lithological control on the elevation of shore platforms in a microtidal setting the shore platforms on shag point southern new zealand are quasi horizontal surfaces and are developed between supratidal and low water spring levels a range of morphologies occur with more exposed platforms having a distinct low tide cliff in contrast to low tide surfaces where the seaward edge is buried beneath rubble and macro algal growth the platforms range in width from 20 to 80 m and are eroded into late cretaceous early tertiary fine marine sandstones and mudstones shore platforms have formed in two principal lithological units a homogeneous unit that is characterized by few discontinuities and a fractured unit with joints spaced about 0 5 m apart rock hardness is low in both units l type schmidt hammer rebound values of 31 4 and there is little systematic variation in values between the two units in which platforms have developed case hardened concretions within the sandstone are significantly harder than surrounding rock and cause local relief of metre scale as the spherical diagenetic features are eroded from the bedrock they do not however appear to affect broad scale platform geometry joints within the bedrock are a primary control on platform elevation platforms formed in jointed rock occur at the lower portion of the intertidal zone in contrast to platforms formed in unjointed bedrock in which horizontal surfaces occur at or above mean high water spring tide level rock structure therefore appears to be the primary determinant factor of platform geometry at shag point copyright 2006 john wiley sons ltd

rock coast inheritance an example from galicia northwestern spain a shore platform on the western coast of galicia in northwestern spain has been inherited from interglacial stages when sea level was similar to today the wide gently sloping intertidal platform is backed in places by supratidal rock ledges and in other places by a steeper and narrower supratidal ramp the gradient of the intertidal platform is consistent with the relationship between platform gradient and tidal range but the slope of the ramp is much too high the abandoned and degraded sea cliff is grass covered along most of this coast and the ledges and the ramp which extend up to several metres above the highest tides are covered by lichen and in places by salt tolerant plants radiocarbon dated sediments in the cliff which range up to 36 000 years in age lie on top of an ancient beach deposit the former beach remnants of which are found in situ on the ramp and rock ledges as well as two caves that are filled with the dated sediments are probably last interglacial in age the morphological and sedimentary evidence suggests that the supratidal ramp and ledges were also formed during the last interglacial stage whereas the wider intertidal platform is probably the product of several older interglacials when sea level was generally similar to today a general model is proposed for the inheritance of shore platforms in macro and microtidal environments copyright 1999 john wiley sons ltd

greenland meltwater as a significant and potentially bioavailable source of iron to the ocean the micronutrient iron is thought to limit primary production in large regions of the global ocean meltwater measurements suggest that the greenland ice sheet serves as a significant source of potentially bioavailable iron to the surrounding coastal ocean

surface energy balance and melt thresholds over 11 years at taylor glacier antarctica 11 years ablation 18 cm a 1 was dominated by sublimation with very few occurrences of melt 42 days during 11 years results also indicated that above freezing air temperatures did not necessarily result in melt and in turn melt occurred during subfreezing air temperatures under some conditions for air temperatures near freezing low wind speed was critically important for melt initiation according to the model subsurface melt away from rocks and sediment in the ice occurred three times more frequently than surface melt occurs no deeper than 50 cm below the glacier surface and was small never exceeding 8 by mass the magnitude of subsurface melting and the energy balance indicate that taylor glacier ice is intermediate in optical properties between snow and blue ice

the structure biological activity and biogeochemistry of cryoconite aggregates upon an arctic valley glacier longyearbreen svalbard glacier surfaces support unique microbial food webs dominated by organic and inorganic debris called cryoconite observations from longyearbreen spitsbergen show how these aggregate particles can develop an internal structure following the cementation of mineral grains mostly quartz and dolomite by filamentous microorganisms measurements of carbon and dissolved o2 show that these microorganisms mostly cyanobacteria promote significant rates of photosynthesis average 17 gc g 1 d 1 which assist aggregate growth by increasing the biomass and producing glue like extracellular polymeric substances the primary production takes place not only upon the surface of the aggregates but also just beneath due to the translucence of the quartz particles however since total photosynthesis is matched by respiration average 19 gc g 1 d 1 primary production does not contribute directly to cryoconite accumulation upon the glacier surface the microorganisms therefore influence the surface albedo most by cementing dark particles and organic debris together rather than simply growing over it time lapse photographs show that cryoconite is likely to reside upon the glacier for years as a result of this aggregation these observations therefore show that a better understanding of the relationship between supraglacial debris and ablation upon glaciers requires an appreciation of the biological processes that take place during summer

downwearing rates of vertical limestone surfaces in the intertidal zone gulf of trieste italy abstract in 2007 we installed seven micro erosion meter stations on a vertical limestone slab located in the intertidal zone in the gulf of trieste italy in order to observe rock surface changes at elevations ranging between 0 75 m and 0 75 m m s l furlani et al 2010 in this paper we present the micro erosion metre mem data for most months between february 2008 and may 2013 and the traversing micro erosion metre tmem data collected twice a year since 2007 the mem and tmem data were consistent and indicated that the mean lowering rate ranged between 0 007 mm yr and 0 205 mm yr and 0 001 mm yr and 0 260 mm yr according to the elevation of the stations maximum downwearing rates were observed in the mid lower intertidal zone and decreased upward and downward the natural trend of erosion started in 2010 after 2 years of exposure when the slab formerly smoothed and not colonized by marine organisms started to be acclimated to the local environment after 2010 the erosion rate increased to a maximum of 0 31 mm yr this value can be more representative for long term studies and is similar to the downwearing rates locally collected on natural limestone surfaces this dataset represents the first collection of downwearing rates mainly measured using mems but also tmems on vertical limestone surfaces in an intertidal zone and provides interesting new information for addressing the debate on notch genesis and development the shape of a tidal notch has been found to be consistent with the distribution of erosion rates along the slab even if the present day notch was not surveyed in the gulf of trieste due to the local tectonic subsidence

evolution of cryoconite holes and their contribution to meltwater runoff from glaciers in the mcmurdo dry valleys antarctica cryoconite holes are water filled holes in the surface of a glacier caused by enhanced ice melt around trapped sediment measurements on the ablation zones of four glaciers intaylorvalley antarctica show that cryoconite holes cover about 4 6 of the ice surface they typically vary in diameter from 5 to 145 cm with depths ranging from 4 to 56 cm in some cases huge holes form with 5 m depths and 30 m diameters un like cryoconite holes elsewhere these have ice lids up to 36 cm thick and melt from within each spring about one half of the holes are connected to the near surface hydrologic system and the remainder are isolated the duration of isolation estimated from the chlor ide accumulation in hole waters commonly shows ages of several years with one hole of 10 years the cryoconite holes in the mcmurdo dryvalleys create a near surface hydro logic system tens of cm below the ice surface the glacier surface itself is generally frozen and dry comparison of water levels between holes a few meters apart shows independent cycles of water storage and release most likely local freeze thaw effects control water passage and therefore temporary storage rough calculations indicate that the holes gen erate at least 13 of the observed runoff on the one glacier measured this hydrologic system represents the transition between a melting ice cover with supraglacial streams and one entirely frozen and absent of water abstract cryoconite holes are water filled holes in the surface of a glacier caused by enhanced ice melt around trapped sediment measurements on the ablation zones of four glaciers intaylorvalley antarctica show that cryoconite holes cover about 4 6 of the ice surface they typically vary in diameter from 5 to 145 cm with depths ranging from 4 to 56 cm in some cases huge holes form with 5 m depths and 30 m diameters un like cryoconite holes elsewhere these have ice lids up to 36 cm thick and melt from within each spring about one half of the holes are connected to the near surface hydrologic system and the remainder are isolated the duration of isolation estimated from the chlor ide accumulation in hole waters commonly shows ages of several years with one hole of 10 years the cryoconite holes in the mcmurdo dryvalleys create a near surface hydro logic system tens of cm below the ice surface the glacier surface itself is generally frozen and dry comparison of water levels between holes a few meters apart shows independent cycles of water storage and release most likely local freeze thaw effects control water passage and therefore temporary storage rough calculations indicate that the holes gen erate at least 13 of the observed runoff on the one glacier measured this hydrologic system represents the transition between a melting ice cover with supraglacial streams and one entirely frozen and absent of water

