maps of titan s surface from 1 to 2 5 μm abstract we have acquired resolved images of titan with the adaptive optics systems pueo kir at the cfht hawaii and naos conica at the vlt chile we report here on images and maps when data at several orbital phases are available of titan s surface from observations taken during the last 4 years 2001 2004 in all the methane windows between 1 and 2 5 m namely at 1 08 1 28 1 6 and 2 m we present the only complete maps of titan currently available at 1 3 m a spectral window where titan appears particularly bright in spectroscopy with a resolution of about 200 km at best on the ground our surface maps show the bright and dark regions sharing titan s landscape with as much detail as possible from the ground and with high contrast in most cases from the information gathered by comparing the maps at different wavelengths we derive constraints on the ground s composition our results could complete optimize the return of the cassini huygens mission

titan s atmosphere from voyager infrared observations iii vertical distributions of hydrocarbons and nitriles near titan s north pole abstract the temperature structure and vertical distributions of minor stratospheric constituents in titan s north polar region have been inferred from the study of voyager 1 infrared spectra the data were recorded at grazing incidence over the limb and cover an approximate vertical range of 100 300 km the upper stratospheric temperature is retrieved from an analysis of the 7 7 m methane band in which the emission originates mainly from pressure levels between 0 01 and 5 mbar 120 and 375 km we find the thermal profile at 70 n to be significantly colder by 20 k than the equatorial one vertical distributions of the following absorbers were derived from the best fits obtained in the spectral region 200 1400 cm 1 for three different data sets corresponding to three different altitudes above the satellite s surface c 2 h 2 c 4 h 2 c 2 h 6 c 3 h 4 hcn hc 3 n and c 2 n 2 the mixing ratios of these species increase with height suggesting their formation in the upper stratosphere and above the abundances of c 3 h 8 and c 2 h 4 could only be obtained near the 1 5 mbar level when compared to the abundances derived at the equator we find the nitriles hc 3 n and c 2 n 2 and some of the hydrocarbons c 2 h 4 c 3 h 4 and c 4 h 2 to be considerably enhanced in the north polar region the upper limit of the co 2 abundance obtained near the north pole indicates a depletion of this gas with respect to the equator by a factor of at least 2 current available photochemical models are insufficient to interpret these observations

radar investigation of mars mercury and titan radar astronomy is the study of the surfaces and near surfaces of solar system objects using active transmission of modulated radio waves and the detection of the reflected energy the scientific goals of such experiments are surprisingly broad and include the study of surface slopes fault lines craters mountain ranges and other morphological structures electrical reflectivities contain information about surface densities and to some extent the chemical composition of the surface layers radar probes the subsurface layers to depths of the order of 10 wavelengths providing geological mapping and determinations of the object s spin state radar also allows one to study an object s atmosphere and ionic layers as well as those of the interplanetary medium precise measurements of the time delay to surface elements provide topographic maps and powerful information on planetary motions and tests of gravitational theories such as general relativity in this paper we limit our discussion to surface and near surface probing of mercury mars and titan and review the work of the past decade which includes fundamentally new techniques for earth based imaging the most primitive experiments involve just the measurement of the total echo power from the object the most sophisticated experiments would produce spatially resolved maps of the reflected power in all four stokes parameters historically the first experiments produced echoes from the moon during the period shortly after world war ii see e g evans 1962 but the subject did not really develop until the early 1960s when the radio equipment was sufficiently sensitive to detect echoes from venus and obtain the first doppler strip maps of that planet the first successful planetary radar systems were the continuous wave cw radar at the goldstone facility of the caltech s jet propulsion laboratory and the pulse radar at the mit lincoln laboratory all of the terrestrial planets were successfully studied during the following decade yielding the spin states of venus and mercury a precise value of the astronomical unit and a host of totally new discoveries concerning the surfaces of the terrestrial planets and the moon this work opened up at least a similar number of new questions although the early work was done at resolution scales on the order of the planetary radii very rapid increases in system sensitivities improved the resolution to the order of 100 km but always with map ambiguities recently unambiguous resolution of 100 m over nearly the entire surface of venus has been achieved from the magellan spacecraft using a side looking synthetic aperture radar reviews of the work up to the magellan era can be found in evans 1962 muhleman et al 1965 evans hagfors 1968 see chapters written by g pettengill t hagfors and j evans and ostro 1993 the radar study of venus from the magellan spacecraft was a tour de force and is well described in special issues of science volume 252 april 12 1991 and in the journal of geophysical research volume 97 august 25 and october 25 1992 venus will not be considered in this paper even though important polarization work on that planet continues at arecibo goldstone and the very large array vla in this paper we review the most recent work in earth based radar astronomy using new techniques of earth rotation super synthesis at the vla in new mexico operated by the national radio astronomy observatory and the recently developed long code techniques at the arecibo observatory in puerto rico operated by cornell university note it was recently brought to our attention that the vla software doubles the flux density of their primary calibrators consequently it is necessary to half the radar power and reflectivity numerical values in all of our published radar results from the vla goldstone radar the symbiotic relationship in these new developments for recent advances in our understanding of mercury and mars is remarkable vla imaging provides for the first time unambiguous images of an entire hemisphere of a planet and the long code technique makes it possible to map mars and mercury using the traditional range gated doppler strip mapping procedure which was apparently developed theoretically at the lincoln laboratory by paul green based on a citation in evans 1962 richard goldstein was the first to obtain range gated planetary maps of venus as reported in carpenter goldstein 1963 such a system was developed earlier for the moon as reported by pettengill 1960 and pettengill henry 1962 we first discuss the synthesis mapping technique

