Previous studies suggested the multi-millennial scale changes of Australian-Indonesian monsoon (AIM) rainfall, but little is known about their mechanism. Here, AIM rainfall changes since the Last Deglaciation (~18 ka BP) are inferred from geochemical elemental ratios (terrigenous input) and palynological proxies (pollen and spores). Pollen and spores indicate drier Last Deglaciation (before ~11 ka BP) and wetter Holocene climates (after ~11 ka BP). Terrigenous input proxies infer three drier periods (i.e., before ~17, ~15–13.5, and 7–3 ka BP) and three wetter periods (i.e., ~17–15, ~13.5–7, and after ~3 ka BP) which represent the Australian-Indonesian summer monsoon (AISM) rainfall changes. Pollen and spores were highly responsive to temperature changes and showed less sensitivity to rainfall changes due to their wider source area, indicating their incompatibility as rainfall proxy. During the Last Deglaciation, AISM rainfall responded to high latitude climatic events related to the latitudinal shifts of the austral summer ITCZ. Sea level rise, solar activity, and orbitally-induced insolation were most likely the primary driver of AISM rainfall changes during the Holocene, but the driving mechanisms behind the latitudinal shifts of the austral summer ITCZ during this period are not yet understood.

Volcano is an area which serves as a catchment area for the lowlands. Ability of rock or weathered-soil to absorb the rain water depends on several things, such as lithology and large of slope. Different lithology has different characteristics, including in terms of porosity which is directly related to the ability of rock to store water. Characteristics of lithology in volcanic area can change rapidly, both vertically and laterally. Large of slope in volcanic area that change significantly also can affect the infiltration rate (the seepage of rain) in rock or weathered-soil. Therefore, the influence of lithology and large of slope to the infiltration rate should be proven to predict the infiltration zone in volcanic area. Observations has been conducted on the eastern slopes of Mount Malabar with an area 78 km², at coordinates 7⁰03'28.04" LS - 7⁰10'32.05" LS and 107⁰38'37.64" BT - 107⁰41'50.6" BT. The infiltration rate observed on the weathered-soil using simple single infiltrometer made of PVC pipe 50 cm long, on March-April 2015. The measurement is carried out at several points where the weathered-rock result has been known, as much two times for different slope in each point. 26 measurement points have been obtained from different slopes and weathered-soil of different five-lithology. The results showed that the infiltration rate proportional to the percentage of rock porosity and large of slope. Infiltration rate sequence from the smallest to the greatest are weathered-soil andesites, basaltic andesite, laharic breccias, alteration of dacite, and pyroclastic breccias. The greatest infiltration rate obtained is 10.11 cm/minute in pyroclastic breccia with 25^o slope, while the smallest is 0.0437 cm/minute in pyroclastic breccias with 4^o slope.

Changes of the thermocline depth (DOT) at the Sumba Island offshore are not well-known compared to the DOT changes in the Timor Sea, the main exit passage of the Indonesian Through-flow (ITF). Planktonic foraminiferal assemblages in...

Despite its importance, sea surface paleoproductivity of the western Savu Strait is not well studied. Results from previous studies at the nearby Southwest Sumba and Sumba Strait might not be applicable due to the oceanographic difference. Foraminiferal proxies from gravity core ST10 were applied to generate sea surface paleoproductivity and thermocline depth reconstruction. Foraminiferal Accumulation Rate and Benthic Foraminiferal Accumulation Rate were used as paleoproductivity proxies while the thermocline dwellers’ relative abundance was applied as the thermocline depth proxy. This study suggested paleoproductivity increase during the Last Glacial Maximum (LGM)–~16 ka BP and Holocene (after ~11.65 ka BP) in the western Savu Strait. Thermocline depth was relatively shallower during the LGM–Last Deglaciation and became deeper afterwards. Paleoproductivity increase at LGM–~16 ka BP was caused by the Australian-Indonesian winter monsoon (AIWM)-like condition, characterized by intense coastal upwelling while the Holocene paleoproductivity increase was related to the abrupt rainfall increase which enhanced terrestrial/riverine input. Thermocline depth variability in the western Savu Strait is in-phase with thermocline depth variability in the Java upwelling region, characterized by a shallower thermocline during the LGM–Last Deglaciation (before ~11.65 ka BP) and a deeper thermocline during the Holocene (after ~11.65 ka BP). This thermocline depth shifting indicates a strong Australian-Indonesian Monsoon (AIM) influence on the paleoceanography of the western Savu Strait since LGM.