Abstract

Zonally averaged characteristics of the North Atlantic (NA) thermohaline circulation are investigated in different phases of the Atlantic Multidecadal Oscillation (AMO) index over the past 70 years using ocean objective analyses EN4 and WOA13 and reanalyses GFDL, ESTOC, ORA-S4, and GECCO2. It is shown that similar thermohaline patterns appear in zonally averaged climatic trends and in differences in the composites of anomalies of the potential temperature and salinity fields for all data sets. To find out how the variability in the thermohaline state of waters in the NA is accompanied by the variability in its thermohaline circulation, we have analyzed the variability of the Atlantic Meridional Overturning Circulation (AMOC) stream function. The average AMOC stream functions calculated from ocean objective analyses and reanalyses, reflecting the NA thermohaline circulation, are generally similar to each other. Nonetheless, they can be divided according to their spatial structure into two groups: (EN4, WOA13, and GFDL) and (ESTOC, ORAS4, and GECCO2). In their trends and anomaly composite differences, the AMOC stream functions differ significantly among themselves, as well as from EN4 and WOA13. Moreover, the main distinction is in the sign of climatic trends and composite differences, which determines changes in the direction of the zonally averaged thermohaline circulation. It is found that positive and negative temperature (salinity) anomalies in alternating successive phases of the AMO index circulate with a period of roughly 60 years along the pathway of water in the AMOC, sinking into deep ocean layers at about 60° N and rising toward the surface at 25° N. This process is most pronounced for the EN4 and WOA13 objective analyses and ORAS4 reanalysis. It can be assumed that this mechanism contributes substantially to the formation of the AMO index phases.

中文翻译：

---

海洋目标分析和再分析在大西洋多年代际振荡的不同阶段中北大西洋热盐环流的变异性

摘要

使用海洋客观分析EN4和WOA13并重新分析GFDL，ESTOC，ORA-S4和GECCO2，在过去70年中研究了大西洋多年代际振荡（AMO）指数不同阶段北大西洋（NA）热盐环流的区域平均特征。 。结果表明，相似的热盐模式出现在区域平均气候趋势中，并且存在于所有数据集的潜在温度和盐度场的异常组合中。为了发现北美地区水域的热盐状态的变化如何与其热盐循环中的变化相伴随，我们分析了大西洋子午翻转俯卧环流（AMOC）流函数的变化。通过海洋目标分析和再分析计算得出的平均AMOC流函数，反映NA热盐环流的情况，通常彼此相似。但是，可以根据它们的空间结构将它们分为两类：（EN4，WOA13和GFDL）和（ESTOC，ORAS4和GECCO2）。在趋势和异常复合差异方面，AMOC流功能之间以及EN4和WOA13之间存在显着差异。此外，主要区别在于气候趋势和综合差异的迹象，这决定了区域平均热盐环流方向的变化。结果发现，AMO指数交替相继相中的正，负温度（盐度）异常沿AMOC中的水路径循环了大约60年，沉入约60°N的深海层并向表面在25°N。对于EN4和WOA13客观分析以及ORAS4重新分析，此过程最为明显。可以假定该机制对AMO指数相的形成有很大贡献。