large scale successive boulder impacts on a rigid barrier shielded by gabions debris flows occur in multiple surges boulders entrained within the flow have been reported to incapacitate structures within its flow path single layer cushions such as gabions are often installed to shield debris resisting barriers from boulder impact however most relevant works only focus on single impact and the performance of gabions subjected to successive loading is still not well understood a new large scale pendulum facility was established to induce impact energy of up to 70 kj on an instrumented rigid barrier shielded by 1 m thick gabions the response of the gabions under six successive impacts was investigated results show that the peak boulder impact force given by the hertz equation is at least four times the measured values the recommended load reduction factor kc used in practice can be reduced by a factor of two after six successive impacts at an energy level of 70 kj the transmitted force increases by up to 40 based on the swiss guidelines a 13 increase of gabion thickn

comparison of interannual intrinsic modes in hemispheric sea ice covers and other geophysical parameters recent papers have described 18 year trends and interannual oscillations in the arctic and antarctic sea ice extents areas and enclosed open water areas based on newly formulated 18 2 year ice concentration time series they were obtained by fine tuning the sea ice algorithm tie points individually for each of the four sensors used to acquire the data in this paper these analyses are extended to an examination of the intrinsic modes of these time series obtained by means of empirical mode decomposition which handles both nonstationary and nonlinear data as found in these time series unlike filtering techniques based on fourier analysis our analysis centers on periodicities greater than one year quasi biennial and quasi quadrennial oscillations similar to those observed earlier with a multitaper filtered fourier analysis technique were also observed the intrinsic modes described feature frequency as well as amplitude modulation within their respective frequency bands the slowest varying mode in the antarctic sea ice cover has slightly less than a full period during this 18 2 year time period but the change in sign of its curvature hints at a modal period of about 19 years with important implications for the trend analyses published earlier

trends and patterns in the recent accumulation and oxygen isotopes in coastal dronning maud land antarctica interpretations from shallow ice cores to investigate recent variability in accumulation and d 18 o we synthesize data from five snowcores covering the period1932 96 fromthe sector16 38 w 4 48 e in coastal dronning maudland dml antarctica the d 18 orecords fromthe differentsites areremarkablysimilarand suggestacommon stablemoisturesourceforthis coastal section of dml while the accumulation pattern is local and specific features restricted to the individual sites the overall accumulation pattern is related to the temperature variability as indicated by coastal instrumental records accumulation and d 18 o correlate between 1955 and1985 but deviate thereafter with the proxy temperature record showing a positive trend while accumulation decreased this occurs at the same time as an increase in sea ice extentinthearea whichmayhaveresultedincirculationchangesandmorenortherlystorm paths both stacked accumulation and d 18 o records show that large scale atmospheric sig nals aswellas some pronounced individualevents arerecorded in dmlcoastal ice cores

oscillatory behavior in arctic sea ice concentrations we have done a frequency analysis of the 9 year record of sea ice concentrations obtained with the nasa nimbus 7 scanning multichannel microwave radiometer smmr because of the periodic revisit time of the smmr we are able to examine recurrence of shorter period oscillations as aliased by the revisit frequency and longer period oscillations per se a number of findings result from a sequence of two analysis schemes as follows we have first determined then removed the mean linear trend and seasonal cycle the latter composed of five harmonics of the annual cycle from the time series for each pixel of gridded smmr ice concentration data in the arctic using multiple linear regression we find that the 9 year trends are most positive in the beaufort and east greenland seas whereas the most negative areas are in the barents sea and the sea ice surrounding svalbard this is similar to trend patterns in the lengths of the sea ice season reported earlier by parkinson 1992 in the residual data the standard deviation ranges from 12 to 16 in the central arctic basin considerably above the estimated wintertime ice concentration accuracies of 5 in that region this is in part due to fluctuations in the ice concentration rather than noise secondly we have used fourier analysis and multiple taper filtering techniques to identify tentatively some of these fluctuations as tidal components or multiyear components similar to those found in the el nino southern oscillation index and we show their spatial distribution however there are some high amplitude periodic components that we have not yet been able to identify we show the spatial distribution of one of these components

influence of the antarctic circumpolar wave upon new zealand temperature and precipitation during autumn winter abstract autumn winter temperature and precipitation records at 34 stations over new zealand from 1982 to 1995 are found by empirical orthogonal function eof analysis to fluctuate together with 3 6 yr quasi periodicity similar to that associated with the antarctic circumpolar wave acw which propagates slowly eastward past new zealand in its global traverse around the southern ocean by allowing these eof time sequences to represent new zealand temperature and precipitation indices both the positive temperature index related to warm sea surface temperature sst anomalies around new zealand and the positive precipitation index related to warm cool sst anomalies north and east south and west of new zealand are found these warm cool sst anomalies are associated with poleward equatorward meridional surface wind msw anomalies the same as observed in association with the acw when warm cool sst and poleward equatorward msw anomalies are located north south of new zealand then anomalous

sea level pressure variability around antarctica since a d 1750 inferred from subantarctic tree ring records a tree ring chronology network recently developed from the subantarctic forests provides an opportunity to study long term climatic variability at higher latitudes in the southern hemisphere fifty long 1911 1985 homogeneous records of monthly mean sea level pressure mslp from the southern latitudes 15 65 s were intercorrelated on a seasonal basis to establish the most consistent long term trans polar teleconnections during this century variations in summer mslp between the south america antarctic peninsula and the new zealand sectors of the southern ocean are significantly correlated in a negative sense r 0 53 p 0 001 climatically sensitive chronologies from tierra del fuego 54 55 and new zealand 39 47 were used to develop verifiable reconstructions of summer november to february mslp for both sectors of the southern ocean these reconstructions which explain between 37 and 43 of the instrumentally recorded pressure variance indicate that inverse trends in mslp from diametrically opposite sides of antarctica have prevailed during the past two centuries however the strength of this relationship varies over time differences in normalized mslp between the new zealand and the south america antarctic peninsula sectors were used to develop a summer trans polar index stpi which represents an index of sea level pressure wavenumber one in the southern hemisphere higher latitudes tree ring based reconstructions of stpi show significant differences in large scale atmospheric circulation between the nineteenth and the twentieth centuries predominantly negative stpi values during the nineteenth century are consistent with more cyclonic activity and lower summer temperatures in the new zealand sector during the 1800s in contrast cyclonic activity appears to have been stronger in the mid twentieth than previously for the south american sector of the southern ocean recent variations in mslp in both regions are seen as part of the long term dynamics of the atmosphere connecting opposite sides of antarctica a detailed analysis of the mslp and stpi reconstructions in the time and frequency domains indicates that much of the interannual variability is principally confined to frequency bands with a period around 3 3 3 6 y cross spectral analysis between the stpi reconstruction and the southern oscillation index suggests that teleconnections between the tropical ocean and extra tropical mslp variations may be influencing climate fluctuations at southern latitudes

polynya dynamics a review of observations and modeling 1 polynyas are nonlinear shaped openings within the ice cover ranging in size from 10 to 105 km2 polynyas play an important climatic role first winter polynyas tend to warm the atmosphere thus affecting atmospheric mesoscale motions second ocean surface cooling and brine rejection during sea ice growth in polynyas lead to vertical mixing and convection contributing to the transformation of intermediate and deep waters in the global ocean and the maintenance of the oceanic overturning circulation since 1990 there has been an upsurge in polynya observations and theoretical models for polynya formation and their impact on the biogeochemistry of the polar seas this article reviews polynya research carried out in the last 2 decades focusing on presenting a state of the art picture of the physical interactions between polynyas and the atmosphere sea ice ocean system observational and modeling studies the surface heat budget and water mass transformation within these features are addressed

