Tag Archives: research

UGA Skidaway Institute scientists publish two papers on Arctic processes

The Arctic is experiencing the effects of climate change faster than anywhere on the planet, yet it is one of the least understood regions, due largely to the difficulty of making observations and collecting samples there. With the support of National Science Foundation funding, two University of Georgia Skidaway Institute of Oceanography scientists are studying the biogeochemical processes in the Arctic and recently had their research published in two peer-reviewed science journals.

Postdoctoral researcher Christopher Marsay and assistant professor Clifton Buck have been participants in the international GEOTRACES program which aims to improve the understanding of biogeochemical cycles in the ocean, focusing on important trace elements. Trace elements are present in the ocean in very low concentrations, however some of those elements are essential for marine life and can influence the functioning of ocean ecosystems while others are potentially toxic to plants and animals.

Cliff Buck works with deck equipment during a GEOTRACES cruise in the Pacific Ocean.

“The Arctic part of the GEOTRACES program is particularly important because the region is already showing significant changes as a result of climate change and is relatively poorly studied with respect to many trace elements,” Marsay said.

Marsay is the lead author on both papers, which are the result of analysis of samples he collected on a 64-day GEOTRACES cruise from Dutch Harbor, Alaska to the North Pole and back from August through October 2015.

“On this cruise, our research goals were to describe the chemistry of atmospheric deposition to the region,” Buck said. “These data will then be shared with the scientific community to help better understand biogeochemical cycling of trace elements in the Arctic Ocean.”

The first paper, published in the journal Chemical Geology, describes the concentrations of 11 trace elements in atmospheric samples that Marsay collected during the cruise by pumping large volumes of air through filters. The sources of this material could include natural material from land surfaces, smoke and soot from burning vegetation, and emissions from industrial activity.

“We compare the results to other ocean regions and speculate as to the sources of the material reaching the Arctic,” Marsay said. “An important part of the work is that we used the concentration data to estimate how much of these chemicals settle from the atmosphere to the surface of the ocean.”

In addition to Marsay and Buck, co-authors included David Kadko from Florida International University, William Landing and Brent Summers from Florida State University, and Peter Morton from the National High Magnetic Field Laboratory.

The second paper was published in the journal Marine Chemistry. In it, Marsay and his co-authors examine trace elements in Arctic melt ponds. Melt ponds are a widespread feature of the sea ice in the Arctic during the summer months. As snow melts it forms ponds on top of the ice which eventually drain into the surface ocean.

Chris Marsay collecting samples at the North Pole.

“Melt ponds are an important intermediate step in atmospheric deposition to the surface ocean that is unique to the polar regions and not very well studied,” Marsay said. “Ongoing climate change in the Arctic will change this pathway, and we want to know how that may affect distribution and biological availability of trace elements in the surface ocean.”

The paper brought together measurements of several trace elements made by different research groups involved in the GEOTRACES project. It showed that the chemistry in melt ponds is also influenced by material in sea ice and the seawater beneath the ice, which modifies the chemistry of material deposited from the atmosphere before it reaches the surface ocean.

Additional co-authors on the paper included Ana Aguilar-Islas from the University of Alaska Fairbanks, Jessica Fitzsimmons, Laramie Jensen and Nathan Lanning from Texas A&M University, Mariko Hatta from University of Hawai’i at Manoa, Seth John and Ruifeng Zhang from the University of Southern California, David Kadko from Florida International University, William Landing from Florida State University, Peter Morton from the National High Magnetic Field Laboratory, Angelica Pasqualini from Columbia University, Sara Rauschenberg and Benjamin Twining from the Bigelow Laboratory for Ocean Sciences, Robert Sherrell from Rutgers University, and Alan Shiller and Laura Whitmore from the University of Southern Mississippi.

The two papers can be accessed through the UGA Skidaway Institute website at: https://www.skio.uga.edu/research/research-publications/.

