainfall. Thus late 20th century anthropogenic Indian Ocean warming has probably already produced societally dangerous climate change by creating drought and social disruption in some of the world's most fragile food economies. We quantify the potential impacts of the observed precipitation and agricultural capacity trends by modeling millions of undernourished people as a function of rainfall, population, cultivated area, seed and fertilizer use. Persistence of current tendencies may result in a 50% increase in undernourished people. On the other hand, modest increases in per capita agricultural productivity could more than offset the observed precipitation declines. Investing in agricultural development can help mitigate climate change while decreasing rural poverty and vulnerability.

Paleoceanographic Changes during the Past 95000 Years from the Indian Sector of the Southern Ocean

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Manoj, M. C.; Meloth, T.; Mohan, R.

2012-12-01

High-resolution planktic/benthic foraminiferal stable isotope and mean sortable silt records in a sediment core (SK200/22a) from the sub-Antarctic regime of the Indian sector of Southern Ocean depict the variations in surface and deep water hydrography during the past 95,000 years. The δ18O records of shallow- and deep-dwelling planktonic foraminiferal species (Neogloboquadrina pachyderma, Globigerina bulloides and Globorotalia inflata), primarily reflects the changes in upper water column characteristics. The δ18O records revealed the presence of the Antarctic Cold Reversal and the timing of the variability in major surface warming events appears in phase with the Antarctic temperature variations at the millennial time scale. Comparison between the proxies of sea surface conditions like planktonic δ18O and productivity proxies like carbonate and biogenic opal content in the core indicate that millennial scale sea surface warming fluctuated with productivity. The marine isotopic stage (MIS) 1 and MIS2 are characterized by near constant variations in mean sortable silt values, negating any significant changes in the deep water flow during these periods. The MIS 3 - MIS 5 periods were characterized by a general increase in mean sortable silt value, suggesting a strengthening of bottom-current activity that triggered winnowing at these periods. This is supported by the low δ13C records of epibenthic Cibicidoides wuellerstorfi during the glacials and some parts of MIS3 and MIS 5, confirming older nutrient-rich and poorly ventilated southern sourced deep waters at these periods. The termination I is marked by decrease in flow speed and an increase in the C. wuellerstorfi δ13C values. Comparison of mean sortable silt and C. wuellerstorfi δ13C record with the Antarctic ice core records reveal that pulses of reduced bottom water flow of Circumpolar Deep Water/North Atlantic Deep Water are synchronous with the Antarctic warming events. The decreased flow speed during

New Hampshire / Southern Maine Ocean Uses Atlas: Dominant and Aggregates

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — The Ocean Uses Atlas Project is an innovative partnership between the Coastal Response Research Center (CRRC) and NOAA's Office of Ocean and Coastal Resource...

New Hampshire / Southern Maine Ocean Uses Atlas: Non-Consumptive sector

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — The Ocean Uses Atlas Project is an innovative partnership between the Coastal Response Research Center (CRRC) and NOAA's Office of Ocean and Coastal Resource...

Long-Term Relationships between the Marine Environment, Krill and Salps in the Southern Ocean

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Chung Il Lee

2010-01-01

Full Text Available Long-term variations (1975–2002 in climatology of marine environmental parameters, Antarctic krill, Euphausia superba, and the pelagic tunicate, Salpa thompsoni, were compared within the Atlantic Sector of the Southern Ocean. Sea water temperature in the top 400 m increased at a rate of 0.020–0.030°C ⋅ yr−1, which was accompanied by the dissolved oxygen decline. Top 100 m water layer became fresher with lower concentrations of phosphates and nitrates, while at subsurface layers (200–400 m both salinity and nutrients showed small increasing trend. Unlike phosphates and nitrates, silicate concentrations decreased in the entire water column. Shorter-term water temperature dynamics closely correlated with the El Nino events expressed as the Southern Oscillation Index which in turn was linked to the propagation of the Antarctic Circumpolar Wave (ACW. The variations of sea-ice extent matched well the changes in both air and water temperatures. In general, abundance of krill and salps showed opposite to each other trends. Due to large area considered in this study, no significant relationships between abiotic factors and both krill and salps were found. However, our analysis demonstrated that krill abundance was greater in years with lower sea water temperature, greater sea-ice extent and higher nutrient concentration, while salps showed the opposite pattern.

