cloud top structure of venus revealed by subaru comics mid infrared images abstract we have investigated the cloud top structure of venus by analyzing ground based images taken at the mid infrared wavelengths of 8 66 m and 11 34 m venus at a solar phase angle of 90 with the morning terminator in view was observed by the cooled mid infrared camera and spectrometer comics mounted on the 8 2 m subaru telescope during the period october 25 29 2007 the disk averaged brightness temperatures for the observation period are 230 k and 238 k at 8 66 m and 11 34 m respectively the obtained images with good signal to noise ratio and with high spatial resolution 200 km at the sub observer point provide several important findings first we present observational evidence for the first time of the possibility that the westward rotation of the polar features the hot polar spots and the surrounding cold collars is synchronized between the northern and southern hemispheres second after high pass filtering the images reveal that streaks and mottled and patchy patterns are distributed over the entire disk with typical amplitudes of 0 5 k and vary from day to day the detected features some of which are similar to those seen in past uv images result from inhomogeneities of both the temperature and the cloud top altitude third the equatorial center to limb variations of brightness temperatures have a systematic day night asymmetry except those on october 25 that the dayside brightness temperatures are higher than the nightside brightness temperatures by 0 4 k under the same viewing geometry such asymmetry would be caused by the propagation of the migrating semidiurnal tide finally by applying the lapse rates deduced from previous studies we demonstrate that the equatorial center to limb curves in the two spectral channels give access to two parameters the cloud scale height h and the cloud top altitude zc the acceptable models for data on october 25 are obtained at h 2 4 4 3 km and zc 66 69 km this supports previous results determined from spacecraft observations

wave analysis in the atmosphere of venus below 100 km altitude simulated by the lmd venus gcm a new simulation of venus atmospheric circulation obtained with the lmd venus gcm is described and the simulated wave activity is analysed agreement with observed features of the temperature structure static stability and zonal wind field is good such as the presence of a cold polar collar diurnal and semi diurnal tides at the resolution used 96 longitudes 96 latitudes a fully developed superrotation is obtained both when the simulation is initialised from rest and from an atmosphere already in superrotation though winds are still weak below the clouds roughly half the observed values the atmospheric waves play a crucial role in the angular momentum budget of the venus s atmospheric circulation in the upper cloud the vertical angular momentum is transported by the diurnal and semi diurnal tides above the cloud base approximately 1 bar equatorward transport of angular momentum is done by polar barotropic and mid to high latitude baroclinic waves present in the cloud region with frequencies between 5 and 20 cycles per venus day periods between 6 and 23 earth days in the middle cloud just above the convective layer a kelvin type wave period around 7 3 ed is present at the equator as well as a low latitude rossby gravity type wave period around 16 ed below the clouds large scale mid to high latitude gravity waves develop and play a significant role in the angular momentum balance

calcium carbonate as ikaite crystals in antarctic sea ice 1 we report on the discovery of the mineral ikaite caco3 6h2o in sea ice from the southern ocean the precipitation of caco3 during the freezing of seawater has previously been predicted from thermodynamic modelling indirect measurements and has been documented in artificial sea ice during laboratory experiments but has not been reported for natural sea ice it is assumed that caco3 formation in sea ice may be important for a sea ice driven carbon pump in ice covered oceanic waters without direct evidence of caco3 precipitation in sea ice its role in this and other processes has remained speculative the discovery of caco3 6h2o crystals in natural sea ice provides the necessary evidence for the evaluation of previous assumptions and lays the foundation for further studies to help elucidate the role of ikaite in the carbon cycle of the seasonally sea ice covered regions

temporal evolution of decaying summer first year sea ice in the western weddell sea antarctica abstract the evolution of the main physico chemical properties of the unflooded 90 cm thick first year sea ice cover at the ice station polarstern ispol clean site is described ispol was an international experiment of the german research icebreaker r v polarstern the vessel was anchored to an ice floe for an observation period of 5 weeks during the early summer melt onset in the western weddell sea the clean site was specially designed and accessed so as to prevent any trace metal contamination of the sampling area observations were made at 5 day intervals during december 2004 in the central part of the main floe results show the succession of two contrasting phases in the behavior of the brine network brine channels pockets and tubes initially brine salinity was higher than that of sea water leading to brine migration and a decrease in the mean bulk salinity of the ice cover this process is highly favored by the already high bulk porosity 14 which ensures full connectivity of the brine network gravity drainage rather than convection seems to be the dominant brine transfer process half way through the observation period the brine salinity became lower than that of the sea water throughout the ice column the brine network therefore switched to a stratified regime in which exchange with sea water was limited to molecular diffusion strongly stabilizing the bulk mean sea ice salinity during the transition between the two regimes and in areas closer to ridges slush water resulting from a mixture of snow meltwater and sea water accumulated at the snow ice interface penetrated through the growing honeycomb like structure and replaced the downward draining brines this resulted in a slight local replenishment of nutrients as indicated by dissolved silicic acid however as a whole the described decaying regime in this globally unflooded location with limited snow cover should be unfavorable to the development of healthy and active surface and internal microbial communities the switch from gravity to diffusion controlled transport mechanisms within the ice column also should affect the efficiency of gas exchange across the sea ice cover the observed late build up of a continuous impermeable superimposed ice layer should further significantly hamper gas exchange statistical estimates of the evolution of the ice thickness during the observation period and salinity trends of the under ice water salinity down to 30 m corroborate model predictions of a moderate bottom melting 5 10 cm from ocean heat fluxes

variable winds on venus mapped in three dimensions 1 we present zonal and meridional wind measurements at three altitude levels within the cloud layers of venus from cloud tracking using images taken with the virtis instrument on board venus express at low latitudes zonal winds in the southern hemisphere are nearly constant with latitude with westward velocities of 105 ms 1 at cloud tops altitude 66 km and 60 70 ms 1 at the cloud base altitude 47 km at high latitudes zonal wind speeds decrease linearly with latitude with no detectable vertical wind shear values lower than 15 ms 1 indicating the possibility of a vertically coherent vortex structure meridional winds at the cloud tops are poleward with peak speed of 10 ms 1 at 55 s but below the cloud tops and averaged over the south hemisphere are found to be smaller than 5 ms 1 we also report the detection at subpolar latitudes of wind variability due to the solar tide

carbon dynamics in sea ice a winter flux time series 1 a winter time series of the inorganic carbon system above within and beneath the landfast sea ice of the southern beaufort sea confirmed that sea ice is an active participant in the carbon cycle of polar waters eddy covariance measurements above the ice identified significant vertical co2 fluxes mostly upward away from the ice but with short periods of downward fluxes as well a novel in situ method revealed extremely high pco2 values within the ice that are not inconsistent with theory the total carbon content of the ice increased slightly through the winter season and increasing variability in the vertical profiles as spring began indicated that the inorganic carbon became mobile as the ice began to melt during early winter as the ice formed inorganic carbon concentrations in the surface waters increased dramatically along with salinity partly because of rejection from the ice and partly from advective mixing brine drainage was apparently not sufficient to initiate convection and the excess carbon remained in the surface waters into the summer

