[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 
wet.

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 
climate change.


###
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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