1. General Model Information
Name: ECOHAM1 Ecological North Sea Model Hamburg
Main medium: aquatic
Main subject: population dynamics, biogeochemistry
Type of model:
Keywords: North Sea, primary production, plankton dynamics, phosphorus budget, German Bight, drift experiment,
Dr. Andreas Moll
Institut für Meereskunde
Phone: +49 (0)40 4123 2526
Fax: +49 (0)40 560 57 24
Dr. Andreas Moll
Source of abstract:
The North Sea is part of the north-west European Shelf of the North Atlantic. The circulation is
counter clockwise and shows a strong dependency on the open boundaries. Nutrient inputs from the
Atlantic, the rivers, the sediments and the Wadden Sea causes areas of high productivity. Observations show low
production zones in the stratified regions and higher production in the well- mixed areas. Although there
were big observational programms (Charnock et al., 1994; Sündermann 1994), the capacity of ship and man power
is not enough to study the different regional primary production cycles. One way out is the use
of a numerical model if all the necessary forcing is available.
The "Ecological North Sea Model, Hamburg, Version 1 (ECOHAM1)" is such a model. It was developed in the frame
of the German project KUSTOS in the working group ECOLOGICAL MODELLING as the PhD thesis of Dr. A. Moll. The focus
of my dissertation was to merge a water column model of the phytoplankton-phosphate dynamics (Radach and Moll, 1993)
with a transport model (Pohlmann, 1991) into a three-dimensional primary production model for the North Sea (Moll, 1995).
The aim was to use the model as a tool to quantify the regional productivity on an annual basis. Primary production is
limited in the model by solar radiation, the triggering nutrient phosphate and zooplankton grazing due to prescribed
monthly mean copepod biomass. The horizontal grid size of the numerical model is 20x20 square kilometer, the vertical
resolution is 5 m for the upper 50 m and increasing layer thickness below 50 m up to maximal 19 layers.
The forcing for the model is as close as possible for an actual year (1985-1994), to include the physical short term
variability, that determines the phytoplankton system. The probably most prominent feature of the North Sea dynamics
for annual studies is the residual circulation (integration over the tidal cycle). A three-dimensional baroclinic
circulation model (Pohlmann 1996) provided the daily mean velocities and eddy diffusivities that were used to advect
and diffuse the compontens of the biological model. Phosphate regeneration occured in the pelagic and through a simple
parameterization at the bottom via a benthic detritus pool. Solar radiation was calculated every 30 minutes for each
grid point by an octa-model using daily cloud data (Pätsch 1994). The under water light is modified by self-shading.
The three-dimensional model ECOHAM1 is the simplest model for the analysis of the phytoplankton dynamics, the phosphorus
transports, and the primary productivity in the North Sea. The model based on a simple phosphorus cycle, took only two pelagic
variables as phytoplankton and phosphate into account, used the simplest parameterization for pelagic and benthic regeneration,
and prescribed the copepod biomass for the trophic edge of zooplankton. The model impresses by the results despite its simplicity.
A full description of the simulation of 1986 is given in Moll (1995,1997) and a model animation is available in the
World Wide Web under http://ifmaix7.ifm.uni-hamburg.de/kino.html,
described by Luff et al. (1996).
II. Technical Information
The implementation and running of the model is described by Moll (1997) as an User Guide to ECOHAM1
III. Mathematical Information
CHARNOCK, H., Dyer, K.R., Huthnance, J.M., Liss, P.S., Simpson, J.H. und Tett, P.B. (Eds.). 1994: Understanding the North Sea System. London: Chapman & Hall. 222pp.
LUFF, R., MOLL, A. & POHLMANN, T. 1997. Animation of three-dimensional model results of the North Sea. EOS, 77, 529.
MOLL, A. 1995. Regionale Differenzierung der Primärproduktion in der Nordsee: Untersuchung mit einem drei-dimensionalen Modell. Berichte aus dem Zentrum für Meeres- und Klimaforschung; Reihe B: Ozeanographie, 19, 151pp.
MOLL, A. 1996. ECOHAM - User Guide. Technical Reports of the Institut für Meereskunde Hamburg, 39pp.
MOLL, A. 1997. Modelling primary production in the North Sea. Oceanography, 10(1), 24-26.
PÄTSCH, J. 1994: MOCADOB a Model Generating Synthetical Time Series of Solar Radiation for the North Sea. Berichte aus dem Zentrum für Meeres- und Klimaforschung; Reihe B: Ozeanographie, 16, 67pp.
POHLMANN, T. 1991: Untersuchung hydro- und thermodynamischer Prozesse in der Nordsee mit einem dreidimensionalen numerischen Modell. Berichte aus dem Zentrum für Meeres- und Klimaforschung, 23, 116pp.
POHLMANN, T. 1996: Calculating the annual cycle of the vertical eddy viscosity in the North Sea with a three-dimensional baroclinic shelf sea circulation model. Continent. Shelf Res., 16, 147-161.
RADACH, G. and MOLL, A. 1993: Estimation of the variability of production by simulating annual cycles of phytoplankton in the central North Sea. Prog. Oceanogr., 31, 339-419.
SÜNDERMANN, J. (Ed.). 1994: Circulation and Contaminant Fluxes in the North Sea. Berlin: Springer-Verlag. 654pp.
MOLL, A. (1998): Regional distribution of primary production in the North Sea simulated by a three-dimensional model, J. Mar. Syst., Vol. 16(1-2).
MOLL, A. (1997): Phosphate and plankton dynamics during a drift experiment in the German Bight: simulation of phosphorus-related plankton production, Mar. Ecol.-Prog. Ser., Vol. 156.
MOLL, A. (1995): Regional Distribution of Primary Production in the North Sea Simulated by a Three-Dimensional Model, PhD Thesis, in the DIALOG II Program.
V. Further information in the World-Wide-Web
Homepage of Andreas Moll at IFM HH: http://www.ifm.uni-hamburg.de/~moll/index.html
VI. Additional remarks
Last review of this document by:
Status of the document:
last modified by
Tobias Gabele Wed Aug 21 21:44:42 CEST 2002