Abstract
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 (C-OPS), was based on sensors built with a cluster of 19 state-of-the-art microradiometers spanning 320–780 nm and a novel kite-shaped backplane. The new 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 plus the first major field campaign that used the new instrument, the Malina expedition to the Beaufort Sea 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 C-OPS. A theoretical sensitivity analysis as a function of three water types established by the peak in the remote sensing reflectance spectrum, Rrs(λ), revealed which water types and which parts of the spectrum were the most sensitive to data acquisition uncertainties. Shallow riverine waters were the most sensitive water type, and the ultraviolet and near-infrared spectral end members, which are critical to next-generation satellite missions, 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 high-quality data products, which supported an alternative classification capability based on the spectral diffuse attenuation coefficient, Kd(λ). The Kd(320) and Kd(780) data showed how complex coastal systems can be distinguished two-dimensionally and how near-ice water masses are different from the neighboring open ocean. Finally, an algorithm for predicting the spectral absorption due to colored dissolved organic matter (CDOM), denoted aCDOM(λ), was developed using the Kd(320) / Kd(780) ratio, which was based on a linear relationship with respect to aCDOM(440). The robustness of the approach was established by expanding the use of the algorithm to include a geographically different coastal environment, the Southern Mid-Atlantic Bight, with no significant change in accuracy (approximately 98% of the variance explained). Alternative spectral end members reminiscent of next-generation (340 and 710 nm) as well as legacy satellite missions (412 and 670 nm) were also used to accurately derive aCDOM(440) from Kd(λ) ratios.
Highlights
The Cryosphere traviolet and near-infrared spectral end members, which are A number of international ocean color satellite sensors have critical to next-generation satellite missions, were the most been designed and launched in the last decade and a half sensitive parts of the spectrum
Classification was based on whether data were obtained in the open ocean, near the ice edge, within the Mackenzie River plume, or in coastal waters. Another objective of the results presented here is to initiate the preparedness for the next-generation of ocean color satellites (NRC, 2007; NASA, 2010) with the most capable commercial off-the-shelf (COTS) instrumentation in the shortest time possible while providing baseline results of optically complex coastal waters to contribute to the underlying science questions associated with NASA programs and mission offices
Arctic apparent optical properties (AOPs) were recognized as different than the world ocean used to derive global satellite data products (Cota et al, 2004), the results presented below show that Arctic AOPs are more complex than first established, in part because early studies in these same areas were spectrally restricted
Summary
The Cryosphere traviolet and near-infrared spectral end members, which are A number of international ocean color satellite sensors have critical to next-generation satellite missions, were the most been designed and launched in the last decade and a half sensitive parts of the spectrum. The current challenge in ocean color remote sensing is to extend the open-ocean accomplishments into much shallower waters (McClain et al, 2006), e.g., estuaries and rivers This requirement is driven by the present focus of satellite observations, which are inexorably tied to launching new missions based on novel research topics and ensuring the quality of the ensuing satellite data. Classification was based on whether data were obtained in the open ocean, near the (moving) ice edge, within the Mackenzie River plume, or in coastal waters Another objective of the results presented here is to initiate the preparedness for the next-generation of ocean color satellites (NRC, 2007; NASA, 2010) with the most capable COTS instrumentation in the shortest time possible while providing baseline results of optically complex coastal waters to contribute to the underlying science questions associated with NASA programs and mission offices. Because of the emphasis on the near-shore environment, which is typified by shallow water depths and an optically complex vertical structure, there is the added requirement to demonstrate that the new technology can be validated in waters with unprecedented multidimensional heterogeneity
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