instability waves in the equatorial atlantic ocean abstract evidence is presented for the generation of planetary waves by barotropic instability within the cyclonic shear region of the atlantic ocean s south equatorial current sec immediately following the springtime intensification of the southeast trade wind which accelerates the sec westward a packet of waves with central periodicity of around 25 days is observed lasting for about three cycles independent wavenumber analyses on 1983 and 1984 data give newly identical zonal wavelengths and phase speed estimates of around 1100 km and 50 cm s 1 the waves are anisotropic and spatially inhomogeneous with generation confined primarily to the mixed layer an energetics analysis using 1983 data centered upon the equator at 28 w shows a rapid increase in total perturbation energy tpe reaching values of 2000 erg cm 3 within two weeks the subsequent decrease in tpe at this location is due primarily to meridional pressure work divergence baroclinic instability is negligible because both the meridional

diurnal shear instability the descent of the surface shear layer and the deep cycle of equatorial turbulence a new theory of shear instability in a turbulent environment is applied to eight days of velocity and density profiles from the upper equatorial pacific this period featured a regular diurnal cycle of surface forcing together with a clear response in upper ocean mixing during the day a layer of stable stratification and shear forms at the surface during late afternoon and evening this stratified shear layer descends leaving the nocturnal mixing layer above it using high resolution current measurements the detailed structure of the descending shear layer is seen for the first time linear stability analysis is conducted using a new method that accountsfortheeffectsofpreexistingturbulenceoninstabilitygrowth shearinstabilityfollowsadiurnalcycle linked to the afternoon descent of the surface shear layer this cycle is revealed only when the effect of turbulence is accounted for in the stability analysis the cycle of instability leads the diurnal mixing cycle typically by 2 3h consistent with the time needed for instabilities to grow and break late at night the resulting turbulence suppresses further instabilities lending an asymmetry to the mixing cycle that has not been noticed in previous measurements deep cycle mixing is triggered by instabilities formed as the descending shear layer merges with the marginally unstable shear of the equatorial undercurrent in the morning turbulence decays and the upper ocean restratifies wind accelerates the near surface flow to form a new unstable shear layer and the cycle begins again

modulation of equatorial turbulence by a tropical instability wave 1 strong modulation of turbulent mixing by a westward propagating tropical instability wave tiw was observed in the stratified shear layer between the equatorial undercurrent euc and the surface mixed layer during october and november 2008 at 0 n 140 w the unique deep diurnal cycle mixing in the stratified layer beneath the equatorial cold tongue was observed where nighttime turbulent mixing was a factor of 10 greater than during daytime the turbulent kinetic energy dissipation rate e was 10 6 w kg 1 and the turbulent heat flux was 500 w m 2 at least 5 10 times greater than observed previously in the central equatorial pacific turbulence mixing varied significantly during the four distinct phases of the meridional flow associated with the tiw observations during the northward to southward transition recorded the largest values of reduced shear squared the thickest nighttime surface mixed layer the deepest penetration of the deep cycle turbulence and the largest turbulent heat flux and largest integrated e in the deep cycle layer dcl during steady southward flow the depth of the bases of the nighttime surface mixed layer and of the dcl were the shallowest a 50 m thick layer of strong turbulence was observed immediately above the euc core during the northward to southward and steady southward phases here the average e exceeded 10 6 w kg 1 the eddy diffusivity exceeded 10 3 m2 s 1 and the turbulent heat flux was 500 w m 2 to parameterize mixing in the central equatorial pacific accurately numerical models must simulate the enhancement of mixing associated with tiws and also the variability of mixing in different tiw phases

wave turbulence interactions in the upper ocean part ii statistical characteristics of wave and turbulent components of the random velocity field in the marine surface layer abstract we present the results of an analysis of field data collected by donelan who used a miniature drag sphere to measure velocities beneath wind waves on lake ontario linear statistical techniques are used to separate the velocity into wave and turbulent parts while we mostly aim at demonstrating the effects of surface wind waves on the statistical characteristics of the turbulent field in the upper mixed layer we also interpret several features of the data on the hags of recent theoretical results one of the most intriguing features of the turbulent velocity spectra so obtained is a large peak near the dominant wave frequency we review various possible explanation for this behavior although we prefer a model in which the turbulence is assumed frozen on the timescale of the waves this model requires no new dynamics and gives explicit formulae relating the dissipation rate to the magnitude of the spectral densities for high and low frequencies on this basis we have determined a dissipation leng

bioprotection explored the story of a little known earth surface process abstract bioprotection is identified as an earth surface process however it has been little studied little acknowledged and yet may have major implications for the operation and management of geomorphic systems key early observations are traced back to darwin s voyage of the beagle geikie in the natural environment and watson for the built environment recent field observations and experimental work examining bioprotection are reviewed with a specific focus on lichens and the landscape as are its complex interactions with other processes a conceptual model of bioprotection is presented for the case of an epilithic lichen on a limestone surface

simple climatic indices for the tropical atlantic ocean and some applications two indices related to the sea surface temperature sst variability in the tropical atlantic are proposed one index describes the sst averaged over the whole basin 30 n to 20 s 60 w to 15 e and the other illustrates a meridional dipole between the northern and southern hemispheres the computational method for obtaining these indices is intentionally kept simple the objective being to reproduce the signature of the main results previously provided from more complicated statistical analyses monthly time series for both indices are produced from 1964 up to the present time the whole basin index exhibits principally a sustained warming which has intensified since about 1975 and it has a significant periodicity close to that of the quasi biennial oscillation the dipole index exhibits a decadal scale variation and its building up seems to be related to other worldwide climatic changes as for instance el nino southern oscillation extreme episodes rainfall variabilities over the brazilian nordeste and african sahel

