Ocean-scale modelling of
Calanus finmarchicus
Douglas Speirs
Acknowledgments: Bill Gurney (Strathclyde)
Mike Heath (FRS Aberdeen)
Simon Wood (Glasgow University)
SOC, PML, SAHFOS, US-GLOBEC
Calanus finmarchicus – a marine copepod
2 mm
• Up to 90% of copepod biomass throughout the sub-arctic North Atlantic.
• Important prey species for fish in both shelf and ocean ecosystems.
• Extensive database from field surveys and laboratory experiments.
The life-cycle of Calanus finmarchicus
• Omnivorous, but feeds mainly on phytoplankton.
• x1000 difference in body weight between eggs and adults.
• Stage duration strongly dependent on temperature
• Naupliar survival strongly dependent on food.
• Reproduction & growth in upper layers (<200m).
• Overwinters in a resting state at depths of 500-2000m.
Coupling Life-Cycle to Physical Oceanography
NORTH ATLANTIC OCEAN SHELF SEAS
Overwintering at depth
Export to shelf seas
Growth and reproductionin the upper ocean
In the ocean, Calanus switchesbetween surface and deepcirculation regimes during eachannual cycle.
Each spring, the shelf seas arere-colonised with Calanus fromthe ocean.
Calanus abundance and Circulation
The modelling challenge
The Challenge• Physiologically and spatially explicit demographic model
• Ocean-basin scale – advection plus diffusion
• Hypothesis tests require wide parameter exploration
• Need exceptional computational efficiency
The Solution• Focus on Calanus (physical and biotic environment as given)
• Separate computation of physical and biological components
• Discrete-time approach ( 104 speed-up relative to Lagrangian ensemble)
A Calanus-focussed model
The Biological Model
• Development rate a function of temperature and food
• Diapause entry from end C5
• Fixed fraction of each generation enter diapause
• Diapause exit photoperiod cued
• Surface mortality increases with biomass and temperature
Yearly Population Cycle
Continuous Plankton Recorder Surveys
Test Data – Time Series & CPR
Water column integrated abundance of overwintering C4 and C5 C. finmarchicus
-60 -50 -40 -30 -20 -10 0 10
Longitude
50
55
60
65
70L
atit
ud
e
0 10000 20000 30000 40000 50000
C alanus finm arch icus ( m - 2 , 0 - 3 0 0 0 m )C5
Time Series Test
Gulf of Maine
OWS Mike
surfaceC5-C6
diapauseC5
Diapauser Survey Test
CPR Test
Jan./Feb.
May/Jun.
Jul./Aug.
observed predicted
August Sea Temperature at 20m
The Impact of Transport
Domain Connectivity
Year 1
Year 3
Year 6
Travels of the Great Salinity Anomaly
Conclusions
•Ocean-scale population model feasible•Numerical efficiency is key
•Fractional diapause entry
•Diapause entry late in C5
•Photoperiod-cued diapause exit
•Temperature-dependent mortality
•Limited impact of transport
•High domain connectivity
Washout of a non-developing population from Gulf of Maine
Boundary effects on C5-C6 seasonal cycle
Gulf of Maine Export
Invasion of Gulf of Maine
Future Prospects
•
• Tests on independent data sets (UK-GLOBEC Irminger Sea data)
• Automated parameter optimization
• Hindcasting of decadal trends
• Nested models for shelf regions
• Coupled target species - ecosystem models
Calanus abundance map compiled from data supplied by SAHFOS toNERCMarine Productivity project GR2/2749 and the EU-TASC project
1958-1999 average surface abundance of C. finmarchicus (stage C5 and CVI)
-80 -70 -60 -50 -40 -30 -20 -10 0 10 20 3035
40
45
50
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60
65
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75
80
050100150200250300350400450500550600
Me
an
nu
mb
er
3m
-3
-1.5
-0.5
0.5
1.5
2.5
0 1 2 3 4 5 6 7 8 9 101112
Month
Av
era
ge
ab
un
da
nc
e
-1.5
-0.5
0.5
1.5
2.5
0 1 2 3 4 5 6 7 8 9 101112
Month
Av
era
ge
ab
un
da
nc
e
-1.5
-0.5
0.5
1.5
2.5
0 1 2 3 4 5 6 7 8 9 101112
Month
Av
era
ge
ab
un
da
nc
e
-2
-1
0
1
2
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5
1950 1970 1990
Year
Av
era
ge
ab
un
da
nc
e
-2
-1
0
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5
1950 1970 1990
Year
Av
era
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ab
un
da
nc
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-2
-1
0
1
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1950 1970 1990
Year
Av
era
ge
ab
un
da
nc
e
-6
-4
-2
0
2
4
6
1950 1970 1990
Year
NA
O in
dex
-2
-1
0
1
2
3
4
-6 -4 -2 0 2 4 6NAO index
No
rth
Se
a C
ala
nu
s
1996-onwards
Annual Mean Temperature & Food
Overwintering depths in various regions...
-3500
-2500
-1500
-500
Dep
th (m
)
LS MAR IrB IcB RB NEI FSC ENS NT
-60 -50 -40 -30 -20 -10 0 10
Longitude
50
55
60
65
70
La
titu
de
0 10000 20000 30000 40000 50000
C alanus finm arch icus ( m - 2 , 0 - 3 0 0 0 m )
C5
Calanus abundance map compiled from data supplied by SAHFOS toNERCMarine Productivity project GR2/2749 and the EU-TASC project
Geographical focus of Marine Productivity and other Calanus-centric programmes during the 1990’s..
-80 -70 -60 -50 -40 -30 -20 -10 0 10 20 3035
40
45
50
55
60
65
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75
80
050100150200250300350400450500550600
Me
an
nu
mb
er
3m
-3
Multi-nationalprogrammes:EU-ICOSEU-TASC
National programmes:UK, Norway, Germany, Denmark, Iceland, Canada, USA
NERC MarineProductivity
C5’s & phytoplankton carbon at OWSM
•Diapause occurs at end of C5 stage
•Fixed fraction of each generation