AffectRoute – considering people’s affective responses to environments for enhancing route-planning services

Humans perceive and evaluate environments affectively. Some places are experienced as unsafe, while some others as attractive and interesting. These affective responses to environments influence people’s daily behavior and decision-making in space, e.g., choosing which route to take, or which place to visit. In this article, we report on a methodology of using people’s affective responses to environments for enhancing computer-based route planning. More specifically, we explore a crowdsourcing approach to model and collect people’s affective responses to environments; an Affect-Space-Model and a mobile application are developed to facilitate this crowdsourcing approach; a routing algorithm (named AffectRoute) is then proposed to aggregate and integrate the collected data for automatic route planning. Evaluation with human participants shows that the routes generated by considering people’s affective responses to environments are significantly preferred over the conventional shortest ones, which are employed in car navigation systems and many online route planners. In conclusion, considering people’s affective responses to environments contributes to the improvement of automatic route planning. The proposed method can be integrated into existing route-planning services (e.g., location-based services) to provide users with more satisfying routing results.     

Time-scale and state dependence of the carbon-cycle feedback to climate

Climate and atmospheric CO₂ concentration are intimately coupled in the Earth system: CO₂ influences climate through the greenhouse effect, but climate also affects CO₂ through its impact on the amount of carbon stored on land and in the ocean. The change in atmospheric CO₂ as a response to a change in temperature ( $\varDelta CO_{2}/\varDelta T$ ) is a useful measure to quantify the feedback between the carbon cycle and climate. Using an ensemble of experiments with an Earth system model of intermediate complexity we show a pronounced time-scale dependence of $\varDelta CO_{2}/\varDelta T$ . A maximum is found on centennial scales with $\varDelta CO_{2}/\varDelta T$ values for the model ensemble in the range 5–12 ppm °C^?1, while lower values are found on shorter and longer time scales. These results are consistent with estimates derived from past observations. Up to centennial scales, the land carbon response to climate dominates the CO₂ signal in the atmosphere, while on longer time scales the ocean becomes important and eventually dominates on multi-millennial scales. In addition to the time-scale dependence, modeled $\varDelta CO_{2}/\varDelta T$ show a distinct dependence on the initial state of the system. In particular, on centennial time-scales, high $\varDelta CO_{2}/\varDelta T$ values are correlated with high initial land carbon content. A similar relation holds also for the CMIP5 models, although for $\varDelta CO_{2}/\varDelta T$ computed from a very different experimental setup. The emergence of common patterns like this could prove to usefully constrain the climate–carbon cycle feedback.     

Ecological stability during the LGM and the mid-Holocene in the Alpine Steppes of Tibet?

Arid and Alpine ecosystems are known for extreme environmental changes during the Late Quaternary. We hypothesize that the world's largest Alpine arid ecosystem however, the Alpine Steppes of the Tibetan highlands, remained ecologically stable during the LGM and the mid-Holocene. This hypothesis is tested by distributional range of plant species, plant life forms and rate of endemism. The set of character species has a precipitation gradient between 50 and 350 mm/a, testifying for resilience to precipitation changes. 83% of the species have a wider vertical range than 1000 m used as a proxy for resilience to temperature changes. 30% of the species are endemic with 10 endemic genera, including plate-shaped cushions as a unique plant life form. These findings are in line with palaeo-ecological proxies (δ¹⁸O, pollen) allowing the assumption that Alpine Steppes persisted during the LGM with 3 to 4 K lower summer temperatures.During the mid-Holocene, forests could have replaced Alpine Steppes in the upper catchments of the Huang He, Yangtze, Mekong, Salween and Yarlung Zhangbo, but not in the interior basins of the north-western highlands, because the basins were then flooded, suppressing forests and supporting the environmental stability of this arid Alpine grassland biome.     

