Abichou, T., Kormi, T., Yuan, L., Johnson, T., & Francisco, E. (2015). Modeling the effects of vegetation on methane oxidation and emissions through soil landfill final covers across different climates. Waste Management, 36, 230–240.
Abstract: Plant roots are reported to enhance the aeration of soil by creating secondary macropores which improve the diffusion of oxygen into soil as well as the supply of methane to bacteria. Therefore, methane oxidation can be improved considerably by the soil structuring processes of vegetation, along with the increase of organic biomass in the soil associated with plant roots. This study consisted of using a numerical model that combines flow of water and heat with gas transport and oxidation in soils, to simulate methane emission and oxidation through simulated vegetated and non-vegetated landfill covers under different climatic conditions. Different simulations were performed using different methane loading flux (5–200 g m−2 d−1) as the bottom boundary. The lowest modeled surface emissions were always obtained with vegetated soil covers for all simulated climates. The largest differences in simulated surface emissions between the vegetated and non-vegetated scenarios occur during the growing season. Higher average yearly percent oxidation was obtained in simulations with vegetated soil covers as compared to non-vegetated scenario. The modeled effects of vegetation on methane surface emissions and percent oxidation were attributed to two separate mechanisms: (1) increase in methane oxidation associated with the change of the physical properties of the upper vegetative layer and (2) increase in organic matter associated with vegetated soil layers. Finally, correlations between percent oxidation and methane loading into simulated vegetated and non-vegetated covers were proposed to allow decision makers to compare vegetated versus non-vegetated soil landfill covers. These results were obtained using a modeling study with several simplifying assumptions that do not capture the complexities of vegetated soils under field conditions.
|
Acevedo, M. A., Sefair, J. A., Smith, J. C., Reichert, B., Fletcher Jr, R. J., & Fuller, R. (2015). Conservation under uncertainty: optimal network protection strategies for worst-case disturbance events. J Appl Ecol, 52(6), 1588–1597.
Abstract: Conservation goals are ideally set after a thorough understanding of potential threats; however, predicting future spatial patterns of threats, such as disturbance, remains challenging. Here, we develop a novel extension of network fortification-interdiction models (NFIM) that deals with uncertainty in future spatial patterns of disturbance by optimally selecting sites that will best mitigate a worst-case scenario for a given magnitude of disturbance. This approach uses information on between-patch movement probabilities and patch-specific survival, which can be estimated from mark-recapture data, to optimize life expectancy. Optimization occurs in three interrelated stages: protection, followed by disturbance and then assessment. We applied the modelling approach to two mark-recapture data sets: roseate terns Sterna dougallii in the north-eastern United States and the Everglade snail kite Rostrhamus sociabilis plumbeus in Florida. We contrasted the results to a more conventional approach of protecting sites that maximize connectivity (by minimizing the distances among protected sites) and a bi-objective model that maximizes connectivity and the number of individuals under protection. Protecting sites that best mitigate future worst-case disturbance scenarios consistently resulted in higher predicted life expectancies than protecting patches that minimize dispersal distance. Predicted life expectancy was similar between NFIM and the bi-objective model for the small roseate tern network, yet the NFIM predicted higher life expectancy than any of the scenarios in the bi-objective model in the snail kite network.Synthesis and applications. This application of interdiction models prescribed a combination of patches for protection that results in the least possible decrease in life expectancy. Our analyses of the snail kite and roseate tern networks suggest that managing to protect these prescribed patches by the network fortification -interdiction models (i.e. protecting against the worst-case disturbance scenario) is more beneficial than managing patches that minimize dispersal distance or maximize the number of individuals under protection if the conservation goal is to ensure the long-term persistence of a species.
