The stability of grounding lines on retrograde slopes

TLDR

Retrograde bed slopes at grounding lines, such as those of the West Antarctic Ice Sheet, do not inherently imply instability or proximity to a threshold. The study numerically investigates the stability of marine ice sheets grounded on retrograde bed slopes. The investigation employs two‑dimensional numerical modeling. Stable grounding lines can exist on retrograde slopes, indicating that such beds do not inevitably lead to instability and challenging estimates of WAIS’s near‑future sea‑level contribution. Abstract.

Abstract

Abstract. The stability of marine ice sheets grounded on beds that slope upwards in the overall direction of flow is investigated numerically in two horizontal dimensions. We give examples of stable grounding lines on such retrograde slopes illustrating that marine ice sheets are not unconditionally unstable in two horizontal dimensions. Retrograde bed slopes at the grounding lines of marine ice sheets, such as the West Antarctic Ice Sheet (WAIS), do not per se imply an instability, nor do they imply that these regions are close to a threshold of instability. We therefore question those estimates of the potential near-future contribution of WAIS to global sea level change based solely on the notion that WAIS, resting on a retrograde slope, must be inherently unstable.