the response of black rapids glacier alaska to the denali earthquake rock avalanches 1 we describe the impact of three simultaneous earthquake triggered rock avalanches on the dynamics of black rapids glacier alaska by using spaceborne radar imagery and numerical modeling we determined the velocities of the glacier before and after landslide deposition in 2002 by using a combination of ers 1 ers 2 tandem radarsat 1 and alos palsar synthetic aperture radar data ice velocity above the debris covered area of the glacier increased up to 14 after the earthquake but then decreased 20 by 2005 within the area of the debris sheets mean glacier surface velocity increased 44 within 2 years of the landslides at the downglacier end of the lowest landslide where strong differential ablation produced a steep ice cliff velocities increased by 109 over the same period by 2007 ice velocity throughout the debris area had become more uniform consistent with a constant ice flux resulting from drastically reduced ablation at the base of the debris without further analysis we cannot prove that these changes resulted from the landslides because black rapids glacier displays large seasonal and interannual variations in velocity however a full stokes numerical ice flow model of a simplified glacier geometry produced a reversal of the velocity gradient from compressional to extensional flow after 5 years which supports our interpretation that the recent changes in the velocity field of the glacier are related to landslide induced mass balance changes

modes of the southern extension of the east madagascar current data sets from satellite observations and a nested high resolution model are used to study a source region of the agulhas current altimeter derived geostrophic surface currents are averaged over varying periods providing evidence of the persistence of flow patterns in the extension of the southern branch of the east madagascar current semc south of madagascar the semc separates into one branch toward the agulhas current and into a second branch retroflecting and connecting to the subtropical indian ocean countercurrent sicc good agreement is found between long term mean patterns of observational and model dynamic heights two basic modes are identified in the semc extension with anticyclonic motion favoring retroflection in the northern mozambique basin when the extension is in a southwestward direction and cyclonic motion occurring in the case of the semc flowing westward along the southern madagascar slope a cross correlation sequence between model semc transports and the modal changes in the extension region displays a correlation at about 1 month lag which agrees with eddy propagation time from the semc to the outflow region mean model semc transports are determined using floats released at 21 degrees s and the contribution of the semc to the sicc is obtained using floats injected at 55 degrees e with the model running backward almost half of the semc volume transport contributes to the agulhas system and about 40 of sicc water originates from the semc

micronekton distributions and assemblages at two shallow seamounts of the south western indian ocean insights from acoustics and mesopelagic trawl data micronekton distributions and assemblages were investigated at two shallow seamounts of the south western indian ocean using a combination of trawl data and multi frequency acoustic visualisation techniques la perouse 60 m seamount is located on the outskirts of the oligotrophic indian south subtropical gyre province with weak mesoscale activities and low primary productivity all year round the mad ridge seamount thus termed in this study 240 m is located in the productive east african coastal eafr province with high mesoscale activities to the south of madagascar this resulted in higher micronekton species richness at mad ridge compared to la perouse resulting productivity at mad ridge seamount was likely due to the action of mesoscale eddies advecting larvae and productivity from the madagascar shelf rather than local dynamic processes such as taylor column formation mean micronekton abundance biomass as estimated from mesopelagic trawl catches were lower over the summit compared to the vicinity of the seamounts due to net selectivity and catchability and depth gradient on micronekton assemblages mean acoustic densities in the night shallow scattering layer ssl 10 200 m over the summit were not significantly different compared to the vicinity within 14 nautical miles of mad ridge at la perouse and mad ridge the night and day ssl were dominated by common diel vertical migrant and non migrant micronekton species respectively while seamount associated mesopelagic fishes such as diaphus suborbitalis la perouse and mad ridge and benthosema fibulatum performed diel vertical migrations dvm along the seamounts flanks seamount resident benthopelagic fishes including cookeolus japonicus mad ridge were aggregated over mad ridge summit both during the day and night before sunrise mid water migrants initiated the first vertical migration event from the intermediate to the deep scattering layer dsl la perouse 500 650m mad ridge 400 700 m or deeper during sunrise the other taxa contributing to the night ssl exhibited a successive series of vertical migration events from the surface to the dsl or deeper some scatterers were blocked in their upward and downward migrations due to the seamount topography more commonly known as the sound scattering layer interception topographic blockage hypothesis possible mechanisms leading to the observed patterns in micronekton vertical and horizontal distributions are discussed this study contributes to a better understanding of how seamounts influence the diel vertical migration horizontal distribution and community composition of micronekton and seamount associated resident species at two poorly studied shallow topographic features in the south western indian ocean

seismic stratigraphic framework and depositional history for cretaceous and cenozoic contourite depositional systems of the mozambique channel sw indian ocean this study describes previously unrecognized contourite depositional systems cdss in the mozambique channel which constrain palaeoceanographic models for this area the stratigraphic stacking patterns record nine seismic units su1 to su9 separated by eight major discontinuities a to h oldest to youngest key seismic markers in cds evolutionary history occur during aptian albian 122 ma late cenomanian 94 ma early 38 2 36 2 ma and late 25 23 ma oligocene and early middle miocene 17 15 ma epochs these record onset 122 to 94 ma growth 94 to 25 23 ma maintenance 25 23 to 17 15 ma and burial 17 15 ma to the actual time stages for cdss cdss first develop during the onset stage which coincides with the opening and deepening of the african southern ocean gateway at 122 and 100 ma respectively the growth stage beginning in the late cenomanian 94 ma correlates with the opening and deepening of the equatorial atlantic gateway during the growth stage two major shifts in sedimentary stacking pattern occur which coincide with palaeoceanographic changes during the early 38 2 36 2 ma and late 25 23 ma oligocene these in turn coincide with the onset and local enhancement of antarctic water masses cds growth continued until the early middle miocene during the maintenance stage 17 15 ma most cds growth ceased at the end of the maintenance stage circulation of the north atlantic water mass into the southern hemisphere led to a deepening of antarctic water masses in the area

