microatolls and recent sea level change on coral atolls microatolls are colonies of corals commonly porties which are dead on top but living around their perimeter and are found in intertidal environments on coral atolls they can grow to several metres in diameter their upward growth is constrained by sea level through prolonged exposure at the lowest spring tides1 2 and their dead upper surfaces have been limited by past sea levels they act as natural recorders of sea level which is of particular significance for coral atolls thought to be susceptible to inundation and erosion if sea level rises in response to global warming x radiographs of vertical slices through microatolls from the maldives and cocos keeling islands indian ocean and kiribati pacific ocean record sea level fluctuations over the past few decades there is a high degree of reproducibility between adjacent corals although on cocos we noted geographical variation in the pattern of change around the atoll the majority of microatolls sampled on these atolls record a slight fall in sea level over the past ten years

comment on coral reef death during the 1997 indian ocean dipole linked to indonesian wildfires the indian ocean dipole iod caused anomalous upwelling low sea surface temperatures and low sea surface heights along the north eastern indian ocean in 1997 fig 1 1 abram et al 1 2 suggested that coral mortality occurred along a 400 km stretch of indonesian coastline mentawai

the thorium isotope content of ocean water 232th concentrations of surface and deep pacific ocean waters are 0 01 0 02 dpm 1000 kg 60 pgm kg the230th activity is 0 03 0 13 dpm 1000 kg in surface waters and 0 3 2 7 dpm 1000 kg in deep waters chemical residence times based on in situ production from parent isotopes are about the same for230th and228th in surface waters 1 5 years but are ten times greater for230th in deep waters 10 100 years apparently there are additional sources of230th into deep waters at manop site s manganese nodule tops are enriched in th isotopes by adsorption of th from seawater and not by incorporation of th rich particulates

dynamics of the long period tides abstract the long period tides are a tool for understanding oceanic motions at low frequencies and large scales here we review observations and theory of the fortnightly monthly and pole tide constitutents observations have been plagued by low signal to noise ratios and theory by the complex lateral geometry and great sensitivity to bottom slopes a new spectral element model is used to compute the oceanic response to tidal forcing at 2 week and monthly periods the general response is that of a heavily damped q 5 system with both the energy input from the moon and the dissipation strongly localized in space the high dissipation result is probably generally applicable to all low frequency barotropic oceanic motions over much of the ocean the response has both the character of a large scale and a superposed rossby wave like character thus vindicating two apparently conflicting earlier interpretations to the extent that free waves are excited they are consistent with their being dominated by rossby and topographic rossby wave components although gravity modes are also necessarily excited to some degree in general a modal representation is not very helpful the most active regions are the southern ocean and the western and northern north atlantic these results are stable to changes in geometry topography and tide period on a global average basis the dynamical response of mm is closer to equilibrium than is mf

nloadf a program for computing ocean tide loading the loading of the earth by the ocean tides produces several kinds of signals which can be measured by geodetic technique in order to compute these most accurately a combination of global and local models of the ocean tides may be needed the program nloadf convolves the green functions for loading with ocean tide models using a station centered grid with fixed dimensions making it easy to combine different ocean models without overlap in the convolution the program computes all the quantities of interest gravity displacement tilt and strain and includes the case where measurements are made beneath the surface of the ocean

paleogeodetic records of seismic and aseismic subduction from central sumatran microatolls indonesia we utilize coral microatolls in western sumatra to document vertical deformation associated with subduction microatolls are very sensitive to fluctuations in sea level and thus act as natural tide gauges they record not only the magnitude of vertical deformation associated with earthquakes paleoseismic data but also continuously track the long term aseismic deformation that occurs during the intervals between earthquakes paleogeodetic data this paper focuses on the twentieth century paleogeodetic history of the equatorial region our coral paleogeodetic record of the 1935 event reveals a classical example of deformations produced by seismic rupture of a shallow subduction interface the site closest to the trench rose 90 cm whereas sites further east sank by as much as 35 cm our model reproduces these paleogeodetic data with a 2 3 m slip event on the interface 88 to 125 km from the trench axis our coral paleogeodetic data reveal slow submergence during the decades before and after the event in the areas of coseismic emergence likewise interseismic emergence occurred before and after the 1935 event in areas of coseismic submergence among the interesting phenomenon we have discovered in the coral record is evidence of a large aseismic slip or silent event in 1962 27 years after the 1935 event paleogeodetic deformation rates in the decades before after and between the 1935 and 1962 events have varied both temporally and spatially during the 25 years following the 1935 event submergence rates were dramatically greater than in prior decades during the past four decades however rates have been lower than in the preceding decades but are still higher than they were prior to 1935 these paleogeodetic records enable us to model the kinematics of the subduction interface throughout the twentieth century