in stream uptake and retention of c n and p in a supraglacial stream supraglacial streams form annually during the melt season transporting dissolved solutes from the melting ice and snowpack to subglacial flow paths and the glacier terminus although nutrient and carbon processing has been documented in other supraglacial environments cryoconite holes snowpack little work has examined the potential for in stream nutrient retention in supraglacial streams here we carried out a solute nutrient injection experiment to quantify nh3 p o 4 3 and labile dissolved organic carbon doc retention in a supraglacial stream the experiment was performed on a 100 m stream reach on mendenhall glacier an outlet glacier on the juneau icefield southeastern alaska usa the study stream contained two distinct reaches of equal length the first reach had a lower velocity 0 04 m s 1 and contained abundant gravel sediment lining the ice water interface while the second reach was devoid of bedload sediment and had an order of magnitude higher velocity at the end of the second reach the stream emptied into a moulin which is typical of supraglacial streams on this and other temperate glaciers we found that n and p were transported largely conservatively although no3 increased along the reach suggestive of nitrification labile doc was retained slightly within the stream although rates were low relative to the travel times observed within the supraglacial stream although our findings show that these streams have low processing rates measurable in stream nitrification and dissolved organic matter uptake within this biologically unfavorable environment suggests that supraglacial streams with longer residence times and abundant fine substrate have the potential to modify and retain nutrients during transport to the glacier terminus

nitrogen fixation on arctic glaciers svalbard telling j anesio a m tranter m irvine fynn t hodson a butler c wadham j 2011 nitrogen fixation on arctic glaciers svalbard journal of geophysical research biogeosciences 116 article number g03039

the effect of holocene changes in relative sea level on the morphology of rocky coasts abstract a mathematical wave and weathering model was used to study the effect of holocene changes in relative sea level rsl on rock coast development model runs were made for fast and slow eroding coasts in macro and mesotidal environments using holocene rsl records from sweden northeastern usa southwestern britain central japan western africa and southern australia a further series of otherwise identical runs were made with constant sea level changes in rsl determined the amount of time that marine processes have operated within the modern intertidal zone and rates of wave attenuation and erosion continue to be influenced by subtidal morphology that developed in most areas when rsl was rising to its present level the model suggested that although tidal range is also important holocene rsl changes promoted subhorizontal platform development in australasia and over much of the southern hemisphere and sloping platforms over much of the northern hemisphere shore platforms may have been partly inherited from earlier periods in the holocene when rsl was similar to today s nevertheless most platforms continue to be eroded at all tidal levels where geological and wave conditions are less favourable erosion in the lower intertidal zone has essentially terminated in areas where rsl rose to its present position whereas erosion only occurs today in the lower intertidal zone in places where rsl rose to above its present level in the middle holocene

a constitutive model for the deformation of a rock mass containing sets of ubiquitous joints abstract as part of the rock mass the discontinuities inherently affect the strength and the deformational behavior of rock mass existing models can either handle the pre or post peak deformation of intact rock or joints alone however a model which can determine the failure mode and simulate the complete pre and post deformation of rock mass with multi sets of joints is not yet available this study focusses on rock mass with multi sets of ubiquitous joints and establishes a mathematic model and an associated numerical implementation accounting for the anisotropy in strength and deformation induced by the existence of joints accordingly an approach incorporating the existing models or methods to enable simulation of the complete deformation of rock mass is proposed in addition to the pre and post peak deformation characteristics for intact rock the pre peak deformation of joint such as the closure shear and dilatancy effect as well as its post peak deformation such as the reduction on roughness have also been taken into account a series of comparisons validates that the proposed model is capable of presenting the joint induced anisotropy in strength and deformation of rock mass determining the possible failure modes and reasonably simulating the complete stress strain relationship as well

numerical simulation of a layered rock under triaxial compression layered rock masses are common geological materials their traverse isotropy greatly affects the stress strain analysis of rock masses and fracture mechanical behaviors 1 many scholars have conducted theoretical and experimental studies on the mechanical properties of layered rock masses aimed at exploring a jointed rock mass under failure by sliding along joint planes the earliest study was initiated by jaeger 2 who established the layered rock mass strength description model based on the mohr coulomb criterion thereafter some scholars added supplements and made improvements to this model 3 11 some other scholars conducted research on layered rock masses from the perspective of their nonlinear mechanical behaviors for example duveau and shao 12 adopted the combined nonlinear failure criterion to describe the failure characteristics of layered rock masses tien and kuo 13 used two different materials to facilitate an artificial prefabrication of three groups of layered rock masses of different inclinations the effect of the layer inclination on the overall strength and elastic modulus of rocks was studied and corresponding failure criteria in terms of the two varying models of layered rock failure were established cazacu et al 14 took hydrostatic pressure into account and included the strength criterion expressed by invariant stress based on the quadratic equation failure criterion all these scholars mainly used the uniaxial compression test or the conventional triaxial compression test in their studies however research on the response characteristics of layered rock masses in true triaxial compression is limited lee and pietruszczak 11 proposed a formulation describing the strength anisotropy of transversely isotropic rock masses and used true triaxial compression tests as well as conventional triaxial tests for verification for further

modeling the development of wave cut shore platforms abstract a mathematical model was used to investigate the development of wave cut shore platforms with constant sea level the model considered the effects of deep water wave height spectra period and wavelength breaker height and depth breaker type the width and bottom roughness of the surf zone the gradient of the submarine slope an erosional threshold related to the strength of the rocks the number of hours each year in which the water level is at each intertidal elevation and the amount and persistence of the debris at the cliff foot intertidal erosion rates were calculated according to the force of the surf reaching the shoreline whereas submarine erosion rates were determined using a depth decay variable each of the two hundred and fifty model runs consisted of 300 000 iterations platform width increased and gradient progressively decreased through model runs and states of static equilibrium were attained by the end of one hundred and nine runs when the wave induced force at each point in the intertidal zone had became too weak to continue eroding the rock runs with mesotidal spring tidal range 3 m generally produced subhorizontal platforms with cliff platform junctions at the mean low water neap tidal level a greater variety of profiles was produced in runs with macrotidal spring tidal ranges 9 m although almost 30 of these runs produced gently sloping platforms with average gradients of only 0 3 about two thirds of the simulated profiles had average gradients ranging from about 1 to 3 simulated platform width increased with tidal range and decreased with the rate of submarine erosion rock resistance the roughness or irregularity of the platform surface the amount and persistence of the cliff foot debris and wave period because higher waves break in deeper water than lower waves there was no consistent relationship between simulated platform width and wave height

characterization of dissolved organic matter dom from glacial environments using total fluorescence spectroscopy and parallel factor analysis aquatic dissolved organic matter dom is a major reservoir of reduced organic carbon and has a significant influence on heterotrophic biological productivity and water quality in marine and freshwater environments although the forms and transformations of dom in temperate aquatic and soil environments have been studied extensively this is not the case for glacial environments in this study fluorescent excitation emission matrices eems parallel factor analysis parafac and cluster analysis were used to characterize the fluorescing components of dom in ice and water samples from supraglacial englacial subglacial and proglacial environments of seven glaciers in the canadian arctic norway and antarctica at least five significant fluorescent dom fractions were identified which accounted for 98 2 of the variance in the dataset these included four protein like components and one humic like component the predominantly proteinaceous character of dom from these glaciers is very different from the more humic character of dom described previously from lacustrine fluvial estuarine and marine environments dom from the sampled glaciers is broadly similar in character despite their geographically distinct locations different thermal regimes and inter and intra site differences in potential organic matter sources glacier ice samples had a relatively low ratio of humic like protein like fluorescence while meltwater samples had a higher ratio