long term observations of transport eddies and rossby waves in the mozambique channel data from an array of current meter moorings covering a period of two and a half years are used to estimate the varying transport through the mozambique channel the total transport during this period is small below 1200 m the transport is weak but a prominent deep western boundary undercurrent with cores at 1700 and 2200 m is found that transports 1 5 sv to the north the transport shows a large temporal variability and neither a continuous upper layer western boundary current nor a continuous deep undercurrent is found the variability in the upper layer is dominated by a period of 68 days and results mainly from eddies that migrate southward through the mozambique channel in addition to this southward propagation a westward propagating signal is evident from a space time diagram of the throughflow the signal is interpreted as a mozambique channel rossby normal mode this interpretation is consistent with results from a principal oscillation pattern analysis that estimates normal modes from the data and a quasi geostrophic channel model a detailed inspection of a single eddy event shows that a precursor of an anticyclone is a strong southward current along the madagascar coast that propagates westward to the center of the channel during the westward propagation the current becomes unstable inducing an anticyclone this scenario connects the westward propagating mode with the eddy growth and explains the coincidence of the eddy and rossby mode frequency

remote sensing based analysis of the 1996 surge of northern inylchek glacier central tien shan kyrgyzstan the evolution of northern inylchek glacier and its proglacial lake upper lake merzbacher during its 1996 surge and the surrounding decades is analyzed with remote sensing imagery overall retreat of the glacier from 1943 to 1996 enlarged the lake to 4 km long and 100 m deep the surge in 1996 initiated between 12 september and 7 october and advanced the glacier by 3 7 km to override most of upper lake merzbacher the surge phase probably ended in december 1996 and involved mean flow velocities across the lower trunk of the glacier that reached 50 m d 1 over a 32 day period water displaced by the surge from upper lake merzbacher totalling 1 5 108 m3 in volume accelerated filling of lower lake merzbacher downvalley and helped trigger this marginal ice dammed lake to outburst in a jokulhlaup around late november early december the characteristics and duration of the surge render it as similar to temperate glacier surges elsewhere it may have been facilitated by low basal friction caused by water saturated sediments in the upper lake bed furthermore bathymetric measurements show that the surge evacuated much sediment into the upper lake causing its depth to reduce from 20 to 30 m in 1996 to 8 m by 2005 and 2 m by 2011 the corresponding deposition rates imply glacier catchment specific mean sediment yields of 1 4 to 3 4 103 mg km 2 a 1 in the years after the surge our study documents novel interactions within a cascade system of glaciers and lakes that exhibits surging and outburst flood behavior

in situ measured current structures of the eddy field in the mozambique channel abstract circulation and the related biological production have been studied during five cruises conducted in the mozambique channel mzc between 2005 and 2010 the circulation in the mzc is known to be highly turbulent favouring enhanced primary production as a result of mesoscale eddy dynamics and connectivity throughout the channel due to the variable currents associated with migrating eddies this paper presents the results of in situ measurements that characterize the horizontal and vertical currents in the surface and subsurface layers 0 500 m the in situ data were analysed together with the geostrophic eddy field observed from satellite altimeter measurements different circulation regimes were investigated including the classical anticyclonic eddy generated at the channel narrows 16 s the enhancement of southward migrating eddies by merging with structures both cyclonic and anticyclonic formed in the east of the channel and the presence of a fully developed cyclonic eddy at the channel narrows comparison between in situ measurements s adcp and velocities derived from surface drifters and the geostrophic current derived from sea surface height measurements indicated that the latter can provide a reliable quantitative description of eddy driven circulation in the mzc with the exception that these currents are weaker by as much 30 it is also suggested from in situ observation drifters that the departure from geostrophy of the surface circulation might be linked to strong wind conditions finally our observations highlight that a geostrophic currents need to be considered in future research to facilitate a more comprehensive description of the circulation in this area

the influence of bottom currents on the zambezi valley morphology mozambique channel sw indian ocean in situ current observations and hydrodynamic modelling abstract mixed turbidite contourite systems can be found in oceans where bottom currents and turbidity currents interact the zambezi turbidite system located in the mozambique channel sw indian ocean is one of the largest sedimentary systems in the world in length and area of the related catchments the oceanic circulation in the mozambique channel is intense and complex dominated by eddies flowing southwards and deep currents flowing northwards along the mozambican margin current measurements obtained from moorings at 3400 4050 m water depth in the zambezi and tsiribihina valleys show periods of intense currents at the seafloor with peaks of 40 50 cm s 1 that last up to one month and are not related to turbidity currents these strong bottom current events are correlated with a change in current direction and an increase in temperature the periods of current intensification may be related to eddies since they present similar frequencies around 7 per year moreover modelling results show that during periods of intense deep circulation an anticyclonic eddy is present between the mozambican slope and the centre of the mozambique channel which may block the northward transport of the deep water mass and thus enhance the southward transport along the western slope of madagascar according to our hydrodynamic modelling of the circulation near the seafloor intense currents are often present along the zambezi valley especially along the valley flanks multi channel seismic reflection data show that the zambezi turbidite system does not show the typical characteristics of turbidite systems being dominated by erosional processes which mainly affect the valley flanks levees associated with the valley are absent in the main axis of the system the effect of bottom currents on sedimentation in the basin is evidenced by the low sedimentation rates that witness winnowing in the basin the presence of contouritic sand in the zambezi valley flanks and the abundance of current related bedforms observed in multibeam bathymetry and seismic data the intense oceanic processes observed in the mozambique channel may transport a large part of the fine sediment out of the basin and erode the seafloor even at great depths therefore the zambezi turbidite system could at present be considered as a mixed turbidite contourite system with important implications for source to sink studies

