how accurate are 234th measurements in seawater based on the mno2 impregnated cartridge technique in the past decade a mno2 impregnated cartridge technique has been widely used to extract 234th from seawater one of the inherent assumptions associated with this technique is that all th species in the dissolved phase are subject to extraction by the mno2 cartridges in this study an intercalibration between the cartridge technique and a small volume mno2 coprecipitation technique was carried out to test this assumption we demonstrated that the collection efficiency for 234th could be substantially overestimated by the mno2 cartridge technique this may be the result of organic complexation of a significant portion of 234th in seawater causing this fraction of th to pass through the mno2 cartridges the overestimate in collection efficiency may explain the deep water 234th deficit observed in some oceanographic settings e g the gulf of mexico the middle atlantic bight and the gulf of maine sensitivity tests show that using the cartridge technique can yield 234th based particulate organic carbon export rates that are overestimated by factors of up to 10 furthermore the frequent observed disagreements between th fluxes recorded by shallow sediment traps and estimated using the cartridge method may be ascribed at least partially to this methodological issue

reply to comment by chin chang hung et al on how accurate are 234th measurements in seawater based on the mno2 impregnated cartridge technique

poleward deflection of storm tracks an analysis of 11 years of european centre for medium range weather forecasts data focuses primarily on the vertically averaged high frequency transients the conclusions are discussed in the context of a the winter storm track b monthly variability and c interannual variability a winter storm track results show that the pattern of the forcing by the high frequency eddies along the storm track is highly correlated with the stationary circulation and the forcing itself is primarily responsible for the location of the trough ridge system associated with the stationary flow the results also clarify the role of wind component covariance terms u9y9 and y9 2 2 u9 2 in the column averaged vorticity forcing the simpler term u9y9 has the well known effect of intensifying the anticyclonic cyclonic tendencies on the southern northern side of the jet thereby producing an increase in the barotropic component of the zonal jet the y9 2 2 u9 2 term displays a quadrupole pattern which is also approximately in phase with the trough ridge system associated with the stationary flow b monthly variability eddy activity has been shown to possess a seasonal life cycle increasing during the early fall and reaching a maximum around the month of november then decaying for most of the winter months month to month variations in eddy activity over the pacific ocean show that energy levels increase up through november decreasing thereafter at the same time the trough ridge circulation pattern is intensifying by december baroclinicity in the western pacific has increased substantially and low level eddies are found to break by the middle of the ocean upper level eddies start to break well before reaching the west coast of north america resulting in a displacement of the maximum in y9 2 2 u9 2 westward from its november position and increasing the trough ridge forcing by the high frequency eddies c interannual variability wintertime eddy kinetic energy is seen to extend further eastward through the pacific ocean during the warm phase but displays an abrupt termination during the cold phase anomalies in the eddy transient forcing tend to be quite similar to that of the pacific north american pattern itself the extension of the storm track during the warm phase resembles that of fall conditions and is present in the winter season because the source of low level baroclinicity

234th 238u disequilibria within the california current1 profiles of dissolved and particulate sup 234 th were determined at several stations within the california current modeling of the disequilibria between the sup 234 th and sup 238 u within the surface waters provides for estimates of the residence time of dissolved thorium with respect to particle scavenging the particle residence time and the particulate sup 234 th flux exiting the surface layer the model derived first order scavenging rate constant for dissolved thorium is observed to be proportional to the rate of primary production particle residence times seem to be governed by the rate of zooplankton grazing and the types of zooplankton present model derived particulate sup 234 th fluxes are in good agreement with direct measurements by sediment traps

a statistical study of gravity waves in the polar regions based on operational radiosonde data gravity waves in the lower polar stratosphere are examined using operational radiosonde observations gathered from 33 stations over a period of 10 years both the potential and kinetic energies of the gravity waves vary annually and reach maxima in winter in the arctic and in spring in the antarctic in the antarctic spring a region of large gravity wave energy propagates downward following the movement of a zone of high static stability associated with southern hemispheric warming moreover the enhanced energy region and the high stability zone coincide in the horizontal plane and move gradually from 135 e 50 s to 45 w 70 s over the south pole the vertical and horizontal directions of wave propagation are examined using hodograph analysis in the vertical most gravity waves transfer energy upward in the arctic while the percentage of downward energy propagation is relatively high in winter and spring in the antarctic horizontally gravity waves propagate westward relative to the mean wind in the arctic while in the antarctic the dominant direction varies from station to station the correlation between gravity wave energy in the lower stratosphere and the mean wind is also examined in the arctic gravity wave energy is highly correlated with the surface wind though in the antarctic it correlates with the stratospheric wind these results suggest that gravity waves observed in the arctic are forced by topography whereas in antarctica some sources may exist in the stratosphere one such source candidate is likely to be the polar night jet

