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

Abstract

AbstractBasal friction heavily controls the dynamics of fast‐flowing glaciers. However, the best approach to modeling friction is unclear, increasing uncertainties in projections of future mass loss and sea‐level rise. Here, we compare six friction laws and evaluate them for Petermann Glacier in northern Greenland, using a higher order three‐dimensional ice‐sheet model. We model glacier retreat and mass loss under an ocean‐only warming until year 2300, while not considering the effects of a future warmer atmosphere. Regardless of the friction law, we find that breakup of Petermann's ice shelf is likely to occur within the next decades. However, future grounding‐line retreat differs by 10s of km and estimates of sea‐level rise may quadruple, depending on the friction law employed. A bedrock ridge halts the retreat for four of the laws, and Petermann retreats furthest when applying a Budd or a Coulomb‐type “till law.” Depending on the friction law, sea‐level contributions differ by 133% and 282% by 2300 for 2°C and 5°C ocean warming scenarios, respectively.