interpretations of observed climatological patterns in stratospheric gravity wave variance observational analyses of gravity waves in the stratosphere have revealed various climatological patterns in gravity wave activity seasonal geographical and vertical variations have all been observed in this work a linear model of gravity wave propagation is applied to investigate the underlying causes of some of the observed patterns a collection of monochromatic gravity waves that represent a broad spectrum of wavenumbers and frequencies is input at 6 km altitude in the model propagation of the waves through realistic background atmospheric wind and stability fields is treated with linear ray theory and a simple saturation condition to limit amplitudes to stable values the wave spectrum at the 6 km source height is specified to be constant at all latitudes longitudes and times so the variability that appears at higher altitudes is due entirely to background atmosphere variations before the model results are compared to the observations the spectrum of waves is filtered in a way that mimics the limitations of each of the observation techniques the filtering is described in terms of vertical wavelength and is referred to as the observational filter in a vertically varying background wind gravity waves are doppler shifted in intrinsic frequency and refracted to different vertical wavelengths as they propagate vertically through the atmosphere the observational filter and the wave refraction effects can thus couple in interesting ways that have not been explicitly considered in previous work the model shows that this coupling can give rise to geographical seasonal and vertical variations in gravity wave observations without any variations in the spectrum or amplitude of gravity wave sources in the troposphere thus careful consideration of both the background wind profile and observational filter can greatly affect the interpretation of the observed climatological patterns in gravity wave activity

observational study of ionospheric irregularities and gps scintillations associated with the 2012 tropical cyclone tembin passing hong kong

impact of atmospheric forcing on antarctic continental shelf water masses the antarctic continental shelf seas feature a bimodal distribution of water mass temperature with the amundsen and bellingshausen seas flooded by circumpolar deep water that is several degrees celsius warmer than the cold shelf waters prevalent in the weddell and ross seas this bimodal distribution could be caused by differences in atmospheric forcing ocean dynamics ocean and ice feedbacks or some combination of these factors in this study a highly simplified coupled sea ice mixed layer model is developed to investigate the physical processes controlling this situation under regional atmospheric forcings and parameter choices the 10 yr simulations demonstrate a complete destratification of the weddell sea water column in winter forming cold relatively saline shelf waters while the amundsen sea winter mixed layer remains shallower allowing a layer of deep warm water to persist applying the weddell atmospheric forcing to the amundsen sea model destratifies the water column after two years and applying the amundsen forcing to the weddell sea model results in a shallower steady state winter mixed layer that no longer destratifies the water column this suggests that the regional difference in atmospheric forcings alone is sufficient to account for the bimodal distribution in antarctic shelf sea temperatures the model prediction of mixed layer depth is most sensitive to the air temperature forcing but a switch in all forcings is required to prevent destratification of the weddell sea water column

a global morphology of gravity wave activity in the stratosphere revealed by the gps occultation data gps met using temperature profiles obtained by the gps met gps meteorology experiment from april 1995 to february 1997 we have extracted mesoscale temperature perturbations with vertical wavelengths ranging from 2 to 10 km and background brunt vaisala frequency squared n2 for each occultation event we can evaluate a potential energy ep which is assumed to be caused by atmospheric gravity waves the monthly mean values of ep at 15 20 km around japan showed an annual variation with an enhancement in winter which is consistent with the climatological behavior of the kinetic energy of gravity waves observed with the mu middle and upper atmosphere radar 34 9 n 136 0 e from 1985 to 1989 we have then derived the global distribution of ep at 20 30 km during northern hemisphere winter from november to february our analysis shows that the largest ep values are generally centered around the equator between 25 n and 25 s with considerable longitude variations longitudinal variations of ep at 20 30 km in a latitude range of 30 60 n are also analyzed resulting in larger ep values over the continents than over the pacific ocean using gps met data without antispoofing latitudinal variations of ep are determined in 15 45 km although large ep values are concentrated near the equator at 20 30 km ep tends to become larger at midlatitudes at 30 40 km and higher altitude regions at midlatitudes ep is found to be larger in winter months in both hemispheres height variations of ep indicate a decrease at 25 30 km and a monotonic increase above 30 km

