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Sahara Dust in the Everglades

8 October 2013

This story is at several places with a different emphasis at some of them. At http://phys.org/print300385973.html … there was an abrupt climate shift in the Florida Everglades at 800BC. Obviously, it impacted a larger region than just southern Florida – but this is where the field research took place. A prominent semi permanent high pressure weather pattern commonly known as the Bermuda High dominated the weather. As a result of the shift  tropical storms that routinely struck Florida moved to the south – the Gulf of Mexico. The paper is in PNAS and concerns wind blown Sahara dust that was dumped on the Everglades wetland zone prior to the movement in the storm track. It affected the wetlands by changing the hydrology pattern and nutrient supply which impinged on fauna and flora – and the dust was found in sediments in Everglade water ways (and the dust was missing when the storm track moved). Hence, prior to 800BCD a wetter climate prevailed in southern Florida – and a drier climate ensued thereafter. Modern attempts to revive the Everglades which have suffered from water extraction as the population of Florida has increased and its popularity as a vacation hot spot has mushroomed, are taking place, and it is recognised they could never reproduce the climate prior to 800BC.

We may note that in NW Europe, in contrast, 800BC was marked by a much wetter climate which suggests the jet stream moved permanently south for a couple of centuries, and the polar region expanded, much of a likeness with the situation during the Little Ice Age when global temperatures were on average somewhat below the norm. From the perspective of neo-catastrophism we may wonder what the vector was that caused this abrupt change in climate systems around the world. What is intriguing is at the same point in time there is plenty of evidence of a shift southwards of the monsoon track which affected western Asia, and eastwards as far as China.

The same paper is discussed at www.sciencenews.org/article/african-dust-once-fertilized-everglades?mode… … but in this review it is a much earlier period that is picked out, 2600BC rather than 800BC. In the third millennium BC wind blown dust from the Sahara can be seen to be laid down in the Everglades sediments. This too was caused by an abrupt shift in climate – in the Pyramid Age (or that of Stonehenge) which must be telling us something. How many other abrupt climate changes were teased out of the sediments?

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