nature and timing of large landslides within an active orogen eastern pamir china abstract large scale landsliding involving 106 m3 in volume is important in landscape development in high mountains to assess the importance of large landslides in high mountains four large landslides bulunkou muztagh taheman and yimake were mapped in the ne chinese pamir at the westernmost end of the himalayan tibetan orogen and dated using 10be terrestrial cosmogenic nuclides the bulunkou landslide at the southernmost end of muji valley is composed of 1 7 107 m3 of landslide debris and has an age of 2 0 0 1 ka the muztagh landslide located on the sw side of the massif muztagh ata is composed of 4 7 108 m3 of debris and has an age of 14 3 0 8 ka the taheman landslide located south of muztagh ata is composed of 2 6 108 m3 of landslide debris and has an age of 6 8 0 2 ka the yimake landslide on the northern frontal range of the pamir at the southwestern end of the tarim basin is composed of 1 4 109 m3 of landslide debris and has an age of 7 1 0 6 ka two other large landslides are present in the region the aerpa aigezi on a tributary of the gez river and the bile jiyi on the yarkand river landslides and are composed of 1 6 107 m3 and 5 2 106 m3 of landslide debris respectively however the aerpa aigezi and bile jiyi landslides were not studied in as much detail or dated because of their inaccessibility given the tectonically active nature of this region with numerous active faults and the morphology of the landslides these landslides were likely triggered by earthquakes however other causes including long term increased precipitation and geologic bedrock structure could be important contributing factors in their formation

profiles of dimethylsulphoniopropionate dmsp algal pigments nutrients and salinity in the fast ice of prydz bay antarctica 1 total dimethylsulphoniopropionate dmspt chlorophyll a chl a and algal marker pigments were measured in 12 fast ice cores collected from prydz bay eastern antarctica 68 69 s 77 79 e in october 1997 and november 1998 patterns of dmspt distribution through the ice were similar on spatial scales of meters to tens of kilometers within ice sheets grouped according to growth history this reflects the association of dmsp in fast ice with autotrophic biomass distribution which is intrinsically linked with ice growth and differed between the ice sheets the 12 fast ice cores were divided into three groups on the basis of ice thickness and year concentrations of dmspt ranged widely from 9 to 1478 nm with marked peaks occurring within each core mean dmspt concentrations were higher 200 nm in the medium first year ice 0 7 1 2 m than in the thick 1 2 m first year ice 90 nm mainly because of a local surface algal assemblage that may be atypical the fast ice algal assemblages in surface interior and bottom ice were dominated by diatoms fucoxanthin chl a concentrations 80 dinoflagellates and haptophytes were generally small and variable components of the assemblages peridinin chl a 2 11 and 19 hexanoyloxyfucoxanthin chl a 2 4 respectively our data support the important contribution of diatoms to dmsp production in sea ice nutrient nitrate silicate phosphate concentrations were measured for one group of cores silicate and chl a concentrations were significantly correlated r 0 30 p 1000 nm n 410 the mean dmsp concentrations during spring summer were within the range of 107 322 nm with an overall mean of 178 nm mean dmsp concentrations in antarctic sea ice appear to be comparable between studies and across the antarctic sea ice zone we estimate that the antarctic sea ice zone may contain up to 9 mmole sulphur as dmsp

sedimentation of 13c rich organic matter from antarctic sea ice algae a potential indicator of past sea ice extent organic matter collected in sediment traps at a nearshore marine site in prydz bay east antarctica displayed a pronounced seasonal variation in carbon isotopes expressed as 13 c om winter values were fairly constant near 20 before increasing to above 15 in response to inputs from sea ice algae in early spring particulate organic matter obtained directly from sea ice cores exhibited very high 13 c om values typically 15 but as much as 8 much above the values of organic matter suspended in the water column below the sea ice the sea ice algae contributed 20 of the annual flux of organic matter and the 13 c om measurements from a sediment core at the site suggest that this value is representative of the recent past all of these carbon isotopic compositions are considerably above the extremely 13 c depleted compositions generally 25 to 30 that have been found in many other antarctic and southern ocean studies the elevated 13 c om values derive from considerable depletion of dissolved carbon dioxide and nutrients within the sea ice and to a lesser extent within stratified surface waters induced by melting sea ice thus elevated 13 c om values in southern ocean sediment cores may indicate the presence of sea ice hosted algae rather than temperature or surface co 2 pressure p co 2 variations

cosmic ray labeling of erosion surfaces in situ nuclide production rates and erosion models a number of in situ cosmogenic radionuclides and stable nuclides have been measured in natural exposed rock surfaces with a view to study their in situ production and rock erosion rates 1 the in situ radionuclides can be used for a high resolution tomography of the erosional history of an exposed surface two stable nuclides 3he 21ne and five radionuclides 10be 26al 36cl 14c 39ar having half lives in the range of 300 1 5 106 yr half life are measurable in many rock types a prerequisite for the application of the in situ nuclides for the study of erosional histories of surfaces is a knowledge of their production rates under different irradiation conditions altitude latitude irradiation geometry and shielding relative nuclide production rates can be determined fairly accurately using the extensive available data on cosmic ray neutrons 2 absolute nuclide production rates cannot generally be predicted with any accuracy because of lack of data on excitation functions of nuclides unless some normalization is possible as was done in the case of several cosmic ray produced isotopes in the atmosphere 3 based on a recent natural calibration experiment in which erosion free surfaces exposed to cosmic radiation for 11 000 yrs were sampled the absolute production rates of 10be and 26al in quartz have been accurately estimated for mountain altitudes in sierra nevada 4 the absolute production rates of 10be and 26al in quartz can therefore be estimated fairly accurately for any given latitude and altitude some measurements of 14c in rocks of low erosion rate 5 similarly allow an estimate of its production rate attempts made to measure the in situ production rates of 3he in rocks have not yet led to a convergent production rate in view of the importance of knowing the production rates of isotopes of he ne and ar i present here theoretical estimates of their production rates based on available cross section data i discuss the information that can be extracted from the study of the in situ nuclides in rocks useful parameters characterizing the exposure history of a rock surface are 1 the effective surface exposure age and 2 the time averaged erosion rate the implications of these parameters for single and multiple nuclide studies are discussed in terms of the erosion models considered

