Antarctica’s Ice Shelves: A Dire Warning

Recent research, released on October 12, 2023, has unveiled alarming findings regarding Antarctica’s ice shelves. Over the past 25 years, more than 40 percent of these crucial formations have significantly diminished, potentially hastening the rise of sea levels as they allow land ice to flow into the ocean. This unsettling revelation, supported by extensive satellite image analysis, indicates a broader extent of ice shelf thinning than previously believed, clearly highlighting the profound impact of rising global temperatures on the continent.

Benjamin Davison, the lead author of the study, expressed his astonishment at the scale of deterioration observed, emphasizing that numerous ice shelves, not just the prominent ones, are steadily losing mass without signs of recovery. Ice shelves serve as massive floating barriers, slowing down the movement of land-based ice into the ocean. When these shelves thin or retreat, the flow of land ice accelerates, contributing to rising sea levels. Both the Antarctic and Greenland ice sheets have been responsible for over one-third of recent sea level increases.

The research, conducted by Davison and his team, analyzed more than 100,000 satellite images spanning from 1997 to 2021. The findings revealed that 71 out of 162 ice shelves surrounding Antarctica had reduced in volume, with nearly 50 of them losing more than 30 percent of their initial mass during this period. Surprisingly, some ice shelves had even gained mass, while others remained relatively unchanged.

Traditionally, healthy ice shelves experience a natural cycle of growth and retreat. They continuously flow and may lose mass due to melting or calving, followed by gaining ice from land and regrowth. However, the extensive and persistent shrinking of ice shelves for 25 years is inconsistent with this natural cycle, indicating an alarming trend.

The most substantial reduction in ice shelf size was observed on the western side of Antarctica, where warmer water erodes the shelves from below. Most ice shelves on the western side reported ice loss. The Getz Ice Shelf, for instance, lost 1.9 trillion tons of ice due to melting at its base. The Pine Island Ice Shelf lost 1.3 trillion tons of ice, with a third of that attributed to calving.

In contrast, ice shelves in East Antarctica generally increased in volume or remained stable. This region is less exposed to warm water because of the protective influence of a cold water band along its coast. Nevertheless, pockets of shrinking ice shelves in East Antarctica prompted further investigation, with a theory suggesting that warmer water from the western side might slowly be intruding into the region.

One of the most recent ice shelf collapses occurred in East Antarctica in March 2022 when the Conger Ice Shelf, about the size of New York City, disintegrated in just a few weeks. This event was likely triggered by an unprecedented heat wave in Antarctica, the most intense ever recorded globally.

The impact of ice shelf thinning extends beyond Antarctica. Over the 25-year study period, an estimated 66.9 trillion tons of fresh water from the ice shelves entered the ocean. This influx of freshwater can dilute the saltier ocean water, making it lighter and weakening ocean circulation. Researchers have already observed changes in ocean circulation around Antarctica.

Alex Gardner, an ice scientist not involved in the research, emphasized that these findings align with previous work indicating increased calving and ice shelf mass loss. Multiple studies now confirm the retreat and thinning of Antarctic ice shelves, a trend expected in a warming world.

While the current dataset is not yet long enough to definitively link these changes to climate change, the mounting evidence makes a compelling case. Climate models predict ongoing ice shelf shrinkage in a warming world, eventually reaching a tipping point that could lead to millennial ice sheet disintegration. However, these substantial changes matter even before we reach that point, underscoring the urgency of addressing this environmental crisis.