Large Horizontal Velocity Research Articles

도마 츠카하라 몸 접어 뒤로 두 번 돌기의 운동역학적 분석

This study was conducted to investigate the technical factors of Lu Yu Fu vault actually performed by three men gymnasts participated in artistic gymnastics competition of 2003 summer Universiade in Daegu through the DLT method of three dimensional cinematography. To analyze these vaults, the instant events of Lu Yu Fu were set in the board touchdown(BTD), the board takeoff(BTO), the horse touchdown(HTD), the horse takeoff(HTO), the peak height(PH), the mat touchdown(MTD) respectively and the phases of that vault were set in the board contact(BC), the preflight(PRF), the horse contact(HC), the postflight(POF), the grounding on mat(GM) respectively After calculating the performance times, the CG displacement velocity, the kinetic energy impulse reaction force moment arm torque at the horse, the released angle piked angle addressed angle, the angular momentum angular velocity of whole body in x axis, and the horizontal displacement between the feet and CG, the following conclusions were reached. To perform the better Lu Yu Fu vault, a gymnast must have the large horizontal velocity of whole body with fast run-up, decrease the duration time and the horizontal vertical displacement of whole body in PRF, have the enough time to judge the correct magnitude and direction of force to brake or push the horse so as to lengthen the HC duration time at any cost. Also it is desirable to increase the horizontal vertical displacement of whole body in POF if possible, maintain the adequate piked position to decrease the angular velocity of whole body in x axis, prepare the grounding on mat previously and delay the release of the hand from the body to keep the angular momentum.

Gymnastics

The 16 highest‐scored Roche vaults (G1) performed during the 2000 Olympic Games were compared with those receiving the 16 lowest‐scores (G2). A 16‐mm motion picture camera operating at 100 Hz recorded the vaults during the competition. The results of t tests (p < .05) indicated G1, compared to G2, had (a) shorter time of board support, greater normalised average upward vertical force and backward horizontal force exerted by the board, greater change in the vertical velocity while on the board, and greater vertical velocity at board take‐off, (b) comparable linear and angular motions in pre‐flight, (c) smaller backward horizontal impulse exerted by the horse, smaller loss of the horizontal velocity while on the horse, and greater horizontal and vertical velocities at horse take‐off, (d) greater height and larger horizontal distance of post‐flight, (e) higher body mass centre at knee release, and (f) higher mass centre, greater normalised moment of inertia, and smaller vertical velocity at mat touchdown. Therefore, gymnasts and coaches should focus on sprinting the approach; blocking and pushing‐off the take‐off board rapidly and vigorously; departing the board with a large vertical velocity; exerting large downward vertical force and small forward horizontal force from the handstand position while on the horse; departing the horse with large horizontal and vertical velocities; and completing the majority of the double salto forward near the peak of trajectory and releasing the knees above the top of the horse to prepare for a controlled landing.

PRE-FLIGHT MECHANICAL DIFFERENCES BETWEEN TWO HANDSPRING CATEGORY VALUTS PERFORMED BY ELITE GYMNASTS

The handspring (HS) vault forms the basis for mastering the more advanced handspring and salto forward tucked (HSS) vault, which in turn provides the basis for learning the handspring and double salto forward tucked (Roche) vault with greater ease and safety. The Roche is one of the most advanced and high-risk vaults seen in major competitions today. Pre-flight mechanical variables have important “causal influence” on the subsequent phases and overall performance of the vault. Therefore, the purpose of this study was to identify the pre-flight mechanical variables that are crucial in achieving successful transition from the HS vault to the HSS vault. The subjects were 40 male gymnasts performing the HS vault at the 1987 Pan American Games and 51 male gymnasts performing the HSS vault at the 1988 Olympic Games. The vaults were filmed using a 16-mm camera operating at 100 Hz. Approximately 50 frames were digitized for each vault. A theoretical model was developed to identify the mechanical variables that determine the linear and angular motions of the vaults. The results of t test applied to the data indicated that the HSS vault, compared to the HS vault, had significantly (P < .005): (1) greater horizontal velocity and higher body center of mass (CM) at touchdown (TD) on the board; (2) greater horizontal displacement of body CM and smaller change of the vertical velocity while on the board; (3) greater horizontal velocity, greater normalized angular momentum, and higher body CM at take-off (TO) from the board; (4) smaller horizontal and vertical displacements of body CM, shorter time, and greater angular speed of pre-flight; and (5) greater vertical velocity and lower body CM at TD on the horse. In conclusion, successful transition from the HS vault to the HSS vault is likely when the focus is on achieving: (1) large horizontal velocity at TD on the board by sprinting the approach and departing from it with large horizontal velocity and normalized angular momentum; (2) small horizontal and vertical distances traveled by CM, short time, and rapid body rotation in pre-flight by reaching toward the far-end of the horse with the hands (flexion of the humerus) as quickly as possible upon TO from the board; and, consequently, (3) large vertical velocity and low body CM at TD on the horse to effect successful on-horse and post-flight performance.

