millennial scale sea surface temperature and patagonian ice sheet changes off southernmost chile 53 s over the past 60 kyr 1 glacial millennial scale paleoceanographic changes in the southeast pacific and the adjacent southern ocean are poorly known due to the scarcity of well dated and high resolution sediment records here we present new surface water records from sediment core md07 3128 recovered at 53 s off the pacific entrance of the strait of magellan the alkenone derived sea surface temperature sst record reveals a very strong warming of ca 8 c over the last termination and substantial millennial scale variability in the glacial section largely consistent with our planktonic foraminifera oxygen isotope 18o record of neogloboquadrina pachyderma sin the timing and structure of the termination and some of the millennial scale sst fluctuations are very similar to those observed in the well dated sst record from odp site 1233 41 s and the temperature record from drowning maud land antarctic ice core supporting the hemispheric wide antarctic timing of sst changes however differences in our new sst record are also found including a long term warming trend over marine isotope stage mis 3 followed by a cooling toward the last glacial maximum lgm we suggest that these differences reflect regional cooling related to the proximal location of the southern patagonian ice sheet and related meltwater supply at least during the lgm consistent with the fact that no longer sst cooling trend is observed in odp site 1233 or any sst chilean record this proximal ice sheet location is documented by generally higher contents of ice rafted debris ird and tetra unsaturated alkenones and a slight trend toward lighter planktonic 18o during late mis 3 and mis 2

southwest pacific deep water carbonate chemistry linked to high southern latitude climate and atmospheric co2 during the last glacial termination abstract a greater amount of co2 was stored in the deep sea during glacial periods likely via greater efficiency of the biologic pump and increased uptake by a more alkaline ocean reconstructing past variations in seawater carbonate ion concentration a major component of alkalinity enables quantification of the relative roles of different oceanic co2 storage mechanisms and also places constraints on the timing magnitude and location of subsequent deep ocean ventilation here we present a record of deep water inorganic carbon chemistry since the last glacial maximum lgm 19 23 ka bp derived from sediment core rr0503 83 raised from 1627 m in new zealand s bay of plenty the core site lies within the upper limit of southern sourced circumpolar deep water cdw just below the lower boundary of antarctic intermediate water aaiw we reconstruct past changes in bottom water inorganic carbon chemistry from the trace element and stable isotopic composition of calcite shells of the epibenthic foraminifer cibicidoides wuellerstorfi a record of co 3 2 co 3 2 co 3 2 i n s i t u co 3 2 saturation derived from the foraminiferal boron to calcium ratio b ca provides evidence for greater ice age storage of respired co2 and reveals abrupt deglacial shifts in co 3 2 i n s i t u of up to 30 mol kg 5 times larger than the difference between average lgm and holocene values the rapidity of these changes suggests the influence of changing water mass structure and atmospheric circulation in addition to a decrease in co2 content of interior waters

the cause of carbon isotope minimum events on glacial terminations the occurrence of carbon isotope minima at the beginning of glacial terminations is a common feature of planktic foraminifera carbon isotopic records from the indo pacific sub antarctic and south atlantic we use the 13 c record of a thermocline dwelling foraminifera neogloboquadrina dutertrei and surface temperature estimates from the eastern equatorial pacific to demonstrate that the onset of 13 c minimum events and the initiation of southern ocean warming occurred simultaneously timing agreement between the marine record and the 13 c minimum in an antarctic atmospheric record suggests that the deglacial events were a response to the breakdown of surface water stratification renewed circumpolar deep water upwelling and advection of low 13 c waters to the convergence zone at the sub antarctic front on the basis of age agreement between the absolute 13 c minimum in surface records and the shift from low to high 13 c in the deep south atlantic we suggest that the 13 c rise that marks the end of the carbon isotope minima was due to the resumption of north atlantic deep water influence in the southern ocean

quantitative assessment of volcanic ash hazards for health and infrastructure at mt etna italy by numerical simulation abstract we performed a quantitative hazard assessment to determine the potential impacts of volcanic tephra fall on human health and infrastructure in the vicinity of mt etna italy using the numerical model vol calpuff we explored the dynamics of long lasting weak plume eruptions and their effects on the surrounding region input data are based on credible estimates of the main parameters characterising the expected events as derived from the historically observed and reconstructed explosive record of mt etna monte carlo techniques are used to capture the effects on estimates of finer ash concentration and total ground deposition due to volcanological uncertainties and meteorological variability numerical simulations compute the likelihoods of experiencing critical 10 m volcanic particle vp 10 concentrations in ambient air and tephra ground deposition at various populated locations around the volcano including the city of catania and at key infrastructure such as airports and main roads results show how the towns and infrastructure on the east side of the volcano are significantly more exposed to ash related hazards than those on the west side in accordance with wind statistics simulation outcomes also illustrate how at the sites analysed the amount of deposited particulate matter is proportional to the intensity i e mass flow rate of the event whereas predicted values of vp 10 concentrations are significantly larger for smaller events due to the reduced dispersal of low altitude plumes the use of a simple re mobilization model highlights the fact that particle re suspension needs to be considered in the estimation of vp 10 values our findings can be used to inform civil protection agencies responsible for mitigating tephra fall impacts to human health road transport and aviation safety

