on temperature inversions and the mesospheric surf zone 1 mesospheric thermal inversions are investigated in a numerical simulation with the whole atmosphere community climate model an upward extension of the national center for atmospheric research s community climate model the seasonal character spatial extent and magnitude of the inversion layers are realistic during winter in the model the occurrence of wintertime inversions is a direct consequence of the rapid decay with height of vertically propagating planetary waves which induces large temperature perturbations in the upper mesosphere to maintain hydrostatic equilibrium the magnitude of the inversions is highly correlated with planetary wave amplitude so that large inversions develop during episodes of planetary wave amplification gravity waves do not play a major direct role in the formation of the inversions because the largest thermal tendencies associated with gravity wave breaking occur well above the range of altitudes where inversions are found however gravity waves play an essential indirect role because they set up a critical line in the upper mesosphere where rossby waves break in the mesospheric surf zone

connection between weak stratospheric vortex events and the pacific decadal oscillation we investigate the possible impacts of the pacific decadal oscillation pdo on the occurrence of weak stratospheric polar vortex wsv events in the northern hemisphere winter wsv events which are defined when polar cap geopotential height anomalies at 50 hpa fall below the 10th percentile in winter are observed more frequently during positive pdo phases than during negative pdo phases additionally tropospheric wave forcings that drive wsv events are remarkably different between the two phases of the pdo during the positive pdo phase the vertical propagation of wavenumber one waves plays a predominant role with a rather minor contribution of wavenumber two waves this contrasts with the negative pdo phase when the wsv events are primarily caused by wavenumber two waves this difference is partly related to the pdo induced tropospheric circulation anomalies over the north pacific whose zonal wavenumber one component constructively destructively interferes with climatological planetary scale waves during positive negative pdo winters the predominant wavenumber two wave forcings during the negative pdo phase are likely related to the enhanced tropospheric eddy activity over alaska that results from the poleward shift of the pacific jet in response to the negative pdo

dynamical mechanism for the increase in tropical upwelling in the lowermost tropical stratosphere during warm enso events the brewer dobson circulation strengthens in the lowermost tropical stratosphere during warm el nino southern oscillation enso events dynamical analyses using the most recent version of the whole atmosphere community climate model show that this is due mainly to anomalous forcing by orographic gravity waves which maximizes in the northern hemisphere subtropics between 18 and 22 km especially during the strongest warm enso episodes anomalies in the meridional gradient of temperature in the upper troposphere and lower stratosphere utls are produced during warm enso events accompanied by anomalies in the location and intensity of the subtropical jets this anomalous wind pattern alters the propagation and dissipation of the parameterized gravity waves which ultimately force increases in tropical upwelling in the lowermost stratosphere during cold enso events a similar signal but of opposite sign is present in the model simulations the signals in ozone and water vapor produced by enso events in the utls are also investigated

altered atmospheric responses to eastern pacific and central pacific el ninos over the north atlantic region due to stratospheric interference the two types of el nino that have been identified namely the eastern pacific ep and central pacific cp el ninos are known to exert different climatic impacts on the north atlantic region during winter here we investigate the characteristics of the teleconnection of the two el nino types with a focus on the stratosphere troposphere coupling during the ep el nino polar stratospheric warming and polar vortex weakening frequently occur with a strong tendency for downward propagation near the tropopause consequently the atmospheric pattern within the troposphere over the north atlantic sector during midwinter closely resembles the negative north atlantic oscillation pattern in contrast during cp el nino events stratospheric warming events exhibit a much weaker downward propagation tendency this difference in the stratospheric circulation response arises from the different seasonal evolution of the tropospheric wave response to the two el nino types for the ep el nino the aleutian low begins growing during december and is sustained throughout the entire winter december to february which provides favorable conditions for the continuous downward propagation of the stratospheric warming we also discuss the origin of the difference in the teleconnections from the two types of el nino associated with the distinct longitudinal position of the warm sst anomaly that determines troposphere stratosphere coupling

new models for evolution of magma poor rifted margins based on a review of data and concepts from west iberia and the alps direct observation and extensive sampling in ancient margins exposed in the alps combined with drill hole and geophysical data from the present day iberia margin result in new concepts for the strain evolution and near surface response to lithospheric rupturing at magma poor rifted margins this paper reviews data and tectonic concepts derived from these two margins and proposes that extension leading to thinning and final rupturing of the continental lithosphere is accommodated by three fault systems each of them characterized by a specific temporal and spatial evolution during rifting of the margin by its fault geometry and its surface response the data presented in this paper suggest that margin architecture and distribution of rift structures within the future margin are controlled first by inherited heterogeneities within the lithosphere leading to a contrasting behaviour of the future distal and proximal margins during an initial stage of rifting the place of final break up appears to be determined early in the evolution of the margin and occurs where the crust has been thinned during a first stage to less than 10 kilometres during final break up the rheology of the extending lithosphere is controlled by the thermal structure related to the rise of the asthenosphere and by serpentinization and magmatic processes

global sea level rise published values for the long term global mean sea level rise determined from tide gauge records exhibit considerable scatter from about 1 mm to 3 mm yr this disparity is not attributable to instrument error long term trends computed at adjacent sites often agree to within a few tenths of a millimeter per year instead the differing estimates of global sea level rise appear to be in large part due to authors using data from gauges located at convergent tectonic plate boundaries where changes of land elevation give fictitious sea level trends in addition virtually all gauges undergo subsidence or uplift due to postglacial rebound pgr from the last deglaciation at a rate comparable to or greater than the secular rise of sea level modeling pgr by the ice 3g model of tushingham and peltier 1991 and avoiding tide gauge records in areas of converging tectonic plates produces a highly consistent set of long sea level records the value for mean sea level rise obtained from a global set of 21 such stations in nine oceanic regions with an average record length of 76 years during the period 1880 1980 is 1 8 mm yr 0 1 this result provides confidence that carefully selected long tide gauge records measure the same underlying trend of sea level and that many old tide gauge records are of very high quality

a seismic reflection and gloria study of compressional deformation in the gorringe bank region eastern north atlantic seismic reflection and gloria side scan sonar data obtained on rrs charles darwin cruise cd64 reveal new information on the styles of deformation in the gorringe bank region at the eastern end of the azores gibraltar plate boundary previous studies suggest that gorringe bank was formed by the overthrusting of a portion of the african plate upon the eurasian plate the new seismic data show however that the most intensely deformed region is located south of gorringe bank on the northern flanks of a nw se trending submarine ridge which includes the ampere and coral patch seamounts the deformation is expressed as long wavelength up to 60 km large amplitude up to 800 m folds in the sediments and underlying acoustic basement which in places are associated with one or more reverse faults and as a fabric of short wavelength folds up to 3 km with a ne trend in contrast the same sedimentary units when traced beneath the flanking plains are undeformed except for some faults with a small throw 30 m some of which offset the seafloor gloria data show that recent deformation is broadly distributed over the region structural trends rotate from 45 in the west to 70 in the east of the region nearly perpendicular to the nw verging plate motion vectors as determined from plate kinematic models flexure modelling suggests that a portion of gorringe bank has loaded 152 ma oceanic lithosphere and that a maximum of 50 km of shortening has occurred at gorringe bank since the mid miocene our observations support a model in which there is no single plate boundary in the region rather that the deformation is distributed over a 200 330 km wide zone

a surrogate ensemble study of sea level reconstructions abstract this study investigates the possibility of reconstructing past global mean sea levels reconstruction methods rely on historical measurements from tide gauges combined with knowledge about the spatial covariance structure of the sea level field obtained from a shorter period with spatially well resolved satellite measurements a surrogate ensemble method is applied based on sea levels from a 500 yr climate model simulation tide gauges are simulated by selecting time series from grid points along continental coastlines and on ocean islands reconstructions of global mean sea levels can then be compared to the known target and the ensemble method allows an estimation of the statistical properties originating from the stochastic nature of the reconstructions different reconstruction methods previously used in the literature are studied including projection and optimal interpolation methods based on eof analysis of the calibration period this study also includes methods where these eofs are augm

the el nino southern oscillation enso modoki signal in the stratosphere el nino southern oscillation enso is known to be the largest source of interannual variability in the tropical troposphere however the variability in the tropical pacific since 1979 seems to be associated not only with canonical enso events but also with a variation thereof known as enso modoki which is characterized by warm anomalies in the central pacific west from those occurring during a typical enso this works analyzes the signal of enso modoki in the stratosphere and compares it to canonical enso by using the chemistry climate whole atmosphere community climate model waccm3 5 the results reveal a significant warming in the southern hemisphere polar stratosphere during boreal winter months which propagates downward in early spring this is absent during canonical warm enso events on the other hand in the northern hemisphere stratosphere the anomalous warming typical of canonical el nino episodes during boreal winter is not statistically significant during el nino modoki events these differences are related in waccm3 5 to changes in tropical convection and tropospheric teleconnections associated with each type of event in particular an enhancement and westward displacement of the anomalous convective area during el nino modoki episodes is related to an intensification of the pacific south american teleconnection pattern and a weakening of the aleutian low during cold enso modoki events a significant anomalous cooling is present in the model simulations

