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The existence of Wisconsinan refugial landscapes on eastern Baffin Island, Northwest Territories, Canada, is mainly due to two factors. One is the limitation of the extent of the late Wisconsinan glaciation throughout the Canadian Arctic caused by the extreme high-latitude aridity from the Laurentide Ice Sheet to the south. The other factor is the bedrock configuration. Fiords acted as interdigitating outlets for large volumes of Luarentide ice which left the intervening uplands without ice.

Bigganjargga is the classic locality for the Varangian ice age in northern Scandinavia. The presence of two sets of striations on the underlying quartzite basement has been taken as evidence for a glacial origin of the Bigganjargga diamictite. However, soft-sediment surface structures on the underlying sandstone indicate that it was not consolidated when the diamictite was emplaced. Together with structures in the diamictite this shows that the deposit formed as a debris flow moving northwestwards over an unconsolidated substrate. There is no evidence for glacial origin or contribution for the diamictite material.

A study of the surge-type Dusty Glacier at the ice-dammed lake site , St. Elias Mountains, Yukon reveals that the lake site was occupied at least three times following the decoupling of the tributary glaciers during deglaciation from the peak of the Little Ice Age. The lake formed either during periods of surge of the glacier or during the early part of deglaciation and drainage. The sedimentary history of the lake contains fluvioglacial sand and gravel facies released during drainage.The implications for environmental reconstruction are discussed.

Mountain environments are especially sensitive to climate change. In particular, changes in winter precipitation, summer radiation and summer air temperatures alter the speed and extent to which snow lines migrate up glaciers during the summer. These changes affect the hydrology of glaciers in the short term and the geometry of glaciers in the longer term. Both of these changes alter the magnitude and seasonal pattern of runoff in mountain streams and have important water resource implications.

Reconstructions of late Weichselian glacier coverage on the continental shelves of the Russian Arctic range from a large ice sheet terminating in northern Siberia to isolated ice caps restricted to Arctic archipelagos. This disparity in glacier reconstructions reflects the lack of chronological control on glacial and deglacial landforms. We present new Holocene relative sea-level data from Franz Josef Land and northern Novaya Zemlya, Russia, that place the thickest glacier loads in the northern Barents Sea and not over Novaya Zemlya. Radiocarbon ages from shelf and terrestrial areas at the former ice-sheet margin support deglaciation of the northern Barents Sea between 13.0 and 10.3 ka, considerably later than inferred from isotopic records for the Arctic Ocean. This analysis indicates that the Barents Sea ice sheet was a dominant sea-level reservoir in northern Eurasia, and that glacier loading of Novaya Zemlya was comparatively limited during the last glaciation.

Two exposures of basal ice in Alaska and Greenland, which have previously provided the basis for contrasting models of basal-ice development, are in fact directly comparable. Reinterpretation of previous field descriptions, combined with new structural and sedimentologiral data from West Greenland, facilitates a simple unification of previous models of basal-ice development and a common terminology for the field description of basal-ice sequences. The stratigraphy of the basal-ice sequence at any site indicates the subglacial conditions and processes operating up-glacier of that site. Presented here are interpretations of the major sequence types.

A corrected radiocarbon age of 11,050 ± 14 years before present for an advance of the Franz Josef Glacier to the Waiho Loop terminal moraine on the western flank of New Zealand's Southern Alps shows that glacier advance on a South Pacific island was synchronous with initiation of the Younger Dryas in the North Atlantic region. Hence, cooling at the beginning of the Younger Dryas probably reflects global rather than regional forcing. The source for Younger Dryas climatic cooling may thus lie in the atmosphere rather than in a North Atlantic thermohaline switch., The Younger Dryas cooling was a short-lived climatic reversal [ 10,000 to 11,000 [sup.14]C years before present (B.P.)] superimposed on the last deglaciation. It featured rapid shifts of North Atlantic [...]

It is hypothesised that the Medieval Warm Period was preceded and followed by periods of moraine deposition associated with glacier expansion. Improvements in the methodology of radiocarbon calibration make it possible to convert radiocarbon ages to calendar dates with greater precision than was previously possible. Dating of organic material closely associated with moraines in many montane regions has reached the point where it is possible to survey available information concerning the timing of the medieval warm period. The results suggest that it was a global event occurring between about 900 and 1250 A.D., possibly interrupted by a minor readvance of ice between about 1050 and 1150 A.D.

