measurements of the angle between the wind vector and wind stress vector in the surface layer over the north sea measurements of surface layer turbulence in addition to full meteorological and oceanography quantities over the north sea indicated that the stress vector on long time scales is often aligned with a direction slightly different from the mean wind flow when stratifications were near neutral the angle difference between the stress and wind exhibited a dependence on the heat and momentum fluxes in general the stress vector was observed to be to the left of the flow during stable stratifications while for unstable stratifications it was to the right this finding was consistent using two independent sets of wind stress data i e from marsen 1979 and the north sea platform winter exercise 1985

models of coastally trapped disturbances during the spring and summer the climatological northerly flow along the u s west coast is occasionally interrupted by transitions to southerly flow that have a limited offshore scale and appear to be manifestations of marine layer flow that is rotationally trapped by the coastal mountains existing climatological and observational studies suggest that a synoptic scale offshore flow initiates these coastally trapped disturbances ctds using idealized simulations produced with a 3d nonhydrostatic model the authors find that an imposed offshore flow will produce ctds in idealized coastal environments the imposed flow first weakens the prevailing northerly flow in the marine layer and lowers the pressure at the coast the marine layer flow around this low pressure evolves toward geostrophic balance but is retarded as it encounters the coastal mountains to the south of the low and subsequently deepens the marine layer in this region the elevated marine layer then begins progressing northward as a kelvin wave and later may steepen into a bore or gravity current this progression being the ctd many observed features accompanying ctds are found in the numerical simulations including the formation of a mesoscale pressure trough offshore and deep southerlies in the ctd at the coast stability in the atmosphere above the marine layer can give rise to topographically trapped rossby waves and stronger ctd winds in these stable conditions propagation of wave energy away from the disturbance does not preclude strong quasi steady propagating ctds

local atmospheric forcing during the coastal ocean dynamics experiment 1 a description of the marine boundary layer and atmospheric conditions over a northern california upwelling region as part of the coastal ocean dynamics experiment code meteorological instruments were deployed on buoys and at coastal stations and instrumented aircraft flights and coastal soundings were made to study the three dimensional structure of the marine boundary layer over the continental shelf off northern california during the 1981 and 1982 upwelling seasons these measurements show that after the atmospheric spring transition the airflow in the marine layer is dominated by the north pacific high and the surface wind field over the shelf is characterized by periods of strong 7 15 m s upwelling favorable alongshelf winds lasting for up to 30 days interrupted by shorter periods of much weaker winds directed either equatorward or poleward these periods of weak or reversed winds typically last several days and are called wind relaxations even though they are primarily associated with coastally trapped perturbations of the marine layer along the central and northern california coast and not with a large scale weakening of the north pacific high the atmospheric boundary layer measurements made in code suggest a simple conceptual model which can explain much of the physiology or structure of the marine layer and associated surface wind field during periods of persistent upwelling favorable winds during these periods which represent the quasi steady state regime during the upwelling season the inversion base of the marine layer drops eastward toward the coast until it intersects the coastal mountain range at a height of several hundred meters and the associated thermal wind produces an alongshelf wind jet which has a maximum speed just below the inversion base turbulent mixing tends to homogenize any stratification in the marine layer beneath the jet and couple the jet to the ocean surface producing strong upwelling favorable winds over the shelf day night heating cooling over the narrow coastal strip beneath the marine layer generates a weak cross coast secondary circulation which causes the core of the alongshelf jet to drop in elevation and shift onshore this diurnal change in the marine layer structure explains both the daytime acceleration of the surface winds observed over and near the coast and its offshore decay and the associated offshore increase in the subdiurnal alongshelf wind thus the quasi steady component of the wind stress has a significant curl over the inner shelf during periods of active upwelling this mean summer atmospheric boundary layer regime is occasionally interrupted by synoptic and or mesoscale events or anomalous conditions analysis of the code observations suggests five types of events two primarily synoptic scale conditions which lead to stronger than normal upwelling favorable winds over the shelf and three primarily mesoscale events which lead to wind relaxation about half of the wind relaxation events observed in 1981 and 1982 are believed to be associated with either coastal trapped gravity currents or internal kelvin waves which propagate north ward in the marine layer along the central and northern california coastal mountain range

recent mass changes of glaciers in the russian high arctic 1 glaciers and ice caps are known to contribute significantly to present day sea level rise but there are still glaciated regions where little is known about modern changes in glacier mass one of these regions is the russian high arctic archipelagos which has a total glaciated area of 51 500 km2 we have assessed the glacier mass budget of this region for a 6 year period between october 2003 and october 2009 using independent icesat laser altimetry and grace gravimetry over this period we found that the archipelagos have lost ice at a rate of 9 1 2 0 gt a 1 which corresponds to a sea level contribution of 0 025 mm a 1 approximately 80 of the ice loss came from novaya zemlya with the remaining 20 coming from franz josef land and severnaya zemlya meteorological records of temperature and precipitation for the period 1980 2009 suggest that the recent climatic mass budget is not substantially different from the longer term trend

structure and dynamics of the benguela low level coastal jet generations of coupled atmosphere ocean general circulation models have been plagued by persistent warm sea surface temperature sst biases in the southeastern tropical atlantic the sst biases are most severe in the eastern boundary coastal upwelling region and are sensitive to surface wind stress and wind stress curl associated with the benguela low level coastal jet bllcj a southerly jet parallel to the angola namibia coast however little has been documented about this atmospheric source of oceanic bias here we investigate the characteristics and dynamics of the bllcj using observations reanalyses and atmospheric model simulations satellite wind products and high resolution reanalyses and models represent the bllcj with two near shore maxima one near the angola benguela front abf at 17 5 s and the other near 25 27 5 s whereas coarse resolution reanalyses and models represent the bllcj poorly with a single broad more offshore maximum model experiments indicate that convex coastal geometry near the abf supports the preferred location of the bllcj northern maximum by supporting conditions for a hydraulic expansion fan intraseasonal variability of the bllcj is associated with large scale variability in intensity and location of the south atlantic subtropical high through modulation of the low level zonal pressure gradient

larsen ice shelf has progressively thinned the retreat and collapse of antarctic peninsula ice shelves in tandem with a regional atmospheric warming has fueled speculation as to how these events may be related satellite radar altimeter measurements show that between 1992 and 2001 the larsen ice shelf lowered by up to 0 27 0 11 meters per year the lowering is explained by increased summer meltwater and the loss of basal ice through melting enhanced ocean driven melting may provide a simple link between regional climate warming and the successive disintegration of sections of the larsen ice shelf

volume and area changes of the milne ice shelf ellesmere island nunavut canada since 1950 1 ground penetrating radar gpr surveys of the 205 km2milne ice shelf conducted in 2008 and 2009 are compared with radio echo sounding res data from 1981 to provide the first direct measurements of thinning for any northern ellesmere island ice shelf our results show an average thinning for the ice shelf as a whole of 8 1 2 8 m with a maximum of 30 m over this 28 year period direct line comparisons along a 7 5 km transect near the front of ice shelf indicate a mean thinning of 2 63 2 47 m over the same period reductions in areal extent 29 82 8 4 km2 1950 2009 and volume 13 1 5 0 73 km3 water equivalent w e 1981 2008 2009 indicate that the milne ice shelf has been in a state of negative mass balance for at least the last 59 years a comparison of mean annual specific mass balance measurements with the nearby ward hunt ice shelf whis suggests that basal melt is a key contributor to milne ice shelf thinning glacier inflow to the ice shelf has also reduced markedly over the past 28 years the transition of ice shelf ice to lake ice was the most important source of mass loss a 28 5 km2 epishelf lake now exists on the landward side of the ice shelf given these recent changes disintegration of the milne ice shelf will almost certainly continue in the future

observed dynamics of coastal flow at cape mendocino during coastal waves 1996 abstract airborne in situ and remote meteorological measurements from around cape mendocino california sampled during the coastal waves 1996 field program are analyzed for three different days 7 12 and 26 june 1996 two days conformed to typical summertime conditions with a strong northerly downcoast flow while the wind on the third day was weaker on the first 2 days the flow was supercritical in the sense that the froude number was larger than unity and these 2 days feature expansion fans in the lee of the cape on the third day no such phenomenon was observed all 3 days had a strong thermal wind caused by the marine inversion sloping down toward the coast on the first 2 days the flow aloft was westerly or northerly so that the thermal wind added to the background flow results in a strong jet on the third day the flow aloft was southerly and consequently even with the added thermal wind the northerly flow in the marine layer was too weak to be supercritical the main difference between t

