Antarctic ice sheet response to sudden and sustained ice-shelf collapse (ABUMIP)

Abstract

Antarctica's ice shelves modulate the grounded ice flow, and weakening of ice shelves due to climate forcing will decrease their ‘buttressing’ effect, causing a response in the grounded ice. While the processes governing ice-shelf weakening are complex, uncertainties in the response of the grounded ice sheet are also difficult to assess. The Antarctic BUttressing Model Intercomparison Project (ABUMIP) compares ice-sheet model responses to decrease in buttressing by investigating the ‘end-member’ scenario of total and sustained loss of ice shelves. Although unrealistic, this scenario enables gauging the sensitivity of an ensemble of 15 ice-sheet models to a total loss of buttressing, hence exhibiting the full potential of marine ice-sheet instability. All models predict that this scenario leads to multi-metre (1–12 m) sea-level rise over 500 years from present day. West Antarctic ice sheet collapse alone leads to a 1.91–5.08 m sea-level rise due to the marine ice-sheet instability. Mass loss rates are a strong function of the sliding/friction law, with plastic laws cause a further destabilization of the Aurora and Wilkes Subglacial Basins, East Antarctica. Improvements to marine ice-sheet models have greatly reduced variability between modelled ice-sheet responses to extreme ice-shelf loss, e.g. compared to the SeaRISE assessments.

Rapid postglacial rebound amplifies global sea level rise following West Antarctic Ice Sheet collapse

“…Ice sheet modeling studies have also considered the contribution to GMSL from postglacial uplift of marine-based sectors of WAIS [e.g., ( 17 )]. With some recent exceptions ( 13 , 14 ), these studies commonly refer to volumes of ice mass loss “above floatation,” which typically includes a time-dependent calculation of bedrock uplift beneath the ice and associated reduction in water accommodation space across the simulation.…”

“…Many studies have explored the contribution of the AIS to sea level during interglacial periods ( 18 ) or in a warming world ( 10 , 17 ). For example, the GMSL estimate of 3.26 m for WAIS cited above was based on a simulation that adopted the marine ice sheet instability hypothesis in an analysis of updated maps of Antarctic ice thickness and bedrock topography ( 10 ).…”

ISMIP6-based projections of ocean-forced Antarctic Ice Sheet evolution using the Community Ice Sheet Model

“…These differences, while significant, are small compared to the multi-meter SLR seen in the ABUMIP experiments (Sun et al, 2020) with the abrupt and sustained loss of all floating ice. In ABUMIP, the Ross, Filchner-Ronne, and Amundsen sectors each contribute ∼ 1 m or more of mean SLR when ice shelves are removed (see Table 3 of Sun et al, 2020). Our less dramatic results confirm that the loss of small shelves would be less catastrophic than Ross or Filchner-Ronne collapse.…”

“…3imply a smooth transition to N = 0, with the bed providing little resistance to sliding near the grounding line. As a result, Coulomb friction renders the ice more sensitive to the loss of ice-shelf buttressing (Sun et al, 2020). To study the sensitivity of our results to the basal sliding law, we ran additional spin-ups and projections using Eq.…”

“…CISM participated in two earlier ISMIP6 projects focused on ice sheet model initialization: initMIP-Greenland (Goelzer et al, 2018) and initMIP-Antarctica (Seroussi et al, 2019). More recently, CISM results were submitted for the ISMIP6 projections (Goelzer et al, 2020;, the LARMIP-2 experiments (Levermann et al, 2019), and the Antarctic BUttressing Model Intercomparison Project (ABUMIP; Sun et al, 2020).…”