Sea Level Confusion — Part 2

I’ve been reading, trying to understand better why sea level varies so much from location to location. I conducted a google search and found a site affiliated with Yale University.

The site is called Environment 360.   An article titled The Secret of Sea Level Rise: It Will Vary Greatly By Region  provided a bit of insight and some climate propaganda.  The climate propaganda makes me a bit nervous. If the author is inclined to misrepresent in one area, perhaps the rest of the article is less than impartial.  The first paragraph included the following tidbit:

Recent projections suggest a global average warming of perhaps 3 to 4 degrees C, or 5.4 to 7 degrees F, by the end of this century.

A little later in the article:

Sea level, according to the best current projections, could rise by about a meter by 2100, in large part due to melting of the Greenland and West Antarctic ice sheets.

The article was written in 2010.   Best current projections, give me a break.  In 2010 his best projections would have been IPCC AR4 report published in September of 2007.   That report made no predictions about Greenland and said that data on the Antarctic ice sheet was inconclusive.  AR4 predicted the following in a section titled Projections for Future Changes in Climate:

For the next two decades, a warming of about 0.2°C per decade is projected for a range of SRES emission scenarios

Almost immediately thereafter  sea level rise by 2100 makes an appearance in the form of a chart.  The sea level rise that matched 4 degrees C was …are you ready…between .26 and .59 meter.   The data in the chart (labeled SPM 1 in AR4) showed a range of best guess temperatures from 1.1 to 4.0 degrees C.   4.0 was the highest best guess on the chart.   The author took the highest number possible, and made it sound like the most likely event!

And so far temperature predictions made in the AR4 report have been wild high.

Since Y2K there has been no net change in the temperature of the Earth’s surface.  Temperatures peaked in 1998 and have been wandering in  a narrow range for some 15 years.   Carbon dioxide has been rising steadily, temperature has not.  I have no idea what kind of projections he was referring to.   IPCC projections will, in AR5, almost certainly be less specific.  Nobody likes to have their mistakes so easily documented.

That said the article offers some interesting tidbits about why sea level changes.  Most are short term lasting anywhere from a few days to up to 30 years.   Wind, atmospheric pressure, and changes in the ocean bottom are discussed.    None seemed to help explain the errant data I was seeing (see my last post).   And then I read about gravity!

Supposedly, changes in gravity at the poles can impact sea level.   When the Arctic ice cap shrinks (as it has been doing since the 1970’s) this changes the gravitational force in the area.  Sea level goes down.   And this article predicted significant changes.   The whole thing sounded a bit S.W.A.G.-ish to me.  And given the exaggeration in the beginning of the article I had suspicions.   Still it is an interesting notion.

Another article said that when ice in Greenland melts it can take up to 30 years for that change in sea level to work it’s way around the world.   Another article talked about how difficult is to measure sea level.   The subject seethes with SWAG potential.

NOAA keeps all sorts of data on sea level.   They monitor hundreds of sites (perhaps thousands).   But the sites are not uniformly distributed.   Most are in the USA and in Europe.  Africa has only one official site.  Antarctica has none.

Maybe Antarctica could help explain some of the strangeness of the data.  The ice sheet in Antarctica has been growing in recent years.  2013 has set one record after another.  The ice sheet is the largest it has been (surface area) since satellite data began in 1979,or so says the National Snow and Ice Data Center.  And they have pictures:

It looks like gravitational forces in Antarctica have been increasing in recent years.  Sea level should be higher near the coast of Antarctica and lower in the middle of the Pacific.  It would help explain why Hawaii’s sea level is increasing less than ….say San Francisco.   Perhaps the amount of ice over land in Antarctica might offset the melting in Greenland .

Antarctica and the Arctic might be offsetting each other.

It doesn’t explain why folks in Australia show a rise in sea level that does not persist in California.  Maybe it will even out some time in the next 30 years or so, one way or the other?

Antarctica’s mass is growing.  That’s my best guess for why some sea level data makes no sense.  That and time.   Much of the data in the NOAA data base is less than 30 years old.   There you have it,  my current best wild ass guess.   Absent field measurements of actual sea level activity near Antarctica…who’s to say I’m wrong.

At least I admit I’m guessing!


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