studies of the arctic ice cover and upper ocean with a coupled ice ocean model an ice ocean model has been developed by coupling the hibler ice model to a three dimensional ocean model that consists of a turbulent mixed layer model and an inverse geostrophic model the coupled model has a horizontal grid spacing of 127 km and has 17 vertical levels extending to the ocean bottom the model is forced with 12 hourly general circulation model derived atmospheric fluxes for the year 1986 for which good quality ice edge analyses and buoy tracks were available for comparisons the results are presented for the fifth year of a repetitive simulation with the 1986 fluxes at which time the system has reached a statistical equilibrium the seasonal and geographical variations of the ice cover and the upper few hundred meters of the ocean have been examined including the heat and salt budgets the computed heat fluxes and mixed layer depths mlds fall in the observed seasonal ranges with winter heat fluxes ranging from 15 w m 2 in the central arctic to about 500 w m 2 in the barents sea area and summer fluxes from about 5 w m 2 under the ice to about 30 w m 2 in the various marginal ice zone miz edge areas the corresponding winter mlds are found to be about 25 75 m in the central arctic to a deep 800 m in the greenland sea typical summer mlds are between 5 and 30 m in all seasons the miz was found to be the center of flux activity for both heat and salt with the processes of advection diffusion atmospheric forcing and vertical oceanic fluxes having their largest values here and of comparable magnitudes values of the heat flux components in the miz exceed those found under the ice by an order of magnitude or more and those in the open water region by a factor of 2 for salt the situation is similar except in the summer june through september when a lot of salt flux activity takes place under the ice comparisons are made with naval polar oceanography center npoc analyses for ice concentration and ice edge and with observed arctic buoy tracks in the same 1986 time period the computed ice edge positions have comparable accuracy to previous three dimensional coupled ice ocean studies with too much ice growth during the winter in the barents sea and too little ice east of greenland the ice thickness distributions however are much better with a monotonic increase of the ice thickness from the siberian coast east toward the canadian archipelago with maximum winter values of about 5 6 m

development of a simple upper ocean and sea lce model abstract results are described for three simple numerical models of the upper ocean and sea ice with prescribed atmospheric forcing the ability of each model version to simulate the observed sea surface temperature sst is assessed as a basis of comparison for future coupled experiments with atmospheric gcm s lie upper ocean model versions raw from a slab of fixed thickness to a variable depth mixed layer above a variable exponential temperature gradient representing the seasonal thermocline sea ice thickness is determined thermodynamically by local melting or accretion and the effects of ice transport and leads are neglected each version is tested by integrating to equilibrium with horizontal advection neglected using monthly climatological atmospheric data for a selected north south section in the mid pacific ocean and the results for different model versions are compared with each other and with available observations it is found that the fixed slab version gives realistic sea ice thickness a

on the bering sea ice edge front an oceanographic field program was carried out along the bering sea ice edge in winter 1982 83 to investigate the temperature salinity front associated with and paralleling the winter ice edge currents were measured using taut wire moorings that were in place over winter and an intensive ctd survey was carried out of the frontal structure in midwinter february march the midwinter front separated cold 0 c more saline 32 5 outer shelf water the front had northwestward baroclinic currents paralleling the front ice edge with near surface speeds of 5 6 cm s and an associated transport of about 0 3 106 m3 s these baroclinic currents were superimposed on a regional barotropic along isobath flow resulting in north westward midwinter upper layer flows with monthly mean speeds exceeding 10 cm s an upper layer flow component was directed beneath the ice and provided heat adequate to melt the ice and limit advance of the edge the resulting low salinity meltwater was mixed vertically to maintain the front by wind acting across a highly mobile hydrodynamically rough ice cover subtidal fluctuations were not significantly affected by the front or the ice cover and local winds accounted for less than one quarter of the observed current variability the remainder being probably due to regional variations in the barotropic flow

