Riggs’ Geological Perspective on North Carolina Sea Level

Here’s an interesting presentation on North Carolina sea level that sheds light both on the long term geological history of the area and on why it’s been subjected to particular study. The author is Stanley Riggs, a veteran specialist on the geology of the North Carolina barrier islands.

The PPT nicely shows the steady rise of sea level in the North Carolina area during the Holocene with many good illustrations and pictures, including, for example, stumps in the present day surf. It illustrates how barrier islands have migrated during the process of sea level rise, showing the importance of hurricanes in the migration process. It contains some useful pictures showing the impact of sea level rise on coastal highways, sharply raising questions about the viability of settlements on a surf line that is moving on century scale. Because these settlements are important to North Carolina, it seems to have been a center of this sort of research.

They ask: “SHOULD WE ENGINEER OUR DYNAMIC COASTAL SYSTEM TO KEEP UP WITH THE ONGOING RISE IN SEA LEVEL?” or “OR SHOULD WE BEGIN ADAPTING TO THESE CHANGES NOW TO MAINTAIN A SUSTAINABLE COASTAL SYSTEM AND ASSOCIATED ECONOMY!”

Regardless of one’s position in the climate debate, this sort of question needs to be squarely faced by coastal communities.

One of Riggs’ slides contains the following information on shoreline recession for Mainland Dare County (Roanoke Island also shown is similar:

1817-1851 1700 ft 50 ft/yr
1851-1954 400 ft 4 ft/yr
1954-1997 200 ft 5 ft/yr

I was surprised by the relatively high rate of shoreline recession in the early 19th century relative to more recent recession but I’m not familiar enough with the data to comment on this.

In a supplementary slide, Riggs refers to estimates from Horton, Kemp et al on sea level rise rates as follows:

18000–11000 BP – 49 in/century
11000—8200 BP – 34 in/century
8200-3500 BP – 8 in/century
3500—200 BP – 4 in/century
1800-1900 AD – 8 in/century
1900—2000 AD – 16 in/century
1980—2000 AD – 18 in/century

The Riggs presentation is not dated, but the pdf was made in January 2010 (but it obviously might be an older PPT and merely converted to pdf at that time.)

The new Kemp et al 2011 study draws different conclusions on the past two millenia, stating:

Sea level was stable from at least BC 100 until AD 950. Sea level then increased for 400 y at a rate of 0.6 mm/y [2.3 in/century] followed by a further period of stable, or slightly falling, sea level that persisted until the late 19th century. Since then, sea level has risen at an average rate of 2.1 mm/y [8.2 in/century] representing the steepest century-scale increase of the past two millennia. This rate was initiated between AD 1865 and 1892.

and again later:

From at least BC 100 until AD 950, sea level was stable (0.0 to + 0.1 mm/y). Between AD 850 and 1080 the rate of sea-level rise increased to 0.6 mm/y (0.4 to 0.8 mm/y) for the following 400 y. A second change point at AD 1270–1480 marked a return to stable, or slightly negative, sea level (−0.2 to 0.0 mm/y), which persisted until the end of the 19th century.

Between AD 1865 and 1892 sea-level rise increased to a mean rate of 2.1 mm/y [2.3 in/century] (1.9 to 2.2 mm/y) (12). Sea-level variations in the last 2100 y did not exceed ~0.25 m until the onset of the modern rise in the late 19th century. The modern rate of sea-level rise was greater than any century-scale trend in the preceding 2100 y; a conclusion that is independent of the GIA correction applied.

What accounts for the differences? Dunno for sure, but it might be due to the Kemp et al includes an isostatic adjustment:

A constant rate of subsidence (with no error) was subtracted from the Sand Point (1.0 mm/y) [3.9 in/century] and Tump Point (0.9 mm/y) [3.5 in/century] records.

Quantitatively, the isostatic adjustment is obviously not insignificant for the past two millennia.

The desire to tease a centennial signal out of such coarse data has obviously led the academics into increasingly complicated and more problematic statistical methods. Like their decision that the “appropriate factor” for downweighting was 10. An unsavory statistical process, to say the least, almost as unappetizing as pulling a Rabett out of a hat.

For readers interested in the topic of sea level rise in North Carolina, I urge them to look at the predecessor geological literature to try to get some footing on the actual data prior to the application of obscure and mannomatic methodologies.

57 Comments

  1. j ferguson
    Posted Jun 23, 2011 at 3:23 PM | Permalink

    “rabett” ???

    better left in the hat.

  2. Jeremy
    Posted Jun 23, 2011 at 3:24 PM | Permalink

    I wonder if there’s a “censored” directory in the directory containing the transfer functions used for PME resolution in Kemp 2011.

  3. R.S.Brown
    Posted Jun 23, 2011 at 3:39 PM | Permalink

    Steve,

    There’s an easy to read Bourger Gravity Anomalies map for the US at:

    http://www.zonu.com/detail-en/2009-09-18-8375/Bourger-Gravity-Anomalies-in-the-United-States-1970.html

    You can lift this .jpg, drop it into a file, then use your photo editor to clip it
    down to just the eastern seaboard… the use your +/- viewer to get the details of
    the Virginia, Maryland, North & South Carolina coasts.

