Presentation on theme: "ICP, Sitges, 2013 Modelled insights into climate dynamics of the Cretaceous and Paleogene greenhouse Dan Lunt, Claire Loptson, Alex Farnsworth, Paul Markwick."— Presentation transcript:
ICP, Sitges, 2013 Modelled insights into climate dynamics of the Cretaceous and Paleogene greenhouse Dan Lunt, Claire Loptson, Alex Farnsworth, Paul Markwick (1)What is the role of palaeogeography across the Cretaceous and Paleogene? (2)Where can new data be targetted to obtain a pure climate signal? (3)How does palaeogeography influence Climate Sensitivity?
ICP, Sitges, 2013 Data from Friedrich et al (2012) (1) Introduction What is the role of solar forcing vs. palaeogeographic forcing vs. carbon cycle forcing? Last 150 Ma: Major climate trends, + events
ICP, Sitges, 2013 (1) Introduction CO 2 proxies Solar forcing Palaeogeography Maps from Scoteses Paleomap
ICP, Sitges, 2013 (2a) Previous modelling work (paleogeography) Luyendyk et al, (1972) Barron et al (1980) Real models... Energy balance models... e.g. Westward flow through Tethys. e.g. significant effect on temperature due to continental area (i.e. sea level), and potential importance of desert regions.
ICP, Sitges, 2013 Barron and Peterson (1990) Barron and Washington (1984) Bice et al (2000) Atmosphere-only models... Ocean-only models... (2a) Previous modelling work (paleogeography) e.g. changes in high latitude land area and topography most important drivers... e.g. Eastward flow through Tethys. e.g. Eocene (from SH) vs. Miocene (from NH) ocean overturning
ICP, Sitges, 2013 e.g. Atlantic rifting leads to warming, plus salinity changes usually interpreted as signalling middle Cretaceous warmth. Donnadieu et al (2006) Poulsen et al (2003) Intermediate complexity models... (2a) Previous modelling work (paleogeography) e.g. break-up of continent leads to increased seasonality
ICP, Sitges, 2013 Spicer et al (2008) Huber and Sloan (2001) Atmosphere-ocean models... (2a) Previous modelling work (paleogeography) e.g. modelled seasonality too large wrt. CLAMP, for 3 different Cretaceous palaeogeographies e.g. modelled Eocene meridional temperature gradients interpreted as being too great.
ICP, Sitges, 2013 e.g. Cretaceous climate sensitivity enhanced due to vegetation feedbacks. Zhou et al (2012) (2a) Previous modelling work (CO 2 ) Caballero and Huber (in press) e.g. Eocene climate sensitivity increases at higher temperatures – due to non-linearities in both forcing and cloud feedbacks.
ICP, Sitges, 2013 (3a) Questions to be addressed Current paradigm: Paleogeographical changes less important than greenhouse gas forcing. BUT: Work mostly focussed on a limited number of time periods Lack of consistency across simulations Coarse palaeogeographies Models have improved SO: (1)What is the role of palaeogeography across the Cretaceous/Paleogene? (2)Where can new data be targetted to obtain a pure climate signal? (3)How does palaeogeography influence Climate Sensitivity? (i.e. state dependency).
ICP, Sitges, 2013 (3b) Experimental Design Palaeogeographies provided by Getech and Paul Markwick Created using similar techniques to those outlined in Markwick (2007), based on published lithologic, tectonic and fossil studies, the lithologic databases of the Paleogeographic Atlas Project (University of Chicago), and deep sea (DSDP/ODP) data. Extensively updated from Markwick (2007), e.g. bathymetry, new rotations, more underlying data. Animation removed.
ICP, Sitges, 2013 (3b) Experimental Design The model: HadCM3L How good is it for the palaeo? Lunt et al, Clim. Past (2012) Data compiled by Tom Dunkley Jones.
