Antarctica nears irreversible climate tipping points, scientists warn

08:50

By: Dakir Madiha

Antarctica nears irreversible climate tipping points, scientists warn

Antarctica is edging toward a series of climate tipping points that could trigger irreversible ice loss and long-lasting disruption of global sea levels, according to new research spanning the Antarctic Peninsula, the continent’s vast ice basins and a multimillion-year geological record. Scientists say the choices made this decade on greenhouse gas emissions will largely determine whether the region’s most fragile systems can still be stabilized or are pushed beyond thresholds from which they cannot recover on human timescales.

On the Antarctic Peninsula, one of the fastest-warming parts of the continent, researchers have modeled how the region might respond under different emissions pathways, examining changes across sea ice, ice shelves, marine food webs and extreme weather. In a low-emissions scenario that holds global temperature rise to below 2 degrees Celsius, their work suggests serious impacts would still occur, but many of the most severe outcomes could be averted. Under very high emissions, however, the Peninsula is projected to warm dramatically, winter sea ice would contract, ice shelves such as Larsen C and Wilkins would be at heightened risk of collapse and ice-free days would multiply, reshaping habitats for penguins, krill and other species that underpin Southern Ocean ecosystems.

A separate line of evidence points to the Antarctic ice sheet behaving not as a single, uniform block but as a mosaic of drainage basins, each with its own stability limits. Using coupled ice-sheet and climate modeling, a team led by scientists at the Potsdam Institute for Climate Impact Research and the Max Planck Institute of Geoanthropology mapped out how individual basins respond as global temperatures climb. Some regions lose ice gradually as warming increases, but others exhibit clear tipping points beyond which ice loss accelerates and becomes effectively irreversible over centuries to millennia. Basins in the Amundsen Sea sector that include the Thwaites and Pine Island glaciers, along with parts of the Ronne sector in West Antarctica, may already be close to or past their critical thresholds at around 1.3 degrees of global warming. Large marine-based sectors in both West and East Antarctica that together hold meters of potential sea-level rise are projected to be vulnerable to tipping at global temperatures below about 4 degrees.

To understand how these processes might unfold in a warmer world, an international drilling campaign has recovered a record-breaking sediment core from beneath the West Antarctic Ice Sheet that preserves a climate archive spanning tens of millions of years. Working on the Crary Ice Rise, more than 700 kilometers from the nearest permanent station, the SWAIS2C team melted a hole through 523 meters of ice and extracted 228 meters of mud and rock from the seabed below. Early analyses indicate the core contains layers with microfossils and other material that formed when the area was open ocean or covered by a floating ice shelf, not by the thick grounded ice seen today, implying that the West Antarctic Ice Sheet has retreated significantly during past warm periods. Initial dating suggests the record extends back around 23 million years, including times when global average temperatures exceeded 2 degrees above pre-industrial levels, offering vital clues about how much and how quickly West Antarctica can melt as the planet heats up.

Researchers say these combined findings should be read as a warning that Antarctica is not insulated from human-driven warming, even though it is remote from major population centers. If current emissions trends continue and multiple Antarctic basins move beyond their tipping thresholds, the continent’s contribution to sea-level rise will unfold over many generations, but the commitment to that rise could be locked in within decades. Scientists stress that cutting greenhouse gas emissions rapidly and limiting global temperature rise remains the most effective way to reduce the risk of triggering cascading changes in Antarctic ice sheets, oceans and ecosystems that cannot be reversed on human timescales.