GCOAST Model System

ICON-Coast

The global coastal ocean forms a dynamic and complex transition zone between the land and ocean. It regulates the transport and turnover of biogeochemical substances, which enter the open ocean through river inputs, groundwater exchange, coastal erosion, and flooding. Bacterial or biological decomposition, advective transport, or long-term storage in sediments influence both global distributions and budgets as well as the integrity of marine ecosystems. Global Earth system models have not been able to adequately represent coastal-specific processes so far. With the new model ICON-Coast, it has been possible to represent the global coastal ocean at a higher resolution and, for the first time, to incorporate physical and biogeochemical transformation processes in shallow shelf and marginal seas. This allows us to investigate the function of coastal seas at the global scale by integrating them into global Earth system research.

ICON_ECOSMO refers to the coupling of the ocean model ICON-O (Korn et al. 2022) with the biogeochemical model ECOSMO-E2E (Daewel & Schrum 2013). The FABM 1.0 framework (Bruggeman & Bolding 2014) is used for this purpose. The aim of this modelling approach is to produce regional high-resolution hydrographic-biogeochemical simulations that are embedded in a global simulation using an irregular unstructured ICON grid.

ICON_ECOSMO_MERCY is the combination of the model ICON_ECOSMO described above and the marine chemical transport model MERCY v2.0 (Bieser et al. 2023) which simulates the Hg and MeHg speciation , transport, transformation, and bioaccumulation in the marine environment with the ultimate goal of linking anthropogenic Hg releases to MeHg in seafood.

Icon Mesh Splitter (IMS, Logemann & Klockmann 2024) is a Linux console tool for generating computational grids for ICON-Coast, ICON_ECOSMO or ICON_ECOSMO_MERCY. Global grids are generated that are based on the ETOPO1 topography (Amante & Eakins 2009). IMS always starts with a uniform icosahedral grid of the global sphere with a resolution of about 160 km. The user defines a global matrix of desired grid refinements, which can instruct IMS to refine the grid regionally, creating an irregular grid. In addition, the user can activate a "coastal refinement" for the different refinement levels.

NEMO

In various GCOAST setups, the ocean and sea ice are simulated with the Nucleus for European Modelling of the Ocean (NEMO; Madec et al., 2017), and LIM3 sea-ice dynamics and thermodynamics package. In GCOAST AHOI 1 and 2 as well as in the CoastalFutures project, version 3.6 is used.

ECOSMO E2E

Grafics: H. Weidemann/ Hereon

To address food web related questions in the Baltic Sea, we developed the 3d coupled ecosystem model ECOSMO E2E (Daewel and Schrum, 2016), which is an NPZD-Fish modelling approach that bases on the ecosystem model ECOSMO II (Daewel and Schrum, 2013). The model represents both fish and macrobenthos as functional groups that are linked to the lower trophic levels via predator-prey relationships (Figure). The model allows investigating bottom-up impacts on primary and secondary production and cumulative fish biomass dynamics, but also bottom-up mechanisms on the lower trophic level production. mehr dazu: https://www.hereon.de/institutes/coastal_systems_analysis_modeling/matter_transport_ecosystem_dynamics/models/index

Individual-based models of larval fish

Grafics: Daewel et al. 2015 (Fig. 2)

The early-life history of marine fishes is one of the main determinants of the recruitment variability and an important bottleneck in the adaptation of fish populations to changing climate and anthropogenic disturbances. Individual-based models (IBMs) that simulate the behavior of an individual fish and its interactions with the biotic and abiotic environment are widely used in fisheries science to study starvation, predation and dispersal mortality of fish early-life stages. In CoastalFutures, we are using stand-alone or coupled larval IBMs to better understand how natural and anthropogenic stressors affect mortality and survival of larval fish in the vicinity of the spawning and nursery areas of the commercially important fish species in the North and the Baltic Seas. Read more: https://www.hereon.de/institutes/coastal_systems_analysis_modeling/matter_transport_ecosystem_dynamics/models/index.php.de

MOSSCO-MAECS

The Modular System for Shelves and Coasts (MOSSCO, Lemmen et al. 2018) describes the near coastal and dry-falling bentho-pelagic system with GCOAST components SCHISM or GETM, FABM-coupled OMExDia biogeochemistry and trait-based plankton ecology MAECS. The strengths of this modeling system are the flexible and equitable coupling of many different components across domain interfaces leveraging ESMF and the adaptive description of physiological and behavioural sea life traits. It has been applied to represent successfully trophic cascading across the North Sea coastal gradient (Wirtz 2019, Xu et al. 2020), to describe the ecosystem impact of epistructural and epibenthic filtration (Lemmen 2018, Slavik et al. 2019).

