UNIVERSITY OF BUCHAREST
FACULTY OF PHYSICS

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2026-06-11 23:58
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Conference: Bucharest University Faculty of Physics 2026 Meeting


Section: Atmosphere and Earth Science; Environment Protection


Title:
Atlantic Meridional Overturning Circulation Dynamics Inferred from European Winter Climate Dipoles


Authors:
Adrian BERLIC (1,2), Mihai DIMA (1)


Affiliation:
1) University of Bucharest, Faculty of Physics, 405 Atomistilor Street, 077125, Magurele, Romania

2) National Meteorological Administration, 97 Soseaua Bucuresti - Ploiesti, Bucharest, Romania


E-mail
adrian.berlic@gmail.com


Keywords:
AMOC; European winter climate; red-blue dipole index; Early warning signals (EWS); Rate-induced tipping; Critical slowing down; Climate regime shift


Abstract:
The Atlantic Meridional Overturning Circulation (AMOC) is a key component of the climate system, with strong implications for European winter climate. Recently, its impact on Europe was determined based on reanalysis data, reflected as north-south “Red-Blue” dipolar structures of surface air temperature (SAT) and precipitation. Based on these, dipole indexes considered AMOC reconstructions are derived as differences of the average values for the sectors 0–30°E, 45–70°N, and 20–40°E, 35–45°N. In a multi-dataset framework, the AMOC reconstructions represented by dipole indexes are constructed based on historical reconstructions, reanalyses, and modern ERA5 SAT and precipitation fields. The analysis includes trend diagnostics, subperiod comparisons, early-warning signal (EWS) indicators based on rolling variance and lag-1 autocorrelation, spectral analysis, and phase-space visualization. The historical SAT-based Red–Blue index is reproducible across independent datasets and shows a marked post-1970 increasing trend. EWS indicators generally increase after 1970, particularly in variance and lag-1 autocorrelation. These results can be interpreted in two ways: 1) either as manifestation of a critical slowing down phenomenon which indicates that AMOC is approaching a bifurcation-induced tipping; 2) as an amplification of variance and memory after a rate-induced tipping manifested around 1970. The start of the increasing trend of EWS indicates that the last interpretation is more likely than the former one. Preliminary spectral analysis also suggests enhanced variability in the 20–25 year range, which could be interpreted as an indication that the current AMOC state is not far from its tipping point.