rossby waves in the tropical north pacific and their role in decadal thermocline variability abstract a band of enhanced thermocline variability at 10 15 n in the pacific found in nature also occurs in an ocean general circulation model forced with observed fluxes of momentum heat and freshwater over the period 1958 97 the variability in the model is primarily associated with long baroclinic rossby waves characterized by periods in the decadal range 7 10 yr the waves are forced by westward propagating ekman pumping anomalies east of the date line and propagate at a speed of 13 cm s 1 which is slower than the phase speed of the first mode unforced baroclinic waves 15 16 cm s 1 west of the date line the correlations between thermocline displacements and local ekman pumping are relatively small and the ocean signals have a phase speed of 20 cm s 1 very similar to the phase speed of the first baroclinic mode in the western half of the basin 18 20 cm s 1 the phase speeds of the ocean model signals have been estimated using cospectral analysis while the wkb approximation has been us

decadal variability in the kuroshio oyashio extension simulated in an eddy resolving ogcm abstract through analysis of a hindcast integration of an eddy resolving quasi global ocean general circulation model decadal variability in the kuroshio oyashio extension region is investigated with particular emphasis on that of the subarctic oyashio and the kuroshio extension ke fronts the ke front is deep and is accompanied by a sharp sea surface height ssh gradient with modest sea surface temperature sst gradient in contrast the subarctic front is shallow and is recognized as a zone of tight gradient in sst but not ssh as a decadal scale change from a warm period around 1970 to a cool period in the mid 1980s those fronts in the model migrate southward as observed and the associated pronounced cooling is confined mainly to those frontal zones reflecting the distinctive vertical structure of the fronts the mixed layer cooling is the strongest along the subarctic front whereas the subsurface cooling and the associated salinity changes are most pronounced along the ke front concomitan

revisited relationship between tropical and north pacific sea surface temperature variations 1 the relationship between the tropical and north pacific sea surface temperature sst variations is reexamined following the results of deser and blackmon 1995 db95 based on a much longer period of data 1949 2010 as in db95 the two leading sst modes the el nino southern oscillation enso mode and the north pacific mode represent the sst variations in the pacific domain before 1992 considering the period after 1992 however one needs to consider a new mode of sst variation along with the two modes mentioned to understand the relationship between the tropical and north pacific sst variations a new sst mode known as the warm pool mode exhibits a strong variance in the warm pool region and undergoes a phase shift after the mid 1990s reflecting a warming in the warm pool region and a cooling in the central and eastern equatorial pacific it is found that the warm pool mode accompanies the north pacific oscillation like atmospheric variability over the north pacific through this teleconnection the warm pool mode mostly shows a relationship between the warm pool sst and the associated north pacific sst component and which has some similarities with the north pacific gyre oscillation

origin of decadal el nino southern oscillation like variability in a coupled general circulation model 1 the origin of decadal el nino southern oscillation like variability hereinafter referred to as dev is analyzed in coupled general circulation model cgcm simulations the cgcm experiments test the null hypothesis for the existence of dev that is that dev is linear damped and stochastically forced by atmospheric internal dynamics in order to test this hypothesis we employ the interactive ensemble coupling strategy it is found that the spatially averaged variance of sea surface temperature anomaly ssta and heat content anomaly hca associated with the dev is linearly related to the amplitude of atmospheric internal dynamics this result suggests that the dev is primarily noise forced but that damped coupled feedbacks and or internal ocean dynamics enhance this variability the ssta variability associated with the dev appears to be of a basin type standing mode with a triangular shape however the decadal evolution of the hca associated with the dev shows a systematic westward propagation from the central north pacific and the eastern south pacific both a singular vector analysis and noise variance analysis based on the coupled simulation results support the argument that atmospheric noise in the subtropics leads to the excitation of the dev

interdecadal changes in the enso teleconnection to the caribbean region and the north atlantic oscillation abstract the el nino southern oscillation enso phenomenon and variability in the subtropical north atlantic high sea level pressure slp are known to affect rainfall in the caribbean region an el nino event is associated with drier than average conditions during the boreal summer of year 0 and wetter than average conditions during the spring of year 1 dry conditions during the summer of year 0 of an el nino are associated with the locally divergent surface circulation engendered by the eastward shift of deep convection in the pacific ocean wet conditions during the spring of year 1 of an el nino are associated with the lagged warming of the tropical north atlantic ocean variability in the strength of the north atlantic high is governed mainly by the north atlantic oscillation nao with a positive nao phase implying a stronger than normal high and vice versa the nao is negatively correlated with caribbean rainfall indirectly via anomalous sea surface temperatures sst associated with a

