Climate variability in the North Atlantic Ocean: wind-induced changes in heat content, sea level and overturning.

气候系统被广泛认为是变暖。据估计，提供给气候系统的大部分额外热量都被海洋吸收了。然而，这种海洋变暖并不是均匀发生的。北大西洋是观测最好的盆地，在过去50年里，热带和中纬度地区一直在变暖，但高纬度地区却在变冷。这些热含量的变化与风和地表热通量的大气强迫的变化有关。除了海洋温度的变化外，高纬度地区的盐度也发生了变化，一般都在变淡，而低纬度地区的盐度则在增加，这可能与大气水循环的加强有关。这些海洋特性中的强环流尺度对比表明，风强迫和环流动力学正在发挥重要作用，这可能反映在倾覆和海平面动力学信号的变化中。海洋翻转对这些水团变化的反应似乎令人惊讶：根据我们的历史分析，在过去50年中，副热带环流略有减弱，副极地环流略有加强。这些翻转变化可能反映了风强迫的影响，其中涡旋尺度特性的变化反馈到翻转的变化上。风的影响也直接影响海平面和验潮仪记录的解释：海洋盆地中部上空气压的年际变化与东部边界海平面之间存在着大规模的相关性。在我们的研究中，我们计划：㈠扩大对北大西洋温度和盐度历史数据以及现有的超过40年的验潮记录的分析; ㈡进行模型实验，以揭示风向变化对温度和盐度环流对比的影响，热含量和倾覆之间的关系，以及与海平面的关系;以及（iii）评估海平面验潮仪记录如何受到环流动力学和倾覆的影响，这将用于解释北大西洋海平面上升的长期历史记录的变化。

The climate system is widely accepted as warming. Much of the extra heat provided to the climate system is estimated to have been taken up by the oceans. However, this warming of the oceans is not happening uniformly. For the North Atlantic, the most well observed basin, there has been warming in the tropics and mid latitudes, but cooling at high latitudes over the last 50 years. These changes in heat content are associated with changes in atmospheric forcing from winds and surface heat fluxes. As well as the oceans changing their temperature, there are salinity changes with a general freshening at high latitudes and increase in salinity at low latitudes, perhaps associated with a strengthening in the atmospheric water cycle. The strong gyre-scale contrast in these ocean properties suggest that the wind forcing and gyre dynamics are playing an important role, which are likely to be reflected in changes in the dynamical signals for overturning and sea level. The ocean overturning response to these water-mass changes appears surprising: based on our historical analyses, there is a slightly weakening over the subtropical gyre and slightly strengthening over the subpolar gyre during the last 50 years. These overturning changes might reflect the effect of the wind forcing, where gyre-scale property changes feedback onto changes in the overturning. The effect of the winds also directly affects sea level and the interpretation of the tide gauge record: there are large-scale correlations between the interannual variations in air pressure over the central part of the ocean basins and eastern boundary sea level. In our study, we plan (i) to extend our analyses of the historical data for temperature and salinity over the North Atlantic, as well as the existing tide gauge records longer than 40 years; (ii) conduct model experiments designed to reveal the effect of changing winds on the gyre contrasts in temperature and salinity, on how heat content and overturning are related, and on the relationship with sea level; and (iii) assess how tide gauge records for sea level are affected by gyre dynamics and overturning, which will be used to interpret changes in the long historical records of sea level rise in the North Atlantic.