  Iceberg meltwater is a critical freshwater flux from the cryosphere to the
oceans. Global climate simulations therefore require simple and accurate
parameterisations of iceberg melting. Iceberg shape is an important but often
neglected aspect of iceberg melting. Icebergs have an enormous range of shapes
and sizes, and distinct processes dominate basal and side melting. We show how
different iceberg aspect ratios and relative ambient water velocities affect
melting using a combined experimental and numerical study. The experimental
results show significant variations in melting between different iceberg faces,
as well as within each iceberg face. These findings are reproduced and
explained with novel multiphysics numerical simulations. At high relative
ambient velocities melting is largest on the side facing the flow, and mixing
during vortex generation causes local increases in basal melt rates of over
50%. Double-diffusive buoyancy effects become significant when the relative
ambient velocity is low. Existing melting parameterisations do not reproduce
our findings. We propose several corrections to capture the influence of aspect
ratio on iceberg melting.
