Aridification of Central Asia and uplift of the Altai and Hangay mountains, Mongolia: stable isotope evidence

Central Asia has become increasingly arid during the Cenozoic, though the mechanisms behind this aridification remain unresolved. Much attention has focused on the influence and uplift history of the Tibetan Plateau. However, the role of ranges linked to India-Asia convergence but well north of the Plateau—including the Altai, Sayan, and Hangay—in creating the arid climate of Central Asia is poorly understood. Today, these ranges create a prominent rain shadow, effectively separating the boreal forest to the north from the deserts of Central Asia. To explore the role of these mountains in modifying climate since the late Eocene, we measured carbon and oxygen stable isotopes in paleosol carbonates from three basins along a 650 km long transect at the northern edge of the Gobi Desert in Mongolia and in the lee of the Altai and Hangay mountains. We combine these data with modern air-parcel back-trajectory modeling to understand regional moisture transport pathways at each basin. In all basins, δ¹³C increases, with the largest increase in western Mongolia. The first δ¹³C increase occurs in central and southwestern Mongolia in the Oligocene. δ¹³C again increases from the upper Miocene to the Quaternary in western and southwestern Mongolia. We use a 1-D soil diffusion model to demonstrate that these δ¹³C increases are linked to declines in soil respiration driven by dramatic increases in aridity. Using modern-day empirical relations between mean annual precipitation and soil respiration, we estimate that precipitation has likely more than halved over the Neogene. Given the importance of the Hangay and Altai in steering moisture in Mongolia, we attribute these changes to differential surface uplift of the Hangay and Altai. Surface uplift in the Hangay began by the early Oligocene, blocking Siberian moisture and aridifying the northern Gobi. In contrast, surface uplift of the Altai began in the late Miocene, blocking moisture from reaching western Mongolia. Thus, the northern Gobi became increasingly arid east to west since the late Eocene, likely driven by orographic development in the Hangay during the Oligocene and the Altai in the late Miocene through Pliocene

Photonic quantum technologies

The first quantum technology, which harnesses uniquely quantum mechanical effects for its core operation, has arrived in the form of commercially available quantum key distribution systems that achieve enhanced security by encoding information in photons such that information gained by an eavesdropper can be detected. Anticipated future quantum technologies include large-scale secure networks, enhanced measurement and lithography, and quantum information processors, promising exponentially greater computation power for particular tasks. Photonics is destined for a central role in such technologies owing to the need for high-speed transmission and the outstanding low-noise properties of photons. These technologies may use single photons or quantum states of bright laser beams, or both, and will undoubtably apply and drive state-of-the-art developments in photonics

The impact of foreign direct investment on the productivity of China’s automotive industry

• This study contributes to the existing literature by empirically investigating the effect of FDI inflows on the aggregate labour productivity of China's automotive industry. • A production function model is developed using a panel data set at sub-sector level. Two statistical models: pooled ordinary least squares model (POLS) and fixed effects model (FES) were used to estimate the influence of foreign direct investment on aggregate labour productivity in the industry

Integrating Collaboration, Adaptive Management, and Scenario-Planning: Experiences at Las Cienegas National Conservation Area

There is growing recognition that public lands cannot be managed as islands; rather, land management must address the ecological, social, and temporal complexity that often spans jurisdictions and traditional planning horizons. Collaborative decision making and adaptive management (CAM) have been promoted as methods to reconcile competing societal demands and respond to complex ecosystem dynamics. We detail the experiences of land managers and stakeholders in using CAM at Las Cienegas National Conservation Area (LCNCA), a highly valued site under the jurisdiction of the Bureau of Land Management (BLM). The CAM process at Las Cienegas is marked by strong stakeholder engagement, with four core elements: (1) shared watershed goals with measurable resource objectives; (2) relevant and reliable scientific information; (3) mechanisms to incorporate new information into decision making; and (4) shared learning to improve both the process and management actions. The combination of stakeholder engagement and adaptive management has led to agreement on contentious issues, more innovative solutions, and more effective land management. However, the region is now experiencing rapid changes outside managers' control, including climate change, human population growth, and reduced federal budgets, with large but unpredictable impacts on natural resources. Although the CAM experience provides a strong foundation for making the difficult and contentious management decisions that such changes are likely to require, neither collaboration nor adaptive management provides a sufficient structure for addressing the externalities that drive uncontrollable and unpredictable change. As a result, LCNCA is exploring two specific modifications to CAM that may better address emerging challenges, including: (1) creating nested resource objectives to distinguish between those objectives that may be crucial to maintaining ecological resilience from those that may hinder a flexible response to climate change, and (2) incorporating scenario planning into CAM to explore how climate change may interact with other drivers and alter options for the future, to identify robust management actions, and to prioritize ecological monitoring efforts. The experiences at LCNCA demonstrate how collaboration and adaptive management can be used to improve social and environmental outcomes and, with modifications, may help address the full range of complexity and change that threatens to overwhelm even the best efforts to sustain public lands

