viscous flow features on the surface of mars observations from high resolution mars orbiter camera moc images 10 5 10 7 years of the material our shear stress estimates of 10 1 5 10 2 5 mpa yield strain rates on the order of 10 11 10 16 s 1 which are within the superplastic flow regime of ice mean annual surface temperatures age constraints and strain estimates show that it is possible for a meters thick ice dust mixture to undergo viscous deformation under past or present surface conditions for ice grain sizes 10 mm the meters thick layer in which the viscous flow features formed is morphologically similar to a degraded meters thick ice dust surface deposit dissected mantle terrain locations of the viscous flow features dissected mantle terrain and recent gullies are concentrated in the midlatitude regions and all three show identical distributions as a function of latitude with the maximum frequency of occurrence at 40 n and s the strong association between these small scale flow features and the dissected mantle terrain large scale viscous flow features and recent gullies imply that deposition deformation and removal of ice rich materials has played an important role in the modification of the surface in the midlatitudes of mars during the amazonian and possibly longer index terms 5470 planetology solid surface planets surface materials and properties 5416 planetology solid surface planets glaciation 1863 hydrology snow and ice 1827 1823 hydrology frozen ground 8168 tectonophysics stresses general keywords viscous flow viscous creep dissected mantle terrain ice rich deposits mars climate recent gullies

three dimensional spatial distribution of scatterers in galeras volcano colombia 1 a three dimensional spatial distribution of relative scattering coefficients is estimated for the galeras volcano colombia by an inversion of the coda wave envelopes from 1564 high quality seismic recordings at 31 stations of the galeras seismograph network the inversion reveals a highly non uniform distribution of relative scattering coefficients in the region for the two analyzed frequency bands 4 8 and 8 12 hz strong scatterers show frequency dependence which is interpreted in terms of the scale of the heterogeneities producing scattering two zones of strong scattering are detected the shallower one is located at a depth from 4 km to 8 km under the summit whereas the deeper one is imaged at a depth of 37 km from the earth s surface both zones may be associated with the magmatic plumbing system beneath galeras volcano the second strong scattering zone may be related to a deeper magma reservoir that feeds the system

self similar rupture implied by scaling properties of volcanic earthquakes occurring during the 2004 2008 eruption of mount st helens washington we analyze a group of 6073 low frequency earthquakes recorded during a week long temporary deployment of broadband seismometers at distances of less than 3 km from the crater at mount st helens in september of 2006 we estimate the seismic moment m0 and spectral corner frequency f0 using a spectral ratio approach for events with a high signal to noise snr ratio that have a cross correlation coefficient of 0 8 or greater with at least five other events a cluster analysis of cross correlation values indicates that the group of 421 events meeting the snr and cross correlation criteria forms eight event families that exhibit largely self similar scaling we estimate the m0 and f0 values of the 421 events and calculate their static stress drop and scaled energy er m0 values the estimated values suggest self similar scaling within families as well as between five of eight families i e m0 f0 3 and er m0 constant we speculate that differences in scaled energy values for the two families with variable scaling may result from a lack of resolution in the velocity model the observation of self similar scaling is the first of its kind for such a large group of low frequency volcanic tectonic events occurring during a single active dome extrusion eruption

modality of semiannual to multidecadal oscillations in global sea surface temperature variability 1 repeating the history of study on el nino southern oscillation enso in the 1980s interdecadal oscillation ido in climate variability is currently an area of active research and debate following the recognition of its emerging significance in nature and science in this work a two dimensional propagating modal extraction technique is applied to a reconstructed global monthly sea surface temperature sst data set spanning 1854 through 2007 to examine the spatiotemporal structure of sst variability with an emphasis on the fine modal pattern of idos in the time domain it is revealed that a canonical modal spectrum of decadal to centennial sst variability constitutes four most distinct oscillations with periodicities at 9 0 13 0 21 2 and 62 2 years which are naturally defined as primary modes and are respectively termed as the subdecadal mode the quasidecadal mode the interdecadal mode and the multidecadal mode modes s q i and m they join the energeticannual mode mode a and two major enso modes at 3 7 and 5 8 years modes b and c as well as a dozen of secondary modes ranging from semiannual to multidecadal in determining the key pattern of sst related climate variability in the space domain seven modally dynamic areas analogous to the nino regions for enso are clearly identified and are named as ido zones contrary to enso dominant ido zones are most visible in the extratropical oceans especially in the north atlantic north pacific sectors while secondary signatures are observed in the tropical oceans the array of four primary modes with respect to seven major zones yields a sophisticated yet canonical pattern of idos leading to a basic conclusion that multimodality for a given region and multiregionality for a given mode are fundamental features of the ido system

boulder movement at high northern latitudes of mars 1 we examine a narrow latitudinal band 60 n 70 n on mars to place constraints on the seasonally averaged velocity q of boulder movements over patterned ground these latitudes comprise a region of the northern lowlands where patterned ground covers nearly every surface here boulders meters in diameter are consistently found to be concentrated at or near the cracks that define the polygonal networks indicating a mobilization process because impact craters are the source for many boulders we can use craters and their degradation to estimate the time scales for boulder movement we study and catalog 1018 degraded impact craters 100 m d 1 km in 55 high resolution imaging science experiment hirise images we find that crater degradation occurs on a time scale 1 ma which is too recent for melting related mechanisms in a past warmer epoch clustering of boulders occurs at a time scale of a few ma or shorter which means that boulders on 5 20 m diameter polygons move at seasonal velocities q 1 10 m yr or faster

hirise observations of fractured mounds possible martian pingos 1 early images from the high resolution imaging science experiment hirise camera have revealed small fractured mounds in the martian mid latitudes hirise resolves fractures on the mound surfaces indicating uplift and shows that the mound surface material resembles that of the surrounding landscape analysis of mars orbiter camera moc images shows that in utopia planitia the mounds lie almost exclusively between 35 45 n this range coincides with the peak abundance latitudes of several landforms attributed to ground water or ice including gullies and suggests a ground ice related origin the best terrestrial analogues for the observed mound morphology are pingos although some differences are noted the presence of uncollapsed pingos would indicate the presence of near surface ground ice in the martian mid latitudes at depths greater than the 1 meter sampled by orbital spectrometers pingo formation may require near surface liquid water which is consistent with a shallow groundwater model for the origin of gullies

attenuation of coda waves in new england abstract seismic wave attenuation was measured in new england from the time domain decay of coda wave amplitudes on narrow bandpass filtered seismograms of local earthquakes the frequency band of interest was 0 75 to 10 hz q c f was found to increase with frequency across this band but there was also a difference between the q c f values for short t t 100 sec lapse times of coda wave propagation for the short lapse time data corresponding to wave paths primarily in the upper crust q c f increases from 400 at 3 hz to 1300 at 10 hz for the large lapse time data corresponding to wave paths in the lower crust and upper mantle q c f was found to vary from 660 at 1 hz to 1500 at 10 hz if we interpret this dataset in terms of a model incorporating both scattering and anelastic attenuation we find that the mean free path of seismic waves over this frequency band is 80 km for short lapse times and 400 km for long lapse times if we assume that scattering is entirely responsible for the observed attenuation we find that the minimum mean free path for short lapse times is about 75 km over all frequencies whereas for long lapse times the minimum mean free path decreases from 400 km at 0 75 hz to 90 km at 10 hz

oceanic and atmospheric transport of multiyear el nino southern oscillation enso signatures to the polar regions 1 using monte carlo singular spectrum analysis mc ssa and wavelet transform wt we separate statistically significant components from time series and demonstrate significant co variance and consistent phase differences between ice conditions and the arctic oscillation and southern oscillation indices ao and soi at 2 2 3 5 5 7 and 13 9 year periods the 2 2 3 5 and 5 7 year signals detected in the arctic are generated about three months earlier in the tropical pacific ocean in contrast we show that the 13 9 year signal propagates eastward from the western pacificasequatorialcoupledwaves ecw 0 13 0 15ms 1 and then as fast boundary waves 1 3 ms 1 along the western margins of the americas with a phase difference of about 1 8 2 1 years by the time they reach the arctic our results provide evidence of dynamical connections between high latitude surface conditions tropical ocean sea surface temperatures mediated by tropical wave propagation the wintertime polar vortex and the ao index terms 1620 global change climate dynamics 3309 3309 meteorology and atmospheric dynamics climatology 1620 0312 atmospheric composition andstructure air seaconstituent fluxes 3339 4504 4504 oceanography physical air sea interactions 0312 4522 oceanography physical el nino citation jevrejeva s j c moore and a grinsted 2004 oceanic and atmospheric transport

a transition phase teleconnection of the pacific quasi decadal oscillation the atmospheric circulation patterns associated with the pacific quasi decadal oscillation qdo are investigated using available observational data from 1948 to 2007 previous studies indicate that the pacific qdo is characterized by a distinct lifecycle in the form of sea surface temperature sst patterns in the warm and cool phases of the pacific qdo the sst patterns resemble those associated with the el nino southern oscillation enso during the warm cool and cool warm transitions of the pacific qdo recurrent sst patterns are also clearly visible the rotated empirical orthogonal function analysis on the 10 15 year filtered data shows that the evolutions of sst and atmospheric circulation are well coupled while the warm cool phase pacific qdo generates an enso like circulation pattern the transition phases form a distinct short wave train emanating from southeast asia towards north america this short wave train is particularly robust in the streamfunction of water vapor flux diagnostic analyses of the heat budget the stationary wave flux and a barotropic model indicate that this short wave train is thermodynamically maintained and is likely forced by diabatic heating near southeast asia additional modulations of forcing sources in the western and eastern tropical pacific on this short wave teleconnection are also discussed

