signature of the agulhas current in high resolution satellite derived wind fields abstract 5 years of systematic envisat advanced synthetic aperture radar asar acquisitions and 8 years of observations from the jason 2 altimeter are used to investigate the signature of the agulhas current on high resolution between 1 and 5 km satellite derived winds the satellite wind observations are analysed together with co located ocean current sea surface temperature sst and significant wave height information satellite derived winds cannot be considered current relative over the agulhas current sar and altimeter winds increase in magnitude over the agulhas current in all up down and cross current wind conditions with contributions from both the ocean surface current and sst when winds blow against the current strong accelerations in satellite winds are observed at the agulhas current s inshore front with the strongest winds observed 10 km offshore from the location of maximum sst gradient the strong sst gradient appears to drive a thermal wind with a magnitude of about 1 m s and which intensifies abates the predominant alongfront winds at the agulhas current s northern wall the sar dataset shows abnormally high increases in wind speeds during up current conditions in comparisons to the jason 2 derived winds we argue that these differences are caused by the inability of the cmod type algorithms to taken into account the wave field and provide accurate wind speed estimates in conditions where wave height exceed the expected value for a given wind speed our analysis suggests that wave current interactions in regions of strong current shear produce enhanced sea surface roughness signatures and lead to artificially high estimates of sar derived wind speeds there is future potential in using high resolution sar imagery to map strong ocean current fronts and thus improve our ability to monitor ocean surface currents from space

air sea heat exchange along the northern sea surface temperature front in the eastern tropical pacific abstract the atmospheric response to the oceanic forcing in the eastern pacific along the northern equatorial sea surface temperature sst front is investigated in terms of sensible and latent heat flux during the 6 month period from 28 july 1999 to 27 january 2000 and the 7 month period from 28 june 2000 to 27 january 2001 of particular interest is the atmospheric boundary layer abl response to oceanic tropical instability waves tiws that distort the sst front during may january in normal years in previous studies time series of surface heat fluxes clearly show the influence of tiws but the relationship to spatial patterns of sst and wind speed has been inferred only from sparse in situ data in this study satellite observations are used as a basis for compositing in situ data from moorings to compensate for the lack of a spatially dense mooring array the variability in the position of the sst front caused by westward propagating tiws enables fixed mooring locations to measure the abl response

wind forcing of the coastal circulation off north and northwest iberia comparison of atmospheric models 1 comparisons between observed winds and winds from reanalysis national centers for environmental prediction ncep reanalysis 1 and 2 and forecast meteorological models high resolution limited area model hirlam agencia estatal de meteorologia 0 2 and atmospheric research mesoscale model version 5 meteogalicia with 30 km and 10 km resolution have been performed for the coastal region around northwest and north iberia during a typical autumn downwelling period september december 2002 observations at buoys and coastal stations and quikscat derived winds were employed the analyzed period was dominated by southerly and southwesterly winds associated to the passage of low pressure systems our results show that the westward component is higher on the north coast than on the west coast and that winds are intensified at the western north coast in this situation the performance is similar in all model products in general terms but only hirlam represents the reduction of winds in the cantabrian sea and ncep and mm5 overestimate the magnitude of south southwest winds spatial differences in winds are also obtained for upwelling favorable events associated either with a high pressure system north from iberia at the beginning of the autumn transition northeasterly winds or with conditions after the passage of a low pressure system northwesterly winds the existence of sea surface temperature sst gradients in the coastal region implies that higher resolution boundary sst products for meteorological models are necessary finally the effect of these wind products on the coastal circulation was assessed with a 3 d numerical simulation differences in the expansion confinement of river plumes and the surface speed of the slope current are induced by differences in wind patterns over the shelf and slope area among atmospheric models

