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

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

a general circulation model for upper ocean simulation abstract a general circulation model gcm of the ocean that emphasizes the simulation of the upper ocean has been developed this emphasis is in keeping with its future intent that of an air sea coupled model the basic model is the primitive equation model of bryan and cox with the additions of optional usage of the mellor yamada level 2 5 turbulence closure scheme and horizontal nonlinear viscosity these modifications are intended to improve the upper ocean simulations particularly sea surface temperature and heat content the horizontal grid spacing is 1 latitude 1 longitude and is global in domain the equatorial region between 10 n and 10 s is further refined in the north south direction to resolution there are 12 vertical levels with six levels in the top 70 m the model incorporates varying bottom topography prior to coupling the ocean model to an atmospheric gcm experiments have been carried out to determine the ocean gcm s performance using atmospheric forcing from observed data

kuroshio extension variability and forcing of the pacific decadal oscillations responses and potential feedback abstract a forcing mechanism is sought for the large scale circulation changes in the kuroshio extension region of the western north pacific ocean as inferred by topex poseidon sea surface height ssh data the low frequency signal of the kuroshio extension over the last decade was characterized by a modulation in its zonal mean flow intensity the mean kuroshio extension jet weakened progressively from 1993 to 1996 and this trend reversed after 1997 the ability to simulate the major trends in the observed ssh signals with linear vorticity dynamics leads the authors to conclude that the modulation in the zonal mean jet was remotely forced by wind stress curl anomalies in the eastern north pacific ocean related to the pacific decadal oscillations pdos to be specific the weakening strengthening trend in 1993 96 1997 2001 was caused by westward expansions of negative positive ssh anomalies south of the kuroshio extension and positive negative ssh anomalies north of the kuroshio extension emerg

western boundary currents and frontal air sea interaction gulf stream and kuroshio extension abstract in the northern hemisphere midlatitude western boundary current wbc systems there is a complex interaction between dynamics and thermodynamics and between atmosphere and ocean their potential contribution to the climate system motivated major parallel field programs in both the north pacific kuroshio extension system study kess and the north atlantic climate variability and predictability clivar mode water dynamics experiment climode and preliminary observations and analyses from these programs highlight that complexity the gulf stream gs in the north atlantic and the kuroshio extension ke in the north pacific have broad similarities as subtropical gyre wbcs but they also have significant differences which affect the regional air sea exchange processes and their larger scale interactions the 15 yr satellite altimeter data record which provides a rich source of information is combined here with the longer historical record from in situ data to describe and compare the curr

meridional shift of the kuroshio extension induced by response of recirculation gyre to decadal wind variations abstract the meridional shift of the kuroshio extension to decadal wind variations is examined by analyzing the hindcast simulation of a high resolution 1 12 1 12 north pacific ocean general circulation model ogcm and by conducting a series of idealized ogcm experiments the meridional shift of the kuroshio extension in the hindcast is consistent with observations and former studies using a series of sensitivity experiments in idealized settings the following possible mechanism for this shift is proposed the baroclinic rossby waves that arise in the northern half of the subtropical gyre cannot directly enter the kuroshio oyashio extension region due to the strong kuroshio extension jet when the rossby waves accompanying the negative positive sea surface height anomalies propagate westward and reach the region to the east of the recirculation gyre the difference in thermocline depth between the recirculation gyre and the region to its east becomes larger smaller resulting in stronger weaker baroclinic instabilities these stronger weaker instabilities cause a shallower deeper thermocline in the recirculation gyre to compensate for this shrinking stretching the recirculation gyre migrates southward northward leading to the southward northward shift of the kuroshio extension

integrated seismic electromagnetic workflow for sub basalt exploration in northwest saudi arabia a project involving magnetotellurics shallow em and gravity acquisition was carried out in northwest saudi arabia to improve the imaging of a basalt covered section of the al jawf graben where seismic is particularly noisy the al jawf graben extends from jordan to saudi arabia mesozoic and paleozoic sections contained within the structure have the potential to host multiple oil reservoirs the lack of reliable seismic data in this area motivated the use of a multi geophysics exploration approach electromagnetic em techniques were identified as the optimal complementary geophysical data set in fact the em signal propagates through the resistive basalt cover with minimal attenuation providing information about the underlying conductive sedimentary section a combination of active source time domain em tdem and broadband magnetotelluric mt techniques imaged the base of the shallow basalt cover and its internal variations as well as larger scale faults that control the graben structure integrati

