combined oceanic and atmospheric influences on net accumulation on devon ice cap nunavut canada an annual net accumulation history of the high elevation region of devon ice cap nunavut canada was reconstructed for the period 1963 2003 using five shallow firn cores annual net accumulation decreased significantly after 1989 to explain variability in the reconstructed annual net accumulation record monthly and seasonal moisture source probabilities were calculated for gridcells throughout the arctic during 1979 2003 seasonally moisture source probabilities reach a maximum in northern baffin bay in late summer early fall and approach zero throughout the arctic in winter late summer early fall moisture source probabilities were significantly higher around the north open water now polynya during the 4 year period of highest annual net accumulation during the 1979 2003 period 1984 87 than during the 4 year period with the lowest annual net accumulation 1994 97 this is due to both a significant decrease in the sea ice fraction and a significant increase in low elevation atmospheric transport over the now area during the high net accumulation period anomalously low net accumulation and anomalously high firnification rates during the 1989 2003 period suggest that a change in ice dynamics rather than a change in surface mass balance may explain recent ice cap thickening observed by laser altimetry

time dependent wind driven flow over a shallow midshelf submarine bank 1 during summer 2001 high resolution hydrographic velocity and bio optical surveys were conducted over heceta bank off central oregon north of the bank upwelling over simple bottom topography exhibited a classic response with a midshelf baroclinic coastal jet and upwelled isopycnals the coastal upwelling jet follows the bank topography as it widens offshore before reaching the southern end of the bank where the shelf break turns almost 90 back toward the coast the ensuing adjustment involves the offshelf transport of coastal water and the material it contains the jet meanders anticyclonically in the lee of the bank before resuming its equatorward path seaward of the shelf break a pool of high chlorophyll 15 mg m 3 near surface water is found in the low velocity lee region created by the bank a low temperature high salinity bottom water pool supplied primarily from the south lies over the inshore region of the bank this bottom pool is up to 40 m thick and contains elevated levels of suspended material by creating an east west perturbation in the coastal upwelling front the flow topography interaction introduces an alongshore pressure gradient when southward upwelling favorable winds relax this alongshore pressure gradient can drive flow back to the north this leads to northward flow on the inshore side of the bank ultimately setting up the potential for recirculation around the entire bank complex on a timescale of about 10 days strong northward winds during summer lead to downwelling within 15 km of the coast accompanied by significant 0 2 m s 1 wind driven northward currents

georadar derived estimates of firn density in the percolation zone western greenland ice sheet 1 greater understanding of variations in firn densification is needed to distinguish between dynamic and melt driven elevation changes on the greenland ice sheet this is especially true in greenland s percolation zone where firn density profiles are poorly documented because few ice cores are extracted in regions with surface melt we used georadar to investigate firn density variations with depth along a 70 km transect through a portion of the accumulation area in western greenland that partially melts we estimated electromagnetic wave velocity by inverting reflection traveltimes picked from common midpoint gathers we followed a procedure designed to find the simplest velocity versus depth model that describes the data within estimated uncertainty on the basis of the velocities we estimated 13 depth density profiles of the upper 80 m using a petrophysical model based on the complex refractive index method equation at the highest elevation site our density profile is consistent with nearby core data acquired in the same year our profiles at the six highest elevation sites match an empirically based densification model for dry firn indicating relatively minor amounts of water infiltration and densification by melt and refreeze in this higher region of the percolation zone at the four lowest elevation sites our profiles reach ice densities at substantially shallower depths implying considerable meltwater infiltration and ice layer development in this lower region of the percolation zone the separation between these two regions is 8 km and spans 60 m of elevation which suggests that the balance between dry firn and melt induced densification processes is sensitive to minor changes in melt

landforms as extended composite phenotypes biotic influences on geomorphology and vice versa are ubiquitous this paper explores whether landforms may be extended composite phenotypes of biota based on four criteria process form relationships between biota and landforms evolutionary synchrony selective pressure via ecosystem engineering and niche construction and positive feedback benefitting the engineer organism s coral reefs peat bogs biomantles insect mounds grassland soils salt marshes mangrove swamps and some vegetation dependent sand dune types clearly meet these criteria karst landforms meandering rivers and tree uprooting pit mound systems meet the first three criteria but positive feedback to engineer organisms has not been established research in biogeomorphology will surely identify other extended phenotypes implications are that biological evolution will continue to drive landscape metamorphosis the appearance of new landform types and presumably the disappearance of extended phenotypes associated with extinct species independently of extended phenotypes tightly coupled geomorphological ecological interactions such as coevolution and biogeomorphic forms of ecosystem engineering and niche construction are common the toposphere encompassing earth s landforms is partly a biotic construct some elements would be present in an abiotic world but the toposphere would not exist in anything resembling its contemporary state without a biosphere this raises important questions with respect to earth system evolution the bio litho atmo hydro topo and pedospheres coevolve at the global scale major biotic events have driven revolutions in the other spheres but the atmosphere and the global hydrological system seem to have been relatively steady state at the global scale the toposphere and pedosphere have not this suggests that perhaps landforms and soils provide the major mechanisms or degrees of freedom by which earth responds to biological evolution landforms and soils may thus be the voice of the biosphere as it authors planetary change even if clear biotic signatures are lacking copyright 2015 john wiley sons ltd

sediment transport over an accretional intertidal flat with influences of reclamation jiangsu coast china this paper focuses on the hydrodynamic and suspended sediment transport processes in response to sequential reclamations over the intertidal flat jiangsu coast which used to be one of the widest intertidal flats in china investigations into the sediment transport patterns reveal that net suspended sediment fluxes increased from 102 kg m 1 on the upper intertidal flat to 103 4 kg m 1 on the lower intertidal flat per tidal cycle this variation was caused mainly by the phases of the current velocity suspended sediment concentration ssc local bed geomorphology inundation patterns and extreme weather conditions the longshore component of tidal currents intensifies seaward over the intertidal flat extreme weather conditions e g storms and strong winds were important factors affecting the current velocity structures the intensity of residual currents and the sscs the sscs were characterized by several peaks throughout the tidal cycle these peaks were associated with strong currents combined wave current interactions and intense turbulences due to the initial flood surge furthermore the suspended sediment was finer and contained more clay materials during the flood phase of the tidal cycle than during the ebb fine particles were transported within the upper water column by landward residual currents but coarse particles were transported within the lower water column by seaward residual currents overall residual currents were apt to transport fine grained sediment landward and coarse grained sediment seaward this pattern indicates that the suspended sediment fluxes are highly variable in the water column even for very shallow tidal environments the cross shore component accounted only for a small percentage of the total sediment flux however this part of sediment supply dominated accretion over the intertidal flat the intertidal flat has become narrower and steeper following sequential reclamations a negative feedback process existed to maintain the convex profile shape although the human activities i e reclamation could have modified the natural process the surficial sediment tended to become finer on the mid upper intertidal flat but coarser on the lower intertidal flat following reclamations in response to a reduction in the tidal currents over the intertidal zone and enhancement of wave action over the lower intertidal flat accretion with high rates was maintained by landward transport of sediment in such an accretional system with influences of reclamation the width or slope of the intertidal flat is adjusted continuously before the cease of reclamation the intertidal flat is unable to achieve an equilibrium shape

