Svalbard ice-sheet decay after the Last Glacial Maximum: New insights from micropalaeontological and organic biomarker paleoceanographical reconstructions
Abstract A marine sediment core retrieved from the middle continental slope of the northwestern Barents Sea was analyzed for its geochemical (alkenones) and micropalaeontological (diatoms, coccolithophores and dinocyst) content in order to reconstruct the evolution of upper ocean conditions and ice-sheet dynamics during the last 25 kyr. Additionally, quantitative reconstructions of sea surface conditions (temperature, salinity and sea-ice cover extent) were conducted based on the best analogue technique applied to dinocyst assemblages and on the alkenone unsaturation index. The sediment core contains a post Last Glacial Maximum depositional sequence unaffected by stratigraphic discontinuities. Low salinity and laminated sediments after 20 cal kyr BP, indicate a massive settling of meltwater sediment-laden plumes from the initial melting of the Svalbard-Barents Sea Ice Sheet on Western Svalbard. First record of measurable alkenones, together with a drop of the number of months of sea-ice cover and increase in SSTs suggests an intensification of the influx of Atlantic waters into the study area at ~ 15 cal kyr BP representing the termination of the last glacial period and onset of the Bolling interstadial. The first occurrence of diatoms and increase in the abundance of all microfossils marked the onset of the Holocene at 11.2 cal kyr BP when modern-type sea surface conditions were rapidly established in Western Svalbard. Reconstructions based on dinocyst data and alkenone unsaturation index suggest relatively warm and stable temperatures between 9.9 and 8.9 kyr BP and a decrease of SSTs from 4.2 cal kyr BP to present coinciding with the Holocene Thermal Maximum and the decrease of summer insolation in the high latitude northern hemisphere, respectively.