evidence for the exposure of water ice on titan s surface the smoggy stratosphere of saturn9s largest moon titan veils its surface from view except at narrow wavelengths centered at 0 83 0 94 1 07 1 28 1 58 2 0 2 9 and 5 0 micrometers we derived a spectrum of titan9s surface within these windows and detected features characteristic of water ice therefore despite the hundreds of meters of organic liquids and solids hypothesized to exist on titan9s surface its icy bedrock lies extensively exposed

interdecadal decadal climate variability from multicoral oxygen isotope records in the south pacific convergence zone region since 1650 a d 1 in the south pacific interdecadal decadal oceanic and atmospheric variability referred to as the interdecadal pacific oscillation ipo is most pronounced in the south pacific convergence zone spcz salinity front region here we have used annual average oxygen isotope 18o time series from five coral cores collected from fiji and tonga in this region to construct a fiji tonga interdecadal decadal pacific oscillation f t idpo index of low frequency 9 and 55 years climate variability back to 1650 a d we first demonstrate the consistency between this f t idpo index and a mean sea level msl pressure based spcz position index spi 1891 2000 thus verifying the ability of coral 18o to record past interdecadal decadal climatic variations in this region back to 1891 the f t idpo index is then shown to be synchronous with the ipo index 1856 2000 suggesting that this coral based index effectively represents the interdecadal decadal scale climate variance back to 1650 the regularity of the f t idpo index indicates that interdecadal decadal variability in the spcz region has been relatively constant over the past 350 years with a mean frequency of 20 years variance peaks near 11 and 35 years there is a consistent antiphase correlation of the f t idpo index and the interdecadal decadal components in equatorial pacific coral 18o series from maiana and palmyra this observation indicates that the eastward expansion westward contraction of the eastern salinity front of the western pacific warm pool wpwp occurs simultaneously 1 year with the westward eastward shift of the spcz salinity front during positive ipo negative ipo phases this is the same relationship observed during the phases of the el nino southern oscillation

twentieth century tropical sea surface temperature trends revisited 1 this study compares the global distribution of 20th century sst and marine air temperature trends from a wide variety of data sets including un interpolated archives as well as globally complete reconstructions apart from the eastern equatorial pacific all datasets show consistency in their statistically significant trends with warming everywhere except the far northwestern atlantic the largest warming trends are found in the middle latitudes of both hemispheres two of the sst reconstructions exhibit statistically significant cooling trends over the eastern equatorial pacific in disagreement with the un interpolated sst and marine air temperature datasets which show statistically significant warming in this region twentieth century trends in tropical marine cloudiness precipitation and slp from independent data sets provide physically consistent evidence for a reduction in the strength of the atmospheric walker circulation accompanied by an eastward shift of deep convection from the western to the central equatorial pacific

titan s 2 μm surface albedo and haze optical depth in 1996 2004 1 we observed titan in 1996 2004 with high resolution 2 m speckle and adaptive optics imaging at the w m keck observatory by observing in a 2 m broadband filter we obtain images that have contributions from both titan s surface and atmosphere we have modeled titan s atmosphere using a plane parallel radiative transfer code that has been corrected to agree with 3 d monte carlo predictions we find that titan s surface albedo ranges from 0 02 in the darkest equatorial region of the trailing hemisphere to 0 1 in the brightest areas of the leading hemisphere over the past quarter of a saturnian year haze optical depth in titan s southern hemisphere has decreased substantially from a value of 0 48 in 1996 down to 0 18 in 2004 while the northern haze has been increasing over the past few years as a result of these changes in 2004 the north south haze asymmetry at k band has disappeared

a coral oxygen isotope record from the northern red sea documenting nao enso and north pacific teleconnections on middle east climate variability since the year 1750 a 245 year coral oxygen isotope record from the northern red sea ras umm sidd egypt 28 n in bimonthly resolution is presented the mean annual coral 18o signal apparently reflects varying proportions of both sea surface temperature and 18oseawater variability in conjunction with instrumental observations of climate the coral record suggests for interannual and longer timescales that colder periods are accompanied by more arid conditions in the northern red sea but increased rainfall in the southeastern mediterranean whereas warmer periods are accompanied by decreased rainfall in the latter and less arid conditions in the northern red sea a 70 year oscillation of probably north atlantic origin dominates the coral time series interannual to interdecadal variability is correlated with instrumental indices of the north atlantic oscillation nao the el nino southern oscillation enso and north pacific climate variability the results suggest that these modes contributed consistently to middle east climate variability since at least 1750 preferentially at a period of 5 7 years