changes in melt season characteristics on devon ice cap canada and their association with the arctic atmospheric circulation using june august surface meteorological measurements for 2004 10 we found that the duration of the summer melt season at elevations of 1800 1300 and 1000 m a s l on devon ice cap canada increased at a rate of 3 4 p p p 1 respectively the calculated surface melt rate at 1300m a s l increased from 74 to 133 cm w e a 1 between 2007 and 2010 these changes are linked to two types of change in the arctic atmospheric circulation strengthening of the 500 hpa ridge over the arctic in june july resulted in increases in both the advection of warm air into the region and the occurrence of cloud free conditions over the ice cap causing the available melt energy to increase by 4 24 relative to june july 2007 10 mean conditions more frequent southwesterly low pressure systems in august after 2004 accounted for a 12 38 increase in available melt energy relative to the august 2007 10 daily mean due to advection of warm air into the arctic reduced incoming shortwave radiation and increased net longwave radiation this delayed the timing of freeze up by an average of 5 5 days a 1 p

coastal wind driven circulation in the vicinity of a bank part ii modeling flow over the heceta bank complex on the oregon coast abstract this study investigates wind driven circulation in the vicinity of the heceta bank complex along the oregon shelf numerical experiments forced with steady winds 0 1 pa are conducted upwelling and downwelling cases are compared the asymmetric bank bathymetry is the only configurational difference from the symmetric bank runs analyzed in part i whitney and allen upwelling favorable winds generate an upwelling front and southward baroclinic jet model results indicate the upwelling jet is centered on the 100 m isobath along the straight shelf the jet follows this isobath offshore around the northern part of the bank but separates from sharply turning isobaths in the southern half and flows over deeper waters the jet turns back toward the coast farther downstream inshore of the main jet currents reverse and flow back onto the bank these reversed currents turn southward again at the bank center and join a secondary southward coastal upwelling jet this secondary coastal jet converges wi

control of estuarine sediment dynamics by interactions between currents and waves at several scales abstract the effect of interactions between continuous tidal currents and intermittent waves processes on sediment dynamics and transport is addressed by presenting detailed field measurements of waves boundary layer currents and suspended sediment from an estuarine channel and an adjacent intertidal sandflat in manukau harbour new zealand the aim is to determine in what ways it is necessary to couple waves and currents in numerical models and thereby put limits on the fundamental structure of process based estuarine sediment transport models waves were important on the intertidal flat turbidity switched on and off with the appearance and disappearance of waves wave groups dominated entrainment of bed sediment a wave current boundary layer model explained measured bed shear stress and hydraulic roughness and the measured near bed time averaged suspended sediment concentration was mostly well predicted by a pure wave model both the waves themselves and wave related processes varied markedly over the tidal cycle the variation in the former principally changes in wave height was related to changes in fetch caused by the harbour wide emergence and submergence of intertidal regions the variation in the latter was related to changes in water depth relative to the wavelength of the waves which controlled the penetration to the bed of wave orbital currents in addition to the variation over the tidal cycle in the intensity of wave processes there was also a change in kind which occurred with the arrival at the measurement site of the turbid fringe which is the narrow highly turbid edge of the estuarine water body the relationship between suspended sediment concentration and wave orbital velocity in the turbid fringe was radically different to the relationship in the estuarine water body proper which suggests a change in dynamics perhaps related to breaking waves a hybrid modelling approach is required i e one that treats discrete events but resolves tidal cycle scale variation within the event there is a need to resolve the variation in the wave train over the tidal cycle and the penetration to the bed of wave orbital motions both of which could only be done adequately within an estuary tidal model in contrast to the situation on the intertidal flat where waves intermittently entrained sediment sediment transport in the channel was continuous driven by tidal currents to predict sediment flux in the channel we need to know the upstream sediment transporting capacity of the flow including that contributed by waves the character of the bed sediment and the sediment settling time scale these factors confounded even the simplest notion of flood and ebb dominance which frequently has been applied to understand estuarine morphodynamics

vertical and horizontal structure is suspended sand concentrations and wave induced fluxes over bedforms abstract high resolution measurements of suspended sand concentrations have been made using a multi transducer acoustic back scatter sensor over both steep and flat bedforms under low energy swell conditions with weak currents present on a micro tidal beach in the southwest of england similar measurements were made over steep bedforms in a large scale laboratory wave basin using a wave record simulated from field data a detailed interpretation of the suspension process associated with steep vortex type ripples was made possible with knowledge of the position of the acoustic sensors relative to the bedform geometry analysis of time averaged wave ensemble averaged suspended sediment concentrations and velocity concentration phase angles indicates that the bedforms are an important control on the suspension patterns produced by wave induced flows steep asymmetric ripples under shoaling waves produces greater amounts of suspension than low steepness ripples due to the effects of vortex ejection associated with the steep ripples over rippled beds we find evidence for a significant phase couplined between the resuspended sediment and the bedforms in the near bed region

grain size characteristics of the extant tidal flat sediments along the jiangsu coast china abstract five types of sediments have been identified for the tidal flat deposits along the jiangsu coast 1 fine sand 2 sandy silt 3 silt 4 clayey silt and 5 clay among these the silt deposits including sandy silt silt and clayey silt with median grain diameter of 4 7 are the dominant sediments within this particular intertidal environment they normally have good sorting and are symmetrical or positively skewed and single and or double modal in grain size distribution this type of sediment in terms of grain size characteristics has a very close relationship to its source sediments provided by the two large rivers in the region i e changjiang river and huanghe river the dominant mode for the sediments transported into the environment is suspended load due to the active tidal regime over the region grain size diameters decrease normally from offshore towards onshore in two forms along the jiangsu coast a a step like curve with sharp change occurring at the mud flat and 2 a smooth concave up curve comparing these results with their coastal topographic profiles and sediment dynamic features it is found that form 1 is related to steady accretional progradational tidal flat profiles in the middle part of the coastline and form 2 to erosional stable profiles near the old river deltas the differences in the grain sizes and distribution patterns of the sediments between the northern and the southern parts of the region are mainly due to the difference in sources i e huanghe river sediments dominate the northern part and changjiang river sediments prevail in the southern part except this fluvial control the modern tidal hydrodynamics has also played an important role in the distribution of the coastal and nearshore sediments this is particularly so over the tidal flats rather than in the subtidal offshore area

