Baltic Sea Research Institute Warnemünde

Slides:



Advertisements
Similar presentations
Phase Diagram for Water
Advertisements

Solubility of CO2 and Carbonate Equilibrium
Carbon Dioxide Sources and Sinks: Respiration and Photosynthesis
1 Carbon Cycle 9 Carbon cycle is critically important to climate because it regulates the amount of CO 2 and CH 4 in the atmosphere. Carbon, like water,
Climate Change and the Oceans
Dissolution of calcite in sediments -- metabolic dissolution.
Glacial atmospheric CO 2 lowering must be due to greater storage in ocean at equilibrium, atmospheric pCO 2 determined by Henry’s Law pCO 2 = [CO 2 ] /
The Carbon Cycle The carbon cycle describes the exchange of carbon atoms between various reservoirs within the earth system. The carbon cycle is a geochemical.
1 Acid-base reactions and carbonate system. 2 Topics for this chapter Acid base reactions and their importance Acid base reactions and their importance.
Lecture 10: Ocean Carbonate Chemistry: Ocean Distributions Controls on Distributions What is the distribution of CO 2 added to the ocean? See Section 4.4.
Properties of Seawater Monday we talked about properties of water (Table 7.2) - dissolves solids and gases readily (“universal solvent”) Last time (Wednesday)
Ocean Acidification Sonya Remington
Introduction: coccolithophores
Effects of global warming on the world’s oceans Ashley A. Emerson.
Carbonates Madelon van den Hooven
1 Chapter 7 Ocean Chemistry About solutions and mixtures A solution is made of two components, with uniform (meaning ‘the same everywhere’) molecular properties:
Seawater Chemistry 70% of the Earth is covered by ocean water!
1. Dissolved Inorganic Carbon (DIC) Initially, DIC in groundwater comes from CO 2 – CO 2(g) + H 2 O ↔ H 2 CO 3 ° – P CO2 : partial pressure (in atm) –
Chapter 6: Water and Seawater Fig Atomic structure Nucleus Protons and neutrons Electrons Ions are charged atoms.
Chapter : Seawater Fig Density of seawater to g/cm 3 Ocean layered according to density Density of seawater controlled by temperature,
Chemical and Physical Structures of the Ocean. Oceans and Temperature Ocean surface temperature strongly correlates with latitude because insolation,
The Marine carbon cycle. Carbonate chemistry Carbon pumps Sea surface pCO 2 and air-sea flux The sink for anthropogenic CO 2.
GEOLOGIC CARBON CYCLE Textbook chapter 5, 6 & 14 Global carbon cycle Long-term stability and feedback.
The Chemistry of Seawater An Introduction to the World’s Oceans Sverdrup et al. - Chapter Six - 8th Ed.
Class The Oceans More on the chemistry of the Oceans... DISSOLVED GASES IN SEA WATER Solubility of atmospheric gases Solubility of atmospheric gases.
The Other Carbon Dioxide Problem Ocean acidification is the term given to the chemical changes in the ocean as a result of carbon dioxide emissions.
The Chemical Composition of Seawater Winn Johnson 25 August 2015 Regional Maritime University.
CHEMICAL OCEANOGRAPHY
The Carbon Cycle. Carbon Dioxide and Carbonate system Why is it important? 1. CO 2 regulates temperature of the planet 2. Important for life in the ocean.
Background in Biogeochemistry Some aspects of element composition and behavior are illustrated in Table 1. The major elements include Si, C, Al and Ca.
Carbon Cycle and Ocean Acidification Inspiration 9 V. Soutar.
The Carbon Cycle. Carbon Dioxide and Carbonate system Why is it important? 1. Regulates temperature of the planet 2. Important for life in the ocean 3.
PH and Chemical Equilibrium. Acid-base balance Water can separate to form ions H + and OH - In fresh water, these ions are equally balanced An imbalance.
Goal of this course: What determines the abundance of different elements in the ocean? How does their distribution depend on physical circulation and biological.
Ocean Properties and Chemistry
ESYS 10 Introduction to Environmental Systems March 2
© 2016 Cengage Learning. All Rights Reserved. 7 Oceanography, An Invitation to Marine Science | 9e Tom Garrison Ocean Chemistry.
Marine Biology What it takes to be alive. © 2002 Brooks/Cole, a division of Thomson Learning, Inc. Being Alive What are characteristics of all living.
Shallow water carbonate sedimentation Including partial reviews of : Carbonate chemistry (solubility, saturation state) Metabolic dissolution (impact of.
The Carbon Cycle. Carbon Dioxide and Carbonate system Why is it important? 1. Regulates temperature of the planet 2. Important for life in the ocean 3.
Chemistry of sea water Constancy of composition
Chemical & Physical Properties of SeaWater
Storing carbon dioxide Learning objectives:  Describe the factors determining the relative solubility of a solute in aqueous and non aqueous solvents.
Dissolution of calcite in sediments -- metabolic dissolution.
Chapter 4 Section 2.
Seawater Chemical Properties. 2 / 33 Phases of Substances.
Lecture 9: Ocean Carbonate Chemistry: Carbonate Reactions
G. Bala, Caos Indian institute of Science
Chapter 8—Part 2 Basics of ocean structure The Inorganic Carbon Cycle/
Lecture 10: Ocean Carbonate Chemistry: Carbonate Reactions
Arctic Ocean Model Intercomparison Project, 14th Workshop, Woods Hole
Chapter 7: Ocean Chemistry Insert: Textbook cover photo.
Determination of dissolved oxygen free CO2, total alkalinity, total hardness, calcium, magnesium, ammonia, nitrate and phosphorus.
Ocean Acidification 1.
Carbon cycle theme The Earth’s carbon cycle has a stabilizing mechanism against sudden addition of CO2 to the atmosphere About 50% of carbon emission is.
CHAPTER 5 Water and Seawater
CHAPTER 5 Water and Seawater
The Oceanic Sink Uptake in the mixed layer
Week 12: Nutrient and carbon cycling
70% of the Earth is covered by ocean water!
Ocean Chemistry Unit 5.
California Science Project
Chapter 4 Section 2.
Week 12: Nutrient and carbon cycling
Physical and Chemical Oceanography
하구및 연안생태Coastal management
Lesson 3: Ocean Acidification Chemical Oceanography
Composition of Seawater
Geologic carbon cycle Textbook chapter 5, 6 & 14 Global carbon cycle
Global terrestrial carbon estimation map ecosystem extents
Presentation transcript:

