Paleo–sea ice conditions of the Amundsen Gulf, Canadian Arctic Archipelago: Implications from the foraminiferal record of the last 200 years

摘要

Four boxcores were collected as part of the Canadian Arctic Exchange Shelf Study (CASES) in the Amundsen Gulf at water depths of 59 m to 600 m. Data from these cores help to develop a record of changes in the oceanographic history of the area over the last 200 years, with particular reference to the indication of paleo–sea ice formation, a key element of the Arctic ecosystem. The four sites cover a range of water depths and environments to provide a basis for comparison. The benthic foraminifera of sites CA-06 (253 m water depth) and CA-18 (600 m water depth) show an increase in Arctic Surface Water associated agglutinated foraminifera over the last ～100 years (uppermost 8 to 16 cm). These are indicating a decrease in sea ice cover and in cold saline Arctic Bottom Water influence; these are similar to Canadian Arctic Archipelago postglacial faunas. This contrasts with abundant planktic foraminifera at the same stations, suggesting strong, oceanic Arctic surface influence (little freshwater) in the central Gulf. The foraminifera of sites 403B (59 m water depth) and 415B (56 m water depth), at the outermost edges of Amundsen Gulf, indicate that the present-day location of the winter flaw lead has been in place for at least the last 100 years, with foraminiferal faunas similar to those of the Beaufort Shelf. Additionally, station 415 is on an earlier Holocene shoreline that is covered with cobbles.