storm induced response of a nearshore bar system abstract a nearshore bar system was surveyed periodically through a storm and the following recovery period the data showed a very rapid response of morphology to changing wave conditions and allowed various models on bar formation to be tested under low energy conditions prior to the storm a small bar was surveyed 13 m offshore both the high reflectivity of the beach and the cross shore distance to the bar are consistent with a model of sediment convergence at the node or antinode of a standing wave of incident period such a small scale bar may be a common feature on beaches with steep foreshores and more gentle offshore slopes with the increase in wave height during the storm the bar became better developed and migrated offshore at rates up to 2 2 m h 1 the bar maintained its form in that the ratio of trough depth to crest depth h t h c remained roughly constant the bar was in no way related to processes which would cause the convergence of sediment in the breaker zone through most of the storm the bar crest distance offshore was typically only 10 of the surf zone width analysis of the bar distance offshore in terms of a standing wave motion showed that the causative wave period must have been much longer than that of incident waves probably on the order of a minute surf zone wave data showed significant energy in the infragravity band at these periods although no definite link has been made after the height of the storm the bar had a crescentic morphology the development of this morphology occurred very rapidly with parts of the bar migrating onshore at rates up to 1 2 m h 1 in contrast to the storm during the recovery period h t h c varied by nearly a factor of three analysis of the offshore and longshore length scales showed the bar to be similar to one which would be generated by a standing mode 1 edge wave of period on the order of one minute

uptake of cadmium into calcite shells by planktonic foraminifera abstract planktonic foraminifera were cultured in the laboratory and the uptake of cd into their calcite investigated using cd and sr radiotracers best estimates of the effective distribution coefficient of cd relative to ca in planktonic foraminiferal calcite are 2 4 from these experiments and previously determined values of the sr distribution coefficient within the uncertainty of these estimates planktonic foraminiferal shells reflect seawater cd ca ratios with a proportionality constant similar to that determined for benthic foraminifera cd ca ratios in planktonic and benthic foraminiferal shells from sediment cores may be useful therefore for reconstructing water column profiles of cd ca over time

sea ice ridging in the ross sea antarctica as compared with sites in the arctic at the end of the 1980 austral winter surface roughness measurements were made by laser profilometer during a series of flights over the ross sea pack ice the total track length was 2696 km and 4365 ridges were counted the frequency distribution of individual ridge heights was found to be well described by a negative exponential distribution no clear cut regional variation was noted in ridge heights the distribution of ridge frequencies per kilometer showed a strong positive skew with a modal value of 1 88 the most frequent ridging occurred off the east coast of victoria land comparisons with similar data sets from the arctic indicate that large ridges are significantly more likely in the arctic ocean than in the ross sea utilizing a reasonable model for the geometry of ridges estimates are made of the average thickness of a hypothetical continuous layer composed only of the deformed ice from ridges the noncoastal ross sea value of 0 09 m is less than half of the lowest comparable value from the arctic 0 20 m central beaufort sea where values in excess of 1 0 m have been observed in the shear zones north of greenland

infragravity wave dynamics in a barred coastal region a numerical study this paper presents a comprehensive numerical study into the infragravity wave dynamics at a field site characterized by a gently sloping barred beach the nonhydrostatic wave flow model swash was used to simulate the local wavefield for a range of wave conditions including mild and storm conditions the extensive spatial coverage of the model allowed us to analyze the infragravity wave dynamics at spatial scales not often covered before overall the model predicted a wavefield that was representative of the natural conditions supporting the model application to analyze the wave dynamics the infragravity wave field was typically dominated by leaky waves except near the outer bar where bar trapped edge waves were observed relative contributions of bar trapped waves peaked during mild conditions when they explained up to 50 of the infragravity variance near the outer bar the infragravity wave growth was partly explained by nonlinear energy transfers from short waves this growth was strongest for mild conditions and decreased for more energetic conditions when short waves were breaking at the outer bar further shoreward infragravity waves lost most of their energy due to a combination of nonlinear transfers bottom friction and infragravity wave breaking nonlinear transfers were only effective near the inner bar whereas near the shoreline where losses were strongest the dissipation was caused by the combined effect of bottom friction and breaking this study demonstrated the model s potential to study wave dynamics at field scales not easily covered by in situ observations

field observations of swash zone infragravity motions and beach cusp evolution 1 fluid flows consistent with low mode edge waves were evident in video observations of swash motions during a field experiment in which beach cusps developed on an initially smooth beach as beach cusps grew energy lying along low mode dispersion curves increased the most energetic edge wave propagation direction changed from upcoast to downcoast as the orientation of the cusp horns rotated these observations suggest a coupling between morphodynamics and hydrodynamics and are evidence that beach cusp evolution might control low mode edge wave dynamics

linear modeling of infragravity waves during delilah 1 the generation of infragravity waves by directionally spread shortwaves incident on an alongshore uniform beach is investigated two mechanisms responsible for the generation of infragravity waves are considered the release of the bound infragravity waves associated with changes in the spatial variation of the incident shortwave energy and the forcing of trapped waves by obliquely incident directionally spread shortwaves the infragravity wave response is examined using linear shallow water equations taking into account the presence of bottom friction setup of the mean water level rollers and longshore current summing all infragravity contributions due to difference interactions between pairs of shortwave spectral components with the same frequency difference results in infragravity energy density spectra calculated spectra are compared with measured spectra obtained during the delilah field experiment for 11 consecutive days including calm mild and storm conditions in the comparison attention is focused on the frequency distribution of the infragravity energy density throughout the surf zone and the transformation of the root mean square infragravity wave height the measured infragravity response in the frequency range from 0 01 to 0 06 hz is reproduced by the computations with relatively broad spectra offshore and a clear nodal structure closer to shore typically 80 of the infragravity wave height variability is explained by the model of which 30 or less is due to bound infragravity waves differences occur mainly during storm events in which the infragravity energy is underpredicted in the outer surf zone and overpredicted in the inner surf zone

a parameterization of the ice ocean drag coefficient 1 a parameterization of the ice ocean drag coefficient cw was developed through partitioning the oceanic drag force into three components 1 form drag on the floe edge 2 form drag on the ridge keel and 3 skin friction on the ice bottom through these quantities cw was expressed as a function of observable sea ice geometric parameters sensitivity studies were carried out to investigate the influence of varying sea ice conditions on cw the results revealed that cw increases first and then decreases with increasing ice concentration a similar to the observations of the air ice drag coefficient and which is mainly attributed to the nonmonotonic variation of the form drag on the floe edge with ice concentration moreover the form drag on the floe edge is always the dominant component having a proportion of more than 60 in sea ice with a large aspect ratio draft length 1 100 indicating the necessity of including this term in sea ice dynamic models particularly for the marginal ice zone miz the form drag on the ridge keel becomes dominant only when the ridging intensity is extremely high depth spacing 1 20 additionally a large value of cw cannot be caused only by the inclusion of form drag terms but also by large skin friction over rough ice bottoms finally for typical situations in the miz with moderate ridging intensity the parameterization will underestimate cw by approximately 30 for a rough ice bottom and by over 80 for a smooth ice bottom if no form drags are considered

