Collaborative Research: The Norrona Project: An International Collaboration for Sustained Studies of the Meridional Overturning Circulation between Denmark, the Faroes and Iceland

近几年来，大西洋/经向翻转环流(A/MOC)一直是人们关注的焦点。这在很大程度上是因为人们普遍认识到，温暖的咸水流向高纬度--北欧海--有助于塑造中欧和北欧经历的温和气候，并无疑影响整个北半球的气候。因此，交通部的实力和稳定性是气候之谜中的一个关键参数，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，监测暖水通过冰岛-法罗-苏格兰海脊流入北欧海洋的情况，这是一个天然的阻塞点，几乎所有北上流动的水都必须通过。这项工程之所以如此吸引人，是因为有一艘名为诺罗纳(Norröna)的远洋渡轮的存在，在该渡轮上可以使用船载声学多普勒海流计(ADCP)进行海流测量。Norröna每周运营一次，横跨法罗-设得兰海峡和冰岛-法罗海脊，这是两个主要的流入地区。一些意想不到但非常严重的启动问题(气泡缩小阻碍了声学)将项目推迟了两年。拥有该渡轮的公司已经不遗余力地提供帮助，目前正在收集大量数据。最初的四年拨款在去年获得了一年的额外拨款。这一奖项是为了继续和加强该项目4年的时间。首先，尽管泡沫问题已经得到改善，这要归功于一个整流罩和两个涡流发生器，它们将清水从下面带上来，但我们可以而且应该做更多的事情。具体地说，在9月份与船舶设计者合作的数值计算的帮助下，将寻找一个没有气泡的区域，可能更靠近船头。其次，将使用水下相机来验证涡旋发生器的性能和尾迹结构。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，并应导致性能的大幅提高。Norröna下的气泡问题是关于商业船舶上ADCP的使用和放置的一个极其有价值的学习过程。其次，由于最近开发了一种新的自动XBT发射器，也可以通过结合ADCP和XBT数据直接测量热通量。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。科学上，迄今为止最令人惊讶的是法罗-设得兰海峡西侧的大量水流(向南)，因此通过该海峡的净水流似乎是向南的。智力上的优点：冰岛-法罗-苏格兰海脊分隔了两个明显不同的大型水团系统(北大西洋和北冰洋)。这两者之间的交换是由风和浮力在大范围的尺度上强迫推动的。通过监测流入和流出(由于持续的系泊ADCP计划)，人们可以相当详细地检查这些通量对包括众所周知的北大西洋振荡在内的时变大气强迫的时空响应。广泛的影响：该团队在船舶操作的ADCP方面发展了广泛的专业知识。Repeat ADCP使人们能够以高水平分辨率和极大的置信度测量海洋中的洋流和输运。直接测量海流增加了使用水文或测高的动力学方法。高水平分辨率意味着分辨海洋中最高能量的尺度--通常由变形半径定义。我们希望，随着时间的推移，对这项技术的更广泛的了解和使用将有助于改进对各种空间和时间尺度上的洋流的了解。

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.