Impact of postglacial warming on tropical convection and precipitation patterns in the Indonesian Archipelago
Final Report Abstract
Comparison of several high-resolution Mg/Ca and δ18O records from the central Indonesian Archipelago allows evaluation of the spatial heterogeneity of hydroclimate change under changing boundary conditions. Our records consistently show a rise of tropical SST before atmospheric pCO2 started to increase, even though later during the deglaciation low latitude temperature increase was lagging the pCO2 rise. In contrast to previous terrestrial precipitation records, our ice-volume corrected δ18Oseawater records do not support widespread aridity in central Indonesia during the last glacial period. This subject is heavily debated and therefore our evidence for a comparatively wet LGM in central Indonesia has important repercussions on the understanding of tropical rainfall variability and changes on the Walker circulation in a warming climate. These findings, thus, support the hypothesis of a reduction in tropical convection and weakening of the Walker circulation during tropical warming, resulting in a spatially complex precipitation pattern rather than a uniform increase in rainfall. Despite important temporal and special variability of climatic conditions in Central Indonesia during the last glacial and deglaciation several more robust trends in regional climate evolution emerge from the results of this project: • Central Indonesian warming started around 19.2 ± 0.8 ka and, thus, led the onset of the deglacial rise in global CO2 concentrations. • Comparison of δ18Oseawater records from the Celebes Sea, Makassar Strait, Flores Sea and Banda Sea suggests that rainfall isotope and/or amount changes were comparable over Borneo and Sulawesi during the last termination and do not support widespread aridity in central Indonesia during the LGM. • Heavier δ18Oseawater during stadials either reflect a decline in precipitation amount and/or increased δ18Oseawater of rainfall in central Indonesia, suggesting a southward shift of the austral summer position of the ITCZ. • Weakening of the Indonesian Throughflow and reduced precipitation over central Indonesia during the Younger Dryas resemble modern El Niño climate conditions. Important remaining tasks include: • Integration of our findings with numerical climate models, which predict high spatial heterogenity in precipitation and major changes in the Walker circulation associated with tropical warming. • Comparison oft the hydrological changes in the equatorial area of Central Indonesia to the variability of adjacent Northern Hemisphere and Southern Hemisphere monsoonal areas (i.e. South China Sea, Northwest-Australian Margin, NE Indian Ocean). • Resolving the apparent discrepancy between terrestrial (leaf-wax based) and marine precipitation/runoff reconstructions for the LGM – what is the role of seasonality and spatial heterogeneity of precipitation?
Publications
- (2018) Deglacial Warming and Hydroclimate Variability in the Central Indonesian Archipelago. Paleoceanography and Paleoclimatology 33 (9) 974–993
Schröder, Jan F.; Kuhnt, Wolfgang; Holbourn, Ann; Beil, Sebastian; Zhang, Peng; Hendrizan, Marfasran; Xu, Jian
(See online at https://doi.org/10.1029/2018PA003323) - (2016): Variations in sea surface hydrology in the southern Makassar Strait over the past 26 kyr. Quaternary Science Reviews, 154, 143–156
Schröder, J.F., A.E. Holbourn, W. Kuhnt, and K. Küssner
(See online at https://doi.org/10.1016/j.quascirev.2016.10.018) - (2017): Hydrological and vegetation shifts in the Wallacean region of central Indonesia since the Last Glacial Maximum. Quaternary Science Reviews, 157, 152–163
Wicaksono, S.A., J.M. Russell, A.E. Holbourn, and W. Kuhnt
(See online at https://doi.org/10.1016/j.quascirev.2016.12.006) - (2017): Variability of Indonesian Throughflow and Borneo runoff during the last 14 kyr. Paleoceanography, 32
Hendrizan, M., W. Kuhnt, and A.E. Holbourn
(See online at https://doi.org/10.1002/2016PA0030301)
