wind effects on estimates of sea level rise 1 variability in sea level at the longest periods observable in modern records has recently been found to be well correlated with local atmospheric pressure at shorter periods however longshore winds are known to be one of the primary mechanisms for forcing sea level variability on the eastern margins of the ocean there is a remarkable 80 mm drop in mean sea level on both the eastern north pacific and north atlantic coasts between the late 1800s and early 1900s it is found here to be in agreement with longshore wind forcing from the equator up to the latitude of the observed tide stations better resolved data beginning in 1960 show that the delay near the annual period between wind forcing and sea level is approximately 1 month the relative high in sea level in the late 1800s on the west coast of europe appears to have propagated westward across the atlantic as a long rossby wave and then to have been seen on the east coast of the united states because many features in long term sea level variability are correlated with wind forcing on time scales from annual to decades it will be prudent to base conclusions about long term sea level rise on the longest records available the results here are based on forcing by longshore winds the related issue of the extent to which open ocean wind curl may also be responsible is not addressed here nor the extent to which coastal sea level observations are representative of the open ocean

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

predicting north atlantic sea surface temperature variability on the basis of the first mode baroclinic rossby wave model 1 predictability of sea surface temperature sst variations over the north atlantic ocean is studied on the basis of the first mode baroclinic rossby wave model this simple linear wave model can explain about 10 46 of the wintertime sst variability in several regions of the north atlantic basin including the tropics between 5 n and 20 n the eastern subtropics between 27 n and 34 n and the east of newfoundland it is shown that the wintertime sst anomalies can be skillfully predicted up to 3 months ahead in the tropical atlantic 18 months in the eastern subtropical atlantic and 3 years east of newfoundland on the basis of the first mode baroclinic rossby wave adjustment

a new index for the atlantic meridional overturning circulation at 26 n abstractthe atlantic meridional overturning circulation amoc has received considerable attention motivated by its major role in the global climate system observations of amoc strength at 26 n made by the rapid climate change rapid array provide the best current estimate of the state of the amoc the period 2004 11 when rapid amoc is available is too short to assess decadal variability of the amoc this modeling study introduces a new amoc index called amocsv at 26 n that combines the florida straits transport the ekman transport and the southward geostrophic sverdrup transport the main hypothesis in this study is that the upper midocean geostrophic transport calculated using the rapid array is also wind driven and can be approximated by the geostrophic sverdrup transport at interannual and longer time scales this index is expected to reflect variations in the amoc at interannual to decadal time scales this estimate of the surface branch of the amoc can be constructed as long as reliable measu

on the seasonal variability of the canary current and the atlantic meridional overturning circulation the atlantic meridional overturning circulation amoc is continually monitored along 26 n by the rapid mocha array measurements from this array show a 6 7 sv seasonal cycle for the amoc with a 5 9 sv contribution from the upper mid ocean recent studies argue that the dynamics of the eastern atlantic is the main driver for this seasonal cycle specifically rossby waves excited south of the canary islands using inverse modelling hydrographic mooring and altimetry data we describe the seasonal cycle of the ocean mass transport around the canary islands and at the eastern boundary under the influence of the african slope where eastern component of the rapid mocha array is situated we find a seasonal cycle of 4 1 0 5 sv for the oceanic region of the canary current and 3 7 0 4 sv at the eastern boundary this seasonal cycle along the eastern boundary is in agreement with the seasonal cycle of the amoc that requires the lowest contribution to the transport in the upper mid ocean to occur in fall however we demonstrate that the linear rossby wave model used previously to explain the seasonal cycle of the amoc is not robust since it is extremely sensitive to the choice of the zonal range of the wind stress curl and produces the same results with a rossby wave speed of zero we demonstrate that the seasonal cycle of the eastern boundary is due to the recirculation of the canary current and to the seasonal cycle of the poleward flow that characterizes the eastern boundaries of the oceans

