Showing posts with label storm. Show all posts
Showing posts with label storm. Show all posts

Wednesday, September 12, 2012

Storm enters Arctic region

Tropical Storm Leslie hit Newfoundland on September 11, 2012. Leslie was discussed in the earlier post by Paul Beckwith. The NOAA image below gives a 5-day forecast of Leslie's continued path along the coasts of Greenland and Iceland.


That may keep Leslie just out of the Arctic Circle, but this path does make it enter the Arctic Region, i.e. the area where temperatures in the warmest month used to remain under 10°C, or 50°F, as illustrated by the map below.


The image below shows how Leslie's impact on air pressure. The image below is part of a series of images showing how Leslie causes a low pressure area (compressed isobars) that then propagates over the Arctic ocean region. See further images at the Polar Meteorology Group at Ohio State University.


This low pressure region can also be tracked in the 9-panel GFSx forecast below, from Unisys Weather.



Storms are important to the Arctic, they can cause high waves and changes in wave direction, as illustrated by the combined images below from OceanWeather Inc



Storms can cause decline of Arctic sea ice and bring warm water and air into the Arctic. The Diagram of Doom, discussed in more details in an earlier post, pictures ten feedbacks that can cause warming in the Arctic to accelerate. Storms are a factor in many of these feedbacks. 



As illustrated by the NOAA image below, accelerated warming results in high temperature anomalies, increasing the danger of methane releases from sediments under the water.


Paul Beckwith comments that in this case Greenland acts as a barrier to the storm entering the Arctic due to its 3 km ice cap (note also that the thickness of the troposphere is only about 7 km high in the Arctic, meaning that Greenland extends up in altitude to cover >40% of the atmosphere in which weather occurs). What this means is that the storm will be diverted from directly crossing Greenland.

Paul adds a warning: In this case we are lucky in that the storm passes below and to the right of Greenland and then heads past Iceland on its way to north of Scotland. A worse scenario for the Arctic and the sea ice there would be if the storm stalled of the western coast of Greenland and slowly tracked up north through the Davis Strait and across the Canadian archipelago and then directly into the Arctic to the west of Greenland. Such a storm would have devastating consequences to the Arctic and the sea ice (not to mention Greenland, mostly on the coasts). Lots of heat and moisture would be transferred into the Arctic by such a storm.

Tuesday, August 28, 2012

Diagram of Doom



Above diagram was part of a poster displayed at the 2011 AGU meeting in San Francisco by the Arctic Methane Emergency Group (AMEG). It was accompanied by the following text: In the Arctic, three problems are compounding one another: emissions causing global warming, sea ice loss causing accelerated warming, and methane releases further accelerating Arctic warming, with the danger of triggering runaway global warming.

The diagram pictures three kinds of warming and their main causes:
  1. Emissions by people causing global warming, with temperatures rising around the globe, including the Arctic.
  2. Soot, dust and volatile organic compounds settling down on snow and ice, causing albedo change. More heat is absorbed, rather than reflected as was previously the case. This causes accelerated warming in the Arctic.
  3. Accelerated warming in the Arctic threatening to weaken methane stores in the Arctic with the danger that methane releases will trigger runaway global warming.

The diagram also pictures two feedback effects that make things even worse:
  • Albedo feedback: Accelerated warming in the Arctic speeds up sea ice loss, further accelerating albedo change.
  • Methane feedback: Methane releases in the Arctic further add to the acceleration of warming in the Arctic, further contributing to weaken Arctic methane stores and increasing the danger that methane releases will trigger runaway global warming.

Albedo change in the Arctic comprises a number of elements, as depicted in the image below, from the 2004 report Impacts of a Warming Arctic - Arctic Climate Impact Assessmentby the International Arctic Science Committee.  


As described in various posts at this blog over time, there are further points that should be taken into account. Regarding sea ice loss, it's clear that where sea ice retreats, more open water appears, with the result that less sunlight is reflected back into space. Accelerated warming will also affect the integrity of the remaining sea ice, as well as of the snow and ice cover on land, including glaciers. This further adds to the albedo effect, causing less sunlight to be reflected back into space. Similarly, further feedbacks could be added or described in more detail.

