south polar residual cap of mars features stratigraphy and changes abstract the south residual polar cap of mars rich in co2 ice is compositionally distinct from the north residual cap which is dominantly h2o ice the south cap is also morphologically distinct displaying a bewildering variety of depressions formed in thin layered deposits which have been observed to change by scarp retreat over an interval of one mars year malin et al 2001 science 294 2146 2148 the climatically sensitive locale of the residual caps suggests that their behavior may help in the interpretation of recent fluctuations or repeatability of the mars climate we have used mars global surveyor mars orbiter camera moc images obtained in three southern summers to map the variety of features in the south residual cap and to evaluate changes over two mars years mars y the images show that there are two distinct layered units which were deposited at different times separated by a period of degradation the older unit 10 m thick has layers approximately 2 m thick the younger unit has variable numbers of layers each 1 m thick the older unit is eroding by scarp retreat averaging 3 6 m mars y a rate greater than the retreat of 2 2 m mars y observed for the younger unit the rates of scarp retreat and sizes of the different types of depressions indicate that the history of the residual cap has been short periods of deposition interspersed with longer erosional periods erosion of the older unit probably occupied 100 150 mars y one layer may have been deposited after the mariner 9 observations in 1972 residual cap layers appear to differ from normal annual winter deposits by having a higher albedo and perhaps by having higher porosities these properties might be produced by differences in the depositional meteorology that affect the fraction of high porosity snow included in the winter deposition

insolation values for the climate of the last 10 million years new values for the astronomical parameters of the earth s orbit and rotation eccentricity obliquity and precession are proposed for paleoclimatic research related to the late miocene the pliocene and the quaternary they have been obtained from a numerical solution of the lagrangian system of the planetary point masses and from an analytical solution of the poisson equations of the earth moon system the analytical expansion allows the direct determination of the main frequencies with their phase and amplitude numerical and analytical comparisons with the former astronomical solution ber78 are performed so that the accuracy and the interval of time over which the new solution is valid can be estimated the corresponding insolation values have also been computed this analysis leads to the conclusion that the new values are expected to be reliable over the last 5 ma in the time domain and at least over the last 10 ma in the frequency domain

an expanded calibration model for inferring lakewater and air temperatures from fossil chironomid assemblages in northern fennoscandia chironomid temperature inference models based on an expanded data set of surface sediment and limnological data from 53 subarctic lakes in northern fennoscandia have been developed using eight different numerical techniques each based on slightly different underlying statistical models or ecological assumptions the study sites are mostly small shallow bathymetrically simple oligotrophic lakes with a ph range from 5 0 to 7 8 a total organic carbon range from 2 5 to 12 6 mg l 1 a mean july lakewater temperature ranging from 6 1 to 15 4 c and a mean july air temperature ranging from 8 5 to 14 9 c a series of redundancy analyses rda identified sediment organic content maximum lake depth and lakewater temperature as being the most important explanatory variables variance partitioning by partial rdas further suggested that each of these variables accounted for a significant fraction of variance independent from each other different cali bration models were assessed on the basis of their statisti

microcraters on mars evidence for past climate variations mars climate models predict hundredfold or greater variations in the mass of the martian atmosphere due to large amplitude variations in mars obliquity through time the production rates of impact craters on the martian surface should be greatly affected by these atmospheric mass variations we have constructed a simulation of the meteor bombardment of mars which shows that during periods of the lowest theoretical atmospheric mass the production rates of centimeter sized hypervelocity impact craters are increased significantly these results imply that limited in situ observations of microcraters visible on martian rock faces could validate major aspects of the astronomical theory for climate change on mars

dust and ice deposition in the martian geologic record abstract the polar layered deposits of mars demonstrate that thick accumulations of dust and ice deposits can develop on the planet if environmental conditions are favorable these deposits appear to be hundreds of millions of years old and other deposits of similar size but of greater age in nonpolar regions may have formed by similar processes possible relict dust deposits include from oldest to youngest noachian intercrater materials including arabia mantle deposits noachian to early hesperian south polar pitted deposits early hesperian hellas and argyre basin deposits late hesperian electris deposits and the amazonian medusae fossae formation these deposits typically are hundreds of meters to a couple kilometers thick and cover upward of a million or more square kilometers the apparent persistence of dust sedimentation at the south pole back to the early hesperian or earlier and the early growth of tharsis during the late noachian and perhaps earlier indicates that extensive polar wandering is unlikely following the middle noachian a scenario for the overall history of dust and perhaps ice deposition on mars includes widespread voluminous accumulations perhaps planetwide during the noachian as impacts volcanism and surface processes generated large amounts of dust the arabia deposits may have formed as ice availability and dust accumulation waned during the early hesperian thick dust sedimentation became restricted to the south pole and the deep hellas and argyre basins the north polar sedimentary record prior to the amazonian is largely obscured deposits at electris and medusae fossae may have resulted from local sources of fine grained material perhaps volcanic eruptions

stereo topography of the south polar region of mars volatile inventory and mars polar lander landing site viking stereo images and topographic maps reveal that the south polar layered deposits of mars are topographically complex and morphologically distinct from the north polar layered deposits the dominant feature is a 500 km wide topographic dome that rises 3 km above the surrounding plains this dome underlies the residual ice cap but is at least 50 larger in area erosional scarps and terraces indicate that this dome was once more extensive and has undergone erosional retreat adjacent to the dome layered deposits form a vast plateau 1 1 5 km high extending 1000 km beyond and to one side of the residual south polar cap this plateau is relatively flat at kilometer scales although it is cut in places by troughs and depressions which have locally steep scarps up to 2 km high and sloping up to roughly 10 contiguously flat kilometer scale regions the size of the mars polar lander mpl landing ellipse are present these are in the form of plateaus 100 300 km wide and 1 2 km high one of the largest of these plateaus has been proposed as a landing site for the mars polar lander mpl the volume associated with the south polar layered deposits may be comparable to those of the layered deposits at the north pole although this doubles the current probable inventory of surface ice on mars it still falls far short of accounting for the inferred volume of water on mars in the past

