For most people, the world’s largest waterfall brings to mind towering cliffs, crashing waters and famous landmarks like Niagara Falls or Angel Falls. However, the largest waterfall on Earth is nowhere to be seen.
It lies hidden in the depths of the ocean between Greenland and Iceland, where an unusual natural process has been occurring for thousands of years. Every second, billions of liters of dense icy seawater sink beneath the warmer waters of the Atlantic Ocean, creating a massive underwater waterfall dwarfing any waterfall on land. Although not visible from the surface, this fascinating phenomenon plays a crucial role in the movement of ocean currents and the global climate system.
Here’s how this hidden giant formed, why it exists, and why scientists continue to study it closely.
The extraordinary science behind A Waterfall under the ocean
The Denmark Strait is located between Greenland and Iceland, connecting the North Sea to the North Atlantic Ocean. At first glance, there is nothing on the surface to indicate what is happening below. Ships pass through the area without seeing any clear sign of the massive movement taking place hundreds of meters below.Unlike waterfalls on land, these waterfalls are entirely within the ocean.
Cold, dense seawater moves under a layer of warm, lighter Atlantic water. When it reaches an underwater ridge, gravity pulls the heavier water down the slope, producing what scientists describe as an underwater flood rather than a freely falling layer of water.
How the seabed turns an ocean current into a waterfall
Seawater behaves differently depending on its coldness and salinity. Waters from the North Seas are cooler and denser than the relatively warmer waters of the Irminger Sea to the south, according to the National Oceanic and Atmospheric Administration (NOAA).
When the two meet, the heavier water naturally settles beneath the lighter layer.This change in density allows cold water to cross the threshold of the Denmark Strait before descending along the Greenland continental slope. The underwater landscape provides the drop, while gravity does the rest.Instead of diving vertically, the dense current follows the contours of the sea floor over a long distance. Friction, the shape of the ocean floor, and the Earth’s rotation affect the path it takes as it continues south.
The amount of water moving under the Denmark Strait
The numbers involved are difficult to visualize. The downdraft transports approximately 3.5 million cubic meters of water every second, equivalent to about 3.5 billion liters moving continuously through the system.In comparison, the flow over the world’s largest surface waterfalls represents only a small fraction of this amount.The vertical drop is also noticeable. Depending on how scientists define a flood, the depression ranges from about 2.4 km to more than 3.5 km.
The National Oceanic and Atmospheric Administration uses the larger number when describing the entire underwater cataract system, making it the tallest known waterfall on Earth.These measurements should not be interpreted as a giant cliff hiding under the sea. The stream descends gradually over steep terrain rather than falling in a single vertical dive.
Why the flow of a waterfall never stays the same
Although the Denmark Strait flood is often described using a single flow rate, it is by no means constant.Oceanographers measure transport in units called sverdrup, where one sverdrup represents one million cubic meters of water per second. Various research campaigns have recorded values ranging from approximately 2.5 to five Sverdrup, depending on the period observed, the instruments used and the specific place where the measurements were taken.The current also changes as it travels. Turbulence attracts surrounding seawater into the dense flow, a process known as drainage.
As a result, the overflow gradually becomes warmer and less dense while the total volume of water moving downstream actually increases.
How researchers monitor the hidden waterfall
Studying the world’s largest waterfall requires instruments, not direct observation.Scientists deploy moorings fixed to the seafloor, equipped with current meters, acoustic Doppler sensors, and equipment that records temperature, pressure and salinity. Research vessels also lower instrument packages through the water column to create detailed profiles of the dense flow.The work is demanding. Equipment must withstand strong currents and great depths for long periods, while fishing activity and harsh conditions can threaten expensive anchors. Because flow varies over days and weeks, a single scan captures only one moment within a much larger system.
How does the underwater waterfall connect to the Atlantic Ocean?
The significance of the Denmark Strait flood extends beyond the waterfall comparison.After descending into the depths of the Atlantic Ocean, the dense water becomes part of the lower branch of the Atlantic overturning circulation, a network of ocean currents that redistribute heat, salt and water around the Atlantic Basin.Overflow from the Denmark Strait is just one contributor to this larger circulation, along with other deep-water pathways from the North Seas. However, it represents one of the main routes through which dense northern waters reach the depths of the North Atlantic.Scientists continue to study how these floods respond to long-term changes in ocean temperature, freshwater inputs and climate because they form part of a much broader system that affects conditions across the Atlantic.