polar margin dunes and winds on mars the approximately concentric arrangement of layered deposits and dune fields at the two martian poles may reflect a nearly steady state dispersal of material from the polar deposits data on effective surface winds from high resolution viking images combined with theory of local winds suggest that the northern dunes are in part confined to a latitude band by winds generated by their own low albedo dispersal of the dark sand from the southern polar region is not subject to this kind of feedback because the irregular topography prevents areal accumulations sufficiently extensive to produce winds

models of climate cycles recorded in martian polar layered deposits abstract layered strata observed in orbital images of polar sedimentary terrains on mars have been hypothesized to contain information about recent variations in the martian climate celestial mechanicians have determined that mars has experienced large amplitude quasi periodic variations in obliquity and eccentricity planetary meteorologists have inferred that the resulting changing patterns of solar heating must have had dramatic effects on martian climate accordingly it might be possible to link the known recent history of orbit axial variations with the physical characteristics of the most recently deposited strate determined from orbital imagery our paper explores that possibility quantitatively for various models of the formation of the polar layered deposits and the layering developed within them we modeled the formation of polar layered deposits during the past 10 my for two general classes of model uniform deposition rate udr models assume that the major constituent of the layered deposits is deposited at a uniform rate and that layering is established by climate induced variations in the concentration of a minor constituent climate modulated deposition rate cmdr models assume that the deposition rate of the major constituent is controlled by climate and that layer boundaries correspond to intervals of nondeposition in both models abrupt changes in deposition regime occur when a function of the orbit axial parameters crosses a threshold value detailed physical mechanisms for the control of sedimentation by orbit axial variations were developed for two specific models of the cmdr type in one model the deposits are assumed to be primarily composed of dust in the other they are assumed to be predominantly water ice we calculated the times at which abrupt changes in deposition regime occur and determined the relative thicknesses of successive layers which can be compared against layer thicknesses made from orbital imagery in all these models obliquity variations exert the dominant influence on the sequential variations in layer thickness although eccentricity and precession index longitude of perihelion may take recognizable contributions as well the layer patterns for the north and south polar deposits are identical for the dust model and only slightly different for the ice model but this is at least partly a consequence of simplifying assumptions the sequential variation in layer thickness is also very sensitive to those model parameters which control the fraction of time for which deposition occurs when the climate threshold for deposition is low deposition occurs a large fraction of the total time and characteristic patterns form with one thick layer and a number of much thinner ones such patterns would be easily recognized in photogeological measurements of layer thickness when the threshold for deposition lies in the mid range with respect to excursions of the climate function deposition occurs approximately half of the time and there is only slight modulation of layer thickness when the threshold for deposition is high deposition occurs only a small fraction of the total time and groups of layers form which are separated form other groups by long periods of nondeposition the stratigraphic unconformities that separate groupings of five to ten layers in the polar deposits may indicate that the martian polar region has experienced such a depositional history the feasibility of using these model results to verify the theory of climate control of polar stratigraphy on mars and to gain additional insights into the significant processes is considered the stratigraphy issues raised here are also explored in the context of recent work on the interpretation of stratigraphy of ocean margins from this comparison there emerge some valuable insights into the stratigraphic effects of periods of nondeposition and the uncertaintiesin interpreting images of exposed polar strata on mars

stratigraphic relationships within martian polar cap deposits abstract deposits of layered ice and dust accumulate on the smooth and banded terrains of the north and south polar cap deposits while erosion of equator facing slopes of layered terrain expose these layers banded terrain occurs at exposures of irregular layers resulting from slight erosion of the feather edges of layers deposited on pole facing trough walls these deposits unconformably overlap onto adjacent layered terrain stripping of layers occurs in areas of strong multidirectional wind forming striped terrain local wind scour has also produced steep scarps with crescentic planform often associated with dune fields positioned immediately downwind unconformities are common within layered deposits in areas of complex topography at the north pole these indicate that episodes of deposition of 5 10 layers alternate with slight erosion of pole facing trough walls troughs that strike north south alternate between erosional widening and deepening and depositional infilling creating multiple unconformities troughs near the equatorward limit of polar deposits increase in relief by deposition on adjacent smooth terrain and locally by erosional deepening troughs may migrate poleward replacing the relief increase by depositional infilling when they near the poles

