Summary of newsletters 4 and 5 of the working committee for international collaboration in geomorphology     

H. Jesse Walker 《地球表面变化过程与地形》1989,14(5):457-458

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Sea Level change: Environmental and socio-economic impacts     

H. Jesse Walker 《GeoJournal》1992,26(4):511-520

The coast was among the first of the earth’s environments to be subjected to human modification; modification that was both direct and indirect, as it is today. During the last 4.000 to 5.000 years, human impacts on the coast were at what was basically a stable sea level. Because many of the modifications were made to protect against unusual events such as typhoons and tsunami, humans developed a variety of techniques for protecting shorelines. Recent calculations that a rapid sea level rise (in response to greenhouse warming) is imminent, has prompted concerned efforts at meeting the socio-economic impacts that are likely to occur. These impacts, rather than being localized and temporary as has been true in the recent past, are likely to be universal and long-lasting. This thought, penned by Blaise Pascal, was accompanied by an artistic interpretation by Corita Kent inNewsweek, June 14,1976, p. 87.  相似文献   

Sub‐Permil Interlaboratory Consistency for Solution‐Based Boron Isotope Analyses on Marine Carbonates     

Marcus Gutjahr  Louise Bordier  Eric Douville  Jesse Farmer  Gavin L. Foster  Ed C. Hathorne  Brbel Hnisch  Damien Lemarchand  Pascale Louvat  Malcolm McCulloch  Johanna Noireaux  Nicola Pallavicini  James W. B. Rae  Ilia Rodushkin  Philippe Roux  Joseph A. Stewart  Franois Thil  Chen‐Feng You 《Geostandards and Geoanalytical Research》2021,45(1):59-75

Boron isotopes in marine carbonates are increasingly used to reconstruct seawater pH and atmospheric pCO₂ through Earth’s history. While isotope ratio measurements from individual laboratories are often of high quality, it is important that records generated in different laboratories can equally be compared. Within this Boron Isotope Intercomparison Project (BIIP), we characterised the boron isotopic composition (commonly expressed in δ¹¹B) of two marine carbonates: Geological Survey of Japan carbonate reference materials JCp‐1 (coral Porites) and JCt‐1 (giant clam Tridacna gigas). Our study has three foci: (a) to assess the extent to which oxidative pre‐treatment, aimed at removing organic material from carbonate, can influence the resulting δ¹¹B; (b) to determine to what degree the chosen analytical approach may affect the resultant δ¹¹B; and (c) to provide well‐constrained consensus δ¹¹B values for JCp‐1 and JCt‐1. The resultant robust mean and associated robust standard deviation (s*) for un‐oxidised JCp‐1 is 24.36 ± 0.45‰ (2s*), compared with 24.25 ± 0.22‰ (2s*) for the same oxidised material. For un‐oxidised JCt‐1, respective compositions are 16.39 ± 0.60‰ (2s*; un‐oxidised) and 16.24 ± 0.38‰ (2s*; oxidised). The consistency between laboratories is generally better if carbonate powders were oxidatively cleaned prior to purification and measurement.  相似文献   

Imaging mantle transition zone thickness with SdS-SS finite-frequency sensitivity kernels     

Jesse F. Lawrence  Peter M. Shearer 《Geophysical Journal International》2008,174(1):143-158

We invert differential SdS-SS traveltime residuals measured from stacked waveforms and finite-frequency sensitivity kernels for topography on the 410- and 660-km discontinuities. This approach yields higher resolution images of transition zone thickness than previous stacking methods, which simply average/smooth over topographic features. Apparent structure measured using simple stacking is highly dependent upon the bin size of each stack. By inverting for discontinuity topography with a variety of bin sizes, we can more accurately calculate the true structure. The inverted transition zone model is similar to simple stack models with an average thickness of 242 km, but the lateral variations in thickness are larger in amplitude and smaller in scale. Fast seismic velocities in 3-D mantle models such as SB4L18 correlate with areas of thicker transition zone. The elongated curvilinear regions of thickened transition zone that occur near subduction zones are narrow and high amplitude, which suggests relatively little lateral spreading and warming of subducted lithosphere within the transition zone. The anomalously thin transition zone regions are laterally narrow, and not broadly continuous. If these variations in transition zone thickness are interpreted as thermal in nature, then this model suggests significant temperature variations on small lateral scales.  相似文献   

