High salinities in the Atlantic and low salinities in the Pacific are critical ocean features, impacting ocean circulations and climate. Here, using observational data, we reveal that the Atlantic–Pacific salinity contrast has amplified during the past half-century. Notably, in the 0–800 m, 20°–40° N band, the Atlantic–Pacific salinity contrast increased by 5.9% ± 0.6% since 1965. A decomposition of heaving and spicing modes suggests vital contributions of wind and ocean warming, in addition to known surface freshwater fluxes. Specifically, ocean surface warming leads to poleward migration of thermocline outcrop zones, while surface wind changes cause upper-layer convergence in mid-latitudes. These processes lead to substantial upper-layer salinity increases in the North Atlantic but have much weaker signatures in the North Pacific, determined by the inter-basin difference in climatological salinities. This work highlights the complexity of ocean salinity response to climate change, underscoring the unexpected importance of wind- and heat-driven processes in the Atlantic–Pacific salinity contrast.

大西洋的高盐度和太平洋的低盐度是重要的海洋特征，影响海洋环流和气候。在这里，利用观测数据，我们发现大西洋与太平洋的盐度差异在过去的半个世纪中有所扩大。值得注意的是，在0-800米、20°-40°N波段，大西洋-太平洋盐度对比自1965年以来增加了5.9%±0.6%。对起伏和扰动模式的分解表明风和海洋变暖的重要贡献，除了已知的地表淡水通量之外。具体而言，海洋表面变暖导致温跃层露头区向极地迁移，而表面风的变化导致中纬度地区上层辐合。这些过程导致北大西洋上层盐度大幅增加，但北太平洋的特征要弱得多，这是由流域间气候盐度差异决定的。这项工作强调了海洋盐度对气候变化响应的复杂性，强调了风和热驱动过程在大西洋-太平洋盐度对比中意想不到的重要性。