Polar ocean stratification in a cold climate.

Science.gov (United States)

Sigman, Daniel M; Jaccard, Samuel L; Haug, Gerald H

2004-03-04

The low-latitude ocean is strongly stratified by the warmth of its surface water. As a result, the great volume of the deep ocean has easiest access to the atmosphere through the polar surface ocean. In the modern polar ocean during the winter, the vertical distribution of temperature promotes overturning, with colder water over warmer, while the salinity distribution typically promotes stratification, with fresher water over saltier. However, the sensitivity of seawater density to temperature is reduced as temperature approaches the freezing point, with potential consequences for global ocean circulation under cold climates. Here we present deep-sea records of biogenic opal accumulation and sedimentary nitrogen isotopic composition from the Subarctic North Pacific Ocean and the Southern Ocean. These records indicate that vertical stratification increased in both northern and southern high latitudes 2.7 million years ago, when Northern Hemisphere glaciation intensified in association with global cooling during the late Pliocene epoch. We propose that the cooling caused this increased stratification by weakening the role of temperature in polar ocean density structure so as to reduce its opposition to the stratifying effect of the vertical salinity distribution. The shift towards stratification in the polar ocean 2.7 million years ago may have increased the quantity of carbon dioxide trapped in the abyss, amplifying the global cooling.

Understanding Rossby wave trains forced by the Indian Ocean Dipole

Science.gov (United States)

McIntosh, Peter C.; Hendon, Harry H.

2018-04-01

Convective variations over the tropical Indian Ocean associated with ENSO and the Indian Ocean Dipole force a Rossby wave train that appears to emanate poleward and eastward to the south of Australia and which causes climate variations across southern Australia and more generally throughout the Southern Hemisphere extratropics. However, during austral winter, the subtropical jet that extends from the eastern Indian Ocean into the western Pacific at Australian latitudes should effectively prohibit continuous propagation of a stationary Rossby wave from the tropics into the extratropics because the meridional gradient of mean absolute vorticity goes to zero on its poleward flank. The observed wave train indeed exhibits strong convergence of wave activity flux upon encountering this region of vanishing vorticity gradient and with some indication of reflection back into the tropics, indicating the continuous propagation of the stationary Rossby wave train from low to high latitudes is inhibited across the south of Australia. However, another Rossby wave train appears to emanate upstream of Australia on the poleward side of the subtropical jet and propagates eastward along the waveguide of the eddy-driven (sub-polar) jet into the Pacific sector of the Southern Ocean. This combination of evanescent wave train from the tropics and eastward propagating wave train emanating from higher latitudes upstream of Australia gives the appearance of a continuous Rossby wave train propagating from the tropical Indian Ocean into higher southern latitudes. The extratropical Rossby wave source on the poleward side of the subtropical jet stems from induced changes in transient eddy activity in the main storm track of the Southern Hemisphere. During austral spring, when the subtropical jet weakens, the Rossby wave train emanating from Indian Ocean convection is explained more traditionally by direct dispersion from divergence forcing at low latitudes.