evolution of first year and second year snow properties on sea ice in the weddell sea during spring summer transition observations of snow properties superimposed ice and atmospheric heat fluxes have been performed on first year and second year sea ice in the western weddell sea antarctica snow in this region is particular as it does usually survive summer ablation measurements were performed during ice station polarstern ispol a 5 week drift station of the german icebreaker rv polarstern net heat flux to the snowpack was 8 w m 2 causing only 0 1 to 0 2 m of thinning of both snow cover types thinner first year and thicker second year snow snow thinning was dominated by compaction and evaporation whereas melt was of minor importance and occurred only internally at or close to the surface characteristic differences between snow on first year and second year ice were found in snow thickness temperature and stratigraphy snow on second year ice was thicker colder denser and more layered than on first year ice metamorphism and ablation and thus mass balance were similar between both regimes because they depend more on surface heat fluxes and less on underground properties ice freeboard was mostly negative but flooding occurred mainly on first year ice snow and ice interface temperature did not reach the melting point during the observation period nevertheless formation of discontinuous superimposed ice was observed color tracer experiments suggest considerable meltwater percolation within the snow despite below melting temperatures of lower layers strong meridional gradients of snow and sea ice properties were found in this region they suggest similar gradients in atmospheric and oceanographic conditions and implicate their importance for melt processes and the location of the summer ice edge

the percolation phase transition in sea ice sea ice exhibits a marked transition in its fluid transport properties at a critical brine volume fraction p c of about 5 percent or temperature t c of about 5 c for salinity of 5 parts per thousand for temperatures warmer than t c brine carrying heat and nutrients can move through the ice whereas for colder temperatures the ice is impermeable this transition plays a key role in the geophysics biology and remote sensing of sea ice percolation theory can be used to understand this critical behavior of transport in sea ice the similarity of sea ice microstructure to compressed powders is used to theoretically predict p c of about 5 percent

tank study of physico chemical controls on gas content and composition during growth of young sea ice during an ice tank experiment samples were taken to study the processes of acquisition and alteration of the gas properties in young first year sea ice during a complete growth warming cooling cycle the goal was to obtain reference levels for total gas content and concentrations of atmospheric gases o2 n2 co2 in the absence of significant biological activity the range of total gas content values obtained 3 5 to 18 ml of gas per kilo of ice was similar to previous measurements or estimates however major differences occurred between the current and quiet basins showing the role of water dynamics at the ice water interface in controlling bubble nucleation processes extremely high co2 concentrations were observed in all the experiments up to 57 in volume parts it is argued that these could have resulted from two unexpected biases in the experimental settings concentrations of bubbles nucleated at the interface are controlled by diffusion both from the ice water interface towards the well mixed reservoir and between the interface water and the bubble itself this double kinetic effect results in a transition of the gas composition in the bubbles from values close to solubility in sea water towards values close to atmospheric as the ice cover builds up

simulations of ice ocean dynamics in the weddell sea 2 interannual variability 1985 1993 investigations of sea ice ocean interaction on the continental shelf in the southwestern weddell sea reveal a strong correlation between fluctuations of atmospheric forcing and the variability of sea ice formation anomalies of meridional wind stress in the inner weddell sea are consistent with the phase of the antarctic circumpolar wave acw positive anomalies of northward wind stress cause an increase of sea ice export in the same and of sea ice formation in the following year leading to an increased production of high salinity shelf water driven by a varying zonal density distribution over the continental shelf the circulation in the filchner ronne ice shelf cavity fluctuates between two modes each of which features a characteristic distribution of basal freezing and melting regions thus signals of interannual atmospheric variability propagate into the deep ocean and the sub ice shelf cavities

equations for determining the gas and brine volumes in sea ice samples on a etabli des equations utilisables pour determiner le taux de gaz inclus dans la glace de mer a partir de mesures de densite de salinite et de temperature dans des gammes de temperatures entre 2 c et 30 c inversement ces relations peuvent etre utilisees pour calculer la densite de la glace de mer en fonction de la temperature et de la salinite en prenant en compte a la fois la presence de gaz et de cristaux de sel dans la glace on donne aussi des equations qui permettent le calcul du volume de gaz et d eau salee dans la glace a des temperatures autres que celle pour laquelle la densite a ete determinee

solar locked and geographical atmospheric structures inferred from a venus general circulation model with radiative transfer abstract solar locked and geographical atmospheric structures of daily averaged wind and temperature on venus were investigated using an atmospheric general circulation model with venusian topography and a two stream radiative code and were compared with wind fields obtained from the akatsuki ultraviolet imager the horizontal wind fields simulated around the subsolar region are similar to the observed ones at the cloud top mid latitude jets of 120 m s 1 and an equatorial fast flow of 90 m s 1 are formed around the cloud top a poleward flow of 8 m s 1 is formed above the cloud layer where solar heating is strong around the cloud top a poleward flow of 1 m s 1 is confined within the equatorward flank of the jet core whereas an indirect circulation is formed in the jet core by the eddy heat fluxes owing to the thermal tide and baroclinic waves in solar fixed coordinates the subsolar to antisolar circulation is predominant around the cloud top thus differences are significant between the zonal and dayside averages of the meridional wind and its related fluxes within the cloud layer this suggests the zonal mean meridional wind of the hadley circulation eddy momentum and heat fluxes from the one side hemisphere must be estimated carefully in the experiment including topography a near surface subrotation is formed in latitudinal zones over high land and mountains a weakly stable layer is formed at 10 20 km at low latitudes and the zonal wind is weakened at the cloud top over the aphrodite terra regional stationary modification of the atmospheric structure due to topographical waves appears in the cloud layer

antarctic sea ice and palaeoproductivity variation over the last 156 000 years in the indian sector of southern ocean abstract antarctic sea ice plays a vital role in global climate via its impact on ocean circulation biological productivity and co2 partitioning between the ocean and the atmosphere however very little is known about its past history especially in the southwestern indian sector of the southern ocean so we here provide new quantitative records of winter sea ice concentration wsic and duration wsid sea surface temperatures sst and productivity in sediment core sk 200 33 55 s 45 e from the permanently open ocean zone over the last 156 000 years the new records combined with regional records indicate that the hydrological structures migrated northward by a few degrees of latitude during all glacial periods with the southern antarctic circumpolar current front reaching the core site the antarctic polar front located at 46 s and the winter sea ice wsi probably extending to 49 s in contrast hydrological fronts and wsi edge migrated poleward by a couple of degrees of latitude during the early holocene and last interglacial comparison to sst and wsi records from different sectors of the so suggests higher amplitude variations in wsi in the atlantic sector as compared to the indian and western pacific sectors over the last glacial interglacial cycle which we attribute to the presence of the weddell gyre transporting far to the north the sea ice produced in the weddell sea the new records also suggest a drop in productivity in the pooz during glacial periods probably related to greater wsi extent and reduced growing season