autumn sea ice thickness ridging and heat flux variability in and adjacent to terra nova bay ross sea antarctica the variability of sea ice thickness and snow depth observed from the r v nathaniel b palmer in late may 1998 in and adjacent to terra nova bay tnb ross sea antarctica is described conductive heat fluxes are estimated on the basis of the observed snow and ice thicknesses there was only 6 areal coverage of open water in tnb and 87 of the areal coverage of unridged ice was 0 3 m thick between the western and eastern margins of tnb there were increases in the area weighted unridged ice thickness 0 05 0 25 m and the areal extent of ridging 2 5 18 5 ridged ice accounted for 44 66 of the total ice mass in tnb and was as vital to thickening the ice cover as it was outside the bay where 30 60 of the total ice mass was contained within the 5 35 of ice that was ridged satellite passive microwave special sensor microwave imager ssm i data show that the extensive ice cover in tnb was normal for this time of year probably because of the blocking effect of thick ridged 100 concentration pack ice outside the bay despite the extensive ice cover in tnb there was an order of magnitude difference in area weighted mean heat flux between the bay and the pack ice for example depending on the choice of bulk snow thermal conductivity value ks 0 14 or 0 31 w m 1 k 1 the heat flux values for unridged ice were 199 or 216 w m 2 in tnb versus 35 or 49 w m 2 on the inbound pack ice leg and 20 or 39 w m 2 on the outbound pack ice leg factoring in the contribution of ridges to the ice thickness distribution decreased the heat flux in the bay and the pack ice by 25 or 36 depending on ks the greatest proportion of the heat flux in tnb occurred through the ice no more than 30 of the heat loss was from open water since the ice conditions observed in tnb were apparently normal for the time of year the heat fluxes also must have been quite normal

contributions of the siberian shelf polynyas to the arctic ocean intermediate and deep water the role of the open water regions or polynyas in the winter ice pack over the siberian continental shelves in the production of arctic ocean intermediate and deep water is examined through use of a combination of passive microwave satellite data coastal weather station data and oceanographic data the satellite data allow us to derive a time series of the open water areas of selected polynyas for the 1978 1982 winters the polynyas which occur north of svalbard around franz josef land along the west coast and north end of novaya zemlya and to the east of severnaya zemlya and the taymyr peninsula are the primary oceanographic contributors the open water time series for these polynyas are used in combination with coastal weather station data to estimate the heat loss from each polynya for the region north of svalbard which is historically known as whalers bay the study shows that the heat loss is sufficient to provide the observed cooling of the west spitsbergen current for the other polynyas the heat loss is used to compute the ice production rates and the oceanic salt flux we then use the historic oceanographic salinities with the salt fluxes to estimate the contribution of each polynya to the arctic ocean water masses if we assume that the salt contributes only to the arctic intermediate water our results show that the shelves are capable of producing about 20 60 of this water alternatively if the salt contributes only to the deep water of the eurasian basin then without consideration of the mixing of the bottom water with the greenland and norwegian sea water the contribution from the shelves yields a renewal time of about 100 years our results imply that there is insufficient water produced in the shelf polynyas to perform all of the roles that have been historically assigned to it

cadmium chemical tracer of deepwater paleoceanography the oceanic distribution of cadmium resembles that of phosphorus because the cadmium content of foraminiferal shells is governed by the cadmium content of seawater planktonic and benthic fossil shells can be used to infer nutrient distributions within ancient oceans empirical studies demonstrate that cadmium in benthic foraminiferal shells is related to the bottom water composition through a proportionality constant d 2 9 this constant is the same for each of the species studied cibicidoides wuellerstorfi cibicidoides kullenbergi nuttallides umbonifera and uvigerina spp downcore cadmium data from high quality pacific and atlantic sediment cores suggest that the cadmium inventory of the ocean did not change significantly between the most recent glacial maximum and the present hence changes in the cadmium content of fossils at a site directly reflect changes in nutrient distributions due to altered oceanic circulation patterns studies of cadmium in pleistocene sediments show that deep ocean circulation patterns were significantly different during the most recent glacial maximum in the western north atlantic ocean the nutrient content of waters from 2500 to 3500 m was twice as high during glacials as during interglacial periods signifying an increase in the proportion of waters of antarctic origin in this depth interval and a decrease but not a cessation in the flux of north atlantic deep waters through this depth range below 3500 m the nutrient increase was greater indicating a higher proportion of antarctic bottom water above 2500 m the nutrient content was lower during glacial periods than it has been during interglacial times the cd content of high latitude north atlantic and southern ocean surface waters does not show a significant glacial interglacial change which argues against theories for changes atmospheric carbon dioxide that require changes in high latitude nutrient concentrations

chemical properties of brackish water ice in the bothnian bay the baltic sea the behavior of major ions 18 o dissolved organic carbon doc and trace elements was studied during the initial freezing of low saline water 3 practical salinity units in a freezing experiment samples were also collected from first year sea ice from pack ice in the bothnian bay northern baltic sea during initial ice formation the major ion ratios in sea ice indicated variable behavior with some ions showing relative enrichment sulfate calcium and magnesium conservative behavior sodium or relative depletion potassium compared to sea water at the same salinity doc iron and aluminum showed enrichment in the ice while zinc was depleted to salinity lead was detected in surface snow ice layers only implying atmospheric accumulation first year sea ice with a variable growth and thermal history showed behavior for major ions similar to that observed in new ice however for trace elements the picture was much more complicated most likely due to active secondary processes such as atmospheric supply and biological activity ice growth has a potential impact on the chemical budgets and cycling of some elements especially those which are selectively rejected retained during sea ice formation particularly in the shallow parts of the bothnian bay covered with a land fast ice cover

ross sea ice motion area flux and deformation abstract the sea ice motion area export and deformation of the ross sea ice cover are examined with satellite passive microwave and radarsat observations the record of high resolution synthetic aperture radar sar data from 1998 and 2000 allows the estimation of the variability of ice deformation at the small scale 10 km and to assess the quality of the longer record of passive microwave ice motion daily and subdaily deformation fields and radarsat imagery highlight the variability of motion and deformation in the ross sea with the passive microwave ice motion the area export at a flux gate positioned between cape adare and land bay is estimated between 1992 and 2003 a positive trend can be seen in the winter march november ice area flux that has a mean of 990 103 km2 and ranges from a low of 600 103 km2 in 1992 to a peak of 1600 103 km2 in 2001 in the mean the southern ross sea produces almost twice its own area of sea ice during the winter cross gate sea level pressure slp gra

sea ice ridging in the eastern weddell sea in august 1986 sea ice ridge heights and spatial frequency in the eastern weddell sea were measured using a ship based acoustical sounder using a minimum ridge sail height of 0 75 m a total of 933 ridges were measured along a track length of 415 km the ridge frequency varied from 0 4 to 10 5 ridges km 1 the mean height of the ridges was found to be about 1 1 m regardless of the ridge frequency these results are compared to other ridging statistics from the ross sea and found to be similar comparison with arctic data however indicates that the height and frequency of the ridges are considerably less in the weddell sea than in the arctic whereas in the arctic the mean ridge height tends to increase with the ridge frequency we found that this was not the case in the weddell sea where the mean ridge height remained constant irrespective of the ridge frequency estimates of the contribution of deformed ice to the total ice thickness are generally low except for a single 53 km section where the ridge frequency increased by an order of magnitude this resulted in an increase in the equivalent mean ice thickness due to ridging from 0 04 m in the less deformed areas to 0 45 m in the highly deformed section these values were found to be consistent with values obtained from drilled profile lines during the same cruise

lack of a significant temperature influence on the incorporation of cd into benthic foraminiferal tests 1 benthic foraminiferal cd ca is an important proxy for seawater paleonutrient concentrations and therefore deep ocean paleocirculation although previous work suggests that the incorporation of cd into benthic foraminiferal calcite is insensitive to temperature at least one species of planktonic foraminifer appears to be strongly influenced the present study provides a closer look at the relationship between benthic cd partition coefficients and temperature using new and previously published data from the bahama banks neither calcitic taxa nor the aragonitic hoeglundina elegans exhibits any consistent changes in partition coefficients over the range 4 to 18 c

