reconstructing el nino southern oscillation using data from ships logbooks 1815 1854 part ii comparisons with existing enso reconstructions and implications for reconstructing enso diversity a systematic comparison of el nino southern oscillation reconstructions during the early to mid nineteenth century is presented using a range of proxy and documentary sources reconstructions of the boreal winter southern oscillation index soi using data from ships logbooks presented in a companion paper are evaluated and compared to previous enso reconstructions comparisons between enso reconstructions and the instrumental soi during a period of overlap 1876 1977 are made these same proxy and documentary reconstructions are then compared to the logbook based reconstructions over 1815 1854 the logbook based reconstructions compare best with a recent multi proxy reconstruction that used signals taken from different teleconnection regions and they have an improved agreement with multi proxy records compared to a previous attempt to reconstruct the soi from ships logbook data the logbook based and the multi proxy reconstructions are found to capture el nino events better than la nina events and east pacific el nino events better than central pacific el nino events thus suggesting a degree of bias in the historical reconstructions these findings have important implications for future enso reconstructions with a need for an increased understanding of the effects of different enso flavours for future reconstructions

an evaluation of the statistical homogeneity of the twentieth century reanalysis the twentieth century reanalysis 20cr holds the distinction of having the longest record length 140 year 1871 2010 of any existing global atmospheric reanalysis if the record can be shown to be homogenous then it would be the first reanalysis suitable for long term trend assessments including those of the regional hydrologic cycle on the other hand if discontinuities exist then their detection and attribution either to artificial observational shocks or climate change is critical to their proper treatment previous research suggested that the quintupling of 20cr s assimilated observation counts over the central united states was the primary cause of inhomogeneities for that region the same work also revealed that depending on the season the complete record could be considered homogenous in this study we apply the bai perron structural change point test to extend these analyses globally a rigorous evaluation of 20cr s in homogeneity is performed composed of detailed quantitative analyses on regional seasonal inter variable and intra ensemble bases the 20cr record is shown to be homogenous natural for 69 89 years at 50 of land grids based on analysis of the july 2 m air temperature on average 54 41 of the grids between 60 s and 60 n are free from artificial inhomogenetites in their february july time series of the more than 853 376 abrupt shifts detected in 26 variable fields over two monthly time series approximately 72 are non climate in origin 25 exceed 1 8 standard deviations of the preceding time series the knock on effect of inhomogeneities in 20cr s boundary forcing and surface pressure data inputs to its surface analysis fields is implicated in the future reassessing these inhomogeneities will be imperative to achieving a more definitive attribution of 20cr s abrupt shifts

global climatic anomalies associated with extremes in the southern oscillation abstract composite temperature and precipitation anomalies during various stages of an event in the southern oscillation so have been computed for several hundred stations across the globe large regions of coherent significant signals are shown to exist for both extremes of the so with warm event signals generally opposite to those during cold events in addition during the year preceding the development of an event in the so year 1 climatic anomalies tend to be opposite to those during the following year year 0 this confirms that the biennial tendency of the so over the pacific indian ocean sectors is also present in more remote regions with climatic signals related to the so many of the signals are consistent enough from event to event to be useful for extended range forecasting purposes

desiccation mechanism for formation of giant polygons on earth and intermediate sized polygons on mars results from a pre fracture model we present a pre fracture incrementally non linear elastic hydric model to constrain the models of formation of giant spacing of 20 300 m desiccation cracks on earth and possibly intermediate sized 80 to 350 m polygonal networks of cracks located in many impact craters on mars which have been interpreted to form by desiccation as opposed to thermal contraction el maarry et al 2010 the results of the model show that tensile stresses rise monotonically with desiccation however in soils with diffusivities below 10 4 m2 s it is not possible to generate high enough stresses to cause fracturing on the other hand intermediate values between 10 2 and 10 4 m2 s create optimum conditions for the formation of cracks at the time scales suggested for the formation of giant desiccation polygons on earth our model clearly shows that for typical diffusivity values of clayey soils with a considerable amount of smectites enough stress can build up to stimulate cracking of various spatial scales these results corroborate earlier assumptions that giant desiccation polygons on earth occur through lowering of the water table rather than surface evaporation extending the model to mars shows that soils would crack within similar diffusivity limits but in slightly longer periods of time owing to the lower gravity finally a model for formation of desiccation cracks on mars is presented that shows that two main conditions need to be fulfilled for desiccation cracks to occur under current martian climatic conditions namely that the thermal and soil diffusivity conditions 1 allow for the formation of an unsaturated zone with a considerable thickness while at the same time 2 limiting the growth of the permafrost downward which would disrupt the cracking process

the south pacific meridional mode as a thermally driven source of enso amplitude modulation and uncertainty abstractthis study seeks to identify thermally driven sources of enso amplitude and uncertainty as they are relatively unexplored compared to wind driven sources pacific meridional modes are argued to be wind triggers for enso events this study offers an alternative role for the south pacific meridional mode spmm in enso dynamics not as an enso trigger but as a coincident source of latent heat flux lhf forcing of enso ssta that if correctly incorrectly predicted could reduce increase enso prediction errors we utilize a coupled model simulation in which enso variability is perfectly periodic and each el nino experiences identical wind stress forcing differences in el nino amplitude are primarily thermally driven via the spmm when el nino occurs coincidentally with positive phase spmm the positive spmm lhf anomaly counteracts a fraction of the lhf damping of el nino allowing for a more intense el nino if the spmm phase is instead negative the spmm lhf amplifies the lhf damping of el nin

interdecadal change in the principal mode of winter spring precipitation anomaly over tropical pacific around the late 1990s evidence show that the dominant mode of winter spring precipitation anomaly over the tropical pacific experienced a pronounced interdecadal change around 1998 based on the extended empirical orthogonal function eeof technique a zonal dipole pattern of precipitation anomaly is dominant during the pre 1998 period corresponding to a positive principle component pc1 positive precipitation anomaly over the equatorial eastern pacific ep decays eastward from winter to spring which is identified as an eastward decaying ep mode during the post 1999 period there is a zonal triple pattern with enhanced precipitation over the equatorial central pacific cp and reduced precipitation over the western north pacific and equatorial southeastern pacific with a positive pc1 this triple pattern of precipitation anomaly maintains with decreasing amplitude from winter to spring which is called the fixedly decaying cp mode for short such interdecadal shift is controlled by differing sea surface temperature sst anomaly pattern the interdecadal differences of winter spring wind stress and thermocline over tropical pacific might result in the interdecadal change in the sst anomaly and then precipitation mode via modulating physical oceanic feedback processes in addition the effect of two distinct precipitation modes on the north pacific teleconnection and north american surface temperature anomaly was strikingly different before 1998 the eastward decaying ep mode might induce a significant tropical northern hemisphere tnh like teleconnection only in winter leading to a north to south pattern of north american temperature anomaly which is greatly limited in spring after 1999 a northwest to southeast response of north american temperature sustains from winter to spring resulting from the maintenance of the pacific north america pna like pattern simulated by the fixedly decaying cp mode

reconstructing twentieth century sea surface temperature variability in the southwest pacific a replication study using multiple coral sr ca records from new caledonia 1 coral based climate reconstructions typically have not used multiple cores from a region to capture and replicate a climate signal largely because of concerns of coral conservation analytical expense and time constraints coral sr ca reproducibility through the twentieth century was investigated using three intracolony and three intercolony coral records from the reefs offshore of amedee island new caledonia different sampling resolutions were examined in coral sr ca fortnightly and monthly and 18o fortnightly monthly and seasonally as well as similar scale subsampling of the daily in situ sea surface temperature sst record the mean coral sr ca 18o and sst values do not change as a function of sampling resolution the coral sr ca signal is highly reproducible the average absolute offset between coeval monthly sr ca determinations between any two coral time series is 0 035 0 026 mmol mol 1 0 65 c which is less than twice the analytical precision of the coral sr ca measurements the stack average of the monthly coral sr ca variations and monthly anomalies are significantly correlated with monthly in situ sst 1967 1992 r 0 96 and 0 64 respectively p 0 05 and n 302 and 1 grid monthly sst data product 1900 1999 r 0 95 and 0 56 respectively p 0 05 and n 1198 the coral sr ca sst reconstruction exhibits interannual and decadal timescale fluctuations that exceed those observed in the gridded sst record which may reflect true differences between sst at a shallow reef site and those averaged over a 1 grid box or inadequacies in the methodology used to create the gridded sst product when few observations are available a warming trend of 0 6 c is observed in the twentieth century coral sr ca sst record

coral δ18o based reconstruction of el nino southern oscillation from the northern south china sea since 1851 ad abstract el nino southern oscillation enso is the largest source of interannual climate variability over the globe knowledge of enso variability back to the pre instrumental period and earlier can help to enhance our understanding of its mechanisms and impacts here we use the coral record from the northern south china sea where the interannual climate variability is associated with enso activity to reconstruct enso variability over the past 150 years our record together with other enso chronologies indicated not only the weakened enso activity between 1930s and 1960s but also the larger variations of el nino activity relative to that of la nina based on the sliding window method the comparison between the scs and pacific enso band coral records revealed the relatively stronger climatic coupling between the scs and the equatorial central eastern pacific compared with that between scs and western pacific indicating the reliability of teleconnection relationship between the scs climate and enso our result indicated that the coral 18o record from the scs could contribute to the pan pacific enso reconstructions

