summary of the results from the lunar orbiter laser altimeter after seven years in lunar orbit in june 2009 the lunar reconnaissance orbiter lro spacecraft was launched to the moon the payload consists of 7 science instruments selected to characterize sites for future robotic and human missions among them the lunar orbiter laser altimeter lola was designed to obtain altimetry surface roughness and reflectance measurements the primary phase of lunar exploration lasted one year following a 3 month commissioning phase on completion of its exploration objectives the lro mission transitioned to a science mission after 7 years in lunar orbit the lola instrument continues to map the lunar surface the lola dataset is one of the foundational datasets acquired by the various lro instruments lola provided a high accuracy global geodetic reference frame to which past present and future lunar observations can be referenced it also obtained high resolution and accurate global topography that were used to determine regions in permanent shadow at the lunar poles lola further contributed to the study of polar volatiles through its unique measurement of surface brightness at zero phase which revealed anomalies in several polar craters that may indicate the presence of water ice in this paper we describe the many lola accomplishments to date and its contribution to lunar and planetary science

fluid dynamics of oceanic thermocline ventilation abstract a flux form of the potential vorticity pv equation is applied to study the creation and transport of potential vorticity in an ocean gyre generalized pv fluxes j vectors and the associated pv flux fines are used to map the creation by buoyancy forcing of pv in the mixed layer and its transport as fluid is subducted through the base of the mixed layer into the thermocline the pv flux lines can either close on themselves recirculation or begin and end on the boundaries ventilation idealized thermocline solutions are diagnosed using j vectors which vividly illustrate the competing process of recirculation through western boundary currants and subduction from the surface potential vorticity flux vectors are then used to quantify the flux of mass passing invisidly through a surface across which potential vorticity changes discontinuously but at which potential density and velocity are continuous such a surface might be the base of the oceanic mixed layer or in a meteorological context

a viscoelastic coupling model for the cyclic deformation due to periodically repeated earthquakes at subduction zones vertical displacements due to periodic reverse faulting events in an elastic plate overlying a viscoelastic maxwell half space are obtained and compared with the observed deformation cycle coseismic strain release postseismic transients interseismic strain accumulation from japan the viscoelastic effects including the influence of buoyant restoring forces are obtained using the method developed by rundle and plate convergence and strain accumulation are incorporated following the procedure suggested by savage the resulting deformation cycle is compared with that of an analogous elastic half space dislocation model in which postearthquake effects are due to transient aseismic slip below the coseismic fault cyclic deformation is similar but not identical for the two models and observations from southwest japan suggest the superiority of the viscoelastic coupling model in particular inclusion of the effects of steady state flow in the asthenosphere overcomes a defect of the elastic half space model and results in agreement with the observed interseismic movement pattern several aspects of the postseismic deformation its landward migration and its transition to the interseismic phase of the cycle are explained as well but the short duration of near trench transients relative to those observed farther inland is not matched the success of a buried slip model in explaining early postseismic near trench movements and asthenospheric flow in accounting for cumulative postearthquake transient motions suggests the existence of a transition zone between lithosphere and asthenosphere whose behavior is brittle elastic in the short term and ductile for longer term deformation and such a modification may reconcile remaining discordant observations however reasonable variations in coupling model parameters cannot account for observed differences in the deformation cycle in other parts of japan and these regional differences remain unexplained

seismic structure of the northeastern japan convergent margin a synthesis many studies recently made on the basis of seismic observations have revealed a detailed structure of the crust and the upper mantle beneath the northeastern japan arc and its relationship to seismic and volcanic activity spatial distributions of the depths to the conrad and the moho discontinuities estimated from shallow earthquake data and seismic explosion data show that both discontinuities are deep in the middle of the land area and shallow toward the coastlines of the japan sea and the pacific ocean the pn velocity has a lateral variation it is as low as 7 5 km s beneath the land area while that beneath the japan sea and the pacific ocean is 8 0 8 2 km s it changes abruptly at the transition zones which are located along the coastlines precise structure and location of the subducted pacific plate beneath the land area is inferred from converted or reflected seismic waves at the top or bottom of the plate the pacific plate is composed of a thin 5 km low velocity upper layer and a thick high velocity lower layer its total thickness being 80 90 km the upper plane seismicity of the double seismic zone is confined to the thin low velocity upper layer which probably corresponds to the subducted former oceanic crust the lower plane seismicity lies at the middle of the high velocity lower layer and the lower half of the plate below it is incapable of generating earthquakes the shallower portion of the upper surface of the plate beneath the pacific ocean along which major seismicity with low angle thrust faultings is actually occurring is also located by seismic observations on land and in the sea the pacific plate subducts at an extremely low angle of 5 for the first 25 km depth and then the dip steepens rather abruptly to 30 normal fault type events at the top of the plate have not been detected in the portion where the downward bending is the largest but have been ditected near the trench axis where it is rather small tomographic inversions for seismic velocity structure clearly delineate the inclined high velocity pacific plate with a thickness of 80 90 km and low velocity zones in the crust and the mantle wedge beneath active volcanoes seismic attenuation tomography also shows similar zones of low q value beneath active volcanoes although its spatial resolution is much lower the low velocity zones with 2 6 velocity lows are continuously distributed from the upper crust just beneath active volcanoes to a depth of 100 150 km in the mantle wedge and are approximately parallel to the dip of the underlying pacific plate these low velocity zones probably reflect the pathway of magma ascent from a depth in the mantle wedge to the earth s surface corresponding to a portion of the subduction induced secondary mantle wedge flow

