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 CO2A guide for students

Breaking waves

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.

Seeing the bigger picture

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.

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.

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.

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.

Average wave height (m) Air-sea flux of CO2. Blue: CO2 sink, red: source of CO2 to the atmosphere.

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.

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.

Carbon dioxide is emitted when we burn fossil fuels

Current pH

lower pH more H+

lower pH more H+lower pH

more H+

The effect of increasing acidity on development of mussel shells.

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.

Images courtesy of Dreamstime.com (oil refinery - Zacarias Pereira Da Mata; Arctic fjord - Erectus).

Satellites, Seas and CO2The experiment

The bottle experiment

IntroductionThe 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)

Method1. 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.

Questions/discussion1. 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?

OutcomesAt 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.

Solu

bilit

y of

CO

2 in

wat

er (g

/L)

Temperature (°C)

0.3

0.2

0.1

00 10 20 30

roomtemperature

refrigeratortemperature

Carbon dioxide in the oceans

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.

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 ↔ H2CO3

carbon dioxide water 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):

H2CO3 ↔ H+ + HCO3-

carbonic acid 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+ + CO32- ↔ HCO3

-

hydrogen ion 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.

C

O

OH

O

CH3

O

C

+ HCO3- ↔

C

O

O-

O

CH3

O

C

+ H2O + CO2

aspirin bicarbonate aspirin water carbon ion ion dioxide

Satellites, Seas and CO2Further resources

Videos

Satellites, Seas and CO2 videoDr 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 animationA 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 publicA 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

Websites

Plymouth Marine LaboratoryAn independent, impartial provider of scientific research and contract services relating to the marine environment. http://www.pml.ac.uk

This is a PML contribution to the UK National Centre for Earth Observation http://www.nceo.ac.uk

Oceanflux Greenhouse Gases projectThe 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 data, satellite observation, and models.http://www.oceanflux-ghg.org/

UK Ocean AcidificationResearch Programme

NERC UK Ocean Acidification Research ProgrammeA £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/

Publications

Frequently asked questions about ocean acidificationConcise, 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 acidificationEight 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

Hot, sour and breathless - ocean under stressA 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