The fine particles created by glacial comminution of carbonate minerals are susceptible to interaction with meltwater, and the isotopic composition of fine carbonate in glacial deposits has the potential of recording this interaction. Here, we focus on the carbonate fraction of glacial sediment and debris within basal ice at the Tsanfleuron Glacier, Switzerland. Size separates of basal ice debris and melt-out tills show a collinear isotopic trend interpreted as a mixing line between detritus (Delta18O(sub PDB) = -5 per thousand and Delta13C(sub PDB) = 0.6 per thousand) and authigenic calcite, which in one case had Delta18O values as light as -18.7 per thousand and Delta13C values as light as -5.7 per thousand. In most cases, the finer fractions (with calcite crystals as small as 0.1 micrometer) are enriched in the isotopically light component, which is interpreted to form largely by freezing in basal ice. The isotopic compositions of ice and included gases could be influenced by this process. Melt-out tills inherit the authigenic calcite; thus, carbonate-bearing till should no longer be regarded simply as clastic sediment.

Results from laboratory experiments show that ice at its melting temperature regelated through dense, three-dimensional arrays of clasts abrading a rock bed. Regelation theory for an isolated, stationary array of clasts successfully approximates periods when ice separated from the bed, thermal gradients, and clast-bed contact forces, despite the relative motion of clasts and incoming heat from the bed. The process may entrain sediment at glacier beds and restrict deposition to zones where sediment in ice is concentrated, effective pressure is low, and basal melting is rapid.

During the 1989 melt season, ten tracer experiments were conducted to investigate seasonal, diurnal, and spatial variations in the internal drainage system in the ablation area of Storglaciaren, Sweden. Dye was injected into moulins, and dye concentration and discharge were monitored in two streams at the glacier terminus, Sydjakk and Nordjakk. Dye emerged only in Sydjakk. Transit velocities ranged from 0.07 to 0.29 m/s, implying that drainage was through a well-defined conduit system. Velocity and discharge relations suggest that these conduits are part of a multi-branched arborescent network of individually braided, wide, low passages. A progressive decline in dispersivity during the early part of the melt season reflects structural changes in these conduits, presumably including a decrease in the degree of braiding and an increase in size. The system reached its late-season configuration in early August, by which time the energy dissipated by the flowing water would have sufficed to melt between 0.7 and 21 m cube of ice per meter of conduit length, depending on conduit size. Potential closure rates exceed melt rates on conduit walls throughout most of the drainage system, and so conduits are probably full of water during periods of higher daily discharge, with water pressures exceeding atmospheric pressure. Variations in tracer-return curves and dispersivity on a diurnal time scale also appear to reflect changes in the degree of braiding, in this case resulting from drowning of low divides between channels as discharge increases.

Reconstructions of the ice-surface morphology of several lobes of the southern Laurentide Ice Sheet reinforce previous arguments that this sector of the ice sheet was thin and low sloping. Driving stresses, estimated from the geometry of the reconstructed ice surfaces, are 0.7-4.3 kPa for the 14 ka Des Moines Lobe, 0.9-1.2 kPa for the 14 ka James Lobe, 0.9-1.7 kPa for the 18-20 ka Lake Michigan Lobe, 1.8-2.9 kPa for the 15-18 ka Chippewa Sublobe, and 17-22 kPa for the 15-18 ka Green Bay Lobe. Previous estimates of rates of ice-margin advance (450-2,000 m/yr) indicate moderate-to-fast ice velocities for the ice lobes. Reconstructed driving stresses and velocity estimates of the Des Moines, James, and Lake Michigan Lobes are analogous to the distal ends ('ice plains') of low-sloping (0.4 x [10.sup.-3]) but fast moving (500 m/yr) West Antarctic ice streams, whose dynamics have been attributed to sliding and/or subglacial sediment deformation by pervasive shear. These reconstructions support recent models of the Laurentide Ice Sheet which include movement by sliding or by subglacial sediment deformation along its southern, western, and northwestern sectors; evidence for either mechanism should be represented in the sedimentologic and geomorphic records. Thin ice in these regions indicates that the Laurentide Ice Sheet contained less ice volume and represented less of an orographic obstacle to atmospheric circulation than has been considered in models of the ice sheet on a rigid bed with steep profiles.

