Global Warming

[Anomalocaris]

Doesn't the deep ocean take on the order of centuries to react to such?

Different thing. Currently Northern Europe is kept at temperatures unusually warm for its high latitude by the strength of warm equatorial current in the Atlantic. This current is powered by evaporation generated differential salinity Basically, as the warm equatorian surface water moves north, parts of it evaporates while leaving its salt in the water, making the warm surface water progressively more saline as it moves north. Eventually when the warm water near the poles it had become so saline that its density surpass the density of the cold water at depth, so it sinks, displacing the cold water at depth southward, driving what is effectively a salinity powered vertical convection cell whose width is equal to the entire height of north Atlantic.

If global warming were to occur in great strength, precipitation in temporate climates at intermediate latitudes around 20-30 degrees would increase greatly, creating much more freshwater run off into the Atlantic near the equaltor. This has the effect of diluting the salinity of Atlantic surface waters at its source. When the equatorial surface water becomes sufficiently dilute, it would no longer be able to evaporate enough on the way north to gain the sort of salinity needed for it to sink near the poles. So the Atlantic warm equatorian current stops flowing north. When this happens Northern Europe regains the climate appropriate to its latitude and effective turns into Siberia.

So in a severe global warming scenario, UK and North Europe would enter a deep freeze. North Atlantic would freeze over each winter down to the latitude of the Thames. You would need icebreakers to get to Antwerp. The opening of Arctic thought by some to be one side economic benefit of global warming would totally reverse. The arctic ocean would freeze solid again.