Silicon isotope fractionation during magmatic differentiation

The Si isotopic composition of Earth’s mantle is thought to be homogeneous (δ³⁰Si = −0.29 ± 0.08‰, 2 s.d.) and not greatly affected by partial melting and recycling. Previous analyses of evolved igneous material indicate that such rocks are isotopically heavy relative to the mantle. To understand this variation, it is necessary to investigate the degree of Si isotopic fractionation that takes place during magmatic differentiation. Here we report Si isotopic compositions of lavas from Hekla volcano, Iceland, which has formed in a region devoid of old, geochemically diverse crust. We show that Si isotopic composition varies linearly as a function of silica content, with more differentiated rocks possessing heavier isotopic compositions. Data for samples from the Afar Rift Zone, as well as various igneous USGS standards are collinear with the Hekla trend, providing evidence of a fundamental relationship between magmatic differentiation and Si isotopes. The effect of fractionation has been tested by studying cumulates from the Skaergaard Complex, which show that olivine and pyroxene are isotopically light, and plagioclase heavy, relative to the Si isotopic composition of the Earth’s mantle. Therefore, Si isotopes can be utilised to model the competing effects of mafic and felsic mineral fractionation in evolving silicate liquids and cumulates.At an average SiO₂ content of ∼60 wt.%, the predicted δ³⁰Si value of the continental crust that should result from magmatic fractionation alone is −0.23 ± 0.05‰ (2 s.e.), barely heavier than the mantle. This is, at most, a maximum estimate, as this does not take into account weathered material whose formation drives the products toward lighter δ³⁰Si values. Mass balance calculations suggest that removal of continental crust of this composition from the upper mantle will not affect the Si isotopic composition of the mantle.     

Petrogenetic and geotectonic significance of Neoproterozoic suprasubduction mantle as revealed by the Wizer ophiolite complex,Central Eastern Desert,Egypt

Ophiolite complexes, formed in a suprasubduction zone environment during Neoproterozoic time, are widely distributed in the Eastern Desert of Egypt. Their mantle sections provide important information on the origin and tectonic history of ocean basins these complexes represent. The geochemistry and mineralogy of the mantle section of the Wizer ophiolite complex, represented by serpentinites after harzburgite containing minor dunite bodies, are presented. Presence of antigorite together with the incipient alteration of chromite and absence of chlorite suggests that serpentinization occurred in the mantle wedge above a Neoproterozoic subduction zone. Wizer peridotites have a wide range of spinel compositions. Spinel Cr# [100Cr/(Cr + Al)] decrease gradually from dunite bodies (Cr# = 81–87) and their host highly depleted harzburgites (Cr# = 67–79) to the less depleted harzburgites (Cr# = 57–63). Such decreases in mantle refractory character are accompanied by higher Al and Ti contents in bulk compositions. Estimated parental melt compositions point to an equilibration with melts of boninitic composition for the dunite bodies (TiO₂ = ~<0.07–0.22 wt%; Al₂O₃ = 9.4–10.6 wt%), boninitic-arc tholeiite for the highly depleted harzburgites (TiO₂ = <0.09–0.28 wt%; Al₂O₃ = 11.2–14.1 wt%) and more MORB-like affinities for the less depleted harzburgites (TiO₂ = ~<0.38–0.51 wt%; Al₂O₃ = 14.5–15.3 wt%). Estimated equilibrium melts are found in the overlying volcanic sequence, which shows a transitional MORB–island arc geochemical signature with a few boninitic samples. Enrichment of some chromites in TiO₂ and identification of sulfides in highly depleted peridotites imply interaction with an impregnating melt. A two-stage partial melting/melt–rock reaction model is advocated, whereby, melting of a depleted mantle source by reaction with MORB-like melts is followed by a second stage melting by interaction with melts of IAT–boninitic affinities in a suprasubduction zone environment to generate the highly depleted harzburgites and dunite bodies. The shift from MORB to island arc/boninitic affinities within the mantle lithosphere of the Wizer ophiolite sequence suggests generation in a protoarc-forearc environment. This, together with the systematic latitudinal change in composition of ophiolitic lavas in the Central Eastern Desert (CED) of Egypt from IAT–boninitic affinities to more MORB-like signature, implies that the CED could represent a disrupted forearc-arc-backarc system above a southeast-dipping subduction zone.