Short‐term stream water temperature observations permit rapid assessment of potential climate change impacts          下载免费PDF全文

Peter Caldwell  Catalina Segura  Shelby Gull Laird  Ge Sun  Steven G. McNulty  Maria Sandercock  Johnny Boggs  James M. Vose 《水文研究》2015,29(9):2196-2211

Assessment of potential climate change impacts on stream water temperature (T_s) across large scales remains challenging for resource managers because energy exchange processes between the atmosphere and the stream environment are complex and uncertain, and few long‐term datasets are available to evaluate changes over time. In this study, we demonstrate how simple monthly linear regression models based on short‐term historical T_s observations and readily available interpolated air temperature (T_a) estimates can be used for rapid assessment of historical and future changes in T_s. Models were developed for 61 sites in the southeastern USA using ≥18 months of observations and were validated at sites with longer periods of record. The T_s models were then used to estimate temporal changes in T_s at each site using both historical estimates and future T_a projections. Results suggested that the linear regression models adequately explained the variability in T_s across sites, and the relationships between T_s and T_a remained consistent over 37 years. We estimated that most sites had increases in historical annual mean T_s between 1961 and 2010 (mean of +0.11 °C decade^?1). All 61 sites were projected to experience increases in T_s from 2011 to 2060 under the three climate projections evaluated (mean of +0.41 °C decade^?1). Several of the sites with the largest historical and future T_s changes were located in ecoregions home to temperature‐sensitive fish species. This methodology can be used by resource managers for rapid assessment of potential climate change impacts on stream water temperature. Copyright © 2014 John Wiley & Sons, Ltd.  相似文献   

Long-term research catchments to investigate shrub encroachment in the Sonoran and Chihuahuan deserts: Santa Rita and Jornada experimental ranges     

Enrique R. Vivoni  Eli R. Pérez-Ruiz  Zachary T. Keller  Eric A. Escoto  Ryan C. Templeton  Nolie P. Templeton  Cody A. Anderson  Adam P. Schreiner-McGraw  Luis A. Méndez-Barroso  Agustin Robles-Morua  Russell L. Scott  Steven R. Archer  Debra P. C. Peters 《水文研究》2021,35(2):e14031

Woody plant encroachment is a global phenomenon whereby shrubs or trees replace grasses. The hydrological consequences of this ecological shift are of broad interest in ecohydrology, yet little is known of how plant and intercanopy patch dynamics, distributions, and connectivity influence catchment-scale responses. To address this gap, we established research catchments in the Sonoran and Chihuahuan Deserts (near Green Valley, Arizona and near Las Cruces, New Mexico, respectively) that represent shrub encroachment in contrasting arid climates. Our main goals in the coordinated observations were to: (a) independently measure the components of the catchment water balance, (b) deploy sensors to quantify the spatial patterns of ecohydrological processes, (c) use novel methods for characterizing catchment properties, and (d) assess shrub encroachment impacts on ecohydrological processes through modelling studies. Datasets on meteorological variables; energy, radiation, and CO₂ fluxes; evapotranspiration; soil moisture and temperature; and runoff at various scales now extend to nearly 10 years of observations at each site, including both wet and dry periods. Here, we provide a brief overview of data collection efforts and offer suggestions for how the coordinated datasets can be exploited for ecohydrological inferences and modelling studies. Given the representative nature of the catchments, the available databases can be used to generalize findings to other catchments in desert landscapes.  相似文献   

Modelling how vegetation cover affects climate change impacts on streamflow timing and magnitude in the snowmelt‐dominated upper Tuolumne Basin,Sierra Nevada          下载免费PDF全文

Nicoleta C. Cristea  Jessica D. Lundquist  Steven P. Loheide II  Christopher S. Lowry  Courtney E. Moore 《水文研究》2014,28(12):3896-3918

We investigated, through hydrologic modelling, the impact of the extent and density of canopy cover on streamflow timing and on the magnitude of peak and late summer flows in the upper Tuolumne basin (2600–4000 m) of the Sierra Nevada, California, under current and warmer temperatures. We used the Distributed Hydrology Soil Vegetation Model for the hydrologic modelling of the basin, assuming four vegetation scenarios: current forest (partial cover, 80% density), all forest (uniform coverage, 80% density), all barren (no forest) and thinned forest (partial cover, 40% density) for a medium‐high emissions scenario causing a 3.9 °C warming over a 100‐year period (2001–2100). Significant advances in streamflow timing, quantified as the centre of mass (COM) of over 1 month were projected for all vegetation scenarios. However, the COM advances faster with increased forest coverage. For example, when forest covered the entire area, the COM occurred on average 12 days earlier compared with the current forest coverage, with the rate of advance higher by about 0.06 days year^?1 over 100 years and with peak and late summer flows lower by about 20% and 27%, respectively. Examination of modelled changes in energy balance components at forested and barren sites as temperatures rise indicated that increases in net longwave radiation are higher in the forest case and have a higher contribution to melting earlier in the calendar year when shortwave radiation is a smaller fraction of the energy budget. These increases contributed to increased midwinter melt under the forest at temperatures above freezing, causing decreases in total accumulation and higher winter and early spring melt rates. These results highlight the importance of carefully considering the combined impacts of changing forest cover and climate on downstream water supply and mountain ecosystems. Copyright © 2013 John Wiley & Sons, Ltd.  相似文献   

