In the mid-1990s, the Inter-governmental Panel on Climate Change (IPCC) released an in-depth report on how human activity was affecting the global climate system. An office of the United Nations Environment Programme and the World Meteorological Organization, the IPCC evaluates scientific data related to climate change for world governments as well as UN agencies. The report, which stretched to more than 2,000 pages, included a concise summation. Due to natural variability and uncertainties, it stated, the ability of scientists to quantify human impact on climate change was limited. “Nevertheless, the balance of evidence suggests that there is a discernible human influence on global climate,” the report read.
Since then, while the overall conclusion has not changed, the amount of published research on the subject has grown significantly, says Philippe Tortell, a University of British Columbia Department of Earth, Ocean & Atmospheric Sciences professor and researcher of marine biogeochemical cycles. Twenty years ago, there was little understanding of the effect of carbon dioxide (CO2) — a major greenhouse gas (GHG) created by the burning of fossil fuels — on the oceans. Today, Tortell is part of a group of scientists from 35 nations who are collaborating under the umbrella of GEOTRACES, an international research program seeking greater understanding of the biogeochemical cycles in and large-scale distribution of trace elements and their isotopes in all the world’s major ocean basins.
A membrane inlet mass spectrometer on board the research vessel the CCGS Amundsen is used to measure the CO2, O2 and DMS levels in Arctic seawater. Photo Credit: Nina Schuback
Although considerable research has been undertaken since 1996, there is still much for us to learn about the ocean’s geochemical makeup, as well as the effect of climate and climate active gases on seawater — due in no small part to the complexity of the system. Key questions prevail: when it comes to the role and importance of trace elements and isotopes in the ocean, what is normal, what is anthropogenic and how will changes affect global weather patterns, water temperatures and chemical speciation in the long term?
In an effort to make sense of this Arctic enigma, Tortell and a team of about 40 researchers, including UBC marine geochemist Roger Francois, the Canada Research Chair in Marine Geochemistry for Global Climate Change, spent six weeks last summer on the Canadian Coast Guard research ship CCGS Amundsen, a $5 million expedition to accumulate data through sampling activities and experimentation. The goal was to establish baseline information on the chemical, biological and physical makeup of Arctic waters. Such information, says Tortell, is vital to understanding and ultimately predicting the effect of increasing global temperatures and four key climate active gases: CO2, dimethylsulfide (DMS), methane (CH4) and nitrous oxide (N2O), which impact not only marine ecosystems but also regulate the radiative balance of the planet by absorbing energy from the sun or reflecting it back into space. “If we want to understand how the Arctic Ocean functions as a system, what its current state is now, how it may change in the future, we need ship-based observations across the whole Arctic,” says Tortell. The building of such research data, as part of the GEOTRACES collaboration, “is critical,” Tortell adds. “We have an unprecedented level of detail in the distribution of all these chemicals. This gives us powerful information about how the system works and how it may evolve in the future.”
At the root of such concerns is the concentration of atmospheric CO2, which has been increasing since the industrial revolution. The level of CO2 in the atmosphere is higher, in fact, than at any time in the past 700,000 years, says Tortell. This figure is derived from studies of ancient air bubbles that are trapped in ice. During the ice ages, CO2 levels were around 200 parts per million (ppm) and have since risen beyond 400 ppm. This rise corresponds to the increase in fossil fuel emissions. Data from the US National Aeronautics and Space Administration (NASA) in the US indicates that 2016 is set to be another record-breaking year. The 10 warmest years since 1880 have all occurred since 2000.
The ocean plays a vital role in this anthropogenic shift, as it absorbs CO2, acting as a natural regulator and ultimately having a powerful influence on climate. A 2015 journal article, titled “Rapid anthropogenic changes in CO2 and pH in the Atlantic Ocean 2003-2014” in Global Biogeochemical Cycles, notes that the rise to 397 ppm of CO2 from 355 ppm in 1989, is causing “an increase in the global temperature which is associated with adverse climate change effects. The rise is modulated as a result of the uptake of roughly one half of anthropogenic CO2 emissions by the oceans and land.”
Such dramatic changes, Tortell says, amount to “the largest experiment that human kind has ever done — and we happen to be conducting it on our own planet. We’re trying hard to think how this experiment will pan out and how it will influence our societies and the way we live. We need a crystal ball to look into the future and say, ‘What will the earth’s climate system look like in 10 years, 50 years, 100 years?’ We don’t really have a very good answer,” says Tortell, whose work is supported in part by the Peter Wall Institute for Advanced Studies in Vancouver.
