Announcements. What are the effects of anthropogenic CO 2 on the ocean? 12/7/2017. UN Commitment to plastics in the ocean

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1 Announcements UN Commitment to plastics in the ocean Today: Quiz on paper by Lee et al Climate change and OA Review for final exam (Tuesday 8 AM) Course evaluation What are the effects of anthropogenic CO 2 on the ocean? Changing CO 2 concentrations Effects on ocean temperature, salinity Stratification, reduction of mixing Ocean acidification 1

2 Average annual temperature ( C) 12/7/2017 CO 2 concentration on Mauna Loa, HI. Keeling curve Water temperature change Near Victoria, B.C. (~1 C) Year How does increased water temperature affect ocean productivity? Global ocean productivity declined over a decade due to increased stratification and reduced nutrient input to surface waters. Behrenfeld et al Nature Behrenfeld et al Nature 2

3 Net primary productivity anomaly and MEI Multivariate El Niño index Net primary productivity and stratification anomalies Behrenfeld et al Nature Heuristic model of climate change effects Doney 2006, Nature Effects of climate change on arctic ecosystems physical properties nanoplankton & bacterioplankton pigments & nitrate picoplankton Arctic now possesses mostly seasonal, not multi-year ice Observed changes in water-column properties and phytoplankton communities in the Canada Basin (Arctic Ocean). From Li et al. Science 2009 Terrestrial data from ice cores, tree rings, and lake sediments, that are correlated with ice extent indicate melting unprecedented in 1450 y (Kinnard et al. 2011, Nature) 3

4 Bottom-up and top-down effects Bering Sea zooplankton decline J. Napp / N. Shiga Fur Seal Pups at the Pribilof Is. Thousands of pups Fur seal pups, St. Paul Island, Mean pups Error bars = 95% CI Fur seal pups, St. George Island, Thousands of pups 75 Mean pups Error bars =95% CI Year NMML, NOAA Changes in sea ice and wave height along the coastline of the Beaufort Sea, Arctic Ocean (Overeem et al. 2011) 4

5 Effects of warming Decreased productivity in low latitudes due to increased stratification and reduced nutrient supply Increased productivity in high latitudes due to increased stratification and ice loss (light availability) Sea-level rise Changes in community structure Latitudinal shifts in species geographic ranges Shifts to smaller phytoplankton (reduced biological pump) Changes timing of organism reproductive cycles Food-web disruption Pacific Northwest waters are susceptible to OA Pacific Northwest waters are susceptible to OA Carbonate system in Bellingham Bay Low levels of ph and aragonite saturation found in Puget Sound and Hood Canal (Feely et al. 2010) Low ph primarily due to water column respiration. What about Bellingham Bay? Deep water in Bellingham Bay water has low ph! CO 2 + H 2 0 H 2 CO 3 H + + HCO 3-2H + + CO 3 2- DIC (dissolved inorganic carbon) = CO 2 + HCO 3- + CO 3 2- ph = -log{h + } Alkalinity = HCO CO H 2 BO HBO (others) + OH + - H + Aragonite saturation = Ω arg = [Ca 2+ ][CO 3 2- ] Ksp DIC and Alkalinity are conservative, the rest vary with seawater conditions Strategy: Make precise measurements of DIC and ph. Calculate the other components using chemical equilibrium models (CO2SYS). 5

6 Studying the carbonate system in Bellingham DIC and Alkalinity Samples collected by CTD-rosette at 4 sites DIC measured by NDIR ph measured by cresol purple light absorbance Respiration rates Sediment incubations Nooksack R samples WWTP data D C A B Lowest ph = 7.5 Lowest Ω arg = 0.5 D C D C B B A A 6

7 Oxygen consumption (µmol L -1 d -1 ) Oxygen consumption (µmol L -1 d -1 ) Water column respiration ( DIC, Alkalinity unchanged) D C Stn C Oxygen consumption (µmol L -1 d -1 ) Oxygen consumption (µmol L -1 d -1 ) DIC and Alkalinity sources to Bellingham Bay Sedimentary processes increase BOTH DIC and Alkalinity Change in DIC in incubated sediment cores Change in alkalinity in incubated sediment c B A Stn B DIC and Alkalinity sources to Bellingham Bay DIC and Alkalinity sources to Bellingham Bay 7

8 DIC and Alkalinity sources to Bellingham Bay Box model of northern Bellingham Bay ph Measured sources and Se lhaem sinks of DIC and buoy Alkalinity Calculated change in ph Photosynthesis and Ω arg in bottom water Outflow Questions: What processes create low ph bottom water? How will ph change in the future with increased atmospheric CO 2? Inflow Nooksack River Mixing Respiration Gas exchange Respiration Upwelling Sediment fluxe Box model of northern Bellingham Bay ph Measured sources and Se lhaem sinks of DIC and buoy Alkalinity Calculated change in ph Photosynthesis and Ω arg in bottom water Outflow Questions: What processes create low ph bottom water? How will ph change in the future with increased atmospheric CO 2? Inflow Nooksack River Mixing Respiration Gas exchange Respiration Upwelling Sediment fluxe 8

9 DIC (mm) Deep water salinity (psu) 12/7/2017 Box model geometry, measurements Nooksack R discharge Modeled changes in DIC, ph, Alkalinity and Ω arg DIC and Alkalinity increasing Apr 4- May-4 Surface water ph ph and aragonite saturation decreasing Apr 4-May-4 Modeled changes in DIC, ph, Alkalinity and Ω arg Slower estuarine circulation leads to increased DIC and decreased ph Deep-water water Salinity: salinity 2017 Modeled changes in DIC, ph, Alkalinity and Ω arg Water column respiration drives the decline in ph and aragonite saturation With respiration Without respiration With respiration Without respiration 9

10 Modeled changes in DIC, ph, Alkalinity and Ω arg How does ocean acidification affect ph in Bellingham Bay? Modeled changes in DIC, ph, Alkalinity and Ω arg Past changes in atmospheric CO 2 estimated to have reduced Bellingham Bay ph by ~0.1 (~25%) and Ω arg by ~0.2 Intergovernmental Panel on Climate Change scenarios Recalculate starting DIC using preindustrial CO 2 concentration and future projections CO 2 DIC DIC = CO 2 Revelle Factor Model evaluates expected ph, etc. in 2070, under business as usual scenario (RCP 8.5) van Vuuren, D.P. et al (2011) Modeled changes in DIC, ph, Alkalinity and Ω arg Future changes in atmospheric CO 2 predicted to reduce Bellingham Bay ph by ~0.15 (40%) and Ω arg by ~0.2 Corrosive water in Bellingham Bay Bottom water ph and Ω arg are low compared to elsewhere in Puget Sound Water column and sedimentary respiration drive declining ph Water column respiration increases DIC but not alkalinity Sedimentary processes supply BOTH DIC and alkalinity The rate of mean circulation in the bay (and thus bottom water residence time) also contributes to low ph. Reduced Nooksack R flow in summer (predicted by regional climate models) along with increasing atmospheric CO 2 will lead to future declines in bottom water ph and Ω arg 10

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