An international scientific team which was drilling
beneath the bed of the Arctic Ocean announced that the region had
enjoyed a sub-tropical climate around 55 million years ago.
The Arctic Coring Expedition (Acex) recovered sediment
cores from nearly four hundred metres (1,300 feet) below the sea floor.
Fossilised algae in the cores showed that the sea temperature was once
about 20C, instead of the average now, -1.5C.
The expedition, which relied on three icebreakers
during its work, headed back to Tromso in Norway in September 2004,
its work now done.
Unlocking the Arctic's history
The scientists, from eight nations, recovered the
cores from below the sea floor in waters 1,300 metres deep (4,260
feet). Acex was taking cores from the Lomonosov Ridge between Siberia
and Greenland. The ridge, 1,500 kilometres long (930 miles), rises to
800 metres (2,625 feet) below sea level and is topped by 450 metres
(1,475 feet) of layered sediments.
The scientists who took part in the expedition said,
before they set sail from Tromso in August 2004, that their findings
would help science to work out how long the Arctic sea ice, now in
retreat, had persisted.
The cores they extracted showed that the Arctic Ocean
was once a subtropical, shallow sea. The evidence, Acex said, was in
the form of tiny algal fossils found in the cores, which were once
marine plants and animals. They dated back to a period known as the
Palaeocene-Eocene thermal maximum, a brief period which occurred around
fifty-five million years ago.
The period was characterised by an extremely warm
climate that created a natural greenhouse effect, which caused massive
amounts of carbon to be deposited in both sea and air. Atmospheric
carbon levels at the time are thought to have been about 2-3,000 parts
per million (ppm), compared with almost 380 ppm today.
The algae found in the Lomonosov cores, which lived
only in subtropical conditions, prove how warm the Arctic once was,
according to Acex. The findings also showed that the ocean's temperature
was once similar to the waters off New York in August.
Dr Michael Kaminski, a palaeontologist from University
College London, UK, said that a mass extinction of sea-bottom-living
organisms was being caused by these conditions. This eventually resulted
in many species disappearing. Only a few hardy survivors endured the
There was also evidence that part of the Arctic Ocean
was once a freshwater lake, probably when the Lomonosov Ridge was part
of what is now Siberia. The last 250,000 years of Arctic history were
known already in some detail thanks to cores taken from the Greenland
Coping with nature
Professor Jan Backman of Stockholm University, one of
the two chief scientists of Acex, provided the final note to the report
by saying that sediment records now existed that went back to a period
around fifty-six million years ago, with their source resting on eighty
million year-old bedrock.
The early history of the Arctic Basin would be
re-evaluated based on the scientific results that were collected on this