geochemistry and petrology of the galeras volcanic complex colombia abstract the galeras volcanic complex gvc has erupted lavas and pyroclastic flows ranging from basaltic andesites to dacites during the last million years the chemical composition of the volcanic products has been fairly constant characterized by calc alkaline high silica medium potassium andesites variations from basaltic andesites to dacites have occurred during individual stages but overall composition and petrographic characteristics are quite constant the guaca cinder cone is the exception being more alkaline rather than calc alkaline the trace element and ree contents of the gvc samples suggest that sediments or fluids from the subducted sediments are involved in the generation of the magmas at the source region although high sr and ba contents are also present in the upper continental crust the high b levels are consistent with the contribution of sediment related elements small degrees of partial melting of a hydrated mantle wedge are consistent with the observed distribution of ree plus the addition of highly soluble elements from the subducted sediments crystal fractionation at depths of about 36 km approximately 12 kbar of a hydrated tholeiitic basalt melt can produce andesites and basaltic andesites having a phase assemblage of amphibole plagioclase clinopyroxene magnetite ilmenite and apatite the magma then re equilibrates at higher levels reaching levels as shallow as 10 km about 2 5 to 3 kbar and crystallizing orthopyroxene and large amounts of plagioclase at these shallow levels amphibole is no longer stable and re equilibrates to oxides pyroxene and plagioclase the melts become saturated with respect to most volatiles by depressurization and crystallization in the gvc we observe that it is not necessary to have large volumes of highly differentiated magma to cause caldera forming eruptions

possible closed system pingo and ice wedge thermokarst complexes at the mid latitudes of utopia planitia mars abstract on earth hydrostatic or closed system pingos csps are perennial ice cored mounds formed by the freeze thaw cycling of water when or as thermokarst lakes lose their water by drainage or evaporation the mounds vary in shape from circular or sub circular to elongate are sub kilometre in their long axes and may reach decametres in height often the mounds show summit depressions radial fractures and single tiers or benches as the csps degrade small scale debris flows or slumps occur end stage degradation typically exhibits debris laden ramparts elevated metres above the surrounding terrain typically the csps originate and develop where deep and continuous permafrost is ice rich i e infused with excess ice as it is in the tuktoyaktuk coastlands of northern canada mid to northern alaska and northeast russia in these areas or regions the terrain often is populated by a thermokarst lakes and alases thermokarst lake basins absent of water b fields of small scale ice wedge polygons either low centred or high centred relative to the polygon margins and c melt water filled or emptied polygon margin troughs or corner pits individual troughs and pits connected by means of the local topographical gradient comprises beaded stream systems or networks here we report describe and discuss a suite of candidate csps at the mid latitudes of utopia planitia up 35 50 n 80 115 e the morphologies scale and height of the martian mounds as well as the surface textures and characteristics landscape features and spatially associated landforms are consistent with the csps observed in ice rich regions on earth the up mounds are nested in or reside adjacent to flat floored possibly thermokarstic depressions small scale polygons some of which exhibit low or high centres relative to their margins and connected polygon margin depressions or pits that mirror beaded stream systems in ice rich terrain on earth the size frequency distribution of craters in our study region precludes a surface younger than 100 ma thus the csp like mounds in up and the pre mound periglacial revisions of the landscape presented by us may be markers of freeze thaw cycling that occurred much earlier in the amazonian epoch than most of the current discussions about periglaciation in up suggest

an investigation of the el nino southern oscillation cycle with statistical models 1 predictor field characteristics we have developed two sets of linear models for predicting equatorial pacific sea surface temperatures ssts from the indo pacific trade wind field and the near global sea level pressure slp field the models were constructed using a combination of extended empirical orthogonal functions eeofs and canonical correlation analysis cca a new approach in geophysical modeling our results are of interest both as they show the dominant modes of evolution in the slp and wind fields through the el nino southern oscillation cycle and with respect to the problem of predicting equatorial ssts this paper deals with the first issue above and describes some statistical composites that typify the development of features in the predictor fields over periods of years the results of the eeof analyses clearly show slowly propagating anomalies in both the near global slp and trade wind fields the cca analysis which highlights the co evolution of the two fields suggests a strong coupling between the two and depicts the anomalous features as migrating centers of divergence and convergence that first appear over the eastern indian ocean these features propagate slowly eastward amplify as they expand into the western pacific decline as they cross the central ocean then reamplify over the eastern pacific as reamplification takes place new opposing anomalies appear in the indo pacific descriptions of the predictor data sets and details of the statistical techniques used may also be found in this paper the sst data model validation techniques and forecast model results are presented in a companion paper graham et al this issue

maximal wavelet filter and its application to bidecadal oscillation over the northern hemisphere through the twentieth century based on a wavelet transform a new method referred to as maximal wavelet filter mwf is proposed to extract temporal structure changes of a climatic oscillation which varies its pattern corresponding to the changes of the oscillation period the mwf is a bandpass filter having a narrow pass band the central frequency of which temporally varies according to the periods of maximal wavelet amplitudes for a specific region mwf is applied to wintertime sea level pressures slps in the northern hemisphere from 1899 to 2000 to extract slp changes associated with the bidecadal oscillation bdo which distributes globally but has the strongest amplitudes in the north pacific in the pacific sector the bdo center of action captured by the mwf was located over alaska in the first few decades of the record and then moved southward to the central north pacific from 1920 to 1950 with maximal bdo amplitudes in the middle of the century the southward migration was accompanied by the previously reported increase of the oscillation period from 15 to 20 years on the other hand atlantic slp variations coherent with the pacific bdo had large amplitudes in midlatitudes high latitudes in the early late part of the twentieth century in association with these spatial structure changes the pattern of the recent bdo resembles the pattern of the arctic oscillation the analysis of the sea surface temperatures ssts gridded from the comprehensive ocean atmosphere data set coads and the newly digitized kobe collections suggests that bdo pattern in the ssts also shifted toward the south between the first and last few decades of the twentieth century furthermore covariability between the land air temperatures and aleutian low strength is observed through the twentieth century for alaska but only after 1940 for the midlatitudes of western north america and hawaii indicating that the bdo influence was limited to the high latitudes in the first few decades of the twentieth century in these regions consistent with the spatial structure changes in the slp field over the north pacific

a lagged warm event like response to peaks in solar forcing in the pacific region abstract the forced response coincident with peaks in the 11 yr decadal solar oscillation dso has been shown to resemble a cold event or la nina like pattern during december february djf in the pacific region in observations and two global coupled climate models previous studies with filtered observational and model data have indicated that there could be a lagged warm event or el nino like response following the peaks in the dso forcing by a few years here observations and two climate model simulations are examined and it is shown that dynamical coupled processes initiated by the response in the tropical pacific to peaks in solar forcing produce wind forced ocean rossby waves near 5 n and 5 s these reflect off the western boundary producing downwelling equatorial kelvin waves that contribute to transitioning the tropical pacific to a warm event or el nino like pattern that lags the peaks in solar forcing by a few years

possible pingo fields in the utopia basin mars geological and climatical implications abstract the presence of pingos on mars has been hypothesized since the period of the viking mission in fact a diverse range of pingo like features has been found at various martian sites including elysium chryse and utopia planitiae in the northern lowlands due to the morphology and the geological setting some of those features were interpreted in different ways creating some controversies as happened in athabasca valles this reflects the complexity of interpreting these features by remote sensing and multiple plausible interpretations of the same feature with the objective of identifying new possible pingos or rootless cones on mars we selected a study area in utopia planitia 10 55 n 210 260 w where the presence of both features is possible due to its geological history volcanic and hydrological we analyzed more than 2100 mars orbiter camera moc narrow angle images in addition to viking thermal emission imaging system themis and high resolution stereo camera hrsc images together with mars orbiter laser altimeter mola derived digital elevation models dems with a geographic information system gis we found in 94 moc narrow angle images dome cone and ring shaped features we analyzed them from morphological and morphometrical points of view in order to compare them with relevant features on mars and earth we tested different possible origins for those features following the approach of multiple working hypotheses we conclude that the dome cone and ring shaped features could be pingos which is in agreement with their geological settings regarding the driving heat source for the formation of the purported pingos we propose the existence of a heat source possibly a magma chamber underneath the surface of the utopia basin together with possible climatic shifts the past activities of the heat source may have caused melting of ground ice the pingo growth due to freezing of the water would have occurred during the following cold climatic conditions

volcanic terrain and the possible periglacial formation of excess ice at the mid latitudes of utopia planitia mars at the mid latitudes of utopia planitia up mars a suite of spatially associated landforms exhibit geomorphological traits that on earth would be consistent with periglacial processes and the possible freeze thaw cycling of water the suite comprises small sized polygonally patterned ground polygon junction and margin pits and scalloped rimless depressions typically the landforms incise a dark toned terrain that is thought to be ice rich here we investigate the dark toned terrain by using high resolution images from the hirise as well as near infrared spectral data from the omega and crism the terrain displays erosional characteristics consistent with a sedimentary nature and near infrared spectra characterised by a blue slope similar to that of weathered basaltic tephra we also describe volcanic terrain that is dark toned and periglacially modified in the kamchatka mountain range of eastern russia the terrain is characterised by weathered tephra inter bedded with snow ice wedge polygons and near surface excess ice the excess ice forms in the pore space of the tephra as the result of snow melt infiltration and subsequently in situ freezing based on this possible analogue we construct a three stage mechanism that explains the possible ice enrichment of a broad expanse of dark toned terrain at the mid latitudes of up 1 the dark toned terrain accumulates and forms via the regional deposition of sediments sourced from explosive volcanism 2 the volcanic sediments are blanketed by atmospherically precipitated h2o snow ice or an admixture of the two either concurrent with the volcanic events or between discrete events and 3 under the influence of high obliquity or explosive volcanism boundary conditions tolerant of thaw evolve and this in turn permits the migration cycling and eventual formation of excess ice in the volcanic sediments over time and through episodic iterations of this scenario excess ice forms to decametres of depth

