Maury Project Ocean Acidification 17 JUL 2017 Image Credit: NOAA NOS (http://oceanservice.noaa.gov/oceans/ohh/#1)

Today’s Objectives Review CO2 levels as a Greenhouse Gas to include its sources, sinks, atmospheric lifetime, and relative importance to radiative forcing Relate increasing atmospheric CO2 levels to Ocean pH. Discuss sources, sinks, rates, and transport pathways in the global carbon cycle and the relative timescales in for carbon cycling. Discuss anthropogenic alterations to the Global Carbon cycle to include deviations from steady-state. List the four major species of dissolved inorganic carbon in seawater that make up total dissolved organic carbon [SCO2]. Understand the thermal equilibrium reactions between [CO2], [H2CO3], [HCO3-], and [CO32-], in seawater. Know the relationship between [H+] and pH and the typical range for pH in seawater. Discuss how photosynthesis and respiration influence the pH of seawater. Differentiate between the lysocline and the calcium carbonate compensation depth (CCD).

Today’s Objectives List the four major species of dissolved inorganic carbon in seawater that make up total dissolved organic carbon [SCO2]. Understand the thermal equilibrium reactions between [CO2], [H2CO3], [HCO3-], and [CO32-], in seawater. Know the relationship between [H+] and pH and the typical range for pH in seawater. Discuss how photosynthesis and respiration influence the pH of seawater. Differentiate between the lysocline and the calcium carbonate compensation depth (CCD).

Today’s Objectives Know the relationship between solubility of calcium carbonate, shell formation and dissolution and pH. Define alkalinity, total alkalinity (TA), and carbonate alkalinity (CA). Write the major equilibrium reactions that influence the aqueous carbonate system. Mathematically relate CA, [SCO2], [HCO3-], [CO32-], [H+] and pH in seawater. Understand how photosynthesis, respiration, shell formation and shell dissolution affect [SCO2] and alkalinity in seawater. Discuss ocean acidification, its scale, and the potential impacts on marine organisms.

Weather vs. Climate Weather – State of the atmosphere at a given point in time and space (short temporal/small spatial scale) Climate - Long-term statistically averaged weather conditions for a defined spatial scale (regional or global) Long term defined by WMO as ≥ 30 years Includes variability and extremes Climate in a wider sense is the state, including a statistical description, of the climate system – IPCC (2007)

Does not require contact or a material medium Energy Transfer Conduction: Transfer of energy from one atom or molecule to another when they are in direct contact…vibrations or electrons Convection: Transfer of energy through fluid motion Radiation: Transfer of energy by the emission of electromagnetic waves Does not require contact or a material medium

Electromagnetic Spectrum E = hc/l = hu → c = lu E = Energy (J) h = Plank’s Constant (6.626 x 10-34 J-sec) c = velocity of light (2.998 x 108 m/sec) = frequency (1/sec) l = wavelength (m) All matter above Absolute Zero (0 K or -273°C) radiates energy

Radiation Laws 𝑭 𝑺𝑼𝑵 = 𝝈 × 𝑻 𝑺𝑼𝑹𝑭−𝑺𝑼𝑵 𝟒 = 6.3 x 107 W/m2 Blackbody – Object that emits/absorbs EM radiation at 100% efficiency From Plank’s Law it follows that the energy emitted by a blackbody is proportional to the fourth power of the body’s absolute temperature (Stefan-Boltzmann Law): 𝑭 𝑺𝑼𝑵 = 𝝈 × 𝑻 𝑺𝑼𝑹𝑭−𝑺𝑼𝑵 𝟒 = 6.3 x 107 W/m2 Where: 𝑭 𝑺𝑼𝑵 =Average flux of radiative energy from the sun W m 2 𝝈=5.670 x 10 −8 W K 4 ∙m 2 (Stefan−Boltzmann Constant) 𝑻 𝑺𝑼𝑹𝑭−𝑺𝑼𝑵 =5780 K ~6000K = Avereage surface temperature of the Sun K Graybody F = esT4 e = Emissivity (% energy radiated relative to a blackbody) From Plank’s Law it follows that the wavelength at which a blackbody emits most strongly is inversely proportional to the absolute temperature (Wien Displacement Law): 𝝀 𝒎−𝑺𝒖𝒏 = 𝜶 𝑻 𝑺𝑼𝑹𝑭−𝑺𝑼𝑵 = 0.5 x 10-6 m = 0.5 mm (visible light) Where: 𝝀 𝒎−𝑺𝒖𝒏 = Wavelength of peak emission m 𝜶=2.898 x 10 −3 m∙K (Wien Displacement Constant)

