reduced atlantic storminess during last glacial maximum evidence from a coupled climate model the last glacial maximum lgm 21 000 yr before present was the time of maximum land ice extent during the last ice age a recent simulation of the lgm climate by a state of the art fully coupled global climate model is shown to exhibit strong steady atmospheric jets and weak transient eddy activity in the atlantic sector compared to today s climate in contrast previous work based on uncoupled atmospheric model simulations has shown that the lgm jets and eddy activity in the atlantic sector are similar to those observed today with the main difference being a northeastward extension of their maxima the coupled model simulation is shown to agree more with paleoclimate proxy records and thus is taken as the more reliable representation of lgm climate the existence of this altered atmospheric circulation state during lgm in the model has implications for understanding the stability of glacial climates for the possibility of multiple atmospheric circulation regimes and for the interpretation of paleoclimate proxy records

an assessment procedure for glacial hazards in the swiss alps glacial hazards such as ice avalanches glacial lake outburst floods and debris flows have caused severe damage in populated mountain regions such as the swiss alps assessment of such hazards mus

causes of reduced north atlantic storm activity in a cam3 simulation of the last glacial maximum abstract the aim of this paper is to determine how an atmosphere with enhanced mean state baroclinity can support weaker baroclinic wave activity than an atmosphere with weak mean state baroclinity as a case study a last glacial maximum lgm model simulation previously documented to have reduced baroclinic storm activity relative to the modern day climate simulated by the same model despite having an enhanced midlatitude temperature gradient is considered several candidate mechanisms are evaluated to explain this apparent paradox a linear stability analysis is first performed on the jet in the modern day and the lgm simulation the latter has relatively strong barotropic velocity shear it was found that the lgm mean state is more unstable to baroclinic disturbances than the modern day mean state although the three dimensional jet structure does stabilize the lgm jet relative to the eady growth rate next feature tracking was used to assess the storm track seeding and temporal growth of distur

wave packets and life cycles of troughs in the upper troposphere examples from the southern hemisphere summer season of 1984 85 abstract in this paper reanalysis data for the southern hemisphere summer season of 1984 85 produced by the european centre for medium range weather forecasts have been analyzed to examine wave packets and life cycles of baroclinic waves a semiobjective algorithm has been devised to track wave packets it is found that the perturbations in the upper troposphere are dominated by wave packets some of these wave packets can be tracked for several weeks during which they can make up to two trips around the latitude circle the energy life cycles of waves that make up several of these wave packets were analyzed and apart from the incipient waves that started the wave packets most of the subsequent wave development was found to be dominated by convergence and divergence of energy fluxes rather than due to baroclinic or barotropic conversions demonstrating that these wave packets are indeed coherent entities that propagate due to downstream development or dispersion the energy life cycle of the most

poleward deflection of storm tracks an analysis of 11 years of european centre for medium range weather forecasts data focuses primarily on the vertically averaged high frequency transients the conclusions are discussed in the context of a the winter storm track b monthly variability and c interannual variability a winter storm track results show that the pattern of the forcing by the high frequency eddies along the storm track is highly correlated with the stationary circulation and the forcing itself is primarily responsible for the location of the trough ridge system associated with the stationary flow the results also clarify the role of wind component covariance terms u9y9 and y9 2 2 u9 2 in the column averaged vorticity forcing the simpler term u9y9 has the well known effect of intensifying the anticyclonic cyclonic tendencies on the southern northern side of the jet thereby producing an increase in the barotropic component of the zonal jet the y9 2 2 u9 2 term displays a quadrupole pattern which is also approximately in phase with the trough ridge system associated with the stationary flow b monthly variability eddy activity has been shown to possess a seasonal life cycle increasing during the early fall and reaching a maximum around the month of november then decaying for most of the winter months month to month variations in eddy activity over the pacific ocean show that energy levels increase up through november decreasing thereafter at the same time the trough ridge circulation pattern is intensifying by december baroclinicity in the western pacific has increased substantially and low level eddies are found to break by the middle of the ocean upper level eddies start to break well before reaching the west coast of north america resulting in a displacement of the maximum in y9 2 2 u9 2 westward from its november position and increasing the trough ridge forcing by the high frequency eddies c interannual variability wintertime eddy kinetic energy is seen to extend further eastward through the pacific ocean during the warm phase but displays an abrupt termination during the cold phase anomalies in the eddy transient forcing tend to be quite similar to that of the pacific north american pattern itself the extension of the storm track during the warm phase resembles that of fall conditions and is present in the winter season because the source of low level baroclinicity

fukushima derived radionuclides in the ocean and biota off japan the t hoku earthquake and tsunami of march 11 2011 resulted in unprecedented radioactivity releases from the fukushima dai ichi nuclear power plants to the northwest pacific ocean results are presented here from an international study of radionuclide contaminants in surface and subsurface waters as well as in zooplankton and fish off japan in june 2011 a major finding is detection of fukushima derived 134cs and 137cs throughout waters 30 600 km offshore with the highest activities associated with near shore eddies and the kuroshio current acting as a southern boundary for transport fukushima derived cs isotopes were also detected in zooplankton and mesopelagic fish and unique to this study we also find 110mag in zooplankton vertical profiles are used to calculate a total inventory of 2 pbq 137cs in an ocean area of 150 000 km2 our results can only be understood in the context of our drifter data and an oceanographic model that shows rapid advection of contaminants further out in the pacific importantly our data are consistent with higher estimates of the magnitude of fukushima fallout and direct releases stohl et al 2011 atmos chem phys discuss 11 28319 28394 bailly du bois et al 2011 j environ radioact 10 1016 j jenvrad 2011 11 015 we address risks to public health and marine biota by showing that though cs isotopes are elevated 10 1 000 over prior levels in waters off japan radiation risks due to these radionuclides are below those generally considered harmful to marine animals and human consumers and even below those from naturally occurring radionuclides

