On Sallenger et al (2012) – Hotspot of Accelerated Sea Level Rise on the Atlantic Coast of North America
Guest post by Bob Tisdale
John Droz Jr. asked me to comment on the Sallenger et al (2012) paper Hotspot of Accelerated Sea Level Rise on the Atlantic Coast of North America. As you’ll recall, John Droz Jr. has reported on pending North Carolina legislation about rising sea level. Refer to the WattsUpWithThat posts here and here. Apparently, North Carolina lawmakers are concerned about the use of the word “accelerated” in Sallenger et al (2012). So I took an initial look at the sea level data for the Atlantic Coast “Hotspot”.
The shift in trends around 1990 noted in Sallenger et al (2012) appears to be a function of the natural variability of the North Atlantic.
In fact, Sallenger et al (2012) in their closing comments state that this is a possibility, but it was impossible for them to tell due to the limited availability of data (my boldface):
In regard to the role of cycles, the single ~ 60-yr pattern in Fig. 4a does not seem associated with 10–30 yr sea-level variations discussed in ref. 27. With our limited series length, the presence of cycles, for example associated with natural ocean variability and/or AMO, is indeterminate. In the Holocene geologic record of an NEH marsh, the authors of ref. 28found evidence of several rapid SLR increases separated by 900 yr or more that they associated with gyre changes. Regardless, our correlations suggest that should temperatures rise in the twenty-first century as projected, the NEH SLRD will continue to increase. If future sea-level variability is forced by aerosols and/or is part of a cycle, SLR in the NEH may also alternately fall below and rise above projections of IPCC scenarios alone.
Our analyses support a recent acceleration of SLR on ~ 1,000 km of the east coast of North America north of Cape Hatteras. This hotspot is consistent with SLR associated with a slowdown of AMOC.
In other words, Sallenger et al (2012) note there is an accelerated rate at which sea level is rising for a portion of the Atlantic coast of the United States, starting around 1990, but they don’t know the cause. In the opening sentence of the above quote, they comment about the observed 60-year cycles in the Atlantic Multidecadal Oscillation and how they do not agree with the results of their reference 27, which is Frankcombe and Dijkstra (2009) Coherent multidecadal variability in North Atlantic sea level.
The abstract of Frankcombe and Dijkstra (2009) reads:
Tide gauge records from around the North Atlantic are examined and found to show variability on 20–30 year time scales. Sea surface height variability along the western boundary of the North Atlantic shows a particularly strong and coherent signal. Similar variability is also found in an ensemble of runs using a state-of-the-art climate model (GFDL CM2.1). This sea surface height variability is linked to variability of temperatures in the upper layers of the ocean and thence to the Atlantic Multidecadal Oscillation. The variability is consistent with the excited internal ocean mode mechanism of multidecadal variability derived from idealised models and the timescale is consistent with that derived from observations of sub-surface temperature variability.
The last sentence Frankcombe and Dijkstra (2009) reads:
The long tide gauge records analysed here certainly point to the importance of the 20–30 year period over the 50–70 year period more commonly associated with the AMO.
Immediately, one wants to examine a time-series graph of the “Hotspot” sea level data in the Sallenger et al (2012) paper to get an idea of what the multidecadal variability in the data looks like. If there’s a 20-30 cycle in the data, and if the last cycle started in 1990, then odds are the cycle has already peaked and has started back down again. Also, picking the last break point in a dataset with known multidecadal variability, adding before and after trends to the data, and then stating the data during the last period has accelerated has a familiar ring to it. It sounds very similar to the nonsensical tactic the IPCC tried in FAQ 3.1 Figure 1 from their 4thAssessment Report to show that global surface temperatures were warming at an accelerated rate.
Curiously, there were no time-series graphs of the “hotspot” sea level anomalies in Sallenger et al (2012). That raises the question: what didn’t they want to show?
