temporal analysis of water masses and sea ice formation rate west of the antarctic peninsula in 2008 estimated from southern elephant seals srdl ctd data abstract as an alternative method to collect oceanographic data in the polar oceans especially during winter when traditional methods are very difficult to be used sea mammals can be tagged with satellite relay data loggers with ctd capabilities srdl ctd using data from nine southern elephant seals ses mirounga leonina tagged during a field campaign of the meop br project the brazilian counterpart to the marine mammal exploration of the oceans pole to pole this work presents a temporal analysis of the water masses and the sea ice formation rate at the western part of the antarctic peninsula ap during 2008 we found that the seasonal and local processes controlling the surface and intermediate layers of the ocean produced differences in the water mass composition and the sea ice formation rates in our study region sea ice formation rates ranged from less than 1 cm day in deep sea waters off the northern part of the ap to 14 cm day at the vicinity of ice shelves such as the abbot and wilkins ice shelves further south in the ap maximum sea ice formation rates as expected occurred during autumn to winter after the successive collapse events of the wilkins ice shelf wis in 2008 the sea ice formation rate endured significant reductions even when sea ice concentrations were high in the region these reductions observed by ses in the vicinity of wis can be associated with freshwater input derived from shelf collapses the presence of the circumpolar deep water cdw over the continental shelf west of the ap affected the sea ice formation rate by both contributing to the observed low sea ice coverage and to the acceleration of the ice shelf melting another process that demonstrated influence on the formation of sea ice was the advection of more saline waters in the oceanic layer considered here for the application of salt balance equation this advection resulted in unrealistic sea ice formation rates in regions where there was no sea ice cover the data and results presented here can be used to feed and to validate climate ocean atmosphere coupled models the data can be combined with other more traditional meteorological and oceanographic data in order to provide a better understanding of both oceanic and ocean atmosphere coupled processes yet not very well known in our study region

hydrography and energetics of a cold subpolar fjord andvord bay western antarctic peninsula abstract fjords along the western antarctic peninsula contain rich marine ecosystems and tidewater glaciers potentially sensitive to ocean change but much is unknown about the physical oceanography of these fjords this paper presents a comprehensive description of the physical environment of andvord bay a glacial fjord located in the gerlache strait on the northern end of the peninsula measurements were collected as part of the fjordeco program between november 2015 and march 2017 including during three research cruises and from a number of fixed installations sub surface moorings time lapse cameras and automatic weather stations andvord bay is located just north of a sill in the gerlache strait this sill inhibits the direct influence of warm upper circumpolar deep water from the shelf and deep waters in the fjord are therefore relatively cold as a result glaciers in andvord bay are not subject to the substantial ocean driven retreat observed farther south on the peninsula instead mass flux from the glaciers occurs mainly through calving the influence of meltwater in andvord bay is small compared to glacial fjords in the arctic and in the south shetland islands although summer freshening is evident in the fjord near surface layer likely as a result of glacial inputs the combination of surface freshening and the absence of strong mean wind forcing in the fjord results in salinity stratification extending well into the euphotic zone providing advantageous conditions for phytoplankton blooms andvord bay is generally dynamically quiet compared to the ambient ocean with the exception of during local katabatic wind events exchange with the gerlache strait is weak although the deep waters of the fjord are replenished on an annual scale through slow lateral exchange with the outside in addition deep convection may play a role in ventilating subsurface waters in winter

nature and human impact on nile delta coastal sand dunes egypt this paper deals with the types distribution and origin of recent sand dunes in the coastal sector extending between el burullus lake and the damietta nile river branch egypt sand samples were studied for grain size distribution and mineralogical composition it has been found that most of the dunes in the study area have been subjected to deterioration and removal due to the construction of summer resort buildings and making the international coastal highway the remnant constitutes a belt of foredunes on the shore of baltium extending westward to burg el burullus village

emplacement and tectonic implications of the mid proterozoic peralkaline flowers river igneous suite north central labrador abstract the flowers river igneous suite ca 1270 ma is composed of several discrete plutons of peralkaline granite eccentrically surrounding a circular area of felsic subaerial volcanic rocks dikes of peralkaline granite are oriented tangentially and radially to the volcanic center individual plutons which vary from ring shaped or arcuate to irregular in plan view were emplaced at or near the surface during and or following cogenetic volcanism these features coupled with a remarkable bulls eye aeromagnetic anomaly pattern imply that the flowers river igneous suite is a rudimentary ring complex individual ring dikes were substantially enlarged and modified by piecemeal stoping during emplacement preservation of the volcanic terrain from subsequent erosion appears to reflect cauldron subsidence of the roof of the largest granite pluton the flowers river igneous suite was emplaced in a stable intracratonic environment immediately following a period of substantial uplift and erosion this uplift was permanent induced isostatically by the addition of large volumes of mantle derived magmas during the mid proterozoic heat from the mantle derived magmas together with decompression during uplift and erosion caused small degrees of partial melting in the lower crust and the formation of independent pockets of a type magma these melts intruded the extended crest of the uplifted region forming isolated felsic volcanic centers including the flowers river igneous suite

characterization of sea ice cover motion and dynamics in marguerite bay antarctic peninsula abstract as part of the u s globec southern ocean program data from two automatic weather stations awss on small islets and upward looking acoustic doppler current profilers adcps and an upward looking sonar uls on sub surface moorings have been analyzed to produce time series of atmospheric forcing sea ice thickness sea ice and ocean velocities and sea ice momentum balances within marguerite bay and at mid shelf on the central west antarctic peninsula continental shelf for the austral winter spring seasons of 2001 and 2002 both years had roughly seven months of nearly complete sea ice cover but ice onset was about two months earlier in 2002 than 2001 mostly due to extremely cold surface air temperatures in marguerite bay during may june 2002 sea ice draft was quite variable but generally thickened with time reaching 2 3 m by the end of september before thinning in october 2002 a polynya was observed at one site within marguerite bay that lasted for 4 days the sea ice motion and dynamics in marguerite bay were analyzed when sea ice draft was greater than 2 m wind stress during these periods was predominantly southward and southeastward wind stress sea ice and near surface water motion were partially correlated with sea ice motion greater than water motion large wind stress and sea ice and water motions occurred during short energetic events of a few days or shorter however the rms wind stress sea ice and water velocities were small about 0 3 n m 2 8 16 cm s 1 and 5 7 cm s 1 respectively mean sea ice motion was southward but quite small of order 2 cm s 1 while mean near surface water motion was not statistically different from zero the dominant sea ice momentum balance was between wind and internal ice stresses on time scales of several days and longer with water stress coriolis and tilt terms playing secondary roles the mean southward wind stress was balanced within uncertainty by the mean northward internal ice stress the strong and variable internal ice stresses were likely due to the onshore winds the thickness of the sea ice and the nearby coastline

