1. The Effect of Increasing CO 2 on the World’s Oceans Mark Carson UW School of Oceanography

2. Essential take-home messages Ocean acidification is a separate issue from anthropogenic global warming The chemistry involved is well understood Confounded by unknown bio-feedbacks Various negative impacts on ocean biology (and thus our economies) are likely

3. Well, we all know quite a bit about it already, but in summary:Well, we all know quite a bit about it already, but in summary: Plants (including phytoplankton and some bacteria) use it: CO 2 + H 2 O + sunlight CH 2 O + O 2 Animals (including many bacteria) respire it: O 2 + CH 2 O CO 2 + H 2 O + energy And we (plus Nature to a degree) produce it through burning organic matter: nC y H 2y+2 + mO 2 (+ xN 2 ) wCO 2 + vH 2 O (+ rCO + sNO q ) + energy! What is Carbon Dioxide? Photo by Mark Carson

4. Fossil Fuel CO 2 100s of millions of years in the making of fossil fuel reservoirs Out of perhaps 6500 Gt (billion tons) of recoverable fossil fuel C, we have consumed ~ 220 Gt C in 200 yrs 1,2 Coal is the fastest growing fossil fuel; reserves depleted in less than 200 yrs at current rate 3 1 Pilson, 1998; 2 Sabine et al. 2004; 3 IEA, 2006 Photo by Mark Carson

5. CO 2 Residence Time Residence time is some substance stays within some reservoir. There is some uncertainty regarding the residence time in the atmosphere One recent estimate suggests that 17-33% of anthropogenic CO 2 will remain in the atmosphere after a 1000 yrs 1. A lower limit puts the residence time at over 100 yrs, though this is unlikely. 1: Archer, JGR, 2005 Photo by Mark Carson

6. Graphics sources: “Carbon Dioxide” Wikipedia article (top); GEMS GHG Flux Inversion (middle and bottom)

7. A Helpful Ocean The oceans have absorbed between 25 – 50% of the anthropogenic CO 2 emitted during the Industrial Era 1,2 Increases surface CO 2 and deep ocean CO 2 via sinking of particulate organic matter (POM) Offsets the global warming effect by reducing atmospheric CO 2 concentrations 1: Sabine and Feely, 2007; 2: NOAA Ocean Acidification Fact Sheet, May 2008

8. Ocean color (Chl) Apr 09 Source: AQUA MODIS Monthly Chlorophyll concentration, level 3, April 2009; oceancolor.gsfc.nasa.gov

9. The global carbon cycle Source: Sabine et al 2004 PCC slide no. 040

10. The “biological carbon pump” Graphic: Sunda, Nature, 2010

11. Pteropod, or sea butterfly, Clio Pyramidata, Up to 2 cm size The biological players Graphics: pteropod: www.ipsl.jussieu.fr/~jomce Coccolithophorid: www.biol.tsukuba.ac.jp/~ik awa/shiraiwaHP Foraminifera: O. R. Anderson, accessed from the Micro Scope website Foraminifera, Globigerinoides species, Usu. Less than 1 mm Coccolithophorid, E. Huxleyi, About 6 μm in size

12. Marine Carbon Chemistry When you add CO 2 to seawater, CO 2 + H 2 O H 2 CO 3 H 2 CO 3 (carbonic acid) dissociates as an acid in solution: H 2 CO 3 HCO 3 - + H + CO 3 2- + 2H + [CO 2 + H 2 CO 3 sometimes written CO 2 (aq)] Bicarbonate ion Carbonate ion Hydrogen (hydronium) ions pH

13. Source: (upper left) Feely et al. 2006, science brief; (right bottom) After Doney et al. 2009 Seawater time series from Aloha station, Hawaii: hahana.soest.hawaii.edu (CO 2 data from Mauna Loa, Hawaii)

14. Carbonate Chemistry Source: Raven et al 2005

15. Calcium Carbonate Ca 2+ + CO 3 2- CaCO 3 Two major crystal forms: calcite and aragonite Aragonite is more soluble Forams and coccolithophores form tests of calcite Pteropods and coral reefs form aragonite Aragonite Calcite Graphic sources: Wikipedia

16. Saturation A solution is saturated with a substance when additional amounts don’t dissolve, and normally the substance can precipitate out. The surface oceans are supersaturated with respect to calcium carbonate, although it doesn’t precipitate inorganically at these levels.

17. Aragonite Saturation Saturated = 1; supersaturated > 1; undersaturated < 1 Tropical waters have higher supersaturation than the polar waters Heading into the late 21 st century, polar waters will start to approach undersaturation with respect to aragonite Source: Feely, et al., Oceanography, Dec 2009

18. Shell malformation Graphics: NOAA OA Fact Sheet, 2008 (top); J. Cubillos (from www.aad.gov.au; bottom) (b) Pteropod shell formation in high CO 2 Coccolithophorid shell formation in high CO 2 conditions (right)

19. Coral reefs Corals may not be able to grow and maintain reefs after 840 ppm CO 2 is reached, Fig. 1 1 Corals also will suffer if ocean temperatures increase due to GHG Already, due to non- climate-impact human activity, over a quarter of reefs have collapsed or are in danger 2 ~100 million people rely on coral reefs in some way 3 1: NOAA OA Fact Sheet, 2008 2: Wilkinson, 2004; 3: Hoegh-Guldberg, 2005

20. The power of life Organisms can take acquired energy and apply it to things like binding Ca 2+ and CO 3 2- together Some plankton will fail in higher pH waters, some will survive. Some may thrive. The Cliffs of Dover were formed by some species of coccolithophorids during the Cretaceous period, a period of very high CO 2 concentrations Graphics source: Wikipedia

21. Various responses to increased CO 2 Note that the few species just benefit from increased CO 2 in this study Source: Doney et al. 2009

22. Problems The ability for plankton to acclimate quickly is uncertain Seems likely that some species (like pteropods) may decline to some degree Any decline in plankton or reefs will have consequences for the food webs All organisms will have to “put more energy” into calcifying due to the carbonate chemistry issues presented here

23. Impacts Reduction of coral reef building and healthy calcareous shell formation in plankton Impacts on larval forms of fish and shellfish U.S. spends about $60 million on fish and seafood per year (3 rd largest consumer in world) U.S. fish stocks estimated at over $250 million Source: NOAA Ocean Acidification Fact Sheet, May 2008

24. Reduced oceanic carbon sink? Increased CO 2 in the oceans will reduce the ocean uptake of CO 2 –Limiting iron-utilization by diatoms et al. 1 –Making calcifiers use HCO 3 - and release CO 2 back into the water 2 –Population declines in plankton / reefs due to acidification 3 Ocean warming due to GHG effect; warmer liquids can’t contain as much dissolved gas The strength of these feedbacks is uncertain though; other possible theories include a strengthening of the oceanic carbon sink 4 Sources: 1: Shi et al. 2010; 2: WBGU report, Jan. 2006; 3: NOAA OA Fact Sheet, 2008; 4: e.g., Engel et al. 2004

25. “… human beings are now carrying out a large scale geophysical experiment of a kind that could not have happened in the past nor be reproduced in the future.” - Revelle and Suess, 1957 Source: Pilson, 1998

26. Thanks! Source: (left) www.aad.gov.au/default.asp?casid=37046; (right) R. Feely, NOAA / PMEL