Scientists are looking for new answers about
changes in our weather.
"If we're going to be able to predict what's
going to happen in the future, we need to be
able to look backwards,"
Researchers from the University of Texas are
underground looking for clues about Texas
weather.
In this wild section of Natural Bridge
Caverns, Dr. Jay Banner and his team collect
glass slides they placed here a month ago.
They're looking for calcite deposits. The same
mineral that creates these beautiful
formations.
The formations grow extremely slowly. The
largest are hundreds of thousands of years old.
To study them is like looking back in time.
"What we're doing is using the growth rate of
the calcite as a proxy for rainfall in this
region,"
"We're able to sample and extract those small
amounts of calcite and chemically analyze them
to see what kind of chemical records there are
that we may interpret as changes in water flow
and/or climate change in the past," Dr. Jay
Banner with the UT Geological Sciences said.
From the Natural Bridge Caverns, these
samples will be heading back to the lab for
detailed chemical analysis.
There are stalagmite samples called
speleothems. When sawed in half and polished,
they show growth rings like a tree. This record
goes back thousands of years.
Researchers drill out small samples of the
rock for processing in a clean room. They're
looking for a natural radioactive element in the
rock called strontium.
"It's those relative differences in the
isotope makeup of different rocks, minerals and
waters that tell us something about their
history and their age," Banner said.
Now the samples go to a mass spectrometer to
sort out the different atoms.
"The smaller sample we can measure, the more
precisely we can measure it. The better age
resolution we can get when we're looking at our
records of climate change," Banner said.
Banner's work is already producing
results.
"What we found is that during the last great
Ice Ages, Texas was a much wetter place than it
is today," Banner said.
"A lot of people would contend that some of
the climate change that we're seeing or may see
in the future is all due to natural variability.
But without that natural baseline before humans
came to this area, we might not be able to tell
that," UT Research Associate Charles Jackson
said.
The data is helping other researchers who
model climate change.
"Our challenge is to simulate the climate
reconstructions that are observed within these
speleothems," Jackson said, "The record itself
is a data point which we can check the reality
of our model."
Banner says the reality is that humans are
changing their environment.
"We're really facing some important changes
in our environment, a number of which will be
induced by human effects," Banner said.
The climate record Banner and his colleagues
have uncovered goes back about 70,000 to the end
of the last Ice Age. New techniques are allowing
scientists to see detailed season to season
variation in the cave formations. Banner said he
hopes this could lead to a better understanding
of how El Nino effects
Texas.
