2,462 research outputs found
El Niño increases the risk of lower Mississippi River flooding
© The Author(s), 2017. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Scientific Reports 7 (2017): 1772, doi:10.1038/s41598-017-01919-6.Mississippi River floods rank among the costliest climate-related disasters in the world. Improving flood predictability, preparedness, and response at seasonal to decadal time-scales requires an understanding of the climatic controls that govern flood occurrence. Linking flood occurrence to persistent modes of climate variability like the El Niño-Southern Oscillation (ENSO) has proven challenging, due in part to the limited number of high-magnitude floods available for study in the instrumental record. To augment the relatively short instrumental record, we use output from the Community Earth System Model (CESM) Last Millennium Ensemble (LME) to investigate the dynamical controls on discharge extremes of the lower Mississippi River. We show that through its regional influence on surface water storage, the warm phase of ENSO preconditions the lower Mississippi River to be vulnerable to flooding. In the 6â12 months preceding a flood, El Niño generates a positive precipitation anomaly over the lower Mississippi basin that gradually builds up soil moisture and reduces the basinâs infiltration capacity, thereby elevating the risk of a major flood during subsequent rainstorms. Our study demonstrates how natural climate variability mediates the formation of extreme floods on one of the worldâs principal commercial waterways, adding significant predictive ability to near- and long-term forecasts of flood risk.This work was funded through the Postdoctoral Scholar Program of the Woods Hole Oceanographic Institution and the Voss Environmental Postdoctoral Fellows Program at Brown University
Global-scale proxy system modeling of oxygen isotopes in lacustrine carbonates: 2 new insights from isotope-enabled-model proxy-data comparison
Proxy System Modelling (PSM) is now recognised as a crucial step in comparing climate model output with proxy records of past environmental change. PSMs filter the climate signal from the model, or from meteorological data, based on the physical, chemical and biological processes of the archive and proxy system under investigation. Here we use a PSM of lake carbonate ÎŽ18O to forward model pseudoproxy time-series for every terrestrial grid square in the SPEEDY-IER isotope enabled General Circulation Model (GCM), and compare the results with 31 records of lake ÎŽ18O data from the Americas in the NOAA Paleoclimate Database. The model-data comparison shows general patterns of spatial variability in the lake ÎŽ18O data are replicated by the combination of SPEEDY-IER and the PSM, with differences largely explained by known biases in the models. The results suggest improved spatial resolution/coverage of climate models and proxy data, respectively, is required for improved data-model comparison, as are increased numbers of higher temporal resolution proxy time series (sub decadal or better) and longer GCM runs. We prove the concept of data-model comparison using isotope enabled GCMs and lake isotope PSMs and outline potential avenues for further work
Tropical Cyclone Frequency: Turning Paleoclimate Into Projections
Future changes to tropical cyclone (TC) climate have the potential to dramatically impact the social and economic landscape of coastal communities. Paleoclimate modeling and paleohurricane proxy development offer exciting opportunities to understand how TC properties (like frequency) change in response to climate variability on long time scales. However, sampling biases in proxies make it difficult to ascertain whether signals in paleohurricane records are related to climate variability or just stochasticity. Short observations and simulation biases prevent TC models from capturing the full range of climate variability and TC characteristics. Integration of these two data types can help address these uncertainties. Robust data model comparison in paleotempestology will require (a) simulating TCs using new paleoclimate data assimilation products and climate model ensembles, (b) building a central repository of open access paleohurricane proxies, (c) compiling paleohurricane records, and (d) filling key gaps in the existing paleohurricane networks. Incorporating the combined information from both paleohurricane proxies and paleo TC simulations into risk assessments for coastal communities could help improve adaptation strategies
Structural Stability and Renormalization Group for Propagating Fronts
A solution to a given equation is structurally stable if it suffers only an
infinitesimal change when the equation (not the solution) is perturbed
infinitesimally. We have found that structural stability can be used as a
velocity selection principle for propagating fronts. We give examples, using
numerical and renormalization group methods.Comment: 14 pages, uiucmac.tex, no figure
Multiple Front Propagation Into Unstable States
The dynamics of transient patterns formed by front propagation in extended
nonequilibrium systems is considered. Under certain circumstances, the state
left behind a front propagating into an unstable homogeneous state can be an
unstable periodic pattern. It is found by a numerical solution of a model of
the Fr\'eedericksz transition in nematic liquid crystals that the mechanism of
