William Connolley wrote:
> On 24/09/2007, Zeke Hausfather <[EMAIL PROTECTED]> wrote:
> >
> > The risk of Northern Europe plunging into
> > a new Ice Age due to global warming have been overplayed in the media
> > to an extent not supported by the science.
>
>
> Good so far
>
> The THC is a global ocean circulation driven by changes in density and
> > salinity of ocean waters.
>
>
> I think that there are hideously complex oceanographic reasons why this
> isn't fully accurate. the THC *is* the global thermo/haline circulation but
> isn't fully driven by density differences - wind forcing is important. You
> cannot truely separate the two. Did RC do this? RMG might know the truth -
> there is a Theorem in in.
Yes, the so-called western boundary currents are primarily wind
driven. There's one in the North Atlantic (the Gulf Stream) and a
similar one in the North Pacific. Those currents don't promote deep
sinking at present, in fact, there's said to be no THC in the North
Pacific. The waters from the Gulf Stream which do eventually sink
originate as a branch of the Gulf Stream and may also be influenced by
the atmospheric motion above. AIUI, the eventual THC sinking is not
caused by the wind, although there is some upwelling of deep water
elsewhere due to wind forcing. In any event, it appears that the Gulf
Stream would continue to circulate about the mid-latitude gyre of the
North Atlantic, absent tie THC.
One should be aware that the water in the North Atlantic Gyre is the
saltiest water in the main oceans. The water in the Mediterranean Sea
is saltier and water flowing out along the bottom of the Strait of
Gibralter sinks to some depth below the surface of the North
Atlantic. The water further north has been diluted by precipitation
and is thus less dense, which is the reason the sinking water must
first be first cooled almost to freezing. If there were no high
latitude THC, I think the salt in the mid latitudes would accumulate
and eventually result in sinking at another mid-latitude location.
This would likely result in a considerably different ocean from what
we now see, as the sinking water would be relatively warm.
E. S.
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