influence of sea ice on the thermohaline circulation in the arctic north atlantic ocean a fully prognostic coupled ocean ice model is used to study the sensitivity of the overturning cell of the arctic north atlantic system to sea ice forcing the strength of the thermohaline cell will be shown to depend on the amount of sea ice transported from the arctic to the greenland sea and further to the subpolar gyre the model produces a 2 3 sv increase of the meridional circulation cell at 25n at the simulation year 15 corresponding to a decrease of 800 km in the sea ice export from the arctic previous modeling studies suggest that interannual and decadal variability in sea ice export of this magnitude is realistic implying that sea ice induced variability in the overturning cell can reach 5 6 sv from peak to peak

anatomy of north pacific decadal variability abstract a systematic analysis of north pacific decadal variability in a full physics coupled ocean atmosphere model is executed the model is an updated and improved version of the coupled model studied by latif and barnett evidence is sought for determining the details of the mechanism responsible for the enhanced variance of some variables at 20 30 yr timescales the possible mechanisms include a midlatitude gyre ocean atmosphere feedback loop stochastic forcing remote forcing or sampling error decadal variability in the model is expressed most prominently in anomalies of upper ocean streamfunction sea surface temperature sst and latent surface heat flux in the kuroshio oyashio extension koe region off japan the decadal signal off japan is initiated by changes in strength and position of the aleutian low the atmospheric perturbations excite sst anomalies in the central and eastern north pacific with opposing signs and canonical structure the atmospheric perturbations also change the ekm

ocean dynamics and the nature of air sea interactions over the north atlantic at decadal time scales the dependence of the air sea interactions over the north atlantic on the ocean dynamics is explored by analyzing multicentury integrations with two different coupled ocean atmosphere models one is a coupled general circulation model cgcm in which both the atmospheric and the oceanic components are represented by general circulation models gcms the second coupled model employs the same atmospheric gcm but the oceanic gcm is replaced by a fixed depth mixed layer model so that variations of the ocean dynamics are excluded the coupled model including active ocean dynamics simulates strong multidecadal variability in the sea surface temperature sst of the north atlantic with a monopolar spatial structure in contrast the coupled model that employs an oceanic mixed layer model and thus does not carry active ocean dynamics simulates a tripolar sst anomaly pattern at decadal time scales the tripolar sst anomaly pattern is characterized by strong horizontal gradients and is by definition the result of the action of surface heat flux anomalies on the oceanic mixed layer the differences in the spatial structures of the dominant decadal sst anomaly patterns yield rather different atmospheric responses while the response to the monopolar sst anomaly pattern is shallow and thermal the response to the tripolar sst anomaly pattern involves changes in the transient eddy statistics the latter can be explained by the strong horizontal sst gradients that affect the surface baroclinicity which in turn affects the growth rate of the transient eddies the differences in the atmospheric response characteristics yield completely different response patterns in the coupled run with active ocean dynamics the sea level pressure slp anomalies exhibit a rather homogeneous pattern that resembles somewhat the east atlantic pattern eap while a dipolar north atlantic oscillation nao like slp anomaly pattern is simulated in the coupled run without active ocean dynamics

atlantic multidecadal oscillation and northern hemisphere s climate variability proxy and instrumental records reflect a quasi cyclic 50 80 year climate signal across the northern hemisphere with particular presence in the north atlantic modeling studies rationalize this variability in terms of intrinsic dynamics of the atlantic meridional overturning circulation influencing distribution of sea surface temperature anomalies in the atlantic ocean hence the name atlantic multidecadal oscillation amo by analyzing a lagged covariance structure of a network of climate indices this study details the amo signal propagation throughout the northern hemisphere via a sequence of atmospheric and lagged oceanic teleconnections which the authors term the stadium wave initial changes in the north atlantic temperature anomaly associated with amo culminate in an oppositely signed hemispheric signal about 30 years later furthermore shorter term interannual to interdecadal climate variability alters character according to polarity of the stadium wave induced prevailing hemispheric climate regime ongoing research suggests mutual interaction between shorter term variability and the stadium wave with indication of ensuing modifications of multidecadal variability within the atlantic sector results presented here support the hypothesis that amo plays a significant role in hemispheric and by inference global climate variability with implications for climate change attribution and prediction

multidecadal climate variability in the greenland sea and surrounding regions a coupled model simulation pronounced oscillations of ocean temperature and salinity occur in the greenland sea in a 2000 year integration of a coupled ocean atmosphere model the oscillations involving both the surface and subsurface ocean layers have a timescale of approximately 40 80 years and are associated with fluctuations in the inten sity of the east greenland current the greenland sea temperature and salinity variations are preceded by large scale changes in near surface salinity in the arctic which appear to propagate out of the arctic through the east greenland current these anomalies then propagate around the subpolar gyre into the labrador sea and the central north atlantic these oscillations are coherent with previously identified multi decadal fluctuations in the intensity of the north atlantic thermohaline circula tion the oscillations in the g eenland sea are related to atmospheric variability negative cold anomalies of surface air temperature are associated with negative cold sea surface temperature sst anomalies in the greenland sea with amplitudes up to 2oc near green land declining to several tenths of a degree c over north western europe the c01d sst anomalies and intensified east greenland current are also associated with enhanced northerly winds over the greenland sea

atlantic thermohaline circulation in a coupled general circulation model unforced variations versus forced changes a 1200 yr unforced control run and future climate change simulations using the parallel climate model pcm a coupled atmosphere ocean land sea ice global model with no flux adjustments and relatively high resolution 2 8 for the atmosphere and 2 3 for the oceans are analyzed for changes in atlantic ocean circulations for the forced simulations historical greenhouse gas and sulfate forcing of the twentieth century and projected forcing for the next two centuries are used the atlantic thermohaline circulation thc shows large multidecadal 15 40 yr variations with mean peak amplitudes of 1 5 3 0 sv 1 sv 10 6 m 3 s 1 and a sharp peak of power around a 24 yr period in the control run associated with the thc oscillations there are large variations in north atlantic ocean heat transport sea surface temperature sst and salinity sss sea ice fraction and net surface water and energy fluxes which all lag the variations in thc strength by 2 3 yr however the net effect of the sst and sss variations on upper ocean density in the midlatitude north atlantic leads the thc variations by about 6 yr which results in the 24 yr period the simulated sst and sea ice spatial patterns associated with the thc oscillations resemble those in observed sst and sea ice concentrations that are associated with the north atlantic oscillation nao the results suggest a dominant role of the advective mechanism and strong coupling between the thc and the nao whose index also shows a sharp peak around the 24 yr time scale in the control run in the forced simulations the thc weakens by 12 in the twenty first century and continues to weaken by an additional 10 in the twenty second century if co2 keeps rising but the thc stabilizes if co2 levels off the thc weakening results from stabilizing temperature increases that are larger in the upper and northern atlantic ocean than in the deep and southern parts of the basin in both the control and forced simulations as the thc gains loses strength and depth the separated gulf stream gs moves southward northward while the subpolar gyre centered at the labrador sea contracts from expands to the east with the north atlantic current nac being shifted westward eastward these horizontal circulation changes which are dynamically linked to the thc changes induce large temperature and salinity variations around the gs and nac paths

