A DEEP-SEA CORAL RECORD OF NORTH ATLANTIC RADIOCARBON THROUGH THE YOUNGER DRYAS: EVIDENCE FOR INTERMEDIATE/DEEP WATER REORGANIZATION

• Main Authors: Selene F. Eltgroth, Jess F. Adkins, Laura F. Robinson, John Southon, Michaele Kashgarian
• Other Authors: The Pennsylvania State University CiteSeerX Archives
• Format: Text
• Language: English
• Subjects: North Atlantic Deep Water; North Atlantic
• Online Access: http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.425.1066; http://thesis.library.caltech.edu/2104/4/03Chapter3.pdf

Our record of Younger Dryas intermediate depth seawater � 14 C measured in North Atlantic deep-sea corals supports a link between abrupt climate change and intermediate ocean variability. Our data show that northern source intermediate water (~1700m) was replaced by 14 C depleted southern source water at the onset of the event, consistent with a reduction in the rate of North Atlantic Deep Water formation. This transition requires the existence of large, mobile gradients of � 14 C in the ocean during the Younger Dryas. The � 14 C water column profile from Keigwin (2004) provides direct evidence for the presence of one such gradient at the beginning of the Younger Dryas (~12.9 ka), with a 100 ‰ offset between shallow (<~2400m) and deep water. Our early Younger Dryas data are consistent with this profile and also show a � 14 C inversion, with 35 ‰ more enriched water at ~2400m than at ~1700m. Over the rest of the Younger Dryas our intermediate/deep water coral � 14 C data gradually increases while the atmosphere � 14 C drops. For a very brief interval at ~12.0 ka and at the end of the Younger Dryas (11.5 ka), intermediate water � 14 C (~1200m) approached atmospheric � 14 C. These enriched � 14 C results suggest an enhanced initial � 14 C content of the water and demonstrate the presence of large lateral � 14 C gradients in the intermediate/deep ocean. The transient � 14 C enrichment at ~12.0 ka occurred in the26 middle of the Younger Dryas and demonstrates that there is at least one time when the intermediate/deep ocean underwent dramatic change but with much smaller effects in other paleoclimatic records.