Swell

Geology

Drift ice

Biology

Ice shelf

Geomorphology

Ice sheet

Oceanography

Antarctic sea ice

Sea ice

Ice divide

Arctic ice pack

Ice calving

Cryosphere

Lactation

Lead (geology)

Pregnancy

Antarctic ice sheet

Climatology

Genetics

Fast ice

Nature

Understanding the causes of recent catastrophic ice shelf disintegrations is a crucial step towards improving coupled models of the Antarctic Ice Sheet and predicting its future state and contribution to sea-level rise. An overlooked climate-related causal factor is regional sea ice loss. Here we show that for the disintegration events observed (the collapse of the Larsen A and B and Wilkins ice shelves), the increased seasonal absence of a protective sea ice buffer enabled increased flexure of vulnerable outer ice&nbsp;shelf margins by ocean swells that probably weakened them to the point of calving. This outer-margin calving triggered wider-scale disintegration of ice shelves compromised by multiple factors in preceding years, with key prerequisites being extensive flooding and outer-margin fracturing. Wave-induced flexure is particularly effective in outermost ice shelf regions thinned by bottom crevassing. Our analysis of satellite and ocean-wave data and modelling of combined ice shelf, sea ice and wave properties highlights the need for ice sheet models to account for sea ice and ocean waves. Less sea ice allowed ocean swells to flex weakened ice shelves in Antarctica, contributing to their collapse.

Antarctic ice shelf disintegration triggered by sea ice loss and ocean swell