formation of patterned ground and fine scale soil development within two late holocene glacial chronosequences jotunheimen norway abstract chronosequences of 250 to 130 years were established on two late holocene glacier forelands in the jotunheimen region of southern norway patterned features occurring within chronologically established time units were studied young patterned features forming 10 20 years after deglaciation are frost active vegetation cover is minimal within the young patterned features consisting of bryophytes organic crusts soil development within patterned ground is also minimal absent because frost action retards horizonization with time and distance from the glaciated ice margin frost activity declines within the patterned features suggesting that a thin active periglacial zone exists near the ice margin initially frost activity decreases at the borders of the features with the centers stabilizing later in time this results in fine scale soil heterogeneity and variations of soil development fine scale pedogenic development is first encountered at the borders of patterned ground that has developed on terrain exposed since the 1930s yet soil development is predominantly absent at the centers of patterned ground with time and distance from the ice margin frost activity declines and allows patterned features to homogenize from border to center positions in regard to soil characteristics across the chronosequences soils within patterned features pedogenically follow previous soil chronosequence studies evolving from usda classifications of entisols into inceptisols frost disturbance within patterned ground however produces a lag effect that results in longer periods of time for pedogenesis to occur and thinner soils than that of the surrounding terrain

biogeomorphology revisited looking towards the future although biogeomorphological research is well established with many studies on a range of two way interrelations between organisms and geomorphology in different environments there is little consensus over what constitutes biogeomorphology why it might be useful and where it is heading starting with definitions of core biogeomorphic processes we consider the need for future biogeomorphological studies to evaluate the crucial links between bioprocesses biological community dynamics and inorganic earth surface processes five key applications of biogeomorphological research are identified the roles of organisms in environmental reconstruction trace fossil analysis extraterrestrial geomorphology environmental engineering and the built environment some key research directions and methodological challenges for future biogeomorphological research include expanding the spatial and temporal coverage of datasets investigating the role of bioprocesses in landform development tackling scale issues investigating the relevance of nonlinear dynamical ideas to biogeomorphology and developing better sampling and monitoring techniques for bioprocesses

geomorphology and ecology unifying themes for complex systems in biogeomorphology the interaction of geomorphic and ecologic landscape components has been largely conceptualized as independent in one direction geomorphic processes and landforms shape the distribution of biota conversely in the other direction biota modify geomorphic processes and landforms increasingly the interactions between geomorphic and ecological components are more circular and developmentally intertwined in this paper i integrate these two independent perspectives within the framework of complexity theory i outline four themes that characterize complex systems in biogeomorphology multiple causality and the concept of recursivity the influence of organisms that function as ecosystem engineers the expression of an ecological topology and ecological memory implicit in all of these themes is the recognition that biogeomorphic systems are open and path dependent they may exhibit a range of assembly states from self reinforcing stability domains to more transient configurations of organisms and environment

tangential stress beneath wind driven air water interfaces the detailed structure of the aqueous surface sublayer flow immediately adjacent to the wind driven air water interface is investigated in a laboratory wind wave flume using particle image velocimetry piv techniques the goal is to investigate quantitatively the character of the flow in this crucial very thin region which is often disrupted by microscale breaking events in this study we also examine critically the conclusions of okuda kawai toba 1977 who argued that for very short strongly forced wind wave conditions shear stress is the dominant mechanism for transmitting the atmospheric wind stress into the water motion waves and surface drift currents in strong contrast other authors have more recently observed very substantial normal stress contributions on the air side the availability of piv and associated image technology now permits a timely re examination of the results of okuda et al which have been influential in shaping present perceptions of the physics of this dynamically important region the piv technique used in the present study overcomes many of the inherent shortcomings of the hydrogen bubble measurements and allows reliable determination of the fluid velocity and shear within 200 m of the instantaneous wind driven air water interface the results obtained in this study are not in accord with the conclusions of okuda et al that the tangential stress component dominates the wind stress it is found that prior to the formation of wind waves the tangential stress contributes the entire wind stress as expected with increasing distance downwind the mean tangential stress level decreases marginally but as the wave field develops the total wind stress increases significantly thus the wave form drag represented by the difference between the total wind stress and the mean tangential stress also increases systematically with wave development and provides the major proportion of the wind stress once the waves have developed beyond their early growth stage this scenario reconciles the question of relative importance of normal and tangential stresses at an air water interface finally consideration is given to the extrapolation of these detailed laboratory results to the field where the present findings suggest that the sea surface is unlikely to become fully aerodynamically rough at least for moderate to strong winds

geomorphology and ecosystems challenges and keys for success in bridging disciplines geomorphology plays a fundamental role in controlling many ecosystem processes and in turn ecosystems can have a profound influence on many geomorphic forms and processes over the past few decades a proliferation of research has developed at the interface of geomorphology and ecosystems ecology the 2005 binghamton symposium brought together some of the leading researchers from both communities to address these critical interfaces between the disciplines this paper reviews some of the aspects of the disciplines of geomorphology and ecosystems ecology and the papers presented at the symposium the papers in this volume illustrate the current status of the disciplines the difficulties in bridging the disciplines and the issues that are emerging as research priorities

scale matters a multi resolution study of the determinants of patterned ground activity in subarctic finland abstract numerical studies of earth surface processes in relation to their environment are one of the central topics in physical geography however collinearity between explanatory variables and spatial autocorrelation can hinder the detection of key environmental correlates underlying response explanatory variables relationships identified by traditional regression methods moreover conclusions about the potential importance of environmental variables have generally made on analysis conducted only at one spatial scale resolution in this study a variation partitioning method provided a framework to obtain new insights into the relative roles of different factors determining patterned ground activity at multiple spatial resolutions the variation in the distribution of the sorted and non sorted patterned ground was decomposed into independent and joint effects of relief soil and spatial variables geographical location based on a multi resolution system of 1 ha 25 ha and 100 ha cells covering in total 100 km 2 of a subarctic landscape in northern finland the independent effects of relief and soil variables captured the largest fraction of the variation in the non sorted patterned ground distribution while relief had a major contribution for sorted patterned ground activity the independent effect of spatial autocorrelation on sorted patterned ground was higher than that on non sorted patterned ground however a considerable amount of variation in the distribution of both patterned ground types was accounted for by the joint effects of explanatory variables and may thus be causally related to two or all three groups of variables our analyses produced often contradicting results at different resolutions consequently this has substantial implications for the study of geomorphological systems since the choice of resolution can have a major effect on the inferences of analyses our results draw attention to the roles of resolution and spatial autocorrelation in the study of geomorphological systems

