How unusual is recent warming in the Arctic? How do arctic environments really respond to warming climate? Geologic records can provide some answers. Specifically, insolation-driven warmth across the Arctic during the Last Interglacial period (ca. 130 to 116 thousand years ago) and the early to middle Holocene (ca. 9-5 thousand years ago) provides geologically accessible analogs for future arctic warming and its impacts. And by providing a picture of what a warmer Arctic really looks like, paleoclimate reconstructions from these past warm periods can be used to test and improve climate and ice sheet models.

This talk will describe recent efforts to reconstruct the warm climates of the Last Interglacial and early Holocene on and near Greenland using insect assemblages preserved in lake sediments. Terrestrial temperature reconstructions for the Last Interglacial are rare in the heavily glaciated North Atlantic Arctic region due to widespread erosion of sediments by continental ice sheets during the Last Glacial Maximum. To address this problem, we exploit special glacial geologic settings where cold-based Pleistocene ice cover preserved ancient lake sediments in situ. In contrast, Holocene lake sediment records are widespread across the region, allowing for comparison of records across an ever-growing network of sites. Our reconstructed Holocene summer temperature anomalies are larger than those typically inferred from annually-integrated indicators from the ice sheet itself, agree well with the timing of climate shifts inferred from other archives, and suggest significant spatial heterogeneity of Holocene climate change around Greenland. Future work will apply geochemical proxy methods (oxygen isotopes of aquatic organic materials and hydrogen isotopes of leaf waxes) in parallel with insect-based reconstructions to infer additional aspects of climate during the Holocene and Last Interglacial.