1. Emanuele Di Lorenzo 1, Mike Foreman 2, Bill Crawford 2 1 Scripps Institution of Oceanography, UCSD, San Diego 2 Institute of Ocean Sciences, Sidney BC Modeling the Generation of Haida Eddies

2. l Formed off Queen Charlotte Islands l clockwise rotation l heights up to 40cm above background ocean l diameters up to 200km l depth to at least 1000m l warmer & fresher l can last more than two years What are Haida Eddies?

3. l carry plankton, larvae, & nutrients offshore Þreduce productivity on shelf but increase productivity offshore ÞPacific cod recruitment in Hecate Strait shows strong negative correlation with mean sea level previous winter Þre-stock fish populations around seamounts l fishery managers would like predictive capability Importance

4. l Background &importance l Previous studies l Model details l Simulations: Þannual cycle Þgeneration mechanism Þsensitivity studies l Future work l Summary Overview

5. ¶ Thomson & Wilson (1987) Þtidal residual eddy west of CSJ · Thomson & Gower (1998) satellite observations Þbaroclinic instability from reversal in poleward winds ¸ Melson et al (1999) & Murray et al (2001) models (NRL) Þbaroclinic instability: Þrelaxation of poleward wind or Kelvin waves ÞBUT coastline omitted inland seas ¹ Crawford et al. (2001) analysis Þoutflows past Cape St James Þlab experiments of Cenedese & Whitehead (2000) Previous Generation Studies

6. Region of Interest & Data Locations

7. l ROMS : Þ8 km horizontal resolution Þ20 vertical levels Þno tides ÞNCEP or Faucher et al (1999) monthly average winds Þradiation/relaxation to TS climatology on boundaries (Marchesiello et al, 2001) Þinitial & open boundary conditions from Levitus et al (1994) monthly climatology Model Details

8. l 12 year run with repeat annual cycle forcing of wind, boundary TS, & nudged surface heat flux Annual Cycle Simulations

9. l Model phase lag comparison vs tide gauges Þ0° = Jan 1 Þmax difference  1 month (30°) l model amps (cm) too small Þcoarse resolution, underestimated forcing (NCEP winds nearshore ?) Annual Cycle Simulations (cont’d)

10. l Constant Jan forcing l 5-day time sequences of SSH & SST l distinct small eddies formed at 200, 205, 211, 216, 222 l all except 222 merge l strong eddies form during times of stronger southward flows east of CSJ Eddy Generation Mechanism6.5 8.5 6.5 8.5 6.5 8.5 6.5 8.5 200 208 216 224 201 209 217 225 202 210 218 226 203 211 219 227 204 212 220 228 205 213 221 229 206 214 222 230 207 215 223 231

11. l All performed with constant Jan forcing: ¬average SSH from previous run ­constant f: eddies formed but drift northward along topography ®barotropic: no eddies formed, flow follows depth contours Sensitivity Tests

12. ¯constant depth: no eddy °constant depth & artificial coast in Hecate: standing eddy - no detachment/drift westward Þbut meanders in northward flow do produce eddies that drift westward ±2nd order advection instead of 3rd: strong eddies not formed - anticyclonic circulation quickly dissipates Þlots of animations on http://horizon.ucsd.edu/movies/haida Sensitivity Tests (cont’d)

13. ¶ finer resolution · tides & buoy winds Þtidal speeds over 1m/s east of CSJ  residual eddies Þbetter nearshore winds ¸ simulation of 1997- 98 El Nino Future Work

14. l Haida Eddies generated by advection of buoyant water around Cape St. James Þin winter when winds are toward NW Þwith strong flows, several smaller eddies can merge Þimportant biologically Þprevious model simulations incomplete BUT “baroclinic instability” from wind relaxation may be generation mechanism elsewhere along shelf l ROMS Þreproduced seasonal signal & revealed relevant generation processes Þfurther studies planned with higher resolution, better winds, & tides l more details in Di Lorenzo et al, submitted to DSRII Summary

15. l Rick Thomson: current meter & CTD data l Josef Cherniawsky: TP data l Patrick Cummins, John Morrison, Frank Whitney: helpful discussions l Trish Kimber: figures l partial funding from NOAA/NASA (EDL), SSF/DFO (MF & BC) Acknowledgements