Sediment-color record from the Northeast Atlantic reveals patterns of millennial-scale climate variability during the past 500,000 years

A 500,000-yr-long deep-sea sediment-color record from the Northeast Atlantic was investigated to reconstruct the evolution of late Pleistocene climate variability on millennial time scales. Variations of the red-green color intensity are probably caused by climatically induced changes in the ice-rafted input of red-colored iron-bearing terrigenous material to the core site. The resolution of the age model impedes the detection of distinct spectral features at sub-Milankovitch periodicities. Hence, millennial-scale climate variability is quantified as time-dependent variance of the high-pass filtered color time series. The course of the estimated variance shows distinct patterns, which can be linked to continental ice mass. During the past 500,000 yr, large-amplitude millennial-scale climate variability occurs only if continental ice mass exceeds a threshold level, equivalent to sea level at approximately 4010 of the lowering during the last glacial maximum. (C) 2002 University of Washington.