Anyone dreading the onset of winter might shiver at the thought
of the frigid Arctic. But a team of 19 scientists, including a
University geology professor and a former University graduate,
braved the region’s chill this fall to confirm that balmy,
subtropical weather once dominated the North Pole.
- Yung-Hsuan Chiu
- Swedish icebreaker Oden smashes through ice last month for the Arctic Coring Expedition. The ship, one of three expedition vessels, was fitted with scientific equipment and living space for scientists from eight countries. (Courtesy of Professor Martin
Last month, the team brought home the first deep sediment
samples ever drilled below Arctic ice. Previous attempts to obtain
sediments from the Arctic Ocean had been cut short by encroaching
ice floes, which can push a drilling ship out of position. During
this year’s expedition, two large icebreaking vessels,
accompanied by a smaller icebreaker fitted as a drilling ship,
shattered oncoming rafts of ice up to 3 meters thick. The ships
— provided by the European Consortium for Ocean Research
Drilling — held a fixed position in shifting ice for as long
as eight days.
“The most profound success of this expedition is that no
one’s ever been able to drill in moving ice before,”
said Prof. Kate Moran of Rhode Island University, the
expedition’s co-chief scientist. In three weeks, the team
recovered 339 meters of oceanic mud that span 80 million years of
Arctic history.
The sediment cores, which arrive onboard in long plastic
cylinders, record geological clues that provide a crucial record of
changing climate at the Pole. Most importantly, Moran said, the
sediments include an interval considered the warmest in
Earth’s history since the extinction of the dinosaurs —
the Paleocene-Eocene Thermal Maximum, which occurred 55 million
years ago. Scientists had predicted a warm climate for the Arctic
during the PETM, but the expedition’s researchers are the
first to show unequivocally that no ice covered the Pole at that
time.
By studying the cores, scientists hope to learn how warm polar
conditions developed. University geological sciences Prof. Ted
Moore, who traveled with the expedition as a paleontologist, said
studying the PETM interval will augment our understanding of global
warming.
“It’s the only time that the Earth’s climate
was as warm as it’s soon predicted to be, so it’s of
immediate interest,” Moore said. Canadian and American
scientists have documented melting ice at the North Pole this year
and attributed it to global warming, CBS News reported in
September.
Moore searches for climate clues in tiny organisms that live in
ocean waters. When the microscopic creatures die, their remains
fall to the sea floor and are preserved in sediments.
In the Arctic cores, Moore and other paleontologists found an
array of organisms that need not only warm conditions but also
relatively fresh water — water much less saline than the
modern Arctic Ocean. Because fresh water is less dense than salty
ocean waters, Moore explained, Arctic fresh waters would have
resisted mixing with the rest of the ocean. His findings suggest
that warm Arctic waters can’t be explained by mixing in
warmer waters from further south. This conclusion contradicts
researchers who theorize that a pulse of warm water from the
Equator produced warming at the poles, he said.
Instead, atmospheric changes are more likely to have caused
Arctic warming, he explained — such as an increase of carbon
dioxide in the atmosphere, currently thought to be the culprit of
modern global warming. “It’s strengthened the case that
the atmosphere is the true cause of warm high latitudes.”
University of Michigan alum and Rice University Prof. Jerry
Dickens, who studied the PETM at Michigan, also accompanied the
expedition.
“Throughout the years, there’s probably about 10 to
15 people at Michigan who have done a lot of work on (the
PETM),” he said. “The first understanding of this
event, what it signified and what its implications are — that
was all Michigan first.”
Dickens said researchers have only uncovered the tip of the
iceberg, so to speak, and that more discoveries will follow as
study of the cores continues.
“For me, I think what’s nice is what’s going
to come in the future, when we can put this in perspective,”
he said. “I’ve got lots of things to work on that I
didn’t expect before.”