shelf cross shore flows under storm driven conditions role of stratification shoreline orientation and bathymetry abstractnumerical simulations are used to study the response of long bay south carolina a typical coastal embayment with curved coastline located on the south atlantic bight to realistic climat

enhancement of wind driven upwelling and downwelling by alongshore bathymetric variability steady wind driven flow along a shelf of changing width is described with a frictional barotropic model valid in the limit of small rossby and burger number in these limits an alongshore wind drives enhanced onshelf transport in a coastal ocean if the shelf widens downwind and the change in shelf width only affects the flow in the direction of kelvin wave propagation downwave from the change in shelf width there is enhanced onshore transport of cold nutrient laden bottom water if the winds favor upwelling and the shelf narrows in the direction of kelvin wave propagation this enhanced transport extends a considerable distance away from the change in shelf width but becomes concentrated near the shelf break far from the change in width isobath curvature on the scale of the shelf width significantly modifies local cross shelf transport the cross shelf transport of nutrient rich water during upwelling is expected to be enhanced from point eugenia to la jolla san luis obispo to monterey and point reyes to cape mendocino on the west coast of north america

the frictional nearshore response to forcing by synoptic scale winds abstract an analytic barotropic model was used to study the nearshore frictional response to synoptic scale wind forcing the results depend only on the region where the surface and bottom ekman layers interact strongly and the water is consequently well mixed thus the conclusions apply even to shelves where baroclinic effects are not negligible father offshore the main findings are as follows i the blocking of the surface ekman flux which drives the shelf flow is a consequence of the interaction of ekwan layers in the nearshore region the interaction transfers progressively more of the surface stress directly to bottom stress as the depth decreases the consequent decrease in ekman flux toward the shore creates an ekman flux divergence which drives the interior flow ii the region over which the shelf is effectively forced is narrow it extends approximately from where the depth divided by the ekman layer e folding scale is 0 2 to where it is 2 5 iii simple equations for pressure and the

spatial and temporal variability of coastal storms in the north atlantic basin over the past three to four decades there has been a growing awareness of the important controls exerted by large scale meteorological events on coastal systems for example definitive links are being established between short term timescales of 5 10 years beach dynamics and storm frequency this paper assesses temporal variability of coastal storms both tropical and extratropical and the wave climatology in the north atlantic basin nab including the gulf of mexico with both storm types the empirical record shows decadal scale variability but neither demonstrates highly significant trends that can be linked conclusively to natural or anthropogenic factors tropical storm frequencies have declined over the past two or three decades which is perhaps related to recent intense and prolonged el ninos some forecasts predict higher frequencies of tropical storms like that experienced from the 1920s to the 1960s to occur in coming decades results from general circulation models gcms suggest that overall frequencies of tropical storms could decrease slightly but that there is potential for the generation of more intense hurricanes these data have important implications for the short term evolution of coastal systems there is strong suggestion that extratropical systems have declined overall over the past 50 100 years but that there is an increase in frequency of very powerful storms especially at higher latitudes both enso and the north atlantic oscillation nao are shown to have associations with frequencies and tracking of these systems these empirical results are in general agreement with gcm forecasts under global warming scenarios analyses of wave climatology in the nab show that the last two to three decades have been rougher at high latitudes than several decades prior but this more recent sea state is similar to conditions from about 100 years ago the recent roughness at sea seems to be related to high nao index values which are also expected to increase with global warming thus when coupled to an anticipated continued rise in global sea level this trend will likely result in increasing loss of sediment from the beach nearshore system resulting in widespread coastal erosion

momentum balances on the north carolina inner shelf four months of moored current pressure temperature conductivity wave and wind observations on the north carolina shelf indicate three dynamically distinct regions the surf zone the inner shelf between the surf zone and the 13 m isobath and the midshelf in the surf zone the along shelf momentum balance is between the cross shelf gradient of the wave radiation stress and the bottom stress the linear drag coefficient in the surf zone is about 10 times larger than seaward of the surf zone on the inner shelf the along shelf momentum balance is also frictional the along shelf wind stress and pressure gradient are balanced by bottom stress in the cross shelf momentum balance the pressure gradient is the superposition of roughly equal contributions from the coriolis force geostrophy and wave setdown from shoaling unbroken surface gravity waves at midshelf the along shelf momentum balance is less frictional and hence flow accelerations are important the cross shelf momentum balance is predominantly geostrophic because the greater depth and smaller bottom slope at midshelf reduce the importance of wave setdown the cross shelf density gradient is in thermal wind balance with the vertical shear in the along shelf flow in depths as shallow as 10 m the dominant along shelf momentum balances provide a simple estimate of the depth averaged along shelf current in terms of the measured forcing i e wind stress wave radiation stress divergence and along shelf pressure gradient that reproduces accurately the observed cross shelf variation of the depth averaged along shelf current between the surf zone and midshelf

