Following a series of weekend winter storms across the northern U.S., below-freezing temperatures have gripped large swaths of the county and thrown many Americans into hardcore survival mode. In New York City, temperatures are expected to plummet 49 degrees Fahrenheit in just 12 hours’ time.
In Minnesota, schools were closed for the first time in 17 years as winter temperatures sank to as low as minus 30 degrees Fahrenheit. "A person not properly dressed could die easily in those conditions," said Scott Trueett, a meteorologist for the National Weather Service.
It’s turning out to be a painfully cold winter, colder in many cities than it has been in decades, and many are wondering why. Where are these extreme temperatures coming from? And what’s to be expected? While extreme weather in the U.S. is in large part due to a “polar vortex” creeping down over the Northern hemisphere from the North Pole, Scientists say weather patterns around the globe are largely the result of climate change in Antarctica.
"Antarctica is one of the key drivers of the global climate system," Tony Press, head of the Antarctic Climate & Ecosystems Co-operative Research Centre in Hobart, Australia, told The Sydney Morning Herald. "Changes in Antarctica will affect not only the Antarctic region but Australia and the rest of the planet."
Every year, Antarctica’s ice shrinks in the summer and expands in the winter. According to the Sydney Morning Herald, the change in Antarctic ice coverage swells from about 3 million square kilometers at the end of every summer to nearly 19 million square kilometers at the end of every winter. It’s a landmass in constant flux.
But every year, a little bit less of the ice refreezes during the winter. Studies have found Antarctica has lost about 100 billion tons of ice a year since 1993, which has partly contributed to global sea levels rising 0.14 inches a year since the early 1990s. Some regions of West Antarctic have seen a 7 percent drop in sea-ice extent each decade.
On the other hand, Antarctic ice coverage has increased 1 percent per decade, which seems to contradict the notion that global warming -- average overall surface temperatures have risen roughly 1.5 degrees Fahrenheit over the last 100 years -- is causing the ice to melt. But scientists warn not to confuse weather patterns with worldwide climate change.
“Regionally, climate change can vary markedly across the Earth so to detect human influences on the climate system climate scientists must consider the Earth as a whole,” John Turner, who leads the Climate Variability and Modeling project at the British Antarctic Survey, wrote in an article for the Guardian. "What is clear is that the impact of climate change on ice at both poles is complex."
He added: “In the Antarctic the increase in annual mean sea ice extent is only just over 1 percent per decade, making it impossible at present to separate natural variability from any human influence.”
Scientists believe some of the additional sea ice in Antarctica, especially in the eastern regions, might be the result of melting land-based ice sheets, causing surrounding ocean temperatures to cool down. This fresh water then freezes and becomes sea ice.
A 2013 study in the Journal of Climate found that converging winds around the South Pole could also explain a majority of the increase in ice extent around the Antarctic. “The polar vortex that swirls around the South Pole is not just stronger than it was when satellite records began in the 1970s, it has more convergence, meaning it shoves the sea ice together to cause ridging,” the study’s authors explained. “Stronger winds also drive ice faster, which leads to still more deformation and ridging. This creates thicker, longer-lasting ice, while exposing surrounding water and thin ice to the blistering cold winds that cause more ice growth.”
Future research into Antarctic sea ice melt will focus on the thickness of the ice around the edges of Antarctica and the effect of ice melt on global sea levels.