Finding the Deep Water Masses of the Atlantic Ocean (Activity 8)

Water Mass Abbreviations: NADW = North Atlantic Deep Water; MI = Mediterranean Intermediate ; SW = Surface Water; AAIW = Antarctic Intermediate Water ; AABW = Antarctic Bottom Water

Evaluation:

1. If a person had a very long fishing line, why might it be possible to catch an Antarctic species of shark while fishing at the Equator?
   • It may be possible to catch an Antarctic species of shark at the Equator with a very long fishing line because sharks could travel in Antarctic bottom water, which can sometimes be found at the Equator.
2. Wind driven surface currents travel at approximately one kilometers per hour, while density driven deep ocean currents travel much slower, about one meter per hour. How long would it take Antarctic Bottom Water to travel to the North Atlantic sample site at 45°N, approximately 9,000 km from its Antarctic source area?
   • Nine million hours, or 375,000 days, or 1,026.7 years.
3. What relationships can you describe between water temperature and salinity at the 0° sample site?
   • Salinity generally falls with temperature, although it increases between 5°C and 3°C.
4. What happens to the water density at the 45°N sample site?
   • Water density shows an overall increase with temperature declines at the 45°N site, although it does fall between 13°C and 10°C.
5. From the Temperature-Density-Salinity Graph, what happens to the density of seawater at temperature increases? As the temperature decreases the density of the seawater does what?
   • According to the graph, as temperature increases, density falls. As temperature decreases, density rises.
6. What factor(s) increase sea surface water density at high latitudes?
   • At Northern latitudes, the North Atlantic Gyre moves surface water clockwise, affecting density by changing water temperature and salinity.
7. What factor(s) cause the density of the surface water in the low latitude regions to increase?
   • At Southern latitudes, the South Atlantic Gyre moves surface water counter-clockwise, affecting density by changing water temperature and salinity. The sun also warms the water in lower latitudes.
8. Explain why density driven circulation in the ocean depths is caused by the interaction of the atmosphere and the ocean.
   • Atmospheric circulation works with oceanic circulation to distribute thermal energy along the earth's surface. Atmospheric winds enhance ocean currents and can produce spray, which causes salt to enter into the atmosphere. This reduces the salinity of the ocean, thus affecting density. Winds also produce waves which increases water movement and may modify temperature and/or salinity.
9. Why is the sun considered the source of energy for driving the density circulation in ocean depths? Explain.
   • The sun is considered the source of energy for driving density circulation because it increases lower latitude waters, forcing water to flow to the less dense Northern waters.