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• Acoustic emission (AE) technique was firstly proposed to analyze ablation mechanism of CFRP laser cutting, and it was used as a guide to improve the material removal rate. • Two processing mechanism of thermal ablation (TA) and mechanical denudation (MD) were found through the analysis of the time-domain characteristics of AE signal. • The scanning speed and interval were optimized under the guidance of the RMS value of AE signal, resulting in a maximum material removal rate of 12.2 × 107 μm3/s. The ablation mechanism of CFRP laser cutting refers to complex thermal and mechanical behaviour, and should be investigated. Two processing mechanisms of thermal ablation (TA) and mechanical denudation (MD) were found. TA resulted from the vaporization of the material formed by the accumulation of laser energy, which is reflected by RMS of AE signal < 0.14 V. MD resulted from the material that was stripped from the substrate under the impact of the plasma plume, which is reflected by 0.14 V < RMS < 0.175 V; The processing mechanism of MD exists simultaneously in the same trajectory and adjacent trajectory scanning. When the mechanism of MD in the same trajectory scanning is most severe, RMS also reaches the maximum value of 0.23 V; The RMS has the same variation law as the material removal rate. When the removal rate reaches the maximum value of 12.2 × 107 μm3/s, the RMS curve also reaches its highest point, and the model prediction accuracy is greater than 89%. [ABSTRACT FROM AUTHOR]

Total suspended sediment (TSS) data for 1960–1970 and from recent investigations (1990–2000) are used to evaluate the variability in sediment yield of the Sanaga catchment (Cameroon) and the equivalent rates of erosion. At the annual and seasonal time scales, total suspended sediment concentrations for the Mbam sub-catchment are three to four times higher than for the Sanaga basin, reflecting the higher sensitivity of the former to erosion. Classical clockwise hysteresis loops are observed in both sub-catchments, despite a significant increase in human-induced catchment changes. At the multi-year time frame (over a 40-year period), it appears that the second half of the 1990s is marked by a downward trend in TSS. This shift is due to the control infrastructures (river impoundments and ponds) installed in certain parts of the whole catchment, combined with a drop in annual rainfall and river discharge.Editor Z.W. Kundzewicz; Associate editor not assigned [ABSTRACT FROM PUBLISHER]

Research into the magnitude of fluvial transport was carried out in the non-glacierised polar Dynamisk Bekken catchment in the region of Petunia Bukta, in the central part of West Spitsbergen. The study period included two ablation seasons ( July- August) in 2008 and 2009. The stream flows from the glacial cirque cutting the north-western edge of the Wordiekammen Massif. The bedrock is composed of sedimentary rocks. The Dynamisk Bekken is periodic stream, mainly fed from snow cover from June to early September. The other components of the feeding in the ablation seasons are less effective precipitation and groundwater from the active layer of permafrost. Medium discharge was 27.4 dm3 s-1 ranging from 0.1 to 250.8 dm3 s-1. Average ionic composition of the water indicates the hydrogeochemical sulphate-bicarbonate-calcium type. A tendency of systematic increase in the proportion of sulphates and decreasing share of bicarbonate ions in the ionic composition of water during the ablation season was observed. This correlates with the gradual decrease in the discharge rate and the decrease of the meltwater in the stream feed. The proportion of geogenic components in the dissolved load material outflow from the catchment is 75%. It consists of mainly bicarbonates, sulphates and calcium, which are derived from the dissolving of limestone, gypsum and anhydrite. The average value of the chemical denudation was 0.35 t km-2 d-1 and the mechanical denudation 0.32 t km-2 d-1. The results are similar to those obtained in previous years, reflecting the relatively large stability of the polar environment. [ABSTRACT FROM AUTHOR]

Abstract: A series of investigations of water and sediment discharge from the glacierized Ebba River catchment (53km2, located in the Billefjorden area in the central part of Spitsbergen) was carried out during the ablation seasons of 2008–2010. The study included hydrometric measurements at the catchment closing profile, identification of meteorological factors, and specification of the suspended and dissolved sediment load and of the water's chemical composition. The study evidenced a typical water regime for proglacial rivers, as well as its diversification in subsequent ablation seasons being determined mainly by thermal conditions. Moreover, during the study, the chemical (1tkm −2 d −1) and mechanical denudation (2.7tkm −2 d −1) indices were calculated. These rates documented the independent nature of the water supply system and the water and matter dynamics of the glacierized catchment. [Copyright &y& Elsevier]

A unique data set of suspended sediment transport from the Breelva, which drains the Werenskioldbreen (Southwestern Spitsbergen), is reported for the period 2007–2012. This basin is thoroughly described hydrologically, glaciologically, and chemically. However, until now there was a lack of full recognition of mechanical denudation. This study extends the information on quantitative suspended sediment load (SSL), amounting to 37.30–130.94 kt per year, and also underlines the importance of its modification by high discharge events, triggered by intense snowmelt or heavy rainfall. The large floods during the hydrologically active season transported even 83% of the total SSL. The variability of the SSL is controlled by glacial storage and release mechanisms. Particularly interesting is the second half of the hydrologically active season when intense rainfall events plays a key role in shaping the sediment supply pattern. The main source of fine mineral matter is the basal moraine, drained by subglacial outflows. Their higher mobilization occurs when the hydrostatic pressure increases, often as a result of rainwater supply to the glacier system. An increasing precipitation trend for Hornsund fjord region determines a positive trend predicted for sediment flux. [ABSTRACT FROM AUTHOR]