Glycerol dialkyl glycerol tetraether variations in the northern Chukchi Sea, Arctic Ocean, during the Holocene

Abstract. Glycerol dialkyl glycerol tetraethers (GDGTs) have become a useful tool in paleoclimate research in ocean environments, but their applications in the Arctic are yet to be developed. GDGTs were analyzed in three sediment cores from the northern/northeastern margin of the Chukchi Sea to test the applicability of GDGT proxies for reconstructing sea surface temperature and sea-ice variability in the Holocene. Interpretation was enabled by an earlier investigation of GDGT composition in surface sediments from the study area. Low GDGT concentrations and high BIT and CBT values in core sediments older than ca. 8 ka probably indicate heavy sea-ice conditions in combination with terrestrial inputs during deglaciation and incomplete sea-level rise. Higher concentrations of isoprenoid GDGTs after ca. 8 ka, consistent with an increase in total organic carbon and some other biogenic proxies, are interpreted to represent increased primary production combined with elevated sedimentation rates. These patterns were likely controlled by sea-ice conditions and variations in Pacific water inflow. Geographic heterogeneity in these processes is indicated by differences in GDGTs distribution patterns between cores across the Chukchi margin. TEX₈₆ and TEX₈₆^L indices potentially indicative of sea surface temperatures appear to show millennial-scale variability, but the controls on these fluctuations are yet to be understood.