NSIDC Reports The Smallest Maximum Arctic Sea Ice Extent

The National Snow and Ice Data Center just announced a news release, that the winter of 2014-15 had the lowest maximum sea ice extent since satellite records were started in 1979.

So what? This is yet another indicator of the effects of ongoing warming of the planet as part of the current trend in global climate change.  If you look at the map above you may not think that the difference between the 1981-2010 average is that compelling, but the bottom line is that the winter maximum sea ice extents and the summer minimum sea ice extents in the Arctic continue to drop as the years go on.  

This means that we continue to slide farther and farther down the climate change chute - impacts have always been predicted to be most extreme and obvious in the Arctic than anywhere else on the planet.  But if this is happening in the Arctic we should not be surprised to see other effects elsewhere...increasing temperatures, increasing intensities of storms, shifting weather and precipitation patterns, sea level rise, etc.

Oh, and a few more tidbits of information...the first time the Arctic maximum winter sea ice extent dropped below the 1981-2010 average was in 1995, and the last year the Arctic maximum sea ice extent matched or exceeded the 1981-2010 average was in 2003.  Every year since 2004 has had Arctic maximum winter sea ice extents below the long-term average...that's 11 years running! 

Click on the link below for more detailed information from the NSIDC:

Lowest Maximum Arctic Sea Ice Extent in Recorded History

Quick Arctic Update - 15 Sept 2014

We are near the traditional end of the Arctic sea ice melt season, so I thought I'd check in and post a quick update.  Two years ago, 2012 set the the all-time recorded sea ice melt record (so far) with a minimum sea ice extent over 3 million square kilometers below the 1981-2010 average.  By comparison the 2014 Arctic sea ice melt season looks fairly tame, but don't be fooled, the current sea ice extend is creeping up on 1.5 million square kilometers below the long-term average, and it's still declining.  

This year's minimum sea ice extend will almost certainly not reach the record set in 2012, but it was a significant melt all the same.  This melt qualifies 2014 to be the 6th largest Arctic sea ice melt year on record, exceeded only by 2007, 2008, 2010, 2011, and 2012.  The other years, 2009 and 2013 were just shy of this year's mark.  This also means that the eight years with the greatest Arctic se ice melt were the past 8 years.  It looks like a trend is forming....the bottom line, the sea ice melt is becoming more extensive as time goes on. 

(Graphs courtesy of the National Snow and Ice Data Center, Univ of Colorado at Boulder, NSIDC.org)

Holy Cow! Look at that decline in Arctic sea ice!

I haven't posted anything about much here lately, though there has been a lot going on.  For example the launch of the Carbon Observatory Satellite (http://www.huffingtonpost.com/2014/07/02/carbon-observatory-2-satellite_n_5550826.html?utm_hp_ref=green), but I just had to place a short post when I checked the Arctic sea ice extent today at the NSIDC.org site.

The graph below shows the relationship between the current sea ice extent (blue line) and the extent in 2012 (green dashed line), the year that generated the smallest sea ice extent so far, and the long-term average sea ice extent (dark gray line).  The rate of sea ice melt through mid-June 2014 wasn't really much out of the ordinary, just 500,000 km2 below the long term average (just!?), but over the past couple of weeks the sea ice extent has plummeted!  It's now about 1.2 million km2 below the average extent for this time of year.  

Yikes!

If this sea ice melt rate keeps up we could see another record low extent or close to it.  And yet another indicator from the high Arctic that the effects of climate change are not going to be going away anytime soon.

This is also the second month running where the atmospheric carbon dioxide level did not dip below 400 ppm, the second month it's ever been this high in human history...at least for the last several hundred thousand years.

Hang on, it could get interesting and exciting to see just how far things will go before there is general acceptance and outcry that something be done, at least in the USA.

Think green!

It's a bit early for the Arctic sea ice melt, but...

It's been a while since I posted anything about the state of the Arctic, but when I checked the National Snow and Ice Database website this morning I thought it was worth a few words.

The graph below shows the Arctic sea ice extent between Nov 2013 and Feb 12, 2014.  There are a couple of notable things here.  First, the ice extent has been between 250,000 and 500,000 square kilometers below the 1981-2010 average the entire time.  This doesn't come as a shock to anyone who follows the Arctic, but it's just an ongoing confirmation of a warming Arctic.

