bluuebunny/crossref_metadata_2025_split huggingface dataset:
Glaciation, erosion and the evolution of the Transantarctic Mountains, Antarctica
Authors: Kerr Andrew , Gilchrist Alan 
Published: September 2017

Modelling studies of the tectonic evolution of the Transantarctic Mountains in Antarctica have drawn differing conclusions as to the primary mechanisms involved. None has considered the role of the East Antarctic ice sheet in detail. We use a denudation—flexural model to examine the isostatic response of the continental margin to glacial erosion to determine whether glacial processes have played a role in forcing mountain uplift.The conclusion is that, although there are insufficient data formally to delimit the role of glacial erosion, available geophysical and geomorphological data are not inconsistent with the results of the differential denudation model, providing certain conditions are met. These results indicate that the current topography of the Transantarctic Mountains can be simulated, in part, from the isostatic response of the lithosphere to glacial erosion. The short wavelength and high amplitude of the Transantarctic Mountains do not require a low flexural rigidity in the unrated lithosphere, provided there is a fast escarpment retreat from the rift hinge, high escarpment denudation rates and a large differential in denudation between the coastal zone and the interior.
The effect of ice-sheet thickness change on the accumulation history inferred from GISP2 layer thicknesses
Authors: Cutler Nadine N. , Raymond C.F. , Waddington E. D. , Meese D.A. , Alley R.B. 
Published: September 2017

Net accumulation rates at the Greenland summit have been inferred using layer-thickness data from the GISP2 ice core with corrections for strain using a non-linear, one-dimensional flow model of an ice sheet. The flow model accounts for thickness changes in ice-sheet in response to mass-balance variations. The model is used to investigate how net accumulation-rate changes affect the time evolution of: (1) the ice-sheet thickness. (2) the vertical strain rate, and (3) the corresponding internal annual-layer structure. The model, parameterized to fit the present net accumulation rate and thickness of the Greenland ice-sheet summit, has a characteristic time constant for adjustment to accumulation-rate changes of about 6000a and yields an ice sheet 200-400 m thinner than its present thickness during the last glacial period.Accumulation-rate histories inferred from GISP2 layer-thickness data using both a constant- and a variable-thickness model are compared. The variable-thickness model predicts accumulation rates about 25% lower than the constant-thickness model. Our results also indicate that high-frequency changes in accumulation rates (i.e. alter the Younger Dryas event) are consistent with earlier analyses. However, sensitivity tests indicate that the accumulation-rate history cannot be precisely determined. Our analysis defines an envelope of likely accumulation histories bounded above by the accumulation history inferred by the constant-thickness model. Predictions become increasingly uncertain for old ice because of (1) intrinsic difficulties associated with this inverse problem, and (2) decreased accuracy of the data.
A 485 year record of atmospheric chloride, nitrate and sulfate: results of chemical analysis of ice cores from Dyer Plateau, Antarctic Peninsula
Authors: Dai Jihong Cole , Thompson Lonnie G. , Mosley-Thompson Ellen 
Published: September 2017

Detailed ionic analyses of Dyer Plateau snow show that major soluble impurities in snow consist of sodium (Na+), chloride (Cl−), nitrate (NO3−), sulfate (SO42−), and acidity (H+). The ratios of Na+ to Cl− concentrations are close to that of sea water, indicating little or no fractionation of sea-salt aerosols. The analyses of core sections from three sites along a 10 km transect show that local spatial variation of snow chemistry in this area is minimal and that temporal (decadal, inter-annual and sub-annual) variations in snow chemistry are very well preserved.Anion analyses of the upper 181 m section of two 235 m ice cores yield a data set of 485 years (1505-1989) of annual snow accumulation and fluxes of Cl−, NO3−, and non-sea-salt (nss) SO42−. No significant long-term trends are observed in any of the anion fluxes. This is consistent with other Antarctic ice-core records showing no significant anthropogenic atmospheric pollution in the high southern latitudes. Linear regression analysis shows that Cl− flux is independent of snow-accumulation rate. Significant positive correlations are found between accumulation rate and both NO3− flux and background nss-SO42− flux. These results suggest that dry deposition is primarily responsible for air-to-ground Cl− flux while wet deposition dominates the NO3− and nss-SO42− flux (≥90% and ≥75%, respectively). The nss-S042− fluxes provide a chronology of explosive volcanic emissions reaching the Antarctic region for the past 485 years.
Change in position and altitude of a small outlet glacier during the period 1943–92: Leverett Glacier, West Greenland
Authors: Van Tatenhove Frank G.M. , Roelfsema Chris M. , Blommers Geert , Voorden Anton Van 
Published: September 2017

