Ocean heat content refers to the amount of heat that the Earth's oceans store. During the last part of the 20th century, scientists and conservationists became concerned with ocean temperatures, suspecting the world's oceans were warming up. Today, ocean heat content measurements are an essential part of determining variations in climate and taking steps to protect ocean life.
Since oceans cover over 70% of Earth's surface, they can store very large amounts of heat energy. Water has the highest known specific heat of any substance, so it stores heat energy effectively. When the sun warms the Earth, a thin layer of the ocean heats up. This layer transmits heat lower in the ocean by the actions of waves on the surface and convection. However, most of the heat energy stays within 500 meters of the surface. Tropical oceans are heated the most, and the heat energy is spread through convection to the poles.
Heat stored in the ocean can be released into the air and dispersed throughout the atmosphere. This increases temperatures at the surface of the ocean and in the air. A very small increase in the temperature of the ocean, even a fraction of a degree, represents a massive amount of energy, and could conceivably cause changes in temperature around the world.
In the 90's, scientists from the National Oceanographic Data Center collected data from the world's oceans to provide evidence that suggested the world's oceans were warming up. The results showed that the oceans' average temperature had increased 0.06 degrees Fahrenheit. This was the first solid evidence that ocean temperatures had increased during the period 1955-1996, and opened the door for further monitoring of ocean heat content. The research also confirmed that the oceans accounted for 80% of the Earth's increase in heat content during this period.
In 2004, the ARGO Network was deployed, a collection of 3,000 floats that monitor ocean data including temperature and salinity around the world. The floats descend to 2,000 meters to take readings, then rise to the surface to transmit the data to satellites. The increased monitoring of ocean heat content is important as it provides further information about Earth's oceans and their impact on the environment.
Ocean heat content can influence weather and climates around the globe. It is important for ocean conservation because changing water temperatures affect ocean life and ecosystems significantly.