Small Ice Masses Research Articles

Limitations of precipitation reconstructions using equilibrium-line altitudes exemplified for former glaciers in the Southern Black Forest, Central Europe

Abstract To further elucidate the Late Pleistocene glacial history of mid-elevation mountainous regions in Central Europe, 10Be cosmic-ray exposure (CRE) dating was applied to moraines in the Zastler Tal Valley in the Southern Black Forest. Periods of glacier recession from moraines in this valley began no later than 16 ka, 15 ka, and 13 ka. CRE ages of moraines in this and other parts of the Southern Black Forest cluster around 17–16 ka and 15–14 ka, thus suggesting a common forcing of glacier recession. Equilibrium-line altitudes (ELAs) during moraine formation were calculated for precipitation reconstruction. Observed spatial discrepancies in ELAs at ca. 15–14 ka are explained best by the size of snow-contributing areas. The reconstructed annual precipitation at the ELA for ca. 16 ka and ca. 15 ka is affected by large uncertainties, representing a wide range from ~50% to ~150% of present-day values. Due to various factors, such as drifting snow, the lower bounds of the estimates appear most realistic, thus concurring with the common hypothesis of less precipitation during the last glacial termination than today in Central Europe. Further research is needed before ELAs of small ice masses can be employed for precise precipitation estimates.

Persistent mass loss of Triangular Glacier, James Ross Island, north-eastern Antarctic Peninsula

AbstractThe retreat rates of Triangular Glacier since 1979 and its mass changes during the period 2014/15–2019/20 indicate the sensitive response of small ice masses on the eastern side of the Antarctic Peninsula to air temperature evolution. This cirque glacier in the northern part of James Ross Island receded rapidly during the period of regional warming in the late 20th century, losing 30.8% of its surface area between 1979 and 2006 (−1.7% a−1). The retreat rate then dropped to −0.3% a−1following the regional cooling trend, but started to accelerate again (−0.8 to −2.3% a−1) with increasing air temperature since the summer 2014/15. Since the glaciological year 2015/16, Triangular Glacier has experienced enhanced snow melt, wind scour and permanent mass loss with annual mass balance ranging from −0.08 ± 0.35 to −0.56 ± 0.25 m w.e. The largest mass loss was observed in the glaciological year 2019/20, which included the warmest summer of the observation period. The cumulative mass balance of −1.66 ± 0.83 m w.e. over the years 2014/15–2019/20 is consistent with the termination of the positive mass-balance period that occurred in the north-eastern Antarctic Peninsula from 2009/10 to 2014/15.

ДИНАМИКА ОБРАЗОВАНИЯ НАЛЕДИ В УСЛОВИЯХ ВОСТОЧНОГО ЗАБАЙКАЛЬЯ: ИССЛЕДОВАНИЕ С ИСПОЛЬЗОВАНИЕМ ДАННЫХ ДИСТАНЦИОННОГО ЗОНДИРОВАНИЯ ЗЕМЛИ

Small and large ice masses are found annually on the territory of Russia. They are common in eastern Russia, and are one of the problems of the Transbaikal Territory. In the winter period of 2018-2019, the Chita region of the Transbaikal Territory was the most active in terms of icing. The aim of the work is to study the dynamics of ice formation in the conditions of the Eastern Transbaikal Territory in order to prevent their development in an emergency situation. The object of the research is the ice near the village Smolenka, Chita District, Transbaikal Territory. To study the process of ice formation in this area, a method for studying ice from space surveys from the Sentinel-2 satellite has been chosen with checking the data obtained by the route method. The application of this method enables to see the change in the area and the dynamics of the ice movement in the period 2016-2020. Satellite images from the Sentinel-2 satellite have shown that in the selected study area during the period from 2016 to 2019, the maximum size of ice has been recorded on March 18-March 21, and the beginning of the ice formation – on February 10–18. During the route studies, it has been revealed that the ice layering lasted from mid-November to the end of February, as a result of this, on February 21, 2020, there was a threat of flooding of residential buildings on the street Lugovaya and the "Emergency" regime was introduced within the boundaries of this street. The route studies that took place during the emergency recovery operations confirmed the data, obtained from the satellite images from the Sentinel-2 satellite. The measurement error has been within acceptable limits. It is revealed that the combined use of remote sensing of space images from the Sentinel-2 satellite and route research allows more accurately identifying the unfavorable dynamics of ice formation, including small ones, making forecasts and promptly taking action in case of emergencies

