Is There an Orbital Signal in the Polar Layered Deposits on Mars?

Do the polar layered deposits on Mars reflect orbital control or stochastic variability? It is first useful to determine whether an orbital signal would be detected, even if present. An estimate of the uncertainty in the time-depth relationship of the polar stratigraphy shows that nonlinearities in this relationship and noise in the signal will hamper or preclude detection of orbital forcing, even if layer composition is directly proportional to insolation. Indeed, stratigraphic sections of the north polar layered deposits reconstructed from spacecraft images yield no clear evidence of orbital control and are largely consistent with an autoregressive, stochastic formation process. There is, however, a broad rise in spectral power centered on a wavelength of roughly 1.6 m that appears in many of the stratigraphic sections. This bedding may record a time scale associated with processes internal to Mars' climate system, perhaps related to dust storms. Alternatively, if formed in response to variations in Mars' obliquity or orbital precession, the 1.6 m bedding implies that the ~1-km-thick upper north polar layered deposits formed over 30–70 Myr.Earth and Planetary Science

True polar wander driven by late-stage volcanism and the distribution of paleopolar deposits on Mars

The areal centroids of the youngest polar deposits on Mars are offset from those of adjacent paleopolar deposits by 5-10 degrees. We test the hypothesis that the offset is the result of true polar wander (TPW), the motion of the solid surface with respect to the spin axis, caused by a mass redistribution within or on the surface of Mars. In particular, we consider TPW driven by late-stage volcanism during the late Hesperian to Amazonian. There is observational and qualitative support for this hypothesis: in both North and South, observed offsets lie close to a great circle 90 degrees from Tharsis, as expected for polar wander after Tharsis formed. We calculate the magnitude and direction of TPW produced by mapped late-stage lavas for a range of lithospheric thicknesses, lava thicknesses, eruption histories, and prior polar wander events. If Tharsis formed close to the equator, the stabilizing effect of a fossil rotational bulge located close to the equator leads to predicted TPW of <2 degrees, too small to account for observed offsets. If, however, Tharsis formed far from the equator, late-stage TPW driven by low-latitude, late-stage volcanism would be 6-33 degrees, similar to that inferred from the location of paleopolar deposits. 4.4+/-1.3x10^19 kg of young erupted lava can account for the offset of the Dorsa Argentea Formation from the present-day south rotation pole. This mass is consistent with prior mapping-based estimates and would imply a mass release of CO2 by volcanic degassing similar to that in the atmosphere at the present time. The South Polar Layered Deposits are offset from the spin axis in the opposite sense to the other paleopolar deposits. This can be explained by an additional contribution from a plume beneath Elysium. We conclude with a list of observational tests of the TPW hypothesis.Comment: Accepted by Earth and Planetary Science Letters. 3 tables, 8 figure

Paternal Psychosocial Characteristics and Corporal Punishment of their 3-Year Old Children

This study uses data from 2,309 biological fathers who participated in the Fragile Families and Child Wellbeing Study (FFCWS) to examine associations between psychosocial characteristics and levels of corporal punishment (CP) toward their 3-year old children over the past month. Results indicate that 61% of the fathers reported no CP over the past month, 23% reported using CP once or twice, and 16% reported using CP a few times in the past month or more. In multivariate models controlling for important socio-demographic factors as well as characteristics of the child, fathers’ parenting stress, major depression, alcohol use, and drug use were significantly associated with greater use of CP, whereas involvement with the child and generalized anxiety order were not. Girls were less likely to be the recipient of CP than boys, and child externalizing behavior problems but not internalizing behavior problems were associated with more CP.Fragile families, childbearing, nonmarital childbearing, fartherhood, fathers, corporal punishment, behavior problems, stress, depression

IDA: An implicit, parallelizable method for calculating drainage area

Models of landscape evolution or hydrological processes typically depend on the accurate determination of upslope drainage area from digital elevation data, but such calculations can be very computationally demanding when applied to high-resolution topographic data. To overcome this limitation, we propose calculating drainage area in an implicit, iterative manner using linear solvers. The basis of this method is a recasting of the flow routing problem as a sparse system of linear equations, which can be solved using established computational techniques. This approach is highly parallelizable, enabling data to be spread over multiple computer processors. Good scalability is exhibited, rendering it suitable for contemporary high-performance computing architectures with many processors, such as graphics processing units (GPUs). In addition, the iterative nature of the computational algorithms we use to solve the linear system creates the possibility of accelerating the solution by providing an initial guess, making the method well suited to iterative calculations such as numerical landscape evolution models. We compare this method with a previously proposed parallel drainage area algorithm and present several examples illustrating its advantages, including a continent-scale flow routing calculation at 3 arc sec resolution, improvements to models of fluvial sediment yield, and acceleration of drainage area calculations in a landscape evolution model. We additionally describe a modification that allows the method to be used for parallel basin delineation.National Science Foundation (U.S.). Geomorphology and Land-Use Dynamics Program (Award EAR-0951672

