There are three ways to keep track of the amount of sea ice in the Arctic: extent, area, and volume. Volume gives you the most useful information, in terms of how much ice is left and how fast it is diminishing, but it is also the hardest to measure accurately. To get an idea of the current conditions of Arctic ice, we can take a closer look at the ice area, a measure of the amount of water with ice cover of any thickness.
Arctic Ice By the Numbers
Bear with me—this isn’t as complicated as it looks. In the following chart, Arctic ice area levels are represented by lines of different colors for each year. Notice how, at the lowest levels, around day 244, the levels tend to fall into four groups, separated by small gaps. (Click image to enlarge):
At the lowest part of the bottom curve is 2012 by itself. Just above that is a cluster of four years, 2007, 2008, 2010 and 2011. Just above that are three years, 2009, 2013, and 2014. Above that are 2006 and all the years prior. 2015 is represented by the yellow line, which had dropped to 3.83 million km2 as of Aug 7, 2015 (day 219). As you can see, it appears to be heading toward a much lower level than 2014. It looks likely to run close to the 2007 grouping.
Meanwhile, I’m also watching the Southern Ocean, where it is mid-winter. This time last year Antarctic sea ice was approaching its all-time greatest extent. Scientists anticipate climate change induced conditions could increase the spread of ice even more, until it finally begins to succumb to warmer air and water. Here’s the current conditions there. As of this writing, the southern hemisphere sea ice area is unusually low, which means the global sea ice area is also at a near-record low. But it is the Arctic multi-year ice I find most interesting right now:
You can see how small is the area of thick ice, the parts colored orange and red. Whether or not this year is a record low for Arctic sea ice, that tells me the ice that remains is not robust. Thinner ice melts more quickly, so we are still heading toward an ice-free Arctic; not this year, nor next, but not many years in the future. I won’t say that’s another nail in our coffin, because we aren’t dead yet, but it does not portend well for our kids. Once we lose that natural air conditioning of summer Arctic ice cover, expect massive changes in our weather patterns. What we have experienced in the last few years is just a foretaste.