Seismic Inference using Genetic Algorithms

A flood of reliable seismic data will soon arrive. The migration to largertelescopes on the ground may free up 4-m class instruments for multi-sitecampaigns, and several forthcoming satellite missions promise to yieldnearly uninterrupted long-term coverage of many pulsating stars. We willthen face the challenge of determining the fundamental properties of thesestars from the data, by trying to match them with the output of ourcomputer models. The traditional approach to this task is to make informedguesses for each of the model parameters, and then adjust them iterativelyuntil an adequate match is found. The trouble is: how do we know that oursolution is unique, or that some other combination of parameters will notdo even better? Computers are now sufficiently powerful and inexpensivethat we can produce large grids of models and simply compare all ofthem to the observations. The question then becomes: what range ofparameters do we want to consider, and how many models do we want tocalculate? This can minimize the subjective nature of the process, but itmay not be the most efficient approach and it may give us a false sense ofsecurity that the final result is correct, when it is really justoptimal. I discuss these issues in the context of recent advances inthe asteroseismological analysis of white dwarf stars.     

The Citation Impact of Digital Preprint Archives for Solar Physics Papers

Papers that are posted to a digital preprint archive are typically cited twice as often as papers that are not posted. This has been demonstrated for papers published in a wide variety of journals, and in many different subfields of astronomy. Most astronomers now use the arXiv.org server (astro-ph) to distribute preprints, but the solar physics community has an independent archive hosted at Montana State University. For several samples of solar physics papers published in 2003, I quantify the boost in citation rates for preprints posted to each of these servers. I show that papers on the MSU archive typically have citation rates 1.7 times higher than the average of similar papers that are not posted as preprints, while those posted to astro-ph get 2.6 times the average. A comparable boost is found for papers published in conference proceedings, suggesting that the higher citation rates are not the result of self-selection of above-average papers. Editors’ Note: This paper lies outside the normal purview of Solar Physics papers, however the editors feel that the content is of sufficient importance for all Solar Physics authors and readers to merit its publication.     

Correction to: Leveraging HPC accelerator architectures with modern techniques — hydrologic modeling on GPUs with ParFlow

Computational Geosciences - A Correction to this paper has been published: https://doi.org/10.1007/s10596-021-10065-y     

Macrobenthic infaunal communities associated with deep‐sea hydrocarbon seeps in the northern Gulf of Mexico

There are thousands of seeps in the deep ocean worldwide; however, many questions remain about their contributions to global biodiversity and the surrounding deep‐sea environment. In addition to being globally distributed, seeps provide several benefits to humans such as unique habitats, organisms with novel genes, and carbon regulation. The purpose of this study is to determine whether there are unique seep macrobenthic assemblages, by comparing seep and nonseep environments, different seep habitats, and seeps at different depths and locations. Infaunal community composition, diversity, and abundance were examined between seep and nonseep background environments and among three seep habitats (i.e., microbial mats, tubeworms, and soft‐bottom seeps). Abundances were higher at seep sites compared to background areas. Abundance and diversity also differed among microbial mat, tubeworm, and soft‐bottom seep habitats. Although seeps contained different macrobenthic assemblages than nonseep areas, infaunal communities were also generally unique for each seep. Variability was 75% greater within communities near seeps compared to communities in background areas. Thus, high variability in community structure characterized seep communities rather than specific taxa. The lack of similarity among seep sites supports the idea that there are no specific infauna that can be used as indicators of seepage throughout the northern Gulf of Mexico, at least at higher taxonomic levels.     

Some Biases in Sampling Multilevel Piezometers for Volatile Organics

Multilevel piezometers are cost-effective monitoring devices for determining the three-dimensional distribution of solutes in ground water. Construction includes flexible tubing (plastic or Teflon®). Their sampling is subject to a number of'potential biases, particularly: (1) losses of volatile organic solutes via volatilization, (2) sorption onto the flexible tubing of the piezometers, (3) leaching of organics from this tubing, and (4) collection of unrepresentative samples due to inadequate piezometer flushing. It is shown that these biases are minimal or are easily controlled in most situations.
Another source of bias has been recognized. Organic solutes present in ground water above the screened level can penetrate the flexible plastic or Teflon tubing and contaminate the sampled water being drawn through this tubing. Laboratory tests and field results indicate this transmission causes low organic contaminant concentrations to be erroneously attributed to ground water which is free of such contaminants. The transmitted organics apparently desorb from the plastic tubing during flushing of even 40 piezometer volumes.
Recognition of this transmission problem provides for a better interpretation of existing organic contaminant distribution data. Caution is advised when considering the use of these monitoring devices in organic solute contaminant studies.     