topographic controls on the surging behaviour of sabche glacier nepal 1967 to 2017 abstract using a combination of landsat pleiades and corona satellite imagery from 1967 to 2017 we map changes in the terminus position ice surface velocity and surface elevation of sabche glacier and report the first observations of surging behaviour in central nepal our observations show that sabche glacier surged four times over the last 50 years the three most recent surges occurred at 10 to 11 year cycles which is one of the shortest surge cycles ever recorded detailed analysis of the most recent surge 2012 onwards indicates that the glacier advanced 2 2 km and experienced maximum velocities of 1 6 0 10 m day 1 during this surge there was a surface elevation gain at the terminus of up to 90 6 19 m a 1 with a corresponding surface lowering of between 10 6 19 and 60 6 19 m a 1 3 km up glacier of the terminus this transfer of mass amounted to a volume of 2 7 107 0 1 107 m3a 1 sabche glacier is the first surge type glacier to be observed in the central himalayas but this is consistent with a previous global analysis which indicates that surge type glaciers should exist in the region we hypothesise that the surge is at least partially controlled by subglacial topography whereby a major subglacial overdeepening and constriction 3 km up glacier of the terminus provides resistance to glacier flow from the accumulation area to the ablation area this overdeepening appears to store mass until a threshold is crossed after which the glacier flows out of the subglacial depression and rapidly surges over a bedrock lip and down the valley thus whilst the surges are likely to be facilitated by subglacial processes e g changes in subglacial hydrology and or basal thermal regime the topographic setting of the glacier appears to be modulating both the timing and duration of each surge

interaction of dipole eddies with the western continental slope of the mozambique channel abstract sea level anomaly sla data were used to track a southward propagating eddy dipole along the western slope of the mozambique channel over some 6 months in april 2005 this dipole with the cyclone to the south was close to the continental slope off southern mozambique the contact zone between the contra rotating vortices and the slope was surveyed by ship using onboard s adcp and ctd lines the data showed strong 1 4 m s 1 southward geostrophic currents over the slope adjacent to the anticyclone with horizontal divergence over the shelf edge significant slope upwelling between the dipole and the shelf was evident concomitant with enhanced nutrient and chlorophyll levels enriching shelf near surface waters satellite observations depicted a 300 km long surface chlorophyll filament extending offshore in the frontal zone between the contra rotating vortices a satellite tracked drifter deployed at the coastal base of this filament confirmed the offshore advection of chlorophyll enriched shelf water which ultimately wrapped around the cyclone and filling its centre the slope upwelling was also clearly evident in hourly temperature data collected by a recorder deployed on a nearby reef zambia reef in a depth of 18 m according to the sla data the dipole took several weeks to pass zambia reef causing prolonged bouts of upwelling that finally ceased when it left the continental slope and moved southwards into the open ocean further analysis showed that lone anticyclones and cyclones against the mozambique continental shelf also induce slope upwelling as a result of horizontal divergence created by the radial circulation of the vortex in the case of cyclones the divergence occurs north of the contact zone overall this case study confirms that eddies moving southwards along the western side of the mozambique channel are the main mechanism for pumping nutrients into the otherwise oligotrophic surface waters and moreover provide a vigorous mechanism for shelf open ocean exchange

hummocky debris landforms in the chapursan valley karakoram range pakistan a glacio geomorphological investigation this paper contributes to the discussion on the development of hummocky debris landforms by gradual versus catastrophic processes in high mountain areas it focuses on the upper chapursan valley karakoram range pakistan in which the valley floor and adjacent sediment cones are covered with an outstanding hummocky debris landscape over a length of about 10 km and a width of up to 1 km with individual hummocks reaching about 10 m in height these landforms overlap with the zone of permanent settlement according to local legends and reports of early travellers in this region one of the largest settlement concentrations formerly occurred in the upper chapursan valley and was destroyed by a natural disaster in order to study the formation of the debris landforms in more detail geomorphological field investigations sedimentological studies a comparison of satellite images an analysis of historical data and interviews with the local inhabitants have been carried out the results show that complex geomorphological processes consisting of a glacier advance and followed by glacier lake outbursts and ice avalanches have contributed to the formation of the hummocky debris landforms the kit ke jerav and yishkuk glaciers seem to have experienced extraordinary fluctuations in historical and recent times