chaotic obliquity and the nature of the martian climate recent calculations of the martian obliquity suggest that it varies chaotically on timescales longer than about 107 years and varies between about 0 and 60 we examine the seasonal water behavior at obliquities between 40 and 60 up to several tens of centimeters of water may sublime from the polar caps each year and possibly move to the equator where it is more stable co2 frost and co2 h2o clathrate hydrate are stable in the polar deposits below a few tens of meters depth so that the polar cap could contain a significant co2 reservoir if co2 is present it could be left over from the early history of mars also it could be released into the atmosphere during periods of high obliquity causing occasional periods of more clement climate

evidence for a widespread climatic anomaly at around 9 2 ka before present 1 the 8 2 ka event was triggered by a meltwater pulse mwp into the north atlantic and resultant reduction of the thermohaline circulation thc this event was preceded by a series of at least 14 mwps their impact on early holocene climate has remained almost unknown a set of high quality paleoclimate records from across the northern hemisphere shows evidence for a widespread and significant climatic anomaly at 9 2 ka b p this event has climatic anomaly patterns very similar to the 8 2 ka b p event cooling occurred at high latitudes and midlatitudes and drying took place in the northern tropics and is concurrent with an mwp of considerable volume 8100 km3 as the 9 2 ka mwp occurs at a time of enhanced baseline freshwater flow into the north atlantic this mwp may have been despite its relatively small volume sufficient to weaken thc and to induce the observed climate anomaly pattern

mars south polar spring and summer behavior observed by tes seasonal cap evolution controlled by frost grain size thermal emission spectrometer tes observations of the recession phase of mars south polar cap are used to quantitatively map this recession in both thermal and visual appearance geographically nonuniform behavior interior to the cap is characterized by defining several small regions which exemplify the range of behavior for most of the cap while temperatures remain near the co2 frost point albedos slowly increase with the seasonal rise of the sun then drop rapidly as frost patches disappear over a period of 20 days a cryptic region remains dark and mottled throughout its cold period tes observations are compared with first order theoretical spectra of solid co2 frost with admixtures of dust and h2o the tes spectra indicate that the cryptic region has much larger grained solid co2 than the rest of the cap and that the solid co2 here may be in the form of a slab the mountains of mitchel remain cold and bright well after other areas at comparable latitude apparently as a result of unusually small size of the co2 frost grains we found little evidence for a significant presence of h2o although co2 grain size may be the major difference between these regions incorporated dust is also required to match the observations a self cleaning process carries away the smaller dust grains comparisons with viking observations indicate little difference in the seasonal cycle 12 martian years later the observed radiation balance indicates co2 sublimation budgets of up to 1250 kg m 2 regional atmospheric dust is common localized dust clouds are seen near the edge of the cap prior to the onset of a regional dust storm and interior to the cap during the storm

quantitative palaeotemperature records inferred from fossil pollen and chironomid assemblages from lake gilltjarnen northern central sweden palaeotemperature reconstructions based on radiocarbon dated fossil pollen and chironomid stratigraphies obtained from lake gilltjarnen provide evidence of climate changes during the last 11 000 years in the boreal zone of northern central sweden the records show consistent trends during the early and mid holocene indicating low temperatures at 11 000 10 000 cal yr bp followed by a rising trend and a period of maximum values from about 7000 to 4000 cal yr bp at 3000 cal yr bp the chironomid inferred temperature values rise abruptly deviating from the late holocene cooling trend indicated by the pollen based reconstruction and most of the other palaeotemperature records from central scandinavia probably as a result of local limnological changes in lake gilltjarnen and its catchment comparison of the present results with a lake level reconstruction from lake ljustjarnen ca 100 km southwest of lake gilltjarnen shows that the low early holocene temperatures were associated with high lake levels at 10 500 8500 cal yr bp whereas low lake levels and dry conditions prevailed during the period of high temperatures at between 7500 and 5000 cal yr bp probably due to high summer evapotranspiration and lower precipitation copyright 2006 john wiley sons ltd

mineralogy textures and whole rock geochemistry of advanced argillic alteration hugo dummett porphyry cu au deposit oyu tolgoi mineral district mongolia advanced argillic aa alteration is developed over a vertical interval of 500 m above and enclosing late devonian quartz monzodiorite intrusions that accompany porphyry style cu au mineralization at the hugo dummett deposit the aa alteration is mainly in basaltic rocks and locally extends into the overlying dacitic ash flow tuff for about 100 m the aa zone overprints porphyry style quartz veins associated with quartz monzodiorite intrusions but at least partly precedes high grade porphyry style bornite mineralization mineralogically it consists of andalusite corundum residual quartz titanium oxides diaspore alunite aluminum phosphate sulfate aps minerals zunyite pyrophyllite topaz kaolinite and dickite as well as anhydrite and gypsum but is dominated by residual quartz and pyrophyllite alteration zonation is not apparent except for an alunite bearing zone that occurs approximately at the limit of strong quartz veining whole rock geochemistry shows that the aa alteration removes most major elements except si al ti and p and removes the trace elements sc cs and rb v zr hf nb ta u and th are relatively immobile whilst light rees la to nd sr ba and ga can be enriched middle rees sm to gd are moderately depleted y and heavy rees tb to lu are strongly depleted except in two unusual samples where middle to heavy rees are enriched