The Hecht vault performed at the 1995 World Gymnastics Championships: Deterministic model and judges' scores

The aim of this study was to determine the mechanical variables that govern success of the Hecht vault. The participants were 122 male gymnasts from 30 countries performing the vault at the 1995 World Gymnastics Championships. The vaults were filmed using a Photosonics 16-mm motion picture camera operating at 100 Hz. Approximately 80 frames were digitized for each vault analysed. The method of Hay and Reid was used to develop a theoretical model to identify the mechanical and physical variables that determine linear and angular motions of the vault. Correlational analysis was used to establish the strength of the relationship between the causal mechanical variables identified in the model and the judges' scores. Significant correlations (P ≪ 0.005) indicated that the following were important determinants of success: large horizontal and vertical velocities at take-off from the board and the horse; large vertical and angular distances of pre-flight; large vertical impulses of high force and short duration exerted on the horse and the resulting large changes in vertical velocity on the horse; and large horizontal and vertical distances and long times of post-flight. Of the 18 significant variables identified in the present study, the angular distance of pre- and post-flights, the horizontal velocity and angular momentum at take-off from the horse, and the average moment of inertia and duration of post-flight collectively accounted for 57% of the variation in the judges' scores.

Three-Dimensional Analysis of Handspring with Full Turn Vault: Deterministic Model, Coaches' Beliefs, and Judges' Scores

The purpose of the study was to identify mechanical variables that govern successful performance of the handspring with full turn vault. Subjects were 67 male gymnasts from 25 countries performing the vault during the 1992 Olympic Games. The vaults were filmed by two 16-mm Locam II DC cameras operating at 100 Hz. Approximately 80 frames per subject were digitized for each camera view. Direct linear transformation (DLT) was used to calculate the 3-D coordinates of the digitized body points. The method of Hay and Reid (1988) was used to develop a theoretical model to identify the mechanical variables that determine linear and angular motions of the vault. Significant correlations (p &lt; .005) indicated that the following were important determinants for success: large horizontal velocity, large horizontal kinetic energy term, and overall translational kinetic energy term at takeoff from the board; short duration, small vertical displacement of the center of gravity (CG), and small somersaulting angular distance of preflight; large vertical velocity and large vertical kinetic energy term at takeoff from the horse; and large "amplitude of postflight," that is, large horizontal and vertical displacements of CG and long duration of flight; great height of CG during the second quarter-tum in postflight; and small point deduction for landing.

Carbon-13 constraints on the seasonal inorganic carbon budget at the BATS site in the northwestern Sargasso Sea

The seasonal budget of dissolved inorganic carbon ( C) in the mixed layer at the U.S. JGOFS Bermuda Atlantic Time-series Study (BATS) site is assessed on the basis of a 4-yr time series (1991–1994) of high-precision C, alkalinity and the 13C/ 12C ratio of C. Compared to previous studies, our budget is constrained by observed changes in 13C/ 12C , which permit calculation of the net community production. We are thus able to quantitatively separate all processes that contribute to the observed seasonal cycle in the mixed layer. Uncertainties in the C budget are determined using a Monte Carlo method. We found that net community production is mainly responsible in generating the observed C drawdown of about 26 μmol kg -1 between April and October by removing on the average −40±4 μmol kg -1 from the mixed layer. This net community production occurs in the absence of measurable nitrate and phosphate concentrations. We hypothezise that N 2 fixation in combination with vertical migration may be large enough to meet the biological nutrient demand in the mixed layer during this summer/fall period. Physical processes do not explain the observed summer/fall drawdown except when very improbably large horizontal advective velocities are assumed. Annual net community production of 2.3±0.9 mol m -2 is not well constrained by 13C/ 12C , but if tentatively extrapolated to the whole euphotic layer, it is well within the range of estimates based on a wide variety of methods. The region around BATS is computed to be a moderate sink for atmospheric CO 2 with an annual uptake of 1.8±0.5 mol m -2, with about 25% of this influx associated with the uptake of anthropogenic CO 2.

