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HB-1-8

Linking the Late Holocene variability of Svalbard glaciers and ice caps to oceanic heat advection

PhD student :Martin Bartels
Project supervisors :D. Hebbeln, R. Stein (Germany)
M. Kienast, C. Hillaire-Marcel (Canada)
Key hypothesis
(1) Climatic signals communicated to western Svalbard by the advection of Atlantic Waters have been propagated unsmoothed further eastward into the Arctic realm. (2) In spite of an increasing distance from the heat and moisture source of the West-Spitsbergen Current, glaciers on northern and eastern Svalbard react as sensitive to changing climate forcing as the West-Spitsbergen glaciers.
Bathed by the comparably warm waters of the West-Spitsbergen Current (WSC), the northernmost extension of the North Atlantic Current, the Svalbard archipelago between 77°N and 80°N is a unique setting. Via these direct ocean link, climatic signals generated in the North Atlantic e.g. by variations in the Atlantic Meridional Overturning Circulation (AMOC), can be rapidly communicated to the high Arctic. Thus, within the high Arctic the Svalbard region has been, is and will be among the most sensitive regions with respect to climate variability. Past changes in the intensity of heat advection to Svalbard during the last glacial and the deglaciation impacted on the waxing (i.e. by moisture supply, Hebbeln et al. 1994) and waning (i.e. by warming) of the large Svalbard ice sheet. Especially the decay of the Svalbard and also other regional ice sheets left distinct traces by accumulations of ice-rafted detritus (IRD) in the sediments of the Nordic Seas. Thus, marine archives, ideally combined with terrestrial archives, provide detailed information on oceanic heat advection and the response of regional ice sheets. However, under Holocene conditions only individual glaciers and small ice caps existed on Svalbard, nevertheless still covering 60% of the archipelago. Although still being sensitive to climate variability their Holocene history, and thus, their response to Holocene scales of climate forcing, is less well constrained, as under Holocene conditions regional heterogeneity has to be considered. To understand the regional sensitivity to climate change, Svalbard, with its numerous fjord systems, offers a wide variety of well-suited marine paleoarchives combining information about oceanic forcing and (local) glacier response. In the western part of the archipelago these archives have been extensively exploited revealing a consistent pattern of the Holocene development of the glaciers marked by lowest glacier extents between 9 and 5 cal. kyrs BP and maximum spreads around the Little Ice Age. In addition, an increased 20th century warming around Svalbard is reflected both in marine records and in ice core data. However, all these findings are based on field evidence from the western part of Svalbard that directly faces the relatively warm WSC. In contrast, only very few paleoclimate data exist from the eastern part of Svalbard that is bathed by cold Arctic Waters. These data corroborate a strong early Holocene climate optimum. The ice core records from Svalbard, although reaching back only for ~600 yrs clearly reveal significant paleoclimate variability also for eastern Svalbard (Nordaustlandet) which for the last 400 yrs appears to be linked to the regional sea ice extent. To assess how Holocene climatic signals communicated to western Svalbard by Atlantic Waters propagated eastward to eastern Svalbard and consequently further into the high Arctic requires stratigraphically longer paleorecords from the northern and eastern fjords of Svalbard that have been largely missing so far.
New sediment cores available from several fjord sites along northern and eastern Svalbard now provide the chance to trace the response of the Svalbard archipelago to Holocene climate variability along a continuous west-east transect from relatively warm and moist West-Svalbard to dry and cold East-Svalbard. Focusing on the oceanic forcing (as reflected in temperature and productivity records) and the regional to local glacier response (as reflected by the input of terrigenous sediments) sedimentary records from this still poorly investigated parts of the archipelago will be investigated and later on combined with existing paleoenvironmental records from western Svalbard. Based on this, a comprehensive analysis of the regional sensitivity to climate change at this “Gate to the High Arctic” will be generated. In this way, the project is directly related to HB-9, CA-8 and the modeling aspects presented in HB-4, HB-11 and CA-13.Considering the entire Holocene with a clear focus on the only poorly constrained Late Holocene past hydrographic variations (i.e. the marine forcing) in selected shelf and fjord settings will be reconstructed by means of foraminiferal stable isotope analyses and accompanied by analyses of organic and carbonate materials (Corg, N, CaCO3, 13Corg and 15N) to assess changes in paleoproductivity. Second, glacier activity (i.e. the terrestrial response) will be assessed by tracing sediment accumulation (AMS-14C-dating) and sediment composition (grain sizes, ice-rafted detritus, XRF) that are assumed to be closely linked to the dynamics of the glaciers draining into the fjords. Ideally, if the temporal resolution of the new cores allows, these records will be linked to the 600 yrs ice core records to benchmark the sedimentary record to the modern trends. This is basically the approach that has been successfully followed also for the West-Spitsbergen fjords.