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At least 1,549 records · Page 86Linked to original sources
USGS1996

The stable oxygen and carbon isotopic record from a coral growing in Florida Bay: a 160 year record of climatic and anthropogenic influence

A 160 year record of skeletal δ 13 C and δ 18 O was examined in a specimen of the coral Solenastrea bournoni growing in Florida Bay. Variations in the δ 18 O of the skeleton can be correlated to changes in salinity while changes in the δ 13 C reflect cycling of organic material within the Bay. Based on the correlation between salinity and skeletal δ 18 O, we have concluded that there has been no long term increase in salinity in this area of Florida Bay over the past 160 years. Using salinity correlations between the various basins obtained from instrumental data, we have been able to extend our interpretations to other parts of Florida Bay reaching similar conclusions. In contrast to current ideas which have focused on changes in Florida Bay water quality over the past 20-yr history of the Bay as causative in its decline, we have determined that changes in water quality in this basin were already set in motion between 1905 and 1912 by the construction of the Florida East Coast Railway from Miami to Key West. The construction of the railway resulted in the restriction of the exchange of water between the Florida reef tract and the Gulf of Mexico causing Florida Bay to become more eutrophic. Evidence of this process is observed in the sudden shift to relatively lower δ 13 C values coincident with railway construction. Natural events also appear to have influenced the water in the Bay. Between 1912 and 1948 frequent hurricanes had the effect of increasing exchange of water between the Bay and reef tract and removing large quantities of organic rich sediments. However, since 1948 the number of hurricanes affecting the area has decreased and the products of the oxidation of organic material have been increasingly retained within the basin promoting the initiation of eutrophic conditions.

Florida↗
USGS1994

Prehistoric Alaska: The land

Many Alaskans know the dynamic nature of Alaska’s landscape firsthand. The 1964 earthquake, the 1989 eruption of Mount Redoubt volcano, the frequent earthquakes in the Aleutians and the ever-shifting meanders of the Yukon and Kuskokwim rivers remind them of constant changes to the land. These changes are part of the continuing story of the geologic growth and development of Alaska during hundreds of millions of years. By geologic time, Alaska has only recently come into existence and the dynamic processes that formed it continue to affect it. The landscape we see today has been shaped by glacier and stream erosion or their indirect effects, and to a lesser extent by volcanoes. Most prominently, if less obviously, Alaska has been built by slow movements of the Earth’s crust we call tectonic or mountain-building. During 5 billion years of geologic time, the Earth’s crust has repeatedly broken apart into plates. These plates have recombined, and have shifted positions relative to each other, to the Earth’s rotational axis and to the equator. Large parts of the Earth’s crust, including Alaska, have been built and destroyed by tectonic forces. Alaska is a collage of transported and locally formed fragments of crusts As erosion and deposition reshape the land surface, climatic changes, brought on partly by changing ocean and atmospheric circulation patterns, alter the location and extent of tropical, temperate and arctic environments. We need to understand the results of these processes as they acted upon Alaska to understand the formation of Alaska. Rocks can provide hints of previous environments because they contain traces of ocean floor and lost lands, bits and pieces of ancient history.

Alaska↗
USGS2018

Global and Arctic climate sensitivity enhanced by changes in North Pacific heat flux

Arctic amplification is a consequence of surface albedo, cloud, and temperature feedbacks, as well as poleward oceanic and atmospheric heat transport. However, the relative impact of changes in sea surface temperature (SST) patterns and ocean heat flux sourced from different regions on Arctic temperatures are not well constrained. We modify ocean-to-atmosphere heat fluxes in the North Pacific and North Atlantic in a climate model to determine the sensitivity of Arctic temperatures to zonal heterogeneities in northern hemisphere SST patterns. Both positive and negative ocean heat flux perturbations from the North Pacific result in greater global and Arctic surface air temperature anomalies than equivalent magnitude perturbations from the North Atlantic; a response we primarily attribute to greater moisture flux from the subpolar extratropics to Arctic. Enhanced poleward latent heat and moisture transport drive sea-ice retreat and low-cloud formation in the Arctic, amplifying Arctic surface warming through the ice-albedo feedback and infrared warming effect of low clouds. Our results imply that global climate sensitivity may be dependent on patterns of ocean heat flux in the northern hemisphere.