Irradiance - Solar Constant Irradiance - amount of electromagnetic energy incident on a surface perpendicular to the incoming radiation at the top of the atmosphere Mars Inverse Square Law - radiation from a (point) source decreases as a function of 1/distance2 𝑺 𝑬𝑨𝑹𝑻𝑯 = 𝑭 𝑺𝑼𝑵 × 𝟒 ×𝝅 × 𝑹 𝑺𝑼𝑵 𝟐 ) (𝟒 ×𝝅 × 𝒓 𝑬𝑨𝑹𝑻𝑯 𝟐 Where: 𝑺 𝑬𝑨𝑹𝑻𝑯 =Mean annual irradiance Solar Constant reaching a plane perpendicular to the top of the Eart h ′ s atmosphere ( W m 2 ) 𝟒 ×𝝅 × 𝑹 𝑺𝑼𝑵 𝟐 =Surface Area of the solar sphere m 2 𝟒 ×𝝅 × 𝒓 𝑬𝑨𝑹𝑻𝑯 𝟐 =Surface Area of the Earth ′ s orbital sphere m 2 → 𝑺 𝑬𝑨𝑹𝑻𝑯 = 𝑭 𝑺𝑼𝑵 × 𝑹 𝑺𝑼𝑵 𝟐 ) ( 𝒓 𝑬𝑨𝑹𝑻𝑯 𝟐 𝑺 𝑬𝑨𝑹𝑻𝑯 ~ 1360 - 1370 W/m2 = SOLAR CONSTANT SUN RSUN = 6.96 x 108 m rEarth = 1.5 x 1011m Earth 2.25 x 1011m rMars = SMARS = 𝑭 𝑺𝑼𝑵 × 𝑹 𝑺𝑼𝑵 𝟐 ) ( 𝒓 𝑴𝑨𝑹𝑺 𝟐 SMARS ~ 450 - 600 W/m2 𝑺𝑾 𝑰𝑵↓ = 𝑺 𝑬𝑨𝑹𝑻𝑯 𝟒 = (𝟏𝟑𝟔𝟖 𝑾 𝒎 𝟐 𝟒) ~ 𝟑𝟒𝟐 𝑾 𝒎 𝟐

Incoming Solar Radiation

Earth’s Atmosphere Pressure (millibars) Altitude (km) Temperature (°C) Mesopause Stratopause Tropopause -100 100 10 20 30 40 50 60 70 80 90 110 120 1000 1 0.1 0.01 0.001 0.0001 0.00001 Altitude (km) Pressure (millibars) Temperature (°C) THERMOSPHERE MESOSPHERE STRATOSPHERE TROPOSPHERE Streete, 1991 r Warm (less dense air) below cold (more dense) air = convection… THIS IS WHERE/WHY WEATHER HAPPENS

Radiation and the Earth’s Atmosphere Reflection - Energy is redirected with no loss (shortwave)* Scattering – Energy is diffused randomly (shortwave) Absorption – Energy is retained and converted (shortwave and longwave) Transmission – Energy passes through (shortwave and longwave)

Incoming (Shortwave) Solar Radiation - Absorption by Stratospheric Ozone (O3) Absorption – Energy is retained and converted Natural Ozone production/destruction in the Stratosphere (Chapman Cycle) absorbs incoming short-wave radiation (200-310 nm, (900 nm))

Incoming (Shortwave) Solar Radiation - Scattering Gases, small particles and/or aerosols randomly diffuse incident radiation in different directions Function of wavelength of incoming radiation and radius of scattering particle Shorter wavelengths scatter more readily than longer wavelengths Three types of scattering: Raleigh Scattering Gas molecules, dust Mie Scattering Larger particles, aerosols Non-Selective Scattering Water Droplets → SWIN ↓= (SW + sw)↓; where SW = direct, sw = diffuse/scattered

Incoming (Shortwave) Solar Radiation – Absorption by Water Vapor Atmospheric Water Vapor (H2O) absorbs shortwave radiation in the near IR band Streete, 1991 Pidwirny, M. (2006). "Physical Properties of Water". Fundamentals of Physical Geography, 2nd Edition. Date Viewed: 11JAN11. http://www.physicalgeography.net/fundamentals/8a.html

Albedo Albedo (a) is amount of incident radiation that is reflected by a surface 10-80%

Type of Surface Albedo Tropical forest 0.10-0.15 Woodland 0.15-0.20 deciduous 0.15-0.20 coniferous 0.05-0.15 Farmland/natural grassland 0.16-0.26 Bare Soil 0.05-0.40 Semi-desert/stony desert 0.20-0.30 Sandy desert 0.30-0.45 Tundra 0.18-0.25 Water (0-60 deg) < 0.08 Water (60-90 deg) 0.10-1.0 Fresh snow/snow-covered permanent snow 0.80-0.95 Snow-covered ice 0.75-0.85 Sea ice 0.25-0.60 Snow-covered evergreen forest 0.20-0.60 snow-covered deciduous forest 0.25-0.50 Snow-covered farmland/natural grassland 0.55-0.85 Clouds low 0.60-0.70 middle 0.40-0.60 high (cirrus) 0.18-0.24 cumuliform 0.65-0.75 Burroughs, CH. 2, p. 28, Table 2.1: The proportion of sunlight reflected by different surfaces (albedo)

Clouds and Feedback Cloud Forcing/Feedback is a Function of: Type/Altitude Thickness/Optical Depth Water Vapor Content

