Much more gorgeous, it was solely within the mid-2010s that Antarctic sea ice was at file highs—at the least highs since satellite tv for pc observations started—having elevated barely however steadily within the years since 1979.
That latest development of Antarctic sea ice has been in stark distinction with that of the Arctic, a area that’s now warming as much as 4 occasions quicker than the remainder of the planet and has been steadily shedding ice for many years. That’s as a consequence of a phenomenon known as Arctic amplification: Melting ice exposes darker ocean water or land, which absorbs extra of the solar’s power than white ice, which in flip results in extra warming.
The Antarctic is a distinct beast: It’s a frozen continent surrounded by open ocean, whereas the Arctic is an ocean of floating ice enclosed by land, like Russia, Alaska, and northern Canada. Antarctica’s ice is insulated, in a way, by robust, chilly ocean currents that swirl across the continent. Plus, Antarctica’s elevation is kind of excessive, offering further cooling.
Antarctica’s sea ice—which kinds when seawater freezes—is distinct from the continent’s ice sheets and cabinets. An ice sheet rests on the land, and might be 1000’s of toes thick. It turns into an ice shelf when it begins floating on coastal waters. Whereas Antarctica’s ice sheets and cabinets have certainly been deteriorating because the planet warms, the continent’s sea ice is rather more seasonal, waxing and waning dramatically between winter and summer season.
Shedding that sea ice gained’t add to sea ranges, simply as melting ice cubes floating in a glass of water gained’t trigger the glass to overflow. (The ice is already displacing the water.) However sea ice performs a crucial function in defending Antarctica’s colossal ice cabinets from deteriorating, and people may dramatically elevate ocean ranges in the event that they break aside. If it completely melts, the Thwaites Glacier, aka the Doomsday Glacier, may add 10 toes to sea ranges. Sea ice protects Thwaites and different glaciers as a result of it acts like a buffer, absorbing the power of winds and waves that might in any other case erode them. It additionally cools the air passing over coastal waters, additional stopping the melting of ice cabinets.
This yr, the coast of West Antarctica has been significantly devoid of sea ice. “It is the realm the place local weather scientists are most involved about potential large contributions from the ice sheet to international sea stage rise,” says Maksym. “This yr, we see completely no sea ice in any respect in that space, which is, I believe, just about the primary time that has occurred. Then there are some earlier research that confirmed that in the event you take away sea ice, you lose the type of buttressing results, and that may speed up the breakup of the ice shelf.”
However that’s not the one international impact the lack of sea ice can have: When seawater freezes into ice, the denser brine that’s left over sinks to the seafloor, creating deep currents that rush away from Antarctica. The much less sea ice, the weaker these currents. “This may have an effect on the effectivity with which the oceans will distribute power, and in the end have an effect on the worldwide local weather,” says geographer Marilyn Raphael at UCLA, who research the area. “What occurs in Antarctica would not keep in Antarctica.”