This application of interdiction models prescribed a combination of patches for protection that results in the least possible decrease in life expectancy. Our analyses of the snail kite and roseate tern networks suggest that managing to protect these prescribed patches by the network fortification -interdiction models (i.e. protecting against the worst-case disturbance scenario) is more beneficial than managing patches that minimize dispersal distance or maximize the number of individuals under protection if the conservation goal is to ensure the long-term persistence of a species.
|
Ali, M. M., Nagamani, P. V., Sharma, N., Venu Gopal, R. T., Rajeevan, M., Goni, G. J., et al. (2015). Relationship between ocean mean temperatures and Indian summer monsoon rainfall: Ocean mean temperature and Indian summer monsoon rainfall. Atmos. Sci. Lett., 16(3), 408–413.
Abstract: Besides improving the understanding of the physics of the challenging problem of monsoon prediction, it is necessary to evaluate the efficiency of the input parameters used in models. Sea-surface temperature (SST) is the only oceanographic parameter applied in most of the monsoon forecasting models, which many times do not represent the heat energy available to the atmosphere. We studied the impacts of ocean mean temperature (OMT), representing the heat energy of the upper ocean, and SST on the all India summer monsoon rainfall through a statistical relation during 1993�2013 and found that OMT has a better link than SST.
|
Alvarez, R. A. (2015). Hurricane Mitigation for the Built Environment. Boca Raton, FL: CRC Press.
Abstract: Focusing on coastal regions affected by tropical cyclones, Hurricane Mitigation for the Built Environment highlights vulnerability, natural hazards, risk, damage, emergency management, and hazard mitigation as they relate to the threat and occurrence of hurricanes. The product of more than 25 years of the author’s experiences with post-event assessments and studies of hurricane damage, it looks particularly at common sequences of failures and oversights in planning for a hurricane that amplify the damage caused by storms.
This book combines observations of actual damage to the built environment in coastal regions caused by hurricanes with applied research and testing. It uses case studies and imagery from recent storms to show some of the strengths and weaknesses of infrastructure, landscaping, and city planning. The case studies also illustrate, in great detail, what community planning efforts have worked and those that have failed.
The book also goes beyond analyzing immediately visible structural damages following a hurricane. It addresses long-term issues such as beach erosion and struggling tourism economies. It also describes specific, realistic, and essential mitigation measures for reducing the damage potential of future hurricanes and urges developers, designers, and owners to incorporate new knowledge into the design of new buildings or into the retrofitting of existing buildings. By applying the information presented in this book, communities susceptible to recurring hurricanes can reduce storm damage as well as the potential for extended losses that frequently follow a hurricane.
|
Anderegg, W. R. L., Hicke, J. A., Fisher, R. A., Allen, C. D., Aukema, J., Bentz, B., et al. (2015). Tree mortality from drought, insects, and their interactions in a changing climate. New Phytol, 208(3), 674–683.
Abstract: Climate change is expected to drive increased tree mortality through drought, heat stress, and insect attacks, with manifold impacts on forest ecosystems. Yet, climate-induced tree mortality and biotic disturbance agents are largely absent from process-based ecosystem models. Using data sets from the western USA and associated studies, we present a framework for determining the relative contribution of drought stress, insect attack, and their interactions, which is critical for modeling mortality in future climates. We outline a simple approach that identifies the mechanisms associated with two guilds of insects - bark beetles and defoliators - which are responsible for substantial tree mortality. We then discuss cross-biome patterns of insect-driven tree mortality and draw upon available evidence contrasting the prevalence of insect outbreaks in temperate and tropical regions. We conclude with an overview of tools and promising avenues to address major challenges. Ultimately, a multitrophic approach that captures tree physiology, insect populations, and tree-insect interactions will better inform projections of forest ecosystem responses to climate change.
|
Anderson, B. T., & Perez, R. C. (2015). ENSO and non-ENSO induced charging and discharging of the equatorial Pacific. Clim Dyn, 45(9-10), 2309–2327.
