Improving projections of sea level contribution from the Greenland ice sheet by modeling calving dynamics
Abstract
The contribution of the Greenland ice sheet to global sea-level rise has increased rapidly during the last two decades and is currently ∼ 0.8 mm/year. As observations show a clear, accelerating increasing trend in both global temperature and ice mass loss from the Greenland ice sheet, how much mass the Greenland ice sheet is going to lose over the next century and beyond is one of the most urgent questions in understanding the implication of climate change. Estimating future ice sheet contributions to sea-level rise is currently an active area of research and numerical ice sheet modeling is our best tool to address this question.
This thesis provides an estimate of sea-level contribution from Greenland with a new generation ice sheet model that fully accounts for changes of 200+ Greenland glaciers. First, we introduce modeling of calving dynamics which is one of the most important processes contributing to mass loss from outlet glaciers around the coast of Greenland. We test and compare calving laws in an ice sheet model and assess which calving law has better predictive abilities for each glacier. We then apply the best calving law to Nioghalvfjerdsfjorden and Zachariae Isstrøm glaciers in northeast Greenland to investigate the response of these fast-changing glaciers to future climate forcing.
We extend our model to the entire Greenland ice sheet to estimate the future sea-level contribution from Greenland. Compared to previous studies, we calibrate our model at the individual glacier scale with a moving boundary capability to better constrain the retreat of marine-terminating glaciers. We find that the Greenland ice sheet will contribute 79.2 to 167 mm to sea-level between 2007 and 2100 under the most extreme warming scenarios. Our simulations show that discharge from ice dynamics will contribute to the total mass loss from Greenland more than previously estimated, implying that future scientific focus should remain on not only atmospheric processes but also the ice front of marine-terminating glaciers.