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Ohnemus joins UGA Skidaway Institute faculty

Chemical oceanographer Daniel Ohnemus has joined the faculty of UGA Skidaway Institute of Oceanography and the UGA Department of Marine Sciences as an assistant professor.

Ohnemus received his bachelor’s degree from Williams College and his Ph.D. in chemical oceanography from the Massachusetts Institute of Technology and Woods Hole Oceanographic Institution Joint Program. He joined UGA Skidaway Institute following a postdoctoral appointment at Bigelow Laboratory for Ocean Sciences in East Boothbay, Maine.

Ohnemus’ research focuses on marine particles—the mixture of living organisms and non-living chemicals that transport and transform material within the oceans.

“All living organisms need small ‘trace’ amounts of elements like iron and copper to live,” Ohnemus said. “Unlike on land where plants can get these elements from soil, algae in the oceans have to get them from much rarer things like dust, other cells or seawater itself. The limited availability of these elements is an important control on many marine ecosystems.”

The son of a lobsterman and an elementary school educator, Ohnemus grew up on Cape Cod and became fascinated with the ocean at a young age. In fourth grade, his class visited Woods Hole to take part in a satellite video call with marine scientists off the Galapagos Islands. Seeing underwater robots explore a coral reef got Ohnemus hooked on marine science.

At Williams College, he pursued a double major in biology and chemistry. After graduation, he returned to Woods Hole, first as a research technician and later as a graduate student. After earning his Ph.D., he completed a postdoctoral appointment at the Bigelow Laboratory for Ocean Sciences, continuing to concentrate on marine particles and trace elements.

Glider partners come to the rescue during Hurricane Irma

Hurricane Irma presented an interesting problem to UGA Skidaway Institute scientist Catherine Edwards and other glider operators in the Southeast. They had several autonomous underwater vehicles or “gliders” deployed off the east coast as the hurricane approached, including Skidaway Institute’s glider, “Modena.” Edwards and the others were confident the gliders themselves would be safe in the water, but the computer servers that control them would not.

Catherine Edwards works on “Modena.”

The gliders are equipped with satellite phones. Periodically, they call their home server, download data and receive instructions for their next operation. It was expected that Skidaway Institute would lose power for at least several days (as did happen). However, Skidaway’s backup server partner at the University of South Florida’s marine science facility in St. Petersburg, Fla. was also directly in the storm’s projected path.

“In the week before she hit, Irma sort of blew up our hurricane emergency plans,” Edwards said.

Several other options, including Teledyne Webb’s back-up servers and Rutgers University were not feasible for technical reasons. Glider operators at Texas A&M University came to the rescue. Catherine was able to instruct “Modena” to switch its calls over the Texas A&M server. No data was lost and “Modena” continued its mission.

According to Edwards, two big lessons emerged from the experience.

“First, most of us rely on nearby or regional partners for emergency and backup support, but disasters are regional by nature, and the same Nor’easter or hurricane can take you down along with your backup,” she said. “Second, there aren’t a lot of glider centers that can absorb several gliders on a day’s notice, and there are some compatibility and operations issues involved, so it is best to identify our potential partners and build out these steps into our emergency plans well in advance.”

UGA Skidaway Institute scientist to spend winter 2020 locked in Arctic ice

Cliff Buck

Spending the Christmas holidays and the better part of January and February on a ship frozen solid in the Arctic ice cap isn’t most people’s idea of a great way to spend the winter. However, University of Georgia Skidaway Institute of Oceanography scientist Cliff Buck is planning to do just that. Buck is part of a major, international research project named Multidisciplinary drifting Observatory for the Study of Arctic Climate or “MOSAiC.” The goal of the project is to sail the German ice breaker Research Vessel Polarstern into the Arctic Ocean until it becomes locked in the ice and leave it there for a year, all the while using it as a headquarters for scientists to study Arctic climate change.

