Jh. Harms et al., Modelling the Northeast Atlantic circulation: implications for the spring invasion of shelf regions by Calanus finmarchicus, ICES J MAR, 57(6), 2000, pp. 1694-1707
The appearance in spring of the copepod Calanus finmarchicus in continental
shelf waters of the northeastern Atlantic has been hypothesized to be main
ly attributable to invasion from across the continental slope rather than i
n situ overwintering. This paper describes the application of a hydrodynami
c circulation model and a particle-tracking model to Northeast Atlantic wat
ers in order to assess the influence of the flow field and ascent migration
parameters on the spring invasion of C. finmarchicus. For hydrodynamic mod
elling, the Hamburg Shelf-Ocean Model(HAMSOM) was applied to the North Atla
ntic and Nordic Seas and forced with daily mean atmospheric data. Simulated
flow fields from HAMSOM serve as forcing functions for a particle-tracking
model of the same region. The robustness of the simulated shelf invasion i
n three target boxes of the Northeast Atlantic Shelf was assessed by means
of a sensitivity analysis with respect to variations in four key migration
parameters: overwintering depth, ascent rate. ascent timing, and depth duri
ng residence in upper layers. The invasion of the northern North Sea and No
rwegian Shelf waters is more sensitive to ascent migration parameters than
invasion of the Faroese Shelf. The main reason for enhanced sensitivity of
the North Sea invasion is the time and space-dependent flow structure in th
e Faroe-Shetland Channel. Dense aggregations of overwintering C. finmarchic
us are found in the Channel, but because of the complex Row field only a pr
oportion of the overwintering stock has the capacity to reach the North Sea
. (C) 2000 International Council for the Exploration of the Sea.