Ocean observing satellites and models reveal anomalous surface properties associated with the 2016 Bonnet Carré Spillway opening and a 2016 Flower Garden Banks mortality event. Marine bio-optical and physical processes in northeastern Gulf of Mexico are largely driven by river discharge and wind-driven circulation. Satellite observations and regional ocean model output were used to evaluate these processes and their interactions over large spatial areas. Climatology of Visible Infrared Imaging Radiometer Suite (VIIRS) ocean color imagery and Navy Coastal Ocean Model American Seas (AMSEAS) output for the region were generated to explore temporal variability and detect anomalous events. Here we present the 2016 and 2017 time series of 1.) 8-day 750 m resolution VIIRS observations for chlorophylla, diffuse attenuation coefficient, and euphotic depth; and 2.) 8-day 3 km AMSEAS output for surface temperature, salinity and currents. From these time series, we derive temporal anomalies for each parameter. Results from longer term anomalies show elevated ocean color values across the region following a January 2016 river flooding event, and Bonnet Carré Spillway opening, that persist through summer months. The elevated values are compared with river discharge rates and known events (i.e. July and October 2016 Flower Garden Banks mortality), revealing the impacts of the flooding to the region. Results from shorter term anomalies highlight the stages and migration of specific impacts, such as possible upwelling at Flower Garden Banks (January 2016) observed in currents and chlorophyll-a fields.
The seasonal cycle in surface biological, optical and physical properties across the river dominated Mississippi (MS)
Shelf changed during years 2015 to 2017 at different locations across the shelf. VIIRS satellite and ocean model
products were used to monitor cycles for different properties of both the nowcast and anomalous water properties. MS
Shelf water properties vary spatially between offshore waters and coastal MS Sound waters, as well as temporally
throughout the year. Ten selected regions spanning east to west from the MS Sound to the shelf break characterized the
cross shelf seasonal fluctuations in satellite-derived chlorophyll-a, backscattering, euphotic depth, sea surface
temperature, and modeled salinity currents. The seasonal relationships between physical and bio-optical properties were
determined for different regions across the shelf and the seasonal eastward movement of the MS river plume across the
shelf was identified in June. Yearly MS Sound seasonal cycles of coastal bio-physical properties are different from the
shelf regions’ offshore seasonal cycles and indicate a time-lag between the bio-optical responses to the physical
properties. Bio-optical and physical results on the shelf indicated seasonal movements of the MS River plume locations.
Results show the seasonal bio-physical response of the shelf waters which can be used to address and understand the
timing of data collection and how ocean events are influenced by the natural seasonal cycle interactions between
biological and physical properties. The seasonal cycle study will enable the ability to monitor the shelf water quality and
to identify non-typical conditions and the impact of an event on the cycle. Correlations between the monthly seasonal
cycle of bio-optical and physical properties such as salinity, ocean color, chlorophyll-a and particle scattering were not
consistent over the shelf. Seasonal cycles of salinity and chlorophyll-a show improved correlation if chlorophyll-a is
delayed one month from the salinity at offshore locations on the shelf. Results of the seasonal trends support how data
collected at a single image location on the shelf during a certain month can be different from other seasons. The
seasonal cycle of the dynamic anomaly properties (DAP) of bio-physical properties were determined to show how
seasonal abnormal changes and trends at locations across the shelf can provide a method for seasonal adaptive
sampling. The yearly differences in monthly cycles from 2015 to 2017 at shelf locations, identified elevated
chlorophyll-a in several months of 2016 and yearly temperature differences in multiple areas. The seasonal cycle of
Euphotic depth, solar UV light penetration, showed a maximum peak (deeper Euphotic depth) at certain shelf locations
during the months of September and October and minimal penetration in Aug of 20152016,2017. This information
could be useful to understand months for maximum oil UV degradation in case of an oil spill
The dynamic bio-optical and physical ocean properties within the Gulf of Mexico (GoM) have been identified by the Ocean Weather Laboratory. Ocean properties from VIIRS satellite (Chlorophyll and Bio-Optics and SST) and ocean-circulation models (currents, SST and salinity) were used to identify regions of dynamic changing properties. The degree of environmental change is defined by the dynamic anomaly of bio-optical and physical environmental properties (DAP). A Mississippi River plume event (Aug 2015) that extended to Key West was used to demonstrate the anomaly products. Locations where normal and abnormal ocean properties occur determine ecological and physical hotspots in the GoM, which can be used for adaptive sampling of ocean processes. Methods are described to characterize the weekly abnormal environmental properties using differences with a previous baseline 8 week mean with a 2 week lag. The intensity of anomaly is quantified using levels of standard deviation of the baseline and can be used to recognize ocean events and provide decision support for adaptive sampling. The similarities of the locations of different environmental property anomalies suggest interaction between the bio-optical and physical properties. A coral bleaching event at the Flower Garden Banks Marine Protected Area is represented by the salinity anomaly. Results identify ocean regions for sampling to reduce data gaps and improve monitoring of bio-optical and physical properties.
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