Ocean Acidification in Coastal Waters and other Vulnerable Ocean Regions

1. Ocean Acidification in Coastal Waters and other Vulnerable Ocean Regions Rik Wanninkhof, NOAA/AOML, Miami Fl, USA With contributions from: S. Alin; D. Bakker; N. Bates; A. Borges; W.-J. Cai; L.-Q Chen; F. Chavez; S. Doney; R. Feely; D. Gledhill; K. Helme; E. Jones; K. K. Liu; S. Lohrenz; D. Manzello; J. Mathis; B. McNeil; P. Raymond; J. Salisbury; E. Shadwick; H. Thomas; C. Sweeney

2. Ocean Acidification in Coastal Waters and other Vulnerable Ocean Regions Focus is on regions where changes in water column inorganic carbon dynamics are significant compared to the anthropogenic CO2 (Canthro) input with respect to the pCO2, CO32-, pH and W. Lohrenz et al.

3. Changes of Ocean Acidification over Time from Input of Canthro Large Changes since start of Industrial Revolution: ∆pCO2 ≈ 100 µatm ∆pH ≈ -0.13 ∆CO32- ≈ -40 µM ∆ WAr ≈ -0.7 2x

4. The Chemistry of Ocean Acidification Increased CO2 levels in surface ocean due to uptake of anthropogenic CO2 CO2 + H2O = HCO3- + H+ CO32- + H+ = HCO3- decreased CO32- leads to decrease saturation states (Ar) impacting [calcifying] organisms A saturation state of 1 is generally considered an absolute threshold However, impacts to ecosystems occur at much higher states. The rate of change and natural variability likely important

5. Particular Issues in the High Latitude and Coastal Oceans • Unique physical/chemical attributes of coastal and high latitude oceans  1. Saturation state, Ar naturally low in colder waters (with high TCO2/TA ratio) 2. Upwelling of subsurface waters with low CO32- and Ar due to remineralization 3. Ice melt & fresh water inflow lowers CO32- and Ar 4. Continental input (deposition & nutrients & alkalinity) direct and indirect effects B. Habitat of shallow water corals and other calcifying organisms C. Highly productive D. EEC (its in our back yard) (economic value of fisheries and tourism) • This presentation only focuses on A.

6. Physical and Biogeochemical Processes that Affect Coastal and other Vulnerable Regions • High Latitude: high TCO2/TA ratio; low SST • Shallow Upwelling • Deep Upwelling • (Changing) Ice dynamics • Riverine Input • Wet and Dry Deposition of Sulfur and Nitrogen Compounds • Multi-Stressor • Small-scale nature of the processes and small scales of the physical and biogeochemical forcing means that the magnitude effects are not always fully represented in global and regional models

7. Effect of Temperature and pCO2 on W • Close to W= 1 andsmall addition of DIC (Canthro or Cbio) leads to larger change in pCO2 • Lower temperature, lower W • Change in H+ in response to pCO2 change is nearly linear but a function of temperature

8. High Latitude: Closer to the edge Steinacher et al. 2009 Oceanography Mag

9. High Latitude: Antarctic marginal seas- Deep upwelling • High TCO2/TA; low SST • Naturally low saturation state • Deep upwelling: Canthro signal is diluted and • will delay reaching W threshold (≈ 3 decades) • High biological productivity • Large seasonal cycle (pCO2≈ 150-420) Sweeney,2004 McNeil et al. 2010. GRL

10. Antarctic- Weddell Sea- Ice Dynamics and OA • Ice formation- low W under ice due to CaCO3 ppt and inclusion in ice brines • Amplifies seasonal variations Ca2++ 2HCO3- + 5H2O↔ CaCO3 *6H2O(s) + CO2. Ice formation: decrease W Ice melt and dissolution: increase W “The net effect of ikaite precipitation in brine is to reduce the concentration of dissolved inorganic carbon (DIC) and total alkalinity (TA), whilst increasing the fugacity of CO2 (fCO2, eq. 1). Any brine rejected during winter or released during ice melt transfers these inorganic carbon characteristics to the underlying water. One implication of these processes is that during sea ice growth, the winter mixed layer becomes isolated from the atmosphere (Klatt et al., 2002), allowing levels of fCO2 to reach supersaturation beneath the sea ice. During sea ice melt in spring and summer, any remaining carbonate minerals within the ice are thought to be released into the water column where they re-enter the carbon cycle through dissolution. According to eq. (1), this would increase TA and DIC and reduce fCO2 of the water.” (Jones et al. Tellus 2010) Jones et al. Tellus, 2010

