Perilous Times and Climate Change
Dramatic Ocean Circulation Changes Revealed
by Staff Writers
Cardiff UK (SPX) Jan 18, 2011
The unusually cold weather this winter has been caused by a change
in the winds. Instead of the typical westerly winds warmed by
Atlantic surface ocean currents, cold northerly Arctic winds are
influencing much of Europe.
However, scientists have long suspected that far more severe and
longer-lasting cold intervals have been caused by changes to the
circulation of the warm Atlantic ocean currents themselves.
Now new research led by Cardiff University, with scientists in the
UK and US, reveals that these ocean circulation changes may have
been more dramatic than previously thought.
The findings, published in the journal Science, show that as the
last Ice Age came to an end (10,000 - 20,000 years ago) the
formation of deep water in the North-East Atlantic repeatedly
switched on and off. This caused the climate to warm and cool for
centuries at a time.
The circulation of the world's ocean helps to regulate the global
climate. One way it does this is through the transport of heat
carried by vast ocean currents, which together form the 'Great
ocean conveyor'.
Key to this conveyor is the sinking of water in the North-East
Atlantic, a process that causes warm tropical waters to flow
northwards in order to replace the sinking water.
Europe is kept warmer by this circulation, so that a strong
reduction in the rate at which deep water forms can cause
widespread cooling of up to 10 degrees Celsius.
Lead author Dr David Thornalley, Cardiff School of Earth and Ocean
Sciences, explains how the scientists studied changes in ocean
circulation: "We retrieved ocean sediment cores from the seafloor
of the Northeast Atlantic which contained the shells of small
organisms.
"We used these shells to examine the past distribution of
radiocarbon in the ocean. Radiocarbon is a radioactive form of
carbon that acts like a natural stopwatch, timing how long it has
been since water was last at the sea surface.
"This allows us to determine how quickly deep water was forming in
the Northeast Atlantic at different times in the past."