Investigating Holocene ice margin retreat and readvance in Southwest Greenland using GIA modeling, Holocene sea level records, geodetic observations and present-day tide gauge records

Abstract:

Global coastlines are changing drastically due to sea level rise in response to recent climatic changes. Ice melt from the Greenland Ice Sheet (GrIS) is a major contributor to present-day and future sea level rise. However, the future contribution from the GrIS remains uncertain. Understanding the response of the GrIS to historic warming can improve projections of its future behavior. In this study we investigate the sensitivity of the GrIS to warming during the Holocene. More specifically, we investigate the Holocene ice margin retreat and readvance in Southwest Greenland as this area has been exposed to a warmer climate during the Holocene Thermal Maximum. We use a glacial isostatic adjustment (GIA) model paired with a range of 1D and 3D viscoelastic Earth structures and two ice sheet models, ICE6G and Huy3. The ice sheet models are used in their original form and in an altered form in which the late-Holocene ice margin retreat and readvance in Southwest Greenland is varied in timing and extent. The modeled relative sea level response is compared to paleo sea level observations in Southwest Greenland to explore the trade-off between Earth structure and ice reconstruction. Next, we extract the predicted present-day solid Earth deformation from our GIA models and compare it to the present-day uplift measured by the Nuuk GNET station after it has been corrected for elastic effects. Lastly, we compare our model predictions of present-day sea level change to observations from two tide gauges in Nuuk (1958-2002 and 2014-2020) after they have been corrected for non-GIA contributors to present-day sea level change (contemporary ice melt, steric effects and terrestrial water exchange). Each data set allows us to constrain the GIA model suite (ice and solid Earth parameters) and, in particular, we investigate what timing and amount of ice margin retreat and readvance is permitted by the data. Preliminary results show that some degree of ice margin retreat is necessary. However, this might be smaller than what has been suggested by Huy3.