Global Warming: Cascadia’s possible future
The flooding potential of Cascadia is not only caused by sea levels backing up rivers and streams, it will be caused by a warming and melting of the permafrost. Permafrost will release vast amounts of water into our above and below ground hydrology. There will be no place untouched by these changes, no high ground, are we prepared?
After seeing Al Gore's new documentary "Inconvenient Truth" I started thinking about an event that created the Columbia Gorge and the Willamette Valley. It happened at the end of the last age. I want to share this with you to get a conversation started.
The point of this essay is to get discussion started about how global warming will affect people everywhere. There will be no places on the globe left untouched by these changes. Are we prepared?
Many people I know who live in the Portland area and the Willamette Valley think that as the sea levels rise we will be immune to the drastic changes. Some believe that only those living on seaboards will be displaced. However, as Gore's docu-movie and others point out. Not only are the ice caps melting but the tundra is melting (think permafrost). A huge body of fresh water is about to be released into ground water, streams and rivers, lakes, and the atmosphere. How will this affect people in the Cascadia? Aside from the affect on weather a great deal of underground water is about to be released into the biosphere. According to several sources, anyone in low-lying areas will be affected. And, people in high lying areas will find it hard to find potable water. Some say that the super-fund sites and chemical dumps that have been contained along rivers and streams and underground vaults (think the Umatilla Chemical Depot in Hermiston, Oregon or the areas of the Willamette River around North Portland) will add high level pollution to this released water. Beyond the discussion of pollution, there needs to be a discussion about water borne disease and increasing and changing insect populations.
But for now, I only want to discuss - hydrological changes - vast bodies of water moving through large geographical areas. Water moving under the top layers and across the surface of Cascadia.
This flooding potential of Cascadia is not only caused by sea levels backing up rivers and streams, it will be caused by a warming and melting of the permafrost.
The events of the past I would like to focus on in this essay are called the Missoula Floods or the Bretz Floods. What is the relationship between the melting of permafrost and the Missoula flood? There is evidence that the Missoula flood happened at a time that permafrost melted at the end of the last ice age. A general warm up of the world happened. The melt was so vast and powerful it changed the way water and moisture is distributed all over the globe. Glacial lakes burst, and rivers, streams and lakes changed or were formed. In some areas of the world, water disappeared entirely. Huge deserts were formed.
While the glacial lakes that created this flood do not exist now, the Missoula flood example shows how water (hydrology) can be affect whole areas of the planet, when it is unleashed, or when it dries up.
What happens when permafrost melts? Why should we be concerned?
EARTH'S FROZEN GROUND
* Permafrost is permanent year-round frozen ground
* Soils many cm below surface never rise above 0C
* Only top few cm thaw in summer - "active layer"
* Many regions have been like this for 1,000s of years
* Major thaw changes water distribution in ecosystem
* Sequestered carbon released; buildings destabilized
In Ellesmere Island, Canada, a combination of warmer temperatures and sunny days has triggered an increasing frequency of detachment events, or landslides, over the past 25 years, compared with the previous 75, according to Antoni Lewkowicz, professor of geography at the University of Ottawa.
A detachment event occurs on a slope when the bottom of the active layer - the layer of thawing and freezing ground above permafrost - becomes slick with melted ice, causing it to slide off from the permafrost below.
But in this case, the amount of temperature increase is not so important as the rate of increase, Dr Lewkowicz found.
Meltwater from ice that warms slowly drains away. When ice warms quickly, water pools, creating a frictionless surface between the active layer and the permafrost. Like a stroll across a sloping icy pavement, a fall is almost certain.
"We have records from this particular site for about 10 or 12 years," said Dr Lewkowicz. "The years when active layer detachments have taken place have been times when we've had this rapid thaw down at the bottom of the active layer."
The slides may cut a wide swath hundreds of metres across, but extend only 50 or 60cm deep.
"They're almost skin-like landslides, moving across the permafrost," said Dr Harris.
The exposed permafrost, warmed by the air, now produces a new active layer.
Permafrost melt during the time of these floods contributed to the Missoula Flood. Water from the melt was distributed over thousands of miles. These waters created much of the geographic structure of the Columbia Gorge, the Portland area and the Willamette Valley all the way past Eugene.
Here is a Wikipedia definition that is easy to follow: (follow the link for some great graphics)
The Missoula Floods (also known as the Spokane Floods or the Bretz Floods) refer to the cataclysmic floods that swept periodically across eastern Washington and down the Columbia River Gorge at the end of the last ice age.
The floods were the result of the periodic sudden rupture of the ice dam on the Clark Fork River that created Glacial Lake Missoula. After each rupture of the ice dam, the waters of the lake would rush down the Clark Fork and the Columbia River, inundating much of eastern Washington and the Willamette Valley in western Oregon. After the rupture, the ice would reform, recreating Glacial Lake Missoula once again.
The mechanism by which the ice
What is a hydraulic dam? It is the restriction of the rate of water flow caused by a narrowed reach in a river valley. During a valley-filling flood, the narrows restrict flow, thus causing water upstream to pond partly and temporarily. The most spectacular example of a hydraulic dam during the Ice Age Floods was Wallula Gap, which restricted nearly 200 cubic miles of water in a huge, temporary pond in Pasco basin. On the lower Columbia, a narrows near Kalama also briefly ponded floodwater. This narrows thus helped to back up floodwater upstream, flooding not only the Portland-Vancouver basin but also the Willamette Valley to beyond Eugene.
Links to learn more
Deserts forming and over a billion people on the planet without clean drinking water - http://news.bbc.co.uk/1/hi/sci/tech/3747724.stm
Map of a short list of Oregon's superfund sites: http://www.deq.state.or.us/wmc/cleanup/npl0.htm
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