mechanisms of crustal anatexis a geochemical study of partially melted metapelitic enclaves and host dacite se spain to shed light on the mechanisms of crustal anatexis a detailed geochemical study has been conducted on minerals and glasses of quenched anatectic metapelitic enclaves and their host peraluminous dacites at el hoyazo se spain anatectic enclaves composed of plagioclase biotite sillimanite garnet glass k feldspar cordierite graphite formed during the rapid heating and overstepped melting of a greenschist facies metapelite and finally equilibrated at 850 508c and 5 7 kbar glass appears as melt inclusions within all mineral phases and in the matrix of the enclaves and has a major element composition similar to that of peraluminous leucogranites melt inclusions and matrix glasses have normative quartz orthoclase albite compositions that plot in the vicinity of h2o undersaturated haplogranite eutectics melt inclusions show some compositional variability with high li cs and b low y first row transition elements frte and rare earth elements ree and zircon and monazite saturation temperatures of 665 7508c they are interpreted as melts produced by muscovitebreakdown melting reactions at the onset of the process of rapid melting and mostly under h2o undersaturated conditions compared with melt inclusions matrix glasses show less compositional variability lower large ion lithophile element contents higher y frte and ree and higher zircon and monazite saturation temperatures 695 8158c they are interpreted as former melts recording the onset of biotite dehydration melting matrix glasses in the dacite are compositionally different from glasses in the enclaves hence the genetic connection between metasedimentary enclaves and dacite is not as straightforward as previous petrographic and bulk major element data suggest this opens the possibility for some alternative interpretation this study shows the following 1 melt inclusions provide a window of information into the prograde evolution of anatexis in the enclaves 2 melting occurred for the most part under h2o undersaturated conditions even if because of the rapid heating the protolith preserved most of the structurally bound h2o contained at greenschist facies up to the beginning of anatexis such that the excess h2o maximized the amount of h2o undersaturated melt generated during anatexis 3 although a large proportion of accessory minerals are currently shielded within major mineral phases they have progressively dissolved to a considerable extent into the melt phase along the prograde anatectic path as indicated by the relative clustering of accessory mineral saturation temperatures and closeness of these temperatures to those of potential melting reactions 4 the dacite magma was probably produced by coalescence of melts

multi method dating comparison for mid pleistocene rangitawa tephra new zealand abstract the rangitawa tephra a widespread mid pleistocene marker in the new zealand region is dated by fission track thermoluminescence tl infrared stimulated luminescence irsl k ar and single crystal laser fusion sclf 40 ar 39 ar methods as well as by matching to the astronomical timescale via oxygen isotope stratigraphy in deep sea cores fifty one independent numerical age estimates for rangitawa tephra range from 173 to 456 ka however only 15 of these results are considered to be reliable five zircon fission track results four isothermal plateau fission track itpft age estimates on glass shards four sclf 40 ar 39 ar results and two astronomically calibrated age estimates from deep sea cores the weighted mean of the nine reliable fission track age determinations is 345 12 ka in excellent agreement with the weighted mean of 340 7 ka for the two reliable astronomically calibrated age estimates the weighted mean of the four reliable 40 ar 39 ar results 302 8 ka is significantly younger and further ar ar dating is recommended to investigate this difference since the tl and irsl dating methods are experimental for sediments beyond 200 ka we have excluded these from the group of reliable age results tl and irsl results on dunesand appear to be systematically younger than tl results on loess and loess results depend upon analytical procedures

the 1997 1998 oceanic el nino signal along the southeast and northeast pacific boundaries an altimetric view changes in the sea surface heights ssh and geostrophic currents along the eastern boundaries of the pacific north central and south america are examined during the 1997 1998 el nino using altimeter data and proxy winds these show that symmetric ssh signals left the equator and propagated into both hemispheres in two episodes with primary periods of high equatorial ssh during may july and october december 1997 these are the distant signals from the mid latitude perspective as the signals spread poleward in each hemisphere their loss of symmetry demonstrates the degree to which they were altered by topographic features local winds and or local currents the first four eofs are calculated for 2 d ssh fields in 10 wide strips along the eastern margins 60 n 60 s and extending out along the equator from the coast to 110 w these account for approximately 40 of the overall variability and represent the main features of the seasonal cycles and el nino interannual variability snapshots of the 2 d ssh fields depict the structure of the el nino signal at different phases of its evolution

mapping the u s west coast surface circulation a multiyear analysis of high frequency radar observations signals with phase speeds of o 10 and o 100 to 300 km day 1 and time scales of 2 to 3 weeks the signals with slow phase speed are only observed in southern california it is hypothesized that they are scattered and reflected by shoreline curvature and bathymetry change and do not penetrate north of point conception the seasonal transition of alongshore surfacecirculationforcedbyupwelling favorablewindsandtheirrelaxationiscapturedinfine detail submesoscaleeddies identifiedusingflowgeometry haverossbynumbersof0 1to3 diameters in the range of 10 to 60 km and persistence for 2 to 12 days the hfr surface currents resolve coastal surface ocean variability continuously across scales from

pushing the boundaries glacial interglacial variability of intermediate and deep waters in the southwest pacific over the last 350 000 years glacial interglacial changes in southern ocean s air sea gas exchange have been considered as important mechanisms contributing to the glacial interglacial variability in atmospheric co2 hence understanding past variability in southern ocean intermediate to deep water chemistry and circulation is fundamental to constrain the role of these processes on modulating glacial interglacial changes in the global carbon cycle our study focused on the glacial interglacial variability in the vertical extent of southwest pacific antarctic intermediate water aaiw we compared carbon and oxygen isotope records from epibenthic foraminifera of sediment cores bathed in modern aaiw and upper circumpolar deep water ucdw 943 2066 m water depth to monitor changes in water mass circulation spanning the past 350 000 years we propose that pronounced freshwater input by melting sea ice into the glacial aaiw significantly hampered the downward expansion of southwest pacific aaiw consistent with climate model results for the last glacial maximum this process led to a pronounced upward displacement of the aaiw ucdw interface during colder climate conditions and therefore to an expansion of the glacial carbon pool

oceanographic and climatic changes over the past 160 000 years at deep sea drilling project site 594 off southeastern new zealand southwest pacific ocean high resolution textural carbonate microfossil and oxygen 18o and carbon 13c stable isotopic analyses are presented for the late quaternary isotopic stages 1 to 6 interval of a core at deep sea drilling project site 594 situated just south of the present subtropical convergence in northernmost subantarctic surface waters on the southern flank of chatham rise in the southwest pacific downcore alternations of pelagic and hemipelagic oozes correspond to interglacial and glacial episodes respectively interglacial oozes contain a northern subantarctic assemblage of planktonic foraminifera with rare cool subtropical species while glacial oozes are characterized by species typical of southern most subantarctic waters and include radiolaria with affinity for antarctic waters the planktonic 18o record for the site supports a 3 6 c temperature change in near surface waters between interglacial and glacial stages and indicates that during stage 5e the near surface waters were about 1 c warmer than at present a pronounced cooling during stage 5d matches that of the vostok ice core d record and negative excursions at the end of stages 2 and 6 support a southern latitude warming preceding northern hemisphere deglaciation benthic foraminifera typical of cold intermediate to deep waters can increase dramatically in abundance in the hemipelagic ooze intervals when 18o results suggest a temperature drop in glacial stage bottom waters of 2 4 c possibly a result of upward displacement of antarctic intermediate water by circumpolar deep water at the site the foraminiferal 13c records support a reduced influence of north atlantic deep water in the southwest pacific during glacial stages when nutrient enhancement occurred in both bottom and surface waters despite the pronounced changes between interglacial and glacial conditions inferred at site 594 contributed to by a substantial northward shift by at least 5 of latitude in the position of the antarctic convergence south of new zealand during glacial episodes we conclude that the subtropical convergence remained locked to chatham rise approximately 44 s throughout stages 1 to 6 major compression of the intervening belt of subantarctic water during glacial episodes and the associated very steep thermal gradients and intensified atmospheric and oceanic circulation patterns that developed in this part of the southwest pacific account for the harsh frigid environment reported for on land southern new zealand at these times

glacial interglacial ocean climate variability from planktonic foraminifera during the mid pleistocene transition in the temperate southwest pacific odp site 1123 abstract planktonic foraminiferal assemblages and artificial neural network estimates of sea surface temperature sst at odp site 1123 41 47 2 s 171 29 9 w 3290 m deep east of new zealand reveal a high resolution history of glacial interglacial g i variability at the subtropical front stf for the last 1 2 million years including the mid pleistocene climate transition mpt most g i cycles of 100 kyr duration have short periods of cold glacial and warm deglacial climate centred on glacial terminations followed by long temperate interglacial periods during glacial deglacial transitions maximum abundances of subantarctic and subtropical taxa coincide with sst minima and maxima and lead ice volume by up to 8 kyrs such relationships reflect the competing influence of subantarctic and subtropical surface inflows during glacial and deglacial periods respectively suggesting alternate polar and tropical forcing of southern mid latitude ocean climate the lead of ssts and subtropical inflow over ice volume points to tropical forcing of southern mid latitude ocean climate during deglacial warming this contrasts with the established hypothesis that southern hemisphere ocean climate is driven by the influence of continental glaciations based on wholesale changes in subantarctic and subtropical faunas the last 1 2 million years are subdivided into 4 distinct periods of ocean climate 1 the pre mpt 1185 870 ka has high amplitude 41 kyr fluctuations in sst superimposed on a general cooling trend and heightened productivity reflecting long term strengthening of subantarctic inflow under an invigorated antarctic circumpolar current 2 the early mpt 870 620 ka is marked by abrupt warming during mis 21 followed by a period of unstable periodicities within the 40 100 kyr orbital bands decreasing sst amplitudes and long intervals of temperate interglacial climate punctuated by short glacial and deglacial phases reflecting lower meridional temperature gradients 3 the late mpt 620 435 ka encompasses an abrupt decrease in the subantarctic inflow during mis 15 followed by a period of warm equable climate poorly defined low amplitude g i variations in ssts during this interval are consistent with a relatively stable stf and evenly balanced subantarctic and subtropical inflows possibly in response to smaller less dynamic polar icesheets 4 the post mpt 435 0 ka is marked by a major climatic deterioration during mis 12 and a return to higher amplitude 100 kyr frequency sst variations superimposed on a long term trend towards cooler ssts and increased mixed layer productivity as the subantarctic inflow strengthened and polar icesheets expanded

dinoflagellate cysts from sediment traps deployed in the bellingshausen weddell and scotia seas antarctica dinoflagellate cysts have been recovered from six long term 1 2 yr sediment trap moorings deployed in the bellingshausen weddell and scotia seas antarctica these traps mostly moored near the sea bed to sample the nepheloid layer were located both within and to the north of the maximum sea ice limit the numbers of cysts together with the composition of the assemblages reinforce the importance of the maximum sea ice limit as a modern biogeographic boundary for the distribution of dinoflagellate cysts cysts derived from heterotrophic dinoflagellates make up the highest proportions within the assemblages recovered from the traps one trap sampled the export production revealing little difference in cyst flux over those sampling the nepheloid layer cyst flux appears to be highest in areas closest to the antarctic convergence north of the maximum sea ice limit and to high nutrient availability there are however differences between the sediment trap assemblages and those recovered from core top samples at the same or nearby sites these differences in the greater number of cysts and in the higher numbers of round brown protoperidinium cysts in the traps may reflect annual differences in the primary productivity and or cyst production in the area in some areas the sediment record may preserve little information about local surface water productivity because of the activity of bottom water currents for example those arising from the antarctic circumpolar current