Reconstruction of Loch Lomond Stadial (Younger Dryas) glaciers on Ben More Coigach, north-west Scotland, and implications for reconstructing palaeoclimate using small ice masses

A significant inventory of evidence exists for Loch Lomond Stadial (LLS; ≈Younger Dryas) glaciation in Scotland, with recent work focused on satellite icefields. However, studies of more marginal settings are important for assessing the influence of topoclimatic factors on glacier functioning and, crucially, the impact of these on glacier-derived palaeoclimatic reconstructions. We present systematic assessments of snowblow and avalanching contributions, informed by modern analogues, and test these using the first detailed palaeoglaciological reconstructions of three corrie glaciers on Ben More Coigach, north-west Scotland. Based on morphostratigraphic principles, and lithostratigraphic evidence from the region, these have been attributed to the LLS, with the reconstructions yielding an average equilibrium-line altitude (ELA) of 328 ± 16 m. A glacier-derived sea-level equivalent precipitation value of 1903 ± 178 mm a−1 is inferred for the LLS, suggesting wetter conditions than currently and contradicting assertions of a more arid LLS climate. Comparison with published palaeoprecipitation estimates indicates Ben More Coigach does not conform to expected regional precipitation gradients. We argue that these discrepancies reflect topographically enhanced snow accumulation, which lowered the ELA from the ‘true’ climatic ELA. This highlights the importance of assessing the influence of topoclimatic factors when applying small glaciers in palaeoclimatic reconstructions.

A review of iceberg and bergy bit hydrodynamic interaction with offshore structures

This paper establishes the current state of the art in the subject of iceberg and bergy bit motion during interaction and impact with offshore structures. Our particular interest in the present case is the influence of hydrodynamic interaction on change in velocity as small ice masses approach a larger structure in open water. Iceberg impacts are a design driver for structures located in offshore regions subject to drifting glacial ice. It is found that although many studies note that near-field effects influence the velocity and trajectory of drifting bergs prior to impact, the understanding of near-field hydrodynamic effects such as negative wave drift force, fluid cushioning, shadowing, reduction in impact velocity, and hydrodynamic damping, is incomplete. These effects are more obvious for small ice masses and bergy bits and although they have been identified qualitatively, there is very little quantitative information available. The inability to properly account for these phenomena generally leads to overestimation in impact velocity and consequently input impact energy. Better understanding of hydrodynamic interaction between small icebergs and offshore structures in very close proximity could improve load predictions by improving the estimation of input energy.

Rangewide glaciation in the Sierra Nevada, California

The 600-km-long Sierra Nevada underwent extensive Pleistocene glaciation except for its southernmost 100 km. Presently, ∼1700 small glaciers and ice masses near the crest of the range occur above 3250 m in elevation; these covered an area of ∼50 km 2 in 1972. Fourteen of the largest glaciers decreased by about one half in area during the period from 1900 to 2004. Rock glaciers, generally glacial ice covered by 1–10 m of rockfall debris, occur in about the same span of the range as ice and permanent snowfields. They are, on average, lower by 200–300 m, apparently because of the insulating layer of rocky rubble that protects their internal ice from the sun’s heat and from wind. The principal Pleistocene glacial stages are the Sherwin (ca. 820 ka), Tahoe (170–130 and ca. 70 ka), Tioga (14–28 ka), and Recess Peak (13 ka). Some 7040 glacial lakes, produced primarily by quarrying from bedrock, were mostly exposed after recession of the Tioga glacial stage. The lakes largely mark the area of primary snow accumulation. Below the lower limit of the lakes, ice flowed downward into river-cut canyons, forming major trunk glaciers within the zone of ablation. The range is in general a westward-tilted block upfaulted on its east side. Therefore, the main late Pleistocene trunk glaciers (Tahoe/Tioga) west of the crest extend 25–60 km, whereas those east of the crest extend only 5–20 km. Because of higher precipitation northward, glacial features such as the toes of existing glaciers and rock glaciers, as well as the late season present-day snowline, all decrease in elevation northward. Likewise, the elevation of the lower limit of glacial lakes, an indication of the zone of snow accumulation during the late Pleistocene, decreases about the same degree. This similarity suggests that the overall climate patterns of the late Pleistocene, though cooler, were similar to those of today. The east slope glaciers show a similar northward depression, but they are ∼500–1000 m higher. The upper part of the glacial system was erosive over a broad highland area as the evenly distributed ice in the accumulation zone moved to lower elevation. The abundant lake basins record this erosive action. The lower part of the glacier system was largely confined to major preexisting river canyons in which melting dominated. The average of rangewide estimates of the equilibrium line altitude (ELA)—the boundary between the upper snow and ice accumulation zone and the lower ablation zone—of many late Pleistocene glaciers parallels, and is only 200–300 m above, the altitude of the lower limit of the lakes. Hence, the lake zone provides a means of estimating the ELA.

