New model provides more accurate predictions of sea level rise | Polarjournal
The new ice shelf-ocean model estimates the shape of cavities beneath ice shelves to improve modelling of ocean-ice interactions that cause melting beneath the ice shelf. Photo: Pete Harmsen

A new Antarctic ice shelf-ocean model is revolutionizing predictions of future sea level rise and challenging previous ideas about the melting of Antarctic ice shelves.

An Australian research team has developed the most detailed model of its kind, enabling researchers to predict the response of Antarctic ice shelves to a warmer ocean. It is the first model to incorporate tides and state-of-the-art estimates of the shape of the cavities under the ice shelf at a high spatial resolution of two kilometres. This allows the visualisation of small-scale ocean processes that transport heat to the ice shelf.

“More than half the ice lost from Antarctica today is thought to occur beneath its floating ice shelves, where warm ocean water melts the underside,” Dr. Ben Galton-Fenzi says, a glaciologist at the Australian Antarctic Division, in a press release.

It was previously thought that melting rates were highest deep below the ice shelf in the area of the grounding line, where the ice shelf rests on the continent. However, the new model shows completely different results. Most of the mass loss comes from shallower ice that is less than 500 meters deep, Dr. Galton-Fenzi said. The melting rates there are relatively low, but the area is much larger.

The researchers divided the Southern Ocean into hundreds of millions of chunks in the model in order to simulate the interactions between the Southern Ocean and the Antarctic ice sheet much more accurately than with previous models. Using the supercomputer of the Australian National Computational Infrastructure, the researchers then calculated the exchange of momentum, salinity and temperature between the individual chunks and obtained a detailed picture of the ocean currents. Thanks to a special coordinate system, the new model also accurately represents the seafloor.

Visualization of the new ice shelf-ocean model.

“Until now, the only available estimate of Antarctic-wide melting beneath ice shelves comes from satellite observations and models of surface processes that have high uncertainties and which don’t tell us anything about how the ocean actually does the melting,” Dr. Galton-Fenzi says. “The supercomputer enables us to model the very complex physics that occurs between the ocean and the underside of ice shelves.”

In the next step, the ice shelf-ocean model will be coupled with an ice sheet model, which represents the surface melting, in order to determine the contribution of the Antarctic to sea level rise more precisely. According to Dr. Galton-Fenzi, future extensions of the model will also investigate how ocean sediments and lakes that form under the ice sheet influence the stability of the ice sheet.

The new model was developed as part of an international project of the Intergovernmental Panel on Climate Change (IPCC), which aims to improve the models used to simulate the Earth’s climate system.

Julia Hager, PolarJournal

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