Carbon Castaway-UM Researcher Creates Unique Sensors to Study the World’s Water

Last winter Mike DeGrandpre found himself in the middle of the Pacific Ocean, 1,000 miles from land. He’d come to that remote, forbidding corner of the world — home to little more than sharks and flying fish — to study the Earth’s marine-carbon cycle.

BY CARY SHIMEK- UM Research View

DeGrandpre, a University of Montana oceanographer and analytical chemist, is interested in quantifying how much carbon dioxide oceans and other waterways take in from the atmosphere. The 38-year-old Helena native also wants to understand the oceans’ mechanisms for uptake of CO2.

He says his research could lead to a more thorough understanding of the world’s carbon cycle, as well as climate change caused by growing accumulation of greenhouse gases such as CO2.

So from Jan. 28 to March 2, DeGrandpre journeyed to the equatorial Pacific to study the rates of CO2 gas exchange in that region. Normally the oceans take in much more carbon dioxide than they release, but that region is interesting because it’s actually a CO2 source.

“There is a lot of upwelling there, and the deeper water is CO2 rich,” he says. “So when that water comes to the surface it degasses. It’s all caused by the circulation pattern of the globe, which moves ocean water in these huge gyres.”

DeGrandpre voyaged aboard a 280-foot National Oceanic and Atmospheric Administration research vessel manned by 25 crew members and more than 30 scientists.

“The ship only goes 14 knots, so it still took us two weeks to get where we were going,” he says. “We were at least 1,000 miles from any place. It really makes you realize how important it is to not fall overboard. The only thing out there are sharks and you, and they would certainly find you in a big hurry.”

During his voyage DeGrandpre’s primary research tool was a sensor he invented — a Submersible Autonomous Moored Instrument for CO2, or SAMI-CO2. These sensors are plastic cylinders about 6 inches wide and a foot long. They usually are placed a few feet underwater on permanent moorings or on floating drifters, which sample the water wherever the wind and currents carry them.

He says the sensors work much like pH paper, which measures the degree of acidity or alkalinity of a solution by changing color. CO2 is an acidic gas that forms carbonic acid when it dissolves in seawater. SAMIs use pH indicators that change color in the presence of carbonic acid, and this color change is recorded by an optical light measurement. A data logger then stores the information in a memory chip. In other words, the instruments record how much carbon dioxide is dissolved in the water.

DeGrandpre developed the SAMI from 1990 to 1993 while doing postdoctoral work at the Woods Hole Oceanographic Institution on Cape Cod. He further improved the sensor after joining UM six years ago, and a patent is pending on those advancements. In addition, he and Missoula businessman David Irwin have set up a spinoff company, Sunburst Sensors, to manufacture SAMIs for researchers. The sensors cost $15,000 each, and sale of SAMIs and related services already has totaled $200,000.

“We have this unique tool that nobody else has,” DeGrandpre says. “We can now study these marine systems in more detail than has been possible in the past. And the great thing is that SAMIs are autonomous — you can leave them for months, and they do the work for you.”

On last winter’s high-profile research cruise, DeGrandpre released SAMIs into the Pacific on floating drifters. Each drifter had a global positioning system transmitter that emitted its location every three hours. The drifters would spend days sampling the ocean before the research vessel returned for them, and finding the drifters was sometimes difficult in the watery vastness.

DeGrandpre says many of his sensors were fouled by gooseneck barnacles, which latched onto the drifters.

“These barnacles grew faster than knapweed in Montana,” he says. “In coastal regions they are not so much a problem because there are organisms that eat them. But out where we were, these little shellfish were about the only things out there. And since they are biological organisms they respire CO2, which throws off our readings. It was a problem we didn’t expect.”

Despite the setbacks, DeGrandpre learned that daily heating from the equatorial sun drives carbon dioxide out of the water because of a decrease in solubility of CO2. “It’s sort of like the warm soda pop experiment,” he says. “When you heat it up it goes flat a lot faster. We went out there to quantify that effect.”

DeGrandpre says his SAMIs — which he affectionately calls his “droids” — have been placed off the coasts of countries around the world, including Canada, England, Norway, New Zealand, Greenland and South Africa. There is a SAMI in Lake Superior, and, closer to home, SAMIs have characterized the CO2 cycles of Montana’s Placid Lake, Clark Fork River and Flathead Lake.

He says being an oceanographer in landlocked Montana has not been a problem in the Information Age. As an example, he calls up a computer screen that gives real-time readings from a SAMI placed 6.2 miles off the coast of New Jersey. From his UM office, DeGrandpre can remotely control a winch that moves the Jersey SAMI up and down to different depths to gain a vertical profile of the ocean. He also mails SAMIs around the world to have other researchers install them.

“They weigh 100 pounds, so we have spent tens of thousands of dollars on Federal Express,” he says.
DeGrandpre says there are really two aspects to his work: developing new sensors and interpreting the data collected from them. His research team hasn’t made major breakthroughs in CO2 research, but its members have published some novel papers on CO2 cycling in aquatic environments. His breakthroughs have been more on the sensor-development side. He also provides valuable data that help other researchers test their CO2-cycle models.

DeGrandpre constantly strives to improve and simplify his sensors. He imagines inexpensive, disposable drifters that would relay their information via satellite transmission. Also, his lab already is at work developing autonomous pH and alkalinity sensors.

He says graduate and undergraduate students play vital roles in his research, working in the lab, troubleshooting instrument problems and raising issues from a fresh perspective.

“Without their help many interesting questions would never be explored, and because of their efforts new ideas and new directions have been generated,” he says. “It’s also rewarding to help students achieve a high level of expertise and then watch them go on to become confident professionals.”

DeGrandpre says oceans are vitally important for storing away excess CO2 pumped into the atmosphere, and research hints that oceans are storing away more carbon then ever before. Seawater sequesters two gigatons of carbon annually, but even with this increased workload there are two gigatons accumulating in the atmosphere every year.

“We need to understand what mechanisms within the ocean drive this uptake of CO2,” DeGrandpre says. “And if the climate does change, how will that affect these mechanisms? Will this lead to a positive or negative feedback for the uptake of CO2?”

Many questions remain, and maybe a bunch of SAMIs from UM will help provide the answers.

http://www.umt.edu/discovery/default.htm