thermal and dynamical changes of the zonal mean state of the thermosphere during the 2009 ssw gaia simulations changes of the zonal mean state of the thermosphere during the 2009 stratospheric sudden warming ssw have been investigated using the ground to topside model of atmosphere and ionosphere for aeronomy gaia model both the zonal mean thermal and dynamical structure of the thermosphere exhibit pronounced changes during the ssw in terms of zonal mean temperature and winds first the zonal mean temperature above 100 km altitude drops at all latitudes except for in a narrow band around 60 n such temperature perturbations are found to be dominantly caused by changes in direct heating cooling processes related to solar radiation and thermal heat conduction at high latitudes but by dynamical processes in tropical regions second the zonal mean zonal wind experiences a strong westward perturbation in the tropical thermosphere along with distinct change in the meridional circulation this change consists of two parts one is a global scale north to south flow accompanied with upwelling downwelling in the northern southern polar region the other is a fountain like flow in tropical lower thermosphere the large enhancement of semidiurnal tides is suggested to be the primary cause for the fountain like flow

application of thermochronology to hydrothermal ore deposits thermochronology finds many applications in economic geology utilizing temperature sensitive radiometric dating techniques to reveal low temperature upper crustal processes can elucidate many aspects of deposit genesis including timing and duration of mineralization processes rate of exhumation and erosion of intrusive ore deposits and comparative preservation potential the tools are utilized to best advantage when combined with other thermochronometry techniques that provide complementary information in addition when thermochronometers are combined with geochronometers e g zircon u pb over 800 c of thermal history is revealed from emplacement to erosion fig 1 with the advent of computational algorithms that provide more accurate and detailed models of thermochronology results the economic geologist has a powerful tool to use when assessing economic favorability of a region or prospect this chapter summarizes the various ways that low temperature thermochronometers have been utilized in studies of economic mineralization and primarily focuses on studies of porphyry ore deposits these deposits are well characterized and provide a good platform from which to demonstrate the extended understanding of ore formation processes that is provided by thermochronology studies in this section we review the fundamental application of u th he fission track and 40ar 39ar thermochronometry methods to mineralized systems we then present a synopsis of how these techniques can be used in thermal history analysis either alone or in combination with other chronometers in order to provide more information on deposit genesis the discussion is presented from low through to higher temperature thermochronometers corresponding to their presentation on figure 1 u th he thermochronology as documented earlier in the volume u th he thermochronology is based on measuring the accumulation of radiogenic 4he produced from u and th decay the daughter helium is retained until the mineral is heated to a temperature at which its structure and helium retentivity change this closure temperature varies from

migrating and nonmigrating semidiurnal tides in the upper atmosphere excited by tropospheric latent heat release migrating and nonmigrating semidiurnal tides

the ktb apatite fission track profiles building on a firm foundation abstract deep boreholes serve as natural laboratories for testing thermochronometers under geological conditions the kontinentale tiefbohrung ktb is an interesting candidate because the geological evidence suggests that approximate isothermal holding since the last documented exhumation in the late cretaceous to palaeocene is a reasonable assumption for the thermal histories of the ktb samples we report 30 new apatite fission track ages and 50 new mean confined track lengths determined on cores from the 4 km deep pilot hole the and external detector ages are consistent with the population ages from earlier studies and together define a clear age profile the mean track lengths from this and earlier studies reveal the effects of experimental factors the measured age and length profiles are compared with the predictions of 24 annealing models for isothermal holding there are clear discrepancies between the measured and calculated profiles down to 1 5 km depth the measured mean track lengths are shorter than the predicted the balance of methodological evidence indicates that this is due to seasoning i e a shortening of the fossil confined tracks without attendant age reduction from 2 5 to 4 0 km depth the mean track lengths are longer than the predictions this suggests that the bias model that weights the probabilities of observing tracks of different length and which is based on experiments relating surface track densities to mean track lengths is not appropriate for confined tracks experimental and methodological factors are sometimes difficult to disentangle but present a sufficient margin for there to be no need to go against the independent geological evidence unknown geological events cannot be ruled out but their existence cannot be inferred from the fission track data alone much less can the nature or magnitude of such events be specified

observations of global ionospheric responses to the 2009 stratospheric sudden warming event by formosat 3 cosmic 1 the global ionospheric response to a stratospheric sudden warming ssw is studied using three dimensional electron density maps derived from radio occultation observations of formosat 3 cosmic during the 2009 ssw periods results show that the ionospheric electron density at eia crests exhibit a morning early afternoon increase followed by an afternoon decrease and an evening increase indicative of a semidiurnal component during the ssw period which is consistent with recent studies the latitude altitude electron density slice maps show that the ssw related modifications of the equatorial plasma fountain interact with the existing summer to winter neutral winds and resulting in a north south asymmetry the global ionospheric response shows a clear longitudinal dependence in the equatorial plasma fountain enhancement during morning early afternoon inferred from the duration of the equatorial ionization anomaly eia enhancement following the enhancement prominent global eia reductions resulting from the equatorial plasma fountain weakening in the afternoon sector are seen the ionospheric response to the 2009 ssw event is also compared with the usual seasonal variation during january february 2007 instead of showing the electron density increase in the northern hemisphere and decrease in the southern hemisphere as the usual seasonal variation does the ssw period ionosphere shows prominent global electron density reductions in the afternoon period during the 2009 ssw event

quantifying exhumation from apatite fission track analysis and vitrinite reflectance data precision accuracy and latest results from the atlantic margin of nw europe

equatorial vertical drift modulation by the lunar and solar semidiurnal tides during the 2013 sudden stratospheric warming during the 2013 stratospheric sudden warming ssw period the jicamarca unattended long term investigations of the ionosphere and atmosphere julia radar at jicarmarca peru observed low latitude vertical drift modulation with lows of 0 12 m s daytime maximum drifts between 6 13 and 22 25 january and enhanced drifts up to 43 m s between 15 snd 19 january the ncar thermosphere ionosphere mesosphere electrodynamics general circulation model reproduces the prevailing vertical drift feature and is used to examine possible causes the simulations indicate that the modulation of the vertical drift is generated by the beating of the semidiurnal solar sw2 and lunar m2 tides during the ssw period the beating is observable since the magnitudes of lunar and solar semidiurnal tidal amplitudes are comparable the theoretical beating frequency between sw2 and m2 is 1 15 13 day which may be modified due to phase changes this study highlights the importance of the lunar tide during ssw periods and indicates that the equatorial vertical drift modulation should be observable at other longitudes as well

thermal diffusivity measurements of porous methane hydrate and hydrate sediment mixtures 1 an experiment has been constructed to measure thermal diffusivity of methane hydrate and methane hydrate sand sediment mixtures thermal diffusivities of porous methane hydrate 40 pore space filled with methane gas and mixtures of methane hydrate with platte valley sand and blake ridge sediment have been measured between the temperature range 265 k and 281 k at pressures between 4 35 and 7 65 mpa thermal diffusivities of porous methane hydrate ranged between 3 1 10 7 and 3 3 10 7 m2 s thermal diffusivity of 0 4 porosity methane hydrate was found to have inverse dependence on temperature whereas the thermal diffusivity of methane hydrate sediment sand mixtures has positive temperature dependence thermal diffusivity of methane hydrate sand sediment mixtures increased with increasing hydrate volume fraction to a maximum between about 30 and 35 vol in sand and between about 20 and 40 vol in sediment after the maxima the thermal diffusivities decreased with increasing hydrate volume fraction

