The sea level of Massachusetts ‘Remarkably Stable’ for a Century

Written by Albert Parker

Boston, Massachusetts Travel Guide - Must-See Attractions ...

I wrote this piece as a comment to a wrong paper in the journal “Estuarine, Coastal and Shelf Science” claiming the sea levels of Massachusetts have dramatically accelerated over the last few decades, where all the evidence says they have been perfectly stable over the last century.

I believe that nobody could look at graphs of the monthly average mean sea levels measured by tide gauges, with regular, natural oscillations, about a constant linear trend, over more than one hundred years, and say the sea levels have dramatically accelerated over the last few decades. However, this the norm, rather than the exception.

Thus, I proposed to the editor of the journal, Dr. David Burdige, a polite, simple, but effective, comment, asking where was the evidence for the accelerating claims when I was not able to spot any difference in between the sea level oscillations about the same linear trend before and after 1990, in the tide gauges of Massachusetts, same of every other long-term tide gauge of the world.

The below manuscript, everything but offensive, and everything but a “personal opinion”,  was rejected by the editor that responded to me

I have decided to not publish your commentary on this paper.  In reaching this decision I want to make clear that the decision is not based on my opinion of the merits of the points you make in your piece.  Whether your points are, or are not, valid is not relevant here.  Rather, this decision is based on my conclusion that publishing your work as a non-peer reviewed commentary of this paper is not the appropriate approach. More specifically, my concerns stem from the fact that the points you raise here are based on your interpretation of existing data without providing us with any discussion and explanation of the statistical and/or analytical techniques used in your data analysis.  Without this information it is difficult-to-impossible for the reader to critically examine the assumptions you make in your data analysis, and ultimately determine whether they agree or disagree with the conclusions you reach.

Worth to mention, the editor first promised to do the right thing,

I  am writing to let you know how we will handle your comment on the paper by Gonneea et al. that was recently published in ECSS. I will be sending a copy of your comment to the authors of this manuscript requesting a reply from them to your comment. Once I have received their reply I will go though your comments and their reply, edit them as necessary and then publish them back to back in the same issue of the journal. I will not send you their reply to your comment before these are published.”

 Then he changed his mind.

It should not be an issue to ask the authors of a paper to comment the public domain data that are conflicting with their paper, but it seems this is now impossible in the peer review.

The rates of rising are traditionally computed by linear fittings of the monthly average mean sea level times series (slope = M)

y = B + M·x
and the acceleration is traditionally computed by parabolic fittings  (acceleration = 2·A)

y = B’ + M·x + A·x²

where y is the monthly average mean sea level and x is the time.  The subsidence rates are similarly computed by linear fittings of the GPS position time series. If the proposed public domain information of relative mean sea levels from tidal gauges and position of GPS domes close to the tide gauges, analyzed with basic linear and quadratic fittings very well explained in the weblinks and the additional cited reference works, is not an “evidence” that Dr. David Burdige should have considered, but only my “personal interpretation”, it is unclear to me which “superior solid science” is supporting the wrong accelerating claim of the published paper.

Gonneea et al. (2019) claim the relative sea history for Cape Cod, MA, USA was characterized by a stable rise at 0.9 mm/yr. for most of the past 1,500 years, that they explain by a glacial isostatic adjustment (GIA) of 1.2 mm/yr. relatively constant over the past 5,000 years, from the ICE-6G model. They say that before 1850, the primary driver of relative sea-level rise along the U.S. Atlantic coast were the land level changes associated with the spatially variable GIA. Then, they say that since 1850 there has been a recent acceleration in relative sea-level rise that they attribute to thermal expansion of ocean water, melting of land ice, and changes to ocean circulation patterns. In conclusion, they say that from 1850 to 2015, the sea level rose at +2.3 mm/yr. up to a maximum rate of +3.2 mm/yr. occurring in the last decade, that they say are a nearly threefold increase over the previous 1500 years. This reconstruction of the relative sea-level pattern for Massachusetts in general, and Cape Cod, in particular, is incorrect for three good reasons.