Global monsoons in the mid-Holocene and oceanic feedback

Energy Technology Data Exchange (ETDEWEB)

Liu, Z.; Kutzbach, J. [Center for Climatic Research, University of Wisconsin-Madison, 1225 W. Dayton Street, Madison, WI 53706 (United States); Harrison, S.P. [Max Planck Institute for Biogeochemistry, P.O. Box 100164, 07701 Jena (Germany); Otto-Bliesner, B. [National Center for Atmospheric Research, PO Box 3000, Boulder, CO 80307 (United States)

2004-03-01

The response of the six major summer monsoon systems (the North American monsoon, the northern Africa monsoon, the Asia monsoon, the northern Australasian monsoon, the South America monsoon and the southern Africa monsoon) to mid-Holocene orbital forcing has been investigated using a coupled ocean-atmosphere general circulation model (FOAM), with the focus on the distinct roles of the direct insolation forcing and oceanic feedback. The simulation result is also found to compare well with the NCAR CSM. The direct effects of the change in insolation produce an enhancement of the Northern Hemisphere monsoons and a reduction of the Southern Hemisphere monsoons. Ocean feedbacks produce a further enhancement of the northern Africa monsoon and the North American monsoon. However, ocean feedbacks appear to weaken the Asia monsoon, although the overall effect (direct insolation forcing plus ocean feedback) remains a strengthened monsoon. The impact of ocean feedbacks on the South American and southern African monsoons is relatively small, and therefore these regions, especially the South America, experienced a reduced monsoon regime compared to present. However, there is a strong ocean feedback on the northern Australian monsoon that negates the direct effects of orbital changes and results in a strengthening of austral summer monsoon precipitation in this region. A new synthesis is made for mid-Holocene paleoenvironmental records and is compared with the model simulations. Overall, model simulations produce changes in regional climates that are generally consistent with paleoenvironmental observations. (orig.)

Glacial greenhouse-gas fluctuations controlled by ocean circulation changes.

Science.gov (United States)

Schmittner, Andreas; Galbraith, Eric D

2008-11-20

Earth's climate and the concentrations of the atmospheric greenhouse gases carbon dioxide (CO(2)) and nitrous oxide (N(2)O) varied strongly on millennial timescales during past glacial periods. Large and rapid warming events in Greenland and the North Atlantic were followed by more gradual cooling, and are highly correlated with fluctuations of N(2)O as recorded in ice cores. Antarctic temperature variations, on the other hand, were smaller and more gradual, showed warming during the Greenland cold phase and cooling while the North Atlantic was warm, and were highly correlated with fluctuations in CO(2). Abrupt changes in the Atlantic meridional overturning circulation (AMOC) have often been invoked to explain the physical characteristics of these Dansgaard-Oeschger climate oscillations, but the mechanisms for the greenhouse-gas variations and their linkage to the AMOC have remained unclear. Here we present simulations with a coupled model of glacial climate and biogeochemical cycles, forced only with changes in the AMOC. The model simultaneously reproduces characteristic features of the Dansgaard-Oeschger temperature, as well as CO(2) and N(2)O fluctuations. Despite significant changes in the land carbon inventory, CO(2) variations on millennial timescales are dominated by slow changes in the deep ocean inventory of biologically sequestered carbon and are correlated with Antarctic temperature and Southern Ocean stratification. In contrast, N(2)O co-varies more rapidly with Greenland temperatures owing to fast adjustments of the thermocline oxygen budget. These results suggest that ocean circulation changes were the primary mechanism that drove glacial CO(2) and N(2)O fluctuations on millennial timescales.

Role of zooplankton dynamics for Southern Ocean phytoplankton biomass and global biogeochemical cycles

DEFF Research Database (Denmark)

Le Quéré, Corinne; Buitenhuis, Erik T.; Moriarty, Róisín

2016-01-01

zooplankton community, despite iron limitation of phytoplankton community growth rates. This result has implications for the representation of global biogeochemical cycles in models as zooplankton faecal pellets sink rapidly and partly control the carbon export to the intermediate and deep ocean....

An assessment of oceanic seabird abundance and distribution off the southern Brazilian coast using observations obtained during deep-water fishing operations.