burgess shale type biotas were not entirely burrowed away burgess shale type biotas occur globally in the cambrian record and offer unparalleled insight into the cambrian explosion the initial phanerozoic radiation of the metazoa deposits bearing except

alongshore momentum balance analysis on a cuspate foreland 1 nearshore measurements of waves and currents off cape hatteras north carolina u s a are used to investigate depth averaged subtidal circulation and alongshore momentum balances in the surf and inner shelf region around a cuspate foreland data were collected on both sides of the cape representing shorefaces with contrasting shoreline orientation north south vs northwest southeast subjected to the same wind forcing in the nearshore the subtidal flow is aligned with the local coastline orientation while at the cape point the flow is along the existing submerged shoal suggesting that cape associated shoals may act as an extension of the coastline alongshore momentum balance analysis incorporating wave current interaction by including vortex and stokes coriolis forces reveals that in deep waters surface and bottom stress are almost in balance in shallower waters the balance is complex as nonlinear advection and vortex force become important furthermore linearized momentum balance analysis suggests that the vortex force can be of the same order as wind and wave forcing farther southwest of cape hatteras point wind and wave forcing alone fail to fully explain subtidal flow variability and it is shown that alongshore pressure gradient as a response to the wind forcing can close the momentum balance adjacent tide gauge data suggest that the magnitude of pressure gradient depends on the relative orientation of local coastline to the wind vector and in a depth averaged sense the pressure gradient generation due to change in coastline orientation even at km length scale is analogous to the effect of alongshore variable winds on a straight coastline

local diurnal wind driven variability and upwelling in a small coastal embayment the oceanic response to high frequency local diurnal wind forcing is examined in a small coastal embayment located along an understudied stretch of the central california coast we show that local diurnal wind forcing is the dominant control on nearshore temperature variability and circulation patterns a complex empirical orthogonal function ceof analysis of velocities in san luis obispo bay reveals that the first mode ceof amplitude time series which accounts for 47 9 of the variance is significantly coherent with the local wind signal at the diurnal frequency and aligns with periods of weak and strong wind forcing the diurnal evolution of the hydrographic structure and circulation in the bay is examined using both individual events and composite day averages during the late afternoon the local wind strengthens and results in a sheared flow with near surface warm waters directed out of the bay and a compensating flow of colder waters into the bay over the bottom portion of the water column this cold water intrusion into the bay causes isotherms to shoal toward the surface and delivers subthermocline waters to shallow reaches of the bay representing a mechanism for small scale upwelling when the local winds relax the warm water mass advects back into the bay in the form of a buoyant plume front local diurnal winds are expected to play an important role in nearshore dynamics and local upwelling in other small coastal embayments with important implications for various biological and ecological processes

model simulations of the gulf of maine response to storm forcing 1 the storm response of the gulf of maine georges bank region was investigated using the dartmouth three dimensional nonlinear finite element coastal ocean circulation model called quoddy with uniform density and quadratic bottom stress a suite of model hindcast experiments were conducted for the 4 8 february 1987 period that featured a strong nor easter the model was forced at the open ocean boundaries by the m2 semidiurnal tidal sea level and in the interior by realistic surface wind stresses and in some cases atmospheric pressure the reference model run with just tidal and wind stress forcing and a time space constant bottom drag coefficient cd of 0 005 captured 65 of the observed detided low pass filtered or subtidal sea level variance of a representative array of coastal and bottom pressure stations in the gulf however there remained large unexplained model observed sea level differences particularly during the storm model sensitivity testing to a realistic range of constant cd values did not improve model results significantly however results of a model run in which atmospheric pressure forcing derived through linear interpolations of regional measurements was added to wind stress forcing captured 82 of the observed subtidal sea level variance

effects of coastline geometry on upwellings abstract the shallow water equations applied to a two layer ocean are solved in order to study the cited of capes on upwellings first analytical solutions of the linearized version of these equations are given for academic right angle corners two cases must be envisaged depending on whether or not the wind favorable to upwelling is parallel to one coast or to the other then the nonlinear version of the equations is solved by using a numerical model dealing with the finite elements method capes of various shapes are studied numerical results can be interpreted in the light of analytical solutions the major observed phenomena are a difference in the interface elevation between the upwind and downwind coasts and a generation of currents flowing in opposite direction to the wind in the bottom layer both effects are due to the generation of kelvin waves by the variability of the coast

