San Diego Researchers Study Waves And How They Impact Global Climate
Monday, November 12, 2018
Photo by Matthew Bowler
Kim Prather, distinguished chair in atmospheric chemistry, Scripps Institution of Oceanography
San Diego researchers are hoping a sophisticated set of experiments will give them a better understanding of how the ocean helps modulate the planet’s climate.
Scripps Institution of Oceanography scientists just landed a second multimillion-dollar, five-year grant from the National Science Foundation so they can get a better understanding of the ocean’s effect on the atmosphere.
The Center for Aerosol Impacts on Climate and the Environment, CAISE, is focused on a long wooden building on the Scripps campus.
UCSD undergrad student Ikran Ibrahim got a taste of the project when she was in high school, leading a tour of her peers.
“It was just a normal tour and I was leading a bunch of high school students and they were supposed to be asking the grad students questions,” Ibrahim said.
But she ended up dominating the question and answer session.
“It was a very big nerd moment because I get all excited about it,” Ibrahim said.
Her curiosity actually led to a lab assistant post once she was accepted at UC San Diego, and when KPBS spoke with her, she was standing beside a 30-meter-long tank that nearly stretched the length of the lab building.
This glass and metal flume was designed to recreate what the ocean does naturally.
“So we have a gigantic paddle,” Ibrahim said as she pointed to the water moving inside the channel.
That paddle goes back and forth at regular intervals, pushing the water inside the long tank.
Every push creates a wave that pulses down the narrow channel, and those waves roll until they hit a ramp about 20 feet down the manufactured gully.
“As it kind of comes up,” Ibrahim said as she pointed at the tank, “there’s a giant metal ramp that kinda replicates the beachfront as it rises up to the actual beach.”
That artificial beach forces the waves to curl and then break.
“And once it gets to the actual height of the metal platform, it creates the waves which kind of come crashing, which releases the aerosols that we want to capture,” Ibrahim said.
Aerosols are particles that get trapped in the air bubbles pushed down by the crashing wave. The turbulent water pushes those bubbles down, but they quickly surface, pop and release trapped particles into the atmosphere.
And those tiny particles are what researchers are measuring.
The wave machine is sealed up during experiments so sensitive instruments can capture how many airborne particles the wave action creates.
“The purpose of the air ducting you see on the north-end side, as well as the air ducting that goes into the tent and head-space, is to provide as clean of air as possible,” said Christopher Lee, the lab manager.
Running the experiment with very clean air allows scientists to measure how many aerosols are pushed into the atmosphere as waves crash along the shore.
“It also happens, not only at the shoreline as we are simulating here, but also in the open ocean when the winds are high enough and they’re able to generate the whitecap,” Lee said.
Pollution can fill the atmosphere with particles, but dust and sea spray are the two most common sources.
Understanding how that system works could reveal the ocean’s role in affecting global climates.
“Basically, what we were able to do is bring the whole real world atmosphere-ocean into the lab, where we can isolate just the parts coming out of the ocean,” said Kim Prather, the Scripps Institution of Oceanography professor who runs The Center for Aerosol Impacts on Climate and the Environment.
Prather wants to understand how many aerosols are pushed airborne in sea spray, because aerosols can help the planet moderate small changes.
Current global climate models are not sophisticated enough to account for the ocean’s influence, even though the particle’s impacts could be significant.
“So if things start to get too warm, it can change what it’s emitting, which will change the clouds and make things cooler. So there are these feedbacks where the natural system is trying to maintain the temperature of our planet,” Prather said.
The ocean cannot compensate for the dramatic changes that are already underway, according to Prather, but understanding the system gives scientists a sharper view of the future.
The next step in the research is already underway.
It requires construction of a more complex wave machine.
That device will allow scientists to gauge how other influences impact the ocean.
“It’ll add wind. We’re going to add sunlight. We’re going to add human pollution. So now we can start looking at the interactions between humans and the natural system, but in a more controlled way,” Prather said.
The resulting research will help scientists understand how human activity impacts the planet’s climate, and Prather said that could also greatly improve the accuracy of existing climate models.
Better models mean scientists will have a better sense of where the planet’s climate is heading.
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