iron control of past productivity in the coastal upwelling system off the atacama desert chile 1 biogenic opal and organic carbon vertical rain rates in sediment cores reveal a strong cyclicity in the productivity of the upwelling system off presently arid northern chile during the last 100 000 years changes in productivity are found to be in phase with the precessional cycle 20 000 years and with inputs of iron from the continent during austral summer insolation maxima increased precipitation and river runoff in the region appear to have brought high inputs of iron mainly from the andes to the coastal ocean enhancing primary productivity there we interpret our results as providing evidence for iron control of past productivity in this upwelling system and for a tight link between productivity and orbital forcing at midlatitudes

superdarn observations of daytime mstids in the auroral and mid latitudes possibility of long distance propagation 1 the propagation parameters of daytime medium scale traveling ionospheric disturbances mstids are investigated for the first time using near simultaneous superdarn radar data obtained at auroral and middle latitudes the observations suggest that mstids can propagate from auroral to mid latitudes with persistent propagation parameters if the dominant propagation direction is approximately equatorward however statistical analysis implies that a portion of mstids with higher horizontal phase velocity are unable to reach the mid latitude due to enhanced dissipation and the reduction of the ion drag effect

identification of high latitude acoustic gravity wave sources using the goose bay hf radar observations of medium scale acoustic gravity waves using the goose bay hf radar are presented data were examined for the period of november and december 1991 and days that showed evidence of traveling ionospheric disturbances tids were selected for analysis tids were identified in the hf radar data by quasi periodic enhancements of the power in the ground scattered portion of the radar signal various parameters were determined from the data including the wave frequency the wavelength the propagation direction and the phase velocity it was found that multiple wave packets from multiple directions are often present simultaneously source times and locations were identified from data from 2 days december 5 and 6 1991 and these were compared with data from the greenland magnetometer chain the source times and locations were found to correspond to sudden magnetometer deflections indicating the correlation of gravity wave sources with the occurrence of ionospheric electrojet current surges finally the source times and locations were examined in local time and magnetic latitude and it was found that the sources were clustered in two locations near the magnetospheric cusp and near 1600 mlt at about 75 magnetic latitude

greater supply of patagonian sourced detritus and transport by the acc to the atlantic sector of the southern ocean during the last glacial period reconstructing past detrital flux and provenance in the southernocean provides information about changes in source regions associated with climate variations and transport pathways we present a lastglacial maximum lgm to holocene comparison of 230th normalised fluxes combined with sediment provenance data pb nd and sr isotopes from a latitudinal core transect in the eastern atlanticsector of the southernocean odp leg 177 cores we compare the radiogenic isotopic composition ic of detritus in these cores to that of cores proximal to potential source areas we observe a well defined latitudinal holocene gradient in both detrital flux and provenance of sediment high detrital fluxes in the north are associated with terrigenous material derived from southern africa while low detrital fluxes in the south are associated with supply from southern south america west antarctica and the south sandwich islands the data suggest that this well defined holocene gradient in detrital flux and sediment provenance is controlled by the flow of the antarctic circumpolar current acc and the position of its frontal zones the lgm is characterised by 2 to 6 times higher than modern detrital fluxes at most odp leg 177 sites the lgm detrital fluxes do not show a latitudinal trend and suggest a greatersupply of glaciogenic detritussourced from southern south america glacialpatagonian outwash sediments 5 m fraction were analysed and compared to the bulk compositions of the marine sediments the pb ic of the patagonian sediments is very similar to the glacial ic of sediments in the scotia sea and at 49 s latitude in the eastern atlanticsector we propose that the glacial ic of sediments is controlled by increased delivery of patagoniandetritus initially supplied by glaciers and then transported at depth via the acc

