Showing posts with label sediment. Show all posts
Showing posts with label sediment. 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.