Late quaternary paleo-climatic records from Alaskan Loess: Identifying causes of natural climate variability

Magnetic susceptibility profiling and magnetic remanence studies, x-ray sedigraph analysis, scanning electron microscope image studies, tephrochronology, and fission-track dating of thick loess deposits in Alaska reveal a continuous record of the chronology and pattern of past climate changes at high latitudes. Long-term climate changes in Alaska appear to have closely followed global patterns over at least the last 200,000 years. Radiocarbon and fission-track dating demonstrate agreement between the timing of climate changes recorded in terrestrial loess deposits and records from marine and ice cores. Spectral analyses of loess proxy climate time-series reveal power at orbital frequencies, providing evidence for the Milankovitch model of climate change. Many short-term climate events, lasting only 102 - 103 years, are also recorded in loess sections. Some of these short-term events appear to reflect transient changes in global atmospheric CO2 contents of 25-50% documented by studies of ice cores, and provide evidence for changes in the global Greenhouse effect due to natural variations of atmospheric CO2 content