Ice-cover History and Paleoceanographic Change of the Western Arctic Ocean (Mendeleev Ridge) using Be isotopes

Friday, 19 December 2014
A J Timothy Jull1, Kyeong J Kim2,3 and Seung-Il Nam3, (1)University of Arizona, Tucson, AZ, United States, (2)NASA Ames Research Center, Moffett Field, CA, United States, (3)KIGAM Korea Institute of Geoscience and Mineral Resources, Daejeon, South Korea
A new investigation of paleoclimate and environmental changes using beryllium isotopes in sediment from the Mendeleev Ridge of the western Arctic Ocean was accomplished using a 39 cm-long box core record. The age of core PS72/396-3 appears to date back to MIS 5.d based on the stratigraphy of beryllium isotopes and paleomagnetic data and other isotopic data of this study, AMS 14C ages and oxygen and carbon isotopes of planktonic foraminifera N. pachyderma sin. Both authigenic 10Be and 9Be records show that there are three major cold periods during MIS 5.d and reveals a much longer warm period after the second cold period based on 9Be record. The 10Be stratigraphy also reveals a paleomagetic excursion at 45 kyr which is comparable to other records. At depths from 22 to 25 cm, the lowest 10Be signal may be due to the highest paleomagnetic intensity, which is indicated as an age of 75 kyr from other records. However, a reduction in cosmogenic 10Be could be due to ice cover, and is correlated with δ18O evidence fo a cold period. Interestingly, 9Be data show that constant input of 9Be to the Mendeleev Ridge is observed for this time period. During this time period, TOC (%) values also show a similar pattern. The record of authigenic 9Be is inversely correlated to that of Ca and proportional to opal production. These observations confirm that 9Be can also be a good proxy as a climatic tracer. This study may be a useful approach for understanding Arctic climate change.