Computing transport budgets along the shelf and across the shelf edge in the northern Benguela during summer (DJF) and winter (JJA)

Abstract

The northern Benguela shelf region supports a highly productive marine ecosystem and regional fisheries. Transport flux budgets are computed for four regions across this shelf using a regional ecosystem model based on MOM-4. The model is able to adequately simulate many of the regional circulation features associated with the northern Benguela upwelling system. The flux budget calculations are consistent with previous work in that upwelling is stronger in the south (22–25°S) during summer (DJF), whereas in winter (JJA) the two northern regions (16–19°S, 19–25°S) showed stronger regional upwelling. Based on the model results, it is suggested that an increase in off-shelf transport through the mixed layer as well as a diminishing influence from the poleward undercurrent during winter (JJA) accounts for the latter, while the strengthened poleward undercurrent combined with a strong on-shelf transport during summer could account for the increased upwelling between 22 and 25°S. These flux budget results may provide an important platform for the quantification of nutrient and oxygen budgets across this ecosystem in the future.