Talk by Dr. Henning Bauch, Mainz Academy of Sciences – Niels Bohr Institute - University of Copenhagen

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Talk by Dr. Henning Bauch, Mainz Academy of Sciences

The AMOC’s Role During Past Interglacials


Abstract
Although good access to a wide array of paleoclimate archives allows
for a robust understanding of the Holocene climate system, rather
little is still known about older interglacials, and in particular, on
the propagation of the meridional-driven North Alantic surface ocean
heat transfer ("AMOC") into the high Arctic. Comparing between various
peak interglacials along such a transect is central to learn more
about the ”natural range” of forcing and feedback mechanisms of our
present climate system. During the last interglacial period
(MIS5e/Eemian), for instance, overall climatic conditions were
comparable to the Holocene, but with higher temperatures than during
the Holocene. While this pattern seems consistent in marine and
terrestrial records within the mid-northern latitudes, proxy records
from the polar North would suggest rather cold surface waters for
MIS5e. A similar, but even more extreme, picture emerges when studying
the cross-latitudinal surface ocean temperature patterns of the
interglacial peaks of MIS9 and 11. Although recognized as very
prominent interglacials in Antarctic ice cores as well as in the North
Atlantic, little of that ocean warmth is found in the polar North
during these latter two interglacials, independent of their different durations.

Because of the importance of overturning processes in the polar North
for the global ocean circulation, it appears as if the hydrological
system of the Arctic is the likely candidate to influence the
efficiency of the interglacial ”AMOC” thereby not only causing
intra-interglacial climate perturbations such as known from historical
times, but affecting the interglacial period on a whole. Moreover, the
observed contrasts in the meridional ocean heat flux during past
interglacials has further-reaching implications also for a climatic
evaluation of the present time. It is indicated that certain factors
of the Arctic climate system, that is the highly dynamical interaction
between sea ice, atmosphere and ocean, play a crucial role for both
interglacial regionality as well as for climate change on a more global scale.