BTW, did you know that according to the National Climactic Data Center (NCDC) of the National Oceanographic and Atmospheric Administration (NOAA) that the last time that an annual global average temperature was cooler than the 20th century average was in 1976?  Yep, that's 37 years ago (http://www.ncdc.noaa.gov/).  I shared this with one of my classes of university students yesterday and realized as I said it that all of them were born well after 1976, so they have known only a warming world.  That's a sobering thought.

The second thing the graph shows that's interesting, though not yet significant is what happened over the last week or two.  If you notice the average sea ice extent usually reaches its maximum coverage around the end of February or early March.  The extent does show some ups and downs, as clearly shown in the 2011-2012 (dotted) line.  This year's data are shown on the blue line.  Anyway, so what?  Data of the last week or two show a leveling off and then decline in sea ice cover.  If this continues, and I'd be extremely surprised if it did this early in the season, we could really be in for a doozie of a sea ice loss year in the Arctic.  It's much more likely that this is just a temporary blip.  

Stay tuned.  Life is interesting.  

Holy cow! The 2013 Arctic sea ice melt is accelerating like crazy!

I know I just posted on the Arctic Ocean sea ice melt, but, well, that was three days ago.  And three days ago it looked like an acceleration of sea ice melt might have been on the way, but I'd say that now it's official!  Look at the difference between the 1981-2010 baseline trend and the observed sea ice melt between the latter half of June and July 4th.  Wow!

I did a little math, and here's what I came up with.

On June 21st the historical baseline (1981-2010) showed sea ice extent at about 11.4 million km2 and 10.55 million km2 on July 4th.  That's a difference of 850,000 km2 of sea ice, or a melt rate of about 65,400 km2 of sea ice per day.

By comparison, the observed time period between June 21st and July 4th 2013 showed a sea ice extent of 11.1 million km2 on June 21st and an extent of 9.6 million km2 on July 4th.  That's a difference of 1.5 million km2 over that time period for a daily sea ice melt rate of about 115,400 km2 per day.

The observed melt rate for 2013 over the past two weeks or so is therefore nearly double the baseline melt rate for the same time period.  It's doubtful that this melt rate can be maintained for long, but the next few weeks will give us a good indication about whether the 2012 sea ice minimum extent record is in jeopardy. That is, if the current sea ice melt rate will be sustained, at least over the short term.

So, it's true, things are really starting to warm up in the Arctic.

Stay tuned...it's going to be an interesting summer!

Time to check in on the Arctic Ocean summer sea ice melt - 1 July 2013

It's been a while since I posted anything about what's happening in the Arctic Ocean.  In a word, the summer 2013 sea ice melt is "on".  So far this spring/summer, sea ice cover has declined from a winter maximum ice extent of just over 15 million km2 down to 10.5 million km2 as of yesterday (6-30-2013).

The maps below shows that sea ice melt is progressing much faster than the 1981-2010 average in Hudson Bay, the Barents Sea, Baffin Bay, and other areas around the Canadian Archipelago.  Sea ice melt in the Bering and Chukchi Seas are right on the historical average.

The graph below courtesy of NSIDC.org shows the relationship between the 2013 Spring/Summer melt and that of the 1981-2010 average and the 2012 all time record low sea ice melt.  The current melt is currently about midway between the historic average melt and the record melt for this time of year.  The rate of sea ice melt has really increased (as indicated by the steep downward turn in the blue line on the graph below) over the past week or so.  The rate of sea ice melt will really have to speed up, though, if it's going to have a chance of catching last year's record pace. 

If you follow these kinds of data on a regular basis, like I do, you might be surprised to see the current rate of sea ice melt is as close as it is to the historic rate of sea ice melt.  That's because NSIDC recently updated their baseline data for comparisons from a 22-year average (1979-2000) to a 30 year average (1981-2010), since that is standard practice for baselines whenever possible.  You can read more about that change by clicking this link: http://nsidc.org/arcticseaicenews/2013/06/updating-the-sea-ice-baseline/.  FYI, the NSIDC made this change on June 18, 2013.