an investigation of the el nino southern oscillation cycle with statistical models 1 predictor field characteristics we have developed two sets of linear models for predicting equatorial pacific sea surface temperatures ssts from the indo pacific trade wind field and the near global sea level pressure slp field the models were constructed using a combination of extended empirical orthogonal functions eeofs and canonical correlation analysis cca a new approach in geophysical modeling our results are of interest both as they show the dominant modes of evolution in the slp and wind fields through the el nino southern oscillation cycle and with respect to the problem of predicting equatorial ssts this paper deals with the first issue above and describes some statistical composites that typify the development of features in the predictor fields over periods of years the results of the eeof analyses clearly show slowly propagating anomalies in both the near global slp and trade wind fields the cca analysis which highlights the co evolution of the two fields suggests a strong coupling between the two and depicts the anomalous features as migrating centers of divergence and convergence that first appear over the eastern indian ocean these features propagate slowly eastward amplify as they expand into the western pacific decline as they cross the central ocean then reamplify over the eastern pacific as reamplification takes place new opposing anomalies appear in the indo pacific descriptions of the predictor data sets and details of the statistical techniques used may also be found in this paper the sst data model validation techniques and forecast model results are presented in a companion paper graham et al this issue

antarctic intermediate water circulation and variability in a coupled climate model the variability of antarctic intermediate water aaiw in a long term natural integration of a coupled climate model is examined the mean state of the climate model includes a realistic representation of aaiw which appears centered on the su 5 27 2 kg m23 density surface hereinafter s 27 2 both in observations and the model an assessment of ventilation rates on the s 27 2 surface suggests that this particular climate model forms aaiw in a mostly circumpolar fashion with a significant contribution from antarctic surface water this motivates the assessment of oceanic variability along this core aaiw isopycnal surface complex empirical orthogonal function analyses decompose the variability into three dominant modes showing circumpolar patterns of zonal wavenumber 1 2 and 3 on the s 27 2 density surface the modes contain eastward propagating signals at interannual to centennial time scales mechanisms forcing this variability are investigated using heat and salt budget analyses at the wintertime outcrop of the s 27 2 surface such an approach ignores the mechanism of aaiw variability sourced by subantarctic mode water variations which has been examined previously and is for the most part beyond the present study variability in meltwater rates and atmospheric heat and freshwater fluxes are found to dominate the intermediate water variability at the outcrop region in contrast northward ekman transport of heat and salt plays a significant but localized role in aaiw temperature salinity variability there is also an important contribution from the antarctic circumpolar current to the variability at the outcrop region via zonal transport of heat and salt while the magnitude of aaiw natural variability can be large near the outcrop of the salinity minimum layer recent observations of cooling and freshening at depth are suggested to be beyond that of the unperturbed system

teleconnections in the southern hemisphere abstract teleconnections are calculated from monthly mean anomalies of sea level pressure and 500 mb geopotential height for the southern hemisphere 10 90 s for five month winter and summer seasons the monthly means were calculated from australian analyses for the period from june 1972 to november 1980 zonally averaged anomalies at both sea level and 500 mb display an out of phase relation between low and high latitudes and in midlatitudes are negatively correlated with anomalies in the subtropics and polar regions in winter a striking zonal wavenumber 3 pattern is found over the southern ocean anomalies in 500 mb geopotential heights at 50 s 95 e 58 s 150 w and 38 s 15 w exhibit strong positive correlations while showing weaker negative correlations with heights over antarctica and in low latitudes a similar pattern appears in sea level pressure in summer anomalies in 500 mb geopotential height over the three subtropical continents appear to occur out of phase with anomalies over the su

prevalence of the antarctic circumpolar wave over the last two millenia recorded in dronning maud land ice 1 the influence of atmospheric circulation patterns on sea salt aerosol deposition in the study area of the new epica european project for ice coring in antarctica deep drilling in dronning maud land dml antarctica has been investigated comparison of ice core records with reanalysis data showed that recent sea salt concentrations are strongly influenced by the occurrence of a blocking high pressure ridge over the eastern and enhanced storm activity over the western atlantic sector of the southern ocean so leading to marine intrusions thus enhanced sea salt export into dml these variations occur with periods of 4 5 and 12 14 yr the prior being associated with the antarctic circumpolar wave acw the prevalence of these periodicities in a 2000 year ice core record from dml shows for the first time that the acw is a prevalent feature of so atmosphere dynamics over the last two millennia

a recent sea ice retreat west of the antarctic peninsula satellite passive microwave data show a record decrease in sea ice extent in the bellingshausen sea from mid 1988 through early 1991 the change coincides with more southerly surface winds increased cyclonic activity and rising surface air temperatures which reached historic highs along the west coast of the antarctic peninsula in 1989 preceded by high ice cover in 1986 87 the retreat was most evident during summer in the formerly perennial sea ice field over the continental shelf ocean heat storage probably contributed to the persistence and coastal propagation of this anomaly

ice shelf elevation changes due to atmospheric pressure variations the inverse barometer effect ibe is the isostatic response of ocean surface height to changes in atmospheric pressure p air at a rate of about 1 cm hpa 1 the ibe is a significant contributor to variability of ice shelf surface elevation ice as we demonstrate with simultaneous global positioning system measurements of ice and local measurements of p air from the amery brunt and ross ice shelves antarctica we find that an ibe correction is justified for frequencies covering the weather band 0 03 0 5 cpd cycles per day the ibe correction reduces the standard deviation of the weather band signal of ice from 9 cm to 3 cm with this correction the largest remaining high frequency error signal in ice is the inaccuracy of the present generation of antarctic tide models estimated to be of order 10 cm for most of antarctica

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

a southern hemisphere booster of super el nino a distinct class of el nino events with extreme magnitude termed super el nino events in this study is identified after removing decadal variation these events occurred in 1972 1973 1982 1983 and 1997 1998 they are distinguished not only by their size but also by associated features such as a southern hemispheric transverse circulation that is not similarly robust in other el nino events this transverse circulation is characterized by a low level equatorward flow which spins off from a high sea level pressure anomaly around australia and then merges into the deep convection anomalies over the central pacific and by an upper level southward divergent flow which branches off from the convection center and connects to the subsidence of the australia high it is suggested that this transverse cell peaking in boreal summer serves as an effective booster during the developing stage of a super el nino by intensifying tropical pacific low level westerly winds

atmosphere sea ice low frequency variability with a simple model of the southern hemisphere summary a simple primitive equation general circulation model sgcm is used as a representation of an aquaplanet with no orography to model constant southern hemisphere winter conditions the statistical signie cance of the decadal and quasi biennial variability is erst assessed in a long time sgcm run by means of a frequencydomain statistical decomposition the modelled long wave atmospheric pattern is then associated with the observed southern hemisphere annular mode as suggested by previous studies using the same sgcm a simple linear relationship between the low level wind and the ice velocity is then introduced into the sgcm to investigate the feedbacks between the sea ice cover and the baroclinic waves the zonal mean state reached by the sea ice cover in a long coupled run a few hundred years exhibits characteristics similar to the observations investigation of the low frequency variability in the coupled simulation leads to the following results 1 statistically signie cant variability is observed on interdecadal decadal interannual and quasi biennial time scales 2 interdecadal decadal and quasi biennial signals are associated with the atmospheric annular mode that forces changes in the northward extent of the sea ice cover at all southern ocean longitudes 3 the interannual signal 3 6 year period exhibits spatio temporal patterns and propagation speed similar to the wellknown antarctic circumpolar wave