long term variability in the equatorial middle atmosphere zonal wind the high resolution doppler imager hrdi on the upper atmosphere research satellite uars has provided measurements of the horizontal wind field in the stratosphere mesosphere and lower thermosphere since november 1991 this data set which spans a period of more than 3 years has facilitated an investigation of the long term behavior of the background circulation on a nearly global basis at middle and high latitudes the zonal circulation is characterized by an annual oscillation at low latitudes 30 the most prominent long term variation above the stratopause is the mesosphere semiannual oscillation msao which maximizes near the equator at an altitude of between 80 and 85 km further analysis of the time series reveals an additional strong variation with an amplitude near 30 ms 1 and a period of about 2 years this feature shows the same altitude and latitude structure as the msao and exhibits a phase relationship with the stratospheric quasi biennial oscillation qbo observations from the christmas island mf radar 2 n 130 w confirm the presence of this mesospheric qbo mqbo these observations support recent findings from a modeling study which generates an mqbo via the selective filtering of small scale gravity waves by the underlying winds they traverse

boundary layer upper ocean and ice observations in the greenland sea marginal ice zone during the 1984 marginal ice zone experiment a coordinated ocean boundary layer and mixed layer experiment was carried out in concert with a complete heat and mass balance study in the summer marginal ice zone miz of the greenland sea the measurements were made at two drifting ice stations and included observations of ocean boundary layer turbulence profiles of water temperature salinity and velocity ice ablation ice concentration solar radiation and spectral albedos ocean conditions were found to be extremely variable the ice and water velocities were heavily influenced by tidal and inertial motions with amplitudes from 6 to 12 cm s 1 in the course of the drift a 30 km eddy was crossed wherein ice and water velocities exceeded 15 cm s 1 the northern extension of the east greenland polar front was encountered and a northward flow of atlantic water into the arctic basin was observed below the eastern edge of the front but the drift station never moved quite far enough west to be caught in the southward transport of arctic surface water heat from the ocean was a major factor in ice melt and when the ice was over atlantic water it was the dominant factor the events that had the greatest impact on the ice were two outbreaks during which off ice winds blew the ice across warm ice edge ocean fronts once south of these fronts and over surface water as warm as 1 c the ice bottom melted at rates up to 100 kg m 2 d 1 the rapid changes in stratification associated with the outbreaks had a dramatic impact on the drag and heat transfer coefficients the drag coefficient relative to the square of the relative water velocity at 30 m ranged from 0 002 to 0 02 and averaged 0 006 the heat transfer coefficient relative to the friction velocity u and the mixed layer temperature elevation above freezing ranged from 0 0025 to 0 009 and averaged 0 0038 in agreement with the idea that stratification inhibits turbulent exchange the heat transfer coefficient decreased when stratification increased in fact the observed melt rates can be simulated well if molecular heat and salt transfer through a thin near surface laminar boundary layer are accounted for as well as transfer through the turbulent outer boundary layer also in agreement with turbulent boundary layer theory the drag coefficient decreased when stratification increased slightly above neutral however for the large increases in surface stratification the drag coefficient increased this was due to the generation of internal gravity waves by ice bottom roughness because the surface exchange coefficients are so sensitive to surface stratification which is in turn highly variable in the miz accurate simulations of ice motion and ice melt will require realistic estimates of stratification and a good understanding of the relation between the ice ocean interactions and upper ocean conditions

on measuring the off equatorial conductivity before and during convective ionospheric storms 1 one of the biggest unknowns in the cis esf convective ionospheric storms equatorial spread f space weather problem now can be measured radio occultations of the gps constellation will be measurable on a regular basis during the cosmic constellation observing system for meteorology ionosphere and climate and c nofs communications navigation outage forecast system satellite era these measurements can be used to determine the plasma density versus height and hence the off equatorial height integrated conductivity