southern ocean seasonal temperature and subtropical front movement on the south tasman rise in the late quaternary 1 the subtropical front stf marking the northern boundary of the southern ocean has a steep gradient in sea surface temperature sst of approximately 4c over 0 5 of latitude presently in the region south of tasmania the stf lies nominally at 47s in the summer and 45s in the winter we present here sst reconstructions in a latitudinal transect of cores across the south tasman rise southeast of australia during the late quaternary sst reconstructions are based on two paleotemperature proxies alkenones and faunal assemblages which are used to assess past changes in sst in spring and summer the north south alignment in core locations allows reconstruction of movement of the stf over the last 100 ka surface water temperatures during the last glaciation in this region were 4c colder than today additional temperature changes greater in magnitude than 4c seen in individual cores can be attributed to changes in the water mass overlying the core site caused by the movement of the front across that location during the penultimate interglacial sst was 2c warmer and the stf was largely positioned south of 47s movement of the stf to the north occurred during cool climate periods such as the last marine isotope stages 3 and 4 in the last glaciation the front was at its farthest north position becoming pinned against the tasmanian landmass it moved south by 4 latitude to 47s in summer during the deglaciation but remained north of 45s in spring throughout the early deglaciation after 11 ka b p inferred invigoration of the east australia current appears to have pushed the stf seasonally south of the east tasman plateau until after 6 ka b p when it achieved its present configuration

distribution of organic walled marine and terrestrial palynomorphs in surface sediments offshore eastern new zealand organic walled dinoflagellate cyst dinocyst and terrestrial spore pollen assemblages are analysed from 38 modern surface sediments offshore eastern new zealand from 33 to 54 s water depths of 79 to 4680 m and spanning the prominent chatham rise the most diverse abundant and best preserved marine and terrestrial assemblages are observed on the northern flank of chatham rise coincident with the subtropical front region being an area of enhanced biological activity and primary productivity dinocyst assemblages are dominated by the gonyaulacoid autotrophic taxa impagidinium nematospheropsis labyrinthus operculodinium centrocarpum spiniferites and peridinioid heterotrophic brigantedinium taxa with preferences for cooler e g selenopemphix antarctica and warmer e g impagidinium strialatum water masses are identified in distribution records and canonical correspondence analysis of the nine environmental parameters measured dinocyst assemblages were strongly correlated to sea surface temperature february and chlorophyll a autumn terrestrial spores and pollen dominate palynomorph assemblages in many sites and primarily reflect the presence of lowland podocarp broadleaf forest of onshore eastern new zealand spores and bisaccate pollen dominate assemblages with angiosperm pollen comprising up to 10 in the chatham rise area pollen from plants restricted to northern regions has been transported south via subtropical surface currents this pilot study shows that palynomorph assemblages offshore new zealand including the high terrigenous input margin of eastern north island can provide suitable proxy records for characterisation of coeval marine and terrestrial changes through time

the influence of non equilibrium isotope fractionation on the quaternary calcareous nannofossil stable isotope signal in the southwest pacific ocean dsdp site 594 oxygen and carbon isotope values from calcareous nannofossils in the mid late quaternary brunhes interval of core from dsdp site 594 off eastern south island new zealand are compared with the 18o and 13c signal of planktic and benthic foraminifers from the same samples nannofossil 18o values appear strongly affected by non equilibrium fractionation in agreement with previous in vitro studies the nannofossil 18o and 13c signals show a strong down core cross correlation and a significant positive linear correlation this is interpreted as the result of kinetic isotope effects producing non equilibrium fractionation of both18o and13c a previously reported isotope stage carbon shift appears to be related mainly to a pacific wide reduction in the abundance of gephyrocapsids rather than to any significant change in the partitioning of carbon isotopes the strong correlation between nannofossil 18o and 13c can also be interpreted as being influenced by increased productivity during glacial intervals and decreased productivity during interglacials in subantarctic waters

geochemistry of the granitic rocks and their minerals from serra da estrela central portugal abstract several types of hercynian peraluminous granitic rocks ranging from biotite muscovite granodiorite to muscovite granite occur in the horst of serra da estrela variation diagrams of most major and trace elements of the rocks and biotites and cr and v of muscovites show fractionation trends however nb li rb k rb li mg variation diagrams of the rocks and muscovites and also of sn cs cs k of the muscovites indicate that the muscovite granite probably originated by another mechanism least squares analysis of major elements and modelling of trace elements indicate that the coarse grained porphyritic biotite muscovite granite granite porphyry and fine to medium grained muscovite biotite granite were derived from the granodiorite magma by fractional crystallization of plagioclase quartz and biotite emplacement of granodiorite magma took place at 3 5 3 kb and 720 c granites and granite porphyry probably originated about 690 c but were completely crystallized about 520 c o2 was about 10 17 for the granodiorite and hcl hf was higher whereas log h2o hcl was lower in the granodiorite than in the other granitic rocks of the fractionated series the coarse grained porphyritic biotite muscovite granite was hydrothermally altered between 400 350 c and 260 230 c at about 1 5 1 kb the hydrothermal fluids were probably mainly meteoric in origin but some fluids released during the late stage of granite solidification might also have been involved

dynamics of remotely forced intraseasonal oscillations off the western coast of south america abstract six years of sea level observations at six locations along the south american coast from peru to chile were analyzed at intraseasonal frequencies periodicity 1 2 months a high resolution low frequency numerical coastal model having realistic shelf and slope topography and bottom friction and forced by an equatorial signal was used to analyze the intraseasonal coastal dynamics at these latitudes the following results were obtained lagged correlations between sea level stations imply a sea level poleward propagation of 250 km day 1 the frictionless vertical wall theory poleward phase speed was considerably less at 216 km day 1 model runs with realistic bottom friction and shelf and slope bottom topography gave poleward phase speeds much closer to that observed for typical parameters the phase speed was 253 km day 1 both bottom friction and topography significantly affect the propagation speed past work has shown that the sea level amplitude should grow alongshore like f f coriolis

low frequency variability of the north pacific ocean the roles of boundary and wind driven baroclinic rossby waves 1 the effects of the sea level variability along the eastern boundary of the north pacific ocean including those associated with el nino southern oscillation have been considered an important factor in determining the low frequency large scale variability of the ocean interior through rossby waves generated at the eastern boundary this hypothesis is examined in this study using 8 years worth of the sea surface height observations made by the topex poseidon satellite the timescales of interest are longer than 90 days with the annual cycle removed the results indicate that the influence of the eastern boundary of the north pacific ocean has limited offshore extent varying from 3000 4000 km at 10 n to 200 300 km at 50 n the variability in the ocean interior is primarily driven by wind with only a minor influence from the boundary simulations of a linear two layer model of the ocean driven by wind stress curl are correlated with the observations the effects of wind forcing accumulate along the characteristics of long nondispersive rossby waves in the time longitude domain these wind driven rossby waves overwhelm the boundary driven waves in the ocean interior where there are only some small residual effects of the boundary driven waves however these small effects become clearer after the simulated wind driven variability is removed from the observations index terms 4556 oceanography physical sea level variations 4504 oceanography physical air sea interactions 0312 4215 oceanography general climate and interannual variability 3309 keywords rossby waves satellite altimetry el nino north pacific eastern boundary

thermal isolation of campbell plateau new zealand by the antarctic circumpolar current over the past 130 kyr 1 campbell plateau occupies a key position in the southwest pacific sector of the southern ocean the plateau confines and steers the antarctic circumpolar current acc along its flanks isolating the subantarctic plateau from cold polar waters oxygen and carbon isotope records from campbell plateau cores provide new records of water mass stratification for the past 130 kyr during glacial climes strengthening of the subantarctic front saf caused waters over the plateau flanks to be deeply mixed and 3 c cooler waters of the plateau interior remained stratified and isolated from the cold southern waters in the west waters cooled markedly 4 c owing to reduced entrainment of tasman sea water marked cooling also occurred north of campbell plateau under increased entrainment of polar water by a branch of the saf the acc remained along the flanks of campbell plateau during the last interglacial when interior waters were stratified and warmer by 1 c than now

geochemistry of the granites and their minerals from paredes da beira penedono northern portugal abstract seven types of hercynian peraluminous muscovite biotite granites t 1 t 5 and muscovite granites t 6 and t 7 occur in the paredes da beira penedono area microscopically they show some small metasomatic effects e g microclinization of plagioclase sericitization of feldspars small chloritization of biotite small amounts of late stage white mica and kaolinization of microcline three different types of white mica muscovite sericite and late stage white mica can be chemically distinguished in a ti mg na diagram variation diagrams of major and trace elements and elemental ratios of granites and muscovites show trends of fractionation from the muscovite biotite granites to the muscovite granites least squares analysis of major elements and modelling of trace elements indicate that the muscovite granite t 7 might have been derived from the muscovite biotite granite magma t 1 by fractional crystallization of quartz k feldspar plagioclase muscovite biotite and ilmenite elemental variation diagrams of granites biotites and muscovites also suggest trends of fractionation a from the muscovite biotite granite t 1 to the muscovite biotite granite t 4 b in the muscovite biotite granite t 5 c in the muscovite granite t 6 however the small metasomatic effects make it difficult to test fractional crystallization the granite t 5 has a large range of composition from the least to the most silicic samples similar to the variation of compositions of the granites in the sequence t 1 t 4 the granite t 1 and the least silicic samples of the granite t 5 would have their origin in two distinct pulses of granite magma and probably have originated by partial melting of metasedimentary materials emplacement of granite magmas took place at 700 c and 4 kbar they were completely crystallized at 450 c and slightly metasomatically altered at 370 c log f h 2 o f hf is smaller in the muscovite granites than in the muscovite biotite granites log f h 2 o f hcl increases and log f hcl f hf and log f h 2 o f hf decrease in the sequence t 1 t 4 of muscovite biotite granites

orbitally influenced vegetation record of the mid pleistocene climate transition offshore eastern new zealand odp leg 181 site 1123 a census of plio pleistocene 5 0 ma terrestrial palynomorph assemblages from odp site 1123 located 1100 km offshore eastern new zealand and in a water depth of 3290 m reveals marked variations in warm cyathea tall tree podocarpus prumnopitys dacrydium cupressinum and cold halocarpus phyllocladus nothofagus fusca type coprosma climate indicator species at milankovitch scale periodicities time series analysis indicates that the vegetation record is covariant with marine climate proxies carbonate content and is strongly coherent at the 40 ka and 100 ka orbital frequency a pronounced increase in amplitude and a coeval decrease in frequency of climate cycles from 40 to 100 ka occurs between 0 92 and 0 62 ma and provides a rare vegetation record of a fundamental reorganisation of earth s climate system the mid pleistocene climate transition despite the long distance from land and great water depth terrestrial palynomorphs are relatively abundant in this high resolution marine sediment record where they reflect a southern north island source the predominance of robust spores and buoyant pollen cyathea podocarpus prumnopitys indicates considerable current sorting and degradation of more delicate morphotypes during transport across the eastern north island shelf little evidence is found for sorting and transport processes being significantly modulated by climate