midlatitude atmospheric transient eddy feedbacks influenced enso associated wintertime pacific teleconnection patterns in two pdo phases the el nino southern oscillation enso associated wintertime atmospheric teleconnection patterns in two pacific decadal oscillation pdo phases are investigated using era 20c reanalysis data for 1950 2010 a strengthened enso associated pacific north american pna teleconnection pattern presents in pdo positive phase while a west pacific wp pattern over northwestern pacific and a squeezed pna pattern coexist when enso occurs in pdo negative phase the dynamical role of atmospheric transient eddy feedbacks to the teleconnection patterns are highlighted in the present study when enso occurs in pdo positive phase the uniform strengthened westerly jet anomalies downstream of the climatological main body of jet accompany with energetic transient eddy anomalies over northeastern pacific the transient eddy feedbacks largely enhance and favor the strengthened pna pattern when enso occurs in pdo negative phase the strengthened westerly jet anomalies appear to separate into two parts one locating north of the climatological main body of jet and the other at the downstream the accompanied transient eddy anomalies also split into two parts under such conditions the transient eddy feedbacks are limited over northeastern pacific and favor a weak pna pattern however the transient eddy anomalies over northwestern pacific strengthen and the feedbacks also strengthen and largely contribute to the wp pattern moreover the transient eddy anomalies over northwestern pacific seem to be anchored along the anomalously poleward strengthened oceanic subarctic frontal zone safz in pdo negative phase the enhanced atmospheric baroclinicity anomalies coupled with the strengthened safz energize atmospheric transient eddy anomalies and work as the potential maintenance in shaping the wp pattern

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

a reassessment of u th and14c ages for late glacial high frequency hydrological events at searles lake california u th isochron ages of tufas formed on shorelines suggest that the last pluvial event in lake lahontan and searles lake was synchronous at about 16 500 cal yr b p equivalent to a radiocarbon age of between 14 000 and 13 500 yr b p whereas the timing of this pluvial event determined by radiocarbon dating is on the order of 1000 yr younger the timing of seven distinct periods of near desiccation in searles lake during late glacial time has been reinvestigated for u th age determination by mass spectrometry u th dating of evaporite layers in the interbedded mud and salt unit called the lower salt in searles lake was hampered by the uncertainty in assessing the initial230th 232th of the samples the resulting ages corrected by a conservative range of initial230th 232th ratios suggest close correlation of the abrupt changes recorded in greenland ice cores dansgaard oeschger events and wet dry conditions in searles lake between 35 000 and 24 000 cal yr b p

a possible mechanism for the north pacific regime shift in winter of 1998 1999 1 this study examines a possible mechanism for the north pacific regime shift in the winter of 1998 1999 since the 1976 1977 climate regime shift the sea surface temperature sst in the north pacific has exhibited a long term warming trend in the western and central regions which is mainly due to the two regime shifts that occurred in the winter of 1988 1989 and 1998 1999 respectively in particular the 1998 1999 regime shift is characterized by a dipole like structure along 40 n where a significant warming is prominent in the southwestern and central north pacific the slow dynamic adjustments of sst and zonal wind to the meridional heat exchange through thermal advection may be responsible for the 1998 1999 regime shift we also assert that an intrinsic multidecadal sst oscillation in the north pacific contributes to the 1998 1999 regime shift furthermore another possibility which is associated with the oceanic teleconnection from the tropics to the midlatitude is also briefly discussed citation jo h s s w yeh and c h kim 2013 a possible mechanism for the north pacific regime shift in winter of 1998 1999 geophys res lett 40 4 380 4385 doi 10 1002 grl 50798

long term el nino southern oscillation enso like variation with special emphasis on the south pacific mechanisms for el nino southern oscillation enso like decadal 7 35 years variability are analyzed using observational data when a decadal positive temperature anomaly occurs in the eastern tropical pacific the atmospheric response excites negative wind stress curl in the western tropical south pacific which causes the thermocline to shoal and induce a negative temperature anomaly there the cold anomaly moves northwestward to the western and central equatorial region and then turns eastward along the equator to reverse the original temperature anomaly in the east the eastward propagation of the oceanic signal along the equatorial thermocline correlates with a zonal wind anomaly the cold anomaly in the east grows through tropical air sea interaction and induces a positive wind stress curl in the western tropical south pacific associated with the atmospheric teleconnection in the southern hemisphere subsequent evolution of the negative phase is similar to that of the positive phase the complete scenario for this enso like decadal variability due to the air sea interaction processes within the tropics has a period of 14 years we also discuss enso like variation on the interdecadal 35 years timescale with possible relationship to the 1976 1977 climate regime shift

