Are we warming our planet? Evidence from an undersampled ocean [Prof Toby Sherwin]
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The physical chemistry of the atmosphere, and the relation between Greenhouse gas concentration and temperature, are well understood and have been since the 19th century, although our understanding of the role of water vapour is far from perfect. A large part of the global warming of the Earth's surface takes place in the ocean, which covers 70% of the globe and is the main source of water vapour. Reliable measurements of sea surface temperature from ships started in 1853 and are now continued with drifting buoys that can profile down to 1000 m. Although these observations are sparse compared with the size of the ocean, they nevertheless all reveal a consistent rise in ocean temperature that translates into a slow rise in sea level due to thermal expansion. SAMS is one of an international group of laboratories surrounding the north Atlantic that monitor the global ocean circulation. We have seen a rapid rise in temperature west of Scotland that can be attributed in part to global warming, but also to changes in circulation patterns of the Atlantic. Modern tools, such as remotely operated marine gliders that can dive to 1000 m, are changing the way we make observations and will enable us to improve our understanding of the way in which the ocean circulation behaves over long periods of time. [Presentation at the UHI Climate Change Summit 2010 by Toby Sherwin, Toby Sherwin, Professor of Oceanography, Scottish Association of Marine Science (SAMS) UHI]
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Are we warming our planet? Evidence from an undersampled ocean [Prof Toby Sherwin]
- 1. Are we warming our planet? Evidence from an undersampled ocean Toby Sherwin UHI Professor of Oceanography Scottish Association for Marine Science Oban
- 2. The number of Americans who think that Global Warming is exaggerated (%)
- 3. UHI Climate Conference June 2010 Why Greenhouse Gases are important to our climate
- 4. John Tyndall’s experiment of 1859 Showed that CO 2 is a greenhouse gas and speculated on its effect on climate
- 5. UHI Climate Conference June 2010 The Composition of the Atmosphere The pink shaded boxes show the greenhouse gases. Without these gases in the atmosphere the Earth would be about 21 o C cooler than it is today (i.e. -6 o C instead of 15 o C that it is today). variable (0 – 1 x 10 -3 ) O 3 Ozone 0.001 ppm - CFCs 0.3 ppm N 2 O Nitrous Oxide 1.8 ppm CH 4 Methane 380 ppm (.038%) CO 2 Carbon dioxide variable (0 – 2%) H 2 O Water vapour 21% O 2 Oxygen 78% N 2 Nitrogen Proportion Symbol Gas Adapted from Houghton, Global Warming, Cambridge Uni Press
- 6. UHI Climate Conference June 2010 The natural CO2 balance in the atmosphere CO 2
- 7. UHI Climate Conference June 2010 The natural plus man made CO2 balance in the atmosphere CO 2
- 8. UHI Climate Conference June 2010 The Greenhouse Effect satellite CO 2 absorbs outgoing radiation
- 9. UHI Climate Conference June 2010 Satellites show that greenhouse gases block outgoing radiation (and hence insulate the atmosphere) CO 2 ozone water vapour methane etc
- 10. UHI Climate Conference June 2010 The molecular structure and the different rovibrational energy states of the gases of the atmospheric is extremely well understood symmetric stretch v 1 = 7.5 μ m => IR inactive asymmetric stretch v 3 = 4.3 μ m bend v 2 = 15 μ m bend v 2 o c o symmetric stretch v 1 = 2.74 μ m asymmetric stretch v 3 = 2.66 μ m bend v 2 = 6.25 μ m H o H o H 2 O (water vapour) CO 2 (carbon dioxide)
- 11. UHI Climate Conference June 2010 1800 1900 2000 Early scientific investigations: 1900 Tyndall Arrhenius Fourier Callendar Keeling
- 12. UHI Climate Conference June 2010 Keeling’s observations of CO 2 in Hawaii 1960 2000 1980 320 380 CO 2 in ppm
- 13. UHI Climate Conference June 2010 1900
- 14. UHI Climate Conference June 2010 1900
- 15. UHI Climate Conference June 2010
- 16. UHI Climate Conference June 2010 ice field Sea level rise 21,000 years ago the sea was about 120 m lower than it is today … … and the Earth was ~5 o C cooler
- 17. UHI Climate Conference June 2010 How sea surface temperatures have increased with time
- 18. UHI Climate Conference June 2010 70% of the Earth is covered with water
- 19. UHI Climate Conference June 2010 Early observations of ocean temperature Sea surface temperature measurement methodology was standardised in 1853 No of observations per month at end of 19th Century HMS Challenger (1858) standard bucket (1891) canvas bucket (pre WWII) insulated bucket
- 20. UHI Climate Conference June 2010 How the number of observations has increased surface drifter The increase in ocean observations since 1850
- 21. UHI Climate Conference June 2010 The long term rise in sea surface temperature Mean surface temperature Change in surface temperature since 1975 1900
- 22. UHI Climate Conference June 2010 ARGO profiling drifters tracked by satellite 1000 m 2000 m surface satellite Heat content in the upper ocean 1994 2010 Lyman et al ., Nature, May 2010
