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) “…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

Strange Attractors  Lorenz attractor  Meteorologist, 1963

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  Palynology – Size of catchment  Dendrochronology – Coherent climate signals  Packrats – Range from midden along with coherent ecosystems  Temporal coverage  Dendrochronology – 1,000 years on average  Palynology – often 10,000 years  Marine Sediments – 100,000 years

Resolution  Sampling interval  Dendrochronology – Annual  Lake Sediments – years  Marine Sediments – years  Sedimentation Rate  Non-Continuous Records  Glacial Advances

Frequency Dependence  Low Frequency Signal  High Frequency Signal

Inertia  Response Time - Lags  Pollen Assemblages – 100 years for the vegetation to respond to climate change  Insect Assemblages – Quick generation time, so change very quickly with climate  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

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 paleo records  Synthesis

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