spatio temporal structure of the pentadecadal variability over the north pacific abstract using a multi taper frequency domain singular value decomposition mtm svd a pentadecadal oscillation was detected in the winter spring sea level pressure slp field over the north pacific and surface air temperature in north america which was significant at the 95 confidence level the mtm svd captured the different slp and air temperature distributions between the winter and spring seasons in a consistent manner the pentadecadal slp signature in the spring season is centered nearer the west coast of north america than in the winter season this zonal displacement is consistent with the prominent springtime pentadecadal air temperature variability in mid latitude western north america a wavelet analysis of the pacific decadal oscillation index pdoi showed that the regime shifts in the 1920s 1940s and 1970s involved simultaneous phase reversals of the bidecadal and pentadecadal variations the two interdecadal variations are synchronized with one another such that a half period of the pentadecadal oscillation one epoch of an individual regime corresponds to one and half periods of the bidecadal oscillation these results are consistent with the wavelet analysis of the north pacific index npi similar resonance between the bidecadal and pentadecadal variations is evident in air temperatures over alaska the bidecadal and pentadecadal signals have different seasonality in these time series suggesting that although the two interdecadal variations arise from two different physical mechanisms they interact with each other the most distinct seasonal difference was observed in mid latitude western north america where the bidecadal variation prevails only in the winter season and the pentadecadal variation only in the spring season alaska air temperatures in the winter and winter spring of 1999 were the coldest since 1977 as were springtime air temperatures in mid latitude western north america in contrast to the warm anomalies that prevailed in this region during 1977 98 the npi and pdoi also exhibited an opposite polarity in 1999 to the respective regime mean polarities these anomalous conditions in winter and spring seasons of 1999 may signify a major regime shift in 1998 1999 in order to verify whether or not a regime shift did occur in 1998 1999 a careful examination of additional data in coming ten or so years will be necessary

decadal variability in the kuroshio oyashio extension simulated in an eddy resolving ogcm abstract through analysis of a hindcast integration of an eddy resolving quasi global ocean general circulation model decadal variability in the kuroshio oyashio extension region is investigated with particular emphasis on that of the subarctic oyashio and the kuroshio extension ke fronts the ke front is deep and is accompanied by a sharp sea surface height ssh gradient with modest sea surface temperature sst gradient in contrast the subarctic front is shallow and is recognized as a zone of tight gradient in sst but not ssh as a decadal scale change from a warm period around 1970 to a cool period in the mid 1980s those fronts in the model migrate southward as observed and the associated pronounced cooling is confined mainly to those frontal zones reflecting the distinctive vertical structure of the fronts the mixed layer cooling is the strongest along the subarctic front whereas the subsurface cooling and the associated salinity changes are most pronounced along the ke front concomitan

role of the ocean in the decadal climate change in the north pacific 1 i have investigated features of decadal climate variability in the north pacific and clarified the role of the ocean in controlling them by analyzing historical data sets and executing experiments with a low order model detailed investigation of the variability of the wintertime aleutian low and water temperature in the subarctic frontal region implies a new scenario for the mechanism of the decadal variability the decadal variability can be interpreted as the transition process between two stable states cold and warm period in midlatitude atmosphere when the transition to a cold period occurs sea surface temperature in the subarctic frontal region begins to be lowered not only through the surface processes but by westward propagation of cold anomaly from eastern subarctic region as a baroclinic rossby wave as a result the meridional gradient of sea surface heat flux yq0 decreases its magnitude and then the forcing of the aleutian low is weakened when this weakening exceeds a threshold the transition from a cold to a warm period occurs abruptly after the transition to a warm period yq0 in turn increases its magnitude through the opposite processes to cause the reverse transition the timescale of this cycle is mainly determined by the propagation speed of a baroclinic rossby wave the el nino and southern oscillation variability both in the atmosphere and ocean can also affect the timescale by causing the thresholds for transitions to be temporarily exceeded experiments with a four variable low order model support the proposed mechanism of the decadal variability

rossby waves in the tropical north pacific and their role in decadal thermocline variability abstract a band of enhanced thermocline variability at 10 15 n in the pacific found in nature also occurs in an ocean general circulation model forced with observed fluxes of momentum heat and freshwater over the period 1958 97 the variability in the model is primarily associated with long baroclinic rossby waves characterized by periods in the decadal range 7 10 yr the waves are forced by westward propagating ekman pumping anomalies east of the date line and propagate at a speed of 13 cm s 1 which is slower than the phase speed of the first mode unforced baroclinic waves 15 16 cm s 1 west of the date line the correlations between thermocline displacements and local ekman pumping are relatively small and the ocean signals have a phase speed of 20 cm s 1 very similar to the phase speed of the first baroclinic mode in the western half of the basin 18 20 cm s 1 the phase speeds of the ocean model signals have been estimated using cospectral analysis while the wkb approximation has been us

spatio temporal variability in suspended particulate matter concentration and the role of aggregation on size distribution in a coral reef lagoon this paper presents the concentration and size distribution of suspended particles in the south west coral reef lagoon of the island of new caledonia data are provided by filtration techniques optical backscattering obs measurements and in situ laser diffraction particle sizing the concentration of suspended particles increased from reef to land a bottom nepheloid layer occurred over the entire lagoon and was more distinct on the nearshore area small particles were more abundant in the bottom nepheloid layer than in the overlying water column the concentration of suspended particles showed more variability over space than over time conversely the particle size distribution of suspended particles showed more variability at a given location over a month time variability than at a given moment over the lagoon space variability analysis showed that aggregates represented a large fraction of suspended particles microscope visualization and chemical analysis of a sample suggest the inclusion of a transparent exopolymeric matrix the relative abundance of aggregates over suspended particle volume concentration was found to increase as the quantity of suspended particle decreased the spatial distribution of the relative abundance of aggregates suggests more aggregates proximal to coral reefs the high concentration of aggregates at low turbidity and the spatial distribution of the relative abundance infer that aggregation is induced by the presence of organic ligands unlike optical backscattering and light attenuation measurements that are size sensitive measurements of suspended particle concentration in situ laser diffraction particle sizing provides a relevant optical measurement of suspended particulate matter in such an aggregate dominated system

optical backscattering by particles in arctic seawater and relationships to particle mass concentration size distribution and bulk composition the magnitude and spectral shape of the optical backscattering coefficient of particles b bp lambda is being increasingly used to infer information about the particles present in seawater relationships between b bp and particle properties in the arctic are poorly documented and may differ from other oceanic regions which contribute the majority of data used to develop and parameterize optical models we utilize recent field measurements from the chukchi and beaufort seas to examine relationships between the spectral backscattering coefficient of particles in seawater and the mass concentration bulk composition and size distribution of the suspended particle assemblage the particle backscattering coefficient spanned six orders of magnitude from the relatively clear waters of the beaufort sea to extremely turbid waters on the mackenzie shelf this coefficient was highly correlated with the mass concentration of particles and to a lesser extent with other measures of concentration such as particulate organic carbon or chlorophyll a increased backscattering and high mass specific b bp lambda was associated with mineral rich assemblages that tended to exhibit steeper size distributions while reduced backscattering was associated with organic dominated assemblages having a greater contribution of large particles our results suggest that algorithms which employ composition specific relationships can lead to improved estimates of particle mass concentration from backscattering measurements in contrast to theoretical models however we observe no clear relationship between the spectral slope of b bp lambda and the slope of the particle size distribution in this environment

anatomy of north pacific decadal variability abstract a systematic analysis of north pacific decadal variability in a full physics coupled ocean atmosphere model is executed the model is an updated and improved version of the coupled model studied by latif and barnett evidence is sought for determining the details of the mechanism responsible for the enhanced variance of some variables at 20 30 yr timescales the possible mechanisms include a midlatitude gyre ocean atmosphere feedback loop stochastic forcing remote forcing or sampling error decadal variability in the model is expressed most prominently in anomalies of upper ocean streamfunction sea surface temperature sst and latent surface heat flux in the kuroshio oyashio extension koe region off japan the decadal signal off japan is initiated by changes in strength and position of the aleutian low the atmospheric perturbations excite sst anomalies in the central and eastern north pacific with opposing signs and canonical structure the atmospheric perturbations also change the ekm

an extensive region of off ridge normal faulting earthquakes in the southern indian ocean an unusually large number of off ridge earthquakes have occurred within a broad region astride the southeast indian ridge the source mechanisms of nine of these earthquakes in lithosphere from 4 to 27 m y old have been determined with a formal inversion technique based on matching observed and synthetic p and sh waves all events occur in the oceanic mantle from 8 to 22 km below the seafloor the seismic moment and duration of faulting obtained from the inversion constrain the stress drop to lie between a few tens of bars and a few hundred bars for most of the events all of the off ridge earthquakes are characterized by normal faulting mechanisms with the t axes nearly parallel to the nearby ridge axis in sharp contrast to typical mid ocean ridge or intraplate earthquakes a variety of possible tectonic processes which might produce normal faulting in young oceanic lithosphere are considered as possible causes including bending stresses thermal stresses of various origins differential subsidence at a fracture zone off ridge volcanism latitudinal plate motions on a nonspherical earth basal shear stress from small scale convection and plate wide perturbations of the stress field due to the continental collision between india and asia no single mechanism is adequate to explain all the observed off ridge normal faulting earthquakes an apparent asymmetry in the observed seismicity with respect to the ridge suggests that the earthquakes on the antarctic and indian plates are caused by different processes the antarctic plate events can be satisfactorily attributed to the release of thermal and bending stresses associated with a residual depth anomaly between the kerguelen plateau and the southeast indian ridge a region which has been suggested as the site of a horizontal pipe for flow in the asthenosphere from the kerguelen hot spot to the vicinity of amsterdam and st paul islands on the southeast indian ridge the off ridge earthquakes in the indian plate are speculatively attributed to part of the plate wide response of the lithosphere to the ongoing continental collision

