contribution of small glaciers to global sea level observed long term changes in glacier volume and hydrometeorological mass balance models yield data on the transfer of water from glaciers excluding those in greenland and antarctica to the oceans the average observed volume change for the period 1900 to 1961 is scaled to a global average by use of the seasonal amplitude of the mass balance these data are used to calibrate the models to estimate the changing contribution of glaciers to sea level for the period 1884 to 1975 although the error band is large these glaciers appear to account for a third to half of observed rise in sea level approximately that fraction not explained by thermal expansion of the ocean

drainage events from a glacier dammed lake bear glacier alaska remote sensing and field observations abstract we investigated drainage events from a glacier dammed lake on bear glacier alaska and associated outburst floods and hazards the glacier dammed lake which we call ice lake is 17 5 km up glacier from bear glacier s terminus at bear glacier lake we combine field observations and remote sensing to examine temporal changes in the size of ice lake the frequency and timing of its drainage and down glacier propagation of its outburst floods we found that in recent years ice lake has likely drained every year or two in late summer or fall august october with outbursts generally following the damming of sufficient water to create a lake area of between 0 35 and 0 5 km2 ice lake has migrated downvalley to the south since the 1990s likely as a result of thinning of the glacier that dams it in situ measurements of a drainage event in october 2010 showed that ice lake drained over a period of days which manifested at bear glacier lake as a gradual multiday increase and then decrease in water levels glacial lake outburst flooding at bear glacier creates risks for sea kayakers in bear glacier lake and may be relevant to understanding the effects of climate warming on glacier dammed and proglacial lakes

glacier changes in southeast alaska and northwest british columbia and contribution to sea level rise 1 the digital elevation model dem from the 2000 shuttle radar topography mission srtm was differenced from a composite dem based on air photos dating from 1948 to 1987 to determine glacier volume changes in southeast alaska and adjoining canada srtm accuracy was assessed at 5 m through comparison with airborne laser altimetry and control locations measured with gps glacier surface elevations lowered over 95 of the 14 580 km2 glacier covered area analyzed with some glaciers thinning as much as 640 m a combination of factors have contributed to this wastage including calving retreats of tidewater and lacustrine glaciers and climate change many glaciers in this region are particularly sensitive to climate change as they have large areas at low elevations however several tidewater glaciers that had historically undergone calving retreats are now expanding and appear to be in the advancing stage of the tidewater glacier cycle the net average rate of ice loss is estimated at 16 7 4 4 km3 yr equivalent to a global sea level rise contribution of 0 04 0 01 mm yr

accelerating thinning of kenai peninsula glaciers alaska 1 temperate mountain glaciers are thinning at high rates and significantly contributing to sea level rise due to these glaciers remote locations remote sensing and digital elevation models dems are an effective way to calculate their thinning rates and contribution to sea level rise comparisons of 1950s united states geological survey usgs and 2000 shuttle radar topographic mission srtm dems with dems produced from lidar profiles of glacier center lines indicate thinning rates from the mid 1990s to 1999 0 72 0 13 m y 1 accelerated by a factor of 1 5 as compared with 1950 to mid 1990s 0 47 0 01 m y 1 for glaciers on the harding icefield overall comparison of usgs and srtm dems indicate the harding icefield and grewingk yalik glacier complex alaska are thinning 0 61 0 12 m y 1 from 1950 to 1999

time scale for adjustment of glaciers to changes in mass balance the length of time tm over which a glacier responds to a prior change in climate is investigated with reference to the linearized theory of kinematic waves and to results from numerical models we show the following tm may in general be estimated by a volume time scale describing the time required for a step change in mass balance to supply the volume difference between the initial and final steady states the factor f in the classical estimate of m l u where i is glacier length and u is terminus velocity has a simple geometrical interpretation ft is the ratio of thickness change averaged over the full length i to the change at the terminus although both u and f relate to dynamic processes local to the terminus zone the ratio f u and therefore tm are insensitive to details of the terminus dynamics in contrast to conclusions derived from some simplified kinematic wave models a more robust estimate of tm independent of terminus dynamics is given by tm h b where h is a thickness scale for the glacier and b is the mass balance rate negative at the terminus we suggest that tm for mountain glaciers can be substantially less than the 1o2 103 years commonly considered to be theoretically expected

