Scaling and Modeling of Larval Settlement Satoshi Mitarai Oct. 19, 2005

GOAL OF “FLOW” Assess larval dispersal scales using idealized simulations of California Current Develop simple modeling to establish source-destination relationships –Without fluid dynamics simulations, which are time consuming

WHAT’S NEW? Weak upwelling case is added Larval dispersal scales are quantified A simple model to establish source- destination relationships is proposed –Accounts for spatial scales properly

TEMPERATURE FIELD (TOP VIEW) Strong upwelling Weak upwelling Summer Winter

MEAN TEMPERATURE FIELD (SUMMER) Simulation CalCOFI Shows reasonable agreement with CalCOFI data (Averaged over 6 realizations)

MEAN TEMPERATURE FIELD (WINTER) Simulation CalCOFI Shows a good agreement with CalCOFI data (Averaged over 6 realizations)

LARVAL TRAJECTORIES SummerWinter Eddies sweep larvae into “packet” which stays together thru much of pelagic stage

LAGRANGIAN STATISTICS 3.4 / / / 4.6 Poulain et al (1998) 4.3 / / / 3.5 Swenson et al (2001) 1.6 / / / 5.7 Winter Simulations 3.1 / / / 3.7 Summer Simulations Diffusivity Zonal / Merid Length Scale Zonal / Merid Time scale Zonal / Merid Data Set Winter shows more correlation in time & less diffusivity

LARVAL TRANSPORT & SETTLEMENT Summer Winter More settlers are observed in winter

ONLY SETTLERS SummerWinter

ALONGSHORE DISPERSAL KERNEL SummerWinter Gaussian fitting More alongshore travel distance in summer (Obtained from 6 realizations) AVG = -122 km, STD = 103 kmAVG = -80 km, STD = 92 km

CROSS-SHORE DISPERSAL KERNEL Lognormal fitting SummerWinter More offshore travel distance in summer Settlers move out nearshore habitat before settle (Obtained from 6 realizations)

ARRIVAL DIAGRAM Summer 15 days 21 days 43 km 64 km Using variogram … Winter

CONNECTIVITY MATRIX Summer Winter 48 km 53 km

SUMMARY Travel distance & survivability shows difference between summer & winter –More travel distance in summer –Lower survivability in summer Settlement scales do not show much difference between summer & winter –Arrival length ~ 50 km –Arrival time ~ a few weeks –Connectivity length ~ 50 km

CONNECTIVITY MATRIX MODEL Diffusion model Spiky kernel model Neither one accounts for spatial structures

A NEW MODEL FOR CONNECTIVITY MATRIX Idea: model settlement events as a summation of “settlement packets” –Number –Size –Source locations –Travel distance Rossby radius (~50 km) Randomly (uniform distribution) Randomly (dispersal kernel)

Determine # of settlement packets N = (T/t) (L/l) f (D/l) NUMBER OF SETTLEMENT PACKETS T: Larval release duration t: Lagrangian correlation time L: domain size l: Rossby radius f: survivability D: standard deviation of dispersal kernel Total # of released packets # of settlement events per packet

MODEL PREDICTIONS SummerWinter Accounts for spatial structures

DIFFUSION LIMIT Packet model 1 season 6 seasons 12 seasons 120 seasons 1 season 6 seasons 12 seasons Diffusion Flow simulation Diffusion model

NEXT STEPS Use proposed model in F 3 model Investigate effect of larval behavior –Preliminary study has been already done Investigate effect of coastal topography

LAGRANGIAN STATISTICS 3.4 / / / 4.6 Poulain et al (1998) 4.3 / / / 3.5 Swenson et al (2001) 1.6 / / / 5.7 Winter Simulations 3.1 / / / 3.7 Summer Simulations Diffusivity Zonal / Merid Length Scale Zonal / Merid Time scale Zonal / Merid Data Set Simulations: 6 realizations, 6000 particles Swenson et al (2001): late spring to early fall, , 124 drifters, 18N-40N Poulain et al (1998): early spring to late fall, , 29 drifters, 18N-36N