Simulating the Last Interglacial Greenland stable water isotope peak: The role of Arctic sea ice changes

Abstract

Last Interglacial (LIG), stable water isotope values (18 O) measured in Greenland deep ice cores are at least 2.5‰ higher compared to the present day. Previous isotopic climate simulations of the LIG do not capture the observed Greenland 18 O increases. Here, we use the isotope-enabled HadCM3 (UK Met Office coupled atmosphere-ocean general circulation model) to investigate whether a retreat of Northern Hemisphere sea ice was responsible for this model-data disagreement. Our results highlight the potential significance of sea ice changes on the LIG Greenland isotopic maximum. Sea ice loss in combination with increased sea surface temperatures, over the Arctic, affect 18 O: water vapour enriched in heavy isotopes and a shorter distillation path may both increase 18 O values over Greenland. We show, for the first time, that simulations of the response to Arctic sea ice reduction are capable of producing the likely magnitude of LIG 18 O increases at NEEM, NGRIP, GIPS2 and Camp Century ice core sites. However, we may underestimate 18 O changes at the Renland, DYE3 and GRIP ice core locations. Accounting for possible ice sheet changes is likely to be required to produce a better fit to the ice core measurements.

Sea-ice feedbacks influence the isotopic signature of Greenland Ice Sheet elevation changes: Last Interglacial HadCM3 simulations

“…A1 and Table A1). We follow the methodology of Holloway et al (2016Holloway et al ( , 2017 and Malmierca-Vallet et al (2018) on sea ice forcing. This set of simulations help us explore both changes in the extent (land-ice fraction) and elevation of the GIS.…”

“…The different behaviour found at Camp Century site is likely linked to the reduced winter sea ice concentration over the Baffin Bay on both decreased and increased elevation change scenarios ( Fig. 3 d and f); reduced sea ice concentration permits more moisture to penetrate inland Greenland (Malmierca-Vallet et al, 2018;Sime et al, 2013).…”

“…We use the sea ice retreat simulations of Malmierca-Vallet et al (2018) to isolate the impacts of δ 18 O due to sea ice variation.…”

A multi-model CMIP6 study of Arctic sea ice at 127 ka: Sea ice data compilation and model differences

“…Stronger LIG spring and summertime insolation contributed to this warmth, as well as feedbacks amplifying the initial insolation signal, in particular feedbacks related to the 25 marine and land cryosphere. Previous climate model simulations of the LIG, forced by appropriate greenhouse gas (GHG) and orbital changes, have failed to capture the observed high temperatures at higher latitudes (Malmierca-Vallet et al, 2018;Masson-Delmotte et al, 2011;Otto-Bliesner et al, 2013;Lunt et al, 2013). Models used during the previous Coupled Model Intercomparison Project 5 (CMIP5) disagree on the magnitude of Arctic sea ice retreat during the LIG: the diversity of sea ice behaviour across models was linked to the spread in simulated surface temperatures and in the magnitude of the polar 30 amplification (Otto-Bliesner et al, 2013;Lunt et al, 2013;IPCC, 2013).…”

“…40 Alongside a previous lack of a common experimental protocol, our ability to evalutate CMIP models has previously been hindered by difficulties in determining LIG sea ice extent from marine core evidence (e.g. Otto-Bliesner et al, 2013;Sime et al, 2013;Malmierca-Vallet et al, 2018;Stein et al, 2017). Planktonic foraminifers representative of subpolar, seasonally open waters lived in the central part of the Arctic Ocean.…”