Kevin Arrigo: Studying Climate Change
Studying climate change is challenging. Climate is influenced by many factors, including things such as the shape of Earth's orbit around the sun and the concentration of trace gases in the atmosphere. In turn, climate influences many things on Earth's surface, including everything from large-scale circulation in the oceans to the distribution and functioning of ecosystems on the planet. How does an individual scientist go about doing research on such a complex system? Kevin Arrigo (Figure 1), a biological oceanographer and professor at Stanford University, has two key strategies: He uses multiple research methods in combination, and he collaborates with many other scientists. In his work, Arrigo uses laboratory experiments on phytoplankton, analysis of satellite imagery, computer modeling, and field observations. He shares the results obtained through these multiple research methods with scientists in other disciplines to put together big ideas about how climate affects a given ecosystem.
In 2010, his work brought him to the Arctic Ocean, where he served as lead scientist on a large, collaborative, NASA-funded research cruise. What does leading such a significant scientific undertaking involve, and how did Arrigo end up there? Arrigo's path to the Arctic Ocean and the day-to-day challenges they encountered on the cruise illustrate many important aspects of the process of science, including the collaborative nature of science, the influence of society, chance, and scientific institutions on research directions, and the variety of roles that scientists play in their work.
The path to the Arctic
Arrigo always knew he wanted to be a scientist, but he attributes his early interest in ecosystems and ocean science to an unlikely origin: a local travel show broadcast in his hometown of suburban Detroit, George Pierrot Presents. Sometimes the show featured footage of coral reefs as the backdrop to a Caribbean vacation, and it was the jawfish (Figure 2) that hooked him. Jawfish are known for being entertaining aquarium fish because of the burrows they build using gravel and because of their tendency to spit gravel at fish that come too close. He says, "I was fascinated by the jawfish. They were just the coolest things and that is when I got the bug."
While jawfish might have been his start, it wasn't just one animal that kept him coming back for more. He wanted to understand how all the species, from fish down to microbes, interacted with each other and with their environment. Growing up, he describes buying fish tanks and setting them up as realistically as possible to watch the species interact. "People are always fascinated by the big stuff," Arrigo says. "They want to see the turtle and the sharks, but I like to go and just sit at a coral head and watch all the interactions between the invertebrates."
"All the interactions" is one way to describe a whole ecosystem. An ecosystem includes all the living organisms in a particular area as well as the abiotic factors – that is, the non-living factors – that the organisms rely on. These abiotic factors include things like the amount of sunlight and rainfall an area receives, or the temperature and salinity of the ocean around the reef.
Looking at the whole ecosystem, as opposed to just one species within it, helps scientists understand how plants and animals interact with each other and with the environment. One of Arrigo's motivations in studying ecosystems is that, if we understand how the whole ecosystem functions, we can become better equipped to protect or preserve it effectively. Arrigo's early research focused on how the Southern Ocean ecosystem functions; specifically, he used satellite imagery to describe and estimate the distribution of phytoplankton. Phytoplankton are also called primary producers in the ocean, which means that they are able to photosynthesize, taking energy from the sun in combination with CO2 and converting it to oxygen. As a result, Arrigo can use the estimate of phytoplankton distribution to determine the amount of CO2 taken up through primary production in the region (Arrigo and McClain, 1994). Arrigo is still interested in ecosystems and how they function, and he shares that interest with Stanford undergraduates by teaching a course on coral reef ecosystems in Australia every fall.
An ecosystem refers to
A shift in focus: Biogeochemistry
More recently, Arrigo's research focus has shifted towards biogeochemistry, or the study of the biological, geological, and chemical processes that interact within a system. This field places particular emphasis on how elements and nutrients like nitrogen, carbon, and sulfur cycle through the atmosphere, hydrosphere, biosphere, and geosphere on both long and short timescales: These processes are known as biogeochemical cycles (see our modules on The Carbon Cycle and The Nitrogen Cycle). Arrigo attributes the shift in part to pressure from the general academic and scientific communities. "To write a successful grant proposal to get funding for research," something he says he spends a lot of his time doing, "you have to mention climate change or carbon cycling." In other words, Arrigo is following his interests, but also responding to the influence of scientific institutions and funding agencies (see our module on Scientific Institutions and Societies), which are emphasizing climate change because of society's need for more scientific knowledge in this area.
