Research Topics

Picture of the modular model system GCOAST (Image: HZG)

Framework GCOAST (Geesthacht Coupled cOAstal model SysTem)

The GCOAST (Geesthacht Coupled cOAstal model SysTem) is built upon a flexible and comprehensive coupled model system integrating the most important key components of the regional and coastal systems and, additionally, allowing to include information from observations. In total it encompasses three major model pathways:

  • atmosphere-ocean-waves interactions
  • the dynamics and fluxes at the land-sea transition
  • the coupling of the marine hydrosphere and biosphere

GCOAST is not an earth system model that simulates all aspects of the earth system as one allembracing model but a modular system of different models each developed for a specific earth system compartment. Based upon a specific scientific question different models from GCOAST can be selected for use. These models can be plugged together by couplers (OASIS3-MCT, ESMF, FABM) at different levels of coupling granularity, which handle the exchange of information between model combinations, individual models, and processes.

GCOAST combines the efforts of a number of working groups at the Institute for coastal Research. The groups from the research unit “System Analysis and Modelling” develop and apply different GCOAST model components for their scientific research. The group “Regional Atmospheric Modelling” uses and develops the regional atmospheric models COSMO-CLM and ICON-CLM which includes already a component for Land/Surface/Soil and Lakes, and the hydrological discharge model HD. The group “Hydrodynamics and Data Assimilation” contributes to the ocean models NEMO and SCHISM, wave model WAM and drifter models. The group “Matter Transport and Ecosystem Dynamics” utilizes and develops the ecosystem model ECOSMO as well as models for marine chemistry and benthic processes. The group “Ecosystem Modelling” develops and applies multi-level coupling infrastructure through ESMF and FABM, ecological models for suspended matter, the pelagic and benthic domains (MAECS, MSPEC) and the sea floor OMEXDIA for near-shore and estuarine research.

Examples for application of GCOAST

Triggered by the need for novel modelling capacity, GCOAST system is designed to handle cross compartment fluxes of water and energy between the atmosphere and ocean thought the dynamic wave interface, dynamics and biogeochemistry in the land ocean transition and marine ecosystems and benthic-pelagic coupling, transport and transformation of environmental pollutants.

Wiese et al. (2019) studied the effects of the coupled COSMO-CLM/WAM models on the atmospheric planetary boundary layer. The improved prediction of wave height and surface winds by applying a coupled atmosphere/wave model was shown by Wahle et al. (2017). It has been demonstrated that coupling between waves and ocean models increase the sea level in the coastal areas (Staneva et al., 2017, Ponte et al., 2019), changes sea temperature and salinity (Alari et al., 2016, Schollen et al., 2017, Staneva et al., 2018), mixing and ocean circulation (Staneva et al., 2017), upwelling (Wu et al., 2019), leading to better agreement with in-situ and satellite measurements (Staneva et al., 2017, Cavaleri et al., 2018; Staneva et al., 2019).

Comparisons with available atmospheric and oceanic observations also showed that the use of the coupled system reduces the prediction errors in the coastal ocean especially under severe storm conditions (Mey-Frémaux et al., 2019, Staneva et al., 2019, Lewis et al., 2019) and is of crucial importance for drifter simulations (Staneva et al., 2018). Studies concerning the internal variability when coupling atmosphere, hydrology, ocean and sea ice were undertaken by Ho-Hagemann et al. (2019, submitted). In a recent study on biogeochemical processes in the Elbe estuary, Pein et al. (2019) demonstrated the systems capacity to simulate processes in a coupled hydrosphere-biosphere modeling framework. Multi-model couplings developed by Lemmen et al. (2018) have been, e.g., applied for assessing ecosystem impacts of offshore wind farms (Slavik et al. 2019).