ice layer and surface crust permeability in a seasonal snow pack ice layers in snowpacks are thought to retard or obstruct gas and melt water flow through the pack yet there has been little published information on the permeability of ice layers in seasonal snow in this paper investigations of ice layer permeabilities are reported for prominent ice layers 1 to 3 mm thick in a seasonal snowpack for distinct fairly solid ice layers 1 to 3 mm thick permeabilities ranged from 1 to 19 x 10 10 m 2 these values are significantly lower than values for the surrounding snow within 24 h early in the melt season the permeability of the surface crust increased 160 from approximately 70 to 120 x 10 10 m 2 this increase in permeability was accompanied by a small increase in grain size and a decrease in albedo the snow air interface can exhibit dramatic changes in transport properties over relatively short periods of time even without precipitation events these changes driven by the surface meteorology affect transport properties such as permeability as well as albedo

how well does wind speed predict air sea gas transfer in the sea ice zone a synthesis of radon deficit profiles in the upper water column of the arctic ocean we present 34 profiles of radon deficit from the ice ocean boundary layer of the beaufort sea including these 34 there are presently 58 published radon deficit estimates of k the air sea gas transfer velocity in the arctic ocean 52 of these estimates were derived from water covered by 10 sea ice or more the average value of k collected since 2011 is 4 0 1 2 m d 1 this exceeds the quadratic wind speed prediction of weighted kws 2 85 m d 1 with mean weighted wind speed of 6 4 m s 1 we show how ice cover changes the mixed layer radon budget and yields an effective gas transfer velocity we use these 58 estimates to statistically evaluate the suitability of a wind speed parameterization for k when the ocean surface is ice covered whereas the six profiles taken from the open ocean indicate a statistically good fit to wind speed parameterizations the same parameterizations could not reproduce k from the sea ice zone we conclude that techniques for estimating k in the open ocean cannot be similarly applied to determine k in the presence of sea ice the magnitude of k through gaps in the ice may reach high values as ice cover increases possibly as a result of focused turbulence dissipation at openings in the free surface these 58 profiles are presently the most complete set of estimates of k across seasons and variable ice cover as dissolved tracer budgets they reflect air sea gas exchange with no impact from air ice gas exchange

southern ocean co2 sink the contribution of the sea ice we report first direct measurements of the partial pressure of co2 pco2 within antarctic pack sea ice brines and related co2 fluxes across the air ice interface from late winter to summer brines encased in the ice change from a co2 large oversaturation relative to the atmosphere to a marked undersaturation while the underlying oceanic waters remains slightly oversaturated the decrease from winter to summer of pco2 in the brines is driven by dilution with melting ice dissolution of carbonate crystals and net primary production as the ice warms its permeability increases allowing co2 transfer at the air sea ice interface the sea ice changes from a transient source to a sink for atmospheric co2 we upscale these observations to the whole antarctic sea ice cover using the nemo lim3 large scale sea ice ocean and provide first estimates of spring and summer co2 uptake from the atmosphere by antarctic sea ice over the spring summer period the antarctic sea ice cover is a net sink of atmospheric co2 of 0 029 pg c about 58 of the estimated annual uptake from the southern ocean sea ice then contributes significantly to the sink of co2 of the southern ocean

thermal tides in the atmosphere of venus comparison of model results with observations a linearized primitive equation lpe model is developed to study thermal tides in the atmosphere of venus the lpe model describes diurnal and semidiurnal oscillations of a cyclostrophically balanced atmosphere in which zonal velocity varies with altitude and latitude the numerical algorithm follows staniforth and daley the solar thermal forcing is increased algebraically in time to separate the forced tidal response from free atmospheric oscillations parameters of the basic state and forcing agree with pioneer venus observations results of the model are compared with the solar fixed component of brightness temperature variations measured by taylor et al and elson using data from the pioneer venus orbiter infrared radiometer oir the comparison is made by convolving the computed model radiances with the weighting functions of the oir channels agreement between lpe model results and oir observations is excellent two interesting features of the oir data are accounted for namely the slow variation of phase with altitude and the dominance of the semidiurnal oscillation over the diurnal oscillation success of the lpe model opens the way for calculating tidal transports of heat and momentum and assessing the role of tides in maintaining the venus super rotation

experimental evidence for carbonate precipitation and co2 degassing during sea ice formation chemical and stable carbon isotopic modifications during the freezing of artificial seawater were measured in four 4 m3 tank incubations three of the four incubations were inoculated with a non axenic antarctic diatom culture the 18 days of freezing resulted in 25 to 27 cm thick ice sheets overlying the residual seawater the ice phase was characterized by a decrease in temperature from 1 9 to 2 2oc in the under ice seawater down to 6 7oc in the upper 4 cm of the ice sheet with a concurrent increase in the salinity of the under ice seawater and brine inclusions of the ice sheet as a result of physical concentration of major dissolved salts by expulsion from the solid ice matrix measurements of ph total dissolved inorganic carbon ct and its stable isotopic composition d13ct all exhibited changes which suggest minimal effect by biological activity during the experiment a systematic drop in ph and salinity normalized ct by up to 0 37 phsws units and 376 mol c kg 1 respectively at the lowest temperature and highest salinity part of the ice sheet were coupled with an equally systematic 13c enrichment of the ct calculations based on the direct ph and ct measurements indicated a steady increase in the in situ concentration of dissolved carbon dioxide co2 aq with time and increasing salinity within the ice sheet partly due to changes in the dissociation constants of carbonic acid in the low temperature high salinity range within sea ice the combined effects of temperature and salinity on the solubility of co2 over the range of conditions encountered during this study was a slight net decrease in the equilibrium co2 aq concentration as a result of the salting out overriding the increase in solubility with decreasing temperature hence the increase in the in situ co2 aq concentration lead to saturation or supersaturation of the brine inclusions in the ice sheet with respect to atmospheric pco2 3 5x10 4 atm when all physico chemical processes are considered we expect co2 degassing and carbonate mineral precipitation from the brine inclusions of the ice sheet which were saturated or highly supersaturated with respect to both the anhydrous calcite aragonite vaterite and hydrated ikaite carbonate minerals

the gas transfer through polar sea ice experiment insights into the rates and pathways that determine geochemical fluxes sea ice is a defining feature of the polar marine environment it is a critical domain for marine biota and it regulates ocean atmosphere exchange including the exchange of greenhouse gases such as co2 and ch4 in this study we determined the rates and pathways that govern gas transport through a mixed sea ice cover n2o sf6 3he 4he and ne were used as gas tracers of the exchange processes that take place at the ice water and air water interfaces in a laboratory sea ice experiment observation of the changes in gas concentrations during freezing revealed that he is indeed more soluble in ice than in water ne is less soluble in ice and the larger gases n2o and sf6 are mostly excluded during the freezing process model estimates of gas diffusion through ice were calibrated using measurements of bulk gas content in ice cores yielding gas transfer velocity through ice kice of 5 10 4 m d 1 in comparison the effective air sea gas transfer velocities keff ranged up to 0 33 m d 1 providing further evidence that very little mixed layer ventilation takes place via gas diffusion through columnar sea ice however this ventilation is distinct from air ice gas fluxes driven by sea ice biogeochemistry the magnitude of keff showed a clear increasing trend with wind speed and current velocity beneath the ice as well as the combination of the two this result indicates that gas transfer cannot be uniquely predicted by wind speed alone in the presence of sea ice

