Predicted terrestrial carbon loads to lakes under future climate scenarios

Background/Question/Methods

Riverine transport of organic carbon to the ocean is a significant shunt in the global carbon cycle and the concentration of total organic carbon (TOC) in rivers and lakes is vital for ecosystem properties and water quality for human use. Here we address the question: How will the changing climate affect the concentration and flux of TOC?

By use of a large dataset comprising chemical variables and detailed catchment information in ~1000 Norwegian pristine lakes covering a wide climatic range, we were able to predict total organic carbon concentrations with high accuracy. We further predict future TOC concentrations, using a “space-for-time” approach and a downscaled, moderate, climate change scenario.

  Results/Conclusions

Northern, boreal regions likely will experience strong increases in organic carbon export from catchments to surface waters.

The study suggests that the median concentrations of organic carbon (OC) in Norwegian lakes will increase by 65 %, from the current median of 2.0 to 3.3 mg CL^-1. This is a long-term effect, primarily mediated by increased terrestrial vegetation cover in response to climate change. Increases in lake DOC were inversely related to projected changes in runoff, yielding an estimated 28% overall increase in DOC export.

The increase OC will have severe impacts on food-webs, productivity and human use. Given the robustness of the estimates and the general applicability of the parameters, we suggest that these findings would be relevant to boreal areas in general.