acceleration of the contribution of the greenland and antarctic ice sheets to sea level rise 1 ice sheet mass balance estimates have improved substantially in recent years using a variety of techniques over different time periods and at various levels of spatial detail considerable disparity remains between these estimates due to the inherent uncertainties of each method the lack of detailed comparison between independent estimates and the effect of temporal modulations in ice sheet surface mass balance here we present a consistent record of mass balance for the greenland and antarctic ice sheets over the past two decades validated by the comparison of two independent techniques over the last 8 years one differencing perimeter loss from net accumulation and one using a dense time series of time variable gravity we find excellent agreement between the two techniques for absolute mass loss and acceleration of mass loss in 2006 the greenland and antarctic ice sheets experienced a combined mass loss of 475 158 gt yr equivalent to 1 3 0 4 mm yr sea level rise notably the acceleration in ice sheet loss over the last 18 years was 21 9 1 gt yr2 for greenland and 14 5 2 gt yr2 for antarctica for a combined total of 36 3 2 gt yr2 this acceleration is 3 times larger than for mountain glaciers and ice caps 12 6 gt yr2 if this trend continues ice sheets will be the dominant contributor to sea level rise in the 21st century

the extreme melt across the greenland ice sheet in 2012 1 the discovery of the 2012 extreme melt event across almost the entire surface of the greenland ice sheet is presented data from three different satellite sensors including the oceansat 2 scatterometer the moderate resolution imaging spectroradiometer and the special sensor microwave imager sounder are combined to obtain composite melt maps representing the most complete melt conditions detectable across the ice sheet satellite observations reveal that melt occurred at or near the surface of the greenland ice sheet across 98 6 of its entire extent on 12 july 2012 including the usually cold polar areas at high altitudes like summit in the dry snow facies of the ice sheet this melt event coincided with an anomalous ridge of warm air that became stagnant over greenland as seen in melt occurrences from multiple ice core records at summit reported in the published literature such a melt event is rare with the last significant one occurring in 1889 and the next previous one around seven centuries earlier in the medieval warm period given its rarity the 2012 extreme melt across greenland provides an exceptional opportunity for new studies in broad interdisciplinary geophysical research

suspended sediment transport processes on tidal mud flat in jiangsu province china the intertidal mud flat in jiangsu province is an open or semi open tidal flat with a moderately high tidal range this paper analyses characteristics of tidal current and suspended sediment concentration on the intertidal flat comparison is then made with characteristics on the intertidal flat of the dutch coastline wadden sea and similar areas the suitability and limitations of applying the lag mechanism to an open or semi open macrotidal flat is examined residual water and sediment circulation on the intertidal flat show they can be divided into a series of longshore cells which form individual hydrodynamical sedimentary units

rapid loss of firn pore space accelerates 21st century greenland mass loss 1 mass loss from the two major ice sheets and their contribution to global sea level rise is accelerating in antarctica mass loss is dominated by increased flow velocities of outlet glaciers following the thinning or disintegration of coastal ice shelves into which they flow in contrast 55 of post 1992 greenland ice sheet gris mass loss is accounted for by surface processes notably increased meltwater runoff a subtle process in the surface mass balance of the gris is the retention and refreezing of meltwater currently preventing 40 of the meltwater to reach the ocean here we force a high resolution atmosphere snow model with a mid range warming scenario rcp4 5 1970 2100 to show that rapid loss of firn pore space by 50 at the end of the 21st century quickly reduces this refreezing buffer as a result gris surface mass loss accelerates throughout the 21st century and its contribution to global sea level rise increases to 1 7 0 5 mm yr 1 more than four times the current value

comparison of elastic moduli from seismic diving wave and ice core microstructure analysis in antarctic polar firn we compared elastic moduli in polar firn derived from diving wave refraction seismic velocity analysis firn core density measurements and microstructure modelling based on firn core data the seismic data were obtained with a small electrodynamic vibrator source near kohnen station east antarctica the analysis of diving waves resulted in velocity depth profiles for different wave types p sh and sv waves dynamic elastic moduli of firn were derived by combining p and s wave velocities and densities obtained from firn core measurements the structural finite element method fem was used to calculate the components of the elastic tensor from firn microstructure derived from x ray tomography of firn core samples at depths of 10 42 71 and 99 m providing static elastic moduli shear and bulk moduli range from 0 39 to 2 42 gpa and 0 68 to 2 42 gpa respectively the elastic moduli from seismic observations and the structural fem agree within 8 5 for the deepest achieved values at a depth of 71 m and are within the uncertainty range our observations demonstrate that the elastic moduli of the firn can be consistently obtained from two independent methods which are based on dynamic seismic and static tomography and fem observations respectively for deeper layers in the firn below 10 m depth

thermal tracking of meltwater retention in greenland s accumulation area 1 poorly understood processes controlling retention of meltwater in snow and firn have important implications for greenland ice sheet s mass balance and flow dynamics here we present results from a 3 year 2007 2009 field campaign studying firn thermal profiles and density structure along an 85 km transect of the percolation zone of west greenland we installed one or two thermistor strings at 14 study sites each string having 32 sensors spaced between 0 and 10 m depth data from our network of over 500 sensors were collected at 15 60 min intervals for 1 2 years thereby recording the thermal signature of meltwater infiltration and refreezing during annual melt cycles we document three types of heating of firn related to different mechanisms of meltwater motion and freezing including heterogeneous breakthrough events wetting front advance and year round heating from freezing of residual deep pore water vertically infiltrating meltwater commonly penetrates through cold firn accumulated over decades even where ice layers are present at the previous summer surface and where ice layer thickness exceeds several decimeters the offset between the mean annual air temperature and the 10 m firn temperature reveals the elevation dependency of meltwater retention along our transect the firn is 10 c warmer than the mean annual air temperature at the region where meltwater runoff initiates during 2007 2009 runoff was limited to elevations lower than 1500 m with no sharp runoff limit rather the ratio of retention to runoff transitioned from all retention to all runoff across a 20 km wide zone

on the spatial structure of coastal circulation off newport oregon during spring and summer 2001 in a region of varying shelf width 1 a time series of hourly surface current maps in the shelf waters off newport oregon was made during april september 2001 using five seasonde hf current mappers during coastal advances in shelf transport coast the surface currents responded rapidly to the changing winds in repeated patterns that were strongly affected by bottom topography an equatorward current jet repeatedly formed in response to upwelling winds its strength but not its trajectory covarying with the meridional wind stress near cape foulweather 44 8 n where the shelf begins to widen the jet rotates weakens and trends offshore to the south first along then across the isobaths below cape foulweather inshore of the jet a lee region of generally weak currents was commonly observed the equatorward jet core was most commonly observed near the 80 m isobath between 45 0 n and 44 4 n but transited offshore between spring and summer over heceta bank at newport 44 6 n it was rarely observed less than 8 km from the coast a second inshore equatorward jet previously unknown was observed repeatedly south of waldport 44 4 n sustained downwelling wind episodes produced poleward currents though less responsively north of cape foulweather strongest poleward flow was generally trapped near the coast surface currents were correlated with the northward wind except regionally far from shore over heceta bank responding within half a day response to the wind varies spatially being intensified in the narrow shelf northern region the equatorward jet persists through periods of zero wind forcing coastal sea level covaries with the meridional wind and the primary mode of ocean current response

