Investigating the feedbacks between CO2, vegetation and the AMOC in a coupled climate model
Investigating the feedbacks between CO2, vegetation and the AMOC in a coupled climate model
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DOI：
10.1007/s00382-019-04634-2
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发表时间：
2019-09-01
期刊：
影响因子：
4.6
通讯作者：
Singarayer, Joy
中科院分区：
文献类型：
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作者：
Armstrong, Edward;Valdes, Paul;Singarayer, Joy
大西洋经向翻转环流（AMOC）是气候系统的重要组成部分，但其对陆地生物圈的敏感性却被忽视。在这里，HadCM 3耦合气候模式运行千年的时间尺度，调查植被和AMOC之间的反馈，在增加CO2。农业转换（称为土地利用变化; LUC）的影响和模拟的“背景”植被（称为土地覆盖变化; LCC）的作用进行了研究。LUC使高作物比例地区的气候变冷，这是由于干旱增加。LCC被证明是在更高的CO2，在北方半球和亚马逊枯死的树线向北迁移的演变。这通常会增强主要由气候变化引起的气候变化的影响。格陵兰岛-冰岛-挪威（GIN）海域的密度对驱动AMOC至关重要。增加CO2会降低区域海面密度，减少对流并削弱AMOC。LCC的列入被证明是负责这种削弱的一个显着比例，反映了放大效应，它对气候变化。这会降低GIN海的表面密度。在升高的CO2（1400 ppm）的列入动态植被被证明是驱动器的AMOC强度从6%到20%的减少。尽管LUC的冷却效果，对AMOC的影响被证明是小的，反映了它对GIN海密度的影响最小。这些结果表明，包括动态植被在未来的AMOC研究使用HadCM 3的重要性，但LUC可能是微不足道的。然而，在其他气候模型的背景下，植被的重要性可能会被其他系统性模型偏差所掩盖。
The Atlantic Meridional Overturning Circulation (AMOC) is an important component of the climate system, however its sensitivity to the terrestrial biosphere has been largely overlooked. Here the HadCM3 coupled climate model is run for millennial timescales to investigate the feedbacks between vegetation and the AMOC at increasing CO2. The impact of agricultural conversion (termed land-use change; LUC) and the role of the simulated 'background' vegetation (termed land cover change; LCC) are investigated. LUC cools climate in regions of high crop fraction due to increased albedo. LCC is shown to evolve at higher CO2, with a northward migration of the tree line in the Northern Hemisphere and dieback of the Amazon. This generally acts to enhance the impact of climate change primarily due to albedo changes. Density in the Greenland-Iceland-Norwegian (GIN) Seas is crucial in driving the AMOC. Increasing CO2 decreases regional sea surface density, reducing convection and weakening the AMOC. The inclusion of LCC is shown to be responsible for a significant proportion of this weakening; reflecting the amplification effect it has on climate change. This acts to decrease the surface density in the GIN Seas. At elevated CO2 (1400 ppm) the inclusion of dynamic vegetation is shown to drive a reduction in AMOC strength from 6 to 20%. Despite the cooling effect of LUC, the impact on the AMOC is shown to be small reflecting minimal impact it has on GIN Sea density. These results indicate the importance of including dynamic vegetation in future AMOC studies using HadCM3, but LUC may be insignificant. In the context of other climate models however, the importance of vegetation is likely to be overshadowed by other systemic model biases.