Current transport versus continental inputs in the eastern Indian Ocean: Radiogenic isotope signatures of clay size sediments

Analyses of radiogenic neodymium (Nd), strontium (Sr), and lead (Pb) isotope compositions of clay-sized detrital sediments allow detailed tracing of source areas of sediment supply and present and past transport of particles by water masses in the eastern Indian Ocean. Isotope signatures in surface sediments range from −21.5 (ɛNd), 0.8299 (87Sr/86Sr), and 19.89 (206Pb/204Pb) off northwest Australia to +0.7 (ɛNd), 0.7069 (87Sr/86Sr), and 17.44 (206Pb/204Pb) southwest of Java. The radiogenic isotope signatures primarily reflect petrographic characteristics of the surrounding continental bedrocks but are also influenced by weathering-induced grain size effects of Pb and Sr isotope systems with superimposed features that are caused by current transport of clay-sized particles, as evidenced off Australia where a peculiar isotopic signature characterizes sediments underlying the southward flowing Leeuwin Current and the northward flowing West Australian Current (WAC). Gravity core FR10/95-GC17 off west Australia recorded a major isotopic change from Last Glacial Maximum values of −10 (ɛNd), 0.745 (87Sr/86Sr), and 18.8 (206Pb/204Pb) to Holocene values of −22 (ɛNd), 0.8 (87Sr/86Sr), and 19.3 (206Pb/204Pb), which documents major climatically driven changes of the WAC and in local riverine particle supply from Australia during the past 20 kyr. In contrast, gravity core FR10/95-GC5 located below the present-day pathway of the Indonesian throughflow (ITF) shows a much smaller isotopic variability, indicating a relatively stable ITF hydrography over most of the past 92 kyr. Only the surface sediments differ significantly in their isotopic composition, indicating substantial changes in erosional sources attributed to a change of the current regime during the past 5 kyr

Past dynamics of the Australian monsoon: precession, phase and links to the global monsoon concept

International audiencePast variations in the dynamics of the Australianmonsoon have been estimated from multi-proxy analysis ofa core retrieved in the Eastern Banda Sea. Records of coccolithand pollen assemblages, spanning the last 150 000years, allow reconstruction of past primary production in theBanda Sea, summer moisture availability, and the length ofthe dry season in northern Australia and southeastern Indonesia.The amount of moisture available during the summermonsoon follows typical glacial/interglacial dynamics witha broad asymmetrical 100-kyr cycle. Primary productionand length of the dry season appear to be closely related,given that they follow the precessional cycle with the samephase. This indicates their independence from ice-volumevariations. The present inter-annual variability of both parametersis related to El Ni˜no Southern Oscillation (ENSO),which modulates the Australian Winter Monsoon (AWM).The precessional pattern observed in the past dynamics ofthe AWM is found in ENSO and monsoon records of otherregions. A marked shift in the monsoon intensity occurringduring the mid Holocene during a period of constant ice volume,suggests that low latitude climatic variation precedesincreases in global ice volume. This precessional pattern suggeststhat a common forcing mechanism underlies low latitudeclimate dynamics, acting specifically and synchronouslyon the different monsoon systems

Anti-litter bins : persuasion through non-interactive design

Norms are effective in guiding behaviour, but only when they are active at the time of action. Two studies were performed to test littering norm activation by bin design. The first was a scenario, showing that explicit norm activation was more effective than implicit activation through design. However, the various types of norms showed the same pattern of effects for both explicit and implicit activation. The field study showed that both explicit norm activation through a verbal prompt and implicit activation through design had significant effects, reducing the amount of litter by 50%. Effectiveness of activation by design was even slightly more effective than explicit activation. Within the context of persuasive technology, the study demonstrates that even noninteractive design and technology can instigate major behaviour changes

Anti-litter bins : persuasion through non-interactive design

Norms are effective in guiding behaviour, but only when they are active at the time of action. Two studies were performed to test littering norm activation by bin design. The first was a scenario, showing that explicit norm activation was more effective than implicit activation through design. However, the various types of norms showed the same pattern of effects for both explicit and implicit activation. The field study showed that both explicit norm activation through a verbal prompt and implicit activation through design had significant effects, reducing the amount of litter by 50%. Effectiveness of activation by design was even slightly more effective than explicit activation. Within the context of persuasive technology, the study demonstrates that even noninteractive design and technology can instigate major behaviour changes