observed tidal currents outside block island sound offshore decay and effects of estuarine outflow 1 an array of moored profiling current meters on the inner continental shelf 15 65 m deep is used to investigate tidal currents outside the block island sound and long island sound estuarine system the m2 constituent dominates due to near resonant semi diurnal estuarine response vertical mean m2 currents rotate clockwise in time in ellipses elongated toward the estuary mouth with little sensitivity to complex local bathymetry semi major axes decay sharply offshore 55 to 20 cm s over 10 km in agreement with the nearly inverse square radius dependence of a kinematic theory estimated tidal volume exchange out of block island sound to the south is 2 9 105 m3 s observed vertical structure of m2 ellipses in the deepest 10 20 m amplitude decay ellipse flattening major axis turning clockwise phase advance is generally captured well by optimally fit frictional solutions despite the fact that they omit bathymetry and include stratification only indirectly through its influence on eddy viscosity in the upper water column vertical structure varies seasonally mid depth ellipses enlarge in spring near surface ellipses are larger smaller than optimal fit solutions in fall winter spring observed seasonal average estuarine outflow includes surface intensified coriolis deflected mean flow that strengthens and spreads farther offshore in spring richardson numbers based on moored hydrographic profiler records suggest spring stratification suppresses deep eddy viscosities which in frictional solutions can explain mid depth ellipse enlargement an inviscid theory for mean flow modifications due to ambient vorticity of estuarine outflow currents is shown to be the most plausible explanation for observed seasonal changes in near surface tidal ellipses

earliest triassic claystone breccias and soil erosion crisis abstract chemostratigraphic methods 13corg for pinpointing the permian triassic boundary in nonmarine rocks of antarctica australia and south africa have drawn attention to unusual claystone breccias at this horizon of the greatest extinction in the history of life on earth these rocks differ from other breccias in having a high proportion of clasts with birefringence microfabrics sepic plasmic fabrics characteristic of soils and can be called sepic pedoliths in the terminology of soil science at many localities earliest triassic sepic pedoliths are thin 5 15 cm beds but some fill shallow paleochannels and pinch out laterally other non marine breccias at the permian triassic boundary are dominated by fragments of coal pedogenic carbonate nodules and deeply weathered volcanic rock fragments earliest triassic sepic pedoliths record an unusually severe and widespread episode of soil erosion associated with forest dieback at the permian triassic boundary comparable sepic pedoliths are found in debris flows after clear cutting of forests in western oregon today studies of these modern deposits show that sepic soil peds do not withstand weathering for more than a few months such clayey clasts are held together mainly by roots and fungi which decay rapidly in soils and streams these modern analogs demonstrate that terminal permian soil erosion was rapid and profound sepic pedoliths are also known at other times of mass extinction such as the triassic jurassic boundary but are not yet known before the devonian advent of trees and forested clayey soils

late miocene drying of central australia abstract a back to the future approach to climate change refines neogene records of paleoclimatic cooling and drying as future climate states for a warming world near alcoota station in central australia is a late miocene fossil mammal site for alcoota 10 ma and ongeva 8 ma local faunas the alcoota fauna includes the largest known land bird dromornis stirtoni and early diprotodontid kolopsis torus but the geologically younger ongeva fauna has a larger diprotodontid zygomaturus gilli these faunas are evolutionary predecessors of australian pleistocene megafauna calcareous paleosols recorded a marked turn toward aridity compared with underlying thick lateritic duricrusts which lack fossils laterites of likely middle miocene age are evidence of wet 1100 mm mean annual precipitation tropical 17 c mean annual temperature paleoclimates but these were deeply eroded and redeposited by the time of the late miocene mammals a succession of 19 paleosols of 5 pedotypes were recognized in the 19 m thick section with shallow calcareous nodule bk horizons as evidence of mean annual precipitation ranges from 100 to 400 mm and mean annual range of precipitation of 50 mm very similar to the modern climate of alcoota 296 mm precipitation with 56 mm difference between wet and dry month this was neither a rainforest nor monsoonal paleoclimate and vegetation inferred from paleosols was open woodland and gallery woodland similar to that of today central australia was not covered by monsoon rainforest during the late miocene and its paleoclimatic history of neogene desertification matches well that of other parts of the world