coupled north atlantic slope water forcing on gulf of maine temperatures over the past millennium to investigate ocean variability during the last millennium in the western gulf of maine gom we collected a 142 year old living bivalve arctica islandica l in 2004 and three fossil a islandica shells calibrated 14cams 1030 78 ad 1320 45 ad 1357 40 ad for stable isotope and growth increment analysis a statistically significant relationship exists between modern gom temperature records shell isotope derived 30 m r 0 79 p 0 007 prince 5 50 m r 0 72 p 0 019 boothbay harbor sst r 0 76 p 0 011 and labrador current lc transport data from the eastern newfoundland slope during 1993 2003 in all cases as lc transport increased gom water temperatures decreased the following year decadal trends in the north atlantic oscillation nao and the atlantic multidecadal oscillation amo influence gom water temperatures in the most recent period with water temperatures decreasing during nao and amo negative modes most likely linked to lc transport and gulf stream interaction mean shell derived isotopic changes 18oc during the last 1 000 years were 0 47 and likely reflect a 1 2 c cooling from 1000 ad to present based on these results we suggest that observed cooling in the gom during the last millennium was due to increased transport and or cooling of the lc and decreased gulf stream influence on the gom

hysteresis behavior of the atlantic ocean circulation identified in observational data abstract on the basis of the multidecadal component of a fram strait sea ice export reconstruction and on a sea surface temperature proxy for changes in the ocean circulation a bifurcation diagram for two cycles of the atlantic ocean multidecadal oscillation is constructed it suggests a hysteresis behavior that is consistent with nonlinear convective adjustment to changes in deep water formation in the north atlantic and with the meridional overturning circulation bistability associated with two distinct configurations of the north atlantic subpolar gyre simulated in response to idealized carbon dioxide increase the nonlinear dynamics of the atlantic ocean circulation emphasized here on the basis of observational data adds to the hysteresis behavior shown in theoretical and numerical studies

a simulation of thermohaline effects of a great salinity anomaly abstract model simulations of an idealistic great salinity anomaly gsa demonstrate that variability in the sea ice export from the arctic when concentrated to short pulses can have a large influence on the meridional heat transport and can lead to an altered overturning state one single freshwater disturbance resulting from excess ice export as in 1968 can disrupt the deep mixing process the critical condition for a large oceanic response is defined by the intensity duration and timing of the ice pulse in particular as it exits through the denmark strait a recovery from this event takes several years for advection and diffusion to remove the salinity anomaly concurrently the influence of the gsa propagates to the subtropics via the boundary currents and baroclinic adjustment as a result of this adjustment there are large up to 20 changes in the strength of the overturning cell and in the meridional heat transport in the subtropics and subpolar areas simulations show a temperature sali

simulated atlantic multidecadal oscillation during the holocene abstractthe atlantic multidecadal oscillation amo and its possible change during the holocene are examined in this study using long term simulations of the earth system model community earth system models cosmos a quasi persistent 55 80 yr cycle characterizing in the north atlantic sea surface temperature is highly associated with the multidecadal variability of the atlantic meridional overturning circulation amoc during the holocene this mode can be found throughout the holocene indicating that the amo is dominated by internal climate variability stronger than normal amoc results in warmer than normal surface temperature spreading over almost the whole north hemisphere in particular the north atlantic ocean during the warm phase of the amo more precipitation is detected in the north atlantic low and high latitudes it also generates a dipolar seesaw pattern in the sea ice anomaly the results reveal that the influence of the amo can be amplified by a more vigorous amoc variability during t

relationships between atmospheric internal variability and the responses to an extratropical sst anomaly abstract the january and february responses of a gcm to an imposed extratropical pacific sst anomaly are compared with the patterns of the model s internal variability relevant patterns of internal variability are diagnosed from ensembles of model control runs by regressing monthly mean geopotentials and temperatures against low level temperatures in the vicinity of the sst anomaly and by eof analysis these patterns are found to play a significant role in determining the local and the remote responses to the sst anomaly different responses to the sst anomaly in the gcm s january and february climates are largely explained by the differences in the regression patterns and in the leading eof the gcm response may be considered as comprising a direct linear response to low level heating that is local to the forcing and baroclinic and an eddy forced component that closely resembles patterns of the model s internal variability it is equivalent barotropic and extends over the entire hemisphere the results

fram strait ice export during the nineteenth and twentieth centuries reconstructed from a multiyear sea ice index from southwestern greenland abstract historical observations of multiyear ice called storis in the southwest greenland waters exist from the period 1820 2000 obtained from ship logbooks and ice charts it is argued that this ice originates in the arctic ocean and has traveled via the fram strait southward along the greenland coast in the east greenland current and around the southern tip of greenland therefore it is hypothesized that these observations can be used as proxies for reconstructing the fram strait ice export on an annual basis an index describing the storis extent is extracted from the observations and a linear statistical model formulated relating this index to the fram strait ice export the model is calibrated using ice export values from a hindcast study with a coupled ocean ice model over the period 1949 98 subsequently the model is used to reconstruct the fram strait annual ice export in the period 1820 2000 the model has significant skill calculated on independent data based on this reconstruction

a link between fram strait sea ice export and atmospheric planetary wave phase 1 a link is found between the variability of fram strait sea ice export and the phase of zonal wave 1 in slp for the period 1958 1997 previous studies have found that the link between ice export through fram strait and the nao is inconsistent over time scales longer than the last two decades inconsistent and low correlations are also found between fram strait ice export and the ao index the phase of zonal wave 1 explains 60 70 of the simulated ice export variance after the removal of two anomalous phases in 1966 and 1967 unlike the nao and ao links these high variances are consistent for both the first and second halves of the 40 year period this consistency is attributed to the sensitivity of wave 1 phase to the presence of secondary low pressure systems in the barents sea that serve to drive arctic sea ice southward through fram strait

annular modes in the extratropical circulation part i month to month variability the leading modes of variability of the extratropical circulation in both hemispheres are characterized by deep zonally symmetric or annular structures with geopotential height perturbations of opposing signs in the polar cap region and in the surrounding zonal ring centered near 458 latitude the structure and dynamics of the southern hemisphere sh annular mode have been extensively documented whereas the existence of a northern hemisphere nh mode herein referred to as the arctic oscillation ao has only recently been recognized like the sh mode the ao can be defined as the leading empirical orthogonal function of the sea level pressure field or of the zonally symmetric geopotential height or zonal wind fields in this paper the structure and seasonality of the nh and sh modes are compared based on data from the national centers for environmental prediction national center for atmospheric research reanalysis and supplementary datasets the structures of the nh and sh annular modes are shown to be remarkably similar not only in the zonally averaged geopotential height and zonal wind fields but in the mean meridional circulations as well both exist year round in the troposphere but they amplify with height upward into the stratosphere during those seasons in which the strength of the zonal flow is conducive to strong planetary wave mean flow interaction midwinter in the nh and late spring in the sh during these active seasons the annular modes modulate the strength of the lagrangian mean circulation in the lower stratosphere total column ozone and tropopause height over mid and high latitudes and the strength of the trade winds of their respective hemispheres the nh mode also contains an embedded planetary wave signature with expressions in surface air temperature precipitation total column ozone and tropopause height it is argued that the horizontal temperature advection by the perturbed zonal mean zonal wind field in the lower troposphere is instrumental in forcing this pattern a companion paper documents the striking resemblance between the structure of the annular modes and observed climate trends over the past few decades

wind effect on the atlantic meridional overturning circulation via sea ice and vertical diffusion effects of wind and fresh water on the atlantic meridional overturning circulation amoc are investigated using a fully coupled climate model the amoc can change significantly when perturbed by either wind stress or freshwater flux in the north atlantic this study focuses on wind stress effect our model results show that the wind forcing is crucial in maintaining the amoc reducing wind forcing over the ocean can cause immediately weakening of the vertical salinity diffusion and convection in the mid high latitudes atlantic resulting in an enhancement of vertical salinity stratification that restrains the deep water formation there triggering a slowdown of the thermohaline circulation as the thermohaline circulation weakens the sea ice expands southward and melts providing the upper ocean with fresh water that weakens the thermohaline circulation further the wind perturbation experiments suggest a positive feedback between sea ice and thermohaline circulation strength which can eventually result in a complete shutdown of the amoc this study also suggests that sea ice variability may be also important to the natural amoc variability on decadal and longer timescales