Statistical Study of Network Jets Observed in the Solar Transition Region: a Comparison Between Coronal Holes and Quiet-Sun Regions     

Nancy Narang  Rebecca T. Arbacher  Hui Tian  Dipankar Banerjee  Steven R. Cranmer  Ed E. DeLuca  Sean McKillop 《Solar physics》2016,291(4):1129-1142

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The impact of natural versus anthropogenic aerosols on atmospheric circulation in the Community Atmosphere Model     

Robert J. Allen  Steven C. Sherwood 《Climate Dynamics》2011,36(9-10):1959-1978

The equilibrium response of atmospheric circulation to the direct radiative effects of natural or anthropogenic aerosols is investigated using the Community Atmosphere Model (CAM3) coupled to two different ocean boundary conditions: prescribed climatological sea surface temperatures (SSTs) and a slab ocean model. Anthropogenic and natural aerosols significantly affect the circulation but in nearly opposite ways, because anthropogenic aerosols tend to have a net local warming effect and natural aerosols a net cooling. Aerosol forcings shift the Intertropical Convergence Zone and alter the strength of the Hadley circulation as found in previous studies, but also affect the Hadley cell width. These effects are due to meridional gradients in warming caused by heterogeneous net heating, and are stronger with interactive SST. Aerosols also drive model responses at high latitudes, including polar near-surface warming by anthropogenic aerosols in summer and an Arctic Oscillation (AO)-type responses in winter: anthropogenic aerosols strengthen wintertime zonal wind near 60°N, weaken it near 30°N, warm the troposphere, cool the stratosphere, and reduce Arctic surface pressure, while natural aerosols produce nearly opposite changes. These responses are shown to be due to modulation of stratospheric wave-driving consistent with meridional forcing gradients in midlatitudes. They are more pronounced when SST is fixed, apparently because the contrast in land-ocean heating drives a predominantly wavenumber-2 response in the northern hemisphere which is more efficient in reaching the stratosphere, showing that zonal heating variations also affect this particular response. The results suggest that recent shifts from reflecting to absorbing aerosol types probably contributed to the observed decadal variations in tropical width and AO, although studies with more realistic temporal variations in forcing would be needed to quantify this contribution.  相似文献   

Modeling the time-dependent response of the Asian summer monsoon to obliquity forcing in a coupled GCM: a PHASEMAP sensitivity experiment   总被引：1，自引：0，他引：1  

Guang-Shan Chen  Zhengyu Liu  Steven C. Clemens  Warren L. Prell  Xiaodong Liu 《Climate Dynamics》2011,36(3-4):695-710

To study the time-dependent response of the Asian summer monsoon to obliquity forcing, we analyze a 284,000-year long transient simulation produced by a fully coupled global climate model (GCM) using a new phase mapping (PHASEMAP) approach. Here we focus on understanding the phase response of monsoonal circulation to insolation forcing at the Earth-orbital obliquity band (41 Kyr). Our results show that the East Asian summer monsoon (EASM) can be divided into two geographic regions: the North East Asian summer monsoon (NEASM) and the South East Asian summer monsoon (SEASM). The Indian summer monsoon (ISM) and the SEASM are in phase at the obliquity band, strengthened with an increase in obliquity from Obliquity minima (Omin) to Obliquity maxima (Omax). The NEASM is out of phase with the ISM and SEASM, weakened with an increase in obliquity from Omin to Omax. We hypothesize that the inverse phase between the NEASM and the ISM at the obliquity band results from an ISM–NEASM teleconnection linked to the formation mechanism of the Bonin High.  相似文献   

Assessing social-ecological coupling: Agriculture and hypoxia in the Gulf of Mexico     

Stefanie Hufnagl-Eichiner  Steven A. WolfLaurie E. Drinkwater 《Global Environmental Change》2011,21(2):530-539

