Mixing along continental slopes affects North Atlantic Deep Water

Abstract

In the northern Atlantic Ocean, cold salty water from the Arctic Ocean sinks to form North Atlantic Deep Water, a current that hugs the bottom of the ocean as it travels south toward Antarctica. The formation of this water mass is vital to large‐scale global ocean circulation and the spread of heat and nutrients across the planet's waters—when deep waters surface, they form warm surface currents such as the Gulf Stream, which are swept by wind back to the North Atlantic, where they cool and sink, beginning the cycle anew. In the Faroe‐Shetland Channel, so named because it lies between Scotland's Shetland Islands and Denmark's Faroe Islands, deep water masses that are tributaries to North Atlantic Deep Water abut the steep continental slopes that bracket the channel. The ebb and flow of ocean tides there produce horizontal and vertical waves that travel long distances and may break on the slopes like waves on a beach. These waves, called internal tides, were monitored and modeled by Hall et al., who sought to understand how they affect the mixing of different water masses that pass through the channel. They found that strong mixing due to internal tides on the slopes that bound the Faroe‐Shetland Channel may be an important mechanism by which North Atlantic Deep Water acquires the physical and chemical properties that it carries across the globe. (Journal of Geophysical Research‐Oceans, doi:10.1029/2010JC006213, 2011)