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At least 667 records · Page 37Linked to original sources
USGS2012

Use of weather types to disaggregate general circulation model predictions

General circulation models (GCMs) simulate climatic conditions with a grid cell resolution on the order of 100,000 km 2 . This resolution is inadequate to assess the effects of climatic change on water resources at a regional scale. A method has been developed that uses weather-type analysis as a tool to spatially disaggregate GCM predictions to make them useful for water resource studies. The method has been applied to the Delaware River basin to predict the effects of doubling atmospheric carbon dioxide on precipitation patterns in the region. An application of the technique to the Delaware River basin indicates that future climatic conditions will show minimal changes in weather-type frequency, implying that air circulation patterns will remain unchanged. Results of this study indicate that changes in regional precipitation patterns under a doubling of atmospheric carbon dioxide will be a result of within-type changes in weather characteristics.

Journal of Geophysical Research↗
USGS2023

Permafrost microbial communities and functional genes are structured by latitudinal and soil geochemical gradients

Permafrost underlies approximately one quarter of Northern Hemisphere terrestrial surfaces and contains 25–50% of the global soil carbon (C) pool. Permafrost soils and the C stocks within are vulnerable to ongoing and future projected climate warming. The biogeography of microbial communities inhabiting permafrost has not been examined beyond a small number of sites focused on local-scale variation. Permafrost is different from other soils. Perennially frozen conditions in permafrost dictate that microbial communities do not turn over quickly, thus possibly providing strong linkages to past environments. Thus, the factors structuring the composition and function of microbial communities may differ from patterns observed in other terrestrial environments. Here, we analyzed 133 permafrost metagenomes from North America, Europe, and Asia. Permafrost biodiversity and taxonomic distribution varied in relation to pH, latitude and soil depth. The distribution of genes differed by latitude, soil depth, age, and pH. Genes that were the most highly variable across all sites were associated with energy metabolism and C-assimilation. Specifically, methanogenesis, fermentation, nitrate reduction, and replenishment of citric acid cycle intermediates. This suggests that adaptations to energy acquisition and substrate availability are among some of the strongest selective pressures shaping permafrost microbial communities. The spatial variation in metabolic potential has primed communities for specific biogeochemical processes as soils thaw due to climate change, which could cause regional- to global- scale variation in C and nitrogen processing and greenhouse gas emissions.

The ISME Journal↗
USGS2014

Methane hydrates in nature - Current knowledge and challenges

Recognizing the importance of methane hydrate research and the need for a coordinated effort, the United States Congress enacted the Methane Hydrate Research and Development Act of 2000. At the same time, the Ministry of International Trade and Industry in Japan launched a research program to develop plans for a methane hydrate exploratory drilling project in the Nankai Trough. India, China, the Republic of Korea, and other nations also have established large methane hydrate research and development programs. Government-funded scientific research drilling expeditions and production test studies have provided a wealth of information on the occurrence of methane hydrates in nature. Numerous studies have shown that the amount of gas stored as methane hydrates in the world may exceed the volume of known organic carbon sources. However, methane hydrates represent both a scientific and technical challenge, and much remains to be learned about their characteristics and occurrence in nature. Methane hydrate research in recent years has mostly focused on: (1) documenting the geologic parameters that control the occurrence and stability of methane hydrates in nature, (2) assessing the volume of natural gas stored within various methane hydrate accumulations, (3) analyzing the production response and characteristics of methane hydrates, (4) identifying and predicting natural and induced environmental and climate impacts of natural methane hydrates, (5) analyzing the methane hydrate role as a geohazard, (6) establishing the means to detect and characterize methane hydrate accumulations using geologic and geophysical data, and (7) establishing the thermodynamic phase equilibrium properties of methane hydrates as a function of temperature, pressure, and gas composition. The U.S. Department of Energy (DOE) and the Consortium for Ocean Leadership (COL) combined their efforts in 2012 to assess the contributions that scientific drilling has made and could continue to make to advance our understanding of methane hydrates in nature. COL assembled a Methane Hydrate Project Science Team with members from academia, industry, and government. This Science Team worked with COL and DOE to develop and host the Methane Hydrate Community Workshop, which surveyed a substantial cross section of the methane hydrate research community for input on the most important research developments in our understanding of methane hydrates in nature and their potential role as an energy resource, a geohazard, and/or as an agent of global climate change. Our understanding of how methane hydrates occur in nature is still growing and evolving, and it is known with certainty that field, laboratory, and modeling studies have contributed greatly to our understanding of hydrates in nature and will continue to be a critical source of the information needed to advance our understanding of methane hydrates.

