pacific modulation of accelerated south indian ocean sea level rise during the early 21st century the south indian ocean has shown an unprecedented sea level rise during the early 21st century sea level rise in the south indian ocean is found to be 37 quicker than the global mean sea level during 2000 2015 observational datasets and long term proxy records identify pacific origin of the south indian ocean sea level rise our results indicate that co evolution of the cold phase of pacific decadal oscillation pdo and prolonged la nina like condition enhances the equatorial pacific easterlies stronger in phase association of these major pacific climate modes and equatorial pacific easterlies enhances the indonesian throughflow itf transporting fresh and warm water anomalies from western tropical pacific into the south indian ocean as a result south indian ocean sea level rise has accelerated more than the global with 40 contribution from the halosteric sea level primarily through the itf transport and a secondary from the local processes during 2000 2015 the co evolution of pdo and the south indian ocean sea level is also evident from the long term proxy records indicating that the association is part of an internal mode of variability modulated on decadal time scales the finding from the study cautions that accelerated heat and freshwater intrusion from the western pacific with the co evolution of pdo and la nina like condition may lead to the accelerated sea level rise and marine heat waves in the south indian ocean imposing threats to the life of coral reefs and marine ecosystems

tectonics of the hellenic trench a synthesis of sea beam and submersible observations abstract detailed bathymetric investigations were performed in four zones of the hellenic trench system in 1978 using the multi narrow beam echo sounder sea beam on r v jean charcot in 1979 a field study using the 3000 m submersible cyana was conducted in three of the four sites covered by sea beam we summarize here the principal tectonic results of these studies and publish the corresponding sea beam maps it is shown that compressional structures affect the sedimentary cover of the outer wall and trench whereas extensional tectonics is present on the inner wall in addition there is evidence that most of the upper sedimentary cover is not subducted but rather piles up in front of the trench to form the mediterranean ridge we suggest that the surface limit of the zone of mechanical decoupling occurs near the base of the inner wall we show that the gross structure of the trench as well as the strain pattern observed is controlled by the kinematics of subduction and we discuss its evolution since its initiation about 13 m y ago

strain distribution over the east mediterranean ridge a synthesis incorporating new sea beam data abstract we present the results of several multi narrow beam sea beam traverses of the mediterranean ridge on board r v jean charcot these results can be considered to be complementary in resolution and coverage to the previously published long range side scan sonar gloria results a characteristic of the mediterranean ridge is the presence over about half of its surface of an extensive fold system affecting the messinian and plio quaternary cover which is dissected by conjugate strike slip faults the resolution of sea beam was used to map the main characteristics of folding and faulting this analysis together with previously available data enables us to define the strain pattern over the mediterranean ridge we thus now have an overall view of the strain pattern from a marginal basin aegea through the hellenic trench and adjacent sea floor to the opposite continent the bottom of the hellenic trench is a boundary between an extensional domain to the north and a compressional one to the south the southern domain is strongly affected by the presence of the lybian promontary it is related to the formation of an accretionary ridge due to the inability of the upper 3 4 km of sediments to subduct this ridge is similar to the accretionary prism but it is much wider with respect to its height probably because of the existence of a decollement over a level of overpressure the hellenic trench then is in the situation of a fore arc basin its origin is due to the fact that the aegean continental slope is not vertical but rather has a small 4 dip as a result a sedimentary wedge symmetric but shorter than the main accretionary wedge develops over the buried portion of the slope it is characterized by landward thrusts such an origin probably applies to fore arc basins in general

paleomagnetic results from mio pliocene marine sedimentary series in crete abstract paleomagnetic measurements have been conducted on mio pliocene marine sedimentary series from crete in order to detect any eventual rotation of this island the results obtained from 14 stable sites of tortonian age 7 m y yield a paleomagnetic pole not significantly different from either the european or the african ones showing that crete has not undergone any significant rotation since that epoch