an anomalous late season change in the regional sea ice regime in the vicinity of the mertz glacier polynya east antarctica 1 this paper examines a major late season shift in atmospheric circulation over the east antarctic sea ice zone that occurred in october 1999 the mean wind direction at 65 s 145 e changed from south southeasterly to west southwesterly resulting in almost a complete reversal of the climatological east wind drift pattern in large scale sea ice advection over the southern ocean sector 135 170 e by comparison with national centers for environmental prediction national center for atmospheric research reanalysis time series from 1980 to 2000 this shift is shown to be unusual in terms of both its persistence and impact although similar though less prolonged patterns occurred in 1984 and 1985 lasting from october 1999 to february 2000 it had a profound impact on sea ice concentration and extent over a vast area by coinciding with the period of maximum ice extent and persisting through to the springtime melt phase it also contributed to the rapid annual meltback of sea ice it also had a large and complex effect on the behavior of the globally important mertz glacier polynya and on the areal extent of thick perennial sea ice to the east while a midlatitude blocking high pattern provided the initial impetus for the shift in 1999 the persistence of west southwesterly winds through february 2000 appears to relate to an unusually persistent southward migration of the antarctic circumpolar trough act in addition to the prolonged 1999 episode a strong seasonal signal is apparent throughout the mean wind speed and direction time series related to the act migration although less persistent than in 1999 this annual shift has implications for the observed dramatic annual meltback of east antarctic sea ice

signature of the brazil malvinas confluence argentine basin in the isotopic composition of planktonic foraminifera from surface sediments we explored the potential to use the stable isotopic compositions of planktonic foraminifera as a proxy for the position of the brazil malvinas confluence bmc in the argentine basin for this purpose we measured the oxygen and carbon isotopic compositions of globigerinoides ruber pink and white varieties measured separately globigerinoides trilobus globigerina bulloides globorotalia inflata and globorotalia truncatulinoides left and right coiling forms measured separately from a latitudinal transect of 56 surface sediment samples from the continental slope off brazil uruguay and argentina between 20 and 48 s lowest oxygen isotopes values were found in g ruber pink followed by g ruber white and g trilobus reflecting the highly stratified near surface water conditions north of the bmc globigerina bulloides was present mainly south of the bmc and records subsurface conditions supporting earlier plankton tow studies globorotalia inflata and g truncatulinoides left and right were both available over the whole transect and calcify in the depth level with the steepest temperature change across the bmc accordingly the 18 o of these species depict a sharp gradient of 2 at the confluence with remarkably stable values north and south of the bmc our data show that the oxygen isotopic composition of g inflata and g truncatulinoides left and right are the most reliable indicators for the present position of the bmc and can therefore be used to define the past migration of the front if appropriate cores are available

low frequency variability of the antarctic circumpolar wave this study evaluates the antarctic circumpolar wave acw variability in the southern ocean using a 27 year series of sea surface temperature sst and sea level pressure slp from a cross covariance analysis we find that the strongest covariation between the extratropical wavenumber 2 in sst and in slp is during the austral summer in the south pacific ocean examination of the time series reveals two timescales of variability a wavenumber 2 structure in sst and slp anomalies correlates well at interannual ia timescales when enso driven teleconnections seem to energize the acw moreover in the 1973 1999 epoch the acw has been modulated by interdecadal id variability possibly related to the southern oscillation

generation mechanism of the south pacific subtropical dipole abstractdistinct pattern of interannual variability in sea surface temperature sst in the south pacific i e the south pacific subtropical dipole spsd is examined using outputs from a coupled general circulation model the spsd appears as the second empirical orthogonal function eof mode of the sst anomalies in the south pacific and is associated with a northeast southwest oriented dipole of positive and negative sst anomalies in the central basin the positive and negative sst anomaly poles start to develop during austral spring reach their peak during austral summer and gradually decay afterward close examination of mixed layer heat balance yields that the sst anomaly poles develop mainly because warming of the mixed layer by shortwave radiation is modulated by the anomalous mixed layer thickness over the positive negative pole the mixed layer becomes thinner thicker than normal and acts to enhance reduce the warming of the mixed layer by climatological shortwave radiation this thin

dominant covarying climate signals in the southern ocean and antarctic sea ice influence during the last three decades abstracta composite dataset comprising geopotential height sea surface temperature zonal and meridional surface winds precipitation cloud cover surface air temperature latent plus sensible heat fluxes and sea ice concentration has been investigated with the aim of revealing the dominant time scales of variability from 1982 to 2013 three covarying climate signals associated with variations in the sea ice distribution around antarctica have been detected through the application of the multiple taper method with singular value decomposition mtm svd features of the established patterns of variation over the southern hemisphere extratropics have been identified in each of these three climate signals in the form of coupled or individual oscillations the climate patterns considered here are the southern annular mode sam the pacific south american psa teleconnection the semiannual oscillation sao and the zonal wavenumber 3 zw3 mode it is shown that most of the sea ice temporal variance i

an improved real time global sea surface temperature analysis abstract the monthly global sea surface temperature sst analysis of reynolds using real time in situ and satellite sst data has now been improved by using sea ice data to simulate ssts in ice covered regions the simulated ssts now become the external boundary condition for the analysis solution this technique eliminates any high latitude satellite biases and extends the analysis to the ice edge the analysis with the ice data has been computed for the period january 1982 to present

simple coupled midlatitude climate models a set of simple analytical models is presented and evaluated for interannual to decadal coupled ocean atmosphere modes at midlatitudes the atmosphere and ocean are each in sverdrup balance at these long timescales the atmosphere s temperature response to heating determines the spatial phase relation between sst and sea level pressure slp anomalies vertical advection balancing heating produces high low slp lying east of warm cold sst anomalies as observed in the antarctic circumpolar wave acw the decadal north pacific mode and the interannual north atlantic mode zonal advection in an atmosphere with a rigid lid produces low slp east of warm sst however if an ad hoc equivalent barotropic atmospheric response is assumed high slp lies east of warm sst relaxation to heating produces behavior like the observed north atlantic decadal pattern with low slp over warm sst meridional advection in the atmosphere cannot produce the observed sst slp patterns the dominant balance in the ocean s temperature equation determines the phase speed of the modes the coupled mode is nondispersive in all models examined here indicating the need for additional processes for modes with an sst slp offset as observed in the acw and north pacific ekman convergence acting as a heat source causes eastward propagation relative to the mean ocean flow sverdrup response to ekman convergence acting on the mean meridional temperature gradient causes westward propagation relative to the mean ocean flow when the ocean temperature adjusts through surface heat flux alone the mode is advected by the mean ocean flow and is damped relaxation to heating in the atmosphere when operating with sverdrup response in the ocean produces the only complete solution presented here that exhibits growth with an e folding timescale of order 100 days this solution appears appropriate for the north atlantic decadal mode in northern hemisphere basins with meridional boundaries the same sets of dynamics create the observed sst slp phase relation an additional factor is the creation of sst anomalies through variations in the western boundary current strengths which are related to the zonally integrated wind stress curl over the whole basin if barotropic and hence fast adjustment is assumed the resulting positive feedback can maintain or strengthen the coupled anomalies in the north pacific and interannual north atlantic modes