a first description of the antarctic peninsula coastal current abstract we present hydrographic and shipboard adcp data collected during the fall april june and winter july august and moored velocity observations collected from 2001 to early 2002 on the west antarctic peninsula wap shelf during the southern ocean global ecosystems dynamics so globec program in fall a geostrophically balanced buoyant current flows southward along the coast this antarctic peninsula coastal current apcc forms during the ice free season and extends from adelaide island to alexander island although its path inside marguerite bay is uncertain during the fall of 2001 the apcc had a volume transport of 0 32 0 13 sv and a freshwater transport relative to a reference salinity of 34 4 of 126 50 km 3 yr 1 from early july to late october the apcc disappears from the coast as the freshwater input from the coast diminishes and sea ice forms on the shelf an examination of the relative sizes of the freshwater sources suggests runoff from land and precipitation over the ocean are the primary sources for the apcc

collision induced rifting the grenville orogeny and the keweenawan rift of north america abstract we propose that the keweenawan rift formed as a result of convergence related to the synchronous grenville orogeny this proposal is based on 1 1 isotopic ages in the keweenawan rift and the grenville province are similar according to the best u pb and rb sr dates the grenville orogeny existed from 1150 to 1100 ma and keweenawan rifting occurred 1120 1100 ma 2 2 a similar modern orogenic belt and rift relationship in the middle east serves as an actualistic model the red sea gulf of aden rift system has formed as a continuous series of coalesced pull apart basins and is opening parallel to the orogenic front of the zagros and bitlis mountains rifting began in the early miocene while the collision began in the eocene suggesting that rifting is related to the collision 3 3 many other ancient rift collision pairs have a similar age relationship and geometrical configuration based on comparisons of these tectonic regimes we have derived a model whereby these rifts formed as a result of strike slip faults forming in either the foreland or the hinterland of orogenic zones

geochemistry and rb sr geochronology of associated proterozoic peralkaline and subalkaline anorogenic granites from labrador anorogenic granites of middle to late proterozoic age in the davis inlet flowers bay area of labrador are subdivided on the basis of petrology and geochemistry into three coeval suites two of these are high temperature anhydrous hypersolvus granites a peralkaline aegirine sodic calcic to sodic amphibole bearing suite and a non alkaline fayalite pyroxene bearing suite the third is a group of non alkaline subsolvus hornblende biotite bearing granites associated with the hypersolvus peralkaline suite is a group of genetically related syenites and quartz syenites the granites cut ca 3 000 ma old archaean gneisses as well as elsonian layered basic intrusions of the nain complex one of these a crudely layered mass which ranges in composition from gabbro to diorite and monzonite appears to be related to the syenites the peralkaline granites and some of the syenites are extremely enriched in the high field strength elements such as y zr nd as well as rb ga and zn and have low abundances of ba sr and most of the transition elements in contrast the non alkaline hypersolvus and subsolvus granites do not show the same degree of enrichment concentration of the highly charged cations in the peralkaline suite is believed to be the result of halogen rich fluid activity during fractionation of the magma the sodic evolution trend in the peralkaline suite is reflected mineralogically by the development of aegirine and aegirine hedenbergite solid solutions and by a spectacular amphibole compositional range from katophorite through winchite richterite riebeckite to arfvedsonite and ferro eckermannite accessory phases which are ubiquitous in these rocks include aenigmatite astrophyllite fluorite monazite and zircon the non alkaline hypersolvus granites typically contain iron rich phases such as fayalite eulite ferrosilite hedenbergite and annite rich biotite in the subsolvus granites amphiboles range in composition from edenite through common hornblende to actinolite and also coexist with annite rich biotite

chronologie rb sr et k ar du granite peralcalin du lac brisson labrador central nouveau quebec a rb sr whole rock isochron gives an age of 1189 32 ma for the peralkaline granite of lake brisson k ar data on amphiboles yield an age of 1163 21 ma which further confirms our dating such an age allows the corresponding magmatism to be attributed to the late stage of the gardar anorogenic province which till now has been unknown in labrador

acoustically inferred zooplankton distribution in relation to hydrography west of the antarctic peninsula abstract the relationship between the distribution of zooplankton especially euphausiids euphausia and thysanoessa spp and hydrographic regimes of the western antarctic peninsula continental shelf in and around marguerite bay was studied as part of the southern ocean globec program surveys were conducted from the rvib n b palmer in austral fall april june and winter july august of 2001 acoustic video and environmental data were collected along 13 transect lines running across the shelf and perpendicular to the western antarctic peninsula coastline between 65 s and 70 s depth stratified net tows conducted at selected locations provided ground truthing for acoustic observations in fall acoustic volume backscattering strength at 120 khz was greatest in the southern reaches of the survey area and inside marguerite bay suggestive of high zooplankton and micronekton biomass in these regions vertically highest backscattering was in the 150 450 m depth range associated with modified circumpolar deep water cdw the two deep troughs that intersect the shelf break were characterized by reduced backscattering similar to levels observed off shelf and indicative of lower zooplankton biomass in recent intrusions of cdw onto the continental shelf estimates of dynamic height suggested that geostrophic circulation likely caused both along and across shelf transport of zooplankton by winter scattering had decreased by an order of magnitude 10 db in the upper 300 m of the water column in most areas and high backscattering levels were found primarily in a deep 300 m scattering layer present close to the bottom the seasonal decrease is potentially explained by advection of zooplankton vertical and horizontal movements and mortality predictions of expected backscattering levels based on net samples suggested that large euphausiids were the dominant source of backscattering only at very particular locations and depths and that copepods siphonophores and pteropods were more important in many locations

