the apparent effects of the mt pinatubo eruption on the greenland ice sheet melt extent the indirect climatological effects of major volcanic eruptions can be of great importance because of the complex feedbacks that exist in the global climate system one such effect is the melt area reduction on the greenland ice sheet using passive microwave satellite data for the period 1979 1995 the melt conditions of the ice sheet before and after the 1991 mt pinatubo eruptions are examined statistical tests indicate that an observed drop following the eruptions has a 97 to 99 probability of being outside the limits of undisturbed variability furthermore this anomaly diminishes as the time from the eruption increases these characteristics in conjunction with an observed increasing melt trend prior to the eruptions indicate that mt pinatubo has had a significant effect on the melt conditions and consequently the energy balance characteristics of the greenland ice sheet

rise in frequency of surface melting at siple dome through the holocene evidence for increasing marine influence on the climate of west antarctica 1 a new melt layer history from siple dome west antarctica indicates notable late holocene summertime warming visual stratigraphic analyses of the 1004 m ice core identified 62 years with melt layers melting events began around 11 7 ka followed by a period of no melting from 8 8 6 6 ka melt layer frequency increased from 6 6 ka to the present with the 1000 year average melt layer frequency reaching a maximum of 2 at 0 8 ka we use our millennial scale archive of melt events as a unique seasonal paleothermometer to elucidate changes in west antarctic holocene summer climate our calibration suggests the change in melt frequency from 0 to 2 may represent a summer temperature increase of 2 c from the middle to late holocene this temperature change cannot be explained entirely by local change in ice elevation or summer insolation and is in contrast to east antarctic climate records which show peak warmth in the early holocene followed by stable or decreasing temperature we interpret the rise in melt frequency as evidence of an increasing marine influence on the ross sea sector of west antarctica although the surface elevation of siple dome has not changed greatly the continued lateral retreat of the west antarctic ice sheet from its last glacial maximum configuration across the outer continental shelf and the delayed drawdown in ice thickness from the adjacent coastal marie byrd land region in conjunction with periods of increased cyclogenesis perhaps related to variations in enso would allow a moderated maritime climate to more easily reach west antarctica

crustal accretion beneath the koyna coastal region india and late cretaceous geodynamics abstract in 1967 a major earthquake in the koyna region attracted attention to the hitherto considered stable indian shield the region is covered by a thick pile of deccan lava flows and characterized by several hidden tectonic features and complex geophysical signatures although deep seismic sounding studies have provided vital information regarding the crustal structure of the koyna region much remains unknown the two available dss profiles in the region have been combined along the trend of bouguer gravity anomalies unified 2 d density modelling of the koyna crust mantle suggests a ca 3 km thick and 40 km wide high velocity high density anomalous layer at the base of the crust along the coastline the thickness of this anomalous layer decreases gradually towards the east and ahead of the koyna gravity low the layer ceases to be visible based on the seismic and gravity data interpretation in the geodynamical rheological boundary conditions the anomalous layer is attributed to igneous crustal accretion at the base of the crust it is suggested that the underplated layer is the imprint of the magmatism caused by the deep mantle plume when the northward migrating indian plate passed over the reunion hotspot

greenland ice sheet surface melt extent and trends 1960 2010 observed meteorological data and a high resolution 5 km model were used to simulate greenland ice sheet surface melt extent and trends before the satellite era 1960 79 and during the satellite era through 2010 the model output was compared with passive microwave satellite observations of melt extent for 1960 2010 the average simulated melt extent was 15 5 for the period 1960 72 simulated melt extent decreased by an average of 6 whereas 1973 2010 had an average increase of 13 with record melt extent in 2010 the trend in simulated melt extent since 1972 indicated that the melt extent in 2010 averaged twice that in the early 1970s the maximum and mean melt extents for 2010 were 52 9 5 10 5 km 2 and 28 5 2 10 5 km 2 respectively due to higher than average winter and summer temperatures and lower than average winter precipitation for 2010 the southwest greenland melt duration was 41 60 days longer than the 1960 2010 average while the northeast greenland melt duration was up to 20 days shorter from 1960 to 1972 the melting period with a 10 melt extent decreased by an average of 3 days a 1 after 1972 the period increased by an average of 2 days a 1 indicating an extended melting period for the ice sheet of about 70 days 40 and 30 days in spring and autumn respectively

integrated pan arctic melt onset detection from satellite active and passive microwave measurements 2000 2009 1 an integrated pan arctic melt onset data set is generated for the first time by combining estimates derived from active and passive microwave satellite data using algorithms developed for the northern high latitude land surface ice caps large lakes and sea ice the data set yields new insights into the spatial and temporal patterns of mean melt onset date mmod and the associated geographic and topographic controls for example in the terrestrial arctic tree fraction and latitude explain more than 60 of the variance in mmod with the former exerting a stronger influence on mmod than the latter elevation is also found to be an important factor controlling mmod with most of the arctic exhibiting significant positive relationships between mmod and elevation with a mean value of 24 5 m d 1 melt onset progresses fastest over land areas of uniform cover or elevation 40 80 km d 1 or both and slows down in mountainous areas on ice caps and in the forest tundra ecotones over sea ice melt onset advances very slowly in the marginal seas while in the central arctic the rate of advance can exceed 100 km d 1 comparison of the observed mmod with simulated values from the third version of the canadian coupled global climate model showed good agreement over land areas but weaker agreement over sea ice particularly in the central arctic where simulated mmod is about 2 3 weeks later than observed because of a cold bias in simulated surface air temperatures over sea ice

soil and sediment properties affecting the accumulation of mercury in a flood control reservoir abstract mercury accumulations in some fish species from grenada lake in north mississippi exceed the food and drug administration standards for human consumption this large flood control reservoir serves as a sink for the skuna and yalobusha river watersheds whose highly erodible soils contribute to excessively high sediment yields and impaired water quality this study was conducted to characterize the distribution of total hg in watershed soils and determine the relationship between the easily transportable clay organic c oc and fe oxide fractions and the movement of hg from upland sources to reservoir sinks cores were collected from soils of different land use representative of the three soil orders alfisols entisols and vertisols found in the watersheds sediment cores were collected from the yalobusha river and grenada lake in the laboratory soil cores were sampled by horizon while sediment cores were sampled in 10 cm increments these samples were characterized for total hg particle size distribution oc fe oxide contents and ph mercury concentrations ranged from 10 to 112 g kg 1 in the soil profiles with average regression coefficient r 2 values of 0 104 0 362 and 0 06 for hg versus clay oc and fe oxides respectively river sediment cores had hg concentrations ranging from 0 to 38 g kg 1 and significant 1 level r 2 values of 0 611 0 447 and 0 632 versus clay oc and fe oxides respectively mercury concentrations in the lake sediment ranged from 0 to 125 g kg 1 the r 2 values for hg versus clay oc and fe oxides in the lake sediment were 0 813 0 499 and 0 805 respectively all significant at the 1 level these results indicate that total hg is poorly correlated with the clay oc and fe oxide fractions at depth in the soil profiles because maximum hg concentrations occur in the surface horizons due to atmospheric in fall the statistically significant r 2 values for hg versus these components in the sediment cores are the result of particulate clay fe oxides and finely divided oc sorption of hg from solution during the runoff and sediment transport process the higher correlations for the lake sediment reflect an enrichment of the hg laden clay fraction relative to stream sediment through flocculation and sedimentation processes in the slack water environment of the reservoir

characterization and formation of melt layers in polar snow observations and experiments from west antarctica author posting international glaciological society 2005 this article is posted here by permission of international glaciological society for personal use not for redistribution the definitive version was published in journal of glaciology 51 2005 307 312 doi 10 3189 172756505781829395

spatiotemporal variations of snowmelt in antarctica derived from satellite scanning multichannel microwave radiometer and special sensor microwave imager data 1978 2004 1 we derived the extent onset date end date and duration of snowmelt in antarctica from 1978 to 2004 using satellite passive microwave scanning multichannel microwave radiometer smmr and special sensor microwave imager ssm i data a wavelet transform based method was developed to determine and characterize melt occurrences about 9 12 of the antarctic surface experiences melt annually this is more than twice the surface melt extent measured in greenland seasonally surface melt primarily takes place in december january and february and peaks in early january regression analysis over the 25 year period of study reveals a negative interannual trend in surface melt nevertheless the trend inference is not statistically significant large year to year fluctuations characterize the interannual variability extremely high melt occurred in the 1982 1983 and 1991 1992 summers while extremely weak melt occurred in the 1999 2000 summer a strong correlation with air temperature suggests that the melt index can serve as a diagnostic indicator for regional temperature variations periodic melting has been observed over ross ice shelf ronne filchner ice shelf the west antarctic ice streams and outlet glaciers in the transantarctic mountains the antarctic peninsula west ice shelf shackleton ice shelf amery ice shelf and the ice shelf along the princess ragnhild coast experienced the most persistent and intensive melt and should be closely monitored for their stability in the future given the recent disintegration of the larsen ice shelf a and b