Journal of Chemical and Engineering Data↗
USGS2010

Quantifying restoration success and recovery in a metal-polluted stream: A 17-year assessment of physicochemical and biological responses

Evaluating the effectiveness of stream restoration is often challenging because of the lack of pre-treatment data, narrow focus on physicochemical measures and insufficient post-restoration monitoring. Even when these fundamental elements are present, quantifying restoration success is difficult because of the challenges associated with distinguishing treatment effects from seasonal variation, episodic events and long-term climatic changes.2. We report results of one of the most comprehensive and continuous records of physical, chemical and biological data available to assess restoration success for a stream ecosystem in North America. Over a 17 year period we measured seasonal and annual changes in metal concentrations, physicochemical characteristics, macroinvertebrate communities, and brown trout Salmo trutta populations in the Arkansas River, a metal-contaminated stream in Colorado, USA.3. Although we observed significant improvements in water quality after treatment, the effectiveness of restoration varied temporally, spatially and among biological response variables. The fastest recovery was observed at stations where restoration eliminated point sources of metal contamination. Recovery of macroinvertebrates was significantly delayed at some stations because of residual sediment contamination and because extreme seasonal and episodic variation in metal concentrations prevented recolonization by sensitive species. Synthesis and applications. Because recovery trajectories after the removal of a stressor are often complex or nonlinear, long-term studies are necessary to assess restoration success within the context of episodic events and changes in regional climate. The observed variation in recovery among chemical and biological endpoints highlights the importance of developing objective criteria to assess restoration success. Although the rapid response of macroinvertebrates to reduced metal concentrations is encouraging, we have previously demonstrated that benthic communities from the Arkansas River remained susceptible to other novel anthropogenic stressors. We suggest that the resistance or resilience of benthic macroinvertebrate communities to novel stressors may be effective indicators of restoration success that can account for the non-additive (e.g. synergistic) nature of compound perturbations. ?? 2010 The Authors. Journal compilation ?? 2010 British Ecological Society.

Journal of Applied Ecology↗
USGS2008

A fully distributed implementation of mean annual streamflow regional regression equations

Estimates of mean annual streamflow are needed for a variety of hydrologic assessments. Away from gage locations, regional regression equations that are a function of upstream area, precipitation, and temperature are commonly used. Geographic information systems technology has facilitated their use for projects, but traditional approaches using the polygon overlay operator have been too inefficient for national scale applications. As an alternative, the Elevation Derivatives for National Applications (EDNA) database was used as a framework for a fully distributed implementation of mean annual streamflow regional regression equations. The raster “flow accumulation” operator was used to efficiently achieve spatially continuous parameterization of the equations for every 30 m grid cell of the conterminous United States (U.S.). Results were confirmed by comparing with measured flows at stations of the Hydro-Climatic Data Network, and their applications value demonstrated in the development of a national geospatial hydropower assessment. Interactive tools at the EDNA website make possible the fast and efficient query of mean annual streamflow for any location in the conterminous U.S., providing a valuable complement to other national initiatives (StreamStats and the National Hydrography Dataset Plus).

Journal of the American Water Resources Associatio↗
USGS2018

Projected 21st century coastal flooding in the Southern California Bight. Part 1: Development of the third generation CoSMoS model

Due to the effects of climate change over the course of the next century, the combination of rising sea levels, severe storms, and coastal change will threaten the sustainability of coastal communities, development, and ecosystems as we know them today. To clearly identify coastal vulnerabilities and develop appropriate adaptation strategies due to projected increased levels of coastal flooding and erosion, coastal managers need local-scale hazards projections using the best available climate and coastal science. In collaboration with leading scientists world-wide, the USGS designed the Coastal Storm Modeling System (CoSMoS) to assess the coastal impacts of climate change for the California coast, including the combination of sea-level rise, storms, and coastal change. In this project, we directly address the needs of coastal resource managers in Southern California by integrating a vast range of global climate change projections in a thorough and comprehensive numerical modeling framework. In Part 1 of a two-part submission on CoSMoS, methods and the latest improvements are discussed, and an example of hazard projections is presented.