Abstract: It is well established that variations in extratropical North Pacific wind stress fields can influence the state of the tropical Pacific 12-15 months prior to the maturation of boreal winter El Nio/Southern Oscillation (ENSO) events. While most research has focused on accompanying variations in the North Pacific trade winds and underlying sea surface temperatures that subsequently shift equatorward via anomalous air-sea interactions-e.g. meridional mode dynamics-observational and numerical model analyses indicate empirical and dynamical links exist between these same trade-wind variations and concurrent changes in subsurface temperatures across the equatorial Pacific, which can also serve as a key initiator of ENSO events. This paper shows that within an observationally-constrained ocean reanalysis dataset this initiation mechanism-termed the trade-wind charging (TWC) mechanism-is induced by the second leading mode of boreal winter zonal wind stress variability over the tropical Pacific and operates separately from ENSO-induced recharge/discharge of the equatorial Pacific heat content. The paper then examines the characteristics and evolution of the ENSO and TWC modes. Results indicate that the oceanic evolution for both modes is consistent with wind stress induced vertically-integrated, meridional mass transport into and out of the equatorial Pacific-i.e. a charging and discharging of the equatorial Pacific-despite having distinctly different wind stress anomaly patterns. The process-based similarity between these two modes of tropical Pacific wind stress variability suggests that both can produce a charging/discharging of the equatorial Pacific, however one (the ENSO mode) represents part of the ENSO cycle itself and the other (the TWC mode) represents a separate forcing mechanism of that cycle.
|
Angelo, C. L., & Daehler, C. C. (2015). Temperature is the major driver of distribution patterns for C4 and C3 BEP grasses along tropical elevation gradients in Hawaii, and comparison with worldwide patterns. Botany, 93(1), 9–22.
Abstract: The distribution patterns of C4 and C3 grasses in relation to climate have attracted much attention, but few studies have examined grass distributions along tropical elevation gradients. Previous studies identified either temperature, precipitation, or both variables as the major climatic factor(s) driving these distributions. Here we investigated relative dominance of C4 grasses in relation to climate along five elevation gradients in Hawai�i. The transition temperature between C4 and C3 BEP (Bambusoideae, Ehrhartoideae, and Pooideae) grasses (where their relative dominance is equal) was determined; in our study, the subfamily Bambusoideae was not included. A worldwide synthesis of previous studies testing climatic factors and transition temperatures associated with C4 and C3 grass distributions was also carried out. Mean July maximum temperature was significantly correlated with C4 dominance along all elevation transects in Hawai�i, while precipitation was only correlated along three transects when precipitation was correlated with temperature. A spatially explicit multiple regression model indicated that C4 relative cover was best explained by temperature. Temperature appears to be the major climatic factor shaping distribution patterns of C4 and C3 BEP grasses in Hawai�i. According to the worldwide analysis, temperature primarily influenced grass distribution patterns more often in temperate studies (70%) than in tropical studies (45%). Degree of correlation or covariance between temperature and precipitation was rarely reported in previous studies, although this can strongly affect conclusions. C4-C3 BEP transition temperatures (mean July maximum) ranged from 18 to 21 °C in Hawai�i; these transition temperatures are lower than those reported in temperate localities (26�31 °C), but similar to transition temperatures for other localities at tropical latitudes (21�22 °C). A warming climate is likely to shift C4 grass dominance upward in elevation, threatening higher elevation native communities by perpetuating a grass�fire cycle.
|
Angelo, C. L., & Pau, S. (2015). Root biomass and soil delta 13C in C3 and C4 grasslands along a precipitation gradient. Plant Ecol, 216(4), 615–627.