examples of the horizontal propagation of quasi stationary waves abstract examples of the diagnostic of the horizontal propagation of stationary wave activity proposed by plumb are presented for a simple model of the atmospheric response to thermal forcing in the tropics for the observed southern hemisphere winter mean stationary waves and for several cases of anomalous quasi stationary waves in both the northern and southern hemispheres for the simple model the propagation of wave activity out of the tropics is clear from the observational data the apparent sources of anomalous stationary wave activity are located in the regions of the major middle latitude jets and storm tracks in both hemispheres in most cases the results suggest that midlatitude processes such as instabilities of the jet stream or interaction with transient eddies are the major mechanisms for forcing anomalous stationary waves there are indications that rossby like wave propagation from low latitudes plays a role in forcing anomalous stationary waves associated with southern oscillation ev

subtropical sst dipole events in the southern indian ocean sea surface temperature sst anomalies in the subtropical southern indian ocean show interannual dipole events that are seasonally phase locked to the austral summer a positive phase of the event is characterized by cold sst anomalies in the eastern part i e off australia and warm sst anomalies in the southwestern part south of madagascar such an event is found to produce above normal rainfall over many regions in south central africa the cooling of sst in the eastern part is mainly caused by the enhanced evaporation this is associated with stronger winds along the eastern edge of the subtropical high which is strengthened and shifted slightly to the south during the event on the other hand relative decrease in the seasonal latent heat loss due to reduced evaporation dominates the warming in the southwestern part evolution of such subtropical dipole events shows quite a contrast to that of the tropical dipole events discovered recently in the indian ocean

the influence of the indian ocean dipole on antarctic sea ice abstractthis study explores the impact of the indian ocean dipole iod on the southern hemisphere sea ice variability singular value decomposition svd of september november sea ice concentration and sea surface temperature sst anomalies reveals patterns of el nino southern oscillation enso in the pacific and the iod in the equatorial indian ocean the relative importance of the iod s impact on sea ice in the pacific sector of antarctica is difficult to assess for two reasons 1 enso generates larger anomalies in the pacific and weddell sea and 2 many of the positive negative iods co occur with el nino la nina west of the ross sea sea ice growth can be attributed to the negative heat fluxes associated with cold meridional flow between high and low pressure cells generated by the effects of the iod however the locations of these positive and negative pressure anomaly centers tend to appear north of the sea ice zone during combined enso iod events reducing the influence of the iod on sea i

downslope convection north of elephant island antarctica influence on deep waters and dependence on enso 1 we present a long time series 1992 2001 of bottom temperature from 1040m on the continental slope north of elephant island antarctic peninsula a strong annual signal is apparent with minimum temperatures during or following the austral winter and a range similar to that found in much shallower waters on the adjacent shelf individual convective events are observable as large amplitude cold spikes that are confined to the period of seasonally coldest temperatures these plumes are dense enough to seasonally displace the circumpolar deep water and directly inject cold water into the deep open ocean the coldest water occurred when anomalous sea ice conditions were prevalent caused by the strong 1997 98 enso event we thus expect repeats of such strong convective events on enso timescales the observed long term warming and reduction in sea ice along the peninsula may however act to suppress this mode of ventilating the deep southern ocean

the thermal oceanographic signal of el nino reconstructed from a kiritimati island coral central equatorial pacific sea surface temperature sst anomaly is a critical predictor of basin wide oceanographic and atmospheric effects of the el nino southern oscillation enso phenomenon we employ two geochemical thermometers measured on coralline aragonite to reconstruct an independent proxy based measure of central equatorial pacific sea surface temperature anomaly in addition we assess the observational error associated with extraction of large scale sst anomalies from 18o and sr ca measurements on the basis of paired data for the 1981 1987 period rms error for the estimation of sst from kiritimati coral 18o is about 0 4 c assuming no seawater 18o influence for sr ca the observational error is about 0 5 c singular spectrum analysis of the 18o time series suggests that 1 3 of the variance is explained by sst anomaly and that this variance may be separated from other signals in the frequency domain the interannual component of the 18o record shares 70 variance with the interannual component of local sst anomaly estimates 0 84 and correlates as highly with nino3 region 150 w 90 w 5 n 5 s sst anomaly estimates comparison of annual averages of the 18o data with analyzed sst for 55 years suggests that the error in deriving annually averaged sst anomalies at kiritimati is about 0 4 c a global sst correlation analysis suggests significant correlation with the rest of the pacific basin and the tropical indian and atlantic sectors the ocean wide level of correlation achieved using the coral data is indistinguishable from that achieved using the nino3 sst anomaly index and suggests that a few well located coral reconstructions with low observational error may be sufficient to reconstruct the global sst anomaly field associated with enso activity

the antarctic circumpolar wave a combination of two signals abstract a simplified view of the possible mechanisms behind the antarctic circumpolar wave acw interannual variability is provided by a frequency domain decomposition of several observed atmospheric and oceanic variables two significant interannual signals with different temporal and spatial characteristics are identified in the southern ocean and most of the variance of the acw in the interannual band can be accounted for by a linear combination of them the first signal has a period of oscillation of around 3 3 yr and a zonal wavenumber 3 structure across the southern ocean it involves self sustained fluctuations inherent in the southern ocean and driven by coupled air sea interactions in which the atmosphere and the ocean mutually force one another this signal is represented by an atmospheric standing oscillation with centers at fixed locations around antarctica and a propagating oceanic pattern in which the surface antarctic circumpolar current plays an essential role the second signal has a

changes in dissolved oxygen in the southern ocean with climate change 1 climate models predict that increasing greenhouse gases in the atmosphere will change our climate however the range of observations available to assess these model predictions is limited we have utilized an ocean biogeochemical model to project the impact of climate change on the oxygen cycle in the ocean and the air sea exchange of oxygen with climate change our model predicts an outgassing of oxygen from the ocean in the model the southern ocean is the region that displays the largest change in the air sea exchange of oxygen with climate change the reduced oxygen uptake in the southern ocean is dominated by a reduction in convective mixing and in the subduction rate of bottom water which decreases the amount of dissolved oxygen in the southern ocean our model results suggest that dissolved oxygen is sensitive to changes in southern ocean circulation revealing the potential to use dissolved oxygen to test model predictions of climate change from southern ocean observations collected 28 years a part we observed a decrease in dissolved oxygen that was consistent with model climate change simulation this provides credibility to the climate model predictions additional analysis and observations of dissolved oxygen are needed to substantiate our climate model simulations

ice core evidence for antarctic sea ice decline since the 1950s the instrumental record of antarctic sea ice in recent decades does not reveal a clear signature of warming despite observational evidence from coastal antarctica here we report a significant correlation p