Incoming (Shortwave) Solar Radiation Budget SUN Vis Space UV, Vis, IR Earth’s surface and clouds reflect some Vis = albedo ~ 31% total O3 Production and destruction of stratospheric ozone absorbs UV Vis, IR H2O Vis Water Vapor absorbs near-IR and vibrates and rotates = heating Gas, dust, water droplets, etc. scatter some Vis Vis (IR) Earth’s Surface absorbs remaining Vis 𝑺𝑾 𝑵𝑬𝑻↓ = 𝑺𝑾 𝑰𝑵↓ − 𝑺𝑾 𝑹𝑬𝑭𝑳𝑬𝑪𝑻↑ 𝑺𝑾 𝑹𝑬𝑭𝑳𝑬𝑪𝑻↑ = 𝑺𝑾 𝑰𝑵↓ ×𝒂 → 𝑺𝑾 𝑵𝑬𝑻↓ = 𝑺𝑾 𝑰𝑵↓ − 𝑺𝑾 𝑰𝑵↓ ×𝒂 → 𝑺𝑾 𝑵𝑬𝑻↓ = 𝑺𝑾 𝑰𝑵↓ × 𝟏−𝒂 𝑺𝑾 𝑵𝑬𝑻↓ = 𝑺𝑾 𝑨𝑩𝑺−𝑺𝑼𝑹𝑭↓ + 𝑺𝑾 𝑨𝑩𝑺−𝑨𝑻𝑴↓

Actual TEARTH (avg.) = 288K = 15°C Earth as a Blackbody Assume all incoming solar radiation reaches the Earth’s surface and the Earth re-radiates it a Blackbody with no atmosphere: Use Stefan-Boltzmann Law to Solve for Earth’s Effective Surface Temperature: SWIN↓ = LWOUT↑ = 𝝈 × 𝑻 𝑺𝑼𝑹𝑭−𝑬𝑨𝑹𝑻𝑯 𝟒 SWIN↓ = mean annual incoming shortwave solar radiation flux to the Earth system ( W m 2 ) LWOUT↑ = mean annual outgoing longwave solar radiation flux leaving the surface of the Earth ( W m 2 ) = 5.670 x 10-8 Wm-2K-4 𝑻 𝑺𝑼𝑹𝑭−𝑬𝑨𝑹𝑻𝑯 = Effective surface temperature of Blackbody Earth without albedo (ºC) TEARTH = 279K = 6 °C Actual TEARTH (avg.) = 288K = 15°C

Earth as a Blackbody with Albedo Actual 𝑻 𝑺𝑼𝑹𝑭−𝑬𝑨𝑹𝑻𝑯 ~ 288K (~ 15°C) Assume incoming solar radiation reaches the Earth, 30% is reflected by the Earth’s albedo, and the rest reaches the surface and the Earth re-radiates it a Blackbody with no atmosphere: Use Stefan-Boltzmann Law to Solve for Earth’s Effective Surface Temperature: 𝑺𝑾 𝑵𝑬𝑻↓ = 𝑺𝑾 𝑰𝑵↓ × 𝟏−𝒂 = 𝑳𝑾 𝑶𝑼𝑻↑ = 𝝈 × 𝑻 𝑺𝑼𝑹𝑭−𝑬𝑨𝑹𝑻𝑯 𝟒 Where: SWIN↓ = mean annual incoming shortwave solar radiation flux to the Earth system ( W m 2 ) SWNET↓ = mean annual net incoming shortwave solar radiation flux to the surface of the Earth ( W m 2 ) LWOUT↑ = mean annual outgoing longwave solar radiation flux leaving the surface of the Earth ( W m 2 ) = 5.670 x 10-8 Wm-2K-4 a = Earth’s Average Albedo = 31% 𝑻 𝑺𝑼𝑹𝑭−𝑬𝑨𝑹𝑻𝑯 = Effective surface temperature of Blackbody Earth with albedo (ºC) 𝑻 𝑺𝑼𝑹𝑭−𝑬𝑨𝑹𝑻𝑯 = 254K = -18 °C Actual 𝑻 𝑺𝑼𝑹𝑭−𝑬𝑨𝑹𝑻𝑯 ~ 288K (~ 15°C) → GREENHOUSE EFFECT (natural) +33°C!!!

Terrestrial Radiation Assume Earth radiates as a Blackbody Use Wien Displacement Law to Solve for wavelengths at which the Sun and the Earth emit most strongly: lmax-EARTH = a/TEARTH lmax-EARTH = Wavelength of maximum energy emission for the Earth (m) a = 2.898 x 10-3 mK TEARTH = 288K = Average Surface Temperature of the Earth (K) lmax-EARTH = 10 x 10-6 m = 10 mm (IR) Earth re-emits absorbed (shortwave) solar radiation as IR (longwave) radiation

Solar and Earth Radiation

Outgoing (Longwave) Radiation from the Earth – Thermals, Evapotranspiration Some of the incoming (shortwave) radiation absorbed by the Earth is used to: Generate thermals – atmospheric convection Evapotranspiration Remaining energy is re-emitted towards space as IR (longwave) radiation = HEAT

