Mixing in the Equatorial Atlantic's Cold Tongue- Chipods on PIRATA Moorings

混入赤道大西洋的冷舌——PIRATA 系泊处的 Chipods

• 批准号: 1431518
• 负责人: James Moum
• 金额: $ 150万
• 依托单位: Oregon State University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2014
• 资助国家: 美国
• 起止时间: 2014-09-01 至 2020-09-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1431518&HistoricalAwards=false
• 关键词: Mixing; Equatorial; Atlantic; Cold; Tongue

The eastern equatorial Pacific and Atlantic Oceans are marked by relatively cool surface water, referred to as the Pacific and Equatorial cold tongues. Although smaller than the Pacific cold tongue, the Atlantic cold tongue is expansive, spanning several degrees latitude across the Equator and tens of degrees longitude. These cold tongues act as sinks for atmospheric heat and are critical to the global heat balance. The seasonal cycle in sea surface temperature varies in magnitude decreasing from east to west along the equator. Peak cooling occurs in boreal summer, first in the east and progressing westward. The Atlantic's cold tongue exerts considerable regional influence on both sides of the ocean, contributing to variable rainfall over Northeast Brazil and to weather patterns in densely populated areas of western Africa. However, measurements in the Atlantic cold tongue comparable to those made in the Pacific cold tongue do not presently exist. This project will close this gap and discern primary differences between the equatorial mixing regimes in the Pacific and Atlantic basins. A post-doctoral associate will participate in a broad analysis of the new observations and be trained in equatorial dynamics. Undergraduate engineering students will be employed in summer months to help with construction and testing of instrumentation. The Mary's Peak webcam will continue to be supported. This is a webcam installed on the roof of the Oceanography building at the Oregon State University that provides a visualization of natural fluid flows traced by clouds, providing an educational glimpse into fluid motions in the atmosphere. This project will also complement ongoing measurements in the Pacific cold tongue, theoretical analyses of Tropical Instability Waves, and ongoing international studies in the tropical Atlantic. The data set will be archived and shared with the community.Away from the equator, the annual cycle in sea surface temperature (SST) is related to seasonally-varying solar heating. Despite the fact that the equatorial oceans are heated year round by the atmosphere, they also exhibit an annual cycle in SST. Recent, yet distinct, measurements in the equatorial cold tongues of both Pacific and Atlantic Oceans establish the dominant role that mixing plays in boreal summer cooling of the sea surface to produce this annual cycle in SST. At least two significant, and puzzling, differences exist between the two cold tongues. Firstly, measurements from the Atlantic show that the deep diurnal mixing cycle (below the mixed layer but above the core of the Equatorial Undercurrent), which is so critical to mixing in the upper equatorial Pacific, is not present in the Atlantic. Secondly, climate models predict a Pacific cold tongue that is too cool and an Atlantic cold tongue that is too warm. The now well-established PIRATA (Pilot Research Moored Array in the Tropical Atlantic) array is providing new insight into equatorial Atlantic dynamics and its role in critical weather patterns on both sides of that ocean. This project will use it as the backbone to measure the vertical structure and short-time variability of cold tongue mixing in the Atlantic, for comparison to what has been learned from the Pacific cold tongue. Five newly-developed mixing meters (chi-pods) will each be deployed on two equatorial PIRATA moorings at 10W and 23W across the Atlantic cold tongue for a period of four years. These two moorings have dense upper ocean sampling, surface meteorology, and vertical profiles of ocean currents to complement the mixing measurements. These new observations will establish seasonal and inter-annual variations of cold tongue mixing and how it influences SST and the observed weakening of the Atlantic cold tongue, and also define the mechanisms for differences in Pacific and Atlantic mixing that creates the bipolar climate model responses in SST trends.

东赤道太平洋和大西洋的地表水相对较冷，被称为太平洋和赤道冷舌。虽然大西洋冷舌比太平洋冷舌小，但它是广阔的，横跨赤道的几个纬度和经度的几十度。这些冷舌充当大气热量的汇，对全球热平衡至关重要。海表温度的季节变化周期沿赤道自东向西递减。降温高峰出现在北方夏季，首先在东部，然后向西推进。大西洋的冷舌对大洋两岸都有相当大的区域性影响，对巴西东北部的降雨变化和西非人口稠密地区的天气模式都有影响。然而，目前在大西洋冷舌上所做的测量与在太平洋冷舌上所做的测量没有可比性。该项目将缩小这一差距，并辨别太平洋和大西洋盆地赤道混合状态之间的主要差异。一名博士后助理将参与对新观测结果的广泛分析，并接受赤道动力学方面的培训。本科工程专业的学生将在夏季被雇佣来帮助建造和测试仪器。玛丽峰网络摄像头将继续得到支持。这是一个安装在俄勒冈州立大学海洋学大楼屋顶上的网络摄像头，它提供了由云追踪的自然流体流动的可视化，提供了对大气中流体运动的教育一瞥。该项目还将补充正在进行的太平洋冷舌测量、热带不稳定波的理论分析以及正在进行的热带大西洋国际研究。该数据集将被存档并与社区共享。远离赤道，海表温度（SST）的年循环与季节变化的太阳加热有关。尽管赤道海洋全年都受到大气的加热，但它们也表现出海温的年循环。最近，在太平洋和大西洋的赤道冷舌上进行的不同测量表明，混合在北方夏季海面冷却中起着主导作用，从而产生了海温的年循环。这两种冷舌之间至少存在着两个显著而令人费解的差异。首先，来自大西洋的测量表明，对赤道太平洋上部的混合至关重要的深层日混合循环（在混合层之下，但在赤道潜流核心之上）在大西洋中并不存在。其次，气候模型预测太平洋冷舌过于凉爽，大西洋冷舌过于温暖。现已建立的PIRATA（热带大西洋系缆导航研究阵列）阵列为赤道大西洋动力学及其在海洋两岸关键天气模式中的作用提供了新的见解。本项目将以它为主干，测量大西洋冷舌混合的垂直结构和短时变异性，并与太平洋冷舌的研究结果进行比较。5台新开发的混合仪表（chi-pods）将分别部署在大西洋冷舌10W和23W的两个赤道PIRATA系泊处，为期4年。这两个系泊处有密集的上层海洋采样、地面气象学和洋流垂直剖面，以补充混合测量。这些新的观测结果将确定冷舌混合的季节和年际变化，以及它如何影响海温和观测到的大西洋冷舌减弱，并确定太平洋和大西洋混合差异的机制，这些差异造成了海温趋势的两极气候模式响应。