How climate model biases skew the distribution of iceberg meltwater

Wagner, TJW, Eisenman I.  2017.  How climate model biases skew the distribution of iceberg meltwater. Geophysical Research Letters. 44:GL071645.


The discharge of icebergs into the polar oceans is expected to increase over the coming
century, which raises the importance of accurate representations of icebergs in global climate models
(GCMs) used for future projections. Here we analyze the prospects for interactive icebergs in GCMs
by forcing an iceberg drift and decay model with circulation and temperature fields from (i) state-of-the-art
GCM output and (ii) an observational state estimate. The spread of meltwater is found to be smaller for the
GCM than for the observational state estimate, despite a substantial high wind bias in the GCM—a bias
that is similar to most current GCMs. We argue that this large-scale reduction in the spread of meltwater
occurs primarily due to localized differences in ocean currents, which may be related to the coarseness of
the horizontal resolution in the GCM. The high wind bias in the GCM is shown to have relatively little impact
on the meltwater distribution, despite Arctic iceberg drift typically being dominated by the wind forcing.
We find that this is due to compensating effects between faster drift under stronger winds and larger
wind-driven wave erosion. These results may have implications for future changes in the Atlantic meridional
overturning circulation simulated with iceberg-enabled GCMs.