some insights into the characteristics and dynamics of the chilean low level coastal jet abstract the characteristics and dynamics of the chilean low level coastal jet cllcj are examined here through diagnosing real time mesoscale model forecasts in support of the variability of the american monsoon system vamos ocean cloud atmosphere land study vocals and additional sensitivity simulations the forecasted surface winds over the southeast pacific compare favorably with available observations according to the forecasts and sensitivity simulations the southeast pacific high pressure system seph plays a primary role in driving the cllcj the andes significantly intensify the cllcj mainly through interacting with the seph and anchoring a baroclinic zone along the chilean coast the land sea differential heating also enhances the cllcj by strengthening the coastal baroclinic zone based on the location of the seph center the cllcj can be separated into two types a strong forcing jet with the seph close to the central chilean coastline and a weak forcing jet with the seph centered fa

warm ocean is eroding west antarctic ice sheet 1 satellite radar measurements show that ice shelves in pine island bay have thinned by up to 5 5 m yr 1 over the past decade the pattern of shelf thinning mirrors that of their grounded tributaries the pine island thwaites and smith glaciers and ocean currents on average 0 5 c warmer than freezing appear to be the source the synchronised imbalance of the inland glaciers is the result of reduced lateral and basal tractions at their termini and the drawdown of grounded ice shows that antarctica is more sensitive to changing climates than was previously considered

catalina eddies and coastally trapped disturbances abstract observations show that coastally trapped disturbances ctds often accompany catalina eddies that appear in the southern california bight in a previous modeling study of ctds using simple environments and forcings simulations of ctds also evolved a mesoscale eddy that played a critical role in ctd formation and evolution in this study the simple environments and forcings are extended to model the southern california bight and simulations produce both catalina eddies and ctds the simulated catalina eddies and the mesoscale eddies in the previous ctd studies are dynamically equivalent the primary mechanism for eddy formation in the simulations is lee troughing and eddies and ctds are produced provided that 1 there is sufficient stratification in the environment 2 the offshore flow is of sufficient strength breadth and duration and 3 there is sufficient terrain to produce significant lee troughing the simulations show that ctds can propagate out of the bight region when synoptic winds

21st century evolution of greenland outlet glacier velocities earlier observations on several of greenland s outlet glaciers starting near the turn of the 21st century indicated rapid annual scale and large 100 increases in glacier velocity combining data from several satellites we produce a decade long 2000 to 2010 record documenting the ongoing velocity evolution of nearly all 200 of greenland s major outlet glaciers revealing complex spatial and temporal patterns changes on fast flow marine terminating glaciers contrast with steady velocities on ice shelf terminating glaciers and slow speeds on land terminating glaciers regionally glaciers in the northwest accelerated steadily with more variability in the southeast and relatively steady flow elsewhere intraregional variability shows a complex response to regional and local forcing observed acceleration indicates that sea level rise from greenland may fall well below proposed upper bounds

satellite derived volume loss rates and glacier speeds for the juneau icefield alaska we provide a high resolution map of elevation change rates dh dt at the juneau icefield jif southeastern alaska in order to quantify its contribution to sea level rise between 2000 and 2009 2013 we also produce the first high resolution map of ice speeds at the jif which we use to constrain flux and look for acceleration we calculate dh dt using stacked digital elevation models dems from the advanced spaceborne thermal emission and reflection radiometer aster instrument and the shuttle radar topography mission srtm taking into account srtm c band penetration via comparison with srtm x band elevations overall the jif is losing mass less rapidly 0 13 0 12mw e a than other alaskan icefields 0 79mw e a we determine glacier speeds using pixel tracking on optical image pairs acquired from 2001 to 2010 by aster from radar image pairs acquired between 2007 and 2011 and from radar interferometry in 1995 we detect seasonal speed variations but no interannual acceleration ruling out dynamics as the cause of the observed thinning thinning must therefore be due to the documented warming in the region flux measurements confirm this for mendenhall glacier showing that calving constitutes only 2 5 5 of mass loss there

channel avulsion on alluvial fans in southern arizona historical aerial photographs and field observations on five fluvially dominated alluvial fans in southern arizona demonstrate that channel avulsion invariably occurs where bank heights are low and often at channel bends channel abandonment occurs through stream capture when overland flow from the main channel accelerates and directs headward erosion of smaller channels heading on the fan surface five distinct channel morphologies observed on the fans are related to different stages of the avulsion process and can be used to identify areas on a fan surface that are prone to avulsion a descriptive model of channel avulsion illustrates how the morphology of a single channel reach will evolve through time as it captures the main flow path and is itself eventually abandoned immediately following avulsions small preexisting channels that capture flow from the main channel will typically experience three fold or greater increases in channel width subsequent large floods can be stably conveyed through these high capacity reaches an uninterrupted sequence of sediment charged small flows however will eventually begin to back fill the wide channels as vegetation growth stabilizes the banks the stabilized and back filled channels are now prone to abandonment during large floods because the decrease in the channel s capacity leads to the generation of overland flow beyond the margins of the shallowed channels the action of the small aggrading floods is critical in the avulsion process since the greatest amount of overland flow is generated where bank heights are lowest as a result both small and large floods are effective agents of landscape change on the fans channel avulsions on the five fans are not completely random events in space and time because their occurrence is controlled by the relative positioning of low banks along the main channel and smaller channels draining the fan surface consequently the location and timing of future channel avulsions can potentially be anticipated in an effort to improve flood hazard assessment on fluvial fans in the rapidly urbanizing southwestern united states

vertical structure of the southwest monsoon low level jet over the central and eastern arabian sea abstract the vertical structure of the low level wind jet over the arabian sea during the southwest monsoon is modeled by using the geostrophic wind shear thermal wind and a two layer boundary layer model we show that geostrophic wind shear is dominant above the low level wind maximum while turbulent momentum exchange is dominant below both effects combine to produce a low level wind jet model results compare well with observations obtained from a research aircraft during the 1979 summer monsoon experiment

on the role of sloping terrain in the forcing of the great plains low level jet abstract the summertime great plains low level jet llj has been the subject of numerous investigations during the past several decades characteristics of the llj include nighttime development of a pronounced wind maximum of typically 15 20 m s 1 at levels 300 800 m above the surface and a clockwise rotation of the wind maximum during the course of the night maximum frequency of occurrence of the llj is found in the southern great plains theories proposed to explain the diurnal wind maximum of the great plains llj include inertial oscillation of the ageostrophic wind the diurnal oscillation of the horizontal pressure field associated with heating and cooling of the sloping terrain and the western boundary current interpretations a simple equation system and output from the 12 km horizontal resolution weather research and forecasting nonhydrostatic mesoscale model nam for july 2008 are used to provide evidence as to the importance of the great plains topography in driving the llj summertime heati

the structure of gradually transforming marine stratocumulus during the astex first lagrangian experiment summary an analysis of the mean and turbulent structure of the planetary boundary layer is presented using aircraft data obtained during the atlantic stratocumulus transition experiment e rst lagrangian experiment the analysis of the mean vertical structure relies mostly on slant proe le data however part of the analysis also uses socalled porpoise runs in the vicinity of the cloud top the analysis of the turbulence structure utilizes all of the data horizontal eight legs as well as slant proe les and presents both scaled turbulence statistics and a spectral analysis the purpose is to investigate details in the temporal development of the e rst lagrangian experiment and to study the turbulent structure in order to e nd scale relations that can be utilized in improved modelling of the stratocumulus capped boundary layer the hypothesis is that so called cloud decoupling has a signie cant impact on the turbulence scaling the measured cloud water is corrected to become consistent between the two participating aircraft the corrected maximum cloud water is more constant in time than in previous studies of the erst lagrangian it is suggested that previously analysed temporal variability may be an artefact of using two different instruments to measure cloud water the cloud top jump in equivalent potential temperature is positive in the erst three eights sufe ciently large for a stable cloud top but decreases and becomes negative for the last two eights in line with the breaking up of the cloud eeld the upper part of the boundary layer warms and dries more rapidly than the lower suggesting entrainment to be a dominant factor in the development of the cloud the analysis of the porpoise e ight legs illustrates how sharp features at the cloud top inversion are smoothed out while analysing several proe les eight legs or even entire eights rather than normalizing each proe le with the height to the local cloud top scaling of the turbulent e uxes and the velocity variances shows that the cloud layer is decoupled throughout almost the entire erst lagrangian it is also shown that while surface layer scaling is appropriate for the marine atmospheric boundary layer mabl the cloud layer turbulence scales with convective scaling the lowfrequency spectrum has no spectral gap with the exception of the vertical velocity and continues to increase with decreasing frequency with only a change in slope this indicates the presence of mesoscale motions the cospectra of the turbulent euxes are very noisy throughout when averaging several spectra into height intervals the scales of the turbulence as indicated by the peak in the averaged spectra appear to vary with height above the surface in the mabl but to be height independent in the cloud layer an attempt to calculate a dissipation length scale shows scatter but is consistent with a dissipation length scale increasing linearly with height in the mabl but being roughly constant or possibly parabolic with height in the cloud layer

