How robust is the long-run relationship between temperature and radiative forcing?

This paper examines the robustness of the long-run, cointegrating, relationship between global temperatures and radiative forcing. It is found that the temperature sensitivity to a doubling of radiative forcing is of the order of 2 ± 1°C. This result is robust across the sample period of 1850 to 2000, thus providing further confirmation of the quantitative impact of radiative forcing and, in particular, CO₂ forcing, on temperatures.     

俄罗斯勘察加半岛热泉的地球化学和微生物学

勘察加半岛位于欧洲板块、北美板块和太平洋板块交汇的过渡带上,是世界火山活动最活跃的地区之一.其众多的热液系统不断的向地表释放地热气体和流体.以N2和CO2为主的地热气体也经常含有高浓度的H2,CH4和H2S.大气水和熔岩水构成了勘察加热泉水的主要源,水体温度从20 ℃到＞90 ℃不等.水化学性质变化同样显著,pH范围从3.1到9.8.热泉水溶解盐以氯化钠为主,同时包括K+,H3BO3,H4SiO4,Ca2+和SO42-等其他多种溶解组分.此区域也有以直链烷烃为主的石油形成.从勘察加的热泉系统中已分离出至少24种嗜热微生物.尽管其中大多数是异养微生物,但根据其生存环境的特点,自养微生物在热泉系统中可能同样很多.这些微生物对碳、硫和铁在热液系统中的生物地球化学循环有着非常重要的作用.目前,非培养的方法和生物定量的手段已用来研究勘察加热泉中微生物生态及其所具有的生物地球化学功能.     

Microbial carbon cycling in oligotrophic regional aquifers near the Tono Uranium Mine, Japan as inferred from δC and ΔC values of in situ phospholipid fatty acids and carbon sources

Microorganisms are ubiquitous in deep subsurface environments, but their role in the global carbon cycle is not well-understood. The natural abundance δ¹³C and Δ¹⁴C values of microbial membrane phospholipid fatty acids (PLFAs) were measured and used to assess the carbon sources of bacteria in sedimentary and granitic groundwaters sampled from three boreholes in the vicinity of the Tono Uranium Mine, Gifu, Japan. Sample storage experiments were performed and drill waters analyzed to characterize potential sources of microbial contamination. The most abundant PLFA structures in all waters sampled were 16:0, 16:1ω7c, cy17:0, and 18:1ω7c. A PLFA biomarker for type II methanotrophs, 18:1ω8c, comprised 3% and 18% of total PLFAs in anoxic sedimentary and granitic waters, respectively, sampled from the KNA-6 borehole. The presence of this biomarker was unexpected given that type II methanotrophs are considered obligate aerobes. However, a bacterium that grows aerobically with CH₄ as the sole energy source and which also produces 56% of its total PLFAs as 18:1ω8c was isolated from both waters, providing additional evidence for the presence of type II methanotrophs. The Δ¹⁴C values determined for type II methanotroph PLFAs in the sedimentary (−861‰) and granite (−867‰) waters were very similar to the Δ¹⁴C values of dissolved inorganic carbon (DIC) in each water (∼−850‰). This suggests that type II methanotrophs ultimately derive all their carbon from inorganic sources, whether directly from DIC and/or from CH₄ produced by the reduction of DIC. In contrast, δ¹³C values of type II PLFAs in the sedimentary (−93‰) and granite (−60‰) waters indicate that these organisms use different carbon assimilation schemes in each environment despite very similar δ¹³C_CH4 values (∼−95‰) for each water. The δ¹³C_PLFA values (−28‰ to −45‰) of non-methanotrophic bacteria in the KNA-6 LTL water do not clearly distinguish between heterotrophic and autotrophic metabolisms, but Δ¹⁴C_PLFA values indicate that >65% of total bacteria filtered from the KNA-6 LTL water are heterotrophs. Ancient Δ¹⁴C values (∼−1000‰) of some PLFAs suggest that many heterotrophs utilize ancient organic matter, perhaps from lignite seams within the sedimentary rocks. The more negative range of δ¹³C_PLFA values determined for the KNA-6 granitic water (−42‰ to −66‰) are likely the result of a microbial ecosystem dominated by chemolithoautotrophy, perhaps fuelled by abiogenic H₂. Results of sample storage experiments showed substantial shifts in microbial community composition and δ¹³C_PLFA values (as much as 5‰) during 2-4 days of dark, refrigerated, aseptic storage. However, water samples collected and immediately filtered back in the lab from freshly drilled MSB-2 borehole appeared to maintain the same relative relationships between δ¹³C_PLFA values for sedimentary and granitic host rocks as observed for samples directly filtered under artesian flow from the KNA-6 borehole of the Tono Uranium Mine.     