heat flow and heat generation in the churchill province of the canadian shield and their palaeotectonic significance six new heat flow determinations are presented for proterozoic mobile belts of the churchill province of the canadian shield an area that was affected by several stages of the hudsonian orogenic sequence 1 9 1 6 ga ago with other previously published values the mean of eight determinations considered reliable and representative and corrected for the effects of pleistocene glaciation is 44 7 mw m 2 heat generation measurements have also been made values range from 0 1 1 04 w m 3 a linear relation between heat flow and heat production is apparent the heat flow axis intercept is 37 mw m 2 and the scale depth is 11 km compared with 28 mw m 2 and 13 6 km for the archaean superior province approximately 20 of the churchill heat flow appears to be derived from radioactive decay in the upper crust compared with 30 for the superior province and shields as a whole the observations imply that the heat flow heat production relation for the churchill province should be written as q qc qe a0b where qc is equivalent to the reduced heat flow for the archaean terrain b is similar for the two and qe is an additional component of heat flow in the proterozoic mobile belts of the churchill province a speculative tectonic model is presented it is suggested that rifting along two axes of an original craton which had lateral variations in near surface radiogenic element concentration followed by erosion of the radiogenic layer and subsequent reconvergence of the cratonic segments led to widespread redistribution of radioactive elements into the reactivated inter rift crustal block one result would be that crustal temperatures are higher in that part of the churchill province than in the superior

global maps of venus nightside mean infrared thermal emissions obtained by virtis on venus express one of the striking features about venus atmosphere is its temporal variability and dynamics with a chaotic polar vortex large scale atmospheric waves sheared features and variable winds that depend on local time and possibly orographic features the aim of this research is to combine data accumulated over several years and obtain a global mean state of the atmosphere focusing in the global structure of the clouds using the cloud opacity and upper cloud temperatures we have first produced global maps using the integrated radiance through the infrared atmospheric windows centred around 1 74 m and 2 25 m that show the spatial variations of the cloud opacity in the lower clouds around 44 48 km altitude and also provide an indirect estimation of the possible particle size we have also produced similar global maps using the brightness temperatures seen in the thermal region at 3 8 m and 5 0 m which provide direct indication of the temperatures at the top of the clouds around 60 70 km altitude these maps have been generated using the complete dataset of the visible and infrared thermal imaging spectrometer mapping channel virtis m on board venus express with a wide spatial and long temporal coverage in the period from may 2006 until october 2008 our results provide a global view of the cloud opacity particle size and upper cloud temperatures at both hemispheres showing the main different dynamical regions of the planet the profiles obtained also provide the detailed dependencies with latitude local time and longitude diagnostic of the global circulation flow and dynamics at various altitude layers from about 44 up to 70 km over the surface

latitudinal variations of co and ocs in the lower atmosphere of venus from near infrared nightside spectro imaging abstract spectro imaging of venus nightside in the 2 3 m window provides a powerful means of probing the lower atmosphere in the 25 40 km altitude range we present observations recorded at the nasa irtf in february 2003 and august 2004 using the spex spectro imager in the 2 1 2 5 m region abundances of co and ocs have been derived as a function of latitude for different longitudes the co abundance increases by about 15 between the equatorial region and higher latitudes 40 no longitudinal or temporal variations are observed the ocs abundance shows the opposite variation in observational sets with sufficient s n these variations and anticorrelation are consistent with upwelling motions in the equatorial region and downwelling at higher latitudes

a heat production model of a shield area and its implications for the heat flow heat production relationship the pikwitonei and sachigo subprovinces of central manitoba provide a cross sectional view of the superior province crust to constrain thermal models of the crust we measured heat production and thermal conductivity in rocks from this terrain using standard gamma ray spectrometry and divided bar techniques these data when used in a two dimensional model of shield crust show that estimates of surface heat flow and surface heat production yield the well known linear relationship between surface heat production and surface heat flow observed for heat flow provinces this demonstrates that determinations of heat production with depth based on inversion of the linear heat production heat flow relationship are non unique

dynamics of pco2 and related air ice co2 fluxes in the arctic coastal zone amundsen gulf beaufort sea we present an arctic seasonal survey of carbon dioxide partial pressure pco 2 dynamics within sea ice brine and related air ice co 2 fluxes the survey was carried out from early spring to the beginning of summer in the arctic coastal waters of the amundsen gulf high concentrations of pco 2 up to 1834 matm were observed in the sea ice in early april as a consequence of concentration of solutes in brines caco 3 precipitation and microbial respiration caco 3 precipitation was detected through anomalies in total alkalinity ta and dissolved inorganic carbon dic this precipitation seems to have occurred in highly saline brine in the upper part of the ice cover and in bulk ice as summer draws near the ice temperature increases and brine pco 3 shifts from a large supersaturation 1834 matm to a marked undersaturation down to almost 0 matm this decrease was ascribed to brine dilution by ice meltwater dissolution of caco 3 and photosynthesis during the sympagic algal bloom the magnitude of the co 2 fluxes was controlled by ice temperature through its control on brine volume and brine channels connectivity and the concentration gradient between brine and the atmosphere however the state of the ice interface clearly affects air ice co 2 fluxes

physical and biological properties of early winter antarctic sea ice in the ross sea this work presents the results of physical and biological investigations at 27 biogeochemical stations of early winter sea ice in the ross sea during the 2017 pipers cruise only two similar cruises occurred in the past in 1995 and 1998 the year 2017 was a specific year in that ice growth in the central ross sea was considerably delayed compared to previous years these conditions resulted in lower ice thicknesses and chl a burdens as compared to those observed during the previous cruises it also resulted in a different structure of the sympagic algal community unusually dominated by phaeocystis rather than diatoms compared to autumn winter sea ice in the weddell sea awecs cruise the 2017 ross sea pack ice displayed similar thickness distribution but much lower snow cover and therefore nearly no flooding conditions it is shown that contrasted dynamics of autumnal winter sea ice growth between the weddell sea and the ross sea impacted the development of the sympagic community mean median ice chl a concentrations were 3 5 times lower at pipers and the community status there appeared to be more mature decaying based on phaeopigments chl a ratios these contrasts are discussed in the light of temporal and spatial differences between the two cruises

