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Public release date: 21-Mar-2002[ Print | E-mail | Share ] [
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Contact: Michael [email protected]
410-516-7160Johns Hopkins University
Scientist probes fossil oddity: Giant redwoods near North
Pole
Once upon a time, Axel Heilberg Island w as a very strange
place.
Located within the Arctic Circle north of mainland Canada, a
full 8/9ths of the way from the equator to the North Pole, the
uninhabitedCanad ian island is far enough north to make Iceland
look like a g reat spot for a w inter getaway, and today theres not
much to it beyondmiles of rocks, ice, a few mosse s, and many
fossils.
The fossils tell of a different era, though, an odd time about
45 million years ago when Axel Heilberg, still as close to the
North Pole as it isnow, wa s covered in a forest of redw ood-like
trees known a s metasequoias.
Hope Jahren, an a ssistant professor o f earth and planetary
sciences in the Krieger School of Arts and Sciences a t The Johns
HopkinsUniversity, recently published results that partially
demystified Axel Heilbergs vanished forests. Jahren and colleague
Leo Sternberg of the
University of Miami uncovered evidence that the Axel Heilbergs
forests probably received equatorial water and warmth from a
prehistoricwe ather pa ttern unlike anything in existence
today.
Other challenging mysteries remain, including how a forest could
develop given the sunlight it would receive on Axel Heilberg.
Because of itsclosene ss to the North Pole both now and in the time
of the redwoo ds, Axel Heilberg spe nds four months of each year in
continuoussunlight and four months of ea ch year in continuous da
rkness.
We don t have p lants tha t can survive unde r tho se conditions
today, let alone fore sts, Jahre n says . Fo r a t ree to e ndure
four months ofdaylight is like you or I going w ithout sleep for
four months .
Through a grant from the Andrew Mellon Foundation, Jahrens
research group has made three summer visits to Axel Heilberg,
excavating
hundreds of fossil metasequoias. The fossils are immaculately
well-preserved.
Some o f this stuff looks a bout like driftwood on the bea ch,
but its 45 million years old , Jahren sa ys. These fossils are
chemicallypreserved a t a level you usua lly would e xpect to see
in something thats only 1,000 years old.
Thats ideal for Jahren, who s tudies the pres ence of isotopes
of elements like carbon, nitrogen and oxygen in living and
fossilized plants.Isotopes are forms of an element that differ only
by the addition o f one or more suba tomic particles known as
neutrons. Different isotopesof the sa me element have different
mass, w hich affects the way plants use them.
Jarhen, the winner of last year's Geological Society of America
Donath Medal for most promising young scientist, studies the
isotopes tolearn more about plants' relationship to weather and
climate change. In her group's first major Axel Heilberg results,
published in the
January issue of the Geological Societys GSA Today, they
measured the presence of isotopes of oxygen and hydrogen in the
fossilizedmetasequoias.
The w ood o f any tree g row ing a nyw here reco rds fairly fa
ithfu lly the oxygen and hydro ge n che mistry of the w ater the
plant has acce ss tothrough precipitation, Jahren explains. And
theres a great deal of difference between the chemistry of water
that arrives at a certainlocation after being transported [in
evaporate d form] great distances o ver land versus the chemistry
of water tha t arrives at a place afterbeing transported over wa
ter or not be ing transported very far.
Jahren and co-author Sternberg chemically compared the fossil
isotope levels with those found in water in contemporary
precipitation
patterns over great distances of forested lands in the Amazon.
They were a ble to show that wa ter traveling from near the e
quator almostdue no rth across the continents to the vicinity of
Axel Heilberg w ould have oxygen a nd hydrogen isotope signatures
that matched thosefound in the fossils.
While it might seem mind-boggling to have the equator watering
the north pole, Jahren notes that other major climatological
differences atthe time included the lack of a north polar ice
cap.
It s ve ry ha rd to expla in the isotope chemis try of the pre
cipita tion us ing a ny o the r model o f water t ranspo rt, Jahren
says . So we thinkwe ve basically solved a piece of the puzzle.
As for the other major piece of the puzzle -- survival of the
trees through extended periods of light and dark -- Jahrens group
is working tosee if the isotope chemistry of the fossils can he lp
them learn how the metasequoias metabolism compared to those of
contemporaryplants.
Did the y funct ion s imilarly to how plants function now?
Jahren as ks. Or d id they have s trategie s tha t pla nts either
no longe r have o r nolonger employ? Were they fundamentally
different? These fossils a re really forcing us to expand our ideas
of how ecosystems can w ork.
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