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At least 613 records · Page 34Linked to original sources
USGS2026

Large streamflow differences between forested and urbanized watersheds in the energy-limited eastern United States: The role of evapotranspiration and impervious surfaces

Urban forests and other green infrastructures have been viewed as part of the “Nature-based Solutions” (NbS) to mitigate emerging urban environmental change. This study focuses on the role of evapotranspiration (ET) in regulating water balances of small watersheds in the eastern United States. We compared streamflow and ET patterns at daily, monthly and annual scales and linked these hydrological variables to the physical properties of 11 paired watersheds dominated by forests (FW) or urban (UW) land covers. The annual precipitation ranged from 1028 mm to 1683 mm and potential ET (PET) from 815 mm to 1450 mm. The mean annual flow/precipitation (Q/P) ratios were 0.26 ± 0.13 and 0.41 ± 0.1 for FW and UW, respectively. Overall, UW had lower annual ET (772 mm in UW vs. 947 mm in FW), but higher mean annual and (∼58% higher), monthly water yield (17%–186% higher), and peakflow rates (up to 100 times higher) than FW. The streamflow differences between FW and UW were most pronounced during the growing season and early winter (June-November). The mean Q/P ratios for 30 large hurricane events (2016–2021) were 0.12 ± 0.11 and 0.38 ± 0.23 for FW and UW, respectively. The flow rates in the dormant season (around December-May) in UW were similar or lower than FW. We developed conceptual models to explain the seasonal and storm event streamflow differences using background climate (PET), ET, and land surface characteristics. Urban NbS designs should factor in strategies that maximize ET while minimizing impervious surfaces enhancing watershed “sponge” and “pump” functions.

eastern United States↗
USGS2017

A high-elevation, multi-proxy biotic and environmental record of MIS 6-4 from the Ziegler Reservoir fossil site, Snowmass Village, Colorado, USA

In North America, terrestrial records of biodiversity and climate change that span Marine Oxygen Isotope Stage (MIS) 5 are rare. Where found, they provide insight into how the coupling of the ocean–atmosphere system is manifested in biotic and environmental records and how the biosphere responds to climate change. In 2010–2011, construction at Ziegler Reservoir near Snowmass Village, Colorado (USA) revealed a nearly continuous, lacustrine/wetland sedimentary sequence that preserved evidence of past plant communities between ~ 140 and 55 ka, including all of MIS 5. At an elevation of 2705 m, the Ziegler Reservoir fossil site also contained thousands of well-preserved bones of late Pleistocene megafauna, including mastodons, mammoths, ground sloths, horses, camels, deer, bison, black bear, coyotes, and bighorn sheep. In addition, the site contained more than 26,000 bones from at least 30 species of small animals including salamanders, otters, muskrats, minks, rabbits, beavers, frogs, lizards, snakes, fish, and birds. The combination of macro- and micro-vertebrates, invertebrates, terrestrial and aquatic plant macrofossils, a detailed pollen record, and a robust, directly dated stratigraphic framework shows that high-elevation ecosystems in the Rocky Mountains of Colorado are climatically sensitive and varied dramatically throughout MIS 5.

Colorado↗
USGS2014

Temporal and spatial distributions of cold-water corals in the Drake Passage: insights from the last 35,000 years

Scleractinian corals have a global distribution ranging from shallow tropical seas to the depths of the Southern Ocean. Although this distribution is indicative of the corals having a tolerance to a wide spectrum of environmental conditions, individual species seem to be restricted to a much narrower range of ecosystem variables. One way to ascertain the tolerances of corals, with particular focus on the potential impacts of changing climate, is to reconstruct their growth history across a range of environmental regimes. This study examines the spatial and temporal distribution of the solitary scleractinian corals Desmophyllum dianthus, Gardineria antarctica, Balanophyllia malouinensis, Caryophyllia spp. and Flabellum spp. from five sites in the Drake Passage which cross the major frontal zones. A rapid reconnaissance radiocarbon method was used to date more than 850 individual corals. Coupled with U-Th dating, an age range of present day back to more than 100 thousand years was established for corals in the region. Within this age range there are distinct changes in the temporal and spatial distributions of these corals, both with depth and latitude, and on millennial timescales. Two major patterns that emerge are: (1) D. dianthus populations show clear variability in their occurrence through time depending on the latitudinal position within the Drake Passage. North of the Subantarctic Front, D. dianthus first appears in the late deglaciation (~17,000 years ago) and persists to today. South of the Polar Front, in contrast, early deglacial periods, with a few modern occurrences. A seamount site between the two fronts exhibits characteristics similar to both the northern and southern sites. This shift across the frontal zones within one species cannot yet be fully explained, but it is likely to be linked to changes in surface productivity, subsurface oxygen concentrations, and carbonate saturation state. (2) at locations where multiple genera were dated, differences in age and depth distribution of the populations provide clear evidence that each genus has unique environmental requirements to sustain its population.