greenland snow accumulation estimates from satellite radar scatterometer data data collected by the c band ers 2 wind scatterometer escat the ku band adeos 1 nasa scatterometer nscat and the ku band seawinds on quikscat qscat satellite instruments are used to illustrate spatiotemporal variability in snow accumulation on the greenland ice sheet microwave radar backscatter images of greenland are derived using the scatterometer image reconstruction sir method at 3 day intervals over the periods 1991 1998 and 1996 1997 for escat and nscat respectively the backscatter coefficient normalized to 40 incidence a and gradient in backscatter b in the range 20 60 are compared with historical snow accumulation data and recent measurements made in the program for arctic regional climate assessment parca shallow snow pits empirical relationships derived from these comparisons reveal different exponential relationships between c and ku band a values and dry snow zone mean annual accumulation q frequency difference images between overlapping scatterometer images suggest that c band data are more sensitive to snow layering and buried inhomogeneities whereas ku band data are more sensitive to volume scattering from recently accumulated snow direct comparisons between nscat b values and in situ q measurements show a linear relationship between ln q and b with a negative rank correlation of r 0 8 the root mean square residual in fitting regression line equation ln q 3 08 17 83b to the data is 0 05 m snow water equivalent this simple ku band empirical relationship is exploited to investigate decadal changes in dry snow zone accumulation between seasat 1978 and nscat 1996 additional comparisons between nscat and recent qscat 1999 data reveal significant upslope shifts in the dry snow line along the southwestern flank of the ice sheet recent acceleration in the increase in intensity of scattering is observed in the percolation zone suggesting increased melting between 2000 and 3000 m elevation in the southern half of the ice sheet

contamination of two oregon reservoirs by cinnabar mining and mercury amalgamation two reservoirs in western oregon contain mercury contaminated sediment and fish as a result of historic mercury mining in the cottage grove lake watershed and mercury amalgamation used in gold mining in the dorena lake watershed on average sediment in cottage grove lake contains ten times as much mercury as sediment from dorena lake 2 720 versus 0 242 ppm mercury content in cottage grove lake sediment shows a sharp initial decrease and leveling off with time that reflects the end of the major cinnabar mining phase deposition of other heavy metals appears to be linked to the clay content of sediment mercury input to dorena lake has remained fairly constant with time but small increases in mercury are associated with the deposits of large floods copper lead and zinc input to dorena lake exhibits a marked decrease and leveling off related to the end of commercial mining for these metals

trace metal storage in recent floodplain sediments along the dill river central germany abstract trace metals are stored in near channel floodplain sediments along many rivers in industrial and mined watersheds of western european countries such as germany in this paper i document the distribution of cu pb and zn in 13 cores collected from near channel floodplain sediments along a 25 km reach of the dill river in central germany mean concentrations of the three trace metals exceed background concentrations an indication of anthropogenic enrichment along the study reach many individual samples have concentrations several times the background levels and exceed standards for trace metals contained in the german federal soil protection act metal concentrations generally peak at depths of 0 2 to 0 7 m below the floodplain surface and are assumed to represent the period of maximum metal releases to the environment through upstream industrial activity ore mining or both in eight of the cores radiocarbon ages obtained below the depth of peak metal concentrations provide maximum dates for sediment accumulation of between 90 and 1700 years ago with most ages clustering in the period of 90 to 300 years ago the ages and depth to peak metal concentrations indicate 0 6 to 1 0 m of floodplain sedimentation over the last 150 to 300 years 0 3 0 4 cm y 1 which exceed sedimentation amounts and rates found in surrounding watersheds surface sediments contain lower metal concentrations suggesting deposition recently of cleaner sediments trace metals stored along the dill river serve as a reminder that stores of contaminants exist in geomorphically sensitive locations of the fluvial system these legacy sediments bear the chemical imprint of industrial or mining activities that no longer occur in the watershed

growth of greenland ice sheet interpretation an observed 0 23 m year thickening of the greenland ice sheet indicates a 25 to 45 excess ice accumulation over the amount required to balance the outward ice flow the implied global sea level depletion is 0 2 to 0 4 mm year depending on whether the thickening is only recent 5 to 10 years or longer term 100 years if there is a similar imbalance in the northern 60 of the ice sheet area the depletion is 0 35 to 0 7 mm year increasing ice thickness suggests that the precipitation is higher than the long term average higher precipitation may be a characteristic of warmer climates in polar regions

floodplain storage of sediment contaminated by mercury and copper from historic gold mining at gold hill north carolina usa abstract previous research on the environmental consequences of mining has shown that metal contaminants can have long lasting impacts on water quality and aquatic ecosystems because of the remobilization of sediment associated contaminants that have been stored in floodplains we examined the magnitude and distribution of mercury hg and copper cu contamination of floodplain deposits associated with nineteenth century gold au mining activities in the gold hill mining district north carolina a comparison of post mining metal concentrations in overbank deposits with sediment quality guidelines indicates that overall about 21 are contaminated above the probable effect concentration pec above which adverse effects are expected to occur more often than not for both cu and hg the highest contamination occurs upstream near the mine source where 51 of the samples exceed the pec for hg and 57 exceed the pec for cu of the three different methods used to estimate metal mass storage the most reliable estimate suggests that about 6 8 mg of hg and 619 mg of cu currently reside in floodplain deposits within this watershed although overbank sediment storage increases downstream and with valley width about 75 of the hg and cu mass are stored in the upstream portion of the watershed hg mass storage displays a strong negative relationship with cross sectional stream power but the relationship between cu mass storage and stream power is insignificant we used vertical changes in overbank metal concentrations and the mining history to estimate a mean sedimentation rate of 2 7 cm y 1 during the most intensive period of au mining at gold hill 1842 1856 that is three times the long term 1842 2007 rate of 0 9 cm y 1 long term average rates at gold hill are comparable to those reported elsewhere in the eastern piedmont the downstream increase in long term rates may indicate a spatial and temporal lag effect where the locus of deposition shifts downstream with time

observation and characterization of radar backscatter over greenland characterization of the microwave signature of the greenland snow surface enables delineation of the different snow facies and is a tool for tracking the effects of climate change a new empirical observation model is introduced that uses a limited number of parameters to characterize the snow surface based on the dependence of radar backscatter on incidence angle azimuth angle spatial gradient and temporal rate of change the individual model parameters are discussed in depth with examples using data from the nasa scatterometer nscat and from the c band european remote sensing ers satellite advanced microwave instrument in scatterometer mode the contribution of each model term to the overall accuracy of the model is evaluated the relative contributions of the modeled dependencies vary by region two studies illustrating applications of the model are included first interannual changes over the greenland ice sheet are investigated using nine years of ers data surface changes are observed as anomalies in the spl sigma spl deg model parameters second intraannual variations of the surface are investigated these changes are observed in the average backscatter normalized to a given observation geometry the results indicate that the model can be used to obtain a more complete understanding of multiyear change and to obtain low variance high temporal resolution observations of intraannual changes the model may be applied for increased accuracy in scatterometer synthetic aperture radar sar and wide angle sar studies

impacts of pre vs postcolonial land use on floodplain sedimentation in temperate north america abstract this paper evaluates the relative importance of anthropogeomorphic sedimentation on floodplains in the mid latitudes of north america before and after the arrival of euroamericans geohistorical and geoarchaeological theories have emerged that have conflicts concerning the relative effectiveness of pre and postcolonial anthropogeomorphic change in north america many geoarchaeologists paleoecologists historians and cultural geographers have concluded that intensive precolonial land use resulted in substantially humanized landscapes prior to the arrival of colonists this presents a geomorphic paradox to fluvial geomorphologists and river restorationists who interpret buried floodplain soils as evidence of landscape stability evidence for these theories is reviewed from a geomorphic perspective while making distinctions between ecological and geomorphic change and recognizing spatial and temporal variability in some locations mid millennial land use generated erosion and floodplain sedimentation subsequent indigenous population declines and reductions in land use intensity may have been followed by precolonial geomorphic stability and pedogenesis an abandoned landscape hypothesis that floodplain soils developed on precolonial anthropogenic alluvium and were subsequently buried should be considered where indigenous populations and land use activities were high variability is also noted in postcolonial floodplain sedimentation many stratigraphic studies show that rates of sedimentation increased greatly after colonization in response to land clearance for agriculture timbering and mining an inventory of studies that document postcolonial floodplain sediment shows strong spatial patterns most studies of postcolonial sedimentation cluster in the eastern usa from the mid atlantic southward and in the mississippi valley from wisconsin to mississippi but many occurrences of mining sediment are scattered throughout the west few of the studies reviewed in the west document anthropogenic floodplain sediment from agriculture or logging although more thorough regional inventories could change that vast areas of temperate north america do not have historical deposits that are well represented in the scientific literature so assumptions that legacy sediment on floodplains is ubiquitous are ill founded spatial and temporal variations in pre and postcolonial floodplain sedimentation are complex and more research is needed to fill in the knowledge gaps

residence time indicators in groundwater the east midlands triassic sandstone aquifer the east midlands triassic sherwood sandstone aquifer which has been the subject of detailed radiometric age studies is used to investigate both inert and reactive constituents of groundwater as indicators of residence time detailed resampling of the aquifer in 1992 has provided a considerable body of new inorganic geochemistry data though without radiocarbon several inert indicators are defined including the isotopic ratios 18o 2h 36cl noble gas ratios as well as the halogen elements cl br f i and their element ratios these form a group of essentially unreactive tracers primarily reflecting changing rainfall inputs and palaeoclimatic conditions except at outcrop where human impacts are also seen clearly the concentrations of cl mainly from atmospheric sources remain below 25 mg l 1 cl over a distance of some 30 km from outcrop reactive indicators the result of time dependent water rock interactions include 13c mg ca sr ca na cl and show diagnostic trends along the flow lines however the concentrations of certain trace elements li rb cs mn and mo which are not limited by solubility constraints show linear trends along the present day flow gradient this water rock interaction is taking place in groundwaters with low total mineralisation and it can be demonstrated that reactions involving these elements and isotopes are occurring entirely within the aquifer since high salinity groundwaters are found below the sherwood sandstone there is good correlation between some of the elements and 14c activities in the 1977 data set and this has been used to derive a concentration age relationship for the 1992 set of data a chemical timescale for the aquifer is then established using a li and b a combination of five trace elements the age of the fresh groundwater is thus shown to be up to 100 ka bp indicating the likelihood of semi continuous recharge during the devensian glacial period preceding the glacial maximum when no recharge occurred 10 20 ka bp this approach may be of value in extending groundwater dating beyond the radiocarbon timescale as well as interpreting sites where no radiocarbon data are available the scatter from the mean age line indicates those groundwaters which are derived from either rapid or slower than average flow zones within the aquifer as well as age stratification this stratification is borne out by a depth profile of groundwater from a new borehole near to outcrop which is shown by a combination of chemical and isotopic tracers to contain holocene overlying late pleistocene water

