A New Eulerian Iceberg Module for Climate Studies.

Icebergs modulate the effective location of freshwater input from ice sheets into the ocean and therefore play an important role for the climate, especially during times of increased ice discharge (e.g., Heinrich events). None of the models participating in the Paleo Modeling Intercomparison Project simulations of the Last Glacial Maximum or the last deglaciation included icebergs. Here, we present a newly developed dynamic/thermodynamic iceberg module that was specifically designed to be incorporated in climate models used for long‐term climate simulations with interactive ice sheets. In contrast to the widely used Lagrangian iceberg models, it is formulated in an Eulerian framework. This simplifies coupling to ocean models and enhances computational efficiency for glacial climates. In a set of sensitivity experiments, where the module was implemented into an Earth System Model, we validate the model for present‐day climate conditions and test its sensitivity to key parameters. Further, we investigate the effect of iceberg hosing on the Atlantic meridional overturning circulation (AMOC) as compared to traditional freshwater hosing. Varying the hosing rate slowly in time yields a good approximation of the hysteresis curve of the AMOC. We find that the sensitivity of the AMOC to iceberg hosing is stronger than to freshwater hosing in the same ocean point, but weaker as compared to a latitude belt forcing in the North Atlantic. This emphasizes the 2e necessity to include interactive icebergs in long‐term coupled climate simulations to realistically represent melt patterns and the response of the AMOC to freshwater input from melting ice sheets. Plain Language Summary: Icebergs transport frozen water from calving ice sheets far away from the coasts and release meltwater along their path while slowly melting. The sensitivity of the Atlantic meridional overturning circulation depends on the location of the meltwater input. As the transport and melt of icebergs determine the location of meltwater input into the ocean, it is obvious that icebergs are an important component of the climate system. Unfortunately, they are not included in most climate models, partly as they are computational quite expensive. Existing iceberg modules can follow groups of icebergs, and may be prohibitively computationally expensive when applied on very long timescales. Here we introduce a different approach. We do not follow each group of icebergs but describe the iceberg distribution using equations for concentrations and different size classes. This formulation is adequate for climate purposes, and simplifies the incorporation into ocean models. The difference in the climate response to iceberg calving and the widely used freshwater hosing is relatively large. This emphasizes the importance of including interactive iceberg modules into climate models for a realistic simulation of ice discharge events. Key Points: A new Eulerian iceberg module for climate studies is introducedThe Eulerian approach simplifies the incorporation of icebergs into standard ocean general circulation modelsExperiments with a comprehensive climate model demonstrate that iceberg discharge has different impact on Atlantic meridional overturning circulation compared to freshwater [ABSTRACT FROM AUTHOR]