Showing posts with label thickness. Show all posts
Showing posts with label thickness. Show all posts

Large Falls in Arctic Sea Ice Thickness over May 2014

Comparing ice thickness (in meters) on May 2, 2014 (left) and May 30, 2014 (right, forecast run May 25, 2014)
Arctic sea ice has shown large falls in thickness in many areas over the course of May 2014, as shown on above image. The animation below also compares the situation between May 2, 2014, and May 30, 2014 (as forecast by Naval Research Laboratory on May 23, 2014). Ice thickness is in meters.


Thickness is an important indicator of the vulnerability of the ice. If only looking at sea ice extent, one might (wrongly) conclude that sea ice retreat was only minor and that everything looked fine. By contrast, when looking at thickness, it becomes evident that large falls have occurred over the course of May 2014.

Falls at the edges of the sea ice can be expected at this time of the year, but the large fall closer to the center is frightening. On the one hand, it appears to reflect cyclonic weather and subsequent drift of the ice. On the other hand, it also indicates how vulnerable the sea ice has become. Last year, a large area showed up at the center of the sea ice where the ice became very thin, as discussed in July 2013 in the post Open Water at North Pole and again in the September 2013 post North Hole.

The appearance of huge weak areas at the center of the sea ice adds to its vulnerability and increases the prospect of total sea ice collapse, in case of one or more large cyclones hitting the Arctic Ocean later this year. To highlight the dangerous situation, the main image from a post earlier this month is again added below.


Adding to the concerns are huge sea surface temperature anomalies, as illustrated by the image below, showing anomalies at May 23, 2014, and created by Harold Hensel with ClimateReanalyzer and Google Earth.

[ click on image to enlarge ]
The image below shows sea surface anomalies on May 26, 2014, with an overlay of land temperatures, as created by Harold Hensel and edited by Sam Carana.


The image shows sea surface temperatures on the Northern Hemisphere that are 1.44 degrees Celsius warmer than the baselline temperature, despite large areas with cold water partly resulting from the huge amounts of meltwater flowing down along the edges of Greenland into the North Atlantic Ocean. The graph below shows Northern Hemisphere and Global sea surface temperature anomalies over May 2014.

By comparison, current (May 27, 2014) surface temperature anomalies of 0.64°C globally and 0.84°C for the NH. The image below shows annual temperature anomalies (land and ocean data).



Meanwhile, the development of this year's 'north hole' at the center of the sea ice appears to persist, as illustrated by the image below.






Arctic Methane Impact

The image below covers a period of just over one day. On November 26, 2013, peak readings were as high as 2392 ppb.



The green circle highlights an area with high methane levels just north of Greenland. This methane likely originates from hydrates along the fault line that crosses the Arctic Ocean. As the Naval Research Laboratory animation below shows, sea ice in that area is rather thick. How it is possible for the methane to appear there? The answer must be, it seems, that there is so much movement in the sea ice in this area, that there are many cracks through which the methane can rise.



Above animation shows how a huge part of the sea ice, meters thick, is pushed along the edges of Greenland into the Atlantic Ocean, as a result of strong winds, as also illustrated by the animation below.



Methane has now been showing up prominently over the entire Arctic Ocean for more than a month and it doesn't look like this situation is coming to an end soon. The animation shows methane over the Arctic Ocean over a period of six days, with each frame covering a period of one day.



What is the impact of all this methane on temperatures over the Arctic? The NOAA image below shows surface temperature anomalies for a 30-day period.


When temperatures are averaged over longer periods, peaks will obviously show up less severe. Yet, on above image an area shows up in the Arctic where anomalies have averaged 15 degrees Celsius or more over this 30-day period.


When looking at individual days, anomalies of over 20 degrees Celsius can show up, on above image over quite a large area. While the weather can vary a lot and depends on a lot of factors, there is no doubt that the methane cloud hanging over the Arctic Ocean will have contributed to such anomalies. Since this methane isn't just going away soon, this spells bad news for what is ahead in the Arctic.


And while most efforts to contain global warming focus on ways to keep global temperature from rising with more than 2°C, a polynomial trendline already points at global temperature anomalies of 5°C by 2060. Even worse, a polynomial trend for the Arctic shows temperature anomalies of 4°C by 2020, 7°C by 2030 and 11°C by 2040, threatening to cause major feedbacks to kick in, including albedo changes and methane releases that will trigger runaway global warming that looks set to eventually catch up with accelerated warming in the Arctic and result in global temperature anomalies of 20°C+ by 2050.



