The deuterium concentration profile in a first-year Antarctic sea-ice cover is used to deduce a growth-rate curve, applying a previously published model. Time variations of the conductive heat flux throughout the growth period are then estimated from this growth-rate curve. Results indicate that the isotopic determination of sea ice growth rate can be considered as an alternate method for determining the conductive heat flux through a young sea-ice cover. However, there is need for a further test of the method by measuring in situ temperatures and growth rates during the formation of first-year sea ice, and by analyzing the isotopic composition of ice samples taken simultaneously along selected profiles during the growth period.

Ten Landsat Thematic Mapper images together show Ice Streams E, D and most of Ice Stream C on Siple Coast, West Antarctica. The images are interpreted to reveal aspects of both spatial and temporal evolution of the ice streams. Onset of ice-stream flow appears to occur at distributed sites within the ice-stream catchment, and the apparent enhanced flow continues in channels until they join, forming the main ice stream. Most crevassing on these ice streams is associated with features of horizontal dimensions between 5 and 20 km. We suggest these features are caused by bed structures which may be an important source of restraint to ice flow, similar to ice rumples on ice shelves. A pattern of features near the grounding line of the now-stagnant Ice Stream C are interpreted as having formed because there was a period of reduced flux before the ice stream stopped.

The North and South Klawatti glaciers are adjacent glaciers in the North Cascade Mountains of Washington state. During 1947–61 North Klawatti Glacier lost volume, equivalent to a mean decrease in thickness of 8.3 m over the glacier area, whereas South Klawatti Glacier gained volume, equivalent to an increase in thickness of 5.8 m. Although the glaciers are in the same climate, they have different distributions of area with altitude, resulting in different responses to climatic variations.

A quadratic equation is assumed to approximate the relation of mass balance to altitude for both Klawatti glaciers. The coefficients of the equation are derived by comparing the calculated mass change to the mass change for each glacier estimated from topographic maps. The resultant relation of mass balance to altitude is the mean for the time period between maps (1947–61).

Steady-state longitudinal profiles of both glaciers were obtained by shifting the existing mass-balance versus altitude curve by a magnitude equal to the measured mean annual mass balance. To produce steady-state conditions, the equilibrium-line altitudes of both glaciers would need to move less than 90 m (85 m higher for South Klawatti Glacier and 88 m lower for North Klawatti Glacier).

In the 1870s and 1880s, after a long period of cold conditions, most of the glaciers of Svartisen ended near their maximum Neoglacial limit. Subsequent changes, although principally a response to the climatic controls of mass balance, have been influenced by glacier geometry, including area/altitude relations and aspect, and by glacier dynamics. Calving has played a principal role in the decrease of size of two of the larger glaciers, Austerdalsisen and Flatisen, both of which became unstable once the grounded distal sections of their tongues lost contact with their beds. Mass balance variations reflect climatic controls of the length of the accumulation and ablation seasons, as well as changes of summer temperature. The mass balance record of Engabreen, a maritime outlet of the Vestre Svartisen ice cap, monitored since 1970 by the Norwegian Water Resources and Energy Administration, is not representative of the area as a whole: the more continental glaciers of Østre Svartisen are likely to experience negative net balances when that of Engabreen is slightly or moderately positive. However, the pattern of year-to-year changes of net balance is similar, not only for the Svartisen area as a whole, but also for a larger area.

The first ice-core record of both the Holocene and Wisconsin/Würm Late Glacial Stage (LGS) from the subtropics has been extracted from three ice cores to bedrock from the Dunde ice cap on the north-central Qinghai-Tibetan Plateau. Ice thicknesses at the ice-cap summit average 138 m, the bedrock surface is relatively flat, surface and basal temperatures are −7.3 and −4.7°C, respectively and the ice cap exhibits radial flow away from the summit dome. These records reveal a major change in the climate of the plateau ∼10 000 years ago and suggest that LGS conditions were colder, wetter and dustier than Holocene conditions. This is inferred from the more negative δ18O ratios, increased dust content, decreased soluble aerosol concentrations, and reduced ice-crystal sizes, which characterize the LGS part of the cores. Total β radioactivity from shallow ice cores indicates that over the last 24 years the average accumulation rate has been ∼400 mm a−1 at the summit. The ice cores have been dated using a combination of annual layers in the insoluble dust and δ18O in the upper sections of core, visible dust layers which are annual, and ice-flow modeling. The oxygen-isotope record which serves as a temperature proxy indicates that the last 60 years have been the warmest in the entire record.