Deep-Sea Research Part II: Topical Studies in Ocea↗
USGS2015

Fluvial-aeolian interactions in sediment routing and sedimentary signal buffering: an example from the Indus Basin and Thar Desert

Sediment production and its subsequent preservation in the marine stratigraphic record offshore of large rivers are linked by complex sediment-transfer systems. To interpret the stratigraphic record it is critical to understand how environmental signals transfer from sedimentary source regions to depositional sinks, and in particular to understand the role of buffering in obscuring climatic or tectonic signals. In dryland regions, signal buffering can include sediment cycling through linked fluvial and eolian systems. We investigate sediment-routing connectivity between the Indus River and the Thar Desert, where fluvial and eolian systems exchanged sediment over large spatial scales (hundreds of kilometers). Summer monsoon winds recycle sediment from the lower Indus River and delta northeastward, i.e., downwind and upstream, into the desert. Far-field eolian recycling of Indus sediment is important enough to control sediment provenance at the downwind end of the desert substantially, although the proportion of Indus sediment of various ages varies regionally within the desert; dune sands in the northwestern Thar Desert resemble the Late Holocene–Recent Indus delta, requiring short transport and reworking times. On smaller spatial scales (1–10 m) along fluvial channels in the northern Thar Desert, there is also stratigraphic evidence of fluvial and eolian sediment reworking from local rivers. In terms of sediment volume, we estimate that the Thar Desert could be a more substantial sedimentary store than all other known buffer regions in the Indus basin combined. Thus, since the mid-Holocene, when the desert expanded as the summer monsoon rainfall decreased, fluvial-eolian recycling has been an important but little recognized process buffering sediment flux to the ocean. Similar fluvial-eolian connectivity likely also affects sediment routing and signal transfer in other dryland regions globally.

Indus Basin, Thar Desert↗
USGS2022

Sensitivity of headwater streamflow to thawing permafrost and vegetation change in a warming Arctic

Climate change has the potential to impact headwater streams in the Arctic by thawing permafrost and subsequently altering hydrologic regimes and vegetation distribution, physiognomy and productivity. Permafrost thaw and increased subsurface flow have been inferred from the chemistry of large rivers, but there is limited empirical evidence of the impacts to headwater streams. Here we demonstrate how changing vegetation cover and soil thaw may alter headwater catchment hydrology using water budgets, stream discharge trends, and chemistry across a gradient of ground temperature in northwestern Alaska. Colder, tundra-dominated catchments shed precipitation through stream discharge, whereas in warmer catchments with greater forest extent, evapotranspiration and infiltration are substantial fluxes. Forest soils thaw earlier, remain thawed longer, and display seasonal water content declines, consistent with greater evapotranspiration and infiltration. Streambed infiltration and water chemistry indicate that even minor warming can lead to increased infiltration and subsurface flow. Additional warming, permafrost loss, and vegetation shifts in the Arctic will deliver water back to the atmosphere and to subsurface aquifers in many regions, with the potential to substantially reduce discharge in headwater streams, if not compensated by increasing precipitation. Decreasing discharge in headwater streamflow will have important implications for aquatic and riparian ecosystems.

Alaska↗
USGS2007

Effects of river discharge on abundance and instantaneous growth of age-0 carpsuckers in the Oconee River, Georgia, USA

