About 9,000 years ago, a shocking event occurred in Antarctica: a significant part of the eastern ice sheet collapsed. This rapid change was triggered by warmer ocean waters. Researchers are now focusing on this ancient event to learn more about how climate changes impact vast ice bodies like the East Antarctic Ice Sheet.
Antarctica’s ice holds enough water to raise global sea levels by about 190 feet if it all melted. New findings from sediment samples near Japan’s Syowa Station connect this ancient collapse to warm currents in the ocean.
Led by Prof. Yusuke Suganuma at Japan’s National Institute of Polar Research, the study examined how the Antarctic ice sheets reacted to historical warming. The team analyzed sediment cores from Lutzow-Holm Bay to uncover the timeline of the ice-shelf collapse.
The researchers found that during the early Holocene—a warm period right after the last ice age—temperatures were even higher than today. By studying unique isotopes and marine fossils, they dated the ice-shelf breakup to around 9,000 years ago.
A key player in this collapse was the circumpolar deep water, a warm, salty current that flows deep beneath the surface around Antarctica. Approximately 9,000 years ago, this warmed water surged onto the continental shelf, undermining floating ice shelves and making them unstable.
Once the ice shelves fractured, they couldn’t hold back the inland ice, leading to faster flow toward the ocean. Climate models indicate that warm deep water lingered in the bay, emitting repeated bursts of ocean heat before the collapse.
Moreover, researchers identified a feedback loop involving melting ice and ocean conditions. As meltwater entered the ocean, it freshened the surface water, which allowed warm deep water to move closer to land. This created a situation where more fresh water drove more ice melting, trapping warm water and accelerating the loss of ice shelves.
Historically, conditions in Dronning Maud Land contributed to a rapid collapse, including rising sea levels and seabed topography that guided warm water toward ice fronts. As the ice mass decreased, the land beneath it rebounded, which briefly raised local sea levels, allowing warm water to infiltrate the ice shelves more easily.
Today, the situation is alarming. In West Antarctica, glaciers like Thwaites and Pine Island are retreating quickly due to warm seawater reaching their bases. Observations show that layers of modified deep water are eroding the ice shelves, just as happened thousands of years ago.
For many years, scientists viewed East Antarctica as stable because much of it rests on rock above sea level. However, new reconstructions suggest that even these areas can thin quickly if warm water finds its way beneath the ice. Recent satellite data show ongoing ice loss, particularly in vulnerable regions.
The Antarctic climate system is also concerning. The Antarctic Circumpolar Current, a powerful water flow, redistributes heat and freshwater around the Southern Ocean. Historically, meltwater influence has shifted the density of Southern Ocean waters, pushing warm currents toward East Antarctica. Current climate models indicate that freshwater from ice melt may hinder water mixing, allowing warmth to creep closer to the ice, increasing the risk of destabilization.
If East Antarctica collapses at rates similar to the past, global sea levels could rise considerably faster than current estimates. Even a small increase in sea level this century could reshape coastlines worldwide, leading to more frequent flooding and saltwater issues for coastal communities.
Experts warn that our decisions now will shape sea levels for generations to come. The patterns discovered in ancient Antarctic sediments demonstrate how quickly ice systems can react when warm ocean water and meltwater combine, underscoring the urgent need to address climate change.
For further insights into this research, you can read more in Nature.
Source link
Environment
