Ruth Curry indicates on a globe the location of the Gulf Stream

When Jules Verne called the Gulf Stream "the sea's greatest river" he was not far off. In the last couple of decades, oceanographers have come to understand the central role it plays in the enormous ocean currents that circle the globe. Scientists have their own conception of the Gulf Stream -- as a "Great Ocean Conveyor Belt" that brings a third of all the sun's heat that falls on the North Atlantic up to northern latitudes, in the process warming the northeast US, Europe and Scandinavia. The Ocean Conveyor is driven by a giant recirculation pump that's created in the Nordic Seas, north of Iceland, where the warm Gulf Stream is cooled by Arctic winds. The cooled waters sinks, pushing deep water back south again.

Ruth Curry, at the Woods Hole Oceanographic Institution, has found that in recent decades significant amounts of freshwater have been flowing into the Nordic Seas from the Arctic Ocean to the north. Freshwater floats on top of salt water, so the freshening of the Nordic Seas could potentially disrupt the operation of the Ocean Conveyor's recirculation pump, in turn reducing or even shutting down the flow of the Gulf Stream.