Reasons for the Lack of Mixing Between the Atlantic and Pacific Oceans
Several key factors contribute to the inability of the Atlantic and Pacific Oceans to mix:
Density Differences
The Atlantic Ocean is divided into two sections: the northern part, which features warmer and more saline waters, and the southern part, characterized by colder and denser waters. Similarly, the Pacific Ocean is divided into northern waters that are less saline and less dense due to abundant seasonal rainfall, and southern waters near the South Pole, which are cold and less saline because of limited evaporation. It is well-established that warmer waters have lower density than colder waters, and freshwater is less dense than saline water. However, the degree of density difference is insufficient for one body of water to float over the other, yet it is significant enough to prevent them from mixing.
Salinity Levels
Salinity is closely linked to the hydrological cycle (the natural water cycle). Increased evaporation enhances seasonal rainfall, thereby reducing salinity levels. Conversely, decreased evaporation rates in colder regions help maintain freshwater characteristics and lower salinity. These salinity discrepancies between the two oceans further hinder their mixing.
Chemical Composition
The melting glaciers from the Arctic, flowing toward the Atlantic Ocean, transport a significant amount of sediments, clay, and minerals such as iron, which can elevate the salinity of the waters. Additionally, the occurrence of acid rain, surface water pollution, or the rapid melting of Arctic ice due to climate change can alter the chemical makeup of the surface waters in the oceans.
Surface Tension Force
This force arises due to the attraction between the molecules of a single substance. Due to the differing densities between the two oceans, the magnitude and characteristics of this surface tension force vary, thereby inhibiting any potential mixing.
Coriolis Effect
The Coriolis effect influences ocean waters and their movement direction. In the northern hemisphere, ocean currents rotate clockwise, whereas in the southern hemisphere, they move counterclockwise. This opposing movement of the waters from the Atlantic Ocean flowing northward against those from the Pacific Ocean moving southward makes their mixing almost impossible.
Halocline Phenomenon
When the colder, low-density, and low-salinity waters of the Pacific Ocean meet the warmer, high-salinity, and high-density waters of the Atlantic Ocean, the Pacific waters tend to flow beneath the Atlantic waters rather than rising above them. This interaction creates a distinct vertical boundary due to differences in the color of freshwater compared to saltwater, as well as varying light refraction indices between the two water types. This phenomenon is known as “halocline” (Thermohaline Circulation).
Other Seas and Oceans Exhibiting Non-Mixing Phenomena
This phenomenon is also observed in several other seas and oceans, including:
- The North Sea and the Baltic Sea.
- The Mediterranean Sea and the Atlantic Ocean.