Dense shelf water formation at coastal polynyas in the Weddell Sea
For any climate signal to leave an imprint on the Antarctic Bottom Water (AABW) that fills the World Ocean abyss, it has to pass through the process of bottom water formation in the marginal seas of the Southern Ocean. An indispensable component of AABW is the dense shelf waters created on the conti...
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ftawi:oai:epic.awi.de:30938 2023-05-15T13:46:52+02:00 Dense shelf water formation at coastal polynyas in the Weddell Sea Haid, Verena Timmermann, Ralph Heinemann, G. Ebner, L. 2012 application/pdf https://epic.awi.de/id/eprint/30938/ https://epic.awi.de/id/eprint/30938/1/scar_2012_poster.pdf https://hdl.handle.net/10013/epic.39816 https://hdl.handle.net/10013/epic.39816.d001 unknown https://epic.awi.de/id/eprint/30938/1/scar_2012_poster.pdf https://hdl.handle.net/10013/epic.39816.d001 Haid, V. , Timmermann, R. , Heinemann, G. and Ebner, L. (2012) Dense shelf water formation at coastal polynyas in the Weddell Sea , XXXII SCAR and Open Science Conference, Portland, Oregon, U. S. A., 13 July 2012 - 25 July 2012 . hdl:10013/epic.39816 EPIC3XXXII SCAR and Open Science Conference, Portland, Oregon, U. S. A., 2012-07-13-2012-07-25 Conference notRev 2012 ftawi 2021-12-24T15:37:52Z For any climate signal to leave an imprint on the Antarctic Bottom Water (AABW) that fills the World Ocean abyss, it has to pass through the process of bottom water formation in the marginal seas of the Southern Ocean. An indispensable component of AABW is the dense shelf waters created on the continental shelves around Antarctica, particularly in the Ross and Weddell Seas. At coastal polynyas we find strong atmospheric cooling and high freezing rates that lead to a strong salinification of the water column. Here the bulk of High Salinity Shelf Water (HSSW) is formed. The impact of coastal polynyas on ice production and water mass formation in the southwestern Weddell Sea was studied employing the Finite Element Sea ice-Ocean Model (FESOM) of Alfred Wegener Institute, Bremerhaven. FESOM is a coupled system of a primitive-equation, hydrostatic ocean model and a dynamic-thermodynamic sea ice model. Simulations were conducted on a global unstructured mesh with a strong focus on the southwestern Weddell Sea coastline (up to 3 km resolution). The model runs were initialised in 1980 and forced with NCEP reanalysis data (daily resolution). For 2008 also higher-resolution GME data and results from the regional COSMO atmosphere model of University Trier were applied as atmospheric forcing data. The period 1990-2009 is used for data analysis. Our simulations indicate that mean winter sea ice production within the coastal polynyas exceeds the surrounding area’s ice production by a factor of 7, giving a polynya contribution to total sea ice formation of 3 %. This small percentage is due to their even smaller areal percentage (0.4 %), and also the existence of leads and small polynyas in the ‘ice-covered’ ocean. The latter contribute substantially to sea ice production, but not to bottom water formation since they are transient elements that open, move and close dependent on the ice drift, whereas coastal polynyas are fixed in space and often open for days, enabling the salinification necessary for HSSW formation. From our simulations we derive a mean HSSW-formation of 4.2∙10^5 km^3/winter, but only 0.5 Sv thereof are exported over the shelf break, the rest stays on the shelf and is warmed and diluted during the following summer. The WSBW formation rate for the southwestern Weddell Sea continental shelf in our simulation is about 6.3∙10^4 km^3/yr (2 Sv), which is on the low side but still reasonable compared to independent estimates. Conference Object Antarc* Antarctic Antarctica Sea ice Southern Ocean Weddell Sea Alfred Wegener Institute for Polar- and Marine Research (AWI): ePIC (electronic Publication Information Center) Antarctic Southern Ocean The Antarctic Weddell Sea Weddell |
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Open Polar |
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Alfred Wegener Institute for Polar- and Marine Research (AWI): ePIC (electronic Publication Information Center) |
op_collection_id |
ftawi |
language |
unknown |
description |
