STUDY: Antarctic Sea Ice Loss Driven By ‘Natural Variability,’ Not Global Warming
A series of strong storms late last year brought warm winds down to Antarctica that melted a South Carolina-sized chunk of sea ice every day, leading to the lowest sea ice coverage on record for the South Pole.
And it likely had nothing to do with man-made global warming, according a new study published in the journal Geophysical Research Letters.
“There’s no indication this is anything but just natural variability,” John Turner, a climate scientist with the British Antarctic Survey, told the American Geophysical Union’s (AGU) blog Friday.
“It highlights the fact that the climate of the Antarctic is incredibly variable,” Turner said.
Turner and his colleagues found that while sea ice decline is an indicator of global warming, Antarctic sea ice decline in 2016 was likely caused by a series of Southern Ocean storms in the fall. Antarctic sea ice had actually been increasing up until this point, hitting record levels in late 2014.
Those storms brought warm air and strong winds to the South Pole that rapidly melted the surrounding sea ice. A strong El Nino also ramped up temperatures throughout 2016.
Scientists have struggled for years to find the signal of man-made warming in Antarctica, but the region still seems to be dominated by natural variability. South Pole sea ice, for example, is only about 3 feet thick and sensitive to strong winds.
Most climate models predicted South Pole sea ice would shrink as the planet warmed, much like Arctic sea ice. But the models were wrong, and sea ice grew since the satellite record began in the late 1970s.
“It is tempting to think that the 2016 low ice conditions may mark this turn toward decreasing ice, but that temptation is not warranted,” Walt Meier, a sea ice scientist at NASA who did not take part in the study, told AGU.
“It’s too soon to tell whether the low ice conditions are an ephemeral downturn or the start of something more long-term,” Meier said.
Turner said global warming could become more apparent as more greenhouse gases are emitted into the atmosphere, but right now, they can’t blame the fall storms in 2016 on human activity.
“This doesn’t mean that climate change isn’t happening, just that, at least through 2015 for Antarctic sea ice, the climate change signal could not be distinguished from natural variability,” Meier said.
Scientists worry global warming will cause the rapid melting of Antarctica’s glaciers, which would increase the rate of sea level rise. Sea level rise has been pretty consistent for the last hundred years or so.
Even so, The New York Times recently likened potential sea level rise from Antarctic glaciers to Biblical-level floods.
“I don’t think the biblical deluge is just a fairy tale,” Terence Hughes, a retired glaciologist told NYT. “I think some kind of major flood happened all over the world, and it left an indelible imprint on the collective memory of mankind that got preserved in these stories.”
A 2015 NASA study found Antarctica’s ice sheet increased in mass from 1992 to 2008. The study found ice gains in Eastern Antarctica more than offset ice loss from melting glaciers in the west.
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