大西洋经向翻转环流对岁差响应的气候背景依赖性

邓凤飞; 张旭

doi:10.12284/hyxb2022099

大西洋经向翻转环流对岁差响应的气候背景依赖性

doi: 10.12284/hyxb2022099

邓凤飞^1,,
张旭^{1, 2, 3, ,}

1.
兰州大学资源环境学院西部环境教育部重点实验室，甘肃兰州 730000
2.
中国科学院青藏高原研究所古生态与人类适应团队，北京 100101
3.
青藏高原地球系统与资源环境国家重点实验室，北京 100101

基金项目: 国家自然科学基金（42075047）；国家重点研发项目（2020YFA0608902）

详细信息

作者简介:
邓凤飞（1997-），女，河南省洛阳市人，从事古气候模拟研究。E-mail：dengff19@lzu.edu.cn

通讯作者:
张旭（1986-），男，教授，博士生导师，从事古气候模拟研究。E-mail：xu.zhang@itpcas.ac.cn

中图分类号: P731.27
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出版历程
- 收稿日期: 2021-07-14
- 修回日期: 2022-03-01
- 网络出版日期: 2022-04-14
- 刊出日期: 2022-08-29

Background climate dependence of Atlantic meridional overturning circulation responding to precessional change

Deng Fengfei^1
,,
Zhang Xu^{1, 2, 3
, ,}

1.
Key Laboratory of Western China’s Environmental Systems, Ministry of Education, College of Earth and Environmental Sciences, Lanzhou University, Lanzhou 730000, China
2.
Alpine Paleoecology and Human Adaption, Institute of Tibetan Research, Chinese Academy of Sciences, Beijing 100101, China
3.
State Key Laboratory of Tibetan Plateau Earth System, Resources and Environment, Beijing 100101, China

摘要

摘要: 大西洋经向翻转环流（Atlantic Meridional Overturning Circulation，AMOC）是气候系统重要的组成部分，其强度变化可直接影响南北半球的热量分配，厘清其变化机理对全球变暖背景下的未来预估至关重要。海洋沉积物记录发现，在晚更新世，AMOC的变化与地球岁差周期有紧密联系，但其物理机理尚不清楚。本文利用海洋−大气耦合气候模型—COSMOS（ECHAM5/JSBACH/MPIOM）模型，通过敏感试验，分析在冰盛期冷期和间冰期暖期气候背景下，AMOC对地球岁差变化的响应机理。结果表明：岁差降低引起的北半球夏季太阳辐射增强，会导致间冰期暖期背景下的AMOC显著减弱，但对冰盛期AMOC的影响并不明显。通过进一步分析发现，在间冰期暖期，夏季太阳辐射增强，造成高低纬大西洋海表的升温，同时促进北大西洋高纬度地区的局地降水，两者导致北大西洋表层海水密度降低，共同削弱大西洋深层水生成。而在冰盛期冷期，大西洋高低纬度地区的响应对AMOC的影响反向—副热带升温触发的海盆尺度低压异常，通过其南侧的西风异常削弱大西洋向太平洋的水汽输送，导致净降水增多，海表盐度下降；同时，高纬度升温造成的海冰减少，促进了海洋热丧失，海表失热变重，有利于大西洋深层水的生成，最终两者的共同作用导致AMOC对岁差变化的响应偏弱。本文系统揭示了不同气候背景下，岁差尺度AMOC变化的控制机理，对理解晚更新世AMOC重建记录中持续存在的岁差周期具有重要启示意义。
- 大西洋经向翻转环流 /
- 岁差周期 /
- 热带水文循环 /
- 气候背景依赖
Abstract: The Atlantic meridional overturning circulation (AMOC) is an important component of the climate system, of which change in the strength can affect meridional heat distribution between the northern and southern hemispheres. Proxy records show that changes in Atlantic Ocean circulation during the Late Pleistocene is associated with precessional cycle, but its physical mechanism remains unclear. Here we use a fully coupled climate model to investigate dynamics associated with AMOC changes in precessional band under glacial-interglacial climate conditions. Our results show that increase in boreal summer insolation can effectively weaken the AMOC during warm interglacial periods, while this weakening effect is reduced under glacial maximum. We further demonstrate that during the warm interglacial period increase in boreal summer insolation leads to sea surface warming and subpolar rainfall increase in North Atlantic, which jointly reduces sea surface density and hence the strength of deep water formation. During the glacial maximum period, climate responses to precessional change is of anti-phase impacts on the AMOC. At the low latitudes, a low pressure anomaly triggered by subtropical warming weakens atmospheric moisture export from the subtropical Atlantic to Pacific, increasing in net precipitation and hence freshening tropical sea surface in the North Atlantic. At the high latitudes, the warming-induced sea ice retreat promotes ocean heat loss via the enlarged ice-free area, and hence tends to strengthen the vertical mixing. The combined effects of low- and high-latitude responses finally leads to a trivial weakening of the AMOC. Overall, our results provide a systematic understanding of governing mechanism for precessionally-induced AMOC change under glacial-interglacial climatic backgrounds, shedding light on our interpretation of precessional periodicity in reconstructed ocean circulation changes during the Pleistocene.
- Atlantic meridional overturning circulation /
- precessional cycle /
- tropical hydroclimate /
- climate background dependence

HTML全文

图 1 工业革命前时期强（P_min）、弱（P_max）季节性背景下大气层顶辐射强迫差异场（修改自文献[27]）

Fig. 1 Anomalous field of solar radiation reaching the top of the atmosphere between strong (P_min) and weak (P_max) seasonal background under pre-industrial period (modified from reference [27])

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图 2 强、弱季节性背景下大西洋经向翻转环流（AMOC）的差异场