buoyancy driven interannual sea level changes in the southeast tropical pacific 1 it is commonly held that interannual to decadal sea level variability patterns mainly represent the ocean s response to wind forcing this view is based in part on modeling studies of wind driven sea level changes along the tropical pacific however because buoyancy forcing and other generating mechanisms are usually ignored this paradigm may overemphasize the role of winds focusing on the southeast tropical pacific we use a data constrained ocean state estimate to demonstrate that distinct mechanisms including the ocean s response to buoyancy forcing as well as nonlinear processes can also contribute to interannual sea level variability contrary to the notion that buoyancy driven sea level changes are dynamically passive such changes exhibit a strongly nonlocal dynamically active character made manifest in westward propagating waves as similar findings apply elsewhere accurate modeling of interannual to decadal regional sea level changes requires consideration of a variety of forcing mechanisms including but not limited to the winds

a simple model of interannual displacements of the gulf stream interannual variations in the latitude of the north wall of the gulf stream 1966 1999 can be hindcast by a simple model forced solely by monthly values of the north atlantic oscillation nao index the model is a modified version of the one dimensional model developed by d behringer et al and utilizes the observed tendency for the centers of the azores high and the iceland low to move north or south as the nao strengthens or weakens only one parameter the active upper layer thickness is changed from the original values although the model incorporates the thermal feedback on the wind stress used by behringer et al the results are almost unchanged without it in generating the gulf stream position the model averages the nao index over several months and introduces a time lag of at least a year these delays are associated with the time taken for the lateral advection of heat the model results are also compared with estimates of the latitude of the gulf stream made by a gangopadhyay et al 1977 1988 and by t m joyce et al 1955 1997 and with the series of gulf stream transports 1954 1997 constructed by r g curry and m s mccartney the model reproduces the observed weakness of the seasonal variations in comparison to interannual variations the nao data are used to hindcast the annual latitude of the gulf stream for the period 1825 1999 the results show that since 1970 the gulf stream may have been more consistently farther south than during any period of the past 170 years

variability of sea surface height and circulation in the north atlantic forcing mechanisms and linkages abstract simulations with a coarse resolution global ocean model during 1958 2004 are analyzed to understand the inter annual and decadal variability of the north atlantic analyses of empirical orthogonal functions eofs suggest relationships among basin scale variations of sea surface height ssh and depth integrated circulation and the winter north atlantic oscillation nao or the east atlantic pattern eap indices the linkages between the atmospheric indices and ocean variables are shown to be related to the different roles played by surface momentum and heat fluxes in driving ocean variability in the subpolar region variations of the gyre strength ssh in the central labrador sea and the nao index are highly correlated surface heat flux is important in driving variations of ssh and circulation in the upper ocean and decadal variations of the atlantic meridional overturning circulation amoc surface momentum flux drives a significant barotropic component of flow and makes a noticeable contribution to the amoc in the subtropical region momentum flux plays a dominant role in driving variations of the gyre circulation and amoc there is a strong correlation between gyre strength and ssh at bermuda

on the observability of oceanic gyres abstractthis study examines the observability of a stratified ocean in a square flat basin on a midlatitude beta plane here observability means the ability to establish in a finite interval of time the time dependent ocean state given density observations over the same interval and with no regard for errors the dynamics is linearized and hydrostatic so that the motion can be decomposed into normal modes and the observability analysis is simplified an observability gramian a symmetric matrix is determined for the flows in an inviscid interior in frictional boundary layers and in a closed basin its properties are used to establish the condition for complete observability and to identify optimal data locations for each of these flows it is found that complete observability of an oceanic interior in time dependent sverdrup balance requires that the observations originate from the westernmost location at each considered latitude the degree of observability increases westward due to westward prop