characterizing long island sound outflows from hf radar using self organizing maps abstract the surface outflows from the long island sound are examined from one year records of hf radar codar observations synoptic flow patterns are identified using manual classification empirical orthogonal function eof decomposition and self organizing maps som four characteristic flow patterns for the spring summer and fall winter seasons each are obtained through a 2 2 som array the som is confirmed by comparison with manual classification and is shown to be a significant improvement over eof classification it is suggested that the degrees of freedom of the leading eof modes can be used as a constraint on the otherwise arbitrary som dimension the relationship between the flow patterns and the winds also can be conveniently examined in som the outflows are shown to interact strongly with the ambient coastal currents both of which are under the influence of the winds this result challenges the conventional wisdom which often treats the outflows independent of the ambient currents the advantage of using som in synthesizing and interpreting synoptic hf radar observations is clearly demonstrated

high pressure phase relations and thermodynamic properties of caal4si2o11 cas phase abstract phase relations in caal4si2o11 were examined at 12 23 gpa and 1000 1800 c by multianvil experiments a three phase mixture of grossular kyanite and corundum is stable below about 13 gpa at 1000 1800 c at higher pressure and at temperature below about 1200 c a mixture of grossular stishovite and corundum is stable indicating the decomposition of kyanite above about 1200 c caal4si2o11 cas phase is stable at pressure higher than about 13 gpa the triple point is placed at 14 7 gpa and 1280 c the equilibrium boundary of formation of cas phase from the mixture of grossular kyanite and corundum has a small negative slope and that from the mixture of grossular stishovite and corundum has a strongly negative slope while the decomposition boundary of kyanite has a small positive slope enthalpies of the transitions were measured by high temperature drop solution calorimetry the enthalpy of formation of caal4si2o11 cas phase from the mixture of grossular kyanite and corundum was 139 5 15 6 kj mol and that from the mixture of grossular stishovite and corundum was 94 2 15 4 kj mol the transition boundaries calculated using the measured enthalpy data were consistent with those determined by the high pressure experiments the boundaries in this study are placed about 3 gpa higher in pressure and about 200 c lower in temperature than those by zhai and ito zhai s ito e 2008 phase relations of caal4si2o11 at high pressure and high temperature with implications for subducted continental crust into the deep mantle phys earth planet inter 167 161 167 combining the thermodynamic data measured in this study with those in the literature dissociation boundary of cas phase into a mixture of ca perovskite corundum and stishovite and that of grossular into ca perovskite plus corundum were calculated to further constrain the stability field of cas phase the result suggests that the stability of cas phase would be limited at the bottom of transition zone and top of the lower mantle when sediments are subducted into the deep mantle it is also suggested that cas phase may be stable at the depth of the upper part of the lower mantle when partial melting of basalt occurs at the depth

spring summer frontogenesis at the mouth of block island sound 2 combining acoustic doppler current profiler records with a general circulation model to investigate the impact of subtidal forcing 1 the use of a one layer inverse model to improve the fidelity of a three dimensional primitive equation model is explored in the region just south of block island sound in the middle atlantic bight the inverse model based on the theory of bennett and mcintosh produces a solution to the linear shallow water equations that minimizes model data misfit and the resulting open boundary velocity variance the massachusetts institute of technology general circulation model is configured regionally and includes realistic tidal forcing surface warming and wind stress as well as climatological buoyancy gradients between the estuary and the shelf a 15 day record from two acoustic doppler current profiler moorings deployed in spring 2000 south of the entrance of block island sound allows assessment of the forward model and provides data to improve subtidal boundary conditions model data misfit decreases notably for both the depth averaged and vertically sheared flow indicating that improvements to the depth averaged circulation positively impact the three dimensional circulation in this shallow shelf environment the role of wind stress in modulating the position of the buoyant plume that characterizes the regional hydrography is also examined a distinctly three dimensional circulation is observed with a growing offshore plume at the mouth of the sound during northward stress followed by rapid alongshelf advection during periods of southwestward or weak winds although on the timescales considered here wind stress forcing dominates the buoyancy driven motion it is overwhelmed by the tidally driven rectified flow just south of montauk point which provides the inshore boundary of the front even in downwelling favorable conditions

