Water transport among the world ocean basins within the water cycle
Event: 2020 Ocean Surface Topography Science Team Meeting (virtual)
Session: Science II: Large Scale Ocean Circulation Variability and Change
Presentation type: Type Forum
Global water cycle involves water-mass transport on land, atmosphere, ocean, and among them. Quantification of such transport, and especially its time evolution, is essential to identify footprints of the climate change and helps to constrain and improve climatic models. In the ocean, net water-mass transport among the ocean basins is a key, but poorly estimated parameter presently. We propose a new methodology that incorporates the time-variable gravity observations from the GRACE satellite (2003-2016) to estimate the change of water content, and that overcomes some fundamental limitations of existing approaches. We show that the Pacific and Arctic Oceans receive an average of 1916 (95% confidence interval [1812, 2021]) Gt/month (~0.72 ± 0.02 Sv) of excess freshwater from the atmosphere and the continents that gets discharged into the Atlantic and Indian Oceans, where net evaporation minus precipitation returns the water to complete the cycle. This is in contrast to previous GRACE-based studies, where the notion of a seesaw mass exchange between the Pacific and Atlantic/Indian Oceans has been reported. Seasonal climatology as well as the interannual variability of water-mass transport are also reported.