Technical Note: Animal-borne CTD-Satellite Relay Data Loggers for real-time oceanographic data collection

Abstract

Abstract. The increasing need for continuous monitoring of the world oceans has stimulated the development of a range of autonomous sampling platforms. One novel addition to these approaches is a small, relatively inexpensive data-relaying device that can be deployed on marine mammals to provide vertical oceanographic profiles throughout the upper 2000 m of the water column. When an animal dives, the CTD-Satellite Relay Data Logger (CTD-SRDL) records vertical profiles of temperature, conductivity and pressure. Data are compressed once the animal returns to the surface where it is located by, and relays data to, the Argos satellite system. The technical challenges met in the design of the CTD-SRDL are the maximising of energy efficiency by minimising size, whilst simultaneously maintaining the reliability of an instrument that cannot be recovered and is required to survive its lifetime attached to a marine mammal. The CTD-SRDLs record temperature and salinity with an accuracy of better than 0.005°C and 0.02 respectively. However, due to the limited availability of reference data for post-processing, data are often associated with slightly higher errors. The potential to collect large numbers of profiles cost-effectively makes data collection using CTD-SRDL technology particularly beneficial in regions where traditional oceanographic measurements are scarce. Depending on the CTD-SRDL configuration, it is possible to sample and transmit hydrographic profiles on a daily basis, providing valuable and often unique information for a real-time ocean observing system.

Temperature signature of high latitude Atlantic boundary currents revealed by marine mammal‐borne sensor and Argo data

“…After QC there were 12,623 Argo profiles in our study region. The temperature profiles collected from marine mammal‐mounted autonomous Satellite Relay Data Loggers (SRDLs) [ Boehme et al , 2009] result from tagging of hooded seals, harp seals, grey seals and beluga whales by Fisheries and Oceans Canada off east Greenland, the Newfoundland Shelf, the Gulf of St. Lawrence and Hudson Bay respectively between July 2003 and May 2008 [e.g., Andersen et al ., 2010] (Figure 1c). Full details of the data retrieval process and quality control are given in the .…”

Atlantic water variability on the SE Greenland continental shelf and its relationship to SST and bathymetry

“…Between 2004 and 2010, a total of 104 individual seals were fitted with satellite relay depth loggers (SRDLs) that reported time, maximum dive depth, and location. We used SRDL Series 9000 units manufactured by the Sea Mammal Research Unit of St. Andrews University, UK [e.g., Lydersen et al ., ; Boehme et al ., ]. Raw location data are determined by the Argos satellite system and subsequently filtered using an algorithm based on the speed of the animal between location fixes [ Freitas et al ., ].…”

How Many Seals Were There? The Global Shelf Loss during the Last Glacial Maximum and Its Effect on the Size and Distribution of Grey Seal Populations

“…These SRDLs collect and process dive information (e.g. dive profile shape and maximum depth) and transmit these data via the Argos satellite system [32]–[34]. Argos also provide position information [35], [36] giving approximately 5 locations per day per seal while they are at sea.…”