So as of now, the 2013 sea ice melt is not threatening to break last year's record minimum sea ice extent.  But the only way to know what is going to happen is to be patient and keep checking back.

Have a great summer, but I hope that not too much sea ice melts!

Ice melt from the Greenland Ice Cap in 2012 smashed all previous records

The National Snow and Ice Data Center (NSIDC.org) just posted data on the 2012 Greenland ice cap melt.  It smashed all previous satellite records.

According to the NSIDC this was the first time since 1979 (the first satellite coverage of Greenland) that every point on the entire Greenland ice cap reached melt conditions for at least part of the melt season.  This is shocking news, since some of the ice cap is over 2 miles above sea level, and should be high enough in both latitude and altitude to stay below freezing all year long.  But, alas, temperatures climbed above freezing everywhere on the ice cap.

The graph below shows the historical average percentage of the Greenland ice cap that experienced melt conditions on a daily basis.  You should note that historically essentially no ice melts from Jan to April and Oct through December, and that the historical melt season starts in April and runs through September.  The data also show that on average only about 25% of the ice cap experiences melt conditions.

The red line in the graph below shows the 2012 melt extent.  Compare it to dashed blue line showing the historical average.  What should you be seeing here?  (Continued below the graph.)

You will, I hope, notice a few things.  One is that there was a spring melt event in late March where more than 10% of the ice cap reached melt conditions.  This was at least two months earlier than the historical average reaches that extent.  It was a short event, but it occurred all the same.  The biggest thing you should see is that the melt extent during the summer reached up 90%.  Historically only about 25% of the ice cap experiences melt conditions.  In short, the 2012 Greenland ice cap melt exceeded anything observed so far in modern times.

The map below shows the 1979-2007 average of the cumulative number of days areas of the ice cap reached melt conditions.  Historically, the north edge of the ice cap experienced about 10-15 days of melt conditions.  The central east coast had even fewer than that.  And the SW coast experienced the most.  Now let's take a look at the cumulative number of melt days across the ice cap during 2012...look at the second map down.

The map below shows a frightening increase in the number of melt days even in regions mainly resistant to melting in previous years.  For example, the northern edge of the ice cap experienced 100+ days of ice melt, the central east coast had 50-60 days, and the SW coast also had 100+ days. In fact, all ice cap edges experienced shocking numbers of days of melt conditions during 2012.  And, as mentioned above, even the center of the ice cap reached melt conditions for a few days.

The map below shows air temperature anomalies for June-August 2012 compared to historical averages.  What this means is that the closer a region is to the red end of the scale, the warmer is is compared to historical averages, and the closer it is to the purple end, the cooler it was.  The map shows that the entire ice cap experienced increased temperatures compared to the historical average.  

The SW coast was especially hard-hit with temperatures in the +3.0oC range, while the center of the ice cap had temperatures that were 1oC to 2oC above average.  Nowhere in Greenland experienced below average temperatures during this time period.

The bottom line is that during 2012 Greenland's ice cap experienced unprecedented ice melt conditions compared to data from the satellite record (since 1979).

Should we be concerned about this?  I am.

Well, there is a chance that this could have been an isolated warmer than average year, but all other data from the Arctic in terms of temperatures, sea ice cover, etc., indicates that this kind of extreme melt year will most likely become more frequent if the forcing factors driving climate change are not mitigated.

Climatologists and oceanographers predict that if the entire Greenland ice cap were to melt, we would most likely see global sea level rise of about +7.0 meters (that's over 20 ft).  That would be catastrophic and make the flooding that occurred during Hurricane Sandy look like a nice day in the park.

Come on people, it's time to get to work doing things that will mitigate the effects of climate change.

That's my 2 cents' worth...

Why has it been so cold in the western USA lately?

The western United States experienced an extremely mild, dry winter during 2011-12.  This year (2012-13), however, things are different - it's cold, cold, cold! and wetter than last year, too.

For example, where I live in SE Idaho, we have been experiencing low temperatures in the -10 to -20oF range over the last week or so.

Why is it so much colder than last year?

Last year's mild winter can be explained in part by ongoing global warming, but prevailing weather conditions over the Arctic also matter.

