Multi-vehicle coordinated measurements of meteorology, surface waves, and upper ocean turbulence in the Icelandic Basin

Sophia Merrifield, Massachusetts Institute of Technology, Cambridge, United States, Louis C St. Laurent, Applied Physics Laboratory University of Washington, Seattle, United States, Justin Shapiro, Applied Physics Laboratory, University of Washington, Seattle, United States, Harper L Simmons, University of Alaska Fairbanks, Fairbanks, United States and Eric Terrill, University of California San Diego, Scripps Institution of Oceanography, La Jolla, United States
Abstract:
Traditional ship-based methods of measuring near-surface turbulence are easily contaminated by the wakes of surface vessels and have been limited to calm conditions when towed systems can be safely deployed. With the advent of unmanned platforms, the ability to collect persistent observations in remote and harsh conditions has expanded substantially. Accurate measurements of turbulence require a mechanically-quiet host-platform such as a buoyancy glider, however, vehicles of this type are unable to concurrently measure surface forcing and are too slow to persistently track surface-drifting assets.

Over a 9-week span of 2019, a novel set of concurrent measurements of the air-sea interface and upper ocean were collected from two unmanned vehicles, a Teledyne-Webb G2 Slocum Glider equipped with a Rockland Scientific Microrider and a Boeing-Liquid Robotics SV3 Wave Glider. The two platforms performed a cooperative sampling mission that minimized separation distance to generate a coincident dataset of upper ocean turbulence, stratification, directional surface waves, upper ocean currents, and meteorological forcing. The seasonal mixed layer was shallow during the field campaign (<50m) and a number of storms with wind speeds exceeding 35kts and significant wave heights exceeding 8m deepened the mixed layer episodically. As part of the same project, measurements in 2018 captured similar surface conditions with a deeper MLD (>200m) and are presented for reference (H. Simmons abstract). Observations are compared to existing parameterizations of wind, wave-breaking, and convectively-driven turbulence. Significant deviations between parameterizations and observations showcase the need for future development of boundary layer turbulence schemes and novel observational techniques in extreme sea-states, conditions in which minimal if any measurements exist.

Back to: Turbulent Mixing of the Ocean Surface Boundary Layer: Observation, Simulation, and Parameterization II