You probably learned in school that our planet has four oceans: the Atlantic, Pacific, Indian, and Arctic. More recent maps also include the Southern (or Antarctic) Ocean. While having named ocean regions is a helpful tool, these oceans are all connected, with currents flowing between them. Even nearly enclosed seas such as the Mediterranean and the Red Sea are part of the same world ocean.
However, these oceans each have distinctive characteristics that set them apart, including the two largest, the Atlantic and the Pacific. For example, did you know that the Atlantic is saltier than the Pacific?
There are several factors that contribute to the higher surface salinity level of the Atlantic over its sister ocean. Overall, the Pacific receives a greater influx of freshwater than the Atlantic, both from rivers and from areas of increased rainfall, which lowers its overall salinity. The Pacific generally has lower surface temperatures, which means less evaporation, whereas the Atlantic experiences more evaporation and thus more concentrated salt levels.
Additionally, the Atlantic experiences the strong Atlantic Meridional Overturning Circulation (AMOC), which transports salty water north from the tropics, creating areas of deep water in the North Atlantic with high salt concentrations. The Pacific Ocean doesn’t experience such strong overturning circulation.
Notably, the Red Sea and the Mediterranean are even saltier than the Atlantic. In those locations, seawater evaporates faster than it can be replaced by rain and other freshwater inputs, contributing to a higher overall salt content. Additionally, those seas are largely enclosed except for narrow straits, making it difficult for additional seawater to flow in.
In 2012, NASA’s Aquarius instrument made detailed observations of ocean surface salinity from space, compiling a color-coded map of the amount of salt dissolved in the water at different locations around the globe. This visually confirmed what oceanographers already knew: that the Atlantic is saltier than both the Pacific and Indian Oceans.
More about the world’s oceans:
- By a significant margin, the Pacific is the world’s largest and deepest ocean. It has an area of roughly 63.8 million sq miles (165.25 million sq km) and an average depth of 14,040 feet (4,280 m).
- Coming in second for both area and depth, the Atlantic Ocean covers around 41.1 million sq miles (107 million sq km) and has an average depth of 11,962 feet (3,646 m).
- The meeting point of the Pacific and Atlantic Oceans is Cape Horn. Located at the southern tip of Chile, this is a turbulent region where a strong eastward current brings water from the Pacific into the Atlantic.
