Interglacial and Holocene temperature reconstructions based on midge remains in sediments of two lakes from Baffin Island, Nunavut, Arctic Canada

Midge remains (Insecta: Diptera: Chironomidae and Chaoboridae) from two upland lake basins on the Cumberland Peninsula of Baffin Island were analyzed and the results used in a transfer function to reconstruct paleotemperatures. This upland region remained ice-free throughout the last glacial cycle and the two lake basins retain sediments deposited during the previous interglacial period as well as during the Holocene period, but they did not accumulate sediment during most of the glacial period. Midge remains are abundant and well preserved at both sites. Midge-inferred summer surface water temperatures and mean July air temperatures were estimated using an inference model built on modern samples spanning a geographic range extending from Devon Island, Canada to Maine, USA. Data from twenty-nine new surface samples from Baffin Island were added to an existing inference model. The new weighted averaging (WA) model for summer surface water temperature yields r2jack = 0.88 and RMSEP = 2.22 °C for summer water temperatures, and r2jack = 0.88 and RMSEP = 1.53 °C for mean July air temperatures. Reconstructions at both sites indicate that summer temperatures during the last interglacial were higher than at any time in the Holocene, and 5 to 10 °C higher than present. Peak Holocene temperatures occurred in the first half of the period, and have decreased since about the mid-Holocene.