Climate change is expected to alter the hydrological and biogeochemical processes of aquatic systems.
A 50-year of monitoring data in Finland shows that climate is a more important driver than forestry or acid position on riverine carbon fluxes (Lepistö, A. et al., 2014). Summer total organic carbon (TOC) concentrations were positively correlated with precipitation and soil moisture. While spring TOC concentrations were negatively correlated with max soil frost depth. Drought condition may also lead to higher TOC concentrations and fluxes in the coming years (1998-2000).
Similar results were found in other 30 boreal Finnish rivers (Mattsson et al., 2015). Seasonal variations of TOC were controlled by climate change and changing runoff regime. High fluxes of TOC were observed during rainfall or after snowmelt events, which led to a high flow of river channel.
In Mississippi River Basin, Dynamic Land Ecosystem Model (DLEM) shows that climate variability and extreme events (such as flooding and drought) were primary drivers of the seasonal and interannual carbon export variations (Tian et al., 2015). The maximum of carbon fluxes occurred in wet years.
As the climate keeps warming, the high-latitude regions are considered to be more sensitive to climate change. Thus riverine carbon export in such regions is dominated by climate factors. On the other hand, global climate change will increase the incidence of extreme events, which will significantly modify the riverine carbon transport process. The “pulse” and “shunt” of hydrological events may trigger a large amount of carbon release to aquatic systems (Raymond et al., 2016).
In conclusion, the climate impact on riverine carbon export exists globally. Not only in the sensitive zones, but also in general regions. Climate variations modify hydrological and biogeochemical cycles in different levels and patterns.
More information: Lepistö, A. et al. (2014). Almost 50 years of monitoring shows that climate, not forestry, controls long‐term organic carbon fluxes in a large boreal watershed. Global Change Biology, 20(4), 1225-1237, DOI: 10.1111/gcb.12491.
Mattsson, T. et al. (2015). Spatial and temporal variability of organic C and N concentrations and export from 30 boreal rivers induced by land use and climate. Science of the Total Environment, 508, 145-154, DOI: 10.1016/j.scitotenv.2014.11.091.
Raymond, P. A. et al. (2016). Hydrological and biogeochemical controls on watershed dissolved organic matter transport: pulse‐shunt concept. Ecology, 97(1), 5-16, 10.1890/14-1684.1.
Tian, H. et al. (2015). Climate extremes dominating seasonal and interannual variations in carbon export from the Mississippi River Basin. Global Biogeochemical Cycles, 29(9), 1333-1347, DOI: 10.1002/2014GB005068.