Die Bodenstruktur des Indischen Ozeans und dessen Geschichte

Zusammenfassung Grundzüge des Bodenreliefs und geophysikalisch-geotektonische Kenntnisse im Bereiche des Indischen Ozeans ermöglichen es, Art und Reihenfolge seiner Entwicklung zu skizzieren. Eine erste, parallel den Breitengraden während der Alttrias-Zeit aufgerissene Tiefspaltenzone unter dem Riesenkontinent Gondwanaland trennte die Antarktis von Südamerika-Afrika-Indien-Australien. Durch Querdehnung der Spalten drangen gewaltige basaltische Magmamassen empor. Sie erweiterten wie in Island die aufklaffenden Brüche und drängten die Kontinente auseinander, so daß die vier genannten Großschollen bis über die heutige Lage des 50.° Süd nordwärts verlagert wurden. Hinter ihnen blieb ihre alte, basische und vulkanisch tätige Unterlage zurück als erster Südteil des Indischen Neu-Ozeans. Unregelmäßige Hemmungen bei der Norddrift der Teilschollen dürften zwischen diesen méridionale Blattspalten erzwungen haben.Deren östlichste trennte zunächst jungtriassisch Australien ab von Indien und den anderen westlichen Kontinentalschollen. Diese méridionale Blattspalte wurde zu einer mittelozeanischen Schwelle und drängte einerseits Australien an seinen Platz gegen Osten, andererseits Indien zusammen mit Lemurien gegen Westen. Dann riß die Carlsberg-Mittelindische Schwelle auf und rückte Lemurien westwärts, Indien ostwärts bis zum 90.° Ost. Von der Mittelkreidezeit an wurde die Indische Scholle gegen Norden bis vor den Himalaya verlagert. Sie kam in der Oberkreidezeit an.Dies bewirkte keine neue Mittelozeanische Spaltenschwelle mehr. Vielmehr hatte sich eine regional das gesamte Untergrundsgebiet des Indischen Ozeans erfassende Unterströmung gegen Norden entwickelt. Sie floß unter Himalaya und Tibet noch weiter gegen N und E, wo sie das bekannte Dach der Erde im Tertiär emporstemmte.Die möglichen Begründungen enthält der nachfolgende Text.

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It is possible to reconstruct the nature and sequence of development of the Indian Ocean through knowledge of the topology and through geophysical-geotectonic research.The first deep fault zone situated under the great continent Gondwanaland, went parallel to the latitude during the lower Triassic Period and separated the Antarctic from South America, Africa, India and Australia. The basaltic magma was pushed up through the transverse expansion of the crevices. The opened cracks were widened like in Iceland and presed the continents apart. In this way the 4 great continents mentioned above, were pushed northwards farther than the 50° lat. S of today. Behind them remained the old, basic, and volcanicaly active foundation as the first southern floor of the Indian Ocean. Irregular retardations during the northern drift of parts of the continents probably had caused meridial fissures (Blatt-Spalten).The eastern most part of the fissures first divided in the Upper Triassic Period Australia from India and the other western continental blocks. These meridial fissures grew to a middle ocean rise and pushed on one side Australia to the east, and on the other side India together with Lemur to the west.The Carlsberg-Middle-Ocean Rise then shoved Lemur westward and India eastward to 90° E. Beginning in the Middle Cretaceous Period, the Indian block moved to the north and reached the Himalayas in the Upper Cretaceous Period. This did not cause any new middle ocean Spaltenschwelle. On the contrary, in the underground region of the Indian Ocean an underflow to the north had developed. It flowed under the Himalaya and Tibet and even more to the north and east where the famous roof of the Earth originated.The possible reasons are given in the following text.

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Résumé Le relief du fond de la mer et des faits géophysicaux et géotectoniques dans la région de l'Océan Indien rendent possible d'esquisser la façon de laquelle cet Océan s'est formé. Une zone primaire de fissures profondes formée pendant le Trias inférieur et située parallèle aux degrés de latitude au-dessous du continent gigantesque Gondwanaland séparait la région antarctique d'une part et l'Amérique du Sud, l'Afrique, les Indes et l'Australie d'autre part. A la suite d'une expansion de fissures d'énormes masses basaltiques se levèrent. Celles-ci élargirent les fentes, comme en Islande, et renforcèrent la séparation des continents. C'est pourquoi les quatre boucliers cités furent poussés au-delà de 50° degré de latitude vers le Nord. Leur soubassement basique et volcanique restait à sa place et formait la première partie méridionale du nouvel Océan Indien. Des obstacles irréguliers freinèrent le mouvement vers le Nord des divers boucliers, ce qui peut avoir causé les décrochements parallèles aux méridians.Le décrochement le plus oriental séparait d'abord, au Trias supérieur, l'Australie des Indes et des autres boucliers continentaux à l'Ouest. Le linéament décroché se transforma en un seuil au milieu de l'Océan et poussa d'une part l'Australie vers sa place orientale, d'autre part les Indes avec la Lémurie vers l'Ouest. Puis le linéament Carlsberg au milieu de l'Océan Indien s'ouvrit et transporta la Lémurie vers l'Ouest, les Indes vers l'Est. Dès le Crétacé moyen le bouclier indien a été transporté vers le Nord jusqu'au Himalaya. Il y arriva pendant le Crétacé supérieur.Ceci ne causa plus une nouvelle élévation au milieu de l'Océan. Plutôt il s'était produit une subfluence générale dirigée vers le Nord et emportant le soussol entier de l'Océan Indien. Cette subfluence se prolongea au-dessous de l'Himalaya et du Tibet vers le NE, soulevant au Tertiaire le célèbre Toit de la Terre.Dans la suite les raisons de cette opinion seront exposées.

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Climatological aspects of the tropical convective boundary layer

The characteristics of a boundary layer depend both on conditions at the surface and in the interior of the medium. In the undisturbed tropics, the latter are largely determined by subsidence and by infrared radiational cooling. One-dimensional models are used to establish relationships between the inversion height, subsidence, upper-air humidity and sea-surface temperature. In particular, it is shown that a universally colder tropical ocean would probably be covered by more extensive clouds.Contribution No. 1700 Rosenstiel School of Marine and Atmospheric Science, University of Miami.