holocene sea levels and palaeoenvironments malay thai peninsula southeast asia sedimentological and palynological investigations of great songkhla lakes east coast of the malay thai peninsula southeast asia reveal sedimentary sequences rich in palynomorph assemblages dominated by pollen of mangroves and freshwater swamps compared with other regions in southeast asia the assemblages are of relatively low diversity geochronological data indicate that the great songkhla lakes record one of the earliest mangrove environments in southeast asia 8420 8190 cal yr bp which are subsequently replaced by a freshwater swamp at 7880 7680 cal yr bp owing to the decline of marine influence sea level observations from great songkhla lakes and other areas of the malay thai peninsula reveal an upward trend of holocene relative sea level from a minimum of 22 m at 9700 9250 cal yr bp to a mid holocene high stand of 4850 4450 cal yr bp which equates to a rise of c 5 5 mm yr the sea level fall from the high stand is steady at c 1 1 mm yr geophysical modelling shows that hydroisostasy

east asian monsoon evolution and reconciliation of climate records from japan and greenland during the last deglaciation abstract east asian monsoon eam evolution during the last deglaciation has been shown repeatedly to be aligned with paleoclimatic changes in the north atlantic based on climate reconstructions comparing asian speleothem records with greenland ice cores in contrast to this finding paleoclimatic reconstructions based on lake suigetsu sediment cores suggest that past eam variability in japan was not always coherent with climatic variability recorded in greenland ice cores we resolve this discrepancy using an absolute dated stalagmite 18 o record that covers the period between 15 5 and 10 7 thousand years before present ka before ad 1950 this stalagmite record is from nearby maboroshi cave japan and shows climate changes that are synchronous with those of chinese caves and greenland ice cores our results support an effective teleconnection between low and high latitudinal climate systems during the transitions into the bolling allerod ba warming at 14 6 ka and the younger dryas cooling at 12 8 ka in the north atlantic however our results also indicate monsoonal intensification during the ba coincident with decreasing temperatures in greenland from 14 6 to 12 8 ka we explain this decoupling as a result of the interhemispheric bipolar seesaw climate system discrepancies between lake suigetsu radiocarbon age data sets and other radiocarbon calibration archives can also be removed when our maboroshi record is used to adjust the lake suigetsu age model as well as resolving temporal ambiguities in the lake suigetsu paleoclimate record

a 20th century acceleration in global sea level rise 1 multi century sea level records and climate models indicate an acceleration of sea level rise but no 20th century acceleration has previously been detected a reconstruction of global sea level using tide gauge data from 1950 to 2000 indicates a larger rate of rise after 1993 and other periods of rapid sea level rise but no significant acceleration over this period here we extend the reconstruction of global mean sea level back to 1870 and find a sea level rise from january 1870 to december 2004 of 195 mm a 20th century rate of sea level rise of 1 7 0 3 mm yr 1 and a significant acceleration of sea level rise of 0 013 0 006 mm yr 2 this acceleration is an important confirmation of climate change simulations which show an acceleration not previously observed if this acceleration remained constant then the 1990 to 2100 rise would range from 280 to 340 mm consistent with projections in the ipcc tar

tectonics and history of the andaman sea region abstract the andaman sea is an active backarc basin lying above and behind the sunda subduction zone where convergence between the overriding southeast asian plate and the subducting australian plate is highly oblique the effect of the oblique convergence has been formation of a sliver plate between the subduction zone and a complex right lateral fault system the late paleocene collision of greater india and asia with approximately normal convergence started clockwise rotation and bending of the northern and western sunda arc the initial sliver fault which probably started in the eocene extended through the outer arc ridge offshore from sumatra through the present region of the andaman sea into the sagaing fault with more oblique convergence due to the rotation the rate of strike slip motion increased and a series of extensional basins opened obliquely by the combination of backarc extension and the strike slip motion these basins in sequence are the mergui basin starting at 32 ma the conjoined alcock and sewell rises starting at 23 ma east basin separating the rises from the foot of the continental slope starting at 15 ma and finally at 4 ma the present plate edge was formed alcock and sewell rises were separated by formation of the central andaman basin and the faulting moved onshore from the mentawai fault to the sumatra fault system bisecting sumatra

