Marine Ecosystems Research Department - jamstec japan agency ...

Japan Marine Science and Technology Center
Mutsu Research Group
10
33.2
10/6/01
33.15
8
10/26/01
11/5/01
33.1
Temp. (deg-C)
6
4
9/16/01
11/25/01
sal
33.05
33
Salinity (PSU)
2
9/26/01
10/16/01
11/15/01
12/05/01
12/25/01
1/14/02
3/2/02
32.95
temp
32.9
9/6/01
0
0 40 80 julian day 120 160
32.85
Fig. 4 Seasonal variability in water temperature and salinity at 50m observed by using MMP
2. Study on the past marine environmental changes
Since FY, a paleoceanography project, "Study
on the past marine environmental changes" has been
carried out as one of the Research Projects in Mutsu
Institute for Oceanography (MIO).
We focus on reconstructing the natural variability of
global and regional climate recorded in the deep-sea
sediment during the late Quaternary. We are seeking
to clarify the following themes:
a) Changes in sea surface temperature and surface
current systems
b) Changes in biogeochemical cycles in the ocean
(Carbon Cycle)
c) Changes in global thermohaline circulation
We also seek to find new paleo-proxies and to
develop the paleo-proxies as follows:
- Proxies of chronology (Compound-specific radiocarbon
analysis and amino acid chronology)
- Proxies of nutrients and temperature (analysis of
trace elements such as Cd, Mg, Ca contained in
foraminiferal tests with culture experiments of
foraminifers)
We introduce the following two results as the main
results of this research project in FY.
() The past change in intermediate/deep water in the
North Pacific since the Last Glacial Maximum is not
well understood because of sparse data in this region.
Sediment core MR-K PC collected from the continental
slope off northern Japan (˚.'N,
˚.'E; m depth) was used for estimating the
paleo ventilation by using foraminiferal radiocarbon
( C) technique. The C contents in planktonic and benthic
foraminifers were measured by the accelerator mass
spectrometry (AMS). Some samples were prepared by
using a micro-scale preparation technique (Uchida et al.,
submitted) because they contained only small amounts
of foraminifers. Our preliminary result indicates that
there was significant variation in mid-depth ventilation
during the last deglaciation in the northwest Pacific,
especially in the Bølling–Allerød (ca.– ka) and
Younger Dryas (ca..– ka) intervals. The middepth
ventilation in the northwest Pacific was significantly
reduced in the Bølling–Allerød warming, while
the resumption of ventilation was started at the onset
of the Younger Dryas cooling (Ahagon and Uchida,
submitted). The latter may support the idea that
the intermediate water formation in NW Pacific
was strengthened in contrast to the interruption of
North Atlantic Deep Water formation during the
Younger Dryas.
() There are few conventional dating methods that
can be used to estimate the geological age of siliceous
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