Showing posts with label maximum. Show all posts
Showing posts with label maximum. Show all posts

Friday, February 26, 2016

Three kinds of warming in the Arctic

The Arctic is prone to suffer from three kinds of warming. Firstly, the Arctic is hit particularly hard by emissions, as discussed in earlier posts such as this one and this one.

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).

Again, this very high level was likely caused by methane originating from the seafloor of the Arctic Ocean, at a location on the Gakkel Ridge just outside the East Siberian Arctic Shelf (ESAS), as discussed in the earlier post. This conclusion is supported by the methane levels at various altitudes over the ESAS, as recorded by both the MetOp-1 and MetOp-2 satellites in the afternoon, as illustrated by the combination image below showing methane levels at 469 mb.

The situation is dire a calls for comprehensive and effective action as described in the Climate Plan.


- Feedbacks in the Arctic

- Albedo changes in the Arctic

- The time has come to spread the message

- Greenhouse gas levels and temperatures keep rising

- Arctic sea ice area at record low for time of year

- Has maximum sea ice extent already been reached this year?

- Global sea ice extent record minimum - Arctic Sea Ice Blog

- Warming of the Arctic Fueling Extreme Weather

- Climate Plan

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

Sunday, March 15, 2015

Strong Winds And Waves Batter Arctic Sea Ice

As Earth warms, the intensity of storms is rising across the globe. At least eight people died in Vanuatu, as it was hit by Cyclone Pam. "It hit Port Vila at an incredible 340 kilometres an hour", mentions a recent news report. The left part of the image below shows Cyclone Pam reaching speeds as high as 144 kilometers an hour (89.48 mph, green circle) on March 12, 2015, 1500Z, while three further cyclones feature on the Southern Hemisphere. 

At the same time, on the Northern Hemisphere, winds reached speeds as high as 101 km/h (62.76 mph, bottom green circle), 120 km/h (74.56 mph, middle green circle) and 112 km/h (69.59 mph, top green circle), as shown on the right part of above image.

The image on the right shows winds with speeds as high as 125 km/h (77.67 mph) batter the coast of Greenland on March 13, 2015 (green circle).

The image below shows strong winds moving from the North Atlantic into the Arctic Ocean on March 13, 2015. 

The video below, with forecasts for March 13 - 20, 2015, shows strong winds battering the Arctic Ocean at both the Pacific and Atlantic ends.

The combination image below shows winds around Greenland (top) and winds penetrating the Arctic Ocean (bottom).

Waves as high as 41.5 ft (12.65 m) were recorded between Svalbard and Norway on March 13, 2015 (green circle on the left part of the image below), while waves as high as 23.13 ft (7.05 m) were recorded close to the edge of the sea ice on March 15, 2015 (green circle on the right part of the image below).

The updated image below shows waves higher than 10 m (33 ft) near Svalbard close to the edge of the sea ice on March 16, 2015 (green circle).

Meanwhile, it more and more looks like the 2015 sea ice extent maximum was reached on February 25, as illustrated by the image below.

The image below (added later, ed.) shows Arctic sea ice area up to March 18, 2015 (top), and Arctic sea ice extent up to March 20, 2015 (bottom). Briefly, the difference between area and extent could be compared to Swiss cheese. Area is the cheese without the holes, while extent measures the cheese in addition to the holes. For more on this, see this NSIDC FAQ.

Strong winds can cause high waves that can break up the sea ice. At the same time, strong winds can speed up currents that push sea ice out of the Arctic Ocean, while bringing warmer water into the Arctic Ocean, as illustrated by the image below.

The image below shows sea surface temperatures of 20.9°C (69.62°F, green circle left) recorded off the coast of North America on March 14, 2015, an anomaly of 12.3°C or 26.54°F.

[ click on image to enlarge ]
The image below shows sea surface temperature anomalies in the Arctic Ocean on March 15, 2015.

The big danger is that warm water will trigger further releases of methane from the seafloor of the Arctic Ocean. Peak daily methane levels recorded in early 2015 averaged a very high 2370 parts per billion, as illustrated by the image below.

Natalia Shakhova et al. estimate the accumulated methane potential for the Eastern Siberian Arctic Shelf (ESAS, rectangle on image right) alone as follows:
- organic carbon in permafrost of about 500 Gt;
- about 1000 Gt in hydrate deposits; and
- about 700 Gt in free gas beneath the gas hydrate stability zone.

Hydrates can become destabilized by pressure changes that can be caused by earthquakes and resulting shockwaves and landslides, or that can be caused by wild temperature swings.

Hydrates can also become destabilized by a small temperature rise that can be caused by influx of warmer water from outside the Arctic Ocean or by warm surface water being mixed down by storms.

Waters in the ESAS are quite shallow, averaging less than 50 m depth over its 2x10ˆ6 km2 area, while methane hydrates in the ESAS can exist at depths as shallow as 20 m.

Where heat is able to penetrate the sediment along cracks, some hydrate destabilization can occur, which in turn can trigger larger destabilization, as methane escaping from a hydrate expands to 160 times its earlier volume; this explosive expansion can cause further destabilization of sediments containing methane in the form of hydrates and free gas.

The situation is dire and calls for comprehensive and effective action, as discussed at the Climate Plan blog.