Baltic Sea Research Institute Warnemünde The Baltic Sea CO2 system and carbon cycle Bernd Schneider Baltic Sea Research Institute Warnemünde Germany

CO2 in seawater: Chemical equilibria and characteristic variables Part 1 CO2 in seawater: Chemical equilibria and characteristic variables CO2 solubility; CO2 reactions with water; the buffer (re-equilibration) reaction; CO2 partial pressure; total CO2; pH; alkalinity;

CO2 solubility in seawater: atmosphere CO2 solubility constant, ko [ (mol/kg)/atm ]: CO2: 380 ppm (0.038 %) pCO2 = 380 µatm seawater But: In most cases seawater is not at equilibrium with CO2 in the atmosphere!

CO2 reactions with seawater: Definition:

CO2 equilibria in seawater: Almost spontaneous equilibration! k1 ( S=7 ) k2( S=7 )

Main reaction (buffer reaction): CO2 re-equilibration after physically (temperature, salinity) and/or biologically (production or decomposition of organic matter) imposed changes of the CO2 system: Main reaction (buffer reaction): k1/k2 ( S=7 ) k1/k2 ( T=10°C )

Characteristic (measurable) variables of the CO2 system: 1. pH Baltic Sea: Surface water: 8.0 – 8.6 Deep water: down to 7.3 2. CO2 partial pressure, pCO2 Baltic Sea surface water: 100 – 600 µatm (atmosphere: 380 µatm) The difference between the atmospheric and the surface water pCO2 (disequilibrium) causes CO2 gas exchange: FCO2 – CO2 flux k – gas exchange transfer velocity

3. Total CO2, CT Baltic Sea (highly dependent on the region): 1400 – 1700 µmol/kg (central Baltic Sea) Relative composition of CT in clean water (CT = 23 µmol/kg) and Baltic seawater (CT = 1570 µmol/kg): 88% 96% 12% 0.0001% 1.3% 2.7%

4. Alkalinity, AT 1. Dissolution of CaCO3 in river water: 2. Reaction of the CO2 system: 3. The consumption of CO2 leads to undersaturation and CO2 uptake from the atmosphere: 4. The reaction stops when both equilibrium with the atmospheric CO2 and with CaCO3 solubility is reached (controlled by the increase of HCO3-).

CONCLUSION: The amount of CaCO3 dissolved in river water and transported into the sea controls mainly the total CO2 ! 5. According to the ion balance the dissolution of CaCO3 corresponds to an excess of bases (proton acceptors) over H3O+, which is the major contribution to the alkalinity in seawater: 6. The excess of proton acceptors can be determined by titration with an acid (HCl). The titration also captures also other proton acceptors present in seawater: mainly borate and - at anoxic conditions- ammonia and hydrogen sulphide. Thus the total alkalinity, AT, is given by:

Alkalinity in the Baltic Sea: (Baltic-C data, Matti Perttilä)

CO2 partial pressure, pCO2 4. pH SUMMARY: Four variables are characterizing the marine CO2 system: Total CO2, CT Total alkalinity, AT CO2 partial pressure, pCO2 4. pH conservative, not dependend on temperature and pressure (depth) dependend on temperature and pressure (depth) Two variables are necessary to determine the whole CO2 system on the basis of the equilibrium constants (co2sys programme by Pelletier, Lewis and Wallace): ko (Weiss, 1976) k1, k2 (Millero et al., 2006)

Physical and biogeochemical control on the marine CO2 system Part 2 Physical and biogeochemical control on the marine CO2 system temperature changes; biomass production; mineralization of organic matter (oxic, anoxic);

Effect of temperature changes on the pCO2, [CO32-] and pH: The equilibrium of the buffer reaction is a useful tool to estimate changes of the CO2 system: with: With increasing temperature both the pCO2 (about 4% per °C) and [CO32-] must increase!

