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| Titel |
Mid- to late Holocene oxygen isotopes from Voldafjorden, western Norway |
| VerfasserIn |
Heidi Kjennbakken, Hans Petter Sejrup, Haflidi Haflidason |
| Konferenz |
EGU General Assembly 2011
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 13 (2011) |
| Datensatznummer |
250045998
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| Zusammenfassung |
| Basin-water in deep-silled Norwegian fjords is primarily influenced by inflowing
Atlantic water, originating from the Norwegian Atlantic Current (NwAC). Previous
studies suggest that benthic foraminiferal oxygen isotope records from deep-silled
fjords are strongly influenced by variability in the NwAC. The objective of this
study is to investigate the mid- to late Holocene temperature development in the
basin water of a deep-silled fjord; Voldafjorden, utilizing two benthic foraminifer
oxygen isotope records. The oxygen isotope analyses are performed on the two
benthic foraminifer species Uvigerina mediterranea and Cassidulina laevigata.
The age model is based on 10 radiocarbon dates on marine carbonates and on one
plant macro fossil, showing that the two records extend from 6000 to 2200 cal yr
BP with an average time-resolution of 17 years. The δ18O C. laevigata record has
systematically larger amplitudes compared to the δ18O U. mediterranea record. This is most
likely related different life-cycles/periods of calcifications. The oxygen isotope
results show a clear shift towards higher values between 5000 and 4000 cal yr BP,
interpreted to reflect a temperature drop in the basin water of c. 1 Ë C. After the
temperature drop, the high-frequency variability (centennial and multi-decadal) changes
abruptly towards higher amplitudes and the centennial sub-periodicity changes,
where a pronounced 370 year cycle in the δ18O C. laveigata record disappears
after 3800 cal yr BP. The basin-water cooling indicates that the temperature of
the inflowing Atlantic water dropped. The following change in high-frequency
variability suggests a transition towards more variable conditions after the cooling. |
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