Analysis of Acoustic Observations of Double‐Diffusive Finestructure in the Arctic Ocean. Issue 18 (23rd September 2020)

• Record Type: Journal Article
• Authors: Shibley, Nicole C.; Timmermans, Mary‐Louise; Stranne, Christian
• Is Part Of: Geophysical research letters. Volume 47:Issue 18(2020)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2020-09-23
• Subjects: double diffusion -- Arctic Ocean -- mixing processes -- acoustic measurements; Geophysics -- Periodicals; Planets -- Periodicals; Lunar geology -- Periodicals; 550
• DOI: 10.1029/2020GL089845
• Languages: English
• ISSNs: 0094-8276

Abstract

Abstract: Double‐diffusive convection may occur if both temperature and salinity increase with depth, as in the Arctic Ocean. The process is identifiable by a staircase structure, with mixed layers separated by high‐gradient interfaces in temperature and salinity. These staircases, which persist if turbulence levels are weak, are widely present in the Arctic Ocean and responsible for transporting heat toward the overlying sea ice. Acoustic observations (reflection coefficients) from a broadband echo sounder are analyzed here to track the detailed evolution of interfaces in the Arctic's double‐diffusive staircase. We infer interface thicknesses from reflection coefficient profiles and find that thicknesses appear to be related to water column displacements. Further, we relate reflection coefficients to interface stratification and interpret stratification changes in the context of turbulence acting to thicken interfaces. The high‐resolution capabilities of the echo sounder allow for insights into how double‐diffusive heat fluxes and inferred mixing levels may vary in space/time. Plain Language Summary: Heat contained in the Arctic Ocean influences the overlying sea ice cover and Arctic climate. One important mode of ocean heat transport is double‐diffusive convection, which may occur when both temperature and salinity increase with depth. Double‐diffusive convection manifests as distinct layered structures (staircases), which are prominent throughout the Arctic Ocean. Here, we use a time series of acoustic measurements with high temporal and spatial resolution to track a double‐diffusive staircase. The high‐resolution acoustic data allow for an investigation of real‐time changes in double‐diffusive features, which are then related to larger‐scale water column motions. These results shed light on the processes affecting the evolution of double‐diffusive staircases and heat transport in a warming Arctic Ocean. Key Points: High‐resolution acoustic imaging allows for a detailed analysis of double‐diffusive staircases and their finestructure in the Arctic Ocean Double‐diffusive interface thicknesses and stratifications may be inferred from acoustic observations, providing insight on heat fluxes Interface thicknesses appear to be related to water column displacements, and associated stratification changes may be due to turbulence