Active AMOC-NAO coupling in the IPSL-CM5A-MR climate model
Active AMOC-NAO coupling in the IPSL-CM5A-MR climate model
复制标题
IPSL-CM5A-MR 气候模型中的主动 AMOC-NAO 耦合
DOI：
10.1007/s00382-015-2953-y
复制
发表时间：
2016
期刊：
影响因子：
4.6
通讯作者：
Gastineau Guillaume
中科院分区：
文献类型：
--
作者：
Wen Na;Frankignoul Claude;Gastineau Guillaume
使用控制模拟的滞后最大协方差分析 (MCA)，在 IPSL-CM5A 中分辨率气候模型中研究大气对 AMOC 变化的响应。冬季检测到强烈的大气响应，在北大西洋约 9 年 AMOC 增强后出现类似 NAO 的负响应，其模式与 AMOC 变化的第二种模式大致相似。该响应是通过 AMOC 的海表温度足迹和相关的表面热通量阻尼建立的，海表温度异常的偶极子由墨西哥湾流地区的冷海表温度和北大西洋洋流周围更东北的温暖海表温度组成。偶极子海温异常模式与AMOC在其主导的20年周期的变化同步演化，因此MCA检测到的滞后的类NAO响应实际上反映了近同步的AMOC对大气的影响，这种影响在短时滞上被AMOC较强的大气强迫所掩盖。因此，大气对 AMOC 增强的响应是一种类似 NAO 的正模式，同时阿留申群岛上空出现异常低压，这与 MCA 延迟 9 年检测到的情况相反。由于NAO对AMOC也有贡献，模型中AMOC与NAO之间存在正反馈，大气反馈强度约为大气强迫的1/4，增强了AMOC的低频变率。海洋和大气主导模态之间的超前滞后关系以及 NAO 的强劲 20 年周期进一步证实了这一点。
The atmospheric response to the AMOC variability is investigated in the IPSL-CM5A medium resolution climate model, using lagged maximum covariance analysis (MCA) of a control simulation. A robust atmospheric response is detected in winter, with a negative NAO-like response following by about 9-year an AMOC intensification in the North Atlantic, with a pattern broadly resembling the second mode of AMOC variability. The response is established through the SST footprint of the AMOC and the associated surface heat flux damping, with a dipole of SST anomalies made of cold SST in the Gulf Stream region and warm SST further northeast around the North Atlantic Current. The dipole SST anomaly pattern evolves synchronously with the AMOC changes at its dominant 20-year period, so that the lagged NAO-like response detected by MCA actually reflects the near-synchronous AMOC influence on the atmosphere, which is masked at short time lag by the stronger atmospheric forcing of the AMOC. The atmospheric response to an intensification of the AMOC is thus a positive NAO-like pattern, together with an anomalous low pressure over the Aleutians, opposite to that detected at 9-year lag by the MCA. Since the NAO also contributes to force the AMOC, there is a positive feedback between AMOC and NAO in the model, with the atmospheric feedback strength about 1/4 of that of the atmospheric forcing, which enhances the low frequency variability of AMOC. This is further confirmed by the lead-lag relation between the dominant mode of ocean and atmosphere, and by the robust 20-year period of the NAO.