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

Abstract

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

Permafrost Organic Carbon Mobilization From the Watershed to the Colville River Delta: Evidence From 14C Ramped Pyrolysis and Lignin Biomarkers

“…Itkillik yedoma samples were collected using SIPRE corer at the Itkillik yedoma exposure site in 2011 (Kanevskiy et al, ) and oven dried at 90°C. The CR‐24 river sediment (upper ~5 cm) was collected from a slough connected to the Colville River main channel in August 2012 (Hanna et al, ). Sediment cores L1 and L3 were collected in the delta using a Rossfelder P‐3 submersible vibracorer in August 2010 (Schreiner et al, ) and subsampled at 2 cm intervals.…”

Dual isotope evidence for sedimentary integration of plant wax biomarkers across an Andes-Amazon elevation transect

“…For example, lignin (Aufdenkampe et al, 2007;Goñi et al, 2000), terpenoids (Giri et al, 2015;Medeiros et al, 2012) and plant wax biomarkers (Freymond et al, 2018;Häggi et al, 2016;Hemingway et al, 2016;Hoffmann et al, 2016;Tao et al, 2015) have been used in riverine systems to trace biogenic OC derived from vascular plant biomass. In addition, biomarkers for microbial activity have been used to trace bacterial and archaeal components of terrestrial biospheric OC production exported by rivers (Hanna et al, 2016;Hemingway et al, 2017;Kim et al, 2012;Wagner et al, 2014).…”

A multi-proxy investigation of late-Holocene temperature change and climate-driven fluctuations in sediment sourcing: Simpson Lagoon, Alaska

“…Previous examination of potential brGDGT sources within the Colville system reveal that brGDGT distributions are consistent throughout the Colville watershed soils, shoreline sediments, Colville River sediments, and adjacent Simpson Lagoon sediments, and that in situ production within the Colville system has a limited impact on the applicability of the MBT′/CBT paleothermometer in this setting (Hanna et al, 2016). In addition, reconstructed temperatures from modern sediments collected from the Colville River, catchment, shoreline tundra, and Simpson Lagoon show good agreement with instrumental summer (JJAS) air temperatures on the North Slope of Alaska, exhibiting a seasonal bias that has been observed by other researchers in high latitude settings (Pautler et al, 2014;Rueda et al, 2009Rueda et al, , 2013Shanahan et al, 2013).…”