fundamentals of fission track thermochronology fission track ft analysis has developed into one of the most useful techniques used throughout the geologic community to reconstruct the low temperature thermal history of rocks over geological time the ft method is based on the accumulation of narrow damage trails i e fission tracks in uranium rich mineral grains e g apatite zircon titanite and natural glasses which form as a result of spontaneous nuclear fission decay of 238u in nature price and walker 1963 fleischer et al 1975 the time elapsed since fission tracks began to accumulate is estimated by determining the density of accumulated tracks in a particular material in relation to the uranium content of that material chemical etching can be used to enlarge fission tracks that have formed within a mineral in order to make them readily observable under an ordinary optical microscope price and walker 1962 if a host rock is subjected to elevated temperatures fission tracks that have formed up to that point in time are shortened progressively and eventually erased by the thermal recovery i e annealing of the damage fleischer et al 1975 because thermal diffusion basically governs the annealing process the reduction in ft length is a function of heating time and temperature importantly fission tracks are partially annealed over different temperature intervals within different minerals this characteristic allows for the construction of time temperature paths of many different rock types by a plotting ft and other isotopic ages from different minerals versus their closure temperatures which is applicable in the case of a monotonous cooling history e g wagner et al 1977 zeilter et al 1982 and or by b the inverse modeling of observed ft age and confined track length data e g corrigan 1991 lutz and omar 1991 gallagher 1995 ketcham et al 2000 see also ketcham 2005

early cretaceous denudation related to convergent tectonics in the baikal region se siberia we present 24 new apatite fission track aft ages and 18 track length measurements from the baikal region se siberia most samples have aft ages between 140 and 100 ma with relatively high mean track lengths c 13 2 m the relationship between aft ages elevation and mean track lengths indicate that the samples record rapid cooling during the early cretaceous 140 120 ma as also shown by thermal history inversion of track length distributions cooling took place during a late jurassic early cretaceous orogenic phase related to closure of the mongol okhotsk ocean and reflected in the exhumation of metamorphic core complexes followed by thrusting and reverse faulting basin inversion and large vertical motions the variation in aft ages throughout the study area can be partly explained by differences in geothermal structure but differential denudation also played a role minimum amounts of early cretaceous denudation are estimated at 2 3 km

longitudinal variation of the lunar tide in the equatorial electrojet the atmospheric lunar tide is one known source of ionospheric variability the subject received renewed attention as recent studies found a link between stratospheric sudden warmings and amplified lunar tidal perturbations in the equatorial ionosphere there is increasing evidence from ground observations that the lunar tidal influence on the ionosphere depends on longitude we use magnetic field measurements from the champ satellite during july 2000 september 2010 and from the two swarm satellites during november 2013 february 2017 to determine for the first time the complete seasonal longitudinal climatology of the semidiurnal lunar tidal variation in the equatorial electrojet intensity significant longitudinal variability is found in the amplitude of the lunar tidal variation while the longitudinal variability in the phase is small the amplitude peaks in the peruvian sector 285 e during the northern hemisphere winter and equinoxes and in the brazilian sector 325 e during the northern hemisphere summer there are also local amplitude maxima at 55 e and 120 e the longitudinal variation is partly due to the modulation of ionospheric conductivities by the inhomogeneous geomagnetic field another possible cause of the longitudinal variability is neutral wind forcing by nonmigrating lunar tides a tidal spectrum analysis of the semidiurnal lunar tidal variation in the equatorial electrojet reveals the dominance of the westward propagating mode with zonal wavenumber 2 sw2 with secondary contributions by westward propagating modes with zonal wavenumber 3 sw3 and 4 sw4 eastward propagating waves are largely absent from the tidal spectrum further study will be required for the relative importance of ionopsheric conductivities and nonmigrating lunar tides

natural long term annealing of the zircon fission track system in vienna basin deep borehole samples constraints upon the partial annealing zone and closure temperature abstract fission track ft analysis of zircon from cretaceous and tertiary sandstone samples in vienna basin boreholes has provided constraints for the thermal stability of the zircon ft system over a geological timescale confined track lengths and ages were measured for samples from depths of 1 5 7 5 km the deepest with a present environmental temperature of 200 c mean track lengths range from 10 3 to 10 8 m indistinguishable within error from the unannealed reference length of 10 7 0 1 m 1 standard error thus showing no sign of systematic downhole reduction central zircon ages are consistently older than stratigraphic ages of parent rocks with no single grain ages significantly younger than their respective stratigraphic ages such ft age and length evidence strongly suggests that the tracks have not been significantly annealed since sediment deposition because the present geothermal regime as well as sample burial depths have been near constant for at least the past 5 m y the lower temperature limit of the zircon ft partial annealing zone is 200 c for a heating duration of the order of 5 10 m y such evidence from long term natural annealing is compatible with a zircon ft partial annealing zone cf 200 350 c derived by the extrapolation of laboratory annealing results based on onfined track length measurements but cannot alone discriminate between different annealing models for the zircon ft closure temperature a perhaps over simplified concept these results are consistent with the oft quoted temperature of 250 c for cooling rates of 10 100 c m y

an inverse method of modeling thermal histories from apatite fission track data abstract apatite fission track ft ages and track length distributions are important sources of information about the thermal histories of rocks recent advances in the understanding of track annealing in apatite provide a solution to the forward problem of predicting ft ages and track length distributions that result from a given thermal history in this paper a method is presented to address the inverse problem estimation of the thermal history from ft data the inverse method uses an iterative approach the downhill simplex to systematically modify a starting thermal history to achieve satisfactory statistical agreement between the predicted and observed ft age and track length distribution however because of analytical uncertainties a unique thermal history does not exist monte carlo simulations are used to take into account the uncertainties in the data and yield a spectrum of possible thermal histories the results are based on the isothermal annealing model of laslett et al 1 chem geol isot geosci sect vol 65 but because the method uses forward predictions and not an analytical formula specific to a single annealing model alternative annealing models could be used within the same framework this method is an improvement in interpreting fission track data because the range of thermal histories permitted by the data can be evaluated to demonstrate the method it is applied to several sets of test data created by forward modeling of idealized thermal histories the results show that the age at which the sample cooled through its closure temperature and the most general features of the thermal history are revealed however data from partially annealed samples have wide spectra that reflect large uncertainties in the form of the thermal history for such samples ft data alone are not likely to provide strong tests of geologic hypotheses conversely geologic information may play a crucial role in constraining the thermal history spectrum in application to uplift related cooling this inverse method can provide much more realistic assessments of the cooling rate and its uncertainty than are otherwise possible

morphology of ionospheric f2 region variability associated with sudden stratospheric warmings the effect of sudden stratospheric warming ssw on the f2 region ionosphere has been extensively analyzed for the major event of year 2009 apart from a few reports on other major and minor events morphology of ionospheric responses during ssw can be better comprehended by analyzing such warming events under different solar geomagnetic and meteorological conditions we investigate the features of f2 region variability following the ssw events of 2010 2011 2012 2013 2014 2015 and 2016 using ionosonde data from the asian region covering a broad latitudinal range from 26 6 n to 45 1 n we find perceptible ionospheric variations in electron densities during these warming events which is accompanied by a large variation of 117 within enhancements as compared to a meagre variation of 11 within depressions during these events we also examine six months data at these latitudes and longitudes and find that the maximum and minimum variation in f2 layer critical frequency is observed during each ssw period the influence of quasi stationary 16 day planetary waves is seen during these ssw events further a recently proposed parameter ssw integrated strength by vieira et al 2017 to characterize ssw event with respect to ionosphere is also examined it is seen that it does not fit well for these seven ssw events at these latitudes and longitudes