east west thrusting and anomalous magnetic declinations in the sierra gorda betic cordillera southern spain abstract structural and palaeomagnetic studies in the sierra gorda sierra de loja located in the external zone of the betic cordillera indicate that westward directed thrusting is not associated with significant rotations about a vertical axis detailed mapping and slip vector analysis show that the sierra gorda is a thrust complex composed of three thrust sheets the uppermost thrust places early jurassic pelagic carbonates on top of jurassic to oligocene sediments that form a large doubly plunging footwall syncline the eastern limb of this syncline has been overturned and is tectonically thinned as a result of the overthrusting palaeomagnetic results from mesozoic and tertiary sediments both within and around the perimeter of the sierra gorda indicate that 1 the average remanence vector of the seven late jurassic localities sampled within the sierra gorda has a direction d 328 and i 38 that is not significantly different from the expected declination for the upper jurassic of stable iberia and 2 there is no significant difference between the remanences in the two upper thrust sheets indicating that differential rotation did not occur during the initiation and displacement on the thrusts in contrast the one late jurassic site that was sampled to the west of the sierra gorda is rotated like the rest of the subbetics 60 clockwise of the reference direction the unrotated directions obtained in the sierra suggest either that it has rotated in a clockwise sense concordant with the rest of the subbetic zone and has then been backrotated or that it has never rotated relative to stable iberia in the latter simpler hypothesis the unrotated declinations may be explained in terms of orthogonal convergence along an irregular continental margin

tower based measurements of normalized radar cross section from lake ontario evidence of wind stress dependence we report here the dependence of the normalized radar cross section nrcs on incidence angle azimuth angle wind speed wind stress and atmospheric stratification for ku band microwave backscatter from a lake the measurements were made in autumn 1987 on lake ontario using a rotating microwave system mounted on a research tower operated by the canada centre for inland waters the results show that at intermediate incidence angles the nrcs on the lake generally increases faster with wind speed than it does on the ocean we attribute this to the larger atmospheric drag coefficients which exist on the lake compared with the ocean and we show that the results are more consistent with a dependence of the nrcs on wind stress than on wind speed near the surface we find a stratification dependence of the nrcs similar to that previously reported at c band and show that at 40 and 60 incidence angles this dependence can be removed by parameterizing the nrcs in terms of either the friction velocity or neutral wind speed at a 20 incidence angle the stratification dependence is not removed by this procedure

validating the nscat winds in the vicinity of the pacific intertropical convergence zone it is known that the nscat winds are influenced by precipitation and so are potentially in error in regions of high rainfall such as the pacific itcz we assess this potential error by comparing nscat winds to other products and by determining the possible impact on modeling the pacific necc in the latitude band of the itcz there are large differences between wind products from the ecmwf and nscat a comparison with tao buoy winds shows a bias of nscat data towards a higher zonal wind stress at 8 n the spatial distribution of this bias distorts the ekman pumping velocity across the itcz and results in a necc that is 0 1 0 2 m s weaker than that forced by the ecmwf winds this is not a trivial amount during the spring when the strength of the necc in the eastern pacific is of the same magnitude

paleomagnetic evidence for rotation of the iberian peninsula and the external betic cordillera southern spain abstract paleomagnetic investigations of jurassic cretaceous and tertiary sites in the external betic cordillera indicate that while the observed remanence vectors have inclinations which are conformable with the expected inclinations for stable iberia declinations deviate significantly these results indicate that 1 the mesozoic limestones of the penibetic have been rotated clockwise with respect to stable iberia and 2 there is a differential rotation between the cretaceous sites dec 61 11 and the jurassic sites dec 38 8 the differential rotation of 23 between the late jurassic and late cretaceous is consistent with the cretaceous anticlockwise rotation of the iberian peninsula with respect to eurasia it follows that during this time period this part of the betic mobile belt waspart of the continental margin of the iberian peninsula a study which was confined to a single unbroken stratigraphic section west of ronda indicates that most of the anticlockwise rotation 20 probably occurred between the cenomanian and the campanian the anticlockwise rotation of these rocks must have been followed by a clockwise rotation of at least 60 to account for the observed clockwise declination anomalies

warm core ring velocities inferred from nscat the nasa scatterometer nscat was designed to estimate from space the wind velocity relative to the ocean surface velocity assuming that the spatial scale of the meteorological forcing giving rise to the wind is large compared with the diameter of a warm core ring it should be possible to obtain information about the currents in the ring from the demeaned scatterometer winds to test this hypothesis 14 nscat passes obtained within three days of clear avhrr derived sea surface temperature images showing a warm core ring were analyzed for evidence of circulation in the rings the residual wind vectors for the 14 scatterometer passes were binned and averaged by radial distance from ring center the mean azimuthal component of the speed compares well with adcp data collected in one of the rings a maximum of 0 89 m s 50 km from ring center compared with 0 88 m s and 1 0 m s for the two adcp transects both also at 50 km from ring center

