According to the NSIDC, sea ice creation during April measured 1.5 million sq. km. This melt rate was approximately normal for the month, so April′s extent remained below average again. Instead of measuring near 15 million sq. km., April 2013′s average extent was only 14.37 million sq. km., a 630,000 sq. km. difference. In terms of annual maximum values, 2013′s 15.13 million sq. km. was 733,000 lower than normal.
Barents Sea (Atlantic side) ice once again fell from its climatological normal value during the month after remaining low during most of the winter. Kara Sea (Atlantic side) ice temporarily recovered from its wintertime low extent and reached normal conditions, which is also different from spring 2012′s conditions, before 2013 melt caused the extent to fall below normal conditions again. The Bering Sea (Pacific side), which saw ice extent growth due to anomalous northerly winds in 2011-2012, saw similar conditions in December 2012 through February 2013. This caused anomalously high ice extent in the Bering Sea again this winter. As it did previously this winter, an extended negative phase of the Arctic Oscillation allowed cold Arctic air to move far southward and brought warmer than normal air to move north over parts of the Arctic. The AO’s tendency toward its negative phase in recent winters is related to the lack of sea ice over the Arctic Ocean in September each fall. Warmer air slows the growth of ice, especially ice thickness. This slow growth allows more melt than normal during the subsequent summer, which helps establish and maintain negative AO phases. This is a destructive annual cycle for Arctic sea ice.
In terms of climatological trends, Arctic sea ice extent in April has decreased by 2.3% per decade, the lowest of any calendar month. This rate is closest to zero in the late winter/early 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 (much 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 (e.g., 2011) – 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.
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 than normal this winter. Similar conditions occurred during the past six boreal winters. Sea ice creation during February measured 766,000 sq. km. Despite this rather rapid growth (38% higher than normal), February′s extent remained well below average for the month. Instead of measuring near 15.64 million sq. km., February 2013′s average extent was only 14.66 million sq. km., a 980,000 sq. km. difference! The Arctic likely reached its maximum annual extent about 10 days ago. In terms of annual maximum values, 2013′s 15.13 million sq. km. was 733,000 lower than normal.February’s relatively high rate of ice formation for February related to the lack of existing sea ice at the beginning of the month. Without ice already in the Ocean, new ice formed as winter continued.
Barents Sea (Atlantic side) ice finally edged toward its climatological normal value during the month after remaining low this winter, as it did in the past 10 winters. Kara Sea (Atlantic side) ice recovered from low extent the past couple of months, which is different from February 2012′s conditions. The Bering Sea (Pacific side), which saw ice extent growth due to anomalous northerly winds in 2011-2012, saw similar conditions in December 2012 through February 2013. This caused anomalously high ice extent in the Bering Sea again this winter. As it did previously this winter, a negative phase of the Arctic Oscillation allowed cold Arctic air to move far southward and brought warmer than normal air to move north over parts of the Arctic. The AO’s tendency toward its negative phase in recent winters is related to the lack of sea ice over the Arctic Ocean in September each fall.
In terms of climatological trends, Arctic sea ice extent in February has decreased by 2.9% per decade, the lowest of any calendar month. This rate is closest to zero in the late winter/early 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 (much 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 (e.g., 2011) – 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 February 11, 2013:
As is normal for this time of year, there is not a large difference between these two graphics. Any differences are primarily due to storm systems’ presence that push ice around, or the lack thereof. The lack of sea ice in the Barents Sea (north of Europe) 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 and then out into the Atlantic. The sea ice on the Atlantic side would be among the first that currents transport and then melt during the spring. With sea ice missing on the Atlantic side, currents will more easily transport Arctic sea ice to southern latitudes where it melts.
Many people questioned the overall health of the Arctic ice pack earlier this month when images (like the one below) and video documented extensive cracks in the ice in the Chukchi and Beaufort Seas. A fellow blogger (and new author!) emailed me about this phenomenon and I wrote that I would blog my thoughts on the topic. As Andrew Freedman wrote, “According to the National Snow and Ice Data Center (NSIDC) in Boulder, Colo., this fracturing event appears to be related to a storm that passed over the North Pole on Feb. 8, 2013, creating strong off-shore ice motion. The event is unusual but not unheard of, as similar patterns were seen in early 2011 and 2008. However, the NSIDC said the fracturing this time is more extensive.” The worry is the extent and size of the cracks and leads as well as the early calendar date at which they are all appearing – up to weeks before normal.
I found this article on the topic and agree with Greg Laden, the author. The cracks and leads might be a big deal or they might not. We will have to wait until the minimum sea ice extent occurs in September before we issue judgment. The scientifically sound course of action would be to wait until early cracks appeared in multiple seasons and then see what the range of response later in the year is. For all we know, the cracks could allow for even more ice to form in March than normal and delay the onset of melting. It strikes me as scientifically unsound and even irresponsible to conjecture about the existence and effect of processes, which we do not understand well. If scientists crow about upcoming devastating Arctic sea ice loss this year and reality doesn’t conform to their wishes, how much credibility with the public do they engender? I think observers should stay patient and discuss the phenomena and effects we do understand – there is plenty of material with which to work!
Figure 3 – NOAA AVHRR infrared picture of Arctic sea ice on 20130312.
The following graph of Arctic ice volume from the end of February demonstrates:
Figure 4 – PIOMAS Arctic sea ice volume time series through February 2013.
As the graph shows, volume (length*width*height) hit another record minimum in June 2012. Moreover, the volume remains far from normal since it just returned to the -2 standard deviation envelope (light gray). 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 the Powerball 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 February’s areal extent time series data:
Figure 5 – NSIDC Arctic sea ice extent time series through late March 2013 compared with last five years’ data and climatological norm (dark gray line) and standard deviation envelope (light gray).