Fig. 2 Atlantic meridional overturning circulation (AMOC) anomaly between strong and weak seasonal background

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图 3 工业革命前（PI）（a, c）和末次盛冰期（LGM）（b, d）背景下不同气候要素的差异场

a. PI时期夏季海表温度−气压差异场；b. LGM时期夏季海表温度−气压差异场，a和b中填色代表温度差异，黑色等值线代表海平面气压差异（hPa）；c. PI时期夏季海表有效降水−水汽输送差异场；d. LGM时期夏季海表有效降水−水汽输送差异场，c和d中填色代表有效降水差异，箭头代表水汽通量差异（单位：kg/（m·s））

Fig. 3 Climate response to changes in precession under pre-industrial (PI) (a, c) and the glacial maximum period (LGM) (b, d) backgrounds

a. Summer sea surface temperature-pressure difference field in PI period; b. the summer sea surface temperature-pressure difference field in LGM period, the coloring represents the temperature difference, and the black isoline represents the sea level pressure difference (hPa) field; c. the summer sea surface effective precipitation-water vapor transport difference field in PI period; d. the summer sea surface effective precipitation-water vapor transport difference field in LGM period, the coloring represents the difference of effective precipitation, and the arrow represents the difference of water vapor flux (unit : kg/(m·s))

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图 6 工业革命前（PI）和末次盛冰期（LGM），最高值与最低值的夏季海冰密集度和冬季垂直混合层深度的差异场

a. PI时期夏季海冰密集度的差异场；b. LGM时期夏季海冰密集度的差异场；c.PI时期冬季垂直混合深度的差异场；d. LGM时期冬季垂直混合深度的差异场。绿线和红线分别对应P_max和P_min时期15%海冰密集度分界线

Fig. 6 Anomalous fields of summer sea ice concentration and winter vertical mixing layer depth between P_min and P_max under pre-industrial (PI) and the glacial maximum (LGM) conditions

a. The difference field of sea ice concentration in summer in PI period; b. the difference field of sea ice concentration in summer in LGM period; c. the difference field of vertical mixing layer depth in winter in PI period; d. difference field of vertical mixing layer depth in winter in LGM period. Green and red lines represent 15% sea ice concentration in P_max and P_min, respectively

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图 4 工业革命前（PI）和末次盛冰期（LGM）时期年均海表密度（a, d）、温度（b, e）、盐度（c, f）差异场（上行为强季节背景，下行是弱季节性背景）

Fig. 4 Difference fields of average annual sea surface density (a, d), temperature (b, e) and salinity (c, f) during pre-industrial (PI) and the glacial maximum (LGM) periods (strong seasonal background on the top and weak seasonal background on the bottom)

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图 5 强、弱季节性情景北半球高纬年均有效降水差异场

Fig. 5 Annual effective precipitation difference field at high latitude in the Northern Hemisphere under strong and weak seasonal scenarios

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A2 工业革命前（PI）和末次盛冰期（LGM）年均海冰分布

A2 Climatology mean annual sea ice distribution during pre-industrial (PI) and the glacial maximum (LGM) periods

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图 7 强、弱季节性背景北半球高纬地表气温差异场

绿线和红线分别对应 P_max和 P_min时期 15% 海冰密集度分界线

Fig. 7 Surface air temperature anomaly field at high latitude in the Northern Hemisphere under strong and weak seasonal background

Green and red lines represent 15% sea ice concentration in P_max and P_min , respectively

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A1 工业革命前（PI）和末次盛冰期（LGM）强、弱季节性情景下的大西洋经向翻转环流分布

a, c是强季节性背景；b, d是弱季节性背景

A1 Spatial pattern of the Atlantic meridional overturning circulation under P_min and P_max in pre-industrial (PI) and the glacial maximum (LGM) periods

a,c. PI climate background; b, d. LGM climate background

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表 1 具体试验设置

Tab. 1 Specific experimental settings

试验名称	CO₂含量 /10⁻⁶	CH₄含量 /10⁻⁹	N₂O含量 /10⁻⁹	偏心率	倾角 /(°)	岁差 /(°)	等效海平面/m
ORB001	280	760	270	0.04	23.446	90	0
ORB002	280	760	270	0.04	23.446	270	0
ORB01lgm	185	350	200	0.04	24.5	90	116
ORB02lgm	185	350	200	0.04	24.5	270	116

下载: 导出CSV

A1 6°~14°N，90°~75°W区域的水汽输送（单位：kg/（m·s））

A1 Integrated water vapor transport across area in 6°−14°N, 90°−75°W (unit: kg/(m·s))

试验名称	水汽输送	年均	春季	夏季	秋季	冬季	5−9月
ORB001	纬向	−126.76	−182.286	−144.391	8.16864	−188.532	−113.281
	经向	−9.96022	−26.442	30.3474	12.409	−56.1552	30.7718
	合成后	127.151	184.194	147.545	14.8563	196.717	117.386
ORB002	纬向	−175.303	−195.216	−233.976	−73.5462	−198.475	−200.19
	经向	−13.9999	−32.7454	31.0561	16.0139	−70.3243	29.0856
	合成后	175.861	197.943	236.028	75.2694	210.565	202.292
ORB01lgm	纬向	−92.5443	−159.29	−49.1301	−15.8694	−145.887	−59.1867
	经向	−11.8552	−17.5885	27.6077	−12.4783	−44.9616	22.9494
	合成后	93.3006	160.258	56.3556	20.1877	152.659	63.4803
ORB02lgm	纬向	−142.635	−176.768	−165.993	−58.9051	−168.875	−146.019
	经向	−17.2861	−27.6586	22.6438	−1.23924	−62.8904	20.189
	合成后	143.679	178.919	167.53	58.9181	180.205	147.408

下载: 导出CSV

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