The principal points of water input to a glacier are the bergschrund in cirques, and crevasse fields lower on the glacier. Crevasse fields commonly occur over convexities at the heads of overdeepening in glacier beds. The amplitude of subglacial water-pressure fluctuations is large just down-glacier from these points of water input. Erosion by quarrying is likely in such areas. Erosion is thus inferred to be localized on the headwalls of cirques and overdeepenings. In the case of overdeepenings, this leads to a positive feedback process in which a perturbation in the bed causes crevassing at the surface, resulting in erosional forces that accentuate the perturbation. When subglacial water flows up an adverse bed slope leading out of a cirque or overdeepening, much of the viscous energy dissipated is used to warm the water to keep it at the pressure melting temperature as the ice thins and pressure decreases. In such situations, subglacial conduits are maintained by high water pressures rather than by melting of conduit walls. In the limit, water pressures apparently become so high that water is forced out along the ice-bed interface and the conduits collapse. The products of erosion are then no longer flushed out, and a protective till layer accumulates. By limiting erosion on such adverse bed slopes, this till layer controls the geometry of these over-deepened basins.

Ice sheets terminating in water may provide geologic evidence to reconstruct iceberg-calving rates and hence provide insight to ice-sheet mass balance at certain locations. Recent work reported an empirical relation for 12 modern tidewater glaciers in Alaska in which iceberg-calving rate is directly related to the average water depth. The former Laurentide ice sheet split into tidewater glaciers in the troughs of Mount Desert Island, Maine, and deposited moraine banks as sea level transgressed onto the island. Paleoshorelines were at least 65 m and probably as high as 90 m above present-day sea level. With 75 m shoreline elevation, the average water-depth values correspond to iceberg calving rates of 650 to 2100 m/yr. The total ice-volume flux minus the iceberg-calving flux is equal to the rate of change in terminus position times the terminus area. Because the terminus is stationary when moraines are deposited, the calving flux is equal to the discharge flux at that time. Calculated discharge fluxes for Mount Desert Island range from 0.65 to 2.9 X [10.sup.3.m.sup.3]/yr; the average is 1.7 X [10.sup.3.m.sup.3.]/yr across a unit width of the terminus. Consideration of the ice-sheet geometry and estimated precipitation and temperature conditions indicates that most of this flux must come from ice-sheet thinning rather than mass accumulation. The geometry of this analysis dictates that all of these estimates are minimum values.

Distribution of drumlins on the Ontario Lowlands and the northern Appalachian Plateau of New York State are utilized in a glaciological model that estimates thicknesses of the Late Wisconsin Ice Sheet along five glacial flowlines over the central section of the Finger Lakes. Dynamics of the model are based upon a force balance approach that incorporates variable width of a flowband, bedslope, radius of curvature, and center of outflow location. Drumlin axes along five hydrostatic isograms were projected northward. Points of axes convergence define the center of outflow in the eastern Ontario Basin. Flowlines along the axial trace of the major Seneca and Cayuga Troughs and bordering interfluves were constructed southward to the Valley Heads Moraine System. Calculation of flowline geometry for any assumed basal shear stress requires neither information on ice temperature nor the flow law of ice. Ice thicknesses for each flow line were calculated for [[tau].sub.b] values of .5, 1.0, and 1.5 bar. Ice thicknesses at 1 bar range from a minimum of 1,932 m for the Seneca Trough flowline to a maximum of 2,093 m at the Keuka-Seneca interfluve flowline. Raising or lowering [[tau].sub.b] by .5 bar results in maximum thickness differences of +21% and -26%, respectively. Simulating ice recession, a series of ice-marginal, terminal positions were plotted for a basal shear stress of 1 bar. These predicted terminal positions agree well with locations of mapped moraine deposits. These probable value of basal shear support the presence of glacial flow representative of internal deformation rather than basal sliding. Although recent interpretations of the formation of the Finger Lakes focus on ice streams facilitated by large volumes of subglacial meltwater, our evidence discounts the presence of ice streams and supports the existence of outlet glaciers in the troughs of the Finger Lakes.