northern timing of deglaciation in the eastern equatorial pacific from alkenone paleothermometry 1 the equatorial cold tongue ect of the eastern pacific is the most dynamic ocean region in the world s tropics and sets the tempo for global climate anomalies arising from el nino southern oscillation enso events this region s deglaciation history and relationship with north and south polar climates remains poorly understood impeding integration of tropical pacific ocean atmosphere dynamics and enso variability in our understanding of glacial cycles here we present alkenone reconstructions of sea surface temperature sst across the last glacial termination from five ect cores east of the galapagos islands a composite index of sst based on these demonstrates strong temporal affinity with the two step deglaciation of the northern hemisphere composed of two distinct warming steps at the beginning of the bolling and the end of the younger dryas intervals within dating uncertainty warming in the ect began in phase with the bolling excursion was followed by a 2 3 ka plateau and resumed with a second pulse at the end of the younger dryas on the basis of our reconstructions about two thirds of the warming materialized at or after the end of the younger dryas implying a marked delay in the region s response to deglaciation the results challenge the prevailing paradigm that ect deglacial history conforms to an antarctic timing commonly attributed to advection from the southern ocean through an interior oceanic link or to synchronous response of both regions to co2 forcing our results emphasize instead the role of dynamical adjustments linked to northern hemisphere processes most likely transmitted through the atmosphere

termination 1 timing in radiocarbon dated regional benthic δ18o stacks benthic 18o changes are often assumed to be globally synchronous but studies comparing 2 9 radiocarbon dated records over the most recent deglaciation termination 1 have proposed differences in the timing of benthic 18o change between the atlantic and pacific intermediate and deep and north and south atlantic because of the relatively small number of records used in these previous studies it has remained unclear whether these differences are local or regional in scale here we present seven regional benthic 18o stacks for 0 40 kyr b p that include 252 records with independent regional age models constrained by 852 planktonic foraminiferal 14c dates from 61 of these cores we find a 4000 year difference between the earliest termination onset in the intermediate south atlantic at 18 5 95 confidence interval 17 9 19 0 kyr b p and the latest in the deep indian at 14 5 14 1 15 0 kyr b p the termination onset occurs at 17 5 kyr b p in the intermediate and deep north atlantic deep south atlantic and deep pacific however throughout the termination deep north atlantic benthic 18o leads the deep pacific by an average of 1000 year and a maximum of 1700 year additionally the intermediate pacific termination onset at 16 5 16 1 16 9 kyr b p demonstrates that intermediate depth benthic 18o change was not globally synchronous these regional stacks provide better age models than a global stack across termination 1 and potentially important constraints on deglacial ocean circulation changes

constraint of the co2 rise by new atmospheric carbon isotopic measurements during the last deglaciation 1 the causes of the 80 ppmv increase of atmospheric carbon dioxide co2 during the last glacial interglacial climatic transition remain debated we analyzed the parallel evolution of co2 and its stable carbon isotopic ratio 13co2 in the european project for ice coring in antarctica epica dome c ice core to bring additional constraints agreeing well but largely improving the taylor dome ice core record of lower resolution our 13co2 record is characterized by a w shape with two negative 13co2 excursions of 0 5 during heinrich 1 and younger dryas events bracketing a positive 13co2 peak during the bolling allerod warm period the comparison with marine records and the outputs of two c cycle box models suggest that changes in southern ocean ventilation drove most of the co2 increase with additional contributions from marine productivity changes on the initial co2 rise and 13co2 decline and from rapid vegetation buildup during the co2 plateau of the bolling allerod

subantarctic mode water in the southeast pacific effect of exchange across the subantarctic front 1 this study considered cross frontal exchange as a possible mechanism for the observed along front freshening and cooling between the 27 0 and 27 3 kg m 3 isopycnals north of the subantarctic front saf in the southeast pacific ocean this isopycnal range which includes the densest subantarctic mode water samw formed in this region is mostly below the mixed layer and so experiences little direct air sea forcing data from two cruises in the southeast pacific were examined for evidence of cross frontal exchange numerous eddies and intrusions containing polar frontal zone pfz water were observed north of the saf as well as a fresh surface layer during the summer cruise that was likely due to ekman transport these features penetrated north of the saf even though the potential vorticity structure of the saf should have acted as a barrier to exchange an optimum multiparameter omp analysis incorporating a range of observed properties was used to estimate the cumulative cross frontal exchange the omp analysis revealed an along front increase in pfz water fractional content in the region north of the saf between the 27 1 and 27 3 kg m 3 isopycnals the increase was approximately 0 13 for every 15 of longitude between the 27 0 and 27 1 kg m 3 isopycnals the increase was approximately 0 15 for every 15 of longitude a simple bulk calculation revealed that this magnitude of cross frontal exchange could have caused the downstream evolution of samw temperature and salinity properties observed by argo profiling floats

a three dimensional eulerian model for transport and deposition of volcanic ashes abstract volcanic ash fallout represents a serious threat to people living near active volcanoes because it can produce several undesirable effects such as collapse of roofs by ash loading respiratory sickness air traffic disruption or damage to agriculture the assessment of such volcanic risk is therefore an issue of vital importance for public safety and its mitigation often requires to evaluate the temporal evolution of the phenomenon through reliable computational models we develop an eulerian model named fall3d for the transport and deposition of volcanic ashes the model is based on the advection diffusion sedimentation equation with a turbulent diffusion given by the gradient transport theory a wind field obtained from a meteorological limited area model lam and the source term derived from by buoyant plume theory it can be used to forecast either ash concentration in the atmosphere or ash loading on the ground model inputs are topography meteorological data given by a lam mass eruption rate and a particle settling velocity distribution a test application to the july 2001 etna eruption is presented

the vol calpuff model for atmospheric ash dispersal 2 application to the weak mount etna plume of july 2001 1 here the application of the vol calpuff model by barsotti et al to a weak plume erupted from mount etna in july 2001 is presented and discussed the reconstruction of the explosive event was obtained by using high resolution weather forecasts produced by a mesoscale nonhydrostatic model and volcanic source data coming from observations and analytical studies the plume rise and atmospheric dispersal models were investigated over 5 d of eruption mostly in terms of column height aerial ash concentration and ground deposition modeling results are shown as a function of various source conditions and compared to independent observations derived from satellite images and deposit mapping the application of vol calpuff clearly highlights the crucial role played by meteorological conditions in determining dispersal dynamics some of the most important effects described by the model are 1 the large wind field influence on the plume height determination and tilting 2 the contrasting dispersal patterns of ash particles of different sizes 3 the complex and somehow nonintuitive distribution of ash on the ground resulting in preferential directions of dispersal and quite irregular deposit patterns and 4 the impossibility to reproduce both the column height and the deposit accumulation pattern by adopting a steady state vent mass flow rate over the investigated 4 d period due to observed temporal changes in eruption dynamics modeling results also suggest the need for further integration of simulation outcomes with remote sensing and field reconstructions on ash dispersal processes in future

