Modal shift in North Atlantic seasonality during the last deglaciation
Change-over from a glacial to an interglacial climate is considered as transitional between two stable modes. Palaeoceanographic reconstructions using the polar foraminifera Neogloboquadrina pachyderma highlight the retreat of the polar front during the last deglaciation in terms of both its decreas...
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ftcopernicus:oai:publications.copernicus.org:cpd72396 2023-05-15T17:14:59+02:00 Modal shift in North Atlantic seasonality during the last deglaciation Brummer, Geert-Jan A. Metcalfe, Brett Feldmeijer, Wouter Prins, Maarten A. Hoff, Jasmijn Ganssen, Gerald M. 2019-04-16 application/pdf https://doi.org/10.5194/cp-2018-144 https://www.clim-past-discuss.net/cp-2018-144/ eng eng doi:10.5194/cp-2018-144 https://www.clim-past-discuss.net/cp-2018-144/ eISSN: 1814-9332 Text 2019 ftcopernicus https://doi.org/10.5194/cp-2018-144 2019-12-24T09:49:18Z Change-over from a glacial to an interglacial climate is considered as transitional between two stable modes. Palaeoceanographic reconstructions using the polar foraminifera Neogloboquadrina pachyderma highlight the retreat of the polar front during the last deglaciation in terms of both its decreasing abundance and stable oxygen isotope values (δ 18 O) in sediment cores. While conventional isotope analysis of pooled N. pachyderma shells show a warming trend concurrent with the retreating ice, new single shell measurements reveal that this trend is composed of two isotopically different populations that are morphologically indistinguishable. Using modern time-series as analogues for interpreting down-core data, glacial productivity in the mid North Atlantic appears limited to a single maximum in late summer, followed by the melting of drifting icebergs and winter sea ice. Despite collapsing ice sheets and global warming during the deglaciation, a second <q>warm</q> population of N. pachyderma appears in a bimodal seasonal succession separated by the subpolar G. bulloides . This represents a shift in the timing of the main plankton bloom from late to early summer in a deglacial intermediate mode that persisted for ca. 10,000 years until the last deglaciation ended. When seawater temperatures exceeded the threshold values, first the <q>cold</q> (glacial) then the <q>warm</q> (deglacial) population of N. pachyderma disappeared, whilst G. bulloides with a greater tolerance to higher temperatures persisted throughout the Holocene to the present day in the mid-latitude North Atlantic. Single specimen δ 18 O of polar N. pachyderma reveal a steeper rate of ocean warming during the last deglaciation than appears from conventional pooled δ 18 O average values. Text Neogloboquadrina pachyderma North Atlantic Sea ice Copernicus Publications: E-Journals |
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Copernicus Publications: E-Journals |
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ftcopernicus |
language |
English |
description |
Change-over from a glacial to an interglacial climate is considered as transitional between two stable modes. Palaeoceanographic reconstructions using the polar foraminifera Neogloboquadrina pachyderma highlight the retreat of the polar front during the last deglaciation in terms of both its decreasing abundance and stable oxygen isotope values (δ 18 O) in sediment cores. While conventional isotope analysis of pooled N. pachyderma shells show a warming trend concurrent with the retreating ice, new single shell measurements reveal that this trend is composed of two isotopically different populations that are morphologically indistinguishable. Using modern time-series as analogues for interpreting down-core data, glacial productivity in the mid North Atlantic appears limited to a single maximum in late summer, followed by the melting of drifting icebergs and winter sea ice. Despite collapsing ice sheets and global warming during the deglaciation, a second <q>warm</q> population of N. pachyderma appears in a bimodal seasonal succession separated by the subpolar G. bulloides . This represents a shift in the timing of the main plankton bloom from late to early summer in a deglacial intermediate mode that persisted for ca. 10,000 years until the last deglaciation ended. When seawater temperatures exceeded the threshold values, first the <q>cold</q> (glacial) then the <q>warm</q> (deglacial) population of N. pachyderma disappeared, whilst G. bulloides with a greater tolerance to higher temperatures persisted throughout the Holocene to the present day in the mid-latitude North Atlantic. Single specimen δ 18 O of polar N. pachyderma reveal a steeper rate of ocean warming during the last deglaciation than appears from conventional pooled δ 18 O average values. |
format |
Text |
author |
Brummer, Geert-Jan A. Metcalfe, Brett Feldmeijer, Wouter Prins, Maarten A. Hoff, Jasmijn Ganssen, Gerald M. |
spellingShingle |
Brummer, Geert-Jan A. Metcalfe, Brett Feldmeijer, Wouter Prins, Maarten A. Hoff, Jasmijn Ganssen, Gerald M. Modal shift in North Atlantic seasonality during the last deglaciation |
author_facet |
Brummer, Geert-Jan A. Metcalfe, Brett Feldmeijer, Wouter Prins, Maarten A. Hoff, Jasmijn Ganssen, Gerald M. |
author_sort |
Brummer, Geert-Jan A. |
title |
Modal shift in North Atlantic seasonality during the last deglaciation |
title_short |
Modal shift in North Atlantic seasonality during the last deglaciation |
title_full |
Modal shift in North Atlantic seasonality during the last deglaciation |
title_fullStr |
Modal shift in North Atlantic seasonality during the last deglaciation |
title_full_unstemmed |
Modal shift in North Atlantic seasonality during the last deglaciation |
title_sort |
modal shift in north atlantic seasonality during the last deglaciation |
publishDate |
2019 |
url |
https://doi.org/10.5194/cp-2018-144 https://www.clim-past-discuss.net/cp-2018-144/ |
genre |
Neogloboquadrina pachyderma North Atlantic Sea ice |
genre_facet |
Neogloboquadrina pachyderma North Atlantic Sea ice |
op_source |
eISSN: 1814-9332 |
op_relation |
doi:10.5194/cp-2018-144 https://www.clim-past-discuss.net/cp-2018-144/ |
op_doi |
https://doi.org/10.5194/cp-2018-144 |
_version_ |
1766073109029322752 |