the stress state implied by dislocation models of subduction deformation dislocation models of the earthquake cycle are often employed to predict surface deformations above a subduction zone however these models being based entirely on a kinematic formulation of subduction behaviour place no constraints on the subsurface stress field here the stress state predicted by an elastic dislocation model is shown to exhibit characteristics inconsistent with those anticipated based on physical models of subduction behaviour in particular the model predicts an unreasonable distribution of stress along the interface between the overriding and subducting plates the net shear traction integrates to zero along the interface so significant shear must act on the overriding plate in the updip direction opposite to that of the relative direction of motion of the subducting slab quantitative calculations using an elastic half space representation of the earth are employed to illustrate the inconsistencies inherent in the dislocation model analytic expressions for this case are extended to allow for calculation of the stress components over the entire half space

subduction zones an introduction to comparative subductology abstract the subduction model for trench arc back arc systems was deduced more or less as a logical consequence of sea floor spreading many features in these systems such as thrust type inter plate earthquakes and deep earthquakes along wadati benioff zones are readily explained by the subduction model but other features such as extensional spreading and high heat flow in back arc regions and arc volcanism are difficult to explain an approach to solve these problems may be to recognize the existence of the two basically different modes of subduction one chilean type causing a compressional stress regime in the arc and back arc regions the other mariana type causing a tensional stress regime implications of the two types of the mode of subduction for some tectonic problems such as vertical movement and sediment accretion at trenches are discussed with special reference to the results of recent dsdp active margin drilling in discussing the possible causes of the two modes it is suggested that the large scale thermal and stress regimes in the back arc areas may not be the direct products of simple subduction but of some additional factors involving much greater energy such as mantle flow associated with the motion of major plates finally the possible great importance of various types of collision accretion and erosion at subduction zones is emphasized

persistently illuminated regions at the lunar poles ideal sites for future exploration abstract the lunar reconnaissance orbiter camera lroc provides multi temporal and high resolution imaging of the north and south polar regions these images delimit illuminated areas from those in shadow and are used to analyze the illumination environment of the polar regions over the course of a lunar year the wide angle camera wac provides repeat imaging of the north and south pole at a frequency of roughly 2 h with a ground sampling distance of 100 m the lroc narrow angle camera nac acquires images with a ground sampling distance of 0 5 2 0 m providing the means to construct high resolution maps that reveal illuminated terrain under varying lighting conditions with the multi temporal coverage provided by the wac and the high resolution images from the nac the lroc dataset enables a more comprehensive analysis of the illumination conditions near the lunar poles than any previous image based dataset furthermore these images are used to validate previously published numerical models that simulate polar illumination conditions from our analysis of the lroc images we identified localized regions where the lunar surface remains illuminated for nearly 94 of the year with the longest eclipsed period lasting only 43 h we also identified small illuminated peaks tens of meters across in areas previously modeled to be in shadow together the wac and nac dataset provide direct high resolution observations of the actual surface illumination environment of potential exploration sites near the lunar poles

mapping and characterization of non polar permanent shadows on the lunar surface abstract we present the first globally complete inventory of permanent shadows on the lunar surface that are detectable with the current global instrument datasets including discovery of regions with persistent shadows over geologic time periods as close to the equator as 58 of latitude these results were obtained through application of a ray tracing technique to the latest global topographic datasets from the lunar reconnaissance orbiter our analysis reveals that 13 361 km2 of surface in the northern hemisphere and 17 698 km2 in the southern hemisphere are permanently shadowed we present maps showing the locations of all the permanent shadows detectable using these datasets then turn our focus toward the permanent shadows farthest from the poles each permanent shadow on the equator side of 65 of latitude is shown in detail surface brightness temperature data derived from the diviner mid infrared radiometer on board the lunar reconnaissance orbiter have been analyzed for four of these locations and found to have mid day temperatures 75 120 k less than nearby comparison locations that experience direct daytime illumination in some cases the permanently shadowed locations have nighttime temperatures 10 25 k lower than surroundings the temperature results support our finding that these non polar craters are permanently shadowed the surface brightness temperature results also raise interesting questions about their ability to cold trap volatiles discovery of these non polar permanently shadowed regions increases possible locations of water resources and high priority exploration targets on the moon