calcium carbonate as ikaite crystals in antarctic sea ice 1 we report on the discovery of the mineral ikaite caco3 6h2o in sea ice from the southern ocean the precipitation of caco3 during the freezing of seawater has previously been predicted from thermodynamic modelling indirect measurements and has been documented in artificial sea ice during laboratory experiments but has not been reported for natural sea ice it is assumed that caco3 formation in sea ice may be important for a sea ice driven carbon pump in ice covered oceanic waters without direct evidence of caco3 precipitation in sea ice its role in this and other processes has remained speculative the discovery of caco3 6h2o crystals in natural sea ice provides the necessary evidence for the evaluation of previous assumptions and lays the foundation for further studies to help elucidate the role of ikaite in the carbon cycle of the seasonally sea ice covered regions

sedimentary sterols as biogeochemical indicators in the southern ocean abstract abundances and isotopic compositions of sterols and of total organic carbon in surface sediments were measured at 18 stations in the ross sea antarctica ten sterols 5 cholestan 3 ol cholestanol cholest 5 en 3 ol cholesterol cholest 5 22e dien 3 ol 24 methyl 5 cholest 22e en 3 ol brassicastanol 24 methyl cholest 5 22e dien 3 ol brassicasterol 24 ethyl 5 cholestan 3 ol sitostanol 24 ethyl cholest 5 en 3 ol sitosterol 24 ethyl cholest 5 22e dien 3 ol stigmasterol 4 23 24 trimethyl 5 cholestan 3 ol dinostanol and 4 23 24 trimethyl 5 cholest 22e en 3 ol dinosterol are most widely distributed polytopic vector analysis of the variations in abundance resolved four sources for these compounds an assemblage of phytoplankton characteristic of the ross sea polynya diatoms and associated consumers zooplankton and processes associated with heterotrophic dinoflagellates concentrations of stanols were strongly correlated with those of dinosterol and dinostanol concentrations of total organic carbon toc ranged from 0 1 to 1 2 and were lowest on crests and banks and higher in basins the mole fraction of organic carbon occurring as sterols ranged from 3 to 1100 ppm values were lowest at stations with anomalously old toc estimated from regional variations in the radiocarbon age of acid insoluble organic carbon thus pointing to weathering and redistribution of surface sediments as important factors in the differential degradation of sterols and toc the difference in first order rate constants for the degradation of these materials is ca 0 002 yr 1 stigmasterol and the c27 sterols were significantly enriched in 13c relative to other sterols the abundance of 13c in toc at four western stations was 4 higher than elsewhere abundances of 13c in all sterols at these stations is also 4 higher than elsewhere indicating enrichment of 13c in the entire biological community independent observations of p co 2 in surface waters together with known relationships between isotopic fractionation and the concentration of dissolved co2 show that the isotopic zonation in organic carbon is due entirely to dynamic drawdown of co2 in western surface waters at those locations late melting of ice produces salinity gradients that inhibit mixing of co2 from deeper waters

tectonic denudation and topographic development in the spanish sierra nevada 1 the denudation history of the rapidly uplifting western part of the spanish sierra nevada was assessed using apatite fission track aft ages and 10be analyses of bedrock and fluvial sediments major contrasts in the denudation history are recorded within the 27 km2 rio torrente catchment upland areas are characterized by low relief low slope angles and locally the preservation of shallow marine sediments which have experienced 2 km of denudation since circa 4 ma the minimum denudation rates of 0 4 mm yr 1 derived from aft also contrast with the slow medium term 104 years erosion rates 0 044 0 015 mm yr 1 estimated from 10be measurements at high elevations the local medium long term contrasts in denudation rates within the high sierra nevada indicate that much of the unroofing occurs by tectonic denudation on flat lying detachments in lower elevation parts of the catchment rapid river incision coupled to rock uplift has produced 1 6 km of relief implying that the rivers and adjacent hillslopes close to the edge of the orogen are sensitive to normal fault driven changes in base level however these changes are not transmitted into the low relief slowly eroding upland areas thus the core of the mountain range continues to increase in elevation until the limits of crustal strength are reached and denudation is initiated along planes of structural weakness we propose that this form of tectonic denudation provides an effective limit to relief in young orogens

dynamics of the carbon dioxide system in the dead sea because the dead sea is a ca chloride hypersaline lake and is virtually lifeless it is an excellent system to investigate the physical and chemical paths of the carbon cycle in terrestrial aquatic environments that are generally overwhelmed by biologic carbon fluxes the dead sea is known to form massive aragonite deposits in the form of varves at present and during the lisan period late pleistocene the commonly accepted season for the main aragonite precipitation was summer and the trigger for precipitation was attributed to evaporation and the warming of surface water whitening events to determine the main carbon fluxes in the dead sea we followed changes in the carbonate system of the mixed layer from february 1993 to december 1994 after stratification formed due to heavy flooding during the winter of 1992 the stratification isolated the mixed layer a relatively small reservoir from the main brine body causing an amplification of the chemical signals the data show that partial pressure of co2 in the lake was very high 2000 matm total alkalinity and total carbon of the mixed layer decreased with time whereas d 13 c increased the high pco2 originates from precipitation of aragonite and implies that in many aquatic systems it may originate from an inorganic process and not only from degradation of organic matter thermodynamic calculation estimated the degree of aragonite saturation to be 15 when 10 of dead sea brine with a high ca content mixed with 90 runoff freshwater with high bicarbonate content therefore mixing during winter flooding triggers massive aragonite deposition in the dead sea the general conclusion is that inorganic carbonate precipitation by mixing of two solutions one supplying ca 21 and the other hco3 should be considered in the evaluation of the carbonate system in a wide range of aquatic environments a mass balance model for total alkalinity total carbon and carbon isotopes reveals two main carbon sinks and one carbon source the sinks are a chemical deposition of aragonite 1 4 mol z m 22 z y 21 and co2 escape to the atmosphere 4 mol z m 22 z y 21 and the source is bicarbonate input by floods 2 1 mol z m 22 z y 21 the precipitation rate of the present dead sea is approximately sixfold lower than the average precipitation rate during the lisan period implying a wetter climate during that period the present co2 escape rate from the mixed layer is twice the bicarbonate input and threefold the aragonite precipitation rate indicating a net co2 loss we suggest that such a scenario is possible if the dead sea was meromictic stratified for a very long period of time copyright 2001 elsevier science ltd

