Lagrangian circulation on the SAB: implications for larval dispersal and retention

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Lagrangian circulation on the SAB implications
for larval dispersal and retention

• Karen Edwards
• Committee Meeting
• August 9, 2005

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Outline

• Chapter 1 model validation. Lagrangian
  circulation on the Southeast U.S. Continental
  Shelf implications for larval dispersal and
  retention
• Papers submitted June 2005.
• Chapter 2 Lagrangian descriptions of 2-D marine
  larval dispersal kernels.
• Chapter 3 - Larval dispersal and arrival kernels
  at GRNMS

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2D Dispersal Kernels

• A dispersal curve or dispersal kernel, the
  probability that a larva will settle at a given
  distance from its release location.
• Defining a dispersal kernel is a bio-physical
  problem - it is the interaction between the
  organisms behavior and the physical flow field it
  is in.
• Physical factors
• Passive advection and diffusion
• Intermittent/episodic events
• Interannual variability
• Long-term modulations (ENSO,NAO)
• Biological Factors
• Larval Behavior
• Along-trajectory mortality feeding, predation,
  physical environment

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2D dispersal kernels

• Using climatological flow fields, look at
• Season of release
• Diffusion coefficient
• Duration (15d, 30d, 45d)
• Release location (onshore vs offshore, north vs.
  south)
• Intraseasonal variability - individual months
  within seasons

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Climatology Wind Fields
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Climatology Flow Fields
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Particle Tracking Model

• Lagrangian particle tracking with turbulent kick
• Gaussian random walk (or random flight)
• Displacements

ß is from a standard normal distribution Kx and
Ky are eddy diffusivities in the east-west (x)
and north-south (y) directions
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Monthly Results
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Monthly Results
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Principal Component Analysis
Figures 2.1 and 2.2 from Preisendorfer, PCA
Analysis in Meteorology and Oceanography
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2D Dispersal kernels

• Principal component analysis (PCA) define the
  following parameters
• d mean dispersal distance (km)
• ? dispersal direction (degrees from East)
• s11 and s22 estimate of variance of underlying
  population, rotated by
• ?m the principal angle (direction in which
  variance is a maximum)

Where sxx and syy are the variances of the
original data set and sxy is the covariance
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2D Dispersal Kernels
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2D Dispersal kernels
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K-test
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K-test
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QUODDY - AH
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Release Duration
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Release Duration
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Release Location
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Release Location
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Release Location
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GRNMS dispersal kernels

• Look at dispersal and arrival kernels for GRNMS
• Model behavior for black sea bass and bank sea
  bass
• Look at inter-annual variability
• 2000, 2001 and 2002
• Include passive drifters and behavior.

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Interannual variability Passive Drifters