first estimates of the contribution of caco3 precipitation to the release of co2 to the atmosphere during young sea ice growth 1 we report measurements of ph total alkalinity air ice co2 fluxes chamber method and caco3 content of frost flowers ff and thin landfast sea ice as the temperature decreases concentration of solutes in the brine skim increases along this gradual concentration process some salts reach their solubility threshold and start precipitating the precipitation of ikaite caco3 6h2o was confirmed in the ff and throughout the ice by raman spectroscopy and x ray analysis the amount of ikaite precipitated was estimated to be 25 mol kg 1 melted ff in the ff and is shown to decrease from 19 to 15 mol kg 1 melted ice in the upper part and at the bottom of the ice respectively co2 release due to precipitation of caco3 is estimated to be 50 mol kg 1 melted samples the dissolved inorganic carbon dic normalized to a salinity of 10 exhibits significant depletion in the upper layer of the ice and in the ff this dic loss is estimated to be 2069 mol kg 1 melted sample and corresponds to a co2 release from the ice to the atmosphere ranging from 20 to 40 mmol m 2 d 1 this estimate is consistent with flux measurements of air ice co2 exchange our measurements confirm previous laboratory findings that growing young sea ice acts as a source of co2 to the atmosphere caco3 precipitation during early ice growth appears to promote the release of co2 to the atmosphere however its contribution to the overall release by newly formed ice is most likely minor

the ice thickness distribution across the atlantic sector of the antarctic ocean in midwinter during the first leg of the winter weddell sea project antarktis v 2 cruise of f s polarstern the entire width of the antarctic sea ice zone was traversed in the vicinity of 0 longitude in the period july 18 to september 10 1986 ice thicknesses were measured by direct drilling and by helicopter profiling using an exstar 100 mhz impulse radar system in addition aerial photography of the ice cover was done from 100 to 2000 m altitude using a 70 mm aerial camera mounted in the helicopter the results of the point measurements drilling are reported in this paper together with an indication of how the radar and photography data will be used to extend them so as to yield area averaged ice thickness distributions it was found that the main ice type across the entire width of the ice cover was consolidated pancake ice occurring in vast floes this formed out of a 250 km wide band at the advancing ice edge which comprised a concentrated field of individual pancakes in a matrix of frazil ice preferred thicknesses of undeformed floes were 40 60 cm of ice covered with 5 15 cm of snow the individual pancakes attained almost all of this thickness before consolidation subsequent congelation growth was slow estimated at 0 4 cm d 1 the floes contained much small scale roughness on the upper and lower surfaces due to rafting of pancakes at the time of consolidation but pressure ridging was modest except in the far south a few very thick 8 11 m multiyear floes were observed embedded in the pack at latitudes beyond 66 s

a detailed study of the distribution of heat flow and radioactivity in new hampshire u s a abstract we present a set of 39 new determinations of heat flow and radiogenic heat production for several different geological environments in the state of new hampshire u s a with the extensive data set now available for the state the linear relation of heat flow and heat production appears as a very useful generalization for the study of the heat flow field of a geological province our measurements indicate that the vertical distribution of radiogenic heat production is similar in plutonic and metasedimentary rocks our data are compatible with the linear relationship established earlier by f birch and his co workers in 1968 young granites are markedly enriched in radioactive elements and those which do not outcrop are revealed by anomalies in the general relation of heat flow versus radioactivity heat flow is high for plutons by low elsewhere the mean heat flow through metasedimentary formations is 1 15 cal cm2 s 48 mw m2 a value near the mean heat flow for old cratons the lowest heat flow measured is 0 76 cal cm2 s 32 mw m2 for a unit poor in radioactivity the heat flow field grades smoothly into the low heat flow regions of the canadian shield the new hampshire region is in thermal equilibrium its heat flow is in secular equilibrium with the heat generated by crustal sources and that supplied from the mantle in this area the thermal perturbations due to orogenic events decrease below the detection level in less than 200 275 ma the thickness of the layer which is thermally affected during continent continent collision type orogenies cannot be greater than about 190 km

maintenance of strong rotational winds in venus middle atmosphere by thermal tides the cloud level atmosphere of venus takes little more than 4 days to complete one rotation whereas the solid planet below has a 243 day period computer simulations of the circulation of the venus middle atmosphere between 40 and 85 kilometers as driven by solar radiation absorbed in the clouds reproduce i the observed cloud level rotation rate ii strong vertical shears above and below the cloud tops and iii midlatitude jets and strong poleward flow on the day side simulated circulations converge to yield nearly the same zonal winds when initialized with both stronger or weaker rotation rates these results support the hypothesis that the observed cloud top rotation rate is maintained by statistical balance between fluxes of momentum by thermal tides and momentum advection by mean meridional circulation

physical and biogeochemical properties in landfast sea ice barrow alaska insights on brine and gas dynamics across seasons 1 the impacts of the seasonal evolution of sea ice physical properties on ice ocean biogeochemical exchanges were investigated in landfast ice at barrow alaska from january through june 2009 three stages of brine dynamics across the annual cycle have been identified based on brine salinity brine volume fraction and porous medium rayleigh number ra these are sea ice bottom layer convection full depth convection and brine stratification we further discuss the impact of brine dynamics on biogeochemical compounds in sea ice stable isotopes of water d 18o nutrients no3 po43 nh4 microalgae chlorophyll a and inert gas argon in general full depth convection events favor exchanges between sea ice and seawater while brine stratification limits these exchanges however argon responds differently to brine dynamics than the other biogeochemical compounds analyzed in this study this contrast is attributed to the impact of bubble nucleation on inert gas transport compared to the other biogeochemical compounds we present a scenario for argon bubble formation and evolution in sea ice and suggest that a brine volume fraction approaching 7 5 10 is required for inert gas bubbles to escape from sea ice to the atmosphere

arise antarctic remote ice sensing experiment in the east 2003 validation of satellite derived sea ice data products preliminary results are presented from the first validation of geophysical data products ice concentration snow thickness on sea ice hs and ice temperature ti from the nasa eos aqua amsr e sensor in east antarctica in september october 2003 the challenge of collecting sufficient measurements with which to validate the coarse resolution amsr e data products adequately was addressed by means of a hierarchical approach using detailed in situ measurements digital aerial photography and other satellite data initial results from a circumnavigation of the experimental site indicate that at least under cold conditions with a dry snow cover there is a reasonably close agree ment between satellite and aerial photo derived ice concentrations i e 97 2 3 6 for nt2 and 96 5 2 5 for bba algorithms vs 94 3 for the aerial photos in general the amsr e concentration represents a slight overestimate of the actual concentration with the largest discrepancies occurring in regions containing a relatively high proportion of thin ice the amsr e concentrations from the nt2 and bba algorithms are similar on average although differences of up to 5 occur in places again related to thin ice distribution the amsr e ice temperature ti product agrees with coincident surface measurements to approximately 0 58c in the limited dataset analyzed regarding snow thickness the amsr hs retrieval is a significant underestimate compared to in situ measurements weighted by the percentage of thin ice and open water present for the case study analyzed the underestimate was 46 for the overall average but 23 compared to smooth ice measurements the spatial distribution of the amsr e hs product follows an expected and consistent spatial pattern suggesting that the observed difference may be an offset at least under freezing conditions areas of discrepancy are identified and the need for future work using the more extensive dataset is highlighted

characteristic features in venus nightside cloud top temperature obtained by akatsuki lir abstract mid infrared images of almost the entire venus nightside hemisphere obtained by the longwave infrared camera lir onboard akatsuki on december 9 and 10 2010 reveal that the brightness temperature of the cloud top ranges from 237 k in the cold polar collars to 243 k in the equatorial region significantly higher than the values obtained by venera 15 other characteristic features of the temperature distributions observed are zonal belt structures seen in the middle and low latitudes and patchy temperature structures or quasi periodic streaks extending in a north south direction in the northern middle latitudes and southern low latitudes

