Song, Y., and Forget, G. (2026)
Presented at:
Ocean Sciences Meeting 2026Mode waters control the fate of anthropogenic heat/carbon uptake in the ocean. Yet their trends, variability, and the underlying interplay of processes remain inadequately understood. Using two data-driven temperature reanalysis products that cover 1980-2022 (OCCA2 and IAPv4), we analyze 11 mode water source regions and find widespread warming, strongest in the Northern Hemisphere where decadal signal is also large. Southern Hemispshere mode waters, in contrast, show a predominance of interannual variability and smaller warming trends. Closed heat budget estimates reveal that convective mixing preferentially controls North Atlantic mode water temperature variations, whereas advection tends to dominate elsewhere. However, mode water heat budgets generallly show significant compensation between diffusive and advective contributions. This intricacy reflects the interplay between diabatic mixed layer processes and the largely adiabatic ocean interior where advection dominates.