parameter uncertainty refreezing and surface energy balance modelling at austfonna ice cap svalbard 2004 08 we apply a physically based coupled surface energy balance and snowpack model to a site close to the equilibrium line on austfonna ice cap svalbard over the 2004 08 melt seasons to explain contributions to the energy available for melting and to quantify the significance of refreezing the model is forced using in situ meteorological measurements and precipitation downscaled from erainterim reanalysis applying a monte carlo approach to determine the tunable parameters of the model we estimate the uncertainty related to the choice of parameter values multiple criteria are evaluated to identify well performing parameter combinations evaluating the model performance with respect to longwave outgoing radiation snow and ice temperatures and surface displacement on average over the investigated melt seasons 1 june to 15 september net radiation and sensible heat contributed 90 2 and 10 2 respectively to the mean energy available for melting snow and ice the energy consumed by subsurface heat exchange reduced runoff by 15 2 in 2004 and 49 3 in 2008 refreezing of meltwater and rain was estimated to be 0 37 0 04mw e a 1on average over the five seasons which represents a considerable reduction of mass loss during summer our findings suggest that refreezing potentially exerts a decisive control on glacier mass balance in persistently snow or firncovered areas

optical dating of holocene tidal deposits from the southwestern coast of the south yellow sea using different grain size quartz fractions abstract the tidal flat deposit provides ideal sedimentary records for paleoenvironmental studies reliable chronology is crucial to utilize this archive for deciphering the history of environmental changes in this study we applied optically stimulated luminescence osl dating method to a holocene tidal flat sequence using both coarse grained cg 90 200 m and fine grained fg 4 11 m quartz extracts from a sedimentary core yz07 in western coast of the south yellow sea the luminescence characteristics of the two grain size fractions were investigated and then their resulting osl ages were systematically compared the results suggested that most tidal flat deposits are well bleached and their fg quartz ages are generally consistent with cg quartz ages while some samples have cg ages underestimated compared with fg likely resulted from the k feldspar contamination for cg quartz hence we applied post ir osl dating and pulsed osl dating techniques they could overcome the problems caused by feldspar contamination and yielded identical dates as fg osl ages all osl ages are generally in stratigraphic order in contrast the 14c ages are much more disorder and characterized with severe inversions finally the age framework of the tidal flat sequence under this study was constructed based on the 30 osl ages and one acceptable radiocarbon age according to the age depth model three main periods of sedimentation rate sr variation were identified these sr changes are probably associated with sea level rise fall history and the depocenter landward seaward movement as well as the transition of depositional process within the holocene delta initiation the depositional environment changes were also reflected in sedimentological features of the tidal flat deposits in our study area

retention of greenland runoff by refreezing implications for projected future sea level change melting produced at the surface of subfreezing permeable firn does not freely percolate but instead refreezes near its point of origin raising the firn temperature and decreasing the pore space if sufficient meltwater is introduced the firn will warm to 0 c and subsequent water will fill the remaining pore space without freezing only after the residual water content of the firn is exceeded will water flow through the firn and possibly escape as runoff this process prevents summer melt on high arctic glaciers and ice caps from escaping in its entirety and it must be accounted for in modeling glacier runoff on the basis of surface energy balance a model is presented here which describes in a simple way the transient process of infiltration refreezing and runoff in a future warming climate the model is applied to greenland for which predictions of runoff induced sea level rise that do not consider the refreezing process could be as much as 5 0 cm too high over 150 years

morphological evolution of jinshan trough in hangzhou bay china from 1960 to 2011 abstract an extensive system of tidal channels starting with jinshan trough in the east is located along the north shore of hangzhou bay china this contribution investigates the morphological evolution of jinshan trough by using 17 bathymetric charts from a series covering a period of 51 years from 1960 to 2011 three stages of evolution during this period are distinguishable based on the morphology and annual mean volume data the first stage 1960 1987 is characterized by extension of the trough the second stage 1987 1996 is a relatively stable period with some adjustments in the trough morphology the third stage 1996 2011 is marked by the processes of erosion and deposition in the beginning of the period and a subsequent slow erosion process spatio temporal variability of the trough was evaluated by using empirical orthogonal function eof analysis the first eigenfunction indicates that erosion is the main evolution process and there exists three stages similar to those distinguished from volume variations the second eigenfunction mainly reflects erosion and deposition in the northwest part of the trough located in the flood tidal current shadow area of the artificial headland in jinshan the third eigenfunction mainly reflects annual fluctuations of erosion and deposition in the side slope at the artificial headland in jinshan a particularly intense erosion process occurred between 1996 and 1998 the major effects on morphological evolution in jinshan trough from 1960 to 2011 were investigated and tentative conclusions were presented continuous coastal reclamations in jinshan had the most pronounced effect on the morphological evolution during the first and the second stages the storm surge had a pronounced effect on the evolution at the beginning of the third stage

modeling bottom mixed layer variability on the mid oregon shelf during summer upwelling abstract results from a model of wind driven circulation are analyzed to study spatial and temporal variability in the bottom mixed layer bml on the mid oregon shelf in summer 2001 the model assimilates acoustic doppler profiler velocities from two cross shore lines of moorings 90 km apart to provide improved accuracy of near bottom velocities and turbulence variables in the area between the mooring lines model results suggest that the response of the bml thickness to upwelling and downwelling favorable winds differs qualitatively between an area of simple bathymetric slope at 45 n and a wider shelf area east of stonewall bank 44 5 n at 45 n the bml grows in response to downwelling favorable conditions in agreement with known theories east of stonewall bank the bml thickness is increased following upwelling events in this area the southward upwelling jet detaches from the coast and flows over a wider part of the oregon shelf creating conditions for ekman pumping near the bottom based on

the relative importance of wind strength and along shelf bathymetric variations on the separation of a coastal upwelling jet abstract a high resolution numerical model with idealized topography is used to investigate the degree to which a coastal upwelling jet separates from the shelf as it flows around a submarine bank depending on the wind strength and the horizontal scale of the bank experiments were run using several wind forcing magnitudes and submarine banks with different geometries so as to explore a wide range of the flow strength as measured by the rossby number ro and the ratio of the squares of the internal rossby radius of deformation and curvature of the topography as denoted by the burger number bu the intensity of the jet separation is strongly dependent on both parameters with maximum separation with increasing ro and bu close to 1 when large amounts of upwelled water are exported toward deeper waters for small bu separation is minimal and independent of ro for high ro the degree of separation decreases at large bu since the bank acts only as a small perturbation to the flow term balances in the a

helium isotopes in paleofluids and present day fluids of the larderello geothermal field constraints on the heat source 1 the he isotope composition of paleofluids entrapped in fluid inclusions of hydrothermal minerals is compared with the present day fluid composition of the larderello geothermal field almost constant values of 3he 4he m 3he 4he air r ra over time indicate that no important changes have occurred in the deep source of gases at least during the last 3 8 million years on a regional scale a correlation has been found between the r ra spatial distribution heat flow and bouguer gravity anomaly high values of r ra and heat flow and low bouguer anomaly values indicate that the larderello field is an area of preferential escape for mantle derived fluids a positive correlation has also been found between the r ra spatial distribution and a major seismic reflector named the k horizon a deep magma source refilled by periodic gas input from the mantle is the most likely source of 3he enriched fluids and the anomalously high heat flow the nearly constant value of r ra clearly indicates that input of fresh mantle material has occurred up to recent times clear evidence of mixing between mantle and crustal fluids indicates that the high r ra is the lower limit of the actual mantle value which is suggested to be similar to the subcontinental european mantle the decrease of r ra over time in the peripheral part of the larderello field indicates that important changes in the feeding fracture system and or cooling rate have occurred in these areas