wind driven surface waves on titan the surface of titan represents the largest surface area in the solar system essentially unexplored although recent observations from hubble space telescope and ground based telescopes using adaptive optics have given perhaps the first low resolution indications of its nature whilst early models citing global oceans have been all but abandoned substantial bodies of liquid up to several hundred kilometers in extent are not precluded if such reservoirs do exist then in the presence of any surface winds it is expected that wind driven surface waves will be generated as on earth gravity remains the dominant controlling factor for such waves with surface tension and viscous effects only becoming significant below wavelengths of several centimeters empirical models used for terrestrial wind driven sea waves are adapted to investigate the properties of such waves on titan using predicted parameters for titan s liquids significant wave height peak period wavelength phase speed and wave steepness are predicted as a function of wind speed and liquid body extent it is found that waves will grow to a limiting height limiting wavelength and limiting period which are all inversely proportional to gravity the limiting significant wave height under the action of a 1 m s 1 titan wind over 50 km for example is predicted to be 0 2 m compared to 0 02 m on earth under similar circumstances more interesting however is the wave growth prior to this limiting value a useful visualization is that surface waves on a titan sea arising from surface wind speeds of 0 3 and 1 m s 1 will resemble in scale waves on earth generated by terrestrial winds of 1 and 3 m s 1 respectively these particular titan waves will have nearly 3 times the period and travel almost 3 times slower than the terrestrial waves however the wave parameters predicted in this work have potential surface mission implications for the european space agency s huygens probe which will land on titan in 2004 conversely their measurement by instruments on board huygens and nasa s cassini spacecraft could yield important planetological information

clay mineral composition of pampean loess argentina abstract this paper summarizes current knowledge on clay minerals on the pleistocene and holocene pampean loess detrital illite is the predominant clay mineral of the vitroclastic loess with minor amounts of montmorillonite and kaolinite minerals the illite with a small k content corresponds to a highly illitic illite smectite component in paleosols its crystallinity index decreases and there are more expandable interlayers as in the chinese loess

titan evidence for seasonal change a comparison of hubble space telescope and voyager images abstract images of titan were obtained by the hubble space telescope hst on 26 august 1990 comparison with voyager 1 and voyager 2 images obtained 10 and 9 years earlier shows that the seasonal hemispheric brightness asymmetry has reversed near 440 and 550 nm wavelengths with the northern hemisphere now being brighter an additional noisy hst image at 889 nm wavelength for which there are no analogous voyager data suggests that the southern hemisphere may have been brighter than the northern at that wavelength in 1990

last millennium climate and its variability in ccsm4 abstractan overview of a simulation referred to as the last millennium lm simulation of the community climate system model version 4 ccsm4 is presented the ccsm4 lm simulation reproduces many large scale climate patterns suggested by historical and proxy data records with northern hemisphere nh and southern hemisphere sh surface temperatures cooling to the early 1800s common era by 0 5 c nh and 0 3 c sh followed by warming to the present high latitudes of both hemispheres show polar amplification of the cooling from the medieval climate anomaly mca to the little ice age lia associated with sea ice increases the lm simulation does not reproduce la nina like cooling in the eastern pacific ocean during the mca relative to the lia as has been suggested by proxy reconstructions still dry medieval conditions over the southwestern and central united states are simulated in agreement with proxy indicators for these regions strong global cooling is associated with large volcanic erup

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

global scale surface spectral variations on titan seen from cassini vims we present global scale maps of titan from the visual and infrared mapping spectrometer vims instrument on cassini we map at 64 near infrared wavelengths simultaneously covering the atmospheric windows at 0 94 1 08 1 28 1 6 2 0 2 8 and 5 m with a typical resolution of 50 km pixel or a typical total integration time of 1 s our maps have five to ten times the resolution of ground based maps better spectral resolution across most windows coverage in multiple atmospheric windows and represent the first spatially resolved maps of titan at 5 m the vims maps provide context and surface spectral information in support of other cassini instruments we note a strong latitudinal dependence in the spectral character of titan s surface and partition the surface into 9 spectral units that we describe in terms of spectral and spatial characteristics

spatially resolved images of titan by means of adaptive optics abstract images of titan were acquired with the adonis adaptive optics system installed at the eso 3 6 m telescope in la silla chile the near infrared range from 1 2 5 m was covered in 1994 and 1995 in the methane atmospheric windows at 1 3 1 6 and 2 0 m with narrow band filters and cvf diffraction limited images were obtained 0 14 arcsec at 2 m thus allowing us to resolve the titan disk we have corrected the images for systematic effects removed center to limb variation and applied deconvolution processes to our data the contrast on the images is on the order of 30 both the leading and trailing hemispheres were observed the 2 m images presented in this paper show a broad bright feature on the surface of titan s leading hemisphere near 114 lcm which is in agreement with the hst images and with spectroscopy performed at these longitudes from the ground that show a higher geometric albedo on titan s leading side high quality flat fielding of our data has highlighted the presence of at least two main bright spots within the equatorial region the trailing hemisphere of titan s surface is not completely dark but shows brightness near the poles with some north to south asymmetry the northern latitudes are uniformly brighter than the lower equatorial and southern latitudes factor of about 2 our results bring new constraints on the models of the satellite s surface

