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| Titel |
Comparing historical and modern methods of sea surface temperature measurement – Part 2: Field comparison in the central tropical Pacific |
| VerfasserIn |
J. B. R. Matthews, J. B. Matthews |
| 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 ; 9, no. 4 ; Nr. 9, no. 4 (2013-07-30), S.695-711 |
| Datensatznummer |
250018113
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| Publikation (Nr.) |
 copernicus.org/os-9-695-2013.pdf |
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| Zusammenfassung |
| Discrepancies between historical sea surface temperature (SST) datasets have
been partly ascribed to use of different adjustments to account for variable
measurement methods. Until recently, adjustments had only been applied to
bucket temperatures from the late 19th and early 20th centuries, with the
aim of correcting their supposed coolness relative to engine cooling water
intake temperatures. In the UK Met Office Hadley Centre SST 3 dataset
(HadSST3), adjustments have been applied over its full duration to
observations from buckets, buoys and engine intakes. Here we investigate
uncertainties in the accuracy of such adjustments by direct field comparison
of historical and modern methods of shipboard SST measurement.
We compare wood, canvas and rubber bucket temperatures to 3 m seawater intake
temperature along a central tropical Pacific transect conducted in May and
June 2008. We find no average difference between the temperatures obtained
with the different bucket types in our short measurement period
(∼1 min). Previous field, lab and model experiments have
found sizeable temperature change of seawater samples in buckets of smaller
volume under longer exposure times.
We do, however, report the presence of strong near-surface temperature
gradients day and night, indicating that intake and bucket measurements
cannot be assumed equivalent in this region. We thus suggest bucket and buoy
measurements be considered distinct from intake measurements due to
differences in sampling depth. As such, we argue for exclusion of intake
temperatures from historical SST datasets and suggest this would likely
reduce the need for poorly field-tested bucket adjustments. We also call for
improvement in the general quality of intake temperatures from Voluntary
Observing Ships. Using a physical model we demonstrate that warming of
intake seawater by hot engine room air is an unlikely cause of overly warm
intake temperatures. We suggest that reliable correction for such warm
errors is not possible since they are largely of unknown origin and can be
offset by real near-surface temperature gradients. |
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