Assessment of lightning-related damage and disruption in Canada

This article assesses the extent and costs of lightning-related damage and disruption in Canada. Lightning routinely damages property and disrupts economic and social activities. Affected sectors include health; property and casualty insurance; forestry; electricity generation, transmission, and distribution; agriculture; telecommunications; transportation; and tourism and recreation—the first four sectors are the most important in terms of contributing to overall impacts and costs. Secondary data and extrapolations from U.S. studies were used to develop cost estimates for the health, property, forestry, and electricity sectors. Aggregated, annual lightning-related damage and disruption costs in Canada range from CA$600 million to CA$600 million to CA1 billion. Forestry and electricity damages accounted for over 85% of the total. The estimates are both preliminary and conservative. In terms of continued research, additional or more refined studies using Canadian empirical data are warranted for the insurance and electricity sectors. Detailed insurance claim or outage data would permit analysis at the storm level and potentially discern finer-scaled risk patterns. Further effort is also required to evaluate risk or damage prevention measures, particularly those that relate to expanded or enriched use of the Canadian Lightning Detection Network data by both public and private sector clients. Both the degree of adoption and efficacy or cost-effectiveness should be investigated.     

Interaction between a river and its wetland: evidence from the Murray River for spatial variability in diatom and radioisotope records

Sinclair Flat is small wetland, located within the gorge section of the Murray River floodplain. situated near Blanchetown, South Australia, the wetland is closely linked to the River and, since regulation, has become permanently inundated. High summer evaporation rates deplete the volume of water within the wetland. However, this is compensated by perennial inflow via a permanent inlet from the River. This site provides an opportunity to explore the relative contribution of river and wetland diatom flora to the sediment record, and the fluvial and aerial contribution of radiometric isotopes to the system. The geochronological and biostratigraphic data provide an insight into the history of the water quality of Sinclair Flat. Evidence exists for the River being a source of sediments and isotopes and of diatom species typical of the main river channel. Prior to 1950, Sinclair Flat was an oligotrophic, oligosaline, clear-water wetland. The wetland shifted gradually to an environment that favoured clear-water benthic species, most likely as a consequence of changes following river regulation in the 1920s, although the capacity to date these sediments is limited. During the 1950s, the wetland became plankton dominated. Peaks in epiphytic diatoms during the 1960s suggest increased emergent macrophyte cover. The contemporary condition is of a connected, turbid, eutrophic and mesosaline lagoon. The ecological condition of Sinclair Flat has diverged considerably from its historical range of condition. This record supports evidence from upstream of widespread state switches in the Murray–Darling Basin floodplain wetlands. This record also lends considerable weight to modern studies attesting to the degraded state of the waterways of the Murray–Darling Basin and the impact of river regulation practices on the water quality of these ecosystems.     