upper ocean variability in west antarctic peninsula continental shelf waters as measured using instrumented seals abstract temperature profile data for the west antarctic peninsula wap continental shelf waters collected from freely ranging instrumented seals crabeater lobodon carcinophagus and leopard hydrurga leptonyx were used to demonstrate that these platforms can be used to supplement traditional oceanographic sampling methods to investigate the physical properties of the upper water column the seal derived profiles were combined with temperature profiles obtained from ship based ctd measurements and from a numerical circulation model developed for the wap to describe changes in temperature structure heat content and heat flux in the upper ocean waters of the wap continental shelf the seal derived data documented the fall to winter transition of the surface waters and the shelf wide presence of modified circumpolar deep water cdw below 150 200 m on the wap continental shelf the heat content of the upper 200 m calculated from the seal derived temperature profiles ranged between 1000 and 1500 mj m 2 similar estimates were obtained from simulated temperature distributions the seal derived temperature measurements provided broader space and time resolution than was possible using any other currently available oceanographic sampling method as such the seal derived measurements provided a valuable dataset for evaluation of temperature fields obtained from a numerical circulation model

distribution of zooplankton on the continental shelf off marguerite bay antarctic peninsula during austral fall and winter 2001 abstract the marguerite bay region of the western antarctic peninsula is known to support a large population of krill during the summer and is hypothesized to be a site of successful overwintering of krill the distributions of zooplankton biomass abundance and taxonomic composition at six locations on or near the continental shelf at marguerite bay were determined for fall and winter 2001 as a part of the southern ocean globec program water column zooplankton were sampled using a 1 m 2 mocness samples were analyzed for taxonomic composition size and estimated biomass using silhouette analysis characteristics of four categories small and large copepods small and large krill were described in detail total biomass and abundance were markedly reduced in winter relative to fall the vertical distributions of total abundance and biomass and of taxonomic composition were associated with the hydrographic structure of the water column larger larval krill were observed at all locations during winter than during fall krill were relatively unimportant to total biomass and abundance at most locations while copepods frequently dominated both biomass and abundance in fall greatest abundance and biomass of larval krill were observed on the continental shelf in association with a persistent clockwise gyre located to the west of adelaide island during winter much lower abundances of larval krill were present in the water column throughout the study region high abundance and biomass of juvenile and adult krill were observed only in laubeuf fjord marguerite bay during fall

water mass properties and circulation on the west antarctic peninsula continental shelf in austral fall and winter 2001 abstract hydrographic measurements made during the us southern ocean global ocean ecosystem dynamics cruises which took place from april to june and july to september 2001 provide a description of changes in water mass distributions and circulation patterns in the marguerite bay region of the west antarctic peninsula continental shelf that result from seasonal variability and offshore forcing by the southern boundary of the antarctic circumpolar current acc the primary seasonal change in water mass properties is the reduction in antarctic surface water and replacement by a thick winter water layer the primary effect of the acc is to pump warm 1 5 c salty 34 65 34 7 and nutrient rich circumpolar deep water cdw onto the continental shelf below 200 m at specific sites that correspond to bathymetric features such as marguerite trough the cdw intruded onto the continental shelf moved across shelf and entered marguerite bay this flow pattern was observed during both cruises suggesting that onshelf intrusions of cdw are a regular occurrence on this shelf the number of cdw intrusions observed suggests that 4 6 events can occur in a year regions where cdw intrusions occur are characterized by surface waters that are above freezing in winter diffusive heat fluxes based on estimated diffusivities are insufficient for the observed rate of temperature decay of cdw intrusions localized bathymetrically controlled vertical mixing is suggested as the primary heat transfer mechanism the hydrographic and acoustic doppler current profiler measurements show a southwesterly flowing coastal current along adelaide island that enters the north side of marguerite bay and exits around alexander island this current which may result from seasonal coastal buoyancy forcing was present in fall and winter but was better developed in fall this current may be part of a larger cyclonic gyre that overlies the northern part of the area surveyed during the two cruises

distribution of larval krill and zooplankton in association with hydrography in marguerite bay antarctic peninsula in austral fall and winter 2001 described using the video plankton recorder the western antarctic peninsula is a critical locus of antarctic krill euphausia superba abundance and thought to be a site of successful overwintering particularly for the larval stages a primary goal of the southern ocean globec program was to describe factors that contribute to the overwintering success of krill in this region as part of this effort we conducted video plankton recorder vpr surveys during austral fall and winter 2001 the vpr survey yielded high resolution distributions of larval krill other plankton and marine snow in relation to hydrography from a series of transect lines orthogonal to the coast on the continental shelf of the western antarctic peninsula four taxa larval krill copepods polychaetes pteropods and marine snow were numerous during fall much lower abundances of all categories were present during winter with only larval krill copepods and polychaetes present in any abundance distributions of plankton and marine snow were associated with water mass types and the vertical structure of the environment particularly for larval krill that were primarily associated with the pycnocline during fall larval krill were present across the entire shelf with high abundances at the shelf break copepods were most numerous at depth during fall consistent with ontogenetic migration to depth at the onset of winter

extreme anomalous atmospheric circulation in the west antarctic peninsula region in austral spring and summer 2001 02 and its profound impact on sea ice and biota exceptional sea ice conditions occurred in the west antarctic peninsula wap region from september 2001 to february 2002 resulting from a strongly positive atmospheric pressure anomaly in the south atlantic coupled with strong negative anomalies in the bellingshausen amundsen and southwest weddell seas this created a strong and persistent north northwesterly flow of mild and moist air across the wap in situ satellite and ncep ncar reanalysis nnr data are used to examine the profound and complex impact on regional sea ice oceanography and biota extensive sea ice melt leading to an ocean mixed layer freshening and widespread ice surface flooding snow ice formation and phytoplankton growth coincided with extreme ice deformation and dynamic thickening sea ice dynamics were crucial to the development of an unusually early and rapid short retreat season negative ice extent anomaly strong winds with a dominant northerly component created an unusually compact marginal ice zone and a major increase in ice thickness by deformation and over rafting this led to the atypical persistence of highly compact coastal ice through summer ecological effects were both positive and negative the latter including an impact on the growth rate of larval antarctic krill and the largest recorded between season breeding population decrease and lowest reproductive success in a 30 yr adelie penguin demographic time series the unusual sea ice and snow cover conditions also contributed to the formation of a major phytoplankton bloom unexpectedly the initial bloom occurred within compact sea ice and could not be detected in sea viewing wide field of view sensor seawifs ocean color data this analysis demonstrates that sea ice extent alone is an inadequate descriptor of the regional sea ice state conditions from both a climatic and ecological perspective further information is required on thickness and dynamics deformation

