Warm-Season Annual to Decadal Temperature Variability for Hokkaido, Japan, Inferred from Maximum Latewood Density and Ring Width Data

We present a warm season (April–September) temperature reconstructionfor Asahikawa, north central Hokkaido, Japan for AD 1557–1990. The reconstruction, which accounts for 34% of the temperature variancefrom 1925–1990, is based on maximum latewood density data from Saghalinspruce (Picea glehnii) growing at timberline (1340–1390 m) at MountAsahidake, Hokkaido. We only present a high frequency (prewhitened or white noise) version of the reconstruction because there is an unexplained offset in the mean between the actual and estimated temperature data for an earlier period of overlap from 1891–1924. The coldest summer in the reconstruction is 1718, forwhich the estimated value is 12.89 ° C, nearly four standard deviations (SD) below the mean. A colder-than-average year is reconstructed for 1641 (13.30° C, nearly 3 SD below mean), following the eruption of Komagatake, Hokkaido which began in July, 1640. The Asahikawa density chronology, shows decadal modes of variation with statistically significant spectral peaks prior to around 1850. A tree-ring width chronology for this same site (AD 1532–1990) is in phase with a tree-ring width record from centralKamchatka prior to around 1850, but out of phase since that time. This pattern suggests, as has been hypothesized for temperature-sensitive tree-ring records from the eastern Pacific sector (Alaska and Patagonia), that a decadal mode of climate variation was more dominant in the Pacific sector prior to about 1850, after which a higher frequency (ENSO-type) mode may have become more pronounced, at least until recent decades. Additional data from the northwestern Pacific is needed to compare to these findings.     

Lithium in spilites

During spilitisation the abundance of Li increases from about 12 ppm in normal basaltic rocks to an average of 75 ppm, with some spilites containing up to 190 ppm. This is relatively far greater than the increase of <50% in Na. Also the ratio CaO/Al₂O₃ decreases from about 1.0 to <0.1 and the H₂O content increases markedly.Alteration of this kind requires waters rich in both Na and Li, with the material added having a ratio 10⁵ Li/Na of about 750: the ratio for seawater is 1.8 but most subsurface waters have higher ratios and are more likely agents of spilitisation.Volcanic hydrothermal brines have suitable Li and Na abundances and are known to have reacted with fresh basalts to produce spilitic alteration: in cases of spilitisation of volcanogenic sediments, reaction with non-volcanic brines may have occurred. In both cases the waters must initially have high CO₂ and low Ca activities.     

Use of remote sensing to document changes in marsh vegetation following the Amoco Cadiz oil spill (Brittany, France, 1978)

Image analysis of historical aerial photographs was used to examine the effects of the Amoco Cadiz oil spill and resulting clean-up on marsh ecology. Two heavily oiled marsh systems were compared. The marsh which received no clean-up recovered to its prior condition. The marshes in the system cleaned by sediment removal were extensively altered as a result of changes in intertidal height of the sediment surface.     

Satellite Measurements of Albedo and Radiant Temperature from Semi-Desert Grassland along the Arizona/Sonora Border

Along the international border separatingthe U.S. (Arizona) and Mexico (Sonora), differencesin the grazing intensity of domestic livestock arecommonly presumed to have created a large differencein vegetation cover between the two countries. Thisvegetation difference is reportedly responsible for anextensive albedo and temperature discontinuity thatmay be affecting regional climate. In this study, weused Landsat Thematic Mapper data to examinetrans-border differences in these two biophysicalparameters. Albedo and radiant temperature estimateswere computed for 25 km-long (east-west) transectsthrough semi-desert grassland on each side of theborder at two different times of year. Only smallaverage trans-border differences in these parameterswere found, and in some cases average albedo andtemperature data were essentially equal on each sideof the border. In addition, we found significantspatial heterogeneity in conditions on both sides ofthe border. These results suggest that, based on asmall sample, it may be difficult to assess whetherthere are significant differences in biophysicalproperties of semi-arid grassland between Arizona andMexico in the vicinity of the border. We concludethat more extensive spatial and temporal sampling iscritical in assessing any possible trans-borderdifferences in average terrain conditions that mightaffect climate, and that this data must be coupledwith more extensive meteorological data to assesswhether a difference in climate also exists.     

