Following publications have been announced by our Institute of Coastal Systems – Analysis and Modeling. For further information please contact the marked authors and co-authors of the publications:
The lockdown of large parts of Chinese economy beginning in late January 2020 lead to significant regional changes of aerosol loads, which suggests a reduction of backscatter and consequently a regional warming in the following months. Using local data and a numerical experiment with a limited area model, we have examined how strong this response may have been. The observed (local and reanalysis) observations point to a warming of less than 1.0 K, the simulations to a warming of the order of 0.5 K. These numbers are uncertain, because of large-scale natural variability and an ad-hoc choice of aerosol optical depth anomaly in the simulation. Thus, the result was, in short, that there was actually a weak warming of a few tenth of degrees, while noteworthy changes in circulation or in precipitation were not detected. More specifically, we found that at selected central China stations temperatures were found to be higher than in previous two years. This warming goes with a marked diurnal signal, with a maximum warming in the early afternoon (06 UTC), weakest at night (18 UTC). This may be related to a general warming of large swaths of Asia (including Siberia, which is not related to local aerosol forcing). Indeed, also the stations outside the immediate strong lockdown region are showing warming, albeit a weaker one. Thus, the difference 2020 minus 2019/2018 may overestimate the effect. The ad-hoc series of numerical experiments indicates that the simulated changes are robust and suffer little from internal dynamical variability. In particular, the overall reduction of the aerosol optical depth does not lead to phases of larger intermittent divergence among the model simulations, irrespective of the aerosol load. Instead, the simulations with reduced anthropogenic aerosol load show more a mere locally increased temperature. This may indicate that the aerosol effect is mostly thermodynamic in all local air columns in the region.
Jacob, B., & Stanev, E.V. (2021): Understanding the Impact of Bathymetric Changes in the German Bight on Coastal Hydrodynamics: One Step Toward Realistic Morphodynamic Modeling. Front. Mar. Sci. 8:640214, doi:10.3389/fmars.2021.640214
The hydrodynamic response to morphodynamic variability in the coastal areas of the German Bight was analyzed via numerical experiments using time-referenced bathymetric data for the period 1982–2012. Time-slice experiments were conducted for each year with the Semi-implicit Cross-scale Hydroscience Integrated System Model (SCHISM). This unstructured-grid model resolves small-scale bathymetric features in the coastal zone, which are well-resolved in the high-resolution time-referenced bathymetric data (50 m resolution). Their analysis reveals the continuous migration of tidal channels, as well as rather complex change of the depths of tidal flats in different periods. The almost linear relationship between the cross-sectional inlet areas and the tidal prisms of the intertidal basins in the East Frisian Wadden Sea demonstrates that these bathymetric data describe a consistent morphodynamic evolutionary trend. The numerical experiment results are streamlined to explain the hydrodynamic evolution from 1982 to 2012. Although the bathymetric changes were mostly located in a relatively small part of the model area, they resulted in substantial changes in the M2 tidal amplitudes, i.e., larger than 5 cm in some areas. The hydrodynamic response to bathymetric changes largely exceeded the response to sea level rise. The tidal asymmetry estimated from the model appeared very sensitive to bathymetric evolution, particularly between the southern tip of Sylt Island and the Eider Estuary along the eastern coast. The peak current asymmetry weakened from 1982 to 1995 and even reversed within some tidal basins to become flood-dominant. This would suggest that the flushing trend in the 1980s was reduced or reversed in the second half of the studied period. Salinity also appeared sensitive to bathymetric changes; the deviations in the individual years reached ~22 psu in the tidal channels and tidal flats. One practical conclusion from the present numerical simulations is that wherever possible, the numerical modeling of near-coastal zones must employ time-referenced bathymetry data. The second, perhaps even more important conclusion, is that the progress of morphodynamic modeling in realistic ocean settings with multiple scales and varying bottom forms is strongly dependent on the availability of bathymetric data with appropriate temporal and spatial resolution.
Cirano, M., Charria, G., De Mey-Frémaux, P., Kourafalou, V.H., & Stanev, E. (2021): Coastal Ocean Forecasting Science supported by GODAE OceanView Coastal Oceans and Shelf Seas Task Team (COSS-TT) – Part II. Ocean Dynamics, doi:10.1007/s10236-021-01464-x
The regional and coastal ocean, as a complex interface area where land, hydrology, atmosphere, and ocean interact, concentrates a wide range of actors dealing with increasing socioeconomic and environmental issues. Under the pressure of the impacts of climate change, forecasting the coastal ocean remains a key challenge.
The International Coastal Ocean and Shelf Seas Task Team (COSS-TT) community within the OceanPredict program (former GODAE OceanView) fosters multidisciplinary research efforts dedicated to the coastal ocean from the land/ocean interface to the shelf/open ocean exchange regions, in support of regional and coastal ocean forecasting. Following the first topical collection (De Mey et al. 2017), this second one offers research conducted within the COSS-TT themes.
After a successful sixth international COSS-TT meeting in 2018, new steps were outlined in the integration of knowledge and capabilities in regional and coastal ocean forecasting. Two major community events defined these next steps for ocean prediction (GODAE OceanView Symposium 2019—OceanPredict’19) and ocean observation (OceanObs’19). The OceanObs’19 conference called for the global ocean observing community and users to “advance the frontiers of ocean observing capabilities from the coast to the deep ocean… at the boundaries between the ocean and air, seafloor, land, ice, freshwater, and human-populated areas” and to “improve the uptake of ocean data in models for understanding and forecasting of the Earth system”. These statements emphasize the need to improve the synergy between model and observations to develop regional and coastal ocean observing and forecasting capabilities (De Mey-Frémaux et al. 2019; Davidson et al. 2019). These 2018–2019 initiatives are well aligned to the scientific foundation of the United Nations Decade of Ocean Science for Sustainable Development (2021–2030). The COSS-TT community appears as a key actor of Ocean Decade Challenges related to regional and coastal ocean prediction (for example, CoastPredict: Observing and Predicting the Global Coastal Ocean).
In this framework, the COSS-TT community centered this second topical collection around scientific priorities in agreement with ongoing open research fields and new identified priorities (in bold are addressed priorities in this second topical collection): (a) advances in integrated, multi-platform, long-term monitoring of physical, geochemical and biological parameters in coastal regions and coastal observatories; (b) development of fine-scale coastal ocean models; (c) downscaling approaches from large-scale to regional and coastal-scale models (methods for quantitative assessment, regional and coastal array design, downscaling approaches and data assimilation and predictability in coastal ocean forecasting systems); (d) coastal-scale atmosphere-wave-ocean couplings; (e) ecosystem response to physical drivers; (f) probabilistic approaches and risk assessment in the coastal ocean (including extreme events, impact and signature of climate change, science in support of the mitigation of coastal hazards); (g) science in support of applications in coastal oceans; and (h) synergy between coastal modelling and coastal altimetry.