Making sense of senseless sea level scares in Norfolk Virginia – 60% of the rise is from subsidence, the remainder from landfill settling

One of the problems with so called “science writers” in the mainstream media today is that few of them have the wherewithal and training to do some basic sanity checking. Lori Montgomery of the Washington Post illustrates this lack of competence perfectly in a piece this weekend titled: In Norfolk, evidence of climate change is in the streets at high tide .

You just have to laugh at one of the pictures included as seen above. I’m not sure if the Chrysler Museum (seen in the background) is mocking posited climate change induced sea level rise or preparing for it. But rubber duckies aside, Ms. Montgomery doesn’t seem to have the skills to even investigate the ridiculous claim of over 5 ½ feet of sea level rise by 2100, much less apply a sanity check to it. In her article is this easily challenged statement:

As the city was contemplating that enormous price tag, the Virginia Institute of Marine Science (VIMS) last year delivered more bad news: If current trends hold, VIMS scientists said, by the end of this century, the sea in Norfolk would rise by 5½ feet or more.

The claim is accompanied by this graph and text, which ups the rise to frightening levels based on model projections:

The problem is particularly urgent in Norfolk and the rest of Tidewater Virginia — which the National Oceanic and Atmospheric Administration has ranked second only to New Orleans in terms of population threatened by sea-level rise — due to a fateful convergence of lousy luck. First, the seas are generally rising as the planet warms. Second, the Gulf Stream is circulating more slowly, causing more water to slosh toward the North Atlantic coast. In 2012, the U.S. Geological Survey declared a 600-mile stretch of coastline, from North Carolina’s Cape Hatteras to Boston, a “sea-level rise hotspot,” with rates increasing at three to four times the global average.

Third, the land around Norfolk is sinking, a phenomenon called “subsidence,” due in part to continuing adjustments in the earth’s crust to the melting of glaciers from the last ice age. Plus, the city is slowly sinking into the crater of a meteor that slammed into the mouth of the Chesapeake Bay 35 million years ago.

Put it all together, as VIMS scientists did when they were asked by the General Assembly to study recurrent flooding in tidewater Virginia, and models suggest tides ranging from 1½ feet to 7½ feet higher by 2100.

Let’s look at some less scary graphs, like this one that should have been included in Ms. Montgomery’s article, but wasn’t:

Source: http://tidesandcurrents.noaa.gov/sltrends/sltrends_station.shtml?stnid=8638610

The Sewell’s Point tide gauge is the closest fully operational one, as apparently NOAA closed the one nearest downtown Norfolk back in 1985:

Source: http://tidesandcurrents.noaa.gov/sltrends/sltrends_station.shtml?stnid=8638660

You’d think that with such a “crisis” looming, they’d have kept that tide gauge operational.

The most important thing to note is that unlike the steeply vertical graph in the WaPo article showing up to 8 feet of projected sea level rise, there is no acceleration visible in either of these two tide gauge graphs. They illustrate the slow, linear, subsidence that Nature has been doing for thousands of years.

So, let’s do the math to see if the data and claims match. We’ll use the worst case value from Sewell’s Point tide gauge of 4.44mm/year, which over the last century measured the actual “business as usual” history of sea level in concert with rising greenhouse gas emissions in the atmosphere. with no “mitigation” done in the last century of measurements.

Their claim is for the “business as usual” scenario: “by the end of this century, the sea in Norfolk would rise by 5½feet or more.”

1. At the year 2014, there are 86 years left in this century.
2. 86 years x 4.44 mm/year = 381.84 mm
3. 381.84 mm = 15.03 inches (conversion here)

Gosh, 15.03 inches is quite a long ways from “5½feet or more”.

As seen in the caption for the scary WaPo graph, the entire premise of Ms. Montgomery’s article is based on projections related to greenhouse gas emissions, with those emissions set to accelerate sea level rise, yet as we see from the tide gauge graphs, even while GHG gases increased in the atmosphere in the last century, there is no visible acceleration, no curve upwards towards anything that would hint at their worst case scenario.

Ms. Montgomery also relies heavily on a single source for her article, the Virginia Institute of Marine Science (VIMS), who seem to be big on modeling, with claims that suggest the entire Ross Sea will be (not might be) ice free by 2100. With certainty like that, no wonder they are freaking out feckless WaPo reporters.

A little Google-Fu might have helped, I wonder if Ms. Montgomery has read this report from VIMS, published in 2010:

Chesapeake Bay Land Subsidence and Sea Level Change An Evaluation of Past and Present Trends and Future Outlook (PDF)

The cover is interesting, as it shows the “lumpiness” of global sea level rise.