links between iron supply marine productivity sea surface temperature and co2 over the last 1 1 ma received 3 july 2008 revised 9 october 2008 accepted 27 october 2008 published 14 february 2009 1 paleoclimatic reconstructions have provided a unique data set to test the sensitivity of climate system to changes in atmospheric co2 concentrations however the mechanisms behind glacial interglacial g ig variations in atmospheric co2 concentrations observed in the antarctic ice cores are still not fully understood here we present a new multiproxy data set of sea surface temperatures sst dust and iron supply and marine export productivity from the marine sediment core ps2489 2 odp site 1090 located in the subantarctic atlantic that allow us to evaluate various hypotheses on the role of the southern ocean so in modulating atmospheric co2 concentrations back to 1 1 ma we show that antarctic atmospheric temperatures are closely linked to changes in so surface temperatures over the last 800 ka and use this to synchronize the timescales of our marine and the european project for ice coring in antarctica epica dome c edc records the close correlation observed between iron inputs and marine export production over the entire interval implies that the process of iron fertilization of marine biota has been a recurrent process operating in the subantarctic region over the g ig cycles of the last 1 1 ma however our data suggest that marine productivity can only explain a fraction of atmospheric co2 changes up to around 40 50 ppmv occurring at glacial maxima in each glacial stage in this sense the good correlation of our sst record to the edc temperature reconstruction suggests that the initial glacial co2 decrease as well as the change in the amplitude of the co2 cycles observed around 400 ka was most likely driven by physical processes possibly related to changes in antarctic sea ice extent surface water stratification and westerly winds position

carbon isotopic disequilibrium in polar planktonic foraminifera and its impact on modern and last glacial maximum reconstructions calibration studies of neogloboquadrina pachyderma sinistral coiling hereinafter referred to as n pachyderma s in the south atlantic raise questions about the interpretation of this species carbon isotope composition as a paleoceanographic tracer of southern ocean surface nutrient contents carbon isotope disequilibrium between 13c of total co2 tco2 of seawater and 13c of n pachyderma s increases systematically between 70 and 40 s several effects could cause the observed carbon isotope disequilibrium including a combination of foraminiferal diet calcification temperature and carbonate ion chemistry combining these corrections to the 13c of n pachyderma s improves the reconstruction of the 13c of seawater tco2 between 0 and 200 m in the modern south atlantic with these corrections applied the 13c for equilibrium calcite reconstructed from n pachyderma s at the last glacial maximum is very similar to preindustrial values suggesting that one cannot rule out the possibility that surface nutrient concentrations in the south atlantic ocean were comparable to today however the magnitude of the uncertainties associated with these corrections make it difficult to assess absolute paleonutrient concentrations with much confidence

biogenic carbonate and ice rafted debris heinrich layer accumulation in deep sea sediments from a northeast atlantic piston core abstract biogenic carbonate mass accumulation rates show distinct quaternary glacial interglacial changes in a mid latitude northeast atlantic deep sea core during the last 208 kyr these were generally higher during interglacials averaging 2 2 g cm 2 kyr than during glacial periods with a maximum average of 1 2 g cm 2 kyr intervals containing high ice rafted debris have very low biogenic carbonate accumulation rates paleo primary productivity estimates based on biogenic carbonate accumulation rates are generally higher during interglacials averaging 80 gc m 2 yr than during glacials which average 49 gc m 2 yr maximum estimate short intervals with possibly reduced primary productivity correspond to heinrich layers which are the result of pulses of massive iceberg production and rapid melting in the north atlantic we identified thirteen heinrich layers in isotopic stages 7 to 2 they have calendar ages of about 201 189 182 183 164 167 146 149 142 128 131 64 67 52 54 40 43 29 31 21 and 15 kyr these heinrich layers contain large amounts of ice rafted debris including detrital carbonate low amounts of coccoliths and planktic foraminifera mainly neogloboquadrina pachyderma sinistral the upper five heinrich layers are almost barren of coccoliths and the fourth layer is also free of foraminifera the virtual absence of coccoliths is interpreted to reflect reduced coccolithophorid productivity in the photic zone due to low salinity of surface waters and to blockage of light by ice and suspended materials shed off by melting icebergs considering the limited use of other proxies such as organic carbon diatom and benthic foraminifera due to their very low content abundance in the sediments biogenic carbonate mass accumulation rates offer a workable paleo primary productivity proxy in open ocean sediments of the carbonate dominated northeast atlantic

