Pollen-inferred vegetation and environmental changes in the central Tibetan Plateau since 8200 yr BP

The ecotone between alpine steppe and meadow in the central Tibetan Plateau is sensitive to climate changes. Here we used the pollen records from three lakes in this region to reconstruct the evolution of local vegetation and climate since 8200 cal. yr BP. The history of temperature and precipitation was reconstructed quantitatively with multi-bioclimatic indexes and a transfer function from pollen records. Results show that the steppe/meadow dominated during the period of 8200–6500 cal. yr BP, especially 8200–7200 cal. yr BP, indicating the central Tibetan Plateau was controlled by strong monsoon. The steppe dominated during the periods of 6000–4900, 4400–3900, and 2800–2400 cal. yr BP. The steppe decreased gradually and the meadow expanded during the period of 4900–4400 cal. yr BP. Three century-scale drought events occurred during 5800–4900, 4400–3900 and 2800 cal. yr BP, respectively. The first time when the regional climate shifted to the present level was at 6500 cal. yr BP in the central Plateau. Since 3000 cal. yr BP, the temperature and precipitation have decreased gradually to the present level. However, the cold climate between 700–300 cal. yr BP likely corresponds to the Little Ice Age. Supported by Chinese Academy of Sciences 100 Talents Project (Grant No. 29082762), National Natural Science Foundation of China (Grant Nos. 40671196, 40372085, 49371068, 49871078), and U.S. National Science Foundation (Grant Nos. ATM-9410491, ATM-008194)     

Phase relations in silicic systems at one-atmosphere pressure

An important control on magma rheology is the extent to which the magma crystallizes during ascent as a result of the effective undercooling created by volatile exsolution. To assess this undercooling, we need to know the final (anhydrous) one-atmosphere phase relations of silicic magmas. For this reason, we have performed one-atmosphere controlled-fO₂ crystallization experiments on dacitic to rhyolitic melt compositions (67–78 wt% SiO₂) and determined equilibrium phase assemblages, melt fractions, and some phase compositions over a range of temperatures. Experiments were run at oxygen fugacities between NNO+1 and NNO+2 and temperatures of 1,000 to 1,250°C. Constant phase compositions and sample crystallinities in runs longer than 3.5 days suggest that these runs closely approached compositional equilibrium. Additionally, melting experiments with similar compositions yielded results closely resembling those obtained in crystallization experiments. All samples have liquidus temperatures between 1,250 and 1,200 °C, with plagioclase the liquidus phase for the two most mafic samples and quartz for the most silicic sample. When associated glass compositions are projected into the Qz-Ab-Or system they define a revised one-atmosphere quartz-feldspar cotectic 5–10% less quartz normative than previously estimated. Glass compositions from each sample plot along this cotectic between 1,100 and 1,000 °C, consistent with the plagioclase-quartz co-crystallization textures found in runs at these temperatures. This cotectic constrains glass compositions to a maximum silica content of 76±1 wt% SiO₂. Reported glass compositions in excess of 77 wt% SiO₂ in volcanic samples suggest non-equilibrium crystallization, perhaps a consequence of large melt undercoolings.Editorial responsibility: I. Carmichael     

Altered landscapes, altered livelihoods: The shifting experience of informal waste collecting during Hanoi’s urban transition

A growing body of literature is concerned with urbanization processes in contemporary Vietnam and how the country’s globalizing cities of Hanoi and Ho Chi Minh City are increasingly becoming spaces of consumption. However, much less is known about how these changing spaces accommodate labour, and in turn support livelihoods. Using published empirical data on Hanoi’s informal waste collectors from 1992 [DiGregorio, M., 1994. Urban Harvest: Recycling as a Peasant Industry in Northern Vietnam. East–West Center, Hawaii, pp. 1–212] and my own data, including a survey of 575 waste collectors and 44 interviews, collected on Hanoi’s informal waste collectors in 2006, I explore the experiences of informal waste collectors (waste pickers and itinerant junk buyers) in Vietnam’s capital city of Hanoi. I argue that Vietnam’s globalizing economy and urban transition have been a catalyst for the growth of the informal waste collector population in Hanoi as well as a partial player in the gendering of this group and the work they undertake.     