Nature Communications↗
USGS2026

Global change and threats to waterbirds in the Asian flyways

Avian migration represents one of nature’s most spectacular phenomena, providing critical ecological services and acting as an indicator of environmental change. Flyways are geographical ranges through which migrating bird species move, and the flyway concept has been used to identify countries that share species to highlight their collective responsibility for conservation. Of the nine recognized global waterbird flyways, the Central Asian Flyway (CAF) and the East Asian–Australasian Flyway (EAAF) are among the most important areas in Eurasia, supporting millions of waterbirds across a vast network of habitats. We proposed this special issue in Avian Research entitled “Global Change and Threats to Waterbirds in the Asian Flyways” to synthesize recent findings from 12 papers covering a wide range of topics. The CAF stretches from the Siberian tundra through Central Asia including Mongolia, the Qinghai-Tibet Plateau, the Trans-Caucasus, and the Himalayas, extending south to the Indian subcontinent and parts of the Middle East. The EAAF spans eastern Siberia and Alaska to Southeast Asia, Australia, and New Zealand, including China, Japan, the Korean Peninsula, and the Russian Far East. These two flyways include 47 countries comprising critical wetlands, river basins, and coastal areas, which are vital breeding, stopover, and wintering grounds for waterbirds. Seasonal migration in these flyways is fundamentally influenced by climate and weather conditions, land cover dynamics, and anthropogenic activities, and contributes significantly to ecological processes such as pest control, nutrient cycling, and organism dispersal. However, migratory waterbirds and their habitats are undergoing enormous challenges. Changes in climate, habitat availability and connectivity, and human activities are altering the phenology, distribution, population dynamics, and health of the migratory bird populations. As migratory waterbirds travel across international boundaries, understanding their movements and responses to environmental change requires collaborative, cross-border research efforts that promote knowledge sharing and interdisciplinary approaches.

Avian Research↗
USGS2000

Simulated influences of Lake Agassiz on the climate of central North America 11,000 years ago

Eleven thousand years ago, large lakes existed in central and eastern North America along the margin of the Laurentide Ice Sheet. The large-scale North American climate at this time has been simulated with atmospheric general circulation models, but these relatively coarse global models do not resolve potentially important features of the mesoscale circulation that arise from interactions among the atmosphere, ice sheet, and proglacial lakes. Here we present simulations of the climate of central and eastern North America 11,000 years ago with a high-resolution, regional climate model nested within a general circulation model. The simulated climate is in general agreement with that inferred from palaeoecological evidence. Our experiments indicate that through mesoscale atmospheric feedbacks, the annual delivery of moisture to the Laurentide Ice Sheet was diminished at times of a large, cold Lake Agassiz relative to periods of lower lake stands. The resulting changes in the mass balance of the ice sheet may have contributed to fluctuations of the ice margin, thus affecting the routing of fresh water to the North Atlantic Ocean. A retreating ice margin during periods of high lake level may have opened an outlet for discharge of Lake Agassiz into the North Atlantic. A subsequent advance of the ice margin due to greater moisture delivery associated with a low lake level could have dammed the outlet, thereby reducing discharge to the North Atlantic. These variations may have been decisive in causing the Younger Dryas cold even.

