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

active and passive microwave signatures of antarctic firn by means of field measurements and satellite data the angular dependence and polarization behaviour of back scattering and emission of polar firn at 5 2 ghz and 10 3 ghz were measured during an oversnow traverse in dronning maud land antarctica the signatures emphasize the importance of snow stratification in the interpretation of microwave remote sensing measurements highest backscattering coefficients and little angular variations were observed for refrozen firn near the coast in permanently dry snow areas with high accumulation rates and homogeneous snow morphology showed low backscattering coefficients and high emissivities pronounced layering and related density variations in low accumulation zones resulted in increased polarization differences of brightness temperatures and increased like polarized backscattering coefficients this behaviour is confirmed by the analysis of c band scatterometer measurements of the active microwave instrument aboard the european space agency s ers 1

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

teleconnections in the southern hemisphere abstract teleconnections are calculated from monthly mean anomalies of sea level pressure and 500 mb geopotential height for the southern hemisphere 10 90 s for five month winter and summer seasons the monthly means were calculated from australian analyses for the period from june 1972 to november 1980 zonally averaged anomalies at both sea level and 500 mb display an out of phase relation between low and high latitudes and in midlatitudes are negatively correlated with anomalies in the subtropics and polar regions in winter a striking zonal wavenumber 3 pattern is found over the southern ocean anomalies in 500 mb geopotential heights at 50 s 95 e 58 s 150 w and 38 s 15 w exhibit strong positive correlations while showing weaker negative correlations with heights over antarctica and in low latitudes a similar pattern appears in sea level pressure in summer anomalies in 500 mb geopotential height over the three subtropical continents appear to occur out of phase with anomalies over the su

new constraints on the age geochemistry and environmental impact of high arctic large igneous province magmatism tracing the extension of the alpha ridge onto ellesmere island canada

sea ice atmosphere signal of the southern oscillation in the weddell sea antarctica abstract composite analysis of weekly ship and shore observations of the weddell sea pack ice for extreme events of the southern oscillation so occurring in the 1929 62 period reveals strong variations in ice water concentrations in the early and late summer melt season substantially reduced ice concentrations more open water occur in december and early january of warm el nino events yr0 compared with the summer before yr 1 and appear connected with the change to a stronger cyclonic atmospheric circulation over higher latitudes of the south atlantic similarly consistent meteorology sea ice associations appear to characterize the mid to late summer of warm so events yr0 compared with yr0 of cold events there is some evidence that the regionally dependent pressure and wind reversals and possibly the associated sea ice concentration changes in the weddell sector have become more marked during so events occurring since about the early 1950s some corroboration of changes in the sea ice

seismicity at the border between central and southern apennines italy re evaluation of the early 1984 instrumental earthquake abstract we re evaluate the 1984 abruzzo lazio earthquake on the basis of original seismological data discussed in light of previous interpretations from other authors this sequence characterized by two distinct mainshocks ms 5 8 and ms 5 2 neis having low spatial and temporal separation developed at the border between central and southern apennines the sequence originated in a narrow area adjacent to the main nw se structures belonging to the apenninic chain crossed by fault segments with different orientation the spatio temporal evolution of the seismicity the focal mechanisms of some aftershocks never obtained before and waveform analysis suggest that the sequence developed in several stages the beginning of the two main stages was marked by two events ms 5 8 and ms 5 2 and the entire sequence was strongly controlled by the structural heterogeneity in the medium involved in the stress release process the ruptures nucleated on a ene wsw striking fault segment belonging to the nne striking ortona roccamonfina tectonic line and propagated towards ene the presence of the nw se structures belonging to the apennine chain and their geometry acted as a barrier to the spread of the aftershocks northeastward as a consequence a local concentration of static stress in the area enclosed between the northern edge of the rupture segment of the first mainshock and the nw striking structures triggered the ms 5 2 event on a w e pre existing fault segment in turn the static stress changes due to the second mainshock activated adjacent ne sw and nw se fault segments the nw striking structures belonging to the apennines acted as a structural barrier halting the propagation of the ruptures nucleating on a fault segment that belongs to the nne striking ortona roccamonfina tectonic line

