Sea Level as an Indicator of Interannual Variability of Water Circulation and Climate in the North Atlantic

The paper analyzes the relationship between the interannual variability of sea level characteristics, water circulation, and various climatic indices in the North Atlantic. Sea level gradients Δh at the ends of local sections characterizing the geostrophic current components, as well as average sea level value at these sections hav, have been calculated at latitudinal sections of 26° N (80–15° W) and 56° N (57–10° W) for the period 1993–2022 according to altimetric data available since 1993. The section at latitude 26° N serves as a reference for the STG (Subtropical Gyre), and the one at latitude 56° for the SPG (Subpolar Gyre). It is shown that Δh and hav in the local sections (57°–38°, 38°–28°, and 28°–10° W) of latitude 56° N have a significant correlation with climatic indices, being especially high for the eastern 28°–10° W section. A high statistical relationship has been noted between sea level changes in the 56° N section and sea surface temperature in the northern seas, which shows the weakening of the deep-sea convection with the sea level rise in the Labrador and Irminger Seas, as well as in the Greenland Basin. Statistical parameterization of Atlantic meridional overturning circulation (AMOC) and QUMO (reverse water flow due to recirculation of the subtropical gyre) has been carried out for the latitude section at 56° N according to the sea level data. The accuracy of estimating AMOC and QUMO is shown to be in the range of 89–96% of the contribution to variance. The integral North Atlantic Circulation index representing the difference in the sea level at latitudinal sections of 26° (80°–15° W) and 56° (57°–10° W) can be used as a characteristic of the circulation in the system of cyclonic and anticyclonic gyres (SPG and STG). Taking into account its high statistical relationship with the North Atlantic Oscillation and other indices, it can serve as an important indicator of interannual variability of water circulation and climate in the North Atlantic.