Ice Sheets Go "Underwater"

Nature has been delivering some concerning news lately. A new example: Antarctica's ice shelves have shrunk by 40%, with almost half of them showing "no signs of recovery," according to scientists who attribute these changes to climate change. Warm water from the western part of the continent has melted the ice, while in the east, ice shelves have either remained the same or expanded due to colder water in that region.

Scientists at the University of Leeds in England calculated that 67 trillion metric tons of ice were lost in the western region, while 59 trillion metric tons were added to the eastern region between 1997 and 2021, resulting in a net loss of 7.5 trillion metric tons. These ice shelves are located at the end of glaciers and slow down their flow into the ocean. When ice shelves shrink, glaciers release larger amounts of freshwater into the sea, which can disrupt ocean currents in the Antarctic Ocean.

"There's a mixed picture of ice shelf change, and it's to do with the ocean temperature and ocean currents around Antarctica," said Dr. Benjamin Davison, an Earth observation expert and the lead researcher of the study. "The western half is exposed to warm water, which can quickly erode ice shelves from below, while much of East Antarctica is currently shielded from warm water nearby by a strip of cold water along the coast," he added.

Scientists have been measuring ice changes year by year using satellites that can access the ice through the thick cloud cover during the long polar nights. They analyzed over 100,000 space images to assess the condition of the ice shelves, which can have secondary effects on the rest of the world. The 67 trillion metric tons of freshwater released into the ocean over the 25-year period affect ocean currents that transport heat and nutrients worldwide. Saltwater sinks to the ocean floor, helping to drive these currents. However, a larger quantity of freshwater disrupts this system because it takes longer to reach the ocean floor.

Scientists estimate that the loss of ice is a result of climate change, as in a natural variation cycle, there would be more ice that "grows back." "We would expect the majority of ice shelves to go through rapid short-term shrinking cycles, then be replaced," Benjamin Davison said. "Instead, we see almost half of them shrinking with no sign of recovery." According to observations, the Getz ice shelf lost the most ice, over 1.9 trillion metric tons during the study period. Only 5% of this loss was due to calving, a phenomenon in which ice chunks break off from ice shelves and become icebergs. The rest was due to melting. Another 1.3 trillion metric tons of ice were lost from the Pine Island ice shelf, with about a third due to calving and the rest to melting.