OC3570 Cruise Project Presentation: Slocum Glider Study Presented by LT Kim Freitas 11 March 2008

Purpose of Experiment Importance to the Navy To learn the operational characteristics of the Slocum glider To explore the quality of the data gathered by the glider To analyze the oceanography data collected by the glider and draw some basic conclusions from the data Understanding the ocean environment to exploit tactical advantages Understanding the glider data in order to best ingest it into models Importance to the Navy

Glider Basics Specifications Weight: 52 Kg Hull Diameter: 21.3 cm Vehicle Length: 1.5 meters Depth Range: 4 - 200 meters Speed, projected: 0.4 m/sec horizontal Energy: Alkaline Batteries Endurance:[ Dependent on measurement and communication type] 30 days Range: 1500 km Navigation: GPS, and internal dead reckoning, altimeter Sensor Package: Conductivity, Temperature, Depth Communications: RF modem, Iridium satellite, ARGOS, Telesonar modem Courtesy of Webb Research

Glider in Motion Click for video Courtesy of Rutgers University, YouTube, and Peter Guest

Experiment Layout Glider deployed near eastern waypoint Diving profile – to 200m at constant angle (26º), then back to surface Collecting scientific data on the downcast Once reaches western waypoint, turn around for waypoint one Expected to take 2 trips per day

Glider’s Actual Track Due to stormy conditions, glider was set off its track It tried to return to waypoints, but could not overcome the current Ended up abandoning mission From Cruise Log: Glider89 (deploy) 36-38.54 122-05.19 24/ 0055 Glider89 (recover) 37-13.75 122-48.35 29/ 1619

Data Manipulation When the glider abandoned its mission, it “parked” – parked data not included Of 90k+ data points, about 2/3 unusable due to NaN observations Turbidity, fluorescence, conductivity – still some NaNs due to different sampling frequency

Lessons Learned Before the Data Analysis Not enough self-generated momentum Probably not ideal for cross-current studies, especially during storms Best to set glider to collect on downcast AND upcast Is there a better way to “tune” the scientific package for better data (fewer NaNs)?

Temperature (ºC)

Salinity (psu)

Sound Speed

Density (kg/m3)

Temperature-Salinity Plot

Data Binned by Depth Majority of the variability was contained in 30-80m of water No clear separation of hi/lo temp variability by further binning

Data Binned by Distance Low temp in first 6km Low-high transition in second 6km High-median transition in third Little variability for rest of mission Suggests variability in time – calm weather at first followed by onset of storm

Temperature-Salinity-Depth Both the high temp pocket and the low temp pocket are in the 30-80m range Deeper water much more “normal”

Salinity Variability at 50m 50m sample representative of the TS variable water High salinity, drops to low salinity, transitions to mid then low

Discussion/Conclusion Learned some features of the glider and how to better set the scientific package Quality of the data collected – not the best, but we have some ideas for how to make it better on future deployments Oceanographic data indicates highly variable layer from 30-80m – perhaps some spatial water mass features Discovered what data results from the glider use, a better mission plan, and how to use that data to understand the environment

Questions?