Guest Post by Willis Eschenbach
A reader who posts under the name “tokyoboy” sent a link to a very interesting sea level record from the Japanese Meteorological Agency. It covers the period 1906–2010, and when I first saw it I thought they’d made some mistake.
So I got their data, and plotted it up. I also got the satellite records for the area. Finally, I got records of one of the sites that the Japanese used, but I obtained it from the PSMSL records. All of them agree very well, so I am forced to assume that there are no obvious errors in the Japanese records. Figure 1 shows the results:
Figure 1. Japanese sea level records. Two records marked “Japan” are from the citation above. They are averages of long-term records since 1906 (4 sites, blue line), and shorter-term records since 1960 (16 sites, red line). Satellite records (green, 1993-2010) are from the University of Colorado interactive wizard. Wajima records (purple, 1930-2010) are from the PSMSL.
You can see why I thought there was a mistake. Sea level around Japan rose steadily from 1906 to 1950. Then it dropped for fifteen years and bounced around until 1980. Since then it has risen again, but it is about 20 mm lower than it was in 1950.
Now, I can’t find anything at all wrong with the data. The satellite record agrees with the Japanese averages, as does the PSMSL record. So we have to assume it is accurate.
But it is unlike any record I’ve seen of the global average change in sea level. That global record climbs steadily over the century.
I’m happy for suggestions and comments, as I’m in mystery over this one. It’s one of the great things about the climate, always more puzzles to solve.
w.
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Is that data corrected for the land rising or subsiding? With the high level of earthquakes in Japan I would expect that earth movement has more effect on sea level than actual changes in sea level.
The Japanese land moves a lot and obviously not only when quakes strike…how’s that for an answer?
Willis
Sea level varies with atmospheric pressure as well as the volume of water in the oceans. Japan is in a seismically active zone so the earth’s crust will be moving up and down by some amount. Determining an average sea level is not an easy task. Remember the arguments between John Daly and John Hunter over the mean sea level mark on Dead Man’s Isle made by Lemprier in the 19thC. The mark is still 300mm or so above current MSL.
Yes, my initial thought is tectonic activity.
Anthony, as you are aware, Japan is plainly one of the most seismic regions on the planet…
This has implications: correlating sea-level rise and fall with local large seismic events, most notably 1923 and 1995? Most certainly, the Sendai region subsided more than a meter after the March 2011 earthquake, but there are almost certainly other ‘aseismic’ swellings and subsidences in the Japanese archipelago which would have a direct influence on sea levels recorded there.
And I should have addressed “Willis” above^^^
Japan sits on the edge of tectonic plates – perhaps that makes the land rise and sink?
Here in Scandinavia the sea level steadily sinks contrary to global trends, but that’s easily explained by the land rise still active since the last ice age.
Anthony, How do the lows & highs in the Japanese data compare to where GISS, etc. have “adjusted” the data over time–compare with your “blink charts” & maybe the source of disagreement will flash into view!
I would think earthquakes could be the cause. It is a very geologically active area.
Agree with above two posters, it will be the changes in coastal formations. Japan has constant tremors and quakes. Last time I was there a twenty second shake rocked the hotel in Tokyo I was staying in, various bits flew around the room, don’t recall off hand how many in that area but loads a year.
Had a strange experience many years before that when living there for a while on the edge of Kyoto. Taking a break in the garden sitting on the ground watching the paddy fields a little below me I felt and heard a tremor coming from a distance away to the mountains around me, and it was coming in a straight thin line directly under where I was sitting, happened very quickly. Saw the line of it shaking the trees in the distance and watched as it came under me and carried on.
Well, it looks like global temperature (without UHI).
My initial thought was Godzilla.
Gojira!!
And they’re also deep, this the latest one:
http://www.ibtimes.com/articles/275033/20120101/japan-earthquake-2012-strong-quake-shakes-new.htm
January 1, 2012 10:14 AM EST
Less than a year after Japan was devastated by a massive earthquake and tsunami in 2011, the first strong earthquake of 2012 has struck Japan.
The strong earthquake with a magnitude of 6.8 shook Japan off the country’s coast on Sunday, the first day of the new year, according to the U.S. Geological Survey.
The USGS said the earthquake struck 495 kilometers (307 miles) south-southwest of Tokyo at a depth of 348.5 kilometers (216.6 miles). Because the jolt was so deep, it was less likely to cause damage at the surface than quake last March 11, which caused a tsunami and, ultimately, a nuclear crisis in the country.
However, there were no reports of damage this time around, and the Pacific Tsunami Warning Center did not issue a tsunami warning.
Average sea level is always a function of tectonic subsidence and rise. It is generally accepted that mean sea level has been rising at a constant rate of 2mm/yr over the last century. Local variation will be the result of tectonic activity which can have a rate as high as 9cm/yr. (Usually much lower.) Bangledesh and the Mississippi delta are excellent examples of a subsiding landmass. Conversely parts of Canada, Europe and the US are still isostatically rebounding from the last glaciation at a rate that exceeds sea level rise.
Simple. Overfishing and 10-year fallout from Hiroshima and Nagasaki led to a serious depletion of ocean fish stocks in the 1950s. Because of the lack of fish, the volume of the Ocean around Japan was reduced. As the fish stocks recovered, so did the ocean volume, affecting its level.
/silliness
I see that no-one has come up with the obvious answer.
‘Global Average Sea Level’ is a useless metric. Like an average telephone number it is meaningless.
Sloshing.
Several people have proposed geophysical movements. However, the changes in the record seem too abrupt for such a cause. There’s a discussion of the issue at the PSMSL, but it doesn’t really resolve anything.
w.
If tectonic in origin do all the 4/16 sites move up or down at the same time, or do some go up and some go down. I am doubtful if they (the sites) move in the same direction at the same time. How does the data compare with Iceland, New Zealand and the Bay of Naples three areas of volcanism I can think of, or the Eastern Mediterranean which I think is quite seismically active. I am sure that others can suggest better areas for comparison. If there is similar deviation from the norm then perhaps it is down to the earth moving.
“Here in Scandinavia the sea level steadily sinks”
Well.. another place where the sea level sinks…
“That global record climbs steadily over the century.”
No it doesn’t.
Look at other specific localities. i suspect Japan is not the only locality whose trend differs from the Wikipedia graph.
I have put together a video of the entire set of Permanent Service for Median Sea Level (PSMSL) data set to music. (I admit it – I’m a geek). The idea it to visually look for an acceleration of rise rate in the graphs. The first two minutes of text may be a little boring, but they explain the context.
If interested, have a look here…
http://climatesanity.wordpress.com/2012/01/29/sea-level-data-set-to-music-yeah-thats-right/
Tom
As so many others have said, sea level is usually measured relative to land and if the land frequently bounces up and down…
I think Willis addresses landmass movement by pointing out that Japanese measurements match satellite measurements, even through the recent massive quake.