teleconnective response of the pacific north american region atmosphere to large central equatorial pacific sst anomalies abstract a prominent year round ensemble response to a global sea surface temperature sst anomaly field fixed to that for january 1992 near the peak of a major warm el nino southern oscillation episode was observed in a 20 yr integration of the general circulation model used for operational seasonal prediction by the u s national weather service this motivated a detailed observational reassessment of the teleconnections between strong sst anomalies in the central equatorial pacific ocean and pacific north america region 700 hpa heights and u s surface temperatures and precipitation the approach used consisted of formation of monthly mean composites formed separately from cases in which the sst anomaly in a key area of the central equatorial pacific ocean was either large and positive or large and negative extensive permutation tests were conducted to test null hypotheses of no signal in these composites the results provided a substantial case for the presence of teleconnections to either the pos

north american rainfall and temperature prediction response to the diversity of enso research has shown that there is significant diversity in the location of the maximum sea surface temperature anomaly ssta associated with the el nino southern oscillation enso in one extreme warm ssta peak near the south american coast often referred to as eastern pacific of ep el nino and at the other extreme warm ssta peak in the central pacific central pacific or cp el nino due to the differing tropical pacific ssta and precipitation structure there are differing extratropical responses particularly over north america recent work involving the north american multi model ensemble nmme system for intra seasonal to inter annual prediction on prediction of the differences between el nino events found excess warming in the eastern pacific during cp el nino events this manuscript investigates the ensemble and observational agreement of the nmme system when forecasting the north american response to the diversity of enso focusing on regional land based 2 meter temperature and precipitation nmme forecasts of north american precipitation and t2m agree with observations more often during ep events ensemble agreement of nmme forecasts is regional for instance ensemble agreement in southeast north america demonstrates a strong connection to nino3 precipitation and ssta amplitude during warm enso events ensemble agreement in northwest north america demonstrates a weak connection to nino4 precipitation and ssta amplitude during warm enso events still other regions do not show a strong connection between ensemble agreement and strength of warm enso events

how well do current climate models simulate two types of el nino in this study we evaluate the fidelity of current climate models in simulating the two types of el nino events using the pre industrial output in cmip3 archives it is shown that a few climate models simulate the two types of el nino events to some extent while most of the models have serious systematic problems in simulating distinctive patterns of sea surface temperature sst and precipitation anomaly associated with the two types of el nino that is they tend to simulate a single type of el nino it is shown that the ability of climate models in simulating the two types of el nino is related to the sensitivity of the atmospheric responses to the sst anomaly patterns models whose convective location is shifted to the east west as the sst anomaly center moves to the east west tends to simulate the two types of el nino events successfully on the other hand models whose location of convective anomaly is confined over the western or central pacific tends to simulate only the single type of el nino event it is also shown that the confinement of the convective anomaly over the western or central pacific is closely linked to the dry bias and the associated cold bias over the eastern pacific that is because positive el nino sst anomalies over the eastern pacific cannot increase local convection effectively when the total ssts are still too cold due to a cold bias this implies that the realistic simulation of climatology especially over the equatorial eastern pacific is essential to the successful simulation of the two types of el nino

field investigation of dried lakes in western united states as an analogue to desiccation fractures on mars potential desiccation polygons pdps tens to hundreds of meters in size have been observed in numerous regions on mars particularly in ancient 3 gyr old terrains of inferred paleolacustrine playa geologic setting and in association with hydrous minerals such as smectites therefore a better understanding of the conditions in which large desiccation polygons form could yield unique insight into the ancient climate on mars many dried lakebeds playas in western united states display large 50 m wide desiccation polygons which we consider to be analogues for pdps on mars therefore we have carried out fieldwork in seven of these dried lakes in san bernardino and the death valley national park regions complemented with laboratory and spectral analysis of collected samples our study shows that the investigated lacustrine playa sediments have a a soil matrix containing 40 75 clays and fine silt by volume where the clay minerals are dominated by illite muscovite followed by smectite b carbonaceous mineralogy with variable amounts of chloride and sulfate salts and significantly c roughly similar spectral signatures in the visible near infrared vis nir range we conclude that the development of large desiccation fractures is consistent with water table retreat in addition the comparison of the mineralogical to the spectral observations further suggests that remote sensing vis nir spectroscopy has its limitations for detailed characterization of lacustrine playa deposits finally our results imply that the widespread distribution of pdps on mars indicates global or regional climatic transitions from wet conditions to more arid ones making them important candidate sites for future in situ missions

enso variability during mis 11 424 374 ka from tridacna gigas at huon peninsula papua new guinea marine isotope stage 11 mis 11 from 424 000 to 374 000 yrs ago included one of the longest and warmest interglacials of the last 800 000 yrs and is a potential analogue for the holocene due to the similarity of earth s orbital configuration at this time the question of how the el nino southern oscillation enso responds to warmer background climates remains unanswered and is critical to understand how the enso system will evolve under the influence of anthropogenic warming in this study we present a 35 yr long high resolution record of mis 11 climate variability in the western pacific warm pool wpwp based on coupled measurements of skeletal mg ca and 18o in giant tridacna gigas clams from huon peninsula papua new guinea the 18o of modern t gigas from huon peninsula faithfully records sea surface temperature salinity rainfall and regional enso variability the geochemical integrity of the mis 11 t gigas for recording paleo enso events was established through trace element screening detailed petrography and sem analysis the fossil t gigas 18o record indicates that enso was operating during a 35 yr window in mis 11 but with fewer events of shorter duration compared to those experienced during the last 100 yrs the suppressed enso variability in the mis 11 t gigas record corresponds with a reduction in the amplitude of the average annual cycle in 18o values distinctive changes in local insolation seasonality and t gigas 18o brought about by changes in earth s orbit provide an additional geochronological constraint on the timing of reef growth at huon peninsula to around 402 ka during the mis 11 3 sub stage 424 395 ka

pacific sea surface temperature field reconstruction from coral δ18o data using reduced space objective analysis 1 a systematic methodology for the reconstruction of climate fields from sparse observational networks of proxy data employing the technique of reduced space objective analysis is applied to the reconstruction of gridded pacific ocean basin sea surface temperature sst from coral stable isotope 18o data for the period 1607 1990 in this approach we seek to reconstruct only the leading modes of large scale variability which are both observed in the modern climate and resolved in the proxy data we find that the coral data verifiably resolve two spatial patterns of sst variability the first and dominant pattern is that of the el nino southern oscillation enso a second pattern reflects uniform changes over most of the pacific basin calibration and verification tests for 1856 1990 show that root mean square variance is small 0 5 c rms and reconstruction errors are large 0 6 c rms limiting interpretation to the tropical region periods of enhanced enso activity similar to those observed in the past two decades are evident in the reconstruction for the early nineteenth century the changing frequency of enso warm phase events appears to coincide with warming of the pacific mean state inferred from similar reconstruction efforts using tree ring indicators over the last two centuries

monsoon tropical ocean interaction in a network of coral records spanning the 20th century abstract the 20th century evolution of basin wide gradients in surface ocean properties provides one essential test for recent models of the interaction between the asian monsoon and the tropical ocean because various feedback mechanisms should result in characteristic regional patterns of variability although the instrumental record of climate variability in the tropics is essentially limited to the last few decades the stable isotopic composition of living corals provides an effective means for extending the instrumental observations here we present two coral isotopic records from the indonesian maritime continent and we use these records with other previously published records to describe i the relationship between western pacific and central pacific climate variability over the past century with special emphasis on the biennial band and ii the strength of the west east indian ocean dipole we find that the amplitude of the biennial cycle in the pacific did not vary inversely with the strength of enso el nino southern oscillation as might be expected from some models of monsoonal feedback on the central pacific instead the biennial variability was modulated on decadal timescales throughout much of the pacific we also show that the zonal oxygen isotopic gradient in the indian ocean coral records was significantly correlated with central pacific sea surface temperature on a variety of timescales thus it is likely that this coral dipole was a product of strong enso like teleconnections over the indian ocean as opposed to being the result of unique indian ocean or monsoonal dynamics

asymmetry in the duration of el nino and la nina abstract el nino and la nina are not a simple mirror image but exhibit significant differences in their spatial structure and seasonal evolution in particular sea surface temperature sst anomalies over the equatorial pacific cold tongue are larger in magnitude during el nino compared to la nina resulting in positive skewness of interannual sst variations the associated atmospheric deep convection anomalies are displaced eastward during el nino compared to la nina because of the nonlinear atmospheric response to sst in addition to these well known features an analysis of observational data for the past century shows that there is a robust asymmetry in the duration of el nino and la nina most el ninos and la ninas develop in late boreal spring summer when the climatological cold tongue is intensifying and they peak near the end of the calendar year after the mature phase el ninos tend to decay rapidly by next summer but many la ninas persist through the following year and often reintensify in

