Greenhouse Warming Reduces Global Energy Conversion Into Oceanic Lee Waves

Oceanic lee waves play an important role in dissipating wind‐driven ocean circulations and powering turbulent diapycnal mixing. Here we investigate impacts of the greenhouse warming on global energy conversion into lee waves using a linear theory of lee wave generation and output from a high‐resolution (0.1° for the ocean) coupled global climate model. The global energy conversion rate into lee waves under the historical (1930s) climate condition is estimated to be 193.0 ± 3.0 GW. Under the high carbon emission scenario, this conversion rate is projected to decrease by about 20% by the end of 21st century, due to weakened bottom large‐scale mean flows, mesoscale eddies and stratification. The decrease of the conversion rate is widespread and particularly pronounced in the Gulf Stream and Drake Passage. Plain Language Summary Oceanic lee waves, a kind of stationary internal gravity waves, are generated when bottom flows impinge on small‐scale uneven topography. They provide an energy pathway from wind‐driven large‐scale circulations to microscale turbulent mixing. Theories predict that the energy conversion into lee waves depends on the stratification and flow speed near the sea floor, both of which are likely to weaken under the greenhouse warming. In this study, we use a high‐resolution coupled global climate model to estimate the response of global energy conversion into lee waves to the greenhouse warming. Our results show that, under the high carbon emission scenario, the global energy conversion into lee waves at the end of the 21st century will decrease by 20% compared to its level in the 1930s. Key Points The response of energy conversion into lee waves to greenhouse warming is investigated with a high‐resolution coupled global climate model Lee wave conversion rate is projected to decrease by ∼20% by the end of 21st century under the high carbon emission scenario This decrease is attributed to the weakened bottom large‐scale flows, mesoscale eddies and stratification