hydrological characteristics of the drainage system beneath a surging glacier a rare combination of natural circumstances permits assessment of current theories on water flow beneath glaciers outburst floods from the subglacial lake grimsvotn in iceland took place before during and after surging of skei ararjokull the glacier beneath which the outburst floods drain the observable drainage patterns associated with these floods show the different nature of the basal water conduit system of the glacier during surge and non surge phases during surge conditions basal water is dispersed slowly across the bed in a distributed drainage system but when the glacier is not surging water is transported rapidly through a system of tunnels

recent volume and area changes of kaskawulsh glacier yukon canada recent surface elevation changes of kaskawulsh glacier yukon canada are quantified by comparing an air photo derived dem from 1977 and airborne lidar measurements from 1995 2000 and 2007 surface area changes are assessed using historical aerial photography from 1956 and satellite imagery from 1977 to 2007 combined these measurements provide some of the first detailed records of volume change of a large yukon glacier between 1977 and 2007 kaskawulsh glacier underwent a decrease in area of 1 53 and a decrease in volume of 3 27 5 94 km 3 w e the terminus also retreated by 655 m over the period 1956 2007 there was relatively minor volume change over the period 1977 95 0 01 km 3 w e a 1 while over the periods 1995 2000 and 2000 07 volume losses occurred at a relatively constant rate of 0 51 and 0 50 km 3 a 1 w e respectively since 1995 thinning has been prominent throughout the ablation zone while relative stability and even slight thickening has occurred in the accumulation zone these findings are similar to those recently observed at other nearby alaskan glaciers

karakoram glacier surge dynamics quincey d j braun m glasser n f bishop m p hewitt k luckman a 2011 geophysical research letters 38 article number l18504

remote sensing of glacier change in west greenland accounting for the occurrence of surge type glaciers automated glacier mapping from thresholded band ratios of multispectral satellite data is a well established technique to update glacier inventories over large and remote regions the local glaciers and ice caps on greenland are of particular interest for such efforts as they have been only partly mapped mainly during the 1940s 60s and their potential contribution to global sea level rise could be large here we use three landsat etm scenes from 2001 covering disko island qeqertarsuaq and the nuussuaq and svartenhuk peninsulas west greenland to map the glacier extent in 2001 of 1172 entities we also manually digitize little ice age lia extents from clearly visible trimlines for a subsample of 500 entities in this region with numerous surge type glaciers the related area change calculation is challenging and we consider different samples with and without known surging glaciers for the three regions the mean area changes are 28 20 and 23 respectively when known surge type glaciers are excluded the glaciers on smaller islands and peninsulas closer to the margin of the ice sheet show a lower mean area change of 15 moreover lower 16 and upper 21 bounds are calculated for the overall area changes in the entire region between the lia and 2001 using different upscaling assumptions cumulative length changes since the lia are found to be slightly lower for surge type glaciers

dynamics of a small surge type glacier using one dimensional geophysical inversion we investigate the dynamics of a small surge type valley glacier as part of a study to characterize glacier response to climate in the donjek range southwest yukon canada pole displacements were measured using kinematic gps techniques during three consecutive summer field seasons measured surface velocities range from 10m a 1 over the lower 1500 m of the 5 km long glacier to a maximum of 25 35 m a 1 over the upper 3500 m basal velocities along an approximate flowline are reconstructed from the measured surface velocities using inverse methods control tests are used to validate the inversion scheme and sensitivity tests are performed to evaluate the influence of the flow law coefficient shape factor and longitudinal averaging length inversion of the real data shows that basal motion accounts for 50 100 of the total surface motion along the flowline based on these results and several other lines of evidence we suggest this glacier may be undergoing a slow surge

