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Abstract:
Data set on colored dissolved organic matter (CDOM) absorption and dissolved organic carbon (DOC) in the Fram Strait (~78°50’ N), collected during the annual Norwegian Polar Institute’s research and monitoring cruises to the Fram Strait Arctic Outflow Observatory. CDOM data has been collected annually since 2009 in August September, and DOC during a number of years.
Version 1 includes a350, S275-295 and DOC data. Data is provided in a tab formatted text file, with headings on the first row. Missing values are indicated with NaN.
Quality
Samples for analysis of colored dissolved organic matter (CDOM) absorbance were filtered (0.2 µm membrane filter) into pre-combusted amber glass vials immediately after collection. Samples were stored in dark at +4°C until analysis, typically within a month. CDOM was quantified as the absorption coefficient in the spectral range from 250 to 650 nm using a Shimadzu UV-2401PC spectrophotometer and 100 mm quartz cells with ultrapure water as reference, with a precision of 0.025 m-1. In this data set, CDOM absorption is presented as the absorption coefficient at 350 nm (a350, in m-1). The CDOM absorption spectral slope (S275-295, in µm-1) is also presented in the data set and was obtained by applying an exponential function to the 275–295 nm spectral range.
Samples for the analysis of dissolved organic carbon concentration (DOC, in µM) were collected only during the cruises in 2009, 2010, 2012, 2014 and 2016. The samples were collected directly into acid-washed high-density polyethylene bottles (HDPE) and stored frozen. These samples were not filtered, and therefore technically represent TOC, however, at this time of year concentrations of particulates are at very low levels compared to eastern Fram Strait (Pavlov et al., 2015), and therefore the majority is dissolved (DOC). DOC in 2009-2012 was quantified using a Shimadzu TOC-VCPH analyzer after acidification to pH 2 and sparging oxygen. In 2014-2016 DOC was measured on an OI Analytical 1030D TOC analyzer after acidification to pH 2 and sparging with ultrahigh purity helium. Reproducibility between the two instruments was confirmed to be <5% with replicate measurements of samples from 2014. The accuracy of DOC quantification was controlled by analyzing the Hansell seawater DOC consensus reference material (CRM).