decadal variability of east australian current transport inferred from repeated high density xbt transects a ctd survey and satellite altimetry a time series of the net geostrophic transport through the tasman sea representing the flow of the east australian current eac extension is determined from a full depth ctd section 15 years of high density xbt transects and satellite altimetry data a section between sydney and wellington px34 has been occupied four times per year since 1991 with high resolution xbt sampling two methods to infer baroclinic transport from proxy data along the section are presented the first uses shallow xbt transects to derive geostrophic transport relative to a deep 2000 m reference level in the second approach synts the subsurface temperature and salinity structure are inferred from satellite surface height and temperature fields using a model developed from historical in situ observations the baroclinic transport is then computed in the usual manner the methods are validated using both a full depth ctd occupation of the px34 section and further transects crossing the eac in the northern tasman sea there is close agreement between the 49 xbt and synts px34 transport estimates obtained between 1992 and 2006 the time series of transport through the sydney wellington section shows a range of temporal signals from eddyscale seasonal interannnual to decadal in particular we note that the net eac flow ranges from 5 sv in 1995 to a maximum of 16 sv in 2000 2001 this decadal variation confirms the eac response to a spin up of the south pacific circulation forced by changes in the basin wide winds and matches the changes in oceanic properties observed in the tasman sea

development of shore platforms on kaikoura peninsula south island new zealand ii the role of subaerial weathering the role of subaerial weathering in the development of shore platforms on kaikoura peninsula is investigated evidence for weathering came from a number of distinctive surface morphologies on platforms salt crystal growth water layer weathering and slaking schmidt hammer test data showed that weathering had occurred and that rock strength was reduced through weathering by as much as 50 weathering processes on shore platforms rely on repeated wetting and drying and for this reason the number of wetting and drying cycles was estimated it was found that the number of wetting and drying cycles depend not only on the pattern of tidal water levels but also on algae growth and desiccation the number of cycles ranged from 104 to 379 per year at elevations low in the tide range fewer cycles occurred the greatest number occurring between the peaks of spring and neap tides and where rainfall adds to the number the zone of most cycles was estimated to occur between 0 6 and 0 9 m above mean sea level on the more landward margins of platforms it is at these elevations that the highest rates of erosion occur based on these results it is argued that the development of shore platforms at kaikoura results from subaerial weathering caused by repeated wetting and drying this is contrary to the view that shore platforms result from marine erosion

sea stack formation and the role of abrasion on beach mantled headlands sea stacks are common and striking coastal landforms but few details are known about how how quickly and under what conditions they form we present numerical and analytical models of sea stack formation due to preferential erosion along a pre existing headland to address these basic questions on sediment rich rocky coasts as sea cliffs erode and retreat they produce beach sediment that is distributed by alongshore sediment transport and controls future sea cliff retreat rates depending on their width beaches can encourage or discourage sea cliff erosion by acting either as an abrasive tool or a protective cover that dissipates wave energy seaward of the cliff along the flanks of rocky headlands where pocket beaches are often curved and narrow due to wave field variability abrasion can accelerate alongshore directed sea cliff erosion eventually abrasion induced preferential erosion can cut a channel through a headland separating it from the mainland to become a sea stack under a symmetrical wave climate i e equal influence of waves approaching the coastline from the right and from the left numerical and analytical model results suggest that sea stack formation time and plan view size are proportional to preferential erosion intensity caused by for example abrasion and or local rock weakness from joints faults or fractures and initial headland aspect ratio and that sea stack formation is discouraged when the sediment input from sea cliff retreat is too high i e sea cliffs retreat quickly or are sand rich when initial headland aspect ratio is too small and the headland is rounded much wider in the alongshore direction at its base than at its seaward apex the headland is less conducive to sea stack formation on top of these geomorphic and morphologic controls a highly asymmetrical wave climate decreases sea stack size and discourages stack formation through rock sediment interactions copyright 2014 john wiley sons ltd

short term rock surface expansion and contraction in the intertidal zone transverse micro erosion meter tmem stations were installed in rock slabs from shore platforms in eastern canada the slabs were put into artificial sea water for 1 6 or 11 hours representing high mid and low tidal areas respectively the tmems were used to record changes in surface elevation as the rocks dried during the remainder of the 12 h of a semi diurnal tidal cycle a similar technique was used on the same rock types at intertidal tmem stations in the field as the rocks dried during low tide argillite and basalt surface contraction was from 0 to 0 04 mm there was little surface expansion sandstones contracted by up to 0 03 mm in the field but there was almost no contraction in the laboratory argillite and basalt contraction tended to be greatest in the upper intertidal zone and to increase with rates of longer term surface downwearing but there was little relationship with rock hardness or air temperature and humidity changes in elevation at the same points at tmem stations in the laboratory and field were quite consistent from one tidal cycle to the next but there were considerable variations within single tidal cycles between different points within each station the data suggest that contraction within the elevational zone that is normally submerged twice a day by the tides is by alternate wetting and drying short term changes in elevation are generally low compared with annual rates of downwearing owing to erosion but they may generate stresses that contribute to rock breakdown copyright 2007 john wiley sons ltd

organic carbon export from the greenland ice sheet abstract glacial meltwater exports a unique type of organic carbon to marine systems distinct from non glacially derived riverine export potentially capable of stimulating downstream marine primary productivity here we describe for the first time the bulk level dissolved organic carbon doc and particulate organic carbon poc isotopic composition of glacial meltwater draining the greenland ice sheet gris these data in conjunction with an earlier study that investigated the molecular level composition of gris dissolved organic matter collectively describe the concentration radiocarbon content and lability of organic carbon in subglacial discharge from a land terminating outlet glacier during a melt season by scaling up our measurements across the ice sheet we estimate that the annual doc flux from the gris 0 08 tg y is equivalent to that from a small arctic river discharge q 3 y and that the annual poc flux from the gris 0 9 tg y may be comparable to that of a large arctic river q 200 km 3 y the doc flux is derived primarily from beneath the glacier subglacial 75 in the early season and from surface ice melt up to 100 transmitting through the subglacial environment at the peak of the meltseason the poc flux is primarily derived from the subglacial environment throughout the meltseason the early season low flow glacier discharge contains higher doc concentrations 0 5 4 1 mg l 1 and exports more enriched carbon 14 c doc 250 compared to the peak season high flow discharge when the concentrations are lower 0 1 0 6 mg l 1 and the 14 c is more depleted 14 c doc 400 conversely the poc export 1 4 13 2 mg l 1 14 c poc 250 shows no temporal variation in either concentration or radiocarbon content throughout the meltseason dissolved ion loads in concomitant samples reflected the seasonal evolution of the subglacial drainage system confirming the influence of subglacial hydrology on the composition of the bulk carbon pools based on this work we conclude that 1 different mechanisms control the doc and poc flux from glacial systems 2 chemically distinct doc pools are accessed by seasonally evolving hydrological flow paths and 3 the gris can deliver labile carbon which may also be 14 c depleted to downstream proglacial and marine environments

the hydrochemistry of meltwaters draining a polythermal based high arctic glacier south svalbard i the ablation season solute and runoff time series at finsterwalderbreen svalbard provide evidence for considerable basal routing of water and the existence of at least two contrasting subglacial chemical weathering environments the hydrochemistry of a subglacial upwelling provides evidence for a snowmelt fed subglacial reservoir that dominates bulk runoff during recession flow high concentrations of cl and crustal ions high pco2 and ratios of so2 4 so2 4 hco 3 close to 0 5 indicate the passage of snowmelt through a subglacial weathering environment characterized by high rock water ratios prolonged residence times and restricted access to the atmosphere at higher discharges bulk runoff becomes dominated by icemelt from the lower part of the glacier that is conveyed through a chemical weathering environment characterized by low rock water ratios short residence times and free contact with atmospheric gases these observations suggest that icemelt is routed via a hydrological system composed of basal ice marginal englacial and supraglacial components and is directed to the glacier margins by the ice surface slope upwelling water flows relatively independently of icemelt to the terminus via a subglacial drainage system possibly constituting flow through a sediment layer cold basal ice at the terminus forces it to take a subterranean routing in its latter stages the existence of spatially discrete flow paths conveying icemelt and subglacial snowmelt to the terminus may be the norm for polythermal based glaciers on svalbard proglacial mixing of these components to form the bulk meltwaters gives rise to hydrochemical trends that resemble those of warm based glaciers these hydrochemical characteristics of bulk runoff have not been documented on any other glacier on svalbard to date and have significance for understanding interactions between thermal regime and glacier hydrology 1998 john wiley sons ltd