observations of sea ice ridging in the weddell sea sea ice surface topography data were obtained by helicopter borne laser profiling during the first finnish antarctic expedition finnarp 89 the measurements were made near the ice margin at about 73 s 27 w in the eastern weddell sea on december 31 1989 and january 1 1990 five transects ranging in length from 127 to 163 km and covering a total length of 724 km are analyzed with a lower cutoff of 0 91 m the overall ridge frequency was 8 4 ridges km and the average ridge height was 1 32 m the spatial variations in ridging were large for 36 individual 20 km segments the frequencies were 2 16 ridges km and the mean heights were 1 16 1 56 m the frequencies and mean heights were weakly correlated the distributions of the ridge heights followed the exponential distribution the spacings did not pass tests for either the exponential or the lognormal distribution but the latter was much closer in the 20 km segments the areally averaged thickness of ridged ice was 0 51 0 28 m ranging from 0 10 to 1 15 m the observed ridge size and frequency are greater than those known for the ross sea compared with the central arctic the weddell sea ridging frequencies are similar but the ridge heights are smaller possibly as a result of differences in snow accumulation

roughness variability of sea ice and snow cover thickness profiles in the ross amundsen and bellingshausen seas investigation of top and bottom surface roughness was carried out on snow and ice thickness profiles sampled on 57 floes in the ross amundsen and bellingshausen seas between may and september 1995 an objective classification scheme was used to group the studied sea ice floes according to the degree of deformation they had undergone different roughness criteria and methods were applied to the classified floes roughness variances and other properties such as fractal dimensions derived from fourier spectra depend critically on the deformational history of the floes under consideration the wavelet transform is presented as a new two dimensional method to find dominant structure lengths and at the same time localize them in the studied profiles finally air water and ice surface drag coefficients are calculated from the surface roughness characteristics air drag coefficients ranged between 1 1 and 1 7 103 and increased with increasingly deformed ice

sediment transport near the break point associated with cross shore gradients in vertical eddy diffusivity sediment clouds entrained and mixed vertically into the water column at the breakpoint were observed to advect offshore with the return current following wave breaking at a natural beach an advection diffusion model is applied to this phenomenon providing for cross shore gradients in vertical eddy diffusivity within and beyond the surf zone which result in differential entrainment and settlement near the break point results indicate that the horizontal gradient in turbulent vertical sediment mixing can provide a significant mechanism for bar generation even if the surface gravity and infra gravity waves remain uncoupled quantitative estimates of the rate of bar accretion are obtained after calibrating the sediment transport model using field measurements of currents and suspended sediment loads in the absence of other processes accretion rates of order 20 mm hour associated with the horizontal gradient in vertical diffusivity are predicted on the offshore bar

edge wave trapping and amplification on barred beaches theoretical predictions show that edge waves may be trapped on bars providing a possible mechanism for bar growth simple solutions to the linear shallow water equations reveal that bar trapping is controlled by the depth of the water over the bar hbar and the geometry of the inshore trough relative to the bar for specific geometries amplification over the bar approaches an order of magnitude or more as the phase speed approaches where amplification is defined as the surface displacement over the bar relative to the surface displacement at the shoreline the amplification increases with the cross shore length scales of the profiles the amplification is somewhat frequency dependent generating stronger currents at the location of the bar in specific frequency ranges previous work showed that particular edge wave modes have the correct length scales to generate beach features such as bars and beach cusps but field observations notably shoreline run up data frequently show no evidence of edge wave energy being concentrated at the appropriate frequencies however for bar trapped modes edge wave energy is concentrated at the location of the bar therefore this edge wave energy will not necessarily be evident in shoreline measurements strong correlation exists between the energy distribution of the longshore component of the orbital velocity observed in data collected at superduck october 11 1986 and the distribution expected for a white edge wave spectrum at the shoreline this suggests that bar trapped edge waves exist in particular at incident wave frequencies

sea ice topography of the arctic ocean in the region 70 degrees w to 25 degrees e in october 1976 a cooperative experiment was made to survey the sea ice topography in the european sector of the arctic ocean h m submarine sovereign acquired 4000 km of ice draft data by using an upward looking sonar while a canadian forces aircraft flew along the submarine s track and acquired 2200 km of ice elevation data by using a laser profilometer the two types of profile were processed in corresponding 100 km section lengths and the following statistical analyses and comparisons were made i probability density functions o f ice draft and elevation each distribution shows a peak for young ice and for undeformed multi year ice at large ice thicknesses the distributions take the analytical form of a negative exponential the mean drafts enable two distinct geographical ice regimes to be identified there is an offshore zone of very heavy pressure ridging extending up to 400 km from the coasts of ellesmere island and of north greenland with mean ice draft in the range 5 0 to 7 5 m while out in the central arctic ocean the mean ice draft is lower 3 9 5 1 m and the characteristics of the ice cover remain homogeneous over a length scale of 1000 km the transition between the two regimes is abrupt taking place in less than 25 km data from the same part of the central arctic taken in march 1971 showed a mean ice draft 0 3 m lower while data from the central beaufort sea showed a mean draft more than 0 8 m lower ii level ice distributions ice with a local gradient of less than 1 in 40 was defined as level ice and used as an indicator of the quantity and thickness distribution of undeformed i e thermodynamically grown ice in the arctic ocean the distribution has a mode at 3 0 3 1 m draft and level ice percentages are in the range 30 40 bottom side and 70 80 top side in the offshore zone and 45 55 bottom and 85 95 top in the central arctic thus about half of the arctic ice cover consists of deformed ice iii pressure ridge spacings the spacings of ridge keels fit a negative exponential distribution characteristic of randomness except at close spacings where there is a deficit of keels explained as a geometrical effect and at very large spacings where there is an excess due to the contribution of polynyas the distribution of sail spacings exhibits these two effects but also differs from a random distribution at moderate sail separations iv ridge elevations and drafts keel drafts fit a law of form p h d oc exp ah 2 d h except for an excess of keels at drafts beyond 20 m there is a positive correlation between mean keel draft and keel frequency there are 3 5 4 5 keels per kilometre with draft exceeding 9 m in the offshore zone and 2 3 in the central arctic sail elevations fit a law of form p h d h x exp a h d h with a positive correlation between mean sail elevation and sail frequency the sail elevation and ice elevation distributions can be related by assuming that all thick ice is contained in pressure ridges of triangular cross section v keel sail comparison for the 21 corresponding 100 km sections there are positive correlations between mean sail height and mean keel draft and between keel frequency and sail frequency from these it is possible to convert a sail distribution computed from a laser profile into a keel distribution enabling sea ice bulk characteristics to be derived from airborne surveys alone vi leads and polynyas a lead was defined as a continuous sequence of depth points greater than 5 m long and not exceeding 1 m draft the number density n d of leads per kilometre of width d m fits the power law n d 15 d 2 exceptionally wide leads were concentrated in the offshore zone and in the marginal ice zone close to the open water of the greenland sea

estimating the annual cycle of sea ice thickness and volume in the ross sea antarctic sea ice thickness and concentration derived from satellite based ice charts are compared to contemporaneous ship based estimates of the same parameters collected in the ross sea between 130 w and 160 e from 1995 to 1998 thickness variability exists on the scale of individual ice chart polygons tens of kilometers but found compatible with wmo thickness ranges except in areas with high concentration of ridging very good agreement is found between the thickness distributions on the regional scale of the ross sea with an annual climatological average thickness of 0 65 m for the ice charts in comparison to 0 76 m for the ship based measurements given these analyses we proceed by examining resulting annual cycle and interannual sea ice thickness and volume estimates for the ross sea region resolved to weekly time intervals the weekly thickness estimates show the influence of thicker ice advected from the amundsen sea new ice produced adjacent to ross ice shelf and changes in the ross sea polynya the relationship between weekly ice extent and volume indicate a lag one to nine weeks of volume mass due to thickness processes during the growth season which differs from lateral extent in 1996 1998 while both extent and volume are more similar during the melt season the maximum extent and volume occur simultaneously in 1995 1997 but in 1998 the volume peak lags extent by almost 5 weeks moreover thickness variability is found to be more sensitive than extent to climate events during the 1996 la nina and 1997 98 el nino episodes we postulate therefore that ice thickening processes evolve somewhat independent of sea ice extent these results contradict some existing model studies which show that sea ice thickness and extent co vary hence the thickness estimates here demonstrate the importance of measured ice thickness which responds distinctly different from extent in response to dynamic and thermodynamic processes during the annual cycle