Science.gov (United States)

Branco, J O; Fracasso, H A A; Pérez, J A A; Rodrigues-Filho, J L

2014-08-01

The use of discarded fish over baited hooks used in longline fishery, and fish caught in gillnets, as a food source for gulls, albatrosses and petrels has been intensively studied in northern and southern oceans. This study describes the occurrence and abundance of seabirds observed from 20 foreign vessels which operated during the period between July 2001 and May 2005, off the southeastern and southern Brazilian coast. A total of 353,557 seabirds were observed; comprising eight families and 28 species. The most abundant species was Procellaria conspicillata followed by Daption capense, Puffinus gravis, Thalassarche melanophrys and Oceanites oceanicus. Ten species of seabirds (392 individual birds) were incidentally captured in gillnets; and 122 birds (9 species) by longline hooks, with P. gravis, D. capense and Procellaria aequinoctialis having the largest capture rates.

Partial pressure (or fugacity) of carbon dioxide, salinity and other variables collected from Surface underway observations using Carbon dioxide (CO2) gas analyzer, Shower head chamber equilibrator for autonomous carbon dioxide (CO2) measurement and other instruments from NATHANIEL B. PALMER in the South Pacific Ocean, Southern Oceans and Tasman Sea from 1997-01-12 to 1998-01-09 (NCEI Accession 0157323)

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — NCEI Accession 0157323 includes Surface underway, chemical, meteorological and physical data collected from NATHANIEL B. PALMER in the South Pacific Ocean, Southern...

The Ocean Carbon States Database: a proof-of-concept application of cluster analysis in the ocean carbon cycle

Science.gov (United States)

Latto, Rebecca; Romanou, Anastasia

2018-03-01

In this paper, we present a database of the basic regimes of the carbon cycle in the ocean, the ocean carbon states, as obtained using a data mining/pattern recognition technique in observation-based as well as model data. The goal of this study is to establish a new data analysis methodology, test it and assess its utility in providing more insights into the regional and temporal variability of the marine carbon cycle. This is important as advanced data mining techniques are becoming widely used in climate and Earth sciences and in particular in studies of the global carbon cycle, where the interaction of physical and biogeochemical drivers confounds our ability to accurately describe, understand, and predict CO2 concentrations and their changes in the major planetary carbon reservoirs. In this proof-of-concept study, we focus on using well-understood data that are based on observations, as well as model results from the NASA Goddard Institute for Space Studies (GISS) climate model. Our analysis shows that ocean carbon states are associated with the subtropical-subpolar gyre during the colder months of the year and the tropics during the warmer season in the North Atlantic basin. Conversely, in the Southern Ocean, the ocean carbon states can be associated with the subtropical and Antarctic convergence zones in the warmer season and the coastal Antarctic divergence zone in the colder season. With respect to model evaluation, we find that the GISS model reproduces the cold and warm season regimes more skillfully in the North Atlantic than in the Southern Ocean and matches the observed seasonality better than the spatial distribution of the regimes. Finally, the ocean carbon states provide useful information in the model error attribution. Model air-sea CO2 flux biases in the North Atlantic stem from wind speed and salinity biases in the subpolar region and nutrient and wind speed biases in the subtropics and tropics. Nutrient biases are shown to be most important in

The Ocean Carbon States Database: A Proof-of-Concept Application of Cluster Analysis in the Ocean Carbon Cycle

Science.gov (United States)

