There has been a lot of news about the Arctic sea ice going around lately. None of it has been good. But, by now, that isn't a surprise. For those who haven't been keeping track, the tally on climate change news has been overwhelmingly in favor of the bad news variety.
A new study
has come out that used an extensive amount of data from multiple sources. They used data
collected by under-ice submarines, IceBridge plane flights, satellite data and even onsite measurements made by hand. Their research led to the conclusion the thickness of sea ice has decreased by 65% between 1975 and 2012. The specific number for September, when the ice is at its least extent, is even worse. They found the September thickness had decreased by 85%
over that same time period. Not only has the extent decreased by 40% since 1980, but what is left is also 65% thinner. This means we can expect to see the rate of sea ice extent loss accelerate in the years to come. We can't be sure of the exact time table on that loss, but we can be sure it is coming.
With that in mind, I have to wonder what the data are telling us about the state of the ice right now. It appears there may be a serious problem with the ice extent.
This is a plot of the ice extent as reported by the National Snow and Ice Data Center (NSIDC):
The dark, solid line is the 1981 - 2010 average ice extent for the year. The dark, dashed line is the ice extent for 2012, the year with the record low minimum extent, which occurs in September. The purplish colored line is the extent for 2006, the year with the lowest maximum extent, which occurs in March. The blue line is the extent for this year. If you look closely, you can see the extent has been very close to a record low for the entire winter and now has turned lower. Instead of increasing extent, we are seeing decreasing extent. There are still about two weeks of ice growth season remaining, but this reduction in ice cannot be good. If we have actually passed maximum extent for the year, this would represent the smallest maximum extent ever recorded. And now, we find out it is also 65% thinner that it used to be.
In fact, the data indicate we may have already passed maximum ice extent for this year. Take a look at the ice temperature data from the Polar Portal:
I am not a fan of their selection for color distribution because it makes it difficult to judge the temperature accurately, but we can see the edge of the ice is already at, or above, the freezing point for water. That color extends well into the interior of the ice covered area. In other words, the ice is melting, not forming.
Take a look at one more graphic:
The light blue line indicates the average ice extent for this date. You can easily see just how much water area used to have ice this time of year and no longer does. In particular, look at the Gulf of Bothnia between Sweden and Finland. The blue line indicates it used to be completely frozen over. And, we're not talking about centuries ago. This is the 1979 - 2000 average. A mere three decades ago people were able to walk across that gulf, but not any more.
This data all leads me to believe we have already witnessed the sea ice maximum extent for this year. Like I said, there are still a couple of weeks to go in the season so I might be wrong. Hopefully, I am. Because if I'm right, the sea ice extent is not only much smaller this year, but it is also much thinner and we might be facing a bad melt season.
Is your graphic for the arctic sea ice extent showing the correct year?ReplyDelete
No, it wasn't. It is now. Thank you.ReplyDelete