decay of such periodic unstable states is the propagation of a second front
which replaces the unstable pattern by a another unstable periodic state with
larger wavelength. The speed of this second front and the periodicity of the
new state are analytically calculated with a generalization of the marginal
stability formalism suited to the study of front propagation into periodic
unstable states. PACS: 47.20.Ky, 03.40.Kf, 47.54.+rComment: 12 page
Regional genetic structure in the Magellanic penguin (Spheniscus magellanicus) suggests metapopulation dynamics
Using microsatellite markers and mitochondrial DNA (mtDNA) sequences (cytochrome oxidase 1 gene), we estimated levels of genetic structuring among nine Magellanic Penguin (Spheniscus magellanicus) colonies distributed throughout three major reproductive regions of the South Atlantic Ocean. Overall, breeding colonies showed relatively high levels of genetic diversity at both nuclear and mtDNA markers (mean heteorzygosity: He = 0.598; mean allelic diversity: A = 7.11; mtDNA haplotype diversity: h = 0.812). A hierarchical analysis of molecular variance based on microsatellite data showed limited genetic structuring of breeding colonies, with 99% of the variation explained by differences among individuals and 0.7â1.0% attributed to differences among the three regions. The mtDNA analysis revealed higher levels of genetic structuring, with 3.43% of the variation explained by regions and 2.24% explained by colonies within the regions. Furthermore, a Mantel test revealed a significant association between geographic and genetic distances among colonies. The limited genetic structuring we detected is likely a result of (1) population intermixing through natal dispersal and (2) the large effective sizes of the reproductive colonies, both of which prevent genetic differentiation at neutral markers, balanced with (3) the regional association of breeding colonies to distinct feeding grounds and (4) a recent expansion of the population. Our results suggest that the demographic dynamics of breeding colonies of Magellanic Penguins may be framed under a metapopulation model, in which colonies with large numbers of breeding pairs could be considered source populations for maintaining the overall abundance of this species in the Atlantic Ocean
Physiological condition in Magellanic Penguins: Does it matter if you have to walk a long way to your nest?
Colony edges, as opposed to interiors, are often considered less advantageous nesting places in colonial species. For temperate-breeding penguins, inland colony edges should be less desirable than other edges, as there are added costs of walking farther inland, and ambient temperatures are higher. During settlement and incubation, we compared body condition and baseline and stress-induced levels of the hormone corticosterone in male Magellanic Penguins (Spheniscus magellanicus) nesting on the sea edge of a colony with those nesting on the inland edge, \u3e800 m from shore. Body condition in both groups was significantly lower during settlement than during incubation, but was similar in both groups within breeding stages. Corticosterone levels were similar between breeding stages and for groups within each breeding stage. While body condition can vary over time, penguins appear to be well buffered to physiological extremes, as they do not show modification of corticosterone levels with variations in nesting conditions
Double-Cropped Field Pea Crop Rotation Study
Farmers are continually searching for a third crop to complement the corn-soybean rotation. Field peas can be substituted for most of the soybean meal in swine rations and is more economical than soybean meal,so there is a huge potential market for field peas in Iowa. Field peas are a short season crop which makes double cropping a potential possibility
Age and food deprivation affects expression of the glucocorticosteriod stress response in Magellanic penguin (Spheniscus magellanicus) chicks
We examined how the glucocortical stress response in freeâliving Magellanic penguin (Spheniscus magellanicus) chicks changes with age and whether adrenocortical function of chicks within a brood varies in relation to food provisioned by adults. Chicks showed little corticosterone response to capture stress shortly after hatching, an intermediate response around 45âd posthatch, and a robust stress response near fledging. However, in response to an adrenocorticotropic hormone (ACTH) challenge, hatchlings were capable of secreting corticosterone at adultâlike levels. The larger sibling in broods of two showed a similar gradual stressâresponse development pattern. In contrast, by day 45, when differences in body condition were well established between siblings, the smaller, foodâdeprived chicks significantly increased baseline levels of corticosterone but showed normal stressâinduced levels. Near fledging, baseline levels had returned to normal, but stressâinduced levels were lower than expected. Similar to altricial species, normally developing semialtricial Magellanic penguin chicks do not express a robust corticosterone stress response until near fledging. Chronic stressors such as food deprivation cause corticosterone use to be upâregulated earlier than expected. However, in cases of extended chronic stress, downâregulation may ensue, thus avoiding the negative effects of chronically elevated levels of corticosterone
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