initial transient response of the winter polar stratospheric vortex to idealized equatorial pacific sea surface temperature anomalies in the ncar waccm abstractperpetual winter simulations using the ncar whole atmosphere community climate model waccm are conducted to document the differences of the initial transient response of the boreal winter northern hemisphere stratospheric polar vortex to central cpw and eastern pacific warming epw events idealized patches of positive sea surface temperature sst anomalies are superimposed onto a climatological sst field to mimic canonical cpw and epw forcings a 20 member ensemble was created by varying initial atmospheric conditions for both cpw and epw cases in the ensemble average the vortex weakens under both cpw and epw forcing indicated by a negative zonal mean zonal wind tendency this tendency is mainly tied to changes in the eddy driven mean meridional circulation mmc a negative anomaly in the eddy momentum flux convergence also plays a secondary role in the weakening the vortex response however differs dramatically among individual ensemble members a few ensemble members exhibit initial

global and regional sea level change during the 20th century sea level variations prior to the launch of satellite altimeters are estimated by analyzing historic tide gauge records recently a number of groups have reconstructed sea level by applying eof techniques to fill missing observations we complement this study with alternative methods in a first step gaps in 178 records of sea level change are filled using the pattern recognition capabilities of artificial neural networks afterward satellite altimetry is used to extrapolate local sea level change to global fields patterns of sea level change are compared to prior studies global mean sea level change since 1900 is found to be 1 77 0 38 mm yr 1 on average local trends are essentially positive with the highest values found in the western tropical pacific and in the indian ocean east of madagascar where it reaches about 6 mm yr 1 regions with negative trends are spotty with a minimum value of about 2 mm yr 1 south of the aleutian islands although the acceleration found for the global mean 0 0042 0 0092 mm yr 2 is not significant local values range from 0 1 mm yr 2 in the central indian ocean to 0 1 mm yr 2 in the western tropical pacific and east of japan these extrema are associated with patterns of sea level change that differ significantly from the first half of the analyzed period i e 1900 1950 to the second half 1950 2000 we take this as an indication of long period oceanic processes that are superimposed to the general sea level rise

the quest for the africa eurasia plate boundary west of the strait of gibraltar the missing link in the plate boundary between eurasia and africa in the central atlantic is presented and discussed a set of almost linear and sub parallel dextral strike slip faults the swim1 faults that form a narrow band of deformation over a length of 600 km coincident with a small circle centred on the pole of rotation of africa with respect to eurasia was mapped using a new swath bathymetry compilation available in the area offshore sw portugal these faults connect the gloria fault to the rif tell fault zone two segments of the plate boundary between africa and eurasia the swim faults cut across the gulf of cadiz in the atlantic ocean where the 1755 great lisbon earthquake m 8 5 8 7 and tsunami were generated providing a new insight on its source location

reconstruction of historical sea surface temperatures using empirical orthogonal functions abstract studies of climate variability often rely on high quality sea surface temperature sst anomalies although the high resolution national centers for environmental prediction formerly the national meteorological center optimum interpolation oi sst analysis is satisfactory for these studies the oi resolution cannot be maintained before november 1931 due to the lack of satellite data longer periods of ssts have come from traditional analyses of in situ ship and buoy sst observations alone a new interpolation method is developed using spatial patterns from empirical orthogonal functions e0fs that is a principal component analysis to improve analyses of sst anomalies from 1950 to 1981 the method uses the more accurate oi analyses from 1982 to 1993 to produce the spatial eofs the dominant eof modes which correspond to the largest variance are used as basis functions and are fit in a least squares sense to the in situ data to determine the time dependence of each mode a complete field

40ar 39ar ages for the alkaline volcanism and the basement of gorringe bank north atlantic ocean abstract gorringe bank is situated on the europe africa plate boundary at the eastern end of the azores gibraltar fracture zone it has two summits gettysburg bank to the southwest and ormonde bank to the northeast we applied the 40 ar 39 ar stepwise heating method to date six samples of the alkaline volcanic rocks two gabbros from the ormonde bank and a dolerite from the gettysburg bank the results that the alkaline volcanism lasted probably for less than 6 ma 66 60 ma although the nature of this volcanism precludes any subduction feature during its setting the alkaline volcanism of ormonde is probably linked to upper cretaceous eocene compressive tectonic events the basement rocks of gorringe bank reveal distrubed 40 ar 39 ar age spectra one plagioclase and one biotite from a gabbro give evidence for a thermic event whose age is tentatively estimated at about 75 ma and related to a variation in the direction of the relative movement between europe and africa the more probable age given by a plagioclase of another gabbro and by a dolerite 110 ma corresponds to tilting northeastward of the gorringe massif

propagation and initiation mechanisms of the madden julian oscillation 1 an observational study of the propagation and onset mechanisms of the madden julian oscillation mjo is performed using cyclostationary empirical orthogonal function analysis and a kelvin rossby wave decomposition method for the noaa outgoing longwave radiation and the ncep ncar reanalysis data in these analyses two different regions of surface convergence are observed ahead of mjo convection by different wind components as previously found in a sst coupled gcm simulation at the leading edge of enhanced convection the friction induced meridional convergence appears during the developing phase when the enhanced convection is located over the indian ocean and the maritime continents another region of surface convergence is identified just east of an enhanced convection core and this tends to pull the convective core to the east the surface convergence is formed by zonal wind convergence and kelvin and rossby waves both play a comparable role in the formation of the convergence zone therefore the frictional kelvin rossby wave cisk conditional instability of the second kind is regarded as a primary factor for the eastward propagation of the mjo over the western indian ocean moistening in the boundary layer occurs 2 weeks earlier than the beginning of a new mjo cycle this moistening accompanies low level convergence by encircling kelvin waves which propagated from the region of enhanced convection during the previous cycle as well as by rossby waves generated from the region of reduced convection over the indian ocean this earlier formation of the boundary layer moisture convergence provides a favorable environment for triggering new convection this interaction of kelvin and rossby waves also accounts for the suppression of convection from the western side of the convection core for example over the indian ocean anomalous surface divergence appears at the western edge of the enhanced convection due to both circumnavigating kelvin waves from the region of reduced convection of the previous cycle and rossby waves from the region of the enhanced convection itself thus the mjo is a self maintaining and self generating form of tropical variability through the interaction between convection and large scale circulation in the presence of boundary layer dynamics

morphotectonic characterization of major bathymetric lineaments in gulf of cadiz africa iberia plate boundary insights from analogue modelling experiments abstract new high resolution multi beam bathymetry data allowed the recognition of several bathymetric lineaments ca 100 km long trending wnw ese in seafloor sediments of the gulf of cadiz offshore sw iberia the interpretation of multi channel mcs profiles crosscutting these lineaments showed that they are controlled by underlying deep seated faults which have endured a polyphase reactivation history to get insights on the recent tectonic evolution of these structures we performed two sets of analogue modelling experiments assuming 1 right lateral strike slip basement faulting and coupled passive shearing affecting an overlying soft cover and 2 low angle transpressive deformation along a narrow shear band overlying the fault our results show a good correlation between the experimentally obtained structural patterns and the natural morphotectonic lineaments allowing the use of some of the observed natural features as strain gauges based on this we conclude that the study lineaments correspond to the bathymetric expression of ongoing dextral wrenching reactivation of wnw ese pre existing faults and we estimate the age of this tectonic reactivation as being ca 1 8 ma i e form late pliocene to present day these characteristics agree with the most recent kinematic models derived from geodetic observations indicating that present day convergence between nubia and iberia is subparallel to the newly identified lineaments and occurs at a 4 mm yr rate

post spreading deformation and associated magmatism along the iberia morocco atlantic margins insight from submarine volcanoes of the tore madeira rise abstract a new high resolution bathymetric map combined with a regional digital elevation model dem analysis reveal the modalities of occurrence and emplacement of post spreading magmatism along the nne ssw oriented 1000 km long tore madeira rise tmr as well as its relationship with the activity of major fault systems including the estremadura fault system esf and the azores gibraltar fracture zone agfz morphological and structural analysis of the bathymetric map were performed to map volcanic features such as eruptive cones vents and fissures together with faults along the tmr the new bathymetric map shows that the main nnw sse seamount alignment is formed by three structurally distinct volcanic massifs the tore the josephine and the southern volcanic groups the majority of the volcanoes of each group emplaced within or along specific portion of pre existing faults esf and agfz including splay fault releasing bend fault tips and interaction zones between different segments magmas were channelled into sub vertical pre existing lithospheric faults that acted as preferential pathways for the vertical magma ascent migration and final eruption of magma are controlled by the local stress variation induced by complex fault geometries change in plate kinematics as well as strong shear zone anisotropy as suggested by the emplacement within localised areas of transtension we conclude that post spreading magma emplacement in the southern part of the iberia margin was related to the development of a transtensional plate boundary between the iberian and african plate during the late cretaceous more generally our findings emphasize that the distribution of volcanism as the expression of the interaction between shallow plate tectonic and mantle processes should be included in plate kinematic reconstruction this study also demonstrates that the accurate mapping of oceanic seafloor is pivotal to better understand tectono magmatic evolution of volcanic seamount chains and geological processes in oceanic domains

impact of tropical sst on stratospheric planetary waves in the southern hemisphere abstractthe impact of tropical sea surface temperature sst on stratospheric planetary waves in the southern hemisphere sh is investigated in austral spring using observed sst and reanalysis data for the past three decades maximum covariance analysis indicates that the tropical sst and the sh stratospheric planetary wave activity are primarily coupled through two modes the leading two modes show the la nina like and the central pacific el nino like sst anomalies in their positive polarities respectively which each are related to enhanced stratospheric planetary wave activity these two modes also introduce phase shifts to the stratospheric stationary planetary waves a westward shift is seen for la nina and an eastward shift for warm sst anomalies is seen in the central pacific the eliassen palm fluxes associated with the two modes indicate that the anomalous stratospheric wave activity originates in the troposphere and propagates upward over the mid high latitudes so that the linkages between tr