south indian countercurrent and associated fronts a striking feature of the south indian ocean circulation is the presence of the eastward south indian countercurrent sicc that flows in a direction opposite to that predicted by the classical theories of wind driven circulation several authors suggest that the sicc resembles the subtropical countercurrents stccs observed in other oceans which are defined as narrow eastward jets on the equatorward side of subtropical gyres where the depth integrated flow is westward these jets are associated with subsurface thermal fronts at thermocline depths by the thermal wind relation however the subsurface thermal front associated with the sicc has not been described to date other studies conjecture an important role for salinity in controlling the sicc in the present work we analyze three argo based atlases and data from six hydrographic cruises to investigate whether the sicc is accompanied by permanent thermal and density fronts including salinity effects the seasonal cycle of these fronts in relation to the sicc strength is also investigated we find that the sicc is better described as composed of three distinct jets which we name the northern central and southern sicc we find that the southern sicc around 26 s has an associated thermal front at subsurface depths around 100 200 m with salinity being of secondary importance the southern branch strength is related to mode waters poleward of the front similar to a stcc like current however the sicc multiple jet structure seems to be better described as resulting from pv staircases

analyses of fault mechanisms and expansion of southwestern anatolia since the late miocene abstract neotectonic field studies and detailed analyses of neogene and quaternary fault mechanisms in southwestern anatolia enable us to recognize a succession of compressional and extensional events and to characterize the direction of corresponding regional stresses the three most important compressive phases occurred during the miocene and a much smaller one near the plio quaternary boundary the last one or two interrupted a widespread extension of much greater duration and amplitude the whole tectonic evolution resembles that of the aegean the large extension by normal faulting is consistent with a minimum stress along a nne ssw average direction it appears that this direction was n s during the pliocene and changed to ne sw sometime during the quaternary this dominant nne ssw extension which began during late miocene or earliest pliocene was related to the development of the southwestern anatolian graben system

active deformation of a segment of arc the strait of kythira hellenic arc greece abstract a field analysis of late cenozoic faults has been carried out in the southwest hellenic arc on the islands of kythira and antikythira as well as on both sides of the strait in southeast peloponnisos and western crete the previously unknown geological structure of antikythira is briefly described together with accurate bathymetric data obtained using a multi beam echo sounder on submarine fault scarps the results of studies on land lead to a new interpretation of the neotectonic deformation of this segment of the hellenic arc the submersion of the strait is a consequence of extension related to normal faulting the extension rate being faster than in adjacent segments of the arc the direction of extension related to late pliocene quaternary normal faulting is determined from on land information the existence of oblique en echelon normal faults indicates that dextral deformation plays a role within the kythira strait in connection with the opening of the adjacent cretan sea triggered by subduction beneath the hellenic arc the whole pattern of fault systems in southeast peloponnisos as inferred from teledetection and field studies is consistent with the clockwise rotation that has been independently proposed and verified by palaeomagnetic studies the kythira strait thus provides an example of a complex transform extensional deformation and rotation between two major segments of external arc

mesoscale eddy characteristics in the interior subtropical southeast indian ocean tracked from the leeuwin current system abstract two oppositely rotating mesoscale eddies originating from the leeuwin current were captured during a research cruise in the interior southeast indian ocean in august 2012 a few hundred kilometers off the west coast of australia the two eddies had different vertical structures the anticyclonic eddy had stronger vertical shear above 200 m and a less stratified thermocline below the mixed layer while the cyclonic eddy had a more barotropic structure in the upper 500 m compared with the same types of eddies sampled in 2003 close to the australian coast the 2012 anticyclonic eddy had a larger radius deeper isothermal depths and higher peak velocity whereas the 2012 cyclonic eddy had a similar structure with the 2003 survey we use an argo float and three surface drifters deployed and trapped in the anticyclonic eddy to track its evolution over a 4 month period the eddy was observed to propagate 1000 km further to the west indicating that the leeuwin current properties of the eddy may be preserved for over 2000 km off the west coast of australia the eddy appeared to have experienced radial excursions relative to the eddy center with periodicity of 4 6 days and 15 days during their anticlockwise motions the radial movements of the drifters appeared to be constrained by the radial momentum balance within the eddy the importance of eddy distortions to ocean primary production in anticyclonic eddies in the southeast indian ocean warrants further studies