stable isotope composition of dissolved inorganic carbon and particulate organic carbon in sea ice from the ross sea antarctica 1 we examined controls on the carbon isotopic composition of sea ice brines and organic matter during cruises to the ross sea antarctica in november december 1998 and november december 2006 brine samples were analyzed for salinity nutrients total dissolved inorganic carbon co2 and the 13c 12c ratio of co2 particulate organic matter from sea ice cores was analyzed for percent particulate organic carbon poc percent total particulate nitrogen tpn and stable carbon isotopic composition 13cpoc co2 in sea ice brines ranged from 1368 to 7149 mol kg 1 equivalent to 1483 to 2519 mol kg 1 when normalized to 34 5 psu salinity s co2 the average salinity of ross sea surface waters sea ice primary producers removed up to 34 of the available co2 an amount much higher than the maximum removal observed in sea ice free water carbonate precipitation and co2 degassing may reduce s co2 by a similar amount e g 30 in the most hypersaline sea ice environments although brine volumes are low in very cold ice that supports these brines brine ranged from 2 6 to 8 0 while 13cpoc ranged from 30 5 to 9 2 isotopic enrichment of the co2 pool via net community production accounts for some but not all carbon isotopic enrichment of sea ice poc comparisons of s co2 and 13cpoc within sea ice suggest that ep the net photosynthetic fractionation factor for sea ice algae is 8 smaller than the ep observed for phytoplankton in open water regions of the ross sea these results have implications for modeling of carbon uptake and transformation in the ice covered ocean and for reconstruction of past sea ice extent based on stable isotopic composition of organic matter in sediment cores

the aftershock sequence of the 2015 april 25 gorkha nepal earthquake l b adhikari 1 u p gautam 1 b p koirala 1 m bhattarai 1 t kandel 2 r m gupta 1 c timsina 1 n maharjan 1 k maharjan 2 t dahal 2 r hoste colomer 3 4 y cano 3 m dandine 3 a guilhem 3 s merrer 3 p roudil3 and l bollinger3 1national seismological centre department of mines and geology lainchaur kathmandu nepal e mail adhikari research gmail com 2regional seismological centre department of mines and geology surkhet birendranagar nepal 3cea dam dif f 91297 arpajon france 4laboratoire de geologie ecole normale superieure cnrs 24 rue lhomond f 75004 paris france

experimental evidence for carbonate precipitation and co2 degassing during sea ice formation chemical and stable carbon isotopic modifications during the freezing of artificial seawater were measured in four 4 m3 tank incubations three of the four incubations were inoculated with a non axenic antarctic diatom culture the 18 days of freezing resulted in 25 to 27 cm thick ice sheets overlying the residual seawater the ice phase was characterized by a decrease in temperature from 1 9 to 2 2oc in the under ice seawater down to 6 7oc in the upper 4 cm of the ice sheet with a concurrent increase in the salinity of the under ice seawater and brine inclusions of the ice sheet as a result of physical concentration of major dissolved salts by expulsion from the solid ice matrix measurements of ph total dissolved inorganic carbon ct and its stable isotopic composition d13ct all exhibited changes which suggest minimal effect by biological activity during the experiment a systematic drop in ph and salinity normalized ct by up to 0 37 phsws units and 376 mol c kg 1 respectively at the lowest temperature and highest salinity part of the ice sheet were coupled with an equally systematic 13c enrichment of the ct calculations based on the direct ph and ct measurements indicated a steady increase in the in situ concentration of dissolved carbon dioxide co2 aq with time and increasing salinity within the ice sheet partly due to changes in the dissociation constants of carbonic acid in the low temperature high salinity range within sea ice the combined effects of temperature and salinity on the solubility of co2 over the range of conditions encountered during this study was a slight net decrease in the equilibrium co2 aq concentration as a result of the salting out overriding the increase in solubility with decreasing temperature hence the increase in the in situ co2 aq concentration lead to saturation or supersaturation of the brine inclusions in the ice sheet with respect to atmospheric pco2 3 5x10 4 atm when all physico chemical processes are considered we expect co2 degassing and carbonate mineral precipitation from the brine inclusions of the ice sheet which were saturated or highly supersaturated with respect to both the anhydrous calcite aragonite vaterite and hydrated ikaite carbonate minerals

integration between ground based and satellite sar data in landslide mapping the san fratello case study abstract the potential use of the integration of psi persistent scatterer interferometry and gb insar ground based synthetic aperture radar interferometry for landslide hazard mitigation was evaluated for mapping and monitoring activities of the san fratello landslide sicily italy intense and exceptional rainfall events are the main factors that triggered several slope movements in the study area which is susceptible to landslides because of its steep slopes and silty clayey sedimentary cover in the last three centuries the town of san fratello was affected by three large landslides developed in different periods the oldest one occurred in 1754 damaging the northeastern sector of the town in 1922 a large landslide completely destroyed a wide area in the western hillside of the town in this paper the attention is focussed on the most recent landslide that occurred on 14 february 2010 in this case the phenomenon produced the failure of a large sector of the eastern hillside causing severe damages to buildings and infrastructures in particular several slow moving rotational and translational slides occurred in the area making it suitable to monitor ground instability through different insar techniques ps insar permanent scatterers sar interferometry techniques using ers 1 ers 2 envisat radarsat 1 and cosmo skymed sar images were applied to analyze ground displacements during pre and post event phases moreover during the post event phase in march 2010 a gb insar system able to acquire data continuously every 14 min was installed collecting ground displacement maps for a period of about three years until march 2013 through the integration of space borne and ground based data sets ground deformation velocity maps were obtained providing a more accurate delimitation of the february 2010 landslide boundary with respect to the carried out traditional geomorphological field survey the integration of gb insar and psi techniques proved to be very effective in landslide mapping in the san fratello test site representing a valid scientific support for local authorities and decision makers during the post emergency management