strontium calcium ratios in modern porites corals from the great barrier reef as a proxy for sea surface temperature calibration of the thermometer and monitoring of enso high precision sr ca ratios are reported for porites corals from davies reef at 19 s on the midshelf of the great barrier reef australia skeletal growth parameters were also determined from coral slabs using x ray photographs and densitometry measurements a calibration of the sr ca thermometer has been obtained using in situ measured sea surface temperatures which gives sr ca 10 10 48 0 01 0 0615 0 0004 t wheret is in c this calibration applies to different species of porites and a large range of annual extension and calcification rates provided sampling follows a major growth axis biases of 1 2 c have been observed in the low density margins where growth is hampered by interfering fans of corallites the analytical and the long term reproducibility of sr ca derived temperatures are both better than 0 3 c 2 coral growth parameters such as the extension rate or density generally appear to respond to environmental changes such as rainfall but do not affect the sr ca partitioning between coralline aragonite and seawater no correlation has been found between calcification rate and sr ca variations consistent with sr ca being mainly controlled by temperature in the great barrier reef the interannual variability in sst is primarily related to the el nino southern oscillation phenomenon and is typically marked by a cold anomaly during the winter preceding the mature warm phase instrumental records show that the surface waters of the coral sea around 19 s have experienced a significant cooling associated with the el ninos of 1965 1972 and 1982 1983 which the porites corals record faithfully the coral derived temperatures for the period from 1965 to 1993 show an increase of 1 3 c which has occurred mainly since 1979 this warming is larger in magnitude but consistent with the trend for the southern hemisphere land and marine temperature records which shows an increase of around 0 4 c

correlation between the pacific north american pattern and the eastward propagation of sea surface temperature anomalies in the north pacific lag correlation and singular value decomposition analyses reveal that the pacific north american pattern is correlated with eastward propagating sea surface temperature sst anomalies in the north pacific the eastward movement of sst anomalies is also clear in one point lag correlation maps and longitude time plot of low pass filtered time series the timescale for the sst anomalies to travel across the north pacific is 1 year it is speculated that the propagation is related to the air sea interactions in the north pacific these findings provide observational support for the atmospheric bridge theory proposed by lau and nath 1994

evolution of directional wave spectra in the marginal ice zone a new model tested with legacy data abstractfield experimental data from a 1980s program in the greenland sea investigating the evolution of directional wave spectra in the marginal ice zone are reanalyzed and compared with the predictions of a new phase resolving three dimensional model describing the two dimensional scattering of the waves by the vast number of ice floes that are normally present the model is augmented with a dissipative term to account for the nonconservative processes affecting wave propagation observations reported in the experimental study are used to reproduce the ice conditions and wave forcing during the experiments it is found that scattering alone underestimates the attenuation experienced by the waves during their passage through the ice field with dissipation however the model can replicate the observed attenuation for most frequencies in the swell regime model predictions and observations of directional spreading are in agreement for short to midrange wave periods where the wave field quickly becomes

the cold ocean warm land pattern model simulation and relevance to climate change detection abstract surface air temperatures from a 1000 yr integration of a coupled atmosphere ocean model with constant forcing are analyzed by using a method that decomposes temperature variations into a component associated with a characteristic spatial structure and a residual the structure function obtained from the coupled model output is almost identical to the so called cold ocean warm land cowl pattern based on observations in which above average spatial mean temperature is associated with anomalously cold oceans and anomalously warm land this pattern features maxima over the high latitude interiors of eurasia and north america the temperature fluctuations at the two continental centers exhibit almost no temporal correlation with each other the temperature variations at the individual centers are related to teleconnection patterns in sea level pressure and 500 mb height that are similar to those identified in previous observational and modeling studies as in observations variations in the polarity

the modeled atmospheric response to midlatitude sst anomalies and its dependence on background circulation states abstract the atmospheric response to a midlatitude sst anomaly in the north pacific and its dependence on background flow are examined in a gcm experiments are conducted using the same warm sst anomalies but two different model states perpetual january and perpetual february the atmospheric responses to the sst anomalies are statistically significant in both january and february but are completely different the anomalous circulation in january is characterized by a trough decaying with height immediately downstream of the sst anomalies in february the anomalous circulation is dominated by a downstream ridge growing with height the patterns of the anomalous heights in the two months are nearly orthogonal vorticity and thermodynamic budgets are diagnosed to illustrate how the anomalous circulations are maintained over the sst anomalies low level convergence and ascent are observed in both months in january the anomalous convergence is balanced by a residual due primarily to the forcing by submont

