Monthly-Resolved Cave Proxy Evidence for Northward Gulf Stream Migration During the Little Ice Age

The Gulf Stream forms part of the upper-ocean limb of the Atlantic Meridional Overturning Circulation (AMOC), playing an essential role in redistributing heat northward and greatly influencing regional climates in the North Atlantic. Understanding Gulf Stream path and strength variability on longer timescales is vital to contextualise its present-day weakening and to fully appreciate its sensitivity to forcing. We present a 558-year long (1456–2013) proxy record of sea surface temperature from a Bermudan stalagmite using an indirect magnesium-temperature calibration based on a connection to wind speed. Our monthly-resolved terrestrial palaeo-oceanographic temperature reconstruction indicates that the Gulf Stream was likely positioned further south than today during the Little Ice Age. We suggest that a combination of reduced Gulf Stream transport, enhanced Labrador Current and Deep Western Boundary Current transport, and an extended negative North Atlantic Oscillation phase, caused the Gulf Stream to be at lower latitudes during the Little Ice Age, before migrating northward as the Little Ice Age abated.