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

大多数全球气候模式预测，与目前相比，在未来的气候情景中，向北的海洋热量输送将在北纬60度以北增加。这种热传输的增加让人想起最近在北冰洋欧亚海盆西部的大西洋层观察到的变暖的解释。这意味着，像那些在不久的过去发生的变暖，这已被归因于风的变化，也可能发生在未来由于温室气体的强迫。这项工作假设，在未来的温室效应情景中，热传输的增加是响应于从常年过渡到第一年冰在巴伦支海和北冰洋，并且在秋季和冬季伴随着热损失和盐水排斥的增加。海冰的产生排斥了盐水，推动了重力对流，从而产生了密集的陆架沃茨，并促进了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，冰的产生-热传输的相互作用必须超过北极地区降水和径流增加所带来的稳定性增加。这种机制将进一步加速从常年冰到第一年冰的过渡，并减少未来的总体海冰覆盖。共同体气候系统模式第三版（CCSM 3）是一个完全耦合的大气-海洋模式，可以明确地解决海冰厚度分布，显示了向北的海洋热量输送（和纬向翻转环流）的峰值大约在同一时间，在未来的情况下，冰生产在北冰洋的峰值。这是一项由两部分组成的研究：第一个目标是研究在未来全球气候模式的情景中，北欧海和北冰洋的热传输增加的原因，并评估这种增加对海冰覆盖的后果。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，以及在未来气候变化情景中，海冰厚度分布与海洋热量向北极输送增加的关系。海冰-海洋系统之间正反馈的研究可以解释在气候模型的温室效应情景中看到的海洋热量输送到北极的增加。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。这项工作还将发展一种预测冰厚分布随气候扰动而变化的一般方法。

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.