decadal variability of the kuroshio extension observations and an eddy resolving model hindcast abstract low frequency variability of the kuroshio extension ke is studied using observations and a multidecadal 1950 2003 hindcast by a high resolution 0 1 eddy resolving global ocean general circulation model for the earth simulator ofes in both the ofes hindcast and satellite altimeter observations low frequency sea surface height ssh variability in the north pacific is high near the ke front an empirical orthogonal function eof analysis indicates that much of the ssh variability in the western north pacific east of japan is explained by two modes with meridional structures tightly trapped along the ke front the first mode represents a southward shift and to a lesser degree an acceleration of the ke jet associated with the 1976 77 shift in basin scale winds the second mode reflects quasi decadal variations in the intensity of the ke jet both the spatial structure and time series of these modes derived from the hindcast are in close agreement with observations a linear rossby wave

variability of the kuroshio extension jet recirculation gyre and mesoscale eddies on decadal time scales abstract twelve years of sea surface height ssh data from multiple satellite altimeters are used to investigate the low frequency changes and the interconnections of the kuroshio extension ke jet its southern recirculation gyre and their mesoscale eddy field the dominant signal is characterized by the steady weakening of the ke jet recirculation gyre from 1993 to 1996 followed by a gradual strengthening after 1997 during the weakening period of 1993 96 the ke path migrated southward in general and this path migration reversed in direction during the strengthening period of the ke jet and recirculation gyre after 1997 by hindcasting the ssh signals using linear vorticity dynamics it was found that weakening strengthening in the ke jet and recirculation gyre is consistent with westward propagation of negative positive ssh anomalies generating in the eastern north pacific and strengthening during their westward propagation when the ke jet and recirculation gyre were in a weak mode during 19

determination of calcium carbonate and sodium carbonate melting curves up to earth s transition zone pressures with implications for the deep carbon cycle abstract melting of carbonated eclogite or peridotite in the mantle influences the earth s deep volatile cycles and bears on the long term evolution of the atmosphere existing data on the melting curves of calcium carbonate caco3 and sodium carbonate na2co3 are limited to 7 gpa and therefore do not allow a full understanding of carbon storage and cycling in deep earth we determined the melting curves of caco3 and na2co3 to the pressures of earth s transition zone using a multi anvil apparatus melting was detected in situ by monitoring a steep and large increase in ionic conductivity or inferred from sunken platinum markers in recovered samples the melting point of caco3 rises from 1870 k at 3 gpa to 2000 k at 6 gpa and then stays within 50 k of 2000 k between 6 and 21 gpa in contrast the melting point of na2co3 increases continuously from 1123 k at 3 gpa to 1950 k at 17 gpa a pre melting peak in the alternating current through solid caco3 is attributed to the transition from aragonite to calcite v accordingly the calcite v aragonite liquid invariant point is placed at 13 1 gpa and 1970 40 k with the clapeyron slope of the calcite v to aragonite transition constrained at 70 k gpa the experiments on caco3 suggest a slight decrease in the melting temperature from 8 to 13 gpa followed by a slight increase from 14 to 21 gpa the negative melting slope is consistent with the prediction from our ab initio simulations that the liquid may be more compressible and become denser than calcite v at sufficiently high pressure the positive melting slope at higher pressures is supported by the ab initio prediction that aragonite is denser than the liquid at pressures up to 30 gpa at transition zone pressures the melting points of caco3 are comparable to that of na2co3 but nearly 400 k and 500 k lower than that of mgco3 the fusible nature of compressed caco3 may be partially responsible for the majority of carbonatitic melts found on earth s surface being highly calcic it also provides a plausible explanation for low degree melts of carbonated silicate rocks being particularly calcic at these depths the melting curves of caco3 and na2co3 overlap with the estimated ocean island geotherm at transition zone pressures indicating that carbonatitic melt is readily generated from multi component carbonate systems in the transition zone the occurrence of such melt between the 410 and 660 km depths may facilitate the formation of ultradeep diamonds produce low velocity regions within the transition zone and create a barrier to carbonate subduction into the lower mantle