dual aircraft investigation of the inner core of hurricane norbert part i kinematic structure abstract on 24 25 september 1984 air motions and physical processes in the eyewall region of hurricane norbert were investigated with two national oceanic and atmospheric administration noaa aircraft operations center aoc wp 3d research aircraft one aircraft equipped with the airborne doppler radar flew repeated radial penetrations of the eyewall mapping the three dimensional wind field throughout a 40 km radius of the storm center these data provide the first complete documentation of the three dimensional wind field of the inner core of a hurricane on spatial scales of 10 25 km in the horizontal and 1 km in the vertical and temporal scales of 1 2 h the wind field was asymmetric and the asymmetry varied with altitude as altitude increased the location of the maximum tangential wind sloped upwind from left of the storm track at 1 km altitude to right of the storm track above 3 km the radial wind at 1 km altitude was inward in front of the storm and outward behind this pattern in the radial

eastern tropical pacific hydrologic changes during the past 27 000 years from d h ratios in alkenones 1 the tropical pacific plays a central role in the climate system by providing large diabatic heating that drives the global atmospheric circulation quantifying the role of the tropics in late pleistocene climate change has been hampered by the paucity of paleoclimate records from this region and the lack of realistic transient climate model simulations covering this period here we present records of hydrogen isotope ratios dd of alkenones from the panama basin off the colombian coast that document hydrologic changes in equatorial south america and the eastern tropical pacific over the past 27 000 years a and the past 3 centuries in detail comparison of alkenone dd values with instrumental records of precipitation over the past 100 a suggests that dd can be used as a hydrologic proxy on long timescales our records indicate reduced rainfall during the last glacial period that can be explained by a southward shift of the mean position of the intertropical convergence zone and an associated reduction of pacific moisture transport into colombia precipitation increases at 17 ka in concert with sea surface temperature sst cooling in the north atlantic and the eastern tropical pacific a regional coupled model forced by negative sst anomalies in the caribbean simulates an intensification of northeasterly trade winds across central america increased evaporative cooling and a band of increased rainfall in the northeastern tropical pacific these results are consistent with the alkenone sst and dd reconstructions that suggest increasing precipitation and sst cooling at the time of heinrich event 1

variability of subantarctic mode water and antarctic intermediate water in the drake passage during the late twentieth and early twenty first centuries a time series of the physical and biogeochemical properties of subantarctic mode water samw and antarctic intermediate water aaiw in the drake passage between 1969 and 2005 is constructed using 24 transects of measurements across the passage both water masses have experienced substantial variability on interannual to interdecadal time scales samw is formed by winter overturning on the equatorward flank of the antarctic circumpolar current acc in and to the west of the drake passage its interannual variability is primarily driven by variations in wintertime air sea turbulent heat fluxes and net evaporation modulated by the el nino southern oscillation enso despite their spatial proximity the aaiw in the drake passage has a very different source than that of the samw because it is ventilated by the northward subduction of winter water originating in the bellingshausen sea changes in aaiw are mainly forced by variability in winter water properties resulting from fluctuations in wintertime air sea turbulent heat fluxes and spring sea ice melting both of which are linked to predominantly enso driven variations in the intensity of meridional winds to the west of the antarctic peninsula a prominent exception to the prevalent modes of samw and aaiw formation occurred in 1998 when strong wind forcing associated with constructive interference between enso and the southern annular mode sam triggered a transitory shift to an ekman dominated mode of samw ventilation and a 1 2 yr shutdown of aaiw production the interdecadal evolutions of samw and aaiw in the drake passage are distinct and driven by different processes samw warmed by 0 3 c and salinified by 0 04 during the 1970s and experienced the reverse trends between 1990 and 2005 when the coldest and freshest samw on record was observed in contrast aaiw underwent a net freshening by 0 05 between the 1970s and the twenty first century although the reversing changes in samw were chiefly forced by a 30 yr oscillation in regional air sea turbulent heat fluxes and precipitation associated with the interdecadal pacific oscillation with a sam driven intensification of the ekman supply of antarctic surface waters from the south contributing significantly too the freshening of aaiw was linked to the extreme climate change that occurred to the west of the antarctic peninsula in recent decades there a freshening of the winter water ventilating aaiw was brought about by increased precipitation and a retreat of the winter sea ice edge which were seemingly forced by an interdecadal trend in the sam and regional positive feedbacks in the air sea ice coupled climate system all in all these findings highlight the role of the major modes of southern hemisphere climate variability in driving the evolution of samw and aaiw in the drake passage region and the wider south atlantic and suggest that these modes may have contributed significantly to the hemispheric scale changes undergone by those waters in recent decades

antarctic sea ice and the control of pleistocene climate instability a hypothesis is presented for the origin of pleistocene climate instability based on expansion of antarctic sea ice and associated changes in the oceans salinity structure the hypothesis assumes that thermohaline overturning is dominated by the reconfigured conveyor of toggweiler and samuels 1993b in which deepwater upwelling is restricted to high southern latitudes the reconfigured conveyor is shown to be potentially stabilized in an on mode by precipitation at high southern latitudes and potentially destabilized into on and off modes by the counteracting influence of antarctic sea ice the mechanism is clarified by the use of a hydraulic analogue we hypothesize that this mechanism accounts for dominant patterns of thermohaline overturning and climate instability between pleistocene warm and cold periods the hypothesis is shown to be consistent with a range of paleoceanographic evidence and to potentially account for details of observed rapid climate changes during glacial and interglacial periods including aspects of interhemispheric timing

