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Indian Ocean SST Signals in a Tree-Ring Record of Java Drought

Indian Ocean SST Signals in a Tree-Ring Record of Java Drought. Rosanne D’Arrigo Lamont-Doherty Earth Observatory. Collaborators: Rob Allan, Jonathan Palmer, Rob Wilson, John Sakulich, Satria Bijaksana, La Ode Ngkoimani, Paul Krusic, Jason Smerdon, Siti Zulaikah.

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Indian Ocean SST Signals in a Tree-Ring Record of Java Drought

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  1. Indian Ocean SST Signals in a Tree-Ring Record of Java Drought Rosanne D’Arrigo Lamont-Doherty Earth Observatory Collaborators: Rob Allan, Jonathan Palmer, Rob Wilson, John Sakulich, Satria Bijaksana, La Ode Ngkoimani, Paul Krusic, Jason Smerdon, Siti Zulaikah

  2. Monsoon Asia Tree-Ring Data Network

  3. Why study Indonesia??

  4. Composite Peak El Niño Precipitation

  5. El Niño and Global Rainfall

  6. Indonesian Drought and El Niño

  7. Indonesian Drought and El Niño

  8. The Indonesian Teak Tree-Ring Resource *difficulty of tropical dendro studies *lack of seasonality, few suitable species *few living stands remain

  9. Subfossil Java Teak

  10. Tree-Ring Records for Indonesia

  11. INDONESIA TREE RINGS AND ENSO DROUGHT = DECREASED TREE GROWTH

  12. Java PDSI: Tree-Ring (Blue) and Coral (Pink) Data

  13. Java PDSI Reconstruction(D’Arrigo et al. (2006, GRL)

  14. MTM Spectral Analysis of Java PDSI Reconstruction

  15. A tropical Pacific ENSO-related signal has been documented in the Java teak. Is there also an Indian Ocean climate signal in this proxy data?

  16. Indian Ocean Dipole Mode Saji et al. (1999): Coupled Ocean-Atmosphere Phenomenon Positive IOD feedbacks: Intensified Easterlies, Increased Upwelling, Cool Eastern SSTs, Shallowing Thermocline; Indonesian Drought Opposite in West: Convection, Increased Rains East Africa

  17. SAJI ET AL. (1999) COMPOSITE INDIAN OCEAN DIPOLE EVENT

  18. Is the Indian Ocean Dipole distinct from the ENSO system?

  19. CONTROVERSY: Saji et al. (1999): Indian Ocean Dipole distinct from ENSO ALTERNATIVE VIEW: Allan et al. (2001, 2003): Dipole integral part of ENSO system of biennial, classical, protracted, quasi-decadal events (Allan and D’Arrigo 1999) Saji et al. : did not consider seasonal, spatio-temporal evolution of ENSO

  20. Note: Although we describe relationships between Indonesian drought and Indian Ocean variability, we do not suggest that this dipole variability is distinct from ENSO. Rather, the evidence from this study supports the theory that the opposite is true.

  21. INDIAN OCEAN INSTRUMENTAL AND PROXY CLIMATE INDICES

  22. Abram et al. (2003) Coral Records from the Mentawai Islands, Sumatra

  23. JAVA PDSI AND INDIAN OCEAN DIPOLE SST AND WIND INDICES

  24. CORRELATIONS BETWEEN JAVA PDSI RECON AND TROPICAL INDO-PACIFIC CLIMATE INDICES INDEX PDSI SEASON YEARS Saji DMI -0.64 Sep-Oct 41 Kaplan DMI -0.70 Sep-Oct 45 EQWIN 0.73 Sep-Oct 39 Ext. Kapl. DMI -0.49 Sep-Oct 134 Ext. EQWIN 0.54 Jul-Oct 103 Nino 3.4 SST -0.58 Aug-Nov 114

  25. NINO 3.4 SSTs DIPOLE JAVA PDSI POST-1958 POST-1880

  26. JAVA PDSI RECON AND INDIAN OCEAN RIM RAINFALL SEPT-OCT OCT-NOV

  27. TROPICAL PROXIES: IOD AND ENSO HISTORY

  28. 1877 El Niño And Positive IOD *also in Mentawai corals *Estim. 20 million deaths across Asia

  29. Is there an Indian monsoon connection?

  30. PDSI DROUGHTS: STRONG AND WEAK MONSOONS

  31. MAJOR JAVA DROUGHTS VS STRONG/WEAK INDIAN MONSOONS: LINK RELATED TO EQUATORIAL WINDS, ANOMALOUS CONVERGENCE OFF INDIA; BUT NOT WELL UNDERSTOOD STRONG MONSOONS (POSITIVE IODS, OR DECADAL ENSO?) WEAK MONSOONS (EL NINOS)

  32. GADGIL ET AL (2003); IHARA ET AL. (2007): 1. NINO3SST+ EQWIN = BETTER ISMR MODEL THAN EITHER ALONE 2. DURING EL NINOS, CAN HAVE STRONGER ISMR BUT NEED NEGATIVE EQWIN

  33. ABRAM ET AL. (2006): DURING HOLOCENE, STRONGER MONSOONS (WEAKER ENSO) AND PROLONGED, MORE FREQUENT INDONESIAN DROUGHT-IODS THUS WITH GLOBAL WARMING, IF INCREASED MONSOON INTENSITY, MAY DRIVE STRONG, ANOMALOUS EASTERLY WINDS, INCREASED DROUGHT OVER INDONESIA

  34. JAVA PDSI AND EQWIN 1958-1997: r = -0.57 Sep-Oct Nino 3.4 SST r = 0.73 Sep-Oct EQWIN NINO SST + EQWIN: ar2 52.4% Nino SST+DMI=ar2 48% 2-variable model: Better estimate of Java drought than either alone

  35. SUMMARY Tree-ring records from Indonesia are sensitive to drought, ENSO variability and western Pacific Warm Pool SSTs over recent centuries. 2. This study shows that such records are also sensitive to Indian Ocean SST and wind variability, related to IODs. Indonesian drought may be better explained by a combination of Indian Ocean dipole indices and ENSO SSTs than either index alone. Our findings support the interpretation that the IO dipole is part of the ENSO system, but this does not rule out other sources IO variability.

  36. 5. Our analyses suggest that Indonesian drought can co-occur with an El Nino and weak Indian monsoon, but also with IODs and strong Indian monsoons. As ENSO-monsoon link has weakened, IOD-monsoon link has intensified. 6. More research is needed to better understand the complex interplay between (protracted) ENSO, Indian Ocean SSTs/winds and the Asian monsoon, and how these systems are evolving with global warming, in order to improve monsoon predictions over Indonesia, India and SE Asia.

  37. Funded by the National Science Foundation Thanks to the Indonesian Institute of Sciences

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