ALBERT

Description: If all biotic sinks of atmospheric CO2 reported were added a value of about 0.4 Gt C/yr would be found. For each category, a very high (non-conservative) estimate was used. This still does not provide a sufficient basis for achieving a balance between the sources and sinks of atmospheric CO2. The bulk of the discrepancy lies in a combination of errors in the major terms, the greatest being in a combination of errors in the major terms, the greatest being in the net biotic release and ocean uptake segments, but smaller errors or biases may exist in calculations of the rate of atmospheric CO2 increase and total fossil fuel use as well. The reason why biotic sinks are not capable of balancing the CO2 increase via nutrient-matching in the short-term is apparent from a comparison of the stoichiometry of the sources and sinks. The burning of fossil fuels and forest biomass releases much more CO2-carbon than is sequestered as organic carbon.

Description: The hypothesis that the rate of atmospheric CO2 increase has been reduced due to increased net storage of carbon in forests, coastal oceans, and the open sea, caused by eutrophication of the biosphere with nitrogen and phosphorus, is examined. The potential for carbon storage, the balance of C, N, and P, and man's influence on the forests, rivers, coastal oceans, and the open sea is studied and discussed. It is concluded that biotic carbon sinks are small relative to the rate of CO2 release from fossil fuel; therefore, storage is limited. Man has reduced the stocks of carbon held in forests and soils and there is a redistribution of C, N, and P from the land to the oceans.

Description: The biomarker composition of dissolved organic carbon (DOC) of the six largest Arctic rivers was studied between 2003 and 2007 as part of the PARTNERS Project. Samples were collected over seasonal cycles relatively close to the river mouths. Here we report the lignin phenol and p-hydroxybenzene composition of Arctic river DOC in order to identify major sources of carbon. Arctic river DOC represents an important carbon conduit linking the large pools of organic carbon in the Arctic/Subarctic watersheds to the Arctic Ocean. Most of the annual lignin discharge (〉75%) occurs during the two month of spring freshet with extremely high lignin concentrations and a lignin phenol composition indicative of fresh vegetation from boreal forests. The three large Siberian rivers, Lena, Yenisei, and Ob, which also have the highest proportion of forests within their watersheds, contribute about 90% of the total lignin discharge to the Arctic Ocean. The composition of river DOC is also characterized by elevated levels of p-hydroxybenzenes, particularly during the low flow season, which indicates a larger contribution from mosses and peat bogs. The lignin composition was strongly related to the average 14C-age of DOC supporting the abundance of young, boreal-vegetation-derived leachates during spring flood, and older, soil-, peat-, and wetland-derived DOC during groundwater dominated low flow conditions, particularly in the Ob and Yukon Rivers. We observed significant differences in DOC concentration and composition between the rivers over the seasonal cycles with the Mackenzie River being the most unique, the Lena River being similar to the Yenisei, and the Yukon being most similar to the Ob. The observed relationship between the lignin phenol composition and watershed characteristics suggests that DOC discharge from these rivers could increase in a warmer climate under otherwise undisturbed conditions.