the surges of variegated glacier alaska u s a and their connection to climate and mass balance one of the questions still unanswered concerning the surge behavior of glaciers concerns their quasi periodic occurrence some results on the phenomenological connection between local cumulative balance and surge initiation of variegated glacier alaska u s a are discussed here based on climate data from neighboring weather stations an empirical relation between precipitation temperature and local mass balance is established and used to reconstruct the annual balance at a location in the accumulation area back to 1905 between the last four surges in 1946 47 1964 65 1982 83 and 1994 95 the ice equivalent cumulative balance was 43 5 m on average with a 1 error of 1 2 m although the existence of a surge level cannot be directly interpreted in physical terms it explains the variable length of the quiescent periods of variegated glacier by variations in the accumulation rate prior to the surge we use the surge level to hindcast former unobserved surges to compare the results with other surge datings obtained from photographs and to establish a complete surge history for variegated glacier for the 20th century

variegated glacier alaska usa a century of surges a 1995 surge of variegated glacier alaska usa is discussed in the context of its six 20th century predecessors especially the previous surge in 1982 83 which was studied in detail the average time between surge initiations is 15 years the 1995 surge was considerably weaker than its predecessors having a single phase or at most a very weak second phase the 1995 surge confirms that there is a seasonal cycle with surge initiation in winter and termination in the first part of the melt season and a correlation between weather and both surge termination date and surge extent two days of record high temperature correlated with the termination of the 1995 surge the most obvious issue is the absence of a strong second surge phase as there was in the 1982 83 surge culminating in a surge extent more in line with that of the predecessors this is considered in the light of a simple criterion for surge initiation and re initiation which depends upon the evolving basal shear stress

flow thermal structure and subglacial conditions of a surge type glacier temperature measurements in a subpolar surge type glacier reveal a distinctive thermal structure associated with the boundary between the ice reservoir and receiving areas in the receiving area the glacier is cold based but bottom temperature has increased as much as 0 5 c between 1981 and 1982 and the basal heat flux is roughly 10 times the expected geothermal flux water percolation through permeable subglacial material is the probable energy source deformation of the substrate could destroy this drainage system and trigger a surge

contribution of alaskan glaciers to sea level rise derived from satellite imagery over the last 50 years retreating glaciers and ice caps gic contributed 0 5 mm yr to sea level rises slr and one third is believed to originate from ice masses bordering the gulf of alaska however these estimates of ice wastage in alaska are based on methods that measure a limited number of glaciers and extrapolate the results to estimate ice loss for the many thousands of others how these methods capture the complex pattern of decadal elevation changes at the scale of individual glacier and mountain range is unclear here combining a comprehensive glacier inventory with elevation changes derived from sequential digital elevation models dems we found that between 1962 and 2006 alaskan glaciers lost 41 9 8 6 km 3 yr water equivalent w e and contributed 0 12 0 02 mm yr to slr our ice loss is 34 lower than previous estimates reasons for our lower values include the higher spatial resolution of our glacier inventory and the reduction of ice thinning under debris and at the glacier margins which were not resolved in earlier work estimates of mass loss from gic in other mountain regions could be subject to similar revisions

geometric evolution and ice dynamics during a surge of bakaninbreen svalbard bakaninbreen svalbard started surging in 1985 and developed a steep surge front where fast moving ice impinged on stagnant non surging ice this front which was 20 25 m high in 1985 became a steep and heavily crevassed fcature about 60 m high the surge continued through 1986 95 annual surge front propagation rate was 1 0 1 8 km a 1 during 1985 89 this rate dropped considerably during 1989 95 and the front became less steep front propagation occurred largely by longitudinal compression and vertical extension of the ice and the effects of over riding appear minor ice velocities were slowe than the average propagation rate of the front the surge affected bakanin breen in four zones upper region where extensiv e flow fast propagation rates and negative vertical strain occurred resulting in widespread crevassing and stranded blocks tens of metres above the post surge ice surface 2 mid glacier region where initial strong compression was associated with ice thickening which started before the arrival of the surge front horizontal strain rates were very low but vertical strain rates were up to 300 mm d 1 as the front passed the horizontal velocity increased and about 500 m behind it became extensive negative vertical strain and ice down draw occurred as ice vclocities dropped 3 surge front where ice velocity w as high but vertical strain remained positive associated with compression 4 lower region below the front where only compression occurred resulting in the formation of a fore bulge a thickening of the ice of up to 50 m above pre surge levels the fore bulge affected the whole 1 7 km below the now halted surge front the glacier has not advanced ba kaninbreen s surge was characterized by a long active phase approximately 10 years low ice velocities and low basal shear stresses compared to glaciers in lower latitudes and an indistinet surge termination