The Oconee River in middle Georgia, U.S.A., has been regulated by the Sinclair Dam since 1953. Since then, the habitat of the lower Oconee River has been altered and the river has become more incised. The altered environmental conditions of the Oconee River may limit the success of various fish populations. Some obligate riverine fishes may be good indicator species for assessing river system integrity because they are intolerant to unfavourable conditions. For example, many sucker species require clean gravel for feeding and reproduction. Further, age-0 fishes are more vulnerable than adults to flow alterations because of their limited ability to react to such conditions. In this study, we investigated the relationship between abundance and growth of age-0 carpsuckers to river discharge in the Oconee River. A beach seine was used to collect age-0 carpsuckers (Carpiodes spp.) from littoral zones of the lower Oconee River from May through July of 1995 to 2001. Regression models were used to assess whether 12 river discharge categories (e.g. peak, low, seasonal flows) influenced age-0 carpsucker abundance or instantaneous growth. Our analysis indicated that abundance of age-0 carpsuckers was significantly negatively related to number of days river discharge was >85 m3 s-1(r2=0.61, p=0.04). Estimates of instantaneous growth ranged from 0.10 to 0.90. Instantaneous growth rates were significantly positively related to summer river discharge (r2=0.95, p<0.01). These results suggest that (1) moderate flows during spawning and rearing are important for producing strong-year classes of carpsuckers, and (2) river discharge is variable among years, with suitable flows for strong year-classes of carpsuckers occurring every few years. River management should attempt to regulate river discharge to simulate historic flows typical for the region when possible. Such an approach is best achieved when regional climatic conditions are considered.

River Research and Applications↗
USGS2026

Big data for small streams: Leveraging a coarse national model to enhance fine-resolution stream temperature predictions

Predictive stream temperature models are commonly used to address spatial and temporal gaps in observational data because stream temperature information is essential for environmental management decisions. National models capture broad patterns driven by climate, topography, and seasonality, but often lack the spatial resolution to simulate fine-scale variation in groundwater discharge, riparian shading, or tributary inflows. In contrast, watershed models may simulate finer-resolution patterns but miss regional drivers or be limited by scarcity of observations. To generate watershed-extent, fine-resolution stream temperature predictions, we developed 18 multiscale machine-learning models that leverage (a) a broad-extent, coarse-resolution stream temperature model and (b) finer-resolution observations and predictor data. The coarse-resolution model simulates daily stream temperature across the conterminous United States on the National Hydrologic Geospatial Fabric (13.7 km median reach length; 865,364 km total). The fine-resolution models simulate daily stream temperature on the National Hydrography Dataset Plus version 2 (1.5 km median; 5,192,808 km total). We compared multiscale models to seven purely broad- (national) or watershed-extent models, testing them in eight watersheds (436–985 km 2 ) with differing hydrologic settings and under realistic data availability scenarios. Especially when observations within a watershed were scarce, multiscale models generated more accurate predictions than national or watershed-specific models. A recurrent graph convolution neural network pretrained on coarse predictions and fine-tuned on watershed-specific observations was most accurate across watersheds and data scenarios. These results highlight that leveraging both coarse, national results and watershed-specific data can increase model accuracies, particularly when observations within a watershed are spatially or temporally limited.

Water Resources Research↗
USGS2018

Groundwater discharge characteristics for selected streams within the Loup River Basin, Nebraska, 2014–16