evidence for nonlinear coupling of solar and enso signals in indian temperatures during the past century significant fluctuations have been observed in indian temperatures during past century in order to identify the statistical periodicities in the maximum and minimum temperature data of different indian zones we have spectrally and statistically analyzed the homogeneous regional temperature series from the western himalayas the northern west the north central the north east ne the west coast the east coast and the interior peninsula for the period of 107 years spanning over 1901 2007 using the multitaper method mtm and singular spectrum analysis ssa methods the first ssa reconstructed the principal component of all the data sets representing a nonlinear trend indicating a monotonic rise in temperature probably due to greenhouse gases and other forcing that varies from region to region we have reconstructed the temperature time series using the second to tenth oscillatory principal components of all the eight regions and computed their power spectral density using mtm our analyses indicate that there is a strong spectral power in the period range of 2 7 years and 53 years which are matched respectively with the known el nino southern oscillation enso periods and ocean circulation cycles further the spectral analysis also revealed a statistically significant but riven cycle in a period range of 9 8 13 years corresponding to the schwabe cycle in all indiaian maximum and minimum temperature records and almost all the zonal records except in the ne data in some of the cases the 22 year double sunspot hale cycle cycle was also identified here invariably the splitting of spectral peaks corresponding to solar signal indicated nonlinear characteristics of the data and therefore even small variations in the solar output may help in catalyzing the coupled el nino atmospheric enso cycles by altering the solar heat input to the oceans we therefore conclude that the indian temperature variability is probably driven by the nonlinear coupling of enso and solar activity

influence of the antarctic circumpolar wave on el nino and its multidecadal changes from 1950 to 2001 1 the slow eastward phase propagation of covarying sea surface temperature sst and sea level pressure slp anomalies in the antarctic circumpolar wave acw persisted in the midlatitude southern ocean from 1950 to 2001 its northern extent reached into the subtropical south indian and south pacific oceans where it influenced the magnitude and phase of el nino in the eastern equatorial pacific ocean this is corroborated by the observation that multidecadal changes in the acw can also explain multidecadal changes in the way el nino evolved over the last half of the twentieth century before 1977 el nino evolved from the slow eastward phase propagation of a coupled sst slp wave across the subtropical south pacific ocean to south america then equatorward along the eastern boundary to the equator during this epoch the acw expanded equatorward into a warmer subtropical south pacific ocean accounting for the subtropical coupled sst slp wave that initiated el nino after 1977 el nino evolved from the slow eastward phase propagation of a coupled sst slp wave across the tropical pacific ocean during this epoch the acw receded from a colder subtropical south pacific ocean but expanded into a warmer subtropical south indian ocean there it spawned a coupled sst slp wave directed equatorward into the warm pool north of australia thereafter propagating eastward into the eastern equatorial pacific ocean to initiate el nino if this pattern of global warming persists into the 21st century then the acw will continue to influence el nino through the south indian ocean

decadal fluctuations in the western pacific recorded by long precipitation records in taiwan a 110 year precipitation record in taiwan located at the western edge of the subtropical north pacific depicts a pronounced quasi decadal oscillation qdo the qdo in taiwan exhibits a fluctuating relationship with the similar decadal variations of sea surface temperature sst anomalies in the central equatorial pacific known as the pacific qdo a regime change was observed around 1960 such that the decadal variation of taiwan s precipitation became more synchronized with the pacific qdo s coupled evolutions of sst and atmospheric circulation than before while the underlying pattern of the pacific qod did not change using long term reanalysis data and cmip5 single forcing experiments the presented analysis suggests that increased sst in the subtropical western pacific and the strengthened western extension of the north pacific subtropical anticyclone may have collectively enhanced the relationship between the taiwan precipitation and the pacific qdo this finding provides possible clues to similar regime changes in quasi decadal variability observed around the western pacific rim

a global quasi biennial wave in surface temperature and pressure and its decadal modulation from 1900 to 1994 zonal wave number frequency spectra of surface temperature st and sea level pressure slp anomalies extending around the global tropical ocean at 10 n from 1950 to 1997 display significant peaks for 2 0 and 2 4 year periods dominated by eastward propagating zonal wave numbers of global scale applying complex principal component analysis to quasi biennial st slp and surface wind sw anomalies for 25 years from 1973 to 1997 separates this global quasi biennial wave gbw from corresponding global standing modes with patterns and evolution of the former similar to those observed in the global el nino southern oscillation wave white and cayan 2000 but centered on the equatorial waveguide and taking only 3 to 4 years instead of 4 to 6 years to transit the global tropical ocean at 0 30 to 0 40 m s 1 we find the gbw contributing to the quasi biennial signal in nino 3 st and slp indices with amplitude twice that of global standing mode in the gbw the ocean forces the atmosphere with sw anomalies directed toward warm sea surface temperature anomalies while the atmosphere forces the ocean with sw induced kelvin waves on the equator and sw induced sensible plus latent heat flux and or vertical mixing anomalies elsewhere both advancing st anomalies eastward examining the gbw from 1900 to 1994 finds its amplitude modulated by the decadal signal of 10 year periodicity robust weak when tropical temperature gradients and trade winds were stronger weaker than normal

lithic dominated pyroclastic flows at galeras volcano colombia an unrecognized volcanic hazard yellow hydrothermally altered lithic dominated pyroclastic breccia deposits having only a minor juvenile component at galeras volcano colombia contain evidence that they were emplaced as hot fluidized true pyroclastic flows the distribution of the flows around the caldera rim their transport mechanisms inferred from grain size analyses and the presence of charcoal and coarse channel and fine overbank facies indicate that these deposits were emplaced as true pyroclastic flows these deposits are the result of a regularly repeated eruption sequence involving clearing of vent material as a prelude to more typical pumiceous pyroclastic flows recognition of the mode of origin of these deposits is important in terms of understanding vulcanian type eruption and flow emplacement mechanisms failure to recognize the explosive eruption origin of these deposits at galeras and other volcanoes could result in serious underestimation of potential hazards

thermokarst lakes and ponds on mars in the very recent late amazonian past the history of water is fundamental to understanding the geological evolution of mars and to questions concerning the possible development of life on the red planet today mars is cold and dry it

sub kilometre intra crater mounds in utopia planitia mars character occurrence and possible formation hypotheses abstract at the middle latitudes of utopia planitia 35 45 n 65 101 e hundreds of small sized mounds located in sub kilometre impact craters dot the landscape their shape varies from circular to crescentic and their height ranges from 10 to 50 m often metre to decametre pitting is observed as is metres thick banding or stratification mound albedo is relatively high i e 0 16 the plain s terrain in the region previously linked to the latitude dependent mantle ldm of ice dust displays pitting and albedo similar to the small intra crater mounds some workers have suggested that the mounds and the plain s terrain share a common ice dust origin if so then scrutinising the mounds could provide analogical insight on the key geological characteristics and spatial distribution of the ldm itself other workers have hypothesised that the mounds are eroded sedimentary landforms or periglacial mounds underlain by a perennial ice core closed system pingos in this article we develop and then discuss each of the three mound hypotheses in a much more substantial manner than has been done hitherto towards this end we use high resolution images present a detailed regional map of mound distribution and establish a regional platform of topographical analysis using mola data superposed on a large scale ctx mosaic although the ice dust hypothesis is consistent with some observations and measurements we find that a loess based sedimentary hypothesis shows greater plausibility of the three hypotheses evaluated the pingo or periglacial one is the weakest

global sst slp waves during the 20th century 1 a discrete number of global signals in covarying sea surface temperature sst and sea level pressure slp dominated climate variability from 40 s to 60 n during the 20th century they are the quasi biennial 2 2 year period interannual 3 to 7 year period band quasi decadal 11 year period and interdecadal 17 year period signals a joint frequency domain analysis of sst and slp anomalies over the global ocean finds these signals composed of mixed global standing modes and traveling waves that are similar in pattern and evolution on each period scale the global traveling wave is composed of global zonal wavenumbers 1 and 2 directed eastward with a phase speed that takes 1 to 2 cycles to traverse the global ocean between 40 s and 20 n the existence of these global traveling waves may enhance the predictability of regional climate variability

an improved real time global sea surface temperature analysis abstract the monthly global sea surface temperature sst analysis of reynolds using real time in situ and satellite sst data has now been improved by using sea ice data to simulate ssts in ice covered regions the simulated ssts now become the external boundary condition for the analysis solution this technique eliminates any high latitude satellite biases and extends the analysis to the ice edge the analysis with the ice data has been computed for the period january 1982 to present