Methane Levels going through the Roof

On November 9, 2013, methane readings well over 2600 ppb were recorded at multiple altitudes, as illustrated by the image below.

[ click on image to enlarge ]
On November 9, 2013, p.m., methane readings were recorded as high as 2662 parts per billion (ppb), at 586 millibars (mb) pressure, which corresponds with an altitude of 14384.6 feet or 4384.4 meters.

Where did these high levels occur? Methane levels were low on the southern hemisphere and, while there were some areas with high readings over North America and Asia, there were no areas as wide and bright yellow as over the Arctic Ocean (the color yellow indicating readings of 1950 ppb and higher on above map).

As discussed in a previous post, huge amounts of methane are now escaping from the seabed of the Arctic Ocean, penetrating the sea ice, and entering the atmosphere, in a process that appears to be accelerating, resulting in huge amounts of methane in the atmosphere over the Arctic Ocean.

The image below gives an idea of the height of this level, compared to historic levels, and how fast levels of methane (CH4) have been rising compared to levels of two other greenhouse gases, i.e. carbon dioxide (CO2) and nitrous oxide (N2O).


Recent peak levels of methane over the Arctic Ocean may well have been even higher, since NOAA didn't release any readings for November 5-7, 2013.

Meanhwile, sea ice extent has stopped growing, as illustrated by the NSIDC graph below.


Data from the Cryosphere Today show that the area covered by sea ice has actually fallen over the past few days, as illustrated by the image below.

[ click on image to enlarge ]
There are several reasons why sea ice isn't growing, including high temperature anomalies in the Arctic, as illustrated by the NOAA image below, showing surface temperature anomalies of over 20 degrees Celsius on November 7, 2013.


High methane levels are contributing to temperature anomalies, by trapping additional sunlight in the atmosphere over the Arctic Ocean.

Furthermore, strong winds have hit the sea ice, as the recent post Methane, Faults and Sea Ice warned. Strong winds are pushing sea ice inward in the Kara Sea and in the Chukchi Sea, while pushing sea ice - up to 5 meters thick - out of the Arctic Ocean along the coast of Greenland, as illustrated by the Naval Research Laboratory animation below.


The Naval Research Laboratory image below shows ice speed and drift on November 9, 2013.


So, could Arctic sea ice collapse and totally disappear in September 2014? Posts at this blog have repeatedly warned about this, e.g. in this post. The image below, created by Wipneus, shows an exponential trendline pointing at zero volume sea ice in September 2016.
All data over the past two decades have fallen within the 95% confidence limits of an exponential trendline that points at imminent loss of all Arctic sea ice within years. September 2013 may have been "only" the 4th lowest on record, but such variability can be expected and may well cause sea ice to disappear completely as early as September 2014.

Strong winds can speed up such a collapse. On this point, it's good to remember what Prof. Peter Wadhams warned about in 2012:
". . apart from melting, strong winds can also influence sea ice extent, as happened in 2007 when much ice was driven across the Arctic Ocean by southerly winds (not northerly, as she stated). The fact that this occurred can only lead us to conclude that this could happen again. Natural variability offers no reason to rule out such a collapse, since natural variability works both ways, it could bring about such a collapse either earlier or later than models indicate.

In fact, the thinner the sea ice gets, the more likely an early collapse is to occur. It is accepted science that global warming will increase the intensity of extreme weather events, so more heavy winds and more intense storms can be expected to increasingly break up the remaining ice, both mechanically and by enhancing ocean heat transfer to the under-ice surface."
Guy McPherson lists 26 feedbacks that speed up warming, and many of these feedbacks occur in the Arctic, as described in the post Diagram of Doom.

Soon, calculates Prof. Peter Wadhams, the albedo loss due to decline of snow and ice in the Arctic will effectively more than double the net radiative forcing resulting from the emissions caused by all people of the world. Additional warming caused by methane releases from the Arctic seabed could be even more devastating.

Hopefully, more people will realize the urgency of the situation and realize the need for a comprehensive and effective plan of action as described here.


