Abstract
Preparis Channel is the very important exchange path of energy and materials between the northern Bay of Bengal and Andaman Sea (AS). A set of hydrographic measurements, a microstructure profiler, and a deep mooring were used to determine the characteristics of water masses, turbulent mixing, and flows in the Preparis Channel. The unprecedented short-term mooring data reveal that a deep current in the deep narrow passage (below 400 m) of the Preparis Channel flows toward the Bay of Bengal (BoB) with a mean along-stream velocity of 25.26 cm/s at depth of 540 m; above the deep current, there are a relatively weak current flows toward the AS with a mean along-stream velocity of 15.46 cm/s between 500 m and 520 m, and another weak current flows toward the BoB between 430 m and 500 m. Thus, a sandwiched vertical structure of deep currents (below 400 m) is present in the Preparis Channel. The volume transport below 400 m is 0.06 Sv (1 Sv = 106 m3/s) from the AS to the BoB. In the upper layer (shallower than 300 m), the sea water of the AS is relatively warmer and fresher than that in the BoB, indicating a strong exchange through the channel. Microstructure profiler observations reveal that the turbulent diffusivity in the upper layer of the Preparis Channel reaches O(10−4 m2/s), one order larger than that in the interior of the BoB and over the continental slope of the northern AS. We speculate that energetic high-mode internal tides in the Preparis Channel contribute to elevated turbulent mixing. In addition, a local “hotspot” of turbidity is identified at the deep mooring site, at depth of about 100 m, which corresponds to the location of elevated turbulent mixing in the Preparis Channel.
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Acknowledgements
Bathymetry data for the AS were acquired from global sea-floor topography (https://topex.ucsd.edu/cgi-bin/get_data.cgi). The authors thank the crew of R/V Xiangyanghong 06 and R/V Xiangyanghong 10 for their considerable assistance in the cruise observation.
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The Global Change and Air-Sea Interaction II Project under contract Nos GASI-01-EIND-STwin and GASI-04-WLHY-03; the Scientific Research Fund of the Second Institute of Oceanography, Ministry of Natural Resources under contract No. JB2106; the Global Change and Air-Sea Interaction II Project under contract No. GASI-04-WLHY-01; the Leading Talents of Science and Technology Innovation in the Zhejiang Provincial Ten Thousand Talents Program under contract No. 2020R52038; the Oceanic Sustainability-Based Marine Science and Technology Cooperation in Maritime Silk Road and Island Countries.
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Ye, R., Zhou, F., Ma, X. et al. Observed characteristics of flow, water mass, and turbulent mixing in the Preparis Channel. Acta Oceanol. Sin. 42, 83–93 (2023). https://doi.org/10.1007/s13131-022-2021-5
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DOI: https://doi.org/10.1007/s13131-022-2021-5