There is something called the Arctic Oscillation (AO).  The AO has two phases, a positive and a negative phase.  During the Positive Phase of AO, low pressure sits over the Arctic and a high pressure system dominates around 45oN.  During the Negative phase of AO, the opposite occurs; a high pressure system dominates the Arctic and low pressure exists around 45oN.

You can learn more about it at this site provided by the National Snow and Ice Data Center (http://nsidc.org/arcticmet/patterns/arctic_oscillation.html)

The bottom line is that the AO can switch between its positive and negative phases over a matter of weeks to decades.  The dominating phase of AO can have a significant impacts on the weather over the northern hemisphere.

 (Images courtesy of NSIDC.org)

The image above left shows the effects of the "Positive Phase of Arctic Oscillation".  During the positive phase (low pressure system over the Arctic) masses of cold Arctic air stay farther north, and the western USA stays warmer and drier than usual.  At the same time, coastal Eastern Canada gets colder air than usual.  During the Positive phase the North Atlantic storm track can also move farther north than usual, bringing cold, wet winter weather to northern Europe.  According to NSIDC.org, we have been experiencing mainly the positive phase of AO since the 1970s.   

The image above right shows the effects of the "Negative Phase of Arctic Oscillation."  During the negative phase (high pressure over the Arctic), low pressure is much more common around 45oN, and this phase recently developed.  During the negative phase colder, wetter air masses than usual are pulled farther south by the low pressure system over western North America.  Along with this we normally see the Atlantic storm track pushed farther south, bringing precipitation to the Mediterranean instead of northern Europe.  

There are, of course, many other oscillating weather patterns that contribute to conditions we experience, but the AO is one recently switched phases.

Global Warming also plays an important role in generating weather.  Even though the Arctic is cold, much more heat than normal is stored there, and it has to go someplace.  One thing this does is increase the amount of atmospheric activity and can contribute energy to the polar jet stream, pushing it farther south than usual.  The map below shows the jet stream track for 14 January 2013:

The map above shows the jet stream pushing as far south as northern Mexico.  My son happens to be there, and he reported recently that they are experiencing freezing temperatures and even snow!  

Knowing something about the Arctic Oscillation effects of global warming help us understand weather we experience.

I hope this was helpful.

Is the house on fire? Indications of climate change - 2012

I'm not an alarmist, but there are times to be alarmed - like when your house is on fire, or when you see the headlong approach of unswerving headlights.

When it comes to global climate, is the house on fire?

Record-settting number of high temperature records

The most recent data I could find on daily temperature records in the USA was from July 2012.  According to the National Climate Data Center, there were 23,283 new record high temperatures set across the United States from Jan-July 2012.

There are also some other troubling data and scenarios out there.

In mid-July a compelling article on climate change and current weather and climate patterns by Bill McKibben appeared in Rolling Stone Magazine.  You can read it in its entirety by clicking the link below.  

http://www.rollingstone.com/politics/news/global-warmings-terrifying-new-math-20120719

Building on data presented in that article we are now entering the 329th consecutive month with average temperatures above the 20th century average.  Yes, you read that right...329th month...that's nearly 27.5 years where EVERY month's average was above the 1900-1999 average temperature.  Now it is expected that any set of data from a natural system would include variability - year to year rainfall totals, temperature fluctuations, your heart rate, your annual body mass fluctuations, etc.  But when we see over 27 years of monthly average temperature data above the average of that for an entire century of temperature readings, we should probably sit up and think about what's going on.

If temperature fluctuations were behaving completely randomly, with no long-term temperature increase or decrease, we would predict that a given month's average temperature has a 50% chance (probability = 0.5) of being above average.  The chances of two consecutive months being above average would be 0.5 x 0.5 = 0.25 (= a 25% chance of happening by random chance alone).  So, what are the odds of observing 329 consecutive months with average temperatures above the 1900-1999 average temperature by random chance alone?  to get the answer to this question you need to multiply 0.5 by itself 329 times.  The answer is, according to the Rolling Stone article 3.7 x 10^-99.  That means that there is a 0.00000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000037% chance of that happening by random chance alone.  That's such a small likelihood of happening that it's time to look for things that could be driving that other than random chance.

The prime suspect?  A trend of global climate change, i.e., global warming.

