mesoscale oceanographic processes beneath the ice of fram strait a major component of the fram strait marginal ice zone experiment was the investigation of air sea ice interactions processes and circulation patterns found behind the local ice edge and on scales greater than 10 kilometers mesoscale and large scale neutrally buoyant floats ice tethered cyclesondes and helicopter based measurements were used to obtain uniquely integrated and consistent views of the mesoscale ocean features beneath the ice cover of fram strait within the vicinity of the yermak plateau three distinct regions of mesoscale motion were observed that coincided with the shallow topography of the plateau the northward flowing atlantic water over the western flank of the plateau and the strong current shear zone of the east greenland polar front a subice meander of the front was also observed which was probably occluded subsequently

an inverse modeling study in fram strait part i dynamics and circulation abstract in order to reconstruct the circulation in the northern greenland sea between 77 n and 81 n and the exchanges with the arctic ocean through fram strait a variational inverse model is applied to the density field observed in summer 1984 during the mizex 84 experiment an estimate of the three dimensional large scale pressure field is obtained in which the solution is decomposed into a limited number of vertical modes and the mode amplitudes are described by piece wise polynomials on a finite element grid the solution should be consistent with a frictional depth integrated vorticity balance and with the density data the global model parameters are tuned to ensure agreement between the retrieved geostrophic velocity and independent currentmeter data in a companion paper schlichtholz and houssais 1999b the same method but without dynamical constraint is applied to the same hydrographic dataset to perform a detailed water mass analysis and to estimate individual water mass transports a comprehensive picture of the summer geostrophic circulation in fram strait is obtained in which northward recirculations in the east greenland current egc and various recirculations from the west spitsbergen current wsc to the egc are identified it is suggested that the branch of the wsc following the upper western slope of the yermak plateau turns westward beyond 81 n and recirculates southward along the lower slope then merging with a westward recirculating branch south of 79 n at 79 n a southward net transport of 6 5 sv is found in the egc which combined with a northward net transport of only 1 5 sv in the wsc results in a fairly large outflow of 5 sv from the arctic ocean to the greenland sea the inverse solutions show that in summer the local induction of vorticity by the wind stress curl or by meridional advection of planetary vorticity should be small so that in the egc and in the wsc the vorticity balance is mainly achieved between the bottom pressure torque and dissipation of vorticity through bottom friction a substantial barotropic flow associated with along slope potential energy gradients is indeed identified on both sides of the strait

development and demise of a fringing coral reef during holocene environmental change eastern ningaloo reef western australia abstract reefs lining the western exmouth gulf located at the northern limit of the 300 km long ningaloo reef in western australia represent modern incipient coral reefs and veneers of non reef building coral algal communities on exposed pleistocene or give up holocene reef surfaces acquisition of sixteen cores alongside u series tims dates were used to confirm the nature of the pleistocene foundation and characterise holocene reef development three calcretised pleistocene units were identified as 1 the last interglacial mis 5e reef directly underlying holocene units 2 a mid pleistocene mis 7 bioclastic conglomerate unit and 3 a pleistocene alluvial fanglomerate eight holocene reef facies total thickness of 1 8 5 3 m included coral framework facies domal arborescent mixed tabulate and encrusting and detrital facies carbonate sand skeletal rubble and alluvial fan deposits holocene ages range from 7 93 to 5 8 ka bp with vertical accretion ranging from 1 46 to 9 88 mm year avg 4 11 mm year highest rates of accretion and thickest accumulation occurred in the most seaward and deepest cores composed of massive coral framestone and coralline algal crusts a six stage holocene chronology is proposed including 1 coastal inundation from 8 to 8 5 ka bp 2 initiation start up from 8 to 7 5 ka bp 3 rapid growth catch up and back step from 7 5 to 7 ka bp 4 rapid aggradational growth catch up from 7 to 6 5 ka bp 5 reef decline give up and detrital buildup from 6 5 to 5 8 ka bp and 6 detrital buildup and progradation from 5 8 ka bp to present changes in reef facies and the ultimate demise of the holocene reef probably involved a combination of increased sea level coastal flooding and erosion during the mid holocene highstand with associated increase in sedimentation turbidity and decline in water quality burial by sediment buildup during the mid holocene highstand and detrital progradation during the mid to late holocene regression and the introduction of alluvial sediment during cyclones and other severe storms to an already stressed community modern communities have thus shifted from coral dominated to bored macroalgal pavements this study shows that integration of reef development processes with response to environmental change can be used to assess future pressures on coral reef ecosystems globally

facies outcrop gamma ray and c o isotopic signature of exposed miocene subtropical continental shelf carbonates north west cape western australia abstract exposed uplifted miocene carbonate sequences of the cape range north west cape western australia provide outcrop analogues of seismic sequences from offshore parts of the shelf facies include deep shelf marls very fine and fine packstone larger foram wackestone floatstone and muddy rudstone foram coralline algal skeletal fragment packstone wackestone shallow seagrass facies lagoonal wackestone mudstone with scattered corals and tidal flat laminites the exposed early miocene units include the mandu highstand a sequence in the tulki and one in the middle miocene trealla limestone sequences contain decameter scale 5 20 m thick 4th order parasequences evident on gamma ray logs and by facies stacking that shallow and coarsen up they appear to be due to eccentricity driven sea level changes which may have been up to 50 m higher frequency meter scale parasequences of deep water marl up into larger foram rudstone floatstone perhaps precession obliquity are evident at the base of the exposed mandu section these parasequences are not merely random storm deposits this is indicated by the covariance of c and o isotopes with the lighter values associated with deepening and deposition of deep shelf marls and the heavier values being associated with shallowing and deposition of larger foram facies the uplifted miocene continental shelf sediments of the north west cape preserve a record of eustasy paleoclimate and paleoceanography and thus provide a window into factors affecting the shelf that can be compared with coeval better studied deep sea cores

variability in the greenland sea as revealed by a repeated high spatial resolution conductivity temperature depth survey this paper deals with the mesoscale variability of water masses in the greenland sea and its implications for bottom water formation the results are based on two conductivity temperature depth surveys performed in successive years the same section in the central greenland basin was sampled in 1989 and 1990 an additional transect across fram strait was carried out in 1990 the transects extended from shelf to shelf with a station spacing of 18 km throughout the data set reveals a surprisingly strong horizontal variability of space scales between 20 and 60 km in the entire greenland sea not only in the frontal zones the area investigated is subdivided into four hydrographical regimes for which mesoscale variability is discussed in detail a noteworthy result is the major change of the deep sea thermal structure within 1 year the classical pattern with upward doming cold waters in the central basin was found in 1989 but was replaced by a capped structure with a warm intermediate layer in 1990 the implications of the observed changes are discussed with respect to deep water formation a mechanism based on differential compressibility is proposed which is able to introduce negative heat input selectively into the bottom layer it is shown that the fine structure of temperature profiles observed in summer can be used as a tracer for the occurrence of deep convection during the preceding winter convective depths are concluded of about 2200 m for 1989 and of only about 250 m for 1990

evidence for ocean acidification in the great barrier reef of australia geochemical records preserved in the long lived carbonate skeleton of corals provide one of the few means to reconstruct changes in seawater ph since the commencement of the industrial era this information is important in not only determining the response of the surface oceans to ocean acidification from enhanced uptake of co2 but also to better understand the effects of ocean acidification on carbonate secreting organisms such as corals whose ability to calcify is highly ph dependent here we report an 200 year d 11 b isotopic record extracted from a long lived porites coral from the central great barrier reef of australia this record covering the period from 1800 to 2004 was sampled at yearly increments from 1940 to the present and 5 year increments prior to 1940 the d 11 b isotopic compositions reflect variations in seawater ph and the d 13 c changes in the carbon composition of surface water due to fossil fuel burning over this period in addition complementary ba ca d 18 o and mg ca data was obtained providing proxies for terrestrial runoff salinity and temperature changes over the past 200 years in this region positive thermal ionization mass spectrometry ptims method was utilized in order to enable the highest precision and most accurate measurements of d 11 b values the internal precision and reproducibility for d 11 b of our measurements are better than 0 2 2r which translates to a precision of better than 0 02 ph units our results indicate that the long term pre industrial variation of seawater ph in this region is partially related to the decadal interdecadal variability of atmospheric and oceanic anomalies in the pacific in the periods around 1940 and 1998 there are also rapid oscillations in d 11 b compositions equivalent changes in ph of almost 0 5 u the 1998 oscillation is co incident with a major coral bleaching event indicating the sensitivity of skeletal d 11 b compositions to loss of zooxanthellate symbionts importantly from the 1940s to the present day there is a general overall trend of ocean acidification with ph decreasing by about 0 2 0 3 u the range being dependent on the value assumed for the fractionation factor a b3 b4 of the boric acid and borate species in seawater correlations of d 11 b with d 13 c during this interval indicate that the increasing trend towards ocean acidification over the past 60 years in this region is the result of enhanced dissolution of co2 in surface waters from the rapidly increasing levels of atmospheric co2 mainly from fossil fuel burning this suggests that the increased levels of anthropogenic co2 in atmosphere has already caused a significant trend towards acidification in the oceans during the past decades observations of surprisingly large decreases in ph across important carbonate producing regions such as the great barrier reef of australia raise serious concerns about the impact of greenhouse gas emissions on coral calcification 2009 elsevier ltd all rights reserved

holocene and pleistocene fringing reef growth and the role of accommodation space and exposure to waves and currents bora bora society islands french polynesia holocene fringing reef development around bora bora is controlled by variations in accommodation space as a function of sea level and antecedent topography and exposure to waves and currents subsidence ranged from 0 to 0 11 m kyr 1 and did not create significant accommodation space a windward fringing reef started to grow 8 7 kyr bp retrograded towards the coast over a pleistocene fringing reef until ca 6 0 kyr bp and then prograded towards the lagoon after sea level had reached its present level the retrograding portion of the reef is dominated by corals calcareous algae and microbialite frameworks the prograding portion is largely detrital the reef is up to 13 5 m thick and accreted vertically with an average rate of 3 12 m kyr 1 lateral growth amounts to 13 3 m kyr 1 reef corals are dominated by an inner pocillopora assemblage and an outer acropora assemblage both assemblages comprise thick crusts of coralline algae palaeobathymetry suggests deposition in 0 to 10 m depth an underlying pleistocene fringing reef formed during the sea level highstand of marine isotope stage 5e and is also characterized by the occurrence of corals coralline algal crusts and microbialites a previously investigated leeward fringing reef started to form contemporaneously 8 78 kyr bp but is thicker up to 20 m and solely prograded throughout the holocene a shallow pocillopora assemblage and a deeper water montipora assemblage were identified but detrital facies dominate at the holocene reef base only basalt was recovered the holocene windward leeward differences are a consequence of less accommodation space on the eastern island side that eventually led to a more complex reef architecture as a result of higher rates of exposure and flushing the reef framework on the windward island side is more abundant and experienced stronger cementation in the pleistocene the environmental conditions on the leeward island side were presumably unfavourable for fringing reef growth

flux of ice rafted detritus from sea ice in the fram strait abstract a three year particle flux record from the eastern fram strait between greenland and svalbard revealed a rather untypical seasonal flux pattern compared to other particle flux studies from the nordic seas in the eastern fram strait this pattern is characterised by a sudden four to six fold increase of the particle flux in january when no daylight is available to support any biological productivity comparison with sea ice distribution maps led to the conclusion that the sudden increase in the flux is due to ice rafted detritus released from sea ice which originated from the svalbard archipelago and from the northern barents sea detailed grain size analyses of the silt fraction indicated the 10 m fraction of the lithogenic matter to be clearly enriched due to ird input even more important is the observation that lithogenic material 40 m occurs exclusively during the ice rafting event and therefore appears to be a suitable indicator for ird transported on sea ice thus in addition to coarse ird e g 500 m which is mainly derived from icebergs the analysis of fine ird 40 m in deep sea sediments can be used to reconstruct paleo sea ice extensions

