Marine Ecosystems Research Department - jamstec japan agency ...

Japan Marine Science and Technology Center
Ocean Observation and Research Department
Fig.11 Potential temperature distribution on salinity 31.3 psu,
which was from the JWACS 2002 observation.
Fig.12 Distribution of sea ice in the western Arctic Ocean on July
19 2002 observed by NOAA AVHRR.
the Barrow Canyon. Thus, it would be an old one that
enters in the previous summer.
Just before the JWACS observation, a symptom
of the sea ice retreat was observed from the
NOAA/AVHRR satellite image on July (Fig.).
The ice concentration over the Northwind Ridge is
much lower than the surrounding area. This implies
that sea ice in this area was just about to melt. The distribution
of PSW well corresponds to the spatial pattern
of the low sea ice concentration area. It should be
noted that the distribution of PSW controls the sea ice
extent in the western Arctic Ocean. Previous studies
suggests that sea ice reduction of the Arctic Ocean
would be strongly associated with the inflow from the
Atlantic Ocean. However, this result suggests that sea
ice reduction in the western Arctic Ocean is associated
with the inflow from the Pacific Ocean. Further study
is necessary to clarify the mechanism of sea ice decay
in the western Arctic Ocean, i.e. the PSW prevents sea
ice formation in winter and further ice melt occurs due
to ice albedo feedback for the coming summer.
In the eastern Arctic Ocean, we have been carrying
out drifting buoy (J-CAD) observations since in
collaboration with NPEO Project. In , J-CAD
was deployed on the multi-year ice in the Amundsen
Basin (.N, .E). J-CAD drifted from the
Amundsen Basin through the Arctic Mid Ocean
Ridge, the Nansen Basin, the Yermak Plateau, and the
Fram Strait, and went to the Greenland Sea. Figure
shows potential temperature-salinity diagrams in the
Amundsen Basin, over the Arctic Mid Ocean Ridge,
and in the Nansen Basin observed by J-CAD . Water
mass characteristics are clearly different among the
above three regions. There are also frontal structures
at both boundaries between the Amundsen Basin and
the Arctic Mid Ocean Ridge and between the Arctic
Mid Ocean Ridge and the Nansen Basin. Especially in
the Cold Halocline Layer, which prevents upward heat
(a) Amundsen Basin
(b) Arctic Mid Ocean Ridge
(c) Nansen Basin
250
250
250
3
3
3
200
200
200
2
2
2
Tpot-0 [C]
1
0
150
100
Tpot-0 [C]
1
0
150
100
Tpot-0 [C]
1
0
150
100
-1
50
-1
50
-1
50
-2
33.5 34 34.5 35
Salinity [psu]
0
-2
33.5 34 34.5 35
Salinity [psu]
0
-2
33.5 34 34.5 35
Salinity [psu]
0
Fig.13 Potential temperature-Salinity diagrams (a) in the Amundsen Basin, (b) over the Arctic Mid Ocean
Ridge, and (c) in the Nansen Basin. The data was observed by J-CAD 4.
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