ms mb discrimination study of mining explosions in wyoming usa and in qianan china we investigate the use of intermediate period surface wave magnitude m s and high frequency body wave magnitude m b from regional mining explosions for event discrimination by using techniques originally intended for separating earthquakes from explosions with teleseismic observations the actual values of m s and m b suggest that the surface waves generated by long duration mining explosions can make them appear earthquakelike the data from the single anomalous shot indicate that if a significant part of the total explosives is simultaneously detonated the event will move into the explosion population data for this study are taken from a portable broadband deployment in wyoming recording mining explosions in the powder river basin and a broadband network currently deployed in northeast china the magnitudes m s vmax and m b were estimated for five kiloton size mining explosions four in wyoming and one in qianan china the resulting network m s m b data were compared with data from a previous study that included earthquakes and contained single fired explosions stevens and day 1985 bonner et al 2003 although the previous studies mostly examined events larger than those in this study the wyoming and china mining events plot in the earthquake population data from the anomalous wyoming event a blast in which a failure of the timing system caused a large portion of the blast pattern to simultaneously detonate plot in the explosion population with m b 4 4 the simultaneous detonation of a large portion of blast array increased the body wave magnitude but had little effect on surface wave magnitude

penetration depth of interferometric synthetic aperture radar signals in snow and ice digital elevation models of glaciated terrain produced by the nasa jet propulsion laboratory jpl airborne interferometric synthetic aperture radar insar instrument in greenland and alaska at the c 5 6 cm wave length and l band 24 cm frequencies were compared with surface elevation measured from airborne laser altimetry to estimate the phase center of the interferometric depth or penetration depth p on cold polar firn at greenland summit p 9 2m at c and 14 4m at l band on the exposed ice surface of jakobshavn isbrae west greenland p 1 2 m at c and 3 3 m at l band except on smooth marginal ice where p 15 5 m on colder marginal ice of northeast greenland p reaches 60 to 120 m at l band on the temperate ice of brady glacier alaska p is 4 2 m at c and 12 6 m at l band with little dependence on snow ice conditions the implications of the results on the scientific use of insar data over snow ice terrain is discussed

investigations on intra annual elevation changes using multi temporal airborne laser scanning data case study engabreen norway key issues of glacier monitoring are changes in glacier geometry and glacier mass as accurate direct measurements are costly and time consuming the use of various remote sensing data for glacier monitoring is explored one technology used and described here is airborne laser scanning the method enables the derivation of high quality digital elevation models dems with a vertical and horizontal accuracy in the sub metre range between september 2001 and august 2002 three laser scanner data acquisition flights were carried out covering the whole area of engabreen norway and corresponding well to the measurement dates for the mass balance year 2001 02 the data quality of the dems is assessed e g by comparing the values with a control area which has been surveyed independently or gps ground profiles measured during the flights for the whole glacier surface elevation change and consequently volume change is calculated quantified and compared with traditional mass balance data for the same time interval for the winter term emergence submergence velocity is determined from laser scanner data and snow depth data and is compared with velocity measurements at stakes the investigations reveal the high potential of airborne laser scanning for measuring the extent and the topography of glaciers as well as changes in geometry area volume

elevation and volume changes on the harding icefield alaska airborne surface elevation profiles of the harding icefield south central alaska were made in 1994 and 1996 thirteen glaciers were profiled along with the upper region of the icefield the profiles were compared to u s geological survey topographic maps made in the 1950s to obtain elevation and volume changes comparison of the changes for the different glaciers shows no significant correlation between volume change and the type of glacier or characteristics such as location aspect size slope or terminus changes estimated total volume change for this 43 year period is about 34 km 3 which corresponds to an area average elevation change of 21 m the estimated error in this elevation change of 5 m is mainly due to errors in the maps at higher elevations our measurements provide an accurate baseline against which future determinations of volume change can be made

