May 17, 2017
Dzwonkowski, B., A. Greer, C. Briseno-Aveno, J. Krause, I. Soto Ramos, F. Hernandez, A. Deary, J. Wiggert, D. Joung, P. Fizpatrick, S. O’Brien, S. Dykstra, Y. Lau, M. Cambazoglu, G. Lockridge, S. Howden, A. Shiller, and W.M. Graham (2017) Influence of estuarine-exchange on the coupled bio-physical water column structure during the fall season on the Alabama shelf, Continental Shelf Research. 140(15), 96-109.
Abstract: Estuarine-shelf exchange can drive strong gradients in physical and biogeochemical properties in the coastal zone and exert a significant influence on biological processes and patterns. Physical, biogeochemical, and plankton data from an across-shelf transect extending south of Mobile Bay, Alabama, in conjunction with regional time series data, were used to determine the relative importance of estuarine-shelf interactions on the physical-biological structuring of the shelf environment during fall conditions (i.e., well-mixed, low discharge). This period was also characterized by a relatively unique weather event associated with the remnants of Hurricane Patricia, which drove a meteorological flushing of estuarine water onto the shelf. Survey data indicated generally low N:P ratios across the shelf, with slightly elevated dissolved inorganic nitrogen in the Region of Freshwater Influence (ROFI) that extended approximately 30 km offshore. The ROFI had higher values of chlorophyll-a, diatom-specific production, marine snow, and primary productivity, with notable contributions from the larger size cells (>5 µm). Furthermore, stratification provided a niche opportunity for Trichodesmium sp. aggregates, a typically oligotrophic cyanobacteria, at the offshore edge of the ROFI. The lens of estuarine water may have limited the vertical extent to which this population was mixed, providing enhanced light availability relative to the well-mixed offshore conditions. Following the biogeochemical trend, the highest zooplankton abundances were also located within the estuarine outflow. While limited in spatial extent, the distinct geochemical and biological characteristics within the ROFI demonstrate the ecological impacts that estuarine-sourced waters can have during periods of generally low productivity in the Mississippi Bight. Continue reading –>
December 20, 2016
Tzeng, M. W., Dzwonkowski, B., & Park, K. (2016). Data processing for a small-scale long-term coastal ocean observing system near Mobile Bay, Alabama. Earth and Space Science, 3(12), 510–522.
Abstract: The oceanographic community routinely collects time series data of hydrography, water current velocity, and other basic physical, chemical, and biological properties of the marine environment. Such data are essential for establishing baseline characteristics of marine and estuarine ecosystems. However, the task of taking the raw data files as downloaded from a variety of instruments from multiple manufacturers, and converting them into file formats that can be used to address specific research questions, can be highly complex and time consuming. To illustrate some of these complexities, we have thoroughly documented the data processing steps for a small coastal ocean observing system near Mobile Bay, Alabama, that has been in operation since 2004. Our goals were to produce documentation and data provenance in sufficient detail for full science reproducibility of all studies that use data from this system, provide a template for other ocean observation operations, and highlight a need for better recognition of the significant amount of time and expertise often required to do both the data processing and the documentation for long-term observational systems. Continue reading —>
May 17, 2016
Arnone, R., R. Vandermeulen, P. Donaghay, H. Yang. (2016). Surface Biomass Flux across the Coastal Mississippi Shelf , SPIE Security and Defense: Proc. SPIE 9827, Ocean Sensing and Monitoring VIII, 98270Z (May 17, 2016).
Abstract: The exchange of water masses across the Mississippi shelf was used to determine the chlorophyll flux for an eight month period in 2013 through the major Mississippi River discharge period in Spring and Fall. Circulation models (NCOM and HYCOM) and SNPP satellite chlorophyll products were used to monitor the changes in the shelf transport and surface biological impact. The physical and biological response of cross shelf exchange was observed in rapidly changing dynamic movements of river plumes across the shelf as identified by the models and satellite products. Six sections on the shelf identified exchange corridors of transport and biomass chlorophyll flux of surface waters between the coast and offshore waters. During the eight month period, the nearshore waters show high carbon chlorophyll flux, averaging -60 x103 kg chl extending to offshore waters. However, at the outer shelf break, a significant carbon flux was observed moving shoreward onto the shelf from offshore waters, averaging +100 x103 kg chl, which is attributed to the dynamic Mississippi River plume. Results indicate a significant amount of offshore surface waters containing biological carbon can exchange across the shelf, clearly demonstrated through the combination of biological satellite products and physical models. © (2016) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Continue reading —>
April 13, 2016
Lockridge, G., Dzwonkowski, B., Nelson, R., & Powers, S. (2016). Development of a Low-Cost Arduino-Based Sonde for Coastal Applications. Sensors, 16(4), 528.
