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The changing currents of an interconnected ocean
New cascades of Arctic water spark concern
“The profound, climate-driven transformation of the Arctic can radically alter CO2 balance in downstream oceanic regions. It is crucial to understand how changing deliveries of meltwater, nutrients and organic matter in the western North Atlantic impact carbon fluxes regionally and globally.”
Emerging science reveals the ocean's ability to absorb CO2 and regulate temperatures is changing in ways we don’t understand. These critical shifts are not accounted for in climate targets – a risk we can no longer take. With support from the Canada First Research Excellence Fund, Dalhousie is leading an ocean-first approach to tackle climate change and equipping Canada with the knowledge, innovations, and opportunities to secure a positive climate future.
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Laval oceanographer, Dr. Jean-Éric Tremblay, seeks to understand how the nutrient and freshwater content of waters that flow out of the Arctic are changing and affecting biological carbon fluxes at a variety of scales in the ocean.
“Nutrients are the fundamental building blocks of all life,” says Dr. Tremblay. “The cycling and availability of nutrients largely set the biomass that marine algae and animals can reach and, consequently, their impact on marine carbon fluxes.”
The ocean is highly interconnected. Currents dictate how nutrients are redistributed horizontally between ocean areas. Freshwater content of the upper ocean affects how nutrients move vertically through the stratified layers of the ocean, between the deep reservoir and the surface, where algae can use them. The ocean’s nitrogen cycle also includes microbial processes that lead to net losses or gains of nutrients over time, modulating the ocean’s ability to capture carbon dioxide.
With his students and postdoctoral fellows, Dr. Tremblay investigates nutrient dynamics in the ocean and their changes by analyzing time-series of ship-based measurements gathered at key locations along the path of major currents in the western Arctic, the northwest Atlantic and the St. Lawrence system.
Using sensors and assays, measurements are collected for physical water properties, nutrient concentrations, nitrogen cycling processes, and the characterization of particulate organic matter.
A major concern is that key ocean areas like the deep-water formation node in the Labrador Sea and the fishing grounds that span the eastern North American shelf lay in the path of the massive water outflow descending from the high Arctic.
Much like waterfalls on land, cascades of Arctic water converge into the eastern North Atlantic carrying the telltale signs of a polar ocean transformed by amplified warming and freshwater loading from melting multi-year sea ice and glaciers.
Resulting changes in stratification, circulation pathways, pH, nutrient load and biological productivity are bound to have major repercussions on marine carbon fluxes, regionally at first and globally as meltwater and nutrients propagate through the ocean.
Dr. Tremblay is now focused on Baffin Bay, a major nexus for the redistribution of fresh water, nutrients, and dissolved organic matter entering and exiting through major ocean gateways. The region is also home to several Inuit communities that rely on the ocean for subsistence.
His current work with these communities is seeking to better understand the cumulative impacts of local and remote climate-driven changes on the biogeochemistry of seawater, and how these impacts are affecting the quantity and nutritional qualities of carbon-rich, lipid-replete marine foods.
Dr. Tremblay looks forward to the establishment of a new coastal observatory consisting of a research station and autonomous sampling platforms making use of the latest sensor developments. He says they will be instrumental in reducing uncertainty in the seasonality, inter-annual variability and change of water properties and ecosystem functioning in a key area linking the Arctic and the North Atlantic.
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