Warming and lateral shift of the Gulf Stream from in situ observations since 2001

As the poleward-flowing western boundary current of the North Atlantic ocean, the Gulf Stream plays a key role in the climate system and exerts substantial control on adjacent coastal systems. Observations from an 8-year-long series of autonomous underwater glider surveys are used to create a three-dimensional seasonal climatology of Gulf Stream properties along the US East Coast. Temperature, salinity, and density anomalies relative to this climatology are then computed using more than 25,000 Argo and glider observations spanning from 2001 to 2023. These anomalies show that the Gulf Stream west of 68°W has experience both surface-intensified warming due to heat uptake and a lateral shift toward the coast at a rate of 5±2 km per decade. Compared to the turn of the 21st century, the Gulf Stream along the US East Coast now has an O(10)-m-thick surface layer of warmer (by about ~1 °C) and lighter (by ~0.3 kg m-3) water, contributing to increased ocean stratification. These results particularly highlight the key role of sustained underwater glider surveys in detecting climate change signals along the margins of ocean basins.