the accuracy of rainfall estimates by radar as a function of range high spatial resolution data were collected for nearby convective storms by using a volume scanning weather radar with 200m resolution and for stratiform events by using a high resolution 20m vertically pointing radar errors in the estimation of rainfall by the scanning radar due to the radar beam intersecting or overshooting features such as the bright band were simulated by using these high resolution images it was found that these effects define a maximum useful range for the radar that is a strong function of the prevailing meteorological conditions e g bright band height intense cell diameter and height sudden changes in bright band height over short times and the large scatter observed in its thickness limit the accuracy with which corrections for the vertical profile of reflectivity may be precalculated in stratiform rain events a scheme for using a vertically pointing radar to produce these corrections in real time is proposed the convective events show enough significant storm to storm variability that caution is required in extending the useful range of the radar too far

the occurrence of the dinoflagellate cyst apectodinium costa downie 1976 lentin williams 1977 in the moray and montrose groups danian to thanetian of the uk central north sea

molecular transformation and degradation of refractory dissolved organic matter in the atlantic and southern ocean more than 90 of the global ocean dissolved organic carbon doc is refractory has an average age of 4000 6000 years and a lifespan from months to millennia the fraction of dissolved organic matter dom that is resistant to degradation is a long term buffer in the global carbon cycle but its chemical composition structure and biochemical formation and degradation mechanisms are still unresolved we have compiled the most comprehensive molecular dataset of 197 fourier transform ion cyclotron resonance mass spectrometry ft icr ms analyses from solid phase extracted marine dom covering two major oceans the atlantic sector of the southern ocean and the east atlantic ocean ranging from 50 n to 70 s molecular trends and radiocarbon dating of 34 dom samples comprising 14c values from 229 to 495 were combined to model an integrated degradation rate for bulk doc resulting in a predicted age of 24 ka for the most persistent dom fraction first order kinetic degradation rates for 1557 mass peaks indicate that numerous dom molecules cycle on timescales much longer than the turnover of the bulk doc pool estimated residence times of up to 100 ka and the range of validity of radiocarbon dating changes in elemental composition were determined by assigning molecular formulae to the detected mass peaks the combination of residence times with molecular information enabled modelling of the average elemental composition of the slowest degrading fraction of the dom pool in our dataset a group of 361 molecular formulae represented the most stable composition in the oceanic environment island of stability these most persistent compounds encompass only a narrow range of the molecular elemental ratios h c average of 1 17 0 13 and o c average of 0 52 0 10 and molecular masses 360 28 and 497 51 da in the weddell sea doc concentrations in the surface waters were low 46 3 3 3 m while the organic radiocarbon was significantly more depleted than that of the east atlantic representing average surface water dom ages of 4920 180 a these results are in accordance with a highly degraded dom in the weddell sea surface water as also shown by the molecular degradation index ideg obtained from ft icr ms data further we identified 339 molecular formulae which probably contribute to an increased doc concentration in the southern ocean and potentially reflect an accumulation or enhanced sequestration of refractory doc in the weddell sea these results will contribute to a better understanding of the persistent nature of marine dom and its role as an oceanic carbon buffer in a changing climate

high resolution biostratigraphic zonation for the uk central north sea paleocene abstract this paper presents the high resolution biostratigraphic zonation scheme for the paleocene of the central north sea area uk and the application to formation characterization well correlation reservoir modelling and wellsite activities the scheme is developed from detailed and consistently recorded palynological events supported by microfossil data which have been applied successfully to the majority of proprietary biostratigraphic studies from the basin nine zones and 29 subzones have been defined based on first downhole occurrence fdo or abundance events with chronostratigraphic significance and can be consistently correlated across the studied area the nine biozones are described based on a dominant palynological marker from base upward senoniasphaera inornata and spiniferites magnificus danian isabelidinium viborgense and palaeoperidinium pyrophorum selandian cordosphaeridium gracile spiniferites fentonii spiniferites rhomboideus areoligera gippingensis and base apectodinium spp thanetian the defined bioevents have been consistently linked with the published lithostratigraphy stratigraphic sequences and interpreted depositional environments

