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| Titel |
Oceanic dominance of interannual subtropical North Atlantic heat content variability |
| VerfasserIn |
M. Sonnewald, J. J.-M. Hirschi, R. Marsh |
| Konferenz |
EGU General Assembly 2012
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 14 (2012) |
| Datensatznummer |
250063987
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| Zusammenfassung |
| Ocean heat content varies on a range of timescales, with significant impact on the local
climate through interactions with the atmosphere. This variability can be driven either
by oceanic or atmospheric heat transport for a local body of water. To diagnose
the relative contributions and respective timescales, this study uses a box model
forced with GCM output to investigate the heat content variability of the upper 800m
of the subtropical North Atlantic from 26°N to 36°N. The ocean and air-sea heat
flux data needed to force the box model is taken from a 19 year (1985 to 2006)
simulation performed with the 1-12° version of OCCAM. The box model heat content is
compared to the corresponding heat content in OCCAM for verification. The main
goal of the study is to identify to what extent the interannual to subannual ocean
heat content variability is of atmospheric or oceanic origin. To this end, the box
model was subject to a range of scenarios forced either with the full (detrended)
ocean and air-sea fluxes, or their deseasoned counterparts. This revealed that in all
cases, the seasonal variability was dominated by the subannual component of the
air-sea flux, which produced a seasonal range of ~0.41°C. However, on longer
timescales the interannual oceanic heat transport dominates, with changes of up to
~0.16°C.
The technique is subsequently appplied to observational data. For the ocean
heat fluxes, we use data from the RAPID programme at 26°N, and at 36°N heat
transport is inferred using a linear regression model from the oceanic low-frequency
transport in OCCAM. The air-sea flux from OCCAM is used for the period 2004
to 2006 when the RAPID timeseries and the OCCAM simulation overlap, and a
climatology is used for the air-sea flux from 2006 onwards. The results confirm that on
longer (>2 years) timescales the ocean dominates the ocean heat content variability.
This work illustrates that oceanic divergence significantly impacts the ocean heat
content variability on timescales relevant for applications such as hurricane forecasts,
and thus that understanding the underlying mechanisms is of great socioeconomic
importance. |
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