Gulf Stream destabilization point

'''DEFINITION'''

The destabilization point of the Gulf Stream marks the longitude where the current transitions from a boundary-following current to an open-ocean jet. It is identified using the 25 cm SSH contour, from detrended Absolute Dynamic Topography (ADT), a standard method validated in multiple studies (Lillibridge & Mariano, 2013; Rossby et al., 2014; Andres, 2016; Chi et al., 2021; Guo et al., 2023).

Monthly Gulf Stream paths from 1993 to present are divided into 0.5° longitude bins, and the northernmost latitude of the SSH contour is used to compute the latitudinal variance in each bin. The destabilization point is defined as the first longitude where this variance reaches 0.42°², which represents half the maximum variance observed across the full time series ( Sánchez-Román et al., 2024).

A 95% confidence interval is computed from monthly estimates, and a 5-year running mean is applied to smooth high-frequency fluctuations. Longitudinal shifts of the destabilization point can exceed 1400 km, influenced by climate modes such as the North Atlantic Oscillation (NAO) (Sánchez-Román et al., 2024).

'''CONTEXT'''

The Gulf Stream is a major western boundary current which forms the northward flowing path of the Atlantic Meridional Overturning Circulation (AMOC). It carries near-surface warm waters from the Gulf of Mexico to the subpolar North Atlantic, playing an important role in its climate variability and change. Interannual lateral displacements in the Gulf Stream’s position impact associated water transport to subpolar regions, altering the global climate system (Guo et al., 2023).

Tracking the destabilization point provides an early indicator of structural changes in the North Atlantic circulation system. Its position directly reflects the length of the stable jet segment and the onset region of meanders. The observed shifts indicate modifications in the jet’s structure, its stability, and its interaction with oceanic variability. Its evolution reveals a significant westward migration followed by an eastward shift over the past three decades.

'''KEY FINDINGS'''

The results reveal a low-frequency westward and southward displacement of the Gulf Stream destabilization point between 1995 and 2012, followed by a previously unreported reversed migration starting in 2013. These changes affect the intensity of mesoscale variability and the transport of waters toward the subpolar North Atlantic. They appear to be correlated with the dynamics of the North Atlantic Oscillation, whose successive phases modulate the position of the current.

'''DOI (product):''' https://doi.org/10.48670/mds-00377