biogeochemistry of dissolved organic matter in an anoxic intertidal creek bank abstract seawater circulation in permeable coastal sediments is driven by tidal changes in hydraulic gradients the resulting submarine groundwater discharge is a source of nutrients and dissolved organic matter dom to the water column yet little is known about the cycling of dom within tidal sediments because the molecular dom characterization remains analytically challenging one technique that can dissect the multitude of molecules in dom is ultrahigh resolution fourier transform ion cyclotron resonance mass spectrometry ft icr ms to aim at a high resolution dom analysis we study the seasonal turnover and marine and terrestrial sources of dom in an intertidal creek bank of the southern north sea down to 3 m depth and link the biogeochemical processes to ft icr ms data and the analyses of inorganic porewater chemistry 13 c of solid phase extracted dissolved organic carbon spe doc dissolved black carbon dbc and dissolved carbohydrates dcho increasing concentrations of dissolved fe mn p total alkalinity dissolved nitrogen doc and a concomitant decrease of sulfate along the seawater circulation path from the upper tidal flat to the tidal flat margin indicate continuous microbial activity the relative increase of si concentrations unsaturated aliphatics peptide molecular formulae and isotopically more 13 c enriched spe doc towards the tidal flat margin suggests that remineralization processes mobilize dom from buried algal diatoms and microbial biomass porewater in sediments 13 c depleted spe doc and highly unsaturated compounds which are probably derived from eroded peats suggesting rapid removal of bioavailable marine dom such as dcho from the water column and selective enrichment of terrestrial dom dbc concentrations are highest in the discharging porewater close to the tidal creek suggesting that the intertidal flat is an important dbc source to the coastal ocean porewater dom accumulating at the low water line is enriched in n and s we hypothesize that this is partly due to dom reacting with dissolved sulfide and ammonium which may increase the refractory character of the dom hence making it less bioavailable for in situ active microbes

finescale structure and microphysics of coastal stratus observations were made of unbroken marine stratus off the coast of oregon using the combined capabilities of in situ probes and a 95 ghz radar mounted on an aircraft reflectivity and doppler velocity measurements were obtained in vertical and horizontal planes that extend from the flight lines data from three consecutive days were used to examine echo structure and microphysics characteristics the clouds appeared horizontally homogeneous and light drizzle reached the surface in all three cases radar reflectivity is dominated by drizzle drops over the lower two thirds to four fifths of the clouds and by cloud droplets above that cells with above average drizzle concentrations exist in all cases and exhibit a large range of sizes the cells have irregular horizontal cross sections but occur with a dominant spacing that is roughly 1 2 1 5 times the depth of the cloud layer doppler velocities in the vertical are downward in all but a very small fraction of the cloud volumes the cross correlation between reflectivity and vertical doppler velocity changes sign at or below the midpoint of the cloud indicating that in the upper parts of the clouds above average reflectivities are associated with smaller downward velocities this correlation and related observations are interpreted as the combined results of upward transport of drizzle drops and of downward motion of regions diluted by entrainment the in situ measurements support these conclusions

using mesoscale model winds for correcting wind drift errors in radar estimates of surface rainfall summary for operational radars at middle and high latitudes even the lowest beam of a scan sequence may be above the melting layer for a considerable proportion of the total range this means that surface rainfall estimates are inferred from measurements made in the snow and ice snow and ice are more susceptible to wind drift than rain because of the low fall speed of around 1 m s 1 sampling these wind induced fall streak patterns results in a displacement of the radar rainfall eld when compared to ground measurements to date wind drift corrections have only been attempted in the rain but corrections of around 2 km are generally smaller than the resolution of the grid on which the rainfall eld is reported observational evidence from this study shows fall streaks in the snow can lead to displacements of the order of 10 20 km a signican t eect especially in colder climates and seasons in this paper a method for calculating and applying a wind drift correction between the top of the fall streak and the bright band height is presented the forecast wind prole from the mesoscale version of the uk met oce unied model um is used to calculate the vertical shear of the horizontal wind we assume the shear and the fall speed in the layer are constant results show that the method is able to reproduce observed displacements from high resolution radar data in the range height plane assessing the eect of applying the method in plan view shows an improvement in the placement of rainfall at the ground reected by an increase in the calculated skill scores the displacement can be corrected to within 20 this also shows that whereas wind drift corrections in the rain have been found to be insignican t corrections in the snow are not applying a wind drift correction also appears to reduce the variability of vertical proles of reectivit y vpr when they are extracted along a fall streak path and lead to a smaller reectivit y lapse rate locally this would suggest that at least part of the reported variability in vprs is due to wind eects