Utilización de técnicas de láser escáner terrestre en la monitorización de procesos geomorfológicos dinámicos: el manto de nieve y heleros en áreas de montaña

This paper presents the application of a long range terrestrial laser scanner for monitoring snow accumulation and evolution of glaciers in the Pyrenees. With this study we are showing the great potential of the methodology presented for studies in mountain environments, particularly in research related to the cryosphere monitoring in relation to climate variability and the complex topography typical of mountain environments. We present a comprehensive protocol for the acquisition and processing of point clouds measured by a laser scanner (RIEGL LPM-321) for the generation of digital terrain models, in order to compare the models obtained at different times. Thus it is possible to obtain snow thickness and changes of ice thickness. As case studies, results from two small ice masses located in the massif of Monte Perdido and snow accumulation on a small basin located in the Tena Valley are presented.

The effective density of small ice particles obtained from in situ aircraft observations of mid‐latitude cirrus

AbstractThe effective ice‐particle density, parametrized through a mass–dimension relation, is widely used in ice microphysical schemes for weather and climate models. In this study, we use aircraft‐based observations in mid‐latitude cirrus taken during the Constrain field programme in 2010. The low temperatures and a humidity often close to ice saturation meant that the typical ice particles observed were small (maximum dimension 20–800 µm) and ice water contents were low (0.001–0.05 g m−3). Two new instruments are included in this study: the Small Ice Detector Mark‐2 (SID‐2) and the deep‐cone Nevzorov Total Water Content probe. SID‐2 is a new single‐particle light‐scattering instrument and was used to identify and size small ice particles (10–150 µm). The deep‐cone Nevzorov probe is shown to be able to collect small ice masses with sufficient sensitivity. The focus of this article is on the effective density of small ice particles (both pristine ice crystals and small aggregates up to 600 µm maximum dimension). Due to instrument limitations in previous studies, the effective density of small ice particles is questionable.Aircraft flights in six cirrus cases provided ice‐particle measurements throughout the depth of the cirrus. The particle size distribution (PSD) was mostly bimodal. The smaller ice‐crystal mode dominated the PSD near cloud top and the larger ice‐aggregate mode dominated near cloud base. A mass–dimension relation valid for both ice crystals and aggregates was found that provided a best fit to the observations. For small ice particles (less than 70 µm diameter) the density is constant (700 kg m−3), while for larger ice crystals or aggregates the mass–dimension relation is m(D) = 0.0257D2.0. These measurements allow testing of the diagnostic split between ice crystals and aggregates used in the Met Office Unified Model.

