Classic climate feedback: Arctic Sea Ice Extent lowest on record and still shrinking

"This is a profound — and profoundly depressing — moment in the history of our planet," said Shaye Wolf, climate science director at the Center for Biological Diversity’s Climate Law Institute. "The sea-ice death spiral, coming during one of the warmest summers in American history, is just one more clear sign of the deepening climate crisis that we ignore at our own peril."

Related: Sea ice volume: Multi-year arctic sea ice reducing dramatically | Climate Code Red Blog: Big call: Cambridge prof. predicts Arctic summer sea ice "all gone by 2015"

Arctic sea ice stood at 4.10 million square kilometers (1.58 million square miles) according to the National Snow and Ice Data Center (NSIDC) and NASA. The previous record minimum set in 2007 was 4.17 million square kilometers (1.61 million square miles).

While 2007 provided ideal summer melting conditions, this year weather conditions were less remarkable. According to NSIDC Director Mark Serreze, "The previous record, set in 2007, occurred because of near perfect summer weather for melting ice. Apart from one big storm in early August, weather patterns this year were unremarkable. The ice is so thin and weak now, it doesn't matter how the winds blow."

"The Arctic used to be dominated by multiyear ice, or ice that stayed around for several years," NSIDC scientist Walt Meier said. "Now it's becoming more of a seasonal ice cover and large areas are now prone to melting out in summer."

Sea ice extent is just one indicator that the Arctic is rapidly warming. Sea Ice thickness and the level of multiyear ice are also important indicators which affect sea ice extent, with strong signs that both these are shrinking substantially.

Dr James Renwick, Associate Prof of Physical Geography at Victoria University of Wellington New Zealand commented: “The reason the ice has receded so quickly is that so much of it now ‘first-year’ ice, ice that formed only since last autumn. In the 1980′s, first-year ice was very much in the minority and much of the arctic was covered in thicker multi-year ice. Such thin first-year ice is much more susceptible to break-up by storm winds, and just melts more rapidly. Now, the ice extent has fallen below the previous record low from 2007. Sea ice extent will doubtless keep decreasing for the next few weeks, most likely putting the 2012 minimum at less than 4 million square kilometres for the first time since records began in the late 1970s. No doubt as the Arctic winter draws nearer, ice will refreeze over the Arctic Ocean. But how thin, how fragile it has become."

Classic climate feedback at work

“This is a classic climate feedback at work, the ‘ice-albedo feedback’." said Renwick, "Ice, being white, reflects sunlight. Ocean, being dark, absorbs sunlight. Once warming starts and ice starts melting, more sunlight is absorbed by the exposed ocean surface, speeding the warming and melting more ice, and so on. This event unfolding in the Arctic Ocean right now should be a wake-up call to governments world-wide, that climate change is a serious threat, and it is not distant menace, it is on our doorstep today.”

Shaye Wolf from the Center for Biological Diversity drew attention to the rapid loss of sea ice also posing a severe threat to endangered polar bears, ice seals, walruses and other Arctic animals that rely on sea ice for survival. "Polar bears, seals and other Arctic wildlife will bear the deadly brunt of ice loss, but all of us will be hurt by the world’s quickly warming climate if we don't act now," Wolf said.

"This is not a fluke, not an anomaly"

Professor Jeff Kargel, glaciologist at the University of Arizona, in a long comment gathered by the UK Science media Centre, said:

“This latest dramatic season of record-fast meltback of sea ice is an indisputable indicator of historically unprecedented rapid climate change over a vast area. This is not a fluke, not an anomaly; it's not a short-term random variation, some minor phenomenon with negligible impact, or something operative over geologic time scales. This is huge, and it's fast. It's also something that has been underway for several decades now, but something particularly dramatic seems to have been happening the last few years, as we have also seen with Greenland ice sheet melting right to the summit, and extreme weather events around the globe. I really don't understand why something in the global system seems to have switched. I do understand that the deep-time record in ice cores and sediment cores points to dramatic climate switches having been thrown (naturally) in Earth's past. This time, a period of climatic stability lasting for millennia--with some minor fluctuations-- may be unsettled by anthropogenic changes in atmospheric composition.

“It may be that something in the Earth's oceans has reached a point where expected climate change due to greenhouse gases is forcing a "catch-up" with modeled predictions. Whether a global ocean dynamics switch has been thrown, or whether the Arctic Ocean is operating as its own little system at the poleward edge of the global system, I don't know. But even the layperson can see that climate far outside the Arctic of the last several years is different than climate of preceding decades. Now we are seeing it hit the Arctic very hard. It does make one wonder what's next and how this Arctic shift will play out globally as feedbacks take hold.

“The seasonally minimum late summer coverage by Arctic sea ice is now close to half of what it was when I was starting my science career. The Arctic sea ice reduction is a continuation of decades of reduced sea ice. When I was at Tuktoyaktuk, Northwest Territories, Canada, about 3 years ago, I was shocked to see the sea ice far out to sea in July, on the distant horizon, and a few days later its edge was beyond the horizon, nowhere to be seen, when I had expected the sea ice still to be washing ashore and only beginning the break up near the land. I was there to study the lowland permafrost, which also was undergoing rapid degradation due to the same global warming influences that were being felt around the globe.

“This phenomenon underscores the complex realities of climate change, where one change induces another and another and another.... In this case, global and Arctic warming has caused reduction in the frozen ice of the Arctic Ocean; that is causing a reduction in reflectivity of the Arctic, which causes further absorption of sunlight and further heating of the surface, and further melting. As the Arctic Ocean warms, the consequences will be felt far and wide. We already have heard about impacts on polar bears, but impacts will be felt far inland as weather patterns and long-term climate undergoes secondary shifts on top of what the direct influence of greenhouse gases already is. This will be manifested in changing glaciers in the northern high latitudes and changing winter weather in North America, Europe, and Asia.”

Bob Ward, policy and communications director at the Grantham Research Institute on Climate Change and the Environment at London School of Economics and Political Science, said:

"Polar scientists agree that it is the rise in global average temperature, driven by increasing levels of greenhouse gases in the atmosphere, that is driving this rapid loss of Arctic ice. At the current rate of warming, we can expect within a few decades that Arctic sea ice will disappear completely during the summer months.

“Not only is this having a big impact on Arctic wildlife, such as polar bears, that rely on sea ice for their habitats, but the rapid loss in sea ice is accelerating global warming. Ice reflects more sunlight than sea water, so more heat is being absorbed, increasing the amount of warming."

Bob Ward called for stronger action by governments at the next climate change talks auspiced by the United Nations in Bangkok next week. "This record-breaking melt in the Arctic is a clear indicator for governments meeting next week in Bangkok, Thailand, at the latest round of international negotiations about climate change, that the current pace and scale of reductions in greenhouse gases are a wholly inadequate response to the magnitude of the impacts of global warming.” he said.

Strong pollution cuts were also emphasised by Shaye Wolfe, “Deep and rapid carbon pollution cuts are essential to slow the warming of the Arctic and maintain a safe climate for the rest of the globe,” said Wolf. “Reductions in the powerful greenhouse pollutants methane and black carbon are also needed to slow warming in the short term.”

Sources:

• NASA Earth Observatory, 28 August 2012, Arctic Sea Ice Drops below 2007 Record: Image of the Day
• NSIDC media release, 27 August 2012, Media Advisory: Arctic sea ice breaks lowest extent on record
• Center for Biological Diversity, August 27, 2012 - Arctic Summer Sea Ice Melts to New Historic Low
• New Zealand Science Media Centre, 29 August 2012 - Record Arctic sea ice loss – experts respond