When you hear climate change, what do you think?

Rising temperatures

Rising levels of CO2 in atmosphere

Rising levels of CO2 in oceans http://www.youtube.com/watch?v=W9cS0rl_NyI

http://www.youtube.com/watch?v=d0kacyyLVB4&feature=related

Rising sea level melting of land ice thermal expansion of water

Life in a hotter, higher CO2 world

What role do the oceans play in climate?

Exchange and transfer of heat Oceans carry heat from the tropics (equator) to the poles, to maintain

Earth's temperature

Exchange and transfer of CO2 (and O2)

What are the sources of increased CO2 in the atmosphere? Deforestation Fossil fuels Cement production

Oceans are main reservoirs of readily available carbon dioxide (CO2)

The cold, deep water in the ocean is the main reservoir of dissolved CO2

Oceans and heat

Solar energy is absorbed by both oceans and continents. BUT--because the oceans cover over 70% of Earth's surface and are darker than the continents--they absorb more of the sun's energy

Oceans not only absorb lots of energy from the sun--they can also store lots of solar energy in the form of heat AND they can do this with very little change in temperature

High specific heat of water 80% of heat generated by global warming is stored in the

oceans

Atmosphere and Oceans in Motion

Half of the incoming solar radiation is absorbed by the ocean

Energy is stored in the water as it is picked up by winds which blow over the ocean surface

When the wind releases the water as precipitation the heat energy of the water is released into the atmosphere causing an increase in temperature

The oceans' waters are constantly on the move

Sunlight warms the surface of the ocean in the tropics

Wind-driven surface currents carry the heat toward the poles

In the North Atlantic, the warm currents from the tropics feed the North Atlantic Current (in red on figure on next slide)

As the current flows northward toward Norway and Greenland, it loses heat to the atmosphere and cools down

In winter the water near Norway and Greenland gets so cold and dense it sinks all the way to the bottom of the ocean

The cold bottom water feeds bottom currents (in blue and green on figure)

Eventually, mixing brings the bottom water back to the surface in other parts of the ocean, sometime as far away as the North Pacific

When the water gets to the surface, sunlight warms the water, and the cycle starts over

Global Conveyor Belt – thermohaline circulation

Global Conveyor Belt – thermohaline circulation

Surface processes determine density (and other properties) of water

Because of the high specific heat of water, the oceans store heat

Currents transport heat

Global Carbon Cycle Exchange of carbon between different reservoirs

(atmosphere, ocean, fossil fuels, land)

Ocean is largest active reservoir

More CO2 in atmosphere, more CO2 in oceans

Global Carbon Cycle

How much carbon is in each reservoir? Land = Most in rock/soil Ocean = Most in deep ocean

What is the residence time in each reservoir?

Alive = 5 yrsDead = 30 yrs.Soil/rocks = 1000 yrs.

3 yrs.

Surface = 6 yrsMid-water = 100 yrs.Deep = 100,000 yrs.

Oceans in a High CO2 World

Oceans absorb and release CO2

More CO2 in the atmosphere, more CO2 in the oceans

CO2 reacts with water to form an acid

What is an acid? Any chemical compound that, when dissolved in water,

gives a solution with a hydrogen ion (H+) greater than in pure water

Measured by pH scale pH = -log [H+] higher [H+] = lower pH

0–6 = acid, 7 = neutral, 8–14 = alkaline Each is a power of 10 difference in acidity

pH scale

Oceans in a High CO2 World

When CO2 dissolves, it reacts with water to form a balance of chemical species: dissolved free carbon dioxide (CO2(aq)), carbonic acid (H2CO3), bicarbonate (HCO−

3) and carbonate (CO2−3)

The ratio of these species depends on temperature and pH

Dissolving CO2 increases [H+]

Lower pH

What are the factors that determine how much CO2 dissolves in seawater?

Solubility determined by temperature Colder water holds more CO2 than warmer water

Ocean circulation

Areas of convergence = downwelling = sink for CO2

Old, dense water

Areas of divergence = upwelling = source of CO2

More CO2 than atmosphere

Biology Photosynthesis/respiration Recycling of matter in surface versus burial to deep ocean

Oceans are a sink for CO2

Circulation transports dissolved CO2

Areas of deep water formation have high CO2

What happens as water gets older and makes voyage around the globe? What happens

when this water surfaces?

Oceans in a High CO2 World

Where do we see the most change in CO2?

Why?

CO2 and “Old” WaterCO2

CO2 + H2O organic carbon + O2

CO2 + H2O organic carbon + O2

euphotic zone

CO2 + H2O organic carbon + O2

sediments

photosynthesisrespiration

respiration

120m

Aragonite Saturation State in West Coast Waters May-June 2007

Old, CO2 rich water

Ocean Acidification in WA Waters

Effects of Ocean Acidification http://abcnews.go.com/GMA/video/ocean-acid-10445789

Impacts on organisms that build shells and plates out of calcium carbonate (CaCO3) More acidic (lower pH) = less carbonate

Vulnerable organisms: Bivalves (mussels, clams, oysters) Coccolithophorids (phytoplankton) Pteropods, foraminifera (zooplankton) Coral reefs

Coccolithophore

PteropodCorals

Status of Ocean Acidification

Slowing growth of Great Barrier Reef 14% reduction in skeletal formation since 1990

Experimental corrosion of calcium shells Pteropod (48 hrs) b = acid, c = normal seawater

Deformed coccoliths

Status of Ocean Acidification

Impact on biodiversity Number of species Ecosystem function

Impact on marine foodwebs

Ocean Acidification & Marine Foodweb

What will the impact of ocean acidification be on the marine foodweb?

What will happen to the Deadliest Catch?

Coccolithophore bloom in the Bering Sea

Benthic organisms

Salmon

Marine Mammals

Status of Ocean Acidification

~1/3 of fossil-fuel CO2 dissolves in ocean

Between 1751 and 1994 surface ocean pH is estimated to have decreased from approximately 8.2 to 8.1

Logarithmic scale of pH; approximately a 25% increase in H+

Estimated that it will drop by a further 0.3 to 0.5 units by 2100

Global Conveyor Belt

The deep circulation shown in the picture is important for two reasons:

Cold water carries carbon dioxide deep into the ocean, taking it away from the atmosphere and

Surface currents that sink and feed deep currents carry much more heat toward Europe than currents that stay on the surface

Understanding Ocean Acidification

Chemistry of oceans depends on chemistry of atmosphere

More CO2 in atmosphere = more CO2 in oceans

More CO2 in oceans = more acidic oceans (lower pH)

More acidic oceans = negative impact on algae and animals with shells or skeletons made of calcium carbonate