As you can see, this year’s extent (light blue cuve) grew more rapidly in December than February. This graph also shows that this year’s extent remained at historically low levels through the winter, well below average values (thick gray curve), just as it did in the previous five winters, which are also shown on this graph. In this month’s version, NSIDC also plotted the previous four years’ data (2008 through 2012). You can also see what happened to conditions during late March and early April last spring (dark green curve). A late season freeze surge occurred, which delayed the date of maximum extent by a number of weeks. Last year’s surge has no bearing on what might happen over the next couple of weeks this year. Weather conditions and some low-frequency climate oscillations (AO) are different this year and have more bearing on ice conditions than last year’s date of maximum extent.
Antarctic Pictures and Graphs
Here is a satellite representation of Antarctic sea ice conditions from February 11, 2013:
Ice growth is easily visible around the continent. There is more Antarctic sea ice today than there normally is on this date in the year. The reason for this is the extra ice in the Weddell Sea (east of the Antarctic Peninsula that juts up toward South America). This ice exists this austral summer due to an anomalous atmospheric circulation pattern: persistent high pressure west of the Weddell sea pushed sea ice north. The same winds that pushed the sea ice north also moved cold Antarctic air over the Sea, which has kept ice melt rate well below normal. A similar mechanism helped sea ice form in the Bering Sea so far this winter. Where did the anomalous winds come from? We can again point to a climatic relationship.
The difference between the noticeable and significant 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. The vortex and associated anomalous high pressure centers kept ice and cold air over places such as the Weddell Sea this year.
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). The strong Antarctic polar vortex will likely weaken back to a more normal state and anomalous high pressure centers that keep ice flowing into the ocean will not form as often. 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 Greenland ice sheet melt. Were we to face a 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 through mid-March:
Given the lack of climate policy development to date, Arctic conditions will likely continue to deteriorate for the foreseeable future. The Arctic Ocean will soak up additional energy (heat) from the Sun due to lack of reflective sea ice. Additional energy in the climate system creates cascading and nonlinear effects throughout the system. For instance, excess energy pushes the Arctic Oscillation to a more negative phase, which allows anomalously cold air to pour south over Northern Hemisphere land masses while warm air moves over the Arctic during the winter. This in turn impacts weather patterns throughout the year across the mid-latitudes.
More worrisome for long-term concerns is the heat that impacts land-based ice. As glaciers and ice sheets melt, sea-level rise occurs. Beyond the increasing rate of sea-level rise due to thermal expansion (excess energy, see above), storms have more water to push onshore as they move along coastlines. We can continue to react to these developments as we’ve mostly done so far and allocate billions of dollars in relief funds because of all the human infrastructure lining our coasts. Or we can be proactive, minimize future global effects, and reduce societal costs. The choice remains ours.
Errata
Here are my State of Polar Sea Ice posts from February and January 2013. For further comparison, here is my State of Polar Sea Ice post from March 2012.
Update
I meant to include the following two graphs in this post because of the historical nature they represent.
The difference between these two graphics is obvious since they were taken near the time of minimum area (2012) and maximum area (2013). In terms of magnitude, the freeze season of 2012-2013 produced the highest amount of frozen ice area in the modern record (11.168 million sq. km.). The value of ice area last September was the lowest on record and the value of ice area earlier this month was the highest in four years. March’s area value occurred because of the factors I discussed above that boil down to this: the relative lack of thick ice in recent winters permitted rapid ice growth, albeit thin ice that melts quickly the following year. In addition to new record low area values in the future, significant oscillations from minimum to maximum and back again are likely to occur in the future as well. This does not contradict climate change; it is a manifestation of climate change. I hope write more about this topic soon, but countries are reconstructing international policy (military and economic) as a result of the changes seen in the Arctic. Those policy shifts will have societal repercussions, which I venture say few people realize today.
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 than normal. Similar conditions occurred during the past six boreal winters. Sea ice creation during January measured 1.36 million sq. km. Despite this rather rapid growth, January′s extent remained well below average for the month. Instead of measuring near 14.84 million sq. km., January 2013′s extent was only 13.78 million sq. km., a 1.06 million sq. km. difference! The Barents Sea recorded lower than average sea ice, which is an unusual condition for January. Kara Sea ice recovered from low extent the past couple of months. The Bering Sea, which saw ice extent growth due to anomalous northerly winds in 2011-2012, saw similar conditions in December 2012 and January 2013. This has caused anomalously high ice extent in the Bering Sea. Previously this winter, a negative phase of the Arctic Oscillation allowed cold Arctic air to move far southward and brought warmer than normal air to move north over parts of the Arctic. The AO has returned to a more neutral phase in the past month, which has kept Arctic air closer to where it normally is this time of year.
In terms of longer, climatological trends, Arctic sea ice extent in January has decreased by 3.2% 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 (e.g., 2011) – 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 January 9, 2013:
The lack of sea ice in the Barents Sea (north of Europe) 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 more easily transport Arctic sea ice to southern latitudes where it melts.
Overall, the health of the ice pack is not healthy, as the following graph of Arctic ice volume from the end of January demonstrates:
Figure 3 – PIOMAS Arctic sea ice volume time series through January 2013.
As the graph shows, volume (length*width*height) hit another record minimum in June 2012. Moreover, the volume remains far from normal since it just returned to the -2 standard deviation envelope (light gray). 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 the Powerball 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 January’s areal extent time series data:
As you can see, the extent (light blue line) grew rapidly in November but still remained at historically low levels through the winter. 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. In this month’s version, NSIDC also plotted the previous four years’ data. You can see the effect of the wintertime conditions that I described above: the difference between a year’s extent and the average value in January or February 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.
