Oceanographers sometimes classify seawater as either “spicy”, meaning warm and salty, or “minty”, when it is cooler and has a lower salt content. Temperature and salinity are important factors because of their effect on the density of seawater.
Cold water is heavier and tends to sink, which can drive large-scale movement. This contributes, for example, to the well-known El Niño oscillation off South America. Salty water is also denser, and again tends to sink.
These two effects may cancel each other out though, so spicy water, which is warmer but saltier, can have the same density as cooler but fresher minty water.
In some sea areas, such as the Bay of Bengal, salty and minty bodies of water with the same density swirl against each other. Understanding the mixing process is important because it affects the temperature at the surface, a key factor in the formation of seasonal monsoon rains.
There is concern that the Arctic Ocean is becoming spicier because of climate change. Previously, water density in this region was determined largely by the salt levels.
Rising temperatures may lead to spicy intrusions and warm water persisting at the surface and not mixing with minty water below. This could have a profound effect on the formation of sea ice and accelerate its disappearance.