Integrating In-Situ Observations with Process-Based Modelling of the Sea
Ice Floe Size Distribution
Abstract
The lateral size of sea ice floes is receiving increasing attention as
an important variable for the polar climate system. We have developed a
model for prognostic evolution of the floe size distribution, which
emerges due to five key physical processes: new ice formation, welding
of floes in freezing conditions, lateral growth and melt, and fracture
of floes by ocean surface waves. As a result of the model’s foundation
in the governing physics, free parameters occurring in the equations can
be directly constrained by observations. Initial model experiments
provided insight into the relative importance of various processes,
showing floe freezing processes were particularly important for
simulation of the floe size distribution. Previously, physical
descriptions of lateral growth and welding together of floes had not
been constrained by observations. This motivated an analysis of images
obtained by drifting wave buoys (SWIFTs) deployed in the autumn Arctic
Ocean to quantify these processes in-situ for the first time. We
separated floe area growth due to welding from that due to lateral
expansion, and compared observations to our physical descriptions of the
individual processes. We also found a strong limitation on floe sizes
imposed by the wave field. These results have been used to inform new
physical descriptions of processes important for the sea ice floe size
distribution.