Response of Franz Josef Glacier Ka Roimata o Hine Hukatere to climate change

Understanding the response of relatively small ice masses to climate change on a century-to-century timescale is important because of their significant contribution to sea level change in the recent past, and their likely contribution in the next century. Franz Josef Glacier, with its excellent terminus position record, location in the Southern Hemisphere, and its extreme sensitivity to climatic changes, is a key data point for understanding the magnitude and mechanisms of past and future climate changes. Here, we use a reconstructed mass balance record to drive an ice flow model which simulates the general retreat of the glacier during the 20th century. The model is then used to project future glacier variations, based on regionally downscaled climate change scenarios. The results indicate that, under a mean climate change scenario, the glacier will retreat 5 km and lose 38% of its mass by 2100. Different scenarios give a range of recession from 3.9 to 6.4 km, and a range of volume loss from 26% to 58%. On a global scale, the magnitude of the retreat is at the upper end of the range calculated for other, similar sized, glaciers.

Recent changes in high-latitude glaciers, ice caps and ice sheets

The glaciers and ice sheets of the world contain enough ice to raise sea level by approximately 70 meters if they were to disappear entirely, and most of this ice is located in the climatically sensitive polar regions. Fortunately changes of this magnitude would probably take many thousands of years to occur, but recent discoveries indicate that these ice masses are responding to changes in today s climate more rapidly than previously thought. These responses are likely to be of great societal significance, primarily in terms of their implications for sea level, but also in terms of how their discharge of freshwater, through melting or calving, may impact ocean circulation. For millions of years, oceans have risen and fallen as the Earth has warmed and cooled, and ice on land has shrunk and grown. Today is no different in that respect, as sea levels have been rising at a rate of nearly 2 m per year during the last century (Miller and Douglas 2004), and 3 mm/yr in the last 12 years (Leuliette et al. 2004). What is different today, however, is that tens - perhaps hundreds - of millions of people live in coastal areas that are vulnerable to changes in sea level. Rising seas erode beaches, increase flood potential, and reduce the ability of barrier islands and coastal wetlands to mitigate the effects of major storms and hurricanes. The costs associated with a one-meter rise in sea level are estimated to be in the hundreds of billions of dollars in the United States alone. The worldwide costs in human terms would be far greater as some vulnerable low-lying coastal regions would become inundated, especially in poorer nations that do not have the resources to deal with such changes. Such considerations are particularly important in light of the fact that a one meter sea level rise is not significantly outside the 0.09 to 0.88 range of predictions for this century (IPCC 2001), and rises of this magnitude have occurred in the past in as little as 20 years (Fairbanks 1989). While the expansion of the warming oceans is estimated to be about a third of recent sea level rise, (Miller and Douglas 2004) the greatest potential for significantly increasing sea level lies in the Greenland and Antarctic ice sheets. For different reasons, each exhibits characteristics that suggest they are potentially unstable. In Antarctica, large portions of the ice cover rest on a soft bed that lies below sea level, making it vulnerable to runaway retreat. The Greenland ice sheet experiences considerable melt, which has the potential to rapidly accelerate the flow of ice toward the sea. While smaller ice masses, such as the Alaskan Glaciers and the Canadian ice caps, do not have anywhere near the same potential to impact sea level as the vast ice sheets do, many are melting rapidly, posing a significant near-term threat.

Evaluation of bergy bit populations on the Grand Banks

Shuttle tankers and hydrocarbon production platforms operating on the Grand Banks of Newfoundland must be designed for some level of ice loading. In some cases, high ice loads can result from relatively small icebergs, bergy bits, or growlers. This is particularly true when wave-induced ice motions are significant (in high sea states) or when vessel speeds are high (e.g., a transiting tanker). Safe and economic operations can be achieved by designing structures that are strong enough to withstand ice loads, planning for and managing ice to reduce the risk of collisions, or a combination of the two. In all cases, accurate information on the number of small ice masses is important. Unfortunately, reliable information on small ice mass populations is not available. The extensive, detailed aerial surveys that would be required to build up meaningful statistics on bergy bit populations would be prohibitively expensive, and other methods of estimating bergy bit populations are required for the development of a reliable database. The approach used in this study was a reanalysis of International Ice Patrol (IIP) operational iceberg observations. Although the IIP does not detect and report all bergy bits and growlers, their database contains critical information on the location of small ice masses in relation to the aircraft track, and the prevailing visibility and sea-state conditions. By resampling only those ice masses observed when detection conditions were favourable, and within a prescribed distance from the aircraft, more accurate bergy bit statistics have been determined. A convenient measure of the number of bergy bits and growlers is the ‘small ice mass to parent iceberg’ (SIMPI) ratio. This relates the number of small glacial ice masses to the number of parent icebergs from which most small ice masses are calved. The average SIMPI ratio for the study region was 0.59. Some interesting phenomena revealed in the study include the apparent geographical variation in the small ice mass to parent iceberg ratio, with increasing values to the north and west. The ratio also varied seasonally. Of the months in which sufficiently large numbers of icebergs were observed to produce meaningful statistics, the SIMPI ratio was lowest in March (0.25) and highest in May (0.81).

