Geoduck Crossdating and Chronology Development

dendrolab.indstate.edu

Geoduck Crossdating and Chronology Development

Geoduck Crossdating and

Chronology Development

by the

Sclerochronology Group 2006


Geoduck are longlived,

with max age

of ~150y

• Live subtidal to

~110 m, buried in

the sediment

• Commercially

harvested

Introduction


Objectives

• Demonstrate crossdating in geoduck

• Generate multidecadal chronology

• Establish climate-growth relationships

• Assess linkages with terrestrial

chronologies.


Sample Location

• “Tree Nob” sample

British Columbia,

Canada


• Previously prepared

specimens were used

• An acetate peel was

made of a cross section

taken from the hinge

plate area

Sample Prep

Samples provided by Pacific Biological

Station at Nanaimo, BC


Imaging

• Several images were captured from each

specimen


Images were first “tiled” together…


1965

Signature years

1994/1998


• A measurement

transect was

established

• Growth

increments were

delineated

• 2 sets of

measurements

per specimen


COFECHA

• First pass interseries correlation r = 0.62

– Resolved some data handling and cross-dating

errors

• Second pass: r = 0.68

• Final pass r = 0.716 (no errors)


Chronology development

• ARSTAN detrending: negative exponential


“ Tree Nob”geoduck chronology

Ring width index

2

1.8

1.6

1.4

1.2

1

0.8

0.6

0.4

1915

1941

1965

1981

1994

1998

1900 1920 1940 1960 1980 2000

Year


What’s driving growth variability?

• Sea surface temperature

– High values = warm water

• Pacific Decadal Oscillation

– High values = warm water

• El Nino (Northern Oscillation Index)

– Low values = warm water


Figure credit: NOAA Climate Prediction Center

El Niño Ni o / La Niña Ni

Departures from normal….

El Niño La Niña


Pacific Decadal Oscillation

warm phase cool phase

Figure credit: Joint Institute for the Study of the Atmosphere and Ocean: U. Washington


Correlation coefficient

0.8

0.6

0.4

0.2

0

-0.2

-0.4

-0.6

AUG(L)

SEP(L)

OCT(L)

NOV(L)

DEC(L)

JAN

FEB

MAR

APR

Month

MAY

JUN

JUL

AUG

SST PDO NOI

SEP

OCT

NOV

DEC


Ring width index

4

3

2

1

0

-1

-2

-3

PDO

Geoduck increments

1945

regime shift

1890 1910 1930 1950 1970 1990 2010

Year

1977

regime shift


ing width index

2

1.8

1.6

1.4

1.2

1

0.8

0.6

0.4

AK yellow cedar

geoduck

Tree ring chronology comparison

1890 1910 1930 1950 1970 1990 2010

year

correlation r = 0.44


Conclusions

• Strong crossdating; ISC with r = 0.72

– Potentially good age validation tool

• Strong climate-growth relationships

– Potential climate reconstructions

Geoduck increments correlated well with

AK yellow cedar growth rings.


Brought to you by:

Darlene June 27

Medicine Hat, AB Canada

Robyn March 29

Hannibal, MO USA

Barb March 10

Calgary, AB Canada

Bob March 27

Seville, AD Spain

Judy July 12

Nanaimo, BC Canada

Dani November 27

Sao Paulo, SP Brazil

Bryan April 19

Erie, PA USA

Paul February 13

Corvallis, OR USA

Rose May 1

Bellevue, WA USA

Kris NY, USA


Hooray!

That’s all

folks!

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