a glacier inventory for south tyrol italy based on airborne laser scanner data a new approach to glacier inventory based on airborne laser scanner data has been applied to south tyrol italy it yields highly accurate results with a minimum of human supervision earlier inventories from 1983 and 1997 are used to compare changes in area volume and equilibrium line altitude a reduction of 32 was observed in glacier area from 1983 to 2006 volume change derived from the 1997 and 2006 digital elevation models was 1 037 km 3 and an ela rise of 54 m to almost 3000 m a s l was calculated for this period losses vary widely for individual glaciers but have accelerated for all south tyrolean glaciers since the first inventory in 1983

regional seismic observations of the 9 october 2006 underground nuclear explosion in north korea and the influence of crustal structure on regional phases 1 the crustally guided shear wave lg is typically the most prominent phase of a nuclear explosion at regional distance this lg phase is analyzed often to discriminate a nuclear explosion from a natural earthquake in addition the lg phase allows us to determine the size of the detonation a nuclear explosion test in north korea was conducted on 9 october 2006 the epicenter was located close to the eastern shore of the korean peninsula resulting in raypaths that vary significantly according to the azimuths in particular rays radiated in the southern direction experience lateral variation of crustal structures at the continental margin we examine the influence of raypaths on regional seismic phases by comparing the spectra and waveforms from different raypaths three natural earthquakes in north korea are also examined to determine the raypath effect we find that the lg from the nuclear explosion dissipated significantly as result of energy leakage into the mantle resulting from variations in crustal thickness along the portion of the raypath traversing the western tip of the sea of japan east sea some of the leaked energy develops into mantle lid waves sn causing a large energy increase to sn a similar feature is observed in the records of natural earthquakes this feature is confirmed by seismic waveform modeling the raypath effect also causes underestimation of magnitude the lg body wave magnitude mb lg is estimated to be 3 8 4 2 for records from pure continental paths and 2 6 3 4 for records from paths crossing continental margins this result illustrates the need to consider raypath effects for the correct estimation of magnitudes of regional events including a nuclear explosion

21st century increase in glacier mass loss in the wrangell mountains alaska usa from airborne laser altimetry and satellite stereo imagery alaskan glaciers are among the largest regional contributors to sea level rise in the latter half of the 20th century earlier studies have documented extensive and accelerated ice wastage in most regions of alaska here we study five decades of mass loss on high elevation land terminating glaciers of the wrangell mountains 4900 km2 in central alaska based on airborne center line laser altimetry data from 2000 and 2007 a digital elevation model dem from aster and spot5 and us geological survey topographic maps from 1957 the regional mass balance estimates derived from center line laser altimetry profiles using two regional extrapolation techniques agree well with that from dem differencing repeat altimetry measurements reveal accelerated mass loss over the wrangell mountains with the regional mass balance rate evolving from 0 07 0 19 m w e a 1 during 1957 2000 to 0 24 0 16 m w e a 1 during 2000 07 nabesna the largest glacier in this region 1056 km2 lost mass four times faster during 2000 07 than during 1957 2000 although accelerated the mass change over this region is slower than in other glacierized regions of alaska particularly those with tidewater glaciers together our laser altimetry and satellite dem analyses demonstrate increased wastage of these glaciers during the last 50 years

volume change of mccall glacier arctic alaska usa 1956 2003 a long history of research documents that mccall glacier arctic alaska usa continues to lose mass at a rate that is likely increasing with time we present a photo comparison 1958 2003 that visually documents these volume changes along with survey measurements that quantify these losses measurements of longitudinal profiles initially acquired from airborne laser altimetry and repeated by ground based surveys indicate that the areally averaged rate of thinning increased between 1956 93 and 1993 2002 from 0 35 0 07 m a 1 to 0 47 0 03 m a 1 respectively total volume loss was 8 3 107 1 7 107 m3 and 2 7 107 0 2 107 m3 all in water equivalent for these two time periods these profiles also indicate that a 1 km stretch of the mid ablation area is behaving differently from this trend with a rate of thinning that is not changing with time lastly we present a comparison of several methods for calculating volume change and assess their relative errors

