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Scientists say it’s still too early to tell whether climate change is responsible for an extreme heat wave in Antarctica that shattered records as it brought temperatures soaring as high as -12°C, a full 40°C/70°F warmer than normal for this time of year.
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“It is impossible, we would have said until two days ago,” tweeted Stefano Di Battista, a researcher who has published studies on Antarctic temperatures. “From today (March 18) the Antarctic climatology has been rewritten.”
Eastern Antarctic temperatures at this time of year typically register between -60° and -45°C. It is even more unusual that the weather pattern occurred in March, which marks the onset of Antarctica’s low-sunlight fall months, reports The Washington Post.
The warm conditions were caused by an extreme atmospheric river of water vapour in the sky. When the river landed on the east coast it brought rain and moisture that spread over the continent, but a strong high-pressure system prevented the moisture from escaping. While it was trapped in place, the excessive moisture retained more heat than it would have under normal air conditions, while liquid-rich clouds radiated heat towards the surface.
The atmospheric river was projected to exit the continent on Saturday, but scientists said lingering moisture could carry high temperatures through the weekend. Although it is not unusual for warm air to travel over the continent, the extent and intensity this time were way beyond normal.
Jonathan Wille, a researcher studying polar meteorology at Université Grenoble Alpes in France, said the event was similar to June’s Pacific Northwest heat wave that scientists determined was “virtually impossible” without human-caused climate change. He cautioned that this one event could not necessarily be attributed to human actions, but said climate change is “loading the dice” for more temperature extremes.
“We do believe they will become more intense because it’s just simple physics,” Wille told the Post. “But the details, we’re still trying to figure that out. It would be very difficult to say that there’s not a climate change fingerprint on an event like this.”
Climate change is affecting other parts of Antarctica, as well. High temperatures are reducing the mass of ice sheets on the western side of the continent and threatening to destabilize the Thwaites Glacier, a slab the size of Florida that contributes about 4% of annual global sea level rise. The Antarctic heat wave comes on the heels of a bout of exceptional warmth in the Arctic that reached close to the melting point.
Atmospheric rivers are entirely composed of precipitable water (PW). Weight for weight, PW generates a greenhouse energy effect comparable to that of water vapor in a pristine state.
When large overhead supplies of PW are temporarily combined with smaller amounts of ambient surface vapor the greenhouse effect is multiplied accordingly. Each double of total PW in the atmosphere, from any level, at any location, adds about 10C to surface air temperatures, and each bit of increase performs at the speed of light. No “movement of warm air” is required. The real question is about how this particular river managed to penetrate so deeply into the sky over Antarctica’s very dry interior at this time.