Temperature fine structure observations in the tropical North Pacific Ocean

Abstract

Temperature profiles at two locations in the tropical North Pacific Ocean (8°27′N, 150°47′W and 11°43′N, 138°23′W) are analyzed and compared with similar data from the central gyres of the Atlantic and Pacific oceans. The vertical fine structure spectra in the thermocline (300–600 m) divide into two wave number bands, each of which has a distinct slope. For 0.003 < k < 0.1 cpm the power law dependence is about k−2. For 0.1 < k < 0.5 cpm the power law is k−3. The low‐wave number band results agree with internal wave models, and comparison of our data with the other measurements supports the universality of deep ocean internal wave spectra. The high‐wave number spectra suggest that different processes are responsible for these features. Time‐lagged coherence between temperature profiles at one location separated by time lags of up to 10 hours was calculated at the 11°43′N, 138°23′W site. This coherence depended upon the wave number band. For k < 0.04 cpm the coherence had wavelike behavior; however, the semidiurnal tide appeared important. At higher wave numbers, no significant coherence was found.