11. Arctic: Cold, Isolated, Productive, & Riverine inputs Very low W below mixed layer; large seasonal cycle in surface water Admunson Gulf Shadwick, Thomas et al. L&O 2011

12. Arctic: Impact of Changing Ice Cover • Decreased ice-cover with increase invasion of Canthro but • Strong stratification, fresh water input and biological productivity can decrease OA • impacts in surface waters Cai et al., 2010, Science

13. Coastal (Shallow) Upwelling • Upwelling brings nutrients, high CO2, low pH, low Ω, low O2 water to surface • High production offshore of upwelling • Shallow remineralization (increases TCO2/TA and decreases buffer capacity) • Waters contain high Canth and combined with low buffer capacity amplify pCO2 pH, CO32- • changes Alin et al. EOS, AGU Fall meeting,2010

14. Variability in Coastal Upwelling Variability in pCO2 offshore from Monterey CA USA (Chavez and Friedrich) Distance offshore (km) • Coastal upwelling is patchy and episodic due to changes in wind direction and wind • stress • However, pCO2, W, pH well correlated with physical (T) and biogeochemical • parameters (O2) Liu et al. eds. C and N fluxes in continental Margins (2010)

15. Strong Shoaling of Saturation Horizon in Eastern Boundary Upwelling Regimes Small changes in upwelling (wind stress) can have dramatic effect on W Alin, Feely et al., 2010

16. High Latitude (Western Boundary-Wide Shelves): high productivity, riverine input, topography, large seasonal changes Vulnerability of North Atlantic Ocean waters to acidification increases in shallow and high latitude regions, primarily as a function of decreasing temperature and chemical composition Scotian Shelf Maximum effects on W in Fall (end of growing season, cooling, and mixing) Shadwick,Thomas et al. submitted , 2011

17. Riverine Input • Fresh water input with low TA and high pCO2 lead to low W • Function of temperature and TA of river Salisbury et al. 2008 EOS

18. River Inputs: (Anthropogenic) Nutrients- Surface Carbonate chemistry in the coastal zone responds more strongly to eutrophication than to ocean acidification Impact: increasing W in surface (offsets OA) due to pCO2 drawdown Model of Belgian continental shelf Ref- all forcing River- river input Atm CO2- only co2 invasion Wind – only wind varies SST only SST varies Borges et al. 2010

19. River Inputs: (Anthropogenic) Nutrients- Sub-surface decreasing W (increases OA) in subsurface due to remineralization/respiration Mississippi, Gulf of Mexico: Hypoxic region will be undersaturated wrt War in 3X scenario Added impact of lower buffering of subsurface water Cai et al. 2011, PNAS, in prep.

20. (Sub) Tropical Coastal Ecosystem: Corals • Multi-stressor: with temperature threshold of ≈ 30 ˚C (coral bleaching) • High seasonal variability in W due to SST variations • Large(r) decline in W due to T dependence of dW/dpCO2 • Calcification lowers W (local feedback): • Healthy coral reefs lower W than surrounding waters 3.8 3.2 Gledhill et al. 2009, Oceanography Mag

21. Other Causes of Ocean Acidification: Nitrogen and Sulfur deposition Largest effect is caused by enhanced primary productivity (and change in TA) due to N-deposition NO3- supported growth produces alkalinity (1:1) NH4+ supported growth removes alkalinity (1:1) Effects are local and, overall, small The largest surface water anomalies are found in coastal regions surrounding the emission areas, with trends: dpH/dt ≈ 0.02 to 0.12 103 pH units/ yr-1, Canthro: dpH/dt ≈ 0.8 to 1.8 103 pH units/ yr-1 Largest effect is nitrification NH4+ to NO3- Doney et al. 2007 PNAS