observations inferences and mechanisms of the atlantic meridional overturning circulation a review this is a review about the atlantic meridional overturning circulation amoc its mean structure temporal variability controlling mechanisms and role in the coupled climate system the amoc plays a central role in climate through its heat and freshwater transports northward ocean heat transport achieved by the amoc is responsible for the relative warmth of the northern hemisphere compared to the southern hemisphere and is thought to play a role in setting the mean position of the intertropical convergence zone north of the equator the amoc is a key means by which heat anomalies are sequestered into the ocean s interior and thus modulates the trajectory of climate change fluctuations in the amoc have been linked to low frequency variability of atlantic sea surface temperatures with a host of implications for climate variability over surrounding landmasses on intra annual timescales variability in amoc is large and primarily reflects the response to local wind forcing meridional coherence of anomalies is limited to that of the wind field on interannual to decadal timescales amoc changes are primarily geostrophic and related to buoyancy anomalies on the western boundary a pacemaker region for decadal amoc changes is located in a western transition zone along the boundary between the subtropical and subpolar gyres decadal amoc anomalies are communicated meridionally from this region amoc observations as well as the expanded ocean observational network provided by the argo array and satellite altimetry are inspiring efforts to develop decadal predictability systems using coupled atmosphere ocean models initialized by ocean data

low frequency variability of the north pacific ocean the roles of boundary and wind driven baroclinic rossby waves 1 the effects of the sea level variability along the eastern boundary of the north pacific ocean including those associated with el nino southern oscillation have been considered an important factor in determining the low frequency large scale variability of the ocean interior through rossby waves generated at the eastern boundary this hypothesis is examined in this study using 8 years worth of the sea surface height observations made by the topex poseidon satellite the timescales of interest are longer than 90 days with the annual cycle removed the results indicate that the influence of the eastern boundary of the north pacific ocean has limited offshore extent varying from 3000 4000 km at 10 n to 200 300 km at 50 n the variability in the ocean interior is primarily driven by wind with only a minor influence from the boundary simulations of a linear two layer model of the ocean driven by wind stress curl are correlated with the observations the effects of wind forcing accumulate along the characteristics of long nondispersive rossby waves in the time longitude domain these wind driven rossby waves overwhelm the boundary driven waves in the ocean interior where there are only some small residual effects of the boundary driven waves however these small effects become clearer after the simulated wind driven variability is removed from the observations index terms 4556 oceanography physical sea level variations 4504 oceanography physical air sea interactions 0312 4215 oceanography general climate and interannual variability 3309 keywords rossby waves satellite altimetry el nino north pacific eastern boundary

on too fast baroclinic planetary waves in the general circulation abstract recent altimetric observations of the ocean surface reveal signatures of long planetary waves near the annual frequency band comparisons of the observed wave speeds and those predicted by standard linear theory suggest that the latter is inadequate as it yields different westward speeds than those measured in the extratropical latitudes the predicted speeds are typically slower than the observations here the problem of long baroclinic wave propagation in a forced stratified ocean is considered theoretically with a view toward explaining these observations of too fast planetary waves from a quasigeostrophic analysis it is argued that baroclinic waves in a sheared environment are accelerated to the west via their interactions with both the mean advective field and the mean potential vorticity field conditions under which the ratio of actual to linear phase speeds matches the observed ratio are computed and found to be typical of the open ocean extensions of these ideas to continuously st

climatic warming of atlantic intermediate waters abstract interdecadal temperature variability of the atlantic ocean is investigated by differencing hydrographic sections taken from the 1920s through the 1990s a comprehensive reanalysis of north atlantic sections and the inclusion of south atlantic sections show that warming seen previously in the north atlantic extends to the south atlantic the largest statistically significant changes occur on pressure surfaces between 1000 and 2000 decibars db over this pressure range and for latitudes between 32 s and 36 n temperatures have warmed by 0 5 c century 1 at 48 n a cooling of 3 c century 1 occurred between the 1950s and 1980s these isobaric temperature trends are decomposed into ones along surfaces of constant neutral density and ones due to the vertical movement of neutral surfaces the two components are associated with different processes in the southern north atlantic 8 36 n the subthermocline warming between the 1950s and 1980s appears to be due primarily to downward displacements of n