gravity waves in the tropical lower stratosphere a model study of seasonal and interannual variability a model study is presented to clarify the relationship between gravity wave properties observed in the stratosphere and the sources for the waves presumed to be in the troposphere the observations are balloon borne radiosondes launched from cocos island in the tropical indian ocean 12 s 97 e and the analysis of these data is described in a companion paper vincent and alexander this issue the dominant time variations in the observed gravity wave activity are annual and quasi biennial patterns in the zonal momentum flux and kinetic energy density the background zonal winds at this site vary with the same periods and these are known to be capable of causing dramatic variations in the observable properties of the waves even if the sources for the waves are constant in time the results presented here clarify 1 the nature of the sources for the gravity waves observed in the stratosphere 2 the limitations of the observations for observing the full range of gravity wave perturbations potentially present in the atmosphere and 3 the role the observed waves can play in forcing the quasibiennial oscillation qbo in the zonal winds at this latitude the stratospheric waves appear to originate near the height of the tropopause so the source is apparently related to deep convection no seasonal or interannual variations in the convection need be assumed to understand the observations the waves at the tropopause appear to have a phase speed distribution that is narrowly confined near zero phase speed relative to the ground the source is likely related to slowly propagating tropospheric convection and the wind near the tropopause variations observed in the stratospheric data are caused by both the wind shear in the stratosphere and the ability of waves with these characteristics to propagate vertically without severe dissipation higher phase speed waves may be present and could carry significant momentum flux vertically into the stratosphere and mesosphere but would be extremely difficult to see in these radiosonde data the observed waves can contribute substantially to the descent of the eastward shear zones characteristic of the westerly phase of the qbo in the lower stratosphere zonal winds

solid state 13c nmr studies of selected oil shales from queensland australia abstract solid state 13 c nmr techniques of cross polarization with magic angle spinning and interrupted decoupling have been employed to examine the nature of the organic matter in eight kerogen concentrates representing five tertiary deposits in queensland australia the nmr results show that five of the kerogens have high proportions of aliphatic carbon in their organic matter and correspond to type i ii algal kerogens three of the kerogens derived from carbonaceous shales have a high proportion of aromatic carbon in their organic matter and correspond to type iii kerogens the fractions of aliphatic carbon in all the kerogens regardless of type are shown to correlate with the conversion characteristics of the corresponding raw shales during fischer assay interrupted decoupling nmr results show the presence of more oxygen substituted carbon in the carbonaceous shales which may account for the greater co 2 evolution and phenolic materials found in the pyrolysis products of the carbonaceous shales

gravity waves in the tropical lower stratosphere an observational study of seasonal and interannual variability radiosonde observations made at cocos islands 12 s 97 e in the indian ocean between september 1992 and june 1998 are used to study seasonal and interannual variations in gravity wave activity in the lower stratosphere 18 25 km the islands are located in a region of generally strong convection that occurs at all times of the year with the period of strongest convective activity between december and july wet season the prevailing zonal winds during the observational period and height range are westward with a quasi biennial oscillation qbo superimposed time series of wave energy show that largest wave amplitudes occur during the wet season when convection is strongest but a qbo like variation is also apparent maximum energy densities of about 25 j kg 1 occur early 1993 1995 and 1997 at the times when the westward shears are largest wave energy is found to be propagating upward and in the horizontal there is considerable azimuthal anisotropy with predominate eastward propagation against the prevailing wind upward fluxes of zonal momentum flux u w are estimated by combining the temperature and wind information fluxes show a similar temporal behavior to the energy the motion and temperature fields are dominated by waves with vertical wavelengths 2 km using a stokes parameter analysis it is found that the intrinsic frequencies are on average 2 3 times the inertial frequency corresponding to intrinsic periods of 20 25 hours horizontal wavelengths between 200 and 2000 km are inferred with a mean value of about 1000 km the mean intrinsic phase speeds are about 10 ms 1 but ground based phase speeds are centered on 0 ms 1