breakup of the larsen b ice shelf triggered by chain reaction drainage of supraglacial lakes this research is supported by the u s national science foundation under grant geop ant 0944248 awarded to d r m and grants ant 0838811 and arc 0934534 awarded to o v s

rapid retreat acceleration and thinning of glaciar upsala southern patagonia icefield initiated in 2008 the patagonia icefields are characterized by a large number of outlet glaciers calving into lakes and the ocean in contrast to the recent intensive research activities on tidewater glaciers in other regions very few observations have been made on calving glaciers in patagonia we analysed satellite images of glaciar upsala the third largest freshwater calving glacier in the southern patagonia icefield to investigate changes in its front position ice velocity and surface elevation from 2000 to 2011 our analyses revealed a clear transition from a relatively stable phase to a rapidly retreating and fast flowing condition in 2008 the glacier front receded by 2 9 km and the ice velocity increased by 20 50 over the 2008 11 period we also found that the ice surface lowered at a rate of up to 39 m a 1 from 2006 to 2010 this magnitude and the rate of changes in the glacier front position ice velocity and surface elevation are greater than previously reported for glaciar upsala and comparable to recent observations of large tidewater glaciers in greenland our data illustrate details of a rapidly retreating calving glacier in patagonia that have been scarcely reported despite their importance to the mass budget of the patagonia icefields

fusion of multi sensor surface elevation data for improved characterization of rapidly changing outlet glaciers in greenland abstract during the last two decades surface elevation data haven been gathered over the greenland ice sheet gris from a variety of sensor ranging from laser altimetry to stereoscopic dems derived from imaging sensors the spatio temporal resolution the accuracy and the spatial coverage among the data differ widely for example icesat a spaceborne laser profiler has a high temporal resolution but sparse spatial coverage which places the nearest ground track to the calving front of the kangerlussuaq glacier in east greenland our study site 30 km up stream on the other hand stereoscopic dems provide almost continuous spatial coverage but at a lower accuracy this is a typical scenario for many rapidly changing outlet glaciers in greenland where a fusion of the disparate data sets is highly desirable to construct detailed spatio temporal histories of elevation change we present in this paper how our recently developed serac method surface elevation reconstruction and change detection is well suited to cope with this fusion problem more specifically we describe a novel approach to adjust stereoscopic dems to the laser altimetry point cloud based on height corrections determined from the time series of elevation changes calculated by serac these corrections are then used in a height adjustment of the dems

intra and inter annual variability in dynamic discharge from the academy of sciences ice cap severnaya zemlya russian arctic and its role in modulating mass balance

the vertical turbulence structure of the coastal marine atmospheric boundary layer the vertical turbulence structure in the marine atmosphere along a shoreline has been investigated using data from tower and aircraft measurements performed along the baltic coast in the southeast of sweden two properties make the baltic sea particularly interesting it is surrounded by land in all directions within moderate advection distances and it features a significant annual lag in sea surface temperature as compared with inland surface temperature the present data were collected mostly during spring or early summer when the water is cool i e with a stably or neutrally stratified marine boundary layer usually capped by an inversion substantial daytime heating over the land area results in a considerable horizontal thermal contrast measurements were made on a small island on a tower with a good sea fetch and with an airborne instrument package the profile data from the aircraft is from 25 slant soundings performed in connection to low level boundary layer flights the results from the profiles are extracted through filtering techniques on individual time space series individual profiles applying different normalization and finally averaging over all or over groups of profiles the land based data are from a low tower situated on the shoreline of a small islandmore with a wide sector of unobstructed sea fetch several factors are found that add to the apparent complexity of the coastal marine environment the state of the sea appears to have a major impact on the turbulence structure of the surface layer jet shaped wind speed profiles were very common at the top of the boundary layer in about 50 of the cases and distinct layers with increased turbulence were frequently found well above the boundary layer in about 80 of the cases the present paper will concentrate on a description of the experiment the analysis methods and a general description of the boundary layer turbulence structure over the baltic sea 40 refs 16 figs 2 tabs less

marine stratocumulus layers part 1 mean conditions abstract the mean radiational dynamical and thermodynamical structure of the marine stratocumulus topped mixed layers of the california coast is described for two days in june 1976 using data from the ncar electra aircraft we suggest that the synoptic conditions found may be typical of about half of the shallow stratocumulus topped boundary layers that occur in this region during summer the inversion was low near the coast and increased in height to the west consistent with the average westward increase in sea surface temperature north south inversion height change was largely due to entrainment and mean mesoscale vertical motions below the inversion strong winds 12 20 m s 1 from the north and horizontal inhomogeneities resulted in large advection terms in mean field equations the sloping inversion often produced large vertical shears of the actual and geostrophic wind velocities across the inversion because of low liquid water contents 0 1 g kg 1 temperature and water vapor could be measure

turbulence structure of the hurricane boundary layer between the outer rainbands abstract as part of the coupled boundary layers air sea transfer cblast hurricane program flights were conducted to directly measure turbulent fluxes and turbulence properties in the high wind boundary layer of hurricanes between the outer rainbands for the first time vertical profiles of normalized momentum fluxes sensible heat and humidity fluxes and variances of three dimensional wind velocities and specific humidity are presented for the hurricane boundary layer with surface wind speeds ranging from 20 to 30 m s 1 the turbulent kinetic energy budget is estimated indicating that the shear production and dissipation are the major source and sink terms respectively the imbalance in the turbulent kinetic energy budget indicates that the unmeasured terms such as horizontal advection may be important in hurricane boundary layer structure and dynamics finally the thermodynamic boundary layer height estimated based on the virtual potential temperature profiles is roughly half of the boundary

glacier acceleration and thinning after ice shelf collapse in the larsen b embayment antarctica 1 ice velocities derived from five landsat 7 images acquired between january 2000 and february 2003 show a two to six fold increase in centerline speed of four glaciers flowing into the now collapsed section of the larsen b ice shelf satellite laser altimetry from icesat indicates the surface of hektoria glacier lowered by up to 38 6 m in a six month period beginning one year after the break up in march 2002 smaller elevation losses are observed for crane and jorum glaciers over a later 5 month period two glaciers south of the collapse area flask and leppard show little change in speed or elevation seasonal variations in speed preceding the large post collapse velocity increases suggest that both summer melt percolation and changes in the stress field due to shelf removal play a major role in glacier dynamics

aircraft observations of a coastally trapped wind reversal off the california coast abstract the summertime marine atmospheric boundary layer off the california coast is normally characterized by northerly winds associated with the pacific high this pattern is occasionally disturbed by episodes of southerly winds and a finger of fog or low stratus adjacent to the coastline extending approximately 100 km offshore these events propagate northward along the coast with speeds between 5 and 12 m s 1 and have a life span of several days these occurrences have been referred to as coastally trapped wind reversals ctwrs coastally trapped disturbances or southerly surges the ctwr event of 22 25 june 2006 was explored by the university of wyoming king air research aircraft to document the physical characteristics of the wind reversal in an attempt to infer the forcing mechanisms responsible for the propagation two flights from 23 june are presented that are representative of the ctwr during its mature stage sawtooth maneuvers depict the ctwr vertical structure and isobaric legs directly

the marine atmospheric boundary layer jet in the coastal ocean dynamics experiment the vertical and horizontal structure of the atmospheric boundary layer near the northern california coast was investigated during spring upwelling conditions as part of the 1981 coastal ocean dynamics experiment two daytime aircraft flights were devised to measure mean and turbulent quantities for 25 km tracks along and across the continental shelf from 30 to 1200 m altitude the pacific high offshore and an inland thermal low characterized the synoptic situations and equatorward winds resulted which produced intense ocean upwelling the wind profile was found to be jet shaped maximum wind speeds were 25 m s 1 and 16 m s 1 at 400 and 100 m respectively in the two flights above and below the heights of the jet speed maxima the wind speed decreased rapidly sharp density inversions existed at the levels of the peak wind speeds in one flight the inversion also sloped down toward the coast turbulence was effectively confined below the inversions strong zonal temperature gradients above the inversion between the hot land and cool marine air caused a thermal wind for which the wind speed decreased with height below the inversion turbulent stress divergence was large and effective in transferring the horizontal momentum of the wind to the sea slowing the wind there was also a small thermal wind below the inversion but opposite to the one above owing to the well mixed air temperature following the sea surface temperature which was cold at the coast and relatively warmer offshore owing to the upwelling these effects explain the jet shaped wind profile the mean momentum equations show that an acceleration toward the coast can balance the pressure gradient coriolis and turbulent stress divergence forces and there were some observations to support this complete balance was not obtained for the turbulent kinetic energy budget inferred dissipation rates were too large

