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| Titel |
The Impact of Internal Wave Seasonality on the Continental Shelf Energy Budget |
| VerfasserIn |
Juliane U. Wihsgott, Jonathan Sharples, Joanne Hopkins, Matthew R. Palmer, J. A. Mattias Green |
| 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 |
250142872
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| Publikation (Nr.) |
 EGU/EGU2017-6545.pdf |
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| Zusammenfassung |
| Heating-stirring models are widely used to simulate the timing and strength of stratification in
continental shelf environments. Such models are based on bulk potential energy (PE)
budgets: the loss of PE due to thermal stratification is balanced by wind and tidal mixing. The
model often fails to accurately predict the observed vertical structure, as it only considers
forces acting on the surface and bottom boundary of the water column. This highlights the
need for additional internal energy sources to close this budget, and produce an accurate
seasonal cycle of stratification.
We present new results that test the impact of boundary layer and internal wave forcing on
stratification and vertical density structure in continental shelves. A new series of continuous
measurements of full water depth vertical structure, dynamics and meteorological data
spanning 17 months (March’14-July’15) provide unprecedented coverage over a full seasonal
cycle at a station 120 km north-east from the continental shelf break. We observe a highly
variable but energetic internal wave field from the onset of stratification that suggests a
continuous supply of internal PE.
The heating-stirring model reproduces bulk characteristics of the seasonal cycle. While it
accurately predicts the timing of the onset in spring and peak stratification in late summer
there is a persistent 20 J m−3 positive offset between the model and observations throughout
this period. By including a source of internal energy in the model we improve the prediction
for the strength of stratification and the vertical distribution of heat. Yet a constant source of
PE seems to result in a seasonal discrepancy resulting in too little mixing during
strong stratification and too much mixing during transient periods. The discrepancy
seen in the model is consistent with the seasonality observed in the internal wave
field.
We will establish the role that changing stratification (N2) exerts on the internal wave
field and vice versa. Ultimately, we will demonstrate how the strength and vertical range of
shear varies seasonally and what effect it has on supplying PE to midwater mixing. |
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