instruments for particle size and settling velocity observations in sediment transport in this paper we describe two sensors for measurement of particle size distribution and settling velocity distribution these measurements are critical to the correct estimation of the true sediment concentration in the field as well as to evaluating models for transport rates of sediments a multi angle measurement of laser scattering is made and inverted to obtain the particle size distribution since small angle scattering is relatively insensitive to particle composition the size distribution measurements are robust and do not require particle refractive index it is shown that with a knowledge of the size distribution true particulate volume concentration can be obtained unaffected in calibration by changes in particle size distribution the data from bottom boundary layer experiments using the instrument show the presence of temporal variability in size distribution associated with the strength of forcing of the boundary layer the importance of these observations lies in the implication that historical data acquired with single parameter optical or other sensors needs to be revisited in the second instrument analyzing the observation of size distributions during settling in a settling column produces settling velocity estimates in this case the history of concentration of each size class is examined to determine the settling velocity without invoking any assumptions of settling regime settling velocity data from a field experiment off the new jersey coast fit the model wf na 0 45 10 23 a 1 2 n

characteristic variations of sea surface temperature with multiple time scales in the north pacific abstract temporal evolution and spectral structure of sea surface temperature sst anomalies in the north pacific over the last 37 years are investigated on the three characteristic time scales shorter than 24 months hf 24 60 months es and longer than 60 months dc the leading empirical orthogonal function eof for the dc time scale is characterized by a zonally elongated monopole centered at around 40 n 180 the leading eof for the hf time scale is somewhat similar to that for the dc time scale although there are two centers of action with the same polarity at the mid and western pacific the leading eof for the es time scale however exhibits a different pattern whose center of action at the mid pacific is located farther southeastward in the time evolution of the sst anomalies associated with the leading eof of the dc time scale several anomaly periods can be identified that last five years or longer the transition from a persistent period to another with the opposite polarity is gene

large scale variabilities of wintertime wind stress curl field in the north pacific and their relation to atmospheric teleconnection patterns 1 wintertime wind stress curl wsc field in the north pacific is investigated to reveal large scale variabilities and their relation to atmospheric teleconnection patterns it is found that the leading empirical orthogonal function eof and the next three rotated eof modes of wintertime wsc anomalies well correspond to those of atmospheric teleconnection patterns i e pacific north american pna western pacific wp tropical northern hemisphere tnh and eastern pacific ep teleconnection patterns respectively time coefficient of the first eof mode well correlates with the north pacific index and does with the pacific decadal oscillation index to some degree it is also found that sverdrup transports in the two zonal bands of 25 n 30 n and 42 5 n 47 5 n have highly negative correlation and these variations can be represented by the forcing field of the first eof mode the pna forcing makes both subtropical and subpolar gyres spin up spin down simultaneously

maximal wavelet filter and its application to bidecadal oscillation over the northern hemisphere through the twentieth century based on a wavelet transform a new method referred to as maximal wavelet filter mwf is proposed to extract temporal structure changes of a climatic oscillation which varies its pattern corresponding to the changes of the oscillation period the mwf is a bandpass filter having a narrow pass band the central frequency of which temporally varies according to the periods of maximal wavelet amplitudes for a specific region mwf is applied to wintertime sea level pressures slps in the northern hemisphere from 1899 to 2000 to extract slp changes associated with the bidecadal oscillation bdo which distributes globally but has the strongest amplitudes in the north pacific in the pacific sector the bdo center of action captured by the mwf was located over alaska in the first few decades of the record and then moved southward to the central north pacific from 1920 to 1950 with maximal bdo amplitudes in the middle of the century the southward migration was accompanied by the previously reported increase of the oscillation period from 15 to 20 years on the other hand atlantic slp variations coherent with the pacific bdo had large amplitudes in midlatitudes high latitudes in the early late part of the twentieth century in association with these spatial structure changes the pattern of the recent bdo resembles the pattern of the arctic oscillation the analysis of the sea surface temperatures ssts gridded from the comprehensive ocean atmosphere data set coads and the newly digitized kobe collections suggests that bdo pattern in the ssts also shifted toward the south between the first and last few decades of the twentieth century furthermore covariability between the land air temperatures and aleutian low strength is observed through the twentieth century for alaska but only after 1940 for the midlatitudes of western north america and hawaii indicating that the bdo influence was limited to the high latitudes in the first few decades of the twentieth century in these regions consistent with the spatial structure changes in the slp field over the north pacific

tectonic aspects of intraplate seismicity in the northeastern indian ocean abstract since the late cenozoic the northeastern indian ocean region of the indo australian plate has been characterized by tectonic activity that is unusual in a mid plate setting this activity including deformation of the basement and the sediments and a high level of seismicity is typical of plate boundaries the characteristics of the seismicity and other phenomena there bears evidence to the initial stage of diffuse intraplate deformation of oceanic lithosphere it would be reasonable to suggest that the intraplate deformation in the northeastern indian ocean is episodic in behaviour the previous pulse of deformation seems to have occurred in the late miocene when the recent deformation of the sediments and the basement observed on the seismic reflection profiles was generated modern tectonic activity manifesting itself in high seismicity can be related to a new pulse of intraplate deformation a near latitudinal equatorial seismic zone comprising the northern segment of the ninetyeast ridge and northern central indian and cocos basins was suggested on the basis of analysis of seismological data for the eastern indian ocean from 1907 to 1983 the intraplate earthquake epicenters are concentrated in this broad band without distinct physiographic boundaries from nearly 80 e in the central indian basin to the sunda trench northeastern trends of earthquake epicenters that seem to be related to reactivation of some old faults can be observed within this band the orientation of the intraplate seismic zone is approximately similar to that of the continental collision zone at the northern indo australian plate margin the himalaya the possible cause of this high intraplate seismicity might be the southward migration or jumping of the himalayan subduction zone after the subduction there was stopped by the indian continental block due to continental collision the episodic intraplate deformation in the northeastern indian ocean region may manifest a future site of subduction along the southern margin of the indian subcontinent

the early 1950s regime shift in temperature in taiwan and east asia a summer climate regime shift in temperature in taiwan and east asia during the early 1950s was identified in this study the event was characterized by a cooling land warming ocean dipole in east asia and the western north pacific marking the decreasing land sea thermal contrast from the 1940s to the 1950s the corresponding sea surface temperature sst anomaly was characterized by the sign flipping of a north south dipole in the western north pacific from north cool south warm to north warm south cool indicating a weakening north south sst gradient in the area the corresponding change in mean sea level pressure was characterized by the rising pressure in continental east asia and the philippine sea and the falling pressure over the extratropical western north pacific to the east of japan this change was the reflection of a weakening thermal low in the continental east asia a weakening monsoon trough in the tropical western north pacific a strengthening and southwestward expanding ridge in the subtropical western north pacific and a deepening mid latitude trough over eastern china and japan the phase reversal of the sst anomaly in the western north pacific exhibited the characteristics of the pacific decadal oscillation pdo but lagged behind the phase reversal of the pdo in the extratropical north pacific by several years the connection with the pdo is speculated although the mechanism is not understood

fine pattern of natural modes in sea surface temperature variability 1985 2003 abstract a natural mode refers in this study to a periodic oscillation of sea surface temperature sst that is geophysically significant on a global regional or local scale using a newly developed harmonic extraction scheme by chen which has the advantage of being space time decoupled and fully data adaptive a variety of natural modes have been recovered from global monthly sst data for the period of 1985 2003 among them the eight most significant modes are identified as primary modes whose spatial patterns are presented along with their phase distributions at seasonal time scales a 4 month primary mode is uncovered in addition to the well documented annual and semiannual cycles at interannual time scales the dominant el nino southern oscillation enso variability is found to be composed of at least five primary modes with well defined central periods around 18 25 32 43 and 63 months at time scales beyond enso a decadal sst signal with an average period of 10 3 yr is observed a un

crustal evolution and sedimentation history of the bay of bengal since the cretaceous multichannel seismic reflection gravity magnetic and bathymetric investigations were made along five latitudinal profiles from the eastern shelf of india to the andaman shelf and four nw se profiles in the western basin off madras seismics on three latitudinal profiles in the bay of bengal the trend of the fracture zones the locations of the magnetic chron 34 and the cretaceous magnetic quiet zone suggest that greater india separated from antarctica after a period of transform motion in the early cretaceous that is about polarity chron m0 120 ma and drifted northwestward negative gravity anomalies are associated with basement rises including the 85 e ridge between the continental margin of india and the ninetyeast ridge magnetic reversals and northward trend of the 85 e ridge support a hotspot origin of the ridge and its emplacement most likely after the cretaceous quiet period juxtaposition of high amplitude hyperbolic reflections down faulted continental blocks buried under thick sediments and associated gravity and magnetic anomalies mark the boundary between continental and oceanic rocks at the foot of continental slope about 80 km seaward of the present continental shelf edge eight seismic sequences as thick as 8 5 km overlie the early cretaceous oceanic basement and include four unconformities lower eocene upper oligocene upper miocene and upper pleistocene which have been correlated to the major geologic tectonic events we also interpret the late cretaceous early tertiary features on the eastern flank of the buried 85 e ridge as carbonate reefs the observation of steep subduction of older cold indian plate beneath the burmese plate near the andaman islands suggests the sunda arc in this region as low to intermediate stress subduction zone

a laboratory evaluation of the laser in situ scattering and transmissometery instrument using natural sediments abstract the lisst laser in situ scattering and transmissometery instrument was designed by sequoia scientific to measure the particle size distributions and concentrations of sediment suspensions in the field environment to understand the lisst s performance with natural sediments from a variety of marine sources several experiments were performed to compare the lisst s results to traditional sieving filtering and weighing techniques the lisst was able to correctly locate the peak of a unimodal particle size distribution and resolve the two peaks of a bimodal distribution if they are separated by at least 1 for sediment sizes of 5 to 250 m unlike a single frequency scattering sensor for sediment concentration which require sediment size specific calibration constants the lisst is able to accurately measure sediment concentration with a single calibration constant for varying size distributions within the size range of 5 to 250 m the lisst was also found to adequately represent the particle volumetric size distribution for two different samples from marine environments

a numerical investigation of the subduction process in response to an abrupt intensification of the westerlies abstract a three dimensional ocean general circulation model forced by idealized zonal winds is used to investigate the effect of an abrupt intensification of westerly winds on the subduction process four experiments are carried out 1 a control experiment with standard wind stress forcing 2 an intensified winds experiment with wind stress that is larger in the region of the westerlies than the control 3 an increased surface cooling experiment and 4 an experiment with both intensified wind stress and surface cooling experiments 2 through 4 which contain surface anomalous forcing are run from the steady state obtained in experiment 1 the control experiment the results obtained for each of these runs are compared to the control experiment a subarctic tracer injection experiment is also carried out to verify the differences in the subduction process of each of these experiments in the wind stress intensified experiment an examination of the subsurface temperature field shows that negative t