Outgoing (Longwave) Radiation from the Earth – The “Greenhouse Effect” Absorption – Energy is retained and converted Greenhouse Gases (GHGs) absorb outgoing longwave radiation at discreet energies and vibrate and rotate → heat the troposphere: CO2, H2O, CH4, N2O, CFCs, (O3*) Water vapor is the most important GHG in the Earth’s Atmosphere: High Relative Concentration Highly Variable Absorbs at Multiple Wavelengths Streete, 1991

Image created by Robert A. Rohde / Global Warming Art

Outgoing (Longwave) Earth Radiation Budget LWNET↑ = LWTW↑ + LWABS-SPACE↑ IR radiation not absorbed by atmosphere escapes into space = transmittance window (TW) Some absorbed IR radiation emitted into space by the atmosphere SWNET↓ IR IR Tropopause Some energy used CO2 H2O CH4 N2O CFC’s H2O Thermals Evapotranspiration GHG and Water Vapor in Clouds absorbs IR, vibrates and rotates = heating; back radiated towards Earth IR Earth surface re-emits remaining energy as IR radiation IR

Earth’s Radiation Balance SW= Shortwave Solar Radiation Flux LW= Longwave Radiation Flux from the Earth SWIN↓ LW SW LW LW SW QNET = SWNET↓ + LWNET↑ @ Steady-State, QNET = 0 → 0 W/m2 = 235 W/m2 + - 235 W/m2 SW SW LW Tropopause Scattering not shown… LW SW LW SW LW LW LW LW The mean annual radiant energy and heat balance of the Earth. From Fig 1.3, IPCC AR 2 WG 1, 1995; Houghton et al., 1996; Kiehl and Trenberth (1996).

Solar and Terrestrial Radiation Statement of Steady-State… Energy In = Energy Out SWNET↓ + LWNET↑ = 0 = QNET But what happens if not Steady-State?... Energy In ≠ Energy Out SWNET↓ + LWNET↑ ≠ 0 = ∆QNET → Change in net radiation below the tropopause = Radiative Forcing (RF) Annual Storage Rate (est.) Last 100 Years = 0.5 – 1.5 W/m2

Earth’s Mean Annual Radiation Budget - Revisited Hartmann, D.L., A.M.G. Klein Tank, M. Rusticucci, L.V. Alexander, S. Brönnimann, Y. Charabi, F.J. Dentener, E.J. Dlugokencky, D.R. Easterling, A. Kaplan, B.J. Soden, P.W. Thorne, M. Wild and P.M. Zhai, 2013: Observations: Atmosphere and Surface. In: Climate Change 2013: The Physical Science Basis. Contribution of Working Group I to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change [Stocker, T.F., D. Qin, G.-K. Plattner, M. Tignor, S.K. Allen, J. Boschung, A. Nauels, Y. Xia, V. Bex and P.M. Midgley (eds.)]. Cambridge University Press, Cambridge, United Kingdom and New York, NY, USA, pp. 159–254, doi:10.1017/CBO9781107415324.008. Hartmann, et al., IPCC AR5 WG1, 2013, Climate Change 2013: The Physical Science Basis, CH2, Fig. 2.11

The Radiative Forcing Concept (RF) Radiative Forcing (RF) = change in net energy (flux) at the Earth’s tropopause (DQNET) caused by a change imposed on the Earth’s Climate System; causes Climate Response, or change in the equilibrium condition of the Earth’s Climate System (i.e. DTSURF). According to the RF Concept, RF (+/- DQNET) can be related to a change in Earth’s Surface Temperature (+/- DTSURF) by the following equation: DTSURF = RF x l; Where, l = climate sensitivity parameter Strengths: Convenient first order measure of relative climatic importance of different climate forcing agents Computationally efficient/simple Relatively accurate Weaknesses: Assumes linearity of different forcing factors Does not handle climate system complexity well (i.e. feedback) Does not include climate parameters other than temperature Applies to global scale; not regional or less IPCC SAR, 1996; Ramaswamy et al., 2001; IPCC AR4 WG1 CH2, 2007.

(Indirect effects as well…i.e. stratospheric H2O from CH4) IPCC AR5 WG1 SPM, Fig. SPM5 Volcanic Eruptions? Contrails? Hartmann, D.L., A.M.G. Klein Tank, M. Rusticucci, L.V. Alexander, S. Brönnimann, Y. Charabi, F.J. Dentener, E.J. Dlugokencky, D.R. Easterling, A. Kaplan, B.J. Soden, P.W. Thorne, M. Wild and P.M. Zhai, 2013: Observations: Atmosphere and Surface. In: Climate Change 2013: The Physical Science Basis. Contribution of Working Group I to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change [Stocker, T.F., D. Qin, G.-K. Plattner, M. Tignor, S.K. Allen, J. Boschung, A. Nauels, Y. Xia, V. Bex and P.M. Midgley (eds.)]. Cambridge University Press, Cambridge, United Kingdom and New York, NY, USA, pp. 159–254, doi:10.1017/CBO9781107415324.008. Changes in RF Factors (i.e. fossil fuel burning, deforestation) cause changes in RF Terms or Agents (LL-GHG’s, albedo) which has a direct effect on RF → Climate Response (Indirect effects as well…i.e. stratospheric H2O from CH4)

