Intrinsic Variability of the Atlantic Meridional Overturning Circulation at Interannual-to-Multidecadal Time Scales
Intrinsic Variability of the Atlantic Meridional Overturning Circulation at Interannual-to-Multidecadal Time Scales
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年际至数十年时间尺度上大西洋经向翻转环流的内在变化
DOI：
10.1175/jpo-d-14-0163.1
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发表时间：
2015
影响因子：
3.5
通讯作者：
Grégorio S
中科院分区：
文献类型：
--
作者：
Grégorio S
本文研究了大西洋纬向翻转环流（AMOC）的低频变率， °全球海洋-海冰模拟，特别侧重于其内部产生的（即，“固有”）组分。一个327年的气候变化模拟，由一个重复的季节周期驱动（即，缺乏年际时间尺度的强迫），自发地产生一个显着的分数R的年际到十年的AMOC方差在50年的“完全强迫”后报（再分析大气强迫，包括年际时间尺度）。这个内在方差分数R略微取决于AMOC是在位势坐标还是密度坐标中计算的，以及气候模拟中考虑的周期，但在模拟中尺度涡旋时（在1/4 °和2/4 °）， 在34°S处，R值可达30%-50%，25°N附近可达20%-40%，湾流附近可达40%-60%。在34°S和墨西哥湾流附近，约25%的纬向热量输送年际变率归因于内禀过程。由327年1/4 °气候模拟建立的傅立叶和小波谱进一步表明，固有AMOC变率的谱峰（i）出现在年际到年代际的特定频率上，（ii）经常延伸到整个纬向尺度的涡旋，（iii）在这327年中的随机变化，和（iv）有时匹配的光谱峰值中发现的充分强迫后报在北大西洋。在多年代际时间尺度上也检测到了固有的AMOC变率，在35°S和25°N之间（15-30年周期）和整个流域（50-90年周期）具有显著的纬向相干性。
The low-frequency variability of the Atlantic meridional overturning circulation (AMOC) is investigated from 2, ¼°, and ° global ocean–sea ice simulations, with a specific focus on its internally generated (i.e., “intrinsic”) component. A 327-yr climatological ¼° simulation, driven by a repeated seasonal cycle (i.e., a forcing devoid of interannual time scales), is shown to spontaneously generate a significant fractionRof the interannual-to-decadal AMOC variance obtained in a 50-yr “fully forced” hindcast (with reanalyzed atmospheric forcing including interannual time scales). This intrinsic variance fractionRslightly depends on whether AMOCs are computed in geopotential or density coordinates, and on the period considered in the climatological simulation, but the following features are quite robust when mesoscale eddies are simulated (at both ¼° and ° resolutions);Rbarely exceeds 5%–10% in the subpolar gyre but reaches 30%–50% at 34°S, up to 20%–40% near 25°N, and 40%–60% near the Gulf Stream. About 25% of the meridional heat transport interannual variability is attributed to intrinsic processes at 34°S and near the Gulf Stream. Fourier and wavelet spectra, built from the 327-yr ¼° climatological simulation, further indicate that spectral peaks of intrinsic AMOC variability (i) are found at specific frequencies ranging from interannual to multidecadal, (ii) often extend over the whole meridional scale of gyres, (iii) stochastically change throughout these 327 yr, and (iv) sometimes match the spectral peaks found in the fully forced hindcast in the North Atlantic. Intrinsic AMOC variability is also detected at multidecadal time scales, with a marked meridional coherence between 35°S and 25°N (15–30 yr periods) and throughout the whole basin (50–90-yr periods).
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