on the hydrography of the northeast water polynya the water masses and circulation in the area of the northeast water polynya located on the east greenland shelf north of 79 n are described on the basis of an r v polarstern cruise during spring and summer 1993 the baroclinic flow shows northward components close to the east greenland coast and eastward components at the northern limit of the polynya an anticyclonic half circle is formed by this and the southward flowing east greenland current in the south the circle is not closed the upper water column occupied by polar water is affected by this circulation pattern while deeper waters in the trough system of the area seem to spread independently different types of deep waters are found in different troughs all being of atlantic origin though they seem not to be directly connected to return atlantic water it is shown that what is called polar water must be formed at least partly on the greenland shelf and that deepwater formation does not occur in the investigated area

sedimentary evolution of the holocene subaqueous clinoform off the shandong peninsula in the yellow sea abstract a subaqueous clinoform wraps around the end of the shandong peninsula in the yellow sea the clinoform previously called the shandong mud wedge is up to 40 m thick nearshore and thins seaward its origin has been controversial since it was first noted in the 1980s for our recent investigation offshore of the northeastern shandong peninsula high resolution shallow seismic profiles covering about 1700 km were obtained and two drilling cores penetrating the clinoform were recovered we described the lithofacies characteristics identified benthic foraminifera and ostracoda measured grain size analyzed the mineral components of the cores and obtained ams 14 c dates on 28 samples to decipher the sedimentary evolution of the clinoform in response to postglacial sea level changes the shallow seismic profiles show that the clinoform comprises three units a lowermost seismic unit su 3 less than 2 3 m thick showing a retrogradational aggradational stacking pattern with subhorizontal internal reflectors a middle seismic unit su 2 up to 35 m thick showing a prograding reflection pattern with mostly seaward stepping reflectors separated by several erosive surfaces and an uppermost seismic unit su 1 maximum thickness 18 m exhibiting an aggradational reflection pattern with subparallel reflectors the three seismic units are bounded on the bottom by distinct erosion surfaces analyses of the two cores indicate that the clinoform comprises three depositional units du 1 du 2 and du 3 in descending order corresponding respectively to su 1 su 2 and su 3 the depositional units are distinguished by lithofacies characteristics and the downcore distributions of benthic foraminiferal and ostracod assemblages mineral components of the cores suggest that the clinoform s provenance is predominantly yellow river derived sediments ams 14 c dates suggest that du 3 was formed from about 11 6 to 9 6 cal kyr bp du 2 from 9 6 to 6 5 cal kyr bp and du 1 after ca 6 5 cal kyr bp some major meltwater pulse mwp events during the deglacial transgression were registered in the clinoform stratigraphy with the basal surfaces sediments of du 3 and du 2 corresponding respectively to mwp 1b ca 11 6 11 3 cal kyr bp and mwp 1c ca 9 6 9 2 cal kyr bp events and with du 2 being largely formed after the 8 4 8 2 cal kyr meltwater event rapid centennial to multidecadal scale flooding events were presumably responsible for the erosive surfaces separating the downlapping internal reflectors in su 2 the change of depositional pattern from progradational in su 2 to aggradational in su 1 is attributed to a change from strong dominantly to and fro tidal currents to the modern circulation in the bohai sea as well as to the weakening of the tidal current field during the highstand after about 6500 cal yr bp as a product of complex interactions among sediment supply sea level changes and hydrodynamic regimes the clinoform can be regarded as the distal part of the tidal depositional system in the eastern bohai sea which was largely derived from the yellow river

archean gold bearing quartz veins at the sigma mine abitibi greenstone belt quebec part i geologic relations and formation of the vein system the sigma deposit consists of an archean gold bearing vein system in metavolcanic rocks intruded by an irregular body of porphyritic diorite both affected by regional deformation and in turn cut by younger undeformed feldspar porphyry dikes the veins cut all rock types and are composed chiefly of quartz and tourmaline with minor amounts of carbonates pyrite chlorite scheelite and free gold they were emplaced during or after a greenschist facies metamorphism postdating the intrusion of feldspar porphyry dikes the veins were not significantly affected by any subsequent metamorphism or tectonism two principal types of veins occur in the mine subvertical veins and subhorizontal veins they are contemporaneous and cogenetic subvertical veins occur within steeply dipping east west trending ductile shear zones along which reverse subvertical displacements have taken place the veins occupy openings created by overriding of undulations and irregularities of foliation and slip planes during progressive shearing movements within the shears subhorizontal veins occupy extensional fractures which developed between ductile shear zones preferentially in the more competent host rocks these veins were formed by one or several episodes of open space filling geologic relations indicate that the mineralized veins were emplaced progressively in a dynamic tectonic environment during and shortly after the formation of ductile shear zones a structural analysis has shown that the ductile shear zones and the two vein types can be related to a single strain ellipsoid of the following orientation the z axis trending north south and horizontal the y axis plunging 10 degrees west and the x axis plunging 80 degrees east the deformation responsible for the generation of ductile shear zones and emplacement of the veins is ascribed to a late north south trending compression postdating regional deformation

cooling of the west spitsbergen current isopycnal diffusion by topographic vorticity waves 1 we investigate the heat budget in the west spitsbergen current on the basis of theoretical considerations and current meter data across the slope at 78 83 n between september 1997 and september 1998 the dispersion relation for topographically trapped waves along the west spitsbergen slope with a barotropic along slope velocity is calculated by use of an idealized numerical model signal processing and coherence calculations of the current meter data show that barotropic vorticity waves with enhanced energy at the diurnal period exist along the slope a wave length of 32 km is given by the dispersion relation for the 24 hour period and a corresponding second mode with a 35 hour period coherence calculations and complex demodulations of the current meter time series confirm the spatial and temporal variations given by the dispersion relation the eddy characteristics of the first two modes are used to estimate the heat loss of the warm core of the west spitsbergen current by isopycnal eddy diffusion we present the first isopycnal heat loss estimates obtained through dynamical considerations of the west spitsbergen current and compare them with earlier diagnostic estimates for the mean heat loss in the subsurface layers within the standard errors we estimate the heat flux to be o 1000 w m2 throughout the year except for the summer months june july if the 9798 heat flux time series are representative for the subsurface layer between 100 and 500 m depth the heat loss is on the same order of magnitude as the mean winter value of 1050 w m2 from earlier diagnostic estimates

modern coral reefs of western atlantic new geological perspective contrary to popular belief of the late 1960s western atlantic holocene reefs have a long history and are not feeble novice nearshore veneers that barely survived postglacial temperatures rather the growth of these reefs kept pace with the rising seas of the holocene transgression and their development was for the most part controlled by offshore wave energy conditions and the relationship between changing sea levels and local shelf topography thus the outer shelves of the eastern caribbean in areas of high energy have relict reefs consisting predominantly of acropora palmata a robust shallow water coral the flooding of adjacent shelves during the postglacial transgression introduced stress conditions that terminated the growth of these reefs when about 7 000 r ago shelf water conditions improved scattered deeper water coral communities reestablished themselves on these stranded shelf edge reefs and fringing and bank barrier reefs began to flourish in shallow coastal areas at the same time the fragile and rapidly growing acropora cervicornis and other corals flourished at greater depths on the more protected shelves of the western caribbean and the gulf of mexico as a result late holocene buildups more than 30 m thick developed in those areas

mechanisms of spur and groove development and implications for reef platform evolution contemporary understanding of holocene coral reef development is based primarily on sub surface investigations of reef flat back reef and lagoon zones few studies of holocene fore reef development exist constituting a significant gap in our understanding of reef evolution the spur and groove sag zone is a distinct understudied feature of fore reefs worldwide we review sag development from previous studies and present 29 new sag short cores with 52 14c and u th ages from six fore reef regions of heron and one tree reefs the first such data from the great barrier reef remarkably we found that sags do not necessarily accrete in the same direction as their adjacent reef flat we identified three modes of reef flat and sag lateral accretion mode 1 lagoonward accretion of both the reef flat and sags mode 2 lagoonward accretion of the reef flat but seaward accretion of the sags mode 3 seaward accretion of both the reef flat and sags most sag zones five of the six studied accreted in a seaward direction modes 2 or 3 hydrodynamic conditions and local topography appear to be the dominant factors determining which mode occurs episodic high energy events are also likely to play an important role in sag formation our findings suggest that traditionally held models of reef evolution whereby lagoonal mature reefs fill developing into senile platform reefs may not hold rather reef flats may continue to expand seaward on their leeward and semi exposed fronts to increase in size while maintaining their lagoons

back to the future the history of acroporid corals at the flower garden banks gulf of mexico usa fossil elkhorn corals acropora palmata were discovered at the flower garden banks fgb on the shelf margin off the texas coast in 2006 radiocarbon dating revealed an a palmata dominated community aged 10 157 6838 cal bp the acropora reefs correspond in time to an interval of warmer than present sea surface temperatures ssts during the holocene thermal maximum htm the subsequent demise of a palmata in the middle holocene was a consequence of the inability of the shallowest reef facies to keep pace with rising sea level following complete submergence of the banks possibly coupled with decreasing ssts following the htm in 2007 the first fossil staghorn corals acropora cervicornis were discovered at the fgb based on radiocar bon dating of these corals to 1027 211 cal bp it appears that populations of a cervicornis flourished in deeper waters 25 32 m depth on the edges of the banks until the peak of the little ice age lia when they died pre sumably from cold water exposure the recent return of a palmata to reefs of the fgb associated with increasing sea temperatures appears to be both an echo of the past and a harbinger of the future 2013 published by elsevier b v

global change and modern coral reefs new opportunities to understand shallow water carbonate depositional processes human activities are impacting coral reefs physically biologically and chemically nutrification sedimentation chemical pollution and overfishing are significant local threats that are occurring worldwide ozone depletion and global warming are triggering mass coral bleaching events corals under temperature stress lose the ability to synthesize protective sunscreens and become more sensitive to sunlight photo oxidative stress also reduces fitness rendering reef building organisms more susceptible to emerging diseases increasing concentration of atmospheric co2 has already reduced caco3 saturation in surface waters by more than 10 doubling of atmospheric co2 concentration over pre industrial concentration in the 21st century may reduce carbonate production in tropical shallow marine environments by as much as 80 as shallow water reefs decline worldwide opportunities abound for researchers to expand understanding of carbonate depositional systems coordinated studies of carbonate geochemistry with photozoan physiology and calcification particularly in cool subtropical transition zones between photozoan reef and heterotrophic carbonate ramp communities will contribute to understanding of carbonate sedimentation under environmental change both in the future and in the geologic record cyanobacteria are becoming increasingly prominent on declining reefs as these microbes can tolerate strong solar radiation higher temperatures and abundant nutrients the responses of reef dwelling cyanobacteria to environmental parameters associated with global change are prime topics for further research with both ecological and geological implications

pliocene pleistocene coastal events and history along the western margin of australia coastal deposits along the western coastal margin of australia a region of relative tectonic stability record plio pleistocene events and processes affecting the inner shelf and adjacent hinterland tectonic deformation of these deposits is more apparent in the carnarvon basin and rather less so in the perth basin the most complete record comes from the perth basin where units of pliocene and pleistocene ages are well represented in the perth basin the predominantly siliciclastic yoganup formation ascot formation and bassendean sand represent a complex of shoreline inner shelf and regressive dune facies equivalents the deposition of which began at an undetermined stage of the pliocene through to the early pleistocene the deposition of this sequence closed with a major regression and significant faunal extinction bioclastic carbonates characterize the middle and late pleistocene of the perth and carnarvon basins fossil assemblages include a distinct subtropical element unknown from the ascot formation and suggesting a strengthening of the leeuwin current the estuarine arcoid bivalve anadara trapezia characterizes assemblages of oxygen isotope stages 5 and 7 in the perth and carnarvon basins where it is now extinct deposits of substage 5e perth basin also record a southerly expansion of warm water corals and other fauna consistent with shelf temperatures warmer than present new uranium series ages on corals from marine sequences of the tantabiddi member of the bundera calcarenite of the western cape range are consistent with the double peak hypothesis for levels of substage 5e but the evidence remains less than conclusive initial uranium series dates from the bibra and dampier formations of shark bay indicate that both derive from the late pleistocene these numerical ages contradict previous interpretations of relative ages obtained from field studies the age relationship of the units requires further investigation