the propagation of a surge front on bering glacier alaska 2001 2011 bering glacier alaska usa has a 20 year surge cycle with its most recent surge reaching the terminus in 2011 to study this most recent activity a time series of ice velocity maps was produced by applying optical feature tracking methods to landsat 7 etm imagery spanning 2001 11 the velocity maps show a yearly increase in ice surface velocity associated with the down glacier movement of a surge front in 2008 09 the maximum ice surface velocity was 1 5 0 017 km a 1 in the mid ablation zone which decreased to 1 2 0 015 km a 1 in 2009 10 in the lower ablation zone and then increased to nearly 4 4 0 03 km a 1 in summer 2011 when the surge front reached the glacier terminus the surge front propagated down glacier as a kinematic wave at an average rate of 4 4 2 0 km a 1 between september 2002 and april 2009 then accelerated to 13 9 2 0 km a 1 as it entered the piedmont lobe between april 2009 and september 2010 the wave seems to have initiated near the confluence of bering glacier and bagley ice valley as early as 2001 and the surge was triggered in 2008 further down glacier in the mid ablation zone after the wave passed an ice reservoir area

spatial variations in present day deformation kenai peninsula alaska and their implications from four years of global positioning system gps measurements we find significant spatial variations in present day deformation between the eastern and western kenai peninsula alaska sites in the eastern kenai peninsula and prince william sound move to the nnw relative to north america in the direction of pacific north america relative plate motion velocities decrease in magnitude from nearly the full plate rate in southern prince william sound to about 30 mm yr at seward and to about 5 mm yr near anchorage in contrast sites in the western kenai peninsula move to the sw in a nearly trenchward direction with a velocity of about 20 mm yr the data are consistent with the shallow plate interface offshore and beneath the eastern kenai and prince william sound being completely locked or nearly so with elastic strain accumulation resulting in rapid motion in the direction of relative plate motion of sites in the overriding plate the velocities of sites in the western kenai along strike to the southwest are opposite in sign with those predicted from elastic strain accumulation these data are incompatible with a significant locked region in this segment of the plate boundary trenchward velocities are found also for some sites in the anchorage area we interpret the trenchward velocities as being caused by a continuing postseismic transient from the 1964 great alaska earthquake there may be significant along strike differences in the long term behavior of the plate interface between the western and eastern kenai based on roughly coincident boundaries in the coseismic slip distribution cumulative postseismic uplift present day plate coupling and stress field the present postseismic response appears to generate purely trenchward motion suggesting a creep process that is purely dip slip our observations suggest that postseismic processes after the largest earthquakes can influence patterns of deformation for decades after the event

estimating volume change of mountain glaciers using srtm and map based topographic data this paper describes a method for estimating the volume change of mountain glaciers using the shuttle radar topography mission srtm c band data 2000 and a digital elevation model dem generated from topographic maps this approach was developed with srtm data and topographic maps of 1 25 000 scale 1977 from the akshiirak glaciers tien shan central asia the dem for 1977 was generated using 10 m contour lines from 18 map sheets covering the akshiirak massif and surrounding area the nominal vertical accuracy of the maps is 3 3 m the standard deviation of the differences between the map derived dem and the srtm data on glacier free areas of less than 25deg is 6 3 m a single localized region in the western periphery of the study area with systematic error in the srtm data from 20 to 12 m on a 30 km spatial scale was found and excluded from the error analysis assuming a 10 m map error on the upper snow covered glacier areas the estimated root mean square error of the glacier surface change is 8 2 m from 1977 to 1999 the average glacier surface thinning is 15 1 m and the estimated volume loss is 6 15 km3 the rate of the akshiirak glacier volume loss has increased by 2 7 times compared with historical data from 1943 to 1977 the srtm data show an opportunity for quantifying climatic and dynamic surface elevation changes in mountain glaciers ice cloud and land elevation satellite icesat laser altimetry and srtm data could also be used for the estimation of short term surface changes of mountain glaciers

