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Results for “Climatic Change”

Search indexed USGS publications on groundwater, aquifers, geologic maps, mineral resources and earthquakes. Explore source records by subject and place.

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At least 901 records · Page 50Linked to original sources
USGS2009

Responses of stream nitrate and dissolved organic carbon loadings to hydrological forcing and climate change in an upland forest of the northeast USA

[1] In coming decades, higher annual temperatures, increased growing season length, and increased dormant season precipitation are expected across the northeastern United States in response to anthropogenic forcing of global climate. We synthesized long-term stream hydrochemical data from the Sleepers River Research Watershed in Vermont, United States, to explore the relationship of catchment wetness to stream nitrate and DOC loadings. We modeled changes in growing season length and precipitation patterns to simulate future climate scenarios and to assess how stream nutrient loadings respond to climate change. Model results for the 2070–2099 time period suggest that stream nutrient loadings during both the dormant and growing seasons will respond to climate change. During a warmer climate, growing season stream fluxes (runoff +20%, nitrate +57%, and DOC +58%) increase as more precipitation (+28%) and quick flow (+39%) occur during a longer growing season (+43 days). During the dormant season, stream water and nutrient loadings decrease. Net annual stream runoff (+8%) and DOC loading (+9%) increases are commensurate with the magnitude of the average increase of net annual precipitation (+7%). Net annual stream water and DOC loadings are primarily affected by increased dormant season precipitation. In contrast, decreased annual loading of stream nitrate (−2%) reflects a larger effect of growing season controls on stream nitrate and the effects of lengthened growing seasons in a warmer climate. Our findings suggest that leaching of nitrate and DOC from catchment soils will be affected by anthropogenic climate forcing, thereby affecting the timing and magnitude of annual stream loadings in the northeastern United States.

Vermont↗
USGS2017

Shallow marine response to global climate change during the Paleocene-Eocene Thermal Maximum, Salisbury Embayment, USA

The Paleocene-Eocene Thermal Maximum (PETM) was an interval of extreme warmth that caused disruption of marine and terrestrial ecosystems on a global scale. Here we examine the sediments, flora, and fauna from an expanded section at Mattawoman Creek-Billingsley Road (MCBR) in Maryland and explore the impact of warming at a nearshore shallow marine (30–100 m water depth) site in the Salisbury Embayment. Observations indicate that at the onset of the PETM, the site abruptly shifted from an open marine to prodelta setting with increased terrestrial and fresh water input. Changes in microfossil biota suggest stratification of the water column and low-oxygen bottom water conditions in the earliest Eocene. Formation of authigenic carbonate through microbial diagenesis produced an unusually large bulk carbon isotope shift, while the magnitude of the corresponding signal from benthic foraminifera is similar to that at other marine sites. This proves that the landward increase in the magnitude of the carbon isotope excursion measured in bulk sediment is not due to a near instantaneous release of 12 C-enriched CO 2 . We conclude that the MCBR site records nearshore marine response to global climate change that can be used as an analog for modern coastal response to global warming.

Maryland, New Jersey, Pennsylvania, Virginia↗
USGS2017

Estimating current and future streamflow characteristics at ungaged sites, central and eastern Montana, with application to evaluating effects of climate change on fish populations

A common statistical procedure for estimating streamflow statistics at ungaged locations is to develop a relational model between streamflow and drainage basin characteristics at gaged locations using least squares regression analysis; however, least squares regression methods are parametric and make constraining assumptions about the data distribution. The random forest regression method provides an alternative nonparametric method for estimating streamflow characteristics at ungaged sites and requires that the data meet fewer statistical conditions than least squares regression methods. Random forest regression analysis was used to develop predictive models for 89 streamflow characteristics using Precipitation-Runoff Modeling System simulated streamflow data and drainage basin characteristics at 179 sites in central and eastern Montana. The predictive models were developed from streamflow data simulated for current (baseline, water years 1982–99) conditions and three future periods (water years 2021–38, 2046–63, and 2071–88) under three different climate-change scenarios. These predictive models were then used to predict streamflow characteristics for baseline conditions and three future periods at 1,707 fish sampling sites in central and eastern Montana. The average root mean square error for all predictive models was about 50 percent. When streamflow predictions at 23 fish sampling sites were compared to nearby locations with simulated data, the mean relative percent difference was about 43 percent. When predictions were compared to streamflow data recorded at 21 U.S. Geological Survey streamflow-gaging stations outside of the calibration basins, the average mean absolute percent error was about 73 percent.

