I’ve been monitoring Arctic ice cover via a couple of sources all summer. If you remember last year’s headlines, the record melt of the up-til-now permanent ice sheet was near the top. This summer’s ice extent hasn’t been at the all-time low that last year’s was, due to a variety of factors. That could be changing. The NSIDC has an automatically updating time-series graph of arctic sea ice extent (>15%). This year’s extent looked similar to last year’s through May and especially June. Most of July was a different story – conditions changed and the melt occurred at a more climatological rate, which is less than last year’s.
The end of July clearly shows a different story from the remainder of the month. The slope of of the time series has two identifiable inflection points – points after which the rate of decrease is greater than it was before. The area between last year’s curve is slowly closing while the area between this year’s curve and the climatological mean is growing – not the pattern we want to see for a stable, long-term Arctic ice sheet.
Last year’s record melt meant that a great deal of long-term ice had finally melted. The ice that formed over the winter had the advantage of not being snowed upon much, allowing the ice thickness to rebound to moderate levels. However, that ice was very new and therefore more susceptible to remelting, which could be what this graph is displaying.
Another thing to note from this graph: today’s current conditions (extent) is already less than the climatological mean. That’s not good news.
The melt season lasts about another month and a half or so. That’s a lot of time and if conditions remain unfavorable, this year’s ice extent could come close to matching last year’s record.
Here is another look at conditions. This map updates daily as well, so it won’t be useful for very long. So let’s look at a comparative plot of one week ago to today. And here is a comparative plot of four weeks ago to today. The rapid melt evident in the time series plot is within this time frame. That’s what ~3.5 million square kilometers of melted ice looks like. It’s about 9 Germanys. It’s about 5 Alaskas. It’s about 1 India. Imagine an ice sheet the size of the country of India melting in less than one month. That’s about 2.5 times faster than the ice normally melts, by the way.