impact of arid surface megacracks on hydrocarbon reservoir properties the megacrack pattern of the ephemeral north panamint dry lake california united states is characterized by variably sized polygons with diameters ranging from hundreds of meters to meters the evolution and subsurface extent of this polygonal pattern and a probable tectonic link are examined by ground resistivity measurements and surface mapping crack development is initiated by the shrinking of clays caused by changes in water content near the surface for crack evolution the following processes are proposed cavities develop at approximately 1 m 3 ft depth during a subsurface phase followed by the collapse of the overburden into the existing cavities to form the surface cracks cracks are filled by wind blown sand and dried out lake sediments from collapsing crack walls following burial differences in competence between crack fill and surrounding playa lake sediments provide zones of structural weakness that might channelize stress release and faulting ground resistivity measurements confirmed the extent of the cracks to a depth of more than 3 m 9 ft the megacrack pattern is compared to a rotliegende upper permian tight gas field located in the southern permian basin of northwestern germany situated in a comparable geologic setting there a multidirectional polygonal pattern is recorded on horizon slices of three dimensional seismic data and compares well to our observations from the panamint valley the rotliegende pattern is associated with low offset faults which are proposed to be responsible for subtle reservoir compartmentalization

reconstructing enso the influence of method proxy data climate forcing and teleconnections in this study we compare three newly developed independent nino3 4 sea surface temperature sst reconstructions using data from 1 the central pacific corals 2 the texmex region of the usa tree rings and 3 other regions in the tropics corals and an ice core which are teleconnected with central pacific ssts in the 20th century although these three reconstructions are strongly calibrated and well verified inter proxy comparison shows a significant weakening in inter proxycoherenceinthe 19thcentury thisbreakdownin commonsignalcouldberelatedtoinsufficient data dating errors in some of the proxy records or a breakdown in el nino southern oscillation s enso s influence on other regions however spectral analysis indicates that each reconstruction portraysenso likespectralproperties superposedepochanalysisalsoshowsthateachreconstruction shows a generally consistent el nino like response to major volcanic events in the following year while duringyearst 4tot 7 la nina like conditions prevail theseresults suggest thateachofthe series expresses enso like behaviour but this behaviour does not appear to be spatially or temporally consistent this result may reflect published observations that there appear to be distinct types of enso variability depending on location within the tropical pacific future work must address potential dating issues within some proxies i e sampling of multiple coral heads for one location as well as assessing the time stability of local climate relationships with central pacific ssts more emphasis is needed on sampling new and extending old coral proxy records from the crucial central and eastern tropical pacific region copyright 2009 john wiley sons ltd and crown copyright 2009

the importance of ship log data reconstructing north atlantic european and mediterranean sea level pressure fields back to 1750 local to regional climate anomalies are to a large extent determined by the state of the atmospheric circulation the knowledge of large scale sea level pressure slp variations in former times is therefore crucial when addressing past climate changes across europe and the mediterranean however currently available slp reconstructions lack data from the ocean particularly in the pre 1850 period here we present a new statistically derived 5 5 resolved gridded seasonal slp dataset covering the eastern north atlantic europe and the mediterranean area 40 w 50 e 20 n 70 n back to 1750 using terrestrial instrumental pressure series and marine wind information from ship logbooks for the period 1750 1850 the new slp reconstruction provides a more accurate representation of the strength of the winter westerlies as well as the location and variability of the azores high than currently available multiproxy pressure field reconstructions these findings strongly support the potential of ship logbooks as an important source to determine past circulation variations especially for the pre 1850 period this new dataset can be further used for dynamical studies relating large scale atmospheric circulation to temperature and precipitation variability over the mediterranean and eurasia for the comparison with outputs from gcms as well as for detection and attribution studies

reconstructing el nino southern oscillation using data from ships logbooks 1815 1854 part i methodology and evaluation the meteorological information found within ships logbooks is a unique and fascinating source of data for historical climatology this study uses wind observations from logbooks covering the period 1815 to 1854 to reconstruct an index of el nino southern oscillation enso for boreal winter djf statistically based reconstructions of the southern oscillation index soi are obtained using two methods principal component regression pcr and composite plus scale cps calibration and validation are carried out over the modern period 1979 2014 assessing the relationship between re gridded seasonal era interim reanalysis wind data and the instrumental soi the reconstruction skill of both the pcr and cps methods is found to be high with reduction of error skill scores of 0 80 and 0 75 respectively the relationships derived during the fitting period are then applied to the logbook wind data to reconstruct the historical soi we develop a new method to assess the sensitivity of the reconstructions to using a limited number of observations per season and find that the cps method performs better than pcr with a limited number of observations a difference in the distribution of wind force terms used by british and dutch ships is found and its impact on the reconstruction assessed the logbook reconstructions agree well with a previous soi reconstructed from jakarta rain day counts 1830 1850 adding robustness to our reconstructions comparisons to additional documentary and proxy data sources are provided in a companion paper

teleconnections in the geopotential height field during the northern hemisphere winter abstract contemporaneous correlations between geopotential heights on a given pressure surface at widely separated points on earth referred to as teleconnections in this paper are studied in an attempt to identify and document recurrent spatial patterns which might be indicative of standing oscillations in the planetary waves during the northern hemisphere winter with time scales on the order of a month or longer a review of existing literature on the subject reveals the existence of at least four such patterns the north atlantic and north pacific oscillations identified by walker and bliss 1932 a zonally symmetric seesaw between sea level pressures in polar and temperature latitudes first noted by lorenz 1951 and what we will refer to as the pacific north american pattern which has been known to operational long range forecasters in this country since the 1950 s a data set consisting of nmc monthly mean sea level pressure and 500 mb height analyses for a 15 year period is used as a basis fo

a nonstationary enso nao relationship due to amo modulation abstractmany previous studies have demonstrated a high uncertainty in the relationship between el nino southern oscillation enso and the north atlantic oscillation nao in the present work dec

application of manley rowe relation in analyzing nonlinear interactions between planetary waves and the solar semidiurnal tide during 2009 sudden stratospheric warming event

contrasting eastern pacific and central pacific types of enso abstract surface observations and subsurface ocean assimilation datasets are examined to contrast two distinct types of el nino southern oscillation enso in the tropical pacific an eastern pacific ep type and a central pacific cp type an analysis method combining empirical orthogonal function eof analysis and linear regression is used to separate these two types correlation and composite analyses based on the principal components of the eof were performed to examine the structure evolution and teleconnection of these two enso types the ep type of enso is found to have its sst anomaly center located in the eastern equatorial pacific attached to the coast of south america this type of enso is associated with basinwide thermocline and surface wind variations and shows a strong teleconnection with the tropical indian ocean in contrast the cp type of enso has most of its surface wind sst and subsurface anomalies confined in the central pacific and tends to onset develop and decay in situ

reliability of coral isotope records from the western pacific warm pool a comparison using age optimized records stable isotope analysis of two separate corals from nauru island in the warm pool of the western tropical pacific confirm that coral oxygen isotopes are a robust recorder of environmental variables coral delta 18 o faithfully records interannual variability even when strongly influenced by kinetic effects interannual to decadal variability of coral delta 13 c remains enigmatic only one of the two corals exhibits the expected light delta 13 c response in the interannual band coral delta 18 o from this region has a great similarity to global instrumental temperature records reflecting the impact of the pacific warm pool and variations of the indonesian low in concert with el nino southern oscillation on global climate since 1896 coral delta 18 o has exhibited a cumulative decrease of 0 7 parts per thousand which reflects a combination of warming and more frequent el nino events precipitation affecting the surface waters of this region

estimating central equatorial pacific sst variability over the past millennium part ii reconstructions and implications abstractreducing the uncertainties surrounding the impacts of anthropogenic climate change requires vetting general circulation models gcms against long records of past natural climate variability this is particularly challenging in the tropical pacific ocean where short sparse instrumental data preclude gcm validation on multidecadal to centennial time scales this two part paper demonstrates the application of two statistical methodologies to a network of accurately dated tropical climate records to reconstruct sea surface temperature sst variability in the nino 3 4 region over the past millennium while part i described the methods and established their validity and limitations this paper presents several reconstructions of nino 3 4 analyzes their sensitivity to procedural choices and input data and compares them to climate forcing time series and previously published tropical pacific sst reconstructions the reconstructions herein show remarkably similar behavior at decadal to multidecadal s