We carried out laboratory experiments with a test tank in a cold room to estimate heat flux through coastal polynyas, which have great effects on climate in the polar regions. The estimation of heat flux from water to air was made with measurements of cooling rate of water temperature and of the rate of ice production as a function of wind speed and water salinity. Both rates increased with increasing wind speed and water salinity. The major factor that governs heat flux is the size of the open water area. In an open water area continuously maintained by a strong cold wind, rapid production of frazil ice and its downwind transport occur simultaneously; so the open water serves as an efficient ice factory. In the case of NaCl solution, supercooled water with salinity greater than 23.1‰ is denser than water at its freezing point. Therefore, the formation and sinking of the supercooled water occur in the persistent open water; this results in great lowering of water temperature and underwater-ice production. Strong wind and high salinity enhance the supercooling effect.

The glaciers of central Asia provide suitable locations from which to recover continuous, high-resolution glaciochemical records on a continental scale. Although the glaciochemical investigations undertaken to date in central Asia are few in number and limited in terms of spatial coverage and length of record, some preliminary observations can be made concerning regional and seasonal trends in snow chemistry in this region.

The sodium chloride ratio for most snow samples collected in central Asia approaches the ratio found in sea water (0.86 in μeq kg−1), reflecting a marine source for these constituents. Sodium and chloride concentrations are, on average, 3–10 times higher in the Himalayas than in the Karakoram, demonstrating the greater influence of monsoonal sources of moisture in the Himalayas. Very high sodium concentrations from Khel Khod Glacier probably reflect a local crustal source from surrounding ice-free areas. Low nitrate concentrations were found in snow collected from the southern margin of the Himalayas and high concentrations in snow deposited on the north margin of the Himalayas. This strong regional trend in the spatial distribution of nitrate suggests the influx of continental aerosols, rich in nitrate, originating from the arid regions of central Asia. High calcium concentrations measured in snow from Mount Everest and the north-west corner of China are also indicative of dust derived from the arid regions of central Asia. Very high sulfate concentrations found in snow from the Tien Shan and the Bogda Shan most likely reflect local anthropogenic sources. The altitude effect on isotopie composition is not apparent from snow samples collected in central Asia.

Understanding the processes which control the chemical content of snow, the local-to-regional scale complexities, and the seasonal variability are fundamental steps necessary to assess the potential for recovering representative long-term glaciochemical records from central Asia.

The retreat of the West Greenland ice sheet from its Sisimiut (Wisconsinan) glacial maximum, was punctuated by a series of Stillstands or small readvances that formed numerous moraines. These landforms have been interpreted in the past as the result of short-term, regional falls in ablation-season temperatures. However, mapping of the geomorphological evidence south of Ilulissat (Jakobshavn) suggests that retreat behaviour was not primarily governed by climate, and therefore that the former ice margins are not palaeoclimatically significant. During warm climate ice-sheet wastage, the successive quasi-stable positions adopted by the ice margin were largely governed by topography. The retreat of the inherently unstable calving glaciers was arrested only at topographically-determined locations where stability could be achieved.

This paper summarizes typical energy-balance data for a variety of polar terrain types, to aid in a better understanding of climate and climate change. Terrain types examined include closed boreal forests, open woodlands, tundra, the pack ice of the Arctic Ocean, glaciers and large ice sheets. For each of these terrains energy-balance-related parameters, including albedo, surface roughness, and thermal diffusivity of the subsurface and their seasonal variations are considered. Components of the surface energy balance, and particularly the net radiation or radiation balance, are presented on a seasonal basis. Net radiation is shown to be a poor indicator of climate, if used as the sole parameter, contradicting earlier conclusions by some climatologists. Large differences are shown between the energy balances of the various terrains in summer, with the boreal forest and the tundra acting as major heat sources for the surrounding terrains, and the glaciers acting as major heat sinks. In winter, thin pack ice is the major source of heat energy. These factors not only affect the regional climates of the Arctic, but influence global climate through feedback processes.