On infimum Dickey–Fuller unit root tests allowing for a trend break under the null

Trend breaks appear to be prevalent in macroeconomic time series. Consequently, to avoid the catastrophic impact that unmodelled trend breaks have on power, it is standard empirical practice to employ unit root tests which allow for such effects. A popularly applied approach is the infimum ADF-type test. Its appeal has endured with practitioners despite results which show that the infimum ADF statistic diverges to −∞−∞ as the sample size diverges, with the consequence that the test has an asymptotic size of unity when a break in trend is present under the unit root null hypothesis. The result for additive outlier-type breaks in trend (but not intercept) is refined and shows that divergence to −∞−∞ occurs only when the true break fraction is smaller than 2/32/3. An alternative testing strategy based on the maximum of the original infimum statistic and the corresponding statistic constructed using the time-reversed sample data is considered

A 2.5-GHz asymmetric multilevel outphasing power amplifier in 65-nm CMOS

We present a high-efficiency transmitter based on asymmetric multilevel outphasing (AMO). AMO transmitters improve their efficiency over LINC (linear amplification using nonlinear components) transmitters by switching the output envelopes of the power amplifiers among a discrete set of levels. This minimizes the occurrence of large outphasing angles, reducing the energy lost in the power combiner. We demonstrate this concept with a 2.5-GHz, 20-dBm peak output power transmitter using 2-level AMO designed in a 65-nm CMOS process. To the authors' knowledge, this IC is the first integrated implementation of the AMO concept. At peak output power, the measured power-added efficiency is 27.8%. For a 16-QAM signal with 6.1dB peak-to-average power ratio, the AMO prototype improves the average efficiency from 4.7% to 10.0% compared to the standard LINC system

Reply to: Terry, J. and Goff, J. comment on “Late Cenozoic sea level and the rise of modern rimmed atolls” by Toomey et al. (2016), Palaeogeography, Palaeoclimatology, Palaeoecology 451: 73–83

This paper is not subject to U.S. copyright. The definitive version was published in Palaeogeography, Palaeoclimatology, Palaeoecology 469 (2017): 159-160, doi:10.1016/j.palaeo.2016.11.028

Late Cenozoic sea level and the rise of modern rimmed atolls

This paper is not subject to U.S. copyright. The definitive version was published in Palaeogeography, Palaeoclimatology, Palaeoecology 451 (2016): 73-83, doi:10.1016/j.palaeo.2016.03.018.Sea-level records from atolls, potentially spanning the Cenozoic, have been largely overlooked, in part because the processes that control atoll form (reef accretion, carbonate dissolution, sediment transport, vertical motion) are complex and, for many islands, unconstrained on million-year timescales. Here we combine existing observations of atoll morphology and corelog stratigraphy from Enewetak Atoll with a numerical model to (1) constrain the relative rates of subsidence, dissolution and sedimentation that have shaped modern Pacific atolls and (2) construct a record of sea level over the past 8.5 million years. Both the stratigraphy from Enewetak Atoll (constrained by a subsidence rate of ~ 20 m/Myr) and our numerical modeling results suggest that low sea levels (50–125 m below present), and presumably bi-polar glaciations, occurred throughout much of the late Miocene, preceding the warmer climate of the Pliocene, when sea level was higher than present. Carbonate dissolution through the subsequent sea-level fall that accompanied the onset of large glacial cycles in the late Pliocene, along with rapid highstand constructional reef growth, likely drove development of the rimmed atoll morphology we see today.Support for this work was provided through a Jackson School Distinguished Postdoctoral Fellowship to Michael Toomey

The search for a topographic signature of life.

Landscapes are shaped by the uplift, deformation and breakdown of bedrock and the erosion, transport and deposition of sediment. Life is important in all of these processes. Over short timescales, the impact of life is quite apparent: rock weathering, soil formation and erosion, slope stability and river dynamics are directly influenced by biotic processes that mediate chemical reactions, dilate soil, disrupt the ground surface and add strength with a weave of roots. Over geologic time, biotic effects are less obvious but equally important: biota affect climate, and climatic conditions dictate the mechanisms and rates of erosion that control topographic evolution. Apart from the obvious influence of humans, does the resulting landscape bear an unmistakable stamp of life? The influence of life on topography is a topic that has remained largely unexplored. Erosion laws that explicitly include biotic effects are needed to explore how intrinsically small-scale biotic processes can influence the form of entire landscapes, and to determine whether these processes create a distinctive topography