Transcript Chapter 1
Quaternary Environments Paleoclimatic Reconstruction Paleoclimatic Reconstruction “…paleoclimatic data provide the basis for testing hypotheses about the causes of climatic change. Only when the causes of past climatic fluctuations are understood will it be possible to fully anticipate or forecast climatic variations in the future (Bradley and Eddy, 1991).” (Bradley 1999) Thresholds Nonlinear responses Critical thresholds http://kevin.atkinson.dhs.org/fractals/ Strange Attractors Lorenz attractor Meteorologist, 1963 http://www.geocomplexity.com/Global_climate.htm Signal to Noise Ratio Proxy records catalog the phenomenon in which we are interested. This is called signal. At the same time they filter that signal and also respond to other drivers. This we call noise. If you examine the signal to noise ratio you can determine the quality of the record. Calibration Direct information on the phenomenon or other proxy materials are used to demonstrate the relationship. The principle of uniformitarianism. Never 100% accurate. Analog Situations Comparable situations in the past No-Analog situations Multiple proxies Extent Spatial coverage – Size of catchment Dendrochronology – Coherent climate signals Packrats – Range from midden along with coherent ecosystems Palynology Temporal coverage – 1,000 years on average Palynology – often 10,000 years Marine Sediments – 100,000 years Dendrochronology Resolution Sampling interval – Annual Lake Sediments – 50 - 200 years Marine Sediments – 500 - 1000 years Dendrochronology Sedimentation Rate Non-Continuous Records Glacial Advances Frequency Dependence Low Frequency Signal High Frequency Signal Inertia Response Time - Lags Assemblages – 100 years for the vegetation to respond to climate change Insect Assemblages – Quick generation time, so change very quickly with climate Pollen Autocorrelation Dendrochronology - Climate responses Climatic Forcing Factors Proxies record climate change Also record forcing factors Volcanic aerosols Dust in ice cores Carbon Dioxide Methane Nitrous Oxide Feedbacks Positive Feedbacks Negative Feedbacks http://www.geocomplexity.com/Global_climate.htm Dating Utmost importance to determine timing of events Synchronicity of timing Forcing factors Lagged timing Levels of Analysis Level I Field data collection, analysis, and measurements Level II Calibrated and converted to paleo records Level III Regionalized Synthesis paleo records Models Simplify a system to its basic components Types of Models Physical Models Globe Computer Models GCMs Conceptual Flow Models chart Test Hypotheses