wind influence on tidal flat sediment dynamics field investigations in the ho bugt danish wadden sea abstract sediment dynamics on a mixed microtidal flat in a sheltered backbarrier position are shown to vary strongly on short term tidal and monthly timescales bed level changes were 1 mm per tidal period in the absence of winds erosion of 10 to 20 mm within a few hours was possible during high combined current and wave shear stress mean grain size in the upper 1 cm bed sediment varied from 34 to 155 m and was consistently coarser than the mean size of trapped suspended matter 7 10 m threshold for resuspension was low at 0 03 n m 2 no clear correlation was found between resuspension activity and suspended matter concentrations as these concentrations also depend on current induced advection due to tidal asymmetry the net suspended sediment flux was flood directed on average it was 14 kg m 2 per tidal period in the summer and 3 times higher during november when wave activity generally was stronger bed micro topography was followed on digital photos taken every 1 5 h during the two month study period showed that 1 ripples started to develop when wave shear stress exceeded 0 15 n m 2 and 2 their wavelength varied with shear stress

geochemical constraints on the provenance of surface sediments of radial sand ridges off the jiangsu coastal zone east china abstract the jiang harbor centered radial sand ranges rsrs off the jiangsu coast are the largest in the yellow sea however the provenance of the rsrs remains controversial in this study we compare major and trace element geochemistry together with grain size and main mineral composition in carbonate free sediments from rsrs and potential sources onshore and offshore rsr sediments have different grain size characteristics onshore rsr sediments have mean grain sizes of 2 tio 2 li and partly in cs zn and some high field strength elements y zr nb pb and th while depleted in other elements offshore rsr sediments are complicated in geochemical compositions some of them have very high contents of high field strength elements and others are similar to onshore rsr sediments onshore and offshore rsr sediments have different controlling factors of geochemical compositions onshore rsr sediments are influenced by clay size minerals whereas offshore sediments are controlled by heavy minerals the identification of zr nb and ti zr vs k rb shows that onshore and offshore rsrs seem to have similar sources their differences in grain size are a result of hydrodynamic sorting the identification of elemental ratios reveals that sources of rsr sediments are variable in space and time and the inputs of the chinese rivers especially the old yellow river and the yangtze river are still dominant but the effect of the korean field cannot be neglected our findings also demonstrate the potential of elemental ratios such as zr nb and k rb as tracer pairs for provenance of sediments in the yellow sea

sedimentary processes over an intertidal flat a field investigation at hythe flats southampton water uk the sedimentary processes acting over an intertidal flat hythe uk located in southampton water hampshire uk are investigated on the basis of hydrodynamic morphological and sediment transport field measurements bed level changes patterns of suspended sediment transport and shell movement over the tidal flats were examined in order to identify sediment transport pathways and salt marsh mudflat morphological changes overall sediment transport patterns at hythe can be described in terms of suspended sediment and bedload shell transport the hydrodynamic complexity of the tidal flow over the flats determines the patterns of suspended sediments transport during the young flood phase tidal currents present a sw orientation shoreward about 1 h into the flood a change occurs and the currents start flowing in a se direction estuary mouthward this veering of the tidal current controls the hydrodynamic pattern over the mudflat inducing sediment transport towards the estuary mouth conversely shell tracer experiment showed a net landward movement shells are transported over the mudflat deposited at the base of the cliff and eventually transported over the salt marsh where they form extensive chernier deposits shell transport rates can reach up to 0 7 m tide over the upper mudflat shell movement over the salt marsh on cheniers occurred only during storms up to 3 m in a storm event shell induced erosion can become an important parameter on morphological changes of a coastal area shell transport and deposition over the salt marsh surface can contribute to vegetation deterioration as shell deposits migrate over the marsh surface as a result the seaward limit of the salt marsh showed deteriorated vegetation which leads to scouring and consequent surface lowering in terms of bed level changes no seasonal pattern was observed a relationship between mudflat bed erosion and cliff retreat is suggested during periods of high cliff erosion there was a tendency for the mudflats to be stable and conversely mudflat bed erosion was greatest when cliff retreat rates were lowest hence morphological characteristics of hythe intertidal area appear to be controlled by a combination of prevailing hydrodynamic conditions and shell transport over the salt marsh

modeling upwelling circulation off the oregon coast 1 time dependent three dimensional upwelling circulation on the continental shelf off the oregon coast is studied using a primitive equation numerical model a limited area domain with a high resolution curvilinear grid is utilized the response of the coastal ocean to forcing by observed wind stress and heat flux during the summer 2001 time period of the coastal ocean advances in shelf transport coast field experiment is investigated model results are compared to coast current and hydrographic measurements the shelf velocity and density fields are generally characterized by the presence of a southward alongshore coastal jet with an upwelling density front on the shoreward side of the jet the large variability in shelf topography associated with heceta bank exerts a major influence on the shelf velocity and density fields over the bank the alongshore coastal jet is displaced offshore and colder upwelled water extends farther from the coast northward mean flow and upward motion are found inshore of the jet three dimensional flow structures in response to variable shelf bottom topography are presented and an analysis of time and space dependent alongshore momentum balances is applied to clarify the associated dynamics in general northward pressure gradients set up over the bank during southward upwelling winds accelerate currents on the inshore side of the jet northward when the winds relax analysis of term balances in the depth averaged equation for potential temperature shows that during upwelling across shore advection makes the major contribution to cooling over most of the region except inshore over heceta bank where alongshore advection also plays a significant role

a reconciled estimate of glacier contributions to sea level rise 2003 to 2009 glaciers distinct from the greenland and antarctic ice sheets are losing large amounts of water to the world s oceans however estimates of their contribution to sea level rise disagree we provide a consensus estimate by standardizing existing and creating new mass budget estimates from satellite gravimetry and altimetry and from local glaciological records in many regions local measurements are more negative than satellite based estimates all regions lost mass during 2003 2009 with the largest losses from arctic canada alaska coastal greenland the southern andes and high mountain asia but there was little loss from glaciers in antarctica over this period the global mass budget was 259 28 gigatons per year equivalent to the combined loss from both ice sheets and accounting for 29 13 of the observed sea level rise

