Modelling the response of stable water isotopes in Greenland precipitation to orbital configurations of the previous interglacial

The relation between δ¹⁸O of precipitation and temperature has been used in numerous studies to reconstruct past temperatures at ice core sites in Greenland and Antarctica. During the past two decades, it has become clear that the slope between δ ¹⁸O and temperature varies in both space and time. Here, we use a general circulation model driven by changes in orbital parameters to investigate the Greenland δ ¹⁸O–temperature relation for the previous interglacial, the Eemian. In our analysis, we focus on changes in the moisture source regions, and the results underline the importance of taking the seasonality of climate change into account. The orbitally driven experiments show that continental evaporation over North America increases during summer in the warm parts of the Eemian, while marine evaporation decreases. This likely flattens the Greenland δ ¹⁸O response to temperature during summer. Since the main climate change in the experiments occurs during summer this adds to a limited response of δ ¹⁸O, which is more strongly tied to temperature during winter than during summer. A south–west to north–east gradient in the δ ¹⁸O–temperature slope is also evident for Greenland, with low slopes in the south–west and steeper slopes in the north–east. This probably reflects the proportion of continental moisture and Arctic moisture arriving in Greenland, with more continental moisture in the south–west and less in the north–east, and vice versa for the Arctic moisture.