The accumulation of chlorophyll-a concentration near the shore seen from satellites (ESACCI) is reproduced by MAECS thanks to resolving photoacclimationand the light dependence of top-down grazing; small planktivorous fish hides in turbid waters, what suppresses zooplankton. The time series shows short-term and long-term fluctuations in nitrate at LTER station Helgoland. Observation by AWI are mostly captured due to coupling to a realistic physical model (here GETM) and resolving changes in ecophysiologicalcommunity traits as well as temperature dependent food-web effects. (Wirtz 2019). Graphics: Wirtz/Hereon

OSMOSE Model

OSMOSE is a multi-species and individual-based model (IBM) for fish species. Here, the model represents 12 species (pelagic and benthic: Sole, Haddock, Sprat, Saithe, Dab, Sandeed, Herring, Plaice, Cod, Pout, Gurnard and Whiting) of economic interest in the North Sea. The model assumes opportunistic predation based on spatial co-occurrence and size adequacy between a predator and its prey. OSMOSE represents major processes of fish life cycle (growth, reproduction, migration, and mortality). Fish individuals are grouped into schools or ‘super-individuals’ which are characterized by their size, weight, age, species, and geographical location. OSMOSE is a 2D model (horizontal representation) which have a resolution of 10km grid on the horizontal and run with a two-week’s time step. To provide prey field to the fish, OSMOSE is coupled to hydrodynamic and biogeochemical models, here NEMO-ECOSMO. In output, a variety of size-based and species-based ecological indicators are produced at different levels of aggregation: at the species level (e.g. mean size, mean size-at-age, maximum size, mean trophic level, within-species distribution of trophic level), and at the community level (e.g. slope and intercept of size spectrum, Shannon diversity index, mean trophic level of catch). Read more: https://osmose-model.org/

TOCMAIM (Total Organic Carbon–Macrobenthos Interaction Model)

The model has been applied to the North Sea to investigate the spatio-temporal variability of macrobenthic biomass, sediment OC storage, benthic oxygen consumption and human impacts on sedimentary carbon storage. © 2024, Zhang, W. et al., CC BY 4.0. https://doi.org/10.1038/s41561-024-01581-4

TOCMAIM (Total Organic Carbon–Macrobenthos Interaction Model) is developed at Hereon to resolve the interactions between benthic fauna and early diagenesis of organic carbon (OC). Sedimentary OC is divided into three pools depending on its degradability: labile, semi-labile, and refractory. With a Neumann boundary condition of OC fluxes at the sediment–water interface calculated by the pelagic model component (ECOSMO), sedimentary OC content is solved by a mass balance equation in TOCMAIM, taking into account the impacts of oxygen-dependent first-order degradation, macrobenthic uptake, respiration and bioturbation. Temporal change of macrobenthic biomass is calculated on the basis of food availability in the form of OC, temperature, oxygen, and mortality caused by predation and bottom trawling. Bioturbation scales with macrobenthic biomass and is inversely related to local OC resource. Oxygen penetration depth is jointly determined by physical (sediment permeability, porosity, bedform and bottom current velocity) and biogeochemical (carbon remineralization) parameters. TOCMAIM is integrated into the sediment module (MORSELFE) of the 3D hydro-morphodynamic model SCHISM, so that the information of erosion/deposition calculated by the hydro-morphodynamic model can be directly transferred to TOCMAIM to update the fluxes

Global Hydrology Model (HydroPy)

HydroPy (Stacke and Hagemann, 2021) is a state-of-the-art global hydrology model for which no model calibration was performed for its setup. HydroPy usually requires daily input fields of precipitation, 2m temperature, downwelling shortwave and longwave radiation, 2m specific humidity, surface pressure and 10m wind from the respective forcing dataset. However, it also comprises an option to use only precipitation and 2m temperature forcing. Recently it has been equipped with an initial implementation to calculate riverine nitrogen loads.

The model code and more information are available at https://doi.org/10.5281/zenodo.4541380 https://doi.org/10.5281/zenodo.4541380

Hydrological Discharge (HD) Model

The Hydrological Discharge (HD) model (Hagemann et al., 2020) is a well-established river routing model that is implemented in a range of global and regional model systems. As noted in Hagemann et al. (2020), no river specific parameter adjustments were conducted in the HD model to enable its applicability for climate change studies and over catchments, where no daily discharges are available at a downstream station. To simulate discharge with the HD model, it uses the daily or sub-daily input fields of surface and subsurface runoff that need to be provided by the driving model, a hydrological model such as HydroPy, or the land surface scheme of regional climate model, e.g. CCLM or ICON-CLM. The HD model can be run on fixed global regular grids of 0.5° or 1/12° horizontal resolution, and on regional domains at 1/12° resolution. For regional applications over Europe, e.g. within GCOAST-AHOI 1 and 2, it was applied over the European domain, which covers the land areas between -11°W to 69°E and 27°N to 72°N. The HD model is also included as an external component in the ICON open source release 2024.10 (ICON partnership, 2024).

Recently, the HD model has been equipped with a framework to transport biogeochemical compounds and to deliver the respective riverine loads into the ocean. In addition to the freshwater inflow, these comprise, e.g., nitrogen, phosphorus (Elizalde et al, submitted) or PFAS (Simon et al., submitted).

The model code and more information are available at https://doi.org/10.5281/zenodo.4893098. https://doi.org/10.5281/zenodo.4893098