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

observational evidence of alternating zonal jets in the world ocean 1 multiple zonal jets with the east west velocity direction alternating with latitude are discovered in satellite altimetry data the time varying jets are shown to populate every part of the world ocean and its marginal seas and are best seen in the anomaly of geostrophic vorticity at midlatitudes the jets have a meridional wavelength of about 300 kms with r m s sea level velocity and vorticity values of 2 4 cm 6 9 cm s and 1 5 10 6 s 1 correspondingly realistic data from the high resolution ogcm run on the earth simulator are used to justify high vertical coherence of the jets structure and relevance of the jets to an evolving mesoscale eddy field strong coupling between the jets and mesoscale eddies is hypothesized

eddy mean flow interaction in the decadally modulating kuroshio extension system abstract satellite altimeter sea surface height ssh data of the past 16 years are used to investigate the decadal changes of the kuroshio extension ke system that oscillated between a stable and an unstable dynamic state during the stable state of 10 1992 06 1995 and 01 2002 12 2004 the ke jet was intense and had a northerly zonal mean path and a well defined southern recirculation gyre during the unstable state of 07 1995 12 2001 and 01 2005 present the ke jet had a reduced eastward transport and a more southerly flow path transitions between the two dynamic states are caused by the basin scale wind stress curl forcing in the eastern north pacific related to the pacific decadal oscillations pdos or the north pacific gyre oscillations npgos during the positive pdo or negative npgo phase the intensified aleutian low generates negative ssh anomalies in the eastern north pacific through ekman divergence as these wind induced negative ssh anomalies propagate to the west as baroclinic rossby waves they weaken the zonal ke jet and shift its path southward as its path is pushed southward 32 n the deep reaching ke jet has to ride over the shallow shatsky rise generating localized disturbances that lead to their subsequent development along the ke jet west of the shatsky rise the sequence opposite to that listed above occurs when the pdo npgo changes to its negative positive phase after the ke system transitions from a stable to unstable state the enhanced eddy interaction is found to strengthen both the southern recirculation gyre and quasi stationary meanders along the ke s upstream path this nonlinear eddy interaction is important in determining the amplitude of the observed decadal ke variability

evidence for a wind driven intensification of the kuroshio current extension from the 1970s to the 1980s the spatial and temporal characteristics of oceanic thermal variations in the mixed layer and main thermocline of the midlatitude north pacific are distinctive suggesting different physical origins within the main thermocline 400 m depth the variability is dominated by a westward intensified pattern of decadal scale indicative of enhanced eastward geostrophic flow along the southern flank of the kuroshio current extension during the 1980s relative to the 1970s the authors argue that the decadal scale change in the strength of the kuroshio extension was a result of the dynamical adjustment of the oceanic circulation to a decadal variation in wind stress curl according to sverdrup theory four times daily wind stress fields from the national center for atmospheric research national centers for environmental prediction reanalysis project are used to compute the decadal change in sverdrup transport associated with the 1976 77 climate transition it is shown that the decadal changes in sverdrup transport inferred from the wind stress curl field and in observed geostrophic flow inferred from the upper ocean thermal field are consistent both in terms of spatial pattern and magnitude the decadal change in depth averaged geostrophic transport along the kuroshio extension referenced to 1 km is 11 6 sv similar to the sverdrup transport change 11 5 13 9 sv the decadal scale thermocline variation along the western boundary between 308 and 408n exhibits a lag of approximately 4 5 yr relative to the decadal variation in the basin wide wind stress curl pattern this delay may be indicative of the transient adjustment of the gyre scale circulation to a change in wind stress curl via long baroclinic rossby waves

predicting western north pacific ocean climate abstract it is shown that wintertime sea surface temperature anomalies in the confluence region of the kuroshio oyashio currents in the western north pacific can be skillfully predicted at lead times of up to 3 yr the predictions are based on the history of the wind stress over the north pacific and oceanic rossby wave dynamics the predictions may be exploitable in fisheries research and other ecological applications

