EGU24-7739, updated on 08 Mar 2024
EGU General Assembly 2024
© Author(s) 2024. This work is distributed under
the Creative Commons Attribution 4.0 License.

Non-stationarity in the NAO–Gulf Stream SST front interaction

Alessio Bellucci1, Luca Famooss Paolini2, Nour-Eddine Omrani3,5, Panos Athanasiadis4, Paolo Ruggieri2, Casey Patrizio4, and Noel Keenlyside3,5
Alessio Bellucci et al.
  • 1Italian National Research Council (CNR), Institute of Atmospheric Sciences and Climate, Bologna, Italy
  • 2Department of Physics and Astronomy, University of Bologna, Bologna, Italy
  • 3Geophysical Institute, University of Bergen, Norway
  • 4Fondazione Centro Euro-Mediterraneo sui Cambiamenti Climatici (CMCC), Bologna, Italy
  • 5Bjerkenes Centre for Climate Research, Bergen, Norway

The interaction between the North Atlantic Oscillation (NAO) and the latitudinal shifts of the Gulf Stream sea surface temperature front (GSF) has been the subject of extensive investigations. There are indications of non-stationarity in this interaction, but differences in the methodologies used in previous studies make it difficult to draw consistent conclusions. Furthermore, there is a lack of consensus on the key mechanisms underlying the response of the GSF to the NAO. This study assesses the possible non-stationarity in the NAO–GSF interaction and the mechanisms underlying this interaction during 1950–2020, using reanalysis data. Results show that the NAO and GSF indices covary on the decadal timescale but only during 1972–2018. A secondary peak in the NAO–GSF covariability emerges on multi-annual timescales but only during 2005–2015. The non-stationarity in the decadal NAO–GSF co-variability is also manifested in variations in their lead–lag relationship. Indeed, the NAO tends to lead the GSF shifts by 3 years during 1972–1990 and by 2 years during 1990–2018. The response of the GSF to the NAO at the decadal timescale can be interpreted as the joint effect of the fast response of wind-driven oceanic circulation, the response of deep oceanic circulation, and the propagation of Rossby waves. However, there is evidence of Rossby wave propagation only during 1972–1990. Here it is suggested that the non-stationarity of Rossby wave propagation caused the time lag between the NAO and the GSF shifts on the decadal timescale to differ between the two time periods.

How to cite: Bellucci, A., Famooss Paolini, L., Omrani, N.-E., Athanasiadis, P., Ruggieri, P., Patrizio, C., and Keenlyside, N.: Non-stationarity in the NAO–Gulf Stream SST front interaction, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-7739,, 2024.