While still focusing on the Southern and Arctic oceans, the shift to include biogeochemical cycles in his research brought new questions, methods, and motivations to his research. Primarily, he is now coupling his interest in ecosystems with a focus on how climate change may impact those ecosystems and their interactions. In the Southern Ocean, for example, Arrigo began to combine his analysis of satellite imagery with analysis of the phytoplankton themselves, determining that different phytoplankton species had very different rates of CO2 uptake (Arrigo et al., 2002), and that photosynthesis (or primary production) by all species was inhibited with increased ultraviolet radiation that resulted from the ozone hole over the southern hemisphere (Arrigo et al., 2003) (see our module on The Practice of Science: An Introduction to Research Methods to find out more about the ozone hole). Over several years of analyses, Arrigo and his research associate determined that portions of the Southern Ocean are an important "sink" for atmospheric carbon dioxide, meaning that they can remove CO2 from the atmosphere, but that the amount of CO2 absorbed through primary production varied widely from year to year and was strongly correlated with the extent and thickness of sea ice cover (Arrigo and Van Dijken, 2007).
Collaborative research in the Arctic Ocean
Arrigo's research in the Southern Ocean showing the tightly coupled relationship between seasonal ice cover and primary production led him to become interested in the Arctic Ocean as well. Repeated satellite imagery and ship measurements had demonstrated that Arctic sea ice was shrinking at an accelerated rate. What would this mean for primary production?
In 2008, Arrigo gave a presentation about the shrinking Arctic sea ice at an ocean sciences meeting. After his presentation, a program officer in charge of the funding for the Arctic program at NASA approached him. She asked him to help her write a paper about new directions for climate change research in the Arctic that would become a call for proposals to the scientific community (you can read the white paper yourself – see Research under the Resources tab). In other words, while Arrigo had earlier shifted his research focus to address the priorities of funding agencies, in this case, the funding agency was developing its strategy based on Arrigo's research!
This interaction eventually led to his involvement in the NASA-funded Impacts of Climate Change on the Eco-Systems and Chemistry of the Arctic Pacific Environment, or ICESCAPE (Figure 3). ICESCAPE is a four-year-long project designed to investigate questions about the biogeochemistry of a portion of the Arctic Ocean and how climate change may impact the region. The Arctic is already experiencing ecosystem changes due to climate change, and projects such as this one provide valuable information about our changing global climate. The project involves two research cruises through the Arctic Ocean to investigate phytoplankton response to changing sea ice cover, conduct "ground-truthing" of satellite data by making surface measurements to verify the remotely sensed measurements, and measure the impacts of ocean acidification on the Arctic Ocean ecosystem.
ICESCAPE includes over 50 scientists in 11 different research teams from Stanford University and Scripps Institute of Oceanography in California, University of Washington, Woods Hole Oceanographic Institution in Massachusetts, Bermuda Institute of Ocean Sciences, the University of Alaska-Fairbanks, and several other universities and research institutions. Most of the scientists participate in two month-long research cruises to the Chukchi and Beaufort Seas in the Arctic (see Figure 4 for location); the first took place in the summer of 2010 and the second took place in the summer of 2011. Each research team works on a specific question related to the general goal of the project to investigate the impact of climate change in the Arctic.
Arrigo's research team consists of his lab manager, a research associate, two graduate students, and two undergraduate students. One of the team members, an undergraduate who had worked with Arrigo since 2008, decided to miss her graduation from Stanford in order to get a place on the research cruise. It is very competitive to even be selected as one of the research teams on the cruise, and the opportunity to go on a cruise, especially as an undergraduate, is something you don't pass up. In addition to managing his own team, however, Arrigo is the chief scientist on ICESCAPE, meaning he is in charge of managing the logistics before, during, and after each of the two cruises.
The primary role of the chief scientist is to decide how all the research questions will be addressed on the cruise. Initially, each team had written their own plans for addressing their research questions, resulting in some overlap and redundancy. Through the planning process, they refined their research questions as a group and worked together to decide how data will be collected and samples shared between the teams. These decisions, among others, were made via a year of weekly teleconferences in which all of the research teams participated. Once research questions were confirmed and methods established, a plan of sampling locations was laid out (Figure 4).
