| Comments |
P.376 left column bottom paragraph: "[Investigators’] best estimate of the discharge weighted average silicic acid concentration in rivers is 150µM [about 13% lower than the value calculated in the 1980s (ref 5)]. [Their] estimate takes into account updated values for the Amazon (ref 6) and for Siberian rivers (ref 7) and new data for Chinese and other rivers. [Their] value is based on 57% of the world river discharge to the world ocean and on 58% of the area with external drainage. Extrapolating the present data sets to the world river discharge (37,400 km^3/year) gives a total flux F[R](gross) of silicic acid of 5.6±0.6 Tmol (teramole=10^12moles) of Si per year. Approximately 74% of the riverine Si input is from tropical regions and 20% is from temperate regions. The ±0.6 Tmol Si/year uncertainty on the one hand reflects [their] poor knowledge of the seasonal cycle of silica in many rivers, and on the second hand it takes into account the variability in silicic acid concentrations reported during the last several decades." |