State of the Poles – Jan 2012: Arctic Ice Near Historic Lows; Antarctic Ice Above Average

The state of global polar sea ice area in early January 2012 has temporarily returned to climatologically normal conditions (1979-2009).  Arctic sea ice has recovered very quickly after starting the freeze season slowly and Antarctic sea ice has melted more slowly than is normal for this time of year.  Put another way, polar sea ice has recovered from an extensive deficit of -2 million sq. km. area a couple of months ago to no 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 fall were slightly less conducive for Arctic sea ice melt than was the case in 2007, the year that witnessed the record low extent.  As such, December 2011′s extent was the 3rd lowest on record.  Additionally, Arctic sea ice extent on December 31st measured just 13.25 million sq. km.  That was only 561,000 sq. km. more than the 2010 record low extent.  Because the dipole anomaly didn’t set up in the same way or with the same intensity as in 2007, Arctic sea ice extent has measured slightly higher than record minima in recent months.  We can’t count on these types of weather variations in the future, of course.  Another reason ice extent was low but didn’t set another record was the difference in ice motion: sea ice was likelier to remain in the Arctic in 2011 than in 2007 or 2010.

Since September’s record low, Arctic sea ice has refrozen rapidly.  December’s sea ice extent increased by 2.37 million sq. km. (vs. 1.86 million sq. km. average).  This situation mimics that of recent years after ice extent reaches low values in September and the sun sets for the winter.  The ocean released massive amounts of heat to the atmosphere, especially this fall since the AO index has been extremely positive.  This has caused cold air from the continents to be bottled up in a stronger vortex than normal and has drawn heat from the Arctic Ocean as it passes over the warmer fluid.

In terms of longer, climatological trends, Arctic sea ice extent in December has decreased by -3.5% per decade  These rates are more negative this year than the previous year (a trend that has continued).  These rates also use 1979-2000 as the climatological normal.  There is no reason to expect these rates to change significantly any time soon.  Additional low ice seasons will continue.  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 the establishment of a new normal in the Arctic is occurring.  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 December 12, 2011:

Figure 1 – UIUC Polar Research Group‘s Northern Hemispheric ice concentration from 20111212.

Compare this with January 7th’s satellite representation, also centered on the North Pole:

Figure 2 – UIUC Polar Research Group‘s Northern Hemispheric ice concentration from 20120107.

Hudson Bay finally froze over completely.  The sea ice in the Bering Sea formed normally.  What is 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 exceptionally positive AO index during the past couple of months.  As a side note, this phenomenon combined with the moderate La Nina in the Pacific Ocean has led to January being a warm and dry month for most of the U.S. so far.  The AO index is returning to more normal values now, so cold air outbreaks will become more likely in February.

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 2011.

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 the 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 December’s areal extent time series data:

Figure 4 – NSIDC Arctic sea ice extent time series through early January 2012.

As you can see, the sea ice extent has spent all of the fall and early winter well outside of the -2 standard deviation region, just as it has for 5 winters in a row.  It cannot be stated otherwise: these conditions are not indicative of a healthy system.

Antarctic Pictures and Graphs

Here is a satellite representation of Antarctic sea ice conditions from December 12th:

Figure 5 – UIUC Polar Research Group‘s Southern Hemispheric ice concentration from 20111212.

Compare that graphic with the same view from January 7th:

Figure 6 – UIUC Polar Research Group‘s Southern Hemispheric ice concentration from 20120107.

Ice loss is easily visible around the continent.  High ice concentrations remain well into the austral spring east of the Antarctic Peninsula (the land mass that “points” to South America).  Conditions of Antarctic sea ice remain good this year.

Here is the Antarctic sea ice extent time series from December:

Figure 7 – NSIDC Antarctic sea ice extent time series through early January 2012.

After conditions caused a slowdown in melt in late November and early December, the remainder of December and January was marked by normal ice melt rates.  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 December and August.

You can find NSIDC’s January report here.

