Corals as paleoclimatic archivesJens Zinke

PROPERJune 2004, VU Amsterdam

Coral study sites

Massive coral Porites sp.

Coral drilling

Coral core recovery60

cm

Emerged fossil coral Porites

Fossil corals: storm deposits

Environmental tracers in corals

Oxygen isotopes:

- Sea surface temperature- Seawater isotopic composition

Carbon isotopes:

- cloud cover

Sr/Ca, U/Ca, Li/Ca (?):

-Sea surface temperature

U/Ca, Mg/Ca:

-Salinity

U/Th dating of fossil corals

Combined Sr/Ca and d18O:

- Hydrologic balance

14C, Pb-isotopes:

- Ocean circulation- Atmospheric circulation- Upwelling

Ba/Ca, Cd/Ca:

-Terrestrial river runoff- upwelling

Rare Earth Elements (REE):

- biological activity in seawater

Techniques for isotope and trace element ratios:

- Oxygen and carbon isotopes on Mass Spectrometer

- Sr/Ca, Mg/Ca, Ba/Ca on ICP-OES

- U/Ca, Li/Ca, Sr/Ca, Mn/Ca, Ba/Ca on ICP-MS and Laser Ablation ICP-MS

- Sr/Ca, U/Ca, U/Th on TIMS

- Rare Earth Elements with Laser Ablation ICP-MS

- Element mapping and ultra-high-resolution with SIMS and PIXE

Exoskeleton(Aragonite crystals)

Extracellular calcifying fluid

Basal ectodermof coral polyp withsymbiontsfrom seawater

Growth rate effects

slow growth rates (below 3mm/year) = heavy isotopes

McConnaughey, 2003, Coral Reefs 22

Isotopic fractionation

Kinetic fractionation

Non-photosynthetic

photosynthetic

McConnaughey, 2003, Coral Reefs 22

Density banding: first age model

High density = winter

Low density = summer

Major growth axis10-15 m

m

Age model and data interpolation

X-ray with density banding

Madagascar coral record

Zinke et al. 2003, Springer

Calibration vs .instrumental data: Linear Regression

Inverse relationship to temperature in isotopes and Sr/Ca ratios !

Reconstruction of SST: Core top calibration

Calibration/Validation of proxy data: annual means

Combined use of 18O and Sr/Ca: Hydrologic balance

Method in Ren et al., 2002 Geochimica et Cosmochimica Acta 67 (9)

Hendy et al., 2002, Science 295

Time series analysis and advanced statistics

Advanced Statistics: Cross spectral analysis

Zinke et al. 2003

ENSO Teleconnections

ENSO phenomenon

Webster et al., 1999

SST / Wind Precip.Evap.

Summer monsoon (July)

Winter monsoon (January) January

July

Coral sites superimposed on SST and monsoonal winds

Coral records from the Indo-Pacific

Western Indian Ocean coral time series

Pfeiffer, 2002; Pfeiffer et al., 2004, Quaternary Research; Zinke et al. (subm)

Tarawa coral record, Cole et al., 1993, Science 260

Changing El Nino frequency derived from a coral 18O record at Kiribati Island (1°N) located within the Nino3 region in the Pacific

Spatial correlation maps coral vs. Global SST:Indian Ocean - ENSO teleconnection: 1970‘s shift?

before 1970 after 1970

U/Th dating of fossil reef cores (corals) for exact timing of sea level changes

Future needs:

- proxies for environmental changes in coastal waters

- process studies of incorporation of proxies into skeleton

- multiple core replication of single core results

- use of more statistical methods to unravel climate information

- net work of coral records for each ocean basin for large scale climate reconstruction

- collaboration with climate modeling community to test future scenarios

Thank you for your attention!