Analysis of laboratory growler impact tests

Growler impact tests have been performed in IOT's Ice Tank facility. Free-floating parallelepiped-shaped growlers (small glacial ice masses) were impacted with a heavy apparatus (i.e. impact plate) designed to simulate a ship bow. Impacts were conducted at speeds ranging from 0.2 to 3.0 m/s, at three growler orientations, and at impact plate angles of 45°, 30°, and 15°. The impact plate measured forces and incorporated a new panel for pressure measurements. Peak loads increased linearly with impactor speed, and increased with impact plate angle. Growler orientation affected peak impact loads, where the greatest values occurred when the long axis of the growler was normal to the impact plate surface. The duration of the impacts for a particular growler was approximately constant regardless of the test parameters. Thin sections of ice from the zones of impact showed the ice to be relatively intact. Data and thin section observations from a few crushing tests in an MTS machine on samples of the same iceberg ice corroborated with pressure data and thin sections from the growler impact tests. The growlers appeared to be resilient to impacts and could withstand many impacts without significant damage to the bulk ice.

The low-temperature geochemical cycle of iron: From continental fluxes to marine sediment deposition

Suspended sediments from 34 major rivers (geographically wide- spread) and 36 glacial meltwater streams have been examined for their variations in different operationally-defined iron fractions; FeHR (iron oxides soluble in dithionite), FePR (iron soluble in boiling HCl but not in dithionite) and FeU (total iron less that soluble in boiling HCl). River particulates show a close association between FeHR and total iron (FeT), reflecting the effects of chemical weathering which derive oxide iron from, and retain it in close association with, total iron. Consistent with this, continental- scale average FeHR/FeT ratios vary with runoff ratios (average river runoff per unit area/average precipitation per unit area). By contrast, the diminished effects of chemical weathering produce no recognizable association of FeHR with FeT in glacial particulates, and instead both FePR and FeU are closely correlated with FeT, reflecting essentially pristine mineralogy. A comparison of the globally-averaged compositions of riverine particulates and marine sediments reveals that the latter are depleted in FeHR, FePR and FeT but enriched in FeU. The river and glacial particulate data are combined with estimates of authigenic, hydrothermal, atmospheric and coastal erosive iron fluxes from the literature to produce a global budget for FeHR ,F e PR ,F e U and FeT. This budget suggests that the differences between riverine particulates and marine sediments can be explained by; (i) preferentially removing FeHR from the riverine particulate flux by deposition into inner shore reservoirs such as floodplains, salt marshes and estuaries; and (ii) mixing the resulting riverine particulates with FeHR- depleted glacial particulates. Preliminary measurements of inner shore sediments are consistent with (i) above. Phanerozoic and modern normal marine sediments have similar iron speciation characteristics, which implies the existence of a long-term steady state for the iron cycle. This steady state could be maintained by a glacioeustatic feedback, where FeHR-enriched riverine particulates are either more effectively trapped when sealevel is high (small ice masses, diminished glacial erosion), or are mixed with greater masses of FeHR-depleted glacial particulates when sealevel is low (large ice masses, enhanced glacial erosion). Further important controls on the steady state for FeHR operate through the formation of euxinic sediments and ironstones, which also provide sealevel-dependent sinks for FeHR-enriched sediment.