Nature↗
USGS2010

Conceptual understanding and groundwater quality of selected basin-fill aquifers in the Southwestern United States

The National Water-Quality Assessment (NAWQA) Program of the U.S. Geological Survey has been conducting a regional analysis of water quality in the principal aquifer systems in the southwestern United States (hereinafter, “Southwest”) since 2005. Part of the NAWQA Program, the objective of the Southwest Principal Aquifers (SWPA) study is to develop a better understanding of water quality in basin-fill aquifers in the region by synthesizing information from case studies of 15 basins into a common set of important natural and human-related factors found to affect groundwater quality. The synthesis consists of three major components: 1. Summary of current knowledge about the groundwater systems, and the status of, changes in, and influential factors affecting quality of groundwater in basin-fill aquifers in 15 basins previously studied by NAWQA (this report). 2. Development of a conceptual model of the primary natural and human-related factors commonly affecting groundwater quality, thereby building a regional understanding of the susceptibility and vulnerability of basin-fill aquifers to contaminants. 3. Development of statistical models that relate the concentration or occurrence of specific chemical constituents in groundwater to natural and human-related factors linked to the susceptibility and vulnerability of basin-fill aquifers to contamination. Basin-fill aquifers occur in about 200,000 mi 2 of the 410,000 mi 2 SWPA study area and are the primary source of groundwater supply for cities and agricultural communities. Four of the principal aquifers or aquifer systems of the United States are included in the basin-fill aquifers of the study area: (1) the Basin and Range basin-fill aquifers in California, Nevada, Utah, and Arizona; (2) the Rio Grande aquifer system in New Mexico and Colorado; (3) the California Coastal Basin aquifers; and (4) the Central Valley aquifer system in California. Because of the generally limited availability of surface-water supplies in the arid to semiarid climate, cultural and economic activities in the Southwest are particularly dependent on supplies of good-quality groundwater. Irrigation and public-supply withdrawals from basin-fill aquifers in the study area account for about one quarter of the total withdrawals from all aquifers in the United States. Many factors influence the quality of groundwater in the 15 case-study basins, but some common factors emerge from the basin summaries presented in this report. These factors include the chemical composition of the recharge water, consolidated rock geology and composition of aquifer materials derived from consolidated rock, and land and water use. The major water-quality issues in many of the developed case-study basins are increased concentrations of dissolved solids, nitrate, and VOCs in groundwater as a result of human activities. The information presented and the citations listed in this report serve as a resource for those interested in the groundwater-flow systems in the NAWQA case-study basins. The summaries of water-development history, hydrogeology, conceptual understanding of the groundwater system under both predevelopment and modern conditions, and effects of natural and human-related factors on groundwater quality presented in the sections on each basin also serve as a foundation for the synthesis and modeling phases of the SWPA regional study.

Arizona, California, Colorado, Nevada, New Mexico,↗
USGS1982

Evaluation of sediment yield and sediment data-collection network in the Piceance basin, northwestern Colorado

Statistical relationships were developed between suspended-sediment discharge and several regional factors of climate, physiography, and land use in the Piceance basin, northwestern Colorado. The purpose of the study was to evaluate the existing sediment collection network, especially in regard to detecting changes in suspended-sediment discharge due to the development in the basin. Spatial- and time variability were examined using multiple linear regression techniques. Because of the short period of record, monthly mean sediment loads were used to determine shifts or changes in trends due to mining and related activities in the basin. Dummy variable analysis was used to detect these premining and postmining differences in the regression lines and also to detect seasonal differences in the sediment discharge. Differences did exist in the sediment discharge from season to season and before and after mining; however, due to the variability and short period of record the cause of these differences could not be adequately determined. Part of the high variability in sediment discharge was due to variability in the water discharge. Therefore, if the network is to be improved, the emphasis needs to be on improvement of the water-discharge. The results of the monthly mean regression analysis were used in the mean monthly and mean annual analysis for determination of initial network design equations. These were only preliminary in nature and could be improved with additional data. (USGS)

Water-Resources Investigations Report↗
USGS2017

Development of a robust analytical framework for assessing landbird trends, dynamics and relationships with environmental covariates in the North Coast and Cascades Network

