Early Holocene Laurentide Ice Sheet retreat influenced summer atmospheric circulation in the North American Arctic: Evidence from precipitation isotope and temperature proxy records and a climate model

Changes in ice sheet size and configuration impact global moisture and heat transport, but few proxy records examine these impacts. High-latitude precipitation-isotope proxy records are often interpreted to reflect temperature change, but can also reflect changes in moisture source. We present independent sub-centennial-scale records of summer temperature and summer precipitation δ²H from the same lake sediment archive on northeastern Baffin Island. We also examine published TraCE-21k transient model simulation results. These records span from 12 to 7 ka, when the Laurentide Ice Sheet underwent major retreat. The correlation structure between summer temperature and precipitation δ²H on northeastern Baffin Island changed from negative to positive around 10 ka. We interpret this change in correlation structure to indicate a shift in moisture sources to northeastern Baffin Island. TraCE-21k results suggest that moisture sources in this region are controlled by the relative strength of the high pressure systems and associated anticyclonic circulation over the Greenland and Laurentide ice sheets. We therefore interpret the proxy records as follows: when the Laurentide high dominated prior to 10 ka, northerly winds brought cold, dry Arctic air to the region, allowing ²H-enriched local sea breezes to provide most of the moisture to Baffin Island. After 10 ka, the Greenland high dominated, causing southerly flow to carry warm, moist, ²H-depleted air masses to northeastern Baffin Island. Regional centennial-scale cooling events caused by periodic freshwater inputs to the Labrador Sea throughout the Early Holocene were also associated with intervals of ²H-enriched summer precipitation. This study provides evidence that atmospheric circulation was influenced by the waning continental ice sheets. Similar ice-sheet influences are critical to consider when interpreting precipitation isotope proxy records spanning periods of dramatic ice-sheet change. These results demonstrate that precipitation isotopes can reflect changes in atmospheric circulation in the geologic record.