fission track dating of phosphate minerals and the thermochronology of apatite several phosphate minerals have been investigated for their usefulness in geochronology and thermochronology by the fission track method of these apatite ca5 po4 3 f cl oh has proved pre eminently suitable for this purpose for reasons discussed below apatite was one of the first minerals amongst many others to be investigated for fission track dating by fleischer and price 1964 and has subsequently become by far the most important of all the minerals used for dating by this method the usefulness of apatites for fission track dating arises from their near universal tendency to concentrate uranium within their structure at the time of crystallization and their widespread occurrence in all of the major rock groups price and walker 1963 first recognized the possibility that the accumulation of radiation damage tracks in natural minerals from the spontaneous nuclear fission of 238u within their lattices could be used for geological dating they also demonstrated that a simple chemical etching procedure served to enlarge these fission tracks to optical dimensions so that they could be observed and measured under an ordinary optical microscope price and walker 1962b 1963 this simple procedure quickly opened the way for a wide range of nuclear particle track studies in natural minerals and glasses e g fleischer et al 1975 the most important of which was fission track dating fleischer et al 1964 also showed that spontaneous or fossil fission tracks provided an explanation for various anomalous etch pits in apatite which had puzzled crystallographers over many years the essence of a fission track age determination involves measuring the number of tracks that have accumulated over the lifetime of the mineral along with an estimate of the amount of uranium that is present knowing the rate of spontaneous fission decay a geological age can be calculated detailed

time gcm study of the ionospheric equatorial vertical drift changes during the 2006 stratospheric sudden warming this modeling study quantifies the daytime low latitude vertical e b drift changes in the longitudinal wave number 1 wn1 to wn4 during the major extended january 2006 stratospheric sudden warming ssw period as simulated by the national center for atmospheric research thermosphere ionosphere mesosphere electrodynamics general circulation model time gcm and attributes the drift changes to specific tides and planetary waves pws the largest drift amplitude change approximately 5 m s is seen in wn1 with a strong temporal correlation to the ssw the wn1 drift is primarily caused by the semidiurnal westward propagating tide with zonal wave number 1 sw1 and secondarily by a stationary planetary wave with zonal wave number 1 pw1 sw1 is generated by the nonlinear interaction of pw1 and the migrating semidiurnal tide sw2 at high latitude around 90 100 km the simulations suggest that the e region pw1 around 100 130 km at the different latitudes has different origins at high latitudes the pw1 is related to the original stratospheric pw1 at midlatitudes the model indicates pw1 is due to the nonlinear interaction of sw1 and sw2 around 95 105 km and at low latitudes the pw1 might be caused by the nonlinear interaction between de2 and de3 the time evolution of the simulated wn4 in the vertical e b drift amplitude shows no temporal correlation with the ssw the wn4 in the low latitude vertical drift is attributed to the diurnal eastward propagating tide with zonal wave number 3 de3 and the contributions from se2 te1 and pw4 are negligible

present day heat flow thermal history and tectonic subsidence of the east china sea basin the east china sea basin is located in the convergence area between the eurasian plate the pacific plate and the philippine sea plate and consists of two depressions the taibei depression in the west and the xihu depression in the east heat flow measurements show that the east china sea basin is characterized by present day heat flow around 70 6 mw m 2 varying between 55 and 88 mw m 2 no significant difference in heat flow is observed between the xihu and the taibei depressions thermal history reconstruction using vitrinite reflectance suggests that the thermal history was however different in the taibei and the xihu depressions paleo heat flow values when the pretertiary formations experienced their maximum temperature at the end of the paleocene reached a mean of 82 mw m 2 in the taibei depression much higher than the present day value the lower tertiary sediments in the xihu depression experienced maximum temperatures at the end of oligocene 35 4 23 3 ma and reached a mean paleo heat flow value of 83 mw m 2 tectonic subsidence analysis shows that the timing of the major rifting episode was different across the east china sea basin the rifting occurred from the late cretaceous w65 ma to the early eocene w55 ma in the taibei depression followed by thermal subsidence from the late eocene to the end of miocene 23 3 5 2 ma in contrast in the xihu depression the initial subsidence lasted until the early miocene and thermal subsidence to the end of miocene from pliocene to the present an accelerated subsidence took place all along the west pacific margin of asia significant thicknesses of strata were removed from the unconformities in the basin the mean amount of erosion was 1147 m from the paleocene and 1208 m above the oligocene in the taibei depression and 1409 m from the oligocene in the xihu depression q 2004 elsevier ltd all rights reserved

fission track evidence for quaternary uplift of the nanga parbat region pakistan the north striking nanga parbat haramosh massif protrudes into the northwestern himalaya along the axis of a great syntaxis1 2 fig 1 where the hindu kush karakorum and himalayan ranges converge as the indus suture zone3 enters this region from the east it bifurcates into two branches encircling what may be a docked island arc terrane4 the southern branch the main mantle thrust crops out on both flanks of the nanga parbat massif forming a tight structural loop5 this massif and the adjacent terrane contain some of the highest peaks in the himalaya nanga parbat and the indus river located just 20km away define the world s greatest continental relief 6 930 m we report here the discovery of unexpectedly young sphene zircon and apatite fission track dates from the nanga parbat haramosh massif these dates as low as 1 3 myr for zircon and 0 4 myr for apatite imply that during the pleistocene the nanga parbat region was uplifted and eroded at nearly 1 cm yr 1

the relationship between track shortening and fission track age reduction in apatite combined influences of inherent instability annealing anisotropy length bias and system calibration abstract the relationship between reduced track density 0 and reduced mean confined track length l l 0 during annealing has been studied for both spontaneous and induced tracks in four apatite samples with different chemical composition compositional range and origin and with spontaneous tracks giving mean confined track lengths varying from 14 5 m down to 12 3 m in all four apatites induced tracks show a relationship between l l 0 and 0 composed of two regions at higher values the two appear to be equal while at lower values l l 0 is greater than 0 this can be understood qualitatively in terms of the anisotropy of annealing and the bias against revelation of short tracks data from three apatites of uniform composition show near identical relationships in a sample showing a range of apatite compositions the point of divergence from the 1 1 relationship is somewhat higher than in the uniform composition apatites because individual grains anneal at different rates and the presence of highly annealed grains affects the track density more strongly than the mean track length spontaneous tracks show similar relationships to those observed for induced tracks in each sample when the data are renormalised to allow for the natural annealing present in the spontaneous tracks previous studies which led to the idea of length reduction without density reduction for spontaneous tracks did not renormalise density data as well as length data thereby distorting the apparent relationship data for the multi compositional apatite sample where annealing has taken place in geological conditions also agrees with the laboratory annealing data for both spontaneous and induced tracks this consistency suggests that a single process is responsible in all three cases implying that a laboratory based description of annealing can be applied to geological conditions with confidence recognition that spontaneous tracks in apatite are commonly annealed suggests that in general the fission track age should be interpreted as a reflection of both the time over which tracks have been retained and the distribution of etchable track lengths since the latter is a manifestation of the thermal history the fission track age should be interpreted in similar terms

climatology of semidiurnal lunar and solar tides at middle and high latitudes interhemispheric comparison the semidiurnal lunar and solar tides obtained from meteor radar measurements spanning from 2009 until 2013 observed at davis 69 s and rio grande 54 s are presented and compared to the northern hemisphere ones at andenes 69 n and juliusruh 54 n mean tidal differences for both intra and inter hemispheric scenarios are analyzed tidal behavior is also compared against numerical simulations during 2009 and 2013 sudden stratospheric warming ssw time periods possible influences in the southern hemisphere from the local stratosphere are also investigated using modern era retrospective analysis for research and applications version 2 merra 2 datasets the main features of the mean zonal wind are similar in both hemispheres i e stronger amplitudes over mid latitude locations eastward winds during winter and westward below 90 km with eastwards higher up during corresponding summer times on the other hand the semidiurnal solar tides observed in the southern hemisphere show clear differences when compared to the northern hemisphere and between mid and high latitude locations at the same hemisphere these differences are even larger for the semidiurnal lunar tide which shows stronger amplitudes from october to march and march to october over davis and rio grande respectively our results indicate that the lunar tides over the southern hemisphere mid latitudes are more prone to react to the northern hemisphere stratospheric polar vortex influences in agreement with numerical simulations particularly for the time of the 2013 ssw

