Secondly, warming in the Arctic is accelerating due to feedbacks, as discussed on the feedbacks page. Many such feedbacks are related to decline of the snow and ice cover in the Arctic, which is in turn made worse by emissions such as soot.
Thirdly, the most dangerous feedback is release of methane from the Arctic Ocean seafloor, due to hydrates getting destabilized as heat reaches sediments.
Last year, Arctic sea ice reached its maximum extent on February 25, 2015. This year, there was a lot less sea ice in the Arctic on February 25 than there was last year, as illustrated by above image. The difference is about 300,000 square km, more than the size of the United Kingdom.
The image below shows that global sea ice on February 22, 2016, was only 14.22086 million square km in area. It hasn't been that low since satellite records started to measure the sea ice.
A number of feedbacks are associated with the decline of sea ice, such as more sunlight being absorbed by the water, instead of being reflected back into space as it was previously. Furthermore, there are three kinds of warming active in the Arctic, as described above and as depicted by the image below.
Sea ice can reflect as much as 90% of the sunlight back into space. Once the ice has melted away, however, the water of the ocean reflects only 6% of the incoming solar radiation and absorbs the rest. This is depicted in above image as feedback #1.
As Professor Peter Wadhams once calculated, warming due to Arctic snow and ice loss could more than double the net warming now caused by all emissions by all people of the world.
 |
| Professor Peter Wadhams on albedo changes in the Arctic, image from Edge of Extinction |
As the sea ice melts, sea surface temperatures will remain at around zero degree Celsius (32°F) for as long as there is ice in the water, since rising ocean heat will first go into melting the ice. Only after the ice has melted will ocean heat start raising the temperature of the water. Sea ice thus acts as a buffer that absorbs heat, preventing water temperatures from rising. As long as sea ice is melting, each gram of ice will take 334 Joule of heat to change into water, while the temperature remains at 0° Celsius or 32° Fahrenheit. Once all ice has turned into water, all further heat goes into heating up the water. To raise the temperature of one gram of water by one degree Celsius then takes only 4.18 Joule of heat. In other words, melting of the ice absorbs 8 times as much heat as it takes to warm up the same mass of water from zero to 10°C. This is depicted in the image on the right as feedback #14.
Above video, created by Stuart Trupp, shows how added heat at first (A) goes mainly into warming up water that contains ice cubes. From about 38 seconds into the movie, all heat starts going into the transformation of the ice cubes into water, while the temperature of the water doesn't rise (B). More than a minute later, as the ice cubes have melted (C), the temperature of the water starts rising rapidly again.
Methane is a further feedback, depicted as feedback #2 on the image further above. As the water of the Arctic Ocean keeps getting warmer, the danger increases that heat will reach the seafloor where it can trigger release of huge amounts of methane, in an additional feedback loop that will make warming in the Arctic accelerate and escalate into runaway warming.
Sediments underneath the Arctic Ocean hold vast amounts of methane. Just one part of the Arctic Ocean alone, the East Siberian Arctic Shelf (ESAS, see map below), holds up to 1700 Gt of methane. A sudden release of less than 3% of this amount could add 50 Gt of methane to the atmosphere, and experts have warned for many years that they consider such an amount to be ready for release at any time.
Above image gives a simplified picture of the threat, showing that of a total methane burden in the atmosphere of 5 Gt (it is meanwhile higher), 3 Gt that has been added since the 1750s, and this addition is responsible for almost half of all antropogenic global warming. The amount of carbon stored in hydrates globally was in 1992 estimated to be 10,000 Gt (USGS), while a more recent estimate gives a figure of 63,400 Gt (Klauda & Sandler, 2005). Once more, the scary conclusion is that the East Siberian Arctic Shelf (ESAS) alone holds up to 1700 Gt of methane in the form of methane hydrates and free gas contained in sediments, of which 50 Gt is ready for abrupt release at any time.
The warning signs keep getting stronger. Following a peak methane reading of 3096 ppb on February 20, 2016, a reading of 3010 ppb was recorded in the morning of February 25, 2016, at 586 mb (see image below).
The situation is dire a calls for comprehensive and effective action as described in the Climate Plan.
Links
- Feedbacks in the Arctic
http://arctic-news.blogspot.com/p/feedbacks.html
- Albedo changes in the Arctic
http://arctic-news.blogspot.com/2012/07/albedo-change-in-arctic.html
- The time has come to spread the message
http://arctic-news.blogspot.com/2013/12/the-time-has-come-to-spread-the-message.html
- Greenhouse gas levels and temperatures keep rising
http://arctic-news.blogspot.com/2016/01/greenhouse-gas-levels-and-temperatures-keep-rising.html
- Arctic sea ice area at record low for time of year
http://arctic-news.blogspot.com/2016/01/arctic-sea-ice-area-at-record-low-for-time-of-year.html
- Has maximum sea ice extent already been reached this year?
http://arctic-news.blogspot.com/2016/02/has-maximum-sea-ice-extent-already-been-reached-this-year.html
- Global sea ice extent record minimum - Arctic Sea Ice Blog
http://neven1.typepad.com/blog/2016/02/global-sea-ice-extent-minimum-record.html
- Warming of the Arctic Fueling Extreme Weather
http://arctic-news.blogspot.com/2014/06/warming-of-the-arctic-fueling-extreme-weather.html
- Climate Plan
http://arctic-news.blogspot.com/p/plan.html
Last year, Arctic sea ice reached its maximum extent on February 25, 2015. This year, there's a lot less sea ice in the...
Posted by Sam Carana on Friday, February 26, 2016