spatial distribution of trends and seasonally in the hemispheric sea ice covers 1978 1996 we extend earlier analyses of a 8 8 year sea ice data set that described the local seasonal variations and trends in each of the hemispheric sea ice covers to the recently merged 18 2 year sea ice record from four satellite instruments the seasonal cycle characteristics remain essentially the same as for the shorter time series but the local trends are markedly different in some cases reversing sign the sign reversal reflects the lack of a consistent long term trend and could be the result of localized long term oscillations in the hemispheric sea ice covers by combining the separate hemispheric sea ice records into a global one we have shown that there are statistically significant net decreases in the sea ice coverage on a global scale the change in the global sea ice extent is 0 01 0 003 106 km2 per decade the decrease in the areal coverage of the sea ice is only slightly smaller so that the difference in the two the ice free areas within the packs has no statistically significant change

controls on the carbon isotopic composition of southern ocean phytoplankton carbon isotopic compositions of suspended organic matter and biomarker compounds were determined for 59 samples filtered from southern ocean surface waters in january 1994 along two north south transects woce sr3 from tasmania to antarctica and across the princess elizabeth trough pet east of prydz bay antarctica along the sr3 line bulk organic matter show generally decreasing 13c contents southward which are well correlated with increasing dissolved molecular carbon dioxide concentrations co2 aq this relationship does not hold along the pet transect using concentrations and isotopic compositions of molecular compounds we evaluate the relative roles of several factors affecting the 13c of southern ocean suspended particulate organic matter along the woce sr3 transect the concentration of co2 aq plays an important role it is well described by a supply versus demand model for the extent of cellular co2 utilization and its associated linear dependence of isotopic fractionation ep on the reciprocal of co2 aq an equally important factor appears to be changes in algal assemblages along the sr3 transect with their contribution to isotopic fractionation also well described by the supply and demand model when formulated to include the cell surface volume control of supply changes in microalgal growth rates appear to have a minor effect on ep along the pet transect algal assemblage changes and possibly changes in microalgal growth rates appear to strongly affect the carbon isotopic variations of suspended organic matter these results can be used to improve the formulation of modern carbon cycle models that include phytoplankton carbon isotopic fractionation

the effect of biological activity caco3 mineral dynamics and co2 degassing in the inorganic carbon cycle in sea ice in late winter early spring in the weddell sea antarctica a large scale geographical study of the ice pack in the seasonal ice zone of the weddell sea antarctica took place from september to october 2006 sea ice brines with a salinity greater than 58 and temperature lower than 3 6oc were sampled from 22 ice stations the brines had large deficits in total alkalinity and in the concentrations of the major dissolved macronutrients total dissolved inorganic carbon nitrate and soluble reactive phosphorus relative to their concentrations in the surface oceanic water and conservative behaviour during seawater freezing the concentration deficits were related to the dissolved inorganic carbon consuming processes of photosynthesis caco3 precipitation and co2 degassing the largest concentration deficits in total dissolved inorganic carbon were found to be associated with caco3 precipitation and co2 degassing because the magnitude of the photosynthesis induced concentration deficit in total dissolved inorganic carbon is controlled by the size of the inorganic nutrient pool which can be limited in sea ice by its openness to exchange with the surrounding oceanic water

landforms and landscape evolution in the skardu shigar and braldu valleys central karakoram abstract the central karakoram which includes k2 in pakistan is one of the most rapidly rising areas on earth and exhibits complex topography and extreme relief impressive valley fills and glacial landforms are present throughout the valleys the dynamics of landscape evolution of the region are currently not well understood consequently the landforms were mapped and assessed in the skardu shigar and braldu valleys to elucidate the spatio temporal scale dependencies of surface processes active in the region these valleys were examined using geomorphic field methods remote sensing geomorphometry and terrestrial cosmogenic nuclides tcns surface exposure dating the glaciers in this region have oscillated considerably throughout the late quaternary and four glacial stages have been recognized including at least six glacial advances surface processes readjusted after glacier retreat and ubiquitous mass movements and catastrophic landsliding transported material from steep slopes to valley bottoms while glaciofluvial meltwater and glacier outburst floods redistributed sediment down valley glacier geochronology and late holocene ages of the outburst flood deposits indicate that landscape evolution has been dominated by glaciation and paraglaciation during the late quaternary

kinetics of ikaite precipitation and dissolution in seawater derived brines at sub zero temperatures to 265 k abstract the kinetics of calcium carbonate hexahydrate ikaite precipitation and dissolution were investigated in seawater and seawater derived brines at sub zero temperatures using the constant addition experimental technique the steady state rate of these two processes was found to be a function of the deviation of the solution from equilibrium with respect to ikaite and conformed to the same empirical rate law as the anhydrous caco 3 polymorphs calcite and aragonite in addition to the saturation state of the brine with respect to ikaite the salinity of the brine and the temperature of the reaction evidently exerted some control on the ikaite precipitation kinetics while the dissolution kinetics of the polymorph were not noticeably influenced by these two parameters the experimental salinity and temperature conditions were equivalent to those at thermal equilibrium between brine and ice in the sea ice cover of polar seas simple modelling of the co 2 system by extrapolation of the oceanic equivalent to sea ice brines showed that the physical concentration of seawater ions and the changes in ikaite solubility as a function of salinity and temperature both inherent in the sea ice system would be insufficient to drive the emergent brines to ikaite supersaturation and precipitation in sea ice down to 8 c the loss of dissolved inorganic carbon to the gas phase of sea ice and to sympagic autotrophs are two independent mechanisms which in nature could prompt the brine co 2 system towards ikaite supersaturation and precipitation under these conditions the steady state precipitation rate of ikaite was found to be fast enough for rapid formation within short time scales days to weeks in sea ice the observed ikaite dissolution kinetics were also found conducive to short turn over time scales of a few hours to a few days in corrosive solutions such as surface seawater

