Explain the staggering heat and record low sea ice in the Antarctic winter

Worldwide temperature records are dropping as El Niño warms in the Pacific Ocean and summer heats up in the Northern Hemisphere. The planet recently experienced its warmest day Hottest June ever recorded. But some of the most worrisome temperatures of the moment are occurring far away from most humans in Antarctica, where it is currently winter.

the World Meteorological Organization I reported last week that sea ice is at record low levels around Antarctica, 17 percent below average for this time of year. Sea ice expands and contracts with the seasons and ice around Antarctica is still growing, but at the slowest pace seen since satellite observations began in the 1970s.

Sea ice in Antarctica hit a record low for this time of year.

“It’s not something we should feel comfortable with,” Marilyn Raphael, a professor of geography at the University of California, Los Angeles who studies Antarctic sea ice, told Vox. “It shouldn’t be as warm as it is. If this warming continues, it will keep things going.”

While its population includes a handful of scientists (and millions of penguins), Antarctica is incredibly important to the rest of the planet. It’s home to 90% of the world’s ice, which makes up 70 percent of the fresh water on Earth. Most of this ice is on land, up to three miles thick, and if it all melted, it would raise global sea levels by 190 feet. Fortunately, such a bleak scenario is unlikely, but the melting of Antarctic ice is accelerating. For a third of humanity that lives indoors 60 miles from the ocean coastIt will reshape their income, their diets and where they can live.

Antarctica is also fringed by sea ice, which forms when the ocean freezes over. It doesn’t change the total amount of water in the ocean, but ice reflects sunlight while darker waters tend to absorb it, thus heating up. As sea ice retreats, the ocean temperature rises and leads to more melting. Water also expands slightly as it warms, which contributes to sea level rise.

Outside of water levels, Antarctica shapes both ocean currents, which transport nutrients around the world to feed fisheries, and circulation patterns in the atmosphere, which can shape clouds, temperature, and precipitation. on every continent.

But Antarctica still baffles scientists. For years, it defied climate patterns seen in other parts of the world: its sea ice expanded for a while, some of its regions cooled while the rest of the planet warmed. The harsh environment still makes it difficult to get an accurate read of what is happening on the ground. And as the climate changes, the rise in average temperatures will have some of its most profound effects on Antarctica, which in turn will spill over into the skies and seas around the world. So everyone on Earth has to pay attention to what is happening in Antarctica.

“Sea ice, the atmosphere and the oceans all talk to each other,” Jeremy Basessaid Professor of Climate and Space Sciences at the University of Michigan. “We haven’t quite seen the scale of the changes coming.”

Why is it worrying that Antarctica is so hot

The air temperature in Antarctica is unusually high at the moment. Along the Antarctic Peninsula, the part that goes towards South America, it is more than 18 degrees Fahrenheit is warmer than average for this time of year. It is usually about 14 degrees Fahrenheit.

Parts of Antarctica are experiencing temperatures much higher than normal.

It’s still very cold, especially compared to the weather up north, but it’s enough to change the air circulation patterns. The sea surface temperature around Antarctica is also strangely warm. according to David Schneider, a research scientist at the National Center for Atmospheric Research and the University of Colorado Boulder, that’s what sea ice matters most. “If you look at maps of where sea ice is low, it’s low next to places with warm sea surface temperatures,” Schneider said.

The loss of sea ice around Antarctica could have devastating consequences. Without sea ice as a barrier, the warmer ocean waters would begin to lap up the ice on land. When ice extends over the sea, forming ice sheets, warm water can erode it from below, out of sight of most scientific instruments. This is called core melt, and it appears to be particularly intense in West Antarctica around the Thwaites and Pine Island glaciers. The ice front around the Pine Island Glacier has held for 60 years, but has suddenly retreated 18 miles between 2015 and 2020. The Thwaites Glacier is also melting rapidly. On its own, it can Raise global sea level by two feet If it will dissolve completely. Further warming of the ocean will accelerate these trends.

Water temperatures are unusually high around the Southern Ocean right now.

Why is this heat accumulating in the air and water now? In part, it’s for some of the same reasons the northern hemisphere has become so interesting.

The Pacific Ocean is going through its warm phase, known as El Niño, and this year is looking particularly strong. El Niño years are generally associated with warming in most parts of the world, including Antarctica. This tends to disrupt the usual circular pattern of high-altitude air currents known as jet streams. “El Niño is always associated with a weaker polar vortex and a kind of more rippling jet stream,” Schneider said. Ripples in the jet stream allow warmer air from higher latitudes to drift over the southern continent, warming it.

But while El Niño is currently driving up temperatures near the South Pole, climate trends on the continent can be mercury: For decades, sea ice around Antarctica has already been increasing. Between 1979 and 2014, sea ice increased by Approximately 1 percent per decadeAccording to NASA. This was unexpected by most people. Claire Parkinsonsaid a climatologist at NASA’s Goddard Space Flight Center. “There is still no consensus on the cause of the increase in sea ice.”

Around 2015, this trend changed, with sea ice experiencing more fluctuations and declines around the South Pole, and in some years faster than in the Arctic region. Scientists aren’t sure why. “The state of the Antarctic is definitely a puzzle to try to solve,” Parkinson said.

With little understanding of why sea ice around Antarctica is expanding and then shrinking, it’s not clear what the future holds. “I don’t really want to predict whether these sea ice anomalies are the new normal, or whether they will bounce back,” Schneider said. “The jury is kind of still out on this.”

This uncertainty adds urgency to Antarctic research to fill in the blanks. “Even today, we are somewhat outnumbered,” Bases said. “There are a lot of places where you can go out and take a measurement and you’ll be the first person to take a measurement there.”

But as scientists factor in the year-to-year shifts in heat and ice, the general trend still points to a hotter world and all the implications that that entails. “I can tell you, with really high confidence, that sea levels globally are going to continue to rise,” Bases said.