an observational study of the katabatic wind confluence zone near siple coast west antarctica abstract a month long field program to study the springtime katabatic wind confluence zone where katabatic winds converge has been carried out near siple coast west antarctica based on previous observations and numerical studies two surface camps upstream b 83 5 8 136 1 w and south camp 84 5 s 134 3 w were established ground based remote sensing equipment sodar and rass along with conventional observations were used combining the analyses of surface observations and wind and temperature profiles at the above camps the following picture for the cross sectional structure of the confluence zone emerges a relatively cold katabatic airflow which probably comes from fast antarctica occupies the layer between the surface and roughly 500 m acl low level jets are present below 200 m agl and are stronger near the transantarctic mountains diurnal variation is present in this cold drainage flow and decreases toward the transantarctic mountains weak inversion layer tops are found near 500 m a

the inner shelf response to wind driven upwelling and downwelling abstract a two dimensional numerical model is used to study the response to upwelling and downwelling favorable winds on a shelf with a strong pycnocline during upwelling or downwelling the pycnocline intersects the surface or bottom forming a front that moves offshore the characteristics of the front and of the inner shelf inshore of the front are quite different for upwelling and downwelling for a constant wind stress the upwelling front moves offshore at roughly a constant rate while the offshore displacement of the downwelling front scales as t because the thickness of the bottom layer increases as the front moves offshore the geostrophic alongshelf transport in the front is larger during downwelling than upwelling for the same wind stress magnitude because the geostrophic shear is near the bottom in downwelling as opposed to near the surface in upwelling during upwelling weak stratification is maintained over the inner shelf by the onshore flux of denser near bottom water this weak stratif

the effects of tides and oscillatory winds on the subtidal inner shelf cross shelf circulation a two dimensional numerical model is used to investigate the effects of tidal forcing and oscillatory winds on the subtidal cross shelf circulation on the inner shelf bottom topography and initial stratification are representative of the south and middle atlantic bights along the u s east coast results from simulations forced by upwelling winds and no tides are consistent with previous studies of inner shelf circulation the inclusion of tidal forcing leads to increased mixing larger eddy viscosity coefficients and reduced stratification over the shallow regions effectively reducing the wind efficiency to drive cross shelf currents on the inner shelf tidally averaged cross shelf currents are weaker compared to when no tides are considered there is an increase in the width of the region of surface wind driven transport divergence which changes the crossshelf location where upwelling occurs lagrangian analyses indicate that tidal forcing substantially reduces the transport of offshore waters toward the coast and increases the residence time over the inner shelf by up to 70 fluctuating winds with zero mean lead to a rectification of the cross shelf flow on the inner shelf resulting in net upwelling the rectification occurs because the cross shelf transport is nonzero during upwelling wind forcing since dense water is brought to the inner shelf maintaining the stratification but is approximately zero during downwelling winds since surface water is forced under near bottom water destroying the stratification the rectification is more clearly observed when stratification is strong when tidal forcing is weak or absent and when the wind fluctuates at low frequency

a modeling study of shelf circulation off northern california in the region of the coastal ocean dynamics experiment response to relaxation of upwelling winds 1 a two part modeling study of the wind forced flow on the continental shelf off northern california in the region 37 40 n of the coastal ocean dynamics experiment code is pursued this paper involves a process oriented study with idealized wind stress forcing gan and allen 2002 involves forcing with observed winds and heat flux for april may 1982 and comparison of model results with code observations a characteristic but previously unexplained response observed during code following the weakening or relaxation of southward upwelling favorable winds is the time dependent development of northward currents over the inner shelf next to the coast the presence of northward winds is not necessary for this occurrence the objective in this paper is to investigate the dynamics of the shelf flow response to upwelling wind relaxation events under idealized conditions in the basic case experiment a spatially uniform upwelling favorable southward wind stress of 0 1 pa is applied to the ocean initially at rest the stress is held constant for 10 days and then decreased linearly to zero over 3 days in response to the southward wind stress southward alongshore currents develop on the shelf accompanied by upwelling of cold dense water near the coast considerable spatial variability in the shelf flow clearly related to the alongshore variations in coastline and bottom topography is found the alongshore currents tend to separate from the coast south of capes and the coldest surface water is found at those locations as the winds decrease northward currents similar to those observed develop on the inner shelf next to the coast at many alongshore locations examination of the alongshore momentum balances shows that the northward currents are forced by a northward pressure gradient force associated with negative alongshore pressure gradients these pressure gradients are set up by the interaction of the wind forced flow with the alongshore variations in shelf topography in general negative alongshore pressure gradients intensified off pt reyes and pt arena by the gradient wind balance are found south of capes the negative pressure gradients geostrophically balance onshore flow at depth and upwelling is strengthened in these locations north of capes positive pressure gradients that are primarily in balance with nonlinear advective effects are found after the winds cease the forced across shelf circulation weakens and the resulting unbalanced negative pressure gradients south of the capes accelerate the alongshore currents northward processes with similar dynamics are found embedded in the more complex coastal ocean response to observed time varying winds by gan and allen 2002