Intercomparison of snow water equivalent observations in the Northern Great Plains

In the Northern Great Plains, melting snow is a primary driver of spring flooding, but limited knowledge of the magnitude and spatial distribution of snow water equivalent (SWE) hampers flood forecasting. Passive microwave remote sensing has the potential to enhance operational river flow forecasting but is not routinely incorporated in operational flood forecasting. We compare satellite passive microwave estimates from the Advanced Microwave Scanning Radiometer for the Earth Observing System (AMSR‐E) to the National Oceanic and Atmospheric Administration Office of Water Prediction (OWP) airborne gamma radiation snow survey and U.S. Army Corps of Engineers (USACE) ground snow survey SWE estimates in the Northern Great Plains from 2002 to 2011. AMSR‐E SWE estimates compare favourably with USACE SWE measurements in the low relief, low vegetation study area (mean difference = ?3.8 mm, root mean squared difference [RMSD] = 34.7 mm), but less so with OWP airborne gamma SWE estimates (mean difference = ?9.5 mm, RMSD = 42.7 mm). An error simulation suggests that up to half of the error in the former comparison is potentially due to subpixel scale SWE variability, limiting the maximum achievable RMSD between ground and satellite SWE to approximately 26–33 mm in the Northern Great Plains. The OWP gamma versus AMSR‐E SWE comparison yields larger error than the point‐scale USACE versus AMSR‐E comparison, despite a larger measurement footprint (5–7 km² vs. a few square centimetres, respectively), suggesting that there are unshared errors between the USACE and OWP gamma SWE data.     

Model support for forcing of the 8.2 ka event by meltwater from the Hudson Bay ice dome

Previous model experiments of the 8.2 ka event forced by the drainage of Lake Agassiz often do not produce climate anomalies as long as those inferred from proxies. In addition to the Agassiz forcing, there is new evidence for significant amounts of freshwater entering the ocean at 8.2 ka from the disintegration of the Laurentide ice sheet (LIS). We use the Community Climate System Model version 3 (CCSM3) to test the contribution of this additional meltwater flux. Similar to previous model experiments, we find that the estimated freshwater forcing from Lake Agassiz is capable of sustaining ocean and climate anomalies for only two to three decades, much shorter than the event duration of ~150 years in proxies. Using new estimates of the LIS freshwater flux (~0.13 Sv for 100 years) from the collapse of the Hudson Bay ice dome in addition to the Agassiz drainage, the CCSM3 generates climate anomalies with a magnitude and duration that match within error those from proxies. This result is insensitive to the duration of freshwater release, a major uncertainty, if the total volume remains the same. An analysis of the modeled North Atlantic freshwater budget indicates that the Agassiz drainage is rapidly transported out of the North Atlantic while the LIS contribution generates longer-lasting freshwater anomalies that are also subject to recirculation by the subtropical gyre back into the North Atlantic. Thus, the meltwater flux originating from the LIS appears to be more important than the Agassiz drainage in generating 8.2 ka climate anomalies and is one way to reconcile some model-data discrepancies.     

Beyond the “fit”: introducing climate forecasts among organic farmers in Georgia (United States)

Organic farmers are a prime clientele for climate services by virtue of their social profile and vulnerability of produce to climate extremes. The study draws on an online survey and in-depth interviews with organic farmers in Georgia (United States). It shows that organic farmers access and act on climate information in ways that reflect their emphasis on diversified and flexible systems. They favor a pluralistic knowledge base that integrates scientific expertise with place-based experience and intuitive understandings. Their management style combines information at multiple temporal scales and draws on a range of technical and social resources. Translating climate forecasts into usable science for organic farming requires attention to the identities, commitments, and relationships that define the organic farming community.     