mafalda an early warning modeling tool to forecast volcanic ash dispersal and deposition 1 forecasting the dispersal of ash from explosive volcanoes is a scientific challenge to modern volcanology it also represents a fundamental step in mitigating the potential impact of volcanic ash on urban areas and transport routes near explosive volcanoes to this end we developed a web based early warning modeling tool named mafalda modeling and forecasting ash loading and dispersal in the atmosphere able to quantitatively forecast ash concentrations in the air and on the ground the main features of mafalda are the usage of 1 a dispersal model named vol calpuff that couples the column ascent phase with the ash cloud transport and 2 high resolution weather forecasting data the capability to run and merge multiple scenarios and the web based structure of the procedure that makes it suitable as an early warning tool mafalda produces plots for a detailed analysis of ash cloud dynamics and ground deposition as well as synthetic 2 d maps of areas potentially affected by dangerous concentrations of ash a first application of mafalda to the long lasting weak plumes produced at mt etna italy is presented a similar tool can be useful to civil protection authorities and volcanic observatories in reducing the impact of the eruptive events mafalda can be accessed at http mafalda pi ingv it

a geostrophic transport estimate for the florida current from the oxygen isotope composition of benthic foraminifera we present a new method for the quantitative reconstruction of upper ocean flows for during times in the past for the warm t 5 c surface ocean density can be accurately reconstructed from calcite precipitated in equilibrium with seawater as both of these properties increase with decreasing temperature and increasing salinity vertical density profiles can be reconstructed from the oxygen isotopic composition of benthic foraminifera the net volume transport between two vertical density profiles can be calculated using the geostrophic method using benthic foraminifera from surface sediment samples from either side of the florida straits florida keys and little bahama bank we reconstruct two vertical density profiles and calculate a volume transport of 32 sv using this method this agrees well with estimates from physical oceanographic methods of 30 32 sv for the mean annual volume transport we explore the sensitivity of this technique to various changes in the relationship between temperature and salinity as well as salinity and the oxygen isotopic composition of seawater

el nino southern oscillation like variability during glacial terminations and interlatitudinal teleconnections interannual decadal variability in the equatorial pacific el nino southern oscillation enso induces climate changes at global scale but its potential influence during past global climate change is not yet well constrained new high resolution eastern equatorial pacific proxy records of thermocline conditions present new evidence of strong orbital control in enso like variability over the last 275 000 years recurrent intervals of saltier thermocline waters are associated with the dominance of la nina like conditions during glacial terminations coinciding with periods of low precession and high obliquity the parallel dominance of 13c depleted waters supports the advection of antarctic origin waters toward the tropical thermocline this oceanic tunneling is proposed to have reinforced orbitally induced changes in enso like variability composing a complex high and low latitude feedback during glacial terminations

links between eastern equatorial pacific stratification and atmospheric co2 rise during the last deglaciation it is difficult to untangle the mixed influences of high and low latitude climate forcing in the eastern equatorial pacific eep here we test the hypothesis that the southern ocean drove change in the eep via subsurface intermediate waters during the last deglaciation we use the 18o signature of benthic foraminifera to reconstruct water density changes during the last 25 kyr at three intermediate water depths 370 m 600 m and 1000 m in the eep carbonate 18o records a combined signature of temperature and salinity and is therefore more closely related to density than temperature or salinity alone we find that benthic foraminiferal 18o values decreased first in the subsurface simultaneously with rising temperatures over antarctica and propagated up to the surface within 3 kyr the early subsurface response initiated a rapid decrease in density stratification over the upper water column as indicated by reduced 18o gradients between surface and intermediate depths stratification of the upper water column remained low through the termination with stratification minima reached during heinrich stadial 1 and the younger dryas yd synchronous with the two part deglacial rise in atmospheric co2 centennial scale shifts toward heavier 18o signatures at 370 and 600 m during the yd indicate short lived shifts in the subantarctic mode water antarctic intermediate water boundary to shallower intermediate depths we suggest that decreased density gradients during the deglaciation accelerated vertical mixing across the eep and potentially the entire south pacific subtropical gyre which enhanced co2 delivery from depth to the surface ocean and atmosphere

multidecadal warming and shoaling of antarctic intermediate water antarctic intermediate water aaiw is a dominant southern hemisphere water mass that spreads from its formation regions just north of the antarctic circumpolar current acc to at least 20 s in all oceans this study uses an isopycnal climatology constructed from argo conductivity temperature depth ctd profile data to define the current state of the aaiw salinity minimum its core and thence compute anomalies of aaiw core pressure potential temperature salinity and potential density since the mid 1970s from ship based ctd profiles the results are used to calculate maps of temporal property trends at the aaiw core where statistically significant strong circumpolar shoaling 30 50 dbar decade 1 warming 0 05 0 15 c decade 1 and density reductions up to 0 03 kg m 3 decade 1 are found these trends are strongest just north of the acc in the southeast pacific and atlantic oceans and decrease equatorward salinity trends are generally small with their sign varying regionally bottle data are used to extend the aaiw core potential temperature anomaly analysis back to 1925 in the atlantic and to 1960 elsewhere the modern warm aaiw core conditions appear largely unprecedented in the historical record biennially and zonally binned median aaiw core potential temperatures within each ocean basin are with the notable exception of the subtropical south atlantic in the 1950s 70s 0 2 1 c colder than modern values zonally averaged sea surface temperature anomalies around the aaiw formation latitudes in each ocean and sectoral southern annular mode indices are used to put the aaiw core property trends and variations into context

