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# Oceanography

Created page Oceanography and added the link to the Argo project that Nathan mentioned on TWF 305.

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1.

I've read that the journal climate science is going to publish a paper about the global differences of sea levels, which oceanographers only recently began to look at: There seem to be big differences in the sea level height all over the globe, up to 150 meters, i.e. the Indian ocean is 100m below the global average height, and the north Atlantic 50m above it (or vice versa).

Does anyone know any details? (About the paper and/or these global variations?) I have to admit I always thought that there would be differences of a few meters only!

Comment Source:I've read that the journal <a href="http://www.springer.com/earth+sciences+and+geography/meteorology+%26+climatology/journal/10584">climate science</a> is going to publish a paper about the global differences of sea levels, which oceanographers only recently began to look at: There seem to be big differences in the sea level height all over the globe, up to 150 meters, i.e. the Indian ocean is 100m below the global average height, and the north Atlantic 50m above it (or vice versa). Does anyone know any details? (About the paper and/or these global variations?) I have to admit I always thought that there would be differences of a few meters only!
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2.
edited December 2010

It did look surprising. But Wikipedia says variations in salinity give densities typically between 1.02 and 1.03, so over a depth of up to 10 km this amounts to 100 metres of water.

Equally surprising - well it was to me - is that the osmotic pressure of seawater is equivalent to a fall of about 120 metres. This could put osmotic power generation on more or less the same footing as hydro-electric power. Statkraft's site has details.

Comment Source:It did look surprising. But Wikipedia says variations in salinity give densities typically between 1.02 and 1.03, so over a depth of up to 10 km this amounts to 100 metres of water. Equally surprising - well it was to me - is that the osmotic pressure of seawater is equivalent to a fall of about 120 metres. This could put osmotic power generation on more or less the same footing as hydro-electric power. [Statkraft's](http://www.statkraft.com/energy%2Dsources/osmotic%2Dpower/) site has details.
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3.

The main explanation I read about was gravity, with variations of the gravitational field due to land and ice masses, or a lack of mass after a big hit of a meteor - this is a hypothesis for the low level in the Indian ocean.

Comment Source:The main explanation I read about was gravity, with variations of the gravitational field due to land and ice masses, or a lack of mass after a big hit of a meteor - this is a hypothesis for the low level in the Indian ocean.
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4.
edited December 2010

I guess you have to define what you mean by 'variations in height of up to 100 meters'. Do you measure height assuming the Earth is a sphere, or using the WGS84 standard reference ellipsoid, or the geoid, which is the surface of constant gravitational potential, or various standard approximations to this geoid?

It's a complicated business, and the difference between the ellipsoid and various standard approximations to the geoid can amount to roughly 100 meters:

If we're trying to understand something interesting about the oceans, I think it only makes sense to compare them to the geoid, or various standard approximations, which are presumably pretty good by now. I hope that's what people are doing.

Comment Source:I guess you have to define what you mean by 'variations in height of up to 100 meters'. Do you measure height assuming the Earth is a sphere, or using the WGS84 standard [reference ellipsoid](http://en.wikipedia.org/wiki/Reference_ellipsoid), or the [geoid](http://en.wikipedia.org/wiki/Geoid), which is the surface of constant gravitational potential, or various standard approximations to this geoid? It's a complicated business, and the difference between the ellipsoid and various standard approximations to the geoid can amount to roughly 100 meters: <img src = "http://upload.wikimedia.org/wikipedia/commons/thumb/0/08/Geoid_height_red_blue.png/350px-Geoid_height_red_blue.png" alt = ""/> If we're trying to understand something interesting about the _oceans_, I think it only makes sense to compare them to the geoid, or various standard approximations, which are presumably pretty good by now. I hope that's what people are doing.
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5.
edited December 2010
The problem is again that the journalist did not understand it himself or did not bother to explain it :-(

I hope I find the original paper someday.
Comment Source:The problem is again that the journalist did not understand it himself or did not bother to explain it :-( I hope I find the original paper someday.