There is no Neogene denudation conundrum

International audienc

Silicate weathering as a feedback and forcing in Earth's climate and carbon cycle

Current understanding of the long-term carbon cycle posits that Earth's climate is stabilized by a negative feedback involving CO2 consumption by chemical weathering of silicate minerals. This theory holds that silicate weathering responds to climate: when atmospheric pCO2 and surface temperatures rise, chemical weathering accelerates, consuming more atmospheric CO2 and cooling global climate; when pCO2 falls, weathering fluxes decrease, permitting buildup of CO2 and consequent warming. However, the functional dependence of global weathering rates on atmospheric pCO2 (Earth's “weathering curve”) remains highly uncertain, with a variety of mathematical formulations proposed in the literature. We explore the factors influencing this relationship, and how they may have changed over Earth history. We then revisit classic carbon cycle model experiments to demonstrate how the choice of weathering curve has dramatic consequences for the response of the Earth system to several types of climatic and carbon-cycle perturbations. First, the slope of the weathering curve determines the timescale of recovery and the “long tail” of elevated pCO2 following carbon release events. Second, the nature of Earth's weathering curve determines the response of pCO2 to changing volcanic CO2 degassing, which has varied significantly over geologic timescales. Finally, we demonstrate how changes to Earth's weathering curve over time driven by, for example, tectonic or evolutionary processes, can act as a forcing, in addition to a feedback, in the carbon cycle and climate. These examples highlight the importance of constraining Earth's weathering curve, both for improving our understanding of past carbon cycle perturbations and predicting the future impact of anthropogenic carbon release on long timescales

Response to Comment on "Revised paleoaltimetry data show low Tibetan Plateau elevation during the Eocene"

International audienceValdes et al. contest our results, suggesting failings in our modeling approach as well as in our comparison with data. Although their comment points to interesting ideas of improvement, we find that their critique reflects an incomplete understanding of our methods and is not supported by the material they provide

Reconstruction of continental temperatures and oxygen isotope compositions of precipitation based on clumped and oxygen isotope analysis of pedogenic siderites

Earth's climate sensitivity – defined as the temperature increase for a doubling of pCO2 – and the mechanisms responsible for amplification of high latitude warming remain controversial. The latest Paleocene/earliest Eocene (LPEE; 57-55 million years ago) is a time when pCO2 peaked between 1400 and 4000 ppm, which allows us to evaluate the climatic response to high pCO2. Here, we present a reconstruction of continental temperatures and oxygen isotope compositions of precipitation – reflective of specific humidity – based on clumped and oxygen isotope analysis of pedogenic siderites. We show that continental mean annual temperature reached 41 °C in the equatorial tropics, and summer temperatures reached 23 °C in the Arctic. The oxygen isotope compositions of precipitation reveal that compared to the present-day the hot LPEE climate was characterized by an increase in specific humidity and the average residence time of atmospheric moisture and by a decrease in the subtropical-to-polar specific humidity gradient. The global increase in specific humidity reflects the fact that atmospheric vapor content is more sensitive to changes in pCO2 than evaporation and precipitation, resulting in an increase in the residence time of moisture in the atmosphere. Pedogenic siderite data from other super-greenhouse periods support the evidence that the spatial patterns of specific humidity and warmth are related providing new means to evaluate Earth's climate sensitivity