Abstract: This project addresses the need for an expansion in the monitoring of marine environments by providing a detailed description of a low cost, robust, user friendly sonde, built on Arduino Mega 2560 (Mega) and Arduino Uno (Uno) platforms. The sonde can be made without specialized tools or training and can be easily modified to meet individual application requirements. The platform allows for internal logging of multiple parameters of which conductivity, temperature, and GPS position are demonstrated. Two design configurations for different coastal hydrographic applications are highlighted to show the robust and versatile nature of this sensor platform. The initial sonde design was intended for use on a Lagrangian style surface drifter that recorded measurements of temperature; salinity; and position for a deployment duration of less than 24 h. Functional testing of the sensor consisted of a 55 h comparison with a regularly maintained water quality sensor (i.e., YSI 6600 sonde) in Mobile Bay, AL. The temperature and salinity data were highly correlated and had acceptable RMS errors of 0.154 °C and 1.35 psu for the environmental conditions. A second application using the sonde platform was designed for longer duration (~3–4 weeks); subsurface (1.5–4.0 m depths) deployment, moored to permanent structures. Design alterations reflected an emphasis on minimizing power consumption, which included the elimination of the GPS capabilities, increased battery capacity, and power-saving software modifications. The sonde designs presented serve as templates that will expand the hydrographic measurement capabilities of ocean scientists, students, and teachers. Continue reading —>
October 30, 2015
Zaron, E. D., Fitzpatrick, P. J., Cross, S. L., Harding, J. M., Bub, F. L., Wiggert, J. D., et al. (2015). Initial evaluations of a Gulf of Mexico/Caribbean ocean forecast system in the context of the Deepwater Horizon disaster. Frontiers of Earth Science, 9, 1–32.
Abstract: In response to the Deepwater Horizon (DwH) oil spill event in 2010, the Naval Oceanographic Office deployed a nowcast-forecast system covering the Gulf of Mexico and adjacent Caribbean Sea that was designated Americas Seas, or AMSEAS, which is documented in this manuscript. The DwH disaster provided a challenge to the application of available ocean-forecast capabilities, and also generated a historically large observational dataset. AMSEAS was evaluated by four complementary efforts, each with somewhat different aims and approaches: a university research consortium within an Integrated Ocean Observing System (IOOS) testbed; a petroleum industry consortium, the Gulf of Mexico 3-D Operational Ocean Forecast System Pilot Prediction Project (GOMEX-PPP); a British Petroleum (BP) funded project at the Northern Gulf Institute in response to the oil spill; and the Navy itself. Validation metrics are presented in these different projects for water temperature and salinity profiles, sea surface wind, sea surface temperature, sea surface height, and volume transport, for different forecast time scales. The validation found certain geographic and time biases/errors, and small but systematic improvements relative to earlier regional and global modeling efforts. On the basis of these positive AMSEAS validation studies, an oil spill transport simulation was conducted using archived AMSEAS nowcasts to examine transport into the estuaries east of the Mississippi River. This effort captured the influences of Hurricane Alex and a non-tropical cyclone off the Louisiana coast, both of which pushed oil into the western Mississippi Sound, illustrating the importance of the atmospheric influence on oil spills such as DwH. Continue reading —>
September 12, 2015
Dzwonkowski, B., Park, K., & Collini, R. (2015). The coupled estuarine-shelf response of a river-dominated system during the transition from low to high discharge. J. Geophys. Res. Oceans, 120(9), 6145–6163.
Abstract: Opportunistic observations captured the coupled estuarine-shelf interactions as the Alabama coastal region transitioned from a period of low to flood river discharge conditions. The period of focus was 18 February to 10 April 2011 during which time a combination of in situ (water level, salinity and velocity) and remote sensing (ocean color) data provided information on the estuarine and shelf environment prior to, during, and post a major river discharge event that captured a relatively rare spatially synoptic view of the structural evolution of a discharge plume in response to changing forcing conditions. The discharge event generated major changes in the hydrographic conditions and forcing responses within the estuary and on the shelf. The resulting surface advected plume was observed for approximately two weeks, during which time the observed differences in shelf circulation were directly linked to the discharge plume and a plume bulge with anticyclonic circulation was identified at times throughout the event. The plume was exposed to a range of wind conditions which modulated the surface structure: downwelling winds elongated the plume structure and upwelling winds reversed and widened the plume. The influence of wind forcing, even during very low wind (<3.75 m s−1) and large outflow (∼7000 m3 s−1) conditions, was apparent, as a result of the shallow and wide characteristics of the plume. Anticyclonic bulge regions have only been identified in a few systems and the occurrence of this feature on the Alabama shelf has significant implications on transport and fate of river discharge in this region. Continue reading—>
August 24, 2015
Autonomous Underwater Vehicle (AUV) Jubilee 2015 Report
A Gulf of Mexico event to coordinate glider and other ocean observing activities
The AUV Jubilee was an inaugural event to coordinate glider and other in situ ocean data operations in the Gulf of Mexico for the month of July 2015. Our primary goal was to establish an open dialogue and collaboration with scientists across the Gulf, in order to acquire simultaneous ocean observations and leverage off of fellow participants to create a multifaceted and integrated data set. The AUV Jubilee was led by the University of Southern Mississippi’s Ocean Weather Laboratory (http://www.usm.edu/marine/research-owx), which hosted a series of webinars to display real-time satellite ocean color and several ocean circulation models (HYCOM/NCOM), as well as maps of product uncertainty to allow the participating scientists to adaptively sample features of interest (e.g., eddies, river filaments, fronts, etc.). This data fusion tool enabled the display of up-to-date locations of various glider and ship/aerial operations while they were deployed, and facilitated near real-time data exchanges in order to further assist in decision-making for adaptive sampling of ocean features. In addition to real-time operations, all participants were encouraged to submit data to the National Glider Data Assembly Center (NGDAC), so that the data could be available for assimilation into operational physical circulation models. The list of glider participants is shown below in Table 1. The scope of the AUV Jubilee also included an educational outreach component, in which a competitively selected group of highly qualified teachers were brought in for an intensive one week program that included curriculum development, hands on oceanographic experience, and participation in real-time glider operations.
Read the rest of the report here: AUV_Jubilee_2015