satellite and ship studies of coccolithophore production along a continental shelf edge each year since the coastal zone color scanner czcs 1 was launched on the nimbus 7 satellite in november 1978 extensive patches of water giving strong reflectance of visible light have been observed during the early summer along the outer margin of the north west european continental shelf between 45 and 60 n refs 2 3 various hypotheses including coccolithophores phytoplankton with external calcified plates or coccoliths were suggested to explain a comparable feature on landsat images for july 19774 to test these we report here observations made from french and uk research vessels in 1982 using unprocessed czcs images supplied by the university of dundee and centre de meteorologie spatiale in lannion to locate suitable sampling areas immediately before and during the cruise and atmospherically corrected data from the european space agency for subsequent analysis and calibration of the reflectance signals the high reflectance was found to be caused by a surface bloom of the widespread coccolithophore emiliania huxleyi lohm hay et mohler which also produced abundant detached coccoliths this finding is of relevance to recent work both on the ecology of coccolithophores5 including their importance in the sedimentation of biogenic carbon6 7 and lipids8 and in palaeoclimatic studies9 and on the development of reliable remote sensing techniques for the estimation of chlorophyll in oceanic waters10

first high resolution stratigraphic column of the martian north polar layered deposits 1 this study achieves the first high spatial resolution layer scale measured stratigraphic column of the martian north polar layered deposits using a 1m posting dem the marker beds found throughout the upper north polar layered deposits range in thickness from 1 6 m 16 0 m 1 4 m and 6 of 13 marker beds are separated by 25 35 m thin layer sets have average layer separations of 1 6 m these layer separations may account for the spectral power peaks found in previous brightness profile analyses marker bed layer thicknesses show a weak trend of decreasing thickness with depth that we interpret to potentially be the result of a decreased accumulation rate in the past for those layers however the stratigraphic column reveals that a simple rhythmic or bundled layer sequence is not immediately apparent throughout the column implying that the relationship between polar layer formation and cyclic climate forcing is quite complex

semivariograms of digital imagery for analysis of conifer canopy structure semivariograms were used to exploit the spatial information inherent in digital imagery of a variety of douglas fir pseudotsuga menziesii mirbel franco forest stands in the pacific northwest region of the united stataes calculations involved digital numbers from single transects of pixels representative of each stand and from a full spatial matrix of pixels from each stand digitized aerial video images having pixel sizes of 1 m 10 m and 30 m were used at 1 m spatial resolution the ranges of the matrix semivariograms related to the mean tree canopy sizes of the stands the sills responded to the presence of vertical layering in the canopies and to percent canopy cover the transect semivariograms were less representative of overall stand structure but exhibited periodicity that was suggestive of patterns in stand structure semivariograms based on 10 m and 30 m pixels contained significantly less useful information the ranges of the 10 m matrix semivariograms revealed only whether the tree canopy sizes were less than 10 m or were between 10 m and 20 m the sills were greatly reduced but still related well to canopy layering and percent cover periodicity in the transect semivariograms was greatly reduced and in some cases eliminated at 30 m resolution only the sills of the matrix semivariograms contained useful information however actual differences between the sills were small

mesoscale pigment fields in the gulf stream observations in a meander crest and trough in september october 1988 and april 1989 a series of hydrographic transects were completed across the gulf stream front in a meander crest and meander trough respectively one of the main experimental objectives was to relate the spatial distribution of chlorophyll to the physical fields of gulf stream meanders chlorophyll distributions are derived from conductivity temperature depth ctd fluorescence profiles calibrated with discrete pigment samples collected from bottles at several depths at various stations objective analysis oa maps and vertical sections in stream coordinates of chlorophyll on density surfaces show the chlorophyll distribution was strongly related to the structure of the gulf stream front in particular chlorophyll concentrations greater than 0 4 mg m 3 were at or inshore of the gulf stream north wall characteristic length scales of chlorophyll distribution determined from the horizontal and temporal correlation function are the same order 50 100 km as length scales of the physical variables the maximum chlorophyll concentrations in the vertical were from the surface to 50 m depth on the western flank of the meander crest and deepened to 75 to 100 m depth on the eastern flank this coincides with the deepening of the 24 4 25 7 surfaces from the western to the eastern flank of the meander crest although in the spring cruise the maximum chlorophyll concentrations were also found at depths between the surface and 100 m there were no clear distinctions in pigment distributions between the western and eastern transects of a relatively weak trough maximum chlorophyll concentrations 1 0 1 5 mg m 3 from the 1989 spring bloom in slope waters were about double those observed in the 1988 fall data the primary physical mechanisms influencing the mesoscale pigment distribution in gulf stream meanders observed in this study are 1 outcropping of nutrient bearing strata in the spring 2 meander induced upwelling of nutrients along sloping isopycnals and 3 gulf stream ring interactions

