Intro to Ocean Acidification Flashcards
(23 cards)
What is ocean acidification?
The reducing pH of the ocean as CO2 concentrations rise through increasing absorption.
What developments did the industrial revolution involve?
- Development of new energy systems
- Development of the chemistry industry
- Changes in agriculture and land use
What are the two types of “effects” on the environment driven by industrial changes?
- Direct effects -> fluxes of material into oceans
- Indirect effects -> climate change and altered ocean circulation
What are four main anthropogenic sources of atmospheric CO2?
- Burning of fossil fuels
- Deforestation
- Changes in land use
- Energy and cement production
What are the three main sinks of anthropogenic CO2?
- Atmosphere
- Oceans
- Land
What is the oceanic uptake of CO2 in terms of the percentage of emissions?
20-35% of CO2 emissions
Summarise atmospheric CO2 in the past 800,000 years (before the industrial revolution). What does it show and what are the units?
172 - 290 ppmv today
(Parts per million per volume)
This shows natural fluctuations between this range.
Summarise the changes in atmospheric CO2 from the industrial revolution to the present. What does this show?
280 - >410 ppmv
This shows the rapid change outside of natural fluctuations over a very short time scale.
How much has atmospheric CO2 increased by in the last 30 years and what change has this caused in seawater pH?
CO2 increased by 50% in the past 30 years.
Seawater pH has reduced by 0.1 units (this is a 30% increase in acidity as pH is on a logarithmic scale).
What is the “natural” pH of the ocean?
8-8.1
How does the ocean naturally buffer against pH changes? What does this mean for calcifiers?
CO2 diffusing into seawater reacts with H2O to form bicarbonate and H+ ions.
These excess H+ ions can react with carbonate ions to also form bicarbonate, reducing H+ concentration (and reducing acidity).
However: reduces availability of carbonate, reducing CaCO3 formation.
Which latitudes are most exposed to pH changes? Why?
Higher latitudes -> this is because CO2 is more soluble in colder water.
What is the equation for the saturation state of CaCO3 in seawater?
omega = [Ca2+] x [Co3 2-] / K’sp
(K’sp is the apparent solubility product of CaCO3 in seawater)
What does a saturation state > 1 mean? What conditions is this likely to be associated with in terms of Ca2+ and CO3 2- concentrations?
Supersaturation -> Precipitation of CaCO3 is more likely to occur.
This is typically related to high concentrations of Ca2+ and CO3 2-, meaning more CaCO3 can form.
How is increasing CO2 in seawater changing the saturation state? How does this happen chemically?
It is reducing the saturation state, meaning more dissolution of CaCO3.
This occurs due to a reduction of CO3 2- in seawater as it increasingly reacts with H+ ions to form bicarbonate (the H+ ions come from the reaction of CO2 with H2O).
What does the solubility product (K’ sp) vary with in terms of saturation?
- Pressure
- Temperature
- Salinity
What is it called when the CaCO3 saturation state is below 1?
Undersaturation - net dissolution.
How do CaCO3 saturation states vary latitudinally? Why?
Shallow warm tropical waters = higher saturation states = more CaCO3 precipitation
Cold high-lat regions and at depth = lower saturation states = more dissolution
This is because CO2 solubility increases at colder temperatures.
How can calcifying organisms support calcification?
Increasing pH and CO32- concentrations via energy-consuming ion transport processes.
What are two forms of CaCO3?
- Aragonite
- Calcite
Which of the polymorphs of CaCO3 is more soluble? What does this mean?
Aragonite - this means dissolution is greater for aragonite (K’ sp is lower for aragonitic CaCO3).
Which organisms are associated with aragonitic CaCO3?
- Tropical corals
- Cold-water corals
- Pteropods
- Molluscs
Which organisms are associated with calcitic CaCO3?
- Coccolithophores
- Foraminifera
- Echinoderms
- Crustaceans