glacial interglacial dynamics of the eastern equatorial pacific cold tongue intertropical convergence zone system reconstructed from oxygen isotope records record mean late holocene lh last glacial maximum lgm d 18 o amplitudes ranging between 1 0 and 1 3 we estimate that mean sea surface temperatures sst in this region during the lgm were on average 1 5 0 5 c lower than the lh larger d 18 o amplitudes are observed in sites north of the equator indicating a spatial pattern of reduced meridional sst gradient across the equator during the lgm this result is supported by comparison of mg ca sst reconstructions from two sites straddling the equator we interpret the reduction of this gradient during the lgm as evidence for a less intense cold tongue intertropical convergence zone itcz frontal system a more southerly position of the itcz and weaker southeast equatorial trades in the eep indexterms 1620 global change climate dynamics 3309 3339 meteorology and atmospheric dynamics ocean atmosphere interactions 0312 4504 3344 meteorology and atmospheric dynamics paleoclimatology 4231 oceanography general equatorial oceanography 4267 oceanography general paleoceanography keywords cold tongue itcz oxygen isotopes tropical pacific

an investigation into the sensitivity of idealised vortex interactions to initial conditions and island topography 1 this paper is aimed at investigating the effects of topography and initial conditions on self organization based on numerical experiments using the quasi geostrophic barotropic vorticity equation with topography term and advection equation models the results show that if the topography s maximum height is less than 1 5 km then the mutual rotation of the two meso vortices do not self organize however a single larger scale vortex is formed if this maximum topography height is larger than 1 5 km when there is no topography present two meso vortices do not self organize but if a meso vortex is added then self organization occurs and a synoptic scale typhoon like vortex forms

the last glacial termination a major puzzle of paleoclimatology is why after a long interval of cooling climate each late quaternary ice age ended with a relatively short warming leg called a termination we here offer a comprehensive hypothesis of how earth emerged from the last global ice age a prerequisite was the growth of very large northern hemisphere ice sheets whose subsequent collapse created stadial conditions that disrupted global patterns of ocean and atmospheric circulation the southern hemisphere westerlies shifted poleward during each northern stadial producing pulses of ocean upwelling and warming that together accounted for much of the termination in the southern ocean and antarctica rising atmospheric co2 during southern upwelling pulses augmented warming during the last termination in both polar hemispheres

role of tropics in changing the response to milankovich forcing some three million years ago appeared in regions that today have intense oceanic upwelling the eastern equatorial pacific and the coastal zones of southwestern africa and california there was furthermore a significant change in the earth s response to milankovich forcing obliquity signals became large but those associated with precession and eccentricity remained the same the latter change in the earth s response can be explained by hypothesizing that the global cooling during the cenozoic affected the thermal structure of the ocean it caused a gradual shoaling of the thermocline around 3 ma the thermocline was sufficiently shallow for the winds to bring cold water from below the thermocline to the surface in certain upwelling regions this brought into play feedbacks involving

2001 flank eruption of the alkali and volatile rich primitive basalt responsible for mount etna s evolution in the last three decades abstract since the early 1970s enhanced eruptive activity of mount etna has been accompanied by selective geochemical changes in erupted lavas among which a gradual increase of alkalis whose origin is still debated here we provide further insight into the origin of this recent evolution based on a detailed study of the chemistry and dissolved volatile content of melt inclusions trapped in olivine crystals of unusual plagioclase poor primitive basalt that was extruded during a highly explosive flank eruption in july august 2001 two types of lava were erupted simultaneously along a n s fracture system trachybasalts from the upper vents 2950 2700 m were simply drained out by fracturing of the central volcanic conduit they are identical to summit crater lavas and contain mg poor olivines fo 70 72 with evolved and volatile poor melt inclusions that represent late stage crystallisation during shallow open conduit degassing in contrast plagioclase poor basalt 80 of total extruded through the lower vents 2550 2100 m derived from lateral dyke intrusion of a more primitive and volatile rich magma across the sedimentary basement this primitive melt is best preserved in rare fo 82 4 80 5 skeletal olivines present in lapilli deposits from the most powerful activities at the 2550 m vent its high dissolved contents of h 2 o 3 4 wt co 2 0 11 to 0 41 wt s 0 32 wt cl 0 16 wt and f 0 094 wt point to its closed system ascent from 400 to 250 mpa 12 to 6 5 km depth b s l however the predominance of euhedral olivine phenocrysts with common reverse zoning cores fo 76 78 and rims fo 78 80 and decrepited inclusions shows that most of the erupted basalt derived from a slightly more evolved crystallizing body of the same magma that was invaded by the uprising primitive melt prior to erupting the few preserved inclusions in these olivines indicate pre eruptive storage of that magma body at about 5 km depth b s l in coherence with seismic data we propose that the 2001 flank eruption resulted from gradual overpressuring of etna s shallow plumbing system due to the influx of volatile rich primitive basalt that may have begun several months in advance we find that this basalt is much richer in alkalis 2 0 wt k 2 o and has higher s cl 2 0 but lower cl k and cl f ratios than all pre 1970s etnean lavas 1 4 wt k 2 o s cl 1 5 as further exemplified by melt inclusions in entrained olivine xenocrysts combining these new observations with previously published data we argue that the 2001 basalt represents a new alkali rich basic end member feeding mt etna only few amount of which had previously been extruded during a 1974 peripheral eruption and more recently during brief paroxysmal summit events over the last three decades this new magma has progressively mixed with and replaced the former k poorer trachybasalts filling the plumbing system leading to extrusion of gradually more primitive and alkali richer lavas its geochemical singularities cannot result from shallow crustal contaminations instead they suggest the involvement of an alkali richer but cl poorer arc type component during recent magma genesis beneath etna