outcrop versus core and geophysical log interpretation of mid cretaceous paleosols from the dakota formation of kansas abstract paleosols of the mid cretaceous late albian to early cenomanian dakota formation in kansas and nebraska are well exposed in road river and clay pit exposures but show systematic overprinting by modern weathering examination of deep drill cores reveals that modern weathering effects include 1 oxidation of pyrite to jarosite 2 reaction of jarosite and calcite to clear selenite and 3 oxidation of sphaerosiderite and siderite nodules to hematite surface oxidation in this region extends no deeper than 2 m from the surface hematite nodules and coatings of leaves are found in core only at one stratigraphic horizon which was not as appears in outcrop a laterite transformed matrix density and photoelectric absorption logs of cores reveal that kaolinite clays are most abundant within deeply weathered paleosols sayela pedotype at this stratigraphic level near the albian cenomanian boundary when angiosperm forests were especially diverse and lived in a subtropical humid climate other paleosols of the early cenomanian were less deeply weathered and fossil plants of this age included temperate humid angiosperm mangal and swamp woodland but conifer dominated floodplain forests this short lived mid cretaceous warm wet spike has also been recognized in other paleosols of minnesota utah nevada and new mexico and coincides with marine black shale of the breitstroffer event midcontinental marine transgression a sequence stratigraphic boundary and a marked increase in early angiosperm diversity

on the accuracy of hf radar surface current measurements intercomparisons with ship based sensors high frequency hf radar systems can provide periodic two dimensional vector current estimates over an area approaching 1000 km as the use of these hf systems has gained wider acceptance a number of attempts have been made to estimate the accuracy of such systems however comparisons of hf radar current estimates with in situ sensors are difficult to interpret since hf systems measure currents averaged over an area of 1 km 2 and to a depth of only 50 cm while in situ sensors measure currents at a point and somewhat greater depths 1 to 10 m previous studies of the accuracy of hf radar technology have thus attributed the differences observed between hf radar and in situ sensors to an unknown combination of vertical shear horizontal inhomogeneity in situ instrument errors and hf radar system errors this study examines the accuracy of hf radar current measurements using data from the 1993 high resolution remote sensing experiment conducted off cape hatteras north carolina data from four shipborne in situ current meters are compared with data from an ocean surface current radar oscr a commercial current measuring radar we attempt to discern the predominant sources of error in these data by using multiple simultaneous measurements from different sensors and by examining the variation of observed current differences as a function of location the results suggest an upper bound on the accuracy of the oscr derived radial currents of 7 to 8 cm s the measurement of near surface currents in the coastal environ ment is an important problem

