Activity 3A-Global Ocean Conveyor Belt
Unit 3- Hydrosphere
Background Information for the Teacher
Activity
NSES
Earth Science Std D:
Water, which covers the
majority of the earth's
surface, circulates
through the crust, oceans,
and atmosphere in what
is known as the "water
cycle." Water evaporates
from the earth's
surface, rises and cools
as it moves to higher
elevations, condenses
as rain or snow, and
falls to the surface
where it collects in lakes,
NSES
oceans, soil, and in rocks
Physical Sci
underground.
Standard B:
Energy is transferred in Global patterns of
many ways. Heat moves atmospheric movement
influence local weather.
in predictable ways,
Oceans have a major
flowing from warmer
effect on climate, because
objects to cooler ones,
water in the oceans holds
until both reach the
a large amount of heat.
same temperature.
The sun is the major
The sun is a major
source of energy for
source of energy for
phenomena on the
changes on the earth's
earth's surface, such
surface
as growth of plants,
winds, ocean currents,
and the water cycle.
History and Nature of
Science Std G:
Scientists formulate
and test their
explanations of nature
using observation,
experiments, and
theoretical and
mathematical models.
In this hands-on
activity, learners
create a model which
demonstrates how
colder, saltier water
sinks under warmer,
fresher water. This
temperature and
density phenomenon
drives the ocean
currents, which
distribute heat around
our planet.
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CLEP
CLEP
2A: Earth’s climate
is influenced by
interactions involving the
Sun, ocean, atmosphere,
clouds, ice, land, and life.
Climate varies by region
as a result of local
differences in these
interactions.
2B: Covering 70% of
Earth’s surface, the
ocean exerts
a major control on
climate by dominating
Earth’s energy and
water cycles. It has the
capacity to absorb large
amounts of solar energy.
Changes in ocean
circulation caused by
tectonic movements or
large influxes of fresh
water from melting polar
ice can lead to significant
and even abrupt changes
in climate, both locally
and on global scales.
2F: The
interconnectedness of
Earth’s systems means
that a significant change
in any one component of
the climate system can
influence the equilibrium
ofthe entire Earth system.
Positive feedback loops
can amplify these effects
and trigger abrupt
changes
in the climate system.
Activity 3A-Global Ocean Conveyor Belt
Unit 3- Hydrosphere
Background Information for the Teacher
CLEP
ELF
Hydrosphere 1 b: Water
7A: Melting of ice sheets
transports energy,
and glaciers, combined
with the thermal expansion solutes, and sediments
of seawater as the oceans as it moves through the
warm, is causing sea level water cycle’s different
to rise. Interconnectedness reservoirs. Oceanic
of Earth’s systems means energy transport has a
major impact on regional
that a significant change
and global climate.
in any one component of
the climate system can
Hydrosphere 2: The
influence the equilibrium
of the entire Earth system. ocean circulates water
Positive feedback loops can around the Earth on time
amplify these effects and scales varying from
seasonal to hundreds of
trigger abrupt changes
years.
in the climate system.
ELF
Hydrosphere 2 b:
Thermohaline circulation
is driven by differences
in the density of water
masses due to changes in
salinity and temperature.
This circulation incorporates
intermediate and deepwater currents in a threedimensional pattern.
ELF
Hydrosphere 2 d: Plate
tectonic motions change
the size and shape of
ocean basins, and alter
coastlines and features
on the seafloor. These
changes influence ocean
circulation patterns over
long timescales.
NSES: National Science Education Standards (http://www.csun.edu/science/ref/curriculum/reforms/nses/index.html)
CLEP: Climate Literacy Essential Principles (http://www.climatescience.gov/Library/Literacy/)
ELF: Environmental Literacy Framework (www.andrill.org/education/elf)
Additional Resources:
The Great Ocean Conveyor Belt
NOAA animation
Animations
http://sos.noaa.gov/datasets/Ocean/
ocean_conveyor_belt.html
http://oceanservice.noaa.gov/education/
kits/currents/08affect.html
http://www.cmar.csiro.au/currents/
animations.htm
http://oceanservice.noaa.gov/education/kits/currents/06conveyor.html
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Activity 3A-Global Ocean Conveyor Belt
Unit 3- Hydrosphere
Background Information for the Teacher
In this example of the journey of the great ocean conveyor belt, we begin with the process that forms the deep
ocean mass known as the Mid-Atlantic Deep Water that forms in the North Atlantic Ocean. Off the coast of
Greenland, especially during the fall and winter months, cold winds from northern Canada and Greenland cool
the surface waters, causing them to freeze and form new sea-ice. Sea ice formation, combined with surface
evaporation, creates cold, salty, and very dense ocean water. The cold, dense, and salty water sinks to the bottom
of the ocean and begins to flow south along the ocean floor near the coasts of North and South America. As it
approaches Antarctica, it encircles the Antarctic continent. Eventually the cold, deep water flows northward and
splits into the three ocean basins. There, it moves upwards (due to upwelling) and warms as it flows onward.