sea ice and oceanic processes on the ross sea continental shelf we have investigated the spatial and temporal variability of antarctic sea ice concentrations on the ross sea continental shelf in relation to oceanic and atmospheric forcing sea ice data were derived from nimbus 7 scanning multichannel microwave radiometer smmr brightness temperatures from 1979 1986 ice cover over the shelf was persistently lower than above the adjacent deep ocean averaging 86 during winter with little month to month or interannual variability the large spring ross sea polynya on the western shelf results in a longer period of summer insolation greater surface layer heat storage and later ice formation in that region the following autumn newly identified pennell and ross passage polynyas near the continental shelf break appear to be maintained in part by divergence above a submarine bank and by upwelling of warmer water near the slope front warmer subsurface water enters the shelf region year round and will retard ice growth and enhance heat flux to the atmosphere when entrained in the strong winter vertical circulation temperatures at 125 m depth on a mooring near the ross ice shelf during july 1984 averaged 0 15 c above freezing sufficient to support a vertical heat flux above 100 w m2 monthly average subsurface ocean temperatures along the ross ice shelf lag the air temperature cycle and begin to rise several weeks before spring ice breakout the coarse smmr resolution and dynamic ice shelf coastlines can compromise the use of microwave sea ice data near continental boundaries

trace element proxies for surface ocean conditions a synthesis of culture calibrations with planktic foraminifera abstract the trace element composition of planktic foraminiferal calcite provides a useful means of determining past surface ocean conditions we have assembled the results of culture experiments for three species of symbiont bearing planktic foraminifera globigerinoides ruber globigerinoides sacculifer and orbulina universa and one symbiont barren species globigerina bulloides to evaluate their responses to temperature salinity ph carbonate ion and dissolved inorganic carbon dic growth conditions trace element ratios li ca b ca mg ca sr ca mn ca cd ca ba ca na ca and u ca were measured simultaneously on samples grown with the same culture techniques which provides robust relatable calibrations that may be used together in multi proxy paleoceanographic studies our data confirm that temperature is the dominant control on foraminiferal mg ca under the ranges of conditions studied and that the potential effects of salinity and co32 on mg ca of these tropical species across late pleistocene glacial cycles are relatively small carbonate system experiments suggest that sr ca may be useful for reconstructing large dic changes na ca increases with salinity in g ruber pink but not in g sacculifer as these emerging proxy relationships become more firmly established the synthesis of multiple trace element ratios may help paleoceanographers isolate the effects of different environmental parameters in paleo records calcification rates g day vary among species and do not respond consistently to any experimental parameter comparison of our calcification rates with those observed in inorganic calcite precipitation experiments suggest that foraminifera calcify 100 more slowly than inorganic calcites grown in similar solutions we suggest that calcification rate does not typically exert a dominant control on trace element partitioning in planktic foraminiferal calcite though it may play a role for some elements under certain circumstances differences in average growth rate cannot explain composition differences among species pointing to alternative controls that may be biological in origin

cadmium zinc copper and barium in foraminifera tests the concentrations of cadmium zinc copper and barium have been determined on 2 mg samples of single species foraminifera populations cleaning techniques were tested using north atlantic core tops and followed by a detailed downcore study for the last 30 000 years in south atlantic core v22 174 raw foram tests cleaned by crushing followed by ultrasonic removal of fine grained material and dissolved in a ph 5 5 acetate buffer contain appreciable amounts of trace elements associated with ferromanganese and alumino silicate contaminants a reductive complexing cleaning treatment reduces ferromanganese contamination by 1 2 orders of magnitude acetate buffers at ph 5 5 complex iron and raise the solubility of ferromanganese oxides these buffers are unsuitable for separating carbonate lattice bound trace elements from the fraction associated with ferromanganese phases improved mechanical and ultrasonic reductive cleaning combined with a mild dissolution in distilled water under 1 atm pco2 reduces contaminant levels another order of magnitude the cd and zn concentrations order 10 8 mole cd mole ca and 10 5 mole zn mole ca of species with low surface area show an increase with decreasing isotopic temperatures this increase is consistent with the increasing concentrations of these metals from low values in surface waters to higher values at depth the variance of cd and zn over the last 30 000 years in the central south atlantic is consistent with the probable variability of the dissolved trace elements at the calcification levels of the species analyzed cu and ba are irreproducible and probably sensitive to residual contaminant phases the trace element content of the tests differs from levels observed in a recent coprecipitation study foraminifera may be a significant vector in zinc cycling in the ocean

isotopic composition and origin of lacustrine brines in the arctic meromictic lakes in the arctic archipelago were analyzed to determine whether the isotope content of the water molecule might confirm their oceanic origin the 25 m bottom layer of lake garrow on little cornwallis island is filled with a homogeneous sodium chloride solution with 2 6 times the chloride concentration of seawater 52 g l 1 its 18o value is around 10 with respect to v smow and its 2h is eight times the oxygen value 85 in lake sophia on cornwallis island the deep stratum 25 m thick is less concentrated 35 g l 1 cl 1 and shows slightly higher 18o and 2h values 9 and 75 respectively chemocline and surficial waters result from mixing between bottom waters and meteoric waters the chemical and isotopic signals are interpreted as evidence of diagenesis through subpermafrost or intrapermafrost freezing of aquifers once filled with seawater at some time during postglacial emergence

cd ca ratios of in situ collected planktonic foraminiferal tests 1 the cd ca ratios of planktonic foraminiferal tests have been used to reconstruct surface water nutrient utilization and paleoproductivity the reliability of this proxy has hitherto not been comprehensively studied however to fill this gap we present novel cd ca data for in situ sampled and sedimentary planktonic foraminifers of the species globigerinoides ruber g sacculifer globigerina bulloides orbulina universa and globorotalia truncatulinoides from the arabian sea and the north atlantic the cd ca ratios obtained for g ruber sampled from the live habitat generally display a correlation with seawater phosphate content but no such trend is observed for g sacculifer this distinct behavior may reflect different ecological niches or species specific incorporation of cd into the calcite shells of the organisms the cd ca ratios of g ruber g sacculifer and g bulloides from surface sediments are consistently higher than those obtained for live collected specimens of the same species postdepositional alteration of the tests is unlikely to be responsible for these systematic differences rather they appear to reflect a combination of factors including the formation of calcite crusts with high cd contents the different timescales that are represented by in situ and sedimentary foraminiferal tests and the dominance of tests from periods of high productivity in sediments our results also reveal higher cd ca ratios for live g ruber than for settling tests of the same species this suggests that planktonic foraminiferal shells are partially dissolved while they individually settle through the water column sedimentary tests however will be less affected by dissolution processes because these shells are primarily deposited in mass sinking events which feature much higher settling velocities than those experienced by single settling shells