For any climate signal to leave an imprint on the Antarctic Bottom Water (AABW) that fills the World Ocean abyss, it has to pass through the process of bottom water formation in the marginal seas of the Southern Ocean. An indispensable component of AABW is the dense shelf waters created on the continental shelves around Antarctica, particularly in the Ross and Weddell Seas. At coastal polynyas we find strong atmospheric cooling and high freezing rates that lead to a strong salinification of the water column. Here the bulk of High Salinity Shelf Water (HSSW) is formed. The impact of coastal polynyas on ice production and water mass formation in the southwestern Weddell Sea was studied employing the Finite Element Sea ice-Ocean Model (FESOM) of Alfred Wegener Institute, Bremerhaven. FESOM is a coupled system of a primitive-equation, hydrostatic ocean model and a dynamic-thermodynamic sea ice model. Simulations were conducted on a global unstructured mesh with a strong focus on the southwestern Weddell Sea coastline (up to 3 km resolution). The model runs were initialised in 1980 and forced with NCEP reanalysis data (daily resolution). For 2008 also higher-resolution GME data and results from the regional COSMO atmosphere model of University Trier were applied as atmospheric forcing data. The period 1990-2009 is used for data analysis. Our simulations indicate that mean winter sea ice production within the coastal polynyas exceeds the surrounding area’s ice production by a factor of 7, giving a polynya contribution to total sea ice formation of 3 %. This small percentage is due to their even smaller areal percentage (0.4 %), and also the existence of leads and small polynyas in the ‘ice-covered’ ocean. The latter contribute substantially to sea ice production, but not to bottom water formation since they are transient elements that open, move and close dependent on the ice drift, whereas coastal polynyas are fixed in space and often open for days, enabling the salinification necessary for HSSW formation. From our simulations we derive a mean HSSW-formation of 4.2∙10^5 km^3/winter, but only 0.5 Sv thereof are exported over the shelf break, the rest stays on the shelf and is warmed and diluted during the following summer. The WSBW formation rate for the southwestern Weddell Sea continental shelf in our simulation is about 6.3∙10^4 km^3/yr (2 Sv), which is on the low side but still reasonable compared to independent estimates. |
format |
Conference Object |
author |
Haid, Verena Timmermann, Ralph Heinemann, G. Ebner, L. |
spellingShingle |
Haid, Verena Timmermann, Ralph Heinemann, G. Ebner, L. Dense shelf water formation at coastal polynyas in the Weddell Sea |
author_facet |
Haid, Verena Timmermann, Ralph Heinemann, G. Ebner, L. |
author_sort |
Haid, Verena |
title |
Dense shelf water formation at coastal polynyas in the Weddell Sea |
title_short |
Dense shelf water formation at coastal polynyas in the Weddell Sea |
title_full |
Dense shelf water formation at coastal polynyas in the Weddell Sea |
title_fullStr |
Dense shelf water formation at coastal polynyas in the Weddell Sea |
title_full_unstemmed |
Dense shelf water formation at coastal polynyas in the Weddell Sea |
title_sort |
dense shelf water formation at coastal polynyas in the weddell sea |
publishDate |
2012 |
url |
https://epic.awi.de/id/eprint/30938/ https://epic.awi.de/id/eprint/30938/1/scar_2012_poster.pdf https://hdl.handle.net/10013/epic.39816 https://hdl.handle.net/10013/epic.39816.d001 |
geographic |
Antarctic Southern Ocean The Antarctic Weddell Sea Weddell |
geographic_facet |
Antarctic Southern Ocean The Antarctic Weddell Sea Weddell |
genre |
Antarc* Antarctic Antarctica Sea ice Southern Ocean Weddell Sea |
genre_facet |
Antarc* Antarctic Antarctica Sea ice Southern Ocean Weddell Sea |
op_source |
EPIC3XXXII SCAR and Open Science Conference, Portland, Oregon, U. S. A., 2012-07-13-2012-07-25 |
op_relation |
https://epic.awi.de/id/eprint/30938/1/scar_2012_poster.pdf https://hdl.handle.net/10013/epic.39816.d001 Haid, V. , Timmermann, R. , Heinemann, G. and Ebner, L. (2012) Dense shelf water formation at coastal polynyas in the Weddell Sea , XXXII SCAR and Open Science Conference, Portland, Oregon, U. S. A., 13 July 2012 - 25 July 2012 . hdl:10013/epic.39816 |
_version_ |
1766245472542916608 |