storm track dynamics this paper reviews the current state of observational theoretical and modeling knowledge of the midlatitude storm tracks of the northern hemisphere cool season observed storm track structures and variations form the first part of the review the climatological storm track structure is described and the seasonal interannual and interdecadal storm track variations are discussed in particular the observation that the pacific storm track exhibits a marked minimum during midwinter when the background baroclinicity is strongest and a new finding that storm tracks exhibit notable variations in their intensity on decadal timescales are highlighted as challenges that any comprehensive storm track theory or model has to be able to address physical processes important to storm track dynamics make up the second part of the review the roles played by baroclinic processes linear instability downstream development barotropic modulation and diabatic heating are discussed understanding of these processes forms the core of our current theoretical knowledge of storm track dynamics and provides a context within which both observational and modeling results can be interpreted the eddy energy budget is presented to show that all of these processes are important in the maintenance of the storm tracks the final part of the review deals with the ability to model storm tracks the success as well as remaining problems in idealized storm track modeling which is based on a linearized dynamical system are discussed perhaps on a more pragmatic side it is pointed out that while the current generation of atmospheric general circulation models faithfully reproduce the climatological storm track structure and to a certain extent the seasonal and enso related interannual variations of storm tracks in depth comparisons between observed and modeled storm track variations are still lacking

three dimensional structure of frontal waves and associated salinity minimum formation along the kuroshio extension abstract high resolution hydrographic observations were conducted in september 2002 to describe the detailed structure of frontal waves along the kuroshio extension frontal waves were observed both in the upper and intermediate layers which corresponded to the depths of north pacific subtropical mode water and north pacific intermediate water respectively the frontal wave in the upper layer preceded the intermediate depth frontal wave by about 1 4 wavelength the vertical phase lag created situations in which the low salinity oyashio water in the intermediate layer was superimposed below the upper layer high salinity kuroshio water thus forming a vertical salinity minimum the frontal waves with a wavelength of about 200 km and a phase speed of 0 2 0 3 m s 1 propagating in the downstream direction were consistent with those from satellite images vertical velocity fields were estimated with the quasigeostrophic omega equation downwelling around the trough from the crest to trough of the intermedia

ice avalanches some empirical information about their formation and reach evaluation d apres l etude d environ 100 avalanches de glace des zones de rupture et des distances d arret

organization of storm tracks in zonally varying flows abstract a simple two layer quasigeostrophic model is employed to investigate the sensitivity of storm tracks to changes in an externally imposed zonally varying large scale flow zonally asymmetric temperature and horizontal deformation fields are varied systematically in order to compare the effects of baroclinicity and horizontal deformation on storm track dynamics the sensitivity of the storm tracks to uniform barotropic zonal flows is also examined the results show two competing processes for storm track organization one associated with a local maximum in baroclinicity and the other with a local minimum in horizontal deformation when the equilibrium state consists of a zonally symmetric temperature field and a barotropic stationary wave the maximum in synoptic scale transient eddy energy storm track is located in the entrance region of the upper jet just downstream of the point of minimum horizontal deformation as zonal variations in baroclinicity become large keeping the upper layer horizo

hazardous processes and events from glacier and permafrost areas lessons from the chilean and argentinean andes glacier and permafrost hazards such as glacial lake outburst floods and rock ice avalanches cause significant socio economic damages worldwide and these processes may increase in frequency and magnitude if the atmospheric temperature rises in the extratropical andes nearly 200 human deaths were linked to these processes during the twentieth century we analysed bibliographical sources and satellite images to document the glacier and permafrost dynamics that have caused socio economic damages in this region in historic time including glacial lake outburst floods ice and rock ice avalanches and lahars to unravel their causes and geomorphological impacts in the extratropical andes at least 15 ice dammed lakes and 16 moraine dammed lakes have failed since the eighteenth century causing dozens of floods some floods rank amongst the largest events ever recorded 5000 106 m3 and 229 106 m3 respectively outburst flood frequency has increased in the last three decades partially as a consequence of long term decades to centuries climatic changes glaciers shrinkage and lake growth short term days to weeks meteorological conditions i e intense and or prolonged rainfall and high temperature that increased meltwater production have also triggered outburst floods and mass movements enormous mass failures of glaciers and permafrost 10 106 m3 have impacted lakes glaciers and snow covered valleys initiating chain reactions that have ultimately resulted in lake tsunamis and far reaching 50 km flows the eruption of ice covered volcanoes has also caused dozens of damaging lahars with volumes up to 45 106 m3 despite the importance of these events basic information about their occurrence e g date causes and geomorphological impact which is well established in other mountain ranges is absent in the extratropical andes a better knowledge of the processes involved can help to forecast and mitigate these events copyright 2014 john wiley sons ltd

characteristics of wave packets in the upper troposphere part i northern hemisphere winter abstract gridded data produced by the ecmwf reanalysis project have been analyzed to document the properties of wave packets in the northern hemisphere winter midlatitude upper troposphere based on results from earlier investigations 300 hpa meridional wind variations were chosen for analysis wave packet envelopes were also defined by performing complex demodulation on the wind data the properties of the wave packets are mainly illustrated using time lagged one point correlation maps performed both on and wave packet envelopes the results show that over most regions in the northern hemisphere winter with the exception of the deep tropics and near the aleutian low medium scale waves dominant wavenumber 5 8 exhibit the characteristics of downstream development and occur within wave trains that propagate with eastward group velocities much faster than the phase speeds of individual phases of the waves their group velocity is highly correlated with the local time mean 200 400 hpa wind while the

on the dynamics of a storm track abstract an idealized primitive equation model is used to determine the factors controlling the dynamics and maintenance of eddy activity in a storm track the results show that localized regions of enhanced baroclinicity do not necessarily lead to localization of eddy activity by studying the energetics of the storm track it is shown that while baroclinic conversion does indeed correlate with the region of maximum baroclinicity it is the downstream radiation of energy through the ageostrophic geopotential fluxes which acts as a trigger for the development and maintenance of eddy activity over less baroclinic regions extending the region of eddy activity much further downstream from the region of high baroclinicity examples of eddy life cycles are given that show that convergence and divergence of ageostrophic fluxes can dominate baroclinic and barotropic conversion especially in regions with weak baroclinicity factors that may limit the zonal extent of a storm track are discussed evidence of down