the ice thickness distribution across the atlantic sector of the antarctic ocean in midwinter during the first leg of the winter weddell sea project antarktis v 2 cruise of f s polarstern the entire width of the antarctic sea ice zone was traversed in the vicinity of 0 longitude in the period july 18 to september 10 1986 ice thicknesses were measured by direct drilling and by helicopter profiling using an exstar 100 mhz impulse radar system in addition aerial photography of the ice cover was done from 100 to 2000 m altitude using a 70 mm aerial camera mounted in the helicopter the results of the point measurements drilling are reported in this paper together with an indication of how the radar and photography data will be used to extend them so as to yield area averaged ice thickness distributions it was found that the main ice type across the entire width of the ice cover was consolidated pancake ice occurring in vast floes this formed out of a 250 km wide band at the advancing ice edge which comprised a concentrated field of individual pancakes in a matrix of frazil ice preferred thicknesses of undeformed floes were 40 60 cm of ice covered with 5 15 cm of snow the individual pancakes attained almost all of this thickness before consolidation subsequent congelation growth was slow estimated at 0 4 cm d 1 the floes contained much small scale roughness on the upper and lower surfaces due to rafting of pancakes at the time of consolidation but pressure ridging was modest except in the far south a few very thick 8 11 m multiyear floes were observed embedded in the pack at latitudes beyond 66 s

morphology of sea ice pressure ridges in the northwestern weddell sea in winter altimeter during winter weddell outflow study with the german r v polarstern in 2006 an optimal cutoff height of 0 62 m derived from the best fits between the measured and theoretical ridge height and spacing distributions was first used to separate pressure ridges from other sea ice surface undulations it was found that the measured ridge height distribution was well modeled by a negative exponential function and the ridge spacing distribution by a lognormal function next based on the ridging intensity ri the ratio of mean ridge sail height to mean spacing all profiles were clustered into three regimes by an improved k means clustering algorithm ri 0 01 0 01 0 026 denoted as c1 c 2 and c3 respectively mean and standard deviation of sail height was 0 99 0 07 m in regime c1 1 12 0 06 m in c2 and 1 17 0 04 m in c3 respectively while the mean spacings and standard deviations were 232 240 m 54 20 m and 31 5 6 m these three ice regimes coincided closely with distinct sea ice regions identified in a satellite radar image where c1 corresponded to the broken ice in the marginal ice zone and level ice formed in the larsen polynya c2 corresponded to the deformed first and second year ice formed by dynamic action in the center of the study region and c3 corresponded to heavily deformed ice in the outflowing branch of the weddell gyre the results of our analysis showed that the relationship between the mean ridge height and frequency was well modeled by a logarithmic function with a correlation coefficient of 0 8 although such correlation was weaker when considering each regime individually the measured ridge height and frequency were both greater than those reported by others for the ross sea compared with reported values for other parts of the antarctic the present ridge heights were greater but the ridge frequencies and ridging intensities were smaller than the most extreme of them meanwhile average thickness of ridged ice in our study region was significantly larger than that of the coastal ross sea showing the importance of deformation and ice age for ice conditions in the northwestern weddell sea

a three dimensional model of wave attenuation in the marginal ice zone 1 a three dimensional model of wave scattering by a large array of floating thin elastic plates is used to predict the rate of ocean wave attenuation in the marginal ice zone in terms of the properties of the ice cover and the incoming wavefield this is regarded as a small step toward assimilating interactions of ocean waves with areas of sea ice into oceanic general circulation models numerical results confirm previous findings that attenuation is predominantly affected by wave period and by the average thickness of the ice cover it is found that the shape and distribution of the floes and the inclusion of an archimedean draft has little impact on the attenuation produced the model demonstrates a linear relationship between ice cover concentration and attenuation an additional study is conducted into the directional evolvement of the wavefield where collimation and spreading can both occur depending on the physical circumstances finally the attenuation predicted by the new three dimensional model is compared with an existing two dimensional model and with two sets of experimental data with the latter producing convincing agreement

wave variance partitioning in the trough of a barred beach the wave induced velocity field in the nearshore is composed of contributions from incident wind waves f 0 05 hz surface infragravity waves f 2 g where fis the frequency 2 f c is the radial alongshore wavenumber 2re l l being the alongshore wavelength is the beach slope and g is the acceleration due to gravity using an alongshore array of current meters located in the trough of a nearshore bar mean depth 1 5 m we investigate the bulk statistical behaviors of these wave bands over a wide range of incident wave conditions the behavior of each contributing wave type is parameterized in terms of commonly measured or easily predicted variables describing the beach profile wind waves and current field over the 10 day period the mean contributions to the total variance of the incident infragravity and shear wave bands were 71 5 14 3 and 13 6 for the alongshore component of flow mean rms oscillations of 44 20 and 19 cm s 1 respectively and 81 9 10 9 and 6 6 for the cross shore component mean rms oscillations of 92 32 and 25 cm s 1 respectively however the values varied considerably the contribution to the alongshore cross shore component of flow ranged from 44 888 4 58 5 95 8 for the incident band to 6 2 26 6 2 5 32 4 for the infragravity band and 3 433 1 0 6 14 3 for the shear wave band incident wave oscillations were limited by depth dependent saturation over the adjacent bar crest and varied only with the fide the infragravity wave rms oscillations on this barred beach are best parameterized by the offshore wave height consistent with previous studies on planar beaches comparison with data from four other beaches of widely differing geometries shows the shoreline infragravity amplitude to be a near constant ratio of the offshore wave height the magnitude of the ratio is found to be dependent on the iribarren number 0 h lo 1 2 shear waves are as previous observation and theory suggest oltman shay et al 1989 bowen and holman 1989 significantly correlated with a prediction of the seaward facing shear of the longshore current

the thickness distribution of sea ice and snow cover during late winter in the bellingshausen and amundsen seas antarctica data collected from a voyage of rv nathaniel b palmer to the bellingshausen and amundsen seas during august september 1993 are used to investigate the thickness distribution of sea ice and snow cover and the processes that influence the development of the first year pack ice the data are a combination of in situ and ship based measurements and show that the process of floe thickening is highly dependent on ice deformation in particular rafting and ridging play important roles at different stages of floe development rafting is the major mechanism in the early stages of development and core structure data show the mean thickness of individual layers of crystals to be only 0 12 m most ice 0 6 m having some surface deformation blocks within ridge sails are typically in the range 0 3 0 6 m thick and ship based observations estimate approximately 25 of the pack exhibits surface ridging when corrected for biases in the observational methods the data show that the dominant ice and snow thickness categories are 0 7 m and 0 2 0 5 m respectively and account for 40 and 36 of the surface area of the pack ice approximately 8 of the pack is open water an estimate of the effects of ridging on the distribution of ice mass within the pack suggests that between 50 and 75 of the total mass is contained within the 25 of the pack that exhibits surface ridging

physical characteristics of summer sea ice across the arctic ocean sea ice characteristics were investigated during july and august on the 1994 transect across the arctic ocean properties examined from ice cores included salinity temperature and ice structure salinities measured near zero at the surface increasing to 3 4 at the ice water interface ice crystal texture was dominated by columnar ice comprising 90 of the ice sampled surface albedos of various ice types measured with radiometers showed integrated shortwave albedos of 0 1 to 0 3 for melt ponds 0 5 for bare discolored ice and 0 6 to 0 8 for a deteriorated surface or snow covered ice aerial photography was utilized to document the distribution of open melt ponds which decreased from 12 coverage of the ice surface in late july at 76 n to almost none in mid august at 88 n most melt ponds were shallow and depth bore no relationship to size sediment was pervasive from the southern chukchi sea to the north pole occurring in bands or patches it was absent in the eurasian arctic where it had been observed on earlier expeditions calculations of reverse trajectories of the sediment bearing floes suggest that the southernmost sediment was entrained during ice formation in the beaufort sea while more northerly samples probably originated in the east siberian sea some as far west as the new siberian islands

