Preliminary annual estimates of regional nitrate supply in the southern Benguela using coastal sea level fluctuations as a proxy for upwelling

Abstract

First-order estimates of annual potential new production are presented for the southern Benguela upwelling region for the decade of the 1980s. Using satellite images of sea surface temperature and a 10-year record of sea level, preliminary estimates of potential new production for 12-month periods between May and June inclusive were made for the period 1980/81 to 1989/90. The annual period was selected so as to encompass the upwelling season (austral spring and summer) and to optimize the interaction between
upwelling and biological response. The range of these estimates was 5.16 × 1013 to 6.19 × 1013 gC.year–1, with a mean of 5.60 × 1013 gC.year–1. The trend in the estimates was found to be consistent with related variables
and their validity, in terms of order of magnitude, was tested against 15NO3-N uptake rates measured in the southern Benguela and scaled to a regional level. In addition, they were subjected to an intra- and interregional
comparison.