observations of gulf stream induced and wind driven upwelling in the georgia bight using ocean color and infrared imagery ocean color and infrared imagery from aircraft and satellite sensors are combined with in situ measurements of currents chlorophyll temperature salinity coastal winds and sea level to study upwelling events in the georgia bight where the gulf stream and continental shelf waters strongly interact these interactions were observed over an 8 day period in april 1980 during which five independent upwellings occurred the upwellings included a nearshore wind driven upwelling enhanced by topographic effects three gulf stream filament induced upwellings and what appears to have been a gulf stream meander induced event the chlorophyll distributions as inferred from the imagery are found to be reliable tracers which indicate filamentary circulation and propagation and advective routes by which nearshore water moves offshore the propagation of two of the filaments and the meander are studied in detail using the imagery and mooring array temperature time series both techniques yield nearly identical results for the phase speeds of each event there is evidence that one of the filaments accelerated as it entered into the charleston bump area where the gulf stream deflects offshore the other filament exhibited a steady deceleration as it moved past cape canaveral and eventually lost any semblance of wave motion also includedmore are data from april 1979 which offer corroborating evidence of filamentary structure and circulation intercomparisons of field measurements and the nimbus 7 coastal zone color scanner estimates of surface pigment concentrations show excellent agreement over the range of 0 1 7 0 mg m sup 3 54 references 22 figures 6 tables less

observations of the north polar region of mars from the mars orbiter laser altimeter elevations from the mars orbiter laser altimeter mola have been used to construct a precise topographic map of the martian north polar region the northern ice cap has a maximum elevation of 3 kilometers above its surroundings but lies within a 5 kilometer deep hemispheric depression that is contiguous with the area into which most outflow channels emptied polar cap topography displays evidence of modification by ablation flow and wind and is consistent with a primarily h2o composition correlation of topography with images suggests that the cap was more spatially extensive in the past the cap volume of 1 2 3 10 6 to 1 7 3 10 6 cubic kilometers is about half that of the greenland ice cap clouds observed over the polar cap are likely composed of co 2 that condensed out of the atmosphere during northern hemisphere winter many clouds exhibit dynamical structure likely caused by the interaction of propagating wave fronts with surface topography

pigment distribution in the caribbean sea observations from space abstract the caribbean is a semi enclosed tropical sea which is generally considered oligotrophic but that is influenced by nearly 20 of the annual discharge of the world s rivers amazon and orinoco rivers and by seasonal upwelling along the southern margin to investigate the role of these nutrient sources on the productivity of the region we mapped the distribution of pigments in the eastern caribbean east of 80 w using a series of coastal zone color scanner czcs images collected between november 1978 and december 1982 five additional images were examined for the period 1983 1986 the images revealed a seasonal cycle in the spatial structure of near surface pigment during january may there were high pigment concentrations 0 5 mg m 3 along the continental margin south of 14 n where upwelling occurred very little pigment 3 105 km2 this plume reached puerto rico around september october and drifted westward slowly losing its color signature we estimate that the discharge of the orinoco contributes 2 12 of the daily nitrogen requirements of the phytoplankton growing in the river plume and leads to the fixation of 7 29 105 tons of carbon per year the rest of the nitrogen demand appears to be met by nitrogen cycling the large scale 100 km pigment distribution patterns in the caribbean sea seem to be controlled by wind stress flux of water through the basin and river discharge westward advection of atlantic water probably dominates the flow during the first half of the year restricting the dispersal of blooms to the southern half of the caribbean while flushing the central and northern portions as the influx of atlantic water decreases in the second half of the year local ekman transport driven by the trade winds becomes dominant and surface waters drift northwestward throughout the basin the seasonal sequence of changes in pigment distribution patterns was consistent from year to year except in 1980 and 1984 when wind conditions in the caribbean were anomalous close scrutiny of the 4 years of czcs images did not reveal any evidence of large scale 300 km eastward flowing currents in the central caribbean this supports the view that previous observations of countercurrents were based on partial sampling of eddies of 100 250 km diameter

