Greenlandic tidewater glacier response to long-term climate change

This project will model the advance and retreat of major Greenlandic tidewater glaciers over the last 1000 years, and forecast their sensitivity to future climate change for the next 200 years.

Iceberg calving from tidewater glaciers has contributed more than half of the total mass loss of the Greenland Ice Sheet over the past four decades, and observations have shown that episodes of increased iceberg discharge have coincided with rising air temperatures and/or the occurrence of warmer coastal waters into fjords within which they discharge. Despite significant advances in understanding over the last two decades, major uncertainties still remain in understanding how sensitive iceberg calving rates are to climate-induced exchanges of heat and freshwater around marine terminating ice sheet margins. This is partly because we do not know the long-term, multi-decadal to centuries historical context of the ice-ocean system that links our understanding of contemporary process with longer term glacier response to climate. This project will seek to improve confidence in multi-decadal to centennial projections of ice sheet behaviour through validating model performance over these timescales including prolonged episodes of glacier advance and retreat.

This PhD will exploit a unique reconstruction of the advance and retreat of a major Greenlandic tidewater glacier over the last 1000 years (Pearce et al, 2022), using the latest state of the art models to test calving-climate relationships. Model calibration and validation will focus upon Kangiata Nunaata Sermia (KNS), a dynamic tidewater glacier in SW Greenland, where recent investigations have dated glacial geomorphology and sedimentology evidence to reconstruct glacier advance during the first half of the last millennium (led by lead supervisor Mair), and monitored contemporary change from remote sensing and in situ field observations (led by co-supervisor Lea). Modelling work by co-supervisor Nias has also demonstrated the need for these longer-term perspectives informed by recent observations in improving knowledge of future ice sheet contributions to sea level.

Building on previous modelling by co-supervisors Nias (across Antarctic and Arctic sites) and Lea (at KNS, looking at periods of stability and retreat), this PhD studentship will apply the Ice-sheet and Sea-level System Model (ISSM) to run an ensemble of models calibrated and validated against our well-constrained record of past change. Model climate and ocean thermal forcings will include (i) appropriate palaeoclimate reconstruction data and methodologies for the past millennium and (ii) the CMIP6 GCM data base for current and future simulations. Fieldwork will include involvement in the maintenance of existing field monitoring equipment at KNS’s neighbouring glacier, Narsap Sermia. The project will obtain tuned parameter sets that satisfy model performance objectives and investigate the sensitivity of parameterisations for basal sliding, mass-balance, calving relationships, subglacial hydrology and basal drag. In addition to exploring future projections of the response of KNS to future climate scenarios we anticipate transferring the most optimal model ensemble to other key tidewater glaciers in Greenland to contribute to efforts to better understand ice sheet stability.

We invite applications from highly motivated students with expertise in any numerate area of Earth System Sciences.