Satellites, Seas and CO2
A guide for students
This guide accompanies the video “Satellites, Seas and CO2” presented by
Dr Jamie Shutler, Plymouth Marine Laboratory, and produced by the
ESA OceanFlux Greenhouse Gas project
It is intended to provide background information to the film and to enable
students to perform the experiment shown in the film.
Satellites, Seas and CO2
A guide for students
The oceans cover two thirds of the surface of the earth and influence our
atmosphere and our climate. The gas carbon dioxide (CO2) is of particular
importance as it contributes to global warming by absorbing radiation, causing
the atmosphere to heat up and re-radiate heat back down to the ground. It is this
insulating property of CO2, rather like the glass in a greenhouse, that causes it to
be known as a greenhouse gas.
Carbon dioxide is emitted when we
burn fossil fuels
The oceans can act as a sink for CO2. If these natural
stores did not exist the earth would be warming
at much greater rate that what we observe today.
However, when CO2 enters the oceans it alters the
chemistry of the water and makes it more acidic
(see box on CO2 and the oceans) which can have
devastating effects on marine organisms.
It would be impossible to take water samples
throughout the globe to measure CO2 and
temperature, so to see what is happening to the
oceans we need to use satellites which look back
down at the Earth.
It is difficult and expensive to take
measurements of CO2 and temperature
around the globe, so to see the bigger
picture we need to use satellites.
Wind data can be used to estimate whitecapping, and in combination with temperature
can be used to estimate the flux, or movement of CO2 between the surface waters and the
atmosphere. This flux can then be used to estimate how much CO2 is going into the ocean.
The oceans in the cold polar regions act as a sink for CO2 - absorbing the gas and reducing
the amount of CO2 in our atmosphere. However, in some hot equatorial regions the
ocean actually acts as a source of CO2 to the atmosphere.
When this flux of CO2 is
obtained from several
different satellites over
many years it can give us a
greater understanding of
how CO2 is moving between
the atmosphere and ocean
and ultimately enable us to
improve our predictions of
future climate scenarios.
Average wave height (m)
lower pH
more H+
lower pH
more H+
lower pH
more H+
The effect of increasing acidity on
development of mussel shells.
Breaking waves
Seeing the bigger picture
In the OceanFlux Greenhouse Gas project
satellites are being used with a range of different
sensors, including:
»» an infrared sensor - used to estimate the
surface temperature of the water; and
»» a radar instrument - used to measure wind
speed and estimate the magnitude of waves.
Current pH
The Envisat satellite is
in orbit 500 miles above
the earth. It is the size
of two double decker
buses, travels at a speed
of 16,000 miles per hours
and goes round the earth
14 times every day.
Air-sea flux of CO2. Blue: CO2 sink,
red: source of CO2 to the atmosphere.
Images courtesy of Dreamstime.com (oil refinery - Zacarias Pereira Da Mata; Arctic fjord - Erectus).
As a wave breaks, whitecapping
appears - which is where the seawater
captures a pocket of air. This air then
goes into the sea as a bubble, and
as the bubble disperses the gases
dissolve into the ocean.
These bubbles of air contain CO2, and
thus waves can influence the amount
of CO2 that goes into the ocean.
Satellites, Seas and CO2
The experiment
The bottle experiment
Carbon dioxide in the oceans
Introduction
Atmospheric CO2 absorbed by the oceans not only makes
the water more acidic but also causes changes to the
chemistry of the water, such as reducing the number of
carbonate ions available. This can have a devastating effect
upon marine life, particularly calcifying animals such as
mussels and corals, which rely upon the supply of carbonate
ions as the building blocks to form their shells and skeletons.
The oceans absorb one third of the
carbon dioxide emitted each year, and
this changes the chemistry of the water,
which can have an impact on marine life.
The amount of CO2 which can dissolve
in the seawater is mostly dependent on
the temperature of the water and this
can be illustrated with the following
experiment using bottles of carbonated
drinks. Carbonated drinks contain CO2
which is dissolved in the liquid under
high pressure (see box).
Equipment
»»
»»
»»
»»
2 bottles of carbonated drink
2 aspirin tablets
Thermometer
Stopwatch (optional)
Method
1. Take two identical bottles of carbonated drink and place one in the
refrigerator overnight and keep the other at room temperature (or
even better leave it in the sun!).
2. Carefully open both bottles and take the temperature of each drink.
3. Place an aspirin in each bottle at the same time to release the
contained CO2.
4. Observe what happens to the drink in each bottle, you may want to
use a stopwatch so that you can note the times when things happen.
When CO2 dissolves in seawater it can either:
»» Remain as a dissolved gas, which can freely exchange
between the ocean and atmosphere and can be taken
up by marine plants and phytoplankton. The oceans
have a limited capacity to hold dissolved CO2.
»» Combine with molecules of water to form a weak
acid called carbonic acid (H2CO3), the same acid that
is found in carbonated drinks (see bottle experiment).