winter habitat use and foraging behavior of crabeater seals along the western antarctic peninsula we quantified the winter and spring movement patterns and foraging behavior of adult crabeater seals lobodon carcinophagus and the influence of sea ice and bathymetry on their foraging behavior thirty four seals 16 m 18 f were outfitted with satellite relay data loggers srdls in the marguerite bay region of the antarctic peninsula 671s 671w during the austral winters of 2001 and 2002 tags transmitted position and dive information for between 4 and 174 days overall winter activity patterns differed significantly from previously reported data collected during the summer seals in this study dived deeper 9270 2 m range 6 713 m and longer 5 26 min70 6 range 0 2 23 6 min hauled out during the night rather than the day and showed seasonal shifts in foraging patterns consistent with foraging on vertically migrating prey while these patterns were more pronounced in 2001 than in 2002 there were no strong differences in patterns of habitat use between the 2 years some animals made long distance movements furthest movements 664 km to northeast 1147 km to southwest but most seals remained within 300 km of their tagging location within the marguerite bay crystal sound region seals appeared to favor foraging locations on the continental shelf within the 50 to 450 m depth range with a tendency to avoid depths of 600 m or greater in both years seals remained deep within the pack ice throughout the winter and did not move into regions with less ice cover seals were more likely to be located in shallow water where the bathymetric gradients were greatest and in areas of higher

springtime ice motion in the western antarctic peninsula region abstract oscillatory motion of sea ice is examined using two ice drifting buoys separated by 1 latitude near 66 s during the winter to spring transition in the marguerite bay region west of the antarctic peninsula the buoys motions exhibit spectrally distinct periods 12 87 0 04 and 13 03 0 04 h respectively despite highly correlated motion between them r2 is 0 62 and 0 81 for u and v respectively the periods shift with latitude and nearly match the local inertial periods 13 00 and 13 10 h respectively the oscillations are further examined with respect to the kinematics involved in the breakup process of sea ice these include hourly resolved manifestations of circular trajectories semi circular oscillations with compressed trajectory cusps and accordion like compressions along straight line trajectories oscillations are found in all trajectory types over the lifetime of both buoys several months traditional circular and semi circular oscillations are particularly prominent during two episodes one of which is preceded by strong wind events and a substantial decrease in ice thickness and concentration these episodes combine with seasonally warming temperatures to break up and melt the sea ice cover we discuss potential relationships between the degradation of the ice pack during spring breakup and the increase in energy at near inertial frequencies including the appearance of a non linear cascade of energy within the ice from the low frequencies commensurate with storms and fortnightly tides to semi diurnal frequencies we further comment on the implications this type of high frequency motion has on local biological ecosystems specifically we find that sea ice semi diurnal oscillations are at their peak during the final decay of sea ice just before springtime primary productivity begins hence the oscillatory motion of sea ice not only serves as an effective mixing agent within the ice ocean mixed layer but also serves as an effective seeding platform for distributing phyto and zooplankton overwintering within and around the ice floes

lagrangian simulation of transport pathways and residence times along the western antarctic peninsula abstract the relative contribution of ocean circulation in producing areas where marine mammals and other predators concentrate to produce biological hot spots along the continental shelf of the western antarctic peninsula wap was investigated with numerical lagrangian particle tracking simulations circulation distributions used in the lagrangian simulations were obtained from the regional ocean modeling system roms configured for the wap region with a horizontal resolution of 4 km and a vertical resolution of 24 sigma layers to determine release points for the floats the simulated circulation fields were first analyzed to estimate scales of temporal variability the temporal decorrelation scales of the simulated surface flow over most of the wap shelf were 2 3 days however decorrelation scales of about 40 days were found for the surface flow in the southern part of marguerite bay temporal decorrelation scales for the flow below the permanent pycnocline at the depth of circumpolar deep water cdw intrusions below 250 m were between 40 and 70 days along the northern flank of marguerite trough and extending into marguerite bay near adelaide island anvers island and the offshore side of alexander island the velocity decorrelation scales varied between 40 and 60 days floats were released in the wap simulated circulation fields along the outer and mid shelf at a range of depths in different seasons the simulated particle trajectories showed preferred sites for across shelf transport with marguerite trough being a primary pathway for movement of floats into marguerite bay crystal sound and the inner shelf region the three primary biological hot spots crystal sound laubeuf fjord and off alexander island were sites with the longest particle residence times being 18 27 days for alexander island and crystal sound to almost 35 days for laubeuf fjord however the source regions and circulation processes that provided the input of particles differed for each site the lagrangian particle tracking results showed the importance of the circulation in developing localized biological hot spots along the wap perhaps by facilitating aggregation of planktonic prey

geohazard assessment of sand dunes between jeddah and al lith western saudi arabia serious hazards have taken place in urban areas and road construction in saudi arabia because of the presence of accumulations of drifting sand dunes several researches which carried out investigative work to solve this problem were reviewed three locations of dune fields along the area between jeddah and al lith were investigated the dune forms was identified detailed field investigations showed that barchan dunes are dominant in the area the sands from the studied locations were found to be similar in grain size and shape parameters mineralogically the sand reflects the composition of the surrounding igneous and metamorphic rocks regression analyses were performed and empirical relationships between dune height width windward length slip face length and rate of movements were developed relatively strong relations exist between these parameters the most important geometric parameter controlling dune movement with wind speed and direction is determined to be the dune height a reasonable similarity occurs between the barchan dunes in the study area and those existing in al nufud al jafurah sand seas and khulays area the studied dune fields pose some natural hazards on the roads and the surrounding buildings and constructions in the villages along the area between jeddah and al lith especially during wind storms