Downwasting of the Tasman Glacier, South Island, New Zealand: Changes in the terminus region between 1971 and 1993

Abstract Downwasting has altered the morphology of the terminus region of the Tasman Glacier between 1971 and 1993. Rapid melting began in the late 1960s in a few isolated melt ponds in the centre and in a small elongated lakelet at the eastern lateral moraine. These ponds and lakes grew rapidly in size during the 1970s and coalesced to form a large melt lake by about 1990. This melting has led to a disintegration of the entire terminus region, and now occurs as far as 3 km upstream from the old terminus. The main front of the glacier has retreated c. 1.5 km since 1982. The breaking up of the glacier has been accelerated by the onset of iceberg calving—a process which probably started in 1991. The icebergs can have volumes of several millions of cubic metres before they break up into smaller ice masses that melt slowly during the summer. A temperature survey has shown that the melt lake is almost isothermal (0.3–0.5°C). A poorly understood convection mechanism prevents suspended silt from settling and cau...

Numerical Modeling of the Late Weichselian Svalbard-Barents Sea Ice Sheet

Previous reconstructions of the ice cover of the Svalbard-Barents Sea region during the late Weichselian have ranged from small ice masses on Svalbard to complete inundation of the Barents Shelf region by an ice sheet several kilometers thick. We have used a time-dependent finite-difference numerical model to undertake a new glaciological reconstruction for the Svalbard-Barents Sea Ice Sheet over the last 30,000 yr. The numerical model requires environmental forcing functions in the form of air temperature and precipitation and their behavior with respect to altitude, together with sea-level change and an iceberg calving relation. Ice buildup on Svalbard is calculated to have begun 28,000 yr ago, and maximum dimensions were reached by 20,000 yr ago, covering Svalbard and the northwestern Barents Sea with a center of mass (1.3 km thick) around eastern Svalbard. Decay was complete by about 10,000 yr ago. The margin of the modeled ice sheet at its maximum is in good agreement with observed sea-floor morphological features, but there are discrepancies in timing between the modeled ice sheet decay and (i) a dated meltwater spike in Fram Strait and (ii) the observed rebound curves for Svalbard. An inverse approach was used to predict ice sheet decay, and it was found that increasing the rate of iceberg calving within the model produces a deglaciation some 2000 yr earlier, which is compatible with these two independent datasets. The reconstruction is also compatible with geological evidence on the isostatic response of Bjørnøya, close to the southern limit of the ice sheet, and seismically observed deposits, interpreted to be ice. proximal facies, located in the northwestern Barents Sea. Our time-dependent model reconstructions of the Svalbard-Barents Sea Ice Sheet indicate ice cover over only the northwestern Barents Sea during the late Weichselian, but this does not preclude the presence of ice derived from Fennoscandia and the Kara Sea region elsewhere in the Barents Sea.

A Model Study of the Wave-Induced Motion of Small Icebergs and Bergy Bits

Wave tank studies were conducted to determine the kinematics of “small” ice masses in storm waves typical of the Grand Banks region (10–14-s periods, 12–15-m heights). The models tested spanned the range of full-scale masses from growlers and bergy bits (10–103 tonnes), to small icebergs (104–105 tonnes). In open water, models smaller than 1/13 wavelength behaved essentially as particles of fluid. The corresponding full-scale kinetic energies associated with such motions could exceed 107 J. Models approximately 1/2 wavelength in size could attain energies in the surge direction in excess of 109 J, largely through wave diffraction effects. Significant heave resonance motions were also seen. Tank studies additionally revealed that wave-driven ice-structure impacts of substantial energy could occur, although wave diffraction from the structure could also have a considerable influence on nearby ice motion. The conclusion is reached that wave-induced motion of small ice masses represents a significant environmental hazard to the operation of offshore structures in ice-infested waters.