improving sea level reconstructions using non sea level measurements 1 we present a new method for reconstructing sea level involving cyclostationary empirical orthogonal functions cseofs while we show results from a cseof reconstruction using basis functions computed from satellite altimetry and subsequently fit to tide gauge data our focus is on how other ocean observations such as sea surface temperature can be leveraged to create an improved reconstructed sea level data set spanning the time period from 1900 to present basis functions are computed using satellite measurements of sea surface temperature and using a simple regression technique these basis functions are transformed to represent a similar temporal evolution to corresponding satellite altimeter derived sea level basis functions the resulting sea level and sea surface temperature basis functions are fit to tide gauge data and historical sea surface temperature data respectively to produce a reconstructed sea level data set spanning the period from 1900 to present we demonstrate the use of this reconstructed data set for climate monitoring focusing primarily on climate signals in the pacific ocean the cseof reconstruction technique can be used to create indices computed solely from sea level measurements for monitoring signals such as the eastern pacific ep el nino southern oscillation enso central pacific cp enso and pacific decadal oscillation pdo the ep enso cp enso and pdo signals are all well represented in the cseof reconstruction relying solely on sea level measurements from 1950 to present however significant improvement can be made in reconstructing these signals during the first half of the twentieth century by including sea surface temperature measurements in the sea level reconstruction procedure

enso influences on southern hemisphere column ozone during the winter to spring transition 1 this study investigates how the el nino southern oscillation enso modulates the distribution of column ozone during the southern hemisphere sh winter to spring transition when a zonal asymmetry in column ozone develops near 55 s with a maximum south of australia enso differences in column ozone and planetary wave structure are explored for the average of seven el nino en versus six la nina ln events during 1982 2004 a westward shift in convection during ln corresponds to a 30 50 westward shift of sh planetary wave and column ozone patterns the extratropical lower stratospheric temperature anomalies are inversely correlated with tropical anomalies in similar longitude bands and are highly correlated with local column ozone anomalies the tropical signal is communicated to higher latitudes by modulating subtropical anticyclones with distinctive responses for en and ln years for each month during august and en a subtropical anticyclone extends from south america to south africa and the wave one asymmetry of the antarctic vortex is more pronounced and shifted eastward along with column ozone in september and en a strong anticyclone exists over south africa with a corresponding cold ozone poor anomaly in the stratosphere diminishing the western edge of the ozone maximum in october and ln a strong anticyclone exists over australia with an amplified trough on its poleward flank this trough is overlain by an ozone rich warm anomaly which expands the western edge of the ozone maximum and the polar vortex asymmetry is amplified and rotated westward

a general circulation model study of january climate anomaly patterns associated with interannual variation of equatorial pacific sea surface temperatures abstract a general circulation model has been run in the perpetual january mode to produce several long term simulations each distinguished by a different imposed equatorial pacific sea surface temperature from each of them simulations we have extracted an eight member ensemble of 90 day averaged fields ensemble mean difference maps are presented in this paper together with an estimate of the statistical significance of features which appear in thee maps these results are compared with observational studies in the literature that present difference maps of northern hemisphere winter fields composited according to some index related to the two extremes of equatorial pacific sea surface temperature variation the results show many anomaly patterns of high statistical significance that are also in good agreement with those observed in the tropics them include 990 mb wind sea level pressure and rainfall anomalies constituting the southern oscillation as well as a 200 mb height anomaly at all longitud

low frequency variations in global mean sea level 1950 2000 1 low frequency variability in global mean sea level gmsl is studied for the period 1950 2000 by interpolating sparse tide gauge data to a global grid using empirical orthogonal functions eofs of sea level variability determined from topex poseidon t p altimeter data results are based on data with long term trends removed the fact that the results do not have secular trends is an artifact of the analysis and should not be interpreted as an indication that sea level is not rising the eof reconstruction technique is discussed and the resulting gmsl time series is compared to gmsl time series from geosat and t p altimetry and proxy gmsl time series estimated from global sea surface temperature data the error assessment suggests the accuracy of the gmsl time series reconstructed from the tide gauge data is 2 4 mm rms for a 1 year running mean smoothing and about 1 mm for a 5 year running mean smoothing several el nino la nina events are evident in the gmsl as well as significant low frequency variability at a 10 12 year period gmsl appears to have been generally lower than normal in the late 1960s throughout the 1970s and in the 1980s gmsl appears to have been generally higher than normal in the late 1950s and early 1960s and in the early 1980s and has been rising throughout the 1990s when t p is observing the implication of the low frequency signals on the determination the secular rate of gmsl from satellite altimetry is discussed

propagation of enso temperature signals into the middle atmosphere a comparison of two general circulation models and era 40 reanalysis data the vertical propagation of the el nino southern oscillation enso temperature signal has been analyzed in two general circulation models the whole atmosphere community climate model and the middle atmosphere european center hamburg model and in the era 40 reanalysis data set monthly mean data have been used and composite differences el nino la nina have been computed our results show that the enso signal propagates into the middle atmosphere by means of planetary rossby waves significant wave like anomalies are observed up to around 40 km this propagation is strongly influenced by the zonal mean zonal winds being most effective in midlatitudes of the northern hemisphere because enso events tend to peak in northern winter when stratospheric winds are westerly in the northern hemisphere and allow vertical propagation of rossby waves in addition zonal mean temperature anomalies are observed in the middle atmosphere in the tropics and at polar latitudes of the northern hemisphere these anomalies are the result of changes in the residual mean meridional circulation our analysis reveals that during an el nino event vertical wave propagation and divergence of eliassen palm flux are enhanced forcing a stronger residual circulation in the stratosphere which cools the tropics and warms the higher latitudes this pattern is highly significant in the models during certain months but much less in the era 40 data where other sources of variability in particular the quasi biennial oscillation also influence the residual circulation

response of the antarctic stratosphere to two types of el nino events this study is the first to identify a robust el nino southern oscillation enso signal in the antarctic stratosphere elninoeventsbetween1979and2009areclassifiedaseitherconventional coldtongue events positive sst anomalies in the nino 3 region or warm pool events positive sst anomalies in the nino 4 region the 40 yr ecmwf re analysis era 40 ncep and modern era retrospective analysis for research and applications merra meteorological reanalyses are used to show that the southern hemisphere stratosphere responds differently to these two types of el nino events consistent with previous studies cold tongue events do not impact temperatures in the antarctic stratosphere during warm pool el nino events the poleward extension and increased strength of the south pacific convergence zone favor an enhancement of planetary wave activity during september november on average these conditions lead to higher polar stratospheric temperatures and a weakening of the antarctic polar jet in november and december as compared with neutral enso years the phase of the quasi biennial oscillation qbo modulates the stratospheric response to warm pool el nino events the strongest planetary wave driving events are coincident with the easterly phase of the qbo

an examination of observed southern oscillation effects in the northern hemisphere stratosphere abstract the effects of the southern oscillation on the december february mean circulation in the northern hemisphere stratosphere were investigated using 34 years of data no evidence for a significant relation between the southern oscillation so and the zonally averaged flow is found for any region poleward of 20 n the effects of the tropical quasi biennial oscillation qbo on the zonal mean flow are much stronger and this complicates the detection of 50 effects some more suggestive results are evident when hemispheric maps of height anomalies at 50 or 30 mb are composited for the warm extremes of the 50 the present findings are broadly consistent with earlier suggestions that on average the aleutian high is intensified during the warm extremes of the southern oscillation even using the 34 years of data now available however the statistical significance of this relationship cannot be demonstrated unequivocally once again the separation of so effects from qbo influences in the limited data a

tropical sst preconditioning of the sh polar vortex during winter 2002 the response of the southern hemisphere sh polar atmosphere to the tropical sea surface temperature sst during the 2002 winter spring season is investigated by using a general circulation model gcm the sh stratospheric winter of 2002 was particularly unusual characterized by a weaker than normal polar vortex during the whole season it also registered at the end of september the first major warming yet observed in the sh this event is unexpected in the sh and it is supposed to be induced by a preconditioning of the polar vortex starting at the beginning of the winter atmospheric gcm experiments with prescribed sst boundary conditions are performed the sensitivity of the antarctic dynamics to the tropical sst of 2002 a year characterized by an el nino event of moderate intensity is studied and the uniqueness of the 2002 tropical oceanic condition is investigated through the comparison of the simulated response of the climatic system to 2002 and 1997 tropical sst 1997 being a year with a strong el nino event model results highlight a primary role played by the tropical sst of 2002 in the development of the peculiar characteristics of the antarctic dynamics during the winter months that appears to be a necessary condition for the generation of the anomalous destabilization of the polar vortex during the following spring results for june 2002 show a strong generation of vertically propagating waves resulting from the tropical sst that through the perturbation of the westerly jet at middle latitudes produces a preconditioning of the polar vortex by affecting the wave refraction index the particular structure of the tropical sst anomalies during the winter of 2002 is thought to have influenced the subsequent preconditioning of the stratospheric vortex