Abstract: Many studies have investigated the aboveground distributions of C3 and C4 grasses along climatic gradients because they illustrate complex interactions between abiotic and biotic controls on ecosystem functions. Yet few studies have examined belowground components of these distributions, which may present very different patterns compared with aboveground measures. In this study, we surveyed grass species cover and collected soil and root samples from field plots at 100–150-m elevation intervals along a climatic gradient in Hawai‘i. We examined how the relationship between soil carbon isotopic composition (δ13C), a proxy for C4 dominance, and % C4 cover changed along a climatic gradient. We also evaluated root biomass to determine if belowground dominance reflects aboveground patterns under climate variation. Results showed that soil δ13C under predicted C4 dominance in wetter sites. The relationship between % C4 cover and soil δ13C became more negative with increasing mean annual precipitation (MAP) based on a linear mixed-effects model (F 1,34 = 12.25, P < 0.01). Soil δ13C in wetter sites indicated a larger C3 contribution than estimated by aboveground cover, which was in part due to C3 root biomass increasing (P < 0.05), whereas C4 root biomass did not change along the precipitation gradient. C3 and C4 grasses appear to allocate disproportionately belowground; thus, a different understanding of C4 ecological dominance (biomass or productivity) may emerge when considering both the above and belowground components. Our results show that belowground allocation and interpretation of soil δ13C need to be more carefully considered in global vegetation and carbon models and paleoecological reconstructions of C4 dominance.
|
Arienzo, M. M., Swart, P. K., Pourmand, A., Broad, K., Clement, A. C., Murphy, L. N., et al. (2015). Bahamian speleothem reveals temperature decrease associated with Heinrich stadials. Earth and Planetary Science Letters, 430, 377–386.
Abstract: Temperature reconstructions across Heinrich stadials 1-3 are presented from an absolute-dated speleothem from Abaco Island in the Bahamas to understand the nature of climate change across these intervals in the subtropical Atlantic. The stalagmite carbonate record, dated by the U-Th geochronometry technique, includes higher delta O-18 and delta C-13 values within Heinrich stadials 1, 2, and 3 followed by rapid declines at the end of the stadials. To aid in the interpretation of these results, the delta O-18 of fluid inclusions associated with the Heinrich stadials were also analyzed. These measurements, which allowed for the relative influence of temperature and delta O-18 of precipitation to be distinguished, demonstrate minimal changes in the delta O-18 of fluid inclusions, suggesting that change's in the delta O-18 values of the speleothem carbonate associated with Heinrich stadials 1-3 are principally driven by an average similar to 4 degrees C temperature decrease, rather than a change in the delta O-18 of the rainfall (hence rainfall amount). These findings support previous work in the North Atlantic and are consistent with the climate response to a weakening of the Atlantic meridional overturning circulation.
|
Aronson, R. B., Smith, K. E., Vos, S. C., & et al. (2015). No barrier to emergence of bathyal king crabs on the Antarctic shelf. PNAS, 112(42), 12997–13002.
Abstract: For tens of millions of years, cold conditions have excluded shell-crushing fish and crustaceans from the continental shelf surrounding Antarctica. Rapid warming is now allowing predatory crustaceans to return. Our study of the continental slope off the western Antarctic Peninsula showed that abundant, predatory king crabs comprise a reproductively viable population at 841- to 2,266-m depth. Depth profiles of temperature, salinity, habitat structure, food availability, and predators indicate that there are no barriers to prevent king crabs from moving upward onto the outer shelf at 400�550 m. A cold-water barrier above 200 m could be breached within the next few decades. Emergence of king crabs on the shelf could have catastrophic consequences for the unique seafloor communities of Antarctica.
|
Asseng S, E. F., Martre P, Rosenzweig C, Jones JW, Hatfield JL, Ruane AC, Boote KJ, Thorburn PJ, Rötter RP, Cammarano D, Brisson N, Basso B, Martre P, Aggarwal PK, Angulo C, Bertuzzi P, Biernath C, Challinor AJ, Doltra J, Gayler S, Goldberg R, Grant R, Heng L, Hooker J, Hunt LA, Ingwersen J, Izaurralde RC, Kersebaum KC, Muller C, Naresh Kumar S, Nendel C, O'Leary G, Olesen JE, Osborne TM, Palosuo T, Priesack E, Ripoche D, Semenov MA, Shcherbak I, Steduto P, Stockle C, Stratonovitch P, Streck T, Supit I, Tao F, Travasso M, Waha K, Wallach D, White JW, Williams JR, Wolf J. (2015). Benchmark data set for wheat growth models field experiments and AgMIP multi-model simulations. Open Data Journal for Agricultural Research, 1, 1–5.
