A series of videos on Youtube and TikTok have garnered a lot of views as they show a strange dividing line in the middle of the ocean, with one side of the ocean dark and the other lighter.
According to Live Science, such ‘boundaries’ often appear in the area of estuaries flowing into the sea, or near the shelf of glaciers floating in the ocean. However, in videos posted on social networks, the poster claimed that the dividing line was the boundary between the Pacific Ocean and the Atlantic Ocean, and asserted that this was ‘proof’ that the water of the two oceans do not mix with each other.
Below the video, many viewers asked various questions. Does that strange dividing line really exist? Do the oceans of the Pacific and Atlantic oceans mix, or is there a clear separation?
The meeting point between the Atlantic and Pacific Oceans, at the Beagle Canal, Tierra del Fuego, Chile. (Photo: DEA/GIANNI OLIVA/Getty Images)
According to Nadín Ramírez, an oceanographer at the University of Concepción in Chile, the answer is yes, as the waters constantly mix with each other. Accordingly, the waters of the Pacific and Atlantic oceans mix at different rates in different places, while climate change has a certain impact on this rate.
Imagine you pour instant cream into a cup of coffee. The liquids will mix well, but at a slow rate. The same thing happens in videos or images that show the boundaries between different ocean waters. Since seawater on one side can be saltier, cleaner or colder, these differences take time to neutralize.
Naturally, the neutralization speed will be faster under the influence of strong wind and big waves. It is like using a spoon to stir a cup of coffee so that the cream dissolves faster in the cup.
According to the scientists, the mixing rate of sea water from the Pacific and Atlantic oceans will take place faster in some places than in others.
For example, two oceans meet near the southern tip of South America, home to a series of small islands. Between those islands, currents move relatively slowly, and the Strait of Magellan is a popular route for ships to pass. In the Beagle Channel, water from melting glaciers creates lines between freshwater and saltwater, creating a scene that looks a bit like the searing lines in the YouTube video.
Notably, in the area where the Strait of Magellan joins the Atlantic Ocean, there is a separation line that is hard to see with the naked eye, but can be detected by oceanographers with measurements.
On the measurement graph, a blue strip of water appears in the Atlantic Ocean. Meanwhile, Pacific ocean water has a different color due to more rain and lower salinity. But this boundary line only exists at sea for a while, before being erased by storms and waves.
In some open areas between South America and Antarctica, such as Drake Strait – where waves can reach up to 18m high, the mixing of sea water between the two oceans is even more intense.
Seawater also mixes in the great depths of the ocean. The daily tides pull water back and forth on the bumpy seabed, said Casimir de Lavergne, a researcher at the Sorbonne University and the French National Center for Scientific Research (CNRS). That causes a lot of noise.
But seawater from different sources can also move around the ocean without much mixing. The ocean is like a pie with many different layers, but those layers are water. In the middle layer, away from both the surface and the seafloor, water mixes more slowly because of less turbulence.
Oceanologists also distinguish between mixing and exchanging seawater. Mixing means “irreversibly altered bodies of water”. Thanks to global ocean currents, the Pacific and Atlantic oceans exchange water continuously.
A strong current around Antarctica’s Southern Ocean pulls water clockwise across Drake Strait from the Pacific to the Atlantic. It also takes water from ocean basins around the world, and then pumps it back. Another current moves water from the Pacific Ocean through the Indian Ocean and around the tip of South Africa to feed into the Atlantic Ocean from the other direction.
Water always mixes at the edges of these streams. But because the different layers don’t mix completely, oceanographers can track different bodies of water as they move around the globe.
In general, the Pacific and Atlantic oceans blend together, but it’s not as simple as two bodies of water just mixing. The differences in density, temperature and salinity between the two oceans create barriers that prevent their water from mixing with each other easily. However, there are some areas where the two oceans mix, such as the Drake Strait and the Gulf of Mexico.
Refer to Live Science