tearing and breaking off of subducted slabs as the result of collision of the panama arc indenter with northwestern south america we present two regional lithospheric cross sections that illustrate eastward and southeastward dipping subducted slabs to depths of 315 km beneath the surface of colombia in northwestern south america these cross sectional interpretations are based on relocated earthquake hypocentral solutions models supported on gravity and magnetic regional data and coda q q c tomography the method of tomographic imaging based on spatial inversion of the coda wave has advantages of providing information on the lateral variations of the anelastic properties and thermal structure of the lithospheric system mapping of earthquake defined benioff zones combined with tomographic imaging reveals the presence of an 240 km long east west striking slab tear named here the caldas tear the proposed caldas tear separates a zone of shallow 20 30 dipping southeastward subduction in the area of colombia adjacent to panama and the caribbean sea which is not associated with subduction related volcanism from an area of steeper 30 40 dipping slab adjacent to the eastern pacific ocean that is associated with an active north south chain of active arc volcanoes we propose that the caldas slab tear separating these two distinct subducted slabs originally formed as the southern boundary of the panama indenter an extinct island arc that began subducting beneath northwestern south america about 12 ma the area south of the panama indenter is miocene oceanic crust of the nazca plate which subducts eastward beneath northwestern south america at normal angles and melts to form a north south trending active volcanic arc in addition to the formation of the caldas tear we propose that impedance of the thicker crustal area of the panama arc indenter over the past 12 ma may have led to down dip break off of previously subducted oceanic crust that is marked by an extremely concentrated and active earthquake swarm of intermediate depth earthquakes beneath east central colombia

coda wave imaging of the long valley caldera using a spatial stacking technique numerous geological and seismological studies of the long valley caldera eastern california suggest that it is at present an active magmatic system tomographic measurements utilising local and regional earthquake data have traditionally been made on the principle direct arrivals this paper presents the results from a technique developed to image the s wave attenuation structure we measure the attenuation value of the s wave coda from almost 17 000 vertical component seismograms a more stable estimate of q is determined from coda waves which are less sensitive to local path effects than direct waves as they sample a volume we find that the resultant tomograms produced from spatial stacking show a high attenuation anomaly qs 125 centred within the caldera compared with qs 220 outside the caldera

positive feedbacks between the antarctic circumpolar wave and the global el nino southern oscillation wave atmospheric and oceanic teleconnections link the antarctic circumpolar wave acw in the southern ocean white and peterson 1996 and the global el nino southern oscillation enso wave gew in the tropical indo pacific ocean white and cayan 2000 both signals characterized by eastward phase propagation and 3 to 5 year period variability we extend the tropical standing mode of enso into the extratropics by regressing the nino 3 sea surface temperature sst index against sea level pressure slp anomalies over the globe finding the pacific south america psa pattern in slp anomaly cai and baines 2001 straddling drake passage in the southern ocean the amplitude of this psa pattern is similar to1 3 that of the acw in this domain and thus cannot be considered its principal driver on the other hand suppressing the tropical standing mode of enso in interannual st surface temperature and slp anomalies over the globe allows the gew to be observed much more readily whereupon its eastward phase propagation across the warm pool is found to remotely force the acw in the eastern pacific and western atlantic sectors of the southern ocean through atmospheric teleconnections sardeshmukh and hoskins 1988 which propagate along with it subsequently the acw propagates this imposed gew signal throughout the remainder of the southern ocean as a coupled wave in covarying st and slp anomalies whereupon entering the indian sector 1 5 to 2 5 years later it spawns a northern branch which takes another 1 5 to 2 5 years to propagate the acw signal equatorward into the warm pool south of indonesia there it interferes constructively with the gew thus the two forms of teleconnection one fast and directed from the tropics to the high southern latitudes via the atmosphere and the other slow and directed from the high southern latitudes to the tropics via the ocean complete a global circuit of 3 to 5 year duration that reinforces both the acw and gew and influences the tropical standing mode of enso

examples of the horizontal propagation of quasi stationary waves abstract examples of the diagnostic of the horizontal propagation of stationary wave activity proposed by plumb are presented for a simple model of the atmospheric response to thermal forcing in the tropics for the observed southern hemisphere winter mean stationary waves and for several cases of anomalous quasi stationary waves in both the northern and southern hemispheres for the simple model the propagation of wave activity out of the tropics is clear from the observational data the apparent sources of anomalous stationary wave activity are located in the regions of the major middle latitude jets and storm tracks in both hemispheres in most cases the results suggest that midlatitude processes such as instabilities of the jet stream or interaction with transient eddies are the major mechanisms for forcing anomalous stationary waves there are indications that rossby like wave propagation from low latitudes plays a role in forcing anomalous stationary waves associated with southern oscillation ev

small scale polygonal features on mars seasonal thermal contraction cracks in permafrost a time dependent viscoelastic model of thermal stress in martian ice rich permafrost is developed to test the hypothesis that small scale polygonal features observed from orbit and by the viking lander 2 are the result of thermal contraction cracking as commonly occurs in terrestrial permafrost results indicate that significant tensile stress occurs in martian ice rich permafrost as a result of seasonal cycles in the ground temperature using conservative rheological parameters appropriate for ice at low temperatures tensile stresses poleward of about 20 to 30 latitude easily exceed the tensile strength assumed to be 2 to 3 mpa and fractures should readily form in the equatorial regions special conditions may allow tensile stresses to approach the tensile strength these results support a thermal contraction origin of observed small scale polygonal features and emphasize the utility of these features as valuable morphological indicators of ground ice

co evolution of polygonal and scalloped terrains southwestern utopia planitia mars abstract thermal contraction crack polygons and scalloped depressions two of the most common landforms found in utopia planitia mars have previously been linked to the presence of ice rich deposits in the subsurface although the formation and evolution of these features individually are relatively well understood little to no effort has been directed towards elucidating possible interactions that occur between them during their development thus the overarching goal of this research was to investigate if there is an evolutionary link between polygonal and scalloped terrains by correlating metrics representing polygon and scallop maturity a variety of statistical analyses were performed using hirise and mola datasets to quantify interactions between four sets of polygonal and scalloped terrains our results demonstrate the existence of a negative relationship between polygonal subdivision and surface elevation indicating that polygon networks become more evolved as the surface subsides these results suggest that the permafrost landscape in utopia planitia may once have been extremely ice rich and that multiple geomorphic processes may be responsible for its evolution ultimately this work demonstrates that landscape reconstruction is more complete when a system approach is followed quantifying interactions between landforms as opposed to examining an individual landform in isolation

the indication of martian gully formation processes by slope area analysis the formation process of recent gullies on mars is currently under debate this study aims to discriminate between the proposed formation processes pure water flow debris flow and dry mass wasting through the application of geomorphological indices commonly used in terrestrial geomorphology high resolution digital elevation models dems of earth and mars were used to evaluate the drainage characteristics of small slope sections data from earth were used to validate the hillslope debris flow and alluvial process domains previously found for large fluvial catchments on earth and these domains were applied to gullied and ungullied slopes on mars in accordance with other studies our results indicate that debris flow is one of the main processes forming the martian gullies that were being examined the source of the water is predominantly distributed surface melting not an underground aquifer evidence is also presented indicating that other processes may have shaped martian crater slopes such as ice assisted creep and solifluction in agreement with the proposed recent martian glacial and periglacial climate our results suggest that within impact craters different processes are acting on differently oriented slopes but further work is needed to investigate the potential link between these observations and changes in martian climate

stratigraphical evidence of late amazonian periglaciation and glaciation in the astapus colles region of mars abstract recent modeling of the meteorological conditions during and following times of high obliquity suggests that an icy mantle could have been emplaced in western utopia planitia by atmospheric deposition during the late amazonian period costard f m forget f madeleine j b soare r j kargel j s 2008 lunar planet sci 39 abstract 1274 madeleine b forget f head j w levrard b montmessin f 2007 lunar planet sci 38 abstract 1778 astapus colles aba is a late amazonian geological unit located in this hypothesized area of accumulation that comprises an icy mantle tens of meters thick tanaka k l skinner j a hare t m 2005 us geol surv sci invest map 2888 for the most part this unit drapes the early amazonian vastitas borealis interior unit abvi to a lesser degree it overlies the early amazonian vastitas borealis marginal unit abvm and the early to late hesperian up plains unit hbu2 tanaka k l skinner j a hare t m 2005 us geol surv sci invest map 2888 landscapes possibly modified by late amazonian periglacial processes costard f m kargel j s 1995 icarus 114 93 112 mcbride s a allen c c bell m s 2005 lunar planet sci 36 abstract 1090 morgenstern a hauber e reiss d van gasselt s grosse g schirrmeister l 2007 j geophys res 112 doi 10 1029 2006je002869 e06010 seibert n m kargel j s 2001 geophys res lett 28 899 902 soare r j kargel j s osinski g r costard f 2007 icarus 191 95 112 soare r j osinski g r roehm c l 2008 earth planet sci lett 272 382 393 and glacial processes milliken r e mustard j f goldsby d l 2003 j geophys res 108 e6 doi 10 1029 2002je002005 5057 mustard j f cooper c d rifkin m k 2001 nature 412 411 414 tanaka k l skinner j a hare t m 2005 us geol surv sci invest map 2888 have been reported within the region researchers have assumed that the periglacial and glacial landscapes occur within the same geological unit the aba i e morgenstern a hauber e reiss d van gasselt s grosse g schirrmeister l 2007 j geophys res 112 doi 10 1029 2006je002869 e06010 tanaka k l skinner j a hare t m 2005 us geol surv sci invest map 2888 in this study we use hirise high resolution image science experiment mars reconnaissance orbiter imagery to identify the stratigraphical separation of the two landscapes and show that periglacial landscape modification has occurred in the geological units that underlie the aba not in the aba itself moreover we suggest that the periglacial landscape extends well beyond the perimeter of the aba and could be the product of wet cold climate processes these processes involve freeze thaw cycles and intermittently stable liquid water at or near the surface by contrast we propose that the aba is a very recent late amazonian geological unit formed principally by dry cold climate processes these processes comprise accumulation by atmospheric deposition and ablation by sublimation