use of multiproxy records on the agulhas ridge southern ocean ocean drilling project leg 177 site 1090 to investigate sub antarctic hydrography from the oligocene to the early miocene 1 ocean drilling program odp site 1090 on the agulhas ridge in the south atlantic sector of the southern ocean is ideally located to capture changes in southern ocean circulation patterns using samples taken from cored sediments we construct multiproxy records of productivity biogenic barium baex opal and caco3 mass accumulation rates mars nutrient and organic carbon burial reactive phosphorus pr mars and redox conditions u and mn enrichments to investigate hydrographic conditions associated with climatic shifts from the oligocene through the early miocene orbitally induced cyclicity in u and mn enrichments 100 kyr suggests shifts in deepwater characteristics however caco3 dissolution coincident with low u and mn enrichments does not indicate low oxygen corrosive waters similar to modern conditions these observations indicate that a well developed modern type antarctic circumpolar current acc did not yet exist over the period from 30 to 20 ma with two potential consequences the southern ocean was not functioning as a silica trap permitting a broader distribution of silica that may have facilitated organic carbon burial in the ocean in general and the lack of a deeply mixing acc may have facilitated organic carbon burial in the southern ocean both the relative high opal mars coincident with low caco3 mars and absolute high pr mars burial of organic carbon suggest a powerful mechanism for pco2 drawdown

opal sedimentation shifts in the world ocean over the last 15 myr biogenic silica opal accumulation records were used to trace mechanisms consequence and geographic pattern of shifts in the main locus of opal deposition of the world ocean over the last 15 myr over this time interval the main opal sink seems to have moved from the north atlantic to the pacific equatorial pacific eastern equatorial pacific eastern boundary current upwelling systems california namibia peru and finally to the southern ocean the interplay between opal deposition and a series of climatic tectonic oceanographic and biologic events has been analyzed and discussed these events include the cenozoic global cooling trend intensified glaciation in antarctica late miocene early pliocene biogenic bloom development of northern hemisphere glaciation nhg closing of the panama seaway transition of the climate system from a monopolarto a bipolar glaciated world mid pleistocene revolution mpr nutrient availability evolution of diatoms and c4 plants and changes in continental weathering rates while the observed shifts are mostly traceable to oceanic reorganizations and global climatic evolution conditions favorable to opal deposition involve the above mentioned complex mix of processes for this reason the interpretation of opal deposition records might not always be straightforward we however believe that it can still provide clear indications of large scale oceanographic reorganizations in the geological past d 2004 elsevier b v all rights reserved

an analysis of tidal and planetary waves in the neutral winds and temperature observed at low latitude e region heights we present an extensive analysis of tidal and planetary waves in the altitude range of 94 to 144 km for the january 20 30 1993 period using the temperature and winds measured by the arecibo incoherent scatter radar isr this is the first time that simultaneous observational results for the 6 8 12 24 hour tides and a quasi 2 day planetary wave at e region heights have been reported at tropical latitudes in order to derive the major oscillations from the mainly daytime data we fill in the nighttime periods with assumed data values and large error bars when valid measurements are not obtainable and then fit the data using the measured and assumed errors as weight simulated results show that such a method is demonstratively better than leaving the nighttime as a gap the salient features of the tidal analysis results include the following 1 despite their large day to day variabilities in amplitude the 6 8 hour oscillations are shown to be upward propagating tides 2 the vertical wavelength of the semidiurnal tide in the zonal wind lengthens from 25 to 110 km for the altitude range from 94 to 135 km while the vertical wavelength of the meridional wind remains constant the semidiurnal component of the meridional wind experiences little dissipation above 106 km which is indicative of the turbopause height 3 the diurnal tide which has often been assumed to be negligible in earlier observations can be quite substantial above 110 km 4 a 2 day planetary wave dominates the diurnal and semidiurnal tides in the meridional wind between 97 and 108 km continuous isr operation during the january 20 30 1993 campaign also provides an opportunity to examine the tidal variability both in phase and amplitude

aeolian dust in east antarctica epica dome c and vostok provenance during glacial ages over the last 800 kyr aeolian mineral dust archived in antarctic ice cores represents a key proxy for quaternary climate evolution the longest and most detailed dust and climate sequences from polar ice are provided today by the vostok and by the epica dome c edc ice cores here we investigate the geographic provenance of dust windborne to east antarctica during early and middle pleistocene glacial ages using strontium and neodymium isotopes as tracers the isotopic signature of antarctic dust points towards a dominant south american origin during marine isotopic stage mis 8 10 12 and back to mis 16 and 20 as deduced from edc core data provide evidence for a persistent overall westerly circulation pattern allowing efficient transfer of dust from south america to the interior of antarctica over the last 800 kyr some small but significant dissimilarity between old and recent glacial ages suggests a slightly reduced patagonian contribution during ancient glaciations

