Assessing the origin, transformation and transport of terrestrially derived carbon in river systems is critical to regional and global carbon cycles, particularly in carbonate terrains, which represent the largest carbon reservoir on the earth's surface.
Despite the possible benefits, junior researchers may feel that they shouldn't be spending precious time on anything that takes them away from their science, says Britta Voss, a postdoc at the U.S. Geological Survey in Boulder, Colorado, who studies carbon in river systems.
Compared with the slow, top-down melting of permafrost, thermokarst failures unleash rapid bursts of carbon-rich organic material, as rivulets of water from the melting ice cut deep channels into the soil and transport the carbon into rivers or the ocean.
This review includes quantitative estimates of the global riverine transport of NOM from the continents to the oceans and the corresponding average concentration of total organic carbon in rivers, methods of isolation and characterization of NOM from inland waters, and simple statistical summaries of the most commonly reported chemical properties of NOM.
It can also enter as dissolved organic carbon through rivers and is converted by photosynthetic organisms into organic carbon.
The CO2 flux from the water surface to the atmosphere during a flood event is three times greater than during base flow, suggesting that excess precipitation flushes soil organic carbon to the river through interflow and enhances the loss of terrestrial carbon via river water to the atmosphere.
The researchers found that the concentration of particulate organic carbon in the river water increased greatly during flooding caused by two typhoons in 2004.
In a report in Nature Geoscience, the researchers calculate that the typhoon effect is so great that over several decades, almost all of the transport of organic carbon by the river occurs during storm-caused floods.
Terrestrial allochthonous sources could support around 68 86% of the particulate organic carbon in the river plume and glacier melting areas, whereas fatty acid concentrations were maximal in the surface waters of the Pascua and Baker river plumes.
Climate information from a suite of global climate models (GCMs) is used to drive models assessing the agricultural impact of changes in temperature, precipitation, carbon dioxide concentrations, river floods, and sea level rise for the 2040 2069 period in comparison to a historical baseline.
These results indicate that catchment lithologies, particularly whether carbonate or siliciclastic, as well as flow, are critical to carbon budgets in rivers and thus are linked to the global carbon cycle.