This reaction can be shown as:
CO2+ H2O
carbon dioxide
Solubility of CO2 in water (g/L)
carbonic acid
Then the carbonic acid dissolves in water and breaks apart
into its constituent ions, a hydrogen ion and a bicarbonate
ion (the same as in baking soda):
0.3
↔H++ HCO3-
H2CO3
0.2
carbonic acid
0.1
refrigerator
temperature
room
temperature
+
hydrogen ion
0
10
20
Temperature (°C)
hydrogen ion
bicarbonate ion
Most of these hydrogen ions will then combine with
carbonate ions in the seawater to form addition
bicarbonate ions, although some will stay as hydrogen
ions and reduce the pH of the seawater.
H+
0
↔H2CO3
water
30
Questions/discussion
1. Which bottle produced the most bubbles?
2. Which bottle overflowed first?
3. Use the graph above to determine the solubility of CO2 for each of
your bottles - how does this help to explain what happened in your
experiment?
Outcomes
At the end of this experiment students should be able to:
»» explain the differences in solubility of CO2 at different temperatures;
»» observe the effect of temperature on the rate of a reaction; and
»» have a basic understanding of the concept of ocean acidification.
For further experiments we recommend looking at The other CO2 problem
- ocean acidification.
CO32-
↔HCO3-
carbonate ion
bicarbonate ion
This means that when CO2 dissolves in seawater there
will be an increase in dissolved CO2, hydrogen ions,
and bicarbonate ions and a decrease in the number of
carbonate ions and the pH of the seawater, contributing
to the phenomenon of ocean acidification.
This same reaction occurs in carbonated drinks when CO2
is dissolved in the liquid. When aspirin is added to the
carbonated drink it reacts with the bicarbonate ion to
produce water and carbon dioxide gas which we can see
bubbling out of the bottles in the experiment.
O
C
O
C
OH
+ HCO3- ↔
O
C
+ H2O + CO2
O
CH3
C
O
aspirin
O-
CH3
O
bicarbonate
ion
aspirin water
ion
carbon
dioxide
Satellites, Seas and CO2
Further resources
Videos
Satellites, Seas and CO2 video
Dr Jamie Shutler of Plymouth Marine Laboratory
explains the OceanFlux Greenhouse Gases
project, which is a two year project funded by the
European Space Agency. The aim of the project is
to improve the quantification of air-sea exchanges
of greenhouse gases.
https://www.youtube.com/watch?v=4uak0vVGgGY
The other CO2 problem animation
A short, powerful and entertaining animation
about the issue of ocean acidification, produced
by Ridgeway School (Plymouth, UK) and Plymouth
Marine Laboratory.
https://www.youtube.com/watch?v=F5w_FgpZkVY
Ocean acidification: connecting
science, industry, policy and public
A short film about ocean acidification which brings
together a wide range of stakeholders including,
HSH Prince Albert II of Monaco, school children,
a Plymouth fishmonger, a UK government Chief
Scientific Adviser, representatives from industry
and policy making departments, as well as a group
of internationally recognised expert scientists.
https://www.youtube.com/watch?v=kCp8cetvtL8
Publications
Hot, sour and breathless - ocean under
stress
Frequently asked questions about
ocean acidification
Concise, understandable summaries of current
knowledge of ocean acidification. Produced
by the US Ocean Carbon and Biogeochemistry
Program and the UK Ocean Acidification Research
Programme.
https://darchive.mblwhoilibrary.org/
handle/1912/5373?show=full
The other CO2 problem - ocean
acidification
Eight experiments to help young people
understand the basics of ocean acidification.
Teachers will find information on the preparation
and running of the experiments as well as answers
to any questions.
http://www.bioacid.de/upload/downloads/press/
BIOACID_Experiments_en.pdf
A guide to the triple stresses facing the ocean
- rising temperatures, ocean acidification and
ocean deoxygenation. Written in clear, easy to
understand language it explains how these three
interacting factors will cause substantial changes
in marine physics, chemistry and biology.
http://www.oceanacidification.org.uk/PDF/Ocean_
under_Stress_English.pdf
Websites
UK Ocean Acidification
Research Programme
Plymouth Marine Laboratory
An independent, impartial provider of scientific
research and contract services relating to the
marine environment. http://www.pml.ac.uk
Oceanflux Greenhouse Gases project
The Oceanflux Greenhouse Gases project is
a two year project funded by the European
Space Agency, the objective is to improve the
quantification of air-sea exchanges of greenhouse
gases. The project aims to develop and validate
new and innovative products combining field
This is a PML contribution to the UK National Centre data, satellite observation, and models.
for Earth Observation http://www.nceo.ac.uk
http://www.oceanflux-ghg.org/
NERC UK Ocean Acidification Research
Programme
A £12m, 5 year research programme seeking to
understand ocean acidification in order to provide
data and advice to develop mitigation and
adaptation strategies. Contains a section with links
to many further resources.
http://www.oceanacidification.org.uk/