Holocene temperature history of northwest Greenland – With new ice cap constraints and chironomid assemblages from Deltasø

摘要: Abstract Arctic temperature shifts drive changes in carbon cycling, sea ice extent and Greenland Ice Sheet mass balance, all of which have global ramifications. Paleoclimate data from past warm periods provide a unique means for assessing the sensitivity these systems to warming climate, but magnitude timing many parts are poorly known. Here we assess orbital-scale Holocene change northwest near margin sheet using subfossil insect assemblages lake Deltaso. Based upon sedimentation history this currently proglacial lake, also place constraints on extents adjacent North Cap, large independent cap. Reconstructed summer temperatures were warmer than present at onset lacustrine following regional deglaciation by Sheet, sometime between 10.8 10.1 ka BP. Deltaso experienced warmest ∼10 6.2 BP, followed progressive cooling that continued through late as insolation declined, culminating lowest during pre-industrial last millennium. chironomids indicate peak early least 2.5–3 °C modern 3.5–4 °C We infer based sediment organic biogenic content response declining temperatures, Cap reached its present-day size ∼1850 AD, having been smaller most preceding Holocene. Our synthesis paleoclimate evidence Greenland, Ellesmere Island northern Baffin Bay supports trends inferred Deltaso, suggests quantitative reconstructions may represent minimum bound warming. Collectively, records region >4 °C Intense warmth around argues against delayed warmer-than-present conditions due influence nearby waning Laurentide has implications understanding Sheet's climate change.