Abstract: The data set includes a current representative management treatment from detailed, quality-tested sentinel field experiments with wheat from four contrasting environments including Australia, The Netherlands, India and Argentina. Measurements include local daily climate data (solar radiation, maximum and minimum temperature, precipitation, surface wind, dew point temperature, relative humidity, and vapor pressure), soil characteristics, frequent growth, nitrogen in crop and soil, crop and soil water and yield components. Simulations include results from 27 wheat models and a sensitivity analysis with 26 models and 30 years (1981-2010) for each location, for elevated atmospheric CO2 and temperature changes, a heat stress sensitivity analysis at anthesis, and a sensitivity analysis with soil and crop management variations and a Global Climate Model end-century scenario.
|
Asseng, S. (2015). Uncertainties of Climate Change Impacts in Agriculture. In Procedia Environmental Sciences (Vol. 29, 304).
Abstract: Crop simulation models are often used to estimate the impact of climate change on agricultural production. But, simulated climate change impacts vary across agricultural impact models due to differences in model structures and parameter values. When comparing crop models with standardised inputs, uncertainties in simulated impacts increased with higher temperatures(1) and CO2 concentrations(2,3). These uncertainties in impact simulations are larger due to crop models, than due to downscaled general circulation models(2). Impact uncertainties can be reduced by improving model routines and parameters with detailed field experimentations. However, multi-model ensemble medians also supply an improved prediction above individual models(4). Less uncertainty in describing how climate change may affect agricultural productivity is needed to assist in the development of adaptation strategies and policies.
|
Asseng, S., Ewert, F., Martre, P., Rotter, R. P., Lobell, D. B., Cammarano, D., et al. (2015). Rising temperatures reduce global wheat production. Nature Climate change, 5, 143–147.
Abstract: Crop models are essential tools for assessing the threat of climate change to local and global food production1. Present models used to predict wheat grain yield are highly uncertain when simulating how crops respond to temperature2. Here we systematically tested 30 different wheat crop models of the Agricultural Model Intercomparison and Improvement Project against field experiments in which growing season mean temperatures ranged from 15 °C to 32 °C, including experiments with artificial heating. Many models simulated yields well, but were less accurate at higher temperatures. The model ensemble median was consistently more accurate in simulating the crop temperature response than any single model, regardless of the input information used. Extrapolating the model ensemble temperature response indicates that warming is already slowing yield gains at a majority of wheat-growing locations. Global wheat production is estimated to fall by 6% for each °C of further temperature increase and become more variable over space and time.
|
Atwood, T. B., Connolly, R. M., Ritchie, E. G., Lovelock, C. E., Heithaus, M. R., Hays, G. C., et al. (2015). Predators help protect carbon stocks in blue carbon ecosystems. Nature Climate Change, 5(12), 1038–1045.
Abstract: Predators continue to be harvested unsustainably throughout most of the Earth's ecosystems. Recent research demonstrates that the functional loss of predators could have far-reaching consequences on carbon cycling and, by implication, our ability to ameliorate climate change impacts. Yet the influence of predators on carbon accumulation and preservation in vegetated coastal habitats (that is, salt marshes, seagrass meadows and mangroves) is poorly understood, despite these being some of the Earth's most vulnerable and carbon-rich ecosystems. Here we discuss potential pathways by which trophic downgrading affects carbon capture, accumulation and preservation in vegetated coastal habitats. We identify an urgent need for further research on the influence of predators on carbon cycling in vegetated coastal habitats, and ultimately the role that these systems play in climate change mitigation. There is, however, sufficient evidence to suggest that intact predator populations are critical to maintaining or growing reserves of 'blue carbon' (carbon stored in coastal or marine ecosystems), and policy and management need to be improved to reflect these realities.
|
Aumen, N. G., Havens, K. E., Best, G. R., & Berry, L. (2015). Predicting Ecological Responses of the Florida Everglades to Possible Future Climate Scenarios: Introduction. Environmental Management, 55(4), 741–748.