an edge detection technique to estimate melt duration season and melt extent on the greenland ice sheet using passive microwave data the melt extent duration and melt season on the greenland ice sheet were estimated using an edge detection technique on passive microwave data from the ssm i and smmr instruments 18 19v ghz channel for the period 1979 to 1997 the annual brightness temperature tb time series at a pixel location that experiences summer melt has a steep rise and drop in tb with the onset and end of melt respectively a derivative of gaussian edge detector is used to detect edges corresponding to the onset and end of melt the time lapsed between the first upward and last downward edge on the annual tb time series gives an estimate of the melt season and the time lapsed between successive upward and downward edges gives the duration of melt while the maximum melt extent increased by 18 the total duration of melt increased by 3 7 and the total melt season decreased by 3 8 during the period 1979 1997

aquifer chemistry of thermal waters of the godavari valley india abstract the results of a chemical study of thermal waters from three hot springs two water discharges in a mine at 180 m depth and four wells drilled for exploration of coal and water resources in the godavari valley indicate 1 a deep flow path within the lower gondwanas upper carboniferous lower triassic for agnigundala thermal water which has been found to be in equilibrium with quartz montmorillonite and kaolinite at 150 c 2 medium depth circulation also through lower gondwana sedimentary rocks and equilibrium with quartz at 100 c for waters of buga manguru and bhuttayagudem and 3 circulation within sedimentary formations for the thermal waters of the pagdaru and bhimdole areas waters of the last areas show disequilibrium but are within the stability field of kaolinite the aquifer temperature is most likely to be about 156 c for the agnigundala around 100 c for the buga and not more than 100 c for the other systems

nature of the crust in the laxmi basin 14 20 n western continental margin of india 1 the nature of the crust in the laxmi basin western margin of india is an uncertain issue more importantly this has implications on paleogeographic reconstructions of the western indian ocean we have analyzed three geophysical data sets and modeled gravity and magnetic anomalies for determining nature of the crust basement of the laxmi basin includes numerous highs which make the basement uneven and shallower compared to the western basin the laxmi basin is characterized by a broad gravity high and a narrower prominent gravity low within it while within the basin the broad anomaly gradually increases toward north the panikkar ridge is associated with the gravity low which is comparable at least in sign to known negative gravity anomaly of the laxmi ridge intrusive structures mapped in the laxmi basin coincide with significant magnetic anomalies which were earlier interpreted as seafloor spreading anomalies model studies reveal that the laxmi basin consists of 14 km thick stretched continental crust in which magmatic bodies have been emplaced whereas the panikkar ridge remains less altered stretched continental crust the crust of the laxmi basin is mostly thinner than crust under the laxmi ridge and continental margin in addition to the rift drift related stretching of the continental margin the laxmi basin possibly has undergone extra stretching in e w direction during the pre tertiary period at 68 ma deccan volcanism on western india may have disrupted the initial conditions that were leading to onset of spreading in the basin subsequently the reunion hot spot had emplaced the volcanic material within the stretched thinned continental crust we interpret the laxmi basin as a failed rift undergone stretching following intraplate kinematics prior to deccan volcanism

an algorithm for time series analysis of ice sheet surface elevations from satellite altimetry a new method to derive the seasonal elevation signal from a continuous time series of altimeter crossover data is presented the method utilizes the complete set of intrasatellite crossover data to provide fine temporal resolution and to significantly reduce random measurement errors this is an improvement over the standard time series method that only uses those data referenced to a single time period at the beginning of the satellite mission

human impact on regional groundwater composition through intervention in natural flow patterns and changes in land use schot p p and van der wal j 1992 human impact on regional groundwater composition through intervention in natural flow patterns and changes in land use j hydrol 134 297 313 the relations between groundwater composition land use soil conditions and flow patterns on a regional scale are studied for the gooi and vechtstreek area in the netherlands this densely populated area consists of a glacier created ridge with dry sand soils bordered by the vecht and eem river plains with wet peat and clay soils r mode factor analysis and q mode cluster analysis were applied to a set of 1349 groundwater analyses to determine the factors controlling groundwater composition and the main resulting water types the results indicate that groundwater composition in the study area is affected on a regional scale by human activities through changes in land use and intervention in natural flow patterns on the ridge ground water is recharged by precipitation which dissolves carbonates from the matrix of the sandy aquifer increased solute concentrations in shallow ground water especially of nitrate sulphate and potassium indicate increased pollution resulting from urbanization and increasingly intensive agricultural activity over the past decades in the vecht river plain infiltration occurs as a result of drainage of polders and groundwater extraction on the ridge recharge occurs by precipitation and from polluted surface water to which ammonium organic complexes and carbonic acid are added through decomposition of organic matter in the peat and clay soils the carbonic acid results in enhanced dissolution of carbonates present in the soil and the underlying sandy aquifer oxygen depletion and subsequent low redox potentials result in denitrification dissolution of manganese and iron oxides and sulphate ro duction the flow of ground water from high level to low level polders causes displacement of a former stagnant brackish groundwater body under the vecht river plain accompanied by increased mixing of fresh and brackish ground water

hydrogeochemistry of the thermal waters from the yenice geothermal field denizli basin southwestern anatolia turkey abstract the chemical and isotopic properties of thermal waters kamara and cizmeli and cold springs from the yenice geothermal field ygf in southwestern anatolia turkey are investigated in order to establish a conceptual hydrogeochemical hydrogeological model these thermal waters derive from menderes metamorphic rocks and emerge along normal faults they are commonly used for heating of greenhouses and bathing facilities discharge temperatures of thermal waters are 32 c to 57 c mean 51 c for kamara and 35 c to 68 c mean 47 c for cizmeli whereas deep groundwaters are 15 c to 20 1 c mean 17 c and shallow groundwaters are 12 to 16 c mean 15 c kamara and cizmeli thermal waters are mostly of na ca hco3 so4 type whereas deep groundwaters are ca mg hco3 and mg ca hco3 types and shallow groundwaters are mainly mg ca so4 hco3 and ca mg hco3 types in the reservoir of the geothermal system dissolution of host rock and ion exchange reactions changes thermal water types high correlation in some ionic ratios e g na vs cl k vs cl hco3 vs cl and high concentrations of some minor elements e g as sr b cl f in thermal waters likely derive from enhanced water rock interaction water samples from ygf have not reached complete chemical re equilibrium possibly as a result mixing with groundwater during upward flow geothermal reservoir temperatures are calculated as 89 102 c for kamara and 87 102 c for cizmeli fields based on the retrograde and prograde solubilities of anhydrite and chalcedony based on the isotope and chemical data a conceptual hydrogeochemical hydrogeological model of the ygf has been constructed very negative 18o and 2h isotopic ratios kamara mean of 8 43 and 56 9 respectively and cizmeli mean of 7 96 and 53 7 respectively and low tritium values

a simple energy balance model to calculate ice ablation at the margin of the greenland ice sheet apres avoir etabli les relations donnees climatiques taux d enlevement de la glace dans 2 glaciers du groenland un modele simple de bilan energetique est effectue pour calculer le taux d enlevement de la glace aux bordures du glacier

variations in snowpack melt on the greenland ice sheet based on passive microwave measurements a simple microwave emission model is used to simulate 37 ghz brightness temperatures associated with snowpack melt conditions for locations across the greenland ice sheet the simulated values are utilized as threshold values and compared to daily gridded smmr and ssm i passive microwave data in order to reveal regions experiencing melt the spatial extent of the area classified as melting is examined on a daily monthly and seasonal may august basis for 1979 91 the typical seasonal cycle of melt coverage shows melt beginning in late april a rapid increase in the melting area from mid may to mid july a rapid decrease in melt extent from late july through mid august and cessation of melt in late september seasonal averages of the daily melt extents demonstrate an apparent increase in melt coverage over the 13 year period of approximately 3 8 annually significant at the 95 confidence interval this increase is dominated by statistically significant positive trends in melt coverage during july and august in the west and southwest of the ice sheet we find that a linear correlation between microwave derived melt extent and a surface measure of ablation rate is significant in june and july but not august so caution must be exercised in using the microwave derived melt extents in august nevertheless knowledge of the variability of snowpack melt on the greenland ice sheet as derived from microwave data should prove useful in detecting climate change in the arctic and examining the impact of climate change on the ice sheet

aquifer chemistry of the puga and chumatang high temperature geothermal systems in india abstract results of a chemical study of the fluids from drill holes and hot springs of puga and chumatang areas in the northwestern part of the himalaya are presented and discussed in this paper the thermal waters of puga and chumatang are of na hco 3 cl and na hco 3 types respectively a comparison between these waters their chemical classification and activity studies suggest a flow path within a quartzitic schistose basement containing quartz k feldspar and illite and in clayey terrains containing montmorillonite and illite the chemistry of thermal waters also indicate their association with magmatic activity the chemical geothermometers indicate the possible existence of a geothermal reservoir at puga with temperature 250 c the chumatang area has a comparatively cooler reservoir with a temperature of 150 180 c

