Showing posts with label feedback. Show all posts
Showing posts with label feedback. Show all posts

Saturday, September 29, 2012

Accelerated Warming in the Arctic

Why is warming in the Arctic accelerating and where will this lead to?

Where does the extra heat go? 

Global warming is causing Earth to heat up. As shown on the image below, by Nuccitelli et al., most heat goes into the oceans.



Warming of water in the Arctic Ocean

White arrows mark ice drift directions. Red arrows mark
the transport path of warm Atlantic water entering the
Arctic where it submerges under the cold, ice-covered
surface layer.  Robert Spielhagen (IFM-GEOMAR, Kiel)
Global warming is heating up the oceans big time. As above image shows, the global ocean heat content has been rising for many years.

The Arctic is affected in particular by the Thermohaline Circulation.

Water flowing into the Arctic Ocean from the Atlantic Ocean is about 2°C warmer today than it has been for at least 2,000 years, according to a study published in Science. The current of warm water lies 50 metres below the surface, and can reach 6°C in summer — warm compared to Arctic surface waters, which can be -2°C.

At the same time, cold water and sea ice are driven out of the Arctic Ocean, along the edges of Greenland. The net result is a marked increase in the temperature of the water in the Arctic Ocean, especially the top layer of the water which causes the sea ice to melt.


The Arctic radiates comparatively less heat into space 

Cold layers of air close to the surface make it difficult for infrared radiation to go out to space, according to a study published in Science. These layers do warm up, but warming of these layers is directed downwards, thus amplifying warming in the Arctic.


Surface air temperatures in the Arctic are rising rapidly

Anomalies for surface air temperatures are higher in the Arctic than anywhere else on Earth. This is illustrated by the interactive images and text in the box at the bottom of this post.

The increase in temperature anomalies appears to be an exponential rise. This is caused not only by the above-described impacts of cold air close to the surface, but also by feedback effects as further described below.


Feedbacks further accelerate warming in the Arctic

Feedbacks are described in more detail in posts such as Diagram of Doom (image below) and Changes to Polar Vortex affect mile-deep ocean circulation patterns.


One such feedback is albedo change — retreat of Arctic sea ice results in less sunlight being reflected back into space, as further discussed in Albedo Change in the Arctic. Loss of Arctic sea ice is effectively doubling mankind's contribution to global warming. Increased absorption of the sun's rays is the equivalent of about 20 years of additional CO2 being added by man, Professor Peter Wadhams said in a recent BBC article.

One of the most threatening feedbacks is release of methane that are held in the currently frozen seabed. As the seabed warms up, it starts to release methane in what can be rather abrupt ways. Due to methane's high global warming potential, this can further accelerate local warming, triggering further methane releases, in a vicious circle that threatens to spiral into runaway global warming.

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. 


Opening further Doorways to Doom


Until now, the Arctic has been protected from overheating in a number of ways.
 


Negative Arctic Oscillation conditions are associated with
higher pressure in the Arctic and a weakened polar vortex
(yellow arrows). A weakened jet stream (black arrows) is  
characterized by larger-amplitude meanders in its trajectory
and a reduction in the wave speed of those meanders.
Snow and ice that grows in winter will act as a buffer when temperatures rise in summer. A bright snow and ice cover will reflect most sunlight back into space. Furthermore, a lot of the sunlight that isn't reflected will be consumed by the process of turning snow and ice into water, which occurs while temperatures remain at the melting point of 0°C (32°F, 273.15 K).

The Arctic is further protected from overheating by the polar vortex and jet stream, which act to keep cold air in the Arctic and keep warm air out. However, accelerated warming in the Arctic is now causing the polar vortex and jet stream to weaken. 


Accelerated warming in the Arctic alters the polar jet stream by slowing its speed and by increasing its waviness. Larger swings in the jet stream allow frigid air from the Arctic to plunge farther south, as well as warm, moist tropical air to penetrate northward, explains Jennifer Francis, research
professor at the Institute of Marine and Coastal
Sciences at Rutgers University.

The polar jet stream can travel at speeds greater than 100 mph. Here, the fastest winds are colored red; 
slower winds are blue. View animated version here. Credit: NASA/Goddard Space Flight Center

What is described above can be regarded as an "open doors feedback". It's like leaving the doors open when it's cold inside and hot outside.

Accelerated warming in the Arctic comes with many such feedbacks, e.g. higher temperatures and more open water in the Arctic can also be expected to increase the danger that storms will batter the sea ice with greater ferocity. This is depicted in the image below.




In many ways, this is opening the doorways to doom. The biggest danger is that temperature rises will cause Arctic methane stores to weaken, resulting in huge amounts of methane to be released, triggering warming that could escalate into runaway global warming.  

The image below shows the sea surface temperature anomaly for August 27, 2012, by the National Oceanic and Atmospheric Administration (NOAA).



Rising temperatures in the Arctic threaten to trigger methane releases, as shown on the poster below.




The poster is also part of the presentation below:


Friday, August 17, 2012

Opening the Doorways to Doom

Snow and ice protect the Arctic from overheating in summer. Firstly the brightness of the snow and ice cover ensures that most sunlight gets reflected back into space. Secondly, a lot of the sunlight that isn't reflected will be consumed by the process of turning snow and ice into water, which occurs while temperatures remain at the melting point of 0°C (32°F, 273.15 K). 

The Arctic is further protected from overheating by the polar jet stream, which keeps cold air in the Arctic and keeps warm air out. 
The polar jet stream can travel at speeds greater than 100 mph. Here, the fastest winds are colored red; slower winds are blue. View animated version here. Credit: NASA/Goddard Space Flight Center

Accelerated warming in the Arctic can alter the polar jet stream in a number of ways, firstly by slowing its speed and secondly by increasing its waviness. Larger swings in the jet stream allow frigid air from the Arctic to plunge farther south, as well as warm, moist tropical air to penetrate northward, explains Jennifer Francis, research professor at the Institute of Marine and Coastal Sciences at Rutgers University. 

Accelerated warming in the Arctic comes with many feedbacks, and this "open doors feedback" is only one of them. Higher temperatures and more open water in the Arctic can also be expected to increase the danger that storms will batter the sea ice with greater ferocity. 



In many ways, it's opening the doorways to doom. The biggest danger is that Arctic methane stores will weaken, causing huge amounts of methane to be released, triggering warming that could escalate into runaway global warming.  

Wednesday, May 2, 2012

Temperature rise projections

The Climate Emergency Institute recently produced the image below. For more background, see the institute's page on the warming that Earth's is already committed to even if people's emissions were suddenly stopped. Also see the institute's warning on Food Security.