on some possible interactions between internal waves and sea ice in the marginal ice zone the ice edges of the world ocean are generally the site at times when winds are blowing off the ice of regularly spaced surface bands of ice floes these bands have size scales of the order of 1 10 km and their long axes are oriented approximately normal to the wind direction available oceanic temperature and salinity data from the bering and greenland sea ice edge regions suggest that these ice bands are commonly underlain by a two layered density structure which is maintained by net melting along the ice edges linear internal wave theory is applied to these data to compute first mode interfacial wave phase speeds a simple analytical model is developed that demonstrates the feasibility of generation of such interfacial internal waves by the stress discontinuity due to off ice winds blowing over either a stationary or a moving ice edge it is qualitatively shown that the computed internal wave phase speeds and wavelengths are under many conditions compatible with the speeds and spacings of the surface ice bands this compatibility suggests in turn that coupling between internal waves and ice bands may commonly occur some possible implications of the generation and presence of these internal waves upon other ice edge processes such as air sea heat and momentum transfer are qualitatively discussed

stratosphere perturbed by the 2011 mw9 0 tohoku earthquake this study examined the formosat 3 cosmic radio occultation soundings of total electron content in the ionosphere from 150 to 550 km and refractivity index in the lower atmosphere from 0 to 60 km after during the 2011 mw9 0 tohoku earthquake tsunami the refractivity index observations show the first evidence of the tohoku earthquake tsunami induced vertical oscillations in the lower atmosphere the atmospheric oscillations with vertical wavelength ranging from 0 5 to 8 km and from 10 to 40 km respectively appear in the stratosphere and ionosphere after the earthquake onset the short vertical wavelengths suggest that the oscillations are the atmospheric oscillatory tail due to the wavefront of the earthquake tsunami the radio occultation technique is a tool for detecting the atmospheric waves induced by earthquake or some other sources plain language summary it has been well known that the sudden uplift of the earth s surface due to earthquake tsunami significantly disturbs the upper atmosphere and ionosphere however the evidence of earthquake tsunami induced waves in the lower atmosphere is insufficient due to the lack of observation supporting here the formosat 3 cosmic f3 c radio occultation refractivity index is for the first time to capture the tohoku earthquake induced vertical oscillations at the stratosphere altitudes from 30 to 40 km the results in this study not only shed lights on understanding of earthquake tsunami waves perturbing the whole atmosphere but also suggest that the radio occultation technique can benefit to the earthquake tsunami warning system

a coupled one dimensional sea ice ocean model a prognostic one dimensional mixed layer pycnocline model describing the vertical structure of the upper ocean is coupled to a thermodynamic sea ice model the coupled prognostic model is compared with the more usual sea ice model overlying a fixed mixed layer with constant oceanic heat flux and is then applied to investigate the effect of temporal and regional variations of the entrained oceanic heat flux on the sea ice cover in both polar regions in the southern ocean a standard simulation is compared with two perturbation experiments which both describe the occurrence of a polynya in the arctic ocean the effect of possible soviet river diversions is investigated finally the response of the coupled model to paleoclimatic forcing and boundary conditions is presented