Evaluation of ERTS-I Imagery for Inventory Work of Perennial Snow Patches in Central Japan

In order to make the inventory of perennial snow patches in central Japan as a part of the I.H.D. world inventory of perennial ice and snow masses, observations have been continued by the author and collaborators by taking photographs of snow patches from the air every autumn since 1968. The results obtained during the period from 1968 to 1970 were published as the Atlas of perennial snow patches in central Japan (Higuchi and Iozawa, 1971). The flight for observation in 1972 was made on 13 October, just after 5 October 1972 when the Earth resources technology satellite (ERTS-I) imagery of central Japan was obtained. Therefore it was possible to compare the ERTS imagery of perennial snow patches in central Japan with aerial photographs of them. The perennial snow patches can be classified as (a) snow patches developed mainly from avalanching, (b) those developed mainly from snow drifting, and (c) those developed from both. The perennial snow patches in central Japan are mainly those of types (a) and (b). Since the prevailing wind direction in winter is north-west in this area, snow drifting and also avalanching of drifted snow occur at the eastern side of the mountains running southwards from the Sea of Japan. Therefore, 65% of the perennial snow patches of type (a) and 70% of those of type (b) are located at the eastern side of mountains. Fortunately, the ERTS imagery of this area was obtained at a local time when the solar azimuth was 143° so that many of the snow patches were in sunshine. Therefore, comparison of the ERTS imagery of snow patches with aircraft photographs in this case can be used as the data to discuss the limit of observation of small ice and snow masses by this satellite. It was found from comparisons between the ERTS-I MSS imagery of band 4 (0.5 to 0.6 μm), band 5 (0.6 to 0.7 μm) and band 6 (0.7 to 0.8 μm) that the band 4 imagery was best to distinguish snow patches. Snow patches of type A were most clearly seen on the imagery. Since they are located in the valleys where avalanching occurs, the contrast between the white snow surface and the dark valley walls was quite clear. For instance, it was easy on the imagery to find four long snow patches (No. 12 701, 12 708, 12 718 and 12 720 in the Atlas) at the eastern slope of the mountain Tsurugi Dake (2 998 m above sea-level), their width being 30-50 m and their length 1 000-l 500 m. It was difficult on the imagery to distinguish snow patches of type (b) from an exposed surface, since they are not so long as those of type (a), but circular and small. However, big ones of type (b) can be found on the imagery when they are located near ridges in the sunshine. For instance, the snow patch No. 18 509 in the Atlas was seen on the imagery, its size being 200 m X 100 m. Snow patches of type (c) are few and this type seems most difficult to find on the imagery, since they located at the bottom of cirque valleys in the shadow.

Evaluation of ERTS-I Imagery for Inventory Work of Perennial Snow Patches in Central Japan

In order to make the inventory of perennial snow patches in central Japan as a part of the I.H.D. world inventory of perennial ice and snow masses, observations have been continued by the author and collaborators by taking photographs of snow patches from the air every autumn since 1968. The results obtained during the period from 1968 to 1970 were published as the Atlas of perennial snow patches in central Japan (Higuchi and Iozawa, 1971). The flight for observation in 1972 was made on 13 October, just after 5 October 1972 when the Earth resources technology satellite (ERTS-I) imagery of central Japan was obtained. Therefore it was possible to compare the ERTS imagery of perennial snow patches in central Japan with aerial photographs of them.The perennial snow patches can be classified as (a) snow patches developed mainly from avalanching, (b) those developed mainly from snow drifting, and (c) those developed from both. The perennial snow patches in central Japan are mainly those of types (a) and (b). Since the prevailing wind direction in winter is north-west in this area, snow drifting and also avalanching of drifted snow occur at the eastern side of the mountains running southwards from the Sea of Japan. Therefore, 65% of the perennial snow patches of type (a) and 70% of those of type (b) are located at the eastern side of mountains. Fortunately, the ERTS imagery of this area was obtained at a local time when the solar azimuth was 143° so that many of the snow patches were in sunshine. Therefore, comparison of the ERTS imagery of snow patches with aircraft photographs in this case can be used as the data to discuss the limit of observation of small ice and snow masses by this satellite.It was found from comparisons between the ERTS-I MSS imagery of band 4 (0.5 to 0.6 μm), band 5 (0.6 to 0.7 μm) and band 6 (0.7 to 0.8 μm) that the band 4 imagery was best to distinguish snow patches. Snow patches of type A were most clearly seen on the imagery. Since they are located in the valleys where avalanching occurs, the contrast between the white snow surface and the dark valley walls was quite clear. For instance, it was easy on the imagery to find four long snow patches (No. 12 701, 12 708, 12 718 and 12 720 in the Atlas) at the eastern slope of the mountain Tsurugi Dake (2 998 m above sea-level), their width being 30-50 m and their length 1 000-l 500 m. It was difficult on the imagery to distinguish snow patches of type (b) from an exposed surface, since they are not so long as those of type (a), but circular and small. However, big ones of type (b) can be found on the imagery when they are located near ridges in the sunshine. For instance, the snow patch No. 18 509 in the Atlas was seen on the imagery, its size being 200 m X 100 m. Snow patches of type (c) are few and this type seems most difficult to find on the imagery, since they located at the bottom of cirque valleys in the shadow.