potential vorticity distribution in the north pacific abstract vertical sections and maps of potential vorticity 1f z for the north pacific are presented on shallow isopycnals high potential vorticity is found in the tropics subpolar gyre and along the eastern boundary of the subtropical gyre all associated with ekman upwelling low potential vorticity is found in the western subtropical gyre subtropical mode water in a separate patch near the sea surface in the eastern subtropical gyre and extending around the gyre and near sea surface outcrops in the subpolar gyre the last is analogous to the subpolar mode water of the north atlantic and southern ocean meridional gradients of potential vorticity are high between the subtropical and subpolar gyres at densities which outcrop only in the subpolar gyre lateral gradients of potential vorticity are low in large regions of the subtropical gyre on these isopycnals on slightly denser isopycnals which do not outcrop in the north pacific there are large regions of low potential vorticity gradients

assessment of thermal change in cold avalanching glaciers in relation to climate warming high elevation glaciers covered by cold firn are undergoing substantial warming in response to ongoing climate change this warming is affecting the ice rock interface temperature the primary driver of avalanching glacier instability on steep slopes prediction of future potential instability therefore requires appropriate modeling of the thermal evolution of these glaciers application of a state of the art model to a glacier in the french alps taconnaz has provided the first evaluation of the temperature evolution of a cold hanging glacier through this century our observations and three dimensional modeling of the glacier response velocity thickness temperature density and water content to climate change indicate that taconnaz glacier will become temperate and potentially unstable over a large area by the end of the 21st century the risk induced by this glacier hazard is high for the populated region below and makes observation and modeling of such glaciers a priority

why is the spreading of the north pacific intermediate water confined on density surfaces around σθ 26 8 abstract the north pacific intermediate water characterized by a salinity minimum confined to density surfaces of 26 7 26 9 exists throughout the subtropical gyre and has been observed to originate in the subarctic north pacific the physical processes that determine the density range on which the npiw resides are not yet well understood this study attempts to clarify these processes by combining observational data and a simple advection diffusion isopycnal model due to the regional excessive precipitation over evaporation the salinity in the upper layer subarctic north pacific generally decreases with decreasing water depth both alongisopycnal advection and diffusion work to carry this salinity depth characteristic into the subtropical circulation for the isopycnal surfaces overlying the npiw however this transport mechanism is hindered by the seasonal outcropping the outcropping not only blocks the fresh subarctic water from advecting and diffusing along these isopycnals into the subtropi

the role of stationary eddies in shaping midlatitude storm tracks transient and stationary eddies shape the extratropical climate through their transport of heat moisture and momentum in the zonal mean the transports by transient eddies dominate over those by stationary eddies but this is not necessarily the case locally in particular in storm track entrance and exit regions during winter stationary eddies and their interactions with the mean flow dominate the atmospheric energy transport here it is shown that stationary eddies can shape storm tracks and control where they terminate by modifying local baroclinicity simulations with an idealized aquaplanet gcm show that zonally localized surface heating alone e g ocean heat flux convergence gives rise to storm tracks which have a well defined length scale that is similar to that of earth s storm tracks the storm tracks terminate downstream of the surface heating even in the absence of continents at a distance controlled by the stationary rossby wavelength scale stationary eddies play a dual role within about half a rossby wavelength downstream of the heating region stationary eddy energy fluxes increase the baroclinicity and therefore contribute to energizing the storm track farther downstream enhanced poleward and upward energy transport by stationary eddies reduces the baroclinicity by reducing the meridional temperature gradients and enhancing the static stability transports both of sensible and latent heat water vapor play important roles in determining where storm tracks terminate

how well can we simulate complex hydro geomorphic process chains the 2012 multi lake outburst flood in the santa cruz valley cordillera blanca peru changing high mountain environments are characterized by destabilizing ice rock or debris slopes connected to evolving glacial lakes such configurations may lead to potentially devastating sequences of mass movements process chains or cascades computer simulations are supposed to assist in anticipating the possible consequences of such phenomena in order to reduce the losses the present study explores the potential of the novel computational tool r avaflow for simulating complex process chains r avaflow employs an enhanced version of the pudasaini 2012 general two phase mass flow model allowing consideration of the interactions between solid and fluid components of the flow we back calculate an event that occurred in 2012 when a landslide from a moraine slope triggered a multi lake outburst flood in the artizon and santa cruz valleys cordillera blanca peru involving four lakes and a substantial amount of entrained debris along the path the documented and reconstructed flow patterns are reproduced in a largely satisfactory way in the sense of empirical adequacy however small variations in the uncertain parameters can fundamentally influence the behaviour of the process chain through threshold effects and positive feedbacks forward simulations of possible future cascading events will rely on more comprehensive case and parameter studies but particularly on the development of appropriate strategies for decision making based on uncertain simulation results 2017 the authors earth surface processes and landforms published by john wiley sons ltd

kuroshio temporal and spatial variations south of japan determined from inverted echo sounder measurements 1 the affiliated surveys of the kuroshio off ashizuri misaki asuka project is a collaboration between scientists in japan and the united states to improve our understanding of the structure and dynamics of the kuroshio off the coast of southwest japan in this project an array of nine inverted echo sounders and nine current meter moorings were deployed for 2 years 1993 1995 along a line extending 1000 km from shikoku numerous hydrographic profiles along this section were used to determine the regional gravest empirical modes gems which relate vertical profiles of temperature and specific volume anomaly to vertical acoustic echo time these gems were used in conjunction with the inverted echo sounder data to calculate 2 year time series of entire sections of relative geostrophic velocity and temperature current meter data provided absolute velocity references for the geostrophic velocity sections in addition a time series of kuroshio position was determined from the gem temperature sections it shows three big 80 km displacement and three little offshore meanders of the kuroshio occurring in february may june and october of both years this suggests a 4 month periodicity possibly phase locked to the annual cycle the meanders may be caused by mesoscale eddies arriving from the east the observed meanders were preceded by low kuroshio volume transport and were followed by high kuroshio volume transport the kuroshio volume and temperature transports were highly variable with respective means of 65 4 sv and 3 7 0 2 pw and standard deviations of 20 sv and 0 9 pw