Abstract: Florida’s Everglades stretch from the headwaters of the Kissimmee River near Orlando to Florida Bay. Under natural conditions in this flat landscape, water flowed slowly downstream as broad, shallow sheet flow. The ecosystem is markedly different now, altered by nutrient pollution and construction of canals, levees, and water control structures designed for flood control and water supply. These alterations have resulted in a 50 % reduction of the ecosystem’s spatial extent and significant changes in ecological function in the remaining portion. One of the world’s largest restoration programs is underway to restore some of the historic hydrologic and ecological functions of the Everglades, via a multi-billion dollar Comprehensive Everglades Restoration Plan. This plan, finalized in 2000, did not explicitly consider climate change effects, yet today we realize that sea level rise and future changes in rainfall (RF), temperature, and evapotranspiration (ET) may have system-wide impacts. This series of papers describes results of a workshop where a regional hydrologic model was used to simulate the hydrology expected in 2060 with climate changes including increased temperature, ET, and sea level, and either an increase or decrease in RF. Ecologists with expertise in various areas of the ecosystem evaluated the hydrologic outputs, drew conclusions about potential ecosystem responses, and identified research needs where projections of response had high uncertainty. Resource managers participated in the workshop, and they present lessons learned regarding how the new information might be used to guide Everglades restoration in the context of climate change.
|
Barrett, R. T. S., Hollister, R. D., Oberbauer, S. F., & Tweedie, C. E. (2015). Arctic plant responses to changing abiotic factors in northern Alaska. American Journal of Botany, 102(12), 2020–2031.
Abstract: PREMISE OF THE STUDY: Understanding the relationship between plants and changing abiotic factors is necessary to document and anticipate the impacts of climate change.
METHODS: We used data from long-term research sites at Barrow and Atqasuk, Alaska, to investigate trends in abiotic factors (snow melt and freeze-up dates, air and soil temperature, thaw depth, and soil moisture) and their relationships with plant traits (inflorescence height, leaf length, reproductive effort, and reproductive phenology) over time.
KEY RESULTS: Several abiotic factors, including increasing air and soil temperatures, earlier snowmelt, delayed freeze-up, drier soils, and increasing thaw depths, showed nonsignificant tendencies over time that were consistent with the regional warming pattern observed in the Barrow area. Over the same period, plants showed consistent, although typically nonsignificant tendencies toward increasing inflorescence heights and reproductive efforts. Air and soil temperatures, measured as degree days, were consistently correlated with plant growth and reproductive effort. Reproductive effort was best predicted using abiotic conditions from the previous year. We also found that varying the base temperature used to calculate degree days changed the number of significant relationships between temperature and the trait: in general, reproductive phenologies in colder sites were better predicted using lower base temperatures, but the opposite held for those in warmer sites.
CONCLUSIONS: Plant response to changing abiotic factors is complex and varies by species, site, and trait; however, for six plant species, we have strong evidence that climate change will cause significant shifts in their growth and reproductive effort as the region continues to warm.
|
Bastola, S., & Misra, V. (2015). Seasonal hydrological and nutrient loading forecasts for watersheds over the Southeastern United States. Environmental Modelling & Software, 73, 90–102.
