Günther Radach

University of Hamburg | UHH · Institut für Meereskunde (IMee)

The capability of the ocean to draw down carbon from the atmosphere and to export it to great depths depends not only on the biological production in the euphotic zone but as well on the respiratory processes within the euphotic zone and in the mesopelagic zone. But in contrary to the marine carbon fixation where due to the available satellite- bas...

We determined the monthly and annual riverine freshwater, nitrogen (N) and phosphorus (P) loading into the North Sea from Belgium, The Netherlands, and Germany for the years 1977–2000. An average of 133 km3 yr−1 of the 309 km3 yr−1 precipitation into the watershed is carried by the rivers into the sea. Total freshwater discharge fluctuates with a s...

The aim of this review is to provide an overview of the status of validation of eleven biogeochemical and ecological models of the greater North Sea (COHERENS, CSM-NZB, DCM-NZB, DYMONNS, ECOHAM, ELISE, ERSEM, FYFY, GHER, NORWECOM, POLCOMS-ERSEM) showing the realism achieved as well as the problems hindering a better degree of validity of the models...

The state-of-the-art in modelling the marine ecosystem of the greater North Sea is reviewed, providing an overview especially about three-dimensional models that describe and predict how the marine ecosystem of the greater North Sea area functions and how concentrations and fluxes of biologically important elements vary in space and time, throughou...

The impact of sea surface temperature and wind stress on primary production, export production, and CO 2 air–sea exchange at the ESTOC station (291N, 15.51W) north of the Canary Islands is the focus of our investigations. A one-dimensional carbon and nitrogen cycling model was applied for the 10-year period 1987–1996. The simulation results compare...

The reaction of the population of Calanus finmarchicus to relatively extreme annual cycles of weather in the North Sea was investigated by one-dimensional model simulations. A population dynamics model for C. finmarchicus was coupled with a physical and a biological upper-layer model for phosphate, phytoplankton and detritus to simulate the develop...

Radach, G. 1998. Quantification of long-term changes in the German Bight using an ecological development index. – ICES Journal of Marine Science, 55: 587–599. During recent decades, remarkable long-term changes have taken place in many coastal ecosystems of north-west European shelf seas. These changes have been described in many papers, but an ove...

The mean annual cycle of the net energy flux through the sea surface and of the heat storage are investigated in detail using observations of the Light Vessel LV Elbe 1 for the period 1962-1986 in the German Bight and at Ocean Weather Ship OWS Famita for the period 1965-1978 in the central North Sea. The investigation confirms the general geographi...

The general characteristics of the continental coastal zone, with nutrient concentrations, primary production and biomass high near the coast but decreasing with distance from the coast, are simulated by a box-refined version of the ecosystem model ERSEM. Aggregated model results compared to the literature as well as to two different three-dimensio...

The ecosystem model ERSEM II has been used to hindcast the development of the ecosystem of the North Sea during the years 1955 to 1993. The simulation was driven by the box-aggregated output from a general circulation model of the North Sea of corresponding duration; radiation, river inputs, atmospheric input and boundary conditions at the borders...

A large amount of nutrient and chlorophyll data from the North Sea were compiled and organised in a research data base to produce annual cycles on a relatively fine spatial resolution of 1° in each horizontal direction. The data originate from many different sources and were partly provided by the ECOMOD data base of the Institut fur Meereskunde in...

A one-dimensional model of the pelagic ecosystem was developed and applied to the spring bloom in the northern North Sea making use of the data set obtained during the Fladenground experiment FLEX '76. The physical submodel is the second-order turbulence closure model of level 2 type developed by Mellor and Yamada (1974, 1982). The biological submo...

From November 1989 to March 1992, the German Federal Maritime and Hydrographic Agency (BSH) carried out surveys of major physical and chemical parameters in the German Bight in connection with the TUVAS project (‘Transport, transfer and variability of contaminants and nutrients in the German Bight’). During roughly the same period, the interdiscipl...

For the German Bight a cadmium budget has been set up, compiling data from several interdisciplinary experiments during the last years (ZISCH, PRISMA, KUSTOS and TUVAS). The largest pools are contained in the sediments of the German Bight. The advective transports carry large amounts of cadmium through the German Bight. It seems that less cadmium l...

An overview is presented of the North-West European Shelf Programme. including objectives, aspects of database management, time-series analysis, and analysis of spatial distribution of various parameters. Examples of some results are given. (C) 1996 International Council for the Exploration of the Sea

Mean seasonal cycles in time series of salinity, nutrients, chlorophyll and Zooplankton at 8 locations on the Northwest-European shelf were analysed in relation to each other and with respect to their timing and magnitude during a period most of the time series overlap (1980-1984). A relatively late spring bloom in April/May with low chlorophyll va...