logistic regression modeling of rock glacier and glacier distribution topographic and climatic controls in the semi arid andes abstract logistic regression is applied to a random sample of surface points in the semi arid andes of santiago and mendoza chile argentina 32 45 34 30 s 12 000 km 2 above 3000 m a s l to identify local and regional controls on rock glacier and glacier distribution the study area is among the areas with the greatest abundance of rock glaciers worldwide the explanatory variables used for model selection are related to local and regional morphometric and climatic characteristics the models achieve a very good fit area under the roc curve 0 84 for rock glaciers and 0 95 for glaciers and are able to reproduce the regional distribution pattern model results are used to determine the optimal morphographic and climatic niche of rock glaciers and glaciers in the study area and help explain the presence of low elevation rock glaciers under favorable topoclimatic conditions

conditions for feedbacks between geomorphic and vegetation dynamics on lateral moraine slopes a biogeomorphic feedback window little ice age lateral moraines represent one of the most important sediment storages and dynamic areas in glacier forelands following glacier retreat simultaneous paraglacial adjustment and vegetation succession affect the moraine slopes geomorphic processes e g debris flows interrill erosion gullying solifluction disturb and limit vegetation development while increasing vegetation cover decreases geomorphic activity thus feedbacks between geomorphic and vegetation dynamics strongly control moraine slope development however the conditions under which these biogeomorphic feedbacks can occur are insufficiently understood and major knowledge gaps remain this study determines feedback conditions through the analysis of geomorphic and vegetation data from permanent plots in the turtmann glacier foreland switzerland results from multivariate statistical analysis i confirm that dryas octopetala l is an alpine ecosystem engineer species which influences geomorphic processes on lateral moraines and thereby controls ecosystem structure and function and ii demonstrate that biogeomorphic feedbacks can occur once geomorphic activity sufficiently decreases for d octopetala to establish and cross a cover threshold in the subsequent ecosystem engineering process the dominant geomorphic processes change from flow and slide to bound solifluction increasing slope stabilization induces a decline in biogeomorphic feedbacks and the suppression of d octopetala by shrubs we conceptualize this relationship between process magnitude frequency and species resilience and resistance to disturbances in a biogeomorphic feedback window concept our approach enhances the understanding of feedbacks between geomorphic and alpine vegetation dynamics on lateral moraine slopes and highlights the importance of integrating geomorphic and ecological approaches for biogeomorphic research copyright 2015 john wiley sons ltd

modeling biogeophysical interactions in nonsorted circles in the low arctic 1 we investigate biogeophysical processes that cause differential frost heave in nonsorted circles north of the alaska s brooks range the main objective is the development of a numerical thermo mechanical model of a nonsorted circle the presented model includes mass momentum and energy conservation laws for water ice and soil we applied this model to simulate differential frost heave at the franklin bluffs site and obtained a good quantitative agreement with measured dynamics of soil temperature water content and frost heave for other locations such as at the sagwon hills and howe island sites we obtained qualitative agreement with frost heave measurements sensitivity analysis shows that the most active development of differential frost heave occurs for nonsorted circles within waterlogged areas as observed in field measurements for well drained sites model results and field observations show that the differential frost heave is much smaller in magnitude comparing to that of the water logged sites sensitivity of the model to alternation of the vegetation cover shows that a strong heterogeneity in the vegetation cover promotes active development of the differential frost heave for nonsorted circles with vegetation on top of the circle the computed differential heave is less pronounced the radius of the nonsorted circle influences the magnitude of the frost heave the computed maximum frost heave in the center of the circle corresponds to 1 1 5 meter diameter nonsorted circles for nonsorted circles with larger diameters computed frost heave in the center of a circle is smaller compared to the heave at the circle circumference

biogeomorphic interactions in the turtmann glacier forefield switzerland glacier forefields are dynamic environments dominated by active paraglacial processes and simultaneous vegetation succession triggered by glacier retreat since the little ice age while these dynamics are accelerating in the last decades owing to climate change interactions between vegetation and geomorphic processes and components and the resulting patterns are only partly understood using a biomorphic approach based on preexisting geomorphic and glaciological data geomorphic activity was classified and mapped in the turtmann glacier forefield switzerland vegetation and environmental parameters were sampled vegetation analysis was subsequently carried out with vegetation classification and ordination for identifying relationships to environmental parameters a paraglacial impact on vegetation succession could be shown and differentiated according to geomorphic activity on constant terrain age biogeomorphic concepts were then applied to explain these patterns three biogeomorphic succession phases were identified and related to degrees of activity species composition and strength of interactions integrating our results into the paraglacial concept we show how the paraglacial adjustment of a glacier forefield is significantly affected by biogeomorphic interactions

classification of sorted patterned ground areas based on their environmental characteristics skagafjorður northern iceland a multivariate statistical method factor analysis of mixed data and hierarchical classification was used to classify the environmental settings where sorted patterned ground develops in a wet oceanic periglacial area skagafjor ur northern iceland a total of 750 periglacial features distributed over 75 sites were studied nine explanatory variables were assessed by fieldwork and using a digital elevation model the variables were subdivided into three groups latitude topography and soil characteristics and then integrated into a geographical information system furthermore a correlation between the environmental variables and an intrinsic variable patterned ground mesh diameter was determined by a bivariate test the results show that sorted patterned ground are spread over three homogenous areas mostly differentiated by altitude insolation grain size characteristics and type of drift in addition feature diameters differ significantly from one group to another finally it appears that patterned ground diameters are positively correlated with i the proportion of clay to medium silt content r 0 35 ii altitude r 0 51 and especially with iii clast length r 0 97 this strong relationship with clast length is observed in each homogenous patterned ground area at both site and feature scales

wind stress and near surface shear in the equatorial atlantic ocean the upper ocean response to wind stress is examined using 8 months of unique near surface moored velocity temperature and salinity data at 0 n 23 w in the equatorial atlantic the effects of wind stress and shear on the time varying eddy viscosity are inferred using the surface shear stress boundary condition parameterizations of eddy viscosity as a function of wind stress and shear versus wind stress alone are then examined in principle eddy viscosity should be proportional to the inverse shear but how it is represented implicitly or explicitly can affect estimates of the near surface flow field this result may explain some discrepancies that have arisen from using parameterizations based only on wind stress to characterize the effects of turbulent momentum mixing