tropospheric precursors of anomalous northern hemisphere stratospheric polar vortices regional extratropical tropospheric variability in the north pacific and eastern europe is well correlated with variability in the northern hemisphere wintertime stratospheric polar vortex in both the ecmwf reanalysis record and in the whole atmosphere community climate model to explain this correlation the link between stratospheric vertical eliassen palm flux variability and tropospheric variability is analyzed simple reasoning shows that variability in the north pacific and eastern europe can deepen or flatten the wintertime tropospheric stationary waves and in particular its wavenumber 1 and 2 components thus providing a physical explanation for the correlation between these regions and vortex weakening these two pathways begin to weaken the upper stratospheric vortex nearly immediately with a peak influence apparent after a lag of some 20 days the influence then appears to propagate downward in time as expected from wave mean flow interaction theory these patterns are influenced by enso and october eurasian snow cover perturbations in the vortex induced by the two regions add linearly these two patterns and the quasi biennial oscillation qbo are linearly related to 40 of polar vortex variability during winter in the reanalysis record

experiments in reconstructing twentieth century sea levels abstract one approach to reconstructing historical sea level from the relatively sparse tide gauge network is to employ empirical orthogonal functions eofs as interpolatory spatial basis functions the eofs are determined from independent global data generally sea surface heights from either satellite altimetry or a numerical ocean model the problem is revisited here for sea level since 1900 a new approach to handling the tide gauge datum problem by direct solution offers possible advantages over the method of integrating sea level differences with the potential of eventually adjusting datums into the global terrestrial reference frame the resulting time series of global mean sea levels appears fairly insensitive to the adopted set of eofs in contrast charts of regional sea level anomalies and trends are very sensitive to the adopted set of eofs especially for the sparser network of gauges in the early 20th century the reconstructions appear especially suspect before 1950 in the tropical pacific while this limits some applications of the sea level reconstructions the sensitivity does appear adequately captured by formal uncertainties all our solutions show regional trends over the past five decades to be fairly uniform throughout the global ocean in contrast to trends observed over the shorter altimeter era consistent with several previous estimates the global sea level rise since 1900 is 1 70 0 26 mm yr 1 the global trend since 1995 exceeds 3 mm yr 1 which is consistent with altimeter measurements but this large trend was possibly also reached between 1935 and 1950

internal variability of the troposphere stratosphere coupled system simulated in a simple global circulation model internal variability of a troposphere stratosphere coupled system is investigated in a series of numerical experiments with a simple global circulation model under a perpetual winter condition in order to examine the relative importance of forced planetary waves in the interaction with the zonal mean zonal flow and baroclinic disturbances amplitude of a sinusoidal surface topography of zonal wavenumber 1 or 2 is swept as an experimental parameter 1000 day integrations are performed for 110 combinations of the external parameters intraseasonal variability of the extratropical winter stratosphere in the parameter sweep experiment of the zonal wavenumber 1 topography is classified into four regimes dependent on the topographic amplitude i a nearly radiative equilibrium state ii small undulations of the polar vortex iii intermittent breakdowns of the polar vortex or occurrence of stratospheric sudden warming events and iv a usually weak and warm state of the polar vortex the behavior of planetary waves in the stratosphere is characterized by linear propagation in regime i and by quasi linear or weakly nonlinear wave mean flow interaction in regime ii in regimes iii and iv on the other hand it is in a highly nonlinear state reflecting the occurrence of sudden warming events and the usually distorted polar vortex respectively the northern hemisphere winter stratosphere corresponds to regime iii in the intraseasonal variations while the southern counterpart is close to regime ii a lag correlation analysis shows that the dynamical linkage between the stratosphere and the troposphere is also dependent on the regimes the vertical linkage is primarily the upward control in regime i planetary waves are generated by nonlinear interaction of baroclinic disturbances in the troposphere and propagate into the stratosphere in regime ii stratospheric variations are largely confined in the stratosphere although planetary waves are generated in the troposphere the linkage in regime iii on the other hand is inevitably two way planetary wave variability has upward influence from the troposphere to the stratosphere as well as the zonal mean zonal wind shows preconditioning in the troposphere before stratospheric sudden warming events downward propagation of signals to the upper troposphere are also seen in the zonal mean temperature in high latitudes it is higher than normal at the final stage of the sequence of sudden warming events the linkage is also two way in regime iv

northern hemisphere mid winter vortex displacement and vortex split stratospheric sudden warmings influence of the madden julian oscillation and quasi biennial oscillation we investigate the connection between the equatorial madden julian oscillation mjo and different types of the northern hemisphere mid winter major stratospheric sudden warmings ssws i e vortex displacement and vortex split ssws the mjo ssw relationship for vortex split ssws is stronger than that for vortex displacement ssws as a result of the stronger and more coherent eastward propagating mjos before vortex split ssws than those before vortex displacement ssws composite analysis indicates that both the intensity and propagation features of mjo may influence the mjo related circulation pattern at high latitudes and the type of ssws a pronounced quasi biennial oscillation qbo dependence is found for vortex displacement and vortex split ssws with vortex displacement split ssws occurring preferentially in easterly westerly qbo phases the lagged composites suggest that the mjo related anomalies in the arctic are very likely initiated when the mjo related convection is active over the equatorial indian ocean around the mjo phase 3 further analysis suggests that the qbo may modulate the mjo related wave disturbances via its influence on the upper tropospheric subtropical jet as a result the mjo related circulation pattern in the arctic tends to be wave number one wave number two 25 30 days following phase 3 i e approximately phases 7 8 when the mjo related convection is active over the western pacific during easterly westerly qbo phases which resembles the circulation pattern associated with vortex displacement vortex split ssws

tropospheric stratospheric wave propagation during el nino southern oscillation 1 traditional and 3 d extended eliassen palm ep fluxes for the globe between the 3 and 600 hpa levels are used to calculate el nino southern oscillation enso composites few of the warm minus cold departures of the traditional ep fluxes are significant at the 95 confidence level in contrast the enso composite differences of the longitudinally dependent extended ep flux have broad regions of significance for a wide range of latitudes longitudes and heights during an enso event there are significant vertical fluxes of wave energy across the tropopause over the subtropical pacific in addition there is substantial meridional exchange of wave energy in the upper troposphere and lower stratosphere in this region proceeding northward the changes in the stratosphere are associated with meridional exchanges of wave energy and strong vertical fluxes of wave energy across the pacific and north america the higher latitude changes have a westward tilt with height and eastward group velocities both suggesting the importance of rossby waves in the atlantic region there are strong downward fluxes of wave energy which may be part of an important enso pathway into europe overall these results strongly suggest the importance of nonzonally averaged dynamics in the stratospheric responses to enso

138 121 ma asthenospheric magmatism prior to continental break up in the north atlantic and geodynamic implications along the galicia and gorringe banks and in the iberia abyssal plain of the north atlantic unroofed sub continental mantle fills the gap between true oceanic crust and the continental crust margin these lithospheric peridotites are intruded by gabbros and dolerites and locally covered by basalts primary magmatic zircons extracted from gabbros and meta gabbros of the two banks were dated by the u pb chronometer and initial hafnium isotope signatures hfi were determined on the same grains for mt gettysburg at gorringe gabbro emplacement ages of 137 5 0 5 2 ma and 135 7 0 8 ma are obtained and corresponding hfi lie at 20 5 0 3 2 and 19 5 0 4 substantiating magma formation from severely lile depleted mantle domains gabbro zircons from mt ormonde at gorringe yield a much younger age of 77 1 0 4 ma and the hf isotopes document an intermediately lile depleted mantle source having a hfi of 7 6 0 4 given its age and hf signature emplacement of this rock can be ascribed to the alkaline magmatic event that also affected the iberian continent in upper cretaceous time concerning the galicia section zircons from a meta gabbro yield an emplacement age of 121 7 0 4 ma and a hfi of 14 0 0 2 and a hfi of 14 6 0 2 is obtained for zircons from a previously dated meta gabbro of identical age these results indicate magma extraction from mantle reservoirs that are slightly less lile depleted than those sampled by the about 20 myr older gorringe gabbros the data demonstrate that magmatism occurring prior to complete separation of europe from america was essentially of asthenospheric origin both the 138 135 ma ages for the gorringe gabbros and 122 ma ages for the galicia gabbros are at least 5 myr older than the oldest sediments on gorringe and the break up unconformity at the galicia bank respectively magma source signatures of the syn rift gabbros are in agreement with values expected for differently depleted cretaceous morb type mantle reservoirs and the age difference for magmatism between the gorringe and galicia banks suggests a rate of 4 4 0 3 cm yr for northward progression of continental rifting based on the new results a structural model for iberia america rifting is discussed putting forward the idea that magma emplacement produces a level of weakness and decollement between the rifting crust and its underlying lithospheric mantle

gorringe ridge gravity and magnetic anomalies are compatible with thrusting at a crustal scale summary the main features of the deep structure of the gorringe ridge are analysed on the basis of gravity and magnetic measurements as well as seismic profiles drill holes rock dredges submersible observations and seismicity data the gravity and magnetic models of the gettysburg and ormonde seamounts which form the gorringe ridge suggest that the moho is approximately flat and the upper part of the ridge corresponds to a northwestwards vergent fold this structure is the result of a northwestward vergent thrust that deformed the oceanic crust with a minimum slip of approximately 20 km the activity of the thrust probably started 20 myr and produced the recent stages of seamount uplift the seamount is mainly composed of gabbros of the oceanic crust serpentinized rocks and alkaline basalts the large antiform located in the hangingwall of the thrust is probably deformed by minor faults this oceanic ridge is a consequence of the oblique convergence between the african plate and the overlapping eurasian plate