east pacific ocean eddies and their relationship to subseasonal variability in central american wind jets subseasonal variability in sea surface height ssh over the east pacific warm pool off central america is investigated using satellite observations and an eddy resolving ocean general circulation model ssh variability is organized into two southwest tilted bands on the northwest flank of the tehuantepec and papagayo wind jets and collocated with the thermocline troughs eddy like features of wavelength similar to 600 km propagate southwestward along the high variance bands at a speed of 9 13 cm s wind fluctuations are important for eddy formation in the gulf of tehuantepec with a recurring interval of 40 90 days when forced by satellite wind observations the model reproduces the two high variance bands and the phase propagation of the tehuantepec eddies our observational analysis and model simulation suggest the following evolution of the tehuantepec eddies on the subseasonal timescale in response to the gap wind intensification a coastal anticyclonic eddy forms on the northwest flank of the wind jet and strengthens as it propagates offshore in the following two to three weeks an energetics analysis based on the model simulation indicates that besides wind work barotropic and baroclinic instabilities of the mean flow are important for the eddy growth both observational and model results suggest a re intensification of the anticyclonic eddy in response to the subsequent wind jet event off papagayo ocean eddy formation is not well correlated with local wind jet variability in both the gulfs of tehuantepec and papagayo subseasonal ssh variability is preferentially excited on the northwest flank of the wind jet factors for this asymmetry about the wind jet axis as well as the origins of wind jet variability are discussed

ocean currents evident in satellite wind data satellite mounted radar scatterometers designed to quantify surface winds over the ocean actually measure the relative motion between the air and the ocean surface estimates of the wind stress from conventional surface wind measurements are usually derived neglecting ocean currents however when the relative motion is used the differences in the estimated stress can be as large as 50 near the equator and may even reverse sign during an el nino this assertion is supported by the strong relationship between the surface currents measured by the tropical atmosphere ocean tao array in the pacific ocean and the differences between the winds estimated from scatterometer data and those measured by tao anemometers the fact that the scatterometer measures relative motion and not wind alone makes scatterometer derived stress a more accurate representation of the boundary condition needed for both atmospheric and oceanic models than stress fields derived neglecting ocean currents

upper equatorial pacific ocean current and salinity variability during the 1996 1998 el nino la nina cycle the recent el nino la nina cycle exhibited striking patterns of current and salinity variability in the upper equatorial pacific ocean this evolution is described from mid 1996 through 1998 using a remarkable data set of 35 meridional conductivity temperature depth ctd acoustic doppler current profiler adcp sections along with buoy data the sections nominally from 8 s to 8 n between 165 e and 95 w were occupied over the course of 27 months a wide range of current variability was sampled with currents that appeared or disappeared some time during the cycle including an equatorially trapped eastward surface current the equatorial undercurrent the northern branch of the south equatorial current and the north equatorial countercurrent basin wide interannual changes in upper ocean and pycnocline zonal transports were as large as 64 32 106 m3 s 1 changes in the salinity structure included a deep and fresh mixed layer in the central equatorial pacific that built up during the el nino and was then disrupted by upwelled salty water with the onset of la nina a very fresh mixed layer observed in the eastern equatorial pacific late in the el nino and a reduction in the strength of the meridional equatorial salinity gradient within the pycnocline to one third of the usual value during the el nino finally the zonal transports above the thermocline from 5 s to 5 n were well correlated with the rate of change of warm water volume west of the individual ctd adcp sections

