The Impact of Global Ice Sheet Evolution on North Sea Glacial Isostatic Adjustment during the Last Interglacial

The Last Interglacial (LIG) period (130 - 115 ka) was the last time in Earth’s history that the Greenland and Antarctic ice sheets were smaller than those of today due, in part, to polar temperatures reaching 3 - 5 °C above pre-industrial values. Similar polar temperature increases are predicted in the coming decades and the LIG period could therefore help to shed light on ice sheet and sea level mechanisms in a warming world.

The North Sea region is a promising study site for the reconstruction of both the magnitude and rate of LIG sea-level change as well as the identification of relative, individual ice sheet contributions to sea level. The impact of glacial isostatic adjustment (GIA) is particularly significant for the North Sea region due to its proximity to the former Eurasian ice sheet, which deglaciated during the penultimate deglaciation leading into the LIG. The evolution of the local Eurasian and global ice sheets during the penultimate glacial cycle has left a complex spatio-temporal pattern of GIA during the LIG, both regionally and globally. In addition, interpretation of the LIG record is further complicated by uncertainties in ongoing earth deformation and sea level evolution since the LIG. However, there are large uncertainties in the geometry and evolution of global ice sheets before the Last Glacial Maximum and, in particular, a major source of uncertainty for North Sea LIG records is the geometry and evolution of the Eurasian ice sheet during the Penultimate Glacial Maximum (PGM).

We produce a range of plausible global ice sheet histories spanning the last 400 thousand years that vary in penultimate deglaciation characteristics including glacial maximum ice sheet volume, deglaciation timing, and the ice volume distribution of the Eurasian ice sheet. This novel PGM Eurasian component is constructed with the use of a simple ice sheet model (Gowan et al. 2016) enabling systematic variation in the thickness of each ice sheet region within known uncertainty ranges. We then employ a gravitationally consistent sea level model (Kendall et al. 2005) with a range of viscoelastic Earth structure models to calculate the global GIA response to each ice history and to infer which input parameters the North Sea LIG signal is most sensitive to. This work will improve our understanding of the GIA effects on near field relative sea level during previous interglacials and will enable a systematic quantification of uncertainties in LIG sea level in the North Sea.