Antarctic sea ice has been at record levels for months, here’s what that means

Antarctic sea ice has reached record levels in recent months. It’s not a great sign for the planet, which has hit record temperatures in the last week, but it’s also not as bad as the decades-long melt taking place in the Arctic.

Monitoring sea ice, which is frozen seawater floating on the surface of the ocean near the poles, is one way climate scientists measure global warming.

“Sea ice is sensitive to warming temperatures. A small change from just below to just above freezing temperatures is the difference between ice and ocean. Thus, it is an early indicator of change in the environment,” Walt Meier, senior research scientist at the National Snow and Ice Data Center at the University of Colorado, he told CNBC.

The two poles of the earth are warming at a faster rate than anywhere else on the planet, Howard Diamond, climate science program manager at the US National Oceanic Atmospheric Administration’s Air Resources Laboratory, told CNBC.

“The poles are warming at a faster rate of change than anywhere else on the planet; but the equator is still the hottest region on the planet, and as it continues to warm along with the rest of the planet, its the rate of change is lower than at the poles,” Diamond told CNBC.

Antarctica, which includes the South Pole, is an ice-covered land mass, surrounded by sea ice and the Southern Ocean.

On Feb. 21, sea ice in Antarctica set a record low for the second consecutive year, dating back to 1979, which dates back to National Snow and Ice Data Center records.

Since then, the amount of sea ice has continued to reach record levels.

“We’ve had three record summers in the last few years (2016/17, 2022 and 2023), plus the current winter growing season is unlike anything we’ve seen in our 45 years of continuous satellite observations,” Will Hobbs, a physical oceanographer and co-head of the sea ice project for the Australian Antarctic Program Partnership, he told CNBC. “This is a very sudden change, since up until 2015, Antarctica’s coverage was increasing, not decreasing like the Arctic.”

Because Antarctic sea ice decline is new, it’s too early to know exactly why this is happening, according to scientists who study sea ice flows at the poles.

“As for the question ‘Is this climate change?’, the scientific community probably isn’t ready to say that yet,” Will Hobbs, a physical oceanographer and sea ice project co-lead for the Australian Antarctic, told CNBC. Program Partnerships. It’s “the million-dollar question,” Hobbs said, and answering it “will keep us busy for a few more years.”

That said, it’s not good news.

“What we can say for sure is that this type of collapse has been predicted, though not for a few decades, so the best-case scenario is that we’re glimpsing Antarctica’s future,” Hobbs told CNBC. “The worst case is that the ice doesn’t recover and the future has arrived a few decades earlier than we hoped and expected.”

Because sea ice floats, it doesn’t directly cause sea level rise, Hobbs told CNBC. He thinks of ice cubes melting in a glass of water.

But sea ice levels have an indirect impact on sea level rise. “Antarctic ice sheets, which could cause massive sea level rise, are being held back from sliding into the ocean by floating ice shelves, and those are melting,” Hobbs told CNBC. “Sea ice protects those ice shelves from being flexed and cracked by ocean waves, and is also a ‘shadow’ that prevents the water in front of those ice shelves from warming in the summer sunlight.”

The Arctic is an ocean covered by a layer of sea ice and surrounded by land. The amount of sea ice in the Arctic in June was the 13th lowest on record, according to data from the National Snow and Ice Data Center.

“While Antarctica is more extreme at the moment, the Arctic has been more extreme for a long time. As I said, Antarctica had a record extent until 2014, the year the record extent in the Arctic was in 1979, the very first year of the record,” Meier told CNBC.

As sea ice trends have persisted longer and there is more data available for the region, it is also more clearly attributable to global warming.

“Absolutely, we’ve known for a few years, at least over the last 10 to 15 years, that the loss of Arctic sea ice was unequivocally due to human-driven climate change,” Hobbs told CNBC.

Sea ice thickness is one way to measure its age because sea ice gets thicker as it ages because it survives summer melt seasons and grows bigger in winters, Meier told CNBC. Sea ice in the Arctic would tend to be 10 to 13 feet thick, while in Antarctica it has been closer to 3 to 6.5 feet thick. But most of the thickest and oldest ice has melted in the Arctic and what’s left is closer to 6.5 feet thick.

“Despite the recent record extent in Antarctica, the thickness hasn’t changed much. So the subsurface change in Arctic sea ice is much more pronounced than the change in Antarctic sea ice,” Meier told CNBC.

In addition to sea ice, both poles have quite massive amounts of ice on land.

Annual loss of land ice in the Arctic since 2002 has been 276 billion tons a year versus 146 billion tons a year in Antarctica, NOAA’s Diamond told CNBC. “They’re both in the same downward direction,” she said.

While sea ice does not directly contribute to sea level rise, land ice melt does.

“The melting of these ice sheets is accelerating rapidly, right now they’re losing about 400 billion tons of ice every year. That’s enough ice to cover all of New York City by about 1,000 feet of ice and that’s only one ice loss. year,” Notz told CNBC.

The melting of land ice in parts of the Antarctic ice sheet may be approaching a “tipping point,” Notz told CNBC.

“With just a little additional warming, the loss of parts of the ice sheet could become unstoppable for many centuries or millennia to come, even if we cool the climate again. This is because some processes within the ice sheet become autonomous as they accelerate and increasingly independent of the warming that triggered the initial ice loss,” Notz said.