Time series analysis of ice-rafted debris accumulation in the Irminger basin, 0-630 ka

Recently published isotopic records and point count records of biogenic, volcanic and nonvolcanic terrigenous (ice-rafted debris; IRD) sediment components from ODP Hole 919A in the Irminger basin, northern North Atlantic, generated a comprehensive dataset and complicated climate signals from which general trends and developmental steps in the paleoceanographic reconstruction for the last 630 kyr were identified. To extract any rhythmic cycles embedded in this long term, unevenly-spaced dataset (avg. sample resolution of 1.3 kyr), spectral analyses of the oxygen isotope and IRD records were performed using SPECTRUM and REDFIT. Accounting for coring gaps, results show a dominant eccentricity cycle in the O-isotope record and an unexpected dominant half-precession cycle (11.5 kyr) in the IRD record. Obliquity frequencies are not robust and there is no precession frequency. Millennial pacing (3-7 kyr) of both records is observed when analyzing the complete time series and is confirmed in higher resolution intervals (e.g., last glacial, MIS 8), suggesting that suborbital patterns of climate change and IRD input to the Irminger basin extend back at least 300 kyr, and possibly 600 kyr.