c vector for identification of oceanic secondary circulations across arctic fronts in fram strait 1 secondary circulation referring to the motion relative to a basic flow geostrophic and hydrostatic balanced occurs often in the ocean such as deep convection and circulations driven by fronts and eddies it affects the general circulation and the mass heat salt and energy balance the oceanic secondary circulation is difficult to measure directly but is easy to be identified by pseudovorticity using routine observations a c vector method commonly used in atmospheric mesoscale moist frontogenesis is applied to oceanography for identifying frontal secondary circulation in fram strait using conductivity temperature depth data collected during a large scale hydrographic survey on r v valdivia cruise 54 of the eastern greenland sea and fram strait from 16 march to 5 april 1987 possible application of this method to large scale motion is also discussed

a new model of holocene reef initiation and growth in response to sea level rise on the southern great barrier reef the fossil record provides valuable data for improving our understanding of both past and future reef resilience and vulnerability to environmental change the spatial and temporal pattern of the initiation of the holocene great barrier reef presents a case study of reef response to rapid sea level rise past studies have been limited by the lack of well dated and closely spaced reef core transects and have not closely examined the composition of the reef building communities through time this study presents 80 new high precision u sbnd th and 5 radiocarbon ages from twelve new cores located along three transects across different geomorphic and hydrodynamic settings of one tree reef southern great barrier reef to document three distinct stages of holocene reef development in unprecedented detail temporal constraints on changing paleoecological assemblages of coral coralline algae and associated biota revealed three distinct phases of reef development consisting of 1 a fast shallow and clear water reef initiation from 8 2 until 8 ka 2 a shift to slower deeper and more turbid water reef growth from 8 to 7 ka and 3 a return to shallow and rapid branching coral growth in clear water conditions as the reef catches up to sea level a minimum lag prior to reef initiation of 700 years was identified which differs in length depending on reef environment and pleistocene substrate height in this new model reef growth initiated on the topographically lower leeward margin and patch reef prior to the start of windward margin development contrary to the traditional reef growth model while there was a shift to conditions less favorable for reef growth at 8 ka this did not prevent the slow accretion of more sediment tolerant coral communities the majority of the reef reached sea level by 6 ka this new conceptual model of holocene reef growth provides new constraints on changes in paleoenvironment that controlled reef community composition and growth trajectories through sea level rise following inundation

holocene development of the yellow river s subaqueous delta north yellow sea high resolution seismic profiles from the north yellow sea reveal a 20 40 m thick subaqueous clinoform delta that wraps around the eastern end of the shandong peninsula extending into the south yellow sea this complex sigmoidal oblique clinoform containing an estimated 400 km 3 of sediment overlies prominent relict transgressive surfaces the nearshore topset of the clinoform 50 m contain less than 1 m of holocene sediment with low sedimentation rates 1 mm year in contrast to other clinoforms the shandong clinoform appears to be a compound subaqueous deltaic system with what we interpret to be proximal and distal phases of clinoform development the underlying proximal sequence formed proximally between f11 and 9 2 ka in response to a temporary pause in the rapid postglacial sea level rise after the meltwater pulse 1b mwp 1b and increased discharge from the yellow river to the north yellow sea due to intensification of the summer monsoon a flooding surface appears to separate the proximal and distal phases corresponding to the next rapid sea level rise 9 5 9 2 ka bp mwp 1c since 9 2 ka bp an overlying distal sedimentary sequence has accumulated reflecting the backstepping and shifting river mouth westward to the gulf of bohai some inputs from coastal erosion and nearby small streams may be locally important along shore transport cross shelf advection and upwelling in the north yellow sea have reworked post lgm sediment and have helped maintain the morphology of the clinoform in the shandong mud wedge d 2004 elsevier b v all rights reserved

the future of coral reefs in an age of global change coral reefs are the only ecosystem that is strongly defined by a geological component most definitions require that the biological community produces its own build up of calcium carbonate in terms of reef building the geological record reveals that coral reefs have flourished over the past few million years particularly during interglacial periods based on our observations of modern day reefs which are limited to the past few centuries we tend to link coral reef health to carbonate production however reef ecosystems face future global scale environmental changes that may decrease their reef building capacity in contrast to past discussions of the factors which determine reef building potential by a coral reef community the essential question that arises from this review is how important is reef building to a coral reef community

new evidence for drowned shelf edge reefs in the great barrier reef australia we present four new high resolution multibeam bathymetry datasets from the shelf edge of the northern great barrier reef gbr analysis of these data combined with chirp sub bottom profiles and existing submersible observation data provides a fresh insight into the detailed morphology and spatial distribution of submerged reefs and terraces at the shelf edge an extensive and persistent line of drowned shelf edge reefs exist on the gbr margin in about 40 to 70 m they appear as barrier reefs up to 200 m wide and comprising twin parallel ridges of rounded pinnacles subtle yet consistent terrace and step features lie between 78 and 114 m seaward of the shelf edge reefs in the southern study area submersible observations confirm that the drowned reefs now provide a favorable hard substrate for live soft corals and algae they form a consistent and extensive seabed habitat that extends for possibly 900 km along the gbr shelf edge the submerged reef and terraces features may reflect a complex history of growth and erosion during lower sea levels and are now capped by last deglaciation reef material

stratigraphic architecture and evolution of a barrier seagrass bank in the mid late holocene shark bay australia abstract within the faure sill complex shark bay western australia a combination of remote sensing analysis seismic stratigraphy and cores to ground truth together with radiocarbon dating demonstrate the interconnection between sediment body morphologies seagrass related substrates and pre existing topography and reveal the system as a channel bank complex sea level fluctuations appear to have largely controlled the hydrodynamic conditions of the bank contributing to each stage of its evolution 1 not earlier than 8 5 8 0 ka bp in a lowstand period after an erosive event of underlying palaeosurfaces seagrass establishment progressively contributed to initiating bank growth 2 around 6800 years bp bank accumulation reached its apex in conjunction with a rapid sea transgression 3 during the late holocene succeeding a slow decline to present sea level bank growth continued to fill available accommodation space and a number of hiatuses indicating temporal and spatial discontinuities within the process of bank building are recognised average depositional rates of bank building 1 3 m ka conform to previous estimates derived for seagrass banks but rates are strongly facies dependent attesting to the dynamic nature of this channel bank complex the extensive seagrass meadows are essential for a wide range of aspects of the environment of the shark bay area not only are they particularly important for the entire shallow benthic ecosystem but they also had a major role in the partial closure of the southern basins and hence determining the development of hypersaline conditions and associated oolitic microbial and evaporitic facies in hamelin pool and l haridon bight moreover this system has a critical role in producing sequestering and storing organic carbon

late glacial to post glacial sea levels in the western indian ocean late glacial to post glacial sea level changes provide direct evidence of the progress of melting of large ice sheets during the last deglaciation but although the correlation between ice and ocean volumes is incontrovertible the causal link is commonly obscured local effects including tectonics isostatic and hydroisostatic responses and equatorial ocean syphoning impose additional signals that hide the true picture a detailed regional study of the western indian ocean based on the analysis of drill cores carried out through modern reefs in combination with observations and sampling of reef foreslopes and investigations of outcrops provides a comprehensive data base sites from a range of tectonic settings include the microcontinental margins of madagascar the granitic seychelles and the isolated volcanic islands of reunion mauritius and the comoros in which the effects of subsidence can be shown to be small these cover a range of latitudes and comparisons with adjacent sites on continental margins allow the construction of sea level curves that closely reflect the eustatic response and disengage this from the effects of other mechanisms the mayotte foreslope in the comoro islands provides the first coral reef record of sea level change during the early deglaciation in the indian ocean 110 115 m below present sea level between 18 000 and 17 000 yr bp two distinctive reef terraces at 90 and 60 m water depth are dated at 13 600 yr bp and partly attributed to the younger dryas period 12 700 11 600 cal yr bp reef drowning at around 13 500 yr bp may correspond to meltwater pulse 1a and although there were surges in the rate of sea level rise most notably between 11 950 and 11 350 yr bp there is little evidence to support a well defined meltwater pulse 1b reconstructed holocene sea level curves are in good agreement and reflect a rapid sea level rise of about 6 mm yr 1 between 10 000 and 7500 yr bp followed by a clear inflection around 7500 yr bp when the rate fell to 1 1 mm yr 1 modern reefs started to grow 8000 9000 years ago in the post glacial period the rate of sea level rise was 1 1 5 mm yr 1 before stabilization at its present level 3000 2500 years ago curves for the 10 000 6000 yr 1 bp interval correspond closely with those predicted by theoretical models but lie below these in the subsequent period in particular and with the exception of the margins of the madagascar microcontinent influenced by hydroisostatic processes they do not reflect predicted higher sea level stands during the late holocene

sea ice thickness distribution in fram strait hm nuclear submarine sovereign has obtained the first synoptic measurements of the ice thickness distribution in fram strait the main outflow from the arctic ocean the ice nearest the ice edge is of quite different character from ice in the interior of the strait with a greater proportion of first year ice and less pressure ridging an estimate of the ice flux through fram strait can be made from the distribution of mean ice drafts

mesoscale eddies in the fram strait marginal ice zone during the 1983 and 1984 marginal ice zone experiments during the summer marginal ice zone experiment in fram strait in 1983 and 1984 fourteen mesoscale eddies in both deep and shallow water were studied between 78 o and 81on sampling combined satellite and aircraft remote sensing observations conductivity temperature depth observations drift of surface and subsurface floats and current meter measurements typical scales of these eddies were 20 40 km rotation was mainly cyclonic with a maximum speed in several cases subsurface of up to 40 cm s observations further suggest that the eddy lifetime was at least 20 to 30 days five generation sources are suggested for these eddies several of the eddies were topographically trapped while others primarily formed by combined baroclinic and barotropic instability moved as much as 10 15 km d with the mean current the vorticity balance in the nontrapped eddies is dominated by the stretching of isopycnals accompanied by a change in the radial shear in the most completely observed eddy south of 79on the available potential energy exceeded the kinetic energy by a factor of 2 quantitative estimates suggest that the abundance of these eddies enhances the ice edge melt up to 1 2 km d

geomorphic evidence of major sea level fluctuations during marine isotope substage 5e cape cuvier western australia abstract a detailed geomorphologic and morphostratigraphic investigation of raised marine terraces at cape cuvier western australia reveals two morphologically distinct units a lower well developed accretional reef terrace between 3 and 5 5 m above mlws mean low water springs hereafter denoted as represents an extended interval of stable sea level an upper erosional terrace and incipient coralgal rim between 8 5 to 10 5 m represents a brief sea level stillstand at this higher elevation these features suggest the lower and upper terraces developed during discrete sea level events in an attempt to better define the timing of emplacement of each marine unit 20 coral samples collected along vertical and lateral reef growth axis from both terraces were analysed with u series dating unfortunately all coral samples exhibited elevated 234 u initial values suggesting that pervasive uptake of 234 u enriched uranium and 230 th thorium had occurred despite the shortcomings of absolute dating a succession of events can be resolved though morphostratigraphic relationships comparison of the facies relationships coral growth and morphostratigraphic features between the lower and upper terraces indicates that an early to mid mis 5e stillstand at 3 to 5 m was followed by a late rise to 8 5 to 10 5 m this agrees with an emerging global view of mis 5e sea level history derived from stable carbonate platforms rejecting the hypothesis that these higher sea level benchmarks are an artefact of localized tectonic processes