tropical variability and stratospheric equatorial waves in the ipslcm5 model the atmospheric variability in the equatorial regions is analysed in the earth system model pre industrial simulation done at ipsl in the framework of cmip5 we find that the model has an interannual variability of about the right amplitude and temporal scale when compared to the el nino southern oscillation enso but that is too confined to the western pacific at the intra seasonal periods the model variability lacks of large scale organisation and only produces one characteristic madden julian oscillation every 10 winters typically at shorter time scales and in the troposphere the model has rossby and kelvin convectively coupled equatorial waves ccews but underestimates the kelvin ccews signal on olr in the model stratosphere a composite analysis shows that the temperature and velocities fluctuations due to the kelvin waves are quite realistic in the model nevertheless the stratospheric waves are less related to the convection than in the observations suggesting that their forcing by the midlatitudes plays a larger role still in the model the kelvin waves are not predominantly occurring during the life cycle of the tropospheric kelvin ccews a behaviour that we find to be dominant in the observations the composite analysis is also used to illustrate how the waves modify the zonal mean flow and to show that the model kelvin waves are too weak in this respect this illustrates how a model can have a reasonable kelvin waves signal on the velocities and temperature but can at the same time underestimate their amplitude to modify the mean flow we also use this very long simulation to establish that in the model the stratospheric equatorial waves are significantly affected by enso hence supporting the idea that the enso can have an influence on the quasi biennial oscillation

southern hemisphere summer mesopause responses to el nino southern oscillation abstractin the southern hemisphere sh polar region satellite observations reveal a significant upper mesosphere cooling and a lower thermosphere warming during warm enso events in december an opposite pattern is observed in the tropical mesopause region the observed upper mesosphere cooling agrees with a climate model simulation analysis of the simulation suggests that enhanced planetary wave pw dissipation in the northern hemisphere nh high latitude stratosphere during el nino strengthens the brewer dobson circulation and cools the equatorial stratosphere this increases the magnitude of the sh stratosphere meridional temperature gradient and thus causes the anomalous stratospheric easterly zonal wind and early breakdown of the sh stratospheric polar vortex the resulting perturbation to gravity wave gw filtering causes anomalous sh mesospheric eastward gw forcing and polar upwelling and cooling in addition constructive inference of enso and quasi biennial oscillation qbo could lead to st

the effect of signal to noise ratio on the study of sea level trends abstract extracting secular sea level trends from the background ocean variability is limited by how well one can correct for the time varying and oscillating signals in the record many geophysical processes contribute time dependent signals to the data making the sea level trend difficult to detect in this paper cyclostationary empirical orthogonal functions cseofs are used to quantify and improve the signal to noise ratio snr between the secular trend and the background variability obscuring this trend in the altimetric sea level record by identifying and removing signals that are physically interpretable over the 16 yr altimetric record the snr arising from the traditional least squares method for estimating trends can be improved from 4 0 of the ocean having an snr greater than one to 9 9 when using a more sophisticated statistical method based on cseofs from a standpoint of signal detection this implies that the secular trend in a greater portion of the ocean can be estimated with a hig

the southern oscillation part v the anomalies in the lower stratosphere of the northern hemisphere in winter and a comparison with the quasi biennial oscillation abstract the mean anomalies of 50 mb height in the northern winter for seven warm events in the southern oscillation show a weak polar vortex and an enhanced aleutian high in the mean for six cold events the polar vortex is unusually strong and the aleutian high is weakened and displaced far to the southwest these anomalies are consistent with the corresponding anomalies in sea level pressure pattern the warm events of 1963 and 1982 did not fit this pattern as in both years the polar vortex was cold and intense these events happened in years when volcanoes injected large amounts of gases and aerosols into the stratosphere and the temperature of the tropical stratosphere became unusually high in other warm events the temperature of the tropical stratosphere was abnormally low the mean anomalies of the quasi biennial oscillation for the winter as a whole west minus east phase computed from years with no cold or warm events are zonally symmetrical and shaped as four concentric regions with alternatin

influences of enso on stratospheric variability and the descent of stratospheric perturbations into the lower troposphere abstractthe linkage between el nino southern oscillation enso and north atlantic oscillation nao through the stratospheric pathway is examined using a global coupled climate model gfdl climate model version 3 cm3 with increased vertical resolution and extent in the stratosphere as compared to an earlier model gfdl climate model version 2 cm2 it is demonstrated that the relationship between enso and nao is stronger in cm3 than in cm2 it is found that enso plays an important role in modulating the frequency of occurrence of the stratospheric polar vortex anomalies through enhancement attenuation of the amplitudes of zonal wavenumbers 1 and 2 especially in late winter a higher frequency of weak strong stratospheric vortex events is simulated in cm3 during el nino la nina episodes the weak vortex events during el nino winters are preceded by enhancement of the zonal wave 1 pattern and weakening of zonal wave 2 pattern these modified tropospheric planetary waves propagate upward and then w

coral patch and ormonde seamounts as a product of the madeira hotspot eastern atlantic ocean terra nova 22 494 500 2010 abstract new detailed swath bathymetry and bottom samples from coral patch and ormonde seamounts provide constraints on the emplacement of the madeira hotspot in the eastern atlantic ocean swath bathymetric data document that coral patch is a composite structure made up of at least nine distinct volcanic centres lithified pelagic carbonates infilling fissures in lava blocks constrain a minimal age for the volcanism in the early miocene and represent the first documentation of coral patch acting as an offshore terrigenous starved seamount at coral patch as already observed at the ormonde seamount volcanism was emplaced on top of a pre existing relief resulting from the regional tectonic compressive regime

petrology of the alkaline volcanism of gorringe bank southwest portugal abstract alkaline volcanic rocks of the gorringe bank overlie typical oceanic crust made up of spilitized dolerites differentiated gabbroic and ultramafic rocks two main series are distinguishable in alkaline volcanics one from nephelinite to phonolite the other from lamprophyre to trachyte each sequence is differentiated by fractional crystallization with separation of clinopyroxene in the first one and kaersutite and mica in the second an intermediate suite is rich in lamprophyric and trachytic ocelli and in cognate ijolitic inclusions hypotheses on the origins of the more mafic lavas and on the influence of fluids like h 2 o and co 2 are discussed these series have a similar petrology to that of the sines and monchique complexes which intrude the continental crust at the same time on the same structural trend the alkaline rocks of gorringe are among the most alkaline series of the atlantic islands close to those of fernando de noronha and trindade where similar rocks occur

the signature of enso in global temperature and precipitation fields derived from the microwave sounding unit abstract global temperature anomalies associated with enso are investigated making use of a 13 year record of gridded temperature and precipitation data from the microwave sounding unit msu the warm phase of the enso cycle during this period was characterized by an overall warming of the tropical troposphere superimposed upon a distinctive equatorially symmetric dumbbell shaped pattern straddling the equator near 140 w accompanied by negative anomalies along the equator over the western pacific by means of singular value decomposition svd analysis it is shown that this pattern fluctuated in phase with the displacements of convective activity over the equatorial pacific as reflected in the anomalies in outgoing longwave radiation olr and msu precipitation fields fluctuations in mean tropical tropospheric temperature lagged the olr anomalies and the related temperature pattern by about 3 months the same dumbbell shaped pattern was evident with reversed polarity in the lower stratosphere tog

the 6 5 day wave and its seasonal variability in the middle and upper atmosphere 1 the zonal wave number 1 planetary wave of period near 6 5 days is a robust feature in the mesosphere and lower thermosphere mlt region with prominent seasonal variability as revealed by ground based and satellite observations this wave and its seasonal variability are well reproduced in a recent one model year run of the national center for atmospheric research thermosphere ionosphere mesosphere electrodynamics general circulation model time gcm with its lower boundary specified according to the national centers for environmental prediction analysis year 1993 wavelet analysis of the model output shows that in the mlt region the wave maximizes before and after the equinoxes and minimizes at solstices the wave amplitudes at the equinoxes are smaller than the peaks before and after but are still larger than the wave amplitudes at solstices however at the lower boundary near 30 km the wave peaks are predominantly between fall and the following spring by examining the episodes of maximum and minimum wave amplitude and by conducting additional control experiments using the time gcm the structure of this planetary wave and the factors determining the wave characteristics and seasonal variability are studied in detail it is found that the wave source mean wind structure instability and the critical layers of the wave can all affect the wave response in the mlt region and can have a strong seasonal dependence before and after equinox the wave follows the waveguide and propagates from the stratosphere to the summer mesosphere mesopause where it may amplify due to baroclinic barotropic instability such instability is usually absent from the equinoctial atmosphere so that there is no wave amplification at equinox at solstice the wave decays significantly when propagating away from its winter source due to the strong eastward winter stratospheric jet in the summer side the westward jet is also strong and the meridional and vertical extension of the critical layer of the wave is large enough to enclose the instability in the summer mesosphere mesopause at middle to high latitudes the wave is thus reflected away and prevented from reaching and amplifying at the unstable region the seasonal variation of the quasi two day wave which has zonal phase speed similar to the 6 5 day wave is also studied using similar diagnostics it is further shown that within certain seasonal window periods the variability in the mlt especially the summer mlt may closely track the lower atmospheric variability associated with these waves

asymmetry and nonlinearity of the influence of enso on the northern winter stratosphere 1 observations the el nino southern oscillation enso has significant effects on the extratropical stratosphere this study explores the nonlinearity and the asymmetry of these influences by distinguishing the different effects of four types of enso moderate el nino strong el nino moderate la nina and strong la nina it is revealed that the moderate el nino and the strong la nina are much more efficient than the strong el nino and the moderate la nina respectively in modulating the northern winter stratospheric variability resulting in significant nonlinearity and asymmetry the tropical rainfall anomalies induced by a moderate el nino or a strong la nina are centered over the central equatorial pacific region near the dateline while the convection responses to a strong el nino or a moderate la nina are centered farther eastward accordingly the anomalous pacific north america wave train pattern is modulated by enso in a nonlinear and asymmetric way which leads the large nonlinear and asymmetric components of the vertical eliassen palm e p flux responses to enso the increase of planetary wave activity in the extratropical stratosphere in moderate el nino winters is thus greater than in strong el nino winters whereas a strong la nina gives a larger decrease in propagation than a moderate la nina the relatively strong weak e p flux responses to moderate strong el nino and strong moderate la nina explain the remarkable nonlinearity and asymmetry in the response of the extratropical stratosphere to enso

multidecadal variations of the surface kuroshio between 1950s and 2000s and its impacts on surrounding waters based on the analyses of 59 year 1950 2008 surface geostrophic velocities the multidecadal changes of kuroshio from the eastern luzon to the southern japan are investigated result shows that the upstream kuroshio from the east of luzon to southern east china sea suffers much more obvious multidecadal changes except for the decade of 1980 the kuroshio east of luzon possesses a multidecadal tendency opposite to that east of taiwan besides 1980s the multidecadal change of kuroshio bordering taiwan is mainly governed by the eddy activity off the eastern taiwan while the wind stress curl plays a major role in the kuroshio in the east of luzon and in the luzon strait the wind stress induced ekman transport plays a secondary role in regulating the kuroshio east of luzon in addition the multidecadal fluctuation of kuroshio east of luzon also modulates the westward intrusion in the luzon strait instead the ekman transport dominated the whole upstream kuroshio area from the eastern luzon to the vicinity of taiwan during the exceptional decade of 1980 associated changes of water properties in the northern south china sea and southern east china sea are also ascribed to the multidecadal changes of surface kuroshio in the upstream area

the influence of enso on winter north atlantic climate 1 although the influence of the el nino southern oscillation on the extra tropical climate is well established for the pacific basin and north american regions there is no clear consensus as to whether there are reproducible effects from enso on the north atlantic and west european regions in this study we present a revised analysis of past el nino teleconnections by stratifying el nino events according to amplitude we find a highly non linear yet robust response to enso that changes sign over the eastern north atlantic as the amplitude of the el nino anomaly increases results from a series of experiments with a general circulation model indicate that the response to strong enso events is reproducible given the sea surface temperature anomalies in the tropical pacific the response to moderate el nino events resembles the negative phase of the north atlantic oscillation as found in previous studies

why might stratospheric sudden warmings occur with similar frequency in el nino and la nina winters 1 the effect of el nino southern oscillation enso on the frequency and character of northern hemisphere major mid winter stratospheric sudden warmings ssws is evaluated using a meteorological reanalysis data set and comprehensive chemistry climate models there is an apparent inconsistency between the impact of opposite phases of enso on the seasonal mean vortex and on ssws el nino leads to an anomalously warm and la nina leads to an anomalously cool seasonal mean polar stratospheric state but both phases of enso lead to an increased ssw frequency a resolution to this apparent paradox is here proposed the region in the north pacific most strongly associated with precursors of ssws is not strongly influenced by el nino and la nina teleconnections in the observational record both la nina and el nino lead to similar anomalies in the region associated with precursors of ssws and consistent with this there is a similar ssw frequency in la nina and el nino winters a similar correspondence between the penetration of enso teleconnections into the ssw precursor region and ssw frequency is found in the comprehensive chemistry climate models the inability of some of the models to capture the observed relationship between la nina and ssw frequency appears related to whether the modeled enso teleconnections result in extreme anomalies in the region most closely associated with ssws finally it is confirmed that the seasonal mean polar vortex response to enso is only weakly related to the relative frequency of ssws during el nino and la nina

a 20th century acceleration in global sea level rise 1 multi century sea level records and climate models indicate an acceleration of sea level rise but no 20th century acceleration has previously been detected a reconstruction of global sea level using tide gauge data from 1950 to 2000 indicates a larger rate of rise after 1993 and other periods of rapid sea level rise but no significant acceleration over this period here we extend the reconstruction of global mean sea level back to 1870 and find a sea level rise from january 1870 to december 2004 of 195 mm a 20th century rate of sea level rise of 1 7 0 3 mm yr 1 and a significant acceleration of sea level rise of 0 013 0 006 mm yr 2 this acceleration is an important confirmation of climate change simulations which show an acceleration not previously observed if this acceleration remained constant then the 1990 to 2100 rise would range from 280 to 340 mm consistent with projections in the ipcc tar

impact of enso on the atmospheric variability over the north atlantic in late winter role of transient eddies abstractthe dynamical mechanism for the late winter teleconnection between el nino southern oscillation enso and the north atlantic oscillation nao is examined using the output from a 2000 yr integration of a coupled general circulation model gcm the coupled model captures many salient features of the observed behavior of both enso and nao as well as their impact on the surface climate in late winter both the observational and model data indicate more occurrences of negative phase of nao in late winter during el nino events and positive nao in la nina episodes the potential role of high frequency transient eddies in the above teleconnection is diagnosed during el nino winters the intensified transient disturbances along the equatorward shifted north pacific storm track extend their influences farther downstream the eddy induced negative height tendencies are found to be more coherent and stronger over north atlantic than that over north pacific these negative height tendencies over the north

a reassessment of global and regional mean sea level trends from topex and jason 1 altimetry based on revised reference frame and orbits 1 mean sea level trends from topex and jason 1 altimeter data are recomputed using unified geophysical modeling and the new itrf2005 terrestrial reference frame for the entire altimetric time series with consistent orbits based on satellite laser ranging slr and doris tracking data we obtain a global rate of 3 36 0 41 mm yr over the 14 year period from 1993 to 2007 the regional sea level trends computed with the new reference frame show significant north south hemispherical offsets of 1 5 mm yr relative to trends based on the previous 1995 era frame regional sea level trend comparisons for the time periods of 1993 1999 and 1999 2005 reveal strong basin scale polarities and pronounced inter decadal variability with a relative increase in the global mean sea level trend of 1 5 0 7 mm yr in the latter seven years

reconstructing sea level using cyclostationary empirical orthogonal functions 1 cyclostationary empirical orthogonal functions derived from satellite altimetry are combined with historical sea level measurements from tide gauges to reconstruct sea level fields from 1950 through 2009 previous sea level reconstructions have utilized empirical orthogonal functions as basis functions but by using cyclostationary empirical orthogonal functions and by addressing other aspects of the reconstruction procedure an alternative sea level reconstruction can be computed the procedure introduced here is capable of capturing the annual cycle and el nino southern oscillation enso signals back to 1950 with correlations between the reconstructed enso signal and common enso indices found to be over 0 9 the regional trends computed from the new reconstruction show good agreement with the trends obtained from the satellite altimetry but some discrepancies are seen when comparing with previous sea level reconstructions over longer time periods the computed rate of global mean sea level rise from the reconstructed time series is 1 97 mm yr from 1950 to 2009 and 3 22 mm yr from 1993 to 2009

association of tropical pacific sea surface temperatures with the stratospheric holton tan oscillation in the northern hemisphere winter 1 based on 45 years of the european centre for medium range weather forecasting era 40 reanalysis dataset and the noaa extended reconstructed sea surface temperature sst data the associated anomalies in the stratospheric holton tan oscillation hto with the tropical eastern pacific sst in the northern hemisphere winter are investigated it is found that the hto which is induced by equatorial quasi biennial oscillation qbo is significant in the cold sst phase but the hto becomes much weaker in the warm sst phase the conventional qbo modulation on the planetary wave propagation in the stratosphere is only significant when the sst anomaly is cold in the tropical eastern pacific however the modulation tends to be weak when the sst anomaly is warm it is suggested that this difference may arise from the interaction between the tropical eastern pacific sst and the qbo associated planetary wave propagation

using a large ensemble of simulations to assess the northern hemisphere stratospheric dynamical response to tropical volcanic eruptions and its uncertainty the observed strengthening of the northern hemisphere nh polar vortex after tropical volcanic eruptions appears to be underestimated by coupled climate models however there is only a limited number of observed eruptions which makes the attribution of volcanic signals difficult because the polar vortex is also influenced by other external forcing factors as well as internal variability we show with a 100 member ensemble of historical 1850 2005 simulations with the mpi esm lr that an ensemble larger than what is provided by the coupled model intercomparison project phase 5 cmip5 models is needed to detect a statistically significant nh polar vortex strengthening the most robust signal can be found when only the two strongest eruptions krakatau and pinatubo are considered in contrast to including smaller eruptions to increase the sample size for these two strongest eruptions also the mean of 15 cmip5 models shows a statistically significant strengthening of the nh polar vortex

controls of mantle plumes and lithospheric folding on modes of intraplate continental tectonics differences and similarities summary mantle plume activity and lithospheric folding by far field stresses exerted from plate boundaries are two important end members as mechanisms for continental intraplate deformation the topographic expression of mantle plume impingement on continental lithosphere and lithospheric folding has some striking similarities observations from a number of areas in europe s intraplate lithosphere demonstrate that these mechanisms commonly interact in space and time we present the results of thermomechanical modelling addressing the role of factors such as the presence of a hot upper mantle the spatial dimensions of the plume and the time constants involved in the temporal succession of plume activity and lithospheric folding by stress accumulation in intraplate continental lithosphere the results demonstrate that both the processes plume lithosphere interactions and folding may interact resulting either in strong amplification attenuation or modification of their surface expression these inferences are compatible with a number of key observations on the nature and the temporal succession of topography evolution in the alpine foreland the pannonian basin the scandinavian continental margin and the iberian peninsula

geomorphology of the iberian continental margin abstract the submarine features and processes around the iberian peninsula are the result of a complex and diverse geological and oceanographical setting this paper presents an overview of the seafloor geomorphology of the iberian continental margin and the adjacent abyssal plains the study covers an area of approximately 2 3 million km 2 including a 50 to 400 km wide band adjacent to the coastline the main morphological characteristics of the seafloor features on the iberian continental shelf continental slope continental rise and the surrounding abyssal plains are described individual seafloor features existing on the iberian margin have been classified into three main groups according to their origin tectonic and or volcanic depositional and erosional major depositional and erosional features around the iberian margin developed in late pleistocene holocene times and have been controlled by tectonic movements and eustatic fluctuations the distribution of the geomorphological features is discussed in relation to their genetic processes and the evolution of the margin the prevalence of one or several specific processes in certain areas reflects the dominant morphotectonic and oceanographic controlling factors sedimentary processes and the resulting depositional products are dominant on the valencia catalan margin and in the northern part of the balearic promontory strong tectonic control is observed in the geomorphology of the betic and the gulf of cadiz margins the role of bottom currents is especially evident throughout the iberian margin the galicia portuguese and cantabrian margins show a predominance of erosional features and tectonically controlled linear features related to faults

the crustal structure of the nw moroccan continental margin from wide angle and reflection seismic data summary the atlantic margin off morocco with its neighbouring jurassic oceanic crust is one of the oldest on earth it is conjugate to the nova scotia margin of north america the sismar marine seismic survey acquired deep reflection seismic data as well as wide angle seismic profiles in order to image the deep structure of the margin characterize the nature of the crust in the transitional domain and define the geometry of the synrift basins we present results from the combined interpretation of the reflection seismic wide angle seismic and gravity data along a 440 km long profile perpendicular to the margin at 33 34 n extending from nearly normal oceanic crust in the vicinity of coral patch seamount to the coast at el jadida and approximately 130 km inland the shallow structure is well imaged by the reflection seismic data and shows a thick sedimentary cover that is locally perturbed by salt tectonics and reverse faulting the sedimentary basin thickens from 1 5 km on the normal oceanic crust to a maximum thickness of 6 km at the base of the continental slope multichannel seismic mcs data image basement structures including a few tilted fault blocks and a transition zone to a thin crust a strong discontinuous reflection at 12 s two way travel time twt is interpreted as the moho discontinuity as a result of the good data quality the deep crustal structure depth and velocity field is well constrained through the wide angle seismic modelling the crust thins from 35 km underneath the continent to approximately 7 km at the western end of the profile the transitional region has a width of 150 km crustal velocities are lowest at the continental slope probably as a result of faulting and fracturing of the upper crust uppermantle velocities could be well defined from the ocean bottom seismometer obs and land station data throughout the model

implementation of a gravity wave source spectrum parameterization dependent on the properties of convection in the whole atmosphere community climate model waccm 1 this article describes the implementation of a new source spectrum parameterization for convectively generated gravity waves in the whole atmosphere community climate model version 2 waccm2 this parameterization is active in the tropics and is interactive with the underlying convection the gravity wave spectrum at each model grid point and time step is determined based on the convective heating depth tropospheric wind and the convective heating rate this parameterization introduces more realistic spatial and temporal distributions of gravity wave activity and yields gravity wave characteristics related to the underlying wave source we present the estimated gravity wave momentum flux phase speed spectra at 100 hpa as well as the gravity wave drag in the middle and upper atmosphere using the new source spectrum representation we also show the effects of this more physically based parameterization on the structure of the stratospheric and mesospheric semi annual oscillations of the zonal wind compared to a simulation with uniform gravity wave distribution we conclude that the interaction of the gravity wave parameterization with tropospheric characteristics is a positive step toward a more physical representation of the middle and upper atmosphere

effect of el nino southern oscillation on the dynamical thermal and chemical structure of the middle atmosphere 1 a simulation of the middle atmosphere is presented using a general circulation model gcm forced with observed sea surface temperature for the period 1950 2000 the gcm extends to the lower thermosphere and reproduces realistic dynamical and temperature distributions the period contains several el nino and la nina events which are identified using the nino3 index composite anomalies of relevant meteorological fields are obtained by stratifying the northern winter season according to the nino3 index these anomalies have the structure of vertically propagating planetary waves extending from the troposphere to the mesosphere circulation anomalies in the middle atmosphere are accompanied by large temperature anomalies that are of opposite sign in the stratosphere and mesosphere the former being warmer and the latter colder during el nino events near the summer mesopause changes in momentum deposition by parameterized gravity waves results in warming during el nino detailed statistical analysis is used to determine the significance of these anomalies a chemical transport simulation is carried out using output from the gcm it shows that when the lower stratosphere is colder as during la nina events some ozone depletion takes place conversely when the lower stratosphere is warmer and more disturbed as is the case during el nino events heterogeneous chemical processes are inhibited

the 40ar 39ar age dating of the madeira archipelago and hotspot track eastern north atlantic the 40ar 39ar ages for 35 volcanic rocks and 14c ages for two charcoal samples from the madeira archipelago and ampere seamount eastern north atlantic are presented the volcanic evolution of madeira can be divided into a voluminous shield stage 4 6 0 7 ma and a subsequent low volume posterosional stage 70 myr old hotspot which formed porto santo island 11 1 14 3 ma seine ampere 31 ma corral patch and ormond 65 67 ma feraud et al 1982 1986 seamounts and the serra de monchique 70 72 ma mcintyre and berger 1982 complex in southern portugal age and spatial relationships result in a calculated absolute african plate motion above the hotspot of 1 2 cm yr around a rotation pole located at 43 36 n 24 33 w

the effects of the indo pacific warm pool on the stratosphere sea surface temperature sst in the indo pacific warm pool ipwp plays a key role in influencing east asian climate and even affects global scale climate change this study defines ipwp nino and ipwp nina events to represent the warm and cold phases of ipwp sst anomalies respectively and investigates the effects of these events on stratospheric circulation and temperature results from simulations forced by observed sst anomalies during ipwp nino and nina events show that the tropical lower stratosphere tends to cool during ipwp nino events and warm during ipwp nina events the responses of the northern and southern polar vortices to ipwp nino events are fairly symmetric as both vortices are significantly warmed and weakened however the responses of the two polar vortices to ipwp nina events are of opposite sign the northern polar vortex is warmed and weakened but the southern polar vortex is cooled and strengthened these features are further confirmed by composite analysis using reanalysis data a possible dynamical mechanism connecting ipwp sst to the stratosphere is suggested in which ipwp nino and nina events excite teleconnections one similar to the pacific north america pattern in the northern hemisphere and a rossby wave train in the southern hemisphere which project onto the climatological wave in the mid high latitudes intensifying the upward propagation of planetary waves into the stratosphere and in turn affecting the polar vortex

a note on the geochronology of the iberian alkaline province abstract a critical assessment of previously published ages and new k ar results for two complexes in the iberian alkaline province monchique and sintra lead to the conclusion that two separate magmatic episodes occurred around 72 and 82 ma since emplacement of these alkaline rocks is undoubtedly related to rifting and subsequent changes in the atlantic ocean floor spreading geometry accurate timing of magmatic events within the iberian alkaline province is of fundamental significance

el nino modoki and its possible teleconnection 1 using observed data sets mainly for the period 1979 2005 we find that anomalous warming events different from conventional el nino events occur in the central equatorial pacific this unique warming in the central equatorial pacific associated with a horseshoe pattern is flanked by a colder sea surface temperature anomaly ssta on both sides along the equator empirical orthogonal function eof analysis of monthly tropical pacific ssta shows that these events are represented by the second mode that explains 12 of the variance since a majority of such events are not part of el nino evolution the phenomenon is named as el nino modoki pseudo el nino modoki is a classical japanese word which means a similar but different thing the el nino modoki involves ocean atmosphere coupled processes which include a unique tripolar sea level pressure pattern during the evolution analogous to the southern oscillation in the case of el nino hence the total entity is named as el nino southern oscillation enso modoki the enso modoki events significantly influence the temperature and precipitation over many parts of the globe depending on the season the impacts over regions such as the far east including japan new zealand western coast of united states etc are opposite to those of the conventional enso the difference maps between the two periods of 1979 2004 and 1958 1978 for various oceanic atmospheric variables suggest that the recent weakening of equatorial easterlies related to weakened zonal sea surface temperature gradient led to more flattening of the thermocline this appears to be a cause of more frequent and persistent occurrence of the enso modoki event during recent decades

improved extended reconstruction of sst 1854 1997 abstract an improved sst reconstruction for the 1854 1997 period is developed compared to the version 1 analysis in the western tropical pacific the tropical atlantic and indian oceans more variance is resolved in the new analysis this improved analysis also uses sea ice concentrations to improve the high latitude sst analysis and a modified historical bias correction for the 1939 41 period in addition the new analysis includes an improved error estimate analysis uncertainty is largest in the nineteenth century and during the two world wars due to sparse sampling the near global average sst in the new analysis is consistent with the version 1 reconstruction the 95 confidence uncertainty for the near global average is 0 4 c or more in the nineteenth century near 0 2 c for the first half of the twentieth century and 0 1 c or less after 1950