magnetic and bathymetric investigations over the vema region of the central indian ridge tectonic implications abstract magnetic and bathymetric data were collected along n50 e profiles in the vema region 7 12 s 64 70 e across five ridge segments of the central indian ridge cir anomalies up to a5 10 ma identified by generating synthetics for each profile show asymmetric spreading though inter segmental variations in spreading rate have been observed the mean half spreading rate increases from 1 8 cm yr in the region north of vema transform to 2 1 cm yr south of the vema transform the average spreading rate for the last 10 ma has not always been symmetric the interpretation of magnetic and bathymetric data shows the complex nature of this part of the cir which could probably be attributed to i the short ridge segment ii interaction with fracture zone and iii interaction between the cir and the wide boundary zone wbz separating the indian and australian plates

the effects of decadal oscillations of the curl τ 0 line on intergyre water exchange and temperature variability abstract the effect of meridional movement of the curl 0 line on the intergyre transport is investigated by passive tracer experiments in a double gyre circulation furthermore the contribution to temperature distribution is considered the nonlinear quasigeostrophic reduced gravity model is employed to express a fundamental baroclinic ocean response parameter studies show that a decadal wind migration causes the intergyre exchange much more effectively than does an annual wind migration the efficiency of the intergyre exchange is primarily determined by the wind migration period relative to the necessary time in which a tracer crosses the ocean basin from west to east the meridional movement of the curl 0 line can induce temperature change through two processes 1 entrainment of subtropical subpolar water into the subpolar subtropical gyre along the eastern boundary and 2 a vertical movement of the thermocline propagating as a rossby wave the temperature variability is similar to the

interdecadal thermocline variability in the north pacific for 1958 97 a gcm simulation an ocean general circulation model is forced with the ncep reanalysis wind stress for 1958 97 to understand mechanisms of ocean subsurface variability with relatively high horizontal 1 83 18 and vertical 41 levels resolutions the model produces mode waters on a range of density surfaces in the western central and eastern north pacific in qualitative agreement with observations these mode waters appear as a thermostad or a region of weak stratification in the upper thermocline as they flow southward from their formation regions in the kuroshio and its extension in the model subsurface temperature variability in the central subtropical gyre reaches a maximum within the thermostad in contrast to what might be expected from the linear baroclinic rossby wave theory this variance maximum is associated with the longitudinal shift in the path of mode waters in particular deepened mixed layer and accelerated eastward currents in the kuroshio extension by wind changes in the mid 1970s act cooperatively to move the central mode waters toward the east causing large subsurface temperature anomalies besides the local maximum in the central north pacific subtropical gyre two additional maxima of the subsurface anomaly are identified in the northwestern and southern parts of the gyre respectively among these subsurface anomaly centers the one in the northwestern north pacific has a strong effect on the model sea surface temperature suggesting that the kuroshio and its extension are a key region to decadal interdecadal ocean atmosphere interaction finally possible effects of atmospheric thermal forcing are discussed

quasi periodicity and global symmetries in interdecadal upper ocean temperature variability recent studies find interannual i e 3 to 7 year decadal i e 9 to 13 year and interdecadal i e 18 to 23 year periodicities and a trend dominating global sea surface temperature sst and sea level pressure slp variability over the past hundred years with the interdecadal signal dominating sub el nino southern oscillation enso frequencies we isolate interdecadal frequencies in sst and slp records by band passing with a window admitting 15 to 30 year periods from 1900 to 1989 the rms of interdecadal filtered sst and slp anomalies is largest in the extratropics and eastern boundaries first mode empirical orthogonal functions eofs explain about half the interdecadal variance in both variables with the tropical warm phase peaking near 1900 1920 1940 1960 and 1980 from 1955 to 1994 eof spatial patterns of interdecadal sst slp and 400m temperature t400 anomalies reveals global reflection symmetries about the equator and global translation symmetries between ocean basins with tropical and eastern ocean ssts warmer cooler than normal covarying with stronger weaker extratropical westerly winds cooler warmer ssts in western central subarctic and subantarctic frontal zones safzs stronger weaker subtropic and subarctic gyre circulations in north pacific and north atlantic oceans and warmer cooler basin and global average ssts of 0 1 c or so evolution of interdecadal variability from the tropical warm phase to the tropical cool phase is propagative also characterized by reflection and translation symmetries during the tropical warm phase cool sst anomalies along western central safzs are advected slowly eastward to the eastern boundaries and subsequently advected poleward and equatorward by the mean gyre circulation the latter conducting extratropical sst anomalies into the tropics a delayed action oscillation model is constructed that yields the quasiperiodicity of interdecadal variability in a manner consistent with these global symmetries in both pattern and evolution

interannual to interdecadal changes in the bering sea and concurrent 1998 99 changes over the north pacific abstract sea surface temperatures ssts upper water heat storage hs sea level displacements slds sea ice concentration sics in the bering seas and associated atmospheric circulations are analyzed to identify dominant interannual to interdecadal variations as a representative time series of the sst variations principal component pc of the first mode of a seasonally combined empirical orthogonal function eof is employed the corresponding eof spatial pattern exhibits the smallest amplitudes in winter and largest in summer pc1 is characterized by a warming trend throughout the record 1921 2001 with the warmest year in 1997 which is followed by rapid cooling until 1999 the warming from 1995 1997 and cooling from 1997 1999 are commonly found in hs along the southern rim of the bering sea and also accompanied by sld rise and fall respectively the sic variability corresponding to sst pc1 is prominent in the eastern bering sea in spring with correlations as high as 0 7 but good correlations were mainly observed prior to 1990 the correlations between the sst pc1 and sea level pressures slps also suggest that the spring atmospheric circulation anomalies play an important role in the variations of the sst and sea ice in the bering sea the cooling and sld fall in the late 1990s in the bering sea might be related with a possible major regime shift in 1998 1999 which was discussed by minobe 2000 hare and mantua 2000 and schwing and moore 2000 in the 1998 99 change over the north pacific ssts and hs increased abruptly both in the kuroshio oyashio extension region and the central north pacific accompanied by cooling in the eastern north pacific at the same time slds rose from japan to 160 w roughly along kuroshio extension path with a tongue like structure the tongue like sld rise is likely forced by wintertime atmospheric anomalies associated with slp increase in the eastern north pacific

interannual and interdecadal variability of the south atlantic convergence zone interannual variations of the summertime january march atmospheric circulation over subtropical south america are examined during the period 1958 97 using the national centers for environmental prediction national center for atmospheric research reanalysis data it is found from an empirical orthogonal function analysis that an anomalous upper tropospheric large scale stationary eddy in the lee of the andes tends to accompany a dipole in anomalous vertical motion an anomalous cyclonic anticyclonic eddy accompanies an intensified diffuse south atlantic convergence zone sacz with anomalous descent ascent to the southwest the cold core equivalent barotropic vertical structure of the anomalous cyclonic eddy and the 200 hpa vorticity balance are both characteristic of a stationary rossby wave the tendency for the eddy to be advected downstream by the mean westerlies is compensated by meridional advection of planetary vorticity and stretching associated with vertical motion the anomalous cyclonic flow at low levels reinforces the thermally direct circulation associated with the sacz a weak funneling of submonthly rossby wave activity into this descent region is also identified the interannual time series of the eddy is significantly correlated with north south dipolar sea surface temperature sst anomalies over the southwest atlantic one standard deviation 200 hpa wind speed anomalies of up to 5 m s21 are accompanied by sst anomalies of up to 0 38c a near cyclic 15 yr component is identified which the authors corroborate from independent analyses of southwest atlantic ssts and river flows both are

generation mechanism of quasidecadal variability of upper ocean heat content in the equatorial pacific ocean 1 we investigate the relationship between oceanic and atmospheric anomaly fields in the tropical pacific on the quasidecadal qd 10 to 18 years scale is explored it is suggested that the anomalous wind stress curl in the tropical south pacific can generate the equatorial upper ocean heat content ohc anomalies on the qd scale via the sverdrup transport resembling that of the recharge discharge oscillator model for the dynamics of el nino southern oscillation enso the results also show that the wind stress curl anomalies in the tropical south pacific are accompanied by enso like qd scale anomaly patterns of the sea level pressure and sea surface temperature furthermore the results indicate that the equatorial qd scale ohc anomalies can also be generated by the enso like propagations of the ohc anomalies in the tropical north and south pacific this study presents a systematic linkage between the enso like qd scale ohc propagation in the tropical north and south pacific the sverdrup transport variation in the tropical south pacific and the enso like qd scale sst and slp anomalies in the tropical pacific

decadal changes in the north pacific oceanic frontal zones as revealed in ship and satellite observations 1 influence of decadal climate changes upon the north pacific subarctic and subtropical oceanic frontal zones np safz and np stfz respectively is documented both satellite and ship measured sea surface temperature sst data reveal the strong confinement of wintertime decadal sst anomalies to those frontal zones the satellite data indicate that the wintertime np safz tended to be narrow and shift northward under the weakened surface westerlies during a warm event in the early 1990s the opposite was the case under the enhanced westerlies during a cool event in the mid 1980s decadal scale modulations in the frontal intensity are also evident in the satellite data a diagnosis based on a simple linearized mixed layer model suggests that the observed anomalous frontal intensity was contributed by the sign reversal of anomalous wind stress curl through the ekman processes and by an anomaly dipole of the net heat flux around the safz these decadal scale modulations in the np safz and their relationships with decadal fluctuations in the local surface westerlies are confirmed in the ship measured data over the 4 recent decades it is found that the safz happens to be a region where the decadal variability in the surface westerlies are unlikely to be masked by the higher frequency fluctuations as it almost coincides with the ridge trough line of the remote atmospheric response to the el nino southern oscillation

modes of interannual and interdecadal variability of pacific sst abstract the multichannel singular spectrum analysis has been used to characterize the spatio temporal structures of interdecadal and interannual variability of sst over the pacific ocean from 20 s to 58 n using the comprehensive ocean atmosphere data set from 1950 to 1993 three modes with distinctive spatio temporal structures were found they are an interdecadal mode a quasi quadrennial qq oscillation with a period of 51 months and a quasi biennial qb oscillation with a period of 26 months the interdecadal mode is a standing mode with opposite signs of sst anomalies in the north pacific and in the tropical pacific the amplitude of this mode is larger in the central north pacific than in the tropical pacific this mode contributes 11 4 to the total variance it is associated with cooling in the central north pacific and warming in the equatorial pacific since around 1976 77 the qq oscillation exhibits propagation of sst anomalies northeastward from the philippine sea and then eastward along 4