Montana↗
USGS2003

Climate change and Arctic ecosystems: 1. Vegetation changes north of 55°N between the last glacial maximum, mid-Holocene, and present

A unified scheme to assign pollen samples to vegetation types was used to reconstruct vegetation patterns north of 55??N at the last glacial maximum (LGM) and mid-Holocene (6000 years B.P.). The pollen data set assembled for this purpose represents a comprehensive compilation based on the work of many projects and research groups. Five tundra types (cushion forb tundra, graminoid and forb tundra, prostrate dwarf-shrub tundra, erect dwarf-shrub tundra, and low- and high-shrub tundra) were distinguished and mapped on the basis of modern pollen surface samples. The tundra-forest boundary and the distributions of boreal and temperate forest types today were realistically reconstructed. During the mid-Holocene the tundra-forest boundary was north of its present position in some regions, but the pattern of this shift was strongly asymmetrical around the pole, with the largest northward shift in central Siberia (???200 km), little change in Beringia, and a southward shift in Keewatin and Labrador (???200 km). Low- and high-shrub tundra extended farther north than today. At the LGM, forests were absent from high latitudes. Graminoid and forb tundra abutted on temperate steppe in northwestern Eurasia while prostrate dwarf-shrub, erect dwarf-shrub, and graminoid and forb tundra formed a mosaic in Beringia. Graminoid and forb tundra is restricted today and does not form a large continuous biome, but the pollen data show that it was far more extensive at the LGM, while low- and high-shrub tundra were greatly reduced, illustrating the potential for climate change to dramatically alter the relative areas occupied by different vegetation types.

Journal of Geophysical Research D: Atmospheres↗
USGS2010

It's not just about climate change - What about soils?

Vladimir Vernadsky was one of the giants of geochemistry. Considered the founder of the fi eld of biogeochemistry and a true pioneer in “whole Earth” studies, he realized by 1945 that “Man under our very eyes is becoming a mighty and ever-growing geological force.” In the intervening 65 years, his “ever-growing force” has become a tidal wave. The global population has been increasing exponentially since the beginning of the industrial revolution, and as a result has increased by nearly a factor of three between 1945, when his observation was published, and today (see fi gure). Current projections anticipate a population exceeding 9 billion by 2050. This explosive human population growth has been fueled by ancient hydrocarbons and has come with high costs. Most Earth scientists are concerned with the implications of the rapid accumulation of greenhouse gases in the atmosphere. The consequences include a climate state without polar ice, acidifying oceans, and increasingly variable water fl uxes. The rate and extent of these and many other negative climate-related impacts, and how to mitigate them, have caused a vigorous discussion on climate change that is in the news on a nearly daily basis.

Elements↗
USGS2022

Fires, floods and other extreme events – How watershed processes under climate change will shape our coastlines

Ongoing sea-level rise has brought renewed focus on terrestrial sediment supply to the coast because of its strong influence on whether and how long beaches, marshes and other coastal landforms may persist into the future. Here, we summarise findings of sediment discharge from several coastal rivers, revealing that infrequent, large-magnitude events have disproportionate influence on the morphodynamics of coastal landforms and littoral cells. These event-dominated effects are most pronounced for small, steep mountainous rivers that supply beach and wetland sediment along the world’s active tectonic margins, although infrequent events are important drivers of sediment discharge for rivers worldwide. Additionally, extreme events (recurrence intervals of decades to centuries) that follow wildfires, earthquakes, volcanic eruptions, extreme precipitation or – most notably – combinations of these factors can redefine coastal sediment budgets and morphology. Some of these extreme events (e.g., wildfires plus rainfall) are increasing in magnitude and frequency under modern climate warming, with the likely result of increasing sediment flux to affected coastlines. Climate change is also altering watershed processes in both high latitudes and high altitudes, resulting in increased sediment supply to downstream catchments. We conclude that sediment inputs to coastal systems are highly variable with time, and that the variability and trends in sediment input are as important to characterise as long-term averages.