The total global average temperature hasn't increased all that much so far in the past 100 years or so...only 0.8oC.  And if we are seeing significant changes with only this small change in global temperature, what could happen when we reach 2oC?  - the projected limit that we could reach without incurring MAJOR global environmental and ecological effects?

BTW, climate models suggest that the atmosphere-ocean-earth system may be able to accommodate the emission of another 595 gigatons of CO2 into the atmosphere before we reach the 2oC mark.  But guess what?  The cumulative proven reserves of fossil fuels currently controlled by energy companies and countries with nationalized mining and extraction = 2,795 gigatons of fossil fuel.  That's just the fossil fuel that we know about.  That's 5x the total we can emit before hitting the 2oC mark.

Are there other indicators are there that climate is shifting?  Check out some of my other postings.

Record sea ice melt season reduces sea ice extent to only about 50% of its historical average

It's nearly the middle of September, the traditional end of the sea ice melt season in the Arctic Ocean.  The rate of sea ice melt has slowed over the past few days, perhaps signaling the beginning of the end of the Arctic Ocean sea ice melt season for 2012, but it's not completely done yet, and it's been a crazy summer in the Arctic!

Do you see what I see?  The extent of sea ice cover in the Arctic Ocean is WAY smaller now than the 1979-2000 average (orange lines) with only ~51% of the 1979-2000 average sea ice cover remaining today.

Consider this...

The average sea ice cover (extent) in the Arctic from 1979-2000 was about 6.7 million square kilometers.  Right now there is only about 3.45 million square kilometers of sea ice in the Arctic (as shown above).  The area of ice that is MISSING is shown on the map below.  Sea ice extent has NEVER been this low.

How does this compare to the previous sea ice melt record?  The previous sea ice melt record was in 2007.  The dark gray line on the graph below shows the 1979-2000 average sea ice cover.  The dashed green line shows the sea ice cover during 2007, and the blue line shows sea ice cover during 2012.  The 2012 ice melt smashed the 2007 record, with over 750,000 km2 more sea ice melting than in 2007.

Interestingly, the high amount of sea ice melt in 2007 was largely the result of an unusual Arctic weather year.  It had huge high pressure regions over large areas of the polar north, and lots and lots of sunshine, which meant lots of sea ice melting.  In 2012 however weather conditions did not appear to be set up to produce lots of sea ice melt.  There was a major cyclonic low pressure system that produced lots of cloud cover.  And that combined with associated winds normally slows sea ice melt.  But not this year.  It has just apparently gotten too warm overall in the Arctic for that kind of weather system to slow sea ice melt as much as it used to.

Maybe the sea ice melt in 2007 and 2012 were just statistical outliers.  I would have considered that as a possibility...until I saw the data for sea ice in the Arctic for the years between 2007 and 2012.

The graph below shows the sea ice cover data for the years 2007-2012 plus the 1979-2000 average.  An outlier is an observation that falls well outside of the observed long term trend.  What we see when we look at the data is that every year since 2007, and others not shown here, all fall well outside the 1979-2000 average.  But because there are getting to be so many years outside that average they collectively no longer can really be considered outliers.  Instead, they are possibly representing a new trend.

I just read an extremely interesting paper on what is and has been going on in the Arctic with respect to sea ice.  I recommend it highly if you are seriously interested in this topic.

• Stroeve, J. C., et al. 2012. The Arctic's rapidly shrinking sea ice cover: a research synthesis. Climate Change 110:1005-1027 DOI 10:1007/s10585-011-0101-1

Here is a link to a PDF file containing that paper: 

https://arcus.org/files/projects/supplemental/674/stroeve_etal_seaice_synthesis_2011.pdf

One of the things I found most compelling in Stroeve's article was the analysis of sea ice extent over the last 30+ years.  The conclusion is that the rate of sea ice loss is no longer linear.  Annual sea ice extents are dropping faster over the past decade than during previous decades.  The upper graph shows the rate of sea ice loss 1979-1998 in blue, and the rate of sea ice loss 1999-2010 in red.  The significant difference in these rates of sea ice loss is worth noting.  Stroeve's paper refers to models that suggest that the Arctic could become ice free in the summer as soon as 30 years from now.    

On the heels of this year's record sea ice melt, however, some climatologists are starting to suggest the possibility of a summer free of ice in the Arctic as soon as 10 years from now.  Yow!

