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| 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.
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| 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.
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| Hot air ballooning over the badlands of Cappadocia |
Jonathan @jrdean_uk
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