To determine the multidecadal signal in the East Coast “Hotspot” sea level data, I downloaded Permanent Service for Mean Sea Level (PSMSL) tidal gage-based sea level data, same dataset used in Sallenger et al (2012), from the KNMI Climate Explorer. It can be found there on their Monthly station datawebpage. As you many of you are aware, the tidal gage-based sea level data is sparse, rarely continuous, and few have more than a few decades of data. In other words, it’s troublesome to work with, which is one of the reasons I rarely look at sea level data. So I selected the stations with the longest data, 70 years or more, along the Atlantic coast that were included in the “hot-spot” group of Sallenger et al (2012), from North Carolina to Massachusetts, that were also relatively continuous; that is, they did not have a lot of missing data. They included New York (Battery), Philadelphia (Pier9N), Atlantic City, Boston, Newport, Hampton Roads, and Sandy Hook. Since John Droz was interested in North Carolina, I added Wilmington, NC to the mix. We’ll call the combination of those datasets “Hotspot+1”. The Wilmington data had the shortest term, so it set the start year of 1935. Not too surprisingly, it had the lowest trend from 1935 to 2008. Refer to Figure 1. However, since we’re going to detrend the data, its lower trend would have little influence on this preliminary look at the East Coast sea level data. Note: The PSMSL data at the KNMI climate Explorer ends in 2008. Sallenger et al (2012) ended their analyses in 2009, so we’ve only lost a year.
Figure 1
Figure 2 presents the average sea level anomalies of those “Hotspot+1” stations along with the linear trend. Assuming the average sea level anomalies of the 8 stations used in this presentation provide a curve that’s similar to the stations Sallenger et al (2012) used for their “Hotspot”, this may illustrate the reason why Sallenger et al (2012) excluded a time series graph for their average “Hotspot” sea level data. It appears sea level anomalies for the “Hotspot+1” stations have been relatively flat since about 1996.
Figure 2
Since one of the points being discussed is decadal to multidecadal variability, we’ll detrend the “Hotspot+1” average, to help show if it exists. Figure 3 presents the detrended average of the “Hotspot+1” sea level anomalies.
Figure 3
First things first: Is there a break point around 1990 when the trends shift? There is definitely a shift in trends before and after 1989/90 in the detrended “Hotspot+1” sea level data, Figure 4. There are also comparable shifts in trend around 1976/77 and about 1981/82, Figure 5 and 6. But Sallenger et al (2012) went through a detailed analysis and elected to discuss the shift around 1990.
Figure 4
HHHHHHH
Figure 5
HHHHHHH
Figure 6
I’ve filtered the detrended “Hotspot+1” average sea level anomalies with a 13-month running-average filter (centered on the 7thmonth) in Figure 7 to reduce the month-to-month variability. The spikes in 1972/73 and 1997/98 may lead one to believe that El Niño-Southern Oscillation (ENSO) events have a major influence on it.
Figure 7
Whatever is causing the sea level anomalies to vary, there is a multidecadal signal visible in the detrended “Hotspot+1” sea level anomalies. See Figure 8. In it, I’ve smoothed the data with a 121-month running-average filter, which is commonly used when illustrating decadal and multidecadal variability like the Atlantic Multidecadal Oscillation. Now we can understand why Sallenger et al (2012) were discussing a multidecadal signal. One very plainly exists.
Figure 8
Looking at the trailing decadal (120-month) trends, Figure 9, we can see very clearly that the trend of the most recent decade (through December 2008) is not as high as it has been in the past. Also note that the peaks in the decadal trends occurred about the time of the three largest El Niño events that weren’t counteracted by volcanic aerosols. They were the El Niño events of 1972/73, 1986/87/88 and 1997/98. The eruption of El Chichon occurred at the same time as the 1982/83 El Niño and likely offset the effects of that El Niño-Southern Oscillation (ENSO) event on the sea level anomaly trends. Oddly, ENSO isn’t mentioned in Sallenger et al (2012). Volcanic aerosols are mentioned in the closing of Sallenger et al (2012), however. Are the volcanic eruptions of El Chichon in 1982 and of Mount Pinatubo in 1991 the reasons for the low, actually negative, decadal sea level trends around the same time? If so, why did sea level trends drop in the early 2000s?
Figure 9
What about the Wilmington, NC sea level anomalies?
The sea level anomalies of Wilmington have a relatively low linear trend compared to the long-term stations used by Sallenger et al (2012). Refer back to Figure 1. Looking at the detrended Wilmington sea level data when smoothed with a 121-month filter, they have a different multidecadal signal than the “Hotspot” average. See Figure 10. The latest upswing started about 1976, then peaked near 1996, and the downswing was still in progress though the end of 2008.
