Observations of Double Diffusive Staircase Edges in the Arctic Ocean

Recent observational studies have provided detailed descriptions of double-diffusive staircases in the Beaufort Sea, characterized by well-mixed intrusions between high-gradient interfaces. These structures result from double-diffusive convection, occurring when cooler fresh water lies atop the warmer saltier Atlantic water layer. In the present study, we investigate the spatial structure of such layers, by analyzing combined high resolution data from a subsurface mooring, a ship-towed profiling conductivity-temperature-depth/ADCP package, and a free-falling microstructure profiler. At large scale, the modular microstructure profiler data suggest a horizontal ragged edge of the layered water masses near the basin boundary. At smaller scales, the mooring data indicate that, in the 300-400 m depth interval, regions of layers abruptly appear. This laterally sharp (of the order of 100 m) interface is advected southwards, as shown by the shallow water integrated mapping system survey conducted nearby. Neither disruption nor formation of layers is directly observed in our data, and we thus interpret our observations as the stable and possibly recent abutment of a layered and an unlayered water masses, now globally advected southwards by a large scale flow.

Automated summary

This study investigates the spatial structure of double-diffusive staircases in the Beaufort Sea using high-resolution observational data. The results reveal irregular edges of layered water masses near the basin boundary at large scale, and abrupt appearance of layers in the 300-400 meter depth interval at smaller scales. The observations suggest that the layers are stably and possibly recently formed by the interaction of layered and unlayered water masses advected southwards by a large-scale flow.