The Gulf Stream path changes and their linkage to the abyssal circulation in the North Atlantic.

The Gulf Stream (GS) is a key element in the Atlantic climate as it plays a dual role of being both the upper limb of the thermohaline circulation as well as the western boundary current of the subtropical gyre. It has been widely documented that movements of the GS axis have profound influences on the local turbulent heat flux, coastal intrusion, eddy activities and biological production. Various indices representing the GS path are derived from the upper ocean states, including satellitesea surface height (SSH), isotherm etc. However, there are significant gaps in our knowledge about the connection between GS path and deep ocean changes. Here we utilize statistical methodology, including Self-Organizing Map (SOM) and Empirical Orthogonal Function (EOF) analysis to investigate the three-dimensional structure for the GS path changes and their impacts on the underneathabyssal ocean circulation. Our study analyzes the three-dimensional hydrographic and velocity fields extracted from NEMO platform for the time period of 1993-2018.

The analysis of SSH using both methods suggests that their leading mode is featured with meridional migration of GS axis with coherent structure across the longitudes. Both the temporary evolution from EOF and frequency of occurrences from SOMreveal that the GS path oscillates on the interannual-decadal scales. There is regime change after 2011 with GS path shifts northward. Similar patterns are obtained from the subsurface salinity fields, but showing that the GS path changes are closely tied to the expansion/retreat of Labrador Current. We will present the corresponding horizontal and vertical patterns in both hydrography and velocity fields, aiming toprovide fundamental insights on the factors driving such GS path changes and their connections with the deep western boundary current.