regional observations of the second north korean nuclear test on 2009 may 25 summary the suspicious seismic event that occurred in the northern korean peninsula on 2009 may 25 was declared to be the second underground nuclear test nk2nd by north korea we investigated the characteristics of nk2nd using seismic signals recorded at regional distance stations in south korea and china the pn lg ratios of nk2nd definitely discriminate this event from two nearby natural earthquakes at frequencies above 4 hz full moment tensor inversion of full waveform data shows that nk2nd had a very large isotropic component pure isotropic moment tensor inversion also resulted in good recovery of observed waveforms with clear indication that nk2nd was explosive in origin the moment magnitude mw from the full moment tensor inversion was estimated to be 4 5 and network averaged values of 4 6 and 3 6 were calculated for rms mb lg and ms vmax respectively although mb ms signature has been considered one of the most reliable discriminants for separating explosions and earthquakes this signature showed poor discrimination in the case of nk2nd the pn lg ratios and moment tensor inversion give more reliable evidence than does the mb ms for classifying the suspicious event in the northern korean peninsula as a possible explosion the characteristics of nk2nd are also quite similar to those of the first north korean nuclear test on 2006 october 9

evolution of glacier dammed lakes through space and time brady glacier alaska usa abstract glacier dammed lakes and their associated jokulhlaups cause severe flooding in downstream areas and substantially influence glacier dynamics brady glacier in southeast alaska is well suited for a study of these phenomena because it presently dams 10 large 1 km 2 lakes our objectives are to demonstrate how brady glacier and its lakes have co evolved in the past and to apply this knowledge to predict how the glacier and its lakes will likely evolve in the future to accomplish these objectives we georeferenced a variety of maps airphotos and optical satellite imagery to characterize the evolution of the glacier and lakes we also collected bathymetry data and created bathymetric maps of select lakes despite small advances and retreats the main terminus of brady glacier has changed little since 1880 however it downwasted at rates of 2 3 m y between 1948 and 2000 more than the regional average the most dramatic retreat 2 km and downwasting 120 m have occurred adjacent to glacier dammed lakes and are primarily the result of calving brady glacier is a former tidewater glacier with continued downwasting brady glacier may return to a tidewater regime and enter into a phase of catastrophic retreat the situation at brady glacier is not unique and the lessons learned here can be applied elsewhere to identify future glacier dammed lakes jokulhlaups and glacier instability

holocene glacier fluctuations in alaska abstract this review summarizes forefield and lacustrine records of glacier fluctuations in alaska during the holocene following retreat from latest pleistocene advances valley glaciers with land based termini were in retracted positions during the early to middle holocene neoglaciation began in some areas by 4 0 ka and major advances were underway by 3 0 ka with perhaps two distinct early neoglacial expansions centered respectively on 3 3 2 9 and 2 2 2 0 ka tree ring cross dates of glacially killed trees at two termini in southern alaska show a major advance in the ad 550s 720s the subsequent little ice age lia expansion was underway in the ad 1180s 1320s and culminated with two advance phases respectively in the 1540s 1710s and in the 1810s 1880s the lia advance was the largest holocene expansion in southern alaska although older late holocene moraines are preserved on many forefields in northern and interior alaska tidewater glaciers around the rim of the gulf of alaska have made major advances throughout the holocene expansions were often asynchronous with neighboring termini and spanned both warm and cool intervals suggesting that non climatic factors were important in forcing these advances however climatic warming appears to have initiated most rapid iceberg calving retreats large glaciers terminating on the forelands around the gulf of alaska may have had tidewater termini early in the holocene but have progressively become isolated from the adjacent ocean by the accumulation and subaerial exposure of their own sediments

alaska tidewater glacier terminus positions 1948 2012 a significant portion of the world s glacier ice drains through tidewater outlets though much remains unknown about the response to recent climate change of tidewater glaciers we present a 64 year record of length change for 50 alaska tidewater glaciers we use u s geological survey topographic maps to provide a base length for glaciers before 1970 using all available cloud free landsat images we manually digitize calving front outlines for each glacier between 1972 and 2012 resulting in a total of more than 10 000 outlines tidewater glacier lengths vary seasonally focusing on the 36 glaciers terminating in tidewater throughout the study period we find a mean standard deviation seasonal variation of 60 85 m a 1 we use these oscillations to determine the significance of interannual changes in glacier length all 36 glaciers underwent at least one period 1 year of significant advance or retreat 28 glaciers underwent at least one period of both significant advance and retreat over the entire period 1948 2012 24 of these glaciers retreated a total uncertainty of 107 95 0 29 km 11 advanced a total of 7 71 0 20 and one chenega glacier did not change significantly retreats and advances are highly variable in time several glaciers underwent rapid short term retreats of a few years duration these retreats occurred after large changes in summer sea surface temperature anomalies further study is needed to determine what triggered these retreats no coherent regional behavior signal is apparent in the length record although two subregions show a coherence similar to recent observations in greenland

