Publication Date:
2017-02-08
Description:
Reduced surface–deep ocean exchange and enhanced nutrient consumption by phytoplankton
in the Southern Ocean have been linked to lower glacial atmospheric CO2. However,
identification of the biological and physical conditions involved and the related processes
remains incomplete. Here we specify Southern Ocean surface–subsurface contrasts using a
new tool, the combined oxygen and silicon isotope measurement of diatom and radiolarian
opal, in combination with numerical simulations. Our data do not indicate a permanent glacial
halocline related to melt water from icebergs. Corroborated by numerical simulations, we find
that glacial surface stratification was variable and linked to seasonal sea-ice changes. During
glacial spring–summer, the mixed layer was relatively shallow, while deeper mixing occurred
during fall–winter, allowing for surface-ocean refueling with nutrients from the deep reservoir,
which was potentially richer in nutrients than today. This generated specific carbon and opal
export regimes turning the glacial seasonal sea-ice zone into a carbon sink.
Repository Name:
EPIC Alfred Wegener Institut
Type:
Article
,
isiRev
Format:
application/pdf
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