Collaborative Research: Representing calving and iceberg dynamics in global climate models

Iceberg calving accounts for approximately 50% of the ice mass loss from the Greenland and Antarctic ice sheets. By changing a glacier’s geometry, calving can also significantly perturb the glacier’s stress-regime far upstream of the grounding line (defined as the location where grounded ice goes afloat). This process can enhance discharge of ice across the grounding line and increase ice-sheet contribution to sea level rise. Once calved, icebergs drift into the open ocean where they melt, redistributing freshwater to the ocean and altering water mass properties. This affects the large-scale ocean circulation, by injecting freshwater and altering water geochemical composition by transporting sediments frozen at their base that originated at Antarctic and Greenland continents.

To date, there is neither a consistent representation of calving processes in the continental icesheet models nor a self-consistent representation of iceberg evolution and its effects on ocean circulation in global ocean models. The proposed Climate Processing Team aims to fill these gaps by (1) developing parameterizations of calving processes that are suitable for continental-scale ice-sheet models that simulate the evolution of the Antarctic and Greenland ice sheets, and implement these parameterizations in the GFDL climate model and its stand-alone ice-sheet model component; (2) developing a physically based iceberg component for inclusion in the large-scale ocean circulation model and implement it in the GFDL coupled climate model and (3) compiling the data sets of the glaciological and oceanographic observations that are necessary to test, validate and constrain the developed parameterizations and models. New observational and modeling tools, including the widespread availability of abundant high-resolution satellite imagery and numerical models capable of simulating calving from outlet glaciers and ice shelves and subsequently track iceberg evolution, position us to make a significant advance in our understanding of ice sheet dynamics, sea level rise andassociated climate feedbacks.

The proposed research is directly relevant to NOAA’s long-term goal of Climate Adaptation and Mitigation. It addresses the NOAA objective to improve scientific understanding of the changing climate system and its impacts. Iceberg calving is a crucial component of the mass balance and dynamics of ice sheets, yet it remains poorly represented in ice sheet models. Moreover, success in predicting both sea level rise and the influence of increased freshwater discharge into the polar oceans over the coming centuries hinges on improving the representation of key physical processes, like calving, in ice sheet models. In addition, this research is relevant to the long-term goal To understand Climate Variability and Change to Enhance Society’s Ability to Plan and Respond, and it directly supports the planning requirements for NOAA’s long-term goal to promote “Resilient Coastal Communities and Economies”. Our focus on improvement of cryospheric processes (ice-sheet modeling) is aimed to improve NOAA’s Earth System Models (Competition Name: Modeling, Analysis, Predictions, and Projections Program – Research to Advance Climate and Earth System Models, Priority Area 2).