Investigating Near-Surface Ocean Heating and Mixing Processes in the Presence of Surface Material

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Solar radiation is the largest form of heating of the upper ocean and is unique to the air-sea flux balance due to its penetration beneath the ocean surface. It has been speculated that near-surface heating is enhanced in the presence of algal blooms and surface slicks but this has not been accounted for in current models. Although surface slicks are common in the world oceans, our knowledge of how these slicks impact ocean heating has been limited due to the lack of appropriate observational tools. By using ship-deployed high-endurance Unoccupied Aerial Vehicles (UASs), the investigators targeted large-scale slicks and covered 10s of km2 several times a day. The project is a quantum advance in utilizing UAS technology for science. This investigation will provide new insights into the distribution of heat in the upper ocean due to the presence of surface slicks. This project will improve models of the daily cycles of surface ocean heating, global biogeochemical cycles, and sea surface temperature. These results are in great demand within the regional modeling community of the South Pacific, Maritime Continent, and Indian Ocean. The project will foster the development of the next generation of scientists in Oceanography. The inverstigators will create teaching materials for their existing course at Columbia University. They will also work closely with K-12 teachers in the greater New York City area and with large numbers of students from underrepresented groups through the Earth2Class Workshops.This research project will analyze measurements made onboard the R/V Falkor in November-December 2019 in the Southwest Pacific near Fiji from a combination of novel tools. UASs were equipped with hyperspectral visible, and broadband thermal infrared cameras to study the albedo of sea surface biogenic slicks as well as the sea-surface skin temperature (SST). UASs and ship-based instrumentation measured air-sea heat/radiative fluxes and SST; an autonomous catamaran sampled sea-surface microlayer surfactants and the surface microlayer algae populations; drifters measured the near-surface response of the upper ocean temperature, salinity, ocean currents, and turbulence; spectro-radiometric profiles provided estimates of net radiant flux at depth; and shipboard infrared imaging measured the response of ocean surface SST important to upper-ocean heating. The results will further our understanding of the role cyanobacteria blooms and surface slicks play in physical air-sea interaction. The analyses will expand our knowledge of the upper-ocean mixed layer response to algal blooms and provide novel observations of near-surface ocean heat budget.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.