Zakharkov S.P., Lazaryuk A.Yu., Gordeychuk T.N., Shtraikhert E.A.
In the coastal areas of Peter the Great Bay (the Sea of Japan), the influence of ice thickness, snow cover on its surface, and the concentration of chlorophyll a in the layer under ice on the value of subglacial illumination at 60 hydrological stations from January to March 2010–2016 was studied. Deglacial illumination was determined using remote sensing methods, which allowed us to conclude that the seasonal averages of illumination in the studied region are sufficient for the development of phytoplankton under ice. The influence of a hole for measuring parameters under ice on subglacial illumination is estimated. It was shown that the “hole effect” did not appear at depths below 2 m. Measurements were performed from ice at hydrological stations using the autonomous probing system SBE‐19plus (Sea-Bird Electrons. Inc., USA). The attenuation of illumination was evaluated in two two-meter layers by the coefficients: K 20 — (logarithm of the ratio PAR2/PAR0 — “ice+ice water”) and K 42 — Lg (PAR4/PAR2) — in the water layer between horizons of 2 and 4 m. A direct relationship was established between the weakening of the illumination and the thickness of the ice in the case of an experiment in one day (03.11.2010). The coefficient of determination was positive and significant. If we compare these parameters throughout the winter period, a meaningful relationship could not be established. Presumably, other factors are superimposed on the relationship between illumination and ice thickness. We have confirmed that one of these factors is the concentration of chlorophyll-a in the subglacial layer of water. The daytime interval was also revealed when the subglacial illumination does not feel much dependence on the deglacial illumination.