Sea levels The hawaiian case

Here is the depth map off Hilo on Big Island Hawaii:

http://geopubs.wr.usgs.gov/open-file/of00-124/fig22.html

The Islands of Hawaii have been the focus of geophysical study for a long
time

Darwin concludes from his studies of atolls that the pacific is an area of
subsidence.
On Hawaii Big Island the following submerged beaches have been found and
dated

http://volcano.und.nodak.edu/vwdocs/vwlessons/activities/e_number8.html


terrace   time(y)   depth (m)
I         20000      133
II       133000      426
III      253000      693
IV       346000      925
V        440000     1180

(Campbell, J. F., 1986, Subsidence rates for the southeastern Hawaiian Islands 
determined from submerged terraces: Geo-Marine Letters, v. 6, no. 3, p. 139-146.)

This leads to a near constant subsidence rate of 2.46 mm/yr
since the last ice age the average relative sea level rise was 6.65 mm/yr
(133000/20000)
The current observed relative sea level rise (Hilo Gauge) is 3.39 mm/yr
http://www.ntf.flinders.edu.au/TEXT/CONF/cook2000/papers/Mitchell2.pdf
(W. Mitchell, J. Chittleborough, B. Ronai and G.W. Lennon)

Monthly data from PSMSL for Hilo:
http://www.pol.ac.uk/psmsl/pubi/met.monthly.data/760061.metdata


We can derive now an eustatic (global) sealevel rise of

6.65 - 2.46 = 4.19 mm/yr since the last ice age
and
3.39 - 2.46 = 0.93 mm/yr since 1930

For the last 20 years the trend is even less.

There is no observed  increase in the sea level rise in the 20th century.
Despite global warming.

So for this century my forecast is:

0.93 mm/year
or for 2000-2100
9.3 cm (3.6 in)

Hans

comment added 27 Feb 2003

An anonymous reviewer comments:


I have found what is probably a reliable estimate of the relative sea 
level rise and its uncertainty at Hilo from:


http://ilikai.soest.hawaii.edu/uhslc/gpsd/CGPS.html

which is:

4.3 +/- 0.2 mm/year

This is quite different from the 3.39 mm/year, which was obtained from
figures from the National Tidal Facility Australia. They are clearly
inconsistent with the +/- 0.2 mm/year uncertainty estimate.

If we choose this latter number, we get a eustatic (global) sealevel rise 
of:

4.3 - 2.46 = 1.84 mm/yr since 1930

(with an uncertainty of at least +/- 0.2 mm/year).

-- i.e. near the top end of the "IPCC" range for the global average.



Reply:
3.242 is the result of the linear trend from the monthly data from 
Hilo published by PSMSL:


http://www.pol.ac.uk/psmsl/pubi/met.monthly.data/760061.metdata

I don't know how Mark Merrifield and Mike Bevis found a trend of 4.3 
using the same data....

3.242-2.46 = 0.782 

fairly close to the flinders average of 0.8 for the pacific



I guess you should take it up with Mark Merrifield. However, you
should note that the "flinders average of 0.8 for the pacific" was based
on the 27 longest records available, 12 of which were shorter than 40
years. This data set therefore falls far short of the 60-70 years minimum
specified by Douglas (2001) for a reliable estimate of long-term trend.



Here is the subsidence history of Big Island Hawaii:





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page updated 22 may 2002, links updated 5 august 2005