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.

Preparis海峡是孟加拉湾北部与安达曼海（AS）之间非常重要的能源和物质交换通道。一组水文测量、微观结构剖面仪和深系泊设备用于确定 Preparis 海峡中水团、湍流混合和流动的特征。史无前例的短期系泊数据显示，Preparis 海峡深窄通道（400 米以下）的深水流以 25.26 厘米/秒的平均顺流速度流向孟加拉湾 (BoB)，深度为540米；深水流上方500～520 m处有一股相对较弱的流向AS，平均顺流速度为15.46 cm/s，430～500 m处有一股微弱的流向BoB。因此，Preparis Channel 中存在深水流（400 m 以下）的夹层垂直结构。400 m 以下的体积传输为 0.06 Sv（1 Sv = 10⁶ m ³ /s) 从 AS 到 BoB。在上层（浅于 300 m），AS 的海水比 BoB 的海水相对温暖和新鲜，表明通过通道进行了强烈的交换。微观结构剖面仪观测表明，Preparis Channel 上层湍流扩散系数达到O (10 ⁻⁴ m ²/s), 比 BoB 内部和北部 AS 大陆坡上的大一个数量级。我们推测 Preparis Channel 中的高能高模内部潮汐有助于增强湍流混合。此外，在深度约 100 米的深部系泊点发现了一个局部浑浊“热点”，这对应于 Preparis 海峡中湍流混合升高的位置。