Mixing Across the Pacific Equatorial Cold Tongue

赤道太平洋的冷舌是海洋净热量吸收的广阔区域。要保持这些较低的海面温度，需要结合次表层混合或横向/垂直平流来向下输送表面热量。目前尚不清楚混合是否起主导作用，但已经确定赤道上层海洋中丰富的流体动力学过程驱动着强烈的湍流。在热带不稳定波(TIW)通过期间对赤道140W的有限观测提供的证据表明，次表层湍流热通量增加了10倍，足以使地表水域每月降温2摄氏度。这表明混合本身可以维持赤道冷舌的可能性，这一猜想得到了气候学证据的支持，即热带不稳定波增强了海面冷却。情报价值：自2005年以来，使用新型自给式仪器(CHI-Pod)在赤道140W进行的系泊混合测量提供了更完整的时间评估。这些系泊记录表明，不仅在短时间尺度上有相当大的变化，而且湍流水平也有显着的季节变化，与海表面温度的年周期大约90-180°不同。然而，空间结构的时变部分是完全未知的。海流、温度和盐度的强跨赤道梯度意味着混合过程中的梯度可能也很强。目前还无法区分时间周期和空间梯度。本项目将在140W到95W之间扩展赤道地区热带海洋-大气系泊阵列上的混合测量。这4个系泊设备中的每一个都将配备5个Xi-Pod，从这些系泊设备获得的数据分析将得到来自140W的过去工艺实验的现有数据和102.5W的详细的补充工艺实验的补充。该项目的主要目标是量化(1)沿和跨越冷舌的混合的时空变化结构；(2)混合在维持冷舌方面的作用；(3)TIW在赤道混合中的作用；(4)湍流在消耗TIW能量方面的作用。本科生将参加过程实验。工科本科生将在夏季的几个月里受雇，帮助进行电子和机械施工以及仪器测试。2013年夏天，一名大气科学本科生将受雇审查和记录玛丽峰网络摄像头(http://marycam.coas.oregonstate.edu/index.html)的存档数据，以供公众传播。该项目是对首席调查人员和几名同事正在进行的热带不稳定波理论分析的补充。在该项目中获得的数据将与海洋混合问题气候进程小组共享，并成为国家海洋和大气管理局管理的热带大气海洋阵列方案存档数据集的一部分。该项目是对美国CLIVAR(气候可变性和可预测性)项目的贡献。

The cold tongue in the Equatorial Pacific is an expansive region of net ocean heat uptake. Maintaining these cool sea surface temperatures requires a combination of subsurface mixing or lateral/vertical advection to transport surface heat downward. Whether mixing plays the dominant role is not yet clear, but it has been established that a rich set of fluid dynamical processes in the upper equatorial ocean drives intense turbulence. Evidence from limited observations on the Equator at 140W during the passage a Tropical Instability Wave (TIW) revealed a ten-fold increase in subsurface turbulent heat flux, sufficient to cool surface waters by 2 degree Celsius per month. This suggests the possibility that mixing alone could maintain the equatorial cold tongue, a conjecture supported by climatological evidence that sea surface cooling is enhanced by Tropical Instability Waves.Intellectual Merit: Since 2005, moored mixing measurements on the Equator at 140W using a novel self-contained instrument (chi-pod) provide a more complete temporal assessment of the mixing. These moored records indicate not only considerable variability on short time scales but also significant seasonal variations in turbulence levels that are roughly 90-180° out-of-phase with the annual cycle in Sea Surface Temperature. However, the time-varying part of the spatial structure is completely unknown. Strong cross-equatorial gradients in currents, temperature and salinity imply that gradients in mixing are likely to be strong as well. At present, it is impossible to distinguish temporal cycles from spatial gradients.This project will expand the measurements of mixing on the Tropical Atmosphere-Ocean mooring array along the equator between 140W and 95W. Each of these 4 moorings will be outfitted with 5 chi-pods and the analysis of the data obtained from these moorings will be supplemented by existing data from past process experiments at 140W and a detailed, complementary process experiment at 102.5W. The main goals of he project are to quantify (1) the time- and spatially-varying structure of mixing along and across the cold tongue; (2) the role of mixing in maintaining the cold tongue; (3) the role of TIWs in equatorial mixing; and (4) the role of turbulence in consuming TIW energy.Broader Impacts: A post-doctoral associate will participate in a broad analysis of the Tropical Atmosphere Ocean Array and mixing measurements and be trained in equatorial dynamics. College graduate students will participate in the process experiment. Undergraduate engineering students will be employed in the summer months to help with both electronics and mechanical construction and testing of instrumentation. An undergraduate atmospheric science student will be employed in the summer of 2013 to review and document archived data from the Mary's Peak webcam (http://marycam.coas.oregonstate.edu/index.html) for public dissemination.This project complements ongoing theoretical analyses of Tropical Instability Waves conducted by the lead investigators and several colleagues. Data obtained in the project will be shared with the Climate Process Team on ocean mixing and become part of the archived data sets of the Tropical Atmosphere Ocean Array Program managed by the National Oceanic and Atmospheric Administration. This project is a contribution to the U.S. CLIVAR (CLImate VARiability and predictability) Porgram.