During the RV "Polarstern" expeditions ARK VIII/2 and ARK IX/4 sediment cores were recovered along the northern continental slope of the Barents- and Kara-Sea in order to obtain more information about sea-ice coverage, ice sheet build-up/decay and extension of the warm Westspitsbergen Current during the last glacial/interglacial periods. Here, we present first results of a detailed and high resoluted geochemical and sedimentological study
The stratigraphic interpretation of the investigated cores is based on oxygen isotope analysis (N. pachyderma sin.).
During Last Glacial Maximum (LGM) the ice advance onto the Barents Sea Shelf occured around 22 ky followed by an ice advance to the shelf edge at about 18 ky. The decay of the ice-sheet started at 14,8 ky combined with a typical meltwater event and a higher input of ice rafted detritus (Elverhøi, 1995). Current investigation have revealed that during isotope stage 3 and 2 the Atlantic water have reached the western coast of Spitsbergen at least six times supporting the build-up and the decay of the Svalbard-Barents-ice-sheet (Dokken, 1995).
The main objects of this study are to map the distribution of the Atlantic water during LGM between Spitsbergen and Franz Josef Archipelago and, additionally, if there are any signals of Atlantic water advection in isotope stage 6. To support the stratigraphic framework, to distinguish between marine productivity and terrigenous organic input, and
to estimate the paleo-water temperature (Alkenones/
UK37-index) detailed GC and GC/MS-analysis and UV-spectrometer-analysis will performed.
Preliminary results can be summarized as follows:
Signals for advection of Atlantic Water during the last 30 ky can be followed as far as the west coast of Franz Josef Archipelago. Especially, the maximal carbonate content
(19 %), which are related to highest planktic foraminifera abundances, at the end of stage 3 and in the middle part of stage 2, confirm these assumption. The build-up and the decay of the Svalbard-Barents-Sea-Ice-Sheet are illuminated by typical IRD-signals joined by higher C/N-ratios (until 13) and lower hydrogen indices (about 50 mgHC/gC) at the beginning and the end of stage 2. The enrichment of organic carbon (TOC) (1,5 %) during these times is caused by higher input of terrigenous organic matter. In particular, during the extension of the ice-sheet at the beginning of stage 2, high input of reworked terrigenous organic material from mesozoic sediments of the Spitsbergenbanken and the Central Barents Sea are documented both on the western continental slope of Spitsbergen (Elverhøi, 1995) and in the northern part of the Barents Sea between Spitsbergen and Franz Josef Land (this study).
Furthermore, similar signals are recognizable in isotope stage 6. Although heavier oxygen isopes (4.5 ”) depict glacial conditions, two second carbonate maximum (15-19 %) related to high planktic foraminifera contents occur. Between these two maximums, a higher terrigenous input of organic matter (C/N-ratio: 9, hydrogen index: 50 mgHC/gC)) and an increase of IRD are remarkable. It is assumed that, at this time interval, the ice sheet extended beyond the present day coast line and reached the shelf edge as in stage 2.
As a preliminary conclusion we assume that during isotope stage 6 a similar moisture supply caused by the advection of Atantic water or a coastal polynya triggered by extremely strong katabatic wind system from the ice-sheet supported the build-up and the decay of the Barents-Kara-Ice-Sheet similar to the stage 3-2 situation.
Dokken, T.M., Ph.D. thesis, 175 pp. Institute of Biology and Geology, University of Tromsö, Norway (1995).
Elverhøi, A. et al., Quaternary Research (submitted) (1995).