Fluctuations in the position and surface altitude of Leverett Glacier, a small outlet glacier at the western margin of the Greenland ice sheet, are determined from a photogrammetric analysis. During the Greenland Ice-Margin Experiment (GIMEX) 1992 expedition, six control points were measured on the exposed rock surrounding Leverett Glacier, using a distancemeter (AGA 220 Geodimeter) and theodolite (Wild T2). Photogrammetric measurements were carried out on an analytical plotter (Zeiss Planicomp C100). The altitude of points could be photogrammetrically measured with a maximum error of 0.86 m.The data on the altitude changes of Leverett Glacier presented here are the first in West Greenland that span a time period of nearly 50 years. During the period 1943–68 the rate of altitude change was –0.6 m w.e.a−1. The thickening rate during the period 1968–85 was + 1.2 m w.e.a−1. Thickening continued dining the period 1985–92 at a rate of + 0.4 m w.e.a−1. This recent thickening is significant when compared to year-to-year variation in ablation. Trends in air temperature from the nearby climate station at Kangerlussuaq are consistent with the possibility that observed changes in the altitude of the glacier surface are the result of local changes in meteorological conditions determining ablation rates.
Recent variations of calving glaciers in Patagonia, South America, revealed by ground surveys, satellite-data analyses and numerical experiments
Authors: Naruse Renji , Aniya Masamu , Skvarca Pedro , Gasassa Gino 
Published: September 2017

Large retreats were revealed for most glaciers in Patagonia, South America, by analyzing satellite images and air photographs. For example, Glaciar O’Higgins retreated 13 km during 41 years from 1945 to 1986 and Glaciar Upsala retreated about 3 km between 1968 and 1990. During the 41 years former period, however, the southern tongue of Glaciar Pio XI advanced by up to 8.5 km and Glaciar Moreno remained almost in a steady state. Considerable ice-thinning rates, from 3.0 to 11 ma−1, were measured by surveying surface profiles in the ablation areas of Tyndall and Upsala glaciers, respectively, during the period from 1985 (or 1990) to 1993. The ice thickness of Glaciar Moreno, however, has changed very little.Numerical experiments using a simple mass-balance model show that a 100 m rise in the equilibrium-line altitude due to climatic change would result in about a 200–350 m rise in the frontal altitude at Glaciar Upsala corresponding to a retreat of 5–8 km, while it would cause only about a 70–100 m rise at Glaciar Moreno. The large difference between these two neighbouring glaciers results from the difference in contributions of the calving amount to the total mass balance, as well as the difference in the altitudinal distributions of drainage areas.
Spring-season climate variability in the central Canadian Arctic Islands
Authors: Agnew T. A. , Silis A. 
Published: September 2017

The Resolute Bay area in the central Canadian Arctic Islands is in a region of maximum variability in 50 kPa heights in spring. This is the northern part of an oscillation in large-scale atmospheric circulation called the Baffin Island West Atlantic Oscillation (BWA). The historical record of temperature at Resolute Bay, Northwest Territories, over the 1948–93 period is compared with circulation patterns for extremely warm and cold spring seasons, using a composite technique and a simple index of the intensity of the BWA. The extremely cold spring of 1992, the second coldest of the 46a record, was probably caused by reduced solar radiational forcing due to the increased dust veil caused by Mount Pinatubo.Within each spring season, large-scale synoptic conditions provided an important control on the timing of critical stages leading to full snow melt on the sea-ice surface. The first stage is the change from dominance of the region by wintertime continental polar air to the frequent invasion of maritime polar air masses, resulting in increased cloud cover and reduced frequency of Arctic inversions. The second stage is the transition to full melt on the ice with a sharp drop in surface albedo. During the spring on 1993, the first stage was triggered by a major storm which moved through the area on 9–10 May 1993. The second snow-melt stage was triggered by a stationary upper ridge which remained over the area for a 2 week period from 15 May to early June and produced clear to scattered-cloud conditions and high downward solar radiation.
Iceberg Melt-Driven Convection Inferred from Field Measurements of Temperature
Authors: Josberger Edward G. , Neshyba Steve 
Published: September 2017