Cross-posted at SquareState.

State of the Poles – Dec 2011: Arctic Ice Continues Low; Antarctic Ice Above Average

I haven’t written about polar ice conditions for a few months due to lack of time thanks to school.  Hopefully my time availability moving forward will be high enough to keep this series going.

The state of global polar sea ice area in early December 2011 has temporarily returned to near climatologically normal conditions (1979-2009).  Arctic sea ice has recovered very quickly after starting the freeze season slowly and Antarctic sea ice is benefiting from weather conditions preventing extensive melt at the edges in much the same way as it did last year at the same time.  Since my last post (covering August conditions), polar sea ice has generally recovered from an extensive deficit of negative 2 million sq. km.  The long time that sea ice area spent near this dramatic condition is unprecedented in the modern era.  Poor conditions established this development across the Arctic this year.

Arctic Ice

According to the NSIDC, weather conditions this fall were slightly less conducive for Arctic sea ice melt than was the case in 2007, when the record low extent was recorded.  As such, 2011′s extent was the 2nd lowest on record.  Specifically, Arctic sea ice extent measured on 4.33 million sq. km. on September 9th.  That was only 160,000 sq. km. more than the 2007 record low extent (about 3.7% of the minimum extent measured this year, a very small difference by comparison).  For additional perspective, 2011′s minimum was 2.38 million sq. km. less than the 1979-2000 average yearly minimum.  My prediction that 2011 wouldn’t miss 2007′s record by much unfortunately turned out to be true.  One reason 2011′s minimum didn’t set a record was because the dipole anomaly didn’t set up in the same way or with the same intensity as 2007′s.  We can’t count on these types of weather variations to disallow record lows in the future, of course.  Another reason was the difference in ice motion: sea ice was likelier to remain in the Arctic in 2011 than in 2007.

Since September’s record low, Arctic sea ice has refrozen rather rapidly.  September’s average sea ice extent was 4.61 million sq. km. (vs. 7.04 million sq. km. average).  October’s average sea ice extent was 7.10 million sq. km. (vs. 9.29 million sq. km. normally).  November’s average was 10.01 million sq. km. (vs. 11.31 million sq. km.).  During the fall, sea ice extent remained near record lows set per month in years past (2007 & 2010).

In terms of longer, climatological trends, Arctic sea ice extent in September has decreased by -12% per decade; in October has decreased by -6.6% per decade; in November by -4.7% per decade.  These rates are more negative this year than the previous year (a trend that has continued).  These rates also use 1979-2000 as the climatological normal.  There is no reason to expect these rates to change significantly any time soon.  Additional low ice seasons will continue.  The specific value for any given month during any given year is, of course, influenced by local weather conditions.  But it becomes clearer every year that a new normal is being established in the Arctic.  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 10, 2011:

Figure 1 – UIUC Polar Research Group‘s Northern Hemispheric ice concentration from 20110910.

Compare this with August 7th’s satellite representation, also centered on the North Pole:

Figure 2 – UIUC Polar Research Group‘s Northern Hemispheric ice concentration from 20110807.

Compare both of these with December 12th’s satellite representation (note that the AMRS-E instrument failed during early October; replacement data is available at a lower resolution):

Figure 3 – UIUC Polar Research Group‘s Northern Hemispheric ice concentration from 20111212.

There is more ice at this time of year in the Bering Sea and Hudson Sea than there were last year.  There is missing ice north of Scandinavia – this is the result of anomalously warm conditions in that region during the past month or so.

Overall, the health of the remaining ice pack is not healthy, as the following graphs of Arctic ice volume from the end of August and November demonstrate:

Figure 4 – PIOMAS Arctic sea ice volume time series through August 2011.

Figure 5 – PIOMAS Arctic sea ice volume time series through December 2011.

