Response of Greenland outlet glaciers to temporal variability in terminus motion over centennial time scales

As improved numerical ice sheet models are being used to provide 21st century sea-level rise projections more readily, it is important to develop our understanding of uncertainties and potential systematic biases in these projections. Over the last decade, ice sheet model capabilities have rapidly evolved and models are starting to simulate moving boundaries at outlet glacier termini to better represent ice sheet dynamics. Previous studies of Greenland outlet glaciers have shown that the terminus position can strongly control mass loss during glacier retreat. However, the impact of the representation of terminus positions in these models on the mass change that they simulate has not yet been studied thoroughly. One key question is the temporal variability in ice front migration on the modeled response: real glaciers have regular discrete calving events, whereas models generally simulate calving as a continuous process. At what temporal scale do these process need to be modeled in order to correctly capture glacier dynamic response? Here, we quantify the sensitivity of modeled glacier mass change to the frequency of terminus motion. Using an idealized outlet glacier geometry, we examine the glacier's response to specified terminus retreat and advance oscillations at various periods ranging from one year to one century. We investigate the impact of different frequencies of terminus motion on the magnitude of noise-induced drift in the mass of the glacier. We also explore the impact of model resolution and ice flow physics on our results. Our findings will help guide the implementation of terminus position dynamics in ice sheet models as well as the frequency of observations needed to validate these models and will contextualize centennial sea-level rise projections.