An Observing System for the Meridional Overturning Circulation and Ocean Heat Transport in the Subtropical North Atlantic: Extension of the RAPID-MOCHA Program

气候模式表明，大西洋经向翻转环流（MOC）及其伴随的海洋热通量在年际时间尺度上变化很大。根据一些模式，除了MOC几乎可以停止的气候突变情景外，“正常”的年代际变化可能在其长期平均值的20%至30%之间。然而，直到最近，还没有直接测量系统能够提供经向翻转环流的定期估计，以确定其自然变率或评估这些模式预测。这样的系统现在部署在大西洋的26.5-N，作为英美联合防御系统的一部分RAPID-MOCHA项目，自2004年3月以来一直在持续观测MOC。知识价值：该项目的目标是将该测量系统再维持6年，从2008年到2014年，以便获得大西洋MOC和相关经向海洋热通量的十年时间序列。这一目标不同于更成熟的方法，但它是互补的，即占用高分辨率带跨盆地水文剖面，以不规则间隔估计MOC和热通量。需要进行定期估计，以确定变率的幅度和主要的时间尺度，即气候季节周期，并帮助滤除频率较高的“噪音”，这些“噪音”可能会混淆对时间间隔很广的跨流域部分的长期热通量变化的确定。拟议的观测将提供必要的数据，以记录观测到的MOC变率的频谱，并评估海洋再分析模式中的MOC变率。该建议的更广泛影响是为MOC的长期监测提供基础，以便了解其与观测到的气候波动的关系，并提高我们评估气候模式预测的能力。拟议的项目继续与英国国家海洋学中心和德国马克斯普朗克研究所的研究人员进行成功的合作。该项目的这一组成部分将在2008年3月至2014年3月的6年期间内维护东大西洋的系泊部分，并继续与NOAA的科学家合作，维护巴哈马群岛东部半年一次的水文/低adcp部分。英国将支持跨盆地的水文巡航和沿着26.5 n扩展的系泊阵列，以完成连续时间序列观测系统。更广泛的影响：沿大西洋26.5-N的MOC观测系统将提供必要的确定数据集，以记录观测到的MOC变率频谱，并评估海洋再分析模式中MOC变率的真实性。该项目的预期成果将为MOC的长期观测奠定基础，从而了解其与观测到的气候波动的关系，并进一步提高我们评估气候模式预测的能力。在项目第一阶段启动的与英国科学家的国际合作将继续进行。将向两名研究生提供最先进的海洋观测技术培训。该项目是对美国CLIVAR（气候变率和可预测性）计划的贡献

Climate models suggest that the meridional overturning circulation (MOC) in the Atlantic, and the accompanying oceanic heat flux, vary considerably on interannual time scales. In addition to abrupt climate change scenarios in which the MOC can virtually shut off, the "normal" interdecadal variation may range from 20% to 30% of its long-term mean value, according to some models. However, until recently no direct measurement system had been put in place that could provide regular estimates of the meridional overturning circulation to determine its natural variability or to assess these model predictions. Such a system is now deployed along 26.5-N in the Atlantic as part of the joint U.K./U.S. RAPID-MOCHA program, which has been continuously observing the MOC since March 2004.Intellectual merit: The goal of this project is to maintain this measurement system for an additional 6 years, from 2008 through 2014, so that a decade-long time series of the Atlantic MOC and associated meridional ocean heat flux can be obtained. This goal is different from, but complementary to, the more established method of occupying high-resolution zonal trans-basin hydrographic sections to estimate the MOC and heat flux at irregular intervals. Regular estimates are needed to determine the magnitude and dominant time scales of variability, the climatological seasonal cycle, and to help filter out the higher frequency "noise" that may alias the determination of longer term heat flux variations from trans-basin sections that are widely spaced in time. The proposed observations will provide the data necessary to document the spectrum of the observed MOC variability and to assess the MOC variability in ocean reanalysis models. The broader impacts of the proposal are to provide the basis for long-term monitoring of the MOC, so that its relationship to observed climate fluctuations can be understood, and our ability to assess climate model predictions can be improved. The proposed program continues a successful collaborative effort with investigators from the U.K. National Oceanography Centre and the Max Planck Institute in Germany. This component of the project will maintain the moored component in the eastern Atlantic for a six-year period extending from March 2008 to March 2014, and continue the collaboration with NOAA scientsits in the maintenance of the semiannual hydrographic/lowered-ADCP sections east of the Bahamas. The U.K. will support trans-basin hydrographic cruises and an extended array of moorings along 26.5-N that will complete the continuous time series observing system. Broader Impacts: The MOC observing system along 26.5-N in the Atlantic will provide the definitive data set necessary to document the spectrum of the observed MOC variability, and to assess the realism of MOC variability in ocean reanalysis models. The anticipated legacy of this program will be in laying the groundwork for long-term observation of the MOC, so that its relationship to observed climate fluctuations can be understood, and our ability to assess climate model predictions can be further improved. The international collaboration with UK scientists initiated under the first phase of the project will be continued. Training in state of the art ocean observational techniques will be provided to two graduate students.This project is a contribution to the U.S. CLIVAR (CLImate VARiability and predictability) program