bombay gravity high and eruption of deccan flood basalts india from a shallow secondary plume abstract the western margin of india especially the area surrounding the gravity high of bombay is covered by a thick pile of deccan flood basalts the massive eruption is one of the largest continental volcanic events at the cretaceous tertiary biological mass extinction boundary 65 ma ago the area is characterized by several hidden tectonic features and their origin and evolution have remained controversial in the search for magma source structure attention was focused on an unusual oval shaped positive gravity anomaly over the bombay coastal zone the gravity analysis indicates the presence of two subsurface structures at depths of 4 5 0 5 km and 18 2 km these depths correspond to the top of the crustal basaltic layer and an upwarped moho discontinuity respectively the positive gravity anomaly in three dimensional analysis reveals a possible magma conduit structure and the near absence of the granitic layer the unusually shallow moho layer coincides with the region of a broad high heat flow anomaly average heat flow more than 80 mw m2 the geophysical signatures from the neighborhood show that the asthenosphere has welled up considerably and is located at a depth of about 40 km high heat flow and asthenospheric depth estimates suggest melting conditions at very shallow depths it is suggested that the highly differentiated magma associated with the major eruptive phase of deccan traps did not originate at the d layer it is hypothesized that magma was brought to the surface by a major secondary plume at a much shallower depth within the lithosphere and possibly at the crust mantle boundary as a consequence of subcrustal erosion and secondary melting caused by the extreme velocity of india during the late cretaceous and early tertiary substantial melting of the base of the lithosphere due to frictional heating might have resulted in the accumulation of a large quantity of magma below the thinned lithosphere at the pre existing fracture zone near the continental margin the presence of a magmatic conduit structure above the moho derived from the inversion of gravity data and other tectonic conditions suggests a possible triggering of the magma reservoir by a large bolide impact 10 km diameter at the cretaceous tertiary boundary near bombay

behaviour of thermal waters through granite rocks based on residence time and inorganic pattern summary thermal waters are certainly a substantial asset of the galicia region of spain they can be regarded as worth developing because of their human health implications and if thermal tourism is promoted their importance to the local economy in this paper the chemistry of major and trace inorganic elements in about 45 thermal springs and wells discharging in the same hydrographical system are presented and discussed for handling the results of all measurements graphical representations of b li vs so 4 2 cl ratios hill piper diagram discriminant analysis da and principal component analysis pca were employed all this with the intention to classify based on their inorganic pattern both thermal springs and wells waters but also waters circulating through adamellite and granodiorite rocks the results of the hydrogeochemistry analysis showed three main water families sulphated chlorinated and bicarbonated waters the results show also the presence of saline materials with chloride influence in the deeper aquifer allowing its classification in deeper and younger shallow waters

evaluation of reservoir temperatures and local utilization of geothermal waters of the konkan coast india abstract geochemical studies on fifteen geothermal manifestations 38 70 c from the konkan coast geothermal province of india have been used to evaluate the reservoir temperatures activity studies of the minerals and the waters present in the reservoirs suggest that the thermal waters are in equilibrium with montmorillonite kaolinite and quartz at about 100 c reservoir temperatures of these geothermal systems as estimated by geochemical thermometers are 88 to 128 c and thus too low for economic electricity production

amsr e melt patterns on the southern patagonia icefield passive microwave 37 ghz vertically polarized v brightness temperature tb measure ments from the advanced microwave scanning radiometer for earth observing system amsr e are used to monitor the extent and timing of snowmelt on the southern patagonia icefield spi in chile and argentina twice daily tb s for 2002 08 for high elevation 1200 m a s l pixels exhibit a bimodal histogram typical of snow covered regions in yukon alaskan icefields and the greenland ice sheet the low count between the two populations represents the tb threshold for melt 252 k this tb value with the 18 k diurnal amplitude variation threshold quantifies onset and duration of the spring melt refreeze period and is used to identify melt regimes and seasonal tb signals tb histograms for pixels west of the andean divide have a normal distribution above the melt threshold we interpret the tb histogram as controlled by surface moisture the shape and position with respect to tb are retained with changes in both latitude and elevation and the region is known to have a moist climate tb is not driven by seasonal temperature changes in the northwest sector of the icefield because the tb threshold is exceeded 75 of the time for all pixels the spring melt refreeze period has shortened by a mean of 10 days a 1 and a mean of 16 days a 1 for pixels with bimodal distributions between 2002 and 2008

use of mining contaminated sediment tracers to investigate the timing and rates of historical flood plain sedimentation abstract changes in land use practices following european settlement in the 1830s produced accelerated sedimentation on virtually all valley floors in the blue river watershed wisconsin the contamination of sediments by pb and zn mining allowed us to calculate cross valley rates of flood plain sedimentation for three time periods the pre mining period 1830 1900 the mining period 1900 1920 and the post mining period 1920 1997 most of the eight valley floors examined contained multiple presettlement surfaces significantly higher rates of sedimentation occurred on the lower flood plain surfaces while the terraces were high enough to prevent sedimentation from most floods higher rates of sedimentation on the lower surfaces eventually reduced valley floor relief and consequently lateral differences in sedimentation rates tributaries and larger valleys downstream exhibited differences in the timing and rates of historical flood plain sedimentation while rates of sedimentation were high during the pre mining period in tributary valleys the lower valleys were receiving little or no pre mining alluvium little pre mining alluvium was found in mid basin reaches suggesting that most of the pre mining sedimentation was limited to headwater locations during the mining period lateral channel migration and the development of meander belts increased the conveyance capacity of tributary and mid basin channels which decreased overbank flooding and produced lower rates of sedimentation during the post mining period the meander belt channels also had an effect on the lower portion of the watershed by increasing flood magnitudes and the transport of sediment downstream thereby shifting the locus of sedimentation from the tributaries to the larger lower valleys sedimentation rates in the largest most downstream site were an order of magnitude higher during the post mining period than any of the sites upstream

seasonal variations in the isotopes of oxygen and hydrogen in geothermal waters from bakreswar and tantloi eastern india implications for groundwater characterization abstract 18o and d values of non thermal and thermal waters from the bakreswar and tantloi geothermal areas indicate a meteoric origin for the thermal springs both non thermal and thermal waters undergo seasonal isotopic variations being enriched in 18o and d in the winter relative to the rainy season for non thermal waters this is due to a higher rate of evaporation in winter as a consequence of depleting atmospheric humidity the effect is more pronounced for surface waters than groundwaters the degree of variation is in general very low for thermal waters the difference in issuing temperature as well as small variations in the stable isotopic composition and tritium content of the springs are suggestive of very low to moderate dilution of thermal waters by nearby shallow groundwater agnikund the hottest spring 71 c is least diluted 10 by local non thermal waters and hence is the best representative of deep seated thermal water the presence of very low amounts of tritium 0 6 0 5 to 1 9 0 5 tu in thermal waters indicates their long subsurface circulation time 50 years similar 18 o and d values for bakreswar and tantloi spring waters point to their origin from the same meteoric water and therefore they are genetically related recharge of the springs is likely to take place somewhere in the vicinity of gondwana basins occurring along the central part of the chotanagpur plateau

hot springs and the geothermal energy potential of jammu kashmir state n w himalaya india abstract india has an estimated geothermal power potential of 10 600 mwe but this potential is entirely undeveloped at present the geothermal atlas of india prepared by the geological survey of india gsi in 1991 describes some 340 hot spring sites and identifies more than 300 sites with geothermal potential in at least seven key geothermal provinces throughout india there are more than 20 hot spring sites in jammu kashmir state mainly in the chenab valley in the lesser central himalaya the kashmir valley and in the high himalaya region of ladakh at least three localities in the ladakh region chamuthang and puga in the indus valley and panamik in the nubra valley are considered to have geothermal power generation potential of between 3 and 20 mwe the puga hot spring area located at the junction of the indian and tibetan plates along the indus suture zone has the greatest potential for the near term development of geothermal energy in the indian subcontinent the area exhibits vigorous geothermal activity in the form of hot springs mud pools sulphur and borax deposits covering an area of c 15 km 2 the discharges are concentrated in an east west elongated area of some 4 km 2 near the mouth of the puga valley the puga geothermal field is bounded by faults and its reservoir rocks consist of granite gneiss and schist there is both direct and indirect evidence to support the existence of an active magmatic system at a depth of 5 7 km geophysical surveys have delineated a conspicuous low resistivity zone below the puga field systematic and comprehensive evaluation of the geothermal potential of the puga area began in 1973 thirty four wells have been drilled in the puga geothermal field to date at least 17 of which have resulted in mixed steam and water blow outs the discharges from some of the wells have temperatures of more than 120 c thermal studies indicate temperatures of more than 220 c at a depth of about 2 5 km below the puga valley corresponding to the main reservoir level chemical thermometry also suggests a reservoir temperature of 250 c while reservoir modelling studies suggest temperatures of up to 160 c at a depth of 450 m the high concentration of lithium rubidium and cesium in the geothermal water has been interpreted as indicating a magmatic source and young granitic intrusions and shallow crustal melting processes have been postulated as the most likely heat source for the puga geothermal field it is estimated that more than 5000 mwh of geothermal energy is available at puga which could be used for heating for greenhouse cultivation and eventually to generate electricity studies have indicated that there is a 90 probability that the puga field could sustain a 20 mwe power plant if the puga geothermal field could be developed it is very likely that it could be followed by the development of the chamuthang and panamik fields jammu kashmir state suffers from an acute shortage of power particularly in the mountainous region of ladakh the development of geothermal potential would provide for baseload needs especially in the winter months when the region s hydro power stations are frequently either shut down or working at significantly reduced efficiency because of freezing of the indus river however any development would need to be undertaken with great care to avoid damaging ladakh s vulnerable high altitude desert environment and its unique plant and animal life