interdecadal variations of the thermohaline circulation in a coupled ocean atmosphere model abstract a fully coupled ocean atmosphere model is shown to have irregular oscillations of the thermohaline circulation in the north atlantic ocean with a time scale of approximately 50 years the irregular oscillation appears to be driven by density anomalies in the sinking region of the thermohaline circulation approximately 52 n to 72 n combined with much smaller density anomalies of opposite sign in the broad rising region the spatial pattern of see surface temperature anomalies associated with this irregular oscillation bears an encouraging resemblance to a pattern of observed interdecadal variability in the north atlantic the anomalies of sea surface temperature induce model surface air temperature anomalies over the northern north atlantic arctic and northwestern europe

wind driven shifts in the latitude of the kuroshio oyashio extension and generation of sst anomalies on decadal timescales abstract the causes of decadal variations of north pacific sea surface temperatures ssts are examined using a hindcast performed with an ocean general circulation model thermodynamically coupled to an atmospheric mixed layer model ogcm aml model and forced by the time history of observed surface winds the shift in north pacific ocean climate that occurred around 1976 77 is focused on since this is the best observed example available after the 1976 77 shift the aleutian low deepened and moved to the southeast of its previous position this placed anomalous cyclonic flow over the north pacific the sst response as simulated by the ocean model consisted of two components a fast and local part and a delayed and remote part in the central pacific stronger westerlies cool the ocean by increased equatorward ekman drift here the dynamical cooling is sufficiently large that the surface fluxes damp the sst anomaly this ekman response is fast and local and cools the ssts beginning in 1977 and persistin

a hemispheric mechanism for the atlantic multidecadal oscillation abstract the physical processes associated with the 70 yr period climate mode known as the atlantic multidecadal oscillation amo are examined based on analyses of observational data a deterministic mechanism relying on atmosphere ocean sea ice interactions is proposed for the amo variations in the thermohaline circulation are reflected as uniform sea surface temperature anomalies in the north atlantic these anomalies are associated with a hemispheric wavenumber 1 sea level pressure slp structure in the atmosphere that is amplified through atmosphere ocean interactions in the north pacific the slp pattern and its associated wind field affect the sea ice export through fram strait the freshwater balance in the northern north atlantic and consequently the strength of the large scale ocean circulation it generates sea surface temperature anomalies with opposite signs in the north atlantic and completes a negative feedback the authors find that the time scale of the cycle is associated with the

sea ice anomalies observed in the greenland and labrador seas during 1901 1984 and their relation to an interdecadal arctic climate cycle two independent ice data sets from the greenland and labrador seas have been analyzed for the purpose of characterizing interannual and decadal time scale sea ice extent anomalies during this century sea ice concentration data for the 1953 1984 period revealed the presence of a large positive anomaly in the greenland sea during the 1960s which coincided with the great salinity anomaly an upper ocean low salinity water mass that was observed to travel cyclonically around the northern north atlantic during 1968 1982 this ice anomaly as well as several smaller ones propagated into the labrador sea and then across to the labrador and east newfoundland coast over a period of 3 to 5 years a complex empirical orthogonal function analysis of the same data also confirmed this propagation phenomenon an inverse relation between sea ice and salinity anomalies in the greenland labrador sea region was also generally found an analysis of spring and summer ice limit data obtained from danish meteorological institute charts for the period 1901 1956 indicated the presence of heavy ice conditions i e positive ice anomalies in the greenland sea during 1902 1920 and in the late 1940s and generally negative ice anomalies during the 1920s and 1930s only limited evidence of the propagation of greenland sea ice anomalies into the labrador sea was observed however probably because the data were from the ice melt seasons on the other hand several large ice anomalies in the greenland sea occurred 2 3 years after large runoffs in the early 1930s and the late 1940s from northern canada into the western arctic ocean similarly a large runoff into the arctic during 1964 1966 preceded the large greenland sea ice anomaly of the 1960s these facts together with recent evidence of climatic jumps in the northern hemisphere tropospheric circulation suggest the existence of an interdecadal self sustained climate cycle in the arctic in the greenland sea this cycle is characterized by a state of large sea ice extent overlying an upper layer of cool relatively fresh water that does not convectively overturn which alternates every 10 15 years with a state of small sea ice extent and relatively warm saline surface water that frequently overturns

stochastically forced multidecadal variability in the north atlantic a model study observations show a multidecadal signal in the north atlantic ocean but the underlying mechanism and cause of its timescale remain unknown previous studies have suggested that it may be driven by the north atlantic oscillation nao which is the dominant pattern of winter atmospheric variability to further address this issue the global ocean general circulation model nucleus for european modelling of the ocean nemo is driven using a 2 000 years long white noise forcing associated with the nao focusing on key ocean circulation patterns we show that the atlantic meridional overturning circulation amoc and sub polar gyre spg strength both have enhanced power at low frequencies but no dominant timescale and thus provide no evidence for a oscillatory ocean only mode of variability instead both indices respond linearly to the nao forcing but with different response times the variability of the amoc at 30 n is strongly enhanced on timescales longer than 90 years while that of the spg strength starts increasing at 15 years the different response characteristics are confirmed by constructing simple statistical models that show amoc and spg variability can be related to the nao variability of the previous 53 and 10 winters respectively alternatively the amoc and the spg strength can be reconstructed with auto regressive ar models of order seven and five respectively both statistical models reconstruct interannual and multidecadal amoc variability well while on the other hand the ar 5 reconstruction of the spg strength only captures multidecadal variability using these methods to reconstruct ocean variables can be useful for prediction and model intercomparision

interdecadal variations in north atlantic sea surface temperature and associated atmospheric conditions abstract evidence is presented for a distinct pattern of ocean atmosphere relationship associated with interdecadal variability in the north atlantic region using a century of surface marine observations it is shown that middle and high latitude sea surface temperature sst display a long term fluctuation with negative anomalies before 1920 and during the 1970s and 1980s positive sst conditions prevailed from about 1930 to 1960 the pattern of interdecadal sst variability is constructed by subtracting the average field during 15 cold years from that during a similar interval of warm years the early century warming and the more recent cooling display a similar spatial pattern in both cases the pattern is basin scale and largely of one polarity with maxima in the vicinity of iceland in the labrador sea and northeast of bermuda the corresponding differences in surface atmospheric conditions are determined by averaging and subtracting in the same manner fields of sea level pressure slp and surf

high frequency environmental changes and deposition processes in a 2 kyr long sedimentological record from the cap breton canyon bay of biscay the core md03 2693 43 39 258 n 01 39 805 w 431 m water depth was collected on an abandoned meander of the capbreton canyon se bay of biscay filled over the last millennia by very high sedimentation rates mean sedimentation rate of 1 2 cm yr linked to its specific environmental location and fine grained clayed sediment decantation from the proximal canyon axis this archive thus permits to undertake the study of late holocene regional climatic patterns at a decadal temporal resolution in the present work we use data derived from planktonic foraminifera assemblages coupled to a multiproxy approach that associates grain size measurements x ray fluorescence xrf elemental analysis and stable oxygen isotope on globigerina bulloides shells to infer sea surface temperature sst and sea surface salinity sss changes over the last two millennia signals reconstructed in the bay of biscay show significant oscillations that are consistent with well known temperature anomalies such as the little ice a