el nino southern oscillation enso and decadal scale climate variability at 10 n in the eastern pacific from 1893 to 1994 a coral based reconstruction from clipperton atoll we have developed a 101 year 1893 1994 subseasonal oxygen 18o and carbon 13c isotopic time series from clipperton atoll in the eastern pacific using the coral porites lobata in agreement with linsley et al 1999 we find that seasonal and interannual coral 18o variability at clipperton results from variability in both water temperature and salinity three new coral time series demonstrate the reproducibility of a secular coral 18o trend of 0 35 since 1910 but show varying 13c trends strong decadal scale variability in the 18o record appears related to the pacific decadal oscillation pdo through postulated changes in the strengths of the equatorial counter current and north equatorial current interannual variability in this coral 18o record is directly related to the el nino southern oscillation enso and isolation of this frequency band indicates reduced enso variability in the eastern equatorial pacific in the period 1925 to 1940 in agreement with instrumental and other pacific coral records

quantifying errors in coral based enso estimates toward improved forward modeling of δ18o 1 the oxygen isotopic ratio 18o in tropical pacific coral skeletons reflects past el nino southern oscillation enso variability but the 18o enso relationship is poorly quantified uncertainties arise when constructing 18o data sets combining records from different sites and converting between 18o and sea surface temperature sst and salinity sss here we use seasonally resolved 18o from 1958 to 1985 at 15 tropical pacific sites to estimate these errors and evaluate possible improvements observational uncertainties from kiritimati new caledonia and rarotonga are 0 12 0 14 leading to errors of 8 25 on the typical 18o variance multicoral syntheses using five to seven sites capture the principal components pcs well but site selection dramatically influences enso spatial structure using sites in the eastern pacific western pacific warm pool and south pacific convergence zone spcz captures eastern pacific type variability while central pacific type events are best observed by combining sites in the warm pool and spcz the major obstacle to quantitative enso estimation is the 18o climate conversion demonstrated by the large errors on both 18o variance and the amplitude of the first principal component resulting from the use of commonly employed bivariate formulae to relate sst and sss to 18o errors likely arise from either the instrumental data used for pseudoproxy calibration or influences from other processes 18o advection atmospheric fractionation etc at some sites modeling seasonal changes to these influences reduces conversion errors by up to 20 this indicates that understanding of past enso dynamics using coral 18o could be greatly advanced by improving 18o forward models

assessing spatial variability in el nino southern oscillation event detection skill using coral geochemistry 1 the el nino southern oscillation enso drives interannual climate variability but evidence of its preinstrumental expression is limited to proxy data and model inference we develop a skill assessment technique using instrumental records of sea surface temperature sst and sea surface salinity sss and apply it to a suite of 23 coral 18o records a common enso proxy we compare coral proxy skill with pseudoproxy records constructed from instrumental data to establish the expected proxy response to enso events and constrain proxy sensitivity the central pacific has a balanced response toward enso events the western pacific warm pool favors el nino expression and the south pacific convergence zone preferentially records la nina events however all three regions display high sensitivity to enso variability presenting promising targets for future coral paleoclimate reconstructions eastern pacific coral records display surprisingly low enso sensitivity despite the presence of large enso related sst anomalies suggesting nonclimatic influences comparisons between the pseudoproxy and coral skill ratings provide a test to highlight where these nonclimatic impacts that may affect coral record skill networks of proxy data skill ratings may better delineate the spatial structure of the sst and sss response to enso variability a feature of the climate system that is currently poorly reproduced in climate models

global atmospheric sensitivity to tropical sst anomalies throughout the indo pacific basin abstract the sensitivity of the global atmospheric response to sea surface temperature sst anomalies throughout the tropical indian and pacific ocean basins is investigated using the ncep mrf9 general circulation model gcm model responses in january are first determined for a uniform array of 42 localized sst anomaly patches over the domain results from the individual forcing experiments are then linearly combined using a statistically based smoothing procedure to produce sensitivity maps for many target quantities of interest including the geopotential height response over the pacific north american pna region and regional precipitation responses over north america south america africa australia and indonesia perhaps the most striking result from this analysis is that many important targets for seasonal forecasting including the pna response are most sensitive to sst anomalies in the nino 4 region 5 n 5 s 150 w 160 e of the central tropical pacific with lesser and sometimes opposite s

analysis of the non linearity in the pattern and time evolution of el nino southern oscillation in this study the observed non linearity in the spatial pattern and time evolution of el nino southern oscillation enso events is analyzed it is shown that enso skewness is not only a characteristic of the amplitude of events el ninos being stronger than la ninas but also of the spatial pattern and time evolution it is demonstrated that these non linearities can be related to the non linear response of the zonal winds to sea surface temperature sst anomalies it is shown in observations as well as in coupled model simulations that significant differences in the spatial pattern between positive el nino versus negative la nina and strong versus weak events exist which is mostly describing the difference between central and east pacific events central pacific events tend to be weak el nino or strong la nina events in turn east pacific events tend to be strong el nino or weak la nina events a rotation of the two leading empirical orthogonal function modes illustrates that for both el nino and la nina extreme events are more likely than expected from a normal distribution the bjerknes feedbacks and time evolution of strong enso events in observations as well as in coupled model simulations also show strong asymmetries with strong el ninos being forced more strongly by zonal wind than by thermocline depth anomalies and are followed by la nina events in turn strong la nina events are preceded by el nino events and are more strongly forced by thermocline depth anomalies than by wind anomalies further the zonal wind response to sea surface temperature anomalies during strong el nino events is stronger and shifted to the east relative to strong la nina events supporting the eastward shifted el nino pattern and the asymmetric time evolution based on the simplified hybrid coupled rechoz model of enso it can be shown that the non linear zonal wind response to sst anomalies causes the asymmetric forcings of enso events this also implies that strong el ninos are mostly wind driven and less predictable and strong la ninas are mostly thermocline depth driven and better predictable which is demonstrated by a set of 100 perfect model forecast ensembles

optimal sites for coral based reconstruction of global sea surface temperature we determine the structure of a network of sites from which coral based proxy measurements of sea surface temperature sst variability minimize the error in a reconstruction of the large scale features of the global sst field for a wide range of coral derived sst observational error and several minimization criteria sites in the equatorial oceans especially the central and eastern equatorial pacific best minimize the error in the reconstruction if the observational error is sufficiently low additional optimal sites are in selected subtropical locations if the observational error is high the error is minimized by resampling the most important equatorial sites the marginal return on additional sites diminishes rapidly and is not sensitive to the size of the observational error two sites reduce the analysis error by half as much as 10 sites while the first 6 7 sites achieve half the error reduction of all 65 sites in the analysis domain in the extratropics the reduction of reconstruction error is small and gradual while error in the tropical pacific is sharply reduced by 2 3 sites and gradually thereafter these results suggest that a limited set of redundantly sampled sites with uncorrelated and low observational error 0 3 0 6 c will provide the best approach to reconstruction of large scale features of the sst field from coral data for the preinstrumental period

eastern pacific sea surface temperature since 1600 a d the δ18o record of climate variability in galapagos corals we measured stable oxygen isotope ratios and skeletal growth rates in the massive corals pavona clavus and p gigantea from the west coast of isabela island galapagos to assess interannual to decadal climate variability in the eastern pacific comparisons of instrumental data sets show that sea surface temperatures sst in the galapagos region are representative of a broad portion of the eastern equatorial pacific the site is especially well suited for long term studies of the el nino southern oscillation enso phenomenon as it lies within the eastern pacific center of action for thermal anomalies associated with enso the p gigantea isotope record is nearly monthly in resolution spans the period 1961 1982 and shows strong correlation with a galapagos instrumental sst record r 0 90 for annual averages cross spectral analysis shows that sst can explain greater than 80 of the variance in 18o at both the annual cycle and within the high frequency portion of the enso band 3 5 years the p clavus record is annual in resolution extends from 1587 to 1953 a d and was obtained from a 10 m diameter colony preserved within the urvina bay uplift because seawater 18o variations in the region are very small we interpret the urvina bay coral 18o record in terms of annual average sst the isotopic record appears to be a very good but not perfect indicator of enso events and shows good correspondence with the historical enso reconstruction of quinn et al 1987 a number of low 18o excursions that we observe during the 17th and 18th centuries very likely represent enso events that are missing from the historical tabulations most interannual 18o variations between 1607 and 1953 a d represent annual average temperature excursions of 1 to 2 5 c during the little ice age the annual 18o series correlates well with many north american tree ring records and shows low temperatures during the early 1600s and early 1800s and relatively warmer conditions during the 1700s unlike most northern hemisphere tree ring and instrumental records we see no evidence at this site for warming between 1880 and 1940 but rather observe a slight cooling 28 of the total variance the main enso mode is centered at 4 6 years and accounts for 12 of the total variance additional significant oscillations occur at periods of 3 3 6 8 11 17 22 and 34 years both annual growth rate and 18o show variance at periods equivalent to the solar and solar magnetic periods e g 11 and 22 years respectively in addition the amplitude of the 11 year 18o cycle generally varies with the amplitude of the solar cycle supporting previous suggestions that the solar cycle may modulate interannual to decadal climate variability in the tropics the dominant oscillatory modes both within the enso and interdecadal frequency bands shift to shorter periods from the early to middle 1700s and again from the middle to late 1800s this may reflect major reorganizations within the tropical ocean atmosphere system and suggests that tropical pacific climate variability is linked across timescales ranging from years to decades

