K. Soetaert et al., Numerical modelling of the shelf break ecosystem: reproducing benthic and pelagic measurements, DEEP-SEA II, 48(14-15), 2001, pp. 3141-3177
Citations number
60
Categorie Soggetti
Aquatic Sciences","Earth Sciences
Journal title
DEEP-SEA RESEARCH PART II-TOPICAL STUDIES IN OCEANOGRAPHY
A coupled pelagic-benthic biogeochemical model, embedded in a turbulence-cl
osure formulation is employed for the Goban Spur shelf-break area (northeas
t Atlantic). Our main objectives are to examine the impact of in situ atmos
pheric conditions on ecosystem dynamics, to reproduce biogeochemical distri
butions in the water column and the sediments, and to derive a nitrogen bud
get for the area. Given a data set of atmospheric forcing conditions at 3-h
intervals, the model successfully explains the time evolution of the tempe
rature field. Most biochemical water column properties are reasonably well
simulated, both in timing and in magnitude. Some of the short-term variabil
ity, apparent in the data, can be reproduced, suggesting that this may resu
lt from variability in the in situ atmospheric forcing. In summer, intermit
tent mixing events generate increased ammonium and nitrate concentrations i
n the upper water column, consistent with observations. These short-term nu
trient injections substantially increase euphotic zone production, mainly b
y stimulating new production. The model also reproduces a set of benthic nu
trient profiles, measured on two occasions, both qualitatively and quantita
tively. The results suggest that there is a significant variability in bent
hic properties.
A tentative nitrogen budget for the Goban Spur shelf break area is proposed
. The sediments account for about 7% of organic nitrogen respiration; about
42% occurs in the euphotic zone, and the remaining 50% takes place in the
water column below the euphotic zone. About 3% of the annual primary produc
tion of organic nitrogen is denitrified in the sediments and is replenished
from lateral sources in the model. Nitrification mainly takes place in the
water column below the euphotic zone (66%); sedimentary nitrification and
ammonium oxidation in the euphotic zone both account for 17%. Over the year
, only 55% of euphotic zone nitrogen assimilation is based on the in situ r
egenerated inorganic nitrogen, the remainder is mainly supplied by mixing f
rom below the euphotic zone, either in the form of nitrate (72%) or ammoniu
m (28%). The implications of these nitrogen pathways in the euphotic zone o
n the measured f-ratio are discussed. (C) 2001 Elsevier Science Ltd. All ri
ghts reserved.