A modest quantity of groundwater flowing through Alaska’s tundra is emitting substantial amounts of carbon into the ocean, which could intensify climate change, as revealed by new research from The University of Texas at Austin.
A modest quantity of groundwater flowing through Alaska’s tundra is releasing substantial amounts of carbon into the ocean, potentially exacerbating climate change, according to recent findings from The University of Texas at Austin.
Researchers have discovered that although this groundwater constitutes only a small part of the total water that reaches the sea, it is releasing an approximate 230 tons of organic carbon each day along the nearly 2,000-kilometer coastline of the Beaufort Sea during the summer months. This carbon emission is comparable to that of free-flowing rivers in the region during the same period.
“Our study indicates that there is an enormous amount of organic carbon and carbon dioxide being emitted through fresh groundwater discharge in the summer,” stated Cansu Demir, who spearheaded the research while pursuing her doctoral degree at the UT Jackson School of Geosciences. She is currently a postdoctoral research associate at Los Alamos National Laboratory.
The findings were recently published in Geophysical Research Letters.
As the tundra thaws and the flow of submarine groundwater increases, Demir noted that the carbon flowing from land to sea could potentially turn ocean surface waters into a carbon source for the atmosphere. The CO2 released through groundwater may also contribute to ocean acidification.
This study is groundbreaking as it directly observes the discharge of fresh water into submarine environments where the land meets the sea. Prior to this research, it was believed that fresh submarine groundwater discharge in this part of the Arctic was quite limited, according to Demir.
Furthermore, this study is the first to differentiate freshwater—which can originate from rain, snowmelt, thawed surface ice, and possibly some permafrost thaw—from the total groundwater discharge. Earlier research on groundwater discharge in the Arctic included recirculated saltwater that infiltrated the ground from the coastal area.
By employing direct observations and various modeling and thermal techniques, the researchers found that during the summer, the fresh groundwater entering the Beaufort Sea north of Alaska accounts for 3-7% of the total discharge from three major rivers in that region. This volume is surprisingly significant, according to Demir, who noted it is comparable to the amounts of fresh groundwater discharge seen in temperate regions at lower latitudes. Although this groundwater volume is a small portion of the overall river flow, it carries a comparable amount of carbon.
“In that small volume of water, the groundwater transports nearly an equivalent amount of organic carbon and nitrogen as the rivers,” she remarked.
As groundwater flows beneath the surface through soils and sediments towards the coast, it gathers organic matter, inorganic matter, and nutrients along the way. When it comes into contact with permafrost, the carbon intake can be particularly high. Permafrost acts like a subterranean reservoir, storing substantial amounts of water and organic matter. When this ice melts and merges with groundwater flow, it carries significant quantities of carbon with it.
“The Arctic coast is transforming right before our eyes,” said Bayani Cardenas, a co-author of the study and a professor in the Jackson School’s Department of Earth and Planetary Sciences. “As permafrost melts, it evolves into coastal and submarine aquifers. Even without this thawing, our studies are among the first to directly demonstrate the presence of such aquifers.”
Alongside contributing to global climate change, this influx of carbon and nitrogen could greatly affect Arctic coastal ecosystems, according to Demir. For instance, ocean acidification might increase the vulnerability of various organisms on and beneath the seafloor, including crustaceans, clams, and snails.
As permafrost continues to melt due to climate change, the volume of freshwater reaching the ocean underground may grow, further increasing the release of greenhouse gases into coastal waters.