    You’ll find some expandable North Carolina geology maps at:

    http://gis.enr.state.nc.us/sid/bin/index.plx?client=zGeologic_Maps&site=9A1M

    The separate Litho-Tectonic map for North Carolina makes you wonder where the
    supposed land subsidence mentioned in the Kemp, Horton, Mann et al. study is
    coming from dynamically. It doesn’t seem to be a description of the physical
    reality of the North Carolina shore. One especially wonders how it could ever
    be used in describing valid proxy sites for the entire US Atlantic coast.

  4. MarkB
    Posted Jun 23, 2011 at 4:25 PM | Permalink

    Here in Massachusetts, we deal with this subject every time a Nor’Easter pulls a few houses into the sea. Trawlers drag up Mastodon tusks from the bottom of George’s Bank every so often, from the time during the last Ice Age when sea level was dramatically lower and the shore was far to the east. The arm of Cape Cod once extended far to the east as well, in various forms, with islands coming and going over centuries as sea level rose. During a single year in 1991, three storms hit Nantucket Island and peeld off 30 feet of the eastern shore. Nantucket is exposed to the ocean currents, with only offshore shoals to protect it from the Atlantic. As a result, far more shoreline is lost to changes offshore than to sea level rise. Before I ever heard of global warming, I was told that Nantucket only has hundreds of years before it disappears under the waves due to erosion.

    • Tim Cohn
      Posted Jun 23, 2011 at 7:16 PM | Permalink

      Some years ago my son and I did a quick study of the erosion rate along Martha’s Vineyard’s South Beach. Using historical maps and aerial photographs, we found that it had been a surprisingly steady 5 feet/year since at least the 1840s.

      website: http://www.timcohn.com/QBA/

  5. Michael Jankowski
    Posted Jun 23, 2011 at 4:43 PM | Permalink

    Kemp has been publishing his stuff at conferences for years concerning sea level rise in NC http://www.sas.upenn.edu/earth/andrewk_a.htm

    Same general co-authors on his publications http://www.sas.upenn.edu/earth/andrewk_p.htm

    Now Mann has been added to the mix.

    I wonder who approached who.

    • R.S.Brown
      Posted Jun 23, 2011 at 8:42 PM | Permalink

      Michael Jankowski @ Jun 23, 2011 at 4:43 PM

      Michael,

      When you look at Ben Horton’s curriculum vitae at:

      http://www.sas.upenn.edu/earth/pdf/BPHCV-short.pdf

      You’ll see in various spots:

      Conference abstracts (first author only)

      Horton, B.P., 2010, Holocene Sea level changes along the Atlantic Coast of the United
      States, Lecture Series, Pennsylvania State University, January 20,
      2010. @—Penn State’s main Campus.

      Alone, this would be a tenuous connection to the between the University of Pennsylvania
      sea level rise/foraminifera troop to the Penn State contingent of the “Team”.

      Andrew Kemp is listed in Ben Horton’s curriculum vitae as one of his “grad students
      supervised”. (PhD 2009) Kemp is also listed as one of Horton’s “post doctoral scholars
      sponsored” for 2009-2010, during Horton’s Penn State lectures period.

      However, a meeting of the minds seems more possible given Andy Kemp’s Conference Authorship
      found at the link you provided:

      http://www.sas.upenn.edu/earth/andrewk_a.htm

      Kemp, A.C., Horton, B.P., Corbett, D.R., Culver, S.J. and van de Plassche, O. Late Holocene
      sea-level rise on the Outer Banks of North Carolina, USA. American Quaternary Association
      Biennial Meeting 2008, State College, PA @—– Penn State’s main campus

      There was plenty of opportunity for the Horton, et al. from the University of Pennsylvania
      to be in face to face contact with the Mann led “Team” at Pennsylvania State University.

      Kemp may well have tagged along with Horton, et alia to the 2010 Penn State lectures.

      When you look at Horton’s coauthors over the past few years, you begin to wonder if there
      might be an undocumented social/professional web of pal reviewers among the extensive
      sea level rise/foraminifera crowd.

  6. Posted Jun 23, 2011 at 5:34 PM | Permalink

    Perhaps Kemp et al 2011 didn’t consider that foraminifera might migrate downwards through the sediment layers, in a similar way to CO2-laden air diffusing downwards through up to 95 layers of compacted snow and solid ice (and remaining unchanged in composition en route).

  7. Matthew W.
    Posted Jun 23, 2011 at 6:10 PM | Permalink

    Chuckle !!!

    “pulling a Rabett out of a hat”

    Nice call back !!!!

  8. Ron Cram
    Posted Jun 23, 2011 at 6:33 PM | Permalink

    Another expert on North Carolina shoreline is Duke University Professor Orrin Pilkey, author of the book “Useless Arithmetic: Why Environmental Scientists Can’t Predict the Future.” Of course, the book draws on his experience with computer modeling of coastlines, but I’m certain Pilkey knows something of their history as well. It would be interesting to have him comment on the Kemp paper.

    • Posted Jun 23, 2011 at 11:20 PM | Permalink

      he probably not a climate expert

      • Ron Cram
        Posted Jun 24, 2011 at 9:54 AM | Permalink

        Mosh,
        True. But he doesn’t need to be to have studied the history of sea level and its effects on the North Carolina shoreline. His book talks about the history of failure to model shorelines and his reasons for concluding that computer modeling of nature is not possible.