multivariate statistical analysis of geochemical data as indicative of the hydrogeochemical evolution of groundwater in a sedimentary rock aquifer system summary the study of groundwater hydrogeochemistry of the paleozoic basses laurentides sedimentary rock aquifer system in quebec produced a large geochemical dataset groundwater samples were collected at 153 sites over a 1500 km2 study area and analyzed for major and minor ions the large number of data can lead to difficulties in the integration interpretation and representation of the results two multivariate statistical methods hierarchical cluster analysis hca and principal components analysis pca were applied to a subgroup of the dataset to evaluate their usefulness to classify the groundwater samples and to identify geochemical processes controlling groundwater geochemistry this subgroup consisted of 144 samples and 14 parameters ca2 mg2 na k hco 3 cl so 4 2 fe2 mn2 br sr2 f ba2 hs seven geochemically distinct clusters c1 c7 resulted from the hca samples from clusters c3 c4 c6 and c7 are mostly located in preferential recharge areas the majority of these samples have ca mg hco3 recharge groundwater c3 c6 c7 and na hco3 evolved groundwater c4 samples from the other three clusters c1 c2 c5 are characteristic of an aquifer system under confined conditions the majority of these samples have na hco3 evolved groundwater c1 c5 and na cl ancient groundwater that exhibits elevated concentrations in br c2 in addition to recognizing the importance of hydrogeological conditions on groundwater geochemistry the distribution of clusters also showed the importance of the geological formations on minor and trace elements such as fe2 mn2 sr2 f and ba2 the first five components of the pca account for 78 3 of the total variance in the dataset component 1 is defined by highly positive loadings in na cl and br and is related to groundwater mixing with champlain sea water and solute diffusion from the marine clay aquitard the high positive loadings in ca2 and mg2 of component 2 suggest the importance of dissolution of carbonate rocks in this aquifer system from their characteristic loadings the first two components are defined as the salinity and hardness components respectively components 3 5 are related to more local and geological effects the integration of the hca and the pca with conventional classification of groundwater types as well as with the hydrogeological and geological contexts allowed the division of the region into four main geochemical areas providing an improved regional picture of the aquifer system dynamics and hydrogeochemical evolution of groundwater the following factors were recognized as influencing the evolution of groundwater identified in every geochemical area 1 geological characteristics including sedimentary rock type and till mineralogy 2 hydrogeological characteristics represented by the level of confinement and the hydraulic gradient and 3 the geological history including the latest glaciation and the champlain sea invasion with its integrated approach this hydrogeochemical study contributes to the characterization and understanding of complex groundwater flow systems and provides an example of the long term geochemical evolution of hydrogeological systems after a major perturbation in this case seawater invasion

recent changes in the microwave scattering properties of the antarctic ice sheet time series satellite microwave data are used to monitor and quantify changes in the scattering properties of the antarctic ice sheet daily ers scatterometer escat and special sensor microwave imager ssm i image data acquired since 1992 are analyzed to understand the seasonal and interannual changes over the ice sheet for regions of the ice sheet where azimuthal modulation is negligible seasonal cycles are observed in both the escat amplitude spl sim 0 5 db and ssm i data amplitude spl sim 10 k these cycles are attributed to seasonal changes in surface temperature interannual variability in the time series signatures appears to be associated with accumulation there is also evidence to suggest that shifts in the wind direction can alter the backscatter through azimuthal modulation over the period 1992 97 large trends are observed in the escat 1 k yr sup 1 signatures over several regions in antarctica these changes typically occur over ice shelves and at the margins of the ice sheet where previous melt events have occurred and where accumulation is relatively high 300 mm yr sup 1 it is likely the large changes result from the successive burial of an efficient scattering layer formed by refreezing after a melt event prior to 1992 there is also evidence to suggest that similarly large changes can be observed in the interior of the ice sheet due to the burial of depth hear layers in order to monitor long term change in the properties of the antarctic ice sheet it is necessary to remove the seasonal cycle from time series microwave data such anomaly data can then be used to understand the link between escat and ssm i with accumulation and wind shifts

mapping greenland accumulation rates using observations of thermal emission at 4 5 cm wavelength accurate predictions of sea level rise over the coming century will require improved knowledge of the processes controlling accumulation on the great ice sheets the sparsity of accumulation rate observations both temporally and spatially hinder development of this understanding we introduce a new method to observe accumulation rates averaged over roughly a decade using satellite observations of microwave emission at 4 5 cm wavelength focusing in this paper on greenland at this wavelength scattering by the grain fabric in firn is unimportant relative to quasi reflection from density and thus dielectric permittivity stratification we show observationally a strong link between random firn density stratification on scales of millimeters to centimeters and accumulation rate we then show theoretically how the observed density stratification can produce and is consistent with observations of polarization of 4 5 cm wavelength emission we employ observations from the scanning multichannel microwave radiometer smmr and previously published ground observations of accumulation rates in greenland to complete specification of the relationship between accumulation rate and polarization the relationship is sufficiently accurate to serve as a basis for mapping accumulation rate fields we compare our satellite derived maps with previously published maps based on syntheses of ground data we find broad agreement between the two types of maps though the satellite derived map indicates more strongly the importance of topography and prevailing weather patterns in determining detailed accumulation rate patterns finally we discuss possible refinements and the prospects for improved satellite derived maps based on a new generation of sensors about to be launched

legacy sediment lead and zinc storage in channel and floodplain deposits of the big river old lead belt mining district missouri usa abstract the old lead belt of southeastern missouri was one of the leading producers of pb ore for more than a century 1869 1972 large quantities of contaminated mine waste have been and continue to be supplied to local streams this study assessed the magnitude and spatial distribution of mining contaminated legacy sediment stored in channel and floodplain deposits of the big river in the ozark highlands of southeastern missouri although metal concentrations decline downstream from the mine sources the channel and floodplain sediments are contaminated above background levels with pb and zn along its entire 171 km length below the mine sources mean concentrations in floodplain cores 2000 mg kg 1 for pb and 1000 mg kg 1 for zn extend 40 50 km downstream from the mining area in association with the supply of fine tailings particles that were easily dispersed downstream in the suspended load mean concentrations in channel bed and bar sediments ranging from 1400 to 1700 mg kg 1 for pb extend 30 km below the mines while zn concentrations of 1000 3000 mg kg 1 extend 20 km downstream coarse dolomite fragments in the 2 16 mm channel sediment fraction provide significant storage of pb and zn representing 13 20 of the bulk sediment storage mass in the channel and can contain concentrations of 4000 mg kg 1 for pb and 1000 mg kg 1 for zn these coarse tailings have been transported a maximum distance of only about 30 km from the source over a period of 120 years for an average of about 250 m y about 37 of the pb and 9 of the zn that was originally released to the watershed in tailings wastes is still stored in the big river a total of 157 million mg of contaminated sediment is stored along the big river with 92 of it located in floodplain deposits that are typically contaminated to depths of 1 5 3 5 m these contaminated sediments store a total of 188 549 mg of pb and 34 299 mg of zn of which 98 of the pb and 95 of the zn are stored in floodplain deposits most of the metal mass in channel deposits is stored near the mines with 72 of the pb and 78 of the zn occurring in the 25 km of channel proximal to the mine source although environmental assessments of streams contaminated by mines often focus on evaluating metal concentrations in the geochemically active fine sediment fractions about 60 of the pb stored in channels is associated with coarse dolomite tailings fragments deposited in channels within 25 km of the mines the magnitude and basinwide distribution of pb and zn storage in legacy floodplain sediments ensures that remobilization by bank erosion will be a continuing problem for water quality far into the future

behaviour of major elements and some trace elements li rb cs sr fe mn w f in deep hot waters from granitic areas abstract analyses of selected hot springs in more than sixty areas in granites from europe are presented concentrations of major elements and of some trace elements li rb cs sr fe mn w f in high ph waters are not significantly affected by processes during uprise from the deep reservoir to the surface re equilibrations mixing with surficial waters normalized to k or na concentrations of all other elements are related to the aquifer temperature the knowledge of aquifer temperature and total electric charge of mobile elements cl s possibly f allows us to predict both major elements within 50 and trace elements within a factor 2 or 3 concentrations in alkaline waters from granites

geochemical and isotope hydrological characterisation of geothermal resources at godavari valley india thermal waters at the godavari valley geothermal field are located in the khammam district of the telangana state india the study area consists of several thermal water manifestations having temperature in the range 36 76 c scattered over an area of 35 km2 the thermal waters are na hco3 type with moderate silica and tds concentrations in the present study detailed geochemical major and trace elements and isotope hydrological investigations are carried out to understand the hydrogeochemical evolution of these thermal waters correlation analysis and principal component analysis pca are performed to classify the thermal waters and to identify the different geochemical processes controlling the thermal water geochemistry from correlation matrix it is seen that tds and ec of the thermal springs are mainly controlled by hco3 and na ions in pca thermal waters are grouped into two distinct clusters one cluster represents thermal waters from deeper aquifer and other one from shallow aquifer lithium and boron concentrations are found to be similar followed by rubidium and caesium concentrations different ternary plots reveal rock water interaction to be the dominant mechanism for controlling trace element concentrations stable isotopes 18o 2h data indicate the meteoric origin of the thermal waters with no appreciable oxygen 18 shift the low tritium values of the samples originating from deeper aquifer reveal the long residence time 50 years of the recharging waters xrd results of the drill core samples show that quartz constitutes the major mineral phase whereas kaolinite dolomite microcline calcite mica etc are present as minor constituents quartz geothermometer suggests a reservoir temperature of 100 20 c which is in good agreement with the values obtained from k mg and mg corrected k mg ca geothermometers

