Precession and ice sheet control of hydroclimate in Arctic East Beringia over the past 240,000 years

Key orbital-scale climate drivers governing Arctic hydroclimate change during the Late Quaternary are poorly constrained due to the lack of long and continuous records. Here we present a 240,000-year hydroclimate reconstruction from Imuruk Lake, Alaska, representing the longest continuous sedimentary record in the North American Arctic. Our high-resolution analyses of elemental composition, grain size and color spectra show prominent precession and obliquity variance. Wavelet analyses suggest strongly persistent local summer-insolation and ice volume forcing on Eastern Beringia hydroclimate changes. Importantly, we find that the amplitude of precession-scale variability in precipitation and chemical weathering during glacial intervals is stronger than that during interglacial intervals, differing from most proxy records that indicate weaker precession variability during the glacial intervals. Our results are consistent with a 300-kyr transient model simulation using CCMS3, indicating prominent insolation forcing on precipitation at the precession band, and that the advance of the Laurentide Ice Sheet during the glacials increased precipitation in Eastern Beringia (counter-intuitively) by deflecting Westerly moisture to northwest Alaska. We propose that precession-induced summer insolation as well as changes in ice topography are dominant controls on orbital-scale precipitation changes in Eastern Beringia over the past 240,000 years.