greenland ice sheet contribution to sea level rise buffered by meltwater storage in firn observations of firn structure and meltwater retention on the greenland ice sheet s percolation zone a region of the ice sheet that is perennially covered by snow and firn quantify the capacity of the firn to store future surface meltwater and to delay expansion of the area contributing to sea level rise the extent and the fate of surface melt on the greenland ice sheet are important factors contributing to sea level change the pore spaces in firn a type of partly compacted snow can be filled by meltwater and thus act as a temporary reservoir here joel harper et al show that the greenland ice sheet parts of which are permanently covered by snow and firn can buffer several hundred gigatonnes of meltwater for several decades although this buffering capacity is only temporary and cannot be easily regained it has the potential to delay the pace of near term sea level rise surface melt on the greenland ice sheet has shown increasing trends in areal extent and duration since the beginning of the satellite era1 2 3 records for melt were broken in 20054 20075 20106 and 20127 much of the increased surface melt is occurring in the percolation zone a region of the accumulation area that is perennially covered by snow and firn partly compacted snow the fate of melt water in the percolation zone is poorly constrained some may travel away from its point of origin and eventually influence the ice sheet s flow dynamics and mass balance and the global sea level whereas some may simply infiltrate into cold snow or firn and refreeze with none of these effects here we quantify the existing water storage capacity of the percolation zone of the greenland ice sheet and show the potential for hundreds of gigatonnes of meltwater storage we collected in situ observations of firn structure and meltwater retention along a roughly 85 kilometre long transect of the melting accumulation area our data show that repeated infiltration events in which melt water penetrates deeply more than 10 metres eventually fill all pore space with water as future surface melt intensifies under arctic warming a fraction of melt water that would otherwise contribute to sea level rise will fill existing pore space of the percolation zone we estimate the lower and upper bounds of this storage sink to be 322 44 gigatonnes and gigatonnes respectively furthermore we find that decades are required to fill this pore space under a range of plausible future climate conditions hence routing of surface melt water into filling the pore space of the firn column will delay expansion of the area contributing to sea level rise although once the pore space is filled it cannot quickly be regenerated

tidally induced flow structure over intertidal flats previous investigations have assumed that a significant linear relationship betweenuz lnzis sufficient to define a logarithmic velocity profile given by the von karman prandtl equation however it is demonstrated here that such a criterion alone is insufficient an internal consistency analysis is developed to establish realistic logarithmic velocity profiles in the estimation of boundary layer parameters associated with intertidal flat environments the analytical procedure includes i onward linear regression to establish the relationship between apparentu values and near bed current speeds uz here the observedu50is used ii an assessment of the constant and correlation coefficient within theu uzrelationship iii calculation ofz0andc50values on the basis of the slope of the regression line and iv undertaking a comparison between the derivedz0andc50and those obtained using the instantaneous velocity profiles the internal consistency is shown to be enhanced if the data are filtered before a more detailed analysis this approach is applied to the analysis of 192 current velocity gradient rig data sets collected from the intertidal flats of the loughor estuary and swansea bay south wales and the wash eastern england overall less than 40 of the data sets are logarithmic in character with variations between the various stations nevertheless boundary layer parameters were determined for most locations non logarithmic profiles on intertidal flats are considered to be caused by i rotary tidal currents ii wind effects iii wave action and other short period oscillations and iv topographically induced secondary flows measurement errors can lead also to deviations from an idealized logarithmic profile

tidal current ridges in the southwestern yellow sea abstract large tidal current ridges tidal sand banks in the southwestern yellow sea are located offshore of northern jiangsu province china these ridges radiate to a depth of 20 30 m the dimensions of the ridge system are about 200 km long and 90 km wide their morphology indicates the strong influence of tidal currents the ridges are composed of well sorted fine sands size range is 2 4 the grain size distributions of the sands show that the sands are transported and deposited by tidal currents the ridge system formed on the abandoned yellow river and ancient yangtze river deltas has an abundant sand supply from the former deltas of particular importance is the existence of two tidal wave systems in the yellow sea the rotary ti al wave system in the southern yellow sea and the pacific progressive tidal wave system propagated into the southern ridge area of the southwestern yellow sea under the interaction of the two tidal wave systems the huge tidal current system in the southwestern yellow sea has formed

changes in accumulation area firn stratigraphy and meltwater flow during a period of climate warming devon ice cap nunavut canada 1 to document climate driven changes in firn stratigraphy and their implications for meltwater flow patterns within firn on the devon ice cap nunavut during the 21st century summer warming 500 mhz ground penetrating radar gpr surveys were conducted along a 40 km transect in each spring from 2007 to 2012 these linear gpr surveys were supplemented by four 190 m by 100 m gpr grid surveys and 36 firn cores increased meltwater percolation and infiltration ice formation associated with high surface melt rates since 2005 modified the firn stratigraphy substantially over a horizontal distance of nearly 30 km the most dramatic change involved the growth of a thick ice layer within the firn body this layer grew primarily by upward accretion over an initial widespread ice layer formed during summer 2005 it thickened by between 0 5 and 4 5 m over the study period and filled much of the pore volume in the upper part of the firn reducing vertical percolation of meltwater into deeper sections of the firn and thus the water storage potential of much of the firn reservoir heterogeneous percolation of surface meltwater promoted by rolling topography played an important role in meltwater infiltration and drainage encouraging lateral flow at the tops of small hills and ponding and refreezing of meltwater beneath surface depressions

meltwater percolation impermeable layer formation and runoff buffering on devon ice cap canada the retention of meltwater in the accumulation area of the greenland ice sheet and other arctic ice masses buffers their contribution to sea level change however sustained warming also results in impermeable ice layers or ice slabs that seal the underlying pore space here we use a 1 d physically based high resolution model to simulate the surface mass balance smb percolation refreezing ice layer formation and runoff from across the high elevation area of devon ice cap canada from 2001 to 2016 we vary the thickness of the impermeable ice layer at which underlying firn becomes inaccessible to meltwater thick near surface ice layers are established by an initial deep percolation the formation of decimetre ice layers and the infilling of interleaving pore space the cumulative smb increases by 48 by varying impermeable layer thickness between 0 01 and 5 m within this range we identify narrower range 0 25 1 m that can simulate both the temporal variability in smb and the observed near surface density structure across this range cumulative smb variation is limited to 6 and 45 49 of mass retention takes place within the annually replenished snowpack our results indicate cooler summers after intense mid 2000s warming have led to a partial replenishment of pore space

experiment inspired numerical modeling of sediment concentration over sand silt mixtures abstract a series of flume experiments has been conducted to investigate sediment transport of sand silt mixtures in both wave only and wave with current conditions two types of sediments collected from a typical silty tidal flat were used a silt sized mixture with median grain size of 46 m and a very fine sand sized mixture with median grain size of 88 m a high concentration layer hcl was observed near the bottom together with ripples under wave only conditions sediment concentrations inside the hcl are quasi stationary with the bulk richardson number approaching a constant value the thickness of the hcl can be scaled with approximately two times the damped wave boundary layer thickness for the concentration profiles we find that the vertical profile of the silt concentration appears different from the profile of the sand concentration since the silt concentration decreases logarithmically within hcl while homogeneously distributes outside the hcl finally the reference concentration formulation of van rijn 2007b was recalibrated for the silt classes and applied in a multi fraction model to predict the vertical concentration profile for silt and sand classes the results show a promising agreement with the measurements for both wave only and wave with current conditions