Within the past month, the magnitude of ice volume anomaly grew less severe, but remains in the 2nd standard deviation from the median.  Just like the sea ice extent has a negative trend, the sea ice volume is decreasing by 2900 +/-1000 cubic kilometers per decade.  The volume anomaly spent a substantial amount of time beneath the 2nd st. dev. value this year, just as it did last year.  The declining trend in volume ensures that future years will witness additional low areal extents.

Switching back from volume to area, take a look at September’s and December’s areal extent time series data:

Figure 6 – NSIDC Arctic sea ice extent time series through early September 2011.

Figure 7 – NSIDC Arctic sea ice extent time series through early December 2011.

Antarctic Pictures and Graphs

Here is a satellite representation of Antarctic sea ice conditions from September 10th:

Figure 8 – UIUC Polar Research Group‘s Southern Hemispheric ice concentration from 20110910.

Compare that graphic with the same view from December 12th (again, the AMSR-E instrument failed in October and these data are what everybody is currently working with):

Figure 9 – UIUC Polar Research Group‘s Southern Hemispheric ice concentration from 20111212.

Ice loss is easily visible around the continent.  High ice concentrations remain well into the austral spring east of the Antarctic Peninsula (the land mass that “points” to South America).

Here is the Antarctic sea ice extent time series from September:

Figure 10 – NSIDC Antarctic sea ice extent time series through early September 2011.

For comparison, here is the same data series from December:

Figure 11 – NSIDC Antarctic sea ice extent time series through early December 2011.

You can see how recent weather conditions have slowed the rate of ice melt in the past few weeks.  As weather conditions are highly variable from week to week, I expect the rate of  melt to increase again soon: the +/- 2 standard deviation envelope is close to the average, as shown in Figure 11.  Conditions were different in the early austral spring between 2010 and 2011.  They are now much more similar in value.

The biggest reason for the different trends seen in Arctic and Antarctic data?  It’s the so-called ozone hole.  One project I did this semester was a literature review on the mechanisms and projections of ozone loss in the stratosphere.  I will post most of that material on this blog after I make some adjustments.  Put simply, ozone absorbs UV radiation (high energy) and re-radiates that energy as heat into the stratospheric air.  As CFCs and other compounds have introduced halogens to the stratosphere and as UV radiation has released reactive forms of those halogens, ozone loss has occurred.  As ozone concentrations decrease, less heat is re-radiated to the stratosphere.  Colder air has therefore been present over Antarctica than otherwise would be the case.  Greenhouse gases have reinforced this process.  As CFC levels decrease in the future, however, stratospheric and columnar warming should occur.  After a few more decades, global warming will have more influence over Antarctica and we will see how sea- and land-based ice is then affected.

Errata

Here are my State of the Poles posts from August and July.

You can find NSIDC’s December report here.

Cross-posted at SquareState.

State of the Poles – Aug 2011: Arctic Ice Near Record Low; Antarctic Ice Back To Average

The state of global polar sea ice area in early August 2011 continues to fare poorly: well below climatological conditions (1979-2009) persist, as they have for every month so far this year.

Sea ice in the Arctic continues to track significantly below average, between the second worst and worst readings during July (depending on the day) in the modern era.  Weather conditions around Antarctica returned to normal during July, recovering from a temporary stall in freezing that occurred during June.  Global sea ice area therefore tracked well below normal during July, reaching for historical lows reached only three times before now.  During July, global sea ice area hovered near the negative 2 million sq. km. anomaly mark.  To date, this is the longest stretch of time that such a negative anomaly has stayed near 2 million sq. km.

To help put this in context, only three previous times in recent history have seen conditions as bad as they are today: in 2007, 2008 and 2010.  The difference between these previous occurrences and current conditions is profound: they previously occurred around September, when Arctic ice reached its annual minima.   Will a new record low global sea ice area be recorded this year?  Stay tuned.  There is only one more month of melting to go in the Northern Hemisphere, while the Southern Hemisphere’s freezing rate will slow down.