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

mechanisms of mid to outer shelf transport of shoreline released tracers abstracttransport of shoreline released tracer from the surfzone across the shelf can be affected by a variety of physical processes from wind driven to submesoscale with implications for shorelin

cross shore variation of wind driven flows on the inner shelf in long bay south carolina united states and exceeded 0 1 n m 2 vertical mixing occurred the two layered flow pattern disappeared and currents were directed alongshore with the wind at all sites and throughout the water column in the fall near bed flows close to the shore water depth 7 m were often reduced compared to or opposed those measured farther offshore under southwestward winds a simplified analysis of the depth averaged alongshore momentum balance illustrates that the alongshore pressure gradient approached or exceeded the magnitude of the alongshore wind stress at the same time that the nearshore alongshore current opposed the wind stress and alongshore currents farther offshore in addition the analysis suggests that the wind stress is reduced closer to shore so that the alongshore pressure gradient is large enough to drive the flow against the wind

inner shelf response to cross shelf wind stress the importance of the cross shelf density gradient in an idealized numerical model and field observations this study investigates the effects of horizontal and vertical density gradients on the inner shelf response to cross shelf wind stress by using an idealizednumericalmodel and observations from a mooredarray deployed south of martha s vineyard massachusetts in two dimensional no along shelf variation numerical model runs of an initially stratified shelf a cross shelf wind stress drives vertical mixing that results in a nearly wellmixed inner shelf with a cross shelf density gradient because of the sloping bottom the cross shelf density gradient causes an asymmetric response to on and offshore wind stresses for density increasing offshore an offshore wind stress drives a near surface offshore flow and near bottom onshore flow that slightly enhances the vertical stratification and the cross shelf circulation an onshore wind stress drives the reverse cross shelf circulation reducing the vertical stratification and the cross shelf circulation a horizontal richardson number is shown to be the nondimensional parameter that controls the dependence of the wind driven nondimensional cross shelf transport on the cross shelf density gradient field observations show the same empirical relationship between the horizontal richardson number and transport fraction as the model predicts these results show that it is the cross shelf rather than vertical density gradient that is critical to predicting the inner shelf cross shelf transport driven by a cross shelf wind stress

near resonant ocean response to sea breeze on a stratified continental shelf abstract the spatial structure and temporal characteristics of sea breeze and the associated coastal ocean response in the northwest gulf of mexico are investigated using moored instruments hydrographic stations and wind measurements near the study area of 30 n motions in the diurnal inertial band dib may be significantly enhanced by a near resonant condition between local inertial and diurnal forcing frequencies wavelet analysis is used to quantify the results results indicate that diurnal sea breeze variability peaks in summer and extends at least 300 km offshore with continuous seaward phase propagation the maximum dib oceanic response occurs in june when there is a shallow mixed layer strong stratification and an approximately 10 day period of continuous sea breeze forcing dib current variance decreases in july and august as the consequence of the deepening of the mixed layer and a more variable phase relationship between the wind and current river discharge varies interannually and can s