chironomid inferred late glacial air temperatures at whitrig bog southeast scotland this paper presents the first chironomid inferred mean july air temperature reconstruction for the late glacial in britain the reconstruction suggests that the thermal maximum occurred early in the interstadial with temperatures reaching about 12 degreesc there was then a gradual downward trend to about 11 degreesc punctuated by four distinct cold oscillations of varying intensity at the beginning of the younger dryas mean july temperatures fell to about 7 5 degreesc but gradually increased to about 9 degreesc before a rapid rise at the onset of the holocene the chironomid inferred temperature curve agrees closely both in general trends and in detail with the grip ice core oxygen isotope curve the reconstructed temperatures are 2 4 degreesc lower than coleopteran inferred temperatures but are closer to those inferred from plant macrofossils and glacial equilibrium line altitudes during the younger dryas copyright c 2000 john wiley sons ltd

holocene climatic instability a prominent widespread event 8200 yr ago the most prominent holocene climatic event in greenland ice core proxies with approximately half the amplitude of the younger dryas occurred 8000 to 8400 yr ago this holocene event affected regions well beyond the north atlantic basin as shown by synchronous increases in windblown chemical indicators together with a significant decrease in methane widespread proxy records from the tropics to the north polar regions show a short lived cool dry or windy event of similar age the spatial pattern of terrestrial and marine changes is similar to that of the younger dryas event suggesting a role for north atlantic thermohaline circulation possible forcings identified thus far for this holocene event are small consistent with recent model results indicating high sensitivity and strong linkages in the climatic system

new martian paradigms several interrelated paradigms concerning the nature and the evolution of mars are discussed these include an impact origin of the northern lowland mars as a water rich planet former oceans in the northern lowlands a warm wet climate on early mars and the possibility of ancient life on mars locations on mars suggested for the search of possible ancient life include the heavily cratered terrain dissected by valley networks possible lacustrine deposits in valles marineris the oxidizing layer below the surface sites along the fringes of the hypothetical northern circumpolar ocean and in evaporite deposits

waxing and waning of the perennial north polar h2o ice cap of mars over obliquity cycles abstract the perennial north polar h2o ice cap of mars is investigated with the dynamic thermodynamic ice sheet model sicopolis computational results for flow velocities ice temperatures and surface accumulation ablation rates are presented for the steady state with present conditions as well as for transient scenarios over idealized obliquity cycles with periods of 1 3 myr and 125 kyr the transient simulations lead to a stop and go type dynamics with a cold and almost stagnant modern ice cap and a warmer flowing ice cap for past large obliquity periods the most likely scenario for the present ice cap comprises an ice volume of 1 2 million km3 a maximum thickness of 3 km the absence of pronounced local isostasy h2o ice accumulation rates of the order of tenth mm water equivalent w e per earth year yr flow velocities of the order of mm yr and an ice base far below pressure melting

mariner 9 television calibration revisited improved processing of the mariner 9 television data allows more accurate photometric analysis of the images returned in 1971 1972 by the first successful mars orbiting spacecraft these data include good synoptic coverage of the planet and the highest resolution images yet obtained of the south polar region errors in calibration are comparable to but still greater than those of the viking orbiter cameras calibration data and software are now available to interested parties as part of the planetary image cartography system through the u s geological survey in flagstaff arizona

the deglaciation of clyde inlet northeastern baffin island arctic canada the behaviour of ice sheets as they retreated from their last glacial maximum lgm positions provides insights into lateglacial and early holocene ice sheet dynamics and climate change thepatternofdeglaciationofthelaurentideicesheet lis inarcticfiordlandscapescannow bewelldatedusingcosmogenicexposuredating weusecosmogenicexposureandradiocarbonages to constrain the deglaciation history of clyde inlet a 120km long fiord on northeastern baffin island the lis reached the continental shelf during the lgm retreated from the coastal lowlands by 12 5 0 7ka n 3 and from the fiord mouth by 11 7 2 2ka n 4 rapid retreat from the outer fiord occurred 10 3 1 3ka n 6 with the terminus reaching the inner fiord shortly after 9 4ka n 2 where several moraine systems were deposited between ca 9 4 and ca 8 4ka these moraines represent fluctuations of the lis during the warmest summers since the last interglaciation and this suggests that the ice sheet was responding to increased snowfall before retreating from the head of clyde inlet the lis margin fluctuated at least twice between ca 7 9 and ca 8 5ka possibly in response to the 8 2ka cold event copyright 2006 john wiley sons ltd

perennial water ice identified in the south polar cap of mars the inventory of water and carbon dioxide reservoirs on mars are important clues for understanding the geological climatic and potentially exobiological evolution of the planet1 from the early mapping observation of the permanent ice caps on the martian poles2 3 the northern cap was believed to be mainly composed of water ice whereas the southern cap was thought to be constituted of carbon dioxide ice however recent missions nasa missions mars global surveyor and odyssey have revealed surface structures4 altimetry profiles5 underlying buried hydrogen6 and temperatures of the south polar regions that are thermodynamically consistent with a mixture of surface water ice and carbon dioxide7 here we present the first direct identification and mapping of both carbon dioxide and water ice in the martian high southern latitudes at a resolution of 2 km during the local summer when the extent of the polar ice is at its minimum we observe that this south polar cap contains perennial water ice in extended areas as a small admixture to carbon dioxide in the bright regions associated with dust without carbon dioxide at the edges of this bright cap and unexpectedly in large areas tens of kilometres away from the bright cap

