Nav: Home

EPFL researchers make a key discovery on how alpine streams work

March 18, 2019

An EPFL study has prompted scientists to rethink a standard approach used to calculate the velocity of gas exchange between mountain streams and the atmosphere. Research conducted in streams in Vaud and Valais indicate that equations used to predict gas exchange based on data from lowland streams undershoots the actual gas exchange velocity in mountain streams on average by a factor of 100.

This discovery - appearing in Nature Geoscience - will enable scientists to develop more accurate models of the role that mountain streams play in global biogeochemical fluxes. Considering that more than 30% of the Earth's surface is covered by mountains, the ramifications of this discovery are considerable.

The study was conducted at EPFL's Stream Biofilm and Ecosystem Research Laboratory (SBER), within the School of Architecture, Civil and Environmental Engineering (ENAC).

More turbulence

In aquatic ecosystems, such as the world's oceans, streams and lakes, numerous aquatic organisms, ranging from bacteria to fish, respire oxygen and exhale CO2. These gases must therefore be continually "exchanged" from the atmosphere to the water and vice-versa. Because mountain streams often flow over steep drops and rugged terrain, this creates a lot of turbulence and causes air bubbles to be trapped in the water, appearing white (aka 'white water').

These bubbles accelerate the gas exchange. Strikingly, the same mechanism is at work when white-capped waves appear on the surface of rough seas. Until now, scientists have ignored the contribution from air bubbles and have used the same approach to calculate gas exchange velocities in mountain streams than in calm lowland streams.

More precise calculations

It is intuitive that the rugged terrain would influence gas exchange in mountain streams, but no evidence had been collected to test this hypothesis until 2016. That's when EPFL researchers installed more than 130 environmental sensors in mountain streams in Vaud and Valais to study this physical phenomena and related biogeochemical fluxes. To measure gas exchange velocity as accurately as possible, one of the SBER scientists and first author of the study - Amber Ulseth - along with others, added small amounts of argon as a tracer gas to the streams. Argon is a naturally occurring gas that is harmless to aquatic ecosystems.

Using cutting-edge analytical methods in the laboratory, Amber Ulseth and colleagues were able to quantify loss of argon from the streamwater. Next, they modeled the gas exchange velocity from the downstream loss of the tracer gas in the streamwater. Their results reveal that the gas exchange velocity in mountain streams is on average 100 times higher than predicted from equations developed from similar tracer gas experiments in low-land streams.

Major implications

"Our findings have major implications. They suggest that we have been underestimating the effects of all the small but abundant mountain streams in our biogeochemical models. This opens up a new research avenue," says Tom Battin, Director of SBER and coauthor of the study. His lab is already looking into extensions of this research, such as developing a new model to predict CO2 emissions from mountain streams worldwide.
-end-


Ecole Polytechnique Fédérale de Lausanne

Related Atmosphere Articles:

Primitive atmosphere discovered around 'Warm Neptune'
A pioneering new study uncovering the 'primitive atmosphere' surrounding a distant world could provide a pivotal breakthrough in the search to how planets form and develop in far-flung galaxies.
NASA's MAVEN reveals Mars has metal in its atmosphere
Mars has electrically charged metal atoms (ions) high in its atmosphere, according to new results from NASA's MAVEN spacecraft.
Northern oceans pumped CO2 into the atmosphere
The Norwegian Sea acted as CO2 source in the past.
Study opens new questions on how the atmosphere and oceans formed
A new study led by The Australian National University has found seawater cycles throughout the Earth's interior down to 2,900km, much deeper than previously thought, reopening questions about how the atmosphere and oceans formed.
How a moon slows the decay of Pluto's atmosphere
A new study from the Georgia Institute of Technology provides additional insight into relationship between Pluto and its moon, Charon, and how it affects the continuous stripping of Pluto's atmosphere by solar wind.
Fossil fuel formation: Key to atmosphere's oxygen?
For the development of animals, nothing -- with the exception of DNA -- may be more important than oxygen in the atmosphere.
Researchers dial in to 'thermostat' in Earth's upper atmosphere
A team led by the University of Colorado Boulder has found the mechanism behind the sudden onset of a 'natural thermostat' in Earth's upper atmosphere that dramatically cools the air after it has been heated by violent solar activity.
New biochar model scrubs CO2 from the atmosphere
New Cornell University research suggests an economically viable model to scrub carbon dioxide from the atmosphere to thwart global warming.
Venus-like exoplanet might have oxygen atmosphere, but not life
The distant planet GJ 1132b intrigued astronomers when it was discovered last year.
Middle atmosphere in sync with the ocean
In the late 20th century scientists observed a cooling at the transition between the troposphere and stratosphere at an altitude of about 15 kilometers.

Related Atmosphere Reading:

Best Science Podcasts 2019

We have hand picked the best science podcasts for 2019. Sit back and enjoy new science podcasts updated daily from your favorite science news services and scientists.
Now Playing: TED Radio Hour

Anthropomorphic
Do animals grieve? Do they have language or consciousness? For a long time, scientists resisted the urge to look for human qualities in animals. This hour, TED speakers explore how that is changing. Guests include biological anthropologist Barbara King, dolphin researcher Denise Herzing, primatologist Frans de Waal, and ecologist Carl Safina.
Now Playing: Science for the People

#SB2 2019 Science Birthday Minisode: Mary Golda Ross
Our second annual Science Birthday is here, and this year we celebrate the wonderful Mary Golda Ross, born 9 August 1908. She died in 2008 at age 99, but left a lasting mark on the science of rocketry and space exploration as an early woman in engineering, and one of the first Native Americans in engineering. Join Rachelle and Bethany for this very special birthday minisode celebrating Mary and her achievements. Thanks to our Patreons who make this show possible! Read more about Mary G. Ross: Interview with Mary Ross on Lash Publications International, by Laurel Sheppard Meet Mary Golda...