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

impact of the atlantic multidecadal oscillation on north pacific climate variability 1 in this paper we found that the atlantic multidecadal oscillation amo can contribute to the pacific decadal oscillation pdo especially the component of the pdo that is linearly independent of el nino and the southern oscillation enso i e the north pacific multidecadal oscillation npmo and the associated pacific north america pna pattern using a hybrid version of the gfdl cm2 1 climate model we show that the amo provides a source of multidecadal variability to the north pacific and needs to be considered along with other forcings for north pacific climate change the lagged north pacific response to the north atlantic forcing is through atmospheric teleconnections and reinforced by oceanic dynamics and positive air sea feedback over the north pacific the results indicate that a north pacific regime shift opposite to the 1976 77 shift might occur now a decade after the switch of the observed amo to a positive phase around 1995 citation zhang r and t l delworth 2007 impact of the atlantic multidecadal oscillation on north pacific climate variability geophys res lett 34 l23708

the influence of atlantic sea surface temperature anomalies on the north atlantic oscillation abstract the influence of atlantic sea surface temperature sst anomalies on the atmospheric circulation over the north atlantic sector during winter is investigated by performing experiments with an atmospheric general circulation model these consist of a 30 yr run with observed sst anomalies for the period 1961 90 confined geographically to the atlantic ocean and of a control run with climatological ssts prescribed globally a third 30 yr integration with observed ssts confined to the south atlantic is made to confirm present findings the simulated interannual variance of 500 hpa wintertime geopotential heights over the north atlantic attains much more realistic values when observed atlantic ssts are prescribed circulation patterns that resemble the positive phase of the north atlantic oscillation nao become more pronounced in terms of the leading eof of winter means and a cluster analysis of daily fields the variance of an interannual nao index increases by fivefold over its control value atl

modes of interannual and interdecadal variability of pacific sst abstract the multichannel singular spectrum analysis has been used to characterize the spatio temporal structures of interdecadal and interannual variability of sst over the pacific ocean from 20 s to 58 n using the comprehensive ocean atmosphere data set from 1950 to 1993 three modes with distinctive spatio temporal structures were found they are an interdecadal mode a quasi quadrennial qq oscillation with a period of 51 months and a quasi biennial qb oscillation with a period of 26 months the interdecadal mode is a standing mode with opposite signs of sst anomalies in the north pacific and in the tropical pacific the amplitude of this mode is larger in the central north pacific than in the tropical pacific this mode contributes 11 4 to the total variance it is associated with cooling in the central north pacific and warming in the equatorial pacific since around 1976 77 the qq oscillation exhibits propagation of sst anomalies northeastward from the philippine sea and then eastward along 4

role of the gulf stream and kuroshio oyashio systems in large scale atmosphere ocean interaction a review abstract ocean atmosphere interaction over the northern hemisphere western boundary current wbc regions i e the gulf stream kuroshio oyashio and their extensions is reviewed with an emphasis on their role in basin scale climate variability sst anomalies exhibit considerable variance on interannual to decadal time scales in these regions low frequency sst variability is primarily driven by basin scale wind stress curl variability via the oceanic rossby wave adjustment of the gyre scale circulation that modulates the latitude and strength of the wbc related oceanic fronts rectification of the variability by mesoscale eddies reemergence of the anomalies from the preceding winter and tropical remote forcing also play important roles in driving and maintaining the low frequency variability in these regions in the gulf stream region interaction with the deep western boundary current also likely influences the low frequency variability surface heat fluxes damp the low frequency sst anomalies ove

the forced and intrinsic low frequency modes in the north pacific abstract conditional maximum covariance analysis is applied to investigate the coherent patterns between the tropical and north pacific sst and the north pacific 500 hpa geopotential height anomalies two leading modes are identified one is an intrinsic midlatitude mode the north pacific np mode for which sst anomalies are mainly confined to the extratropical north pacific the other is a tropical ocean atmosphere coupled mode the enso mode in which an enso like sst pattern dominates the tropics but extratropical sst anomalies are relatively weak the np and enso modes exhibit distinct spatial and temporal characteristics for the np mode atmospheric variation leads to changes in sst while for the enso mode the opposite is true the np mode displays a persistence barrier during august september whereas the enso mode has a march april persistence barrier the upper tropospheric jet stream associated with the np and enso mode intensifies respectively over the central north pacific and the subtrop

dynamics and mechanisms of decadal variability of the pacific south america mode over the 20th century in this paper decadal variability of the pacific south america psa mode is examined from year 1871 to 2008 based on the newly developed ocean and atmosphere reanalysis products the psa mode mirroring the pacific north america mode in the northern hemisphere emerges as the second eof mode of 500 mb geopotential height anomalies the mode displays substantial interannual decadal variability with distinct timescales between 3 8 and 10 18 years respectively the decadal variability of the psa mode is found to be associated with the coupled ocean atmosphere interaction over the subtropical south and tropical pacific the subduction of the subtropical temperature anomalies in the south pacific in conjunction with the tropical subtropical atmospheric teleconnection plays important role in the decadal variability of the psa mode