neoglacial lake alsek lowell glacier a large valley glacier in the st elias mountains of southwestern yukon territory advanced across alsek valley and blocked south flowing alsek river many times during the neoglacial interval the resulting lake termed neoglacial lake alsek extended east of the front of the st elias mountains and inundated parts of dezadeash valley that presently are populated lake alsek at its maximum was about 200 m deep at the glacier dam and over 100 km long staircase flights of beaches wave cut benches layers of driftwood and thin lacustrine sediments provide evidence of the former lake giant dunes and flood terraces on the floor of alsek valley indicate that the lake emptied catastrophically when the lowell glacier dam failed several phases of lake alsek have been identified each was preceded and followed by intervals during which the lake was empty and the present southward drainage pattern in alsek valley prevailed historical records radiocarbon and tree ring dates on driftwood and r

is there a single surge mechanism contrasts in dynamics between glacier surges in svalbard and other regions 1 during the 1990s monacobreen a 40 km long tidewater glacier in svalbard underwent a major surge we mapped the surge dynamics using ers synthetic aperture radar images differential dual azimuth interferometry and intensity correlation tracking a series of 11 three dimensional 3 d velocity maps covering the period 1991 1997 show a months long initiation and years long termination to the surge with no indication of a surge front travelling downglacier during the surge the front of the glacier advanced 2 km the velocity and derived strain rate increased by more than an order of magnitude and maximum ice flow rates measured during 1994 were 5 m d 1 the spatial pattern of both velocity and strain rate was remarkably consistent and must therefore be controlled by spatially fixed processes operating at the glacier bed we combine these results with those published in the literature to construct a typical svalbard glacier surge cycle and compare this to surge dynamics of glaciers from other cluster regions especially those of variegated glacier in alaska the strong contrast in dynamics suggests that there exist at least two distinct surge mechanisms

evolution of variegated glacier alaska u s a prior to its surge on presente l evolution saison apres saison des changements dans la geometrie et la vitesse du glacier et on tente de rattacher ces variations a la deformation de la glace et au glissement basal

regional correlation analysis between seismic heterogeneity in the lower mantle and subduction in the last 180 myr implications for mantle dynamics and rheology we have carried out a regional correlation analysis between the seismic structure of the lower mantle and the reconstructions of subduction sites in the past 180 myr with the aim of estimating individual styles of slab motion over different parts of the earth the correlation patterns obtained for three subduction branches west pacific east pacific and alpine himalayan are remarkably different in the west pacific the subducting slabs tend to be stagnant beneath the 660 km discontinuity while basically no subducted lithosphere has been detected below the depth of 1000 km in contrast the lithosphere subducted beneath the americas seems to penetrate through the lower mantle continuously showing correlation peaks at depth intervals of 800 1100 km and 1900 2500 km in the alpine hi malayan region significant correlation has been found below the 660 km discontinuity for recent subduction and in the mid mantle for subduction younger than 120 myr an increase in the correlation close to the core mantle boundary nevertheless indicates that under certain circumstances the slabs can reach the bottom of the mantle in the west pacific and in the alpine himalayan regions as well the correlation peak at a depth of around 1000 km is common to all the subduction branches however its depth rather varies for different subduction zones and thus it is not clear whether this correlation maximum may be associated with a global mid mantle discontinuity

basal conditions beneath a soft bedded polythermal surge type glacier bakaninbreen svalbard original article can be found at http www sciencedirect com science journal 10406182 copyright elsevier ltd and the international union for quaternary research inqua doi 10 1016 s1040 6182 01 00053 2 full text of this article is not available in the uhra

