Multi-model calibration and combination of tropical seasonal sea surface temperature forecasts

Different combination methods based on multiple linear regression are explored to identify the conditions that lead to an improvement of seasonal forecast quality when individual operational dynamical systems and a statistical–empirical system are combined. A calibration of the post-processed output is included. The combination methods have been used to merge the ECMWF System 4, the NCEP CFSv2, the Météo-France System 3, and a simple statistical model based on SST lagged regression. The forecast quality was assessed from a deterministic and probabilistic point of view. SSTs averaged over three different tropical regions have been considered: the Niño3.4, the Subtropical Northern Atlantic and Western Tropical Indian SST indices. The forecast quality of these combinations is compared to the forecast quality of a simple multi-model (SMM) where all single models are equally weighted. The results show a large range of behaviours depending on the start date, target month and the index considered. Outperforming the SMM predictions is a difficult task for linear combination methods with the samples currently available in an operational context. The difficulty in the robust estimation of the weights due to the small samples available is one of the reasons that limit the potential benefit of the combination methods that assign unequal weights. However, these combination methods showed the capability to improve the forecast reliability and accuracy in a large proportion of cases. For example, the Forecast Assimilation method proved to be competitive against the SMM while the other combination methods outperformed the SMM when only a small number of forecast systems have skill. Therefore, the weighting does not outperform the SMM when the SMM is very skilful, but it reduces the risk of low skill situations that are found when several single forecast systems have a low skill.     

Evaluating the performance of CMIP3 and CMIP5 global climate models over the north-east Atlantic region

One of the main sources of uncertainty in estimating climate projections affected by global warming is the choice of the global climate model (GCM). The aim of this study is to evaluate the skill of GCMs from CMIP3 and CMIP5 databases in the north-east Atlantic Ocean region. It is well known that the seasonal and interannual variability of surface inland variables (e.g. precipitation and snow) and ocean variables (e.g. wave height and storm surge) are linked to the atmospheric circulation patterns. Thus, an automatic synoptic classification, based on weather types, has been used to assess whether GCMs are able to reproduce spatial patterns and climate variability. Three important factors have been analyzed: the skill of GCMs to reproduce the synoptic situations, the skill of GCMs to reproduce the historical inter-annual variability and the consistency of GCMs experiments during twenty-first century projections. The results of this analysis indicate that the most skilled GCMs in the study region are UKMO-HadGEM2, ECHAM5/MPI-OM and MIROC3.2(hires) for CMIP3 scenarios and ACCESS1.0, EC-EARTH, HadGEM2-CC, HadGEM2-ES and CMCC-CM for CMIP5 scenarios. These models are therefore recommended for the estimation of future regional multi-model projections of surface variables driven by the atmospheric circulation in the north-east Atlantic Ocean region.     

A missing piece from a bigger puzzle: declining occurrence of a transient group of bottlenose dolphins off Southeastern Brazil

Bottlenose dolphins are widespread off South America with patchy distributions throughout coastal, nearshore and offshore waters. Only limited information on the connectivity between individuals from these different habitats exists, despite the importance of understanding the overall population structure. A group of bottlenose dolphins in an insular habitat off Brazil may help provide evidence of the structure of a larger pelagic population in Brazilian waters. It is unknown whether the dolphins that use this habitat seasonally are part of an open population, a closed population of transient animals, or even individuals from offshore or nearshore groups. To explore the nature of these seasonal visitors we combined two strategies. First, by assessing the population parameters, we described a small group of individuals (maximum of 38 individuals in 2004 and five individuals in 2010) characterized by wide‐ranging behavior, low survival probabilities (64%) and an apparent population decline. Secondly, by exploring their social organization at a fine scale, we observed that within a stable group, the dyadic associations are fluid and mostly of short duration, similar to well‐known coastal bottlenose dolphin societies. The evidence of a non‐structured social network seems to be coupled with apparent seasonal use of this insular protected area for calf rearing and/or reproductive strategies. Overall, our findings suggest that this group may not be an aggregation of individuals from different populations in a specific area, but a relatively stable group formed by the same animals. While continuing research efforts are necessary along the South America coast, the abandonment of the study area by this group may hamper the understanding of population structure and connectivity among pelagic and coastal populations of bottlenose dolphins, as well as the ecological and behavioral mechanisms driving their seasonal occurrence in oceanic habitats.     

