Sandy Tops List of 2012 Extreme Weather & Climate Events
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No. 4 — Steamy Arctic Events Alarm Climate Scientists
The continental U.S. had its warmest year on record in 2012, but things were unprecedentedly steamy at the top of the globe as well. And what transpired there -- from a falling snow cover, an alarming rate of melting of Greenland’s ice cap, and a melt back of Arctic sea ice -- was worrisome to climate scientists, who have long predicted that climate change would strike the Arctic faster and harder than the rest of the globe.
During the spring, snow cover across North America and Eurasia dropped to the lowest level ever seen. A few months later in July, fully 97 percent of Greenland’s ice cap -- which covers most of that enormous island -- experienced at least some surface melting. That hasn’t happened since at least the 1800s. During that same month, a glacier in northern Greenland shed a slab of ice twice as big as Manhattan Island. And finally in August, the ice that covers the Arctic Ocean melted back more than it has since satellite observations began in the 1970s, and kept on dropping right through mid-September.
But the loss of sea ice was perhaps the most startling news.
Late-summer sea ice in the Arctic Ocean has been on a downward spiral since the late 1970s, but the downward trend isn’t perfectly smooth. Some years actually see more ice than the year before, as wind patterns and ocean currents in a given summer might enhance or hold back that season’s melting. However, the long-term trend has been toward diminished summer sea ice cover. Studies have shown that this trend is due to a combination of manmade climate change and natural climate variability.
In 2012, ice coverage reached a new low — and not by a small amount, either. As of September 16, according to the National Snow and Ice Data Center (NSIDC), just 1.32 million square miles (2.41 million square kilometers) of ice were left floating in the Arctic Ocean, a whopping 18 percent less than the previous record of 1.61 million square miles (4.17 million square kilometers), set in 2007. The amount of sea ice that melted between March and September, the NSIDC said, would be enough to cover Canada and Texas, combined. The melt rate was so fast, in fact, that the old record was shattered weeks before the new low was reached.
NSIDC scientist Julienne Stroeve told Climate Central that’s especially significant because “the 2007 minimum was, in large part, driven by [unusual weather patterns], and this summer we shattered the 2007 minimum under more normal summer circulation patterns.”
It’s all consistent, however, with scientists’ understanding of the role sea ice plays in the Arctic Ocean and the global climate. When it’s there, the ice’s bright, white surface reflects sunlight back into space. When it melts, the darker sea water it exposes absorbs more of that light, heating the ocean and the air above. When the ice refreezes in the fall and winter, it’s thinner, and prone to melting even more easily in future seasons, exposing even more water and setting up a feedback loop that could leave the Arctic Ocean seasonally ice-free by later this century. Computer models predict this may occur by 2050, and some scientists think it will happen even earlier.
The side effects of declining Arctic sea ice are already being seen, and are occurring faster than scientists expected just a few years ago. To start with, some scientists think that warmer Arctic sea and air temperatures are now influencing the jet stream in the northern hemisphere, leading to more extreme weather events.
A wavier jet stream that features more frequent “blocking” events, or stuck weather patterns, could be leading, paradoxically, to stormier winters in the U.S. and Europe. This is an area of active scientific research, and many climate scientists remain skeptical that Arctic sea ice loss has already started to change the weather in lower latitudes, although it’s widely recognized that melting sea ice is warming the Arctic climate.
In addition, the extra heat building in the Arctic is accelerating the pace of global warming overall. Another problem is that warm air is already starting to melt the permafrost that pervades the soil in northern Alaska, Canada and Siberia. That could release carbon from organic matter that has been frozen for many thousands of years — yet another feedback that could accelerate global climate change.
This year also saw a record low spring snow cover in North America and Eurasia, and the rate of snow cover loss in springtime has been even faster than the rate of sea ice loss. The loss of spring snow cover affects the length of the growing season, the timing and dynamics of spring river runoff, permafrost thawing, and wildlife populations. This was the third time in five years that North America saw a record-low spring snow cover, and the fifth year in a row that Eurasia has. Warmer air temperatures have played a large role in driving this trend, since during the past decade no part of the Arctic has been cooler than the 30-year average.
Warmer ocean water, meanwhile, is destabilizing glaciers that drain Greenland’s massive ice cap, which holds enough fresh water to raise sea level by more than 20 feet. Warm air over the Arctic in 2012 triggered the most widespread surface melt on the Greenland ice cap on record.
All the melting has also encouraged an increase in both shipping and oil exploration in Arctic waters, threatening to bring pollution to these formerly pristine waters — and also posing new risks to the men and women living and working there.
Ongoing Coverage of the Planet's Polar Regions
Visualizing 2012’s Record Arctic Sea Ice Melt
Forget the Melting Arctic, Sea Ice in Antarctica is Growing!
It’s Official: Arctic Sea Ice Shatters Record Low
A Closer Look at Arctic Sea Ice Melt and Extreme Weather
‘Astonishing’ Ice Melt May Lead to More Extreme Winters
Greenland Glacier Sheds Two Manhattans' Worth of Ice
(Read each of the Top 10 events by following the page links below)