Now showing 1 - 6 of 6
  • Publication
    Dynamic Clusters to Infer Topologic Controls on Environmental Transport of River Networks
    ( 2022) ;
    Juthika Roy
    ;
    Arvind Singh
    The knowledge of structural controls of river networks (RNs) on transport dynamics is important for modeling and predicting environmental fluxes. To investigate impacts of RN’s topology on transport processes, we introduce a systematic framework based on the concept of dynamic clusters, where the connectivity of subcatchments is assessed according to two complementary criteria: minimum- and maximum-flow connectivity. Our analysis from simple synthetic RNs and several natural river basins across the United States reveals the key topological features underlying the efficiency of flux transport and aggregation. Namely, the timing of basin-scale connectivity at low-flow conditions is controlled by the abundance of topologically asymmetric junctions (side-branching), which at the same time, result in a slow-down of the flux convergence at the outlet (maximum-flow). Our results, when compared with observed topological trends in RNs as a function of climate, indicate that humid basins exhibit topologies which are “naturally engineered” to slow-down fluxes.
      44  7
  • Publication
    Earthcasting: Geomorphic Forecasts for Society
    Over the last several decades, the study of Earth surface processes has progressed from a descriptive science to an increasingly quantitative one due to advances in theoretical, experimental, and computational geosciences. The importance of geomorphic forecasts has never been greater, as technological development and global climate change threaten to reshape the landscapes that support human societies and natural ecosystems. Here we explore best practices for developing socially relevant forecasts of Earth surface change, a goal we are calling “earthcasting”. We suggest that earthcasts have the following features: they focus on temporal (1–100years) and spatial (1m–10km) scales relevant to planning; they are designed with direct involvement of stakeholders and public beneficiaries through the evaluation of the socioeconomic impacts of geomorphic processes; and they generate forecasts that are clearly stated, testable, and include quantitative uncertainties. Earthcasts bridge the gap between Earth surface researchers and decision-makers, stakeholders, researchers from other disciplines, and the general public. We investigate the defining features of earthcasts and evaluate some specific examples. This paper builds on previous studies of prediction in geomorphology by recommending a roadmap for (a) generating earthcasts, especially those based on modeling; (b) transforming a subset of geomorphic research into earthcasts; and (c) communicating earthcasts beyond the geomorphology research community. Earthcasting exemplifies the social benefit of geomorphology research, and it calls for renewed research efforts toward further understanding the limits of predictability of Earth surface systems and processes, and the uncertainties associated with modeling geomorphic processes and their impacts.
      52  3
  • Publication
    Unique superdiffusion induced by directionality in multiplex networks
    The multilayer network framework has served to describe and uncover a number of novel and unforeseen physical behaviors and regimes in interacting complex systems. However, the majority of existing studies are built on undirected multilayer networks while most complex systems in nature exhibit directed interactions. Here, we propose a framework to analyze diffusive dynamics on multilayer networks consisting of at least one directed layer. We rigorously demonstrate that directionality in multilayer networks can fundamentally change the behavior of diffusive dynamics: from monotonic (in undirected systems) to non-monotonic diffusion with respect to the interlayer coupling strength. Moreover, for certain multilayer network configurations, the directionality can induce a unique superdiffusion regime for intermediate values of the interlayer coupling, wherein the diffusion is even faster than that corresponding to the theoretical limit for undirected systems, i.e. the diffusion in the integrated network obtained from the aggregation of each layer. We theoretically and numerically show that the existence of superdiffusion is fully determined by the directionality of each layer and the topological overlap between layers. We further provide a formulation of multilayer networks displaying superdiffusion. Our results highlight the significance of incorporating the interacting directionality in multilevel networked systems and provide a framework to
      375  2Scopus© Citations 2
  • Publication
    Climate Signatures on Lake And Wetland Size Distributions in Arctic Deltas
    Lake areas in arctic deltas exhibit a lognormal distribution associated with a simple mechanistic growth process. 2. Wetland areas exhibit a power law distribution consistent with inundated topography. 3. Colder arctic deltas have larger average lake sizes, likely due to thicker permafrost restricting sub-lake hydrologic connectivity.
      15  3Scopus© Citations 1
  • Publication
    Evolution and transformation of early modern cosmological knowledge: a network study
    We investigated the evolution and transformation of scientifc knowledge in the early modern period, analyzing more than 350 diferent editions of textbooks used for teaching astronomy in European universities from the late ffteenth century to mid-seventeenth century. These historical sources constitute the Sphaera Corpus. By examining diferent semantic relations among individual parts of each edition on record, we built a multiplex network consisting of six layers, as well as the aggregated network built from the superposition of all the layers. The network analysis reveals the emergence of fve diferent communities. The contribution of each layer in shaping the communities and the properties of each community are studied. The most infuential books in the corpus are found by calculating the average age of all the out-going and in-coming links for each book. A small group of editions is identifed as a transmitter of knowledge as they bridge past knowledge to the future through a long temporal interval. Our analysis, moreover, identifes the most impactful editions. These books introduce new knowledge that is then adopted by almost all the books published afterwards until the end of the whole period of study. The historical research on the content of the identifed books, as an empirical test, fnally corroborates the results of all our analyses.
    Scopus© Citations 6  550  14
  • Publication
    Channel Network Control on Seasonal Lake Area Dynamics in Arctic Deltas
    The abundant lakes dotting arctic deltas are hotspots of methane emissions and biogeochemical activity, but seasonal variability in lake extents introduces uncertainty in estimates of lacustrine carbon emissions, typically performed at annual or longer time scales. To characterize variability in lake extents, we analyzed summertime lake area loss (i.e., shrinkage) on two deltas over the past 20 years, using Landsat-derived water masks. We find that monthly shrinkage rates have a pronounced structured variability around the channel network with the shrinkage rate systematically decreasing farther away from the channels. This pattern of shrinkage is predominantly attributed to a deeper active layer enhancing near-surface connectivity and storage and greater vegetation density closer to the channels leading to increased evapotranspiration rates. This shrinkage signal, easily extracted from remote sensing observations, may offer the means to constrain estimates of lacustrine methane emissions and to develop process-based estimates of depth to permafrost on arctic deltas.
    Scopus© Citations 2  602  3