Global polar sea ice area in early January 2013 remains below climatological normal conditions (1979-2009), but has improved in the past month. Antarctic sea ice loss is occurring at a climatological normal rate. Arctic sea ice gain is slightly more rapid than normal, but we should expect this given the record low extent that occurred in September 2012. Polar sea ice recovered from an extensive deficit of -2.5 million sq. km. area late last year to a -500,000 sq. km. anomaly within the last week.
In March-April 2012, global sea ice area was above normal, but sea ice area anomaly quickly turned negative and then spent an unprecedented length of time near the -2 million sq. km. deficit in the modern era in 2012. Generally poor environmental conditions (warm surface temperatures and certain wind patterns) established and maintained this condition, predominantly across the Arctic last year. For the third time in modern history, the minimum global sea ice area fell below 17.5 million sq. km. and for the fourth time in modern history, the anomalous global sea ice area fell below -2 million sq. km. This is a significant development given that Antarctic sea ice area has been slightly above average during the past few years. This means that the global anomaly is almost entirely due to worsening Arctic ice conditions.
The rapid ice melt and record-setting area and extent values that occurred in 2012 are the top weather/climate story for 2012, in my opinion. I think we have clearly seen a switch to new conditions in the Arctic. Whether these events will occur in similar magnitude or are merely transitory as the Arctic continues to move to a new stable state that the climate will not achieve for years or decades remains to be seen. The problem is we don’t know all of the ramifications of moving toward or achieving that new state. Additionally, I don’t think we want to know.
According to the NSIDC, weather conditions once again caused less freezing to occur on the Atlantic side of the Arctic Ocean and more freezing on the Pacific side. Similar conditions occurred during the past six years. Sea ice creation during December measured 2.33 million sq. km. Despite this rather rapid growth, December′s extent remained far below average for the month. Instead of measuring near 13.36 million sq. km., December 2012′s extent was only 12.2 million sq. km., a 1.16 million sq. km. difference! The Barents and Kara Seas remained ice-free, which is a very unusual condition for them in December. Recent ice growth in the Seas has slightly alleviated this state, but this is happening very late in the season. The Bering Sea, which saw ice extent growth due to anomalous northerly winds in 2011-2012, saw similar conditions in December 2012. This has caused anomalously high ice extent in the Bering Sea. Temperatures over the Barents and Kara Seas were 5-9°F above average while temperatures over Alaska were 4-13°F below average. The reason for this is another negative phase of the Arctic Oscillation, which allows cold Arctic air to move southward. This allows warm sub-arctic air to move north.
In terms of longer, climatological trends, Arctic sea ice extent in December has decreased by 3.5% per decade. This rate is closest to zero in the spring months and furthest from zero in late summer/early fall months. Note that this rate also uses 1979-2000 as the climatological normal. There is no reason to expect this rate to change significantly (more or less negative) any time soon, but increasingly negative rates are likely in the foreseeable future. Additional low ice seasons will continue. Some years will see less decline than other years (like this past year) – but the multi-decadal trend is clear: negative. The specific value for any given month during any given year is, of course, influenced by local and temporary weather conditions. But it has become clearer every year that humans have established a new climatological normal in the Arctic with respect to sea ice. This new normal will continue to have far-reaching implications on the weather in the mid-latitudes, where most people live.
Arctic Pictures and Graphs
The following graphic is a satellite representation of Arctic ice as of September 17, 2012 (yes, it’s been that long since I’ve written a Polar post):
Figure 1 – UIUC Polar Research Group‘s Northern Hemispheric ice concentration from 20120917.
Here is the similar image from January 9, 2013:
Figure 2 – UIUC Polar Research Group‘s Northern Hemispheric ice concentration from 20130109.
September’s picture shows the minimum extent that occurred in 2012. You can easily see the substantial growth of sea ice since then. This comparison provides a good opportunity to point out something important: even in an epoch of anthropogenic global warming, the Arctic will continue to see wintertime sea ice. There is no solar radiation warming the surface directly and temperatures fall well below freezing for a long time. The loss of sea ice will continue to occur and will worsen significantly in the summer. That loss of ice when the sun is overhead is what climate scientists expect to drive numerous changes around the globe. Incoming solar radiation, instead of being largely reflected back out into space, will instead be mostly absorbed by a darker ocean. That radiation will stay in the Earth’s climate system as heat, which will cause many cascading effects to occur – effects we largely do not know about because we’ve never lived on a planet with missing summer sea ice at a pole.
The lack of sea ice in the Barents and Kara Seas (north of Europe and far western Russia) is problematic because wind and ocean currents typically pile sea ice up on the Atlantic side of the Arctic. Sea ice presence in the Bering Sea (between Alaska and Russia) does not alleviate this problem because currents take ice from that area and transport it into the Arctic. That sea ice will be among the first to melt completely come spring. With sea ice missing on the Atlantic side, currents will transport Arctic sea ice to southern latitudes where it melts. The possibility that January’s picture will look similar to September’s picture is therefore higher in 2013 than it was in say 1983.
