Ocean Acidification Lecture Images from Washington State Blue Ribbon Panel on Ocean Acidification Report, 2012 Hilary Palevsky palevsky@uw.edu

Absorbing CO2 changes ocean pH Gary Braasch Photography http://www.worldviewofglobalwarming.org Hawaii (Mauna Loa) South Pole Gary Braasch Photography http://www.worldviewofglobalwarming.org Hawaii (ALOHA) Bermuda (BATS) Canary Is. (ESTOC) This slide shows increasing atmospheric CO2 at Mauna Loa in Hawaii and at the South Pole (a), and that at the same time, CO2 in the ocean has been increasing and pH has been decreasing at the three locations where we have been measuring for a long time. The pictures on the right show the work that goes into collecting all the data in these graphs – the top two are of the atmospheric CO2 time series at Mauna Loa and the bottom picture is of a UW Oceanography undergraduate student measuring ocean pH in a lab on a research ship. ESTOC = Estación Europea de Series Temporales Oceánicas de Canarias BATS = Bermuda Atlantic Time Series ALOHA = A Long-term Oligotrophic Habitat Assessment (at HOT = Hawaii Ocean Time-series) IPCC AR5, Figure SPM.4

What is pH all about anyway? pH = -log[H+] Decrease in pH = increase in acidity Logarithmic scale A decrease of 1 unit is a 10× increase in [H+] A decrease of 0.1 unit (observed to date) is a 26% increase in [H+] Figure from WA State Blue Ribbon Panel on Ocean Acidification

Ocean carbonate chemistry CO2 dissolution in water: CO2 + H2O ↔ H2CO3 H2CO3 ↔ H+ + HCO3- HCO3- ↔ H + + CO32- Forming CaCO3 shells: Ca2+ + CO32- ↔ CaCO3 Ω = [Ca2+][CO32-]/Ksp When Ω < 1, water is undersaturated and CaCO3 will dissolve

Calcifying organisms Geoduck Blue mussel Pink calcifying algae Urchins Dungeness crab Juvenile king crab Examples of Puget Sound organisms that build shells, skeletons or other hard parts from CaCO3 Images from Washington State Blue Ribbon Panel on Ocean Acidification Report, 2012

Pteropods: OA poster child Zooplankton, swimming snail Food for young salmon Shells dissolve in low pH waters Observed dissolution in situ in Southern Ocean (Bednaršek et al., 2012) Images from Washington State Blue Ribbon Panel on Ocean Acidification Report, 2012 Pteropods dissolve in water with pH and carbonate chemistry expected for 2100

OA in the California Current System This figure is from a paper that uses a model to show how pH and the aragonite saturation state off the west coast of the US have changed over the industrial period and are projected to change in the future. Caption from Gruber et al. 2012: Temporal evolution of ocean acidification in the California CS from 1750 until 2050 for the A2 scenario. (A to C) Maps illustrating the evolution of annual mean surface pH, showing the decrease in pH for 1750, 2005 and 2050. (D to F) Offshore depth sections depicting the general decrease of the annual mean saturation state of seawater with regard to aragonite and the shoaling of the saturation depth (i.e. omega_arag = 1) for the same three years. The white lines in (A) to © indicate the position of the offshore section. Gruber et al., 2012

OA in the California Current System Feely et al., 2008 These data are from real measurements made off the west coast of the US. Upwelling along the coast brings up cold waters that have low pH and high dissolved inorganic carbon and CO2, which brings water that is undersaturated with respect to aragonite close to the surface.

Impact on oyster hatcheries in the Pacific Northwest Taylor Shellfish Hatchery, Dabob Bay, WA Whiskey Creek Hatchery, Netarts Bay, OR Barton et al., 2012 WA Blue Ribbon Panel Report

Future projections IPCC AR5 SPM.7 RCP 8.5 (high future emissions) RCP 2.6 (low future emissions) IPCC AR5 SPM.8