Antarctic Pictures and Graphs
Here is a satellite representation of Antarctic sea ice conditions from January 9, 2013:
Ice loss is easily visible around the continent. There is slightly more Antarctic sea ice today than there normally is on this date in the year. The reason for this is the extra ice in the Weddell Sea (east of the Antarctic Peninsula that juts up toward South America). This ice exists this winter due to an anomalous atmospheric circulation pattern: persistent high pressure west of the Weddell sea pushed sea ice north. The same winds that pushed the sea ice north also moved cold Antarctic air over the Sea, which has kept ice melt rate well below normal. A similar mechanism helped sea ice form in the Bering Sea so far this winter.
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 February 11th:
Given the lack of climate policy development to date, Arctic conditions will likely continue to deteriorate for the foreseeable future. The Arctic Ocean will soak up additional energy from the Sun due to lack of reflective sea ice. Additional energy in the climate system creates cascading effects through the system. The energy pushes the Arctic Oscillation to a negative phase, which allows anomalously cold air to pour south over Northern Hemisphere land masses while warm air moves over the Arctic. This impacts weather patterns throughout the year.
More worrisome for long-term concerns is the heat that impacts land-based ice. As glaciers and ice sheets melt, sea-level rise occurs. Beyond the increasing rate of sea-level rise, storms have more water to push onshore as they move along coastlines. We can continue to react to these developments as we’ve mostly done so far. Or we can be proactive, minimize future global effects, and reduce societal costs. The choice remains ours.
Errata
Here are my State of the Poles posts from January and September.
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.
Arctic Ice
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):
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:
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:
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:
Antarctic sea ice extent remained at or above average to some extent through the austral spring and early summer, which is good news.
Policy
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.
Errata
Here are my State of the Poles posts from September and July.
Judging by recent search terms used to get to this blog and the relative recent peak in traffic, readers have been searching for this post. I wanted to wait a little longer into the month so that I could capture the expected Arctic minimum, which officially occurred on the 16th of September. The NSIDC announced this date, after which I started gathering the plots that are found below. This post will be longer than it usually is because this year’s minimum shattered the record minimum set in 2007, which shattered the previous record set in 2005. Most of the post is made up of figures, so I encourage readers to at least view them to get a good picture of today’s conditions. I’m purposefully framing things this way to relay the truly stunning situation the Arctic is in today. 2012 is additional proof the Arctic cryosphere is searching for a new stable point, but hasn’t found it yet. That does not bode well for the rest of the globe. With that, let’s begin.
The state of global polar sea ice area in mid-September 2012 remains significantly below climatological normal conditions (1979-2009). Arctic sea ice loss is solely responsible for this condition. In fact, if Antarctic sea ice were closer to its normal value, the global area would be much lower than it is today. Arctic sea ice melted quickly in August and the first half of September because it was thinner than usual and winds helped push ice out of the Arctic where it could melt at lower latitudes; Antarctic sea ice has refrozen at a faster than normal rate during the austral winter. Polar sea ice recovered from an extensive deficit of -2 million sq. km. area late last year to a +750,000 sq. km. anomaly in March 2012 before falling back to a -2.2 million sq. km. deficit earlier this month.
After starting the year at a deficit from normal conditions, sea ice area spent an unprecedented length of time near the -2 million sq. km. deficit in the modern era in 2011 (i.e., almost the entire calendary year). Generally poor environmental conditions (warm surface temperatures and certain wind patterns) established and maintained this condition, predominantly across the Arctic last year. The last time global sea ice area remained near 19 million sq. km. during May was in 2007, when the Arctic extent hit its modern day record minimum. The maximum in the boreal spring the past two years was ~19.5 million sq. km.
Conditions were prime for another modern-day record sea ice extent minimum to occur in September. Specific weather conditions helped to determine how 2012′s extent minimum ranks compared to the last 33 years, but it was the overall poor condition of Arctic sea ice that contributed to this year’s record low values.
The state of global polar sea ice area in early August 2012 remains significantly below climatological normal conditions (1979-2009). Arctic sea ice loss is solely responsible for this condition during this boreal summer. Arctic sea ice melted quickly in July because it was thinner than usual and winds helped push ice out of the Arctic where it could melt at lower latitudes; Antarctic sea ice has refrozen at a slightly above normal rate during the austral winter. Polar sea ice recovered from an extensive deficit of -2 million sq. km. area late last year to a +750,000 sq. km. anomaly in March 2012 before falling back to a -1.8 million sq. km. deficit.
After starting the year at a deficit from normal conditions last year, sea ice area spent an unprecedented length of time near the -2 million sq. km. deficit in the modern era in 2011. Generally poor environmental conditions (warm surface temperatures and certain wind patterns) established and maintained this condition, predominantly across the Arctic last year. Conditions were slightly “better” than they were in 2007 or even in 2011 during July. As we know from past experience, that can change rather quickly as Arctic sea ice melts in August and early September on its way to its yearly minimum.
Conditions are prime for another modern-day record sea ice extent minimum to occur in early September. Specific weather conditions over the next month will determine how 2012′s extent minimum ranks compared to the last 33 years. There is a very impressive low pressure system currently in the Arctic Ocean; a strong storm that normally doesn’t occur in July/August. This might seem at first to indicate that sea ice melt might not occur, but the energy being exerted on the ocean and ice is actually more likely to assist in ice melt. This is because of the turbulent motion imparted on the ocean by the storm’s winds, which repeatedly submerge ice in warmer water. The winds also bring warmer sub-surface water up to the surface. After the storm clears and within the following week, we shall see what effects the storm had on the thin Arctic ice. The concentration maps below in particular will take a few days to report the effect – they are five-day averages of measurements so that spurious data do not unduly affect ice condition assessment.