north polar stratigraphy and the paleo erg of mars an accurate self consistent way of coregistering the imaging and topographic data sets of the mars global surveyor mission was developed and used to begin a stratigraphic analysis of the northern polar region a distinct change in the layering style exists at a definite stratigraphic horizon near the base of the north polar layered deposits occurrences of the contact between two distinct layered units can be mapped hundreds of kilometers apart at nearly the same mars orbiter laser altimeter mola elevation the lower layered unit has a consistent association with sand dunes leading to the conclusion that it is an eroding sand rich deposit that predates most of the overlying north polar layered deposits which exhibits the expected features of a dust ice mixture these results suggest that an areally extensive erg was in existence before the present ice cap and that the present circumpolar erg is likely composed of material reworked from this older deposit the volume of this lower unit is estimated to be on the order of 10 5 km 3 the presence of this deposit implies that there existed a period in mars history when there was no icy polar cap a dramatic climatic change leading to the deposition of the upper layered icy unit in the present day polar layered deposits represents a major event in mars history however owing to uncertainties in the mechanics of layered deposits formation such an event cannot be dated at this time

spatial scales in czcs chlorophyll imagery of the southeastern u s continental shelf1 a 1 yr time series of coastal zone color scanner czcs imagery of continental shelf waters off the southeastern u s was statistically analyzed to determine dominant scale lengths in the range from 2 to 100 km for near surface chlorophyll chl variability for each image we extracted two dimensional matrices of czcs chl concentrations from each of 10 study areas variograms structure functions were calculated for both the along and across shelf dimension of each data matrix although we designed the study areas to focus on along shelf variability the variograms were used to determine whether the images contained nonrandom structure and if so to estimate its scale lengths outer shelf czcs chl distributions lacked apparent spatial structure in about 50 of the data matrices vs 10 for the inner shelf matrices in general scale length increased with distance offshore and did not change with season for example the mean scale length n 30 images for along shelf czcs chl variability on the inner shelf off georgia was 32 km vs 84 km n 18 images for the outer shelf wc propose that gulf stream frontal eddies are the principal determinants of outer shelf scale length and that topographic effects on the position of a coastal salinity front determine scale length on the inner shelf off georgia and south carolina

the effects of martian orbital variations upon the sublimation and relaxation of north polar troughs and scarps abstract the north polar layered deposits pld of mars are climatologically significant because they represent the largest actively exchanging reservoir of martian water the kilometer scale topography of the north pld is dominated by troughs and scarps which exhibit highly correlated surface slopes and total depths the most widespread theories of pld evolution presume that the asymmetrical nature of north pld troughs characterized by equatorward facing slopes that are generally steeper than poleward facing slopes is the result of preferential h 2 o sublimation from equatorward facing trough walls however our orbitally modulated simulations indicate that there is no long term sublimation advantage of equatorward facing trough walls because of the effects of obliquity upon the slope dependence of sublimation rate in contrast we propose that viscous relaxation of subsurface water is consistent with the slope and depth distributions of north pld troughs and scarps the results of our finite element simulations suggest that a mere 2 k difference in the subsurface temperatures of opposing trough walls is sufficient to produce the observed slope disparity due to the slower rate of uplift of colder poleward facing trough walls both our sublimation and relaxation simulations indicate that present day north pld troughs have formed since 5 ma and are not sites of long term deposition additionally our results imply that glacial flow may govern the large scale evolution of the north pld especially at high obliquity