intra crater glacial processes in central utopia planitia mars abstract we describe and interpret a series of previously unidentified glacial like lobes 34 43 n 107 125 e that were discovered as part of a survey of large d 5 km impact craters in utopia planitia one of the great northern plains of mars the lobes have characteristics that are consistent with a glacial origin evidence includes curvilinearity of form lineations and ridges and surface textures that are thought to form by the sublimation of near surface volatiles the lobes display morphologies that range from wedge shaped to near circular to elongate the flow directions are towards the northern walls in the case of craters with large single lobes and in all directions in the case of the largest d 30 km craters concentric crater fill is also interspersed within craters of our study region with such craters having much higher filling rates than those with flow lobes we suggest that the impact crater population in south west utopia planitia demonstrates a spectrum of glacial modifications from low levels of filling in the case of craters with elongate lobes at one extreme to concentric crater fill in highly filled craters at the other

modeling concentric crater fill in utopia planitia mars with an ice flow line model abstract impact craters in the mid latitudes of mars are commonly filled to variable degrees with some combination of ice dust and rocky debris concentric surface features visible in these craters have been linked to debris transportation and glacial and periglacial processes concentric crater fill ccf observed today are interpreted to be the remains of repeated periods of accumulation and sublimation during the last tens to hundreds of million years previous work suggests that during phases of high obliquity ice accumulates in crater interiors and begins to flow down steep crater slopes slowly filling the crater during times of low obliquity ice is protected from sublimation through a surface debris layer consisting of dust and rocky material here we use an ice flow line model to understand the development of concentric crater fill in a regional study of utopia planitia craters we address questions about the influence of crater size on the ccf formation process the time scales needed to fill an impact crater with ice and explore commonly described flow features of ccf we show that observed surface debris deposits as well as asymmetric flow features can be reproduced with the model using surface mass balance data from global climate models and a credible obliquity scenario we find that craters less than 80 km in diameter can be entirely filled in less than 8 my beginning as recently as 40 ma ago uncertainties in input variables related to ice viscosity do not change the overall behavior of ice flow and the filling process we model ccf for the utopia planitia region and find subtle trends for crater size versus fill level crater size versus sublimation reduction by the surface debris layer and crater floor elevation versus fill level

interdecadal sea surface temperature sea level pressure coupled variability in the south pacific ocean 1 the main coupled sea surface temperature sst sea level pressure slp variability at interdecadal timescale in the south pacific is studied by means of correlation and combined complex empirical orthogonal function cceof analyses the sst slp coupled variability presents a bidecadal cycle from mid 1950s to 1970s and a decadal cycle from 1980s to early 1990s reproducing the enso like interdecadal oscillation particularly the first sst slp cceof mode describes the bidecadal cycle characterized by westward progression of sst and slp anomalies along the tropical pacific while the second sst slp cceof mode shows the decadal cycle with eastward development during both bidecadal and decadal cycles the sst fluctuations in the eastern equatorial pacific and along the western coast of south america are primarily forced by equatorial zonal wind variability specially during the bidecadal cycle the alongshore sst variability south of 30 s is maintained and reinforced by meridional coastal wind fluctuations associated with a stationary slp pattern off southern chile this stationary slp pattern appears connected to sst fluctuations in the central tropical pacific

patterns of coherent climate signals in the indian ocean during the 20th century 1 qbo enso and bdo fluctuations are identified in the indian ocean from a joint frequency domain analysis of sea surface temperature sst and sea level pressure slp conducted over the 20th century within the enso band 3 to 7 year period local fractional variance lfv is maximum near 3 4 year period revealing spatially coherent sst and slp variability propagating eastward from the horn of africa and southwest indian ocean respectively toward the eastern tropical indian ocean within the qbo band 2 1 to 2 8 year period lfv is maximum near 2 2 year period revealing spatially coherent sst and slp variability propagating northward and eastward from southwestern ocean toward the south china sea the 3 4 year period enso signal diminished in intensity in the 1920s and 1950s whilst the 2 2 year period qbo signal diminished in the 1910s 1940s and 1950s as observed for the global qbo and enso signals white and tourre 2003

patterns of coherent decadal and interdecadal climate signals in the pacific basin during the 20th century two distinct low frequency fluctuations are suggested from a joint frequency domain analysis of the pacific ocean 30 s 60 n sea surface temperature sst and sea level pressure slp the lowest frequency signal reveals a spatially coherent interdecadal evolution in phase sst and slp anomalies are found along the subarctic frontal zone safz it is symmetric about the equator with tropical sst anomalies peaking near 15 latitudes in the eastern pacific the other low frequency signal reveals a spatially coherent decadal evolution it is primarily a low latitude phenomenon tropical sst anomalies peak in the central equatorial ocean with evidence of atmospheric teleconnections these interdecadal and decadal signals join the enso and quasi biennial signals in determining dominant patterns of pacific ocean natural climate variability relative phasing and location of the sst and slp anomalies for the decadal enso and the quasi biennial signals are similar to one another but significantly different from that of the interdecadal signal

an antarctic circumpolar wave in surface pressure wind temperature and sea ice extent the southern ocean is the only oceanic domain encircling the globe it contains the strong eastward flow of the antarctic circumpolar current and is the unifying link for exchanges of water masses at all depths between the world s major ocean basins1 as these exchanges are an important control on mean global climate the southern ocean is expected to play an important role in transmitting climate anomalies around the globe interannual variability has been often observed at high southern latitudes and observations of sea ice extent suggest that such features propagate eastwards around the southern ocean2 3 here we use data from a variety of observational techniques to identify significant interannual variations in the atmospheric pressure at sea level wind stress sea surface temperature and sea ice extent over the southern ocean these anomalies propagate eastward with the circumpolar flow with a period of 4 5 years and taking 8 10 years to encircle the pole this system of coupled anomalies which we call the antarctic circumpolar wave is likely to play an important role in climate regulation and dynamics both within and beyond the southern ocean

a delayed action oscillator shared by biennial interannual and decadal signals in the pacific basin 1 biennial interannual and decadal signals in the pacific basin are observed to share patterns and evolution in covarying sea surface temperature sst 18 c isotherm depth z18 zonal surface wind zsw and wind stress curl wsc anomalies from 1955 to 1999 each signal has warm sst anomalies propagating slowly eastward along the equator generating westerly zsw anomalies in their wake these westerly zsw anomalies produce cyclonic wsc anomalies off the equator which pump baroclinic rossby waves in the western central tropical north pacific ocean these rossby waves propagate westward taking 6 12 and 36 months to reach the western boundary near 7 n 12 n and 18 n on biennial interannual and decadal period scales respectively there they reflect as equatorial coupled waves propagating slowly eastward in covarying sst z18 and zsw anomalies taking 6 12 and 24 months to reach the central eastern equatorial ocean these equatorial coupled waves produce a delayed negative feedback to the warm sst anomalies there the decrease in rossby wave phase speed with latitude the increase in meridional scale of equatorial sst anomalies with period scale and the associated increase in latitude of rossby wave forcing are consistent with the delayed action oscillator dao model used to explain el nino however this is not true of the western boundary reflection of rossby waves into slow equatorial coupled waves this requires modification of the extant dao model we construct a modified dao model demonstrating how the various mechanisms and the size and sources of their delays yield the resulting frequency of each signal

correlations between so2 flux and long period seismicity at galeras volcano the 14 january 1993 eruption of galeras volcano in colombia which killed six scientists and three tourists1 was followed by a larger eruption on 23 march 19932 both eruptions were preceded by episodes of long period seismicity the source of long period seismic events has been modelled extensively3 8 as the resonance within a fluid filled crack induced by pressure transients in the fluid5 7 here we use the so2 flux from galeras volcano measured remotely to infer the degassing history during the episode of long period events preceding the 23 march eruption so2 flux and long period seismicity have been monitored separately elsewhere to forecast volcanic activity9 13 our results show how the combination and correlation of the two methods can be used to interpret the movement of gases from the magma body to the surface and to monitor the pressure buildup leading to an eruption at explosive volcanoes

linkages between 200 mb tropical and extratropical circulation anomalies during the 1986 1989 enso cycle abstract nmc operational wind analyses have been used to document the 200 mb circulation anomalies during the solstice seasons of the 1987 1989 enso cycle using the one level vorticity balance diagnostic approach the 200 mb rossby wave anomalous source distribution was derived as departures from a three year mean for the single warm phase season january march 1987 the effective rossby wave anomaly sources were found to be generally quite small within 15 of the equator poleward of about 15 the anomalous 200 mb divergence through the planetary vorticity divergence anomaly stretching term is the dominant factor in determining the anomalous 200 mb vorticity source distribution its jfm standard deviation around 30 35 n was an order of magnitude larger than that found in the deep tropics the january march and june august 200 mb circulation differences between the warm and cold phase of the 1987 1989 enso cycle are described the enso cycle linkages between the equatorial pacific convection anomali

