Ocean and Climate

Adopted from NASAhttp://oceanmotion.org/html/

background/climate.htm#rain (By: Robert Stewart)

Earth and the Ocean• Water covers nearly 71% of

Earth’s surface• The ocean stores huge

quantities of energy, and heat exchange between the ocean and atmosphere drives the winds and atmospheric circulation around the world.– These winds in turn drive ocean

surface currents

• Ocean has moderating effect on climate– Absorbs carbon dioxide and

excess heat

Source: NASA Earth Observatory

Ocean Life• Without an ocean, Earth

might be more like Venus– Most abundant gas in

Venus’s atmosphere is carbon dioxide

– Surface is hot enough to melt lead

• Carbon dioxide only makes up 0.038% of Earth’s atmosphere– May be increasing because

of burning fossil fuels and smaller tropical rainforests

The Planet Venus Source: NASA Planetary Photojournal

Ocean Life• The differences between the atmospheres

Earth and Venus can be linked back to ocean life– Photosynthetic organisms, whether they are

single-celled phytoplankton floating on or near the ocean surface or plants growing on land, take up carbon dioxide from the environment and use the sun’s energy to build carbohydrates.

– This process releases oxygen, which is the source of oxygen in the atmosphere.

Pictures from Phytoplankton, Source: NASA SeaWiFS

Cycle Created by Photosynthetic Ocean Organisms

• Other organisms eat primary producers carbohydrates passed through food chain organisms use carbs as fuel and structural building blocks organisms break down carbs for energy using cellular respiration (uses oxygen and releases carbon dioxide) organisms die, decomposers break them down

Without Decomposition…• Some parts of

organisms don’t decompose– Plankton, coral and

mollusks build skeletons/shells of calcium carbonate

– Pressure and heat cement some of these and over millions of years rocks such as limestone, marble and dolomite are created

Life in the ocean has produced vast layers of limestone and marble rock. El Capitan, Capitan Reef, Guadaloupe Mountains National Park, Texas. This is a coral reef from the Permian period.Credit: Mark Eberle, Fort Hayes State University.

Without Decomposition in the Ocean

• Sediment buries remains of organisms

• Deprived of oxygen needed for decomposition, these remains may transform into deposits of coal, oil and natural gas– This locks up more carbon

• When we burn these fossil fuels for energy, we release the carbon dioxide into the environment

The Ocean and Heat

• The ocean absorbs heat when the air is warm and releases heat when air is cool.

• In the tropics, where energy from the sun is at its greatest, the exchange of heat between ocean and atmosphere drives much of the global atmospheric circulation

For scientists to understand climate, they must also determine what drives the changes within the Earth's radiation balance. From March 2000 to May 2001, the CERES instrument measured some of these changes and produced new images that dynamically show heat (or thermal radiation) emitted to space from Earth's surface and atmosphere (right sphere) and sunlight reflected back to space by the ocean, land, aerosols, and clouds (left sphere).The image above is from April 2001.Credit: CERES Press Release Images, NASA

The Ocean and Heat• Sunshine heats up surface of land and

ocean, but heats the ocean more slowly– Most of the heating of the ocean takes place

in the tropics– While ocean surface currents carry some of

the heat north and south away from the tropics, the bulk of the energy is released back into the atmosphere

– Some heat is released in the form of infrared radiation

– Greenhouse gases, most notably water vapor from the ocean, but also carbon dioxide, trap this heat, warming the atmosphere

Sea surface temperatures for spring 2004.Credit: Norman Kuring, GSFC, NASA

The Ocean and the Atmosphere

• The most important mechanism is latent heat release or evaporation. Over the ocean, latent heat is the engine that drives atmospheric circulation

The water cycle circulates both water and energy throughout Earth’s system. The cycle begins with evaporation of water from the surface. Evaporation of water is the source of atmospheric moisture that carries heat energy away from Earth’s surface.Credit: The Asian Monsoon CD, GSFC, NASA

Water Cycle and Atmosphere

• As the sun beats down and the ocean warms, water from the upper layer of the ocean evaporates The conversion of liquid to vapor requires a lot of energy, so evaporation cools the top layer  Trade winds carry the vapor to the area where the north and south trade winds converge called the intertropical convergence zone (ITCZ) There the moist air rises and cools

Water Cycle and Atmosphere Continued

• The water vapor condenses on tiny particles suspended in the air called nuclei, forming clouds This condensation releases energy, heating the surrounding air The warmed air then rises higher, drawing up more moisture from the ocean More vapor then condenses higher in the atmosphere and releases more heat, causing the air to rise further, and so on The result is towering clouds that dump up to five meters of rain per year over some parts of the tropical ocean

Evaporation and Condensation

Credit: The Asian Monsoon CD, GSFC, NASA

Hurricanes

• This same process fuels hurricanes. At the centers of these storms, moist air rising from the warm ocean heats up as the vapor condenses. Warm air is less dense, so the atmospheric pressure drops. More moist air then rushes in off the ocean due to the pressure gradient, rotating counterclockwise due to the Coriolis effect. This air rises up, and condensation releases more heat, intensifying the storm and further lowering the pressure. (Hurricanes generally don’t form close to equator because the Coriolis effect is weak.)

Illustration Credit: Tinka Sloss, New Media Studio, Inc.

Earth’s Circulation Systems• The major circulation

systems of the Earth are illustrated above. On or near the equator, where average solar radiation is greatest, air is warmed at the surface and rises. This creates a band of low air pressure, centered on the equator known as the intertropical convergence zone (ITCZ). The Intertropical Convergence Zone draws in surface air from the subtropics.

The Ocean and Climate Change

• The ocean is a buffer for climate change– Ocean can hold 40 times more carbon dioxide

than the atmosphere– Carbon dioxide dissolves in cold water near

the Arctic and Antarctic • In the winter, the cold water sinks as part of

ocean’s overturning circulation and CO2 is carried deeper

• After 100s of years, winds and tides pull water back to the surface and CO2 is released again

Ocean and Climate Change• Ocean water also

absorbs tremendous quantities of heat

• As the atmosphere warms due to the buildup of greenhouse gases, it transfers some of this heat to the ocean, slowing the pace of climate change

The global carbon cycle shows the carbon reservoirs in billions of tons of carbon and exchanges between the reservoirs in billions of tons/year. The numbers on the figure are annual averages over the period 1980 to 1989.

Source: Vital Climate Graphics, United Nations Environment Programme, UNEP/GRID Arendal.

Marine Organisms and Cloud Formation• Many plankton release a chemical

called dimethyl sulfide into the atmosphere – This chemical undergoes a series of

reactions in the air to form sulfate particles

– Vapor condenses around these particles to form clouds

– These clouds have smaller droplets than other clouds

– hey therefore are brighter and reflect more sunlight back out into space, preventing the sunlight from reaching and heating Earth’s surface

Phytoplankton in the ocean produce dimethyl sulfide (DMS) that is converted to sulfate aerosols (SO4), which influence the amount of sunlight reflected by clouds.

The Ocean and Rain• Some of the most consequential rainfalls are

generated by the seasonal monsoons, especially over Asia – The heavy monsoon rains over much of Asia not only

provide these countries with critical moisture, they release tremendous amounts of latent heat which helps drive atmospheric circulation

• A similar process fuels the North American monsoons, which provide important summer rainfall to the southwestern United States and northwestern Mexico.

– Visit http://www.vets.ucar.edu/vg/CCM3T170/index.shtml for video

Everything is Connected!

Source: Climate Change Impacts on the United States

Some of the many ways the ocean influences climate by exchanging heat, water, and chemical compounds with the atmosphere.