22. Take Home Messages • Coastal and other vulnerable seas are impacted to larger degree by OA: • * Lower temperatures are higher TCO2/TAlk (Arctic and Antarctic) • * Margins with Upwelling of waters • * Larger changes in pCO2 • Deep upwelling- slower rate of OA (dilution of Canth) • Shallow upwelling greater rate of OA (low buffer factor and Canth) • River dominated margins: • * In surface waters • + Smaller changes in pCO2: dilution fresh water • + pCO2 drawdown eutrophication • * In sub-surface water • + remineralization • + multi stressor (hypoxia) • Ice: • * Ice dynamics (capping of surface water) • * Fresh water dynamics • * ppt of metastable carbonate in brines= increase pCO2 • Corals: • * Multi-stressor (temperature) • * Local effects (temperature, calcification) • Many of the processesare not fully incorporated in projections due to small scale and difficulties representing them in models

23. References: Alin, S. R., R. A. Feely, A. G. Dickson, J. M. Hernandez-Ayon, L. W. Juranek, M. D. Ohman, and R. Goericke (2010), Predictive relationships for pH and carbonate saturation in the Southern California Current system using oxygen and temperature data, 2010 Fall Meeting AGU, San Francsco CA, 13-17 Dec, Abstract OS23A-1570. Borges, A. V., and N. Gypens (2010), Carbonate chemistry in the coastal zone responds more strongly to eutrophication than to ocean acidification, Limnol and Oceanogr., 55, 346-353. Cai, W.-J., et al. (2010), Decrease in the CO2 uptake capacity in an ice-free Arctic Ocean basin, Science, 1, DOI: 10.1126/science.1189338. Cai, W.-J., et al. (2011), Eutrophication-driven hypoxia and increasing atmospheric pCO2 enhance ocean acidification and denitrification, Proc Natl Acad Sci USA, In preparation. Doney, S. C., N. Mahowald, I. Lima, R. A. Feely, F. T. Mackenzie, J.-F. Lamarque, and P. J. Rasch (2007), Impact of anthropogenic atmospheric nitrogen and sulfur deposition on ocean acidification and the inorganic carbon system, Proc Natl Acad Sci USA, 104, doi 10.1073 pnas.0702218104. Gledhill, D. K., R. Wanninkhof, and C. M. Eakin (2009), Observing Ocean Acidification from Space, Oceanography, 22(4), 48-59. Jones, E. M., D. C. E. Bakker, H. J. Venables, M. J. Whitehouse, R. E. Korb, and A. J. Watson (2010), Rapid changes in surface water carbonate chemistry during Antarctic sea ice melt, Tellus Series B-Chemical and Physical Meteorology, 62(5), 621-635. Liu, K.-K., L. Atkinson, R. Quinones, and L. Talaue-McManus (Eds.) (2010), Carbon and nutrient fluxes in continental margins, Springer, Heidelberg. McNeil, B. I., A. Tagliabue, and C. Sweeney (2010), A multi‐decadal delay in the onset of corrosive acidified waters in the Ross Sea of Antarctica due to strong air‐sea CO2 disequilibrium, Geophys. Res. Lett., 37, L19607, doi:19610.11029/12010GL044597. Salisbury, J. E., and M. Green (2008), Episodic acidfication of coastal waters, EOS Trans., 89(50), 513-514. Shadwick, E. H., Thomas, H., Chierici, M., Else, B., Fransson, A., Michel, C., Miller, L.A., Mucci, A., Niemi, A., Papakyriakou, T.N. and Tremblay, J.-ﾉ (2011) (2011), Seasonal variability of the inorganic carbon system in the Amundsen Gulf region of the Southeastern Beaufort Sea Limnol and Oceanogr., 56(1), 303-322, doi:310.4319/lo.2011.4356.4311.0303. Shadwick, E. H., and H. Thomas (2011), Carbon Dioxide in the Coastal Ocean: A Case Study in the Scotian Shelf Region, in Ocean Year Book, edited, p. in press, Dalhousie University, Dalhousie NS Canada Steinacher, M., F. Joos, and T. L. Frolicher (2009), Box 5. Modeling Ocean Acidification in the Arctic Ocean, Oceanography, 22(4), 198-199. Sweeney, C. (2004), The annual cycle of surface CO2 and O2 in the Ross Sea: A model for gas exchange on the continental shelves of Antarctica, in Biogeochemistry of the Ross Sea, edited by G. R. DiTullio and R. B. Dunbar, pp. 295-312, AGU, Washington DC.

24. Extra slide The effect of sea-ice melt Jones, Bakker, et al. 2010