Quaternary Environments Paleoclimate Models

Types of Models  Simplify a system to its basic components  Types of Models  Physical Models  Globe  Statistical Models  Regression Equations  Conceptual Models  Flow chart  Computer Models  GCMs  Test Hypotheses

Types of Models  Energy Balance Models (EBMs) – Surface temperature as a result of energy balance  Zero-Dimension – Whole Earth  One-Dimension – Earth in zonal bands with latitudinal heat transfer  Two-Dimensions – Lat/Long or Latitude/Altitude changes  Statistical –Dynamical Models (SDMs)  Use parameterized input equations to describe changes through time  Radiative Convective Models (RCMs)  Radiative processes in vertical columns  General Circulation Models (GCMs)  Use physical laws to drive all changes  Coupled Ocean-Atmosphere GCMs

Statistical-Dynamical Model of variations of Northern Hemisphere ice volume over the last 200,000 years forced by CO 2 and Insolation

Schematic Diagram of atmosphere and ocean computational boxes in a coupled GCM

Levels of Complexity and Coupling of Ocean-Atmosphere Models

Problems With Current Models  Expense and Time  Resolution  Unknown Quantities  Cloud cover and feedback  Difference in response times between various components of the model  Lacking land surface, cryosphere, biogeochemical cycles, and biome components  Climate System Models (CSMs) being developed

Estimated Response and Equilibrium Times for Different Components of the Climate System

Model Experiments  Are changes in orbital parameters enough to cause a glacial event?  Insolation as an input  Also needed increased cloudiness, increased soil moister, a shallow mixed layer in the ocean, and lower CO 2  Feedbacks include increased sea ice, lower SSTs in summer, and presence of permanent snow cover on land

Difference in Solar Radiation at the Top of the Atmosphere 115 kya

Modeled Snow Depth in August for 115 kya

Input Parameters for COHMAP Simulation

Output from COHMAP, Split Jet Stream During LGM

Modeling Forward  Models can be tested against paleorecords then these models can be used to predict future change  Multiple model outputs to estimate future change

Two Environment Canada models showing change from to Differences are based on a change in the depth and vigor of vertical mixing in the Southern Ocean

Climatic Research Unit, University of East Anglia Scaling down from a GCM through a Regional Climate Model to the landscape