Latto, Rebecca; Romanou, Anastasia

2018-01-01

In this paper, we present a database of the basic regimes of the carbon cycle in the ocean, the 'ocean carbon states', as obtained using a data mining/pattern recognition technique in observation-based as well as model data. The goal of this study is to establish a new data analysis methodology, test it and assess its utility in providing more insights into the regional and temporal variability of the marine carbon cycle. This is important as advanced data mining techniques are becoming widely used in climate and Earth sciences and in particular in studies of the global carbon cycle, where the interaction of physical and biogeochemical drivers confounds our ability to accurately describe, understand, and predict CO2 concentrations and their changes in the major planetary carbon reservoirs. In this proof-of-concept study, we focus on using well-understood data that are based on observations, as well as model results from the NASA Goddard Institute for Space Studies (GISS) climate model. Our analysis shows that ocean carbon states are associated with the subtropical-subpolar gyre during the colder months of the year and the tropics during the warmer season in the North Atlantic basin. Conversely, in the Southern Ocean, the ocean carbon states can be associated with the subtropical and Antarctic convergence zones in the warmer season and the coastal Antarctic divergence zone in the colder season. With respect to model evaluation, we find that the GISS model reproduces the cold and warm season regimes more skillfully in the North Atlantic than in the Southern Ocean and matches the observed seasonality better than the spatial distribution of the regimes. Finally, the ocean carbon states provide useful information in the model error attribution. Model air-sea CO2 flux biases in the North Atlantic stem from wind speed and salinity biases in the subpolar region and nutrient and wind speed biases in the subtropics and tropics. Nutrient biases are shown to be most important

Invertebrate diversity in southern California

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — This shapefile displays mean invertebrate diversity within 5 minute grid cells. The Shannon Index of diversity was calculated from Southern California Coastal Water...

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

2018-01-01

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.

Evaluation of PMIP2 and PMIP3 simulations of mid-Holocene climate in the Indo-Pacific, Australasian and Southern Ocean regions

Directory of Open Access Journals (Sweden)

D. Ackerley

2017-11-01

Full Text Available This study uses the simplified patterns of temperature and effective precipitation approach from the Australian component of the international palaeoclimate synthesis effort (INTegration of Ice core, MArine and TErrestrial records – OZ-INTIMATE to compare atmosphere–ocean general circulation model (AOGCM simulations and proxy reconstructions. The approach is used in order to identify important properties (e.g. circulation and precipitation of past climatic states from the models and proxies, which is a primary objective of the Southern Hemisphere Assessment of PalaeoEnvironment (SHAPE initiative. The AOGCM data are taken from the Paleoclimate Modelling Intercomparison Project (PMIP mid-Holocene (ca. 6000 years before present, 6 ka and pre-industrial control (ca. 1750 CE, 0 ka experiments. The synthesis presented here shows that the models and proxies agree on the differences in climate state for 6 ka relative to 0 ka, when they are insolation driven. The largest uncertainty between the models and the proxies occurs over the Indo-Pacific Warm Pool (IPWP. The analysis shows that the lower temperatures in the Pacific at around 6 ka in the models may be the result of an enhancement of an existing systematic error. It is therefore difficult to decipher which one of the proxies and/or the models is correct. This study also shows that a reduction in the Equator-to-pole temperature difference in the Southern Hemisphere causes the mid-latitude westerly wind strength to reduce in the models; however, the simulated rainfall actually increases over the southern temperate zone of Australia as a result of higher convective precipitation. Such a mechanism (increased convection may be useful for resolving disparities between different regional proxy records and model simulations. Finally, after assessing the available datasets (model and proxy, opportunities for better model–proxy integrated research are discussed.

Evaluation of PMIP2 and PMIP3 simulations of mid-Holocene climate in the Indo-Pacific, Australasian and Southern Ocean regions

Science.gov (United States)

Ackerley, Duncan; Reeves, Jessica; Barr, Cameron; Bostock, Helen; Fitzsimmons, Kathryn; Fletcher, Michael-Shawn; Gouramanis, Chris; McGregor, Helen; Mooney, Scott; Phipps, Steven J.; Tibby, John; Tyler, Jonathan