dynamic instability of marine terminating glacier basins of academy of sciences ice cap russian high arctic ice sheets and smaller ice caps appear to behave in dynamically similar ways both contain slow moving ice that is probably frozen to the bed interspersed with fast flowing ice streams and outlet glaciers that terminate into the ocean academy of sciences ice cap akademii nauk ice cap 5570km2 severnaya zemlya russian high arctic provides a clear example of this varied flow regime we have combined satellite measurements of elevation change and surface velocity to show that variable ice stream dynamics dominate the mass balance of the ice cap since 1988 the ice cap has lost 58 16 gt of ice corresponding to 3 of its mass or 0 16mm of sea level rise the climatic mass balance is estimated to be close to zero and terminus positions have remained stable to within a few kilometers implying that almost all mass loss has occurred through iceberg calving the ice cap calving rate increased from 0 6 gt a 1 in 1995 to 3 0 gt a 1 in 2000 02 but has recently decreased to 1 4 gt a 1 due to a likely slowdown of the largest ice stream such highly variable calving rates have not been reported before from high arctic ice caps suggesting that these ice masses may be less stable than previously thought

massive destabilization of an arctic ice cap abstract ice caps that are mostly frozen at the bedrock ice interface are thought to be stable and respond slowly to changes in climate we use remote sensing to measure velocity and thickness changes that occur when the margin of the largely cold based vavilov ice cap in the russian high arctic advances over weak marine sediments we show that cold based to polythermal glacier systems with no previous history of surging may evolve with unexpected and unprecedented speed when their basal boundary conditions change resulting in very large dynamic ice mass losses an increase in annual mass loss by a factor of 100 over a few years we question the future long term stability of cold and polythermal polar ice caps many of which terminate in marine waters as the climate becomes warmer and wetter in the polar regions

orographically trapped coastal wind events in the pacific northwest and their oceanic response three ageostrophic orographically trapped wind events in the coastal zone of the pacific northwest are examined time series of wind speed wind direction air temperature sea level pressure ocean currents and ocean temperature are utilized to establish the general features of these events and to characterize the oceanic response it is suggested that these atmospheric events are highly nonlinear bores or gravity currents rather than quasi linear kelvin waves observed oceanic responses include a drop in sea surface temperature sst of 1 3 c offshore to approximately 150 km approximately the atmospheric rossby radius and a rise in sst of similar magnitude within 15 km of the shore a set of reduced gravity fully nonlinear single layer models is utilized to investigate the dynamics of the atmospheric features and their oceanic response and a possible air sea interaction the models reproduce several of the first order features of the air and sea phenomena such as the development of the atmospheric front and the wake of near inertial waves in the ocean

a review of postglacial emergence on svalbard franz josef land and novaya zemlya northern eurasia the pattern of postglacial emergence in the barents sea is pivotal to constraining the timing of deglaciation and extent and thickness of the last ice sheet in northern eurasia this review unites records of holocene relative sea level from svalbard franz josef land and novaya zemlya to better understand the geometries of past ice sheet loads emergence data from northern eurasia confine the maximum area of glacier loading to the northwestern barents sea where 100 m of emergence is measured on kongs ya deglacial unloading commenced on western and northern spitsbergen c 13 12 14 c ka ago and by c 10 5 14 ck a on eastern svalbard and more distal sites on franz josef land and novaya zemlya the marine limit phase c 13 12 14 c ka on western and northern spitsbergen is characterized by the construction of spits indicating a dominance of long shore drift over stormgenerated fetch reflecting extensive sea ice coverage of coastal areas at sites in proximity to the ice sheet margin on western and northern spitsbergen there is evidence for a transgressive regressive cycle c 6 4 14 c ka possibly reflecting back migration of displaced mantle material a modern transgression is inferred from the marine erosion of 17th century cultural features and 14 c ages of whalebone and terrestrial peat buried by modern storm gravels that place sea level at its present position by c 2 to 1 ka ago the greatest observed emergence on franz josef land occurs on bell island with a marine limit at 49 m aht formed c 10 14 c ka available emergence data since 9 ka show rising strandlines toward the southwest at b0 3 m km the northern limit of emergence on franz josef land is poorly constrained because relative sea level data is sparse north of 80 30 0 n in contrast to svalbard and franz josef land the marine limit on northern novaya zemlya is only 10 15 m above high tide and formed between 6 5 and 5 0 14 c ka when global sea level was stabilizing all sites show little apparent emergence during the past 2 ka with the youngest raised landforms at identical heights to storm beaches this minimal glacio isostatic signature on novaya zemlya and on vaygach island where deglaciation commenced 10 ka ago indicates ice sheet thicknesses of o1 5 km the spatial variation in emergence for the barents sea indicates that western and northern spitsbergen and novaya zemlya were near the reactive margin of the ice sheet and these areas sustained the briefest ice coverage 2 6 ka and were probably not in isostatic equilibrium in contrast central and eastern svalbard and southern franz josef land were beneath a substantial ice load and probably sustained this load for c 10 14 c ka and achieved isostatic equilibrium isostasy residual from an ice sheet model portrays well the general pattern of uplift and load response at the centre of ice sheets but deviates substantial at the ice sheet margin or areas covered by thin ice like novaya zemlya

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

surface melt induced acceleration of greenland ice sheet flow ice flow at a location in the equilibrium zone of the west central greenland ice sheet accelerates above the midwinter average rate during periods of summer melting the near coincidence of the ice acceleration with the duration of surface melting followed by deceleration after the melting ceases indicates that glacial sliding is enhanced by rapid migration of surface meltwater to the ice bedrock interface interannual variations in the ice acceleration are correlated with variations in the intensity of the surface melting with larger increases accompanying higher amounts of summer melting the indicated coupling between surface melting and ice sheet flow provides a mechanism for rapid large scale dynamic responses of ice sheets to climate warming

evolution of stable internal boundary layers over a cold sea the situation studied in this paper relates to air flow from a heated land surface out over a water surface with much lower temperature observations from the baltic sea where this kind of situati

rapid collapse of northern larsen ice shelf antarctica in january 1995 4200 square kilometers of the northern larsen ice shelf antarctic peninsula broke away radar images from the ers 1 satellite complemented by field observations showed that the two northernmost sections of the ice shelf fractured and disintegrated almost completely within a few days this breakup followed a period of steady retreat that coincided with a regional trend of atmospheric warming the observations imply that after an ice shelf retreats beyond a critical limit it may collapse rapidly as a result of perturbated mass balance

from ice shelf tributary to tidewater glacier continued rapid recession acceleration and thinning of rohss glacier following the 1995 collapse of the prince gustav ice shelf antarctic peninsula glasser n f scambos t a bohlander j truffer m pettit e davies b j 2011 journal of glaciology 57 203 397 406

aircraft observations of the ekman layer during the joint air sea interaction experiment results are presented from an observational study of the mid latitude atmospheric boundary layer over the sea the data were obtained mainly by instrumented aircraft as part of the joint air sea interaction experiment jasin the eight occasions chosen for study are characterized by small surface buoyancy fluxes and the conditions are well described as near neutral and barotropic in the absence of low level inversions a well mixed ekman layer is observed on each occasion but is limited to a depth of approximately 0 2u f accurate measurements of horizontal gradients including pressure together with improved wind observations and turbulent flux measurements enabled each of the terms of the momentum balance to be evaluated throughout the depth of this layer these terms were found to balance quite closely were well described by ekman scaling and were consistent with the requirements of the measured turbulent kinetic energy balance the latter suggests that the main shear production terms are dissipated locally and that little is exported to upper levels in the ekman layer to enable significant deepening by entrainment although only a slight increase in instability appears to be needed to alter this balance conditions in which such boundary layer structure might be observed are suggested values of various coefficients used in schemes for relating surface fluxes to mean quantities cd ce cg a b are derived and compared with previous measurements spectral analysis reveals that most of the turbulent transport is confined to a distinct high wavenumber region whose characteristics vary as a function of ekman layer depth and stability parameters this is superimposed on larger scale fluctuations which do not vary appreciably within the ekman layer and which therefore dominate the variances in the upper regions as the intensity of the smaller scale turbulence decreases strongly with height finally further implications of this interpretation are discussed with particular reference to the heat and water vapour balance these imply that removal of water vapour from the ekman layer is accomplished by transfer related to cloud activity marking a significant change in the mechanism of turbulent transport at the top of this layer the relationship between these and similar results obtained concurrently by different methods is also discussed