Approaching Arctic Ocean Annual Sea Ice Maximum Extent For 2012

One of my favorite climate-related web sites is the http://nsidc.org/. This is the site of the National Snow and Ice Data Center, housed at the University of Colorado, Boulder.  This is a great place to check on the state of snow and ice around the globe: the Arctic, the Antarctic, Greenland, mountain glaciers, etc.

The NSIDC posts a near-real time map and graph showing the current sea ice extent and recent trend of sea ice compared with a baseline average of the years 1979 through 2000.

Anyway, it's late February 2012, and according to the baseline data, this is the time of year that we are approaching maximum sea ice extent for the year.  The NSIDC defines an area to be "covered" by sea ice if a location has at least 15% of its surface area covered by sea ice.

Here is the most recent map showing sea ice cover, compared to the 1979-2000 baseline average:

The orange line on the map shows the baseline average extent of sea ice cover from the years 1979-2000. The white area shows the reported current extent of at least 15% sea ice cover based on satellite data provided by NASA.gov.  NSIDC scientists note that there is more ice than usual in the Bering Sea north of the Aleutian Islands - remember the challenge faced by residents of Nome, Alaska, earlier this winter when sea ice prevented shipping from reaching them?  At same time, just about everyplace else in the Arctic shows a lower sea ice extent than the historical baseline.  This is especially true in the Kara Sea and Arctic Ocean North of Scandinavia.

The figure below shows that we are fast approaching the annual sea ice maximum for 2012.  The maximum extent is usually reached sometime between mid-February and mid-March, so we are in the window.  Current Arctic sea ice extent (blue line) shows that the current sea ice extend is about 1.2 million square kilometers less than the historic baseline (dark gray line).  The current extent is also well below the + 2 standard deviation range (light gray zone) around the average baseline.  This means that yet again, the current sea ice extent is statistically significantly lower than the baseline.  And sea ice extent in the Arctic is comparable to the sea ice extent observed in 2006-2007 which produced the lowest summer sea ice extent on record.

Is this the record lowest extent for this date?  No.  The record for the lowest extent for this date goes to February 2011: last year - when we also saw the second lowest summer sea ice extent on record.

Does this mean that we will have a record low sea ice extent in Summer 2012?  No one knows.  The lowest sea ice extent is a product of not only a warming climate, but of prevailing short-term wind patterns and other weather conditions between now and then.  All we can really do is sit back and see what does happen.

So, until next time, keep an eye on the sky, the thermometer, and the ice.  Cheers!

Arctic sea ice melt the second largest on record

Starting in 1979, NASA started using satellites to monitor sea ice cover in Arctic Ocean. Each summer and fall climatologists and other interested people (like me) look forward with interest, and in some cases anxiety, to see how much of the sea ice melts during a given calendar year.  I, for one, have been following this annual cycle of sea ice production and melt for many years.

Scientists at the National Snow and Ice Data Center at the University of Colorado, Boulder, collect and analyze the NASA data and provide near real time updates on the status of Arctic sea ice, among lots of other things, throughout the year.  You can access their analysis as well as many fine sources of raw data at their website: http://nsidc.org/index.html

Sea ice extent is defined by the NSIDC as the total area that has at least 15% of sea ice cover.  Arctic sea ice floats.  This means that wind, wave, and current action together with other physical factors cause the sea ice to be constantly on the move.  It forms pressure ridges, and is constantly shifting.  In the Spring, temperatures increase and ice starts to melt, crack, and move.  If wind is particularly strong it will drive the melting ice together and expose larger areas of open water, especially between the shore and the ice pack.  When wind action is less powerful the ice remains more spread out and the 15% ice cover extends over a larger area.

The pink lines on the map below shows the 1979-2000 average sea ice extent (minimum of 15% ice cover).  The white area represents the area actually covered by at least 15% sea ice for the minimum sea ice extent for 2011.  The 2011minimum sea ice extent is significantly lower than the historical average.  (All images in this posting are courtesy of the NSIDC.)

This year the minimum sea ice extent is the second lowest ever recorded. 

