Global Warming
9:50 am
Mon June 25, 2012

Study: Rising seas will hit Calif. hardest, but Washington still sees damage

Rising sea levels in the Puget Sound region may prove costly to taxpayers. A city like Olympia could have to re-build its sewer system. Other cities may find waterfront roads washed out.

The culprit is global warming. Warmer water expands, bringing sea levels higher. And glacial ice that is above water now is expected to chunk off and fall into oceans, causing additional sea level rise.

A new report from the National Research Council in Washington DC looks specifically at the West Coast, as compared to global sea level rise over the next century.  It says the problem here won’t be as bad as in California, which is expected to see sea levels slightly higher than projected globally.

The report found sea levels in Washington and Oregon are predicted to rise about 2 feet over the next century. Most of California could see a three and a half foot rise.

Scientists say damage from storm surges and high waves increases exponentially as the base water level at shorelines inches up. Governments need to prepare.

Robert Dalrymple, the chairman of the committee that wrote the report, says the reason sea level is predicted to rise less here is because geological forces are at work. The land is being pushed up as tectonic plates shift off the coast along the Cascadia subduction zone.

“And so in Oregon and Washington, you have the land rising as well as the sea level rising. And the effect is that the rising land cancels out part of the rising sea level. And so that’s why those two states have a lower sea level than does California.”

The difference is almost a foot and a half.

But Tom Ackerman, a climate scientist who directs the University of Washington's Joint Institute for the Study of the Atmosphere and Ocean, says they did a study showing that that effect isn’t actually as strong in some portions of Puget Sound. The further south you head, the less the land rises.

So, he says, Washington’s major cities, Tacoma and Seattle, are more at risk, and could actually see rising sea levels almost as high as in California.

Seattle’s Duwamish River and its port are right at sea level now.

“And so, when you start talking about sea level rise of a couple of feet, you’re going to have to do a lot in the port area. And the same thing is going to be true in Tacoma. And those are big parts of the Northwest infrastructure. ”

In many other cities, sewage and storm water systems may need to be rebuilt. And some coastal areas may need to move roads and houses.

The study also notes that if there is an earthquake of magnitude 8 or more, Western Washington could suddenly sink an additional three feet,  more than doubling the impact of the gradual sea level rise from global warming.