nutrients in the southern ocean globec region variations water circulation and cycling abstract as part of the us southern ocean global ecosystem dynamics so globec study on the west antarctic peninsula wap continental shelf four surveys were conducted along a grid of close spaced stations lying within an area composed of marguerite bay mb and the adjacent continental margin the surveys occurred in the autumn and winter of both 2001 and 2002 a detailed repetitive plan of the so globec surveys permitted the delineation of the important features of nutrient processes horizontal intrusions of upper circumpolar deep water onto the wap continental shelf do not appear to produce fluxes of nitrate and phosphate onto the shelf but appear to lead to a dilution of the silica inventory on the shelf high silica concentrations 115 m observed in the near bottom waters on the shelf were most likely generated locally through dissolution of opal in sediments nutrient deficits and net community production ncp were calculated by the integration of decreases in nutrient concentrations in the mixed layer below corresponding values in the underlying remnant winter water layer waters in mb and other coastal areas were strongly depleted in nutrients deficits of total inorganic nitrogen tin no3 no2 nh4 and silica were 0 6 mol m 2 and 2 5 mol m 2 respectively and enriched in ammonium stocks 0 25 mol m 2 relative to other parts of the grid especially in the autumn of 2001 autumn ncp values calculated from tin deficits in mb equaled or exceeded autumnal ncp values from the joint global ocean flux study ross sea study in 1997 observed n p and si n removal ratios were 12 4 1 6 and 3 9 1 2 respectively in 2001 and 11 1 1 3 and 4 1 1 1 respectively in 2002 these results strongly suggest the dominance of diatoms in the study region co location of maxima in ammonium stocks with the areas of the highest tin and silica deficits indicated a spatial coupling between primary and heterotrophic production in both years this co location highlights the finding that temporal trends in ammonium were usually the opposite of trends in the other nutrients

a new tide model for the antarctic ice shelves and seas we describe a new tide model for the seas surrounding antarctica including the ocean cavities under the floating ice shelves the model uses data assimilation to improve its fit to available data typical peak to peak tide ranges on ice shelves are 1 2 m but can exceed 3 m for the filchner ronne and larsen ice shelves in the weddell sea spring tidal ranges are about twice these values model performance is judged relative to the 5 10 cm accuracy that is needed to fully utilize ice shelf height data that will be collected with the geoscience laser altimeter system scheduled to be launched on the ice cloud and land elevation satellite in late 2002 the model does not yet achieve this level of accuracy except very near the few high quality tidal records that have been assimilated into the model some improvement in predictive skill is expected from increased sophistication of model physics but we also require better definition of ice shelf grounding lines and more accurate water column thickness data in shelf seas and under the ice shelves long duration tide measurements bottom pressure gauge or gps in critical data sparse areas particularly near and on the filchner ronne and ross ice shelves and pine island bay are required to improve the performance of the data assimilation model

the effect of climate change on the mobility and stability of coastal sand dunes in ceara state ne brazil the coast of ceara state in ne brazil is covered by vast fields of active and stabilized coastal sand dunes its tropical climate is characterized by two seasons wet and dry with wind intensity determined by the meridional shift of the intertropical convergence zone the wind power is negatively correlated with precipitation and precipitation is negatively correlated with the difference between sea surface temperatures of the tropical atlantic north and south of the equator we present a model suggesting that during the late pleistocene wind power determined the mobility and stability of the dunes sand dunes accumulated during periods of high wind power as it is today and stabilized when wind power was low once the dunes were stabilized by vegetation they could not be activated even by increased wind power samples that were taken for luminescence dating from 25 stabilized dunes along the coasts of ceara gave ages ranging from135 ka to 100 yr we postulate that these luminescence ages fall at the beginning of wet periods in ne brazil characterized by low wind power these paleoclimatic wet periods correlate well with the cold periods of stades in greenland ice core records

on the characteristics of internal tides and coastal upwelling behaviour in marguerite bay west antarctic peninsula abstract internal waves and coastal upwelling have important roles in both physical oceanography and marine ecosystems via processes such as mixing of water masses and transfer of heat and nutrients to biologically active layers in this paper we use quasi weekly hydrographic profiles and moored records of temperature salinity and water velocity to investigate the nature of internal tides and coastal upwelling behaviour in northern marguerite bay at the western antarctic peninsula within ryder bay a near coastal site in northern marguerite bay atmospherically forced oscillations of the water column with periods around 2 7 days are observed associated with wind induced coastal upwelling and downwelling sea ice cover is seen to play a role in the seasonal suppression of these oscillations significant internal tides also are observed at this site a range of processes are seen to be important in controlling internal tide variability including changes in local stratification and sea ice conditions both diurnal and semidiurnal internal tidal species are observed despite the study region being poleward of the critical latitude for diurnal internal tides this suggests that at least the diurnal internal tides are generated close to the study location and we investigate likely sources

shelf ocean exchange and hydrography west of the antarctic peninsula a review the west antarctic peninsula wap is a highly productive marine ecosystem where extended periods of change have been observed in the form of glacier retreat reduction of sea ice cover and shifts

impact of the 1997 98 enso on upper ocean characteristics in marguerite bay western antarctic peninsula 1 a year round sequence of hydrographic casts is used to trace the evolution of the upper ocean waters in marguerite bay western antarctic peninsula wap between 1998 and 2002 winter 1998 was anomalous showing an unusually deep mixed layer that became progressively more saline until spring reaching salinities as high as 34 0 the remnant of this mixed layer the winter water ww was the deepest and most saline observed atmospheric and cryospheric conditions were anomalous during winter 1998 at both local and regional scales locally we observed low sea ice concentrations high air temperatures and a high frequency of northerly winds these are the local manifestations of the strong enso event of 1997 1998 that was then rapidly weakening at the regional scale this enso produced significant anomalies in the sea ice distribution throughout the amundsen bellingshausen sea area and a large scale low pressure anomaly over the southeast pacific was seen to be responsible for the warm northerly winds we use a coupled mixed layer ice production model to investigate the enso driven forcings for the anomalous ocean conditions observed in winter 1998 this reveals that ice production is the main control on upper ocean stratification and that the deep saline mixed layer in 1998 was forced by anomalous sea ice conditions on spatial scales larger than purely local we conclude that the near coastal hydrography along the peninsula shows a profound response to enso with atmospheric and cryospheric forcings both implicated

detachment faulting and the evolution of passive continental margins major detachment faults play a key role in the lithospheric extension process in the basin and range province and may also be important in other continental extension terranes such detachment faulting leads to an inherent asymmetry of extensional structure and of uplift subsidence patterns detachment models developed for the formation of metamorphic core complexes can also be applied to the formation of passive continental margins we therefore suggest the existence of upper plate and lower plate passive margins these give rise to a complementary asymmetry of opposing margins after continental breakup transfer faults offset marginal features and allow margins to switch from upper plate to lower plate characteristics along strike

