Direct observations of wave-sea ice interactions in the Antarctic
Marginal Ice Zone
Abstract
Wave energy propagating into the Antarctic marginal ice zone affects the
quality and extent of the sea ice, and wave propagation is therefore an
important factor for understanding and predicting changes in sea ice
cover. Sea ice is notoriously hard to model and in-situ observations of
wave activity in the Antarctic marginal ice zone are scarce, due to the
extreme conditions of the region. Here, we provide new in-situ data from
two drifting Surface Wave Instrument Float with Tracking (SWIFT) buoys
deployed in the Weddell Sea in the austral winter and spring in 2019.
The buoy location ranges from open water to more than 200 km into the
sea ice. We estimate the attenuation of swell with wave periods 8-18 s,
and find an attenuation coefficient α =
4 · 10-6 to 7 · 10-5 m-1 in
spring, and approximately five-fold larger in winter. The attenuation
coefficients show a power law frequency dependence, with power
coefficient 3.3 in spring and 4 in winter. The in-situ data also shows a
change in wave direction, where wave direction tends to be more
perpendicular to the ice edge farther into the sea ice. A possible
explanation for this might be a change in the dispersion relation caused
by changing sea ice composition. These observations can help shed
further light on the influence of sea ice on waves propagating into the
Marginal Ice Zone, aiding development of coupled wave-sea ice models.