Tag Archives: Arctic Sea Ice Loss

Arctic Sea Ice: A System In Collapse

For the last 25 years or so there has been a decrease in the amount of ice that remains on the surface of the Arctic Ocean every summer. This is a trend that can be attributed to global warming, which in turn, can be attributed to the steady release of previously fossilized Carbon to the atmosphere by the burning of coal, oil, and natural gas. But over the last few years, this decrease in ice has been much more dramatic. The trend has steepened. The formation and melting of ice has to do with air and water temperatures. This in turn can be affected by how much ice there is, because ice reflects energy from the sun, while open water absorbs it. There are other factors as well having to do with the distribution of air masses. It is all very complicated, but the bottom line is that reduction in ice can lead to further reduction in ice. It is quite possible that the recent very steep declines in Arctic sea ice represents not just a trend that happens to be, for random reasons, a bit steeper than usual for a while, or that it is even a long term change in the rate of inter-annual loss. Rather, it could be that the phenomenon of summer sea ice in the Arctic is simply something that is no longer sustainable because of new conditions caused by climate change, and that the sea ice we see now is mainly the remnant of a previously existing, no longer operational, system. Time will tell. Probably not much time, in fact. If the recent dramatic reduction in summer ice is a random blip, then the amount of summer sea ice over the next five years or so may go up rather than down. If the recent reduction is a result of a different relationship between sun’s energy, water temperature, air temperature, and ice formation, then over the next five years or so the trend of declining ice should continue and at some point settle on a new equilibrium with variation around a new mean.

There is probably a rule of thumb that could be applied here. One of the most important Quasi-cyclic climate variations, the El Niño–Southern Oscillation (ENSO), has an average period of about 5 years. Let’s assume that a full cycle is a strong El Niño followed by opposite conditions for the same period of time. Conservatively, we might want to let a climate change in some part of the Earth’s system to run for 10 years without changing direction before we can be pretty sure that it isn’t just a perturbation that will later readjust. Consider a ten-year rule of thumb in relation to the following graphic showing Arctic sea ice from 1979-2012:

That’s a nice graph, produced by Andy Lee Robinson. Robinson created this very nice looking animation from data he had earlier depicted in a simpler two dimensional form, which actually is in some ways more dramatic (It’s a moving GIF, click to watch it move, then come back!):


The story behind these graphs, including data sources, is summarized in this post by Peter Sinclair.

In these graphics, the last seven years show sea ice surface area occurring several years in a row at a much lower average than previously, and with a steady decline continuing. But there is a strong declining trend that actually starts earlier, closer to 2002. It is a little hard to put an exact year on this. If there is a new equilibrium being reached, when we look back on these data in a decade or so, where would we start the trend? Late 1990s? 2000? 2002? 2007? Hard to say.

But there is a problem with this view of the Arctic: The sea ice that rebuilds every winter starts with a core of “old ice” which during cold trends is added to every year. This is thick ice. A huge amount of the volume of sea ice in a give year, say back in the 1970s, is actually stacked up vertically. This ice has been melting as well, and climate scientists who study the arctic regard the decline of this old ice as more important than the simple reduction in surface area. In other words, the important area here might be volume rather than surface area. Volume is harder to measure over the long period because the instrumentation needed to make good volume estimates is has not been applied to the Arctic for very long, but we do have an idea of what has happened.

Have a look at this demonstration of the importance of volume:

The following graphic and the video I just showed you are both from Andy Lee Robinson:

If we look at volume rather than surface area over time, in a graph from here, we get something like this:

Each of the colored ringoids on this graph is a decadal average of ice volume around the seasonal cycle. The drop in volume each year is a function of both decreased ice formation in the summer and decrease in volume, but the latter, volume, is driving the change you see here. Noticed that each decade has less ice volume than the previous decade. Also noice that the 2000-2009 decade is dramatically smaller in volume than the previous decades, and the last few years have at least the same amount of decrease. This shows that the dramatic drop in Arctic sea ice may be a thing that has been happening both very recently and for enough years that the 10-year rule of thumb may already apply. We’ll see what happens over the next few years.

Arctic Ice Loss

You all know that the Arctic Ice melts more each summer than ever before. In a few years, the Arctic will be ice free during the summer. The rate of annual melting is greater than expected even just a few years ago. Please note that the increasing melt of Arctic sea ice does not bode well for the associated Greenland Ice Sheet which is also showing signs of melting at a higher rate than expected. The melting of Arctic sea ice has a number of important environmental implications, but the melting of the Greenland Glacier has that plus more; it will contribute significantly to sea level rise.

Several days ago the National Environment Research Council of the UK put out some new information from the European Space Agency’s CryoSat-2 satellite program:

Arctic sea ice volume has declined by 36 per cent in the autumn and 9 per cent in the winter between 2003 and 2012, a UK-led team of scientists has discovered.

Researchers used new data from the European Space Agency’s CryoSat-2 satellite spanning 2010 to 2012, and data from NASA’s ICESat satellite from 2003 to 2008 to estimate the volume of sea ice in the Arctic.

They found that from 2003 to 2008, autumn volumes of ice averaged 11,900 km3. But from 2010 to 2012, the average volume had dropped to 7,600 km3 – a decline of 4,300 km3. The average ice volume in the winter from 2003 to 2008 was 16,300 km3, dropping to 14,800 km3 between 2010 and 2012 – a difference of 1,500 km3.

The most important thing here is the decrease in volume, which really means a decrease in thickness, of the sea ice. The ice in the Arctic partially melts every year, then refreezes. Much of the ice, in the past, never melted, and served as the base for new winter ice every year as we cycle through the seasons. But over the last few years, this “old ice” has been disappearing. This results in changes to sea temperatures, reflection of sunlight, and air temperatures which, in turn, change the nature of the northern end of the overall system of global air currents. The result of his has been a change in the relationship between more southerly air currents that are part of the process of moving heat from the equator (where the effects of the sun are stronger) towards the poles. The result of this has been a change in the nature, distribution, and typical movement patterns of cold air masses, warm air masses, and storm. Thus, extreme cold snaps in the northerly range of where people live in the Northern Hemisphere, and heat waves to the south of this, the formation of more severe northerly storm, and, apparently, the higher chance of severe North Atlantic storms slamming into highly populated areas of North America.

Here’s a video explaining one important aspect of the new findings, from Climate Nexus (Hat tip MNM)

The video is not entirely accurate. We should not forget Polar Bears! And, scientists are less hapless in their understanding of the implications of ice melt than the video suggests (see commentary above).