Sea-ice pressure ridges in East Antarctica

Sea-ice extent and concentration are routinely measured using satellite sensors. However, regional estimates of sea-ice thickness cannot be measured directly from space, and largely depend on field observations with in the pack ice. One difficulty is estimating the amount of ice contained in pressure ridges. These ridges can contribute substantially to the total ice volume, yet are highly variable both spatially and temporally. Here we provide estimates of sea-ice ridge height and frequency in the East Antarctic region around 65° S, 140° E. We calculate ridge height distributions using high-resolution (< 1 m) digital aerial photography collected in August 1995. Wc examine the ridge height distribution and ridge concentration from near the coast of Antarctica northwards to the marginal ice zone. The area-averaged volume of ice in ridges contributes 0.06-1.35 m to the undeformed ice thickness in winter. There is a band of less deformed ice centred around 65° S, with more highly deformed ice to the south. Similar features are identified in satellite synthetic aperture radar data collected over the same region in August 1995 and 1996, and in observations of sea-ice characteristics collected during field experiments.