Climate change is occurring at a higher rate in the Arctic than in other regions. That rate of change is not reflected well in climate change models, mostly due to the lack of year-round observations in the Arctic.

“We care about this because the Arctic is turning out to be one of the more sensitive parts of the planet when it comes to climate change,” Buck said. “It’s warming at rates much higher than other parts of the world, and as it warms, many things are happening, such as the reduction in the expanse of sea ice.”

Those changes have implications on the means and rates that materials flow into the region, which, in turn, affect plant and animal life. Buck’s role will be to monitor the atmospheric deposition of trace elements like iron. Trace elements appear in the ocean in minute concentrations — parts per billion or even parts per trillion. However, they play a key role in the growth of phytoplankton — the tiny marine plants that form the very base of the marine food web and produce approximately half the oxygen in our atmosphere. In much of the world’s ocean, it is the presence or scarcity of iron that regulates the growth of phytoplankton.

Buck and his colleagues hope to develop a better understanding of how trace elements make their way from the upper atmosphere to the ice cap. They can arrive either as little particles, floating in the atmosphere and settling like dust, or they can fall as part of a raindrop or snowflake.

“In the Artic, the composition and abundance of aerosols tend to vary seasonally which is the reason it is important to get a series of observations over a long time scale to see how deposition rates of these aerosols change over the course of a year,” Buck said. “We care about that because in areas removed from river input and other continental influences, atmospheric deposition can be the primary source of trace elements like iron for the surface ocean.”

Buck and colleagues from Florida International University and Florida State University will use a technique utilizing a radioactive isotope of beryllium, itself a trace element, to measure the rate of atmospheric deposition. Beryllium-7 is created only in the upper atmosphere by the exposure of nitrogen and oxygen to cosmic rays, and has a half-life of 53 days. By measuring the concentration of beryllium-7 in samples, Buck will be able to estimate the rate beryllium and other trace elements are being deposited on the surface.

R/V Polarstern
Photo credit: Stephanie Arndt/Alfred Wegener Institute

The research team will take turns working on the ship in shifts of two months at a time. As many as 40 to 50 scientists might be on the R/V Polarstern during each shift, collecting samples and making a wide range of observations throughout the year. Buck is tentatively scheduled to be on board from mid-December 2019 through mid-February 2020.

“I really have no one to blame but myself for being assigned a winter shift,” Buck said. “It is very difficult to make these measurements during the winter, so it is very important to us to insure those winter samples are collected properly. When I said that out loud, they said ‘so I guess you want to go in the winter.’”

Although locked in the Arctic ice cap, the R/V Polarstern will not be stationary. The area where the researchers anticipate the ship will be frozen is subject to a surface current called the Transpolar Drift which propels sea ice from the East Siberian Sea to the Fram Strait, off the east coast of Greenland. The R/V Polarstern could drift as much as 1,500 miles during its year locked in the ice cap.

“The Arctic Ocean is a very interesting place with a lot of wind and a lot of physics going on up there,” Buck said. “You may not perceive the movement, but you will be moving.”

Buck’s participation in the MOSAiC project is funded by a four-year, $350,412 grant from the National Science Foundation Arctic System Science Program.

Skidaway Institute graduate students participate on a glider team cruise off Cape Hatteras

Skidaway Institute graduate students Kun Ma and Lixin Zhu recently joined a science cruise on the Research Vessel Savannah off Cape Hatteras, North Carolina. The cruise, which ran from May 31-June 5, was led by Jeffrey Book from the U.S. Naval Research Laboratory. The main objective of this cruise was to test and demonstrate the use of gliders together in teams and to assimilate the data into ocean forecast models. The cruise was 22 days in total, divided into three legs. Ma and Zhu were part of the third leg.

Kun Ma cocking the Niskin bottles on a Conductivity-Temperature-Depth array.

