Parisians sipping coffee in outdoor cafe´s owe their comfort to the circulation patterns of the North Atlantic Ocean. Surface currents carry warm water from the tropics to high latitudes, where the water grows colder and hence denser. In the far north, this dense, cold, and salty water sinks to depths from one to six kilometers, where it forms the southward‐flowing deep water of the North Atlantic, as depicted in the schematic in figure 1. Because the ocean exchanges heat with the atmosphere, any disruption in this so‐called meridional overturning circulation (MOC) is likely to impact the climate on the adjoining land masses.