As Arctic warms, its waters emit carbon: Study

Sediment from Canadas Mackenzie River flows into the Beaufort Sea in milky swirls in this 2017 satellite image. Scientists have studied how river flow can release carbon dioxide in this part of the Arctic Ocean. Credit: NASA Earth Observatory / Jesse Allen (using Landsat data from USGS)

When it comes to influencing climate change, the world’s smallest ocean punches above its weight. It is estimated that the cold waters of the Arctic absorb up to 180 million metric tons of carbon annually more than three times what New York City emits annually making it one of the critical carbon sinks on Earth. But recent findings show that melting permafrost and carbon-rich runoff from Canada’s Mackenzie River are prompting part of the Arctic Ocean to release more carbon dioxide (CO).2) than it absorbs.

The study, published earlier this year in Geophysical Research Letters , explores how scientists use the latest computer modeling to study rivers like the Mackenzie, which flow into a region of the Arctic Ocean called the Beaufort Sea. Like many parts of the Arctic, the Mackenzie River and its delta have faced all-time warmer temperatures in recent years, leading to increased melting and thawing of waterways and landscapes. – see.

In this muddy corner of Canada’s Northwest Territories, the continent’s second largest river system ends a thousand-mile journey that began near Alberta. Along the way, the river acts as a conveyor belt for mineral nutrients as well as organic and inorganic matter. That material flows into the Beaufort Sea as a soup of dissolved carbon and sediment. Some of the carbon is eventually released, or outgassed, into the atmosphere by natural processes.

Scientists consider the southeastern Beaufort Sea to be weak to moderate CO2 sinks, which means it absorbs more greenhouse gases than it releases. But there is much uncertainty due to the lack of data from the remote region.

To fill the void, the study team adapted a global biogeochemical ocean model called ECCO-Darwin, developed by NASA’s Jet Propulsion Laboratory in Southern California and the Massachusetts Institute of Technology in Cambridge. The model assimilates nearly all available ocean observations collected over two decades by sea-based and satellite instruments (e.g., sea level observations from the Jason series of altimeters, and seabed pressure from the GRACE and GRACE Follow-On missions. ).

Scientists used the model to simulate the flow of fresh water and the elements and compounds it carries including carbon, nitrogen, and silica for nearly 20 years (from 2000 to 2019).

The researchers, from France, the US, and Canada, found that the river discharge caused severe outgassing in the southeastern Beaufort Sea that caused the carbon balance, leading to net CO.2 emissions of 0.13 million metric tons per year which is roughly equivalent to the annual emissions from 28,000 gasoline powered vehicles. The release of CO2 into the atmosphere varies between seasons, more pronounced in the warmer months, when river flows are high and there is less sea ice to cover and trap the gas.

As the Arctic warms, its waters emit carbon

Like a conveyor belt of carbon, the Mackenzie River, seen here in 2007 from NASAs Terra satellite, flows through an area of ​​nearly 700,000 square miles (1.8 million square kilometers) on its journey northward to the Arctic Ocean. Some of the carbon comes from melting permafrost and peatlands. Credit: NASA/GSFC/METI/ERSDAC/JAROS, and US/Japan ASTER Science Team

Ground zero for climate change

Scientists have studied for decades how carbon cycles between the open ocean and the atmosphere, a process called air-sea CO.2 flux. However, the observational record is sparse along the Arctic coast, where terrain, sea ice, and long polar nights make long-term monitoring and experiments challenging.

“With our model, we try to assess the real contribution of coastal peripheries and rivers to the Arctic carbon cycle,” said lead author Clment Bertin, a scientist at Littoral Environnement et Socits in France. .

Such insights are important because about half the area of ​​the Arctic Ocean is made up of coastal waters, where the land meets the sea in a complex embrace. And while the study is focused on a particular corner of the Arctic Ocean, it helps tell a bigger story of environmental change taking place in the region.

Since the 1970s, the Arctic has warmed at least three times faster than anywhere else on Earth, changing its waters and ecosystems, scientists say. Some of these changes promote more CO2 outgassing the region, while others lead to more CO2 to be absorbed.

For example, because of the melting of Arctic soil and more melting of snow and ice, rivers flow faster and discharge more organic matter from permafrost and peatland into the ocean. On the other hand, the microscopic phytoplankton floating near the surface of the ocean are increasingly taking advantage of the shrinking sea ice to flourish in the newfound open water and sunlight. These plant-like marine organisms absorb and absorb CO from the atmosphere2 during photosynthesis. The ECCO-Darwin model was used to study these blooms and the relationships between ice and life in the Arctic.

Scientists are tracking these large and seemingly small changes in the Arctic and beyond, as our oceans remain a critical buffer against a changing climate, sequestering 48% of the carbon produced to burn fossil fuels.

More information:
C. Bertin et al, Biogeochemical River Runoff Drives Intense Coastal Arctic Ocean CO2 Outgassing, Geophysical Research Letters (2023). DOI: 10.1029/2022GL102377

Citation: As the Arctic warms, its waters emit carbon: Study (2023, December 21) retrieved 22 December 2023 from

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