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

climate forcing and the initiation of glacier advance during mis 2 in the north sikkim himalaya india abstract the present study investigates the relics of the most extensive glacier advances and their retreat in the transitional climatic zone of the chopta valley northern sikkim himalaya with an aim to understand the forcing factors the optically stimulated luminescence osl dating of the stratigraphically oldest glacier advance and its retreat in the chopta valley revealed that the glacier advanced at 28 2 8 ka and sustained through the global last glacial maximum glgm 26 5 ka and 19 ka mix et al 2001 the deglaciation is manifested by recessional moraine ridge dated at 18 2 2 ka comparing the results of the present study with the existing glacial chronologies from the himalayan region it has been observed that irrespective of the geographical locations the intensified mid latitude westerlies during the glgm and the associated decrease in winter temperature was the major driver of glacier advance during the mis 2

eddies in the southern mozambique channel abstract the agulhas current system contains one of the world s strongest western boundary currents and plays an important part in the warm water path of the global thermohaline circulation however there have been few surveys of the source regions of the agulhas current and thus little in situ measurement of their variability utilizing the more than 5 year record of seawifs data we examine the eddy activity present in the southern portion of the mozambique channel the two sources of agulhas input from the central indian ocean southward flow through the mozambique channel and westward flow around the southern limit of madagascar both show great temporal variability with no clear seasonal signal a number of large 200 km diameter anticyclonic rings intermittently propagate poleward along the western edge of the channel sweeping coastal waters into mid channel their passage past maputo appears to affect the circulation of the lee eddy in the delagoa bight the eastern side of the channel is mainly characterized by cyclonic eddies these are made manifest in the lee of the southern tip of madagascar although it is not clear whether many form there or just develop a visible presence due to entrainment of high chlorophyll coastal waters several of these cyclonic eddies then appear to move in west southwesterly direction the chlorophyll data do reveal the apparent east madagascar retroflection on occasions but do not show clear examples of the pinching off of anticyclonic eddies however surface waters from the east madagascar current may reach the african mainland on occasions when no retroflection is present

rapid advance of two mountain glaciers in response to mine related debris loading rapid glacier advance is known to occur by a range of mechanisms however although large scale debris loading has been proposed as a process for causing rapid terminus advance it has rarely been observed we use satellite remote sensing data to observe accelerated glacier terminus advance in response to massive supraglacial loading on two glaciers in kyrgyzstan over a 15 year period mining activity has led to the dumping of spoil of up to 180 m thick on large parts of these valley glaciers we find that the termini of these glaciers advance by 1 2 and 3 2 km respectively at a rate of up to 350 m yr 1 our analysis suggests that although enhanced basal sliding could be an important process massive supraglacial loads have also caused enhanced internal ice deformation that would account for most or all of the glacier terminus advance in addition narrowing of the glacier valley and mining and dumping of ice alter the mass balance and flow regime of the glaciers although the scale of supraglacial loading is massive this full scale experiment provides insight into glacier flow acceleration response where small valley glaciers are impacted by very large volumes of landslide debris

surge of hispar glacier pakistan between 2013 and 2017 detected from remote sensing observations abstract this study analyses the behaviour of an actively surging glacier hispar in pakistan using remote sensing methods we used 15 m panchromatic band of landsat 8 oli from 2013 to 2017 to assess the changes in glacier velocity glacier geomorphology and supraglacial water bodies for the velocity estimation correlation image analysis cias was used which is based on normalized cross correlation ncc of satellite data on screen digitization was employed to quantify changes in the glacier geomorphology and dynamics of supraglacial water bodies on the glacier our velocity estimates indicate that the upper part of the glacier is presently undergoing an active surge which not only affects the debris distribution but also impacts the development of supraglacial water bodies velocities in the actively surging part of the main glacier trunk and its three tributaries reach up to 900 m yr 1 the surge of hispar also impacts the distribution of supraglacial debris causing folding of the medial moraines features present on the glacier surface changes in the number and size of supraglacial lakes and ponds were also observed during the observation period from 2013 to 2017

detailed characterization of a cold antarctic eddy 1 eddy formation in the southern ocean plays a critical role in meridional exchanges of heat and salt it has also been shown to have a significant impact on primary productivity and on the creation of preferred feeding regions for birds and other predators this eddy formation is not geographically uniform but is concentrated in certain specific regions particularly where the antarctic circumpolar current crosses shallow bathymetry one such region is at the south west indian ridge where eddies are formed that subsequently drift past the prince edward islands we have studied such an eddy in detail it was at least 1000 m deep had a radius of 60 90 km a heat content of 5 40 1019 j and rotated at a rate of 1 revolution every 5 days altimetric observations show that it was formed at 51 s 32 e and that its intensity as expressed as its sea level anomaly declined by 40 of the original value within 144 days this relatively rapid dissipation suggests that these eddies do not have a lifetime of more than 14 months during that period they will have carried their anomalous heat and salt content about 1 5 degrees of latitude

multiple origins of large hummock deposits in alai valley northern pamir implications for palaeoclimate reconstructions abstract this paper interprets the origin of several of the largest hummocky landform assemblages in the alai valley northern pamir a formerly glaciated intermontane depression the vast hummocky deposits in the koman suu and achik tash river catchments are found to be of two contrasting modes of formation glacial hummocks deposited during koman and lenin glaciers withdraw and avalanche hummocks produced during catastrophic koman and lenin rock avalanches the origins of the deposits we assessed through remote and field based geomorphological mapping as well as sedimentological investigations which included clast analysis and the identification of micro scale agglomerates indicative of rock avalanche emplacement both the koman and lenin rock avalanches were large catastrophic events with run outs of 34 and 24 km respectively and a volume over 1 109 m3 each that occurred subsequent to glacier withdrawal from the area the complex conditions on the moment of the rock avalanche emplacement promoted unusual deposits geomorphology and extensive run outs the landslide landforms formed over the pre existing glacial hummocks and fluvial deposits and are geomorphologically and sedimentologically distinct from the larger glacial hummocks the reconstruction of this sequence of events has implications for how hummock dating should be interpreted this research illustrates large scale catastrophic landsliding in the glacial environment and adds to the ongoing debate about the misidentification of rock avalanche deposits as of glacial origin and their relevance to palaeoclimatological and palaeoseismological reconstructions

