Budgets for conservative tracers are used to determine the flow through the Irish Sea and combined with avaliable data on nutrient distrubutions and imputs to estimate non-conservative nutrient fluxes. Stady state salinity and caesium-137 balances yield consistent estimates of the flow through the Irish Sea of O = 6*104 m3 s-1. Using both tracers together with a mass balance allows the inclusion of seperate diffusive flux terms and results in a diffusivity estimate of K=450 m2 s-1 and a reduced flow of O = 4*104 m3 s-1. These values are, however, sensitive to the gradinets of salinity and caesuim-127 concentration, which are not well defined by the observations.
Following the LOICZ procedures, salinity and mass balance were combined with analogous statements for dissolved inorganic phosphorus (DIP) and dissolved inorganic nitrogen (DIN), in order to asses the non-consevative process rates. With regard to phosphourus, but it was found that the Irish sea is close to balance with a slight net uptake of dissolved inorganic phosphorus, but the implied excess of uptake over release is not significant on account of uncertanties in the observations of boundary values and imputs. The DIN budget is subject to comparable uncertanties in the input data but does, however, indicate a significant imbalance with an average rate of dinitrification of the order 0.3 mol N m-2 y-1.
The implications of these budget results and their limitations are considered in relation to the application of the budgeting approch to areas with sparse data coverage. While the application of box model disiplines to conservative tracers can lead to satisfactory estimates of advective transport, the extension to non-conservative componants reqiures extensive data to adequately scecify the boundary values and imput parameters avaraged over the seasonal cycle.
Reference:- J. H. Simpson and T. P. Rippeth. Estuarine, Coastal and Shelf Sciance (1998) 47, 707-714