Ma is a new University of Georgia doctoral student at Skidway, working mainly on a National Science Foundation-funded photochemistry project with professors Jay Brandes and Aron Stubbins. This was her first science cruise and she collected some particulate organic matter and dissolved inorganic carbon samples. She also helped Skidaway Institute researcher Bill Savidge by collecting some chlorophyll samples in order to calibrate the chlorophyll sensor on the CTD instrument, an instrument used to collect water samples and measure those samples’ properties, such as Conductivity (a proxy for salinity), Temperature and Depth.

Lixin Zhu in immersion suit during safety trainning

Zhu is a visiting doctoral student in Aron Stubbins’s lab from East China Normal University. He collected filtered water samples on the cruise. Zhu will analyze the color and fluorescence of dissolved organic matter, and dissolved black carbon concentrations. In addition, Zhu performed solid phase extraction and collected high-resolution real-time data on colored organic matter with the underway scientific computer system on the ship. Eventually, he will combine these data with other field data collected in the South Atlantic Bight area to see the overall dynamics of dissolved black carbon.

“I am glad that we overcame seasickness, and it’s really cool to see that the glider team controlled six gliders at the same time aboard,” Zhu said. “Furthermore, their working approach and decision making process, based on real-time data, modeling and satellite results, impressed me a lot.”

Jay Brandes collaborator on research paper

UGA Skidaway Institute professor Jay Brandes is a collaborator on a recent publication focusing on the roles of methane, iron and microbes in regulating the temperature of the primordial ocean. The research team was led by Georgia Tech Ph.D. student Marcus Bray. An article describing the project, can be found here.

 

UGA Skidaway Institute researchers probe complex Atlantic Ocean currents

Dana Savidge

The ocean off the coast of North Carolina has a complex system of ocean currents that make it one of the least understood areas on the U.S. Eastern Seaboard. University of Georgia Skidaway Institute of Oceanography professor Dana Savidge is leading a team of scientists, including UGA Skidaway Institute scientist Catherine Edwards, working to unravel the mysteries of the complex ocean currents near Cape Hatteras.

The four-year project, informally called PEACH: Processes driving Exchange At Cape Hatteras, was launched in early 2016 and is funded by a $5 million grant from the National Science Foundation to better understand the relationship between the waters of the continental shelf and the deep ocean.

“The U.S. continent, like others, has a shallow ocean immediately around it, called the continental shelf. It’s like an apron that extends out from the shoreline and it is fairly shallow, only about 60 meters deep,” Savidge said. “At its outer edge, the bottom drops sharply into the deep ocean, which can be miles deep.”

Exchange at the shelf edge can push cold, nutrient-rich water from the deep ocean onto the shelf, which drives productivity of marine algae and the food web that it supports.

“There’s a reason people love offshore fishing at the edge of the Gulf Stream,” said Edwards. “Areas with regular exchange of shelf and deep waters are often known hot spots for commercial and recreational fishing.”

One reason Cape Hatteras attracted the researchers’ attention is that two opposing deep ocean currents collide there, making the ocean there highly dynamic. The warm Gulf Stream hugs the edge of the continental shelf as it flows north from the tip of Florida. At Cape Hatteras, the Gulf Stream opposes a colder current, the Slope Sea Gyre current, that moves southward along the mid-Atlantic coast. There, the Gulfstream breaks away from the coast toward northern Europe.

There is a convergence of shelf currents at Cape Hatteras as well, as cool shelf waters of the mid-Atlantic continental shelf meet the warm salty shelf waters from the south. Each of these currents, on the shelf and at the shelf edge, has a distinct temperature, salinity, and often a biological signal that reflects the origin of the water it carries. The team will measure these properties and ocean currents to better understand the exchange processes.

During the first year of the study, the researchers prepared and installed a network of sophisticated, high-tech instruments on the shore and in the ocean to monitor and capture the movement of water and changing properties like temperature and salinity. Together with scientists from the University of North Carolina and North Carolina State University, the team has worked with ocean models to better understand the interaction between shelf currents and the deeper currents of the Gulf Stream and the Slope Sea Gyre.

