Superheated seawater seeps underground and causes further melting of Antarctic ice.

Antarctica’s continental ice is melting at the top and, to a greater extent than previously thought, at the bottom as well. The leakage of warmer seawater between the ice on land and the soil that supports it causes more of the frozen layer to melt, which could worsen sea level rise.

This is a “new turning point,” as researchers from the Cambridge Antarctic Survey and the University of Oxford called it, publishing their work in Nature Geophysics.

The process they studied is that ocean water, which is becoming warmer due to the greenhouse effect, gets between the layer of ice on the coast and the land that supports it. This melts the ice and opens cavities, which in turn allow more superheated water to enter the loop.

Ultimately, this process lubricates the movement of continental ice sheets towards the coast and their fall out to sea. And this fall of large masses of frozen water into the ocean increases sea level rise because it new water that is added.

The researchers modeled the phenomenon and concluded that a “very small increase” in sea temperature leads to a “very large loss” of ice. “We found that rising sea temperatures could push the seas past the point of no return,” they warn. What’s more, they add, “it may not be easy to detect from early symptoms.” Some kind of quiet threat.

Sea level rise is caused both by the expansion of water as it becomes warmer and by the loss of large amounts of land ice, such as that found in Antarctica or Greenland (rather than the typical sea ice of the Arctic Ocean). .

Over the past 100 years, sea levels have risen by 160–210 mm. But half of that increase has occurred since 1993, according to NASA. “Current growth rates have not been seen in recent millennia.”

Existential danger

Although this phenomenon is measured in millimeters, it threatens entire countries, such as the island states of Micronesia, where a small increase affects their very existence. In fact, the inhabitants of the Guna Yala archipelago in Panama have already been resettled by their government on the continent due to this phenomenon. They are not the first. An indigenous community in the US has already received funds to leave their land: San Charles Island in 2018 because 90% of the surface was eaten away by the sea.

In addition, rising levels pose a problem for other places, such as Spain, where most of the population is concentrated in coastal areas – almost 40%, about 18.6 million people. Rising sea levels mean, without going any further, increased flooding when its waters reach inland during, for example, coastal storms.

“Our results show that the ice sheet over Antarctica is more sensitive to melting – and therefore contributes more to global sea level rise – than we previously thought,” the British scientists conclude.