greenland ice sheet surface melt and its relation to daily atmospheric conditions abstractmelt area is one of the most reliably monitored variables associated with surface conditions over the full greenland ice sheet gris surface melt is also an important indicator of surface mass balance and has potential relevance to the ice sheet s global sea level contribution melt events are known to be spatially heterogeneous and have varying time scales to understand the forcing mechanisms it is necessary to examine the relation between the existing conditions and melt area on the time scales that melt is observed here we conduct a regression analysis of atmospheric reanalysis variables including sea level pressure near surface winds and components of the surface energy budget with surface melt the regression analysis finds spatial heterogeneity in the associated atmospheric circulation conditions for basins in the southern gris there is an association between melt area and high pressure located south of the denmark strait which allows for southerly flow over the western half of th

geochemical characteristics of water and sediment of the indus river trans himalaya india constraints on weathering and erosion abstract the indus river carries a huge amount of chemical and sediment load while traversing the himalayas the present study deals with the chemistry of major ions ca mg hco3 na k cl so4 sio2 and trace metal contents ba sr zn ni cu co mn of the river indus one of its major tributaries the river beas many adjoining hot and cold water springs and the high altitude lake 5700 m kyung tso although anthropogenic activities like farming grazing and tourism have started in large parts of this terrain our study indicates that chemistry of indus water is influenced mostly by the lithology of the basin and most of its ionic concentration appears to have been derived from weathering of carbonates and silicates in the catchment area for the first time bed and suspended sediments of the river indus have also been studied and compared with average post archean shale pas and greywacke the sediments of the indus river in its headwater region closely reflect the exposed portion of the crust in its catchment area the headwater part of the indus basin in ladakh and karakorum is characterised by rapid uplift and therefore subject more to intense physical weathering than chemical weathering as is evidenced by the suspended and dissolved load carried by the river physical weathering and erosion is expected to have major controls on the grain size and therefore the chemical nature of the sediments

a five year record of summer melt on eurasian arctic ice caps abstract climatologies and annual anomaly patterns 2000 04 of melt season duration and dates of melt onset freeze up on eurasian arctic ice masses were derived from quick scatterometer quikscat backscatter data severnaya zemlya russia has later melt onset earlier freeze up and shorter melt seasons than svalbard norway novaya zemlya russia in all three archipelagos 2001 was the longest melt season and 2000 was the shortest anomalously long short melt seasons on svalbard were associated with negative positive sea ice concentration anomalies along the north coast in june and august annual mean melt duration was strongly correlated with the mean june august ncep ncar reanalysis 850 hpa air temperature allowing reconstruction of melt durations for the period of 1948 2005 the 2000 04 pentad had the second or third longest mean melt duration of all pentads in the 1950 2004 epoch while the 1950 54 pentad probably had the longest integration of these results with previous results from gre

geochemical evaluation of thermal springs in odisha india the indian state of odisha has a number of thermal springs these thermal springs are located at eight places attri tarabalo deulajhari magarmuhan bankhol badaberena taptapani and boden and belong to mahanadi geothermal province which is an archean pre cambrian geothermal province the thermal water discharging from these springs shows moderately acidic to moderately alkaline character ph 5 05 8 93 and the temperature ranges from 28 boden to 58 c tarabalo total dissolved solids tds also shows a wide variation between 16 9 bankhol and 595 mg l deulajhari a wide variation in the chemical characteristics of the thermal waters has been observed as they are located in different geological settings based on water chemistry all the thermal springs can broadly be grouped into three water types na cl ca hco3 and na hco3 the thermal spring water from attri tarabalo and deulajhari belongs to na cl water type which is due to the circulation through granitic rocks higher concentrations of cl and f in these thermal waters further suggest limited mixing and longer residence time as compared to the other areas where ca hco3 and na hco3 water types were found anion variation diagram clearly indicates that the thermal waters from attri tarabalo and deulajhari are fast ascending and fall in the mature water field thus their chemical signatures can be used to determine the reservoir temperature however in other areas water chemistry is shaped by near surface groundwater mixing processes and thus the chemical geothermometers may not be applicable to determine the reservoir temperature no appreciable temporal variations have been observed in the water chemistry of the thermal waters

snowmelt on the greenland ice sheet as derived from passive microwave satellite data abstract the melt extent of the snow on the greenland ice sheet is of considerable importance to the ice sheet s mass and energy balance as well as arctic and global climates by comparing passive microwave satellite data to field observations variations in melt extent have been detected by establishing melt thresholds in the cross polarized gradient ratio xpgr the xpgr defined as the normalized difference between the 19 ghz horizontal channel and the 37 ghz vertical channel of the special sensor microwave imager ssm i exploits the different effects of snow wetness on different frequencies and polarizations and establishes a distinct melt signal using this xpgr melt signal seasonal and interannual variations in snowmelt extent of the ice sheet are studied the melt is found to be most extensive on the western side of the ice sheet and peaks in late july moreover there is a notable increasing trend in melt area between the years 1979 and 1991 of 4 4 per year which came to an abrupt halt in 1

mass balance of higher elevation parts of the greenland ice sheet satellite radar and aircraft laser altimeter data and a volume budget comparison of total snow accumulation with total ice discharge give three independent estimates of the recent mass balance of parts of the greenland ice sheet above 2000 m elevation results show the entire region on average to be in balance to within 10 mm yr 1 with very low rates of regional thickness change dh dt in the northeast but high rates with large spatial variability in the south only the volume budget estimates show significant thinning in the northwest but thinning in this area is also inferred from local measurements of ice vertical velocities down boreholes south of latitude 68 n there has been rapid thickening west of the ice divide with equally rapid thinning in the southeast but with large differences between the three estimates of dh dt throughout this region the radar data apply to the period 1978 1988 the laser data are for 1993 1994 1998 1999 and the volume budget calculations represent conditions over at least the last few decades consequently many of the differences between results could be caused by temporal changes particularly in snow accumulation rates that occurred since the 1970s however taken with other information our results suggest long term thickening in the southwest and possibly quite recent onset of rapid thinning in the southeast

recent changes in heavy metal contamination at near channel positions of the lahn river central germany abstract short term monitoring of heavy metal concentrations along rivers affords the opportunity to examine the persistence of contaminants in the fluvial environment this paper examines changes in the concentrations of cu pb and zn at near channel positions along a 75 km reach of the lahn river an agrarian watershed in central germany between 2000 and 2007 thirty three sites sampled in 2000 were re sampled in 2007 in order to document changes in trace metal contamination the concentrations of cu and pb decreased between 2000 and 2007 whereas the concentration of zn was statistically unchanged the pb concentration decreased at 82 of the sample sites over the study period whereas cu concentrations decreased at 70 of the sites site to site variation in the concentrations of pb with distance downstream from potential source areas declined between 2000 and 2007 the downstream variation in cu also decreased over the study period albeit to a lesser degree the decrease in pb and to a lesser extent cu concentrations adjacent to the lahn river appears to reflect the recent reductions in the release of trace elements to the environment zinc concentrations were unchanged suggesting that it is derived from different sources than are cu and pb or is cycling through the watershed differently than cu and pb lower concentrations of cu and pb in channel bank sediments translate to a reduced risk of future downstream heavy metal pollution in the study area

mercury contamination of active channel sediment and floodplain deposits from historic gold mining at gold hill north carolina usa a reconnaissance investigation of mercury contamination associated with historic gold mining in north carolina usa revealed high concentrations of mercury in channel and floodplain sediments downstream from the gold hill mining district the most intense period of mining activities in this region occurred in the 1840s and 1850s when mercury amalgamation was used to recover fine gold particles from milled ore this paper evaluates mercury concentrations measured in active channel sediments and two cores recovered from historic floodplain deposits of the lower portion of dutch buffalo creek mercury concentrations in these cores range from 0 01 to 2 2 mg kg with maximum concentrations more than 35 times background levels a later peak in copper concentrations is associated with the operation of a large copper mine between 1899 and 1906 following the most intense periods of mining both mercury and copper concentrations decrease upcore to constant levels of about twice pre mining background concentrations results suggest that vertical trends in mercury and other trace metals provide a useful tool for interpreting rates of historic floodplain sedimentation in the piedmont of north carolina

the natural and human structuring of rivers and other geomorphological systems a tribute to william l graf this special issue honors the contributions of william l graf to geomorphology and river science a hallmark of will s work over the course of his career has been a focus on the natural and human structuring of river systems more broadly will has been an innovator and leader who has shaped the way in which geomorphologists conduct research through his work he has made fundamental contributions to basic fluvial theory to the understanding of human impacts on river systems and to policy relevant science he has demonstrated by example how to pursue policy relevant science and to participate in science based policy formulation his contributions to river science can be classified into several themes 1 the hydrology and geomorphology of suburban drainage systems 2 riparian vegetation and river systems 3 the spatial structure and dynamics of incised channels 4 the dynamics of dryland river systems 5 heavy metals in river systems 6 dams and dam removal and 7 water and public policy the papers in this special issue reflect many aspects of these themes and address topics related to 1 the understanding of rivers and other geomorphic systems in the midst of dynamic physical change 2 human influences on geomorphic processes 3 the intersection of geomorphology and public policy and 4 the fusion of geomorphic analysis and giscience