surface glaciochemistry of taylor valley southern victoria land antarctica and its relationship to stream chemistry we have analysed a series of surface samples from the alpine glaciers of taylor valley southern victoria land antarctica for their geochemical composition this was done to better establish the role of glaciochemical variation on the chemical composition of meltwater streams emanating from the glaciers the chemistry of the snow and ice changes with proximity to the ocean and with elevation of the glacier surface the aeolian transport of dry valley dust as indicated by both chemical and particulate matter variations is a major process affecting the overall glacier chemistry and the chemistry of the meltwaters streams originating on the western edges of the glaciers are more impacted by the aeolian input as they are in the direct path of the major regional wind direction our data strongly suggest that the variation in stream geochemistry in taylor valley is a result in part of the differences in chemical composition of glacier melt copyright 2003 john wiley sons ltd

molecular characterization of dissolved organic matter associated with the greenland ice sheet abstract subsurface microbial oxidation of overridden soils and vegetation beneath glaciers and ice sheets may affect global carbon budgets on glacial interglacial timescales the likelihood and magnitude of this process depends on the chemical nature and reactivity of the subglacial organic carbon stores we examined the composition of carbon pools associated with different regions of the greenland ice sheet subglacial supraglacial proglacial in order to elucidate the type of dissolved organic matter dom present in the subglacial discharge over a melt season electrospray ionization esi fourier transform ion cyclotron resonance ft icr mass spectrometry coupled to multivariate statistics permitted unprecedented molecular level characterization of this material and revealed that carbon pools associated with discrete glacial regions are comprised of different compound classes specifically a larger proportion of protein like compounds were observed in the supraglacial samples and in the early melt season spring subglacial discharge in contrast the late melt season summer subglacial discharge contained a greater fraction of lignin like and other material presumably derived from underlying vegetation and soil these results suggest 1 that the majority of supraglacial dom originates from autochthonous microbial processes on the ice sheet surface 2 that the subglacial dom contains allochthonous carbon derived from overridden soils and vegetation as well as autochthonous carbon derived from in situ microbial metabolism and 3 that the relative contribution of allochthonous and autochthonous material in subglacial discharge varies during the melt season these conclusions are consistent with the hypothesis that given sufficient time e g overwinter storage resident subglacial microbial communities may oxidize terrestrial material beneath the greenland ice sheet

measuring erosion with the micro erosion meter contributions to understanding landform evolution abstract we review the contribution made to understanding landform evolution through the use of the micro erosion meter mem and the variant the traversing micro erosion meter tmem the mem has allowed the direct measurement of bedrock erosion in terrestrial and coastal settings as well as of building stone as recorded in mem measurements world wide the average rate of surface lowering on shore platforms is 1 486 mm a 1 and on terrestrial rock surfaces measured lowering rates are on average 0 903 mm a 1 reported means obscure significant variation in rates from a range of environmental settings and lithologies the mem has in a number of examples allowed the identification of the contribution of individual processes in polygenetic settings particularly in shore platform studies the dynamic nature of rock weathering has been highlighted where the tmem has revealed rock surfaces swelling and contracting at time scales ranging from hours to years the mem will continue to provide useful data on erosion rates and processes but the most fruitful investigations will be those that combine the t mem with other techniques that transcend time and space scale issues in erosion and process measurement

origin of crystalline cold desert salts in the mcmurdo region antarctica abstract the distribution of crystalline salt minerals in deposits in the mcmurdo region of antarctica has been examined to study the origin of these salts sulphate chloride sodium and calcium salts are most frequently encountered salts containing chloride and sodium ions become less common away from the coast sulphate salts are more regularly distributed but tend to be related isotopically to sea water sulphate salts containing magnesium ion tend to exist mainly on substrates composed of basic igneous rocks whereas calcium and carbonate salts are present on all rock types in the region these distributions show that salts of marine origin are regionally and quantitatively most important but that chemical weathering of mafic materials in rocks and soils is also significant however biological volcanic and hydrothermal processes are or have been active contributing to salts in local areas that include penguin rookeries and eastern taylor valley the summit area of erebus volcano and subsurface rocks respectively

modelling the impacts of a nitrogen pollution event on the biogeochemistry of an arctic glacier a highly polluted rain event deposited ammonium and nitrate on midtre love nbreen svalbard european high arctic during the melt season in june 1999 quasi daily sampling of glacial runoff showed elevated ion concentrations of both ammonium nh4 and nitrate no3 collectively dissolved inorganic nitrogen din in the two supraglacial meltwater flows but only elevated no3 in the subglacial outburst time series analysis and flow chemistry modelling showed that supra and subglacial assimilation of nh4 were major impacts of this deposition event supraglacial assimilation likely occurred while the pollution event din resided within a the supraglacial slush layer estimated din half life 40 50 hours with the lifetime of no3 exceeding that of nh4 by 30 potentially such processes could affect preservation of din in melt influenced ice cores subglacial routing of event din and its multi day storage beneath the glacier also enabled significant assimilation of nh4 to occur here 60 of input which may have been either released as particulate n later during the melt season or stored until the following year our results complement existing mass balance approaches to the study of glacial biogeochemistry show how modelling can enable time resolved interpretation of process dynamics within the biologically active melt season and highlight the importance of episodic polluted precipitation events as din inputs to arctic glacial ecosystems

shore platform downwearing in eastern canada micro tidal gaspe quebec abstract work has been conducted in the laboratory and field on a micro tidal subhorizontal shore platform in argillaceous rocks at mont louis in gaspe quebec surface downwearing rates for 450 rock samples were measured over 3 years in the laboratory at the neap low mid and high tidal levels under semi diurnal tidal conditions de ionized water was used to determine the role of wetting and drying and artificial sea water for the additional effect of salt and possibly chemical weathering another 300 samples were immersed in de ionized water or artificial sea water for 90 min every 1 2 or 3 weeks representing conditions between the neap and spring high tidal levels and exposed in air for 90 min every 1 2 or 3 weeks to represent conditions between the neap and spring low tidal levels surface downwearing was recorded in the field at 34 transverse micro erosion meter tmem stations most of which were installed along 4 shore normal profiles in 2004 and 2005 mean downwearing rates in the laboratory ranged from 1 25 mm yr 1 at the neap high tidal level to 0 63 mm yr 1 at the neap low tidal level downwearing was much slower between the neap and spring tidal levels and it was uniformly slow below the neap low tidal level the presence of salts inhibited downwearing within the neap tidal range where wetting and drying was dominant and promoted it between the neap and spring high and low tidal levels surface swelling was fairly common in the field and the mean downwearing rate 0 242 mm yr 1 was much lower than in the laboratory possibly because the tmem stations were installed in harder rocks modeling supports the contention that the mont louis platform was cut initially by waves at a higher elevation and then lowered by weathering in the last few thousand years as relative sea level fell to its present elevation

forty three years of micro erosion meter monitoring of erosion rates on shore platforms at kaikōura peninsula south island new zealand abstract using micro erosion meters mem and traversing micro erosion meters tmem surface lowering rates of shore platforms on kaik ura peninsula south island new zealand have been measured over a total of 43 years this record is the longest monitored network of this type since 1973 erosion rates have been calculated over two two year periods 1973 1975 n 31 and 1993 1996 n 55 and at decadal scales 1973 1993 n 15 1973 2004 n 12 1993 2004 n 46 1993 2008 n 34 1993 2016 n 18 1973 2016 n 6 after 43 years surface lowering rates remain similar to previously published rates at an average of 0 525 to 1 181 mm a 1 statistical analysis shows that erosion rates over all measurement periods are derived from the same population thus short term rates derived from two years of monitoring remain indicative of decadal rates of erosion variations between measurement periods are best explained by the loss of the more rapidly eroding bolt sites these losses point to the difficulty of maintaining monitoring over longer time scales a means of statistical manipulation previously published allows for these losses to be accounted for in determining long term rates of platform lowering in november 2016 a mw 7 8 earthquake raised the kaik ura peninsula approximately 0 8 1 m elevating much of the shore platforms above the tide range this earthquake has reset the mem record ending this long running erosion monitoring site of shore platform surface lowering however the mem network is now being used to monitor post earthquake response of the uplift shore platforms and new marine terraces