can long term variability in the gulf stream transport be inferred from sea level recent studies by sturges and collaborators suggest a simple but powerful technique to estimate climatic changes in the transport of the gulf stream from the difference between the oceanic sea level calculated with a simple wind driven rossby wave model and the observed coastal sea level the hypothesis behind this technique is tested using 40 years of data 1950 to 1989 obtained from a three dimensional atlantic ocean model forced by observed surface data the analysis shows that variations in sea level difference between the ocean and the coast are indeed coherent with variations of the gulf stream transport for periods shorter than 1 year or longer than 4 5 years the results obtained from the three dimensional model confirm the findings of the simple rossby wave model that decadal climatic changes in the gulf stream transport vary considerably with latitude

mechanisms of decadal sea level variability in the eastern north atlantic and the mediterranean sea decadal sea level variations from tide gauge records along the western european coast and in the mediterranean sea commencing in the late 19th and early 20th centuries are examined relative to large scale atmospheric forcing recent studies have provided evidence for a link between sea level in the eastern north atlantic and atmospheric forcing however the nature of this relationship is still unclear here the outputs of a regional barotropic model and a nearly global baroclinic model are used in conjunction with wind stress and heat flux data to explore the physical mechanisms responsible for the observed sea level variability all tide gauge records show significant decadal variability up to 15 cm and are highly correlated with the nao and among themselves at decadal periods there is a coherent sea level signal that affects the eastern boundary of the north atlantic northward of 25 n and is limited to a narrow band of the order of a few hundred kilometers along the coast this band tends to become narrower towards higher latitudes we find that longshore wind and wave propagation along the boundary are the major contributors to coastal sea level variability but no significant contribution from mass redistribution linked to changes in the strength of the subtropical gyre is observed the mass component dominates sea level in the mediterranean and is mainly driven by mass exchanges with the atlantic which explains the correlation between both regions southward of 25 n sea level changes are mainly driven by heat advection through ekman fluxes

contrasting records of sea level change in the eastern and western north atlantic during the last 300 years we present a new 300 year sea level reconstruction from a salt marsh on the isle of wight central english channel uk that we compare to other salt marsh and long tide gauge records to examine spatial and temporal variability in sea level change in the north atlantic our new reconstruction identifies an overall rise in relative sea level rsl of c 0 30 m since the start of the eighteenth century at a rate of 0 9 0 3 mmyr 1 error in variables changepoint analysis indicates that there is no statistically significant deviation from a constant rate within the dataset the reconstruction is broadly comparable to other tide gauge and salt marsh records from the european atlantic demonstrating coherence in sea level in this region over the last 150 300 years in contrast we identify significant differences in the rate and timing of rsl with records from the east coast of north america the absence of a strong late 19th early 20th century rsl acceleration contrasts with that recorded in salt marsh sediments along the eastern usa coastline in particular in a well dated and precise sea level reconstruction from north carolina this suggests that this part of the north carolina sea level record represents a regionally specific sea level acceleration this is significant because the north carolina record has been used as if it were globally representative within semi empirical parameterisations of past and future sea level change we conclude that regional scale differences of sea level change highlight the value of using several regionally representative rsl records when calibrating and testing semi empirical models of sea level against palaeo records this is because by using records that potentially over estimate sea level rise in the past such models risk over estimating sea level rise in the future

dynamical suppression of sea level rise along the pacific coast of north america indications for imminent acceleration 1 long term changes in global mean sea level msl rise have important practical implications for shoreline and beach erosion coastal wetlands inundation storm surge flooding and coastal development altimetry since 1993 indicates that global msl rise has increased about 50 above the 20th century rise rate from 2 to 3 mm yr 1 at the same time both tide gauge measurements and altimetry indicate virtually no increase along the pacific coast of north america during the satellite epoch here we show that the dynamical steric response of north pacific eastern boundary ocean circulation to a dramatic change in wind stress curl xy which occurred after the mid 1970s regime shift can account for the suppression of regional sea level rise along this coast since 1980 alarmingly mean xy over the north pacific recently reached levels not observed since before the mid 1970s regime shift this change in wind stress patterns may be foreshadowing a pacific decadal oscillation regime shift causing an associated persistent change in basin scale xy that may result in a concomitant resumption of sea level rise along the u s west coast to global or even higher rates

