| Summary: | Ocean circulation in the Challenger Deep is rarely investigated due to sparse observations. Based on hydrographic data collected by two super-deep Chinese "Sea-Wing" gliders during September–October 2018, we analyzed water properties and ocean circulation structures in this trench. Results showed that the horizontal distribution of water properties is approximately a three layer structure, changing from a northeast-southwest structure to a north-south structure then to an east-west structure as the depth increases from 3,000 to 7,000m. This structure is a joint result of the water uplift, advection, and diffusion in the trench. The westward geostrophic flow, with 1.29Sv (1Sv=106m3 s−1) volume transport, dominates the deep layer of the Challenger Deep, gradually weakening with depth. The unexpectedly large volume transport, twice that of previous studies, might be due to temporal variations of LCDW (Lower Circumpolar Deep Water) intrusion from the Southern Ocean and different reference levels.
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