coherence between the great salt lake level and the pacific quasi decadal oscillation the lake level elevation of the great salt lake gsl a large closed basin lake in the arid western united states is characterized by a pronounced quasi decadal oscillation qdo the variation of the gsl elevation is very coherent with the qdo of sea surface temperature anomalies in the tropical central pacific also known as the pacific qdo however such coherence denies any direct association between the precipitation in the gsl watershed and the pacific qdo because in a given frequency the precipitation variation always leads the gsl elevation variation therefore the precipitation variation is phase shifted from the pacific qdo this study investigates the physical mechanism forming the coherence between the gsl elevation and the pacific qdo pronounced and coherent quasi decadal signals in precipitation streamflow water vapor flux and drought conditions are found throughout the great basin recurrent atmospheric circulation patterns develop over the gulf of alaska during the warm to cool and cool to warm transition phases of the pacific qdo these circulation patterns modulate the water vapor flux associated with synoptic transient activities over the western united states and in turn lead to the qdo in the hydrological cycle of the great basin as the gsl integrates the hydrological responses in the great basin the hydrological qdo is then transferred to the gsl elevation because the gsl elevation consistently lags the precipitation by a quarter phase about 3 yr in the quasidecadal time scale these processes take an average of 6 yr for the gsl elevation to eventually respond to the pacific qdo this creates a half phase delay of the gsl elevation from the pacific qdo thereby forming the inverse yet coherent relationship between them tree ring reconstructed precipitation records confirm that the quasi decadal signal in precipitation is a prominent feature in this region

a global el nino southern oscillation wave in surface temperature and pressure and its interdecadal modulation from 1900 to 1997 zonal wavenumber frequency spectra of sea surface temperature sst anomalies along the equator in the indo pacific basin for the 98 years from 1900 to 1997 and of surface temperature st and sea level pressure slp anomalies extending around the globe along 10 n for the 48 years from 1950 to 1997 display significant peak spectral energy density for standing and eastward propagating waves of 3 7 year periods and 120 360 zonal wavelengths the global standing wave is the familiar southern oscillation but the global propagating wave represents a new paradigm for the el nino southern oscillation enso global distributions of the phase velocities for this global enso wave finds covarying slp and st anomalies propagating eastward along the mean path of the intertropical convergence zone itcz with the global zonal wavenumber 1 2 component taking 4 6 years to cross the tropical indian pacific and atlantic oceans at a zonal average speed of 90 60 longitude per year along this path the interannual sst and slp anomalies are directly out of phase since thermocline depth anomalies underneath the itcz in the pacific ocean propagate westward white et al 1985 we view the global enso wave as a slow coupled sst wave trapped onto the itcz separating the global enso wave from the southern oscillation using complex empirical orthogonal function analysis finds the amplitude of the propagating wave to be half that of the standing wave with the former latter accounting for one third two thirds of the interannual variability in nino 3 sst and slp indices during the 1980s the global enso wave is shown to be responsible for the eastward propagation of covarying zonal surface wind and thermocline depth anomalies across the equatorial pacific ocean and through this mechanism is able to influence both the phasing and intensity of el nino examining the persistence of the global enso wave from 1900 to 1997 finds it and the intensity of el nino in the eastern equatorial pacific ocean modulated by interdecadal change both were strong weak or absent during decades of global tropical cooling warming

decadal to bi decadal rainfall variation in the western pacific a footprint of south pacific decadal variability 1 decadal to bi decadal rainfall variation in the western pacific during july october in the second half of the 20th century was identified in this study this 10 20 year quasi periodic oscillation was found associated with the leading sea surface temperature sst pattern in the south pacific which is called the 10 20 year south pacific inter decadal oscillation spdo it is suggested that the 10 20 year fluctuation of the spdo resulted in significant decadal to bi decadal rainfall variation along the western pacific coast the anomalous divergent circulations were likely driven by the ssta sst anomaly and resulted in the anomalous rainfall in eastern australia and the maritime continent it is conjectured that the ssta in the western south pacific led to an anomalous hadley like circulation in the western pacific and indirectly affected the convection activity in the philippine sea which in turn impacted the rainfall in the philippines taiwan and korea

tornillo type seismic signals at galeras volcano colombia 1992 1993 abstract unusual low frequency seismic events called tornillos screws at the observatorio vulcanologico y sismologico de pasto ovsp have been observed at galeras volcano during 1992 1993 of six eruptions that occurred between july 1992 and june 1993 five were preceded by episodes of tornillo signals these signals are characterized by 1 a waveform having a homogeneous distribution of frequencies 2 a long coda lasting up to several minutes 3 a small amplitude compared to the duration and 4 a slow decay of the coda the tornillo signals have been grouped into thirteen principal forms the 1992 1993 tornillos showed four main periods of occurrence each of which was followed by an eruption episode i occurred from 11 to 16 july 1992 and consisted of nine events episode ii lasted from 23 december 1992 to 14 january 1993 with twenty events episode iii was observed from 13 february to 23 march 1993 with 74 events episode iv lasted from 10 april to 7 june 1993 with 109 events the seismic activity at galeras in april may 1993 was characterized mainly by the occurrence of tornillo signals the behavior of these signals was similar to that before previous episodes ending with eruptions these observations permitted us to forecast the 7 june 1993 eruption several days to weeks beforehand the occurrence of tornillos is the most important criterion for determining the probability of an eruption at galeras in the current period of reactivation the maximum daily number of tornillos and the longest duration of individual events occur near the end of each episode within an individual episode the durations of single events increase progressively near to the point of eruption a positive correlation is observed between the total number of pre eruptive tornillo signals during an episode and the volume of material ejected by the eruption these observations may suggest that the presence of tornillos is an indication of variations in the physical conditions between the fluid and the surrounding solid material within the volcano and they constitute an important tool for forecasting future eruptions at galeras

unusual low frequency volcanic seismic events with slowly decaying coda waves observed at galeras and other volcanoes abstract events with slowly decaying coda waves are observed in active andesitic volcanoes associated mainly with vulcanian type eruptions or large gas emissions however these signals are also recorded in some quiescent volcanoes these unusual signals are considered to be related to magmatic activity and generally occur beneath the active crater the signals have been observed to be a short term precursor galeras volcano colombia 1992 1993 asama yama volcano japan 1983 after eruption tokachi dake volcano japan 1989 during seismic swarms meakan dake volcano japan 1982 and during quiescence puracevolcano colombia 1994 1995 tarumai volcano japan 1970 1971 1975 spectral analysis reveals common characteristics for this type of signal the spectrum is characterized by one or several sharp frequency peaks fundamental frequencies are not affected by epicentral distance azimuth or travel time indicating a source effect the damping coefficient for coda waves ranges from 0 002 to 0 02 and is related to large values of the quality factor q c ranging from 250 to 25 respectively these parameters may be the result of large amounts of gas bubbles in the magma body

distribution and evolution of scalloped terrain in the southern hemisphere mars abstract scalloped depressions are a unique martian surface morphology found in the northern and southern hemisphere latitude dependent dust and ice rich surface mantles these features exhibit a distinct asymmetric north south slope profile characterized by steep pole facing scarps flat floors and gentle equator facing slopes we examined high resolution stereo camera hrsc images of the southern hemisphere to determine their longitudinal distribution which revealed that a majority of scalloped terrain is located in the region of the southern wall of the hellas basin and northern malea planum a detailed map of this area was produced where scallops were found to contour the southern wall of the basin and where the ice rich mantle was seen to be thickest scalloped terrain is concentrated along the topographic highs near the amphitrites and peneus paterae and areal extent and depth decreases with increasing depth into the basin we also examined existing hypothesis for the formation and evolution of scalloped depressions using high resolution imaging science experiment hirise images and data from the thermal emission imaging system infrared themis ir and the thermal emission spectrometer tes our approach provides regional context for the development of scalloped terrains within the southern hemisphere and offers detailed evidence of scallop depressions forming around small cracks presumably caused by thermal contraction morphometric measurements show that scalloped depressions can be as much as 40 m deep with typical depths of between 10 and 20 m our observations of scallop formation and development in the southern hemisphere support a solar insolation model proposed by previous researchers e g morgenstern a hauber e reiss d van gasselt s grosse g schirrmeister l 2007 j geophys res 112 citeid e06010 lefort a russell p s thomas n mcewen a s dundas c m kirk r l 2009a j geophys res 114 e04005 lefort a russell p s thomas n 2009b icarus in press observations made using hirise images suggest that scalloped depressions most likely form from small cracks in the mantle which become larger and deeper through sublimation of interstitial ice from within the mantle sublimation is likely enhanced on equator facing slopes because of increased solar insolation which accounts for the asymmetric slope profile and hemispherical orientation and is demonstrated by themis ir images we suggest that sublimation lag deposits can possibly be removed by dust devils or strong slope winds related to the hellas basin offering an explanation as to why scalloped terrain is so abundant only in this area of the southern hemisphere daytime maximum summer temperatures suggest that sublimation in the study area of malea planum is possible under current conditions if the sublimation lag is removed while it cannot be ruled out that scalloped terrain in malea planum is presently evolving we attribute the extensive distribution to geologically recent obliquity excursions when conditions were more conducive to mesoscale modification of the ice rich mantle

sea surface temperature induced cyclogenesis in the antarctic circumpolar wave 1 an antarctic circumpolar wave acw of 3 to 4 year period propagated eastward around the southern ocean in covarying sea surface temperature sst and sea level pressure slp anomalies from 1983 through 1992 composed of two wavelengths that circled most of the global ocean along the midlatitude storm track near 40 s in this acw positive sst anomalies drove upward latent heat flux positive precipitation pcp and mid to upper level diabatic heating anomalies in the troposphere the latter balanced principally by the cooling tendency from deep convection white and chen 2002 one hypothesis has the anomalous pcp and deep convection in this acw arising from that in more frequent and or stronger extratropical cyclones in the synoptic storm aggregate here we verify this hypothesis finding negative slp anomalies in this acw collocated with positive extratropical cyclone intensity eci and extratropical cyclone density ecd anomalies in the annual synoptic storm aggregate because individual extratropical cyclones are 3 to 4 times smaller than slp anomalies in the acw their density and intensity appear to be modulated by anomalous zonal sst gradients in the acw these results are corroborated by finding greater interannual pcp anomalies over southeast australia collocated with positive sst anomalies occurring on the eastern side of covarying negative slp and positive eci and ecd anomalies in the acw along the mid latitude storm track because positive interannual pcp anomalies over southeast australia derive from the integral of rainfall from more dense and or intense extratropical cyclones in the aggregate the same is true for the acw propagating eastward along the midlatitude storm track over the remainder of the southern ocean