运用生物地理学理论与遥感影像寻找本·拉登

本·拉登到底在哪里？这是我们这个时代最重要的政治问题之一。在这篇文章中,我们依据反映生物分布和灭绝规律的生物地理学理论(距离衰减理论、岛屿生物地理理论、本·拉登个人数据),结合遥感数据(陆地卫星 ETM+、航天雷达地形测图、QuickBird),从全球、区域、局部三个空间尺度分析并最终指出本·拉登当前最可能的所在地。这是第一次运用科学手段来确定本·拉登居所。该方法具有可重复性：一旦美国情报部门提供新的信息,便可通过该方法重新定位本·拉登当前最有可能的藏身场所。     

Zircon-scale insights into the history of a Supervolcano,Bishop Tuff,Long Valley,California, with implications for the Ti-in-zircon geothermometer

Zircon has the outstanding capacity to record chronological, thermal, and chemical information, including the storage history of zoned silicic magma reservoirs like the one responsible for the Bishop Tuff of eastern California, USA. Our novel ion microprobe approach reveals that Bishop zircon rims with diverse chemical characteristics surround intermediate domains with broadly similar compositions. The highest Y, REE, U, and Th concentrations tend to accompany the largest excesses in Y + REE³⁺:P beyond what can be explained by xenotime substitution in zircon. Apparent Ti-in-zircon temperatures of <720°C for zircon rims are distinctly lower than most of the range in eruption temperatures, as estimated from FeTi-oxide equilibria and zircon solubility at quench. While permissive of crystallization of zircon at near-solidus conditions, the low Ti-in-zircon temperatures are probably better explained by sources of inaccuracy in the temperature estimates. After apparently nucleating from different melts, zircons from across the Bishop Tuff compositional spectrum may have evolved to broadly similar chemical and thermal conditions and therefore it is possible that there was no significant thermal gradient in the magma reservoir at some stage in its evolution. There is also no compelling evidence for punctuated heat ± chemical influxes during the intermediate stages of zircon growth. Judging by the zircon record, the main volume of the erupted magma evolved normally by secular cooling but the latest erupted portion is characterized by a reversal in chemistry that appears to indicate perfusion of the magma reservoir by—or zircon entrainment in—a less evolved melt from the one in which the zircons had previously resided.     

Mesoarchean (3.0 and 2.86 Ga) host rocks of the iron oxide–Cu–Au Bacaba deposit,Carajás Mineral Province: U–Pb geochronology and metallogenetic implications

The Bacaba iron oxide–copper–gold deposit, situated within a WNW–ESE-striking shear zone in the Carajás Domain, Carajás Mineral Province, is hosted by the Serra Dourada Granite, the Bacaba Tonalite, and crosscutting gabbro intrusions, which were intensely affected by sodic (albite–scapolite), potassic, chloritic, and hydrolytic hydrothermal alteration. This deposit is located 7 km northeast of the world-class Sossego iron oxide–copper–gold deposit and might represent a distal and deeper portion of the same or related hydrothermal system. The U–Pb laser ablation inductively coupled plasma–mass spectrometry data for zircon from a sodically altered sample of the Serra Dourada Granite yielded a 2,860±22 Ma (MSWD=11.5) age. Three samples from the Bacaba Tonalite, including one with potassic alteration and two with Cu–Au mineralization, rendered the 3,001.2±3.6 Ma (MSWD=1.8), 2,990.9±5.8 Ma (MSWD=1.9), and 3,004.6±9 Ma (MSWD=2.2) ages, respectively. The ca. 2.86 and ca. 3.0 Ga ages are interpreted as the timing of the igneous crystallization of the Serra Dourada Granite and the Bacaba Tonalite, respectively, and represent the oldest magmatic events recognized in the Carajás Domain. The Serra Dourada Granite and the Bacaba Tonalite are interpreted to greatly predate the genesis of the Bacaba deposit. A genetic link is improbable in the light of the similarities with the Sossego deposit, which is also hosted by younger ca. 2.76 Ga metavolcano-sedimentary units of the Itacaiúnas Supergroup. In this context, the iron oxide–copper–gold deposits in the southern sector of the Carajás Domain could be mainly controlled by important crustal discontinuities, such as a regional shear zone, rather than be associated with a particular rock type. These results expand the potential for occurrences of iron oxide–copper–gold deposits within the Mesoarchean basement rocks underlying the Carajás Basin, particularly those crosscut by Neoarchean shear zones.     