svalbard glacier elevation changes and contribution to sea level rise 1 we compare satellite altimetry from the ice cloud and land elevation satellite icesat 2003 2007 to older topographic maps and digital elevation models 1965 1990 to calculate long term elevation changes of glaciers on the svalbard archipelago results indicate significant thinning at most glacier fronts with either slight thinning or thickening in the accumulation areas except for glaciers that surged which show thickening in the ablation area and thinning in the accumulation areas the most negative geodetic balances occur in the south and on glaciers that have surged while the least negative balances occur in the northeast and on glaciers in the quiescent phase of a surge cycle geodetic balances are related to latitude and to the dynamical behavior of the glacier the average volume change rate over the past 40 years for svalbard excluding austfonna and kvitoya is estimated to be 9 71 0 55 km3 yr 1 or 0 36 0 02 m yr 1 w equivalent for an annual contribution to global sea level rise of 0 026 mm yr 1 sea level equivalent

regional phase excitation and propagation in the lop nor region of central asia and implications for p lg discriminants ital pn and ital lg spectra for lop nor explosions and nearby earthquakes were analyzed for source and propagation effects using a modified inversion method of ital xie 1993 spectral analyses were performed on waveform data from incorporated research institution for seismology chinese digital seismic network kazakhstan and krgyzstan networks ital pn amplitude variations of a factor of 20 are observed across the small aperture lt 200 km kyrgyzstan network and are probably related to three dimensional moho structure close to the network comparisons of ital pn amplitudes and spectral ratios provide evidence for nonisotropic radiation pattern effects in the case of earthquakes and overshoot in explosion time histories complex source effects are born out in our inversion results 1 logarithm of seismic moment m sub 0 from ital pn and ital lg spectra scale linearly with body wave magnitude m sub b for explosions 5 0 le m sub b le 6 0 and for earthquakes 4 0 le m sub b le 5 5 2 pn m sub 0 estimates are similar to lg m sub 0 for earthquakes but are higher than lg m sub 0 for explosions 3 corner frequency f sub c scale as quarter root of m sub 0 for explosions and cube root for earthquakes 4 at the same m sub 0 level pn f sub c aremore 4 endash 5 times higher than lg f sub c for earthquakes and explosions and 5 ital pn source spectra are characterized by significant overshoot for explosions our results suggest that the cause of maximum separation between earthquake and explosion populations on plots of p lg spectral ratios which typically occurs for frequencies above explosion pn f sub c between 2 and 4 hz for explosions in this study may be related to overshoot in the reduced velocity potential copyright 1999 american geophysical union less

validation of high resolution grace mascon estimates of glacier mass changes in the st elias mountains alaska usa using aircraft laser altimetry we acquired center line surface elevations from glaciers in the st elias mountains of alaska northwestern canada using aircraft laser altimetry during 2000 05 and compared these with repeat measurements acquired in 2007 the resulting elevation changes were used to estimate the mass balance of 32 900 km 2 of glaciers in the st elias mountains during september 2003 to august 2007 yielding a value of 21 2 3 8gta 1 equivalent to an area averaged mass balance of 0 64 0 12 m a 1 water equivalent w e high resolution 2 arc degrees spatial and 10 day temporal gravity recovery and climate experiment grace mass balance estimates during this time period were scaled to glaciers of the st elias mountains yielding a value of 20 6 3 0 gt a 1 or an area averaged mass balance of 0 63 0 09 m a 1 w e the difference in balance estimates altimetry minus grace was 0 6 4 8 gta 1 well within the estimated errors differences likely resulted from uncertainties in subgrid sampling of the grace mass concentration mascon solutions and from errors in assigning an appropriate near surface density in the altimetry estimates the good correspondence between grace and aircraft altimetry data suggests that high resolution grace mascon solutions can be used to accurately assess mass balance trends of mountain glacier regions that are undergoing large changes

