The Local Ecological Effect of Long Tailed Jaegers Nesting in the Subarctic

While carrying out geomorphological field work in the Ruby Range, Yukon Territory ... during the summers of 1967 and 1968, an extension of the known breeding grounds of the long tailed jaeger (Stercorarius longicaudus) was observed. A pair of these birds nested on the same southeast-facing slope both years and their presence affected the local ecology in significant ways. For example, they maintained a constant vigil and promptly chased away any predator which came close to the slope. This provided an umbrella for other animals on the slope such as ground squirrels, pika, marmot, and ptarmigan. As a result the population of these animals was higher and their behaviour was more uninhibited than in surrounding areas. This became even more noticeable, by contrast, upon returning to the field in the summer of 1972 and finding the jaegers missing. The feather remains of one adult jaeger were discovered and the atmosphere on the slope was very different. ...Although the Ruby Range is approximately 900 km south of the previously documented nesting area of the long tailed jaeger, several jaegers were sighted here. My research was concerned with solifluction lobe development in the Ruby Range and detailed work was carried out on four adjacent slopes facing southeast, southwest, east, and north. ... The jaegers' nest was located in approximately the same place both years, on a lobe tread in a small basin between two mossy hummocks. ... Occasionally we would hear the jaegers begin their high shrill calls and look in the direction they were flying to see an eagle .... The same treatment was allotted other predators such as wolf, fox, bear, and wolverine. ... The virtual elimination of predators from the slope during the summer was somewhat counterbalanced by the jaegers themselves, however, since they harvested many small rodents on the slope, i.e., shrews, lemmings, voles, and mice of various kinds. But for the larger burrowing mammals, such as ground squirrels, pika, marmot, as well as the ptarmigan, it provided a rather trouble-free existence. On a comparative basis the population of burrowing animals was vastly greater on the southeast-facing slope than the other exposures, and although the major explanation for this may be because of the more favourable environment on the south-east, it is nevertheless felt that the jaegers' presence contributed significantly to the relatively high population. ... there was a clear and observable difference in the ecology of the slope because of the jaegers' presence. Such ecological relationships are replete in nature and we have a great deal to learn about and from them

The Collapse of Solifluction Lobes as a Factor in Vegetating Blockfields

In the Ruby Mt area of southwestern Yukon, tongues and islands of vegetation occur in certain blockfields, which through normal processes develop soil and vegetation only very slowly, due to a lack of near-surface water and great diurnal temperature extremes during summer. The collapse occurs when the lobes move from the meadow onto the steeper slope of the blockfield where composition of vegetation changes and where there is a deeper active layer. Once collapsed, they flow downslope transporting clumps of vegetation which may establish themselves along the mud-flow channel or levee. Thus certain arctic and alpine slopes are vegetated more quickly than would otherwise be possible.L'effondrement de lobes de solifluxion, facteur de colonisation des champs de blocs par la végétation. Selon les processus normaux, le développement du sol et de la végétation dans les champs de blocs est très lent. C'est pourquoi, dans les monts Ruby, dans le sud-ouest du territoire du Yukon, on est surpris de trouver des langues et des îlots de végétation au milieu de certains champs de blocs. On propose comme mécanisme responsable de ce phénomène l'effondrement des lobes de solifluxion des pentes voisines. En passant de la pente douce de l'alpe à celle, plus forte, des champs de blocs, les lobes ne peuvent plus se maintenir à cause de cette pente plus prononcée, du changement de composition de la végétation et de l'épaisseur plus grande du mollisol. En s'effondrant, les lobes fluent le long de la pente, entraînant des masses de végétation qui s'établissent quelque part le long du chenal de coulée ou sur ses levées. De cette façon, de petits avant-postes de végétation se créent et accélèrent ainsi le processus qui, autrement, serait interminablement plus long

