Understanding the mechanisms behind high glacial productivity in the southern Brazilian margin
This study explores the mechanisms behind the high glacial productivity in the southern Brazilian margin (SBM) during the last 70 kyr using planktonic foraminifera assemblage and subsurface temperature information derived using the modern analogue technique. We show that enhanced glacial productivit...
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Veröffentlicht in: | Climate of the past 2019-05, Vol.15 (3), p.943-955 |
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Sprache: | eng |
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Zusammenfassung: | This study explores the mechanisms behind the high glacial
productivity in the southern Brazilian margin (SBM) during the last 70 kyr using
planktonic foraminifera assemblage and subsurface temperature information derived using the modern analogue technique. We show that enhanced glacial
productivity was driven by the synergy of two mechanisms operating in
different seasons: (i) enhanced productivity in the upwelling region
during short austral summer events; and (ii) the persistent presence of the
Plata Plume Water (PPW) due to prolonged austral winter conditions. We suggest
that the upwelling systems in the southern Brazilian margin were more
productive during the last glacial period due to the enhanced Si supply for
diatom production by high-Si thermocline waters preformed in the
Southern Ocean. We hypothesize that orbital forcing did not have a major
influence on changes in upwelling during the last glacial period. However,
the more frequent northward intrusions of the Plata Plume Water were
modulated by austral winter insolation at 60∘ S via changes in the
strength of alongshore southwesterly winds. After the Last Glacial Maximum, the reduced
Si content of thermocline waters decreased upwelling productivity, while
lower austral winter insolation decreased the influence of the Plata Plume
Water over the southern Brazilian margin, reducing regional productivity. |
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ISSN: | 1814-9332 1814-9324 1814-9332 |
DOI: | 10.5194/cp-15-943-2019 |