Explaining Thermokarst

Froghair & Sally Forth requested further elaboration on thermokarst. I did reply in the comment section of "The Changing Alaskan Arctic/ Sub-arctic" to them but apparently they wanted more. So, on popular request I will attempt to explain it....

Thermokarst (see picture taken on Bering Island, Russia) is surface topography that results when the ice on top of a surface underlain by permafrost melts creating a hummocky ground surface. Because the surface is underlain by permafrost (esentially frozen ground that never gets heated above 32F [0C]) the water from the melting surface snow and ice has no where to go, i.e. it can't just soak into the ground. So instead it tends to puddle or pond up in lower lying areas. These puddles start to melt the permafrost underneath by acting as an insulating, warming mass. As the permafrost melts the frozen ground depresses as it is consoldiated under the weight of the surface water - this is called thermokarsting. This is how a thermakarst puddle becomes a lake and how they eventually connect to each other.

As the melting of permafrost excelerates with other warming influences (such as it not being as cold for as long of periods to refreeze the permafrost) thermokarsting increases sometiems resulting in large pieces of collapsed ground (you can see pictures of this occuring here: http://www.mines.edu/~mgooseff/web_tkarst/tkarst_proj.html). A friend of mine from grad school, Dr. Katey Walter, has studied another worrying effect of increased thermokarsting - the release of ground methane gas by releasing organic material that was trapped in the permafrost into these thaw lakes (thermokarst lakes). This methane (CH4) is then released into the atmosphere which in turn accelerates global warming even more. In addition, when thermokarsting occurs in forested regions it often leads to boggy landscapes that cannot support trees (and sometimes you get the drunken tree affect - I have pictures of this somewhere but I can't find them at the moment...).

Note: I believe you may find a more comprehensive exlaination of thermokarst in this article by De Schutter: http://ougseurope.org/rockon/surface/thermokarst.asp.

The Changing Alaskan Arctic/ Sub-Arctic

Warning, I'm going to get on my soapbox a little here. People ask me all the time if I've noticed the effects of climate change in the north. I have. As a scientist I have seen reams of data from various colleagues that all show the same worrying trends. I am not going to talk about data or figures here though, I want to present my personal observations about the changes that have occurred in the time that I have lived in Alaska. In the last seven years folks. The arctic is sort of the bell weather of change but I know that changes like this are happening all over the world in your communities too - all the "unusual" & "record setting" weather is just one example. Dispersed in between my observations will be photos (taken from the air) of icebergs and glaciers that I have the privilege to experience in my landscape that are melting away - I want to share with you the beauty of this ice, especially if you have never seen it before and as it is particularly vulnerable to climate change. And a quick note: I will not be replying to comments that demand that this isn't happening, I mean come on, even the current US president Dubya has finally admitted it is. If you believe there is no change or that the degree of change is natural arguing with you is like arguing with a believer over some sacredly held interpretation of text; it's pointless. I will however, address thoughtful questions.

Permafrost is melting. This is causing houses to sink and tilt into the landscape, causing bike paths & roads that were once even surfaces to bump up. It is causing lakes to disappear (through a process called thermakarst). Ironically, the ice roads that oil companies use to access their wells are melting meaning they can use them less and less time out of the year.

Lakes & wetlands are disappearing both because of thermakarst & because of increased air temperatures.

As lakes & wetlands disappear they fill in with shrubs and trees. The habitats of wild things that like marshy land shrinks. More lakes freeze solid in the winter as they are shallower. This means less fish stock (including the economically valuable salmon) is surviving the winter which means there are less fish in the oceans.

The ice is melting. Glaciers are melting for multiple reasons. As the temperature of sea water has raised a degree the are melting faster where they meet the ocean, with increased heat in the atmosphere more of them is evaporating into the air, with increased rain caused by changing weather patterns they are pooling up more and melting from the top down as well as the bottom up.

Calving glacier melting is causing changes in water temperature and availability of ice for habitat of ice seals. The bergs are lasting less and less long into the season, the calving occurs with greater frequency.

Glacier melting and warmer temperatures have increased the shrub & tree lines in the arctic. Whole landscapes and views that once existed have disappeared.

Increased fires in interior Alaska have led to a decrease in trees and an increase in heat loss to the atmosphere and a reduction in CO2 recycling by plants and an increase in smoky skies which affect living quality.

Bug infestations such as birch bark beetle and leaf miner which used to cycle every ten years have now been heavy for three years running in interior Alaska causing these trees to be drier and more susceptible to flame. Between flame & bugs the lowlands of Alaska may become grassland while the uplands become shrubby.

Changing winds have increased the impact of mosquitoes on caribou & reindeer on the north slope as these animals are finding less and less relief. More die from insect harassment and from the energy required to keep moving to keep them off.

The ocean is rising. Arctic villages are sinking into the waves and are having to be pulled back from the edges.

The oceans are not freezing as completely or as securely to the shore. Fast ice, which allows both polar bears and people to get out on the ice is disappearing stranding polar bears on land causing an increase in bear/ human conflict.

The rivers are not freezing as completely for as long. Rivers are the traditional method of getting around bush Alaska and the time that they are unstable - where you can not dog mush, snow machine, or boat on them - is increasing making communities more isolated.

Snow is not what it used to be. It falls later, it melts earlier. If you question this note that the last 3 years the famous Iditarod sled dog race re-start location has had to be moved north from it's traditional location as there is not enough snow.

Parasites are showing up in Alaskan wild animals that have never been seen in Alaska before.

The arctic is the place where change is happening fastest. Look around you, every where people are saying "This is really abnormal weather" or "Record year for this (fill in the blank with the weather in your area)". This is happening everywhere the world over. The climate is changing folks. And it is our habits that are doing it.

Note: I do not use "global warming" as I feel this term is both mis-leading and a political salve. People feel better if you talk about warming, they feel they wouldn't mind if it warmed. But the truth is that it is global change which exacerbates all climate patterns. It makes the cold colder in the winter, the hot hotter in the summer, the dryness dryer, the wetness wetter, and the storms bigger and more unpredictable. The US administration which has belatedly admitted that climate change is happening would prefer us to use warming because warming sounds milder. It lulls us and keeps us from acting - words are power and how we describe something can take or give strength to it.