        Not as thorough as the book, of course, but have you read his paper titled Useless Arithmetic? http://nctc.fws.gov/EC/Resources/Decision_Analysis/List_Serve_Attachments_files/PilkeyArticle2008.pdf

        • Posted Jun 24, 2011 at 10:51 AM | Permalink

          Orrin Pilkey (the “Little Round Guy”, not to his face) is a sharp old bird, pretty much Mr. Barrier-Island and Coastal Geomorphology. He’s been making waves on the Carolina coast since I was a student at UNC, (mumble) years ago. Glad to see his still kicking over Establishment cans.

          I don’t know Stanley Riggs personally, but he has a good rep. I owe my classmate at the ECU Geology Dept. an email — maybe I’ll ask his opinion.

          As always, Steve, you’re an amazingly thorough researcher. Keep it up!

          Cheers — Pete Tillman
          Consulting Geologist, Arizona and New Mexico (USA)

  9. BillyBob
    Posted Jun 23, 2011 at 6:34 PM | Permalink

    NC has been hit by 403 hurricanes/cyclones (Wikipedia).

    This is what happens to salt marshes when the eye comes within 40km:

    “Hurricane Andrew made landfall on the Louisiana coast on August 26, 1992, with the eye passing 40 km southwest of a salt marsh pond already under study.

    Storm surges ranging from 1-3 m in proximity to the pond resulted in the deposition of a mud layer, several centimeters thick, in many areas inundated by the storm surge.

    Analysis of pond sediment cores distinguished a hurricane mud layer characterized as a composite sediment, containing indicators of estuarine, brackish, and freshwater sources. The composite nature of the hurricane sediment is indicated by a higher diatom species diversity coupled with a more even species representation. Other distinguishing characteristics of the mud layer include lower marine diatom abundance, larger mean grain size, more poorly sorted sediment, and lower amounts of nitrogen in the sediment. Hurricane Andrew appears to have altered the geochemistry of the pond through the reduction of sulfide in the sediment allowing the proliferation of aquatic submerged flora (Najas sp.), resulting in a diatom assemblage shift towards epiphytic species. The submerged stand was still present two years after the hurricane landfall, and the diatom population has yet to revert to the pre-hurricane community.”

    http://www.jstor.org/pss/4298846

    • Jit
      Posted Jun 24, 2011 at 2:08 AM | Permalink

      I’d assume that the authors didn’t use pond sediments but those from the salt marsh surface. Of course, salt pans are dynamic and appear/disappear at regular intervals.

      Presumably if you stick your corer into an area that has been a salt pan in the last 1,000 years, the evidence of that would be in the ‘jumbled’ foraminifera in one layer, and the sample would be thrown out.

      By taking enough cores, you could get around this.

      A more fundamental issue is that salt marshes go through irregular cycles of accretion/erosion, depending on the situation nearer to low water. I don’t see any way to get an accurate calibration for dating your cores.

      It’s not like a lake with regular annual melts (a la Tiljander)… it’s worse.

      • BillyBob
        Posted Jun 24, 2011 at 4:24 PM | Permalink

        I get the impression from looking at abstracts, if the salt marsh was actually “readable” then every hurricane should show up.

        “Lithostratigraphic and radiocarbon data from the inland section of Pattagansett River Marsh, Connecticut, show that this sheltered part of the salt marsh underwent significant erosion twice during the past 600 yr, each time followed by rapid and complete infilling of the eroded space with tidal mud and low marsh and high marsh peat. We argue that the erosion cannot be attributed to increases in tidal prism or to lateral migration of tidal channels. The ±2σ age range (A.D. 1390–1470) for the first low marsh growth in the older regressive sequence agrees well with the age range (A.D. 1400–1440) for a hurricane deposit 60 km to the east. The younger regressive sequence is dated with the greatest probability to the period A.D. 1640–1670, i.e., shortly after the hurricanes of A.D. 1635 and 1638. Our conclusion that the most likely cause of the erosion was hurricane activity is relevant to paleostorm research and the study of marsh sensitivity to and recovery from storm erosion.”

        http://geology.gsapubs.org/content/34/10/829.abstract

  10. Posted Jun 23, 2011 at 6:35 PM | Permalink

    I’m not up to speed with your statistical concern here and don’t dispute it. However I don’t see anything otherwise remarkable about the authors’ (Kemp et al., 2011) conclusion that “Sea-level variations in the last 2100 y did not exceed ~0.25 m until the onset of the modern rise in the late 19th century.”

    Just about any prognosis/prediction related to climate, and particularly global warming, is irrelevant if it doesn’t show consistency with and/or aknowledgement of the past multiple cycles of glacial oscillation. Many aspects of that set of episodes, are no longer controversial. Accordingly, the planet cannot ‘emerge’ from a recent ice age without warming and resultant sea level rise. 2 mm/year is of no significance, in my opinion, in this context.

    • Ron Cram
      Posted Jun 23, 2011 at 6:56 PM | Permalink

      Michael,
      Part of the problem with the Kemp paper is it appears to be Hockey Stick Redux. The power of the Hockey Stick is making natural variability in the past go away. MBH98 completely photoshopped the temp history of the planet. The Medieval Warm Period disappeared from view as did the Little Ice Age. Any warming then looks completely unnatural and potentially catastrophic.