holocene climatic instability a prominent widespread event 8200 yr ago the most prominent holocene climatic event in greenland ice core proxies with approximately half the amplitude of the younger dryas occurred 8000 to 8400 yr ago this holocene event affected regions well beyond the north atlantic basin as shown by synchronous increases in windblown chemical indicators together with a significant decrease in methane widespread proxy records from the tropics to the north polar regions show a short lived cool dry or windy event of similar age the spatial pattern of terrestrial and marine changes is similar to that of the younger dryas event suggesting a role for north atlantic thermohaline circulation possible forcings identified thus far for this holocene event are small consistent with recent model results indicating high sensitivity and strong linkages in the climatic system

diagnostic study of the fram strait marginal ice zone during summer from 1983 and 1984 marginal ice zone experiment lagrangian observations from 1984 marginal ice zone experiment observations in fram strait three main results concerning large scale mesoscale and summer marginal ice zone miz features are presented and discussed in this paper regarding the large scale the main conclusion is that the east greenland current egc is a narrow stable current in contradiction with past results presenting the egc as a broad and unstable current in the mesoscale the west spitsbergen current wsc and the norwegian current are the main generators for eddies in fram strait these eddies propagate northwestward preferentially following topographic features like fracture zones which are quite abundant in this region in our opinion these wsc eddies represent an important part of the atlantic water recirculation in fram strait when approaching the east greenland continental slope they interact with the egc and they form well developed eddies these ice edge eddies associated with ice edge tongues are quite recognizable with remote sensing techniques the summer marginal ice zone in fram strait is clearly characterized by sea ice concentrations from 1 10 to 3 10 and floe sizes limited to 1 km or less there is a well defined limit which separates the pack ice from the miz where no big ice floes are ever recorded the breaking action of waves and swell propagating into the ice are likely to be the only mechanisms explaining such a drastic filtering effect according to their amplitudes and directions winds and eddies act in the miz in shrinking or stretching this zone

a new coral reef province in the gulf of carpentaria australia colonisation growth and submergence during the early holocene abstract multibeam sonar mapping drill cores and underwater video data have confirmed the existence of a previously unknown coral reef province in the gulf of carpentaria australia seven reefs comprised of coral limestone that support living corals have been mapped so far and as many as 50 other reefs may exist in the region u th ages show that reef growth commenced shortly after limestone pedestals were submerged by rising sea level around 10 5 kyr bp making them the oldest holocene reefs known in australia reef growth persisted for 2 0 kyr but it had ceased at most locations by 7 0 kyr bp measurements of reef growth rates 0 95 to 4 m kyr 1 indicate that the reefs were unable to keep pace with contemporaneous rapid sea level rise 10 m kyr 1 which is consistent with a give up reef growth history core samples from reef platforms demonstrate that pleistocene limestone is exposed at depths of 27 and 30 m below present mean sea level these depths represent regionally significant phases of reef growth during a prolonged sea level still stand we conclude that the reefs are therefore mostly relict features whose major phase of growth and development relates to an earlier pre holocene sea level still stand

coupling of air and sea surface temperatures in the eastern fram strait during the last 2000 years the arctic has undergone significant changes in the last 20 30 years the understanding of these changes is limited by the time span or resolution of existing climate records the main gateway of h

an open system model for u series age determinations of fossil corals the source of excess 234u in fossil corals and its relationship to u series age determinations has been an outstanding problem in geochronology for more than 20 years with increasing numbers of u series isotope measurements in corals and significant improvements in analytical precision through mass spectrometry it is increasingly apparent that a substantial fraction of observed isotope ratios cannot be reasonably explained by closed system decay moreover observations of a positive correlation between 234u 238u and 230th 238u ratios in corals from the same terrace are difficult to explain however the decay of dissolved uranium and recoil mobilization of uranium daughters produce particle reactive 234th and 230th and the coupled addition of these th isotopes could simultaneously increase coral 234u 238u and 230th 238u here we present a quantitative model based on decay dependent redistribution of 234th and 230th permitting calculation of open system coral ages these equations provide a general solution to the recoil redistribution problem applicable to any alpha decay series while measured isotope ratios of corals from the three youngest stratigraphically defined barbados terraces are inconsistent with closed system decay they fall in broadly linear arrays agreeing with model predictions isotopic arrays of older barbados corals and corals from terraces around the world are also consistent with model predictions suggesting the open system model is generally applicable corals with extreme isotopic compositions that are impossible to produce by closed system decay are consistent with the limited range of isotopic compositions predicted by the model at ages older than 600 ka for corals from a single terrace 234th and 230th redistribution appears to be a source of systematic conventional age error even for corals with slightly elevated 234u however open system ages are consistent even for corals with extremely elevated 234u for the youngest three barbados terraces mean open system terrace ages are consistent with mean conventional terrace ages calculated from pristine samples if the most accurate conventional ages are from corals with an initial 234u 238u identical to modern seawater then the open system model will improve the accuracy of coral u series age determinations and dramatically increase the number of reliable ages

intrusion related high temperature gold quartz veining in the cosmopolitan howley metasedimentary rock hosted gold deposit northern territory australia in the proterozoic cosmopolitan howley gold deposit northern australia quartz vein hosted gold mineralization occurs predominantly within 50 m of the noncarbonaceous footwall of carbonaceous slates although abundant veins farther away from or within carbonaceous slate are barren except for hydrofracture stock works in the hinge zone the gold bearing quartz veins qv1 are bedding concordant and occur in hornfels and slate in the steeply dipping fold limbs of the howley anticline the qv1 veins formed near the peak of contact metamorphism 550 degrees 620 degrees c and 240 200 mpa following the intrusion of the cullen granite batholith the vein alteration assemblage is k feldspar biotite andalusite or cordierite and mineralization was accompanied by large scale potassium metasomatism whereas sodium and calcium were leached from the country rocks the qv1 veins were overprinted first by superposed folding and then by reverse faulting later transpressional strike slip faulting was accompanied by extensive retrograde alteration the precipitation of sulfide lenses delta 34 s arsenopyrite 0 3 to 4 8 quartz veins qv2 with subeconomic gold enrichments and barren pegmatitic veins qv3 the involvement of a magmatic fluid in ore genesis at the cosmo howley deposit is indicated by 1 high fluorine contents in biotite from the alteration selvages of the gold quartz veins qv1 f 5 573 6 616 ppm 49 000 ppm at mt shoobridge 7 km west 2 mutual crosscutting relations of gold quartz veins with aplite dikes 3 the location of the deposit above i type granite at a vertical distance of less than 2 km most likely or 1 km and 4 the high salinity of the mineralizing fluid as estimated from the cl content of biotite in the alteration halos of the veins a magmatic derivation of the sulfur in the auriferous sulfides is consistent with isotopic data 0 3 to 7 2 5a4s calculated oxygen isotope compositions of the fluids which precipitated the successive generations of quartz veins qvi delta 18 o sub h 2 o 13 6 qv3 delta 18 o sub h 2 o 11 8 indicate that the isotopically heavy country rock chert nodules delta 18 o or 18 5 was infiltrated by an isotopically light

reef drowning during the last deglaciation evidence for catastrophic sea level rise and ice sheet collapse elevations and ages of drowned acropora palmata reefs from the caribbean atlantic region document three catastrophic metre scale sea level rise events during the last deglaciation these catastrophic rises were synchronous with 1 collapse of the laurentide and antarctic ice sheets 2 dramatic reorganization of ocean atmosphere circulation and 3 releases of huge volumes of subglacial and proglacial meltwater this correlation suggests that release of stored meltwater periodically destabilized ice sheets causing them to collapse and send huge fleets of icebergs into the atlantic massive inputs of ice not only produced catastrophic sea level rise drowning reefs and destabilizing other ice sheets but also rapidly reduced the elevation of the laurentide ice sheet flipping atmospheric circulation patterns and forcing warm equatorial waters into the frigid north atlantic such dramatic evidence of catastrophic climate and sea level change during deglaciation has potentially disastrous implications for the future especially as the stability of remaining ice sheets such as in west antarctica is in question

consistent fluctuations in intermediate water temperature off the coast of greenland and norway during dansgaard oeschger events abstract rapid warmings epitomize the dansgaard oeschger events that are recorded in greenland ice cores and imprinted in ocean sediment cores while the abrupt climate changes appear connected to perturbations in sea ice and ocean circulation it is unclear how the water masses within the nordic seas responded and were influenced by the inflowing atlantic water in the absence or presence of sea ice high resolution reconstructions of benthic mg ca together with stable isotopes of carbon and oxygen 13c and 18o show a recurring warming 2 5 0 5 c occurring consistently at the inflow and outflow of the nordic seas at intermediate depths down to 1500 m during greenland stadials 9 6 using idealized numerical simulations with an eddy resolving ocean model we investigate the impact of an isolating sea ice cover and freshwater lid in the nordic seas with the presence of an extensive sea ice cover the warm atlantic water entering the nordic seas in the east retains its heat as it exits in the west the depth of the recirculating warm atlantic water increases when including an external freshwater source at the surface of the nordic seas these findings support the view that cold stadials are accompanied by pervasive intermediate water warming across the nordic seas given the current rates of arctic sea ice loss these results provide a potential mechanism for water column destabilization and inception of abrupt climate change

late quaternary evolution of coral reefs on a cool water carbonate margin the abrolhos carbonate platforms southwest australia late quaternary coral reefs have developed on the southwestern australian margin which has otherwise been characterised by cool water carbonates since the eocene the houtman abrolhos coral reefs are at the limits of existence extending with the assistance of the leeuwin current a poleward flowing warm water stream into a region dominated by more temperate communities coring in the easter group reefs supported by high precision dating by both view the mathml source tims and 14 c methods has shown vigorous coral growth with reefs over 26 m thick in the holocene and over 15 m thick in the last interglacial each of the three abrolhos platforms consists of a central platform composed of last interglacial reefs about which windward and leeward holocene reefs developed asymmetrically reef peritidal and eolian facies comprise the emergent last interglacial limestones which are extensively calcretized with reef facies up to 5 m above msl the last interglacial high stand lasted for at least 10 ka from 130 to 120 ka and possibly 15 ka from 132 to 117 ka holocene reef facies are also emergent by 0 5 m and are overlain by peritidal and storm ridge facies in an upward shallowing sequence windward 10 m thick and leeward 26 m thick holocene reefs in the easter group show contrasting lithofacies the wave exposed windward reefs consist of a slow growing association of coralline algal bindstones and coral framestones whereas fast growing coral framestones dominate the more protected leeward reefs the leeward reefs commenced growth 10 000 years ago and grew to the present sea level by 6500 years ago generating holocene constructional topography consisting of blue hole terrain in the leeward parts of the platforms

branching of atlantic water within the greenland spitsbergen passage an estimate of recirculation atlantic water aw supplies the largest source of heat mass and salt to the arctic ocean via fram strait greenland spitsbergen passage yet it represents only a fraction of the atlantic water that resides in the greenland iceland norwegian and barents seas this is a result of both the branching of the central core of aw along its northward flow and the modification of its t s signature through air sea ice interactions and internal mixing this paper addresses the quantitative analysis of the three dominant atlantic water cores within fram strait and north of 76 n using an 11 year 1977 to 1987 hydrographic database spatial variations of heat volume and salt along its flow path of some 600 km showed that the major core of atlantic water that directly enters the arctic ocean svalbard branch did not extend past 20 e of the 9719 km3 of atlantic water existing within the region one third resided within the svalbard branch the remainder 22 and 45 were held within the return atlantic current and the yermak branches respectively restricting the analysis to a southern limit of 79 n effectively removed the return atlantic current and showed a nearly equal split between the two remaining branches work completed by bourke et al 1988 indicated that the yermak branch is largely recirculated to the south if true this analysis supports rudels 1987 model estimate of a 50 recirculation of aw within this region

porphyroblast nucleation growth and dissolution in regional metamorphic rocks as a function of deformation partitioning during foliation development in regional metamorphic rocks the partitioning of deformation into progressive shearing and progressive shortening components results in strain and strain rate gradients across the boundaries between the partitioned zones these generate dislocation density gradients and hence chemical potential gradients that drive dissolution and solution transfer phyllosilicates and graphite are well adapted to accommodating progressive shearing without necessarily building up large dislocation density gradients within a grain because of their uniquely layered crystal structure however most silicates and oxides cannot accommodate strain transitions within grains without associated dislocation density gradients and hence are susceptible to dissolution and solution transfer as a consequence zones of progressive shearing become zones of dissolution of most minerals and of concentration of phyllosilicates and graphite exceptions are mylonites where strain rates are commonly high enough for plastic deformation to dominate over diffusion rates and therefore over dissolution and solution transfer porphyroblastic minerals cannot nucleate and grow in zones of active progressive shearing as they would be dissolved by the effects of shearing strain on their boundaries however they can nucleate and grow in zones of progressive shortening and this is aided by the propensity for microfracturing in these zones which allows rapid access of fluids carrying the material presumed to be necessary for nucleation and growth zones of progessive shortening also have a number of characteristics that help to lower the activation energy barrier for nucleation this includes a build up of stored strain energy relative to zones of progressive shearing in which dissolution is occuring porphyroblast growth is generally syndeformational and previously accepted criteria for static growth are not valid when the role of deformation partitioning is taken into account porphyroblasts in a contact aureole do not grow statically either as microfracturing associated with emplacement allows access of fluids in a fashion that is similar to microfracturing in zones of progressive shortening the criteria used for porphyroblast timing can be readily accommodated in terms of deformation partitioning reactivation of deforming foliations and a general lack of rotation of porphyroblasts with the spectacular exception of genuinely spiralling garnet porphyroblasts

reworking processes and deposits in coral reefs during very high energy events example from a pleistocene coral formation 125 ka la desirade island lesser antilles abstract abundant literature has documented the ecological impact of very high energy hurricane type events and high energy storm type events on modern coral reefs and sediment transport in previous studies sedimentary processes are often deduced from geophysical image analysis and scuba diving observations few field based studies have been devoted to the impact of very high energy disturbance on the structure and ecology of holocene and pleistocene coral reefs and very few to the sedimentary processes acting around these reefs this research examines the structure of the late pleistocene end of mis5e stage reefs of la desirade island guadeloupe archipelago lesser antilles and focuses on the poorly known reworking processes and related coral breccia sedimentation surrounding these reefs fieldwork was performed to document two coral fragment rich breccia interbedded with coral patches the breccia predominantly show the same petrography but differ in their internal structure showing a massive breccia type and a stratified breccia type this work infers that these breccia are the result of gravity induced high density mass flows triggered by high to very high energy events such as storms and hurricanes damage and reworking vary according to the type of very high energy event prior to transport storms are thought to have broken the heads of branching and columnar coral colonies and broken and overturn isolated lamellar and massive colonies hurricanes particularly their eye walls may have reworked much more sediment than storms and may have also destabilised entire several metre sized columnar colonies from the flank of coral patch reefs we propose the name coral debrite for these coral breccia deposits caused by gravity induced debris flows the reworked deposits are interbedded between two coral reef levels of which the main coral species vertical succession should record the end of marine isotope stage 5e sea level rise thus reworking is believed to occur during the transitional stage between a glacial and an interglacial period

chronostratigraphy and geomorphology of washover fans in the exmouth gulf nw australia a record of tropical cyclone activity during the late holocene abstract washover fans typically form due to barrier overwash or breaching and coastal inundation and generally represent geomorphological and depositional evidence of intense storms few studies have investigated the chronostratigraphy of washover fans in order to infer magnitude frequency patterns of extreme wave events over longer time scales here we present new data on the chronostratigraphy of late holocene washover fans in the exmouth gulf western australia by using ground penetrating radar and unmanned aerial vehicle uav survey techniques as well as geomorphological sedimentological and chronological investigations this study aims to i provide a detailed characterization of the washover fans geomorphology and stratigraphical architecture ii document depositional processes involved in their formation iii establish a chronostratigraphy based on optically stimulated luminescence osl and iv understand the significance of the washover fans for recording past tropical cyclone tc activity the fans consist of multiple sequences of sand shell debris and coral rubble comprising depositional units related to tc induced inundation the units are separated by palaeosurfaces with incipient soil formation formed during periods of reduced depositional activity in combination with the interpretation of a uav based high resolution digital surface model multiple phases of reactivation are inferred osl results allow the establishment of a local long term tc record and suggest storm induced deposition at 170 360 850 and 1300 years ago further units were dated to 1950 2300 and 2850 years ago the chronology of tc events is consistent with other work relating tc activity with el nino southern oscillation enso and sea surface temperature sst patterns corroborating the regional palaeotempestological relevance of this unique geomorphological record

fringing reef growth and morphology a review abstract fringing reefs are generally not simple veneers of coral growth along tropical shorelines extensive research over the past few decades based on radiocarbon dating of holocene reef deposits has indicated that they can develop in a complex variety of ways even though the surface morphology may appear relatively simple the principal factor that appears to determine the growth and morphology of fringing reefs is the available accommodation space sea level fluctuations are important primarily because the sea surface determines the absolute accommodation space for a given reef this means that a reef established during a period of sea level rise will be able to accrete vertically as space is created above it if however the reef establishes at or grows to the sea surface thereby occupying all the available accommodation space it can no longer accrete vertically and begins to build laterally the morphology and chronostratigraphy of a range of holocene fringing reefs are described on the basis of which six fringing reef growth models are identified in model a the fringing reef is established at depth and primarily accretes vertically towards the sea surface reef growth in model b initiates at sea level and due to the lack of vertical accommodation space grows laterally model c has a similar morphology to model b however the reef progrades over a non reefal sediment wedge episodic lateral and vertical growth occurs in model d with a stepwise progradation of the reef front the remaining models are characterised by seaward reef framework behind which unconsolidated sediments accumulate in model e reef crest growth forms a barrier leading to the development of a backreef lagoon model f has a similar morphology to model e except that the reef crest is formed by hurricane rubble accumulation rather than framework accretion and is periodically reworked

the west spitsbergen current as seen by sofar floats during the arctemiz 88 experiment statistics differential kinematic properties and potential vorticity balance sofar floats were launched at 300 m depth in the west spitsbergen current wsc in september 1988 this lagrangian data set is used to compute statistical parameters to produce local maps of mean velocity kinetic energy and eddy kinetic energy and to study dispersion and diffusion in the wsc despite the limited number of float trajectories the values obtained for the diffusivities order 1 0 x 10 7 cm 2 s 1 are close to those found in other regions of the atlantic ocean the molinari and kirwan 1975 method is used to compute the differential kinematic properties divergence vorticity shear and stretching the conservation of potential vorticity in the region of the yermak plateau is not correctly verified this is mainly due to the jet structure of the wsc and the shape of the cluster leading to a biased estimate of the relative vorticity however the results based only on five float trajectories over 30 days are encouraging and not inconsistent with the properties of the west spitsbergen current the existence of a new eastward branch of the wsc passing just over the top of the yermak plateau is confirmed

freshwater outbursts to the oceans from glacial lake agassiz and their role in climate change during the last deglaciation abstract lake agassiz was the largest lake in north america during the last deglaciation as the laurentide ice sheet lis retreated large volumes of water stored in this proglacial lake were episodically released into the oceans these waters were variably routed to the gulf of mexico arctic ocean north atlantic ocean and hudson bay during this period the three largest cooling events in the northern hemisphere closely followed 4 of the 5 largest outbursts from lake agassiz 1 the younger dryas which was preceded by a release of 9500 km 3 2 the preboreal oscillation preceded by releases of 9300 km 3 and 5900 km 3 and 3 the 8 2 ka cold event preceded by a 163 000 km 3 outburst these are respectively fluxes of 0 30 sv 0 29 sv 0 19 sv and 5 2 sv if released in 1 year because the influx of freshwater reaching the north atlantic ocean can inhibit thermohaline circulation partly depending on whether the ocean was in a glacial interglacial or transitional mode of circulation we believe that at least these large outbursts from lake agassiz may have provided the triggers for changes in ocean circulation and in turn for widespread climate change

distribution of planktic foraminifera at the ice margin in the arctic fram strait planktic foraminifera were collected in net tows 63 m along two east west transects at 78 and 80 n in the fram strait northern nordic seas at five concurrent depth intervals in the upper 200 m of the water column in the ice free zone absolute abundances in the upper 200 m of the water column up to 500 individuals m3 were obtained along the ice margin the absolute abundances reached up to 1250 ind m3 while in the ice covered areas not more than 50 ind m3 have been found surprisingly these strong variations in abundance are not accompanied by significant changes in faunal assemblages between the ice free and the ice covered regions neogloboquadrina pachyderma is the dominant species in most samples making up to 60 of the total faunal assemblage globigerina quinqueloba contributes 38 and all other species combined make up only 2 of the total fauna both absolute and relative abundances of the collected foraminifera are strongly dependent on the mesh size used using smaller mesh sizes provides a wider species spectrum which is of special interest for paleoceanographic reconstructions in the nordic seas where fossil assemblages 150 m often consist of only one species the specific hydrographic conditions in the fram strait with warm atlantic waters underlying cold polar surface waters result in a rather atypical depth distribution of the planktic foraminifera all species seem to prefer the temperate atlantic waters between 50 m and 200 m thus the species composition as well as geochemical tracers do not reflect the surface ocean conditions which again has potentially interesting implications for paleoceanographic reconstructions

an inverse modeling study in fram strait part ii water mass distribution and transports abstract a water mass analysis is carried out in fram strait between 77 15 and 81 15 n based on three dimensional large scale potential temperature and salinity distributions reconstructed from the mizex 84 hydrographic data collected in summer 1984 combining these distributions with the geostrophic flow field derived from the same data in a companion paper schlichtholz and houssais 1999 the heat fresh water and volume transports are estimated for each of the water masses identified in the strait twelve water masses are selected based on their different origins among them the polar water pw enters fram strait from the arctic ocean both over the greenland slope and over the western slope of the yermak plateau in the atlantic water aw range four modes with distinct geographical distributions are indentified in the deep water range the eurasian basin deep water ebdw is confined to the lena trough and to the molloy deep area where it is involved in a cyclonic circulation the warm and shallower mode of the norwegian sea deep water nsdw concentrated to the west is mainly seen as an outflow from the arctic ocean while the cold and deeper mode essentially observed to the east enters the strait from the greenland sea apart from the ebdw there is a tendency for all water masses of polar origin to flow along the greenland slope the two most abundant water masses the aw and the nsdw occupy as much as 67 of the total water volume the southward net transport of pw through fram strait is about 1 sv at 78 9 n at the same latitude the net transport of aw is southward and equal to about 1 7 sv only the transport of the warm mode aww is northward amounting to 0 2 sv the overall net outflow of the deep waters to the greenland sea is about 2 6 sv two upper water masses the fresh aw f and the cold awc mode of the aw and one deep water mass the nsdw appear to be produced in the strait with production rates between 77 6 and 79 9 n of about 0 2 1 0 and 1 7 sv respectively a southward net fresh water transport through the strait of about 2000 km 3 yr 1 relative to a salinity of 34 93 is mainly due to the pw the net heat transport relative to 0 1 c is northward but undergoes a rapid northward decrease suggesting an area averaged surface heat loss of 50 100 w m 2 in the strait