millennial scale climate changes on south georgia southern ocean abstract the location of south georgia 54 s 36 w makes it a suitable site for the study of the climatic connections between temperate and polar environments in the southern hemisphere because the mass balance of the small cirque glaciers on south georgia primarily responds to changes in summer temperature they can provide records of changes in the south atlantic ocean and atmospheric circulation we use grey scale density weight loss on ignition and grain size analyses to show that the proportion of glacially eroded sediments to organic sediments in block lake was highly variable during the last 7400 cal yr b p we expect that the glacial signal is clearly detectable above noise originating from nonglacial processes and assume that an increase in glacigenic sediment deposition in block lake has followed holocene glacier advances we interpret proglacial lake sediment sequences in terms of summer climate warming and cooling events prominent millennial scale features include cooling events between 7200 and 7000 5200 and 4400 and 2400 and 1600 cal yr b p and after 1000 cal yr b p comparison with other terrestrial and marine records reveals that the south georgian record captures all the important changes in southern hemisphere holocene climate our results reveal a tentative coupling between climate changes in the south atlantic and north atlantic because the documented temperature changes on south georgia are anti phased to those in the north atlantic

dynamics of sea surface temperature anomalies in the southern ocean diagnosed from a 2d mixed layer model we analyze the processes responsible for the generation and evolution of sea surface temperature anomalies observed in the southern ocean during a decade based on a 2d diagnostic mixed layer model in which geostrophic advection is prescribed from altimetry anomalous air sea heat flux is the dominant term of the heat budget over most of the domain while anomalous ekman heat fluxes account for 20 40 of the variance in the latitude band 40 60 s in the acc pathway lateral fluxes of heat associated with anomalous geostrophic currents are a major contributor dominating downstream of several topographic features reflecting the influence of eddies and frontal migrations a significant fraction of the variability of large scale sst anomalies is correlated with either enso or the sam each mode contributing roughly equally the relation between the heat budget terms and these climate modes is investigated showing in particular that anomalous ekman and air sea heat fluxes have a co operating effect with regional exceptions hence the large sst response associated with each mode it is further shown that enso or sam locked anomalous geostrophic currents generate substantial heat fluxes in all three basins with magnitude comparable with that of atmospheric forcings for enso and smaller for the sam except for limited areas enso locked forcings generate sst anomalies along the acc pathway and advection by mean flows is found to be a non negligible contribution to the heat budget exhibiting a wavenumber two zonal structure characteristic of the antarctic circumpolar wave by contrast sam related forcings are predominantly zonally uniform along the acc hence smaller zonal sst gradients and a lesser role of mean advection except in the southwest atlantic while modeled sst anomalies are significantly correlated with observations over most of the southern ocean the analysis of the data model discrepancies suggests that vertical ocean physics may play a significant role in the nonseasonal heat budget especially in some key regions for mode water formation

satellite altimetry the marine geoid and the oceanic general circulation for technical reasons the general circulation of the ocean has historically been treated as a steady laminar flow field the recent availability of extremely highaccuracy and high precision satellite altimetry has provided a graphic demonstration that the ocean is actually a rapidly time evolving turbulent flow field to render the observations quantitatively useful for oceanographic purposes has required order of magnitude improvements in a number of fields including orbit dynamics gravity field estimation and atmospheric variability with five years of very high quality data now available the nature of oceanic variability on all space and time scales is emerging including new findings about such diverse and important phenomena as mixing coefficients the frequency wavenumber spectrum and turbulent cascades because the surface elevation is both a cause and consequence of motions deep within the water column oceanographers soon will be able to provide general circulation numerical models tested against and then combined with the altimeter data these will be complete three dimensional timeevolving estimates of the ocean circulation permitting greatly improved estimates of oceanic heat carbon and other property fluxes

processes controlling upper ocean heat content in drake passage 1 a 16 year record of expendable bathythermograph transects across drake passage is used to examine variability in upper ocean heat content that is not associated with the annual cycle links between upper ocean heat content and anomalous heat fluxes winds two large scale climate indices and mesoscale eddies and meanders are examined results suggest that interannual variations in surface heat fluxes explain 5 to 10 of the variance in upper ocean heat content anomalous surface heat fluxes are linked to meridional wind anomalies upstream of drake passage which in turn are linked to forcing by el nino southern oscillation enso and the southern annular mode sam enso and sam are correlated with upper ocean heat content at near zero lags and statistically significant correlations occur at longer time lags as well the impact of mesoscale eddies and meanders on upper ocean heat content is explored with the use of a tracked eddy database an empirical relationship is constructed relating upper ocean heat content anomalies to eddy length scales and amplitudes eddies and meanders are estimated to account for more than one third of the nonannual cycle variance in drake passage upper ocean heat content

the pattern and variability of antarctic sea ice drift in the indian ocean and western pacific sectors sea ice drift physically redistributes pack ice and changes ice extent concentration and through deformation the ice thickness distribution in this paper data are presented from 39 satellite tracked buoys deployed during various seasons from 1985 to 1996 in the sea ice of the southern ocean off east antarctica between 20 and 160 e longitude the dominant features of the ice motion in the region are a westward drift parallel to the bathymetry near the antarctic continent a cyclonic circulation cell in prydz bay and eastward drift of the ice to the north of the zonal shear zone the oceanic circulation along the coast is generally barotropic and the ice drift is well correlated with bottom topography northward outflows the locations of which are determined by both bottom topography and the seasonally varying position of the zonal shear zone allow the discharge of sea ice from the westward drift in the south into the northerly belt of eastward flow but with considerable variability in the net northward ice transport the ice translation monitored by the buoys is used to derive the spatial pattern of the ice velocity field the daily average ice drift speed in the westward flow is 0 23 m s 1 19 8 km d 1 with considerable spatial and temporal variability and in the eastward flow the average is 0 17 m s 1 15 1 km d 1 seasonal and interannual ice drift variabilities are analyzed the results are compared with satellite data of sea ice extent and concentration over the same time as well as with hydrographic observation of the position of the antarctic divergence

an antarctic circumpolar wave in surface pressure wind temperature and sea ice extent the southern ocean is the only oceanic domain encircling the globe it contains the strong eastward flow of the antarctic circumpolar current and is the unifying link for exchanges of water masses at all depths between the world s major ocean basins1 as these exchanges are an important control on mean global climate the southern ocean is expected to play an important role in transmitting climate anomalies around the globe interannual variability has been often observed at high southern latitudes and observations of sea ice extent suggest that such features propagate eastwards around the southern ocean2 3 here we use data from a variety of observational techniques to identify significant interannual variations in the atmospheric pressure at sea level wind stress sea surface temperature and sea ice extent over the southern ocean these anomalies propagate eastward with the circumpolar flow with a period of 4 5 years and taking 8 10 years to encircle the pole this system of coupled anomalies which we call the antarctic circumpolar wave is likely to play an important role in climate regulation and dynamics both within and beyond the southern ocean

ocean circulation variations associated with the antarctic circumpolar wave altimeter data analysis indicates persistent sea surface height ssh anomalies propagating eastward about the antarctic continent the spatial and temporal characteristics match variations in the atmosphere and sea surface temperature sst that are associated with the antarctic circumpolar wave acw during the observation time period the ssh appears quasiperiodic with a dominant 4 year period and 180 longitude wavelength thus the ssh signature of the acw appears as two anomalies on opposite sides of the antarctic continent propagating eastward at 10 cm s the ssh response to observed wind forcing agrees in terms of amplitude and phase with simple quasigeostrophic dynamics