interannual flow along the northern coast of the gulf of mexico 1 past work has shown that the interannual wind stress curl in the north atlantic generates rossby waves that reach the eastern u s coast and affect coastal sea level both there and along the northern coast of the gulf of mexico tide gauge and topex poseidon satellite sea level height measurements show that this interannual signal penetrates all the way around the gulf of mexico shelf to the yucatan peninsula with local alongshore interannual wind stress increasing the signal amplitude between pensacola and the texas louisiana shelf satellite observations show the seaward spatial structure of the sea level and the associated geostrophic flow in theory this flow should depend on the angle of the shelf edge with respect to due north and the loop current mean shelf edge flow off the northern boundary 90 in agreement with theory the signal behaves as a coastal kelvin wave the sea level amplitude falling quickly away from the shelf edge with first baroclinic radius of deformation scale off the western boundary 180 the interannual sea level amplitude falls rapidly seaward of the shelf edge consistent with short western boundary scales however off the eastern boundary small formed by the west coast of florida the fall in interannual sea level amplitude seaward of the shelf edge is inconsistent with long rossby wave theory interannual geostrophic gulf of mexico shelf edge flows may reach amplitudes of the order of 10 cm s 1 but along shelf flow amplitudes are a few centimeters per second or less even so weak shelf flows of interannual frequency can transport particles many hundreds of kilometers

fluorine as a tool in the petrogenesis of quartz bearing magmatic associations applications of an improved f oh biotite apatite thermometer grid abstract fluorine contents of whole rock and biotites allow to discriminate quartz bearing magmatic associations through the nature of protoliths and petrogenetic processes f and rb are used to discriminate crustal and mantle derived melts with the exception of calcalkaline association in which mantle contribution may be significant the other quartz bearing associations are essentially derived from crustal melting by biotite and or amphibole vapor absent reactions based on experimental data and on an improved biotite apatite thermometer grid closure temperatures from near liquidus to near solidus conditions as well as fh2o fhf evolution during cooling are determined for the different magmatic associations it appears that the liquidus temperature and fh2o fhf decreases in the order high silica alkaline high k calcalkaline and calcalkaline associations while the solidus temperature follows an inverse order the fh2o fhf values for the peraluminous associations vary over a wide range and overlap the fh2o fhf values of the high k calcalkaline and calcalkaline associations

an expanded modern dinoflagellate cyst dataset for the southwest pacific and southern hemisphere with environmental associations organic walled dinoflagellate cyst dinocyst assemblages were examined in 120 sea floor sediment samples from the southwest sw pacific to highlight dinocyst distribution in the region from these 120 samples census counts of 40 samples were added to previously published census data from the southern hemisphere to form a modern dataset of 311 samples sh 311 cluster analysis k means clustering of a 98 sample sub set from the sw pacific nz 98 reveals four distinct assemblages which coincide with modern subantarctic surface water the subtropical front and two clusters from subtropical surface water a similar clustering of the sh 311 dataset reveals an additional three assemblages two associated with polar waters colder than those sampled in the sw pacific and one that may be endemic to the south atlantic ocean multivariate ordination canonical correspondence analysis and redundancy analysis indicates that the dinocyst assemblages change most along a sea surface temperature sst gradient in both the regional sw pacific and southern hemisphere datasets sst accounts for 38 to 56 of the species environmental relationship after removal of covarying variables and contributes 2 3 times the explainable inertia than the other environmental variables tested both modern datasets sh 311 and nz 98 are suitable as a training set for quantitative palaeotemperature transfer functions applied to late quaternary records with the caveat that the modern assemblage also displays sensitivity to productivity shoreline proximity bottom water oxygen and water mass variation that may be exploited in certain situations c 2013 elsevier b v all rights reserved

altimeter derived surface circulation in the large scale ne pacific gyres part 1 seasonal variability abstract the seasonal variability of sea surface height ssh and currents are defined by analysis of altimeter data in the ne pacific ocean over the region from central america to the alaska gyre the results help to clarify questions about the timing of seasonal maxima in the boundary currents as explained below the long term temporal mean of the ssh values must be removed at each spatial point to remove the temporally invariant and large signal caused by the marine geoid we refer to the resulting ssh values which contain all of the temporal variations as the residual ssh our main findings are 1 the maximum surface velocities around the boundaries of the cyclonic alaska gyre the alaska current and the alaska stream occur in winter at the same time that the equatorward california current is weakest or reversed forming the poleward davidson current the maximum surface velocities in the california current occur in summer these seasonal maxima are coincident with the large scale atmospheric wind forcing over each region 2 most of the seasonal variability occurs as strong residuals in alongshore surface currents around the boundaries of the ne pacific basin directly connecting the boundaries of the subpolar gyre the subtropical gyre and the equatorial current system 3 seasonal variability in the surface velocities of the eastward north pacific current west wind drift is weak in comparison to seasonal changes in the surface currents along the boundaries 4 there is an initial appearance next to the coast and offshore migration of seasonal highs and lows in ssh alongshore velocity and eddy kinetic energy eke in the alaska gyre similar to the previously described seasonal offshore migration in the california current 5 the seasonal development of high ssh and poleward current residuals next to the coast appear first off central america and mainland mexico in may june prior to their appearance in the southern part of the california current in july august and their eventual spread around the entire basin in november december similarly low ssh and equatorward transport residuals appear first off central america and mexico in january february before spreading farther north in spring and summer 6 the maximum values of eke occur when each of the boundary currents are maximum

planktic foraminifera based sea surface temperature record in the tasman sea and history of the subtropical front around new zealand over the last one million years abstract planktic foraminiferal assemblages in a composite section from two cores md06 2989 2986 off the west coast of new zealand s south island 42 43 5 s provide a 1 myr mis 31 1 sea surface temperature sst record 3 4 kyr resolution in the tasman sea a significant overall faunal change occurred near the end of the mid pleistocene climate transition mpt at 600 ka mis 15 mean annual ssts were estimated using the artificial neural network ann method glacial interglacial g i cycles in the mpt had 9 c sst range whereas in the post mpt sst range was 6 7 c the sst and faunal changes imply that the subtropical front stf migrated 6 in latitude to lie just north of the sites in mpt glacials mis 28 16 but only migrated 3 5 north in post mpt glacials these g i latitudinal migrations of the stf west of new zealand contrast with the situation east of new zealand where migrations of both the stf and subantarctic front were prevented by the chatham rise and campbell plateau subtropical water is inferred to have only flowed around the south of new zealand as it does today during mis 11 and the late pleistocene holocene mis 5 1

circumpolar structure and distribution of the antarctic circumpolar current fronts 2 variability and relationship to sea surface height 1 in part 1 of this study we showed that the antarctic circumpolar current acc consisted of multiple fronts each of which was consistently associated with a particular contour of sea surface height ssh or approximate streamline in part 2 we have used maps of ssh to examine the variability of the acc fronts between 1992 and 2007 the ssh label associated with each frontal branch is nearly constant around the circumpolar belt the front labels are also nearly constant in time the bands of enhanced ssh gradient i e fronts occur along the same streamlines throughout the 15 year period of observations both short and long period changes of the ssh frontal labels of the acc are small based on a tight relationship between dynamic height and cumulative baroclinic transport of the acc the baroclinic transport variability of the individual branches of the acc is also expected to be small the major change in the total acc baroclinic transport occurs in the drake passage the streamline associated with the northern branch of the saf saf n does not pass through drake passage and the waters carried by this branch are not observed there instead the transport of the saf n turns north in the pacific to supply the export of water to the indian ocean north and south of australia strong eddy activity in the southeast pacific acts to dissipate the hydrographic signature of the saf n there in the atlantic the saf n reappears as the same streamline is again associated with enhanced ssh gradients to the east of the brazil malvinas confluence zone while the large changes in ssh have occurred in the southern ocean between 1992 and 2007 there are strong regional differences because the acc fronts are robustly associated with particular ssh contours the changes in ssh reflect shifts in the position of the acc fronts in the circumpolar average each of the acc fronts has shifted to the south by about 60 km the changes in ssh in the southern ocean are largely due to changes in ocean circulation rather than warming and freshening by atmospheric fluxes much larger changes in ssh are observed in some locations of the southern ocean particularly where the fronts interact with large scale topography the northern branch of the pf pf n near the kerguelen plateau is an extreme example where the pf n followed a path around the northern end of kerguelen plateau between 1992 and 1997 passed through the fawn trough after 2003 and oscillated between the two paths between 1997 and 2003

poleward propagating subinertial alongshore surface currents off the u s west coast 1 the network comprising 61 high frequency radar systems along the u s west coast uswc provides a unique high resolution and broad scale view of ocean surface circulation subinertial alongshore surface currents show poleward propagating signals with phase speeds of o 10 and o 100 300 km d 1 that are consistent with historical in situ observations off the uswc and that can be possibly interpreted as coastally trapped waves ctws the propagating signals in the slow mode are partly observed in southern california which may result from scattering and reflection of higher mode ctws due to curvature of shoreline and bathymetry near point conception california on the other hand considering the order of the phase speed in the slow mode the poleward propagating signals may be attributed to alongshore advection or pressure driven flows a statistical regression of coastal winds at national data buoy center buoys on the observed surface currents partitions locally and remotely wind forced components isolates footprints of the equatorward propagating storm events in winter off the uswc and shows the poleward propagating signals year round

a one million year history of a north south segment of the subtropical front east of new zealand 1 planktic foraminiferal assemblages from ocean drilling program odp site 1119 and deep sea drilling project dsdp site 594 are used to estimate sea surface temperatures ssts over the past 900 kyr marine isotope stages miss 23 1 in the southwest pacific ocean east of new zealand comparison of these long sst records allows us to document the cyclic migrational history of water masses and fronts especially of the n s oriented segment of the subtropical front stf known as the southland front during most interglacials summer ssts were 10 12 c in both sites indicating that both were overlain by subantarctic water saw and that the southland front was located landward of them during the peaks of miss 11 and 5 5 summer sst estimates were considerably warmer than modern suggesting that the southern edge of the e w trending stf expanded southward over the bounty trough and the southland current contained a greater proportion of subtropical water stw than it does today during most glacials summer ssts in inshore odp site 1119 7 10 c were 4 c warmer than in dsdp site 594 this implies that the southland front migrated offshore with lowered sea levels to lie between the two sites during mis 20 ssts in odp site 1119 dropped to those of dsdp site 594 indicating that there was no southland front in existence and no detectable stw entrained in the southland current flowing around the south end of new zealand the low glacial sst estimates in dsdp site 594 4 c might be a result of persistent eddies of circumpolar subantarctic water spinning off the subantarctic front into the bounty trough during glacials