accelerated ice discharge from the antarctic peninsula following the collapse of larsen b ice shelf acceleration exceeds 27 km 3 per year and ice is thinning at rates of tens of meters per year we attribute this abrupt evolution of the glaciers to the removal of the buttressing ice shelf the magnitude of the glacier changes illustrates the importance of ice shelves on ice sheet mass balance and contribution to sea level change index terms 1827 hydrology glaciology 1863 1863 hydrology snow and ice 1827 3349 meteorology and atmospheric dynamics polar meteorology 6924 radio science interferometry 9310 information related to geographic region antarctica citation rignot e g casassa p gogineni w krabill a rivera and r thomas 2004 accelerated ice discharge from the antarctic peninsula following the collapse of larsen b ice shelf geophys res lett 31 l18401 doi 10 1029 2004gl020697

recharge of a subglacial lake by surface meltwater in northeast greenland observations of rapid persistent elevation gains that occur on the ice surface above a subglacial lake as the lake is refilled with surface meltwater during the summer melt period in greenland show that surface meltwater may be trapped and stored at the bed of an ice sheet affecting ice dynamics downstream the discovery of a 70 metre deep collapse basin near the summit of the largest and most northerly peripheral ice cap of greenland and the use of high resolution stereo satellite imagery to monitor its evolution suggests that surface meltwater can be trapped and stored beneath the greenland ice sheet previously meltwater from the surface of the ice sheet had been assumed to drain efficiently through the basal hydrologic system during the summer melt period rapid persistent elevation gains occur on the ice surface above a subglacial lake as the lake is refilled with surface meltwater and stored at least on annual time scales these findings have potential implications for our understanding of ice sheet temperature and velocity in a warming climate surface meltwater production on large ice sheets is expected to increase if this water is delivered to the ice sheet base it may have important consequences for ice dynamics for example basal water distributed in a diffuse network can decrease basal friction1 2 and accelerate ice flow3 4 5 6 7 8 whereas channelized basal water can move quickly to the ice margin where it can alter fjord circulation and submarine melt rates9 10 less certain is whether surface meltwater can be trapped and stored in subglacial lakes beneath large ice sheets here we show that a subglacial lake in greenland drained quickly as seen in the collapse of the ice surface and then refilled from surface meltwater input we use digital elevation models from stereo satellite imagery and airborne measurements to resolve elevation changes during the evolution of the surface and basal hydrologic systems at the flade isblink ice cap in northeast greenland during the autumn of 2011 a collapse basin about 70 metres deep and about 0 4 cubic kilometres in volume formed near the southern summit of the ice cap as a subglacial lake drained into a nearby fjord over the next two years rapid uplift of the floor of the basin which is approximately 8 4 square kilometres in area occurred as surface meltwater flowed into crevasses around the basin margin and refilled the subglacial lake our observations show that surface meltwater can be trapped and stored at the bed of an ice sheet sensible and latent heat released by this trapped meltwater could soften nearby colder basal ice11 and alter downstream ice dynamics12 13 heat transport associated with meltwater trapped in subglacial lakes should be considered when predicting how ice sheet behaviour will change in a warming climate

svalbard glacier elevation changes and contribution to sea level rise 1 we compare satellite altimetry from the ice cloud and land elevation satellite icesat 2003 2007 to older topographic maps and digital elevation models 1965 1990 to calculate long term elevation changes of glaciers on the svalbard archipelago results indicate significant thinning at most glacier fronts with either slight thinning or thickening in the accumulation areas except for glaciers that surged which show thickening in the ablation area and thinning in the accumulation areas the most negative geodetic balances occur in the south and on glaciers that have surged while the least negative balances occur in the northeast and on glaciers in the quiescent phase of a surge cycle geodetic balances are related to latitude and to the dynamical behavior of the glacier the average volume change rate over the past 40 years for svalbard excluding austfonna and kvitoya is estimated to be 9 71 0 55 km3 yr 1 or 0 36 0 02 m yr 1 w equivalent for an annual contribution to global sea level rise of 0 026 mm yr 1 sea level equivalent

application of kinematic wave theory for predicting flash flood hazards on coupled alluvial fan piedmont plain landforms a rainstorm that caused a severe flash flood on the piedmont plain at the toe positions of two alluvial fans located to the west of the organ mountains in dona ana county new mexico usa is analysed the space time distributions of rainfall are evaluated from the next generation weather radar nexrad and overland flow is modelled as kinematic wave the spatial distribution of rainfall shows a topographic control the greatest rainfall depth duration and intensity occurred at the higher elevation mountain slopes and decreased with decreasing elevation from the alluvial fans to the piedmont plain the alluvial fan piedmont plain system is modelled by coupling divergent and rectangular overland flow planes explicit finite difference approximations hybridized with the analytical method of characteristics are made to the kinematic wave equations to account for the spatial and temporal distribution of the rainfall and variable boundary conditions simulation results indicate that sheet flow floodwater elevations rise 1 in a nonlinear fashion from the apex to toe positions of the alluvial fans and 2 near linearly from the toe positions of the alluvial fans onto the piedmont plains with the formation of kinematic shocks near the middle to the upstream end of the plane at times between the initiation of the rainstorm and the time of concentration of the plane thus the maximum flooding occurs at the middle or upstream sections of the piedmont plains regardless of the pattern of space time variability of rainfall these results are in agreement with observed geomorphologic features suggesting that piedmont plains are naturally flood prone areas this case study demonstrates that flood hazards on piedmont plains can exceed those on alluvial fans the models presented in this study suggest that the flood hazard zones on coupled alluvial fan piedmont plain landforms should be delineated transverse to the flow directions as opposed to the flood hazard zones with boundaries in the longitudinal direction of the axis of an alluvial fan copyright 2003 john wiley sons ltd

preferred directions of flow on alluvial fans in this paper modifications of the method used to delineate flood plains on active alluvial fans for the national flood insurance program are suggested given new data regarding the deviations of channels from the medial radial line at the apex of the fan in the original methodology it was assumed that every point on an alluvial fan contour had an equal probability of being impacted during a flood event that is a uniform probability distribution was assumed data now available suggest that a normal distribution better describes the probability of points on an alluvial fan contour being hit during a flood event results from an example of the application of the modified methodology are compared with the results obtained using the original methodology

assessing the performance of 20 25 m footprint waveform lidar data collected in icesat data corridors in greenland 1 the precision and accuracy of surface elevation measurements of the greenland ice sheet provided by 20 25 m footprint waveform laser altimetry is assessed using data collected by nasa s lvis airborne lidar in september 2007 repeated data acquisitions from two 850 km long transects over the ice sheet and a 30 km long transect in the summit area are evaluated for consistency and compared to in situ data for validation comparisons to data collected by nasa s icesat system reveal good agreement in the summit area differences are better than 0 07 m 1 except for l3c where it is 0 13 m with mean offsets of 0 09 to 0 16 m depending on the campaign within the feeder zone to jakobshavn glacier ice elevation decreases of up to 12 m 2004 2008 are observed the results suggest that 25 m waveform lidar can measure ice sheet elevation precisely and accurately and that the measurement scheme could be used to complement the legacy icesat measurements

supercritical flow interaction within the cape blanco cape mendocino orographic complex abstract supercritical flow interaction occurring in the marine boundary layer between closely spaced coastal capes is investigated with a mesoscale numerical prediction model as an extension of previous work the u s navy s coupled ocean atmosphere mesoscale prediction system coamps is used to perform idealized model simulations with marine layers of varying upstream froude number to elucidate the different flow responses for a single convex bend the impact upon the supercritical flow of introducing a series of closely spaced coastal bends is then investigated the expansion fan is significantly reduced in magnitude and size by the formation of a compression wave at a blocking concave bend approximately 150 km downstream building upon the idealized marine layer response real data forecasts are then examined for several time periods of supercritical flow interaction between cape blanco oregon and cape mendocino california observations from the coastal waves 1996 cw96 field program were colle

a millennial scale record of arctic ocean sea ice variability and the demise of the ellesmere island ice shelves 1 sea ice ice shelves at the apex of north america 80 n constitute the oldest sea ice in the northern hemisphere we document the establishment and subsequent stability of the ward hunt ice shelf and multiyear landfast sea ice in adjacent fiords using 69 radiocarbon dates obtained on holocene driftwood deposited prior to coastal blockage these dates 47 of which are new record a hiatus in driftwood deposition beginning 5500 cal yr bp marking the inception of widespread multiyear landfast sea ice across northern ellesmere island this chronology together with historical observations of ice shelf breakup 1950 to present provides the only millennial scale record of arctic ocean sea ice variability to which the past three decades of satellite surveillance can be compared removal of the remaining ice shelves would be unprecedented in the last 5500 years this highlights the impact of ongoing 20th and 21st century climate warming that continues to break up the remaining ice shelves and soon may cause historically ice filled fiords nearby to open seasonally

