Turbulent diapycnal mixing in the northwestern Pacific

Abstract

Nearly vertical mixing in the oceans across surfaces of constant density (isopycnals), known as diapycnal mixing, transports heat, modifies water masses, and maintains stratification. This mixing needs to be included in models of large‐scale ocean circulation and climate models, but it is not fully understood. Some studies have suggested that wind is a key source of energy for diapycnal mixing in the deep ocean, but observational and modeling studies have been contradictory. To learn more, Jing et al. used data from recent hydrographic studies to study turbulent diapycnal mixing in the subtropical northwestern Pacific Ocean, a region that encompasses a range of ocean conditions, including both flat and rough seafloor. They examined spatial and seasonal variations as well as the role of eddies. They found that enhanced mixing occurred over rougher seafloor. Over flatter seafloor the researchers found that mixing is probably stirred by wind near the surface, with eddies playing an important role in enhancing mixing at greater depths. In the upper 600 meters of the ocean, the wind and diapycnal mixing varied seasonally, with stronger winds and mixing in winter and weaker winds and mixing in summer. This is different from the midlatitude northwestern Pacific, where seasonality of diapycnal mixing can be found at 1500‐meter depth. (Journal of Geophysical Research‐Oceans, doi:10.1029/2011JC007142, 2011)