Tortell’s research embraces the complex movement of water masses from the Atlantic and Pacific oceans as well as melting glacier waters that merge, swirl and float on the surface in the Arctic along horizontal and vertical gradients, carrying varying amounts of chemicals like salts. These different water masses have distinct chemical signatures due to their temperature and salt content, acting as a marker for how seawater is circulating around the globe, says Tortell.
University of British Columbia ocean researcher Philippe Tortell. Photo credit: Nina Schuback
Oxygen (O2) is another important marker of ocean changes. O2 indicates biological activity such as the presence of microscopic plants in the ocean, which are mostly single-cell phytoplankton, Tortell adds.
The photosynthesis of phytoplankton is the foundation of the marine food web and one of the pillars of ocean health. One of the key questions is how this mechanism will be affected by an increase in atmospheric CO2. From a biochemical perspective, increasing CO2 in the ocean should stimulate phytoplankton photosynthesis, possibly a positive outcome, says Tortell. However, this boost in ecosystem productivity could backfire. The bumper crop of new phytoplankton will eventually die, resulting in a rain of organic particles falling down into deeper waters. This material is digested by other organisms that consume organic matter and O2. An explosion in their numbers could trigger an O2 deficit, which is not only harmful to sea creatures but could lead to the formation of GHGs N2O and CH4, Tortell says. (N2O also destroys stratospheric ozone.)
Roger Francois, Canada Research Chair in Marine Geochemistry for Global Climate Change. Photo credit: Nelly Francois
Tortell is studying another organic compound called DMS, which is part of the chemical mixture that is partly responsible for the ocean’s unmistakable, intoxicating scent. DMS is released by tiny phytoplankton. Studies show varying amounts of DMS in the Arctic, due to that what Tortell calls “hydrographic frontal zones,” which are sharp or abrupt transitions in water salinity or temperature. These are associated with areas where there is localized melting of sea water ice or river mouths. Melting glacier ice is a factor in the changing ocean ecosystem and NASA reports that global ice surfaces have been shrinking by 13.4 percent every decade since 1980, causing an annual 3.4 millimetre rise in sea levels.
DMS is gassed into the atmosphere, where it oxidizes, forming sulphate aerosols that create condensation nuclei for cloud formation. Thus DMS is a factor in the radiative balance of the planet, as overcast skies reflect sunlight back into space. Clearly an important cog in the planet’s ecosystem, Tortell is researching how DMS is influenced by — as well as influences — climate change. At this moment, however, it is questions rather than answers that loom large. “How does DMS change with melting ice? How does it change with warming oceans or with changes in phytoplankton abundance and composition? I think that’s where we’re at for the moment with DMS.”
Such queries may be answered soon. The data that Tortell and the GEOTRACES compile will be fed into mathematical computer models incorporating the physical, chemical and biological processes of the Arctic to ultimately provide accurate predictions of the effects of climate change.
Francois was chief scientist, alongside Tortell, during last summer’s excursion to the Arctic. His research interests lie more with oceanic chemical minutiae, specifically the radioactive isotopes thorium-230 (230Th) and protactinium-231 (231Pa). Both are products of the radioactive decay of uranium, which is naturally found in seawater at a level of around three parts per billion. These isotopes settle in sediments, leaving behind a record of their distribution in time and can also be measured in samples taken from different depths of the water column. Their distribution in the water column also allows Francois to trace the path of deep-water currents in the Arctic, which are driven not by wind but water density, which changes in accordance with temperature and salinity. They are a crucial means by which life-giving nutrients and contaminants are circulated in the deep. Knowing the trajectory and velocity of these currents would be particularly crucial to prepare for a worse-case scenario, such as an oil spill, if drilling for crude in the Arctic were to go ahead, Francois says.
Francois began monitoring the radioisotopes 230Th and 231Pa in 2007. Using this baseline, he has been able to use changes in the levels of 230Th and 231Pa to monitor how deep-water currents are evolving as the climate changes. “The melting of the sea ice in summer changes the way the surface water mixes and will change the supply of nutrients to surface water, thus changing the productivity in this part of the ocean,” says Francois, who collects seawater and analyzes its 230Th and 231Pa levels using mass spectrometry back at his UBC lab.