macronutrient supply uptake and recycling in the coastal ocean of the west antarctic peninsula nutrient supply uptake and cycling underpin high primary productivity over the continental shelf of the west antarctic peninsula wap here we use a suite of biogeochemical and isotopic data collected over five years in northern marguerite bay to examine these macronutrient dynamics and their controlling biological and physical processes in the wap coastal ocean we show pronounced nutrient drawdown over the summer months by primary production which drives a net seasonal nitrate uptake of 1 83 mol n m 2 yr 1 equivalent to net carbon uptake of 146 g c m 2 yr 1 high primary production fuelled primarily by deep sourced macronutrients is diatom dominated but non siliceous phytoplankton also play a role strong nutrient drawdown in the uppermost surface ocean has the potential to cause transient nitrogen limitation before nutrient resupply and or regeneration interannual variability in nutrient utilisation corresponds to winter sea ice duration and the degree of upper ocean mixing implying susceptibility to physical climate change the nitrogen isotope composition of nitrate 15nno3 shows a utilisation signal during the growing seasons with a community level net isotope effect of 4 19 0 29 we also observe significant deviation of our data from modelled and observed utilisation trends and argue that this is driven primarily by water column nitrification and meltwater dilution of surface nitrate this study is important because it provides a detailed description of the nutrient biogeochemistry underlying high primary productivity at the wap and shows that surface ocean nutrient inventories in the antarctic sea ice zone can be affected by intense recycling in the water column meltwater dilution and sea ice processes in addition to utilisation in the upper ocean

burying processes carried out by a mobile transversal dunefield paracuru county state of ceara brazil the migration of dunes and the consequent burying of the city of paracuru by a transversal dunefield with perpendicular ridges oriented to the dominant windstream have been investigated overlapping aerial photographs taken during different flights have been used as a reference two sediment transportation directions were identified the first is fed by the prevailing easterly winds the second corresponds to the secondary southeasterly winds with the maintenance of current wind conditions and pluvial precipitation dunes will bury part of paracuru town in approximately 120 years within this context the geological evolution model that was applied proved to be satisfactory for the comprehension of sediment transportation mechanisms along the transversal dunes considering the prognosis in relation to paracuru and its urban growth towards the dunefield it is necessary to continue to study aeolian dynamics aiming to develop support for the elaboration of future projects directed towards environmental management of the area

variability in the freshwater balance of northern marguerite bay antarctic peninsula results from δ18o abstract we investigate the seasonal variability in freshwater inputs to the marguerite bay region western antarctic peninsula using a time series of oxygen isotopes in seawater from samples collected in the upper mixed layer of the ocean during 2002 and 2003 we find that meteoric water mostly in the form of glacial ice melt is the dominant freshwater source accounting for up to 5 of the near surface ocean during the austral summer sea ice melt accounts for a much smaller percentage even during the summer maximum around 1 the seasonality in meteoric water input to the ocean around 2 of the near surface ocean is not dissimilar to that of sea ice melt around 2 in 2002 and 1 in 2003 contradicting the assumption that sea ice processes dominate the seasonal evolution of the physical ocean environment close to the antarctic continent three full depth profiles of oxygen isotopes collected in successive decembers 2001 2003 indicate that around 4 m of meteoric water is present in the water column at this time of year and around 1 m of sea ice formed from this same water column the predominance of glacial melt is significant since it is known to be an important factor in the operation of the ecosystem for example by providing a source of nutrients and modifying the physical environment to control the spatial extent and magnitude of phytoplankton blooms the western antarctic peninsula is undergoing a very rapid change in climate with increasing ocean and air temperatures retreating glaciers and increases in precipitation associated with changes in atmospheric circulation as climate change continues we expect meteoric water inputs to the adjacent ocean to rise further sea ice in this sector of the antarctic has shown a climatic decrease and we expect a reduction in oceanic sea ice melt fractions if this change continues continued monitoring of the oceanic freshwater budget at the western peninsula is needed to track these changes as they occur and to better understand their ecological consequences

a sand budget for the alexandria coastal dunefield south africa the sand in the alexandria coastal dunefield is derived from the sandy beach which forms the seaward boundary of the dunefield sand is blown off the beach onto the dunefield by the high energy onshore directed dominant wind the dunefield has been forming over the past 6500 years sand transport rates calculated from dune movement rates and wind data range from 15 to 30 m3 m 1 yr 1 in an ene direction the sand transport rate decreases with increasing distance from the sea due to a reduction in wind speed resulting from the higher drag imposed upon the wind by the land surface aeolian sand movement rates of this order are typical of dunefields around the world the total volume of sand blown into the dunefield is 375 000 m3 yr 1 sand is being lost to the sea by wave erosion along the eastern third of the dunefield at a rate of 45 000 m3 yr 1 the dunefield thus gains 330 000 m3 of sand per year this results in dunefield growth by vertical accretion at about 1 5 mm yr 1 and landward movement at about 0 25 m yr 1 the dunefield is a significant sand sink in the coastal sand transport system the rate of deposition in coastal dunefields can be 10 times as high as rates of deposition in continental sand seas the higher rate of deposition may result from the abundant sand supply on sandy beaches and the higher energy of coastal winds wind transport is slow and steady compared to fluvial or longshore drift transport of sediment and catastrophic aeolian events do not seem to be significant in wind laid deposits

some implications of ekman layer dynamics for cross shelf exchange in the amundsen sea theexchangeofwarm saltyseawateracrossthecontinentalshelvesoffwestantarcticaleadstosubsurface glacial melting at the interface between the ocean and the west antarctic ice sheet one mechanism that contributesto the cross shelf transportis ekmantransportinduced by along slope currentsoverthe slope and shelf break an investigation of this process is applied to the amundsen sea shelfbreak region using recently acquiredandhistoricalfielddatatoguidetheanalyses along slopecurrentswereobservedattransectsacross the eastern and western reaches of the amundsen slope currents in the east flowed eastward and currents farther west flowed westward under the eastward flowing currents hydrographic isolines sloped upward paralleling the seabed in this layer declining buoyancy forces rather than friction were bringing the velocity to zero at the seabed thebasin water in the easternpart ofthe shelfwas dominatedby wateroriginating from 800 1000 m depth off shelf suggesting that transport of such water across the shelf frequently occurs the authors show that arrested ekman layers mechanism can supply deep water to the shelf break in the eastern section where it has access to the shelf because no unmodified off shelf water was found on the shelf in the western part bottom layer ekman transport does not appear a likely mechanism for delivery of warm deep water to the western shelf area warming of the warm bottom water was most pronounced on the western shelf where the deep water temperature increased by 0 68c during the past decade

