Structure and variability of
the upper layer of the
Western Subarctic Gyre
Tomowo Watanabe
National Research Institute of Fisheries
Science
Fisheries Research Agency
CONTENTS
1. Characteristics of the oceanographic conditions of
adjacent sea of Japan
-Analysis of SST field of WNP2. Spatial and vertical structure of the Western Subarctic
Gyre (WSG)
-Oceanographic data from Salmon resource survey3. Variability of the WSG
1.Characteristics of the oceanographic conditions of adjacent sea of Japan
ANALYSIS of SST field in Winter
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We constructed the Map of climatology of
SST for March by using the JMA analyzed
data set for Western North Pacific
1(lat.)x1(lon.), 10day-mean, 54years (19502003)
Intensive air-sea interaction in winter
construct the basic state of the
oceanographic conditions and SST field in
the late winter (March) reflect the result of
the interaction
1.Characteristics of the oceanographic conditions of adjacent sea of Japan
ANALYSIS of SST field in Winter
Climatology of March SST for 1950-2003
CI=1.0
Strong Front systems
are formed in the
transition zone, east
of Honshu.
The Geographical
position of these
fromts are stationary.
1.Characteristics of the oceanographic conditions of adjacent sea of Japan
ANALYSIS of SST field in Winter
Standard Deviation of March SST for 1950-2003
CI=0.2
Low
1.2
0.8
Low
0.4
Large variability area
extended in the
transition zone.
The year-to-year
variation at Center
region of WSG and
the Kuroshio
recirculation area low
1.Characteristics of the oceanographic conditions of adjacent sea of Japan
ANALYSIS of SST field in Winter
Correlation Map for March SST OFF TOHOKU
The correlation pattern
of the SST in the WNP
are classified into two.
One is centered at the
transition zone and the
other is widely
distributed pattern in
the subtropical area.
Significant Positive
correlations extend in
the frontal area along
the 35-45N (Centered at
40N)
1.Characteristics of the oceanographic conditions of adjacent sea of Japan
ANALYSIS of SST field in Winter
Subsurface temperature difference for the shift in the mid-1970’s
Marked interdecadal
signal appeared in the
mid-latitude area of
the Western North
Pacific.
The deep structure
indicating the signal
reflected systematic
meridional movement
of the front system.
1.Characteristics of the oceanographic conditions of adjacent sea of Japan
ANALYSIS of SST field in Winter
Time-Longitude section of March SST anomaly along 39-42N
It is evident that the
Decadal to
Interdecadal
variations concurrently
appeared along the
40N.
And short time scale
phenomena are also
included in the coastal
area.
1.Characteristics of the oceanographic conditions of adjacent sea of Japan
ANALYSIS of SST field in Winter
SST off TOHOKUVariation of SST off TOHOKU in winter
3.0
2.0
1.0
0.0
-1.0
-2.0
-3.0
1950
1960
1970
1980
W_SST
1990
2000
2010
Time series of SST in the winter
off TOHOKU, annual mean
southern limit of Oyashio, areal
average of 500hpa height in the
Eastern North Pacific.
Interdecadal scale variations are
dominant.
3YRM
OYASHIO
Variation of Southern Limit of Oyashio (annual mean)
Variation of 500hpa height in the Eastern North Pacific in winter
EP 500hpa
H
3.0
3.0
2.0
2.0
1.0
1.0
0.0
0.0
-1.0
-1.0
-2.0
-2.0
-3.0
-3.0
1950
1960
1970
1980
1990
EP_500hpa
3YRM
2000
2010
1950
1960
1970
1980
Annual_O1
1990
3YRM
2000
2010
1.Characteristics of the oceanographic conditions of adjacent sea of Japan
ANALYSIS of SST field in Winter
Correlation Map for March SST OFF NOJIMASAKI
CI=0.2
Significant Positive
correlations widely
distributed in the
kuroshio recirculation
area and Japan sea,
Yellow sea and South
China sea.
1.Characteristics of the oceanographic conditions of adjacent sea of Japan
ANALYSIS of SST field in Winter
Correlation Map of MOI vs March SST
Same pattern of the
SST correlation pattern
for off Noima-saki is
obtaind in correlation
map with MOI.