observations of sst induced perturbations of the wind stress field over the southern ocean on seasonal timescales the surface wind stress response to sea surface temperature sst over the latitude range 308 608 si n the southern ocean is described from the national aeronautics and space administration s quikscat scatterometer observations of wind stress and reynolds analyses of sst during the 2 yr period august 1999 to july 2001 while ocean atmosphere coupling at midlatitudes has previously been documented from several case studies this is the first study to quantify this relation over the entire southern ocean the spatial structures of the surface wind perturbations with wavelengths shorter than 108 latitude by 308 longitude are closely related to persistent spatial variations of the sst field on the same scales the wind stress curl and divergence are shown to be linearly related respectively to the crosswind and downwind components of the sst gradient the curl response has a magnitude only about half that of the divergence response this observed coupling is consistent with the hypothesis that sst modification of marine atmospheric boundary layer mabl stability affects vertical turbulent mixing of momentum inducing perturbations in the surface winds the nonequivalence between the responses of the curl and divergence to the crosswind and downwind sst gradients suggests that secondary circulations in the mabl may also play an important role by producing significant perturbations in the surface wind field near sst fronts that are distinct from the vertical turbulent transfer of momentum the importance of the wind stress curl in driving ekman vertical velocity in the open ocean implies that the coupling between winds and sst may have important feedback effects on upper ocean processes near sst fronts

sst induced surface wind variations over the brazil malvinas confluence satellite and in situ observations abstract the confluence of the brazil malvinas currents maintains strong sea surface temperature sst fronts in the midlatitude southwestern atlantic year round sst effects on near surface stability and surface wind variations are examined in this region using satellite and in situ datasets satellite observations show strong weak surface wind speeds over the warm brazil cold malvinas current a novel feature of this study is the construction of a high resolution surface meteorological dataset that is based on historical ship observations analysis of this new in situ dataset reveals an increased reduced sea air temperature difference over the brazil malvinas current indicating destabilization stabilization in the atmospheric boundary layer these results are consistent with the sst induced vertical mixing mechanism for wind adjustment the sst effect on the near surface atmosphere is observed both in the climatology and on interannual time scales in the brazil malvinas confluence along a zo

somali current rings in the eastern gulf of aden 1 new satellite based observations reveal that westward translating anticyclonic rings are generated as a portion of the somali current accelerates northward through the socotra passage near the mouth of the gulf of aden rings thus formed exhibit azimuthal geostrophic velocities exceeding 50 cm s are comparable in overall diameter to the width of the gulf of aden 250 km and translate westward into the gulf at 5 8 cm s ring generation is most notable in satellite ocean color imagery in november immediately following the transition between southwest boreal summer and northeast winter monsoon regimes the observed rings contain anomalous fluid within their core which reflects their origin in the equator crossing somali current system estimates of socotra passage flow variability derived from satellite altimetry provide evidence for a similar ring generation process in may following the winter to summer monsoon transition cyclonic recirculation eddies are observed to spin up on the eastern flank of newly formed rings with the resulting vortex pair translating westward together recent shipboard and lagrangian observations indicate that vortices of both sign have substantial vertical extent and may dominate the lateral circulation at all depths in the eastern gulf of aden

statistical distribution of wave induced drift for random ocean waves in finite water depth abstract based on the linear random wave solutions of water wave equations in finite water depth a theoretical statistical distribution of the wave induced drift is derived the parameters involved in the distribution can be determined by the water depth and the wave spectrum of ocean waves as an illustrative example we consider a simple wind generated sea and the parameters are calculated for typical wind speeds and water depths by using phillips spectrum the behaviours of the distribution and the effects of wind speed and water depth on the distribution are investigated

measurements of turbulent vertical kinetic energy in the ocean mixed layer from lagrangian floats d asaro in previous work using nearly neutrally buoyant lagrangian floats in a wind forced mixed layer found w2 5 where w2 is the mean square vertical velocity and u is the friction velocity estimated 2 au from shipboard meteorological measurements using bulk formulas depth profiles of a z 5 w 2 z within 2 u the mixed layer showed a maximum value of a z of about 2 which is 1 75 2 times that measured in solidwall turbulent boundary layers driven by a wall stress alone this result implied that the ocean mixed layer was more energetic than shear driven turbulent boundary layers driven by the same stress here these results are verified using observations of vertical velocity in the mixed layer from 72 float days of data from two lagrangian floats in the north pacific ocean in the autumn of 2000 these floats were more neutrally buoyant than those used previously by d asaro thus reducing possible biases wind stress was estimated from quick scatterometer satellite measurements and is thus subject to errors and biases different from those in d asaro s previous work despite these instrumental differences the new results are very similar to those of the previous work except that no corrections for internal wave velocities are needed the values of w 2