winter to winter recurrence of sea surface temperature salinity and mixed layer depth anomalies abstract the mean seasonal cycle of mixed layer depth mld in the extratropical oceans has the potential to influence temperature salinity and mixed layer depth anomalies from one winter to the next temperature and salinity anomalies that form at the surface and spread throughout the deep winter mixed layer are sequestered beneath the mixed layer when it shoals in spring and are then re entrained into the surface layer in the subsequent fall and winter here we document this re emergence mechanism in the north pacific ocean using observed ssts subsurface temperature fields from a data assimilation system and coupled atmosphere ocean model simulations observations indicate that the dominant large scale sst anomaly pattern that forms in the north pacific during winter recurs in the following winter the model simulation with mixed layer ocean physics reproduced the winter to winter recurrence while model simulations with observed ssts specified in the tropical pacific and a 50 m slab in the north pacific did not this difference between the model results indicates that the winter to winter sst correlations are the result of the re emergence mechanism and not of similar atmospheric forcing of the ocean in consecutive winters the model experiments also indicate that sst anomalies in the tropical pacific associated with el nino are not essential for re emergence to occur the recurrence of observed sst and simulated sst and sss anomalies are found in several regions in the central north pacific and are quite strong in the northern 50 n part of the basin the winter to winter autocorrelation of sss anomalies exceed those of sst since only the latter are strongly damped by surface fluxes the re emergence mechanism also has a modest influence on mld through changes in the vertical stratification in the seasonal thermocline

the transition region mode water of the north pacific and its rapid modification abstractusing argo float data this study examined the formation region spatial distribution and modification of transition region mode water trmw which is a recently identified pycnostad in the subtropical subarctic transition region of the north pacific the basin scale boundary region between subtropical and subarctic water masses analyses of the formation fields of water masses within and around the transition region reveal that trmw forms in a wide area from the western to central transition region and is separated from the denser variety of central mode water d cmw to the south by a temperature and salinity front trmw has temperatures of 4 9 c and salinities of 33 3 34 0 making it colder and fresher than d cmw trmw has a density range of 26 3 26 6 and thick trmw is widely distributed in the transition region however the range of the t s properties at trmw cores is substantially reduced downstream within 10 20 longitude from the formation region by gradually losing its fresh and c

interdecadal variability over the north pacific in a multi century climate simulation interdecadal variability in the north pacific region is investigated in a 500 y control integration of the hamburg echam lsg coupled ocean atmosphere general circulation model the spectrum is predominantly red but a significant peak with a period of about 18 y is detected in the spectrum of sea surface temperature sst this peak is shown to be associated with an irregular oscillation that involves both the model ocean and atmosphere the sst sea level pressure and geopotential height at 500 hpa all undergo a primarily standing oscillation with an extensive monopole structure centered near the date line the surface anticyclone is situated to the northeast of the warm sst anomaly and there is a small westward tilt with height temporal changes are approximately in phase the anomalous surface heat flux accompanying the warm phase of sst is primarily out of the ocean but is compensated by anomalous warm advection by surface currents allowing the sst anomaly to persist oceanic thermocline anomalies propagate northward in the western pacific and lag the atmosphere indicating a disequilibrium with the atmosphere sub surface thermal advection appears to play an important role a comparison is made between the model s 18 y oscillation and oscillatory components identified in an analysis of the gisst observational sst dataset which have periods of approximately 6 and roughly 30 y

on the dynamics of the coupled mixed layer thermocline system and the determination of the oceanic surface density abstract a simple model of the oceanic mixed layer is coupled to a model of the ventilated thermocline the model allows a combination of advection and surface heating to determine the position of the outcrop lines of the isopycnals the resulting isopycnal outcrops determine the circulation in the ventilated thermocline as in the 1983 study by luyten pedlosky and stommel lps the isopycnal outcrop line is affected by both ekman wind drift and the surface geostrophic flow hence the outcrop position and the thermocline circulation am coupled the mixed layer and the thermocline models are extremely simple each is modeled by layers of constant density the mixed layer in which the isopycnals are vertical is distinguished by the ability of fluid to cross the interfaces between adjacent layers under the influence of atmospheric heating the heating is parameterized in terms of the departure of the isopycnal line from the position it would have if the ocean were heated but at rest although in most ma

crust and upper mantle velocity structure beneath the northern and central indian ocean from the phase and group velocity of rayleigh and love waves abstract fundamental mode rayleigh and love waves generated by nine earthquakes which occurred in the central indian ocean with epicentres extending to 40 s and recorded at seven wwssn stations of central asia have been used to determine the phase and group velocity along various paths across the northern and central indian ocean the dispersion characteristics of rayleigh and love waves show a thick crust of 23 km thickness this anomalous crustal thickening having quasi continental oceanic structure may be explained by assuming the gradual transformation of top mantle material into material having either crustal like velocity or slightly lower than moho velocity p wave velocity 7 72 km s 1 s wave velocity 4 45 km s 1 the velocity structure down to a depth of 200 km has been obtained across the northern and central indian ocean a low velocity zone of 90 km with p wave velocity of 7 85 km s 1 and s wave velocity of 4 37 km s 1 is estimated to be centred at a depth of 78 km from the water surface this low shear velocity in the mantle may be caused by the partial melting and elevated temperature there the observed dispersion data for rayleigh and love waves also exhibit a strong anisotropy along different paths in the crust and upper mantle the observed dispersion data for rayleigh and love waves that cross the ninety east ridge are characterized by lower phase and group velocities as compared to waves having paths in a more western direction than this ridge axis however the phase velocities for rayleigh and love waves are characterized by lower values across the ninety east ridge as compared to the normal oceanic structure

the reemergence of sst anomalies in the north pacific ocean abstract sea surface temperature sst data and two different upper ocean temperature analyses are used to study the winter to winter recurrence of sst anomalies in the north pacific ocean the ssts recur when temperature anomalies that form in the deep ocean mixed layer in late winter early spring are isolated from the atmosphere in the summer seasonal thermocline and then reemerge at the surface when the mixed layer deepens during the following fall winter this reemergence mechanism is evaluated over the basin by correlating the time series of the leading pattern of ocean temperature anomalies in the summer seasonal thermocline 60 85 m in august september with sst anomalies over the course of the year the results indicate that the dominant large scale sst anomaly pattern that forms in the north pacific during late winter with anomalies of one sign in the central pacific and the opposite sign along the coast of north america is sequestered in the seasonal thermocline in summer and returns to the

propagation of north pacific interdecadal subsurface temperature anomalies in an ocean gcm propagation of subsurface north pacic inter decadal variations is investigated with an ocean general cir culation model forced by observed sea surface temperature anomalies subsurface temperature anomalies subducted in the central subtropical north pacic take a more westward pathway than a passive temperature tracer and reach the western boundary to the north of the bifurcation latitude this prevents them from extending into the equator on the boundary between the subtropical and the subarctic gyres on the other hand the upper 500 m heat content anomaly is found to propagate eastward as high vertical modes of rossby waves advectedbythemean eastward cur rent this notion is supported by a sign reversal in temper ature anomaly underneath

earthquake source mechanisms from body waveform inversion and intraplate tectonics in the northern indian ocean double couple point source parameters for 11 of the largest intraplate earthquakes in the northern indian ocean during the last 20 y were determined from a formal inversion of long period p and sh waveforms nine of the events have centroid depths at least 17 km below the seafloor well into the upper mantle two have centroid depths as great as 39 km using the source mechanisms of these earthquakes we distinguish two major intraplate tectonic provinces in the northern indian ocean to the west of the ninetyeast ridge in the southern bay of bengal intraplate earthquakes have thrust faulting mechanisms with p axes oriented n s the centroid depths of these earthquakes range from 27 to 39 km below the seafloor lithospheric shortening in this region is thus accomplished by thrust faulting in the strong core of the oceanic upper mantle while other geophysical evidence suggests that shallow sedimentary and crustal layers apparently deform predominantly by folding in the immediate vicinity of the ninetyeast ridge earthquakes display strike slip mechanisms with left lateral motion on planes parallel to the ridge this type of faulting occurs from at least 10 s to the northern end of the ninetyeast ridge near 10 n where the ridge meets the sunda arc seismic activity diminishes to the east of the ninetyeast ridge but is also characterized by strike slip faulting despite these variations in deformational style the inferred orientation of greatest compressive stress in the northern indian ocean displays a consistent long wavelength pattern over a large portion of the indian plate varying smoothly from nearly n s in the bay of bengal to nw se in the northeastern indian ocean this plate wide stress pattern and the high level of intraplate seismicity in the northern indian ocean are likely the results of substantial resistance along the himalayan continental collision zone to the continued northward motion of the western portion of the indian plate oceanic intraplate earthquakes in other regions where the level of deviatoric stress associated with the long wavelength part of the stress field is likely to be smaller need not be comparably reliable indicators of the plate wide stress field

simple coupled midlatitude climate models a set of simple analytical models is presented and evaluated for interannual to decadal coupled ocean atmosphere modes at midlatitudes the atmosphere and ocean are each in sverdrup balance at these long timescales the atmosphere s temperature response to heating determines the spatial phase relation between sst and sea level pressure slp anomalies vertical advection balancing heating produces high low slp lying east of warm cold sst anomalies as observed in the antarctic circumpolar wave acw the decadal north pacific mode and the interannual north atlantic mode zonal advection in an atmosphere with a rigid lid produces low slp east of warm sst however if an ad hoc equivalent barotropic atmospheric response is assumed high slp lies east of warm sst relaxation to heating produces behavior like the observed north atlantic decadal pattern with low slp over warm sst meridional advection in the atmosphere cannot produce the observed sst slp patterns the dominant balance in the ocean s temperature equation determines the phase speed of the modes the coupled mode is nondispersive in all models examined here indicating the need for additional processes for modes with an sst slp offset as observed in the acw and north pacific ekman convergence acting as a heat source causes eastward propagation relative to the mean ocean flow sverdrup response to ekman convergence acting on the mean meridional temperature gradient causes westward propagation relative to the mean ocean flow when the ocean temperature adjusts through surface heat flux alone the mode is advected by the mean ocean flow and is damped relaxation to heating in the atmosphere when operating with sverdrup response in the ocean produces the only complete solution presented here that exhibits growth with an e folding timescale of order 100 days this solution appears appropriate for the north atlantic decadal mode in northern hemisphere basins with meridional boundaries the same sets of dynamics create the observed sst slp phase relation an additional factor is the creation of sst anomalies through variations in the western boundary current strengths which are related to the zonally integrated wind stress curl over the whole basin if barotropic and hence fast adjustment is assumed the resulting positive feedback can maintain or strengthen the coupled anomalies in the north pacific and interannual north atlantic modes