Figure 10
The running decadal trends for Wilmington, Figure 11, reveal they have been negative since 2002. That is, on a decadal basis, sea level anomalies in Wilmington have been falling, not rising, since 2002. Have they risen since 2008? It makes one wonder why Sallenger et al (2012) chose to exclude the last few years of data from their analyses!
Figure 11
SOURCE
The source of the data presented in this post is the KNMI Climate Explorer, specifically their Monthly station data.
CLOSING
North Carolina is considering new legislation about the rise is sea level. It would be a shame if the incomplete analysis and data presentation by Sallenger et al (2012) and their use of the word “accelerated” influenced it.
SHAMELESS BOOK PLUG
My book If the IPCC was Selling Manmade Global Warming as a Product, Would the FTC Stop their deceptive Ads? is available in pdf and Kindle editions. An overview of my book is provided in the above-linked post. Amazon also provides a Kindle preview that runs from the introduction through a good portion of Section 2. That’s about the first 15% of it. Refer also to the introduction, table of contents, and closing in pdf form here.
I continue to make progress on my upcoming book about El Niño-Southern Oscillation and hope to publish pdf and Kindle editions by late July, early August 2012.
Related articles
- Sea Level Rise Accelerating Along The U.S. Atlantic Coast (thesciencebulletin.wordpress.com)
- Sea-level rise accelerates faster on US east coast (newscientist.com)
- Scientists warn US east coast over accelerated sea level rise (guardian.co.uk)
- Sea-level rise accelerates faster on US east coast (newscientist.com)
- US East Coast set for severe sea level rise – TG Daily (tgdaily.com)
Try controling for ENSO via the multivariate ENSO index. You can also control for the AMO the same way. This will give a relatively pure underlying SLR trend.
Thanks, Anthony.
Bob, re your books: get some advice on titling. Your first book title tells the whole story and has the flavour of a partisan, activist-type harangue. Your excellent analyses and illustrations would be read by a lot more people if you had a more neutral, matter-of-fact title.
I can accept that due to gravity winds and currents one part of the ocean can be higher than another but for one part to rise faster than another one of these factors will have to change too.
If not the bulge will rapidly disperse.
That seems so obvious that it shouldn’t need to be posted.
A few editing comments: you are missing the captions for figures 4 and 5, also in your closing you state,”about the rise is sea level.” should it be, “about the rise of sea level.”?
Great work as usual !!
“What didn’t they want to show” Volumes 1 through 6 !!
Just days ago, a claim of 1 foot sea level rise in California in 10 years has started being promoted.
WUWT ought to run an article on that too, since we can save the record, screenshots, printouts, etc. to show to people 10 years from now (or even halfway there in 5 years) when nothing like such materializes. After all, 1 foot rise is a blatantly large claim, so people can readily notice its lack even with their own eyes if they live by a beach. Such is from a very fancy publication (following the usual technique of dazzle people with verbosity and superficial sophistication so they don’t question the actual figures and assumptions) by the National Research Council and others, so it can be saved for use 5-10 years from now as a great illustration of how appeal to authority doesn’t work when the authorities have been corrupted (by hardcore activists reaching the top plus the temptations of the regulatory class):
http://www.nap.edu/catalog.php?record_id=13389
To quote part of the article on Popular Science, which is titled as follows:
“Sea Level Rising Rapidly on Both Coasts, Could Even Flood San Francisco Airport in a Decade“:
“According to research from the U.S. Geological Survey, the tides in a 1,000-kilometer stretch of coast from Cape Hatteras, N.C. to Boston have been rising at between 2 and 3.7 mm per year from 1950 to 2009. Doesn’t sound like a lot, but it’s two to four times more than the global rate of .6 to 1 mm per year. Looking ahead to the future, another study on the West Coast projects that, barring an earthquake or other unforeseen circumstance, California’s sea levels will also rise faster than the global average. The slightly sinking state is projected to lose one foot of land in 10 years, two feet by 2050, and 5.5 feet within the century, while its neighbors, Washington and Oregon, will end up better off, actually falling a little below the global average. Worldwide, scientists estimate that global rising sea level average to be nine inches higher by 2030, 1.5 feet by 2050, and 4.5 feet by 2100.”