estimates of the regional distribution of sea level rise over the 1950 2000 period abstract topex poseidon satellite altimeter data are used to estimate global empirical orthogonal functions that are then combined with historical tide gauge data to estimate monthly distributions of large scale sea level variability and change over the period 1950 2000 the reconstruction is an attempt to narrow the current broad range of sea level rise estimates to identify any pattern of regional sea level rise and to determine any variation in the rate of sea level rise over the 51 yr period the computed rate of global averaged sea level rise from the reconstructed monthly time series is 1 8 0 3 mm yr 1 with the decadal variability in the computed global mean sea level it is not possible to detect a significant increase in the rate of sea level rise over the period 1950 2000 a regional pattern of sea level rise is identified the maximum sea level rise is in the eastern off equatorial pacific and there is a minimum along the equator in the western pacific and in the eastern indian ocean a g

a regional index of northeast pacific variability based on satellite altimeter data 1 an index of climate variability to monitor the state of the upper ocean is proposed for the northeast ne pacific ocean based on sea surface height ssh data from satellite altimetry while sea surface temperature sst is often used characterize ocean variability ssh reflects the integrated influence of temperature and salinity anomalies through the water column a canonical correlation analysis shows that ssh and sst anomalies vary coherently at large spatial scales and low frequencies over the region ssh anomalies are less subject to short period variability and the temporal components for ssh resemble smoothed low pass filtered versions of the sst components also examined is the relationship between the sst based pacific decadal oscillation pdo index and the large scale upper ocean variability reflected in the leading principal component of ssh anomalies the comparison demonstrates that the ssh principal component provides a robust index of regional climate variability that is less noisy than the pdo the results are used to examine the 1998 2002 climate event over the ne pacific

origin and geochemical evolution of the madeira tore rise eastern north atlantic the madeira tore rise located 700 km off the nw african coast forms a prominent ridge in the east atlantic the age and origin of the rise are controversial this study presents major and trace element sr nd pb hf isotope and 40ar 39ar age determinations from volcanic rocks dredged from different sites along the rise in addition isotopic compositions of rock samples from great meteor seamount in the central atlantic are presented the new radiometric and paleontologically constrained ages identify two major episodes of volcanism the first is the base of the rise circa 80 to 95 ma and the second is seamounts on the rise 0 5 16 ma it is proposed that interaction of the canary hot spot with the mid atlantic spreading center formed the deep basement of the madeira tore rise and the j anomaly ridge west of the atlantic spreading center in the mid cretaceous age and geochemical data and plate tectonic reconstructions suggest however that the recovered late cretaceous volcanic rocks represent late stage volcanism from the time when the madeira tore rise was still close to the canary hot spot long after moving away from the influence of the canary hot spot the madeira tore rise was overprinted by late cenozoic volcanism miocene to pleistocene volcanism at the northern end of the rise can be best explained by decompression mantle melting beneath extensional sectors of the azores gibraltar fracture zone african eurasian plate boundary the geochemical compositions of these volcanic rocks suggest that the magmas were variably contaminated by enriched material within or derived by melting of enriched material underplated at the base of the lithosphere possibly originating from the cretaceous canary plume alternatively these late cenozoic volcanic rocks may have derived from decompression melting of enriched pyroxenitic eclogitic material in the upper mantle isotopically more depleted pliocene to pleistocene volcanism at the southern end of the madeira tore rise may be related to the nearby madeira hot spot

gyre scale atmospheric pressure variations and their relation to 19th and 20th century sea level rise 1 most of the long tide gauge records in the north atlantic and north pacific commonly used to estimate global sea level rise and acceleration display a marked difference in behavior in the late 1800 s early 1900 s compared to the latter half of the 20th century the rates of sea level rise tend to be lower in the 19th compared to 20th century we show this behavior may be related to long term gyre scale surface pressure variations similar to those associated with the northern annular mode as sea level pressure increases decreases at decadal and longer timescales at the centers of the subtropical atmospheric gyres sea level trends along the eastern margins in each ocean basin decrease increase this is not an isostatic response the scaling between local surface pressure and sea level at interannual and longer timescales is 3 to 6 times greater than expected by that mechanism rather it appears to be the result of large possibly gyre scale changes in ocean circulation some evidence is also presented indicating slow 2 cm sec westward propagation of sea level changes in the atlantic from the west coast of europe to the east coast of the u s which produce the decadal variability seen there

eastern segment of the azores gibraltar line central eastern atlantic an oceanic plate boundary with diffuse compressional deformation new seismic reflection images across the eastern segment of the azores gibraltar line west of the collisional area between the african and iberian plates have revealed a complex pattern of compressional deformation involving the mesozoic oceanic lithosphere the compressional deformation developed in a region of slow plate convergence and is diffused at different lithospheric levels across an area spanning 200 km from the gorringe ridge to the seine plain the convergence between the african and iberian plates has been active since tertiary time and our results indicate that no subduction zone exists across this part of the plate boundary

global glacial isostasy and the surface of the ice age earth the ice 5g vm2 model and grace abstract the 100 kyr quasiperiodic variation of continental ice cover which has been a persistent feature of climate system evolution throughout the most recent 900 kyr of earth history has occurred as a consequence of changes in the seasonal insolation regime forced by the influence of gravitational n body effects in the solar system on the geometry of earth s orbit around the sun the impacts of the changing surface ice load upon both earth s shape and gravitational field as well as upon sea level history have come to be measurable using a variety of geological and geophysical techniques these observations are invertible to obtain useful information on both the internal viscoelastic structure of the solid earth and on the detailed spatiotemporal characteristics of glaciation history this review focuses upon the most recent advances that have been achieved in each of these areas advances that have proven to be central to the construction of the refined model of the global process of glacial isos

a comparative study of sea level reconstruction techniques using 20 years of satellite altimetry data sea level reconstructions extend spatially dense data sets such as those from satellite altimetry by decomposing the data set into basis functions and fitting those functions to in situ tide gauge measurements with a longer temporal record we compare and evaluate two methods for reconstructing sea level through an idealized study the compared sea level reconstruction methods differ in the technique for calculating basis functions i e empirical orthogonal functions eofs versus cyclostationary eofs cseofs reconstructions are created using archiving validation and interpretation of satellite oceanographic aviso satellite altimetry data and synthetic tide gauges synthetic tide gauge records are simulated using historical distributions and real high frequency signal to test reconstruction skill the cseof reconstructions show high skill in reproducing variations in global mean sea level gmsl and ocean climate indices and are affected less by both limited tide gauge distribution and added high frequency tide gauge signal than eof reconstructions typically cseof reconstructions slightly underestimate sea level amplitudes while eof reconstructions overestimate sea level amplitudes in some cases significantly both of these results are accentuated with decreasing quality of the synthetic tide gauge data set additionally we investigate how the reconstructions differ when reconstructing with more of the variance retained in the basis functions increasing the variance explained by the basis functions from 70 to 90 reduces the efficacy of an eof reconstruction to reproduce common ocean indices when noise is included in the tide gauge data sets these results show that in the idealized comparative cases examined the cseof method of sea level reconstruction creates more robust reconstructions especially when less than ideal tide gauge data are used

seismic images and magnetic signature of the late jurassic to early cretaceous africa eurasia plate boundary off sw iberia over the last two decades numerous studies have investigated the structure of the west iberia continental margin a non volcanic margin characterized by a broad continent ocean transition cot however the nature and structure of the crust of the segment of the margin off sw iberia is still poorly understood because of sparse geophysical and geological data coverage here we present a 275 km long multichannel seismic reflection mcs profile line ar01 acquired in e w direction across the horseshoe abyssal plain to partially fill the gap of information along the sw iberia margin line ar01 runs across the inferred plate boundary between the iberian and the african plates during the opening of the central atlantic ocean the boundary separates crust formed during or soon after continental rifting of the sw iberian margin from normal seafloor spreading oceanic crust of the central atlantic ocean line ar01 has been processed and pre stack depth migrated to show the tectonic structure of the crust across the palaeo plate boundary this boundary is characterized by a 30 40 km wide zone of large basements highs related to landward dipping reflections which penetrate to depths of 13 15 km and it marks a change in the character of the basement structure and relief from east to west in this study we have used pre stack depth migrated images the velocity model of line ar01 and magnetic data available in the area to show that the change in basement structure occurs across the fossil plate boundary separating african oceanic crust of the m series m21 m16 to the west from the transitional crust of the iberian margin to the east

dynamical connection between the stratospheric arctic vortex and sea surface temperatures in the north atlantic we used two long term reanalysis datasets and time slice simulations to examine the decadal relationship between the stratospheric arctic vortex sav and sea surface temperature anomalies sstas in the north atlantic and the dynamic mechanisms involved in the linkage between the two our results show that there is a significant decadal linkage between sstas over the north atlantic and the sav where warmed cooled sstas over the north atlantic in association with its principal mode correspond to a weakened strengthened sav the warmed north atlantic sstas tend to result in a weakened sav via two dynamic processes 1 constructive interference at high latitudes with a ridge in the atlantic sector and a trough in the pacific accompanied by a negative north atlantic oscillation like pattern over the north atlantic and a weakened aleutian low over the north pacific and 2 more wavenumber 1 waves propagated into the arctic stratosphere by modifying the baroclinic term of the zonal mean background state and altering the propagating conditions around the tropopause over the arctic results from reanalysis and model simulations both suggest that a strengthening wave intensity in the high latitude troposphere and more upward propagation of the planetary wavenumber 1 wave in response to the warmed north atlantic sstas conjunctly contribute to the increased planetary wave flux in the arctic stratosphere facilitating a weakened sav these results provide a new understanding of what dynamic processes control the sav and will help to predict the stratosphere on decadal timescales