the role of back pressure in the atmospheric response to surface stress induced by the kuroshio abstractthe effect of ocean current drag on the atmosphere is of interest as a test case for the role of back pressure because the response is independent of the thermally induced modulation of the boundary layer stability and hydrostatic pressure the authors use a regional atmospheric model to investigate the impact of drag induced by the kuroshio in the east china sea on the overlying winter atmosphere ocean currents dominate the wind stress curl compared to the impacts of sea surface temperature sst fronts wind stress convergences and divergences are weakly enhanced even though the ocean current is almost geostrophic these modifications change the linear relationships coupling coefficients between the wind stress curl divergence and the sst laplacian crosswind and downwind gradients clear signatures of the ocean current impacts are found beyond the sea surface sea surface pressure back pressure decreases near the current axis and precipitation increases over the downwind region however

seasonality of the kuroshio path destabilization phenomenon in the okinawa trough a numerical study of its mechanism abstract previous observations have indicated that the kuroshio s path in the northern okinawa trough of the east china sea is destabilized and accompanied by meanders with periods of 1 3 months during the winter spring period the present study investigates the mechanism responsible for this recurrent seasonally fixed phenomenon a hypothetical mechanism is constructed based on both a simple wind driven ekman pumping model acting within the kuroshio and a bifurcation model of the kuroshio path states in the northern okinawa trough established in the previous study a high resolution ocean general circulation model is used to examine the hypothetical mechanism the numerical model reveals the following mechanism the wintertime northerly wind prevailing over the okinawa trough blows against the kuroshio generating ekman divergence and hence upwelling within the inshore side of the kuroshio from the sum of the earth s rotation and the geostrophic current shear a necessary condition for this upwelling

high resolution satellite measurements of the atmospheric boundary layer response to sst variations along the agulhas return current abstract the marine atmospheric boundary layer mabl response to sea surface temperature sst perturbations with wavelengths shorter than 30 longitude by 10 latitude along the agulhas return current arc is described from the first year of sst and cloud liquid water clw measurements from the advanced microwave scanning radiometer amsr on the earth observing system eos aqua satellite and surface wind stress measurements from the quikscat scatterometer amsr measurements of sst at a resolution of 58 km considerably improves upon a previous analysis that used the reynolds sst analyses which underestimate the short scale sst gradient magnitude over the arc region by more than a factor of 5 the amsr sst data thus provide the first quantitatively accurate depiction of the sst induced mabl response along the arc warm cold sst perturbations produce positive negative wind stress magnitude perturbations leading to short scale perturbations in the wind stress curl and divergence fields that are li

comparative measurements of magnetic susceptibility anisotropy in red sandstones abstract the anisotropy of magnetic susceptibility of triassic red sandstones from northern bavaria plattensandstein formation is very weak within the maximum susceptibility plane the anisotropy resulting from the shape and size of cylindrical red bed samples can exceed and obscure the lineation of the sedimentary fabric when measured with a spinner magnetometer this frequently observed error can be eliminated when the cylindrical specimens are drilled perpendicular to bedding alternatively cubic samples which are measured on a susceptibility bridge are not affected by this error

linear wind forced beta plumes with application to the hawaiian lee countercurrent abstracttwo numerical ocean models are used to study the baroclinic response to forcing by localized wind stress curl i e a wind forced plume which is a circulation cell developing to the west of the source region and composed of a set of zonal jets with implications for the hawaiian lee countercurrent hlcc an idealized primitive equation model regional ocean modeling system roms and a global eddy resolving general circulation model ocean general circulation model for the earth simulator ofes in addition theoretical ideas inferred from a linear continuously stratified model are used to interpret results in roms vertical mixing preferentially damps higher order vertical modes the damping thickens the plume to the west of the forcing region weakening the near surface zonal jets and generating deeper zonal currents the zonal damping scale increases monotonically with the meridional forcing scale indicating a dominant role of vertical viscosity over diffusion a consequence of the

scatterometer winds explain damped rossby waves 1 westward propagating waves in the north pacific ocean from 10 16 n are overwhelmed by a zonally coherent response at the annual period as observed in sea surface height ssh anomalies from the topex poseidon altimeter ssh from a simple model of wind forced rossby waves and from seasonal heating are compared with observed ssh to understand the processes responsible for the observed signal the seasonal heating cycle is out of phase and too weak to explain the ssh the oceanic response to wind stress curl forcing more closely resembles the observations but the response to ncep reanalysis winds does not show a strong annual cycle wind stress curl from the quikscat seawinds scatterometer has a strong and zonally coherent annual cycle that produces a corresonding strong annual signal in ssh the model forced by scatterometer winds demonstrates that the response to ekman pumping is the source of the strong annual cycle in the ssh