outlet glacier response to the 2012 collapse of the matusevich ice shelf severnaya zemlya russian arctic the matusevich ice shelf mis located within the severnaya zemlya archipelago in the russian arctic rapidly broke apart between 10 august and 7 september 2012 we examine the response of the outlet glaciers that fed the mis from local ice caps to the removal of the ice shelf we use spaceborne laser altimetry and multiple optically derived digital elevation models to track ice surface elevation change rates dh dt between 1984 and 2014 glacier speeds are measured by pixel tracking from optical and radar imagery between 2010 and 2014 and interferometric synthetic aperture radar in 1995 to compare precollapse and postcollapse velocities we find that the three main outlet glaciers that fed the mis are thinning an order of magnitude more rapidly than most of the rest of severnaya zemyla based upon icesat data from 2003 to 2009 recent 2012 to 2014 thinning rates are three to four times faster than the 30 year average thinning rate calculated between 1984 and 2014 the springtime speeds of the largest outlet glacier issledovateley have increased more than 200 at the terminus between april 2010 and april 2014 to date changes in surface elevation dh dt and velocity at the outlet glaciers near mis are smaller than glacier responses to ice shelf collapse in antarctica it is possible that the mis was already very weak prior to the 2012 collapse and unable to support back stress further observations are required to assess whether the thinning and nonmelt season glacier speeds are continuing to accelerate

antarctic grounding line mapping from differential satellite radar interferometry 1 the delineation of an ice sheet grounding line i e the transition boundary where ice detaches from the bed and becomes afloat in the ocean is critical to ice sheet mass budget calculations numerical modeling of ice sheet dynamics ice ocean interactions oceanic tides and subglacial environments here we present 15 years of comprehensive high resolution mapping of grounding lines in antarctica using differential satellite synthetic aperture radar interferometry dinsar data from the earth remote sensing satellites 1 2 ers 1 2 radarsat 1 and 2 and the advanced land observing system alos palsar for years 1994 to 2009 dinsar directly measures the vertical motion of floating ice shelves in response to tidal oceanic forcing with millimeter precision at a sample spacing better than 50 m simultaneously over areas several 100 km wide in contrast with earlier methods that detect abrupt changes in surface slope in satellite visible imagery or altimetry data on stagnant and slow moving areas we find that breaks in surface slope are reliable indicators of grounding lines but on most fast moving glaciers and ice streams our dinsar results reveal that prior mappings have positioning errors ranging from a few km to over 100 km a better agreement is found with icesat s data also based on measurements of vertical motion but with a detection noise one order of magnitude larger than with dinsar overall the dinsar mapping of antarctic grounding lines completely redefines the coastline of antarctica

interferometric estimation of three dimensional ice flow using ascending and descending passes satellite radar interferometry sri provides an important new tool for determining ice flow velocity interferometric measurements made from a single track direction are sensitive only to a single component of the three component velocity vector observations from along three different track directions would allow the full velocity vector to be determined a north south looking synthetic aperture radar sar could provide these observations over large portions of the globe but not over large areas of the polar ice sheets the authors develop and demonstrate a technique that allows the three component velocity vector to be estimated from data acquired along two track directions ascending and descending under a surface parallel flow assumption this technique requires that there are accurate estimates of the surface slope which are also determined interferometrically to demonstrate the technique the authors estimate the three component velocity field for the ryder glacier greenland their results are promising although they do not have yet ground truth data with which to determine the accuracy of their estimates

sedimentary record of disintegrating ice shelves in a warming climate antarctic peninsula 1 seafloor sediments from beneath the former larsen a and prince gustav ice shelves document the recent breakup of the shelves and provide evidence for interpretation of previous events at three of five sites sediment texture coarsens upward with up to 40 sand at the surface radiometric 210pb dating shows this to have occurred between 1985 and 1993 several years before breakup of the shelf and that rates of accumulation of sediment on the seafloor doubled to quadrupled during this period these events are related to the release of eolian sediment in periodic rapid draining of small lakes and crevasses on the ice shelf before breakup x ray radiographs of sediment cores also document the recent influx of coarse particles gravel related to ice rafting during ice shelf disintegration because sediment is released irregularly in time and space from well separated point sources on the ice shelf during at least several years before final disintegration only a portion of the seafloor is affected

boundary layer development and gravity waves in conventionally neutral wind farms while neutral atmospheric boundary layers are rare over land they occur frequently over sea in these cases they are almost always of the conventionally neutral type in which the neutral boundary layer is capped by a strong inversion layer and a stably stratified atmosphere aloft in the current study we use large eddy simulations les to investigate the interaction between a large wind farm that has a fetch of 15 km and a conventionally neutral boundary layer cnbl in typical offshore conditions at the domain inlet we consider three different equilibrium cnbls with heights of approximately 300 m 500 m and 1000 m that are generated in a separate precursor les we find that the height of the inflow boundary layer has a significant impact on the wind farm flow development first of all above the farm an internal boundary layer develops that interacts downwind with the capping inversion for the two lowest cnbl cases secondly the upward displacement of the boundary layer by flow deceleration in the wind farm excites gravity waves in the inversion layer and the free atmosphere above for the lower cnbl cases these waves induce significant pressure gradients in the farm both favourable and unfavourable depending on location and case a detailed energy budget analysis in the turbine region shows that energy extracted by the wind turbines comes both from flow deceleration and from vertical turbulent entrainment though turbulent transport dominates near the end of the farm flow deceleration remains significant i e up to 35 of the turbulent flux for the lowest cnbl case in fact while the turbulent fluxes are fully developed after eight turbine rows the mean flow does not reach a stationary regime a further energy budget analysis over the rest of the cnbl reveals that all energy available at turbine level comes from upwind kinetic energy in the boundary layer in the lower cnbl cases the pressure field induced by gravity waves plays an important role in redistributing this energy throughout the farm overall in all cases entrainment at the capping inversion is negligible and also the work done by the mean background pressure gradient arising from the geostrophic balance in the free atmosphere is small

observed directional characteristics of the wind wind stress and surface waves on the open ocean sonic anemometer data were taken during the surface waves processes program swapp in march 1990 in the north pacific measurements of the wind stress vector span several strong wind events significant angles between the wind stress vector and the mean wind vector are seen simultaneous measurements of the directional wave field were made with a surface scanning doppler sonar the data suggest that the wind stress direction is influenced by the direction of the surface waves especially for stronger winds overall the stress vector lies between the mean wind and the mean wave directions at the higher wind speeds over 8 6 m s there is a nonzero correlation between the variations in wave directions and stress directions as well finally the stress and wave component directions have similar frequency dependence over the frequency band where wave energy is nonnegligible suggesting a dynamic link

numerical simulations of the boundary layer jet off the southeastern coast of china abstracta strong coastal boundary layer jet cblj 8 m s 1 off the southeastern coast of china around 28 n 122 e is found from the july 2006 11 hourly model data simulated by the advanced research weather research and forecasting model wrf arw with a 9 km horizontal grid the southerly cblj has a jet core at the 925 hpa level located along the western periphery of the west pacific subtropical high wpsh the cblj is mainly contributed by large scale enhancement by diurnal forcing and orographic effects by the coastal terrain along the southeastern china coast and the terrain of taiwan although the geostrophic winds offshore are faster in the afternoon due to the larger east west pressure gradient caused by land surface heating over the china plain the cblj has a nocturnal 0200 lst maximum in the afternoon hours easterly ageostrophic winds driven by differential land sea thermal heating develop at low levels after sunset with the disappearance of land surface heating the ageostrophic win

flume tank study of surface morphology and stratigraphy of a fan delta the morphodynamics of a river flood on a fan delta and its resultant stratigraphic and sedimentary signatures have been studied by means of a flume experiment under controlled boundary conditions the experiment revealed that deposition was dominant in flood periods when the channels were highly loaded with sediments in contrast erosion was dominant in periods of low flow mouth bars were formed when a subaqueous channel began to backfill the development of a mouth bar began with progradation in the down dip direction and proceeded by aggradation then retrogradation and finally transverse growth a channel bifurcated in multiple stages by sequentially forming mouth bars or by simultaneously forming arrays of mouth bars during the bifurcation the diffluent point moved upstream which resulted in channel migration and the development of a delta lobe flood events triggered fan delta front slide slump deposits

numerical study of the diurnal cycle along the central oregon coast during summertime northerly flow abstract a triply nested mesoscale atmospheric numerical model is used to study the dynamics of the diurnal cycle of the summertime lower atmosphere along the central oregon coast simulations of four consecutive days in september 1998 during which the winds were strong and northerly are analyzed comparisons with profiler observations suggest that the model performed well enough to provide a useful estimate of the diurnal circulation during the four days of interest the low level wind pattern has a broad maximum between cape blanco and cape mendocino with a large north south gradient along the oregon coast the low level jet undergoes diurnal horizontal and vertical displacements which partially resemble previous observational and modeling results along the california coast in both the model and the profiler data there is a minimum in northerly wind between 1500 and 1800 utc 0700 and 1000 local time and a double maximum in offshore flow above the marine boundary layer with peaks near 0700 and

thermal mesoscale circulations on the baltic coast 2 perturbation of surface parameters a three dimensional numerical study of an observed seabreeze sb is presented in a companion paper part 1 this paper part 2 addresses the influence of various forcing parameters emanating from the physical surface and perturbing the control run the control run in part 1 reveals that the sb stage is preceded by a coastal jet cj stage and that even moderate terrain seems to have a strong influence on the coastal mesoscale circulation the parameter sensitivity analysis attempts to identify the hierarchy of surface effects on the previously observed and modeled dynamics while the background airflow parameters remain unchanged seven perturbation runs are presented two topographic three land surface and two sea surface temperature perturbations it is shown that the terrain elevations h 0 206m have profound impact on the flow and its time history the main offshore island has a notable impact but does not change the main flow structure surface temperature perturbations modify the cj pattern dictated by the mesoscale thermal wind they also influence the sb shape more but the sb front propagation less the sb at one coast is locked up in phase with another sb at an almost perpendicular coast i e the first sb waits until the other sb removes the opposing ambient flow this is governed by the specific distribution of land and water and by the direction of the ambient flow against the coastline introduced sst gradients have minor to moderate localized influence on the dynamics for this case

aircraft observations and numerical simulations of the developing stage of a southerly surge near southern california abstractsummertime low level winds in the marine boundary layer off the california coast are predominantly from the north this pattern is interrupted periodically by southerly winds and low stratus that can propagate for hundreds of kilometers northward along the coast these events have been termed coastally trapped disturbances coastally trapped wind reversals and southerly surges their forcing has been the subject of extensive study and debate southerly surges remain difficult to forecast yet have a significant impact on coastal activities the beginning stage of a southerly surge on 16 june 2012 was explored during the precision atmospheric marine boundary layer experiment measurements of the horizontal wind and pressure field in the marine layer offshore from cape arguello hours prior to the onset of the surge were made using the university of wyoming king air research aircraft airborne measurements show that a horizontal pressure field is established with higher pressure to the south just pri

recent retreat of major outlet glaciers on novaya zemlya russian arctic influenced by fjord geometry and sea ice conditions substantial ice loss has occurred in the russian high arctic during the past decade predominantly on novaya zemlya yet the region has been studied relatively little consequently the factors forcing mass loss and the relative contribution of ice dynamics versus surface melt are poorly understood here we evaluate the influence of atmospheric oceanic forcing and variations in fjord width on the behaviour of 38 glaciers on the northern ice cap novaya zemlya we compare retreat rates on land versus marine terminating outlets and on the kara versus barents sea coasts between 1992 and 2010 90 of the study glaciers retreated and retreat rates were an order of magnitude higher for marine terminating outlets 52 1 m a 1 than for land terminating glaciers 4 8 m a 1 we identify a post 2000 acceleration in marine terminating glacier retreat which corresponded closely to changes in sea ice concentrations retreat rates were higher on the barents sea coast which we partly attribute to lower sea ice concentrations but varied dramatically between individual glaciers we use empirical data to categorize changes in along flow fjord width and demonstrate a significant relationship between fjord width variability and retreat rate results suggest that variations in fjord width exert a major influence on glacier retreat

mapping the grounding zone of the ross ice shelf antarctica using icesat laser altimetry we use laser altimetry from the ice cloud and land elevation satellite icesat to map the grounding zone gz of the ross ice shelf antarctica at 491 locations where icesat tracks cross the grounding line gl ice flexure in the gz occurs as the ice shelf responds to short term sea level changes due primarily to tides icesat repeat track analysis can be used to detect this region of flexure since each repeated pass is acquired at a different tidal phase the technique provides estimates for both the landward limit of flexure and the point where the ice becomes hydrostatically balanced we find that the icesat derived landward limits of tidal flexure are in many places offset by several km and up to 60 km from the gl mapped previously using other satellite methods we discuss the reasons why different mapping methods lead to different gl estimates including instrument limitations variability in the surface topographic structure of the gz and the presence of ice plains we conclude that reliable and accurate mapping of the gl is most likely to be achieved when based on synthesis of several satellite datasets

thermal mesoscale circulations on the baltic coast 1 numerical case study a three dimensional mesoscale numerical model is utilized to investigate a well documented seabreeze event taken from experimental data the simulations are not set up as a model validation instea

modelling alluvial fan morphology a mathematical model which estimates the scale independent sediment surface profile of alluvial fans has been developed this model utilizes a diffusive sediment transport model and an unsteady radial flow conservation relationship these equations are approximately solved assuming a quasi steady state closure with appropriate modelling assumptions for two end member fan types 1 fans where most of the fan surface is depositionally active denoted here as homogeneous and 2 fans characterized by channelling and sediment sorting processes the fundamental result for these two fan types is a dimensionless sediment profile relationship which approximates most fan surfaces the model suggests that the overall dimensionless morphology of alluvial fans is governed more by fundamental diffusion principles in sediment deposition than by individual environmental or basin characteristics additionally this work potentially can be extended to model temporal variation in fan development preliminary comparison with alluvial fan profiles is reasonable indicating that this model provides useful qualitative and quantitative information relating to alluvial fan process and morphology copyright 1999 john wiley sons ltd

glacier surface velocities in alpine terrain from optical satellite imagery accuracy improvement and quality assessment the worldwide retreat of mountain glaciers has important consequences for the water food and power supply of large and densely populated areas in south and central asia successful mitigation of the hydrological impacts on societies as well as assessing glacier related hazards require large scale monitoring of glacier dynamics however detailed glaciological data from the asian highlands are lacking due to its size and difficult accessibility we have applied a novel technique for precise orthorectification co registration and sub pixel correlation of advanced spaceborne thermal emission and reflection radiometer aster satellite imagery to derive surface velocities of himalayan glaciers our approach allows for the correction of offsets due to attitude effects and sensor distortions as well as elevation errors if a digital elevation model dem from the shuttle radar topography mission srtm was used for orthorectification after post processing the error on the displacements is on the order of 2 4 m per correlation translated into annual velocities this error is reduced increased when the correlated images are more less than a year apart through application of a filtering procedure and several quality tests the consistency of the results is validated to provide confidence in the remotely sensed velocity measurements despite the lack of ground control this novel approach allows fast easy and economically viable acquisition of detailed glaciological data in areas of difficult access and provides a means for large scale monitoring of glaciers in high mountainous terrain

experimental steep braided flow application to flooding risk on fans flooding processes occurring on alluvial fans are considerably different from those occurring along single thread rivers with well defined floodplains active erosion rapid sedimentation and the uncertainty in flow path make the prediction of flood evolution and extent difficult based on a large scale experiment this study investigates the long term evolution of the flow on a steep noncohesive sediment surface resembling a complex of merged alluvial fans the results are pertinent to the assessment of flooding hazard on alluvial fans at any given time the average flow occupancy was 21 of the surface however the flow was characterized by active channel switching and overflow processes the percentage of the surface remaining dry was found to decay harmonically with time a reworking time was defined as the time at which half of the surface that was initially dry remained dry whereas the other half was inundated at least once an empirical expression was developed in which reworking time is proportional to the average cross sectional area of flow and inversely proportional to the sediment supply