distribution and modification of north pacific intermediate water in the kuroshio oyashio interfrontal zone abstract a multiship ctd survey was conducted in the kuroshio oyash interfrontal zone in the area of 30 41 n 140 e 180 from may to june 1992 to examine the distribution modification process and formation site of north pacific intermediate water npiw low salinity oyashio water and high salinity kuroshio water merge along the kuroshio extension just off the east coast of japan and together flow eastward eastward geostrophic transport and salinity across the kuroshio strong current indicate that the mixture of the kuroshio and oyashia waters along the kuroshio extension can produce new npiw transport estimate suggests that the new npiw bifurcates into the interfrontal zone and into the recirculation of the subtropical gyre a salinity minimum structure can he also created due to the isopycnal mixing along the kuroshio extension between the oyashio and kuroshio waters which have different salinity and vertical velocity structures the low salinity oyashio water seen along the oyashio branches and t

satellite altimeter monitoring the kuroshio transport south of japan in 1993 1995 we carried out observations of the kuroshio south of japan including direct current measurements and repeated hydrographic surveys along a satellite track of the topex poseidon altimeter the velocity field of the kuroshio is determined by geostrophic calculation using the repeated hydrographic survey data referenced to velocities observed at mid and abyssal depths the volume transport of the kuroshio is estimated from this velocity field the estimated transports of the kuroshio have a high correlation with sea surface height differences across the kuroshio having this relationship and using the altimeter data we obtained a time series of the kuroshio transport over seven years at ten day intervals the kuroshio transport excluding contributions by local recirculations is estimated to be 42 106 m sec on average the correlation between sea surface height difference and transport provides a practical method of long term monitoring of the kuroshio transport using satellite altimetry

the impact of wave packets propagating across asia on pacific cyclone development abstract in this paper ecmwf 40 yr reanalysis data have been examined to study the influence of upper level wave packets propagating across asia into the pacific on surface cyclone development over the pacific previous studies have shown that in winter wave packets propagate across asia over two branches a northern branch over siberia and a southern branch along the subtropical jet across southern asia results presented here show that subsequent to the presence of wave packets on either branch the frequency of occurrence of deep cyclones defined as cyclones with central pressure below 960 hpa as well as explosively deepening cyclones those with a deepening rate of 1 bergeron or more are significantly enhanced this enhancement also clearly follows the wave packet eastward as it propagates across the pacific wave packets from the two branches are found to interfere with each other such that if wave packets of the appropriate configuration are present on both the northern and southern branch s

magnetic enhancement paths in loess sediments from tajikistan china and hungary saturation magnetization and saturation remanence of 139 loess and paleosol samples from tajikistan china and hungary increase linearly with low field susceptibility in all sections investigated thus magnetic enhancement is caused by increasing quantities of ferrimagnetic minerals the observed variations of high field susceptibility h are attributed to variations in the amount of clay minerals as h is linearly correlated with the 2 m grain size mineral fraction the magnetic enhancement process is compared with a theoretical mixing model based on two magnetic mineral assemblages with different but invariable coercivities the two component model provides a good approximation to the data from hungary and the magnetically enhanced paleosol samples in tajikistan and china discrepancies between model calculation and data arise in the behaviour of the loess samples in tajikistan here a three component model improves the agreement between data and mixing calculation the magnetic enhancement in the loess in tajikistan and china is different from the one in the paleosols and the link between paleoclimate and susceptibility is not as straightforward as in the hungarian loess paleosol sequence

midwinter suppression of baroclinic wave activity in the pacific abstract seasonal variations in baroclinic wave activity and jet stream structure in the northern hemisphere are investigated based upon over 20 years of daily data baroclinic wave activity at each grid point is represented for each day by an envelope function the lowpass filtered time series of the squared highpass filtered geopotential height baroclinic wave activity over the atlantic exhibits a single maximum in january whereas in the pacific it exhibits peaks in late autumn and in early spring and a significant weakening in midwinter which is more evident at the tropopause level than near the surface this suppression occurs despite the fact that the low level baroclinity and the intensity of the jet stream are strongest in midwinter based on the analysis of 31 day running mean fields for individual winters it is shown that over both the oceans baroclinic wave activity is positively correlated with the strength of the upper tropospheric jet for wind speeds up to 45 m s 1 when the strength of t

classification and kinematics of the planpincieux glacier break offs using photographic time lapse analysis herein we present results obtained from time lapse imagery acquired by a digital single lens reflex camera during 2014 18 used to monitor the planpincieux glacier on the italian side of the grandes jorasses mont blanc massif we processed the images using image cross correlation to measure the surface kinematics of the most active lobe of the glacier that presents a high velocity and frequent ice detachments during the monitoring we observed two or three periods of sharp acceleration per year that culminated with large break offs followed by analogous decelerations overall we registered more than 350 failures with a volume 100 m3 of which 14 events had volumes larger than 10 000 m3 the study identified a monotonic positive relationship between the velocity and failure volume that may be used to estimate the volume of the collapses before an event we identified the thresholds of velocity and acceleration that characterise the activation of the speed up periods the study allowed the characterisation of three different instability processes that lead to the break off of ice chunks from the glacier terminus i disaggregation ii slab fracture and iii water tunnelling failure which can be differentiated based on the rheology the volume involved and the trigger process