influence of orbital forcing and sea level changes on sedimentation patterns in the timor sea during the last 260 ka a multiproxy study of core md98 2166 makes it possible to investigate the influence of orbital forcing and sea level changes on timor sea sedimentation during the last 260 ka spectral analysis reveals a strong imprint of obliquity in all proxies this is particularly puzzling for the caco3 and total organic carbon toc records since recent data obtained on nearby core md01 2378 collected at a shallower water depth showed a concentration of spectral power in the eccentricity and precession bands our results suggest that while sedimentary record in shallower core md01 2378 shows a clear low latitude response that of core md98 2166 reflects a stronger influence of high latitude forcing through deepwater changes in addition rock eval analyses show that part of the organic carbon could be of terrestrial origin especially during glacial periods this suggests that glacial interglacial toc fluctuations not only reflect changes of marine productivity and or preservation at the seafloor but also reflect enhanced input of terrestrial material during periods of low sea level

terrigenous input and paleoproductivity in the southern ocean the geochemistry of several sites along the polar front zone of the southern ocean revealed significant changes in terrigenous input and productivity on glacial timescales our records indicate concentrations and fluxes of terrigenous elements i e fe al and ti are low during interglacials and increase tenfold to twentyfold during glacials phosphorus accumulation reactive p concentrations and p ti ratios exhibit similar trends as the terrigenous components suggesting increased export production during glacials in all cores elemental ratios remain relatively constant indicating terrigenous sources at each site have not likely varied over the past 250 kyr iron accumulation rates for these sites are 10 times higher during glacials than interglacials and exceed the estimated regional eolian fluxes by 50 times the source of this terrigenous material is thus likely to be hemipelagic rather than direct eolian input or ice rafting and we speculate fe upwelled from this source may have stimulated glacial productivity in the southern ocean

arecibo s thermospheric gravity waves and the case for an ocean source 1 wave like disturbances in electron density ne have been observed in the thermosphere above arecibo observatory puerto rico throughout its 45 year history however only recently has it become evident that these waves are continuously present in the arecibo thermosphere the wave characteristics are fairly constant between day and night and from season to season high resolution electron density measurements obtained by applying the coded long pulse radar technique to photoelectron enhanced langmuir waves are presented these new observations strongly suggest that the perturbations in electron density are the result of internal acoustic gravity waves agws propagating through the arecibo thermosphere the agws appear to be broadbanded in wave number space the downward phase trajectories of ne ne between 400 and 120 km combined with the low horizontal phase velocities obtained from airglow measurements support the idea that the agws are not ducted but rather are locally produced in addition the altitudes at which major peaks in ne ne are observed follow theoretical estimates for nonducted waves the nominal period of the agws is 60 min at 250 km altitude but periods of 20 min are also evident at lower attitudes classic sources of agws do not appear to be consistent with the arecibo observations of a continuous flux of background agws ray tracing of the agws combined with 630 0 nm airglow observations point to a source location in the atlantic ocean that is roughly 2100 km east northeast of arecibo internal ocean waves generated in response to the internal tide at the mid atlantic ridge are the most likely source of arecibo s thermospheric agws

climatology of medium scale traveling ionospheric disturbances observed by the midlatitude blackstone superdarn radar a climatology of daytime midlatitude medium scale traveling ionospheric disturbances mstids observed by the blackstone super dual auroral radar network superdarn radar is presented mstids were observed primarily from fall through spring two populations were observed a dominant population heading southeast centered at 147 geographic azimuth ranging from 100 to 210 and a secondary population heading northwest centered at 50 azimuth ranging from 75 to 25 horizontal velocities ranged from 50 to 250 m s 1 with a distribution maximum between 100 and 150 m s 1 horizontal wavelengths ranged from 100 to 500 km with a distribution peak at 250 km and periods between 23 and 60 min suggesting that the mstids may be consistent with thermospheric gravity waves a local time lt dependence was observed such that the dominant southeastward population decreased in number as the day progressed until a late afternoon increase the secondary northwestward population appeared only in the afternoon possibly indicative of neutral wind effects or variability of sources lt dependence was not observed in other parameters possible solar geomagnetic and tropospheric mstid sources were considered the auroral electrojet ae index showed a correlation with mstid statistics reverse ray tracing with the hindgrats model indicates that the dominant population has source regions over the great lakes and near the geomagnetic cusp while the secondary population source region is 100 km above the atlantic ocean east of the carolinas this suggests that the dominant population may come from a region favorable to either tropospheric or geomagnetic sources while the secondary population originates from a region favorable to secondary waves generated via lower atmospheric convection

