This year's Arctic sea ice cover currently is the sixth-lowest on modern record, a ranking that raises ongoing concerns about the speed of ice melt and the effects of ice loss on global weather patterns, geopolitical fights, indigenous peoples and wildlife, scientists said yesterday.

In an analysis, the National Snow and Ice Data Center said the sea ice extent as of Sept. 16 was 2 million square miles, an amount just below revised estimates for 2009, the former sixth place finisher, said Julienen Stroeve, a scientist at the center. While this year's annual minimum has not yet been officially declared and may not be for a few days, the sixth-place ranking for 2013 is not expected to change, she said.

"As is typical for this time of year, winds or currents can compact or spread apart the ice, resulting in small daily fluctuations," the center said in its analysis.

This year's ice extent is roughly 50 percent higher than last year's level of 1.32 million square miles, a fact that spawned a recent wave of charges in the British press that the world is experiencing "global cooling" rather than catastrophic climate change. The U.K.-based tabloid Daily Mail proclaimed the "return of the ice cap" in a September headline, a statement echoed by conservative radio host Rush Limbaugh and others.

However, this year's ice cover remains far below the 1981-2010 average, indicating an ongoing, long-term decline of ice because of warming temperatures, according to scientists.

"We are still on a one-way street of losing ice," said James Overland, an oceanographer at the National Oceanic and Atmospheric Administration. That ice loss is shifting global weather patterns, making the Arctic ocean more acidic and threatening Arctic wildlife and communities, he said.

Overland recently co-authored a study predicting an ice-free Arctic summer in the first half of this century and said he will soon be releasing additional data projecting that an area 100 miles north of Alaska will witness open water five months out of the year by 2030, as opposed to the current two months.

He and other scientists emphasized that this year's 50 percent rebound stemmed from normal weather variations, not an unusual climate shift. The last seven years witnessed the seven lowest minimum extents since satellite observations began in 1979, and there was last a record high with Arctic ice cover two decades ago, according to federal data.

The thickness of the ice, and its overall volume, may be a more important measure of what is happening in the Arctic over the long term, even though it is not as simple to measure, said Overland. Wind and weather can cause annual fluctuations in the ice extent, while the overall volume remains relatively flat, he said.

Thinning ice close to minimum record
"We use ice extent, because it's the most consistent," said Walt Meier, a research scientist at NASA's Goddard Space Flight Center.

European Space Agency's CryoSat mission said earlier this month that the volume of the ice continues to thin, despite variations in the ice extent, for example. Last winter, the ice volume hit 15,000 cubic kilometers, an amount about half what it was 30 years ago, according to the agency.

"The autumn volume of the sea ice (as opposed to the extent) is still close to its minimum record," Robert Meisner, spokesman for European Space Agency, said yesterday.

The reason, then, why the Arctic ice extent jumped 50 percent this year in comparison to 2012, is a combination of weather and storm patterns, explained Meier. A significant factor was that last year witnessed a record low, and it is typical for there to be a rebound year in that circumstance, he said.

Unusually warm temperatures and a powerful storm that hit the Arctic's open waters in the summer helped drive 2012's record melt, he said. The storm last year helped carry unusually warm water to other parts of the Arctic, further fueling melt, he said.

"Water is even more effective at melting the ice than the air, because it transfers the heat much more efficiently," he said.

By contrast, this year witnessed low pressure over the Arctic, which helped bring sun-blocking clouds that helped keep temperatures cool in the spring, Meier said. The low pressure also brought several Arctic storms, but they did not hit at as opportune times for ice loss, and instead brought a lot of cold air, he said.

Strong winds in February and March churned things up a bit, but it was still cold enough for refreezing, he said.

"The low pressure tends to spread out the ice over a larger area, slowing the decline in extent," he added. A 50 percent rebound level from a prior year is high, but not unprecedented, he said.

Security group calls U.S. unprepared for Arctic changes
The analysis from the National Snow and Ice Data Center comes on the heels of several scientific and policy papers in the past week warning about the consequences of Arctic ice loss. This morning, the American Security Project is releasing a paper concluding that the U.S. government is failing to plan for the complicated geopolitics arising from ice decline.

The paper from the research organization notes, for instance, that the Navy and Coast Guard have one medium-sized icebreaker currently in service, while Russia operates 25. Finland and Sweden have seven. This month, Russia announced it was reopening an Arctic base on the Novosibirsk Islands.

Earlier this year, a study in the Proceedings of the National Academy of Sciences reported that ships may be able to travel through previously inconceivable routes across the North Pole and through the famed Northwest Passage by midcentury (ClimateWire, March 5).

The Security Project calls for the Defense Department to be much more involved in the region to match the militaries of other Arctic nations, and questions whether current policy frameworks, such as an Arctic strategy released by the Coast Guard this year, will be enough to prepare for potential oil spills, accidents and shipping traffic challenges.

"There is insufficient infrastructure to ensure safe navigation, initiate search and rescue missions, or to coordinate pollution response. This is most evident in the lack of Arctic ports for ships in distress," the paper states.

Similarly, the U.S. Geological Survey released a study last week, published in PLOS ONE, finding that roughly 20 percent of the Arctic waters of the Canadian basin have "become more corrosive," threatening the entire food web. The decline of sea ice spurs the process, by allowing open water to absorb carbon dioxide.

The research team -- which utilized 34,000 data records from 2010 and 2011 -- concluded that melting sea ice is diluting seawater and reducing the concentrations of the carbonate minerals critical as building blocks for the shells of marine life.

"Nowhere on Earth have we documented such large scale, rapid ocean acidification," said USGS oceanographer Lisa Robbins, in a statement.

Reprinted from Climatewire with permission from Environment & Energy Publishing, LLC., 202-628-6500