A study conducted by the University of Maine, showed that two large glaciers in West Antarctica could be losing ice faster than in the past five thousand years. The rapid melting of glaciers may lead to a significant rise in sea level in the coming centuries.
Over the past few decades, the West Antarctic ice sheet has receded and weakened at an accelerating rate. The Thwaites and Pine Island glaciers, which extend deep into the core of the ice sheet, are of particular concern. These glaciers are vulnerable to melting rapidly because they lie on a sloping layer within the land, where warm ocean water can flow under the floating portions of the glacier’s tongues and erode the ice sheet at their base, potentially leading to the loss of excess ice.
Excessive retreat of these two glaciers could reduce the size of the ice sheet in West Antarctica, contributing to a global sea level rise of up to 3.4 meters in the coming centuries.
However, it is assumed that the glaciers may have been much smaller in the recent geological past – that is, during the Middle Holocene, an era more than 5,000 years ago, which was much warmer than they are today. If they were smaller, they should have grown again later, which raises hope that they can do so again in the future.
A catastrophic scenario for the future of global sea level in a warming world.
An international team of researchers led by the University of Maine looked at relative changes in sea level near glaciers over the past 5,000 years as an indirect way to determine if they were much lower than they are today in the Middle Holocene, and then did so. Expanded again, writes EurekAlert.
The relative sea level at a given location depends on the amount of water in the ocean, but also on local changes in the shape of the Earth’s crust due to the loading and unloading of glaciers. Thus, reconstructions of relative sea level over time can be used to quantify large-scale changes in glacier progress and retreat.
The team, led by Scott Braddock, a doctoral student at the University of Maine, used radiocarbon dating of seashells on ancient beaches that are now above sea level to reconstruct changes in relative sea levels over time. The shape of the resulting curve is related to the growth and retreat of glaciers.
The results show a steady decline in relative sea levels over the past 5,000 years. This pattern is consistent with relatively stable glacial behaviour, with no evidence of widespread retreat or advance. Furthermore, the researchers found that the rate of relative sea-level decline for mussels was nearly five times lower than it is today. The most likely reason for such a large difference is the recent and rapid ice loss in the area.
Vital arteries in the heart of the West Antarctic ice cap have exploded.
“Our paper indicates that these vulnerable glaciers have been relatively stable over the past millennia, but that their current rate of melting is accelerating and raising global sea levels,” said co-author Dylan Rudd, lecturer at Imperial College London. “These high rates of ice melt today may indicate that those vital arteries in the core of the West Antarctic ice sheet have burst, resulting in accelerated ocean flow, which could be catastrophic for global sea level in the future.”
The researchers also compared their results with existing models of ice-crust dynamics. They found that the models do not accurately represent the history of sea level revealed by their data. This study helps form a more accurate picture of the region’s history and suggests that models need to be improved.
Although the new evidence does not rule out the possibility of slight fluctuations in the Thwaites and Pine Island glaciers over the past 5,000 years, the researchers conclude that the simplest explanation for their data is that these glaciers have been relatively stable from the mid-Holocene until recently—and that the current rate of river retreat The glacier could have been unprecedented in the past five thousand years.
The study was published in the journal Nature Geoscience.
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