Accordingly, ten feedbacks can be identified, and described as follows:
  1. Albedo feedback: Accelerated warming in the Arctic speeds up the decline of ice and snow cover, further accelerating albedo change. 
  2. Methane feedback: Methane releases in the Arctic further add to the acceleration of warming in the Arctic, further contributing to weaken Arctic methane stores and increasing the danger that methane releases will trigger runaway global warming. 
  3. Currents feedback: Sea ice loss can cause vertical sea currents to weaken, reducing the cooling effect they had on the seabed. This can thus further cause sediments to warm up that can contain huge amounts of methane in the form of free gas and hydrates. 
  4. Storms feedback: Increased frequency and intensity of storms can cause substantially more vertical mixing of the sea water column, causing more warming of the seabed, thus further contributing to the warming of sediments, as above. 
  5. Storms feedback: Accelerated warming in the Arctic can result in more storms, causing mixing of cold Arctic air with warmer air from outside the Arctic. The net result is a warmer Arctic. 
  6. Storms feedback: More open waters can result in more storms that can push the ice across the Arctic Ocean, and possibly all the way out of the Arctic Ocean. 
  7. Storms feedback: Storms also cause more waves that break up the sea ice. Smaller pieces of ice melt quicker than large pieces. A large flat and solid layer of ice is also less susceptible to wind than many lighter and smaller pieces of ice that will stand out above the water and capture the wind like the sails of yachts. 
  8. Storms feedback: Storms cause waters to become more wavy. Calm waters can reflect much sunlight back into space, acting as a mirror, especially when the sun shines under a low angle. Wavy waters, on the other hand, absorb more sunlight. 
  9. Fires feedback: More extreme weather comes with heatwaves and storms. Thus, this is in part another storms feedback. The combination of storms and fires can be deadly. Heatwaves can spark fires that, when fueled up by storms, turn into firestorms affecting huge areas and causing huge amounts of emissions. Storms can whip up particles that when deposited on ice, snow or the bare soil, can cause more sunlight to be absorbed. 
  10. Open doors feedback: Accelerated warming in the Arctic causes the polar vortex and jet stream to weaken, causing more extreme weather and making it easier for warm air to enter the Arctic.

These ten feedback are depicted in the diagram below. 


Friday, August 17, 2012

Arctic sea ice updates




Above diagram shows sea ice extent as calculated by the Polar View team at the University of Bremen, Germany.

Paul Beckwith warns that a second cyclone is threatening to batter the remaining sea ice soon.

View Paul's presentation by clicking on the link below.
https://docs.google.com/file/d/0ByLujhsHsxP7cnB0bXhNNFFSQjQ/edit


Or, view the presentation in the window below (it may take some time for the file to fully load).

Tuesday, August 14, 2012

Sea ice extent update August 14, 2012

The National Snow and Ice Data Center (NSIDC) at the University of Colorado has released an update. Excerpts follow below, for the full post, see A summer storm in the Arctic.

Arctic sea ice extent during the first two weeks of August continued to track below 2007 record low daily ice extents. As of August 13, ice extent was already among the four lowest summer minimum extents in the satellite record, with about five weeks still remaining in the melt season.

Arctic sea ice extent as of August 13, 2012. Credit: National Snow and Ice Data Center
The average pace of ice loss since late June has been rapid at just over 100,000 square kilometers (38,000 square miles) per day. However, this pace nearly doubled for a few days in early August during a major Arctic cyclonic storm, discussed below.

Unlike the summer of 2007 when a persistent pattern of high pressure was present over the central Arctic Ocean and a pattern of low pressure was over the northern Eurasian coast, the summer of 2012 has been characterized by variable conditions. Air tempertures at the 925 hPa level (about 3000 feet above the ocean surface) of 1 to 3 degrees Celsius (1.8 to 5.4 degrees Fahrenheit) above the 1981 to 2012 average have been the rule from central Greenland, northern Canada, and Alaska northward into the central Arctic Ocean. 

Cooler than average conditions (1 to 2 degrees Celsius or 1.8 to 3.6 degrees Fahrenheit) were observed in a small region of eastern Siberia extending into the East Siberian Sea, helping explain the persistence of low concentration ice in this region through early August.

August 6, 2012, 06:00 GMT surface weather analysis, showing a very strong cyclone over the central Arctic Ocean north of Alaska. The isobars (lines of equal pressure) are very tightly packed around the low pressure system, indicating strong winds. Greenland is on the right side of the figure, Canada at the bottom. Credit: Canadian Meteorological Centre
A low pressure system entered the Arctic Ocean from the eastern Siberian coast on August 4 and then strengthened rapidly over the central Arctic Ocean. On August 6 the central pressure of the cyclone reached 964 hPa, an extremely low value for this region. It persisted over the central Arctic Ocean over the next several days, and slowly dissipated. The storm initially brought warm and very windy conditions to the Chukchi and East Siberian seas (August 5), but low temperatures prevailed later.

On three consecutive days (August 7, 8, and 9), sea ice extent dropped by nearly 200,000 square kilometers (77,220 square miles). This could be due to mechanical break up of the ice and increased melting by strong winds and wave action during the storm.