temporal distribution of diastems in deposits of an open coast tidal flat with high suspended sediment concentrations abstract based on field observations of the preservation potential and genesis of couplets and small sequences diastems occur within tidal flat deposits at scales of semi tidal daily monthly and yearly intervals thus tidal flat deposition is riddled with more diastems of different scales than previous assumptions units that are apparently complete when examined at longer time scales actually contain many diastems when examined at a shorter time scale diastems within tidal flat deposits are generated not only by high magnitude storm waves which occur during typhoon seasons but also by daily erosion produced by tides and weak waves during calm weather seasons the missing intervals in diastems generated by storm waves can be several days to several years preservation potential of storm generated small sequences is of the order of one third diastems generated by erosion by tides and weak waves can have spans from a semidiurnal cycle to several days they are easily overlooked because of the low magnitude destruction and lack of distinctive sedimentary features net erosion by tides and weak waves is unexpectedly increased by day to day processes alternations of sandy and muddy laminae are related to tidal rhythm but individual laminae can be separated by a significant diastem documentation of erosion by tides and weak waves under normal non typhoon conditions is the principal focus of this report

coastal wind driven circulation in the vicinity of a bank part i modeling flow over idealized symmetric banks abstract this study examines how coastal banks influence wind driven circulation along stratified continental shelves numerical experiments are conducted for idealized symmetric banks the standard bank 200 km long and 50 km wide has dimensions similar to the heceta bank complex along the oregon shelf model runs are forced with 10 days of steady winds 0 1 pa upwelling and downwelling cases are compared the bank introduces significant alongshelf variability in the currents and density fields upwelling favorable winds create an upwelling front and a baroclinic jet flowing opposite coastal trapped wave propagation that bend around the standard bank approximately centered on the 90 m isobath the upwelling jet is strongest over the upstream bank half where it advects a tongue of dense water over the bank there is a current reversal shoreward of the main jet at the bank center upwelling is most intense over the upstream part of the bank while there is reduced upwelling and even downwelling over

wind driven modification of the alaskan coastal current 1 across shelf transects over the eastern flank of barrow canyon were obtained in august 2005 with an autonomous underwater vehicle auv here the shelf topography creates a choke point in which a substantial portion of pacific inflow from the bering strait is concentrated within 30 km of the coast providing an ideal setup for monitoring the flow with the auv four transects extending 10 km offshore of barrow alaska inshore of the 80 m isobath were used in conjunction with a process oriented numerical model to diagnose the wind driven modification of the alaskan coastal current poleward transports of 0 12 sv were consistent among all sections although the transport weighted temperature was about 1 c colder in the transect obtained during peak winds an idealized numerical model reproduces the observed hydrographic structure and across shelf circulation reasonably well in that 1 winds were not sufficient to reverse the poleward flow 2 upwelling was most pronounced in the nearshore and 3 the onshore return flow occurred throughout the interior as opposed to the bottom boundary layer the across shelf circulation provides a possible mechanism for a meltwater intrusion observed on the offshore side of the auv transect made during peak winds also of interest is that the observed anticyclonic shear was much stronger u y f than previously measured in the region

sharply increased mass loss from glaciers and ice caps in the canadian arctic archipelago the canadian arctic archipelago contains one third of the global volume of land ice outside the ice sheets but its contribution to sea level change is largely unknown gardner et al use three independent techniques to reveal that mass loss from the archipelago was 92 12 gigatonnes per year in 2007 09 about three times greater than in 2004 06 and coincident with warmer summer temperatures the record is too short to allow a firm conclusion on longer term trends but it is clear that the canadian arctic archipelago is a significant contributor to sea level rise mountain glaciers and ice caps are contributing significantly to present rates of sea level rise and will continue to do so over the next century and beyond1 2 3 4 5 the canadian arctic archipelago located off the northwestern shore of greenland contains one third of the global volume of land ice outside the ice sheets6 but its contribution to sea level change remains largely unknown here we show that the canadian arctic archipelago has recently lost 61 7 gigatonnes per year gt yr 1 of ice contributing 0 17 0 02 mm yr 1 to sea level rise our estimates are of regional mass changes for the ice caps and glaciers of the canadian arctic archipelago referring to the years 2004 to 2009 and are based on three independent approaches surface mass budget modelling plus an estimate of ice discharge smb d repeat satellite laser altimetry icesat and repeat satellite gravimetry grace all three approaches show consistent and large mass loss estimates between the periods 2004 2006 and 2007 2009 the rate of mass loss sharply increased from 31 8 gt yr 1 to 92 12 gt yr 1 in direct response to warmer summer temperatures to which rates of ice loss are highly sensitive 64 14 gt yr 1 per 1 k increase the duration of the study is too short to establish a long term trend but for 2007 2009 the increase in the rate of mass loss makes the canadian arctic archipelago the single largest contributor to eustatic sea level rise outside greenland and antarctica

bed level changes on intertidal wetland in response to waves and tides a case study from the yangtze river delta short term bed level variability in tidal wetlands has important implication both for ecology and engineering in this study we combined in situ measurements with model simulations to quantify short term bed level changes on a meso macrotidal wetland in the yangtze river delta on the middle flat we observed erosion during neap to mean tides under onshore moderate to strong winds and bed recovery during subsequent spring tides when winds were both offshore and weaker suggesting that winds can overturn the neap spring cyclicity of bed level changes even on meso macrotidal mudflats the magnitude of bed level changes was smaller on both sides of the middle flat while the smallest changes occurred on the salt marsh observed bed level changes were reconstructed using a single point bed level change model which incorporates in situ measured parameters of hydrodynamics waves and currents suspended sediment concentrations and bed sediment properties we conclude that the relative importance of waves and tides in intertidal wetland erosion and accretion can vary temporally due to changes in balance between wave and tidal energies and spatially because of changes in elevation and vegetation in the cross shore profile our study also reflects the advantage of combination of in situ measurement with simulation in detecting short term variability of tidal flats

net sediment transport patterns inferred from grain size trends based upon definition of transport vectors reply abstract a new approach to the analysis of the grain size trends associated with net sediment transport directions in shallow marine environments is developed here two specific trends modified from mclaren and bowles 1985 on the basis of a literature review are used to define a grid of trend vectors such vectors are filtered and transformed into transport vectors it is suggested that an ordered pattern of the transport vectors represents net transport paths the orderliness of the derived pattern is examined on the basis of a significance test using the average length of the transport vectors as a criterion both the filtering operation and the significance test procedure are based upon the assumption that the trend vectors which are not associated with net transport have the same probability of being in any direction the technique is applied to data from yangpu harbour southern china the technique can be applied to inner continental shelf and coastal environments for such an analysis the area under investigation should be sampled at an interval large enough to reflect the real grain size trends resulting from net sediment transport but small compared with the dimensions of the sedimentary environment the time scale of the results depends upon the sampling depth applicability of the technique is likely to be somewhat limited where the environment is highly variable over short distances furthermore due to its statistical character the analysis may fail to identify net transport patterns

