Antarctic ice shelves are melting from below, and understanding the basal melt rate is crucial because it largely governs future global sea level rise and the pace of shelf breakup.

The central unknown is how fast basal melting and ice-shelf breakup will proceed, shaping future coastlines and necessitating continued observation and improved modeling.

In the Denman catchment, retreat is likely to proceed in an unstable, tipping-point-driven manner, raising the risk of accelerated ice loss.

A team led by Dr. Ben Galton-Fenzi synthesized nine models and estimated about 843 billion tonnes of ice lost annually from basal melting in recent decades.

Under-ice waters near the shelves sit around minus 2.2 degrees Celsius due to pressure, creating some of the coldest, darkest oceans and complicating direct measurements.

Possible outcomes range from regional to centuries-spanning impacts, with current greenhouse gas targets aimed at limiting destabilization of Antarctic ice sheets.

Experts are highly confident that ice sheets will continue to lose mass, but the exact rate and magnitude remain highly uncertain, affecting projections.

Basal melt interacts with surface snowfall and calving, contributing to overall ice change; satellite data suggest Antarctica lost about 93 billion tonnes between 1992 and 2020.

Autonomous Argo floats have provided rare under-shelf data, revealing warm-water contact with the Denman shelf that could translate to about 1.5 meters of potential global sea level rise.

Urgent questions remain about how meltwater may slow major ocean circulations and alter the global climate system, indicating gaps in predictive understanding.