Interactive movements of outlet glacier tongue and landfast sea ice in Lutzow-Holm Bay, East Antarctica, detected by ALOS-2/PALSAR-2 imagery

The Shirase Glacier, one of the fastest-flowing outlet glaciers in East Antarctica, flows into a bay that is usually covered by landfast sea ice. Although the presence of landfast ice is considered to stabilize glacier tongue, quantitative assessments are insufficient. We investigated the spatiotemporal variations in the flow velocities of both the glacier tongue and the surrounding landfast ice using a correlation method with ALOS-2/PALSAR-2 images, before and after a landfast-ice collapse in April 2017. After the collapse, the glacier tongue flow accelerated by 8-15% (0.20-0.38 km a(-1)). After reestablishment of landfast ice, the flow velocity of the landfast ice in contact with the glacier terminus is 20%-90% of the flow velocity of the glacier terminus The estimates of interactive changes in the motions of both glacier ice and sea ice can be used to quantify the buttress effect, which is a key factor affecting the mass budget of Antarctic outlet glaciers.