Since September, the polar night of winter has been spreading steadily southward in the Arctic. But sea ice hasn’t been keeping pace.
During October, growth of the floating ice was held back by significantly warmer temperatures than average. All told, October saw the fourth lowest extent of Arctic sea ice for the month in records stretching back 46 years to 1979, according to the latest analysis by the National Snow and Ice Data Center.
An expanding black circle marks the spread of polar night in the Arctic in this animation of images acquired by the NOAA-20 satellite between Sept. 4 and Nov. 7. The view is straight down at the North Pole in the center. Each frame in the animation covers two days, and the black circle is indicative of an expanding area that sees no sunlight as winter progresses. (Credit: NASA Worldview)
Including last month, the Arctic has lost an average of 31,000 square miles of sea ice every year during October, the NSIDC analysis found. Given this linear trend, October has seen the loss of 1.38 million square miles of sea ice since 1979 — an area roughly equal to five times the size of Texas.
The Arctic’s relatively sluggish sea ice growth since the start of winter follows a summer that ended with the sixth lowest minimum extent on record. With less ice to reflect away sunlight, greater expanses of Arctic waters were exposed to summer sunlight, enabling them to absorb more solar energy. This, in turn, likely has helped inhibit the wintertime growth of the ice.
“Arctic climate warming continues to lead an unfortunate path of change for the planet,” NSIDC researchers recently wrote. It’s all part of what they described as “the new abnormal.”
This graph plots the monthly October ice extent for 1979 through 2024, revealing a decline of 9.5 percent per decade. (Credit: National Snow and Ice Data Center)
Meanwhile, in Antarctica…
The seasons are reversed in the Southern Hemisphere, of course. So, as wintery conditions have widened in the north, summer warmth has been spreading in the south.
Antarctic sea ice likely reached its annual maximum summer extent on September 19. This maximum for the year was the second lowest since 1979. Since then, warming temperatures have taken a toll. October closed out with the second lowest extent for the month.
Why care about floating ice around a continent at the bottom of the world? As in the Arctic, the sea ice reflects sunlight back into space. And this helps cool a progressively over-heating planet. As the extent of sea ice declines, we’ll have less of that help in the face of the global heating we’re causing with our emissions of greenhouse gases.
In Antarctica, sea ice surrounding the continent also buttresses gigantic ice sheets, slowing the flow of glacial ice into the ocean. As the buttresses disintegrate, more ice from the land can flow into the sea, hastening sea level rise.
A New Report
Next week, 50 leading cryosphere scientists will be releasing their annual report at the COP29 climate conference in Baku, Azerbaijan. Among other things, the report will address the weakening refrigeration effect resulting from loss of sea ice at both poles. It will also detail the impacts and costs to the global economy from loss of snow and ice around the world. Stay tuned…
Source : Discovermagazine