      In this post, Steve is pointing out that previous reconstructions of sea level have shown a significant natural variability. The Kemp paper shows almost zero variability for centuries, until industrial man shows up to spoil things and cause a tremendous sea level rise of 8 inches in the last century – “the steepest century-scale increase of the past two millennia.”

      Scare-mongering… it’s what they do.

      • Posted Jun 23, 2011 at 8:55 PM | Permalink

        I agree with that and understand the context better, thanks.

  11. Roger Knights
    Posted Jun 23, 2011 at 8:30 PM | Permalink

    Two N’s in “millennia”

  12. Jimmy Haigh
    Posted Jun 23, 2011 at 8:40 PM | Permalink

    There is just so much wrong with the Kemp paper I don’t know where to start. Sea level rise is relative. It’s a very complex subject with multiple factors involved. An apparent sea level rise may be due to the fact that the land is subsiding. This is probably the case in this part of Carolina.

    Steve: they make an allowance for subsidence, which, as I pointed out, is more or less the same as the opening apparent sea level rise prior to isostatic adjustment for much of the period

  13. Geoff Sherrington
    Posted Jun 23, 2011 at 10:55 PM | Permalink

    In Charleston. SC, those lovely homes on the Battery Street waterfront are traditionally made of wood, because there is a wide, sandy coastal plain to the inland, with few rocks sticking out. The dynamics of such coastal plains favour seawards creep and downwards movement with compaction and dewatering. One would expect, on averge, a downward land movement of a selected horizon for the very long time the coastal plain has been forming.

    This is apart from effects like isostsasy, which can act either upwards or downwards from time to time.

    I am unsure of the purpose of the rported work. It is hardly illuminating to publish that two points on a soft coastline are moving relative to each other. Besides, the topic of ocean level change is in a period of uncertainty. Here are 2 recent papers with world authority Anny Cazenave as author, a year or two apart:

    In the first part of this study, we propose a new calculation
    of the global MSL from January 1993 to June 2008 using
    new standards for the processing of the T/P and Jason-1 data.
    This new calculation highlights a reduction in the rate of sea
    level rise since 2005, by approximately 2 mm/yr.

    http://www.ocean-sci.net/5/193/2009/os-5-193-2009.pdf

    Compare with a year 2010 paper:
    While in some regions, reasonably good agreement is observed, discrepancy is noticed in some others due to still large regional trend errors in Argo and GRACE data, as well as to a possible (unknown) deep ocean contribution. In terms of global mean, interannual variability in altimetry-based minus steric sea level and GRACE-based ocean mass appear significantly correlated. However, large differences are reported when short-term trends are estimated (using both GRACE and Argo data). This prevents us to draw any clear conclusion on the sea level budget over the recent years from the comparison between altimetry-based, steric sea level, and GRACE-based ocean mass trends, nor does it not allow us to constrain the Glacial Isostatic Adjustment correction to apply to GRACE-based ocean mass term using this observational approach.

    http://sealevel.colorado.edu/content/regional-and-interannual-variability-sea-level-over-2002-2009-based-satellite-altimetry-ar-0

    That is fairly cear, n’est ce pas?

  14. AntonyIndia
    Posted Jun 23, 2011 at 11:06 PM | Permalink

    “They ask: “SHOULD WE ENGINEER OUR DYNAMIC COASTAL SYSTEM TO KEEP UP WITH THE ONGOING RISE IN SEA LEVEL?” or “OR SHOULD WE BEGIN ADAPTING TO THESE CHANGES NOW TO MAINTAIN A SUSTAINABLE COASTAL SYSTEM AND ASSOCIATED ECONOMY!”

    Regardless of one’s position in the climate debate, this sort of question needs to be squarely faced by coastal communities.”

    Fully agree. Big coastal changes have occurred since oceans can to existence billions of years ago and also during modern man’s last few centuries. The Dutch have spend quite a lot of money to keep their coastline in place and even to expand it. Many nations have much longer coastlines and much less funds, so other strategies should be considered and discussed. I don’t see this happening today.

  15. R.S.Brown
    Posted Jun 24, 2011 at 12:55 AM | Permalink

    Michael Jankowski,

    When you look at Ben Horton’s curriculum vitae at:

    http://www.sas.upenn.edu/earth/pdf/BPHCV-short.pdf

    You’ll see in various spots:

    Conference abstracts (first author only)

    Horton, B.P., 2010, Holocene Sea level changes along the Atlantic Coast of the United States,
    Lecture Series, Pennsylvania State University, January 20, 2010, at
    Penn State’s main Campus.

    This might be a tenuous connection to the between the University of Pennsylvania sea level
    rise/foraminifera cadre to the folks at Penn State. However…

    Andrew Kemp is listed in Ben Horton’s curriculum vitae as one of his “grad students
    supervised”. (PhD 2009) Kemp is also listed as one of Horton’s “post doctoral scholars
    sponsored” for 2009-2010, during Horton’s Penn State lectures period.

    A meeting of the minds seems more probable given Andy Kemp’s Conference Authorship
    found at the link you provided:

    http://www.sas.upenn.edu/earth/andrewk_a.htm

    Kemp, A.C., Horton, B.P., Corbett, D.R., Culver, S.J. and van de Plassche, O. Late Holocene
    sea-level rise on the Outer Banks of North Carolina, USA. American Quaternary Association
    Biennial Meeting 2008, State College, PA ., again at Penn State’s main campus

    There was plenty of opportunity for the Horton UPenn troop to be in face to face contact with
    the Mann led “Team” at Penn State.