the dynamics of idealized katabatic flow over a moderate slope and ice shelf summary a non hydrostatic numerical weather prediction model has been employed to simulate idealized katabatic flows over a moderate slope and adjoining ice shelf the topography of coats land and the adjoining brunt ice shelf antarctica has been used this is typical of much of the antarctic coastline the regional atmospheric modeling system version 4 3 has been adapted for simulations over compacted snow most notably through changes to the multi layer soil model the simulations are initialized using clear sky conditions and at rest on the slope a shallow katabatic flow develops the winds becoming approximately steady on the slope by 12 h the peak downslope winds are about 7 m s 1 at 30 m above the snow surface the katabatic flow depth ranges from 50 to 100 m down the slope over the ice shelf the katabatic flow peters out while a pool of cold air develops primarily through sensible heat loss into the surface and partially balancing the net radiative heat loss to space near surface and sounding data from the model simulations compare well with archetypal and typical katabatic flow observations especially after some tuning of the model s turbulence parametrization an analysis of the downslope flow dynamics shows the buoyancy force is generally balanced by the inertial force except towards the foot of the slope where it is balanced by upslope forces related to gradients in the potential temperature deficit and katabatic layer height caused by the pool of cold air over the ice shelf over time the cooling of the ice shelf boundary layer leads to an apparent retreat of the katabatic flow from the ice shelf and some way up the slope the dynamical analysis explains the surface climatology observed such that the persistent katabatic winds of coats land rarely reach the brunt ice shelf the simulated katabatic flow moves from shooting to tranquil towards the foot of the slope this transition acts to trigger a train of internal gravity waves which propagate energy upwards away from the katabatic flow jump previous studies have also found shooting to tranquil katabatic flow transitions so to generalize these findings would suggest that internal gravitywave generation is ubiquitous around much of coastal antarctica and greenland

barotropic tides in the south atlantic bight 1 the characteristics of the principal barotropic diurnal and semidiurnal tides are examined for the south atlantic bight sab of the eastern united states coast we combine recent observations from pressure gauges and adcps on fixed platforms and additional short term deployments off the georgia and south carolina coasts together with national ocean service coastal tidal elevation harmonics these data have shed light on the regional tidal propagation particularly off the georgia south carolina coast which is perforated by a dense estuary tidal inlet complex etic we have computed tidal solutions for the western north atlantic ocean on two model domains one includes a first order representation of the etic in the sab and the other does not include the etic we find that the etic is highly dissipative and affects the regional energy balance of the semidiurnal tides nearshore inner and midshelf model skill at semidiurnal frequencies is sensitive to the inclusion of the etic the numerical solution that includes the etic shows significantly improved skill compared to the solution that does not include the etic for the m2 constituent the largest tidal frequency in the sab overall amplitude and phase error is reduced from 0 25 m to 0 03 m and 13 8 to 2 8 for coastal observation stations similar improvement is shown for midshelf stations diurnal tides are relatively unaffected by the etic

response of south carolina continental shelf waters to wind and gulf stream forcing during winter of 1986 the south carolina shelf water response to strong winter atmospheric forcing and gulf stream variations over the slope is discussed with the aid of a comprehensive set of atmospheric and oceanic observations made during project gale genesis of atlantic lows experiment a mixed response is observed to wind and gulf stream forcing subtidal variability of inner and middle shelf waters is primarily a barotropic forced response to coherent synoptic scale alongshore winds this response is not trapped over the shelf as has been found for other wide non equatorial shelves but is also significant at the shelf edge possibly because of the comparable widths of the shelf and slope the outer shelf also shows a significant gulf stream influence the gulf stream appears to have two preferred position modes either onshore with the stream flowing over the charleston bump and along the shelf break or offshore when the stream can be located up to 100 km east of the shelf break transition between the two states is rapid subtidal variability in the outer shelf is dominated by weekly period frontal eddies and meanders when the stream is in an onshore mode and by persistent southward flow when the stream is offshore this southward flow is produced by enlarged cyclonic eddies with upwelled centers located over the slope between the offshore stream and the shelf edge sometimes referred to as the charleston gyre positive mean alongshore sea level slopes at the shelf edge due to the persistence of the cyclonic gyres are geostrophically balanced by mean onshore flow which transports upwelled waters onto the shelf enhancing the biological productivity of the area relative to other regions of the south atlantic bight

a validation of the antarctic mesoscale prediction system using self organizing maps and high density observations from snowweb abstractthis study compares high resolution output 1 1 km horizontal grid length from twice daily forecasts produced by the antarctic mesoscale prediction system amps with a dense observational network east of ross island covering 10 000 km2 15 snowweb stations significantly increased the number of observation stations in the area to 19 during the 2014 15 austral summer collocated virtual stations created from amps output are combined with observations producing a single dataset of zonal and meridional wind components used to train a self organizing map som the resulting som is used to individually classify the observational and amps datasets producing a time series of classifications for each dataset directly comparable to the other analysis of class composites shows two dominant weather patterns low but directionally variable winds and high but directionally constant winds linked to the ross ice shelf airstream ras during ras events the amps and snowweb data displayed good temporal cl