Preprints
https://doi.org/10.5194/gmd-2020-321
https://doi.org/10.5194/gmd-2020-321

Submitted as: development and technical paper 27 Oct 2020

Submitted as: development and technical paper | 27 Oct 2020

Review status: a revised version of this preprint was accepted for the journal GMD and is expected to appear here in due course.

Improved representation of river runoff in Estimating the Circulation and Climate of the Ocean Version 4 (ECCOv4) simulations: implementation, evaluation and impacts to coastal plume regions

Yang Feng1,2,3,7, Dimitris Menemenlis4, Huijie Xue1,2, Hong Zhang4, Dustin Carroll5,4, Yan Du1,2, and Hui Wu6 Yang Feng et al.
  • 1State Key Laboratory of Tropical Oceanography, South China Sea Institute of Oceanology, Chinese Academy of Science, Guangzhou, China
  • 2Southern Marine Science and Engineering Guangdong Laboratory, Guangzhou, China
  • 3Institution of South China Sea Ecology and Environmental Engineering, Chinese Academy of Sciences, Guangzhou, China
  • 4Jet Propulsion Laboratory, California Institute of Technology, Pasadena, California, USA
  • 5Moss Landing Marine Laboratories, San José State University, Moss Landing, California, USA
  • 6State Key Laboratory of Estuarine and Coastal Research, East China Normal University, Shanghai, China
  • 7Guangdong Key Laboratory of Ocean Remote Sensing, South China Sea Institute of Oceanology, Chinese Academy of Sciences

Abstract. In this study, we improve the representation of global river runoff in the Estimating the Circulation and Climate of the Ocean (ECCO) framework, allowing for a more realistic treatment of coastal plume dynamics. We use a suite of experiments to explore the sensitivity of coastal plume regions to runoff forcing, model grid resolution, and grid type. The results show that simulated Sea-Surface Salinity (SSS) is reduced as the model grid resolution increases. Compared to Soil Moisture Active Passive (SMAP) observations, simulated SSS is closest to SMAP when using Daily, Point-source Runoff (DPR) and the intermediate resolution LLC270 grid. The Wilmott skill score, which quantifies agreement between models and observations, yields up to 0.92 for large rivers such as the Amazon. There was no major difference in SSS for tropical and temperate coastal rivers when the model grid type was changed from cube-sphere to latitude-longitude-polar-cap. We also found that using DPR forcing and increasing model resolution from the coarse resolution LLC90 grid to the intermediate resolution LLC270 grid elevates the river plume area, volume, and freshwater transport, along with stabilizing stratification and generally shoaling the mixed layer depth (MLD). Additionally, we find that the impacts of increasing model resolution from intermediate resolution LLC270 grid to high resolution LLC540 grid are regionally dependent. The Mississippi River Plume is more sensitive than others regions, possibly because the wider and shallower Texas-Louisiana shelf drives a stronger baroclinic effect, as well as relatively weak sub-grid vertical mixing and adjustment in this region. The results indicate that due to the complex bathymetry and dynamic behaviour of coastal environments, it may be challenging for spatially-unified resolution models to capture process-rich fidelity and obtain computational efficiency for coastal interfaces on a global scale. Our results offer a benchmark for representing Land-Ocean-Aquatic-Continuum (LOAC) processes in global models and data assimilation products and will help advance predictions of land-ocean-atmospheric feedbacks seamlessly in the next generation of earth system models.

Yang Feng et al.

 
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Yang Feng et al.

Data sets

Improved representation of river runoff in Estimating the Circulation and Climate of the Ocean Version 4 (ECCOv4) simulations: implementation, evaluaiton and impacts to coastal plume regions Hong Zhang https://doi.org/10.5281/zenodo.4095613

Model code and software

Improved representation of river runoff in Estimating the Circulation and Climate of the Ocean Version 4 (ECCOv4) simulations: implementation, evaluaiton and impacts to coastal plume regions Yang Feng https://doi.org/10.5281/zenodo.4106405

Yang Feng et al.

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Short summary
Simulating coastal plume regions has been improved in global ECCOv4 with a series sensitivity tests. We find modeled SSS is closer to SMAP when using daily point-source runoff as well as increase the resolution from coarse to intermediate. Besides, the plume characteristics, freshwater transport, and critical water properties are modified greatly. But these may not happen when further increase to high resolution. The study will advance modelling land-ocean-atmosphere feedback seamlessly in ESMs.