active overbank deposition during the last century south river virginia abstract we quantify rates of overbank deposition over decadal to centennial timescales along the south river in virginia using four independent methods detailed mercury profiles sampled adjacent to the stream channel preserve the peak historic mercury concentration on suspended sediment dating from 1955 to 1961 and suggest sedimentation rates of 8 to 50 cm 100 years sediment accumulation over the roots of trees suggest rates of 0 to 100 cm 100 years with significantly higher values on levees and lower values on floodplains farther from the channel profiles of 137cs and 210pb from two eroding streambanks are fit with an advection diffusion model calibrated at an upland reference site these methods suggest sedimentation rates of 44 to 73 cm 100 years mercury inventories from 107 floodplain cores combined with a previously published reconstruction of the history of mercury concentration on suspended sediment provide spatially comprehensive estimates of floodplain sedimentation median sedimentation rates are 3 8 cm 100 years for the

windsat passive microwave polarimetric signatures of the greenland ice sheet windsat has systematically collected the first global fully polarimetric passive microwave data over both land and ocean as the first spaceborne polarimetric microwave radiometer it was designed to measure ocean surface wind speed and direction by including the third and fourth stokes parameters which are mostly related to the asymmetric structures of the ocean surface roughness although designed for wind vector retrieval windsat data are also collected over land and ice and this new data has revealed for the first time significant land signals in the third and fourth stokes parameter channels particularly over greenland and the antarctic ice sheets the third and fourth stokes parameters show well defined large azimuth modulations that appear to be correlated with geophysical variations particularly snow structure melting and metamorphism and have distinct seasonal variation the polarimetric signatures are relatively weak in the summer and are strongest around spring this corresponds well with the formation and erosion of the sastrugi in the dry snow zone and snowmelt in the soaked zone in this paper we present the full polarimetric signatures obtained from windsat over greenland and use a simple empirical observation model to quantify the azimuthal variations of the signatures in space and time

geothermal mineral equilibria the dominant reaction determining the chemistry of fluids in a geothermal system of the new zealand type consists of the conversion of primary plagioclase by co2 to calcite and clays with log pco2 15 26 7850 t 273 2 temperature t in c subsequent reactions involving secondary minerals control relative co2 h2s contents the distribution of mineral phases throughout a geothermal system reflects the stepwise conversion of thermodynamically unstable primary phases through a series of intermediate metastable phases to a thermodynamically stable secondary assemblage the relative stabilities of these phases was evaluated on the basis of their solubilities the least soluble aluminiumsilicate representing the thermodynamically most stable phase under a given set of conditions observed assemblages of secondary minerals in geothermal systems represent indicators allowing mineral fluidinteraction conditions to be evaluated on the basis of multi component mineral stability diagrams

spatial patterns of historical overbank sedimentation and floodplain evolution blue river wisconsin abstract increased soil erosion and overbank flooding associated with land use changes following european settlement have buried pre settlement floodplain surfaces in many driftless area watersheds with as much as several meters of alluvium this paper examines the processes influencing spatial variations in the storage of post settlement vertical accretion alluvium and the impact on floodplain evolution in the blue river watershed wisconsin the cross sectional area of historical vertical accretion sediments stored on floodplains was measured at 41 cross valley transects in the 208 km2 watershed the storage of historical overbank sediments is influenced by valley width stream power and the development of meander belts post settlement alluvial storage increases with valley width and decreases with cross sectional stream power in a multivariate regression model valley width and cross sectional stream power explain 67 of the variance in the amount of post settlement alluvium the development of meander belts enlarged channels confined between alluvial terraces by accelerated lateral channel migration influences historical floodplain storage by decreasing the influence of valley width and modifying stream power characteristics for flows greater than bankfull meander belts are located in headwater and mid basin valley reaches where high stream power produces rapid lateral channel migration whereas low gradient channels in downstream valleys lack the power necessary to migrate laterally and develop meander belts meander belts influence the spatial pattern of historical sedimentation by 1 containing large magnitude floods and preventing overbank flow 2 increasing sediment transport capacities 3 initiating the erosion of previously deposited historical sediments 4 reducing the attenuation of flood peaks and 5 increasing the amount of sediment routed downstream to wide low gradient valley bottoms lacking meander belts continued high rates of lateral channel migration will eventually be damped as widening of the meander belt decreases flow depths and stream power

calculated variations of annual ice ablation at the margin of the greenland ice sheet west greenland 1961 90 annual ice ablation has been measured at three locations at the margin of the greenland ice sheet nordbogletscher for 6 years 1977 78 to 1982 83 qaman rssup sermia 8 years 1979 80 to 1986 87 and at paakitsup akuliarusersua 7 years 1982 83 to the present as the data sets cover different periods it is difficult to compare ablation directly between the three sites however measured series at each site can be extended over the last 30 years 1961 90 by simulations using climatic data and the extended data series can be compared

detection and monitoring of stratigraphic markers and temperature trends at the greenland ice sheet project 2 using passive microwave remote sensing data satellite passive microwave sensors provide a sensitive means of studying ice sheet surface processes that assists ice core interpretation and can extend local observations across regional scales analysis of special sensor microwave imager ssm i brightness temperature tb data supports ice core research in two specific ways first the summer hoar complex layers used to date the holocene portion of the greenland ice sheet project 2 ice core can be defined temporally and spatially by ssm i 37 ghz vertically v and horizontally h polarized b ratio v h trends second comparison of automatic weather station temperatures to ssm i 37 ghz v tb data shows that they are an effective proxy temperature record in this region also the tb data can be correlated with proxy temperature trends from stable isotope ratio 18o and d profiles from snow pits and this allows the assignment of dates to specific snow depths

spatial distribution of trace elements in floodplain alluvium of the upper blackfoot river montana the mike horse mine tailings dam in western montana was partially breached in 1975 due to heavy rainfall and a failed drainage bypass approximately 90 000 tons of metal and arsenic enriched tailings flowed into beartrap creek and the blackfoot river the spatial distribution of trace elements as cd cu mn pb and zn in floodplain alluvium of the upper blackfoot river were examined along 20 transects in the upper 105 river kilometers downstream from the tailings dam trace element concentrations decrease with distance from the failed dam with as reaching background concentrations 15 km from the mike horse dam cd and pb at 21 km cu at 31 km and mn and zn at 37 km distance from the mike horse tailings dam and mine area is the dominating factor in explaining trace element levels with r 2 values ranging from 0 67 to 0 89 maximum floodplain trace element concentrations in the upper basin exceed us epa ecological screening levels for plants birds and other mammals and reflect adverse hazard quotients for exposure to as and mn for atv motorcycle use trace element concentrations in channel bank and bed alluvium are similar to concentrations in floodplain alluvium indicating active transport of trace elements through the river and deposition on the floodplain the fine fraction 2 mm of floodplain alluvium is dominated by sand sized particles 2 0 0 05 mm with cu and mn significantly correlated with silt sized 0 05 0 002 mm alluvium ongoing remediation in the headwaters area will not address metal contamination stored downstream in the channel banks and on the floodplain additionally some trace elements cu mn and zn were conveyed farther downstream than were others as cd pb

ice layers as an indicator of summer warmth and atmospheric blocking in alaska samples were collected from a snow pit and shallow firn core near kahiltna pass 2970 m a s l denali national park alaska usa in may 2008 the record spans autumn 2003 to spring 2008 and reveals clusters of ice layers interpreted as summertime intervals of above freezing temperatures high correlation coefficients 0 75 1 00 between annual ice layer thickness and regional summertime station temperatures for 4 years n 4 indicate ice layer thickness is a good proxy for mean and extreme summertime temperatures across alaska at least over the short period of record a rex block aka high over low pattern a downstream trough over hudson bay canada and an upstream trough over eastern siberia occurred during the three melting events that lasted at least 2 weeks about half of all shorter melting events were associated with a cut off low traversing the gulf of alaska we hypothesize that a surface to bedrock core extracted from this location would provide a high quality record of summer temperature and atmospheric blocking variability for the last several hundred years

passive microwave ssm i satellite predictions of valley glacier hydrology matanuska glacier alaska 1 we advance an approach to use satellite passive microwave observations to track valley glacier snowmelt and predict timing of spring snowmelt induced floods at the terminus using 37 v ghz brightness temperatures tb from the special sensor microwave imager ssm i we monitor snowmelt onset when both tb and the difference between the ascending and descending overpasses exceed fixed thresholds established for matanuska glacier melt is confirmed by ground measured air temperature and snow wetness while glacier hydrologic responses are monitored by a stream gauge suspended sediment sensors and terminus ice velocity measurements accumulation area snowmelt timing is correlated r2 0 61 to timing of the annual snowmelt flood peak and can be predicted within 5 days

