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| Titel |
Reconstructing bottom water temperatures from measurements of temperature and thermal diffusivity in marine sediments |
| VerfasserIn |
F. Miesner, A. Lechleiter, C. Müller |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1812-0784
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| Digitales Dokument |
URL |
| Erschienen |
In: Ocean Science ; 11, no. 4 ; Nr. 11, no. 4 (2015-07-09), S.559-571 |
| Datensatznummer |
250117264
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| Publikation (Nr.) |
 copernicus.org/os-11-559-2015.pdf |
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| Zusammenfassung |
| Continuous monitoring of oceanic bottom water temperatures is a complicated
task, even in relatively easy-to-access basins like the North or Baltic seas.
Here, a method to determine annual bottom water temperature variations from
inverse modeling of instantaneous measurements of temperatures and sediment
thermal properties is presented. This concept is similar to climate
reconstructions over several thousand years from deep borehole data. However,
in contrast, the presented method aims at reconstructing the recent
temperature history of the last year from sediment thermal properties and
temperatures from only a few meters depth. For solving the heat equation, a
commonly used forward model is introduced and analyzed: knowing the bottom
water temperature variations for the preceding years and the thermal
properties of the sediments, the forward model determines the sediment
temperature field. The bottom water temperature variation is modeled as an
annual cosine defined by the mean temperature, the amplitude and a phase
shift. As the forward model operator is non-linear but low-dimensional,
common inversion schemes such as the Newton algorithm can be utilized. The
algorithms are tested for artificial data with different noise levels and for
two measured data sets: from the North Sea and from the Davis Strait. Both
algorithms used show stable and satisfying results with reconstruction errors
in the same magnitude as the initial data error. In particular, the
artificial data sets are reproduced with accuracy within the bounds of the
artificial noise level. Furthermore, the results for the measured North Sea
data show small variances and resemble the bottom water temperature
variations recorded from a nearby monitoring site with relative errors
smaller than 1 % in all parameters. |
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