Long-Term Tsunami Data Archive Supports Tsunami Forecast, Warning, Research, and Mitigation     

Paula K. Dunbar  Kelly J. Stroker  Vanita R. Brocko  Jesse D. Varner  Susan J. McLean  Lisa A. Taylor  Barry W. Eakins  Kelly S. Carignan  Robin R. Warnken 《Pure and Applied Geophysics》2008,165(11-12):2275-2291

In response to the 2004 Indian Ocean tsunami, the United States began a careful review and strengthening of its programs aimed at reducing the consequences of tsunamis. Several reports and calls to action were drafted, including the Tsunami Warning and Education Act (Public Law 109–424) signed into law by the President in December 2006. NOAA’s National Geophysical Data Center (NGDC) and co-located World Data Center for Geophysics and Marine Geology (WDC-GMG) maintain a national and international tsunami data archive that fulfills part of the P.L. 109-424. The NGDC/WDC-GMG long-term tsunami data archive has expanded from the original global historical event databases and damage photo collection, to include tsunami deposits, coastal water-level data, DART? buoy data, and high-resolution coastal DEMs. These data are used to validate models, provide guidance to warning centers, develop tsunami hazard assessments, and educate the public about the risks from tsunamis. In this paper we discuss current steps and future actions to be taken by NGDC/WDC-GMG to support tsunami hazard mitigation research, to ultimately help save lives and improve the resiliency of coastal communities.  相似文献   

Modeling a Large-Scale Historic Aquifer Test: Insight into the Hydrogeology of a Regional Fault Zone     

Daniel R. Hadley  Daniel B. Abrams  George S. Roadcap 《Ground water》2020,58(3):453-463

Faults can act as flow barriers or conduits to groundwater flow by introducing heterogeneity in permeability. We examine the hydrogeology of the Sandwich Fault Zone, a 137 km long zone of high-angle faults in northern Illinois, using a large-scale historic aquifer test. The fault zone is poorly understood at depth due to the majority of the faults being buried by glacial deposits and its near-vertical orientation which limits geologic sampling across faults. The aquifer test—perhaps one of the largest in terms of overall withdrawal in North American history—was conducted in 1942 at a facility adjacent to the fault zone. More than 34,000 m³/day was pumped for 37 days from nine multiaquifer wells open to the stratified Cambrian-Ordovician sandstone aquifer system. We modeled the aquifer test using a transient MODFLOW-USG model and simulated pumping wells with the CLN package. We tested numerous fault core/damage zone conceptualizations and calibrated to drawdown values recorded at production and observation wells. Our analysis indicates that the fault zone is a low-permeability feature that inhibits lateral movement of groundwater and that there is at least an order of magnitude decrease in horizontal hydraulic conductivity in the fault core compared to the undeformed sandstone. Large head declines have occurred north of the fault zone (over 300 m since predevelopment conditions) and modifying fault zone parameters significantly affects calibration to regional drawdown on a decadal scale. The flow-barrier behavior of the fault zone has important implications for future groundwater availability in this highly stressed region.  相似文献   

Empirical observations and numerical modelling of tides,channel morphology,and vegetative effects on accretion in a restored tidal marsh     

Jesse R. Fleri  Sara Lera  Alessandro Gerevini  Lorie Staver  William Nardin 《地球表面变化过程与地形》2019,44(11):2223-2235

