Oceanic Heat Transfer

We know that the Ice age ended over 10,000 years ago and we know that it took around three thousand years for the ice to melt to current levels. I discuss the likely reasons for the ending of the Ice Age in my chapter Pleistocene Nonconformity posted earlier.

Amazingly, we also know that the Northern Hemisphere at least experienced a climate warmer than todays for the next 5000 years up to around 3000 years ago. In an earlier post, I posited that this was a reflection of the Antarctic cold water mass reaching its maximum extent.

We now live in a semi stable regime in which temperatures in the Northern Hemisphere attempt to converge on their Bronze Age highs, yet constrained by some mechanism that likely injects surplus cold water into the south Atlantic ultimately chilling the Gulf stream by a degree or two. An engine of this nature easily accounts for the little ice age and the known variations that have been experienced.

Currents are driven in the Atlantic around two Gyres which are induced by the Coriolis force. It is very much like the foot print of an eggbeater with the center flow feeding into the Caribbean. Rather obviously, a major increase of cold Antarctic surface water which is at least 5 degrees colder at the boundary contact even in the southern latitudes, would have a chilling effect on the equatorial waters that ultimately form the Gulf Stream.

At present, each year, the Atlantic equatorial zone receives a quantity of solar energy that we can conveniently name Q. This quantity does not vary. Q is eventually delivered, almost intact into the arctic and is discharged melting winter sea ice. The point that I want to make here is that there is no credible or significant mechanism in the Northern Hemisphere capable of altering this exchange. I question whether it can even be varied significantly by any force at work in the Northern Hemisphere.

Yet a little ice age must have been induced by a reduction in Q delivered to the Arctic. Barring extraordinary variation in Solar output which I think is rubbish, we have only one remaining choice. That is a sharp jump in the amount of cold water injected into the south Atlantic. The temperature differential is so large, that only a moderate shift in flow will be sufficient to achieve our ends.

And we do know that the surface waters around Antarctica can be pulsed by shifts in winds alone. Right now, unfortunately we have little knowledge of the workings of the exchange mechanisms between the South Polar current and the various currents interacting with it. However, learning how to measure the current flow rates of ocean currents (particularly the Benguela Current) is timely, and integrating that information into our models rather wise.

A simple change in the mix of source waters for the Benguela Current could have a huge multiplier effect on Equatorial surface temperatures. Scary thought!

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