TY - CONF
T1 - Impact of the salt leakage through the Indian-Atlantic ocean gateway on the Atlantic MOC
AU - Marino, G.
AU - Zahn, R.
AU - Ziveri, P.
AU - Ziegler, M.
AU - Hall, I. R.
AU - Elderfield, H.
PY - 2012/4/1
Y1 - 2012/4/1
N2 - Freshwater perturbation in the northern North Atlantic exerts a strong
influence on the stability of the Atlantic meridional overturning
circulation (AMOC) with potentially severe impacts on the regional and
global climates. The occurrence of ice rafted detritus (IRD) in the
glacial sediments of the North Atlantic testifies to past episodes of
Laurentide ice sheet surging that also coincided with AMOC curtailments
and prominent climate deterioration in the Northeast Atlantic and
Western Europe. The equally abrupt warming shifts observed in Greenland
ice core and North Atlantic sediment core records that characterize the
end of each IRD event have been related to the rapid resumption of AMOC
and its associated heat transport. The hysteresis response, under
glacial boundary conditions, of the AMOC to freshwater forcing suggests
that a reduction in this forcing may have been sufficient to trigger the
rapid AMOC resumptions revealed by several palaeoceanographic records.
But recent modelling studies allude to the potential importance of a
salt surplus, originating in the Indian Ocean and transported to the
South Atlantic via the Agulhas leakage, that may have acted as a
positive feedback on the AMOC strengthening. This possibility, however,
has yet to be adequately tested with palaeoproxy reconstructions. We
present a suite of multi-centennial-scale palaeoceanographic records
spanning a full glacial cycle from the Southwest African margin and
Agulhas Plateau that have been generated as part of the EU Marie Curie
GATEWAYS project. The sediment cores are positioned such that they
monitor the leakage of Agulhas water into the Atlantic and the Agulhas
Return Current that straddles the South Atlantic subtropical front on
its way to the Indian Ocean. Paired Mg/Ca-δ18O analyses on the
planktonic foraminifera Globigerinoides ruber and Globigerina bulloides
reveal millennial-scale surface ocean temperature and salinity changes
at the core sites that reflect recurrent oscillations of the Agulhas
Leakage. Coeval changes in the IRD record from the Agulhas Plateau
allude to pronounced latitudinal migrations of regional oceanic fronts
during the Agulhas leakage events. The timing of events in our records
of surface ocean conditions (temperature, salinity, IRD) are
out-of-phase with similar events in the North Atlantic, suggesting that
the Agulhas leakage, via its impact on the AMOC activity, may be a
significant climate forcing on millennial timescales during the Late
Pleistocene.
AB - Freshwater perturbation in the northern North Atlantic exerts a strong
influence on the stability of the Atlantic meridional overturning
circulation (AMOC) with potentially severe impacts on the regional and
global climates. The occurrence of ice rafted detritus (IRD) in the
glacial sediments of the North Atlantic testifies to past episodes of
Laurentide ice sheet surging that also coincided with AMOC curtailments
and prominent climate deterioration in the Northeast Atlantic and
Western Europe. The equally abrupt warming shifts observed in Greenland
ice core and North Atlantic sediment core records that characterize the
end of each IRD event have been related to the rapid resumption of AMOC
and its associated heat transport. The hysteresis response, under
glacial boundary conditions, of the AMOC to freshwater forcing suggests
that a reduction in this forcing may have been sufficient to trigger the
rapid AMOC resumptions revealed by several palaeoceanographic records.
But recent modelling studies allude to the potential importance of a
salt surplus, originating in the Indian Ocean and transported to the
South Atlantic via the Agulhas leakage, that may have acted as a
positive feedback on the AMOC strengthening. This possibility, however,
has yet to be adequately tested with palaeoproxy reconstructions. We
present a suite of multi-centennial-scale palaeoceanographic records
spanning a full glacial cycle from the Southwest African margin and
Agulhas Plateau that have been generated as part of the EU Marie Curie
GATEWAYS project. The sediment cores are positioned such that they
monitor the leakage of Agulhas water into the Atlantic and the Agulhas
Return Current that straddles the South Atlantic subtropical front on
its way to the Indian Ocean. Paired Mg/Ca-δ18O analyses on the
planktonic foraminifera Globigerinoides ruber and Globigerina bulloides
reveal millennial-scale surface ocean temperature and salinity changes
at the core sites that reflect recurrent oscillations of the Agulhas
Leakage. Coeval changes in the IRD record from the Agulhas Plateau
allude to pronounced latitudinal migrations of regional oceanic fronts
during the Agulhas leakage events. The timing of events in our records
of surface ocean conditions (temperature, salinity, IRD) are
out-of-phase with similar events in the North Atlantic, suggesting that
the Agulhas leakage, via its impact on the AMOC activity, may be a
significant climate forcing on millennial timescales during the Late
Pleistocene.
M3 - Abstract
SP - 8815
ER -