Vertical mixing of the Pacific Summer Water generated by anticyclonic eddies captured by ice-tethered profiler

초록

Eddies in the ocean can have powerful influences on the heat transport, nutrient supply, and biochemical processes. In our study, a long-term observation data obtained in the Canada Basin, Arctic, by an ice-tethered profiler equipped with modular acoustic velocity sensor was utilized to investigate the effect of eddies on the vertical mixing. With 3-hr interval, it measured vertical profiles of velocity, temperature, salinity, and pressure between 10?250 m during August 2014?May 2015. The time series shows that most anticyclonic eddies are located in the depths of 100?250 m. During the period when the anticyclonic eddy is observed, the density profile shows a distinct lens-shaped feature with the cold water mass inside. Its vertical length is in the range of 50?150 m, and the estimated vorticity near it exhibits a negative core surrounded by positive values. The Richardson number is much smaller than 1 and the eddy diffusivity exceeds 10-4 m2/s near the anticyclonic eddy, suggesting the vertical mixing can be promoted by the eddy to deliver the deep, nutrient-enriched water to the mixed layer. It implies that the cold-core anticyclonic eddies can play an important role in generating the vertical mixing in the subsurface layer between 100?200 m where the wind-force is apparently hard to reach.