On the response of Southern Ocean water-masses to atmospheric meridional moisture advection

2003 ◽  
Vol 30 (8) ◽  
Author(s):  
Oleg A. Saenko ◽  
Matthew H. England
Keyword(s):  
Southern Ocean ◽  
Water Masses ◽  
Ocean Water ◽  
Moisture Advection

scholarly journals An assessment of Southern Ocean water masses and sea ice during 1988–2007 in a suite of interannual CORE-II simulations

2015 ◽  
Vol 94 ◽  
pp. 67-94 ◽  
Author(s):  
Stephanie M. Downes ◽  
Riccardo Farneti ◽  
Petteri Uotila ◽  
Stephen M. Griffies ◽  
Simon J. Marsland ◽  
...  
Keyword(s):  
Southern Ocean ◽  
Sea Ice ◽  
Water Masses ◽  
Ocean Water

scholarly journals The effect of greenhouse gas concentrations and ice sheets on the glacial AMOC in a coupled climate model

2016 ◽  
Author(s):  
Marlene Klockmann ◽  
Uwe Mikolajewicz ◽  
Jochem Marotzke
Keyword(s):  
Southern Ocean ◽  
Greenhouse Gas ◽  
Radiative Forcing ◽  
Ice Sheets ◽  
Deep Ocean ◽  
Water Masses ◽  
Ocean Water ◽  
Deep Ocean Water ◽  
Ghg Reduction ◽  
Orbital Configuration

Abstract. Simulations with the Max Planck Institute Earth System Model (MPI-ESM) are used to study the sensitivity of the AMOC and the deep ocean water masses during the Last Glacial Maximum to different sets of forcings. Analysing the individual contributions of the glacial forcings reveals that the ice sheets cause an increase of the overturning strength and a deepening of the North Atlantic Deep Water (NADW) cell, while the low greenhouse gas (GHG) concentrations cause the overturning strength to decrease and the NADW cell to shoal. The effect of the orbital configuration is negligible. The effects of the ice sheets and the GHG reduction balance each other in the deep ocean so that no shoaling of the NADW cell is simulated in the full glacial state. Experiments in which different GHG concentrations with linearly decreasing radiative forcing are applied to a setup with glacial ice sheets and orbital configuration show that GHG concentrations below the glacial level are necessary to cause a shoaling of the NADW cell with respect to the preindustrial state in MPI-ESM. For a pCO2 of 149 ppm, the simulated overturning state and the deep ocean water masses are in best agreement with the glacial state inferred from proxy data. Sensitivity studies confirm that brine release and shelf convection in the Southern Ocean are key processes for the shoaling of the NADW cell. Shoaling occurs only when Southern Ocean shelf water contributes significantly to the formation of Antarctic Bottom Water.

scholarly journals The effect of greenhouse gas concentrations and ice sheets on the glacial AMOC in a coupled climate model

2016 ◽  
Vol 12 (9) ◽  
pp. 1829-1846 ◽  
Author(s):  
Marlene Klockmann ◽  
Uwe Mikolajewicz ◽  
Jochem Marotzke
Keyword(s):  
Southern Ocean ◽  
Greenhouse Gas ◽  
Radiative Forcing ◽  
Ice Sheets ◽  
Deep Ocean ◽  
Water Masses ◽  
Ocean Water ◽  
Deep Ocean Water ◽  
Ghg Reduction ◽  
Orbital Configuration

Abstract. Simulations with the Max Planck Institute Earth System Model (MPI-ESM) are used to study the sensitivity of the AMOC and the deep-ocean water masses during the Last Glacial Maximum to different sets of forcings. Analysing the individual contributions of the glacial forcings reveals that the ice sheets cause an increase in the overturning strength and a deepening of the North Atlantic Deep Water (NADW) cell, while the low greenhouse gas (GHG) concentrations cause a decrease in overturning strength and a shoaling of the NADW cell. The effect of the orbital configuration is negligible. The effects of the ice sheets and the GHG reduction balance each other in the deep ocean so that no shoaling of the NADW cell is simulated in the full glacial state. Experiments in which different GHG concentrations with linearly decreasing radiative forcing are applied to a setup with glacial ice sheets and orbital configuration show that GHG concentrations below the glacial level are necessary to cause a shoaling of the NADW cell with respect to the pre-industrial state in MPI-ESM. For a pCO2 of 149 ppm, the simulated overturning state and the deep-ocean water masses are in best agreement with the glacial state inferred from proxy data. Sensitivity studies confirm that brine release and shelf convection in the Southern Ocean are key processes for the shoaling of the NADW cell. Shoaling occurs only when Southern Ocean shelf water contributes significantly to the formation of Antarctic Bottom Water.

