Harald Sverdrup and the MOC

The sverdrup, named after oceanographer Harald Sverdrup (1888–1957), is used to measure the volumetric rate of transport of ocean currents. It’s equal to one million cubic metres per second. Researchers have looked at what might happen if fresh-water flow into the Arctic Ocean were to increase by one sverdrup for ten years. They found that it could stop the Meridional Overturning Circulation (MOC) which in northern latitudes depends for its motive power on the cooling of an upper layer of saltier water. And that would cut off the transport of warm water to northern Europe from the Gulf of Mexico and drastically affect the UK’s climate.

The sverdrup is a unit
Of ocean volume flow.
It’s used in Arctic modelling
(I thought you’d like to know).

Now Greenland’s massive ice sheet
Is shrinking, and its ice
Could do just what the models do,
Which isn’t very nice:

Fresh water, say researchers,
If dumped at such a rate
Into the Arctic Ocean,
Could change its present state.

Its sea ice and albedo
Would both reduce; and so
The Gulf Stream’s North Atlantic Drift
Would be the first to go.

The globe is getting warmer,
The evidence is clear:
Those sverdrup flows of melted ice
Will not just disappear.

If we don’t cut emissions,
The MOC will die;
And GeoVerse’s readers
Will know the reason why.

[Image: Wikipedia Commons]
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