general aspects of a t213l256 middle atmosphere general circulation model 1 a high resolution middle atmosphere general circulation model gcm developed for studying small scale atmospheric processes is presented and the general features of the model are discussed the gcm has t213 spectral horizontal resolution and 256 vertical levels extending from the surface to a height of 85 km with a uniform vertical spacing of 300 m gravity waves gws are spontaneously generated by convection topography instability and adjustment processes in the model and the gcm reproduces realistic general circulation in the extratropical stratosphere and mesosphere the oscillations similar to the stratopause semiannual oscillation and the quasi biennial oscillation qbo in the equatorial lower stratosphere are also spontaneously generated in the gcm although the period of the qbo like oscillation is short 15 months the relative roles of planetary waves large scale gws and small scale gws in maintenance of the meridional structures of the zonal wind jets in the middle atmosphere are evaluated by calculating eliassen palm diagnostics separately for each of these three groups of waves small scale gws are found to cause deceleration of the wintertime polar night jet and the summertime easterly jet in the mesosphere while extratropical planetary waves primarily cause deceleration of the polar night jet below a height of approximately 60 km the meridional distribution and propagation of small scale gws are shown to affect the shape of the upper part of mesospheric jets the phase structures of orographic gws over the south andes and gws emitted from the tropospheric jet stream are discussed as examples of realistic gws reproduced by the t213l256 gcm

a study of the low frequency inertio gravity waves observed during the pyrenees experiment the purpose of this paper is to analyze and interpret the onset of some well characterized transient inertio gravity waves observed during the pyrex pyrenees experiment campaign the data used are the high resolution soundings launched every 6 hours on both sides of the ridge in agreement with other observations made during the field campaign certain among those soundings often show steady mountain waves it appears that those waves are often transients and are followed by well characterized inertio gravity waves propagating upward and downward from the level where the initial mountain waves are large to interpret those observations it is suggested that the observed inertio gravity waves result from the geostrophic adjustment of the large scale flow that follows the transit and eventually the breaking of the main mountain wave this hypothesis is supported by an analytical calculation of inertio gravity waves emission from a momentum deposit that lasts a finite time the spatial extent of this forcing are also finite and its maximum amplitude is a fraction of the measured mountain drag

small phytoplankton drive high summertime carbon and nutrient export in the gulf of california and eastern tropical north pacific summertime carbon nitrogen and biogenic silica export was examined using 234th 238u disequilibria combined with free floating sediment traps and fine scale water column sampling with in situ pumps isp within the eastern tropical north pacific and the gulf of california fine scale isp sampling provides evidence that in this system particulate carbon pc and particulate nitrogen pn concentrations were more rapidly attenuated relative to 234th activities in small particles compared to large particles converging to 1 5 mol dpm 1 by 100 m comparison of elemental particle composition coupled with particle size distribution analysis suggests that small particles are major contributors to particle flux while absolute pc and pn export rates were dependent on the method used to obtain the element 234th ratio regional trends were consistent across measurement techniques the highest c fixation rates were associated with diatom dominated surface waters yet the highest export efficiencies occurred in picoplankton dominated surface waters where relative concentrations of diazotrophs were also elevated our results add to the increasing body of literature that picoplankton and diazotroph dominated food webs in subtropical regions can be characterized by enhanced export efficiencies relative to food webs dominated by larger phytoplankton e g diatoms in low productivity pico nanoplankton dominated regions where small particles are major contributors to particle export findings from this region are compared globally and provide insights into the efficiency of downward particle transport of carbon and associated nutrients in a warmer ocean where picoplankton and diazotrophs may dominate therefore we argue the necessity of collecting multiple particle sizes used to convert 234th fluxes into carbon or other elemental fluxes including 50 m since they can play an important role in vertical fluxes especially in oligotrophic environments our results further underscore the necessity of using multiple techniques to quantify particle flux given the uncertainties associated with each collection method

inertia gravity waves spontaneously generated by jets and fronts part i different baroclinic life cycles abstract the spontaneous generation of inertia gravity waves in idealized life cycles of baroclinic instability is investigated using the weather research and forecasting model two substantially different life cycles of baroclinic instability are obtained by varying the initial zonal jet the wave generation depends strongly on the details of the baroclinic wave s development in the life cycle dominated by cyclonic behavior the most conspicuous gravity waves are excited by the upper level jet and are broadly consistent with previous simulations of o sullivan and dunkerton in the life cycle that is dominated by anticyclonic behavior the most conspicuous gravity waves even in the stratosphere are excited by the surface fronts although the fronts are no stronger than in the cyclonic life cycle the anticyclonic life cycle also reveals waves in the lower stratosphere above the upper level trough of the baroclinic wave these waves have not been previously identified in idealized simulations the sensiti

mls observations of atmospheric gravity waves over antarctica 1 stratospheric gravity waves over antarctica are studied with the radiance variances observed by upper atmosphere research satellite microwave limb sounder uars mls strong wave activities are found during august and september in 1992 1994 over the drake passage region 290 315 longitude and 50 s 70 s latitude where the enhancement seems associated with the topography of both south america and antarctic peninsula tips during the same period significant gravity wave activities are also evident along the antarctic coastal region the vertical growth of the wave variance shows a scale height of 14 km at low altitudes for both drake passage and the coastal regions but reduces substantially at high altitudes the growth rate transition occurs at a lower altitude in the drake passage region where the variance is larger the gravity wave activities observed near the antarctic may contribute significantly to the formation of polar stratospheric clouds psc because of the overlapping with the vortex edge and with the psc activities as observed by claes cryogenic limb array etalon spectrometer

the effect of large scale transient eddies on the time mean flow in the atmosphere abstract the effect of horizontal transports of momentum and heat by transient eddies te on the time mean flow is studied by examining the relevant terms in a local budget of quasi geostrophic potential vorticity two long term observational data sets are used and results for the northern hemisphere winter are presented the results indicate that eddy beat fluxes in the free atmosphere exert a dissipative influence on both the zonally averaged flow and the stationary waves on the oilier hand eddy momentum transports tend to force cyclonic circulations over the semi permanent icelandic and aleutian surface lows and anticyclonic circulations over the oceanic high pressure cells in the subtropics the forcing of the time mean flow arising from horizontal te heat transports is generally stronger than the forcing associated with eddy momentum transports the net eddy of eddy transports of heat and momentum is to dissipate the potential enstrophy of the stationary waves the characteristic time scale asso

variability of the observed midlatitude storm tracks in relation to low frequency changes in the circulation pattern abstract the principal modes of month to month variability of the wintertime storm tracks over the north pacific and north atlantic are identified by empirical orthogonal function analysis of the root mean square statistics of bandpass 2 5 6 day filtered geopotential height data for 19 yr one of the two leading modes depicts fluctuations in the level of synoptic scale activity without any noticeable spatial displacement of the storm track axes whereas the other mode is associated with meridional shifts of the storm tracks from their time averaged positions higher order modes are indicative of diversion or truncation of cyclone tracks in particular geographical regions it is demonstrated that the leading storm track modes are linked to some of the best known monthly averaged teleconnection patterns the dipolar western pacific and western atlantic patterns for the monthly mean flow are seen to be accompanied by marked changes in the intensity of the storm tracks over the western oceans whereas the m

case studies of nonorographic gravity waves over the southern ocean emphasize the role of moisture two case studies of nonorographic gravity waves are carried out for wave events that occurred over the southern ocean in november 2005 mesoscale simulations were carried out with the weather and research forecast model the simulated waves were compared to observations from superpressure balloons of the vorcore campaign and from the high resolution dynamic limb sounder satellite satisfactory agreement is found giving confidence in the estimations of wave parameters and amplitudes for the amplitudes both the model and observations provide a lower bound for different reasons waves are found in the lower stratosphere with horizontal wavelengths of the order of 150 200 km in the horizontal 5 8 km in the vertical corresponding to intrinsic frequencies between 5 and 10 f where f is the coriolis parameter although the tropospheric flow is very different between the two cases there are features which are common and appear significant for the gravity waves these include intense localized updrafts associated with convection in the troposphere and a displaced polar vortex inducing strong winds in the stratosphere above the frontal region relative to theoretical expectations the simulations emphasize the role of moisture intrinsic frequencies are significantly higher than those expected for waves produced by dry spontaneous generation from jets to quantify the contribution of moisture dry simulations were carried out yielding momentum fluxes over oceanic regions that were 2 5 times weaker identification of the generation mechanisms in these complex flows calls for further study and these should include moisture and a realistic stratospheric jet

export flux of poc in the main stream of the kuroshio 1 particulate organic carbon poc export fluxes were measured using both a drifting sediment trap and a 234th approach ratio of poc 234th multiple 234th flux in the main steam of the kuroshio in august 2006 the poc fluxes measured by sediment traps and the 234th approach at 65 90 120 and 140 m ranged from 20 to 54 mg m 2 d 1 and 26 to 67 mg m 2 d 1 respectively the results show that using poc 234th ratios in intermediate particles 10 53 m and sinking particles is more comparable to the poc flux measured by sediment traps therefore the poc export fluxes within the euphotic zone estimated by sediment trap and 234th approaches are complementary methods for measuring poc flux in the kuroshio

234th balance and implications for seasonal particle retention in the eastern bering sea th abstract as part of the bering ecosystem study bering sea integrated ecosystem research program best bsierp distributions of 234 th in the water column and sediments were measured at approximately 60 stations over the shelf and slope oceanic regions of the eastern bering sea during spring and summer of 2009 and 2010 during this study period the inventory of sediment excess 234 th 234 thxs on the shelf was determined to be 1 3 of the total 234 th deficit in the overlying water column the average focusing factor ffth sediment 234 thxs water column 234 th deficit was 0 3470 23 in addition the export flux of 234 th from the shelf to the slope oceanic region was determined to be on average 30 of the total production of 234 th throughout the shelf taken together these results indicate that 234 th and associated particles are largely retained on the shelf and that shelf sediments represent a sink for particles in contrast the ffth in the slope oceanic region was higher averaging 1 5271 34 the higher ffth at the slope is attributed primarily to enhanced scavenging removal and sediment deposition of 234 th associated with periods of high biogenic particle flux at the marginal ice zone during the spring sea ice retreat a more general conclusion is that the ocean margin of the eastern bering sea may serve as an accumulation area for particles and associated reactive chemicals

the impact of marginal ice zone processes on the distribution of 21opb 21opo and 234th and implications for new production in the bellingshausen sea antarctica abstract the vertical distributions of 21opb 210po and 234th in both dissolved and particulate phases of seawater were measured at five stations along the 85 w meridian in the bellingshausen sea antarctica sea ice conditions during the expedition ranged from fully ice covered fast ice to open water away from the marginal ice zone concurrent primary productivity and algal chlorophyll measurements revealed a band of high productivity at approximately 67 30 s which remained in a rather static location during ice melt back along the transect a progressive increase in removal scavenging and sinking of 210pb 210po and 234th occurred towards the north open water conditions application of a simple irreversible scavenging model and particulate organic carbon and organic nitrogen to radionuclide ratios measured on suspended particulate matter allows the calculation of export production for this region under fast ice conditions some removal of phytodetritus from the euphotic zone was observed 1 2 mgc m 2 day 1 representing a low proportion of the primary production f ratio of 0 02 near the antarctic continental margin upwelling of regenerated dissolved 210po was found at the open water site near the algal band new production had risen to 27 252 mgc m 2 day 1 but a greater proportion of the original primary production was removed by sinking detritus f ratio of 0 03 0 33 comparison of 210po and 234th as tracers of of export production indicates considerable differences with 210po yielding rather lower rates of export flux compared to 234th radionuclide estimates of new production are significantly greater than those obtained by traditional sediment trap methods this may be due to the dynamic nature short duration and spatial variability of algal growth in the southern ocean

does 234th 238u disequilibrium provide an accurate record of the export flux of particulate organic carbon from the upper ocean the magnitude of the flux of biogenic particulate organic carbon poc exported from the surface waters of the world ocean and remineralized at depth is critical to constraining models of the global carbon cycle yet remains controversial the use of upper ocean sediment traps is still one of the primary tools for determining this export flux although trap fluxes have been shown to vary significantly because of hydrodynamic and sample collection biases over the past decade 234 th increasingly has been used as a tracer to estimate poc export from the euphotic zone by multiplying the depth integrated 234 th flux by the poc 234 th ratio of sinking particles the accuracy of this technique is highly dependent on the natural variability in the poc 234 th ratio and 234 th flux yet the significance of this variability to estimates of poc export remains uncertain based on an analysis of new 234 th and poc data from the labrador sea and a review of 25 previous independent field studies we report that poc export fluxes can vary 2 10 times or more solely because of variability in the poc 234 th ratio and procedures used to estimate the 234 th flux recommended improvements include studies of the biological chemical and physical mechanisms controlling 234 th organic matter interactions in seawater detailed comparisons of poc 234 th ratios in size fractionated and sediment trap material increased spatial and temporal sampling density of 234 th and more standardized procedures to calculate the 234 th export flux

sensitivity study for mesoscale simulations of gravity waves above antarctica during vorcore the observations from the vorcore campaign september 2005 january 2006 provide a unique dataset for the study of gravity waves in the lower stratosphere because of their wide coverage 150 000 observations from the south pole to about 40 s and of the quasi lagrangian nature of the superpressure balloons used numerical simulations with a mesoscale model are undertaken in order to investigate further the observed gravity waves their sources and the induced momentum fluxes the need for a high spatial resolution makes it necessary to find a compromise between the size of the model domain and the length of the simulations we describe preliminary simulations used to determine the best configuration of the model for this purpose and show that the simulations compare reasonably well with the observations model results complement the observations and provide new insights into orographic and non orographic wave sources copyright 2010 royal meteorological society

vertical and horizontal particle transport in the coastal waters of a large lake an assessment by sediment trap and thorium 234 measurements 1 the horizontal and vertical flux of particulate material in the nearshore of southern lake michigan 0 40 m was estimated with the naturally occurring radionuclide 234th horizontal fluxes of 234th supplemented apparent vertical fluxes of 234th in the water column based on local 234th 238u disequilibria by a factor of 7 14 reinforcing the importance of lateral transport in coastal environments calculated onshore transport of particulate material across the 40 m isobath was as high as 1 1 106 kg km 1 d 1 and exceeds estimates of terrigenous riverine and bluff erosion loading estimates of onshore flux of organic carbon exceeded areal primary productivity by as much as 300 and should be considered in nearshore carbon budgets bottom tethered sediment traps placed 5 m above the bottom measured sedimentation rates that were 1 order of magnitude lower than 234th derived mass fluxes from the water column and 2 orders of magnitude lower than 234th derived mass fluxes to the lakebed we ascribe this difference to under collecting by the sediment trap either because of trap hydrodynamics or flux occurring below the trap capture plane cross shore fluxes showed a periodicity of 4 days and correlated strongly with a topographic vorticity wave that is present throughout the year in southern lake michigan the impact of this wave as a driver of bidirectional cross shore flux on biogeochemical cycling and both nearshore and offshore food webs has not yet been explicitly considered