exposed plate interface in the european alps reveals fabric styles and gradients related to an ancient seismogenic coupling zone 1 we present observations from a continuous exposure of an ancient plate interface in the depth range of its former seismogenic zone in the central alps of europe related to late cretaceous early tertiary subduction and accretion of the south penninic lower plate underneath the adriatic upper plate the material forming the exposed plate interface zone has experienced flow and fracturing over an extended period of time followed by syncollisional exhumation thus reflecting a multistage evolution fabric formation and metamorphism however chiefly record the deformation conditions of the precollisional setting along the plate interface we identify an unstable slip domain from pseudotachylytes occurring in the temperature range between 200 and 300 c this zone coincides with a domain of intense veining in the subduction melange with mineral growth into open cavities indicating fast possibly seismic rupture evidence for transient near lithostatic fluid pressure as well as brittle fractures competing with mylonitic shear zones continues into the region below the occurrence of pseudotachylytes possibly reflecting a zone of conditionally stable slip the zone above the unstable slip area is devoid of veins but displays ample evidence of fluid assisted processes similar to the deeper zone solution precipitation creep and dehydration reactions in the melange matrix hydration and sealing of the base of the upper plate seismic rupture here is possibly expressed by ubiquitous localized deformation zones we hypothesize that trenchward sealing of parts of the plate interface as well as reaction enhanced destruction of upper plate permeability is an important component localizing the unstable slip zone this relation may result from the competition of the pervasive presumably interseismic pressure solution creep destroying permeability and building elevated fluid pressure until the strength threshold is reached with seismic failure

coral evidence for earthquake recurrence and an a d 1390 1455 cluster at the south end of the 2004 aceh andaman rupture coral records of relative sea level change provide a history of vertical interseismic and coseismic deformation along the coast of northern simeulue island sumatra and reveal details about earthquakes in the 10th and 14th 15th centuries a d along the southern end of the december 2004 m w 9 2 sunda megathrust rupture over a 56 year period between a d 1390 and 1455 northern simeulue experienced a cluster of megathrust ruptures associated with total uplift that was considerably more than in 2004 uplifted corals at two sites constrain the first event of the cluster to a d 1393 3 and 1394 2 2 a smaller but well substantiated uplift occurred in northern simeulue in 1430 3 an inferred third uplift in a d 1450 3 killed all corals on the reef flats of northern simeulue the amount of uplift during this third event though confirmed only to have exceeded 28 and 41 cm at two sites probably surpassed the 100 and 44 cm that occurred respectively at those sites in 2004 and it was likely more than in 2004 over all of northern simeulue the evidence for past earthquake clustering combined with the inference of considerably greater uplift in a d 1390 1455 than in 2004 suggests that strain may still be stored along the southernmost part of the 2004 rupture interseismic subsidence rates recorded by northern simeulue coral microatolls have varied by up to a factor of 4 at some sites from one earthquake cycle to another

interseismic deformation above the sunda megathrust recorded in coral microatolls of the mentawai islands west sumatra past half century vary from 2 to 14 mm yr 1 and increase southwestward toward the subduction trench the pattern is consistent with rates of subsidence measured by a sparse network of continuously recording global positioning system cgps stations and with locking of a 400 km long section of the underlying subduction megathrust between about 1s and 4s this record of subsidence and tilting extending nearly a century into the past implies that the region is advancing toward the occurrence of another giant earthquake however evidence of episodic rather than steady subsidence reflects a behavior that is more complex than simple elastic strain accumulation and relief most prominent of these episodes is an extensive emergence subsidence couplet in about 1962 which may be the result of rapid aseismic slip on the megathrust between the islands and the trench lower subsidence rates recorded by the corals since about 1985 may reflect failure on many small patches within the locked section of the megathrust