All studies and models of air—sea-ice interactions suffer from a paucity of information about the oceanic heat flux, which exerts a controlling influence on the sea-ice energy and mass balance. The role of the oceanic heat flux in the sea-ice energy and mass balance is discussed. The performance of ice-ocean models depends on a satisfactory specification of this rarely measured oceanic parameter. A method for determining the oceanic heat flux by measuring the temperatures and thickness of sea ice is described. The results obtained using this method and the data collected during the fall of 1988 in the eastern Arctic are presented. Values of the oceanic heat flux ranging from 0 to 37 W m−2 were estimated from observations taken in the region north-east of Fram Strait. The oceanic heat flux in this region varied in both time and space.

A preliminary late-Holocene glacial chronology from the west flank of the southern Kenai Mountains, Alaska, is characterized by two major episodes of advance. Outlet glaciers of both the Harding Icefield and the Grewingk-Yalik ice complex were expanding across their present positions at 545 A.D. and again during the Little Ice Age, about 1500 A.D. The earliest of these Neoglacial advances is dated by radiocarbon ages from the outer rings of tree trunks rooted near the margins of Grewingk and Dinglestadt glaciers. Subsequently, ice margins retreated some distance behind their present positions allowing marked soil development before the last readvance through mature forest. Wood preserved in lateral moraines at Grewingk Glacier and from an uprooted stump at Tustemena Glacier date this later ice advance. Tree-ring ages, correlated with lichen diameters, suggest that this last advance was widespread and culminated in its Neoglacial maximum about 1800 A.D.. Since this time, glacier retreat has dominated in the area, punctuated by at least two pauses. Historical accounts and photographs document a mean rate of retreat of 27 m a−1 for the past century with partial control exerted by calving of ice margins into proglacial lakes.

Deuterium content, microparticle concentration, ice crystal size and bubble concentration have been studied along an 82 m ice core drilled down to the bedrock in the ice-sheet margin in East Antarctica. The Last Glacial Maximum (LGM) is distinctly marked by low deuterium content, high concentration of microparticles, small ice crystals and high bubble concentrations. This core covers a significant part of the Last Glacial Period with ice from a warmer period recovered around a depth of 60 m.

Rapid melting of continental ice during deglaciations has been hypothesized to shift the thermohaline circulation of the world ocean to a mode radically different from the one dominated by the North Atlantic, such as operates today. This scenario has been referred to as the halocline catastrophe. We consider here the freezing, transport, and melting of sea ice in the North Atlantic sector as a possible modern analog to such events.

The rejection of salt during the freezing and subsequent development of sea ice results, by early summer, in ice with only 5–10% of its original salt content. Since sea ice several meters thick is typically formed annually in the polar regions, the distillation rates from freezing are fully comparable to those from evaporation in such highly evaporative basins as the Red Sea. If the ice is subsequently exported from its production area, then freezing and melting are the oceanic equivalent of the hydrologic cycle. In the Arctic, the major ice outflow from the 107 km2 of the Polar Basin occurs east of Greenland, where the exodus represents a fresh-water transport of at least 2800 km3 a−1. This is a discharge more than twice that of North America’s four largest rivers combined.

The fresh water can subsequently be traced around the subpolar gyre of the North Atlantic, on its way transferring small but significant amounts of buoyancy into the interior convective gyres, e.g. in the Greenland Sea. The convection which occurs in these gyres under present climatic conditions makes them major ventilation and water mass formation sites for the deep world ocean, but because the density of sea water at constant pressure and low temperature is almost solely dependent on salinity, the convection is extremely sensitive to changes in the freshwater supply to the gyres. Small variations in the supply will be transferred into the deep ocean by convection, where they will be manifested by a cooling and freshening, such as has recently been observed in the deep North Atlantic. However, if the surface layers are freshened too much, cooling even to the freezing point will be insufficient to initiate convection. Instead, the convective gyres will be capped by a fresh-water lid, essentially what has been proposed in the halocline catastrophe scenarios. During such events, sea ice will form in the gyres, sometimes with disastrous consequences, as occurred north of Iceland during the late 1960s when, during the extreme years of 1965 and 1968, the entire north and east coasts of Iceland were enveloped by sea ice; at the same time, renewal to the north of the deep ocean waters diminished or ceased.