holocene sea level determination relative to the australian continent u th tims and 14c ams dating of coral cores from the abrolhos islands u th tims and 14 c ams measurements are presented from two coral cores from the easter group of the houtman abrolhos islands between 28 s and 29 s on the western continental margin of australia the u th measurements on the morley core from morley island cover a depth interval from 0 2 m above present sea level to 24 4 m below present sea level and comprise eleven samples the ages vary between 6320 50 a at 0 2 m above sea level and 9809 95 a at 24 4 m below sea level all errors are 2 the mean growth rate is 7 1 0 9 m ka the 14 c dates of selected morley core corals show that the 14 c ages are 1000 a younger than their corresponding u th ages which agrees with previous results the main purpose of our 14 c measurements is to be able to compare them precisely with other coral cores where no u th measurements are available the u th measurements of the suomi core from suomi island cover a depth interval from 0 05 m to 14 2 m below present sea level and consist of four samples the ages vary between 4671 40 a at 0 05 m below sea level and 7102 82 a at 14 2 m below sea level with a mean growth rate of 5 8 0 2 m ka the growth history of both cores is explained by a simple model in which the growth rates of the morley core can be interpreted as reflecting local rates of sea level rise whereas the suomi core is interpreted as reflecting lateral growth during the past 6000 a our results indicate that sea level relative to the western margins of the australian continent was about 24 m lower than present at about 9800 a b p 14 c gives a date of 8500 a b p sea level then rose and reached a highstand slightly higher than the present position at about 6300 a b p 14c date 5500 a this highstand declined but was still higher than present at 4600 a b p this is in agreement with previous observations along the australian coastal margins and with observations from the huon peninsula papua new guinea our results are very similar to theoretical numerical models which take into consideration water loading and isostatic compensation and viscous mantle flow in contrast coral cores from barbados show that corals with a 14 c age of 5500 a b p are some 10 m b p s l we interpret the difference between the barbados core and the morley core as resulting from additional flooding of barbados by water redistribution due to changes in the earth s geoid but not reflecting global sea level rise or major addition of melt waters over the past 6000 a the difference in the geoid at barbados between 6000 a b p and the present will require a refinement in the geophysical models precise 230 th tims measurements on continental coasts will be required to provide an adequate data base for modelling deformation flow of mantle material and sea level height

traces of historical tropical cyclones and tsunamis in the ashburton delta north west australia although the north western coast of western australia is highly vulnerable to tropical cyclones and tsunamis little is known about the geological imprint of historic and prehistoric extreme wave events in this particular area despite a number of site specific difficulties such as post depositional changes and the preservation potential of event deposits both tropical cyclones and tsunamis may be inferred from the geomorphology and the stratigraphy of beach ridge sequences washover fans and coastal lagoons or marshes a further challenge is the differentiation between tsunami and storm deposits in the geological record particularly where modern deposits and or historical reports on the event are not available this study presents a high resolution sedimentary record of washover events from the ashburton river delta western australia spanning approximately the last 150 years a detailed characterization of event deposits is provided and a robust chronostratigraphy for the investigated washover sequence is established based on multi proxy sediment analyses and optically stimulated luminescence dating combining sedimentological geochemical and high resolution optically stimulated luminescence data event layers are assigned to known historical events and tropical cyclone deposits are separated from tsunami deposits for the first time the 1883 krakatoa and 1977 sumba tsunamis are inferred from sedimentary records of the north western part of western australia it is demonstrated that optically stimulated luminescence applied in coastal sedimentary archives with favourable luminescence characteristics can provide accurate chronostratigraphies even on a decadal timescale the results contribute to the data pool of tropical cyclone and tsunami deposits in holocene stratigraphies however they also demonstrate how short lived sediment archives may be in dynamic sedimentary environments

the role of sea ice and other fresh water in the arctic circulation salinity stratification is critical to the vertical circulation of the high latitude ocean we here examine the control of the vertical circulation in the northern seas and the potential for altering it by considering the budgets and storage of fresh water in the arctic ocean and in the convective regions to the south we find that the present day greenland and iceland seas and probably also the labrador sea are rather delicately poised with respect to their ability to sustain convection small variations in the fresh water supplied to the convective gyres from the arctic ocean via the east greenland current can alter or stop the convection in what may be a modern analog to the halocline catastrophes proposed for the distant past the north atlantic salinity anomaly of the 1960s and 1970s is a recent example it must have had its origin in an increased fresh water discharge from the arctic ocean similarly the freshening and cooling of the deep north atlantic in recent years is a likely manifestation of the increased transfer of fresh water from the arctic ocean into the convective gyres finally we note that because of the temperature dependence of compressibility a slight salinity stratification in the convective gyres is required to efficiently ventilate the deep ocean

the ice cover in the greenland and norwegian seas the seasonal sea ice cover of the northern north atlantic is reviewed comprising the ice of the east greenland current the ice cover around svalbard and the ice of the barents sea as far east as franz josef land the review considers various types of ice cover 1 the fast ice along the coasts and in fjords including sikussak or very old fast ice of exceptional thickness 2 the transition zone between the fast ice and the main pack including the positions and causes of recurring winter polynyas and the nature of the shear zone in ne greenland 3 the constitution dynamics and seasonal extent of the drifting pack ice including interannual variations 4 the processes of air ice ocean interaction which occur in the marginal ice zone where the pack ice is influenced by an open ocean boundary

postglacial sea level changes in the northern south china sea continental shelf evidence for a post 8200 calendar yr bp meltwater pulse abstract a postglacial sea level record reconstructed through the study of 25 cores and 10 grab samples obtained from the siliciclastic dominated northern south china sea continental shelf between hong kong and dongsha is presented the seven sedimentary facies recognized are 1 pleistocene overconsolidated mud facies affected by palaeosol development due to sub aerial exposure during the last glacial maximum lgm 2 bioclastic sandy gravel facies occurring at a present day seabed depth exceeding 120 m 3 lgm bioclastic beach dune sand facies at a present day seabed depth between 110 and 120 m 4 postglacial siliciclastic beach dune sand facies formed during at least two episodes of sea level stillstands at present day seabed depths between 80 and 90 m and 30 and 50 m respectively 5 postglacial transgressive sand facies of late pleistocene to early holocene age radiocarbon dating shows that this facies was deposited in two stages before and after the 8200 calendar yr bp cold event 6 postglacial sand and gravel dominated facies with acoustic turbidity at a present day seabed depth of about 50 m 7 postglacial mud facies based on the radiocarbon ages obtained from samples located above and below the holocene pleistocene hiatus in the two innermost shelf cores and large variations of atmospheric radiocarbon concentration found during the last glacial period in a submerged stalagmite from the bahamas beck et al 2001 science 292 2453 2458 ages exceeding 8200 calendar yr bp are likely to represent minimum values ages postdating this limit which are less affected by variations of atmospheric radiocarbon concentration indicate the presence of a post 8200 calendar yr bp cold event meltwater pulse caused by eustatic sea level rise from approximately 40 m below present to the present level by about 6000 calendar yr bp inaccuracies of the pre 8200 calendar yr bp radiocarbon ages may be attributed to large variations of atmospheric 14 c during the postglacial period with greenhouse gases released from the sub aerially exposed continental shelf probably accounting for a significant proportion

significance of shallow core transects for reef models and sea level curves heron reef great barrier reef a sequence of shallow reef cores from heron reef great barrier reef provides new insights into holocene reef growth models isochron analysis of a leeward core transect suggests that the north western end of heron reef reached current sea level by ca 6 5 kyr bp and then prograded leeward at a rate of ca 19 6 m kyr between 5 1 kyr and 4 1 kyr bp pre 1950 to the present reef margin a single short core on the opposing margin of the reef is consistent with greater and more recent progradation there further to the east one windward core reached modern sea level by ca 6 3 kyr bp suggesting near keep up behaviour at that location but the opposing leeward margin behind the lagoon reached sea level much more recently hence heron reef exhibited significantly different reef growth behaviour on different parts of the same margin mean reef accretion rates calculated from within 20 m of one another in the leeward core transect varied between ca 2 9 m and 4 7 m kyr depending on relative position in the prograding wedge these cores serve as a warning regarding the use of isolated cores to inform reef growth rates because apparent aggradation at any given location on a reef varies depending on its location relative to a prograding margin only transects of closely spaced cores can document reef behaviour adequately so as to inform reef growth models and sea level curves the cores also emphasize potential problems in u series dates for corals within a shallow ca 1 5 m zone beneath the reef flat apparent age inversions restricted to that active diagenetic zone may reflect remobilization and concentration of th in irregularly distributed microbialites or biofilms that were missed during sample vetting importantly the th containing contaminant causes ages to appear too old rather than too young as would be expected from younger cement

an ice water vortex at the edge of the east greenland current during the y mer 80 cruise in august 1980 we observed an ice feature of 60 km diameter having the shape of a breaking wave it lay at the edge of the east greenland drift ice in fram strait with its center at 79 15 n 00 38 e and the wave was breaking upstream relative to the east greenland current two conductivity temperature and depth sections across the feature in n s and e w directions revealed warm up to 4 3 c water some 60 km inside the polar front in lenses centered at 40 m depth but with an effect to beyond 600 m the temperature anomalies were accompanied by salinity anomalies so that there was little net effect on the density profile the form of the sections together with the ice distribution observed by vertical photography from a helicopter and surface motion observed by tracking four radar transponders all suggest that the feature is a vortex produced by an instability in the polar front it has similar characteristics to vortices investigated experimentally and theoretically by griffiths and linden 1981a b 1982 and observationally by wadhams et al 1979

absolute transport estimates of total and individual water masses in the northern greenland sea derived from hydrographic and acoustic doppler current profiler measurements 1 conductivity temperature depth transects across the greenland sea and fram strait provide geostrophic shear velocity profiles which were absolutely referenced using the simultaneous measurements from a vessel mounted acoustic doppler current profiler the measurements are performed mainly in 1997 with supplements in 1998 1995 and 1994 the observations confirm that all currents within the area have a strong barotropic component so that calculations based on the geostrophic method underestimate the transports considerably particulars for the transports of mass and heat are given for all individual and total water masses in the area meanders and eddies on horizontal scales between 20 and 70 km affect the total transport in the west spitsbergen current significantly the atlantic water transports range between 2 and 7 sv mainly dominated by the cross sectional area occupied by this water mass the total northward heat transport across 75 n is estimated as 54 7 tw and across 79 40 n as 42 tw in september 1997

timing and duration of the last interglacial evidence for a restricted interval of widespread coral reef growth abstract we report new mass spectrometric u series ages for eight last interglacial fossil reefs along the continental margin of western australia corals were selected in growth position from localities that are characterized by apparently low levels of diagenesis and relative tectonic stability so that the fossil reefs provide critical information on last interglacial sea levels without requiring corrections for tectonic movements in addition we have improved the constraint on the timing of onset of reef growth by recovering drill core coral from the base of the reefs uranium and thorium isotopes were measured with high levels of precision leading to improvements in age resolution and allowing samples which have undergone diagenetic exchange of uranium and thorium to be more easily identified and discarded these data supplement our previous results for rottnest island and leander point leading to more than seventy mass spectrometric u series ages from which constraints can be placed on the timing duration and character of the last interglacial sea level highstand reliable ages show that reef growth started contemporaneously at 128 1 ka along the entire western australian coastline while relative sea levels were at least 3 m above the present level because western australia is located far from the former penultimate glacial maximum ice sheets and are not significantly effected by glacial unloading these data constrain the timing of onset of the last interglacial period to 128 1 ka assuming reef growth started soon after sea level approached interglacial levels a unique regressive reef sequence at mangrove bay constrains the timing of termination of the last interglacial period to 116 1 ka the major episode of reef building however both globally and locally along the western australian coast is restricted to a very narrow interval occurring from 128 ka and 121 ka suggesting that global ocean surface temperatures were warm and or sea levels were stable enough to allow prolific reef growth only during the earlier part of the last interglacial