effect of sudden stratospheric warming on lunar tidal modulation of the equatorial electrojet 1 using the equatorial electrojet eej peak current intensity as deduced from champ magnetic observations from the years 2001 through 2009 we investigated the relationship between sudden stratospheric warming ssw and lunitidal signatures in the tropical ionosphere there is a practically one to one correspondence between midwinter ssw periods and the strongest 13 day modulation of the eej strength as observed by champ that is all the midwinter ssw periods from december 2001 to august 2009 were accompanied by an enhanced 13 day modulation of the eej strength no other geophysical phenomenon brought about as strong a 13 day modulation as those of the midwinter ssw periods during each midwinter ssw period the amplified 13 day modulation of the eej strengths starts roughly within 1 week around the first peak in stratospheric temperature difference an oscillation with a period of 13 26 days is predicted by the lunitidal equation when considering the precession of the champ orbit when fitting the lunitidal equation to the eej modulations during the midwinter ssw periods consistent phase delays of 4 4 0 3 days of the tidal signal emerge for all the cases the results suggest that the pronounced 13 day modulation of the eej strength is related to an enhancement of the lunar tide in the ionosphere by the ssw effect

on modeling migrating solar tides recent updates and extensions to a steady state two dimensional linearized model of global scale atmospheric waves have facilitated improved calculations of the subset of those waves which are subharmonics of a solar day and propagate with the apparent motion of the sun the model improvements are briefly described and some updated predictions of the migrating solar diurnal component are highlighted the latter represent the first numerical modeling effort to examine the seasonal variability of the migrating diurnal harmonic as it propagates into the mesosphere and lower thermosphere

lunar and solar tidal variabilities in mesospheric winds and eej strength over tirunelveli 8 7 n 77 8 e during the 2009 major stratospheric warming 1 mesospheric wind observations by the medium frequency radar and geomagnetic field observations at tirunelveli 8 7 n 77 8 e 1 75 n dip angle are used to study the relative importance of solar and lunar influences in the variabilities of mesospheric tides and equatorial electrojet eej strength during the unprecedented major stratospheric sudden warming ssw of 2009 it is observed that the afternoon reversal in the eej popularly known as counter electrojet occurs consecutively for several days during the ssw event when there is an enhancement of solar semidiurnal tide in both zonal wind at 90 km and eej strength over tirunelveli although the amplitude of lunar tides also shows enhancement it is much less than that of solar the diurnal tidal amplitude in zonal wind and eej strength also shows large enhancement just before the onset of ssw however solar semidiurnal tide dominates diurnal tide during the ssw the diurnal tidal phase in zonal wind shifts to a few hours earlier during the ssw the lunar semidiurnal tidal phase shifts to later hours in both zonal wind and eej strength the main observation of the present study is that the large semidiurnal tide observed during the ssw 2009 is mostly solar driven and only partly lunar driven although tidal planetary wave interaction also may play a vital role although a similar behavior is noticed during the ssw 2006 also the large lunar semidiurnal tide observed in the eej strength without having large lunar semidiurnal tide in the underlying mesospheric winds needs further investigation

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

lunar tide in the equatorial electrojet in relation to stratospheric warmings 1 the relationship between sudden stratospheric warmings ssws and large amplitude lunar tides in the equatorial electrojet eej is studied analysis of ground magnetometer data shows that the lunar tide in the eej is maximum during the northern winter season except in the pacific ocean region since ssws are also a northern winter phenomenon it is suggested that the relation between the large lunar tide in the eej and the ssw may possibly be coincidental the lunar tide in the geomagnetic variations at huancayo is anomalously large compared with other eej stations an examination of geomagnetic variations at eej stations during ssw events shows that afternoon counter electrojets are frequently present at new moon and full moon though the relationship is sometimes broken the observation of large lunar eejs when no ssw is present and of various different delay times suggests that other atmospheric processes are likely to be in play

responses of quasi 2 day waves in the mlt region to the 2013 ssw revealed by a meteor radar chain we present an analysis of the responses of quasi 2 day waves qtdws to the 2013 sudden stratosphere warming ssw in the mesosphere and lower thermosphere mlt region the study is based on data collected by a meteor radar chain along the 120 e meridian in the northern hemisphere which consists of four stations at mohe 52 5 n 122 3 e beijing 40 3 n 116 2 e wuhan 30 5 n 114 6 e and sanya 18 3 n 109 6 e it is the first time that an enhancement of the qtdw in the neutral wind during the 2013 ssw is observed in the midlatitudes in the northern hemisphere during the ssw the amplification of the qtdw in the low latitudes is the most prominent and the direction of the mean zonal wind shows clear reversion from eastward to westward the consistent variations of the qtdws and the mean neutral wind at the four stations are very likely associated with the ssw

thermal instability of gas hydrate bearing sediments some issues abstract the overall stability of marine strata holding gas hydrates is dependent on their shear strength characteristics these characteristics in turn are dependent on thermal flux that is imposed for dissociation of the hydrates for the safe and efficient extraction of methane gas from the hydrate bearing sediments due to the imposition of thermal flux on these sediments their fabric structure and pore space hydrate saturation changes which impacts the overall stability of the sea bed estimating stability conditions in such a multiphase and dynamic system necessitates collection of undisturbed samples without compromising their in situ thermodynamic conditions this is a daunting task given the huge cost of procuring samples and the challenge of maintaining an undisturbed sample with in situ thermodynamic conditions till it is brought to the laboratory synthesizing hydrate bearing sample sediments in laboratory for conducting studies to identify heat migration mechanisms and thermal property measurements and linking them to the shear strength characteristics provides an affordable solution to this problem with this in view a critical review of the available literature dealing with laboratory synthesis of hydrate bearing sediments their thermal and strength characteristics the coupled phenomenon of heat and fluid migration and its impact on the overall stability of marine sediments has been conducted and presented in this paper this will facilitate understanding the factors governing and the mechanism of heat transfer in a multiphase system the changes in the system brought about by the hydrate dissociation front and the overall impact on the stability of seabed

the jameson land basin east greenland a fission track study of the tectonic and thermal evolution in the cenozoic north atlantic spreading regime abstract the late mesozoic and cenozoic thermal history of the jameson land basin is constrained by new apatite and zircon fission track ft data of surface permian to jurassic sedimentary rocks the results show a general regional thermal evolution related to burial to temperatures close to and in excess of the maximum temperatures of the apatite annealing interval 125 c followed by cooling mainly due to cenozoic uplift and erosion faulting and differential movements in the basin generally occurred after cooling below the apatite partial annealing zone paz 75 125 c however in the northern part of the basin the data suggest a thicker sediment cover or localized heating related to an earlier fracture zone both apatite ft analysis and vitrinite reflectance values reveal a postmature signature for the studied rocks in the northeastern jameson land and premature to mature for the western central and southern jameson land rocks with respect to generation of hydrocarbons the chemical variations of apatite enhance the possibility of recognizing sample positions near maximum temperatures in the paz furthermore the pb zn mineralization pattern closely follows the tertiary maturity trend given by the ft data the type and distribution of mineralization suggest that it was influenced by the regional thermal evolution of the basin in the northeast domain circulating fluids may have overprinted the regional thermal record before ca 20 ma basaltic dyke and sill intrusions 55 45 ma locally caused resetting of apatite ft ages but generally the direct influence from upper crustal magmatic activity played only a minor role the thermal evolution in northeast jameson land is related to the late tectonic evolution of the northeast atlantic involving a change in ridge position at ca 25 ma which followed the passage of the proto icelandic mantle plume at 63 40 ma