lithium isotope geochemistry of sediments and hydrothermal fluids of the guaymas basin gulf of california abstract lithium isotopic compositions of hydrothermally altered sediments of deep sea drilling project dsdp site 477 477a as well as high temperature vent fluids of the guaymas basin have been determined to gain an understanding of lithium exchange during fluid sediment interaction at this sediment covered spreading center unaltered turbidite of the basin has a 6 li value of 10 5 7 heavier than fresh oceanic basalts contact metamorphism induced by a shallow sill intrusion results in a decrease of the lithium content of the adjacent sediments and a lighter isotopic value 8 below the sill sediments altered by a deep seated hydrothermal system show strong depletions in lithium while lithium isotopic compositions vary greatly ranging from 11 to 1 the shift to lighter composition is the result of preferential retention of the lighter isotope in recrystallized phases after destruction of the primary minerals the complexity of the isotope profile is attributed to inhomogeneity in mineral composition the tortuous pathway of fluids and the temperature effect on isotopic fractionation the range of lithium concentration and 6 li values for the vent fluids sampled in 1982 and 1985 overlaps with that of the sediment free mid ocean ridge systems the lack of a distinct expression of sediment input is explained in terms of a flow through system with continuous water recharge the observations on the natural system agree well with the results of laboratory hydrothermal experiments the experimental study demonstrates the importance of temperature pressure water rock ratio substrate composition and reaction time on the lithium isotopic composition of the reacted fluid high temperature authigenic phases do not seem to constitute an important sink for lithium and sediments of a hydrothermal system such as guaymas are a source of lithium to the ocean the ready mobility of lithium in the sediment under elevated temperature and pressure conditions also has important implications for lithium cycling in subduction zones

a possible k t boundary bolide impact site offshore near bombay and triggering of rapid deccan volcanism abstract the temporal coincidence of a major biological mass extinction including dinosaurs the well known iridium excess anomaly at the cretaceous tertiary k t boundary and the eruption of deccan flood basalts at about 65 ma has aroused global interest among geologists and biologists it is widely debated whether the mass extinction and iridium anomaly are due to an asteroid impact or the massive outpouring of extensive deccan volcanism an oval shaped unusual positive gravity anomaly 10 000 km 2 in area near bombay has attracted our attention during a search for an impact site near deccan basalts a detailed gravity interpretation indicates the presence of a fossil conduit structure of 12 km height extending from a shallow crust mantle boundary at 18 km to an approximate depth of 6 km from the surface the conduit structure with a maximum diameter of about 35 km at its base may originate from cracking of a weak pre deccan trap shallow upwarped mantle the structure may have been caused by a bolide impact which triggered the eruption of massive flood basalts deccan traps on the western margin of the fast moving indian plate an impact in this locality can explain the sudden detachment of the arcuate seychelles block from india as well as the large scale reorganisation of plate boundaries in the indian ocean our hypothesis of impact triggered volcanism at 65 ma advocates a bimodal cause for the mass extinction at the k t boundary extraordinary geothermal and structural conditions of the nearby region are also discussed as circumstantial evidence to support the twin cause mechanism by weakened features and the presence of partial melt at subcrustal depth

melt season duration and ice layer formation on the greenland ice sheet 2000 2004 1 time series of enhanced resolution quikscat images were used to map the extent and duration of surface melt and the distribution of ice layer formation on the greenland ice sheet in the period 2000 2004 apart from the bare ice and the mixed pixels 10 along the ice sheet margin where melt cannot be determined reliably annual melt duration and melt anomaly maps were produced across the ice sheet 90 for each summer over the 5 year period the mean melt duration for the ice sheet ranged from 14 3 to 20 5 d the proportion of the ice sheet that experienced melting in a given year ranged from 44 2 to 79 2 extensive melt in 2002 was caused by a single melt event of a few days duration this event was associated with the intrusion of a ridge of high pressure from the north atlantic ocean that brought warm air onto the ice sheet the change in biweekly averaged backscatter between the freeze up periods in the current and previous falls was used to identify changes in the distribution of ice layers in snow between successive melt seasons the year 2002 had the maximum melt extent and duration and ice layer formation extended to higher elevations than in other years interannual changes in the distribution of ice layer formation may be associated with changes in surface height that are not necessarily indicative of mass balance changes mapping of ice layer formation is thus potentially useful for interpreting both real and apparent height changes measured by altimetry

the role of geomorphic processes in the transport and fate of mercury in the carson river basin west central nevada the historic processing of precious metal ores mined from the comstock lode of west central nevada resulted in the release of substantial but unquantified amounts of mercury contaminated mill tailings to the carson river basin geomorphic and stratigraphic studies indicate that the introduction of these waste materials led to a period of valley floor aggradation that was accompanied by lateral channel instability the combined result of these geomorphic responses was the storage of large volumes of mercury enriched sediment within a complexly structured alluvial sequence located along the carson river valley much of the contaminated sediment is associated with filled paleochannels produced by the cutoff and abandonment of meander loops and their subsequent infilling with contaminated particles geochemically these deposits are characterized by variations in mercury levels that exceed three orders of magnitude continued lateral instability coupled with an episode of channel bed incision followed the decline of comstock mining and has reexposed contaminated debris within the banks of the river erosion of bank sediments reintroduces mercury enriched particles to the modern channel bed it is suggested on the basis of geochemical and sedimentological data that during the bank erosion process much of the mercury associated with fine 63 valley fill deposits are carried downstream without being incorporated to any appreciable extent within the channel bed sediments in contrast mercury associated with larger and denser particles particularly mercury gold silver amalgam grains are accumulated in the channel bed sediments as the river traverses polluted reaches of the carson river valley concentration patterns developed along the modern channel indicate that the valley fill is the primary source of mercury to the river today thus these data imply that efforts to reduce the influx of mercury to the aquatic environment should examine methods for reducing bank erosion rates

the chemistry of geothermal waters in iceland i calculation of aqueous speciation from 0 to 370 c abstract a computer programme has been developed to calculate the composition and aqueous speciation of geothermal reservoir waters including ph redox potential and gas partial pressures the programme is specifically suited to handle geochemical data from wet steam wells hot water wells and boiling hot springs but it may also be used for non thermal waters solubility data for selected geothermal minerals are incorporated to facilitate the study of solution mineral equilibria the programme may also be used to study chemical changes in water chemistry accompanying boiling variable degassing and cooling and how these changes disturb solution mineral equilibria

processes controlling the distribution of boron and chlorine in natural waters in iceland abstract the concentrations of b and cl in natural waters in iceland lie in the range 0 001 10 and 1 20 000 ppm respectively lowest concentrations occur in surface and groundwaters in the central highlands highest cl concentrations are found in high temperature waters on the reykjanes peninsula and highest b concentrations in well waters from high temperature geothermal systems in the axial zones of the active volcanic belts the b and cl contents of icelandic basalts are 0 1 6 6 and 75 750 ppm respectively these large variations are considered to result from variable degassing during consolidation as well as concentration variations in the initial magma tholeftes are lowest in both elements av 1 2 ppm b and 170 ppm ci transitional basalts intermediate av 2 1 ppm b and 240 ppm ci and alkali basalts highest av 3 8 ppm b and 340 ppm cl cl b ratios in tholeiites are most often within 25 50 but somewhat lower in alkali basalts most geothermal waters contain b and cl within 0 05 1 and 10 100 ppm respectively these rather low values are attributed to the low content of b and cl in the basaltic rock the b and cl distribution in the icelandic natural waters indicate that these elements act as essentially incompatible their sources of supply include 1 the atmosphere seawater spray and aerosols 2 the rock with which the water interacts 3 seawater groundwater and 4 magma intrusions in surface water and nonthermal groundwater the dominant source of supply of cl is seawater spray and aerosols but the soil and rock contribute often significantly to the b in these waters their cl b ratio is similar to that of seawater 1330 or somewhat lower boron and cl concentrations generally increase with water temperature warm waters cl b ratios intermediate between those of seawater and basalt with increasing temperature this ratio decreases and gradually approaches that of the rock some high temperature geothermal waters have as low cl b ratios as 1 and b concentrations as high as 10 ppm the cause is either b degassing of the magmatic intrusive heat source or phase separation in the producing aquifer some low temperature waters

new precipitation and accumulation maps for greenland annual total precipitation and the annual accumulation on the greenland ice sheet are evaluated and presented in two maps the maps are based on accumulation measurements of 25 1 pits and cores obtained from the upper accumulation zone and precipitation measurements made at 35 meteorological stations in the coastal region to construct the accumulation map the annual precipitation was split into solid and liquid precipitation components annual total precipitation exceeding 2500 mm w e occurs on the southeastern tip of greenland while the minimum precipitation is estimated to occur on the northeastern slope of the ice sheet the mean annual precipitation for all of greenland is 340 mm w e the largest annual accumulation of about 1500 mm w e is found on the glaciers in the southeastern corner of greenland while the smallest accumulation is found on the northeastern slope of the ice sheet west of danmarkshavn the mean accumulation on the greenland ice sheet is estimated at 310 mm w e the regional difference in accumulation is examined with respect to the 850 hpa m bar level circulation the present surface topography is found to play an important role in determining regional accumulation on the ice sheet

persistent surface snowmelt over antarctica 1987 2006 from 19 35 ghz brightness temperatures 1 persistent melting e g continuing for more than three days or for one consecutive day and night is mapped in antarctica 1987 2006 using night and day time special sensor microwave imager brightness temperatures tb at 19 35 ghz horizontal polarization snowmelt is indicated when tb and relative daily difference exceed threshold values respectively tc and t computed for each pixel and year or when both daytime and nighttime tb exceed tc results from an electromagnetic model suggest that the minimum detectable liquid water content ranges between 0 2 and 0 5 in volume we find that melting areas have been moving inland since 1987 a first time extensive melting 1987 2006 is detected over the transantarctic mountains on january 2005 875 km inland and 2000 m above sea level melting extent and index have been decreasing over antarctica since 1987 although either positive and negative trends are observed from a sub continental scale analysis