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Hurricane Harvey deposited over 90×109 m 3 of rainwater over central Texas, USA, during late August/early September 2017. During four cruises (June, August, September and November 2017) we observed changes in hydrography and nutrient and oxygen concentrations in Texas coastal waters. Despite intense terrestrial runoff, nutrient supply to the coastal ocean was transient, with little phytoplankton growth observed and no hypoxia. Observations suggest this was probably related to the retention of nutrients in the coastal bays and rapid uptake by phytoplankton of nutrients washed out of the bays, as well as dilution by the sheer volume of rainwater and the lack of significant carbon reserves in the sediments, despite the imposition of a strong pycnocline. By the November cruise conditions had apparently returned to normal, and no long-term effects were observed. [ABSTRACT FROM AUTHOR]

Hurricane Harvey deposited over 90 billion cubic meters of rainwater over central Texas, USA, during late August/early September 2017. During four cruises (June, August, September and November 2017) we observed changes in hydrography, nutrient and oxygen concentrations in Texas coastal waters. Despite intense terrestrial runoff, nutrient supply to the coastal ocean was transient, with little phytoplankton growth observed and no hypoxia. Observations suggest this was probably related to the retention of nutrients in the coastal bays, rapid uptake by phytoplankton of nutrients washed out of the bays, as well as dilution by the sheer volume of rainwater, and the lack of significant carbon reserves in the sediments, despite the imposition of a strong pycnocline. By the November cruise conditions had apparently returned to normal and no long-term effects were observed. [ABSTRACT FROM AUTHOR]

Abstract: A numerical hydrodynamic simulation of the Texas–Louisiana continental shelf circulation is compared with hydrographic and moored observations of temperature, salinity, and current velocity. The spatial and temporal structure of the model error suggests that the model is able to reproduce the observed broad-scale features and seasonal patterns faithfully. However, there are energetic features that have small spatial and temporal scales, 30–50km and 5–12days, that are not reproduced in the model. These small-scale features are not well resolved concurrently in both space and time by most modern hydrographic and moored measurements, and thus appear as observational noise when comparing observations with numerical simulations. We demonstrate that these features are reproduced statistically within the model in terms of mean and variance, but are not reproduced exactly. Thus, these features create a substantial noise floor that constrain assessments of model skill to large spatial and temporal scales. [Copyright &y& Elsevier]

Abstract: Hypoxia of the northern Gulf of Mexico is a recurrent summer phenomenon that is principally driven by the combined effects of nutrient loading and stratification introduced onto the continental shelf mainly from effluents derived from the Mississippi and Atchafalaya Rivers. Spatially detailed observations along and across the continental shelf in the central and western areas of coastal Louisiana, where hypoxia is most frequent and severe, reveal that the spatial variability (horizontal and vertical) of dissolved oxygen concentration is closely linked to physical processes including the spatial geometry of local topographic features. The along shelf spatial variability of dissolved oxygen is estimated to have a principal wavelength of approximately 50km that is phase-locked with the location of three shallow shoals along the coastline. Based on a comparison with the historical record, the area between these shoals coincides with areas of more frequent hypoxia. These results may have important implications for coastal management strategies by identifying physically controlled hotspots in the central and western Louisiana shelf where monitoring efforts can be most efficiently targeted. [Copyright &y& Elsevier]

Stratification has been proved to be essential to the development and sustainment of bottom hypoxia off the Texas-Louisiana shelf. Observations indicate that bottom hypoxia does not always arise under strong stratification, especially in spring/winter season when the strong stratification is transient. A simple oxygen model is coupled with a high-resolution hydrodynamic model to further investigate linkage between stratification and oxygen dynamics. We put forward a definition of stratification when vertical stratification maxima exceeds some critical value. This duration time is longest in summer and shortest in winter, and is identified regulating the horizontal and vertical extensions of bottom hypoxia. A long duration of strong stratification expands over the shelf, defining a stratification envelope within which bottom hypoxia occurs with high probability. Persistent strong stratification also acts to reserve local oxygen depletion, facilitating the growth of the hypoxic layer thickness. The main pycnocline is identified to be the upper limit of the top reach of bottom hypoxia. • Stratification duration is longest in summer and shortest in winter. • The duration regulates the horizontal and vertical extents of bottom hypoxia. • The main pycnocline is identified to be the upper limit of top reach of bottom hypoxia. [ABSTRACT FROM AUTHOR]