18 Oct 2023
Around 40% of floating ice shelves have significantly reduced in volume over past 25 years.Copernicus Sentinel-1 missionand the European Space Agency’s CryoSat satellite mission, has revealed alarming findings about the state of Antarctica’s ice shelves:
Around 40% of these floating shelves have significantly reduced in volume over the past quarter-century. While this underscores the accelerating impacts of climate change on the world's southernmost continent, the picture of ice deterioration is mixed.
The study, funded by ESA’s Earth Observation Science for Society programme and published last week in Science Advances, is based on 100,000 satellite radar images to produce a major assessment of the ‘state of the health’ of Antarctica’s ice shelves.
These massive floating extensions of the continent’s ice sheet play a crucial role in stabilising the region’s glaciers by acting as buttresses, slowing the flow of ice into the ocean. The researchers comment: “The Antarctic, therefore, faces a double whammy – as the ice shelves get smaller, the rate of ice lost from the ice sheet increases.”
The research team, led by scientists from the University of Leeds, UK, found that 71 of the 162 ice shelves around Antarctica have reduced in volume, releasing almost 67 trillion tonnes of meltwater into the ocean. Apart from the issue of the ice shelves losing mass, this addition of freshwater into the ocean could have implications for ocean circulation patterns. Moreover, the research team found that almost all the ice shelves on the western side of Antarctica experienced ice loss. In contrast, most of the ice shelves on the eastern side remained intact or increased in mass.
Benjamin Davison, a research fellow at the University of Leeds, UK, said, “There is a mixed picture of ice-shelf deterioration, and this is to do with the ocean temperature and ocean 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 by a band of cold water at the coast.”
Similarly, the Pine Island Ice Shelf lost 1.3 trillion tonnes of ice. Around a third of this loss – 450 billion tonnes – was due to calving. The rest was because of melting from the underside of the ice shelf. In contrast, the Amery Ice Shelf – on the other side of Antarctica and surrounded by much colder waters – gained 1.2 trillion tonnes of ice.
‘No sign of recovery’
Dr Davison added, “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.”
Anna Hogg, also from the University of Leeds, said, “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 owing to melting and calving.
“Many of the ice shelves have deteriorated a lot: 48 lost more than 30% of their initial mass over just 25 years. This is further evidence that Antarctica is changing because the climate is warming,” she said.
The Copernicus Sentinel-1 mission is Europe’s prime radar mission, providing images no matter whether it is day or night and whatever the weather. ESA’s CryoSat carries a radar altimeter to measure changes in the height of the ice, which are needed to calculate changes in actual ice volume.
ESA’s ice mission
ESA’s Mark Drinkwater said, “Monitoring and tracking climate change across the vast Antarctic continent requires a satellite system that captures data routinely throughout the year.
“Together with the historical data acquired by its ESA predecessors ERS-1, ERS -2 and Envisat, the Sentinel-1 mission has revolutionised our ability to take stock of floating ice shelves, as a bellwether for mass balance and the health of the Antarctic ice sheet. In the near future, we will further augment Antarctic monitoring with three new polar-focused missions CRISTAL, CIMR and ROSE-L.”