radiaxial fibrous calcite as early burial open system cement isotopic evidence from permian of china abstract the nanpanjiang basin of south china occupies about 100 000 km2 in southern guizhou and eastern yunnan provinces and northwestern guangxi autonomous region the basin contains a thick paleozoic carbonate sequence overlain by about 3 000 m of triassic basinal deposits permian carbonate rocks comprise a large portion of the paleozoic strata and form several platforms separated by basins containing dark thin bedded limestones siliceous shales and cherts the platform margins are rimmed by sponge or algal reefs radiaxial fibrous calcite rfc is the most abundant cement in very coarse sponge or algal debris of upper permian reef and fore reef sediments exposed along the western margin of the nanpanjiang basin small volumes of syndepositional cements interpreted to have been fibrous magnesian calcites and botryoidal aragonite predate rfc coarse blocky burial calcite postdates rfc evidence that rfc was precipitated during sediment deposition was not found rfc occurs as isopach layers up to 15 mm thick and exhibits white gray and black bands about 1 mm wide the presence of microdolomite inclusions in these cements indicates that they were originally magnesian calcites dgr18o of rfc cements are more positive than any of the earlier or later components of the reef and fore eef facies analyses of successive bands reveals the most positive dgr18o near the center of the isopach layers dgr13c of successive bands reveals generally more negative values toward the centers of layers rfc layers are interpreted to have precipitated during early burial of the platform margin while reef and fore reef sediments were in communication with seawater cement layers recorded isotopic characteristics of seawater as platform edge sediments subsided through the water column at the basin margin dgr18o of successive bands records cooler water at depth in the basin followed by geothermal warming dgr13c records increased incorporation of light carbon as the platform subsided through the oxygen minimum zone followed by a return to normal values at depth these data and interpretations suggest rfc layers precipitated very slowly during time spans commensurate with those of subsiding platforms millions of years isotopic characteristics of rfc may not reflect shallow seawater rather they may reflect burial environments where dgr18o is affected by cooler water and dgr13c is affected by biologic activity end of article last page 261

elevation volume and terminus changes of nine glaciers in north america nine glaciers in alaska and washington u s a originally mapped as part of the international geophysical year igy in 1957 58 were re mapped between 1993 and 1996 eight using airborne surface elevation profiling and the ninth using ground based kinematic global positioning system methods elevation volume and terminus changes were determined for the approximately 38 year period between the igy mapping and the profiling all nine glaciers showed substantial thinning at lower elevations seven of the nine thickened at higher elevations none of the glaciers had a significant net volume increase two had close to zero change and the others had a decrease for the eight glaciers for which we could obtain quantitative information the mean thickness change was 10 m with a large scatter 8 m standard deviation the volume and terminus changes had no clear geographic pattern and no simple relationship between volume change and terminus advance or retreat was identified the largest error in the estimated volume changes is due to map errors

laser profiling over antarctic ice streams methods and accuracy we assess the accuracy and precision of the u s national science foundation s support office for aerogeophysical research soar laser profiling system for mapping topography and detecting surface elevation changes of west antarctic ice streams the procedures used to process calibrate and validate the laser navigation and global positioning system gps data are presented the primary objective is to produce surface elevations with the best possible resolution repeat surveys of a grid of lines over whillans ice stream and ice streams c and e were conducted in the 1997 98 and 1999 2000 seasons the procedure has been calibrated using special test flights conducted over areas that have been surveyed with precise geodetic gps equipment mounted on snowmobiles after calibration agreement between the two surfaces is 10 cm rms the accuracy and precision of the procedure have been evaluated at points where laser flight lines cross over one another the accuracy of the system is found to range from 0 09 to 0 22 m

monitoring of strain release in central and northern california using broadband data systematic cataloguing of seismic moment depth and mechanism of regional earthquakes down to magnitude m 4 can now be achieved in close to real time using data from sparse networks of digital broadband stations the procedure we have developed relies on 3 independent methods for the determination of moment tensor providing confidence limits on the results we show the results of application to the seismicity in central and northern california for a one year period starting in march 1992 and illustrate how patterns of stress and strain release can now be monitored systematically and reliably in a timely fashion