ICP, Sitges, 2013 Phase 1Phase 2Phase 3Phase 4 Deep ocean temperature 50-years400-years 57-years years Pre-industrial CO 2 Pre-industrial SSTs Paleogeography's Uniform Veg Lakes4xCO 2 TRIFFID Solar constants Ozone concentrations Creation of islands Baratropic stremfunction No Ice + 2 x CO 2 Ice + 2 x CO 2 Ice + 4 x CO 2 (3b) Experimental Design (consistent across all simulations) Simulation spinup – from Alex Farnsworth
ICP, Sitges, 2013 (4) Results Global means...
ICP, Sitges, 2013 (4) Results SSTs... e.g. Maximum warmth shifts from W. Pacific to E. Indian ocean in Late Eocene. Zonal mean relatively constant. ENSO is a constant feature. Winter Arctic and Southern Ocean seaice for all time periods. Animation removed.
ICP, Sitges, 2013 (4) Results Regions of deep water formation... e.g. N. Pacific deep water formation in earliest Cretaceous, gone by Middle Cretaceous. Mid and late Cretaceous and early Eocene little mixing. North Atlantic deep water formation kicks off ~40 Ma. Animation removed.
ICP, Sitges, 2013 (4) Results Vegetation... e.g. Expansive N and S American deserts in early Cretaceous. Green Sahara develops in late Eocene. Animation removed.
ICP, Sitges, 2013 (4) Results Single sites...
ICP, Sitges, 2013 (4) Results Implications for site targetting... Where are the locations with least paleography-related change; i.e. Where to go for a pure CO2 signal: MarineTerrestrial
ICP, Sitges, 2013 (4) Results Climate Sensitivity Only one (two) true sensitivity – Earth System Sensitivity. Either to (a) Wm -2 or (b) ΔCO 2 This is neither! Modellers imagination - Charney+vegetation.
ICP, Sitges, 2013 (4) Results Climate Sensitivity 3.3 o C2.8 o C3.0 o C2.8 o C 3.0 o C3.2 o C2.5 o C
ICP, Sitges, 2013 Summary Cretaceous and Paleogene simulations broadly support the paradigm that carbon cycle dominates over palaeogeography forcing. BUT, at single sites, the temperature changes due to palaeogeography alone can be very large. AND, other aspects of the system, such as ocean circulation and vegetation, can also show very large palaeogeographically-driven changes. Simulations can point to where a pure CO 2 signal could be obtained. Climate Sensitivity is a function of palaeography, varying by 30% through the late and mid Cretaceous.
ICP, Sitges, 2013 (5) Future work CESM simulations Early Cretaceous gridLate Cretaceous grid Modern DMS emissions paleo-tised Early Cretaceous DMS emissions Late Cretaceous DMS emissions
ICP, Sitges, 2013 (5) Future work NERC project: Cretaceous-Paleocene-Eocene: Exploring Climate and Climate Sensitivity Complete CO 2 sensitivities Ice sheets [e.g. role of CO 2, gateways and ice sheets at E-O boundary] Model internal parameter sensitivity studies. Data compilations (Stuart Robinson, Oxford). Back-out model-derived CO 2 record Equivalent future simulations Sagoo et al, Phil Trans, in press. Kiehl et al, Phil Trans, in press. Lunt et al, Phil Trans, in press..
ICP, Sitges, 2013 (5) Future work Complete Neogene simulations. Role of orbital forcing PMIP working group on pre-Pliocene climates Joint venture between data and modelling communities Model output available.
ICP, Sitges, 2013Dan Lunt Warm Climates of the Past – A lesson for the future? Special Issue of Phil Trans A All papers now in press Including contributions from: Badger, DeConto, Dowsett, Foster, Hansen, Haywood, John, Kiehl, Lunt, Otto- Bliesner, Pagani, Pancost, Pearson, Sagoo, Valdes, Zachos, Zeebe, Zhang. Early Eocene, ~ Ma Mid-Pliocene, ~ Ma Last Interglacial, ka...future, 2100 Using the palaeo to inform the future
ICP, Sitges, 2013 (4) Results Precipitation... e.g. Amazon desiccates in late Oligocene. East Asian monsoon system initiates in middle Eocene. North Atlantic storm tracks intensify in late Eocene. Animation removed.