Surface nitrate utilization in the Bering sea since 180 kA BP: Insight from sedimentary nitrogen isotopes

Type Article
Date 2016-03
Language English
Author(s) Riethdorf Jan-Rainer1, 2, Thibodeau BenoitORCID2, 3, Ikehara MinoruORCID4, Nuernberg Dirk2, Max Lars5, Tiedemann RalfORCID5, Yokoyama Yusuke1, 6
Affiliation(s) 1 : Univ Tokyo, Atmosphere & Ocean Res Inst, Dept Ocean Floor Geosci, 5-1-5 Kashiwanoha, Kashiwa, Chiba 2778564, Japan.
2 : Helmholtz Ctr Ocean Res Kiel GEOMAR, Wischhofstr 1-3, D-24148 Kiel, Germany.
3 : Univ Tokyo, Atmosphere & Ocean Res Inst, Dept Chem Oceanog, 5-1-5 Kashiwanoha, Kashiwa, Chiba 2778564, Japan.
4 : Kochi Univ, Ctr Adv Marine Core Res, B200 Monobe Nankoku, Kochi 7838502, Japan.
5 : Alfred Wegener Inst Polar & Marine Res, Handelshafen 12, D-27570 Bremerhaven, Germany.
6 : Japan Agcy Marine Earth Sci & Technol, Inst Biogeosci, 2-15 Natsushimacho, Yokosuka, Kanagawa 2370061, Japan.
Source Deep-sea Research Part Ii-topical Studies In Oceanography (0967-0645) (Pergamon-elsevier Science Ltd), 2016-03 , Vol. 125-126 , P. 163-176
DOI 10.1016/j.dsr2.2015.03.007
WOS© Times Cited 16
Keyword(s) Bering Sea, Quaternary, Nitrogen isotopes, Nitrate utilization
Abstract

We present high-resolution records of sedimentary nitrogen (delta N-15(bulk)) and carbon isotope ratios (delta C-13(bulk)) from piston core S0201-2-85KL located in the western Bering Sea. The records reflect changes in surface nitrate utilization and terrestrial organic matter contribution in submillennial resolution that span the last 180 kyr. The delta N-15(bulk) record is characterized by a minimum during the penultimate interglacial indicating low nitrate utilization (similar to 62-80%) despite the relatively high export production inferred from opal concentrations along with a significant reduction in the terrestrial organic matter fraction (m(terr)). This suggests that the consumption of the nitrate pool at our site was incomplete and even more reduced than today (similar to 84%). delta N-15(bulk) increases from Marine Isotope Stage (MIS) 5.4 and culminates during the Last Glacial Maximum, which indicates that nitrate utilization in the Bering Sea was raised during cold intervals (MIS 5.4, 5.2, 4) and almost complete during MIS 3 and 2 (similar to 93-100%). This is in agreement with previous hypotheses suggesting that stronger glacial stratification reduced the nutrient supply from the subeuphotic zone, thereby increasing the iron-to-nutrient ratio and therefore the nitrate utilization in the mixed surface layer. Large variations in delta N-15(bulk) were also recorded from 180 to 130 ka BP (MIS 6), indicating a potential link to insolation and sea-level forcing and its related feedbacks. Millennial-scale oscillations were observed in delta N-15(bulk) and delta C-13(bulk) that might be related to Greenland interstadials.

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Riethdorf Jan-Rainer, Thibodeau Benoit, Ikehara Minoru, Nuernberg Dirk, Max Lars, Tiedemann Ralf, Yokoyama Yusuke (2016). Surface nitrate utilization in the Bering sea since 180 kA BP: Insight from sedimentary nitrogen isotopes. Deep-sea Research Part Ii-topical Studies In Oceanography, 125-126, 163-176. Publisher's official version : https://doi.org/10.1016/j.dsr2.2015.03.007 , Open Access version : https://archimer.ifremer.fr/doc/00421/53261/