Atmospheric Greenhouse Gases Increase in GR 2007–Present? Growth Rate (GR) of CO2: 1.66 ppm/yr since 1978 GR of CO2: 1.43 ppm/yr ’78-’95 1.91 ppm/yr 1995-Present GR of N2O 0.7 ppb/yr since 1978 GR of CH4: Decline in GR 1983-1999 → Steady-State 1999-2007 Increase in GR 2007–Present? GR of CFCs: Constant GR 1978-1987 Decreasing GR 1987-2000 Negative RG 2000-Present Figure 2. Global average abundances of the major, well-mixed, long-lived greenhouse gases - carbon dioxide, methane, nitrous oxide, CFC-12 and CFC-11 - from the NOAA global air sampling network are plotted since the beginning of 1979. These gases account for about 96% of the direct radiative forcing by long-lived greenhouse gases since 1750. The remaining 4% is contributed by an assortment of 15 minor halogenated gases (http://www.esrl.noaa.gov/gmd/aggi/)..

Effective “Atmospheric Lifetime” Time for Anthropogenic GHGs IPCC 2007 AR4 FAQ Effective Atmospheric Lifetime of a gas in the atmosphere is defined as the time it takes for a perturbation to be reduced to 37% of its initial amount = Time for an instantaeous pulse input to the atmosphere to decay to 0.368 of its original value. For CO2 the specification of an atmospheric lifetime is complicated by the numerous removal processes involved → complex modeling of the decay curve. Accepted values ~ 100 years. Amounts of an instantaneous injection of CO2 remaining after 20, 100, and 500 years, used in the calculation of the Global Warming Potentials (GWPs) in IPCC (2007) AR 4.

Perturbed Global Biogeochemical Cycle Hartmann, et al., IPCC AR5 WG1, 2013, Climate Change 2013: The Physical Science Basis, CH6, Fig. 6.2

Closed Loop Perturbed Global CO2 Cycle Timescales Matter!!! Hartmann, et al., IPCC AR5 WG1, 2013, Climate Change 2013: The Physical Science Basis, CH6, Fig. 6.1

Cycling of Carbon Dioxide Short-Term (100–102 yrs): Photosynthesis - Removes CO2 from the Atmosphere Respiration - Releases CO2 back into the Environment Fossil Fuel Combustion, Deforestation - Releases CO2 back into the Atmosphere Medium-Term (102–106 yrs): Photosynthesis/ Organic Carbon Burial, Sequestration in lithosphere and deep ocean - Removes CO2 from the Atmosphere MacKenzie,F.T. (2003) Long-Term (106+ years): Rock Weathering - Removes CO2 from the Atmosphere Marine Plankton Shell Formation, Plate Tectonics and Volcanoes - Releases CO2 back into the Environment Hartmann, et al., IPCC AR5 WG1, 2013, Climate Change 2013: The Physical Science Basis, CH6, Fig. FAQ6 2-1

Effective “Atmospheric Lifetime” Time for Anthropogenic GHGs IPCC TAR Table 1: Examples of greenhouse gases that are affected by human activities. [Based upon Chapter 3 and Table 4.1]   CO2 (Carbon Dioxide) CH4 (Methane) N2O (Nitrous Oxide) CFC-11 (Chlorofluoro-carbon-11) HFC-23 (Hydrofluoro-carbon-23) CF4 (Perfluoro-methane) Pre-industrial concentration about 280 ppm about 700 ppb about 270 ppb 40 ppt Concentration in 1998 365 ppm 1745 ppb 314 ppb 268 ppt 14 ppt 80 ppt Rate of concentration change b 1.5 ppm/yr a 7.0 ppb/yr a 0.8 ppb/yr -1.4 ppt/yr 0.55 ppt/yr 1 ppt/yr Atmospheric lifetime 5 to 200 yr c 12 yr d 114 yr d 45 yr 260 yr >50,000 yr a Rate has fluctuated between 0.9 ppm/yr and 2.8 ppm/yr for CO2 and between 0 and 13 ppb/yr for CH4 over the period 1990 to 1999. b Rate is calculated over the period 1990 to 1999. c No single lifetime can be defined for CO2 because of the different rates of uptake by different removal processes. d This lifetime has been defined as an "adjustment time" that takes into account the indirect effect of the gas on its own residence time.

Mean annual atmospheric carbon dioxide growth rate at Mauna Loa Observatory, Hawaii (http://www.esrl.noaa.gov/gmd/ccgg/trends/#mlo_full)

Global Carbon Emissions Total Global Carbon Emissions ~ 7.8 Gt-C/yr http://www.ucsusa.org/global_warming/science_and_impacts/science/each-countrys-share-of-co2.html#.V868rvkrK70

Atmospheric GHGs – CO2 Hartmann, et al., IPCC AR5 WG1, 2013, Climate Change 2013: The Physical Science Basis, CH6, Fig. 6.8

Atmospheric Radiocarbon (14C) Exponential Decrease Over Time is Result of: Radioactive Decay of “Bomb Pulse” Equilibration w/ Land and Ocean Sink Input of Radiocarbon “Dead” Carbon from Fossil Fuel Burning http://cdiac.esd.ornl.gov/trends/co2/cent-scha.html