Algae Bloom or Clathrates

There has been some discussion lately as to whether the high levels of methane observed over the Arctic Ocean originated from algae bloom or from clathrates (i.e methane hydrates).

The image below, from Arctic.io, does indeed indicate extensive algae bloom.

[ click on image to enlarge ]
The green color indicates extensive algae bloom, especially in areas where the sea water has been very warm recently, as discussed in earlier posts such as 'Is the North Pole now ice-free?' The image below shows sea surface temperature anomalies as at September 30, 2013.

[ click on image to enlarge ]
Indeed, no surprise to see extensive algae bloom, especially close to Svalbard, where the highest anomalies were recorded. The question is, however, where the methane came from that has showed up so prominently over the Arctic Ocean recently. The animation below shows methane readings over the past week, against a recent sea ice concentration map.



[ click on image to enlarge ]


These high methane levels appear to show up over the sea ice, rather than over open water. This makes it more likely that the methane originates from deep sea clathrates. The color red indicates that the sea ice has maximum concentration, so there will be few holes in the ice where algae can grow. As the top image shows, the green color shows up in areas with open water, rather than over areas covered with ice.

The image below shows sea ice thickness for the same date as the sea ice concentration map.



Even at places where the sea ice has been very thin recently, such as on the North Pole and as discussed in the post North Hole, it is now at least some 30 cm thick, making it unlikely that algae are grow there.

In conclusion, it is likely that the methane originates from deep sea clathrates, and that is a very scary development.


Is the North Pole now ice-free?

Is the North Pole now ice-free? It could well be that, by the time you read this, there will be no ice left at all at the North Pole. The image below, created by Sam Carana from a nowcast from the Naval Research Laboratory, run on September 17, 2013 and valid for September 18, 2013, shows open water extending all the way to a spot very close to the North Pole.


As the color indicates, sea ice thickness in this area is virtually zero (i.e. ice-free). This development of an ice-free area at the North Pole has been discussed in earlier posts such as:
  • Arctic sea ice thickness falls by 2m in 21 days in some areas (June 13, 2013)
  • Open Water In Areas Around North Pole (June 22, 2013), describing areas around the North Pole where sea ice thickness had fallen to virtually zero, i.e. open water. 
  • Open Water at North Pole (July 22, 2013), descibing a wide corridor that had developed with very thin ice between the North Pole and Siberia. The post added that surface water on top of this thin ice could extend along this corridor, all the way from the North Pole to edge of the ice, in which case the surface water effectively becomes part of open water.
  • North Hole (September 2, 2013), describing areas close to the North Pole where ice volume had fallen to virtually zero, while pointing at how devastating the impact of sea surface temperature anomalies can be. 
This sea ice thinning in areas close to the North Pole has been one of the most important developments in 2013. Yet, many people keep watching sea ice extent.

Why was Arctic sea ice not smaller in extent in 2013 than in 2012?

The comparison below shows both volume and the extent of the sea ice for the same day in 2013 (left), respectively 2012 (right). Natural variability can make Arctic sea ice slightly smaller or larger than projected. There are many factors that influence things from year to year, such as weather conditions, sea currents and temperatures of the water in the Atlantic and Pacific Oceans; some factors are discussed in more detail below.


The above comparison shows a lot more ice north of Alaska in 2013 (above left) than in 2012 (above right). The comparison below shows that salinity levels in the Beaufort Sea were lower in 2013 (below left) than in 2012 (below right).


Seawater typically has a salinity level of over 3%; it freezes at about −2°C (28°F). Where mixing occurs with fresh water runoff from melting glaciers and permafrost, the water in the Arctic Ocean can become substantially less saline. Other substances added to the water, such as sand, can also cause a freezing point drop. The freezing and melting point of fresh water (i.e. zero salinity) is 0°C (or 32°F).  Less salinity means the water will remain frozen until the temperature reaches levels closer to 0°C.

Thinning continues

Heatwave conditions in Alaska caused greater melting of the permafrost. The result was more fresh water run-off through the MacKenzie River into the Beaufort Sea. This has contributed to keep sea ice extent larger in 2013. Yet, the warm water has also contributed to further thinning of the ice, reinforcing warnings that the sea ice looks set to disappear altogether within years. 


As illustrated by the above image by Neven, from the Arctic Sea Ice blog, average Arctic sea ice thickness (crudely calculated by dividing PIOMAS (PI) volume numbers with Cryosphere Today (CT) sea ice area numbers) has been very low in 2013.