Arctic Ice
According to the NSIDC, the weather conditions that caused less freezing to occur on the Atlantic side of the Arctic Ocean and more freezing on the Pacific side shifted in late spring/early summer this year to conditions that aided rapid melting across the Arctic – a continuation of similar events in the past six years. Sea ice melt during July was not the fastest on record: 2.97 million sq. km. vs. 3.53 million sq. km. in July 2007! Still, July′s extent was far below average for the month, as some of the graphs below demonstrate. In fact, the extent set multiple daily record lows in July, as shown by one of the graphs below. Arctic sea ice extent on in July averaged 7.94 million sq. km. Ice in the Laptev, East Siberian and Kara Seas remained very much below normal, themselves setting daily record lows during July. The Bering Sea, which saw ice extent growth due to anomalous northerly winds in the late winter/early spring witnessed the record high extent melt back to zero in an extremely short time period earlier this year. The NSIDC included the following in their analysis:
Temperatures at the 925 hPa level (about 3,000 feet above the ocean surface) were typically 1 to 3 degrees Celsius (1.8 to 5.4 degrees Fahrenheit) above the 1981 to 2010 average over the Beaufort Sea and regions to the north, as well as over Baffin Bay. By contrast, temperatures were 1 to 3 degrees Celsius below average over the Norwegian Sea.
In terms of longer, climatological trends, Arctic sea ice extent in July has decreased linearly by 7.1% per decade. This rate is lowest in the spring months and highest 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. 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: significantly 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 helped establish a new 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 July 7, 2012:
Figure 1 – UIUC Polar Research Group‘s Northern Hemispheric ice concentration from 20120707.
Compare this with August 6th’s satellite representation, also centered on the North Pole:
The sea ice in the Canadian archipelago and along the northern coast of Russia determine whether the Northwest and Northeast passages open up or not. You can see by comparing the two graphs that the ice is nearly completely melted in the Canadian archipelago. The ice is also mostly melted along the entire northern coast of Russia – just a little remains in the Eastern Siberian sea. Last year, both passages opened again. I continue to think that the Northern Passage will likely open sometime this month. The Northeastern Passage might not open this year, but if it doesn’t, it won’t do so by a thin margin. You can also see in Figure 2 that the dominant wind direction has been toward Greenland. This allows ice to stack up against a landmass and not be exported as quickly out into the Atlantic Ocean where it is likelier to melt. The aforementioned Arctic Ocean storm has shifted wind direction somewhat across the basin, so I don’t expect all of the ice in Figure 2 to remain come September.
Overall, the health of the remaining ice pack is not healthy, as the following graph of Arctic ice volume from the end of July demonstrates:
Figure 3 – PIOMAS Arctic sea ice volume time series through July 2012.
As the graph shows, volume 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). Figure 3 demonstrates how anomalous conditions are for sea ice in the Arctic. The volume has exceed the -4 standard deviation this year as well as the past two years. I understand that most readers don’t have an excellent handle on statistics, but conditions between -1 and -2 standard deviations are not very common; 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. 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 after conditions returned to near the -1 standard deviation envelope in late 2011/early 2012, as it did in early 2011, volume has once again fallen rapidly outside of the -2 standard deviation area. That means that natural conditions are not the likely cause; rather, another cause is much more likely to be responsible for this behavior.
I found a new graph that shows this and some additional information in a slightly different way:
Figure 4 – PIOMAS Arctic Sea Ice Volume from 1980 through July 2012.
This figure shows volume as a function of date. 2012 is the red curve, which is plotted against the average volume of 2010 through July 2012 (yellow), the average volume of the 2000s (green), the average volume of the 1990s (blue), and the average value of the 1980s (violet). Individuals years from 1979-2011 are indicated by the light gray curves. It is once again clear how anomalous recent conditions are compared to conditions from the latter part of the 20th century. It further shows how rapidly conditions have changed: the volume differences implied by this graph are astounding. The minimum volume typically occurs in early September, which we are approaching again in 2012.
Switching back from volume to area, take a look at July’s areal extent time series data:
This is the time series graph that the NSIDC occasionally includes in their monthly reports. I present only this graph and not the graph updated daily throughout the month because of the historical context this graph provides. The ice that piled up in the winter wasn’t thick enough to prevent rapid melt to occur (see early June 2012). The effect of the thickening over the winter on September’s minimum extent will indicate how helpful the early season winds were in building sea ice that doesn’t melt every year back up. Right now, the situation doesn’t look good for September extent. During June, as I wrote above, melting occurred at record rate, resulting in a return to record low extent conditions by the middle of June. 2012′s extent has been below 2007′s for over two months and has been challenging all-time daily record minimums for almost two months. You can also see in this time series graph that conditions since 2007 have clearly differed from the normal conditions established from 1979-2000 (light gray contours surrounding the dark gray mean value).
Figure 6 – NSIDC northern hemisphere sea ice area (not extent) from the past two years only (blue) and the 1979-2008 mean (gray). The red curve shows the anomaly from the mean.
Note in Figure 6 how low the sea ice area is in the beginning of August 2012: -2.157 million sq. km.! Note two additional things. 1) The 2012 area value already is less than the climatological mean value by ~1.5 million sq. km. 2) The 2012 area value is only ~0.5 million sq. km. higher than the minimum recorded in 2011. The area value has slid just slightly under 3 million sq. km. only twice before: 2007 and 2011. Unless weather conditions change radically in the next couple of weeks, 2012 is also very likely to witness another sea ice area value under 3 million sq. km. The link above also shows that sea ice area was lower than 4 million sq. km. only during the past 5 years. Back in the 1980s, the area didn’t fall beneath 5 million sq. km. except for two years (1984, 1989). This is simply another way of noting that the Arctic environment has changed substantially in the past generation. One more note about the anomaly value (-2.157 here): 2007′s lowest anomaly currently ranks as the modern-day record: -3.6 million sq. km. 2012′s anomaly value is obviously far away from that, but has spent the most time below -2 million sq. km. than any year except 2007.