During 2015-2016, we completed development of a new analytical framework for landbird population monitoring data from the National Park Service (NPS) North Coast and Cascades Inventory and Monitoring Network (NCCN). This new tool for analysis combines several recent advances in modeling population status and trends using point-count data and is designed to supersede the approach previously slated for analysis of trends in the NCCN and other networks, including the Sierra Nevada Network (SIEN). Advances supported by the new model-based approach include 1) the use of combined data on distance and time of detection to estimate detection probability without assuming perfect detection at zero distance, 2) seamless accommodation of variation in sampling effort and missing data, and 3) straightforward estimation of the effects of downscaled climate and other local habitat characteristics on spatial and temporal trends in landbird populations. No changes in the current field protocol are necessary to facilitate the new analyses. We applied several versions of the new model to data from each of 39 species recorded in the three mountain parks of the NCCN, estimating trends and climate relationships for each species during 2005-2014. Our methods and results are also reported in a manuscript in revision for the journal Ecosphere (hereafter, Ray et al.). Here, we summarize the methods and results outlined in depth by Ray et al., discuss benefits of the new analytical framework, and provide recommendations for its application to synthetic analyses of long-term data from the NCCN and SIEN. All code necessary for implementing the new analyses is provided within the Appendices to this report, in the form of fully annotated scripts written in the open-access programming languages R and JAGS.

Natural Resource Report↗
USGS2021

Past abrupt changes, tipping points and cascading impacts in the Earth system

The geological record shows that abrupt changes in the Earth system can occur on timescales short enough to challenge the capacity of human societies to adapt to environmental pressures. In many cases, abrupt changes arise from slow changes in one component of the Earth system that eventually pass a critical threshold, or tipping point, after which impacts cascade through coupled climate–ecological–social systems. The chance of detecting abrupt changes and tipping points increases with the length of observations. The geological record provides the only long-term information we have on the conditions and processes that can drive physical, ecological and social systems into new states or organizational structures that may be irreversible within human time frames. Here, we use well-documented abrupt changes of the past 30 kyr to illustrate how their impacts cascade through the Earth system. We review useful indicators of upcoming abrupt changes, or early warning signals, and provide a perspective on the contributions of palaeoclimate science to the understanding of abrupt changes in the Earth system.

Nature Geoscience↗
USGS2020

Soil organic carbon stocks and sequestration rates of inland, freshwater wetlands: Sources of variability and uncertainty

Impacts of land use, specifically soil disturbance, are linked to reductions of soil organic carbon (SOC) stocks. Correspondingly, ecosystem restoration is promoted to sequester SOC to mitigate anthropogenic greenhouse gas emissions, which are exacerbating global climate change. Restored wetlands have relatively high potential to sequester carbon compared to other ecosystems, but SOC accumulation rates are variable, which leads to high uncertainty in sequestration rates. To assess soil properties and carbon sequestration rates of freshwater mineral soil wetlands, we analyzed an extensive database of SOC concentrations from the Prairie Pothole Region (549 wetlands over 160,000 km 2 ), which is considered one of the largest wetland ecosystems in North America. We demonstrate that SOC of wetland catchments varies among inner, transition, toe slope, and upland landscape positions (LSPs), as well as among land uses and soil depth segments. Soil organic carbon concentrations were greatest in the inner portion of the catchment (66 Mg ha −1 ) and progressively decrease towards the upland LSP (43 Mg ha −1 ). We also conducted a regional extrapolation based on LSP- and land-use-specific SOC stocks, and estimated that wetland and upland areas of PPR wetland catchments contain 141 and 178 Tg of SOC in the upper 15 cm of the soil profile, respectively. Regressing SOC by restoration age (years restored) showed that sequestration rates, which differ by LSP and depth, ranged from 0.35 to 1.10 Mg ha −1 year −1 . Using these SOC sequestration rates, along with data from natural and cropland reference sites, we estimated that it takes 20 to 64 years for SOC levels of restored wetlands to return to natural reference conditions, depending on LSP and depth segment. Accounting for LSP reduces uncertainty and should refine future assessments of the greenhouse gas mitigation potential from wetland restoration.