high pressure transitions in the system mgal2o4 caal2o4 a new hexagonal aluminous phase with implication for the lower mantle abstract phase transitions in mgal 2 o 4 and caal 2 o 4 and in the binary system mgal 2 o 4 caal 2 o 4 were established at high pressures and high temperatures mgal 2 o 4 spinel dissociates to periclase and corundum at 15 16 gpa and 1200 c 1600 c with an equilibrium boundary of p gpa 12 3 0 0023 t c the mixture recombines into a phase with calcium ferrite structure at about 26 5 gpa at 1600 c at 780 c 1400 c caal 2 o 4 crystallizes with the calcium ferrite structure at pressure above 8 9 gpa at lower pressures phases iii and iv are stable on the join mgal 2 o 4 caal 2 o 4 solubility of mgal 2 o 4 component into caal 2 o 4 rich calcium ferrite is limited to about 10 mol at 20 21 gpa and 1200 c and a new phase with composition of mg x ca 1 x al 2 o 4 x 0 66 0 8 was found to be stable at pressure above 15 gpa powder x ray diffraction data show that the new phase possesses hexagonal symmetry moreover it is interpreted that an al rich phase observed in high pressure assemblage of mid ocean ridge basalt morb above 25 gpa by irifune and ringwood irifune t ringwood a e 1993 phase transformations in subducted oceanic crust and buoyancy relationships at depths of 600 800 km in the mantle earth planet sci lett 117 101 110 has the same structure as the hexagonal phase found in this study rather than calcium ferrite structure and another al rich phase synthesized at 24 27 gpa in high pressure experiments from natural pyrope rich garnet starting material is also similar to the hexagonal phase these results suggest that aluminous phase of the hexagonal structure would be one of major constituent minerals of subducted oceanic crust in the upper part of the lower mantle

seismic waves converted from velocity gradient anomalies in the earth s upper mantle summary modelling of elastic wave propagation in 1 d structures is frequently performed using reflectivity techniques in which the earth s velocity profile is approximated by stacks of homogeneous layers the complete reflection transmission r t response of a zone with arbitrary 1 d depth variation including both gradients and discontinuities in material properties can however be calculated using invariant embedding techniques results from earlier studies are here extended to derive exact expressions for r t matrices in arbitrary 1 d anisotropic media using a form of born approxi mation valid for thin scatterers and which does not assume small perturbations in material properties the r t matrices are solutions to a system of non linear ordinary differential equations of ricatti type and may be manipulated using standard r t matrix algebra in an equivalent description the wavefield within the heterogeneous zone is considered in terms of depth dependent contributions from up and downgoing waves propagating within the embedding reference medium this leads to efficient calculation of the internal wavefield using r t matrices of the heterogeneous stratification and portions thereof at minor additional expense mode conversion of teleseismic p and s phases from velocity gradients is examined by way of examples and comparison with three component data from broad band stations of the yellowknife seismic array the frequency dependence of such wave interactions depends on the differences in vertical slowness between incident and scattered modes it is shown that significant energy is converted from transition zones with extent l p 2 a broader interval than will generally produce intramode reflections a layer structure identified from ps conversions near 75 km depth below the slave craton is shown to be compatible with a 10 km thick gradient zone in which anisotropy increases from ambient levels to vp 5 per cent vs 2 5 per cent at a discontinuous upper boundary this characterization supports a previous interpretation as the upper strata of a former oceanic plate juxtaposed against overriding lithosphere during an ancient episode of shallow subduction

phase transformations in a harzburgite composition to 26 gpa implications for dynamical behaviour of the subducting slab abstract the mineralogy adopted by a depleted harzburgite composition has been studied over the pressure interval 5 26 gpa at temperatures of 1300 1400 c the pyroxene garnet component of the harzburgite composition harzburgite minus 82 wt olivine transforms to majorite garnet by 18 19 gpa and further disproportionates to the assemblage of garnet stishovite mg 2 sio 4 spinel above 20 gpa at still higher pressures first ilmenite 22 24 gpa and then perovskite mgsio 3 24 26 gpa are found to coexist with garnet garnet disappears at 26 gpa and almost complete transition to perovskite is achieved at this pressure the mineral proportions and density profiles in the subducting oceanic lithosphere modelled by a combination of 80 harzburgite 20 primitive morb compositions are calculated as a function of depth under conditions isothermal with surrounding pyrolite mantle and also for a temperature distribution in which the slab is substantially cooler than surrounding mantle to below 700 km under isothermal conditions the slab has a density similar to surrounding mantle to a depth of 600 km however between 600 and 700 km the slab is up to 0 08 g cm 3 denser than surrounding mantle this is caused primarily by the higher alumina content in pyrolite as compared to harzburgite which causes the transition to perovskite in pyrolite to occur at substantially higher pressures than in harzburgite the presence of alumina also smears out the garnet perovskite transition in pyrolite over a depth interval of 50 km whereas this transformation is much sharper in the harzburgite composition calculations based on the observed phase equilibria also show that a subducted cool slab remains much denser by 0 1 0 3 g cm 3 than surrounding mantle to a depth of 700 km but possesses a density similar to surrounding mantle below this depth these results have important implications for the dynamical behaviour of slabs possessing different thermal regimes when they encounter the 670 km discontinuity and also for the nature of this discontinuity