interannual and interdecadal variations of sea surface temperature in the east asian marginal seas abstract interannual and interdecadal variability of sea surface temperature sst in the east asian marginal seas eams from 1951 to 1996 are investigated and the teleconnection of the eams to the equatorial ocean is studied using empirical orthogonal function analysis and coherency analysis the eams have significant coherency with the nino 3 4 sst at 2 to 3 year periods with a phase lag of 5 9 months in the sst anomaly ssta the eams also showed a higher coherency with a 6 year oscillation with a phase lag of 18 22 months for the 6 year variability the ssta of the nino 3 4 is highly coherent with the latent and sensible heat flux anomaly of the southern east sea indicating that the variability of the southern east sea is related to that in the nino 3 4 region through the ocean atmosphere interactions the southern east sea also has a higher coherency with the east china sea cooling in the southern east sea and sudden warming in the northern east sea were found to have occurred around 1965 1966 in the records of interdecadal variability the decadal and interdecadal variabilities of the eams were found to be teleconnected to the western equatorial pacific whereas the interannual variability was highly correlated to the central equatorial pacific which is represented by nino 3 4 sst

the role of finite mixed layer thickness in the structure of the ventilated thermocline abstract a model of the ventilated thermocline consisting of three adiabatic layers surmounted by a mixed layer of finite thickness is presented the mixed layer depth density increase continuously northward and these attributes of the mixed layer are specified the effect of the mixed layer on the thermocline circulation is explicitly calculated the mixed layer thickness and its variation play a significant role in shifting the trajectories of the streamlines westward the shadow zones enlarge more rapidly south of the outcrop lines the finite mixed layer depth and its increase northward produce shadow zones in each of the adiabatic layers of the thermocline the augmentation of the ventilation rate i e the rate at which fluid enters the thermocline from the mixed layer in excess of the ekman pumping is directly proportional to the northward gradient of the mixed layer potential vorticity the enhancement is greatest in regions where the circulation is surface intensified i e above the eastern sh

heat content variability related to enso events in the pacific abstract anomaly fields of upper ocean heat content ohc in the pacific basin from 30 s to 60 n over a 45 yr period are analyzed with special reference to their relationship with el nino southern oscillation enso events in the present study for convenience the ohc is defined as vertically averaged temperature from the sea surface to 300 m depth based on a cluster analysis it is found that interannual variability with a period of 3 6 yr is dominant in the eastern and western tropical pacific while multidecadal variability with a period of approximately 20 yr is dominant in mid to high latitudes in order to focus attention on the relationship between ohc anomalies and enso events 3 6 yr variations are extracted by a bandpassed filtering with half power points at 3 and 6 yr periods the result clearly shows the cyclic and anticlockwise propagation of ohc anomalies on the circuit in the northern tropical pacific that is an eastward propagation along the equator a northward propagation at the e

contrasting inherent optical properties and particle characteristics between an under ice phytoplankton bloom and open water in the chukchi sea abstract variability in the inherent optical properties iops of seawater and characteristics of the particle assemblage were examined along a transect in the chukchi sea during july 2011 this transect encompassed samples from open waters of the marginal ice zone exhibiting low concentrations of chlorophyll a chl a 3 as well as an extensive phytoplankton bloom chl a 30 mg m 3 beneath consolidated pack ice measurements included the spectral coefficients for particulate beam attenuation backscattering and absorption bulk indicators of particle concentration and composition and the particle size distribution within the bloom microphytoplankton contributed 95 to the total chl a and relatively small amounts of nonalgal particles were present this assemblage exhibited low chl a specific phytoplankton absorption coefficients 0 006 m 2 mg 1 at 676 nm indicating a strong influence of pigment packaging and a weak spectral dependence of the particulate backscattering coefficient in contrast the phytoplankton community in nutrient depleted surface waters outside the sea ice had a strong contribution of picoplankton to chl a 54 and an increased abundance of nonalgal particles the chl a specific phytoplankton absorption coefficient approached maximum values at 676 nm 0 023 m 2 mg 1 and particle backscattering had much stronger spectral dependence additional samples from near the sea floor exhibited characteristics of either mineral dominated assemblages or a mixture of mineral and organic particles and also displayed optical differentiation from the surface samples the marked contrast in absorption attenuation and backscattering properties of these ecological regimes suggest that they can be discriminated from optical measurements available on a variety of in situ and remote sensing platforms

when will the summer arctic be nearly sea ice free 1 the observed rapid loss of thick multiyear sea ice over the last 7 years and the september 2012 arctic sea ice extent reduction of 49 relative to the 1979 2000 climatology are inconsistent with projections of a nearly sea ice free summer arctic from model estimates of 2070 and beyond made just a few years ago three recent approaches to predictions in the scientific literature are as follows 1 extrapolation of sea ice volume data 2 assuming several more rapid loss events such as 2007 and 2012 and 3 climate model projections time horizons for a nearly sea ice free summer for these three approaches are roughly 2020 or earlier 2030 10 years and 2040 or later loss estimates from models are based on a subset of the most rapid ensemble members it is not possible to clearly choose one approach over another as this depends on the relative weights given to data versus models observations and citations support the conclusion that most global climate model results in the cmip5 archive are too conservative in their sea ice projections recent data and expert opinion should be considered in addition to model results to advance the very likely timing for future sea ice loss to the first half of the 21st century with a possibility of major loss within a decade or two

historical seismicity and rates of crustal deformation along the margins of the ordos block north china earthquakes in china show an empirical relation between seismic moment m 0 and the areal distribution of modified mercalli intensities vi and viii log m 0 16 66 0 91 log a viii and log m 0 14 35 1 16 log a vi where a and m 0 are measured in squared kilometers and newton meter respectively the empirical relations may be used to estimate m 0 for historical earthquakes in china to within a factor of three on average when sufficient isoseismal data exist this observation and an extensive collection of isoseismal maps are used to estimate m 0 for large earthquakes that occurred along the margins of the ordos block during the last 700 yr focal parameters of the historical events are inferred from the orientation and displacements across quaternary faults average rates of crustal deformation are then estimated from the 700 yr historical record with formulas that relate the occurrence rate of seismic moment in a region to rates of crustal strain the shanxi and northern ningxia graben systems are situated along the eastern and northwestern edges of the ordos block respectively normal faults in the two systems trend northeasterly and are characterized by a component of right lateral slip the deformation resulting from slip during earthquakes in each of the respective fault systems is estimated at about 0 5 to 1 0 mm yr of both right lateral shear and north by northwest extension the weihe graben system bounds the southern edge of the ordos block strikes easterly and conjugate to the shanxi and northern ningxia fault systems and exhibits left lateral normal fault displacements the average rate of deformation across weihe is described by about 1 0 mm yr of north by northwest extension and 1 5 mm yr left lateral east west shear the hetao fault system delineates the northern edge of the ordos block and displays quaternary faults similar in orientation and mechanism to that observed in weihe although mapped faults in hetao exhibit evidence of quaternary displacement crustal deformation rates are not estimated because there exists no historical record of large earthquakes in the area in southern ningxia at the southwest boundary of the ordos block deformation occurs by slip on left lateral strike slip faults oriented in an easterly azimuth and thrust faults with strikes ranging from southeast to south the average deformation rate in southern ningxia is found to be about 4 0 mm yr of east by northeast contraction and 10 0 mm yr of left lateral shear deformation of each of the fault systems is consistent with a regional compressive stress that trends northeast and results in an average of about 3 0 mm yr each of contraction at n70 e and extension of n160 e across the entire region inasmuch as uncertainties in estimates of m0 for historical earthquakes are about a factor of three a similar uncertainty is attached to rates of crustal strain determined in this manner

a comparison of decadal climate oscillations in the north atlantic detected in observations and a coupled gcm abstract decadal climate variations in the atlantic ocean found in observational fields and a coupled general circulation model cgcm are investigated in particular physical processes responsible for the phase reversal are compared observed and modeled decadal variations have dominant periodicities around 12 3 and 9 9 yr respectively both variations show similar spatial features sea surface temperature sst anomalies in the western subtropical atlantic sandwiched by those with opposite sign to the north and south and a dipole of sea level pressure anomalies which resemble the north atlantic oscillation their temporal evolutions are however different from each other suggestive of different dynamics of the oscillation in the observations sst and surface layer 0 100 m temperature anomalies move eastward from the subtropical western atlantic to the european coast along the gulf stream northward propagation of sst anomalies are also found along the western boundaries including the gulf of me

focal depths and fault plane solutions of earthquakes under the tibetan plateau we compare synthetic and recorded p wave forms to place constraints on the focal depths and fault plane solutions of 16 crustal earthquakes beneath the highest parts 4000 m of the tibetan plateau fault plane solutions for all 16 events show combinations of normal and strike slip faulting with t axes oriented approximately east west none of these solutions show thrust faulting thus the data corroborate previous inferences that the active tectonics are dominated by east west extension focal depths for all 16 events are less than 15 km and appear to be between 5 and 10 km this style of deformation and these depths of faulting are similar to those in the basin and range province of the western united states two intermediate depth events below the crust of southern tibet also show primarily normal faulting with east west t axes the solution for one discussed by chen et al 1981 is unambiguous the solution for the other the event of august 1 1973 27 59 n 89 17 e 85 10 km mb 4 9 is less certain both apparently occurred in the mantle beneath a thick aseismic lower crust and their occurrence suggests that brittle deformation occurs there in response to a stress field similar to that operating at shallow depths beneath tibet

upper ocean thermal variations in the north pacific during 1970 1991 abstract a newly available extensive compilation of upper ocean temperature profiles was used to study the vertical structure of thermal anomalies between the surface and 400 m depth in the north pacific during 1970 1991 a prominent decade long perturbation in climate occurred during this time period surface waters cooled by 1 c in the central and western north pacific and warmed by about the same amount along the west coast of north america from late 1976 to 1988 comparison with data from coads suggests that the relatively sparse sampling of the subsurface data is adequate for describing the climate anomaly the vertical structure of seasonal thermal anomalies in the central north pacific shows a series of cold pulses beginning in the fall of 1976 and continuing until late 1988 that appear to originate at the surface and descend with time into the main thermocline to at least 400 m depth individual cold events descend rapidly 100 m yr 1 superimposed upon a slower cooling 15 m yr 1 the inter

an interdecadal climate cycle in the south atlantic and its links to other ocean basins a singular value decomposition analysis and a combined complex empirical orthogonal function analysis are performed on 80 years of monthly sea surface temperature sst and sea level pressure slp data from the south atlantic region the analyses reveal the existence of interdecadal fluctuations in the coupled atmosphere ocean system with a period of around 20 years the sst anomalies are observed to propagate anticyclonically around the south atlantic basin following the subtropical gyre circulation at the same time a westward propagation of slp anomalies across the basin generates changes in the atmospheric circulation that appear to reinforce such sst anomalies through anomalous exchanges of heat it is thus proposed that the dominant physical processes involved in this interdecadal cycle include the horizontal advection of heat by the ocean currents and changes in the atmosphere ocean heat fluxes through local air sea interactions the global sst and slp patterns that accompany the different phases of the south atlantic cycle are also presented they show similarities with other well known interdecadal signals observed by several investigators in other ocean basins e g the low frequency part of the north atlantic oscillation this suggests that the south atlantic signal described in this study may be a regional aspect of global interdecadal variability

phytoplankton blooms beneath the sea ice in the chukchi sea in the arctic ocean phytoplankton blooms on continental shelves are often limited by light availability and are therefore thought to be restricted to waters free of sea ice during july 2011 in the chukchi sea a large phytoplankton bloom was observed beneath fully consolidated pack ice and extended from the ice edge to 4100 km into the pack the bloom was composed primarily of diatoms with biomass reaching 1291 mg chlorophyll a m 2 and rates of carbon fixation as high as 3 7 g c m 2 d 1 although the sea ice where the bloom was observed was near 100 concentration and 0 8 1 2 m thick 30 40 of its surface was covered by melt ponds that transmitted 4 fold more light than adjacent areas of bare ice providing sufficient light for phytoplankton to bloom phytoplankton growth rates associated with the under ice bloom averaged 0 9 d 1

enso like interdecadal variability 1900 93 a number of recent studies have reported an enso like eof mode in the global sea surface temperature sst field whose time variability is marked by an abrupt change toward a warmer tropical eastern pacific and a colder extratropical central north pacific in 1976 77 the present study compares this pattern with the structure of the interannual variability associated with the enso cycle and documents its time history back to 1900 the analysis is primarily based on the leading eofs of the sst anomaly and anomaly deviation fields in various domains and the associated expansion coefficient or principal component time series which are used to construct global regression maps of sst sea level pressure slp and a number of related variables the use of anomaly deviations i e departures of local sst anomalies from the concurrent global mean sst anomaly reduces the influence of global mean sst trends upon the structure of the eofs and their expansion coefficient time series an important auxiliary time series used in this study is a southern oscillation index based on marine surface observations by means of several different analysis techniques the time variability of the leading eof of the global sst field is separated into two components one identified with the enso cycle related variability on the interannual timescale and the other a linearly independent residual comprising all the interdecadal variability in the record the two components exhibit rather similar spatial signatures in the global sst slp and wind stress fields the sst signature in the residual variability is less equatorially confined in the eastern pacific and it is relatively more prominent over the extratropical north pacific the corresponding slp signature is also stronger over the extratropical north pacific and its counterpart in the cold season 500 mb height field more closely resembles the pna pattern the amplitude time series of the enso like pattern in the residual variability reflects the above mentioned shift in 1976 77 as well as a number of other prominent features including a shift of opposite polarity during the 1940s

anelasticity of the crust and upper mantle beneath north and central india from the inversion of observed love and rayleigh wave attenuation data the fundamental mode love and rayleigh waves generated by earthquakes occurring in kashmir nepal himalaya northeast india and burma and recorded at hyderabad new delhi and kodaikanal seismic stations are analysed love and rayleigh wave attenuation coefficients are obtained at time periods of 15 100 seconds using the spectral amplitude of these waves for 23 different paths along northern across burma to new delhi and central across kashmir nepal himalaya and northeast india to hyderabad and kodaikanal india love wave attenuation coefficients are found to vary from 0 0003 to 0 0022 km 1 for northern india and 0 00003 km 1 to 0 00016 km 1 for central india similarly rayleigh wave attenuation coefficients vary from 0 0002 km 1 to 0 0016 km 1 for northern india and 0 00001 km 1 to 0 0009 km 1 for central india backus and gilbert inversion theory is applied to these surface wave attenuation data to obtainq 1 models for the crust and uppermost mantle beneath northern and central india inversion of love and rayleigh wave attenuation data shows a highly attenuating zone centred at a depth of 20 80 km with lowq for northern india similarly inversion of love and rayleigh wave attenuation data shows a high attenuation zone below a depth of 100 km the inferred lowq value at mid crustal depth high attenuating zone in the model for northern india can be by underthrusting of the indian plate beneath the eurasian plate which has caused a low velocity zone at this shallow depth the gradual increase ofq 1 from shallow to deeper depth shows that the lithosphere asthenosphere boundary is not sharply defined beneath central india but rather it represents a gradual transformation which starts beneath the uppermost mantle the lithospheric thickness is 100 km beneath central india and below that the asthenosphere shows higher attenuation a factor of about two greater than that in the lithosphere the very lowq can be explained by changes in the chemical constitution taking place in the uppermost mantle

moment tensor solutions of earthquakes in the indian ocean from surface waves and their tectonic implications rayleigh and love waves generated by sixteen earthquakes which occurred in the indian ocean and were recorded at 13 wwssn stations of asia africa and australia are used to determine the moment tensor solution of these earthquakes a combination of thrust and strike slip faulting is obtained for earthquakes occurring in the bay of bengal thrust strike slip or normal faulting or either of the combination is obtained for earthquakes occurring in the arabian sea and the indian ocean the resultant compressive and tensional stress directions are estimated from more than 300 centroid moment tensor cmt solution of earthquakes occurring in different parts of the indian ocean the resultant compressive stress directions are changing from north south to east west and the resultant tensional stress directions from east west to north south in different parts of the indian ocean the results infer the counterclockwise movement of the region 0 33 s and 64 e 94 e stretching from the rodriguez triple junction to the intense deformation zone of the central indian ocean and the formation of a new subduction zone island arc beneath the intense deformation zone of the central indian ocean and another at the southern part of the central indian basin the compressive stress direction is along the ridge axis and the extensional stress manifests across the ridge axis the north south to northeast south west compression and east west to northwest southeast extension in the indian ocean suggest the northward underthrusting of the indian plate beneath the eurasian plate and the subduction beneath the sunda arc region in the eastern part the focal depth of earthquakes is estimated to be shallow varying from 4 to 20 km and increasing gradually in the age of the oceanic lithosphere with the focal depth of earthquakes in the indian ocean

sea surface salinity measurements in the historical database 1 we have examined historical distributions of sea surface salinity sss observations in a data set consisting of a combination of the world ocean database 1998 wod98 and a thermosalinograph and bucket salinity database collected from volunteer observing ships it is well known that sss in much of the world s ocean is measured infrequently or not at all we find that 27 of one degree squares in the world ocean open and coastal excluding the arctic ocean had no observations of sss in the historical database and 70 had 10 or fewer systematic sampling of sss more than 10 000 observations per year globally did not start until after 1960 most sss observations in the wod98 are concentrated in the north sea and coast of northern europe the east and west coasts of north america and around japan about 28 of sss measurements are in coastal waters we plotted frequency histograms of sss for some selected well sampled one degree squares in the north atlantic and tropical pacific we found most frequency histograms to be non gaussian the main departure from normal distribution is due to anomalous low salinity measurements creating a negative skewness this conclusion is verified as a global phenomenon by examining statistics of mean median sss difference within one degree squares this quantity is found to be predominantly negative over the global ocean these anomalous low salinity values may be due to rainfall events but there are other plausible physical mechanisms like frontal movement and eddy activity there were also areas where the distributions were bimodal due to the presence of meandering fronts with little cross frontal mixing examples are shown where the non gaussian nature of the distributions in the areas examined is both a short term and a long term phenomenon that is the distributions are skewed on a nearly instantaneous 1 month basis and averaged over long time periods 1 years this has important implications for climatologies because the differences between mean and modal sss for the analyzed one degree squares is of order 0 1 furthermore the implication for validation studies for remote sensing missions is that the studies must make enough measurements of sss to determine the extent to which the probability density is not gaussian

heat transfer and intraplate deformation in the central indian ocean nineteen new heat flow measurements made across deformed oceanic lithosphere in the central indian ocean and previously published data show that heat flow is significantly higher than predicted by models for cooling oceanic lithosphere over much of the region many of the temperature depth profiles are nonlinear upward convection of water is the most likely explanation for the curvature of the temperature profiles since other possible causes including variations in bottom water temperatures conductivity changes with depth in the sediments and experimental error can be eliminated this interpretation requires water velocities of the order of 7 x 10 sup 8 m s which is unusual because the lithosphere is relatively old 72 82 m y and a thick sedimentary cover 1 2 5 km is present these observations suggest that the processes causing deformation of the plate have increased the heat flux through the sediment water interface we infer that extra heat is being generated at shallow depths perhaps less than 35 km in the plate although the specific mechanism by which deformational energy is converted into heat is difficult to determine

a numerical model of the ventilated thermocline abstract a steady state numerical solution is found for an idealized rectangular ocean basin driven by wind and surface buoyancy flux a three dimensional primitive equation model is used in agreement with recent analytical modeling the thermocline in the numerical solution consists of three regions quite distinct in their ventilation characteristics forming the greater part of the subtropical thermocline is an unventilated pool zone located in the core of the subtropical gyre and a ventilated zone to the east the unventilated shadow zone lies farther east and toward the equator analysis of potential vorticity on constant density surfaces is used to study the structure of the thermocline a small but intense zone of convection located in the western boundary outflow caused by rapid heat loss to the atmosphere produces source water for the ventilated zone this water of extremely low potential vorticity mode water is distributed widely into the subtropical thermocline the pool forms equ