on the mystery of the perennial carbon dioxide cap at the south pole of mars a perennial ice cap has long been observed near the south pole of mars the surface of this cap is predominantly composed of carbon dioxide ice the retention of a co 2 ice cap results from the surface energy balance of the latent heat solar radiation surface emission subsurface conduction and atmospheric sensible heat while models conventionally treat surface co 2 ice using constant ice albedos and emissivities such an approach fails to predict the existence of a perennial cap here we explore the role of the insolation dependent ice albedo which agrees well with viking mars global surveyor and mars express albedo observations using a simple parameterization within a general circulation model in which the albedo of co 2 ice responds linearly to the incident solar insolation we are able to predict the existence of a perennial co 2 cap at the observed latitude and only in the southern hemisphere further experiments with different total co 2 inventories planetary obliquities and surface boundary conditions suggest that the location of the residual cap may exchange hemispheres favoring the pole with the highest peak insolation

interglacial and holocene temperature reconstructions based on midge remains in sediments of two lakes from baffin island nunavut arctic canada abstract midge remains insecta diptera chironomidae and chaoboridae from two upland lake basins on the cumberland peninsula of baffin island were analyzed and the results used in a transfer function to reconstruct paleotemperatures this upland region remained ice free throughout the last glacial cycle and the two lake basins retain sediments deposited during the previous interglacial period as well as during the holocene period but they did not accumulate sediment during most of the glacial period midge remains are abundant and well preserved at both sites midge inferred summer surface water temperatures and mean july air temperatures were estimated using an inference model built on modern samples spanning a geographic range extending from devon island canada to maine usa data from twenty nine new surface samples from baffin island were added to an existing inference model the new weighted averaging wa model for summer surface water temperature yields r 2 jack 0 88 and rmsep 2 22 c for summer water temperatures and r 2 jack 0 88 and rmsep 1 53 c for mean july air temperatures reconstructions at both sites indicate that summer temperatures during the last interglacial were higher than at any time in the holocene and 5 to 10 c higher than present peak holocene temperatures occurred in the first half of the period and have decreased since about the mid holocene

high resolution record of northern hemisphere climate extending into the last interglacial period high resolution record of northern hemisphere climate extending into the last interglacial period

preliminary geological assessment of the northern edge of ultimi lobe mars south polar layered deposits we have examined the local base of the south polar layered deposits spld exposed in the bounding scarp near 72 74 s 215 230 w where there is a clear unconformable contact with older units sections of layering up to a kilometer thick were examined along the bounding scarp permitting an estimate of the thinnest individual layers yet reported in the spld rhythmic layering is also present locally suggesting a similarly rhythmic variation in environmental conditions and a recorded climate signal at least in some spld strata locally angular unconformities may be present as has been reported for the north polar layered deposits npld and may likewise imply intervals of subaerial erosion in the spld the outcropping layers display a broad range of weathering styles and may reflect more diverse conditions of depositions erosion and diagenesis than might have been expected from simple aeolian depostion modulated only by astronomically driven climatic fluctuations an unexpected finding of our study is the presence of locally abundant small pits close to the bounding scarp these quasi circular negative rimless features probably originated as impact craters and were modified to varying degrees by local endogenic processes as well as locally variable blanketing a nominal exposure age for the most heavily cratered region in our study area is about 2 million years and the crater statistics appear consistent with those for the overall spld although there are large uncertainties in the absolute ages implied by the crater size frequency statistics as in all martian crater ages another new finding is the presence of mass wasting features along the steepest portion of the retreating bounding scarp as well as a number of examples of brittle fracture consistent with large scale slumping along the bounding scarp and probably also ancient basal sliding both subhorizontal and high angle faults appear to be exposed in the bounding scarp but the dips of the faults are poorly constrained these fractures along with the relatively undeformed layers between them suggest to us that whatever horizontal motion may have taken place outward from the central cap region was accomplished by ancient basal sliding rather than large scale glacial like flow or ice migration by differential ablation as proposed recently for the northern permanent cap and underlying npld we have also obtained the first direct estimate of the regional dip of the spld around 2 3 outward northward in one area

post glacial vegetation reconstruction and a possible 8200 cal yr bp event from the low arctic of continental nunavut canada climate models suggest that the global warming during the early to mid holocene may have partly resulted from the northward advance of the northern treeline and subsequent reduction of the planetary albedo we investigated the holocene vegetation history of low arctic continental nunavut canada from a radiocarbon dated sediment core from tk 2 lake a small lake ca 200 km north of the limit of the forest tundra the pollen and loss on ignition data indicate the presence of dwarf shrub tundra in the region since the beginning of organic sedimentation at ca 9000 cal yr bp with dominance of betula especially since 8700 cal yr bp at 8100 7900 cal yr bp the dominance of the shrub tundra was punctuated by a transient decline of betula and coincident increases of ericaceae undiff vaccinium type and gramineae this suggests an abrupt disturbance of the betula glandulosa population approximately simultaneously with the sudden 8200 cal yr bp event in the north atlantic however in the absence of other sites studied in the area linkage to the 8200 cal yr bp event remains tentative the lack of any evidence of forest tundra in the region constrains the northern limit of the mid holocene advance of the forest tundra boundary in central northern canada consequently our results show that the climate models imposing a mid holocene advance of the limit of the forest tundra to the arctic coast of canada may have overestimated the positive climatic feedback effects that can result from the replacement of tundra by the boreal forest copyright 2003 john wiley sons ltd