The image below shows that annual minimum volumes appear to follow an exponential trend downward to zero, firstly reached in September 2015, followed by zero ice in the surrounding months over subsequent years.

Some people have objected against using PIOMAS data for such projections, with arguments ranging from suggestions that PIOMAS data were not reliable, that natural variability could prove such projections to be wrong, to questioning whether an exponential trend was appropriate. Nonetheless, it seems that over the years arguments in favor of an exponential trend have only become stronger:
  • Further measurements such as by CryoSat have confirmed that the PIOMAS data are indeed reliable and that the sea ice decline may well be even more dramatic. 
  • Natural variability goes both ways, it can either speed up or slow down ice melt. Had there been less runoff from the MacKenzie River, the sea ice in 2013 may not have been able to refreeze after being hit by cyclones several times. Next year we may not be so lucky and sea ice could disappear altogether, due to natural variability.  
  • Thick ice along the northern coast of Greenland is indeeed more persistent because of on-shore winds that cause the ice to drift and pile-up there. This would favor a Gompertz (or Sigmoid) trend in extrapolations (see image on the right). However, the new development of an ice-free North Pole shows that the sea ice is capable of breaking up abruptly, not only from the outer edges toward Greenland, but also starting at the North Pole and even moving from there toward Greenland. Moreover, as the 30-day animation below shows, thick sea ice north of Greenland can thin very quickly, suggesting it could well disappear altogether within one season.  


Sea ice can thin rapidly, even when it is multiple meters thick 

Earlier in 2013, much warm water entered the Arctic Ocean from the mouths of rivers, as discussed in the post Arctic Ocean is turning red. As said, this resulted in lower salinity levels in the Beaufort Sea that prevented cyclones from demolishing the sea ice altogether. Nonetheless, the joint impact of cyclones and warm water does appear to have caused rapid decline of the thick ice north of Greenland and Canada, as earlier discussed in an earlier post

Furthermore, sea surface temperatures have been recorded close to Svalbard that are far higher than even in the waters closer to the Atlantic Ocean. This phenomenon is illustrated by the image below, showing sea surface temperatures (top) and sea surface temperature anomalies (underneath). 


In some of these spots, sea surface temperatures are well over 10°C (50°F). Where does this heat come from? 

These hot spots could be caused by undersea volcanic activity; this is the more dangerous as the area has seen methane bubbling up from hydrates that have become destabilized; such dangers have been discussed repeatedly, e.g. in the post Runaway Global Warming. Hot spots can also contribute to even more dramatic thinning of the sea ice, including the thickest parts. 

In conclusion, there is no reason to assume that the sea ice in the Arctic will somehow magically recover. Instead, there are many indications that exponential decline of Arctic sea ice will continue. Less salinity may have temporarily prolonged the extent of the sea ice in some areas, but as sea surface temperatures keep rising, the ever thinner ice looks set to collapse within years, with dire consequences. This calls for comprehensive and effective action, such as described at the ClimatePlan blog.  


Related posts

- Arctic sea ice thickness falls by 2m in 21 days in some areas
Arctic-news.blogspot.com/2013/06/arctic-sea-ice-thickness-falls-by-2m-in-21-days-in-some-areas.html

- Open Water In Areas Around North Pole
Arctic-news.blogspot.com/2013/06/open-water-in-areas-around-north-pole.html

- Open Water at North Pole
Arctic-news.blogspot.com/2013/07/open-water-at-north-pole.html

- North Hole
Arctic-news.blogspot.com/2013/09/north-hole.html

- CryoSat - New Dimensions on Ice
esa.int/Our_Activities/Observing_the_Earth/Living_Planet_Symposium_2013/New_dimensions_on_ice

- Arctic Ocean is turning red
Arctic-news.blogspot.com/2013/08/arctic-ocean-is-turning-red.html

- Cyclone raging on thin ice
Arctic-news.blogspot.com/2013/08/cyclone-raging-on-thin-ice.html

- Runaway Global Warming
Geo-engineering.blogspot.com/2011/04/runaway-global-warming.html

- Climate Plan
ClimatePlan.blogspot.com

Arctic Sea Ice in Free Fall

Arctic Sea Ice has declined dramatically recently. The recent image below, by the Danish Meteorological Institute, shows the decline in extent over the past few days, with extent calculated by including all areas with ice concentration higher than 30%.