Antarctic Pictures and Graphs
Here is a satellite representation of Antarctic sea ice conditions from July 7th:
Ice gain is less easily visible around the continent than it was a few months ago. As a reminder, the difference between long-term Arctic ice loss and 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. That 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. For now, we should perhaps consider the lack of global warming signal due to lack of ozone as relatively fortunate.
Finally, here is the Antarctic sea ice extent time series from August 6th:
Antarctic sea ice extent had remained at or above average to some extent through the late austral fall and through the austral winter, which is good news. The difference in conditions from the first part of 2011 to the similar time period in 2012 is obvious: NSIDC measured last July’s extent near the bottom of the standard deviation envelope while this year’s extent is much healthier.
Errata
Here are my State of the Poles posts from July and June.
The state of global polar sea ice area in early July 2012 has once again fallen significantly below climatological normal conditions (1979-2009). Arctic sea ice loss is solely responsible for this change in condition since last month. Arctic sea ice melted quickly in June because it was thinner than usual and winds helped push ice out of the Arctic where it could melt at lower latitudes; Antarctic sea ice has refrozen at a near normal rate during the late austral autumn and early austral winter. Polar sea ice recovered from an extensive deficit of -2 million sq. km. area late last year to a +750,000 sq. km. anomaly in March 2012 before falling back to a -1.8 million sq. km. deficit.
After starting the year at a deficit from normal conditions last year, sea ice area spent an unprecedented length of time near the -2 million sq. km. deficit in the modern era in 2011. Generally poor environmental conditions (warm surface temperatures and certain wind patterns) established and maintained this condition, predominantly across the Arctic last year. The last time global sea ice area remained near 19 million sq. km. through May was in 2007, when the Arctic extent hit its modern day record minimum. The maximum in the boreal spring the past two years was ~19.5 million sq. km.
Conditions are prime for another modern-day record sea ice extent minimum to occur in September. Specific weather conditions over the next two months will determine how 2012′s extent minimum ranks compared to the last 33 years.
Arctic Ice
According to the NSIDC, the weather conditions that caused less freezing to occur on the Atlantic side of the Arctic Ocean and more freezing on the Pacific side shifted in late spring/early summer this year to conditions that aided rapid melting across the Arctic – a continuation of similar events in the past six years. Sea ice melt during June was the fastest on record: 2.86 million sq. km.! As such, June′s extent was far below average for the month. In fact, the extent set multiple daily record lows in June, as one of the graphs below will show. Arctic sea ice extent on in June averaged 10.97 million sq. km. Barents and Kara Sea ice remained very much below normal, themselves setting daily record lows during June. Additional areas, such as the Hudson Bay and the Laptev Sea are also now experiencing anomalously low extent conditions. The Bering Sea, which saw ice extent growth due to anomalous northerly winds in the late winter/early spring witnessed the record high extent melt back to zero in an extremely short time period. Overall, near surface temperatures were warmer than average (by 1.8 to 7.2F at the 925hPa level) across the Arctic Ocean.
In terms of longer, climatological trends, Arctic sea ice extent in June has decreased by 3.7% per decade. This rate is lowest in the spring months and highest 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. 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 helped establish a new 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 June 7, 2012:
The sea ice in the Bering Sea, as mentioned above, completely melted due to the ice’s young age and thin depth. What remained missing last winter and early spring was the sea ice north of Scandinavia. This is the result of anomalously warm waters from the Gulf Stream being drawn further north than is normal. This is due to the positive AO index & NAO index during the last boreal winter and spring. As a side note, this phenomenon combined with the most recent, moderate La Niña in the Pacific Ocean has led to Dec-Jun being anomalously warm and dry for most of the U.S. Indeed, this year has been the warmest Jan-Jun period on record in the US, as I will detail in a separate post. These conditions were joined by anomalously warm conditions along the Arctic coast on three continents. Those conditions helped melt the ice near the coast more rapidly than is normal.
The sea ice in the Canadian archipelago and along the northern coast of Russia determine whether the Northwest and Northeast passages open up or not. Last year, both passages opened again. What will happen in 2012? Given today’s information, I would venture a guess that they will be open.
Overall, the health of the remaining ice pack is not healthy, as the following graph of Arctic ice volume from the end of June demonstrates:
Figure 3 – PIOMAS Arctic sea ice volume time series through May 2012.
As the graph shows, volume hit another record minimum in June. 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. 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 after conditions returned to near the -1 standard deviation envelope in late 2011/early 2012, as it did in early 2011, volume has once again fallen rapidly outside of the -2 standard deviation area. That means that natural conditions are not the likely cause; rather, another cause is much more likely to be responsible for this behavior.
Switching back from volume to area, take a look at June’s areal extent time series data:
As you can see, the extent in April briefly matched average conditions before a relatively warm spell melted ice quickly in mid-April. The ice that piled up in the winter wasn’t thick enough to prevent rapid melt to occur. The effect of the thickening over the winter on September’s minimum extent will indicate how helpful the early season winds were in building sea ice that doesn’t melt every year back up. Right now, things don’t look good for September extent. During June, as I wrote above, melting occurred at record rate, resulting in a return to record low extent conditions by the middle of June. 2012′s extent has been below 2007′s for about one month now. In fact, the melt of early June began the day after I posted my last State of the Poles post.
