Diurnal Rhythms in Optical Observations from a Profiling Wirewalker to Estimate Productivity During EXPORTS

Melanie Feen, University of Rhode Island, Narragansett, RI, United States and Melissa Omand, University of Rhode Island, Graduate School of Oceanography, Narragansett, RI, United States
Diurnal cycles in bio-optical observations during the 2018 EXPORTS cruise in the North Pacific were observed on a Wirewalker, a wave-powered, autonomous, drifting sensor platform. The Wirewalker collected profiles of chlorophyll fluorescence, beam attenuation, backscatter, dissolved oxygen, and photosynthetically active radiation (PAR) from the surface to 500 m depth approximately every 40 minutes for eight-day deployments. Given the high-resolution nature of observations and the availability of night-time casts, PAR and backscatter measurements, an assessment of multiple methods for correction of non-photochemical quenching (NPQ) was conducted. With the NPQ corrected fluorescence observations, as well as the beam attenuation data, estimates of productivity were obtained to better constrain biogeochemical fluxes in the subpolar North Pacific.