Modeling the Freshening and Cooling Event in the Subpolar North Atlantic Ocean and its Impact on Thermohaline Circulation

在过去的40年里，亚极地北大西洋发生了大范围、全深度的冷却和清新。与此同时，北欧海域流经法罗浅滩海峡的流量减少，这是形成北欧反兴奋剂机构的一个关键过程。观察表明，北欧海和大西洋之间的相互作用可能在这一事件的发展中发挥了关键作用。PI建议使用数值模式来研究引起观测到的变化的机制和相互作用，并评估它们对热带和亚热带大西洋的温盐环流(THC)和海洋环流的影响。由于这种交换所固有的动力和尺度与公海上的大气环流有很大的不同，大多数海洋大气环流模式(OGCM)还不足以模拟北欧海和大西洋之间的相互作用。在美国国家科学基金会之前的一笔赠款的支持下，PI和Jim Price博士开发了一个耦合的OGCM/边际海洋模型，其具体目的是将其应用于北大西洋次极地。这个耦合模式代表了研究北欧海溢流、陆架断裂处的密度流卷吸和公海过程之间相互作用的最先进的数值工具。该模式将被用来研究(1)过去40年北大西洋涛动持续的正状态如何影响北欧海域的淡水收支；(2)通过丹麦海峡和法罗浅滩海峡的溢出如何响应北欧海洋的淡水强迫；(3)溢出的源水的淡水如何影响陆架断裂处的夹带率，从而影响NADW的性质和产量；(4)THC如何响应NADW产量的变化；(5)风生环流在这次冷却和淡化事件中发挥了什么作用；(6)低纬海洋环流对NADW和THC变化的响应。

ABSTRACTOCE-0351055Large-scale and full-depth cooling and freshening have occurred in the subpolar North Atlantic Ocean in the last four decades. This was accompanied by a reduction of the Nordic Seas overflow through the Faroe Bank Channel, a key process for the NADW formation. Observations indicated that interaction between the Nordic Seas and the Atlantic Ocean may have played a key role in the development of this event. The PI proposes to use numerical models to study mechanisms and interactions that give rise to the observed changes, and to assess their impacts on the thermohaline circulation (THC) and on ocean circulations in the tropical and subtropical Atlantic Ocean. Since the dynamics and scales inherent to such exchanges are very different from that of the general circulation over the open ocean, most ocean general circulation models (OGCMs) are not yet adequate for modeling interactions between the Nordic Seas and the Atlantic Ocean. Supported by a previous NSF grant, the PI and Dr. Jim Price have developed a coupled OGCM/marginal-sea model with the specific purpose of applying it in the subpolar North Atlantic Ocean. This coupled model represents a state of the art numerical tool for studying interactions among the Nordic Seas overflow, the density current entrainment at shelf breaks, and open ocean processes. The model will be used to address (1) how the sustained positive state of North Atlantic Oscillation in the last 4 decades a?ected the fresh water budget in the Nordic Seas; (2) how the overflow through the Denmark Strait and Faroe Bank Channel responded to the fresh water forcing in the Nordic Seas; (3) how the freshening of the overflowed source water a?ected the entrainment rate at shelf breaks and thus the property and production of NADW; (4) how the THC responded to changes in NADW production; (5) what role the wind-driven circulation played in this cooling and freshening event; (6) how the circulation in the low-latitude ocean responded to the NADW and THC changes.