An expendable bathythermograph (XBT) survey around an iceberg grounded in 100 m of water shows that iceberg melt-driven convection significantly alters the surrounding water properties in two ways, by a general cooling of the water in the upper 40 m by as much as 3 deg and by the formation of isothermal layers with a 5 m vertical-length scale in the pycnocline. Both of these effects become more pronounced as the distance to the iceberg decreases. The overall cooling of the upper layers supports the upwelling concept of Neshyba (1977) and of Josberger and Martin (in preparation*), while the formation of a step-like structure supports the cell formation idea of Huppert and Turner (1978) and Huppert and Josberger (1980).Synoptic surface surveys around the iceberg show the existence of melt plumes containing water of a lower temperature than the adjacent water, and these plumes are detectable at distances of 0.5 km.Concentrated rhodamine placed at depths of 14 and 18 m adjacent to an ice wall sloping down-ward at a 30° angle flowed upward along the ice. The dye reached the surface immediately next to the ice in 240 s and 540 s, respectively, to give a characteristic upward velocity of approximately 0.07 m s−1. The dye then dispersed outward away from the iceberg until it was no longer visible.
Interface Tracking in Digitally Recorded Glaciological Data
Authors: Cooper A.P.R. 
Published: September 2017

As more data are recorded in digital form the importance of automatically extracting parameters of glaciological significance increases. This paper addresses the problem, with particular reference to tracking bedrock or internal reflectors in digitally recorded Radio Echo Sounding (RES) data. It has been found that the simplest solution to this problem is a “supervised” system, where operator decisions may be added interactively, either on operator command or upon loss of track. Increasing internal decision making within the program may reduce the number of operator interventions required, but is unlikely to eliminate them completely.Algorithms are presented and discussed for determining the position of the interface, for predicting the position of the interface in successive records, for determining the loss of track condition, and for re-acquiring track after loss of track.
Seasat Altimeter Observations of an Antarctic “Lake”
Authors: Cudlip W. , McIntyre N.F. 
Published: September 2017

The word “lake” in the context of Antarctica has been used to describe both surface features (10–12 km in size) and areas of liquid water on the bedrock beneath the ice sheet (typically a few kilometres in size and at a depth of over 3000 m), There has been however only limited evidence for a relationship between the two phenomena.This paper reports an analysis of Seasat altimeter observations of an extremely flat area on the surface of the East Antarctic ice sheet, approximately 30 km in extent, centred at 68.6°S 136.0°E and close to the edge of the sub-glacial Astrolabe Basin. It has a regional slope of between zero and 0.01° , and non-random variations in height along track of about ± 1m on the scale of a few kilometres. The average radar backscatter coefficient is 5±2 dB in the region of the Astrolabe Basin, compared to a more usual value of about 10 dB for other areas of the ice sheet. A computer enhanced Landsat image of the region clearly shows the rougher steeper terrain to the North, with the surface in and around the flat area appearing totally smooth and featureless.NSF/SPRI/TUD radio echo-sounding data from the region, although limited in extent, shows a relatively strong signal (indicative of ice at the pressure melting point) over a large region. The signal under the flat area, however, is particularly strong and smooth, confirming the association between the surface feature and a bedrock lake 3800 m below.
Evidence for Atmospheric Cold-trap Processes in the Noninverted Emission Spectrum of Kepler-13Ab Using HST/WFC3
Authors: Beatty Thomas G. , Madhusudhan Nikku , Tsiaras Angelos , Zhao Ming , Gilliland Ronald L. , Knutson Heather A. , Shporer Avi , Wright Jason T. 
Published: September 2017

