Matthew Mazloff (Scripps Institution of Oceanography)
Sebastiaan Swart (CSIR)
A Southern Ocean air-sea flux workshop was held 21-23 September 2015 in Frascati, Italy. Hosted by the European Space Research Institute (ESRIN), and sponsored by the Southern Ocean Observing System (SOOS), the World Climate Research Programme (WCRP), the European Space Agency (ESA), the US National Oceanic and Atmospheric Administration (NOAA), and US CLIVAR, this meeting brought 48 researchers together to discuss the current state of knowledge with regards to Southern Ocean air-sea exchanges. Research topics were diverse, and presentations focused on knowledge gaps and emerging capabilities.
Southern Ocean deployments (a) of South African Wave Gliders are collecting CO2 flux (b) and weather measurements over multiple months. (c) A CSIR Carbon Wave Glider is retrieved from the Subantarctic after a 3-month deployment.
A theme throughout the meeting was determining the air-sea flux accuracy requirements to address the critical science needs. Discrepancies in various atmospheric reanalysis, and also in products inferred from ocean inversions, imply that Southern Ocean air-sea flux products are not yet accurate enough to address many of these questions. However the mood of the meeting was optimistic, as recent technological developments give hope that high-quality flux observations will be increasingly attained. Technologies reaching maturity include autonomous wave gliders (see Figure), unmanned aerial vehicles, aircraft observations, and new moorings (the Southern Ocean Flux Station, the Ocean Observatories Initiative moorings in the southeast Pacific and the Argentine Basin). The benefit and feasibility of correcting for airflow distortion around research vessels was demonstrated, giving hope for improved shipboard flux measurements. Discussions also covered the need for methods to put in situ measurements in context via remote sensing, and for extrapolating data via synthesis with numerical models.
Given the existence of these new capabilities, three primary recommendations were proposed. The first is for the formation of a SOOS capability working group that will oversee carrying out of all recommendations, and coordinate air-sea flux research efforts. The second recommendation is given that in situ measurements of air-sea heat and momentum fluxes are now mature, these should be listed as Essential Climate Variables, with specific requirements for accuracy and precision of measurements. The third recommendation is for the development of a pilot project to demonstrate the feasibility of a large-scale Southern Ocean air-sea flux observing system. This pilot study is envisioned to be based around existing mooring and satellite infrastructure, augmented by targeted in situ observations. In the context of the Southern Ocean's energetic eddy fields, the pilot study goal will be to determine in situ measurement accuracy, and coverage requirements for constraining assimilation efforts and for validating and calibrating satellite observations.