outwash plains and thermokarst on mars abstract the spatial distribution of different types of rampart craters on mars suggests a hemispheric asymmetry in the distribution of ground ice the northern plains especially major topographic depressions near the terminations of outflow channels have high percentages of rampart craters two of these basins acidalia and utopia planitiae received extraordinarily large amounts of water and sediment from the chryse and elysium outflow channels in both regions the analysis of high resolution viking pictures 12 m pixel indicates a concentration of kilometer scale depressions that are similar in size and form to thermokarstic features in yakutia siberia and parts of the arctic coastal plain of north america accordingly we infer that 1 utopia planitia and acidalia planitia may contain thick laterally continuous ice rich sedimentary deposits related to outflow channel forming floods and 2 these areas of mars may have experienced thermokarstic processes similar to modern thermokarstic processes in some periglacial regions of earth

tropical pacific high latitude south atlantic teleconnections as seen in δ18o variability in antarctic coastal ice cores 1 we use a network of eight ice cores from coastal dronning maud land dml antarctica to examine the role of the tropical enso el nino southern oscillation in the temporal variability of 18o in annual accumulation the longest record from the s100 ice core covering the period 1737 1999 is used to analyze the teleconnections between the tropical pacific and coastal dml on decadal scales and longer a shorter stacked coastal dml 18o series spanning 1955 1999 is constructed to assess the variability of enso teleconnection on interannual scales results suggest that on typical enso timescales of 2 6 years the strength of the teleconnection varies in time being stronger for years with generally negative phase of the southern annular mode sam on the timescales of approximately two decades bidecadal positive isotope anomalies are associated with oceanic warming and a westward sea surface temperature sst gradient in the equatorial pacific bidecadal variability in sam forced by the tropical pacific is proposed as a critical element in the teleconnection our analysis suggests that a multidecadal positive trend in the annual mean 18o values from the analyzed cores can be indicative of the atmospheric warming that begun in this part of the dml already in the 1910s the trend in 18o quantified in terms of long term surface air temperature sat changes is consistent with the instrumental data yet we speculate that the accurate estimation of sat trends requires an assessment of the potential role of secular sam and sea ice extent changes in shaping the isotopic signal

a model of degassing at galeras volcano colombia 1988 1993 galeras volcano reactivated in early 1988 as evidenced by increased seismicity gas emissions and fumarole temperatures and had a series of explosive eruptions in may 1989 during 1989 1990 the volcano was characterized by high so 2 flux reaching 5000 t metric tons day this period of strong degassing was followed by upward movement of magma july september 1991 and the emplacement of a lava dome october november 1991 since november 1991 long period seismicity and so 2 flux have decreased indicating that the conduit has partially sealed itself probably by crystallization and solidification of the magma on july 16 1992 the dome was destroyed by an explosion consistent with pressurization due to sealing and degassing in a nonporous medium continued pressurization beneath the volcano is indicated by eruptions on january 14 march 23 april 4 april 13 and june 7 1993 glass inclusion and matrix glass analyses support a hypothesis of significant magma degassing at depth in the magma chamber and in the conduit this degassing has reduced the h 2 o s and cl contents of the magma but the f content appears to have increased due to crystallization of anhydrous mineral phases and to the low fluid melt partition coefficient for f despite its degassed state galeras is currently a dangerous volcano because the sealing process forces gas saturated magma to release volatile components into confined spaces thereby causing pressurization and explosive eruptions

a quasi biennial signal in western us hydroclimate and its global teleconnections on interannual time scales quasi cyclic activity in the troposphere is generally thought to arise from chaotic feedback processes and therefore to be unpredictable in nature here evidence is presented for periodic clockwork climate behavior seen as a stable quasi biennial qb oscillation in western us winter precipitation estimated at a period of 2 16 0 05 years in the western us the qb precipitation mode has an influence comparable to that of enso with strongest effects observed at central latitudes of the region the oscillation displays systematic phase shifting with respect to the annual cycle signifying a stable nonseasonal and strongly periodic qb mechanism the cycle in precipitation results proximally from a meridional standing pressure wave over the north american pacific coast analysis of monthly pressure data confirms the nonseasonal periodic character of the oscillation which appears to have maintained phase from the mid 20th century to recent years the regional qb pressure cycle is traced to a quasi synchronous pulsation of meridional pressure waves in the extratropics of both hemispheres termed a biennial annular mode oscillation bamo the bamo oscillates in quadrature with a weaker 26 month signal in the tropical southern oscillation due to a shorter period both oscillations operate independently of the stratospheric quasi biennial oscillation qbo

global scale modes of surface temperature variability on interannual to century timescales using 100 years of global temperature anomaly data we have performed a singular value decomposition of temperature variations in narrow frequency bands to isolate coherent spatio temporal modes of global climate variability statistical significance is determined from confidence limits obtained by monte carlo simulations secular variance is dominated by a globally coherent trend with nearly all grid points warming in phase at varying amplitude a smaller but significant share of the secular variance corresponds to a pattern dominated by warming and subsequent cooling in the high latitude north atlantic with a roughly centennial timescale spatial patterns associated with significant peaks in variance within a broad period range from 2 8 to 5 7 years exhibit characteristic el nino southern oscillation enso patterns a recent transition to a regime of higher enso frequency is suggested by our analysis an interdecadal mode in the 15 to 18 years period range appears to represent long term enso variability this mode has a sizeable projection onto global average temperature and accounts for much of the anomalous global warmth of the 1980s a quasi biennial mode centered near 2 2 years period and a mode centered at 7 to 8 years period both exhibit predominantly a north atlantic oscillation nao temperature pattern a potentially significant decadal mode centered on 11 to 12 years period also exhibits an nao temperature pattern and may be modulated by the century scale north atlantic variability

spatial and temporal correlation between coda q and seismicity in china a map of coda q at 1 hz q was constructed for china by analyzing more than 1000 seismograms from 80 seismic stations distributed throughout china the resultant contour map of q shows a strong correlation with the epicenters of historic great earthquakes in china the high q regions are devoid of the epicenters and the low q regions are full of them a remarkably linear relation was found between the logarithm of coda q and the maximum earthquake within the area sampled by coda waves radius of about 150 km from each station when we consider earthquakes which occurred from 1700 to present roughly speaking if q is 1000 m max is about 4 and if q is 100 m max is about 8 this relation will be very useful for siting critical facilities such as nuclear power plants and waste disposal sites we also found evidence in support of the migration of low q region coincident with the well known migration of high seismicity region over the distance of several hundred kilometers during the period of several hundred years if the migration is due to a diffusion process the diffusion constant is of the order of 100 km2 yr which agrees very well with those associated with the aftershock migration fluid injection and vp vs anomaly comparison of coda q with q1 estimated from the intensity data shows that they agree very well for q1 150 supporting the validity of the s to s single backscattering model for coda waves for q1 150 however coda q becomes constant independent of q1 this behavior is qualitatively consistent with numerical experiments of frankel and clayton and suggests that coda q may be measuring the intrinsic q of about 150 for these regions where q1 150 this limiting coda q value may depend on regions because coda q lower than 100 has been observed in some active regions in this study and also coda q as low as 30 to 40 has been reported in california mexico and italy

regionalization of crustal coda q in the continental united states a contour map of crustal q sub 0 values for the entire united states is presented based on a scattering model to explain the coda waves of local and near regional earthquakes these coda q sub 0 values are in good agreement with q of lg waves data are obtained from over 250 local earthquakes with most magnitudes between 3 0 and 5 0 recorded by 25 wwssn and 27 lrsm stations throughout the continental united states these two sets of data provide a range of frequencies from 0 5 to 3 5 hz a frequency dependence of q is observed in the range of frequencies considered a power law dependence of the form q q sub 0 f f sub 0 sup eta is assumed the value of frequency dependence eta is found to be maximum in the tectonically active western united states and least in the stable regions of the central and south central united states the lowest q sub 0 values are obtained in the western united states with values ranging from 140 to 200 in the coastal plains average crustal q sub 0 values for the basin and range province vary from 200 to 300 increasing gradually to 400 in the colorado plateau region q sub 0 valuesmore in the columbia plateau vary from 200 to 400 q sub 0 values increase very rapidly along the central and southern rocky mountains from 400 to 800 east of the rocky mountains q sub 0 values increase gradually in the interior plains to a maximum value of around 1300 in the mississippi embayment region farther east q sub 0 values decrease gradually to an almost constant value of 1000 along the appalachian mountains coastal regions of eastern and northeastern united states have a crustal q sub 0 value between 900 to 700 regions of north central and gulf coastal plains show low q sub 0 values ranging from 600 to 400 and less the source factor b f sub p a measure of the intensity of scattering was obtained for several different regions of the continental united states regions of high q sub 0 values exhibit low intensity of scattering less