The interaction of a point vortex with a wall-bounded vortex layer

The interaction of a point vortex with a layer of constant vorticity, bounded below by a wall and above by an irrotational flow, is investigated as a model of vortex–boundary layer interaction. This model calculates both the evolution of the interface which separates the vortex layer from the irrotational flow and the trajectory of the vortex. In order to determine the conditions which lead to sustained unsteady interaction, three cases are investigated where the mutual interaction between the vortex and interface is initially assumed to be weak. (i) When a weak point vortex lies outside the layer, the vortex moves with a horizontal speed that is small relative to the long-wave phase speed of interfacial waves. A uniformly valid solution is found for the interface evolution. This solution shows that for long times the interface and the vortex approach an equilibrium state. (ii) When a weak vortex lies inside the layer, the vortex is convected by the mean flow and moves with a horizontal speed which matches the phase speed of an interfacial wave. This results in a strong interaction between the vortex and the interfacial wave. On the interface, a monochromatic wavetrain forms upstream of the vortex and acts to attract or repel the point vortex. The displacement of the vortex due to the wavetrain results in the modulation of the amplitude and wavelength of the wavetrain. If the point vortex is attracted toward the interface the horizontal speed of the vortex slows and disturbances directly above the vortex focus and grow leading to the ejection of vorticity. (iii) When the point vortex lies close to the wall and it is sufficiently strong it propagates downstream with a large horizontal velocity. In this case, the amplitude of the interfacial disturbance is independent of the vortex strength. Again, the vortex and the interface approach an equilibrium state. The results of this paper indicate that when the horizontal speed of the vortex matches the phase speed of the interfacial disturbance, it is necessary to account for the vertical displacement of the vortex in order to predict the behaviour of vortex–boundary layer interactions.

A Three-Dimensional Analysis of the Men’s Compulsory Vault Performed at the 1992 Olympic Games

The 20 highest scored handspring with full-turn vaults performed during the 1992 Olympic Games were compared with those receiving the 20 lowest scores. Hypotheses were that the vaults receiving high scores would (a) demonstrate larger horizontal velocity at takeoff from the board and larger vertical velocity at takeoff from the horse and (b) demonstrate greater amplitude of postflight, higher center of gravity (CG) at the completion of the full twist, and superior landing performance than those receiving low scores. Two 16-mm Locam II DC cameras, each operating at a nominal frame rate of 100 Hz, recorded the vaults. It was concluded that the vaults receiving high scores demonstrated (a) larger horizontal velocity and translational kinetic energy at takeoff from the board, larger vertical velocity and translational kinetic energy at takeoff from the horse, and greater amplitude of postflight; (b) greater heights of CG from the beginning of the second-quarter twist to halfway through the third-quarter twist; and (c) superior landing performance than those receiving low scores.

New Light on the Heart of Darkness of the Solar Chromosphere

Solar carbon monoxide spectra indicate the existence of a cool (less than 4000 kelvin) component to the solar chromosphere coexisting with the hot, bright gas at 6000 to 7000 kelvin. However, both the existence and the location of the cool component have been controversial. New high-resolution spectra show that carbon monoxide goes into emission just beyond the limb, allowing it to be probed without photospheric contamination. The cool component has temperatures as low as 3000 to 3500 kelvin and appears to cover 50 to 85 percent of the quiet solar surface. There is a steep temperature rise to normal chromospheric temperatures at a height of 900 to 1100 kilometers. Large horizontal velocities are seen, suggesting that the cool component is maintained by the supersonic adiabatic expansion of upwelling gas in overshooting granules.

Blocking and Postflight Techniques of Male Gymnasts Performing the Compulsory Vault at the 1988 Olympics

The purpose of this study was to identify the mechanical factors that are crucial to successful performance of blocking and body control for salto forward and kickout in the handspring and salto forward tucked vault. A 16-mm camera operating at 100 Hz was used to record the performances. The subjects were 51 male gymnasts participating in the 1988 Olympic Games. It was hypothesized that some mechanical factors identified in the model were significantly correlated with successful performance of blocking and body control for salto forward and kickout as rated by the judges. Significant correlations indicated that a large horizontal velocity at touchdown on horse is an important prerequisite for effective blocking and subsequent performance of postflight. The results also indicated that the body’s moment of inertia should be minimized by assuming the full tuck position just before or near the peak of flight, which maximizes the time and height available for executing the kickout in midair. The small angular speed of body rotation due to early kickout and the long-held extended body position as it travels a large horizontal distance are not only effective in the expression of artistic amplitude for virtuosity points but are also crucial for control in landing.