quasi 10 day wave and semidiurnal tide nonlinear interactions during the southern hemispheric ssw 2019 observed in the northern hemispheric mesosphere

september 2019 antarctic sudden stratospheric warming quasi 6 day wave burst and ionospheric effects an exceptionally strong stationary planetary wave with zonal wavenumber 1 led to a sudden stratospheric warming ssw in the southern hemisphere in september 2019 ionospheric data from esa s swarm

reconstructing el nino southern oscillation enso from high resolution palaeoarchives el nino southern oscillation enso is one of the most important coupled ocean atmospheric phenomena to cause global climate variability on interannual timescales efforts to understand recent apparently anomalous enso behaviour are hampered by the phenomenon s unstable non stationary nature and the limitations inherent in palaeoclimate records in this paper the complexities associated with isolating enso signals in observational and palaeoclimate records are reviewed the utility and limitations of high resolution tree ring coral speleothems ice and documentary proxy data for enso reconstruction are discussed to overcome the regional biases contained within each palaeoclimatic source it is necessary to compare complementary signals derived from multiple proxy climate records to date there have been limited attempts to reconstruct large scale enso using these multiproxy methodologies a critique of the complexities associated with previous approaches of reconstructing discrete enso events and atmospheric oceanic indices is provided abundant potential remains to better characterise teleconnection patterns propagation signatures and non stationary features of large scale enso behaviour if key uncertainties in enso dynamics such as the response of extreme events to natural human forcing are to be adequately assessed then complementary attempts must be made to model the historic synoptic conditions with apparent changes in reconstructed indices copyright 2006 john wiley sons ltd

primary surface rupture associated with the mw 7 1 16 october 1999 hector mine earthquake san bernardino county california the m w 7 1 hector mine earthquake occurred within the mojave desert portion of the eastern california shear zone and was accompanied by 48 km of dextral surface rupture complex northward rupture began on two branches of the lavic lake fault in the northern bullion mountains and also propagated southward onto the bullion fault lesser amounts of rupture occurred across two right steps to the south surface rupture was mapped using postearthquake 1 10 000 scale aerial photography field mapping provided additional detail and more than 400 fault rupture observations of these approximately 300 measurements were used to characterize the slip distribution en echelon surface rupture predominated in areas of thick alluvium whereas in the bedrock areas rupture was more continuous and focused within a narrower zone measured dextral offsets were relatively symmetrical about the epicentral region with a maximum displacement of 5 25 0 85 m 1 vertical slip was a secondary component and was variable with minor west side down displacements predominating in the bullion mountains field and aerial photographic evidence indicates that most of the faults that ruptured in 1999 had had prior late quaternary displacement although only limited sections of the rupture show evidence for prior holocene displacement 1 fn 1

new views of tropical paleoclimates from corals abstract corals offer a rich archive of past climate variability in tropical ocean regions where instrumental data are limited and where our knowledge of multi decadal climate sensitivity is incomplete in the eastern equatorial pacific coral isotopic records track variations in enso related changes in sea surface temperature further west corals record variability in sea surface temperature and rainfall that accompanies zonal displacement of the indonesian low during enso events these multi century records reveal previously unrecognised enso variability on time scales of decades to centuries outside the enso sensitive equatorial pacific long term trends towards recent warmer wetter conditions suggest the tropics respond to global forcings new coral paleothermometers indicate that surface ocean temperatures in the tropical southwestern pacific were depressed by 4 6 c during the younger dryas climatic event and rose episodically during the next 4000 yr high temporal resolution measurements of sr ca and 18 o in corals provide information about the surface ocean hydrologic balance and can resolve the seasonal balance between precipitation and evaporation radiocarbon measurements in corals coupled with ocean circulation models may be used to reconstruct near surface ocean circulation past mixing rates and the distribution of fossil fuel co2 in the upper ocean most recently seasonal to interannual variations in the radiocarbon of corals from the equatorial pacific have been linked to the redistribution of surface waters associated with the enso

surface temperature patterns associated with the southern oscillation abstract the typical global and large scale regional temperature patterns associated with the low warm and high cold phases of the southern oscillation so are investigated a total of 12 separate regions were found to have consistent temperature patterns associated with low phase of the so while 11 areas were found to have temperature patterns associated with the high phase of these areas 9 have expected temperature patterns during both phases of the so in the tropics temperature anomalies are of the same sign as the so related sea surface temperature sst anomaly in all land regions except for one area in the west pacific three extratropical responses to the low phase of the so are found over north america and one is found in japan high so temperature patterns were found in the extratropies for japan western europe and northwestern north america the identified temperature responses are more consistent in tropical regions than in the extratropies the so can influence the estimation of

evidence for stratosphere sudden warming ionosphere coupling due to vertically propagating tides 1 observations of the global positioning system gps total electron content tec are used to study the coupling between the 2009 sudden stratospheric warming ssw and ionospheric perturbations the observations reveal both migrating and nonmigrating perturbations to the semidiurnal tide in the equatorial ionization anomaly crest region that are associated with changes in electric fields induced by the tidal dynamo in particular a significant enhancement is observed in the nonmigrating semidiurnal westward propagating tide with zonal wavenumber 1 sw1 in gps tec during the ssw the sw1 perturbations in the low latitude ionosphere are found to oscillate with a similar period as planetary wave 1 activity in the northern hemisphere stratosphere this connection is attributed to the nonlinear interaction between tides and planetary waves and strongly supports the theory that planetary wave tide interaction is the primary mechanism coupling ssws to ionospheric variability enhancements are also observed in the nonmigrating semidiurnal tide with zonal wavenumber 0 s0 during this time period and may be related to the nonlinear interaction between the migrating semidiurnal tide and planetary wave 2 the connection between planetary wave 2 and s0 is however less clear which may be attributed to differences in the zonal mean zonal winds in the mesosphere and lower thermosphere during the times of peak planetary wave 1 and planetary wave 2 activity we conclude that the changing zonal winds during ssws play an important role in the coupling between ionospheric variability and the forcing from planetary waves of lower atmospheric origin during ssws

sand boils without earthquakes sedimentary deformation caused by liquefaction has become a popular means for inferring prehistoric strong earthquakes in this report we describe a new mechanism for generating such features in the absence of earthquakes sand boils and a 180 m long sand dike formed in fremont valley california when sediment laden surface runoff was intercepted along the upslope part of a 500 m long preexisting ground crack flowed subhorizonally in the crack and then flowed upward in the downslope part of the crack where it discharged as sand boils on the land surface if the sand boils and their feeder dike were stratigraphically preserved they could be misinterpreted as evidence for earthquake induced liquefaction

macropolygon morphology development and classification on north panamint and eureka playas death valley national park ca abstract panamint and eureka playas both located within death valley national park exhibit a host of surficial features including fissures pits mounds and plant covered ridges representing topographic highs and lows that vary up to 2 m of relief from the playa surface aerial photographs reveal that these linear strands often converge to form polygons ranging in length from several meters to nearly a kilometer these features stand out in generally dark contrast to the brighter intervening expanse of flat plant free desiccated mud of the typical playa surface ground truth mapping of playa features with differential gps global positioning system was conducted in 1999 north panamint valley and 2002 eureka valley high resolution digital maps reveal that both playas possess macropolygons of similar scale and geometry and that fissures may be categorized into one of two genetic groups 1 shore parallel or playa interior desiccation and shrinkage and 2 tectonic induced cracks early investigations of these features in eureka valley concluded that their origin may have been related to agricultural activity by paleo indian communities although human artifacts are abundant at each locale there is no evidence to support the inference that surface features reported on eureka playa are anthropogenic in origin our assumptions into the genesis of polygons on playas is based on our fortuitous experience of witnessing a fissure in the process of formation on panamint playa after a flash flood may 1999 our observations revealed a paradox that saturation of the upper playa crusts contributes to the establishment of some desiccation features follow up visits to the same feature over 2 yrs time are a foundation for insight into the evolution and possible longevity of these features

geological landscapes of the death valley region death valley s location and climate make it one of the most dramatic geological landscapes on earth the region lies near the western edge of cratonic north america and so it contains a record of plate boundary effects that date back to the proterozoic these effects include rifting and the development of the passive margin during the late proterozoic crustal shortening and sierra nevada magmatism largely during the mesozoic and crustal extension and magmatism during the late cenozoic because crustal extension continues today the region also showcases spectacular landforms that relate to active mountain building when combined with this geology death valley s harsh climate makes it unique as the hottest and

estimating central equatorial pacific sst variability over the past millennium part i methodology and validation abstractconstraining the low frequency lf behavior of general circulation models gcms requires reliable observational estimates of lf variability this two part paper presents multiproxy reconstructions of nino 3 4 sea surface temperature over the last millennium applying two techniques composite plus scale cps and hybrid regularized expectation maximization regem truncated total least squares ttls to a network of tropical high resolution proxy records this first part presents the data and methodology before evaluating their predictive skill using frozen network analysis fna and pseudoproxy experiments the fna results suggest that about half of the nino 3 4 variance can be reconstructed back to a d 1000 but they show little lf skill during certain intervals more variance can be reconstructed in the interannual band where climate signals are strongest but this band is affected by dating uncertainties which are not formally addressed here the cps reliably estimates interannual varia

