Modelling Ancient Earth Climate Alan Haywood School of Earth & Environment, University of Leeds With thanks to Paul Valdes, Jane Francis, Dan Lunt, Vicky Peck, Mark Williams and Harry Dowsett CONTENT: Rationale Models and Modelling Eocene/Oligocene - Bipolar Glaciation? Estimates of Earth System Sensitivity - Climate Vs Earth System Sensitivity - The Pliocene - Palaeo estimates of Earth System Sensitivity Motto and Philosophy Everything comes to those who wait Occam's razor: if all things are equal then the simplest solution is probably correct Why? Understand climate dynamicsUnderstand climate dynamics Test Earth System ModelsTest Earth System Models Where are we now? Simulation of the historical or near-historical record Simulation of the historical or near-historical record Analysis of the observed record of variability Analysis of the observed record of variability Projection for the next 100 years Projection for the next 100 years Primary Research Focus in Climate Change Science Greatest Strengths Spatial and temporal character of the observations. Measurement of physical quantities that define the state of the atmosphere and ocean. Greatest Weaknesses Sense of change. Sense of the integration of the Earth System. Greatest Strengths Spectacular sense of change (Furry Alligator Syndrome) True integrated system response Greatest Weaknesses Proxies rather than state variables Limited spatial and temporal resolution In contrast: A Research Focus in Earth History The greatest weaknesses in a research focus on the modern record are the greatest strengths of Earth System History ClimateHistory The Climate System General Circulation Models Model needs to simulate albedo, emissivity and general circulation. Use first principles Newton's Laws of Motion 1 st Law of Thermodynamics Conservation of Mass and Moisture Hydrostatic Balance Ideal Gas Law Components of an Earth System Model Aerosols: Dust and Sulphates Aerosols: Regional Model: High Resolution Regional Model: High Resolution Cryosphere- Lithosphere Model Model AtmosphericChemistryAtmosphericChemistry Atmospheric General Circulation Model Land Surface Hydrology Hydrology Ocean General Circulation Model Ocean Carbon Cycle Ocean Carbon Cycle Terrestrial Carbon Cycle Cycle Brief history of numerical modelling ATMOSPHERE LAND OCEANICESULPHUR CARBONCHEMISTRY ATMOSPHERE LAND OCEANICESULPHUR CARBON ATMOSPHERE LAND OCEANICESULPHUR ATMOSPHERE LAND OCEANICE ATMOSPHERE LAND OCEAN ATMOSPHERE LAND ATMOSPHERE Development of Met. Office Climate Models Component models are constructed off-line and coupled in to the climate model when sufficiently developed 1960s Present 1990 HadCM3 GCM 20 Ocean Levels 19 Atmospheric Levels Atmospheric resolution: 3.75 by 2.5 degrees Ocean resolution :1.25 by 1.25 19 levels in atmosphere 20 levels in ocean 2.5 lat 3.75 long 1.25 THE HADLEY CENTRE THIRD COUPLED MODEL - HadCM3 no flux adjustments 30km -5km Bipolar Glaciation at the E/O Boundary? Greenhouse to Icehouse transition Zachos et al., 2001 First permanent ice sheet on Antarctica pCO 2 decrease Sea level fall of m CCD deepened by ~1 km/carbon cycle reorganisation Initiation of NADW Opening of tectonic gateways Biotic overturn in plants and animals >8 C cooling in North America/ aridification of the Himalayas How much ice? Fossil Cladophlebis Ferns Dickinsonia antarctica 3D preserved conifer branches in concretions Araucaria araucana Nothofagaceae Fossil Nothofagaceae Nothofagus cunninghamii How much ice? Site 1263 ~1.2 100 kyr 30 kyr ODP Site 1263 Riesselman et al O. umbonatus image from Douglas, 1973 But what does it represent? How much ice volume? How much temperature? Observed sea level fall* Model simulation *10 m sea level fall = 0.1 1 C = 0.22 Modern Antarctic ice vol.* At least 3 C? More ice? Or both? Benthic 18 O = Ice growth + cooling ? In the Earliest Oligocene. NADW formation was just beginning Antarctica was the principal source of deep water formation Cooling expected to be transmitted to deep-waters ATLANTIC PACIFIC INDIAN Late Eocene ATLANTIC PACIFIC INDIAN Early Oligocene Benthic Mg/Ca suggests no cooling? Lear et al., 2000 South Atlantic DSDP Site ~3000 m paleodepth (1 km above CCD) no change in temperature DSDP Site 522 Pacific ODP Site ~3800 m paleodepth (similar to CCD) ~2 C warming ODP Site 1218 Lear et al., 2004 So the inevitable happens Will we find cooling at shallower sites (?) South Atlantic ODP Site 1263 Paleodepth ~ 2.1 km Paleo-lysocline ~ 3.8 km Paleo-CCD ~ 4.2 km prior to CCD deepening at E-O O Modern Atlantic estimates after Anderson and Archer, 2002 Assumptions/hopes 1.Similar CO 3 2- gradient 2. Mg/Ca response less at high CO 3 2- concentrations Modelling approach Aim Predict effect of an Antarctic ice sheet on global ocean in Early Oligocene Model parameters HadCM3L 2 x pre-industrual pCO 2 Solar constant 0.3 % Paleogeography of Rupelian (Markwick et al., 2001) Vegetation cover predicted by TRIFFID Quick Practice Effect of growing an East Antarctic ice sheet Model initially run for 800 years Ocean temperature at 3962 m (C) E. Oli - E. Oli Ann xboya-xboyc Ocean temperature at 5 m (C) E. Oli - E. Oli Ann xboya-xboyc But, model did not reach equilibrium Upper ocean integral of temperature (300 m) ~ 0.75 C cooling Model with modern Antarctic ice volume Model run extended to 2200 years Ocean temperature at 3962 m (C) E. Oli - E. Oli Ann xboya1-xboyc1 Ocean temperature at 5 m (C) E. Oli - E. Oli Ann xboya1-xboyc1 2200 yr Surface ocean response to ice sheet Ocean temperature at 5 m (C) E. Oli - E. Oli Ann xboya1-xboyc1 After 800 years O ODP Site 1263 Ocean temperature at 5 m (C) E. Oli - E. Oli Ann xboya-xboyc After 2200 years Upper ocean approaching equilibrium ~ 1 C cooling Upper ocean integral of temperature (1.3 C cooling Lower ocean integral of temperature (>300 m) Model with modern Antarctic ice volume Benthic 18 O = Ice growth + cooling How much ice volume? How much temperature? Observed sea level fall* Model *10 m sea level fall = 0.1 1 C = 0.22 Modern Antarctic ice vol.* ? How much did deep waters cool? ? Upper ocean integral of temperature (