Impact of Satellite Remote Sensing Data on Simulations of Coastal Circulation and Hypoxia on the Louisiana Continental Shelf

Abstract

Abstract:We estimated surface salinity flux and solar penetration from satellite data, and performed model simulations to examine the impact of including the satellite estimates on temperature, salinity, and dissolved oxygen distributions on the Louisiana continental shelf (LCS) near the annual hypoxic zone. Rainfall data from the Tropical Rainfall Measurement Mission (TRMM) were used for the salinity flux, and the diffuse attenuation coefficient (Kd) from Moderate Resolution Imaging Spectroradiometer (MODIS) were used for solar penetration. Improvements in the model results in comparison with in situ observations occurred when the two types of satellite data were included. Without inclusion of the satellite-derived surface salinity flux, realistic monthly variability in the model salinity fields was observed, but important inter-annual variability was missed. Without inclusion of the satellite-derived light attenuation, model bottom water temperatures were too high nearshore due to excessive penetration of solar irradiance. In general, these salinity and temperature errors led to model stratification that was too weak, and the model failed to capture observed spatial and temporal variability in water-column vertical stratification. Inclusion of the satellite data improved temperature and salinity predictions and the vertical stratification was strengthened, which improved prediction of bottom-water dissolved oxygen. The model-predicted area of bottom-water hypoxia on the Louisiana shelf, an important management metric, was substantially improved in comparison to observed hypoxic area by including the satellite data.

Eutrophication‐induced acidification of coastal waters in the northern Gulf of Mexico: Insights into origin and processes from a coupled physical‐biogeochemical model

“…Setup and validation of the circulation model are described in detail by Hetland and DiMarco [, ]. Satellite‐derived attenuation coefficients for shortwave radiation [ Schaeffer et al ., ; Ko et al ., ] are used to simulate realistic bottom boundary layer thicknesses in the circulation model [ Fennel et al ., ]. The circulation model is coupled with the pelagic N‐cycle model of Fennel et al .…”

Modeling Spatiotemporal Patterns of Ecosystem Metabolism and Organic Carbon Dynamics Affecting Hypoxia on the Louisiana Continental Shelf

“…The NCOM hydrodynamic model used with CGEM accurately simulates sea surface elevation, salinity, water temperature, and density (sigma‐t) which are key indicators of cross‐shelf circulation (Ko et al, 2016; Lehrter et al, 2013). Because hypoxia is sensitive to rates of vertical mixing, we evaluated the model's ability to reproduce density stratification.…”

“…Physical transport and mixing for the model domain (Figure 1) was simulated using the Navy Coastal Ocean Model (NCOM; Martin, 2000) as described in (Fennel et al, 2016; Ko et al, 2016; Lehrter et al, 2013; Lehrter et al, 2017). The model grid has a resolution of 2 × 2 km in the horizontal (surface grid shown in Figure 1) and 20 equally spaced sigma layers for from 5 to 100 m depth with up to 14 hybrid coordinate layers at depths greater than 100 m. The grid was nested within the Intra‐Americas Sea Nowcast/Forecast System (IASNFS) (Ko et al, 2008; Ko & Wang, 2014), covering the Gulf of Mexico and Caribbean Sea which provided physical initial conditions and dynamic boundary forcing conditions on the eastern, southern, and western boundaries of the model grid (Figure 1).…”

“…The model grid has a resolution of 2 × 2 km in the horizontal (surface grid shown in Figure 1) and 20 equally spaced sigma layers for from 5 to 100 m depth with up to 14 hybrid coordinate layers at depths greater than 100 m. The grid was nested within the Intra‐Americas Sea Nowcast/Forecast System (IASNFS) (Ko et al, 2008; Ko & Wang, 2014), covering the Gulf of Mexico and Caribbean Sea which provided physical initial conditions and dynamic boundary forcing conditions on the eastern, southern, and western boundaries of the model grid (Figure 1). MODIS‐Aqua satellite‐derived light attenuation data (Schaeffer et al, 2011) were incorporated into the hydrodynamic model to improve simulation of the vertical distribution of heat in the water column, which affects density stratification (Ko et al, 2016). Freshwater inputs were based on discharge time series from the Mississippi (USACOE gauge 01100) and Atchafalaya Rivers (USACOE gauge 03045) and 92 additional small gauged flows as obtained from USGS.…”

Preface: Remote Sensing in Coastal Environments

“…Ko et al [3] demonstrated the impact of including satellite imagery in simulations of coastal circulation and hypoxia. Using TRMM rainfall data to improve surface salinity flux estimates, and the diffuse attenuation coefficient (K d ) from MODIS to improve estimates of solar penetration, they observed model improvements in water-column heat distribution and hypoxia extent, in comparison with in situ observations.…”