sea surface temperature and salinity reconstruction from coral geochemical tracers massive scleractinian corals secrete an aragonitic skeleton which incorporates a large array of chemical tracers corals present several advantages for palaeoclimate research they grow continuously and can live up to 1000 years they are easy to date and they can be sampled at high resolution weekly to monthly resolution both live and fossil corals can be collected in the field in the past two decades significant efforts have been made to identify robust tracers of sea surface temperature sst and salinity sss in corals to date sr ca and 18o are considered to be the most reliable sst tracers although changes in seawater 18o can significantly alter sst reconstructed from coralline 18o because these variations in seawater 18o can be linked to sss changes this initial problem can in fact be turned into an advantage and provide us with an sss tracer the sst component in the coral 18o signal can either be evaluated through sr ca measurements or in some case simply filtered out however there is still much uncertainty concerning the exact mode of incorporation of trace elements and stable isotopes into the coral skeleton the effects of growth rate light intensity feeding habits ph and water chemistry are still poorly documented a review of the strength and weaknesses of sr ca and 18o is presented together with some examples of sst and sss reconstructions other potential sst tracers are also reviewed it is expected that the ability to grow corals in aquarium under controlled conditions and that the development of sophisticated analytical techniques at the micrometric level should help us understand better the robustness of each tracers and the factors controlling their incorporation in coral aragonite

a coral based reconstruction of sea surface salinity at sabine bank vanuatu from 1842 to 2007 ce climate variability associated with the el nino southern oscillation enso results in large sea surface temperature sst and sea surface salinity sss anomalies in many regions of the tropical pacific ocean we investigate interannual changes in sss driven by enso in the southwestern pacific at sabine bank vanuatu sbv 166 04 e 15 94 s using monthly variations in coral 18o from 1842 to 2007 ce we develop and apply a coral 18o sss transfer function which is assessed using a calibration verification exercise 1970 2007 ce the 165 year reconstructed sss record contains a prominent trend toward freshening from 1842 to 2007 ce mean sss for 1842 1872 ce is 35 46 0 28 psu which contrasts with a mean value of 34 85 0 31 psu for 1977 2007 ce with a freshening trend during the latter part of the 20th century that is not unprecedented with respect to the overall record variance in the record is concentrated in the interannual 42 and interdecadal 29 bands the sbv sss record matches well with a similarly reconstructed sss time series at malo channel vanuatu which is located 120 km to the east of sbv this regional signal is likely driven by enso related changes in the spcz and interdecadal changes in surface water advection the pattern of interdecadal variability at sbv agrees reasonably well with coral records of interdecadal variability from fiji and tonga especially in the pre 1940 portions of the records further evidence for the regional extent of the salinity signal at sabine bank vanuatu

a multicentury stable isotope record from a new caledonia coral interannual and decadal sea surface temperature variability in the southwest pacific since 1657 a d a 335 year stable isotope record from a new caledonia coral 22 s 166 e helps fill a large gap in historical climate reconstructions although the long term coral 18o based sea surface temperature sst trend is one of warming there are notable decadal fluctuations especially in the early 18th and early 19th centuries mean annual ssts between 1658 and 1900 are estimated to be 0 3 c lower than the 20th century average with interdecadal excursions of 0 5 0 8 c time series analyses of the coral isotope record reveals significant concentrations of variance in the el nino band an inderdecadal spectral peak is present but its robustness requires additional statistical evaluation a secular but irregular decrease in coral 13c values begins in the mid 1800s and may reflect the anthropogenic perturbation of the carbon reservoir these and other results indicate that the new caledonia coral isotope record is a valuable source of information on southwest pacific climate history

two hundred fifty years of reconstructed and modeled tropical temperatures 1 recent large scale palaeoclimate reconstructions of past temperature have been essentially biased to the extratropics owing to a paucity of proxy data in tropical regions herein we describe the first coral based reconstruction of sea surface temperatures ssts for the whole of the tropics 30 n 30 s it was developed from 14 disparate coral records located in the indian and pacific oceans over the most replicated period the reconstruction explains 57 of the tropical sst variance however the strength of this signal weakens markedly as the number of coral records decreases the reconstruction is robust between 1850 and 1993 but some fidelity is indicated back as far as the mid 18th century these results suggest that ambiguities in the low frequency domain of 18o measurements can be partially overcome by pooling together multiple time series from different locations around the tropics agreement with simulations from two general circulation models indicates that the late 20th century is likely the warmest period in the tropics for the last 250 years and that this recent warming can only be explained by anthropogenic forcing the high frequency variability is dominated by the el nino southern oscillation the reconstruction owing to the small number of coral records is unfortunately restricted both in time and space therefore we hope that this study will spur the palaeoclimate community to develop new and longer proxy series to improve the current meager data base of temperature sensitive series in the tropics

atmospheric and oceanic evidences of el nino southern oscillation events in the south central pacific ocean from coral stable isotopic records over the last 137 years we measured 18o and 13c in porites lutea collected in the moorea lagoon where the instrumental records show that an el nino southern oscillation enso event implies both a cloud cover decrease and a weak sea surface temperature sst increase two proxies allow an enso record to be reconstructed at moorea the annual 13c anomaly associated with the south pacific convergence zone motion and an annual 18o anomaly showing increased sst the frequency bands exhibited by the singular spectral analysis ssa and the multitaper method of the annual 18o and 13c records are centered on 2 5 and 5 2 years and 2 4 and 3 2 years respectively which are the main enso modes we used ssa to reconstruct enso events at moorea over the past 137 years results indicate that climate variability at this site is strongly affected by enso events

two types of el nino events cold tongue el nino and warm pool el nino abstract in this study two types of el nino events are classified based on spatial patterns of the sea surface temperature sst anomaly one is the cold tongue ct el nino which can be regarded as the conventional el nino and the other the warm pool wp el nino the ct el nino is characterized by relatively large sst anomalies in the nino 3 region 5 s 5 n 150 90 w while the wp el nino is associated with sst anomalies mostly confined to the nino 4 region 5 s 5 n 160 e 150 w in addition spatial patterns of many atmospheric and oceanic variables are also distinctively different for the two types of el nino events furthermore the difference in the transition mechanism between the two types of el nino is clearly identified that is the discharge process of the equatorial heat content associated with the wp el nino is not efficient owing to the spatial structure of sst anomaly as a result it cannot trigger a cold event it is also demonstrated that zonal advective feedback i e zonal adve

a multiproxy index of the el nino southern oscillation a d 1525 1982 1 an understanding of past variability in the el nino southern oscillation enso on interannual interdecadal and longer time scales would be useful in assessing recent observed changes to enso and in determining the realism of climate model simulations using tree ring coral and ice core data we reconstruct a proxy based enso index between a d 1525 and 1982 unlike most previous studies which have drawn climate proxies from limited geographic regions our network is pacific basin wide using enso sensitive proxies from the western equatorial pacific new zealand the central pacific and subtropical north america by considering multiple teleconnection regions this network provides a more robust proxy enso signal the common signal recorded in the multiproxy network has a high correlation with the southern oscillation index soi nino 3 4 sea surface temperature nino3 4 sst and a combined ocean atmosphere enso index cei the proportion of instrumental variance explained is 47 for the soi 48 for nino3 4 sst and 52 for the cei the proxy enso index also displays skill in reproducing warm and cold extremes of the soi the proxy enso index over the last 450 years shows considerable amplitude and frequency modulation in the 3 10 year band on multidecadal time scales there is a relative reduction in the amplitude of high frequency variability during the sixteenth early seventeenth and mid eighteenth centuries in contrast high frequency enso variability has increased over the last 200 years variability during the first half of the twentieth century is similar to that evident in the nineteenth century

the response of enso flavors to mid holocene climate implications for proxy interpretation the response of el nino southern oscillation enso to mid holocene boundary conditions remains an open question paleoclimate proxies and climate model simulations do not agree in the magnitude of the reduction of enso variability while recent proxy evidence from fossil corals from the central pacific show that the reduction in mid holocene enso variability compared to the end of the twentieth century is not different from the reduction during other holocene time intervals this is inconsistent with the interpretation of lake and ocean sediment records from the eastern pacific which show a significant reduction compared to all other holocene periods in order to reconcile the seemingly conflicting proxy evidence from the eastern and central pacific we hypothesize that enso remained active during the mid holocene however there was a change in the spatial pattern of the sea surface temperature anomalies also known as enso flavors using national center for atmospheric research s community climate system model version 4 forced with mid holocene orbital conditions we find that the frequency of occurrence of the strongest eastern pacific ep events decreases in the mid holocene and their variance is reduced by 30 while the frequency of central pacific cp events slightly increases and their variance does not change we also find a shift in the seasonality of ep events but not in that of cp events lastly mid holocene ep events develop more slowly and decay faster the differential response of enso flavors to mid holocene forcing is remotely forced by the west pacific where a weakening of the trade winds in early boreal spring in the mid holocene initiates an anomalous downwelling annual kelvin wave which reaches the eastern pacific during the enso development season weakens the upper ocean stratification and results in reduced enso upwelling feedback the simulated reduction in the ep flavor versus the cp flavor in the mid holocene is consistent with proxy evidence the teleconnection patterns of the two flavors with temperature precipitation and salinity are distinct and proxies from different regions of the pacific might be recording variability associated with only one of the flavors or some combination of their relative effects