terrigenous dissolved organic matter in the arctic ocean and its transport to surface and deep waters of the north atlantic isotopic compositions of dom are depleted in 13 cb y 1 2 relative to those in the atlantic and pacific the large contribution of terrigenous dom from arctic rivers is responsible for the elevated concentrations of doc in polar surface waters the distribution of terrigenous dom in polar surface waters is very heterogeneous but on average we estimate 14 24 of the doc is of terrestrial origin stable nitrogen isotopic compositions were useful for distinguishing dom of pacific and atlantic origins as well as terrigenous and marine origins the size distribution and composition of lignin phenols provide some evidence of photochemical transformations of terrigenous dom but it appears this process is not extensive in polar surface waters the extent to which terrigenous dom is removed from the arctic ocean by microbial degradation is less clear and warrants further study physical transport of terrigenous doc to the north atlantic is a major mechanism for its removal from the arctic the east greenland current alone exports 4 4 6 6 tg of terrigenous doc annually to the north atlantic terrigenous doc of arctic origin was identified for the first time in components of north atlantic deep water preliminary estimates indicate that 1 tg of terrigenous doc is exported from the arctic in denmark strait overflow water with an additional 0 7 tg in classical labrador sea water together these exports compose approximately 25 33 of the terrigenous doc discharged annually to the arctic via rivers

a novel molecular approach for tracing terrigenous dissolved organic matter into the deep ocean marine dissolved organic matter dom contains one of the largest exchangeable organic carbon pools on earth riverine input represents an important source of dom to the oceans yet much remains to be learned about the fate of the dom linking terrestrial to oceanic carbon cycles through rivers at the global scale here we use ultrahigh resolution mass spectrometry to identify 184 molecular formulae that are indicators of riverine inputs referred to as t peaks and to track their distribution in the deep north atlantic and north pacific oceans the t peaks were found to be enriched in the amazon river to be highly correlated with known tracers of terrigenous input and to be observed in all samples from four different rivers characterized by vastly different landscapes and vegetation coverage spanning equatorial amazon and congo subtropical altamaha and arctic kolyma regions their distribution reveals that terrigenous organic matter is injected into the deep ocean by the global meridional overturning circulation indicating that a fraction of the terrigenous dom introduced by rivers contributes to the dom pool observed in the deep ocean and to the storage of terrigenous organic carbon this novel molecular approach can be used to further constrain the transfer of dom from land to sea especially considering that fourier transform ion cyclotron resonance mass spectrometer analysis is becoming increasingly frequent in studies characterizing the molecular composition of dom in lakes rivers and the ocean

us gulf coast vegetation dynamics during the latest palaeocene abstract pollen and spore floras from the bear creek section in western alabama us gulf coast record vegetation events from the lower to middle tuscahoma formation late palaeocene mid np9 sporomorphs are abundant and well preserved in these sediments and are used as a proxy to record vegetation change over time we present results from both palynofloral and clay mineral analyses in the interval approximately 0 4 0 1 my before the paleocene eocene thermal maximum petm a period of transient and intense global warming that had a profound effect on animal and plant groups in high latitudes an important factor that has a significant bearing on our understanding of turnover across the petm is that of climate environmental stability prior to the petm in terrestrial ecosystems palynological analysis with a between sample resolution of 4 10 5 yr clay mineral suites show the dominance of smectite and illite throughout the studied section with minor fluctuations in the abundance of kaolinite ranging from 2 to 10 that indicates a high seasonality of precipitation throughout our studied section the exact stratigraphic position of the petm is unknown on the us gulf coast but data from existing publications suggests there is little change in the vegetation type across the palaeocene eocene boundary with no major immigration or turnover events dinocysts are restricted in both diversity and occurrence but apectodinium homomorphum is present with 30 abundance throughout the studied section and provides some evidence that the apectodinium acme is not correlative with the petm at middle latitudes