Origin and Significance of Wet Spots on Scraped Surfaces in the High Arctic

In the western Queen Elizabeth Islands, Northwest Territories, where most of the petroleum exploration in the High Arctic is being conducted, much of the low lying land is covered with sorted and non-sorted circles and polygons 0.5-2.0 m in diameter. ... Much of the oil-camp construction takes place on the coastal low-lands on polygonal surfaces composed of sandy to silty loams. When these surfaces are scraped and reworked for camp areas and air strips in summer, it is common for them to have numerous wet spots which become soft and spongy and of jelly-like consistency when equipment is moved across them .... a small study was conducted in 1972 at the Sunoco Camp no. 3002 on the northeast side of King Christian Island (77° 44'N, 101° 15'W), approximately 3.5 km from the sea. There the surface soils consist of fine marine sediments intermixed with small pebbles. The entire camp area and the Hercules landing strip are built on a surface covered with non-sorted polygons. ... Excavations were made on both the disturbed surface, where the damp spots occurred, as well as in the undisturbed area adjacent to the camp. ... From the information obtained during the excavations in each of the areas described, it is possible to understand more clearly the mechanisms responsible for the features. The wet spots in the cleared work-area are located at the foci of ground-ice accumulations which occur at the margins and intersections of the non-sorted patterned ground. The occurrence of ground-ice at the perimeters of the non-sorted polygons is explained by the contraction cracks which form and outline the patterned ground. Moisture from the scanty precipitation (especially blowing snow) accumulates in the cracks and eventually becomes incorporated in the underlying frozen ground as ice veins. Since the cracks are areas of greater moisture (as well as microhabitats), the plants tend to congregate in them and in turn reinforce the moisture content by (1) their greater moisture-holding capacity, (2) more efficient moisture entrapment, and (3) retarding the rate of thaw owing to the slightly greater insulation they provide. Once such a surface is disturbed, as it was in this case by light blading with a bulldozer, the vegetation is destroyed (at least the above- surface parts). Greater thawing may then occur, during which the moisture is drawn to the surface by capillary action as melting of the ground ice takes place. These bladed areas increase soil compaction and therefore thermal conductivity, and so melt is accelerated. In addition, the organic matter and remaining live plant material in the crack act as a "wick" drawing the moisture to the surface. A last but very important factor is the movement of heavy equipment over the surface. ... Their main area of concentration was in the work area in front of the camp where there was continual movement of equipment. The repetitive application of pressure over an area rich in ground ice ... has a "pumping" action whereby moisture is slowly forced to the surface. This constant agitation distributes the water throughout the mass, and the material becomes "quick" owing to the reduction of intergranular pore pressure. This results in loss of cohesion, and the material becomes spongy and jelly-like when pressure is applied. The practical significance of this brief investigation is that the wet spots will probably not increase in size or the surface deteriorate further, but in fact there should be an improvement. It appeared from discussion with camp managers on two islands that, after two or three summers of use of the surface and scraping, the wet spots dry out. The best approach to the use of these vegetated (and therefore ice-rich) non-sorted, patterned ground surfaces in the High Arctic is to clear the areas before thawing occurs in the spring, and if possible not to use them heavily during the first one or two summers. By the second or third summer much of the ground ice will have thawed, so there should be less chance of major problems with wet and soft spots - unless the summer is unusually wet, as it was 1973

Stochastic Backgrounds of Gravitational Waves from Cosmological Sources: Techniques and Applications to Preheating

Several mechanisms exist for generating a stochastic background of gravitational waves in the period following inflation. These mechanisms are generally classical in nature, with the gravitational waves being produced from inhomogeneities in the fields that populate the early universe and not quantum fluctuations. The resulting stochastic background could be accessible to next generation gravitational wave detectors. We develop a framework for computing such a background analytically and computationally. As an application of our framework, we consider the stochastic background of gravitational waves generated in a simple model of preheating.Comment: Replaced with published version: Phys. Rev. D 78, 063541 (2008

The Collision of Two Black Holes

We study the head-on collision of two equal mass, nonrotating black holes. We consider a range of cases from holes surrounded by a common horizon to holes initially separated by about $20M$, where $M$ is the mass of each hole. We determine the waveforms and energies radiated for both the $\ell = 2$ and $\ell=4$ waves resulting from the collision. In all cases studied the normal modes of the final black hole dominate the spectrum. We also estimate analytically the total gravitational radiation emitted, taking into account the tidal heating of horizons using the membrane paradigm, and other effects. For the first time we are able to compare analytic calculations, black hole perturbation theory, and strong field, nonlinear numerical calculations for this problem, and we find excellent agreement.Comment: 14 pages, 93-