longshore current and wave height modulation at tidal frequency inside the surf zone data were acquired continuously during the 19 day delilah nearshore experiment with a specific objective of examining variability of the longshore current at tidal frequencies it is hypothesized that breaking wave heights inside the surf zone are strong functions of the depth which are modulated by the tidal variations and since radiation stress is a function of the wave height longshore currents are forced at the tidal frequency inside the surf zone the measured longshore current variations at tidal frequency are the same order of magnitude as the mean longshore current variations for moderate wave height conditions indicating that the tide is a dominant mechanism associated with longshore current variability simulations of the magnitude and phase of the longshore current variability with tide elevation using the model by thornton and guza 1986 are used to explain observations the measured tidal elevation and longshore current are in phase in the inner surf zone and out of phase in the outer surf zone as predicted by the model verifying the hypothesis

ice properties in the greenland and barents seas during summer resultats d analyse de carotte de glace de mer dans l arctique europeen les proprietes de la glace sont mises en rapport avec les conditions generales de la distribution de glace leur epaisseur et leur relief dans la zone exploree interpretation de la salinite sur les glaces de premiere annee et pluri annuelles

bar generating cross shore flow mechanisms on a beach random waves normally incident on a dissipative beach induce a variety of cross shore flows such as asymmetric oscillatory flow wave grouping induced long wave flow breaking induced turbulent flow and momentum decay induced undertow these flows are identified analyzed and hindcasted in a set of laboratory experiments with the aim of revealing the role of each of the flow mechanisms in the two dimensional case of bar generation on a beach

experimental determination of trace element partition coefficients in cultured benthic foraminifera abstract we present the first trace metal partition coefficients obtained from reproducing cultures of deep sea benthic foraminifera paleoceanographically important species including juvenile bulimina marginata cibicidoides pachyderma and uvigerina peregrina were maintained in sediment microcosms at 10 c 35 psu and ph 8 for 1 3 years juvenile foraminifera were separated cleaned and dissolved under clean conditions for determination of trace metal partition coefficients on recently deposited 1 3 months foraminiferal calcite in addition to the deep sea species we analyzed a shallow water benthic foraminifer ammonia beccarii overlying water samples were collected from the microcosms concurrent to the period of calcification 3 months prior to separation ba ca partition coefficients d ba were measured in replicate for benthic foraminifera species bulimina marginata 0 24 0 07 uvigerina peregrina 0 24 0 06 ammonia beccarii 0 20 0 04 the d ba for bulimina marginata and uvigerina peregrina were found to closely match the range from the ontong java plateau sample size limitations allowed for only one analysis of d ba for cibicidoides pachyderma however our nonreplicated d ba of 0 5 0 1 falls within the accepted range of core top samples 0 37 0 06 we report a d cd for ammonia of 1 0 0 5 for cibicidoides of 4 2 for bulimina of 3 1 and for uvigerina 2 1 which all fall within the ranges reported for core top calibrations the large uncertainties in d cd reflect variation in dissolved cd concentration in the artificial seawater reservoir due to loss and replacement of cd during the course of the experiment the variability between species is probably the result of variability in pore water cd in the sediment culture system and may reflect habitat effects

late pleistocene nutrients and sea surface productivity in the south china sea a record of teleconnections with northern hemisphere events surface nutrient variations during the last 200 000 years have been reconstructed based on the cd ca ratios in the tests of planktonic foraminifera neogloboquadrina dutertrei and the biogenic opal content from two gravity cores retrieved from the northern and northwestern parts of the south china sea scs the cd ca ratios obtained from n dutertrei in recent sediments from fourteen box cores distributed over the scs basin reflect present nutrient levels in the overlying surface waters areas with relatively high cd ca values in the surface sediments are in the region of high chlorophyll a in the northern south china sea near the dongsha islands consistent with previous observation high values of cd ca found in sediments east of vietnam and east of the nansha islands may be a result of increased nutrients due to local upwelling induced by the summer monsoon core 17940 2 raised from the northern continental slope of the scs exhibits exceptional high sedimentation rates 25 85 cm kyr for the last 35 kyr the cd ca ratios in this core are relatively higher during the periods of late d 18 o stage 3 and the mid holocene core 17950 2 with an average sedimentation rate of 5 cm kyr offers a continuous long record back to d 18 o stage 7 in general cd ca values in the downcore records are higher during interglacials and progressively increase as the interglacials proceed values peak around the times of optimum climate conditions and correlate with periods of increased opal wt correlations in the interval of overlap between the two records support the interpretation that variations in cd ca ratios in core 17940 2 are not an individual signal but can be replicated of special interest in this study is the tentative correlation between cd ca peaks in the scs record and the timing of iceberg discharge events heinrich events in the north atlantic mass accumulation rate mar of opal data from core 17950 2 indicate high surface productivity during glacial intervals corresponding to oxygen isotope stages 6 4 and 2 the increase in surface productivity during glacials from the northern scs is contemporaneous with an intensified winter monsoon as recorded by the terrestrial loess deposits the agreement with wind strength recorded in the loess plateau from mainland china supports the

surf zone longshore currents and random waves field data and models abstract analytic and numerical models for longshore currents generated by obliquely incident random waves am compared with field observations five days of observations were selected during which the waves were narrow banded in both frequency and direction in keeping with model assumptions the extensive measurements included radiation stress and wave directional spectra in 9 m depth and a closely spaced array of current and pressure sensors on a line perpendicular to shore the longshore current models are based on balancing the gradient of the radiation stress with the alongshore bed shear and reynold s stresses assuming stationary wave conditions and straight and parallel bottom contours the spatial variation of wave height required to determine the gradient of the radiation stress is modeled using linear random wave theory given hrms in 9 m depth the model predicts hrms at shoreward locations with an average error of less than 9 using a nonlinear bottom shear stress formulation and the meas

li sr mg and na in foraminiferal calcite shells from laboratory culture sediment traps and sediment cores abstract constant temperature laboratory culture experiments of the planktonic foraminiferal species globigerinoides sacculifer brady suggest that the ratios of li and sr to ca in the shells are a function of these ratios in the culture solutions mg ca and na ca in the shells did not vary with changes of these ratios in the culture solution these are the first direct determinations of the relationship between foraminiferal shell chemistry and solution composition the possibility of temperature dependence for the minor elemental composition of foraminiferal shells was also investigated in the laboratory and by analysis of several planktonic and one benthic foraminiferal species from sediment trap and sediment core samples the sr ca mg ca and na ca ratios in the natural samples roughly correlate with calcification temperature whereas differences in the li ca ratios are small and not systematically related to temperature however laboratory culture experiments at 20 c and 30 c showed no variation in the li ca sr ca mg ca and na ca ratios with calcification temperature for the planktonic foraminifera g sacculifer and orbulina universa therefore observed differences in the sr ca mg ca and na ca ratios for the sediment trap and core foraminiferal samples cannot be ascribed to direct effects of calcification temperature but may be due to some other environmental factor which is correlated with temperature

longshore current on a barred beach field measurements and calculation measurements of the longshore current on a barred beach made during the 1990 duck experiment on low frequency and incident band longshore and across shore hydrodynamics delilah field data collection project conducted at duck north carolina revealed an unexpected and persistent broad peak in the current velocity in the trough between the nearshore bar and the shore this paper introduces longshore current and associated wave measurements from delilah together with a numerical model capable of describing the field observations an existing numerical model of the mean current is modified to include a general transport equation for the mean turbulent kinetic energy created by wave breaking and reynolds stress components needed to calculate the longshore current and mean water level are reexpressed to include the turbulent momentum transport in comparison to predictions from the original model the modified model produces much improved agreement with the measured current velocity on the barred profiles in the field measurements and with the velocity profile and mean water level generated on a uniformly sloping laboratory beach by monochromatic waves three forms of a bottom friction coefficient are examined and the open channel flow manning friction coefficient is selected because of best agreement and consistency values of the manning friction coefficient required to calibrate the model agree with values normally assigned to the related bottom roughness in open channel flow