Streams in the Loup River Basin are sensitive to groundwater withdrawals because of the close hydrologic connection between groundwater and surface water. Groundwater discharge is the primary component of streamflow in the Loup River Basin and constitutes more than 90 percent of streamflow in the central part of the Sand Hills. To improve the understanding of geologic controls and various climatic and land-use changes on groundwater discharge, the U.S. Geological Survey (USGS), in cooperation with the Upper Loup Natural Resources District (NRD), the Lower Loup NRD, and the Nebraska Environmental Trust, studied the spatial and temporal characteristics of groundwater discharge within the Loup River Basin. This report documents the methods of data collection and analysis, which include the collection of approximately 350 river miles of aerial thermal infrared imagery and continuous groundwater-level and temperature data from six streamflow-gaging stations within the Loup River Basin. The results from the stream reconnaissance and examination of aerial thermal infrared imagery demonstrated the influence of the surficial and subsurface geology on the spatial characteristics of groundwater discharge to streams in the Loup River Basin. At the headwaters of the South Loup River, streamflow is sustained and increased from focused groundwater discharge emanating from Quaternary deposits at many small (less than 0.1 cubic foot per second) focused points. The volume of water produced from this dense network of focused groundwater discharge points along the North Fork South Loup River is sufficient to provide approximately 40 percent of the flow measured at the South Loup River at Arnold, Nebraska streamflow-gaging station (USGS station 06781600) during the irrigation season. Approximately 5 miles downstream from the South Loup River at Arnold, Nebr., streamflow-gaging station, the river incises into Pliocene-age sand and gravel deposits, which provide additional groundwater discharge to the stream. The streamflow of the South Loup River increases by a factor of 5 across a 62-mile reach of the middle South Loup River. Increases in streamflow along the upper Dismal River result from a dense network of focused groundwater discharge points within semiconsolidated Pliocene-age deposits. Below the Dismal River near Thedford, Nebr., streamflow-gaging station (USGS station 06775900), the Dismal River incises into the Ogallala Formation over a short reach before flowing over coarser, more permeable Quaternary-age alluvial deposits. Diffuse groundwater discharge sustains and increases the streamflow of the lower Dismal River in this reach. Groundwater sapping was evident on some stream reaches and has increased the size and flow of focused groundwater discharge points. Previous researchers have documented streambed incision and groundwater sapping on the upper Dismal River that have created and enlarged focused groundwater discharge points capturing additional groundwater. Similar processes appear to have played a role in the formation of larger focused groundwater discharge points, which sustain the flow of the middle South Loup River. The constant flow of groundwater into the South Loup River has removed finer-grained Quaternary sediments and further exposed Pliocene-age gravel deposits. Headward erosion is evident where some of the large focused groundwater discharge points have incised their own draws and terminate in bowl-like depressions away from the stream. Within the Loup River NRDs, the percentage of groundwater-irrigated land in a stream basin is one factor that affects groundwater discharge to streams. A striking example was at the South Loup River at Saint Michael, Nebr., groundwater and streamflow-gaging station (USGS station 06784000) where the shallow groundwater levels declined below the level of the stream during the middle to late part of the growing season (July to September) when consumptive groundwater use was at its peak. The South Loup River Basin above the South Loup River at Saint Michael, Nebr., streamflow-gaging station has the highest percentage of groundwater-irrigated row crops of all the basins examined in this study. Continuous groundwater and surface-water levels measured at the North Loup River at the Taylor, Nebr., streamflow-gaging station (USGS station 06786000) indicate that the stream is receiving groundwater throughout the year; however, when consumptive groundwater use peaks during the middle to late part of the growing season (July to September), the difference in elevation between the groundwater level and the stream elevation decreases, which indicates a reduction in the amount of groundwater discharge received.

Nebraska↗
USGS2021

Heed the data gap: Guidelines for using incomplete datasets in annual stream temperature analyses

Stream temperature data are useful for deciphering watershed processes important for aquatic ecosystems. Accurately extracting signal trends from stream temperature is essential for predicting responses of environmental and ecological indicators to change. Missing data periods are common for various reasons, and pose a challenge for scientists using temperature signal analysis to support stream research and ecological management objectives. However, the sensitivity of estimated temperature signal patterns to missing data has not been thoroughly evaluated, despite the potentially large impact on interpretation. In this study, we explored the effects of simulated missing daily data on the characterization of annual water temperature signals measured at headwater sites in the Pacific Northwest and Mid-Atlantic regions of the USA. For each site, we used linear regressions of sine-waves fitted to complete (365-d) and partial (7–357 consecutive missing data points) annual datasets of daily mean water temperature and computed three thermal parameters (mean, phase, and amplitude), which together can indicate thermally and ecologically influential watershed processes (e.g., depth and magnitude of groundwater discharge). Expected values (derived from complete datasets) ranged from 7.0 to 12.6 °C, 205 to 254 d, and 1.9 to 9.5 °C for annual mean, phase, and amplitude, respectively. While annual phase and amplitude could be accurately estimated (i.e., within 95–99% confidence intervals of expected values) with up to approximately two months of consecutively missing data, annual mean temperature required more complete datasets. We found that datasets with less than seven weeks of consecutively missing data enabled estimation of all annual signal parameters with reasonable accuracy (>75% probability of being within the 95–99% confidence intervals of expected values). Imputation of missing data expanded this range to approximately 20 weeks, with the greatest improvements in parameter estimation between 9 and 27 weeks of imputed missing data. However, caution should be exercised when applying this technique. For example, imputation improved the accuracy of parameter estimation for most sites, but accuracy decreased for some sites exhibiting strong groundwater influence. The timing of consecutive missing data points within a year had inconsistent effects on annual thermal parameter estimates among regions, years, and individual parameters. Utilizing sites with more than approximately seven consecutive weeks of missing data or 20 weeks of imputed data increases the probability of mischaracterization of annual stream thermal regimes. Understanding this limitation is vital for identifying the potential of streams to serve as climate refugia for ecological indicator species and effective future management of stream systems.

