Waliur Rahaman

Bio: Waliur Rahaman is an academic researcher from Physical Research Laboratory. The author has contributed to research in topics: Geology & Geochemistry. The author has an hindex of 12, co-authored 28 publications receiving 472 citations. Previous affiliations of Waliur Rahaman include Esso & National Centre for Antarctic and Ocean Research.

Climate control on erosion distribution over the Himalaya during the past ~100 ka

Abstract: Sediment samples from a 50-m-long core representing ~100 ka of deposition, taken from the Ganga Plain on the campus of the Indian Institute of Technology, Kanpur, were analyzed for Sr and Nd isotope compositions. Both 87 Sr/ 86 Sr and ϵ Nd vary significantly with depth in the core, 0.72701–0.76708 and −14.4 to −16.6, respectively, within the range for silicate rocks of the Higher and the Lesser Himalaya. The variations in the isotope compositions reflect variations in the mixing proportion of sediments from the Higher and Lesser Himalaya, the two major sediment sources to the Ganga. The opposite trends in 87 Sr/ 86 Sr and ϵ Nd depth profiles further confirm this hypothesis. The isotope profiles exhibit two major excursions, ca. 20 ka and ca. 70 ka ago, coinciding with periods of precipitation minima and larger glacial cover. These excursions are the result of a decrease in the proportion of sediment from the Higher Himalaya due to a decrease in monsoon precipitation and an increase in glacial cover that are in turn caused by lower solar insolation. This study highlights the significant influence of climate on erosion in the Himalaya.

Piecing together the Ganges-Brahmaputra-Meghna River delta: Use of sediment provenance to reconstruct the history and interaction of multiple fluvial systems during Holocene delta evolution

Abstract: Three main rivers—the Ganges, Brahmaputra, and Meghna—coalesce in the Bengal basin to form the world’s largest delta system, which serves as filter and gateway between the Himalayan collision and vast Bengal fan repository. New insights into the Holocene construction of the Ganges-Brahmaputra-Meghna delta, with a focus on river sedimentation, channel migration, and avulsion history, are presented here using the Sr geochemistry of bulk sediments as a provenance tracer. The sediment load of each river transmits a distinct Sr signature owing to differences in source rocks from the Himalaya, Tibet, and local regions, allowing for effective tracking of river channels and stratigraphic development within the delta. In the early Holocene, vigorous delta aggradation occurred under rapid sea-level rise and high river discharge and supported the construction of sand-dominated stratigraphy by laterally mobile, braided-stream channels. However, the vertically (i.e., temporally) uniform, but geographically distinct, Sr signatures from these deposits indicate that the Ganges, Brahmaputra, and Meghna fluvial systems remained isolated from one another and apparently constrained within their lowstand valleys. By the mid-Holocene, though, delta stratigraphy records spatially and temporally nonuniform Sr signatures that hallmark the onset of avulsions and unconstrained channel migration, like those that characterize the modern Ganges and Brahmaputra fluvial systems. Such mobility developed in the mid-Holocene despite declining discharge and sea-level rise, suggesting that earlier channel behavior had been strongly influenced by antecedent topography of the lowstand valleys. It is only after the delta had aggraded above the valley margins that the fluvial systems were able to avulse freely, resulting in numerous channel reorganizations from mid-Holocene to present. These channel-system behaviors and their role in delta evolution remain coarsely defined based only on this initial application of Sr-based provenance tools, but the approach is promising and suggests that a more complete understanding can be achieved with continued study.

The Dominant Role of Extreme Precipitation Events in Antarctic Snowfall Variability

Abstract: Antarctic snowfall consists of frequent clear-sky precipitation and heavier falls from intrusions of maritime airmasses associated with amplified planetary waves. We investigate the importance of different precipitation events using the output of the RACMO2 model. Extreme precipitation events consisting of the largest 10% of daily totals are shown to contribute more than 40% of the total annual precipitation across much of the continent, with some areas receiving in excess of 60% of the total from these events. The greatest contribution of extreme precipitation events to the annual total is in the coastal areas and especially on the ice shelves, with the Amery Ice Shelf receiving 50% of its annual precipitation in less than the 10 days of heaviest precipitation. For the continent as a whole, 70% of the variance of the annual precipitation is explained by variability in precipitation from extreme precipitation events, with this figure rising to over 90% in some areas.

River Discharge to the Coastal Ocean: A Global Synthesis

Abstract: Foreword 1. Introduction 2. Runoff, erosion and delivery to the coastal ocean 3. Temporal variations 4. Human impacts Appendices. Global River Database: Appendix A: North and Central America Appendix B: South America Appendix C: Europe Appendix D: Africa Appendix E: Eurasia Appendix F: Asia Appendix G: Oceania References Index.

Atmospheric Science: An Introductory Survey

Abstract: John M Wallace and Peter V Hobbs London: Academic 1977 pp xvii + 467 price £12.80 This is a comprehensive textbook for undergraduate courses in atmospheric physics. It contains general physical meteorology (atmospheric hydrostatics, cloud physics, radioactive transfer and thermodynamics), some selected topics of special interest (aerosol physics, aeronomy and physical climatology) and dynamic meteorology describing and interpreting large scale atmospheric motions.

Environmental Chemistry of the Elements

Abstract: All chapters of the previous edition [see HbA 37, 2103] have been completely rewritten to cover the rapid increase in research in this area. The number of literature citations have been reduced by referring to recent review articles and the book aims at a comprehensive and critical rather than encyclopaedic summary of the data of environmental chemistry. The 1st 4 chapters deal with air, water, rocks and soils; the cycling of C, N, H, O2 and S in the biosphere are covered in 1 chapter and the elemental Other CABI sites 