Tidal marshes form at the confluence between estuarine and marine environments where tidal movement regulates their developmental processes. Here, we investigate how the interplay between tides, channel morphology, and vegetation affect sediment dynamics in a low energy tidal marsh at the Paul S. Sarbanes Ecosystem Restoration Project at Poplar Island. Poplar Island is an active restoration site where fine-grained material dredged from navigation channels in the upper Chesapeake Bay are being used to restore remote tidal marsh habitat toward the middle bay (Maryland, USA). Tidal currents were measured over multiple tidal cycles in the inlets and tidal creeks of one marsh at Poplar Island, Cell 1B, using Acoustic Doppler Current Profilers (ADCP) to estimate water fluxes throughout the marsh complex. Sediment fluxes were estimated using acoustic backscatter recorded by ADCPs and validated against total suspended solid measurements taken on site. A high-resolution geomorphic survey was conducted to capture channel cross sections and tidal marsh morphology. We integrated simple numerical models built in Delft3d with empirical observations to identify which eco-geomorphological factors influence sediment distribution in various channel configurations with differing vegetative characteristics. Channel morphology influences flood-ebb dominance in marshes, where deep, narrow channels promote high tidal velocities and incision, increasing sediment suspension and reducing resilience in marshes at Poplar Island. Our numerical models suggest that accurately modelling plant phenology is vital for estimating sediment accretion rates. In-situ observations indicate that Poplar Island marshes are experiencing erosion typical for many Chesapeake Bay islands. Peak periods of sediment suspension frequently coincide with the largest outflows of water during ebb tides resulting in large sediment deficits. Ebb dominance (net sediment export) in tidal marshes is likely amplified by sea-level rise and may lower marsh resilience. We couple field observations with numerical models to understand how tidal marsh morphodynamics contribute to marsh resilience. © 2019 John Wiley & Sons, Ltd.  相似文献   

Accessibility to food retailers and socio‐economic deprivation in urban New Zealand     

Jesse Wiki  Simon Kingham  Malcolm Campbell 《New Zealand geographer》2019,75(1):3-11

The spatial locations of food retailers are considered to be an influential aspect of population consumption patterns. Such contextual relationships are often related to socio‐economic deprivation, with disparities in accessibility having important implications. This study used Geographic Information Systems and an Enhanced Two‐Step Floating Catchment Area model of spatial accessibility to further understand such relationships within urban areas of New Zealand. Findings, while mixed, indicate that there is generally increased accessibility to all food retailers in highly deprived areas. Understanding these socio–spatial relationships in local environments has important implications for policy initiatives, health outcomes and sustainable development.  相似文献   

Quantification of the seasonal hillslope water storage that does not drive streamflow          下载免费PDF全文

David N. Dralle  W. Jesse Hahm  Daniella M. Rempe  Nathaniel J. Karst  Sally E. Thompson  William E. Dietrich 《水文研究》2018,32(13):1978-1992

The relationship between seasonal catchment water storage and discharge is typically nonunique due to water storage that is not directly hydraulically connected to streams. Hydraulically disconnected water volumes are often ecologically and hydrologically important but cannot be explicitly estimated using current storage–discharge techniques. Here, we propose that discharge is explicitly sensitive to changes in only some fraction of seasonally dynamic storage that we call “direct storage,” whereas the remaining storage (“indirect storage”) varies without directly influencing discharge. We use a coupled mass balance and storage–discharge function approach to partition seasonally dynamic storage between these 2 pools in the Northern California Coast Ranges. We find that indirect storage constitutes the vast majority of dynamic catchment storage, even at the wettest times of the year. Indirect storage exhibits lower variability over the course of the wet season (and in successive winter periods) than does direct storage. Predicted indirect storage volumes and dynamics match field observations. Comparison of 2 neighbouring field sites reveals that indirect storage volumes can occur as unsaturated storage held under tension in soils and weathered bedrock and as near‐surface saturated storage that remains on hillslopes (and is eventually evapotranspired). Indirect storage volumes (including moisture in the weathered bedrock) may support plant transpiration, and our method indicates that this important water source could be quantified from precipitation and stream discharge records.  相似文献   

Tracking a Governance Transition: Identifying and Measuring Indicators of Social Forestry on the Willamette National Forest     

Jesse Abrams  Heidi Huber-Stearns  Hannah Gosnell  Anna Santo  Stacie Duffey  Cassandra Moseley 《社会与自然资源》2020,33(4):504-523

Abstract

National Forests in the United States have undergone a spatially and temporally uneven governance transition in response to social and economic pressures and contemporary policy changes, with many national forest units moving from a wholly government-led “dominant federal” model to a more collaborative “social forestry” model in which nonfederal actors have greater influence and authority. Here we report on an effort to develop a suite of indicators designed to capture some of the most tangible elements of a transition from dominant federal to social forestry modes of governance. We pilot test these data on the Willamette National Forest using data from a variety of sources internal and external to the USDA Forest Service. We assess the suitability of these indicators for tracking governance transitions and discuss their applicability to other national forest units nationwide.  相似文献