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

Abstract

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.

Attribution of Space‐Time Variability in Global‐Ocean Dissolved Inorganic Carbon

“…Furthermore, we do not include biogeochemical runoff (i.e., DIC and nutrients, Mayorga et al., 2010), which may be critical for accurate simulation of Arctic Ocean biogeochemistry (Le Fouest et al., 2013, 2015). Future efforts should incorporate time‐varying, point‐source global freshwater (Feng et al., 2021) and biogeochemical runoff (Resplandy et al., 2018) to improve the simulated ocean sink in coastal (Chen et al., 2013) and high‐latitude regions (Hopwood et al., 2018, 2020; Wadham et al., 2019). Finally, ECCO‐Darwin does not contain an explicit representation of bottom sediment dynamics.…”

Sea surface salinity short-term variability in the tropics

“…4a). The STV in the outflow of the Congo River near the coast of Africa is much smaller in the model than in the mooring data, possibly due to the model's use of climatological river outflow (Feng et al, 2021;Fekete et al, 2002). A similar set of maps for the RE was created for the model output but is not included here for brevity.…”

Influence of Nonseasonal River Discharge on Sea Surface Salinity and Height

“…Feng et al. (2021) has conducted a preliminary assessment of the impact of JRA55‐do discharge in various ECCO solutions of different resolutions, including LLC270. The use of higher‐resolution models would be of interest to further investigate the impacts of nonseasonal discharge on SSS and SSH near the river mouths.…”