Persistent landfast sea ice supports early stages of ice shelf formation

Melange and multi-year fast ice is known to be able to suppress calving and dampen long-period ocean swells at the termini of marine-terminating glaciers. Currently, the effectiveness of fast ice at suppressing calving and/or providing direct buttressing to grounded ice remains controversial. Here we show that the interaction between tidewater glaciers and persistent fast ice can support the early stages of ice-shelf formation, as evidenced by localized areas of the northern Antarctic Peninsula that have undergone decadal cooling. We find that during persistent fast ice occupation, calving almost completely ceased, and a floating glacier tongue formed. As the glacier tongue advances it interacts with the fjord walls, increasing the resistive lateral stress on the lower glacier. This is similar to the well-known formation process of Arctic-style ice shelves in Ellesmere Island and Northern Greenland, for example, the recently collapsed Hunt Fjord Ice Shelf. 

We have identified several ice shelf or glacier tongue areas in Antarctica that have both highly persistent fast ice and thicker glacier ice advancing into these fast ice protected areas. These regions include the Larsen B embayment (2011-2022), Land Glacier and Nickerson Ice shelf (~1960s-present), Shackleton and West ice shelves, and the Lützow-Holm Bay region (past few decades). For these case study regions, we present preliminary data of ice shelf and upstream glacier velocity change, grounded glacier thickness change, and a synthesis of climate data to confirm a locally cooling climate in these areas. Our analysis will offer essential quantifiable evidence on the extent to which fast ice enhances the stability of upstream glacier ice, and will seek to test several components of the overall ice tongue/ice shelf advance process.