investigation of the complex dynamics and structure of the 2010 eyjafjallajokull volcanic ash cloud using multispectral images and numerical simulations 1 we investigated the structure and evolution of the 2010 eyjafjallajokull volcanic cloud and its dispersal over iceland and europe integrating satellite multispectral images and numerical simulations data acquired by medium resolution imaging spectrometer meris and advanced spaceborne thermal emission and reflection radiometer aster have been analyzed to quantify the cloud extent and composition the vol calpuff dispersal code was applied to reconstruct the transient and 3 d evolution of the cloud source parameters estimated on the base of available a posteriori volcanological data sets have been used quantitative comparisons between satellite retrievals and modeling results were performed for two selected instants of time during the first and third eruptive phases on a regional scale sensitivity of the model to initial volcanological conditions has been analyzed at continental scale several complex non intuitive features of cloud dynamics have been highlighted and strengths and limitations of the adopted methods identified the main findings are the level of quantitative agreement between satellite observations and numerical results depends on ash cloud composition particle sizes and concentration with better agreement for smaller particles and higher concentrations the agreement between observations and modeling outcomes also depends on the temporal stability of volcanological conditions and the complexity of the meteorological wind field the irregular dispersion of ash as reconstructed from satellite data and numerical modeling can be well explained by the different response of particle sizes to strong vertical wind shear and by resuspension processes acting at ground level eruptive source conditions are the main source of uncertainty in modeling especially during an ongoing crisis and at long range scales

sea surface temperature variability in the pacific sector of the southern ocean over the past 700 kyr 1 in spite of the important role played by the southern ocean in global climate the few existing paleoceanographic records in the east pacific sector do not extend beyond one glacial interglacial cycle hindering circumpolar comparison of past sea surface temperature sst evolution in the southern ocean here we present three alkenone based pleistocene sst records from the subantarctic and subtropical pacific we use a regional core top calibration data set to constrain the choice of calibrations for paleo sst estimation our core top data confirm that the alkenone based uk37 and uk 37values correlate linearly with the sst in a similar fashion as the most commonly used laboratory culture based calibrations even at low temperatures down to 1 c rendering these calibrations appropriate for application in the subantarctic pacific however these alkenone indices yield diverging temporal trends in the pleistocene sst records on the basis of the better agreement with 18o records and other sst records in the subantarctic southern ocean we propose that the uk37 is a better index for sst reconstruction in this region than the more commonly used uk 37 index the uk37 derived sst records suggest glacial cooling of 8 c and 4 c in the subantarctic and subtropical pacific respectively such extent of subantarctic glacial cooling is comparable to that in other sectors of the southern ocean indicating a uniform circumpolar cooling during the pleistocene furthermore our sst records also imply massive equatorward migrations of the antarctic circumpolar current acc frontal systems and an enhanced transport of acc water to lower latitudes during glacials by the peru chile current

radiocarbon age anomaly at intermediate water depth in the pacific ocean during the last deglaciation 1 benthic and planktonic 14c ages are presented for the last glacial termination from marine sediment core vm21 30 from 617 m in the eastern equatorial pacific the benthic planktonic 14c age differences in the core increased to more than 6000 years between heinrich 1 time and the end of the younger dryas period several replicated 14c ages on different benthic and planktonic species from the same samples within the deglacial section of the core indicate a minimal amount of bioturbation scanning electron microscopy reveals no evidence of calcite alteration or contamination the oxygen isotope stratigraphy of planktonic and benthic foraminifera does not indicate anomalously old glacial age values and there is no evidence of a large negative stable carbon isotope excursion in benthic foraminifera that would indicate input of old carbon from dissociated methane it appears therefore that the benthic 14c excursion in this core is not an artifact of diagenesis bioturbation or a pulse of methane a benthic 14c stratigraphy reconstructed from the 14c ages from the deglacial section of vm21 30 appears to match that of baja margin core mv99 mc19 gc31 pc08 705 m but the magnitude of the low 14c excursion is much larger in the vm21 30 record this would seem to imply that the vm21 30 core was closer to the source of 14c depleted waters during the deglaciation but the source of this co2 remains elusive

climate impact of late quaternary equatorial pacific sea surface temperature variations magnesium calcium data from planktonic foraminifera in equatorial pacific sediment cores demonstrate that tropical pacific sea surface temperatures ssts were 2 8 0 7 c colder than the present at the last glacial maximum glacial interglacial temperature differences as great as 5 c are observed over the last 450 thousand years changes in sst coincide with changes in antarctic air temperature and precede changes in continental ice volume by about 3 thousand years suggesting that tropical cooling played a major role in driving ice age climate comparison of sst estimates from eastern and western sites indicates that the equatorial pacific zonal sst gradient was similar or somewhat larger during glacial episodes extraction of a salinity proxy from the magnesium calcium and oxygen isotope data indicates that transport of water vapor into the western pacific was enhanced during glacial episodes

interactions between a barotropic vortex and an idealized subtropical ridge part i vortex motion abstract a series of barotropic modeling experiments are used to examine the motion of a vortex in the vicinity of an idealized subtropical ridge the vortex propagation is highly correlated with the absolute vorticity gradient in the initial imposed environment the signal is degraded when radial band averages are used to calculate the environmental advection and absolute vorticity gradient components it is shown here that this is due partially to the difficulties in separating the cyclone from its environment application of the modeling results to climatological mean fields indicates that considerable variations in vortex propagation can occur