First, Gonneea et al. (2019) fail to acknowledge the existence of localized land subsidence along the East coast of the United States, that is mostly due to water withdrawal (Clawges, and Price, 1999; Galloway, Jones, and Ingebritsen, 1999). This phenomenon was already relevant for more than a century ago (Johnson, 1910).

Second, a proper estimation of recent land subsidence is provided by GPS monitoring of domes (Blewitt, Hammond, and Kreemer, 2018), that is returning much better estimates of local land movements than an everything but accurate global glacial isostatic adjustment model. Subsidence is a complex local phenomenon that cannot be simply explained by a global glacial isostatic adjustment model.

Third, the relative sea-level rise is properly measured by tide gauges, and all the long term trend tide gauges, of record length exceeding 100 years to properly compute trends and accelerations cleared of the multi-decadal oscillations of periodicity quasi-60 years (Chambers et al., 2012), consistently show no such a thing like the dramatic sea level acceleration from 2.3 mm/yr. to the 3.2 mm/yr. over the last decade that is claimed by the authors (Dean & Houston, 2013; Holgate, 2007; Houston & Dean, 2011; Parker, 2013;  Parker & Ollier, 2017).

Figure 1 presents the time series of the monthly average relative mean sea levels for Massachusetts – in the NOAA web site, Massachusetts has three tide gauges, 8443970 Boston; 8447930 Woods Hole; and 8449130 Nantucket Island – as well as the GPS time series of the position of domes nearby the tide gauges. The sea level images are from sealevel.info, www.sealevel.info, the GPS position images are from Nevada Geodetic Laboratory, geodesy.unr.edu.

Boston is close enough to be considered a long-term-trend tide gauge. With date range 1921/1 to 2017/12, the rate of rising is +2.817 mm/yr. and the acceleration is -0.00300 mm/yr² (negative). With date 2014.2204 to 2019.1650, the vertical motion of the nearby MAMI GPS dome -0.649 mm/yr.   This gives the latest absolute (Wöppelmann et al., 2009; Parker, 2018) rate of rising of the sea level +2.817-0.649=2.168 mm/yr. about the same of what Gonneea et al. (2019) claim for most of the past 165 years.

The closest to Boston and Massachusetts strictly long-term-trend tide gauge is Portland, Maine.  The relative sea-level pattern is similar. In Portland, with date range 1912/1 to 2017/12, the rate of rising is less, +1.868 mm/yr., but the acceleration is similarly small and negative -0.00694 mm/yr².

In Woods Hole, the tide gauge record is shorter. Also, worth to mention, this record has a gap, with a possible misalignment of the data collected before 1965 and after 1969.  Only the rate of rising can be computed, not the acceleration. With date range 1932/8 to 2017/12, the rate of rising is +2.858 mm/yr. With date 2013.7112 to 2019.1458, the vertical motion of the nearby MAF1 GPS dome is +0.089 mm/yr.   This gives the latest absolute rate of rising of the sea level +2.858 +0.089 =2.947 mm/yr. slightly larger of what Gonneea et al. (2019) claim for most of the past 165 years.

In Nantucket Island, that is a much shorter record, only the rate of rising can be computed, not the acceleration. With date range 1965/1 to 2017/12, the rate of rising is 3.650 mm/yr. With date 2008.7474 to 2019.1650, the vertical motion of the nearby IMTS GPS dome is -1.381 mm/yr.   This gives the latest absolute rate of rising of the sea level +3.650 -1.381 =2.269 mm/yr. about the same of Boston and about the same of what Gonneea et al. (2019) claim for most of the past 165 years.

In the measured sea-level records, there is no trace of an accelerating sea-level rise that has increased from +2.3 mm/yr. since 1850 to the maximum rate of +3.2 mm/yr. occurring in the last decade. The acceleration of Boston is small and negative, not large, and positive.