extent and duration of antarctic surface melting the extent and duration of surface melting on the antarctic ice shelves and margins of the antarctic ice sheet are derived from satellite passive microwave data for 1978 87 the occurrence of surface melting in daily maps of t b is indicated by a marked increase in microwave brightness temperature t b which is caused by moisture in the near surface firn t b increases of more than 30 deg above the annual mean t b are chosen to indicate melting most antarctic surface melting occurs during december and january the observed melting is correlated with regional air temperatures but some melt patterns also appear to be related to katabatic wind effects the correlations suggest that the surface melting in antarctica increases about 3 5 10 6 d km 2 per degree of summer temperature increase the surface melt index duration times area of melting calculated for antarctica is 24 10 6 d km 2 averaged over nine summers the observed inter annual and regional variability is large surface melting was most extensive during the 1982 83 summer 36 10 6 d km 2 and least extensive during the 1985 86 summer 15 10 6 d km 2 the data indicate a decline in surface melting over the 9 years but meaningful inferences regarding trends in surface melting are precluded by the large inter annual variability

measuring snow and glacier ice properties from satellite satellite remote sensing is a convenient tool for studying snow and glacier ice allowing us to conduct research over large and otherwise inaccessible areas this paper reviews various methods for measuring snow and glacier ice properties with satellite remote sensing these methods have been improving with the use of new satellite sensors like the synthetic aperture radar sar during the last decade leading to the development of new and powerful methods such as sar interferometry for glacier velocity digital elevation model generation of ice sheets or snow cover mapping some methods still try to overcome the limitations of present sensors but future satellites will have much increased capability for example the ability to measure the whole optical spectrum or sar sensors with multiple polarization or frequencies among the methods presented are the satellite derived determination of surface albedo snow extent snow volume snow grain size surface temperature glacier facies glacier velocities glacier extent and ice sheet topography in this review emphasis is put on the principles and theory of each satellite remote sensing method an extensive list of references with an emphasis on studies from the 1990s allows the reader to delve into specific topics

modeling the enso modulation of antarctic climate in the late 1990s with the polar mm5 abstract the polar fifth generation pennsylvania state university ncar mesoscale model mm5 is employed to examine the el nino southern oscillation enso modulation of antarctic climate for july 1996 june 1999 which is shown to be stronger than for the mean modulation from 1979 to 1999 and appears to be largely due to an eastward shift and enhancement of convection in the tropical pacific ocean this study provides a more comprehensive assessment than can be achieved with observational datasets by using a regional atmospheric model adapted for high latitude applications polar mm5 the most pronounced enso response is observed over the ross ice shelf marie byrd land and over the weddell sea ronne filchner ice shelf in addition to having the largest climate variability associated with enso these two regions exhibit anomalies of opposite sign throughout the study period which supports and extends similar findings by other investigators the dipole structure is observed in surface temperature meridio

a link between microwave extinction length firn thermal diffusivity and accumulation rate in west antarctica 1 the relationship between time series of physical surface temperature and microwave brightness temperature of polar firn depends both on the physical properties of the firn and the surface temperature history in perennially dry firn this relationship is well characterized by a timescale referred to as the extinction diffusion time which is the ratio of the microwave extinction length squared to the firn thermal diffusivity the extinction diffusion time is calculated over antarctica from 1982 to 1999 by comparing thermal infrared observations of physical surface temperature from the advanced very high resolution radiometer avhrr with passive microwave brightness temperatures measured by the scanning multichannel microwave radiometer smmr and special senor microwave imager ssm i independent estimates of accumulation rate are derived both from ice cores and from spatially extensive ground and airborne radar echo sounding lines the extinction diffusion time is found to vary linearly with accumulation rate from approximately 10 to 50 cm yr ice equivalent over a large area in west antarctica although this simple relationship does not appear to hold at very low or very high accumulation rates these results suggest that the extinction diffusion time holds promise as a viable proxy for accumulation rate variability on polar ice sheets

