Mid- to late Holocene climate variability of the Maritime Continent

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

AI is a viable alternative to high throughput screening: a 318-target study

: High throughput screening (HTS) is routinely used to identify bioactive small molecules. This requires physical compounds, which limits coverage of accessible chemical space. Computational approaches combined with vast on-demand chemical libraries can access far greater chemical space, provided that the predictive accuracy is sufficient to identify useful molecules. Through the largest and most diverse virtual HTS campaign reported to date, comprising 318 individual projects, we demonstrate that our AtomNet® convolutional neural network successfully finds novel hits across every major therapeutic area and protein class. We address historical limitations of computational screening by demonstrating success for target proteins without known binders, high-quality X-ray crystal structures, or manual cherry-picking of compounds. We show that the molecules selected by the AtomNet® model are novel drug-like scaffolds rather than minor modifications to known bioactive compounds. Our empirical results suggest that computational methods can substantially replace HTS as the first step of small-molecule drug discovery

Mittel- bis spätholozäne Klimavariabilität des Maritimen Kontinentes

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

Faunal analysis and Mg/Ca records of planktic foraminifera in sediment core SO189/2_039KL

Climate phenomena like the monsoon system, El Niño Southern Oscillation (ENSO) and the Indian Ocean Dipole (IOD) are interconnected via various feedback mechanisms and control the climate of the Indian Ocean and its surrounding continents on various timescales. The eastern tropical Indian Ocean is a key area for the interplay of these phenomena and for reconstructing their past changes and forcing mechanisms. Here we present records of upper ocean thermal gradient, thermocline temperatures (TT) and relative abundances of planktic foraminifera in core SO 189-39KL taken off western Sumatra (0°47.400' S, 99°54.510' E) for the last 8 ka that we use as proxies for changes in upper ocean structure. The records suggest a deeper thermocline between 8 ka and ca 3 ka compared to the late Holocene. We find a shoaling of the thermocline after 3 ka, most likely indicating an increased occurrence of upwelling during the late Holocene compared to the mid-Holocene which might represent changes in the IOD-like mean state of the Indian Ocean with a more negative IOD-like mean state during the mid-Holocene and a more positive IOD-like mean state during the past 3 ka. This interpretation is supported by a transient Holocene climate model simulation in which an IOD-like mode is identified that involves an insolation-forced long-term trend of increasing anomalous surface easterlies over the equatorial eastern Indian Ocean

Late Holocene pollen and organic walled dinoflagellate cysts analyses of sedimet cores from the Java Sea

The pollen, spore and organic walled dinoflagelletas cyst associations of two marine sediment cores from the Java Sea off the mouths of Jelai River (South Kalimantan) and Solo River (East Java) reflect environment and vegetation changes during the last ca 3500 years in the region. A decline in primary forest taxa (e.g. Agathis, Allophylus, Dacrycarpus, Dacrydium, Dipterocarpaceae, Phyllocladus, and Podocarpus) suggest that the major change in vegetation is caused by the forest canopy opening that can be related to human activity. The successively increase of pollen of pioneer canopy and herb taxa (e.g. Acalypha, Ficus, Macaranga/Mallotus, Trema, Pandanus) indicate the development of a secondary vegetation. In Java these changes started much earlier (ca at 2950 cal yr BP) then in Kalimantan (ca at 910 cal yr BP) and seem to be more severe. Changes in the marine realm, reflected by the dinoflagellate cyst association correspond to changes in vegetation on land. They reflect a gradual change from relatively well ventilated to more hypoxic bottom/pore water conditions in a more eutrophic environment. Near the coast of Java, the shift of the water trophic status took place between ca 820 and 500 cal yrs BP, while near the coast of Kalimantan it occurred as late as at the beginning of the 20th century. We observe an increasing amount of the cyst of Polykrikos schwarzii, cyst of P. kofoidii, Lingulodinium machaerophorum, Nematosphaeropsis labyrinthus and Selenopemphix nephroides at times of secondary vegetation development on land, suggesting that these species react strongly on human induced changes in the marine environment, probably related to increased pollution and eutrophication