response of nannoplankton to major changes in sea surface temperature and movements of hydrological fronts over site dsdp 594 south chatham rise southeastern new zealand during the last 130 kyr abstract a high resolution history of paleoceanographic changes in the subpolar waters of the southern margin of the subtropical convergence zone during the last 130 kyr is present in foraminiferal assemblages of dsdp site 594 the foraminifera indicate that sea surface temperatures during the last interglacial climax were warmer than today and that between substage 5d through to the end of isotope stage 2 temperatures were mostly cooler than holocene temperatures the paleotemperatures suggest that 1 the subtropical convergence was located over the site during substage 5e later moving further north then moving southwards to near the site during the holocene and 2 the polar front was positioned over the site during glacial stages 6 4 2 and possibly parts of stage 3 several major events are indicated by the nannofloral assemblages during these large changes in sea surface temperature and associated reorganization of ocean circulation first the time progressive trends between e huxleyi and medium to large gephyrocapsa are unique to this site with e huxleyi dominating over medium gephyrocapsa during stages 5c a middle part of stage 4 and after the middle point of stage 3 this unusual trend may at least partly be caused by the shift of the polar front across the site second upwelling flora e huxleyi and small placoliths increase in abundance during stages 1 3 and 5 suggesting that upwelling or disturbance of water stratification took place during the interglacials thirdly there are no significant differences between the distribution patterns of the various morphotypes of medium to large gephyrocapsa and the combined value of all medium gephyrocapsa increases in abundance during glacials stages 2 and 4 and the end of stage 6 similar to the abundance trends in benthic foraminifera finally subordinate nannofossil taxa also show distinctive climatic trends during the last glacial cycle 1 syracosphaera spp are present in increased abundance during warmer extremes in climate substages 5e 5a and stage 1 2 coccolithus pelagicus and calcidiscus leptoporus dominate the subordinate nannofossil taxa and their relative proportions seem to provide a useful paleoceanographic index with c pelagicus dominating when the polar front zone is over the site stages 6 4 and 2 whilst c leptoporus is relatively more abundant when the stc is positioned over the site stages 1 and 5e increased abundance of c pelagicus also can indicate intensified coastal upwelling

pleistocene variability of the subtropical convergence at east tasman plateau evidence from planktonic foraminiferal mg ca odp site 1172a combined measurements of mg ca and stable oxygen isotopes in tests of the planktonic foraminifer g bulloides from ocean drilling program odp site 1172a east tasman plateau allowed us to reconstruct sea surface temperature sstmg ca sea surface salinity sss and hence variations in the subtropical convergence stc in the southwestern tasman sea over the last four major glacial interglacial changes during interglacials the commonly enhanced sstmg ca and sss correspond to a lowered marine productivity and a lowered terrigenous flux implying that the stc separating cool high nutrient subantarctic surface water from warm saline oligotrophic subtropical surface water and hence the band of zonal westerlies responsible for the eolian dust flux were located south of east tasman plateau the warm east australian current was well established during warm periods and propagated far south during glacial times sstmg ca and sss were lower while both marine productivity and eolian flux increased such conditions prevailed during glacial marine isotope stages mis 12 mis 10 and to a lesser degree mis 6 and implied the extended northward influence of subantarctic surfacewater and a shift of the stc to 44 s the overall climatic signal at site 1172a appears to be largely attenuated when compared to published climate records from comparable latitudes to the west and to the east sstmg ca amplitudes were more pronounced in the subantarctic indian ocean and at chatham rise they exhibit a consistent pattern suggesting that latitudinal shifts of the stc occurred synchronously in the subantarctic indian ocean and at chatham rise but were largely damped at east tasman plateau due to the influence of the east australian current

el nino sea level and currents along the south american coast comparison of observations with theory abstract interannual sea level fluctuations along the south american coast and 7 3 year long current records at 30 s off central chile were examined with a low frequency linear numerical model the model includes stratification and shelf and slope bottom topography which varies alongshore the coastal flow is driven by interannual alongshore wind stress and an interannual alongshore pressure gradient resulting from el nino la nina pressure fluctuations at the equator calculations suggest that along the south american coast the coastal interannual variability is primarily due to the remote equatorial forcing rather than interannual coastal alongshore wind stress past work using this model has shown that due to the scattering of lower vertical modes to higher ones by bottom friction the model predicts a low frequency jet trapped near the bottom along the continental slope until now adequate interannual current time series were unavailable to check this prediction analysis of the observations shows th

vegetation and climate in southern hemisphere mid latitudes since 210 ka new insights from marine and terrestrial pollen records from new zealand abstract paleo vegetation records developed from marine sedimentary sequences offer considerable potential for examining changes in terrestrial climate beyond the range of 14 c dating because they can be independently dated by 18 o stratigraphy here we present the first pollen record of vegetation from a marine core site in the tasman sea tan0513 14 42 18 s 169 53 e 110 km west of new zealand s south island an independent chronology provided by correlating the globigerina bulloides 18 o record at tan0513 14 to a global isotope stack shows that the record extends back to 210 ka glacial to interglacial changes in palynomorph content are characterised by shrub and podocarp broadleaf forest taxa respectively and are correlated with similar changes in the ca 150 kyr long terrestrial pollen record from okarito pakihi bog 110 km to the south southeast both records are placed on the same timescale by matching variations in dacrydium cupressinum and fuscospora between sites with a unique tie point provided by the ca 25 4 ka kawakawa tephra our southern hemisphere mid latitude vegetation records show forest extent is greatest during periods of low ice volume high mean annual sea surface temperature masst and anti phased with local insolation intensity however there are several features not attributable to changes in mean annual temperature first a fundamental change in forest composition occurred at termination ii tii with a loss of southern beech nothofagus from the study area second the amplitude of masst change through mis 5 is not reflected in corresponding changes in forest extent suggesting other feature s of regional climate seasonality frostiness ice cover exert important controls over vegetation patterns at these latitudes

moored observations of the current and temperature structure over the continental slope off central california 1 a basic description of the variability current meter data have been analyzed from seven moorings on the continental slope along the central california coast from point piedras blancas to point reyes the goal was to examine the subtidal variability in the 100 m to 1000 m depth range particularly with regard to alongshore propagating events and interactions with eddies and meanders of the california current offshore the 2 year time series available off point sur were first analyzed in conjunction with the local and remote surface wind stress and coastal synthetic subsurface pressure and then correlated with shorter coincident current records moored at similar depths to the north and south the poleward flowing california undercurrent was the most prominent feature at all the moorings except at one site located well into the monterey submarine canyon the strongest poleward flows over the slope occurred in 3 to 4 month bursts not phase locked with the seasons with vector speeds exceeding 40 cm s 1 south of the canyon an approximately monthly signal was identified which propagated poleward upward and offshore the behavior of this signal was consistent with that of an internal coastal kelvin wave generated at the surface by remote wind stress to the south and was likely not of equatorial origin the wave was apparently scattered by the abrupt topography of the canyon since its energy persisted to the north of the canyon but with unstable phase at least three eddy meander interaction events were observed these warm deep 1000 m anticyclonic features reversed the flow over the slope to equatorward when they moved onshore and interrupted the flow of the undercurrent one event forced anomalously strong 15 cm s 1 onshore flows off monterey bay and offshore flows off point sur while quantitative transport estimates could not be made with this sparse data set it seems apparent that such events play a significant role in the exchange of water properties between the shelf and the deep ocean

the annual cycle of circulation of the southwest subtropical pacific analyzed in an ocean gcm abstract an ocean gcm interpreted in light of linear models and sparse observations is used to diagnose the dynamics of the annual cycle of circulation in the western boundary current system of the southwest pacific ocean the simple structure of annual wind stress curl over the south pacific produces a large region of uniformly phased stationary thermocline depth anomalies such that the western subtropical gyre spins up and down during the year directing flow anomalies alternately toward and away from the boundary at its northern end near 10 s the response of the western boundary currents is to redistribute these anomalies northward toward the equator and southward to the subtropical gyre a redistribution that is determined principally by linear rossby processes not boundary dynamics when the subtropical gyre and south equatorial current sec are strong in the second half of the year the result is both increased equatorward transport of the new guinea coastal current and poleward transport a

the record of continental dust from australia in tasman sea sediments abstract the flux of aeolian dust from australia to sediments of the tasman sea has increased during glacial stages of the last four glacial cycles low fluxes of dust from australia before 350 ka were followed by an increase in stage 10 and high fluxes in peak glacial periods thereafter the initiation of higher dust fluxes in stage 10 is consisten with previous estimates of the age of onset of aridity in the source area dust flux to the tasman sea is thought to record the intensity of deflation from the source area in interior southeastern australia which was marked by arid conditions and possibly greater windiness during the last glacial a transect of five cores from the central tasman sea revealed consistently low dust fluxes north of 33 s increasing southward to approximately 40 s glacial to interglacial movement of the northern boundary of the dust plume governed by the position of the subtropical ridge was less than 6 latitude probably closer to 3 350 km the position of the dust plume determined in this study and its response to climate change are significantly different from a previous reconstruction based on the measurement of quartz content of the non biogenic sediment fraction

planktic foraminiferal and sea surface temperature record during the last 1 myr across the subtropical front southwest pacific planktic foraminiferal faunas and modern analogue technique estimates of sea surface temperature sst for the last 1 million years myr are compared between core sites to the north odp 1125 178 faunas and south dsdp 594 374 faunas of the present location of the subtropical front stf east of new zealand faunas beneath cool subtropical water stw north of the stf are dominated by dextral neogloboquadrina pachyderma globorotalia inflata and globigerina bulloides whereas faunas to the south are strongly dominated by sinistral n pachyderma 80 95 in glacials with increased g bulloides 20 50 and dextral n pachyderma 15 50 in interglacials beneath subantarctic water or saw canonical correspondence analysis indicates that at both sites sst and related factors were the most important environmental influences on faunal composition greater climate related faunal fluctuations occur in the south significant faunal changes occur through time at both sites particularly towards the end of the mid pleistocene climate transition mis18 15 e g decline of globorotalia crassula in stw disappearance of globorotalia puncticulata in saw and during mis8 5 interglacial sst estimates in the north are similar to the present day throughout the last 1 myr to the south interglacial ssts are more variable with peaks 4 7 c cooler than present through much of the early and middle pleistocene but in mis11 mis5 5 and early mis1 peaks are estimated to have been 2 4 c warmer than present these high temperatures are attributed to southward spread of the stf across the submarine chatham rise along which the stf appears to have been dynamically positioned throughout most of the last 1 myr for much of the last 1 myr glacial sst estimates in the north were only 1 2 c cooler than the present interglacial except in mis16 mis8 mis6 and mis4 2 when estimates are 4 7 c cooler these cooler temperatures are attributed to jetting of saw through the mernoo saddle across the chatham rise and or waning of the stw current to the south glacial sst estimates were consistently 10 11 c cooler than present similar to temperatures and faunas currently found in the vicinity of the polar front one interpretation is that these cold temperatures reflect thermocline changes and increased circumpolar surface water spinning off the subantarctic front as an enhanced bounty gyre along the south side of the chatham rise for most of the last 1 myr the temperature gradient across the stf has been considerably greater than the present 4 c during glacial episodes the stf in this region did not migrate northwards but instead there was an intensification of the temperature gradient across it interglacials 4 11 c glacials 8 14 c