antarctic pressure and temperature anomalies surrounding the minimum in the southern oscillation index the purpose of our research is to analyze surface pressure and temperature patterns in antarctica for relationships with the el nino southern oscillation enso using monthly anomalies of surface pressure and temperature in antarctica lag correlations are made to the southern oscillation index soi and annual composites are created for years where enso is in a warm phase comparisons are made to annual composites for nonwarm phase years and to six individual enso warm phases occurring between 1957 and 1984 we found a sharp change in the sign of the pressure and temperature anomalies between the year before and the year after the minimum in the soi we hypothesize that the temperature and pressure anomaly patterns are related through a thickness argument to the 500 mbar southern hemispheric flow and the australian branch of the southern oscillation

pre existing cross structures and active fault segmentation in the northern central apennines italy abstract the multideformed axial zone of the apennines provides a great opportunity to explore the influence of pre existing cross structures inherited from pre quaternary tectonic phases on the segmentation of quaternary active seismogenic extensional faults detailed geological and structural data and their comparison with seismological data show that although the attitudes strike and dip of oblique pre existing faults are certainly an important factor in determining a segment boundary the size of the inherited oblique structures seems to be more crucial pre existing cross structures with lengths ranging from several kilometers to a few tens of kilometers show a twofold behavior they can act as segment barriers during the rupture of a single fault segment or they can be reactivated as transfer zones inducing the activation of two adjacent segments that belong to the same fault system regional basement crustal oblique pre existing cross structures with lengths ranging from several tens of kilometers to hundreds of kilometers commonly nne striking may act as persistent structural barriers that halt both fault segment and fault system propagation thus determining their terminations and maximum sizes in the northern central apennines the nne striking ancona anzio valnerina and ortona roccamonfina tectonic lineaments although having been repeatedly reactivated since the mesozoic represent the most important examples of these structures moreover probably due to their misorientation with respect to the present extensional stress field regional nne striking pre existing structures appear to be less likely to produce strong magnitude events no surface evidence for quaternary faulting has been found thus far and historical and instrumental seismicity shows only m m 7 event on the other hand is more likely to occur along the n nw s se trending normal fault systems lastly we propose a model that can explain the different sizes of fault segments and fault systems on the basis of their location with respect to the persistent structural barriers and their spacing in this view our results may contribute to a more reasonable assessment of the nature and size of future surface ruptures in the northern central apennines which are of critical importance to estimating seismic hazard

the 2001 seismic activity near isernia italy implications for the seismotectonics of the central southern apennines abstract we analyze the seismic activity that occurred in 2001 near the city of isernia southern apennines with the aim to add information on the seismotectonics of the transition zone between central and southern apennines seismic activity lasted for 9 months showing the typical behaviour of swarms a large number of events of low magnitude without a distinct main shock and clustered in space and time the maximum magnitude md of the events was 3 3 comparable with the magnitude md of the background seismicity of the area hypocentral distribution of the events maximum depth 15 km suggests that seismic activity took place along a best fitting plane striking n33 e and steeply dipping eastward the results of the strain analysis performed on selected well constrained focal mechanisms indicate that most of the ruptures associated to the 2001 seismic sequence occurred along n s to ne sw striking faults characterized by strike slip to normal movements this kinematics is consistent with a prevailing nw se extension this direction of extension already observed in the 1997 98 seismic sequence which occurred at about 35 km toward se from the 2001 epicentral area is not consistent with that one assumed at regional scale on the basis of the analysis of focal mechanisms of stronger earthquakes the results of the 1997 98 and 2001 seismic sequences discussed in light of the available geological and geophysical data evidence that i in this portion of the apennine chain low magnitude seismic sequences cluster along ne sw striking faults that move in response to a nw se extension and ii the ne sw striking faults along which the 1997 98 and the 2001 seismic sequences occurred mark the southeastern and northwestern tips of the nw se fault segment responsible for the 1805 earthquake

