Late-Holocene formation of Lake Michigan beach ridges correlated with a 70-yr oscillation in global climate

A radiocarbon-dated series of 75 beach ridges, formed at regular intervals averaging 72 yr over the past 5400 yr, provides further support for the existence of a 70-yr oscillation in Northern Hemisphere climate, postulated recently from instrument data representing less than two cycles of this climate oscillation. Results from this study lend support to the interpretation that internal variations in the ocean-atmosphere system are an important factor in climate fluctuations on a decadal-centennial time scale. A temperature oscillation with a period of about 70 yr has been a previously unrecognized but fundamental part of the global climate system since at least the middle Holocene. (C) 1996 University of Washington.