sea surface temperature and sea surface height variability in the north pacific ocean from 1993 to 1999 1 correlations between advanced very high resolution radiometer pathfinder sea surface temperature sst and topex sea surface height ssh anomalies are calculated for the 7 year period 1993 1999 in the equatorial and north pacific these correlations provide measures of ssh and sst covariability and are obtained using an empirical orthogonal function analysis separately on the two fields and a singular value decomposition svd method on both fields simultaneously these correlations reveal distinct sst ssh states a warm elevated period from january 1993 to december 1994 a cooler lower phase spanning january 1995 through december 1996 and the strongly variable el nino southern oscillation enso period spanning 1997 1999 the relationships between these sst ssh states and the dominant interannual and interdecadal modes of pacific variability are investigated through correlations with indices for the southern oscillation pacific north american pna pattern and pacific decadal oscillation pdo when including the tropics significant correlations between the first svd mode of the sst ssh covariability and the interannual enso pattern and interdecadal pdo pattern are evident restricting the focus to the extratropical north pacific reveals significant correlations with only the interdecadal pdo pattern while the first mode reveals connections to the enso and pdo patterns the second svd mode indicates significant correlations to the pna pattern for both the tropical and extratropical pacific

increased surface seawater pco2 in the eastern bering sea shelf an effect of blooms of coccolithophorid emiliania huxleyi 1 increased surface seawater pco2 observed in the eastern bering sea shelf long 168 w 160 w lat 54 n 68 n were examined in relation to blooms of the coccolithophorid emiliania huxleyi using data obtained from r v mirai cruises once or twice annually august october 1998 2002 a principal component analysis demonstrated that there are two spatial scales of pco2 variability associated with e huxleyi blooms one is a small scale variation 0 2 in latitude which shows a decrease of pco2 by 18 atm relative to surrounding waters the other is a large scale variation 10 0 in latitude with spatial gradient in pco2 of up to 250 atm detailed analyses show that the large scale variation is associated with diatom blooms while the small scale variation is associated with coccolithophorid blooms with a calcification photosynthesis 1 0 and thus that seawater pco2 is affected by the composition of marine ecosystems and its response to climate variability sst rise also contributed to increased pco2

a younger thinner arctic ice cover increased potential for rapid extensive sea ice loss 1 satellite derived estimates of sea ice age and thickness are combined to produce a proxy ice thickness record for 1982 to the present these data show that in addition to the well documented loss of perennial ice cover as a whole the amount of oldest and thickest ice within the remaining multiyear ice pack has declined significantly the oldest ice types have essentially disappeared and 58 of the multiyear ice now consists of relatively young 2 and 3 year old ice compared to 35 in the mid 1980s ice coverage in summer 2007 reached a record minimum with ice extent declining by 42 compared to conditions in the 1980s the much reduced extent of the oldest and thickest ice in combination with other factors such as ice transport that assist the ice albedo feedback by exposing more open water help explain this large and abrupt ice loss

age dependence of oceanic intraplate seismicity and implications for lithospheric evolution we have determined depths for 16 oceanic intraplate earthquakes using body wave modeling a data set composed of these and 11 other well constrained depths shows that the maximum depth of seismicity deepens with increasing lithospheric age and appears to be bounded by a 700 800 c isotherm the maximum depth to which intraplate earthquakes occur is approximately equal to the flexural elastic thickness but much less than the seismic thickness from surface wave dispersion the maximum faulting depth is consistent with the predictions of rapid weakening at high temperatures for dry olivine rheologies determined by experimental rock mechanics oceanic intraplate earthquakes can occur at greater depths and temperatures than has previously been reported for continental crustal events presumably because oceanic lithosphere is stronger at high temperatures both the number of earthquakes and the cumulative seismic moment decrease with lithospheric age the cause of this trend is unclear possibilities include nonrandom location of preexisting weak zones with respect to the age provinces fault strengthening with age or a decrease in the stress level a decrease in intraplate stress with age is opposite that expected from ridge push stresses which increase with age but may result either from thermoelastic stresses which are greatest in young lithosphere or near ridge stress concentrations due to local heterogeneities in the spreading process

interdecadal variability of the pacific ocean model response to observed heat flux and wind stress anomalies variability of the pacific ocean is examined in numerical simulations with an ocean general circulation model forced by observed anomalies of surface heat flux wind stress and turbulent kinetic energy tke over the period 1970 88 the model captures the 1976 77 winter time climate shift in sea surface temperature as well as its monthly seasonal and longer term variability as evidenced in regional time series and empirical orthogonal function analyses examination of the surface mixed layer heat budget reveals that the 1976 77 shift was caused by a unique concurrance of sustained heat flux input anomalies and very strong horizontal advection anomalies during a multi month period preceding the shift in both the central pacific region where cooling occurred and the california coastal region where warming occurred in the central pacific the warm conditions preceding and the cold conditions following the shift tend to be maintained by anomalous vertical mixing due to increases in the atmospheric momentum flux tke input into the mixed layer which deepens in the model after the shift from the early 1970s to the late 1970s and 1980s since the ocean model does not contain feedback to the atmosphere and it succeeds in capturing the major features of the 1976 77 shift it appears that the midlatitude part of the shift was driven by the atmosphere although effects of midlatitude ocean atmosphere feedback are still possible the surface mixed layer heat budget also reveals that in the central pacific the effects of heat flux input and vertical mixing anomalies are comparable in amplitude while horizontal advection anomalies are roughly half that size in the california coastal region in contrast where wind variability is much weaker than in the central pacific horizontal advection and vertical mixing effects on the mixed layer heat budget are only one quarter the size of typical heat flux input anomalies

faulting associated with large earthquakes and the average rate of deformation in central and eastern asia we determine approximate average rates of deformation in portions of eastern and central asia for the last 80 years these rates are based on estimates of source dimensions average displacements seismic moments and orientations of faults of all large earthquakes m 7 5 and as many other major earthquakes m 7 0 as possible in asia since 1900 a major part of this study is the compilation of these data for separate parts of asia we combine seismic moment tensors to estimate the average rotational strain or deformation tensors for these regions for the last 80 years we estimate that shortening across the tien shan has occurred at 11 mm yr between 5 and 19 mm yr left lateral shear on easterly trending planes in mongolia in northwestern tibet gansu and ningxia and on the xianshuihe fault in western sichuan has been very rapid more than 10 mm yr in each region and apparently as rapid as 40 mm yr in northwestern tibet gansu and ningxia slower rates of a few to 10 mm yr appear to characterize east west extension and conjugate north south shortening of tibet the earthquake history of the himalaya is consistent with rates of underthrusting of more than 10 mm yr but is probably less than the convergence rate of india with eurasia of about 50 mm yr the overall strain field is consistent with a large part of india s penetration into eurasia being absorbed by the extrusion of material out of india s way as a result southeast china moved at about 21 mm yr east southeast with respect to eurasia in the last 80 years with an uncertainty of about a factor of 2 in this estimated rate

a pan atlantic decadal climate oscillation sea surface temperature sst variabilities on time scales of 10 14 years have been documented in various parts of the atlantic ocean here we present observational evidence that these regional variabilities are part of a coherent pan atlantic decadal oscillation pado characterized by zonal bands of sst and wind anomalies stacked in the meridional direction with alternate polarities from the south atlantic all the way to greenland we propose that the interaction of wind evaporation and sst is key to establishing this interhemispherical pado based on results from a new ocean atmosphere coupling model forced by extratropical wind forcing the model successfully reproduces the observed decadal oscillation in both sst and wind velocity over the tropics this decadal extratropical forcing of the tropics is in sharp contrast to the well known tropics to extratropics teleconnection that operates on interannual time scales in association with el nino southern oscillation enso

global scale modes of surface temperature variability on interannual to century timescales using 100 years of global temperature anomaly data we have performed a singular value decomposition of temperature variations in narrow frequency bands to isolate coherent spatio temporal modes of global climate variability statistical significance is determined from confidence limits obtained by monte carlo simulations secular variance is dominated by a globally coherent trend with nearly all grid points warming in phase at varying amplitude a smaller but significant share of the secular variance corresponds to a pattern dominated by warming and subsequent cooling in the high latitude north atlantic with a roughly centennial timescale spatial patterns associated with significant peaks in variance within a broad period range from 2 8 to 5 7 years exhibit characteristic el nino southern oscillation enso patterns a recent transition to a regime of higher enso frequency is suggested by our analysis an interdecadal mode in the 15 to 18 years period range appears to represent long term enso variability this mode has a sizeable projection onto global average temperature and accounts for much of the anomalous global warmth of the 1980s a quasi biennial mode centered near 2 2 years period and a mode centered at 7 to 8 years period both exhibit predominantly a north atlantic oscillation nao temperature pattern a potentially significant decadal mode centered on 11 to 12 years period also exhibits an nao temperature pattern and may be modulated by the century scale north atlantic variability

strain deformation in the northern indian ocean abstract seismicity focal mechanisms and moment tensors are used to estimate the strain deformation for earthquakes which occurred during the last 80 yrs in the northern indian ocean up to 38 s the shear strain deformation values are 0 47 10 8 near the owen s fracture zone 0 26 10 8 in the north carlsberg ridge 0 51 10 8 in the south carlsberg ridge 4 92 10 8 in the chagos laccadive ridge 0 21 10 8 in the rodriguez fracture zone 0 9 10 8 in the southwest mid indian ocean ridge 0 16 10 8 in the southeast mid indian ocean ridge 0 15 10 8 in the ninety east ridge and 2 11 10 8 in the sunda arc the high shear strain obtained in the area 6 s 10 s and 65 e 72 e suggests that the earthquakes here are characterized by high creep strength 20 kbars of material in the vicinity of the earthquake epicentral regions the slip rates obtained from the seismic moment are found to vary from 0 30 to 9 85 mm yr in different parts in the northern indian ocean the maximum slip rate is obtained for the chagos laccadive ridge moment tensor values obtained in different parts of the northern indian ocean suggest that the e w extension and the n s compression are predominant vertical compression crustal thinning is observed in the western areas whereas vertical extension crustal thickening occurs in eastern parts of the northern indian ocean the tension and compression strain deformation values estimated in different parts of the northern indian ocean support the hypothesis of ocean floor spreading and continental collision of the indian and eurasian plates the principal stress directions obtained from the moment tensor of earthquakes show that the compressive stress field is acting approximately in the alignment of the ridge and that the extensional stress is perpendicular to the ridge axis vertical compressions are more prominent near the owen s fracture zone in the chagos laccadive ridge and in the southwest mid indian ocean ridge whereas vertical extension is prominent in the sunda arc and the ninety east ridge