weaker gulf stream in the florida straits during the last glacial maximum as it passes through the florida straits the gulf stream consists of two main components the western boundary flow of the wind driven subtropical gyre and the northward flowing surface and intermediate waters which are part of the global conveyor belt compensating for the deep water that is exported from the north atlantic ocean1 the mean flow through the straits is largely in geostrophic balance and is thus reflected in the contrast in seawater density across the straits2 here we use oxygen isotope ratios of benthic foraminifera which lived along the ocean margins on the boundaries of the florida current during the last glacial maximum to determine the density structure in the water and thereby reconstruct transport through the straits using the geostrophic method a technique which has been used successfully for estimating present day flow3 our data suggest that during the last glacial maximum the density contrast across the florida straits was reduced with the geostrophic flow referenced to the bottom of the channel at only about two thirds of the modern value if the wind driven western boundary flow was not lower during the last glacial maximum than today these results indicate a significantly weaker conveyor belt component of the gulf stream compared to present day values whereas previous studies based on tracers suggested that deep waters of north atlantic origin were not widespread during glacial times indicating either a relatively weak or a shallow overturning cell our results provide evidence that the overturning cell was indeed weaker during glacial times

tropical cyclogenesis via convectively forced vortex rossby waves in a shallow water primitive equation model abstract this work examines further the problem of tropical cyclogenesis by convective generation of vertical vorticity within a preexisting cyclonic circulation whose initial maximum tangential wind is approximately 5 m s 1 this paper validates and extends recent work examining the suggested upscale cascade mechanism in a three dimensional quasigeostrophic framework using a simple shallow water primitive equation swpe numerical model and helps clarify certain aspects of the rossby adjustment problem on a nonresting basic state for finite amplitude nonaxisymmetric disturbances the swpe approach serves as a meaningful intermediate step between the quasigeostrophic and full physics frameworks and allows a simple investigation of the effects of unbalanced dynamics contributions of gravity waves and rossby numbers of order unity the authors compare quantitative results of the two models on the storm spinup time and magnitude for asymmetric initial conditions whose mass and wind field are out of balanc

carbon isotope evidence for changes in antarctic intermediate water circulation and ocean ventilation in the southwest pacific during the last deglaciation 1 deep sea sediment core fr1 97 gc 12 is located 990 mbsl in the northern tasman sea southwest pacific where antarctic intermediate water aaiw presently impinges the continental slope of the southern great barrier reef analysis of carbon 13c and oxygen 18o isotope ratios on a suite of planktonic and benthic foraminifera reveals rapid changes in surface and intermediate water circulation over the last 30 kyr during the last glacial maximum there was a large 13c offset 1 1 between the surface dwelling planktonic foraminifera and benthic species living within the aaiw in contrast during the last deglaciation termination 1 the 13cplanktonic benthic offset reduced to 0 4 prior to an intermediate offset 0 7 during the holocene we suggest that variations in the dominance and direction of aaiw circulation in the tasman sea and increased oceanic ventilation can account for the rapid change in the water column 13cplanktonic benthic offset during the glacial interglacial transition our results support the hypothesis that intermediate water plays an important role in propagating climatic changes from the polar regions to the tropics in this case climatic variations in the southern hemisphere may have led to the rapid ventilation of deep water and aaiw during termination 1 which contributed to the postglacial rise in atmospheric co2

on the interaction of tropical cyclone scale vortices ii discrete vortex patches the interaction of vortex patches in relation to the observed scales and features reported in part i of this paper is investigated it is found that the initial approach of compound vortices such as tropical cyclones arises from distortion of their weaker outer vorticity fields care needs to be taken in applying simple concepts such as the propagation of each vortex on the gradient of its neighbour for similar vortices the initial interaction consists of mutual orbit and approach with only minor fluctuations in shape once the vortices approach to within a critical separation distance rapid merger occurs a simplified expression for this critical distance is derived and it indicates that binary tropical cyclones must approach to within 150 300 km before merger of the cores can occur when vortices have substantial differences in size or intensity the smaller weaker system shears into the outer circulation of the other and no core merger occurs it is suggested that this is typical of the interaction between tropical cyclones and both the monsoon trough and embedded mesoscale convective complexes the motion of interacting vortices consists largely of a mutual orbit which scales according to their relative sizes and intensities an important finding however is that higher frequency meanders may develop this indicates that a tropical cyclone interacting with a monsoonal shear zone may develop internal asymmetries and a trochoidal oscillations as a direct result of such interaction further weak mesoscale vortices within the cyclone circulation may continue to cause a track meander long after they have been sheared beyond the resolving capacity of atmospheric observations

southern ocean contributions to the eastern equatorial pacific heat content during the holocene abstract temperature reconstructions from a shallow core 375 m from the peru margin are used to test the influence of subantarctic mode water samw on the eastern equatorial pacific eep thermostad and thus the effect of southern high latitude climate on interior ocean heat content ohc temperature estimates based on mg ca measurements of planktonic and benthic foraminifera neogloboquadrina dutertrei and uvigerina spp respectively show higher temperatures in the early holocene a cooling of 2 by 8 kyr b p and after relatively stable temperatures to the present the temperature signal is similar in direction and timing to a rather robust holocene climate signal from the southern high latitudes suggesting it originated there and was advected to the core site in the eep based on the n dutertrei and uvigerina mg ca temperature and 13c records we conclude that samw acted as a conduit transporting the southern high latitude climate to the interior of the equatorial pacific we propose that the early holocene warmth is related to a southward migration of the subtropical front which enhanced the influence of warm subtropical water in the region of samw formation and was then transported to the eep thermostad the early holocene warmth recorded in the eep thermostad has a muted sea surface temperature expression indicating this mechanism is important for sequestering heat in the ocean interior

the coalescence of two east australian current warm core eddies two warm core eddies coalesced in about 20 days as their centers rotated around a point on the contracting line that joined them in the process of forming the new eddy the subsurface isothermal isohaline signature layer of one eddy was uplifted and somewhat depleted while that of the other was depressed