thermal constraints on the seismogenic portion of the southwestern japan subduction thrust for coastal cities an important factor in earthquake hazard from subduction zone earthquakes is the landward extent of the seismogenic portion of the subduction thrust fault in this study we test the hypothesis that the maximum downdip extent is defined by a critical temperature we have developed a transient thermal model for the nankai subduction zone of southwest japan to allow comparison of the thermally estimated downdip extent of the seismogenic zone with that from 1 seismicity and tsunami data for two great subduction earthquakes 2 the coseismic faulting extent of these events estimated from geodetic deformation data and 3 the interseismic locked zone determined from interseismic geodetic data the nankai margin has extensive heat flow and heat production data to control thermal models and thus crustal temperatures it has earthquake tsunami and geodetic data that constrain the coseismic rupture portion of the subduction thrust fault for past great earthquakes and the portion of the thrust fault that is locked and storing interseismic elastic strain on the nankaido margin off shikoku island the thermal model indicates that a temperature of 350 c taken to be the limit for seismic initiation from laboratory and field data is reached on the subduction thrust fault 150 km from the trench a transition zone into which rupture may extend with decreasing offset taken to be 450 c extends an additional 45 km downdip the thermal model results are in excellent agreement with the maximum downdip extent of coseismic displacement for the 1946 nankaido ms 8 2 earthquake off shikoku island and with the downdip extent of the present locked zone in the region of the 1944 tonankai ms 8 2 earthquake to the northeast the subduction angle is much steeper and the thermal models indicate a narrower downdip seismogenic extent the seismogenic locked zone from earthquake and geodetic data is also narrower thus our analysis of the southwest japan margin indicates that all three constraints on the downdip extent of the seismogenic zone thermal coseismic and interseismic geodetic data are in general agreement the study also supports the hypothesis that the seismogenic portion of subduction thrust faults is limited primarily by temperature the thermal control implies that subduction thrust faults with shallow dip have wider seismogenic zones compared to those with steep dip the subducting plate age and thus heat flow and the thickness of the insulating sediments on the incoming plate are also very important to the thermal regime and thus to the seismogenic width the relation of the maximum seismic rupture area to the interseismic locked zone is particularly important for earthquake hazard estimation on subduction margins such as cascadia where there have been no great historical events

cooling spirals and recirculation in the subtropical gyre abstract the influence of cooling in a western boundary current on the recirculation of parcels in the subtropical gyre and their eventual transfer into the subpolar gyre is investigated it is shown that heat loss to the atmosphere and the resulting vertical convection of dense water in the gulf stream of a general circulation primitive equation model forces a counterclockwise spiral of the velocity vector with depth a cooling spiral parcels that pass through this region of cooling are forced to cross under the upper level trajectories from south to north in opposite sense to the beta spiral experienced in the interior of the subtropical gyre this crossing of trajectories is an important consequence of the cooling in the western boundary current as it influences both scale and structure of the subtropical gyre recirculation a simple expression is derived that relates the spatial scale of the recirculation to the cooling rate in the western boundary current and the wind forcing in the subtropical gyre

selection of the mars exploration rover landing sites 1 the selection of meridiani planum and gusev crater as the mars exploration rover landing sites took over 2 years involved broad participation of the science community via four open workshops and narrowed an initial 155 potential sites 80 300 30 km to four finalists based on science and safety engineering constraints important to the selection included 1 latitude 10 n 15 s for maximum solar power 2 elevation less than 1 3 km for sufficient atmosphere to slow the lander 3 low horizontal winds shear and turbulence in the last few kilometers to minimize horizontal velocity 4 low 10 m scale slopes to reduce airbag spin up and bounce 5 moderate rock abundance to reduce abrasion or strokeout of the airbags and 6 a radar reflective load bearing and trafficable surface safe for landing and roving that is not dominated by fine grained dust the evaluation of sites utilized existing as well as targeted orbital information acquired from the mars global surveyor and mars odyssey three of the final four landing sites show strong evidence for surface processes involving water and appear capable of addressing the science objectives of the missions which are to determine the aqueous climatic and geologic history of sites on mars where conditions may have been favorable to the preservation of evidence of possible prebiotic or biotic processes the evaluation of science criteria placed meridiani and gusev as the highest priority sites the evaluation of the three most critical safety criteria 10 m scale slopes rocks and winds and landing simulation results indicated that meridiani and elysium planitia are the safest sites followed by gusev and isidis planitia

a lagrangian method to isolate the impacts of mixed layer subduction on the meridional overturning circulation in a numerical model large differences in the atlantic meridional overturning circulation amoc exhibited between the available ocean models pose problems as to how they can be interpreted for climate policy a novel lagrangian methodology has been developed for use with ocean models that enables a decomposition of the amoc according to its source waters of subduction from the mixed layer of different geographical regions the method is described here and used to decompose the amoc of the centre national de recherches meteorologiques cnrm ocean model which is approximately 4 5 sv 1 sv 106 m3 s 1 too weak at 26 n compared to observations contributions from mixed layer subduction to the peak amoc at 26 n in the model are dominated by the labrador sea which contributes 7 51 sv but contributions from the nordic seas the irminger sea and the rockall basin are also important these waters mostly originate where deep mixed layers border the topographic slopes of the subpolar gyre and nordic seas the too weak model amoc can be explained by weak model representations of the overflow and of irminger sea subduction these are offset by the large labrador sea component which is likely to be too strong as a result of unrealistically distributed and too deep mixed layers near the shelf

