Inverse Echo Sounding: Using measured water depth to calculate water temperature and its variation over time
Inverse echo sounding is a new method used to calculate average temperature difference in the water column using difference in recorded depth of a single point of the sea floor over time. The object of the proposed investigation is to test the hypothesis that the method of inverse echo sounding is an accurate technique in being able to identify changes in average water temperature of the water column over time. It is proposed that the average temperature data calculated by inverse echo sounding will not be significantly different from XBT and CTD averaged temperature profiles at the two sites. Therefore it will be another technique that provides rapid detection of average temperature change in the water column allowing large scale ocean processes to be investigated. Ideally, reverse echo sounding increases the speed of water temperature collection, but the errors of the method have not yet been fully explored. This proposed research focuses on two sites: the Cross Seamount and the Loihi Seamount. Cross Seamount is an inactive seamount with a summit approximately 300m below sea level and the Loihi Seamount actively expels hydrothermal fluids at depths below 980m. Both of these sites have different geologic and hydrothermal settings and will provide interesting study sites to investigate how average temperature changes with time in the water column. The EM302 multibeam system will provide a bathymetric map of the region and using Caris® software accurate depth measurement of a specific position can be observed. This data will then be input into the Mackenzie Equation in order to calculate average water temperature. An XBT will be deployed at each location to record a temperature profile and a CTD will be launched at each site to get a more precise temperature profile; all the temperature data will then be compared and differences analysed.