The Chesapeake Bay Interpretive Buoy System and the Winter of 2015: Problems and Solutions

摘要

The NOAA Chesapeake Bay Interpretive Buoy System (CBIBS) is a network of observational platforms managed by the NOAA Chesapeake Bay Office (NCBO) that provides continuous real-time environmental data from the Chesapeake Bay to a wide variety of users. The ten buoys deployed throughout the Bay also support the National Park Service's Captain John Smith Chesapeake National Historical Trail and provide the observational backbone for educational tools used in research and classrooms. Standard buoys are AXYS Watchkeeper platforms equipped with sensors measuring wind, weather, water quality parameters, current profiles, waves, and underwater acoustic animal tracking telemetry. Through a partnership with MARACOOS, CBIBS applies U.S. Integrated Ocean Observing System QARTOD standards to quality control the data, and delivers the real-time data broadly: online via a dedicated interpretive web portal (buoybay.noaa.gov); through dedicated mobile apps; to other data services such as MARACOOS, National Data Buoy Center, and WeatherFlow; and by phone service (877-BUOYBAY). Since the deployment of the system beginning in 2007, only the three northernmost buoys in the system (Susquehanna, Upper Potomac, and Patapsco) have been regularly removed for winter, while the others remain in the water and unharmed. The severe winter of 2015 was an anomalous year in weather and water conditions that caused significant damage to many of the buoys. Several strong, relatively late season cold air outbreaks (e.g., February 14 - 17, 2015) accompanied by gale force winds were followed by sustained low temperatures. The cold winds led to significant events of freezing spray, which accumulated and remained on the buoy superstructures. The iced buoy's righting moments decreased until they were horizontal, and several froze into the surface ice in that position for extended periods of time. The poor weather, rapid thickening of surface ice, and lack of available ice-capable service vessels precluded expedient recovery, and further damage from ice and water ensued. Several buoys were lifted off station and were subjected to significant hull and structural damage. In consideration of the significant loses of equipment and observing down time, NCBO and partners MARACOOS and AXYS are considering preventive actions that can monitor conditions and prevent and mitigate damage when exposed to similar future conditions. Possible actions include: 1. Estimating ice accumulation potential from forecast and measured wind, temperature, and wave conditions; modeling buoy righting moment changes due to ice accumulation; using those to monitor and forecast likelihood of buoy capsize. 2. We have successfully deployed low surface area spar 'ice buoys' on the northernmost moorings in past winters; instrumenting those buoys to provide basic overwinter air and water quality measurements would enhance the winter observing network and make us more likely to remove fully instrumented, more expensive buoys. 3. Modify the existing buoy structure to minimize ice accumulations 4. Identify water intrusion locations (seen in Watchkeeper buoy hulls and battery wells, Watchman controller enclosures, and TriAXYS wave modules) and make appropriate design changes 5. Include sensors to monitor buoy orientation (mean pitch/roll, horizon and hull imaging) in order to identify and address righting moment problems early 6. Change winter maintenance schedules and vessel availability to respond quickly to developing situations. The winter of 2015 was an anomalous year that has motivated us to improve the buoy and observing system design by implementing one or some of these engineering solutions that will help prevent water intrusion, ice damage, and resulting system down time in the future. This paper will describe the anomalous conditions, the resulting damage to the CBIBS system, explore the causes, and suggest proposed solutions.