local time dependence of the thermal structure in the venusian equatorial upper atmosphere comparison of akatsuki radio occultation measurements and gcm results plain language summary temperature profiles of the venus atmosphere obtained by the akatsuki radio occultation measurements showed a prominent local time dependence above 65 km altitude at low latitudes equatorward of 35 degrees a zonal wavenumber 2 component is predominant in the temperature field and its phase i e isothermal surfaces descend with local time suggesting its downward phase propagation a general circulation model gcm for the venus atmosphere afes venus reproduced the local time dependent thermal structure qualitatively consistent with the radio occultation measurements based on a comparison between the radio occultation measurements and the gcm results the observed zonal wavenumber 2 structure is attributed to the semidiurnal tide applying the dispersion relationship for internal gravity waves to the observed wave structure the zonally averaged zonal wind speed at 75 to 85 km altitudes was found to be significantly smaller than that at the cloud top the decrease of the zonal wind speed with altitude is attributed to the momentum deposition by the upwardly propagating semidiurnal tide excited in the cloud layer akatsuki radio occultation measurements showed the local time dependence of the venus atmosphere in the equatorial region by comparing the measurements with a general circulation model it is attributed to the upward propagating semidiurnal tide generated in the cloud layer and then we proposed a new method to estimate the zonal wind speed above the cloud layer where any optical instruments cannot be measured for the first time

desalination processes of sea ice revisited 1 we reexamine five processes that have been suggested to be important for the loss of salt from sea ice these processes are the initial fractionation of salt at the ice ocean interface brine diffusion brine expulsion gravity drainage and flushing with surface meltwater we present results from analytical and numerical studies as well as from laboratory and field experiments that show that among these processes only gravity drainage and flushing contribute to any measurable net loss of salt we show that during ice growth the salinity field is continuous across the ice ocean interface hence there is no immediate segregation of salt at the advancing front

ocean acidification and calcium carbonate saturation states in the coastal zone of the west antarctic peninsula the polar oceans are particularly vulnerable to ocean acidification the lowering of seawater ph and carbonate mineral saturation states due to uptake of atmospheric carbon dioxide co2 high spatial variability in surface water ph and saturation states for two biologically important calcium carbonate minerals calcite and aragonite was observed in ryder bay in the coastal sea ice zone of the west antarctic peninsula glacial meltwater and melting sea ice stratified the water column and facilitated the development of large phytoplankton blooms and subsequent strong uptake of atmospheric co2 of up to 55 mmol m 2 day 1 during austral summer concurrent high ph 8 48 and calcium carbonate mineral supersaturation aragonite 3 1 occurred in the meltwater influenced surface ocean biologically induced increases in calcium carbonate mineral saturation states counteracted any effects of carbonate ion dilution accumulation of co2 through remineralisation of additional organic matter from productive coastal waters lowered the ph 7 84 and caused deep water corrosivity aragonite 0 9 in regions impacted by circumpolar deep water episodic mixing events enabled co2 rich subsurface water to become entrained into the surface and eroded seasonal stratification to lower surface water ph 8 21 and saturation states aragonite 1 8 relative to all surface waters across ryder bay uptake of atmospheric co2 of 28 mmol m 2 day 1 in regions of vertical mixing may enhance the susceptibility of the surface layer to future ocean acidification in dynamic coastal environments spatially resolved studies are essential to elucidate the natural variability in carbonate chemistry in order to better understand and predict carbon cycling and the response of marine organisms to future ocean acidification in the antarctic coastal zone

biogeochemical impact of snow cover and cyclonic intrusions on the winter weddell sea ice pack sea ice is a dynamic biogeochemical reactor and a double interface actively interacting with both the atmosphere and the ocean however proper understanding of its annual impact on exchanges and therefore potentially on the climate notably suffer from the paucity of autumnal and winter data sets here we present the results of physical and biogeochemical investigations on winter antarctic pack ice in the weddell sea r v polarstern awecs cruise july august 2013 which are compared with those from two similar studies conducted in the area in 1986 and 1992 the winter 2013 was characterized by a warm sea ice cover due to the combined effects of deep snow and frequent warm cyclones events penetrating southwards from the open southern ocean these conditions were favorable to high ice permeability and cyclic events of brine movements within the sea ice cover brine tubes favoring relatively high chlorophyll a chl a concentrations we discuss the timing of this algal activity showing that arguments can be presented in favor of continued activity during the winter due to the specific physical conditions large scale sea ice model simulations also suggest a context of increasingly deep snow warm ice and large brine fractions across the three observational years despite the fact that the model is forced with a snowfall climatology this lends support to the claim that more severe antarctic sea ice conditions characterized by a longer ice season thicker and more concentrated ice are sufficient to increase the snow depth and somehow counter intuitively to warm the ice

venus cloud top winds from tracking uv features in venus monitoring camera images 1 to date dynamical observations of the venus clouds have delivered mainly either only short term or long term averaged results with the venus monitoring camera vmc it finally became possible to investigate the global dynamics with a relatively high resolution in space and time on a long term basis our findings from manual cloud feature wind tracking in vmc uv image sequences so far show that the details of the mesospheric dynamics of venus appear to be highly variable although the general rotation of the atmosphere remained relatively stable since mariner 10 more than 30 years ago by now there are indications of short term variations in the general circulation pattern of the venus atmosphere at cloud top level in some cases significant variations in the zonal wind properties occur on a timescale of days in other cases we see rather stable conditions over one atmospheric revolution or longer at cloud top level it remains an interesting question whether the irregularly observed midlatitude jets are indeed variable or simply become shielded from view by higher h2so4 haze layers for varying time intervals winds at latitudes higher than 60 s are still difficult to obtain track because of low contrast and scarcity of features but increasing data is being collected over all it was possible to extend latitudinal coverage of the cloud top winds with vmc observations thermal tides seem to be present in the data but final confirmation still depends on synthesis of visible and infrared thermal imaging spectrometer and vmc observations on night and dayside although poorly resolved meridional wind speed measurements agree mainly with previous observations and with the presence of a hadley cell spanning between equatorial region and about 45 s latitude

the effect of lateral deformation on heat flow heat production relations deformation that takes place following the fractionation of heat producing elements can cause the relationship of surface heat flow and heat production to deviate from a simple linear trend lateral transport by low angle normal faulting or thrust faulting may place the near surface rocks above rocks with different thermal properties even for a simple model the relationships can be complex but some constraints can be placed on the vertical distribution of heat generation and layer thickness measurements at many sites in a province could produce an overall linear trend of surface flux and heat production departures from linearity may be found at sites that were disturbed transported following the latest cycle of radioelement fractionation the amount of departure from linearity is a function of the thickness of the transported layer and the thermal properties of underlying layers

