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Ocean Acidification and the Future Global Carbon Cycle:

Text notes to accompany the lecture of
Dr. Jack Barth

"Keeling Curve" - Slide 2

- shows composition of our atmosphere over time

- CO2 concentrations go up and down over the seasons on short, annual time frames, (Earth "breathing in and out") but overall, the concentraton of CO2 has steadily risen over the last several decades

Antarctic Ice Core Record - Slide 5

- ice traps gases from the atmosphere from the time that it was formed. Can extract ancient air from the bubbles in the ice.

- get CO2 plus an indication of past temperatures, going back ~800,000 years

- CO2 mainly at 2 ppm until recently ("recently" being 450,000 years)

- temperature curve roughly matches CO2 concentration curve

- 15,000 to 20,000 years ago we had an ice age

- humans have affected the system as well, and we know this based on actual data plus physical-chemical-biological models of the Earth system

- global temps projected to go up 2-4 degrees, global CO2 concentration projected to go up 400 ppm over next 100 years

Recent Emissions - Slide 6

- Amount of fossil fuel emissions into the atmosphere a great concern (industry, cars, cows, other emissions)

- What is a gigaton? A billion tons of CO2!

- Even w/discussions among governments around the world and with scientists, we are not doing very well here. Actual emissions higher than worst IPCC projected scenarios!

Carbon Inventories - Slide 7

- What is CO2 going in to? Pie chart

- PgC = gigaton

- 10e15 g, 38,000 gigatons of CO2 in ocean

- the oceans do a great deal to absorb CO2

- but we are still concerned about the atmospheric sliver of the pie

In the 1990s... - Slide 8

- So how do we know about this as ocean scientists?

- Ocean scientists go to sea 40-50 days at a time and collect thousands of water samples, from the seafloor up through the water column to the sea surface. We can measure the carbon (C) and oxygen (O) in the water samples

- WOCE = World Ocean Circulation Experiment

This is a map of the station locations from the global survey of carbon measurements as part of WOCE, the World Ocean Circulation Experiment. The red stations indicate measurements collected as part of the US WOCE one time survey. The yellow stations were a part of NOAA’s OACES program. We have also made an effort to incorporate as much international data as possible. The blue stations in the Indian Ocean are from the French. Pacific data came from the Australians, Japanese, and Canadians. Much of the new Atlantic work was performed by the Europeans. The synthesis began in the Indian Ocean. These cruises had the best coordination are required the least effort to synthesize. We have just completed the Pacific synthesis and are now moving on to the Atlantic. All together we hope to have something on the order of 100,000 unique sample locations with at least two measured carbon parameters.

- gives us historic baseline from which to move forward

Penetration of Human-Causes CO2 into Ocean - Slide 9

- Sabine et al. WOCE data - sampled on ship - previous measurements of CO2 into the ocean at air-sea interface

- human-caused CO2 reaches deep into the ocean

- oceans take up CO2 out of the atmosphere. Can the oceans keep that up in order to save us?

Rising Atmospheric CO2 - Slide 10

- Too much CO2 into the oceans could change the natural rate of air-sea exchange

- Chemistry of the ocean is indeed changing

- 22 million tons of CO2 per DAY goes into the ocean!

- Note the chemical equation:
CO2 + H2O <--> Carbonic Acid <--> Bicarbonate ion + H ion <-->Carbonate ion + H ion

- carbonic acid part is where notion of "ocean acidification" comes from

- carbonate ion can go into bicarbonate or shells. If it decreases then less is available for CaCO3 needed by animals to make their shells or coral reefs

- Projections are for CO2 in ocean to go UP, carbonate ion to go DOWN, pH to go DOWN

- organisms that need CaCO3 won't be able to get enough and they will start to dissolve (no protective shells)

Ocean Measurements of pCO2 and pH / Ocean Acidification - Slides 11-13

- Do we believe this will happen?

- YES, from pCO2 (concentration of CO2) and pH measurements in water samples from places such as Station Aloha

- CaCO3 (or aragonite) goes into the shells

- What will changes in ocean chemistry do to organisms and ecosystems?

- More CO2 means less carbonate ion in ocean, more dissolving of shells, disappearance of shell-bearing species

Predictions of Ocean Acidification - Slide 14

- Ocean distribution of CO2 and carbonate ion with knowledge that animals cannot calcify or make shells. This example focuses on corals

- Warm colors = aragonite or CaCO3 is in solution for animals to use

- 1765 = healthy ocean, but now we are at marginal levle

- By year 2100 we will be in real trouble

- There is no debate about this in the scientific community

Coccolithophores, Pteropods - Slides 16-17

- Back to the sediments - electron microscope picture of tiny plankton in the ocean (coccolithophores), as well as pteropds (tiny snails)

- Pictures show shells dissolving

Open Ocean Food Webs - Slides 18-19, 23

- oceanic food webs - what do we care about the little pteropod guys in the food web? Well, the little guys are part of the food chain that eventually feeds the fish that we DO care about. This is food that we use as a food and view as an icon for a healthy ocean

What we know about the biological impacts... Slide 20

- in the lab we can shock these organisms with changes in pH to see how they react. Scientists at UCSB experimenting with how changes in pH and temp in the lab affecting sea urchins. Poor sea urchins not able to form arms.

- in nature the time frames are much longer

- can organisms adapt to changes in environmenta? Will more genetically diverse critter develop and help save the biodiversity of the oceans

- We shall see, but we now that acidity will increase in short term, temps will too.

Where will the future take us? - Slide 21

- graph shows change in # of types of animals (genera)

- high CO2, drop in # of species, lack of corals

How will these changes affect the global carbon cycle? Slide 22

- If we change ocean-Earth-atmosphere system we get feedbacks, both positive (more climate change) and negative (less climate change)

Ocean Food Web Animation - Slide 23

- healthy to unhealthy ocean dominated by just bacteria in a non-healthy future

Acidic Waters... - Slide 24

- how about bringing this home to Oregon?

- Oregon data show how low pH water is exposed very near shore

Dissolved Oxygen and PCO2 Measured Off Oregon - Slide 25-27

- temperature, salinity, pCO2 also measured offshore

- CO2 numbers are very high nearshore

- this affects sea urchins, barnacles in nature (e.g., tide pools), also commercial oyster hatcheries

- with too low a pH critters cannot calcify (make shells)


- CO2 going up exponentially - this is a rate that we can continue to project from our scientific data and models

- the oceans help by absorbing literally tons of CO2 - thank goodness for the oceans

- we (humans) have changed the pH of the oceans by 0.1 and we are heading for a whopping 0.3

- our emissions on land WILL change the ocean

- we still need to know more so scientific studies continue in earnest!

- check out the special issue of Oceanography to go more in depth!

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