Estimating the size and travel distance of Klapperhorn Mountain debris flows for risk analysis along railway, Canada

Debris flows occurring on Klapperhorn Mountain in the Yellowhead Pass in the Canadian Rocky Mountains pose a significant hazard to railway operations at the base of the mountain. The size （volume） and travel distance of these debris flows play an important role in assessing the risk to the railway. GIS analysis, airphoto interpretation together with field work were undertaken on two debris flows located at track mileage 54.0 and 54.3. Characteristics of these two debris flow events were analyzed, including debris flow path morphology and event behavior. Their sizes and travel distances were estimated using an empirical-statistical model （UBCDFLOW） under different initiation conditions. Their potential impact on the railway bridge was evaluated using a bridge blockage ratio.     

DIVIDING THE OCEAN SEA*

ABSTRACT. The conventional view of global hydrography, which maps three or four oceans (Pacific, Atlantic, Indian, and, sometimes, Arctic) did not emerge until the late nineteenth and early twentieth centuries. Previously, markedly different conceptions of sea space prevailed, conceptions that changed not only to reflect new discoveries but also in accordance with changing intellectual fashions. By examining the history of global hydrography and by entertaining novel schemes of oceanic division, one can see the world afresh and perhaps discover connections that are obscured by conventional geographical divisions.     

Inferred variables in data assimilation: quantifying sensitivity to inaccurate error statistics

The ability of data assimilation systems to infer unobserved variables has brought major benefits to atmospheric and oceanographic sciences. Information is transferred from observations to unobserved variables in two ways: through the temporal evolution of the predictive equations (either a forecast model or its adjoint) or through an error covariance matrix (or a parametrized approximation to the error covariance). Here, it is found that high frequency information tends to flow through the former route, low frequency through the latter. It is also noted that using the Kalman Filter analysis to estimate the correlation between the observed and unobserved variables can lead to a biased result because of an error correlation: this error correlation is absent when the Kalman Smoother is used.     

Assessment and control of organic and other contaminants associated with the Stardust sample return from comet 81P/Wild 2

Abstract– Numerous potential sources of organic contaminants could have greatly complicated the interpretation of the organic portions of the samples returned from comet 81P/Wild 2 by the Stardust spacecraft. Measures were taken to control and assess potential organic (and other) contaminants during the design, construction, and flight of the spacecraft, and during and after recovery of the sample return capsule. Studies of controls and the returned samples suggest that many of these potential sources did not contribute any significant material to the collectors. In particular, contamination from soils at the recovery site and materials associated with the ablation of the heatshield do not appear to be significant problems. The largest source of concern is associated with the C present in the original aerogel. The relative abundance of this carbon can vary between aerogel tiles and even within individual tiles. This C was fortunately not distributed among a complex mixture of organics, but was instead largely present in a few simple forms (mostly as Si‐CH₃ groups). In most cases, the signature of returned cometary organics can be readily distinguished from contaminants through their different compositions, nonterrestrial isotopic ratios, and/or association with other cometary materials. However, some conversion of the carbon indigenous to the flight aerogel appears to have happened during particle impact, and some open issues remain regarding how this C may be processed into new forms during the hypervelocity impact collection of the comet dust.     

Vegetation patterns, recent pollen deposition and distribution of non-pollen palynomorphs in a polygon mire near Chokurdakh (NE Yakutia, NE Siberia)

Fine-scaled distribution patterns of vegetation and palynomorphs in a polygon mire in NE Siberia were studied in 31 × 31 plots of 1 m² (vegetation) and along a transect at intervals of 1 m (palynomorphs). Pollen and non-pollen-palynomorph contents clearly reflect differences between polygon ridges and centres. For most single pollen types, however, no unambiguous relation with actual plant abundances and distribution exists. High pollen values are restricted to the immediate vicinity of the pollen sources, which is attributed to the low height of the vegetation. For several plant taxa, high pollen values were found to be restricted to particular plant specimens in the population. High values of pollen ascribed to taxa currently absent at the relevant plot show that the sampled mosses contain a pollen signal of several years. Betula exilis produces two morphologically clearly distinct pollen types. The distribution of selected non-pollen palynomorphs correlates to microrelief, moisture regime and/or trophic conditions. The study shows that single palaeo-sections from arctic peatlands should not be over-interpreted with respect to their palaeoecological value. Local vegetation types and site conditions, however, can be accurately reconstructed from the total assemblages and from combined occurrences of specific palynomorph types.     

Modal abundances of CAIs: Implications for bulk chondrite element abundances and fractionations