234th in surface waters distribution of particle export flux across the antarctic circumpolar current and in the weddell sea during the geotraces expedition zero and drake abstract as part of the geotraces polarstern expedition antxxiv 3 zero and drake we have measured the vertical distribution of 234th on sections through the antarctic circumpolar current along the zero meridian and in drake passage and on an ew section through the weddell sea steady state export fluxes of 234th from the upper 100 m derived from the depletion of 234th with respect to its parent 238u ranged from 621 105 to 1773 90 dpm m 2 d 1 this 234th flux was converted into an export flux of organic carbon ranging from 3 1 to 13 2 mmol c m 2 d 1 2 1 9 0 mmol c m 2 d 1 using poc 234th ratio of bulk respectively 50 m suspended particles at the export depth 100 m non steady state fluxes assuming zero flux under ice cover were up to 23 higher in addition particulate and dissolved 234th were measured underway in high resolution in the surface water with a semi automated procedure particulate 234th in surface waters is inversely correlated with light transmission and pco2 and positively with fluorescence and optical backscatter and is interpreted as a proxy for algal biomass high resolution underway mapping of particulate and dissolved 234th in surface water shows clearly where trace elements are absorbed by plankton and where they are exported to depth quantitative determination of the export flux requires the full 234th profile since surface depletion and export flux become decoupled through changes in wind mixed layer depth and in contribution to export from subsurface layers in a zone of very low algal abundance 54 58 s at the zero meridian confirmed by satellite chl a data the lowest carbon export of the acc was observed allowing fe and mn to maintain their highest surface concentrations an ice edge bloom that had developed in december january in the zone 60 65 s as studied during the previous leg had caused a high export flux at 64 5 s when we visited the area 2 months later february march the ice edge bloom had then shifted south to 65 69 s evident from uptake of co2 and dissolved fe mn and 234th without causing export yet in this way the parallel analysis of 234th can help to explain the scavenging behavior of other trace elements

alleviation of a systematic westerly bias in general circulation and numerical weather prediction models through an orographic gravity wave drag parametrization systematic westerly biases in the northern hemisphere wintertime flow of the meteorological office 15 layer operational model and 11 layer general circulation model are described evidence that the failure to parametrize subgrid scale orographic gravity wave drag may account for such biases is presented this evidence is taken from aircraft studies surface pressure drag measurements and studies of the zonally averaged momentum budget a parametrization scheme is described in which the surface stress is proportional to the near surface wind speed and static stability and to the variance of subgrid scale orography the stress is absorbed in the vertical by considering the influence of such gravity wave activity on static stability and vertical wind shear a richardson number dependent wave breaking formulation is devised and the vertical stress profile determined by a saturation hypothesis whereby the breaking waves are maintained at marginal stability it is shown that wave breaking preferentially occurs in the boundary layer and in the lower stratosphere results from a simple zonally symmetric model show how the adjustment to thermal wind balance with a wave drag in the stratosphere warms polar regions by adiabatic descent and decelerates the mean westerlies in the troposphere the influence of the parametrization scheme on integrations of the 11 layer model is described and found to be generally beneficial in a discussion of the reasons why this problem has only recently emerged it is suggested that the satisfactory northern hemisphere winter circulations of previous coarser general circulation models were due to a compensation implied by underestimating both the surface drag and the horizontal flux of momentum by explicitly resolved large scale eddies

momentum flux estimates for south georgia island mountain waves in the stratosphere observed via satellite abstract we show high resolution satellite observations of mountain wave events in the stratosphere above south georgia island in the remote southern atlantic ocean and compute the wave momentum fluxes for these events the fluxes are large and they imply important drag forces on the circulation small island orography is generally neglected in mountain wave parameterizations used in global climate models because limited model resolution treats the grid cell containing the island as ocean rather than land our results show that satellite observations can be used to quantitatively constrain mountain wave momentum fluxes and they suggest that mountain waves from island topography may be an important missing source of drag on the atmospheric circulation

long term budget of zonal momentum in the free atmosphere over europe in winter two sets of aerological data are used to study the time averaged budget of the zonal momentum in the free atmosphere over europe in winter in many respects the budget appears to be different from that reported by holopainen et al 1980 for north america over europe the coriolis force associated with the southward directed ageostrophic meridional flow tends to decrease the westerly momentum a compensating effect is caused by horizontal momentum flux convergence which takes place in the zonal as well as in the meridional plane and is due mainly to transient flow systems large scale turbulence the residual term in the momentum budget indicates that over europe the sub grid scale processes on the average cause a small accelerating effect on the large scale zonal flow in the upper troposphere the residual force over the mountainous region of europe 5 e 30 e 45 n 50 n is a decelerating one in agreement with the results for the corresponding area of north america

geochemical signature related to lipid biomarkers of anmes in gas hydrate bearing sediments in the ulleung basin east sea korea abstract the emission of methane as a greenhouse gas is controlled by the anaerobic oxidation of methane aom which plays an important role in the biogeochemical methane cycle during the second ulleung basin gas hydrate drilling expedition ubgh2 the distribution of lipid biomarkers and their compound specific stable carbon isotope ratios related to methane were investigated in venting and non venting sites ubgh2 3 ubgh2 10 of gas hydrate bearing sediments in the ulleung basin the objective of this study was to understand the microbial signatures related to methane cycling in organic rich sediment in a marginal sea east sea japan sea of the western north pacific the concentrations of methane related specific biomarkers archaeol and sn 2 hydroxyarchaeol at the sulphate methane transition zone smtz sediment depth in ubgh2 3 1 2 mbsf in ubgh2 10 6 8 mbsf are typically higher than in other sediment sections and their 13 c valuesare apparently depleted 73 3 to 102 7 in the ubgh2 3 and ubgh2 10 study sites however the 13 c values of archaeol and sn 2 hydroxyarchaeol between 59 6 and 66 5 are not depleted with the increased methane concentration in the sediments below the smtz in ubgh2 3 compared to the 13 c values about 60 of in situ methane this suggests that methane production processes should be dominant in the deeper sediment sections 2 7 3 8 mbsf rather than methane consumption by anaerobic methanotrophs anmes at the corresponding sediment depths there were also higher 13 c values 47 to 32 for archaeol and sn 2 hydroxyarchaeol in the 3 6 mbsf sections at ubgh2 10 suggesting the prevalence of methanogenic activities however the 13 c values 89 0 to 92 2 of archaeol and sn 2 hydroxyarchaeol were unexpectedly depleted in the deeper sediment section 5 2 mbsf of the venting site ubgh2 3 indicating that the past aom occurred under low sulphate concentrations in the corresponding pore water this study used the biomarker ratio sn 2 hydroxyarchaeol archaeol of archaea as a tool to demonstrate the different anme communities which was supported by 16s rrna analysis in the sediments of venting and non venting sites ubgh2 3 ubgh2 10 consequently the biochemical signatures of methanotrophic and methanogenic activity were found at varying sediment depths at both sites

a three dimensional time dependent approach to calibrating sediment trap fluxes we conducted an experiment to test explicitly the accuracy of upper ocean sediment trap fluxes using the particle reactive radionuclide 234th t1 2 24 1 days two independent vertex style multitrap arrays were used for collection of sinking particles at 95 m and 97 m depths over a four day period in may 1992 at the u s joint global ocean flux study bermuda atlantic time series study bats site samples for total 234th were collected every 8 m between the surface and 96 m and immediately combined for analysis to obtain the vertically integrated activity of 234th we collected a total of 27 samples over the four day period the234th samples were collected daily at each of the two traps and every other day on a 6 6 km grid to characterize the entire source region for particles collected in the traps in situ flow sensors at one trap array indicated low horizontal shear at the trap mouth 5 10 cm s compared to normal values at bats the predicted 234th flux from the watercolumn profiles was not significantly different from zero 30 140 disintegrations per minute m2 d the measured trap 234th flux at both arrays was significantly higher 290 15 dpm m2 d we hypothesize that upper ocean traps at bermuda may overcollect during low flux periods and undercollect during high flux periods thus recording a biased signal of the true particle flux

mean surface stress curl over the oceans as determined from the vorticity budget of the atmosphere abstract the vertically integrated atmospheric vorticity budget over the oceans offers in principle a possibility of determining the surface stress curl from upper wind data without the need to specify a relationship between the surface stress and surface wind results for the wind stress curl obtained by this vorticity method using upper wind data for the period 1968 73 are compared with the recent stress curl calculations by hellerman from surface data the two completely independent methods give basically similar mean latitudinal distributions of the stress curl in the midlatitudes of the southern hemisphere where the transient eddies are the main mechanism of vorticity transfer the two estimates of the basin wide longitudinal averages of the stress curl do not deviate from each other by 20 however in the northern hemisphere the agreement is less this seemingly strange result appears to be due to the sensitivity of the vorticity method to errors in the estimates of vorticity advection by t

observations and simulations of a large amplitude mountain wave breaking over the antarctic peninsula 1 a case study of a large amplitude orographic gravity wave occurring over the antarctic peninsula is presented based on observations from the vorcore balloon campaign and on mesoscale numerical simulations the vorcore campaign september 2005 to february 2006 consisted in the flight of 27 superpressure balloons in the core of the southern hemisphere stratospheric polar vortex at altitudes of 16 19 km from september 2005 to february 2006 on 7 october 2005 one of the balloons exploded as it was flying above the antarctic peninsula the observations collected by another balloon that was flying during the same time period above the peninsula suggest the presence of a very intense gravity wave peak to peak amplitude of the order of 25 30 m s 1 in zonal and meridional velocity disturbances the wave packet is likely undersampled in the balloon observations because of its high intrinsic frequency but the balloon data set is complemented with high resolution numerical simulations carried out with the weather research and forecast model the simulations are validated by comparison with the balloon measurements and show that the wave was breaking in the lower stratosphere at the time and height where the balloon exploded the simulations highlight several consequences of the mountain wave on the stratosphere forcing of the mean flow generation of secondary inertia gravity waves and turbulence and mixing in particular the momentum fluxes are calculated and are found to compare well with the estimates from balloon measurements the large values found are likely extreme values which raises the issue of their representativity to discuss this the balloon measurements are used in conjunction with operational analyses to estimate the frequency of such large amplitude gravity waves i e to provide an estimate of their intermittency