2017-11-01

This study uses the simplified patterns of temperature and effective precipitation approach from the Australian component of the international palaeoclimate synthesis effort (INTegration of Ice core, MArine and TErrestrial records - OZ-INTIMATE) to compare atmosphere-ocean general circulation model (AOGCM) simulations and proxy reconstructions. The approach is used in order to identify important properties (e.g. circulation and precipitation) of past climatic states from the models and proxies, which is a primary objective of the Southern Hemisphere Assessment of PalaeoEnvironment (SHAPE) initiative. The AOGCM data are taken from the Paleoclimate Modelling Intercomparison Project (PMIP) mid-Holocene (ca. 6000 years before present, 6 ka) and pre-industrial control (ca. 1750 CE, 0 ka) experiments. The synthesis presented here shows that the models and proxies agree on the differences in climate state for 6 ka relative to 0 ka, when they are insolation driven. The largest uncertainty between the models and the proxies occurs over the Indo-Pacific Warm Pool (IPWP). The analysis shows that the lower temperatures in the Pacific at around 6 ka in the models may be the result of an enhancement of an existing systematic error. It is therefore difficult to decipher which one of the proxies and/or the models is correct. This study also shows that a reduction in the Equator-to-pole temperature difference in the Southern Hemisphere causes the mid-latitude westerly wind strength to reduce in the models; however, the simulated rainfall actually increases over the southern temperate zone of Australia as a result of higher convective precipitation. Such a mechanism (increased convection) may be useful for resolving disparities between different regional proxy records and model simulations. Finally, after assessing the available datasets (model and proxy), opportunities for better model-proxy integrated research are discussed.

Seasonal and mesoscale variability of oceanic transport of anthropogenic CO2

Directory of Open Access Journals (Sweden)

J.-C. Dutay

2009-11-01

Full Text Available Estimates of the ocean's large-scale transport of anthropogenic CO2 are based on one-time hydrographic sections, but the temporal variability of this transport has not been investigated. The aim of this study is to evaluate how the seasonal and mesoscale variability affect data-based estimates of anthropogenic CO2 transport. To diagnose this variability, we made a global anthropogenic CO2 simulation using an eddy-permitting version of the coupled ocean sea-ice model ORCA-LIM. As for heat transport, the seasonally varying transport of anthropogenic CO2 is largest within 20° of the equator and shows secondary maxima in the subtropics. Ekman transport generally drives most of the seasonal variability, but the contribution of the vertical shear becomes important near the equator and in the Southern Ocean. Mesoscale variabilty contributes to the annual-mean transport of both heat and anthropogenic CO2 with strong poleward transport in the Southern Ocean and equatorward transport in the tropics. This "rectified" eddy transport is largely baroclinic in the tropics and barotropic in the Southern Ocean due to a larger contribution from standing eddies. Our analysis revealed that most previous hydrographic estimates of meridional transport of anthropogenic CO2 are severely biased because they neglect temporal fluctuations due to non-Ekman velocity variations. In each of the three major ocean basins, this bias is largest near the equator and in the high southern latitudes. In the subtropical North Atlantic, where most of the hydrographic-based estimates have been focused, this uncertainty represents up to 20% and 30% of total meridional transport of heat and CO2. Generally though, outside the tropics and Southern Ocean, there are only small variations in meridional transport due to seasonal variations in tracer fields and time variations in eddy transport. For the North Atlantic, eddy variability accounts for up to 10% and 15% of the total transport of

Modification of the deep salinity-maximum in the Southern Ocean by circulation in the Antarctic Circumpolar Current and the Weddell Gyre

Science.gov (United States)