Evaluation of sewage source and fate on southeast Florida coastal reefs

Water, sponge and coral samples were collected from stations impacted by a variety of pollution sources and screened for human enteric viruses as conservative markers for human sewage. While human enteroviruses and adenoviruses were not detected, noroviruses (NoV; human genogroups I and II) were detected in 31% of samples (especially in sponge tissue). Stations near inlets were the only ones to show multiple sample types positive for NoV. Fecal indicator bacteria and enteric viruses were further evaluated at multiple inlet stations on an outgoing tide. Greatest indicator concentrations and highest prevalence of viruses were found at the mouth of the inlet and offshore in the inlet plume. Results suggest that inlets moving large volumes of water into the coastal zone with tides may be an important source of fecal contaminants. Efforts to reduce run-off or unintended release of water into the Intracoastal Waterway may lower contaminants entering sensitive coastal areas.     

Integrating science into management: Ecological carrying capacity of bivalve shellfish aquaculture

Ecosystem-based management (EBM), despite the best efforts of managers, researchers, and policy makers, often falls short of its intended purpose resulting in inadequate protection of resources. Coastal habitats are particularly vulnerable to poor management due to high use and potential for user conflict. EBM can be improved when it is informed by ecological science and considers the socio-economic needs of the community. Communication between scientists and stakeholders can help to prevent adverse outcomes while enhancing protection and sustainability of the coastal environment. In the research presented here, a framework is used to guide and enhance communication between scientists and stakeholders for sustainable management of resources and equity of all users. The outcome of this applied framework is a long-term plan to guide the management of an oyster aquaculture industry using carrying capacity as an estimate for the basis of management decisions. Central to the framework is the Working Group on Aquaculture Regulations (WGAR), which represents a diverse group of stakeholders. The WGAR worked closely with ecological modelers over a two-year period using mass-balance modeling to calculate ecological carrying capacity for oyster aquaculture in two ecosystems: Narragansett Bay and a set of highly flushed temperate lagoons in Rhode Island, USA. Collaboration between scientists and the WGAR greatly improved the models and stakeholder understanding of the science and acceptance of the results. Aquaculture is increasing in coastal regions world-wide and this framework should be easily transferable to other areas suffering from similar user conflict issues.     

A Holocene East Asian winter monsoon record at the southern edge of the Gobi Desert and its comparison with a transient simulation

Climate Dynamics - The East Asian winter monsoon (EAWM) exhibits significant variability on intraseasonal, interannual, and interdecadal time scales and the variability can be extended to Holocene...     

Response of reindeer and caribou to human activities

Petroleum and mineral exploration and extraction, hydroelectric development, atmospheric transport of contaminants, timber harvesting and tourism are increasing worldwide, especially in the Arctic. This development may adversely affect populations of reindeer/caribou ( Rangifer tarandus ) which are the basis of subsistence economies for northern indigenous peoples. Our purpose is to present a survey of the literature that has investigated the response of reindeer/caribou to human activities. Individuals and groups of reindeer/caribou: 1) move away from point sources of disturbance; 2) increase activity and energy expenditure near disturbance; 3) delay crossing or fail to cross linear structures; 4) shift away from areas of extensive and intensive development; and 5) are killed by collisions with vehicles and by hunting along roads. Cows and calves during the calving season are the most easily disturbed group. Bulls in general and all reindeer/caribou during insect harassment are least likely to avoid development areas. Estimation of the proportion of a population that is exposed to disturbance and the implications of this exposure to annual energy budgets, survival and productivity of reindeer/caribou has received little attention. Future advances in understanding the implications of human disturbance to reindeer/caribou will require cumulative effects assessment at annual, population and regional scales. Although some level of cumulative effect is likely, clear separation of cumulative effects of development from natural variation in caribou habitat use and demography will be difficult.