trickle or treat the dynamics of nutrient export from polar glaciers cold based polar glacier watersheds contain well defined supraglacial ice marginal and proglacial elements that differ in their degree of hydrologic connectivity sources of water e g snow ice and or sediment pore water meltwater residence times allochthonous and autochthonous nutrient and sediment loads we investigated 11 distinct hydrological units along the supraglacial ice marginal and proglacial flow paths that drain joyce glacier in the mcmurdo dry valleys of antarctica we found that these units play unique and important roles as sources and or sinks for dissolved inorganic nitrogen and dissolved inorganic phosphorus and for specific fractions of dissolved organic matter dom as waters are routed from the glacier into nutrient poor downstream ecosystems changes in nutrient export from the glacial system as a whole were observed as the routing and residence times of meltwater changed throughout the melt season the concentrations of major ions in the proglacial stream were inversely proportional to discharge such that there was a relatively constant trickle of these solutes into downstream ecosystems in contrast no3 concentrations generally increased with discharge resulting in delivery of episodic pulses of dissolved inorganic nitrogen rich water treats into those same ecosystems during high discharge events dom concentrations or fluorescence did not correlate with discharge rate but high variability in dom concentrations or fluorescence suggests that dom may be exported downstream as episodic treats but with spatial and or temporal patterns that remain poorly understood the strong nutrient specific responses to changes in hydrology suggest that polar glacier drainage systems may export meltwater with nutrient compositions that vary within and between melt seasons and watersheds because nutrient dynamics identified in this study differ between glacier watersheds with broadly similar hydrology climate and geology we emphasize the need to develop conceptual models of nutrient export that thoroughly integrate the biogeochemical and

using synchronous fluorescence spectroscopy and principal components analysis to monitor dissolved organic matter dynamics in a glacier system the molecular characteristics of dissolved organic matter dom reflect both its source material and its biogeochemical history in glacial systems dom characteristics might be expected to change over the course of a melt season as changes in the glacier drainage system cause the mobilization of dom from different om pools to test this hypothesis we used principal components analysis pca of synchronous fluorescence spectra to detect and describe changes in the dom in meltwater from a glacier system in the coast mountains of northern british columbia canada for most of the melt season the dominant component of subglacially routed meltwater dom is characterized by a tyrosine like fluorophore this dom component is most likely derived from supraglacial snowmelt during periods of high discharge a second component of dom is present which is humic in character and similar to dom sampled from a nearby non glacial stream this dom component is inferred to be derived from a moss covered soil environment that has been glacially overrun it is probably entrained into glacial melt waters when the supraglacial meltwater flux exceeds the capacity of the principal subglacial drainage channels and water floods areas of the glacier bed that are normally isolated from the subglacial drainage system another source of dom also appears to be mobilized during periods of high air temperatures it is characterized by both humic and proteinaceous fluorophores and may be derived from the drainage of supraglacial cryoconite holes copyright 2009 john wiley sons ltd

soil phosphorus cycling in an antarctic polar desert abstract soil phosphorus distribution and cycling in the mcmurdo dry valleys is poorly understood despite its importance for contemporary antarctic ecosystem processes we present data from sequential chemical extractions of phosphorus pools from dry valley soils and sediments on tills across a gradient of surface exposure ages and across potential weathering gradients in stream channels the geologically old but poorly weathered soils of the dry valleys have large phosphorus pools relative to in situ biological requirements these pools are dominated by unweathered p fractions comprising between 60 and 90 of total soil phosphorus among sites occurring on tills ranging in surface exposure ages of approximately 103 106 yrs variation in total phosphorus concentration and availability are related to differences in the initial p content of these tills ross sea tills contain basalts and kenyte which contribute to higher concentrations of phosphorus relative to soils developing on tills deposited by advances of the taylor glacier at local scales physicochemical gradients contribute to variation in weathering rates altering the distribution of phosphorus among chemical fractions which differ in their potential mobility and availability to microorganisms for example hyporheic stream sediments exhibit evidence of phosphorus weathering from primary minerals and loss relative to upland soils adjacent to stream channels dry valley landscapes glaciers lakes streams soils are hydrologically connected providing a mechanism for phosphorus weathering and mobilization in soils and sediments to contribute to the nutrient budgets of adjacent aquatic ecosystems we suggest that landscape history till composition and contemporary subsurface and stream hydrology are the primary controls over phosphorus cycling in the mcmurdo dry valleys

rates and patterns of erosion on inter tidal shore platforms kaikoura peninsula south island new zealand this paper presents measured rates of erosion on shore platforms at kaikoura peninsula south island new zealand surface lowering rates were measured with a micro erosion meter and traversing micro erosion meter the mean lowering rate for all shore platforms was 1 130 mm a 1 differences in lowering rates were found between different platform types and lithologies the rate of surface lowering on type a sloping mudstone platforms was 1 983 mm a 1 and 0 733 mm a 1 on type b mudstone platforms subhorizontal on limestone platforms the lowering rate was 0 875 mm a 1 a previously reported cross shore pattern of surface lowering rates from kaikoura was not found rates were generally higher on the landward margins and decreased in a seaward direction season is shown statistically to influence erosion rates with higher rates during summer than winter the interpretation given to this is that the erosive process is subaerial weathering in the form of wetting and drying and salt weathering this is contrary to views of shore platform development that have favoured marine processes over subaerial weathering copyright 1998 john wiley sons ltd

development of shore platforms on kaikoura peninsula south island new zealand abstract the role of waves in shore platform development has been investigated on kaikoura peninsula by direct measurement of waves in deep water and on platforms at high tide this showed that the deepwater wave environment off the kaikoura peninsula is very energetic but the amount of energy delivered to platforms is very low in deep water wave power ranged from 5900 to 106 700 n m s 1 per m of crest when calculated from mean significant wave height and when calculated from maximum wave height it ranged from 31 400 to 5 370 000 n m s 1 per m of crest a comparison of deep water wave energy flux with wave energy flux at the high tide cliff of platforms showed that there was a reduction by as much as five orders of magnitude during storm conditions an analysis of the role of breaking waves revealed that these are ineffective as an erosional agent because the depth of water offshore causes breaking before waves arrive on platform surfaces depth of water controlling wave breaking causes larger storm waves to break further from shore preventing direct attack at the cliff base shear stresses and dynamic forces under waves were calculated from waves measured on shore platforms this showed that these forces never exceeded the compressive strength of the platform rocks at kaikoura it is concluded that wave forces are not directly capable of causing erosion on shore platforms at kaikoura

comparison of cryoconite organic matter composition from arctic and antarctic glaciers at the molecular level abstract glacier surfaces are reservoirs that contain organic and inorganic debris referred to as cryoconite solar heating of this material results in the formation of water filled depressions that are colonized by a variety of microbes and are hypothesized to play a role in carbon cycling in glacier ecosystems recent studies on cryoconite deposits have focused on their contribution to carbon fluxes to determine whether they are a net source or sink for atmospheric co 2 to better understand carbon cycling in these unique ecosystems the molecular constituents of cryoconite organic matter com require further elucidation com samples from four glaciers were analyzed by targeted extraction of plant and microbial derived biomarkers in conjunction with non targeted nmr experiments to determine the com composition and potential sources several molecular proxies were applied to assess com degradation and microbial activity using samples from greenland the canadian arctic and antarctica com from canadian john evans glacier and greenlandic leverett glacier locations was more chemically heterogeneous than that from the antarctic likely due to inputs from higher plants mosses and sphagnum as suggested by the solvent extractable alkyl lipids and sterols and the detection of lignin and sphagnum derived phenols after cupric oxide chemolysis solid state 13 c nuclear magnetic resonance nmr experiments highlighted the bulk chemical functional groups of com allowing for a general assessment of its degradation stage from the alkyl o alkyl proxy whereas solution state 1 h nmr highlighted both microbial and plant contributions to base soluble extracts from these com samples the dominance of 1 h nmr signals from microbial protein peptides in base soluble extracts of com from antarctica joyce glacier and garwood glacier phospholipid fatty acid plfa biomarker detection and the absence of plant derived biomarkers in both the solvent and cupric oxide extracts suggests that this com is dominated by microbial derived material these results indicate that com carbon composition is dependent on the local glacier environment which may have a profound impact on carbon cycling and sequestration on glacier surfaces

