PrinceWilliamSound

ResurrectionBay

Knight Island Passage

Middleton Island

The physical model is run in three dimensions and the data are used to drive a one – dimensional model at each Seward Line station location. Direct comparisons can then be made between GLOBEC field measurements and the model output. Comparisons here are done for the 2001 field season.

Simulation of the Northern Gulf of Alaska Ecosystem

Kenneth O. Coyle (SFOS, University of Alaska)Al Herman (NOAA, Seattle), Sarah Hinkley (NOAA Seattle)Funding Agency: North Pacific Research Board

Mooring Fluorescence Data GAK5 June 2002 – July 2003

Mooring: gbm3; Depth: 14-15 m; Fluorometer Volts

Time (Month/Year)

Jun/02

Jul/02

Aug/02

Sep/02

Oct/02

Nov/02

Dec/02

Jan/03

Feb/03

Mar/03

Apr/03

May/03

Jun/03

Jul/03

Flu

orom

eter

Vol

ts

0.0

0.5

1.0

1.5

2.0

2.5

Major blooms occur in late April, May or early June with low production in March and early April

Model must reproduce the timing and peaks suggested from mooring fluorescence data.Mooring data from Stabeno (PMEL)

Model Simulation: 2001; GAK6

Time (days)

Mar Apr May Jun Jul Aug Sep Oct

Bio

mas

s (m

g C

m-3

)

0

20

40

60

80

100

Large PhytoplanktonSmall Phytoplankton

Average in upper 50 m

1 3 5 7 9 11 13

July

84

< 2 µm>2-10 µm>10 µm

20

40

60

80

0

0

20

40

60

80

1 3 5 7 9 11 13

<2 µm>2-10 µm>10 µm

May

Seward Line StationsComparison of measured and simulated phytoplankton biomass at station GAK6.Simulated peak biomass occurs in mid April and May with magnitudes similar to field measurement by Lessard (University of Washington).

Field measurements

Primary Production: 204.4 g C m-2 y-1

Time

Mar Apr May Jun Jul Aug Sep

mg

C m

-2 d

-1

0

500

1000

1500

2000

2500

GAK1

Primary Production: 172.2 g C m-2 y-1

Time

Mar Apr May Jun Jul Aug Sep

mg

C m

-2 d

-1

0

500

1000

1500

2000

2500

3000

3500

GAK4

Primary Production: 240.8 g C m-2 y-1

Time

Mar Apr May Jun Jul Aug Sep

mg

C m

-2 d

-1

0

1000

2000

3000

4000

GAK9

Primary Production: 198.8 g C m-2 y-1

Time

Mar Apr May Jun Jul Aug Sep

mg

C m

-2 d

-1

0

500

1000

1500

2000

2500

GAK13

GAK 9 2000-2004 Integrated Productivity

00.5

11.5

22.5

33.5

3 3 4 4 5 5 5 7 7 8 8 10 10 12Month

gC

/m2/

day

GAK 13 2000-2004 Integrated Productivity

0

0.5

1

1.5

2

2.5

3

3 3 3 4 4 5 5 7 7 8 8 10 10 12

Month

gC

/m2/

day

GAK 4 2000-2004 Integrated Productivity

0

1

2

3

4

5

3 3 3 3 3 4 4 4 5 5 5 5 5 7 7 7 7 8 8 8 8 1010101212Month

gC

/m2/

day

GAK 1 2000-2004 Integrated Productivity

0

0.5

1

1.5

2

2.5

3

3 3 3 4 4 5 5 7 7 8 8 10 10 10 12Month

gC

/m2/

day

Simulated and measured primary production for stations GAK 1, 4, 9 and 13. Note that the magnitudes of simulated and measured production are similar but mooring data suggest that production may be more peaked than the simulation indicates. Production measurements by Whitledge and Stockwell (University of Alaska).