carbon 13 carbon 12 ratios of sedimentary organic matter from the ross sea antarctica a record of phytoplankton bloom dynamics suspended and sea ice particulate organic carbon poc collected from the ross s 13 in r sea antarctica shows seasonal enrichments in c unrelated to at osphe ic pco2 varia tions the carbon isotopic composition of phytoplankton bloom related poc 5 3cpoc col lected from the southwestern ross sea during a 1992 bloom event is strongly correlated with poc concentration this correlation may be attributed to high growth rates species specific fractionation input from sea ice communities enriched in 3c increased heterotrophic recy cling or high rates of bloom related co2 aq drawdown in the upper water column while all these factors likely contribute to poc 3c enrichment we favor the latter hypothesis because of the link betweenc enrichment and partial isolation of the surface water co2 pool in ar eas of sea ice melt induced stratification of the upper water column the co2 drawdown hy pothesis is further supported by dissolved inorganic carbon 5 3c enrichments of up to 2 3 0 in the vicinity of phytoplankton blooms patterns of isotopic composition and organic carbon concentration in ross sea surface sediments resemble that of the upper water column par ticularly in areas of frequent annually recurrent phytoplankton blooms overall surface sediment 5 c values are 1 3 o enriched relative to surface water poc with the highest 5 3c values found in areas that receive large amounts of phytoplankton bloom detritus future downcore carbon isotopic analyses may prove useful as tracers of bloom dynamics in melt water influenced areas where large enrichments in 3c coincide with high productivity

the new remote sensing derived swiss glacier inventory ii first results complete swiss glacier inventories are available for 1850 reconstructed and 1973 from aerial photography connected to the global land ice measurements from space project a new swiss glacier inventory for approximately the year 2000 sgi 2000 is compiled mainly based on satellite imagery the developed and applied remotesensing and geographical information system gis methods are described in part i of the contribution in part ii the inventory design first result analyses and comparisons with former glacial conditions are presented as basic entries sgi 2000 contains the individual glacier identification planimetric glacier boundaries as derived from image analysis digitized central flowlines and polygonal glacier basin maps all other parameters are automatically deduced from the above entries and a digital elevation model within a gis here we analyze a set of small bernese and valais glaciers of area 2 these glaciers lost about 21 of area from 1973 to 1998 in addition to about 80 during 1850 1973 both with respect to the 1973 area in order to track the latest trend in more detail anintermediate glacier condition has been compiled from satellite imagery of 1985 this analysis gave an increasing speed of area loss 19 for 1985 98

terraces on the florida escarpment implications for erosional processes seabeam bathymetric data and gloria geologic long range inclined asdic sidescan sonar images of a 175 km long section of the florida escarpment in the eastern gulf of mexico show that this carbonate escarpment has been eroded since its initial formation but its morphology suggests that erosional processes have not acted uniformly on the escarpment parts of the escarpment are notched by box canyons that have extremely steep headwalls and may be sites of active ground water sapping the intercanyon areas commonly have previously unrecognized terraces below 2 600 m above 2 600 m the escarpment is steeper and has no terraces the terraces may reflect differences in platform strata exposed at the escarpment that are responding differently to erosional processes

deep crustal structure in the eastern gulf of mexico we use air gun data recorded by ocean bottom seismometers to constrain the velocity structure along gulf of mexico basin opening line 4 a profile extending from the northwestern florida peninsula across the florida escarpment to the central gulf of mexico moderately thinned continental crust with a moho depth of 32 33 km average sediment thickness of 6 km and an average crustal thickness of 27 km is interpreted on the northeast end of the profile offshore florida thinned and intruded continental crust is identified over a horizontal distance of 225 km where the crustal layer thins from 25 km to 6 7 km mean seismic velocities of the crust in this region increase from 6 55 km s to 6 95 km s from northeast to southwest and are evidence for increased magmatic input as rifting developed oceanic crust with an average thickness of 5 6 5 7 km is observed over a distance of 175 km on the southwest end of the profile with an extinct spreading ridge with an axial valley morphology imaged on a coincident seismic reflection profile anomalously high upper oceanic crust velocities of 6 0 6 7 km s are interpreted as massive basalt flows and could reflect increased temperatures during emplacement integrating well seismic reflection and our seismic refraction data allow us to estimate a full spreading rate of 2 2 cm yr for seafloor spreading along the profile this indicates that oceanic crust was emplaced at a slow spreading center

dynamics of pco2 and related air ice co2 fluxes in the arctic coastal zone amundsen gulf beaufort sea we present an arctic seasonal survey of carbon dioxide partial pressure pco 2 dynamics within sea ice brine and related air ice co 2 fluxes the survey was carried out from early spring to the beginning of summer in the arctic coastal waters of the amundsen gulf high concentrations of pco 2 up to 1834 matm were observed in the sea ice in early april as a consequence of concentration of solutes in brines caco 3 precipitation and microbial respiration caco 3 precipitation was detected through anomalies in total alkalinity ta and dissolved inorganic carbon dic this precipitation seems to have occurred in highly saline brine in the upper part of the ice cover and in bulk ice as summer draws near the ice temperature increases and brine pco 3 shifts from a large supersaturation 1834 matm to a marked undersaturation down to almost 0 matm this decrease was ascribed to brine dilution by ice meltwater dissolution of caco 3 and photosynthesis during the sympagic algal bloom the magnitude of the co 2 fluxes was controlled by ice temperature through its control on brine volume and brine channels connectivity and the concentration gradient between brine and the atmosphere however the state of the ice interface clearly affects air ice co 2 fluxes

