The Denmark Strait overflow ( Danish: ''Grønlandspumpen''; Norwegian: ''Grønlandspumpa'', meaning "the Greenland pump") is an

undersea overflow In oceanography, an overflow is a type of deep-water ocean current, circulation in which denser water flows into an adjacent Oceanic basin, basin beneath lighter water. This process is significant in thermohaline circulation, contributing to the gl ...

located in the Denmark Strait between

Greenland Greenland is an autonomous territory in the Danish Realm, Kingdom of Denmark. It is by far the largest geographically of three constituent parts of the kingdom; the other two are metropolitan Denmark and the Faroe Islands. Citizens of Greenlan ...

and

Iceland Iceland is a Nordic countries, Nordic island country between the Atlantic Ocean, North Atlantic and Arctic Oceans, on the Mid-Atlantic Ridge between North America and Europe. It is culturally and politically linked with Europe and is the regi ...

. The overflow transports around of water per second, greatly eclipsing the discharge of the Amazon River into the Atlantic Ocean and the flow rate of the former

Guaíra Falls The Guairá Falls () or Guaíra Falls () were a series of immense waterfalls on the Paraná River along the border between Paraguay and Brazil. The falls ceased to exist in 1982 when they were inundated by the impoundment of the Itaipu Dam reserv ...

. The descending column of water is approximately wide and thick and descends over a length of around . It is formed by the density difference of the water masses either side of the Denmark Strait; the southward-flowing water originating from the

Nordic Seas The Nordic Seas are located north of Iceland and south of Svalbard. They have also been defined as the region located north of the Greenland-Scotland Ridge and south of the Fram Strait-Spitsbergen-Norway intersection. Known to connect the North P ...

is colder and consequently more dense than the Irminger Sea to the south of the strait. At the Greenland–Iceland Risean elevated

ridge A ridge is a long, narrow, elevated geomorphologic landform, structural feature, or a combination of both separated from the surrounding terrain by steep sides. The sides of a ridge slope away from a narrow top, the crest or ridgecrest, wi ...

forming the overflow's apexthe colder water cascades along the seafloor to a depth of around . Due to the

Coriolis effect In physics, the Coriolis force is a pseudo force that acts on objects in motion within a frame of reference that rotates with respect to an inertial frame. In a reference frame with clockwise rotation, the force acts to the left of the moti ...

, the downward flow of water is deflected to the right, resulting in the descending water on the Greenland side of the channel being roughly higher than the opposite side of the channel. The overflow provides one of the main inflows of

North Atlantic Deep Water North Atlantic Deep Water (NADW) is a deep water mass formed in the North Atlantic Ocean. Thermohaline circulation (properly described as meridional overturning circulation) of the world's oceans involves the flow of warm surface waters from the ...

, accounting for around half of dense water overflow between the Nordic Seas and the North Atlantic. The dense and cold water mass that spills across the overflow, known as ''Denmark Strait Overflow Water'' (DSOW), is thought to originate from the modification of water masses in the eastern Nordic Sea, the Greenland Sea, and the Iceland Sea. The North Icelandic Jet and two branches of the

East Greenland Current The East Greenland Current (EGC) is a cold, low-salinity current that extends from Fram Strait (~80N) to Cape Farewell (~60N). The current is located off the eastern coast of Greenland along the Greenland continental margin. The current cuts thr ...

transport the dense water to and across the overflow. DSOW is a key component of the present-day

thermohaline circulation Thermohaline circulation (THC) is a part of the large-scale Ocean current, ocean circulation driven by global density gradients formed by surface heat and freshwater fluxes. The name ''thermohaline'' is derived from ''wikt:thermo-, thermo-'', r ...

and may influence the

Atlantic Multidecadal Oscillation The Atlantic Multidecadal Oscillation (AMO), also known as Atlantic Multidecadal Variability (AMV), is the theorized variability of the sea surface temperature (SST) of the North Atlantic Ocean on the timescale of several decades. While there ...

. Although undersea overflows are usually not considered "waterfalls", the Denmark Strait overflow would be tallest waterfall in the world, with water falling over ; this descent is over three times the height of

Angel Falls Angel Falls (; Pemon: ''Kerepakupai Merú'' or ''Parakupá Vená'') is a waterfall in Venezuela. It is the world's tallest uninterrupted waterfall, with a height of , and a plunge of . The waterfall drops over the edge of the Auyán-tepui m ...

, the world's tallest uninterrupted waterfall over land.

References

Waterfalls of Greenland Waterfalls of Iceland {{Waterfall-stub