thickness structure and properties of level summer multiyear ice in the eurasian sector of the arctic ocean in august and september 1991 thickness structure and properties of level multiyear ice were studied at 66 locations in the eurasian sector of the arctic ocean the mean ice thickness was 2 86 m with 0 31 m of freeboard including 0 08 m deteriorated ice of mean density 370 kg m 3 on the basis of the study of ice cores 61 of the ice cover consisted of undeformed columnar ice the remaining 39 consisted of a mixture of ice types including frazil 18 and deformed ice 9 through microstructural studies six main classes of pores could be identified the mean density of the ice cover increased from 720 kg m 3 at the top to 880 kg m 3 below 0 4 m depth sea ice salinities mean value 2 1 correlate with ice thickness on average salinity profiles exhibit a linear increase from values close to 0 at the top to 2 at 1 m depth with less steep salinity gradients below sampling from different depths within the ice cover indicates that the brine in summer sea ice is strongly stratified the influence of meltwater percolation is evident with salinities around 5 and ph values 15 and 8 at greater depths brine volumes ranging from 80 to 150 are controlled by the thermodynamic equilibrium between the solid and liquid phases gas volumes decrease from 200 at the top to 50 below 1 m depth pore microstructure is highly variable even on small scales salinity and other ice properties do not vary to a large degree between different regions the evolution of level multiyear sea ice is discussed with particular reference to hidden occurrence of deformed ice and the importance of ablation processes

physical properties of summer sea ice in the fram strait the physical properties of sea ice in the fram strait region of the greenland sea were examined during june and july 1984 in conjunction with the marginal ice zone experiment field program most of the ice sampled within fram strait during this period was multiyear thicknesses and other properties indicated that none of the multiyear ice was older than 4 to 5 years snow cover on the multiyear ice averaged 29 cm while that on first year ice averaged only 8 cm deep this difference may be related to enhanced sublimation of the snow on the thinner first year ice the salinity profiles of first year ice clearly show the effects of ongoing brine drainage in that profiles from cores drilled later in the experiment are substantially less saline than earlier cores thin section examinations of crystal structure indicate that about 75 of the ice consisted of congelation ice with typically columnar type crystal structure the remaining 25 consisted of granular ice with only a few occurrences of snow ice the granular ice consisted primarily of frazil found in small amounts at the top of floes but mainly observed in multiyear ridges the horizontally oriented crystal c axes showed various degrees of alignment ranging from no alignment to strong alignments in which the alignment direction changed with depth implying a change in floe orientation with respect to the ocean current at the ice water interface during ice growth evidence of crystal retexturing was observed in the upper meter of nearly every multiyear core this retexturing consisting of grain boundary smoothing and nearly complete obliteration of the ice platelet brine layer substructure is attributed to summer warming

bar trapped edge waves and longshore currents edge waves react to the presence of a mean longshore current as though the current was a change in bottom topography in this way the cross shore shape of the edge wave can be amplified over the current relative to the shoreline in the same way as the edge wave shape can be amplified over bars on a beach with both longshore currents and bars the degree of edge wave amplification or trapping depends on the strength and location of the longshore current shear relative to the steepness of the bottom slope and also on the direction of edge wave propagation relative to the longshore current weak longshore current shear over well developed bars does not significantly alter edge wave trapping over bars simply enhancing or reducing the existing bar trapping effect conversely strong current shears over gentle topography can govern the existence and location of edge wave trapping the extreme example being edge wave trapping on plane beaches where the amplification is entirely due to the existence of mean longshore currents in reality the possibilities are restricted since the shape of the longshore current profile is primarily determined by the pattern of incident wave breaking which itself depends on the beach profile the importance of realistic current shear relative to realistic bottom slope in determining edge wave shape is demonstrated using frequency wavenumber spectra taken during the duck experiment on low frequency and incident band longshore and across shore hydrodynamics delilah at duck north carolina these frequency wavenumber spectra show a general dominance of edge waves traveling with the longshore current in cases where the current shear is strong relative to the bottom slope the location of edge wave trapping changes as the longshore current profile changes with the tide when the bar was well defined the longshore current shear was rarely strong enough to influence the existence or location of edge wave trapping but could have a enhancing effect while past work i e schonfeldt 1995 has suggested that edge waves trapped and amplified on longshore currents may cause bars to form on plane beaches and bars to move on barred beaches these observations suggest that under most conditions edge wave trapping on longshore currents is a subtle effect modulated by sea level changes and is unlikely to produce significant morphological change unless the current is very strong

modification of edge waves by barred beach topography a numerical model to calculate edge wave profiles and wavelengths for arbitrary bottom profiles and given frequency was developed utilizing the model wave equation of berkhoff 1972 following smith and sprinks 1975 surface profiles and longshore wave numbers were found for fixed wave periods using an eigenvalue approach the model was verified by calculating profiles and dispersion for a plane beach of mild slope and comparing results with the analytic solution of eckart 1951 and ursell 1952 the model was then applied to the case of a beach with multiple offshore bars with bar positions determined by the antinodal positions of a standing incident wave of a set frequency calculation of surface profiles for a range of frequencies using a fixed beach indicated that antinodes of the edgewave profiles tend to be trapped by the bars suggesting the possibility that bars affect the long wave climate in such a way as to lead to self maintenance over extended periods no effect of the bars on the dispersion relationship was found and it was concluded that for the particular beach profile used the edge waves respond to the mean beach slope over the offshore length of the profile

laser profiling of the ice surface topography during the winter weddell gyre study 1992 a laser profiler mounted on a helicopter was used to measure the surface topography of sea ice in the weddell sea the measurements were carried out during the cruise antarktis x 4 of r v polarstern as part of the winter weddell gyre study 1992 wwgs 92 the total length of the measured surface profiles amounts to 793 km the observed mean ridge heights and mean ridge spacings are fairly well correlated therefore the ridging intensity r1 which is the ratio of ridge height and spacing was used as a quantitative classifier in order to arrange the laser data into different groups at a cutoff height of 0 8 m the average ridge height and spacing are 1 16 m and 160 m at the lowermost range of ridging intensities r1 0 04 respectively the best fits to the observed ridge height distributions are achieved by negative exponentials at lower ridging intensities as a function of ridge height at the regime of highest ridging intensity as a function of the ridge height squared the distributions of ridge spacing are well described by a lognormal distribution function a simple model is used to estimate the average thickness hd and the areal fraction of ridged ice from the laser data the values of hd range from 3 1m with an areal coverage of 5 at the lowermost range of r1 to 3 7 m with an areal coverage of 31 at the uppermost range if the ridged ice is distributed as a uniform layer over a unit area the corresponding effective thickness values are 0 14 m and 1 16 m respectively mean ridge heights and spacings are determined for different cutoff heights in order to enable comparisons to other measurements the effect of ridges on the surface stress over the ice is estimated using the drag partition theory which is applicable to the regime of lowest ridging intensity the contribution of ice ridge form drag to the total wind drag for an average ridging intensity of 0 007 and a cutoff height of 0 8 m is about 35 to 40 at neutral stability if it is assumed that the aerodynamic roughness length z0 of the intervening ice surface varies between 3 3 10 4 m and 5 5 10 4 m the drag coefficient cdn ranges from 2 08 10 3 to 2 24 10 3 at a reference height of 10 m

