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

近40年来，北大西洋次极区发生了大规模和全深度的降温和降温。与此同时，通过法罗海岸海峡的北欧海溢流减少，这是NADW形成的一个关键过程。观测表明，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，并评估它们对热盐环流（THC）和热带和亚热带大西洋海洋环流的影响。由于这种交换所固有的动力和尺度与公海上的环流非常不同，大多数海洋环流模式（ogcm）尚不足以模拟北欧海和大西洋之间的相互作用。在先前国家科学基金的资助下，PI和Jim Price博士开发了OGCM/边缘海耦合模型，并将其应用于北大西洋的次极地。这个耦合模型代表了研究北欧海溢出、陆架断裂处的密度流夹带和开放海洋过程之间相互作用的最先进的数值工具。该模式将用于解决(1)如何在过去的40年里北大西洋涛动的持续积极状态a？选择了北欧海的淡水预算；(2)通过丹麦海峡和法罗海峡的溢流如何响应北欧海的淡水强迫；(3)如何净化溢出的水源？检测了货架断裂处的夹带速率，从而检测了NADW的性质和产生；(4)四氢大麻酚如何响应NADW产量的变化；(5)风动环流在此次降温降温过程中发挥了怎样的作用；(6)低纬度海洋环流对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.