In this study an overview is given of the time series analysis of monthly mean data of physical, chemical and biological parameters. The time series are available at eight locations on the Northwest European Shelf. The integrated evaluation of those time series gives the opportunity to look for connections between the different parts of the shelf....

During the years 1993 to 1996 the MAST project “Northwest European Shelf Programme (NOWESP)p ]During the years 1993 to 1996 the MAST project “Northwest European Shelf Programme (NOWESP)” has compiled most available observations for nine key state variables, namely temperature, salinity, phosphate, nitrate, nitrite, ammonia, silicate, suspended part...

Fluxes of nutrients (dissolved phosphate, nitrate and silicate) from the Atlantic Ocean (Northern Atlantic and Channel) and Skagerrak to the North Sea were calculated for the upper 30 meters and for the total water depths. Monthly average water flows and their standard deviations were taken from the model calculations of the If M (HAMSOM model) and...

NOWESP has compiled a vast quantity of existing data from the north-west European shelf. Such a focused task is without precedence. It is now highly recommended that one, or a few national and international data centres or agencies should be chosen and properly supported by the E. U., where all available observational data, incl. the NOWESP data, a...

The seasonal cycles of sea surface temperature and other parameters at eight sites on the Northwest European Shelf show an interannual variability in the range of years to decades for the years 1960–1995. Statistical methods like spectral analysis or phase diagrams prove that only a few frequency peaks beyond the annual cycle are of real significan...

A certain class of pelagic ecosystem box models uses the mixed layer depth as the main physical forcing. This paper investigates the influence of the definition and derivation of the mixed layer depth on the simulation results. For this investigation the model of Fasham et al. (1990) (Journal of Marine Research, 48, 591–639) is used to simulate the...

A population dynamics model for Calanus finmarchicus was coupled with a one‐dimensional physical and biological upper layer model for phosphate and phytoplankton to simulate the development of the successive stages of Calanus and study the role of these stages in the dynamics of the northern North Sea ecosystem. The copepod model links trophic proc...

A concise overview is given of the North-West European Shelf Programme (NOWESP), concentrating on the philosophy of the project and the coherency of the various contributions to reach the objectives of the project. A short reference is made to all papers, mentioning the new findings. Recommendations for future management of large data sets and for...

Research carried out within the framework of the MAST project NOWESP (North-West European Shelf Programme) was based on a multi-parameter data set of existing marine data, relevant for estimating trends, variability and fluxes on the Northwest European Shelf. The data sets were provided by the partners of the project. Additional data sets were obta...

In the NOWESP project historical data from the Northwest European Shelf were compiled and evaluated to estimate the variability and trends in water movements, concentrations of dissolved and particulate constituents, and fluxes of the relevant substances across the shelf. As an integral part of the project, the NOWESP Research Data Base was created...

The rationale is given of how the gross physical features of the circulation and the stratification of the North Sea have been aggregated for inclusion in the ecosystem box model ERSEM. As the ecosystem dynamics are to a large extent determined by small-scale physical events, the ecosystem model is forced with the circulation of a specific year rat...

Nutrient dynamics for phosphate, nitrate, ammonium and silicate have been simulated with ERSEM, the European Regional Seas Ecosystem Model. From the model results budgets for the dissolved inorganic nutrients and the corresponding particulate fractions have been calculated. The annual cycles of the nutrients phosphate and silicate compare quite wel...

In this Chapter we will show how a “simple model” of the phytoplankton dynamics is able to give valuable insight which may serve for interpretation of data and for planning of further experiments. We will take the ZISCH North Sea data to give an example of interpretation.

A physical and a biological one-dimensional upper layer model for the stimualtion of the annual cycles of both the physical and the phytoplankton dynamics, are used to estimate the annual primary production in the central North Sea. The simulations are driven with actual 3-hourly meteorological standard observations and estimated radiation data for...

A large number of weight values for the different stages of Calanus finmarchicus permits us to show that no overlapping takes place between ranges of structural weights (i.e. without storage) of successive copcpoditc stages at a given temperature and that structural growth is exponential at all temperatures. Nevertheless, in each instar, weights ar...

In the North Sea advective transports are not negligible. Nevertheless, physical properties like sea surface temperature (SST) can be hindcasted with sufficient precision by vertical process water column models. Annual cycles of SST in the southern, central, and northern North Sea can be simulated using physical upper layer models with relatively s...

