Collaborative Research: RAPID: Pilot observations of enhanced near-bottom equatorial turbulence

低纬度深太平洋是已知的翻转环流的一个关键的深海上升流分支的轨迹。这种上升流需要来自密度较低的上层海洋向下的浮力的底辟混合。然而，驱动这一过程的细胞膜机制目前知之甚少，采样相对较少。 该项目将利用西经140度的一个受资助的系泊阵列（国家科学基金会项目OCE-2048660“评估热带不稳定波下增强混合的机制”的一部分），对深海混合进行第一次全年高分辨率赤道观测。受资助的系泊系统计划于2023年底部署。计划在北纬0.5度和3度的系泊处增加仪器，利用点流速计和剖面流速计以及密集布置的温度传感器观察底部边界层，这一试点项目将有助于了解全球环流的低纬度扩散性上涌分支，这是气候的一个基本组成部分。观测结果将用于测试几种假设的深海赤道湍流机制，包括：地球自转水平分量驱动的近海底波浪捕获、地形背风波驱动的混合以及波浪驱动的流体远离赤道的位移产生的惯性不稳定。该项目将推进深赤道动力学和翻转环流的知识，为未来的深赤道太平洋混合观测提供信息。该奖项反映了NSF的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

The low-latitude deep Pacific is known to be the locus of a critical abyssal upwelling branch of the overturning circulation. This upwelling requires diapycnal mixing of buoyancy downward from the less dense upper ocean. However, the diapycnal mechanisms driving this process are currently poorly understood and relatively poorly sampled. This project will leverage a funded mooring array at 140°W (part of the NSF project OCE-2048660 “Evaluating mechanisms for enhanced mixing below tropical instability waves”) to make the first full year, high-resolution equatorial observations of abyssal mixing. The funded moorings are scheduled to be deployed at the end of 2023. Instrumentation will be added to the mooring planned for 0.5 and 3°N latitutde to observe the bottom boundary layer, using point and profiling current meters and a dense positioning of temperature sensors.This pilot project will inform understanding of the low-latitude diffusive upwelling branch of the global circulation, a fundamental component of climate. The observations will be used to test several hypothesized abyssal equatorial turbulence mechanisms including: near-bottom wave trapping driven by the horizontal component of the Earth's rotation, topographic lee-wave- driven mixing, and inertial instability generated through wave-driven displacement of fluid away from the equator. The project will advance knowledge of deep equatorial dynamics and the overturning circulation to inform future observations of mixing in the deep equatorial Pacific.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.