investigation of air temperature on the nightside of venus derived from virtis h on board venus express abstract we present the spatial distribution of air temperature on venus night side as observed by the high spectral resolution channel of virtis visible and infrared thermal imaging spectrometer or virtis h on board the esa mission venus express the present work extends the investigation of the average thermal fields in the northern hemisphere of venus by including the virtis h data we show results in the pressure range of 100 4 mbar which corresponds to the altitude range of 65 80 km with these new retrievals we are able to compare the thermal structure of the venus mesosphere in both hemispheres the major thermal features reported in previous investigations i e the cold collar at about 65 70 s latitude 100 mbar pressure level and the asymmetry between the evening and morning sides are confirmed here by comparing the temperatures retrieved by the virtis spectrometer in the north and south we find that similarities exist between the two hemispheres solar thermal tides are clearly visible in the average temperature fields to interpret the thermal tide signals otherwise impossible without day site observations we apply model simulations using the venus global circulation model venus gcm lebonnois s hourdin f forget f eymet v fournier r 2010b international venus conference aussois 20 26 june 2010 of the laboratoire de meteorologie dynamique lmd we suggest that the signal detected at about 60 70 latitude and pressure of 100 mbar is a diurnal component while those located at equatorial latitudes are semi diurnal other tide related features are clearly identified in the upper levels of the atmosphere

zonal superrotation above venus cloud base induced by the semidiurnal tide and the mean meridional circulation abstract we have calculated the equilibrium zonal wind structure resulting from the interaction of the semidiurnal tide and the mean meridional circulation driven by the zonally averaged solar heating above the venus cloud base the results show that the tidal mechanism proposed by fels and lindzen can account for a substantial fraction and possibly all of the increase of the equatorial wind speed above the cloud base above the cloud tops tidal deceleration may be too small to produce the zonal wind decrease with height inferred from thermal data tidal forcing does not explain the superrotation below the clouds and additional eddy sources are needed to account for the zonal wind structure at mid and high latitudes

effects of sea ice and biogeochemical processes and storms on under ice water fco2 during the winter spring transition in the high arctic ocean implications for sea air co2 fluxes we performed measurements of carbon dioxide fugacity fco2 in the surface water under arctic sea ice from january to june 2015 during the norwegian young sea ice n ice2015 expedition over this period the ship drifted with four different ice floes and covered the deep nansen basin the slopes north of svalbard and the yermak plateau this unique winter to spring dataset includes the first winter time under ice water fco2 observations in this region the observed under ice fco2 ranged between 315 atm in winter and 153 atm in spring hence was undersaturated relative to the atmospheric fco2 although the sea ice partly prevented direct co2 exchange between ocean and atmosphere frequently occurring leads and breakup of the ice sheet promoted sea air co2 fluxes the co2 sink varied between 0 3 and 86 mmol c m 2 d 1 depending strongly on the open water fractions ow and storm events the maximum sea air co2 fluxes occurred during storm events in february and june in winter the main drivers of the change in under ice water fco2 were dissolution of caco3 ikaite and vertical mixing in june in addition to these processes primary production and sea air co2 fluxes were important the cumulative loss due to caco3 dissolution of 0 7 mol c m 2 in the upper 10 m played a major role in sustaining the undersaturation of fco2 during the entire study the relative effects of the total fco2 change due to caco3 dissolution was 38 primary production 26 vertical mixing 16 sea air co2 fluxes 16 and temperature and salinity insignificant this article is protected by copyright all rights reserved

altimetry of the venus cloud tops from the venus express observations 1 simultaneous observations of venus by visible and infrared thermal imaging spectrometer and venus monitoring camera onboard the venus express spacecraft are used to map the cloud top altitude and to relate it to the ultraviolet uv markings the cloud top altitude is retrieved from the depth of co2 absorption band at 1 6 m in low and middle latitudes the cloud top is located at 74 1 km it decreases poleward of 50 and reaches 63 69 km in the polar regions this depression coincides with the eye of the planetary vortex at the same latitude and hour angle cloud top can experience fast variations of about 1 km in tens of hours while larger long term variations of several kilometers have been observed only at high latitudes uv markings correlate with the cloud altimetry however the difference between adjacent uv dark and bright regions does not exceed several hundred meters surprisingly co2 absorption bands are often weaker in the dark uv features indicating that these clouds may be a few hundred meters higher or have a larger scale height than neighboring clouds ultraviolet dark spiral arms which are often seen at about 70 correspond to higher altitudes or to the regions with strong latitudinal gradient of the cloud top altitude cloud altimetry in the polar region reveals the structure that correlates with the thermal emission maps but is invisible in uv images this implies that the uv optically thick polar hood is transparent in the near ir

sensitivity of thermal tides in the venus atmosphere to basic zonal flow and newtonian cooling 1 a numerical model is constructed to investigate sensitivity of thermal tides in the venus atmosphere to distributions of basic mean zonal wind and newtonian cooling rate it is found that the amplitude and spatial structure of the diurnal tide are strongly influenced by the midlatitudinal jets and the newtonian cooling rates in all cases examined in this study the diurnal tide propagates downward in the lower atmosphere below the cloud levels and reaches the ground the semidiurnal tide is generally less dependent on these parameters but its zonal winds are increased in the upper jet regions

heat production and thermal conductivity of rocks from the pikwitonei sachigo continental cross section central manitoba implications for the thermal structure of archean crust the pikwitonei and sachigo subprovinces of central manitoba provide a cross sectional view of the superior province crust in cross section the upper to mid level crust is composed of synformal greenstone belts surrounded by tonalitic gneisses both of which are intruded by granitoid plutons this crustal structure persists downward into the granulite facies where keels of the greenstone belts can be found to constrain thermal models of the crust we measured heat production and thermal conductivity in 60 rocks from this terrain using standard gamma ray spectrometry and divided bar techniques large vertical and lateral heterogeneities in heat production in the upper crust are evident heat production is high in granites and metasedimentary rocks intermediate in tonalite gneisses and low in the portions of greenstone belts dominated by mafic meta igneous rocks in the deeper granulite facies rocks heat production decreases by a factor of two in the tonalitic gneisses and remains low in the high grad

the seasonal cycle of ocean atmosphere co2 flux in ryder bay west antarctic peninsula approximately 15 million km2 of the southern ocean is seasonally ice covered yet the processes affecting carbon cycling and gas exchange in this climatically important region remain inadequately understood here 3 years of dissolved inorganic carbon dic measurements and carbon dioxide co2 fluxes from ryder bay on the west antarctic peninsula wap are presented during spring and summer primary production in the surface ocean promotes atmospheric co2 uptake in winter higher dic caused by net heterotrophy and vertical mixing with circumpolar deep water results in outgassing of co2 from the ocean ryder bay is found to be a net sink of atmospheric co2 of 0 59 0 94 mol c m 2 yr 1 average of 3 years seasonal sea ice cover increases the net annual co2 uptake but its effect on gas exchange remains poorly constrained a reduction in sea ice on the wap shelf may reduce the strength of the oceanic co2 sink in this region