updated estimates of glacier volume changes in the western chugach mountains alaska and a comparison of regional extrapolation methods and 2001 2004 average net balance rates ranged between 3 1 to 0 16 m yr 1 for the tidewater and 1 5 to 0 02 m yr 1 for the nontidewater glaciers we tested several methods for extrapolating these measurements to all the glaciers of the western chugach mountains using a process similar to cross validation predictions of individual glacier changes appear to be difficult probably because of the effects of glacier dynamics which on long multidecadal timescales complicates the response of glaciers to climate in contrast estimates of regional contributions to rising sea level were similar for different methods mainly because the large glaciers whose changes dominated the regional total were among those measured for instance the above sea level net balance rate of columbia glacier 3 1 0 08 km 3 yr 1 water equivalent weq or an equivalent rise in sea level sle of 0 0090 0 0002 mm yr 1 was nearly half of the total regional net balance rate of the western chugach mountain glaciers 7 4 1 1 km 3 yr 1 weq or 0 020 0 003 mm yr 1 sle between 1950 1957 and 2001 2004 columbia glacier is a rapidly retreating tidewater glacier that has lost mass through processes largely independent of climate tidewater glaciers should therefore be treated separately when performing regional extrapolations

an optimized method to calculate the geodetic mass balance of mountain glaciers understanding the effects of climate on glaciers requires precise estimates of ice volume change over several decades this is achieved by the geodetic mass balance computed by two means 1 the digital elevation model dem comparison seqdem allows measurements over the entire glacier however the low contrast over glacierized areas is an issue for the dem generation through the photogrammetric techniques and 2 the profiling method sepm is a faster alternative but fails to capture the spatial variability of elevation changes we present a new framework ssd that relies upon the spatial variability of the elevation change to densify a sampling network to optimize the surface elevation change quantification our method was tested in two small glaciers over different periods we conclude that the sepm overestimates the elevation change by 20 with a mean difference of 1 00 m root mean square error rmse 3 00 m compared with results from the seqdem method a variogram analysis of the elevation changes showed a mean difference of

yield estimates of nevada test site explosions obtained from seismic lg waves a methodology is presented for determining the yield of underground nuclear explosions from lg wave amplitudes the methodology is applied to nevada test site nts explosions for which the data from short period vertical component analog seismographs at three stations are used to develop calibration curves for unsaturated material and water saturated rock source conditions the latter curves are found to provide reasonably accurate estimates of the yields of explosions in other areas of the united states and in the french sahara suggesting that they may be applicable to all continental areas if so they also can provide an estimate of the bias of mb p magnitudes between different continental sites for example the lg data from nts explosions indicate a 0 31 0 02 magnitude unit bias between nts and eastern north america similar to the approximately 0 33 unit bias found between western and eastern north america previously by use of earthquake data

glacier specific elevation changes in parts of western alaska the meltwater from glaciers in alaska contributes strongly to global sea level rise but accurate determination is challenging as only two comparatively small glaciers have long term measurements of annual mass balance gulkana and wolverine simple upscaling of their values to the entire region is error prone as their representativeness is unknown and might be biased alternatively differencing digital elevation models dems from two epochs provides overall volume changes for a longer period of time that can be converted to mass changes using appropriate density assumptions here we combine outlines from two glacier inventories to determine glacier specific elevation changes over a 50 year period for 3180 glaciers in western alaska using dem differencing this allows us to determine the representativeness of the land terminating gulkana and wolverine glaciers for the entire region and to exclude calving glaciers marine and lacustrine from the sample mean changes for all land terminating lake terminating and tidewater glaciers are 0 23 0 44 0 63 0 40 and 0 64 0 66 m a 1 respectively and 0 7 and 0 6 m a 1 for the two mass balance or benchmark glaciers thus fortuitously their changes better represent calving glaciers and the overall mean 0 63 1 14 m a 1 than the change of land terminating glaciers i e they are not representative for their own type different methods of considering potential dem artefacts provide variable mean changes but the same general result