Cambridge Prisms: Coastal Futures↗
USGS2023

Mangrove reforestation provides greater blue carbon benefit than afforestation for mitigating global climate change

Significant efforts have been invested to restore mangrove forests worldwide through reforestation and afforestation. However, blue carbon benefit has not been compared between these two silvicultural pathways at the global scale. Here, we integrated results from direct field measurements of over 370 restoration sites around the world to show that mangrove reforestation (reestablishing mangroves where they previously colonized) had a greater carbon storage potential per hectare than afforestation (establishing mangroves where not previously mangrove). Greater carbon accumulation was mainly attributed to favorable intertidal positioning, higher nitrogen availability, and lower salinity at most reforestation sites. Reforestation of all physically feasible areas in the deforested mangrove regions of the world could promote the uptake of 671.5–688.8 Tg CO 2 -eq globally over a 40-year period, 60% more than afforesting the same global area on tidal flats (more marginal sites). Along with avoiding conflicts of habitat conversion, mangrove reforestation should be given priority when designing nature-based solutions for mitigating global climate change.

Nature Communications↗
USGS2014

Widespread loess-like deposit in the Martian northern lowlands identifies Middle Amazonian climate change

Consistently mappable units critical to distinguishing the style and interplay of geologic processes through time are sparse in the Martian lowlands. This study identifies a previously unmapped Middle Amazonian (ca. 1 Ga) unit (Middle Amazonian lowland unit, mAl) that postdates the Late Hesperian and Early Amazonian lowland plains by >2 b.y. The unit is regionally defined by subtle marginal scarps and slopes, has a mean thickness of 32 m, and extends >3.1 × 10 6 km 2 between lat 35°N and 80°N. Pedestal-type craterforms and nested, arcuate ridges (thumbprint terrain) tend to occur adjacent to unit mAl outcrops, suggesting that current outcrops are vestiges of a more extensive deposit that previously covered ∼16 × 10 6 km 2 . Exposed layers, surface pits, and the draping of subjacent landforms allude to a sedimentary origin, perhaps as a loess-like deposit emplaced rhythmically through atmospheric fallout. We propose that unit mAl accumulated coevally with, and at the expense of, the erosion of the north polar basal units, identifying a major episode of Middle Amazonian climate-driven sedimentation in the lowlands. This work links ancient sedimentary processes to climate change that occurred well before those implied by current orbital and spin axis models.

Geology↗
USGS2016

Reproductive allochrony in seasonally sympatric populations maintained by differential response to photoperiod: Implications for population divergence and response to climate change

Reproductive allochrony presents a potential barrier to gene flow and is common in seasonally sympatric migratory and sedentary birds. Mechanisms mediating reproductive allochrony can influence population divergence and the capacity of populations to respond to environmental change. We asked whether reproductive allochrony in seasonally sympatric birds results from a difference in response to supplementary or photoperiodic cues and whether the response varies in relation to the distance separating breeding and wintering locations as measured by stable isotopes. We held seasonally sympatric migratory and sedentary male dark-eyed juncos ( Junco hyemalis ) in a common garden in early spring under simulated natural changes in photoperiod and made measurements of reproductive and migratory physiology. On the same dates and photoperiods, sedentary juncos had higher testosterone (initial and gonadotropin-releasing hormone induced), more developed cloacal protuberances, and larger testes than migrants. In contrast, migratory juncos had larger fat reserves (fuel for migration). We found a negative relationship between testis mass and feather hydrogen isotope ratios, indicating that testis growth was more delayed in migrants making longer migrations. We conclude that reproductive allochrony in seasonally sympatric migratory and sedentary birds can result from a differential response to photoperiodic cues in a common garden, and as a result, gene flow between migrants and residents may be reduced by photoperiodic control of reproductive development. Further, earlier breeding in response to future climate change may currently be constrained by differential response to photoperiodic cues.

