Estimation of Long-Term Variations in the Thermal Conditions and Distribution of Atlantic and Subarctic Water in the 21st Century in the Norwegian Sea Based on Area Survey Data

The aim of the study is to estimate the spatial and temporal variability of thermal conditions in waters of various origin in the Norwegian Sea in the first decades of the 21st century. The materials comprised oceanographic data collected during the International Ecosystem Surveys in the Norwegian Sea in 2000–2021. The methods involved comparative data analysis, descriptive statistics methods, and correlation analysis. “Boxes” the temperature in which most fully describes the change in temperature of Atlantic and Subarctic waters of the Norwegian Sea, were identified. This is confirmed by the high correlation coefficients for the temperature in the boxes and the water temperature over a wide distribution area of waters of various origin. The interannual temperature variability in the boxes was studied with separation of warm and cold periods. The interannual variability of the distribution boundaries of Atlantic and Subarctic waters was estimated from the position of isotherms at different horizons. A statistically significant relationship is demonstrated between variations in the temperature of Atlantic and Subarctic waters according to the data of the boxes and variations in the distribution boundaries of water masses and position of the frontal zone between them. The results of analysis of in situ data from annual areal surveys make it possible to estimate the interannual variability of the thermal state of waters of various origin in the Norwegian Sea in the absence of standard transects and can be used to predict the distribution of pelagic fish in the area of the sea depending on the oceanographic conditions.