29 August 2012
Satellite measurements showing record low levels of Arctic sea ice have been announced by the US National Snow and Ice Data Center, breaking the previous record from 2007.
The new data shows that sea ice extent in the Arctic has already shrunk to 70,000 square kilometres below the previous record low in 2007, with two or three weeks in the melt season still left to go. The six lowest ice extents in the satellite record have occurred in the last six years, including this year (2007 to 2012).
The Science Media Centre rounded up reaction to the news from climate scientists:
Dr James Renwick, Associate Prof of Physical Geography at Victoria University of Wellington comments:
"A large storm early in August caused the break-up and melt of a vast area of sea-ice in the Arctic Ocean, at a time when ice extent already equalled the record low for the time of year. At the time of most rapid melt in the first week of August, around 200,000 square km was disappearing every day! Nearly the area of New Zealand, every day. It is just jaw-dropping.
"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.
"This is a classic climate feedback at work, the 'ice-albedo feedback'. 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."
The following comment was gathered by our colleagues at the UK SMC:
Prof Jeff Kargel, glaciologist at the University of Arizona, 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."