subaerial weathering versus wave processes in shore platform development reappraising the old hat island evidence one of the longest standing debates in rocky coast geomorphology is whether subaerial weathering or wave processes dominate shore platform evolution the origins of this debate date to the mid nineteenth century when the first descriptions of old hat islands were provided from northern new zealand old hat islands are surrounded by a broad near horizontal shore platform their formation was inferred to relate to subaerial weathering of bedrock to a level of permanent saturation with wave processes acting only to remove the weathered debris to date no detailed topographic surveys have been conducted on the old hat islands in new zealand that initiated this debate in this study we provide the first quantitative data on the original field sites topographical surveying and schmidt hammer hardness testing were conducted on 25 profiles of varying wave exposure in contrast to the classic descriptions platform elevation varies from just above mean high water spring mhws at the most exposed sites to mean high water neap mhwn at the most protected sites or mean sea level msl where beaches occur on the platform surface there is no significant difference between the hardness of the cliffs and the platforms fronting them and no clear relationship between wave exposure and platform width rather than being exclusively dominated by subaerial process the formation of microtidal sheltered old hat island platforms is considered to be a function of i the rate of weathering ii exposure to wave energy iii nearshore water depth and iv rock resistance shore platform elevation in the study area is thought to be a function of the level at which waves erode cliff rock and the action of weathering which lowers platform surfaces the width of platforms is strongly influenced by the ability of waves to dissect the platform edge along vertical joint lines copyright 2010 john wiley sons ltd

direct observations of aluminosilicate weathering in the hyporheic zone of an antarctic dry valley stream abstract this study focused on chemical weathering and bacterial ecology in the hyporheic zone of green creek a mcmurdo dry valley antarctica stream an in situ microcosm approach was used to observe dissolution features on the basal plane surface of muscovite mica four mica chips were buried in december 1999 and dug up 39 d later atomic force microscopy afm of the basal plane surfaces revealed small anhedral 10 a deep etch pits covering 4 of the surfaces from which an approximate basal plane dissolution rate of 8 3 10 18 mol muscovite cm 2 s 1 was calculated on the basis of the geometric surface area for the study period this is an integrated initial dissolution rate on a fresh surface exposed for a relatively brief period over the austral summer and should not be compared directly to other long term field rates the observation of weathering features on mica agrees with previous stream and watershed scale studies in the dry valleys which have demonstrated that weathering occurs where liquid water is present despite the cold temperatures afm imaging of mica surfaces revealed biofilms including numerous small

tidal wetting and drying on shore platforms an experimental study of surface expansion and contraction laboratory experiments have been conducted to measure rock expansion and contraction induced by wetting and drying on intertidal shore platforms in eastern canada almost 800 rock cores and cubes were subjected to between 800 and 1000 tidal cycles the rocks were put into tidal simulators and inundated in de ionized water for 1 6 or 11 h of each 12 h cycle replicating conditions at the high mid and low tidal levels respectively micro erosion meter mem stations were also installed in slabs of argillite sandstone and basalt the slabs were subjected to conditions at the high mid and low tidal levels and a traversing mem was used to measure rock expansion and contraction as the slabs dried in air with variable temperature and humidity during low tide the slabs were also exposed for long periods to air with variable humidity cores and cubes often gained in weight when they absorbed or adsorbed water and retained it for periods ranging from 1 month to 1 year or more although this did not appear to be a prelude to rock breakdown tidal wetting and drying and exposure to humid air caused the argillite and basalt slabs to expand and contract by up to 0 14 and 0 04 mm respectively wetting and drying did not induce expansion or contraction of the sandstone but the sandstone did respond slightly to changes in air humidity the greatest amount of expansion and contraction was at the high tidal level in the argillite and at the mid tidal level in the basalt which is consistent with previously measured rates of downwearing

the influence of rock resistance on coastal morphology around lord howe island southwest pacific an erratum has been published for this article in earth surface processes and landforms 27 7 2004 931 lord howe island in the northern tasman sea is a remnant of a much larger late miocene basaltic shield volcano much of the island s coastline is exposed to waves that have unlimited fetch but a marked contrast is provided by a fringing coral reef and lagoon that very effectively attenuate wave energy along a portion of the western coastline the geology of the island is varied with hard and resistant basalt lavas breccias and tuffs of intermediate resistance and highly erodible eolianites this variability provides an excellent opportunity to examine the in uence of rock resistance on the development of the spectacular rock coast landforms that occur around the island the hardness of rocks and the extent of weathering around the coastline were assessed using a schmidt hammer and statistical analysis was undertaken to remove outlying values on all but one occasion higher mean rebound values were returned from fresh surfaces than weathered surfaces but only half of these differences were statistically signi cant shore platforms with two distinct levels are juxtaposed along two stretches of coastline and schmidt hammer results lend support to hypotheses that the raised surfaces may be inherited features relative rock resistance was assessed through a combination of schmidt hammer data and measurements of joint density and constrained on the basis of morphological data this approach formed a basis for examining threshold conditions for sea cliff erosion at lord howe island in the context of the distribution of resistant plunging cliffs and erosional shore platforms copyright 2004 john wiley sons ltd

meltwater chemistry and solute export from a greenland ice sheet catchment watson river west greenland summary solute export from the greenland ice sheet gris to coastal regions around greenland is likely to increase in the future as a consequence of increasing icemelt production here we present hydrochemical characteristics solute and major ion exports and chemical denudation rates for 2007 2010 for the watson river sector of the gris that drains into the fjord kangerlussuaq the hydrochemistry is dominated by ca2 and hco3 with a relatively high molar k na ratio of 0 6 0 1 typical for meltwaters draining a gneissic lithology low molar ca2 na and mg2 na ratios indicate that weathering of disseminated carbonates contributes less than silicate weathering to the chemical composition the solute export varied between 33 103 2009 and 61 103 tons 2010 showing that increasing discharge leads to increasing solute export at the catchment scale deviations between ion yield estimates derived from use of discharge weighted and mean daily concentrations methods were generally less than 5 indicating that the choice of method is of less importance the chemical denudation rates ranged between 36 and 56 meq m 2 per year which are lower than previous records from glacierized catchments however when normalized by discharge the denudation rates are comparable to other arctic sites when extrapolating the results from the watson river catchment to the entire greenland for 2007 2010 the solute export from greenland meltwater varied between 7 1 106 and 7 8 106 tons whilst the major ion export was between 6 4 106 and 7 3 106 tons dissolved fe a potential biolimiting nutrient for primary productivity in the north atlantic had annual export rates from greenland between 15 103 and 52 103 tons