on apatite fission track dating and the tertiary evolution of west greenland topography abstract combined with geological information apatite fission track aft data can impose valid thermal and temporal constraints however their uncritical interpretation may also lead to unsupported conclusions because fission tracks in apatite undergo measurable shortening even at surface temperatures model artefacts can potentially be mistaken for geological cooling events this problem can be especially acute when older fanning kinetic models are utilized instead of the newest curvilinear ones in any circumstances aft model results must be interpreted with considerable caution and should rarely be considered to supersede conventional geological wisdom the possibility that young cooling events are simply artefacts ought always to be entertained as an example this study considers aft data and model results that have been cited to suggest that today9s high mountains of west greenland are erosional remnants of a landmass uplifted during the neogene however in the best of circumstances the aft data in question are heavily contaminated and in the worst case they carry virtually no geological meaning although geological constraints require the faulted westward facing escarpment of west greenland9s disko region to have been erected after commencement of sea floor spreading in baffin bay the aft model based hypothesis that it was constructed in purely neogene time remains an unproven speculation

quiet variability of equatorial e b drifts during a sudden stratospheric warming event 1 we present strong evidence that during the january 2008 minor sudden stratospheric warming ssw event the equatorial vertical e b drifts exhibit a unique and distinctive daytime pattern we do not think one event causes the other however both events might be related through the global effects of planetary waves the drifts were measured by the jicamarca incoherent scatter radar located under the magnetic equator we have observed an anomalous temporal variation of the vertical e b drifts during the minor ssw event showing a semidiurnal variation with very large amplitudes lasting for several days large differences in the e b drifts were observed during a period of large increase of temperature and a large decrease of mean zonal wind in the high latitude stratosphere 60 90 n this high correlation is an unexpected finding which might shed new light on sources and mechanisms of quiet time ionospheric variability

upper mesospheric lunar tides over middle and high latitudes during sudden stratospheric warming events in recent years there have been a series of reported ground and satellite based observations of lunar tide signatures in the equatorial and low latitude ionosphere thermosphere around sudden stratospheric warming ssw events this lower atmosphere ionosphere coupling has been suggested to be via the e region dynamo in this work we present the results of analyzing 6 years of hourly upper mesospheric winds from specular meteor radars over a midlatitude 54 n station and a high latitude 69 n station instead of correlating our results with typical definitions of ssws we use the definition of polar vortex weaking pvw used by zhang and forbes 2014 this definition provides a better representation of the strength in middle atmospheric dynamics that should be responsible for the waves propagating to the e region we have performed a wave decomposition on hourly wind data in 21 day segments shifted by 1 day in addition to the radar wind data the analysis has been applied to simulations from whole atmosphere community climate model extended version and the thermosphere ionosphere mesosphere electrodynamics general circulation model our results indicate that the semidiurnal lunar tide m2 enhances in northern hemispheric winter months over both middle and high latitudes the time and magnitude of m2 are highly correlated with the time and associated zonal wind of pvw at middle high latitudes m2 in the upper mesosphere occurs after before the pvw at both latitudes the maximum amplitude of m2 is directly proportional to the strength of pvw westward wind we have found that m2 amplitudes could be comparable to semidiurnal solar tide amplitudes particularly around pvw and equinoxes besides these general results we have also found peculiarities in some events particularly at high latitudes these peculiarities point to the need of considering the longitudinal features of the polar stratosphere and the upper mesosphere and lower thermosphere regions for example during ssw 2009 we found that m2 enhances many days before pvw which is not in agreement with most of our results

c nofs observations of the equatorial ionospheric electric field response to the 2009 major sudden stratospheric warming event 1 we present new observations made by the coupled ion neutral dynamics investigation cindi ion velocity meter ivm instrument onboard the communication navigation outage forecasting system c nofs satellite that show the effects of the january 2009 sudden stratospheric warming ssw event on equatorial electric fields we have used ivm observations to construct composite curves of mean equatorial vertical plasma drifts as a function of local time and longitude sector these curves show large upward vertical drifts during morning hours and downward drifts during afternoon our analysis indicates that this pattern could be observed over the range of longitudes where adequate ivm measurements were available from approximately 165 e to about 315 e longitude a clear day to day quasi deterministic variability in the drifts is also observed with the transition from upward to downward drifts occurring at increasing local times from 25 to 30 january 2009 the analysis also suggests some level of longitudinal variability in the magnitude of the drifts these in situ observations are in good agreement with previous ground based measurements of the response of equatorial electric fields to ssw events in particular we found that ivm drift measurements centered around 285 e depart significantly from climatological values but agree exceptionally well with ground based measurements of vertical drifts made by the jicamarca incoherent backscatter radar overall the results agree well with previous studies of ssw events demonstrate the usefulness of the ivm observations and motivate further studies of the variability of the equatorial ionosphere using c nofs

investigation on the variability of the geomagnetic daily current during sudden stratospheric warmings the magnetic field records of the magnetometer networks in the american east asian australian and european african sectors were employed in this present work we used them to investigate equatorial electrojet eej counter electrojet cej tidal variability in eej strength and ionospheric current during the 2005 2006 and 2008 2009 sudden stratospheric warming ssw events in addition to the well investigated tidal variability in eej strength over the american and east asian sectors we investigated that of the african sector for the first time interestingly the tidal components in eej strength during both ssw events clearly exhibit marked longitudinal differences with high moderate and low amplitudes in the american east asian and african sectors respectively an exception found around day 71 in the african sector after the 2008 2009 ssw event had higher solar diurnal tidal component as compared to that of the asian sector over the american sector solar and lunar semidiurnal tides were strongly associated with cej current during both ssw events whereas at the african and east asian sectors such variabilities are not evident a solar diurnal tidal component was strongly related to a reduction in the eej strength over the east asian sector in addition a prolonged period of cej occurrence that begins during the ssw precondition and ends when the ssw was evolving characterized the african sector during both ssw events there is a steady shift in phase at later hours when both ssw events are evolving

the potential volume of oceanic methane hydrates with variable external conditions gas hydrate abundance in marine sediment depends on gas concentration and the available pore space within certain stability limits potentially gas hydrates can occur between the seafloor and a locus of subbottom depths where geothermal gradients intersect gas gas hydrate pore water equilibrium curves perpendicular to a given continental margin the lens shaped area between these two bounding surfaces a sl varies according to seven basic parameters gas composition water activity a w bottom water temperature t b geothermal gradient g slope depth z slb slope gradient z and sea level relative to the shelf break z 0 assuming pure ch 4 gas 35 km 2 of sediment can host gas hydrate across an average continental margin at a pleistocene lowstand a w 0 981 t b 0 c g 0 c z slb 4000 m z 0 04 z 0 0 however this potential area would decrease with smaller a w higher t b greater g shallower z slb steeper z and lower z 0 and increase with opposite external conditions of the basic parameters temperature t b and g and bathymetry z slb and z can particularly influence the distribution of gas hydrate on continental slopes a hydrothermal gradient with e g surface temperatures t b will also decrease a sl although minimally especially if t b is warm the sum of parallel cross sectional areas along a margin combined with porosity o gives the potential volume of gas hydrate v assuming 200 000 km of continental margin with a o of 50 3 5 10 6 km 3 of pore space can contain gas hydrates at present day a volume that compares favorably with previous estimates 1 2 to 6 4 10 6 km 3 although underlying approaches differ fundamentally since the triassic v glob probably has increased significantly because t b has cooled while total margin length has grown this trend was likely punctuated by at least one major decrease nominally 1 5 to 0 7 10 6 km 3 when t b suddenly rose by 5 c during the latest paleocene thermal maximum lptm a prominent global negative 13 c excursion across the lptm may signify massive release of ch 4 associated with this theoretical drop in v glob