Abstract
We observed two eclipses of the Kepler-13A planetary system, on UT 2014 April 28 and UT 2014 October 13, in the near-infrared using Wide Field Camera 3 on the Hubble Space Telescope. By using the nearby binary stars Kepler-13BC as a reference, we were able to create a differential light curve for Kepler-13A that had little of the systematics typically present in HST/WFC3 spectrophotometry. We measure a broadband (1.1–1.65 μm) eclipse depth of 734 ± 28 ppm and are able to measure the emission spectrum of the planet at R ≈ 50 with an average precision of 70 ppm. We find that Kepler-13Ab possesses a noninverted, monotonically decreasing vertical temperature profile. We exclude an isothermal profile and an inverted profile at more than 3σ. We also find that the dayside emission of Kepler-13Ab appears generally similar to an isolated M7 brown dwarf at a similar effective temperature. Due to the relatively high mass and surface gravity of Kepler-13Ab, we suggest that the apparent lack of an inversion is due to cold-trap processes in the planet’s atmosphere. Using a toy model for where cold traps should inhibit inversions, as well as observations of other planets in this temperature range with measured emission spectra, we argue that with more detailed modeling and more observations we may be able to place useful constraints on the size of condensates on the daysides of hot Jupiters.
Stellar Dynamics and Star Formation Histories of z ∼ 1 Radio-loud Galaxies
Authors: Barišić Ivana , van der Wel Arjen , Bezanson Rachel , Pacifici Camilla , Noeske Kai , Muñoz-Mateos Juan C. , Franx Marijn , Smolčić Vernesa , Bell Eric F. , Brammer Gabriel , Calhau João , Chauké Priscilla , van Dokkum Pieter G. , van Houdt Josha , Gallazzi Anna , Labbé Ivo , Maseda Michael V. , Muzzin Adam , Sobral David , Straatman Caroline , Wu Po-Feng 
Published: September 2017

Abstract
We investigate the stellar kinematics and stellar populations of 58 radio-loud galaxies of intermediate luminosities (L
3 GHz > 1023 W Hz−1) at 0.6 < z < 1. This sample is constructed by cross-matching galaxies from the deep VLT/VIMOS LEGA-C spectroscopic survey with the VLA 3 GHz data set. The LEGA-C continuum spectra reveal for the first time stellar velocity dispersions and age indicators of z ∼ 1 radio galaxies. We find that z ∼ 1 radio-loud active galactic nucleus (AGN) occur exclusively in predominantly old galaxies with high velocity dispersions: σ
* > 175 km s−1, corresponding to black hole masses in excess of 108
M
⊙. Furthermore, we confirm that at a fixed stellar mass the fraction of radio-loud AGN at z ∼ 1 is five to 10 times higher than in the local universe, suggesting that quiescent, massive galaxies at z ∼ 1 switch on as radio AGN on average once every Gyr. Our results strengthen the existing evidence for a link between high black hole masses, radio loudness, and quiescence at z ∼ 1.
Far-infrared Spectroscopic Characterization of Anti-vinyl Alcohol
Authors: Bunn Hayley , Soliday Rebekah M. , Sumner Isaiah , Raston Paul L. 
Published: September 2017

Abstract
We report a detailed analysis of the high-resolution far-infrared spectrum of anti-vinyl alcohol, which has been previously identified toward Sagittarius B2(N). The ν
15 OH torsional fundamental investigated here is more than 200 cm−1 removed from the next nearest vibration, making it practically unperturbed and ideal to help refine the ground state rotational constants that were previously determined from 25 microwave lines. We assigned 1335 lines within the ν
15 fundamental centered at 261.5512 cm−1, with J and K

a
ranges of 1–59 and 0–16, respectively. The microwave and far-infrared line positions were fit with Watson-type A- and S-reduced Hamiltonians, with the inclusion of quartic and select sextic distortion terms. This resulted in a significant refinement of the ground state constants, in addition to the determination of the

ν

15

=
1

state constants for the first time. The spectroscopic parameters are in good agreement with the results from anharmonic coupled-cluster calculations, and should be useful in searches for rotationally and/or vibrationally warm anti-vinyl alcohol in interstellar molecular clouds.
Scale-invariant Cosmology and CMB Temperatures as a Function of Redshifts
Authors: Maeder Andre 
Published: September 2017