support for tropically driven pacific decadal variability based on paleoproxy evidence two independent proxy reconstructions of sea surface temperature reflect a common pattern of pacific decadal sea surface temperature variability over the past two centuries since the pattern extends to both the north ern and southern hemispheres this result supports the idea that pacific decadal variability is a basin wide phenomenon originating in thetropics the causes of pacific decadal climate variability here termed pdv are the subject of much debate most work describing pdv has focused on the north pacific where the leading eof of low pass filtered sea surface temperature

reconstructing monitoring and predicting multidecadal scale changes in the north atlantic thermohaline circulation with sea surface temperature sea surface temperature sst observations in the north atlantic indicate the existence of strong multidecadal variability with a unique spatial structure it is shown by means of a new global climate model which does not employ flux adjustments that the multidecadal sst variability is closely related to variations in the north atlantic thermohaline circulation thc the close correspondence between the north atlantic sst and thc variabilities allows in conjunction with the dynamical inertia of the thc for the prediction of the slowly varying component of the north atlantic climate system it is shown additionally that past variations of the north atlantic thc can be reconstructed from a simple north atlantic sst index and that future anthropogenically forced changes in the thc can be easily monitored by observing ssts the latter is confirmed by another state ofthe art global climate model finally the strong multidecadal variability may mask an anthropogenic signal in the north atlantic for some decades

stratigraphic framework of sediment starved sand ridges on a mixed siliciclastic carbonate inner shelf west central florida abstract seismic reflection profiles and vibracores have revealed that an inner shelf sand ridge field has developed over the past few thousand years situated on an elevated broad bedrock terrace this terrace extends seaward of a major headland associated with the modern barrier island coastline of west central florida the overall geologic setting is a low energy sediment starved mixed siliciclastic carbonate inner continental shelf supporting a thin sedimentary veneer this veneer is arranged in a series of subparallel shore oblique and to a minor extent shore parallel sand ridges seven major facies are present beneath the ridges including a basal neogene limestone gravel facies and a blue green clay facies indicative of dominantly authigenic sedimentation a major sequence boundary separates these older units from holocene age organic rich mud facies marsh which grades upward into a muddy sand facies lagoon or shallow open shelf seagrass meadows cores reveal that the muddy shelf facies is either in sharp contact or grades upward into a shelly sand facies ravinement or sudden termination of seagrass meadows the shelly sand facies grades upward to a mixed siliciclastic carbonate facies which forms the sand ridges themselves this mixed siliciclastic carbonate facies differs from the sediment on the beach and shoreface suggesting insignificant sediment exchange between the offshore ridges and the modern coastline additionally the lack of early holocene pre ridge facies in the troughs between the ridges suggests that the ridges themselves do not migrate laterally extensively radiocarbon dating has indicated that these sand ridges can form relatively quickly 1 3 ka on relatively low energy inner shelves once open marine conditions are available and that frequent high energy storm dominated conditions are not necessarily required we suggest that the two inner shelf depositional models presented open shelf vs migrating barrier island may have co existed spatially and or temporally to explain the distribution of facies and vertical facies contacts

simulated low frequency modes of circulation in the arctic ocean the variability of the arctic circulation is investigated for a 43 year period 1951 1993 from a coupled ice ocean model empirical orthogonal function eof analysis shows that the variability of the sea surface height ssh and vertically integrated transport is organized so that in the leading mode the whole arctic operates as a single gyre the mode is associated with the arctic oscillation ao thompson and wallace 1998 and it explains over 70 of the variance in the vertically integrated transport and 25 of the ssh variability the physical interpretation of this mode is derived to arise from its close connection to the atlantic inflow to the arctic the mode shows a major shift toward cyclonic circulation in the end of the 1980s which is associated with a large multiyear pulse of atlantic water to the arctic thus this event appears as the likely initiation of the atlantic layer warming observed during the recent years carmack et al 1995 overall the first mode shows strong decadal variability as reported by proshutinsky and johnson 1997 the second mode of the oceanic circulation which explains 9 of the variance in the transport contains two gyres with opposing cyclonicity in the eurasia and canada basins it projects onto the north atlantic oscillation nao pattern and displays a 14 year cycle which is known to exist in the midlatitude north atlantic surface temperatures deser and blackmon 1993 a further examination reveals that this mode describes the variability of the flow through the barents sea which is modulated by the water mass modification due to the local heat flux variability the apparent nao connection is provided by a simultaneous correlation between the time series of this second mode and the leading heat flux mode in the north atlantic which is associated with nao

a tree ring based reconstruction of the atlantic multidecadal oscillation since 1567 a d 1 we present a tree ring based reconstruction of the atlantic multidecadal oscillation amo which demonstrates that strong low frequency 60 100 yr variability in basin wide 0 70 n sea surface temperatures ssts has been a consistent feature of north atlantic climate for the past five centuries intervention analysis of reconstructed amo indicates that 20th century modes were similar to those in the preceding 350 yr and wavelet spectra show robust multidecadal oscillations throughout the reconstruction though the exact relationships between low frequency sst modes higher frequency 7 25 yr atmospheric modes e g north atlantic oscillation arctic oscillation and terrestrial climates must still be resolved our results confirm that the amo should be considered in assessments of past and future northern hemisphere climates

possible north atlantic origin for changes in enso properties during the 1970s the most intense el nino episodes in more than a century occurred after the 1970s climate shift previous studies show that the characteristics of the el nino southern oscillation enso phenomenon changed synchronously with the shift but the associated causes are not fully understood an analysis of the observed tropical pacific sea surface temperature sst anomalies shows that their increase in the eastern part of the basin after the 1970s is not related to the canonical enso pattern but to the tropical pacific meridional mode tpmm we present observational evidence which supports the hypothesis that the change in the tpmm was triggered by the great salinity anomaly gsa which manifested in the north atlantic during the late 1960s the gsa induced a weak labrador convection and a sst dipole south of greenland the associated atmospheric structure includes a north pacific oscillation sea level pressure dipole in the pacific sector this excites the tpmm which contributes to the intense el nino events and to the enhanced enso s asymmetry observed after the shift our results imply that if the gsa has not an anthropic origin as was suggested then the tropical pacific climate shift has a natural origin this is supported by the end of the north atlantic regime in the 1990s and by the rebound of the tropical pacific after 1998

atlantic multidecadal oceanic variability and its influence on the atmosphere in a climate model the mechanisms controlling the decadal to multidecadal variability of the atlantic meridional overturning circulation moc and its influence on the atmosphere are investigated using a control simulation with the ipsl cm4 climate model the multidecadal fluctuations of the moc are mostly driven by deep convection in the subpolar gyre which occurs south of iceland in the model the latter is primarily influenced by the anomalous advection of salinity due to changes in the east atlantic pattern eap which is the second mode of atmospheric variability in the north atlantic region the north atlantic oscillation is the dominant mode but it plays a secondary role in the moc fluctuations during summer the moc variability is shown to have a significant impact on the atmosphere in the north atlantic european sector the moc influence is due to an interhemispheric sea surface temperature sst anomaly with opposite signs in the two hemispheres but largest amplitude in the northern one the sst pattern driven by the moc mostly resembles the model atlantic multidecadal oscillation amo and bears some similarity with the observed one it is shown that the amo reflects both the moc influence and the local atmospheric forcing hence the moc influence on climate is best detected using lagged relations between climatic fields the atmospheric response resembles the eap in a phase that might induce a weak positive feedback on the moc

response of sea ice to the arctic oscillation abstract data collected by the international arctic buoy programme from 1979 to 1998 are analyzed to obtain statistics of sea level pressure slp and sea ice motion sim the annual and seasonal mean fields agree with those obtained in previous studies of arctic climatology the data show a 3 hpa decrease in decadal mean slp over the central arctic ocean between 1979 88 and 1989 98 this decrease in slp drives a cyclonic trend in sim which resembles the structure of the arctic oscillation ao regression maps of sim during the wintertime january march ao index show 1 an increase in ice advection away from the coast of the east siberian and laptev seas which should have the effect of producing more new thin ice in the coastal flaw leads 2 a decrease in ice advection from the western arctic into the eastern arctic and 3 a slight increase in ice advection out of the arctic through fram strait taken together these changes suggest that at least part of the thinning of sea ice recently observed ov