thermal history and tectonic subsidence of the bohai basin northern china a cenozoic rifted and local pull apart basin the bohai basin is a part of the larger bohai bay basin a cenozoic rifted intraplate basin heat flow measurements show that the bohai basin is characterized by present day heat flow varying between 53 and 74 mw m 2 with a mean of 63 mw m 2 however thermal history analyses derived from vitrinite reflectance vr and apatite fission track aft data indicate that tertiary cooling took place following a period of much higher paleo heat flow 70 90 mw m 2 prior to 25 million years to the present furthermore tectonic subsidence analysis reveals that the bohai basin experienced episodic sub rifting processes from the eocene to the end of the oligocene the post rift thermal subsidence was superimposed by intensified subsidence from the late miocene 12 million years in the bozhong depression and from the early quaternary 2 4 million years in the east liao bay indicating a rejuvenation of sedimentation related likely to transpressional structures developed locally on strike slip faults the present results indicate that there is good agreement between the reconstructed thermal history and the timing of the tectonic subsidence stages within the bohai basin the bohai basin is an early cenozoic rifted and local pull apart sub basin of the larger bohai bay basin 2001 elsevier science b v all rights reserved

lunar tides in total electron content over brazil using data from global navigation satellite systems dual frequency receivers the lunar tides were studied in the ionospheric total electron content tec over brazil from 2011 to 2014 in order to calculate the amplitudes and phases of the lunar tides quiet magnetic days within a 27 day window has been used to remove the solar rotation effects relative residuals tec were calculated by performing a spectral analysis by removing the solar tide contributions lastly a lunar month size window was used to calculate the amplitude and phase of the lunar components lunar diurnal tide amplitudes showed a semiannual variation with maximum in the equinox months for almost all latitudes while lunar semidiurnal amplitudes were larger in december and january and may be related to sudden stratospheric warming events both components did not display significant longitudinal variation what could be due to the short range of longitude 30 degrees lunar diurnal amplitudes were basically uniform over brazil while lunar semidiurnal amplitudes showed some peaks over the equatorial ionization anomaly crest and minimum values near the magnetic equator

thermal properties of methane hydrate bearing sediments and surrounding mud recovered from nankai trough wells this paper presents the measurement of the thermal constants of natural methane hydrate bearing sediments and mud layer samples recovered from wells core samples were recovered from the tokai oki test wells nankai trough japan in 2004 the thermal conductivity thermal diffusivity and specific heat of the samples were simultaneously determined using the hot disk transient method the thermal conductivity of natural hydrate bearing sediments decreased slightly with increasing porosity in addition the thermal diffusivity of hydrate bearing sediments decreased as the porosity increased moreover we also used simple models to calculate the thermal conductivity and diffusivity estimations of the distribution model geometric mean model were relatively consistent with the measured results suggesting that sand grains and hydrates should be independently distributed for hydrate bearing sediments which exhibit a pore filling pattern the measurement results were also consistent with the thermal diffusivity which was estimated by dividing the thermal conductivity obtained from the distribution model by the specific heat taken from the arithmetic mean finally our estimate of the thermal conductivity of silt soil was much lower than that for sand soil in hydrate bearing sediment which suggests that the small grains influence thermal conductivity

atmospheric tide 2 the solar and lunar semidiurnal components solar and lunar semidiurnal wind and temperature oscillations from the surface to 400 km are simulated for average solar activity conditions utilizing the numerical tidal model described in part 1 hough mode decomposition of the solstitial solar semidiurnal tide excited by h2o and o3 insolation absorption below 80 km indicates that it is characterized by a predominance of 2 2 below 60 km about equal contributions of 2 2 2 3 and 2 4 between 70 and 90 km mostly 2 4 with some 2 5 and 2 2 between 90 and 120 km and a predominance of 2 2 above 140 km with secondary contributions from 2 3 and 2 5 the solstitial lunar semidiurnal tide is characterized by a predominance of 2 2 below 70 km 2 4 with secondary contributions from 2 2 2 3 and 2 5 between 80 and 110 km and by 2 2 with a fairly strong secondary contribution from 2 3 above 120 km similar descriptions for both the solar and lunar oscillations apply at equinox except that the asymmetric 2 3 and 2 5 modes are absent relative to the solar component lunar temperature and wind amplitudes are sufficiently large 20 in the lower and upper thermosphere to account for some of the observed variability previously attributed to the solar tide amplitudes of the 2 4 and 2 5 modes above 100 km are significantly affected by mesospheric eddy diffusion coefficients in excess of 2 106 cm s 1 the total solar semidiurnal exospheric temperature oscillation for average solar conditions ranges from 10 20 k poleward of 40 n to 40 60 k equatorward of 30 n and has its origin in three sources of excitation all of comparable importance 1 euv solar radiation absorption in the lower thermosphere 100 200 km 2 in situ momentum coupling due to the interaction of diurnal winds and diurnally varying ion drag and 3 tides propagating upwards from below 100 km in addition the calculations are compared with rocket meteor radar partial reflection thomson scatter and satellite data to evaluate the consistency of the model with observations

observations and simulations of midlatitude ionospheric and thermospheric response to the january 2013 stratospheric sudden warming event using observations from mid latitudes we examine the ionospheric and thermospheric responses to the 2013 stratospheric sudden warming event by comparing data with four simulations performed by the waccm x timegcm and tiegcm the waccm x simulation was nudged by the geos 5 data the two timegcm simulations were nudged by the merra data and by the aforementioned waccm x outputs respectively the standard tiegcm simulation was also performed these four simulations were compared with millstone hill 42 6 n 71 4 w incoherent scatter radar data millstone hill and boulder 40 1 n 105 2 w upper and lower thermospheric wind data the meteor radar data from collm 51 3 n 13 e were also used to examine the zonal wavenumber of the semidiurnal tide sd we evaluate the model simulations of the mesospheric and thermospheric responses to the 2013 ssw the timegcm simulation nudged with the waccm x output has suitable stratospheric input and ionospheric dynamics and can reproduce a sharp rise of hmf2 on january 12 observed by the millstone hill radar the comparison of different models with the lower thermospheric sd tide yielded mixed results the sd tide maintained mostly as a migrating tide for most of the time and matched the tiegcm simulation very well the waccm x appeared to perform better when the observed sd tide displays the large phase shift it also has larger and more variable sd tide amplitude the two timegcm simulations have smaller sd amplitudes in general observations showed complex sd tide patterns after january 20 which was difficult to characterize as a migrating tidal mode

causes of the longitudinal differences in the equatorial vertical e b drift during the 2013 ssw period as simulated by the time gcm during stratospheric sudden warming ssw periods large changes in the low latitude vertical drift have been observed at jicamarca as well as in other longitudinal sectors in general a strengthening of the daytime maximum vertical drift with a shift from prenoon to the afternoon is observed during the january 2013 stratospheric warming significant longitudinal differences in the equatorial vertical drift were observed at jicamarca the previously reported ssw behavior prevails however no shift of the daytime maximum drift was exhibited in the african sector using the national center for atmospheric research thermosphere ionosphere mesosphere electrodynamics general circulation model time gcm the possible causes for the longitudinal difference are examined the timing of the strong ssw effect in the vertical drift 15 20 january coincides with moderate geomagnetic activity the simulation indicates that approximately half of the daytime vertical drift increase in the american sector may be related to the moderate geophysical conditions kp 4 with the effect being negligible in the african sector the simulation suggests that the wind dynamo accounts for approximately 50 of the daytime vertical drift in the american sector and almost 100 in the african sector the simulation agrees with previous findings that the migrating solar tides and the semidiurnal westward propagating tide with zonal wave number 1 sw1 mainly contribute to the daytime wind dynamo and vertical drift numerical experiments suggest that the neutral wind and the geomagnetic main field contribute to the presence absence of a local time shift in the daytime maximum drift in the american african sector

