Suspended Matter, Chl-a, CDOM, Grain Sizes, and Optical Properties in the Arctic Fjord-Type Estuary, Kangerlussuaq, West Greenland During Summer

Optical constituents as suspended particulate matter (SPM), chlorophyll (Chl-a), colored dissolved organic matter (CDOM), and grain sizes were obtained on a transect in the arctic fjord-type estuary Kangerlussuaq (66A degrees) in August 2007 along with optical properties. These comprised diffuse attenuation coefficient of downwelling PAR (K (d)(PAR)), upwelling PAR (K (u)(PAR)), particle beam attenuation coefficient (c (p)), and irradiance reflectance R(-0, PAR).

PAR is white light between 400 and 700 nm. The estuary receives melt water from the Greenland Inland Ice and stations covered a transect from the very high turbid melt water outlet to clear marine waters. Results showed a strong spatial variation with high values as for suspended matter concentrations, CDOM, diffuse attenuation coefficient K (d)(PAR), particle beam attenuation coefficients (c (p)), and reflectance R(-0, PAR) at the melt water outlet.

Values of optical constituents and properties decreased with distance from the melt water outlet to a more or less constant level in central and outer part of the estuary. There was a strong correlation between inorganic suspended matter (SPMI) and diffuse attenuation coefficient K (d)(PAR) (r (2) = 0.92) and also for particle beam attenuation coefficient (c (p); r (2) = 0.93).

The obtained SPMI specific attenuation-K (d) (*) (PAR) = 0.13 m(2) g(-1) SPMI-and the SPMI specific particle beam attenuation-c (p) (*) = 0.72 m(2) g(-1)-coefficients were about two times higher than average literature values. Irradiance reflectance R(-0, PAR) was comparatively high (0.09-0.20) and showed a high (r (2) = 0.80) correlation with K (u)(PAR).

Scattering dominated relative to absorption-b(PAR)/a(PAR) = 12.3. Results strongly indicated that the high values in the optical properties were related to the very fine particle sizes (mean = 2-6 mu m) of the suspended sediment. Data and results are discussed and compared to similar studies from both temperate and tropical estuaries.