characteristics of medium scale traveling ionospheric disturbances observed near the antarctic peninsula by hf radar we present a survey of medium scale traveling ionospheric disturbances mstids observed by a super dual auroral radar network hf radar located in the falkland islands between may 2010 and april 2011 the radar has a field of view that overlooks the antarctic peninsula a known hot spot of gravity wave activity we present observations of radar ground backscatter data in which the signatures of mstids are manifested as structured enhancements in echo power observed periods were in the range 30 80 min corresponding to frequencies of 0 2 0 6 mhz wavelengths were generally in the range 200 800 km and phase speeds in the range 100 300 m s 1 these values are within the ranges typically associated with medium scale gravity waves we find a primary population of northward equatorward propagating mstids which demonstrate an association with enhanced solar wind magnetosphere coupling and a smaller westward propagating population that could be associated with atmospheric gravity waves excited by winds over the andean and antarctic peninsula mountains or by the high winds of the antarctic polar vortex

middle and upper atmosphere radar observations of ionospheric density gradients produced by gravity wave packets by observing the ionospheric f region simultaneously in multiple beams with the middle and upper atmosphere mu radar we have been able to track the passage of gravity waves and measure the horizontal electron density gradients that they produce our previous work on this topic on one day of observations verified that the gradient structure and fluctuations were consistent with a gravity wave source the present work 1 looks at several days of observation to confirm the routine existence of these gradient structures 2 identifies individual wave packets 3 finds evidence that long trains of gravity wave fluctuations are composed of several juxtaposed wave packets of one or two cycles each rather than a single wave of many cycles 4 finds that during quiet periods strong waves are present only during the daytime but during disturbed periods they are present day and night and 5 notes several other characterizations

variations of the antarctic circumpolar current intensity during the past 500 ka 1 we examine the past variations of the antarctic circumpolar current acc by using variations in size and abundance of the magnetic grains deposited by this current at a site east the kerguelen crozet plateau core md00 2375g was taken at a midlatitude site during the antaus cruise conducted in 2000 by the french r v marion dufresne marine isotope stages mis down to mis 13 are identified and an age model is derived from a correlation to the ice core isotopic record obtained from epica in antarctica continuous records of abundance and size of the magnetic grains were obtained using environmental magnetism methods results show a strong modulation of the acc flow intensity in response to glacial and interglacial cycles the low abundance and the small size of magnetic grains indicate that the acc was weak during warm stages and strong during glacial epochs a large modulation is also observed at the sub stage scale during the interglacials a minimum in concentration and grain size occurs at the onset of mis 11 at the mis 6 5 10 9 and possibly 12 11 transitions observed variations suggest a mechanism involving both rapid and progressive variations of the acc flow at deglaciations

medium scale traveling ionospheric disturbances affecting gps measurements spatial and temporal analysis 1 in this work we present a simple technique to estimate the medium scale traveling ionospheric disturbances mstids characteristics such as occurrence velocity vertical propagation with periods lower than 20 min and its application to a set of gps data both temporally and spatially representative near one solar cycle and four local networks in the northern and southern hemispheres respectively some of the main results presented in this paper are the mstids which occur at daytime in local winter and nighttime in local summer related to the solar terminator and modulated by the solar cycle they present equatorward from 100 to 400 m s and westward 50 to 200 m s horizontal propagation velocities respectively the corresponding periods are compatible higher with the theoretical prediction which is given by the neutral atmosphere