The graph below compares the 2011 sea ice minimum extent to the 1979-2000 minimum sea ice extent (dark gray line) for the months of June-September.  The 1979-2000 line presents a baseline value that is useful for comparing annual sea ice extents to the baseline as well as to each other.  The lighter gray area surrounding the 1979-2000 average indicates two standard deviations of the historical data.  This means that observations that fall outside of that light gray area are considered to be statistically different than the baseline value for that date.  Sea ice extents for the years 2007, 2008, 2010, and 2011, are also included in this graph.

The 2011 sea ice minimum reached its minimum in early September, and only 2007 had a smaller sea ice minimum.

The graph below shows the minimum sea ice extend for the month of September from 1979-2011.  You will note that there is considerable variation around the blue line that represents the overall trend.  Sometimes people who do not understand how natural systems work will look at a single month's observation, such as 1992 or 1996, and jump to the conclusion that Earth's climate is not warming after all.  This is a faulty way to think about this kind of data.  A single observation does not always indicate the overall trend of the system.  It is important to realize that Earth's climate, like every natural system, contains variability around the prevailing trend.

OK, here's an example of what I'm talking about with respect to variation around a trend line.   One natural system that everyone is familiar with is heart rate.  Just about everyone knows how to take their pulse.  If you were to take your pulse a doze random times throughout the day, every day for a year those data would reveal two things: 1) your average heart rate; and 2) the amount of variability that exists in your heart rate.  Heart rate data can also reveal longer-range trends if monitoring continues and lifestyle changes.  For example, let's say that you have not been all that active for many years, but you decide to start exercising.  For lack of another option you start to jog, and then run on a regular basis, say 3-4x/week.  After doing this for several months you are consistently running 12-20 miles a week.  If you have been monitoring your heart rate all this time you will probably have seen a drop in your average heart rate as you have gotten in increasingly better shape.  That improvement would be reflected in a lowering average heart rate.  At the same time, you would still see lots of variability in heart rate each day, depending on what you are doing.  That's characteristic of any natural system.

Because there tends to be a lot of variability (also called noise) in the data collected on natural systems, such as Arctic sea ice extent, climatologists recommend that when considering climate trends a data set of at least 30 years, and longer when possible, is needed to identify overall trends.  Sadly, the overall trend of sea ice extent reveals a pattern of increasing sea ice melt.

When we consider differences in prevailing conditions in 2007, the year with the smallest measured sea ice extent, and 2011, the year with the second lowest extent, it's notable that the sea ice extent got as small as it did in 2011.  Why was 2011 a surprise?  The figure below shows the prevailing direction and rate of sea ice movement during the 2007 and 2011.  In 2007 there was a combination of strong prevailing winds and surface currents pushing the ice toward the Canadian/Greenland margins of the Arctic Ocean.  The size of the arrows represent the rate of ice movement (larger and longer arrows mean faster movement).  Remember that sea ice extent is measured in terms of 15% sea ice cover.  This means that there can be significant amounts of water between ice floes and still be included in the area of sea ice cover.  In 2007 forces jammed the ice together, minimizing the amount of water between ice floes, and produced a smaller sea ice extent than ever seen before or since (so far).  By comparison, if you look at the map of sea ice movement in 2011, there was sea ice movement, of course, but the rate and direction of movement was nothing like what was observed in 2007.  Wind and current action did not tend to compact ice in the central Arctic Ocean in 2011 the way they did in 2007.  This means that the low sea ice extent in 2011 is due to a higher amount of sea ice melt rather than due to sea ice compaction.  

The chart below shows the sea ice extents for September for the years 2007-2011 along with the 1979-2000 average.  While the annual sea ice extent data are interesting, showing the 2011 sea ice extent being only 300,000 km2 larger than that of the record minimum in 2007, the most significant result of the analysis to me is that the overall rate of decline in sea ice extent is decreasing significantly.  The overall rate of decline, based on a rolling 10-year average, is now at 12% per decade.  That's a lot!  These data support the explanation that climate change is happening, and that the Earth is warming.

