Poster Session 2, Tuesday,  October  4, 10:40–12:40

Poster 62

Seasonally resolved biases in chlorophyll estimates derived from profiling floats, satellite, and shipboard observations

Models of ocean health (such as primary production) often depend on chlorophyll-a (chl-a) concentrations, based on either ship, satellite, or autonomous platform measurements. Each of these platforms employs a unique method for detecting chl-a, owed to their specific sampling capabilities. For example, ship-based measurements are often made using a bench-top fluorometer or high-performance-liquid-chromatography (HPLC) instrument. Satellite chl-a estimates are derived from light that is reflected from near-surface waters. Autonomous platform measurements come from fluorescence sensors (chl-fl). Because phytoplankton fluorescence is not a consistent metric reflecting chl-a concentration, it is common practice to post-adjust autonomous sensor chlorophyll data (chl-fl) to a single gain factor. We use a compilation of chl-a data from satellites, long-term time series sites, and short-term field expeditions for comparison with chl-fl from a global array of profiling floats, and chl-Kd from a smaller subset of floats carrying radiometers. This work expands on previous efforts (Roesler et al., 2017) to explore the relationship between chl-fl and chl-a (chl-fl:chl-a) over time, space, and depth. Distinct regional and seasonal patterns in the gain correction factor were observed, demonstrating a single gain factor can lead to significant biases in the estimated chl-a concentration. A gridded product of chl-fl:chl-a relationships, based on >10 years of multi-platform observations in some ocean region, is provided at less than 10 degree spatial resolution. The product can be updated as the float array continues to grow with the expansion of the BGC-Argo program.

Jacqueline Long, Monterey Bay Aquarium Research Institute, [email protected], 0000-0001-5880-0009

Joshua Plant, Monterey Bay Aquarium Research Institute, [email protected]

Yui Takeshita, Monterey Bay Aquarium Research Institute, [email protected]

Kenneth Johnson, Monterey Bay Aquarium Research Institute, [email protected]

Andrea Fassbender, NOAA Pacific Marine Environmental Laboratory, [email protected]

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