Seasonal and interannual variations in ocean surface temperature in the area of the Northern Kuril Islands according to satellite data

The average monthly values of ocean surface temperature in the area of the northern Kuril Islands for 1998-2022 are analyzed. On the basis of a 25-year series of observations, the norms are constructed for each month – the average long-term distributions. It is shown that in the coastal area from the Simushir Island to the Fourth Kuril Strait, a cold spot area with very low temperatures (about 6°C) and small annual cycle amplitudes (about 3 °C) is formed in summer. Seasonal fluctuations are characterized by an annual cycle with maximum values in August–September and minimum values in February–March. In general, they are well described in the region by a combination of annual and semi-annual harmonics with amplitudes of 4.9 and 1.1°C, respectively. The interannual variability is reflected in variations of summer maxima with a period of about six years. In the summer and autumn period, outside the cold spot area, there is a steady trend towards an increase in temperature, the most significant in the northwestern Pacific Ocean (about 1°C in 25 years). In the winter-spring season in the Sea of Okhotsk, the reverse situation is observed with a tendency to decrease thermal parameters. When calculating deviations of average monthly temperatures from normal values, it was revealed that large-scale zones with significant temperature anomalies, mainly negative ones, can be formed in the area of the North Kuril Islands, which can pose a serious danger to aquatic organisms.