    Kemp may well have tagged along with Horton to the 2010 Penn State lectures… he’d been
    there before.

  16. Salamano
    Posted Jun 24, 2011 at 3:21 AM | Permalink

    Nearby Cape May, NJ has undergone a tremendous amount of erosion as well…

    http://www.beachapedia.org/State_of_the_Beach/State_Reports/NJ/Beach_Erosion

    Even sections of the town are underwater (3-4 streets worth) since 1850. I wonder how you can separate out ‘storm-based erosion’ from ‘land subsidence’ from ‘sea-level rise’ from ‘isostatic adjustment’, especially when these variables are all seem to be ‘variable’. The region chosen to be studied is certainly anomalous itself, even if there might be a model out there that hindcasts it. What does it mean that only such difficult-to-parse highly anomalous areas of the world (and not an average spot) match the hindcast? (let alone that both the site selection and the model might have been ‘made’ for each other)

  17. Solomon Green
    Posted Jun 24, 2011 at 12:03 PM | Permalink

    Apparent coastal erosion can be caused by many things. Altering the rate of flow of a river being one. It only took a few years after the completion of Nasser’s High Dam on the Nile for the beaches of Alexandria to recede – one, at least, by more than sixty feet.
    A receding shoreline does not necessarily mean a higher sea level.

  18. ferd berple
    Posted Jun 24, 2011 at 2:30 PM | Permalink

    I tried asking this about the Kemp paper over at RC without success:

    Isn’t it generally regarded as poor methodology to splice signals due to the bandpass problem?

    For example, take a noisy signal. Apply a low bandpass filter to the first portion of the signal and a high bandpass filter to the end portion. What you will end up with is a signal that looks quite flat in the first portion and quite spiky in the end portion.

    Looking at the resulting signal you might then incorrectly conclude that the object generating the signal had changed, while in fact the observed change is simply an artifact of the bandpass problem.

    Since it is unlikely that a tidal gauge has the same bandpass as ocean sediments, it would appear that any conclusions drawn from the signal might simply be an artifact of the signal processing. Unless and until the same bandpass filters are applied to both portions of the signal you cannot reliably splice the signals and achieve a significant result.

    For example, it is likely that the ocean sediments are a low bandpass filter. There may well have been spikes in the low bandpass section of the signal similar to what is observed in the tidal gauge. However, these would no longer be visible due to the effects of the filter. Thus, it cannot be ruled out that such spikes are typical of the signal.

  19. Kenneth Fritsch
    Posted Jun 24, 2011 at 3:21 PM | Permalink

    “Part of the problem with the Kemp paper is it appears to be Hockey Stick Redux. The power of the Hockey Stick is making natural variability in the past go away. MBH98 completely photoshopped the temp history of the planet. The Medieval Warm Period disappeared from view as did the Little Ice Age. Any warming then looks completely unnatural and potentially catastrophic.”

    What I find most interesting to the point of being intriguing is that the original hockey stick was much as you say above, but in renditions of MBH progeny reconstructions we see less of the original form and more variation back in time. Through all these publications I have never seen a Mann coauthored paper dwell on the issue that this reconstruction might better represent the climate history, but rather that the reconstruction does not contradict or refute the earlier versions. In my view it was almost as though Mann and authors were begrudgingly moving away from that original hockey stick and all that that iconic graph implied for the scientist/advocate. Now along comes the NC sea level paper that claims that it is a better proxy for the Medieval Warming Period than a Mann reconstruction and that it can lop 0.2 of degree C off that amplitude and regain much of the shape of the original hockey stick. Mann is a coauthor and I would suspect a happier one at that.

  20. rob r
    Posted Jun 24, 2011 at 6:54 PM | Permalink

    Lots of things affect rates of shoreline migration and estuarine sedimentation. Think harbour dredging, breakwater construction, river diversion, extraction of aggregate from rivers, increases or decreases in soil erosion etc. If the rate of sediment supply to the marine environment changes at one point on a coastline this can have impacts that propagate over substantial distances.

  21. Rhoda Ramirez
    Posted Jun 24, 2011 at 7:28 PM | Permalink

    Why, in the name of all that’s good, is someone doing sea level studies on sandy, marshy coastlines? I’d think that some harbors in granit country would give clearer signals.

  22. Salamano
    Posted Jun 24, 2011 at 8:09 PM | Permalink

    So get this…

    Michael Mann says (at RC)

    “[Response: You are confused about the relationship between temperature and sea level in the semi-empirical model. It is the rate of SLR change that is proportional to the temperature. The reason you see such a sharp upward slope in the dotted red line between AD 500 and 1000 is that the relatively warm conditions indicated by the temperature reconstruction is suggesting a fast rate of SLR increase. By contrast, the actual SLR estimate during that same interval is relatively flat, suggesting that temperatures were not as warm as indicated by the temperature reconstruction. That is why, as stated in the paper, the sea level reconstruction appears to suggest that temperatures during AD 500-1000 were not as warm as indicated in the M08 reconstruction (about 0.2C or so cooler on average). -Mike]”

    And then the question is asked:

    “What is the basis that makes the suggestion that the temperatures were not as warm as indicated during AD500-1000 more valid than perhaps the M08 reconstruction suggesting that the SLR estimate instead is incorrect?”