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

paleoclimate proxy perspective on caribbean climate since the year 1751 evidence of cooler temperatures and multidecadal variability 1 annually resolved coral 18o and sr ca records from southwestern puerto rico are used to investigate caribbean climate variability between 1751 and 2004 c e mean surface ocean temperatures in this region have increased steadily by about 2 c since the year 1751 with sr ca data indicating 2 1 0 8 c and 18o data indicating 2 7 0 5 c coral geochemical records from across the tropics demonstrate that regional variability is important for understanding climate variations at centennial time scales a strong multidecadal salinity signal in the oxygen isotope data correlates with observed multidecadal temperature variations in the northern hemisphere instrumental wind and precipitation data indicate that the most recent coral isotopic variations are caused by expansion and contraction of the steep regional salinity gradient forced by trade wind anomalies through meridional ekman transport the timing of the fluctuations suggests that the multidecadal scale wind and surface circulation anomalies might play a role in atlantic temperature variability and meridional overturning circulation but further work is needed to confirm this suggestion

proxy based northern hemisphere surface temperature reconstructions sensitivity to method predictor network target season and target domain abstract results are presented from a set of experiments designed to investigate factors that may influence proxy based reconstructions of large scale temperature patterns in past centuries the factors investigated include 1 the method used to assimilate proxy data into a climate reconstruction 2 the proxy data network used 3 the target season and 4 the spatial domain of the reconstruction estimates of hemispheric mean temperature are formed through spatial averaging of reconstructed temperature patterns that are based on either the local calibration of proxy and instrumental data or a more elaborate multivariate climate field reconstruction approach the experiments compare results based on the global multiproxy dataset used by mann and coworkers with results obtained using the extratropical northern hemisphere nh maximum latewood tree ring density set used by briffa and coworkers mean temperature reconstructions are compared for the full nh tropics and extratropics land and ocean and ext

ground based radar observations of titan 2000 2008 abstract we have observed titan with the arecibo observatory s 12 6 cm wavelength radar system during the last eight oppositions of the saturn system with sufficient sensitivity to characterize its scattering properties as a function of sub earth longitude in a few sessions the green bank telescope was used as the receiving instrument in a bistatic configuration to boost sub radar track length and integration time radar echo spectra have been obtained for a total of 92 viewing geometries with sub earth locations scattered through all longitudes and at latitudes between 7 6 s and 26 3 s close to the maximum southern excursion of the sub earth track we find titan to have globally average radar albedos at this wavelength of 0 161 in the opposite circular polarization sense as that transmitted oc and 0 074 in the same sense sc giving a polarization ratio sc oc of 0 46 these values are intermediate between lower reflectivity rocky surfaces and higher reflectivity clean icy surfaces the variations with longitude in general mirror the surface brightness variations seen through the infrared atmospheric windows xanadu regio s radar reflectivity and polarization ratio are higher than the global averages and suggest that its composition is relatively cleaner water ice or possibly some other material with low propagation loss at radio wavelengths for all echo spectra most of the power is in a broad diffuse component but with a specular component whose strength and narrowness is highly variable as a function of surface location for all data we fit a sum of the standard hagfors scattering law describing the specular component and an empirical diffuse radar scattering model to extract bulk parameters of the surface many areas exhibit very narrow specular reflections implying terrain that are quite flat on centimeter to meter scales over spans of tens to perhaps hundreds of kilometers the proportion of spectra showing these narrow specular echoes has fallen significantly over the observational time span indicating either a latitudinal effect related to terrain differences or changing surface conditions over the past several years a few radar tracks especially those from the 2008 session overlap some high resolution cassini radar imagery swaths to allow a direct comparison with terrain

a large cloud outburst at titan s south pole images of titan acquired over five nights in october 2004 using the adaptive optics system at the keck observatory show dramatic increases in tropospheric cloud activity at the south pole compared with all other images of titan clouds to date during this time titan s south polar clouds brightened to more than 18 times their typical values the cassini ta flyby of titan occurred as this storm was rapidly dissipating we find that the brightness of this cloud outburst is consistent with the dramatic transient brightening of titan observed in atmospheric windows on two nights in 1995 by griffith et al griffith c a owen t miller g a geballe t 1998 nature 395 6702 575 578 if we scale the brightness of the cloud by projecting it onto the equator while apparently infrequent the fact that large cloud events have been observed in different seasons of titan s year indicates that these large storms might be a year round phenomenon on titan we propose possible mechanisms to explain these occasional short term increases in titan s cloud activity