summer melt rates on penny ice cap baffin island past and recent trends and implications for regional climate 1 at latitude 67 n penny ice cap on baffin island is the southernmost large ice cap in the canadian arctic yet its past and recent evolution is poorly documented here we present a synthesis of climatological observations mass balance measurements and proxy climate data from cores drilled on the ice cap over the past six decades 1953 to 2011 we find that starting in the 1980s penny ice cap entered a phase of enhanced melt rates related to rising summer and winter air temperatures across the eastern arctic presently 70 to 100 volume of the annual accumulation at the ice cap summit is in the form of refrozen meltwater recent surface melt rates are found to be comparable to those last experienced more than 3000 years ago enhanced surface melt water percolation and refreezing have led to a downward transfer of latent heat that raised the subsurface firn temperature by 10 c at 10 m depth since the mid 1990s this process may accelerate further mass loss of the ice cap by pre conditioning the firn for the ensuing melt season recent warming in the baffin region has been larger in winter but more regular in summer and observations on penny ice cap suggest that it was relatively uniform over the 2000 m altitude range of the ice cap our findings are consistent with trends in glacier mass loss in the canadian high arctic and regional sea ice cover reduction reinforcing the view that the arctic appears to be reverting back to a thermal state not seen in millennia

measurement and simulation of snow and superimposed ice at the kongsvegen glacier svalbard spitzbergen 1 multiyear glaciometeorological data have been collected at about the equilibrium line of kongsvegen glacier in svalbard during the first summer of the investigation period about 0 6 m of superimposed ice si was built up because of effective meltwater refreeze upon the former glacier surface thus winter accumulation is completely retained from runoff and latent heat is released equivalent to 27 of july net radiation this ice layer as well as part of the former year s ice disappeared during the subsequent summer using a physically based snow model the evolution of the snow pack properties as well as the observed amount of si is successfully reproduced however the latter is only possible by modifying the model s water transport routine to also treat effects of ponding water which have been observed two distinct phases of si formation can be distinguished a first one 15 cm is initiated as soon as meltwater has penetrated to the underlying cold glacier ice toward the end of the melt period however the remaining body of si is rapidly formed because of intense atmospheric cooling the availability of ponding water plays an essential role in this context during the following summer the initial refreezing phase was terminated by exposure of the newly built si at the surface the whole amount of the actual year and the major part of the former year s si was melted then a positive ice albedo feedback process plays an additional role there sensitivity studies prove that the model results and their interpretation do not critically depend on possible uncertainties of input data and model parameters despite their local nature these studies are valuable steps toward understanding the regional distribution of si on arctic glaciers as well as their climate sensitivity remote sensing studies indicate that si presently covers 35 of kongsvegen s surface area

two dimensional tide induced residual sand transport applications to the jiangsu coast china abstract the residual sand d 62 5 m transport rst refers to the tidally averaged rate of horizontal sand transport albeit much smaller than the peak rates it determines the morphological evolution the analytical expression for the tide induced rst has been reported in the condition of one dimensional tidal currents by van de kreeke and robaczewska 1993 here we extended the analytical solution to two dimensional the constituents of the residual m2 and m4 tidal current velocities were used to characterize the collinear tidal current in the orthogonal x and y directions i e cross shore and alongshore respectively while the m2 tidal constituent is dominant in both directions based on the solution rst is controlled by a series of triple interactions of the m2 tidal velocity in the x direction m2 tidal velocity in the y direction and the residual or m4 velocity in the x or y direction the solution was applied to the tide dominated continental shelf of the jiangsu coast china where the alongshore current is much stronger than the cross shore component the results show that the triple interactions of the cross shore m2 tidal velocity um2 the alongshore m2 tidal velocity vm2 and the alongshore residual velocity account for the major parts of both the alongshore and cross shore rst in the nearshore area the rst patterns promote sand accumulation in the shallow nearshore area and generate a narrow and active conduit of coastal alongshore sand transport these findings can be applied in similar marine environments to understand the effects of non linear tidal interactions in rst

acceleration of the greenland ice sheet mass loss as observed by grace confidence and sensitivity abstract we examine the scale and spatial distribution of the mass change acceleration in greenland and its statistical significance using processed gravimetric data from the grace mission for the period 2002 2011 three different data products the cnes grgs dmt 1b and ggfc grace solutions have been used all revealing an accelerating mass loss in greenland though with significant local differences between the three datasets compensating for leakage effects we obtain acceleration values of 18 6 gt yr 2 for cnes grgs 8 8 gt yr 2 for dmt 1b and 14 8 gt yr 2 for ggfc we find considerable mass loss acceleration in the canadian arctic archipelago some of which will leak into the values for greenland depending on the approach used and for our computations the leakage has been estimated at up to 4 7 gt yr 2 the length of the time series of the grace data makes a huge difference in establishing an acceleration of the data for both 10 day and monthly grace solutions an observed acceleration on the order of 10 20 gt yr 2 is shown to require more than 5 yrs of data to establish with statistical significance in order to provide an independent evaluation icesat laser altimetry data have been smoothed to match the resolution of the grace solutions this gives us an estimated upper bound for the acceleration of about 29 7 gt yr 2 for the period 2003 2009 consistent with the acceleration values and corresponding confidence intervals found with grace data

a model study of the response of dry and wet firn to climate change we study the response of firn to a stepwise surface temperature change using a firn model that includes meltwater hydrology and is driven by an idealized surface climate we find that adjustment of dry firn i e without surface melt to surface warming takes longer than a subsequent cooling to the original colder climate mainly because firn compacts faster at higher firn temperatures in contrast wet firn adjusts faster to a surface warming than to a cooling increased meltwater percolation enhances the downward transport of latent heat whereas there is no such mechanism that can enhance the downward transport of a cooling signal thus wastage of firn after surface warming is faster than its regeneration if the warming were reversed furthermore the response of wet firn to temperature change exhibits a complex relation between accumulation rate and the steady state deep firn temperature for high accumulation rates the deep firn temperature is higher because latent heat release upon refreezing is isolated by winter snow as a result the response of wet firn to a temperature change varies strongly with accumulation rate in general the magnitude and the rate of density change is larger in wet firn than in dry firn

a plot scale study of firn stratigraphy at lomonosovfonna svalbard using ice cores borehole video and gpr surveys in 2012 14 spatial heterogeneity of snow and firn properties on glaciers introduces uncertainty in interpretation of point and profile observations and complicates modelling of meltwater percolation and runof

a modeling study of the three dimensional continental shelf circulation off oregon part ii dynamical analysis abstract sixty day simulations of the subinertial continental shelf circulation off oregon are performed for a hindcast study of summer 1999 in part i the model results are shown to compare favorably with in situ currents and hydrographic measurements obtained from an array of moored instruments and field surveys and high frequency radar derived surface currents in this paper the modeled three dimensional time varying circulation and dynamical balances are analyzed providing a detailed synoptic description of the continental shelf circulation off oregon for summer 1999 the circulation is clearly wind driven and strongly influenced by alongshore variations in shelf topography in the region of the coast where the alongshore topographic variations are small the upwelling circulation is consistent with standard conceptual models for two dimensional across shore circulation in the regions where the alongshore topographic variations are greater the upwelling circulation is highly three dimensional ov