The formation of supraglacial debris covers by primary dispersal from transverse englacial debris bands     

Martin P. Kirkbride  Philip Deline 《地球表面变化过程与地形》2013,38(15):1779-1792

Glaciological controls on debris cover formation are investigated from the perspective of primary dispersal of supraglacial debris across a melting ice surface. This involves the migration of angled debris septa outcrops across a melting, thinning glacier ablation zone. Three measures of a glacier's ability to evacuate supraglacial debris are outlined: (1) a concentration factor describing the focusing of englacial debris into specific supraglacial mass loads; (2) the rate of migration of a septum outcrop relative to the local ice surface; and (3) a downstream velocity differential between a slower septum outcrop and the faster ice surface velocity. Measures (1) and (2) are inversely related, while measure (3) increases down‐glacier to explain why slow‐moving, thinning ice rapidly becomes debris covered. Data from Glacier d'Estelette (Italian Alps) are used to illustrate these processes, and to explore the potential for debris cover formation and growth in different glaciological environments. The transition from a ‘clean’, transport‐dominated to a debris‐covered ablation‐dominated glacier is explained by the melting out of more closely‐spaced debris septa, in combination with the geometric interactions of angled septa and ice surface in a field of reducing flow and increasing ablation. The growth and shrinkage of debris covers are most sensitive to glaciological changes at glaciers with gently‐dipping debris‐bearing foliation, but less sensitive at high‐compression glaciers whose termini are constrained by moraine dams and other forms of obstruction. These findings show that a variety of debris‐covered glacier types will show a spectrum of response characteristics to negative mass balance. Copyright © 2013 John Wiley & Sons, Ltd.  相似文献   

The Channel ecosystem,a cross-roads of anthropogenic pressures and scientific studies: Lessons learned from the European INTERREG IV projects (2009–2015)     

《Marine Policy》2016

The English Channel hosts a high density of human activities, which result in strong pressures and impacts on its marine ecosystem. The European Union's INTERREG programme funds projects to promote sustainable development through ecosystem-based management and the development of socio-economic services in the Channel region. An analysis of the themes studied during INTERREG IVA projects to date reveals both gaps that should be addressed in the future, as well as good practices that should be maintained and promoted. This analysis was used to provide advice and recommendations on knowledge gaps which may form the foundation of future projects for European programmes such as those in the next INTERREG project call (2015–2020).  相似文献   

Global air-sea surface carbon-dioxide transfer velocity and flux estimated using ERS-2 data and a new parametric formula   总被引：1，自引：1，他引：0  

YU Tan  HE Yijun  ZHA Guozhen  SONG Jinbao  LIU Guoqiang  GUO Jie 《海洋学报(英文版)》2013,32(7):78-87

Using data from the European remote sensing scatterometer（ERS-2） from July 1997 to August 1998,global distributions of the air-sea CO₂ transfer velocity and flux are retrieved.A new model of the air-sea CO₂ transfer velocity with surface wind speed and wave steepness is proposed.The wave steepness（5） is retrieved using a neural network（NN） model from ERS-2 scatterometer data,while the wind speed is directly derived by the ERS-2 scatterometer.The new model agrees well with the formulations based on the wind speed and the variation in the wind speed dependent relationships presented in many previous studies can be explained by this proposed relation with variation in wave steepness effect.Seasonally global maps of gas transfer velocity and llux are shown on the basis of the new model and the seasonal variations of the transfer velocity and llux during the 1 a period.The global mean gas transfer velocity is 30 cm/h after area-weighting and Schmidt number correction and its accuracy remains calculation with in situ data.The highest transfer velocity occurs around 60°N and 60°S,while the lowest on the equator.The total air to sea CO₂ llux（calculated by carbon） in that year is 1.77 Pg.The strongest source of CO₂ is in the equatorial east Pacific Ocean, while the strongest sink is in the 68°N.Full exploration of the uncertainty of this estimate awaits further data.An effectual method is provided to calculate the effect of waves on the determination of air-sea CO₂ transfer velocity and fluxes with ERS-2 scatterometer data.  相似文献   

Accelerated sediment delivery to continental margins during post-orogenic rebound of mountain ranges     

Thomas Bernard  Hugh D. Sinclair 《Basin Research》2023,35(2):642-661

Changes in sediment flux to continental margins are commonly interpreted in terms of tectonic growth of topography or climatic change. Here, we show that variations in sediment yield from orogenic systems, previously considered as resulting from climate change, drainage reorganisation or mantle processes can be explained by intrinsic mechanisms of mountain belt/foreland basin systems naturally evolving during post-orogenic decay. Numerical modelling indicates an increase of sediment flux leaving the orogenic system synchronous with the cessation of deposition in the foreland basin and the transition from late syn- to post-orogenesis. Experiments highlight the importance of lithospheric flexure that causes the post-orogenic isostatic rebound of the foreland basin. Erosion of the rebounding foreland basin combined with continued sediment flux from the thrust wedge drives an acceleration in sediment outflux towards continental margins. Sediment budget records in natural settings such as the Northern Pyrenees or Western European Alps also indicate accelerated post-orogenic sediment delivery to the Bay of Biscay and Rhône Delta respectively. These intrinsic processes that determine sediment yield to continental margins must be accounted for prior to consideration of additional external tectonic or climatic controls.  相似文献