Antarctica will definitely affect sea levels, but there's a catch: it could rise by 44 cm or drop by 22 cm.

The dimensions of the Antarctic ice sheet are quite difficult to comprehend: on average, the thickness of the ice in the region reaches 2 kilometers, and its total area is nearly twice that of Australia. Research has also indicated that the Antarctic ice sheet holds enough fresh water to raise global sea levels by an astounding 58 meters, according to IFLScience.

Forecasts suggest that the loss of ice from the Antarctic ice sheet is likely to be a major factor in sea level rise by 2100, although its contribution remains uncertain. Most studies indicate that sea levels will inevitably rise within this century, but the contributions from Antarctic ice are still unclear: ranging from an increase of 44 centimeters to a decrease of 22 centimeters.

Scientists note that much of this uncertainty is due to the oceanic processes controlling the fate of the ice sheet occurring at incredibly small scales, making them extremely difficult to measure or model. Fortunately for us, researchers have recently made significant strides in understanding the "ice-ocean boundary layer." This progress has become the subject of a new study published in the journal Annual Reviews.

Retreat, Thinning, and Recession

Glaciers flow into the Southern Ocean at the edges of the Antarctic ice sheet, forming floating ice shelves. These glaciers act as cornerstones, stabilizing the ice sheet, but they are also shrinking.

Previous research has already shown that the ocean is melting the ice shelves from below—a process known as "basal melting." The intensification of basal melting has led to thinning and retreat of the ice sheet in some regions, contributing to rising global sea levels. This process has also slowed the deepest current in the global overturning circulation—a system of ocean currents that circulates around the globe.

Ice shelves are vast, just like the glaciers that feed them. However, the oceanic processes controlling basal melting and the fate of the entire Antarctic ice sheet occur on a millimeter scale. It is known that they take place in a thin layer of ocean just beneath the ice, making them difficult to track.

The boundary layer between the ice shelf and the ocean is cold, located kilometers away from any point and beneath extremely thick ice, so it is no surprise that it has been almost unmeasured. Scientists have attempted to study the layer using other methods, such as computer modeling, but this is not straightforward either. Until recently, tiny movements in the ice-ocean boundary layer made precise modeling of ice melting unattainable.

Studying this layer with other methods, such as computer modeling, also presents a significant challenge. Until recently, tiny movements in the ice-ocean boundary layer made precise modeling of ice melting unattainable.

Microscale Modeling

Computer modeling of oceanic processes is not a new concept in itself. However, only recently has modeling of the ice-ocean boundary layer become possible as computational resources have increased and their costs have become more accessible. Several research groups around the world have taken on this challenge, modeling microscale ocean flow that supplies heat to the ice for melting.

Researchers have focused on uncovering the connection between what the ocean does and how quickly the ice melts. So far, they have identified multiple connections, each indicating a different "melting mode." The authors of the study note that the state of the ocean—including its temperature, salinity, and flow speed—as well as the shape of the ice determine which melting mode is applied.

The shape of the ice is crucial since meltwater is less dense than the surrounding ocean. Just as warm air gathers at the top of a room, fresh, cold meltwater accumulates in depressions on the underside of the ice sheet, insulating the ice from the ocean water below and slowing melting. For steeply sloped ice, the insulating effect is much less pronounced. A vigorous flow of meltwater rising beneath steep ice leads to mixing with warmer ocean waters, which enhances melting.

Breakthrough in Understanding the Impact of the Antarctic Ice Sheet

In the new study, scientists utilized ocean robots deployed by drilling through the ice. This provided researchers with an unprecedented volume of data about the environment beneath the ice shelves.

Through the robots, scientists also discovered a strange and beautiful icy landscape on the underside of the ice shelves. It consists of many different ice formations ranging from centimeters to kilometers in size.

The new insights gained about melting through computer modeling and robots shed light on these features and how they form. The existence of melting modes helps explain the evolution of steep terraces or why different features appear in various parts of the ice shelf.

However, scientists acknowledge that uncertainties remain. For instance, it is still not precisely known how some of these features form.

New simulations that allow the ice-water boundary to shift over time demonstrate "self-sculpting" behavior of melting ice. This is similar to how dunes form and move in the desert. But further research will be needed to trace the formation and evolution of the entire icy landscape.