geomorphic evolution of the malta escarpment and implications for the messinian evaporative drawdown in the eastern mediterranean sea abstract carbonate escarpments are submarine limestone and dolomite cliffs that have been documented in numerous sites around the world their geomorphic evolution is poorly understood due to difficulties in assessing escarpment outcrops and the limited resolution achieved by geophysical techniques across their steep topographies the geomorphic evolution of carbonate escarpments in the mediterranean sea has been influenced by the messinian salinity crisis msc during the msc 5 97 5 33 ma the mediterranean sea became a saline basin due to a temporary restriction of the atlantic mediterranean seaway resulting in the deposition of more than one million cubic kilometres of salt the extent and relative chronology of the evaporative drawdown phases associated to the msc remain poorly constrained in this paper we combine geophysical and sedimentological data from the central mediterranean sea to reconstruct the geomorphic evolution of the malta escarpment and infer the extent and timing of evaporative drawdown in the eastern mediterranean sea during the msc we propose that during a msc base level fall fluvial erosion formed a dense network of canyons across the malta escarpment whilst coastal erosion developed extensive palaeoshorelines and shore platforms the drivers of geomorphic evolution of the malta escarpment after the msc include i canyon erosion by submarine gravity flows with the most recent activity taking place

the role of mass movements on landscape evolution in the central karakoram discussion and speculation abstract mass movement constitutes an important process in the evolution of landscapes in mountain regions however the role of massive slope failures in denudational unloading and landscape evolution has not been extensively studied large scale mass movements in one of the greatest mountain ranges on earth the central karakoram in pakistan were therefore examined to help evaluate their role in landscape evolution in high mountains specifically four major mass movement complexes ghoro choh rock avalanche busper sackung and slope failure gomboro slope failure and urdokas rockslide each comprising 10 6 m 3 of debris were assessed and mapped in detail two of these mass movement complexes the ghoro choh rock avalanche and gomboro slope failure were dated using terrestrial cosmogenic nuclides the ages of occurrence of the mass movement complexes studied in the central karakoram date from the late pleistocene to the holocene the four major mass movement complexes all involved the removal of mass from the tops of mountain ridges and peaks that failed and were subsequently transported towards the bottom of their respective valleys such massive movement of mass is anomalous compared to other forms of mass movement and is generally spatially coincident with exposed deeply buried gneiss dome structures these large scale movements appear to be part of a coupled system involving river incision and glacial debuttrussing although earthquakes might have triggered these mass movements this study illustrates the role of climate forcing which is part of a coupled system of denudational unloading but it is unclear whether high magnitude low frequency events such as these initiate the isostatic and tectonic influx of mass or if sustained high magnitude denudation resulting from a coupled system is responsible for the exhumation of buried structures

first estimates of the contribution of caco3 precipitation to the release of co2 to the atmosphere during young sea ice growth 1 we report measurements of ph total alkalinity air ice co2 fluxes chamber method and caco3 content of frost flowers ff and thin landfast sea ice as the temperature decreases concentration of solutes in the brine skim increases along this gradual concentration process some salts reach their solubility threshold and start precipitating the precipitation of ikaite caco3 6h2o was confirmed in the ff and throughout the ice by raman spectroscopy and x ray analysis the amount of ikaite precipitated was estimated to be 25 mol kg 1 melted ff in the ff and is shown to decrease from 19 to 15 mol kg 1 melted ice in the upper part and at the bottom of the ice respectively co2 release due to precipitation of caco3 is estimated to be 50 mol kg 1 melted samples the dissolved inorganic carbon dic normalized to a salinity of 10 exhibits significant depletion in the upper layer of the ice and in the ff this dic loss is estimated to be 2069 mol kg 1 melted sample and corresponds to a co2 release from the ice to the atmosphere ranging from 20 to 40 mmol m 2 d 1 this estimate is consistent with flux measurements of air ice co2 exchange our measurements confirm previous laboratory findings that growing young sea ice acts as a source of co2 to the atmosphere caco3 precipitation during early ice growth appears to promote the release of co2 to the atmosphere however its contribution to the overall release by newly formed ice is most likely minor

sea ice diatom contributions to holocene nutrient utilization in east antarctica combined high resolution holocene 30sidiat and 13cdiat paleorecords are presented from theseasonal ice zone east antarctica both data sets re ect periods of increased nutrient utilization by diatomsduring the hypsithermal period circa 7800 to 3500 calendar years cal years b p coincident with a higherabundance of open water diatom species fragilariopsis kerguelensis increased biogenic silica productivity bsi and higher regional summer temperatures the neoglacial period after circa 3500 cal years b p isre ected by an increase in sea ice indicative species fragilariopsis curta and fragilariopsis cylindrus upto50 along with a decrease in bsi and 13cdiat 18 to 23 however over this period 30sidiatdata show an increasing trend to some of the highest values in the holocene record average of 0 43 competing hypotheses are discussed to account for the decoupling trend in utilization proxies including ironfertilization species dependent fractionation effects and diatom habitats based on mass balance calculations we highlight that diatom species derived from the semi enclosed sea ice environment may have a confoundingeffect upon 30sidowncorecompositions of the seasonal sea ice zone a diatom composition with approximately28 of biogenic silica derived from the sea ice environment diat si can account for the increased averagecompo sition of 30sidiatduring the neoglacial these data highlight the signi cant role sea ice diatoms can playwith relation to their export in sediment records which has implications on productivity reconstructions fromthe seasonal ice zone