sea ice transport a highly variable link between arctic and north atlantic the variability of the ice volume flux into the northeast atlantic is investigated with an optimized dynamic thermodynamic sea ice model using 40 years 1958 1997 of atmospheric forcing fields derived from the ncep ncar reanalysis project the simulated sea ice export from the arctic exhibits considerable interannual to decadal variability and is primarily a linear response to sea level pressure anomalies over greenland and over the barents and kara seas our model results suggest that ice export anomalies such as in 1968 which supposedly caused the so called great salinity anomaly in the northern north atlantic are not unique but rather frequent events as part of the variability of the arctic climate system

on the relationship between tropical and north pacific sea surface temperature variations abstract empirical orthogonal function analysis of winter sea surface temperature sst anomalies over the pacific domain 60 n 20 s reveals an el nino southern oscillation enso mode that is linked to the eastern north pacific and a north pacific mode that is linearly independent of enso the north pacific mode exhibits maximum amplitude and variance explained along 40 n west of 170 w ssts in this region have decreased by 1 5 c from 1950 to 1987 the cooling in winter has been associated with a strengthening of the overlying westerly winds

haline circulation induced by formation and melting of sea ice a three dimensional coupled ice ocean model is developed and basic numerical experiments for examining effects of freshwater budget associated with formation and melting of sea ice on the thermohaline circulation are performed motion of sea ice affects the freshwater budget in two ways first it horizontally transports freshwater in the form of sea ice second it alters the conditions of sea ice which influence heat budget at the sea surface and thus the rate of formation and melting to separate such effects of ice motion two experiments are designed in one case ice motion is removed and in the other case it is included there appear significant differences in the thermohaline circulation between the two cases these differences are due to the difference in horizontal distribution of salinity which is maintained by the cycle of formation transport and melting of sea ice and the corresponding freshwater budget experiments for investigating dependence of the thermohaline circulation on the distribution of winds and consequent ice motion are also carried out it is demonstrated that wind induced ice motion has major influences on how saline water produced by sea ice formation at high latitudes extends

the role of sea ice and other fresh water in the arctic circulation salinity stratification is critical to the vertical circulation of the high latitude ocean we here examine the control of the vertical circulation in the northern seas and the potential for altering it by considering the budgets and storage of fresh water in the arctic ocean and in the convective regions to the south we find that the present day greenland and iceland seas and probably also the labrador sea are rather delicately poised with respect to their ability to sustain convection small variations in the fresh water supplied to the convective gyres from the arctic ocean via the east greenland current can alter or stop the convection in what may be a modern analog to the halocline catastrophes proposed for the distant past the north atlantic salinity anomaly of the 1960s and 1970s is a recent example it must have had its origin in an increased fresh water discharge from the arctic ocean similarly the freshening and cooling of the deep north atlantic in recent years is a likely manifestation of the increased transfer of fresh water from the arctic ocean into the convective gyres finally we note that because of the temperature dependence of compressibility a slight salinity stratification in the convective gyres is required to efficiently ventilate the deep ocean

energetics of multidecadal atlantic ocean variability abstractoscillatory behavior of the atlantic meridional overturning circulation moc is thought to underlie atlantic multidecadal climate variability while the energy sources and sinks driving the mean moc have received intense scrutiny over the last decade the governing energetics of the modes of variability of the moc have not been addressed to the same degree this paper examines the energy conversion processes associated with this variability in an idealized north atlantic ocean model in this model the multidecadal variability arises through an instability associated with a so called thermal rossby mode which involves westward propagation of temperature anomalies applying the available potential energy ape framework from stratified turbulence to the idealized ocean model simulations the authors study the multidecadal variability from an energetics viewpoint the analysis explains how the propagation of the temperature anomalies leads to changes in ape which are subsequently converted into t

a review of north atlantic modes of natural variability and their driving mechanisms 1 this paper reviews three modes of natural variability that have been identified in the north atlantic ocean namely the north atlantic oscillation nao the atlantic multidecadal oscillation amo and the atlantic meridional mode amm this manuscript focuses on the multidecadal fluctuations of these three modes a range of different mechanisms to initiate phase reversals in these modes on multidecadal timescales has been suggested previously we propose a systematic grouping of these mechanisms into three types that involve respectively 1 the dependency of the atlantic thermohaline circulation thc on salinity 2 the sensitivity of the thc to changes in ocean heat transport and 3 the dependency of the nao to changes in the atlantic meridional temperature gradient some new density data is also provided demonstrating physical links between the thc and the amo

climate signatures on decadal to interdecadal time scales as obtained from mollusk shells arctica islandica from iceland pronounced decadal climate oscillations are detected in a multi centennial record based on shell growth rates of the marine bivalve mollusk arctica islandica from iceland the corresponding analysis of patterns in sea level pressure and temperature exhibit large scale teleconnections with north atlantic climate quantities we find that the record projects onto blocking situations in the northern north atlantic the associated circulation shows a low pressure signature over greenland and the labrador sea and a high pressure system over western europe associated with northeasterly flow towards iceland and weakening in the westerly zonal flow over europe it can be speculated that such circulation affects food availability controlling shell growth on multidecadal time scales the record shows a pronounced variability linked to north atlantic temperature in our record we find enhanced variability of the shell growth rates on multidecadal time scales and it appears that this oscillation has high amplitudes in the 16th to 18th century also consistent with marine alkenone data it is conceivable that these climate oscillations also linked to sea ice export and enhanced blocking are a more pronounced feature during times when the climate was relatively cold

enso like interdecadal variability 1900 93 a number of recent studies have reported an enso like eof mode in the global sea surface temperature sst field whose time variability is marked by an abrupt change toward a warmer tropical eastern pacific and a colder extratropical central north pacific in 1976 77 the present study compares this pattern with the structure of the interannual variability associated with the enso cycle and documents its time history back to 1900 the analysis is primarily based on the leading eofs of the sst anomaly and anomaly deviation fields in various domains and the associated expansion coefficient or principal component time series which are used to construct global regression maps of sst sea level pressure slp and a number of related variables the use of anomaly deviations i e departures of local sst anomalies from the concurrent global mean sst anomaly reduces the influence of global mean sst trends upon the structure of the eofs and their expansion coefficient time series an important auxiliary time series used in this study is a southern oscillation index based on marine surface observations by means of several different analysis techniques the time variability of the leading eof of the global sst field is separated into two components one identified with the enso cycle related variability on the interannual timescale and the other a linearly independent residual comprising all the interdecadal variability in the record the two components exhibit rather similar spatial signatures in the global sst slp and wind stress fields the sst signature in the residual variability is less equatorially confined in the eastern pacific and it is relatively more prominent over the extratropical north pacific the corresponding slp signature is also stronger over the extratropical north pacific and its counterpart in the cold season 500 mb height field more closely resembles the pna pattern the amplitude time series of the enso like pattern in the residual variability reflects the above mentioned shift in 1976 77 as well as a number of other prominent features including a shift of opposite polarity during the 1940s