chemical weathering in the foreland of a retreating glacier chemical denudation rates and strontium isotope ratios in streams vary substantially and systematically in the foreland of the retreating bench glacier in south central alaska to study weathering of young glacier sediments we sampled 12 streams draining a chronosequence of till and moraine soils derived from cretaceous metagraywacke metapelite bedrock both sediment age and vegetation cover increase with distance from the glacier cation denudation rates decline with increasing distance from the glacier whereas silica denudation rates increase carbonate dissolution and sulfide oxidation account for roughly 90 of the solute flux from the youngest sediments biotite alteration accounts for 5 11 of the solute flux its peak contribution is found in the glacier outlet stream silicate weathering is the dominant reaction only in the oldest sediments in a laboratory dissolution experiment using fresh glacial sediment carbonate dissolution dominated the solute flux during the first 700 hours paralleling the behavior of young sediments in the field in contrast to trends in the field the silica flux did not increase after the carbonate was exhausted from the reactor a possible reason for this difference is that establishment of vegetation causes an increase in silicate weathering the 87sr 86sr ratio in the glacier outlet stream is greater than that in proglacial streams and in bulk rock due to a greater contribution of biotite weathering in the outlet than in proglacial streams strontium isotope ratios decline with sediment exposure age in the proglacial streams and are consistent with a carbonate source because the dominant weathering reactions in the young sediments are of carbonate and sulfide rather than silicate minerals weathering at the glacier margin is not an important long term sink for atmospheric co2

modeling the erosion of cohesive clay coasts a model was developed to study the erosion of cohesive clay coasts in macro to non tidal environments the model shares some of the characteristics of previous models including the erosion of bare clay surfaces by wave generated bottom shear stresses and of mobile sediment covered surfaces by abrasion it differs from previous models however in several important ways the morphodynamics of beaches with clay foundations under different wave conditions are based on a previously developed model for beaches on rocky shore platforms sediment thickness along a beach profile is calculated at regular intervals and compared with the maximum thickness that could be moved at that location under prevailing wave conditions wave friction factors are determined where necessary according to the occurrence and morphology of ripples on the bottom in addition to abrasion and the effect of wave induced shear stresses on the clay bottom erosion by stresses generated by wave impact at the bluff foot and on the intertidal platform is calculated using an expression derived from hard rock coastal models tides are represented by their computed tidal duration values the amount of time each year that the water level falls within each 0 1 m vertical interval water depths are modified by wave setup and set down conditions several preliminary model runs were made the profiles were concave in the submarine zone and roughly linear in the intertidal zone equilibrium profiles developed which were maintained as they migrated landwards

modelling the quaternary evolution of shore platforms and erosional continental shelves a mathematical model was used to investigate the effect of glacially induced fluctuations in sea level on the evolution of wave cut shore platforms and erosional continental shelves during the quaternary the model used two deep water wave sets which were used to calculate breaker height and depth and the force of the waves at the waterline according to the width and bottom roughness of the surf zone and the gradient of the submarine slope the model also incorporated an erosional threshold related to the strength of the rocks the number of hours each year in which the water level is at each intertidal elevation and the amount and persistence of the debris at the cliff foot most runs were made using a sea level model that consisted of 26 glacial cycles from 2 million to 0 9 million years ago and nine of approximately twice the amplitude and wavelength in the last 0 9 million years the model emphasized the dynamic association between the contemporary intertidal platform and the continental shelf both surfaces trend towards a state of static equilibrium under oscillating sea level conditions when attenuated waves are unable to continue eroding the rock if there has not been enough time to reduce the gradient of the shallower portions of the continental shelf however intertidal shore platforms can be in a temporary though possibly long lasting state of dynamic equilibrium the model suggests that most platforms are at least in part inherited from one or in many cases more interglacial stages when sea level was similar to today s copyright 2001 john wiley sons ltd

frost weathering and the saturation of coastal rocks measurements were made of the water content in coastal rocks by simulating tidal oscillations in the laboratory and by field measurement in eastern canada if rapid freezing takes place upon exposure to the air saturation levels may be high enough to permit frost weathering in fine grained rocks in the lower portions of the intertidal zone near the high tidal level however it may be dependent upon a supply of water from the ice foot and from melting snow if freezing is slow frost action may be inhibited by desorption of the rocks while they are exposed by the ebb tide there was no evidence of a level of permanent sea water saturation within the intertidal zone ambient temperature and humidity may affect the rate of rock desorption

biogeochemical evolution of cryoconite holes on canada glacier taylor valley antarctica 1 the cryoconite holes of the mcmurdo dry valleys are simple closed biogeochemical systems involving water ice mineral and organic debris which serve as ecosystems for consortia of microorganisms this study is the first to document the seasonal and annual chemical evolution of solutes in cryoconite holes samples of glacier ice frozen cryoconite holes and those containing water were collected during the austral summer of 2005 2006 the isolation age was calculated from the excess cl in the holes and varied from 0 to 5 years a consistent with the last hot summer when the cryoconite holes were open to the atmosphere the holes progressively deepen with isolation age variations in dic doc k and so42 suggest that dissolution of primary minerals in the cryoconite debris cyclical precipitation and dissolution of secondary carbonates net photosynthesis over summer and net respiration during the autumnal freeze are the principal reactions which perturb the seasonal and annual solute concentrations in the holes doc is generated in the holes at a rate of 7 5 g c cm 2 a 1 and non sea salt k accumulates in frozen holes at a rate of 0 073 eq cm 2 a 1 we infer that c cycling is complex even in these otherwise simple systems

tidal wetting and drying on shore platforms an experimental assessment abstract rocks were subjected to wetting and drying cycles with de ionized water under real time conditions using tidal simulators one third of the samples experienced 11 h of exposure and 1 h of inundation over a 12 h tidal cycle representing high tidal conditions one third experienced 6 h of exposure and 6 h of inundation representing mid tidal conditions and one third experienced 1 h of exposure and 11 h of inundation representing low tidal conditions we obtained 324 cores from igneous metamorphic and sedimentary rocks from ontario which were exposed to more than 930 wetting and drying cycles over 16 months we obtained 675 cores and cubes from basalts sandstones and argillites from shore platforms in eastern canada which were exposed to about 700 cycles over 12 months many of the cores and cubes experienced very little to no breakdown particularly those from the igneous and metamorphic rocks of ontario sandstones from a sloping platform in the macrotidal bay of fundy and argillites from a horizontal mesotidal platform in gaspe quebec were the most susceptible rock types with equivalent surface downwearing rates ranging from 0 to 4 mm year 1 the results suggest that downwearing rates decrease with elevation within the intertidal zone probably because rocks require much longer to desorb than to absorb water the experiments demonstrated that wetting and drying can be an important process on shore platforms in some types of rock helping to lower the height and reduce the gradient of sloping macrotidal platforms and to reduce the height of horizontal micro and mesotidal platforms

transverse micro erosion meter measurements determining minimum sample size two transverse micro erosion meter tmem stations were installed in each of four rock slabs a slate shale basalt phyllite schist and sandstone one station was sprayed each day with fresh water and the other with a synthetic sea water solution salt water to record changes in surface elevation usually downwearing but with some swelling 100 measurements the pilot survey the maximum for the tmem used in this study were made at each station in february 2010 and then at two monthly intervals until february 2011 the data were normalized using box cox transformations and analyzed to determine the minimum number of measurements needed to obtain station means that fall within a range of confidence limits of the population means and the means of the pilot survey the effect on the confidence limits of reducing an already small number of measurements say 15 or less is much greater than that of reducing a much larger number of measurements say more than 50 by the same amount there was a tendency for the number of measurements for the same confidence limits to increase with the rate of downwearing although it was also dependent on whether the surface was treated with fresh or salt water about 10 measurements often provided fairly reasonable estimates of rates of surface change but with fairly high percentage confidence intervals in slowly eroding rocks however many more measurements were generally needed to derive means within 10 of the population means the results were tabulated and graphed to provide an indication of the approximate number of measurements required for given confidence limits and the confidence limits that might be attained for a given number of measurements

