Methodological Guidelines Designed to Improve the Quality of Research on Cross-Country Skiing

Cross-country (XC) ski races involve a variety of formats, two different techniques and tracks with highly variable topography and environmental conditions. In addition, XC skiing is a major component of both Nordic combined and biathlon competitions. Research in this area, both in the laboratory and field, encounters certain difficulties that may reduce the reliability and validity of the data obtained, as well as complicate comparisons between studies. Here, 13 international experts propose specific guidelines designed to enhance the quality of research and publications on XC skiing, as well as on the biathlon and Nordic combined skiing. We consider biomechanical (kinematic, kinetic and neuromuscular) and physiological methodology (at the systemic and/or muscle level), providing recommendations for standardization/control of the experimental setup. We describe the types of measuring equipment and technology that are most suitable in this context. Moreover, we also deal with certain aspects of nomenclature of the classical and skating sub-techniques. In addition to enhancing the quality of studies on XC skiing, Nordic combined and biathlon, our guidelines should also be of value for sport scientists and coaches in other disciplines where physiological and/or biomechanical measurements are performed in the laboratory and/or outdoors.

Internal tide generation due to topographically adjusted barotropic tide

<p>We model internal tides generated by the interaction of a barotropic tide with variable topography. For the barotropic part, an asymptotic solution valid over the variable topography is considered. The resulting non-uniform ambient flow is used as a prescribed barotropic forcing for the baroclinic equations (linearized, non-hydrostatic, Euler equations within the Boussinesq approximation).</p><p>The internal-tide generation problem is reformulated by means of a Coupled-Mode System (CMS) based on the decomposition of the baroclinic stream function in terms of vertical basis functions that consistently satisfy the bottom boundary condition. The proposed CMS is solved numerically with a finite difference scheme and shows good convergence properties, providing efficient calculations of internal tides due to 2D topographies of arbitrary height and slope. We consider several seamounts and shelf profiles and perform calculations for a wide range of heights and slopes. Our results are compared against existing analytical estimates on the far-field energy flux in order to examine the limit of validity of common simplifications (Weak Topography Approximation, Knife edge). For subcritical cases, local extrema of the energy flux exist for different heights. Non-radiating topographies are also identified for some profiles of large enough heights. For supercritical cases, the energy flux is in general an increasing function with increasing height and criticality, and does not compare well against analytical results for very steep idealized topographies. The effect of the adjusted barotropic tide in the energy flux and the local properties of the baroclinic field is investigated through comparisons with other semi-analytical methods based on a uniform barotropic tide (Green’s function approach).  A method for estimating the sea-surface signature of internal tides is also provided.</p>

Scale and Value: Challenges in the assessment and representation of geodiversity in Australia

<p>Though interpretations of the concept of geodiversity vary widely between the prominent researchers and practitioners of Australia, most agree that the definition is inclusive of abiotic elements (which can be detected spatially and assessed quantitatively), and their associated values (which can be used in reserve system planning, geotourism and to relate culture and nature to elements and functions). Challenges in Australian geodiversity assessment and representation are three-fold - there is lack of recognition of the concept across the nation, spatial datasets are incomplete or inadequate in some regions, and the spatial extent of some elements extends hundreds of kilometres whilst other potentially equally-significant elements occur at scales of tens of meters.</p><p>In this presentation, I present three case studies of Australian geodiversity. I first explore a regional interpretation of geodiversity, in a spatially-heterogenous protected area in Tasmania - a place that has myriad unique superlative natural values. I demonstrate that the delineation between elements of geodiversity is supported by a geological framework, that facilitates adequate rank comparisons of similar landforms and/or geological types across variable topography and vegetation communities. I then demonstrate the challenges associated with values-based assessment of geodiversity at this scale - that nearly all elements become regionally significant, there are many singular examples that cannot be adequately compared, and that the additional values associated with superlative landform elements may skew the spatial expression of more scientifically significant forms.</p><p>I then present two examples of state (similarity 'provincial') 'geodiversity site' (sensu Brilha 2016) inventories. One is extensively populated, is backed by expertise and universally-accepted criteria that dates back to the founding notions of geodiversity, but nominations are ad hoc and therefore a spatially-systematic ranked system has not been used. Conversely, in the other state example, inventory are systematically allocated on the basis of pre-established criteria - but this state is inherently far less spatially geodiverse than the former example, leading to a situation where the inventory entries of the latter would not be considered significant enough to warrant listing in the former.</p><p>Finally, I present some upcoming future challenges with national-level geodiversity assessment. I show the spatial extent and granularity of our four key national datasets (soils, geology, landform, topography). I present new data that shows the values associated with geodiversity elements that are recognised in IUCNIa-III reserve management plans across Australia. I demonstrate how the comparative dearth of spatial element complexity on the Australian mainland is at odds with the immensely heterogeneous state of Tasmania, and how this may in part have influenced prior thinking regarding the concept and its inherent value to conservation and society.</p><p>The 'Australian Geodiversity Assessment Challenge' raises questions about scale, territory, value, precision and representativeness - all of which are likely to be consistent with attempts to create a unified global geodiversity index or assessment approach. It is hoped that this presentation stimulates discussion among members, and informs the debate on the ways in which geodiversity elements and values can be evaluated at a range of spatial scales.</p>

Cross-Shelf Transport Through the Interaction among a Coastal Jet, a Topographic Wave, and Tides

Shelf break flows are often characterized by along-isobath jets with cross-shelf currents associated with tides and waves guided by variable topography. Here, we address the question: Can a superposition of such flows produce significant aperiodic cross-shelf transport? To answer this question, we use a barotropic analytic model for the jet based on a similarity solution of the shallow water equations over variable topography, a wave disturbance determined by the topography, and a diurnal tidal disturbance. We use standard Lagrangian methods to assess the cross-shelf transport, presenting the results, however, in a Eulerian frame, so as to be amenable to oceanographic observations. The relative roles of the different flow components in cross-shelf transport are assessed through an extensive parameter study. We find that a superposition of all three flow components can indeed produce consequential background aperiodic transport. An application of the model using recent observations from the Texas Shelf demonstrates that a combination of these background mechanisms can produce significant transport under realistic conditions.

The Propagation of Nonlinear Internal Waves under the Influence of Variable Topography and Earth’s Rotation in a Two-Layer Fluid

A nonlinear equation of the Korteweg–de Vries equation usually describes internal solitary waves in the coastal ocean that lead to an exact solitary wave solution. However, in any real application, there exists the Earth’s rotation. Thus, an additional term is required, and consequently, the Ostrovsky equation is developed. This additional term is believed to destroy the solitary wave solution and form a nonlinear envelope wave packet instead. In addition, an internal solitary wave is commonly disseminated over the variable topography in the ocean. Because of these effects, the Ostrovsky equation is retrieved by a variable-coefficient Ostrovsky equation. In this study, the combined effects of both background rotation and variable topography on a solitary wave in a two-layer fluid is studied since internal waves typically happen here. A numerical simulation for the variable-coefficient Ostrovsky equation with a variable topography is presented. Two basic examples of the depth profile are considered in detail and sustained by numerical results. The first one is the constant-slope bottom, and the second one is the specific bottom profile following the previous studies. These indicate that the combination of variable topography and rotation induces a secondary trailing wave packet.