The pattern is thought to
be formed
corresponding to the
east Asian wintertime
monsoon.
One dimensional
process is importanto.
2. Spatial and vertical structure of the WSG
The Western Subarctic Gyre
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Fluctuation of the oceanographic condition of adjacent
sea of Honshu show the close connection to WSG on
the interdecadal scale.
Therefore, we should clarify the structure and
variability of WSG in detail from the view point of
coastal area.
Japan Fisheries Agency maintained the monitoring
network in the WSG for salmon resource for many
years from 1950’s to present.
We are analyzing the the subsurface temperature
data set collected by the network for the purpose.
2. Spatial and vertical structure of the WSG
Monitoring Newtwork
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1956-present
Observations by Training Vessels and
Research Vessels.
Data from commercial vessel are also
included.
165E and the date line monitoring initiated
early 1990’s
165E: Hokko Maru (1992-2000)
The date line: Wakatake Maru (1991present)
2. Spatial and vertical structure of the WSG
Monitoring Network
1991-PRESENT Jun-Jul
1966-1991
Wkatake-Maru
1992-2000 Jul.
Hokko-Maru 165E
*data for the period 1956-1965 was discovered
and will be available in the near future
2. Spatial and vertical structure of the WSG
Spatial structure
Climatology for Jun-Jul subsurface temperature field
2. Spatial and vertical structure of the WSG
Mean section The Date Line
June-July
Temperature Minimum Layer
Strong halocline
in the ridge
region
2. Spatial and vertical structure of the WSG
Mean Section 165E, July
Temperature Minimum Layer
Strong halocline
in the ridge
region
3. Variability of the WSG
Interdecadal Variation
The differences of decadal
mean temperature at 100m
depth is shown.
Cooling in the southern
boundary region and warming in
the Alaskan stream region of
WSG was occurred.
W
C
This change reflected the
strengthening of the WSG after
the mid-1970’s
3. Variability of the WSG
Decadal Variation
Decadal variation of 100m temperature
at 167.5E and 177.5E along the 48N
Decadal variation of TML temperature
5.00
4.00
℃ for TML TEMP
Time-Longitude section of 100m
temperature along the 48N
3.00
2.00
1.00
0.00
-1.00
-2.00
60
65
70
75
167.5E
80
Year
177.5E
85
90
95
NAO
Decadal variation is dominant in
the TML variation and some
relationships with atmospheric
variation were suggested
100
3. Variability of the WSG.
The Date Line, June-July
Temperature Minimum Layer
Strong halocline
in the ridge
region
3. Variability of the WSG
Year-to-Year Variation of TML in the
Date Line , June-July
3. Variability of the WSG
Mean Temperature Section
Bering Sea - east of the Kuril islands,July
Bering Sea
3. Variability of the WSG
Year-to-Year Variation of TML
Bering Sea - east of the Kuril islands, July
3. Variability of the WSG
Year-to-Year Variation of TML
Bering Sea - east of the Kuril islands, July
Year-to-Year variation of temperature of TML
Temperature(50-150m layer)
5
4
3
2
1
0
1990 1992 1994 1996 1998 2000 2002 2004
156-166
167-171
172-182
178-182
East of the kuril islands
Aleutian islands
Center region of
the Bering sea
3. Variability of the WSG
Year-to-Year Variation of TML
Bering Sea - east of the Kuril islands, July
Year-to-Year variation of thickness of TML (<2.0℃)
Thickness(*10m)
12
10
8
6
4
2
0
1990 1992 1994 1996 1998 2000 2002 2004
156-166
East of the kuril islands
167-171
Aleutian islands
172-182
178-182
Center region of
the Bering sea
3. Variability of the WSG
Temperature section along 40N
Wakatake-maru
Relationship between summer (May-July)
SST variation off tohoku and 40N section
(June) for 1992-2003.
CMW
Summary for variability
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SST variations of WNP have two dominant pattern, and the
transition zone pattern indicates the connection between the
adjacent sea of japan and WSG.
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Oceanographic conditions around Japan has close
connection with WSG on interdecadal time scale
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WSG changes on decadal(7-10year) and Interdecadal time
scales.
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It is a future subject to investigate the influence of WSG
variations on decadal time scale to adjacent sea of Japan.