As the above image shows, sea ice extent (30%+ concentration) is now lower than any other year, except 2007 and 2012. Moreover, the sharp decline looks set to continue.

Ice volume and concentration have dropped dramatically, partly as a result of the cyclone that hit the Arctic Ocean a few days ago. The eye of the cyclone is still visible almost exactly above the North Pole on the Naval Research Laboratory image below on the right, where sea ice concentration appears to form a circle.

The sea ice looks set for an all-time record low; all this thin ice looks set to disappear over the next few weeks.

The graph below, also by the Danish Meteorological Institute, calculates sea ice extent by including all areas with 15% or more ice concentration.
The above graph also shows a steep recent descent, although not as pronounced as in the graph at the top that includes spots with 30% or more ice concentration. The graph at the top better illustrates recent drops in ice concentration from, say, 40% to 20%, which can occur quite abruptly due to the impact of a cyclone. 

The Danish Meteorological Institute has meanwhile produced a more recent version of the graph based on spots with 30% or more ice concentration (added below).


The above graph shows an August 15 extent that appears to be back in line with the earlier trend. At first glance, it may appear as if the sea ice has largely recovered from the impact of three cyclones that have hit the Arctic Ocean over the past two months. 

However, these cyclones are likely to have contributed to the appearance and persistence of thin spots in the ice close to the North Pole. This phenomenon was earlier described in posts such as Thin Spots developing in Arctic Sea Ice

The conclusion remains the same as the one drawn then in that post, i.e. that for years, observation-based projections have been warning about Arctic sea ice collapse within years, with dire consequences for the Arctic and for the world at large.

Cyclones can speed up this collapse. On this point, it's good to remember what Prof. Peter Wadhams said in 2012:
". . apart from melting, strong winds can also influence sea ice extent, as happened in 2007 when much ice was driven across the Arctic Ocean by southerly winds (not northerly, as she stated). The fact that this occurred can only lead us to conclude that this could happen again. Natural variability offers no reason to rule out such a collapse, since natural variability works both ways, it could bring about such a collapse either earlier or later than models indicate.

In fact, the thinner the sea ice gets, the more likely an early collapse is to occur. It is accepted science that global warming will increase the intensity of extreme weather events, so more heavy winds and more intense storms can be expected to increasingly break up the remaining ice, both mechanically and by enhancing ocean heat transfer to the under-ice surface."
Hopefully, more people will realize the urgency of the situation and realize the need for a comprehensive and effective plan of action as described here.

Cyclone raging on Thin Ice

Another cyclone is raging over the Arctic Ocean. The Naval Research Laboratory image below shows the speed and drift of the sea ice.

[ click on image to enlarge ]
Last time a cyclone hit the Arctic, this resulted in a temporary increase in area covered by sea ice, as shown on the Cryosphere Today image below. The cyclone pushed down on the sea ice, flattening it and pushing it sideways. 


Note that area as measured by the Cryosphere Today includes all spots that have a 15% or higher concentration of ice. This way of measuring area ignores the fact that the cyclone reduced the sea ice concentration in many spots, from a high sea ice concentration (around 90%) to a lower concentration (less than 80%), as shown on the Naval Research Laboratory image below. 


Furthermore, sea ice has since dropped in thickness, as illustrated by the Naval Research Laboratory image below. 

Much of the ice is now less than one meter thick, while some areas close to the North Pole have ice that is only between zero and half a meter thick.

The cyclone is raging most fiercely in those areas and much of the ice is drifting out into the Atlantic Ocean.

Neven mentioned at the Arctic Sea Ice Blog that average thickness (crudely calculated by dividing PIOMAS (PI) volume numbers with Cryosphere Today (CT) sea ice area numbers, see image below) had a very steep drop in July, similar to the drop in 2010. This year's trend line is now lowest, probably signifying that the ice pack is spread out and thin at the edges (read: melting potential).

[ click on image to enlarge ]
The image below, from the University of Bremen, Germany, shows sea ice concentration on August 11, 2013.