paleoshoreline record of relative holocene sea levels on pacific islands abstract understanding the history of relative holocene sea levels on pacific islands is important for constraining fundamental geodynamic theories interpreting the environments of early human occupation sites and forecasting future environmental conditions on the islands an observational paleoshoreline record is provided by emergent paleoshoreline indicators formed at higher relative sea levels hence standing at higher elevations than modern counterparts emergent paleoshoreline notches in limestone seacliffs record paleo high tide levels and emergent paleoreef flats record paleo low tide levels whereas emergent paleobeachrock locally records paleo intertidal levels both paleonotches and paleoreefs occur along the coasts of high standing islands exposing volcanic bedrock and uplifted reef complexes but low lying coralline atolls lack sufficient relief to preserve paleonotches controls on relative holocene sea level include global eustatic and regional hydro isostatic changes in ambient sea level relative to island landmasses and shifts in the elevations of islands relative to sea level caused by thermal subsidence of the oceanic lithosphere or thermally rejuvenated loci of hotspot volcanism by flexure of the lithosphere under the load of growing volcanic edifices hawaii samoa society islands by arching of the lithosphere over trench forebulges loyalty islands niue bellona rennell and by tectonism within forearc belts between active volcanic chains and trenches mariana islands tonga vanuatu the dominant pattern of relative sea level change where not overprinted by local tectonism or lithospheric flexure was a uniform early holocene rise in eustatic sea level followed by a regionally variable late holocene hydro isostatic drawdown in sea level the resultant was a mid holocene highstand in relative sea level that affected the development of shoreline morphology throughout the tropical pacific ocean the earliest human migrations into intra oceanic island groups of both the northwestern and southwestern pacific ocean followed close on the heels of the mid holocene sea level highstand and took advantage of newly attractive coastal environments engendered by sea level drawdown the effects of the mid holocene highstand were modified to varying degrees in different island groups by geodynamic uplift or subsidence

huge erratic boulders in tonga deposited by a prehistoric tsunami along some coastlines there are erratic boulders apparently emplaced by tsunamis or cyclonic storms evaluating their origin and time of emplacement places constraints on the frequency severity and location of coastal hazards seven such large coral limestone boulders are present near fahefa village on tongatapu island southwest pacific apparently emplaced by a prehistoric tsunami these boulders are 10 20 m above sea level and above any possible source and all are 100 400 m from the present shoreline coral 230th ages indicate that the limestone formed during the last interglacial sea level highstand ca 120 130 ka the largest boulder is 20 times more massive than any reported boulders emplaced by historically documented storms and may be the largest known tsunami or storm erratic worldwide situated above its source we performed computer simulations to assess whether tsunamis produced by earthquakes undersea landslides or volcanoes could emplace the boulders the simulations indicate that either volcanic flank collapse along the tofua arc 30 40 km to the southwest or undersea landslides on the submarine slopes of tongatapu could be responsible either could explain why these boulders are not widespread on tongatapu and instead occur in a localized group along the western coast this study demonstrates that small 1 km3 submarine slope failures sometimes generate locally large tsunamis the fahefa boulders are in a well studied and well populated area yet were unknown to the scientific community until recently this suggests that systematic searches elsewhere for erratic boulders and other tsunami deposits might provide new information for assessing the size and extent of prehistoric tsunamis

reconstruction of tsunami inland propagation on december 26 2004 in banda aceh indonesia through field investigations this paper presents the results from an extensive field data collection effort following the december 26 2004 earthquake and tsunami in banda aceh sumatra the data were collected under the auspices of tsunarisque a joint french indonesian program dedicated to tsunami research and hazard mitigation which has been active since before the 2004 event in total data from three months of field investigations are presented which detail important aspects of the tsunami inundation dynamics in banda aceh these include measurements of runup tsunami wave heights flow depths flow directions event chronology and building damage patterns the result is a series of detailed inundation maps of the northern and western coasts of sumatra including banda aceh and lhok nga

instantaneous global plate motion model from 12 years of continuous gps observations 1 we estimate a global plate motion model for 17 major and minor tectonic plates solely on the basis of analysis of data from 106 globally distributed continuous gps stations spanning the period from january 1991 to july 2003 site positions estimated from 24 hour segments of data are aligned day by day to the international gps service igs realization of the itrf2000 reference frame using a similarity transformation thereby ensuring that the itrf2000 no net rotation condition is preserved linear velocities of a carefully selected set of stations are estimated from the position time series along with annual and semiannual fluctuations and position offsets due to gps instrument changes a white noise plus flicker noise model is applied to estimate realistic uncertainties for the site velocities which are then propagated into the derived plate motion model parameters we also examine the vertical velocities in the site selection process at the scripps orbit and permanent array center we have implemented a procedure whereby the plate motion model is updated on a regular monthly basis to improve its precision and reliability as new data become available and as a baseline against which anomalous motions can be detected

new insights into archean sulfur cycle from mass independent sulfur isotope records from the hamersley basin australia we have measured multiple sulfur isotope ratios 34 s 33 s 32 s for sulfide sulfur in shale and carbonate lithofacies from the hamersley basin western australia the v 33 s values v 33 swn 33 s30 515un 34 s shift from 31 9 to 6 9x over a 22 m core section of the lower mount mcrae shale v2 5 ga likewise sulfide sulfur analyses of the jeerinah formation v2 7 ga yield v 33 s values of 30 1 to 8 1x over a 50 m section of core despite wide variations in v 33 s and n 34 s these two shale units yield a similar positive correlation between v 33 s and n 34 s in contrast pyrite sulfur analyses of the carawine dolomite v2 6 ga yield a broad range in n 34 s 3 2 to 16 2x but a relatively small variation and negative values in v 33 s 32 5 to 31 1x the stratigraphic distribution of n 33 s n 34 s and v 33 s in western australia allows us to speculate on the sulfur isotopic composition of archean sulfur reservoirs and to trace pathways in the archean sulfur cycle our data are explained by a combination of massindependent fractionation mif in the atmosphere and biological mass dependent fractionation in the ocean in the archean volcanic sulfur bearing gas species were photolysed by solar ultraviolet uv radiation in an oxygen free atmosphere resulting in mif of sulfur isotopes aerosols of s8 with v 33 ss 0 and sulfuric acid with v 33 s6 0 formed from the products of uv photolysis and carried mass independently fractionated sulfur into the hydrosphere the signatures of atmospheric photolysis were preserved by precipitation of pyrite in sediments pyrite precipitation was mediated by microbial enzymatic catalysis that superimposed mass dependent fractionation on mass independent atmospheric effects multiple sulfur isotope analyses provide new insights into the early evolution of the atmosphere and the evolution and distribution of early sulfur metabolizing organisms a 2003 elsevier science b v all rights reserved

integrated pb and s isotope investigation of sulphide minerals from the early archaean of southwest greenland we present high spatial resolution secondary ion mass spectrometry sims measurements of pb and s isotopes in sulphides from early archaean samples at two localities in southwest greenland secondary pyrite from a 3 71 ga sample of magnetite quartz banded iron formation in the isua greenstone belt which has previously yielded unradiogenic pb consistent with its ancient origin contains sulphur with a mass independently fractionated mif isotope signature delta 33 s 3 3 parts per thousand this reflects the secondary mineralization of remobilized sedimentary s carrying a component modified by photochemical reactions in the early archaean atmosphere it further represents one of the most extreme positive excursions so far known from the early archaean rock record sulphides from a quartz pyroxene rock and an ultramafic boudin from the island of akilia in the godth a over circle bsfjord have heterogeneous and generally radiogenic pb isotopic compositions that we interpret to represent partial re equilibration of pb between the sulphides and whole rocks during tectonothermal events at 3 6 2 7 and 1 6 ga both these samples have delta 33 s 0 within analytical error and therefore show no evidence for mif sulphur these data are consistent with previous interpretations that the rock cannot be proven to have a sedimentary origin our study illustrates that sims s isotope measurements in ancient rocks can be used to elucidate early atmospheric parameters because of the ability to obtain combined s and pb isotope data but caution must be applied when using such data to infer protolith when information from geological context petrography and chronology i e by pb isotopes is combined and fully evaluated delta 33 s signatures from sulphides and their geological significance can be interpreted with a higher degree of confidence c 2005 elsevier b v all rights reserved