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

Last Interglacial (LIG), stable water isotope values (δ¹⁸O) 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 δ¹⁸O 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 δ¹⁸O: water vapour enriched in heavy isotopes and a shorter distillation path may both increase δ¹⁸O 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 δ¹⁸O increases at NEEM, NGRIP, GIPS2 and Camp Century ice core sites. However, we may underestimate δ¹⁸O 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 LIG ice core δ¹⁸O values.