According to scientists, the amount of ice draining collectively from those half-dozen glaciers increased by 77% from 1973 to 2013.
The researchers studied the Pine Island, Thwaites, Haynes, Smith, Pope and Kohler glaciers, all of which discharge ice into a vast bay known as the Amundsen Sea Embayment in West Antarctica.
The amount of ice released by these six glaciers each year is comparable to the amount of ice draining from the entire Greenland Ice Sheet annually, Jeremie Mouginot, a glaciologist at University of California-Irvine (UC-Irvine), said.
Mouginot and his colleagues used satellite data to look at sequential images of the glaciers from 1973 to 2013. The scientists then calculated how fast the ice was moving by tracking surface features, such as cracks in the ice, to determine the distance the glaciers traveled from month to month and year to year.
While the study considered the six glaciers collectively, it also revealed unprecedented change on the individual glacier level. Thwaites Glacier, the largest of the six with a width of 120 kilometers (75 miles), experienced a decade of near-stability until 2006, when its speed picked up by 0.8 kilometers (half a mile) per year – a 33% increase in speed, according to the study.
Of all the glaciers in the study, Pine Island Glacier accelerated the most since 1973, increasing by 1.7 kilometers (one mile), per year. That's a 75% increase in speed from approximately 2.5 kilometers (1.5 miles) per year in 1973 to 4 kilometers (2.5 miles) per year in 2013.
Scientists also documented even higher rates of increased discharge in some of the smaller glaciers. Smith and Pope Glaciers nearly tripled the amount of ice they drained into the ocean since 1973.
The research team also found that the Pine Island Glacier is accelerating along its entire drainage system—up to 230 kilometers (155 miles) inland from where it meets the ocean.
The study has been published in the journal Geophysical Research Letters.