Ancient plant remains recovered in recent Arctic
Ocean sampling cores shows that during a period of carbon
dioxide-induced global warming, humidity, precipitation and salinity of
the ocean water altered drastically, along with elevated global and
regional temperatures, according to a report in the August 10 issue of Nature.
he Arctic Ocean drilling expedition in 2004
allowed scientists to directly measure samples of biological and
geological material from the beginning of the Paleocene/Eocene thermal
maximum (PETM), a period of rapid, extreme global warming
about 55 million years ago. It has given researchers a direct resource
of measurable information on global warming — from a time when the
overall global temperature was higher and more uniform from the
subtropics to the arctic.
The researchers measured carbon and hydrogen isotopes in fossil
plants remains and reconstructed the pattern of precipitation and
characteristics of the ancient arctic water. “Our results told us a lot
about the way that the large-scale water cycle is affected during
global warming,” said Mark Pagani, professor of geology and geophysics at Yale and principal author of the study.
The large-scale water cycle refers to the way water vapor is
transported from the tropics and subtropics to the poles. “We are all
familiar with the rain and storms that occur when warm air masses meet
cool northern fronts. During the PETM, temperature differences from the
tropics to the poles were lower, reducing rainfall between the
subtropics and the North Pole and increasing the amount of water
transported to the Arctic,” said Pagani. “It looks like a substantial
increase in precipitation led to increased river runoff, lower ocean
salinity, and drastically lower oxygen levels in the Arctic Ocean.”
“It is important to realize that the impact of global warming is
not just about searing hot summers — it also concerns the water cycle.
We need to anticipate big changes in patterns of precipitation as
temperatures rise – where and when it will rain and whether or not
water resources are available,” said Pagani. “This work is potentially
a red flag for things to come.”
Co-author Matthew Huber, an assistant professor
of earth and atmospheric sciences at Purdue University's College of
Science compared data from the research expedition with complex climate-model
simulations to study and predict the effects of greenhouse gases. Their
measurements confirm that the carbon dioxide level increase in the PETM
was at least twice as large as those previously proposed.
“We now have a pretty good correlation between records of past
warmth and higher carbon dioxide concentrations,” Huber said. “What it
tells you is that it's not too difficult to push the climate system to
a warm state. If you work out the numbers, it's almost identical to
what we are expected to do over the next few hundred years.”
Co-authors of the work were Nikolai Pedentchouk at Yale; Appy
Sluijs and Henk Brinkhuis at Utrecht University; Gerald Dickens now at
Rice University; Stefan Schouten and Jaap Sinninghe Damste at the Royal
Netherlands Institute for Sea Research, and “the Expedition 302
Scientists.”
The expedition was an operation of the Integrated Ocean Drilling
Program (IODP), an international marine research program primarily
funded by the National Science Foundation, and Japan’s Ministry of
Education, Culture, Sports, Science and Technology.
Source: Yale University |