Southern Ocean water mass properties and circulation under CMIP6 climate forcing

2021 ◽  
Author(s):  
Andrew Meijers ◽  
David Munday ◽  
Tilla Roy ◽  
Jean-Baptiste Sallée
Keyword(s):  
Southern Ocean ◽  
Water Mass ◽  
Dissolved Inorganic Carbon ◽  
Heat Content ◽  
Water Masses ◽  
Climate Forcing ◽  
Intermediate Water ◽  
Ocean Water ◽  
Mode Water ◽  
Mass Properties

<p>We examine the representation of Southern Ocean water mass properties, circulation and transformation in an ensemble of CMIP6 models, under historical climate forcing conditions and under a range of future climate scenarios. By using a dynamically defined water mass classification scheme based on physical characteristics (salinity minimum, potential vorticity minimum etc) rather than fixed water mass properties, we are able to compare water masses across a range of models, often with significant water mass property differences, as well as within single models where water mass properties change under climate forcing. We find that under strong climate forcing scenarios (ssp585) the heat content of SubAntarctic Mode Water (SAMW), Antarctic Intermediate Water (AAIW) and Circumpolar Deep Water (CDW) all increase consistently across models, while Antarctic Bottom Water (AABW) does not change significantly. Importantly this change is strongly modulated by using dynamic definitions. Both SAMW and AAIW lighten significantly in density, and using time varying definitions their volumes remain relatively constant, whereas using a time invariant definition both experience extremely significant increases in volume and heat content. We show that dynamically it is the ocean interior, CDW and AAIW, that dominate heat uptake under strong forcing. Similarly, dissolved inorganic carbon uptake occurs predominantly in the CDW. In contrast AABW volumes decrease significantly.</p><p>There is a consistent ‘fingerprint’ of temperature change in density space across all models under strong forcing scenarios, with CDW experiencing surface intensified warming as it shoals to the south, and SAMW/AAIW demonstrating cooling and freshening in their subducted layers and a uniform warming in the surface layers. We show that the upper cell of the residual overturning circulation (calculated with the new availability of eddy parametrisation terms in CMIP6) consistently increases across all models evaluated, by 10-50% (up to 10 Sv in some models), while the lower cell is dramatically decreased in strength, declining by up to 70% in some models. We provide evidence that surface warming may be modulated by increased eddy driven upwelling, as well as surface freshening driving the shutdown of AABW formation. Finally we compute a Walin water mass budget, balancing surface forcing, interior storage and meridional export and inferring interior mixing between water masses, and contrast all findings with similar analyses in CMIP5.</p><p> </p>

Fronts, water masses and heat content variability in the Western Indian sector of the Southern Ocean during austral summer 2004

2006 ◽  
Vol 63 (1-2) ◽  
pp. 20-34 ◽  
Author(s):  
N. Anilkumar ◽  
Alvarinho J. Luis ◽  
Y.K. Somayajulu ◽  
V. Ramesh Babu ◽  
M.K. Dash ◽  
...  
Keyword(s):  
Southern Ocean ◽  
Heat Content ◽  
Austral Summer ◽  
Water Masses ◽  
Indian Sector

The role of tides on the carbonate chemistry of a coastal polynya in the south-eastern Weddell Sea

2021 ◽  
Author(s):  
Elise Droste ◽  
Melchor González Dávila ◽  
Juana Magdalena Santana Casiano ◽  
Mario Hoppema ◽  
Gerd Rohardt ◽  
...  
Keyword(s):  
Southern Ocean ◽  
Weddell Sea ◽  
Water Masses ◽  
Total Alkalinity ◽  
The South ◽  
Carbonate Chemistry ◽  
Large Variability ◽  
South Eastern ◽  
Coastal Polynya ◽  
Eastern Weddell Sea

<p>Tides have a large impact on coastal polynyas around Antarctica. We investigate the effect of semi-diurnal tidal cycles on the seawater carbonate chemistry in a coastal polynya hugging the Ekström Ice Shelf in the south-eastern Weddell Sea. This region experiences some of the strongest tides in the Southern Ocean. We assess the implications for the contribution of coastal polynyas to the carbon dioxide (CO<sub>2</sub>) air-sea flux of the Weddell Sea.</p><p>Two site visits, in January 2015 and January 2019, are intercompared in terms of the dissolved inorganic carbon (DIC) concentration, total alkalinity, pH, and CO<sub>2</sub> partial pressure (pCO<sub>2</sub>). The tides induce large variability in the carbonate chemistry of the coastal polynya in the austral summer: DIC concentrations vary between 2174 and 2223 umol kg<sup>-1</sup>.</p><p>The tidal fluctuation in the DIC concentration can swing the polynya from a sink to a source of atmospheric CO<sub>2 </sub>on a semi-diurnal timescale. We attribute these changes to the mixing of different water masses. The amount of variability induced by tides depends on – and is associated with – large scale oceanographic and biogeochemical processes that affect the characteristics and presence of the water masses being mixed, such as the rate of sea ice melt.</p><p>Sampling strategies in Antarctic coastal polynyas should always take tidal influences into account. This would help to reduce biases in our understanding of how coastal polynyas contribute to the CO<sub>2</sub> uptake by the Southern Ocean.</p>

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