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| Titel |
Variability of the ocean heat content during the last millennium – an assessment with the ECHO-g Model |
| VerfasserIn |
P. Ortega, M. Montoya, F. González-Rouco, H. Beltrami, D. Swingedouw |
| 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 ; 9, no. 2 ; Nr. 9, no. 2 (2013-03-04), S.547-565 |
| Datensatznummer |
250018005
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| Publikation (Nr.) |
 copernicus.org/cp-9-547-2013.pdf |
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| Zusammenfassung |
| Studies addressing climate variability during the last millennium generally
focus on variables with a direct influence on climate variability, like the
fast thermal response to varying radiative forcing, or the large-scale
changes in atmospheric dynamics (e.g. North Atlantic Oscillation). The ocean
responds to these variations by slowly integrating in depth the upper heat
flux changes, thus producing a delayed influence on ocean heat content (OHC)
that can later impact low frequency SST (sea surface temperature) variability through reemergence
processes. In this study, both the externally and internally driven
variations of the OHC during the last millennium are investigated using a set
of fully coupled simulations with the ECHO-G (coupled climate model ECHAMA4 and ocean model HOPE-G) atmosphere–ocean general
circulation model (AOGCM). When compared to observations for the last 55 yr,
the model tends to overestimate the global trends and underestimate the
decadal OHC variability. Extending the analysis back to the last one thousand
years, the main impact of the radiative forcing is an OHC increase at high
latitudes, explained to some extent by a reduction in cloud cover and the
subsequent increase of short-wave radiation at the surface. This OHC response
is dominated by the effect of volcanism in the preindustrial era, and by the
fast increase of GHGs during the last 150 yr. Likewise, salient impacts from
internal climate variability are observed at regional scales. For instance,
upper temperature in the equatorial Pacific is controlled by ENSO (El Niño Southern Oscillation) variability
from interannual to multidecadal timescales. Also, both the Pacific Decadal
Oscillation (PDO) and the Atlantic Multidecadal Oscillation (AMO) modulate
intermittently the interdecadal OHC variability in the North Pacific and Mid
Atlantic, respectively. The NAO, through its influence on North Atlantic
surface heat fluxes and convection, also plays an important role on the OHC
at multiple timescales, leading first to a cooling in the Labrador and
Irminger seas, and later on to a North Atlantic warming, associated with a
delayed impact on the AMO. |
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