An Update on the Arctic Sea Ice

Greg Laden — Thu, 06 Apr 2017 12:00:48 +0000

As we pass through Spring on the way to summer, the sea ice in the Arctic is starting to melt. The ice usually peaks by the end of the first week in March or so, then slowly declines for a few weeks, then by about mid-May is heading rapidly towards its likely September minimum.

With global warming the ice has been reaching a lower winter maximum, and a much lower summer maximum. This is caused by warm air and water, and it contributes to global warming. The more ice on the sea for longer, during the northern Summer, reflects away a certain amount of sunlight. With less ice, less sunlight is reflected away. This is called a “positive feedback” but it is not a “positive” thing. It is a negative thing. (But it is not a “negative feedback,” that’s something different!)

We have seen a steady, but mostly recent, decline in sea ice. For years, climate science deniers have been telling us not to worry, the Arctic ice would come back.

But it hasn’t, and it is not going to.

The National Snow and Ice Data Center keeps track of the amount of sea ice on the Arctic. They have a nifty tool that you can use to plot the data from 1979 to the most recently available information, which is generally a today or yesterday. I used that tool to make a series of graphics I’d like to share with you here. Read the captions to get the key interpretations. The bottom line: Arctic sea ice reduction has accelerated and is not showing any sign of stabilizing.

I’m reminded of a saying allegedly uttered by thoracic surgeons. The bleeding always stops. Eventually. In a similar vein, I assume the reduction of Arctic sea ice will eventually stop. Then the Dinosaurs can live in the Arctic again!.

The chart with no year by year data shown. The grey line is the “baseline” which is usually a 20 or 30 year period against which to measure each year. The grey area is the range over which almost all years occur in this baseline. Since it is two standard deviations that is about 95% of the years within the baseline period. Any year outside of that line is a significant anomaly.

These are the first ten years of available data. Notice that during this period, essentially, the 1980s, all the years are above the average for most of the year.

As we shift to the next ten year period, 1990 to 1999, the total ice cover throughout the year is less, close to the baseline average.

This trend continues in more recent years, with almost all years being below the baseline average. Remember that second graph above where all the years were above average? That shows that the baseline is set during a period of actual warming, so it is an underestimate of how much ice should be there. And now, during the period 2000 – 2009, all the years have much less ice than this.

This is the third year in a row that maximum sea ice has broken a record for being low.

Arctic Sea – Greg Laden's Blog

An Update on the Arctic Sea Ice