Journal of Marine Science and Engineering↗
USGS2017

Different historical fire–climate patterns in California

The relationship between annual variation in area burned and seasonal temperatures and precipitation was investigated for the major climate divisions in California. Historical analyses showed marked differences in fires on montane and foothill landscapes. Based on roughly a century of data, there are five important lessons on fire–climate relationships in California: (1) seasonal variations in temperature appear to have had minimal influence on area burned in the lower elevation, mostly non-forested, landscapes; (2) temperature has been a significant factor in controlling fire activity in higher elevation montane forests, but this varied greatly with season – winter and autumn temperatures showed no significant effect, whereas spring and summer temperatures were important determinants of area burned; (3) current season precipitation has been a strong controller of fire activity in forests, with drier years resulting in greater area burned on most United States Forest Service (USFS) lands in the state, but the effect of current-year precipitation was decidedly less on lower elevation California Department of Forestry and Fire Protection lands; (4) in largely grass-dominated foothills and valleys the magnitude of prior-year rainfall was positively tied to area burned in the following year, and we hypothesise that this is tied to greater fuel volume in the year following high rainfall. In the southern part of the state this effect has become stronger in recent decades and this likely is due to accelerated type conversion from shrubland to grassland in the latter part of the 20th century; (5) the strongest fire–climate models were on USFS lands in the Sierra Nevada Mountains, and these explained 42–52% of the variation in area burned; however, the models changed over time, with winter and spring precipitation being the primary drivers in the first half of the 20th century, but replaced by spring and summer temperatures after 1960.

California↗
USGS2005

An online operational rainfall-monitoring resource for epidemic malaria early warning systems in Africa

Periodic epidemics of malaria are a major public health problem for many sub-Saharan African countries. Populations in epidemic prone areas have a poorly developed immunity to malaria and the disease remains life threatening to all age groups. The impact of epidemics could be minimized by prediction and improved prevention through timely vector control and deployment of appropriate drugs. Malaria Early Warning Systems are advocated as a means of improving the opportunity for preparedness and timely response. Rainfall is one of the major factors triggering epidemics in warm semi-arid and desert-fringe areas. Explosive epidemics often occur in these regions after excessive rains and, where these follow periods of drought and poor food security, can be especially severe. Consequently, rainfall monitoring forms one of the essential elements for the development of integrated Malaria Early Warning Systems for sub-Saharan Africa, as outlined by the World Health Organization. The Roll Back Malaria Technical Resource Network on Prevention and Control of Epidemics recommended that a simple indicator of changes in epidemic risk in regions of marginal transmission, consisting primarily of rainfall anomaly maps, could provide immediate benefit to early warning efforts. In response to these recommendations, the Famine Early Warning Systems Network produced maps that combine information about dekadal rainfall anomalies, and epidemic malaria risk, available via their Africa Data Dissemination Service. These maps were later made available in a format that is directly compatible with HealthMapper, the mapping and surveillance software developed by the WHO's Communicable Disease Surveillance and Response Department. A new monitoring interface has recently been developed at the International Research Institute for Climate Prediction (IRI) that enables the user to gain a more contextual perspective of the current rainfall estimates by comparing them to previous seasons and climatological averages. These resources are available at no cost to the user and are updated on a routine basis.

