Modelling the ecosystem dynamics at the Iceland-Faeroes Front: biophysical interactions

Popova, E.E. and Srokosz, M.A. (2009) Modelling the ecosystem dynamics at the Iceland-Faeroes Front: biophysical interactions. Journal of Marine Systems, 77 (1-2), 182-196. (doi:10.1016/j.jmarsys.2008.12.005).

Abstract

The aim of this paper is to examine the impact of mesoscale variability on biological production at high latitudes: specifically, at the Iceland Faeroes Front (IFF). A high (2 km) resolution 3D primitive equation model, coupled to an ecosystem model, initialised with physical and biological observations taken at the IFF, is used for the study. This allows biological production in a realistic complex flow to be examined, in contrast to many previous studies, which have analysed more idealised situations. It is found that the observed and modelled development of the phytoplankton bloom is not significantly limited by nutrients; with grazing and light playing the dominant role in controlling the primary production. The mesocale and sub-mesoscale features have a pronounced impact on the instantaneous primary production, but their effect is variable in time and space and, when averaged over periods longer than the frontal changes timescale of a few days, has little effect on the time-mean value. Water column primary production, averaged over a period of 40 days, shows a smooth distribution with enhanced values south of the front, an area of a persistently deeper upper mixed layer. In contrast, the surface biomass distribution shows a distinctive minimum along the front and is de-coupled from the primary production. If the IFF during the euphotic stage of the bloom is typical of higher latitude frontal zones, where nutrient limitation is not a dominant factor controlling phytoplankton production, this result suggests that over 40 day and longer periods (e.g. annual) the effect of mesoscale variability, both positive and negative, may have little impact on the overall production. Thus resolving mesoscale variability in the coupled physical and biological models at high latitudes may not be as important as in the areas substantially limited by nutrient availability.

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