Abstract
Cosmological models assuming the scale invariance of the macroscopic empty space show an accelerated expansion, without calling for some unknown particles. Several comparisons between models and observations (tests on distances, m−z diagram,

versus

plot, age versus H
0, H(z) versus z, transition braking-acceleration) have indicated an impressive agreement. We pursue the tests with the CMB temperatures

as a function of redshifts z. CO molecules in DLA systems provide the most accurate excitation temperatures

up to

. Such data need corrections for local effects like particle collisions, optical depths, UV radiation, etc., We estimate these corrections as a function of the

ratios from far-UV observations of CO molecules in the Galaxy. The results show that it is not sufficient to apply theoretical collisional corrections to get the proper values of

versus z. Thus, the agreement often found with the standard model may be questioned. The

relation needs further careful attention and the same for the scale-invariant cosmology in view of its positive tests.
Results from EDGES High-band. I. Constraints on Phenomenological Models for the Global 21 cm Signal
Authors: Monsalve Raul A. , Rogers Alan E. E. , Bowman Judd D. , Mozdzen Thomas J. 
Published: September 2017

Abstract
We report constraints on the global 21 cm signal due to neutral hydrogen at redshifts

14.8
≥
z
≥
6.5

. We derive our constraints from low-foreground observations of the average sky brightness spectrum conducted with the EDGES High-band instrument between 2015 September 7 and October 26. Observations were calibrated by accounting for the effects of antenna beam chromaticity, antenna and ground losses, signal reflections, and receiver parameters. We evaluate the consistency between the spectrum and phenomenological models for the global 21 cm signal. For tanh-based representations of the ionization history during the epoch of reionization, we rule out, at

≥
2
σ

significance, models with duration of up to

Δ
z
=
1

at

z
≈
8.5

and higher than

Δ
z
=
0.4

across most of the observed redshift range under the usual assumption that the 21 cm spin temperature is much larger than the temperature of the cosmic microwave background during reionization. We also investigate a “cold” intergalactic medium (IGM) scenario that assumes perfect Lyα coupling of the 21 cm spin temperature to the temperature of the IGM, but that the latter is not heated by early stars or stellar remants. Under this assumption, we reject tanh-based reionization models of duration

Δ
z
≲
2

over most of the observed redshift range. Finally, we explore and reject a broad range of Gaussian models for the 21 cm absorption feature expected in the First Light era. As an example, we reject 100 mK Gaussians with duration (full width at half maximum)

Δ
z
≤
4

over the range

14.2
≥
z
≥
6.5

at

≥
2
σ

significance.
Constraining Reionization with the z ∼ 5–6 Lyα Forest Power Spectrum: The Outlook after Planck
Authors: Oñorbe J. , Hennawi J. F. , Lukić Z. , Walther M. 
Published: September 2017

Abstract
The latest measurements of cosmic microwave background electron-scattering optical depth reported by Planck significantly reduces the allowed space of

H

I

reionization models, pointing toward a later ending and/or less extended phase transition than previously believed. Reionization impulsively heats the intergalactic medium (IGM) to

∼

10

4

K

, and owing to long cooling and dynamical times in the diffuse gas that are comparable to the Hubble time, memory of reionization heating is retained. Therefore, a late-ending reionization has significant implications for the structure of the

z
∼
5
–
6

Lyα forest. Using state-of-the-art hydrodynamical simulations that allow us to vary the timing of reionization and its associated heat injection, we argue that extant thermal signatures from reionization can be detected via the Lyα forest power spectrum at

5
<
z
<
6

. This arises because the small-scale cutoff in the power depends not only the the IGM temperature at these epochs, but is also particularly sensitive to the pressure-smoothing scale set by the IGM full thermal history. Comparing our different reionization models with existing measurements of the Lyα forest flux power spectrum at

z
=
5.0
–
5.4

, we find that models satisfying Planck’s

τ

e

constraint favor a moderate amount of heat injection consistent with galaxies driving reionization, but disfavoring quasar-driven scenarios. We study the feasibility of measuring the flux power spectrum at

z
≃
6

using mock quasar spectra and conclude that a sample of ∼10 high-resolution spectra with an attainable signal-to-noise ratio will allow distinguishing between different reionization scenarios.