entropies of kyanite andalusite and sillimanite additional constraints on the pressure and temperature of the al2sio5 triple point the low temperature heat capacities of kyanite minas gerais brazil andalusite espirito santo brazil and sillimanite reinbolt hills antarctica were measured with an automatic adiabatically shielded calorimeter between approximately l0 and 380 k at 29e 15 k the entropies are e2 30 r0 13 91 39 0 14 and 95 79 ro l4 j mol k for kyanite andalusite and sillimanite respectively our values are 1 8 2 0 and0 4vo smaller than those of todd 1950 our calculated slope for the andalusite sillimanite phase boundary is in significantly better agreement with the phase boundaries of holdaway 1971 than with those of richardson gilbert and bell 1969 and strongly suggest that al and si are ordered in sillimanite to at least ll00 k the thermal debye temperatures d calculated from our heat capacity data in the range 18 k are 1lfi e55 and 730 k for kyanite andalusite and sillimanite respectively for andalusite and sillimanite our values for ofi are in moderate agreement with those calculated from the room temperature adiabatic elastic stifness constants ofvaughan and weidner 1978 838 and 800 k respectively

middle pleistocene sea surface temperature change in the southwest pacific ocean on orbital and suborbital time scales a record of estimated sea surface temperature sst change between 575 and 400 ka has been obtained from planktonic foraminifera at deep sea drilling project site 594 in the southwest pacific ocean the site 594 record indicates that ssts during marine oxygen isotope stage 11 were similar to those of the holocene in contrast to suggestions of warmer than holocene ssts during stage 11 if these ssts reflect global conditions then ice sheet collapse may not require temperatures warmer than in the holocene millennial scale oscillations in sst 3 c occurred within the stage 12 glacial interval spaced every 5 10 k y on time scales similar to those observed within stage 12 in the north atlantic the consistency between these records may require global scale mechanisms capable of producing rapid climate change as suggested for later quaternary intervals

hybrid coastal and interior modes for two dimensional flow in a cylindrical ocean flows on coastal shelves and in the deep interior ocean are often considered separately but transport of fluid between these two regions can have important biologial or environmental consequences this paper considers a linear coupled coastal and deep interior ocean model in the idealized context of a homogeneous two dimensional cylindrical ocean with a rigid lid and axisymmetric step shelf topography both a semianalytical mode matching approach and brute force finite element numerics have been used to analyze the linear dynamics it is shown that hybrid planetary plane rossby and topographic shelf modes emerge the structure of these inviscid modes is clarified by considering their frequency dependence on shelf break radius by contrasting the evolution of hybrid modes to the evolution of pure shelf and pure plane rossby modes considering streamfunction fields and particle paths and by showing solutions of the initial value problem both ocean and laboratory parameter values are considered hybrid modes exchange information between the deep ocean and coastal shelves especially at the intermediate frequencies where the separate planetary rossby mode and topographic shelf mode dispersion curves overlap the role of these modes is particularly clear in an initial value problem wherein a localized initial condition on the southern shelf later leads to large scale interior ocean circulation forced dissipative calculations reveal the sensitivity of resonantly generated hybrid rossby shelf modes to the strength of ekman damping for typical oceanic and laboratory parameter values hybrid modes are altered by increasing ekman damping but do not disappear

upper ocean thermal structure and heat content off the us west coast during the 1997 1998 el nino event based on axbt and satellite altimetry data abstract during the 1997 1998 el nino event extensive oceanic temperature profiles were taken off the coast of california in january and february 1998 using airborne expendable bathythermographs axbts these axbt measurements are compared with altimetry based upper ocean temperature estimates using topex and ers satellite altimetry data the altimetry based temperature estimates are well correlated with the axbt data in particular when combining the two satellite data sets together to form a blended altimeter temperature estimate both the axbt and altimetry data show that the nearshore coastal el nino signal differed from that further offshore the axbt data show that near shore the warm anomalies extended to much greater depths and had greater amplitude a time series of the satellite derived layer averaged temperatures averaged separately over the nearshore and offshore halves of the axbt analysis domain also shows a larger el nino signal in the nearshore half the role of local atmospheric forcing of the coastal oceanic temperature anomalies is analyzed using ncep reanalysis and coastal upwelling data sets the forcing terms include ekman pumping radiation surface heat fluxes precipitation and alongshore wind stresses that drive coastal upwelling expressed as a coastal downwelling index cdi the temperature forcing from all of the terms except the cdi anomalies are small the cdi anomalies can explain most of the slowly varying temperature changes that occur near the coast during a two year period spanning the el nino event as well as some of the larger amplitude rapid monthly warming episodes that appear to be part of the el nino signal several distinct rapid warming episodes however are not correlated with the cdi anomalies and therefore we conclude that the nearshore el nino signal originates from a combination of both a remote oceanic pathway and local atmospheric forcing

equatorially forced intraseasonal propagations along the peru chile coast and their relation with the nearshore eddy activity in 1992 2000 a modeling study 1 a regional eddy resolving oceanic model spanning the 1992 2000 period is used to study the influence of 50 to 80 day intraseasonal equatorial kelvin waves iekw on mesoscale eddy activity off the west coast of peru and northern and central chile the model is shown to realistically simulate nearshore intraseasonal sea level variability poleward propagation of equatorially forced coastal trapped waves along the coastal waveguide and offshore variability related to mesoscale eddies and rossby waves rw in agreement with linear theory rw are confined equatorward of 12 s in the 50 80 days period range south of that critical latitude westward propagation is dominated by energetic mesoscale signals resulting mainly from coastal flow instability sensitivity experiments to the open boundary conditions are then used to estimate to what extent eddy activity is impacted by the remote equatorial forcing a coastal increase in eddy kinetic energy related to the energetic 60 day iekw activity present in the open boundary forcing is evidenced and is largest off northern peru whereas no major changes are observed offshore additional regional simulations with different open boundary conditions corroborate our findings and suggest that this limited effect of iekw on the offshore eddy kinetic energy may be a robust feature citation belmadani a v echevin b dewitte and f colas 2012 equatorially forced intraseasonal propagations along the peru chile coast and their relation with the nearshore eddy activity in 1992 2000 a modeling study j geophys res 117 c04025 doi 10 1029 2011jc007848

application of artificial neural networks to paleoceanographic data abstract artificial neural networks are computer systems that have the ability to learn a set of output or target vectors from a set of input vectors learning is achieved by self adjustment of a set of parameters to minimize the error between a desired output and the actual network output we have explored the potential of this approach in paleoceanography by application of a neural network algorithm to a problem involving prediction of sea surface water temperatures from relative abundances of planktonic foraminifer species in the southern indian ocean we employed a backpropagation bp network to assess how well it was able to predict the actual summer and winter surface water temperatures we compared the results with those obtained from statistical methods previously used for temperature predictions imbrie kipp transfer functions the modern analog technique and soft independent modelling of class analogy the efficiency of predictions was tested using the leaving one out technique in which each of the observations in the data set is left out one at a time while the remaining observations are used to generate a predictor the accuracy of the predictor is then tested on the observation left out by comparison with its actual value a set of tests using 1 2 3 4 5 and 10 neurons processing elements in a 3 layer bp network showed that a network with 3 neurons gave the smallest errors of prediction for both summer and winter temperatures 0 71 and 0 76 respectively corresponding errors for the statistical pattern recognition techniques ranged between 1 01 and 1 26 for summer temperatures and 1 05 1 13 for winter temperatures hence predictions of paleotemperatures from new data on planktonic foraminifer relative abundances in the southern indian ocean may be made with a precision of 0 7 0 8 c using the bp network and 1 0 1 3 c using the statistical pattern recognition procedures the bp network was thus the most successful among the methods employed here for temperature predictions artificial neural networks may therefore be seen as a viable alternative to more conventional approaches to data analysis in paleoceanography

sea surface temperature estimates from the southwest pacific based on planktonic foraminifera and oxygen isotopes planktonic foraminiferal census data were collected on 34 surficial sediment samples from east of new zealand sea surface temperature estimates were derived from the data using the modern analogue technique mat and compared to data from climap s fa 20 equation they were also computed from oxygen isotope analyses of globigerina bulloides the temperature estimates compared well between the three methods and were found to correlate closely with the appropriate seasonal sea surface temperature as measured by satellite the foraminiferal assemblages and derivative temperatures clearly identify the major watermasses and oceanic fronts in the region and thus can be applied to palaeoceanographic analysis of southwest pacific sediments

critical frequencies at ocean boundaries past theoretical work has shown that for low frequency flow at a given ocean boundary location a critical frequency c exists such that for c unforced motion is trapped to the coast while for c energy leaves the coast alternatively for motion of a given frequency on the boundary there exists a critical latitude such that the motion is trapped to the coast poleward of that latitude but equatorward it is not this theory is discussed physically for both meridional and nonmeridional boundaries the simple formula for critical frequency along a nonmeridional boundary is used to document critical periods for the eastern and western atlantic pacific and indian ocean boundaries the theory occasionally breaks down when boundary curvature is too large

southwest pacific ocean response to a warmer world insights from marine isotope stage 5e paleoceanographic archives derived from 17 marine sediment cores reconstruct the response of the southwest pacific ocean to the peak interglacial marine isotope stage mis 5e ca 125 ka paleo sea surface temperature sst estimates were obtained from the random forest model an ensemble decision tree tool applied to core top planktonic foraminiferal faunas calibrated to modern ssts the reconstructed geographic pattern of the sst anomaly maximum sst between 120 and 132 ka minus mean modern sst seems to indicate how mis 5e conditions were generally warmer in the southwest pacific especially in the western tasman sea where a strengthened east australian current eac likely extended subtropical influence to ca 45 s off tasmania in contrast the eastern tasman sea may have had a modest cooling except around 45 s the observed pattern resembles that developing under the present warming trend in the region an increase in wind stress curl over the modern south pacific is hypothesized to have spun up the south pacific subtropical gyre with concurrent increase in subtropical flow in the western boundary currents that include the eac however warmer temperatures along the subtropical front and campbell plateau to the south suggest that the relative influence of the boundary inflows to eastern new zealand may have differed in mis 5e and these currents may have followed different paths compared to today

the use of foraminifera as a record of the past neodymium isotope composition of seawater 1 we present new isotopic data for sedimentary planktonic foraminifera as well as for potential water column and sedimentary sources of neodymium nd which confirm that the isotopic composition of the foraminifera is the same as surface seawater and very different from deep water and sedimentary nd the faithfulness with which sedimentary foraminifera record the isotopic signature of surface seawater nd is difficult to explain given their variable and high nd ca ratios ratios that are often sedimentary foraminifera ratios that are often much higher than is plausible for direct incorporation within the calcite structure we present further data that demonstrate a similarly large range in nd ca ratios in plankton tow foraminifera a range that may be controlled by redox conditions in the water column cleaning experiments reveal in common with earlier work that large amounts of nd are released by cleaning with both hydrazine and diethylene triamine penta acetic acid but that the nd released at each step is of surface origin while further detailed studies are required to verify the exact location of the surface isotopic signature and the key controls on foraminiferal nd isotope systematics these new data place the use of planktonic foraminifera as recorders of surface water nd isotope ratios and thus of variations in the past supply of nd to the oceans from the continents via weathering and erosion on a reasonably sure footing