Ecological Indicators↗
USGS2026

Local water use and climate variability drive water stress and alter ecological flows over the conterminous United States

Consistent, large-scale estimates of water availability are needed to identify and avoid potential conflicts among human and ecosystem uses of water. We present an assessment of water limitation, defined as the monthly balance (difference) between water supply ( ws ) and human consumptive water use ( wc ), for the conterminous United States (CONUS) during water years 2010–2020. We estimate that 26.7 million Americans, 8% of CONUS population, live in areas with chronic high or severe water limitation. Although ws greatly exceeds wc at the CONUS scale, water is limited locally or regionally due to spatial and temporal patterns in climate and wc . Our water limitation metric, the monthly supply and use index (SUI), peaked in 2012 during a widespread drought when 38% of the CONUS land area experienced elevated water stress. The central and Southwestern U.S. experienced the highest SUI due to the combination of low ws and high wc , especially for irrigation. Spatial overlays of SUI and fish habitat ranges, including those of conservation concern, revealed that several species had notable proportions of their habitat exposed to high or severe water limitation during spawning season over the modeled time period, especially the Arkansas River shiner. ws was calculated from two CONUS, physically-based, hydrologic models while wc was calculated from three CONUS models of water use for crop irrigation, thermoelectric power generation, and public supply. The ws and wc values were routed through a stream network and compared to calculate water limitation and SUI for human populations and fish species at the scale of 12-digit hydrologic unit codes. Evaluation of water availability at higher spatial and temporal resolution promotes more comprehensive analyses of the drivers of water availability and can be combined with complementary studies of water quality and water limiting thresholds to better understand the limitations on water availability.

conterminous United States↗
USGS2026

Guidelines for producing integrated 210Pb and 14C age-models

Accurate reconstructions of past environmental changes are crucial in paleoecological research and require reliable chronologies of sedimentary archives. Establishing robust age-models and obtaining the most appropriate proxies for analysis is a complex scientific endeavor, requiring extensive resources and collaboration among specialists, including radiochronologists. Radiometric dating methods, such as 210 Pb and radiocarbon ( 14 C), are frequently employed to establish chronologies in aquatic sedimentary deposits and peat bogs. In this study, we review key aspects of sampling, analysis, and the principles underlying 210 Pb and 14 C age-models, focusing on methods for developing robust joint chronologies for paleoenvironmental research. Drawing largely from the authors' experiences and group discussions during and after a scientific workshop in 2022, we discuss important considerations for site selection, sampling strategies, and radiometric dating to construct integrated 210 Pb and 14 C age-models. Using expert consensus, this group – called Paleostats – aims to provide a set of best practices for other geochronologists with this methods paper. Among our conclusions, we emphasize the importance of accounting for site-specific factors such as prior information on sedimentation rates to establish appropriate sampling and analytical strategies. The use of appropriate coring devices can minimize disturbance to sediments and ensure the core surface remains intact and preserved until sectioning. Where excess 210 Pb is expected, sectioning at intervals of ≤1 cm provides an adequate sampling resolution for 210 Pb dating. Exceptions are possible, allowing for ~2–3 cm sections in areas with confirmed high sedimentation rates (e.g., > 1 cm yr −1 ). Recovering deeper core sections for 14 C dating with sufficient overlap allows for accounting errors in depth estimates made in the field. Special attention is advised during time intervals where validation proxies, such as the human-made radionuclides 137 Cs or post-bomb 14 C, are expected, and to determine the depth of secular equilibrium between 210 Pb and 226 Ra. Radiocarbon analyses are commonly performed by accelerator mass spectrometry, and age models are constructed mainly using Bayesian statistics with Markov Chain Monte Carlo techniques (e.g., Bacon ). A Bayesian approach ( Plum ) is now available for producing 210 Pb age-models, which infers the 210 Pb ex flux, eliminates the need for selecting an equilibrium depth, and allows dating cores with incomplete 210 Pb ex inventory. Plum offers improved chronologies by integrating raw 210 Pb and 14 C data, and these age-models can be enriched with other dating methodologies, such as identifying tephras and other well-recorded historical events. Harmonized reporting would contribute to making radiometric age-models reproducible, which would benefit from an international effort. Using 210 Pb and 14 C to produce integrated age-models may yield better insights into the interplay between natural and recent anthropogenic forcings on ecosystems. This can enhance our understanding of environmental processes and their impacts on climate change, ultimately supporting science-based assessments and decisions.

