Antarctic ice walls vital to climate

Inland Antarctic ice contains large quantities of water, capable of raising global sea levels significantly. The ice gradually moves towards the ocean, increasing the risk of melting, but the stability of these ice shelves has long been questioned by scientists. A recent study published in Nature asserts that glacial ice walls are essential to climate, preventing rising ocean temperatures and keeping ice frozen.

Lead author and professor of oceanography at the University of Gothenburg Anna Wåhlin explains, “Current measurements indicate an increase in melting, particularly near the coast in some parts of Antarctica and Greenland. These increases can likely be linked to the warm, salty ocean currents that circulate on the continental shelf, melting the ice from below,” she said in a press release.

The ocean stores more heat than the atmosphere, and the deep sea surrounding Antarctica stores thermal energy equivalent to heating the air above the continent by 400 degrees. From studying the measurements collected by instruments that Wåhlin’s international research team placed in the ocean around the Gertz glacier in West Antarctica, scientists have come to a better understanding of how the floating glacial ice walls remain stable.

“What we found here is a crucial feedback process: the ice shelves are their own best protection against warm water intrusions,” said Céline Heuzé, climate researcher at the department of earth sciences of Gothenburg University. “If the ice thins, more oceanic heat comes in and melts the ice shelf, which becomes even thinner, etc. It is worrying, as the ice shelves are already thinning because of global air and ocean warming.”

The Gertz glacier has a floating section approximately 300 to 800 meters thick, beneath which seawater flows into the ocean beyond. The glacier culminates in a wall of ice continuing 300-400 meters deep into the ocean. Warm seawater flows beneath this edge, towards the Antarctic continent.

According to the study, we now know that ocean currents are obstructed by the ice edge, limiting the amount of warm water that reaches the continent. “We have long been stumped in our attempts to establish a clear link between the transport of warm water up on the continental shelf and melting glaciers. Now, we understand that only a small amount of the current can make its way beneath the glacier,” said Wåhlin. Approximately two-thirds of the thermal energy that passes from the deep sea towards the continental shelf never makes it to the ice.

Informed by the measurements taken over the course of research, scientists are now better-equipped to predict future sea levels and develop more accurate climate prognoses. “From the Getz glacier, we are receiving measurements of heat transport in the ocean that correspond with the melting ice being measured by satellites. This also means that the floating glaciers — the ice fronts in particular — are key areas that should be closely monitored,” Wåhlin concluded. “If the ice walls were to disappear, much greater levels of thermal energy would be released towards the ice on land.”