Late glacial and deglacial age model and biomarker analyses of sediment core MSM05/5_712-2 from the western continental slope of Svalbard

The transition from last glacial to deglacial and subsequently to modern interglacial climate conditions was accompanied by abrupt shifts in the palaeoceanographic setting in the subpolar North Atlantic. Knowledge about the role that sea ice coverage played during these rapid climate reversals is limited since most marine sediment cores from the higher latitudes provide only a coarse temporal resolution and often poorly preserved microfossils. Here we present a highly resolved reconstruction of sea ice conditions that characterised the eastern Fram Strait - a key area for water mass exchange between the Arctic Ocean and the North Atlantic - for the past 30 ka BP. This reconstruction is based on the distribution of the sea ice biomarker IP25 and phytoplankton derived biomarkers in a sediment core from the continental slope of western Svalbard. During the late glacial (30 ka to 19 ka BP), recurrent advances and retreats of sea ice characterised the study area and point to a hitherto less considered oceanic (and/or atmospheric) variability. A long-lasting perennial sea ice coverage in eastern Fram Strait persisted only at the very end of the Last Glacial Maximum (i.e. from 19.2 to 17.6 ka BP) and was abruptly reduced at the onset of Heinrich Event 1 - coincident with or possibly even inducing the collapse of the Atlantic Meridional Overturning Circulation (AMOC). Further maximum sea ice conditions prevailed during the Younger Dryas cooling event and support the assumption of an AMOC reduction due to increased formation and export of Arctic sea ice through Fram Strait. A significant retreat of sea ice and sea surface warming are observed for the Early Holocene.

Total organic carbon, delta13C, biomarker, diatom distributions in sediment core JM11-FI-19PC

In the light of rapidly diminishing sea ice cover in the Arctic during the present atmospheric warming, it is imperative to study the distribution of sea ice in the past in relation to rapid climate change. Here we focus on glacial millennial scale climatic events (Dansgaard/Oeschger events) using the new sea ice proxy IP25 in combination with phytoplankton proxy data and quantification of diatom species in a record from the SE Norwegian Sea. We demonstrate that expansion and retreat of sea ice varied consistently in pace with the rapid climate changes 90 ka to present, and with this present the first IP25 sea ice proxy record resolving the D/O cyclicity going back in time into Marine Isotope Stage 5a. Sea ice retreated abruptly at the start of warm interstadials, but spread rapidly during the cooling phase of the interstadials and became near-perennial and perennial during cold stadials and Heinrich events, respectively. Low salinity surface water and the sea ice edge spread to the Greenland-Scotland Ridge, and during the largest Heinrich events, probably far into the Atlantic Ocean.