The Deep Circulation Of The Ocean

Activity 2 The Deep Circulation of the Ocean Think About It Date Page F13 Page #  What makes deep ocean waters move? 2

Activity 2 The Deep Circulation of the Ocean Investigate Part A Date Page F14 Page # Hot Cold Actual 3

The Deep Circulation of the Ocean Investigate Part B Date Pages F14-15 Page # Hot Cold Salt Water Actual 4

The Deep Circulation of the Ocean Investigate Part C Date Pages F15-16 Page #

1a. What will happen to the warm water at the heated end of the tank?

1b. What will happen to the water that flows at the surface of the tank at the cooled end?

1c. Draw a diagram to show the convection cell. Use arrows to show the direction of circulation. 5

1d. What causes the circulation of the water?

2a. At first, what happens to the cooled water at the surface?

2b. What will happen to the temperature of the water in the lower part of the tank as time goes by?

2c. With time, what will happen to most of the water in the tank?

2d. With time, where will there still be some motion of water in the tank? 6

Activity 2 The Deep Circulation of the Ocean Digging Deeper Date Pages F17-20 Page # Water in the ocean can sink, rise, or flow horizontally relative to the surrounding water

Ocean currents a predominantly horizontal movement of ocean water

Surface currents flow only in the surface layer of the ocean

Deep currents are controlled by the density of the water

Density of seawater is determined by two factors: 1. temperature 2. salinity

Salinity the concentration of dissolved salts in seawater, expressed as parts per thousand

Temperature has a much greater effect than salinity on seawater density

Temperature the sun heats the Earth’s surface unequally, because the Sun’s rays strike the Earth from nearly 7

overhead at low latitudes but at a very low angle at high latitudes

surface water at low latitudes stays at the surface because it is less dense than the deeper water

Ocean salinity is approximately 35 parts per thousand (35 g of salt per 1000 g of ocean water)

The higher the salinity of ocean water, the more dense the water is

Evaporation from the ocean surface is greater than precipitation onto the ocean 8

surface, increases the salinity, and the water tends to sink

Precipitation where precipitation is greater than evaporation, salinity decreases and the water stays at the surface High latitudes here seawater freezes to form ice, which removes fresh water from the ocean

This increases the salinity of the water left behind, causing it to be the most dense water in the world ocean

Water masses a large region of water within the ocean with about the same temperature and salinity of water

They are named for where they form 9

North Atlantic salinity of 34.9 parts per Deep Water thousand and temp of 3°C

It sinks, moves south and circulates around Antarctica and then moves northward to the Indian or Pacific Ocean

Antarctic Bottom salinity of 34.7 parts per Water thousand and temp of – 0.5°C

It forms at the edge of the Antarctic continent and flows under all other water masses as it moves northward along the deepest part of the ocean bottom 10

Antarctic Bottom Water is the most dense of all deep ocean water masses

Deep circulation the cold waters that form near the surface at high northern and southern latitudes flow toward the equator, and the deep waters gradually rise up toward the surface at low latitudes, where they are warmed and flow back to high latitudes to complete the loop

One cycle of this loop takes between 500 and 2000 years 11 http://www.whoi.edu/page.do? pid=12455&tid=1061&cid=7230&cl=6615&article=9986 http://www.casttv.com/video/m0iizu1/the-thermohaline- circulation-the-great-ocean-conveyor-belt-nasa-video

Oceanographers are not sure about what causes the cold water in the deep ocean to mix with the warm water that lies above

One idea that is becoming widely accepted is that tides cause movement in the shallow coastal oceans as well as the deep ocean

Activity 2 The Deep Circulation of the Ocean Check Your Understanding Date Page F20 Page # 1. What are the two factors that determine the density of a water mass?

2. Would you expect water to be more dense near the poles or near the equator? Explain. 12

3. Explain what an ocean current is in your own words.

4. Why do individual water masses within the oceans retain distinctive physical properties for long periods of time?

Activity 2 The Deep Circulation of the Ocean Understanding and Applying Date Pages F20-21 Page # 1. Fill in the names of the water masses on a copy of the figures. 13

2a. Propose

several mechanisms that could cause these factors to change, thereby changing the 14 density of the water mass.

2b. How would these changes affect ocean circulation patterns?

3. Does wind affect deep ocean circulation? Explain.

4. Explain how the tides may have an impact on deep water circulation in the ocean.

Activity 2 The Deep Circulation of the Ocean Inquiring Further Date Page F22 Page # 1. Investigating density 15 differences

Prepare three separate 250-mL solutions:

•250 mL of water •250 mL of water with 8g of salt •250 mL of water with 4g of salt

Place an egg in each of the three liquids and sketch what you see. Explain.

2. Deep ocean currents and the Earth system

Investigate deep ocean currents and the Earth system. Select one of the following questions for further research:

a. How might volcanic eruptions at divergent boundaries affect deep ocean currents? b. How does 16 atmospheric circulation affect deep ocean circulation? c. How does the rotation of the Earth affect deep ocean circulation? d. How is the biosphere affected by deep ocean circulation?