planetary waves in coupling the stratosphere and mesosphere during the major stratospheric warming in 2003 2004 1 the vertical coupling of the stratosphere mesosphere system through quasi stationary and traveling planetary waves during the major sudden stratospheric warming ssw in the arctic winter of 2003 2004 has been studied using three types of data the uk met office ukmo assimilated data set was used to examine the features of the global scale planetary disturbances present in the winter stratosphere of the northern hemisphere sounding the atmosphere using broadband emission radiometry saber satellite measurements were used as well for extracting the stationary planetary waves in the zonal and meridional winds of the stratosphere and mesosphere radar measurements at eight stations four of them situated at high latitudes 63 69n and the other four at midlatitudes 52 55n were used to determine planetary waves in the mesosphere lower thermosphere mlt the basic results show that prior to the ssw the stratospheremesosphere system was dominated by an upward and westward propagating 16 day wave detected simultaneously in the ukmo and mlt zonal and meridional wind data after the onset of the ssw longer period 22 24 days oscillations were observed in the zonal and meridional mlt winds these likely include the upward propagation of stationary planetary waves from below and in situ generation of disturbances by the dissipation and breaking of gravity waves filtered by stratospheric winds citation pancheva d et al 2008 planetary waves in coupling the stratosphere and mesosphere during the major stratospheric warming in 2003 2004 j geophys res 113 d12105 doi 10 1029 2007jd009011

tidal wind mapping from observations of a meteor radar chain in december 2011 1 this article proposes a technique to map the tidal winds in the mesosphere and lower thermosphere mlt region from the observations of a four station meteor radar chain located at middle and low latitudes along the 120 e meridian in the northern hemisphere a 1 month dataset of the horizontal winds in the altitude range of 80 100 km is observed during december 2011 we first decompose the tidal winds into mean diurnal semidiurnal and terdiurnal components for each station it is found that the diurnal semidiurnal components dominate at the low latitude midlatitude stations their amplitudes increase at lower altitudes and then decrease at higher altitudes after reaching a peak in the mlt region hough functions of the classical tidal theory are then used to fit the latitudinal distribution of each decomposed component the diurnal component is found to be dominated by the first symmetric 1 1 mode yet for the semidiurnal and terdiurnal components the corresponding dominant modes are the second symmetric modes 2 4 and 3 5 and considerable contributions are also from the first antisymmetric modes 2 3 3 4 and second antisymmetric modes 2 5 3 6 based on the decomposed results we further map the horizontal winds in the domains of latitude altitude and local time the mapped horizontal winds successfully reproduce the local time versus altitudinal distributions of the original observations at the four stations thus we conclude that the meteor radar chain is useful to monitor and study the regional characteristics of the tidal winds in the mlt region

variability of surface ocean radiocarbon and stable isotopes in the southwestern pacific we present high precision radiocarbon 14c results and stable isotope 18o and 13c records for a coral from heron island 23 s 152 e and new stable isotope 18o and 13c records for annual coral bands from abraham reef 22 s 153 e in the southern great barrier reef studied earlier druffel and griffin 1993 these tracers provide unique information on the regional water mass history and together these data allow us to constrain the variability of circulation in the upper pacific over the past four centuries first we observe decreases in 18o of coral from abraham reef and heron island indicating an increase in sea surface temperature and or a decrease in surface salinity since 1850 second the small suess effect value 14c decrease from 1880 to 1955 due mostly to fossil fuel co2 observed previously at abraham reef druffel and griffin 1993 is confirmed in the measurements reported here from the heron island coral this value is low compared to those observed in other areas of the ocean druffel 1997 druffel and linick 1978 nozaki et al 1978 between 1880 and 1955 third we report alterations in the correlation between el nino events and the occurrence of low 14c which is indicative of long term change s in circulation in the sw pacific the 14c shifts reported here are not large but even small temporal changes in prebomb 14c suggest that important changes in the large scale state of the ocean have occurred such as a temporal change in circulation

distinct patterns of tropical pacific sst anomaly and their impacts on north american climate abstracta neural network based cluster technique the so called self organizing map som was performed to extract distinct sea surface temperature sst anomaly patterns during boreal winter the som technique has advantages in nonlinear feature extraction compared to the commonly used empirical orthogonal function analysis and is widely used in meteorology the eight distinguishable som patterns so identified represent three la nina like patterns two near normal patterns and three el nino like patterns these patterns show the varied amplitude and location of the sst anomalies associated with el nino and la nina such as the central pacific cp and eastern pacific ep el nino the impact of each distinctive som pattern on winter mean surface temperature and precipitation changes over north america was examined based on composite maps with observational data each som pattern corresponds to a distinguishable spatial structure of temperature and precipitation anomaly over north america which seems

tracking the extent of the south pacific convergence zone since the early 1600s 1 the south pacific convergence zone spcz is the largest and most persistent spur of the intertropical convergence zone at the southeastern edge of the spcz near 170 w and 15 20 s a surface ocean salinity frontal zone exists that separates fresher western pacific warm pool water from saltier and cooler waters in the east this salinity front is known to shift east and west with the phase of the el nino southern oscillation we have generated subannually resolved and replicated coral oxygen isotopic time series from fiji 17 s 179 e and rarotonga 21 5 s 160 w that have recorded interannual displacements of the salinity front over the last 380 years and also indicate that at lower frequencies the decadal mean position of the salinity front and eastern extent of the spcz has shifted east west through 10 to 20 of longitude three times during this interval the most recent and largest shift began in the mid 1800s as the salinity front progressively moved eastward and salinity decreased at both sites our results suggest that sea surface salinity at these sites is now at the lowest levels recorded and is evidence for an unprecedented expansion of the spcz since the mid 1800s the expansion of the spcz implies a gradual change in the south pacific to more la nina like long term mean conditions this observation is consistent with the ocean thermostat mechanism for the pacific coupled ocean atmosphere system whereby exogenous heating of the atmosphere would result in greater warming in the western pacific and a greater east west surface temperature gradient components 8034 words 7 figures 2 tables

coral oxygen isotope records of interdecadal climate variations in the south pacific convergence zone region 1 the south pacific convergence zone spcz a region of high rainfall is a major feature of subtropical southern hemisphere climate and contributes to and interacts with circulation features across the pacific yet its past temporal variability and forcing remain only partially understood here we compare coral oxygen isotopic 18o series spanning a d 1997 1780 and a d 2001 1776 from two genera of hermatypic corals in fiji located within the spcz to examine the fidelity of these corals in recording climate change and spcz interdecadal dynamics one of these coral records is a new 225 year subannually resolved 18o series from the massive coral diploastreaheliopora diploastrea s use in climate reconstructions is still relatively new but this coral has shown encouragingly similar interannual variability to porites the coral genus most commonly used in pacific paleoclimate studies in fiji we observe that interdecadal 18o variance is also similar in these two coral genera and diploastrea contains a larger amplitude interdecadal signal that more closely tracks instrumental based indices of pacific interdecadal climate change and the spcz than porites both coral 18o series record greater interdecadal variability from 1880 to 1950 which is consistent with the observations of folland et al 2002 who reported higher variability in spcz position before 1945 these observations indicate that diploastrea will likely provide a significant new source of long term climate information from the spcz region

modeling the stable water isotope expression of el nino in the pliocene implications for the interpretation of proxy data the el nino southern oscillation enso drives interannual climate variability hence its behavior over a range of climates needs to be understood it is therefore important to verify that the paleoarchives used for pre instrumental enso studies can accurately record enso signals here we use the isotope enabled hadley centre general circulation model hadcm3 to investigate enso signals in paleoarchives from a warm paleoclimate the mid pliocene warm period mpwp 3 3 3 0ma continuous e g coral and discrete e g foraminifera proxy data are simulated throughout the tropical pacific and enso events suggested by the pseudoproxy data are assessed using modeled enso indices hadcm3 suggests that the ability to reconstruct enso from coral data is predominantly dependant on location however since modeled enso is slightly stronger in the mpwp than the preindustrial enso is slightly easier to detect in mpwp aged coral hadcm3 also suggests that using statistics from a number of individual foraminifera individual foraminifera analysis ifa generally provides more accurate enso information for the mpwp than for the preindustrial particularly in the western and central pacific however a test case from the eastern pacific showed that for some locations the ifa method can work well for the preindustrial but be unreliable for a different climate the work highlights that sites used for paleo enso analysis should be chosen with extreme care in order to avoid unreliable results although a site with good skill for preindustrial enso will usually have good skill for assessing mpwp enso this is not always the case