pelagic fishes in the marguerite bay region of the west antarctic peninsula continental shelf abstract pelagic fishes in the marguerite bay region of the western antarctic peninsula wap continental margin were sampled using a 10 m 2 mocness as part of the southern ocean global ocean ecosystems dynamics so globec program sixty two tows were completed during the course of four cruises conducted during the austral fall and winter 22 each during the austral fall and 9 each during the austral winter six thousand and sixty individuals of 34 species representing 13 families were collected in the fall while 672 individuals of 22 species from 10 families were collected in the winter nearly all of the notothenioid specimens collected families artedraconidae bathydraconidae channichthyidae and nototheniidae were either larvae or young juveniles 0 2 years conversely except for the paralepidid notolepis coatsi and the occasional juveniles of the bathylagid bathylagus antarcticus the gonostomatid cyclothone kobayashii or the myctophid electrona antarctica the non notothenioid specimens collected were predominantly adults in the fall the nototheniids pleuragramma antarcticum and trematomus scotti and the myctophid e antarctica numerically dominated the overall assemblage collectively accounting for 89 7 of the total catch in the winter e antarctica cyclothone microdon and b antarcticus were the numerical dominants each contributing 14 20 of the total the pelagic fish community within the marguerite bay region of the wap continental shelf is a variable mixture of mesopelagic and neritic fauna at one extreme is an oceanic assemblage exhibiting high diversity indices and characterized by the genera electrona gymnoscopelus protomyctophum bathylagus cyclothone and notolepis minor components of this group include numerous less common mesopelagic genera e g paradiplospinus lampanyctus benthalbella borostomias and the occasional larval juvenile notothenioid at the other extreme is a coastal assemblage with low diversity indices dominated by larval and juvenile notothenioids particularly pleuragramma antarcticum this assemblage is also characterized by a numerically low but consistent liparid and zoarcid component with the latter group often contributing disproportionately to the total biomass the degree of overlap between the two assemblages and the relative dominance of representative species is directly related to local hydrographic conditions in particular the presence of circumpolar deep water cdw the unique hydrographic conditions of the wap shelf and the accompanying spatial heterogeneity in pelagic ichthyofauna provide a striking contrast to the continental margin areas of the ross weddell davis and dumont d urville seas where sharp temperature gradients near the shelf break result in a clear separation of oceanic and coastal assemblages

ocean acidification and calcium carbonate saturation states in the coastal zone of the west antarctic peninsula the polar oceans are particularly vulnerable to ocean acidification the lowering of seawater ph and carbonate mineral saturation states due to uptake of atmospheric carbon dioxide co2 high spatial variability in surface water ph and saturation states for two biologically important calcium carbonate minerals calcite and aragonite was observed in ryder bay in the coastal sea ice zone of the west antarctic peninsula glacial meltwater and melting sea ice stratified the water column and facilitated the development of large phytoplankton blooms and subsequent strong uptake of atmospheric co2 of up to 55 mmol m 2 day 1 during austral summer concurrent high ph 8 48 and calcium carbonate mineral supersaturation aragonite 3 1 occurred in the meltwater influenced surface ocean biologically induced increases in calcium carbonate mineral saturation states counteracted any effects of carbonate ion dilution accumulation of co2 through remineralisation of additional organic matter from productive coastal waters lowered the ph 7 84 and caused deep water corrosivity aragonite 0 9 in regions impacted by circumpolar deep water episodic mixing events enabled co2 rich subsurface water to become entrained into the surface and eroded seasonal stratification to lower surface water ph 8 21 and saturation states aragonite 1 8 relative to all surface waters across ryder bay uptake of atmospheric co2 of 28 mmol m 2 day 1 in regions of vertical mixing may enhance the susceptibility of the surface layer to future ocean acidification in dynamic coastal environments spatially resolved studies are essential to elucidate the natural variability in carbonate chemistry in order to better understand and predict carbon cycling and the response of marine organisms to future ocean acidification in the antarctic coastal zone

proterozoic basalt dikes in the nain anorthosite complex labrador two sets of proterozoic between 1290 and 1042 ma alkali to transitional basaltic dikes occur sparsely in an area of at least 5000 km2 within the nain anorthosite complex both are compositionally similar in terms of major elements but the set that trends roughly north south hp dikes contains much higher concentrations of incompatible elements than the more abundant dikes that trend roughly east northeast west southwest lp dikes both types have low normative clinopyroxene relative to olivine a characteristic shared with widespread troctolitic rocks in the nain complex low mg numbers and low ni contents suggest that the magmas producing these dikes have undergone extensive fractional crystallization the low normative di content of these dikes suggests that this fractional crystallization occurred at depths equivalent to at least 10 kbar 1000 mpa high equilibration temperatures for coexisting fe ti oxides in the matrices of these dikes indicate that the dikes cooled rapidly and were emplaced near

anorogenic magmatism and the grenvillian orogeny the grenvillian orogeny was preceded by extensive anorogenic volcanism and plutonism in the period 1500 1300 ma in the form of rhyolites epizonal granites anorthosites gabbros alkaline complexes and basic dykes an analogue for the mid proterozoic anorogenic complexes is provided by the 2000 km by 200 km belt of anorogenic complexes in the hoggar niger and nigeria which contain anorthosites gabbros and peralkaline granites and were generated in a cambrian to jurassic rift that farther south led to the formation of the south atlantic an analogue for the 1 106 km2 area of 1500 1350 ma rhyolites and associated epizonal granites that underlie the mid continental united states is provided by the 1 7 106 km2 area of jurassic tobifera rhyolites in argentina which were extruded on the stretched continental margin of south america immediately preceding the opening of the south atlantic the mid proterozoic complexes were intruded close to the continental margin of the grenvillian ocean and were c

circulation and heat fluxes during the austral fall in george vi sound antarctic peninsula abstract a mesoscale survey was conducted in northern george vi sound as part of the united states southern ocean global ocean ecosystems dynamics program in austral fall 2001 to examine the circulation and heat fluxes the absolute dynamic height field is determined from a combination of measured currents detided using model predicted tidal currents streamfunction fitting and the thermal wind equation based on hydrographic measurements the results have revealed surface coastal currents of 0 2 m s 1 intruding into northern george vi sound from marguerite bay mb and mesoscale eddies formed within the deep trough both antarctic surface waters and modified circumpolar deep water were transported into the sound along the eastern side of the sound while ice shelf influenced waters exited to mb along the western side analysis indicates that predominant southward winds during the season were responsible for driving the basin wide circulation in the sound both convergence of horizontal heat transports and vertical upwelling heat fluxes were significant to the contribution or delay of local ice formation in george vi sound which is critical for the austral winter ecosystem