global response of the ionosphere to atmospheric tides forced from below comparison between cosmic measurements and simulations by atmosphere ionosphere coupled model gaia 1 this paper for the first time presents a detailed comparison between simulated and observed global electron density responses to different atmospheric tides forced from below the recently developed earth s whole atmospheric model from the troposphere to the ionosphere called gaia has been used for the simulation of the electron density tidal responses they have been compared with the extracted from the cosmic electron density data tidal responses for the period of time october 2007 to march 2009 particular attention has been paid to the nonmigrating de3 de2 and migrating dw1 sw2 and tw3 electron density responses the gaia model reproduced quite well the cosmic de3 de2 responses both simulations and observations revealed three altitude regions of enhanced electron density responses 1 an upper level response above 300 km height apparently shaped mainly by the fountain effect 2 a response located near altitudes of 200 270 km and 3 a lower thermospheric response situated near 120 150 km height a possible mechanism is suggested for explaining the two lower level responses for the first time the gaia model simulations supported the observational evidence found in the cosmic measurements that the ionospheric wn4 wn3 longitude structure is not generated only by the de3 de2 tide as it has been often assumed as regards the comparison of the migrating dw1 sw2 and tw3 responses the obtained results clearly demonstrate that the gaia model reproduce very well of the sw2 and tw3 cosmic electron density responses the only main discrepancy is seen in the migrating dw1 response the observation does not support the splitting of the simulated response at both sides of the equator this is due mainly to the difference between the saber and gaia sw2 tide in the lower thermosphere as it turned out that the dw1 electron density response strongly depends on the mean features of the lower thermospheric sw2 tide

longitudinal variation of ionospheric vertical drifts during the 2009 sudden stratospheric warming 1 the whole atmospheric model wam initialized with a data assimilation scheme is capable of simulating real sudden stratospheric warming ssw events the electrodynamics in the coupled thermosphere ionosphere and plasmasphere with electrodynamics model ctipe was driven by the wam thermospheric winds in january 2009 to study the response of ionospheric drifts during the ssw simulation results are compared with observations of the vertical drift at jicamarca and the equatorial electrojet eej in the asian sectors early morning upward drift and afternoon downward drift are reproduced in all longitudes in the simulations and are consistent with the available observations results also show that the occurrence time of the early morning upward drift and afternoon downward drift have significant phase differences between different longitudes simulations suggest that during the ssw the longitude dependence of the amplitude and phase of the equatorial vertical plasma drift is caused by the changing magnitudes of the migrating tides modulated by the geometry of the geomagnetic field some additional day to day variability and modulation of the phase structures at different longitudes in ionospheric vertical drifts during the ssw are possibly produced by the short term changes in the non migrating tides and by planetary waves

the sensitivity of gas hydrate reservoirs to climate change perspectives from a new combined model for permafrost related and marine settings abstract gas hydrate reservoirs store large quantities of gas in sediments on continental margins in deep lakes and in continental and relic sub shelf permafrost the gas hydrate structure is only stable at sufficiently low temperature and high pressure and may therefore collapse under changing climatic conditions if a temperature rise or pressure drop e g through falling sea level is effective enough to dissociate hydrate deposits methane the most common gas component in hydrates and a potent greenhouse gas is released from the hydrate structure and may eventually enter into the atmosphere this may generate a positive feedback effect as resulting enhanced greenhouse gas levels would additionally warm the atmosphere and hence maintain or reinforce hydrate dissociation the significance of this mechanism has been debated over the past decades often within the framework of geologically rapid quaternary climatic oscillations and present day climate warming an extensive set of studies has addressed the climate sensitivity of gas hydrate reservoirs in various study areas and geological settings and by means of various approaches no real consensus has yet been reached on the matter in this study we seek to evaluate the sensitivity of gas hydrate reservoirs to changes in global climate from a more general perspective by firstly reviewing the available literature and secondly developing a new numerical model to quantify gas hydrate destabilization under changing environmental conditions qualities of the model include the wide applicability to both marine and permafrost related hydrate reservoirs and the integrative approach combining existing hydrate formation models with a dissocation model that accounts for the consumption of latent heat during hydrate dissociation to determine which settings are most vulnerable and to acquire insight into the extent fashion and rates of hydrate dissociation we apply the model to four distinct types of hydrate reservoirs across a hypothetic high latitude continental margin under two specific cases of climate change the last deglaciation following the last glacial maximum and present day climate warming the simulations indicate that hydrates on the upper continental slope and in association with thin sub shelf permafrost are most sensitive to the imposed climatic variations whereas deepwater and onshore permafrost related reservoirs react in a more stable way however the deep i e at several tens to hundreds of meters subsurface depth stratigraphic type hydrates considered in this study constitute by far the largest fraction of the global gas hydrate volume but dissociate on slow timescales of thousands to hundreds of thousands of years even in the most sensitive environments in contrast shallow i e at or a few meters below the surface or seafloor structural type hydrates are able to respond to climatic variations on sub millennial timescales but the volumes of gas they may release are probably insignificant to the global carbon cycle and climate quaternary and present day climate change do affect the stability of gas hydrate reservoirs but at long timescales where hydrate volumes are large and on short timescales where hydrate volumes are small consequently gas hydrates dissociate to an extent that is too small or at a pace that is too slow to create a strong positive feedback effect while the release of methane from the disintegration of gas hydrates is observed on different margins today it is not likely to have played a leading role in quaternary climatic variations or to become a significant process in the coming centuries as a result of present day rising temperatures

thermal annealing of fission tracks in fluorapatite chlorapatite manganoanapatite and durango apatite experimental results it is well known that the optically measured lengths of fission tracks in apatite crystals are a function of etching conditions crystallographic orientation of the track composition of the crystal and the state of thermal annealing in this study we standardize etching conditions and optimize track length measurability by etching until etch pits formed at the surface of each apatite crystal reached widths of about 0 74 m etching times using 5m hno3 at 21 c were 31 s for otter lake quebec fluorapatite 47 s for durango mexico apatite 33 s for portland connecticut manganoanapatite and 11 s for bamle norway chlorapatite an etching experiment using two etchant strengths 5m and 1 6m hno3 revealed that despite significant differences in etch pit shape fission track length anisotropy with respect to crystallographic orientation of the tracks is not a chemical etching effect a series of 227 constant temperature annealing experiments were carried out on nuclear reactor induced tracks in orient

atmospheric tides in the low latitude e and f regions and their responses to a sudden stratospheric warming event in january 2010 an extensive analysis of atmospheric tides in the low latitude thermosphere and their responses to a major sudden stratospheric warming ssw event 18 23 january 2010 is presented the analysis is based on observational data from the arecibo dual beam incoherent scatter radar important findings of the present study are as follows 1 the diurnal tide with an evanescent phase structure dominates the f region meridional wind field the diurnal tide has a peak amplitude of 45 m s occurring at about 245 km and it is very stable throughout the nine consecutive days observation below 114 km the vertical structures of the diurnal tide in the meridional and zonal components are consistent which resemble the classical solar s 1 s 1 tidal mode 2 the f region semidiurnal tide is much weaker and has larger day to day variability than the diurnal tide in the e region the semidiurnal amplitudes in the meridional and zonal components grow continuously in the altitude ranges from 106 to 121 km and from 100 to 115 km respectively the vertical wavelength of the zonal component is estimated to be 45 km above 100 km which is close to the solar s 2 s 4 and s 2 s 5 tidal modes 3 the semidiurnal and terdiurnal tides respond strongly to the ssw while the impact that the ssw has on the diurnal tide in the meridional wind is limited during the ssw event the amplitudes of the semidiurnal and terdiurnal tides are enhanced in the f region but reduced in the upper e region