bursting layer modeling based on the assumption of the averaged sea surface for strong wind driven currents abstract in the sea which is affected by strong winds that cover the water surface with wind wave breakers the sea surface layer called the bursting layer by authors is generated immediately below the mean water level for treatment of strong wind driven currents it is necessary to model the bursting layer correctly based on observed data however an essential difficulty occurs in that because of large water surface displacement caused by developed wind waves water particle velocities above the wave trough level cannot be measured continuously in the eulerian coordinates when measuring the velocity of strong wind driven currents consequently it is impossible to apply the reynolds average rule to the velocity field above the wave trough level in this study an experiment that uses a wind wave tank with a double bottom is performed to measure the horizontal velocity of currents driven only by the wind stress the vertical distribution up to the mean water level is determined to make its verticall

mapping modeling and visualization of the influences of geomorphic processes on the alpine treeline ecotone glacier national park mt usa spatially explicit digital technologies are integrated within a geographic information science gisc context to map model and visualize selected direct and indirect geomorphic processes that influence the spatial organization of the alpine treeline ecotone ate in glacier national park gnp mt gisc is used to examine alpine treeline and its biotic and abiotic controls through the application of multi resolution remote sensing systems geospatial information and product derivatives and simulations of treeline spatial organization three geomorphic features are examined relict solifluction terraces evidence of nonlinearity in the development of a catena and the locations of isolated boulders the significance of these features is in constraining subsequent geomorphic and biogeographic processes thus leading to disequilibrium exploration of these features though gisc indicates that visualizations for characterizing the relations of geomorphic patterns and processes within a three dimensional context show promise for improved alpine slope models in the future by defining landscape attributes within a spatially and temporally explicit context

seasonal and regional variability of upper ocean diapycnal heat flux in the atlantic cold tongue sst variability within the atlantic cold tongue act region is of climatic relevance for the surrounding continents a multi cruise data set of microstructure observations is used to infer regional as well as seasonal variability of upper ocean mixing and diapycnal heat flux within the act region the variability in mixing intensity is related to the variability in large scale background conditions which were additionally observed during the cruises the observations indicate fundamental differences in background conditions in terms of shear and stratification below the mixed layer ml for the western and eastern equatorial act region causing critical froude numbers fr to be more frequently observed in the western equatorial act the distribution of critical fr occurrence below the ml reflects the regional and seasonal variability of mixing intensity turbulent dissipation rates e at the equator 2 n 2 s are strongly increased in the upper thermocline compared to off equatorial locations in addition e is elevated in the western equatorial act compared to the east from may to november whereas boreal summer appears as the season of highest mixing intensities throughout the equatorial act region coinciding with act development diapycnal heat fluxes at the base of the ml in the western equatorial act region inferred from e and stratification range from a maximum of 90 wm 2 in boreal summer to 55 wm 2 in september and 40 wm 2 in november in the eastern equatorial act region maximum values of about 25 wm 2 were estimated during boreal summer reducing to about 5 wm 2 towards the end of the year outside the equatorial region inferred diapycnal heat fluxes are comparably low rarely exceeding 10 wm 2 integrating the obtained heat flux estimates in the ml heat budget at 10 w on the equator accentuates the diapycnal heat flux as the largest ml cooling term during boreal summer and early autumn in the western equatorial act elevated meridional velocity shear in the upper thermocline contributes to the enhanced diapycnal heat flux within this region during boreal summer and autumn the elevated meridional velocity shear appears to be associated with intra seasonal wave activity

can geodiversity be predicted from space abstract identification of geodiversity at regional and national scales with traditional surveying techniques remains a logistically difficult and often financially prohibitive task earth observation data in combination with statistical modeling may provide a unique approach for mapping and analyzing geodiversity cost efficiently in this study the possibility to map geodiversity using digital elevation models dems and remote sensing rs data was scrutinized in finland northern europe at a landscape scale the main methods in the evaluation of spatial prediction ability of geodiversity and the relative contributions of dem and rs data were generalized additive modeling gam and variation partitioning based on the results geodiversity was mainly determined by polygenetic bedrock topography and fluvial activity and correlated most strongly with variables describing high potential energy and topographical heterogeneity the spatial patterns of geodiversity were robustly predicted across the study areas using multivariate gams the higher predictive performance of the dem versus rs based variables was evident across the study areas in conclusion we propose that statistically based spatial prediction offers an opportunity for characterizing geodiversity of a large area in a systematic repeatable and spatially exhaustive manner

solifluction meets vegetation the role of biogeomorphic feedbacks for turf banked solifluction lobe development vegetation is an important factor influencing solifluction processes while at the same time solifluction processes and landforms influence species composition fine scale distribution and corresponding ecosystem functioning however how feedbacks between plants and solifluction processes influence the development of turf banked solifluction lobes tbls and their geomorphic and vegetation patterns is still poorly understood we addressed this knowledge gap in a detailed biogeomorphic investigation in the turtmann glacier foreland switzerland methods employed include geomorphic and vegetation mapping terrain assessment with unmanned aerial vehicle uav and temperature logging results were subsequently integrated with knowledge from previous geomorphic and ecologic studies into a conceptual model our results show that geomorphic and vegetation patterns at tbls are closely linked through the lobe elements tread risers and ridge a conceptual four stage biogeomorphic model of tbl development with ecosystem engineering by the dwarf shrub dryas octopetala as the dominant process can explain these interlinked patterns based on this model we demonstrate that tbls are biogeomorphic structures and follow a cyclic development during which the role of their components for engineer and non engineer species changes our study presents the first biogeomorphic model of tbl development and highlights the applicability and necessity of biogeomorphic approaches and research in periglacial environments copyright 2016 john wiley sons ltd

a satellite derived climatology of the itcz abstract this paper presents fundamental climatological characteristics of the intertropical convergence zone itcz in a simple concise manner using the highly reflective cloud hrc dataset this satellite derived dataset uses both visible and infrared observations to measure the frequency of occurrence of large scale convective systems over the global tropics at a 1 spatial resolution these dataset characteristics make the hrc particularly well suited for climatological analysis of the itcz because the dataset is based on estimates of organized deep convective cloud systems rather than observations of clouds as a whole and it provides the spatial resolution needed to identify thew large wale convective structures furthermore the dataset covers a time period extending nearly two decades which provides for a fairly robust climatology and the opportunity to examine seasonal and interannual variability of both the convection and the latitude of the itcz