estimation of gravity wave momentum flux and phase speeds from quasi lagrangian stratospheric balloon flights part i theory and simulations a methodology for estimating gravity wave characteristics from quasi lagrangian observations provided by long duration superpressure balloon flights in the stratosphere is reviewed wavelet analysis techniques are used to detect gravity wave packets in observations of pressure temperature and horizontal velocity an emphasis is put on the estimation of gravity wave momentum fluxes and intrinsic phase speeds which are generally poorly known on global scales in the atmosphere the methodology is validated using monte carlo simulations of time series that mimic the balloon measurements including the uncertainties associated with each of the meteorological parameters while the azimuths of the wave propagation direction are accurately retrieved the momentum fluxes are generally slightly underestimated especially when wave packets overlap in the time frequency domain or for short period waves a proxy is derived to estimate by how much momentum fluxes are reduced by the analysis retrievals of intrinsic phase speeds are less accurate especially for low phase speed waves a companion paper part ii implements the methodology to observations gathered during the vorcore campaign that took place in antarctica between september 2005 and february 2006

gravity waves over antarctica and the southern ocean consistent momentum fluxes in mesoscale simulations and stratospheric balloon observations stratospheric balloons from the vorcore campaign have provided a unique description of the gravity wave field in the lower stratosphere above antarctica and the southern ocean during the austral spring of 2005 mesoscale simulations are carried out to analyze further the gravity wave field first the realism of the simulated waves is assessed by comparison to the observations a satisfactory overall agreement is found but different behaviour is noted for orographic waves overestimation in the simulations relative to the observations and non orographic waves underestimation second the gravity wave field is analyzed in more detail than was possible from observations alone it is necessary to distinguish and quantify orographic and non orographic waves separately orographic waves are larger and more intermittent yet affect only a limited geographical region hence although orographic sources stand out as hot spots for gravity waves their contribution to momentum fluxes entering the stratosphere is comparable to or smaller than the contribution of non orographic sources a diagnostic for intermittency the gini coefficient is proposed it clearly marks the distinction between orographic and non orographic sources intermittencies of 0 8 and 0 5 respectively sensitivity to resolution is quite small regarding the spatial structure of the gravity wave field but is significant for the amplitudes the momentum flux values increase by 2 when the horizontal resolution is doubled and possible biases of both simulations and observations are discussed nonetheless the good agreement between observations and simulations and the complementary information on the biases of each dataset promises that in the future these different estimates of gravity wave momentum fluxes may converge copyright 2012 royal meteorological society

estimation of gravity wave momentum flux and phase speeds from quasi lagrangian stratospheric balloon flights part ii results from the vorcore campaign in antarctica the stratospheric gravity wave field in the southern hemisphere is investigated by analyzing observations collected by 27 long duration balloons that flew between september 2005 and february 2006 over antarctica and the southern ocean the analysis is based on the methods introduced by boccara et al in a companion paper special attention is given to deriving information useful to gravity wave drag parameterizations employed in atmospheric general circulation models the balloon dataset is used to map the geographic variability of gravity wave momentum fluxes in the lower stratosphere this flux distribution is found to be very heterogeneous with the largest time averaged value 28 mpa observed above the antarctic peninsula this value exceeds by a factor of 10 the overall mean momentum flux measured during the balloon campaign zonal momentum fluxes were predominantly westward whereas meridional momentum fluxes were equally northward and southward a local enhancement of southward flux is nevertheless observed above adelie land and is attributed to waves generated by katabatic winds for which the signature is otherwise rather small in the balloon observations when zonal averages are performed oceanic momentum fluxes are found to be of similar magnitude to continental values 2 5 3 mpa stressing the importance of nonorographic gravity waves over oceans last gravity wave intermittency is investigated mountain waves appear to be significantly more sporadic than waves observed above the ocean

transient eddy forcing of the time mean flow as identified by geopotential tendencies abstract the forcing of the time mean flow by transient eddies is examined within the framework of a quasi geostrophic equation relating the geopotential tendency to the convergence of transient eddy transports of heat and vorticity the forcing functions of this equation are computed using observed circulation statistics for the wintertime northern hemisphere and solutions are sought for the three dimensional structure of geopotential and temperature tendencies associated with eddies of different time scales in general the geopotential tendencies associated with vorticity fluxes are of the same sign within a given atmospheric column whereas the polarity of the geopotential tendencies associated with heat fluxes in the lower troposphere is opposite to that in the upper troposphere the geostrophic wind tendencies associated with synoptic scale eddies with periods between 2 5 and 6 days are strongest in the vicinity of the oceanic storm tracks the enhanced poleward heat transports by active disturbanc

a diagnostic study of the potential vorticity in a warm blocking anticyclone abstract dynamical features of the warm blocking anticyclone which persisted over europe during the summer of 1976 are studied using national meteorological centre analyses the dynamics am presented from the perspective of quasi geostrophic potential vorticity q the block is shown to be a region of anomalously low almost uniform q computed balances in the 300 mb monthly mean quasi geostrophic potential vorticity equation show that the mean flow advection v q and the eddy forciv q of q are of comparable magnitude and have the tendency to balance one another it is suggested that transfer by synoptic scale systems acts to maintain the q anomaly against its advection downstream