A First Search for Prompt Radio Emission from a Gravitational-Wave Event

Multimessenger observations of the binary neutron star merger GW170817 have enabled the discovery of a diverse array of electromagnetic counterparts to compact binary mergers, including an unambiguous kilonova, a short gamma-ray burst, and a late-time radio jet. Beyond these counterparts, compact binary mergers are additionally predicted to be accompanied by prompt low-frequency radio emission. The successful observation of a prompt radio counterpart would be immensely valuable, but is made difficult by the short delay between the gravitational-wave and prompt electromagnetic signals as well as the poor localization of gravitational-wave sources. Here, we present the first search for prompt radio emission accompanying a gravitational-wave event, targeting the binary black hole merger GW170104 detected by the Advanced LIGO and Virgo gravitational-wave observatories during their second (O2) observing run. Using the Owens Valley Radio Observatory Long Wavelength Array (OVRO-LWA), we search a $\sim900\,\mathrm{deg}^2$ region for transient radio emission within approximately one hour of GW170104, obtaining an upper limit of $2.5\times10^{41}\,\mathrm{erg}\,\mathrm{s}^{-1}$ on its equivalent isotropic luminosity between 27-84 MHz. We additionally discuss plans to target binary neutron star mergers in Advanced LIGO and Virgo's upcoming O3 observing run.Comment: 13 pages + appendices, 7 figures, submitted to Ap

The Head-On Collision of Two Equal Mass Black Holes Peter Anninos

We study the head-on collision of two equal mass, nonrotating black holes. Various initial configurations are investigated, including holes which are initially surrounded by a common apparent horizon to holes that are separated by about $20M$, where $M$ is the mass of a single black hole. We have extracted both $\ell = 2$ and $\ell=4$ gravitational waveforms resulting from the collision. The normal modes of the final black hole dominate the spectrum in all cases studied. The total energy radiated is computed using several independent methods, and is typically less than $0.002 M$. We also discuss an analytic approach to estimate the total gravitational radiation emitted in the collision by generalizing point particle dynamics to account for the finite size and internal dynamics of the two black holes. The effects of the tidal deformations of the horizons are analysed using the membrane paradigm of black holes. We find excellent agreement between the numerical results and the analytic estimates.Comment: 33 pages, NCSA 94-048, WUGRAV-94-

The Pan-STARRS Moving Object Processing System

We describe the Pan-STARRS Moving Object Processing System (MOPS), a modern software package that produces automatic asteroid discoveries and identifications from catalogs of transient detections from next-generation astronomical survey telescopes. MOPS achieves > 99.5% efficiency in producing orbits from a synthetic but realistic population of asteroids whose measurements were simulated for a Pan-STARRS4-class telescope. Additionally, using a non-physical grid population, we demonstrate that MOPS can detect populations of currently unknown objects such as interstellar asteroids. MOPS has been adapted successfully to the prototype Pan-STARRS1 telescope despite differences in expected false detection rates, fill-factor loss and relatively sparse observing cadence compared to a hypothetical Pan-STARRS4 telescope and survey. MOPS remains >99.5% efficient at detecting objects on a single night but drops to 80% efficiency at producing orbits for objects detected on multiple nights. This loss is primarily due to configurable MOPS processing limits that are not yet tuned for the Pan-STARRS1 mission. The core MOPS software package is the product of more than 15 person-years of software development and incorporates countless additional years of effort in third-party software to perform lower-level functions such as spatial searching or orbit determination. We describe the high-level design of MOPS and essential subcomponents, the suitability of MOPS for other survey programs, and suggest a road map for future MOPS development.Comment: 57 Pages, 26 Figures, 13 Table

Portland\u27s Changing Landscape

Occasional Papers in Geography Publication No. 4 What is the nature and character of Portland? What are the conditions, changes and developments that have made it what it is? How does Portland compare with other places? What makes it unique? These are some of the question pursued in this volume. This book contains thirteen chapters discussing various facets of Portland\u27s environmental, economy, and character. It is an up-to-date and comprehensive analysis of dynamics and change in the landscape. An overview is provided of Portland as a city and place to live, as well as its functional significance on a national and international basis. Two threads are woven through the tapestry of these essays. One is that Portland is a big city but with many attributes of a small town. The other is the closeness and accessibility of city and nature. The challenge is how to nurture and maintain both - to have our cake and eat it too. The evidence is clear that most American cities have not been able to achieve this. Only the future can tell how Portland will fare. The authors are all professional geographers or work in closely related fields. All have been involved with the Portland scene for a number of years and are uniquely qualified to write about these topics. While each approaches problems from his or her own perspective, the net result is a summing up, a taking stock of where we have been and where we are going. When considered as a whole the book should provide a better view than we have had of the nature and character of this special place.https://pdxscholar.library.pdx.edu/geog_occasionalpaper/1000/thumbnail.jp