geochemical fingerprints of climate variation and the extreme la nina 2010 11 as recorded in a tridacna squamosa shell from sulawesi indonesia abstract we used a tridacna squamosa tridacnidae bivalvia shell that lived between 2006 and 2012 to reconstruct environmental conditions in south east sulawesi indonesia we focused mainly on estimating the influence of temperature and rainfall on the shell geochemistry as well as enso anomalies comparison of the measured and theoretical 18 o values show clear seasonal variations and confirms that this species secretes its shell at isotopic equilibrium the 18 o in t squamosa shows how the increased rainfall associated with monsoon precipitations in this area influences the 18 o shell signal during the rainy season the correlation between shell 18 o and sst r 2 0 62 decrease in warm wet seasons sst 28 5 c shell mg ca profiles presents better correlation with sst r 2 0 8 than sr ca profiles r 2 0 52 shell ba ca ratio increases during each dry season when primary productivity is maximum secondary ba ca peaks also occur during the certain wet seasons and appear associated with abnormal enhanced runoff shell 13 c co varies with primary productivity and salinity with highest 13 c values occurring during the dry seasons during 2010 11 abnormal values were detected in all geochemical proxies as result of the strong la nina event this calibration study demonstrates the ability of t squamosa shells to accurately reflect present day environmental processes with seasonal resolutions and to define the local signature of hydrological changes associated with enso

the deformation of aegea a finite element study abstract the concentration of extension in southern aegea is a consequence of the velocities imposed along the boundaries of this region this result is demonstrated by using the finite element method and velocities derived independently from the kinematics of the hellenic subduction zone and that of the north anatolian fault the thinning of the lithosphere resulting from this extension is in good agreement with that required to explain the aegean subsidenceand the forces along the boundaries are approximately normal to the aegean arc neotectonic data agree with these results

the hellenic margin from eastern crete to rhodes preliminary results abstract complementary data on previously surveyed areas have been obtained and more than 3000 km of continuous seismic profiles along the eastern hellenic continental margin between eastern crete and rhodes have been made among the important preliminary observations we note the relatively great thickness due to probable coarse rapid fill of the margin sedimentary cover which is also intensively affected by extensional faulting the presence of a well defined sedimentary basin lying between the strabo and pliny trench where evaporitic strata exist but where the acoustic facies also suggest coarse fill is probably derived from surrounding topographical highs exposed to erosion during the messinian finally we observe a progressive and perplexing change of the strabo trench structural pattern from west to east which indicates a more complex tectonic regime than we expected we speculate that at the southern margin of the rhodes basin northward thrusting may now be occurring

freshening anomalies in the indonesian throughflow and impacts on the leeuwin current during 2010 2011 during the 2010 2011 la nina and ningaloo nino excessive precipitations in the maritime continent and indonesian australian basin caused surface waters to freshen by 0 3 practical salinity unit in the southeast indian ocean the low salinity anomalies are observed to be carried westward by the indonesian throughflow and the south equatorial current and transmitted into the poleward flowing eastern boundary current the leeuwin current along the western australian coast low salinity anomalies contribute to about 30 of the anomalous increase of the southward leeuwin current transport during the evolution of the 2010 2011 ningaloo nino resulting in unprecedented warming off the coast of western australia episodical freshening of the leeuwin current has been observed at the rottnest coastal reference station of western australia during extended la nina conditions over the past several decades low salinity anomalies at the station during the 2010 2011 ningaloo nino are comparable with strong historical events

extensional compressional tectonics associated with the aegean arc comparison with the andean cordillera of south peru north bolivia extensional compressional tectonics are analysed along the convergent boundaries of the aegean arc and of the andean cordillera of south peru and north bolivia this paper deals only with deformations of miocene pliocene and pleistocene ages the prevailing regime in the aegean basin is extensional yet two compressional tectonic phases of u miocene l pliocene and of l pleistocene age have been recorded they are also known in many places all around the mediterranean thus forces that induce compressional tectonics in the aegean seem to have their origin outside the region they seem to be linked with changes in the conditions of convergence change in rate between the arabo african and eurasian plates beneath the andean cordillera of south peru north bolivia the subduction zone plunges at an angle of 25 30 as it does under the aegean arc there as in the aegean sea tectonics are predominantly extensional and several short lived compressional phases break up this extensional regime the latter may also be induced by changes of the conditions of convergence here between the nazca and south american plates beneath central peru north of the nazca ridge the subduction zone plunges at a small angle about 10 there neotectonic deformations are different in the recent they are essentially compressional or expressed by strike slip faulting geological data from the aegean and andes seem to demonstrate that the compressional deformation in the crust above subduction zones is strongly controlled by the stress conditions along convergent boundaries