ice loss rates at the northern patagonian icefield derived using a decade of satellite remote sensing abstract we use a satellite based survey of glacier surface elevation changes speeds and surface melt conditions between 2000 and 2011 to quantify mass loss from the northern patagonian icefield npi chile a history of ice elevation change is found by differencing aster digital elevation models dems relative to a void filled version of the dem collected by the shuttle radar topography mission srtm in february 2000 thinning rates have accelerated at lower elevations while above the equilibrium line altitude ela recent thinning rates are not significantly different from those observed in previous studies a volumetric change of 4 06 0 11 km 3 yr is found by summing surface elevation changes over all glaciers in the npi this is regarded as a lower bound because volume loss due to frontal retreat and sub aqueous melting is not included this volume change is converted to a mass loss of 3 40 0 07 gt yr taking into account density differences above and below the equilibrium line we find that the npi is providing at least 0 009 0 0002 mm yr to ongoing sea level change in agreement with previous estimates sub pixel offset tracking of aster image pairs is used to produce glacier displacements over intervals typically ranging from 6 days to 18 months the first whole icefield composite velocity map is presented the terminus of the san rafael glacier on the western side of the npi sustained a peak calving front speed of 19 7 1 2 m day for 7 days in the austral fall of 2007 passive microwave observations indicate that the surface of the accumulation basin of the glacier was wet during this period of rapid motion suggesting that the fast speed may be a consequence of a rise in sub glacial water pressure sourced from melt or rainwater making its way to the glacier bed and reducing basal friction several other outlet glaciers including the benito and hpn1 glaciers on the isolated western side of the icefield accelerated while thinning between 2007 and 2011 marked acceleration also occurred after 2007 at the front of the san quintin glacier the largest outlet glacier of the npi the paucity of thickness measurements at the outlet glaciers means it is impossible to accurately gauge the mass flux of the icefield and thus give a full estimate of the mass balance

recent elevation changes of svalbard glaciers derived from icesat laser altimetry abstract we have tested three methods for estimating 2003 2008 elevation changes of svalbard glaciers from multi temporal icesat laser altimetry a linear interpolation of crossover points between ascending and descending tracks b projection of near repeat tracks onto common locations using digital elevation models dems and c least squares fitting of rigid planes to segments of repeat track data assuming a constant elevation change rate the two repeat track methods yield similar results and compare well to the more accurate but sparsely sampled crossover points most glacier regions in svalbard have experienced low elevation thinning combined with high elevation balance or thickening during 2003 2008 the geodetic mass balance excluding calving front retreat or advance of svalbard s 34 600 km2 glaciers is estimated to be 4 3 1 4 gt y 1 corresponding to an area averaged water equivalent w e balance of 0 12 0 04 m w e y 1 the largest ice losses have occurred in the west and south while northeastern spitsbergen and the austfonna ice cap have gained mass winter and summer elevation changes derived from the same methods indicate that the spatial gradient in mass balance is mainly due to a larger summer season thinning in the west and the south than in the northeast our findings are consistent with in situ mass balance measurements from the same period confirming that repeat track satellite altimetry can be a valuable tool for monitoring short term elevation changes of arctic glaciers

rapid loss of the ayles ice shelf ellesmere island canada 1 on august 13 2005 almost the entire ayles ice shelf 87 1 km 2 calved off within an hour and created a new 66 4 km 2 ice island in the arctic ocean this loss of one of the six remaining ellesmere island ice shelves reduced their overall area by 7 5 the ice shelf was likely weakened prior to calving by a long term negative mass balance related to an increase in mean annual temperatures over the past 50 years the weakened ice shelf then calved during the warmest summer on record in a period of high winds record low sea ice conditions and the loss of a semi permanent landfast sea ice fringe climate reanalysis suggests that a threshold of 200 positive degree days year 1 is important in determining when ice shelf calving events occur on n ellesmere island

variability in the summertime coastal marine atmospheric boundary layer off california usa an analysis of boundary layer structure and surface layer turbulence from measurements off the california coast is presented from data collected by research aircraft during two field experiments the coastal waves 1996 cw96 and the monterey area ship track mast experiments cw96 covers the near coast region in particular in the vicinity of major headlands whereas mast extends offshore along the us west coast coastal modification of the along coast flow occurs on two main horizontal scales firstly a large scale variability is due to the interplay between the shallow near coast marine atmospheric boundary layer mabl and the coastal terrain typically higher than the mabl depth the mabl depth decreases smoothly towards the coast while the wind speed increases to a coastal jet in response to the sloping mabl inversion secondly the flow is affected by supercritical flow dynamics as the wind speed increases and the mabl depth decreases towards the coast the mabl flow becomes supercritical in a shallow water sense as supercritical shallow water flow interacts with major headlands expansion fans form affecting both the wind speed and the mabl depth the combination of cw96 and mast data reveals significant differences between the flow along the coast and that far offshore mabl winds are stronger near the coast whereas aloft the winds are weaker than offshore the near coast mabl is also better mixed turbulence increases towards the coast while the sensible heat flux decreases and often changes sign leading to stable stratification near the coast a length scale determining the across coast influence of the expansion fans is defined from simple inviscid and irrotational shallow water theory data from four days of the cw96 experiment show that this simple theory describes the low level wind speed adequately surface layer turbulence also scales with this simple length scale but the results are complicated by upwelling of cold water giving rise to strong internal boundary layers from terms in the turbulent energy budgets it appears that dissipation of turbulence exceeds local production copyright 2004 royal meteorological society

alluvial fans formed by channelized fluvial and sheet flow i theory alluvial fans and fan deltas are of three basic types those built up primarily by the action of constantly avulsing river and stream channels those constructed by sheet flows and those resulting from the successive deposition of debris flows the present analysis is directed toward the first two types a mechanistic formulation of flow and sediment transport through river channels is combined with a simple quantification of the overall effect of frequent avulsion to derive relations describing the temporal and spatial evolution of mean i e averaged over many avulsions bed slope and elevation in an axially symmetric fan an example of a fan formed predominantly by the deposition of sand is compared to a similar one formed predominantly by the deposition of gravel in each example the case of channelized flow is compared to the case of sheet flow the model is applied to the tailings basin of a mine in the companion paper

accelerating glacier mass loss on franz josef land russian arctic abstract the glaciers of the franz josef land fjl archipelago in the russian arctic are subjected to rapidly warming temperatures but are small contributors to sea level we analyze ice surface elevation data derived from satellite stereo imagery worldview and spot radar altimetry cryosat 2 and a digitized 1953 cartographic map to calculate elevation change rates d h d t mass loss from fjl doubled between 2011 and 2015 compared to 1953 2011 2015 increasing from a rate of 2 18 0 72 gt yr 1 to 4 43 0 78 gt yr 1 this 2011 2015 rate indicates an acceleration in ice loss from that observed in 2003 2009 by multiple studies using icesat and grace glacier thinning rates are spatially highly variable we observe glacier thinning rates of up to 10 m per year and in general we see a trend of increased thinning from the ne towards the sw glacier retreat is widespread and has led to the creation of at least one new island historically ice wastage from fjl is thought to have been relatively small but accelerating ice loss may be the new normal for this archipelago in a warming arctic

recent contributions of glaciers and ice caps to sea level rise satellite measurements of earth s gravity field show that the mass loss of glaciers and ice caps contributed to sea level rise by approximately 0 4 millimetres per year between 2003 and 2010 the extent to which mass loss from ice covered land areas contributes to sea level rise is not known accurately in part because previous global estimates use different techniques for glaciers ice caps and ice sheets the gravity recovery and climate experiment grace satellite has provided monthly measurements of the global gravity field since 2002 using grace data jacob et al assess regional mass loss between 2003 and 2010 and conclude that mass loss from ice covered land areas contributed almost 1 5 mm per year to the sea level rise estimated mass loss from the high mountains of asia was negligible in contrast to some other reports glaciers and ice caps gics are important contributors to present day global mean sea level rise1 2 3 4 most previous global mass balance estimates for gics rely on extrapolation of sparse mass balance measurements1 2 4 representing only a small fraction of the gic area leaving their overall contribution to sea level rise unclear here we show that gics excluding the greenland and antarctic peripheral gics lost mass at a rate of 148 30 gt yr 1 from january 2003 to december 2010 contributing 0 41 0 08 mm yr 1 to sea level rise our results are based on a global simultaneous inversion of monthly grace derived satellite gravity fields from which we calculate the mass change over all ice covered regions greater in area than 100 km2 the gic rate for 2003 2010 is about 30 per cent smaller than the previous mass balance estimate that most closely matches our study period2 the high mountains of asia in particular show a mass loss of only 4 20 gt yr 1 for 2003 2010 compared with 47 55 gt yr 1 in previously published estimates2 5 for completeness we also estimate that the greenland and antarctic ice sheets including their peripheral gics contributed 1 06 0 19 mm yr 1 to sea level rise over the same time period the total contribution to sea level rise from all ice covered regions is thus 1 48 0 26 mm 1 which agrees well with independent estimates of sea level rise originating from land ice loss and other terrestrial sources6

airborne observations of thermal mesoscale circulations in the coastal marine boundary layer airborne observations of thermal mesoscale circulations in the coastal marine boundary layer