Annual production of fish larvae and their prey in relation to size-fractionated primary production (Scotian Shelf, NW Atlantic)   总被引：4，自引：0，他引：4  

Mousseau  Laure; Fortier  Louis; Legendre  Louis 《ICES Journal of Marine Science》1998,55(1):44-57

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Proglacial sediment dynamics from daily to seasonal scales in a glaciated Alpine catchment (Bossons glacier,Mont Blanc massif,France)          下载免费PDF全文

Hervé Guillon  Jean‐Louis Mugnier  Jean‐François Buoncristiani 《地球表面变化过程与地形》2018,43(7):1478-1495

The sediment yields of Alpine catchments are commonly determined from streamload measurements made some distance downstream from glaciers. However, this approach indiscriminately integrates erosion processes occurring in both the glacial and proglacial areas. A specific method is required to ascertain the respective inputs from (i) subglacial and supraglacial sediments, (ii) proglacial hillslopes and (iii) proglacial alluvial areas or sandurs. This issue is addressed here by combining high‐resolution monitoring (2 min) of suspended sediment concentrations at different locations within a catchment with discharge gauging and precipitation data. This methodological framework is applied to two proglacial streams draining the Bossons glacier (Mont Blanc massif, France): the Bossons and Crosette streams. For the Bossons stream, discharge and suspended load data were acquired from June to October 2013 at 1.15 and 1.5 km from the glacial terminus, respectively upstream and downstream from a small valley sandur. These hydro‐sedimentary data are compared with the Crosette stream dataset acquired at the outlet of the Bossons glacier subglacial drainage system. A fourfold analysis focusing on seasonal changes in streamload and discharge, multilinear regression modelling, evaluation of the sandur flux balance and probabilistic uncertainty assessment is used to determine the catchment sediment budget and to explain the proglacial sediment dynamics. The seasonal fluctuation of the sediment signal observed is related to the gradual closing of the subglacial drainage network and to the role of the proglacial area in the sediment cascade: the proglacial hillslopes appear to be disconnected from the main channel and the valley sandur acts as a hydrodynamic sediment buffer both daily and seasonally. Our findings show that an understanding of proglacial sediment dynamics can help in evaluating paraglacial adjustment and subglacial erosion processes. Copyright © 2017 John Wiley & Sons, Ltd.  相似文献   

Hydrological resilience to forest fire in the subarctic Canadian shield     

Christopher Spence  Newell Hedstrom  Suzanne E. Tank  William L. Quinton  David Olefeldt  Stefan Goodman  Nicole Dion 《水文研究》2020,34(25):4940-4958

Understanding the role of forest fires on water budgets of subarctic Precambrian Shield catchments is important because of growing evidence that fire activity is increasing. Most research has focused on assessing impacts on individual landscape units, so it is unclear how changes manifest at the catchment scale enough to alter water budgets. The objective of this study was to determine the water budget impact of a forest fire that partially burned a ~450 km² subarctic Precambrian Shield basin. Water budget components were measured in a pair of catchments: one burnt and another unburnt. Burnt and unburnt areas had comparable net radiation, but thaw was deeper in burned areas. There were deeper snow packs in burns. Differences in streamflow between the catchments were within measurement uncertainty. Enhanced winter streamflow from the burned watershed was evident by icing growth at the streamflow gauge location, which was not observed in the unburned catchment. Wintertime water chemistry was also clearly elevated in dissolved organics, and organic-associated nutrients. Application of a framework to assess hydrological resilience of watersheds to wildfire reveal that watersheds with both high bedrock and open water fractions are more resilient to hydrological change after fire in the subarctic shield, and resilience decreases with increasingly climatically wet conditions. This suggests significant changes in runoff magnitude, timing and water chemistry of many Shield catchments following wildfire depend on pre-fire land cover distribution, the extent of the wildfire and climatic conditions that follow the fire.  相似文献   

Active tectonics,seismicity and geomorphology with special reference to Normandy (France)     

Jean‐Louis Lagarde  Stphane Baize  Daniel Amorese  Bernard Delcaillau  Marianne Font  Philippe Volant 《第四纪科学杂志》2000,15(7):745-758

Integrated studies based on tectonic, seismotectonic and geomorphological analyses indicate that Normandy (northwest France) has been an active area during the Quaternary. Topography and landform discontinuities reflect the dislocation and differential uplift of a late Cenozoic platform. The tectonic activity is represented by (i) active faults, indicated by linear scarps and seismic activity, (ii) offsetting of pre‐existing surfaces, (iii) Plio‐Pleistocene sedimentation restricted within narrow subsiding zones, and (iv) morphometric properties of drainage basins that indicate zones of differential uplift. The inferred strain pattern involves (i) a shortening direction that strikes NW–SE as expected in the European context of Alpine compression, and (ii) a NE–SW trending extension accommodated by NW–SE normal faults. The geomorphological systems encountered in Normandy preferentially record differential vertical displacements. Copyright © 2000 John Wiley & Sons, Ltd.  相似文献