hydrologic connectivity and implications for ecosystem processes lessons from naked watersheds abstract hydrologic connectivity has received great attention recently as our conceptual models of watersheds and water quality have evolved in the past several decades however the structural complexity of most temperate watersheds i e connections among shallow soils deep aquifers the atmosphere and streams and the dynamic seasonal changes that occur within them i e plant senescence which impacts evapotranspiration create significant challenges to characterizing or quantifying hydrologic connectivity the mcmurdo dry valleys a polar desert in antarctica provide a unique opportunity to study hydrologic connectivity because there is no vegetative cover and therefore no transpiration and no deep aquifers connected to surface soils or streams glacier melt provides stream flow to well established channels and closed basin ice covered lakes on the valley floor streams are also connected to shallow hyporheic zones along their lengths which are bounded at 75 cm depth by ice cemented permafrost these hydrologic features and connections provide water for and underpin biological communities hence exchange of water among them provides a vector for exchange of energy and dissolved solutes connectivity is dynamic on timescales of a day to a flow season 6 12 weeks as streamflow varies over these timescales the timescales over which these connections occur is also dynamic exchanges between streams and hyporheic zones for example have been estimated to be as short as hours to as long as several weeks these exchanges have significant implications for the biogeochemistry of these systems and the biotic communities in each feature here we evaluate the lessons we can learn about hydrologic connectivity in the mdv watersheds that are simplified in the context of processes occurring and water reservoirs included in the landscape yet are sensitive to climate controls and contain substantial physical heterogeneity we specifically explore several metrics that are simple and or commonly employed in hydrologic analyses and interpret them in the context of connectivity between and among hydrologic features

glacier meltwater hydrochemistry abstract glacierised areas present an ideal environment in which to study water rock interaction since chemical weathering rates are high and anthropogenic impacts are often minimal detailed investigations of meltwater quality variations have suggested the importance of these environments in estimates of terrestrial chemical erosion and global biogeochemical cycles most notably the role of meltwaters in co2 sequestration during episodes of deglaciation has attracted considerable attention since this may impact on climate at glacial interglacial timescales however there is still considerable uncertainty surrounding estimates of co2 drawdown by meltwaters which remains to be resolved water flow through glaciers exerts an important control on ice mass dynamics and influences the quantity and quality of water delivered to environments downstream of glacierised basins thus the study of the configuration and dynamics of subglacial drainage systems is important not only to enhance scientific understanding but also to allow effective water resource utilisation in glacierised headwater catchments bulk meltwater quality characteristics draining terrestrial ice masses also offer the potential to provide unique information on hydrological and hydrochemical processes operating in the inaccessible subglacial environment here significant advances have been made in understanding the controls on chemical weathering reactions based on the identification of key dissolved indicator species this has allowed water quality variations to be exploited as a tool for both subglacial hydrochemical and hydrological investigations as a result this area of glaciology has received considerable attention in recent years utilising an increasing range of dissolved ions and integrating field and laboratory studies however uncertainty still surrounds certain areas of meltwater quality science including the role of microorganisms in a system which to date has largely been viewed as abiotic a better understanding of the processes and rates of chemical weathering in glacierised environments has the potential to enhance our understanding of the environment and to facilitate the exploitation of water quality variations for both scientific and applied objectives in this paper the development and current state of meltwater quality science as a tool for investigating subglacial hydrology and geochemistry is detailed and problems and future directions identified this will hopefully stimulate wider interest in an important area of aquatic chemistry with significant applied implications

a blue ice ecosystem on the margins of the east antarctic ice sheet freezing temperatures desiccation and high levels of solar radiation make the surface of the antarctic ice sheet one of earth s harshest habitats however our study in the vestfold hills area of east antarctica shows that favourable conditions for microbial production become established just beneath the surface of blue ice areas which collectively cover about 2 of the ice sheet periphery their translucent wind polished surface allows solar heating to create meltwater in a greenhouse type environment at depths of up to 1m melting is intensified around dark debris particles or cryoconite where we found microbiological activity to be greatest rates of photosynthesis average 2060 ngc g cryoconite 1 d 1 were adapted to low light intensities 10 of surface irradiance values and most likely dominated by cyanobacteria and chloroplastida a heterotrophic bacterial community was also found to be active within the cryoconite although average bacterial growth rates 5 7 ngc g cryoconite 1 d 1 were far lower than average community respiration 1870 ng c g cryoconite 1 d 1 the majority of the respired carbon was most likely associated with the autotrophs and several protists therefore blue ice areas constitute oases for microbial life around the periphery of earth s coldest ice sheet

nitrate production beneath a high arctic glacier svalbard natural environmental isotopes of nitrate and ammonium are used in conjunction with major ion chemistry and hydrological data to establish controls upon the biogeochemical cycling of nitrogen beneath a high arctic polythermal glacier midtre lovenbreen here high nitrate concentrations in subglacial meltwaters suggest that the subglacial environment may be furnishing nitrate in excess of that released from the snowpack and glacier ice isotopic values of 18ono3 suggest the provenance of such excess nitrate to be microbial in origin and 15nno3 indicates the source nitrogen compounds to have high 15n values relative to supraglacial runoff we address the nitrification of supraglacial ammonium the mineralization of organic nitrogen and the oxidation of geologic ammonium as potential sources of this additional nitrate mass fluxes of n compounds in a subglacial river and their 15n ratios indicate that the nitrification of supraglacial ammonium delivered to the glacier bed can account for much but not all of the excess nitrate the additional source most likely involves the mineralization of organic nitrogen although 15n values in rock samples suggest that the dissolution of rock derived ammonium cannot be discounted if large fractionation effects occur during dissolution our results therefore agree with previous catchment scale mass balance studies at the site which report a major internal loss of nh4 from the snowpack following melt however at the catchment scale the nh4 loss is greater than the excess of no3 observed in runoff indicating that microbial assimilation of ammonia into organic matter in a range of other habitats is also likely the identification of nh4 assimilation and nitrification further highlights the non conservative behaviour of nitrogen in glacial environments and testifies to the importance of microbially mediated reactions in the biogeochemical cycling of nitrogen in an environment that has until recently been regarded as biologically inert

rocky coasts their role as depositional environments abstract the role of rocky coasts as depositional environments has been generally neglected by rock and depositional coast workers although rock coasts can be hostile sedimentary environments they frequently host a variety of deposits consisting of mixes of boulders and megaclasts to sand and cobbles these deposits include pockets of sand and pebble trapped in topographic depressions or at the foot of scarps and cliffs isolated boulders pocket beaches trapped between headlands and sand to boulder beaches in shallow bays exposed to strong wave action the tectonic setting which is reflected in the degree of geological heterogeneity alongshore together with the wave regime and other elements of the morphogenic environment help to determine the amount and mobility of the sediment and consequently whether it plays an essentially abrasional or protectional role many beaches have a resistant rock foundation which will modulate their response to rising sea level and possibly increased storminess during this century wave refraction and temporal and spatial changes in sediment abrasional and protectional efficacy influence the development of crenulated planforms on coasts with a high degree of geological heterogeneity and possibly on more geologically homogeneous coasts with longshore variations in cliff height or in the amount of sediment theory suggests that these coasts may develop equilibrium planforms with uniform rates of erosion in bays and on headlands or they may undergo a series of cyclical transformations involving alternating increases and decreases in the depth of the bays relative to the headlands

diel stream geochemistry taylor valley antarctica unlike temperate and polythermal proglacial streams the proglacial streams in taylor valley tv antarctica are derived primarily from glacier surface melt with no subglacial or groundwater additions solute responses to flow reflect only the interaction of glacial meltwater with the valley floor surrounding the stream channel we have investigated the major minor and trace element 24 h variations of two proglacial melt streams andersen creek and canada stream originating from the canada glacier in tv antarctica both streams exhibited diel mid austral summer diurnal flow variation with maximum flow being more than 50 times the minimum flow dissolved 0 4 m major minor and trace solute behaviors through diel periods were strongly controlled by the availability of readily solubilized material on the valley floor and hyporheic biological exchanges anderson creek had generally greater solute concentrations than canada stream because of its greater receipt of eolian sediment andersen creek also acquired greater solute concentrations in the rising limb of the hydrograph than the falling limb because of dissolution of eolian material at the surface of the stream channel coupled with minimal hyporheic biological exchange conversely canada stream had less available eolian sediment but a greater hyporheic biological exchange which preferentially removed trace and major solutes in the rising limb and released them in the falling limb given the dynamic nature of discharge eolian and hyporheic biological processes solute loads in tv streams are difficult to predict copyright 2012 john wiley sons ltd