(May 30, 2013 Sea Ice Thickness vs May 30, 2012 Sea Ice Thickness. Images provided by the US Navy via the CICE Arctic Ice Model)
Arctic sea ice is a complex beast. And the manner in which any melt season progresses is likely to be unique to that particular year. Inherent to this complexity are the vast number of factors that impact the ice. Air temperature, sunlight, clouds, fog, ocean temperature, humidity, wind, precipitation, ocean currents, warm water upwelling and a host of other factors all can enhance or impede melt. And it is in analyzing and drawing conclusions from these various complex details that a debate rages over the fate of the Arctic sea ice for 2013. Will we see new record lows in area, extent, or volume? Will the Arctic be nearly ice free soon? Or will this year be a pause in the record Arctic melt trend that has been ongoing since 1979?
Debates even rage over what specific factors may cause melt or prevent it. Is insolation the primary driver of Arctic ice melt and retreat? How powerful a factor is air temperature? Is warm water upwelling the cause of flash melt events that can happen even when the air temperature is below the -2 C freezing point of saltwater?
And it is very worthwhile to debate these issues. Because losing the Arctic sea ice is a big deal. A very big deal. And, inexorably, slower (by around 2030) or faster (between now and 2020) we are losing it. So figuring out how and why this might happen is pretty important.
And then we have the deniers… Those who, inevitably, will use data to support their previously conceived world-views regardless of actual facts or trends.
In one example, Steve Goddard, who can be counted on to invariably predict that sea ice will ‘recover’ during any given year, has made a tabloid out of cherry picked data via his blog ‘RealScience.’ Any time either sea ice area or extent approaches the average trend line in any graphs, he can be counted on to post it as ‘proof’ without context that ‘sea ice never melted in the first place, so what are we all worried about?’ Party on like it’s 1950!
It’s in out of context and niddling little cherry-picked details that those like Goddard live out their forlorn days of denial. The rest of us, on the other hand, have to deal with facts and context and do our best to honestly work out what’s really happening.
Which brings us to late May, 2013 and the question of what’s really going on with this melt season…
Area and Volume
Since 2012 was the last year that sea ice hit new record lows in all measures, we’ll use 2012 as a comparison with the current melt season. This comparison is important in that if 2013 melt beats out 2012 melt by end of summer, we have a new record and the raging melt trend continues with a vengeance. If 2013’s melt doesn’t beat out 2012, it’s no indication that sea ice is recovering. Instead, it shows a pause in the current melt trend. For an actual recovery to be established you’d have to see year after year of expanding and thickening ice. And we’re not anywhere near that. Quite to the contrary, since 1979 we’ve lost 55% of sea ice area and 80% of sea ice volume.
Area and volume. These two measures are the most important when figuring out the health of ice. Area measures how much ice covers the Arctic. Volume measures the total mass of ice. But between these two measures, volume is most important. A foot thick film of ice covering 3 million square kilometers of the Arctic is many times less ice than a ten meter thick sheet covering the same region.
With this established, let’s look first at area. In 2013, area melt proceeded at about the same pace as 2012, slowly progressing through both April and into early May with measurements in the region of past years. However, in 2013, as the second half of May passed, sea ice became more spread out. A number of storms had churned through the Arctic, pushing ice out toward the fringes. This higher coverage delayed melt at the ice edge even as the thicker, central ice thinned. As a result, May 30 sea ice area is at 10.6 million square kilometers, or about the same as May 30th of 1991.
Now, if I were Steve Goddard, I would proclaim that the sea ice has recovered, global warming is bogus, and that the work of 97% of the world’s climate scientists is moot. But since I am not Steve Goddard, I’ll actually provide you with a little more in the way of in-depth analysis.
Since, as we noted above, sea ice area is only part of the story, and a less important part at that, let’s take a look at the most important measure — sea ice volume. Now, the last official volume number we have is from PIOMAS for end of April 2013. And that number shows sea ice volume at its lowest levels ever for that day by about 100 cubic kilometers. Not a huge divergence from the previous record low, but a record low nonetheless. Since we’ll have to wait for the May numbers to come out at around June 15th, we’ll have to rely on proxy data to give us an idea where sea ice volume currently stands. But the start point, at the beginning of the month, was a new record low.
Moving forward, we will use the CICE images above as a comparison. Looking at these images, it is first important to consider what we know about 2012. First, we know that sea ice volume at this time for 2012 was edging back into record low territory as June approached. So the CICE map on the bottom is a picture of a record low or near record low for that date. And for this comparison, we have a visual base-line.
Looking at the 2012 CICE map we immediately notice a few things. First, a degree of thick ice remained just north of the Canadian Arctic Archipelago. Second, we have a number of areas of edge melt occurring in the Kara and Laptev seas, in the Bering, near the Mackenzie Delta, in Baffin Bay, and some slight melt occurring in Hudson Bay.
Now let’s compare this map with the 2013 map. Immediately, we notice that edge melt for 2012 is greater than 2013 at this time. The Kara and Laptev seas, especially show more open water in 2012 than in 2013. Baffin Bay and the Beaufort also show more edge melt. 2013 shows a slightly faster rate of melt for the Bering Sea and Hudson Bay, however. So by looking at these two maps we can confirm what we already know by looking at the sea ice area measurements — the sea ice is more widespread in 2013 than it was in 2012.
It is important to note that Cryosphere Today’s sea ice area measurement doesn’t take into account all the little cracks and holes in the central ice. Their analysis is not so finely detailed. Otherwise, area measures would likely be lower for 2013, because the central ice is cracked and riddled as never before. This cracking and riddling also has an impact on overall sea ice volume.
When looking at volume in the central ice pack regions, we find that total amounts of sea ice in 2013 may well be near 2012 amounts. For the 2013 central ice region shows a remarkable lack of ice. Central sea ice thickness on the CICE map for 2013 is far less than that shown for 2012. Furthermore, 2013 CICE maps show an ongoing erosion and jostling of central sea ice where 2012 saw very few such impacts during May.
In the end, what we see is 2012 with more ice edge melt while 2013 shows more central ice volume loss. And where does that put us in total volume measurements? For more certainty, we will have to wait for the June, 2013 PIOMAS update. However, it is more than reasonable to assume, based on the CICE maps, that current Arctic sea ice volume is near to record low levels.
In the end, 2013 ice is overall thinner and more spread out than 2012 ice. And this state makes it vulnerable to rapid melt, opening of holes in the central ice, separation of large sections of the sea ice, and disruption by storms and strong wind events. Overall, the ice pack is less unified than even 2012. So concern levels remain high for new record losses come end of summer. Much higher, in fact, than sea ice area and extent measures would typically lead one to believe.
And as for shouts of ‘recovery,’ they are hollow as the central Arctic’s sea ice.