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Holocene cooling and Neoglacial sea ice fluctuations in the subpolar North Atlantic

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Müller, J. , Werner, K. , Stein, R. and Moros, M. (2011): Holocene cooling and Neoglacial sea ice fluctuations in the subpolar North Atlantic , AGU Fall Meeting, San Francisco, California, USA, 5 December 2011 - 9 December 2011 .
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Abstract:

The reconstruction of palaeo sea ice coverage in the Arctic realm gained increasing interest throughout the past decades and the approaches to identify ancient sea ice occurrences are manifold. By means of organic geochemical biomarker studies and IRD analyses we reconstruct Holocene sea ice conditions in the subpolar North Atlantic, where the spatial and temporal distribution of sea ice is mainly controlled by the advection of warm Atlantic Water via the West Spitsbergen Current and the export of polar water and sea ice from the Arctic Ocean via the East Greenland Current (Rudels et al., 2005). Variations in the strength of this oceanic circulation regime may either stimulate or reduce the sea ice extent. With high-resolution analyses of sediment cores from the western continental margin of Spitsbergen and the East Greenland shelf we provide new evidence for the highly variable character of the sea ice conditions in this area. The combination of the sea ice proxy IP25 (Belt et al., 2007) with phytoplankton-derived biomarkers (e.g. brassicasterol, dinosterol; Volkman, 2006) enables a reliable reconstruction of sea ice and sea surface conditions, respectively (Müller et al., 2009; 2011). By means of these biomarkers, we identify gradually increasing sea ice occurrences from the Mid to the Late Holocene. These are also traceable in the IRD data and align with the Neoglacial cooling trend. Throughout the past ca. 3,000 years BP we observe a significant short-term variability in the biomarker records, which points to rapid advances and retreats of sea ice at the continental margin of West Spitsbergen. To what extent a seesawing of temperate Atlantic Water advection may account for these sea ice fluctuations requires further investigation. Concurrent variations in Siberian river discharge (Stein et al., 2004) and varying glacier extents in Scandinavia and Spitsbergen (Nesje et al., 2001; Svendsen and Mangerud, 1997), however, strengthen that these fluctuations may be influenced or even controlled by the North Atlantic/Arctic Oscillation (NAO/AO). At the continental shelf of East Greenland, the general Holocene cooling, however, seems to be less pronounced and a notable increase in sea ice coverage did not occur before 1,000 years BP. Phytoplankton-IP25 indices (“PIP25-Index”) are used for more explicit sea ice estimates and display a Mid Holocene shift from a minor sea ice coverage to stable ice margin conditions in Fram Strait. References Belt, S.T. et al., 2007. Organic Geochemistry, 38(1): 16-27. Müller, J. et al. 2009. Nature Geoscience, 2(11): 772-776. Müller, J. et al., 2011. Earth and Planetary Science Letters, 306 (3-4), 137-148. Nesje, A. et al., 2001. The Holocene, 11(3): 267-280. Rudels, B. et al., 2005. Journal of Marine Systems, 55(1-2): 1-30. Stein, R. et al., 2004. Quaternary Science Reviews, 23(11-13): 1485-1511. Svendsen, J.I. and Mangerud, J., 1997. The Holocene, 7: 45-57. Volkman, J.K., 2006. In: J.K. Volkman (Editor), Handbook of Environmental Chemistry. Springer-Verlag, Berlin, Heidelberg, pp. 27-70.

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