In the fight against climate change, the Arctic, our smallest ocean, is playing a surprisingly significant role in the carbon game. Believe it or not, these chilly Arctic waters soak up 180 million metric tons of carbon yearly—more than triple New York City’s yearly emissions.
However, recent discoveries highlight a concerning twist.
As the permafrost in the Arctic thaws and Canada’s mighty Mackenzie River spills its carbon-rich runoff, a noteworthy shift is happening in the Arctic Ocean.
Instead of absorbing more carbon dioxide (CO2), this specific part of the Arctic is actually letting out more than it takes in. The runoff from North America’s mightiest rivers is playing a pivotal role, contributing significantly to the increased emissions of CO2 in the Arctic Ocean.
Is the Arctic warming up?
Absolutely, the Arctic is undergoing a substantial warming trend.
Since the 1970s, it has warmed up three times faster than the global average, showing significant shifts in its hydrological cycle.
This warming isn’t just a temperature shift; it’s producing major transformations in Arctic watersheds and rivers, acting as influencers in shaping the physical and biogeochemical conditions of the coastal Arctic Ocean. The river discharge has invariably increased by 0.22% since 1984.
As if that wasn’t enough, the thawing permafrost adds another layer of complexity. It’s not just about the increase in water flow; it’s altering the essence of what’s being transported.
The dissolved organic carbon (tDOC) making its way to the Arctic Ocean is changing in quantity and quality—considering its sources, compositions, and bioavailability. The Arctic is undergoing a profound makeover, and these changes have broader implications for the entire region.
This thawing process also enhances the connections between watersheds and marine ecosystems. Recent findings indicate the presence of permafrost-driven carbon in the Mackenzie River mouth even during early spring/summer, a period traditionally associated with the fact of only modern.
Decoding the Arctic’s Carbon: ECCO-Darwin Unveils River’s Impact
In the marshy expanse of Canada’s Northwest Territories, the second-largest river system on the continent concludes its thousand-mile journey, originating near Alberta.
Along this extensive route, the river serves as a conveyor of mineral nutrients and organic and inorganic matter, creating a blend of dissolved carbon and sediment that eventually drains into the Beaufort Sea. Some of the carbon undergoes a natural release process, or outgassing, finding its way into the atmosphere.
Traditionally, scientists have considered the southeastern Beaufort Sea a relatively mild to moderately effective CO2 sink, implying that it absorbs more greenhouse gas than it releases. However, a cloud of uncertainty has persisted due to the lack of data from this remote, isolated region.
The research team took a unique approach to address this knowledge gap by employing a global ocean biogeochemical model known as ECCO-Darwin.
This model, crafted at NASA’s Jet Propulsion Laboratory in Southern California and the Massachusetts Institute of Technology in Cambridge, was designed to assimilate a comprehensive dataset.
This dataset encompasses nearly all available ocean observations gathered over over two decades, sourced from sea- and satellite-based instruments. Notable contributors to this dataset include sea level observations from the Jason-series altimeters and ocean-bottom pressure data from the GRACE and GRACE Follow-On missions.
Using the ECCO-Darwin model, the scientists conducted simulations to track the discharge of freshwater along with its cargo of various elements and compounds, including carbon, nitrogen, and silica, over almost two decades, from 2000 to 2019.
The multinational research team, hailing from France, the US, and Canada, uncovered a significant revelation. The discharge from the river was initiating such powerful outgassing in the southeastern Beaufort Sea that it disrupted the carbon balance, resulting in a net CO2 release of 0.13 million metric tons annually.
To put this into an outlook, it’s approximately equivalent to the yearly emissions from 28,000 gasoline-powered cars. Also, the release of CO2 into the atmosphere exhibited seasonal variations, with a more conspicuous impact during warmer months.
Insights from ECCO-Darwin
The transfer of carbon between the ocean and atmosphere, known as air-sea CO2 flux, is a pivotal process.
However, monitoring this phenomenon along the Arctic’s coastal fringes has been challenging due to the rugged terrain, sea ice dynamics, and prolonged polar nights, resulting in a sparse observational record.
Lead author Clément Bertin, a scientist at Littoral Environnement et Sociétés in France, emphasised the significance of their model in unravelling the true impact of coastal peripheries and rivers on the Arctic carbon cycle.
This is particularly crucial as approximately half of the Arctic Ocean’s expanse consists of coastal waters. The changing Arctic landscape plays a dual role in influencing the delicate balance of our oceans.
As Arctic lands undergo thawing and snow and ice melt accelerate, rivers gain momentum, carrying more organic matter from thawed permafrost and peatlands into the ocean. Conversely, microscopic phytoplankton hovering near the ocean surface are seizing the opportunity presented by diminishing sea ice to thrive in the newly exposed water and sunlight.
These plant-like marine organisms play a crucial role in capturing and absorbing atmospheric CO2 through photosynthesis. The ECCO-Darwin model is a valuable tool for studying these intricate dynamics, particularly the interplay between ice and life in the Arctic.
Scientists closely monitor these significant shifts and subtler changes in the Arctic and beyond. This vigilance is vital because our ocean waters act as a crucial buffer against the impacts of a changing climate, sequestering up to 48% of the carbon generated from burning fossil fuels. Understanding these complex interactions is essential for comprehending the broader implications on our planet’s climate and ecosystem health.