Polar Bear Cubs Die More Often With Less Arctic Ice

As Arctic ice thins and melts more and more every year, polar bear cub mortality is rising.  Compared to cubs that don’t have to swim as far to reach sea ice, which had a 19% mortality rate, cubs that are being forced to swim for days without reaching ice had a 45% mortality rate in a recent study.

With less body fat, the cubs can’t maintain their internal body heat as long as adults and they aren’t as buoyant in the water.  The cubs either drown because they can’t keep their noses above water or they succumb to the colder water.

I will point out that this is only one species.  There are many other species we didn’t even know existed that are under similar pressures from our greenhouse pollution.  On top of that, there are yet more species whose fate are being sealed every day we don’t reduce that pollution.

The Anthropocene is underway.  What happens in this Epoch is up to us.

State of the Poles – July 2011: Arctic At Record Low; Antarctic Below Average

The state of global polar sea ice area nearing the middle of July 2011 has gotten much worse than at the beginning of June: well below climatological conditions (1979-2009) continue to persist.

Sea ice in the Arctic continues to track significantly below average, with the 2nd to lowest readings for the month (depending on the day) in the modern era.  Weather conditions around Antarctica caused a temporary stall in sea ice freezing, causing extent conditions to tack toward below average conditions before recently recovering somewhat.  Global sea ice area therefore took a turn for the worse during June and early July, reaching for historical lows reached only a couple of times before now.  Within the last month, global sea ice area reversed the gains made in May toward eliminating the deficit from climatological conditions that characterized the first four months of 2011 and has instead declined rapidly to a 2 million sq. km. deficit by early July.

To help put this in context, only three previous times in recent history have seen conditions as bad as they are today: in 2007, 2008 and 2010.  The difference between these previous occurrences and current conditions is profound: they previously occurred around September, when Arctic ice reached its annual minima.  This, of course, is July.  There are over two months left before melting in the Arctic stops.  Will a new record low sea ice area be recorded this year?  Stay tuned.

State of the Poles – June 2011: Arctic Near Record Low; Antarctic Normal

The state of global polar sea ice area at the beginning of June 2011 remains poor: well below climatological conditions (1979-2009) continue to persist.

Sea ice in the Arctic continues to track significantly below average, with the 3rd lowest readings for the month in the modern era.  Antarctic sea ice recovered somewhat more quickly to normal conditions than was the case the month before.  Global sea ice area has therefore remained near historical lows for an extended period of time this year.  Within the last month, global sea ice area has finally improved from the 1 million sq. km. deficit from climatological conditions that characterized the first four months of 2011.  To help put this in context, only 2006 and 2007 saw similar conditions.  In 2007, the Arctic (and global) sea ice area fell to its lowest extent in modern history.

Arctic Ice

Portions of the Arctic are warmer places in 2011 than at the same point in 2007.  Warmer water than in past years continues to be transported into the Arctic Ocean at rates that are quickening (more warm water faster – not a good thing for ice survivability).  Weather conditions (local pressure centers, resulting wind patterns, etc.) will have the final influence on what conditions in Sep. 2011 look like.  Updating my guess from last month, I don’t think 2011 will challenge the record low extent of 2007.  I think it is likely that Arctic ice extent will end up in the lowest 3 extents on record.

According to the National Snow and Ice Data Center, Arctic sea ice extent in May was the 3rd lowest on record.  Averaged over May 2011, Arctic sea ice extent was only 12.79 million sq. km.  Arctic ice in May almost matched the rate of decrease recorded in May 2010, which was the fastest in the past decade.

The change in May ice extent has been measured at -2.4% per decade by the NSIDC.  What that means is as of the end of May 1978, the Arctic had 14 million sq. km. of sea ice while May 2011′s extent was, as stated above, only 12.79 million sq. km.  After posting record low extent values in 2004 and 2006, the past Mays saw a rebound in extent values.  The past three Aprils looked more like the extents of the 1990s.  Alas, 2011 looks a lot more like 2004 than 2010.

