Ocean Acidification and the Ocean Acidification and the Future Global Carbon Cycle Future Global Carbon Cycle • Rising atmospheric CO 2 • Ocean’s role in uptake of atmospheric CO 2 • Resulting changes in ocean chemistry • Possible outcomes for future oceans • What can we can do to help improve the future? Jack Barth (barth@coas.oregonstate.edu) College of Oceanic & Atmospheric Sciences for further info: “The Future of Ocean Biogeochemistry in a High CO2 World,” Oceanography magazine (Dec. 2009) http://www.tos.org/oceanography/issues/issue_archive/22_4.html Data from Keeling and Whorf, 2004 Rising Atmospheric CO 2 was first discovered by Dr. David Keeling in the mid 1900s. Atmospheric CO 2 Record Northern Hemisphere has larger seasonal variability than southern hemisphere Atmospheric CO 2 levels are rising everywhere in the world. This can easily be seen even with the natural variability. Atmospheric CO 2 was steady for at least 1,000 years before the industrial revolution. “It is very likely that [man-made] greenhouse gas increases caused most of the average temperature increase since the mid-20 century” - Intergovernmental Panel on Climate Change (IPCC) 4th Assessment Report (2007) Antarctic Ice Core Record -10 20 15 10 5 0 -5 450 400 350 300 250 200 150 100 50 0 Thousands of years BP (before present) Temperature change (°C) CO 2 concentration Temperature change (°C) 200 400 CO 2 Concentration (ppmv) 0 550 800 2050 2100 Recent emissions 1990 1995 2000 2005 2010 CO 2 Emissions (GtC y -1 ) 5 6 7 8 9 10 Actual emissions: CDIAC Actual emissions: EIA 450ppm stabilisation 650ppm stabilisation A1FI A1B A1T A2 B1 B2 1850 1900 1950 2000 2050 2100 CO 2 Emissions (GtC y -1 ) 0 5 10 15 20 25 30 Actual emissions: CDIAC 450ppm stabilisation 650ppm stabilisation A1FI A1B A1T A2 B1 B2 50-year constant growth rates to 2050 B1 1.1%, A1B 1.7%, A2 1.8% A1FI 2.4% Observed 2000-2006 3.3% 2007 2006 Recent emissions have been higher than the worst of the IPCC projected scenarios GigatonsC/year Year Carbon Inventories of Reservoirs that Naturally Exchange Carbon on Time Scales of Decades to Centuries Ocean 38,136 PgC Soil=2300 PgC Plants=650 PgC Atm.=775 PgC Preind. Atm. C =76% Ocean Anth. C=0.35% • Oceans contain ~90% of carbon in this 4 component system • anthropogenic component is difficult to detect Anth. C=24% In the 1990s we conducted a global survey of CO 2 in the oceans to learn how much fossil fuel is stored in the ocean. ~72,000 sample locations collected in the 1990s DIC ± 2 µmol kg -1 TA ± 4 µmol kg -1 Penetration of human-caused CO 2 into Ocean • Present-day levels minus pre- industrial (year 1800) • Equivalent to about half of all historical fossil fuel emissions Sabine et al. (Science, 2004) After Turley et al., 2005 Rising atmospheric CO 2 is changing the chemistry of the ocean pH CO 2 + H 2 O H 2 CO 3 HCO 3 2- + H + CO 3 - + H + CO 2 is an acid gas so the addition of 22 million tons of carbon dioxide to the ocean every day is acidifying the seawater…we call this process “ocean acidification” [...]... direction CO3 2- decrease Less efficient uptake positive Calcification decrease lower natural CO2 production negative CaCO3 dissolution-sed higher CO3 2- increasing uptake negative CaCO3 dissolution-water higher CO3 2-/ lower org transport Neg./pos Increasing SST Convert ocean HCO 3- to CO2 positive Increased stratification Reduced mixing and transport positive Increased stratification Lower productivity and uptake... Corals Coral Calcification rate mmol m-2 d-1 3X Glacial 1870 2006 CO2 CO2 Time 200 150 2X 180 280 380 560 840 R2 = 0.843 200 CO2 level in Atmosphere (ppm) 100 150 100 