Earth-Science Reviews↗
USGS2023

Maps of active layer thickness in northern Alaska by upscaling P-band polarimetric synthetic aperture radar retrievals

Extensive, detailed information on the spatial distribution of active layer thickness (ALT) in northern Alaska and how it evolves over time could greatly aid efforts to assess the effects of climate change on the region and also help to quantify greenhouse gas emissions generated due to permafrost thaw. For this reason, we have been developing high-resolution maps of ALT throughout northern Alaska. The maps are produced by upscaling from high-resolution swaths of estimated ALT retrieved from airborne P-band synthetic aperture radar (SAR) images collected for three different years. The upscaling was accomplished by using hundreds of thousands of randomly selected samples from the SAR-derived swaths of ALT to train a machine learning regression algorithm supported by numerous spatial data layers. In order to validate the maps, thousands of randomly selected samples of SAR-derived ALT were excluded from the training in order to serve as validation pixels; error performance calculations relative to these samples yielded root-mean-square errors (RMSEs) of 7.5–9.1 cm, with bias errors of magnitude under 0.1 cm. The maps were also compared to ALT measurements collected at a number of in situ test sites; error performance relative to the site measurements yielded RMSEs of approximately 11–12 cm and bias of 2.7–6.5 cm. These data are being used to investigate regional patterns and underlying physical controls affecting permafrost degradation in the tundra biome.

Environmental Research Letters↗
USGS2003

Sources of global warming of the upper ocean on decadal period scales

Recent studies find global climate variability in the upper ocean and lower atmosphere during the twentieth century dominated by quasi-biennial, interannual, quasi-decadal and interdecadal signals. The quasi-decadal signal in upper ocean temperature undergoes global warming/cooling of ???0.1??C, similar to that occuring with the interannual signal (i.e., El Nin??o-Southern Oscillation), both signals dominated by global warming/cooling in the tropics. From the National Centers for Environmental Prediction troposphere reanalysis and Scripps Institution of Oceanography upper ocean temperature reanalysis we examine the quasi-decadal global tropical diabetic heat storage (DHS) budget from 1975 to 2000. We find the anomalous DHS warming tendency of 0.3-0.9 W m-2 driven principally by a downward global tropical latent-plus-sensible heat flux anomaly into the ocean, overwhelming the tendency by weaker upward shortwave-minus-longwave heat flux anomaly to drive an anomalous DHS cooling tendency. During the peak quasi-decadal warming the estimated dissipation of DHS anomaly of 0.2-0.5 W m-2 into the deep ocean and a similar loss to the overlying atmosphere through air-sea heat flux anomaly are balanced by a decrease in the net poleward Ekman heat advection out of the tropics of 0.4-0.7 W m-2. This scenario is nearly the opposite of that accounting for global tropical warming during the El Nin??o. These diagnostics confirm that even though the global quasi-decadal signal is phase-locked to the 11-year signal in the Sun's surface radiative forcing of ???0.1 W m-2, the anomalous global tropical DHS tendency cannot be driven by it directly.

Journal of Geophysical Research C: Oceans↗
USGS2021

Monthly river temperature trends across the US confound annual changes

Climate variations and human modifications of the water cycle continue to alter the Earth's surface water and energy exchanges. It is therefore critical to ascertain how these changes impact water quality and aquatic ecosystem habitat metrics such as river temperatures. Though river temperature trend analyses exist in the literature, studies on seasonal trends in river temperatures across large spatial extents, e.g. the contiguous United States (US), are limited. As we show through both annual and monthly trend analyses for 20 year ( n = 138 sites) and 40 year ( n = 40 sites) periods, annual temperature trends across the US mask extensive monthly variability. While most sites exhibited annual warming trends, these annual trends obscured sub-annual cooling trends at many sites. Monthly trend anomalies were spatially organized, with persistent regional patterns at both reference and human-impacted sites. The largest warming and cooling anomalies happened at human impacted sites and during summer months. Though our analysis points to coherence in trends as well as the overall impact of human activity in driving these patterns, we did not investigate the impact of river temperature observation accuracy on reported trends, an area needed for future work. Overall, these patterns emphasize the need to consider sub-annual behavior when managing the ecological impacts of river temperature throughout lotic networks.