Donnelly, Matthew; Leach, Harry; Strass, Volker

2017-07-01

The evolution of the deep salinity-maximum associated with the Lower Circumpolar Deep Water (LCDW) is assessed using a set of 37 hydrographic sections collected over a 20-year period in the Southern Ocean as part of the WOCE/CLIVAR programme. A circumpolar decrease in the value of the salinity-maximum is observed eastwards from the North Atlantic Deep Water (NADW) in the Atlantic sector of the Southern Ocean through the Indian and Pacific sectors to Drake Passage. Isopycnal mixing processes are limited by circumpolar fronts, and in the Atlantic sector, this acts to limit the direct poleward propagation of the salinity signal. Limited entrainment occurs into the Weddell Gyre, with LCDW entering primarily through the eddy-dominated eastern limb. A vertical mixing coefficient, κV of (2.86 ± 1.06) × 10-4 m2 s-1 and an isopycnal mixing coefficient, κI of (8.97 ± 1.67) × 102 m2 s-1 are calculated for the eastern Indian and Pacific sectors of the Antarctic Circumpolar Current (ACC). A κV of (2.39 ± 2.83) × 10-5 m2 s-1, an order of magnitude smaller, and a κI of (2.47 ± 0.63) × 102 m2 s-1, three times smaller, are calculated for the southern and eastern Weddell Gyre reflecting a more turbulent regime in the ACC and a less turbulent regime in the Weddell Gyre. In agreement with other studies, we conclude that the ACC acts as a barrier to direct meridional transport and mixing in the Atlantic sector evidenced by the eastward propagation of the deep salinity-maximum signal, insulating the Weddell Gyre from short-term changes in NADW characteristics.

Fronts, water masses and heat content variability in the Western Indian sector of the Southern Ocean during austral summer 2004

Digital Repository Service at National Institute of Oceanography (India)

AnilKumar, N.; Luis, A.J.; Somayajulu, Y.K.; RameshBabu, V.; Dash, M.K.; Pednekar, S.M.; Babu, K.N.; Sudhakar, M.; Pandey, P.C.

of the southern sector of the Indian Ocean (Fu, 1986; Nagata et al, 1988; Park et al, 1993; Orsi et al., 1995; Belkin and Gordon, 1996; Sparrow et al., 1996; Holliday and Read, 1998; Park et al., 1998; Reid, 2003) which emphasized that the areas west... to classify each front based on exact change in its characteristic parameters, the criteria adopted by elsewhere were considered (Peterson and Whitworth, 1989; Orsi et al., 1993; Read and Pollard,1993; Orsi et al.,1995; Belkin and Gordon, 1996; Sparrow 4 et...

Water column distribution and carbon isotopic signal of cholesterol, brassicasterol and particulate organic carbon in the Atlantic sector of the Southern Ocean

Directory of Open Access Journals (Sweden)

A.-J. Cavagna

2013-04-01

Full Text Available The combination of concentrations and δ13C signatures of Particulate Organic Carbon (POC and sterols provides a powerful approach to study ecological and environmental changes in both the modern and ancient ocean. We applied this tool to study the biogeochemical changes in the modern ocean water column during the BONUS-GoodHope survey (February–March 2008 from Cape Basin to the northern part of the Weddell Gyre. Cholesterol and brassicasterol were chosen as ideal biomarkers of the heterotrophic and autotrophic carbon pools, respectively, because of their ubiquitous and relatively refractory nature. We document depth distributions of concentrations (relative to bulk POC and δ13C signatures of cholesterol and brassicasterol combined with CO2 aq. surface concentration variation. While the relationship between CO2 aq. and δ13C of bulk POC and biomarkers have been reported by others for the surface water, our data show that this persists in mesopelagic and deep waters, suggesting that δ13C signatures of certain biomarkers in the water column could be applied as proxies for surface water CO2 aq. We observed a general increase in sterol δ13C signatures with depth, which is likely related to a combination of particle size effects, selective feeding on larger cells by zooplankton, and growth rate related effects. Our data suggest a key role of zooplankton fecal aggregates in carbon export for this part of the Southern Ocean (SO. Additionally, in the southern part of the transect south of the Polar Front (PF, the release of sea-ice algae during the ice demise in the Seasonal Ice Zone (SIZ is hypothesized to influence the isotopic signature of sterols in the open ocean. Overall, the combined use of δ13C values and concentrations measurements of both bulk organic C and specific sterols throughout the water column offers the promising potential to explore the recent history of plankton and the fate of organic matter in the SO.

