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- Title
Interannual Variability in the Absorption and Fluorescence Characteristics of Dissolved Organic Matter in the Canada Basin Polar Mixed Waters.
- Authors
Dainard, P. G.; Guéguen, C.; Yamamoto‐Kawai, M.; Williams, W. J.; Hutchings, J. K.
- Abstract
Dissolved organic matter (DOM) absorption and fluorescence properties were investigated for seawater samples collected from the polar mixed layer (0–30 m) of the Canada Basin in 2010–2012. Sea ice concentration as well as fractions of meteoric and sea ice meltwater (fMW and fSIM) calculated from oxygen isotope ratio (δ18O) were applied to assess the importance of discrete freshwater inputs to the distribution of DOM. Parallel factor analysis identified four humic‐like (C1‐2 and C4‐C5) and one protein‐like (C3) fluorescent components in 380 excitation‐emission matrix spectra. Surprisingly, despite different sea ice cover and biological regimes, DOM composition was largely homogeneous spanning these annual surveys. A strong and reoccurring coastal influence on DOM absorption and humic‐like DOM was observed each year and was particularly pronounced during the summer 2011 survey. Enrichment of DOM humic signal (C1, C2, and C4) in brine‐rich (fSIM < 0) waters relative to sea ice melt‐dominated waters (fSIM > 0; p < 0.05) was found during 2011 and 2012 in the offshore region (>76°N) where coastal influences were minimal (fMW < 0.1). Similar fSIM < 0 were found for 2011 and 2012, either when considering the Canada Basin as a whole or the offshore region (>76°N) exclusively, which could imply that brine formation influenced humic signals in polar mixed layer seawater. Findings herein highlight that future projected changes in freshwater sources and brine production in the Canada Basin will likely implicate the distribution and composition of DOM. Plain Language Summary: In this paper we showed that despite different sea ice cover in summer‐early fall, the average levels and composition of colored dissolved organic matter remained relatively unchanged in surface waters in the Canada Basin in 2010–2012. Only the northwest region experiencing strong brine rejection showed elevated humic signals. We also suggest to use the 140°W line as reference for dissolved organic matter monitoring in the Canada Basin in future studies. Key Points: The absorption and fluorescing characteristics of DOM were relatively homogenous in the Canada Basin in summer/early fall 2010–2012The humic‐like components were more abundant in the brine‐rich mixed layerThe 140°W line is proposed for monitoring DOM compositional changes in the Canada Basin
- Subjects
CANADA Basin; ABSORPTION; FLUORESCENCE; DISSOLVED organic matter; SEA ice thawing
- Publication
Journal of Geophysical Research. Oceans, 2019, Vol 124, Issue 7, p5258
- ISSN
2169-9275
- Publication type
Article
- DOI
10.1029/2018JC014896