a possible mechanism for epeirogenic uplift continental geology is dominated by vertical movements some of these are the result of crustal shortening and extension associated with large horizontal displacements involving processes which are now understood at least in outline however both uplift and subsidence can occur without associated shortening or extension of the continental crust most investigations of such epeirogenic movements have been concerned with subsidence partly because of the economic importance of the resulting sedimentary basins and partly because of the existence of a simple model for the process1 which can account for the development of several basins in some detail2 4 however uplift has been relatively neglected and cannot be produced by the same mechanism the purpose of this paper is to examine whether epeirogenic uplift can result from the intrusion of large thicknesses of basic magma into the lower part of continental crust this suggestion was considered as a possible mechanism for the regional uplift of the colorado plateau by gilbert5 more than 100 years ago and also by holmes6 though both rejected the idea however a recent discussion of no less than 14 different mechanisms for generating uplift7 did not include this process even though it seems able to produce the observed vertical motions and also to account for some of the features of the evolution of sedimentary basins that cannot be explained by the uniform stretching model3 8 9 although the suggestion is not new the argument used here to support it is and depends on an understanding of the relationship between ocean island volcanoes and mantle circulation

drifter measurements of surface currents near marguerite bay on the western antarctic peninsula shelf during austral summer and fall 2001 and 2002 abstract we deployed 24 satellite tracked surface drifters near marguerite bay on the western antarctic peninsula shelf during march may 2001 and february april 2002 the woce style drifters featured holey sock drogues centered at 15 m and were located about 20 times per day by service argos analyses of the drifter tracks show a coastal current that flows toward the southwest along the west coast of adelaide island and into marguerite bay near the southern tip of adelaide island then flows clockwise around the bay near the coast and finally exits the bay near alexander island this coastal current flowed along the eastern boundary of marguerite bay in 2001 but across the central part of the bay in 2002 due to the early presence of sea ice in the southern half of the bay the outflow from the bay continued along the coast of alexander island toward the southwest in 2001 but was directed northwestward across the shelf in 2002 due to the sea ice coverage to the south a mean drifter current speed of about 10 cm s 1 was observed in the coastal current with a maximum speed of about 20 cm s 1 during periods of strong wind stress an intermittent northeastward current was observed near the shelf break the drifter tracks also show that intermittent near inertial currents are common in marguerite bay and over the adjacent shelf during ice free conditions these counterclockwise oscillations had periods near the local inertial period roughly 13 0 h and speeds of 5 20 cm s 1 with a tendency for smaller amplitudes within marguerite bay

water properties on the west antarctic peninsula continental shelf a model study of effects of surface fluxes and sea ice abstract a vertical and time dependent numerical mixed layer and sea ice model is used to analyze processes responsible for sea ice and surface mixed layer water properties on the continental shelf on the west side of the antarctic peninsula atmospheric observations from faraday and palmer stations along with satellite sea ice observations and shipboard water observations four hydrographic cruises between january 1993 to february 1994 are used for forcing and verification the focus of this study is the year 1993 during which the best observations exist however a 16 year simulation is completed to analyze interannual variations of ice thickness and mixed layer depth this model study shows that surface waters of the west antarctic peninsula are heated in the summer by solar radiation and cooled in the winter by sensible heat losses diffusive convection is important for upward heat flux across the pycnocline ice melt in the spring is due to solar warming of open water which then melts ice the direct melting for ice by solar heating is negligible the near closure of surface heat and salt budgets over 1 year supports the minor importance or at least the compensation of near surface lateral exchanges intrusion of upper circumpolar deep water from the antarctic circumpolar current onto the subpycnocline shelf is a critical element of both salt and heat budgets a 16 year simulation 1978 1993 reproduces most high and low ice years as observed by satellite microwave measurements thus supporting the major contribution of thermodynamic local processes in creating sea ice and mixed layer properties

geochemistry of the felsic metavolcanic rocks of the wakeham group a metamorphosed peralkaline suite from the eastern grenville province quebec canada the wakeham group is a suite of low grade greenschist facies rocks located in the eastern grenville province in order of volumetric importance it consists of sandstones acid volcanics and gabbro dykes and sills this report deals with the acid volcanic member of the group primary textural features have in large part been preserved the minerals present include stilpnomelane white mica albite titanite and zircon calculations using 33 chemical analyses show that 29 of the compositions have normative corundum the rocks would therefore appear to be predominantly peraluminous however incompatible trace element data show affinities with other anorogenic peralkaline suites it is proposed that alkali loss probably during the subsequent grenvillian orogeny imposed a peraluminous composition on originally peralkaline rocks the wakeham group cannot be definitively correlated with other metavolcanic rocks found in the region

a model study of circumpolar deep water on the west antarctic peninsula and ross sea continental shelves abstract transport of relatively warm nutrient rich circumpolar deep water cdw onto continental shelves around antarctica has important effects on physical and biological processes however the characteristics of the cdw along the shelf break as well as what happens to it once it has been advected onto the continental shelf differ spatially in the present study high resolution 4 5 km regional models of the ross sea and the west antarctic peninsula coastal ocean are used to compare differences in cdw transport the models compared very well with observations from both regions examining the fluxes not only of heat but also of a simulated dye representing cdw shows that in both cases cdw crosses the shelf break in specific locations primarily determined by the bathymetry but eventually floods much of the shelf the frequency of intrusions in marguerite trough was ca 2 3 per month similar to recent mooring observations a significant correlation between the along shelf break wind stress and the cross shelf break dye flux through marguerite trough was observed suggesting that intrusions are at least partially related to short duration wind events the primary difference between the cdw intrusions on the ross and west antarctic peninsula shelves is that there is more vigorous mixing of the cdw with the surface waters in the ross sea especially in the west where high salinity shelf water is created the models show that the cdw moving across the antarctic peninsula continental shelf towards the base of the ice shelves not only is warmer initially and travels a shorter distance than that advected towards the base of the ross ice shelf but it is also subjected to less vertical mixing with surface waters which conserves the heat available to be advected under the ice shelves this difference in vertical mixing also likely leads to differences in the supply of nutrients from the cdw into the upper water column and thus modulates the impacts on surface biogeochemical processes