Atmospheric Stable Carbon Isotopes (d13C) Decreasing trend of -0.02‰/year in d13C towards more negative values indicative of inputs from fossil fuel burning Allison, C.E., R.J. Francey and P.B. Krummel. δ13C in CO2 from sites in the CSIRO Atmospheric Research GASLAB air sampling network, (April 2003 version). In Trends: A Compendium of Data on Global Change, Carbon Dioxide Information Analysis Center, Oak Ridge National Laboratory, U.S. Department of Energy, Oak Ridge, TN, U.S.A. http://cdiac.esd.ornl.gov/trends/co2/allison-csiro/allcsiro-mlo.html

Mean annual atmospheric carbon dioxide growth rate at Mauna Loa Observatory, Hawaii (http://www.esrl.noaa.gov/gmd/ccgg/trends/#mlo_full)

Hartmann, et al., IPCC AR5 WG1, 2013, Climate Change 2013: The Physical Science Basis, CH6, Fig. 6.8

Figure SPM.4 Multiple observed indicators of a changing global carbon cycle All Figures © IPCC 2013 Figure SPM.4 | (b) partial pressure of dissolved CO2 at the ocean surface (blue curves) and in situ pH (green curves), a measure of the acidity of ocean water. Measurements are from three stations from the Atlantic (29°10’N, 15°30’W – dark blue/dark green; 31°40’N, 64°10’W – blue/green) and the Pacific Oceans (22°45’N, 158°00’W − light blue/light green). Full details of the datasets shown here are provided in the underlying report and the Technical Summary Supplementary Material. {Figures 2.1 and 3.18; Figure TS.5}

Dissolved Gases ↔ N2 > O2 > Ar > CO2 atmosphere N2 > O2 > Ar > CO2 Air-Sea Interface ↔ CO2, HCO3-, CO32- > N2 > O2 > Ar ocean

Dissolved Gases ↔ CO2 Air-Sea Interface CO2(gas) + H2O ↔ H2CO3(aq) ↕ atmosphere CO2 Air-Sea Interface ↔ CO2(gas) + H2O ↔ H2CO3(aq) ocean ↕ H+(aq) + HCO3- ↕ 2H+(aq) + CO32–(aq)

Forms of Inorganic Carbon in Seawater CO2(gas) + H2O ↔ H2CO3(aq) ↔ H+(aq) + HCO3- ↔ 2H+(aq) + CO32–(aq) Carbon is found in many forms in seawater: Dissolved CO2 gas (very little) H2CO3(aq) (very little) HCO3-(aq) CO32-(aq) Together these make up: total dissolved inorganic carbon [CO2] = [HCO3-] + [CO32-] [CO2(g)] + [H2CO3] +

Dissolved Gases – CO2 Solubility of CO2 >> Solubility of O2, N2, Ar CO2(gas) + H2O ↔ H2CO3(aq) ↔ H+(aq) + HCO3- ↔ 2H+(aq) + CO32–(aq) Solubility coefficient:  with temperature  with salinity  with pressure As temperature, more CO2(gas) goes into solution Below thermocline, temperature constant; pressure controls CO2(gas) solubility As pressure, more CO2(gas) goes into solution According to Le Chatlier’s Principle, more CO2(gas) shifts equilibrium to produce more HCO3-(aq) and CO32–(aq) Very little CO2(gas) Mostly HCO3-(aq) and CO32–(aq)

CO2 with Depth SW, CH6, p. 114, Fig. 6.14a

pH of Seawater and the Aqueous Carbonate System SW, CH6, p. 114, Fig. 6.14b

pH of Seawater and the Aqueous Carbonate System Stabilizes the pH of seawater Seawater average pH ~ 7.7; range 7.2 - 8.4 We can use the change in [HCO3-]/[CO32-] to determine an increase or decrease in pH: HCO3- ↔ H+(aq) + CO32–(aq) K = ([H+]·[CO32-])/([HCO3-]) Where: K = 1* 10-9 mol/L → [H+] = K·([HCO3-] / [CO32-] ) pH= -log [H+]

Photosynthesis/Respiration and the pH of Seawater CO2(gas) + H2O ↔ H2CO3(aq) ↔ H+(aq) + HCO3- ↔ 2H+(aq) + CO32–(aq) Surface waters in equilibrium with atm. Are slightly alkaline, pH = 8.1-8.3 pH may rise through rapid extraction of CO2 during photosynthesis (~ 8.4+) Below the photic zone, net release of CO2 thru respiration, pH falls to avg. values ~ 7.7-7.8 Can fall as low as 7.5 in anoxic conditions (sulphate reduction) Can rise as high as 12 in anoxic conditions (CO2 reduction) Photosynthesis → CO2 (gas) + H2O + (g energy + nutrients) → (CH2O)n + O2 (gas) ← Respiration CO2 (gas) + H2O + (thermal energy + nutrients) ← (CH2O)n + O2 (gas)

