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Climate Change and the Oceans Ben McNeil Climate Change Research Centre The University of New South Wales.

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Presentation on theme: "Climate Change and the Oceans Ben McNeil Climate Change Research Centre The University of New South Wales."— Presentation transcript:

1 Climate Change and the Oceans Ben McNeil Climate Change Research Centre The University of New South Wales

2 The Natural Greenhouse Effect Incoming Shortwave Solar Radiation Outgoing Longwave Radiation

3 Global Warming: The Enhanced Greenhouse Effect Outgoing heat gets trapped Greenhouse Gases

4 The Importance of Greenhouse Gases 167  C -63  C 15  C 470  C Predict the temperature on Venus? Extreme Greenhouse Effect

5 The Greenhouse-Intensive Industrial Revolution Billion tonnes of Greenhouse Gas Emissions

6 Earths CO 2 Levels

7 Intergovernmental Panel on Climate Change (2007) 13.6ºC 14.1ºC 14.5ºC 14.3ºC 13.8ºC Atmospheric CO 2 Levels (ppm) Global Mean Temperature The planet has warmed about 0.75°C in the last century Twelve of the last 13 years are the warmest years since 1850 “Warming of the climate system is unequivocal, as is now evident from observations of increases in global average air and ocean temperatures, widespread melting of snow and ice, and rising global mean sea level”,IPCC 4th Assessment Report.

8 Dramatic Warming Evidence from the Arctic Since IPCC Analysis 2007 Stroeve et al. GRL 2007

9 Sea-Level Rise: Observations and Projections

10 Sea-Level Rise: The Big Unknown

11 Implications for the North Atlantic Ocean Normal Circulation Climate Change Effect

12 Atmospheric CO 2 Water Mass Formation and Subduction Oceanic Controls on Atmospheric CO 2 : Thermodynamic Equilibration CO 2 CO 2 is very soluble Ocean circulation stores and transports vast quantities

13 Atmos CO 2 (ppm) Year CO 2 Without Natural Sinks Observed CO 2 Oceanic CO 2 Absorption Importance of the Ocean for Atmospheric CO 2 Atmospheric CO 2 today would be about 450ppm without the ocean!!

14 Ocean Circulation with Climate Change Stratification with warming and freshening Slow-down in overturning circulation

15 Model Projections of Circulation and Carbon Cycle 50% slowdown in overturning circulation 20-30% reduction in oceanic CO 2 uptake Sarmiento, 1998

16 Oceanic Biological Pump with Climate Change Phytoplankton are starved of nutrients due to ocean stratification ~15% reduction by the year 2100 Normal Climate Change Matear (2000)

17 CO 2 + H 2 O  HCO H +  CO H + Unfortunate Consequences of Oceanic Anthropogenic CO 2 Absorption Increase from air- sea exchange CO 2 Decrease Increase pH = -log[H + ] More CO 2 Uptake = More Acidic = Less CO 3 2 -

18 Changing Carbonate Equilibrium in Seawater

19 Calcium Carbonate (CaCO 3 ) Cycle

20 Direct Impact of Elevated CO 2 on Phytoplankton and Coral Reefs Elevated CO 2 levels reduces the calcification rate of phytoplankton and corals Riebesell et al, [2000] (Coccolithophores) High CO 2 Low CO 2 1um

21 Oceans and Climate Change: Summary –Ocean is and will continue to absorb massive amounts of CO 2 and the warmth humans are imposing on earth –Ocean circulation is likely to slowdown in a warmer world leading to Big changes in regional climate Lower CO 2 uptake and therefore more work for us to do Lower biological productivity and consequences to fishing industry –Sea-level rise and its problems –Chemical alterations to calcifying organisms due to ocean acidification


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