- 23. UHI Climate Conference June 2010 Variations closer to home
- 24. UHI Climate Conference June 2010 The Ocean Conveyor, or overturning circulation
- 25. UHI Climate Conference June 2010 The ocean conveyor flows close to Scotland
- 26. SAMS operates an annual section to Iceland Rockall Trough Iceland Basin RRS Discovery
- 27. Rockall Trough The CTD Rockall Scotland
- 28. The upper 800 m of the Rockall Trough has warmed by ~ 1 o C since 1975 Rockall Trough
- 29. UHI Climate Conference June 2010 Labrador Sea North Atlantic Current Sub-Polar Gyre 1990s strong Sub-Polar Gyre
- 30. UHI Climate Conference June 2010 Labrador Sea North Atlantic Current Sub-Polar Gyre 2000s weak Sub-Polar Gyre
- 31. UHI Climate Conference June 2010 New technology being used in Scottish waters
- 32. UHI Climate Conference June 2010 We can improve our data coverage using remotely operated ocean gliders
- 33. UHI Climate Conference June 2010 SAMS gliders – transforming the way we monitor the ocean
- 34. UHI Climate Conference June 2010 Sea level rise
- 35. UHI Climate Conference June 2010 Sea level rise since 1870 (mainly due to thermal expansion of the upper ocean) IOC Annual Reports Series No. 13, UNESCO 2007
- 36. UHI Climate Conference June 2010 Isostatic rebound (mm/year) Mean sea level rise is 2 mm/year
- 37. UHI Climate Conference June 2010 Is it already the day after tomorrow?
- 38. UHI Climate Conference June 2010 Has the Thermohaline Circulation slowed down? Profiles of transport in the Atlantic across 26 o N (opposite Florida) Whole water column Top 1000 m Bottom 5000 m
- 40. UHI Climate Conference June 2010 today Tyndall Centre climate model (from New Scientist, Feb 2006) Act of Union Battle of Hastings Tyndall ‘discovers’ greenhouse effect Lords of the Isles Hearts last won SPL Hearts next win SPL
- 41. UHI Climate Conference June 2010 Loch Drumbuie at dusk Thank you
Notas del editor
- The world is a beautiful but fragile place. Can you see the atmosphere here? What does it take to be an environmental scientist? I would argue (from experience): dedication; objectivity; integrity; knowledge and understanding; humility; open mind; the ability to allow our egos to suffer (that’s the really difficult one) What are our drivers? Interest; love of knowledge for it’s own sake; recognition (amongst peers); financial security What’s not on the list? Desire for fame; or wealth What is our scientific philosophy and methodology? (for oceanographers at least) We’re not laboratory scientists; we can’t determine ‘truth’; we can’t do repeatable experiments in the ocean; we rely on a different method – the building of layers of reinforcing independent evidence none of which is ‘proof’ itself, but all of which build confidence in an idea. And if that idea is confounded by some evidence, then we must think again: is the evidence wrong; are our ideas incomplete; are they totally wrong (our ego will suffer)
- SAMS is pioneering the use of gliders to monitor the state of the surface northerly inflow to the Nordic Seas through the Rockall trough. Using gliders we can cheaply extend both the intensity and value of the observational section across the Rockall Trough and Iceland Basin (started by David Ellett) of temperature and salinity that in different forms can be traced back to the early 1950’s. As the figures show we can launch our glider into the North Atlantic from a fast RHIB directly from our laboratory. The yellow line in the top RH image shows the track that of the sections that are displayed below it. With gliders we are monitoring temperature, salinity, dissolved oxygen, backscatter and fluorescence in the surface ocean at great spatial resolution down to 1000 throughout winter and summer thereby significantly enhancing the scientific value of our observations. The data reveal the complexity of the temperature and salinity structure in the Rockall Tough - intense eddies south of the Anton Dorhn seamount result in strong currents with depth averages of up to 30 cm/s through a depth of 1000 m. Mission 1 ran in the Rockall Trough for 5 months from October 2009 to March 2010 and collected effectively 1778 independent CTD profiles along with measurements of depth integrated velocity. It was a complete success. Following our recent successful trial mission, later this summer our glider (called Talisker) will embark on a second more complete mission to monitor the full Extended Ellett Line from Scotland across to Iceland (to just offshore of the Eyjafjallajokull volcano) SAMS remains fully committed to maintaining and enhancing it’s efforts with what is recognised internationally as one of the most important CTD and nutrient sections anywhere in the North Atlantic In the future we plan to see our gliders supplementing in space and time the existing ship borne sections across the ocean, and participating in exciting new ways of studying ocean processes Toby Sherwin will be talking more about the recent glider mission and SAMS commitment to, and plans with, gliders in his talk on Wednesday.