effects of sample size on the accuracy of geomorphological models abstract commonly the most costly part of geomorphological distribution modelling studies is gathering the data thus guidance for researchers concerning the quantity of field data needed would be extremely practical this paper scrutinises the relationship between the sample size the number of observations varied from 20 to 600 and the predictive ability of the generalized linear model glm generalized additive model gam generalized boosting method gbm and artificial neural network ann in two data settings i e independent and split sample approaches the study was performed using empirical data of periglacial processes from an area of 600 km2 in northernmost finland at grid resolutions of 1 ha 100 100 m and 25 ha 500 500 m a rather sharp increase in the predictive ability of the models was observed when the number of observations increased from 20 to 100 and the level of robust predictions was reached with 200 observations the result indicates that no more than a few hundred observations are needed in geomorphological distribution modelling at a medium scale resolution ca 0 01 1 km2

a strong atlantic meridional mode event in 2009 the role of mixed layer dynamics in the first half of 2009 anomalous cooling of sea surface temperatures ssts in the equatorial north atlantic ena 28 128n triggered a strong atlantic meridional mode event during its peak in april may ssts in the ena were 18c colder than normal and ssts in the equatorial south atlantic 58s 08 were 0 58c warmer than normal associated with the sst gradient were anomalous northerly winds an anomalous southwardshiftoftheintertropicalconvergencezone andseverefloodingin northeastbrazil thisstudyuses in situ and satellite observations to examine the mechanisms responsible for the anomalous cooling in the enaduringborealwinterandspringof2009 itisfoundthatthecoolingwasinitiatedbystrongerthannormal trade winds during january and february 2009 associated with an anomalous strengthening of the subtropical north atlantic high pressure system between 68 and 128n unusually strong trade winds cooled the ocean through wind induced evaporation and deepened the mixed layer anomalously by 5 20 m closer to the equator surface equatorial winds responded to the anomalous interhemispheric sst gradient becoming northwesterly between the equator and 68n the anomalous winds drove upwelling of 0 5 1 m day 21 during march april a period when there is normally weak downwelling the associated vertical turbulent heat flux at the base of the mixed layer led to unusually cool ssts in the central basin further strengthening the anomalous interhemispheric sst gradient these results emphasize the importance of mixed layer dynamics in the evolution of the meridional mode event of 2009 and the potential for positive coupled feedbacks between wind induced upwelling and sst in the ena

vegetation as a major conductor of geomorphic changes on the earth surface toward evolutionary geomorphology earth surface processes and landforms may have coadjusted with plant morphology biomechanics and life history we suggest that the colonization of land by plants at the early silurian and their propagation inside continents represent critical phases of the coupling between geomorphic and biological processes on the earth at a global scale the consideration of this coupling involving geomorphic biological feedback mechanisms at the scales of ecological succession and organisms evolution may promote the emergence of an evolutionary geomorphology copyright 2009 john wiley sons ltd

interaction of geomorphic and ecologic features across altitudinal zones in a subarctic landscape abstract vegetation is often considered to stabilize geomorphic processes an increasing abundance of vegetation may cause negative feedbacks within a periglacial system in this study we explored the importance of vegetation on the occurrence of active cryoturbation dominated feature fields in subarctic finland on a landscape scale the vegetation cryoturbation interaction was studied across three altitudinal zones by applying hierarchical partitioning hp and variation partitioning vp methods that overcome collinearity problems in multivariate analysis firstly our results showed that vegetation factors especially the canopy cover of the field layer vegetation and the total above ground biomass were among the most important environmental variables affecting the occurrence of active cryoturbation features moreover vegetation factors were for the most part positively associated with cryoturbation under the predicted global warming the greening of arctic and subarctic regions may therefore decrease and also increase the activity of the periglacial processes in sparsely vegetated terrain secondly our analyses gave contrasting results of the environmental factors of the periglacial processes across altitudinal zones although the relative importance of the vegetation group was rather constant throughout the zones thus we stress the importance of the spatial study setting in geomorphic studies in topographically varying relief we recommend either taking the altitudinal zonation of the landscape into consideration or studying the features within a predetermined zone to decrease misinterpretations in environment process relationships methodologically our results encourage wider applications of partitioning methods in multivariate settings in geomorphology

sea surface cooling at the equator by subsurface mixing in tropical instability waves changes in the sea surface temperature of equatorial waters have critical effects on the large scale atmospheric circulation shipboard measurements of turbulence kinetic energy dissipation rate indicate that seasonal surface cooling in the central equatorial pacific may be largely caused by mixing induced by tropical instability waves

stratigraphy age and formation of peaty earth hummocks pounus finnish lapland detailed investigations of peaty earth hummocks called pounus were carried out in northemmost finnish lapland in the vicinity of the kevo subarctic research station pounus are complex often vegetated cryogenic mounds formed partly of peat some have a core of mineral soil or several large stones or just one frost heaved boulder covered by peat they belong to the same group of earth hummocks as thufur and non sorted circles the typology of pounus is described and compared with other types of cryogenic earth hummocks stratigraphical study of pounus shows how cryoturbation has deformed the previous soil horizons of typical arctic podzols and has been followed by intense peat growth and later frost reactivation microstructures in pounus confirm the frost activity and several phases of peat growth during their formation alternating warmer and dryer conditions with water table rise and renewed peat formation could be inferred the present stage of development is frost reactivation and peat growth poun

a simple analytical model of the diurnal ekman layer abstractthe effects of time varying turbulent viscosity on horizontal currents in the ocean surface boundary layer are considered using a simple theoretical model that can be solved analytically this model reproduces major aspects of the near surface ocean diurnal cycle in velocity and shear while retaining direct parallels to the steady state ekman solution the parameter dependence of the solution is explored and quantitative measures of the low frequency rectification of velocity and shear are derived results demonstrate that time variability in eddy viscosity leads to significant changes to the time averaged velocity and shear fields with important implications for the interpretation of observations and modeling of the near surface ocean these findings mirror those of more complete numerical modeling studies suggesting that some of the rectification mechanisms active in those studies may be independent of the details of the boundary layer turbulence