Environmental Research Letters↗
USGS2025

Reevaluating the depositional model of the Cenomanian–Turonian Bridge Creek Limestone Member near Pueblo, Colorado, U.S.A.: Roles of changing sedimentation rate on the formation of limestone–marl bedding couplets

Although interbedded limestone–marl couplets in many hemipelagic and pelagic deposits have been commonly attributed to orbital-driven climate cycles, the driving mechanisms of these couplets remain largely controversial. This situation arises from the fact that detailed sedimentologic and petrographic facies characteristics of these fine-grained deposits have rarely been examined closely. In this study we conduct an integrated sedimentologic and petrographic analysis to disentangle causes of the limestone–marl bedding couplets in the Cenomanian–Turonian Bridge Creek Limestone Member (BCL) of the Greenhorn Formation using cores and outcrop near Pueblo, Colorado. By integrating existing geochemical datasets, each of the three general lithologies in the BCL including limestone, marl, and calcareous mudstone can be divided into two facies, a more bioturbated vs. a more laminated facies, in addition to bentonite beds. The variability in sedimentary, bioturbation, and petrographic characteristics of different sedimentary facies types, as well as constraints from the existing orbital time scale, in the BCL indicate changes in sediment accumulation rate or the amount of time recorded by different facies—the limestone, marl, and calcareous facies are interpreted to reflect increasing sedimentation rate. The sedimentary and petrographic facies variations, including but not limited to lithological alternations, in the BCL are interpreted to result from the combined influence of various processes such as bottom currents, bioturbation, early diagenesis, and episodic volcanic input, with some of the above-mentioned processes likely modulated by short-term relative changes in sea level. Results of this study highlight the need for detailed sedimentologic and petrographic studies and consideration of short-term changes in sedimentation rate to fully resolve the causes of the apparent limestone–marl bedding couplets and reliably reconstruct short-term changes in depositional and environmental conditions from the BCL and other similar successions.

Colorado↗
USGS2022

Simulating burn severity maps at 30 meters in two forested regions in California

Climate change is altering wildfire behavior and vegetation regimes in California’s forested ecosystems. Present day fires are seeing an increase in high burn severity area and high severity patch size. The ability to predict future burn severity patterns would support better policy and land management decisions. Here we demonstrate a methodology to first, statistically estimate individual burn severity classes at 30 meters and second, cluster and smooth high severity patches onto a landscape. Our goal here was not to exactly replicate observed burn severity maps, but rather to utilize observed maps as one realization of a random process dependent on climate, topography, fire weather, and fuels, to inform creation of additional realizations through our simulation technique. We developed two sets of empirical models with two different vegetation datasets to test if coarse vegetation could accurately model for burn severity. While visual acuity can be used to assess the performance of our simulation process, we also employ the Ripley’s K function to compare spatial point processes at different scales to test if the simulation is capturing an appropriate amount of clustering. We utilize FRAGSTATS to obtain high severity patch metrics to test the contiguity of our high severity simulation. Ripley’s K function helped identify the number of clustering iterations and FRAGSTATS showed how different focal window sizes affected our ability to cluster high severity patches. High severity patch simulations was comparable between the coarse and fine resolution vegetation datasets. Improving our ability to simulate burn severity will help advance our understanding of the potential influence of land and fuels management on ecosystem-level response variables that are important for decision-makers. Simulated burn severity maps can support managing habitat and estimating risks of habitat loss, protecting infrastructure and homes, improving future wildfire emissions projections, and better mapping and planning for fuels treatment scenarios.