Formation and Maintenance of Shelfbreak Fronts in an Unstratified Flow

A depth-averaged model with no density variations was used by Chapman to describe the formation of a passive tracer front at a shelfbreak. The relevance of this frontogenesis mechanism to cases that allow vertical variations is examined by considering the three-dimensional structure of a passive tracer front with explicit finite vertical mixing and bottom boundary layer dynamics. A three-dimensional primitive-equation numerical model is configured in a channel with a continental shelf, slope, and abyssal plain running the length of the channel. A vertically and horizontally uniform inflow is imposed over the shelf, with a large horizontal velocity shear near the shelfbreak. In the primitive-equation model, the offshore flow is concentrated in the bottom boundary layer while the alongshelf flow distribution is similar to the depth-averaged case; the presence of the bottom topography maintains a strong horizontal shear near the shelfbreak above the bottom boundary layer. This velocity shear causes a smooth passive tracer distribution imposed at the inflow boundary to develop strong cross-shelf gradients near the shelfbreak (i.e., a passive tracer front) within a rather short downstream distance, as in the depth-averaged model. Neutrally buoyant Lagrangian particles initialized above the bottom boundary layer are rapidly advected along the shelf with little cross-shelf motion. However, particles initialized within the bottom boundary layer move quickly offshore toward the shelfbreak and beyond while being advected alongshelf relatively slowly. The shelfbreak does not act as a barrier to the offshore transport of neutrally buoyant particles despite the presence of the passive tracer front. This results in a continuous net offshore transport from the shelf to the deep ocean due to the effects of bottom friction.

The dispersal of winged fruits and seeds differing in autorotative behaviour

The application of micrometeorological models of heavy particle dispersal to winged diaspores (samaras) requires that the diaspores maintain stable flight and that descent velocity is constant with respect to vertical air motion. Others have argued that these assumptions may be invalid for autorotating samaras and that bilaterally symmetric samaras will disperse farther than asymmetric samaras in conditions of large horizontal wind velocities (and (or) high turbulence) because the asymmetric morphology is inherently less stable in flight. Therefore, application of these models may not be appropriate for asymmetric samaras. Experimental and natural releases of asymmetric and symmetric samaras reported here indicate that the two samara morphologies respond similarly to a given flow regime. Thus, in modelling dispersal, the autorotation of the samaras can be ignored, and the samaras can be regarded as heavy particles descending at a constant rate from source to deposition site. Key words: winged seeds, descent velocity, dispersal, Fraxinus americana, Acer negundo, micrometeorological dispersal models.

Techniques Used in Performing the Handspring and Salto Forward Tucked Vault at the 1988 Olympic Games

The purposes of this study were to (a) determine the mechanical factors associated with successful performance of the handspring and salto forward vault at the 1988 Olympic Games, and (b) contrast the findings in this study to those from the 1986 USA Championships to gain additional insight for the improvement of performance. The subjects were 51 male gymnasts in the 1988 Olympic Games. Significant correlations indicated that the following were important determinants for successful results: (a) large horizontal velocity (VH) at takeoff (TO) from floor and board resulting from a fast sprint in the approach run; (b) a large change of vertical velocity (Vv) during the horse contact by means of blocking with arms and shoulders; and (c) large VH and Vv at TO from horse, which ensures great distance and height and a long time of postflight, which the judges are seeking. Comparison of the techniques between the two groups revealed that the Olympic gymnasts achieved significantly greater horizontal velocity in preflight, change of vertical velocity while on horse, and vertical velocity at takeoff from horse, which resulted in a significantly longer time of postflight than for the USA gymnasts. An analysis of the aspect of form in postflight, possibly by means of mechanical variables, should be conducted because it may provide additional insight for improvement for performance of this vault.

