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Seasonal and interannual variability in the East Sea ecosystem: effects of nutrient
transport through the Korea Strait
Chan Joo Jang, and Yuri OhKorea Institute of Ocean Science & Technology
2014 ROMS/TOMS User WorkshopRovinj, Croatia, 26-29 May
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“Why do we care about Biology as physical oceanographers?Because of Physics!”
Courtesy: Francesco
2012.4-5 composite
GOCI CHL
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The East Sea (Japan Sea)Talley et al 2002
Korea
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Cascading sites around the world…
not so many, but powerful drivers of the overall circulation, heat/salt /carbon transfer, and rele-
vant for climate dynamics
Courtesy: Sandro Carniel
From Ivanov et al., PIO (2004) & Durrieu de Madron et al., PIO (2005))
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Deep ConvectionTalley et al 2002
Korea
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Long-Term Mean Chlorophyll-aEast Sea (Japan Sea)
Log (CHL) mg m-3
LC
NKCC SPF
JB
YRYB
SS
TS
UB
NB
OB
EKWC
KS
EKWC: East Korean Warm Cur-rentJB: Japan BasinKS: Korea StraitLC: Liman CurrentNB: Nearshore BranchNKCC: North Korea Cold Cur-rentOB: Offshore BranchSPF: Subpolar FrontSS: Soya StraitTS: Tsugarn StraitUB: Ulleung BasinYB: Yamato BasinYR: Yamato Rise
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CHL variability
Yoon et al (2013)
Gallisai et al. 2012 (Biogeosciences Discus-sions)
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1. Coastal Upwelling(You & Park, 2009)
KOREA
Japan
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2. Nutrient transport through the KS
Nutrient transport through the KS
DIN : Dissolved inorganic NitrogenDIP : Dissolved inorganic phosphorus
◀ The annual mean fluxes of DIN and DIP transported through the KS are rela-tively large compare to other nutrient sources.
Morimoto et al. (2009)
Total 3.59 kmol/s Total 0.29 kmol/s
Vertical cross sections of fluorescence (Aug 2008)
Roh et al. (2012)
▲ The Tsushima intermediate water with high nutrient may contribute to maintain-ing the SCM.
SCM (subsurface chloro-phyll maximum layer)
Yoo and Kim (2004)
S V
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Objective
• To investigate how the nutrient transport through the Korea Strait affect the ecosystem in the East Sea (considering higher primary production in the southern basin)
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Numerical experiments
Hypothesis: Nutrient transport through the KS contributes to the ES ecosystem, mainly to southwestern area.
Two numerical experiments with different nutrient transports:
1)Seasonally varying nutrient flux2)No nutrient flux
Methodology: 3D circulation-biological coupled model
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3D circulation - biologicalcoupled model
Circulation model
Initial condi-tion
Circulation only-modelSpin-up (10 years)
Bound-ary condi-tion(at KS)
T, S : observation2D-U,V : Kim (1996)3D-U,V : observation
ROMS
Biological modelSeasonally varying N flux no N flux
N : WOA2005 P, Z, D : 1.0 mmolN/m3
N : WOA2009 P : 50% of seaWiFS (roms_agrif) Z, D : 20% of seaWiFS
No N flux (bry value = inner value)
1. domain: 126.5˚E-142.5˚E, 33˚N-52˚N
3. Horizontal resolution: 1/6˚4. Vertical layers: 30 layers
2. Topography : ETOPO5
5. forcing: ERA40 (bulk formula)6. Integration: 10 years
+Low trophic biolog-
ical modelNPZD model
N cycle, 7 biochemical processes
Powell et al. (2006)
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Coastal upwelling
Korea
Japan
(You & Park, 2009)
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Idealized Ecosystem model for coastal upwelling
• grid:41x80x16(41km x 80km x 150m)
• IC: T- 22oC at 0m, 14oC at the bottom, S-uniform(35psu)
• Wind stress: southly (0.02, 0.05, 0.1 Pa)
• OBC: Radiation
Wind = 0.02, 0.05, 0.1 Pa
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IC
Upwelling Case (Day 20)wind change effects
0.1 Pa
T P Z D DIN
0.02 Pa
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Model Validation I
Model MLD (m)
0.5 m/s
Model SST ( ℃ ) & surface current (m/s)
Feb
Aug
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Model Validation II
Spring bloom
Fall bloom
Model
Chlorophyll-a concentration (mg/m3)Spring bloom
Fall bloom
SeaWiFS+MODIS (1998-2012)
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Exp 2) No fluxExp 1) Seasonally varying flux
Experiment ResultsChlorophyll-a
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Exp 2) No flux
Exp 1) Seasonally varying flux
nutrientnutrient Chlorophyll-aChlorophyll-a
Exp 2) - Exp1)
nutrient
134 °E
Experiment Results134 °E Chlorophyll-a &
nutrient
4-5 mmol N/m3 1-2
mmol N/m3
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Exp 1) Seasonally varying flux
Exp 2) No flux
MLD
Exp 2) No flux
Exp 1) Seasonally varying
Nutrient
Phyto P
Zoo P
Apr Apr
Apr Apr
Apr Apr
Exp 1) Seasonally varying
Nov Nov
Nov Nov
Nov Nov
Exp 2) No flux
130°E
Experiment ResultsNutrient & phytoplankton &
Zooplankton
130°E
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Conclusion
When there was no nutrient flux through the Korea Strait, the southern East
Sea shows (within limited model resolution & simple NPZD model) :
– Spring bloom considerably weakened
– Fall bloom almost disappeared
– The Subsurface Chlorophyll Maximum layer was not distinct
But, the northern basin shows insignificant changes.
The Nutrient transport through the Korea Strait contributes
to higher primary production in the southern East Sea.
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Challenges & Limitations
• Resolution-1/6 deg (10 km)– EKWC overshooting– UWE, upwelling
• NPZD– Only one compartment of PP & ZP– T dependency (photosynthesis, grazing etc.)
ignored– BC & parameters poorly known
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Future Work
• Nutrient budget analysis• Experiments with yearly- varying nutrient
transport through the KS (with climatologi-cal forcing)
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HVALA THANK YOU
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RCM nestingfor Climate Change Projection
25
North Pacific(Ocean only) → Western N. Pacific (ocean only) → East Sea (Coupled Model)
1/6 x 1/6 deg.
1/12 x 1/12 deg.
1/24 x 1/24 deg.
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Projected Ocean Warmingwinter (2081~2100 – 1981~2000)
26
Color shading: SST changeContours: SSH (red-future)
Relative smaller warm-ing: southward shift of Kuroshio
Ocean projection with a GCM(CanESM2) atmospheric forcing (pseudo global warming)
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Integrated RCM
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Nutrient Supplythrough the Korea Strait
(Kawk et al 2013)
Nitracline
Euphotic depth