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Reply from Nils-Axel Mörner on the problems of estimating Future Sea Level Changes as asked by Albert Parker in letter of January 2, 2018

Authors:
Reply from Nils-Axel Mörner
on the problems of estimating Future Sea Level Changes
as asked by Albert Parker in letter of January 2, 2018
In your Letter, I note the following three statements to reply on:
(1) Garner et al. [1] discuss the rising hazard of storm-surge flooding based on
extremely accelerated projections of sea level rise (SLR) by 2300. Referred to a
zero in 2010, they say SLR may reach 0.6 m by 2050, and 2.6 m by 2100.
They also say SLR may reach 17.5 m by 2300.
(2) Hence, there is a clear need of an experts’ opinion on the sea level rise
that should be considered for coastal planning.
(3) Opinions are therefore requested to you individually as a well renowned sea
level expert.
The list of the experts being contacted is the following:
8. Nils-Axel Mörner <morner@pog.nu>
Reply (mailed back on January 4, 2018):
Sea Lever Research is a separate multi-disciplinary branch of Science
calling for deep knowledge in a wide field of different scientific topics. All
ideas and interpretations must be based on solid observation facts and
the application of physical laws. The historical evolution of ideas and
concepts are important. It is a serious mistake to think that there are
shortcuts in the form of time-series statistics and computer modelling.
There are physical frames to consider. Ice melting requires time and
heating, strictly bounded by physical laws. At the largest climatic jump in
the last 20,000 years viz. at the Pleistocene/Holocene boundary about
11,000 years BP ice melted under extreme temperature forcing; still
sea level only rose at a rate of about 10 mm/yr (or just a little more if one
would consider more extreme eustatic reconstructions). Today, under
interglacial climatic conditions with all the glacial ice caps gone climate
forcing can only rise global sea level by a fraction of the 11,000 BP rate,
which in comparison with the values of Garner et al. [1] would imply:
well below 0.4 m at 2050 instead of +0.6 m
well below 0.9 m at 2100 instead of +2.6 m
well below 2.9 m at 2300 instead of +17.5 m
Consequently, the values given by Garner et al. [1] violate physical laws
and common glaciological knowledge. Therefore, their values must not
be set as standard in coastal planning (point 2 above).
We may also question the reviewing process.
There are different ways of trying to estimate future sea level changes,
such as tide-gauges, satellite altimetry and direct coastal studies (i.e.
morphology, stratigraphy, biological characteristics).
Tide-gauges offer records of the relative changes in sea level. Out of a
total of about 2300 stations (PSMSL), “a global set of ~300 tide gauges
that serves as the backbone of the global in situ sea level network” in the
Global Sea Level Observing System (GLOSS). There is no objective
straightforward solution to estimate any global mean value. University of
Colorado chose 184 global tide gauge records. Their rate distribution has
a marked peak in the zone from ±0.0 to +2.0 mm/yr with a mean value at
+1.14 mm/yr. Because the majority of station used includes a component
of regional subsidence and local sediment compaction, the true mean
sea level value should be <+1.14 mm/yr. In a few areas we have a strict
knowledge bout the crustal component, and are hence able to test the
eustatic component in the tide-gauge record. At Korsör in Denmark, the
zero-isobase (or “hinge”) of uplift has remained stable for the last 8000
years. The mean sea level rise over the last 125 years is +0.81 ±0.18
mm/yr. At Stockholm in Sweden, the absolute uplift over the last 3000
years is strictly measured at +4.9 mm/yr. The mean tide-gauge change is
-3.8 mm/yr, giving a eustatic component of +1.1 mm/yr for the last 150
years. In Amsterdam, the long-term subsidence is known as +0.4 mm/yr.
The Amsterdam/Ijmuiden stations record a relative rise of +1.5 mm/yr,
which give a eustatic component of +1.1 mm/yr.
Satellite altimetry is a new and important tool, which reconstructs the
entire ocean surface changes. Nowhere do the measurements agree
with costal observations, however. Satellite altimetry exceeds tide-gauge
records by about 300%. It has even been accused for manipulation
(IJESI, v. 6, no. 8, 2017, p. 48-51).
Global Loading Adjustment has been widely used in order to estimate
global sea level changes. Obviously, the globe must adjust its rate of
rotation and geoid relief in close agreement with the glacial eustatic rise
in sea level after the last Ice Age. The possible internal glacial loading
adjustment is much more complicated, and even questionable, however.
Direct coastal analysis of morphology, stratigraphy, biological criteria,
coastal dynamics, etc usually offers the far best means of recording the
on-going sea level variations in a correct and meaningful way. It calls for
hard work in the field and deep knowledge in a number of subjects. We
have, very successfully, applied it in the Maldives, in Bangladesh, in Goa
in southern India, and now also in the Fiji Islands. In all these sites, direct
coastal analyses indicate full eustatic stability over the last 50-70 years,
and long-term variations over the last 500 years that are consistent with
“rotational eustasy” or “Global Solar Cycle Oscillations” (GSCO).
Conclusions
The future sea level values given by Garner et al. [1] are deeply wrong
and misleading for coastal planning. They must be rejected as nonsense.
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