Techniques Used by Elite Women Gymnasts Performing the Handspring Vault at the 1987 Pan American Games

The purposes of this study were (a) to determine the mechanical factors associated with successful performance of women’s handspring vault and (b) to contrast the findings to those of men to gain insight for improvement of performance. The subjects were 24 female gymnasts in the 1987 Pan American Games. Significant correlations indicated that the following were important determinants for successful results: (a) large horizontal velocity (VH) and distance of hurdle; (b) large vertical velocity (Vv) at touchdown (TD) on board, a large change of Vv on board, and a short time of board contact; (c) large VH and Vv at takeoff (TO) from board; (d) short time of horse contact; (e) large VH and Vv at TO from horse; (f) high body CG at TO from horse; and (g) great distance and height and a long time of postflight. Comparisons revealed that women had significantly smaller VH and Vv at TD on horse and departed from it with significantly smaller VH and Vv than men. This resulted in significantly less height and distance as well as a shorter time of postflight for women even after adjusting for horse height and subject physique.

Techniques Used by Elite Male Gymnasts Performing a Handspring Vault at the 1987 Pan American Games

The purpose of this study was to determine mechanical factors, through development of the deterministic model, that govern successful performance of the handspring vault. The subjects were 40 elite male gymnasts participating in the 1987 Pan American Games. A motion-picture camera placed with its optical axis at right angles to the runway was used to record the subjects’ performances. Significant correlations indicated that the following were important determinants for success: (a) large horizontal velocity and angular momentum at takeoff from board, (b) shorter time of preflight and smaller relative height of takeoff in preflight, (c) large horizontal breaking force and large vertical force exerted as well as a large loss of angular momentum during horse contact, and (d) large vertical velocity of takeoff from horse. Significant correlation of “on-horse” factors with the judges’ scores indicated that the more the gymnast focused on horse contact and the more vertical the direction of his effort at takeoff, the better the final result. A significant negative correlation revealed that the less the height of CG at touchdown on mat, the more points awarded by judges. This relationship was almost entirely a consequence of the landing angle.

New Frontiers of Seismic Surveying in Antarctica: The Mapping of A Thin Layer at the Base of Ice Stream B (Abstract)

The recent availability of high resolution (greater than 250 Hz) seismic recording equipment in the Antarctic field environment has allowed the acoustical mapping of a previously unobserved subglacial phenomenon. This phenomenon is a thin (less than 10 m), yet continuous, layer at the base of Ice Stream B in West Antarctica. Discovery of this layer came during the 1983–84 austral summer in a seismic reflection survey that covered approximately 10 km2 near the Upstream B field camp (83°31’S, 138°05’W). Although analysis of the seismic data is at a preliminary stage, there is the possibility that this feature could be a basal “lubricating” layer; some sort of lubrication is of course necessary to explain the very large horizontal velocities of these ice streams.During the seismic reflection survey on Ice Stream B, a new digital seismic recording system, developed by the Geophysical and Polar Research Center, was used for the first time under field conditions. Resolution of such a thin layer was possible only because of the very large bandwidth (0–600 Hz) and dynamic range (84 dB) of this device; this bandwidth is about twice that possessed by commercially available seismic recorders. In addition, a new level of portability (i.e. a weight of 40 kg and a power requirement of 90 watts), which should make this device usable in virtually any Antarctic field situation, has been achieved by the application of advanced recording technologies. The portability of this digital seismic recorder, when combined with its large bandwidth and dynamic range, should result in the resolution of a whole new class of intra- and subglacial phenomena, of which the thin basal layer of Ice Stream B is the first example.

New Frontiers of Seismic Surveying in Antarctica: The Mapping of A Thin Layer at the Base of Ice Stream B (Abstract)

The recent availability of high resolution (greater than 250 Hz) seismic recording equipment in the Antarctic field environment has allowed the acoustical mapping of a previously unobserved subglacial phenomenon. This phenomenon is a thin (less than 10 m), yet continuous, layer at the base of Ice Stream B in West Antarctica. Discovery of this layer came during the 1983–84 austral summer in a seismic reflection survey that covered approximately 10 km2 near the Upstream B field camp (83°31’S, 138°05’W). Although analysis of the seismic data is at a preliminary stage, there is the possibility that this feature could be a basal “lubricating” layer; some sort of lubrication is of course necessary to explain the very large horizontal velocities of these ice streams. During the seismic reflection survey on Ice Stream B, a new digital seismic recording system, developed by the Geophysical and Polar Research Center, was used for the first time under field conditions. Resolution of such a thin layer was possible only because of the very large bandwidth (0–600 Hz) and dynamic range (84 dB) of this device; this bandwidth is about twice that possessed by commercially available seismic recorders. In addition, a new level of portability (i.e. a weight of 40 kg and a power requirement of 90 watts), which should make this device usable in virtually any Antarctic field situation, has been achieved by the application of advanced recording technologies. The portability of this digital seismic recorder, when combined with its large bandwidth and dynamic range, should result in the resolution of a whole new class of intra- and subglacial phenomena, of which the thin basal layer of Ice Stream B is the first example.

