Optical properties and optical constituents of the Faroe Islands shelf and off-shelf waters, North East Atlantic

Lars Chresten Lund-Hansen, Eilif Gaard, Høgni Debes

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5 Citations (Scopus)

Abstract

The study comprises a data set of CTD, optical properties—K0(PAR), cp, a(PAR), b(PAR)—and optical constituents—Chl a, SPM, CDOM—from 72 shelf and off-shelf stations in the Faroe Islands (62°N, 7°W) North East Atlantic, in early spring 2005. Results showed that shelf waters surrounding the islands were cold and low saline, whereas off-shelf waters were warmer (~1°C) and more saline (~0.05) PSU. A pronounced oceanographic front separated the two waters, and diffuse light attenuation K0(PAR), beam attenuation cp, Chl a, absorption a(PAR), and scattering coefficient b(PAR) were all significantly higher on the shelf. Analyses showed that off-shelf light attenuation K0(PAR) was governed by Chl a, shown by a high (r2 = 0.64) Chl a–K0(PAR) correlation, whereas light attenuation on the shelf was governed by both Chl a, SPM, and CDOM in combination. A Chl a specific diffuse attenuation coefficient K*0(PAR) of 0.056 (m2 mg−1 Chl a) and a Chl a specific beam attenuation (c*P) of 0.27 (m2 mg−1 Chl a) coefficients were derived for the off-shelf. It is pointed out that Chl a is the single variable that changes over time as no rivers with high SPM and CDOM enter the shelf area. Data were obtained in early spring, and Chl a concentrations were low ~0.5 mg Chl a m−3. Spring bloom Chl a are about 10 mg Chl a m−3 and estimations showed that shelf K0(PAR) will increase about 5 times and beam attenuation about 10 times. The Faroe Islands shelf–off-shelf waters is a clear example where physical conditions maintain some clear differences in optical properties and optical constituents. The complete data set is enclosed.
Original languageEnglish
Pages (from-to)285-293
Number of pages9
JournalHydrobiologia
Volume636
DOIs
Publication statusPublished - 2009

Keywords

  • Diffuse K0(PAR) and beam attenuation (cp) coefficients
  • Chl a
  • Faroe Islands
  • North East Atlantic

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