1. When you hear climate change, what do you think?
Rising temperatures
Rising levels of CO2 in atmosphere
Rising levels of CO2 in oceans
Rising sea level
melting of land ice
thermal expansion of water

2. 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

3. 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

4. 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

5. Global Conveyor Belt – thermohaline circulation
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

6. 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

7. 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

8. 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?
3 yrs.
Alive = 5 yrs
Dead = 30 yrs.
Soil/rocks = 1000 yrs.
Surface = 6 yrs
Mid-water = 100 yrs.
Deep = 100,000 yrs.

9. 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
Refered to previously. Here present in more detail, giving the mechanism.
This is what happens in a greenhouse, that you use to grow plants.
Inconvenient Truth cartoon

10. 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
Border wars - Pentagon study
pH scale

11. 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 CO increases [H+]
Lower pH

12. 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

13. Circulation transports dissolved CO2
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?

14. Oceans in a High CO2 World
Where do we see the most change in CO2?
Why?

15. CO2 and “Old” Water CO2 photosynthesis CO2 + H2O  organic carbon + O2
respiration
CO2 + H2O  organic carbon + O2
euphotic zone
respiration
CO2 + H2O  organic carbon + O2
sediments

16. Ocean Acidification in WA Waters Old, CO2 rich water
Aragonite Saturation State in West Coast Waters
May-June 2007
Ocean Acidification in WA Waters
Old, CO2 rich water
120m 16

17. Effects of Ocean Acidification
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
Border wars - Pentagon study
Corals
Pteropod

18. 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
Border wars - Pentagon study

19. Status of Ocean Acidification
Impact on biodiversity
Number of species
Ecosystem function
Impact on marine foodwebs

20. Ocean Acidification & Marine Foodweb
What will the impact of ocean acidification be on the marine foodweb?

21. What will happen to the Deadliest Catch?
Benthic organisms
Marine Mammals
Coccolithophore bloom in the Bering Sea
Salmon

22. 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
Border wars - Pentagon study

23. 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

24. 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