The ocean is a magnificent reservoir of kinetic energy possessed by currents at diverse spatio-temporal scales. These currents transport heat and material, regulating the regional and global climate. It is generally thought that large-scale ocean circulations should become more energetic under global warming, especially in the ocean’s upper layer. However, using high-resolution global climate simulations, here we demonstrate that the total ocean kinetic energy is projected to be significantly reduced in a warming climate, despite overall acceleration of large-scale ocean circulations in the upper layer. This reduction is primarily attributed to weakened ocean mesoscale eddies in the deep ocean. Enhanced vertical stratification under global warming reduces the available potential energy stored in large-scale ocean circulations, diminishing its conversion into eddy kinetic energy. Our findings reveal a more quiescent deep ocean under global warming and suggest a crucial role of mesoscale eddies in determining the anthropogenic change of total ocean kinetic energy.

海洋是一个巨大的动能库，由不同时空尺度的洋流所拥有。这些洋流输送热量和物质，调节区域和全球气候。人们普遍认为，在全球变暖的情况下，大范围的海洋环流应该变得更加活跃，特别是在海洋上层。然而，利用高分辨率全球气候模拟，我们在这里证明，尽管上层大规模海洋环流总体加速，但在气候变暖的情况下，海洋总动能预计将显着减少。这种减少主要归因于深海海洋中尺度涡流的减弱。全球变暖导致垂直分层增强，减少了大规模海洋环流中储存的可用势能，从而减少了其向涡流动能的转化。我们的研究结果揭示了全球变暖下深海更加静止，并表明中尺度涡流在确定总海洋动能的人为变化中发挥着至关重要的作用。