1. Maury Project Ocean Acidification
17 JUL 2017
Image Credit: NOAA NOS (

2. 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).

3. 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).

4. 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.

5. 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)

6. 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

7. Electromagnetic Spectrum
E = hc/l = hu
→ c = lu
E = Energy (J)
h = Plank’s Constant (6.626 x 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

8. 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)

9. 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 ~ 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 ~ W/m2
𝑺𝑾 𝑰𝑵↓ = 𝑺 𝑬𝑨𝑹𝑻𝑯 𝟒 = (𝟏𝟑𝟔𝟖 𝑾 𝒎 𝟐 𝟒) ~ 𝟑𝟒𝟐 𝑾 𝒎 𝟐

10. Incoming Solar Radiation

11. 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
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

12. 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)

13. 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 ( nm, (900 nm))

14. 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

15. 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.

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

17. Type of Surface Albedo Tropical forest 0.10-0.15 Woodland 0.15-0.20
deciduous
coniferous
Farmland/natural grassland
Bare Soil
Semi-desert/stony desert
Sandy desert
Tundra
Water (0-60 deg)
< 0.08
Water (60-90 deg)
Fresh snow/snow-covered permanent snow
Snow-covered ice
Sea ice
Snow-covered evergreen forest
snow-covered deciduous forest
Snow-covered farmland/natural grassland
Clouds
low
middle
high (cirrus)
cumuliform
Burroughs, CH. 2, p. 28, Table 2.1: The proportion of sunlight reflected by different surfaces (albedo)

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

19. 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↓

20. 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 )
= 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

21. 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 )
= 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!!!

22. 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 = 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

23. Solar and Earth Radiation

24. 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

25. 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

26. Image created by Robert A. Rohde / Global Warming Art

27. 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

28. 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/m 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).

29. 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

30. 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: /CBO
Hartmann, et al., IPCC AR5 WG1, 2013, Climate Change 2013: The Physical Science Basis, CH2, Fig. 2.11

31. 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.

32. (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: /CBO
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)

33. 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
→ Steady-State
Increase in GR 2007–Present?
GR of CFCs:
Constant GR
Decreasing GR
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 These gases account for about 96% of the direct radiative forcing by long-lived greenhouse gases since The remaining 4% is contributed by an assortment of 15 minor halogenated gases (

34. 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 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.

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

36. 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

37. 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

38. 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 b Rate is calculated over the period 1990 to 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.

39. Mean annual atmospheric carbon dioxide growth rate at Mauna Loa Observatory, Hawaii (

40. Global Carbon Emissions
Total Global Carbon Emissions
~ 7.8 Gt-C/yr

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

42. 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

43. 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.

44. Mean annual atmospheric carbon dioxide growth rate at Mauna Loa Observatory, Hawaii (

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

46. 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}

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

48. 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)

49. 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] +

50. 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)

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

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

53. pH of Seawater and the Aqueous Carbonate System
Stabilizes the pH of seawater
Seawater average pH ~ 7.7; range
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+]

54. 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 =
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 ~
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)

55. 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

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

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

58. CCD DEPTHS Atlantic = ~ 5km Pacific = ~ 4,200-4,500 m
Why so different?

59. 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)

60. 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-]

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

62. 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-]

63. 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+  CO H+

64. 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+]

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

66. Total Dissolved Inorganic Carbon (CO2 )
[ΣCO2] is affected by photosynthesis, respiration, and CaCO3 formation/
dissolution
E. huxlei bloom near Sweeden, May, 2010

67. Alkalinity
Not affected by photosynthesis/ respiration, but is affected by CaCO3 formation/ dissolution
Why?
Pteropod- a zooplankter that makes a CaCO3 shell

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

69. 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

70. Ocean “Acidification”
Estimated Changes in pH of Ocean Surface due to Human CO2 Emissions During Industrial Period ( )
Net effect of more CO2:
More H+ and HCO3-
Less CO32–
Figure from:

71. Impacts of Ocean Acidification
Organisms must expend more energy to produce shells

72. [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….

73. Impacts of Ocean Acidification
Organisms must expend more energy to produce shells…
Ecosystem & Food Web Impacts

74. 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 The shell slowly dissolves after 45 days.  Photo credit: David Liittschwager/National Geographic Stock. Used with permission. All rights reserved. National Geographic Images.

75. Coral Reefs - Carbonate
Tropical corals are heterotrophic invertebrate animals (Phylum Cnidaria) that live in symbiosis with a photosynthetic dinoflagellate (Kingdom Protista)
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
pH?
Other?
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…

76. Questions? Joseph P. Smith, Ph.D. Oceanography Department
U. S. Naval Academy
572C Holloway Road, 9D
Annapolis, MD
Tel: