the river orontes in syria and turkey downstream variation of fluvial archives in different crustal blocks the geomorphology and quaternary history of the river orontes in western syria and south central turkey have been studied using a combination of methods field survey differential gps satellite imagery analysis of sediments to determine provenance flow direction and fluvial environment incorporation of evidence from fossils for both palaeoenvironments and biostratigraphy uranium series dating of calcrete cement reconciliation of palaeolithic archaeological contents and uplift modelling based on terrace height distribution the results underline the contrasting nature of different reaches of the orontes in part reflecting different crustal blocks with different histories of landscape evolution upstream from homs the orontes has a system of calcreted terraces that form a staircase extending to 200 m above the river new u series dating provides an age constraint within the lower part of the sequence that suggests underestimation of terrace ages in previous reviews this upper valley is separated from another terraced reach in the middle orontes by a gorge cut through the late miocene early pliocene homs basalt the middle orontes terraces have long been recognized as a source of mammalian fossils and palaeolithic artefacts particularly from latamneh near the downstream end of the reach this terraced section of the valley ends at a fault scarp marking the edge of the subsiding ghab basin a segment of the dead sea fault zone which has been filled to a depth of 1 km by dominantly lacustrine sediments of pliocene quaternary age review of the fauna from latamneh suggests that its age is 1 2 0 9 ma significantly older than previously supposed and commensurate with less uplift in this reach than both the upper and lower orontes two localities near the downstream end of the ghab have provided molluscan and ostracod assemblages that record somewhat saline environments perhaps caused by desiccation within the former lacustrine basin although they include fluvial elements the ghab is separated from another subsiding and formerly lacustrine depocentre the amik basin of hatay province turkey by a second gorge implicit of uplift this time cut through palaeogene limestone the ne sw oriented lowermost reach of the orontes is again terraced with a third and most dramatic gorge through the northern edge of the ziyaret dagi mountains which are known to have experienced rapid uplift probably again enhanced by movement on an active fault indeed a conclusion of the research in which these various reaches are compared is that the crust in the hatay region is significantly more dynamic than that further upstream where uplift has been less rapid and less continuous

diurnally modulated cumulus moistening in the preonset stage of the madden julian oscillation during dynamo abstractatmospheric soundings radar and air sea flux measurements collected during dynamics of the madden julian oscillation dynamo are employed to study mjo convective onset i e the transition from shallow to deep convection in the tropical indian ocean the findings indicate that moistening of the low midtroposphere during the preonset stage of the mjo is achieved by simultaneous changes in the convective cloud population and large scale circulation namely cumuliform clouds deepen and grow in areal coverage as the drying by large scale subsidence and horizontal westerly advection wane the reduction of large scale subsidence is tied to the reduction of column radiative cooling during the preonset stage which ultimately links back to the evolving cloud population while net column moistening in the preonset stage is tied to large scale circulation changes a new finding of this study is the high degree to which the locally driven diurnal cycle invigorates convective clouds and cumulus moiste

turbulent heat and momentum fluxes in the upper ocean under arctic sea ice we report observations of heat and momentum fluxes measured in the ice ocean boundary layer from four drift stations between january and june 2015 covering from the typical arctic basin conditions in the nansen basin to energetic spots of interaction with the warm atlantic water branches near the yermak plateau and over the north spitsbergen slope a wide range of oceanic turbulent heat flux values are observed reflecting the variations in space and time over the five month duration of the experiment oceanic heat flux is weakly positive in winter over the nansen basin during quiescent conditions increasing by an order of magnitude during storm events an event of local upwelling and mixing in the winter time nansen basin highlights the importance of individual events spring time drift is confined to the yermak plateau and its slopes where vertical mixing is enhanced wind events cause an approximate doubling of oceanic heat fluxes compared to calm periods in june melting conditions near the ice edge lead to heat fluxes of o 100 w m 2 the combination of wind forcing with shallow atlantic water layer and proximity to open waters leads to maximum heat fluxes reaching 367 w m 2 concurrent with rapid melting observed ocean to ice heat fluxes agree well with those estimated from a bulk parameterization except when accumulated freshwater from sea ice melt in spring probably causes the bulk formula to overestimate the oceanic heat flux this article is protected by copyright all rights reserved

combined airborne laser and radar altimeter measurements over the fram strait in may 2002 knowledge of sea ice thickness is critical for the prediction of future climate and for assessing the significance of changes in thickness sea ice thickness can be calculated from radar or laser satellite altimetry measurements of freeboard however a lack of knowledge of snow depth introduces significant uncertainties into these calculations this paper compares the first coincident airborne laser and radar altimetry data over sea ice collected during the laser radar altimetry lara field campaign lara was a flight of opportunity that provided valuable data to explore techniques to validate satellite measurements of ice freeboard and the possibility of combining laser and radar measurements over snow covered sea ice to calculate the snow depth two new methods were created to analyse these data sets a new radar retracker and a radar power simulator which models radar returns from the laser data we present the first quantitative analysis of data from the lara laser and radar altimeters and demonstrate the potential of combining laser and radar altimetry to estimate snow depth lara elevation estimates compare well with elevations from the radar altimeter onboard ers 2 at the sub meter level and the study provides lessons for future validation of satellite altimetry data over sea ice laser elevations are consistently higher than the radar elevations over snow covered sea ice as lara was a flight of opportunity no coincident in situ measurements were available nevertheless the difference between the reflecting surface of the laser and radar is consistent with snow depth from climatology and the analysis techniques developed in this paper will be useful for future radar and laser altimetry comparisons

realistic initiation and dynamics of the madden julian oscillation in a coarse resolution aquaplanet gcm 1 the main mechanisms for the initiation and propagation of the madden julian oscillation mjo are still widely debated the capacity of operational global climate models gcms to correctly simulate the mjo is hindered by the inadequacy of the underlying cumulus parameterizations here we show that a coarse resolution gcm coupled to a simple multicloud model parameterization mimicking the observed dynamics and physical structure of organized tropical convection simulates the mjo in an idealized setting of an aquaplanet without ocean dynamics we impose a fixed nonhomogeneous sea surface temperature replicating the indian ocean western pacific warm pool this results in a succession of mjos with realistic phase speed amplitude and physical structure each mjo event is initiated at a somewhat random location over the warm pool and dies sometimes near the eastern boundary of the warm pool and sometimes at a random location way beyond the warm pool also occasionally the mjo events stall at the center of maximum heating this is reminiscent of the fact that in nature some mjos stall over the maritime continent while others reach the central pacific ocean and beyond the initiation mechanism in the model is believed to be a combination of persistent intermittent convective events interacting with observed large scale flow patterns and internal tropical dynamics the large scale flow patterns are associated with planetary scale dry kelvin waves that are triggered by preceding mjo events and circle the globe while congestus cloud decks on the flanks of the warm pool are believed to force rossby gyres which then funnel moisture toward the equatorial region

warm atlantic water explains observed sea ice melt rates north of svalbard warm atlantic water aw that flows northward along the svalbard west coast is thought to transport enough heat to melt regional arctic sea ice effectively despite this common assumption quantitative requirements necessary for aw to directly melt sea ice fast enough under realistic winter conditions are still poorly constrained here we use meteorological data satellite observations of sea ice concentration and drift and model output to demonstrate that most of the sea ice entering the area over the yermak plateau melts within a few weeks simulations using the los alamos sea ice model cice in a 1 d vertically resolved configuration under a relatively wide range of in situ observed atmospheric and ocean forcing show a good fit to observations simulations require high frequency atmospheric forcing data to accurately reproduce vertical heat fluxes between the ice or snow and the atmosphere moreover we switched off hydrostatic equilibrium to properly reproduce ice and snow thickness when observations showed that ice had a negative freeboard without surface flooding and snow ice formation this modeling shows that realistic melt rates require a combination of warm near surface aw and storm induced ocean mixing however if aw is warmer than usual 5 c then lower mixing rates are sufficient our results suggest that increased winter storm frequency and increased heat content of the aw may work together in reducing future sea ice cover in the eurasian basin

biochronology of spanish quaternary small vertebrate faunas abstract thousands of fossils of small vertebrates are recorded in one of the most complete stratigraphic sequences of the continental european pleistocene in the sierra de atapuerca this sequence with a few interruptions spans the last 1 5 million years the stratigraphic series is recorded in six karstic cavities in the sierra de atapuerca from the oldest record to the most modern one these are the sima del elefante gran dolina galeria zarpazos sima de los huesos el portalon and el mirador the faunal successions of continental microvertebrates have made it possible to divide the atapuerca sequence into 7 faunal units atapuerca faunal units ata fus which are based on the first and last local appearances of taxa lo ho the spanish quaternary small vertebrate faunas are grouped into 5 distinct biozones from the oldest to the most recent allophaiomys pliocaenicus allophaiomys lavocati allophaiomys chalinei iberomys brecciensis and iberomys cabrerae these are calibrated with radiometric and palaeomagnetic dating allowing the proposal of a continental biochronological scale for the pleistocene of the iberian peninsula

fluvial deposits as an archive of early human activity progress during the 20 years of the fluvial archives group fluvial sedimentary archives are important repositories for lower and middle palaeolithic artefacts throughout the old world especially in europe where the beginning of their study coincided with the realisation that early humans were of great antiquity now that many river terrace sequences can be reliably dated and correlated with the globally valid marine isotope record potentially useful patterns can be recognized in the distribution of the find spots of the artefacts that constitute the large collections that were assembled during the years of manual gravel extraction this paper reviews the advances during the past two decades in knowledge of hominin occupation based on artefact occurrences in fluvial contexts in europe asia and africa as such it is an update of a comparable review in 2007 at the end of igcp project no 449 which had instigated the compilation of fluvial records from around the world during 2000 2004 under the auspices of the fluvial archives group an overarching finding is the confirmation of the well established view that in europe there is a demarcation between handaxe making in the west and flake core industries in the east although on a wider scale that pattern is undermined by the increased numbers of lower palaeolithic bifaces now recognized in east asia it is also apparent that although it seems to have appeared at different places and at different times in the later lower palaeolithic the arrival of levallois technology as a global phenomenon was similarly timed across the area occupied by middle pleistocene hominins at around 0 3 ma

effect of dry large scale vertical motions on initial mjo convective onset anomalies of eastward propagating large scale vertical motion with 30 day variability at addu city maldives move into the indian ocean from the west and are implicated in madden julian oscillation mjo convective onset using ground based radar and large scale forcing data derived from a sounding array typical profiles of environmental heating moisture sink vertical motion moisture advection and eulerian moisture tendency are computed for periods prior to those during which deep convection is prevalent and those during which moderately deep cumulonimbi do not form into deep clouds convection with 3 7 km tops is ubiquitous but present in greater numbers when tropospheric moistening occurs below 600 hpa vertical eddy convergence of moisture in shallow to moderately deep clouds is likely responsible for moistening during a 3 7 day long transition period between suppressed and active mjo conditions although moistening via evaporation of cloud condensate detrained into the environment of such clouds may also be important reduction in large scale subsidence associated with a vertical velocity structure that travels with a dry eastward propagating zonal wavenumbers 1 1 5 structure in zonal wind drives a steepening of the lapse rate below 700 hpa which supports an increase in moderately deep moist convection as the moderately deep cumulonimbi moisten the lower troposphere more deep convection develops which itself moistens the upper troposphere reduction in large scale subsidence associated with the eastward propagating feature reinforces the upper tropospheric moistening helping to then rapidly make the environment conducive to formation of large stratiform precipitation regions whose heating is critical for mjo maintenance

correlation between the onset of the east asian subtropical summer monsoon and the eastward propagation of the madden julian oscillation abstractusing the daily outgoing longwave radiation olr the pentad climate prediction center merged analysis of precipitation cmap and the 6 h climate forecast system reanalysis cfsr dataset from 1979 to 2010 a composite analysis along with space time wave filtering is performed to examine the linkage between the madden julian oscillation mjo and the onset of the east asian subtropical summer monsoon eassm over 20 30 n 110 120 e the onset of the eassm is shown to be best characterized by the reversal of the mean meridional wind shear related to the rapid reestablishment of the south asian high sah over the southern indochinese peninsula in the upper troposphere the mean date of easmm onset is near the end of april which is about a month earlier than the typical onset of the east asian summer monsoon further analysis indicates that the onset of the eassm and the reestablishment of sah are often associated with the arrival of the wet phase of the tropical mjo over the central and eas

interdecadal changes in snow depth on arctic sea ice snow plays a key role in the growth and decay of arctic sea ice in winter it insulates sea ice from cold air temperatures slowing sea ice growth from spring to summer the albedo of snow determines how much insolation is absorbed by the sea ice and underlying ocean impacting ice melt processes knowledge of the contemporary snow depth distribution is essential for estimating sea ice thickness and volume and for understanding and modeling sea ice thermodynamics in the changing arctic this study assesses spring snow depth distribution on arctic sea ice using airborne radar observations from operation icebridge for 2009 2013 data were validated using coordinated in situ measurements taken in march 2012 during the bromine ozone and mercury experiment bromex field campaign we find a correlation of 0 59 and root mean square error of 5 8 cm between the airborne and in situ data using this relationship and icebridge snow thickness products we compared the recent results with data from the 1937 1954 1991 soviet drifting ice stations the comparison shows thinning of the snowpack from 35 1 9 4 to 22 2 1 9 cm in the western arctic and from 32 8 9 4 to 14 5 1 9 cm in the beaufort and chukchi seas these changes suggest a snow depth decline of 37 29 in the western arctic and 56 33 in the beaufort and chukchi seas thinning is negatively correlated with the delayed onset of sea ice freezeup during autumn

late pleistocene and holocene small and large mammal faunas from the northern urals data from the mammal fauna of the north urals during the late pleistocene and holocene are synthesised analysis of differentiation the degree of small and large mammal faunas during this time has been undertaken only differences of mammal species composition were significant between the late pleistocene and holocene complexes and within these complexes the distinction between faunas was insignificant the transition from the late pleistocene to the holocene complex small mammal faunas occurred in the middle late valdai due to expansion of the forest species in large mammal faunas the process was recorded later in dryas 3 early holocene because of the extinction of some species and others that changed their areas of occupation

geology and mammalian fauna of the middle pleistocene site medzhybozh ukraine abstract qualitative and quantitative faunal associations of molluscs mammals and other vertebrates pisces amphibia reptilia aves have been determined at a new important site at medzhybozh in western ukraine geological and taphonomic conditions of the remains preservation are described the transient mindelian rissian fauna is identified and correlated with the middle pleistocene holsteinian likhvin stage this sequence represents a warm period of the holsteinian followed by with a short cooling in the middle of the period the human cultural material of acheulian and upper palaeolithic age has also been studied at this site it indicates the oldest migration of humans into the region

effect of frequent winter warming events storms and snow on sea ice growth a case from the atlantic sector of the arctic ocean during the n ice2015 campaign

propagation of the madden julian oscillation through the maritime continent and scale interaction with the diurnal cycle of precipitation the convectively active part of the madden julian oscillation mjo propagates eastward through the warm pool from the indian ocean through the maritime continent the indonesian archipelago to the western pacific the maritime continent s complex topography means the exact nature of the mjo propagation through this region is unclear model simulations of the mjo are often poor over the region leading to local errors in latent heat release and global errors in medium range weather prediction and climate simulation using 14 northern winters of trmm satellite data it is shown that where the mean diurnal cycle of precipitation is strong 80 of the mjo precipitation signal in the maritime continent is accounted for by changes in the amplitude of the diurnal cycle additionally the relationship between outgoing long wave radiation olr and precipitation is weakened here such that olr is no longer a reliable proxy for precipitation the canonical view of the mjo as the smooth eastward propagation of a large scale precipitation envelope also breaks down over the islands of the maritime continent instead a vanguard of precipitation anomalies of 2 5 mm day 1 over 10 6 km 2 jumps ahead of the main body by approximately 6 days or 2000 km hence there can be enhanced precipitation over sumatra borneo or new guinea when the large scale mjo envelope over the surrounding ocean is one of suppressed precipitation this behaviour can be accommodated into existing mjo theories frictional and topographic moisture convergence and relatively clear skies ahead of the main convective envelope combine with the low thermal inertia of the islands to allow a rapid response in the diurnal cycle which rectifies onto the lower frequency mjo hence accurate representations of the diurnal cycle and its scale interaction appear to be necessary for models to simulate the mjo successfully

biostratigraphy of the late middle pleistocene middle neopleistocene of the southern urals region abstract a summary of published and unpublished materials on the stratigraphy of the late middle pleistocene middle neopleistocene according to the russian stratigraphic scheme of the southern urals region is given deposits of different origin in the regional stratigraphic units are characterized the results of mammalian investigations provide the basis for the stratigraphical subdivision mollusca and palynology are used for the reconstruction of the palaeoenvironments the stratigraphical positions of the main middle neopleistocene localities and precise definitions of the stratigraphical scheme of the southern urals region are discussed the southern urals subdivisions are correlated with the western european stratigraphical schemes holsteinian saalian interval

meteorological conditions in a thinner arctic sea ice regime from winter to summer during the norwegian young sea ice expedition n ice2015 atmospheric measurements were made over arctic sea ice north of svalbard from winter to early summer january june 2015 during the norwegian young sea ice n ice2015 expedition these measurements which are available publicly represent a comprehensive meteorological data set covering the seasonal transition in the arctic basin over the new thinner sea ice regime winter was characterized by a succession of storms that produced short lived less than 48 h temperature increases of 20 to 30 k at the surface these storms were driven by the hemispheric scale circulation pattern with a large meridional component of the polar jet stream steering north atlantic storms into the high arctic nonstorm periods during winter were characterized by strong surface temperature inversions due to strong radiative cooling radiatively clear state the strength and depth of these inversions were similar to those during the surface heat budget of the arctic ocean sheba campaign in contrast atmospheric profiles during the opaquely cloudy state were different to those from sheba due to differences in the synoptic conditions and location within the ice pack storm events observed during spring summer were the result of synoptic systems located in the barents sea and the arctic basin rather than passing directly over n ice2015 these synoptic systems were driven by a large scale circulation pattern typical of recent years with an arctic dipole pattern developing during june surface temperatures became near constant 0 c on 1 june marking the beginning of summer atmospheric profiles during the spring and early summer show persistent lifted temperature and moisture inversions that are indicative of clouds and cloud processes

plio pleistocene geological record and small mammal faunas eastern shore of the azov sea southern european russia the shoreline of the taganrog gulf of the azov sea at the mouth of don river provides a series of extended upper pliocene and quaternary sections that have been actively studied in the last century this extraglacial region had a complex sedimentary history combining subaerial aggradation with marine fluvial and deltaic sedimentation the well exposed stratigraphical sequence and abundant palaeontological record continuously attract geologists and highlight the region as one of international importance for the addressing of numerous problems of late pliocene and quaternary stratigraphy and palaeogeography fossil mammalian faunas of the region include important eurasian biostratigraphical markers such as stenocranius ex gr hintoni gregaloides lagurini spp and mimomys savini for many years fossil remains of mammals provide decisive clues to the geological history of the region recent geological studies of reference sections have provided data on small mammals palaeomagnetism and palaeogeographical reconstructions in the northeastern part of the azovian region mammalian assemblages indicate the presence of the late pliocene late early pleistocene middle pleistocene and late pleistocene levels and in addition provide a clear biostratigraphical context for the early middle pleistocene transition

thermal conductivity of landfast antarctic and arctic sea ice 1 we present final results from a program to measure the thermal conductivity of sea ice with in situ thermistor arrays using an amended analysis of new and previously reported ice temperatures results from landfast first year fy ice near barrow alaska and mcmurdo sound antarctica are consistent with predictions from effective medium models but 10 15 higher than values from the parameterization currently used in most sea ice models we observe no previously reported anomalous near surface reduction which is now understood to have been an artifact nor a convective enhancement to the heat flow although our analysis is limited to temperatures below 5c at which brine percolation is restricted results for landfast multiyear my ice in mcmurdo sound are also consistent with effective medium predictions and emphasize the density dependence we compare these and historical measurements with effective medium predictions and the representation commonly used in sea ice models developed originally for my arctic ice we propose an alternative expression derived from effective medium models appropriate for both my and fy ice that is consistent with

critical role of snow on sea ice growth in the atlantic sector of the arctic ocean during the norwegian young sea ice n ice2015 campaign in early 2015 a deep snow pack was observed almost double the climatology for the region north of svalbard there were significant amounts of snow ice in second year ice syi while much less in first year ice fyi here we use a 1 d snow ice thermodynamic model forced with reanalyses to show that snow ice contributes to thickness growth of syi in absence of any bottom growth due to the thick snow growth of fyi is tightly controlled by the timing of growth onset relative to precipitation events a later growth onset can be favorable for fyi growth due to less snow accumulation which limits snow ice formation we surmise these findings are related to a phenomenon in the atlantic sector of the arctic where frequent storm events bring heavy precipitation during autumn and winter in a region with a thinning ice cover

observations of flooding and snow ice formation in a thinner arctic sea ice regime during the n ice2015 campaign influence of basal ice melt and storms seven ice mass balance instruments deployed near 83 n on different first year and second year ice floes representing variable snow and ice conditions documented the evolution of snow and ice conditions in the arctic ocean north of svalbard in january march 2015 frequent profiles of temperature and thermal diffusivity proxy were recorded to distinguish changes in snow depth and ice thickness with 2 cm vertical resolution four instruments documented flooding and snow ice formation flooding was clearly detectable in the simultaneous changes in thermal diffusivity proxy increased temperature and heat propagation through the underlying ice slush then progressively transformed into snow ice flooding resulted from two different processes i after storm induced breakup of snow loaded floes and ii after loss of buoyancy due to basal ice melt in the case of breakup when the ice was cold and not permeable rapid flooding probably due to lateral intrusion of seawater led to slush and snow ice layers at the ocean freezing temperature 1 88 c after the storm the instruments documented basal sea ice melt over warm atlantic waters and ocean to ice heat flux peaked at up to 400 w m 2 the warm ice was then permeable and flooding was more gradual probably involving vertical intrusion of brines and led to colder slush and snow ice 3 c the n ice2015 campaign provided the first documentation of significant flooding and snow ice formation in the arctic ice pack as the slush partially refroze snow ice formation may become a more frequently observed process in a thinner ice arctic

the impact of an intense summer cyclone on 2012 arctic sea ice retreat 1 this model study examines the impact of an intense early august cyclone on the 2012 record low arctic sea ice extent the cyclone passed when arctic sea ice was thin and the simulated arctic ice volume had already declined 40 from the 2007 2011 mean the thin sea ice pack and the presence of ocean heat in the near surface temperature maximum layer created conditions that made the ice particularly vulnerable to storms during the storm ice volume decreased about twice as fast as usual owing largely to a quadrupling in bottom melt caused by increased upward ocean heat transport this increased ocean heat flux was due to enhanced mixing in the oceanic boundary layer driven by strong winds and rapid ice movement a comparison with a sensitivity simulation driven by reduced wind speeds during the cyclone indicates that cyclone enhanced bottom melt strongly reduces ice extent for about 2 weeks with a declining effect afterward the simulated arctic sea ice extent minimum in 2012 is reduced by the cyclone but only by 0 15 106 km2 4 4 thus without the storm 2012 would still have produced a record minimum

regional simulation of the october and november mjo events observed during the cindy dynamo field campaign at gray zone resolution abstractthis study investigates the october and november mjo events observed during the cooperative indian ocean experiment on intraseasonal variability in the year 2011 cindy dynamics of the mjo dynamo field campaign through cloud permitting numerical simulations the simulations are compared to multiple observational datasets the control simulation at 9 km horizontal grid spacing captures the slow eastward progression of both the october and november mjo events in surface precipitation outgoing longwave radiation zonal wind humidity and large scale vertical motion the vertical motion shows weak ascent in the leading edge of the mjo envelope followed by deep ascent during the peak precipitation stage and trailed by a broad second baroclinic mode structure with ascent in the upper troposphere and descent in the lower troposphere both the simulation and the observations also show slow northward propagation components and tropical cyclone like vortices after the passage of the mjo active phase

the thermal conductivity of seasonal snow twenty seven studies on the thermal conductivity of snow k eff have been published since 1886 combined they comprise 354 values of k eff and have been used to derive over 13 regression equation and predicting k eff vs density due to large and largely undocumented differences in measurement methods and accuracy sample temperature and snow type it is not possible to know what part of the variability in this data set is the result of snow microstructure we present a new data set containing 488 measurements for which the temperature type and measurement accuracy are known a quadratic equation where is in g cm 3 and k eff is in w m 1 k 1 can be fit to the new data r 2 0 79 a logarithmic expression can also be used the first regression is better when estimating values beyond the limits of the data the second when estimating values for low density snow within the data set snow types resulting from kinetic growth show density independent behavior rounded grain and wind blown snow show strong density dependence the new data set has a higher mean value of density but a lower mean value of thermal conductivity than the old set this shift is attributed to differences in snow types and sample temperatures in the sets using both data sets we show that there are well defined limits to the geometric configurations that natural seasonal snow can take

ocean to ice heat flux at the north pole environmental observatory 1 data from drifting buoys deployed in april 2002 as part of the north pole environmental observatory project have been analysed to estimate ocean heat flux in the time period from 1 may 2002 to 11 mar 2003 prior to late january the observatory remained in deep water but subsequently drifted directly over the yermak plateau a relatively shallow feature north of svalbard while over deep water heat flux was dominated by storage and release of solar energy in the ocean boundary layer during summer the most likely annual average value for 2002 was 2 6 w m 2 less than previous determinations in the western arctic over yermak plateau heat flux at the interface came from mixing of warmer water into the boundary layer from below when the observatory was in water with depths less than 1200 m the average heat flux was around 22 w m 2

links between tropical convection and variations of the extratropical circulation during toga coare abstract data from the intensive observation period of the tropical ocean global atmosphere coupled ocean atmosphere response experiment november 1992 february 1993 have been used to investigate the links between intraseasonal variations in tropical convection and those in forcing of upper tropospheric rossby waves in the extratropics the primary databases are geostationary meteorological satellite imagery and tropical wind analyses from the bureau of meteorology australia a number of 5 day periods showing convection in different locations were chosen for each period mean fields of divergence cloud top temperature and upper tropospheric rossby wave source are presented vorticity budgets are used to demonstrate the processes responsible for the rossby wave source patterns the approach follows earlier studies of links between interannual variations of tropical convection associated with the southern oscillation and variations of the extratropical circulation it is shown that the regions of tropi

dramatic interannual changes of perennial arctic sea ice linked to abnormal summer storm activity 1 the perennial september arctic sea ice cover exhibits large interannual variability with changes of over a million square kilometers from one year to the next here we explore the role of changes in arctic cyclone activity and related factors in driving these pronounced year to year changes in perennial sea ice cover strong relationships are revealed between the september sea ice changes and the number of cyclones in the preceding late spring and early summer in particular fewer cyclones over the central arctic ocean during the months of may june and july appear to favor a low sea ice area at the end of the melt season years with large losses of sea ice are characterized by abnormal cyclone distributions and tracks they lack the normal maximum in cyclone activity over the central arctic ocean and cyclones that track from eurasia into the central arctic are largely absent fewer storms are associated with above average mean sea level pressure strengthened anticyclonic winds an intensification of the transpolar drift stream and reduced cloud cover all of which favor ice melt it is also shown that a strengthening of the central arctic cyclone maximum helps preserve the ice cover although the association is weaker than that between low cyclone activity and reduced sea ice the results suggest that changes in cyclone occurrence during late spring and early summer have preconditioning effects on the sea ice cover and exert a strong influence on the amount of sea ice that survives the melt season

comparison of freeboard retrieval and ice thickness calculation from als asiras and cryosat 2 in the norwegian arctic to field measurements made during the n ice2015 expedition we present freeboard measurements from airborne laser scanner als the airborne synthetic aperture and interferometric radar altimeter system asiras and cryosat 2 siral radar altimeter ice thickness measurements from both helicopter borne and ground based electromagnetic sounding and point measurements of ice properties this case study was carried out in april 2015 during the n ice2015 expedition in the area of the arctic ocean north of svalbard the region is represented by deep snow up to 1 12 m and a widespread presence of negative freeboards the main scattering surfaces from both cryosat 2 and asiras are shown to be closer to the snow freeboard obtained by als than to the ice freeboard measured in situ this case study documents the complexity of freeboard retrievals from radar altimetry we show that even under cold below 15 c conditions the radar freeboard can be close to the snow freeboard on a regional scale of tens of kilometers we derived a modal sea ice thickness for the study region from cryosat 2 of 3 9 m compared to measured total thickness 1 7 m resulting in an overestimation of sea ice thickness on the order of a factor 2 our results also highlight the importance of year to year regional scale information about the depth and density of the snowpack as this influences the sea ice freeboard the radar penetration and is a key component of the hydrostatic balance equations used to convert radar freeboard to sea ice thickness

mjo initiation processes over the tropical indian ocean during dynamo cindy2011 abstracta multination joint field campaign called the dynamics of mjo cooperative indian ocean experiment on intraseasonal variability in year 2011 dynamo cindy2011 took place in the equatorial indian ocean io in late 2011 during the campaign period two strong mjo events occurred from the middle of october to the middle of december referred to as mjo i and mjo ii respectively both the events were initiated over the western equatorial indian ocean wio around 50 60 e using multiple observational data products era interim the ecmwf final analysis and nasa merra the authors unveil specific processes that triggered the mjo convection in the wio it is found that 10 days prior to mjo i initiation a marked large scale ascending motion anomaly appeared in the lower troposphere over the wio the cause of this intraseasonal vertical motion anomaly was attributed to anomalous warm advection by a cyclonic gyre anomaly over the northern io the mjo ii initiation was preceded by a low level specifi

the effect of the mjo on the north american monsoon abstract the effect of the madden julian oscillation mjo in the eastern pacific on the north american monsoon is documented using ncep ncar reanalysis and daily mean precipitation data from 1958 to 2003 it is found that positive zonal wind anomalies in the eastern tropical pacific lead to above normal precipitation in northwest mexico and arizona from several days to over a week later this connection between the tropical pacific and monsoon precipitation appears to be limited to regions influenced by moisture surges from the gulf of california as a similar connection does not exist for new mexico precipitation the evidence suggests that the mjo might affect monsoon precipitation by modulating the strength of low level easterly waves off the coast of mexico which in turn triggers the development of a gulf surge

intraseasonal variability in a dry atmospheric model abstract a long integration of a primitive equation dry atmospheric model with time independent forcing under boreal winter conditions is analyzed a variety of techniques such as time filtering space time spectral analysis and lag regressions are used to identify tropical waves it is evident that oscillations with intraseasonal time scales and a kelvin wave structure exist in the model tropical atmosphere coherent eastward propagations in the 250 hpa velocity potential and zonal wind are found with a speed of about 15 m s 1 the oscillation is stronger in the eastern hemisphere than in the western hemisphere interactions between the tropical and extratropical flows are found to be responsible for the simulated intraseasonal variability wave activity flux analysis reveals that a tropical influence occurs in the north pacific region where a northeastward wave activity flux is found associated with the tropical divergent flow in the western and central pacific in the north atlantic sector on the ot

thin sea ice thick snow and widespread negative freeboard observed during n ice2015 north of svalbard in recent years sea ice conditions in the arctic ocean changed substantially toward a younger and thinner sea ice cover to capture the scope of these changes and identify the differences between individual regions in situ observations from expeditions are a valuable data source we present a continuous time series of in situ measurements from the n ice2015 expedition from january to june 2015 in the arctic basin north of svalbard comprising snow buoy and ice mass balance buoy data and local and regional data gained from electromagnetic induction em surveys and snow probe measurements from four distinct drifts the observed mean snow depth of 0 53 m for april to early june is 73 above the average value of 0 30 m from historical and recent observations in this region covering the years 1955 2017 the modal total ice and snow thicknesses of 1 6 and 1 7 m measured with ground based em and airborne em measurements in april may and june 2015 respectively lie below the values ranging from 1 8 to 2 7 m reported in historical observations from the same region and time of year the thick snow cover slows thermodynamic growth of the underlying sea ice in combination with a thin sea ice cover this leads to an imbalance between snow and ice thickness which causes widespread negative freeboard with subsequent flooding and a potential for snow ice formation with certainty 29 of randomly located drill holes on level ice had negative freeboard