Polar oceans in transition
(03.10.2011) Mention climate change and the Arctic, and most people think polar bears. But for Victor Smetacek, a biological oceanographer at the Alfred Wegener Institute for Polar and Marine Research in Germany, the real symbols of climate change and the Arctic are elephants and tigers, the iconic animals of his home country of India.
"The negative effects of summer sea ice melting will be felt far from the Arctic, far from Norway," he said at a recent international workshop in Trondheim. "The warming of the Arctic will hasten melting of the Greenland Ice Cap. That will lead to flooding in Bangladesh. Where are we going to accommodate those people? Will it still be ethical to maintain India's national parks – with their populations of elephants and tigers – when these people have no place to go?"
Smetacek's questions helped set the stage for a two-day workshop on polar oceans and climate change hosted at the Norwegian University of Science and Technology (NTNU) in early October as a part of its India 2011 programme. Researchers from India, Chile and Germany, and from the Norwegian Polar Institute, the University of Bergen and NTNU gathered in Trondheim to draft a collaborative research plan to answer some of the fundamental questions about how climate change will alter the physical and chemical processes that control polar oceans.
The group included oceanographers, marine chemists, biologists and engineers – scientists who often talk to each other but who need to work more closely together, says the workshop's organizer, Murat Van Ardelan, a marine chemist at NTNU's Sealab. "The complexity of the oceans means that you must cross disciplines," he said. "We cannot understand the interaction between the climate and the biogeochemistry of polar oceans unless we build these networks."
"The ocean is sick"
While much of the weekend workshop focused on specific effects of climate change, such as ocean acidification and altered biogeochemical cycles and food webs, several speakers, including Smetacek, talked about the larger issues that fuel an urgent need for research – and action.
"The ocean is sick," he said, because global warming is causing oceans to warm, and areas where there is no oxygen in the seawater are expanding, which will affect fisheries worldwide. As worrisome as this might be, however, he told the group that sea level rise from melting ice caps poses a far more imminent problem.
"Sea level rise is inevitable," he said. "This is something that we will face in 2-3 decades. …I know I am scaring you, but I need to."
Fertilizing the ocean?
Much of the first day's discussion at the workshop centred around the complex food webs in the polar oceans and how climate change might alter their behaviour – or alternatively, how their behaviour might be altered to help remove CO2 from the atmosphere. Specifically, some studies have suggested that artificially promoting the growth of phytoplankton in the ocean – called geoengineering -- could remove up to 1 gigatonne of carbon from the atmosphere per year. That is just under one-eighth of the carbon dioxide that needs to be removed annually to begin to limit global warming.
Smetacek and his colleague S. Wajih Ahmed Naqvi, who attended the workshop from India's National Institute of Oceanography in Goa, were co-chief scientists on a joint German-Indian ocean fertilization experiment called LOHAFEX conducted in January 2009. The experiment was designed to see how food webs in the Southern Ocean would respond if a patch of ocean was fertilized with iron.
Phytoplankton are tiny floating plants that convert CO2 and sunlight into food for themselves and oxygen for the planet. They also play a role in removing carbon from the atmosphere, because when they die and sink to the ocean floor, the carbon they contain sinks with them. But phytoplankton need a little iron in the water to grow. Because the Southern Ocean off of Antarctica contains all the nutrients phytoplankton need except for iron, it offers a natural laboratory to test the idea.
The importance of silica
But as Naqvi explained, international environmental groups challenged the legality of the experiment, charging that it was a dangerous geoengineering project that violated international resolutions which allowed small-scale research studies but prohibited large-scale iron fertilization of the ocean.
After a three week review by the German government, however, the experiment was allowed to proceed, but was limited to an area where not only iron levels were low, but where silica levels were also low – which is a situation that characterizes about 65 per cent of the area of the Southern Ocean that could be used in iron fertilization. This had a profound effect on the results, Navqi said, and made him realize that "the potential of this system for long term CO2 sequestration is not very high."
The iron did cause phytoplankton to grow, Naqvi explained, but the type that grew were mostly eaten up by zooplankton. If there had been more silica in the seawater where the experiment was conducted, another kind of phytoplankton, called diatoms, would have grown.
Diatoms need silica to make a glassy coating, which protects them from being eaten by zooplankton. Their glassy coat also means they are heavier than other species of phytoplankton, so when they die, they are more likely to sink to the ocean bottom, taking carbon with them. No silica – no diatoms. No diatoms – no – or very little -- carbon sequestration.
Need to understand more
Other workshop participants, such as Sisinthy Shivaji, from India's Centre for Cellular and Molecular Biology in Hyderabad, talked about the importance of understanding the microbial diversity of polar oceans as a possible source of potentially useful bacteria.
Still others, such as Geir Johnsen, a marine biologist working with NTNU's newly created Applied Underwater Robotics laboratory, talked about new kinds of underwater robots and other vehicles that enable scientists to do everything from peer under the ice in frozen polar seas to map the seafloor and use special spectral imaging to examine the health of coral reefs or map the diversity of kelp beds.
Workshop organizer Ardelan presented his own work on the effects on phytoplankton production from natural sources of iron to the Southern Oceans. These natural sources can be in the form of sediments carried from the long slender finger of land called the Antarctic Peninsula, which sticks out into the Southern Ocean near the Drake Passage. Natural additions of iron fuel algal blooms, which in turn can affect the growth of species, such as krill. "Krill are very affected by iron," he said.
Ardelan says he looks forward to building a research network with the invited scientists. Each participant brings special expertise and insights into the puzzle that is the polar oceans, he observed. The effort is important for NTNU, which supported the workshop as a part of the university's India 2011 project as well as its focus on marine research as a strategic area, while the Norwegian Polar Institute is Norway's main research group for polar issues. From an international perspective, "the Chileans are in a perfect location to study the southern oceans," he said. "And India has two polar stations in Antarctica, with a third soon to open, as well as a station in Ny-Ålesund in Svalbard – no other nation has this kind of focus."
A collective international effort to expand our knowledge of what is happening in the polar seas is important because the future remains very unclear, he said. "Climate change could reduce or increase the natural productivity of these (polar) oceans," he said. "We really need to understand more about them."