el nino s tropical climate and teleconnections as a blueprint for pre ice age climates 1 at 2 7 million years ago the warm equable climates of early and middle pliocene time used here to mean from 5 to 2 7 ma were replaced by recurring ice ages most attempts to explain the change appeal either to changes in co2 in the atmosphere or reduced heat transport by the atlantic ocean the sources of the strongest teleconnections in the current climate however lie in the tropics and such connections occur by transport of heat and moisture by the atmosphere the most prominent of these teleconnections link aberrations in sea surface temperatures in the equatorial pacific el nino southern oscillation enso variations with warm and dry or cool and wet anomalies in extratropical climates we show that in most cases early and middle pliocene climate both in equatorial regions and in the extratropics differ from present day climates with the same spatial pattern as that associated with enso for instance not only was canada warmer during early pliocene time than at present as it is during el nino but the region surrounding the gulf of mexico appears to have been cooler and a bit wetter as it commonly is during el nino a virtually permanent el nino like state appears to have characterized pre ice age climates suggesting that transport of heat by the atmosphere was the principal mechanism that maintained extratropical warmth accordingly cooling and the growth of recurring ice sheets in the northern hemisphere resulted from the development of a strong walker circulation and a weakening of the hadley circulation

a physical analysis of the severe 2013 2014 cold winter in north america the severe 2013 2014 cold winter has been examined in the context of the previous 55 winters using the national centers for environmental prediction reanalysis data for the period 1960 2014 north america is dominated by pronounced cold anomalies over the great plains and great lakes in december 2013 and february 2014 but exhibits an east west contrast pattern with warm anomalies over most of the north american west in january 2014 a relevant temperature index defined as land surface temperature anomalies averaged over 40 60 n 105 80 w reveals a warming trend as well as interannual variability with a significant power peak of 6 0 years while 2013 2014 was the second coldest winter during 1960 2014 it is the coldest one in the linearly detrended series with a negative anomaly of 2 63 standard deviations this indicates that the long term warming has made the 2013 2014 winter less severe than it could have been the temperature and circulation variability in association with the zonally symmetric variability of the polar vortex projects weakly on the corresponding anomalies in the 2013 2014 winter whereas the variability associated with the principal mode of north american surface temperature projects strongly on the corresponding anomalies in the winter this mode is associated with a sea surface temperature sst pattern of significant anomalies over the north pacific and north atlantic middle and high latitudes the anomalous atmospheric circulation shows an anticyclonic anomaly over the gulf of alaska bering sea and a cyclonic anomaly downstream over north america it bears resemblance to the north pacific oscillation western pacific pattern and drives the sst in the north pacific over western central canada and the northern u s below average heights are associated with above normal precipitation implying enhanced upward vertical motion and variation of local cloud forcing leading to a variation of the surface energy budget dominated by surface longwave radiation anomalies over north america there is less downwelling longwave radiation at the surface when the atmosphere is cold which is offset by the corresponding reduction in outgoing longwave radiation

mechanisms determining the atmospheric response to midlatitude sst anomalies abstract previous gcm experiments demonstrated that a model atmosphere produces two different responses to a midlatitude warm sst anomaly over the pacific under perpetual january and february conditions to elucidate the mechanisms responsible for the different gcm responses and their dependence on the background flow experiments with two idealized models are conducted experiments with a linear baroclinic model reveal that the gcm responses at equilibrium are primarily maintained by the anomalous eddy forcing the anomalous flow induced directly by an idealized initial heat source exhibits little sensitivity to the background flow eddy feedbacks on the heating induced anomalous flow are examined using a linear storm track model the anomalous eddy forcing produced by the storm track model is sensitive to the basic state the eddy forcing in january acts to shift the heating induced upper level ridge toward the northeast of the gulf of alaska while in february it acts to reinforce the ridge this sugge

the nonlinear transient atmospheric response to tropical forcing abstract ensemble integrations using a primitive equation dry atmospheric model were performed to investigate the atmospheric transient response to tropical thermal forcings that resemble el nino and la nina the response develops in the north pacific within 1 week after the integration the signal in the north atlantic and europe is established by the end of the second week significant asymmetry was found between the responses in el nino and la nina that is similar to the observations that is one feature is that the 550 hpa positive height response in the north pacific of the la nina run is located about 30 west of the negative response of the el nino run another feature is that the responses in the north atlantic and europe for the la nina and el nino cases have similar patterns with the same polarity the first feature is established within 2 weeks of the integration while the second feature develops starting from the end of the second week several factors contribute to this nonlinearity of the

on the cooccurrence of wintertime temperature anomalies over eastern asia and eastern north america the co occurrence of wintertime temperature anomalies over eastern asia and eastern north america is examined the winter days during 1948 2014 are assigned to nine regimes by applying the self organizing map clustering method to the area averaged land surface temperature anomalies over these two regions about half of the winter days are associated with concurrent temperature anomalies the occurrence of the concurrent non concurrent regimes is closely related to the large scale circulation conditions the eurasian teleconnection pattern and the pacific north american teleconnection pattern are two dominant large scale circulation modes associated with the co occurrence of the temperature anomalies through their impacts on the intensities of the corresponding troughs the precursor analysis reveals that the lead time of the early signals for the concurrent cold anomalies is about four days longer than that for the concurrent warm anomalies in addition the average lead time of the precursor signals for the wintertime temperature anomalies over eastern asia is longer than that is over eastern north america