The image below, from the Danish Meteorological Institute (DMI), shows that sea ice extent took a huge dive early August and has consolidated since, as the winds settled down.

Credit: Centre for Ocean and Ice, Danish Meteorological Institute
Note that, to calculate extent, DMI includes areas with ice concentration higher than 30% (NSIDC includes areas that show at least 15% sea ice). 

Saturday, August 11, 2012

Huge cyclone batters Arctic sea ice

The image below shows an unusually large and powerful cyclone that was churning over the Arctic in early August 2012. Two smaller systems merged on August 5 to form the storm, which at the time occupied much of the Beaufort-Chukchi Sea and Canadian Basin, reports NASA Earth Observatory. On average, Arctic cyclones last about 40 hours; as of August 9, 2012, this storm had lasted more than five days.

This cyclone’s central sea level pressure reached about 964 millibars on August 6, 2012—a number that puts it within the lowest 3% of all minimum daily sea level pressures recorded north of 70 degrees latitude, noted Stephen Vavrus, an atmospheric scientist based at the University of Wisconsin.

Image by By NASA Goddard Photo and Video
NASA’s Aqua satellite captured above natural-color mosaic image on August 6, 2012. The center of the storm at that date was located in the middle of the Arctic Ocean.

The combined screenshots (6 & 8 August) below from Oceanweather Inc give an idea of size of the waves churned up by the cyclone.


The storm came in from Siberia, intensified and then positioned itself over the central Arctic, engendering 20 knot winds and 50 mph wind gusts, reports Skeptical Science.

The Arctic Sea Ice Blog covered the unfolding events well, in a series of posts including:
Many excellent comments were also added underneath these posts, e.g. by Steve Coulter who noted that "when fragmented floes are present, each irregular piece of ice acts as a sail in the wind, so the wind transfers momentum more readily to the surface. And each piece of ice, being 90% submerged, quite effectively transfers that momentum to the water. With winds moving in essentially a single direction in any given area, vast volumes of surface water are more readily put into motion. The difference in motion between the surface and deep water inevitably creates mixing."

Such mixing could mean that sediments that have been frozen until now get exposed to warmer water. This could destabilize methane contained in such sediments, either in the form of free gas or hydrates.

John Nissen, Chair of the Arctic Methane Emergency Group (AMEG), comments:
"There are at least three positive feedbacks working together to reinforce one another - and now a fourth on salinity:
  1. The albedo flip effect as sea ice is replaced by open water absorbing more sunlight, warming and melting more sea ice.
  2. As the sea ice gets very thin, it is liable to break up easily and get blown into open water where it will melt more easily.
  3. The open warmer water is allowing increased strength of storms, which break up the ice to make for more open water.
  4. The storms are churning up the sea to a depth of 500 metres, producing salinity at the surface that will mean slower ice formation in winter and more open water next year.
These feedbacks are dangerous for methane. AMEG has been warning that, as the sea ice retreats, storms will warm the sea bed, leading to further release of methane. In ESAS, we only need mixing to a depth of 50 metres - so a storm capable of mixing to 500 metres will really stir things up.

These feedbacks are also dangerous for food security, already damaged through climate extremes induced by Arctic warming, hence our piece in the Huffington Post.

The only way to head off catastrophe is to cool the Arctic, which must involve geoengineering as quickly as possible. We must try to remain positive and determined about this, despite the gloomy news."


Above image shows a retreat in sea ice area to 3.15521 million km2 on the 221st day of 2012, down from 3.91533 million km2 on the 212th day of 2012, from The Cryosphere Today.

The 30-days animation below, from the Naval Research Laboratory, show the recent ice speed and drift.



The 30-days animation below, also from the Naval Research Laboratory, show recent decline of the thickness of the sea ice.  


Friday, August 10, 2012

Sea ice in the Arctic - Shaken and stirred (by a powerful cyclone)

By Paul Beckwith


From my chair, it looks to me like there will be zero sea ice in the Arctic by September 30th of this year 2012.

The massive cyclone in the Arctic of unprecedented size has been chewing up the sea ice for the last week and it looks like over 1 million square km has been lost. A few more cyclones there will finish it off completely.

My presentation on the link below needs polishing, is quite technical in places and is mostly my compilation of blogs and data and comments from other scientists, engineers, and lay-people. It is mostly in chronological order as the storm has progressed.

Sea ice in the Arctic - Shaken and stirred (by a powerful cyclone)
August 3 to 10, 2012, by Paul Beckwith

https://docs.google.com/open?id=0B7jFQnAaMpkXVFNLRUhXUmdaWk0