The upper ocean in the Greenland Sea during 1988-1989 from modal analyses of tomographic data

An ocean acoustic tomography data set was collected in the Greenland Sea between September 1988 and August 1989. This thesis uses the framework of acoustic normal modes to interpret this data, and in turn to provide measurements of the upper ocean.;A simple one-dimensional ocean mixed layer model is used to study the effect of the ocean evolution from summer to winter upon range-independent acoustic propagation. Acoustic normal modes are propagated through the model ocean predictions and the resulting synthetic receptions are compared with data recorded between two of the tomographic moorings. The acoustic normal modes change radically in nature as the sound speed profile changes. In summer (seasonal thermocline) and winter (adiabatic sound speed profile) individual modes show minimal frequency dispersion. Autumn profiles with a shallow surface mixed layer give highly dispersed modes, delaying the final acoustic energy by several hundred milliseconds. This is the largest travel time signal observed in the data.;In winter the individual acoustic normal modes show little frequency dispersion. A technique is developed by which individual mode arrivals can be extracted from the recorded acoustic receptions. This is achieved using a combination of spatial filtering and variable time windowing with data from a six element hydrophone array. Once individual normal modes are isolated, their group velocities, along with ray travel time data, are used in inversions to obtain the range-average sound speed (and hence temperature) profile. The inclusion of normal mode data greatly improves the near-surface resolution of the inversions. Comparisons with conventional measurements are favorable.;Mode group velocity/ray travel time inversions performed at 4-8 hr spacing for a 50 day time period between 14 Jan and 5 Mar 1989 give the range-averaged vertical temperature evolution. Two major events are observed. The first is the disappearance of a cold (...