The cool dense water then becomes part of the wind-driven surface currents, eventually returning to the seas off
the shore of Greenland to begin the process again. This journey can take up to one thousand years to complete.
The conveyor belt is an important part of the global climate system as it is a major transporter of heat from
the equatorial regions to the polar regions. For example, the oceanic conveyor belt and the wind-driven surface
currents are responsible for northern Europe's moderate climate. Northward movement of heat in the Gulf
Stream (a wind-driven surface current) provides the British Isles and Scandinavia with milder temperatures
than landmasses at similar latitudes on other continents.
As Earth’s temperature warms, the polar ice caps may melt, allowing the fresh water that has been locked for
hundreds of thousands of years in the glaciers and ice sheets to enter the ocean, thus reducing the salinity
of the oceans. If the salinity of the North Atlantic surface water drops too low to permit the processes that
contribute to the formation of deep-ocean water masses, the oceanic conveyor belt could slow down or even
stop. The conveyor system has shut down in the past; for example, it shut down between 1400 and 1850 A.D.,
contributing to what is known as the Little Ice Age. During this period, Northern Europe's climate became
markedly colder.
Answers to Student Ponder Questions:
1. What would happen if the conveyor slowed down?
Answer: Some of the Earth's areas would be warmer while others would be colder. An example is England. It is
predicted that if the Gulf Stream slowed, the British Isles, as well as Scandinavia, would become much colder.
2. As the cold, salty water sinks, it carries oxygen to the deep parts of the ocean allowing organisms to thrive.
What do you think would happen to these organisms if the conveyor belt slowed down, or stopped?
Answer: Ocean habitats would change and organisms would have to move or adapt.
As the current moves northward it carries heat from the low latitudes (near the equator) to the polar regions. If
this heat is not transported north, but is trapped in the low latitudes, the ocean temperatures may increase.
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Activity 3A-Global Ocean Conveyor Belt
Unit 3- Hydrosphere
3. How does this activity simulate the melting of the polar ice caps and the potential interference with the global
ocean conveyor belt?
Cold water is denser than warm water, but in this case the cold water is also salty, making it very dense.
The red, warmer water is less dense and floats on top of the cold, dense bottom water.
4. What is the global ocean conveyor belt, what are the processes that control it, and how does it influence
Earth’s climate?
Answer: The global ocean conveyor belt transports heat, as well as dissolved nutrients and gases, throughout the
Earth’s oceans. There are four major deep-water formation sites in the global ocean. These sites are found in the
following four places:
In the North Atlantic there are two sites-one in the Greenland-Norwegian Sea, and the other in the Labrador Sea.
In the Southern Ocean near Antarctica, they are in the Weddell Sea and the Ross Sea.
On a short-term time scale (decades or centuries), these deep-water formation sites and subsequent currents are
the forces that give the "push" that drives the great ocean conveyor belt. These formation sites are in polar regions,
near areas where seasonal sea ice forms. The coldest and densest of these deep-water masses forms in the
Weddell Sea off the coast of Antarctica. It is known as Antarctic Bottom Water.
Unlike surface currents, which are driven by wind, thermohaline currents are driven by density differences in
ocean water. Because the ocean conveyor belt is controlled by dense, cold water, it is frequently called thermohaline
circulation (thermo= temperature; haline =salinity). There is no real beginning or end in this conveyor system,
since it is a continuous loop.
Glossary
Unit
Activity
Vocabulary Word
Hydrosphere
Global Ocean Conveyor
Density
Belt
Hydrosphere
Global Ocean Conveyor
Belt
Ocean current
Hydrosphere
Global Ocean Conveyor
Thermohaline current
Belt
Definition
The calculated mass per unit volume of a substance (Less dense
fluids and gases float on more dense fluids and gases unless they mix.
Hot air is less dense than cold air, which is why hot air balloon rise.)
A continuous and directed movement of the oceans’ water due to winds,
waves, temperature, density, or the movement of the Earth
The thermohaline (thermo = heat; haline = salinity) circulation of the
oceans refers t o the deep- w a t e r current that is driven by cold dense
salty water and warm surface waters.
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