Global estimates of 1000-dbar vertical velocity from Argo floats

Katy Christensen, Alison R Gray and Stephen Riser, University of Washington, School of Oceanography, Seattle, WA, United States
The vertical transport of water in the ocean interior has a large impact on ocean heat flux and the cycling of carbon, oxygen, and nutrients. However, vertical velocities have traditionally been difficult to observe on a global scale due to their vanishingly small magnitudes, together with a lack of spatio-temporal coverage of suitable measurements. Using observational data from the Argo float array and a new method based on the motion of the stratified water column surrounding a float, here we directly estimate vertical motion at 1000 dbar throughout the world’s oceans. In vast areas of the ocean, the resulting vertical velocities have small, undetectable magnitudes; however, we find key areas that exhibit significantly larger vertical motions. We examine the links between these regions of intensified vertical velocity and features such as steep bathymetry, increased baroclinic conversion, and upwelling zones. These observational estimates of vertical velocity help improve our understanding of global ocean circulation and the interactions between the surface and deep oceans.