    [Response: That’s a very fair point. Both alternatives, in my view, are equally viable. Future work will hopefully better pin this down. -Mike]

    Bringing this around full-circle…what does this mean about the real relationship between temperature and sea level? Obviously the semi-empirical model is going with a certain understanding that is not confusing, but it appears the reality may still be confounding. Perhaps a third possibility might exist that both reconstructions are wrong because neither may be validating. I’m glad the principal players are willing to comment on their work post-publication. It’s helpful to see what they’re thinking/considering.

    • Salamano
      Posted Jun 26, 2011 at 9:39 AM | Permalink

      So then Martin Vermeer says (again at RC):

      “my perspective differs a little from Mike’s here. I do not consider it likely that the “knee” at 1000AD and the downturn before that are realistic. It would imply or suggest that sea level around year zero would be a metre or more below present — something that seems to be ruled out by the classical Roman fish tanks result, and so large that, if true, we would probably know about it. Also, we see no similar “knee” in any of the other sea level curves in Figure 3 that appear good enough to make such a statement — Massachusetts, Louisiana.

      There are alternatives to our proposition of a -0.2K temperature offset — which seems a bit large against the apparent quality of this reconstruction, even this far back — but they would be speculative at this point.”

      Can someone help me out here..? It sort of looks like scientists armed with a model discovered a location that supports the model and threw it up for accepted publication (and made sure to further canonize Mann’s proxy-work via citation). All of a sudden it seems like the conclusions of this paper are trying to become the rule (despite the countervailing evidence that perhaps gave this publication its pre-arranged status); all of a sudden it’s only the ‘alternatives’ to their propositions that are ‘speculative’?

      • timetochooseagain
        Posted Jun 26, 2011 at 5:02 PM | Permalink

        Indeed a key problem with the quotes above is that it assumes there are only two possible explanations for why their reconstruction of temps disagrees with their sea level reconstruction, when the temp recon is put into Rhamstorf’s sea level model. Their possible explanations:

        1. The temperature recon is wrong

        2. The sea level recon is wrong

        But there are many more possibilities than that! In addition to the above, explanations include:

        3. The sea level/temperature change relating model is wrong

        4. The model and temps are wrong

        5. the model and sea level are wrong

        6. the sea level and temps are wrong

        7. All three are wrong.

        And of course many nuances are possible as to in what way any of theme is wrong, and how wrong. Knowing what I do, I lean towards some variation of 7. The Kemp paper only mentions possible explanation 1. In the comments Mann admits that 2 is also possible, and he may implicitly accept some form of 6. But less than half of the possible explanations are acknowledged!

        • Salamano
          Posted Jun 26, 2011 at 6:21 PM | Permalink

          So why does a paper that identifies (or discusses) only 1 of 6+ possible alternatives (and indicates the others are speculative) get published, if not to serve as a warning shot across the bow to prepare the way for future papers to ‘confirm’ this initial shadiness with perhaps stronger work?

          It seems like this sort of thing was accomplished with the original Mann work by the papers that followed that made sure his material was cited as seminal.

          Attempts by other individual climate scientists to make a similar ‘shot across the bow’ with a countervailing paper that they hope will be ‘confirmed’ by others usually don’t break through to publication. It must take a team effort to get it all done.

        • Posted Jun 27, 2011 at 6:07 PM | Permalink

          It’s baffling to see the gaping holes in logic and even more baffling that “expert” reviwers don’t at least question the lacuna

        • ferd berple
          Posted Jun 29, 2011 at 4:02 PM | Permalink

          The logic is only baffling if you assume that the author is trying to conduct science according to the scientific method.

          Change your assumption. Consider that the purpose of the Kemp paper is to support a specific hypothesis.

          Multiple locations were examined until one was found that satisfied the hypothesis, and the data from that site was used for the study. The contrary data was not disclosed.

          This then allows them to publish and say the data supports the hypothesis. This was what was done with the hockey stick. Why would this study be any different?

          Having violated the scientific method previously, why assume that this would not be repeated in subsequent studies?

          The assumption that the purpose of the study was to conduct science is in error. The purpose of the study is not to conduct science. It is to provide evidence in support of a hypothesis, while appearing to be science.

        • Posted Jun 26, 2011 at 10:57 PM | Permalink

          Yes, the limit the logical choices and then pick the one they desire.

          I think there is now an interesting case to be made for reconstructing temperature from
          sea levels. After all, they believe in their model and sea level reconstruction more than
          they believe in the mann multiproxy recon. who knows that could add more proxies to a multi proxy study.

          They did not adjust the model
          They did not adjust the sea level proxy
          They Adjusted the temperature recon.

          Which one is low man on the epistemic totem pole? mann08

          Odd that a recon with so many proxies gets bumped down to the bottom.

  23. Posted Jun 25, 2011 at 10:53 AM | Permalink

    Wow, I agree, doing these studies on salty marshlands is not as effective as doing it on more solvent coastlines. That being said, this is still extremely interesting.

  24. Curt Covey
    Posted Jun 26, 2011 at 2:01 PM | Permalink

    Glad to see a purely scientific discussion by Steve. I had become discouraged by the volume of complaints about unfair review practices, old-boy networking, etc. Now I will visit climateaudit.org more often.