seasonal variation of a coastal jet in the long island sound outflow region based on hf radar and doppler current observations 1 surface current hf radar and velocity profile observations obtained as part of the front resolving observational network with telemetry front project over an approximately 2 year period are used to describe the seasonal variability of a coastal jet in the long island sound outflow region the jet is observed in an area of the continental shelf where surface thermal fronts are frequently detected during both summer and winter the current jet is coincident with a band of high summer frontal probability and apparently arises from the interaction between long island sound outflow and larger scale alongshore currents on the shelf the jet reaches peak strength in summer transport of 0 07 sv and is weak or non existent in winter flow is strongest near the surface and weakens with depth with only moderate seasonal variations in the vertical shear the relatively long data set of currents combined with historical hydrographic measurements and buoy wind observations is analyzed to examine the seasonal variability of the terms in the depth averaged momentum balance the depth averaged pressure gradient is partitioned into a steric component evaluated from the hydrography and a non steric component that is estimated as the residual of the computed terms in the momentum equation the depth averaged momentum balance is found to be approximately geostrophic in the across shore direction the seasonal variability in the jet arises due to the shifting balance between buoyancy driven flow that is always downshelf but intensifies somewhat in summer and wind driven flow which dominates in winter when wind stress becomes strongly upwelling favorable

impact of current wave interaction on storm surge simulation a case study for hurricane bob 1 hurricane bob moved up the u s east coast and crossed over southern new england and the gulf of maine with peak marine winds up to 54 m s 100 mph on 19 20 august 1991 causing significant damage along the coast and shelf a 3 d fully wave current coupled finite volume community ocean model system was developed and applied to simulate and examine the coastal ocean responses to hurricane bob results from process study oriented experiments showed that the impact of wave current interaction on surge elevation varied in space and time more significant over the shelf than inside the inner bays while sea level change along the coast was mainly driven by the water flux controlled by barotropic dynamics and the vertically integrated highest water transports were essentially the same for cases with and without water stratification the hurricane induced wave current interaction could generate strong vertical current shear in the stratified areas leading to a strong offshore transport near the bottom and vertical turbulent mixing over the continental shelf stratification could also result in a significant difference of water currents around islands where the water is not vertically well mixed

spring summer frontogenesis at the mouth of block island sound 1 a numerical investigation into tidal and buoyancy forced motion 1 the generation and underlying dynamics of late spring temperature and salinity fronts at the mouth of block island sound in the mid atlantic bight are examined using a three dimensional general circulation model the model is forced by tidal velocities at its outer boundaries an estuary shelf salinity gradient and surface warming runs representing the period from 18 april to 23 may 2000 are investigated through direct examination of the model results and diagnostic calculations that isolate individual processes three mechanisms are identified as significantly contributing to the location and structure fronts observed in this region vertical mixing produces the necessary horizontal temperature structure within and near block island sound but the southern frontal boundary is further affected by the subtidal circulation which is divided into two components defined using a momentum budget analysis tidal currents over the complex bathymetry leads to nonlinearly rectified flows including a headland eddy south of montauk point circumscribing this feature is a baroclinically adjusted buoyant outflow from the long island sound estuary while modifications to the buoyancy forcing can modify the frontal position it necessarily remains offshore of the tidally driven circulation analysis of the salinity anomaly fluxes indicates that both tidal and mean advection are responsible for the overall transport of buoyancy