the south pole region of the moon as seen by clementine the clementine mission has provided the first comprehensive set of high resolution images of the south pole region of the moon within 5 of latitude of the pole an area of an estimated 30 000 square kilometers remained in shadow during a full lunar rotation and is a promising target for future exploration for ice deposits the schrodinger basin 320 kilometers in diameter centered at 75 s is one of the two youngest least modified great multiring impact basins on the moon a large maar type volcano localized along a graben within the schrodinger basin probably erupted between 1 and 2 billion years ago

a dislocation model for the earthquake cycle at convergent plate boundaries summary a kinematic model for the earthquake cycle at convergent plate boundaries has been constructed on the basis of dislocation theory we model the lithosphere asthenosphere system by a stratified semi infinite medium under gravity consisting of an elastic surface layer an intervening layer with maxwell viscoelasticity and an elastic substratum the steady motion of plate convergence is naturally represented by uniform slip at a constant rate on the upper boundary of the descending oceanic plate the occurrence of interplate earthquakes is regarded as a perturbation of the steady state plate motion and represented by a periodic sequence of step slips on a finite seismic zone of the plate interface based on dislocation theory we can show that the steady slip on the interface deeper than the lithosphereasthenosphere boundary does not contribute to surface deformation in the steady state accordingly the surface deformation associated with the earthquake cycle is given by the superposition of viscoelastic responses to the steady slip on the interface shallower than the lithosphere asthenosphere boundary the steady backslip on the seismic zone and the periodic sequence of seismic slips we have computed cyclic patterns of vertical displacements at the free surface for two representative cases taking account of gravity effects the patterns of vertical displacements differ notably in the latter stage of the cycle depending on whether or not the seismic zone extends through the entire thickness of the lithosphere after the completion of one earthquake cycle our model yields a certain amount of permanent deformation resulting from the steady plate convergence the pattern of the permanent deformation that is characterized by steep uplift on the continental side sharp subsidence at the plate boundary and gentle uplift on the oceanic side is irrespective of the cyclic process of stress accumulation and release repeated on the seismic zone the earthquake cycle model developed here provides a possible explanation for the formation of earthquake origin marine terraces

interseismic uplift at the nankai subduction zone southwest japan 1951 1990 uplift as a function of time from 1951 through 1990 has been deduced from annual mean sea level measured at 15 tide gages along the nankai subduction zone southwest japan the recurrence interval for rupture of the nankai subduction zone is about 100 years and the most recent rupture was in late 1946 thus the 1951 1990 uplift record covers most of the first half of the earthquake cycle the precision of the uplift record is better than could be obtained currently by annual global positioning system gps measurements the pre 1960 uplift record shows rapid deformation that appears to terminate in 1959 after 1959 the uplift record is remarkably linear in time significant curvature in the uplift versus time plots is detected at only three of the 15 tide gages the inferred uplift rates are not quantitatively consistent with the predictions of either the viscoelastic coupling or elastic half space models of subduction but the agreement is sufficient to suggest that the causative physical mechanisms have been identified the immediate postseismic response is controlled by the propagation of slip downward along the downdip extension of the coseismic rupture and the interseismic response is caused by the accumulation of a slip deficit on the main thrust zone asthenosphere relaxation is not required to explain the observations

illumination conditions at the lunar polar regions by kaguya selene laser altimeter 1 the sunlit conditions of the lunar polar regions were estimated by using a digital elevation model made by the laser altimeter data onboard the japanese lunar orbiter kaguya selene the result shows that i there are no peaks of eternal light in either north or south polar regions ii most continuously lit surfaces are 89 for north and 86 for south iii there are permanently shadowed regions these information will be useful for the long durable landing experiments on the moon and possibly for the human activity on the moon in the near future

topography of the lunar poles from radar interferometry a survey of cold trap locations detailed topographic maps of the lunar poles have been obtained by earth based radar interferometry with the 3 5 centimeter wavelength goldstone solar system radar the interferometer provided maps 300 kilometers by 1000 kilometers of both polar regions at 150 meter spatial resolution and 50 meter height resolution using ray tracing these digital elevation models were used to locate regions that are in permanent shadow from solar illumination and may harbor ice deposits estimates of the total extent of shadowed areas poleward of 87 5 degrees latitude are 1030 and 2550 square kilometers for the north and south poles respectively