American Naturalist↗
USGS2006

Response of microbial community composition and function to soil climate change

Soil microbial communities mediate critical ecosystem carbon and nutrient cycles. How microbial communities will respond to changes in vegetation and climate, however, are not well understood. We reciprocally transplanted soil cores from under oak canopies and adjacent open grasslands in a California oak-grassland ecosystem to determine how microbial communities respond to changes in the soil environment and the potential consequences for the cycling of carbon. Every 3 months for up to 2 years, we monitored microbial community composition using phospholipid fatty acid analysis (PLFA), microbial biomass, respiration rates, microbial enzyme activities, and the activity of microbial groups by quantifying 13C uptake from a universal substrate (pyruvate) into PLFA biomarkers. Soil in the open grassland experienced higher maximum temperatures and lower soil water content than soil under the oak canopies. Soil microbial communities in soil under oak canopies were more sensitive to environmental change than those in adjacent soil from the open grassland. Oak canopy soil communities changed rapidly when cores were transplanted into the open grassland soil environment, but grassland soil communities did not change when transplanted into the oak canopy environment. Similarly, microbial biomass, enzyme activities, and microbial respiration decreased when microbial communities were transplanted from the oak canopy soils to the grassland environment, but not when the grassland communities were transplanted to the oak canopy environment. These data support the hypothesis that microbial community composition and function is altered when microbes are exposed to new extremes in environmental conditions; that is, environmental conditions outside of their "life history" envelopes. ?? 2006 Springer Science+Business Media, Inc.

Microbial Ecology↗
USGS2006

Effects of historical climate change, habitat connectivity, and vicariance on genetic structure and diversity across the range of the Red Tree Vole (Phenacomys longicaudus) in the Pacific Northwest United States

Phylogeographical analyses conducted in the Pacific Northwestern United States have often revealed concordant patterns of genetic diversity among taxa. These studies demonstrate distinct North/South genetic discontinuities that have been attributed to Pleistocene glaciation. We examined phylogeographical patterns of red tree voles (Phenacomys longicaudus) in western Oregon by analysing mitochondrial control region sequences for 169 individuals from 18 areas across the species' range. Cytochrome b sequences were also analysed from a subset of our samples to confirm the presence of major haplotype groups. Phylogenetic network analyses suggested the presence of two haplotype groups corresponding to northern and southern regions of P. longicaudus' range. Spatial genetic analyses (samova and Genetic Landscape Shapes) of control region sequences demonstrated a primary genetic discontinuity separating northern and southern sampling areas, while a secondary discontinuity separated northern sampling areas into eastern and western groups divided by the Willamette Valley. The North/South discontinuity likely corresponds to a region of secondary contact between lineages rather than an overt barrier. Although the Cordilleran ice sheet (maximum a??12 000 years ago) did not move southward to directly affect the region occupied by P. longicaudus, climate change during glaciation fragmented the forest landscape that it inhabits. Signatures of historical fragmentation were reflected by positive associations between latitude and variables such as Tajima's D and patterns associated with location-specific alleles. Genetic distances between southern sampling areas were smaller, suggesting that forest fragmentation was reduced in southern vs. northern regions.

Molecular Ecology↗
USGS2006

Erosion rates at the Mars Exploration Rover landing sites and long-term climate change on Mars