fronts stratification and mixing in long island and block island sounds spatial patterns of bulk stratification in long island and western block island sounds observed near the fall equinox of 1978 show a strong correlation r 0 79 with contours of the h u3 stratification index derived from tidal stream and depth charts the index delineates stratified transitional and mixed regions with apparent good accuracy with the marginally stratified frontal zones being characterized by log10 h u3 1 5 m 2 s3 these results and theoretical considerations suggest that the index may be a useful parameter in corroborating and predicting frontal boundaries in other moderately stratified estuaries where local buoyancy fluxes are derived from fresh water sources

phase relations of harzburgite and morb up to the uppermost lower mantle conditions precise comparison with pyrolite by multisample cell high pressure experiments with implication to dynamics of subducted slabs

variability of the kuroshio current south of sagami bay as observed using long range coastal hf radars 1 ocean surface currents between cape nojima and hachijo island have been mapped since fall 2000 using a pair of seasonde long range hf radars during september 2000 through december 2001 the no large meander nlm nearshore n and offshore o modes were observed the surface current maps allowed new details to be observed in the structure of these modes and the transitions between them two noteworthy phenomena include blocking of the surface currents when the kuroshio was in an extreme nearshore position behind the zenisu ridge and the kyucho pattern when the current retroflexed from the nlmo position in early 2004 a large meander lm developed and was well established in its historical position south of honshu by august 2004 subsequently the lm continued propagating downstream but stopped when it encountered the izu ridge it then moved back to its original position near 137 5 e and the process repeated itself this east west oscillation resulted in two common positions for the lm south of sagami bay from its more westerly position lmw for west the kuroshio had a very favorable approach to the deep gap between miyake island and the zenisu ridge and the currents were strongly toward the northeast through the region when the meander moved up against the ridge lme for east a strong along ridge current toward the northwest was evident which turned sharply northeast when it encountered the shallow zenisu ridge the dominant timescale for this within mode variability was about 30 days

initial stages of laminar calcrete formation by roots examples from the neogene of central spain thin carbonate laminae formed by root activity are common within miocene detrital deposits of the duero and madrid basins the laminae are about 3 cm thick extending several metres laterally and displace the original detrital sediment which ranges in grain size from fine gravel to sandy clay the thickness morphology microstructure and stable isotope compositions of the laminae indicate that they formed by the activities of roots and associated microorganisms within the soil the laminae are similar to those commonly recognised in thick laminar calcrete profiles three types of laminae are recognised differences in the micromorphology of the laminae are explained as reflecting the different organisms involved and whether calcification occurred when the root was alive or decaying the first type occurs in a profile at paracuellos the jarama where the laminae consist of a mosaic of 20 mm calcite crystals whose arrangement indicates that calcification took place in the medulla of the root and probably occurred while the plant was alive in a second type in the villacadima profile laminae comprise calcified root mats whose formation indicates the interplay of roots and fungi calcification of the cell walls and intracellular spaces took place in the cortices of the roots and not in the medullas as revealed by the presence of central pores in every calcified root a third type of lamina is recognised in profiles at vin egra de moran a and consists of mucilaginous sheets coated by needle fibre calcite crystals the occurrence of associated small root casts indicates that formation of the laminae occurred while the root was decaying and was also influenced by fungal activity these laminae occur within poorly developed soils and their formation was controlled by the relationship between sedimentation erosion and soil formation processes thus the occurrence of these laminae interbedded with detrital sediments reflects environments where sedimentation was relatively low and episodic so after the detrital sediment input surfaces were stable and root mats were able to develop renewed sedimentation accounted for the death of the root mats and the development of new ones on the new surfaces where the sedimentation rate is lower the laminae tend to amalgamate and thicker laminar calcrete profiles form with little or no interbedded detrital sediment