sliding phenomena in a steep section of balmhorngletscher switzerland annual aerial photographs of balmhorngletscher available since 1973 have furnished data on large ice avalanches originating in one particular location the avalanches characteristically occur during an active phase of fast sliding the analysis of a photogrammetric 1 2000 bedrock map of longitudinal ice surface profiles from photographs taken at various times and of velocity measurements by theodolite has shown that the fast sliding and the release of the avalanches in an area of about 250 by 100 m is quite independent of ice thickness it is suggested that besides the slope of the bed rock roughness and topographical features the particular structure of the rock surface in the fashion of tiles on a roof is a factor which influences the processes of fast sliding and avalanche formation it is suggested that meltwater gains access to cavities at the rock steps from where it is dragged along on the ice rock interface getting slowly worked into the basal ice layer many weeks after the beginning of the melt season the evolving acceleration becomes apparent characteristically at the beginning of september once the surface meltwater gains direct access to the bed through fresh crevasses the glacier accelerates progressively as water enters cracks faults and microfissures water pressure effects may become important as cavities grow while the gradual development of the active phase permits to forecast the growing avalanche risk the prediction of the event in time is a long way off if practical at all

simulating the seasonal cycle of the northern hemisphere storm tracks using idealized nonlinear storm track models abstract in this study an idealized nonlinear model is used to investigate whether dry dynamical factors alone are sufficient for explaining the observed seasonal modulation of the northern hemisphere storm tracks during the cool season by construction the model does an excellent job simulating the seasonal evolution of the climatological stationary waves yet even under this realistic mean flow the seasonal modulation in storm track amplitude predicted by the model is deficient over both ocean basins the model exhibits a stronger sensitivity to the mean flow baroclinicity than observed producing too large midwinter eddy amplitudes compared to fall and spring this is the case not only over the pacific where the observed midwinter minimum is barely apparent in the model simulations but also over the atlantic where the october april eddy amplitudes are also too weak when the january amplitude is tuned to be about right the nonlinear model generally produces stronger eddy amplitude with stronger b

frequency and characteristics of glacier floods in the swiss alps damage due to glacier floods in the swiss alps occurs about once every two years at present despite the pronounced retreat of glaciers during the twentieth century and the installation of many water reservoirs which act as flood retention basins over half 60 to 70 of the observed floods are caused by outbursts of marginal glacier lakes or sudden breaks of ice dams and 30 to 40 by ruptures of water pockets in a glacierized mountain region as densely populated as the swiss alps even debris flows triggered by outbursts of very small water masses may be dangerous historical information about glacier floods in the swiss alps although incomplete and heterogeneous is used as an empirical basis for an attempt to recognize potential hazards at an early stage by considering outburst processes volumes of water involved potential peak discharge values lithology and inclination within the reach of glacier streams

cross equator transport of 137cs from north pacific ocean to south pacific ocean beagle2003 cruises abstract the anthropogenic radionuclides such as 137 cs 90 sr 99 tc 129 i and some transuranics are important tracers of transport and biogeochemical processes in the ocean 137 cs with a half life of 30 years a major fission product present in a dissolved form in seawater is a good tracer of oceanic circulation at a time scale of several decades at woce p6 line along 30 s during the beagle cruise in 2003 surface seawater around 80 l was collected a few meters below the ocean surface by a pumping system water column samples from 5 to 20 l were collected using a rosette multisampling system and niskin bottles 137 cs was separated from seawater samples using ammonium phosphomolybdate amp and analysed for 137 cs in low level hpge gamma ray spectrometers results allowed to draw a detailed picture of the distribution of 137 cs in the south pacific ocean along p6 line a 137 cs depth section was depicted from about 160 samples 137 cs concentrations in the subsurface layers ranged from 0 07 0 04 bq m 3 to 1 85 0 145 bq m 3 high in the tasman sea and very low in the eastern region where upwelling occurs water column inventories of 137 cs from surface to 1000 dbar depth ranged from 270 104 to 1048 127 bq m 2 it was concluded that the source of higher 137 cs concentration and inventories in the tasman sea was 137 cs deposited in the mid latitude of the north pacific ocean and transported across the equator during four decades

glacier recession and glacial lake outburst flood studies in zanskar basin western himalaya abstract glacier recession and formation of glacial lakes along with outburst flood hazards are increasing in response to changing climate in the himalayan region this study describes evolution of dalung and padam glaciers and their associated lakes employing multi temporal datasets of landsat mss tm etm indian remote sensing liss iii google earthtm aster gdem and survey of india topographic maps the dalung glacier dg and lake dl are present in suru river catchment whereas the padam glacier pg and lake pl are present in tsarap river catchment of zanskar basin western himalaya from 1962 to 2015 the dg and pg have shrunk at different rates the dg has shrunk by 2 6 0 56 km2 19 2 4 1 at a rate of 0 05 0 01 km2 a 1 whereas the pg has shrunk by 3 4 0 65 km2 12 7 2 4 at a rate of 0 06 0 01 km2 a 1 the frontal recession was recorded as 1 240 0 02 km 15 7 2 0 at a rate of 20 0 4 m a 1 for dg and 2 690 0 5 m 21 3 2 1 at a rate of 50 7 0 1 m a 1 for pg consequently the proglacial glacial lakes have formed indicating an expansion of 20 3 4 dl and 58 4 5 pl during 1990 2015 using integrated criteria of standard indices for the identification of potentially dangerous glacial lakes pdgls the lakes were found to be vulnerable and have a potential to cause breaching in the coming years in order to provide inputs for the emergency action plan one dimensional mike 11 model was used to generate the peak flood hydrographs at the lake and other vulnerable sites downstream highest peak discharge of 3361 7 m3 s 1 dl and 4210 3 m3 s 1 pl were estimated at the lake sites which has reduced to 1520 9 m3 s 1 and 1722 4 m3 s 1 respectively at the outlet sites the reduced discharge at downstream sites still bears the potential to create dangerous flood hazards