Large horizontal surface velocity shears in the ocean obtained from images of refracting swell and in situ moored current data

Aerial photographs showing strong refraction of swell near the northern California coastline were obtained on September 8, 1982. The possibility that this refraction is due to a large horizontal current shear is discussed; a maximum shear value of the order of 10−3 s−1, with the velocity directed along a linear slick‐like front, is calculated from the wave data in the photo. In situ current data obtained at 90 m depth at a nearby midshelf site on two surface moorings separated by 390 m also show occasional periods of large horizontal velocity shear. On January 4, 1982, a maximum horizontal shear of order 10−3 s−1 was observed for several hours. These separate observations taken together indicate that large horizontal surface velocity shears of order 10−3 s−1 occur over the northern California continental shelf, and that large surface current shear can be usefully detected and measured by high flying high resolution sensors.

Net Balance, Surface Lowering, and Ice-Flow Pattern in the Interior of Lewis Glacier, Mount Kenya, Kenya

AbstractObservations obtained in a long-term monitoring program on Lewis Glacier, Mount Kenya, include measurements of net balance and velocity at a stake network over the period 1978–82, and airborne mapping of the glacier surface topography at the beginning and end of this interval. Horizontal and vertical flow components and mass continuity are evaluated along the longitudinal axis of the glacier.The largest horizontal velocity at the surface is about 5 m a−1, while the submergent vertical velocity at the surface in the upper, and the emergent component in the lower glacier are of the order of 1–2 m a−1. Horizontal and vertical flow components in the interior of the glacier are calculated from the surface observations under plausible assumptions. Isotachs and streamlines plotted in a longitudinal–vertical cross-section permit the estimation of representative residence times of ice within Lewis Glacier. The largest values for the longest trajectories with submergence at the surface in the uppermost area of the glacier and emergence near the snout are of the order of a few centuries. However, such estimates are compromised, in particular, by the continuing non-equilibrium conditions of Lewis Glacier.Mass continuity is directly related to the vertical motion field. In the upper area of the glacier the submergence velocity exceeds the rise of glacier surface observed with respect to the stake network, while in the lower glacier the emergent flow component falls short of the local negative net balance. This differing behavior of altitudinal zones is consistent with the fact that actual lowering of the glacier surface topography documented by the repeated airborne mappings is larger than expected from the stake network in the upper but less in the lower glacier. This differing behavior of altitude zones appears mitigated by the tendency for confluence in the upper and diffluence in the lower glacier.

Net Balance, Surface Lowering, and Ice-Flow Pattern in the Interior of Lewis Glacier, Mount Kenya, Kenya

AbstractObservations obtained in a long-term monitoring program on Lewis Glacier, Mount Kenya, include measurements of net balance and velocity at a stake network over the period 1978–82, and airborne mapping of the glacier surface topography at the beginning and end of this interval. Horizontal and vertical flow components and mass continuity are evaluated along the longitudinal axis of the glacier.The largest horizontal velocity at the surface is about 5 m a−1, while the submergent vertical velocity at the surface in the upper, and the emergent component in the lower glacier are of the order of 1–2 m a−1. Horizontal and vertical flow components in the interior of the glacier are calculated from the surface observations under plausible assumptions. Isotachs and streamlines plotted in a longitudinal–vertical cross-section permit the estimation of representative residence times of ice within Lewis Glacier. The largest values for the longest trajectories with submergence at the surface in the uppermost area of the glacier and emergence near the snout are of the order of a few centuries. However, such estimates are compromised, in particular, by the continuing non-equilibrium conditions of Lewis Glacier.Mass continuity is directly related to the vertical motion field. In the upper area of the glacier the submergence velocity exceeds the rise of glacier surface observed with respect to the stake network, while in the lower glacier the emergent flow component falls short of the local negative net balance. This differing behavior of altitudinal zones is consistent with the fact that actual lowering of the glacier surface topography documented by the repeated airborne mappings is larger than expected from the stake network in the upper but less in the lower glacier. This differing behavior of altitude zones appears mitigated by the tendency for confluence in the upper and diffluence in the lower glacier.