Mid- to late Holocene climate variability of the Maritime Continent
|Other Titles:||Mittel- bis spätholozäne Klimavariabilität des Maritimen Kontinentes||Authors:||Kwiatkowski, Cornelia Regula||Supervisor:||Mohtadi, Mahyar||1. Expert:||Hebbeln, Dierk||2. Expert:||Pälike, Heiko||Abstract:||
The Maritime Continent is located within the Indo-Pacific Warm Pool (IPWP) which is described as the largest area of warm sea surface temperatures with the highest rainfall on Earth. Serving as the largest source of atmospheric water vapor and latent heat, it is of crucial importance to global atmospheric and hydrologic circulation. The regional climate is controlled by large-scale phenomena such as the seasonal migration of the Intertropical Convergence Zone (ITCZ), the Australian-Indonesian monsoon system as well as climate anomalies like the Indian Ocean Dipole (IOD) and or oscillations such as El NiAAA /-o-Southern Oscillation (ENSO). Due to the complex topography of the Maritime Continent and very local air-sea interactions, the environmental influence of these phenomena strongly varies across the region today and may have done so during the past. Environmental reconstructions have been conducted by using proxy records from speleothems, corals as well as marine and lacustrine sediments revealing a complex history of climate variations of the Maritime Continent during the Holocene. Mid-to late Holocene sea surface conditions were reconstructed by using trace elements and stable isotopes as well as relative abundances of planktic foraminifera. Additionally, the amount, composition and grain size distribution of bulk sediment was investigated. Based on multi-proxy reconstructions from four marine sediment cores from western, central, and southern Indonesia, this thesis outlines variations in rainfall and upper water column conditions in response to large-scale climate phenomena as the IOD, the Australian-Indonesian monsoon system and ENSO from mid- to late Holocene. In the eastern tropical Indian Ocean (western Indonesia), thermocline temperatures, the thermal gradient of the upper ocean as well as the relative abundances of planktic foraminifera reveal a deeper thermocline between 8 and 3 ka and an uplift of the thermocline for the past 3 ka off western Sumatra. The recorded shoaling of the thermocline and the deduced increased occurrence of upwelling likely results from a more-positive IOD-like mean state of the Indian Ocean during the late Holocene. A transient Holocene climate model simulation reproduces anomalous surface easterly winds over the equatorial eastern Indian Ocean that support the interpretation of more positive IOD-like mean state during the late Holocene compared to the mid-Holocene. In the Makassar Strait (central Indonesia) cooler and fresher sea surface coincide with an increase in terrigenous runoff from eastern Borneo and point to an intensified AustralianIndonesian summer monsoon (AISM) during the late Holocene. Contemporaneously, periods Abstract V characterized by freshwater pulses recorded off eastern Borneo might be related to a strengthened ENSO with intensified El NiAAA /-o and La NiAAA /-a conditions. Sediment composition within the Java Sea (southern Indonesia) suggest variations in precipitation in southern Borneo and eastern Java in response to the Australian-Indonesian monsoon system and ENSO. Drier conditions in southern Borneo but relatively unchanged rainfall in Java around 2 ka indicate more frequent and/or intensified El NiAAA /-o events which are masked by an intensified AISM in Java. Present-day variations in rainfall over Java reveal a close relationship of monsoonal rainfall to northern high latitude climate variations which may have persist also during the past and contributed to the late Holocene intensification of the AISM over the Maritime continent.
|Keywords:||Holocene, Maritime Continent, Indonesia, Java Sea, planktic foraminifera, Mg/Ca, stable isotopes, Ti/Ca, Zr/Rb, Makassar Strait, ENSO, australian-indonesian monsoon, Indian Ocean Dipole, Indian Ocean, G. ruber, sea surface||Issue Date:||28-Oct-2016||URN:||urn:nbn:de:gbv:46-00105640-19||Institution:||Universität Bremen||Faculty:||FB5 Geowissenschaften|
|Appears in Collections:||Dissertationen|
checked on Sep 24, 2020
checked on Sep 24, 2020
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