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At high latitudes, the Sporadic‐E layer (Es layer) is a common phenomenon but is still poorly understood due to sparse measurements and the difficulty of conventional mechanisms to operate. In this study, an interesting case of polar cap Es layer is first studied by using the twin incoherent scatter radars (northward‐looking face of Resolute Incoherent‐Scatter Radar and Resolute Incoherent‐Scatter Radar‐Canada), a Canadian Advanced Digital Ionosonde, and a Magnetometer, all at Resolute, Canada. From several electron density profiles of the twin radars, the horizontal scale of the polar cap Es layer is found to be greater than 350 km. Moreover, the polar cap Es layer is determined to be drifting from the bottom F region (>150 km) to the lower E region. Furthermore, a unique appearance of double polar cap Es layers is observed. As a result, these peculiar signatures inspire a newly proposed process that involves the combination of localized electric fields and gravity waves. Plain Language Summary: The Sporadic‐E layer (Es layer) is a globally common phenomenon, which is comprehensively and unceasingly studied in decades by using the observation measurements and numerical simulations. The remarkable agreements on the characteristics and generation mechanisms of Es layer at middle latitudes have then been almost achieved. However, over the polar region, it is still poorly understood due to sparse measurements and the difficulty of conventional mechanisms to operate. In this study, an interesting case of polar cap Es layer are first reported by using the twin radars of northward‐looking face of Resolute Incoherent‐Scatter Radar and Resolute Incoherent‐Scatter Radar‐Canada, Canadian Advanced Digital Ionosonde, and Magnetometer simultaneously. Through comprehensively studies, the understanding of polar cap Es layer is clearly extended, not only on the characteristics but also on the mechanism processes. The polar cap Es layer is horizontally greater than 350 km; a new process on the generation mechanism is provoked including the functions of particle precipitation and gravity wave. As a consequence, we present a peculiar evidence for the first time to greatly enrich our knowledge on the polar cap Es layer, showing us a new insight on it. Key Points: An amazing example of polar cap Es layer is first presented by the twin radars of northward‐looking face of Resolute Incoherent‐Scatter Radar and Resolute Incoherent‐Scatter Radar‐Canada at Resolute, Canada simultaneouslyThe morphology of the polar cap Es layer is comprehensively furthered, interpreting the horizontal scale size (>350 km) and double layersTo reasonably explain this phenomenon, a new process is hypothesized, consisting of localized electric field and gravity wave [ABSTRACT FROM AUTHOR]

Electron density measured at high latitudes by the Swarm satellites is compared with the measurements by the RISR incoherent scatter radars as the satellites fly by the radars' field of views near Resolute Bay, Canada between 2014 and 2019. More than 200 satellite passes crossing multiple radar beams are considered. Overall, the Swarm-based electron densities are smaller than those measured by the radars by ∼30%. The values are closer to one another at electron densities between 3 10 10 and 15 1010 3 m, corresponding to plasma frequencies between 1.5 and 3.5 MHz. Swarm-measured values are getting progressively smaller than those measured by radars at larger electron densities/plasma frequencies. For the entire range of measured electron densities, the slope of the best fit linear line to the data expressed in terms of electron density is ∼0.62 and offset is 2 1010 3 m. Stronger differences between the instruments were found for observations at nighttime and dawn. [ABSTRACT FROM AUTHOR]

Tropospheric and lower‐stratospheric motions at mesoscales and larger are a mixture of waves and two‐dimensional (2‐D) turbulence. Determining their relative importance is necessary, since waves are capable of coordinated systematic momentum transport accompanying the wave propagation, and associated wind forcing, in ways that 2‐D turbulence is not. This can impact weather forecasting. Using a network of ten windprofiler radars in eastern Ontario and western Quebec in Canada, plus an additional one in the Arctic, the relative roles of internal gravity (buoyancy) waves and two‐dimensional turbulence are examined at temporal scales from about 3–4 hrs to several tens of hours (horizontal spatial scales of typically one or two hundred kilometres to a few thousand kilometres), with the purpose of investigating the respective roles of these two distinct characteristic fluid motions as functions of location, season and year. The emphasis is on studies of spectral slope variability, rather than absolute spectral magnitudes, giving a perspective not previously substantially presented. In particular, we have found a frequency band in which gravity‐wave Doppler shifting produces distinctly different spectral slopes than those predicted for 2‐D turbulence, and these differences are employed to distinguish the flow fields. The network used (excluding the Arctic site) covers an area of ∼106 km2 and includes a variety of different terrains. Radial velocities have been recorded on time scales of minutes for data lengths covering durations of up to 12 years. Altitude coverage is from 1 km to typically 14 km, at 500 m resolution. Results suggest a region from ∼2 to ∼5 km altitude (deeper for some radars) where waves are weaker and 2‐D turbulence appears to be generally more significant, but where occasional bursts of gravity‐wave activity can occur, while above typically 6–8 km, gravity waves increase in significance. There are distinct site‐to‐site variations. [ABSTRACT FROM AUTHOR]

