Ocean's Role in the Odd Couple Affair
We've seen how the atmosphere affects the oceans. Now, how do the oceans affect the atmosphere? Remember, we said this was a "dynamic duo." The oceans are main reservoirs of readily available carbon dioxide (CO2), an important greenhouse gas. The cold, deep water in the ocean is the main reservoir of dissolved CO2. TRY THIS: Shake a hot can of coke and open it. Shake a cold can of coke and open it. What happened? What does this experiment demonstrate? Need I say more? (Check the activity page for an explanation of the demonstration.)
The oceans carry heat from the tropics, that's the area near the equator, to the higher latitudes, the area near the poles, to maintain Earth's temperature. They also take carbon dioxide and hide it from the atmosphere. Here's how it happens. Sunlight warms the surface of the ocean in the tropics. Wind-driven surface currents carry the heat toward the poles. In the North Atlantic, the warm currents from the tropics feed the North Atlantic Current shown in red in the figure. As the current flows northward toward Norway and Greenlamd, it loses heat to the atmosphere and cools down. In winter the water near Norway and Greenland gets so cold and dense it sinks all the way to the bottom of the ocean. The cold bottom water feeds bottom currents shown in blue and green. Eventually, mixing brings the bottom water back to the surface in other parts of the ocean, sometime as far away as the North Pacific. When the water gets to the surface, sunlight warms the water, and the cycle starts over.
The deep circulation shown in the picture is important for two reasons:
1. Cold water carries carbon dioxide deep into the ocean, taking it away from the atmosphere and...
2. Surface currents that sink and feed deep currents carry much more heat toward Europe than currents that stay on the surface. As a result, Norway at 60 degrees is far warmer than southern Greenland and northern Labrador which are at the same latitude.
Questions that come to mind are:
1. Why do temperatures differ at different lattitudes? i.e. 0 degrees (equator) vs 40 degrees N
2. Why do temperatures vary at different locations at the same latitude? i.e. Norway and Northern Labrador--both at 60 degrees N
3. Which has a greater capacity to store heat--the oceans or the atmosphere?
4. Which has a greater heat capacity--water or land? Why?
5. In what way/s does the atmosphere influence the ocean?
6. In what way/s does the ocean influence the atmosphere?
Critical Thinking Questions:
7. What is the atmosphere's source of heat? (Be careful, this one could be tricky!)
8. How would our global climate be different if 71% of Earth was covered by continents and 29% by water? (The name of our planet, Earth, would be more appropriate for one thing.)