the impact of ocean surface currents on sverdrup transport in the midlatitude north pacific via the wind stress formulation abstracta more complete wind stress n formulation takes into account the ocean surface currents vo while the conventional wind stress c popularly used in ocean circulation models is only a function of 10 m winds v10 an analytical solution is derived for the difference of sverdrup transport induced by using n instead of c a scaling analysis of the analytical solution indicates a 6 reduction of the sverdrup transport in the north pacific i e the kuroshio transport in the east china sea when ekman velocity dominates the ocean surface currents because of the quadratic nature of wind stress four nonlinear terms contribute equally to this difference two vorticity torque terms and two speed gradient torque terms a pair of 12 5 yr july 2002 14 hybrid coordinate ocean model simulations that only differ in the wind stress formulation are used to test the analytical solution the model results 2004 14 confirm that using n instead of c reduces the sverdrup transport in the north pacific by 8 17

ground ice recharge via brine transport in frozen soils of victoria valley antarctica insights from modeling δ18o and δd profiles abstract soils in the mcmurdo dry valleys antarctica contain ice and considerable amounts of salt ice often occurs at shallow depth throughout the dry valleys and other areas of hyperarid permafrost notably on mars this common occurrence of shallow ice is enigmatic however since according to published sublimation models it should disappear relatively quickly at rates of order 0 1 mm a 1 due to vapor loss to the atmosphere this loss may be offset by recharge from snowmelt infiltrating and freezing in the soil herein we present a first quantitative estimate of this recharge based on measured vertical profiles of d and 18 o that reveal considerable detail about the sources and sinks of ice we model these profiles taking into account the salt content and a soil temperature record along a 1 6 m depth profile of 10 ka old ice cemented soils in victoria valley antarctica the stable isotopes of ice are enriched in heavy isotopes at the top of the ice cement 20 cm depth both d and 18 o values plotted against depth exhibit a concave upward curve at depth the isotope composition is similar to that of lake victoria and modern meteoric water the concave shape of the isotope profile is suggestive of downward advection dispersion of snowmelt water enriched in heavy isotopes into the ice cement our advection dispersion model coupled with field data enables us to quantify the advective flux and dispersion of melt water into the ice the advective velocity and dispersion coefficient depend on the time since advection began and the ice to brine ratio they are respectively of the order of 10 11 10 10 m s 1 and 10 12 10 11 m 2 s 1 these values suggest that over the 10 ka time period a total of 190 mm water infiltrated into the ice cemented ground the isotope composition and deuterium excess values of the uppermost ice cement can be modeled from snowmelt water enriched in salts using open system rayleigh fractionation to develop the isotopic signature of the upper ice cement requires evaporation of 95 of the snowmelt water based on 190 mm brine infiltrating into the soil requires an initial total of 4 m of snowmelt water this corresponds to 0 4 mm a 1 suggesting that under the current climate condition water from snowmelt is sufficient to compensate modeled sublimation rates and therefore conserve ground ice in victoria valley

moored surface wind observations at four sites along the pacific equator between 140 and 95 w abstract mooted surface wind measurements were recorded along the pacific equator at 140 124 110 and 95 w during portions of 1980 85 minimum record length is one year the annual mean and monthly mean westward speeds at 110 w were about 1 5 m s 1 higher during the year preceding the 1982 83 el nino than in the year following this event the annual cycle which moved westward at 0 8 m s 1 consisted of weak westward and northward speeds in february april and vice versa in september october the spectral slope between 5 day and 0 05 day periods was 1 5 the rms amplitude of the 95 statistically significant diurnal period oscillation was 0 3 m s 1 and the meridional component was nearly twice as large as the zonal component the diurnal period wave was coherent at the 95 confidence level between 95 and 124 w with westward phase propagation of about 138 m s 1 no statistically significant at the 95 confidence level spectral peak was found in the 40 to 50 day intraseasonal period band the s