Arctic Ocean Events - Videos by Paul Beckwith

by Paul Beckwith


Massive Arctic cyclone effect on sea ice in August 2012
Part 1: August 1st to 16th, 2012
http://www.youtube.com/watch?v=nli47-9dT5o

Arctic sea ice motion (speed and direction) is compared to sea ice thickness from August 1st to August 16th, 2012. Sea ice motion is then compared to meteorology (500 mb pressure heights and 200 mb vector winds).




Massive Arctic cyclone effect on sea ice in August 2012
Part 2: August 1st to 16th, 2012
http://www.youtube.com/watch?v=WqwIVEpSg3w

Northern hemisphere meteorology (500mb pressure heights) and Arctic sea ice concentration compared to SST (sea surface temperatures) are examined from August 1st to August 16th, 2012 encompassing the mass persistent cyclone.




Massive Arctic cyclone effect on sea ice in August 2012
Part 3: August 1st to 16th, 2012
http://www.youtube.com/watch?v=HjYxRV0fzz4

Arctic basin SSS (sea surface salinity) is compared to SSH (sea surface height) during the period August 1st to August 16th, 2012 which encompassed a massive persistent cyclone. Detailed meteorology is also examined (tropopause temperature + pressure, surface precipitable water + pressure). Also examined is ocean profile salinity and temperature from an ice tethered buoy.




Massive Arctic cyclone effect on sea ice in August 2012
Part 4:  August 1st to 16th, 2012
http://www.youtube.com/watch?v=aAJRIV8YITY

The jet streams in the Arctic ocean basin are shown (200mb vector winds) from NOAA/ESRL daily data, as well as from 4 times daily data from SFSU. The data is given from August 1st to August 16th, 2012 which encompasses the massive Arctic cyclone.




2013

Arctic sea ice thickness + motion
May 14th to June 10th, 2013
http://www.youtube.com/watch?v=5ljHI0VITgk

Arctic sea ice data from May 14 to June 10, 2013
Left pane shows Arctic sea ice thickness; right pane shows sea ice motion (direction and speed).




Arctic sea ice thickness + motion
July 1st to 17th 2013
http://www.youtube.com/watch?v=cUZr51_yW5s

Arctic sea ice data from July 1st to July 17th, 2013. Left pane shows the Arctic sea ice thickness; right pane shows sea ice motion (direction and speed).




Sea ice concentration, temperature, salinity, and height;
July 1st to 18th, 2013
http://www.youtube.com/watch?v=icUtGqpkFx8

Arctic ocean data from US Navy for
1) sea ice concentration,
2) sea surface temperature (SST),
3) sea surface salinity (SSS), and
4) sea surface height (SSH)




Jet streams
July 1st to July 17th 2013
http://www.youtube.com/watch?v=IFbJCFVSiPI

Northern hemisphere (NH) jet streams are shown from two sources:
1) NOAA/ESRL data collected daily, and
2) SFSU data collect every 6 hours. Data is given for the time period from July 1st to July 17th, 2013.




Meteorology
July 1st to 18th 2013
http://www.youtube.com/watch?v=LONJT8JbM7I

The following meteorology plots are shown for time period July 1st to July 18th, 2013 over the Arctic Ocean between 60 degrees N and 90 degrees N:
1) 500mb pressure levels,
2) 200mb vector winds (jet streams),
3) precipitable water, and
4) tropopause temperatures.

Open Water In Areas Around North Pole

In some areas around the North Pole, thickness of the sea ice has declined to virtually zero, i.e. open water.


What could have caused this open water? Let's go through some of the background.

North Hemisphere snow cover has been low for some time. Snow cover in May 2013 was the lowest on record for Eurasia. There now is very little snow left, as shown on the image right, adapted from the National Ice Center.

Low snow cover is causing more sunlight to be absorbed, rather than reflected back into space. As can be expected, there now are high surface temperatures in many areas, as illustrated by the NOAA image below. Anomalies can be very high in specific cases. Zyryanka, Siberia, recently recorded a high of 37.4 C, against normal high temperatures of 20 C to 21 C for this time of year. Heat wave conditions were also recorded in Alaska recently (satellite image of Alaska below).