State of the Poles – May 2011: Arctic Sea Ice Declined Rapidly; Antarctic Below Average

The state of global polar sea ice area at the beginning of May 2011 remains poor: well below climatological conditions (1979-2009) continue to persist.  Sea ice in the Arctic continues to track significantly below average, with the 5th lowest readings for the month in the modern era.  Antarctic sea ice was slow to recover during April from its annual minimum.  Within the past week, conditions have turned more favorable for new ice to form around the southern continent.  Global sea ice area has therefore remained near historical lows for an extended period of time this year.  For only the third time in the past 30+ years, global sea ice area has started a calendar year with a 1 million sq. km. deficit from climatological conditions.  2006 and 2007 saw similar conditions.  The global sea ice area rebounded back to average conditions in the 2nd half of 2006, but they grew much worse (a 2.5 million sq. km. deficit) in late 2007.  The Arctic is a slightly warmer place in 2011 than at the same point in 2007.  Warmer water than in the past continues to be transported into the Arctic Ocean at rates that are quickening (more warm water faster – not a good thing for ice survivability).  Weather conditions (local pressure centers, resulting wind patterns, etc.) will have the final influence on what conditions in Sep. 2011 look like.  Hazarding a guess, I would say 2011 could very well threaten the record low of 2007 or look similar to the poor conditions of 2010.

Arctic Ice

According to the National Snow and Ice Data Center, Arctic sea ice extent in April was the 5th lowest on record.  Averaged over April 2011, Arctic sea ice extent was only 14.15 million sq. km.  Arctic ice in the first two weeks of April didn’t change very much in its extent.  That changed in the 2nd half of the month.  Increasing solar radiation and thin ice for this time of year has led to a decrease in the ice extent.  That decrease isn’t out of the norm, but the already low extent present at the beginning of the month means today’s extent is anomalously low.

The change in April ice extent has been measured at -2.6% per decade by the NSIDC.  What that means is as of the end of April 1978, the Arctic had 15.5 million sq. km. of sea ice while April 2011′s extent was, as stated above, only 14.15 million sq. km.  And this year’s end of April extent was slightly butressed by a relative lack of change for the better part of 2 weeks or so.  Conditions could be even worse than they are.  2008-2010 April’s were characterized differently than April 2011.  After posting record low extent values every year from 2004-2007, the past three Aprils saw a rebound in extent values.  The past three Aprils looked more like the extents of the 1990s.  Alas, 2011 looks a lot more like 2004 than 2010.

Arctic Pictures and Graphs

The last `State of the Poles` post I did was only a couple of weeks ago.  That said, things certainly look different since that time.  I’ll start with current conditions (yesterday), centered on the North Pole:

Compare this with April 19th’s satellite representation, also centered on the North Pole:

The big difference between these two pictures is the obvious and decrease in sea ice concentration in multiple regions across the Arctic.  You can also see the ice edge receding from where it was on the 19th of April.  Since they were some of the last areas to freeze, it is unsurprising to see melting and melted ice in places like the Hudson Bay, the Newfoundland Sea, the Greenland Sea, the Bering Sea and the Sea of Okhotsk.  It is very surprising to me to see lower ice concentration values near the North Pole.  When I first saw an indication of this a couple of weeks ago, I was hesitant to believe it since the satellite data can look different day-to-day based on the angle from it to the Earth and other factors.  As the days have gone by, this condition hasn’t disappeared, however, which leads me to think that there really are areas of thin ice where thicker ice normally can be found, even at the end of April.

As a whole, here is what the Arctic ice extent looks like in time-series form through May 4th:

You can easily see the rapid decrease in ice extent in the past couple of weeks that followed relatively stable conditions (for the Arctic area as a whole) at the beginning of the month.  As I stated above, this rapid decrease is normal for this time of year, as you can see from the slope of the `Average` time series (dark gray line in the light gray envelope).  The big difference is the poor condition of ice extent at the beginning of April – 2nd lowest in recorded history.  In the past couple of days, the 2011 time series line has approached and met the 2007 time series line.  The 2007 time series was added to this plot to provide additional context.  Since the record low extent was recorded in 2007, it is useful to compare current values and trends to that year’s.

