RESEARCH LETTER Maximum Southwest Greenland Ice Sheet 10.1029/2019GL083164 Recession in the Early Holocene Key Points: A. J. Lesnek1, J. P. Briner2, N. E. Young3, and J. K. Cuzzone4 • We create a database of southwest Greenland ice sheet extents and 1Department of Earth Sciences, University of New Hampshire, Durham, NH, USA, 2Department of Geology, University at retreat rates that can be used to 3 ‐ 4 assess ice sheet model performance Buffalo, Buffalo, NY, USA, Lamont Doherty Earth Observatory, Columbia University, Palisades, NY, USA, NASA Jet • The highest southwest Greenland Propulsion Laboratory, California Institute of Technology, Pasadena, CA, USA ice sheet retreat rates occurred between 10,400 and 9,100 years ago • Our record supports an early Abstract Establishing the timing of maximum Holocene warmth in the Arctic is critical for Holocene Thermal Maximum in southwest Greenland understanding global climate system response to external forcing. In Greenland, challenges in obtaining climate records that span the full Holocene have hampered efforts to robustly identify when the Supporting Information: Holocene Thermal Maximum occurred. Reconstructing land‐based ice sheet history can fill this gap • Supporting Information S1 because these ice sheet regions respond sensitively to summer temperature. We synthesize new and published 10Be and 14C ages from southwest Greenland to map Greenland ice sheet margin positions from 12 to 7 ka and calculate retreat rates from 12 to 0 ka. We found that maximum Greenland ice sheet Correspondence to: A. J. Lesnek, recession occurred between ~10.4 and 9.1 ka. Our reconstruction suggests that summer air
[email protected] temperatures in southwest Greenland were highest from ~10.4 to 9.1 ka, providing support for an early regional Holocene Thermal Maximum.