NASA image June 17, 2013, credit: NASA/Jeff Schmaltz, LANCE MODIS Rapid Response Team, NASA GSFC - from caption by Adam Voiland: "Talkeetna, a town about 100 miles north of Anchorage, saw temperatures reach 96°F (36°C) on June 17. Other towns in southern Alaska set all-time record highs, including Cordova, Valez, and Seward. The high temperatures also helped fuel wildfires and hastened the breakup of sea ice in the Chukchi Sea."
Accordingly, a large amount of relatively warm water from rivers has flowed into the Arctic Ocean, in addition to warm water from the Atlantic and Pacific Oceans.


Sea surface temperatures have been anomalously high in many places around the edges of the sea ice, as also shown on the NOAA image below.


Nonetheless, as the above images also make clear, sea surface temperatures closer to the North Pole have until now remained at or below zero degrees Celsius, with sea ice cover appearing to remain in place. The webcam below from the North Pole Environmental Observatory shows that there still is a lot of ice, at least in some parts around the North Pole.

Webcam #2 of the North Pole Environmental Observatory monitoring UPMC's Atmospheric Buoy, June 21, 2013
So, what could have caused the sea ice to experience such a dramatic thickness decline in some areas close to the North Pole?

Firstly, as discussed in earlier posts, there has been strong cyclonic activity over the Arctic Ocean (see also Arctic Sea Ice blog post). This has made the sea ice more prone and vulnerable to the rapid decline that is now taking place in many areas.

Furthermore, Arctic sea ice thickness is very low, as illustrated by the image below.

Arctic sea ice volume/extent ratio, adapted by Sam Carana from an image by Neven (click to enlarge)
Finally, there has been a lot of sunshine at the North Pole. At this time of year, insolation in the Arctic is at its highest. Solstice (June 20 or June 21, 2013, depending on time zone) is the day when the Arctic receives the most hours of sunlight, as Earth reaches its maximum axial tilt toward the sun of 23° 26'. In fact, insolation during the months June and July is higher in the Arctic than anywhere else on Earth, as shown on the image below.

Monthly insolation for selected latitudes -  adapted from Pidwirny, M. (2006), in "Earth-Sun Relationships and Insolation",  Fundamentals of Physical Geography, 2nd Edition
In conclusion, the current rapid sea ice thickness decline close to the North Pole is mostly due to a combination of earlier cyclonic activity and lots of sunlight, while the sea ice was already very thin to start with. The cyclone broke up the sea ice at the center of the Arctic Ocean, which is turn made it more prone to melting rapidly. The cyclone did more, though, as contributor to the Arctic-news blog Veli Albert Kallio explains:
"The ocean surface freezes if the temperature falls below -2.5C. The reason for the negative melting point is the presence of 4-5% of sea salt. Only in the polar regions does the sea surface cool sufficiently for sea ice to form during winters.

The sea ice cover is currently thinning near the North Pole between 80-90 degrees north. This part of the ocean is very deep. It receives heat of the Gulf Stream from the south: as the warm water vapourises, its salt content to water increases. This densifies the Gulf Stream which then falls onto the sea floor where it dissipates its heat to the overlying water column. The deep basin of the Arctic Ocean is now getting sufficiently warmed for the thin sea ice cover to thin on top of it. The transportation of heat to the icy surface is combined with the winds that push cold surface water down while rising heat to surface."
Indeed, vertical mixing of the water column was enhanced due to cyclonic activity, and this occurred especially in the parts of the Arctic Ocean that also are the deepest, as illustrated by the animation below.
Legend right: Ice thickness in m from Naval Research Laboratory
Legend bottom: Sea depth (blue) and land height (brown/green)
in m from NIBCAO Arctic map at NOAA
The compilation of images below shows how the decline of sea ice has taken place in a matter of weeks.

[ click to enlarge ]
This spells bad news for the future. It confirms earlier analyses (see links below) that the sea ice will disappear altogether within years. It shows that the sea ice is capable of breaking up abruptly, not only at the outer edges, but also at the center of the Arctic Ocean. As the Arctic sea ice keeps declining in thickness, it does indeed look set to break up and disappear abruptly across most of the Arctic Ocean within a few years. Models that are based on sea ice merely shrinking slowly from the outer edges inward should reconsider their projections accordingly.

Related

- Getting the Picture
http://arctic-news.blogspot.com/2012/08/getting-the-picture.html

- Supplementary evidence by Prof. Peter Wadhams
http://arctic-news.blogspot.com/2012/04/supplementary-evidence-by-prof-peter.html