dark material in the polar layered deposits and dunes on mars viking infrared thermal mapping and bistatic radar data suggest that the bulk density of the north polar erg material is much lower than that of the average martian surface or of dark dunes at lower latitudes we have derived a thermal inertia of 245 280 j m 2 s 1 2 k 1 5 9 6 7 10 3 cal cm 2 s 1 2 k 1 for the proctor dune field and 25 150 j m 2 s 1 2 k 1 0 6 3 6 10 3 cal cm 2 s 1 2 k 1 for the north polar erg the uniqueness of the thermophysical properties of the north polar erg material may be due to a unique polar process that has created them the visible and near infrared spectral reflectance of the erg suggests that the dark material may be composed of basalt or ferrous clays these data are consistent with the dark material being composed of basaltic ash or filamentary sublimate residue fsr particles derived from erosion of the layered deposits dark dust may be preferentially concentrated at the surface of the layered deposits by the formation of fsr particles upon sublimation of water ice further weathering and erosion of these areas of exposed layered deposits may form the dark saltating material that is found in both polar regions dark fsr particles may saltate for great distances before eventually breaking down into dust grains re mixing with the global dust reservoir and being recycled into the polar layered deposits via atmospheric suspension

color and albedo of the south polar layered deposits on mars five color albedo units including polar frost have been recognized and mapped in the southern layered deposits on mars atmospheric dust scattering was measured in shadows and modeled in order to remove the component of brightness in mars images due to the atmosphere and quantify the albedo and color of the surface the layered deposits appear to be mantled by red dust except where eolian stripping has exposed the underlying bedrock frost and bare ground are mixed below the resolution of the images in many areas adjacent to the polar cap some of which appear to be younger than the surrounding layered terrain dark material has been deposited in topographic depressions in much of the south polar region including the layered deposits the available observational data suggest that the layered deposits are composed of bright dust ice and a small amount of dark material if the dark material is sand a periodic change in polar winds seems required in order to transport the sand poleward into the layered terrain in any case the observations are not consistent with the layered deposits being composed only of bright dust and ice the mars observer camera and infrared instruments should be particularly useful in this investigation

paleoecological evidence for abrupt cold reversals during peak holocene warmth on baffin island arctic canada a continuous record of insect chironomidae remains preserved in lake sediments is used to infer temperature changes at a small lake in arctic canada through the holocene early holocene summers at the study site were characterized by more thermophilous assemblages and warmer inferred temperatures than today presumably in response to the positive anomaly in northern hemisphere summer insolation peak early holocene warmth was interrupted by two cold reversals between 9 5 and 8 cal ka bp during which multiple cold stenothermous chironomid taxa appeared in the lake the earlier reversal appears to correlate with widespread climate anomalies around 9 2 cal ka bp the age of the younger reversal is equivocal but it may correlate with the 8 2 cal ka bp cold event documented elsewhere widespread abrupt climate shifts in the early holocene illustrate the susceptibility of the climate system to perturbations even during periods of enhanced warmth in the northern hemisphere

comparison of the north and south polar caps of mars new observations from mola data and discussion of some outstanding questions new high resolution data from the mars orbiter laser altimeter mola have provided detailed topographic maps for the north and south polar regions these new data allow one to compare the overall topography and geologic histories of the two polar regions and to highlight some specific outstanding questions in mars polar studies following earlier comparisons using viking and mars global surveyor data the new data show that the centers of symmetry of the polar cap deposits in map view which include both the layered terrain and residual ice are offset from the current rotational pole in antipodal directions offset in the north appears to be due to retreat of the polar materials from predominantly one direction 180 w lines of evidence for movement and melting in different forms e g lobes in young craters kettle like depressions candidate residual mantles overlying polar layered terrain and possible eskers have been seen at both poles the exact timing and causes of movement and melting is yet unknown differences in underlying topography large low flat depression in the north broad cratered high and edge of a large impact basin in the south may influence the accumulation flow and movement of polar material and the storage and movement of meltwater the small number of superposed craters has been interpreted to indicate a late amazonian age for both caps with the southern cap being somewhat older 7 15 106 years than the northern cap 100 103 years the late amazonian aged caps are surrounded and underlain by hesperian aged material indicating an apparent hiatus almost 3 byr in duration this apparent hiatus in the geologic record from the late hesperian to late amazonian at both poles may be accounted for in one of three ways 1 polar caps are recent events in the history of mars this scenario requires that conditions in the late amazonian changed to produce environments favorable for cap formation late in the history of mars or that polar wander brought the caps to their present position very recently 2 the polar caps are oscillating in this scenario caps are periodically deposited and then retreat and disappear possibly due to extremes in the obliquity cycle in this model the present caps are the latest example of cap deposition and represent the type of deposit that has come and gone numerous times in the amazonian 3 the present caps are old but have been renewed in this scenario the present caps have been in their current position for much of the amazonian but some process e g melting flow is periodically destroying preexisting craters to produce cap surfaces that appear very young in terms of crater retention ages documenting the nature of the emplacement history of the present polar deposits and distinguishing among these disparate scenarios for their history are among major challenges facing mars polar studies in the coming years

observational evidence for an active surface reservoir of solid carbon dioxide on mars high resolution images of the south polar residual cap of mars acquired in 1999 and 2001 show changes in the configuration of pits intervening ridges and isolated mounds escarpments have retreated 1 to 3 meters in 1 martian year changes that are an order of magnitude larger than can be explained by the sublimation of water ice but close to what is expected for sublimation of carbon dioxide ice these observations support a 35 year old conjecture that mars has a large surface reservoir of solid carbon dioxide the erosion implies that this reservoir is not in equilibrium with the present environment and that global climate change is occurring on mars

