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Accelerating mass loss of Greenland: firn and the shifting runoff limit

Periodic Reporting for period 1 - CASSANDRA (Accelerating mass loss of Greenland: firn and the shifting runoff limit)

Reporting period: 2019-05-01 to 2020-10-31

Meltwater running off the flanks of the Greenland ice sheet contributes roughly 60% to its mass loss, the rest being due to calving. Only meltwater originating from below the elevation of the runoff limit leaves the ice sheet, contributing to mass loss; melt at high elevations refreezes in the porous firn and does not drive mass loss. Therefore, any shift in the runoff limit modifies mass loss and subsequent sea level rise.

The CASSANDRA project uses computational and field methods to investigate the runoff limit as a powerful yet poorly understood modulator of Greenland mass balance. We will establish a firn observation network on the Greenland ice sheet, perform detailed measurements of firn hydrology and investigate the runoff limit using remote sensing. Our results will lead to improved estimates of Greenland past, present and future mass balance.
The project started with preparation of field gear for all subsequent field campaigns. Due to the pandemic, we had to cancel spring 2020 fieldwork but were luckily able to travel to Greenland in summer 2020. On the Greenland ice sheet we carried out hydrologic observation at the so-called runoff limit. Furthermore different firn models were evaluated and remote sensing studies were carried out.
The CASSANDRA project is intended to shed light on the runoff limit as a powerful yet poorly understood modulator of Greenland mass balance. We expect to develop novel methods to measure firn hydrology and permeability at the runoff limit of the Greenland ice sheet. We also aim at developing remote sensing approaches and models that will lead to improved estimates of Greenland past, present and future mass balance.