Malaria Journal↗
USGS2011

Multilevel regression models describing regional patterns of invertebrate and algal responses to urbanization across the USA

Multilevel hierarchical regression was used to examine regional patterns in the responses of benthic macroinvertebrates and algae to urbanization across 9 metropolitan areas of the conterminous USA. Linear regressions established that responses (intercepts and slopes) to urbanization of invertebrates and algae varied among metropolitan areas. Multilevel hierarchical regression models were able to explain these differences on the basis of region-scale predictors. Regional differences in the type of land cover (agriculture or forest) being converted to urban and climatic factors (precipitation and air temperature) accounted for the differences in the response of macroinvertebrates to urbanization based on ordination scores, total richness, Ephemeroptera, Plecoptera, Trichoptera richness, and average tolerance. Regional differences in climate and antecedent agriculture also accounted for differences in the responses of salt-tolerant diatoms, but differences in the responses of other diatom metrics (% eutraphenic, % sensitive, and % silt tolerant) were best explained by regional differences in soils (mean % clay soils). The effects of urbanization were most readily detected in regions where forest lands were being converted to urban land because agricultural development significantly degraded assemblages before urbanization and made detection of urban effects difficult. The effects of climatic factors (temperature, precipitation) on background conditions (biogeographic differences) and rates of response to urbanization were most apparent after accounting for the effects of agricultural development. The effects of climate and land cover on responses to urbanization provide strong evidence that monitoring, mitigation, and restoration efforts must be tailored for specific regions and that attainment goals (background conditions) may not be possible in regions with high levels of prior disturbance (e.g., agricultural development).

Journal of the North American Benthological Societ↗
USGS2021

Conservation of northwestern and southwestern pond turtles: Threats, population size estimates, and population viability analysis

Accurate status assessments of long-lived, widely distributed taxa depend on the availability of long-term monitoring data from multiple populations. However, monitoring populations across large temporal and spatial scales is often beyond the scope of any one researcher or research group. Consequently, wildlife managers may be tasked with utilizing limited information from different sources to detect range-wide evidence of population declines and their causes. When assessments need to be made under such constraints, the research and management communities must determine how to extrapolate from variable population data to species-level inferences. Here, using three different approaches, we integrate and analyze data from the peer-reviewed literature and government agency reports to inform conservation for northwestern pond turtles (NPT) Actinemys marmorata and southwestern pond turtles (SPT) Actinemys pallida . Both NPT and SPT are long-lived freshwater turtles distributed along the west coast of the United States and Mexico. Conservation concerns exist for both species; however, SPT may face more severe threats and are thought to exist at lower densities throughout their range than NPT. For each species, we ranked the impacts of 13 potential threats, estimated population sizes, and modeled population viability with and without long-term droughts. Our results suggest that predation of hatchlings by invasive predators, such as American bullfrogs Lithobates catesbeianus and Largemouth Bass Micropterus salmoides, is a high-ranking threat for NPT and SPT. Southwestern pond turtles may also face more severe impacts associated with natural disasters (droughts, wildfires, and floods) than do NPT. Population size estimates from trapping surveys indicate that SPT have smaller population sizes on average than do NPT ( P = 0.0003), suggesting they may be at greater risk of local extirpation. Population viability analysis models revealed that long-term droughts are a key environmental parameter; as the frequency of severe droughts increases with climate change, the likelihood of population recovery decreases, especially when census sizes are low. Given current population trends and vulnerability to natural disasters throughout their range, we suggest that conservation and recovery actions first focus on SPT to prevent further population declines.

Journal of Fish and Wildlife Management↗
USGS2013

Hydrologic controls on the transport and cycling of carbon and nitrogen in a boreal catchment underlain by continuous permafrost

Boreal ecosystems represent a large carbon (C) reservoir and a substantial source of greenhouse gases. Hydrologic conditions dictate whether C leached from boreal soils is processed in catchments or flushed to less productive environments via the stream. This study quantified hydrologic and biogeochemical C loss from a boreal catchment underlain by frozen silt, where flowpaths may deepen as the active layer thaws over the summer. We hypothesized a decrease in the magnitude of C mineralization over the summer associated with changing flowpaths and decreasing hydrologic connectivity, organic matter lability, and nitrogen (N) availability. Conservative tracers were used to partition C and N loss between catchment export and biogeochemical processing. Coupling tracers with tributary and porewater chemistry indicated C and N cycling in soil flowpaths, with an exponential decrease over the summer. Nitrate was primarily reduced in hillslope flowpaths and the lack of N reaching the stream appeared to limit C mineralization. Stream export accounted for the greatest loss of C, removing 247 and 113 mol hr −1 in the early and late summer, respectively. Reactivity was related to hydrologic connectivity between the soils and stream, which was greatest early in the summer and following a large flood. While a warming climate may increase storage potential in thawed soils, the early‐season flush of labile material and late‐season runoff through mineral flowpaths may maintain high C export rates. Therefore, we highlight physical export as a dominant cause of aqueous C loss from silty catchments as the Arctic continues to thaw.