microwave limb sounder observations of gravity waves in the stratosphere a climatology and interpretation high horizontal resolution temperature data from the microwave limb sounder mls are analyzed to obtain information about high intrinsic frequency gravity waves in the stratosphere global climatologies of temperature variance at solstice are computed using six years of data a linear gravity wave model is used to interpret the satellite measurements and to infer information about tropospheric wave sources globally uniform sources having several different spectral shapes are examined and the computed variances are filtered in three dimensional space in a manner that simulates the mls weighting functions the model is able to reproduce the observed zonal mean structure thus indicating that the observations reflect changes in background wind speeds and provide little information about the latitudinal variation of wave sources longitudinal variations in the summer hemisphere do reflect source variations since the modeled variances exhibit much less variation in this direction as a consequence of the zonal symmetry of the background winds a close correspondence between the mls variances and satellite observations of outgoing longwave radiation suggests that deep convection is the probable source for these waves the large variances observed over the tip of south america in winter are most certainly linked to orographic forcing but inferences about wave sources in northern hemisphere winter are difficult to make as a result of the high degree of longitudinal and temporal variability in the stratospheric winds comparisons of model results using different source spectra suggest that the tropospheric sources in the subtropics in summer have a broader phase speed spectrum than do sources at middle latitudes in winter

modeling the thermodynamics of a sea ice thickness distribution 2 sea ice ocean interactions in this paper we examine the coupling of an ice thickness distribution model with an ocean mixed layer model the annual cycle of the modeled mixed layer temperature salinity and depth are compared to observations from the drifting ice stations of the arctic ice dynamics joint experiment aidjex the role of the ice thickness distribution in determining the ice ocean coupling is examined we find that the ice thickness distribution is important for the exchange of heat salt and fresh water between the ice and the ocean especially with regard to the effects of thin first year ice several different parameterizations of the ice ocean turbulent heat exchange are compared the results indicate that the storage of heat in the ocean mixed layer is an important physical process for determining the annual average ice thickness double diffusion and the stabilizing effects of meltwater also impact the exchange of heat between the ocean and ice cover questions remain as to the relative importance of these processes and their accurate parameterization in ice ocean coupled models

gravity waves and ionospheric irregularities over tropical convection zones observed by gps met radio occultation gps met observations of the tropical atmo sphere of the southern hemisphere 5 st o 25 s during february 1997 are analysed when a high amount of con vective tropospheric water vapor is at these latitudes en hanced gravity wave activity of the lower stratosphere at h 22 28 km is associated to areas of increased tropospheric water vapor pressure at h 4 6 km regarded as a measure of tropical convection sporadic e and other ionospheric irregularities vertical scales less than 7 km of the meso sphere lower thermosphere are observed to be highly cor related to gravity wave activity in the lower stratosphere and to tropical convection zones we find 4 areas of en hanced ionospheric irregularities and stratospheric wave ac tivity over pacific around 140 w brazil 50 w africa 40 e and indonesia australia 110 e

vertical structure of the ionospheric response following the m w 7 9 wenchuan earthquake on 12 may 2008 the response of the vertical ionospheric electron density structure to the mw 7 9 wenchuan earthquake on 12 may 2008 was recorded by the formosat 3 cosmic f3 c radio occultation ro precise orbit determination pod total electron content tec the horizontal propagation characteristics of the seismo traveling ionospheric disturbances were identified by combining ground based global navigation satellite system gnss tec data and ro tec data the postseismic ionospheric infrasound wavefront with wavelength of around 80 km at altitude of 150 350 km was scanned vertically by an individual ro tec profile a large amount of tec profiles around the epicenter from 0000 to 1200 ut provide evidence of continental earthquake induced vertical oscillations that lasted in the ionosphere for several hours ro observed vertical perturbations appear on both the southward and northward sides of the epicenter the vertical structure of the ionospheric oscillations with wavelength ranging from 10 to 80 km increased with altitude between 230 and 650 km

seasonal variations in the upper arctic ocean as observed at t 3 hydrographic data from t 3 are analyzed to illustrate the behavior of the arctic mixed layer the mixed layer depth fluctuates 11 m annually and mixed layer salinity fluctuates 0 32 the fluctuations in total salt content are consistent with theoretical work by maykut and are in phase with mixed layer depth indicating changes in the mixed layer are controlled by salt flux deepening of the mixed layer brings 0 3 kcal cm 2 yr 1 of heat to the surface from the ocean below

