Spatial Indices of Upwelling - PowerPoint PPT Presentation

Spatial Indices of Upwelling

1) Coastal Topography

• Average spatial patterns of coastal ocean processes are strongly influenced by topography and bathymetry

Broitman and Kinlan 2006 MEPS, In press

Bays

Headlands

COASTAL STRUCTURE

-1.0

(Embayments)

Along-coast Distance (km)

Normalized residual from smoothed coast

0

(Headlands)

+1.0

Scale of Smoothing (km)

COASTAL STRUCTURE

Smoothing Scale=1000 km

COASTAL STRUCTURE

Smoothing Scale=50 km

Coastal Topographic Index

Chile

WNA

S. Africa

Cons

Pros

• Easily calculated
• Data readily available
• Arbitrarily high resolution
• Can index processes at multiple scales

• Indirect index; index of upwelling or any other process depends on nature of coupling
• Not dynamic (no time component)
• Oversimplified?

SST

Spatial Indices of Upwelling

2) SST-derived indices

Coastal SST

latitude

time

longitude

Latitudinal mean at each pixel

Topographic Index and dSST Spatial Series

Correlation between Topo and dSST indices

C) Topo vs. Δ SST

Correlation with Bakun Regional Index

Ecosystem Structure

Spatial patterns of kelp and phytoplankton

Areal cover

Biomass

Spatial Cross-Correlations

chl-a vs. kelp

Spatial Cross-Correlations

A) Topo vs. kelp

B) Topo vs. chl-a

C) Topo vs. Δ SST

Jones et al 1988, Cont Shelf Res

Alongcoast scales: Variogram Analysis

Approximately the same characteristic scale

Variable

Nugget (SE)

Sill (SE)

Range (SE) (km)

Kelp

0.35 (0.09)

0.65 (0.09)

188 (100)

Chl-a

0.13 (0.08)

0.87 (0.08)

178 (34)

ΔSST†

0.008 (0.007)

0.992 (0.007)

151 (18)

Coast Anomaly

0.04 (0.03)

0.96 (0.03)

161 (40)

Alongcoast scales: Variogram Analysis

Onshore Community Patterns

WNA

73 sites

along 6000 km

of coast

South Africa

58 sites along 2000 km of coast

Chile

26 sites

1000 km of coast

What scale of coastal features matter to the process you’re interested in?

Correlation between variable of interest and topographic index at each smoothing scale

0.6

0.4

0.2

Cross-Correlation

0

-0.2

-25

-20

-15

-10

-5

0

5

10

15

20

25

Along-coast Lag Distance (km)

Peak @ 15 km in the poleward direction

Correlations with Coastal Anomaly – South Africa

Correlation with Coastal Anomaly – Mussels

CHILE

SOUTH AFRICA

Chile – Upwelling-Recruitment Dynamics Seen in Bare Space?

Coastal Topography and Physical Forcing

CHILE

SOUTH AFRICA

Correlation with Coastal Anomaly: Mussels

CHILE

SOUTH AFRICA

Correlation with Coastal Anomaly: Trophic Grps

SOUTH AFRICA

CHILE

Long-term Average Recruitment vs. Topography at 21 Coastal Sites

Green=Chthamalus

Black=Balanus

Multiple regression with:

Topo10km, Topo150km, Coastal Coordinate (linear latitudinal trend)

Balanus

r2=0.84, p<0.0001

Other processes correlated with topography

Aside… Hierarchical Bayesian Modeling for Data Integration & Complex Hypothesis Testing

Site 1

Santa Barbara

Site 2

Site 3

Site 4

Offshore

Larval

Pool

Nearshore Ocean

Offshore Ocean

Sea Temp (SST)

Recruitment

Santa Barbara

Recruitment

Current

ChlorophyllA

Recruitment

Current

Current

Recruitment

Current

Offshore

Larval

Pool

16 points in time, each describing previous month

Offshore Ocean

Nearshore Ocean

i = space index , t = time index

2



TS=0

Onshore

Delivery

Offshore

Larval Pool

Combine these

to get Recruitment

Data:

SSTt-TS

Rit

Git

Rit~Poisson(FtHitei)

Likelihood:

i~N(0,2)

Logit(Hit)= 0+1Git+g

g~N(0,m2)

Links:

Ft = k + STS*SSTt-TS

k,S

2

0, 1, m2

Parameters:

N(0,10-3)

vague

IG(10-3,10-3)

vague

IG(2,10)

informative

N(0,10-3)

vague

Priors:

Chl , gate+errror, Gamma

SST , gate+errror, Gamma

SST , gate+errror,

Poisson

SST , gate+errror,

Poisson, site effects