intercomparison of coral oxygen isotope data and historical sea surface temperature sst potential for coral based sst field reconstructions we examine the extent to which the large scale features of the sea surface temperature sst anomaly field are represented by a sparse observational network of coral oxygen isotope 18o time series regression of annually averaged 18o data against gridded estimates of local sst anomaly within the period 1856 1990 confirm the literature regression of 18o anomaly on sst anomaly for indo pacific corals however while interannual sst variability is generally well represented by individual coral time series observed decadal and secular variability does not always display a linear relationship to local sst anomaly instead many records appear to better recover nonlocal large scale phenomena which in turn are related to either the coral local sst or sst covariant changes in seawater 18o we employ empirical orthogonal function eof analysis to identify common patterns of variability in the coral data we find two significant patterns which are interpretable as the oceanographic signature of the el nino southern oscillation enso and as a near global warming in which the eastern equatorial pacific cools a third pattern weakly resembles the pacific decadal oscillation these modes are seen more clearly in a singular vector decomposition svd of the covariance between the coral data and the dominant patterns of large scale historical sst variability the results are consistent with those found in eof and svd analyses of sst data from the coral locations as additional coral based proxy estimates become available they will improve the resolution of the patterns recovered these results suggest that a sparse network of coral data may be used to reconstruct interannual secular and decadal sst variability for preinstrumental periods albeit with large uncertainty

analysis of voyager 2 images of jovian lightning abstract voyager 2 images have been examined and found to contain bright spots due to lightning activity that is confined to two narrow latitude bands centered at 49 n and 13 5 n latitude and to a single region near 60 n latitude no lightning activity is observed in the southern hemisphere even though a large area was observed with the same sensitivity as that used for northern hemisphere observations the brightest band of lightning activity occurs at 49 n but no unusual cloud features can be associated with this activity this result is consistent with the depth of the lightning activity being 80 km below the ammonia clouds and thus not producing readily observed disturbances in the visible clouds the secondary band of lightning activity that appears at 13 5 n is restricted in longitude to the disturbed zone one of the two storms found in this tropical band is very close to the location of a bright cloud feature that extends some 3 5 in latitude if it is assumed that the deflection of this feature is caused by the westerly flow of an air parcel over a hill in the potential temperature surface located at the 5 to 10 bar level then the air parcel moving over the hill would be forced to rise sufficiently high that the free convection level would be reached this situation could be the cause of the lightning activity in this region the energy dissipation rate by lightning activity in the voyager 2 images is 3200 w km2 when attenuation by clouds is considered the energy dissipation rate is approximately 50 greater than that found in the voyager 1 images the ratio of the energy dissipated by jovian lightning to the thermal flux available to drive convection motions is found to be three decades larger than the terrestrial ratio this value is similar to the ratio for the two planets found by ingersoll 1990 for the conversion of thermal energy flux to mechanical energy

toward forward modeling for paleoclimatic proxy signal calibration a case study with oxygen isotopic composition of tropical woods a forward model of the oxygen isotopic composition 18o of wood cellulose is parameterized for time series prediction in tropical environments and driven with meteorological data observed at la selva biological research station costa rica for 1985 2001 monthly resolution model results correlate modestly r 0 34 p 0 05 with observed isotopic data with higher correlation r 0 45 p 0 01 over the earliest 10 years of comparison and nonsignificant correlation over the most recent 6 years of record analysis of model output for la selva suggests that isotopic variations are strongly controlled by rainfall amount the model simulates an analogous but stronger than observed negative isotopic anomaly associated with positive july september rainfall anomalies during el nino southern oscillation enso warm phase event years simulated tree isotope data for the global tropics suggest that a network of well replicated data series from selected locations may resolve the large scale precipitation anomaly pattern associated with enso

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

an 8 century tropical atlantic sst record from the cariaco basin baseline variability twentieth century warming and atlantic hurricane frequency 1 we present the first direct comparison and calibration of a downcore foraminiferal mg ca record to historical instrumental sea surface temperature sst mg ca measured on the planktic foraminifer globigerina bulloides from a cariaco basin sediment core strongly correlate with spring march may instrumental ssts between a d 1870 and 1990 a mg ca sst equation is derived and a paleo sst record is presented spanning the last 8 centuries an interval that includes the end of the medieval warm period and the little ice age the long term record displays a surprising amount of variability the temperature swings are not necessarily related to local upwelling variability but instead represent wider conditions in the caribbean and western tropical atlantic the mg ca sst record also captures the decadal and multidecadal variability observed in records of global land and sea surface temperature anomalies and atlantic tropical storm and hurricane frequency over the late nineteenth and twentieth centuries a divergence between the sst proxy record and atlantic storm frequency around 1970 appears to reflect a fundamental change in atlantic hurricane behavior noted in historical data on average twentieth century temperatures are not the warmest in the entire record but they do show the largest increase in magnitude and fastest rate of sst change over the last 800 a