north atlantic thermal persistence and coherent evolution 1 north atlantic thermal persistence and coherent evolution are examined a region near cape cod and the gulf of maine is identified as the north atlantic na s most thermally persistent with a unique combination of high amplitude long lasting sea surface temperature sst anomalies a mechanism is advanced whereby that region s surface ocean reflects deep upper ocean dynamics with thermal evolution that tracks heat advection by the slowly evolving upper ocean this is consistent with the subtropical gyre playing an active and central role in na climate variability the proposed interpretation is supported by broad high lag correlations between the bermuda potential vorticity time series representing the subtropical gyre state and surface anomalies using the bermuda potential vorticity time series as a dynamical filter successive lag correlation patterns reveal surface oscillations that are not apparent in the raw surface data

characteristics of winter precipitation variation over northern central eurasia and their connections to sea surface temperatures over the atlantic and pacific oceans abstract this study reveals spatial and temporal characteristics of precipitation variability and their teleconnections to sea surface temperatures ssts over the atlantic and pacific oceans by analyzing 68 yr of recent precipitation records over the former soviet union in addition to a general increasing trend of about 0 4 mm yr 1 or 6 decade 1 over much of the study region three major modes of precipitation variation are identified a quasi biennial variation of 2 3 yr is found over the region surrounding the caspian and aral seas an el nino timescale precipitation variation of 4 5 yr is present over southern central siberia and is associated with eastern tropical pacific ssts a quasi decadal timescale variation of about 11 12 yr is evident over central european russia this quasi decadal precipitation variation is closely linked to a major sst anomaly pattern of alternating latitudinal belts over the atlantic and sst variations over the equatorial pacific ocean these associations to ssts are str

the relationship between sea surface temperature anomalies and atmospheric circulation in gcm experiments several 19 year integrations of the hamburg version of the ecmwf t21 general circulation model driven by the monthly mean sea surface temperature sst observed in 1970 1988 were examined to study extratropical response of the atmospheric circulation to sst anomalies in the northern hemisphere in winter in the first 19 years run sst anomalies were prescribed globally gago run and in two others sst monthly variability was limited to extratropical regions moga run and to tropics toga run respectively a canonical correlation analysis cca which select from two time dependent fields optimally correlated pairs of patterns was applied to monthly anomalies of sst in the north alantic and pacific oceans and monthly anomalies of sea level pressure and 500 hpa geopotential height in the northern hemisphere in the gago run the best correlated atmospheric pattern is global and is characterized by north south dipole structures of the same polarity in the north atlantic and the north pacific sectors in the moga and toga experiments the atmospehric response is more local than in the gago run with main centers in the north atlantic and north pacific respectively the extratropical response in the gago run is not equal to the sum of the responses in the moga and toga runs the artificial meridional sst gradients at 25 30 n probably influence the results of the moga and toga runs the atmopsheric modes found by the cca were compared with the normal modes of the barotropic vorticity equation linearized about the 500 hpa winter climate the normal modes with smallest eigenvalues are similar to the model leading variability modes and canonical patterns of 500 hpa geopotential height the corresponding eigenvectors of the adjoint operator which represent an external forcing optimal for exciting normal modes have a longitudinal structure with maxima in regions characterized by enhanced high frequency baroclinic activity over both oceans

pacific sea surface temperature and the winter of 2014 it is shown from historical data and from modeling experiments that a proximate cause of the cold winter in north america in 2013 2014 was the pattern of sea surface temperature sst in the pacific ocean each of the three dominant modes of sst variability in the pacific is connected to the tropics and has a strong expression in extratropical sst and weather patterns beginning in the middle of 2013 the third mode of sst variability was two standard deviations positive and has remained so through january 2015 this pattern is associated with high pressure in the northeast pacific and low pressure and low surface temperatures over central north america a large ensemble of model experiments with observed ssts confirms that sst anomalies contributed to the anomalous winter of 2014

on the role of tropical ocean forcing of the persistent north american west coast ridge of winter 2013 14a abstractthe causes of the high pressure ridge at the north american west coast during winter 2013 14 the driest winter of the recent california drought are examined the ridge was part of an atmosphere ocean state that included anomalies defined relative to a 1979 2014 mean of circulation across the northern hemisphere warm sea surface temperatures ssts in the tropical western and northeastern pacific and the south indian ocean and cool ssts in the central tropical pacific the sst anomalies differ sufficiently between datasets that when used to force atmosphere models the simulated circulation anomalies vary notably in realism recognizing uncertainty in the sst field the authors use idealized tropical sst anomaly experiments to identify an optimal combination of sst anomalies that forces a circulation response that best matches observations the optimal sst pattern resembles that observed but the associated circulation pattern is much weaker than observed suggesting an important but limited