atlantic water advection versus sea ice advances in the eastern fram strait during the last 9 ka multiproxy evidence for a two phase holocene a sediment core from the west spitsbergen continental margin was studied to reconstruct climate and paleoceanographic variability during the last 9 ka in the eastern fram strait our multiproxy evidence suggests that the establishment of the modern oceanographic configuration in the eastern fram strait occurred stepwise in response to the postglacial sea level rise and the related onset of modern sea ice production on the shallow siberian shelves the late early and mid holocene interval 9 to 5 ka was generally characterized by relatively unstable conditions high abundance of the subpolar planktic foraminifer species turborotalita quinqueloba implies strong intensity of atlantic water aw inflow with high productivity and or high aw temperatures resulting in a strong heat flux to the arctic a series of short lived cooling events 8 2 6 9 and 6 1 ka occurred superimposed on the warm late early and mid holocene conditions our proxy data imply that simultaneous to the complete postglacial flooding of arctic shallow shelves and the initiation of modern sea ice production strong advance of polar waters initiated modern oceanographic conditions in the eastern fram strait at 5 2 ka the late holocene was marked by the dominance of the polar planktic foraminifer species neogloboquadrina pachyderma a significant expansion of sea ice icebergs and strong stratification of the water column although planktic foraminiferal assemblages as well as sea surface and subsurface temperatures suggest a return of slightly strengthened advection of subsurface atlantic water after 3 ka a relatively stable cold water layer prevailed at the sea surface and the study site was probably located within the seasonally fluctuating marginal ice zone during the neoglacial period

are catch up reefs an artefact of coring drill cores through modern coral reefs commonly show a time lag in reef initiation followed by a phase of rapid accretion to sea level from submerged foundations the so called catch up response but because of the difficulty of drilling in these environments core distribution is usually restricted to accessible areas that may not fully represent reef history especially if the reef initiated in patches or developed with a prograde or retrograde geometry as a consequence core data have the potential to give a misleading impression of reef development particularly with respect to the timing of initiation and response to sea level rise here we use computer models to simulate keep up reef development and from them quantify variations in the timing of reef initiation and accretion rate using mock cores taken through the completed simulations the results demonstrate that cores consistently underestimate the timing of reef initiation and overestimate the reef accretion rate so that statistically a core through a keep up reef will most likely produce a catch up pattern an initiation lag followed by a phase of rapid accretion to sea level this implies that catch up signatures may be an artefact of coring and that keep up reefs are significantly more common than previous core studies claim

marine geophysical evidence for former expansion and flow of the greenland ice sheet across the north east greenland continental shelf high resolution swath bathymetry and topas sub bottom profiler acoustic data from the inner and middle continental shelf of north east greenland record the presence of streamlined mega scale glacial lineations and other subglacial landforms that are formed in the surface of a continuous soft sediment layer the best developed lineations are found in westwind trough a bathymetric trough connecting nioghalvfjerdsfjorden gletscher and zachariae isstrom to the continental shelf edge the geomorphological and stratigraphical data indicate that the greenland ice sheet covered the inner middle shelf in north east greenland during the most recent ice advance of the late weichselian glaciation earlier sedimentological and chronological studies indicated that the last major delivery of glacigenic sediment to the shelf and fram strait was prior to the holocene during marine isotope stage 2 supporting our assertion that the subglacial landforms and ice sheet expansion in north east greenland occurred during the late weichselian glacimarine sediment gravity flow deposits found on the north east greenland continental slope imply that the ice sheet extended beyond the middle continental shelf and supplied subglacial sediment direct to the shelf edge with subsequent remobilisation downslope these marine geophysical data indicate that the flow of the late weichselian greenland ice sheet through westwind trough was in the form of a fast flowing palaeo ice stream and that it provides the first direct geomorphological evidence for the former presence of ice streams on the greenland continental shelf the presence of streamlined subglacially derived landforms and till layers on the shallow awi bank and northwind shoal indicates that ice sheet flow was not only channelled through the cross shelf bathymetric troughs but also occurred across the shallow intra trough regions of north east greenland collectively these data record for the first time that ice streams were an important glacio dynamic feature that drained interior basins of the late weichselian greenland ice sheet across the adjacent continental margin and that the ice sheet was far more extensive in north east greenland during the last glacial maximum than the previous terrestrial glacial reconstructions showed

large scale oceanography in fram strait during the 1984 marginal ice zone experiment the pattern of large scale circulation in fram strait during summer 1984 is inferred from hydrographic data and water mass analysis and direct current observations by use of surface and subsurface floats the west spitsbergen current carrying warm and salty atlantic water splits into several branches two flowing northward into the arctic ocean and two turning westward causing a recirculation across the main axis of fram strait the individual flow paths are topographically controlled suggesting a strong barotropic component of the circulation

growth history of shallow water carbonates control of accommodation on ecological and depositional processes we explore the role played on the growth of shallow water carbonates by changes in accommodation using case studies from late quaternary to modern carbonate environments i e coral reefs and carbonate platforms and ramps accommodation appears not to influence either primary productivity or community structure k versus r strategists as these are directly governed by nutrient supply but it does control submarine depositional profiles and their stratigraphic expression i e volumetric sedimentary partitioning the growth of communities from incipient to senescent stages is dictated by relative rates of sea level variations although ambient temperatures and trophic conditions may modify the community response a decrease or stabilization of accommodation favours lateral migration thus generating ecological and sedimentary innovations organic carbon production tends to be positively correlated to that of carbonate both declining as accommodation decreases shallow water carbonates develop as a result of the interplay of factors including the types and rates of biological and physical processes applying depositional models of recent shallow water carbonates to the interpretation of ancient carbonate platforms first needs to acknowledge the respective role of the two contrasting phases that operated during the post glacial sea level rise an earlier fast rising phase versus a later slowly rising to stabilizing phase the period of relative sea level stabilization i e the past 6 000 years appears a relevant reference for still stand related carbonate systems furthermore the oligotrophic nutrient model a dominant feature of the modern shallow water tropics can be used as an analogue in reconstructing carbonate growth histories during greenhouse episodes of earth history

first observations of the interaction of ocean swell with sea ice using satellite radar altimeter data the action of ocean waves and swell on sea ice in the marginal ice zone miz controls the size distribution of ice floes and thus affects ice dynamics and the thermodynamics of ice growth and decay an understanding of ice processes is important because of the influence of the sea ice cover on high latitude weather and global climate1 also long term changes in average sea ice extent could provide a sensitive indication of climatic change if the degree of shorter term variability were better understood2 previous observations of the propagation of swell within the ice pack have been limited in spatial and temporal extent3 6 here we present new results from the us seasat satellite which suggest that radar altimetry can provide a powerful means of global synoptic monitoring of the interaction between ocean and ice

physical and biological characteristics of the pelagic system across fram strait to kongsfjorden abstract the fram strait is very important with regard to heat and mass exchange in the arctic ocean and the large quantities of heat carried north by the west spitsbergen current wsc influence the climate in the arctic region as a whole a large volume of water and ice is transported through fram strait with net water transport of 1 7 3 2 sv southward in the east greenland current and a volume ice flux in the range of 0 06 0 11 sv the mean annual ice flux is about 866 000 km2 yr 1 the kongsfjorden krossfjorden fjord system on the coast of spitsbergen or at the eastern extreme of fram strait is mainly affected by the northbound transport of water in the wsc mixing processes on the shelf result in transformed atlantic water in the fjords and the advection of atlantic water also carries boreal fauna into the fjords the phytoplankton production is about 80 g c m 2 yr 1 in fram strait and has been estimated both below and above this for kongsfjorden the zooplankton fauna is diverse but dominated in terms of biomass by calanoid copepods particularly calanus glacialis and c finmarchicus other important copepods include c hyperboreus metridia longa and the smaller more numerous pseudocalanus p minutus and p acuspes microcalanus m pusillus and m pygmaeus and oithona similis the most important species of other taxa appear to be the amphipods themisto libellula and t abyssorum the euphausiids thysanoessa inermis and t longicaudata and the chaetognaths sagitta elegans and eukrohnia hamata a comparison between the open ocean of fram strait and the restricted fjord system of kongsfjorden krossfjorden can be made within limitations the same species tend to dominate but the fram strait zooplankton fauna differs by the presence of meso and bathypelagic copepods the seasonal and inter annual variation in zooplankton is described for kongsfjorden based on the record during july 1996 2002 the ice macrofauna is much less diverse consisting of a handful of amphipod species and the polar cod the ice associated biomass transport of ice amphipods was calculated based on the ice area transport at about 3 55 106 ton wet weight per year or about 4 2 105 t c yr 1 this represents a large energy input to the greenland sea but also a drain on the core population residing in the multi year pack ice myi in the arctic ocean a continuous habitat loss of myi due to climate warming will likely reduce dramatically the sympagic food source the pelagic and sympagic food web structures were revealed by stable isotopes the carbon sources of particulate organic matter pom being ice pom and pelagic pom revealed different isotopic signals in the organisms of the food web and also provided information about the sympagic pelagic and pelagic benthic couplings the marine food web and energy pathways were further determined by fatty acid trophic markers which to a large extent supported the stable isotope picture of the marine food web although some discrepancies were noted particularly with regard to predator prey relationships of ctenophores and pteropods

methods for digital analysis of avhrr sea ice images algorithms for obtaining information on sea ice conditions from advanced very high resolution radiometer avhrr digital imagery are presented these algorithms comprise three steps discrimination of cloud covered areas from ice covered and open water areas estimation of ice concentration and measurement of the sizes of ice floes and open water areas polynyas within the ice field for ice water cloud discrimination a dynamic threshold technique is applied to six combinations of the five spectral channels of the avhrr this results in an image that is useful for ice analyses to derive ice concentration estimates a simple linear relationship between pixel intensity values and amount of ice cover is applied to the visible channel reflectance data the method for obtaining size frequency distributions is based on a size transform of binary realizations of the ice concentration result and is equally applicable to measuring polynyas and ice floes

discovery of a submerged relic reef and shoreline off grand cayman further support for an early holocene jump in sea level abstract drilling close to the base of a submerged sea cliff on the terraced eastern shelf of grand cayman has revealed a relic acropora palmata reef at a depth of 21 m below msl ten cores from its crest are principally composed of cobble sized clasts of a palmata set in a matrix of cemented skeletal grainstone the clasts have a distinctive succession of encrusters that indicate rapid burial a photophilic association of crustose coralline algae foraminifera and vermetid gastropods superimposed by a cryptic association of sclerosponges foraminifera and serpulids in addition to rapid burial u th thermal ionization mass spectrometer tims dating of coral clasts within 1 m of the relic reef surface indicates minor temporal mixing with ages between 8 9 and 8 1 ka such mixing and rapid burial is consistent with a hurricane deposit and is identical to deposits found on the crests of modern reefs in relation to its age the preservation of a 18 5 m intertidal notch cut into the submerged sea cliff on the western shelf of grand cayman implies that the crest of the relic reef has been lowered 1 5 2 m by marine abrasion bioerosion at a rate of 0 25 mm yr 1 reconstructing this eroded section using average holocene accretion rates indicates that the reef likely ceased accreting at 7 6 ka at a depth of 19 m comparing these data with other relic reefs in the caribbean indicates that the relic reef on grand cayman died within 160 years of relic reefs on barbados st croix st thomas and north florida this narrow interval of reef demise also coincides with the time when modern reefs were establishing themselves some 4 9 m higher upslope a fact that can only be resolved by invoking a rapid 6 m jump in sea level 7 5 ka ago such a jump would also account for two unexplained events around this time the restricted interval of global delta initiation and the catastrophic flooding of the glacially lowered black sea

an inflection in the rate of early mid holocene eustatic sea level rise a new sea level curve from singapore this study presents a sea level curve from 9500 to 6500 cal bp for the farfield location of singapore on the sunda shelf in southeast asia the curve is based on more than 50 radiocarbon dates from elevations of 1 43 m to 15 09 m representing sea level index points in intertidal mangrove and shallow marine sediments deposited by sea level rise accompanying deglaciation the results indicate that mean sea level rose rapidly from around 17 m at 9500 cal bp to around 3 m by 8000 cal bp after this time the data suggest but do not unequivocally prove that the rate of sea rise slowed for a period of 300 500 years centred on 7700 cal bp shortly after the cessation of meltwater input to the oceans from the northern hemisphere renewed sea level rise amounting to 3 5 m began around 7400 cal bp and was complete by 7000 cal bp the existence of an inflection in the rate of sea level rise with a slow down centred on 7700 cal bp is broadly consistent with other available sea level curves over this interval and is supported by evidence of stable shorelines and delta initiation elsewhere at this time as well as evidence of comparatively rapid retreat of the west antarctic ice sheet beginning around 7500 cal bp stepped sea level rise occurring shortly after 7500 cal bp and also earlier during deglaciation may have served to focus significant post glacial episodes of human maritime coastal dispersal into comparatively narrow time intervals