We suggest that the present-day Greenland and Iceland seas, and probably also the Labrador Sea, are rather delicately poised with respect to their ability to sustain convection, and that we have in fact during the past several decades seen a small-scale analog to the halocline catastrophe proposed for past deglaciations. A major difference is that the present situation does not require dramatic increases in fresh-water flux to effect a capping of the convection; nor does it depend on deglaciation. Rather, very modest changes in the disposition of the fresh water presently carried by the East Greenland Current can alter or stop the convection; and the principal source of fresh water is sea ice, rather than glacial ice. The essence of the present situation is that the large fresh-water output from the Arctic Ocean, which is the distillate of freezing, passes perilously close to the very weakly stratified convective gyres; and that the stratification in these gyres is easily perturbed, either by variations in the discharge from the Arctic Ocean or by leaks or recirculation from the boundary current.

A nonstationary mathematical model of thermics and dynamics of the Antarctic ice sheet has been developed, taking into consideration the influence of long-term changes of climate.

The influence of climatic variations during the last 100 000 years on the temperature field within the ice sheet has been analysed. Information about climatic changes is based on paleographic data and isotope analyses of ice samples from bore holes at Vostok and Byrd stations.

The input data used include results from field surveys of accumulation, temperatures of upper surface, relief of the base and thickness of the ice sheet along the flowlines in the western and eastern parts of the ice sheet, as well as experimental data on ice rheology.

The computations show that traces of the climatic minimum that took place about 18 000 years ago are found in the temperature field of the Antarctic ice sheet.

The model developed has proved that warming of climate due to the “greenhouse effect” leads to significant changes in the thermal regime in the upper parts of the ice sheet, but will not lead to conditions threatening bottom layers.

Mass-balance data for Blue Glacier are presented for the 31-year period 1956–86. The glacier location is strongly maritime with annual precipitation of 3500 to 5000 mm, most of which falls as winter snow. The low elevation of the glacier results in large amounts of summer ablation and thus significant annual mass exchange. Blue Glacier has been in approximate equilibrium with recent climate during the past 30 years with a slightly positive mean annual net balance of 0.3 m and a terminus advance of 150 m. Comparison with other glaciers in western North America indicates that this pattern of mass increase in response to recent climate is not typical but may be specific to a maritime location.

Due to heavy amounts of winter snowfall, an accumulation area ratio of only 0.5 is sufficient to maintain a zero balance on Blue Glacier. A strong gradient of increasing snowfall with elevation contributes to a linear relationship between net balance and elevation throughout the total altitude range of the glacier. This relationship is consistent over the period of record and is not dependent on an overall net positive balance, as the pattern persists even during periods of strongly negative mass balance. A relationship between measured mass balance and equilibrium-line altitude provides a reasonable method to compute mass balance.

A coupled ocean-atmosphere model is formulated, incorporating an ocean comprised of two surface and one deep-ocean boxes, horizontal and vertical mixing, a thermohaline circulation, and forcing by latitudinal differential surface heating and evaporation. Surface fluxes are determined through coupling with a two-box steady-state atmospheric energy-balance model The hydrological cycle, thermohaline circulation and latitudinal exchange rate in the atmosphere are each controlled by an independent parameter. For a weak hydrological cycle, a cold low-salinity deep-ocean equilibrium exists with deep water produced in high latitudes, resembling the modern ocean; for a strong hydrological cycle, a warm saline deep ocean is found with deep water produced in lower latitudes, similar to proposed models of a Cretaceous ocean. More complex solutions exist for an intermediate range of parameters. These include co-existence of both of the above limiting circulations as stable steady states and an oscillatory solution about the cold deep-ocean limit case. In general for this model, the cold deep-ocean case appears less stable than the warm saline deep-ocean case.

The properties of synthetic aperture radar (SAR) imagery are appropriate for its use to map snow facies. These facies, defined by Benson (1962), are subdivisions of the accumulation area of an ice sheet or polar glacier and represent the interaction of the ice mass with the climate through the processes of snow accumulation and melting. Changes in these climatic parameters are expected to cause changes in the extent and character of these facies. The ability of SAR to discriminate these facies is due to the significant amount of sub-surface volume scattering in the measured radar backscatter signal and the strong absorption of radar energy by liquid water. The amount of volume scattering is dependent on the size and distribution of scatterers in the medium. This dependence varies over the size range of snow grains to ice lenses. Specific examples of the ability to detect different scatterer populations in ice sheets with SAR are shown. Other examples are given to demonstrate the reduction of backscatter signal when liquid water is present.