observed characteristics of mozambique channel eddies 1 the flow in the mozambique channel is dominated by large southward propagating anti cyclonic eddies as opposed to a steady western boundary current these mozambique channel eddies feed their waters into the agulhas current system where they are thought to have a significant influence on the formation of the natal pulse and agulhas ring shedding here we use in situ hydrographic and nutrient data together with satellite altimetry and surface velocity profilers to provide a detailed characterization of the mozambique channel eddies two warm eddies in the channel at 20 s and 24 s had diameters of over 200 km they rotated anti cyclonically with a tangential velocity of over 0 5 m s 1 vertical sections show that the eddies reached to the bottom of the water column relative to the surrounding waters the features were warm and saline the total heat and salt anomalies for the southernmost eddy were computed relative to a reference station close by at 24 s the total anomalies were 1 3 1020 j and 6 9 1012 kg respectively being on par with agulhas rings mozambique channel eddies thus have the potential to form a major contribution to the southward eddy heat flux in the agulhas current system the feature also had positive nutrient and negative oxygen anomalies the large magnitude of the water mass anomalies within the eddy suggests that interannual variability in mozambique channel eddy numbers would have a significant impact on downstream water mass characteristics

sedimentation patterns off the zambezi river over the last 20 000 years marine sediments from continental margins provide high resolution archives of marine and continental climate in particular near large river mouths the zambezi is one of the largest rivers in east africa discharging large amounts of fine grained sediments onto the western margin of the mozambique channel accurate reconstructions of past variations in river discharge can be retrieved from the depositional history of riverine sediments in this study sedimentation patterns along the mozambique margin are inferred from a series of sediment cores spanning the last 20 kyr these cores were retrieved off the zambezi mouth from the shelf and from various depths at the continental slope to provide detailed information on the depositional history of this region high resolution x ray fluorescence and magnetic susceptibility core scanning measurements as well as grain size distributions of the lithogenic sediment fraction and organic matter and carbonate content analyses resolve centennial millennial timescale variations in sediment transport and deposition along the mozambique margin largest changes in lithogenic sediment deposition coincide with the flooding of the mozambique shelf due to deglacial sea level rise and changes in oceanic currents fine grained mainly zambezi sediments were no longer primarily deposited south of the zambezi mouth but increasingly deposited onto the mozambique shelf and transported northwards over the shelf before spilling over to the slope in addition flooding of the shelf initiated remobilization and down slope transport of coarse grained winnowed sediments the heinrich event 1 and younger dryas are clearly indicated as events of increased fine grained sediment deposition along the mozambique margin possibly linked to increased riverine runoff from the zambezi catchment which is in harmony with a southward shift of the intertropical convergence zone itcz and associated african rainfall belts causing wetter conditions this study illustrates that interpreting marine and continental climate proxy records in the vicinity of river deltas in terms of climate change requires proper consideration of sea level and oceanic circulation induced effects on the transport and deposition patterns of fine grained sediments at continental slopes

the january 2018 to september 2019 surge of shisper glacier pakistan detected from remote sensing observations abstract this study analysed the actively surging shisper glacier in the karakoram region of pakistan using earth observation data from landsat 8 oli and planet images changes in the surface glacier velocity supraglacial moraines and debris cover were assessed using landsat 8 data at monthly time steps from january 2018 to may 2019 high resolution data from planet labs was used to precisely detect the snout advance and ice dammed lake expansion downstream cross section profiles of the valley were generated using a moderate resolution digital elevation model to assess the inundation in the event of rapid ice dammed lake drainage correlation image analysis software working on the principle of normalized cross correlation was used to generate time series monthly surface velocity profiles for shisper glacier manual digitization at 1 30000 scale was used to delineate supraglacial moraines and supraglacial debris cover the glacier surface velocity profiles indicate that the ablation zone of the glacier continues to be in an active surge phase resulting in advance of the snout and expansion of the ice dammed lake surface glacier velocities are as high as 48 m d 1 between 18 december 2018 and 8 may 2019 the glacier snout advanced at 6 m d 1 with a total overall advance of 860 m the lake formed due to damming of an outflow stream from mochowar glacier expanded to its maximum area 29 69 ha in may 2019 before drainage started on 23 june 2019 our estimates indicate that the peak discharge in case of rapid drainage could vary between 5033 m3 s 1 and 6167 m3 s 1 and potentially affect infrastructure downstream

machine learning classification of debris covered glaciers using a combination of sentinel 1 2 sar optical landsat 8 thermal and digital elevation data abstract debris cover on glacier surfaces hampers the accurate detection of debris covered ice using traditional techniques based on image band ratios therefore this study tests a new automatic classification scheme for hierarchical mapping of glacier surfaces based on machine learning classifiers including k nearest neighbors knn support vector machine svm gradient boosting gb decision tree dt random forest rf and multi layer perceptron mlp several raster layer combinations synthetic aperture radar sar coherence image derived from sentinel 1 data visible near infrared to short wave infrared bands from sentinel 2 thermal information from landsat 8 and geomorphometric parameters from the advanced land observing satellite alos world 3d 30 m mesh aw3d30 digital elevation model were tested to delineate the debris covered glaciers in the gilgit baltistan pakistan and shaksgam valley china the highest over classification accuracy 97 was obtained using the rf classifier followed by the gb and svm with radial basis function kernel and utilizing all of the multisensor sentinel landsat alos data notably the rf classifier showed to be robust to parameter settings fast and accurate for mapping debris covered ice gb classifier showed similar performance as rf despite it has a moderately lower accuracy compared to rf although svm classifier has a slower in the speed of tuning hyper parameter it still performs the third best classification accuracy as the multisensory data we used is freely and near globally available our methodology potentially could be applied for precise delineation of debris covered glaciers in other areas