The Role of CaCO3 in Buffering Seawater CaCO3(s) ↔ Ca2+(aq) + CO32-(aq) Surface Waters are Supersaturated with respect to calcium carbonate but spontaneous precipitation is infrequent due to inhibition from Mg2+ Shell Formation/Dissolution Ca2+(aq) + 2HCO3-(aq)  CaCO3(s) + CO2 + H2O Calcium + Bicarbonate  Calcium Carbonate + Carbon Dioxide + Water CaCO3(s) + H+ (aq)  Ca2+(aq) + 2HCO3-(aq) CaCO3(s) = Calcite and Aragonite; Aragonite dissolves more easily

Carbonate Compensation Depth Ca2+ Extracted by Marine Organisms to Form CaCO3 Tests (Shells) - 1000 m Sinking Skeletal Remains of Marine Organisms Sediments - 2000 m Calcareous (CaCO3) ooze Depth at which significant dissolution of CaCO3 begins = LYSOCLINE - 3000 m - 4000 m Depth at which most or all of the CaCO3 has dissolved = CCD - 5000 m Siliceous (SiO2) ooze

Factors Affecting CaCO3 Solubility Factors affecting calcium carbonate solubility: Temperature Pressure [CO2] [CaCO3] Particle size Flux

CCD DEPTHS Atlantic = ~ 5km Pacific = ~ 4,200-4,500 m Why so different? http://geology.uprm.edu/Morelock/dpseabiogenic.htm

CO2(gas) + H2O ↔ H2CO3(aq) ↔ H+(aq) + HCO3- Basic Equations/Equilibrium Reactions of the Aqueous Carbonate System that Influence Seawater pH and Alkalinity CO2(gas) + H2O ↔ H2CO3(aq) ↔ H+(aq) + HCO3- ↔ 2H+(aq) + CO32–(aq) Carbon Dioxide + Water ↔ Carbonic Acid ↔ Hydrogen Ion + Bicarbonate ↔ Hydrogen Ion + Carbonate Ca2+(aq) + 2HCO3-(aq)  CaCO3(s) + CO2 + H2O Calcium + Bicarbonate  Calcium Carbonate + Carbon Dioxide + Water CaCO3(s) + H+ (aq)  Ca2+(aq) + 2HCO3-(aq) Calcium Carbonate + Hydrogen Ion  Calcium Ion + Bicarbonate CaCO3 Shell Formation → CaCO3 Shell Dissolution → Photosynthesis → CO2 (gas) + H2O + (g energy + nutrients) → (CH2O)n + O2 (gas) ← Respiration CO2 (gas) + H2O + (thermal energy + nutrients) ← (CH2O)n + O2 (gas)

Total for either equation yields a value ≈ 2 mol/m3 Total Alkalinity The amount of acid required to neutralize all negative charges in seawater is the Alkalinity (capacity to resist change in pH). Total Alkalinity (TA) - net molar concentration in ‘charge equivalents’ of the cations of strong bases in excess of the net molar concentration in ‘charge equivalents’ of the anions of strong acids in solution: TA = [cations of strong bases] - [anions of strong acids] = ([Na+] + [K+] + 2[Mg2+] + 2[Ca2+]) - ([Cl-] + 2[SO42-] + [Br-]) Or, in terms of conjugate pairs of weak acids and weak bases: TA = 2[CO32-] + [HCO3-] + [OH-] + [B(OH)4-] + [HPO42-] + 2[PO43-] + [H3SiO4-] + [NH3] + [HS-] + [NH3] + …- [H+] - [HSO4-] - [HF] - [H3] - … Total for either equation yields a value ≈ 2 mol/m3 ≈ 2[CO32-] + [HCO3-]

The Aqueous CO2/CaCO3 System Shell Dissolution H +(aq) + CaCO3(s) HCO3-(aq) + Ca2+(aq)

Carbonate Alkalinity CA = 2[CO32-] + [HCO3-] The carbonate (CO32-) and bicarbonate (HCO3-) ion concentrations are much higher in seawater than the other carbon species, so we can approximate alkalinity by just using bicarbonate and carbonate ions: Carbonate Alkalinity (CA) = the total amount of hydrogen ions required to neutralize the negative charges of the carbonate and bicarbonate ions = the combined molar concentration of carbonate and bicarbonate ions, expressed in ‘charge-equivalent’ terms. CA = 2[CO32-] + [HCO3-]

CO2+ H2O  H2CO3  HCO3- + H+  CO32- + 2H+ Carbonate Alkalinity The dissolution of calcium carbonate depends on [CO32-] which can be measured indirectly through the measure of [CO2] and alkalinity. Measured by titrating to find out how much H+ it takes to neutralize a solution CO2+ H2O  H2CO3  HCO3- + H+  CO32- + 2H+

