气候变化领域集成服务门户(CCPortal): What causes the AMOC to weaken in CMIP5?

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DOI	10.1175/JCLI-D-19-0547.1
	What causes the AMOC to weaken in CMIP5?
	Levang S.J.; Schmitt R.W.
发表日期	2020
ISSN	0894-8755
起始页码	1535
结束页码	1545
卷号	33 期号:4
英文摘要	In a transient warming scenario, the North Atlantic is influenced by a complex pattern of surface buoyancy flux changes that ultimately weaken the Atlantic meridional overturning circulation (AMOC). Here we study the AMOC response in the CMIP5 experiment, using the near-geostrophic balance of the AMOC on interannual time scales to identify the role of temperature and salinity changes in altering the circulation. The thermal wind relationship is used to quantify changes in the zonal density gradients that control the strength of the flow. At 408N, where the overturning cell is at its strongest, weakening of the AMOC is largely driven by warming between 1000- and 2000-m depth along the western margin. Despite significant subpolar surface freshening, salinity changes are small in the deep branch of the circulation. This is likely due to the influence of anomalously salty water in the subpolar intermediate layers, which is carried northward from the subtropics in the upper limb of the AMOC. In the upper 1000 m at 408N, salty anomalies due to increased evaporation largely cancel the buoyancy increase due to warming. Therefore, in CMIP5, temperature dynamics are responsible for AMOC weakening, while freshwater forcing instead acts to strengthen the circulation in the net. These results indicate that past modeling studies of AMOC weakening, which rely on freshwater hosing in the subpolar gyre, may not be directly applicable to a more complex warming scenario. © 2020 American Meteorological Society.
英文关键词	Buoyancy; Climate models; Water; Atlantic meridional overturning circulations; Density gradients; Geostrophic balance; Interannual time scale; Intermediate layers; Surface buoyancy flux; Surface freshening; Temperature dynamics; Oceanography; air-sea interaction; buoyancy; CMIP; global warming; gyre; meridional circulation; overturn; salinity; surface temperature; Atlantic Ocean; Atlantic Ocean (North)
语种	英语
来源期刊	Journal of Climate
文献类型	期刊论文
条目标识符	http://gcip.llas.ac.cn/handle/2XKMVOVA/171436
作者单位	Woods Hole Oceanographic Institution, Woods Hole, MA, United States
推荐引用方式 GB/T 7714	Levang S.J.,Schmitt R.W.. What causes the AMOC to weaken in CMIP5?[J],2020,33(4).
APA	Levang S.J.,&Schmitt R.W..(2020).What causes the AMOC to weaken in CMIP5?.Journal of Climate,33(4).
MLA	Levang S.J.,et al."What causes the AMOC to weaken in CMIP5?".Journal of Climate 33.4(2020).