sea surface temperature and salinity variability at bermuda during the end of the little ice age 1 we use geochemical and isotope measurements on a 225 year old brain coral diploria labyrinthiformis from the south shore of bermuda 64 w 32 n to construct a record of decadal to centennial scale climate variability the coral was collected alive and annual density bands visible in x radiographs delineate cold and warm seasons allowing for precise dating coral skeletons incorporate strontium sr and calcium ca in relative proportions inversely to the sea surface temperature sst in which the skeleton is secreted previous studies on this and other coral colonies from this region document the ability to reconstruct mean annual and wintertime sst using sr ca measurements goodkin et al 2007 2005 the coral based records of sst for the past 2 centuries show abrupt shifts at both decadal and centennial timescales and suggest that sst at the end of the little ice age between 1840 and 1860 was 1 5 0 4 c colder than today 1990s coral reconstructed sst has a greater magnitude change than does a gridded instrumental sst record from this region this may result from several physical processes including high rates of mesoscale eddy propagation in this region oxygen isotope values 18o of the coral skeleton reflect changes in both temperature and the 18o of seawater ow where ow is proportional to sea surface salinity sss we show in this study that mean annual and wintertime 18o of the carbonate oc are correlated to both sst and sss but a robust quantitative measure of sss is not found with present calibration data in combination however the sr ca and oc qualitatively reconstruct lower salinities at the end of the little ice age relative to modern day temperature changes agree with other records from the bermuda region radiative and atmospheric forcing may explain some of the sst variability but the scales of implied changes in sst and sss indicate large scale ocean circulation impacts as well

underestimation of volcanic cooling in tree ring based reconstructions of hemispheric temperatures a large volcanic eruption in ad 1258 1259 is expected to have caused substantial climate cooling but evidence for this effect is absent from tree ring based temperature reconstructions numerical modelling of tree growth shows that the lack of cooling is probably an artefact caused by low sensitivity to cooling in trees growing near the treeline

titan s surface composition and variability from the near infrared albedo abstract we report observations of titan covering the 1 075 1 28 1 6 and 2 0 m windows which show variations with the orbital phase implying variability of the satellite s geometric albedo as found earlier by other authors the observations cover the region 4400 to 9600 cm 1 and were taken in june 1991 august 1993 and september 1994 using the fourier transform spectrometer at the cfh telescope hawaii the resolving power was 10000 1000 and 300 for the 1991 1993 and 1994 spectra respectively the data sets cover titan s greatest western elongation and opposite conjunctions we find titan s geometric albedo to be about the same 0 29 at 1 28 and 1 075 m on the other hand our observations of uranus show the 1 28 m albedo to be lower by 30 than that in the 1 075 m window the geometric albedos in the 1 6 and 2 0 m methane windows on titan are clearly lower 0 20 and 0 16 respectively at the four wavelengths a noticeable decrease in geometric albedo is observed near greatest western elongation with respect to inferior and superior conjunctions the sum of the existing titan data point to a bright leading side and a darker trailing one with a maximum brightness near 120 20 orbital longitude and a minimum near 230 20 despite important uncertainties in the value of the ch 4 absorption coefficients in the window regions modeling titan s observed albedos strongly suggests the existence of a surface material with a comparable albedo at 1 075 and 1 28 m 0 4 0 5 but much darker at 1 6 and 2 0 m about 0 2 titan s surface spectrum appears consistent with that of hyperion and we suggest that this behavior may be due to the dominant presence of water ice on titan s surface the inhomogeneity of the surface implies that some other material e g hydrocarbon lakes is mixed with water ice in variable proportions

titan s surface revealed by hst imaging we present for the first time relative albedo maps of titan s surface the maps were made from images taken by the hubble space telescope s planetary camera 295 km per pixel through atmospheric windows at 940 and 1080 nm coverage at all longitudes and between 45 s and 60 n was obtained with 14 orbits from 4 18 october 1994 each image is characterized by haze with both limb effects brightening and a large north south contrast subtracting an averaged image from each frame removes haze effects and reveals surface features of 10 maximum contrast many features are clearly visible in multiple images and in both filters but the surface map is dominated by a large bright roughly rectangular feature centered at 110 w 10 s and elongated in an east west direction 4000 2500 km2 this feature and others indicate the diversity of titan s surface we consider the origin of the bright feature in an otherwise dark landscape and suggest that highland washing by methane rainfall is a likely mechanism