ice core evidence for secular variability and 200 year dipolar oscillations in atmospheric circulation over east antarctica during the holocene two holocene ice core records from east antarctica vostok and epica dome c were analysed for dust concentration and size distribution at a temporal resolution of 1 sample per 50 years a series of volcanic markers randomly distributed over the common part of the ice cores from 9 8 to 3 5 kyear bp ensures accurate relative dating 33 years dust size records from the two sites display oscillations structured in cycles with sub millennial and secular scale frequencies that are apparently asynchronous the power spectra of the composite sum of the two dust size records display spectral energy mostly for 150 to 500 year periodicities on the other hand the 200 year band is common to both records and the 200 year components of the two sites are out of phase 100 year lead or lag over 5 5 kyear a phenomenon also reflected by a significant 99 conf lev band in the power spectra of the composite difference of the two size records during long range transport mineral dust originating from the southern hemisphere continents is graded to a variable extent depending on the altitude and duration of atmospheric transport relatively coarse dust is associated with air mass penetration from the middle lower troposphere and conversely relatively fine dust with upper troposphere air masses or the influence of subsidence over the antarctic plateau a hypothesis already proposed for the changes that occurred during the last glacial maximum to holocene transition delmonte et al 2004b moreover we assume that the overall fluctuation of air mass advection over antarctica depends on the meridional pressure gradient with respect to low latitudes i e the antarctic oscillation aao we therefore suggest a regional variability in atmospheric circulation over east antarctica the 150 500 year power spectrum of the composite parameter represents the long term variability of the aao imprinted by secular internal oscillations probably related to the southern ocean climatic system on the other hand the dust composite parameter suggests a persistent atmospheric dipole over east antarctica delivering coarser finer dust particles alternatively to vostok and dome c regions with a bi centennial periodicity indeed a seesaw phenomenon in dust size distribution was already observed at three east antarctic sites during the last deglaciation delmonte et al 2004b and was interpreted as a progressive reduction of the eccentricity of the polar vortex with respect to the geographic south pole interestingly the parameter shows a pronounced 200 year oscillation mode throwing new light on the unresolved question of a possible relationship between climate and solar activity

ice core records as sea ice proxies an evaluation from the weddell sea region of antarctica 1 ice core records of methanesulfonic acid msa from three sites around the weddell sea are investigated for their potential as sea ice proxies it is found that the amount of msa reaching the ice core sites decreases following years of increased winter sea ice in the weddell sea opposite to the expected relationship if msa is to be used as a sea ice proxy it is also shown that this negative msa sea ice relationship cannot be explained by the influence that the extensive summer ice pack in the weddell sea has on msa production area and transport distance a historical record of sea ice from the northern weddell sea shows that the negative relationship between msa and winter sea ice exists over interannual 7 year period and multidecadal 20 year period timescales national centers for environmental prediction national center for atmospheric research ncep ncar reanalysis data suggest that this negative relationship is most likely due to variations in the strength of cold offshore wind anomalies traveling across the weddell sea which act to synergistically increase sea ice extent sie while decreasing msa delivery to the ice core sites hence our findings show that in some locations atmospheric transport strength rather than sea ice conditions is the dominant factor that determines the msa signal preserved in near coastal ice cores a cautious approach is thus required in using ice core msa for reconstructing past sea ice conditions including the need for networks of ice core records and multiproxy studies to assess the significance of past msa changes at different locations around antarctica

a quick response of the equatorial ocean to antarctic sea ice salinity anomalies the potential mechanisms for a quick response of the equatorial ocean to processes occurring in the high latitude southern ocean have been investigated in the southern ocean at the drake passage latitudes there is an zonally unbounded channel the antarctic circumpolar current belt accb it is demonstrated that in a multiconnected domain such as the accb signals generated by anomalies in the southern ocean sea ice cover salinity distribution can propagate in a wave like manner in the form of fast moving barotropic rossby waves a disturbance induced near the drake passage is demonstrated to generate a rossby wave that propagates across the pacific in only a few days this signal is reflected at the western boundary of the pacific and generates an equatorward propagating coastally trapped kelvin wave the resulting temperature anomaly moves northward along the western coastline up to the vicinity of the equator and increases in amplitude over time the anomaly in the western edge of equatorial pacific then begins to propagate eastward along the equator as a trapped equatorial wave after about 2 3 months this wave reaches the eastern coast reflects and generates the coastal trapped wave which propagates north and south along the coastline in both hemispheres this process is suggested as one possible direct mechanism by which the extratropical ocean can induce anomalies in the equatorial ocean

synchronous variability in the southern hemisphere atmosphere sea ice and ocean resulting from the annular mode zonally symmetric fluctuations of the midlatitude westerly winds characterize the primary mode of atmospheric variability in the southern hemisphere during all seasons this is true not only in observations but also in an unforced 15 000 yr integration of a coarse resolution r15 coupled ocean atmosphere model here it is documented how this mode of atmospheric variability known as the southern annular mode sam generates ocean circulation and sea ice variations in the model integration on interannual to centennial timescales that are tightly in phase with the sam the positive phase of the sam is associated with an intensification of the surface westerlies over the circumpolar ocean around 608s and a weakening of the surface westerlies farther north this induces ekman drift to the north at all longitudes of the circumpolar ocean and ekman drift to the south at around 308s through mass continuity the ekman drift generates anomalous upwelling along the margins of the antarctic continent and downwelling around 458s the anomalous flow diverging from the antarctic continent also increases the vertical tilt of the isopycnals in the southern ocean so that a more intense circumpolar current is also closely associated with positive sam in addition the anomalous divergent flow advects sea ice farther north resulting in an increase in sea ice coverage finally positive sam drives increases in poleward heat transport at about 308s while decreases occur in the circumpolar region ocean and sea ice anomalies of the opposite sign occur when the sam is negative the ocean and sea ice fluctuations associated with the sam constitute a significant fraction of simulated ocean variability poleward of 308s year round the robustness of the mechanisms relating the sam to oceanic variability suggests that the sam is likely an important source of large scale variability in the real southern hemisphere ocean

linkages between 200 mb tropical and extratropical circulation anomalies during the 1986 1989 enso cycle abstract nmc operational wind analyses have been used to document the 200 mb circulation anomalies during the solstice seasons of the 1987 1989 enso cycle using the one level vorticity balance diagnostic approach the 200 mb rossby wave anomalous source distribution was derived as departures from a three year mean for the single warm phase season january march 1987 the effective rossby wave anomaly sources were found to be generally quite small within 15 of the equator poleward of about 15 the anomalous 200 mb divergence through the planetary vorticity divergence anomaly stretching term is the dominant factor in determining the anomalous 200 mb vorticity source distribution its jfm standard deviation around 30 35 n was an order of magnitude larger than that found in the deep tropics the january march and june august 200 mb circulation differences between the warm and cold phase of the 1987 1989 enso cycle are described the enso cycle linkages between the equatorial pacific convection anomali

slow oceanic teleconnections linking the antarctic circumpolar wave with the tropical el nino southern oscillation a case study for the period 1982 1994 shows that a major source for the antarctic circumpolar wave is in the western subtropical south pacific where interannual anomalies in sea surface temperature sst and precipitable water prwat form once established these interannual anomalies in tandem with anomalies in sea level pressure slp move south toward the southern ocean the system then migrates east around the globe through a combination of oceanic advection with the antarctic circumpolar current and ocean atmosphere coupling the coincidence of interannual anomalies in sst slp and prwat indicates the extratropical ocean and atmosphere are tightly linked on these timescales large portions of the interannual sst anomalies branch advectively northward into the south atlantic and indian oceans ultimately reaching the tropics in each basin some 6 8 years after appearing in the low latitude pacific this constitutes a slow oceanic teleconnection that is unique in climate dynamics made possible by the continuity of earth s oceans via the southern ocean in the tropical indian ocean these interannual anomalies move east and arrive at the indo pacific transition in advance of the trans pacific propagation of the respective el nino southern oscillation enso phases the interannual sst and prwat anomalies that appear in the subtropical south pacific are directly linked with the enso cycle on the equator through anomalous vertical convection and a regional overturning cell in the troposphere the same cell that initiates fast planetary waves in the atmosphere that carry enso signals around the southern hemisphere on much shorter timescales