a new greenland ice core chronology for the last glacial termination 1 we present a new common stratigraphic timescale for the north greenland ice core project ngrip and grip ice cores the timescale covers the period 7 9 14 8 kyr before present and includes the bolling allerod younger dryas and early holocene periods we use a combination of new and previously published data the most prominent being new high resolution continuous flow analysis cfa impurity records from the ngrip ice core several investigators have identified and counted annual layers using a multiparameter approach and the maximum counting error is estimated to be up to 2 in the holocene part and about 3 for the older parts these counting error estimates reflect the number of annual layers that were hard to interpret but not a possible bias in the set of rules used for annual layer identification as the grip and ngrip ice cores are not optimal for annual layer counting in the middle and late holocene the timescale is tied to a prominent volcanic event inside the 8 2 kyr cold event recently dated in the dye 3 ice core to 8236 years before a d 2000 b2k with a maximum counting error of 47 years the new timescale dates the younger dryas preboreal transition to 11 703 b2k which is 100 150 years older than according to the present grip and ngrip timescales the age of the transition matches the gisp2 timescale within a few years but viewed over the entire 7 9 14 8 kyr section there are significant differences between the new timescale and the gisp2 timescale the transition from the glacial into the bolling interstadial is dated to 14 692 b2k the presented timescale is a part of a new greenland ice core chronology common to the dye 3 grip and ngrip ice cores named the greenland ice core chronology 2005 gicc05 the annual layer thicknesses are observed to be log normally distributed with good approximation and compared to the early holocene the mean accumulation rates in the younger dryas and bolling periods are found to be 47 2 and 88 2 respectively

the hemispherical asymmetry in the martian polar caps an energy balance model is used to study the behavior of co2 ice on mars the effect of the solar zenith angle dependence of albedo is to lengthen co2 ice lifetimes at the poles hemispherical asymmetries in cloud and dust abundance could result in the survival of seasonal co2 ice through summer in the south and not in the north in agreement with observations co2 ice observed in the summertime polar cap in the south could be of recent origin although a permanent co2 polar cap cannot be ruled out

allerod younger dryas lake temperatures from midge fossils in atlantic canada remains of freshwater midges are abundant in lake sediments and their species distributions are closely related to the surface water temperature of lakes their distributions thus provide a powerful tool for paleoclimatology the distribution of species in a core from splan pond in atlantic canada indicates that there were abrupt transitions in late glacial temperatures between warm and cold states the transitions are correlative with the well known warm allerod and cold younger dryas events in europe these data thus confirm the inference from palynological data that these events affected regions on both sides of the atlantic

thermal and albedo mapping of the polar regions of mars using viking thermal mapper observations 1 north polar region we present the first maps of the apparent thermal inertia and albedo of the south polar region of mars the observations used to create these maps were acquired by the infrared thermal mapper irtm instruments on the two viking orbiters over a 30 day period in 1977 during the martian late southern summer season the maps cover the region from 60 s to the south pole at a spatial resolution of 1 of latitude thus completing the initial thermal mapping of the entire planet the analysis and interpretation of these maps is aided by the results of a one dimensional radiative convective model which is used to calculate diurnal variations in surface and atmospheric temperatures and brightness temperatures at the top of the atmosphere for a range of assumptions concerning dust optical properties and dust optical depths the maps show that apparent thermal inertias of bare ground regions decrease systematically from 60 s to the south pole in unfrosted regions close to the south pole apparent thermal inertias are among the lowest observed anywhere on the planet on the south residual cap apparent thermal inertias are very high due to the presence of co2 frost in most other regions of mars best fit apparent albedos based on thermal emission measurements are generally in good agreement with actual surface albedos based on broadband solar reflectance measurements however in the frost free region poleward of 75 s best fit apparent albedos are significantly higher than measured lambert albedos implying that measured brightness temperatures in this area are up to 15 k colder than would be expected for surfaces with the same measured albedos during this season the one dimensional atmospheric model calculations also predict anomalously cold brightness temperatures close to the pole during late summer and after considering a number of alternatives it is concluded that the net surface cooling due to atmospheric dust is the best explanation for this phenomenon the observed systematic decrease in apparent thermal inertia from 60 s to the south pole during this season is also consistent with the predictions of atmospheric model calculations the region of lowest apparent thermal inertia close to the pole which includes the south polar layered deposits is interpreted to be mantled by a continuous layer of aeolian material that must be at least a few millimeters thick the low thermal inertias mapped in the south polar region imply an absence of surface water ice deposits which is consistent with viking mars atmospheric water detector mawd measurements which show low atmospheric water vapor abundances throughout the summer season however these observations do not necessarily imply a complete absence of water thermal model calculations that can reproduce observed diurnal temperature variations in the south polar region show that annual maximum subsurface temperatures at depths ranging from 4 to 20 cm are cold enough to permit the stability of ground ice deposits even if they are in excellent diffusive contact with the atmosphere therefore the presence of near surface ground ice in the south polar region is not inconsistent with the viking irtm and mawd observations

vegetation and climate of the last interglacial on baffin island arctic canada abstract sediment cores recovered from three mid arctic lakes on cumberland peninsula eastern baffin island arctic canada contained two units of unconformably superimposed organic sediment gyttja the upper of which represented sedimentation during the holocene radiocarbon ages on aquatic macrofossils from the lower gyttja suggested it to be 50 ka bp while luminescence ages from two cores constrained the age of this sediment to 90 and betula and alnus pollen grains than did overlying holocene sediments numerical comparisons of fossil pollen assemblages to a data set of 400 modern high latitude lake sediment samples revealed that the last interglacial vegetation of east central baffin island was low arctic in character comparable to present day southwest greenland from applications of both correspondence analysis regression and best modern analogue methodologies we infer july air temperatures of the last interglacial to have been 4 to 5 c warmer than present on eastern baffin island which was warmer than any interval within the holocene on these grounds we ascribe the lower lacustrine unit in these lakes to the climatic optimum of the last interglacial ca 117 to 130 ka bp marine isotopic stage 5e