Antarctic Pictures and Graphs

Here is a satellite representation of Antarctic sea ice conditions from May 4th:

For comparison purposes, here is the similar picture from April 19th:

New sea ice continues to form along the edges of the ice mass from April.  This is occurring at a normal rate.  The extent is still below normal, however, due to the record low extent set back in February.  If ice was freezing at a much higher than average rate, the difference between this year’s extent and normal would be decreasing.

Here is the time series graph of Antarctic sea ice extent with the +/- 2 standard deviations in light gray and the climatological mean in dark gray through May 4th:

This graph shows that ice is freezing at a somewhat faster than average rate.  The difference between conditions at the beginning of April and the end of April is good to see.

Errata

Here are my State of the Poles posts from April and March.

You can find the NSIDC’s May report here.

Cross-posted at SquareState.

New Arctic Ice Assessment: Faster Melt = Faster Sea Level Rise

Most of the projections in the science portion of the IPCC’s 2007 4th Assessment Report have been shown many times since its issuance to be too conservative.  Temperatures have risen faster; ice (sea- and land-based) has melted faster; ocean acidification and warming has happened faster, the number of extreme weather events has increased faster, etc.

I’ve written before about most of these.  I will take this space to write once again about polar ice melting faster than projected (according to observations) and the impact that will have on global coastlines.

According to the executive summary of a new assessment of Arctic climate, the international Arctic Monitoring and Assessment Program (AMAP) reports that Arctic temperatures in the past six years were higher than at any time since measurements began in 1880.  Moreover, feedback mechanisms have already started.

What this means is the arctic sea ice area and global sea level projections made by the IPCC just 4 years ago underestimate this year’s conditions, which means they also very likely underestimate future conditions too.  In an updated projection that has deep significance for billions of people worldwide:

The melting of Arctic glaciers and ice caps, including Greenland’s massive ice sheet, are projected to help raise global sea levels by 35 to 63 inches (90-160 centimeters) by 2100, AMAP said, though it noted that the estimate was highly uncertain.

That’s up from a 2007 projection of 7 to 23 inches (19-59 centimeters) by the U.N. panel, which didn’t consider the dynamics of ice caps in the Arctic and Antarctica.

Is the difference between one-half to 2 feet and 3 feet to 5 feet significant?  Only those of us who are sane seem to think so.  This is but one effect of oil corporations continuing to post record profits quarter after quarter, year after year.  How much infrastructure exists near 5ft above sea level worldwide?  How much is that infrastructure worth?  How much cropland exists at those low altitudes?  How many miles of ruined cropland from rising seas only will occur before widespread food shortages occur?  How much is our lifestyles worth; how much do they really cost?

AMAP scientists will discuss their findings in Copenhagen, Denmark starting tomorrow.

My most recent `State of the Poles` post discussed shorter-term influences on sea ice conditions (monthly to seasonal effects).  I’ve stated in that series that a new regime now exists for the Arctic.  Findings like these support that assessment.

For the hard-core curious, the key findings of the report are reprinted below the fold (h/t ClimateProgress)

State of the Poles – Apr. 2011: Arctic Sea Ice Steady; Antarctic Below Average

The state of global polar sea ice area in the middle of April 2011 remains poor: well below climatological conditions (1979-2009) continue to persist.  Sea ice in the Arctic continues to track significantly below average, with the 2nd lowest readings for the month in the modern era.  Antarctic sea ice has rebounded very slowly from its annual minimum extent, hovering near record low extent values during March and only recently improving in comparison to historical lows in early April.  Global sea ice area has therefore remained near historical lows for an extended period of time this year.  While global sea ice area has rebounded from its yearly minimum, the difference between this year and climatological conditions has been stuck below negative 1 million sq. km. for the first 3.5 months this year.   Those conditions mimic the trend seen in early 2006 and 2007.  2006 saw the global area increase to normal conditions later in the year.  2007, in contrast, did not.  That, of course, was the year that Arctic sea ice extent plummeted to its lowest value on record.  Weather conditions in the Arctic the rest of this year will help determine whether 2011 challenges 2007 for that dubious position.

