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

众所周知，低纬深太平洋是翻转环流的一个关键的深渊上升流分支的中心。这种上升流需要从密度较低的上层海洋向下的浮力的昼夜混合。然而，驱动这一过程的昼夜机制目前还知之甚少，采样也相对较少。该项目将利用140°W的资助系泊阵列(美国国家科学基金会OCE-2048660项目“热带不稳定波下加强混合的评估机制”的一部分)，对深海混合进行第一次全年高分辨率赤道观测。资助的系泊设施计划于2023年底部署。计划在0.5°N和3°N纬度的系泊设施上增加仪器，使用点状和剖面式海流计以及密集放置的温度传感器来观测底部边界层。这一试点项目将使人们了解全球环流的低纬扩散上升分支，这是气候的基本组成部分。这些观测将被用来检验几种假设的赤道深渊湍流机制，包括：由地球自转的水平分量驱动的近底部波捕获，地形背风波驱动的混合，以及通过波驱动的流体移离赤道而产生的惯性不稳定。该项目将促进对深赤道动力学和颠覆环流的了解，为未来观测到赤道深太平洋的混合提供信息。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势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.