Extreme heat in New Zealand: a synthesis

Climatic Change - The usefulness of global integrated assessment model (IAM) results for policy recommendation in specific regions has not been fully assessed to date. This study presents the...     

Snow accumulation and ablation response to changes in forest structure and snow surface albedo after attack by mountain pine beetle

This study quantified changes in snow accumulation and ablation with forest defoliation in a young pine stand attacked by mountain pine beetle, a mature mixed species stand, and a clearcut in south‐central British Columbia. From 2006 to 2012, as trees in the pine stand turned from green to grey, average canopy transmittance increased from 27% to 49%. In the mixed stand, transmittance remained constant at 19%. In 2009, the year of greatest needle loss, average snow surface litter cover in the pine stand was 29% (range 4 – 61%), compared to ≤9% in other years and over double that in the mixed stand. By 2012, litter accumulation in the now‐grey pine stand was only a sixth of that in the mixed stand. Inter‐annual variability in the weather had the greatest effect on snow accumulation and ablation, with the greatest differences between both forested stands and the clearcut occurring in 2010, the year of lowest SWE. Differences in snow accumulation between the pine and mixed stand increased in 2010 as a result of decreased snow interception in the young stand after needlefall. Average ablation rates in the attacked stand were most different from the mixed stand in 2009 and 2012, the years with the largest and smallest over‐winter needle loss, respectively. This study shows that grey, non‐pine, and understory trees moderate snow response to changes in the main canopy. It also highlights the complex interrelationships between ecohydrological processes key to assessing watershed response to forest cover loss in snow dominated hydrologic regimes. Copyright © 2012 John Wiley & Sons, Ltd.     

Internal catchment process simulation in a snow‐dominated basin: performance evaluation with spatiotemporally variable runoff generation and groundwater dynamics

Hydrologic models have increasingly been used in forest hydrology to overcome the limitations of paired watershed experiments, where vegetative recovery and natural variability obscure the inferences and conclusions that can be drawn from such studies. Models are also plagued by uncertainty, however, and parameter equifinality is a common concern. Physically‐based, spatially‐distributed hydrologic models must therefore be tested with high‐quality experimental data describing a multitude of concurrent internal catchment processes under a range of hydrologic regimes. This study takes a novel approach by not only examining the ability of a pre‐calibrated model to realistically simulate watershed outlet flows over a four year period, but a multitude of spatially‐extensive, internal catchment process observations not previously evaluated, including: continuous groundwater dynamics, instantaneous stream and road network flows, and accumulation and melt period spatial snow distributions. Many hydrologic model evaluations are only on the comparison of predicted and observed discharge at a catchment outlet and remain in the ‘infant stage’ in terms of model testing. This study, on the other hand, tests the internal spatial predictions of a distributed model with a range of field observations over a wide range of hydroclimatic conditions. Nash‐Sutcliffe model efficiency was improved over prior evaluations due to continuing efforts in improving the quality of meteorological data collection. Road and stream network flows were generally well simulated for a range of hydrologic conditions, and snowpack spatial distributions were well simulated for one of two years examined. The spatial variability of groundwater dynamics was effectively simulated, except at locations where strong stream–groundwater interactions exist. Model simulations overall were quite successful in realistically simulating the spatiotemporal variability of internal catchment processes in the watershed, but the premature onset of simulated snowmelt for one of the simulation years has prompted further work in model development. Copyright © 2011 John Wiley & Sons, Ltd.     

Compositional variability on the surface of 4 Vesta revealed through GRaND measurements of high‐energy gamma rays

Measurements of the high‐energy gamma‐ray flux emanating from asteroid 4 Vesta by the Dawn Gamma‐Ray and Neutron Detector (GRaND) have revealed variability in the near‐surface elemental composition of the Vestan surface. These observations are consistent with the presence of large (≥8 × 10⁴ km²) regions with distinct, HED‐like elemental compositions. The results agree broadly with other global measurements, such as the macroscopic neutron absorption cross section and spectral reflectance‐derived mineralogic maps. Two distinct regions with eucrite‐like elemental compositions have been identified, the first located primarily within the Lucaria and Marcia quadrangles and the second within Oppia quadrangle. The former region is collocated with some of the oldest, most heavily cratered terrain on Vesta. The interior of the 500 km diameter Rheasilvia impact basin is found to have a composition that is consistent with diogenite‐like material. Taken together, these observations support the hypothesis that Vesta's original crust was composed of basaltic outflows in the form of eucritic‐like material and that the Rheasilvia‐basin‐forming impact exposed lower‐crustal, diogenite‐like material. These measurements also constrain the maximum amount of mesosiderite‐like material to <10% for each 15 × 15° surface element.     

40Ar/39Ar and U-Pb dating in the eastern Pilbara,Australia; temporal constraints on structural and metamorphic events between 3.5 and 2.8 Ga (extended abstract)

Geologie en Mijnbouw -     

Opportunistic Feeding in Mediterranean Blennioid Fishes (Blenniidae and Tripterygion) as Revealed by Experimental Food Provisioning in the Field

Abstract. Consistent differences were found in trophic opportunism between species and between sexes by food provisioning experiments in an assemblage of 15 species of Mediterranean blennioid fishes. The degree of trophic opportunism in the different species was significantly and positively correlated with body size and two features indicative for intensity of male parental care. The degree of trophic opportunism correlated neither with trophic level, depth distribution, or relative abundance. Females of all species in which sex could be distinguished visited the feeding stations at higher frequencies than conspecific males.     

European vegetation during Marine Oxygen Isotope Stage-3

European vegetation during representative “warm” and “cold” intervals of stage-3 was inferred from pollen analytical data. The inferred vegetation differs in character and spatial pattern from that of both fully glacial and fully interglacial conditions and exhibits contrasts between warm and cold intervals, consistent with other evidence for stage-3 palaeoenvironmental fluctuations. European vegetation thus appears to have been an integral component of millennial environmental fluctuations during stage-3; vegetation responded to this scale of environmental change and through feedback mechanisms may have had effects upon the environment. The pollen-inferred vegetation was compared with vegetation simulated using the BIOME 3.5 vegetation model for climatic conditions simulated using a regional climate model (RegCM2) nested within a coupled global climate and vegetation model (GENESIS-BIOME). Despite some discrepancies in detail, both approaches capture the principal features of the present vegetation of Europe. The simulated vegetation for stage-3 differs markedly from that inferred from pollen analytical data, implying substantial discrepancy between the simulated climate and that actually prevailing. Sensitivity analyses indicate that the simulated climate is too warm and probably has too short a winter season. These discrepancies may reflect incorrect specification of sea surface temperature or sea-ice conditions and may be exacerbated by vegetation-climate feedback in the coupled global model.     

Quintessential Cosmology Novel Models of Cosmological Structure Formation

We examine the possibility that a substantial fraction of the total energy density in a spatially flat Universe is composed of a time-dependent and spatially inhomogeneous component whose equation-of-state differs from that of baryons, neutrinos, dark matter, or radiation. In this lecture, we report on our investigations of the case in which the additional energy component, dubbed "quintessence", is due to a dynamical scalar field evolving in a potential. We have computed the effects on the background cosmological evolution, the cosmic microwave background (CMB) and mass power spectrum, finding a broad range of cosmologically viable models. We stress three important features of the quintessence or Q-component: the time evolution of the equation-of-state; the length-scale dependence of the speed of propagation of the fluctuations in the Q-component; and, the contribution of quintessence fluctuations to the CMB anisotropy spectrum. This revised version was published online in July 2006 with corrections to the Cover Date.