Ocean-scale modelling of Calanus finmarchicus

1. 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

2. Calanus finmarchicus – a marine copepod • 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. 2 mm

3. 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.

4. Coupling Life-Cycle to Physical Oceanography

5. Calanus abundance and Circulation

6. 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)

7. A Calanus-focussed model

8. 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

9. Yearly Population Cycle

10. Continuous Plankton Recorder Surveys

11. Test Data – Time Series & CPR

12. Water column integrated abundance of overwintering C4 and C5 C. finmarchicus C5

13. Time Series Test Gulf of Maine OWS Mike surface C5-C6 diapause C5

14. Diapauser Survey Test

15. CPR Test observed predicted Jan./Feb. May/Jun. Jul./Aug.

16. August Sea Temperature at 20m

17. The Impact of Transport

18. Domain Connectivity Year 1 Year 3 Year 6

19. Travels of the Great Salinity Anomaly

20. Conclusions • Fractional diapause entry • Diapause entry late in C5 • Photoperiod-cued diapause exit • Temperature-dependent mortality • Limited impact of transport • High domain connectivity • Ocean-scale population model feasible • Numerical efficiency is key

21. Washout of a non-developing population from Gulf of Maine

22. Boundary effects on C5-C6 seasonal cycle

23. Gulf of Maine Export

24. Invasion of Gulf of Maine

25. 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

26. 1996-onwards 1958-1999 average surface abundance of C. finmarchicus (stage C5 and CVI) Calanus abundance map compiled from data supplied by SAHFOS to NERCMarine Productivity project GR2/2749 and the EU-TASC project

27. Annual Mean Temperature & Food

28. C5 Overwintering depths in various regions...

29. Geographical focus of Marine Productivity and other Calanus-centric programmes during the 1990’s.. Multi-national programmes: EU-ICOS EU-TASC National programmes: UK, Norway, Germany, Denmark, Iceland, Canada, USA NERC Marine Productivity Calanus abundance map compiled from data supplied by SAHFOS to NERCMarine Productivity project GR2/2749 and the EU-TASC project

30. C5’s & phytoplankton carbon at OWSM • Diapause occurs at end of C5 stage • Fixed fraction of each generation