seepage induced erosion of submarine carbonate escarpments a numerical simulation abstract a three dimensional numerical model has been constructed to examine the seepage induced erosional process of the florida carbonate escarpment the erosion takes place either by the mechanical failure associated with the seepage force or the corrosion due to the fluid chemistry the numerical model assumes homogeneous darcian fluid flow and uses the strongly implicit finite different scheme the erosion is reflected in the model as removal of the finite difference cells whose pore pressure gradient exceeds a prescribed critical value for failure seafloor is the surface boundary of zero excess pore pressure the fluid is assumed to enter from the landward side of the formation the model results show that the topographic variation of the surface boundary causes refraction of the fluid flow field and that the flow focuses at the base of the escarpment the seepage induced erosion takes place bottom up steepens the lower escarpment slope and hence further intensifies the flow at the base because of this positive feed back mechanism between the hydrogeological regime and the geomorphogy the escarpment wall keeps retreating landward this mechanism can also be responsible for the formation and growth of the theater headed submarine canyons on the florida escarpment spacing and shape of these canyons are strongly influenced by the geometrical and hydrological parameters of the carbonate escarpment

controls on carbon isotope fractionation by diatoms in the peru upwelling region the fractionation of carbon isotopes during photosynthesis by phytoplankton is quantified for samples of suspended material collected along two transects across the peru continental margin in 1992 the magnitude of fractionation is estimated using the 13c of 24 methylcholesta 5 24 28 dien 3 ol diatoms and compared to that of c37 2 alkenone haptophytes isotopic fractionation by diatoms exhibits a wide range and large scatter when plotted against the reciprocal of the concentration of co2 aq while a strong correlation is observed for fractionation by alkenone bearing haptophytes diatom growth rates calculated from silicate concentrations and assuming monod growth kinetics normalized to co2 aq are well correlated to diatom fractionation factors these results support the concept that growth rates in addition to co2 concentrations impose a control on the fractionation of carbon isotopes by both taxonomic groups of algae in addition the very small fractionation factors for diatoms indicate that species in the peru upwelling region employed mechanisms which actively transport inorganic carbon into cells a size dependence is observed for the 13c of the diatom sterol 24 methylcholesta 5 24 28 dien 3 ol is enriched in 13c in samples of suspended material 20 m relative to the 20 m fraction this suggests that surface area to volume ratios also impose a control on the fractionation of carbon isotopes by diatoms a proposition that is supported by detailed cell geometry and isotopic data for two larger size fractions from one sample

climate change versus landslide origin of fill terraces in a rapidly eroding bedrock landscape san gabriel river california fill terraces along rivers represent the legacy of aggradation periods that are most commonly attributed to climate change in the north fork of the san gabriel river an arid bedrock landscape in the san gabriel mountains california a series of prominent fill terraces was previously related to climate change induced pulses of hillslope sediment supply that temporarily and repeatedly overwhelmed river transport capacity during the quaternary based on field observations digital topographic analysis and dating of quaternary deposits we suggest instead that valley aggradation was spatially confined to the north fork san gabriel canyon and was a consequence of the sudden supply of unconsolidated material to upstream reaches by one of the largest known landslides in the san gabriel mountains new 10 be derived surface exposure ages from the landslide deposits previously assumed to be early to middle pleistocene in age indicate at least three holocene events at ca 8 9 ka ca 4 5 ka and ca 0 5 1 ka the oldest and presumably most extensive landslide predates the valley aggradation period which is constrained by existing 14 c ages and new luminescence ages to ca 7 8 ka the spatial distribution morphology and sedimentology of the river terraces are consistent with deposition from far traveling debris flows that originated within and mined the landslide deposits valley aggradation in the north fork san gabriel canyon therefore resulted from locally enhanced sediment supply that temporarily overwhelmed river transport capacity but the lack of similar deposits in other parts of the san gabriel mountains argues against a regional climatic signal our study highlights the potential for valley aggradation by debris flows in arid bedrock landscapes downstream of landslides that occupy headwater areas

inorganic carbon system dynamics in landfast arctic sea ice during the early melt period we present the results of a 6 week time series of carbonate system and stable isotope measurements investigating the effects of sea ice on air sea co2 exchange during the early melt period in the canadian arctic archipelago our observations revealed significant changes in sea ice and sackhole brine carbonate system parameters that were associated with increasing temperatures and the buildup of chlorophyll a in bottom ice the warming sea ice column could be separated into distinct geochemical zones where biotic and abiotic processes exerted different influences on inorganic carbon and pco2 distributions in the bottom ice biological carbon uptake maintained undersaturated pco2 conditions throughout the time series while pco2 was supersaturated in the upper ice low co2 permeability of the sea ice matrix and snow cover effectively impeded co2 efflux to the atmosphere despite a strong pco2 gradient throughout the middle of the ice column brine pco2 decreased significantly with time and was tightly controlled by solubility as sea ice temperature and in situ melt dilution increased once the influence of melt dilution was accounted for both caco3 dissolution and seawater mixing were found to contribute alkalinity and dissolved inorganic carbon to brines with the caco3 contribution driving brine pco2 to values lower than predicted from melt water dilution alone this field study reveals a dynamic carbon system within the rapidly warming sea ice prior to snow melt we suggest that the early spring period drives the ice column toward pco2 undersaturation contributing to a weak atmospheric co2 sink as the melt period advances

analysis of satellite derived landslide at central nepal from 2011 to 2016 practical landslide detection has been a challenging task for decades due to the limitations of algorithms and complicated landslide cases visual interpretation is still one of the most reliable methods for landslide detection owing to the development of machine learning google earth engine platform and free access to landsat series images this paper presents a pixel level landslide detection model based on change detection using the random forest method in nepal from the year 2012 2016 the annual landsat images are synthesized into one image based on a ranking sequence of ndvi normalized differential vegetation index six more indexes and texture information are calculated as features covering water snow and vegetation enhancement dem digital elevation model is used to provide landscape pattern the synthesized features and landsat images of every 2 nearby years and dem are used to detect landslides in the latter year our model achieves an average producer s accuracy of 68 20 and user s accuracy of 77 01 for landslide detection in terms of the 9278 7443 pixel study image through the 5 years moreover based on the landslide detection results we analyzed the landslide event pattern in central nepal from 2012 to 2016 which accords with the actual cases

