As Antarctica loses more ice, increasing amounts of fresh water enter the ocean and can change Earth's climate. We used a climate model in which Antarctic ice loss responds to changing ocean conditions. We found that this feedback first increases warming near the ice shelves but later slows both Antarctic and global warming by changing the ocean, sea ice, and atmosphere. These results show that including these interactions is important for improving long-term sea-level and climate projections.

Computer models of the Antarctic ice sheet can project how much it will melt in response to climate change. That depends on the properties of the rock and the water beneath the ice, about which we know very little. That means the amount of sea-level in the future is very uncertain. Techniques to reduce that uncertainty do not always work as well as expected. We must get actual measurements of the bottom of the ice to improve our understanding of the ice sheet, and our knowledge of its future.

The future contribution of Antarctica to sea-level rise is strongly dependent on the melting of floating ice shelves by the underlying ocean. Here, we present version 2 of the two-dimensional ocean model LADDIE. We evaluate the model by comparing it to three-dimensional ocean models and satellite observations, showing good performance at low computational cost. With this open-source model, we hope to contribute to the evolution toward more realistic melting in ice sheet model simulations.

We introduce the coupling of a sub-shelf melt model with an ice sheet model to explore how horizontal meltwater flow below ice shelves affects ice sheet mass loss over time. We show that accurately modelling the meltwater flow direction leads to distinct feedbacks and transient volume loss not captured by melt parameterisations that simplify flow direction. Our results highlight the importance of refining the meltwater flow representation in ice sheet models to improve sea level projections.

Ocean warming around Antarctica leads to ice melting and sea-level rise. The meltwater that flows into the surrounding ocean can lead to enhanced warming of the seawater, thereby again increasing melting and sea-level rise. This process, however, is not currently included in climate models. Through a simple mathematical approach, we find that this process can lead to more melting and greater sea-level rise, possibly increasing the Antarctic contribution to 21st century sea-level rise by 80 %.