MAPPING CLIMATIC TEMPERATURE-CHANGES IN THE OCEAN WITH ACOUSTIC TOMOGRAPHY - NAVIGATIONAL REQUIREMENTS

In eddy-resolving hydrodynamic models, first-mode baroclinic Rossby wa ves linked to El Nino/Southern Oscillation are the dominant features w hich change basin-wide temperatures below the seasonal thermocline in the northeast Pacific at periods less than a decade [1]. Simulations a re carried out in which Rossby waves are mapped using acoustic tomogra phy. Based on the model which propagated these waves, a Kalman filter is used to map temperature signals for a year, The modeled data are ta ken from a dense network of acoustic tomography sections, At 300-m dep th, where the temperature perturbations associated with Rossby waves a re about +/- 1 degrees C, 80% to 90% of the model variance is accounte d for with tomographic estimates, The corresponding standard deviation s of the estimates are less than 0.1 degrees C at 400-km resolution, A bout 80% of the model variance is accounted for with tomography when t he navigational errors of the sources and receivers are as poor as one kilometer, Consequently, it may be unnecessary to accurately navigate actual tomographic instruments to map climate change, Modeling result s are insensitive to: 1) a reduction in data due to a significant numb er of instruments which fail; 2) whether the instruments are mobile or fixed; 3) the detailed trajectories of mobile receivers; 4) the shape of the a priori spectrum of ocean fluctuations; 5) the corrections to the acoustic travel-time biases; and 6) the errors in the sound-speed algorithm, In basin-scale arrays, the modeled variance of acoustic tr avel time depends on the horizontal wavenumber of temperature as k(-5. 5), Because sound has little sensitivity to small wavelengths, modeled Rossby waves can be mapped in a day from a few sources and of order t en receivers, The results only depend on the model having large scales in space and time.