regional compensation of subducted lithosphere effects on geoid gravity and topography from a preliminary model abstract it is proposed that the anomalous mass of subducted lithospheric slabs is partially compensated by two mechanisms a by stresses transmitted up the slab to the surface lithosphere causing the trench and b by stresses transmitted through the mantle wedge overlying the slab which cause a broad shallow depression results calculated from a preliminary two dimensional model show that it can give a first order account of observed topography gravity and geoid anomalies in particular the model can reconcile the large mass anomaly predicted for the slab by thermal conduction theory with the smaller than expected gravity and geoid anomalies preliminary results indicate substantial compensation by mechanism a implying rather large stresses at the top of the slab these could be important for theories of earthquake mechanisms and plate driving mechanisms roughly 50 of the possible compensation by mechanism b is indicated the resulting depression the order of 500 m deep and over 500 km wide could explain anomalously deep marginal basins and some marine transgressions of continents

the aegean sea we summarize briefly the main features of a kinematic model of evolution of the aegean area since 13 ma the formation of the aegean sea by extensional tectonics is related to the subduction of the mediterranean floor below the hellenic arc we then make a quantitative estimate of vertical movements in the aegean area on the basis of geological data and demonstrate that the outer arc was built since the beginning of this episode of subduction by vertical uplift the easiest way to explain the uplift is by underplating finally we discuss briefly the dynamics of the subduction marginal sea formation processes in this continental collision framework

crustal block movements from holocene shorelines crete and antikythira greece abstract marks of several shorelines left by sea level stands during the last 4000 yrs occur along the coasts of the islands of crete and antikythira in this area recent movements of the earth s crust were identified by using a systematic survey based on multidisciplinary analyses strengthened by 60 radiometric datings between 4000 and 1700 yr b p a block of lithosphere a about 150 km long fig 10 which included antikythira and the levka mountains in crete underwent a series of ten rapid subsidences from 10 to 25 cm each time without noticeable tilting these movements ended about 1 530 40 yr b p a further block of lithosphere b approximately 200 km long was then uplifted about 10 m and inclined northeastwards in a single event block b includes block a and extends 50 km further eastwards beyond the ida mountains as far as the iraklion sedimentary basin the tectonic movements were preceded by vertically reversed displacements of short duration on at least three occasions if the a block subsidences can be ascribed to gravitational forces then the b block uplift suggests a cause that originated at depth crustal consumption and elastic rebound to the east of the ierapetra graben the sitian peninsula appears to belong to a block of lithosphere c affected by a northeast tilting and separated by an active fault from the crustal block of khrisi koufonisi

the tectonic development of the hellenic arc and the sea of crete a synthesis abstract we use field analyses together with interpretation of aerial photographs orbital imagery and sea beam data to define more accurately the geometry of fault systems in the hellenic arc the tectonics of the area are dominated by extensional processes related to normal faulting we then use sea beam data previous oceanographic studies and extrapolation of field analyses on surrounding islands to describe the fault pattern of the cretan sea basin which is found consistent with the land fault pattern the mechanisms of the late neogene and quaternary deformation of the central and southern aegean region are analysed in terms of stress trajectories as revealed by field studies of fault populations we then examine the subsidence of the sea of crete in terms of a model of uniform stretching of the lithosphere the opening of the sea of crete was cylindrical and did not result in bending of crete this leads us to modify the southern portion of an earlier kinematic reconstruction of aegea in agreement with recent paleomagnetic results the implications of the opening of the sea of crete on the tectonic evolution of the straits to the west and east of crete are discussed finally the uplift of the outer arc is explained by underplating due to subduction