Reference hydrologic networks II: using reference hydrologic networks to assess climate-driven changes in streamflow

Reference hydrologic networks (RHNs) can play an important role in monitoring for changes in the hydrological regime related to climate variation and change. Currently, the literature concerning hydrological response to climate variations is complex and confounded by the combinations of many methods of analysis, wide variations in hydrology, and the inclusion of data series that include changes in land use, storage regulation and water use in addition to those of climate. Three case studies that illustrate a variety of approaches to the analysis of data from RHNs are presented and used, together with a summary of studies from the literature, to develop approaches for the investigation of changes in the hydrological regime at a continental or global scale, particularly for international comparison. We present recommendations for an analysis framework and the next steps to advance such an initiative. There is a particular focus on the desirability of establishing standardized procedures and methodologies for both the creation of new national RHNs and the systematic analysis of data derived from a collection of RHNs

Reference hydrologic networks I: the status and potential future directions of national reference hydrologic networks for detecting trends

Identifying climate-driven trends in river flows on a global basis is hampered by a lack of long, quality time series data for rivers with relatively undisturbed regimes. This is a global problem compounded by the lack of support for essential long-term monitoring. Experience demonstrates that, with clear strategic objectives, and the support of sponsoring organizations, reference hydrologic networks can constitute an exceptionally valuable data source to effectively identify, quantify and interpret hydrological change—the speed and magnitude of which is expected to a be a primary driver of water management and flood alleviation strategies through the future—and for additional applications. Reference hydrologic networks have been developed in many countries in the past few decades. These collections of streamflow gauging stations, that are maintained and operated with the intention of observing how the hydrology of watersheds responds to variations in climate, are described. The status of networks under development is summarized. We suggest a plan of actions to make more effective use of this collection of networks

Late Pleistocene prey mobility in southwestern France and its implications for reconstructing Neandertal ranging behaviors

We thank Sarah Barakat for consultation. We also thank Jenni Henecke, Jen Everhart, Carol Lee, Charisse Carver, and Hope Williams for assistance with 87Sr/86Sr sample preparation. Access to the Metal Geochemistry Center at Yale University was kindly granted by Noah Planavsky, and Dan Asael assisted with 87Sr/86Sr measurement there. Jiuyuan Wang provided important advice on 87Sr/86Sr data correction, and Alice Knaf shared insights into sample elution. We would also like to thank Curtis Marean, Kim Hill, David Strait, Caley Orr, and Ben Schoville for advice and comments on the manuscript. Two anonymous reviewers provided helpful comments that improved the quality of the manuscript. Finally, we thank the late Harold Dibble for access to the Roc de Marsal collections. CRediT authorship contribution statement Jamie Hodgkins: Conceptualization, Data curation, Formal analysis, Funding acquisition, Investigation, Methodology, Project administration, Writing – original draft, Writing – review & editing. Alex Bertacchi: Formal analysis, Methodology, Visualization, Writing – review & editing. Kelly J. Knudson: Conceptualization, Methodology, Writing – review & editing. Troy Rasbury: Conceptualization, Methodology, Writing – review & editing. Julia I. Giblin: Methodology, Resources. Gwyneth Gordon: Conceptualization, Methodology, Writing – review & editing. Ariel Anbar: Resources. Alain Turq: Resources. Dennis Sandgathe: Resources, Writing – review & editing. Hannah M. Keller: Visualization, Writing – review & editing. Kate Britton: Conceptualization, Methodology, Writing – review & editing. Shannon P. McPherron: Conceptualization, Methodology, Writing – review & editing.Peer reviewe

Climate-driven variability in the occurrence of major floods across North America and Europe

Concern over the potential impact of anthropogenic climate change on flooding has led to a proliferation of studies examining past flood trends. Many studies have analysed annual-maximum flow trends but few have quantified changes in major (25–100 year return period) floods, i.e. those that have the greatest societal impacts. Existing major-flood studies used a limited number of very large catchments affected to varying degrees by alterations such as reservoirs and urbanisation. In the current study, trends in major-flood occurrence from 1961 to 2010 and from 1931 to 2010 were assessed using a very large dataset (>1200 gauges) of diverse catchments from North America and Europe; only minimally altered catchments were used, to focus on climate-driven changes rather than changes due to catchment alterations. Trend testing of major floods was based on counting the number of exceedances of a given flood threshold within a group of gauges. Evidence for significant trends varied between groups of gauges that were defined by catchment size, location, climate, flood threshold and period of record, indicating that generalizations about flood trends across large domains or a diversity of catchment types are ungrounded. Overall, the number of significant trends in major-flood occurrence across North America and Europe was approximately the number expected due to chance alone. Changes over time in the occurrence of major floods were dominated by multidecadal variability rather than by long-term trends. There were more than three times as many significant relationships between major-flood occurrence and the Atlantic Multidecadal Oscillation than significant long-term trends

