第七届青年地学论坛

Sediment core ER11-16 from Køge Bugt in southeast (SE) Greenland is used to assess early Holocene palaeoceanographic changes and sediment rafting from icebergs calved from the large outlet glaciers in the area. Diatom analysis reconstructs variability in surface water temperature, salinity, and sea-ice concentrations, while benthic foraminiferal assemblages allow us to reconstruct subsurface ocean conditions. We report warm ocean conditions in Køge Bugt during the early Holocene, caused by relatively intense Irminger Current (IC) subsurface inflow and low sea-ice cover in the polar surface waters of the East Greenland Current. High levels of iceberg rafting occurred in Køge Bugt during the early Holocene, synchronously with warm oceanic temperatures. This is attributed to an increase in iceberg production from the extensive, but retreating, Greenland Ice Sheet. The warm surface conditions were interrupted by a marked and short-lived increase in sea ice around 8200 years ago, providing the first evidence of this cold episode in SE Greenland. After 4500 cal yr BP, sea-ice cover increased with an expansion of the East Greenland Current, suppressing the inflow of warmer subsurface IC water to the SE Greenland shelf. We relate this oceanic shift to the decreased Northern Hemisphere summer solar insolation. Superimposed on this general development, a complex pattern of multi-centennial variability in iceberg rafting is seen in the sedimentary record from core ER11-16. This reflects changes in iceberg production from the nearby glaciers but is also heavily modulated by oceanographic changes on the shelf. This finding highlights that iceberg rafting records should be interpreted in the context of palaeoceanographic changes.

格陵兰，古海洋环境，冰川