the seasonal variation of the mixed layer and the pycnocline under polar sea ice a model of the seasonal variation of the mixed layer and the pycnocline under polar sea ice is compared with observations during the arctic ice dynamics joint experiment aidjex 1975 1976 the model is of the kraus turner type extended to include mixed layer and pycnocline the forcing mechanisms are the mechanical mixing due to ice keel stirring and the surface buoyancy flux due to melting and freezing of sea ice the model is designed to be used for climate studies in conjunction with atmospheric and oceanic general circulation models and with sea ice models

space time variation of mixed layer properties heat and salt fluxes and ice melt in the newfoundland marginal ice zone oceanographic data collected in the newfoundland marginal ice zone in march 1992 are analyzed to study the variation of mixed layer properties across the ice zone the mixed layer depth decreases from 80 m in the interior of the pack ice to 25 m at the eastern ice edge over a distance of 120 km in the open ocean without ice cover the depth is considerably greater 150 200 m the temperature under the pack ice is near freezing a sharp increase in both the temperature and salinity occurs across the ice edge the variation of the mixed layer properties is simulated by integrating a one dimensional bulk mixed layer model coupled to sea ice from november 1991 to march 1992 the initial ocean conditions are obtained from an objective analysis of archived data of november 1991 the forcings are 6 hourly meteorological data from the european centre for medium range weather forecasts ice concentration and thickness are treated as prescribed functions of time extracted from daily ice maps since ice in the area is not locally formed the model simulation is in good agreement with the observations from the model results a detailed analysis of the roles of wind stress ice melt surface cooling and shortwave radiation in the water mass transformation of the upper ocean is carried out there are large differences in the melt rate and water ice heat flux between the times when ice enters the shelf and after the water has been cooled by the ice to near freezing 15 20 cm d 1 and 500 700 wm 2 and 0 2 cm a 1 and 20 50 wm 2 respectively a large portion of the heat in the water column is expended for ice melting from january to march calculations that use surface data such as surface wind and sea surface temperature without considering ice melt can underestimate the net ocean to air heat flux especially at the eastern ice edge in march

observations of mixed layer deepening during an antarctic gale 1 observations of mixed layer deepening made during a gale in february 2005 near an ice shelf fimbulisen antarctica are reported the observations were made from the rrs james clark ross in the lee of the ice shelf using repeated downcasts yo yo of a conductivity temperature depth package together with shipboard meteorological and other measurements the mixed layer deepened from less than 40 m to over 120 m over the course of 27 h with a very rapid deepening from 80 m to 120 m over a period of under 11 h the mixed layer became both colder and fresher with the change in salinity and heat content likely to be caused by melting ice oxygen isotope results suggest the source of the fresh water was melting sea ice rather than precipitation or ice shelf melt the input of melt water at the surface stabilizes the mixed layer so extra energy is required to deepen the mixed layer the observations suggest that approximately 1 8 of the available wind work energy was used to mix the upper water column while the stabilizing surface buoyancy flux inhibits the turbulence in the mixed layer limiting the mixing length to 1 6 m the eventual depth of the mixed layer is in line with estimates based on the planetary length scale u f the rate of mixed layer deepening is given by ue u 0 035 the apparent peak ice melting rate was approximately 60 mm hr 1 although this is likely to be exaggerated by convergence and downwelling

comparison of global distributions of zonal mean gravity wave variance inferred from different satellite instruments gravity wave temperature fluctuations acquired by the crista instrument are compared to previous estimates of zonal mean gravity wave temperature variance inferred from the lims mls and gps met satellite instruments during northern winter careful attention is paid to the range of vertical wavelengths resolved by each instrument good agreement between crista data and previously published results from lims mls and gps met are found key latitudinal features in these variances are consistent with previous findings from ground based measurements and some simple models we conclude that all four satellite instruments provide reliable global data on zonal mean gravity wave temperature fluctuations throughout the middle atmosphere