Winter and autumn daily precipitation patterns in Catalonia,Spain

Summary A principal component analysis (PCA), based on a network consisting of 60 pluviometric gauges and their daily precipitation data, is attempted in order to describe the main winter and autumn patterns governing precipitation in Catalonia (NE Spain). This PCA procedure is applied to the interstation correlation matrix and rotated component loadings are then deduced and extensively interpreted. The PCA results are then used in a clustering process (Average Linkage), leading to two rainfall divisions, one for each season, which are then compared.With 5 Figures     

Ten years on: what can Google Earth offer the geoscience community?

Google Earth has been part of most geoscientists' computer (and mobile) desktops for a decade, and this year Google Earth Professional has become freely available to all with a universal license key. Many users are still, however, not aware of the full potential that it can offer across a range of teaching and research areas in the geosciences. Here a pragmatic look is taken at some of the current key uses in terms of resources and applications and how they can help in research and training educational roles in the geosciences.     

Environmental change over the last millennium recorded in two contrasting crater lakes in western Uganda,eastern Africa (Lakes Kasenda and Wandakara)

The last millennium is a key period for understanding environmental change in eastern Africa, as there is clear evidence of marked fluctuations in climate (effective moisture) that place modern concern with future climate change in a proper context, both in terms of environmental and societal impacts and responses. Here, we compare sediment records from two small, nearby, closed crater lakes in western Uganda (Lake Kasenda and Lake Wandakara), spanning the last 700 (Wandakara) and 1200 years (Kasenda) respectively. Multiproxy analyses of chemical sedimentary parameters (including C/N ratios, δ¹³C of bulk organic matter and δ¹³C and δ¹⁸O of authigenic carbonates) and biotic remains (diatoms, aquatic macrofossils, chironomids) suggest that Kasenda has been sensitive to climate over much of this period, and has shown substantial fluctuations in conductivity, while Wandakara has a more muted response, likely due to the increasing dominance of human activity as a driver of change within the lake and catchment over the length of our record. Evidence from both records, however, supports the idea that lake levels were low from ～AD 700–1000 AD, with increasing aridity from AD 1100–1600, and brief wet phases around AD 1000 and 1400. Wetter conditions are recorded in the 1700s, but drought returned by the end of the century and into the early 1800s, becoming wetter again from the mid-1800s. Comparison with other records across eastern Africa suggests that while some events are widespread (e.g. aridity beginning ～ AD 1100), at other times there is a more complex spatial signature (e.g. in the 1200s to 1300s, and from the 1400s to 1600s). This study highlights the important role of catchment-specific factors (e.g. lakemorphometry, catchment size, and human impact) in modulating the sensitivity of proxies, and lake records, as indicators of environmental change, and potential hazards when regional inference is based on a single site or proxy.     

Quaternary slope processes and morphologies in the upper Sehonghong Valley, eastern Lesotho

Several high south-facing slopes in the southern Drakensberg were glaciated during the Late Quaternary, yet little is known about the slope geomorphic history on equally high slopes that appear not to have been glaciated. To this end, we examine evidence for Late Quaternary slope dynamics in a high alpine valley of eastern Lesotho, with particular attention given to palaeo-environmental signatures offered by deep colluvial mantles along the flanks of the Sehonghong River and pronival ramparts along the upper southerly-facing slopes of the adjoining Thabana-Ntlenyana. Sedimentary exposures were mapped and sampled for clast fabric, clast shape, organic matter content, granulometry and ¹⁴C age determination. Similarly, a pronival rampart was mapped and clast size, shape and fabric determined for various micro-topographic settings. A palaeosol beneath the rampart was also Radiocarbon dated. Findings suggest that the deep and extensive debris mantles on lower south-facing slopes are a product of prolonged colluviation, whilst the more stratified sequences on north-facing slopes indicate greater slope geomorphic-process variability over time. Radiocarbon ages suggest sediment accumulation along the north-facing exposure from at least ∼43 ka. It is proposed that snowcreep and snowpush on high (>3400 m a.s.l.) southeast-facing slopes during a relatively cold, yet moist period at ∼AD 300-1000 initiated boulder movement to form the pronival ramparts.