Seasonal changes in glacial polynya activity inferred from Weddell Sea varves
The Weddell Sea and the associated Filchner-Ronne Ice Shelf constitute key regions for global bottom-water production today. However, little is known about bottom-water production under different climate and ice-sheet conditions. Therefore, we studied core PS1795, which consists primarily of fine-gr...
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ftubkoeln:oai:USBKOELN.ub.uni-koeln.de:45006 2023-05-15T16:13:14+02:00 Seasonal changes in glacial polynya activity inferred from Weddell Sea varves Sprenk, D. Weber, M. E. Kuhn, G. Wennrich, V. Hartmann, T. Seelos, K. 2014 https://kups.ub.uni-koeln.de/45006/ eng eng COPERNICUS GESELLSCHAFT MBH Sprenk, D., Weber, M. E., Kuhn, G., Wennrich, V., Hartmann, T. and Seelos, K. (2014). Seasonal changes in glacial polynya activity inferred from Weddell Sea varves. Clim. Past., 10 (3). S. 1239 - 1252. GOTTINGEN: COPERNICUS GESELLSCHAFT MBH. ISSN 1814-9332 ddc:no doc-type:article publishedVersion 2014 ftubkoeln 2022-11-09T07:28:58Z The Weddell Sea and the associated Filchner-Ronne Ice Shelf constitute key regions for global bottom-water production today. However, little is known about bottom-water production under different climate and ice-sheet conditions. Therefore, we studied core PS1795, which consists primarily of fine-grained siliciclastic varves that were deposited on contourite ridges in the southeastern Weddell Sea during the Last Glacial Maximum (LGM). We conducted high-resolution X-ray fluorescence (XRF) analysis and grain-size measurements with the RADIUS tool (Seelos and Sirocko, 2005) using thin sections to characterize the two seasonal components of the varves at sub-mm resolution to distinguish the seasonal components of the varves. Bright layers contain coarser grains that can mainly be identified as quartz in the medium-to-coarse silt grain size. They also contain higher amounts of Si, Zr, Ca, and Sr, as well as more ice-rafted debris (IRD). Dark layers, on the other hand, contain finer particles such as mica and clay minerals from the chlorite and illite groups. In addition, Fe, Ti, Rb, and K are elevated. Based on these findings as well as on previous analyses on neighbouring cores, we propose a model of enhanced thermohaline convection in front of a grounded ice sheet that is supported by seasonally variable coastal polynya activity during the LGM. Accordingly, katabatic (i.e. offshore blowing) winds removed sea ice from the ice edge, leading to coastal polynya formation. We suggest that glacial processes were similar to today with stronger katabatic winds and enhanced coastal polynya activity during the winter season. Under these conditions, lighter coarser-grained layers are likely glacial winter deposits, when brine rejection was increased, leading to enhanced bottom-water formation and increased sediment transport. Vice versa, darker finer-grained layers were then deposited during less windier season, mainly during summer, when coastal polynya activity was likely reduced. Article in Journal/Newspaper Filchner Ronne Ice Shelf Filchner-Ronne Ice Shelf Ice Sheet Ice Shelf Ronne Ice Shelf Sea ice Weddell Sea Cologne University: KUPS Ronne Ice Shelf ENVELOPE(-61.000,-61.000,-78.500,-78.500) Weddell Weddell Sea |
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Open Polar |
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Cologne University: KUPS |
op_collection_id |
ftubkoeln |
language |
English |
topic |
ddc:no |
spellingShingle |
ddc:no Sprenk, D. Weber, M. E. Kuhn, G. Wennrich, V. Hartmann, T. Seelos, K. Seasonal changes in glacial polynya activity inferred from Weddell Sea varves |
topic_facet |
ddc:no |
description |
The Weddell Sea and the associated Filchner-Ronne Ice Shelf constitute key regions for global bottom-water production today. However, little is known about bottom-water production under different climate and ice-sheet conditions. Therefore, we studied core PS1795, which consists primarily of fine-grained siliciclastic varves that were deposited on contourite ridges in the southeastern Weddell Sea during the Last Glacial Maximum (LGM). We conducted high-resolution X-ray fluorescence (XRF) analysis and grain-size measurements with the RADIUS tool (Seelos and Sirocko, 2005) using thin sections to characterize the two seasonal components of the varves at sub-mm resolution to distinguish the seasonal components of the varves. Bright layers contain coarser grains that can mainly be identified as quartz in the medium-to-coarse silt grain size. They also contain higher amounts of Si, Zr, Ca, and Sr, as well as more ice-rafted debris (IRD). Dark layers, on the other hand, contain finer particles such as mica and clay minerals from the chlorite and illite groups. In addition, Fe, Ti, Rb, and K are elevated. Based on these findings as well as on previous analyses on neighbouring cores, we propose a model of enhanced thermohaline convection in front of a grounded ice sheet that is supported by seasonally variable coastal polynya activity during the LGM. Accordingly, katabatic (i.e. offshore blowing) winds removed sea ice from the ice edge, leading to coastal polynya formation. We suggest that glacial processes were similar to today with stronger katabatic winds and enhanced coastal polynya activity during the winter season. Under these conditions, lighter coarser-grained layers are likely glacial winter deposits, when brine rejection was increased, leading to enhanced bottom-water formation and increased sediment transport. Vice versa, darker finer-grained layers were then deposited during less windier season, mainly during summer, when coastal polynya activity was likely reduced. |
format |
Article in Journal/Newspaper |
author |
Sprenk, D. Weber, M. E. Kuhn, G. Wennrich, V. Hartmann, T. Seelos, K. |
author_facet |
Sprenk, D. Weber, M. E. Kuhn, G. Wennrich, V. Hartmann, T. Seelos, K. |
author_sort |
Sprenk, D. |
title |
Seasonal changes in glacial polynya activity inferred from Weddell Sea varves |
title_short |
Seasonal changes in glacial polynya activity inferred from Weddell Sea varves |
title_full |
Seasonal changes in glacial polynya activity inferred from Weddell Sea varves |
title_fullStr |
Seasonal changes in glacial polynya activity inferred from Weddell Sea varves |
title_full_unstemmed |
Seasonal changes in glacial polynya activity inferred from Weddell Sea varves |
title_sort |
seasonal changes in glacial polynya activity inferred from weddell sea varves |
publisher |
COPERNICUS GESELLSCHAFT MBH |
publishDate |
2014 |
url |
https://kups.ub.uni-koeln.de/45006/ |
long_lat |
ENVELOPE(-61.000,-61.000,-78.500,-78.500) |
geographic |
Ronne Ice Shelf Weddell Weddell Sea |
geographic_facet |
Ronne Ice Shelf Weddell Weddell Sea |
genre |
Filchner Ronne Ice Shelf Filchner-Ronne Ice Shelf Ice Sheet Ice Shelf Ronne Ice Shelf Sea ice Weddell Sea |
genre_facet |
Filchner Ronne Ice Shelf Filchner-Ronne Ice Shelf Ice Sheet Ice Shelf Ronne Ice Shelf Sea ice Weddell Sea |
op_relation |
Sprenk, D., Weber, M. E., Kuhn, G., Wennrich, V., Hartmann, T. and Seelos, K. (2014). Seasonal changes in glacial polynya activity inferred from Weddell Sea varves. Clim. Past., 10 (3). S. 1239 - 1252. GOTTINGEN: COPERNICUS GESELLSCHAFT MBH. ISSN 1814-9332 |
_version_ |
1765998891194384384 |