linking large scale climate variability with arctica islandica shell growth and geochemistry in northern norway the lack of high resolution geographically diverse proxy records from the marine realm limits our understanding of climate dynamics in the north atlantic ocean and arctic during recent centuries we investigate the impact of large scale climate variability on the marine bivalve arctica islandica linnaeus 1767 from northern norway 71 n we evaluate the use of annual shell growth and geochemical records as proxies for north atlantic and arctic climate variability over centennial scales by developing a continuous 113 yr master shell growth chronology and an oxygen isotope record 18o from live caught shell material a relatively strong inverse relationship is observed between both the shell growth and isotopic proxies and large scale north atlantic sea surface temperatures in modern times r 0 54 to 0 90 p 0 05 this relationship is strengthened when using a combined shell growth oxygen isotope multiproxy index r 0 72 to 0 90 p 0 01 the regional spatial pattern of correlation resembles that of the north atlantic current as it bifurcates around 55 n indicating that large scale ocean surface current dynamics play an important role in regulating local ecosystem processes and thus shell growth in northern norway a combined proxy index created using multiple linear regression exhibits a relatively strong and time stable relationship with the atlantic multidecadal oscillation amo r 0 622 p 0 001 since ad 1900 variability in the relationship between the shell based records and the north atlantic oscillation coincide with variations in the amo index suggesting a complex relationship between atmospheric forcing on hydrographic variability and ecosystem dynamics in northern norway

a global el nino southern oscillation wave in surface temperature and pressure and its interdecadal modulation from 1900 to 1997 zonal wavenumber frequency spectra of sea surface temperature sst anomalies along the equator in the indo pacific basin for the 98 years from 1900 to 1997 and of surface temperature st and sea level pressure slp anomalies extending around the globe along 10 n for the 48 years from 1950 to 1997 display significant peak spectral energy density for standing and eastward propagating waves of 3 7 year periods and 120 360 zonal wavelengths the global standing wave is the familiar southern oscillation but the global propagating wave represents a new paradigm for the el nino southern oscillation enso global distributions of the phase velocities for this global enso wave finds covarying slp and st anomalies propagating eastward along the mean path of the intertropical convergence zone itcz with the global zonal wavenumber 1 2 component taking 4 6 years to cross the tropical indian pacific and atlantic oceans at a zonal average speed of 90 60 longitude per year along this path the interannual sst and slp anomalies are directly out of phase since thermocline depth anomalies underneath the itcz in the pacific ocean propagate westward white et al 1985 we view the global enso wave as a slow coupled sst wave trapped onto the itcz separating the global enso wave from the southern oscillation using complex empirical orthogonal function analysis finds the amplitude of the propagating wave to be half that of the standing wave with the former latter accounting for one third two thirds of the interannual variability in nino 3 sst and slp indices during the 1980s the global enso wave is shown to be responsible for the eastward propagation of covarying zonal surface wind and thermocline depth anomalies across the equatorial pacific ocean and through this mechanism is able to influence both the phasing and intensity of el nino examining the persistence of the global enso wave from 1900 to 1997 finds it and the intensity of el nino in the eastern equatorial pacific ocean modulated by interdecadal change both were strong weak or absent during decades of global tropical cooling warming

is the recently reported 65 to 70 year surface temperature oscillation the result of climatic noise in a recent paper schlesinger and ramankutty 1994 we reported finding a 65 to 70 year oscillation in each of the four records of observed global mean surface temperature we also found that the oscillation does not exist everywhere over the earth but rather only over the north atlantic ocean and its bordering continental regions of north america europe and northern africa we proposed three possible causes for our finding 1 random radiative forcing of the climate system that is climatic noise 2 oscillatory forcing external to the climate system such as by a variation in solar irradiance and 3 an oscillation internal to the climate system perhaps not unlike that of the el nino southern oscillation but with a longer timescale in this paper we critically examine the first hypothesis our analysis shows that this hypothesis can be rejected at a very high level of statistical confidence

the great salinity anomaly in the northern north atlantic 1968 1982 the widespread freshening of the upper 500 800m layer of the northern north atlantic which this paper describes represents one of the most persistent and extreme variations in global ocean climate yet observed in this century though a range of explanations have been advanced to explain this event including in situ changes in the surface moisture flux this paper describes the great salinity anomaly as largely though not entirely an advective event traceable around the atlantic subpolar gyre for over 14 years from its origins north of iceland in the mid to late 1960s until its return to the greenland sea in 1981 1982 the overall propagation speed around this subpolar gyre is estimated at about 3cm s 1 of the total salt deficit associated with the anomaly as it passed south along the labrador coast in 1971 1973 about 72 109 tonnes a deficit equivalent to about two thirds of this figure 47 109 tonnes ultimately passed through the faroe shetland channel to the barents sea arctic ocean and greenland sea during the mid 1970s possible effects on deep water formation and on the representativeness of historical section data are discussed

an intimate coupling of ocean atmospheric interaction over the extratropical north atlantic and pacific the inter basin teleconnection between the north atlantic and the north pacific ocean atmosphere interaction is studied using a coupled ocean atmosphere general circulation model in the model an idealized oceanic temperature anomaly is initiated over the kuroshio and the gulf stream extension region to track the coupled evolution of ocean and atmosphere interaction respectively the experiments explicitly demonstrate that both the north pacific and the north atlantic ocean atmosphere interactions are intimately coupled through an inter basin atmospheric teleconnection this fast inter basin communication can transmit oceanic variability between the north atlantic and the north pacific through local ocean to atmosphere feedbacks the leading mode of the extratropical atmospheric internal variability plays a dominant role in shaping the hemispheric scale response forced by oceanic variability over the north atlantic and pacific modeling results also suggest that a century two centuries long observations are necessary for the detection of pacific response to atlantic forcings atlantic response to pacific forcing

multiscale variabilities in global sea surface temperatures and their relationships with tropospheric climate patterns el nino southern oscillation enso is a global phenomenon with significant phase propagation within and between basins this is captured and described in the first mode of a complex empirical orthogonal function ceof analysis of sea surface temperature anomaly ssta from the midnineteenth century through 1991 the global enso from the ssta data plus a linear trend everywhere are subsequently removed in order to consider other global modes of variability uncontaminated by the intra and interbasin effects of enso an ordinary eof analysis of the ssta residuals reveals three non enso modes of low frequency variability that are related to slow oceanic and climate signals described in the literature the first two modes have decadal to multidecadal timescales with high loadings in the pacific they bear some spatial similarities to the enso pattern but are broader more intense at high latitudes and differ in the time domain a ceof analysis confirms that they are not merely the phase related components of a single mode and that all three modes are without significant phase propagation the third mode is a multidecadal signal with maximal realization in the extratropical north atlantic southeast of greenland it is consistent with studies that have documented connections between north atlantic ssta and the tropospheric north atlantic oscillation nao all three ssta modes have midtropospheric associations related to previously classified northern hemisphere teleconnection patterns the relationships between ssta modes and tropospheric patterns are consistent with the ocean atmosphere interactions discussed in previous studies to explain low frequency climate oscillations in the north pacific and north atlantic sectors the first three leading modes of non enso ssta are most related to the tropospheric patterns of the pacific north american the north pacific and the arctic oscillations ao respectively the 500 hpa pattern associated with the third ssta mode also bears similarities to the nao in its atlantic sector this north atlantic mode has a region of high positive ssta loadings in the gulf of alaska which appear to be connected to the north atlantic ssta by a tropospheric bridge effect in the ao

