Robie W. Macdonald
(Biography) Reasearch Interests Arctic Contaminants: Research has been conducted on the movement of contaminants through environmental systems. Classic contaminants such as organochlorines, metals, hydrocarbons, PAH, and some more recent contaminants (nonylphenol ethoxylates), suspected to disrupt development of aquatic organisms, have been investigated. Case studies have been used to illustrate the crucial role of the environment in providing surprises and short-cut pathways, even for chemicals with well-known properties. This work has been published in a wide variety of international journals and several national or international assessments. Biogeochemical cycling on shelves: Over two decades of research on the Canadian Beaufort Shelf has led to a complete revision of processes supplying, transporting and burying organic carbon. This work, which includes the development of regional budgets, assessment of molecular distributions and sources, and isotopic and age structure of organic carbon components, has been published in a wide variety of international journals. Recently, a book summarizing what is known about the Arctic Ocean’s organic carbon cycle has been co-edited. Freshwater in the Arctic: Stable isotope composition of water (18O) over the Arctic’s shelves and basins has been used to distinguish between processes related to ice formation / melting, and the hydrological cycle (runoff). Through transects and time series, insights have been developed on how a small shelf like the Beaufort manages to transmit over 300 km3 of runoff each year while at the same time producing convecting, brine-rich water through salt rejected during ice production. Using landfast ice as a flat plate recorder, the process of under-ice spreading of the Mackenzie River in winter has been determined. Time series over the Beaufort shelf have revealed how the hydrological cycle and the ice cycle are coupled and how that couple will respond to projected global climate change. The isotopic evidence has been used to show that recent changes in the freshwater inventories of the Canada Basin are due more to storage of runoff than of increased ice melt. This loading has clear consequences to our view of change and how that change might be exported by the Arctic Ocean to produce abrupt change in downstream basins — for example, the Greenland or Labrador Seas.
Fisheries and Oceans Canada - Institute of Ocean Sciences
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