Environmental Change:
Discovering the Global Connections
Dr. Nicholas Bates, Senior Research Scientist
What is the common thread that connects research locations as diverse as the inshore coral reefs of Bermuda, the deep ocean of the Sargasso Sea and the
frozen waters of the Arctic Ocean? My research group at BBSR is involved in studies of all these seemingly disparate regions in an effort to understand how common elements such as carbon and nitrogen are
distributed in the ocean, and how they are influenced by changes in ocean circulation, climate, seawater chemistry and marine ecology.Of particular importance to research here at BBSR and elsewhere is the
need to understand the fate of the carbon dioxide released into the atmosphere by human activities, such as fossil fuel use and deforestation. There is growing scientific evidence that carbon dioxide and
other greenhouse gases, for example methane, nitrous oxide and chlorofluorocarbons, have a direct impact on the earth's climate, with profound implications for humanity and for terrestrial and marine
ecosystems around the globe. The world's oceans absorb most of the carbon dioxide released into the atmosphere by human activities, but there is much uncertainty about how atmospheric carbon dioxide is
transferred to the ocean and the impact this transfer process has on the different ocean ecosystems found throughout the world. Recently, our group at BBSR has been actively involved in a large-scale
Arctic Ocean research project, the Western Arctic Shelf-Basin Interactions (SBI) program funded by the U.S. National Science Foundation
. Over the last few decades, the Arctic region has experienced dramatic changes in, for example, climate, weather patterns and sea-ice distributions.
Arctic scientists are increasingly concerned about future environmental changes and impacts, not only for local populations but for the worldwide community. Not surprisingly, environmental change in the
Arctic region has global reach, even as far as the island of Bermuda.The Arctic Ocean is the smallest of the earth's oceans and is largely surrounded by land. This relatively small body of water may
represent only about 1.5 percent of the global ocean, but it receives 10 percent of the world's river runoff. Over the last few decades, as glaciers have melted and permafrost has decreased significantly in
the polar region, the runoff of fresh water into the Arctic Ocean from surrounding watersheds on land has increased. The extent of sea ice that covers the Arctic Ocean has shrunk by an alarming 30 percent
(figure 1)
as the Arctic region has grown warmer. And, like the South Pole, the protective layer of ozone in the upper atmosphere of the Arctic has diminished, exposing the local human population and native animals and plants to higher levels of harmful ultra-violet radiation.
With environmental change, the ecology of the Arctic region and the fates of carbon dioxide and nutrient elements are changing. As part of the SBI project, BBSR researchers
have joined other scientists in the first comprehensive oceanographic studies of the Chukchi and western Beaufort Seas. Expeditions to the Arctic are difficult to undertake at the best of times, but studies conducted from 2002 to 2004 on the U.S. Coast Guard icebreaker
Healy
have provided us with new information about how the flow of Pacific Ocean water into the Arctic, the changing sea-ice conditions and the physical circulation of the Chukchi Sea impact marine phytoplankton and the subsequent cascade of nutritional material and energy up the food chain.
The Arctic Ocean contains more than a quarter of the world's shallow continental shelves. Water from the Pacific Ocean flows into the Arctic Ocean from the Bering Sea through the Bering Strait and then
into the Chukchi Sea. At the same time, sea-ice and cold polar surface waters flow out of the Arctic into the North Atlantic through the Norwegian, Greenland and Labrador Seas
(figure 1).
Pacific Ocean waters flowing into the Arctic through the Bering Strait are laden with nutrients. During the summer, when sea ice retreats from the Bering Sea towards the centre of the Arctic region, intense
growth of tiny marine plants, the phytoplankton, occurs across the vast yet shallow continental shelf of the Chukchi Sea. This phytoplankton food source, in turn, supports large populations of zooplankton,
such as shrimp and copepods; sea-floor animals, for example bivalves and crabs; and fish, seabirds and large mammals, such as seals, polar bears and whales.Our studies are showing that the
ecology of the Chukchi Sea, and the transformations and fate of carbon dioxide and nutrients, influences the rest of the Arctic region. These environmental changes in the Arctic are threatening the
traditions and cultures of Arctic peoples, and the balance of the wildlife in the region. For example, with the retreat of sea ice from the coastline, it will be increasingly difficult for polar bears to
move seasonally from the land onto the ice to hunt seals, their primary food source. The implications of the changes scientists have observed in the Arctic region are not only local, but global. Changes
in sea-ice distributions directly influence the amount of solar radiation absorbed at the earth's surface by altering the planet's ability to reflect that radiation. With less sea ice, the Arctic Ocean
absorbs more of the sun's heat, reinforcing the atmospheric warming observed over the last several decades. What is less clearly known is how the Arctic region influences global ocean circulation and
climate, and the climate feedbacks operating at present and in the future. The increased export of freshwater out of the Arctic Ocean may dampen the formation of deep water in the Greenland, Icelandic and
Norwegian Seas, a process that drives the long-term overturn of deep water, often termed the "ocean conveyor belt." This global recirculation of water masses transports heat from equatorial regions towards
the polar regions. In a warmer world, there should be increased evaporation in the tropical and subtropical regions, and increased precipitation in the sub-polar and polar regions. Indeed, observations over
the last 20 years or so from BBSR's long-term Bermuda Atlantic Time-series Study and Hydrostation "S"
ocean time series show that the subtropical North Atlantic Ocean has become saltier, while other studies have shown that precipitation over the Arctic region has increased significantly. Weather patterns
in the Arctic region and elsewhere are also strongly influenced by climate variability termed the Arctic Oscillation (AO). This phenomenon is similar to the El Niņo-Southern Oscillation that dominates the
equatorial Pacific Ocean. Over most of the past century, the AO has alternated between positive and negative phases, influencing the weather patterns over North America and Europe. Starting in the 1970s,
however, the AO has tended to stay in the positive phase, causing lower-than-normal Arctic air pressure and higher-than-normal temperatures over much of the United States, northern Europe and the subtropical
region of the North Atlantic Ocean, including Bermuda. Clearly, there are many interacting forces at play that influence the world's climate. BBSR's studies of ecological and physical changes in diverse
environments such as the Arctic and the waters surrounding Bermuda may seem disparate but they are, in fact, interconnected. There are many unanswered scientific questions that require study as part of a
quest for a better understanding of the very complex and intricately woven earth system. |
