What the Flux

Climate change and world record atmospheric carbon dioxide concentrations are not new topics in mainstream media. An ample source of information on the planet’s current and future conditions is at our fingertips, but a resounding question from curious minds and climate-change deniers alike is: How do we know the climate is changing? We might have a long list of weather patterns at locations around the world, but how do we get them? And how do we make predictions? The answer would be flux towers.

Standing on a flux tower 138 feet in the air.

This past weekend I toured the National Ecological Observatory Network (NEON) site in Northern Wisconsin, bordering Michigan’s upper peninsula. We lodged at Kemp Natural Resources Station, a summer home for researchers and visiting scientists. NEON collects a variety of ecological data at sites around the globe to create a better understanding of the atmosphere, and the environment in general. At the Wisconsin field site, information such as height and weight was recorded about small mammals. Ticks and mosquitoes were also harvested to find out things like what diseases they carried. Below the ground, soil temperatures were monitored. A sensor on the ground measured solar radiation. Above ground, the flux tower measured atmospheric conditions approximately every ten feet with extremely sensitive instruments that must be frequently maintained and recalibrated.

The NEON tower.

I would be lying if I told you that I know what every single instrument on the tower does. Climate science is a small sliver in the world of science, meaning even scientists have questions about flux towers! Climbing one of these towers also takes special training and certifications, which means that the person climbing and the person interpreting the data have completely separate jobs. Field technicians also play a unique role, checking the machines to make sure they work smoothly and performing quality assurance.

tomahawk lake
Tomahawk Lake was buzzing with Mayflies.

What is a flux tower?

Flux towers measure changes in carbon dioxide, evapotranspiration, latent heat, methane, and more. NEON’s website explains different types of flux measurements very well. Generally, flux towers can provide information at “a distance of approximately 100 times the instrument height above the zero plane displacement (roughly 2/3 of the canopy height)” in the upwind direction as stated on the LI-COR website. This is why there are networks of flux towers all over the world.

The “tall tower” measures flux data and also sends out signals for PBS.

Wind at surface level moves in big vertical circles called eddies. Eddies can bring carbon dioxide down from higher up in the atmosphere, where it can get absorbed by trees and plants, or it can bring gases up where they will disperse and become part of the larger atmosphere. An eddy will pass through the sensor, providing a flux value that tells us how much carbon went down, how much went up, and how much was left behind or deposited. That’s how the name eddy covariance flux tower came about. There are innumerable studies conducted using flux data on topics like where to grow certain crops, how deforestation or reforestation affect the atmosphere, and the effects of climate change.

wind eddies
Wind Eddies from Wikipedia.

Has anyone else climbed before? I used to do ropes courses when I was younger but I’ve since gotten used to the ground and get a little nervous when I’m that high up on a somewhat shaky structure. Do you live in tick country? Or are there other animals and insects that reign over the places you like to camp? Comment to let me know!

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