the role of sea ice and other fresh water in the arctic circulation salinity stratification is critical to the vertical circulation of the high latitude ocean we here examine the control of the vertical circulation in the northern seas and the potential for altering it by considering the budgets and storage of fresh water in the arctic ocean and in the convective regions to the south we find that the present day greenland and iceland seas and probably also the labrador sea are rather delicately poised with respect to their ability to sustain convection small variations in the fresh water supplied to the convective gyres from the arctic ocean via the east greenland current can alter or stop the convection in what may be a modern analog to the halocline catastrophes proposed for the distant past the north atlantic salinity anomaly of the 1960s and 1970s is a recent example it must have had its origin in an increased fresh water discharge from the arctic ocean similarly the freshening and cooling of the deep north atlantic in recent years is a likely manifestation of the increased transfer of fresh water from the arctic ocean into the convective gyres finally we note that because of the temperature dependence of compressibility a slight salinity stratification in the convective gyres is required to efficiently ventilate the deep ocean

regional uplift gas hydrate dissociation and the origins of the paleocene eocene thermal maximum much of the north atlantic region experienced hundreds of metres of transient uplift during the latest paleocene regional uplift should cause dissociation of gas hydrates stored in marine sedimentary strata and the subsequent release of carbon to the atmosphere should enhance warming through the greenhouse effect we have developed models of the spatial distribution of uplift to match observational constraints from sedimentary basins fringing the north atlantic in order to provide quantitative estimates of the carbon released upon uplift these models are coupled to a simple parameterisation of carbon storage in sub seafloor gas hydrates results of modelling indicate that large quantities of carbon can be released by uplift with some models generating over 2000 gt of carbon release the possibility that latest paleocene regional uplift occurred over the same time interval as onset of the paleocene eocene thermal maximum petm around 30 kyr cannot be ruled out using current stratigraphical observations or mantle convection models in this case the uplift mechanism alone can account for the magnitude and timing of the carbon isotope excursion associated with the petm alternatively if the duration of latest paleocene uplift was closer to the upper bound of around 1 myr or if other paleocene uplift events were equally significant then gas hydrate dissociation upon uplift could have contributed to longer term changes in ocean temperature and carbon isotope composition through the late paleocene these temperature changes in combination with development of the north atlantic land bridge during the latest paleocene culmination of uplift may be able to force rapid changes in ocean circulation and cause phenomena such as the petm

fate of the amazon river dissolved organic matter in the tropical atlantic ocean constraining the fate of dissolved organic matter dom delivered by rivers is a key to understand the global carbon cycle since dom mineralization directly influences air sea co2 exchange and multiple biogeochemical processes the amazon river exports large amounts of dom and yet the fate of this material in the ocean remains unclear here we investigate the molecular composition and transformations of dom in the amazon river ocean continuum using ultrahigh resolution mass spectrometry and geochemical and biological tracers we show that there is a strong gradient in source and composition of dom along the continuum and that dilution of riverine dom in the ocean is the dominant pattern of variability in the system alterations in dom composition are observed in the plume associated with the addition of new organic compounds by phytoplankton and with bacterial and photochemical transformations the relative importance of each of these drivers varies spatially and is modulated by seasonal variations in river discharge and ocean circulation we further show that a large fraction 50 76 of the amazon river dom is surprisingly stable in the coastal ocean this results in a globally significant river plume with a strong terrigenous signature and in substantial export of terrestrially derived organic carbon from the continental margin where it can be entrained in the large scale circulation and potentially contribute to the long term storage of terrigenous production and to the recalcitrant carbon pool found in the deep ocean