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Figure 1 – (a) Location of tide gauges (yellow triangle) and nearby GPS domes (yellow square) of Massachusetts. (b) Time series of the monthly average relative mean sea levels and GPS time series of the position of domes nearby the tide gauges for Boston (b,c), Woods Hole (d,e) and Nantucket Island (e,f). The map is reproduced modified from Nevada Geodetic Laboratory, geodesy.unr.edu. The sea level images are reproduced modified from sealevel.info. The GPS position images are reproduced modified from Nevada Geodetic Laboratory, geodesy.unr.edu. 

References

  1. Blewitt, G., W. C. Hammond, and C. Kreemer (2018), Harnessing the GPS data explosion for interdisciplinary science, Eos99,https://doi.org/10.1029/2018EO104623.
  2. Chambers, D., Merrifield, M.A., and Nerem, R.S. (2012). Is there a 60-year oscillation in global mean sea level?. Res. Lett.39(18).
  3. Clawges, R. M., and Price, C. V. (1999), Digital data sets describing principal aquifers, surficial geology, and ground-water regions of the conterminous United States, U.S. Geological Survey Open-File Report 99-77.
  4. Dean, R.G. & Houston, J.R., (2013). Recent sea level trends and accelerations: comparison of tide gauge and satellite results. Coastal Engineering75, pp.4-9.
  5. Galloway, D.L., Jones, D.R., and Ingebritsen, S.E. (1999), Land subsidence in the United States, U.S. Geological Survey Circular 1182, 175 p.
  6. Gonneea, M.E., Maio, C.V., Kroeger, K.D., Hawkes, A.D., Mora, J., Sullivan, R., Madsen, S., Buzard, R.M., Cahill, N. and Donnelly, J.P., (2019). Salt marsh ecosystem restructuring enhances elevation resilience and carbon storage during accelerating relative sea-level rise. Estuarine, Coastal and Shelf Science217, pp.56-68.
  7. Holgate, S. J., (2007). On the decadal rates of sea level change during the twentieth century. Geophysical Research Letters34, L01602.
  8. Houston, J. R. & Dean, R. G. (2011). Sea-Level Acceleration Based on U.S. Tide Gauges and Extensions of Previous Global-Gauge Analyses. Journal of Coastal Research27, pp. 409-417.
  9. Johnson, D.W., (1910). The supposed recent subsidence of the Massachusetts and New Jersey coasts. Science32(829), pp.721-723.
  10. Parker, A., (2013). Sea level trends at locations of the United States with more than 100 years of recording, Natural Hazards65(1), pp.1011-1021.
  11. Parker, A., (2018), Geodetic Observation crucial to Sea-Level Monitoring, Arabian Journal of Geosciences, 11, pp. 239.
  12. Parker, A. & Ollier, C.D. (2017). California sea level rise: evidence based forecasts vs model predictions. Ocean & Coastal Management149, pp. 198-209.
  13. Wöppelmann G., C. Letetrel, A. Santamaria, M-N. Bouin, X. Collilieux, Z. Altamimi, S.D.P. Williams, and B. Martin Miguez, (2009). Rates of sea-level change over the past century in a geocentric reference frame. Res. Lett.36, L12607

 

Update: as the authors were claiming  that from 1850 to 2015, the sea level rose at +2.3 mm/yr. up to a maximum rate of +3.2 mm/yr. occurring in the last decade, that they say are a nearly threefold increase over the previous 1500 years, here below are (1) the monthly average mean sea levels of Boston since the start of the measurements, that is only January 1921. With data up to December 2017, the relative rate of rise is 2.817 mm/yr. then (2) the monthly average mean sea levels of Boston over the last decade, from January 2008 to December 2017. The relative rate of rise is negative -0.28 mm/yr. 

Is there any interest in “what it is” rather than “what is convenient”?

figure 1figure 2

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