comparison of observed hf radar adcp and model barotropic tidal currents in the new york bight and block island sound abstract a three dimensional primitive equation model is used to simulate the barotropically forced semidiurnal tidal currents in the new york bight nyb and block island sound bis model tidal velocity ellipses are verified at historical current meter locations and with measurements from acoustic doppler current profilers adcps and hf radar codar the model reproduces well the regional tidal flow pattern as well as the vertical tidal velocity structure the model misfits typically are 2 4 cm s in amplitude and 5 7 in orientation through comprehensive skill assessment the model s capacity of simulating the three dimensional barotropic tidal currents is clearly demonstrated moreover it is shown that the integrity of hf radar measurements can be assured by verifying with model tidal ellipses

dynamics of the block island sound estuarine plume abstractbuoyant discharge of freshwater from long island sound lis forms a seasonal buoyant plume outside block island sound bis between the coast of long island and the denser shelf waters the plume s seasonal variability and its response to tides winds and surface heating are investigated through a series of process oriented experiments using the regional ocean modeling system roms results show the importance of river discharge wind directions and surface heating in the seasonal variation of the bis buoyant plume in winter and spring the plume is intermediate with a large surface offshore extension detached from the bottom from winter to spring the river discharge increases meanwhile upwelling favorable winds keep dominating they compete with the increase of surface heating and generate a broader buoyant plume in spring than in winter in summer the plume is bottom advected with most of its width in contact with the bottom and is featured with the steepest isopycnals and narrowest pl

influence of wind stress and discharge on the mean and seasonal currents on the alabama shelf of the northeastern gulf of mexico 1 analysis of a relatively long 3 33 years time series of velocity in 20 m of water on the alabama shelf of the northeastern gulf of mexico in conjunction with long term records of wind stress and discharge reveal a better understanding of the seasonal currents analysis of the mean and seasonal signals of the depth averaged velocity shows virtually no mean flow but a relatively small yet significant seasonal signal the 3 cm s 1 seasonal signal is primarily rectilinear in the along shelf direction with peak eastward westward flow during the late spring late fall consistent with the patterns reported in previous basin scale studies of the region the two prominent regional forcing functions wind stress and freshwater discharge show clear seasonal signals the seasonal vertical profiles also show two distinctively different patterns most clearly observed in the fall with a westward maximum flow at the surface that decreases with depth and spring with a subsurface eastward flow and a reduced westward or even eastward surface flow separation of the current velocity into a wind driven component and a non wind driven component demonstrates their counteracting influence on the mean current and maximizes seasonal effects where the minimum maximum seasonal wind driven signal roughly corresponds to the maximum minimum non wind driven signal in late spring early summer late fall early winter on the basis of several sources of indirect evidence it is hypothesized that a freshwater discharge generated barotropic pressure gradient is the primary forcing of the seasonal signal in the non wind driven current

variability in chlorophyll and sea surface temperature fronts in the long island sound outflow region from satellite observations 1 the spatial and temporal patterns of ocean color i e chlorophyll and sea surface temperature sst fronts in the coastal zone of the northwest atlantic were studied over a 2 year period chlorophyll images were derived from the sea viewing wide field of view sensor while sst data were obtained from the advanced very high resolution radiometer both flying onboard earth observing satellites an edge detection algorithm was applied to each of the image sets to identify chlorophyll and thermal fronts persistent chlorophyll and thermal fronts co occurred in the same vicinity of the inner middle shelf and were spatially congruent during second april may june and third july august september quarters and least coincident during the first january february march calculations of the frontogenesis function showed strongest frontogenic tendencies coincident with the chlorophyll and thermal fronts a major finding of this study was the congruence of both chlorophyll and thermal fronts at a time when the coastal current jet was the most robust strongly suggesting that it is the presence of this jet that may be a driving force in establishing these fronts except for a few months per year no clear chlorophyll enhancement was observed at thermal fronts