Collaborative Research: Mode Water Formation in the Lofoten Basin: A Key Element in the Meridional Overturning Circulation

该奖项是根据2009年美国复苏和再投资法案（公法111-5）资助的。北大西洋的深对流区-拉布拉多海和格陵兰海-在驱动大西洋经向翻转环流（AMOC）及其相关的向极热输送中所发挥的传统核心作用在过去十年中受到了严重质疑。特别地，现在已知的是，在这些区域中发生相对较少的下沉和仅有限的表面浮力损失，此外，供给AMOC的稠密水团不是这些区域的直接产物。在北欧海的情况下，格陵兰-苏格兰溢出沃茨包括AMOC的最深分支只含有少量的格陵兰海水，而不是主要是循环的温暖，咸大西洋沃茨的逐步转变的产物。然而，这种转变发生的途径和过程在很大程度上尚不清楚。在这一转变中发挥核心作用的是罗弗敦盆地，它毗邻格陵兰海，位于大西洋流入的两个主要分支之间。温暖的，咸的大西洋沃茨强烈修改，因为他们通过这个盆地，这单独占了北欧海表面浮力损失的很大一部分。这导致形成一种中间对流产物，即罗弗敦盆地模式水。与拉布拉多海水和格陵兰海水不同，罗弗敦盆地模式水可以迅速从盆地输出，是溢出沃茨的直接来源。尽管它的重要性，但是，这个盆地的基本动力学特征和它的中间水团的形成尚未得到解决。该项目的主要智力价值是它的重要性，阐明了AMOC的一个关键方面，即模式水的形成在罗弗敦盆地及其在北欧海洋转型途径的作用。该项目是及时的，因为有越来越多的证据表明，格陵兰海的深对流本身对AMOC的影响有限，同时，我们对中间/密集转化途径的理解大大提高。通过使用拉布拉多海作为参考点，研究人员预计将有助于更普遍地了解存在不同地形和不稳定边界流的对流转化。结合观测和模拟研究将调查模式水形成在罗弗敦盆地及其最终出口。剖面系泊与直接部署在盆地内的RAFOS浮子一起将澄清转化、限制和扩散的年度循环。对现有水文、浮标和遥感数据的分析将有助于指导实地工作，并有助于调查更大范围和更长期的变化。将采用各种模型来研究罗弗敦海盆和北欧海其他地方的转化过程的动力学。最终结果将是对沿着AMOC这一重要分支的海气通量和海洋动力学之间的相互作用有新的认识。更广泛的影响该项目旨在提高我们对地球气候系统中关键过程的理解，北欧海洋转化途径，不仅影响AMOC，而且还影响流入北冰洋的暖流，该地区目前正在发生快速变化。该项目是与几个挪威和其他欧洲集团合作精心规划的，以优化资源和促进国际合作。它包括两个研讨会，以及整个项目的数据，想法和人员交流。最后，它汇集了一组不同的PI，谁将带来互补的技能，这个问题，并包括博士后谁将大大受益于这个项目的多样化和国际科学环境的培训。

This award is funded under the American Recovery and Reinvestment Act of 2009 (Public Law 111-5).The traditionally central role played by the deep convective regions of the North Atlantic - the Labrador Sea and the Greenland Sea - in driving the Atlantic Meridional Overturning Circulation (AMOC) and its associated poleward heat transport has been severely questioned over the last decade. In particular, it is now known that relatively little sinking and only a limited surface buoyancy loss occurs in these regions and, furthermore, that the dense water masses feeding the AMOC are not a direct product of these regions. In the case of the Nordic Seas, the Greenland-Scotland overflow waters comprising the deepest branch of the AMOC contain only small amounts of Greenland Sea Water, and are instead largely the product of the progressive transformation of the circulating warm, salty Atlantic Waters. Yet the pathways and processes through which this transformation occurs are largely unknown. Emerging as playing a central role in this transformation is the Lofoten Basin, which sits adjacent to the Greenland Sea between the two main branches of the Atlantic inflow. The warm, salty Atlantic waters are strongly modified as they transit through this basin, which alone accounts for a substantial fraction of the surface buoyancy loss over the Nordic Seas. This leads to the formation of an intermediate convected product, the Lofoten Basin Mode Water. Unlike Labrador Sea Water and Greenland Sea Water, the Lofoten Basin Mode Water can be rapidly exported from the basin, and is a direct source for the overflows waters. Despite its importance, however, the basic dynamical features of this basin and of its intermediate water mass formation have yet to be addressed. Intellectual MeritThe principal intellectual merit of this project is its importance for elucidating a key facet of the AMOC, namely, mode water formation in the Lofoten Basin and its role in the Nordic Seas transformation pathway. The project is timely since there is growing evidence that the Greenland Sea's deep convection by itself has a limited impact on the AMOC and, at the same time, our understanding of intermediate/dense transformation pathways has greatly improved. By using the Labrador Sea as a reference point, the investigators anticipate contributing to a more universal understanding of convective transformation in the presence of varied topography and an unstable boundary current. The combined observational and modeling study will investigate mode water formation in the Lofoten Basin and its eventual export. A profiling mooring together with RAFOS floats deployed directly within the basin will clarify the annual cycle of transformation, restratification, and dispersal. Analysis of existing hydrographic, float, and remote sensing data will help to guide the field work, and will enable the investigation of larger-scale and longer-term variability. A variety of models will be employed to study the dynamics of the transformation process in the Lofoten Basin and elsewhere in the Nordic Seas. The net result will be a new understanding of the interaction between air-sea fluxes and ocean dynamics along this crucial branch of the AMOC. Broader ImpactsThis project seeks to increase our understanding of a key process in the Earth's climate system, the Nordic Seas transformation pathway, which affects not only the AMOC but, also, the warm inflow into the Arctic Ocean, a region currently undergoing rapid change. The project has been carefully planned in collaboration with several Norwegian and other European groups so as to optimize resources and foster international collaboration. It includes two workshops, as well as exchange of data, ideas, and personnel throughout the project. Finally, it brings together a group of diverse PIs, who will bring complementary skills to this problem, and includes training of a post-doc who will greatly benefit from the diverse and international scientific environment of this project.