how do glaciers surge a review the quasi periodic oscillations between normal and fast motion exhibited by surge type glaciers provide the best observational opportunity to determine limiting conditions that allow fast motion the measurements from variegated glacier prove that its surge motion is caused by rapid sliding induced by high water pressure this arises from a major restructuring of the basal hydraulic system which impedes water discharge prior to and during surge although the evolving glacier geometry and stress distribution play a principal enabling role the seasonal timing of two distinct surge pulses each initiated in winter and terminated in summer indicates a major influence from variable external water inputs this influence is not considered in existing surge models and should promote caution in the use of data from temperate and subpolar surge type glaciers to deduce surge potential in polar ice masses the spatial spreading of surge motion from a zone of local initiation occurs by stress redistribution which may spread the surging zone rapidly upglacier or downglacier inside a region of active ice and by mass redistribution with compressional thickening at the surge front which enables down glacier propagation into less active ice the data from other surge type glaciers including the extensive data from medvezhiy glacier are not inconsistent with the above processes but are inadequate to establish whether completely different mechanisms operate in some surges the way by which water accumulates and produces fast sliding is not established in detail for any surge type glacier and may be different on different glaciers depending for example on the presence or absence of unconsolidated debris between the ice and rock

mesoscale activity in the comoros basin from satellite altimetry and a high resolution ocean circulation model recently it has been shown that anticyclonic eddies are generated in the comoros basin contesting the long held notion of a single large anticyclonic cell the comoros gyre limited knowledge exists about the mesoscale activity within the basin a potential key source of variability for the mozambique channel and subsequently the agulhas current in this paper an automated eddy tracking scheme applied to satellite altimetry data and a high resolution model simulation is used to determine the characteristics of the anticyclonic eddies generated in the comoros basin the generation and characteristics of cyclonic eddies are also investigated the eddy tracking scheme revealed that anticyclonic eddies are primarily generated west of the tip of madagascar due to barotropic instabilities whereas cyclonic eddies are mainly generated along the northwest coast of madagascar as a result of baroclinic instabilities anticyclonic eddies with a mean lifespan of about 3 months reside in the basin for half their lifespan before propagating into the mozambique channel on the other hand the majority of cyclonic eddies with a similar mean lifespan dissipate within the basin initially the anticyclones with translation speeds of 6 8 km d 1 and mean radii of 80 100 km follow the trajectory of the north east madagascar current and turn south upon reaching the african coast the cyclonic eddies tend to be smaller 60 km and have slower translation speeds 2 5 3 5 km d 1 than their anticyclonic counterparts

a surge of bualtar glacier karakoram range pakistan a possible landslide trigger bualtar glacier karakoram range northern pakistan surged during the spring and early summer of 1987 this followed a major episode of three landslides which impacted part of the glacier ablation zone on 30 31 july 1986 in may 1987 surface velocities of 7 m d 1 were measured at one profile down glacier from the landslide deposits where in 1986 velocities were an order of magnitude less surface and hydrological characteristics of the glacier in and down glacier from the landslide deposit were also indicative of surge like behavior in 1987 and a return to pre surge conditions by 1988

geomorphology avalanches and moraines the waiho loop moraine in new zealand s southern alps had long been viewed as a southern icon of a recent glacier response to cooling climate possibly the younger dryas cold event but a closer look has implicated a landslide in this particular glacial advance

a general theory of glacier surges we present the first general theory of glacier surging that includes both temperate and polythermal glacier surges based on coupled mass and enthalpy budgets enthalpy in the form of thermal energy and water is gained at the glacier bed from geothermal heating plus frictional heating expenditure of potential energy as a consequence of ice flow enthalpy losses occur by conduction and loss of meltwater from the system because enthalpy directly impacts flow speeds mass and enthalpy budgets must simultaneously balance if a glacier is to maintain a steady flow if not glaciers undergo out of phase mass and enthalpy cycles manifest as quiescent and surge phases we illustrate the theory using a lumped element model which parameterizes key thermodynamic and hydrological processes including surface to bed drainage and distributed and channelized drainage systems model output exhibits many of the observed characteristics of polythermal and temperate glacier surges including the association of surging behaviour with particular combinations of climate precipitation temperature geometry length slope and bed properties hydraulic conductivity enthalpy balance theory explains a broad spectrum of observed surging behaviour in a single framework and offers an answer to the wider question of why the majority of glaciers do not surge

structure and origin of the subtropical south indian ocean countercurrent 1 the structure of the subtropical south indian ocean countercurrent sicc is revealed by altimeter derived absolute geostrophic surface velocities it is a narrow eastward flowing current between 22 and 26 s confined to planetary wave trains which propagate westward through the indian ocean multi year averaging identifies it as a well defined current between madagascar and 80 e continuing with lower intensity between 90 and 100 e it virtually coincides with the northern limit of subtropical underwater subduction geostrophic currents from hydrographic sections closely correspond to these surface patterns volume transports of the countercurrent down to 800 dbar are of order 107 m3 s 1 evidence is provided for a narrow branch of the south equatorial current sec approaching madagascar near 18 s and feeding the southern east madagascar current emc which appears to continue westward around the southern tip of madagascar it then partially retroflects and nourishes the sicc