Another important application of SAR data is the determination of surface velocity. Coregistration of a SAR and a TM image spanning an eight-year period was completed for an area in south-western Greenland. The composite image shows that, while the network of surface streams is nearly unchanged, their distance from lakes upstream increased over the eight-year interval between images. Because the lakes are likely fixed in space, a result of surface depressions whose positions are determined by the stationary bedrock topography, the displacement of the stream network was used to calculate a surface velocity of 40 ± 10 m per year near the equilibrium line.

Reflection of solar radiation was studied in the seasonal sea-ice zone off East Antarctica on a cruise of the Australian Antarctic Expedition, October-December 1988. Spectral and total albedos were measured for grease ice, nilas, young grey ice, grey-white ice, snow-covered ice, and open water. Spectral measurements covered the region 400–1000 nm wavelength. For ice too thin to support our weight, the radiometers were mounted at the end of a 1.5 m rod extended out the door of a helicopter or from a basket hung from the ship's crane, using a positioning and leveling rack. Corrections had to be applied to the downward radiation flux because the helicopter or the crane was in the field of view of the cosine-collector.

The fractional coverage of each of the ice types (and open water) was estimated hourly for the region near the ship, as well as the thickness of each ice type, and the snow thickness. Observations were carried out continuously during the four weeks the ship was in the ice, supplemented by occasional helicopter surveys covering larger areas. These observations, together with the radiation measurements, make possible the computation of area-average albedo for the East Antarctic sea-ice zone in spring.

One possible cause of glacier terminus variation is climate change. The problem with proving or disproving this hypothesis is that the precise relationship between climate change and glacier flow response is still incompletely understood. In this paper, I examine the relationship between recent glacier terminus fluctuations and climate variations documented since the middle 1800s in the Pacific northwest region of the United States.

Six glaciers located in Washington and one in Oregon are compared in terms of terminus position record, local climate data (temperature, precipitation, snowfall and runoff records) and also in terms of what is known about the flow dynamics of each glacier. A simple model is presented to simulate the observed response behavior of each glacier. The variables modeled here include surface and bed slope, ice thickness, glacier length, sliding and deformation mechanics, seasonality of glacier flow velocity, traveling wave dynamics, snow accumulation and ablation patterns, runoff, regional temperature and precipitation. Mainly, information obtained at Blue, South Cascade and Nisqually glaciers are compared to results obtained by the author at Shoestring Glacier on Mount St. Helens. Others studied include Forsythe, Elliot, Coleman glaciers. The effects of local volcanic eruptions are separated from those attributed to climate change.

Local climate records show that times of cool-wet weather alternate with warm-dry weather on a time scale of 15 to 20 years. In general, no definable long-term trend of annual average temperature and precipitation is apparent in the climate records (starting in the mid-1800s), except for a suggestion of slightly increased annual precipitation in the northern part of Washington since about 1930. The availability and reliability of different types of climate data is discussed in the paper.

At Shoestring Glacier, the observed rapid response to environmental changes (both climate and volcanic) is shown to be directly related to readily-described mechanics of glacier sliding, internal deformation and englacial thrusting along discrete shear zones. For other glaciers, a combination of a rapid sliding response and a slow long-term deformation and sliding response is apparent, and related to that of the Shoestring Glacier.

Where stagnant ice exists at or near a glacier terminus, the response behavior may be further complicated. The stagnant ice is often overthrust and buried by reactivated ice moving down from higher elevations. In other situations, stagnant terminus ice is accreted to the front of the reactivated portion of a glacier and shoved downhill. This behavior is seen at Shoestring and Nisqually glaciers.

Traveling waves (resembling kinematic waves) are apparent at three of the glaciers studied and probably occur to some degree at all the glaciers. Understanding of the details of glacier flow dynamics and existing terminus conditions helped to formulate a simple model that I use to simulate terminus fluctuation records of all seven glaciers.

