Scaling Global Warming Impacts on Ocean Ecosystems: Lessons From a Suite of Earth System Models
Scaling Global Warming Impacts on Ocean Ecosystems: Lessons From a Suite of Earth System Models
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DOI：
10.3389/fmars.2020.00698
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发表时间：
2020-09
期刊：
影响因子：
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通讯作者：
A. Bahl;A. Gnanadesikan;M. Pradal
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文献类型：
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作者：
A. Bahl;A. Gnanadesikan;M. Pradal
气候建模人员用来隔离温室气体增加对地球系统进程的影响的一项重要技术是模拟二氧化碳突然增加的影响。变化的空间模式提供了一个通常比自然变异性大得多的“指纹”。只要对辐射强迫的反应是线性的(二氧化碳增加四倍的影响是二氧化碳加倍的影响的两倍)，这个指纹就可以用来估计历史上温室气体强迫的影响。然而，生物地球化学循环对辐射强迫的线性响应程度很少被测试。在这篇文章中，我们评估了哪些海洋生物地球化学场可能对变化的辐射强迫做出线性响应，哪些不是，以及线性被破坏的地方。我们还证明了由中尺度涡旋表示的横向混合在不同气候模式中显著不同，在调制线性分解中起着重要作用。生物地球化学循环的全球综合地表速率(初级生产力、颗粒输出)以相对线性的方式作出反应，对混合只有中等程度的敏感性。相比之下，内陆海洋的宜居性(由低氧和方解石过饱和决定)表现为非线性行为，对混合非常敏感。这是因为深海以及表层海洋中的某些区域对冬季深对流的强度非常敏感。全球变暖条件下对流的停止受涡旋混合的强烈影响。
An important technique used by climate modelers to isolate the impacts of increasing greenhouse gasses on Earth System processes is to simulate the impact of an abrupt increase in carbon dioxide. The spatial pattern of change provides a “fingerprint” that is generally much larger than natural variability. Insofar as the response to radiative forcing is linear (the impact of quadrupling CO2 is twice the impact of doubling CO2) this fingerprint can then be used to estimate the impact of historical greenhouse gas forcing. However, the degree to which biogeochemical cycles respond linearly to radiative forcing has rarely been tested. In this paper, we evaluate which ocean biogeochemical fields are likely to respond linearly to changing radiative forcing, which ones do not, and where linearity breaks down. We also demonstrate that the representation of lateral mixing by mesoscale eddies, which varies significantly across climate models, plays an important role in modulating the breakdown of linearity. Globally integrated surface rates of biogeochemical cycling (primary productivity, particulate export) respond in a relatively linear fashion and are only moderately sensitive to mixing. By contrast, the habitability of the interior ocean (as determined by hypoxia and calcite supersaturation) behaves non-linearly and is very sensitive to mixing. This is because the deep ocean, as well as certain regions in the surface ocean, are very sensitive to the magnitude of deep wintertime convection. The cessation of convection under global warming is strongly modulated by the representation of eddy mixing.