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| Titel |
Bjerknes Compensation and the Multi-decadal Variability of Heat Transport in the Arctic |
| VerfasserIn |
Stephen Outten, Igor Esau |
| 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 |
250138901
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| Publikation (Nr.) |
 EGU/EGU2017-2039.pdf |
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| Zusammenfassung |
| The meridional transport of heat through both the atmosphere and ocean is a fundamental
component in maintaining the Earth’s climate. Understanding the decadal to multi-decadal
changes of these transports provides an insight into the natural variability of the climate
system and into the flow of heat into the Arctic. Jacob Bjerknes proposed that the total energy
transported by the climate system should remain approximately constant if the ocean heat
storage and fluxes at the top-of-the-atmosphere were unchanging [Bjerknes, 1964]. Since it
is the atmosphere and ocean that transport heat in the climate system, any large
anomalies in the ocean heat transport should be balanced by opposing variations in the
atmospheric heat transport, and vice versa; a process that has since been named Bjerknes
Compensation.
Bjerknes compensation has been identified in the 600-year control run of the Bergen
Climate Model by examining the anomalies of the implied meridional heat transports
in both the ocean and atmosphere. These anomalies show strong anti-correlation
(r=-0.72, p≤0.05), and a multi-decadal variability with a period of approximately 60
years. Spatial patterns associated with this multi-decadal variability highlight part of
the underlying mechanism which occurs through changes in the sea-ice cover in
the North Atlantic sector of the Arctic, which lead to strong ocean-atmosphere
fluxes and the formation of a thermal low that changes the large scale flow over
the Northern Hemisphere. The anomalies in atmospheric heat transport are not
only found to be well correlated to the anomalies in Arctic sea-ice, but also to the
strength of the sub-polar gyre, suggesting a possible feedback of the atmosphere to the
ocean on multi-decadal timescales. Bjerknes Compensation is further identified in a
number of CMIP5 models, though several show key differences from the findings of
existing literature that have examined Bjerknes Compensation in previous models. |
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