sea ice and snow cover characteristics during the winter spring transition in the bellingshausen sea an overview of simba 2007 abstract the sea ice mass balance in the antarctic simba experiment was conducted from the rvib n b palmer in september and october 2007 in the bellingshausen sea in an area recently experiencing considerable changes in both climate and sea ice cover snow and ice properties were observed at 3 short term stations and a 27 day drift station ice station belgica isb during the winter spring transition repeat measurements were performed on sea ice and snow cover at 5 isb sites each having different physical characteristics with mean ice snow thicknesses varying from 0 6 m 0 1 m to 2 3 m 0 7 m ice cores retrieved every five days from 2 sites and measured for physical biological and chemical properties three ice mass balance buoys imbs provided continuous records of snow and ice thickness and temperature meteorological conditions changed from warm fronts with high winds and precipitation followed by cold and calm periods through four cycles during isb the snow cover regulated temperature flux and controlled the physical regime in which sea ice morphology changed level thin ice areas had little snow accumulation and experienced greater thermal fluctuations resulting in brine salinity and volume changes and winter maximum thermodynamic growth of 0 6 m in this region flooding and snow ice formation occurred during cold spells in ice and snow of intermediate thickness in contrast little snow ice formed in flooded areas with thicker ice and snow cover instead nearly isothermal highly permeable ice persisted in spring short lived cold air episodes did not effectively penetrate the sea ice nor overcome the effect of ocean heat flux thus favoring net ice thinning from bottom melt over ice thickening from snow ice growth in all cases these warm ice conditions were consistent with regional remote sensing observations of earlier ice breakup and a shorter sea ice season more recently observed in the bellingshausen sea

atmospheric thermal structure and cloud features in the southern hemisphere of venus as retrieved from virtis vex radiation measurements thermal structure and cloud features in the atmosphere of venus are investigated using spectroscopic nightside measurements recorded by the visible and infrared thermal imaging spectrometer virtis aboard esa s venus express mission in the moderate resolution infrared mapping channel m ir 1 5 m new methodical approaches and retrieval results for the northern hemisphere have been recently described by haus et al haus r kappel d arnold g 2013 planet space sci 89 77 101 http dx doi org 10 1016 j pss 2013 09 020 now southern hemisphere maps of mesospheric temperature and cloud parameter fields are presented that cover variations with altitude latitude local time and mission time measurements from the entire usable data archive are utilized comprising radiation spectra recorded during eight venus solar days between april 2006 and october 2008 zonal averages of retrieved temperature altitude profiles in both hemispheres are very similar and give evidence of global n s axial symmetry of atmospheric temperature structure cold collar and warmer polar vortex regions exhibit the strongest temperature variability with standard deviations up to 8 5 k at 75 s and 63 km altitude compared with about 1 0 k at low and mid latitudes above 75 km the mesospheric temperature field strongly depends on local time at altitudes above about 75 km the atmosphere is warmer in the second half of night while the dawn side at lower altitudes is usually colder than the dusk side by about 8 k local minimum temperature of 220 k occurs at 03 00 h local time at 65 km and 60 s temperature standard deviation at polar latitudes is particularly large near midnight temperature variability with solar longitude is forced by solar thermal tides with a dominating diurnal component the influence of observed cloud parameter changes on retrieved mesospheric zonal average temperature structure is moderate and does not exceed 2 3 k at altitudes between 60 and 75 km the mesospheric thermal structure was essentially stable with julian date between 2006 and 2008 global n s axial symmetry is also observed in cloud structures cloud top altitude at 1 m slowly decreases from 71 km at the equator to 70 km at 45 50 and rapidly drops poleward of 50 it reaches 61 km over both poles average particle size in the vertical cloud column increases from mid latitudes toward the poles and also toward the equator resulting in minimum and maximum zonal average cloud opacities of about 32 and 42 and a planetary average of 36 5 at 1 m zonal averages of cloud features are similar at different solar days but variations with local time are very complex and inseparably associated with the superrotation of the clouds

cloud tracked winds from pioneer venus ocpp images abstract analysis of ultraviolet image sequences obtained from the pioneer venus orbiter cloud photopolarimeter and covering five 80 day periods from 1979 1985 provides the first climatological description of the cloud top circulation on venus the average zonal winds can be characterized as a 5 day retrograde rotation of the whole cloud level atmosphere with weak jets at middle to high latitudes both the midlatitude and equatorial zonal winds vary by about 5 8 m s 1 over time spans of 1 6 years the average meridional circulation is poleward in both hemispheres up to at least 60 latitude consistent with the presence of a thermally direct hadley circulation associated with the clouds the strength of the hadley circulation also varies with time four wave modes are clearly identified a diurnal solar tide a semi diurnal solar tide a 4 day equatorial wave and a 5 day midlatitude wave the semidiurnal tide appears to have an amplitude of about 5 m s 1 and to be approximately constant with time

surface properties and processes of perennial antarctic sea ice in summer ice core and snow data from the amundsen bellingshausen and weddell seas antarctica show that the formation of superimposed ice and the development of seawater filled gap layers with high algal standing stocks is typical of the perennial sea ice in summer the coarse grained and dense snow had salinities mostly below 0 1 per mil a layer of fresh superimposed ice had a mean thickness ranging from 0 04 0 12 m 0 04 to 0 08 m thick gap layers extended downwards from 0 02 to 0 14 m below the water level these gaps were populated by diatom standing stocks up to 439 g l chlorophyll a we propose a comprehensive heuristic model of summer processes where warming and the reversal of temperature gradients cause major transformations in snow and ice properties the warming also causes the re opening of incompletely frozen slush layers caused by flood freeze cycles during winter alternatively superimposed ice forms at the cold interface between snow and slush in the case of flooding with negative freeboard combined these explain the initial formation of gap layers by abiotic means alone the upward growth of superimposed ice above the water level competes with a steady submergence of floes due to bottom and internal melting and accumulation of snow

inorganic carbon transport during sea ice growth and decay a carbon pump in polar seas 1 during sea ice formation in polar areas brine rejection increases the density in the underlying water column and thereby contributes to the formation of deep and intermediate water masses in the world ocean here we present evidence that dissolved inorganic carbon tco2 is rejected together with brine from growing sea ice and that low temperatures may result in a significant change in the ratio of tco2 and alkalinity in arctic sea ice compared with surface waters model calculations show that this sea ice driven carbon pump affects surface water partial pressure of co2 significantly in polar seas and potentially sequesters large amounts of co2 to the deep ocean

measurements of total alkalinity calcium and sulfate in natural sea ice we report precise measurements of salinity chlorinity alkalinity calcium and sulphate in various types of sea ice collected at the canadian expedition to study the alpha ridge cesar ice camp in the arctic ocean and in both first year and multiyear ice collected in fram strait several of the samples showed some relative enrichment of alkalinity and sulphate compared to what would be observed in seawater of the same salinity the relative enrichment was quite varied and did not correspond quantitatively with what has been observed in sea ice produced in the laboratory our results indicate that the temperature and salinity history of sea ice must be crucial in determining the relative composition of salts in natural sea ice and that quantitative geochemical predictions based on the composition of sea ice produced in the laboratory or on a particular specimen of natural sea ice must be made with caution