Net Calcification 50 0 450 400 350 300 250 200 Carbonate ion concentration (µmol kg-1) -5 0 Low CO2 150 100 50 Net Dissolution 50 0 -5 0 High CO2 Langdon & Atkinson, (2005) Predictions of Ocean Acidification and the effects on coral reef calcification... Acidification and the effects on coral reef calcification 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) Coccolithophores pCO2 28 0-3 80 ppmv pCO2 78 0-8 50 ppmv Calcification decreased - 9 to 18% Emiliania huxleyi - 45% Gephyrocapsa...Ocean Measurements of pCO2 and pH Feely et al (2009) Ocean Acidification ⇔ 2HCO 3- CO2 + CO3 2- + H2O Saturation State = Ca2+ + CO3 2- → CaCO3 Ω calcium + carbonate → calcium carbonate Photos courtesy Katie Fagan phase [Ca2+] [CO3 2-] = K*sp, phase Ω > 1 = precipitation Ω = 1 = equilibrium Ω < 1 = dissolution There appears to be a... ocean acidification and sensitivity to CO2/pH perturbation Much of our present knowledge stems from  abrupt CO2/pH perturbation experiments  with single species/strains  under short-term incubations  with often extreme pH changes Hence, we know little about  responses of genetically diverse populations  synergistic effects with other stress factors  physiological and micro-evolutionary adaptations... by another 0.3 units and will likely have dramatic consequences on the ocean ecosystems 5 The rate of CO2 growth may impact the ability of the ocean to adapt to climate change…slowing the rate of growth could determine the structure of the future oceans for further info: “The Future of Ocean Biogeochemistry in a High CO2 World,” Oceanography magazine (Dec 2009) http://www.tos.org /oceanography/ issues/issue_archive/22_4.html... Remineralization Acidic waters brought near the coast by coastal upwelling Possible changes to: • species composition & abundances • food webs • biogeochemical cycles Feely et al (2008) Dissolved oxygen and pCO2 measured off Oregon Aug & Sep hypoxic Courtesy of MI_LOCO (Barth, Adams, Chan) High pCO2/low pH waters may affect oyster hatcheries Whiskey Creek Hatchery, Netarts Bay, OR “Spat” on shell, newly... Courtesy of George Waldbusser (COAS/OSU) How a bivalve shell is formed From McConnaughey & Gillikin 2008 Two sources of Shell Carbonate Seawater HCO3Respired CO2 Two components of shell growth, organic and inorganic Internal shell surface is used to buffer during exposure or stress Calcification in bivalves is an Internal process, Dissolution is primarily External* Courtesy of George Waldbusser (COAS/OSU)... Convert ocean HCO 3- to CO2 positive Increased stratification Reduced mixing and transport positive Increased stratification Lower productivity and uptake positive Increased dust input Increased productivity-N fixers negative Ecosystem structure Lower or higher productivity Pos./neg Future Ocean Food Web – Simpler, more primitive ecosystem based on a low CO2 2 ocean Present Ocean Food Web – Complex ecosystem . locations collected in the 1990s DIC ± 2 µmol kg -1 TA ± 4 µmol kg -1 Penetration of human-caused CO 2 into Ocean • Present-day levels minus pre- industrial (year 1800) • Equivalent to about half. = equilibrium Ω < 1 = dissolution CO 2 + CO 3 2- + H 2 O 2HCO 3 - ⇔ = [Ca 2+ ] [CO 3 2- ] K* sp, phase Ca 2+ + CO 3 2- CaCO 3 → → Photos courtesy Katie Fagan -5 0 50 100 150 200 050100150200250300350400450 Carbonate. Fagan -5 0 50 100 150 200 050100150200250300350400450 Carbonate ion concentration (µmol kg -1 ) Coral Calcification rate mmol m -2 d -1 Net Dissolution Net Calcification 1870 280 2006 380 Low CO 2 High CO 2 -5 0 50 100 150 200 0 0 CO 2 level in Atmosphere (ppm) Glacial 180 560 CO CO 2 2 2X 2X 840 CO CO 2 2 3X 3X There