Wednesday, 19 February 2014

Ancient Climate Secrets by Jonathan Dean

Standing on the rock on which
the first peace treaty in human
history was signed between the
Hittites and the Egyptians
Jonathan Dean started working as a Stable Isotope Apprentice in NIGL this January after he finished his PhD research at the University of Nottingham. Here he tells us a little bit about his research into how lake sediments are revealing secrets of past climates...

I carried out my PhD research (between 2010 and 2013) on the chemistry of lake sediments from central Turkey, supervised by Dr Matthew Jones and Prof Sarah Metcalfe at the University of Nottingham and Prof Melanie Leng and Dr Steve Noble in BGS.  The research was aimed at reconstructing changes in the hydroclimate (i.e. wet vs. dry) of the region over the past 15,000 years. Previously, there were no reconstructions of hydroclimate from the region spanning this time period that were analysed at a sufficiently high resolution to allow changes in climate from one decade to another to be examined. There were a couple of key motivations for my work. Firstly, Turkey is an important region in human history, as it was here that some of the first farming communities sprang from ~10,000 years ago and where important civilisations such as the Hittites developed. My climate data will allow archaeologists to better investigate the links between societal development and climate change.

The other motivation for my research was so we had a climate record which could be better compared to those from other parts of the world, so we can consider the drivers of Near East hydroclimate. In particular, I wanted to investigate how abrupt climate changes seen in the North Atlantic, such as one that occurred 8,200 years ago (the infamous 8.2 event), are expressed in this region. Understanding the form and drivers of these sorts of climate perturbations is particularly important given the concern that human forcing of climate may increase the probability of such events occurring in the future.

Nar lake in July 2010
In 2010, a group from Britain, France and Turkey travelled to Nar lake in Cappadocia, central Turkey and retrieved a 21.5 m long core of sediment from the lake. The top-most sediments were deposited in 2010 and the bottom-most ~15,000 year ago. I then took samples from the sediment at intervals of 30 years or less, and analysed the changes in the ratio of one type (or isotope) of oxygen to another in the calcium carbonate in the sediment. This allowed me to reconstruct how the hydroclimate of the region changed through time. I found some large shifts than occurred within just a few decades. The climate seems to have been wet at the time agriculture developed and droughts appear to have occurred at the same time civilisations such as the Hittites collapsed. Some of this work has been published and I will be writing up further papers in the coming months, as well as being examined for my doctorate next month!

Undertaking isotope analysis on hundreds of samples for my PhD has put me in good stead for my job as a Stable Isotope Apprentice at NIGL. I’ve spent the first few weeks preparing samples and analysing them for oxygen and carbon isotopes, as well as getting on with writing papers from my research.

Hot air ballooning over the badlands of Cappadocia

Jonathan @jrdean_uk

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