A new study, published this week in Science, shows that as ice sheets in Antarctica melt and reduce their weight on the bedrock, it is rising, and lifting the remaining ice out of the warming seawater. The process could delay the rapid ice loss that is leading to rising sea levels.
The research follows ominous news last week, when a consensus estimate published in the journal Nature showed that Antarctica has lost 3 trillion tons of ice over 25 years. In the West Antarctica Ice Sheet, the rate of ice loss tripled over that same period. Scientists projected that this rate of loss could lead to a 3 meter rise in sea levels over the coming centuries.
One of the new study’s authors, Rick Aster, a Colorado State University seismologist, said the rising bedrock “may just buy the world a few extra decades.”
The West Antarctica Ice Sheet is especially susceptible to melting because its bedrock is situated below sea level, with a basin that drops as low as one kilometer below. Some glaciers are currently caught on ridges on the ocean floor, but if they are melted from below by warming seawater, they could be dislodged, with seawater flowing into the basin and lifting ice from the bedrock, causing runaway melting.
The basin was created during the last ice age by the much thicker ice sheets of the era. Now, the bedrock has been rising back up gradually, “like a memory foam mattress,” according to the study’s lead author, Valentina Barletta, a geophysicist at the University of Denmark.
However, it was unclear how much this process would delay ice loss, which would depend on how quickly the crustal rebound occurs.
The researchers used six GPS sensors to track changes in elevation on parts of the bedrock of the Amundsen Sea without ice. Within a few years, they saw a significant rise – as much as four centimeters annually in some areas. Another recent study, published in Nature, showed that a similar process occurred at the end of the last ice age. After the ice shrank, it began growing back as the bedrock rebounded.
The effect is expected to accelerate as more ice is lost, with Barletta projecting the process will be moving three times as rapidly by the end of the century.
However, other scientists warn that the process is not enough to compensate for melting, especially given the world’s carbon emissions and rising temperatures.
National Snow and Ice Data Center glaciologist Ted Scambos, who was not involved in the study, cautioned:
“It’s not a get out of jail free card.”