A hierarchical typology for the channels and bars within aggradational wandering gravel-bed rivers is developed from an examination of a 50 km reach of lower Fraser River, British Columbia, Canada. Unit bars, built by stacking of gravelly bedload sheets, are the key dynamic element of the sediment transfer system, linking sediment transport during individual freshets to the creation, development and remoulding of compound bar platforms that have either a lateral or medial style. Primary and secondary unit bars are identified, respectively, as those that deliver sediment to compound bars from the principal channel and those that redistribute sediment across the compound bar via seasonal anabranches and smaller channels. The record of bar accretion evident in ground-penetrating radar sequences is consistent with the long-term development of bar complexes derived from historical aerial photographs. For two compound bars, inter-annual changes associated with individual sediment transport episodes are measured using detailed topographic surveys and longer-term changes are quantified using sediment budgets derived for individual bars from periodic channel surveys. Annual sediment turnover on the bars is comparable with the bed material transfer rate along the channel, indicating that relatively little bed material bypasses the bars. Bar construction and change are accomplished mainly by lateral accretion as the river has limited capacity to raise bed load onto higher surfaces. Styles of accretion and erosion and, therefore, the major bar form morphologies on Fraser River are familiar and consistent with those in gravelly braided channels but the wandering style does exhibit some distinctive features. For example, 65-year histories reveal the potential for long sequences of uninterrupted accretion in relatively stable wandering rivers that are unlikely in braided rivers. [ABSTRACT FROM AUTHOR]

Ice scouring of lake and sea-floor substrates by the keels of drifting ice masses is a common geological process in modern northern lakes and continental shelves, and was widespread during the Pleistocene. Nonetheless, the importance of scouring as a geological process is not yet matched by many sedimentological studies of scour structures exposed in outcrop. This article presents an integrated study combining outcrop sedimentology and subsurface ground-penetrating radar (GPR) data from a relict late Pleistocene ice-scoured glacial lake floor now preserved below beach sediments in Ontario, Canada. Scours occur along a regressive sequence boundary where deep-water muddy facies are abruptly overlain by shallow-water sands resulting from an abrupt drop in water levels. This has allowed the keels of drifting ice masses to scour into muds. Three-dimensional data gained from the GPR survey show that scours are as much as 2.5 m deep and 7 m wide; they have berms of displaced sediment and are oriented parallel to the former shoreline. Scoured shoreface sediments that fill scours show abundant liquefaction structures, indicating substrate dewatering during repeated scouring events similar to that recently reported in the modern Beaufort Sea in Canada's far north. Marked changes in water depths are typical of glacially influenced lakes and seas, creating opportunities for drifting ice to scour into offshore muddy cohesive facies and be preserved. The data presented here may aid identification in ancient successions elsewhere. [ABSTRACT FROM AUTHOR]

This article discusses the determination of snow water equivalent by acoustic impulse of snowpacks in Saskatchewan and British Columbia, Canada. Depth and density of snow layers was estimated by seismological techniques and frequency-modulated continuous wave radar. This method also estimates the tortuosity of snow. The authors compared the acoustic sounding method with gravimetric sampling to determine snow water equivalent. According to the authors, correlation variations were primarily found with higher water contents and in areas where multiple layers were found.

1. The size of lakes and the size distribution of lakes are important parameters controlling lake function, and how lakes interact with landscapes, the atmosphere and ecosystems. A baseline digital database of lakes could be used to improve understanding of lake function, to extrapolate lake information to regional and global scales, and as a basis for detecting future changes to lakes. 2. This paper examines the capabilities of synthetic aperture radar (SAR) imagery produced by the Japanese Earth Resources Satellite (JERS-1) to map the number and size distribution of lakes in western Arctic Canada, Central Canada and the Pantanal (Brazil). 3. For the Arctic and Pantanal, the total area found within one lake size category increases towards smaller lakes. The opposite was true for the area in Central Canada. The number of lakes in the smallest size category, 0.01 to 0.1 km2, was underestimated for all regions owing to the resolution of the mosaics - 100 × 100m. The number of large lakes in the Pantanal was over-estimated through confusion with intermittent floodways that are scrubby grasslands and bare sand in the dry season and which exhibit low backscattering and therefore appear dark like lakes. 4. The lake distributions were combined with existing data to produce preliminary regional estimates of carbon accumulation. Lakes may accumulate as much as 1.7 and 1.3 t C km-2 yr-1 for the Arctic Canadian and Central Canadian areas, respectively. No estimates were produced for the Pantanal because there are no applicable data on carbon accumulation rates available for that region. [ABSTRACT FROM AUTHOR]

Presents information on a study which examined the use of radar in assessing populations and habitat associations of marbled murrelets in Vancouver Island, British Columbia. Background on marbled murrelets; Methodology; Results of the study.