New Constraints on the Physical and Biological Controls on the Silicon Isotopic Composition of the Arctic Ocean

The silicon isotope composition of silicic acid, δ30Si(OH)4, in the deep Arctic Ocean is anomalously heavy compared to all other deep ocean basins. To further evaluate the mechanisms leading to this condition, δ30Si(OH)4 was examined on US GEOTRACES section GN01 from the Bering Strait to the North P...

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Bibliographic Details
Published in:Frontiers in Marine Science
Main Authors: Mark A. Brzezinski, Ivia Closset, Janice L. Jones, Gregory F. de Souza, Colin Maden
Format: Article in Journal/Newspaper
Language:English
Published: Frontiers Media S.A. 2021
Subjects:
nutrients
biogeochemical cycles
diatoms
silicon isotopes
Arctic Ocean
GEOTRACES
Science
Q
General. Including nature conservation
geographical distribution
QH1-199.5
Arctic
Chukchi Sea
Bering Strait
Canada
Pacific
North Pole
canada basin
Chukchi
Online Access:https://doi.org/10.3389/fmars.2021.699762
https://doaj.org/article/5db4e12671f04077a0565837ec527c9c
Description
Summary:The silicon isotope composition of silicic acid, δ30Si(OH)4, in the deep Arctic Ocean is anomalously heavy compared to all other deep ocean basins. To further evaluate the mechanisms leading to this condition, δ30Si(OH)4 was examined on US GEOTRACES section GN01 from the Bering Strait to the North Pole. Isotope values in the polar mixed layer showed a strong influence of the transpolar drift. Drift waters contained relatively high [Si(OH)4] with heavy δ30Si(OH)4 consistent with the high silicate of riverine source waters and strong biological Si(OH)4 consumption on the Eurasian shelves. The maximum in silicic acid concentration, [Si(OH)4], within the double halocline of the Canada Basin formed a local minimum in δ30Si(OH)4 that extended across the Canada Basin, reflecting the high-[Si(OH)4] Pacific source waters and benthic inputs of Si(OH)4 in the Chukchi Sea. δ30Si(OH)4 became lighter with the increase in [Si(OH)4] in intermediate and deep waters; however, both Canada Basin deep water and Eurasian Basin deep water were heavier than deep waters from other ocean basins. A preliminary isotope budget incorporating all available Arctic δ30Si(OH)4 data confirms the importance of isotopically heavy inflows in creating the anomalous deep Arctic Si isotope signature, but also reveals a surprising similarity in the isotopic composition of the major inflows compared to outflows across the main gateways connecting the Arctic with the Pacific and the Atlantic. This similarity implies a major role of biological productivity and opal burial in removing light isotopes entering the Arctic Ocean from rivers.

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