  25. tty
    Posted Jun 26, 2011 at 3:03 PM | Permalink

    I would like to bring up a matter that has apparently not been discussed up to now in this context, bioturbation. This is the vertical mixing of sediments by burrowing organisms that is a practically universal feature of marine deposits. About the only exception is completely oxygen-free bottoms where nothing but micro-organisms can live. Since a shallow salt-marsh is a very rich habitat I would expect bioturbation to be intense, and consequently that the material at any given depth will vary a great deal in age.
    And indeed this is what we find if we look at Figure one in Kemp et al. 2011. Radiocarbon dates vary widely at the same depth, usually with non-overlapping error bars.

  26. timetochooseagain
    Posted Jun 26, 2011 at 4:29 PM | Permalink

    The average rate of rise for the whole Kemp’s recon covers, as determined by OLS is 1.2 mm a year. I note that their isostatic glacial adjustment has no uncertainty taken into account. If just two tenths of a millimeter more per year and the reconstructed curve would look like this:

    It seems to me that their neglecting of uncertainty in their isostatic adjustment is a source of potentially very large errors.

  27. Posted Jun 26, 2011 at 7:40 PM | Permalink

    I take data drawn from barrier islands with a large grain of salt. The storms have a nasty way of rearranging them. Barnegat Light on Long Beach Island used to have a first and second street. At the moment the first street that exists is 3rd street.

  28. Kenneth Fritsch
    Posted Jun 27, 2011 at 10:08 AM | Permalink

    I have always wondered about climate science, starting with the hockey stick, seemingly being able to declare certain reconstructions of past climate as valid even with rather shaky and unproven methodologies that were used to construct it. When criticism comes from a number of points of the methodology, the defenders merely defend those reconstructions and methodologies by way of focusing on peripheral points of contention. The points of contention with climate reconstructions have pointed to many parts of the methodologies used from cherry picking proxies to failure to match historical variance in the proxy response. Yet the validity of the reconstructions in the climate science community and as part of the general science related consensus on AGW seems to have survived if not thrived. Of course, once there is a publication of a reconstruction it becomes a source for reference in future papers and a reference that does require any equivocations about validity of the referenced work.

    The NC sea level proxy will be a test case, in my view, on whether this gambit of the climate scientist/advocate continues to be successful. NC appears to be a rather shaky piece of work that could resurrect the original hockey stick. We have Mann apparently giving a rare blessing to a reconstruction that counters one of his. Had that -0.2 degrees been a +0.2 degrees do you think we would have seen the same reaction from Mann and cohorts?

  29. Ryan S
    Posted Jun 28, 2011 at 11:22 AM | Permalink

    If you look at Figure S6 of the supporting literature it seems they have exposed themselves to ridicule with their own graphs:

    http://www.pnas.org/content/suppl/2011/06/14/1015619108.DCSupplemental/pnas.1015619108_SI.pdf

    This graph shows the tide gauge data from 1900 onwards to the present day superimposed on the new study (the tide gauge data before 1890 is not real tide gauge data but projection based on modelling). If you actually re-drew that graph to get the new study data to coincide with the tide gauge data, then by 1900 the tide gauge data shows a drop of about 200mm compared to the new proxy which shows a drop of 300mm.

    If the proxy data is already out by 50% after just 100 yrs then would it be unreasonable to suggest it could be 1000% out going back 2000yrs? The matching of proxy data to measured data is very poor (even given that they have chosen a tide gauge data set that shows the greatest increase in sea level of all empirical studies to fit as close as possible to the new proxy).

    I would submit that even a casual review of this new paper would have shown that the new proxy does not fit well with other proxies over the modern period and therefore cannot be reliably used to hindcast to what sea levels were 2000yrs ago. It is probably less accurate than taking the tide gauge data and extrapolating it back by a factor of 10.

  30. NikFromNYC
    Posted Jun 29, 2011 at 6:38 AM | Permalink

    I deal with more simple sea level chicanery here, in a single glance:

    NASA (sea level) info-graphic: http://oi55.tinypic.com/xmpfv4.jpg

  31. Tom
    Posted Jun 29, 2011 at 9:17 AM | Permalink

    NOAA has an interesting map of raw sea level change data from tide gauges all over the world.

    http://tidesandcurrents.noaa.gov/sltrends/sltrends.shtml

    The interesting thing is how much variability there is that cannot possibly be related to global sea level changes. RELATIVE sea level is rapidly falling in Alaska (tectonic) and Scandinavia (isostatic rebound at its type locality). There is a patch of anomalously rapid sea level rise in the Chesapeake area which may be due to isostatic adjustment of the glacial peripheral bulge. Rapid apparent rise in Louisiana and Texas is due to sediment dewatering and compaction.

    There are many variables controlling apparent local sea level change, and they can be >> actual global sea level change. The signal-to-noise ratio is low and any attempt to reconstruct global sea level based on a single location is guaranteed to be virtually meaningless.

    Cursory eyeball-averaging of the map indicates a global average in the 0-1 ft/century range, which is plotted in green.