Records of terminus position studies indicate that three distinct trends exist for this region. The first is a long-term trend of progressive retreat throughout historic times (meaning locally since the early 1800s). The second trend is the dramatic decrease in the rate of retreat and (perhaps temporary) minor readvance of some glaciers (Blue, Nisqually, Forsythe, Coleman, Shoestring glaciers) since 1950. The third trend is the short-term oscillation of glacier terminus positions on a cycle of 15 to 20 years that has occurred since 1950.

Except for a slight hint of increased precipitation since 1950, the long-term variation in glacier terminus positions cannot be explained by local climate records. This may be attributed to the shortness of the available climate records, and the large variance of annual temperature and precipitation data.

Conversely, the high frequency glacier terminus variations (on the order of 10 to 20 years) are well correlated with local temperature and precipitation fluctuations. For example, Nisqually and Shoestring glaciers advanced when the climate pattern became cool-wet and retreated when the climate changed to warm-dry. Very short lag times are implied by the data for several glaciers, and these are discussed in the paper.

Results indicate that certain local glaciers are very sensitive to short-term climate variations on the order of one to ten years. Large glaciers and glaciers flowing slowly down shallow slopes respond more sluggishly to short-term climate changes, as might be expected. Glaciers with the greatest degree of seasonality in their flow behavior, such as Nisqually and Shoestring glaciers, responded most rapidly. Using this information derived from recent glacier and climate records we may be able to better predict future trends of snow accumulation patterns and climate change.

Rabots glaciär and Storglaciären are small valley glaciers located in the Kebnekaise massif of northern Sweden. Rabots glaciär flows west from the summit of Kebnekaise (2114 m) and Storglaciären flows east; thus regional climate affecting the glaciers is the same. The glaciers are of comparable size and geometry, although differences exist in the variation of ice thickness and the subglacial bedrock topography within the respective basins. The thickness of Rabots glaciär appears to be relatively uniform over much of its length and its bed smooth. The bed over which Storglaciären flows is characterized by a “riegel and basin” topography and ice thicknesses vary accordingly.

Advance and retreat of the glaciers during the last 100 years has been documented by historical records and photographs, measurements of ice retreats, and detailed glacial and geological studies. Both advanced to their maximum 20th century extents around 1916. In their subsequent retreat, Rabots glaciär has lagged behind Storglaciären by 10 years.

Mass-balance studies for the years 1981–87 suggest that while the “local” climate for each glacier is slightly different (in terms of the magnitude of acumulation and ablation), variations in local climate are synchronous. Non-synchronous response of the glaciers is therefore attributed to differences in glacier dynamics, which are quite apparent when velocity profiles are compared. Ice velocities on Rabots glaciär vary little from an average of −7.5 m/yr, resulting in a longitudinal strain rate, r, of about 6 × 10−3yr −1. In contrast, values for r on Storglaciären are as high as 2.5 × 10−2 yr−1 owing to greater ice velocities and variation in ice velocity. Since the response time of a glacier is proportional to 1/r, the lower strain rates found on Rabots glaciär probably account for its more sluggish retreat.

A simple, non-diffusive, kinematic wave model is used to analyze the response of the glaciers to a step-like perturbation in mass balance. This model predicts that the response time of Storglaciären is on the order of 30 years and that a new steady-state profile would be attained in about 50 years. The predicted response time of Rabots glaciär is about 75 years, its new steady-state profile being reached after more than 100 years.

More accurate analyses of each glacier's response to climatic change use a time-dependent numerical model which includes the effects of diffusion. The climatic forcing in these modelling efforts is represented by the changes in mass balance resulting from changes in the equilibrium line altitude (ELA). ELAs can be correlated to regional meteorological variables which in turn are used to create a “synthetic” record of ELA variations where necessary. Therefore climatic oscillations since the turn of the century can be simulated by the appropriate changes in ELA. Using synchronous variations of ELAs and their 1916 profiles as datum states, the modeled behavior of Rabots glaciär and Storglaciären shows that: (a) the rates of ice retreat for each glacier are in reasonable agreement with those observed; and (b) Rabots glaciär took slightly longer than Storglaciären to react to the slight warming that occurred shortly after their 1916 advance.