Note that in the image above, the satellite altimetry reports that sea level rise off the coast of Chesapeake Bay is essentially zero. Note the white color and the scale in this image I have prepared from the cover image:

That zero trend for the area suggests there must be other factors as causes of Norfolk’s sea level problems.

I found this part of the report, in the conclusions section, most interesting, note that RSLR stands for “Relative Sea Level Rise”, emphasis mine:

Spatial Comparisons – RSLR rates at all ten bay stations for the 1976-2007 period underscore variability in subsidence rates assuming that the present ASL rise is uniform throughout the Chesapeake Bay area. Given the most likely ASLR rate of 1.8 mm/yr for what may be termed late 20th/early 21st century, inferred subsidence rates vary from -4.00 mm/yr at the Chesapeake Bay Bridge Tunnel, VA, to -1.29 mm/yr at Baltimore, MD (omitting Washington, DC, because of significant serial correlation over 1976-2007). In between these extremes, subsidence rates account for 50-60% of the measured RSLR at water level stations. These findings are in agreement with those of coastal geologists who report evidence of structural faults not only within the Chesapeake Bay Impact Crater in the lower bay but in areas further north in the midsection of the bay (R. Berquist, pers. comm.). High RSLR at Lewisetta, VA, is likely due to additional subsidence induced through local faulting.

Future Outlook – Subsidence will clearly remain a problem as it will continue to add to high RSLR rates locally and heighten the risk of flooding from storm tides in the lower Chesapeake Bay as time goes on. Low-lying areas in communities such as Norfolk, Virginia Beach, Portsmouth, Chesapeake, Hampton and Poquoson are comprised of a patchwork of local areas that are not only vulnerable to storm tides but are experiencing varying rates of subsidence, meaning that some areas within these communities may be facing greater risk than others from global sea level rise going forward. In addition to CORS, other technologies such as airborne LIDAR (Light Detection and Ranging) will be needed to perform repeated mapping of ground topography to track changes in flood elevation contours with time.

So, VIMS says subsidence accounts for 50-60% of the problem that the Washington Post reports will be acceleration due to climate change, melting of the ice caps, etc.. More importantly, they mention nothing about acceleration due to greenhouse gas emissions in that 2010 report. In fact, in the conclusions they say they can’t find any evidence of acceleration of sea level rise, and if it is there, it would be hard to detect, emphasis mine:

Thus, if an absolute sea level (ASL) rate increase of 0.10 mm/yr were to be added in the next decade, its detection as a significant change would be unlikely even if decadal variability were accounted for. An increase on the order of 0.5 mm/yr may be required for a statistical significant acceleration to be confirmed in the years ahead. Meanwhile, time-segment comparisons that account for decadal variability are very likely to witness the smaller changes leading up to it, if indeed an acceleration does develop at this scale.

The problem is that when Norfolk was founded in August 1682, they chose a location close to the sea, for trade purposes, nearly inside of an impact crater with bedrock fractures than has been historically subsiding since the initial impact 35 million years ago.

Source: http://pubs.usgs.gov/circ/2003/circ1262/

Of course they had no idea at the time, and up until the 20th century city leaders probably had no idea of the situation their city was in. Worse, as indicated by this NYT article, filled marshlands are returned to their normal state:

Like many other cities, Norfolk was built on filled-in marsh. Now that fill is settling and compacting. In addition, the city is in an area where significant natural sinking of land is occurring.

Have a look at this Google earth image where WaPo was taking photos, the Chrysler Museum of Art (seen with the rubber duck in the WaPo photo) is clearly marked. It sure looks like fill to me. Note the arrows I added. That is a man-made fill structure.

http://maps.google.com/?ll=36.85616,-76.29529&spn=0.015023,0.020964&t=h&z=16

With the satellite altimetry from the 2010 VIMS report showing essentially a zero sea level rise in the area, it seems to me that nearly all of the issue in Norfolk can be attributed to subsidence from the crater impact fractures, and subsidence from man-made landfill settling where there was originally marshland.

But surely we can discount all that and just blame “climate change” on a wholesale level and add some scary graphs to scare the bejeesus out of readers like the hapless Ms. Montgomery has done. After all, if such projections are to be believed, human greenhouse gas emissions are far more powerful than anything Nature can throw at us.

It just seems easier and more profitable to blame climate change than a poor choice of location because as we’ve seen time and again, by using those magic words, an entire banquet of Federal assistance is spread before them.