The earth’s atmosphere contains 850 gigatons of carbon. However, there are an additional 1,400 gigatons of carbon in the Arctic, waiting patiently for release. These carbon stores reside in the Arctic permafrost, and Arctic warming is now releasing this carbon back into the ecosystem.
When the permafrost thaws, then the carbon is released through a variety of pathways. Some Arctic carbon is transformed into carbon dioxide (CO2) and released into the atmosphere. But other pathways, like groundwater transport, can move that carbon into the coastal ecosystem, thus increasing bio-productivity by feeding organisms at the base of the food chain.
The Arctic contains some of the largest stores of carbon on the surface of the planet. These carbon stores accumulated over tens of thousands of years when organic matter from annual summer growth froze into the permafrost. Typically, in warmer climates, organic matter from dead plants is immediately digested by bacteria. However, in the Arctic, the dead plant material goes into deep freeze before the bacteria can break it down.
Global warming is reversing the process and unfreezing this stored carbon. So, as the Arctic permafrost thaws, bacteria will start feasting on organic matter in the soil. The byproduct of this bacterial party is CO2 and methane, but not all of the carbon is consumed. Significant amounts of carbon dissolve in water and move from the land to the coastal waterways of the Arctic Oceans.
Groundwater flow provides a transport mechanism for moving dissolved carbon. The permafrost melts from the surface downward. So, at some depth, there is an interface between the thawed soil and the frozen soil. This interface is also the boundary between flowing groundwater above the frozen groundwater below.
Recent collaborative research between the University of Texas at Austin’s Marine Science Institute and Jackson School of Geosciences, U.S. Fish and Wildlife Service, and Florida State University sheds light on the importance of these Arctic groundwater systems. Groundwater flowing along the buried permafrost interface carries with it significant concentrations of dissolved carbon. Groundwater, like surface water, flows downhill and eventually finds its way to rivers, streams, and coastal waterways. So, Arctic groundwater is a hidden carbon transport system.
The absence of sunlight
One of the factors that makes groundwater transport significant is the absence of sunlight. Normally, dissolved carbon in water degrades with exposure to sunlight. However, dissolved carbon in groundwater is shielded from sunlight and travels to the coastal waterways with its full carbon load intact. When the water moves from the ground into open water systems, it then delivers a rich source of carbon into the local food web.
The lowest trophic levels of the food chain feed on this carbon. Then increased productivity at the bottom of the food web fuels population growth in species higher up the chain. Some of the carbon delivered via the groundwater systems is centuries old. This old carbon is driving new growth in today’s ecosystems. The recent collaborative research estimates that the amount of carbon delivered to coastal ecosystems by groundwater each summer is approximately equal to the carbon delivered by all of the Arctic rivers.
Release of the Arctic carbon due to global warming produces effects far beyond the Arctic. This ancient stored carbon adds CO2 to the atmosphere and drives further warming. It also increases the productivity of coastal ecosystems. Eventually, the thawing of permafrost may increase the extent of coastal wetlands, creating new carbon sinks through soil and marsh sequestration.
Arctic Warming (Source: ArcheanWeb) – https://archeanweb.com/2019/12/05/arctic-warming-climate-change/ Also:
Permafrost: A ticking carbon bomb (Source: ArcheanWeb) – https://archeanweb.com/2020/05/08/permafrost-a-ticking-carbon-bomb/ Also:
Hidden source of carbon found at the Arctic coast (By Scienmag) – https://scienmag.com/hidden-source-of-carbon-found-at-the-arctic-coast/ Also:
Feature Image: Climate Impacts to Arctic Coasts (By Benjamin Jones, U.S. Geological Survey) (Modified) – https://commons.wikimedia.org/wiki/File:Climate_Impacts_to_Arctic_Coasts_(32682616471).jpg – This image is in the public domain in the United States because it only contains materials that originally came from the United States Geological Survey, an agency of the United States Department of the Interior.