第八届青年地学论坛

Arctic sea ice is a critical element of the climate system by regulating the global heat budget due to the albedo effect and sensitive to changes in atmospheric and oceanic circulation. The Southeast Greenland Shelf is a climatologically sensitive area where sea ice changes are not only affected by local sea ice formation but also drift ice and cold freshwater outflow from the Arctic Ocean by East Greenland Current (EGC), which makes this area challenging for paleo-sea ice reconstruction. Here we presented high-resolution biomarker records in marine sediment core ER11-19 from the Southeast Greenland shelf in the vicinity of Sermilik Fjord over the past 3.5 kyr to assess the sea ice conditions. We analyzed concentrations of sea ice biomarker IP₂₅, the phytoplankton biomarker dinosterol, the terrestrial biomarker long-chain n-alkanes and archaea biomarker GDGTs to reveal sea ice variabilities associated with the known cold/warm phases, i.e. the Roman Warm Period (RWP), Dark Age Cold Period (DACP), Medieval Climate Anomaly (MCA) and Little Ice Age (LIA). It suggests that a nearly open water condition concurrent with generally low primary productivity possibly related to increasing outflow of nutrient depleted Arctic waters.  during the 3.5-2.3 kyr BP. The following RWP (2.3-1.3 kyr BP) is characterized a variable sea-ice cover condition coinciding with the constantly low phytoplankton productivity within the still prevailing relatively warm surface water condition potentially due to the remarkable increasing inflow of Atlantic water. Thereafter, the DACP (1.3-1.0 kyr BP), a phase of severe seasonal sea-ice cover accompanied by increasing phytoplankton productivity, which may relate to the strengthening of EGC and enriched nutrients water inflow after 1.3 kyr BP. The short-lived MCA (1.0-0.8 kyr BP) characterized by a less sea ice over may result from a slight increase of Atlantic water influence. From 0.8 kyr BP onwards, a return of marginal ice zone condition reflected in the elevation of sea-ice concentration and phytoplankton productivity, may indicate a transition from MCA to LIA, and the lowest SSTs may give a hint on the LIA occurred with stable ice edge cover prevailed for 0.5-0.1 kyr BP.

paleo-sea ice; biomarkers; East Greenland; fjord; Late Holocene