Occasionally, I also like to include a supplemental time series graph that the NSIDC report contains. Here is this month’s supplemental graph:
This graph contains all of the same data as the previous graph and adds the time series lines from the previous 4 years. As you can see, extent varies during the same month from year to year. The recent record decline in extent, caused laregly by a change in wind direction and speed, has reduced Arctic ice extent back to ~11 million sq. km., which is far below normal for June. The past two years also saw somewhat similar reductions through June, although the starting values were obviously different. Despite these differences in subsequent years, the minimum ice extent values were quite similar: at or near the record daily lows set in 2010. Will fall 2012 be any different or will the surge in ice growth on the Pacific side of the Arctic help to stave off the worst effects seen in the past five years?
Antarctic Pictures and Graphs
Here is a satellite representation of Antarctic sea ice conditions from June 7th:
Ice gain is less easily visible around the continent than it was the past couple of months. As a reminder, the difference between long-term Arctic ice loss and 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. That 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. For now, we should perhaps consider the lack of global warming signal due to lack of ozone as relatively fortunate.
Finally, here is the Antarctic sea ice extent time series from July 7th:
Antarctic sea ice extent had remained at or above average to some extent through the austral fall and early winter, which is good news. The difference in conditions from the first part of 2011 to the similar time period in 2012 is obvious: NSIDC measured last year’s extent near the bottom of the standard deviation envelope while this year’s extent is much healthier. Despite the shift in preceding conditions, extent in June 2012.
Errata
Here are my State of the Poles posts from June and May .
The state of global polar sea ice area in early June 2012 has once again fallen below climatologically normal conditions (1979-2009). Arctic sea ice loss is primarily responsible for this change in condition since just last month. Arctic sea ice melted quickly in May because it was thinner than usual; Antarctic sea ice has refrozen at a near normal rate during the late austral autumn. Polar sea ice recovered from an extensive deficit of -2 million sq. km. area three months ago to a +750,000 sq. km. anomaly one to two months ago before falling back to a -1 million sq. km. deficit. After starting the year at a deficit last year, sea ice area spent an unprecedented length of time near the -2 million sq. km. deficit in the modern era in 2011. Generally poor environmental conditions established and maintained this condition, predominantly across the Arctic last year. The last time global sea ice area remained near 19 million sq. km. through May was in 2007, when the Arctic extent hit its modern day record minimum.
Arctic Ice
According to the NSIDC, weather conditions during the latter part of the previous winter and spring were less conducive for Arctic sea ice freezing on the Atlantic side of the Arctic while conditions were more conducive than usual for freezing on the Pacific side. Sea ice melt during May was more than normal: 1.62 million sq. km. instead of 1.38 million sq. km. As such, May′s extent was below average for the month in the satellite record. Arctic sea ice extent on in May averaged 13.13 million sq. km. Barents and Kara Sea ice remained very much below normal, more so than in recent years. The Bering Sea, which saw ice extent growth due to anomalous northerly winds in previous months, instead witnessed above normal conditions. Overall, near surface temperatures were warmer than average across the Arctic Ocean.
In terms of longer, climatological trends, Arctic sea ice extent in May has decreased by -2.3% per decade. This rate is lowest in the spring months than the late summer 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. 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 are establishing a new 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 April 28, 2012:
The sea ice in the Bering Sea, as mentioned above, formed more quickly and to a further southern extent than is normally seen, but has largely melted already due to the ice’s young age and thin depth. What remained missing this winter and early spring was the sea ice north of Scandinavia. This is the result of anomalously warm waters from the Gulf Stream being drawn further north than is normal. This is due to the positive AO index & NAO index during the last boreal winter and spring. As a side note, this phenomenon combined with the most recent, moderate La Niña in the Pacific Ocean has led to Dec-May being anomalously warm and dry for most of the U.S. Indeed, this year has been the warmest Jan-May period on record in the US, as I will detail in a separate post.
Overall, the health of the remaining ice pack is not healthy, as the following graph of Arctic ice volume from the end of May demonstrates:
Figure 3 – PIOMAS Arctic sea ice volume time series through May 2012.
As the graph shows, volume hit a record minimum earlier in 2011 before returning to the -2 standard deviation envelope. 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 2 of them occurring in 2 subsequent years under normal conditions are very, very remote indeed. Hence my assessment that “normal” conditions in the Arctic are shifting from what they were in the past few centuries. Note further that after conditions returned to near the -1 standard deviation envelope in late 2011/early 2012, volume has once again fallen rapidly outside of the -2 standard deviation area. The chances that this would happen three separate times in three consecutive years is exceptionally remote. That means that natural conditions are not the likely cause; rather, another cause is much more likely to be responsible for this behavior.
Switching back from volume to area, take a look at May’s areal extent time series data:
This winter allowed the extent to do something it had not done for the most recent handful of winters: a return of ice extent to within the -2 standard deviation envelope. Indeed, the extent in April briefly matched average conditions before a relatively warm spell melted ice quickly in mid-April. The reason for this is a shift in wind conditions: speed and direction both changed from late winter through this last month. Those winds piled sea ice up instead of pushing it apart. The disadvantage: ice extent decreased, as seen in Figure 4. The advantage: ice volume grew, as seen in Figure 3. The effect on this September’s minimum extent will indicate how helpful the early season winds were in building sea ice that doesn’t melt every year back up. During May, as I wrote above, melting occurred at a slightly faster rate than normal, resulting in a return to near-record low extent conditions.
