British and American climate scientists have found evidence that the rate of ice loss in southern Alaska has increased by about five times in the current decade compared to the late 1970s.
“The Alaskan ice sheet is particularly vulnerable to global warming because its entire surface is exposed to high temperatures,” says Bethan Davis, associate professor at Newcastle University in the UK. “In addition, the flat nature of the ice sheet prevents it from retreating into the mountains and finding a new temperature equilibrium, so this process could lead to a significant retreat of these glaciers in the future.”
Scientists reached this conclusion after studying the large Juneau Ice Field located in southern Alaska, which covers an area of about 3.9 thousand square kilometers, and scientists have been following its condition since the middle of the last century.
The researchers focused on how the ice has changed over the past few decades, as average temperatures in the Arctic have been rising rapidly as a result of global warming. They relied on data collected by weather stations in Juneau and other parts of Alaska since 1941, and mapped the Juneau ice using aerial photographs taken in 1948 and 1979.
Comparing these maps with satellite images taken between 1990 and 2019 showed that Juno's ice area and volume were decreasing at a steady rate until 1979, but accelerated sharply in subsequent decades.
The researchers found that the area of this ice mass has shrunk in recent years about five times faster than at the end of the twentieth century, and that the volume of Juneau ice has been shrinking about six times faster in recent years (5.9 cubic kilometers per year) than before 1979 (0.65 cubic kilometers per year). These indicators began to rise even more rapidly, especially after 2005, which reflects the general nature of climate change in the Arctic.
According to the researchers, these results dispel the prevailing belief that the Juneau ice sheet will not begin to shrink until the end of the 21st century, so they should be taken into account when assessing changes in the Arctic as global temperatures continue to rise.