modern warfare as a significant form of zoogeomorphic disturbance upon the landscape abstract the damage exerted by warfare on the physical landscape is one of many anthropogenic impacts upon the environment bombturbation is a term that describes the impacts of explosive munitions upon the landscape bombturbation like many other forms of zoogeomorphology is a disruptive force capable of moving large amounts of sediments and denuding landscapes to the point where changes in micro and mesotopography have long term implications the long term implication of bombturbative actions depends on the type and duration of explosive device that rendered the disturbance and the geographic context of the landscape disturbed i e cultural and physical factors recovery from bombturbative activity in the context of this research is measured by vegetative regrowth and soil development in cratered disturbances a comparison and contrast between the two battlefields of verdun france and khe sanh vietnam show that bombturbative actions have significantly altered the topography at each location thus influencing surface runoff and processes of soil development principals of the runge pedogenic model or the energy of water moving through the soil profile best explain how the varying climate and parent material at each location influence post disturbance soil development rates whereas the data collected at verdun suggest that explosive munitions have put that landscape on diverging path of development thus rendering it much different post disturbance landscape khe sanh displays much different recovery patterns preliminary research at khe sanh indicates that reforestation and soil development following disturbance are not so much influenced by bombturbative patterns as land use activities in the area of study

bubble clouds and the dynamics of the upper ocean this is a review of turbulence in the upper ocean close to the sea surface particularly of the information that has been obtained from sonar observations of bubble clouds produced by breaking wind waves these clouds provide tracers of the turbulent motions and are important especially at high wind speeds in the process of air sea gas transfer the observations of bubble clouds are here related to other measurements of turbulence particularly to direct measurements of currents and temperatures in lakes or at sea and to laboratory studies some novel observations of bubble clouds and breaking waves their frequency and relation to langmuir circulation are presented there is now emerging a pattern of clues that point to the dominance of breaking surface gravity waves as a source of turbulence to a depth below the surface of 0 04 to 0 2 times the wavelength of the dominant breaking waves although the effect of swell has yet to be clarified the relative depth appears to increase with increasing values of w 1 c where w10 is the wind speed and c the phase speed of the dominant waves below this region the generation of turbulence may be dominated by shear stress or convection here turbulence is generally similar to that in the atmospheric boundary layer there are however coherent motions on the scale of the mixing layer that persist for periods of a few minutes to an hour or so to which the transport of a large part of the momentum and heat fluxes can be attributed and which strongly affect the dispersion of buoyant particles or bubbles these motions deserve special study to establish their contribution to heat and momentum transport and hence to determine if or when they should be specifically represented in models of the upper ocean devised for example to describe the dispersion of passive and non passive tracers or the air sea transfer of gases

tropical instability waves at 0 n 23 w in the atlantic a case study using pilot research moored array in the tropical atlantic pirata mooring data temperature salinity velocity and wind from a mooring at 0 n 23 w are used along with satellite data for sea surface temperature and sea level to examine the contribution of tropical instability waves tiws to the energy and heat balance of the equatorial atlantic mixed layer the tiws appear as periodic 20 30 day fluctuations of currents temperature and salinity which intensify beginning in june and peak in late boreal summer the intensification occurs in phase with strengthening of the southeasterly trade winds and the seasonal appearance of the equatorial tongue of cold mixed layer temperatures in 2002 these waves which warm the mixed layer by 0 35 c during summer months are maintained by both barotropic and baroclinic conversions that are of comparable size salinity fluctuations previously neglected increase the magnitude of baroclinic energy conversion

characteristics and palaeoenvironmental significance of relict sorted patterned ground drakensberg plateau southern africa abstract relict large sorted periglacial circles are described from the drakensberg plateau of southern africa morphological and sedimentological data for three populations of patterns occurring on high summit 3400 m a s l interfluves are presented the patterns range between 85 and 904 cm in diameter with centres encircled by primary and in some cases secondary borders patterns are sorted to maximum depths of 85 cm or more with borders occupying trough like depressions to a depth of 26 cm although it is found that contemporary freeze to 40 cm depth still permits some cryogenic activity within smaller patterns it is argued that the larger patterns are degrading owing to limited moisture and freeze duration and intensity the paper provides a literature summary of contemporary environmental parameters from 10 northern hemisphere localities where active relict large periglacial patterns occur findings suggest that patterns over 80 cm in diameter develop where the maat is 1 6 c or less it is demonstrated that the drakensberg palaeo maat reached such low temperatures during the lgm it is thus argued that the patterns developed during the lgm and that smaller varieties became reactivated during holocene cold phases the relict sorted circles provide confirmation for late quaternary permafrost above 3400 m a s l in southern africa the results further suggest pronounced palaeo climatic environmental variation over short spacial scales over southern africa s high plateau

determinants of sediment properties and organic matter in beach and dune environments based on boosted regression trees grain size properties and the variation of organic matter in coastal beach and dune environments are assumed to be controlled by the intensity of aeolian processes time and the sediment source however assumptions are based on relatively limited empirical studies in this study we examined which environmental variables are the main predictors of multiple topsoil properties to achieve this we analysed an extensive dataset systematically collected across all beach zones and a large geographical area at the finnish baltic sea coast characterized by post glacial land uplift we included a comprehensive set of predictors in the analysis and applied boosted regression trees a modern modelling technique particularly suited for analysis without prior assumptions of the data model the results suggest that mean grain size and sorting are mainly determined by northing and fetch northing disturbance and fetch predicted the variation of soil organic matter while litter cover was strongly related to disturbance based on the analyses we were able to identify the main drivers of multiple topsoil properties on land uplift beaches parent material is suggested to determine sediment textural properties which largely masks the effects of transient processes mean grain size and sorting are highly interdependent grains become finer and sorting improves with increasing shore exposure the intensity of momentary geomorphic processes controls the accumulation of litter whereas the slower accumulation of organic matter in the soil is influenced also by the static exposure setting skewness and kurtosis of the grain size distribution are mainly influenced by unmeasured processes potentially relating to the geomorphological origin of the sediment copyright 2014 john wiley sons ltd