asymmetry in the response of central eurasian winter temperature to amo the asymmetry in the teleconnection of the central eurasian winter surface air temperature sat with the atlantic multidecadal oscillation amo is discussed using observations and model simulations observations indicate that the winter sat over central eurasia 30 70 e 30 50 n shows significant positive anomalies during the warm amo period but weak and insignificant anomalies in the cold amo period in general the warm winters in central eurasia are associated with large scale negative sea level pressure anomalies in europe anomalous southwesterly winds at 850 hpa over europe the geopotential height anomalies at 500 hpa in the south of greenland northern europe western asia and the slant north south pattern jet stream anomalies at 200 hpa in the north and south of the caspian sea reverse patterns occur during cold winters these statistically significant features are observed in the warm phase of amo reversed circulation anomalies are observed during the cold phase of amo however these anomalies are weak and not statistically significant furthermore the asymmetry in the atmospheric response to amo is well supported by simulations with a suite of gfdl atmospheric model idealized experiments and four cmip5 models historical experiments both observations and simulations indicate that rossby waves propagating from the north atlantic eastward to eurasia emerge in the warm amo and disappear in the cold amo thus the different propagations of rossby waves induced by the different surface thermal conditions of the warm and cold amo are the potential connection between the north atlantic ocean and central eurasian climate and may explain the asymmetry

rotated global modes of non enso sea surface temperature variability a varimax rotation was applied to the eof modes of global sst derived by enfield and mestas nunez the sst anomaly record is more than a century long with a global complex eof representation of enso and a linear trend removed at every grid point the rotated eof modes capture localized centers of variability that contribute to the larger scale spatial patterns of the unrotated modes the first rotated eof represents a mul tidecadal signal with larger response in the north atlantic the second rotated eof represents an interdecadal fluctuation with larger response in the eastern north pacific and out of phase fluctuations of smaller amplitude in the central north pacific the third rotated eof captures interdecadal fluctuations in the eastern tropical pacific with a dominant peak that coincides with the 1982 83 enso the fourth rotated eof has interdecadal to multidecadal nature with larger response in the central equatorial pacific and quasi symmetric out of phase response in the western north and south pacific the fifth mode represents multidecadal fluctuations with large response at about 408n in the north pacific the sixth mode has interannual to interdecadal timescales with largest response confined to the south atlantic the authors rotated modes are dominated by intra rather than interocean fluctuations supporting the hypothesis that the non enso variability is more regional than global in nature analyses of sea level pressure and surface wind stress show that in general the non enso rotated eofs are consistent with an ocean response to local atmospheric forcing an exception is the eastern tropical pacific mode which is more consistent with an atmospheric response to changes in the ocean sst

can tree ring density data reflect summer temperature extremes and associated circulation patterns over fennoscandia tree ring maximum latewood density mxd records from fennoscandia have been widely used to infer regional and hemispheric scale mean temperature variability here we explore if mxd records can also be used to infer past variability of summer temperature extremes across fennoscandia the first principal component pc1 based on 34 mxd chronologies in fennoscandia explains 50 of the total variance in the observed warm day extremes over the period 1901 1978 variations in both observed summer warm day extremes and pc1 are influenced by the frequency of anomalous anticyclonic pattern over the region summer sea surface temperatures over the baltic north and norwegian seas and the strength of the westerly zonal wind at 200 hpa across fennoscandia both time series are associated with nearly identical atmospheric circulation and sst patterns according to composite map analysis in a longer context the first pc based on 3 millennium long mxd chronologies in central and northern fennoscandia explains 83 of the total variance of pc1 from the 34 mxd chronologies over the period 1901 1978 48 of the total variance of the summer warm day extreme variability over the period 1901 2006 and 36 of the total variance in the frequency of a summer anticyclonic pattern centered over eastern central fennoscandia in the period 1948 2006 the frequency of summer warm day extremes in fennoscandia is likely linked to a meridional shift of the northern mid latitude jet stream this study shows that the mxd network can be used to infer the variability of past summer warm day extremes and the frequency of the associated summer anticyclonic circulation pattern over fennoscandia

an alternative approach to reveal critical behaviour in the case of the mw 6 3 aquila earthquake an independent approach based on a power law relation interconnecting the lead time of precursory signals and the stress drop of forthcoming earthquake confirms the reported evidence that the observed magnetic field anomaly and consequently according to maxwell s laws electric field anomaly prior to mw 6 3 aquila earthquake in 2009 exhibit features of criticality precisely by inserting the data from aquila earthquake in this power law we get an exponent 0 329 which is in excellent agreement with previously found ones and falls within the range values 0 3 0 4 for critical exponents for fracture this fact implies that upon the initiation of the observed magnetic field anomaly and the associated electric signal prior to aquila earthquake the prefocal area enters into a critical stage where nonlinear dynamic processes typical behaviour of a system close to criticality prevail

sea ice switches and abrupt climate change we propose that past abrupt climate changes were probably a result of rapid and extensive variations in sea ice cover we explain why this seems a perhaps more likely explanation than a purely thermohaline circulation mechanism we emphasize that because of the significant influence of sea ice on the climate system it seems that high priority should be given to developing ways for reconstructing high resolution in space and time sea ice extent for past climate change events if proxy data can confirm that sea ice was indeed the major player in past abrupt climate change events it seems less likely that such dramatic abrupt changes will occur due to global warming when extensive sea ice cover will not be present

observed winter salinity fields in the surface layer of the arctic ocean and statistical approaches to predicting large scale anomalies and patterns significant salinity anomalies have been observed in the arctic ocean surface layer during the last decade our study is based on an extensive gridded dataset of winter salinity in the upper 50 m layer of the arctic ocean for the periods 1950 1993 and 2007 2012 obtained from 20 000 profiles we investigate the interannual variability of the salinity fields identify predominant patterns of anomalous behavior and leading modes of variability and develop a statistical model for the prediction of surface layer salinity the statistical model is based on linear regression equations linking the principal components of surface layer salinity obtained through empirical orthogonal function decomposition with environmental factors such as atmospheric circulation river runoff ice processes and water exchange with neighboring oceans using this model we obtain prognostic fields of the surface layer salinity for the winter period 2013 2014 the prognostic fields generated by the model show tendencies of surface layer salinification which were also observed in previous years although the used data are proprietary and have gaps they provide the most spatiotemporally detailed observational resource for studying multidecadal variations in basin wide arctic salinity thus there is community value in the identification dissemination and modeling of the principal modes of variability in this salinity record

subtropical coral reveals abrupt early twentieth century freshening in the western north pacific ocean instrumental climate observations provide robust records of global land and ocean temperatures during the twentieth century unlike for temperature continuous salinity observations in the surface ocean are scarce prior to 1970 and the magnitude of salinity changes during the twentieth century is largely unknown surface ocean salinity is a major component in climate dynamics as it influences ocean circulation and water mass formation here we present an annually resolved reconstruction of salinity variations in the surface waters of the western subtropical north pacific ocean since 1873 based on bimonthly records of 18o sr ca and u ca in a coral from the ogasawara islands the reconstruction indicates that an abrupt regime shift toward fresher surface ocean conditions occurred between 1905 and 1910 observational atmospheric data suggest that the abrupt freshening was associated with a weakening of the winds that drive the kuroshio current system and the associated subtropical gyre circulation we note that the abrupt early twentieth century freshening in the western subtropical north pacific precedes abrupt climate change in the northern north atlantic by a few years the potential for abrupt regime shifts in surface ocean salinity should be considered in climate predictions for the coming decades

holocene climate variability in texas usa an integration of existing paleoclimate data and modeling with a new high resolution speleothem record abstract delineating the climate processes governing precipitation variability in drought prone texas is critical for predicting and mitigating climate change effects and requires the reconstruction of past climate beyond the instrumental record we synthesize existing paleoclimate proxy data and climate simulations to provide an overview of climate variability in texas during the holocene conditions became progressively warmer and drier transitioning from the early to mid holocene culminating between 7 and 3 ka thousand years ago and were more variable during the late holocene the timing and relative magnitude of holocene climate variability however is poorly constrained owing to considerable variability among the different records to help address this we present a new speleothem nbj reconstruction from a central texas cave that comprises the highest resolution proxy record to date spanning the mid to late holocene nbj trace element concentrations indicate variable moisture conditions with no clear temporal trend there is a decoupling between nbj growth rate trace element concentrations and 18o values which indicate that i the often direct relation between speleothem growth rate and moisture availability is likely complicated by changes in the overlying ecosystem that affect subsurface co2 production and ii speleothem 18o variations likely reflect changes in moisture source i e proportion of pacific vs gulf of mexico derived moisture that appear not to be linked to moisture amount