The actual picture, in contrast, is only a few inches rise (or less if we get cooling later), like the few inches rise over the 20th century:
Global sea level over time:
“The first half of the century (1904-1953) had a slightly higher rate (1.91 ± 0.14 mm/yr) in comparison with the second half of the century (1.42±0.14 mm/yr 1954-2003).”*
http://meteo.lcd.lu/globalwarming/Holgate/sealevel_change_poster_holgate.pdf
Another study noted “it is apparent that rates in the 1920-1945 period are likely to be as large as today’s” (Jevrejeva, 2006)
In fact, sea level had an average rise rate per year which was as much in the late 19th century as a century later, despite how human emissions rose by more than a factor of 10 over the period.
Regarding California sea level in particular, the San Diego measurement station history is shown in the publication linked above.
Jevrejeva, S., Grinsted, A., Moore, J.C. and Holgate, S. 2006. Nonlinear trends and multiyear cycles in sea level records. Journal of Geophysical Research 111: 10.1029/2005JC003229
http://www.agu.org/pubs/crossref/2006/2005JC003229.shtml
* Also related, having almost identical figures:
Holgate, S.J. 2007. On the decadal rates of sea level change during the twentieth century. Geophysical Research Letters 34: 10.1029/2006GL028492
http://www.agu.org/pubs/crossref/2007/2006GL028492.shtml
Sea level also responds to atmospheric pressure.
Has anyone looked to see if there were more low or high pressure systems than usual at various times during this period?
I would consider such a book as yours as necessary in a private library as books on solar dynamics. Not because I think there is much connection between solar dynamics and warming or cooling trends, but because the everyday citizen most decidely needs to be and stay informed about the natural universe that surrounds us.
It would seem to me that the only way for sea level to rise in one locale but not in another down the coast is for the land to be sinking in the “hotspot.”
Thanks Bob.
Just the facts as usual, keep it up! there’s a make or break confluence of events coming up in the fall and in 2013 that will break the backs of these manipulators and especially their Powerful political backers and paymasters. Hint USA and Australian elections and the continuing slide down the drain of the EU.
Let’s hope.Lets see?
Good work Bob but….
hmmm… couldn’t find their data huh? Maybe they are just saying coded alleGorically that America’s east coast is beginning to lean to the right, and it’s accelerating, especially in the Carolinas?? Sounds right, but overall definitely leaning to the right. ;).
In November we’ll see if there is a real sea-change. /sarcoff
The actual link to the Popular Science article claiming S.F. flooded in 10 years, as I forgot it in my comment above:
http://www.popsci.com/science/article/2012-06/study-says-california-sea-levels-will-rise-more-five-feet-century
Also I forgot to mention how not only can you look at the San Diego, California measurement station history in http://meteo.lcd.lu/globalwarming/Holgate/sealevel_change_poster_holgate.pdf but that such shows how the
claim of far higher rise in California is just misleading junk at best as usual.
My grandfather built a castle on this swamp and it sunk . My father built a castle on this swamp and it sunk . I built a castle on this swamp and it’s sinking. Subsidence all the way down.
My impression is first of all, the authors take as granted that global warming will have an detectable impact on sea level rise. But neither is this proven despite the physical fact, that warmer water will have a bigger voume than colder water, but other factors are much more powerful to change of sea level.
From 1979 to 1998 unfortunately only the land based stations show a slight increase of air temperature (+0,5 °C), but satellite and radio balloons do not. What the reason for this is, people are guessing, but the majority think it might have to do with urban heat island effect (UHI) and negative selection of stations, which increase the temperature of land bases stations
Looking to the rest, all what the authors of said paper did is cherry picking using the platitude of deviations from mean and call this in case it agrees with their assumptions a “hotspot” and comparison with model results. Is this real science?