an investigation into axisymmetrization of a vortex embedded in horizontal shearing currents 1 the problem of tropical cyclogenesis in a triple scale coexisting system which includes a subtropical high ridge a preexisting cyclonic circulation with the initial maximum tangential wind vbmax of 5 m s 1 and single double or four cluster anomalies is examined in this paper using a shallow water primitive equation swpe model this work validates the recent results concerning the upscale cascade mechanism suggested for tropical cyclogenesis in the double scale coexisting system containing the basic state vortex and anomalies and it is shown that for the double cluster anomaly the mean azimuthal maximum tangential wind of the final vortex is increased and the radius of the maximum tangential wind rmw is contracted in the case of 1 388 kut 0 0 in which kut usmax vbmax with usmax being the maximum of the easterlies south of the initial subtropical ridge which demonstrates an amplification of the vortex within this range of parameter for the single cluster anomaly of large amplitude the anomaly will become a master vortex and for the four cluster one the spin up of the initial basic state vortex will be decreased compared with the case of still environmental currents introducing the subtropical ridge will have the following impact on axisymmetrization in horizontal shearing currents 1 the interaction of a single cluster anomaly with the basic state vortex will occur in the environmental currents with cyclonic vorticity when the anomaly is located initially in the sw se quadrant of the basic state vortex the interaction between the anomaly and the basic state vortex makes the spin up double that in the case of still environmental currents 2 although axisymmetrization of vortex configuration may occur it is mainly limited to the inner region of the vortex with a distinct new nonaxisymmetry in its outer region and there exist a series of cells of smaller scales in the northeastern quadrant of the outer region 3 the total kinetic energy for the inner region of the vortex in the mean increases but fluctuates with time unlike the still environmental currents case in which it increases monotonically

the respiratory health hazards of volcanic ash a review for volcanic risk mitigation studies of the respiratory health effects of different types of volcanic ash have been undertaken only in the last 40 years and mostly since the eruption of mt st helens in 1980 this review of all published clinical epidemiological and toxicological studies and other work known to the authors up to and including 2005 highlights the sparseness of studies on acute health effects after eruptions and the complexity of evaluating the long term health risk silicosis non specific pneumoconiosis and chronic obstructive pulmonary disease in populations from prolonged exposure to ash due to persistent eruptive activity the acute and chronic health effects of volcanic ash depend upon particle size particularly the proportion of respirable sized material mineralogical composition including the crystalline silica content and the physico chemical properties of the surfaces of the ash particles all of which vary between volcanoes and even eruptions of the same volcano but adequate information on these key characteristics is not reported for most eruptions the incidence of acute respiratory symptoms e g asthma bronchitis varies greatly after ashfalls from very few if any reported cases to population outbreaks of asthma the studies are inadequate for excluding increases in acute respiratory mortality after eruptions individuals with pre existing lung disease including asthma can be at increased risk of their symptoms being exacerbated after falls of fine ash a comprehensive risk assessment including toxicological studies to determine the long term risk of silicosis from chronic exposure to volcanic ash has been undertaken only in the eruptions of mt st helens 1980 usa and soufriere hills montserrat 1995 onwards in the soufriere hills eruption a long term silicosis hazard has been identified and sufficient exposure and toxicological information obtained to make a probabilistic risk assessment for the development of silicosis in outdoor workers and the general population a more systematic approach to multi disciplinary studies in future eruptions is recommended including establishing an archive of ash samples and a website containing health advice for the public together with scientific and medical study guidelines for volcanologists and health care workers

an automatic procedure to forecast tephra fallout tephra fallout constitutes a serious threat to communities around active volcanoes reliable short term forecasts represent a valuable aid for scientists and civil authorities to mitigate the effects of fallout on the surrounding areas during an episode of crisis we present a platform independent automatic procedure with the aim to daily forecast transport and deposition of volcanic particles the procedure builds on a series of programs and interfaces that automate the data flow and the execution and subsequent postprocess of fallout models firstly the procedure downloads regional meteorological forecasts for the area and time interval of interest filters and converts data from its native format and runs the calmet diagnostic model to obtain the wind field and other micro meteorological variables on a finer local scale 3 d grid defined by the user secondly it assesses the distribution of mass along the eruptive column commonly by means of the radial averaged buoyant plume equations depending on the prognostic wind field and on the conditions at the vent granulometry mass eruption rate etc all these data serve as input for the fallout models the initial version of the procedure includes only two eulerian models hazmap and fall3d the latter available as serial and parallel implementations however the procedure is designed to incorporate easily other models in a near future with minor modifications on the model source code the last step is to postprocess the outcomes of models to obtain maps written in standard file formats these maps contain plots of relevant quantities such as predicted ground load expected deposit thickness and for the case of or 3 d models concentration on air or flight safety concentration thresholds

millennial scale glacial meltwater pulses and their effect on the spatiotemporal benthicδ18o variability 1 ratios of oxygen isotope values obtained from foraminiferal calcite are one of the most established paleoceanographic proxies they are used in the context of estimating variations in ice volume ocean temperature and salinity and provide a means to date marine sediment cores across different ocean basins our study addresses the question how the 18o of the deglacial meltwater signal propagates into the interior ocean when large scale millennial scale reorganizations of the atlantic meridional overturning circulation amoc are present analyzing a series of idealized tracer injection experiments conducted with an earth system model we find that a substantial weakening of the amoc leads to a massive delay in the export of the glacioeustatic oxygen isotope signal into the deep ocean whereas the atlantic pacific lag in benthic oxygen isotope signals is not increased furthermore it is shown that an amoc cessation causes a decoupling of 18o propagation time and water mass age in particular in the deep pacific our results lend further support to the notion that benthic oxygen isotope records obtained from stacks are not a useful global chronostratigraphic tool during periods of millennial scale global ocean circulation changes the regionally varying delay effect of the deglacial sea level signal studied here adds onto existing uncertainties in the interpretation and decomposition of benthic oxygen isotope in terms of sea level temperature and hydrographic variations