 |
| Titel |
Bottom water variability in the subtropical northwestern Pacific from 26 kyr BP to present based on Mg / Ca and stable carbon and oxygen isotopes of benthic foraminifera |
| VerfasserIn |
Y. Kubota, K. Kimoto, T. Itaki, Y. Yokoyama, Y. Miyairi, H. Matsuzaki |
| Medientyp |
Artikel
|
| Sprache |
Englisch
|
| ISSN |
1814-9324
|
| Digitales Dokument |
URL |
| Erschienen |
In: Climate of the Past ; 11, no. 6 ; Nr. 11, no. 6 (2015-06-03), S.803-824 |
| Datensatznummer |
250117315
|
| Publikation (Nr.) |
 copernicus.org/cp-11-803-2015.pdf |
|
|
|
|
|
| Zusammenfassung |
| To understand bottom water variability in the subtropical northwestern
Pacific, bottom water temperatures (BWTs), carbon isotopes (δ13C), and oxygen isotopes of seawater (δ18Ow) at a
water depth of 1166 m were reconstructed from 26 kyr BP to present. A new
regional Mg / Ca calibration for the benthic foraminifera Cibicidoides wuellerstorfi (type B) was
established to convert the benthic Mg / Ca value to BWT, based on 26
surface sediment samples and two core-top samples retrieved around Okinawa
Island. During the Last Glacial Maximum (LGM), the δ18Ow
in the intermediate water in the northwestern South Pacific was ~0.4‰ lower than in the deep South Pacific, indicating a greater
vertical salinity gradient than at present. This salinity (and probably density)
structure would have led to stratification in the intermediate and deep
Pacific, which would, in turn, have greatly influenced carbon storage during
the glacial time. The benthic Mg / Ca and δ18Ow records suggest changes
that seem to follow Heinrich event 1 (H1) and the Bølling–Alleød
(B/A) and Younger Dryas (YD) intervals, with BWT higher during H1
(~17 kyr BP) and YD (~12 kyr BP) and lower
during B/A (~14 kyr BP). The warming in the bottom water
during H1 suggests increased contribution of North Pacific Intermediate
Water (NPIW) to the subtropical northwestern Pacific and decreased upwelling
of cooler waters from the abyssal North Pacific. During the interval from 17
to 14.5 kyr BP, the BWT tended to decrease successively in association with
a decrease in δ13C values, presumably as a result of increased
upwelling of the abyssal waters to the intermediate depths of the North
Pacific caused by shoaling and enhancement of the southward return flow
of Pacific Deep Water (PDW). During the Holocene, the millennial- to sub-millennial-scale variations in the BWT generally correlate with the sea
surface temperatures in the Okhotsk Sea, the source region of the NPIW,
suggesting that changes in the BWT are linked to changes in the NPIW
production rate. |
| |
|
| Teil von |
|
|
|
|
|
|
|
|