Role of CO2 and Southern Ocean winds in glacial abrupt climate change

Directory of Open Access Journals (Sweden)

M. Montoya

2012-06-01

Full Text Available The study of Greenland ice cores revealed two decades ago the abrupt character of glacial millennial-scale climate variability. Several triggering mechanisms have been proposed and confronted against growing proxy-data evidence. Although the implication of North Atlantic deep water (NADW formation reorganisations in glacial abrupt climate change seems robust nowadays, the final cause of these reorganisations remains unclear. Here, the role of CO2 and Southern Ocean winds is investigated using a coupled model of intermediate complexity in an experimental setup designed such that the climate system resides close to a threshold found in previous studies. An initial abrupt surface air temperature (SAT increase over the North Atlantic by 4 K in less than a decade, followed by a more gradual warming greater than 10 K on centennial timescales, is simulated in response to increasing atmospheric CO2 levels and/or enhancing southern westerlies. The simulated peak warming shows a similar pattern and amplitude over Greenland as registered in ice core records of Dansgaard-Oeschger (D/O events. This is accompanied by a strong Atlantic meridional overturning circulation (AMOC intensification. The AMOC strengthening is found to be caused by a northward shift of NADW formation sites into the Nordic Seas as a result of a northward retreat of the sea-ice front in response to higher temperatures. This leads to enhanced heat loss to the atmosphere as well as reduced freshwater fluxes via reduced sea-ice import into the region. In this way, a new mechanism that is consistent with proxy data is identified by which abrupt climate change can be promoted.

Propagation of Atlantic Ocean swells in the north Indian Ocean: A case study

Digital Repository Service at National Institute of Oceanography (India)

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

An analysis of altimeter significant wave height data of May 2007 revealed the occurrence of an extreme weather event off southern tip of South Africa in the Atlantic Ocean, and generation of a series of very high swells at 40 degrees S...

Dynamics of the Water Circulations in the Southern South China Sea and Its Seasonal Transports.

Science.gov (United States)

Daryabor, Farshid; Ooi, See Hai; Samah, Azizan Abu; Akbari, Abolghasem

2016-01-01

A three-dimensional Regional Ocean Modeling System is used to study the seasonal water circulations and transports of the Southern South China Sea. The simulated seasonal water circulations and estimated transports show consistency with observations, e.g., satellite altimeter data set and re-analysis data of the Simple Ocean Data Assimilation. It is found that the seasonal water circulations are mainly driven by the monsoonal wind stress and influenced by the water outflow/inflow and associated currents of the entire South China Sea. The intrusion of the strong current along the East Coast of Peninsular Malaysia and the eddies at different depths in all seasons are due to the conservation of the potential vorticity as the depth increases. Results show that the water circulation patterns in the northern part of the East Coast of Peninsular Malaysia are generally dominated by the geostrophic currents while those in the southern areas are due solely to the wind stress because of negligible Coriolis force there. This study clearly shows that individual surface freshwater flux (evaporation minus precipitation) controls the sea salinity balance in the Southern South China Sea thermohaline circulations. Analysis of climatological data from a high resolution Regional Ocean Modeling System reveals that the complex bathymetry is important not only for water exchange through the Southern South China Sea but also in regulating various transports across the main passages in the Southern South China Sea, namely the Sunda Shelf and the Strait of Malacca. Apart from the above, in comparision with the dynamics of the Sunda Shelf, the Strait of Malacca reflects an equally significant role in the annual transports into the Andaman Sea.

Behaviour of nickel, copper, zinc and cadmium in the upper 300 m of a transect in the Southern Ocean (57°-62°S, 49°W)

NARCIS (Netherlands)

Nolting, R.F.; Baar, H.J.W. de

1994-01-01

The distributions of Ni, Cu, Zn and Cd in relation to phosphate, nitrate and silicate in the upper 300 m of a transect in the Southern Ocean were studied. This transect covers the Scotia Sea, the Confluence and the Weddell Sea. These three watermasses are clearly separated by their temperature and

The Southern Westerlies during the last glacial maximum in PMIP2 simulations