Impact of mining activities on sediments in a semi-arid environment: San Pedro River, Sonora, Mexico

A study of the San Pedro River (SPR), which is located in a semi-arid region in Sonora, Mexico, was conducted to evaluate the chemical, spatial and temporal (mobilization) trends of potentially harmful metals in its sediment in the rainy and dry seasons. High total concentrations of metals were detected in the following order: Fe > Cu > Mn > Zn > Pb > Cd. All studied metals except for Pb were increased during the dry season showing the effect of climate on the metal distribution in sediments. The results of sequential extraction indicated that the residual and Fe/Mn oxide fractions were the most important with regard to retaining potentially harmful metals in the sediments. In the exchangeable carbonate and Fe oxide fractions, high concentrations of metals were detected, representing high environmental risk. The geoaccumulation index shows slight to moderate contamination in most samples, and sampling point E4 (related to cattle activity) shows strong contamination for Cd, Cu, Pb and Zn. Enrichment factors (EFs) demonstrate anthropogenic origins for Pb (EF: 3–57), Cd (EF: 6–73) and Cu (EF: 1.5–224). This study shows that sediments are impacted by anthropogenic activities related to the mining industry, untreated wastewater discharges from the city of Cananea and cattle activities. Metal mobility in the SPR can disrupt the development of aquatic species in the river.     

Passing volume calculation system (PVCS): computer software for managing data on watersheds that produce mud flows and the case of Quebrada La Cadena,Antofagasta, Chile

Severe storms in desert regions, especially along the coastal area of the Chilean desert, produce very destructive mud flows that last a few hours and constitute the only surface run-off in these events. To date, there is no simple or practical methodology for assessing such mud flows. Given the settlement of mining fields and creation of desert campgrounds, it is increasingly necessary to understand how these water and/or mud flows behave in order to develop structural and non-structural mitigation plans. Thus, herein, we present software known as PVCS, which provides a system for calculating mud volumes after a strong storm. This hydrological and computer tool allows us to calculate the structure and volume of mud passing through the mouth of a hydrographic watershed after a desert rainstorm. To use this software, it is necessary to know the hydrological, meteorological, and morphometric parameters of the watershed under study. These data are entered into a model that estimates the amount of mud that will pass through the mouth with each hour of rain. Simulations can be done with historical data or data designed for future events, thereby allowing the preparation of measures to protect people and property. We use the watershed Quebrada La Cadena to exemplify the use of this software. This drainage basin is located on the western slope of the Chilean Coastal Range in Antofagasta, a city in northern Chile. Here, rain in June 1991 produced a destructive flood that killed nearly one hundred people living at the main mouth of the watershed and caused huge economic losses. Data from this catastrophe have significantly improved the understanding of such flows, and this has been incorporated into the software. The principal value of PVCS lies in its ability to forecast the volume of mud that will result from a storm and hourly outflows that will pass through a specific populated area, mining camp, or industrial plant located in the mouth of a watershed of any size. This information is used to determine the most critical moment, i.e., the time of the largest outflows, which can then be used to organize timely evacuations to safe places for people, animals, and machines. Moreover, the program is methodologically valuable since, in order to implement PVCS, the user must structure information in a hydrological way. In summary, this program simulates different rain scenarios, thereby allowing us to design structural mitigation projects and contingency plans.     

Evolution of Ataúro Island: Temporal constraints on subduction processes beneath the Wetar zone, Banda Arc

Ataúro is a key to understanding the late stage volcanic and subduction history of the Banda Arc to the north of Timor. A volcanic history of bi-modal subaqueous volcanism has been established and new whole rock and trace element geochemical data show two compositional groups, basaltic andesite and dacite–rhyolite. ⁴⁰Ar/³⁹Ar geochronology of hornblende from rhyo-dacitic lavas confirms that volcanism continued until 3.3 Ma. Following the cessation of volcanism, coral reef marine terraces have been uplifted to elevations of 700 m above sea level. Continuity of the terraces at constant elevations around the island reflects regional-scale uplift most likely linked to sublithospheric processes such as slab detachment. Local scale landscape features of the eastern parts of Ataúro are strongly controlled by normal faults. The continuation of arc-related volcanism on Ataúro until at least 3.3 Ma suggests that subduction of Australian lithosphere continued until near this time. This data is consistent with findings from the earthquake record where the extent of the Wetar seismic gap to a depth of 350 km suggests slab breakoff, as a result of collision, commenced at ∼4 Ma, leading to subsequent regional uplift recorded in elevated terraces on Ataúro and neighbouring islands.