how much do we really know about glacier surging some of the ideas about glacier surging are considered mainly but not entirely in the light of observations of temperate glaciers in alaska u s a made within the last 15 years climate has an influence on surge recurrence interval climate and weather also affect surge initiation termination and magnitude regional studies lead to the speculation that subglacial till plays a key role in surging and it has been found under all surge type glaciers studied so far including black rapids and variegated glaciers alaska in most of the glaciers studied till deformation processes dominate the motion in quiescence the linked cavity model of surge triggering and rapid motion is not consistent with these observations but the limited coverage of the observations does not rule it out under parts of the glaciers studied the till observations in alaska raise old questions about the interaction between till and the hydraulic systems of temperate glaciers the role of stored water which observations show to be active even in winter on black rapids glacier is noted

characteristics of the last five surges of lowell glacier yukon canada since 1948 field observations aerial photographs and satellite images are used to reconstruct the past surges of lowell glacier yukon canada since 1948 based on the timing of terminus advances a total of five surges occurred over this time each with a duration of 1 2 years the time between successive surges ranged from 12 to 20 years and appears to have been shortening over time the relatively short advance and quiescent phases of lowell glacier together with rapid increases in velocity during surges suggest that the surging is controlled by a hydrological switch the 2009 10 surge saw ablation area velocities increase by up to two orders of magnitude from quiescent velocities and the terminus increase in area by 5 1 km 2 and in length by up to 2 85 km this change in area was the smallest since 1948 and follows the trend of decreasing surge extents over time this decrease is likely driven by a strongly negative surface mass balance of lowell glacier since at least the 1970s and means that the current town site of haines junction is very unlikely to be flooded by damming caused by any future advances of the glacier under the current climate regime

multi decadal elevation changes on bagley ice valley and malaspina glacier alaska 1 digital elevation models dems of bagley ice valley and malaspina glacier produced by i intermap technologies inc iti from airborne interferometric synthetic aperture radar insar data acquired 4 13 september 2000 ii the german aerospace center drl from spaceborne insar data acquired by the shuttle radar topography mission srtm 11 22 february 2000 and iii the us geological survey usgs from aerial photographs acquired in 1972 73 were differenced to estimate glacier surface elevation changes from 1972 to 2000 spatially non uniform thickening 10 7 m on average is observed on bagley ice valley accumulation area while non uniform thinning 47 5 m on average is observed on the glaciers of the malaspina complex mostly ablation area even larger thinning is observed on the retreating tidewater tyndall glacier these changes have resulted from increased temperature and precipitation associated with climate warming and rapid tidewater retreat

slow surge of trapridge glacier yukon territory canada 1 trapridge glacier a polythermal surge type glacier located in the st elias mountains yukon territory canada passed through a complete surge cycle between 1951 and 2005 air photos 1951 1981 and ground based optical surveys 1969 2005 are used to quantify the modifications in flow and geometry that occurred over this period yearly averaged flow records suggest that the active phase began 1980 and lasted until 2000 the average velocity in the central area of the glacier went from 16 m yr 1 in 1974 to 39 m yr 1 in 1980 it peaked at 42 m yr 1 in 1984 and remained above 25 m yr 1 until 2001 over that interval the flow decelerated by steps in 4 year pulses after a particularly vigorous acceleration in 1997 1999 the glacier gradually slowed to presurge velocities in 2005 the flow was less than 9 m yr 1 digital elevation models are generated by stereographic analysis of air photos for 1951 1970 1972 1977 and 1981 these models are updated annually using ground based survey data and a novel implementation of bayesian kriging over the course of the surge the front of active ice advanced 450 m and the glacier area increased by 10 with an associated thinning of the ice the previous surge of trapridge glacier starting before 1939 and ending before 1951 led to a terminus advance of 1 km comparison of the two surges suggests that the 1930s surge started with a slow progression similar to what we observed in the 1980s and 1990s and switched to a faster flow mode after 1941 this second phase was never attained in the recent surge probably owing to a lack of mass

