Answer to Question 1
The thermohaline conveyor belt is the process by which deep water is transported around the globe. Deep water first forms in the North Atlantic, where downwelling of cold waters with relatively low densities occurs. After downwelling, this deep water moves south to the Antarctic, then to the Indian and Pacific Oceans, and finally to the North Pacific where it resurfaces. The downwelling in the North Atlantic is balanced by surface flows that bring water to the North Atlantic.
The thermohaline conveyor belt is a significant feature of the Earth system in several respects: It plays a dominant role in the recycling of ocean nutrients, and it has a major impact on Earth's climate. Much of the life that exists in the oceans can be found in the near-surface layers, utilizing sunlight for photosynthesisphyto plankton, for exampleor living off the animals that feed on phytoplankton. These plants and animals use the nutrients in ocean water, so the surface layers become relatively depleted in nutrients. When these organisms die, they sink through the water column, decompose, and release the nutrients back into the water. The deeper ocean, therefore, is relatively rich in nutrients. The thermohaline circulation transports these nutrient-rich waters around the globe, returning the nutrients to the surface in areas of upwelling, primarily along the continental margins.
Answer to Question 2
The ocean circulation has a strong influence on global temperatures. The transport of warm surface water toward the poles, to replace the bottom water that forms near the sea-ice margin, is one mechanism by which excess solar energy is transferred poleward. The oceans represent a vast reservoir of heat, absorbing heat from the atmosphere in some areas and releasing it in others. Because water heats up and cools down relatively slowly, pools of water that are cooler than normal or warmer than normal will cool or warm the atmosphere on time periods of months to seasons or yearsthe time needed for the pools of water to heat up or cool down. On much longer time periods, however, the average effect of the oceans on the atmosphere is determined by the overall temperature of the oceans. Most of the water in the oceans lies in the deep oceans, and its temperature is largely determined by the process of bottom-water formation and by the transport of bottom water around the ocean basins. If the process of bottomwater formation changes, the ocean temperatures will changeand so will climate.