Master Thesis Defense by Isabel Schwermer

Title: Modelling the evolution of the Greenland ice sheet over glacial-interglacial cycles

Abstract:
The present-day Greenland ice sheet formed more than 1 Ma ago and has since evolved over repeated glacial-interglacial cycles. Understanding the evolution of the ice sheet in the past can help assess its stability under climate change and predict its future contribution to sea level rise. In this work, we use the PISM together with the dEBM to reconstruct the evolution of the GrIS over the last 1 Ma and investigate patterns of growth and retreat. The dEBM accounts for spatial and temporal variations in solar insolation and includes a parameterization of the melt–albedo feedback, allowing melt sensitivity to vary with climate conditions and orbital forcing.

We performed a transient simulation of the GrIS evolution with PISM-dEBM-simple, forced by a synthetic climate record derived from ice core and benthic d18O. The results indicate repeated episodes of retreat and subsequent regrowth of the GrIS during major interglacials, particularly MIS 5, 9, and 11. Southwestern Greenland was found to be most sensitive to warming, followed by the south, while northern and central Greenland remain glaciated most of the time. The minimum ice extent during MIS 11 leaves only the north-central and central-eastern regions ice-covered, corresponding to a volume of 2.5m sea level equivalent. Across interglacials, spatial patterns of retreat are similar, but the extent of ice loss varies with the intensity of temperature and insolation forcing. The melt–albedo feedback was found to play a key role in amplifying surface melt and driving deglaciation.

Supervisors: Christine Schøtt Hvidberg,  Anne Munck Solgaard (GEUS)
Censor: Nanna B. Karlsson (GEUS)