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

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

tidal effects of disconnected hydrocarbon seas on titan thermodynamic and photochemical arguments1 4 suggest that titan the largest satellite of saturn has a deep ocean of liquid hydrocarbons at visible wavelengths titan s surface is obscured by a thick stratospheric haze but radar observations5 7 have revealed large regions of high surface reflectivity that are inconsistent with a global hydrocarbon ocean titan s surface has also been imaged at infrared wavelengths8 10 and the highest resolution data obtained by the hubble space telescope show clear variations in surface albedo and or topography10 the natural interpretation of these observations is that titan like the earth has continents and oceans but titan s high orbital eccentricity poses a problem for this interpretation as the effects of oceanic tidal friction would have circularized titan s orbit for most configurations of oceans and continents1 11 here we argue that a more realistic topography in which liquid hydrocarbons are confined to a number of disconnected seas or crater lakes may satisfy both the dynamical and observational constraints

geological evolution of titan s equatorial regions possible nature and origin of the dune material in 13 years infrared observations from the visual and infrared mapping spectrometer onboard cassini provided significant hints about the spectral and geological diversity of titan s surface the analysis of the infrared ir signature of spectral units enables constraining the surface composition which is crucial for understanding possible interactions between titan s interior surface and atmosphere here we investigate a selection of areas in the equatorial regions imaged by cassini s instruments which exhibit an apparent transition from the visual and infrared mapping spectrometer ir bright to the ir blue and ir brown units from false color composites using red 1 57 1 27 m green 2 01 1 27 m and blue 1 27 1 08 m by applying an updated radiative transfer model we extract the surface albedo of ir units identified in these regions then we compare them with synthetic mixtures of two expected components on titan s surface namely water ice and laboratory tholins this allows us to reconnect the derived composition and grain size information to the geomorphology observed from radio detection and ranging instrument radar synthetic aperture radar images we interpret ir bright units as hills and plains coated by organic material and incised by fluvial networks erosion products are transported downstream to areas where ir blue units are seen near the ir bright units these units enriched in water ice are most likely outwash plains hosting debris from fluvial erosion farther away from the ir bright units the ir brown units are dominantly made of organics with varied grain sizes ranging from dust to sand sized particles that form the dune fields the transition areas therefore exhibit trends in water ice content and grain size supported by geomorphological observations

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

evidence for surface heterogeneity on titan unlike all other planetary satellites saturn s moon titan has a massive atmosphere1 8 at visible wavelengths a thick stratospheric haze hides the surface from view the emission from titan in the infrared is largely from methane nitrogen and hydrogen also in the stratosphere4 in the near infrared however the extinction from haze decreases and narrow windows exist in which the atmosphere absorbs only weakly9 14 and through which we might therefore catch a glimpse of the surface within two of these windows lemmon et a1 15 16 recently observed a difference in titan s albedo when the satellite was at eastern and western elongation with respect to saturn although these observations could be taken to imply that titan s surface is heterogeneous and therefore is not covered by a global methane ethane ocean as predicted previously7 they could also be explained by transient clouds here i present observations from two more rotational periods which record the same albedo difference indicating that the heterogeneity is most unlikely to be associated with transient features and must be intrinsic to the surface these results also imply that titan is locked in a synchronous orbit about saturn

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

speckle imaging of titan at 2 microns surface albedo haze optical depth and tropospheric clouds 1996 1998 we present results from 14 nights of observations of titan in 1996 1998 using near infrared centered at 2 1 microns speckle imaging at the 10 meter w m keck telescope the observations have a spatial resolution of 0 06 arcseconds we detect bright clouds on three days in october 1998 with a brightness about 0 5 of the brightness of titan using a 16 stream radiative transfer model disort to model the central equatorial longitude of each image we construct a suite of surface albedo models parameterized by the optical depth of titan s hydrocarbon haze layer from this we conclude that titan s equatorial surface albedo has plausible values in the range of 0 0 20 titan s minimum haze optical depth cannot be constrained from this modeling but an upper limit of 0 3 at this wavelength range is found more accurate determination of titan s surface albedo and haze optical depth especially at higher latitudes will require a model that fully considers the 3 dimensional nature of titan s atmosphere

probing titan s atmosphere with the 1995 august stellar occultation abstract on 1995 august 21 saturn s moon titan occulted the 13th magnitude star gsc5254 00997 the predawn event was observed at 2 3 m with the nasa 3 0 m infrared telescope facility we measured the average atmospheric scale height between latitudes 50 s and 67 s by fitting isothermal models to the immersion portion of the occultation lightcurve within the altitude range of 300 to 500 km we find an isothermal scale height of titan s sunset atmosphere of 55 9 km our derived temperature of 180 30 k is consistent with modeled temperature profiles derived from voyager 1 iris observations a coustenis and b bezard 1995 icarus 115 126 140 and the 28 sagittarii occultation event w b hubbard et al 1993 astron astrophys 269 541 563 the atmospheric albedo asymmetry due to low level haze caldwell et al 1992 icarus 96 1 9 is inferred from the difference in titan s center of light determined from precise astrometric measurements of images of titan and the star before and after the occultation and the actual center of titan determined from the occultation analysis we find the southern hemisphere to be brighter than the northern hemisphere a result consistent with combes et al 1997 icarus 129 482 497 gibbard et al 1999 icarus 139 189 201 and smith et al 1996 icarus 119 336 349