dinoflagellate cysts from two sediment traps east of new zealand abstract two discontinuous sediment trap records of organic walled dinoflagellate cyst dinocyst flux each sampling 300 days within the years 2005 2009 were derived from two time incremental traps deployed at 1500 m water depth east of new zealand the traps sampled flux from beneath two distinct surface water masses on either side of the subtropical front i warm seasonally macronutrient depleted subtropical and ii cold micronutrient limited subantarctic waters nineteen dinocyst taxa or taxonomic groups were identified from the trap samples trap assemblages at both sites were dominated by cysts of protoperidiniaceae notably brigantedinium spp which comprised almost 98 of the dinocyst flux the seasonality of the dinocyst flux differed between the traps with a pronounced spring flux in the subtropical trap while seasonal variation in the subantarctic trap was relatively muted in subtropical waters moderate correlation was observed between protoperidiniaceae cyst flux and chlorophyll a concentrations in surface waters in the 3 4 weeks prior to sampling in subantarctic waters there was a weak correlation between protoperidiniaceae cyst flux and reduced intensity of storm induced turbulence during the preceding 2 3 weeks there was a large discrepancy between dinocyst assemblages in the traps and those observed in nearby sea floor sediments protoperidiniaceae dinocysts particularly echinidinium and brigantedinium were highly under represented in the sea floor assemblages these forms are more susceptible to degradation in oxygenated sediments than other dinocysts but inter annual variability in cyst flux or short term variation not covered by sampling discontinuities in the current study could also have contributed to this discrepancy the major differences in the seasonality of dinocyst fluxes between the two water masses examined in this initial study suggest that mean annual rather than seasonal climatologies are more appropriate for dinocyst based quantitative palaeoenvironmental reconstructions in the new zealand region

southwest pacific sea surface conditions during marine isotope stage 11 results from dinoflagellate cysts abstract dinoflagellate cyst dinocyst assemblages are examined from three sw pacific marine sediment cores covering marine isotope stage 11 mis11 423 ka 380 ka md06 2988 and md06 2989 are in the east tasman sea north of the subtropical front stf whilst dsdp594 is in subantarctic surface waters saw off eastern new zealand sea surface temperature sst estimates from dinocyst assemblages indicate that the east tasman sea was 2 5 c warmer than present during the peak warmth of mis11 in the east tasman sea north of the stf there is a two step warming into mis11 in cores md06 2988 and md06 2989 east of new zealand and south of the stf at core site dsdp594 dinocyst sst estimates suggest that mis11 was an extended warm period similar to or slightly warmer than present conditions although data from the early phase prior to 417 ka may be compromised due to insufficient modern analogues at all sites glacial interglacial climatic fluctuations were accompanied by large assemblage changes glacial intervals were characterised by higher abundances of assemblages typical of saw nematosphaeropsis labyrinthus selenopemphix antarctica brigantedinium spp subtropical surface water stw assemblages dominated during the interglacial in the east tasman sea including impagidinium aculeatum i patulum and spiniferites mirabilis whilst assemblages consistent with continued saw influence remained during the interglacial at core site dsdp594 albeit with reduced cold water indicators such as s antarctica the changes are particularly pronounced in the east tasman sea where the stf is inferred to have been located further north during glacials mis12 and mis10 the influence of stw at dsdp594 during mis11 and the holocene is inferred to have been less than during mis5e a qualitative dinocyst based index likely reflecting primary productivity also influenced by oxygen concentration on the sea floor is broadly anti phased with sst on glacial interglacial timescales at all sites

the vertical structure of large scale unsteady currents abstracta linear model based on the quasigeostrophic equations is constructed in order to predict the vertical structure of rossby waves and more broadly of anomalies resolved by altimeter data roughly with periods longer than 20 days and with wavelengths larger than 100 km the subsurface field is reconstructed from sea surface height and climatological stratification the solution is calculated in periodic rectangular regions with a 3d discrete fourier transform the effect of the mean flow on rossby waves is neglected which the authors believe is a reasonable approximation for low latitudes the method used has been tested with an idealized double gyre simulation performed with the miami isopycnal coordinate ocean model micom the linear model is able to give reasonable predictions of subsurface currents at low latitudes below approximately 30 and for relatively weak mean flow however the predictions degrade with stronger mean flows and higher latitudes the subsurface velocities calculate

rossby waves and the interannual and interdecadal variability of temperature and salinity off california abstract previous work has shown that large scale interannual rossby waves largely remotely generated by equatorial winds propagate westward from the coast off southern california these waves have a large scale anomalous alongshore velocity field that is proportional to the time derivative of the interannual sea level anomaly using these results a theory is developed for interannual perturbations to a mean density field that varies both vertically and alongshore like that for the california current region off southern california because both the anomalous vertical and alongshore currents are proportional to the time derivative of the interannual sea level the theory suggests that the anomalous currents associated with the rossby waves acting on the mean temperature field should induce temperature fluctuations proportional to the anomalous dynamic height the alongshore and vertical advections contribute to the temperature fluctuations in the same sense a higher than normal sea level for exampl

p t x conditions of late hercynian fluid penetration and the origin of granite hosted gold quartz veins in northwestern iberia a multidisciplinary study of fluid inclusions and their chemistry quartz veins hosted by late hercynian granites and their host rocks occur across the variscides of the northern iberian peninsula and locally display au as mineralization four separate occurrences at corcoesto tomino penedono and pino have been investigated to determine p t x conditions of formation and likely fluid sources special attention has been paid to fluid chemistry using a multidisciplinary investigation of fluid inclusion gases by raman spectroscopy individual fluid inclusion analysis and mass spectrometry bulk analysis and ion chemistry using microthermometry and bulk leachate chemical analysis two major changes in the chemical and physical environment have been identified 1 a progressive change in the bulk chemical composition from early co2 rich c h o n fluids equilibrated with graphitic metamorphic host rocks to late h2o dominated fluids inferred from their halogen signature to result from an influx of meteoric or upper crustal fluids affecting the basement at the end of variscan orogenesis and 2 changes in the p t conditions from early stage sulphide deposition in quartz veins at ca 450 c and 150 300 mpa towards epithermal conditions ca 260 310 c and 75 mpa at the stage of gold mineralization several chemical trends are shown by the fluid inclusions 1 dilution of the early volatile rich fluids 2 a break of graphite buffering activity demonstrated by the ch4 content increase in the volatile fraction of the latest as mineralizing fluids and 3 increasing contribution of a relatively oxidizing fluid enriched in sulphate and bromide during the latest stages of fluid percolation au stage these latest fluid stages are interpreted as indicative of extended fluid penetration downward in the crust enhanced by late brittle deformation and decompression and played an important role in mass transfer at the end of the hercynian orogeny especially in transport of metals gold ores have formed mostly in granites because main fluid pathways developed in the main structurally active zones which favoured the emplacement of the granites however there is no evidence of genetic link between gold ores and their enclosing granites

the mid brunhes event and west antarctic ice sheet stability the complex cyclical nature of pleistocene climate driven by the evolving orbital configuration of the earth is well known but not well understood a major climatic transition took place at the mid brunhes event mbe ca 430 ka ago after which the amplitude of the ca 100 ka climate oscillations increased with substantially warmer interglacials including periods warmer than present recent modelling has indicated that while the timing of these warmer than present transient wpt events is consistent with southern warming clue to a deglaciation forced slowdown of the atlantic meridional overturning circulation the magnitude of warming requires a local amplification for which a candidate is the feedback of significant west antarctic ice sheet wais retreat we here extend this argument based on the absence of wpts in the early ice core record 450 800 ka ago to hypothesize that the mbe could be a manifestation of decreased wais stability triggered by ongoing subglacial erosion

quaternary tephra marker beds and their potential for palaeoenvironmental reconstruction on chatham island east of new zealand southwest pacific ocean tephras provide one of the most reliable methods of time control and synchronisation within quaternary sequences we report on the identification of two widespread rhyolitic tephras the kawakawa and rangitawa tephras preserved in extensive peat deposits on chatham island 900 km east of new zealand the tephras both products of supereruptions from the taupo volcanic zone occur as pale fine ash dominated layers typically 10 150 mm thick mineralogically they are dominated by rhyolitic glass together with subordinate amounts of quartz feldspar hypersthene hornblende fe ti oxides and zircon phlogopite biotite was identified additionally in rangitawa tephra ages for each tephra were obtained via mineralogical and major element glass composition based correlation with well dated equivalent deposits on mainland new zealand and we also obtained a new zircon fission track age for rangitawa tephra 350 50 ka on chatham island both tephras were erupted at critical times for palaeoenvironmental reconstructions in the new zealand region the kawakawa at ca 27 cal ka near the beginning of the extended lgm early in marine isotope stage mis 2 and the rangitawa at ca 350 ka near the end of mis 10 the time constraints provided by the tephras demonstrate that chatham island peats contain long distance pollen derived from mainland new zealand which provides a reliable proxy for identifying glacial interglacial climate conditions in this case during the mis 11 10 and mis 2 1 cycles the two tephras thus provide important chronostratigraphic tie points that facilitate correlation and synchronisation not only across the quaternary deposits of the chatham islands group but also with climatically significant terrestrial and marine records in the wider new zealand region copyright 2010 john wiley sons ltd

iron and arsenic rich nanoprecipitates associated with clay minerals in sulfide rich waste dumps abstract the relationships between clay minerals and associated iron and arsenic rich phases are a main scientific issue in reactive mine waste dumps therefore this paper documents the composition and morphology of the fine fraction the obtained results indicated that the study sites have similar relative proportions of the detrital materials however major differences were observed in the remainder phases which is in accordance with the mineralogy that was inherited from the respective ore deposits in general the clay mineral assemblage is dominated by the presence of illite halloysite 7 a and beidellite there are also associated minerals such as jarosite and goethite as well as amorphous as rich nanoprecipitates with specific morphologies moreover the results suggested that amd conditions control the physical chemical transformations namely constraining the stability of the secondary phases formed by weathering in the waste dumps acidity is responsible for the degradation of the clay minerals which is reflected in their crystalochemistry structural order disorder and morphology on the contrary jarosite is more stable being a dominant mineral in such environmental conditions the stability of amorphous ferric arsenates or its evolution to a more crystalline phase is dependent on the fe as ratio which is lower in penedono the study of the secondary products especially the nanoparticles puts in evidence their ability to control the mobility of trace elements suggesting potential applications in environmental technology including remediation of reactive mine waste dumps

benthic foraminifera and the late quaternary last 150 ka paleoceanographic and sedimentary history of the bounty trough east of new zealand abstract the bounty trough east of new zealand lies along the southeastern edge of the present day subtropical front stf and is a major conduit via the bounty channel for terrigenous sediment supply from the uplifted southern alps to the abyssal bounty fan census data on 65 benthic foraminiferal faunas 63 m from upper bathyal odp 1119 lower bathyal dsdp 594 and abyssal odp 1122 sequences test and refine existing models for the paleoceanographic and sedimentary history of the trough through the last 150 ka marine isotope stages mis 6 1 cluster analysis allows recognition of six species groups whose distribution patterns coincide with bathymetry the climate cycles and displaced turbidite beds detrended canonical correspondence analysis and comparisons with modern faunal patterns suggest that the groups are most strongly influenced by food supply organic carbon flux and to a lesser extent by bottom water oxygen and factors relating to sediment type major faunal changes at upper bathyal depths 1119 probably resulted from cycles of counter intuitive seaward landward migrations of the southland front sf north south sector of the stf benthic foraminiferal changes suggest that lower nutrient cool subantarctic surface water saw was overhead in warm intervals and higher nutrient bearing warm neritic subtropical surface water stw was overhead in cold intervals at lower bathyal depths 594 foraminiferal changes indicate increased glacial productivity and lowered bottom oxygen attributed to increased upwelling and inflow of cold nutrient rich antarctic intermediate water aaiw and shallowing of the oxygen minimum zone upper circum polar deep water cpdw the observed cyclical benthic foraminiferal changes are not a result of associations migrating up and down the slope as glacial faunas dominated by globocassidulina canalisuturata and eilohedra levicula at upper and lower bathyal depths respectively are markedly different from those currently living in the bounty trough on the abyssal bounty fan 1122 faunal changes correlate most strongly with grain size and are attributed to varying amounts of mixing of displaced and in situ faunas most of the displaced foraminifera in turbiditic sand beds are sourced from mid outer shelf depths at the head of the bounty channel turbidity currents were more prevalent during but not restricted to glacial intervals