Overall, the health of the remaining ice pack is not healthy, as the following graph of Arctic ice volume from the end of December demonstrates:
Figure 3 – PIOMAS Arctic sea ice volume time series through December 2012.
As the graph shows, volume (length*width*height) hit another record minimum in June 2012. Moreover, the volume is far, far outside the 2 standard deviation envelope (lighter gray contour surrounding the darker gray contour and blue median value). I understand that most readers don’t have an excellent handle on statistics, but conditions between -1 and -2 standard deviations are rare and conditions outside the -2 standard deviation threshold (see the line below the shaded area on the graph above) are incredibly rare: the chances of 3 of them occurring in 3 subsequent years under normal conditions are extraordinarily low (you have a better chance of winning your state lottery than this). Hence my assessment that “normal” conditions in the Arctic are shifting from what they were in the past few centuries; a new normal is developing. Note further that the ice volume anomaly returned to near the -1 standard deviation envelope in early 2011, early 2012, and now early 2013. In each of the previous two years, volume fell rapidly outside of the -2 standard deviation area with the return of summer. That means that natural conditions are not the likely cause; rather, another cause is much more likely to be responsible for this behavior: human influence.
Arctic Sea Ice Extent
Take a look at December’s areal extent time series data:
Figure 4 – NSIDC Arctic sea ice extent time series through early January 2013.
As you can see, the extent (light blue line) grew rapidly in October, then remained at historically low levels through November and December. The extent remained well below average values (thick gray line) throughout the fall and early winter. The time series of sea ice extent for previous low years is also shown on this graph, which is what I term NSIDC’s supplemental graph. In this month’s version, they also plotted the previous five years’ data. You can see the effect of the winter-time conditions that I described above: the difference between a year’s extent and the average value in Jan/Feb is smaller than the difference in October. This leads us to examine the differences between the historical mean, the negative two standard deviation (light gray) below that mean, and the 2012-2013 time series. I can come up with a number of adjectives to describe that difference, but I’ll settle with “stunning”.
Antarctic Pictures and Graphs
Here is a satellite representation of Antarctic sea ice conditions from September 17th:
Figure 5 – UIUC Polar Research Group‘s Southern Hemispheric ice concentration from 20120917.
And here is the corresponding graphic from January 9th:
Figure 6 – UIUC Polar Research Group‘s Southern Hemispheric ice concentration from 20130109.
Ice loss is easily visible around the continent, the more so since there is a 3+ month time difference between Figures 5 and 6. There is slightly more Antarctic sea ice today than there normally is on this date in the year. As a reminder, the difference between long-term Arctic ice loss and relative lack of Antarctic ice loss is largely and somewhat confusingly due to the ozone depletion that took place over the southern continent in the 20th century. This depletion has caused a colder southern polar stratosphere than it otherwise would be, reinforcing the polar vortex over the Antarctic Circle. This is almost exactly the opposite dynamical condition than exists over the Arctic with the negative phase of the Arctic Oscillation. The southern polar vortex has helped keep cold, stormy weather in place over Antarctica that might not otherwise would have occurred to the same extent and intensity. As the “ozone hole” continues to recover during this century, the effects of global warming will become more clear in this region, especially if ocean warming continues to melt sea-based Antarctic ice from below (subs. req’d). For now, we should perhaps consider the lack of global warming signal due to lack of ozone as relatively fortunate. In the next few decades, we will have more than enough to contend with from melting on Greenland. Were we to face melting West Antarctic Ice Sheet at the same time, we would have to allocate many more resources. Of course, in a few decades, we’re likely to face just such a situation.
Finally, here is the Antarctic sea ice extent time series from January 9th:
Figure 8 – NSIDC Antarctic sea ice extent time series through early January 2013.
Antarctic sea ice extent remained at or above average to some extent through the austral spring and early summer, which is good news.
I just read an opinion piece in Scientific American regarding the sorry state of Arctic sea ice. The author, a scientist, advocated that we do not have time to negotiate mitigation treaties. In order to save the ice, we have to research and deploy geoengineering technologies. Let me state by position on this clearly and strongly: we do not know the effects from geoengineering (solar radiation management or carbon dioxide removal) and more than the know the range and magnitude of effects from greenhouse gas emissions. Moreover, basic governance structures for geoengineering research do not currently exist, to say nothing of deployment. If you think international climate policy is complex and hasn’t moved forward quickly, you should think long and hard before advocating for geoengineering research and deployment. Single-actors are probably the biggest worry when you consider the lack of accountability if somebody conducts an experiment. The few small-scale experiments that have come close to real-world execution by national government scientists around the world caused quick and severe public outcries. The main reason for this is something that affects most scientific endeavors: the lack of effective communication with the public prior to carrying out research. Engaging the public could be viewed as surrendering power and autonomy. But I view it as a critical component to continued public funding of science and technology research.
You can find NSIDC’s January report here.