glacier velocities across the central karakoram optical matching of aster advanced spaceborne thermal emission and reflection radiometer satellite image pairs is used to determine the surface velocities of major glaciers across the central karakoram the aster images were acquired in 2006 and 2007 and cover a 60 120 km region over baltoro glacier pakistan and areas to the north and west the surface velocities were compared with differential global position system gps data collected on baltoro glacier in summer 2005 the aster measurements reveal fine details about ice dynamics in this region for example glaciers are found to be active over their termini even where they are very heavily debris covered the characteristics of several surge type glaciers were measured with terminus advances of several hundred meters per year and the displacement of trunk glaciers as surge glaciers pushed into them this study is the first synthesis of glacier velocities across this region and provides a baseline against which both past and future changes can be compared

characterisation of mesoscale features and phytoplankton variability in the mozambique channel abstract variability of hydrographic characteristics and phytoplankton distribution associated with mesoscale eddies in the mozambique channel was investigated during four cruises in september 2007 december 2008 november 2009 and april may 2010 satellite altimetry was used to map the location of mesoscale features and together with etopo1 bathymetry was used in a discriminant function analysis to classify in situ sampling stations into five categories namely cyclonic c anti cyclonic a frontal f divergence d and shelf s fluorescence profiles were integrated through four depth ranges in the upper 200 m and used to determine the depth of the maximum chlorophyll a concentration and to model the euphotic zone depth at a depth of 100 m distinctly different hydrographic characteristics were observed between mesoscale features with cyclonic eddies consisting of subtropical surface water and anti cyclonic eddies containing tropical surface water from the indian ocean hydrographic properties at divergence and frontal stations reflected a mixture of these water masses while shelf stations showed considerable variability as a result of the interaction of eddies with the continental slope chlorophyll a concentrations in the surface waters were found to be low with subsurface levels being significantly greater phytoplankton biomass in cyclonic and anti cyclonic eddies was relatively low and not significantly different the interaction of mesoscale eddies with the continental slope on the western side of the channel caused upwelling of cooler nutrient rich water which resulted in elevated phytoplankton biomass in the shelf regions strong currents at the perimeters of these eddies produced offshore advection of the high biomass into the frontal regions

interactions between rock avalanches and glaciers in the mont blanc massif during the late holocene rock avalanches are common in the mont blanc massif which is bordered by valleys with large resident and tourist populations and important highways this paper combines historical data with detailed geomorphological mapping stratigraphic observation and absolute and relative dating to interpret several deposits resulting from rock avalanching onto glaciers nineteen rock falls and rock avalanches are described ranging in volume from 10 000 m3 to 10 106 m3 they occurred between 2500 bp and ad 2007 at six sites the events at three sites miage and drus glaciers and tour des grandes jorasses are characterised by short travel distances those at brenva triolet and frebouge glaciers exhibit excessive travel distances interactions between rock avalanches and glaciers are of four types i rock avalanche triggering where glacial and paraglacial controls include debuttressing of rockwalls due to glacier thinning and retreat oversteepening of rock slopes by glacial erosion and effects of glaciers on permafrost ii rock avalanche mobility in which mobility and travel distance are modified by channelling of rock avalanche debris by moraines and valleys incorporation of ice and snow often 50 for large events and irregularities on the glacier surface iii deposit sedimentology where melting of incorporated ice transforms the final deposit by reducing its thickness typically to 5 m and debris of variable thicknesses is juxtaposed in a hummocky deposit with chaotic piles of angular rock debris and iv glacier dynamics where insulating debris deposited upon a glacier produces a debris covered glacier of different dynamics and high elevated scars can favour the formation of small glaciers

characteristics of the near surface currents in the indian ocean as deduced from satellite tracked surface drifters part i pseudo eulerian statistics using the 1985 2013 record of near surface currents from satellite tracked drifters the pseudo eulerian statistics of the near surface circulation in the indian ocean io are analyzed it is found that the distributions of the current velocities and mean kinetic energy mke in the io are extremely inhomogeneous in space and nonstationary in time the most energetic regions with climatologic mean velocity over 50cms 21 and mke over 500cm 2 s 22 are found off the eastern coast of somalia with maxima of over 100cms 21 and 1500cm 2 s 22 and the equatorial io associated with the strong annually reversing somalia current and the twice a year eastward equatorial jets high eddy kinetic energy eke is found in regions of the equatorial io western boundary currents and agulhas return current with a maximum of over 3000cm 2 s 22 off the eastern coast of somalia the lowest eke 500cm 2 s 22 occurs in the south subtropical gyre between 308 and 408s and the central eastern arabian sea annual and semiannual variability is a significant fraction of the total eke off the eastern coast of somalia and in the central eastern equatorial io in general both the mke and eke estimated in the present study are qualitatively in agreement with but quantitatively larger than estimates from previous studies these pseudo eulerian mke and eke fields based on the most extensivedrifterdatasettodate arethemostpreciseinsituestimatestodateandcanbeusedtovalidatesatellite and numerical results

variability and coherence of the agulhas undercurrent in a high resolution ocean general circulation model abstract the agulhas current system has been analyzed in a nested high resolution ocean model and compared to observations the model shows good performance in the western boundary current structure and the transports off the south african coast this includes the simulation of the northward flowing agulhas undercurrent it is demonstrated that fluctuations of the agulhas current and undercurrent around 50 70 days are due to natal pulses and mozambique eddies propagating downstream a sensitivity experiment that excludes those upstream perturbations significantly reduces the variability as well as the mean transport of the undercurrent although the model simulates undercurrents in the mozambique channel and east of madagascar there is no direct connection between those and the agulhas undercurrent virtual float releases demonstrate that topography is effectively blocking the flow toward the north

slope failure and denudation in the western himalaya slope failures glaciers and rivers constitute the three main agents of denudation in the himalaya failure of slopes is strongly controlled by bedrock geology especially at plate terrane boundaries although climatic and seismic controls of failure also occur slope failure complexes in the western himalaya studied for this report include the pakhar kaghan nanga parbat and atabad hunza areas with 23 different slope failures reported within all the complexes quantification of denudation by mass movement requires measurement of volumes and determination of timing of sediment emplacement and removal where possible to obtain better data on recurrence intervals and total geomorphic work performed in formation of the landscape the relation of mass movement to overall denudation by glaciers and rivers and its role in catastrophic floods and debris entrainment is assessed

