Dataset: North Atlantic CDOM Absorption Coefficients
Deployment: AE1707

Water sampling details

Water samples were gravity filtered from Niskin bottles through 0.2 μm Whatman Polycap 36 AS nylon membrane cartridge filters, directly into combusted borosilicate glass bottles. Filtered sample waters were stored in the dark at 4°C until measurements. Sample waters were left in the dark at room temperature (~20°C) so they were back to room temperature before absorbance measurements.

Measurement details

Absorbance (A(λ)) of the water samples were measured at 250–800 nm at 1.0 nm intervals, in triplicate. May 13th, 2017 samples were measured in 10-cm-pathlength quartz spectrophotometric cuvettes with an Agilent 8453 UV-visible spectrophotometer with ChemStation software; July 17th, 2018 samples were measured in a World Precision Instruments UltraPath capillary cell set at 50 cm pathlength using a Maya Pro 2000 spectrophotometer with SpectraSuite software, and the rest of the samples were measured in the same UltraPath capillary cell set at 200 cm pathlength using the same Maya spectrophotometer.

Milli-Q water was similarly measured to use as blanks. The average absorbance spectra of blanks were subtracted from the absorbance spectra of the sample water. Absorbance spectra were further corrected for potential offsets and instrument drift by subtracting the average absorbance at 690–710 nm, before converting A(λ) to Napierian absorption coefficients (ag(λ); m−1), using the following equation: ag(λ)= A(λ) ln10/L, where L (m) is the pathlength.