Occasionally, I also like to include a supplemental time series graph that the NSIDC report contains. Here is this month’s supplemental graph:
This graph contains all of the same data as the previous graph and adds the time series lines from the previous 5 winters. As you can see, extent varies during the same month from year to year. The recent decline in extent, caused by a change in wind direction and speed, has reduced Arctic ice extent back to ~13 million sq. km., which is well below normal for May. The past three winters also saw similar magnitude reductions through May, although the starting and ending values were obviously different. Despite these differences in subsequent years, the minimum ice extent values were quite similar: at or near the record low set in 2007. Will fall 2012 be any different or will the surge in ice growth on the Pacific side of the Arctic help to stave off the worst effects seen in the past five years?
Antarctic Pictures and Graphs
Here is a satellite representation of Antarctic sea ice conditions from April 28th:
Ice gain is easily visible around the continent. As a reminder, this 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. That 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. For now, we should perhaps consider the lack of global warming signal due to lack of ozone as relatively fortunate.
Finally, here is the Antarctic sea ice extent time series from June 7th:
Antarctic sea ice extent had remained above average to some extent through the austral summer and early spring, which is good news. The difference in conditions from the first part of 2011 to the similar time period in 2012 is obvious: NSIDC measured last year’s extent near the bottom of the standard deviation envelope while this year’s extent is much healthier. Despite the shift in preceding conditions, extent in May 2011 and 2012 returned to normal.
Errata
Here are my State of the Poles posts from May and March.
The state of global polar sea ice area in early May 2012 has convincingly returned to climatologically normal conditions (1979-2009). Arctic sea ice recovered to near-normal conditions after a late start to the freeze season and a late-season slowdown due to certain atmospheric and oceanographic conditions; Antarctic sea ice has melted only slightly more slowly than is normal during the austral autumn. Put another way, polar sea ice has recovered from an extensive deficit of -2 million sq. km. area a couple of months ago to a +750,000 sq. km. anomaly today. That said, sea ice area spent an unprecedented length of time near the -2 million sq. km. deficit in the modern era in 2011. Generally poor environmental conditions established and maintained this condition, predominantly across the Arctic last year.
Arctic Ice
According to the NSIDC, weather conditions this winter and early spring were slightly less conducive for Arctic sea ice freezing on the Atlantic side of the Arctic while conditions were more conducive than usual for freezing on the Pacific side. Melting during April was slightly less than normal: 1.07 million sq. km. instead of 1.21 million sq. km. As such, April′s extent was the near average for the month in the satellite record. Arctic sea ice extent on in April averaged 14.73 million sq. km. Barents Sea ice remained below normal, as it did in recent years. The Bering Sea, which saw ice extent growth due to anomalous northerly winds in previous months, instead witnessed more normal conditions. Overall, near surface temperatures were warmer than average across the Arctic Ocean.
In terms of longer, climatological trends, Arctic sea ice extent in April has decreased by -2.6% per decade. This rate is lowest in the winter months than the late summer 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. 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 are establishing a new 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 March 9, 2012:
Once Hudson Bay finally froze over around the time of the New Year, ice extent grew toward the Atlantic Ocean. The sea ice in the Bering Sea, as mentioned above, formed more quickly and to a further southern extent than is normally seen. What remained missing this winter and early spring is the sea ice north of Scandinavia. This is the result of anomalously warm waters from the Gulf Stream being drawn further north than is normal. This is due to the positive AO & NAO indices during this winter. As a side note, this phenomenon combined with the moderate La Nina in the Pacific Ocean has led to Dec-Apr being an anomalously warm and dry month for most of the U.S. in March and April.
Overall, the health of the remaining ice pack is not healthy, as the following graph of Arctic ice volume from the end of April demonstrates:
Figure 3 – PIOMAS Arctic sea ice volume time series through April 2012.
As the graph shows, volume hit a record minimum earlier in 2011 before returning to the -2 standard deviation envelope. 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 2 of them occurring in 2 subsequent years under normal conditions are very, very remote. Hence my assessment that “normal” conditions in the Arctic are shifting from what they were in the past few centuries.
Switching back from volume to area, take a look at April’s areal extent time series data:
This winter allowed the extent to do something it had not done for the most recent handful of winters: a return of ice extent to within the -2 standard deviation envelope. Indeed, the extent in April briefly matched average conditions before a relatively warm spell melted ice quickly in mid-April. The reason for this is a shift in wind conditions: speed and direction both changed from late winter through this last month. Those winds piled sea ice up instead of pushing it apart. The disadvantage: ice extent decreased, as seen in Figure 4. The advantage: ice volume grew, as seen in Figure 3. The effect on this September’s minimum extent will indicate how helpful the early season winds were in building sea ice that doesn’t melt every year back up.
Occasionally, I also like to include a supplemental time series graph that the NSIDC report contains. Here is this month’s supplemental graph:
This graph contains all of the same data as the previous graph and adds the time series lines from the previous 5 winters. As you can see, extent varies during the same month from year to year. The recent decline in extent, caused by a change in wind direction and speed, has reduced Arctic ice extent back to ~14 million sq. km., which is near normal for late April. The past three winters also saw similar magnitude reductions near the end of April, though the starting and ending values were obviously different. Despite these differences in subsequent years, the minimum ice extent values were quite similar: at or near the record low set in 2007. Will fall 2012 be any different or will the surge in ice growth on the Pacific side of the Arctic help to stave off the worst effects seen in the past five years?
Antarctic Pictures and Graphs
Here is a satellite representation of Antarctic sea ice conditions from March 9th:
Ice gain is easily visible around the continent, especially east of the Antarctic Peninsula. Conditions of Antarctic sea ice remain strong this year. As a reminder, this is largely and somewhat confusingly due to the ozone depletion that took place over the southern continent. This depletion has caused a colder southern polar stratosphere than it otherwise would be, reinforcing the polar vortex over the Antarctic Circle. That 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. For now, we should perhaps consider the lack of global warming signal due to lack of ozone as relatively fortunate.