thermal ionization mass spectrometry u series dating of a hominid site near nanjing china mass spectrometric u series dating of speleothems from tangshan cave combined with ecological and paleoclimatic evidence indicates that nanjing man a typical homo erectus morphologically correlated with peking man at zhoukoudian should be at least 580 k y old or more likely lived during the glacial oxygen isotope stage 16 similar to 620 ka such an age estimate which is similar to 270 ka older than previous electron spin resonance and alpha counting u series dates has significant implications for the evolution of asian h erectus dentine and enamel samples from the coexisting fossil layer yield significantly younger apparent ages that of the enamel sample being only less than one fourth of the minimum age of nanjing man this suggests that u uptake history is far more complex than existing models can handle as a result great care must be taken in the interpretation of electron spin resonance and u series dates of fossil teeth

late quaternary structure and development of the northern ningaloo reef australia ningaloo reef situated on the central west coast is australia s largest fringing reef system extending southward from 22 s for over 200 km its narrow lagoon is backed by a coastal plain which is largely composed of an emergent last interglacial reef on the flank of folded tertiary limestones the west facing reef is exposed to strong oceanic swells across a narrow 8 km continental shelf climatic aridity cyclones tsunamis and the poleward flowing leeuwin current all influence the reef system seismic profiling and a coring and dating program along a transect through a reef pass indicate two periods of reef development in the northern part of the reef holocene and last interglacial seaward of the crest the holocene reef forms either a prominent 500 m wide bulge with 10 m of relief and an abrupt seaward slope or a series of discrete patch reefs holocene reef development is limited to depths of less than 30 m and reaches a maximum thickness of ca 10 15 m below the reef crest u th tims dates from distal parts of the last interglacial section between 18 and 36 m give ages toward the end of the high stand 120 115 ka last interglacial reef growth was more extensive of the two filling much of the available accommodation space perhaps as a result of a stronger leeuwin current this substrate subsequently provided an antecedent foundation for holocene reef development

barotropic instability in the west spitsbergen current 1 barotropic instability in the shoreward branch of the west spitsbergen current is investigated on the basis of data from an array of current meter moorings along 78 83 n across the upper continental slope and shelf break west of svalbard the slowly varying background current profile is modeled as an along slope asymmetric jet anchored to the shelf break numerical linear stability analyses are performed on the idealized current profile and topography revealing the characteristic period wavelength and growth rate of unstable vorticity waves detailed analysis of the ambient current profile in 2007 2008 shows that unstable conditions are present during 40 of the 10 month measurement record depending on the localization width and amplitude of the current jet the resulting vorticity waves are localized at the shelf break and are able to exchange water masses across the oceanic arctic front typical wavelengths and periods are 20 40 km and 40 70 h respectively wavelet coherence and complex demodulation analyses of the current meter data confirm that transient signals of similar periodicity as predicted by the stability analysis exist in the data record prominently during the winter and spring months estimates of the heat loss contribution from isopycnal diffusion reach 1 4 tw during the time intervals when unstable vorticity waves are active at the shelf break implying that the dynamics of the west spitsbergen current play a significant role in the cooling process of the atlantic water on the way to the arctic ocean this cooling corresponds to an along shelf cooling rate of 0 08 c per 100 km

a high precision record of mid late holocene sea level events from emergent coral pavements in the houtman abrolhos islands southwest australia early work on sea levels in southwest australia claimed to recognise a holocene sea level highstand which was not seen in better known sea level records elsewhere at the time more recent work has confirmed that a mid holocene highstand occurred about 6 kyr ago as new data on oscillating sea levels from the region have recently been published a high continuity precisely dated and accurately surveyed record was obtained from emergent coral pavements in the leeward houtman abrolhos islands serventy island a tectonically stable region from where good quality holocene sea level data have been previously obtained from corals from the mid holocene highstand ca 7 u th kyr ago sea level declined linearly during the remainder of the holocene as the carbonate platform prograded leewards hydro isostatic controls are probably significant in the record c 2005 elsevier ltd and inqua all rights reserved

the interaction of an ocean eddy with an ice edge ocean jet in a marginal ice zone remotely sensed images in the east greenland current marginal ice zone region indicate a variety of mesoscale motions these range from isolated monopoles and dipoles to multiple eddy fields recent observations indicate that many of the eddies may be advected into the region from the west spitsbergen current region they then interact with the east greenland current marginal ice zone and its associated along ice edge jet in this paper we illustrate how the ice floe fields can evolve during the interaction of an ocean eddy with an along ice edge ocean jet the effects of eddy sense of rotation flow strength and bottom topography are considered in barotropic and baroclinic two layer numerical experiments initially barotropic experiments involve the combined effects of flat bottom eddy jet interactions and eddy topography interactions over a flat bottom anticyclones interact with the cyclonically sheared side of the jet and move seaward exporting ice away from the ice edge in a dipolar distribution cyclones move toward the jet and are advected downstream a second dipole formation mechanism is associated with eddy topography interaction and is a consequence of the shallow pycnocline depth of the region rapid topographic rossby wave radiation in the lower layer spreads energy along slope and upslope downslope for cyclones anticyclones the upper ocean response to this process is a dipole which propagates parallel to the ice edge with shallow water to the left topographic eastward jet induced and topography induced eddy propagation tendencies combine to enhance cyclone jet interaction and limit anticyclone jet interactions the dipole formation associated with eddy topography interaction is weakened by the presence of the jet but not eliminated eddy induced distortions in the ice edge are suppressed by the stabilizing effect of topography on the jet sensitivity of the initially barotropic results to variation in the rossby number and degree of topographic slope illustrates that eddies are more efficient in producing ice edge distortions for stronger flows and weaker topographic slopes for initially baroclinic simulations over topography results are comparable to flat bottom cases strong upper layer eddy jet interactions can occur independent of topographic effects which are constrained to the lower layer

crack seal fibre growth mechanisms and their significance in the development of oriented layer silicate microstructures abstract an analysis of crack seal fibre growth mechanisms has shown two important implications of the crack seal process for the interpretation of microstructures in low grade metamorphic rocks 1 1 the ability of fibre growth to track the incremental separation history of crack walls depends on details of the nucleation and growth mechanisms 2 2 fibrous crystals may develop cristallographic preferred orientations in certain crack seal situations the microstructures of layer silicates and associated phases developed in several examples of syntectonic intragranular microfracture sites and veins indicates that layer silicate 001 and grain shape preferred orientation can develop during crack seal deformation by oriented growth mechanisms during successive crack seal increments preferred orientation may develop in response to an interaction between anisotropic growth kinetics and the displacement history resulting in preferential rejoining by syntaxial overgrowth of pulled apart grains having fast growth directions parallel to the incremental displacement direction across a microcrack preferred orientation may also be developed and enhanced in crack seal growth sites by overgrowth of previously oriented layer silicates in the microcrack walls in this case the crystallographic preferred orientation need not be simply related to the displacement history during crack seal fibre growth since crack seal processes may operate on all scales down to the minimum size of a microfracture in a deforming rock such mechanisms of layer silicate preferred orientation development are expected to be very significant in developing and enhancing foliation during deformation involving microfracture and solution transfer processes

relationships between gold concentration and structure in quartz veins from the hodgkinson province northeastern australia the hodgkinson province is a tract of multiply deformed silurian devonian rocks in north queensland australia gold bearing quartz veins from the west normanby goldfield in the northern hodgkinson province were emplaced during the permian d4 event broadly coeval with regional granite emplacement taylors fault a major structure that formed during d2 hosts the veins which infill dilatational jogs opened during sinistral normal reactivation of the fault in d4 veins contain graphitic laminations that formed when fault planes segmented wallrocks adjacent to the veins producing tabular clasts that were tectonically sliced into the reefs laminations are the result of progressive shear strain associated with continued movement on the faults which caused strain enhanced dissolution of silicate minerals and residual graphite enrichment in the clasts this process produced graphite coated shear planes that delimit zones of grain size reduction in the veins laminations commonly contain stylolites which nucleated on pronounced sinuosities of the shear planes due to progressive shortening during d4 gold particles have preferentially nucleated in zones of relatively coarser grained quartz adjacent to the shear planes where shortening strain caused microfracturing and allowed fluid access gold may have been introduced with the quartz but was redistributed within the reefs and localized along the laminations by the effects of synchronous progressive deformation regionally gold deposits show close spatial relationships with granite plutons of the permian whypalla supersuite relationships in the west normanby gold field support a regional model of reef emplacement and gold mineralization during the permian d4 event

global sea level fluctuations during the last interglaciation mis 5e the geomorphology and morphostratigraphy of numerous worldwide sites reveal the relative movements of sea level during the peak of the last interglaciation marine isotope stage mis 5e assumed average duration between 13072 and 11972 ka because sea level was higher than present deposits are emergent exposed and widespread on many stable coastlines correlation with mis 5e is facilitated by similar morphostratigraphic relationships a low degree of diagenesis uranium thorium u th ages and a global set of amino acid racemization aar data this study integrates information from a large number of sites from tectonically stable areas including bermuda bahamas and western australia and some that have experienced minor uplift 2 5 m 100 ka including selected sites from the mediterranean and hawaii significant fluctuations during the highstand are evident at many mis 5e sites revealed from morphological stratigraphic and sedimentological evidence rounded and flat topped curves derived only from reef tracts are incomplete and not representative of the entire interglacial story despite predictions of much different sea level histories in bermuda the bahamas and western australia due to glacio and hydro isostatic effects the rocks from these sites reveal a nearly identical record during the last interglaciation the last interglacial highstand is characterized by several defined sea level intervals slis that include sli 1 post glacial mis 6 5e termination ii rise to above present before 130 ka sli 2 stability at 2 to 3 m for the initial several thousand years 130 to 125 ka during which fringing reefs were established and terrace morphology was imprinted along the coastlines sli 3 a brief fall to near or below present around 125 ka sli 4 a secondary rise to and through 3 4 m 124 to 122 ka followed by sli 5 a brief period of instability 120 ka characterized by a rapid rise to between 6 to 9 m during which multiple notches and benches were developed and sli 6 an apparently rapid descent of sea level into mis 5d after 119 ka u th ages are used to confirm the last interglacial age of the deposits but unfortunately in only two cases was it possible to corroborate the highstand subdivisions using radiometric ages sea levels above or at present were relatively stable during much of early mis 5e and the last 6 7 ka of mis 1 encouraging a comparison between them the geological evidence suggests that significant oceanographic and climatic changes occurred thereafter midway through and continuing through the end of mis 5e fluctuating sea levels and a catastrophic termination of mis 5e are linked to the instability of grounded and marine based ice sheets with the greenland gis and west antarctic wais ice sheets being the most likely contributors late mis 5e ice volume changes were accompanied by oceanographic reorganization and global ecological shifts and provide one ominous scenario for a greenhouse world r 2007 elsevier ltd all rights reserved

freshwater forcing of abrupt climate change during the last glaciation large millennial scale fluctuations of the southern margin of the north american laurentide ice sheet occurred during the last deglaciation when the margin was located between about 43 and 49 n fluctuations of the ice margin triggered episodic increases in the flux of freshwater to the north atlantic by rerouting continental runoff from the mississippi river drainage to the hudson or st lawrence rivers we found that periods of increased freshwater flow to the north atlantic occurred at the same time as reductions in the formation of north atlantic deep water thus providing a mechanism for observed climate variability that may be generally characteristic of times of intermediate global ice volume