abrupt equatorial wave induced cooling of the atlantic cold tongue in 2009 1 between may and august 2009 sea surface temperatures ssts in the eastern equatorial atlantic dropped 5 c from 1 c above normal to 1 c below normal the magnitude of this cooling is unprecedented since satellite sst measurements began in 1982 in this study observations and a linear equatorial wave model are used to examine the causes of the sharp decrease in sst it is found that the anomalous cooling along the equator can be traced to an anomalous meridional gradient of sst and associated northwesterly anomalous winds that developed in the equatorial atlantic the preceding spring the anomalous winds forced upwelling equatorial rossby waves that propagated westward during boreal spring and reflected at the western boundary into upwelling kelvin waves during late spring and summer the upwelling kelvin waves propagated eastward along the equator anomalously decreasing sea level and sst during may august

turbulence variability at the equator in the central pacific at the beginning of the 1991 1993 el nino a 38 day 5990 cast microstructure study on the equator performed during the onset of the 1991 1993 el nino shows the effect on small scale activity at 140 w of an equatorial kelvin wave by using two ships data were taken continuously from november 4 to december 12 1991 near the national oceanic and atmospheric administration pacific marine environmental laboratory mooring at o n 140 w the ships occupied the station sequentially with a 3 5 day overlap for intercalibration variability in currents was observed on tidal periods and periods of 4 days presumably equatorially trapped internal gravity waves 8 days cause unknown 20 days tropical instability waves and longer kelvin waves variation in water structure occurred most prominently on the timescale of kelvin waves the diurnal cycle typical of that location was observed nocturnal deepening of the surface mixed layer was accompanied by a deep cycle bursts of turbulence penetrating into the stratified region below the nighttime mixed layer during the observational period one kelvin wave trough and one crest passed through the site changes accompanying the phase change in the kelvin wave included a reversal of the near surface current a deepening of the thermocline and a change of water mass changes in small scale activity included a tenfold decrease of the thermal dissipation rate and a fourfold decrease of the rate of heat transport downward from the mixed layer the nighttime mixed layer deepened from 30 to 60 m the thickness of the stratified region in which nocturnal turbulence bursts occurred the deep cycle region thinned from 40 to 20 m because it was confined between the bottom of the nighttime mixed layer and the low shear region near the core of the undercurrent the decrease in downward heat flux observed at this passage of the downwelling kelvin wave front could explain the rapid sea surface temperature sst increase seen at el nino onsets the magnitude of the change in vertical flux is similar to the magnitude of the change in horizontal advection this process would produce a warmer sst much more quickly than could the advection of warm waters eastward

trade wind fetch related variations in equatorial undercurrent depth speed and transport a dynamical model is developed to examine the dependence of equatorial undercurrent depth speed and volume transport on trade wind fetch the model ocean is linear continuously stratified vertically diffusive and formulated on the equatorial beta plane analytical solutions are derived in closed form for realistic choices of model parameters results indicate that the undercurrent would be significantly shallower and weaker in the atlantic than in the pacific because of the shorter atlantic trade wind fetch

the search for a topographic signature of life landscapes are shaped by the uplift deformation and breakdown of bedrock and the erosion transport and deposition of sediment life is important in all of these processes over short timescales the impact of life is quite apparent rock weathering soil formation and erosion slope stability and river dynamics are directly influenced by biotic processes that mediate chemical reactions dilate soil disrupt the ground surface and add strength with a weave of roots over geologic time biotic effects are less obvious but equally important biota affect climate and climatic conditions dictate the mechanisms and rates of erosion that control topographic evolution apart from the obvious influence of humans does the resulting landscape bear an unmistakable stamp of life the influence of life on topography is a topic that has remained largely unexplored erosion laws that explicitly include biotic effects are needed to explore how intrinsically small scale biotic processes can influence the form of entire landscapes and to determine whether these processes create a distinctive topography

geomorphological limits to self organization of alpine forest tundra ecotone vegetation abstract feedback in the establishment of vegetation has been shown to produce spatial patterns that differ from the geomorphological basis for resources the dynamics of these spatial patterns have been characterized as self organization because local processes produce them at landscape scales geomorphic patterns could however enhance or disrupt the processes that lead to patterns and the interpretation of self organization a simulation model that showed such indication of self organization at alpine forest tundra ecotones is modified to incorporate a geomorphic feature commonly seen in this environment solifluction steps as an exogenous condition in the model analyses linking spatial patterns and rates of advance of vegetation indicate that such geomorphic patterns do not alter the dynamics of vegetation until the size of the patterns is about double that of the dimension within which endogenous dynamics operate the sizes of some geomorphic patterns incorporated in the model are probably larger than any realistic solifluction feature at such ecotones in western north america

simulating nonsorted circle development in arctic tundra ecosystems 1 nonsorted circles ubiquitous to the arctic tundra region are patterned ground features with circular semibarren areas surrounded by vegetation these circles are formed and persist as an ecosystem due to complex soil water energy ice plant relationships and dynamics in the arctic in this paper we present the first model that captures the dynamics of the physical and biological components of the nonsorted circle ecosystem in order to understand its formation and persistence especially in a changing climatic environment we have applied a coupled model describing 1 vegetation dynamics arcveg and 2 coupled heat and moisture transport with phase change wit in the active layer of the soil where such circles are initiated and developed we simulated the system behavior during the formation process starting with a random vegetation development the vegetation provided heterogeneous insulation to the soil surface during freezing the noninsulated areas froze first resulting in preferential ice accumulation in those areas the ice prevented the vegetation from developing further in those areas and thus developed and stabilized the nonsorted circle pattern the model produced a nonsorted circle pattern that was well compared to those observed in the field the model also illustrated that the availability of water was critical for the sustenance and stability of the nonsorted circle the effect of climatic variations on the freezing process on the other hand did not seem to affect the formation and sustenance of nonsorted circles

observations of shear and vertical stability from a neutrally buoyant float measurements of 1 to 5 m shear and strain from a neutrally buoyant float are used to examine the statistics and causes of shear instability in a 9 day record unstable conditions defined as vz n 2 where vz vz are due to higher than average shear rather than lower than average buoyancy frequency and there are no instances of unstable buoyancy frequency or overturns on the 0 5 m spacing of the thermistors shear is dominated by upward propagating near inertial motions unstable events were more frequent when a near inertial wave packet occupied the water parcel tracked by the float groups of unstable events occur roughly every 5 7 hours at scales 2 5 m and much less often at larger scales events typically last 10 min one buoyancy period or longer these time scales appear to be controlled by vertical advection of 1 m fine structure past the float sensors so do not represent the intrinsic time scales of instability turbulent and mixing quantities are estimated from these fine scale measurements giving a dissipation rate of e 2 3 16 10 10 w kg and an eddy diffusivity of k 3 10 6 m2 s in agreement with direct microstructure estimates therefore the float adequately resolves those quantities needed to estimate turbulent dissipation and could be used to monitor turbulent mixing in the ocean