Analysis and enhancement of “coupling” of social-ecological systems (SES) has emerged as a leading theme in sustainability studies. However, as an analytical concept that can support empirical research, coupling has not been adequately developed. This study synthesizes concepts from environmental sociology and ecological sciences to derive three criteria to assess adaptive coupling of an SES: prevention orientation, spatial targeting and temporal targeting. We apply our criteria to the case of nitrogen pollution from agriculture in the Mississippi River Basin (MRB) and resulting hypoxia in the Gulf of Mexico. We analyzed the federal agricultural research and development portfolio to assess the character of investments in knowledge creation and how patterns of investment have changed over time. While superficial assessment of the data suggests that public spending on nitrogen relevant research constitutes a substantive response to the problem of Gulf hypoxia, disaggregating the data highlights an ineffectual response. Specifically, we find that spatial and temporal targeting of investment of socioeconomic resources in the MRB is poorly aligned with the nature of ecological risks confronting the region. In addition to this policy relevant result, our study highlights the importance of geographically referenced data and attention to relevant scales of analysis. Further, the paper demonstrates opportunities to advance concepts and empirical understanding of social-ecological coupling through interdisciplinary research on interfaces that mediate interactions in SES, for example publicly funded research aimed at agricultural practice and environmental conservation in the MRB.  相似文献   

The Impact of Biofilm Growth on Transport of Escherichia coli O157:H7 in Sand     

Aimin Wang  Bin Lin  Brent E. Sleep  Steven N. Liss 《Ground water》2011,49(1):20-31

Understanding the transport behavior, survival, and persistence of pathogens such as Escherichia coli O157:H7 in the subsurface is essential to protection of public health. In this study, the transport of E. coli O157:H7 in a two‐dimensional bench‐scale sand aquifer system, hereafter referred to as the sandbox, was investigated, with a focus on the impact of biofilm development on E. coli retention and survival. Biofilm growth was initiated through flushing with unsterilized groundwater and addition of glucose, nitrate, and phosphate. Retention of E. coli from an injection test in clean sand, prior to promotion of biofilm growth, was approximately 9%. Subsequent to biofilm growth, 47% of injected E. coli cells were retained under similar flow conditions. After 10 d of no flow, sterile water was flushed through the biofouled sandbox and substantial concentrations (up to 1.5 × 10⁵ cells/mL) of E. coli were measured in the effluent indicating that E. coli had survived the starvation period. Confocal laser scanning microscopy revealed that E. coli were located not only on the surface but also within the biofilm. Imposition of starvation conditions resulted in biofilm sloughing and possible mobilization of biofilm‐associated E. coli.  相似文献   

The use of kelp sieve tube sap metal composition to characterize urban runoff in southern California coastal waters     

Fink LA  Manley SL 《Marine pollution bulletin》2011,62(12):2619-2632

This study introduces an innovative method for biomonitoring using giant kelp (Macrocystis pyrifera) sieve tube sap (STS) metal concentrations as an indication of pollution influence. STS was sampled from fronds collected from 10 southern California locations, including two reference sites on Santa Catalina Island. Using ICP-MS methodology, STS concentrations of 17 different metals were measured (n = 495). Several metals associated with pollution showed the highest STS concentrations and most seasonal variation from populations inside the Port of Los Angeles/Long Beach. Lowest concentrations were measured at less-urbanized areas: Santa Catalina Island and Malibu. Some metals showed a spatial gradient in STS metal concentration with increasing distance from point sources (i.e. Los Angeles River). Cluster analyses indicate that polluted seawater may affect kelp uptake of metals essential for cellular function. Results show that this method can be useful in describing bioavailable metal pollution with implications for accumulation within an important ecosystem.  相似文献   

Small plastic debris changes water movement and heat transfer through beach sediments   总被引：1，自引：0，他引：1  

Carson HS  Colbert SL  Kaylor MJ  McDermid KJ 《Marine pollution bulletin》2011,62(8):1708-1713

We investigated the physical properties of beaches contaminated with plastic fragments. We compared sediment cores from Hawai‘i Island’s Kamilo Beach, notable for plastic accumulation, to cores from a nearby beach. Compared to the nearby beach, Kamilo sediments contained more plastics (up to 30.2% by weight), were coarser-grained, and were more permeable (t-test, p < 0.0001). 85% of the fragments were polyethylene, and 95% were concentrated in the top 15 cm of the cores. We constructed artificial cores of standardized grain size and varying plastic-to-sediment ratios. Adding plastic significantly increased the permeability (ANOVA, p = 0.002), which was partially attributed to the fragments increasing the mean grain size. Sediments with plastic warmed more slowly (16% maximum decrease in thermal diffusivity), and reached lower maximum temperatures (21% maximum increase in heat capacity). These changes have a variety of potential effects on beach organisms, including those with temperature-dependent sex-determination such as sea turtle eggs.  相似文献