early holocene climate variability and the timing and extent of the holocene thermal maximum htm in northern iceland the magnitude and timing of holocene maximum warmth in the arctic and sub arctic has been the subject of considerable recent interest particularly in the context of future climate change although lying at a crucial location in the north atlantic close to significant atmospheric and oceanic boundaries terrestrial holocene climatic data from iceland are few and predominantly derive from glacial and palaeoecological evidence here we present new datasets from trollaskagi based on chironomid inferred temperatures ci t using sub fossil chironomids from the same lake sediments supplemented by pollen data july air temperatures have been derived using an icelandic training set and the data suggest optimal temperatures at sea level up to 1 5 c above current levels around 8 k cal yr bp a time when birch woodland was well developed in trollaskagi but when woodland had still not fully developed in the more isolated nw peninsula our data thus suggest that optimal summer warmth did not occur in iceland until 8 kcal yr bp at the earliest possibly lasting until 6 7 kcal yr bp the amount of warming for july was therefore at least 1 5 c but possibly up to 2 3 c higher than the 1961 1990 average on the basis of the tree line data comparison with data from elsewhere in adjacent arctic regions greenland and eastern arctic canada show peak warmth to be later in iceland and less pronounced it also appears that there were enhanced temperature gradients during the first half of the holocene between the two study areas trollaskagi and the nw peninsula and that they influenced patterns of vegetation colonisation with current spatial temperature patterns only developing as holocene climate deteriorated after around 6 kcal yr bp

residual south polar cap of mars stratigraphy history and implications of recent changes abstract the residual south polar cap rspc of mars includes a group of different depositional units of co 2 ice undergoing a variety of erosional processes complete summer coverage of the rspc by 6 m pixel data of the context imager ctx on mars reconnaissance orbiter mro has allowed mapping and inventory of the units in the rspc unit maps and estimated thicknesses indicate the total volume of the rspc is currently 3 and represents less than 3 of the total mass of the current mars atmosphere scarp retreat rates in the co 2 ice derived from comparison of high resolution imaging science experiment hirise data with earlier images are comparable to those obtained for periods up to 3 mars years earlier these rates combined with sizes of depressions suggest that the oldest materials were deposited more than 125 mars years ago most current erosion is by backwasting of scarps 1 12 m in height this backwasting is initiated by a series of scarp parallel fractures in the older thicker unit these fractures form about every mars year in thinner younger materials they form less frequently some areas of the older thicker unit are lost by downwasting rather than by the scarp retreat a surprising finding from the hirise data is the scarcity of visible layering of rspc materials a result quite distinct from previous interpretations of layers in lower resolution images layers 0 1 m thick are exposed on the upper surfaces of some areas but their timescale of deposition is not known late summer albedo changes mapped by the ctx images indicate local recycling of ice although the amounts may be morphologically insignificant compact reconnaissance imaging spectrometer for mars crism data show that the primary material of all the different forms of the rspc is co 2 ice with only small admixtures of water ice and dust

exposed water ice discovered near the south pole of mars the mars odyssey thermal emission imaging system themis has discovered water ice exposed near the edge of mars southern perennial polar cap the surface h2o ice was first observed by themis as a region that was cooler than expected for dry soil at that latitude during the summer season diurnal and seasonal temperature trends derived from mars global surveyor thermal emission spectrometer observations indicate that there is h2o ice at the surface viking observations and the few other relevant themis observations indicate that surface h2o ice may be widespread around and under the perennial co2 cap

spatial and temporal variability of holocene temperature in the north atlantic region the early holocene climate of the north atlantic region was influenced by two boundary conditions that were fundamentally different from the present the presence of the decaying laurentide ice sheet lis and higher than present summer solar insolation in order to assess spatial and temporal patterns of holocene climate evolution across this region we collated quantitative paleotemperature records at sub millennial resolution and synthesized their temporal variability using principal components analysis pca the analysis reveals considerable spatial variability most notably in the time transgressive expression of the holocene thermal maximum htm most of the region but especially areas peripheral to the labrador sea and hence closest to the locus of lis disintegration experienced maximum holocene temperatures that lagged peak summer insolation by 1000 3000 years many sites from the northeastern north atlantic sector including the nordic seas and scandinavia either warmed in phase with maximum summer insolation 11 000 9000 years ago or were less strongly lagged than the baffin bay labrador sea region these spatially complex patterns of holocene climate development which are defined by the pca resulted from the interplay between final decay of the lis and solar insolation forcing

mariner 9 observations of the south polar cap of mars evidence for residual co2 frost the first spacecraft observations of the south residual polar cap of mars were obtained by the mariner 9 orbiter during the martian southern summer season 1971 1972 analyses of viking orbiter observations obtained 3 mars years later have shown that residual carbon dioxide frost was present at the south polar cap in 1977 in this study mariner 9 infrared interferometer spectrometer spectra and television camera images are used in conjunction with multispectral thermal emission models to constrain the temperatures of dark bare ground and bright frost regions within the south residual cap the results provide strong evidence that carbon dioxide frost was present throughout the summer season despite the fact that the residual frost deposits observed by mariner 9 were less extensive than those observed by viking

