What is the point of no return for the melting of the Antarctica ice cap?

With increasingly powerful winter storms eroding British beaches and cliffs, the acceleration of sea level rise is poised to exacerbate the situation. One of the primary culprits responsible for the current annual rise of 3.4mm (0.13in) in sea levels is the massive Greenland ice cap, measuring 3km in thickness, with the potential to raise sea levels by a staggering 7 meters (23ft) if it were to completely melt.

Scientists have been diligently determining the critical temperature at which Greenland’s melting would become irreversible, ushering in the scenario where significant portions of coastal land would be submerged. According to a study published in the journal Nature, this threshold lies between 1.7°C and 2.3°C above pre-industrial levels. Given that global temperatures have already exceeded the 1.5°C mark for some months in recent years, and current projections indicate a potential temperature increase of up to 3°C over this century, we find ourselves perilously close to this tipping point.

While the process of melting would unfold gradually, allowing time for coastal adaptation, the study does offer a glimmer of hope: if we manage to reduce the temperature increase back to 1.5°C in the future, the melting could eventually cease.

However, the researchers caution that by the time we manage to revert to 1.5°C, sea levels will have already risen by 2 to 3 meters compared to their current levels.

In West Antarctica, particularly in the Amundsen Sea, this phenomenon has been in progress for several decades. During this time, ice shelves have been thinning, glaciers are exhibiting accelerated movement towards the ocean, and the ice sheet is diminishing. While the availability of ocean temperature data in this area is limited, climate models suggest that it may have experienced warming due to the effects of climate change.

We focused our modeling efforts on the Amundsen Sea because it represents the most vulnerable section of the ice sheet. Utilizing a regional ocean model, we sought to understand how the process of ice-shelf melting will evolve in this region from the present day to the year 2100. We aimed to determine the extent to which reducing carbon emissions and slowing down the pace of climate change can mitigate ice-shelf melting and, conversely, to what degree such melting has become inevitable, regardless of our efforts.

The melting of ice shelves plays a significant role in the rise of sea levels, but it’s only part of the equation. To estimate the extent of sea-level increase, we need to consider not only ice shelf melt but also simulate the flow of Antarctic glaciers and the accumulation rate of snow on the ice sheet – elements our current model did not encompass.

Nonetheless, there is strong evidence to suggest that the heightened ice-shelf melting in this region will accelerate the rate of sea-level rise. The West Antarctic ice sheet is already making a substantial contribution to the global sea-level rise, shedding approximately 80 billion tonnes of ice annually. This ice sheet holds the potential to raise sea levels by as much as 5 meters, although the precise amount and speed of this melt remain uncertain. Researchers worldwide are diligently working to address this critical question.