Recent developments in high temperature catalytic oxidation techniques (Sugimura and Suzuki, 1988) have raised a number of questions about dissolved organic carbon (DOC). Several key aspects of the DOC pool are still unknown, including its size (Martin & Fitzwater, 1992; Ogawa & Ogura, 1992) and turnover rates (Kirchman et al., 1991; Kepkay & Wells...

The functioning of the German Bight ecosystem is determined largely by nutrient fluxes in and out of the system, namely by the advection of nutrients from the central and southern North Sea, including the influence of the Rhine River; by nutrient inputs through direct continental river runoff into the German Bight (Elbe, Weser, and Ems rivers); and...

Based on recently published data on cadmium concentrations in the different compartments of the North Sea ecosystem, i.e. water, suspended particulate matter, biota and sediments, and based on 3D circulation simulations, a (preliminary) mass balance for cadmium in the North Sea was worked out by estimating the contents in the compartments as well a...

For horizontally homogeneous barotropic conditions, nonrotational tidal (M2) cycles of hydrodynamic fields are computed by the standard k-ε turbulence model for large Reynolds numbers. The characteristic tidal time lag between current and turbulent kinetic energy at the flow reversal turned out to be close to measurements in shallow tidal rivers re...

North Sea ecosystem models published in accessible literature are partitioned into groups with respect to their emphasis on significance and detail of different trophic levels of the ecosystem. These subsets are treated separately in the three main chapters, which deal with relationships with physical dynamics, lower trophic level interactions and...

The model for global radiation at the sea surface proposed by Dobson and Smith was tested for the Inner German Bight, North Sea with an 18-year time series of 3-hourly measurements of cloudiness and daily global radiation. The model, with unchanged parameters that were originally derived for oceanic stations, is suitable for use in coastal seas and...

Monitoring data of the six heavy metals cadmium, copper, iron, manganese, nickel and mercury measured in the German Bight between 1980 and 1985 have been pooled and evaluated by statistical means. The analysis of the spatial distributions was made in horizontal as well as in vertical dimensions. The data have been arranged in classes according to:...

Long-term series of meteorological standard observations at LV ELBE 1, together with those of temperature, salinity, plant nutrients and phytoplankton biomass at Helgoland Reede in the German Bight, are investigated with respect to the changes of the annual cycles during the 23 years from 1962 to 1984. Most meteorological and oceanographic paramete...

Physical processes are important for plankton dynamics on many space and time scales. Based on model simulations, the effect of stratification for the formation of plankton blooms is discussed. Annual phytoplankton simulations incorporate the effect of stratification on algal blooms by a generalized time dependent Sverdrup approach. The simulations...

At a fixed station in the northern North Sea the occurrence of herbivorous and omnivorous zooplankton and the changes in its vertical distribution were studied over 2 1/2 months during the spring phytoplankton bloom in 1976. From a sporadical distribution of relative few plankton organisms in the mixed water column at the end of winter, in the midd...

To study the flow of matter in marine ecosystems means firstly to find out the most important paths of transport to higher trophic levels of the food web, and secondly to quantify the transports. It is critical for these systems, whether primary production is channelled upwards in the food web only through herbivorous zooplankton, or whether part o...

Much of the literature of fisheries science is concerned with the management of single-species populations of fish. But most of the world’s fish populations do not live in isolation from other fish populations. On the contrary, most live in association with many other species, and many are caught in association with others in various kinds of fishi...

The working group adopted a simple definition of herbivores: “Herbivores are simply those animals whose feeding mechanisms and life history strategies favour the ingestion of living autotrophic cells”.

The aim of the modelling approach to the data of the Fladen Ground Experiment (FLEX ‘76) is to contribute to the understanding of the dynamics of the spring phytoplankton bloom in relation to the formation of the seasonal thermocline in the northern North Sea. The simulation model synthesizes hypotheses about the functioning of several important pr...

The effects of vertical eddy viscosity on simple mesoscale waves in the ocean are studied. The decay of Rossby waves is investigated by one-dimensional depth-dependent linear stability problems which are derived for the interior non-viscous or viscous quasigeostrophic flow using parameterizations of the top and bottom boundary layers corresponding...

The objective of this study is to investigate the mechanisms behind the re- gional and seasonal patterns of surface DIC (dissolved inorganic carbon) concentra- tions in the North Atlantic for a late year in the 20th century. A basin-wide biogeo- chemical D model could reproduce the main features of monthly mean near-surface DIC concentrations deriv...