can eddies set ocean stratification abstract a simple theory is presented for the buoyancy anomaly and depth of penetration of a warm lens created by a surface buoyancy flux and ekman pumping in an initially homogeneous rotating fluid it is assumed that the overturning of isopycnals induced by pumping and differential heating balances the counteroverturning tendency of baroclinic instability baroclinic eddies not only develop on the stratified lens but also play a fundamental role in setting its stratification the theory is successfully tested against numerical and laboratory experiments in which the mechanically induced deepening of a buoyant lens is arrested by its baroclinic instability finally the possibility is discussed that the eddy transfer process studied here might play a role in setting the stratification and depth of the main thermocline in the ocean

initial observations from the lunar orbiter laser altimeter lola as of june 19 2010 the lunar orbiter laser altimeter an instrument on the lunar reconnaissance orbiter has collected over 2 0 10 9 measurements of elevation that collectively represent the highest resolution global model of lunar topography yet produced these altimetric observations have been used to improve the lunar geodetic grid to 10 m radial and 100 m spatial accuracy with respect to the moon s center of mass lola has also provided the highest resolution global maps yet produced of slopes roughness and the 1064 nm reflectance of the lunar surface regional topography of the lunar polar regions allows precise characterization of present and past illumination conditions lola s initial global data sets as well as the first high resolution digital elevation models dems of polar topography are described herein

understanding the structure of the subtropical thermocline closing a gyre with a western boundary current imposes a constraint on its vertical structure that requires there to be no net vertical flux of potential vorticity through any closed pressure contour in steady state this constraint resembles the traditional similarity balance for the internal thermocline with additional terms representing friction in the western boundary current and convection in the mixed layer the terms in the integral constraint are diagnosed in a planetary geostrophic ocean model and are used to understand the coexistence of ventilated and internal thermoclines within the subtropical gyre

illumination conditions of the lunar polar regions using lola topography abstract we use high resolution altimetry data obtained by the lunar orbiter laser altimeter instrument onboard the lunar reconnaissance orbiter to characterize present illumination conditions in the polar regions of the moon compared to previous studies both the spatial and temporal extent of the simulations are increased significantly as well as the coverage fill ratio of the topographic maps used thanks to the 28 hz firing rate of the five beam instrument we determine the horizon elevation in a number of directions based on 240 m resolution polar digital elevation models reaching down to 75 latitude the illumination of both polar regions extending to 80 can be calculated for any geometry from those horizon longitudinal profiles we validated our modeling with recent lunar reconnaissance orbiter wide angle camera images we assessed the extent of permanently shadowed regions psrs defined as areas that never receive direct solar illumination and obtained total areas generally larger than previous studies 12 866 and 16 055 km2 in the north and south respectively we extended our direct illumination model to account for singly scattered light and found that every psr does receive some amount of scattered light during the year we conducted simulations over long periods several 18 6 years lunar precession cycles with a high temporal resolution 6 h and identified the most illuminated locations in the vicinity of both poles because of the importance of those sites for exploration and engineering considerations we characterized their illumination more precisely over the near future every year a location near the shackleton crater rim in the south polar region is sunlit continuously for 240 days and its longest continuous period in total darkness is about 1 5 days for some locations small height gains 10 m can dramatically improve their average illumination and reduce the night duration rendering some of those particularly attractive energy wise as possible sites for near continuous sources of solar power

illumination conditions at the lunar south pole using high resolution digital terrain models from lola abstract the illumination conditions of the lunar south pole are investigated using a geometrically adjusted 20 m pixel digital terrain model dtm from laser tracks of the lunar orbiter laser altimeter lola several comparisons with narrow angle camera nac images have been made to cross validate the results illumination conditions were first evaluated over a region of 20 20 km over a one year period october 22 2018 october 22 2019 at surface level and 2 m above ground three potential landing sites are investigated in more detail a 19 year study covering the lunar precessional cycle was carried out at surface level 2 and 10 m above ground for a site found at connecting ridge the ridge connecting the shackleton and de gerlache crater this area was found to be an ideal site for future landing missions with respect to illumination conditions we identified locations receiving sunlight for 92 27 of the time at 2 m above ground and 95 65 of the time at 10 m above ground at these locations the longest continuous periods in darkness are typically only 3 5 days

illumination conditions at the lunar south pole recent remote sensing data strongly suggest that deposits of ice occur in permanently shadowed regions at the lunar poles clementine by providing the first contiguous coverage of the moon has enabled the production of an illumination map of the south pole this map shows the extent of the areas of permanent darkness during winter in this region as well as identifying places on the lunar surface that receive illumination for more than 50 of the lunar day the permanently dark areas are prime candidates for locations of ice deposits while regions that are illuminated for anomalous periods are possible sites for lunar bases in this paper we study in detail the illumination history during a lunar day of some of these sites while we find no area that receives permanent illumination we do find two areas only 10 km apart which collectively receive sunlight for over 98 of the time