cold firn and ice of high altitude glaciers in the alps measurements and distribution modelling the thermal regime of high altitude accumulation areas in the swiss alps was systematically investigated on the jungfraufirn bernese alps on the breithornplateau valais alps and on grenzgletscher valais alps in 1991 1992 and 1994 temperatures were measured in a deep hole 120 m deep and in several shallow holes 14 30 m deep whereas the wide neve of the jungfraufirn at 3400 3600 m a s l and the 3800 m high breithorn plateau seems to be predominantly temperate cold firn and ice temperatures were measured throughout on grenzgletscher 3900 4450 m a s l mean firn temperatures on grenzgletscher vary strongly and range between 3 and 14 c a comparison between the measured temperature profiles and a one dimensional heat conduction calculation shows that the release of latent heat by penetrating and refreezing meltwater decisively influences the thermal pattern of the firn pack a multiple linear regression model based on measured firn temperatures from the european alps and the parameters altitude and aspect yields aspect dependent lower boundaries for the occurrence of cold firn ranging between 3400 northerly aspects and 4150 m a s l southerly aspects a total of 120 glaciers with cold firn areas are found when applying the model to glacier inventory data from the european alps

trapping of synoptic scale disturbances into the north pacific subtropical jet core in midwinter 1 over the northwestern nw pacific a subtropical jet stream develops at 30 n in midwinter as the east asian winter monsoon intensifies eddies with subweekly periods propagating through the midlatitude tropopause into the nw pacific storm track tend to be trapped into the jet core 1000 km away from a surface baroclinic zone at 40 n while lifted up by 3 km the trapping appears to weaken the interaction of the upper level eddies with the baroclinic zone thus acting against eddy amplification and thereby contributing to the midwinter minimum in the eddy activity as observed before the late 1980s since then under the reduced trapping effect by the weakened jet upper level eddies tended to propagate right above the surface baroclinic zone while strongly interacting it even in midwinter as in fall and spring this midwinter tendency acted to enhance the eddy amplification that led to the recent disappearance of the activity minimum

evidence of a periodic ice cliff avalanche on north west ellesmere island n w t canadian high arctic periodicite des avalanches implications dans la geomorphologie et sedimentologie les glaciers sub polaires

the impact of zonal propagation and seeding on the eddy mean flow equilibrium of a zonally varying two layer model this paper investigates the role of zonal propagation for the equilibration of zonally varying flow it is hypothesized that there exist two ideal limits for very small or very large group speed in the first limit the eddies equilibrate locally with the forcing while in the second limit the equilibration can only be understood in a global sense to understand these two limits and to assess which is more relevant for the extratropical troposphere a series of idealized experiments that involves changing the magnitude of the uniform zonal wind is performed the results of the idealized model experiments suggest that the actual troposphere is likely to be in a transition regime between the two limits but perhaps closer to the global than the local limit near the global limit both the eddy amplitude and local baroclinicity over the baroclinic zone are strongly affected by the amount of upstream seeding when the propagation speed is reduced relative to the control run the zonal mean eddy activity decreases because the residence time increases more over the stable part of the channel than along the baroclinic zone with the decrease in upstream seeding the local supercriticality along the baroclinic zone increases although the increase is moderate the decrease in seeding and increase in baroclinicity partially offset the effects of each other leading to only small changes in the maximum eddy amplitude downstream of the baroclinic zone changes in upstream seeding can also be achieved by enhanced damping when the eddies are locally damped the baroclinicity is also enhanced downstream of the damping region due to reduced eddy fluxes for typical parameters the recovery of the eddy amplitude occurs over very long distances based on these idealized results it is argued that the coexistence of enhanced baroclinicity and weaker eddy amplitude over the pacific storm track as compared to the atlantic storm track is consistent with the effects of strong eddy damping over asia

computational experiments on the 1962 and 1970 landslide events at huascaran peru with r avaflow lessons learned for predictive mass flow simulations abstract mass flow simulations are considered important tools for hazard analysis for the simulation of single process mass flows such as debris flows robust tools and reasonable parameter range estimates are available however this is much less the case for more complex mass flows e g involving process chains and flow transformation we explore the challenges of simulating complex flow dominated landslides by back calculating the huascaran events of 1962 and 1970 with r avaflow a two phase mass flow model pudasaini 2012 in a gis based open source simulation framework both events started as rock ice falls on the western slope of the north summit of nevado huascaran cordillera blanca peru and entrained large volumes of glacial till at lower elevation resulting in highly mobile debris avalanches whereas the 1962 event badly affected the village of ranrahirca when spreading over a debris cone the 1970 event overtopped a ridge and led to the complete destruction of the town of yungay well documented in the literature these events provide an opportunity as a natural laboratory for testing innovative mass flow simulation tools and their features in a first step we consider i the 1962 event and ii the 1970 event separately for each of them optimizing the key input parameters in terms of empirical adequacy in a second step we apply the optimized parameter set for i to the 1970 event and the parameter set derived for ii to the 1962 event in a third step we explore the sensitivity of the model outcomes to selected key parameters basal friction angle and entrainment coefficient the results a demonstrate the general ability of r avaflow to reproduce the spatio temporal evolution of flow heights and velocities as well as travel times and volumes of these complex mass flow events reasonably well and b highlight the challenges and uncertainties involved in predictive simulations with parameter sets obtained from back calculations we suggest a strategy to appropriately deal with uncertain outcomes by superimposing the results of multiple simulations

observed eastward progression of the fukushima 134cs signal across the north pacific radionuclide samples taken as part of hydrographic surveys at 30 n in the north pacific reveal that the easternmost edge of fukushima derived 134cs observed at 174 3 w in 2012 had progressed eastward across the basin to 160 6 w by 2013 the 2013 30 n observations indicate surface 134cs concentrations of 3 5 bq m3 between 160 e and 160 w slightly lower concentrations west of 160 e and no detectable signal east of 160 6 w profile samples show 134cs penetration to 500 m west of 180 with shoaling penetration depth toward to the east the near uniform vertical distribution of 137cs between 152 w and 121 3 w in the top 500 m is indicative of trace amounts of radionuclides remaining from weapons testing the physical processes responsible for the deep 134cs penetration in the western pacific appear to be related to distinct water mass subduction pathways however the timing and rapidity of deep penetration over the broad scales observed has yet to be clarified