234th in different size classes of sediment trap collected particles from the northwestern pacific ocean abstract 234 th a surface area specific particle reactive radionuclide has been used to estimate particulate organic carbon poc export fluxes based on the poc 234 th ratio of sinking particles and the 234 th flux in the ocean the poc 234 th ratios from large particles 50 m are conventionally considered to represent sinking particles collected by sediment traps but this assumption has not been thoroughly tested more recently hung and gong 2010 separated sinking particles from the northern south china sea where diatoms are the most dominant group using different nitex screens and found that small 234 th and poc flux however the size distribution of sinking particles has seldom been measured in picoplankton dominated oligotrophic and upwelling conditions here we used nitex screens to separate sinking particles in oligotrophic and upwelling regions additionally images of selected bulk sinking particles not subject to sequential filtration were directly taken by scanning electron microscopy sem to determine the size distribution of sinking particles within the trap collected 234 th pool in the upwelling area the 1 10 and 10 50 m fractions had on average the highest amounts of 234 th while poc did not show significant variations among the different size fractions in the oligotrophic region the 10 50 and 1 10 m fractions had on average the highest amounts of 234 th while the 150 and 10 50 m had elevated shares of poc results thus demonstrate that 234 th was mainly carried by the smaller 234 th flux can be a major fraction of the total sinking flux of this isotope and thus particles smaller than 50 m cannot be ignored because the poc 234 th ratio that is often used is that of large 50 m particles obtained from pump systems not traps

sensitivity of resolved mountain drag to model resolution for map case studies seven mountain wave case studies from the mesoscale alpine programme map have been used to investigate the behaviour of the resolved alpine pressure drag with model horizontal resolution three independent modelling systems show that the magnitude of the resolved surface pressure drag increases monotonically as the horizontal model resolution is increased from 125 km down to a few kilometres a substantial proportion of the drag will still need to be parametrized in the next generation of mesoscale models with horizontal resolutions of 3 or 4 km this is particularly true for the most important drag cases when the jet stream directly above the mountains produces larger wind speeds near mountain crest level resulting in much larger total alpine drags copyright 2006 royal meteorological society

large amplitude mountain wave breaking over greenland abstract a large amplitude mountain wave generated by strong southwesterly flow over southern greenland was observed during the fronts and atlantic storm track experiment fastex on 29 january 1997 by the noaa g iv research aircraft dropwindsondes deployed every 50 km and flight level data depict a vertically propagating large amplitude wave with deep convectively unstable layers potential temperature perturbations of 25 k that deformed the tropopause and lower stratosphere and a vertical velocity maximum of nearly 10 m s 1 in the stratosphere the wave breaking was associated with a large vertical flux of horizontal momentum and dominated by quasi isotropic turbulence the coupled ocean atmosphere mesoscale prediction system coamps nonhydrostatic model with four nested grid meshes with a minimum resolution of 1 7 km accurately simulates the amplitude location and timing of the mountain wave and turbulent breakdown finescale low velocity plumes that resemble wakelike structures emanate from highl

detection of rapid deposition of sea ice rafted material to the arctic ocean benthos using the cosmogenic tracer 7be abstract during three icebreaker cruises in the arctic ocean under different sea ice conditions in 2002 undisturbed benthic surface sediments were collected and assayed for the presence of a short lived t1 2 53 d particle reactive cosmogenic radionuclide 7be that is solely derived from atmospheric deposition under largely ice covered conditions in may june 2002 we did not detect this radionuclide in benthic surface sediments despite significant inventories present in ice rafted snow on the overlying sea ice mean 86 8 bq m 2 32 0 sd n 9 during the july august 2002 shelf basin interactions sbi cruise aboard the uscgc healy and during a simultaneous cruise of the ccgs sir wilfrid laurier on the bering and chukchi shelf which occupied the same general region following retreat and dissolution of arctic ice cover the 7be present in this snow as well as surface deposition on to the sea ice free water surface was detected in many benthic surface sediments including some as deep as 945 m in barrow canyon inventories of 7be in sediments were as high 60 bq m 2 as the entire decay corrected inventory present earlier in some snow samples collected on the sea ice cover other deposition indicators such as the inventories of sediment chlorophyll sediment oxygen respiration rates and 234th derived export fluxes also showed post ice melt particle deposition and vertical transport but in most cases the 7be deposition was not tightly correlated with these other indicators suggesting that 7be sedimentation may not be controlled by the same processes our observations indicate that materials in sea ice including contaminants particulate organic and mineral matter originating from atmospheric deposition or entrained in continental shelf sediments and rafted onto sea ice can be rapidly transported to depth the re distribution of these materials as sea ice drifts and eventually melts has the potential for impacting arctic ocean biogeochemical cycles and contaminant concentrations in areas of the arctic remote from the original point of deposition