I do not want to bore somebody because one know as well as everybody that GMSL is a (by what ever methods better, to say tricks tricks) calculated the mean of local sea levels. I.e. some must be higher (I call it now a “hotspot”) than the global mean, some must be lower. In case they are higher let´s call them “hotspots”. If one would look would to Bangkok or Manila one will see that the hotspot there is much “hotter” (increase of about 1 m in the last 40 years, in Bangkok, unfortunately right now not so easily available on PMSL page as a graph but look here http://www.psmsl.org/train_and_info/geo_signals/) than their specimen “North American Atlantic coast north of Cape Hatteras”. And if they would have compared it with Stockholm ( with a decline of – 3,4 mm/year here http://www.psmsl.org/data/obtaining/stations/78.php) with a decline than they would have seen that this is an example for descending sea level. Or with Triest (http://www.psmsl.org/data/obtaining/stations/154.php) with an increase. In all cases all the variations are rather plausibly explained, but real evidence for this explanations are rare.
Finally I saw that the first reference is Levermann, A., Griesel, A., Hofmann, M., Montoya, M. & Rahmstorf, S. Dynamic sea level changes following changes in the thermohaline circulation. Clim. Dynam. 24, 347–354 (2005).
This people had shown too often, (see Rahmstorf, S a (2007). A semi-empirical approach to projecting future sea-level rise. Science 315:368-370*.) that they love to fudge the results unit they fit. It devaluates every scientific paper which use them a reference.
There must be a “Super Moon” out there……………………..
I too wonder about sea level rise and coastal subsidence (and john’s ancestorial IQ score handed down from grandfather, to father, to son related to castle building ;>)). Given that GPS has only been available recently, it may not be useful in this instance. But it would be interesting to see if there are any SLR records that could be compared to GPS land data. Of course, ideally they would have to be right next to each other.
Gunga Din says:
June 29, 2012 at 9:43 am
There must be a “Super Moon” out there……………………..
==========================
Off topic but speaking of “Super Moons”, the annular eclipse print was just delivered. Thanks.
The geological literature holds the explanation for what has been observed again in the Sallenger et al. (2012) paper. That is, past glaciation of the Northern Hemisphere caused the region to be loaded with the weight of the glacial ice. This in turn caused the extremely viscous mantle below the glacial ice to flow outward and cause a forebulge in the non-ice covered area to the south. After the climate warmed and the ice melted, the process of isostacy began to return the region to equilibrium surface elevations; the formerly ice covered areas began to rise and the forebulge to the south began to be lowered. The coast along Maryland and Virginia has shown the greatest decrease in land surface elevation, which can be mistaken for sea level rise if one is not familiar with the geological history and processes of the area. Unfortunately, this information is contained in things called books! many of which can be found in the library of the US Geological Survey. With regard to the figure from Sallenger et al (2012), if you reverse the sense of the displacement, you will have a fair picture of the process of isostasy; blue indicating land surface moving up and yellow and orange demarking land surface elevation decrease.
One Year Ago:
Mann’s new sea level hockey stick paper
“Figure 1: Two points in salt Marshes in North Carolina are used as the basis for the study:”
One year later, SURPRISE!
Given the time it takes to:
Select all that apply:
A. Fabricate data
B. Maladjust instrumental records
C. Compile computer model results
then write it all up and wait for pal-review to be processed before publishing, surely this qualifies as a rapid backing-up of another exuded product from the undisputed King of the Hockey Sticks. Fully justified as last year’s Mannian output was quickly torn apart by skeptics and desperately needed quick reinforcing, of course.
Henry Clark says:
June 29, 2012 at 9:07 am
“the global rate of .6 to 1 mm per year”
Funny, I thought alarmists usually quoted ~3mm as the annual global sealevel rise.
Which happens to be the same level which is suposedly 3-4 times the global level in the east coast.
Subsidence??
Folks who live around the Houston area such as Baytown know well that since Houston is pumping water out from underground that there is massive subsidence of the land.
http://geochange.er.usgs.gov/sw/changes/anthropogenic/subside/
http://pubs.usgs.gov/circ/circ1182/pdf/07Houston.pdf
I was half way listening to NPR Science Friday. They had someone speaking on this and he was claiming that the rise was related to Coriolis forces and the Gulf Stream. I wasn’t paying close attention so I don’t know exactly what he was trying to say.
I have to agree strongly with Bruce Hemingway. Simple geology knowledge of the East Coast, one would know why the barrier beach coasts are sinking and the rocky coasts are rising. Bob, your map/chart with the amount of rise (in color) just pops out at one.
Doesn’t water run downhill?