Estimation of long-term changes in thermal conditions and distribution of Atlantic and Subarctic water in the XXI Century in the Norwegian Sea on area surveys data

Abstract

   Purpose of the work: assessing the spatial and temporal variability of thermal conditions in waters of various origins in the Norwegian Sea in the first decades of the 21st century.   Materials: oceanographic data collected during the International Ecosystem Surveys in the Norwegian Sea in 2000–2021.   Methods used: comparative data analysis, descriptive statistics methods, correlation analysis.   Results: the “boxes”, temperature in which most fully describes the change in the temperature of the Atlantic and Subarctic waters of the Norwegian Sea, were identified. This is confirmed by the high correlation coefficients of temperature in the “boxes” with the water temperature over a wide area of distribution of waters of various origins. The interannual temperature variability in the “boxes” was studied with the separation of warm and cold periods. An assessment of the interannual variability of the distribution boundaries of the Atlantic and subarctic waters is made by the position of isotherms at different horizons. A statistically significant relationship is shown between changes in the temperature of Atlantic and Subarctic waters according to the “boxes” data and changes in the boundaries of the distribution of water masses and the position of the frontal zone between them.   Practical significance: the results of the 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 origins in the Norwegian Sea in the absence of standard sections and can be used to predict the distribution of pelagic fish in the sea area depending on oceanographic conditions.