On June 11, 2010, after more than a year of planning, the research teams flew to Dutch Harbor, Alaska, where their research vessel, the U.S. Coast Guard Cutter (USCGC) Healy (Figure 5), was waiting. The Healy is owned by the Coast Guard and rented by NASA for the research cruise. It comes with a full crew accustomed to working with scientists out on the water, and a complete shop on board designed to allow the crew, and the scientists, to build whatever they need to do their research. As lead scientist, Arrigo is in charge of interfacing with the captain and serving as the main communicator between the crew and the scientists. Both groups bring their different expertise to make the research cruise successful, and the scientists rely on the crew, who not only keep the ship functioning, but help with the machinery and technical aspects of collecting samples.
A main purpose of the planning process was to ensure
On the water
Once on the water, everyone on the boat is kept informed about the plan for the day on the "Board of Lies," a white board that is projected all over the ship (Figure 6). It is so named because, though it shows the plan for each day, it is usually wrong within minutes of being written down. Ocean conditions, ice, and research logistics change moment to moment and make it impossible to stick to even the best-laid plans. This is not uncommon in scientific research, especially in field work, where it is not possible to control all aspects of the environment, and scientists need to be flexible to accommodate changes and new opportunities.
June in the Arctic is a time of virtually perpetual sunlight, so 24 hours of continuous sampling each day was possible regardless of which 12-hour shift researchers were assigned. The weather was particularly pleasant in 2010, with lots of calm sunny days on the water. This allowed the research teams to collect samples at nearly double the number of locations they expected to reach, both open water samples (Figure 7) and ice station samples (Figure 8).
Arrigo's research team was measuring rates of primary productivity to see how much carbon dioxide phytoplankton consume through photosynthesis. In order to do this, they collected water samples using a Niskin bottle rosette, shown in Figure 9, which is a submersible tool surrounded by twelve 30-liter bottles. These bottles are open on both ends and can be closed at any depth in the water column as the rosette descends. This way, they are able to compare samples from throughout the water column, or they can get a lot of samples from a certain depth. The phytoplankton are then either filtered out right on the ship, or the samples are kept in their bottles for analysis back at Stanford. The team also measured the concentration of carbon, nitrogen, and phosphorous in the water to investigate the role of microorganisms in nutrient cycling.
Despite the pleasant weather, the ship still encountered ice it couldn't break through. Usually the 420-ft Healy is able to barge through the ice by ramming up on top of it, causing the ice to be pushed down, break up and disperse to make room for the ship. But after 12 hours of slamming into an ice shelf with only a few meters of progress, the team decided to turn back. The original plan was to reach the Beaufort Sea, but the ice barrier kept them limited to only sampling from the Chukchi Sea (see Figure 4 for locations). Despite the ice, they collected a much larger number of samples than they had anticipated – their actual sampling locations are shown in Figure 10. Compared with their planned locations, represented by black circles in Figure 4, you can see that they didn't make it as far north or west as they had planned, but there are many more red, green, and blue triangles (indicating sampling locations) than black circles on the plan.
The "Board of Lies" underscores that scientists must
Looking ahead to the next cruise
As soon as they finished their first cruise, Arrigo and the other research teams began looking ahead to the next trip. The direction of their research questions depends in part on when they are able to secure the ship: If it is over a similar time period, they will likely collect a second year of data from the same sites to see how the areas change over time. But they may determine new research questions based on the results of their first cruise, the thickness and extent of the sea ice, or the time of year when they have access to the Healy.
Arrigo is hoping to explore new sites, especially those further north including areas in the Beaufort Sea where they had planned to sample in 2010 but were blocked by ice. This will provide a larger spatial distribution for his data and will give him a better sense of how much carbon dioxide the phytoplankton of the Arctic are taking up. By addressing this question, Arrigo and his team are contributing not only to understanding the impact of climate change in this region, but our understanding of climate in general. You can read about the results of the second IceScape cruise here.
Biological oceanographer Kevin Arrigo investigates questions about changes in polar ecosystems due to a changing climate. This research profile explores Arrigo's expeditions in the Arctic Ocean and examines the different influences on Arrigo’s research projects and his career in general. Factors that guide research are discussed, from obtaining funding, to planning research projects, to conducting research in the field.