[フレーム]
Now on home page

ADS

Possible increase in reservoir age of the surface water in the northwestern Bering Sea during the deglacial period: Evidence of ascending aged North Pacific deepwater?

Abstract

Deglacial parts of the hemipelagic sequences in northwestern Pacific margin including those in the Bering Sea are characterized by the occurrence of two distinct organic-rich, laminated intervals. These laminated intervals are also characterized by increased abundance of siliceous and calcareous micro- and nanno-fossils, and are considered as corresponding to Bolling/Allorod and Preboreal warm periods, respectively. The core MR06-04-PC-23 retrieved from the northwestern part of the Bering slope at the water depth of 1002 m also has two laminated horizons. Oxygen isotope ratio of benthic foraminifera (Uvigerina akitaensis and Buliminella tenuata) in PC-23 shows relatively rapid decreases that coincide with the abrupt increases in carbonate content and slightly precede the onset of deposition of laminated sediments by ca. 300 yrs for the first laminated interval and ca. 100 yrs for the second laminated interval. Judging from variation patterns of oxygen isotope ratio and carbonate content, it is likely that these abrupt decreases in oxygen isotope ratio correspond to the beginning of Bolling/Allorod period and Preboreal period, respectively. However, estimated ages for these two abrupt decreases, based on 14C ages of planktonic foraminifers (8 samples during the deglacial period) using the reservoir age of 380 yrs, are older by ca. 900 yrs and ca. 500 yrs, respectively, if we assume the onsets of these rapid decreases in oxygen isotope ratio and increases in carbonate contents are synchronous with the onsets of Bolling/Allorod and Preboreal. It is unlikely that ventilation only in the northern Bering Sea lead the onsets of Bolling/Allorod and Preboreal. More likely explanation is the temporal increase in the surface water reservoir age in the northern Bering Sea during the deglacial period. Galbraith et al. (2007) demonstrated a sudden decrease in the age of the deep water in the subarctic north Pacific in association with the increase in export production at ca. 14,600 yrs ago and suggested abrupt flushing of deep water and consequent increase in supply of nutrient to the upper ocean. Our result is consistent with ascending of the old and nutrient rich deep water at the northwestern end of the Bering Sea and consequent increase in the surface water reservoir age by as large as 900 years.


Publication:
AGU Fall Meeting Abstracts
Pub Date:
December 2009
Bibcode:
2009AGUFMPP11E..07T
Keywords:
  • 4900 PALEOCEANOGRAPHY;
  • 4901 PALEOCEANOGRAPHY / Abrupt/rapid climate change;
  • 9355 GEOGRAPHIC LOCATION / Pacific Ocean

No Sources Found

🌓

AltStyle によって変換されたページ (->オリジナル) /