mesoscale structure of the mean east australian current system and its relationship with topography abstract we document the mean circulation of the east australian current eac system which is the major western boundary current in the southwest pacific ocean a new high resolution climatology of the region csiro atlas of regional seas cars is used to produce regional fields of steric height and sections of geostrophic velocity the realism of these fields has been enhanced by the high spatial resolution allowance for bathymetric control and the influence of land barriers the increased detail in the maps and sections reveal the major influence that the complex regional topography has on the circulation the results also provide the appropriate resolution for comparison with recent model studies of the region we have been able to both resolve well known features with greater detail and identify previously unrecognized aspects of the circulation important results include 1 the zonal inflow north of 30 s breaks into a series of individual jets after flowing through the island chains as suggested by recent model results 2 the interaction of the zonal inflow with the local topography as it undergoes bifurcation is documented 3 a detailed picture of the evolution of the eac at the western boundary is presented including surface currents and transports 4 separation and recirculation of the eac within the tasman abyssal basin are shown to occur as a double cell structure constrained by bathymetry 5 the eac outflow is resolved as a series of eastward and northeastward currents 6 the path of the tasman front is defined as it interacts with the tasman ridge systems 7 a quasi permanent eddy is identified for the first time adjacent to the norfolk ridge northwest of new zealand

episodic enhancement of phytoplankton stocks in new zealand subantarctic waters contribution of atmospheric and oceanic iron supply 1 around 30 of oceanic waters are high nitrate low chlorophyll hnlc where low iron levels limit algal growth hnlc waters have mainly been studied using shipboard and lab experiments since 1997 remote sensing of phytoplankton via seawifs ocean color has permitted monitoring of the constancy of this hnlc condition i e spatial homogeneity and low temporal variability of chlorophyll over annual cycles these trends can be exploited as episodic iron inputs should be conspicuous by subsequent expression as iron elevated algal stocks subantarctic sa waters near new zealand are hnlc and the proximity of the arid australian landmass and the iron rich subtropical front provide natural laboratories to detect episodic atmospheric and oceanic iron supply respectively two approaches were used oceanic supply was inferred from episodic increases in chlorophyll concentrations in sa waters detected using ocean color archives additional archives were used to confirm the oceanic provenance of iron supply and identify supply mechanism s atmospheric supply was assessed using data on source areas and loads for dust storms monitored in central australia dust transport and its fate was assessed using air mass forward trajectories and seawifs ocean color and aerosol optical depth maps during 1997 2001 episodic elevated chlorophyll events occurred in sa waters southeast of new zealand there was no evidence of these events being mediated by atmospheric iron supply however neither wind driven lateral advection or vertical mixing alone could account for these episodes dust storms over this period sent plumes either into high iron subtropical st waters or into sa waters in early spring when cells are probably light rather than iron limited

ray theory and the scattering of topographic rossby waves by an abrupt change of shelf width and coastline the scattering of topographic rossby waves over a shelf that abruptly changes its width with a step shaped coast is studied by two methods mode expansion which in principle is exact and ray theory for the latter we stress the importance of evaluating the phase field instead of limiting the results to the ray paths as is often done ray theory is found to give a good approximation of the energy flux at low frequency and the correct location and strength of highs and lows of the transport function however ray theory predicts very sharp gradients of this field which imply unrealistically high velocities at the frontier of the region illuminated by a beam these results suggest that ray theory may be an alternative or complement to numerical models for those scattering problems where a complicated topography and or coastline prevents the use of the mode expansion method

glacial interglacial control of terrigenous and biogenic fluxes in the deep ocean off a high input collisional margin a 139 kyr record from new zealand abstract sediment input to the deep ocean off the new zealand collisional plate boundary is large and variable as revealed by a 139 kyr old record from the 34 92 m long core md97 2121 mass accumulation rates mars were derived for terrigenous and biogenic carbonate and silica sedimentary components with temporal control from a stable isotope age model verified by tephra and radiocarbon ages terrigenous mars changed in phase with glacio eustatic fluctuations of sea level highest rates 30 g cm 2 kyr coincided with the late regressive lowstand early transgressive phase of marine isotope stage mis 2 when rivers discharged at or near the shelf edge lesser but still high terrigenous rates 20 30 g cm 2 kyr characterized peak warm phases of early mis 5 and 1 when a strengthened subtropical inflow probably introduced sediment from fluvial and seabed sources to the north of md97 2121 however during prolonged highstands the flux declined as more sediment was retained on a tectonically subsiding shelf with a shore parallel current paradoxically the lowest mars 10 5 g cm 2 kyr occurred in mis 4 either sea level was too high to allow much sediment to escape off shelf or the fluvial input was modest or both these factors despite the terrigenous dominance biogenic mars are high and are 2 4 times larger than sw pacific ocean rates mars were lowest during mis 4 and 3 possibly due to reduced marine production under a lowered input of fluvial micronutrients in contrast mars increased irregularly though glacial maxima to peak at 5 6 g cm 2 kyr carbonate and 2 2 5 g cm 2 kyr silica in early mid mis 5 and 1 such rates reflected the interaction of macronutrient rich subantarctic waters sourced from the south with local micronutrient rich subtropical waters production also responded to warmer temperatures elevated nutrient runoff and a more stratified surface ocean later in mis 5 and 1 fluxes reduced as less productive subtropical waters prevailed that biogenic and aeolian mar profiles are out of phase suggests fe fertilization by aerosolic dust was not a major influence

glacial interglacial variations in quaternary production of marine organic matter at dsdp site 594 chatham rise southeastern new zealand margin abstract caco3 and total organic carbon concentrations organic matter c n and carbon isotope ratios and sediment accumulation rates in late quaternary sediments from dsdp site 594 provide information about glacial interglacial variations in the delivery of organic matter to the chatham rise offshore of southeastern new zealand low c n ratios and nearly constant organic 13c values of 23 indicate that marine production dominates organic matter supply in both glacial and interglacial times during oxygen isotope stages 1 through 6 0 140 ka and 17 through 19 660 790 ka increased organic carbon mass accumulation rates in isotope stages 2 4 6 and 18 record enhanced marine productivity during glacial maxima excursions of organic 13c values to ca 29 in portions of isotope stage 2 suggest that the local concentration of dissolved co2 was occasionally elevated during the last glacial maximum probably as a result of short periods of lowered sea surface temperature dilution of carbonates by clastic continental sediment generally increases at this location during glacial maxima but enhanced delivery of land derived organic matter does not accompany the increased accumulation of clastic sediments

distribution of organic walled dinoflagellate cysts in surface sediments of the southern ocean eastern atlantic sector between the subtropical front and the weddell gyre abstract thirty two surface sediment samples from the southern ocean eastern atlantic sector between the subtropical front and the weddell gyre were investigated to provide information on the distribution of modern organic walled dinoflagellate cysts in relation to the oceanic fronts of the antarctic circumpolar current acc a clearly distinguishable distribution pattern was observed in relation to the water masses and fronts of the acc the dinoflagellate cysts of species characteristic of open oceanic environments such as impagidinium species are highly abundant around the subtropical front whereas south of this front cosmopolitan species such as nematosphaeropsis labyrinthus and the cysts of protoceratium reticulatum characterise the transition from subtropical to subantarctic surface waters the subantarctic surface waters are dominated by the cysts of heterotrophic dinoflagellates such as protoperidinium spp and selenopemphix antarctica the cysts of protoperidinium spp form the dominant part of the assemblages around the antarctic polar front whereas s antarctica concentrations increase further to the south the presence of s antarctica in sediments of the maud rise a region of seasonal sea ice cover reflects its tolerance for low temperatures and sea ice cover a previously undescribed species cryodinium meridianum gen nov sp nov has a restricted distribution pattern between the antarctic polar front and the acc weddell gyre boundary

decadal spinup of the south pacific subtropical gyre abstract an increase in the circulation of the south pacific ocean subtropical gyre extending from the sea surface to middepth is observed over 12 years datasets used to quantify the decadal gyre spinup include satellite altimetric height the world ocean circulation experiment woce hydrographic and float survey of the south pacific a repeated hydrographic transect along 170 w and profiling float data from the global argo array the signal in sea surface height is a 12 cm increase between 1993 and 2004 on large spatial scale centered at about 40 s 170 w the subsurface datasets show that this signal is predominantly due to density variations in the water column that is to deepening of isopycnal surfaces extending to depths of at least 1800 m the maximum increase in dynamic height is collocated with the deep center of the subtropical gyre and the signal represents an increase in the total counterclockwise geostrophic circulation of the gyre by at least 20 at 1000 m a comparison of woce and

recent geographical distribution of organic walled dinoflagellate cysts in the southeast pacific 25 53 s and their relation to the prevailing hydrographical conditions abstract forty eight surface sediment samples from the southeast se pacific 25 53 s are investigated for the determination of the spatial distribution of organic walled dinoflagellate cysts along the western south american continental margin fifty five different taxa are recorded and reflect oceanic or coastal assemblages the oceanic assemblages are characterised by low cyst concentrations and the dominance of autotrophs while the coastal assemblages generally contain a higher number of cysts which are mainly produced by heterotrophic species highest cyst concentrations are observed in the active upwelling system offshore concepcion 35 37 s brigantedinium spp echinidinium aculeatum echinidinium granulatum delicatum and cysts of protoperidinium americanum dominate assemblages related to upwelling echinidinium aculeatum appears to be the best indicator for the presence of all year round active upwelling cells other protoperidinioid cysts may also occur in high relative abundances in coastal regions outside active upwelling systems if the availability of nutrients co responsible for the presence absence of their main food sources such as diatoms and other protists is sufficient the importance of nutrient availability as a determining environmental variable influencing cyst signals on a regional scale se pacific is demonstrated through statistical analyses of the data because of the importance of nutrients uncertainties about the outcomes of quantitative sea surface temperature sst reconstructions modern analogue technique based on dinoflagellate cysts may arise since no interaction between different hydrographical variables is considered in this approach the combination of the se pacific surface sample dataset with other published cyst data from the southern hemisphere resulted in a database which includes 350 samples the sh350 database this database is used to test the accuracy of the quantitative reconstructions by calculating and comparing the estimated versus observed values for each site an attempt to perform quantitative sst reconstructions on the last 25 cal ka of site odp1233 41 s 74 27 w is made and again stresses the importance of other environmental variables such as nutrient availability in determining the dinoflagellate cyst assemblages