opal burial in the equatorial atlantic ocean over the last 30 ka implications for glacial interglacial changes in the ocean silicon cycle 1 the silicic acid leakage hypothesis salh suggests that during glacial periods excess silicic acid was transported from the southern ocean to lower latitudes which favored diatom production over coccolithophorid production and caused a drawdown of atmospheric co2 downcore records of 230th normalized opal fluxes and 231pa 230th ratios from seven equatorial atlantic cores were used to reconstruct diatom productivity over the past 30 ka where a is years and to test the salh downcore records of 231pa 230th ratios and opal fluxes are highly correlated suggesting that they constitute a production based record of opal flux opal flux records support the salh in that glacial opal burial exceeded holocene burial by 1 8 gt opal ka in the area 0 40 w and 5 n 5 s earlier results from the eastern equatorial pacific ocean showed the opposite trend with greater holocene than glacial opal burial but approximately the same magnitude of difference between glacial and interglacial opal burial we suggest four nonexclusive scenarios to explain the data from both basins 1 increased upwelling in the equatorial atlantic and el nino like conditions suppressing upwelling in the eastern equatorial pacific altered the overall nutrient supply to both basins 2 si leaked from the southern ocean because of fe fertilization but was prevented from upwelling in the equatorial pacific because of el nino like conditions during the lgm 3 si leaked from the southern ocean because diatom productivity was limited by increased sea ice extent and was again prevented from upwelling in the equatorial pacific or 4 changes in ocean circulation related to the decreased input of agulhas water to the glacial south atlantic provided excess dissolved si to the equatorial atlantic ocean a deglacial opal pulse is seen in both the atlantic and pacific oceans all four scenarios and the presence of the common deglacial opal pulse suggest a common driver in the southern ocean

the sedimentary record of carboniferous rivers continuing influence of land plant evolution on alluvial processes and palaeozoic ecosystems abstract evidence from modern rivers and the deep time geological record attests to the fundamental importance of plant life for the construction of physical habitats within fluvial environments data from an extensive literature review and original fieldwork demonstrates that many landforms and geomorphic features of modern river systems appear in the palaeozoic stratigraphic record once terrestrial vegetation had adopted certain evolutionary advances for example stable point bars are associated with the onset of rooted plants in the siluro devonian and avulsive and anabranching fluvial systems become common at the same time as extensive arborescent vegetation in the carboniferous in this paper we demonstrate a correlation between the diversification of physical fluvial environments and the expansion of terrestrial fauna and flora with an emphasis on the culmination of these trends within carboniferous alluvial systems many extrinsic factors have been considered as possible controls on the evolutionary timelines of terrestrialization for organisms however a fundamental prerequisite for achieving terrestrial biodiversity was the variety of physical habitats especially riparian systems available for newly evolved organisms in association with abundant lowland meandering systems the widespread appearance across carboniferous alluvial plains of fixed channel and anabranching reaches created further physical landforms for colonization and would have promoted increasingly complex hyporheic flow regimes furthermore the associated increase in arborescent vegetation and supply of large woody debris to inland and coastal rivers would have created a wealth of microhabitats for continental organisms we argue that the expanding extent and diversity of physical alluvial niches during the palaeozoic is an underappreciated driver of the terrestrialization of early continental life the study of the deep time fossil and stratigraphic record also illustrates that vegetation is a fundamental prerequisite for the creation of biogeomorphic alluvial landforms and physical habitats and microhabitats

reconciling down core anticorrelation of diatom carbon and nitrogen isotopic ratios from the southern ocean 1 oceanic nutrient cycling in the southern ocean is supposed to have an important impact on glacial interglacial atmospheric co2 changes and global climate in order to characterize such nutrient cycling over the last two climatic cycles we investigated carbon and nitrogen isotopic ratios of diatom bound organic matter 13cdiat and 15ndiat respectively in two cores retrieved form the atlantic and indian sectors of the antarctic ocean the two cores show the same isotopic patterns the 13cdiat values are depleted during glacial periods and enriched during interglacial periods indicating lower productivity during cold times the 15ndiat values are enriched during glacial periods and depleted during interglacial periods arguing for greater nitrate utilization during cold times taken at face value this apparent contradiction leads to opposite conclusions on the role of the southern ocean biological pump on the atmospheric co2 changes however the two sets of data can be reconciled by a sea ice plus mixing rate scenario that calls upon a balance between the effect of cutting off gas transfer at the ocean atmosphere boundary and the effect of reducing vertical transport of nutrients through the pycnocline