Climate driven trends in historical extreme low streamflows on four continents

Understanding temporal trends in low streamflows is important for water management and ecosystems. This work focuses on trends in the occurrence rate of extreme low-flow events (5- to 100-year return periods) for pooled groups of stations. We use data from 1,184 minimally altered catchments in Europe, North and South America, and Australia to discern historical climate-driven trends in extreme low flows (1976–2015 and 1946–2015). The understanding of low streamflows is complicated by different hydrological regimes in cold, transitional, and warm regions. We use a novel classification to define low-flow regimes using air temperature and monthly low-flow frequency. Trends in the annual occurrence rate of extreme low-flow events (proportion of pooled stations each year) were assessed for each regime. Most regimes on multiple continents did not have significant (p < 0.05) trends in the occurrence rate of extreme low streamflows from 1976 to 2015; however, occurrence rates for the cold-season low-flow regime in North America were found to be significantly decreasing for low return-period events. In contrast, there were statistically significant increases for this period in warm regions of NA which were associated with the variation in the Pacific Decadal Oscillation. Significant decreases in extreme low-flow occurrence rates were dominant from 1946 to 2015 in Europe and NA for both cold- and warm-season low-flow regimes; there were also some non-significant trends. The difference in the results between the shorter (40-year) and longer (70-year) records and between low-flow regimes highlights the complexities of low-flow response to changing climatic conditions

An infant burial from Arma Veirana in northwestern Italy provides insights into funerary practices and female personhood in early Mesolithic Europe

The evolution and development of human mortuary behaviors is of enormous cultural significance. Here we report a richly-decorated young infant burial (AVH-1) from Arma Veirana (Liguria, northwestern Italy) that is directly dated to 10,211–9910 cal BP (95.4% probability), placing it within the early Holocene and therefore attributable to the early Mesolithic, a cultural period from which well-documented burials are exceedingly rare. Virtual dental histology, proteomics, and aDNA indicate that the infant was a 40–50 days old female. Associated artifacts indicate significant material and emotional investment in the child’s interment. The detailed biological profile of AVH-1 establishes the child as the earliest European near-neonate documented to be female. The Arma Veirana burial thus provides insight into sex/gender-based social status, funerary treatment, and the attribution of personhood to the youngest individuals among prehistoric hunter-gatherer groups and adds substantially to the scant data on mortuary practices from an important period in prehistory shortly following the end of the last Ice Age

Changing climate both increases and decreases European river floods

Climate change has led to concerns about increasing river floods resulting from the greater water-holding capacity of a warmer atmosphere. These concerns are reinforced by evidence of increasing economic losses associated with flooding in many parts of the world, including Europe. Any changes in river floods would have lasting implications for the design of flood protection measures and flood risk zoning. However, existing studies have been unable to identify a consistent continental-scale climatic-change signal in flood discharge observations in Europe, because of the limited spatial coverage and number of hydrometric stations. Here we demonstrate clear regional patterns of both increases and decreases in observed river flood discharges in the past five decades in Europe, which are manifestations of a changing climate. Our results—arising from the most complete database of European flooding so far—suggest that: increasing autumn and winter rainfall has resulted in increasing floods in northwestern Europe; decreasing precipitation and increasing evaporation have led to decreasing floods in medium and large catchments in southern Europe; and decreasing snow cover and snowmelt, resulting from warmer temperatures, have led to decreasing floods in eastern Europe. Regional flood discharge trends in Europe range from an increase of about 11 per cent per decade to a decrease of 23 per cent. Notwithstanding the spatial and temporal heterogeneity of the observational record, the flood changes identified here are broadly consistent with climate model projections for the next century, suggesting that climate-driven changes are already happening and supporting calls for the consideration of climate change in flood risk management

Identifying the accumulator: Making the most of bone surface modification data

Taphonomic analysis is an essential component of zooarchaeology, but is employed in different ways within different research traditions. Within the Africanist Palaeolithic literature, there is a strong emphasis on quantitative comparison of proportions of different bone surface modifications to one another and to proportions observed on modern experimental collections. This work has been driven by debates about the taphonomic histories of Oldowan sites that document the subsistence strategies of early Homo, but this specific approach can be usefully applied to a range of contexts across many different time periods and geographic locations. One obstacle to the cross-fertilization of this taphonomic tradition with other zooarchaeological work is the restrictive manner in which data are selected from an assemblage for analysis. To ensure comparability between fossil and modern assemblages, analysts typically exclude specimens with evidence for post-depositional modification not modeled in the experimental data. Although this adds interpretive robustness, it can diminish sample size significantly, sometimes to the point of affecting statistical analyses, and results in much time invested in collecting data that ultimately are not used. Here, we describe a new method for maximizing the number of specimens that can be incorporated into analysis, thus resolving the persistent problem of poor sample sizes to make more statistically robust comparisons to actualistic datasets

Climate-mediated shifts in Neandertal subsistence behaviors at Pech de l’Azé IV and Roc de Marsal (Dordogne Valley, France)

International audienc

Climate-mediated shifts in Neandertal subsistence behaviors at Pech de l’Azé IV and Roc de Marsal (Dordogne Valley, France)

International audienc