Journal of Geophysical Research G: Biogeosciences↗
USGS2011

Trematode communities in snails can indicate impact and recovery from hurricanes in a tropical coastal lagoon

In September 2002, Hurricane Isidore devastated the Yucatán Peninsula, Mexico. To understand its effects on the parasites of aquatic organisms, we analyzed long-term monthly population data of the horn snail Cerithidea pliculosa and its trematode communities in Celestún, Yucatán, Mexico before and after the hurricane (February 2001 to December 2009). Five trematode species occurred in the snail population: Mesostephanus appendiculatoides , Euhaplorchis californiensis , two species of the genus Renicola and one Heterophyidae gen. sp. Because these parasites use snails as first intermediate hosts, fishes as second intermediate hosts and birds as final hosts, their presence in snails depends on food webs. No snails were present at the sampled sites for 6 months after the hurricane. After snails recolonised the site, no trematodes were found in snails until 14 months after the hurricane. It took several years for snail and trematode populations to recover. Our results suggest that the increase in the occurrence of hurricanes predicted due to climate change can impact upon parasites with complex life cycles. However, both the snail populations and their parasite communities eventually reached numbers of individuals and species similar to those before the hurricane. Thus, the trematode parasites of snails can be useful indicators of coastal lagoon ecosystem degradation and recovery.

International Journal for Parasitology↗
USGS2013

Increases in flood magnitudes in California under warming climates

Downscaled and hydrologically modeled projections from an ensemble of 16 Global Climate Models suggest that flooding may become more intense on the western slopes of the Sierra Nevada mountains, the primary source for California’s managed water system. By the end of the 21st century, all 16 climate projections for the high greenhouse-gas emission SRES A2 scenario yield larger floods with return periods ranging 2–50 years for both the Northern Sierra Nevada and Southern Sierra Nevada, regardless of the direction of change in mean precipitation. By end of century, discharges from the Northern Sierra Nevada with 50-year return periods increase by 30–90% depending on climate model, compared to historical values. Corresponding flood flows from the Southern Sierra increase by 50–100%. The increases in simulated 50 year flood flows are larger (at 95% confidence level) than would be expected due to natural variability by as early as 2035 for the SRES A2 scenario.

California↗
USGS2020

Explaining mass balance and retreat dichotomies at Taku and Lemon Creek Glaciers, Alaska

We reanalyzed mass balance records at Taku and Lemon Creek Glaciers to better understand the relative roles of hypsometry, local climate and dynamics as mass balance drivers. Over the 1946–2018 period, the cumulative mass balances diverged. Tidewater Taku Glacier advanced and gained mass at an average rate of +0.25±0.28 m w.e. a–1, contrasting with retreat and mass loss of –0.60±0.15 m w.e. a-1 at land-terminating Lemon Creek Glacier. The uniform influence of regional climate is demonstrated by strong correlations among annual mass balance and climate data. Regional warming trends forced similar statistically significant decreases in surface mass balance after 1989: –0.83 m w.e. a–1 at Taku Glacier and –0.81 m w.e. a–1 at Lemon Creek Glacier. Divergence in cumulative mass balance arises from differences in glacier hypsometry and local climate. Since 2013 negative mass balance and glacier-wide thinning prevailed at Taku Glacier. These changes initiated terminus retreat, which could increase dramatically if calving begins. The future mass balance trajectory of Taku Glacier hinges on dynamics, likely ending the historic dichotomy between these glaciers.