dust induced changes in phytoplankton composition in the tasman sea during the last four glacial cycles 1 an increase in iron supply associated with enhanced dust inputs could be responsible for higher marine phytoplankton production leading to the typically lower glacial atmospheric co2 concentrations as suggested by the iron hypothesis the enhanced dust supply may also have provided the oceans with significant amounts of silica which would have favored the growth of diatoms over coccolithophores as suggested by the silica hypothesis here we present new data on molecular biomarkers in a sediment core from the midlatitudes of the southern hemisphere which reveal dust induced changes in the relative contribution of the phytoplankton to total productivity our results illustrate a shift in the relative abundance of siliceous over calcareous organisms during glacial times when terrestrial aeolian input was enhanced although we did not detect a significant glacial decrease in coccolithophorid productivity the decrease in the caco3 corg rain ratio could have still contributed to some extent in lowering atmospheric co2 levels

glacial to interglacial changes in non carbonate and carbonate accumulation in the sw pacific ocean new zealand abstract fluxes of carbonate and non carbonate terrigenous biogenic siliceous sediment back to a maximum of marine isotope stage mis 6 were determined for 54 cores from off eastern new zealand mass accumulation rates mars were derived using dry bulk densities measured directly from fresh cores or in the case of dry archived samples on estimates from a density carbonate relationship mars exhibit wide spatial and temporal variability in response to i the location of cores relative to the terrigenous source of new zealand current pathways and local oceanographic features and ii palaeoclimatic change for mis 1 2 non carbonate accumulated at a high rate between 27 and 18 ka calendar years due to an influx of waterborne and aeolian terrigenous detritus together with localised production of biogenic silica under a northward intrusion of subantarctic waters and an increase in wind induced upwelling by 18 12 ka non carbonate mars reduced as winds ameliorated and sea level rose to confine some of the terrigenous load to the continental shelf the holocene transgression was accompanied by warmer sea surface temperatures the formation of coastal and lacustrine sediment traps and more widespread terrestrial vegetation these conditions further reduced the deep oceanic non carbonate flux to levels about half those of glacial periods in contrast carbonate mars were lower in cold periods reflecting lower productivity increased dissolution and in the case of the generally productive waters of chatham rise to redistribution by bottom currents however off central new zealand carbonate production was higher on the continental margin possibly because of enhanced upwelling under the strong wind regime of mis 2 such localised effects produced glacial carbonate mars higher than interglacial mis 1 values for the rest of the region carbonate fluxes increased to an early to middle mis 1 maximum before generally declining in recent times

the potential of organic walled dinoflagellate cysts for the reconstruction of past sea surface conditions in the southern ocean abstract in this study we investigate the potential of organic walled dinoflagellate cysts dinocysts as tools for quantifying past sea surface temperatures sst in the southern ocean for this purpose a dinocyst reference dataset has been formed based on 138 surface sediment samples from different circum antarctic environments the dinocyst assemblages of these samples are composed of phototrophic gonyaulacoid and heterotrophic protoperidinioid species that provide a broad spectrum of palaeoenvironmental information the relationship between the environmental parameters in the upper water column and the dinocyst distribution patterns of individual species has been established using the statistical method of canonical correspondence analysis cca among the variables tested summer sst appeared to correspond to the maximum variance represented in the dataset to establish quantitative summer sst reconstructions a modern analogue technique mat has been performed on data from three late quaternary dinocyst records recovered from locations adjacent to prominent oceanic fronts in the atlantic sector of the southern ocean these dinocyst time series exhibit periodic changes in the dinocyst assemblage during the last two glacial interglacial cycles during glacial conditions the relative abundance of protoperidinioid cysts was highest whereas interglacial conditions are characterised by generally lower cyst concentrations and increased relative abundance of gonyaulacoid cysts the mat palaeotemperature estimates show trends in summer sst changes following the global oxygen isotope signal and a strong correlation with past temperatures of the last 140 000 years based on other proxies however by comparing the dinocyst results to quantitative estimates of summer ssts based on diatoms radiolarians and foraminifer derived stable isotope records it can be shown that in several core intervals the dinocyst based summer ssts appeared to be extremely high in these intervals the dinocyst record seems to be highly influenced by selective degradation leading to unusual temperature ranges and to unrealistic palaeotemperatures we used the selective degradation index kt index to determine those intervals that have been biased by selective degradation in order to correct the palaeotemperature estimates we show that after correction the dinocyst based ssts correspond reasonably well with other palaeotemperature estimates for this region supporting the great potential of dinoflagellate cysts as a basis for quantitative palaeoenvironmental studies

geographical distributions of organic walled dinoflagellate cysts in surficial sediments of the benguela upwelling region and their relationship to upper ocean conditions the organic walled cyst content of 41 surface sediment samples from the south eastern south atlantic ocean have been studied to create a dataset that can be used for palaeoceanographic reconstructions in order to obtain insight into which environmental factors influence the distribution of individual cyst species the cyst associations have been compared with oceanographic characteristics of the overlying water masses i e temperature salinity density and stratification gradients the associations and relationships have been established by visual examination of the dataset and the multivariate ordination techniques detrended correspondence analysis and canonical correspondence analysis special attention has been given to the factors of transport and preservation of the cysts five associations have been recognised as being characteristic of 1 areas influenced by coastal upwelling and or river outflow 2 open ocean 3 agulhas current and southern benguela current 4 benguela current and 5 walvis bay shelf break area the factors dominant in influencing either directly or indirectly the cyst distributions appear to be the stratification in the upper 50 m of the water column nutrient concentration and seasonality variations in sea surface temperatures and salinities have only minor effect on cyst distribution

on the use of high resolution satellite data to describe the spatial and temporal variability of sea surface temperatures in the new zealand region a new high resolution 1 1 km regional data set of satellite derived sea surface temperatures sst is developed and validated against drifting and moored buoy data analysis of 5 years of monthly means and related statistics suggests that there is often a coherent relationship between the sst patterns and oceanographic features identifiable relationships are detailed then used to indicate the temporal and spatial characteristics of watermasses fronts and currents for example a gradient analysis suggests that the subtropical front east of new zealand and west of 177 w is bathymetrically locked to the southern flank of the chatham rise near 44 s beyond 177 w it loops southward to a mean position close to 47 s on the northern edge of the bounty plateau adjacent to the subantarctic front near 48 s harmonic analysis of the 60 months of data suggests that spatial variability in the amplitude of the sst annual cycle is related to circulation water mass features and varies from less than 1 c in subantarctic waters to more than 4 c in new zealand nearshore neritic waters the antarctic circumpolar east auckland and east cape currents also display coherent annual cycle amplitude signatures that differ from adjacent water masses however the amplitude of the annual cycle in subantarctic waters south of the chatham rise and north of the pukaki rise and bounty plateau is significantly different from that of this water mass at other similar latitudes an empirical orthogonal function eof analysis of seasonal anomalies shows that 90 of sst variance can be associated with the annual cycle however four eofs are required to explain 50 of the variance in sst monthly anomalies the first of these 25 4 of the variance indicates that anomalies north and east of new zealand are negatively correlated with those in the subantarctic the second eof represents a tasman sea mode and suggests that the tasman sea has been in a warming phase since december 1996 to at least april 1998 this might explain the exceptional size and sign of the sst anomaly in new zealand waters during the 1998 el nino where in february 1998 it reached 3 5 c in northern new zealand waters similar to the amplitude of the annual cycle

calorimetric and phase diagram approaches to two feldspar geothermometry a critique two feldspar geothermometers based on the thermodynamic properties of the limiting binaries ab an and ab or are unsatisfactory because the ternary nature of the feldspar pairs cannot be accounted for and critical points are not generated ternary mixing data are mandatory there are also serious shortcomings in the experimental ternary phase relation data available at present and even ambiguities in the interpretation of the thermodynamic properties of the binaries which preclude development of a practical geothermometer recent work on feldspar zoning patterns in rocks allows some deductions to be made concerning the geometry of the ternary system but there are dilliculties in the interpretation of natural feldspar pairs framework order disorder presents problems which may be insuperable

low frequency baroclinic waves off coastal boundaries abstract the behavior of low frequency baroclinic rossby wave motion in the vicinity of coastal boundaries is investigated using linearized modulated wave theory in a stratified constant depth equatorial plane ocean a primary objective is to obtain an equation that describes large scale low frequency pressure fluctuations along variable geometry ocean boundaries at all latitudes for use in the analysis of coastal sea level observations both eastern and western boundaries are considered and the effect of direct wind stress forcing at the coast is included but our major interest concerns the response along eastern ocean boundaries to incident baroclinic equatorial kelvin waves in that case for an incident wave at a fixed frequency a critical latitude with coriolis parameter f fc exists such that for f fc the waves are coastally trapped the magnitude of fc depends on and on the angle of the coastline

seasonal circulation around tasmania an interface between eastern and western boundary dynamics 1 the seasonal circulation connecting the pacific and indian oceans around tasmania is documented using seasonal maps from satellite altimetry and sea surface temperature sst and in situ mean fields from a high resolution climatology of the region commonwealth scientific and industrial research organisation csiro atlas of regional seas cars in general the surface variability displays a very different character off the east and west coasts off the east coast the variability is generated externally being dominated by the western boundary dynamics of the east australian current eac in the west it is weaker and arises from the seasonal rise and fall of the coastal sea level which is due to the seasonal reversing wind patterns a high variability tongue associated with the eac stretches poleward off the east coast tracing out a waveguide between the major topographic structures it has a broad peak in power between 180 and 365 days 0 08 m which is a surface height expression of the energetic mesoscale eddy activity associated with the eac distinctive summer and winter patterns of the surface circulation are described which are influenced by the eac and the zeehan current zc respectively on the east coast in summer january march there is a poleward advection of warm saline water forced by an episodic coastal boundary flow the cross shelf pressure gradient driving this flow is formed from the difference between the seasonal changes in coastal sea level and the offshore eddies there is a seasonal reversal of this flow in winter with cool fresh modified subantarctic surface waters drawn up from the south off the west coast the zeehan current operates 180 out of phase with the eac it is strongest in winter when it projects warm relatively saline waters down the western tasmania coast and around the southern tip of tasmania there is a sharp division between the eac and zc influence adjacent to the tasman peninsula off southeast tasmania

latitudinal and frequency characteristics of the westward propagation of large scale oceanic variability abstract in the open ocean away from the equator westward propagation is a ubiquitous characteristic of oceanic variability the objectives of the study are to investigate the latitudinal dependence of the frequency of westward propagating variability two dimensional fourier analysis in frequency and zonal wavenumber is applied to time longitude records of sea surface height data obtained from the ocean topography experiment topex poseidon mission the focus of the study is placed on spatial scales larger than the mesoscale the frequency of westward propagation is generally lower than the critical frequency of the first mode baroclinic rossby waves as expected from the conventional theory of rossby waves in a midlatitude ocean however westward propagation with frequency of up to 2 times the critical frequency is also observed at most latitudes this supercritical propagation can be explained by the effects of the vertical shear of the mean flow at midlatitudes and by the effects of the equatorial