on the instability of avalanching glaciers the instability of hanging glaciers and more generally of avalanching glaciers is discussed on the basis of observations performed on several glaciers located in the european alps a classification of avalanching glaciers is proposed which allows a primary appreciation of the danger inherent in these glaciers on the basis of field observations and results of numerical simulations of crevassing the fracture processes which lead to major icefalls as well as their recurrence are analyzed a method for predicting the time of failure is then discussed the disaggregation of the unstable ice masses usually observed prior to large icefalls is investigated and its implications for the forecasting of icefalls analyzed

temperature and accumulation of high altitude firn in the alps data on temperature and accumulation of high altitude firn in the alps are compiled and discussed firn temperature varies with incoming radiation slope aspect at a given altitude the altitudinal gradient of temperature in highly permeable firn bodies appears to be about twice as high as the mean lapse rate of air temperature cold infiltration takes place above about 3500 m a s firn temperatures on the highest peaks are around 15 c accumulation net balance also decreases with increasing altitude from about 3m h20 at 3500 m a s to around 0 5 m h20 at wind exposed sites between 4300 and 4800 m a s l probably this is strongly due to wind erosion and topographical effects however temperature and accumulation not only appear to be interrelated but also seem to be positively correlated to the heat applied to the surface assuming the observed altitudinal gradients have remained constant in time it can be estimated that high altitude firn bodies have become considerably warmer since the last century co2 induced atmospheric warming could lead to a drastic change in the mass turnover and flow activity of high glaciers in wind exposed places where wind erosion of the snowpack becomes a controlling factor of accumulation introduction studies on mass and heat exchange at the surface of alpine firn have usually been carried out at altitudes below about 3500 m a s where firn is temperate and accumulation is high eg lang and others 1977 muller 1977 access to firn regions of higher altitudes is difficult however rather unusual construction work eg refuge lenkins on mont blanc and a number of tunnels dug into the firn of the monte rosa region by j e fisher in the 1950s furnished some information which indicated that at high altitudes firn is cold and accumulation does not further increase with altitude interest in temperature and accumulation of high altitude firn has grown recently in connection with i englacial temperatures 2 ice avalanches and 3 alpine core drilling temperature distribution in the tongue of grenzgletscher one of the largest ice bodies in the alps must be caused by advection of cold ice from high altitudes blatter and haeberli 1984 the frequency of ice avalanches ultimately depends on the accumulation of firn alean 1985 and the stability of steep mountain glaciers seems to depend on firn and ice temperatures rothlisberger 198 1 alean 1984 finally core drilling projects in cold high alpine firn and ice provide important information about the evolution of the composition of the atmosphere in heavily industrialized regions over past decades and centuries eg wagenbach and others in press but require knowledge about the distribution of accumulation in space and time the aims of the present study are to compile information available and point to possible effects of recent atmospheric warming firn temperature temperature measurements from deep pits tunnels and shallow bore holes in high altitude firn of the alps have been compiled by haeberli 1976 cf also hooke and others 1983 new information is available from chli titlis jungfraujoch sphinxgrat and monte rosa colle gnifetti all swiss alps at chli titlis 3070 m a s i 15 m temperature in the summit s 22 m thick firn and ice was 0 7 c 1979 80 cf haeberli and others 1979 temperatures in the sphinxgrat crest were measured in a 70 m borehole through firn ice and perennially frozen rocks in connection with recent construction work at the jungfraujoch the ice rock interface 10 m below the surface at 3525 m a s had a temperature close to 6 c 198 1 temperatures around 14 c at 15 m depth were registered in all core drilling boreholes made so far on colle gnifetti 4450 m a s the fim ice transition in this cold firn saddle occurs about 40 m below the surface schotterer and others 1981 when presently known firn temperatures are compiled figure i two groups seem to exist group i incorporates summits crests and probably also very steep slopes 45 which mainly consist of impermeable ice or high density firn with high concentrations of ice layers temperatures in such ice bodies decrease with increasing altitude at a rate about i c ioo m which is slightly higher than the assumed lapse rate of mean annual air temperature 0 65 c ioo m no temperate firn bodies are known in such situations in contrast more gentle slopes and basins group 2 where highly permeable firn accumulates are temperate up to about 3600 m a s above this upper boundary of the warm infiltration zone of the alps percolating meltwater cannot

are the northern hemisphere winter storm tracks significantly correlated abstract in this study the correlation between the northern hemisphere winter pacific and atlantic storm tracks is examined using the ncep ncar reanalysis and the 40 yr ecmwf re analysis era 40 as well as unassimilated aircraft observations by examining month to month variability in the 250 hpa meridional velocity variance the correlation between the two storm track peaks is found to be as high as 0 5 during the winters between 1975 76 and 1998 99 here it is shown that the correlation between the two storm tracks can be clearly detected from the aircraft data further analyses of the reanalysis data show that the correlation can also be seen in other eddy variance and covariance statistics including the poleward heat flux at the 700 hpa level the correlation between the two storm tracks as seen in both reanalysis datasets is shown to be much weaker during the period 1957 58 1971 72 suggesting a possible regime transition from largely uncorrelated storm tracks to highly correlated storm tracks

water masses labeled with global fallout 137cs formed by subduction in the north pacific 1 we provide a first cross section of the 137 cs concentration along 165 e longitude in the western north pacific the 137 cs profile is characterized by several subsurface cores with high 137 cs including two 137 cs concentration maxima at 20 n one at 250 m 25 5 and one at 400 500 m 26 0 depths the shallower maximum is in the density range of north pacific subtropical mode water npstmw and the deeper one is in the density range of lighter central mode water lcmw the main 137 cs cores therefore were formed by movements of npstmw and lcmw in the interior ocean during the past four decades the 137 cs has been transported from subarctic region to subtropics and tropics as a result of subduction

