[NAFEX] Fossilized midges show sudden climate changes
Donna &/or Kieran
holycow at cookeville.com
Thu Aug 9 10:40:28 EDT 2007
Fossilized midges provide clues to future climate change
Fossilized midges have helped scientists at the University of Liverpool
identify 2 episodes of abrupt climate change that suggest the UK climate is
not as stable as previously thought
Fossilised midges have helped scientists at the University of Liverpool
identify two episodes of abrupt climate change that suggest the UK climate
is not as stable as previously thought.
The episodes were discovered at a study in Hawes Water in Northern
Lancashire, where the team used a unique combination of isotope studies and
analysis of fossilised midge heads. Together they indicated where the
climate shifts occurred and the temperature of the atmosphere at the time.
The first shift detected occurred around 9,000 years ago and the second
around 8,000 years ago. Evidence suggests that these shifts were due to
changes in the Gulf Stream, which normally keeps the UK climate warm and
During each shift the North West climate cooled with an average summer
temperature fall of 1.6 degrees - approximately three times the amount of
temperature change currently attributed to global warming.
Scientists found that the atmosphere cooled rapidly and cold periods lasted
up to 50 years for one event and 150 years for the other. The detection of
these events will allow experts to understand more clearly what can happen
when the climate system is disturbed.
Professor Jim Marshall, from the University's Department of Earth and Ocean
Sciences, explains: "At Hawes Water mud has been deposited continuously
without any gaps, which allows us to measure an accurate timeline of events.
We have monitored the modern environment of the lake for the past eight
years and this has shown us how to read the past climate record from the
ancient mud in the lake.
"Isotope analysis helped us identify the episodes of climate change. We then
used fossilised heads of non-biting midges, which are preserved in every
spoonful of mud. They tell us the temperature at the time the mud was
deposited. We compare the population of midge heads in each sediment sample
with the population of midges in Scandinavian lakes, which span a wide range
of modern day temperatures."
The team found the two abrupt climate changes correlated directly with two
episodes of sharp climate deterioration in areas such as Greenland,
suggesting that a change in the Gulf Stream had occurred.
Professor Marshall added: "People are worried that the melting of the polar
ice caps could result in a slow-down of what we call the 'Atlantic Conveyer'.
This is where cold water that sinks in the far north is replaced by warmer
water from the tropics in its circulation of the North Atlantic Ocean. A
number of studies suggest that the conveyer may be unstable and may be able
to slow down or switch off completely, making our climate suddenly colder.
Our study provides evidence that the two climate shifts we detected were
directly linked to a slow-down in the conveyer."
Scientists believe that this new data will provided a unique test for the
global climate computer models that are being used to simulate future
The research - in collaboration with University of Swansea; the Open
University; University of Exeter; Edge Hill University and University
College London - is published in Geology.
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