A high-resolution cellulose δ 18 O record of Pinus merkusii from Cambodia and its climate implications

A high-resolution cellulose δ 18 O record of Pinus merkusii from Cambodia and its climate implications Mengfan Zhu, Lowell Stott University of Southern California Brendan Buckley LDEO, Columbia University

Motivation How do tree ring stable isotopes record seasonal ecological and climatological influences? Use water isotopes as tracer in the hydrological cycle. Provide a long and continuous observational data of water isotopes. How has atmospheric circulation evolved in the tropical monsoon region?

Introduction: tree ring oxygen isotopes Isotopic composition of soil moisture Relative humidity δ 18 O c : oxygen isotopic ratio of cellulose δ 18 O s : oxygen isotopic ratio of source water ε ao : biochemical autotrophic fractionation factor ε eo : equilibrium fractionation factor for water liquid-vapor phase change ε ko : kinetic fractionation factor for water liquid-vapor phase change f : fraction of leaf water subject to evaporation φ o : fraction of oxygen that exchanges with xylem water h : relative humidity

Introduction: tree ring oxygen isotopes Isotopic composition of soil moisture Wet season Relative humidity Dry season

Study site

Temperature Precipitation Study site Rainy season: May to Oct Dry season: Dec-Jan-Feb Hot season: Mar-Apr-May

Methods Tree cores: Pinus merkusii, KRPM15B, KRPM10A. Microtome cutting: multiple samples per ring. α-cellulose extraction: Modified Brendel method (Gaudinski et al., 2002). Isotope analysis: Thermo Finnigan TC/EA, Delta V Advantage IRMS. Precision: ± 0.3.

Results: seasonal pattern

Results: seasonal pattern IsoGSM: a global rainwater isotopic composition simulation dataset using Scripps Experimental Climate Prediction Center s global spectral model (Yoshimura et al.,2008). GNIP: IAEA s global network of isotopes in precipitation.

Results: seasonal pattern max min max min IsoGSM: a global rainwater isotopic composition simulation dataset using Scripps Experimental Climate Prediction Center s global spectral model (Yoshimura et al.,2008). GNIP: IAEA s global network of isotopes in precipitation.

Results: seasonal pattern Feb Oct max min max min IsoGSM: a global rainwater isotopic composition simulation dataset using Scripps Experimental Climate Prediction Center s global spectral model (Yoshimura et al.,2008). GNIP: IAEA s global network of isotopes in precipitation.

Results: raw cellulose δ 18 O

Results: monthly interpolated δ 18 O Tie points: annual maxima as February, annual minima as October. Linear interpolation between tie points. Average the two cores.

Results: monthly interpolated δ 18 O October δ 18 O anomalies

Discussion: moisture source JJAS: Indian monsoon season, moisture from Indian Ocean-Bay of Bengal. Oct: moisture from South China Sea- Western Pacific Warm Pool.

Discussion: warm pool convection El Niño: weaker convection over the warm pool, less rainout effect, more enriched moisture δ 18 O.

Discussion: warm pool convection Correlation between Oct cellulose δ 18 O and

Discussion: warm pool convection Niño-4 Niño-4 Correlation between Oct cellulose δ 18 O and

Discussion: warm pool convection Correlation between October cellulose δ 18 O and October Niño-4 SST anomalies: r = 0.56

Conclusions 140-years subannual resolution cellulose δ 18 O has been analyzed for Pinus merkusii from Kirirom National Park in Cambodia. The regular seasonal cycles show depleted δ 18 O during monsoon rainy season and enriched δ 18 O in winter dry season. The cellulose δ 18 O minima of each annual rings represent the δ 18 O of rain water in October, when the moisture source is the South China Sea-WPWP. Most recent warm and cold ENSO events are identified in the October cellulose δ 18 O. The October δ 18 O is negatively related to the convection intensity over the South China Sea-WPWP region.

Conclusions 140-years subannual resolution cellulose δ 18 O has been analyzed for Pinus merkusii from Kirirom National Park in Cambodia. The regular seasonal cycles show depleted δ 18 O during monsoon rainy season and enriched δ 18 O in winter dry season. The cellulose δ 18 O minima of each annual ring represent the δ 18 O of rain water in October, when the moisture source is the South China Sea-WPWP. Most recent ENSO events are identified in the October cellulose δ 18 O. The October δ 18 O is negatively related to the convection intensity over the South China Sea-WPWP region.

Conclusions 140-years subannual resolution cellulose δ 18 O has been analyzed for Pinus merkusii from Kirirom National Park in Cambodia. The regular seasonal cycles show depleted δ 18 O during monsoon rainy season and enriched δ 18 O in winter dry season. The cellulose δ 18 O minima of each annual rings represent the δ 18 O of rain water in October, when the moisture source is the South China Sea-WPWP. Most recent ENSO events are identified in the October cellulose δ 18 O. The October δ 18 O is negatively related to the convection intensity over the South China Sea-WPWP region. PhD candidate ZHU, Mengfan mengfanz@usc.edu http://earth.usc.edu/~mengfanz/