1. Ocean Acidification: Global Warming’s Evil Twin Richard A. Feely NOAA/Pacific Marine Environmental Laboratory April 30, 2008 2008 NASA Carbon Cycle & Ecosystems Joint Science Workshop With special thanks to: Carol Turley, Chris Sabine, Jim Orr, Fei Chai, Chris Langdon, Barney Balch, Rik Wanninkhof, Dwight Gledhill, Anne Cohen, Justin Ries, and Sylvia Barry Outline What is ocean acidification? What are the impacts on marine organisms? Satellite-based approaches to investigate ocean acidification Conclusions

2. Since the beginning of the industrial age, the pH and CO 2 chemistry of the oceans (ocean acidification) have been changing because of the uptake of anthropogenic CO 2 by the oceans. Decrease in pH 0.1 over the last two centuries 30% increase in acidity; decrease in carbonate ion of about 16% Ocean Acidification These changes in pH and carbonate chemistry may have serious impacts on open ocean and coastal marine ecosystems. http://www.biol.tsukuba.ac.jp/~inouye Photo: Missouri Botanical Gardens CoralsCalcareous Plankton

3. calciumcarbonate calcium carbonate Saturation State  phase  Ca 2   CO 3 2   K sp,phase *  1  precipitation  1  equilibrium  1  dissolution What we know about the ocean chemistry of …saturation state

4. WOCE/JGOFS/OACES Global CO 2 Survey ~72,000 sample locations collected in the 1990s DIC ± 2 µmol kg -1 TA ± 4 µmol kg -1 Sabine et al (2004) …from field observations What we know about ocean CO 2 chemistry

5.  Because the ocean mixes slowly, half of the anthropogenic CO 2 stored in the oceans is found in the upper 10% of the ocean  From the WOCE/JGOFS global CO 2 survey, the observed anthropogenic CO 2 inventory through 1994 is calculated to be 118±19 Pg C. Sabine et al. Science (2004) What we know about ocean CO 2 chemistry …about human impacts on ocean CO 2 chemistry  What are the impacts of increased CO 2 on marine ecosystems?

6. …from observed aragonite and calcite saturation depths in the global oceans Feely et al. (2004) What we know about ocean CO 2 chemistry

7. Global Water-column Dissolution = 0.5 Pg C yr -1 Modern Aragonite Saturation Horizon Preindustrial Aragonite Saturation Horizon Modern Calcite Saturation Horizon Preindustrial Calcite Saturation Horizon Feely et al. (2004) …from observed shoaling saturation horizons What we know about ocean CO 2 chemistry The aragonite and calcite saturation horizons have shoaled towards the surface of the oceans due to the penetration of anthropogenic CO 2 into the oceans.

8. Coral Reef calcification 1765 Adequate 2000 Marginal 2100 Low Calcification rates in the tropics may decrease by 30% over the next century After Feely et al (in press) with Modeled Saturation Levels from Orr et al (2005) Predictions of Ocean Acidification and the effects on coral reef calcification

9. Experiments on Many Scales Aquaria and Small Mesocosms Biosphere 2 Provided by Mark Eakin Large Scale Mesocosm Facility University of Bergen, Norway SHARQ Submersible Habitat for Analyzing Reef Quality 190 370 700 pCO 2 (ppmv)

10. -50 50 100 150 200 050100150200250300350400450 Carbonate ion concentration Calcification rate, mmol m -2 d -1 Net Dissolution Net Calcification 1870 280 2006 380 Low CO 2 High CO 2 -50 50 100 150 2000 CO 2 level in atmosphere Glacial 180 560 CO 2 2X 840 CO 2 3X The impact of rising atmospheric CO 2 on the surface ocean carbonate chemistry and its potential impact on corals - Biosphere 2 Results Langdon & Atkinson, (2005) R 2 = 0.843

11. Some evidence that shallow corals can survive in polyp form without a calcified structure (D) percent change (average ±SE) in protein per polyp (biomass) and total buoyant weight over 12 months in experimental (pH = 7.4) and control (pH =8.2) seawater (N=20). A two-way analysis of variance (time x pH) revealed significant changes between treatments over time (A) Oculina patagonica Control colony (B) Sea anemone-like polyps following skeleton dissolution in low-pH conditions (C) Solitary polyps reform a colony and calcify after being transferred back to normal seawater following 12 months as soft-bodied polyps in low- pH conditions 1mm Fine & Tchernov, 2007 1mm

12. Scorecard of Biological Impacts of Ocean Acidification

13. Much of our present knowledge stems from  abrupt CO 2 /pH perturbation experiments  with single species/strains  under short-term incubations  with often extreme pH changes...and sensitivity to CO 2 /pH perturbation Hence, we know little about  responses of genetically diverse populations  synergistic effects with other stress factors  physiological and micro-evolutionary adaptations  species replacements  community to ecosystem responses  impacts on global climate change What we know about the biological impacts of ocean acidification

14. Flux Term Flux Estimate mmol CaCO 2 m -2 d -1 Flux Estimate Pg C yr -1 Dissolution from 200 to 1500m Production in the euphotic zone0.4 – 1.00.5 – 1.6 Export from the surface (models)0.3 – 1.10.4 – 1.8 Atlantic0.30.1 Indian1.10.3 Pacific0.80.6 Total1 Export to sediment traps below 2000m*0.24 ± 0.030.4 ± 0.05 Dissolution on seafloor below 2000m Atlantic and Pacific only0.24 ± 0.170.4 ± 0.3 Burial in sediments0.080.1 CaCO 3 Flux Estimates for the Oceans *data from Honjo et al. (2008) Updated from Berelson et al., (2007)

15. Optical estimate PIC is “acid-labile backscattering” (b b ’)…  Measure particulate backscattering (b bp ) with single detector, using raw seawater = b bp raw  Reduce pH below dissociation point for calcite and aragonite (i.e. dissolve CaCO 3 )  Re-measure b bp = b bp acid  b b ’ = b bp raw – b bp acid  PIC [mol PIC(m -3 )] = b b ’/b b *  Good for ship surveys, 2-4 minute pH cycle, resolution of 1-2 samples/km -W.M. Balch

16. Two PIC Algorithms  Two band algorithm (based on absolute nLw440 and nLw550); Balch et al. (2005 Calcium Carbonate Measurements in the Surface Global Ocean based on MODIS Data. JGR-Oceans 110, C07001 doi:10.1029/2004JC002560) Better at background PIC concentrations, saturates at high PIC, atmospheric correction large, provides chl estimate, sensitive to errors in absolute nLw.  Three-band algorithm (based on 670, 765, and 865nm bands; Gordon et al. (2001. Retrieval of coccolithophore calcite concentration from SeaWiFS imagery, Geochemical Research Letters, 28 (8), 1587- 1590.) Best in turbid water, less problems from atmospheric correction, little complication from chl or CDOM -W.M. Balch

17. Let’s compare PIC observations from ship and satellite… NOTE: THESE ARE NOT BLOOMS BUT NORMAL BACKGROUND PIC CONCENTRATIONS! AMT 17 Cruise track -W.M. Balch Particulate Inorganic Carbon Concentrations from Satellite Observations

18. Global calcite: MODIS Aqua June-Aug 2007 Elevated PIC -W.M. Balch

19. Conclusions  Impacts of ocean acidification on ecosystems are largely unknown.  Calcification in many planktonic organisms is reduced at elevated CO 2, but the response is not uniform.  Possible responses of ecosystems are speculative but could involve changes in species composition & abundances - could affect food webs, biogeochemical cycles.  Satellite measurements and observational data can be integrated to provide global views of changing ecosystem dynamics and carbonate budgets.