EVIDENCE FOR MILLENNIAL-SCALE CLIMATE VARIABILITY IN THE SURFACE WATERS ABOVE ODP SITE 984, NE ATLANTIC OCEAN DURING THE LAST GLACIAL INTERVAL (MIS 4-2)

Successful efforts to recover quality high sedimentation rate deep-sea sediment sections from the North Atlantic over the last decades have produced a number of studies demonstrating that climate instability at millennial time-scales is a pervasive component of Late Pleistocene North Atlantic climate. This is particularly true during Marine Isotope Stages (MIS) 4-2, i.e., the last glacial interval. One such high sedimentation rate section was recovered at ODP Site 984, Subpolar Atlantic Ocean where sedimentation rates during MIS 4-2 exceed 17cm/kyr. We have begun to generate more detailed records from MIS 4-2 at Site 984 by reducing our sampling interval from 20 to around 2.0 cm, improving the resolution of our records an order of magnitude, from roughly 1000 to 100-200 years. 422 samples were used to generate high resolution records of changes in the input of ice-rafted detritus (IRD). Superimposing our new high resolution IRD record from the early glacial reveals that Heinrich events 4, 5 and 6 (approximately 7.12, 9.36, and 12.6 MCD respectively) are recorded as much more abrupt and rapid increases in IRD concentrations to 900 or greater lithic grains per gram than were observed in previous low resolution records. Three 1-2 kyr intervals, one following H6, and one following each of the two subsequent IRD events afterwards, contain little IRD. Additional abrupt IRD events are recorded at approximately 11.72, 10.64, 10.44, 8.86, 8.58, 8.46, 6.64, and 6.46 MCD. Thus, our new early glacial IRD record is recording additional abrupt episodic increases in IRD concentrations comparable in intensity to the identified Heinrich events that are also recorded at ODP Site 980 to the southeast. This suggests that ODP Site 984 sediments document a series of more closely spaced episodic increases in IRD concentration that can be more directly related to the Dansgaard/Oeschger events recorded in Greenland ice cores.