Snowmelt runoff and soil moisture dynamics on steep subalpine hillslopes

Snowmelt water supplies streamflow and growing season soil moisture in mountain regions, yet pathways of snowmelt water and their effects on moisture patterns are still largely unknown. This study examined how flow processes during snowmelt runoff affected spatial patterns of soil moisture on two steep sub‐alpine hillslope transects in Rocky Mountain National Park, CO, USA. The transects have northeast‐facing and east‐facing aspects, and both extend from high‐elevation bedrock outcrops down to streams in valley bottoms. Spatial patterns of both snow depth and near‐surface soil moisture were surveyed along these transects in the snowmelt and summer seasons of 2008–2010. To link these patterns to flow processes, soil moisture was measured continuously on both transects and compared with the timing of discharge in nearby streams. Results indicate that both slopes generated shallow lateral subsurface flow during snowmelt through near‐surface soil, colluvium and bedrock fractures. On the northeast‐facing transect, this shallow subsurface flow emerged through mid‐slope seepage zones, in some cases producing saturation overland flow, whereas the east‐facing slope had no seepage zones or overland flow. At the hillslope scale, earlier snowmelt timing on the east‐facing slope led to drier average soil moisture conditions than on the northeast‐facing slope, but within hillslopes, snow patterns had little relation to soil moisture patterns except in areas with persistent snow drifts. Results suggest that lateral flow and exfiltration processes are key controls on soil moisture spatial patterns in this steep sub‐alpine location. Copyright © 2014 John Wiley & Sons, Ltd.     

Distance in the space of energetically bounded Keplerian orbits

In this paper we derive an explicit, analytic formula for the geodesic distance between two points in the space of bounded Keplerian orbits in a particular topology. The specific topology we use is that of a cone passing through the direct product of two spheres. The two spheres constitute the configuration manifold for the space of bounded orbits of constant energy. We scale these spheres by a factor equal to the semi-major axis of the orbit, forming a linear cone. This five-dimensional manifold inherits a Riemannian metric, which is induced from the Euclidean metric on \mathbbR⁶{\mathbb{R}^6}, the space in which it is embedded. We derive an explicit formula for the geodesic distance between any two points in this space, each point representing a physical, gravitationally bound Keplerian orbit. Finally we derive an expression for the Riemannian metric that we used in terms of classical orbital elements, which may be thought of as local coordinates on our configuration manifold.     

Frictional influence on sea level oscillations in Otago Harbour,New Zealand

Oscillations in Otago Harbour, (45° 49’ S, 170° 38’ E) produced by the 1960 Chilean Tsunami are found by spectral analysis to have most of their energy at a period of about 80 min. By numerically integrating a one‐dimensional linear momentum equation and the continuity equation for various sections of the harbour, this period is found to correspond to the quarter wavelength oscillation in the main channel between the mouth of the harbour and the Halfway Islands. The large value of the linear frictional coefficient, calculated from the phase of the tide in the harbour, and the resulting excessive damping, indicates why long period non‐tidal oscillations are generally not found in the harbour.     

Direct measurements of coastal currents around southern New Zealand

Results are presented from direct measurements of subsurface currents at ten coastal positions around the southern half of New Zealand, and from geomagnetic electrokinetograph measurements of surface currents between these positions. Currents on the continental shelf were predominantly tidal. Strongest mean flows were found on the continental slope adjacent to areas where the continental shelf is narrowest. The flow on the west coast of the South Island was southwards south of 44° S, with a maximum mean speed at a depth of 100 m of 0.64 m.s^‐1. On the east coast of the South Island the flow was generally towards the north, with a maximum speed at a depth of 100 m of 0.21 m.s^‐1 near latitude 42° 30’ S.     

Tidal observations on the West Coast,South Island,New Zealand

Harmonic tidal constants, calculated from sea surface elevation observations at Jackson Bay on the West Coast of the South Island, are consistent with available semi‐diurnal and diurnal tidal phase distributions. Current observations taken over a 111 day period at mid‐depth in 1505 m of water on the southern flank of the Challenger Plateau and over a 240 day period in 1430 m of water on the South Island western coast continental slope, are subject to tidal analysis. At both sites there is a component of energy flux directed across the isobaths and only at the northern site for the M2 tide is the phase consistent with a dominant progressive barotropic tide. The successive 30 day harmonic constants at the southern continental slope site exhibit a trend in the M2 tidal ellipse speed and ellipticity suggesting the presence of a regular internal tide. Superposition of ‘internal tidal’ and barotropic tidal flows, as prescribed from progressive‐ and standing‐wave elevations, to fit the observations indicates that the ‘internal tide’ is probably associated with the first baroclinic mode. At the current‐meter depths the speeds of the ‘internal tide’ for the M2 tide are about the same as the barotropic speeds, whereas, the S2 ‘internal tide’ speeds are larger than those of the barotropic tide. The consistency of the trend in ellipse parameters lends support to the theoretical progressive trapped barotropic tidal flows being a good approximation to the actual barotropic tide. Some support for the hypothesis that the S2 tide on the West Coast of New Zealand has a substantial standing wave contribution is given by the northern observations, where the ratio of the S2: M2 internal tidal ellipse current amplitudes are substantially larger than the ratio of the elevations, the internal tide being generated by across‐isobath flows.     