martian north polar layered deposits stratigraphy implications for accumulation rates and flow 1 we have used mars orbiter camera moc images and mars observer laser altimeter mola data to correlate specific layers within the upper 500 m of the martian north polar layered deposits in many troughs using these correlation results we derive relative accumulation rates across the polar layered deposits and through time we identify two major layer sequences one lying stratigraphically above the other each consistent with an overall curving downward layer structure with shallow slopes but with significant localized variations in layer height major disruptions of stratigraphy such as angular unconformities do not appear within the correlated layer sequences on local and broad scales each layer sequence exhibits a different relative accumulation rate pattern indicating that this rate has not remained constant through time and has been affected by localized processes the overall pattern of the lower layer sequence is similar to that of a classic terrestrial ice sheet with a decreasing relative accumulation rate away from the center of the polar layered deposits southward the upper layer sequence exhibits no obvious overall trends we also compare our correlation results to predictions of the effects of simple ice flow on layer structure finding that mass balance patterns have overprinted any effects of large scale ice flow flow has not been significant compared to mass balance in forming the overall structure of the correlated layers

a note on the charleston gyre the deflection of the gulf stream caused by a topographic feature the charleston bump located offshore of savannah georgia results in a quasi stationary cyclonic eddy the charleston gyre which is situated over the continental slope east of charleston and cape romain occasionally the upwelling associated with this eddy produces an enhancement in the surface layer primary production that is great enough to be detected by the nimbus 7 coastal zone color scanner czcs in this note a czcs image with simultaneous hydrography current and wind observations is presented that documents an unusual manifestation of the gyre in addition to the czcs image a seasat synthetic aperture radar sar image is included that clearly indicates the presence of the eddy adjacent to the gulf stream front

periodic climate change on mars review of evidence and effects on distribution of volatiles abstract the polar regions of mars preserve in both their layering and their topography a record of recent climate changes because of the coincidence of the growth of the northern seasonal cap with global dust storms dust may be currently accumulating on the northern cap but conditions at the poles will alternate with the precessional cycle deposition is also modulated by changes in eccentricity and obliquity which interact complexly affecting initiation of global dust storms the stability of volatiles at the surface and global wind regimes formation of spiral valleys and low undulations on the surface of the layered deposits may result from prefential sublimation of volatiles on sunward facing slopes and condensation on the adjacent flats with the rates also modulated by astronomically caused insolation variations lack of impact craters on the surface and lack of interruption of the layers by impact scars suggest that the polar deposits are no more than a few million years old older deposits may have been periodically removed as indicated by etch pitted terrain at the south pole and by superposition relations around the periphery of the present layered deposits evidence of ancient periodic climate changes that occurred before formation of the present layered terrain is fragmentary but includes pedestal craters parallel moraine like ridges and etched ground at high latitudes perturbation of the orbital motions also results in adsorption and desorption of volatiles in the regolith which leads to variations in atmospheric pressure and partial dehydration of the equatorial near surface materials

spiral trough diversity on the north pole of mars as seen by shallow radar sharad we combine observations from ground penetrating radar and optical instruments to conduct a comprehensive survey of spiral troughs on the north polar layered deposits of mars our survey reveals that all north polar troughs have common characteristics but there is strong regional diversity we divide the north polar layered deposits npld into eight regions based on observations of morphology and stratigraphy in order to classify the spiral troughs morphologic features that separate the regions include central promontories topographic undulations bedrock floors and trough asymmetry among others we demonstrate here that the troughs formed during two periods the first generation of troughs formed on the main lobe and in part of gemina lingula during accumulation of 600 m of ice and dust the second generation of troughs formed stratigraphically higher and immediately after large scale erosion in gemini scopuli which we conclude created the slopes necessary for troughs to form we test scenarios of trough evolution and find that only three concurrent processes are required for their formation wind transport insolation induced sublimation and atmospheric deposition our observations are inconsistent with other hypothesized processes to produce spiral troughs including incision after the formation of the npld fracturing due to flowing ice and sublimation driven patterns from insolation