platinum group element geochemistry of continental tholeiites analysis of the long range dyke swarm newfoundland canada abstract the rift related late proterozoic long range continental dykes of western newfoundland have platinum group element pge pd pt rh ru and ir determined concentrations that correlate with indicators of magma evolution e g mg mg mg 0 9 fe tot and magma alkalinity la sm suggesting that metamorphism had a minimal effect on the pge the low melting point lmp pge pd pt and rh and cu behaved incompatibly as magma evolved indicating that sulphide fractionation did not occur and that the dykes hold little economic promise hypotheses that augite a major fractionating phase has an affinity for the pge are not supported primitive rocks tend to have lower ir than evolved rocks and all samples display a negative high melting point hmp pge ru and ir anomaly on mantle normalized diagrams olivine and early chromite fractionation may have decreased the concentrations of these elements the long range dykes confirm that pd ir ratios and absolute lmp pge concentrations tend to decrease with increasing hot spot magma alkalinity the lower pge concentrations in most morb compared with hot spot basalts imply that there are at least two mantle reservoirs for the pge lithosphere overlying mantle sources continental or oceanic has little effect on pge concentrations the apparently similar source region pge concentrations for hot spot basalts suggest that differences in pge concentrations between morb and hot spot basalts reflect incomplete segregation of the pge into the core during its formation and rise of the homogeneously dispersed elements to upper mantle depths in deep mantle plumes

the southern hemisphere westerlies in the australasian sector over the last glacial cycle a synthesis abstract the southern hemisphere westerlies in the southwest pacific are known to have waxed and waned numerous times during the last two glacial cycles though even semi continuous histories of the westerlies extend back no more than about 20 000 years we have good evidence for at least three scales of events a westerly maximum occurs at the last glacial maximum there is less conclusive evidence for another westerly maximum in the late holocene and for a minimum at ca 11 ka it is too early to ascribe even a cycle to these data but there are grounds to suggest that milankovitch precessional forcing may underlie the observed pattern there is also a quasi 2600 year cycle present in antarctic ice cores that appears to correlate to variation in westerly flow there is strong centennial scale variability in historical times the little ice age lia ca 1400 1850 was associated with a poleward shift in the circumpolar trough in the southern ocean strengthened westerly circulation over tasmania and a strengthening of southwesterly circulation and neoglaciation in southern new zealand while the preceding period 800 1400 ad was less certainly marked by reduced westerly flow from modern records we know that decadal and inter annual variability is important e g pacific decadal oscillation high latitude mode also known as the antarctic oscillation el nino southern oscillation only a minority of the proxies examined can identify changes on these temporal scales but data from tree rings ice cores and laminated lake sediments do indicate systematic changes in these phenomena through time rossby wave patterns are shown to play a critical role in long duration events as well as at the synoptic scale we conclude that westerly circulation is as strong now as at any time in the last glacial cycle in addition changes in latitudinal boundaries in the westerlies may be nearly as large in inter annual zonal shifts ca 2 maximum as in glaciation interglaciation movements ca 3 4 there is however reasonable evidence of strengthening weakening across much of the westerly belt at westerly maxima minima such as the lia early holocene

a 700 year record of southern hemisphere extratropical climate variability annually dated ice cores from west and east antarctica provide proxies for past changes in atmospheric circulation over antarctica and portions of the southern ocean temperature in coastal west and east antarctica and the frequency of south polar penetration of el nino events during the period ad 1700 1850 atmospheric circulation over the antarctic and at least portions of the southern hemisphere underwent a mode switch departing from the out of phase alternation of multi decadal long phases of eof1 and eof2 modes of the 850 hpa field over the southern hemisphere as defined in the recent record by thompson and wallace 2000 thompson and solomon 2002 that characterizes the remainder of the 700 year long record from ad 1700 to 1850 lower tropospheric circulation was replaced by in phase behavior of the amundsen sea low component of eof2 and the east antarctic high component of eof1 during the first phase of the mode switch both west and east antarctic temperatures declined potentially in response to the increased extent of sea ice surrounding both regions at the end of the mode switch west antarctic coastal temperatures rose and east antarctic coastal temperatures fell respectively to their second highest and lowest of the record polar penetration of el nino events increased during the mode switch the onset of the ad 1700 1850 mode switch coincides with the extreme state of the maunder minimum in solar variability late 20th century west antarctic coastal temperatures are the highest in the record period and east antarctic coastal temperatures close to the lowest since ad 1700 extratropical regions of the southern hemisphere have experienced significant climate variability coincident with changes in both solar variability and greenhouse gases

comments on southern mid to high latitude variability a zonal wavenumber 3 pattern and the antarctic circumpolar wave in the csiro coupled model abstract variability in the southern atmospheric circulation at mid to high latitudes with a dominant quasi stationary wavenumber 3 pattern has been reported in many observational studies the variability is barotropic in nature with signals in the middle troposphere as well as at the atmosphere ocean interface moreover there are preferred fixed centers for the strongest anomalies these features are well reproduced by the commonwealth scientific and industrial research organisation coupled model on various timescales on the interannual timescale an index of the modeled wavenumber 3 pattern shows little correlation with the modeled southern oscillation index suggesting that the variability associated with wavenumber 3 anomalies is separate to modeled enso like events however the variation of the pattern index is strikingly similar to and highly correlated with the modeled oceanic variability the associated oceanic anomalies move eastward and are similar to those of the observed antarctic circum

forcing of the antarctic circumpolar wave by el nino southern oscillation teleconnections we address several issues regarding the antarctic circumpolar wave acw these include the extent to which the acw is related to el nino southern oscillation enso cycles and the need to reconcile differences between the observed zonal wavenumber 2 pattern and the wavenumber 3 pattern found in coupled ocean atmosphere models in the present study we revisit the sea surface temperature sst signal of the observed acw we find that the associated sst variations may be decomposed into several empirical orthogonal functions eofs that are linearly independent the first four eofs describe 84 of the total variance on timescales of 3 7 years and superposition of sst signals of the four eofs reproduces sst signals of the observed acw given that eof analysis can only describe standing oscillations we then employ complex eof ceof analysis suitable for studying propagating waves the first two ceofs denoted ceofsst1 and 2 account for 70 of the total variance and the sst variability reconstructed from them again reproduces the observed acw the real part of ceofsst1 44 of the total variance is similar to the first real eof eofsst1 both eofsst1 and ceofsst1 may be identified with enso and have a wavenumber 2 zonal pattern in the southern middle to high latitudes ceofsst1 is the major constituent of the acw in the period of 1981 1997 the associated atmospheric circulation displays a pacific south america psa pattern statistical analyses demonstrate that the psa pattern teleconnected to enso is the major mechanism that forces this principal constituent of the acw ceofsst2 26 of the total variance has a zonal wavenumber 3 pattern in the same latitude band similar to that simulated by several coupled models we suggest that if enso is not adequately resolved in coupled models but structures with zonal wavenumber 3 pattern are then the modeled acw would appear to have a zonal wavenumber 3 pattern

