Arctic Ocean Observations and their Outcomes over the ASCSYSDecade - PowerPoint PPT Presentation

Title: Arctic Ocean Observations and their Outcomes over the ASCSYSDecade


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Arctic Ocean Observations and their Outcomes over
the ASCSYS-Decade   Takatoshi  Takizawa /JAMSTEC
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From Silent Arctic to Live Arctic The
ACSYS-decade is an epoch that we began to
recognize the variability of the Arctic Ocean
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In 1990s, classified observational data were
released and many historical datasets such as EWG
Arctic Ocean Atlas (1997, 1998) were complied.
The comparison of 1990s observational results to
the historical data gave us a new outlook of
Changing Arctic
SP31
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Annual minimum sea ice extent and concentration
for 24 years, from 1979 to 2003. The year 2002
showed lowest level of sea ice on record. Credit
NASA Top Story/ NASA Home Page, October 23,
2003 Author J. Comiso Paper is appearing in J.
Climate, 2003
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Annual minimum sea ice extent and concentration
for 24 years, from 1979 to 2003. The year 2002
showed lowest level of sea ice on record. Credit
NASA Top Story/ NASA Home Page, October 23, 2003
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April 2000 March 2001
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Changing Arctic
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• Banner headline of ACSYS-decade
• From Silent Arctic to Live Arctic
• Complexity and Variability
• Findings, Doubts and Objections

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1. Pathway and transport of Atlantic Water 2.
Pathway and transport of Pacific Water 3. Water
mass and halocline
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Pathway and transport of Atlantic Water
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Aagaard 1989
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Rudels et al. 1994
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Apparent mean current speed about 1cm/s
3.5 Sv
East Siberian Sea
Barents Sea
0.5 Sv
Laptev Sea
Kara Sea
Observation ARK IX/4 1993
Apparent tritium/3He age (year) Reference to 45?N
Frank et al. 1998
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Reduced propagation in the western Arctic Barents
Sea Opening to Lomonosov 6-7 yrs Lomonosov to
Alaska 10yrs
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Blue italics The times of transit from North Sea
(60 ?N)
Inventories of contaminant Pb and excess 210Pb .
Circulation pathway of Atlantic Water from
Rudels et al., 1994.
Gobeil et al. (2001)
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Pathway and transport of Atlantic
Water Evolution and spreading of the warm
anomaly event
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Observed time series of AW temperature
Time series of simulated yearly mean AW
temperature
Observed time series of AW temperature
Karcher et al. (2003)
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W2 (1990)
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Warming of the Atlantic water in the Canada Basin
Spatial distribution of temperature maximum in
the Atlantic Layer in 1995-1998 (left) and 2000
(right)
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JAMSTEC, IOS, SCICEX data after 1990
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No Warm water
JAMSTEC, IOS, SCICEX data after 1990
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warm
JAMSTEC, IOS, SCICEX data after 1990
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warm
JAMSTEC, IOS, SCICEX data after 1990
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Warming of Atlantic Water on the eastern flank
of the Northwind Ridge
Increase by 0.4?
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Pathway and transport of Pacific Water
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Aagaard 1989
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Jones (2001)
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September 1988
September 2002
Recorded ice edge retreat
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Summer ice retreat and spatial distribution of
ECSW in 2002
Temperature on S31.3psu
NOAA16 AVHRR July 19 2220UTC
Low sea ice Concentration ? Open water
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Stratification of the Western Arctic Ocean
Ice melt
Atmosphere
Sea Ice
Sea Ice
River Melt Waters
0m
Mixed layer (cold fresh)
20m
Shield
Single halocline (cold)
Upper halocline Shallow temperature maximum
waters (warm)
Pacific Summer Waters
40m
heat source
100m
Winter Water
Pycnostad (cold)
Pacific Winter Water
Lower halocline (cold)
Shield
200m
Main thermocline
Primary heat source
Secondary heat source
300m
heat source
Atlantic Water (Warm salty)
Atlantic Water
Atlantic Water
Pacific Summer Water
1500m
Deep water (Cold Salty)
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Upper Ocean Circulation
Mirai Louis S. St-Laurent 2002 data
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Temperature distribution on S31.3 surface (about
30-50m deep) in 2002
Temperature on S31.3psu
ECSW2001

ECSW2002
No warm water
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Schematic circulation of surface water masses in
the Canada Basin (Shimada et al., 2001)
Beaufort Gyre
Spread of Mackenzie water
       
Spread of Alaskan Coastal Water
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Mike Steele et al. (2003) Accepted
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Water mass and halocline
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Stratification can be classified into three
categories

