Have you ever wondered how long it takes for water to travel through all the oceans on the planet? A new scientific study has the answer.

Using an ocean model that simulates the trajectory of water, scientists were able to conclude that a drop of water in its shortest path takes about 300 years, while in the longest and usual one, it takes almost 3,000 to complete.


Although the world political map indicates that the planet has five major oceans, in reality, it is a single ocean that covers 70% of the Earth’s surface and whose waters are interconnected. This, in essence, can allow a drop of water to travel around the world without having to go through the hydrological cycle.

Scientists Louise Rousselet, Paola Cessi and Gael Forget used a digital simulator known as the Estimation of Ocean Circulation and Climate (ECCO) to calculate the time it takes for a drop of water to travel around the world.

ECCO is an ocean model that works similarly to the one used to determine weather forecasts for the atmosphere. It incorporates over a billion data collected from satellites, robotic floats adrift on the global Argo network, and other sources that it merges into a simulation.


In their simulation, Rousselet and her colleagues followed the paths of water originating from what oceanographers call the lower member of the South Atlantic Inverted Circulation (AMOC), a large flow of water from the Atlantic that moderates temperatures between the equator and the poles.

the water ways

They referenced 65,000 packets of water as runners to an exit gate in the Atlantic, south of the equator. They then used ECCO to observe the water’s path over a period of 25 years and then run through the data on the speed of water spots. This allowed them to see the possible paths water could take for another 25 years, then another 25, and so on for millennia.

According to the data produced by the simulator, the researchers were able to record that about a third of the plots left the Atlantic to continue their journey through the Indian and Southern Pacific Oceans. A journey that would take about 300 years.


About 20% of the water made this 300-year journey, but going deeper and entering the Wedell Sea in Antarctica took 700 years to return to the Atlantic.

The largest amount of water, almost half of the parcels took 2,800 years to return, plunging for approximately 1,000 years into the abyssal Pacific Ocean. This particular water has made its voyage around the world visiting every basin on Earth.


Study conclusions and climate change

In all three cases, the properties of the water parcels varied along the voyage and these changes influenced their speed: “The interaction of water with different densities in the oceans, along with surface winds, is what determines ocean circulation as dense water sinks and light water rises, following labyrinthine paths.”, explain the researchers.

The simulated routes allowed the researchers to record what the temperature and salinity were at various points along the route of the trip. From this, they concluded that the AMOC serves as a channel through which salt is pumped into the Atlantic Ocean.

If this circulation carries salinity, it could mean that recent climate change-induced dynamics in the North Atlantic Ocean could destabilize the AMOC. Several researchers have observed that the North Atlantic Ocean is becoming colder as the melting of glaciers in Greenland accelerates and as relatively fresh water from the Arctic Ocean pours into the Atlantic.


This means that freshwater incursions could disrupt AMOC, potentially triggering extreme climate change, not just around the Atlantic, but eventually across the world.