of about 125,000 years ago. This is the last interglacial
period, when the North Atlantic was warmer, fresher
and sea level was higher than it is today and looked a
lot like what climate models predict it will look by the
end of this century.
“At that time, there were a series of sudden and
large reductions in the influence of these North
Atlantic waters in the deep ocean. These deep water
reductions occurred repeatedly, each lasting for
some centuries before bouncing back. The unstable
circulation operated as if it was near a threshold and
flickered back and forth across it,” says Eirik Vinje
Galaasen, a PhD student and now researcher at UiB’s
Department of Earth Science, who is the lead author
of the paper published in the journal Science.
cooling effect of ocean circulation changes. In any
event, the super cooling or slide into the next ice age
as popularised in a Hollywood blockbuster did not
occur.
Will this happen to the future
Earth?
Many models have actually predicted a slow and
gradual decline in North Atlantic circulation over the
next century. However, different models offer widely
different scenarios for what will happen in the future.
While the climate of the last interglacial is not exactly
what will be the case in a future greenhouse world,
it does share some features, including being fresher
and warmer by a few degrees Celsius in the northern
Atlantic.
“These types of changes hadn’t been noticed before
because they are so short-lived. Geologists hadn’t
focused on century scale ocean changes because
they are difficult to detect,” adds Professor Ulysses
Ninnemann, from UiB’s Department of Earth Science
and Galaasen’s PhD adviser.
Training models, if models can capture the types of
changes we see in the past, may also be doing a good
job at predicting the future. The seafloor evidence
suggests that there were large and fast changes in
circulation the last time the ocean looked the way it
may look by the end of this century.
“Our study demonstrates that deep water formation
can be disrupted by the fresheni