A Compilation of Silicon and Thirty One Trace Elements Measured in the Natural River Water Reference Material SLRS-4 (NRC-CNRC)

The natural river water certified reference material SLRS-4 (NRC-CNRC, National Research Council-Conseil National de Recherches Canada) has been routinely analysed for major and trace elements by six French laboratories. Most measurements were made using inductively coupled plasma-mass spectrometry. For silicon and thirty one trace elements (rare earth elements, Ag, B, Br, Cs, Ga, Ge, Li, P, Pd, Rb, Se, Th, Ti, Tl, W, Y and Zr), no certified values are assigned by NRC-CNRC. We propose some compilation values and related uncertainties according to the results obtained by the different laboratories.     

The 1783 Lakagigar eruption in Iceland: geochemistry,CO2 and sulfur degassing

About 12.3 km³ of basaltic magma were erupted from the Lakagigar fissure in Iceland in 1783, which may have been derived from the high-level reservoir of Grimsvotn central volcano, by lateral flow within the rifted crust. We have studied the petrology of quenched, glassy tephra from sections through pyroclastic cones along the fissure. The chemical composition of matrix glass of the 1783 tephra is heterogeneous and ranges from olivine tholeiite to Fe–Ti rich basalt, but the most common magma erupted is quartz tholeiite (Mg#43.6 to 37.2). The tephra are characterized by low crystal content (5 to 9 vol%). Glass inclusions trapped in plagioclase and Fo₈₆ to Fo₇₅ olivine phenocrysts show a large range of compositions, from primitive olivine tholeiite (Mg#64.3), quartz tholeiite (Mg#43–37), to Fe–Ti basalts (Mg#33.5) which represent the most differentiated liquids and are trapped as rare melt inclusions in clinopyroxene. Both matrix glass and melt inclusion data indicate a chemically heterogeneous magma reservoir, with quartz tholeiite dominant. LREE-depleted olivine-tholeiite melt-inclusions in Mg-rich olivine and anorthitic-plagioclase phenocrysts may represent primitive magma batches ascending into the reservoir at the time of the eruption. Vesicularity of matrix glasses correlates with differentiation, ranging from 10 to 60 vol.% in evolved quartz-tholeiite glasses, whereas olivine-tholeiite glasses contain less than 10 vol.% vesicles. FTIR analyses of olivine-tholeiite melt-inclusions indicate concentrations of 0.47 wt% H₂O and 430 to 510 ppm for CO₂. Chlorine in glass inclusions and matrix glasses increases from 50 ppm in primitive tholeiite to 230 ppm in Fe–Ti basalts, without clear evidence of degassing. Melt inclusion analyses show that sulfur varies from 915 ppm to 1970 ppm, as total FeO^* increases from 9 to 13.5 wt%. Sulfur degassing correlates both with vesicularity and magma composition. Thus sulfur in matrix glasses decreases from 1490 ppm to 500 ppm, as Mg # decreases from 47 to 37 and vesicularity of the magma strongly increases. These results indicate loss of at least 75% of sulfur during the eruption. The correlation of low sulfur content in matrix glasses with high vesicularity is regarded as evidence of the control of a major exsolving volatile phase on the degassing efficiency of the magma. Our model is consistent a quasi-permanent CO₂ flux through the shallow-level magmatic reservoir of Grimsvotn. Following magma withdrawal from the reservoir and during eruption from the Lakagigar fissure, sulfur degassing was controlled by inherent CO₂-induced vesicularity of the magma.     