characteristic frequencies for earthquake families and their tectonic implications evidence from earthquake swarms in the kanto district japan through the analyses of waveform and spectrum for two swarm sequences in the kanto district including the results from 15 earthquake swarsm obtained previously the mechanism of the faulting process in earthquake swarms is clarified in more detail earthquakes occurring in short time intervals consist mainly of events with similar waveforms ands p times these are called earthquake families and many families are observed during a swarm sequence 70 80 percent for example 15 families were observed in the 1983 izu peninsula earthquake swarm the source spectra of earthquake families share the same corner frequency even though their low frequency levels may differ by a factor as great as 1000 and the value of the corner frequency depends on the size of the largest event in the family local variations of corner frequencies within a factor of 25 are found among the earthquake swarms in the kanto district these observations suggest the existence of a characteristic fault length depending on the swarm area and its length may be responsible for the size of the largest event in the family the characteristic fault length is about 100 m for ashio about 400 m for the izu peninsula and about 2 5 km for areas off the chiba prefecture and the magnitudes of the largest events expected from these fault lengths are about 2 5 4 and 6 respectively

ice core evidence of abrupt climate changes ice core records show that climate changes in the past have been large rapid and synchronous over broad areas extending into low latitudes with less variability over historical times these ice core records come from high mountain glaciers and the polar regions including small ice caps and the large ice sheets of greenland and antarctica

source process of the great 1971 solomon islands doublet abstract large underthrusting earthquakes in the solomon islands tend to occur as multiplets separated by a few hours to several days in time and 30 100 km in space the largest sequence a doublet on july 14 1971 m w 8 0 and july 26 1971 m w 8 1 is particularly unusual in that it occured at the junction of two trenches with the july 14 event in the solomon islands trench preceding the july 26 rupture in the new britain trench the location and large moment release of this doublet as well as an incompatibility of published body wave and surface wave focal mechanisms for the july 14 event motivated a detailed study of the source process of the 1971 sequence to satisfy both the surface wave and body wave data we explored the possibility of a change in the faulting geometry during rupture for the july 14 event a fault model that changes orientation from a northwest southeast striking shallow dipping plane similar to the mechanisms of neighboring underthrusting events in the solomon islands trench to a more north south striking plane 70 s after rupture initiation is consistent with the observed rayleigh and love wave amplitude patterns this change in mechanism is suggested by systematic variations in the mechanisms of smaller earthquakes near the cusp in the solomon islands plate a simultaneous inversion of wwssn p wave seismograms for the time location seismic moment and focal mechanism of individual subevents gives results in agreement with the surface wave model although the precise change in mechanism is not well resolved the spatiotemporal distribution of subevents reveals two major pulses of moment release the first occurred on the initial fault near the epicenter at the origin time of the earthquake the second occurred on the north south striking fault 50 70 km northwest of the epicenter 70 s after the origin time the change in mechanism appears to reflect contortion of the slab near the trench junction inversion of wwssn p wave seismograms for the rupture history of the july 26 event reveals a westerly propagating rupture extending 60 km along the new britain trench for both of the 1971 earthquakes regions of high moment release are located in the vicinity of the solomon islands new britain trench junction contortion of the subducting lithosphere as it bends around the arc arc junction may have enhanced the degree of mechanical coupling between the subducting and overriding plates concentrating stress in this region and in turn promoting efficient triggering across the trench junction

