From Early Holocene to Neoglacial conditions – Multiproxy evidence for stepwise cooling in the Arctic Gateway


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Christian.Hass [ at ] awi.de

Abstract

Two high-resolution sediment sequences from the Western Svalbard margin covering the last ca. 10.000 years were studied in order to derive information on the Holocene variability of heat transport to the Arctic Ocean and fluctuations in the position of the marginal ice zone. The Fram Strait, often referred to as the Arctic Gateway, is the only deep-water passage for Atlantic-derived water masses to enter the Arctic Ocean. Northward advection of relatively warm and saline Atlantic Water masses keeps the eastern Fram Strait ice-free all year and controls the Arctic Ocean’s heat budget. We investigated geochemical, micropaleontological, and sedimentological parameters with centennial to multidecadal time resolution at two sites which are located today beneath the Atlantic Water-bearing inner and outer West Spitsbergen Current. Records of planktic and benthic foraminiferal stable isotopes and planktic foraminifer assemblages clearly reveal distinct variations between climatically warmer and colder intervals throughout this period. Strong fluctuations in stable isotope data of the subpolar planktic foraminifer species Turborotalita quinqueloba infer strong variability of summer sea surface conditions probably caused by variable extent of the upper mixed layer and the sea ice margin. Planktic foraminifer fauna imply a stepwise transition from deglacial/Early Holocene to modern-like conditions. Superimposed on the generally strong heat transport to the Arctic Ocean during the Early to Mid-Holocene are repeated short-term coolings such as the 8.2 ka event. Past sea ice conditions were studied by means of the sea ice proxy IP25 and ice rafted detritus and document increasing occurrence of sea ice and/or icebergs since the Mid-Holocene, culminating in the so-called ‘neoglaciation’ trend. The Late Holocene Neoglacial phase was in particular characterized by the dominance of the cold water-indicating planktic foraminifer species Neogloboquadrina pachyderma. Consistent with the decreasing solar insolation, cooler (sub-)surface conditions established after ca 5 cal ka BP most likely related to a weakening of the Atlantic Water advection and strong export of Arctic sea ice through Fram Strait.



Item Type
Conference (Poster)
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Peer-reviewed
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Published
Event Details
American Geophysical Union Fall Meeting, 03 Dec 2012 - 07 Dec 2012, San Francisco.
Eprint ID
32137
Cite as
Werner, K. , Müller, J. , Hass, H. C. and Spielhagen, R. F. (2012): From Early Holocene to Neoglacial conditions – Multiproxy evidence for stepwise cooling in the Arctic Gateway , American Geophysical Union Fall Meeting, San Francisco, 3 December 2012 - 7 December 2012 .


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