Seismological study of the central Ecuadorian margin: Evidence of upper plate deformation

A seismic study of a segment of the convergent margin of Ecuador is presented. During the SISTEUR campaign a network of 24 Ocean Bottom Seismometers (OBS) was deployed on the Carnegie Ridge, one line along the main axes of the ridge and two lines across the strike of the edge of the ridge, during one month. This marine network was complemented with a land network of 20 stations distributed in two lines: one parallel to the margin and the other perpendicular to it.The seismic event recorded by these networks, were located using different crustal models defined from the wide-angle seismic data modeling. Relative location techniques were used to improve earthquake locations. Seismogram waveform modeling allowed us to constrain hypocentral location for events farther than ～50 km from the network. This modeling also provided additional information to constrain the focal mechanisms of these events. The upper limit of the Interplate Seismogenic Zone (ISZ) is estimated to be at a 10 km depth in the region. The background seismic activity of the upper plate provided new insights:1) A seismic cluster that reaches the base of the overriding plate is linked to the Jipijapa-Portoviejo fault. The reactivation of this Quaternary fault is confirmed by focal mechanisms that provide rupture planes parallel to its superficial projection (N10°–N25°).2) The focal mechanisms presented in this study are compatible with a homogeneous regional stress field corresponding to an E–W to ESE–WNW compression and an NNE–SSW extension. The presence of strike-slip deformation, with a reverse component, corresponds to the NNE escape of the North Andean Block. Normal faulting accommodating this movement suggests that this part of the North Andean Block cannot be considered as a rigid block.     

Can Cassini detect a subsurface ocean in Titan from gravity measurements?

Recent models of Titan's interior predict that the satellite contains an ocean of water and ammonia under an icy layer. Direct evidence for the presence of an ocean can be provided on the Cassini mission only by radio science determination of Titan Love number k₂. Simulations that use the five flybys T11, T22 T33, T45, and T68 (the latter two belonging to the extended mission) lead to the result that in the elastic case, where the Love number is real, k₂ will be determined with a one-sigma accuracy of 0.1. In the viscoelastic case, where k₂ is complex, the real and imaginary parts of k₂ will be determined with one sigma accuracies of 0.138 and 0.115, respectively. Ocean and oceanless models that include a viscoelastic rheology are built. In the viscoelastic case, there is a 93% probability to correctly predict the presence or absence of an ocean; this probability improves to 97% in the elastic case.     

Measuring the imprint of orographic rainfall gradients on the morphology of steady‐state numerical fluvial landscapes

We explore the imprint of spatial rainfall patterns on steady‐state landscapes with uniform rock uplift rate. A two‐dimensional (2D) orographic precipitation module is incorporated into the CHILD numerical landscape evolution model to provide a quantitative tool for exploring the co‐evolution of rainfall patterns and fluvial topography. Our results suggest that network organization and planform morphology are strongly impacted by rainfall patterns. Rainfall gradients that are perpendicular to a mountain range front produce narrower watersheds because channels show a tendency to flow along the rainfall gradient, rather than across it. The change in watershed shape is evidenced by smaller values of the exponent on distance in Hack's law and a less peaked width function. Narrower watersheds also lead to an increase in the valley spacing ratio and constrain trunk channels to follow a more direct path to the mountain front. Rainfall gradients also influence the distribution of topography across a watershed. Channel profiles record rainfall patterns in both the channel concavity and the channel steepness index (k_sn). Across short tributaries along which rainfall rate changes little, k_sn decreases systematically with tributary‐averaged rainfall rate. The hypsometric integral (HI), which increases with the amount of topography that is at relatively high elevations within a watershed, is negatively correlated with the profile concavity of the trunk channel. High rainfall rates at the ridge top lead to mainstem channels that have relatively low concavity, and watersheds with relatively higher HI in comparison with landscapes that have uniform rainfall. Finally, we contrast the impacts of rainfall patterns on landscape morphology with those resulting from a linear rock uplift gradient and uniform rainfall. Uplift patterns may have a similar impact on landscape morphology as rainfall gradients, making it challenging to decipher the relative roles of climate and tectonics on landscape evolution without a quantitative assessment of morphologic parameters. Copyright © 2015 John Wiley & Sons, Ltd.