As the Earth battles the consequences of climate change, ranging from heatwaves to wildfires, the planet is expected to confront additional challenges, such as flooding in coastal regions due to the rapidly melting ice sheets.
Scientists claim that 71 of the 162 ice shelves surrounding Antarctica have reduced in volume over 25 years from 1997 to 2021, with a net release of 7.5 trillion tonnes of meltwater into the oceans.
A team of researchers, headed by Dr. Benjamin Davison, a research fellow at the University of Leeds, conducted a recent study on Antarctica’s ice shelves.
ESA’s GOCE satellite and the NASA–German Grace mission animation depicted the ice lost from West Antarctica, causing a dip in Earth’s gravity. Watch below.
Western ice-shelves
Their findings revealed that nearly all ice shelves on the western side of Antarctica experienced a reduction in size. In contrast, most ice shelves on the eastern side either remained stable or expanded in volume.
Scientists estimated nearly 67 trillion tonnes of ice have melted and merged with the ocean waters in the last 25 years. This was counteracted by 59 trillion tonnes of ice being added to the ice shelves, resulting in a net loss of 7.5 trillion tonnes.
Davison stated: “There is a mixed picture of ice-shelf deterioration, and this has to do with the ocean temperature and currents around Antarctica.”
“The western half is exposed to warm water, which can rapidly erode the ice shelves from below, whereas much of East Antarctica is currently protected from nearby warm water by a band of cold water at the coast.”
As a landmark 50 times the size of the UK, Antarctica’s surrounding oceans experience different currents. For instance, the western side of the water moves in a different direction compared to the eastern side.
As a result, these movements drive the warmer water beneath the ice shelves in the western part, contributing to the melting of the ice from below.
“We expected most ice shelves to go through cycles of rapid, but short-lived shrinking, then to regrow slowly. Instead, we see that almost half of them are shrinking with no sign of recovery,” noted Davison.
Human-induced climate consequences
Additionally, Davison attributed the responsibility for the loss of ice to human activities driving global warming, as the natural variation in climate patterns would indicate signs of regrowth on these western ice shelves.
The study explained that the ice shelves are giant bodies of ice floating in the seas surrounding Antarctica, extending from the continent’s ice sheet covering a significant portion of the land.
A statement by the scientists referred to the “ice shelves acting as giant “plugs” at the end of glaciers, slowing down the flow of ice draining into the oceans.” If the ice shelves become thinner or smaller, these natural barriers – ‘plugs’ weaken. Consequently, the glaciers lose ice at a faster rate.
The team studied over 100,000 satellite radar images to estimate the ice shelf loss in Antarctica. The data was collected from mainly CryoSat-2 and Sentinel-1 satellites. CryoSat-2 was the first of the European Space Agency Explorer mission satellites dedicated to monitoring the Earth’s polar ice sheets and glaciers.
The recent study documented significant ice losses on the Getz Ice Shelf–1.9 trillion tonnes in the last 25 years. Just five percent of this loss was caused by calving when large ice chunks break off and move into the ocean. The majority resulted from melting at the base of the ice shelf.
Nearly 1.3 trillion tonnes of ice was lost on the Pine Island Ice Shelf. The third of this depletion was due to calving and the rest was a result of ice melting underneath the ice shelf.
Melting or calving affecting global circulation
However, the Amery Ice Shelf, situated on the opposite side of Antarctica, gained 1.2 trillion tonnes of ice. This gain occurred because it is surrounded by much colder waters, preventing significant melting or calving.
The consequences of melting ice shelves could be disastrous for the ice system in the continent and global circulation, the study warned. It could negatively impact the giant “conveyor belt” in oceans, moving nutrients, heat, and carbon vital for polar ecosystems, sustaining marine life, and climate balance.
The melting ice shelves and merging into the ocean as freshwater could be weakening the ocean circulation system. The statement explained that the study found that in over 25 years, about 66.9 trillion tonnes of this freshwater entered the Southern Ocean around Antarctica.
In the Southern Ocean, heavy, salty water sinks to the ocean floor, a process essential for global ocean currents. Freshwater from Antarctica mixes with salty water, making it lighter and slower to sink. This dilution weakens the ocean circulation system.
Professor Anna Hogg from the University of Leeds and a co-author of the study, stated: “The study has generated important findings. We tend to think of ice shelves as going through cyclical advances and retreats. Instead, we are seeing a steady attrition due to melting and calving.”
She added that many of the ice shelves had deteriorated a lot – 48 lost more than 30 percent of their initial mass over just 25 years.
“This is further evidence that Antarctica is changing because the climate is warming. The study provides a baseline measure to see further changes that may emerge as the climate gets warmer.”