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

trend in northern hemisphere winter atmospheric circulation during the last half of the twentieth century abstract during the last half century the trend in the northern hemisphere tropospheric circulation has been associated with a deepening of both the aleutian and icelandic lows a pattern akin to the cold ocean warm land cowl pattern a simplified dynamical model is used to show that the observed simultaneous deepening trend in both the aleutian and icelandic lows can be largely explained as a hemispheric planetary wave response to tropical diabatic forcing in the indo pacific region in the model the extratropical storm tracks play a role in modulating the wave train tending to enhance weaken the anomalous icelandic aleutian low in the north atlantic north pacific sector the model results also suggest two ways in which the circulation trend over the north atlantic sector could have been influenced by tropical forcing one a direct linear planetary wave response from the eastern tropical pacific and the other an indirect response of the north atlantic storm track to tropical forcing over th

does enso force the pna abstract the primary effect of el nino southern oscillation enso sea surface temperature sst anomalies is to force distinct midlatitude patterns and not only to modify the probability of the internal variability patterns such as the pacific north american pna pattern of wallace and gutzler both the spatial structure and probability distribution of the external enso pattern are distinct from the pna pattern ensemble general circulation model gcm integrations for 30 winters have been analyzed in the pacific north america region these winters span the recent period of 1981 82 through 1998 99 plus 12 earlier winters the entire dataset includes six el nino warm and seven la nina cold events the ensemble size is nine simulations empirical orthogonal function eof analysis is carried out for all gcms and observed seasonal means for the gcm ensemble means and for the gcm deviations about the ensemble means eof 1 of the gcm 200 hpa height z ensemble mean agrees well with eof 1 of all gc

role of the north pacific sea surface temperature in the east asian winter monsoon decadal variability in this study a possible mechanism for the decadal variability in the east asian winter monsoon eawm is proposed specifically the north pacific sea surface temperature sst may play an important role an analysis of the observations shows that the north pacific sst has a remarkable decadal pattern whose phase shifted around the mid 1980s this north pacific sst decadal pattern can weaken the east asian trough and enhance the north pacific oscillation through changing air sea interactions over the north pacific the weak east asian trough enhances the zonal circulation and weakens the meridional circulation over east asia consequently leading to a weaker southward cold surge and east asia warming around the mid 1980s the numerical experiment further confirms the pronounced physical processes in addition over the longer period of 1871 2012 the indices of the eawm and north pacific sst decadal pattern are also highly consistent on the decadal timescale which further confirms the impact of the north pacific sst decadal pattern on the eawm decadal variability

association between catastrophic paleovegetation changes during devonian carboniferous boundary and the formation of giant massive sulfide deposits abstract the iberian pyrite belt sw iberia is one of the largest sulfur anomalies in the earth s crust in the southern iberian pyrite belt more than 820 mt of exhalative massive sulfides were deposited in less than one million years at the devonian carboniferous boundary the shale of the ore bearing horizon contains biomarkers indicating major biogenic activity in a methanogenic setting including a five fold increase in typical vascular plant biomarkers and a significant anomaly in those probably indicating the presence of thermophilic archaea this contrasts with signatures in the average sedimentary rocks of the basin that indicate the sediments settled in oxic to sub oxic environments and that they have only minor biomarkers derived from continental paleoflora these data show that the formation of the mineralization was not only related to major hydrothermal activity synchronous with volcanism but may also have been controlled by the input of large amounts of organic matter mostly derived from the degradation of woodland detritus sourced in the nearby continent this massive influx of organic matter could have accelerated extremophilic microbial activity that used short chain hydrocarbons as electron donors for seawater sulfate reduction resulting in concomitant massive sulfide precipitation we propose that the giant massive sulfide deposits resulted from overlapping of geological and biological processes that occurred at the devonian to carboniferous transition including 1 continent collision during the onset of the variscan orogeny leading to major paleogeographic changes and volcanism 2 dramatic stress of continental ecosystems due to the combination of climatic change volcanism variations in the sea level and erosion on a regional scale 3 major biomass destruction and increase of organic supply to marine environments and 4 generation of anoxic conditions and the thriving of sulfate reducing microorganisms under these conditions massive sulfide deposits formed where venting sulfur poor but metal rich hydrothermal brines flowed into a hydrogen sulfide rich anoxic water column the data presented strongly suggest that there was a temporal and causal relationship between the devonian carboniferous geotectonic climatic and biological crises and the formation of the giant volcano sedimentary massive sulfide deposits of the southern iberian pyrite belt