diabatic and orographic forcing of northern winter stationary waves and storm tracks abstract in this study a dry global circulation model is used to examine the contributions made by orographic and diabatic forcings in shaping the zonal asymmetries in the earth s northern hemisphere nh winter climate by design the model mean flow is forced to bear a close resemblance to the observed zonal mean and stationary waves the model also provides a decent simulation of the storm tracks in particular the maxima over the pacific and atlantic and minima over asia and north america are fairly well simulated the model also successfully simulates the observation that the atlantic storm track is stronger than the pacific storm track despite stronger baroclinicity over the pacific sensitivity experiments are performed by imposing and removing various parts of the total forcings in terms of the nh winter stationary waves in the upper troposphere results of this study are largely consistent with previous studies diabatic forcings explain most of the modeled stationary waves with orographic

slope failures and erosion rates on a glacierized high mountain face under climatic changes in this study rapid topographic changes and increased erosion rates caused by massive slope failures in a glacierized and permafrost affected high mountain face were investigated with respect to the current climatic change the study was conducted at one of the highest periglacial rock faces in the european alps the east face of monte rosa italy pronounced changes in ice cover and repeated rock and ice avalanche events have been documented in this rock wall since around 1990 the performed multi temporal comparison of high resolution digital terrain models dtms complemented by detailed analyses of repeat photography represents a unique assessment of topographic changes and slope failures over half a century and reveals a total volume loss in bedrock and steep glaciers in the central part of the face of around 25 10 6 m 3 between 1988 and 2007 the high rock and ice avalanche activity translates into an increase in erosion rates of about one order of magnitude during recent decades the study indicates that changes in atmospheric temperatures and connected changes in ice cover can induce slope destabiliza tion in high mountain faces analyses of temperature data show that the start of the intense mass movement activity coincided with increased mean annual temperatures in the region around 1990 however once triggered mass movement activity seems to be able to proceed in a self reinforcing cycle whereby single mass movement events might be strongly influenced by short term extreme temperature events the investigations suggest a strong stability coupling between steep glaciers and underlying bedrock as most bedrock instabilities are located in areas where surface ice has disappeared recently and the failure zones are frequently spatially correlated and often develop from lower altitudes progressively upwards copyright 2012 john wiley sons ltd

unraveling driving factors for large rock ice avalanche mobility large rock ice avalanches have attracted attention from scientists for decades and some of these events have caused high numbers of fatalities a relation between rock slope instabilities in cold high mountain areas and climate change is currently becoming more evident and questions about possible consequences and hazard scenarios in densely populated high mountain regions leading beyond historical precedence are rising to improve hazard assessment of potential rock ice avalanches their mobility is a critical factor this contribution is an attempt to unravel driving factors for the mobility of large rock ice avalanches by synthesizing results from physical laboratory experiments and empirical data from 64 rock ice avalanches with volumes 1x106 m3 from glacierized high mountain regions around the world the influence of avalanche volume water and ice content low friction surfaces and topography on the apparent coefficient of friction as a measure of mobility is assessed in laboratory experiments granular ice in the moving mass was found to reduce bulk friction up to 20 while water led to a reduction around 50 for completely saturated material compared with dry flows evidence for the effects of water as a key driving factor to enhance mobility was also found in the empirical data while the influence of the ice content could not be confirmed to be of much relevance in nature besides liquefaction it was confirmed that mobility increases with volumes and that frictional surface characteristics such as flow paths over glaciers are also dominant variables determining mass movement mobility effects of the topography along the flow path as well as channeling are assumed to be other critical factors the results provide an empirical basis to roughly account for different path and flow characteristics of large rock ice avalanches and to find appropriate ranges for friction parameters for scenario modeling and hazard assessments copyright 2011 john wiley sons ltd

the role of the central asian mountains on the midwinter suppression of north pacific storminess abstractthe role of the central asian mountains on north pacific storminess is examined using an atmospheric general circulation model by varying the height and the areas of the mountains a series of model integrations show that the presence of the central asian mountains suppresses the north pacific storminess by 20 30 during boreal winter their impact on storminess is found to be small during other seasons the mountains amplify stationary waves and effectively weaken the high frequency transient eddy kinetic energy in boreal winter two main causes of the reduced storminess are diagnosed first the decrease in storminess appears to be associated with a weakening of downstream eddy development the mountains disorganize the zonal coherency of wave packets and refract them more equatorward as the zonal traveling distance of wave packets gets substantially shorter downstream eddy development gets weaker second the central asian mountains suppress the global baroclinic energy conversion the decre

avalanching glacier instabilities review on processes and early warning perspectives avalanching glacier instabilities are gravity driven rupture phenomena that might cause major disasters especially when they are at the origin of a chain of processes reliably forecasting such events combined with a timely evacuation of endangered inhabited areas often constitute the most efficient action recently considerable efforts in monitoring analyzing and modeling such phenomena have led to significant advances in destabilization process understanding improving early warning perspectives the purpose of this paper is to review the recent progress in this domain three different types of instabilities can be identified depending on the thermal properties of the ice bed interface if cold 1 the maturation of the rupture is associated with a typical time evolution of surface velocities and passive seismic activity a prediction of the final break off is possible using these precursory signs for the two other types water plays a key role in the development of the instability if the ice bed interface is partly temperate 2 the presence of meltwater may reduce the basal resistance which promotes the instability no clear and easily detectable precursory signs are known in this case and the only way to infer any potential instability is to monitor the temporal evolution of the thermal regime the last type of instability 3 concerns steep temperate glacier tongues switching for several days weeks during the melting season into a so called active phase followed in rare cases by a major break off event although the prediction of such events is still far from being achievable critical conditions promoting the final instability can be identified