strain accumulation in western washington the juan de fuca plate is subducted beneath the north american plate off the coast of washington at a rate of about 40 mm yr n68 e the average principal strain rates extension reckoned positive measured in northwestern washington are as follows olympic peninsula 25 km south of port angeles from 1982 through 1990 e 1 0 011 0 027 strain yr n31 e 6 6 and e 2 0 092 0 028 strain yr n59 w 6 6 and near seattle from 1972 through 1985 e 1 0 027 0 019 strain yr n22 e 6 4 and e 2 0 036 0 013 strain yr n68 w 6 4 both strain measurements are consistent with uniaxial contraction in the direction of plate convergence uplift rates inferred from tide gage recordings are about 4 mm yr on the pacific coast and near 0 mm yr farther inland near seattle these deformation rates are consistent with a model of the cascadia subduction zone in which the plate interface beneath the continental slope and outer continental shelf is locked but free to slip farther landward the limited downdip extent of the locked segment of the plate interface is consistent with a shallow depth 20 km of the isotherm 450 c that defines the brittle ductile transition small thrust events diagnostic of seismic subduction should then occur only offshore and at shallow depths the principal strain rates measured from 1972 through 1983 in the back arc region near richland washington are e 1 0 016 0 013 strain yr n03 w 34 and e 2 0 024 0 013 strain yr n87 e 34

a numerical model of the ventilated thermocline abstract a steady state numerical solution is found for an idealized rectangular ocean basin driven by wind and surface buoyancy flux a three dimensional primitive equation model is used in agreement with recent analytical modeling the thermocline in the numerical solution consists of three regions quite distinct in their ventilation characteristics forming the greater part of the subtropical thermocline is an unventilated pool zone located in the core of the subtropical gyre and a ventilated zone to the east the unventilated shadow zone lies farther east and toward the equator analysis of potential vorticity on constant density surfaces is used to study the structure of the thermocline a small but intense zone of convection located in the western boundary outflow caused by rapid heat loss to the atmosphere produces source water for the ventilated zone this water of extremely low potential vorticity mode water is distributed widely into the subtropical thermocline the pool forms equ

optimized traverse planning for future polar prospectors based on lunar topography abstract to fully understand the extensive collection of remotely sensed polar observations by the lunar reconnaissance orbiter and other recent lunar missions we must acquire an array of ground truth measurements a polar rover can sample and assay potential polar resources both laterally and at shallow depths to identify ideal least energy traverses for such a polar prospecting mission we developed a traverse planning tool called r traverse using a fundamental wheel regolith interaction model and datasets from the lunar reconnaissance orbiter camera lunar orbiter laser altimeter and diviner lunar radiometer experiment using the terramechanics model we identified least energy traverses at the 20 m scale around shackleton crater and located one traverse plan that enables the rover to remain illuminated for 94 4 of the lunar year by incorporating this path planning tool during mission planning the feasibility of such a mission can be quantified

a dislocation model of strain accumulation and release at a subduction zone strain accumulation and release at a subduction zone are attributed to stick slip on the main thrust zone and steady aseismic slip on the remainder of the plate interface this process can be described as a superposition of steady state subduction and a repetitive cycle of slip on the main thrust zone consisting of steady normal slip at the plate convergence rate plus occasional thrust events that recover the accumulated normal slip because steady state subduction does not contribute to the deformation at the free surface deformation observed there is completely equivalent to that produced by the slip cycle alone the response to that slip is simply the response of a particular earth model to embedded dislocations for a purely elastic earth model the deformation cycle consists of a coseismic offset followed by a linear in time recovery to the initial value during the interval between earthquakes for an elastic viscoelastic earth model elastic lithosphere over a viscoelastic asthenosphere the postearthquake recovery is not linear in time records of local uplift as a function of time indicate that the long term postseimic recovery is approximately linear suggesting that elastic earth models are adequate to describe the deformation cycle however the deformation predicted for amore simple elastic half space earth does not reproduce the deformation observed along the subduction zones in japna at all well if stick slip is restricted to the main thrust zone as recognized earlier by shimazaki seno and kato the uplift profiles could be explained if stick slips were postulated to extend along the plate interface beyond the main thrust zone to a depth of perhaps 100 km but independent evidence suggests that stick slip at such depths if unlikely less

illumination conditions of the south pole of the moon derived using kaguya topography abstract we have used the kaguya laser altimeter derived topography to conduct a comprehensive study of the illumination conditions at the moon s south pole we have determined by comparing simulated and actual clementine images that the kaguya topography can be used to generate realistic illumination conditions we generated an average illumination map for the year 2020 for the lunar south pole region from this we identified the areas that receive the most illumination the place receiving the most illumination 86 of the year is located close to the rim of shackleton crater at 88 74 s 124 5 e however two other areas less than 10 km apart from each other are collectively lit for 94 of the year we found that sites exist near the south pole that are continuously lit for several months during summer we were also able to map the locations and durations of eclipse periods for these areas finally we analyzed the seasonal variations in lighting conditions from summer to winter for key areas near the south pole we conclude that areas exist near the south pole that have illumination conditions that make them ideal candidates as future outpost sites