The increase of [CO2*] causes an increase of [H3O+] and thus a decrease of pH; The increase of [H3O+] is partly counterbalanced by reaction with [CO32-], hence, the pH decrease is moderate; Excercise-1: The previous considerations were implicitely based on the assumption that no CO2 gas exchange with the atmosphere occurred during warming. Calculate the pH change during a temperature increase from 0°C to 25°C. Produce a plot for pH as a function of temperature and determine the mean pH change per °C for both cases: a. no CO2 exchange with the atmosphere; b. spontanous CO2 equilibration with the atmosphere; The water mass is at equilibrium with the atmosphere and characterized by: S=7, T=10°C, AT=1600 µmol/kg, CT=1570 µmol/kg. Use the co2sys software (Pelletier et al.) with the constants given by Millero et al. (2006) and the total pH scale.

Effect of photosynthesis on the CO2 system: Redfield ratio: C/N/P = 106/16/1 pCO2 changes: Consumption of 4 µmol-nitrate/L corresponding to a CT loss of about 27 µmol/kg: controlled by the Revelle factor:

pH changes during organic matter production: The Revelle factor: Baltic Sea: 20 < R < 30 Ocean: 7 < R < 15 pH changes during organic matter production: (Data from SMHI) The loss of CT by photosythesis at the start of the spring bloom in the beginning of April causes an increase of the pH.

Organic matter production and alkalinity: 1. The removal or addition of CO2 does not affect the alkalinity, because: 2. The uptake of nitrate, NO3- during photosynthesis is accompagnied by the uptake of H3O+ (HNO3). Hence, AT is increasing, but the effect on pCO2 is small. effect of 4 µmol-NO3 uptake

3. Most ocean areas are supersaturated with regard to CaCO3: Under these conditions some plankton organisms form CaCO3 shells. The consumption of CO32- ions decreases the alkalinity and increases the pCO2: Exercise-2: On average the CO32- used for the formation of CaCO3 amounts to 20 % of the production of organic carbon. In the North Atlantic 12 µmol-NO3/L are consumed during the spring bloom. Calculate the change in pCO2 for the case: that no CaCO3 is formed; that CaCO3 is formed; At the start of the spring bloom (T=8°C, S=35) the water has an alkalinity of 2350 µmol/kg and a pCO2 of 410 µatm. Use again the co2sys software.

Organic matter decomposition (oxidation): Reversal of the photosynthesis: But: After consumption of the dissolved oxygen, the sulphur in the sulfate ions acts as oxidizing agent (but not for ammonia): During sulfate reduction the alkalinity is increased. The release of 106 CO2 molecules gives an alkalinity change of: As a consequence the pCO2 increase and pH decrease by the release of CO2 is compensated for by the alkalinity increase!

Excercise-3: The deep water of the Baltic Sea contains 368 µmol/kg oxygen. How much CO2 is released after the entire consumption of the oxygen by mineralization? Before the onset of the mineralization the pCO2 was 400 µatm. How big is the pCO2 after the consumption of all oxygen? (T = 5°C, S=12, AT=1717 µmol/kg) Again, use co2sys.

The Baltic Sea CO2/carbon cycle and ist anthropogenic perturbations Part 3 The Baltic Sea CO2/carbon cycle and ist anthropogenic perturbations Inputs and outputs of inorganic carbon: CT (AT) and organic carbon: dissolved (DOC) and particulate (POC) control the total carbon inventory of the Baltic Sea: atmophere CO2 CT, AT CT, AT North Sea Rivers DOC POC DOC, POC CT, DOC Baltic Sea sediments

The internal CO2/carbon cycle in the Baltic Sea: Relationship between mixing/stratification and CO2 seasonality in the Baltic Proper

Seasonality of biomass production and mineralization above the halocline, detectable by measurements of the surface water pCO2: pCO2 data from the northern Gotland Sea, collected with an automated measurement system deployed on a cargo ship; Seasonal changes in CT calculated from the pCO2 data and the mean alkalinity;

Accumulation of CT in the deep water of the Gotland Sea during a period of stagnation:

Carbon budget for the Gotland Sea deep waterduring stagnation, fluxes in mmol/m2 yr:

Anthropogenic perturbations: Acidification? Increasing atmospheric pCO2 decreases the pH and the CaCO3 saturation. This effect may be enhanced by increasing acidic precipitation over the Baltic Sea. pH decrease during at the start of the spring bloom caused by doubling the pre-industrial atmospheric CO2:

CaCO3 saturation: Decrease of [CO32-] according to: Decrease of CaCO3 saturation at the start of the spring bloom caused by doubling the pre- industrial atmospheric CO2:

But: It is also likely that the alkalinity input into the Baltic Sea will increase because the increasing atmospheric CO2 accelerates the weathering of CaCO3 in the catchment area. This will at least dampen acidification and CaCO3 undersaturation. The final answer on the future Baltic Sea CO2 system will be given by the BONUS Project: Baltic-C !