A satellite image showing the Getz ice shelf. Getz lost 1.9 trillion tonnes of ice over the 25-year study period. The image is a composite made from satellite data recorded between January and September 2023. Credit: European Space Agency.
Key points:
- Using 100,000 satellite radar images, scientists found that over 40 percent of Antarctica’s ice shelves reduced in volume over 25 years.
- Ice shelves on the western side of Antarctica were most impacted by ice shelf loss.
- Human-induced global warming is a key driver of ice loss and the associated freshwater release weakens the global ocean circulation system.
Following a 25-year study, scientists have found that 71 of the 162 ice shelves surrounding Antarctica have reduced in volume with a net release of 7.5 trillion tons of meltwater into the oceans.
The researchers analyzed 100,000 satellite radar images from CryoSat-1, Sentinel-1, and Cryo-Sat2 to assess year-by-year changes in the health of the ice shelves. Their findings, published in Science Advances, indicate that almost all the ice shelves on the western side of Antarctica experienced ice loss, while most eastern ice shelves remained stable or increased in volume. This mixed pattern of ice-shelf changes is the result of ocean temperature and currents around Antarctica. The western half is exposed to warm water that can erode shelves from below, while the eastern portion is protected by a band of cold coastal water.
The team observed significant ice losses on the Getz Ice Shelf, where 1.9 trillion tons of ice were lost over the 25-year period, primarily due to melting at the base of the shelf. On the Pine Island shelf, 1.3 trillion tons of ice were lost, while the Amery Ice Shelf on the other side of the continent gained 1.2 trillion tons of ice.
These ice shelves – extensions of the ice sheet that covers Antarctica – float on the surrounding seas and act as giant “plugs” at the end of glaciers to impede the flow of draining into the ocean. When the shelves thin or get smaller, the plugs weaken and cause an acceleration in the rate of ice loss.
Researchers believe that human-induced global warming is a key factor in ice loss. With natural climate variation, they would expect to observe cycles of rapid but short-lived shrinking with signs of ice regrowth. However, instead, almost half of shelves are shrinking.
The potential disappearance or reduction of ice shelves could have significant impacts on the Antarctica ice system and global ocean circulation, which move nutrients, heat, and carbon. Researchers estimate that 66.9 trillion tons of freshwater entered the Southern Ocean from the ice shelves, diluting salty water and affecting its ability to sink to the ocean floor and drive ocean circulation.
“We tend to think of ice shelves as going through cyclical advances and retreats,” said study co-author Anna Hoff of University of Leeds. “Instead, we are seeing a steady attrition due to melting and calving. This is further evidence that Antarctica is changing because the climate is warming.”