Erosion rates derived from the Gusev cratered plains and the erosion of weak sulfates by saltating sand at Meridiani Planum are so slow that they argue that the present dry and desiccating environment has persisted since the Early Hesperian. In contrast, sedimentary rocks at Meridiani formed in the presence of groundwater and occasional surface water, and many Columbia Hills rocks at Gusev underwent aqueous alteration during the Late Noachian, approximately coeval with a wide variety of geomorphic indicators that indicate a wetter and likely warmer environment. Two-toned rocks, elevated ventifacts, and perched and undercut rocks indicate localized deflation of the Gusev plains and deposition of an equivalent amount of sediment into craters to form hollows, suggesting average erosion rates of ???0.03 nm/yr. Erosion of Hesperian craters, modification of Late Amazonian craters, and the concentration of hematite concretions in the soils of Meridiani yield slightly higher average erosion rates of 1-10 nm/yr in the Amazonian. These erosion rates are 2-5 orders of magnitude lower than the slowest continental denudation rates on Earth, indicating that liquid water was not an active erosional agent. Erosion rates for Meridiani just before deposition of the sulfate-rich sediments and other eroded Noachian areas are comparable with slow denudation rates on Earth that are dominated by liquid water. Available data suggest the climate change at the landing sites from wet and likely warm to dry and desiccating occurred sometime between the Late Noachian and the beginning of the Late Hesperian (3.7-3.5 Ga). Copyright 2006 by the American Geophysical Union.

Journal of Geophysical Research E: Planets↗
USGS2013

Quantifying climate change mitigation potential in Great Plains wetlands for three greenhouse gas emission scenarios

We examined opportunities for avoided loss of wetland carbon stocks in the Great Plains of the United States in the context of future agricultural expansion through analysis of land-use land-cover (LULC) change scenarios, baseline carbon datasets and biogeochemical model outputs. A wetland map that classifies wetlands according to carbon pools was created to describe future patterns of carbon loss and potential carbon savings. Wetland avoided loss scenarios, superimposed upon LULC change scenarios, quantified carbon stocks preserved under criteria of carbon densities or land value plus cropland suitability. Up to 3420 km 2 of wetlands may be lost in the region by 2050, mainly due to conversion of herbaceous wetlands in the Temperate Prairies where soil organic carbon (SOC) is highest. SOC loss would be approximately 0.20 ± 0.15 megagrams of carbon per hectare per year (MgC ha −1 yr −1 ), depending upon tillage practices on converted wetlands, and total ecosystem carbon loss in woody wetlands would be approximately 0.81 ± 0.41 MgC ha −1 yr −1 , based on biogeochemical model results. Among wetlands vulnerable to conversion, wetlands in the Northern Glaciated Plains and Lake Agassiz Plains ecoregions exhibit very high mean SOC and on average, relatively low land values, potentially creating economically competitive opportunities for avoided carbon loss. This mitigation scenarios approach may be adapted by managers using their own preferred criteria to select sites that best meet their objectives. Results can help prioritize field-based assessments, where site-level investigations of carbon stocks, land value, and consideration of local priorities for climate change mitigation programs are needed.

Great Plains↗
USGS2024

Debris-flow entrainment modelling under climate change: Considering antecedent moisture conditions along the flow path

Debris-flow volumes can increase along their flow path by entraining sediment stored in the channel bed and banks, thus also increasing hazard potential. Theoretical considerations, laboratory experiments and field investigations all indicate that the saturation conditions of the sediment along the flow path can greatly influence the amount of sediment entrained. However, this process is usually not considered for practical applications. This study aims to close this gap by combining runout and hydrological models into a predictive framework that is calibrated and tested using unique observations of sediment erosion and debris-flow properties available at a Swiss debris-flow observation station (Illgraben). To this end, hourly water input to the erodible channel is predicted using a simple, process-based hydrological model, and the resulting water saturation level in the upper sediment layer of the channel is modelled based on a Hortonian infiltration concept. Debris-flow entrainment is then predicted using the RAMMS debris-flow runout model. We find a strong correlation between the modelled saturation level of the sediment on the flow path and the channel-bed erodibility for single-surge debris-flow events with distinct fronts, indicating that the modelled water content is a good predictor for erosion simulated in RAMMS. Debris-flow properties with more complex flow behaviour (e.g., multiple surges or roll waves) are not as well predicted using this procedure, indicating that more physically complete models are necessary. Finally, we demonstrate how this modelling framework can be used for climate change impact assessment and show that earlier snowmelt may shift the peak of the debris-flow season to earlier in the year. Our novel modelling framework provides a plausible approach to reproduce saturation-dependent entrainment and thus better constrain event volumes for current and future hazard assessment.

