U5 - Lesson 5: Deep Ocean Currents

•The ocean’s surface water temperature varies with the amount of sunlight received, which depends on latitude (direct or indirect sunlight).

•The thermocline lies below the surface layer. The water temperature here drops fast with depth (300-1000 meters).

•Deep water is cold all year round. The bottom of the ocean is around 0 degrees Celsius (slightly above freezing). It is the same almost anywhere in the globe, even in the topics. 

•Deep-ocean water currents are set in motion by differences in density.

Density Currents

•The density of seawater is affected by temperature and salinity. As the water cools due to the lack of direct sunlight when it reaches the poles, ice forms such as ice burgs (fresh water). The colder, saltier water is dense and sinks. Deep currents carry cold, dense water toward the equator. As the water warms, it becomes less dense and rises.

•Cold, dense water around Labrador, Canada form this deep ocean current.