“Circulation on the continental shelf and the deep ocean can be quite separate things, but their effects on one another can be quite complicated,” Savidge said.
In addition to subsurface packages moored on the sea floor, the PEACH team is taking advantage of modern sampling techniques with shore-based radar systems and autonomous underwater vehicles called gliders to collect data remotely.

Savidge working on a radar antenna on the Outer banks.

Savidge’s hardware contribution to the project is a series of low-power, high-frequency radar stations that scan the waters of the continental shelf and measure the speed and direction of surface currents.

“Measuring surface currents remotely with the radars is a real advantage here,” Savidge said. “They cover regions that are too shallow for mobile vehicles like ships to operate, while providing detailed information over areas where circulation can change quite dramatically over short times and distances.”

An array of radar antennae on an Outer Banks beach.

Savidge’s research technician, Gabe Matthias, installed the radar systems on the beach at Salvo and Buxton, and at the airports at Frisco and Ocracoke, North Carolina. Currently, the researchers are working out the bugs in the system and getting the four stations to work together to paint a composite picture of the surface currents. The radars produce a massive amount of data to be processed.

Edwards leads the effort to use gliders that will operate on the shelf for nearly the entire 16-month experiment. Gliders are shaped like torpedoes and equipped with sensors to measure properties like temperature, salinity and dissolved oxygen. They can be programmed to cruise the underwater environment for weeks at a time, surfacing at regular intervals to transmit its collected data via a satellite phone.

Edwards in her lab with a glider.

Edwards’s specialty is improving the way these gliders sample the coastal waters using information from models and real-time data streams, including surface currents from Savidge’s HF radar. Edwards and doctoral students Qiuyang Tao and Mengxue Hou, co-advised by Edwards and Fumin Zhang of Georgia Tech, have developed new systems that optimize the path of the gliders based on near real-time information about current patterns and how they are expected to change, making operations more efficient and allowing better data collection.

“The glider provides data that help explain how temperature, salinity, and density change in space and time underwater, and the HF radar provides high resolution maps of surface currents every 20 minutes,” said Edwards. “The two systems are highly complementary, and their combination provides an unprecedented view of when, where, and why there is exchange between the shelf and deep ocean.”

According to Savidge, the study should produce a greater understanding of the forces at work at Cape Hatteras with implications across a wide range of interests from fisheries management to pollution control. Microscopic marine plants, known as phytoplankton, are a vital part of the marine ecosystem. Phytoplankton are the very base of the marine food web and they produce approximately half the oxygen in the atmosphere. In addition to tracking deep water inputs that support productivity on the shelf, Savidge said, it would is also be important to understand any processes that transport carbon-rich shelf water back to the deep ocean. When phytoplankton and the rest of the food web convert nutrients into their own biomass, water returned to the deep ocean can carry large quantities of organic carbon with it.

The knowledge gathered at Cape Hatteras will be applicable to other oceans around the world.

“Cape Hatteras is the ideal place to look at these processes that you are going to find elsewhere,” Savidge said. “You have a lot of energetic forcing and everything is concentrated in a very small space, with large variations over short distances. The idea is to understand the processes so you can model them effectively. If you can do that, you can anticipate how circulation on the shelf and exchanges with the deep ocean will respond to changes in the Gulf Stream or the wind over time.”

The project will run through March 2020. The other members of the research team are Harvey Seim and John Bane of the University of North Carolina; Ruoying He of North Carolina State University; and Robert Todd, Magdalena Andres and Glen Gawarkiewicz from Woods Hole Oceanographic Institute.

Savidge expressed special appreciation to the National Park Service and the North Carolina Department of Transportation for providing sites for the radar installations, and the University of North Carolina’s Coastal Studies Institute for help in installing them.