coupling of coastal zone color scanner data to a physical biological model of the southeastern u s continental shelf ecosystem 1 czcs data description and lagrangian particle tracing experiments nine coastal zone color scanner czcs images from the southeastern u s continental shelf area during april 1980 were processed and the resulting chlorophyll distributions were analyzed in conjunction with concurrent flow and temperature fields which were obtained from an optimal interpolation of current meter measurements from 17m the chlorophyll distributions obtained from the czcs showed high chlorophyll concentrations over the shelf and low chlorophyll concentrations over the offshore shelf region the variance of the czcs derived chlorophyll distributions was highest at the shelf break region the chlorophyll patterns at the shelf break varied with time and space and showed shapes characteristic of typical gulf stream frontal eddies high chlorophyll bands that were oriented along shelf isolated high chlorophyll patches and simple waveforms each event observed in the chlorophyll patterns corresponded with a gulf stream frontal eddy event that could be identified in the optimally interpolated flow and temperature fields lagrangian particle tracing experiments were also conducted to track the movement of the features observed in the czcs images the particles traced in these experiments showed movement that was consistent with the evolution of the patterns observed in the czcs chlorophyll distributions results of the lagrangian experiments indicate that the optimal interpolation of the current meter measurements reproduced the flow between successive czcs images these experiments provide evidence that the high chlorophyll bands seen in the czcs chlorophyll distributions were produced by the passing of gulf stream frontal eddy events

north polar region craterforms on mars geometric characteristics from the mars orbiter laser altimeter abstract this study focuses on topographic characterization of ice associated north polar region impact craters and several enigmatic polar craterforms using new information from the mars orbiter laser altimeter mola an instrument aboard the mars global surveyor mgs orbiter we find that for ice associated craters the topography reveals several surprising results not previously apparent from orbital images alone first geometric properties for several impact craters associated with ice and frost deposits suggest that cavity infill is as high as 80 of reconstructed preerosion levels second craters associated with ice also demonstrate unique cavity geometries relative to their nonpolar counterparts finally in some cases ice associated impact features are anomalously deep on the basis of depths modeled from the best available scaling laws we suggest that burial of these impact features by either episodic advance of the polar cap margin or by continuous deposition at the highest rates previously estimated for the north polar region of mars has occurred subsequent stripping has exhumed the features leaving behind cavity infill deposits and a few of these display topographic levels above the surrounding preimpact surface in at least one case cavity interior deposits show layering with a typical thickness of 10 m suggesting episodic deposition and ablation of materials as in the polar layered terrain in addition to ice associated craters we investigated the topography of several enigmatic polar craterforms in particular a few craterforms within 150 km of the permanent north polar cap appear to resemble simple effusive lava shield volcanoes found on earth their geometric properties cannot be reconciled with previous suggestions that they were manifestations of martian hydromagmatic processes i e maar volcanism mola s initial measurements of impact craters and other craterforms in the north polar latitudes of mars support the concept of a geologically recent surface with evidence of effusive volcanism and enhanced sedimentation in addition the measured impact crater depths for ice associated craters suggest at least a few cases of enhanced excavation and thus a possibly weaker target relative to the typical northern hemisphere plains

photoclinometric determination of the topography of the martian north polar cap abstract photoclinometry is useful for the determination of topography for areas which have a uniform albedo the technique is applied to early spring viking images of the martian north polar cap taken when the surface was covered by a nearly uniform frost cover unlike earlier approaches the topographic profiling can be used for surfaces with any photometric function but the strike of the planetary surface relative to the illumination angle must be specified along the profile the resultant profiles are relatively insensitive to misestimation of the photometric functin and slope orientation but are quite sensitive to the assumed values of the reflectance of an equivalent level surface and the atmospheric opacity if it is large

new insights into the late amazonian zonal shrinkage of the martian south polar plateau the martian south polar plateau planum australe comprises the largest known water ice surface deposit on the planet here we present evidence for an episode of extensive polar plateau retreat during the late amazonian which affected regions flanking circum polar terrains located between cavi angusti and sisyphi montes

