November
4, 2003
EXPLANATION
OFFERED FOR ANTARCTICA'S BLOOD FALLS
Researchers have discovered that a reddish deposit seeping out from the face
of a
glacier in Antarctica's remote Taylor Valley is
probably the
last remnant of an ancient salt-water lake. The lake probably formed as
much as
5 million years ago when the sea levels were higher and the ocean
reached far
inland.
Ohio State
University
scientists reported their
conclusions today at the annual meeting of the Geological Society of
America in
Seattle.
Berry
Lyons, a professor of geological sciences and director of OSU's Byrd Polar Research Center,
offered the best explanation to date for a strange, nearly-century-old
discoloration halfway up the face of the Taylor Glacier in Antarctica's
Dry
Valleys.
The Dry Valleys
are well known to polar scientists who have studied these remarkably
snow-free
troughs leading from the Ross Sea onto
the East
Antarctic Ice Sheet.
Geologist
Griffith Taylor first found the red discoloration in 1911 as he
explored the
valley that would one day bear his name. Nearly a half-century later
during the
mid-1960s, University of Wisconsin
scientist
Robert Black discovered that the reddish stain on the polar ice was
really iron
salts, or ferric hydroxide, that was being squeezed out of the ice
sheet.
The
phenomenon came to be called Blood Falls and
its origin has
puzzled researchers ever since.
Lyons,
who heads one of the National Science Foundation's Long-Term Ecological
Research (LTER) sites in Taylor
Valley, led
a team of researchers from Ohio
State,
the University
of Colorado
and Montana
State University
that analyzed
samples of the reddish discharge over a 10-year period. That analysis
suggests
that the reddish salts were deposits formed at the site of an ancient
lakebed
when the ocean receded from the valley.
Perhaps
at a time when this valley resembled more a Scandinavian fjord, some
sea water
was trapped in the lower portion of the valley, Lyons
explained. When the Taylor Glacier
eventually advanced over the top of that lake, the seawater was
essentially
freeze-dried and trapped.
We
think we are looking at the remains of some very old seawater trapped
during
the Miocene period, some 5 million years ago, he said.
Lyons
and his colleagues believe that as the glacier moved forward down
through the
valley, it captured some of the deposit and forced it up into the body
of ice.
Eventually, the deposit reached the margin, or edge, of the glacier and
is
being slowly pushed out or the ice.
As
the reddish, icy sludge melts at the margin of the glacier, it runs off
into Lake Bonney,
one of only four ice-covered lakes in the Dry Valleys.
Three of the lakes Bonney, Fryxell and Hoare are in Taylor
Valley
while Lake
Vanda is in
the nearby Wright Valley.
But each of these lakes is very different chemically and the
explanation for
those differences has puzzled researchers for years.
The
water at the bottom of Lake
Bonney, the
most landward of the Taylor
Valley
three, is saturated with salts, Lyons
said. But Lake
Hoare
a short distance down the valley
from Bonney is filled with fresh water. Lake Fryxell
is also a saltwater lake.
Scientists
have wondered for years how three lakes so close together, with the
same
climate regime and the same geology, can be so different chemically, Lyons
said. We think it
has to do with the ages of these lakes.
"The
research team believes that originally water drained down the valley to
Lake
Fryxell.
But at some point in the past as temperatures warmed, the Canada
Glacier flowed
further into Taylor Valley and
blocked this
flow. Lake
Hoare
was then formed on the lower side
of the Canada Glacier and filled with fresh water from glacial runoff.
Lake Hoare basically forms
only during the
warm times when the Canada Glacier advances down into the valley.
Aside
from the oddity of Blood Falls
itself, a better
understanding of how these lakes formed and exactly when should enhance
our
knowledge of climate history in the region.
We
know that life exists in all of these lakes and we are trying to
understand how
it functions and how it relates to the climate, he said. Were
interested in the
impact of climate change and the effect it will have on these
ecosystems. So we
need to understand how it was affected in the past.
Maybe Blood Falls
is just another lobe of Lake Bonney
that has been
frozen over, or maybe it was a different lake, like Bonney, that
existed when
the glacier had receded further up the valley.
Lyons said the
answers to such questions would only come after drilling through the
glacier to
sample the bedrock below. He said that it is possible that these salt
deposits
might underlie this entire arm of the Taylor Glacier. If that were
true, it
would explain one of the glaciers strange behaviors.
Most
Antarctic glaciers are frozen to the rock below but Taylor
apparently isn't, Lyons
said. That could be because there are salt deposits underneath it which
would
lower the freezing point of the ice and better lubricate the flow of
the
glacier. That probably allows this glacier to move in very different
ways
compared to others.
Along
with Lyons, Kathleen Welch, research scientist at the Byrd
Center,
Diane McKnight from the University
of Colorado
and John Priscu from Montana State University
all contributed to this study. This work was supported in part by the
Division
of Polar Programs within the National Science Foundation and by the Byrd
Polar Research Center.
##
Contact:
Berry Lyons
Ohio State University
614-688-3241
Lyons.142@osu.edu
This
text
derived from:
http://researchnews.osu.edu/archive/bloodfalls.htm
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