CO2 , Alkalinity, and pH 5. pH= -log [H+] 1. Carbonate Alkalinity (A or CA) = [HCO3-] + 2[CO32- ] 2. [CO2 ] = [CO2] + [H2CO3] + [HCO3-] + [CO32- ]; [CO2] + [H2CO3] << [HCO3-] + [CO32-] → [CO2 ] ~ [HCO3-] + [CO32- ] 3. A - [CO2 ] = [HCO3-] + 2[CO32-] - [HCO3-] - [CO32-] = [CO32-] 4. HCO3- ↔ H+(aq) + CO32-(aq) K = ([H+]·[CO32-])/([HCO3-]) Where: K = 1* 10-9 mol/L → [H+] = K·([HCO3-]/[CO32-]) 5. pH= -log [H+]

CO2 , Alkalinity, and pH In general: The greater [CO2 ], the smaller the value of A- [CO2 ] → greater [HCO3-] / [CO32-] → greater [H+] → lower pH

Total Dissolved Inorganic Carbon (CO2 ) [ΣCO2] is affected by photosynthesis, respiration, and CaCO3 formation/ dissolution E. huxlei bloom near Sweeden, May, 2010 http://www.smhi.se/en/theme/algal-blooms-in-the-skagerrak-and-kattegat-1.13039?l=8

Alkalinity Not affected by photosynthesis/ respiration, but is affected by CaCO3 formation/ dissolution Why? Pteropod- a zooplankter that makes a CaCO3 shell http://www.nopp.org/2010/newly-established-ocean-acidification-task-force-holds-first-meeting/#

CO2 , Alkalinity, and pH SW, CH6, p. 119, Fig. 6.15

3.3 Impacts of Future Climate Change 3. Climate change and its impacts…under different scenarios 3.3 Impacts of Future Climate Change Ocean Acidification: The marine carbonate buffer system allows the ocean to take up CO2 far in excess of its potential uptake capacity based on solubility alone, and in doing so controls the pH of the ocean: (1) CO2 + H2O ↔ H2CO3 ↔ H+ + HCO3- ↔ 2H+ + CO32– (2) CO2 + H2O + CO32– ↔ HCO3- + H+ + CO32– ↔ 2HCO3- Net effect of more CO2: More H+ and HCO3- Less CO32– CaCO3 + CO2 + H2O ↔ Ca2++ 2HCO3- IPCC, 2007, AR4, WG1, Ch. 7 http://www.pmel.noaa.gov/co2/OA/background.html

Ocean “Acidification” Estimated Changes in pH of Ocean Surface due to Human CO2 Emissions During Industrial Period (1800-2000) Net effect of more CO2: More H+ and HCO3- Less CO32– Figure from: http://www.pacificscience.org/tfoceanacidification.html

Impacts of Ocean Acidification Organisms must expend more energy to produce shells http://www.pmel.noaa.gov/co2/story/What+is+Ocean+Acidification%3F

[CO2] , Alkalinity, and pH in Tropics How does temperature affect Total Dissolved Inorganic Carbon [ΣCO2]?   As temperature goes up, the solubility of CO2↓ → [ΣCO2]↓ How does temperature affect carbonate alkalinity? → (CA - [ΣCO2])↑ → [CO32-]↑ If [CO32-]↑↑; more precipitation of CaCO3 (spontaneous precipitation…) → alkalinity↓ In short, if temperature affects calcium carbonate solubility, it affects alkalinity….

Impacts of Ocean Acidification Organisms must expend more energy to produce shells… Ecosystem & Food Web Impacts http://www.pmel.noaa.gov/co2/story/What+is+Ocean+Acidification%3F

Impacts of Ocean Acidification Organisms must expend more energy to produce shells The pteropod, or “sea butterfly”, is a tiny sea creature about the size of a small pea. Pteropods are eaten by organisms ranging in size from tiny krill to whales and are a major food source for North Pacific juvenile salmon. The photos below show what happens to a pteropod’s shell when placed in sea water with pH and carbonate levels projected for the year 2100. The shell slowly dissolves after 45 days.  Photo credit: David Liittschwager/National Geographic Stock. Used with permission. All rights reserved. National Geographic Images. http://www.pmel.noaa.gov/co2/story/What+is+Ocean+Acidification%3F

Coral Reefs - Carbonate Tropical corals are heterotrophic invertebrate animals (Phylum Cnidaria) that live in symbiosis with a photosynthetic dinoflagellate (Kingdom Protista) http://oceanservice.noaa.gov/facts/coralwaters.html Tropical reef-building corals cannot tolerate water temps <18°C. Grow optimally in water temps 23°-29°C. Some can tolerate temps as high as 40° C for short periods. Most also require very saline (salty) water 32-42. pH? Other? http://www.emc.maricopa.edu/faculty/farabee/biobk/biobookdiversity_3.html http://www.ncar.ucar.edu/feature/fieldguides/coral/ Coral Bleaching - Corals are stressed by changes in conditions such as temperature, light, or nutrients → breakdown of symbiosis with photosynthetic dinoflagellate (Kingdom Protista) → symbiont leaves host or is expelled → animal host dies…characterized by brown-white skeletal remains… http://oceanservice.noaa.gov/facts/coral_bleach.html

Questions? Joseph P. Smith, Ph.D. Oceanography Department U. S. Naval Academy 572C Holloway Road, 9D Annapolis, MD 21402-1363 Tel: 410-293-6568 Email: jpsmith@usna.edu