dynamics of the surface layer diurnal cycle in the equatorial atlantic ocean 0 23 w a 15 year time series 1999 2014 from the 0 23 w prediction and research moored array in the tropical atlantic pirata mooring which includes an 8 month record october 2008 to june 2009 of high resolution near surface velocity data is used to analyze the diurnal variability of sea surface temperature shear and stratification in the central equatorial atlantic the ocean diurnal cycle exhibits pronounced seasonality that is linked to seasonal variations in the surface wind field in boreal summer and fall steady trade winds and clear skies dominate with limited diurnal variability in sea surface temperature diurnal shear layers with reduced richardson numbers are regularly observed descending into the marginally unstable equatorial undercurrent below the mixed layer conditions favorable for the generation of deep cycle turbulence in contrast in boreal winter and spring winds are lighter and more variable mixed layers are shallow and diurnal variability of sea surface temperature is large during these conditions diurnal shear layers are less prominent and the stability of the undercurrent increases suggesting seasonal covariance between diurnal near surface shear and deep cycle turbulence modulation of the ocean diurnal cycle by tropical instability waves is also identified this work provides the first observational assessment of the diurnal cycle of near surface shear stratification and marginal instability in the equatorial atlantic confirming previous modeling results and offering a complementary perspective on similar work in the equatorial pacific

a model for sorted patterned ground regularity sorted patterned ground refers to polygons nets or stripes defined by rocky borders which are the result of sorting in soil subjected to frost action this paper presents a model in which convection cells driven by unstable density stratification in the aqueous phase result in uneven melting of the underlying ice front during thawing the resulting undulatory ice front with regularly spaced peaks and troughs provides the pattern which results in the regularity observed for certain types of patterned ground in addition the model predicts the width to depth of sorting ratio for both polygons and stripes and explains the characteristic hexagonal shape of sorted polygons the transition from sorted polygons to sorted stripes on sloped terrain and the formation of sorted polygons under water the predicted ratio of width to depth of sorting of 3 81 for sorted polygons is compared with the ratio of width to depth of sorting of 3 57 found from a linear regression analysis of 18 field study data

wind waves and fronts frictional effects in a generalized ekman model abstractocean currents in the surface boundary layer are sensitive to a variety of parameters not included in classic ekman theory including the vertical structure of eddy viscosity finite boundary layer depth baroclinic pressure gradients and surface waves these parameters can modify the horizontal and vertical flow in the near surface ocean making them of first order significance to a wide range of phenomena of broad practical and scientific import in this work an approximate green s function solution is found for a model of the frictional ocean surface boundary layer termed the generalized ekman or turbulent thermal wind balance the solution admits consideration of general more physically realistic forms of parameters than previously possible offering improved physical insight into the underlying dynamics closed form solutions are given for the wind driven flow in the presence of coriolis stokes shear a result of the surface wave field and thermal wind shear arising from a baroclinic

exploring the impact of snow vole chionomys nivalis burrowing activity in the făgăraș mountains southern carpathians romania geomorphic characteristics and sediment budget abstract the potential zoogeomorphological impacts of burrowing animals via soil excavation and spatial redistribution creation of landforms and bioturbation are now well established here we present the first zoogeomorphological study conducted in the f g ra massif southern carpathians romanian carpathians and consider the impact of chionomys nivalis a small rodent living at high elevations in cold climate and petrocolic soil conditions the aims of our study were to highlight the impact of c nivalis burrowing on alpine and subalpine meadows and to calculate the sediment budget related to the rodent s activity we therefore analysed burrow spatial distribution and density and the related contribution to sediment displacement mass transfer and budget two glacial valleys sites between 1705 and 2262 m a s l were selected based on their local topography and burrow density found to be between 0 56 m 2 and 2 44 m 2 one located on the northern slope of the f g ra massif the other on the southern slope within these two sites we investigated 384 burrows divided among nine plots eight 25 m2 and one 100 m2 the slope angle of the plots were between 10o and 45o and the general plot aspects are sw and ne we measured mound dimensions length height width and angle and the depth of each burrow and calculated the total amount of excavated sediment to be 224 130 g with a mean displacement rate of 0 11 0 07 t ha 1 y 1 and a mean transfer of 23 13 7 t m y 1 km2 this preliminary investigation provides reliable zoogeomorphological data that show the activity spatial extent and density of chionomys nivalis differed among the plots the values obtained can be compared with results for other rodents around the world which carry out similar denudation processes in mountainous environments

mixed layer shear generated by wind stress in the central equatorial pacific abstract sixteen months of wind and current profile observations in the central equatorial pacific show the response of the upper ocean shear to local wind forcing the shear at the ocean surface is significantly correlated with the wind stress in direction but not in magnitude implying that the vertical eddy viscosity coefficient is proportional to the square of the wind speed or to the stress using this variable eddy viscosity coefficient in stommel s model of the equatorial undercurrent we calculate shears in the mixed layer that compare well with the observations the flow is downwind on the equator and tends toward and ekman spiral off the equator

seasonality of deep cycle turbulence in the eastern equatorial pacific abstractthe seasonal cycles of the various oceanic and atmospheric factors influencing the deep cycle of turbulence in the eastern pacific cold tongue are explored moored observations at 140 w have shown seasonal variability in the stratification velocity shear and turbulence above the pacific equatorial undercurrent euc in boreal spring the thermocline and euc shoal and turbulence decreases marginal instability clustering of the local gradient richardson number around the critical value of 1 4 evident throughout the rest of the year has not been detected during spring while the daily averaged turbulent energy dissipation in the euc is weakest during the spring it is not clear whether the diurnal fluctuations that define the deep cycle cease large eddy simulations are performed using climatological initial and boundary conditions representative of january april july and october deep cycle turbulence is evident in all cases the mechanism remains the same and the maximum turbulence leve