Before I quit, I want to mention one last thing about scientists and what they do.  They do not want the climate to change, sea ice to melt, polar bears to be at risk, or other consequences of climate change to occur.  What they do want is to try to understand patterns and processes that explain what is happening.  This holds true for all scientists in all fields.  Though, like anyone, they may have pre-existing notions of what they think is happening, scientists are not content to stop there.  They are driven to make observations, analyze data, and then find out what is actually happening.  They then work to find the best explanations for the observations.  Lastly, once scientists have developed their best explanation about what is happening and why, they present that idea to the larger scientific community for critical review.  Only the best ideas, those supported by data and appropriate methods of analysis, survive that review.  

So, what's the bottom line here?  The Arctic polar region is warming, and quickly.  As for the Antarctic, that's a topic for another time.

(Originally posted 10-6-2011)

The Arctic Ocean continues to warm up...July 2011 had a record sea ice minimum

The amount of the Arctic Ocean covered by sea ice is the lowest on record for the month of July, according to The National Snow and Ice Data Center http://nsidc.org/arcticseaicenews/, located at the University of Colorado, Boulder.

This new sea ice minimum for the month of July exceeds even the previous record set in 2007, but toward the end of July the rate of sea ice melt slowed allowing the minimum from 2007 to once again surpass it.  If you look at the graph below (courtesy of the NSIDC.org) you can see the curves for 2007, the year with the standing record minimum sea ice for the year (dotted line) and the sea ice remaining for 2011 (the blue curve).    The sea ice amount for 2011 was less than in 2007 or any other previous year for which we have satellite data.  The rate of sea ice melt slowed at the end of July 2011, but during the past few days the rate of sea ice melt has picked up again.  Don't be surprised if we see a new sea ice minimum this September, but only weather conditions between now and then will determine that.

This map shows the 1979-2000 average sea ice for this time of year (pink lines) and the current amount of sea ice cover shown in white (also courtesy of NSIDC.org).  If you notice, sea ice melt is progressing particularly rapidly along the Russian and western Canadian and Alaskan shorelines.  It makes me wonder how long it will be this year before the NW passage will be ice free again this year.

This graph (courtesy of NSIDC.org) shows the sea ice extent for July 2011 compared to all previous years since 1979.  It shows clearly that it was a record low sea ice total for the month.  It's interesting that there are some people who look at data like these and say, for example, what happened in 2008!?  2009!?  Those were above the descending trend line?  And they conclude, based on one year's data that global warming is not happening.  In fact, years like 2008 and 2009 are to be expected.  We are, after all, looking at a natural trend, and there is always variability around any natural trend.  It's the overall trend of many years worth of data that need to be considered before a conclusion can be made.  In this case, the data all support the conclusion that we are looking at a trend of decreasing sea ice as the years pass.

In addition, climatologists have also been monitoring the age and thickness of sea ice, in addition to sea ice cover.  This graph shows the percent of sea ice cover on the left-hand image, and the age of ice on the right-hand image.  Scientists have discovered that there is less old (>2-3 year old ice) in the Arctic Ocean than in years past.  What this means is that younger, and therefore thinner ice melts faster than older, thicker ice.  And, since the NSIDC uses a 15% ice cover as a threshold for their measurements for their graphs, etc., this graph is particularly telling when it comes to assessing the status of ice cover in the Arctic Ocean.

If you look at the left-hand map, you will see that only a very small percentage of the Arctic Ocean still has 100% ice cover, and a significant area has only 15% or slightly more.  The prevailing winds and currents tend to cause ice to stack up along the north coasts of Greenland, Baffin Island, and other Canadian Arctic islands, so that is why the ice is thicker and older there.

I, for one, would not be a bit surprised if we saw a record or near record maximum sea ice melt this summer.

Interestingly, sea ice melt has no direct affect on sea levels.  When sea ice melts, it's just like ice cubes in your drink melting.  If you marked the level of fluid containing ice cubes in a glass, you will notice that there is no difference before the ice cubes melt and after they melt, because the total amount of water present in the glass does not change.  What we need to consider when it comes to sea level rise are two things, well, at least these two things: land ice/glacier melt (e.g., the Greenland ice cap), and thermal expansion of water.  As the world's oceans warm, the water becomes slightly less dense, and total volume increases.  We will also see increased evaporation, but the vast majority of evaporated sea water falls directly back on the ocean, so that's probably a negligible effect.

So...so what!?  It's still warming up in the Arctic.

Stay tuned!

(Originally posted 8-9-2011)