There is about as much sea ice around Antarctica today as there was a century ago, defying expectations tied to global warming, a new study reports.
A comparison of modern satellite images with ice observations made by early Antarctic explorers, including British Capt. Robert Scott and Ernest Shackleton, revealed that the reach of sea ice around the continent is only about 14 percent less today. The results of the peer-reviewed study were released last week by The Cryosphere, a journal of sea and land ice studies affiliated with the European Geosciences Union.
This finding seems to be in stark contrast to recent scientific observations in the Arctic region, where scientists with NASA and the National Snow and Ice Data Center found that sea ice had reached a wintertime record low in 2016.
“It is difficult to say at this stage why long-term changes in summer sea ice seem to be more pronounced in the Arctic than the Antarctic,” the lead scientist, Jonathan Day of the University of Reading in the United Kingdom, said in an email to AMI Newswire. “They are geographically very different places: The Arctic is an ice-covered ocean surrounded by land, whereas the Antarctic is an ice-covered continent surrounded by ocean, so the climate dynamics are different.”
Because so much of its ice is on land, melting in Antarctica would have a far greater impact on sea levels than ice melt in the Arctic.
Some scientific research and events in the South Pole region have been used by global warming skeptics in recent years to punch holes in the theory of climate change. An examination of what is not melting around the globe provides an important perspective in this debate, according to U.S. Sen. Jim Inhofe (R-Okla.).
“This past December a research expedition of climate scientists got stuck in deep ice in Antarctica,” Inhofe told Congress in early 2014. “It took a couple of weeks and a couple more icebreakers getting stuck before the research vessel was finally freed.”
Research published in the Journal of Climate found that sea ice extent along the eastern coast of Antarctica increased about 1.5 percent per year from 2000 to 2008, Inhofe said in a speech that questioned the accuracy of global warming theories.
The climate of Antarctica seems to have fluctuated significantly over the past century, Day found in his study, alternating between periods of high sea ice cover and low sea ice. But overall, the study did not find an overall downward trend in sea ice.
“We know that sea ice in the Antarctic has increased slightly over the past 30 years, since satellite observations began,” Day said. “Scientists have been grappling to understand this trend in the context of global warming, but these new findings suggest it may not be anything new.”
Some media reports on his research implied that there have been no human-caused changes in Antarctica’s climate, Day said in a blog post. But that idea is misleading since the significant fluctuation in annual sea ice in the region might mask actual effects of global warming, he said.
In addition, it’s important not to confuse measurements of sea ice, which have less potential to raise sea levels, with surveys of ice resting on the continent, Day said, because melting land ice could theoretically raise ocean levels.
A proponent of man-made global warming theory counters that Antarctica’s ice shelves – which lie at the edges of the continent and hold massive ice sheets in place – are a greater concern than the extent of sea ice.
Sophisticated ice sheet models show that the western ice shelf of Antarctica is becoming less stable and that future destabilization and melting could raise sea levels by four feet, Brenda Ekwurzel, director of climate science at the Union of Concerned Scientists, told AMI. The extent of sea ice tends to bounce around year by year due to prevailing winds blowing sea ice outward around the continent, she said, so that sea ice may look substantial in winter but then melt away during the Southern Hemisphere’s summer season. The weakening of ice shelves may be due to warmer ocean waters in the Antarctic getting below the ice shelves.
“Ultimately, (climate) models project that the sea ice is going to be compromised due to global warming,” Ekwurzel said.
Effects on land ice may have reached the point that the loss of ice shelf volume is now unstoppable, according to a study published in October in the journal Nature Communications.
Day’s research showed that the Weddell Sea region, also on the western side of Antarctica, had a significantly larger ice cover a century ago than it does today.