bimodal climate control of shoreline change influenced by interdecadal pacific oscillation variability along the cooloola sand mass queensland australia abstract wave climate in southeast queensland australia has been correlated to changes in the southern oscillation index soi but observations of shoreline change associated with the variable wave climate have been limited due to a paucity of aerial photography lidar and other beach profiling datasets in this region a multi decadal sub annual temporal resolution shoreline dataset spanning 1996 to 2017 was produced using satellite imagery collected by landsat 5 7 and 8 a total of 147 shoreline positions were delineated using the modified normalized difference water index on cloud free imagery and corrected for horizontal offsets forced by variable tide stages at the satellite flyover time the relative influence of soi the southern annular mode sam pacific decadal oscillation pdo and subtropical ridge latitude str l and pressure str p on shoreline dynamics along the cooloola sand mass in queensland are assessed by performing cross correlations between their respective index values and shoreline change distances calculated by the digital shoreline analysis system a bimodal climate control of shoreline change is observed dependent upon the phase of the interdecadal pacific oscillation ipo ipo modulates the impacts of enso on eastern australia through its control over the position of the south pacific convergence zone and elevating lowering of tropical pacific sea surface temperatures during negative ipo soi is negatively correlated to the cooloola sand mass shoreline indicating that the shoreline retreats during negative soi phases during positive ipo the impacts of soi are weakened and the str becomes the primary driver of shoreline change with shoreline response being contingent upon its orientation the sw ne aligned noosa north shoreline erodes in response to poleward movement of the str likely due to the enhanced cross shore wave attack as a result of anti clockwise wave rotation the opposite response is shown at the se nw aligned rainbow beach shoreline which is oriented almost parallel to the incident wave direction and is sheltered by the double island point headland these results suggest that climate control on shoreline change at cooloola sand mass and likely other sand islands in the region is two tiered whereby interdecadal variability of the ipo governs the relative influence of soi and str under the different ipo phases the linked climate and shoreline variability correlation shown in this study provides significant insight into how the cooloola sand mass shoreline will respond to future climate changes under a global warming scenario

gyres driven by combined wind and buoyancy flux abstract the combined effects of buoyancy forcing and wind in a gyre scale steady ocean circulation are modeled using discrete layers with an interfacial flux not necessarily vertical the equations for vorticity conservation of the geostrophic flow in this system are fully nonlinear involving a jacobian for the layer thicknesses these equations are written in a form which can be solved by the method of characteristics the form of these equations invites the interpretation that the geostrophic baroclinic flow is driven by buoyancy and steered by the wind two examples are solved and discussed a subtropical gyre with heating and a subpolar gyre with cooling in each case there are distinct regimes of flow depending upon whether the characteristics originate at the eastern or western boundaries of the model a simple geometrical argument illustrates that the difference between these two regimes the direct and indirect cells depends upon the sign of the true vertical velocity relative to the interf

control of decadal and bidecadal climate variability in the tropical pacific by the off equatorial south pacific ocean abstractdelayed negative feedback processes determining intrinsic decadal and bidecadal time scales for the tropical variability in the pacific are investigated based on climate model experiments by comparing a control run driven by preindustrial forcing and partial blocking runs driven by the same forcing but with ocean temperature and salinity restored to climatology in selected regions subsurface oceanic signals of south pacific origin are shown to precede sst variability in the nino 3 4 region using a linear reduced gravity ocean model driven only by wind stress changes and an offline tracer model oceanic wave adjustment triggered by changes of wind stress curl in the south pacific extratropics is suggested to be essential for the decadal component of the equatorial sst while slower isopycnal advection of subsurface temperature anomalies from the formation region of south pacific eastern subtropical mode water controls the bidecadal component the intrinsic time scales of the tropical variability

bloom dynamics in early opening waters of the arctic ocean we measured the isotopic composition and accumulation of particulate organic matter pom and the uptake of carbon c and nitrogen n in an early bloom of the most productive recurring polynya of the arctic ocean the estimated compensation irradiance at the onset of the bloom was similar to the average for the north atlantic ocean implying that shallow mixing was of critical importance for the bloom s early initiation planktonic pom had a much lower d 13 c than ice pom suggesting that ice algae contributed little to the pelagic biomass the overall isotopic fractionation of pelagic n during bloom development was consistent with in situ diatom growth under saturating irradiance and limiting no soon after the ice cleared rapid physiological changes induced an order of 2 3 magnitude increase in the c and no uptake capacity of diatoms leading to very high f ratios no uptake total 2 2 3 3 n uptake most of the no taken up appeared in the pom so that little net release of reduced n occurred during 2 3 the period of active growth given the tight coupling between photosynthesis and no uptake under n limitation 2 3 the magnitude of primary production in the arctic ocean is expected to respond to changes in n supply

q structure beneath the north and central indian ocean from the inversion of observed love and rayleigh wave attenuation data abstract the fundamental mode love and rayleigh waves generated by 57 earthquakes which occurred in the north and central indian ocean extending to 40 s and recorded at indian seismograph and other wwssn stations such as how shl vis mdr hyb kod chg trd poo bom goa ndi nil and que are analysed love and rayleigh wave attenuation coefficients are estimated at periods of 15 100 s using the spectral amplitude of these waves for 98 different paths across the bay of bengal fan the arabian fan and the north and central indian ocean the large standard deviations observed in the surface wave attenuation coefficients may be a result of regional variation of the attenuative properties of the crust and upper mantle beneath these regions love wave attenuation coefficients are found to vary from 0 000 03 to 0 000 45 km 1 for the bay of bengal fan from 0 000 03 to 0 000 85 km 1 for the arabian fan and from 0 000 03 to 0 000 35 km 1 for the north and central indian ocean similarly rayleigh wave attenuation coefficients vary from 0 000 03 to 0 0004 km 1 for the bay of bengal fan from 0 000 06 to 0 0007 km 1 for the arabian fan and from 0 000 03 to 0 0007 km 1 for the north and central indian ocean backus and gilbert inversion theory is applied to these surface wave attenuation data to obtain average q 1 models for the crust and upper mantle beneath the bay of bengal the arabian fan and the north and central indian ocean inversion of love and rayleigh wave attenuation data shows a high attenuation zone centred at a depth of 120 km q 125 for the bay of bengal fan similarly a high attenuation zone q 40 70 occurs at a depth of 60 160 km for the arabian fan at 100 160 km q 115 for the indian ocean off ninetyeast ridge and at 80 160 km q 80 for the indian ocean across the ninetyeast ridge the q 1 models show a lithosphere thickness of 120 km beneath the bay of bengal fan similarly lithosphere thickness of 70 100 and 80 km is estimated beneath the arabian fan and the indian ocean off ninetyeast ridge and across ninetyeast ridge respectively the base of the lithosphere is identified as the depth at which there is a significant increase in the q 1 value which attains its maximum value in the asthenosphere the thinning of indian lithosphere beneath the arabian fan suggests high temperature below moho depth 60 km from surface which has caused a high attenuation zone at this shallow depth

spatiotemporal variability of interdecadal sea level oscillations in the north pacific 1 the interdecadal variations in the north pacific sea level field were investigated on the basis of two historical tide gauge data sets long term sea level records spanning 100 years but spatially limited in the midlatitudes the cl data set and records from a wider area but with a data length of about 50 years the hcl data set a seesaw like sea level oscillation between the eastern and the western pacific was extracted as the first mode of empirical orthogonal functions eof from the cl data set this mode shows a 22 5 year period of variation that has continued throughout the 20th century a similar variation was found in the hcl data set as the first mode of complex eof ceof though its dominant period was 14 5 years this interdecadal sea level oscillation is the steric sea level change associated with the pacific inter decadal oscillation pdo in the upper ocean temperature field because the temporal evolution and spatial structure in the interdecadal oscillation resemble those of the dominant modal pattern in the temperature field however this mode shows a standing wave characteristic in the midlatitudes rather than propagating though the clockwise phase propagation around the subtropical gyre has been reported in the temperature field another interdecadal oscillation is found in the ceof second mode which was dominant in the 1960s when the first mode was relatively weak the second mode shows a 15 to 16 years period of variation and phase lags of 3 4 years at the subtropical stations relative to those in the midlatitudes

changes in arctic sea ice result in increasing light transmittance and absorption 1 arctic sea ice has declined and become thinner and younger more seasonal during the last decade one consequence of this is that the surface energy budget of the arctic ocean is changing while the role of surface albedo has been studied intensively it is still widely unknown how much light penetrates through sea ice into the upper ocean affecting sea ice mass balance ecosystems and geochemical processes here we present the first large scale under ice light measurements operating spectral radiometers on a remotely operated vehicle rov under arctic sea ice in summer this data set is used to produce an arctic wide map of light distribution under summer sea ice our results show that transmittance through first year ice fyi 0 11 was almost three times larger than through multi year ice myi 0 04 and that this is mostly caused by the larger melt pond coverage of fyi 42 vs 23 also energy absorption was 50 larger in fyi than in myi thus a continuation of the observed sea ice changes will increase the amount of light penetrating into the arctic ocean enhancing sea ice melt and affecting sea ice and upper ocean ecosystems

evolution of interdecadal variability in sea level pressure sea surface temperature and upper ocean temperature over the pacific ocean abstract interdecadal variability in sea level pressure slp and sea surface temperature sst anomalies in the pacific ocean was quasiperiodic from 1900 91 the coherent variability of this phenomenon is investigated using gridded observational data from the turn of the century sst and slp and of upper ocean heat content hs from the recent two and a half decades the nominal cycle in atmosphere ocean variables is roughly two decades long but growth and decay can happen on a shorter timescale e g half a cycle or so the authors divide the full cycle into four phases an onset phase during which a weak slp anomaly pattern off japan takes approximately 2 4 yr to expand eastward leads to large slp anomalies in the region of the aleutian low a quasi stationary growth phase with the midlatitude slp anomaly pattern in the eastern ocean intensifies over a 2 4 yr period the persistent slp anomalies evolve in concert with large sst and hs anomalies of the same polarity located to the south sout