the new remote sensing derived swiss glacier inventory i methods a new swiss glacier inventory is to be compiled from satellite data for the year 2000 the study presented here describes two major tasks 1 an accuracy assessment of different methods for glacier classification with landsat thematic mapper tm data and a digital elevation model dem 2 the geographical information system gis based methods for automatic extraction of individual glaciers from classified satellite data and the computation of three dimensional glacier parameters such as minimum maximum and median elevation or slope and orientation by fusion with a dem first results obtained by these methods are presented in part ii of this paper kaab and others 2002 thresholding of a ratio image from tm4 and tm5 reveals the best suited glacier map the computation of glacier parameters in a gis environment is efficient and suitable for worldwide application the methods developed contribute to the u s geological survey led global land ice measurements from space glims project which is currently compiling a global inventory of land ice masses within the framework of global glacier monitoring haeberli and others 2000

carbonate system evolution at the arctic ocean surface during autumn freeze up based on comprehensive measurements of carbonate system parameters in sea ice brines and surface waters across a variety of ice types in the eastern beaufort sea during november and december of 2007 the newly forming sea ice appeared to release co2 not only was pco2 high within the ice but high salinities and inorganic carbon concentrations in the surface waters directly below the ice and in frost flowers above the ice indicated that brines and co2 were moving out of the ice as it was forming in addition relative to salinity the ice was generally enriched in alkalinity but depleted in total inorganic carbon these observations support the hypothesis that as sea ice forms increasing brine concentrations and caco3 precipitation release co2 however based on this data set we are unable to quantify the relative importance of release to the atmosphere versus to the underlying waters in addition a comparison of three different methods for determining pco2 in sea ice highlights a critical need for additional methodological development copyright 2011 by the american geophysical union

the solubility and stabilization of ikaite caco3 6h2o from 0 to 25 c environmental and paleoclimatic implications for thinolite tufa we determined the solubility of ikaite from 0 to 25 c to model its saturation state in natural waters and test the hypothesis that it is the precursor of the calcite pseudomorphs in thinolite tufa of quaternary lake lahontan reversible solubility at buffered p co 2 yields the following expression for the dissolution constant of ikaite log k ikaite 0 15981 2011 1 t where t circ k and 0 circ c leq t leq 25 circ c derived standard state properties are delta g ikaite circ 2541 9 kjmol 1 pm 0 66 delta h ikaite circ 2973 4 kjmol 1 pm 1 02 s ikaite circ 306 6 jt 1 mol 1 pm 1 2 modeling shows that ikaite is undersaturated at all temperatures in seawater and in alkaline lakes but that it rapidly approaches saturation near 0 c its precipitation in near freezing marine sediments requires large additions of hco 3 to pore fluids from the diagenetic decomposition of organic matter its crystallization in tufas of alkaline lakes howeve

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

a reevaluation of cosmogenic 36cl production rates in terrestrial rocks we have measured 36cl in a suite of 33 rock samples having well constrained exposure histories and ages the 36cl production parameters were estimated by minimizing the squared deviations between the 36cl and independent ages yielding the following production parameters spallation and muon production from ca 2940 200 atoms 36cl mole ca 1 yr 1 spallation from k 6020 400 atoms 36cl mole k 1 yr 1 and neutron production in air 586 40 fast neutrons g air 1 yr 1 the new production constants for spallation on ca and thermal neutron activation are in good agreement with previous results but that for spallation on k is about 50 larger the past decade has seen a rapid growth in the application of terrestrial cosmogenic nuclides produced by cosmic ray particles within rocks at the earth surface nuclear cross sections particularly for reactions initiated by neutrons and muons are not known with sufficient accuracy so production rates for these nuclides must be empirically calibrated using independently dated geological samples direct production estimates for 36cl were first obtained by zreda et al 1991 who measured 36c1 in mineral separates from granitic boulders on moraine crests at chiatovitch creek in the eastern white mountains of california and nevada this data set was the best available at the time but since then several factors have prompted a reevaluation of the 36cl production rates one is that zreda et al 1994 have shown that there can be significant scatter of the cosmogenic ages of individual glacial boulders toward ages younger than that of the moraine due to soil erosion a second factor is that a much wider range of samples is now available for this purpose finally recent theoretical advances in calculating production by thermal neutron absorption liu et al 1994 now permit more realistic calibration of this reaction

inorganic carbon transport during sea ice growth and decay a carbon pump in polar seas 1 during sea ice formation in polar areas brine rejection increases the density in the underlying water column and thereby contributes to the formation of deep and intermediate water masses in the world ocean here we present evidence that dissolved inorganic carbon tco2 is rejected together with brine from growing sea ice and that low temperatures may result in a significant change in the ratio of tco2 and alkalinity in arctic sea ice compared with surface waters model calculations show that this sea ice driven carbon pump affects surface water partial pressure of co2 significantly in polar seas and potentially sequesters large amounts of co2 to the deep ocean

measurements of total alkalinity calcium and sulfate in natural sea ice we report precise measurements of salinity chlorinity alkalinity calcium and sulphate in various types of sea ice collected at the canadian expedition to study the alpha ridge cesar ice camp in the arctic ocean and in both first year and multiyear ice collected in fram strait several of the samples showed some relative enrichment of alkalinity and sulphate compared to what would be observed in seawater of the same salinity the relative enrichment was quite varied and did not correspond quantitatively with what has been observed in sea ice produced in the laboratory our results indicate that the temperature and salinity history of sea ice must be crucial in determining the relative composition of salts in natural sea ice and that quantitative geochemical predictions based on the composition of sea ice produced in the laboratory or on a particular specimen of natural sea ice must be made with caution