do we require adiabatic dissipation schemes in eddy resolving ocean models abstract use of horizontal diffusion of temperature and salinity in numerical ocean models causes spurious diapycnal transfers the veronis effect leading to erosion of the thermocline and reduced poleward heat transports the authors derive a relation between these diapycnal transfers and the dissipation of vorticity gradients an increase in model resolution does not significantly reduce the diapycnal transfers since vorticity gradients cascade to smaller scales and must ultimately be dissipated to maintain numerical stability this is confirmed in an idealized primitive equation ocean model at a variety of resolutions between 1 and 1 8 thus the authors conclude that adiabatic dissipation schemes are required even in eddy resolving ocean models the authors propose and implement a new biharmonic form of the gent and mcwilliams scheme which adiabatically dissipates at the grid scale while preserving larger scale features

current deformation and the width of the seismogenic zone of the northern cascadia subduction thrust evidence has been obtained for the accumulation of elastic strain across the northern cascadia subduction zone that may be released in a future very large subduction thrust earthquake vertical and horizontal strain rates across the southern vancouver island region have been determined through 1 long term trends in tide gauge data 2 changes in repeated accurate leveling surveys 3 changes in repeated high accuracy gravity profiles and 4 horizontal shortening observed in repeated precise positioning surveys the outer coast is uplifting at a rate of a few millimeters per year decreasing landward and shortening is occurring across the 100 km wide coastal region at a rate of about 0 1 microstrain per year mm km 1yr 1 the results are compared with the distribution of strain accumulation predicted from elastic dislocation and viscoelastic models for a subduction thrust fault the location of the fault as used in the models is well defined by multichannel seismic reflection and other geophysical data most of the observed current deformation can be explained by interseismic strain accumulation associated with the subduction thrust of southern vancouver island and northern washington provided the locked portion is restricted to a 60 km wide band offshore beneath the continental shelf and slope this conclusion also results from modeling the coseismic subsidence on the outer coast of vancouver island about 300 years ago deduced from paleoseismicity data the unusually narrow downdip extent of the subduction thrust seismogenic zone that extends little if at all beneath the coast is a consequence of high temperatures associated with the young age of the subducted oceanic lithosphere and the thick blanket of insulating sediments the high temperatures limit brittle seismogenic behavior downdip to where the thrust fault is at a depth of less than 15 km the distance from the seismic portion of the megathrust limits the estimated ground motion at the major centers of vancouver and victoria from this source the narrow width may also limit the earthquake size however events of magnitude well over 8 are possible

the effect of a northward shift in the southern hemisphere westerlies on the global ocean we examine the effect of a northward shift in the position of the southern hemisphere subpolar westerly winds swws on the vertical and horizontal distribution of temperature and salinity in the world ocean a northward shift of the swws causes a latitudinal contraction of the subpolar gyres in the southern hemisphere sh in the indian and pacific this leads to subsurface warming in the subtropical thermocline as the southern margins of the gyres move into latitudes characterised by warmer surface air temperature sat the layers at mid depth below 400 m depth become ventilated by warmer water we characterize the approximation of the ventilated thermocline in our coarse resolution model using a set of passive tracer experiments and illustrate how the northward shift in the swws causes an equatorward shift in the latitude of origin of water ventilating layers deeper than 400 m in the indian and pacific leaving the total surface ventilation of the upper 1200 m unchanged in contrast the latitudinal constraint on the antarctic circumpolar current posed by the drake passage causes a cooling and freshening throughout the atlantic thermocline here subsurface thermocline water originates from higher latitudes under the wind shift on longer timescales atlantic cooling and freshening is reinforced by a reduction in north atlantic deep water nadw formation and surface salinification of the indian and pacific oceans in effect the latitude of zero wind stress curl in the swws regulates the relative importance of the cold water route via the drake passage and the warm water route associated with thermocline water exchange via the indian ocean thus a more northward location of the swws corresponds with a reduced salinity contrast between the indian pacific oceans and the atlantic this results in reduced nadw formation also a more northward location of the swws facilitates the injection of cool fresh antarctic intermediate water into the south atlantic subtropical gyre beyond these changes on a millennial timescale the deep ocean warms throughout the water column in response to the wind shift global salinity stratification also becomes less stable as more saline water remains at the surface and accumulates in the indian and pacific thermocline the freshening of the deep ocean reflects a reduced stirring of the global ocean due to reduced net circulation arising from a misalignment between the westerlies and the topographically constrained acc our results lend support to the idea that a more equatorward location of the sww maximum during glacial climates contributed to cooler and fresher conditions in the atlantic inhibiting nadw

eddy cancellation of the ekman cell in subtropical gyres abstractthe presence of large scale ekman pumping associated with the climatological wind stress curl is the textbook explanation for low biological activity in the subtropical gyres using an idealized eddy resolving model it is shown that eulerian mean ekman pumping may be opposed by an eddy driven circulation analogous to the way in which the atmospheric ferrel cell and the southern ocean deacon cell are opposed by eddy driven circulations lagrangian particle tracking potential vorticity fluxes and depth density streamfunctions are used to show that in the model the rectified effect of eddies acts to largely cancel the eulerian mean ekman downwelling to distinguish this effect from eddy compensation it is proposed that the suppression of eulerian mean downwelling by eddies be called eddy cancellation

