The 1% and 1cm perspective in AOP data products

Biogeosciences Discussions This discussion paper is/has been under review for the journal Biogeosciences (BG). Please refer to the corresponding final paper in BG if available. Abstract A next-generation in-water profiler designed to measure the apparent optical properties (AOPs) of seawater was developed and validated across a wide dynamic range of in-water properties. The new free-falling instrument, the Compact-Optical Profiling System (COPS), was based on a cluster of 19 state-of-the-art microradiometers spanning 5 320–780 nm and a new kite-shaped backplane design. The kite-shaped backplane includes tunable ballast, a hydrobaric buoyancy chamber, plus pitch and roll adjustments, to provide unprecedented stability and vertical resolution in near-surface waters. A unique data set was collected as part of the development activity and the first major field campaign that used the new instrument, the Malina expedition to the Beaufort Sea 10 in the vicinity of the Mackenzie River outflow. The data were of sufficient resolution and quality to show that errors – more correctly, uncertainties – in the execution of data sampling protocols were measurable at the 1 % and 1 cm level with COPS. A sensitivity analysis as a function of three water types established by the peak in the remote sensing reflectance spectrum, R rs (λ), revealed which water types and which parts of 15 the spectrum were the most sensitive to data acquisition uncertainties. Shallow river-ine waters were the most sensitive water type, and the ultraviolet and near-infrared were the most sensitive parts of the spectrum. The sensitivity analysis also showed how the use of data products based on band ratios significantly mitigated the influence of data acquisition uncertainties. The unprecedented vertical resolution provided 20 high quality data products at the spectral end members, which subsequently supported an alternative classification capability based on the spectral diffuse attenuation coefficient , K d (λ). The K d (320) and K d (780) data showed how complex coastal systems can be distinguished two-dimensionally and how near-ice water masses are different from the open ocean. Finally, an algorithm for predicting the spectral absorption due 25 to colored dissolved organic matter (CDOM), denoted a CDOM (λ), was developed using the K d (320)/K d (780) ratio, which was based on a linear relationship with respect to a CDOM (440), with over 99 % of the variance explained. was established by expanding the use of the algorithm to include a geographically different coastal environment, the Southern Mid-Atlantic Bight, …