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| Titel |
Alternating Southern and Northern Hemisphere climate response to astronomical forcing during the past 35 m.y. |
| VerfasserIn |
David De Vleeschouwer, Maximilian Vahlenkamp, Michel Crucifix, Heiko Pälike |
| Konferenz |
EGU General Assembly 2017
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| Medientyp |
Artikel
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| Sprache |
en
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 19 (2017) |
| Datensatznummer |
250144686
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| Publikation (Nr.) |
 EGU/EGU2017-8544.pdf |
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| Zusammenfassung |
| Earth’s climate has undergone different intervals of gradual change as well as abrupt shifts
between climate states. Here we aim to characterize the corresponding changes in climate
response to astronomical forcing in the icehouse portion of the Cenozoic, from the latest
Eocene to the present. As a tool, we use a 35-m.y.-long δ18Obenthic record compiled
from different high-resolution benthic isotope records spliced together (what we
refer to as a megasplice). An important feature of the evolutive spectrum of the
megasplice is the sustained power at the frequency of the 405-kyr long eccentricity cycle
throughout the Oligocene and early to middle Miocene. That power disappears after the
mid-Miocene Climatic Transition, along with a weakening of the power of the
100-kyr short eccentricity cycles. While this general feature has been previously
recognized, this is the first long record where this significant transition is clearly
observed.
We analyze the climate response to astronomical forcing during four 800-k.y.-long time
windows. During the mid-Miocene Climatic Optimum (ca. 15.5 Ma), global climate
variability was mainly dependent on Southern Hemisphere summer insolation,
amplified by a dynamic Antarctic ice sheet; 2.5 m.y. later, relatively warm global
climate states occurred during maxima in both Southern Hemisphere and Northern
Hemisphere summer insolation. At that point, the Antarctic ice sheet grew too big to
pulse on the beat of precession, and the Southern Hemisphere lost its overwhelming
influence on the global climate state. Likewise, we juxtapose response regimes of
the Miocene (ca. 19 Ma) and Oligocene (ca. 25.5 Ma) warming periods. Despite
the similarity in δ18Obenthic values and variability, we find different responses
to precession forcing. While Miocene warmth occurs during summer insolation
maxima in both hemispheres, Oligocene global warmth is consistently triggered when
Earth reaches perihelion in the Northern Hemisphere summer. The presence of a
dynamic cryosphere in the Southern or Northern Hemisphere thus seems to exert the
principal control on the response of global climate to astronomical forcing in the
icehouse of the past 35 m.y. We report an alternation of the driving hemisphere from
the Northern Hemisphere during the late Oligocene, to the Southern Hemisphere
during the MMCO, and back to the Northern Hemisphere during the Quaternary. |
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