Iowa, Minnesota, Montana, North Dakota, South Dako↗
USGS2025

A comprehensive sulfate and DOM framework to assess methylmercury formation and risk in subtropical wetlands

Wetlands play a vital role in contaminant cycling and uptake. Understanding how sulfate (SO 4 2‒ ) influences the conversion of inorganic mercury (Hg(II)) to toxic methylmercury (MeHg) is critical for predicting wetland responses to land use and climate change. Here, we sampled surface and pore waters across SO 4 2‒ gradients in three freshwater Everglades wetlands to assess linkages between SO 4 2‒ , MeHg, dissolved organic matter (DOM), and inorganic sulfide (S(‒II)). Increasing SO 4 2‒ concentrations increase S(‒II) and DOM concentrations and DOM aromaticity. MeHg concentration show a unimodal response to surface water SO 4 2‒ , which reflect high Hg(II) methylation at low-to-intermediate SO 4 2‒ concentration (2-12 mg/L) and low Hg(II) methylation at higher SO 4 2‒ concentrations ( > 12 mg/L). MeHg concentrations in surface waters correlate positively with MeHg concentrations in prey fish. The coherent biogeochemical relationships between SO 4 2‒ and MeHg concentrations and biologic uptake improve MeHg risk assessment for aquatic food webs and are globally relevant due to anthropogenic and climate-driven increases in SO 4 2‒ .

Florida↗
USGS2022

Effects of warming winter embryo incubation temperatures on larval cisco (Coregonus artedi) survival, growth, and critical thermal maximum

Freshwater whitefishes, Salmonidae Coregoninae, are cold stenothermic fishes of ecological and socio-economic importance in northern hemisphere lakes that are warming in response to climate change. To address the effect of warming waters on coregonine reproduction we experimentally evaluated different embryo incubation temperatures on post-hatching survival, growth, and critical thermal maximum of larval cisco ( Coregonus artedi ) sampled from lakes Superior and Ontario. Embryos were incubated at water temperatures of 2.0, 4.4, 6.9, and 8.9 °C to simulate present and increased winter temperatures, and hatched larvae were reared in a common environment. For the populations from both lakes, larval survival and critical thermal maximum were negatively related to incubation temperature, and larval growth was positively related to incubation temperature. The magnitude of change across incubation temperatures was greater in the population sampled from Lake Superior than Lake Ontario for all traits examined. The more rapid decrease in survival and critical thermal maximum across incubation temperatures for larval cisco in Lake Superior, compared to those from Lake Ontario, suggests that Lake Superior larvae may possess a more limited ability to acclimate to and cope with increasing winter water temperatures. However, the rapid increase in growth rates across incubation temperatures in Lake Superior larvae suggests they could recover better from hatching at a small length induced by warm winters, as compared to Lake Ontario larvae. Our results suggest propagation and restoration programs may want to consider integrating natural habitat preferences and maximizing phenotypic variability to ensure offspring are set up for success upon stocking.

Lake Ontario, Lake Superior↗
USGS2003

Eutrophication and carbon sources in Chesapeake Bay over the last 2700 yr: Human impacts in context

To compare natural variability and trends in a developed estuary with human-influenced patterns, stable isotope ratios (δ 13 C and δ 15 N) were measured in sediments from five piston cores collected in Chesapeake Bay. Mixing of terrestrial and algal carbon sources primarily controls patterns of δ 13 C org profiles, so this proxy shows changes in estuary productivity and in delivery of terrestrial carbon to the bay. Analyses of δ 15 N show periods when oxygen depletion allowed intense denitrification and nutrient recycling to develop in the seasonally stratified water column, in addition to recycling taking place in surficial sediments. These conditions produced 15 N-enriched (heavy) nitrogen in algal biomass, and ultimately in sediment. A pronounced increasing trend in δ 15 N of +4‰ started in about A.D. 1750 to 1800 at all core sites, indicating greater eutrophication in the bay and summer oxygen depletion since that time. The timing of the change correlates with the advent of widespread land clearing and tillage in the watershed, and associated increases in erosion and sedimentation. Isotope data show that the region has experienced up to 13 wet-dry cycles in the last 2700 yr. Relative sea-level rise and basin infilling have produced a net freshening trend overprinted with cyclic climatic variability. Isotope data also constrain the relative position of the spring productivity maximum in Chesapeake Bay and distinguish local anomalies from sustained changes impacting large regions of the bay. This approach to reconstructing environmental history should be generally applicable to studies of other estuaries and coastal embayments impacted by watershed development.