Illgraben basin↗
USGS2008

Abrupt climate change and collapse of deep-sea ecosystems

We investigated the deep-sea fossil record of benthic ostracodes during periods of rapid climate and oceanographic change over the past 20,000 years in a core from intermediate depth in the northwestern Atlantic. Results show that deep-sea benthic community "collapses" occur with faunal turnover of up to 50% during major climatically driven oceanographic changes. Species diversity as measured by the Shannon-Wiener index falls from 3 to as low as 1.6 during these events. Major disruptions in the benthic communities commenced with Heinrich Event 1, the Inter-Aller??d Cold Period (IACP: 13.1 ka), the Younger Dryas (YD: 12.9-11.5 ka), and several Holocene Bond events when changes in deep-water circulation occurred. The largest collapse is associated with the YD/IACP and is characterized by an abrupt two-step decrease in both the upper North Atlantic Deep Water assemblage and species diversity at 13.1 ka and at 12.2 ka. The ostracode fauna at this site did not fully recover until ???8 ka, with the establishment of Labrador Sea Water ventilation. Ecologically opportunistic slope species prospered during this community collapse. Other abrupt community collapses during the past 20 ka generally correspond to millennial climate events. These results indicate that deep-sea ecosystems are not immune to the effects of rapid climate changes occurring over centuries or less. ?? 2008 by The National Academy of Sciences of the USA.

Proceedings of the National Academy of Sciences of↗
USGS2015

Chemical and biotic characteristics of prairie lakes and large wetlands in south-central North Dakota—Effects of a changing climate

The climate of the prairie pothole region of North America is known for variability that results in significant interannual changes in water depths and volumes of prairie lakes and wetlands; however, beginning in July 1993, the climate of the region shifted to an extended period of increased precipitation that has likely been unequaled in the preceding 500 years. Associated changing water volumes also affect water chemical characteristics, with potential effects on fish and wildlife populations. To explore the effect of changing climate patterns, in 2012 and 2013, the U.S. Geological Survey revisited 167 of 178 prairie lakes and large wetlands of south-central North Dakota that were originally sampled in the mid-1960s to mid-1970s. During the earlier sampling period, these lakes and wetlands displayed a great range of chemical characteristics (for example, specific conductance ranged from 365 microsiemens per centimeter at 25 degrees Celsius to 70,300 microsiemens per centimeter at 25 degrees Celsius); however, increased water volumes have resulted in greatly reduced variation among lakes and wetlands and a more homogeneous set of chemical conditions defined by pH, specific conductance, and concentrations of major cations and anions. High concentrations of dissolved solids previously limited fish occurrence in many of the lakes and wetlands sampled; however, freshening of these lakes and large wetlands has allowed fish to populate and flourish where they were previously absent. Conversely, the freshening of previously saline lakes and wetlands has resulted in concurrent shifts away from invertebrate species adapted to live in these highly saline environments. A shift in the regional climate has changed a highly diverse landscape of wetlands (fresh to highly saline) to a markedly more homogeneous landscape that has reshaped the fish and wildlife communities of this ecologically and economically important region.

North Dakota↗
USGS2010

Effects of simultaneous climate change and geomorphic evolution on thermal characteristics of a shallow Alaskan lake

We used a hydrodynamics model to assess the consequences of climate warming and contemporary geomorphic evolution for thermal conditions in a large, shallow Alaskan lake. We evaluated the effects of both known climate and landscape change, including rapid outlet erosion and migration of the principal inlet stream, over the past 50 yr as well as future scenarios of geomorphic restoration. Compared to effects of air temperature during the past 50 yr, lake thermal properties showed little sensitivity to substantial (~60%) loss of lake volume, as the lake maximum depth declined from 6 m to 4 m driven by outlet erosion. The direction and magnitude of future lake thermal responses will be driven largely by the extent of inlet stream migration when it occurs simultaneously with outlet erosion. Maintaining connectivity with inlet streams had substantial effects on buffering lake thermal responses to warming climate. Failing to account for changing rates and types of geomorphic processes under continuing climate change may misidentify the primary drivers of lake thermal responses and reduce our ability to understand the consequences for aquatic organisms.

Alaska↗