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

indices of el nino evolution abstract to characterize the nature of el nino southern oscillation enso sea surface temperature sst anomalies in different regions of the pacific have been used an optimal characterization of both the distinct character and the evolution of each el nino or la nina event is suggested that requires at least two indices i sst anomalies in the nino 3 4 region referred to as n3 4 and ii a new index termed here the trans nino index tni which is given by the difference in normalized anomalies of sst between nino 1 2 and nino 4 regions the first index can be thought of as the mean sst throughout the equatorial pacific east of the date line and the second index is the gradient in sst across the same region consequently they are approximately orthogonal tni leads n3 4 by 3 to 12 months prior to the climate shift in 1976 77 and also follows n3 4 but with opposite sign 3 to 12 months later however after 1976 77 the sign of the tni leads and lags are reversed

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

the generation of global rotational flow by steady idealized tropical divergence abstract tropical convective heating is balanced on the large scale by the adiabatic cooling of ascent the horizontal divergence of the wind above this heating may be viewed as driving the upper tropospheric rotational wind field a vorticity equation model is used to diagnose this relationship it is shown that because of the advection of vorticity by the divergent component of the flow the rossby wave source can be very different from the simple fd source often used in particular an equatorial region of divergence situated in easterly winds can lead to a rossby wave source in the subtropical westerlies where it is extremely effective this part of the source can be relatively insensitive to the longitudinal position of the equatorial divergence a divergence field which is asymmetric about the equator can lead to a quite symmetric rossby wave source for a steady frictionless flow the rossby wave source averaged over regions within closed streamfunction or absolute vorticity contours is under cert

interannual and decadal variability of the western pacific sea surface condition for the years 1787 2000 reconstruction based on stable isotope record from a guam coral 1 we present a monthly resolved 213 year stable isotope time series from a coral from guam 13 n 145 e which is located on the northern edge of the western pacific warm pool oxygen isotopic composition of the coral skeleton 18ocoral shows seasonal interannual and decadal variability which documents significant oceanographic changes related to thermal and hydrologic variations in this region the 18ocoral anomaly reflects sea surface temperature sst anomaly and sea surface salinity sss anomaly with significant r values of 0 69 and 0 49 respectively which are strongly linked to oceanographic changes that occur during el nino southern oscillation enso warm and cool phases we identified 46 enso warm el nino and 53 cool phases la nina in the coral record which are consistent with those phases reconstructed by nino 3 4 sst anomaly spectral analyses of the 18ocoral anomaly record for the years 1790 1999 identified significant peaks around 3 to 7 years these results indicate that the guam coral has recorded enso periodicity the 18ocoral anomaly shows decadal variability of 15 to 45 year periodicity with significant shifts 0 2 from warmer to cooler condition and vice versa an accumulative decrease in 18ocoral time series may imply 0 75 c warming of sst and 0 23 freshening of seawater 18o corresponding to a decrease of sss by 0 85 in the northwestern tropical pacific over the last 2 centuries

large scale rossby normal modes during some recent northern hemisphere winters abstractlarge scale rossby normal modes are studied for the northern hemisphere winters of 2005 2006 2008 and 2009 using global observational meteorological analyses spanning the 0 92 km altitude range spectral analysis of geopotential height fields shows pronounced peaks at westward propagating zonal wavenumber 1 near the theoretical locations of the free rossby waves at 25 16 10 and 5 days that in some cases have amplitudes significantly larger than the estimated background spectrum evidence is also found for a wavenumber 2 free mode near 4 days a coherence analysis is used to extract the amplitude and phase of the waves and to isolate those regions of the latitude altitude plane where the signals are statistically significant although the spectral location temporal evolution and vertical structure of several of these waves are suggestive of the presence of rossby normal modes this study shows that in the real atmosphere the waves only occasionally have the global properties of classical

anomalous winter climate conditions in the pacific rim during recent el nino modoki and el nino events present work compares impacts of el nino modoki and el nino on anomalous climate in the pacific rim during boreal winters of 1979 2005 el nino modoki el nino is associated with tripole dipole patterns in anomalies of sea surface temperature precipitation and upper level divergent wind in the tropical pacific which are related to multiple boomerangs of ocean atmosphere conditions in the pacific zonal and meridional extents of those boomerangs reflect their independent influences which are seen from lower latitudes in the west to higher latitudes in the east in the central pacific more moisture is transported from the tropics to higher latitudes during el nino modoki owing to displacement of the wet boomerang arms more poleward toward east discontinuities at outer boomerang arms manifest intense interactions between tropical and subtropical extratropical systems the pacific north american pattern and related climate anomalies in north america found in earlier studies are modified in very different ways by the two phenomena the seesaw with the dry north and the wet south in the western usa is more likely to occur during el nino modoki while much of the western usa is wet during el nino the moisture to the southwestern usa is transported from the northward shifted itcz during el nino modoki while it is carried by the storms traveling along the southerly shifted polar front jet during el nino the east asian winter monsoon related anticyclone is over the south china sea during el nino modoki as compared to its position over the philippine sea during el nino causing opposite precipitation anomalies in the southern east asia between the two phenomena

el nino la nina and the nonlinearity of their teleconnections the paradigm of an atmospheric system varying linearly with respect to extreme phases of the el nino southern oscillation is questioned it is argued that the global response to tropical pacific sea surface temperature forcing will be inherently nonlinear a physical basis for this intrinsic nonlinearity is the thermodynamic control on deep convection climate statistics for warm and cold events of the tropical pacific are analyzed separately for the northern winter periods during 1950 96 composite analysis of 500 mb heights reveal planetary scale teleconnection patterns as noted in earlier studies a new result is the evidence for an appreciable 358 longitude phase shift between the warm and cold event circulation composites and the two wave trains appear to have different tropical origins a large nonlinear component in north american surface climate anomalies is also found which is consistent with such a phase shift in teleconnections in the tropics rainfall anomalies also show evidence of nonlinear behavior the maximum rain anomalies along the equator are located east of the date line during warm events but west of the date line during cold events the interpretation of this behavior is complicated however by the fact that composite warm event sst anomalies are not the exact inverse of their cold event counterparts idealized atmospheric general circulation model agcm experiments are performed in order to test the question of whether the observed nonlinearity is an intrinsic property of the atmospheric system the model is forced with a composite sst anomaly that undergoes a realistic seasonally varying enso life cycle as described by e rasmusson and t carpenter both positive and negative phases of the sst anomaly are used and a 40 member ensemble of warm and cold event model simulations is conducted a nonlinear climate response in the agcm is found that closely resembles the observed composites including a shift in the equatorial positions of the maxmium rain responses and a phase shift of teleconnection patterns in the upper troposphere barotropic model experiments indicate that the inherent nonlinearity in the tropical rain response may itself be responsible for the phase shift in the extratropical teleconnection patterns

case studies of the mesospheric response to recent minor major and extended stratospheric warmings 1 we have studied the mesospheric response to two recent stratospheric warmings by performing short term forecasts at medium 1 5 and high 0 5 spatial resolution under different gravity wave drag gwd scenarios we validated our models with our high altitude analysis that extends from 0 to 90 km for the minor warming of january 2008 reduced upper level orographic gwd weakened the downward residual circulation and cooled the mesosphere parameterized nonorographic gwd increased the simulated mesospheric cooling for the prolonged major warming of 2006 heavily attenuated orographic gwd led to pronounced cooling near 50 km during the extended phase of this event an unusually strong westerly polar vortex reformed in the lower mesosphere which allowed westward propagating nonorographic gravity waves to reach the mesosphere and break with net westward accelerations of over 50 m s 1 d 1 this in turn forced a strong residual circulation yielding descent velocities over 2 cm s 1 between 65 n and 85 n consistent with previous reports of enhanced downward transport of trace constituents the resulting adiabatic heating as evidenced by the unusually vertically displaced stratopause at 80 km is likely a direct consequence of this enhanced gravity wave driven descent high resolution simulations without parameterized gwd were closer to the analysis than medium resolution simulations with parameterized orographic gwd only but still did not fully simulate the mesospheric thermal response specifically the 80 km temperature enhancement was still underestimated in these simulations this suggests that higher spatial resolution is needed to adequately resolve extratropical gravity wave momentum fluxes

enso regimes reinterpreting the canonical and modoki el nino 1 we propose that the first two empirical orthogonal function eof modes of tropical pacific sea surface temperature sst anomalies do not describe different phenomena i e el nino southern oscillation enso and el nino modoki but rather the nonlinear evolution of enso we introduce two new uncorrelated indices e and c based on the leading eofs that respectively account for extreme warm events in the eastern and cold moderate warm events in the central equatorial pacific corresponding to regimes with different evolution recent trends in enso can be described as an increase in the central pacific c variability that is associated with stronger cold events as well as a reduction in the eastern pacific e variability within the cold moderate warm regime consistent with model projections however little can be said observationally with respect to the extreme warm regime