• (A)Nansen Basin Southern Amundsen Basin No or
  weak halocline
• (B) Northern Amundsen Basin Makarov Basin
  Single halocline
• (C)Canada Basin Double halocline and two Tmax
  (two heat source)

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Southern flank of LR
Eastern Amundsen Basin
Barents Sea slope
Evolution of the Arctic Ocean surface water and
halocline. Rudels e et al. (1996)
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Source of Lower Halocline Water
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Data
J-CAD Data
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Observational results in 2002
1. Temperature salinity at 120, 180, 250 m
depths are higher in the Nansen Basin than
in the Amundsen Basin and over the Arctic
Mid Ocean Ridge.
2. Salinity in the convective layer, which
temperature is near freezing point, is
lower in the Nansen Basin than in the Amundsen
Basin and over the Arctic Mid Ocean Ridge.
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Convective cold halocline from Steele and Boyd
(1998)
Cold, salty (winter) mixed layer Fresh
water input sea ice melt and/or low salinity
shelf water
Temperature with the salinity of surface water
inferred from the mixing line is higher than
freezing point. Amundsen Basin
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along-isopycnal
AMOR Nansen Basin
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ltlt Mean Current gtgt
Near the Lomonosov Ridge 4.0 5.0 cm/s
Along-isobath (toward GL) (Apr.-May 2000)
In the Amundsen Basin 2.0 3.0 cm/s LR -gt
AMOR (May-Sep. 2000 Apr.-Jun. 2002)
Over the Arctic Mid Ocean
Ridge 1.5 2.0 cm/s along-isobath (toward
GS) (Sep.-Oct. 2000 Jun.-Oct. 2002)
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ltlt Mean Current gtgt
Over the Arctic Mid Ocean
Ridge 1.5 2.0 cm/s along-isobath (toward
GS) (Sep.-Oct. 2000 Jun.-Oct. 2002)
In the Nansen Basin 2.0 2.5 cm/s WSW
(toward Fram Strait) (Oct. 2002 Feb.2003)
Ocean current at 50-100m depth
Convective cold halocline
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Distribution of CLHW in 2000-02
Convective LHW was advected along the ridge
from the eastern side of the basin and covered
over the AMOR and the Nansen Basin in 2000-02.
We could also find that, in the Amundsen Basin,
ocean current in the Lower Halocline layer had
a direction from LR to AMOR in the spring season
of 2000-2002.
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Speculate the origin of CLHW/LHW from the
climatological data
Depth of S34.1 surface and Freezing Temperature
Departure (FTD) (EWG winter climatology)
Nansen Basin Typical CLHW
Over the AMOR
Amundsen Basin
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Interannual variability
1991-93 CLHW covered only in the Nansen Basin,
which is similar to the result from the
climatology.
1994-96 The line of FTD 0.2 moved to the
boundary between the AMOR and the Nansen
Basin.
1997-99 Moreover, the line moved toward the
Lomonosov Ridge and we could find CLHW
not only in the Nansen Basin but also
over the AMOR and in the Amundsen Basin.
2000-02 Typical CLHW still covers over the AMOR
and the Nansen Basin, but the property
of CLHW has been weakened in the Amundsen Basin.

• These results correspond to the previous results
  on the variability of surface
• salinization in the Eastern Arctic Ocean.
• Change of Cold Halocline was caused by frontal
  shift in the upper ocean
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  rather than only by a change of surface salinity
  !!

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Stratification in the western Arctic Ocean
NOT Halocline, but Pycnostad
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Spreading of halocline water into the basin in
2002
Old halocline water Remote source region

Hanna Canyon
Newly ventilated halocline water
Barrow Canyon
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In closing, I would like to say a few words
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We have too many water masses. I am so confused.
I think we need to re-classify and re-name them.
Lazy days
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The Arctic Ocean has strong seasonality and
locality
Lazy days
Ekwurzel et al. (2001)
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How much do I trust the circulation pathway and
current speed derived from the tracer
distribution ?
Lazy days
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Chemical tracer just says, I am here. I think I
was born at Norwegian Sea and 7 years old.
Pathway ?? Speed??
Chemical tracer Dynamics (Physical
oceanography)
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You shall not discuss the circulation in the
Arctic Ocean without visiting CANADA HOLE and
RUSSIA HOLE (Makarov Basin )
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Recent hydrographic sections with a full sampling
programme for high quality hydrographic and
tracer measurements Adapted from ACSYS HP
Makarov Basin
Canada Hole
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Thank you for your kind attention !
??????? Ocean Observation Research Department