CAREER: Constraining Iceberg Size Distributions and their Climate Impacts in Models

Approximately half of the ice lost from the Antarctic and Greenland Ice Sheets to the ocean occurs in the form of icebergs that break off glaciers and ice shelves. Icebergs melt and release freshwater far from the coast, thereby altering the local ocean waters as well as the large-scale ocean circulation. This has impacts on the climate and ecosystems, motivating current efforts to represent icebergs in climate models. However, past efforts have been hampered by limited knowledge of the size of icebergs when they break off of ice sheets and glaciers, and how their drift, breakup, and melt controls iceberg trajectories and freshwater and nutrient release to the ocean. The project will address these shortcomings by advancing our knowledge of how icebergs are created, how they drift, and how they decay. This will be done using mathematical and computer models of ice and climate processes and comparing the results to observational measurements. The iconic image of icebergs as harbingers of climate change will be leveraged for the educational part of this project, which will explore best practices to communicate risks and uncertainties associated with climate change. This will be done by developing two new university courses: “Ice & Climate Dynamics” for physical science graduate students and “Climate Risks & Uncertainties - how to communicate successfully between scientists, journalists, and the public”. The project will further offer two summer programs bringing together students, early career researchers, and journalists. Iceberg size distributions are a key initial condition in modeling efforts, determining where icebergs will drift, their meltwater is deposited, and sediment is released. To better constrain iceberg size distributions this project will (i) use process models and observational data to quantify present-day calving characteristics of glaciers and ice shelves, both in Greenland and Antarctica; (ii) bring together climate models and state-of-the-art ice sheet model output to estimate how iceberg size distributions will evolve over the coming decades and centuries and what the resulting global and regional climate impacts will be. Current representations of iceberg sizes in models are largely based on sparse, decades-old observations and do not consider spatial and temporal variations. This project is designed to advance these models by resolving spatial and temporal variations of iceberg size distributions. This research leverages recent advances in observing glaciers and icebergs to improve constraints on iceberg simulations and ultimately reduce uncertainties in climate projections. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.