global scale modes of surface temperature variability on interannual to century timescales using 100 years of global temperature anomaly data we have performed a singular value decomposition of temperature variations in narrow frequency bands to isolate coherent spatio temporal modes of global climate variability statistical significance is determined from confidence limits obtained by monte carlo simulations secular variance is dominated by a globally coherent trend with nearly all grid points warming in phase at varying amplitude a smaller but significant share of the secular variance corresponds to a pattern dominated by warming and subsequent cooling in the high latitude north atlantic with a roughly centennial timescale spatial patterns associated with significant peaks in variance within a broad period range from 2 8 to 5 7 years exhibit characteristic el nino southern oscillation enso patterns a recent transition to a regime of higher enso frequency is suggested by our analysis an interdecadal mode in the 15 to 18 years period range appears to represent long term enso variability this mode has a sizeable projection onto global average temperature and accounts for much of the anomalous global warmth of the 1980s a quasi biennial mode centered near 2 2 years period and a mode centered at 7 to 8 years period both exhibit predominantly a north atlantic oscillation nao temperature pattern a potentially significant decadal mode centered on 11 to 12 years period also exhibits an nao temperature pattern and may be modulated by the century scale north atlantic variability

atlantic multidecadal variability in a model with an improved north atlantic current we examine the simulated atlantic multidecadal variability amv in a model that includes a correction for a longstanding problem with climate models namely the misplacement of the north atlantic current the corrected model shows that in the warm amv phase heat is lost by the ocean in the northwestern part of the basin and gained by the ocean to the east suggesting an advective transfer of heat by the mid latitude westerlies the basin wide response is consistent with a role for cloud feedback and is in broad agreement with estimates from observations but is poorly represented in the uncorrected model the corrected model is then used to show that the ocean atmosphere heat transfer is influenced by low frequency variability in the overlying atmosphere we also argue that changing ocean heat transport is an essential feature of our results

equilibrium atmospheric response to north atlantic sst anomalies abstract the equilibrium general circulation model gcm response to sea surface temperature sst anomalies in the western north atlantic region is studied a coarse resolution gcm with realistic lower boundary conditions including topography and climatological sst distribution is integrated in perpetual january and perpetual october modes distinguished from one another by the strength of the midlatitude westerlies an sst anomaly with a maximum of 4 c is added to the climatological sst distribution of the model with both positive and negative polarity these anomaly runs are compared to one another and to a control integration to determine the atmospheric response in all cases warming cooling of the midlatitude ocean surface yields a warming cooling of the atmosphere over and to the east of the sst anomaly center the atmospheric temperature change is largest near the surface and decreases upward consistent with this simple thermal response the geopotential height field displays a baroclinic

north atlantic interdecadal variability oceanic response to the north atlantic oscillation 1865 1997 abstract in contrast to the atmosphere knowledge about interdecadal variability of the north atlantic circulation is relatively restricted it is the objective of this study to contribute to understanding how the north atlantic circulation responds to a forcing by the north atlantic oscillation nao on interdecadal timescales for this purpose the authors analyze observed atmospheric and sea surface temperature sst data along with the response of an ocean general circulation model to a realistic monthly surface flux forcing that is solely associated with the nao for the period 1865 1997 in agreement with previous studies it is shown that the relationship between the local forcing by the nao and observed sst anomalies on interdecadal timescales points toward the importance of oceanic dynamics in generating sst anomalies a comparison between observed and modeled sst anomalies reveals that the model results can be used to assess interdecadal variability of the north atlantic circulation the observed

pacific decadal variability the tropical pacific mode and the north pacific mode pacific decadal variability is studied in a series of coupled global ocean atmosphere simulations aided by two modeling surgery strategies partial coupling pc and partial blocking pb the pc experiments retain full ocean atmosphere coupling in selected regions but constrain ocean atmosphere coupling elsewhere by prescribing the model climatological sst to force the atmospheric component of the coupled system in pb experiments sponge walls are inserted into the ocean component of the coupled model at specified latitudinal bands to block the extratropical tropical oceanic teleconnection both modeling and observational studies suggest that pacific decadal variability is composed of two distinct modes a decadal to bidecadal tropical pacific mode tpm and a multidecadal north pacific mode npm the pc and pb experiments showed that the tropical pacific mode originates predominantly from local coupled ocean atmosphere interaction within the tropical pacific extratropical tropical teleconnections although not a necessary precondition for the genesis of the tropical decadal variability can enhance sst variations in the tropics the decadal memory in the tropics seems to be associated with tropical higher baroclinic modes the north pacific mode originates from local atmospheric stochastic processes and coupled ocean atmosphere interaction atmospheric stochastic forcing can generate a weaker npm like pattern in both the atmosphere and ocean but with no preferred timescales in contrast coupled ocean atmosphere feedback can enhance the variability substantially and generate a basin scale multidecadal mode in the north pacific the multidecadal memory in the midlatitudes seems to be associated with the delayed response of the subtropical subpolar gyre to wind stress variation in the central north pacific and the slow growing decaying of sst anomalies that propagate eastward in the kuroshio extension region oceanic dynamics particularly the advection of the mean temperature by anomalous meridional surface ekman flow and western boundary currents plays an important role in generating the north pacific mode

a signal of persistent atlantic multidecadal variability in arctic sea ice satellite data suggest an arctic sea ice climate system in rapid transformation yet its long term natural modes of variability are poorly known here we integrate and synthesize a set of multicentury historical records of atlantic arctic sea ice supplemented with high resolution paleoproxy records each reflecting primarily winter spring sea ice conditions we establish a signal of pervasive and persistent multidecadal 60 90 year fluctuations that is most pronounced in the greenland sea and weakens further away covariability between sea ice and atlantic multidecadal variability as represented by the atlantic multidecadal oscillation amo index is evident during the instrumental record including an abrupt change at the onset of the early twentieth century warming similar covariability through previous centuries is evident from comparison of the longest historical sea ice records and paleoproxy reconstructions of sea ice and the amo this observational evidence supports recent modeling studies that have suggested that arctic sea ice is intrinsically linked to atlantic multidecadal variability this may have implications for understanding the recent negative trend in arctic winter sea ice extent although because the losses have been greater in summer other processes and feedbacks are also important

multidecadal variability and late medieval cooling of near coastal sea surface temperatures in the eastern tropical north atlantic 1 multidecadal variations in atlantic sea surface temperatures sst influence the climate of the northern hemisphere however prior to the instrumental time period information on multidecadal climate variability becomes limited and there is a particular scarcity of sufficiently resolved sst reconstructions here we present an eastern tropical north atlantic reconstruction of ssts based on foraminiferal mg ca ratios that resolves multidecadal variability over the past 1700 years spectral power in the multidecadal band 50 to 70 years period is significant over several time intervals suggesting that the atlantic multidecadal oscillation amo has been influencing local sst since our data exhibit high scatter the absence of multidecadal variability in the remaining record does not exclude the possibility that sst variations on this time scale might have been present without being detected in our data cooling by 0 5 c takes place between about ad 1250 and ad 1500 while this corresponds to the inception of the little ice age lia the end of the lia is not reflected in our record and sst remains relatively low this transition to cooler ssts parallels the previously reconstructed shift in the north atlantic oscillation toward a low pre 20th century mean state and possibly reflects common solar forcing