Collaborative Research: The Norrona Project: An international collaboration for sustained studies of the Meridional Overturning Circulation between Denmark, The Faroes and Iceland

大西洋/经向翻转环流（A/MOC）是近年来人们日益关注的焦点。这在很大程度上是因为人们普遍认识到，流向高纬度地区的温暖咸水——北欧海——有助于形成中欧和北欧所经历的温和气候，毫无疑问也影响了北半球的气候。因此，MOC的强度和稳定性是气候难题中的一个关键参数，因此具有重大的社会意义。出于这个原因，2005年资助了一个项目，以监测穿过冰岛-法罗-苏格兰山脊流入北欧海的温水，这是一个天然的咽喉，几乎所有向北流动的水都必须经过。这项工程之所以如此吸引人，是因为它有一艘远洋渡轮Norröna，可以利用船上安装的多普勒声学海流计（ADCP）进行海流测量。Norröna每周运行一次，横跨法罗-设得兰海峡和冰岛-法罗山脊，这是两个主要的流入。一些意想不到的，但非常严重的启动问题（气泡缩小阻碍了音响效果）将项目推迟了两年。拥有这艘渡轮的公司已经竭尽全力提供帮助，目前正在收集大量数据。最初的四年拨款在去年增加了一年。该奖项将继续并加强该项目4年。首先，尽管由于一个整流罩和两个涡流发生器将清澈的水从下面带上来，气泡问题已经得到了改善，但还可以而且应该做更多的事情。具体来说，在9月份与船舶设计师合作的数值计算的帮助下，将寻找一个没有气泡的区域，也许更靠近船头。其次，利用水下摄像机对涡发生器的性能和尾迹结构进行验证。Norröna计划在即将到来的冬春季进行干船坞，届时将实施最后的调整，并将大大提高性能。关于adcp在商业船舶上的使用和放置，Norröna下的意外气泡问题是一个非常有价值的学习过程。其次，由于最近开发了一种新的自动化XBT发射器，热通量也可以通过结合ADCP和XBT数据直接测量。第三，研究小组将开始报告有关潮汐信号、EKE活动和流入的新发现。从科学角度来看，迄今为止最大的惊喜是法罗-设得兰海峡西侧的大量水流（向南），以至于通过该海峡的净水流似乎是向南的。知识价值：冰岛-法罗-苏格兰海岭分隔了两个巨大而截然不同的水团系统（北大西洋和北极地中海）。两者之间的交换是由风和浮力在很大范围内推动的。通过监测流入和流出（多亏了持续的系泊ADCP程序），人们可以相当详细地检查这些通量对时变大气强迫的时空响应，包括众所周知的北大西洋涛动。更广泛的影响：该团队在船舶操作adcp方面发展了广泛的专业知识。重复ADCP使人们能够以高水平分辨率和极大的信心测量海洋中的洋流和输送。直接测量电流增加了使用水文或测高的动态方法。高水平分辨率意味着可以分辨海洋中能量最高的尺度——通常由变形半径来定义。我们希望，对这一技术的更广泛的了解和使用，最终将导致在广泛的空间和时间尺度上改进对洋流的了解。

The Atlantic/meridional overturning circulation (A/MOC) has been the focus of growing attention in recent years. Much of this arises from the widespread recognition that the flow of warm, salty water to high latitudes - the Nordic Seas - helps shape the mild climate experienced across central and northern Europe and no doubt influences climate across the northern hemisphere. Thus the strength and stability of the MOC is a key parameter in the climate puzzle and therefore of great societal relevance. For this reason a project was funded in 2005 to monitor the inflow of warm water into the Nordic Seas across the Iceland-Faroe- Scotland ridge, a natural choke point through which virtually all north-flowing water must pass. What made the undertaking so attractive was the existence of an ocean-going ferry, the Norröna, from which current measurements using a vessel-mounted acoustic Doppler current meter (ADCP) could be made. The Norröna operates weekly across the Faroe-Shetland Channel and along the Iceland-Faroe ridge, the two major inflows. Some unexpected, but very serious start-up problems (bubble drawdown that blocks the acoustics) delayed the project by two years. The company that owns the ferry has gone out of its way to be helpful and substantial amounts of data are now being collected. The original four-year grant received a one-year add-on last year. This award is to continue and strengthen the project for an additional 4 years. First, although the bubble problem has been ameliorated thanks to a fairing and two vortex generators that bring clear water up from below, more can and should be done. Specifically, with the help of numerical calculations in collaboration with the ship designer in September an area free of bubbles will be sought, perhaps closer to the bow. Second, using an underwater camera will be used to verify the performance and wake structure of the vortex generators. Norröna is scheduled for dry-dock this coming winter-spring at which time the final adjustments will be implemented and should lead to substantially improved performance. The unanticipated problem of bubbles under the Norröna has been an extremely valuable learning process regarding the use and placement of ADCPs on commercial vessels. Second, thanks to the recent development of a new automated XBT launcher, heat fluxes can also be measured directly by combining the ADCP and XBT data. Third, the team will begin to report new findings about tidal signals, EKE activity, and inflows. Scientifically, the biggest surprise by far has been the substantial flow (to the south) on the western side of the Faroe-Shetland Channel such that the net flow through the channel appears to be to the south.Intellectual Merit: The Iceland-Faroe-Scotland ridge separates two large and distinctly different water mass systems (the North Atlantic and the Arctic Mediterranean). The exchange between the two is driven by both winds and buoyancy forcing over a wide range of scales. By monitoring the inflows and outflows (thanks to sustained moored ADCP programs) one can examine in considerable detail the space-time response of these fluxes to time-varying atmospheric forcing including the well-known North-Atlantic Oscillation.Broader Impacts: This team has developed extensive expertise with vessel-operated ADCPs. Repeat ADCP enables one to measure currents and transports in the ocean at high horizontal resolution and great confidence. Measuring currents directly adds to dynamical methods that use hydrography or altimetry. High horizontal resolution means resolving the most energetic scales in the ocean - often defined by the radius of deformation. We hope that wider knowledge and use of this technology will, in time, lead to an improved knowledge of ocean currents over a wide range of space and time scales.