Earlier this year, a group of forecasters attempted to model sea ice melt for the upcoming summer. The result was a range of forecasts predicting anywhere from 4.1 to 4.9 million square kilometers of sea ice left by the end of this melt season. These predictions were based on observed weather patterns that, in the past, had not been conducive for rapid melt.
Instead, this summer has seen the lowest levels ever for sea ice in the satellite record and likely, according to recent scientific observations, the lowest levels in 3,000 years. Today’s sea ice extent total, according to JAXA, has touched the 3.8 million square kilometer mark, 300,000 square kilometers below the lowest level predicted and more than 430,000 square kilometers below the previous record low set in 2007. It is just the latest goal post reached in a year of extreme and record melt.
So why has this happened? Observations of weather events have shown that conditions were not those typically favorable for a large melt. What changed to make such a rapid and historic melt come to pass? Is it possible the Arctic sea ice has passed a tipping point?
One hint for a potential answer to this question is an analysis of sea ice volume. Since the last record low for sea ice extent set in 2007, sea ice volume measurements have come in consistently lower each year. This year after year decline in total sea ice mass results in much thinner ice. So though the coverage may not have contracted as much, the ice underneath was growing thinner and thinner.
Hold that notion of thin ice in your mind. Now, let’s move on to the issue of weather. Usually, large areas of sea ice aren’t vulnerable to storms. In the past, storms during summer time haven’t contained enough energy to break the thicker ice. But since the ice began melting early in the 20th century, something strange has cropped up. Beginning in the later 20th century, more powerful storms began to form in the Arctic during summertime. These Arctic cyclones packed much more energy than their milder forebears and, over time, the strength of these storms continued to increase.
Now let’s fast forward to this summer. An area of thin, mostly broken sea ice was slowly melting in the Arctic. Then, a powerful storm formed off East Siberia and quickly tore through this ice — scattering it, casting it hither and yon, submerging it in a warming Arctic Ocean. By the time the storm was finished, a huge area of ice had melted.
After the storm, rapid declines continued almost unabated.
So one wonders, has the Arctic sea ice reached a tipping point? Are the number of environmental stresses that can cause rapid melt multiplying? Is the thinning ice just no longer able to absorb any insult of weather, wind, or heat? Or has the warming Arctic Ocean just gotten too hot for summer sea ice overall?
Given the serious anomaly of the 2012 melt season, it would seem a very strong possibility that we have entered a new, dynamic phase of melt. A phase in which past assumptions are rendered moot and the accumulating melt feedbacks are increasingly overwhelming the Arctic climate.