Abstract: We show useful seasonal deterministic and probabilistic prediction skill of streamflow and nutrient loading over watersheds in the Southeastern United States (SEUS) for the winter and spring seasons. The study accounts for forecast uncertainties stemming from the meteorological forcing and hydrological model uncertainty. Multi-model estimation from three hydrological models, each forced with an ensemble of forcing derived by matching observed analogues of forecasted quartile rainfall anomalies from a seasonal climate forecast is used. The attained useful hydrological prediction skill is despite the climate model overestimating rainfall by over 23% over these SEUS watersheds in December–May period. The prediction skill in the month of April and May is deteriorated as compared to the period from December–March (zero lead forecast). A nutrient streamflow rating curve is developed using a log linear tool for this purpose. The skill in the prediction of seasonal nutrient loading is identical to the skill of seasonal streamflow forecast.
|
Battisti, M., Delgado, M. S., & Parmeter, C. F. (2015). Evolution of the global distribution of carbon dioxide: A finite mixture analysis. Resource and Energy Economics, 42, 31–52.
Abstract: Economists and environmental policymakers have recently begun advocating a bottom-up approach to climate change mitigation, focusing on reduction targets for groups of nations, rather than large scale global policies. We advance this discussion by conducting a rigorous empirical analysis of the global distribution of carbon emissions along several important dimensions: groupings, polarization, mobility, and volatility. In contrast to previous work, our empirical analysis is both comprehensive and data-driven. We discuss how robust empirical evidence may aid policymakers in forging a heterogeneous carbon abatement policy.
|
Beerens, J. M., Noonburg, E. G., Gawlik, D. E., & Gao, C. - Q. (2015). Linking Dynamic Habitat Selection with Wading Bird Foraging Distributions across Resource Gradients. PLoS ONE, 10(6), e0128182.
Abstract: Species distribution models (SDM) link species occurrence with a suite of environmental predictors and provide an estimate of habitat quality when the variable set captures the biological requirements of the species. SDMs are inherently more complex when they include components of a species’ ecology such as conspecific attraction and behavioral flexibility to exploit resources that vary across time and space. Wading birds are highly mobile, demonstrate flexible habitat selection, and respond quickly to changes in habitat quality; thus serving as important indicator species for wetland systems. We developed a spatio-temporal, multi-SDM framework using Great Egret (Ardea alba), White Ibis (Eudocimus albus), and Wood Stork (Mycteria Americana) distributions over a decadal gradient of environmental conditions to predict species-specific abundance across space and locations used on the landscape over time. In models of temporal dynamics, species demonstrated conditional preferences for resources based on resource levels linked to differing temporal scales. Wading bird abundance was highest when prey production from optimal periods of inundation was concentrated in shallow depths. Similar responses were observed in models predicting locations used over time, accounting for spatial autocorrelation. Species clustered in response to differing habitat conditions, indicating that social attraction can co-vary with foraging strategy, water-level changes, and habitat quality. This modeling framework can be applied to evaluate the multi-annual resource pulses occurring in real-time, climate change scenarios, or restorative hydrological regimes by tracking changing seasonal and annual distribution and abundance of high quality foraging patches.
|
Bellomo, K., & Clement, A. C. (2015). Evidence for weakening of the Walker circulation from cloud observations: Weakening of Walker Circulation. Geophys. Res. Lett., 42(18), 7758–7766.
Abstract: Climate models simulate a weakening of the Walker circulation in response to increased greenhouse gases, but it has not been possible to detect this weakening with observations because there are not direct measurements of atmospheric circulation strength. Indirect measurements, such as equatorial gradients in sea level pressure (SLP), exhibit trends of inconsistent sign. In this study we estimate the change in midtropospheric velocity ((500)) from observed change in cloud cover, which we argue is more closely tied to the overturning circulation than indirect measurements of SLP at the surface. Our estimates suggest a weakening and eastward shift of the Walker circulation over the last century. Because changes in cloud cover in Atmospheric Model Intercomparison Project simulations forced with increased sea surface temperature are remarkably similar in pattern, sign, and magnitude, we assert that the observed changes in cloud cover and the associated weakening of Walker circulation are at least in part externally forced.
|