Glaciers and the water supply

AN stored enormous in the reserve form of of glacier water ice is : st red in the for of lacier ic : about three-fourths of all the fresh water in the world, equivalent to precipitation over the entire globe for about 60 years. In North America, the volume of water stored as snow and ice in glaciers is many times greater than that stored in all of the lakes, ponds, rivers, and reservoirs on the continent. Most glaciers, however, are in the polar and subpolar regions, and not where most people live. People and glaciers do meet in Alaska, of course. About 3 per cent of that state (about 20,000 sqmi or 52,000 sqkm) is covered by glaciers, and this ice is concentrated in mountains not far from major population centers. Most of the major rivers originate at glaciers, and the peculiar characteristics of glacier runoff (peak flow in midsummer, diurnal fluctuations in runoff, high silt content, glacier outburst floods) do have a pronounced effect on the society and economy of Alaska. The impact of glaciers on water resource development is probably greatest in the Pacific Northwest and the middle and northern Rocky Mountain states. The glaciers there are small, almost inconsequential by Alaskan or arctic standards, but they are an important source of streamflow. The location of glaciers in the United States exclusive of Alaska is shown in Fig. 1, and the numbers and the areas of these glaciers are summarized in Table 1. These data are approximate only; many glaciers occur in relatively inaccessible and poorly mapped areas. A new inventory of glacier ice is underway as a major project of the International Hydrological Decade. The first results of this inventory in the United States indicate that about 20 per cent more glaciers exist in the highly glacerized North Cascade Range of Washington than had been counted in a previous inventory.1 It is likely that the total numbers and areas of glaciers shown in Table 1 represent minimum figures. These glaciers are small but numerous, adding up to a considerable equivalent volume of water, and they release an appreciable amount of water during the summer months. In Washington, as much water is stored as glacier ice (about 40 mil acre-ft or 49 billion cu m) as in all of the reservoirs, lakes, and rivers in the state, and as much water is released to summertime streamflow as is pumped from ground water all year. The importance of these small ice masses to water resource development stems partly from the quantity of water released, but results even more from the seasonal and long-term natural regulation of this water. This regulation makes the water a more reliable source in one respect, but it also makes forecasting its seasonal release virtually impossible by ordinary procedures.

Glaciation of the Coeur d'Alene District, Idaho

Cirques and glaciated valleys are present on northern slopes of peaks exceeding 5500 feet in elevation in the Coeur d9Alene District, Idaho. Glacially striated rock surfaces at the tops of cirque headwalls and on the divides above indicate that ice carapaces were present when the cirques were overfilled during glacial maxima. Freshness of landforms and deposits indicates a Pinedale age for the last widespread glaciation. Small ice masses may have developed within the most sheltered cirques during Temple Lake time. Till of Bull Lake age is present on benches and spurs near the head of the South Fork valley. Striated cobbles in coarse gravel as much as 1250 feet above present drainage levels are believed to be evidence of Buffalo glaciation. Following deposition of the gravel, streams eroded laterally before rejuvenation resulted in excavation of new valleys and exhuming of former valleys. It is possible to identify cirques that were occupied during one, two, or more glacial episodes. Continental ice of Spokane (Wisconsin) age impounded Glacial Lake Coeur d9Alene to an elevation of about 2600 feet. Water level was stabilized by a bedrock spillway at Setters on the western side of the lake. Numerous boulders of granite, plucked from bedrock near Pend Oreille Lake, were rafted into the district on ice bergs. Positions of these erratics indicate that postglacial erosion has been extremely slight.