sudden stratospheric warming event signatures in daytime exb drift velocities in the peruvian and philippine longitude sectors for january 2003 and 2004 1 this paper first describes the technique that has been developed to obtain realistic daytime vertical exb drift velocities in the equatorial ionosphere using two ground based magnetometers one on the magnetic equator and the other located 6 9 away in latitude this technique is then employed to study the unique exb drift signatures associated with sudden stratospheric warming events ssw in both the peruvian and philippine longitude sectors occurring in january 2003 and january 2004 it is found that the semidiurnal shaped signature first appears in the peruvian sector and 3 days later appears in the philippine sector in both sectors the exb drift signature lasts for approximately 5 days

constraints on the fluid supply rate into and through gas hydrate reservoir systems as inferred from pore water chloride and in situ temperature profiles krishna godavari basin india abstract we estimate the rate of upward pore fluid flow and chlorinity cl concentrations at depth through a joint analysis of cl concentration and temperature versus depth profiles obtained from gas hydrate related test sites drilled and cored in the krishna godavari basin off the eastern coast of india cl measured on conventional core samples decreases with depth at all sites but some of the cl profiles show a prominent convex shape whereas in situ temperature profiles obtained by the advanced piston coring temperature probe are mostly linear at all sites established during the national gas hydrate program 02 expedition nghp 02 assuming a one dimensional time dependent model for the advection of pore fluid including the sedimentation effect and depth dependent diffusivity we estimate darcy velocity and the cl concentrations at depth the best fit darcy velocity of 1 2 1 6 10 11 m s was estimated for the sites along the crest of the regional anticlinal structure in the nghp 02 area b which was significantly faster than those on the flanks of the anticline because the thermal diffusion coefficient is much larger than the chloride ion diffusion coefficient estimated darcy velocities are not great enough to generate nonlinear temperature profiles with depth which is consistent with observed linear thermal profiles

relationship of clathrate instability to sediment deformation in the upper neogene of california widespread soft sediment deformation ssd in upper bathyal continental margin sediments has been explained by compaction related dewatering and related physical processes that can destabilize margin sediments we present the hypothesis that ssd in such facies resulted in part from instability of gas hydrates clathrates leading to overpressurization in sediments and resulting fluid flow and brecciation clathrate related deformation must be widespread in upper bathyal continental margin methanogenic sequences at depths where clathrates are destabilized by changes in bottom water temperatures and sea level a close association exists between an array of ssd features with clathrate hosting sediments in ocean drill cores similar features are conspicuous in the partly laminated upper neogene upper bathyal sediments of the sisquoc formation in southern california suggesting that clathrates may have been responsible for abundant and well developed ssd in these units the lithology methane producing organic content and depositional environment of the sisquoc formation are similar to those features in modern clathrate hosting settings these characteristics in conjunction with the upper bathyal paleobathymetry of the unit the geothermal gradient of the region and 13 c values of benthic foraminifera and dolomite concretions suggest the occurrence of clathrates in the shallow subsurface of these sediments we suggest that the analyzed parts of the sisquoc formation represent an exhumed zone of ssd resulting from clathrate instability in the shallow subsurface of the continental margin sedimentary rocks exhibiting an association of ssd features that resulted from clathrate formation and dissociation are named clathrites

thermal and maturation history of jurassic source rocks in the kuqa foreland depression of tarim basin nw china abstract kuqa foreland depression of the tarim basin is one of the largest gas production provinces in china thermal history reconstruction using vitrinite reflectance data indicates that the palaeo heat flow in kuqa depression was relatively high 50 55 mw m 2 during the mesozoic but gradually decreased during the cenozoic to reach the present value of 40 50 mw m 2 the cooling of the kuqa depression is probably attributed to the crust thickening and the rapid sedimentary rate the jurassic source rocks entered conventional oil window at 100 ma and began to generate gas at approximately 75 ma in the kelasu area thermal maturation of the jurassic source rocks accelerated significantly since 23 3 ma especially in the recent 5 2 ma in this foreland depression source rock maturation which is likely controlled mainly by burial history also influenced by the presence of fault thrusting and salt bearing formations

consolidation and break up of the south american platform in southeastern brazil tectonothermal and denudation histories the different tectonic stages that occurred at the end of the proterozoic and during the phanerozoic have an important bearing on the tectonothermal history of the south american platform and its consolidation geochronological data u pb monazite 40ar 39ar whole rock and apatite fission track analysis from precambrian rocks of the southeastern brazilian coastline permit the modeling of a long term thermal history of the crust and constrain variable denudation rates using these data a temperature time diagram reflects a period of accelerated exhumation during the end of the brasiliano orogeny followed by long stability and reactivation of the platform during the rifting phase of the south atlantic ocean u pb zircon and monazite blocking temperature of ca 650 c data from a series of igneous bodies suggest that a tangential and transpressional tectonic regime occurred between 625 and 610 ma during the following escape tectonics between 610 and 590 ma the exhumation process indicates cooling rates of ca 12 c ma 40ar 39ar biotite ages between 540 and 510 ma ca 300 c and a corrected fission track age on apatites 100 c of 480 ma indicate an exhumation event related to block tectonics with huge vertical displacement along shear zones a long stabilization phase with low exhumation and cooling rate around 0 25 c ma was recorded from the cambro ordovician to the mesozoic at 65 ma an acceleration of the exhumation through denudation and reworking of the south american surface with cooling rate of 1 5 c ma is observed the uplift of the mantiqueira and serra do mar mountain ranges along the southeast brazilian coastline works as a climatic barrier provoking lateral erosional processes causing long term scarp retreat combined with intense but progressive denudation towards the continent a denudation of 2 5 to 4 km was calculated for such processes this lateral retreat of escarpments and flexural response can provide important insights regarding marginal isostatic uplift and the evolution of offshore sedimentary basins of southeast brazil

attribution of ionospheric vertical plasma drift perturbations to large scale waves and the dependence on solar activity 1 in this study we quantify the contribution of individual large scale waves to ionospheric electrodynamics and examine the dependence of the ionospheric perturbations on solar activity we focus on migrating diurnal tide dw1 plus mean winds migrating semidiurnal tide sw2 quasi stationary planetary wave one qspw1 and nonmigrating semidiurnal westward wave one sw1 under northern winter conditions when qspw1 and sw1 are climatologically strong from thermosphere ionosphere mesosphere electrodynamics general circulation model simulations under solar minimum conditions it is found that the mean winds and dw1 produce a wave two pattern in equatorial vertical e bdrift that is upward in the morning and around dusk the modeled sw2 also produces a wave two pattern in the ionospheric vertical drift that is nearly a half wave cycle out of phase with that due to mean winds and dw1 sw1 can cause large vertical drifts around dawn while qspw1 does not have any direct impact on the vertical drift wind components of both sw2 and sw1 become large at middle to high latitudes in the e region and kernel functions obtained from numerical experiments reveal that they can significantly affect the equatorial ion drift likely through modulating the e region wind dynamo the most evident changes of total ionospheric vertical drift when solar activity is increased are seen around dawn and dusk reflecting the more dominant role of large f region pedersen conductivity and of the f region dynamo under high solar activity therefore the lower atmosphere driving of the ionospheric variability is more evident under solar minimum conditions not only because variability is more identifiable in a quieter background but also because the e region wind dynamo is more significant these numerical experiments also demonstrate that the amplitudes phases and latitudinal and vertical structures of large scale waves are important in quantifying the ionospheric responses