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 730099
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。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：.zhangxu@lzu.edu.cn

中图分类号: P731.25
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- 文章访问数: 29
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- 被引次数: 0
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

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, Gansu
2.
Alpine Paleoecology and Human Adaption(ALPHA), Chinese Academy of Sciences, Beijing 100101
3.
State Key Laboratory of Tibetan Plateau Earth System, Resources and Environment (TPESRE), Beijing 100101

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COSMOS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 hemisphere. Proxy records show that changes in Atlantic ocean circulation during the Late Pleistocene is associated with precessional cycle (~20 kyr), 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.
- AMOC /
- Precessional cycle /
- Tropical hydroclimate /
- Climate background dependence

HTML全文

图 1 PI时期强弱季节性背景下大气层顶辐射强迫差异场（Pmin-Pmax）^[26]

Fig. 1 Anomalous field of solar radiation reaching the top of the atmosphere between strong (Pmin) and weak (Pmax) seasonal background under PI ^[26]

下载: 全尺寸图片幻灯片

图 2 强弱季节性背景下AMOC的差异场（Pmin-Pmax），图a是PI时期，图b是LGM时期

Fig. 2 AMOC anomaly between strong (Pmin) and weak (Pmax) seasonality scenarios under a) PI and b) LGM conditions

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图 3 PI和LGM背景下不同气候要素的Pmin-Pmax差异场，a) 填色图是PI时期夏季海表温度的差异场，叠加PI时期夏季海表面气压的差异场；b)同a，是LGM时期；c）填色图是PI时期夏季海表净降水的差异场，矢量图是PI时期整层水汽输送的差异场；d）同c，是LGM时期

Fig. 3 Climate response to changes in precession under PI (a, c) and LGM (b, d) backgrounds. a) shaded is summer sea surface temperature anomaly, and contour represents summer sea surface pressure; b) same as a, but for LGM period; c) shaded is the summer sea surface salinity anomaly, and vector is vertical integrated water vapor transport; d) The same as C, is LGM period

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图 4 PI和LGM时期年均海表密度（a,d）、温度(b,e)、盐度(c,f)差异场（上边为强季节背景，下边是弱季节性背景）

Fig. 4 difference fields of average annual sea surface density (a, d), temperature (B, e) and salinity (C, f) during PI and 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地表气温差异场. a) 为PI背景和b) 为LGM背景。

Fig. 5 Surface temperature difference field at high latitude in the northern hemisphere under strong and weak seasonal scenarios a) PI and b) LGM .

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图 6 PI和LGM时期，Pmin与Pmax的夏季海冰密集度和冬季垂直混合层深度的差异场。 a）PI时期夏季海冰的差异；b）LGM时期夏季海冰的差异场；c）PI时期冬季垂直混合的差异场；d）LGM时期冬季垂直混合的差异场。绿线和红线分别是对应Pmax和Pmin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 Pmin and Pmax under PI and LGM conditions. a) the difference of sea ice concentration in summer in PI; b) The difference field of summer sea ice in LGM period; c) The difference field of vertical mixing in winter in PI period; d) Difference field of winter vertical mixing in LGM period. , Green and red lines represent 15% sea ice concentration in Pmax and Pmin, respectively.

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图 7 强弱季节性情景北半球高纬地表气温差异场. a) 为PI背景和b) 为LGM背景。

Fig. 7 Surface air temperature anomaly (Pmin-Pmax) between strong and weak seasonality under a) PI and b) LGM climate background.

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S1 PI时期和LGM时期强弱季节性情景下的AMOC分布（a,c是强季节性背景，b,d是弱季节性背景）

S1 Spatial pattern of the AMOC under Pmin and Pmax in PI and LGM periods a) PI and b) LGM climate background.

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S2 PI和LGM时期年均海冰分布图（a,c是岁差较小时，b,d是岁差较弱时）

S2 climatology mean annual sea ice distribution during PI and LGM periods (a),c) Pmin and b) ,d)Pmax）

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表 1 具体实验设置

Tab. 1 specific experimental settings

实验名称	CO₂ (ppm)	CH₄ (ppb)	N₂O (ppb)	偏心率	倾角 (°)	岁差 (°)	全球冰量（e.s.l.）
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

S1 经过90W,75W,6N,14N这一区域的水汽通量，对水汽输送情况定量化，可以看到，PI和LGM时期，水汽输送减少相当

S1 Quantifying the water vapor flux in 90W, 75W, 6N and 14N, water vapor transport decrease considerably in PI and LGM periods

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

下载: 导出CSV

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