glacier surge mechanism 1982 1983 surge of variegated glacier alaska the hundredfold speedup in glacier motion in a surge of the kind the kind that took place in variegated glacier in 1982 1983 is caused by the buildup of high water pressure in the basal passageway system which is made possible by a fundamental and pervasive change in the geometry and water transport characteristics of this system the behavior of the glacier in surge has many remarkable features which can provide clues to a detailed theory of the surging process the surge mechanism is akin to a proposed mechanism of overthrust faulting

mass balance change as a control on the frequency and occurrence of glacier surges in svalbard norwegian high arctic the end of the little ice age lia in svalbard 76 81 n a climate sensitive region at the northern extreme of strong poleward heat transfer was marked by an abrupt increase in mean annual air temperature of up to 5 c around 1920 glacier mass balance has been consistently negative since this time and large cumulative net losses of mass have occurred at most glaciers energy balance modelling confirms the sensitivity of svalbard glaciers to climate change predicting a negative shift in net mass balance of up to 0 8 m a 1 water equivalent per degree temperature rise this climate related shift in glacier mass balance has reduced the intensity of glacier surge activity in svalbard one glacier known to have surged since the end of the lia has since failed to accumulate the mass required to re initiate the surge cycle and is also now cold at its base and incapable of rapid flow by basal sliding three overviews of the total number of actively surging glaciers in svalbard between 1936 90 show a decrease from 18 to 5 this is significant compared with the expected numbers of surges based on lia conditions post lia climate change in svalbard has therefore affected not only glacier extent but also ice dynamics this is trend will probably continue given co2 induced climate warming

surge front propagation and velocities during the early 1993 95 surge of bering glacier alaska u s a from sequential sar imagery the initiation and propagation of the 1993 95 surge of bering glacier alaska u s a was observed using ers 1 synthetic aperture radar sar imagery images were acquired before and during the surge between november 1992 and october 1993 terrain corrected and co registered imagery was used to measure the propagation of the surge front surface undulations interpreted to be evidence of accelerated flow indicating surge initiation in late winter were observed in the 26 march 1993 image from 19 may to 25 august 1993 the mean propagation velocity of the surge front was 90 m d 1 the surge reached the terminus shortly after 25 august 1993 the central area of the calving terminus then advanced into proglacial vitus lake at a mean rate of 19 md 1 between 9 august and 18 october 1993 feature matching was used to measure discrete velocity vectors between 9 august and 13 september the vectors were kriged onto a uniform grid and used to compute the principal strain rates shattering of the calving front and dramatically increased iceberg calving were accompanied by high compressive strain rates immediately up glacier from the calving front

evidence for temporally varying sticky spots at the base of trapridge glacier yukon territory canada during the 1992 summer field season we installed arrays of plough meters and water pressure transducers beneath trapridge glacier yukon territory canada to study hydromechanical coupling at the ice bed interface diurnal signals recorded with two of these ploughmeters appear to correlate with fluctuations in subglacial water pressure these diurnal variations can be explained by changes in basal resistance to sliding as mechanical conditions at the bed vary temporally in response to changes in the subglacial hydrological system we propose that a lubricating water film associated with high water pressures promotes glacier sliding whereas low pressures cause increased basal drag resulting in sticky areas using a theoretical model we analyze the sliding motion of glacier ice over a flat surface having variable basal drag and show that a consistent explanation can be developed results from our model calculations provide strong support for the existence of time varying sticky spots which are associated with fluctuations in subglacial water pressure

extreme storm events landscape denudation and carbon sequestration typhoon mindulle choshui river taiwan we have performed the first known semicontinuous monitoring of particulate organic carbon poc fluxes and dissolved si concentrations delivered to the ocean during a typhoon sampling of the choshui river in taiwan during typhoon mindulle in 2004 revealed a poc flux of 5 00 105 t associated with a sediment flux of 61 mt during a 96 h period the linkage of high amounts of poc with sediment concentrations capable of generating a hyperpycnal plume upon reaching the ocean provides the first known evidence for the rapid delivery and burial of poc from the terrestrial system these fluxes when combined with storm derived co2 consumption of 1 65 108 mol from silicate weathering elucidate the important role of these tropical cyclone events on small mountainous rivers as a global sink of co2