earthquake doublet in kagoshima japan rupture of asperities in a stress shadow two shallow moderate m 6 earthquakes occurred in the northwestern part of kagoshima prefecture kyushu southern japan i discuss the effect of the stress change due to the first earthquake 26 march 1997 on the occurrence of the second earthquake 13 may 1997 the rupture characteristics of the two earthquakes are inferred in two steps to form the basis of the discussion i first invert strong ground motion data to construct kinematic source models and then estimate the distribution of static stress drop from the derived dislocation distributions the rupture process of the march event is simple and well described with rupture of a single asperity patch of high stress drop on the other hand multiple asperities on conjugate faults ruptured during the may event the maximum value of static stress drop for both earthquakes is about 4 mpa and seems lower than those of other japanese intraplate earthquakes the hypocenter and the largest asperity of the may earthquake are located in a stress shadow caused by the march earthquake thus the rupture history of the may earthquake is difficult to explain with a static stress change model other mechanisms such as fluid migration and dynamic stresses were also investigated but failed to explain the triggering i propose the coupled effect of static change in shear stress and normal stress under the rate and state dependent friction law as a possible mechanism

normal faults and thrusts reactivated by deep fluids the 6 april 2009 mw 6 3 l aquila earthquake central italy 1 on 6 april 2009 a mw 6 3 earthquake occurred in the central apennines italy damaging the city of l aquila and the surrounding country we relocate the october 2008 to 6 april 2009 foreshocks and about 2000 aftershocks occurred between 6 and 30 april 2009 by applying a double difference technique and determine the stress field from focal mechanisms the events concentrate in the upper 15 km of the crust three main nw se to nnw sse striking 30 45 and 80 90 dipping faults were activated during the seismic sequence among these a normal fault and a thrust were reactivated with dip slip movements in response to ne sw extension the structural maturity of the seismogenic fault system is lower than that displayed by other systems in southern apennines because of the lower strain rate of the central sector of the chain with respect to the southern one vp vs increases progressively from october 2008 to the 6 april 2009 main shock occurrence along a nw se strike because of an increment in pore fluid pressure along the fault planes pore pressure diffusion controls the space time evolution of aftershocks a hydraulic diffusivity of 80 m2 s 1 and a seismogenic permeability of about 10 12 m2 suggest the involvement of gas rich co2 fluids within a highly fractured medium suprahydrostatic high fluid pressure about 200 mpa at 10 km of depth within overpressurized traps bounded by preexisting structural and or lithological discontinuities at the lower upper crust boundary are required to activate the april 2009 sequence traps are the storage zone of co2 rich fluids uprising from the underlying about 20 km deep metasomatized mantle wedge these traps easily occur in extensional regimes like in the axial sector of apennines but are difficult to form in strike slip regimes where subvertical faults may cross the entire crust in the apennines fluids may activate faults responsible for earthquakes up to mw 5 6 deep fluids more than tectonic stress may control the seismotectogenesis of accretionary wedges

unmasking the 1349 earthquake source southern italy paleoseismological and archaeoseismological indications from the aquae iuliae fault abstract the 9th september 1349 earthquake was one of the most catastrophic events experienced along the apennines at least three main shocks struck a vast area of the molise latium abruzzi regions and damage was even sustained by the distant monumental buildings of rome the southern most shock mw 6 7 occurred at the border between southern latium and western molise razing to the ground the towns of isernia venafro and cassino amongst others and devastating montecassino abbey as with other medieval catastrophic sequences e g in december 1456 mw 6 5 7 0 this earthquake has not yet been associated to any seismogenic source thus it still represents a thorn in the flesh of earthquake geologists we have here carried out a reappraisal of the effects of this earthquake and through an interpretation of aerial photographs and a field survey we have carried out paleoseismological analyses across a poorly known n130 normal fault that crosses the molise campania border this structure showed repeated surface ruptures during the late holocene the last one of which fits excellently with the 1349 event both in terms of the dating and the rupture dimension on the other hand archaeoseismic analyses have also indicated the faulting of an augustean aqueduct the amount of apparent offset of the aqueduct across the fault traces shows that there were other surface faulting event s during the roman high middle age period therefore in trying to ascertain whether these events were associated with known potentially of 346 ad or 848 ad or unknown earthquakes in the area it became possible that this 20 km long fault here named the aquae iuliae fault is characterized by high slip rates and a short recurrence time this is in agreement with both the similar behaviour of the neighbouring northern matese fault system and with recent gps analyses showing unexpectedly high extension rates in this area