Reconciling down core anticorrelation of diatom carbon and nitrogen isotopic ratios from the Southern Ocean

[1] Oceanic nutrient cycling in the Southern Ocean is supposed to have an important impact on glacial-interglacial atmospheric CO(2) changes and global climate. In order to characterize such nutrient cycling over the last two climatic cycles we investigated carbon and nitrogen isotopic ratios of dia...

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Bibliographic Details
Published in:Paleoceanography
Main Authors: Crosta, X, Shemesh, A
Format: Article in Journal/Newspaper
Language:English
Published: Amer Geophysical Union 2002
Subjects:
Southern Ocean
paleoceanography
geochemistry
diatoms
Antarctic
Antarctic Ocean
Indian
The Antarctic
Antarc*
Sea ice
Online Access:https://archimer.ifremer.fr/doc/00223/33402/31859.pdf
https://doi.org/10.1029/2000PA000565
https://archimer.ifremer.fr/doc/00223/33402/
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Summary:[1] Oceanic nutrient cycling in the Southern Ocean is supposed to have an important impact on glacial-interglacial atmospheric CO(2) changes and global climate. In order to characterize such nutrient cycling over the last two climatic cycles we investigated carbon and nitrogen isotopic ratios of diatom-bound organic matter (delta(13)C(diat) and delta(15)N(diat)- respectively) in two cores retrieved form the Atlantic and Indian sectors of the Antarctic Ocean. The two cores show the same isotopic patterns. The delta(13)C(diat) values are depleted during glacial periods and enriched during interglacial periods, indicating lower productivity during cold times. The delta(15)N(diat) values are enriched during glacial periods and depleted during interglacial periods, arguing for greater nitrate utilization during cold times. Taken at face value, this apparent contradiction leads to opposite conclusions on the role of the Southern Ocean biological pump on the atmospheric CO, changes. However, the two sets of data can be reconciled by a "sea ice plus mixing rate scenario" that calls upon a balance between the effect Of Cutting off gas transfer at the ocean-atmosphere boundary and the effect of reducing vertical transport of nutrients through the pycnocline.

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