Spectral Characteristics of the Beam Attenuation Coefficient in the Atlantic Ocean Tropical Area

V.I. Man’kovsky, E.V. Man’kovskaya✉

Marine Hydrophysical Institute, Russian Academy of Sciences, Sevastopol, Russian Federation

✉ e-mail: emankovskaya@mail.ru

Abstract

The results of measurements of the ε(λ) beam attenuation coefficient (BAC) spectral distribution in the surface waters of the North Atlantic tropical region (NATR) are represented. The data were obtained in the 27th cruise of R/V Akademik Vernadsky (January–April, 1984).

According to the data of the beam attenuation coefficient spectra measurements in the surface waters of the tropical Atlantic northern part, the characteristics of the spectra (440–675 nm range) were obtained. Also, the change of the spectra shape the in the NATR waters with the attenuation coefficient increase was considered. Spectral distributions of the attenuation coefficient in the waters of the principal large-scale NATR currents and in the coastal African waters are presented. A comparison of the mean spectra in oligotrophic waters of the tropical Atlantic and the Pacific Ocean was carried out. It showed the same pattern of the spectral distribution of the attenuation coefficient in these regions.

For an array of empirical functions ε(λ) in the NATR waters, the expansion into orthogonal eigenvectors was carried out. The possibility to reconstruct the spectra using the first orthogonal vector, i.e. by measuring the attenuation coefficient at one wavelength, is shown. The optimal wavelength values, which should be used to reconstruct the spectra, are indicated.

The relation of the chlorophyll concentration in the surface ocean waters of the NATR with the beam attenuation coefficients in three sections of the spectrum with wavelengths of 440, 500 and 551 nm was established. In the NATR coastal waters the relation Cchl = f[ε(λ)] should be considered separately, since it differs significantly from the one in ocean waters. The chlorophyll and attenuation coefficient relations in NATR ocean waters established in this work should be characterized as regional.

Keywords

beam attenuation coefficient, spectral characteristics, reconstruction of spectra, chlorophyll concentration

For citation

Man’kovsky, V.I. and Man’kovskaya, E.V., 2017. Spectral Characteristics of the Beam Attenuation Coefficient in the Atlantic Ocean Tropical Area. Physical Oceanography, (1), pp. 41-52. doi:10.22449/1573-160X-2017-1-41-52

DOI

10.22449/1573-160X-2017-1-41-52

References

  1. Pavlov, V.M., 1974, “Prozrachnost' morskoy vody [Sea water transparency]”, Gidrofizicheskie i gidroopticheskie issledovaniya v Atlanticheskom i Tikhom okeanakh, Moscow, Nauka, pp. 127-139 (in Russian).
  2. Li, M.E., Man'kovskiy, V.I., 2004, “Gidroopticheskie issledovaniya morey i okeanov. Tropicheskaya zona Atlanticheskogo okeana [Hydro-optical studies of the seas and oceans. The Atlantic Ocean tropical zone]”, Razvitie nauk i tekhnologiy v Morskom gidrofizicheskom institute NAN Ukrainy za 75 let, Sevastopol, pp. 280-286 (in Russian).
  3. Man'kovskiy, V.I., 2012, “Spektral'nyy laboratornyy prozrachnomer s peremennoy bazoy [Spectral laboratory transparency meter with a variable base]”, Sistemy kontrolya okruzhayushchey sredy, iss. 17, pp. 56-60 (in Russian).
  4. Pope, R.M., Fry, E.S., 1997, “Absorption spectrum (380-700 nm) of pure water. II. Integrating cavity measurements”, Appl. Optics., vol. 36, iss. 33, pp. 8710-8723.
  5. Kopelevich, O.V., 1983, “Faktory, opredelyayushchie opticheskie svoystva morskoy vody [Factors determining the marine environment optical properties]”, Optika okeana. T. 1. Fizicheskaya optika okeana, Moscow, pp. 150-166 (in Russian).
  6. Kopelevich, O.V., 1983, “Rastvorennye organicheskie veshchestva [Dissolved organic matters]”, Optika okeana. T. 1. Fizicheskaya optika okeana, Moscow, pp. 157-160 (in Russian).
  7. Kopelevich, O.V., 1983, “Maloparametricheskaya model' opticheskikh svoystv morskoy vody [A small parametric model of the optical properties of sea water]”, Optika okeana. T. 1. Fizicheskaya optika okeana, Moscow, pp. 208-235 (in Russian).
  8. Kopelevich, O.V., 1982, “Vosstanovlenie” spektral'nykh velichin pokazatelya oslableniya sveta morskoy vodoy v oblasti 270-590 nm po dannym izmereniy dlya dvukh dlin voln [“Reconstruction" of the spectral values of the sea water beam attenuation coefficient within the range 270-590 nm from measurements for two wavelengths]”, Okeanologiya, vol. 22, no. 3, pp. 392-397 (in Russian).
  9. Finenko, Z.Z., Hoeppfner, N., Williams, R. & Piontkovski S.A., 2003, “Phytoplankton carbon to chlorophyll a ratio: response to light, temperature and nutrient limitation”, Mar. Ecol. J., vol. 2, no. 2, p. 40-64.
  10. Kukushkin, A.S., 2012, “Mnogoletnyaya i sezonnaya izmenchivost' soderzhaniya vzveshennogo organicheskogo veshchestva v verkhnem sloe v glubokovodnykh rayonakh Chernogo morya [Long-term and seasonal variability of the suspended organic matter content in the upper layer in the deep waters of the Black Sea]”, Ustoychivost' i evolyutsiya okeanologicheskikh kharakteristik ekosistemy Chernogo morya, Sevastopol, ECOSI-Gid-rofizika, pp. 242-263 (in Russian).
  11. Behrenfeld, M.J., Boss, E., 2006, “Beam attenuation and chlorophyll concentration as alternative optical indices of phytoplankton biomass”, J. Mar. Res., vol. 64, no. 3, pp. 431-451, doi:https://doi.org/10.1357/002224006778189563

Download the article (PDF)