“Precipitous” fall in Antarctic sea ice since 2014 revealed – “The rapid decline has caught us by surprise and changes the picture completely”
By Damian Carrington
1 July 2019
(The Guardian) – The vast expanse of sea ice around Antarctica has suffered a “precipitous” fall since 2014, satellite data shows, and fell at a faster rate than seen in the Arctic.
The plunge in the average annual extent means Antarctica lost as much sea ice in four years as the Arctic lost in 34 years. The cause of the sharp Antarctic losses is as yet unknown and only time will tell whether the ice recovers or continues to decline.
But researchers said it showed ice could disappear much more rapidly than previously thought. Unlike the melting of ice sheets on land, sea ice melting does not raise sea level. But losing bright white sea ice means the sun’s heat is instead absorbed by dark ocean waters, leading to a vicious circle of heating. […]
Antarctic sea ice had been slowly increasing during the 40 years of measurements and reached a record maximum in 2014. But since then sea ice extent has nosedived, reaching a record low in 2017.
“There has been a huge decrease,” said Claire Parkinson, at NASA’s Goddard Space Flight Center in the US. In her study, published in the journal Proceedings of the National Academy of Sciences, she called the decline precipitous and a dramatic reversal.
The satellite record reveals that a gradual, decades-long overall increase in Antarctic sea ice extents reversed in 2014, with subsequent rates of decrease in 2014–2017 far exceeding the more widely publicized decay rates experienced in the Arctic.
Claire Parkinson, climatologist at NASA’s Goddard Space Flight Center
“We don’t know if that decrease is going to continue,” she said. “But it raises the question of why [has it happened], and are we going to see some huge acceleration in the rate of decrease in the Arctic? Only the continued record will let us know.”
“The Arctic has become a poster child for global warming,” Parkinson said, but the recent sea ice falls in Antarctica have been far worse. She has tracked Antarctic sea ice for more than 40 years. “All of us scientists were thinking eventually global warming is going to catch up in the Antarctic,” she said. […]
Prof Andrew Shepherd at Leeds University in the UK said: “The rapid decline has caught us by surprise and changes the picture completely. Now sea ice is retreating in both hemispheres and that presents a challenge because it could mean further warming.” He said it would also be important to find if the ice’s thickness has changed, as well as its extent. [more]
‘Precipitous’ fall in Antarctic sea ice since 2014 revealed
ABSTRACT: Following over 3 decades of gradual but uneven increases in sea ice coverage, the yearly average Antarctic sea ice extents reached a record high of 12.8 × 106 km2 in 2014, followed by a decline so precipitous that they reached their lowest value in the 40-y 1979–2018 satellite multichannel passive-microwave record, 10.7 × 106 km2, in 2017. In contrast, it took the Arctic sea ice cover a full 3 decades to register a loss that great in yearly average ice extents. Still, when considering the 40-y record as a whole, the Antarctic sea ice continues to have a positive overall trend in yearly average ice extents, although at 11,300 ± 5,300 km2⋅y−1, this trend is only 50% of the trend for 1979–2014, before the precipitous decline. Four of the 5 sectors into which the Antarctic sea ice cover is divided all also have 40-y positive trends that are well reduced from their 2014–2017 values. The one anomalous sector in this regard, the Bellingshausen/Amundsen Seas, has a 40-y negative trend, with the yearly average ice extents decreasing overall in the first 3 decades, reaching a minimum in 2007, and exhibiting an overall upward trend since 2007 (i.e., reflecting a reversal in the opposite direction from the other 4 sectors and the Antarctic sea ice cover as a whole).
SIGNIFICANCE: A newly completed 40-y record of satellite observations is used to quantify changes in Antarctic sea ice coverage since the late 1970s. Sea ice spreads over vast areas and has major impacts on the rest of the climate system, reflecting solar radiation and restricting ocean/atmosphere exchanges. The satellite record reveals that a gradual, decades-long overall increase in Antarctic sea ice extents reversed in 2014, with subsequent rates of decrease in 2014–2017 far exceeding the more widely publicized decay rates experienced in the Arctic. The rapid decreases reduced the Antarctic sea ice extents to their lowest values in the 40-y record, both on a yearly average basis (record low in 2017) and on a monthly basis (record low in February 2017).
