The Younger Dryas Boundary event ... can it survive?

20 Jun 2012

At http://wattsupwiththat.com/2012/06/19/the-intriguing-problem-of-the-youn... ... there is an excellent posting by Don Easterbrook, a geologist from Western Washington University, on the Younger Dryas event, the periods preceding and following it, and temperature fluctuations within it. A lot of this is actually a bit of an eye opener - and the latest research. As the years have progressed a considerable amount of data has accumulated on glacial advance and retreat, especially when it comes to Scandinavia where the research has been intense. Glaciers advanced in many countries - North America, Siberia, the Alps, New Zealand, and the Andes, as well as Sweden and Finland, even in the Scottish highlands (such as Rannoch). Easterbrook also sticks with the old designations, Oldest, Older and Younger Dryas, and the Bolling and the Alleroed warmings, which is useful as anyone wishing to follow up can resort to the old literature as well as the new data.

The expansion of glaciers is evident from the formation of moraines - such as those associated with Loch Lomond. The multiple nature of these moraines in widely separated regions of the world, and in both hemispheres, indicates the YD event consisted of more than just a single drop in temperature - and these occurred virtually simultaneously around the globe, from Patagonia to Finland and from NE America to New Zealand. The GISP ice core shows two peaks within the Younger Dryas that match the glacial record, and the absence of a time lag between the N and S hemispheres glacial fluctuations preclude an oceanic cause and is inconsistent with the idea of fresh water surges into the North Atlantic kick-starting the cooling - nor with a cosmic impact or a volcano (a one off event). The point is worth emphasizing - the consensus explanation (ocean circulation) is invalid - but so too is the impact hypothesis. Something else was going on.

As both C14 and Beryllium 10 production rates changed during the Younger Dryas this may indicate incoming radiation was responsible - or solar flaring. Easterbrook thinks solar fluctuations may be responsible for the YD event - but is this really quite as transparent as he suggests. Is it too easy to blame the Sun?

During the last few years temperatures have fallen and solar flares have become more intense - possibly as a result of shrinkage of the Earth's magnetosphere (the protective sheaf around our planet). Sun spots and solar flares are somewhat more rarer than they were in the early 2000s, probably as a result of the 60 year cycle of 30 years warming and 30 years cooling, but what exactly might spark such cycles is clearly not understand by scientists. They seem to exist and presently, hard to understand anomalies in temperature are being attributed to less or greater activity on the Sun. However, might the solar flaring be a symptom of the Younger Dryas cooling rather than the cause?

In conclusion, Easterbrook adds - the ice core isotope data is significant because they show Late Pleistocene cooling and warming events could not possibly be caused by the very slow orbital changes of the Croll-Milankovitch hypothesis. It was the fact that ice cores openly showed climatic change had happened very quickly, putting the prevailing wisdom in doubt, that led to the development of the ocean circulation hypothesis, in an attempt to salvage Croll-Milankovitch. Once again theory is seen to drive rather than follower observation. The idea that large amounts of fresh water discharged into the North Atlantic to kick start the YD (and other cooling episodes, even in the Holocene) came to dominate paleo-climate literature - and you can read this in just about any tome on the ending of the Ice Age. The outwash of fresh water from inland lakes formed by a melting ice sheet, pouring into the ocean, seems to be a very good explanation - but was never proved one way or the other. It became entrenched and the YDB people had to fight to overcome people convinced by the validity of this hypothesis. Easterbrook has no qualms. He says that because it cooled at the same time in the southern hemisphere as it did in the North Atlantic it simply could not be the explanation - as the ocean circulation system requires a time lapse for the cold fresh water to reach the southern oceans and the Pacific - and the dating evidence is contrary. The idea that the release of water from a cold glacial lake in North America could put the temperature of the Earth into reverse is somewhat concocted - and not your most obvious of answers to the problem. Easterbrook is equally adamant that volcanic eruptions or impacts could have caused a cooling that lasted some 1300 years. He is not, however, taking the Clube and Napier hypothesis into consideration, the idea of the Earth passing through very dusty regions of space or even the streams of dust and debris left behind by a major cometary body, the so called Taurids. This may account for downturns even within the Younger Dryas, with larger fragments causing airbursts over the duration of the passage through the stream of material, but intermittently, or only on the rare occasion. In addition, the idea of dust and debris caught up in the atmosphere, on a continuous basis once the Earth's orbit was enveloped within the stream of material, may account for a lengthy cooling episode. The evidence of repeated catastrophic incidents may be more receptive to the Clube and Napier hypothesis whilst the idea of an impact, one off or otherwise, may be unnecessary. It all depends on what happens with the solar radiation angle. For example, flaring episodes during the Little Ice Age may be responsible for some of the climatic oddities of the time, and peculiar weather events. If Piers Corbyn's view of the causes of weather on Earth are taken into account anything is possible. On the other hand the Electric Universe people may have different ideas. It may in fact be worthwhile to view the Younger Dryas as a sort of extended Little Ice Age, with periods of warmth, even some hot summers, but generally a period that was cooler than normal.

The comments to the article raise other possibilities. For example, at 1.36pm there are links to www.geol.lu.se/personal/seb/Geology.pdf.pdf and www.sciencedirect.com/science/article/pii/S0031018204002597 .... where evidence is found that the Younger Dryas is riddled with interpretation issues. Warm and dry summers make it difficult for glaciers to advance and there is evidence, it is alleged, glaciation actually preceded the onset of the Younger Dryas.