The Mutual Interaction Between Ice Production and Ocean Heat Transport in a Greenhouse Warming Scenario

大多数全球气候模型预测，与现在相比，未来气候情景中向北的海洋热量输送将增加约60N。热量输送的这种增加让人想起了对最近在北冰洋欧亚盆地西部观察到的大西洋层变暖的解释。这意味着，由于温室气体的强迫，未来也可能发生像最近发生的那样的变暖，一些人将其归因于风的变化。这项研究假设，未来温室情景中热量传输的增加是对巴伦支海和北冰洋从常年冰到第一年冰过渡的反应，以及随之而来的秋季和冬季热量损失和盐水排斥的增加。海冰的产生拒绝了盐水，驱动了重力对流，这创造了密集的陆架水域，并鼓励了从大西洋层到表面的热量和质量交换。如果这一假设是正确的，那么在气候变暖的情况下，北极地区的降水和径流增加所带来的稳定性增加，一定会超过冰生产与热量输送之间的相互作用。这种机制将进一步加速从常年冰到第一年冰的过渡，并在未来减少总的海冰覆盖率。利用社区气候系统模式3(CCSM3)的模拟表明，向北的海洋热输送(和经向翻转环流)与北冰洋的冰生产在未来情景中达到峰值的时间大致相同。CCSM3是一个完全耦合的大气-海洋模式，明确地解析了海冰厚度分布。这是一项由两部分组成的研究：第一个目标是利用全球气候模式在未来情景中调查北欧海和北冰洋热量输送增加的原因，并评估这种增加对海冰覆盖的影响。第二个目标是了解海冰厚度分布对温室气体增加的敏感性，以及它与未来气候变化情景中进入北极的海洋热传输增加的关系(如果有的话)。这项对海冰-海洋系统之间正反馈的调查可能解释了在气候模型的温室变暖情景中，进入北极的海洋热传输增加的原因。北极从常年海冰到第一年海冰的转变，以及随之而来的冰产量的增加，是反馈过程的第一步。这项工作还将开发一种通用方法，用于预测冰层厚度分布随气候扰动的变化。

Most global climate models predict an increase in the northward oceanic heat transport north of about 60 N in future climate scenarios as compared to the present day. This increase in heat transport is reminiscent of explanations posed for recent observed warming in the Atlantic layer in the western Eurasian Basin of the Arctic Ocean. An implication is that warmings like those that occurred in the recent past, which have been attributed to wind variations by some, could also occur in the future due to greenhouse gas forcing.This work hypothesizes that the increase in heat transport in the future greenhouse scenario is in response to the transition from perennial to first year ice in the Barents Sea and Arctic Ocean, and the attendant increase in heat loss and brine rejection in fall and winter. Sea ice production rejects brine, driving gravitational convection, which creates dense shelf waters and encourages heat and mass exchange from the Atlantic layer to the surface. If the hypothesis is correct, the ice production-heat transport interaction must outweigh the increase in stability from increased precipitation and runoff in the Arctic in a warmer climate. Such a mechanism would further accelerate the transition from perennial to first year ice and reduce the overall sea ice cover in the future.Simulations with the Community Climate System Model Version 3 (CCSM3), a fully coupled atmosphere-ocean model that explicitly resolves the sea ice thickness distribution, show that northward oceanic heat transport (and the meridional overturning circulation) peak at about the same time that ice production peaks in the Arctic Ocean in a future scenario. This is a two part study: the first objective is to investigate the reason that heat transport increases into the Nordic Seas and Arctic Ocean in future scenarios with global climate models and assess the consequences of this increase for the sea ice cover. The second objective is to understand the sensitivity of the sea ice thickness distribution to increased greenhouse gases, and its relation, if any, to the increase oceanic heat transport into the Arctic in future climate change scenarios. This investigation of a positive feedback between sea ice-ocean system may explain the increase in oceanic heat transport into the Arctic that is seen in greenhouse warming scenarios with climate models. A transformation from perennial sea ice to first year sea ice in the Arctic, and the attendant increase in ice production is the first step of the feedback process. This work will also develop a general method for predicting the change in the ice thickness distribution in response to a climate perturbation.