Abstract— Modal abundances of Ca,Al‐rich inclusions (CAIs) are poorly known and reported data scatter across large ranges. CAIs are Poisson distributed, and if only small areas (<1000 mm²) are studied, the data are probably not representative of the true CAI modal abundances, explaining their reported large scatter in a single chondrite group. We combine reported CAI modal abundances and our own set, and present a complete list of CAI modal abundances in carbonaceous chondrites. This includes (in area%): CV: 2.98, CM: 1.21, Acfer 094: 1.12, CO: 0.99, CK/CV (Ningqiang and Dar al Gani [DaG] 055): 0.77, CK: 0.2, CR: 0.12 and CB: 0.1. CAIs are Poisson distributed and if only small areas are studied, the data are probably not representative of the true CAI modal abundances, Carbonaceous chondrites have excess bulk Al concentrations when compared to the CI‐chondritic value. We find a correlation between this excess and CAI modal abundances and conclude that the excess Al was delivered by CAIs. The excess Al is only a minor fraction (usually ?10 rel%, but 25 rel% in case of CVs) of the bulk chondrite Al and cannot have contributed much ²⁶Al to heat the chondrite parent body. Ordinary, enstatite, R and K chondrites have an Al deficit relative to CI chondrites and only very low CAI modal abundances, if any are present at all. Carbonaceous chondrites also had an initial Al deficit if the contribution of Al delivered by CAIs is subtracted. Therefore all chondrites probably lost a refractory rich high‐T component. Only minor amounts of CAIs are present in the matrix or have been present in the chondrule precursor aggregates. Most CAI size distributions contain more than one size population, indicating that CAIs from within a single meteorite group had different origins.     

Chironomids as indicators of the Holocene climatic and environmental history of two lakes in Northeast Greenland

Schmidt, S., Wagner, B., Heiri, O., Klug, M., Bennike, O. & Melles, M. 2010: Chironomids as indicators of the Holocene climatic and environmental history of two lakes in Northeast Greenland. Boreas, 10.1111/j.1502‐3885.2010.00173.x. ISSN 0300‐9483. Two Holocene sediment sequences from arctic lakes on Store Koldewey, an island in Northeast Greenland, were investigated for fossil chironomid assemblages. A total of 18 and 21 chironomid taxa were identified in 290‐ and 252‐cm‐long sediment sequences from Duck Lake and Hjort Lake, respectively. The chironomid assemblages were very similar in the two lakes. Canonical correspondence analysis (CCA) was used to compare fossil chironomid assemblages from Store Koldewey with chironomid assemblages and environmental conditions presently found in Canadian Arctic lakes and, hence, to infer environmental changes for Northeast Greenland. The first chironomids appeared at c. 9500 cal. a BP in Hjort Lake, and 500 years later in Duck Lake. Taxa typical for cold and nutrient‐poor arctic lakes dominated the earliest assemblages. Chironomid assemblages with taxa typical of higher summer air temperatures and lakes with higher nutrient availability occur between 8000 and 5000 cal. a BP. This period probably marks the regional Holocene thermal maximum, which is relatively late compared with some palaeoenvironmental records from East Greenland. One possible reason could be the location of Store Koldewey at the very outer coast, with local climatic conditions strongly influenced by the cold East Greenland Current. From around 5000 cal. a BP, chironomid assemblages in Duck Lake and Hjort Lake again became more typical of those presently found in Northeast Greenland, indicating relatively cold and nutrient‐poor conditions. This shift coincides with an increase of ice‐rafting debris off East Greenland and an intensification of the East Greenland Current.     

An integrated model of extrusive sand injectites in cohesionless sediments

Clastic injection and surface expression of subsurface sediment remobilization is a phenomenon which is becoming increasingly recognized. However, understanding of the physical mechanisms that control these features remains limited, dominated by inference from outcrop and seismic studies. Here, this limitation is addressed through a set of experiments focused on the development and evolution of fluidization features in non‐cohesive bedded sequences. Fluidization and the onset of piping are shown to occur progressively through a sequence of discrete phases, with initial void formation, development of infiltration horizons, rupture and finally pipe formation. Critically, the style of piping, the stability of piping and the temporal evolution of venting are shown to exhibit considerable variability. In particular, pipes may either be stable or very mobile, migrating laterally over large distances; these produce deposits that are typically interpreted in outcrop as being the product of en masse liquefaction rather than localized, dynamic fluidization. These differing elements are synthesized to produce a model of sand extrudites. In addition, the implications of this model are explored.     

Late Quaternary history of the Kap Mackenzie area,northeast Greenland

Wagner, B., Bennike, O., Cremer, H. & Klug, M. 2010: Late Quaternary history of the Kap Mackenzie area, northeast Greenland. Boreas, Vol. 39, pp. 492–504. 10.1111/j.1502‐3885.2010.00148.x. ISSN 0300‐9483. The Kap Mackenzie area on the outer coast of northeast Greenland was glaciated during the last glacial stage, and pre‐Holocene shell material was brought to the area. Dating of marine shells indicates that deglaciation occurred in the earliest Holocene, before 10 800 cal. a BP. The marine limit is around 53 m a.s.l. In the wake of the deglaciation, a glaciomarine fauna characterized the area, but after c. one millennium a more species‐rich marine fauna took over. This fauna included Mytilus edulis and Mysella sovaliki, which do not live in the region at present; the latter is new to the Holocene fauna of northeast Greenland. The oldest M. edulis sample is dated to c. 9500 cal. a BP, which is the earliest date for the species from the region and indicates that the Holocene thermal maximum began earlier in the region than previously documented. This is supported by driftwood dated to c. 9650 cal. a BP, which is the earliest driftwood date so far from northeastern Greenland and implies that the coastal area was at least partly free of sea ice in summer. As indicated by former studies, the Storegga tsunami hit the Kap Mackenzie area at c. 8100 cal. a BP. Loon Lake, at 18 m a.s.l., was isolated from the sea at c. 6200 cal. a BP, which is distinctly later than expected from existing relative sea‐level curves for the region.