Twenty-first century response of Petermann Glacier, northwest Greenland to ice shelf loss

Abstract

Ice shelves restrain flow from the Greenland and Antarctic ice sheets. Climate-ocean warming could force thinning or collapse of floating ice shelves and subsequently accelerate flow, increase ice discharge and raise global mean sea levels. Petermann Glacier (PG), northwest Greenland, recently lost large sections of its ice shelf, but its response to total ice shelf loss in the future remains uncertain. Here, we use the ice flow model Úa to assess the sensitivity of PG to changes in ice shelf extent, and to estimate the resultant loss of grounded ice and contribution to sea level rise. Our results have shown that under several scenarios of ice shelf thinning and retreat, removal of the shelf will not contribute substantially to global mean sea level (<1 mm). We hypothesize that grounded ice loss was limited by the stabilization of the grounding line at a topographic high ~12 km inland of its current grounding line position. Further inland, the likelihood of a narrow fjord that slopes seawards suggests that PG is likely to remain insensitive to terminus changes in the near future.

Future Projections of Petermann Glacier Under Ocean Warming Depend Strongly on Friction Law

“…The moderate sea‐level contributions found in our Weertman‐simulations are thus consistent with the subdued response found by Hill et al. (2021). However, the maximum melt rates applied by Hill et al.…”

“…They found a sea-level contribution of <1 mm even for their most extreme case involving full ice-shelf collapse and increased basal melt. The moderate sea-level contributions found in our Weertman-simulations are thus consistent with the subdued response found by Hill et al (2021). However, the maximum melt rates applied by Hill et al (2021) (50 m/a) were high-end estimates of present-day conditions (Wilson et al, 2017), and are 33% lower than in our 2°C warming experiments (75 m/a).…”

“…The moderate sea-level contributions found in our Weertman-simulations are thus consistent with the subdued response found by Hill et al (2021). However, the maximum melt rates applied by Hill et al (2021) (50 m/a) were high-end estimates of present-day conditions (Wilson et al, 2017), and are 33% lower than in our 2°C warming experiments (75 m/a). Importantly, the Weertman law used by Hill et al (2021) consistently lead to the lowest sea-level estimates of all friction laws tested here, supporting findings by Brondex et al (2019) for West Antarctic glaciers, and should thus be considered minimum estimates.…”

“…This bedrock ridge was found to provide a strong control on grounding‐line stability also by Hill et al. (2021), who simulated the response of Petermann Glacier due to enhanced basal melt and ice‐shelf breakup using a Weertman friction law and prescribed calving rates. They found a sea‐level contribution of <1 mm even for their most extreme case involving full ice‐shelf collapse and increased basal melt.…”

“…However, depending on basal friction, retreat may also be stopped by a bedrock ridge some 10-15 km upstream of the present-day grounding line (Figure 4d), rendering less than 3 mm sea-level rise for even a strong 5°C warming (Figure 7d). This bedrock ridge was found to provide a strong control on grounding-line stability also by Hill et al (2021), who simulated the response of Petermann Glacier due to enhanced basal melt and ice-shelf breakup using a Weertman friction law and prescribed calving rates. They found a sea-level contribution of <1 mm even for their most extreme case involving full ice-shelf collapse and increased basal melt.…”