NOAA/WDS Paleoclimatology - Arrowhead Lake, Greenland, XRF, Magnetic Susceptibility and d18O Data Over the Past 8300 Years

ABSTRACT SUPPLIED BY ORIGINATOR: Paleotemperature records from ice-free margins of Greenland suggest spatiotemporal heterogeneity in the timing of key climate transitions following retreat of the Greenland Ice Sheet. However, the paucity of high-resolution climate records from this region limits our understanding of the timing, spatial variation, and drivers of Holocene climate variability. Here, we present a middle to late Holocene climate reconstruction based on chitin d18O and sediment geochemistry from lake sediments to elucidate millennial to submillennial-scale drivers of climate in southwestern Greenland. We establish that our site, Arrowhead Lake, is a through-flowing basin with an integrated signal of annual meteoric water with no evidence of evaporative enrichment. Core sediment geochemistry captures the transition from minerogenic-dominated to organic-rich sediments ~8 cal ka BP. Chitin-based d18O measurements of both chironomid head capsules and ephippia exhibit similar temporal variability through the record, broadly decreasing from 8.2 cal ka BP to present, concurrent with decreasing summer insolation and regional Neoglacial cooling. We estimate an average temperature change from the middle to late Holocene at Arrowhead Lake of 2 – 3 ?, comparable to existing chitin d18O estimates of temperature in western Greenland. Depleted d18O values after 3.3 cal ka BP corresponds to the onset of Neoglacial cooling and a slowdown of the Western Greenland Current, and suggests that both temperature and sea-ice variability were important controls on isotopic variability at this site. Highly depleted isotopic values at 8.2 cal ka BP followed by high isotopic variability in the early part of the middle Holocene suggests that our record may capture regional 8.2 ka cooling . This new isotope record provides insight into climate influences during the middle and late Holocene along the western Greenland margin that are important for understanding how ongoing melt of the Greenland Ice Sheet and amplified warming in the Arctic may impact the climate system.