Alaska↗
USGS2024

GNSS reflectometry from low-cost sensors for continuous in situ contemporaneous glacier mass balance and flux divergence

Recent advances in remote sensing have produced global glacier surface elevation change data. Parsing these elevation change signals into contributions from the climate (i.e. climatic mass balance) and glacier dynamics (i.e. flux divergence) is critical to enhance our process-based understanding of glacier change. In this study, we evaluate three approaches for direct, continuous measurements of the climatic mass balance, flux divergence, and elevation change at a site on Gulkana Glacier in Alaska using low-cost GNSS sensors, GNSS interferometric reflectometry (GNSS-IR), banded ablation stakes with time-lapse cameras, and combinations thereof. Cumulative climatic mass balance over the season was 4.85 m and the three approaches were within 0.08 m through early July before the snowpack melted, and within 0.28 m through mid-August. The flux divergence increased from 0.52 ± 0.03 cm d -1 before June 3 to roughly 0.73 cm d -1 after June 27. We demonstrate a single GNSS system fixed atop an ablation stake can measure contemporaneous climatic mass balance, flux divergence, and elevation change based on the antenna’s position and GNSS-IR techniques. The ability of these systems to measure glacier mass balance and flux divergence offers unique opportunities for year-round observations on mountain glaciers in the future.

Alaska↗
USGS2021

Active Mars: A dynamic world

Mars exhibits diverse surface changes at all latitudes and all seasons. Active processes include impact cratering, aeolian sand and dust transport, a variety of slope processes, changes in polar ices, and diverse effects of seasonal CO 2 frost. The extent of surface change has been surprising and indicates that the present climate is capable of reshaping the surface. Activity has important implications for the Amazonian history of Mars: understanding processes is a necessary step before we can understand their implications and variations over time.

Journal of Geophysical Research: Planets↗
USGS2023

Abiotic and biotic factors reduce the viability of a high-elevation salamander in its native range

Amphibian populations are undergoing worldwide declines, and high-elevation, range-restricted amphibian species may be particularly vulnerable to environmental stressors. In particular, future climate change may have disproportional impacts to these ecosystems. Evaluating the combined effects of abiotic changes and biotic interactions simultaneously is important for forecasting the range of future outcomes. This information is necessary to aid conservation decision-making. We use field data to estimate population demographic parameters for an exemplary high-elevation amphibian species, the federally endangered Shenandoah salamander Plethodon shenandoah . These parameters were entered into a Markov projection model which we used to forecast the future population status of the Shenandoah salamander. We found that if the population maintains its current site colonization and persistence rates, it is at the risk of extinction that could be exacerbated by both climate and interspecific competition. Synthesis and applications. Managers have a fundamental objective directed by official policy of maintaining the species ‘for the foreseeable future’. Our evaluation of multiple hypotheses about population drivers reveals that extinction is projected for this species. Our analysis suggests that considering active management need not depend on resolving the uncertainty.

Virginia↗
USGS2015

End-of-winter snow depth variability on glaciers in Alaska

A quantitative understanding of snow thickness and snow water equivalent (SWE) on glaciers is essential to a wide range of scientific and resource management topics. However, robust SWE estimates are observationally challenging, in part because SWE can vary abruptly over short distances in complex terrain due to interactions between topography and meteorological processes. In spring 2013, we measured snow accumulation on several glaciers around the Gulf of Alaska using both ground- and helicopter-based ground-penetrating radar surveys, complemented by extensive ground truth observations. We found that SWE can be highly variable (40% difference) over short spatial scales (tens to hundreds of meters), especially in the ablation zone where the underlying ice surfaces are typically rough. Elevation provides the dominant basin-scale influence on SWE, with gradients ranging from 115 to 400 mm/100 m. Regionally, total accumulation and the accumulation gradient are strongly controlled by a glacier's distance from the coastal moisture source. Multiple linear regressions, used to calculate distributed SWE fields, show that robust results require adequate sampling of the true distribution of multiple terrain parameters. Final SWE estimates (comparable to winter balances) show reasonable agreement with both the Parameter-elevation Relationships on Independent Slopes Model climate data set (9–36% difference) and the U.S. Geological Survey Alaska Benchmark Glaciers (6–36% difference). All the glaciers in our study exhibit substantial sensitivity to changing snow-rain fractions, regardless of their location in a coastal or continental climate. While process-based SWE projections remain elusive, the collection of ground-penetrating radar (GPR)-derived data sets provides a greatly enhanced perspective on the spatial distribution of SWE and will pave the way for future work that may eventually allow such projections.

Alaska↗