regional geomorphology and history of titan s xanadu province titan s enigmatic xanadu province has been seen in some detail with instruments from the cassini spacecraft the region contains some of the most rugged mountainous terrain on titan with relief over 2000 m xanadu contains evolved and integrated river channels impact craters and dry basins filled with smooth radar dark material perhaps sediments from past lake beds arcuate and aligned mountain chains give evidence of compressional tectonism yet the overall elevation of xanadu is puzzlingly low compared to surrounding sand seas lineations associated with mountain fronts and valley floors give evidence of extension that probably contributed to this regional lowering several locations on xanadu s western and southern margins contain flow like features that may be cryovolcanic in origin perhaps ascended from lithospheric faults related to regional downdropping late in its history radiometry and scatterometry observations are consistent with a water ice or water ammonia ice composition to its exposed eroded fractured bedrock both microwave and visible to near infrared v nir data indicate a thin overcoating of organics likely derived from the atmosphere we suggest xanadu is one of the oldest terrains on titan and that its origin and evolution have been controlled and shaped by compressional and then extensional tectonism in the icy crust and ongoing erosion by methane rainfall

a 170 year sr ca and ba ca coral record from the western pacific warm pool 2 a window into variability of the new ireland coastal undercurrent 1 a porites coral from new ireland 2 5 s 150 5 e at the heart of the pacific warm pool records variations of ba ca back to the early 1820s the new ireland coastal undercurrent which flows along the north coast and transports high nutrient thermocline waters is thought to be the main source of the ba enrichment observed in the coral during el nino between the 1850s and the 1960s frequent large ba peaks indicate that nutrients were available during both phases of el nino southern oscillation enso during la nina ba could be advected along the south equatorial current also during this period clusters of ba ca peaks at nearly decadal timescale generally coincide with the return time of a strong el nino in accord with the high decadal variance of nino3 sea surface temperatures ba enrichment in this coral primarily reflects the stratification in the thermocline that controls vertical mixing the coral records long term changes in those properties affecting nutrients in surface waters with reduced ba after the 1960s and even less between 1823 and 1850 these reductions are tentatively attributed to the high rate of warming at the end of the dalton minimum and since the mid 20th century an ensuing weakening of the trade winds may have produced a more stratified equatorial thermocline hindering the transport of ba and nutrients from the undercurrent to the shallow coastal waters north of new ireland

mechanisms of hemispherically symmetric climate variability inspired by paleoclimate evidence that much past climate change has been symmetric about the equator the causes of hemispherically symmetric variability in the recent observational record are examined using the national centers for environmental prediction national center for atmospheric research reanalysis dataset and numerical models it was found that the dominant cause of hemispherically symmetric variability is the el nino southern oscillation during an el nino event the tropics warm at all longitudes and the subtropical jets in both hemi spheres strengthen on their equatorward flanks poleward of the tropical warming there are latitude belts of marked cooling extending from the surface to the tropopause in both hemispheres at all longitudes and in all seasons the midlatitude cooling is caused by changes in the eddy driven mean meridional circulation changes in the transient eddy momentum fluxes during an el nino event force upper tropospheric ascent in midlatitudes through a balance between the eddy fluxes and the coriolis torque the eddy driven ascent causes anomalous adiabatic cooling which is primarily balanced by anomalous diabatic heating using a quasigeostrophic spherical model forced by an imposed surface eddy disturbance of chosen wave number and frequency it is shown that the anomalous eddy momentum fluxes are caused by the impact that the changes in the tropically forced subtropical jets have on the propagation in the latitude height plane of transient eddies changes in zonal winds and associated changes in the meridional gradient of potential vorticity create an anomalous region of low meridional wavenumber in the midlatitudes that refracts waves away both poleward and equatorward tropical forcing of variability in the eddy driven mean meridional circulation is another way in addition to rossby wave teleconnections whereby the tropics can influence extratropical climate unlike teleconnections this mechanism causes climate variability that has strong zonally and hemispherically symmetric components and operates throughout the seasonal cycle

the tide in the seas of titan the surface temperature of titan1 is about 95 k between the melting point 90 6 k and the boiling point 118 k of methane at the total surface pressure of 1 6 bar voyager 1 ir observations1 2 suggest a methane abundance in the lower atmosphere 0 19 of saturation comparison with the mean h2o abundance in the earth s atmosphere suggests1 a ch4 saturation level 0 5 thus the volume mixing ratio of methane is probably about 6 and methane begins to condense out some 40 km above the surface it is therefore a natural speculation that methane exists in the liquid state on the surface of titan the atmospheric ch4 corresponds to a liquid layer 10 m deep but it is unlikely that the buffer for atmospheric methane would have a capacity equal only to that of the atmosphere itself on earth the quantity of water in the oceans is on average several times 104 the quantity of water vapour in the atmosphere thus if titan has oceans of liquid ch4 they are probably 100 m deep we argue here that if this ocean exists the present high eccentricity of titan requires its depth to be 400 m and that such an ocean can be detected by radar techniques