The Ocean: A Whole Lot of Heat
Unlike the atmosphere, the ocean can absorb and release an enormous amount of heat with little change in temperature. As such, the ocean has an enormous impact on Earth's climate, absorbing warmth from the atmosphere during summer and releasing it back during winter.
Ocean Conveyor Belt
Within the ocean, rivers of water of different temperatures and salinities move heat around the globe.
- As warm surface water moves from the tropics to the North Atlantic, it becomes saltier and denser as fresh water evaporates. In the far North Atlantic the water cools and sinks.
- The dense, deep water in the North Atlantic flows all the way to the Southern Ocean, where it is joined by cold water sinking around Antarctica. This deep, cold water spreads out through the Indian and Pacific basins.
- Cold, deep water slowly mixes in the Pacific and returns as a shallow, warm, less salty current to replace sinking waters in the North Atlantic.
- The ocean conveyor belt holds about 15 times the water flowing in all the world's rivers.
- The deep water mixes through the world's ocean in about 1,000 years.
Streams of Water
Fast-moving boundary currents move tremendous amounts of water and heat around the globe. For instance, the Gulf Stream, seen in this false-color image showing water temperatures, is more than 60 miles wide in many places, has an average depth of over 900 meters (about 3,000 feet) and moves as fast as 9 kilometers (nearly 6 miles) per hour.
A Calming Influence
Ocean waters absorb heat during the summer and release it during winter, reducing temperature differences between winter and summer and, in a similar way, between day and night. Away from the oceans, many landlocked areas, such as inland Siberia, experience seasonal temperature swings of over 55°C (about 100°F). By comparison, most of western Europe, which borders the ocean, has much milder winters and summers.