Model Simulation: 2001; GAK6

Time (days)

Mar Apr May Jun Jul Aug Sep Oct

Bio

mas

s (m

g C

m-3

)

0

20

40

60

80

100

Large MicrozooplanktonSmall Microzooplankton

Average in upper 50 m

1 3 5 7 9 11 130

20

40

60

80

100

July

HnanoHdinoCiliates

1 3 5 7 9 11 130

10

20

30

40

50

60

AugustHnanoHdinoCiliates

Seward Line Stations

Comparison of measured and simulated microzooplankton biomass at station GAK6. Magnitudes of simulated and measured biomass are similar. Field data from Lessard (University of Washington)

Field Data

N. plumchrus & N. flemingeri

Month

Mar Apr May Jun Jul Aug Sep Oct

Mea

n ca

rbon

bio

mas

s (m

g m

-3)

0

10

20

30

40

50

19971998199920002001200220032004

Calanoida

Month

Mar Apr May Jun Jul Aug Sep Oct

Mea

n ca

rbon

bio

mas

s (m

g m

-3)

0

20

40

60

80

100

120

19971998199920002001200220032004

Model Simulation: 2001; Gak6

Time (days)

Mar Apr May Jun Jul Aug Sep Oct

Bio

mas

s (m

g C

m-3

)

0

10

20

30

40

50

60

Neocalanus spp.

Small Copepods

Average in upper 100 m

Field Data

Comparison of measured and simulated mesozooplankton biomass at station GAK6. Total zooplankton biomass (top panel, field data) is similar to simulation. Neocalanus biomass in simulation is high for 2001

Model Simulation: 2001; Gak6

Time (days)

Mar Apr May Jun Jul Aug Sep Oct

PA

R (

E m

-2 d

-1)

0

20

40

60

80

100

PAR Fraction = 0.5PAR Fraction = 0.7Ship Time vs Surface Light

Photosynthetically active radiation (PAR) in the model was similar to values measured at the ship’s mast head during cruises, but the range of measured values was substantially greater than simulated values.

Conclusions:The model as currently parameterized was

capable of reproducing broad scale patterns of nutrient concentration, primary production, and biomass of phytoplankton, microzooplankton and mesozooplankton on the northern Gulf of Alaska shelf for 2001.

Remaining Tasks:1)Get the physical model to run with tides.2)Run the model on the 3 km Gulf of Alaska

grid for 2001, 2002, 2003, 2005 and 2006.

Major question: Can the model reproduce the interannual

variability observed in the field data?

The ecosystem model is embedded in a 3-dimensional physical circulation model (ROMS) to link climate forcing to the ecosystem response.

11 Component ModelSlide by G. Gibson

Iron

ROMS

Model and Site Description

SeaWiFS Satellite Chlorophyll May 13 2001Simulated primary production (g C m-2 y-1)

Comparison of simulated primary production and satellite chlorophyll image. Note the elevated primary production and chlorophyll concentration to the west of the Seward Line (arrows) suggesting the model can reproduce physical mechanisms affecting distribution of production on the shelf.

Distribution of Production

Phytoplankton Biomass and Production

Seasonal Zooplankton Biomass

0 50 100 150 200

D istance (km )

-100

-80

-60

-40

-20

0

De

pth

(m

)

N itra te (m M m-3

)

0.01.32.63.85.16.47.79.010.211.512.814.115.316.617.919.220.521.723.024.325.6

0 50 100 150 200

D istance (km )Am m onium (m M m

-3 )

0.00.20.30.50.60.80.91.11.21.41.51.71.82.02.12.32.42.62.72.93.0

0 50 100 150 200

D istance (km )

-100

-80

-60

-40

-20

0

De

pth

(m

)

N itra te (m M m-3

)

0246810121416182022242628303234363840

0 50 100 150 200

D istance (km )Am m onium (m M m

-3 )

00.10.20.30.40.50.60.70.80.911.11.21.31.41.51.61.71.81.92

Simulated

Measured

July 2001

Simulated and measured nitrate and ammonium on Seward Line. The simulation can reproduce the vertical distribution and approximate magnitude of field measurement. Nutrient data from Whitledge (University of Alaska).

Simulated surface nitrate (mM m-3), July 10

The model was capable of producing the high nitrate concentrations above the seasonal thermocline in the Alaska gyre and nitrate exhaustion typical of the shelf during summer.

Seasonal and Geographic Nutrient Distribution

Photosynthetically Active Radiation

Conclusions and Perspectives

Phytoplankton Biomass