Chesapeake Bay↗
USGS2020

Landscape and climatic influences on actual evapotranspiration and available water using the Operational Simplified Surface Energy Balance (SSEBop) Model in eastern Bernalillo County, New Mexico, 2015

The U.S. Geological Survey, in cooperation with the Bernalillo County Public Works Division, conducted a 1-year study in 2015 to assess the spatial and temporal distribution of evapotranspiration (ET) and available water within the East Mountain area in Bernalillo County, New Mexico. ET and available water vary spatiotemporally because of complex interactions among environmental factors, including vegetation characteristics, soil characteristics, topography, and climate. Precipitation data from the Parameter-Elevation Regressions on Independent Slopes Model (PRISM) ( P ) were used in conjunction with actual ET ( ETa ) data from the Operational Simplified Surface Energy Balance (SSEBop) model to estimate available water ( P – ETa ) at 100-meter (m) resolution in the study area. Maps, descriptive statistics, boxplots, regression analyses (continuous data), and multiple comparison tests (categorical data) were used to characterize P , ETa , and available water and their relations to topographic, soil, and vegetation datasets in the East Mountain area. Five categories of the natural land-cover type (evergreen forest, shrub, herbaceous, deciduous forest, and mixed forest) and four categories of developed land-cover type specific to residential intensity (developed open, developed low, developed medium, and developed high) were analyzed individually and in interaction with multiple elevation, tree canopy, and soil texture classes. Annual mean P in 2015 in the East Mountain area was 608 millimeters (mm), and annual mean ETa was 543 mm (89 percent of annual P in 2015), indicating that in 2015, a spatial mean of about 65 mm of water was available for runoff, soil moisture replenishment, or groundwater recharge. Monthly ETa was greatest in July and smallest in January. The intervening months did not show smooth temporal or consistent spatial changes from month to month. Months with lower ETa (January to March, October to December) also tended to have greater available water, indicating that soil moisture (water supply) and potential ET (water demand) may have been out of phase. Regression analyses showed that monthly ETa data had the highest correlation with annual ETa among the atmospheric, topographic, soil, or vegetation datasets, particularly during the early and late growing season (March, April, May, and September). In contrast, monthly P was highly variable and not as highly correlated with annual ETa . Among landscape variables, correlations with annual ETa were highest for tree canopy cover (coefficient of determination [R 2 ] = 0.46). Correlations between ETa and other landscape variables were lower (R 2 = 0.06–0.19): available soil water in the top 100 centimeters, soil bulk density of layer 1, slope, sand content of soil layer 1, soil depth, available soil water in the top 25 centimeters, leaf area index, aspect eastness, and elevation. Evergreen forest areas had the highest annual median ETa , followed by mixed forest, open residential areas, and deciduous forest. Available water typically was higher in landcover types with lower ETa : herbaceous cover, followed by deciduous forest, high-intensity developed areas, and shrub. Deciduous forest had the second highest median available water, despite having the fourth highest ETa , because deciduous forest had greater P than most other areas. Annual median ETa typically was greatest in the second highest elevation band (2,401–2,800 m above the North American Vertical Datum of 1988 [NAVD 88]), and lower in the highest elevation band (2,801–3,254 m above NAVD 88), despite having greater P , likely because of decreased tree canopy cover or a shift from evergreen to deciduous trees at the highest elevations. Annual median ETa increased with tree canopy cover, regardless of landcover type. ETa correlation was higher with tree canopy than with leaf area index or normalized difference vegetation index. This result indicates that it is important to include the thermal band (from satellite multispectral data) in vegetation indices used to describe ETa , perhaps to account for the influence of energy limitation or water limitation on ET. Of all natural landcover types, finer soils had the most available water, whereas coarser soils had the least available water. Relations of soil type with P – ETa were different than with ETa , indicating ET and available water have a complex response to differences in soil type. Further modeling would be useful in determining soils’ infiltration, storage, conductivity, and plant-water availability relations to individual storms for each position in the landscape, as well as the corresponding effects of these processes on ET and available water. The best multivariate linear model for annual ETa had an R 2 value of 0.62. Monthly ETa models had R 2 values between 0.16 and 0.65. Models usually, but not always, performed best during the growing season. These results indicate that even the best multivariate linear models cannot explain a notable amount of the variability in ET. The monthly ETa models with the highest correlations (August and September) followed a July having almost twice the mean precipitation for July (1981–2010), which indicates that a soil-moisture variable is needed to more accurately model monthly ETa . Further study is needed to better characterize this system, the variables that affect ET and available water, and the partitioning of available water into runoff, soil moisture storage, and groundwater recharge.

