Abstract The interannual–multidecadal variability of the temperature and depth of the upper mixed layer (UML) in the North Atlantic (NA) is analyzed on the basis of the ORA-S3 ocean reanalysis data for 1959–2011. A large part of the UML in the NA is characterized by warming and thinning in all seasons in the period under study. After removing a linear trend, the UML temperature and depth anomalies in individual seasons are decomposed into empirical orthogonal functions (EOF). It is found that the three leading EOFs describe more than 50% of the total variability of the UML temperature and depth. The structure of the first EOF is horseshoe-shaped; this EOF represents coherent changes in the UML temperature and depth throughout the NA, which manifest themselves the year round. This mode corresponds to the Atlantic multidecadal oscillation. The spatial structure of the second EOF in the winter–spring period is a tripole and is caused by the North Atlantic Oscillation (NAO). The time coefficient of the second EOF of the UML temperature in the NA and the NAO index strongly correlate both synchronously and when the NAO index is 11 years ahead. The second EOF of the UML temperature in the summer–autumn period is associated with the Atlantic meridional mode. The third EOF is typical for the UML temperature fluctuations in January and corresponds to the East Atlantic Pattern.

中文翻译：

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北大西洋上混合层温度和深度的长期变化模式与气候变化指数之间的联系

摘要 基于 1959-2011 年的 ORA-S3 海洋再分析数据，分析了北大西洋 (NA) 上混合层 (UML) 温度和深度的年际-多年变化。NA 中大部分 UML 的特点是在研究期间的所有季节都变暖和变薄。去除线性趋势后，各个季节的UML温度和深度异常被分解为经验正交函数（EOF）。发现三个领先的 EOF 描述了超过 50% 的 UML 温度和深度的总可变性。第一个EOF的结构是马蹄形；这个 EOF 代表了整个 NA 的 UML 温度和深度的连贯变化，它们全年都表现出来。这种模式对应于大西洋的年代际振荡。冬春季第二次EOF的空间结构是三极的，是由北大西洋涛动（NAO）引起的。NA 中 UML 温度的第二个 EOF 的时间系数与 NAO 指数同步且当 NAO 指数提前 11 年时强烈相关。夏秋季节 UML 温度的第二个 EOF 与大西洋经向模式有关。第三个 EOF 是 1 月份 UML 温度波动的典型特征，对应于东大西洋模式。夏秋季节 UML 温度的第二个 EOF 与大西洋经向模式有关。第三个 EOF 是 1 月份 UML 温度波动的典型特征，对应于东大西洋模式。夏秋季节 UML 温度的第二个 EOF 与大西洋经向模式有关。第三个 EOF 是 1 月份 UML 温度波动的典型特征，对应于东大西洋模式。