Wednesday, April 04, 2007

Lakes and reservoirs underestimated carbon sinks.

As we have mentioned here, the fundamental errors of quantification in the Global carbon cycle by the IPCC, and the Kyoto mechanisms to quantify anthropogenic land use change and mitigation, have lead to flawed assumptions by policymakers.

The global transport of carbon (partly in the form of CO2) among the large reservoirs is called the global carbon cycle. Carbon dioxide emitted into the atmosphere together with the uptake by the terrestrial sinks and oceans governs the carbon dioxide content observed by the global sampling networks. Currently 40-60% of the anthropogenic released carbon dioxide remains in the atmosphere. Our current knowledge is ambiguous whether the rest of the CO2 is being detached by oceans or by terrestrial sinks (soil or vegetation) (Baldocchi et al., 1996) or the sequential cycle is quantified completely.

Based on measurements and model calculations, concluded that there should be a large CO2 sink in the Northern Hemisphere to balance the observed global carbon budget. Some of these papers suggests that this "missing sink" ( 1.4 Gt carbon/year after Schimel, 1995) must be the terrestrial biosphere in the northern temperate latitudes. The 3D atmospheric transport models used for global carbon cycle studies are using CO2 concentration time series measured by the global sampling network (Tans et al., 1996) as input data. The sources or sinks are inferred from the generally small horizontal concentration gradients of CO2 measured by the existing sparse measuring network. Thus locating, characterizing and quantifying the ``missing sink'' requires additional, very high precision CO2 measurements in the relevant geographical regions

In a recent paper published on line we find the cycling of C by inland waterways is substantially more then thought. This has important findings for those arguing against reservoirs and dam catchment’s activities, or indeed irrigation activity, which as we already have observed lowers the regional temperatures.

On Earth, carbon is continually cycling through terrestrial systems, inland waters, the ocean, and the atmosphere. Until little over a decade ago, when calculating the terrestrial component of the global carbon budget, inputs were limited to the ocean and the land. Because inland water bodies cover less than 1% of the Earth’s surface, it was assumed that their contribution was inconsequential.

This view was recently challenged in an Ecosystems paper highlighting the findings of a National Center for Ecological Assessment and Synthesis analysis. Carried out by a team of international scientists, including Institute of Ecosystem Studies Biogeochemist Dr. Jonathan J. Cole, the paper’s senior author, the group reveals that inland water bodies are important areas of terrestrial carbon transformation that deserve inclusion in global carbon cycle assessments.

Take, for instance, the role played by lakes and reservoirs. By burying carbon in their sediments, lakes serve as important regional carbon stores. In aggregate, lakes play a significant role in the global carbon budget. On an annual basis, they bury 40% as much carbon as the ocean. Reservoirs, which are steadily increasing in number, bury more organic carbon than all natural lake basins combined and exceed oceanic organic carbon burial by more than 1.5-fold.

These findings debunk the concept that inland waters are inconsequential when accounting for the global carbon budget; instead they are places of complex and active carbon transformation. The take home message from the authors: "Continental hydrologic networks, from river mouths to the smallest upstream tributaries, do not act as neutral pipes— they are active players in the carbon cycle despite their modest size."


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