New Mexico↗
USGS2024

Wildland fire effects on sediment, salinity, and selenium yields in a basin underlain by Cretaceous marine shales near Rangely, Colorado

Understanding and quantifying soil erosion from rangelands is a high priority for land managers, especially in areas underlain by Cretaceous Mancos Shale, which is a natural source of sediment, salinity, and selenium to surface waters in many areas of western Colorado and eastern Utah. The purpose of this report is to present the results of a U.S. Geological Survey study that assessed sediment, salinity, and selenium yields after the Dead Dog wildfire (fire began June 11, 2017) in northwestern Colorado. Two methodologies were used to quantify erosion, with different data requirements and analytical complexity. The first approach was the use of a process-based erosion model, the Watershed Erosion Prediction Project, which uses inputs of climate, topography, vegetation, and soils data from existing datasets to predict erosion, making this approach easily extensible to other areas. The second approach required more complex data collection and was used to measure erosion and deposition by differencing digital elevation models created from uncrewed aerial vehicle imagery collected in 2016 (pre-fire) and 2021 (post-fire). Sediment, salinity, and selenium yields were calculated from the volumetric estimates of erosion from both methods, and a discussion of factors that may have contributed to overall findings, including vegetation, fire effects, and soil characteristics, is included. The two approaches yielded different outputs. Results from the Watershed Erosion Prediction Project model indicated that almost no erosion occurred after the Dead Dog fire. However, morphological changes in the study basin after the Dead Dog fire were visible in the pre- and post-fire imagery and measured in the digital elevation model differencing technique, with net erosion occurring in channel and landscape extents, though calculated erosion rates and salinity and selenium yields were relatively small. Visible and measured morphological changes consisted primarily of incision and deposition within stream channels and rill incision and expansion on steeper slopes. Widespread sheet erosion was not evident. Much of the new erosion originated within, and immediately below, previously vegetated areas that were then burned by the wildfire. Greater erosion rates and salinity and selenium yields were measured in the channel extent relative to the landscape extent. Calculated erosion rates ranged from 0.24 to 0.45 megagrams per hectare per year. These results indicate that the Dead Dog fire resulted in increased erosion in the study basin, yet these effects were relatively small based on the overall magnitude of modeled and measured erosion from the Watershed Erosion Prediction Project and the digital elevation model differencing technique. Minimal erosion in the basin is likely due to local site characteristics typical of soils derived from Mancos Shale, including the presence of robust physical crusts and biological soil crusts, and limitations of the methods based on data availability. Focusing uncrewed aerial vehicle flights on key areas (individual steep slopes, high-intensity burn areas, specific stream reaches) could likely increase understanding of erosional process with less effort and error than doing landscape-level flights.

