The peninsula — an arm of land that stretches up from the rest of Antarctica toward the southern tip of South America — has warmed about 5°F (2.8°C) in the past 50 years. Unsurprisingly, the region has seen considerable ice melt, and that melt was blamed on the surging air temperatures driven by the broader warming of the planet's atmosphere.
It was clear that there was a distinct pattern of melt from north to south, though. In the northwest, the region of the largest air temperature increase, the glaciers paradoxically seemed fairly stable, while in the cooler southwest there had been considerable retreat.
Cook and her colleagues looked at ocean temperatures along the west coast of the peninsula and found a pattern of temperatures at mid-ocean depths that mirrored what was happening to the glaciers.
“The more we studied this, the more it became apparent that this followed a striking similarity to the glacier retreat rates,” Cook said.
At the southern end of the western side of the peninsula, warm Circumpolar Deep Water that has welled up meets the glaciers and wears away at their fronts.
At the northern end of the peninsula, the glaciers terminate in colder waters that come from a different source, keeping the fronts of those glaciers much more stable.
“This is a great study with convincing evidence that the northern and southern west coast of AP (Antarctic Peninsula) have very different oceanic regimes and the correspondence with the pattern of glacier retreat is undeniably strong,” Eric Rignot, a NASA glaciologist said in an email.
More Measurements Needed
The same Circumpolar Deep Water implicated in the new study is thought to be eroding glaciers elsewhere along the West Antarctic coast, including an adjacent area of the Bellingshausen Sea coast where a recent study suggested melt had been happening for much longer than previously thought.
“This study underscores what many of us in the scientific community have been suggesting for some time, namely that ice losses from around Antarctica owe as much to warmer ocean temperatures reaching parts of Antarctica's coastline as to rises in air temperature,” Robert Bingham, a glaciologist at the University of Edinburgh, said in an email. Bingham, who led the Bellingshausen Sea study, was not part of the new research.
While the glaciers along the Antarctic Peninsula are much smaller than those in the Bellingshausen Area, or the Amundsen Sea Embayment, where some of the fastest-slowing and retreating glaciers are found, their potential to contribute to sea level rise cannot be discounted. While they make up only 4 percent of Antarctica’s total ice sheet area, they have accounted for about 25 percent of its mass loss.
“The AP ice sheet is one of the largest current contributors to sea level rise and as the glaciers here are highly sensitive to changes in the environment they are key indicators of how the ice will respond to future changes,” Cook said.
The study’s findings lay bare the need for better understanding and monitoring of both Antarctica’s glaciers and the oceans lapping at them, Bingham and Rignot said.
“Our ultimate aim must be to predict how ocean-driven ice losses from Antarctica will impact upon global sea level rise,” Bingham said. “To provide such predictions, it's clear that we need a far better understanding of ice-ocean interactions all around the fringes of Antarctica, and in particular to monitor changes occurring in the ice at the same time as changes in the ocean.”