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| Titel |
How did Marine Isotope Stage 3 and Last Glacial Maximum climates differ? – Perspectives from equilibrium simulations |
| VerfasserIn |
C. J. Meerbeeck, H. Renssen, D. M. Roche |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1814-9324
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| Digitales Dokument |
URL |
| Erschienen |
In: Climate of the Past ; 5, no. 1 ; Nr. 5, no. 1 (2009-03-05), S.33-51 |
| Datensatznummer |
250002245
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| Publikation (Nr.) |
 copernicus.org/cp-5-33-2009.pdf |
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| Zusammenfassung |
| Dansgaard-Oeschger events occurred frequently during Marine Isotope Stage 3
(MIS3), as opposed to the following MIS2 period, which included the Last
Glacial Maximum (LGM). Transient climate model simulations suggest that
these abrupt warming events in Greenland and the North Atlantic region are
associated with a resumption of the Thermohaline Circulation (THC) from a
weak state during stadials to a relatively strong state during
interstadials. However, those models were run with LGM, rather than MIS3
boundary conditions. To quantify the influence of different boundary
conditions on the climates of MIS3 and LGM, we perform two equilibrium
climate simulations with the three-dimensional earth system model LOVECLIM,
one for stadial, the other for interstadial conditions. We compare them to
the LGM state simulated with the same model. Both climate states are
globally 2°C warmer than LGM. A striking feature of our MIS3 simulations
is the enhanced Northern Hemisphere seasonality, July surface air
temperatures being 4°C warmer than in LGM. Also, despite some
modification in the location of North Atlantic deep water formation, deep
water export to the South Atlantic remains unaffected. To study specifically
the effect of orbital forcing, we perform two additional sensitivity
experiments spun up from our stadial simulation. The insolation difference
between MIS3 and LGM causes half of the 30–60° N July temperature anomaly
(+6°C). In a third simulation additional freshwater forcing halts the
Atlantic THC, yielding a much colder North Atlantic region (−7°C).
Comparing our simulation with proxy data, we find that the MIS3 climate with
collapsed THC mimics stadials over the North Atlantic better than both
control experiments, which might crudely estimate interstadial climate.
These results suggest that freshwater forcing is necessary to return climate
from warm interstadials to cold stadials during MIS3. This changes our
perspective, making the stadial climate a perturbed climate state rather
than a typical, near-equilibrium MIS3 climate. |
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