Antarctica's vast glaciers could contribute as much as 3.4 meters to global sea level rise over the next few centuries at the current rate of decline.
A new study led by the University of Maine and the British Antarctic Survey, including academics from Imperial College London, has found that Antarctica's Thwaites and Pine Island glaciers are notoriously vulnerable glaciers, and have begun to shrink at a rate not seen in the last 5,500.
The impact can be devastating. Thwaites Glacier is known as the "Doomsday" glacier. With an area of 192,000 sq km and 162,300 sq km, respectively, the Thwaites and Pine Island glaciers have the potential to cause significant global sea level rise.
The researchers measured the rate of local sea level change, which is an indirect way of measuring the loss of ice around glaciers that are at risk of melting due to global warming.
Quoted from Interesting Engineering, the current level alone has raised global sea levels. Antarctica is covered by the East and West Antarctic Ice Sheets, which in turn "feed" several individual glaciers. Thanks to global warming, this ice sheet has been melting at a much accelerated rate over the past few decades.
Co-author Dr. Dylan Rood of Imperial's Department of Earth Science and Engineering said that while these vulnerable glaciers have remained relatively stable over the past few millennia, their current rate of decline is accelerating and already raising global sea levels.
"Currently increasing rates of ice melt may signal that a vital artery from the heart of the West Antarctic Ice Sheet has ruptured, leading to accelerated outflows into the oceans that could potentially be catastrophic for future global sea levels in a warming world," they wrote.
Radiocarbon dating
Based on radiocarbon dating, more than 5,000 years ago, the climate was much warmer than today during the mid-Holocene period. As a result, sea levels are higher and glaciers are smaller.
The researchers saw that period as their starting point and studied sea level fluctuations since then. They examined the remains of ancient Antarctic beaches—including shells and penguin bones using radiocarbon dating.
This technique uses the radioactive decay of carbon locked in shells and bones as a "clock" to tell us how long they have been above sea level.
By knowing the exact ages of these beaches, researchers can tell when each beach appeared and therefore reconstruct local, or "relative" sea level changes over time.
These results indicate a steady decline in relative sea level over the past 5,500 years, which the researchers interpreted as a result of ice loss prior to that time.
They also show that the rate of relative sea level decline since the mid-Holocene is nearly five times less than that measured today. This can be attributed to the recent rapid loss of ice mass.
The researchers also compared their results with global models of the dynamics between ice and Earth's crust. Their data reveal that global models, in fact, do not provide an accurate representation of the history of sea level rise in the area during the mid to late Holocene. This study helps provide a better picture of the region's history.
The most direct interpretation of their data is that this glacier was relatively stable from the mid-Holocene to recent times, and that the current rate of glacier decline doubling over the past 30 years is unprecedented over the past 5,500 years.
"Relative sea level changes allow you to see large-scale crustal loading and unloading by ice. For example, glacier readings, which would result in crustal loading, would slow the rate of relative sea level decline or even potentially lead to the sinking of land below sea level," say the authors. principal Professor Brenda Hall of the University of Maine.
Next, the researchers will drill through the ice to collect the rock beneath, which may contain evidence of whether or not the current rate of accelerating melting could be improved.