topography and stratigraphy of martian polar layered deposits abstract topography and stratigraphy of young sediments in the martian north polar region are being studied from high resolution viking orbiter images to test and constrain theories of terrain evolution driven by cyclical climate change several steepened slopes upon which layers are exposed in section were found to have local relief of 200 to 800 m and slopes ranging from 1 to 8 first attempts to calculate average layer thicknesses from portions of sections yielded results ranging from 14 to 46 m linearly correlated with slope in some cases under the assumption of short range lateral continuity a greater number of layers was inferred to be present than was actually resolved on a particular section when apparent layer thickness are revised accordingly the correlation with slope is destroyed we conclude that images of the shallowest sloping sections of layered deposits should yield the most stratigraphic information and layers thinner than 14 m may occur indeed they may even be common or typical because of the sensitivity of summer frost distribution to local slope and other properties of exposed strata interseasonal comparisons of images promise to enhance the capability to detect layers and differentiate them by material properties

cape romain and the charleston bump historical and recent hydrographic observations a review and analysis of historical and new hydrographic data are presented for the charleston bump region an area of doming isotherms is identified primarily between 31 5 sup 0 and 34 5 sup 0 n and the 200 and 400 m isobaths the highest incidences of doming are found off long bay 86 cape fear 38 and cape romain 25 evidence suggests that low salinity shelf water collects in the doming area off long bay in july and that seasonal fluctuations in the depth of the main thermocline layer in this area are linked to gulf stream transport and local winds at times there is a gradual offshore onshore movement of the gulf stream opposite long bay roughly following the 400 m isobath and at other times an abrupt eastward movement near 32 sup 0 n much of the time there appears to be a direct seasonal relationship between historical seasonal velocity fields and offshore deflection with higher lower velocities corresponding to greater lesser deflection

recent formation and evolution of northern martian polar layered deposits as inferred from a global climate model 1 we present a time marching model which simulates the exchange of water ice between the martian northern cap the tropics and a high latitude surface reservoir net annual exchange rates of water and their sensitivity to variations in orbital rotational parameters are examined using the martian water cycle modeled by the lmd three dimensional global climate model these rates are propagated over the last 10 myr to follow the thickness of the reservoirs the effect of a sublimation dust lag is taken account to test simple models of layer formation periods of high mean polar summer insolation 5 10 ma ago lead to a rapid exhaustion of a northern polar cap and a prolonged formation of tropical glaciers the formation of a northern cap and of a high latitude icy mantle may have started 4 ma ago with the average decrease of polar insolation tropical ice may have disappeared around 2 7 ma ago but small glaciers could have formed during the last peaks of polar summer insolation over the last 4 myr most of the present cap may have formed at the expense of tropical and high latitude reservoirs forming distinct layers at almost each 51 kyr 120 kyr insolation cycle layers thickness ranges from 10 to 80 m variations being produced by the modulation of the obliquity with 2 4 and 1 3 myr periods because only 30 insolation cycles have occurred since 4 ma ago we found an inconsistency between the recent astronomical forcing the observed number of layers and simple astronomically based scenarios of layers formation

mantle convection and crustal evolution on venus venus is probably similar to the earth in that recycling of basaltic crust has been induced by the development of cratons combinations of siliceous crust with high mg fe mantle venus has less remaining energy sources at depth but still enough to to support the great plateaus and to deliver appreciable heat close to the surface by convection the main differences of venus from the earth arise from its lack of water rather than higher temperatures lack of water plus lower stress levels due to lesser energy makes the upper mantle more viscous and hence venus tectonics more driven by bulk mantle rather than boundary layer characteristics making tectonics difficult to infer from magellan imagery will be shallower and more widespread layers of weakness in crustal rocks obscuring the mantle driven patterns

global patterns in cloud forms on mars abstract mariner 9 images and all viking orbiter images through july 1979 were searched for cloud forms a computer accessible catalog was assembled consisting of a classification of cloud type lee wav wave for example and properties directionality wavelength for example lee wave directionality shows a pattern and seasonal variation at high latitudes which is consistent with predictions of theoretical modeling fog and haze occurrence shows no obvious correlation with water abundance or any other simple causal factor lee waves are rare at equatorial latitudes plumes probably dust occur preferentially at locations where strong boundary layer convection is expected