Distribution of branched GDGTs in surface sediments from the Colville River, Alaska: Implications for the MBT′/CBT paleothermometer in Arctic marine sediments

摘要: Significant climate fluctuations in the Arctic over recent past, and additional predicted future temperature changes, highlight need for high-resolution paleoclimate records. coastal environments supplied with terrigenous sediment from rivers have potential to provide annual subdecadal resolution records of variability last few millennia. A tool paleotemperature reconstructions these marine sediments is revised methylation index branched tetraethers (MBT′)/cyclization ratio (CBT) proxy based on glycerol dialkyl (brGDGTs). In this study, we examine source brGDGTs Colville River, Alaska, adjacent Simpson Lagoon reconstruct temperatures evaluate applicability estuarine environments. The catchment soils, fluvial sediments, contain statistically similar brGDGT distributions, indicating that throughout system are soil derived little alteration situ production river or waters. Temperatures reconstructed MBT′/CBT indices surface samples show good agreement regional summer (June through September) temperatures, suggesting a seasonal bias system. addition, paleotemperatures an core spans 75 years, revealing overall warming trend twentieth century consistent trends observed instrumental These results support application brGDGT-based subdecadal-scale estuaries containing organic material sediment-laden, episodic rivers.