spatial patterns in the length of the sea ice season in the southern ocean 1979 1986 the length of the sea ice season summarizes in one number the ice coverage conditions for an individual location for an entire year it becomes a particularly valuable variable when mapped spatially over a large area and examined for regional and interannual differences as is done here for the southern ocean over the years 1979 1986 using the satellite passive microwave data of the nimbus 7 scanning multichannel microwave radiometer three prominent geographic anomalies in ice season lengths occur consistently in each year of the data set countering the general tendency toward shorter ice seasons from south to north 1 in the weddell sea the tendency is toward shorter ice seasons from southwest to northeast reflective of the cyclonic ice atmosphere ocean circulations in the weddell sea region 2 directly north of the ross ice shelf anomalously short ice seasons occur lasting only 245 270 days in contrast to the perennial ice coverage at comparable latitudes in the southern bellingshausen and amundsen seas and in the western weddell sea the short ice season off the ross ice shelf reflects the consistently early opening of the ice cover each spring under the influence of upwelling along the continental slope and shelf and atmospheric forcing from winds blowing off the antarctic continent 3 in the southern amundsen sea anomalously short ice seasons occur adjacent to the coast owing to the frequent existence of coastal polynyas off the many small ice shelves bordering the sea least squares trends in the ice season lengths over the 1979 1986 period are highly coherent spatially with overall trends toward shorter ice seasons in the northern weddell and bellingshausen seas and toward longer ice seasons in the ross sea around much of east antarctica and in a portion of the south central weddell sea

global teleconnections in response to freshening over the antarctic ocean abstract in this paper coupled ocean atmosphere responses to freshening over the antarctic ocean are investigated in a fully coupled model with a series of sensitivity experiments in the model 1 0 sv 1 sv 106 m3 s 1 of freshwater flux is uniformly imposed over the antarctic ocean for 400 yr while the ocean and atmosphere remain fully coupled both locally and elsewhere the model explicitly demonstrates that a freshening of the antarctic ocean can induce a significant local cooling coupled with an intensification of the westerly winds and expansion of sea ice furthermore the cooling can extend to the entire southern extratropical and tropical oceans coupled with an intensification of southeasterly trades and the equatorial trade winds some modest warm anomalies also occur in the northern extratropical oceans forming a sharp interhemispheric sst contrast a series of sensitivity experiments are conducted to understand the mechanisms responsible for transmitting the southern high latitude cooling

influence of large scale teleconnection patterns on methane sulfonate ice core records in dronning maud land records of methane sulfonate ms in ice cores from the high plateau of dronningmaud land dml antarctica drilled in the framework of the european project for icecoring in antarctica are investigated for their potential as an environmental andclimate archive for the atlantic sector of the southern ocean despite postdepositionalchanges years of extraordinary ms concentrations can be clearly detected in the icecore records we use composite anomaly maps of atmospheric parameters from thenational centers for environmental prediction national center for atmospheric researchreanalysis fields for years of extreme ms concentration to detect atmospheric patternscausing ms variability changing atmospheric transport is shown to be an important but not exclusive parameter being conserved in the ms record in dml the oftenhypothesized direct link between high ms concentrations and el nino events is notsupported for the observed region whereas the antarctic dipole adp which ismodulated by el nino southern oscillation conditions exerts significant influence aclear 13 9 year cycle can be found throughout a 2000 year ms record that can be relatedto variations in the adp over the last 300 years a 4 6 year cycle is revealed in thems and sea salt record which vanishes in the deeper part of the ice core as aconsequence of diffusion processes from the long term perspective periods of high msconcentrations are connected to on average higher sea salt aerosol as well reflecting aseasonally independent influence of transport on both species a distinctive period ofefficient atmospheric transport probably due to a pronounced adp could be foundfrom 1200 to 1600 a d

eastward propagating decadal temperature variability in the south atlantic and indian oceans the origin and structure of eastward propagating decadal temperature variability in the south atlantic and indian oceans are investigated by using long term output of coupled general circulation model composite analysis during the warm southwest indian ocean swio years shows that decadal temperature anomalies in the swio region originate in the south atlantic and are associated with density anomalies since the density anomalies propagate at the speed of a few cm s 1 slower than the speed of the background eastward antarctic circumpolar current and exhibit a surface intensified equivalent barotropic structure the eastward propagation of the density anomalies may be attributed to quasi stationary oceanic rossby waves the density anomalies are also accompanied with anomalous ekman pumping indicating an important contribution from the overlying atmospheric variability the role of atmospheric variability is further examined by evaluating the mixed layer heat balance it is found that the warm temperature anomalies in the south atlantic are due to anomalous entrainment and meridional advection these results suggest that the atmospheric variability plays an important role through the ocean mixed layer in generating the eastward propagation of decadal temperature variability from the south atlantic besides the internal ocean variability as suggested in previous studies

evidence for the antarctic circumpolar wave in the sub antarctic during the past 50 years sea surface temperatures have been measured at the islands of marion 47 degrees s 38 degrees e from 1949 to 1998 and gough 40 degrees s 10 degrees w from 1956 to 1998 these are some of the longest records of their kind in the sub antarctic evidence for the passage of the antarctic circumpolar wave is apparent at each island presenting one of the most extended documentation of this phenomenon to date the highest negative correlation between the anomalies in each island s sea surface temperature record and the sea ice extent anomalies is observed directly south of each individual island the sea surface temperature anomalies at gough lead those at marion by about one year in average with mean precession periods of 8 6 8 9 and 10 4 years in the 60s 80s and 90s respectively these precession periods can be compared to those observed in the sea ice extent anomalies

sea level pressure variability in the amundsen sea region inferred from a west antarctic glaciochemical record using european center for medium range weather forecasts ecmwf numerical operational analyses sea ice extent records and station pressure data we investigate the influence of sea level pressure variability in the amundsen sea region on a west antarctic siple dome glaciochemical record empirical orthogonal function analysis of the high resolution siple dome multivariate ice core chemical time series record sdeof1 documents lower tropospheric transport of sea salt aerosols to the site during 1985 1994 the sdeof1 record of high low aerosol transport corresponds to anomalously low high sea level pressure slp in the amundsen sea region spatial correlation patterns between ecmwf monthly slp fields and the annual sdeof1 record suggest that a majority of sea salt aerosol is transported to siple dome during spring september october and november analysis of zonal and meridional wind fields supports the slp sdeof1 correlation and suggests the sdeof1 record is sensitive to changes in regional circulation strength no relationship is found between sea ice extent and the sdeof1 record for the period 1973 1994 to investigate the sdeof1 record prior to ecmwf coverage a spring transpolar index stpi is created using normalized slp records from the new zealand and south america antarctic peninsula sectors and is significantly correlated at least 95 c l with the sdeof1 record on an annual r 5 0 32 p 0 001 and interannual 3 years r 5 0 51 p 0 001 basis dominant periodicities 3 3 and 7 1 years in the annual sdeof1 record 1890 1994 a d suggest that a portion of the recorded interannual variability may be related tropical extratropical enso teleconnections changes in the periodic structure of the full 850 1994 a d siple dome record suggests a shift in slp forcing during the little ice age 1400 1900 a d interval