a high resolution absolute dated holocene and deglacial asian monsoon record from dongge cave china abstract we present a continuous record of the asian monsoon over the last 16 ka from 18o measurements of stalagmite calcite over 900 oxygen isotopic measurements providing information on shifts in monsoon precipitation are combined with a chronology from 45 precise 230th dates 18o and therefore asian monsoon intensity generally follows changes in insolation although changes in 18o are generally accommodated in abrupt shifts in contrast to smoothly varying insolation indicating that threshold effects may be important 18o decreased dramatically 3 at the start of the holocene 11 5 ka and remained low for 6 ka four positive 18o events centered at 11225 97 yr bp 1 05 10880 117 yr bp 1 15 9165 75 yr bp 1 4 and a double event centered at 8260 64 yr bp 1 1 and 8080 74 yr bp 1 0 punctuated this period of high monsoon intensity all four events correlate within error with climate changes in greenland ice cores thus the relationship between the asian monsoon and the north atlantic observed during the glacial period appears to continue into the early holocene in addition three of the four events correlate within error with outburst events from lake agassiz the decline of monsoon intensity in the mid late holocene is characterized by an abrupt positive shift in 18o which occurs at 3550 59 yr bp 1 1 in 100 yr in addition the holocene is punctuated by numerous centennial and multi decadal scale events amplitudes 0 5 to 1 up to half the amplitude of the glacial interstadial events seen in the last glacial period thus holocene centennial and multi decadal scale monsoon variability is significant although not as large as glacial millennial scale variability the monsoon shows a strong connection with northern south american hydrological changes related by changes in itcz position spectral analysis of the 18o record shows significant peaks at solar periodicities of 208 yr and 86 yr suggesting variation is influenced by solar forcing however there are numerous other significant peaks including peaks at el nino frequencies observed for high resolution portions of the record between 8110 and 8250 yr which suggest that changes in oceanic and atmospheric circulation patterns in addition to those forced by solar changes are important in controlling holocene monsoon climate in addition for this high resolution portion we observe a distinctive biennial oscillation of the asian monsoon which has been associated with the tropospheric biennial oscillation tbo

a search for polycyclic aromatic hydrocarbons over the martian south polar residual cap abstract we present our research on compositional mapping of the martian south polar residual cap sprc especially the detection of organic signatures within the dust content of the ice based on hyperspectral data analysis the sprc is the main region of interest for this investigation because of the unique co 2 ice sublimation features that cover the surface these flat floored circular depressions are highly dynamic and we infer frequently expose dust particles previously trapped within the ice during the wintertime here we identify suitable regions for potential dust exposure on the sprc and utilise data from the compact reconnaissance imaging spectrometer for mars crism on board nasa s mars reconnaissance orbiter mro satellite to examine infrared spectra of dark regions assumed to be composed mainly of dust particles to establish their mineral composition to eliminate the effects of ices on sub pixel dusty features and to look for signatures indicative of polycyclic aromatic hydrocarbons pahs spectral mapping has identified compositional differences between depression rims and the majority of the sprc and crism spectra have been corrected to minimise the influence of co 2 ice whilst no conclusive evidence for pahs has been found within the detectability limits of the crism instrument depression rims are shown to have higher water content than regions of featureless ice and there are possible indications of magnesium carbonate within the dark dusty regions

the instability of a south polar cap on mars composed of carbon dioxide abstract if the martian south polar cap were composed of solid carbon dioxide would it be sufficiently stable against collapse under its own weight this question is examined in the light of new experiments on the creep of solid carbon dioxide and new high resolution topographic mapping of the south polar cap the conclusion from a simple model is that with the strongest of three flow laws compatible with the measurements co 2 is strong enough to support a cap of this material with thickness about 1800 m for 10 7 years or more which is the age suggested by the cratering record however none of the three possible flow laws will allow a 3000 m cap the thickness suggested by stereogrammetry to survive for 10 7 years indicating that the south polar ice cap is probably not composed of pure co 2 ice

co2 snow depth and subsurface water ice abundance in the northern hemisphere of mars observations of seasonal variations of neutron flux from the high energy neutron detector hend on mars odyssey combined with direct measurements of the thickness of condensed carbon dioxide by the mars orbiter laser altimeter mola on mars global surveyor show a latitudinal dependence of northern winter deposition of carbon dioxide the observations are also consistent with a shallow substrate consisting of a layer with water ice overlain by a layer of drier soil the lower ice rich layer contains between 50 and 75 weight water indicating that the shallow subsurface at northern polar latitudes on mars is even more water rich than that in the south

mars the regolith atmosphere cap system and climate change abstract a new model for predicting the behavior of the martian regolith atmosphere cap co 2 regime and describing its role in climate change is derived the model describes the time temperature histories of 90 regolith chunks on a latitude depth grid accounting for co 2 exchange by means of laboratory derived expressions relating temperature co 2 pressure p co 2 and adsorbed co 2 mass co 2 polar cap formation and sublimation is accounted for subject to the constraint of constant total co 2 in the atmosphere regolith cap system the influence of differences in regolith adsorption laws for basalt and clay and the influence of variations in regolith depth with latitude regolith thermal diffusivity and total exchangeable co 2 inventory on predicted variations in atmospheric pressure and cap mass are examined the following results are indicated 1 the atmosphere acts as a low capacity conduit through which flows between 10 and 100 times the current atmospheric mass of co 2 between two reservoirs a regolith ocean of adsorbed co 2 and a polar cap cryosphere 2 exchange between these reservoirs is driven by variations of obliquity with the polar cap the dominant co 2 sink at low and the regolith dominating at high atmospheric pressure ranges between 0 1 low and 15 mbar high pressures of up to 25 mbar could result from pre tharsis variations pressure up to 40 mbarare achieved only in models which also call for a huge quasi permanent present co 2 cap which is not apparent 3 at high the atmospheric pressure is buffered by the regolith and satisfies adsorption equilibrium for the 90 chunks as well as conservation of co 2 mass at low a potetially large co 2 cap appears and the atmospheric pressure is buffered by the cap not the regolith 4 the periodic reservoir flushing can account for the observation of simultaneous nonenrichment of 18 o and enrichment of 13 n 5 mars climate history may be divided into three parts a post tharsis formation history as described above b pre tharsis formation with qualitatively similar processes but larger oscillations between reservoirs and larger atmospheric pressure and cap mass variation and c the very early period of channel formation 6 the nature of the response of the three part regolith atmosphere polar cap martian climate system to surface insolation variations may be analogous to that of earth s ocean atmosphere cryosphere system