Gone with the Wind: How Model Biases Skew the Distribution of Iceberg Meltwater

The discharge of icebergs from polar ice shelves and glaciers has increased in recent decades, and it is projected to accelerate during the coming century. This may have far-reaching implications for the global climate system, since icebergs not only affect local water columns and ecosystems, but their meltwater input can impact the large-scale ocean circulation. The associated feedbacks may in turn influence the stability of the ice sheets. Adding realistic representations of icebergs to global climate models (GCMs) may therefore be vital for accurate climate projections. Here, we force an idealized iceberg drift and decay model with circulation and temperature fields from (i) a state-of-the-art GCM and (ii) an observational estimate. We show that biases in the GCM surface wind fields have dramatic impacts on the distribution of freshwater from iceberg melt. This GCM has a bias toward stronger westerlies, which is similar to other current comprehensive GCMs. Counterintuitively, we find the bias toward faster winds leads to a reduced spread of iceberg meltwater.  This suggests that meltwater distributions in GCMs may be confined to a region that is too far north, with implications for large-scale ocean responses.