Branched glycerol dialkyl glycerol tetraethers in Arctic lake sediments: Sources and implications for paleothermometry at high latitudes

Abstract

Branched glycerol dialkyl glycerol tetraethers (brGDGTs) are analyzed in different lakes of the Mackenzie (Canadian Arctic) and Kolyma (Siberian Arctic) River basins to evaluate their sources and the implications for brGDGT-based paleothermometry in high-latitude lakes. The comparison of brGDGT distributions and concentrations in the lakes with those in river suspended particulate matter, riverbank sediments, and permafrost material indicates that brGDGTs in Arctic lake sediments have mixed sources. In contrast to global observations, distributional offsets between brGDGTs in Arctic lakes and elsewhere in the catchment are minor, likely due to the extreme seasonality and short window of biological production at high latitudes. Consequently, both soil-and lake-calibrated brGDGT-based temperature proxies return sensible temperature estimates, even though the mean air temperature (MAT) in the Arctic is below the calibration range. The original soil-calibrated MBT-CBT (methylation of branched tetraethers-cyclisation of branched tetraethers) proxy generates MATs similar to those in the studied river basins, whereas using the recently revised MBT′-CBT calibration overestimates MAT. The application of the two global lake calibrations, generating summer air temperatures (SAT) and MAT, respectively, illustrates the influence of seasonality on the production of brGDGTs in lakes, as the latter overestimates actual MAT, whereas the SAT-based lake calibration accounts for this influence and consequently returns more accurate temperatures. Our results in principle support the application of brGDGT-based temperature proxies in high-latitude lakes in order to obtain long-term paleotemperature records for the Arctic, although the calibration and associated transfer function have to be selected with care.

Warm season bias of branched GDGT temperature estimates causes underestimation of altitudinal lapse rate

“…4), is likely associated with the shallower slope of the MBT 0 -CBT calibration. Similar interpretation has been made by Peterse et al (2014) for their findings that the application of the MBT 0 -CBT calibration resulted in higher MAATs in the Arctic than that using the original MBT-CBT calibration. Since the MBT 0 -CBT calibration overestimated measured MAAT at cold, high elevation (this study) and Arctic area (Peterse et al, 2014), it seems that the MBT-CBT calibration might be better suited to generating reliable MAAT estimates in cold areas.…”

“…Similar interpretation has been made by Peterse et al (2014) for their findings that the application of the MBT 0 -CBT calibration resulted in higher MAATs in the Arctic than that using the original MBT-CBT calibration. Since the MBT 0 -CBT calibration overestimated measured MAAT at cold, high elevation (this study) and Arctic area (Peterse et al, 2014), it seems that the MBT-CBT calibration might be better suited to generating reliable MAAT estimates in cold areas. However, considering the large error (± 5°C) in the calibrations, it would be precarious to determine a suitable calibration based solely on limited data comparison of estimates with measured values.…”

“…Seasonality in brGDGT distributions in lake sediments and more extensive microbial production in warm seasons has been suggested in several studies (e.g. Sun et al, 2011;Shanahan et al, 2013;Wu et al, 2013;Peterse et al, 2014). However, the occurrence of this phenomenon is still unclear for soils.…”

Summer temperature evolution on the Kamchatka Peninsula, Russian Far East, during the past 20 000 years

“…As in situ production can bias temperature reconstructions, particularly in marine settings where the input of terrigenous GDGTs is low (Weijers et al, 2006b;Peterse et al, 2009Peterse et al, , 2014De Jonge et al, 2014), the contribution of terrigenous brGDGTs to the marine sediments needs to be estimated prior to any paleoclimatic interpretation of temperatures derived from CBT-MBT . A common means to estimate the relative input of marine and terrestrial GDGTs is the BIT index (branched and isoprenoid tetraether index), which quantifies the relative contribution of the marine-derived crenarchaeol and terrigenous brGDGTs (Hopmans et al, 2004).…”

Grain Size Associations of Branched Tetraether Lipids in Soils and Riverbank Sediments: Influence of Hydrodynamic Sorting Processes

“…The higher MAT reflected by the Mackenzie River sediment may be explained by the South-to-North flow direction of the river. Additionally, the strong seasonality and related short growth period at this latitude likely causes a bias in brGDGT distributions toward summer temperatures in both soils and river sediments (Peterse et al, 2014).…”