a modeling study of the relative roles of tropical and extratropical sst anomalies in the variability of the global atmosphere ocean system abstract in three parallel experiments an atmospheric general circulation model has been subjected to observed monthly varying sea surface temperature ssi conditions in each of the following domains near global ocean goga run tropical pacific toga run and midlatitude north pacific moga run four independent realizations were obtained for the model response to the sequence of sst anomalies during the 1946 88 period in each of the above regions the principal modes of coupling between the imposed sst forcing and the simulated northern hemisphere wintertime 5 1 5 mb height field in various experiments have been identified using a singular value decomposition svd procedure the leading svd mode for the goga experiment is qualitatively similar to that based on observational data although the amplitudes of the simulated height anomalies are notably lower than the observed value the sst pattern of this mode resembles that associated with el nino events the accompanying 5 1 5 mb height anomaly i

summertime evolution of decadal sea surface temperature anomalies in the midlatitude north pacific abstract to clarify the summertime evolution of decadal sea surface temperature sst anomalies and related physical processes in the midlatitudes of the north pacific numerical solutions of a three dimensional bulk mixed layer model are analyzed focusing on the contribution of the net shortwave radiative forcing at the sea surface a quantitative heat budget analysis for the ocean mixed layer relating to late 1980s decadal sst change reveals that the decadal sst anomalies decay from late spring to early summer over the entire midlatitudes of the north pacific this quasi seasonal decay of the decadal sst anomalies is controlled by an anomalous local thermal damping i e anomalous surface heat fluxes from midsummer to early autumn the anomalous net shortwave radiation flux associated with a meridional shift of the storm track acts to induce strong seasonal damping of the decadal sst anomaly in the northern kuroshio oyashio extension region in contrast in the north of the subtropical frontal region

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

combined effect of el nino southern oscillation and pacific decadal oscillation on the east asian winter monsoon using long term observational data and numerical model experiments the combined effect of the el nino southern oscillation enso and pacific decadal oscillation pdo on the variability of the east asian winter monsoon is examined in the observations it is found that when the enso and pdo are in phase combinations i e el nino positive pdo phase and la nina negative pdo phase a negative relationship between enso and east asian winter monsoon is significantly intensified in other words when el nino la nina occurs with positive negative pdo phase anomalous warm cold temperatures are dominant over the east asian winter continent on the other hand there are no significant temperature anomalies when the enso and pdo are out of phase combinations i e el nino negative pdo phase and la nina positive pdo phase further analyses indicate that the anticyclone over the western north pacific including the east asian marginal seas plays an essential role in modulating the intensity of the east asian winter monsoon under the changes of enso pdo phase relationship long lasting high pressure and warm sea surface temperature anomalies during the late fall winter and following spring over the western north pacific which appear as the el nino occurs with positive pdo phase can lead to a weakened east asian winter monsoon by transporting warm and wet conditions into the east asian continent through the southerly wind anomalies along the western flank of the anomalous high pressure and vice versa as the la nina occurs with negative pdo phase in contrast the anomalous high pressure over the western north pacific does not show a prominent change under the out of phase combinations of enso and pdo numerical model experiments confirm the observational results accompanying dominant warm temperature anomalies over east asia via strong anticyclonic circulation anomalies near the philippine sea as the el nino occurs with positive pdo phase whereas such warming is weakened as the el nino occurs with negative pdo phase this result supports the argument that the changes in the east asian winter monsoon intensity with enso are largely affected by the strength of the anticyclone over the western north pacific which significantly changes according to the enso pdo phase relationship

enso like interdecadal variability in the pacific ocean as simulated in a coupled general circulation model spatial and temporal structures of interdecadal variability in the pacific ocean are investigated using results from an atmosphere ocean coupled general circulation model aogcm the model shows a basin wide spatial pattern of the principal sea surface temperature sst variability similar to the observed one both interdecadal and interannual temporal structures of the sst variability agree well between the observation and the aogcm on the other hand a slab ocean model coupled to the same atmospheric model as the aogcm fails to simulate the observed temporal structure therefore the timescale of the coupled variability is associated with dynamical processes in the ocean a distinct interdecadal mode of the coupled atmosphere upper ocean temperature variability is found in the aogcm with a spatiotemporal structure coherent with the sst variability the mode accompanies an el nino southern oscillation enso like spatial pattern of sst and the surface wind and behaves like a delayed oscillator in enso a wedge shaped anomaly pattern of the upper thermocline temperature is formed in the eastern pacific and its northern subtropical signal propagates westward enhanced by a subtropical wind forcing at the central basin arrival of the subtropical signal at the western pacific around 20 n switches the anomaly of subsurface temperature in the equatorial region through anomalous oceanic heat transport along the western boundary the travel time of the trans pacific signal in the subtropics appears to be responsible for the timescale of this mode the aogcm successfully simulated the second mode of sst with a major variation in the midlatitude north pacific as in the observed sst in the upper ocean heat content we found another distinct mode which is characterized by a midlatitude subtropics dipole pattern migrating around the north pacific subtropical gyre however the associated sst variation of this mode shows a poor correspondence in the dominant interdecadal modes for the observed sst