the updip and downdip limits to great subduction earthquakes thermal and structural models of cascadia south alaska sw japan and chile this study examines thermal and structural controls of the updip and downdip rupture limits of great subduction thrust earthquakes data on past great earthquake seismic limits have been compiled for four continental subduction zones cascadia sw japan south alaska and chile these limits have then been compared to the predictions of several models for what constrains great earthquake rupture temperatures on the subduction thrusts have been estimated by finite element numerical models the landward limits of the observed updip aseismic zones correspond to the position where the thrust temperature reaches about 100 c that is depths of about 2 to 10 km for the subduction zones studied this temperature agrees with the dehydration of stable sliding smectite clays to illite chlorite the temperatures in this region are controlled mainly by the thickness of sediment on the incoming crust and by the crustal age and thus heat flow the downdip limits correspond to the depth on the thrust where either 1 the temperature reaches about 350 c which corresponds to thermally activated stable sliding behavior for crustal rocks with a transition to 450 c or 2 about 40 km depth if 350 c is reached at greater depth depths of about 40 km approximately correspond to the intersection of the thrust with the continental forearc moho and this downdip limit may be a consequence of stable sliding serpentinite or talc and other hydrated forearc mantle rocks the primary temperature controls on the downdip region are the age of the subducting oceanic plate and the thrust dip profile secondary control comes from the thickness of incoming sediment the convergence rate and the radioactive heat generation in the overlying forearc the 100 c updip limit occurs near the trench for young subducting plates with a thick sediment section such as cascadia 6 8 ma and up to 80 km landward for older oceanic crust such as south alaska 50 ma the 350 c downdip thermal limit is applicable for young oceanic plates e g cascadia and nankai whereas the forearc mantle limit applies for older plates e g south alaska and chile except near the chile rise for the margins studied that have experienced great earthquakes there is generally good agreement between the postulated thermal and moho limits and the rupture or seismogenic zone as defined by the distribution of aftershocks and by waveform tsunami and dislocation modeling the downdip limit of the interseismic locked zone from dislocation modeling is also in agreement with these limits

the eastern subtropical pacific origin of the equatorial cold bias in climate models a lagrangian perspective abstractglobal climate models frequently exhibit cold biases in tropical sea surface temperature sst in the central and eastern equatorial pacific here lagrangian particle back trajectories are used to investigate the source regions of the water that upwells along the equator in the ipsl climate model to test and confirm the hypothesis that the sst biases are caused by remote biases advected in from the extratropics and to identify the dominant source regions water in the model is found to be sourced primarily from localized regions along the western and eastern flanks of the subtropical gyres however while the model sst bias is especially large in the northwestern subtropical pacific about 5 c it is found that the eastern subtropics contribute to the equatorial bias the most this is due to two distinct subsurface pathways connecting these regions to the equator the first pathway originating in the northwestern subtropical pacific has relatively long advection time scales close to or exceed

arecibo radar mapping of the lunar poles a search for ice deposits the arecibo 12 6 centimeter wavelength radar system was used to image the polar regions of the moon at a resolution of 125 meters in a search for ice deposits in areas of possible permanent shadow from the sun no areas greater than 1 square kilometer were found with high radar backscatter cross sections and high circular polarization ratios properties suggestive of the presence of ice a number of areas smaller than 1 square kilometer were found with these properties but optical images from spacecraft missions have shown some of these features to be in sunlight arecibo radar images of sinus iridum at latitude 47 n also showed a number of small features with similar properties the coincidence of some of these features with the radar facing slopes of craters and their presence in sunlit areas suggests that very rough surfaces rather than ice deposits are responsible for their unusual radar properties

interseismic deformation at the nankai trough japan subduction zone uplift along the coast of southwestern japan following the 1944 tonankai ms 8 0 and 1946 nankaido ms 8 2 earthquakes has been inferred from the 1950 1985 tide gage records although uplift rates vary with geographic position the temporal dependence at each site can be described as the superposition of an exponentially decaying time constant 5 years transient significant only in the first decade postseismic and a steady interseismic rate the steady interseismic uplift rate is defined only over the 1956 1985 interval but the linearity in time ofthat uplift record is such that uplift over the remainder of the interseismic cycle 80 years might reasonably be expected to occur at the same rate moreover the spatial pattern and magnitude of the steady uplift rate are reasonably close to those predicted by a simple dislocation model of subduction however the currently observed steady uplift rate is not consistent with the uplift rate inferred from geodetic leveling for the final half of the previous earthquake cycle thus either the hypothesis of a steady interseismic uplift rate after the first decade postseismic is wrong or the strain accumulation pattern for one earthquake need not be the same as for the preceding earthquake on the same segment