Colorado↗
USGS2024

Streamflow characteristics and trends in New Jersey, water years 1903–2017

As New Jersey’s population density remains high, so does its requirements for water management. Understanding the streamflow conditions throughout the state and how they may have changed over time is an important part of managing the water resources within the state. The New Jersey Department of Environmental Protection has many responsibilities related to protecting the environment and natural resources and among them is protecting the waters in the lakes, rivers, and streams of New Jersey for current and future use. To support this mission, the U.S. Geological Survey updated high- and low-streamflow statistics for 97 continuous-record streamgages and low-streamflow statistics for 719 partial-record streamgages throughout the state. The continuous-record streamgages included in the study had a minimum of 20 years of record, spanning from 1903 to 2017. This study is an update to previous studies that documented the high- and low-streamflow statistics for New Jersey streams in the 1970s and in 2005. The 1982 report by Gillespie and Schopp documented low-flow characteristics and flow duration for about 400 continuous and partial-record streamgages. The U.S. Geological Survey computed streamflow statistics including, but not limited to, maximum, minimum, and means for period of record, flow durations, nonexceedance high- and low-flow frequencies, base flow, runoff, peak-to-mean flow ratios, and September median streamflow. Overall, both high and low flows are generally increasing in New Jersey, though the results are not uniform across the State. Streamflow trends and changes to duration and frequency statistics can be influenced by local water use, in addition to climate variables. The resulting computations at some streamgages indicated considerable positive change while others showed considerable negative change. Water managers and regulators can use the data provided here and in the companion data release to assess individual stream reaches and watershed management areas to evaluate the available resources and changes, which may have developed during the periods for which streamflow statistics are available.

New Jersey↗
USGS1997

Nearly synchronous climate change in the Northern Hemisphere during the last glacial termination

The climate of the North Atlantic region underwent a series of abrupt cold/warm oscillations when the ice sheets of the Northern Hemisphere retreated during the last glacial termination (17.711.5 kyr ago). Evidence for these oscillations, which are recorded in European terrestrial sediments as the Oldest Dryas/Bolling/Older Dryas/Allerod/Younger Dryas vegetational sequence, has been found in Greenland ice cores. The geographical extent of many of these oscillations is not well known, but the last major cold event (the Younger Dryas) seems to have been global in extent. Here we present evidence of four major oscillations in the hydrological balance of the Owens basin, California, that occurred during the last glacial termination. Dry events in western North America occurred at approximately the same time as cold events recorded in Greenland ice, with transitions between climate regimes in the two regions taking place within a few hundred years of each other. Our observations thus support recent climate simulations which indicate that cooling of the North Atlantic Ocean results in cooling of the North Pacific Ocean which, in turn, leads to a drier climate in western North America.

Nature↗
USGS2021

Current distribution and abundance of Kohala forest birds in Hawai‘i

The Kohala volcano is home to the most spatially isolated population of Hawaiian forest birds on Hawai‘i Island and contains one of the few native bird populations in the state that has not been monitored since the original Hawai‘i Forest Bird Survey (HFBS) in 1979. We surveyed 143 stations across 13 transects in Pu‘u ‘O ‘Umi Natural Area Reserve on Kohala from February through April 2017 and compared our results to data from the 1979 HFBS conducted at 80 stations across three transects in the same location as our study site. We detected 2806 individuals of 15 species and measured relative abundance, relative occurrence, and density for seven species. We observed changes in species densities ranging from −8.4% (Hawai‘i ‘Elepaio, Chasiempis sandwichensis ) to +714% (‘I‘iwi, Drepanis coccinea ). Equivalence testing showed meaningful increases in population densities for all but one species, the Hawai‘i ‘Elepaio. The increases in population densities on Kohala are in stark contrast to the widespread declines in population densities of native species elsewhere in Hawai‘i. Relative occurrence was greater in 2017 than in 1979 for all species except Hawai‘i ‘Elepaios and House Finches ( Haemorhous mexicanus ), and relative abundance increased for all species except Hawai‘i ‘Elepaios, House Finches, and Melodious Laughing Thrushes ( Garrulax canorus ). We also documented the range expansion of Japanese Bush Warblers ( Cettia diphone ) in Kohala. Our results indicate that this spatially isolated avian community remains biologically diverse, and most population densities are increasing in the study area. Our results provide a framework for future surveys and a baseline for understanding possible changes in population and community dynamics as birds respond to climate change and avian disease on Kohala volcano.

Hawai'i↗