Radiogenic isotope (Nd, Pb, Sr) signatures of surface and sea ice-transported sediments from the Arctic Ocean under the present interglacial conditions

ABSTRACT

Under modern conditions, sediments from the large continental shelves of the Arctic Ocean are mixed by currents, incorporated into sea ice and redistributed over the Arctic Basin through the Beaufort Gyre and Trans-Polar Drift major sea-ice routes. Here, compiling data from the literature and combining them with our own data, we explore how radiogenic isotopes (Sr, Pb and Nd) from Arctic shelf surface sediment can be used to identify inland and coastal sediment sources. Based on discriminant function analyses, the use of two-isotope systematics introduces a large uncertainty (ca. 50%) that prevents unequivocal identifications of regional shelf signatures. However, when using all three isotopic systems, shelf provinces can be distinguished within a ca. 23% uncertainty only, which is mainly due to isotopic overlaps between the Canadian Arctic Archipelago and the Barents–Kara seas areas. Whereas the Canadian Arctic shelf seems mostly influenced by Mackenzie River supplies, as documented by earlier studies, a clear Lena River signature cannot be clearly identified in the Laptev–Kara seas area. The few available data on sediments collected in sea-ice rafts suggest sea ice originating mostly from the Laptev Sea area, along with non-negligible contributions from the East Siberian and Kara seas. At last, whereas a clear radiogenic identity of the Mackenzie River in sediments can be identified in the Beaufort Sea margin, isotopic signatures from major Russian rivers cannot be deciphered in modern Siberian margin sediments because of an intense mixing by sea ice and currents of inland and coastal supplies.

KEYWORDS:

• Surface shelf sediments
• discriminant function analysis
• sediment mixing
• unequivocal source identification
• three-isotope system

ABBREVIATIONS:

• BS: Barents Sea
• CAA: Canadian Arctic Archipelago
• CS: Chukchi Sea
• ESS: East Siberian Sea
• KS: Kara Sea
• LS: Laptev Sea

Acknowledgements

The material used in this study was provided by Dr Dennis Darby (Old Dominion University), Dr Leonid Polyak (Byrd Polar Research Center, Ohio State University), Dr Charlotte Sjunneskog (Antarctic Research Facility, Florida State University), Mysti Weber (Oregon State University), James Broda and Ellen Roosen (Woods Hole Oceanographic Institution) and Suzanne MacLachlan (British Ocean Sediment Core Research Facility, National Oceanography Centre). M. Preda (Department of Earth and Atmospheric Sciences, Université du Québec à Montréal) is also thanked for his help with x-ray mineralogical analysis, as is Laure Meynadier, at (Institut de Physique du Globe de Paris) for her help with Sr, Pb and Nd isotope analyses on sea-ice sediments. We thank Professor Laodong Guo (University of Wisconsin–Milwaukee) for providing table data. We must also thank Dr Marcus Gutjahr (GEOMAR, Germany) for many useful comments on an earlier version of the manuscript and the three anonymous reviewers of the paper who contributed constructive comments.

Disclosure statement

No potential conflict of interest was reported by the authors.

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Additional information

Funding

This study has been financially supported by funds from the Québec Government (Fonds de Recherche du Québec – Nature et technologies – Equipe) and the Natural Sciences and Engineering Research Council of Canada (Discovery Grant grant to CHM).