History of metalliferous sedimentation at deep sea drilling site 319 in the South Eastern Pacific

Marked variations in the chemical and mineralogical composition of sediments at Site 319 have occurred during the 15 M.y. history of sedimentation at this site. The change in composition through time parallels the variability observed in surface sediments from various parts of the Nazca Plate and can be related to variations in the proportion of hydrothermal, hydrogenous, detrital and biogenous phases reaching this site at different times. Metal accumulation rates at Site 319 reach a maximum near the basement for most elements, suggesting a strong hydrothermal contribution during the early history of this site. The hydrothermal contribution decreased rapidly as Site 319 moved away from the spreading center, although a subtle increase in this source is detectable about the time spreading began on the East Pacific Rise. The most recent sedimentation exhibits a strong detritalhydrogenous influence. Post-depositional diagenesis of amorphous phases has converted them to ironrich smectite and well-crystallized goethite without significantly altering the bulk composition of the sediment.     

Characterisation of glacial sediments using geophysical methods for groundwater source protection

A sequence of glacial and alluvial deposits overlying the Cretaceous Chalk in Eastern England was characterised using two geophysical techniques: electrical resistivity imaging and electromagnetic (EM) induction. Extensive geological data were available from trenching and boreholes. Synthetic modelling of the electrical resistivity imaging technique was undertaken to identify its limitations and to optimise survey design. The EM induction method provided a quick and cost-effective reconnaissance technique for identifying large-scale lateral variation in lithology, and for siting resistivity profiles and further boreholes. The resistivity imaging technique provided detailed information on the vertical continuity of permeable units, and was able to identify permeable pathways through the sequence. Certain limitations in detecting thin sand or gravel layers underlying electrically conductive clay were seen in both the synthetic and field data. Nevertheless, the study shows that knowledge of these limitations allows interpretation for the purpose of groundwater vulnerability assessment, given that an appropriate amount of invasive investigation has been conducted.     

Transport and release of transition elements during early diagenesis: Sequential leaching of sediments from MANOP Sites M and H. Part I. pH 5 acetic acid leach

Sediments from MANOP sites M and H in the eastern tropical Pacific Ocean can be partitioned into operationally defined phases by means of a sequential leach procedure. This paper reports the results of the first leach in the sequence, an acetic acid solution buffered as p H 5 with sodium acetate. This leach is designed to remove carbonate-bound and sorbed cations. The only cation bound in a consistent ratio to calcium in the carbonate is strontium. The molar ratio is 2 × 10^?3. In contrast, transition metals are sorbed onto the surfaces of other sedimentary particles. The proportions sorbed range from 2 to 10% of the total manganese, about 10% of the total nickel and copper, and less than 1% of the total iron. The pool of sorbed metals in surface sediments is sufficiently large and the rate of biological stirring is sufficiently rapid for this metal reservoir potentially to dominate the porewater reservoir in supplying metals to ferromanganese nodules. A simple model for nodule growth based upon transfer of metals through this reservoir suggests that only 1% of the sedimentary sorbed metals within a radius of 2 to 9 cm is required to support typical nodule growth rates.     

Growth rates of manganese-rich nodules at MANOP Site H (Eastern North Pacific)

Estimates of the growth rates of ferromanganese nodules at MANOP Site H (6°33′N, 92°49′W) lie between 7 and 1200 mm/my. The most probable range (estimated from nodule size distributions, nodule chemistry, accumulation rates of authigenic elements and U-series modeling) is 30–300 mm/my. Such rates are much faster than measured values for most pelagic nodules. The distributions of U-series and stable elements suggest that a typical nodule consists of two compositionally distinct non-detrital components, one rich in Mn, U and Sb, and the other in Fe, Co, REE, Ni, Cu and Th. When the uncorrected U-series data, which do not show simple decay patterns with depth, are normalized to the relative proportion of the Fe-rich component, the data yield well-constrained growth rates of 55 mm/my for a nodule top and 200 mm/my for its bottom. The component enriched in Mn, which is most abundant on nodule bottoms, appears to accrete much faster than the component enriched in Fe.     

An incremental Knox test for the determination of the serial interval between successive cases of an infectious disease

An estimate of the interval between successive infections is essential for surveillance, control, and modeling of infectious diseases. This paper proposes a method for determining the serial interval when the location and time of onset of illness are known. The theoretical underpinning of this method is the intrinsically spatial nature of disease transmission. Successive infections tend to be closer than unrelated cases of disease and, therefore, exhibit spatial clustering. An incremental Knox type analysis of cases is introduced. Cases occurring at a range of time intervals are examined to determine the serial interval. The significance of clustering is determined using a permutation approach under the null hypothesis of space-time independence. The power of this method is evaluated using an individual level, spatially explicit epidemic simulation. The time increment Knox test is robust to multiple introductions and incomplete sampling. Finally, the increment Knox statistic is used to analyze an outbreak of dengue fever in the city of Florida, Puerto Rico during 1991. Results indicate that the likely interval between successive cases during this outbreak is at least 18–19 days.