Changes in the Gulf Stream path over the last 3 decades

Abstract. The Gulf Stream transports warm waters from low to high latitudes in the North Atlantic Ocean, impacting Europe's climate. This study investigates the changing pattern of the Gulf Stream over the last 3 decades as observed in the altimetric record (1993–2022) using monthly averaged altimetry maps together with the outputs from an ocean reanalysis product. The seasonal and yearly evolution of the coordinates (destabilization point) where the Gulf Stream starts to meander and convert from a stable to an unstable detached jet is investigated. At the seasonal scale, the location of this destabilization point presents zonal shifts displacing the Gulf Stream path to the north in summer and fall and to the south in winter and spring. In addition, it presents variations at interannual scale and has varied by more than 1400 km in longitude, showing meridional shifts of 300 km over the altimetric era: it exhibits a low-frequency remarkable shift westward and southward between 1995 and 2012. From that year, the destabilization point displacement inverses, exhibiting a previously unreported migration eastward and northward that translates into a larger fraction of the stable detached jet to the detriment of the unstable meandering jet. Changes in the Gulf Stream path impact both associated mesoscale eddy kinetic energy and waters transported towards the subpolar North Atlantic. The observed shifts of the path destabilization point seem to be linked to North Atlantic Oscillation variability during winter that may play an important role: it presents a negative trend associated with a shift from a positive to a negative phase between 1995 and 2011 and an opposite behavior from a negative to a positive phase from that year until 2020 in agreement with the associated southwestward and northeastward observed migration of the destabilization point.