possible pingos and a periglacial landscape in northwest utopia planitia hydrostatic closed system pingos are small elongate to circular ice cored mounds that are perennial features of some periglacial landscapes the growth and development of hydrostatic pingos is contingent upon the presence of surface water freezing processes and of deep continuous ice cemented permafrost other cold climate landforms such as small sized polygonal patterned ground also may occur in the areas where pingos are found on mars landscapes comprising small elongate to circular mounds and other possible periglacial features have been identified in various areas including utopia planitia where water is thought to have played an important role in landscape evolution despite the importance of the martian mounds as possible markers of water most accounts of them in the planetary science literature have been brief and or based upon viking imagery we use a high resolution mars orbiter camera image eo300299 and superposed mars orbiter laser altimeter data tracks to describe and characterise a crater floor landscape in northwest utopia planitia 64 8 n 292 7 w the landscape comprises an assemblage of landforms that is consistent with the past presence of water and of periglacial processes this geomorphological assemblage may have formed as recently as the last episode of high obliquity a similar assemblage of landforms is found in the tuktoyaktuk peninsula of northern canada and other terrestrial cold climate landscapes we point to the similarity of the two assemblages and suggest that the small roughly circular mounds on the floor of the impact crater in northwest utopia planitia are hydrostatic pingos like the hydrostatic pingos of the tuktoyaktuk peninsula the origin of the crater floor mounds could be tied to the loss of ponded local water permafrost aggradation and the evolution of a sub surface ice core

evidence for recent climate change on mars from the identification of youthful near surface ground ice ground ice in the crust and soil may be one of the largest reservoirs of water on mars1 2 3 near surface ground ice is predicted to be stable at latitudes higher than 40 ref 4 where a number of geomorphologic features indicative of viscous creep and hence ground ice have been observed5 mid latitude soils have also been implicated as a water ice reservoir6 the capacity of which is predicted to vary on a 100 000 year timescale owing to orbitally driven variations in climate7 it is uncertain however whether near surface ground ice currently exists at these latitudes and how it is changing with time here we report observational evidence for a mid latitude reservoir of near surface water ice occupying the pore space of soils the thickness of the ice occupied soil reservoir 1 10 m and its distribution in the 30 to 60 latitude bands indicate a reservoir of 1 5 6 0 104 km3 equivalent to a global layer of water 10 40 cm thick we infer that the reservoir was created during the last phase of high orbital obliquity less than 100 000 years ago and is now being diminished

ice rich periglacial vs icy glacial depressions in the argyre region mars a proposed cold climate dichotomy of landforms on mars so called scalloped depressions are widely observed in utopia planitia up and malea planum mp typically they are rimless metres to decametres deep incised sharply tiered inwardly polygonised and sometimes pitted the depressions seemingly incise terrain that is icy and possibly thermokarstic i e produced by the thermal destabilisation of the icy terrain agewise the depressions are thought to be relatively youthful originating in the late amazonian epoch here we report the presence of similar depressions in the argyre region ar 30 60 s 290 355 e more importantly we separate and differentiate these landforms into two groups ice rich periglacial depressions type 1 and icy glacial depressions type 2a c this differentiation is presented to the mars community for the first time based on a suite of morphological and geological characteristics synonymous with ice complexes in the lena peninsula eastern russia and the tuktoyaktuk coastlands northwest territories canada we propose that the type 1 depressions are ice rich periglacial basins that have undergone volatile depletion largely by sublimation and as the result of thermal destabilisation in keeping with the terms and associated definitions derived of terrestrial periglacial geomorphology ice rich refers to permanently frozen ground in which ice lenses or segregation ice collectively referenced as excess ice have formed we suggest that the depressions are the product of a multi step cold climate geochronology 1 atmospheric precipitation and surface accumulation of an icy mantle during recent high obliquities 2 regional or local triple point conditions and thaw evaporation of the mantle either by exogenic forcing i e obliquity driven rises of aerial and sub aerial temperatures or endogenic forcing i e along argyre impact related basement structures 3 meltwater migration into the regolith at least to the full depth of the depressions 4 freeze thaw cycling and the formation of excess ice 5 sublimation of the excess ice and depression formation as high obliquity dissipates and near surface ice becomes unstable the type 2 depressions exhibit characteristics suggestive of supra glacial dead ice basins and snow ice suncups observed in high alpine landscapes on earth e g the swiss alps and the himalayas like the type 1 depressions the type 2 depressions could be the work of sublimation however the latter differ from the former in that they seem to develop within a glacial like icy mantle that blankets the surface rather than within an ice rich and periglacially revised regolith at near the surface interestingly the type 2 depressions overlie the type 1 depressions at some locations if the periglacial glacial morphological and stratigraphical dichotomy of depressions is valid then this points to recent glaciation at some locations within the ar being precursed by at least one episode of periglaciation this also suggests that periglaciation has a deeper history in the region than has been thought hitherto moreover if the hypothesised differences amongst the argyre based depressions are mirrored in utopia planitia and malea planum then perhaps this periglacial glacial dichotomy and its associated geochronology are as relevant to understanding late period landscape evolution in these two regions as it is in the ar

14c ages and activity for the past 50 ka at volcan galeras colombia abstract volcan galeras is the southernmost colombian volcano with well recorded historic activity the volcano is part of a large and complex volcanic center upon which 400 000 people live historic activity has centered on a small volume cone inside the youngest of several large amphitheaters that breach the west flank of the volcano away from the city of pasto population 300 000 lava flows sio2 between 54 6 and 64 7 wt have dominated activity for more than 1 ma but explosive events have also occurred joint studies by volcanologists from colombia ecuador peru bolivia argentina and the united states produced 24 new14c ages and more than 100 stratigraphic sections to interpret the past 50 ka of activity at galeras including sector collapse events the youngest collapse event truncated 12 8 ka lava flows and may have occurred as recently as 8 to 10 ka tephra fall material rapidly thins and becomes finer away from the vent area the only widespread marker in the

coda wave attenuation imaging of galeras volcano colombia abstract the spatial variation of s wave coda attenuation in the galeras volcano region is analyzed the study region is at present an active magmatic system situated in the southwestern colombian andes is estimated using seismograms from 435 volcano tectonic earthquakes recorded at 31 stations of the galeras seismograph network is then imaged using a 3d spatial stacking procedure the technique is based on the assumption of uniform distribution of over a spheroidal shell with its volume determined by the associated source receiver distance the resultant tomograms also show frequency dependence which is interpreted in terms of the scale of the heterogeneities producing the scattering high attenuation anomalies are detected at high frequencies synthetic tests indicate the validity of the inversion technique

deposition and degradation of a volatile rich layer in utopia planitia and implications for climate history on mars 1 we investigate the surface morphology of a study area in western utopia planitia mars which is characterized by a variety of landforms that resemble those of terrestrial periglacial landscapes polygonally fractured ground and thermokarst like depressions are found to be located in a young mantling deposit with a thickness of several tens of meters we observe a latitudinal dependence of the degradation of this mantling deposit larger depressions whose floors reveal the underlying basement rocks cover a higher fraction of the total terrain in the southern part of the study area than in the northern part indicating a more intense degradation of the mantle in the south all depressions have an asymmetric cross section in north south direction interpreted to be the result of the different solar radiation on differently oriented slopes on the basis of our morphological observations we develop a conceptual model for landscape evolution in western utopia planitia it involves subaerial deposition of a layered ice rich mantle and its subsequent degradation by polygon formation and sublimation a terrestrial analog to the polygonally fractured mantling deposit and its thermokarst like depressions is the siberian ice complex or yedoma which consists of subaerial ice rich deposits and is connected to nonglaciated landscapes with highly continental cold climatic environmental conditions our comparison suggests that no unusual or exotic processes need to be invoked to explain the current morphology of western utopia however the young age of the deposition and degradation implies climatic excursions in the very recent past on mars

thermokarst processes and the origin of crater rim gullies in utopia and western elysium planitia abstract we have identified a number of gullies that could be aqueous in origin near or at the rim of several impact craters in utopia planitia and western elysium planitia 30 0 59 0 n 241 0 291 0 w based on the sharpness of their incisions and the general absence of superposed craters we ascribe a relatively recent origin to the gullies scalloped depressions are commonplace throughout the region as well as on the crater walls rims and floors near the areas of gully issuance occasionally the depressions cross cut the gully debris aprons suggesting that the formation of some depressions is even more recent than that of the gullies previous research has proposed that the depressions are collapse basins formed by thermokarst processes on earth thermokarst landforms occur in areas of low gradient topography where the permanently frozen ground permafrost is ice rich and has undergone a change in thermal equilibrium this change can be triggered by long term or episodic cyclic climate change and accompanying rises in mean temperatures towards 0 c as well as by rises in seasonally sustained summer temperatures well above 0 c in order to explain the origin of the rim or near rim gullies we invoke high obliquity and the possibility that this region of mars experienced obliquity driven rises in temperature atmospheric pressure and humidity sufficient to keep surface water and near surface ground ice stable for extended periods of time we propose that gully formation is closely related to local freeze thaw processes that in turn generate a thermokarst landscape of which the gullies are a part this geological and climatological scenario comprises the following steps 1 an inundation of meltwater at high obliquity due to the thawing of an atmospherically deposited snowpack or ice sheet and the subsequent saturation of the underlying regolith to tens of metres of depth 2 loss of water on the surface perhaps as obliquity decreases slightly followed by the progressive freezing of the saturated regolith this creates an aggrading mass of ice rich regolith 3 obliquity induced temperature rises that engender the thaw drainage and partial evaporation of the near surface ice rich regolith 4 localised formation of thermokarst collapse basins alases as water is evacuated from these basins 5 formation of gullies near or at some impact crater rims as the result of meltwater migration from nearby alases through the thawed regolith to the areas of gully issuance although the plains materials in this region are in part very old possibly hesperian or even noachian the mantling deposits and their deformation by thermokarst processes appears to be relatively young this suggests that recent climatic conditions could have been episodically warmer and wetter than had been previously thought