Arctic Ice

According to the National Snow and Ice Data Center, Arctic sea ice extent in March was the 2nd lowest on record.  Averaged over March 2010, Arctic sea ice extent was only 14.56 million sq. km.  Arctic ice in March and into early April didn’t change very much in its extent.  This is definitely typical for March, but less so for April.  In fact, overall conditions have held steady since mid-February.  While those conditions were extremely low compared to climatological conditions in February, they were less anomalous by the middle of April.  Climatologically, the extent starts to really decrease by the beginning of April, so the extent anomaly has sharply decreased in the past month from 1.1 million sq. km. below normal to “only” 574,000 sq. km. below normal now.  Hopefully that translates to the lack of record low extents later this year.

The change in March ice extent has been measured at -2.7% per decade by the NSIDC.  What that means is as of the end of March 2011, the Arctic has only 14.56 million sq. km. of sea ice extent, while as of the end of January1978, the Arctic had 16.49 million sq. km. of sea ice.  That difference is real and it is significant.

Arctic Pictures and Graphs

I’m going to do something a little different this month and compare April’s satellite imagery of the Arctic to February’s to demonstrate the general lack of difference between the two.

Compare this with February 7th’s satellite representation, centered on the North Pole:

A couple of areas have some lower concentration of sea ice, but the general picture looks the same as it did over two months ago.  One important factor in April’s conditions is the Arctic Oscillation’s return to more positive values since the beginning of the year.  This has allowed colder air to remain in place over the Arctic region.

As a whole, here is what the Arctic ice extent looks like in time-series form through April 19th:

The NSIDC has included the 2007 time-series line as a useful comparative measure for this year’s extent.  After trailing below 2007 conditions for the first 2 months this year, the unchanging extent since early March has meant 2011′s extent is now above 2007′s.  At the end of the 2011 series, you can see that this year’s melt season might finally be in effect.

Antarctic Pictures and Graphs

Here is a satellite representation of Antarctic sea ice conditions from April 19th:

For comparison purposes, here is the similar picture from March 2nd:

Sea ice conditions have obviously increased in the last month, as they should have.  To date, I haven’t seen anything regarding the health of the ice shelves ringing the continent.  The longer there is no news, the better, since those shelves keep the land-based ice on land and not allowing them to escape to the sea.

Here is the time series graph of Antarctic sea ice extent with the +/- 2 standard deviations in light gray and the climatological mean in dark gray through April 19th:

Antarctic sea ice extent has remained on the low side of the climatological envelope of conditions.  So far, April has seen more extensive freezing than did March.  As you can see, conditions this year have been worse than conditions in 2010.  Unlike the Arctic, however, a long-term trend has not been as dramatic in the Antarctic.

Errata

Here are my State of the Poles posts from March and February.

You can find the NSIDC’s April report here. The page is dynamic, so if you’re reading this after April 2011, that month’s report will show up first. If that’s the case, you can look for any report in their archive on the top pull-down tab on the right-hand side of the page.

State of the Poles – Mar. 2011: Record Low Arctic Sea Ice

The state of global polar sea ice area at the end of February 2011 is troublesome: well below climatological conditions continue to persist (1979-2009).  Sea ice in the Arctic continues to track significantly below average, setting a record minimum for the month in the modern era.  Antarctic sea ice continued to hover near record low extent values during February.  Just as it did during early 2006, global sea ice area has double-dipped during the yearly minimum.  Instead of clearly rebounding from that low, as it usually has in the past 40 years, global sea ice is clearly characterized yet again by new conditions.  As of this writing, the global area is -1.4 million sq. km. below average.