7Intergovernmental Panel on Climate Change (2007) Atmospheric CO2 Levels (ppm)Global Mean Temperature14.1ºC13.8ºC13.6ºCThe planet has warmed about 0.75°C in the last centuryTwelve 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.
8Dramatic Warming Evidence from the Arctic Since IPCC Analysis 2007Stroeve et al. GRL 2007
10Sea-Level Rise: The Big Unknown Mention accumulation in interior, loss of ice on the margins due to calving and melting/runoff.
11Implications for the North Atlantic Ocean Normal CirculationClimate Change Effect
12Oceanic Controls on Atmospheric CO2 : Thermodynamic EquilibrationCO2CO2 is very solubleOcean circulation stores and transports vast quantitiesWater Mass Formation and Subduction
13Importance of the Ocean for Atmospheric CO2 Atmos CO2(ppm)YearCO2 Without Natural SinksOceanic CO2 AbsorptionObserved CO2Translating emissions to CO2 concentrationsIllustrates CO2 concentration would be without the natural anthropogenic CO2 sinksThe ocean is the most dominant sinkAtmosphere would be 55ppm higherHowever the oceanic absorption is vulnerable to changes in temperature / circulation changesAtmospheric CO2 today would be about 450ppm without the ocean!!
14Ocean Circulation with Climate Change Stratification with warming and fresheningSlow-down in overturning circulation
15Model Projections of Circulation and Carbon Cycle • 50% slowdown in overturning circulationModelling BGC with climate change-present oxygen, nutrient and carbon uptake changes- nutrient supply changes may impact on the ecosystem affect both higher trophic levels and the carbon export to the deep oceanNeed to continue to make observations to provide continue insight into the behavior of both the physical and biological formulations of the modelNeed to develop and apply models that incorporate the observations and project the impact of climate changeNeed base line observations of the ecosystem. Focus on the lower trophic levels where the links between climate change and marine impacts is more tractable• 20-30% reduction in oceanic CO2 uptakeSarmiento, 1998
16Oceanic Biological Pump with Climate Change NormalPhytoplankton are starved of nutrients due to ocean stratification~15% reduction by the year 2100Climate ChangeMatear (2000)
17Unfortunate Consequences of Oceanic Anthropogenic CO2 Absorption IncreaseIncrease from air-sea exchangeCO2 + H2O HCO H+ CO H+DecreasepH = -log[H+]More CO2 Uptake = More Acidic = Less CO32-
20Direct Impact of Elevated CO2 on Phytoplankton and Coral Reefs Low CO2Elevated CO2levels reduces the calcification rate of phytoplankton and coralsHigh CO2Riebesell et al, (Coccolithophores)1um
21Oceans and Climate Change: Summary Ocean is and will continue to absorb massive amounts of CO2 and the warmth humans are imposing on earthOcean circulation is likely to slowdown in a warmer world leading toBig changes in regional climateLower CO2 uptake and therefore more work for us to doLower biological productivity and consequences to fishing industrySea-level rise and its problemsChemical alterations to calcifying organisms due to ocean acidification