major flux of terrigenous dissolved organic matter through the arctic ocean high latitude rivers supply the arctic ocean with a disproportionately large share of global riverine discharge and terrigenous dissolved organic matter dom we used the abundance of lignin a macromolecule unique to vascular plants and stable carbon isotope ratios 13c to trace the high molecular weight fraction of terrigenous dom in major water masses of the arctic ocean lignin oxidation products in ultrafiltered dom udom 1 000 da from arctic rivers were depleted in syringyl relative to vanillyl phenols s v 0 3 0 5 compared to udom in temperate and tropical rivers s v 0 5 1 2 indicating that gymnosperm vegetation is a major source of terrigenous udom to the arctic ocean high concentrations of lignin oxidation products 83 320 ng l 1 and a depletion of 13c 13c 23 0 to 21 9 in udom throughout the surface arctic ocean indicate that terrigenous udom accounts for a much greater fraction of the udom in the surface arctic 5 33 than in the pacific and atlantic oceans 0 7 2 4 in contrast udom in deep water from the arctic ocean as well as waters from throughout the greenland gyre had relatively low concentrations of lignin oxidation products 24 45 ng l 1 and was enriched in 13c 13c 21 0 to 20 8 terrigenous udom has a relatively short residence 1 6 yr in surface polar waters prior to export to the north atlantic ocean assuming that the bulk of arctic derived dom is compositionally similar to the udom fraction we estimate that 12 41 of terrigenous dom 2 9 10 3 tg c yr 1 discharged by rivers to the arctic ocean is exported to the north atlantic via surface waters of the east greenland current it appears very little terrigenous dom from the arctic is incorporated into north atlantic deep water and distributed globally via deep thermohaline circulation

on the determination of scale ranges for precipitation fields to test some recent theories on the nature of precipitation structure data were collected using radar and a newly developed sonic gauge to investigate precipitation variability at small scales results show that the structure of precipitation below a few tens of meters has very different statistics than at larger scales interpretation of vertically pointing radar data suggests that at small scales a mixing like process occurs because of the differential fall speed of hydrometeors which results in the destruction of small scale structure it is also shown that convection in the melting layer seems to recreate some of the structure that had been lost as snow fell finally over scales of meteorological interest at least four distinct regimes in precipitation variability can be identified

evidence for major input of riverine organic matter into the ocean abstract the changes in the structure of xad 8 isolated dissolved organic matter dom samples along a river penobscot river to estuary penobscot bay to ocean across the gulf of maine transect and from the pacific ocean were investigated using selective and two dimensional 2d nuclear magnetic resonance nmr spectroscopy coupled with elemental and carbon isotope analysis the results provide important insights into the nature of relatively stable structures in the river to ocean continuum and the enigma of the fate of terrestrial dom in the marine system first lignin and carboxyl rich alicyclic molecules crams which are indistinguishable from mass spectrometry were clearly differentiated with nmr spectroscopy nmr unambiguously showed that crams persisted along the river to ocean transect and in the pacific ocean while lignin residues dramatically decreased in abundance from the river to the coastal ocean and the pacific ocean the results challenge a previous conclusion that lignin derived compounds are refractory and can accumulate in the coastal ocean the loss of terrestrial plant derived aromatic compounds such as lignin and tannin residues throughout the sequence of riverine coastal and open ocean dom extracts could also partially explain the decreasing organic carbon recovery by xad 8 isolation and the change in carbon stable isotope composition from riverine dom 13 c 27 6 to ocean dom 13 c 23 0 extracts the observation from advanced nmr of similar cram molecules in xad 8 isolated dom samples from the penobscot river to the penobscot bay and from the ocean refutes a previous conclusion that xad isolated dom samples from seawater and river are distinctly different the alicyclic structural features of crams and their presence as the major structural units in dom extracts from the penobscot river to gulf of maine transect together with the deduced old 14 c age of crams in the ocean imply that terrestrial crams may persist on timescales long enough to be transported into the ocean

characterizing transport between the surface mixed layer and the ocean interior with a forward and adjoint global ocean transport model the theory of first passage time distribution functions and its extension to last passage time distribution functions are applied to the problem of tracking the movement of water masses to and from the surface mixed layer in a global ocean general circulation model the first passage time distribution function is used to determine in a probabilistic sense when and where a fluid element will make its first contact with the surface as a function of its position in the ocean interior the last passage time distribution is used to determine when and where a fluid element made its last contact with the surface a computationally efficient method is presented for recursively computing the first few moments of the first and last passage time distributions by directly inverting the forward and adjoint transport operator this approach allows integrated transport information to be obtained directly from the differential form of the transport operator without the need to perform lengthy multitracer time integration of the transport equations the method which relies on the stationarity of the transport operator is applied to the time averaged transport operator obtained from a three dimensional global ocean simulation performed with an ogcm with this approach the author i computes surface maps showing the fraction of the total ocean volume per unit area that ventilates at each point on the surface of the ocean ii partitions interior water masses based on their formation region at the surface and iii computes the three dimensional spatial distribution of the mean and standard deviation of the age distribution of water

space time variability of the rainfall over the western mediterranean region a statistical analysis 1 this study aims at better understanding the space time statistical properties of rain over a mediterranean region to this end we analyzed temporal spatial and spatio temporal spectra of rain field maps provided by an x band radar situated in the southeast part of france the database extends from 2009 to 2012 and has a spatial and temporal resolution of 1 km2 and 5 min the analysis highlights several scaling regimes which are interpreted in terms of meteorological structures convective cells mesoscale structures and midlatitude cyclones the analysis of spectra per month confirms the dependency of the spectral signature to the underlying meteorological process nevertheless our results also reveal that for a given range of scales 20 45 min in time and 7 20 km in space spectral slope is monthly invariant it means that rain behaves identically in terms of scaling whatever the mechanism that generated it convection front moreover spectral analysis shows that the temporal decorrelation scale is 10 days which can possibly be related to the longest lifetime of a meteorological phenomenon in the region i e about 10 days an approach to compute the scaling anisotropy between space and time is proposed it reveals that over two distinct ranges of scales 7 20 km 20 45 min and 20 70 km 45 min 3 h the scaling anisotropic coefficient is equal to 2 it also reveals that the ratio of spectral slope of 2 d angle averaged spatial spectrum versus 1 d temporal spectrum is equal to 1 over these ranges of scales it suggests a similarity in the second order properties e g correlation of temporal and spatial rain field all these results are important to better understand rainfall statistical behavior and could also be used for the development of downscaling schemes and the validation of numerical weather models

on the driving processes of the atlantic meridional overturning circulation because of its relevance for the global climate the atlantic meridional overturning circulation amoc has been a major research focus for many years yet the question of which physical mechanisms ultimately drive the amoc in the sense of providing its energy supply remains a matter of controversy here we review both observational data and model results concerning the two main candidates vertical mixing processes in the ocean s interior and wind induced ekman upwelling in the southern ocean in distinction to the energy source we also discuss the role of surface heat and freshwater fluxes which influence the volume transport of the meridional overturning circulation and shape its spatial circulation pattern without actually supplying energy to the overturning itself in steady state we conclude that both wind driven upwelling and vertical mixing are likely contributing to driving the observed circulation to quantify their respective contributions future research needs to address some open questions which we outline

the fate of terrigenous dissolved organic carbon in a river influenced ocean margin the mineralization of terrigenous dissolved organic carbon tdoc discharged by rivers can impact nutrient and trace metal cycling biological productivity net ecosystem metabolism and air sea co2 exchange in ocean margins however the extreme heterogeneity of river influenced ocean margins represents a major challenge for quantitative assessments of tdoc transformations and thereby obscures the role of tdoc in biogeochemical cycles here a lignin based optical proxy for tdoc and a shelf wide mass balance approach were used to quantitatively assess the fate of tdoc discharged from the mississippi atchafalaya river system m ars to the louisiana shelf the mass balance revealed that 40 of the tdoc discharged by the m ars during march 2009 2010 was mineralized to co2 on the louisiana shelf with two thirds of the mineralization taking place in the mixed layer a strong seasonality in tdoc mineralization was observed with mineralization rates severalfold higher during summer than during winter independent assessments of specific mineralization processes indicated biomineralization accounted for 94 of the tdoc mineralization on an annual basis and suggest that photochemical transformations of tdoc enhanced biomineralization by 50 in the mixed layer direct photomineralization accounted for a relatively small fraction 6 of the tdoc mineralization on an annual basis this quantitative assessment directly confirms that ocean margins are major sinks of the tdoc discharged by rivers and indicates that tdoc mineralization rates in the shelf mixed layer are sufficiently large to influence whether the louisiana shelf is a net sink or source of atmospheric co2