decadal shifts of the kuroshio extension jet application of thin jet theory abstractmeridional shifts of the kuroshio extension ke jet on decadal time scales are examined using a 1960 2004 hindcast simulation of an eddy resolving ocean general circulation model for the earth simulator ofes the leading mode of the simulated ke represents the meridional shifts of the jet on decadal time scales with the largest southward shift in the early 1980s associated with the climate regime shift in 1976 77 a result confirmed with subsurface temperature observations the meridional shifts originate east of the date line and propagate westward along the mean jet axis a trajectory inconsistent with the traditionally used linear long rossby waves linearized in cartesian coordinates although the phase speed is comparable to that in the traditional framework the zonal scale of these westward propagation signals is about 4000 km and much larger than their meridional scale to understand the mechanism for the westward propagation of the ke jet shifts the authors consider the limit of a thin

annual and interannual variability in the kuroshio current system abstract individual seasonal 300 m temperature maps were constructed over the kuroshio current system from 130 e to 170 w for a 4 year period from summer 1976 through spring 1980 using transpac xbt data and jodc temperature depth data quasi stationary meanders in the kuroshic current system occurred at 137 c i e kuroshio meander at 144 e and 150 e i e lee wave meanders and near 160 e i e meander over the shatsky rise a composite of the paths of the kuroshio i e the 12 c isotherm from the individual seasonal maps and the total variance map finds nodes i e minima and anti nodes i e maxima of variability to have existed along the mean kuroshio path the anti nodes coincided with the location of the quasi stationary meanders the nodes in between zonal propagation of temperature anomalies accounted for 20 30 of the total interannual variance these temperature anomalies propagated eastward at 0 5 1 5 cm s 1 in the region 140 155 e and westward at 1 to 2 cm s 1 in the re

north pacific decadal variability in the community climate system model version 2 abstract north pacific decadal oceanic and atmospheric variability is examined from a 650 yr control integration of the community climate system model version 2 the dominant pattern of winter sea surface temperature sst variability is similar to the observed pacific decadal oscillation with maximum amplitude along the kuroshio extension sst anomalies in this region exhibit significant spectral peaks at approximately 16 and 40 yr lateral geostrophic heat flux divergence caused by a meridional shift of the kuroshio extension forced by basin scale wind stress curl anomalies 3 5 yr earlier is responsible for the decadal sst variability local surface heat flux and ekman heat flux divergence act as a damping and positive feedback respectively a simple linear rossby wave model is invoked to explicitly demonstrate the link between the wind stress curl forcing and decadal variability in the kuroshio extension the rossby wave model not only successfully reproduces the two decadal spectral peaks but a

mechanisms of decadal variability of the wind driven ocean circulation eddy resolving quasigeostrophic simulations of wind driven circulation in a large ocean basin are presented the results show that strong modes of low frequency variability arise in many parameter regimes and that the strength of these modes depends upon the presence of inertial recirculations in the flow field the inertial recirculations arise through advection of anomalous potential vorticity by the western boundary current and are barotropized by the effect of baroclinic eddies in the flow the mechanism of low frequency oscillations is explored with reference to previous studies and it is found that the observed mode can be linked to the gyre mode but is strongly modified by the effect of eddies

long term hydrographic variability in the northwest pacific ocean 1 hydrographic changes in the northwest pacific ocean are examined using data for two time periods 1945 1975 and 1976 1998 the largest changes in t s 2 c 0 2 psu are within the interfrontal zone between the kuroshio extension ke and the subarctic or oyashio front near the shatsky rise and are consistent with a southward shift of the kuroshio bifurcation front kbf other major changes seen are a freshening of 0 04 psu of the newly formed north pacific intermediate water npiw a shoaling over time of the halocline in the center of the western subarctic gyre wsag and a southward shift of the subarctic front between the dateline and 150 w because long term t s changes near the shatsky rise are well correlated we have examined subsurface thermal data at 100 and 200 m depth in the region and found that shifts in front locations show a high degree of correlation with the pdo index on an interannual basis and lagging it by 1 year at 200 m depth