Here is the Antarctic sea ice extent time series from mid-May:
Antarctic sea ice extent has remained above average to some extent for months now, which is good news. The difference in conditions from the first part of 2011 to the similar time period in 2012 is obvious: NSIDC measured last year’s extent near the bottom of the standard deviation envelope while this year’s extent is much healthier.
Errata
Here are my State of the Poles posts from March and January.
The state of global polar sea ice area in early January 2012 has convincingly returned to climatologically normal conditions (1979-2009). Arctic sea ice has recovered very quickly after a late start to the freeze season and a late-season slowdown due to certain atmospheric and oceanographic conditions; Antarctic sea ice has melted only slightly more slowly than is normal during the austral summer. Put another way, polar sea ice has recovered from an extensive deficit of -2 million sq. km. area a couple of months ago to zero anomaly today. That said, sea ice area spent an unprecedented length of time near the -2 million sq. km. deficit in the modern era. Generally poor environmental conditions established and maintained this condition, predominantly across the Arctic this year.
Arctic Ice
According to the NSIDC, weather conditions this winter were slightly less conducive for Arctic sea ice freezing on the Atlantic side of the Arctic while conditions were more conducive for freezing on the Pacific side. As such, February′s extent was the 5th lowest on record. Additionally, Arctic sea ice extent on in February averaged just 14.56 million sq. km. Sea ice extent was well below average in the Barents Sea due to temperatures that were 7-14°F above normal! The Bering and Baffin Seas meanwhile saw ice extent and ice growth, respectively, above normal during the month.
During February, Arctic sea ice refroze more rapidly than is the case for most Februaries. February’s sea ice extent increased by 956,000 sq. km., almost 2X the normal rate – largely due to previously low ice extent conditions in the Baffin Sea. Specific conditions around the Arctic Ocean were highly influenced by the positive phase of the North Atlantic Oscillation.
In terms of longer, climatological trends, Arctic sea ice extent in February has decreased by -3% per decade. This rate is lowest in the winter months than the late summer 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. Additional low ice seasons will continue. Some years will see less decline than other years – 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 a new normal is being established 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 January 7, 2012:
Once Hudson Bay finally froze over around the time of the New Year, ice extent grew toward the Atlantic Ocean. The sea ice in the Bering Sea, as mentioned above, formed more quickly than is normal. What is largely still missing is the sea ice north of Scandinavia. This is the result of anomalously warm waters from the Gulf Stream being drawn further north than is normal. This is due to the positive AO & NAO indices during this winter. As a side note, this phenomenon combined with the moderate La Nina in the Pacific Ocean has led to Dec-Mar being a warm and dry month for most of the U.S. so far
Overall, the health of the remaining ice pack is not healthy, as the following graph of Arctic ice volume from the end of February demonstrates:
As the graph shows, volume hit a record minimum earlier in 2011 before returning to the -2 standard deviation envelope. I know most folks don’t have a very good 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 2 of them occurring in 2 subsequent years under normal conditions are very, very remote. Hence my assessment that “normal” conditions in the Arctic are shifting from what they were in the past few centuries.
Switching back from volume to area, take a look at February’s areal extent time series data:
As you can see, the sea ice extent has spent all of the fall and early winter well outside of the -2 standard deviation envelope, just as it has for 5 winters in a row. It cannot be stated otherwise: these conditions are not indicative of a healthy system. This winter brought something new that the past few winters did not, however a return of ice extent to within the -2 standard deviation envelope. The reason for this is a shift in wind conditions: speed and direction both changed from early winter through this last month. Those winds pushed sea ice apart instead of piling it up. The advantage: ice extent increased, as seen in Figure 4. The disadvantage: ice volume stopped growing, as seen in Figure 3. The effect on this September’s minimum extent will indicate how helpful the early season winds were in building sea ice that doesn’t melt every year back up.
Occasionally, I also like to include a supplemental time series graph that the NSIDC report contains. Here is this month’s supplemental graph:
This graph contains all of the same data as the previous graph and adds time series from 4 of the previous 5 winters. As you can see, extent varies during the same month from year to year. The recent surge in extent, caused by a change in wind direction and speed, has brought Arctic ice extent up to ~15 million sq. km., which is challenging the highest extent in the most recent 6 winters. The maximum 2007 and 2011 ice extent didn’t come close to 15 million sq. km. while 2010 achieved approximately the same value almost a full month later. Despite these differences in subsequent years, the minimum ice extent values were quite similar: at or near the record low set in 2007. Will fall 2012 be any different?
Antarctic Pictures and Graphs
Here is a satellite representation of Antarctic sea ice conditions from January 7th:
Ice loss is less easily visible around the continent in these two images than they were between previous months. High ice concentrations remain well into the austral summer (nearly fall) east of the Antarctic Peninsula (the land mass that “points” to South America). Conditions of Antarctic sea ice remain good this year. As a reminder, this is largely and somewhat confusingly due to the ozone depletion that took place over the southern continent. This depletion has caused the southern polar stratosphere to be colder than it otherwise would be, reinforcing the polar vortex over the Antarctic Circle. That 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. For now, we should perhaps consider the relative fortune the lack of ozone has produced.
Here is the Antarctic sea ice extent time series from February:
Melt rates have been at or near normal throughout the austral summer this year. Year-to-year variation is also present in this graph, which includes the previous winter’s extent as a comparison. At this point, no news is good news. The Arctic is providing more than enough excitement for the time being.
Errata
Here are my State of the Poles posts from January and December.