California↗
USGS2006

Integration of coral reef ecosystem process studies and remote sensing

Worldwide, local-scale anthropogenic stress combined with global climate change is driving shifts in the state of reef benthic communities from coral-rich to micro- or macroalgal-dominated (Knowlton, 1992; Done, 1999). Such phase shifts in reef benthic communities may be either abrupt or gradual, and case studies from diverse ocean basins demonstrate that recovery, while uncertain (Hughes, 1994), typically involves progression through successional stages (Done, 1992). These transitions in benthic community structure involve changes in community metabolism, and accordingly, the holistic evaluation of associated biogeochemical variables is of great intrinsic value (Done, 1992). Effective reef management requires advance prediction of coral reef alteration in the face of anthropogenic stress and change in the global environment (Hatcher, 1997a). In practice, this goal requires techniques that can rapidly discern, at an early stage, sublethal effects that may cause long-term increases in mortality (brown, 1988; Grigg and Dollar, 1990). Such methods would improve our understanding of the differences in the population, community, and ecosystem structure, as well as function, between pristine and degraded reefs. This knowledge base could then support scientifically based management strategies (Done, 1992). Brown (1988) noted the general lack of rigor in the assessment of stress on coral reefs and suggested that more quantitative approaches than currently exist are needed to allow objective understanding of coral reef dynamics. Sensitive techniques for the timely appraisal of pollution effects or generalized endemic stress in coral reefs are sorely lacking (Grigg and Dollar, 1990; Wilkinsin, 1992). Moreover, monitoring methods based on population inventories, sclerochronology, or reproductive biology tend to myopic and may give inconsistent results. Ideally, an improved means of evaluating reef stress would discriminate mortality due to natural causes from morality to anthropogenic causes (Brown, 1988). Models of coral reef ecosystems, parameterized by process measurements and scaled in time-space using remote sensing, have the potential to address pressing research questions that are central to devising valid management strategies (Grigg el al., 1984; Hatcher, 1997b). To attain this goal, ecosystem-level models that integrate studies of physical and chemical forcing with observed biological and geological responses are required. This interdisciplinary approach to understanding reef biogeochemical dynamics can allow investigations that integrate the scales of time and space (Hatcher, 1997a), thereby enabling prediction of coral reef change (Andréfouët and Payri, 2001). In turn, prediction of holistic ecosystem function within various environmental focusing scenarios has substantial promise in mitigating future disturbance. Indeed, management of coral reefs at the ecosystem level has been suggested as the only meaningful approach to preserving coral reefs (Bohnsack and Ault, 1996; Christensen et al., 1996).

Florida↗
USGS2021

Synoptic analysis of a decade of daily measurements of SO2 emission in the troposphere from volcanoes of the global ground-based Network for Observation of Volcanic and Atmospheric Change

Volcanic plumes are common and far-reaching manifestations of volcanic activity during and between eruptions. Observations of the rate of emission and composition of volcanic plumes are essential to recognize and, in some cases, predict the state of volcanic activity. Measurements of the size and location of the plumes are important to assess the impact of the emission from sporadic or localized events to persistent or widespread processes of climatic and environmental importance. These observations provide information on volatile budgets on Earth, chemical evolution of magmas, and atmospheric circulation and dynamics. Space-based observations during the last decades have given us a global view of Earth's volcanic emission, particularly of sulfur dioxide ( SO 2 ). Although none of the satellite missions were intended to be used for measurement of volcanic gas emission, specially adapted algorithms have produced time-averaged global emission budgets. These have confirmed that tropospheric plumes, produced from persistent degassing of weak sources, dominate the total emission of volcanic SO 2 . Although space-based observations have provided this global insight into some aspects of Earth's volcanism, it still has important limitations. The magnitude and short-term variability of lower-atmosphere emissions, historically less accessible from space, remain largely uncertain. Operational monitoring of volcanic plumes, at scales relevant for adequate surveillance, has been facilitated through the use of ground-based scanning differential optical absorption spectrometer (ScanDOAS) instruments since the beginning of this century, largely due to the coordinated effort of the Network for Observation of Volcanic and Atmospheric Change (NOVAC). In this study, we present a compilation of results of homogenized post-analysis of measurements of SO 2 flux and plume parameters obtained during the period March 2005 to January 2017 of 32 volcanoes in NOVAC. This inventory opens a window into the short-term emission patterns of a diverse set of volcanoes in terms of magma composition, geographical location, magnitude of emission, and style of eruptive activity. We find that passive volcanic degassing is by no means a stationary process in time and that large sub-daily variability is observed in the flux of volcanic gases, which has implications for emission budgets produced using short-term, sporadic observations. The use of a standard evaluation method allows for intercomparison between different volcanoes and between ground- and space-based measurements of the same volcanoes. The emission of several weakly degassing volcanoes, undetected by satellites, is presented for the first time. We also compare our results with those reported in the literature, providing ranges of variability in emission not accessible in the past. The open-access data repository introduced in this article will enable further exploitation of this unique dataset, with a focus on volcanological research, risk assessment, satellite-sensor validation, and improved quantification of the prevalent tropospheric component of global volcanic emission.

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