miocene benthic foraminiferal cd ca records south atlantic and western equatorial pacific cadmium to calcium records in benthic foraminifera interpreted in conjunction with carbon isotope records reflect oceanic circulation patterns and oceanic inventories of cd carbon 13 carbon 12 and indirectly phosphorus cd ca ratios have been determined in benthic foraminifera cibicidoides spp for the late middle and early miocene from a site in the south atlantic deep sea drilling project dsdp site 525 leg 74 2500 m walvis ridge and from a site in the western equatorial pacific dsdp site 289 leg 30 2200 m ontong java plateau both sites have well established carbon isotope records for benthic foraminifera typical of the global record dominated by inventory changes cd ca ratios and carbon isotope values were averaged for the miocene in time intervals substantially longer than estimated oceanic residence times of cd c or p oceanic mean cd ca and carbon isotopes were estimated as weighted means of the values from both sites using weighting factors based on replicating modern oceanic means this may tend to underestimate oceanic inventories earlier than the late miocene because of changing water mass dominance at the south atlantic site from these means the oceanic cd inventory appears relatively stable during the miocene while there are large changes in carbon isotope inventories miocene cd inventory estimates are at least 20 lower than published estimates for quaternary stages 1 and 2 increasing oceanic cd inventories over the past 10 m y are consistent with hypotheses of increased river fluxes in the recent geologic past cd ca differences between sites may be indicative of the extent of basin basin fractionation from bottom water circulation although the validity of this comparison depends on how representative each of these two sites is through time for its respective ocean basin the pacific atlantic cd ca difference based on these two sites was larger in the late miocene compared to the middle and early miocene the relationship between cd ca and carbon isotope inventories and intersite gradients for these sites suggests that either oceanic phosphorus inventories or parameters related to marine organic matter composition must have been different in the miocene than at present large changes in the carbon isotope balance reflected as both positive and negative excursions in the carbon isotope inventories occurred with little effect on cd inventories changes in phosphorus fluxes associated with these carbon isotope flux changes may have been compensated for by changing deposition fluxes to other phosphorus sinks phosphorus inventories may have increased from the middle to late miocene with increasingly negative oceanic carbon isotope inventories however confirmation of these suggestions depend on collecting more cd ca and 13c data throughout the miocene oceans and on developing the application of other constraints for these interpretations

thick and deformed antarctic sea ice mapped with autonomous underwater vehicles satellites have documented trends in antarctic sea ice extent and its variability for decades but estimating sea ice thickness in the antarctic from remote sensing data remains challenging in situ observations needed for validation of remote sensing data and sea ice models are limited most have been restricted to a few point measurements on selected ice floes or to visual shipboard estimates here we present three dimensional 3d floe scale maps of sea ice draft for ten floes compiled from two springtime expeditions by an autonomous underwater vehicle to the near coastal regions of the weddell bellingshausen and wilkes land sectors of antarctica mean drafts range from 1 4 to 5 5 m with maxima up to 16 m we also find that on average 76 of the ice volume is deformed ice our surveys indicate that the floes are much thicker and more deformed than reported by most drilling and ship based measurements of antarctic sea ice we suggest that thick ice in the near coastal and interior pack may be under represented in existing in situ assessments of antarctic sea ice and hence on average antarctic sea ice may be thicker than previously thought

silicate weathering and carbon cycle controls on the oligocene miocene transition glaciation changes in both silicate weathering rates and organic carbon burial have been proposed as drivers of the transient mi 1 glaciation event at the oligocene miocene transition omt 23 ma however detailed geochemical proxy data are required to test these hypotheses here we present records of li ca mg ca cd ca u ca 18o 13c and shell weight in planktonic foraminifera from marine sediments spanning the omt in the equatorial atlantic ocean li ca values increase by 1 mol mol across this interval we interpret this to indicate a 20 increase in silicate weathering rates which would have lowered atmospheric co2 potentially forcing the antarctic glaciation circa 23 ma 13c of thermocline dwelling planktonic foraminifera track the global increase in seawater 13c across the omt and during the mi 1 event hence supporting a hypothesized global increase in organic carbon burial rates high 13c previously measured in epipelagic planktonic foraminifera and high cd ca ratios during mi 1 are interpreted to represent locally enhanced primary productivity stimulated by increased nutrients supply to surface waters the fingerprint of high export production and associated organic carbon burial at this site is found in reduced bottom water oxygenation inferred from high foraminiferal u ca and enhanced respiratory dissolution of carbonates characterised by reduced foraminiferal shell weight replication of our results elsewhere would strengthen the case that weathering induced co2 sequestration preconditioned climate for antarctic ice sheet growth across the omt and increased burial of organic carbon acted as a feedback that intensified cooling at this time

numerical modeling of infragravity wave response during delilah 1 the nearshore circulation model shorecirc is applied to simulate the infragravity wave conditions at two intervals during the 1990 delilah campaign at duck n c the model has been extended to solve the energy equation for random short waves on the timescale of the wave groups which acts as a wave driver for the long wave model to simulate the wave conditions an algorithm has been derived which synthesizes a directional offshore wavefield from measured data including the bound directional low frequency components the model data comparison shows that the mean short wave transformation and mean longshore current are predicted well the structure of the infragravity spectrum as measured in the nearshore array is correctly represented albeit that the energy levels are underpredicted in most locations the 2 d frequency longshore wavenumber spectra show that the infragravity wave energy consists mostly of edge waves and that the computations qualitatively resemble the measurements it is shown that for 1 day bar trapped edge waves are present the model is also used to show that the influence of the longshore variability is small for this particular beach and that the directional spreading in the offshore wave field is critical in predicting the nearshore infragravity wave conditions correctly edge waves which propagate against the current are generated by the directionally broad short wave forcing and to a lesser extent by back scattering the nonlinear terms are relatively unimportant for the prediction of the infragravity wave climate the cross shore gradient of the onshore directed radiation stress is the most important of the forcing terms

salinity profiles of antarctic sea ice field data and model results in order to describe and compare sea ice salinity distributions which are of interest in the study of physical and biological ice characteristics as well as ice ocean interaction we have computed composite profiles and fitted third degree polynomials to salinity data of 129 cores from the weddell sea four characteristic profile shapes have been recognized and described through the polynomial coefficients c s i and type profiles the field data have been compared with ideal salinity profiles generated by a simulation scheme based on thermodynamic growth under climatological conditions representative of the weddell sea composite salinity profiles agree well with simulations irrespective of the growth mechanism i e frazil or congelation suggesting that ice properties which depend on salinity or porosity may evolve independent of ice growth conditions analysis of salinity and 18o data in conjunction with the simulations demonstrates that apart from meteorological conditions controlling growth velocity and temperature distribution within the ice flooding and upward brine expulsion are important in raising top salinities as frequently observed low top salinities are typical of ice that has undergone retexturing and differential desalination salinity decreases towards the bottom of a floe are a result of high oceanic heat fluxes and snow cover effects as a consequence of these processes the bulk salinity of weddell sea ice cannot be described by a simple linear age thickness relationship as characteristic of arctic first year ice

planktonic foraminiferal cd ca paleonutrients or paleotemperature records of cd ca in planktonic foraminiferal calcite of globigerinoides bulloides in cores from the subantarctic region of the southern ocean show large glacial interglacial variations with lower cd ca by 0 06 0 10 mol mol 1 at glacial times interpretation of these records in terms of lower dissolved phosphate and inferred higher glacial nutrient utilization has significant implications for glacial atmospheric carbon dioxide pco2 draw down however box core top data for g bulloides in the north atlantic suggest that the incorporation of cd into planktonic foraminifera relative to seawater dcd is temperature sensitive dcd 0 637 exp 0 15t when the subantarctic planktonic cd ca records are corrected for this temperature dependence they show little or no glacial interglacial diferences if as seems likely this observation can be interpreted to indicate a minimal change 0 5 mol kg 1 in surface water phosphate concentrations then the explanation for lowered glacial pco2 must be looked for elsewhere