shifting frontal regimes and its influence on bioproductivity variations during the late quaternary in the indian sector of southern ocean abstract reconstruction of palaeoproductivity from southern ocean is crucial for understanding the functioning of the southern ocean biological pump in the past high resolution records of multi proxy parameters calcium carbonate opal total organic carbon biogenic barium and planktonic carbon isotope ratios 13 c were investigated in two well dated sediment cores sk200 22a and sk200 27 from the indian sector of southern ocean situated to the north and south of antarctic polar front apf respectively the palaeoproductivity records extending 95 ka bp sk200 22a and 75 ka bp sk200 27 revealed inverse relationships between the calcite and opal productivity indicating the influence of shifting nutrient regimes at core sk200 22a reduced calcite productivity during marine isotope stage mis 2 4 and part of mis 3 suggest an equatorward migration of the frontal regimes during glacial intervals compared to this the region south of the apf core sk200 27 was characterized by the near absence of calcite content during the last glacial period and increased opal productivity during mis 1 and mis 3 supporting a southward migration of apf during warmer intervals ba bio records exhibit good correlation with opal records in both the cores and also correlate with that of calcite record at sk200 22a indicating that ba is influenced by the combined opal and calcite productivity the enhanced opal productivity during the glacial periods north of the apf is attributed to the northward shifting of oceanic fronts and associated transfer of nutrients diatom productivity records of sk200 22a reveal significant similarities with the dust records from the antarctic and southern ocean but showed no significant relationships with the diatom record of sk200 27 it is proposed that the dust derived fe input had apparently influenced the palaeoproductivity north of the modern apf but had a minor influence on opal productivity south of the apf comparison with the ice core climate records from antarctica and greenland revealed that bioproductivity peaks in the study region are nearly synchronous with the millennial antarctic warming events remarkably the calcite and opal productivity records at sk200 22a responded differently to the antarctic warming events with opal productivity lagging behind the calcite productivity peaks by 1 2 ka

statistical study of nighttime medium scale traveling ionospheric disturbances using midlatitude airglow images 1 we have investigated statistical characteristics of the nighttime medium scale traveling ionospheric disturbances mstids observed in 630 nm airglow images at two stations rikubetsu 43 5 n 34 8 mlat and shigaraki 34 9 n 25 4 mlat in japan for 1998 2000 near the solar maximum period most of the observed mstids propagate southwestward in the images the typical wavelength velocity period and amplitude are 100 300 km 50 100 m s 0 5 1 5 h and 5 15 respectively seasonal variations in these parameters are not clear the occurrence rate has a major peak 50 60 in summer that appears 2 months earlier at lower latitudes and a minor peak in winter similar occurrence characteristics are obtained from midlatitude spread f signatures using multipoint ionosonde data in japan though the coincidence of the spread f and the mstids in airglow images is only 10 15

a comparison of multiple proxies for export production in the equatorial pacific 1 several commonly used paleoproductivity proxies were compared to evaluate the validity of assumptions and limitations associated with each proxy export production fluxes cexport over glacial interglacial timescales were calculated from previously developed proxy specific algorithms at ttn013 pc72 and ttn013 pc114 both located in the equatorial pacific comparison of data from the same core intervals yields conflicting results despite calibrations based on the same core top samples the periodicity of marine barite excess ba and excess al based cexport records is similar the relative magnitude of cexport when calculated using excess ba and algorithms based on sediment trap data is significantly different than records based on core top calibrations particularly during glacial intervals at both sites bulk sedimentary al ti and ba ti ratios covary however these ratios do not correspond with the downcore records of their respective excess concentrations and their accumulation rates or with contemporaneous records based on marine barite excess ba and excess al accumulation although downcore records based on sediment mass accumulation rates may be compromised by sediment focusing this process cannot explain all the differences observed among the various data sets presented here this implies that some or all of these proxies do not exclusively respond to changes in export production the contradictions among these data highlight the importance of addressing inconsistencies among paleoproxies and re examining assumptions imbedded in proxy fundamentals prior to applying paleoproductivity proxies and interpreting paleoceanographic records