  32. Ryan S
    Posted Jun 29, 2011 at 11:25 AM | Permalink

    @Tom

    If you want to get a grasp of local sea level changes, then check out the history of “Long Beach Harbour” on wikipedia. Sank several feet due to oil extraction at the wilmington field. Long Beach Harbour has two tide gauges. One can speculate what they are likely to tell you about sea level over the longer term.

    The fact is that heavy concrete harbour walls are ideal places to put tide gauges when you want to know if you can dock the QEII or whatever. Not so ideal if you want to monitor sea levels over 100yrs – they have a tendency to sink into the mud or get their foundations washed away. Just google “subsidence” together with “harbour”, “Quay” or “dock” and you will get the picture. Tide gauges will always give high readings for sea level change because of this subsidence – but the tide gauge readings aren’t that worrying anyway.

  33. ferd berple
    Posted Jun 29, 2011 at 3:48 PM | Permalink

    A poster on WUWT noted that sea level rise began to accelerate in the Kemp study about the time large scale tobacco farming was introduced, made practical by pumping of the aquifers to irrigate the tobacco crop. This practice is known to give the appearance of sea level rise, when in fact it is the ground that is sinking.

  34. RickA
    Posted Jul 12, 2011 at 3:19 PM | Permalink

    Does anybody know if the sea level rise data has been adjusted for the temperature change since 1850?

    I know they just adjusted it for GIA – which is really a volume adjustment, as the ocean basins are larger today than 1850, due to glacial rebound and basins sinking (on average).

    But what about the volume change to the ocean based on thermal expansion. It is .8C warmer than 1850, so has the a similar volume adjustment been made to the sea level data to account for thermal expansion?

    I have been unable to determine if both volume adjustments are incorporated into the sea level rise data, or just the GIA adjustment.

    It would seem to me that these two different volume adjustments offset each other.

    It would also seem to me that if one volume adjustment is being made, both should be made.

    • Posted Jul 12, 2011 at 5:07 PM | Permalink

      They don’t adjust for thermal expansion. According to FAQ 5.1 of the AR4
      “During recent years (1993–2003), for which the observing system is much better, thermal expansion and melting of land ice each account for about half of the observed sea level rise, although there is some uncertainty in the estimates. “

      The latest RC post mentions an adjustment (they used it for acceleration) which I was surprised to see is somewhat significant – the amount of water held in manmade reservoirs.

      • John M
        Posted Jul 12, 2011 at 6:08 PM | Permalink

        I wonder if they took the amount of geologic water withdrawn from aquifers into account.

        • Posted Jul 13, 2011 at 12:32 AM | Permalink

          I found this comprehensive site at CSIRO. They list both as causes of observed sea level rise, which I suppose means that they don’t adjust. They say:
          “For example, extraction of water from underground aquifers can increase the mass of the ocean whereas the storage of water in dams can decrease the mass of the ocean.”

        • John M
          Posted Jul 13, 2011 at 4:54 PM | Permalink

          Let me clarify my question.

          By “they” I meant RC.

          I know that it’s a known factor, I’m just wondering if they took it into account.

          I didn’t see it, but I may have missed it.

      • RickA
        Posted Jul 12, 2011 at 6:38 PM | Permalink

        Thanks Nick.

        That is what I thought.

        What I don’t get is why they felt the need to adjust the sea level rise data for the volume change based on sinking basins and rising coasts, but not the need to adjust the data for the volume change based on thermal expansion?

        Doesn’t it make sense to adjust for all volume changes, if they are going to adjust for any?

        The other thing I don’t quite understand is aren’t all the old tide gauge measurements made relative to the coast – in other words not relative to the center of the Earth.

        By adjusting for GIA they are converting a relative measurement (how high sea level is relative to the coast at a particular tide gauge), to an absolute measurement (how high is the sea level, keeping the volume of the basin holding the ocean constant).

        To me, the relative measurement is the important one.

        If sea level rises relative to Florida 1 meter by 2100, I assume a lot of land will be covered.

        However, if Florida rose 1 meter and the ocean rose 1 meter, so no relative difference in land lost to the sea, who cares?

        Any thoughts on these questions are welcome.

  35. Posted Sep 21, 2011 at 10:29 PM | Permalink

    Why yes, recently people have been in the business of rebuilding the barrier islands.

  36. tobyw
    Posted Apr 30, 2014 at 7:15 AM | Permalink

    Why the disparity between satellite sea level data and the NOAA sea level trends such as:

    http://tidesandcurrents.noaa.gov/sltrends/sltrends_station.shtml?stnid=8518750

    If you examine stable sites they range between 2.0-3mm/year up and down the East Coast with no appreciable recent increase other than what appears to be slight 30-ish year cycle, with a 100-year rate of under a foot per century. Barrier island, Gulf coast, West Coast and Alaska are all over the map and should be labeled as such. We need to guard against promiscuous data homogenizers. One factoid I noticed was that sites on opposite sides of Delaware Bay had 4mm and 3mm average annual increases, so much for water seeking its own level, LOL. (Lewes, DE and Cape May, NJ)
    Sites in Maine tend to be about 2mm/year

    Perhaps a site by site analysis in the vein of that done by Anthony Watts for temperature stations is in order.

    Also compare the sea level trends with the predictions in the recent testimony in the Senate http://www.energy.senate.gov/public/index.cfm/hearings-and-business-meetings?ID=d841f31d-9b1a-4e7e-b6df-43c8f4ba11b1

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