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

catastrophic landslides glacier behaviour and moraine formation a view from an active plate margin the influence of large bedrock landslides rock avalanches on the behaviour of glaciers is incompletely recognised here we present an example from an active tectonic margin in south island new zealand where large earthquakes leave a significant imprint on glacial records we demonstrate that terminal moraines on the western side of the southern alps record both ordinary i e climate driven and landslide initiated glacial advances following consideration of the processes involved in rock avalanche initiated moraine construction we suggest ways of determining the nature of the advance that built the terminal moraine the implications of these observations are important in breaking the conventional linkage of individual terminal moraines with climate forcing

effects of rock avalanches on glacier behaviour and moraine formation although large rock avalanches are infrequent sediment production in active orogens is dominated by such events which may strongly influence geomorphic processes where rock avalanches fall onto glaciers they may affect glacier behaviour and moraine formation we outline the processes of rock avalanche initiation and motion and show that supraglacial deposits of rock avalanche debris have distinct sedimentological and thermal properties laboratory experiments on the effects of such debris on ice ablation are supplemented by field data from two rock avalanches in the southern alps new zealand their effects are compared with those of the thinner supraglacial debris that results from small rockfalls and melt out of englacial debris implications of rock avalanche debris cover for glacier behaviour are explored using a mass balance model of the franz josef glacier in new zealand demonstrating a likely supraglacial rock avalanche origin for the waiho loop moraine and considering the potential hazard of a large rock avalanche onto the present day glacier

cyclogeostrophic balance in the mozambique channel three methods are proposed for the inclusion of inertia when deriving currents from sea surface height ssh in the mozambique channel gradient wind perturbation expansion and an iterative method they are tested in a model and applied to satellite altimetry for an eddy of 25 cm amplitude and 100 km radius typical of mozambique channel rings at 18 s the error made with geostrophy is 40 for the anticyclones and 20 for the cyclones inertia could reach one third of the pressure gradient geostrophy underestimates subsurface currents by up to 50 cm s 1 resulting in errors of 30 40 the iterative method results in errors of 50 in mozambique channel rings geostrophic eke reaches 1400 cm2 s 2 while it attains 1800 cm2 s 2 when inertia is added applied to the gulf stream these methods confirm the hypothesis of maximenko and niiler 2006 that centrifugal accelerations should be the main cause for the difference observed between geostrophic and drifter eke this methodology should result in a net improvement for operational surface ocean currents

generation and evolution of a cyclonic ring at drake passage in early 1979 abstract an equatorward meander in the antarctic polar front at drake passage was observed to amplify and pinch off during january and early february 1979 forming a cold core cyclonic current fins with a radius of 50 km this ring appeared to move directly across the passage parallel to a submarine ridge before turning northeastward upon reaching a gap between the ridge and the south american continental rise its net motion was across the polar frontal zone and the ring was last observed to be pushing through the subantarctic front geostrophic surface speeds of up to 90 cm s 1 relative to 3500 m wore observed where the northern sector of the ring and the subantarctic front were in proximity a stability analysis of the banded flow regime across drake passage suggests that necessary conditions for baroclinic instability exist everywhere within the zonal current and those for barotropic instability exist adjacent to the fronts the beat and salt anomalies of this ring relative to the polar frontal zone

deep roots of upper plate faults and earthquake generation illuminated by volcanism 1 for many years the generation mechanism of disastrous intraplate earthquakes in the upper plate of a subduction zone have remained unclear largely because the roots of upper plate intraplate faults have particularly quiet inter seismic nature and limited visibility here we propose that the 2008 mw 6 9 iwate miyagi nairiku japan earthquake occurred on a dipping fault in a volcanic region contains previously unreported co seismic evidence of a ductile shear zone dsz present on the down dip fault extension beneath the seismogenic layer and dsz plays a dominant role in the seismogenesis we found the evidence in the spatial pattern of the co seismic ground displacement which was well captured by synthetic aperture radar reflecting geothermal anomalies there a dynamic forward model including the inter seismic deformation of dsz naturally reproduced this displacement pattern without kinematic inversions and consistently explained other independent observations this finding should make breakthroughs in observational and theoretical studies of earthquake generation

catastrophic landslide deposits in the karakoram himalaya in july 1986 three catastrophic landslides deposited about 20 x 106 cubic meters of debris on bualtar glacier in the karakoram himalaya a sudden acceleration and superficial breakup of the glacier provided an opportunity to examine the fresh deposits in depth beneath a surface layer of large boulders finer materials mainly sand and silt made up half of the total volume the fine materials were formed during the rock avalanche from mostly intact massive rock of the source zone velocity estimates suggest that this disaggregation occurred in less than 2 minutes coarse materials remained in bands of uniform lithology but the fine materials had diffused throughout the landslides a small amount of carbonate appears to have been calcined by frictional heating presumably at the base of the initial sliding masses these observations are relevant to understanding the mechanisms of catastrophic landslides other nearby rock avalanche deposits indicate that landslides are an important geomorphic process in the area and that they pose a continuing risk to human activity