Tuesday, February 23, 2016

Sea Levels Updated

In a previous post I pointed out that while much is uncertain about the impact of global warming, one thing that is happening and will continue to happen whatever we might do, is a significant rise in the sea level.

New research has supported this outcome.  As described in the New York Times, seas are rising at the fastest rate in nearly the last 3,000 years.
The worsening of tidal flooding in American coastal communities is largely a consequence of greenhouse gases from human activity, and the problem will grow far worse in coming decades, scientists reported Monday.


Those emissions, primarily from the burning of fossil fuels, are causing the ocean to rise at the fastest rate since at least the founding of ancient Rome, the scientists said. They added that in the absence of human emissions, the ocean surface would be rising less rapidly and might even be falling.
The increasingly routine tidal flooding is making life miserable in places like Miami Beach; Charleston, S.C.; and Norfolk, Va., even on sunny days 
Though these types of floods often produce only a foot or two of standing saltwater, they are straining life in many towns by killing lawns and trees, blocking neighborhood streets and clogging storm drains, polluting supplies of freshwater and sometimes stranding entire island communities for hours by overtopping the roads that tie them to the mainland.
Such events are just an early harbinger of the coming damage, the new research suggests.
They also confirmed previous forecasts that if emissions were to continue at a high rate over the next few decades, the ocean could rise as much as three or four feet by 2100.
Experts say the situation would then grow far worse in the 22nd century and beyond, likely requiring the abandonment of many coastal cities.
 The consequences of the rising sea level, while not dramatic, is nevertheless noticeable.
The change in frequency of those tides is striking. For instance, in the decade from 1955 to 1964 at Annapolis, Md., an instrument called a tide gauge measured 32 days of flooding; in the decade from 2005 to 2014, that jumped to 394 days.
Flood days in Charleston jumped from 34 in the earlier decade to 219 in the more recent, and in Key West, Fla., the figure jumped from no flood days in the earlier decade to 32 in the more recent.
One of the authors of the new paper, Dr. Rahmstorf [has stated that] with the improved calculations from the new paper, his latest upper estimate is three to four feet.
This is what is going to happen regardless of whatever attempts we make to halt global warming.  It is now too late to prevent it.  In the lifetimes of my grandchildren, the downtown Seattle tunnel costing billions to dig will be filled with Elliot Bay seawater.  Most of the houses built on top of the bluffs surrounding the Puget Sound will fall into the Sound.  Quite a bit of Amtrak's path along the shore will be under water.  The Southcenter Mall will be under water.  Much of the Duwamish River will become Duwamish Bay.  Nearby Cities like Auburn, Puyallup may find themselves on the shore of the new Duwamish Bay.

They'll have to build new locks between Lake Washington and Elliot Bay.  Boats heading for the Bay from the Lake will have to brought up a few more feet.  But I'm wondering about the elevation of the Lake at Renton.  A Duwamish Bay might encroach upon the southern end of the Lake.  Lake Washington could  become a branch of Elliot Bay via a Duwamish Bay.

In an interview, Dr. Rahmstorf said the rise would eventually reach five feet and far more — the only question was how long it would take. Scientists say the recent climate agreement negotiated in Paris is not remotely ambitious enough to forestall a significant melting of Greenland and Antarctica, though if fully implemented, it may slow the pace somewhat. 
Fortunately our house in Burien is 250 feet above sea level.  It will be a safe place for one of our grandchildren someday.