In addition to melting more sea ice, a general increase in global temperatures boosts the surface temperature of the ocean. This increases stratification: warm water on top of cold water makes it more difficult for the two to mix vertically, which causes the supply of nutrients to decrease, adding to what Francois calls expanded oligotrophic zones, areas with decreased biogenic activity. Since the phytoplankton is a main consumer of CO2, this in turn affects the ocean’s ability to absorb this greenhouse gas.
Melting glaciers in the Arctic, especially from the Greenland ice sheet, adds fresh water to the North Atlantic. This could reduce the rate of deep-water formation — one of the main mechanisms redistributing solar heat from the tropical regions to high northern latitudes. While such a slowdown could temporarily mitigate global warming in the affluent regions of the north, it would exacerbate warming in other regions. It would also change precipitation patterns in tropical regions, leading either to more drought or more flooding, Francois says.
Higher temperatures — a direct result of greenhouse gases — are pushing the climate system possibly to the “point of no return,” says Francois. “It may initially change little by little by little — then abruptly and non-reversibly. What the consequences for human society will be is anyone’s guess.”
The calcareous plankter Emiliania huxleyi forms large blooms in seawater. Photo credit: Science Daily
One great illustration of the complex and sometimes contradictory nature of biogeochemical cycles in the ocean has to do with the interplay of two carbon sinks. The first occurs when photosynthetic plankton take up CO2 to build their biomass; the other is when marine organisms like corals, molluscs and some phytoplankton build and maintain shells and exoskeletons using carbonate ions dissolved in the water.
Both mechanisms would seem to remove atmospheric CO2 and store it as non-gaseous chemical species. However, according to University of British Columbia Department of Earth, Ocean & Atmospheric Sciences marine researcher Philippe Tortell, it’s more complicated than that. “What these calcium carbonate-producing organisms do is they actually remove alkalinity from the water, because they take carbonate ions and react them with calcium to form a solid,” Tortell says. This is important because highly alkaline waters, for complicated chemical reasons, actually have a higher capacity to trap atmospheric CO2 into bicarbonate ions than acidic ones.
Tortell gives the example of a large bloom of Emiliania huxleyi, a type of photosynthetic plankton in the group known as coccolithophores. Because they are both photosynthetic and shell-producing, one would think that a large bloom of these organisms would draw down lots of CO2 from the atmosphere. In fact, because they alter the alkalinity of the water they live in, “big blooms of E. huxleyi can actually increase the partial pressure of CO2 at the surface of the water because of the removal of all this alkalinity.”
Such complex interactions show that the results of climate change will not be easy to either track or predict and underline the importance of data-gathering missions like that conducted by Tortell and his colleagues last summer aboard the Canadian Coast Guard research ship the CCGS Amundsen.
Additives in plastics and microplastics affect sea creatures
Peter Ross, senior scientist with the Vancouver Aquarium’s Ocean Pollution Research Program. Photo credit: Vancouver Aquarium
An estimated 700,000 marine animals die each year from plastic garbage, either by becoming entangled in lost fishing nets and rope or by ingesting it, says Peter Ross, the founding director and senior scientist with the Vancouver Aquarium’s Ocean Pollution Research Program. Even when such plastics degrade into microplastics — defined as anything smaller than five millimetres — they continue to cause havoc in the marine ecosystem. This is because the additives in plastics like bisphenol-A (BPA), phthalates, which make plastics flexible, and organobromine compounds like polybrominated diphenyl ethers (PBDEs), which are used as flame retardants, can leach from microplastics into organisms when ingested. These chemicals “are endocrine disrupting compounds,” Ross says.
Microplastics are consumed by fish and invertebrates like molluscs, corals and zooplankton, which mistake them for food. While it is difficult to assess the impact of microplastics and BPA, phthalates and PBDEs in field studies, deleterious effects have been noted under controlled laboratory testing, Ross says. These include estrogenic outcomes such as the feminization of male fish, neurological abnormalities and weakened immune systems. Young marine mammals and organisms are especially susceptible, as their endocrine and hormonal systems are developing, says Ross, whose team has found high rates of plastic — 9,200 particles of plastic per cubic metre — off British Columbia’s West Coast.
Ross says that one key way to mitigate the problem is to support the development of low-chemical personal-care products. For example, retail items like facial scrubs and toothpaste containing microbeads should be banned, as these tiny particles often pass straight through waste treatment systems into the environment. As well, the international community must pressure as well as assist countries — the main culprits being Asian nations — to cease chucking plastic waste into ocean waters. “Plastic pollution in the ocean is a global problem,” Ross says.