Allie Coonin (Brown University, Providence, USA) and Tamara Pico (University of California, Santa Cruz, USA) will present:

“Transient Earth Rheology Temporarily Slows West Antarctic Ice Retreat in Future Climate Projections”

Projections of sea-level change and Antarctic Ice Sheet (AIS) stability under anthropogenic climate change hinge upon accurately describing physical feedbacks that link ice dynamics (marine and terrestrial) with the gravitational, rotational and deformational response of the solid Earth to ice and ocean loading changes. The marine-based West Antarctic Ice Sheet (WAIS) is vulnerable to runaway grounding line retreat. However, the rapid viscoelastic rebound of the bedrock in response to ice retreat has been shown to stabilize its grounding line, aided by the low-viscosity mantle beneath the WAIS. Such bedrock deformation is typically modelled with idealized Maxwell viscoelasticity, despite that rock deformation experiments show that additional transient creep mechanisms occur over societally relevant (~decadal-centennial) timescales that are missing from the Maxwell model. We simulate future AIS evolution, coupled with self-consistent solid Earth deformation and sea level change, for various emissions scenarios (RCP 2.6, 4.5, 8.5), incorporating transient deformation. This more complete treatment of solid Earth deformation delays grounding line retreat as compared to Maxwell projections, with differences of tens of kilometres persisting for decades at Pine Island and Thwaites Glaciers. While transient deformation is unable to prevent the bulk of sea-level rise over the next 500 years, such considerations are crucial to predict the full Earth system response, since AIS meltwater flux to the ocean affects the pace of global temperature rise.