Can we reconstruct the formation of large open ocean polynyas in the Southern Ocean using ice core records?
Large open-ocean polynyas, defined as ice-free areas within the sea ice pack, have been observed only rarely over the past decades in the Southern Ocean. In addition to smaller recent events, an impressive sequence occurred in the Weddell Sea in 1974, 1975 and 1976 with openings of more than 300,000...
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ftcopernicus:oai:publications.copernicus.org:cpd86818 2023-05-15T13:31:38+02:00 Can we reconstruct the formation of large open ocean polynyas in the Southern Ocean using ice core records? Goosse, Hugues Dalaiden, Quentin Cavitte, Marie G. P. Zhang, Liping 2020-08-10 application/pdf https://doi.org/10.5194/cp-2020-91 https://cp.copernicus.org/preprints/cp-2020-91/ eng eng doi:10.5194/cp-2020-91 https://cp.copernicus.org/preprints/cp-2020-91/ eISSN: 1814-9332 Text 2020 ftcopernicus https://doi.org/10.5194/cp-2020-91 2020-08-17T16:22:16Z Large open-ocean polynyas, defined as ice-free areas within the sea ice pack, have been observed only rarely over the past decades in the Southern Ocean. In addition to smaller recent events, an impressive sequence occurred in the Weddell Sea in 1974, 1975 and 1976 with openings of more than 300,000 km 2 that lasted the full winter. Those big events have a huge impact on the sea ice cover, deep-water formation and more generally on the Southern Ocean and the Antarctic climate. However, we have no estimate of the frequency of the occurrence of such large open-ocean polynyas before the 1970s. Our goal here is to test if polynya activity could be reconstructed using continental records, and specifically, observations derived from ice cores. The fingerprint of big open-ocean polynyas is first described in reconstructions based on data from weather stations, in ice cores for the 1970s and in climate models. It shows a clear signal, characterized by a surface air warming and increased precipitation in coastal regions adjacent to the eastern part of the Weddell Sea where several high-resolution ice cores have been collected. The signal of isotopic composition of precipitation is more ambiguous and we thus base our reconstructions on surface mass balance records only. A first reconstruction is obtained by performing a simple average of standardized records. Given the similarity between the observed signal and the one simulated in models, we also use data assimilation to reconstruct past polynya activity. The impact of open ocean polynyas on the continent is not large enough compared to the changes due, for instance, to atmospheric variability to detect without ambiguity the polynya signal and additional observations would be required to discriminate clearly the years with and without open ocean polynya. It is thus reasonable to consider that, in these preliminary reconstructions, some high accumulation events may be wrongly interpreted as the consequence of polynya formation while some years with polynya formation may be missed. Nevertheless, our reconstructions suggest that big open ocean polynyas, such as the ones that were observed in the 1970s, are rare events, occurring at most a few times per century. Century-scale changes in polynya activity are also likely but our reconstructions are unable to assess precisely this aspect at this stage. Text Antarc* Antarctic ice core ice pack Sea ice Southern Ocean Weddell Sea Copernicus Publications: E-Journals Antarctic Southern Ocean The Antarctic Weddell Weddell Sea |
institution |
Open Polar |
collection |
Copernicus Publications: E-Journals |
op_collection_id |
ftcopernicus |
language |
English |
description |
Large open-ocean polynyas, defined as ice-free areas within the sea ice pack, have been observed only rarely over the past decades in the Southern Ocean. In addition to smaller recent events, an impressive sequence occurred in the Weddell Sea in 1974, 1975 and 1976 with openings of more than 300,000 km 2 that lasted the full winter. Those big events have a huge impact on the sea ice cover, deep-water formation and more generally on the Southern Ocean and the Antarctic climate. However, we have no estimate of the frequency of the occurrence of such large open-ocean polynyas before the 1970s. Our goal here is to test if polynya activity could be reconstructed using continental records, and specifically, observations derived from ice cores. The fingerprint of big open-ocean polynyas is first described in reconstructions based on data from weather stations, in ice cores for the 1970s and in climate models. It shows a clear signal, characterized by a surface air warming and increased precipitation in coastal regions adjacent to the eastern part of the Weddell Sea where several high-resolution ice cores have been collected. The signal of isotopic composition of precipitation is more ambiguous and we thus base our reconstructions on surface mass balance records only. A first reconstruction is obtained by performing a simple average of standardized records. Given the similarity between the observed signal and the one simulated in models, we also use data assimilation to reconstruct past polynya activity. The impact of open ocean polynyas on the continent is not large enough compared to the changes due, for instance, to atmospheric variability to detect without ambiguity the polynya signal and additional observations would be required to discriminate clearly the years with and without open ocean polynya. It is thus reasonable to consider that, in these preliminary reconstructions, some high accumulation events may be wrongly interpreted as the consequence of polynya formation while some years with polynya formation may be missed. Nevertheless, our reconstructions suggest that big open ocean polynyas, such as the ones that were observed in the 1970s, are rare events, occurring at most a few times per century. Century-scale changes in polynya activity are also likely but our reconstructions are unable to assess precisely this aspect at this stage. |
format |
Text |
author |
Goosse, Hugues Dalaiden, Quentin Cavitte, Marie G. P. Zhang, Liping |
spellingShingle |
Goosse, Hugues Dalaiden, Quentin Cavitte, Marie G. P. Zhang, Liping Can we reconstruct the formation of large open ocean polynyas in the Southern Ocean using ice core records? |
author_facet |
Goosse, Hugues Dalaiden, Quentin Cavitte, Marie G. P. Zhang, Liping |
author_sort |
Goosse, Hugues |
title |
Can we reconstruct the formation of large open ocean polynyas in the Southern Ocean using ice core records? |
title_short |
Can we reconstruct the formation of large open ocean polynyas in the Southern Ocean using ice core records? |
title_full |
Can we reconstruct the formation of large open ocean polynyas in the Southern Ocean using ice core records? |
title_fullStr |
Can we reconstruct the formation of large open ocean polynyas in the Southern Ocean using ice core records? |
title_full_unstemmed |
Can we reconstruct the formation of large open ocean polynyas in the Southern Ocean using ice core records? |
title_sort |
can we reconstruct the formation of large open ocean polynyas in the southern ocean using ice core records? |
publishDate |
2020 |
url |
https://doi.org/10.5194/cp-2020-91 https://cp.copernicus.org/preprints/cp-2020-91/ |
geographic |
Antarctic Southern Ocean The Antarctic Weddell Weddell Sea |
geographic_facet |
Antarctic Southern Ocean The Antarctic Weddell Weddell Sea |
genre |
Antarc* Antarctic ice core ice pack Sea ice Southern Ocean Weddell Sea |
genre_facet |
Antarc* Antarctic ice core ice pack Sea ice Southern Ocean Weddell Sea |
op_source |
eISSN: 1814-9332 |
op_relation |
doi:10.5194/cp-2020-91 https://cp.copernicus.org/preprints/cp-2020-91/ |
op_doi |
https://doi.org/10.5194/cp-2020-91 |
_version_ |
1766019655106822144 |