wind forcing of the atlantic thermocline along 32 n at low frequencies abstract the bermuda tide gauge record extends back to the early 1930s that sea level fluctuations there are highly coherent with dynamic height from hydrographic data has two interesting implications first it should contain information about the low frequency circulation of the atlantic furthermore because dynamic height contains information on heat storage it might on the limited timescales accessible in the record also contain clues about climate a simple model of wind forcing of the atlantic from the african coast to bermuda uses the levitus mean density data to estimate the long rossby wave speed as a function of longitude sea level and thermocline variability estimated this way are in remarkably good agreement with observations at periods of more than a few years duration the peak to peak sea level signal is 18 cm which is nearly 25 of the slope across the gulf stream at this latitude the model results suggest that the variability is largest somewhat to the east of bermuda fluctuatio

information from low density expendable bathythermograph transects north atlantic mean temperature structure and quasi decadal variability the 1999 ocean observing system conference recommended that the low density ld expendable bathythermograph xbt network be discontinued contingent on the completion of studies showing that the global argo network and or satellite altimetry can provide equivalent information herein information content in north atlantic ld lines relative to quasi decadal variability in upper layer temperature structure is addressed as the first step in achieving this recommendation two ld lines are located in the subpolar gyre and support results from previous studies of shorter length that ocean advection and not only air sea fluxes plays an important role particularly in the eastern gyre in determining the characteristics of the water masses transported to the source regions of north atlantic deep water several sections cross the gulf stream and labrador current they provide evidence to support the hypothesis that changes in the intensity of labrador current properties cause meridional motions of the gulf stream decadal variability in the subtropical gyre of the north atlantic has been attributed to westward propagation of temperature anomalies by the mean currents and planetary waves modeling studies suggest that these signals are dominant in the thermocline at the northern latitudes order 30 of the subtropical gyre similar calculations from a line crossing the subtropical gyre at these same latitudes shows no indication of westward propagation quasi decadal signals in upper layer temperature are coincident across the entire gyre with some suggestion of eastward motion of temperature anomalies one line on the southern boundary of the subtropical gyre does include westward signal movement from the eastern boundary based on the information content of individual lines recommendations are made relative to the continuation of specific transects until it has been demonstrated that argo and satellite altimetry can provide equivalent results

decadal variability in the large scale sea surface height field of the south pacific ocean observations and causes large scale sea surface height ssh changes in the extraequatorial south pacific ocean are investigated using satellite altimetry data of the past 12 yr the decadal ssh signals in the 1990s were dominated by an increasing trend in the 30 50 s band and a decreasing trend in the central south pacific ocean poleward of 50 s in recent years since 2002 there has been a reversal in both of these trends spatially varying low frequency ssh signals are also found in the tropical region of 10 25 s where the decadal ssh trend is negative in the eastern basin but positive in the western basin to clarify the causes for these observed spatially varying ssh signals a 11u2 layer reduced gravity model that includes the wind driven baroclinic rossby wave dynamics and the responses forced by ssh changes along the south american coast was adopted the model hindcasts the spatially varying decadal trends in the midlatitude and the eastern tropical regions well accumulation of the wind forced ssh anomalies along rossby wave characteristics is found to be important for both previously reported long term trends and their reversals in recent years the boundary forcing associated with the time varying ssh signals along the south american coast is crucial for understanding the observed ssh signals of all time scales in the eastern tropical south pacific basin but it has little impact upon the midlatitude interior ssh signals

regional dynamics of seasonal variability in the south china sea abstract dynamics of the seasonal cycle of sea surface height ssh in the south china sea scs are studied using observations as well as numerical and theoretical models seasonal variability of the scs is interpreted in light of large scale dynamics and rossby waves it is found that the seasonal cycle over most of the scs basin is determined predominantly by the regional ocean dynamics within the scs the ssh variability is shown to be forced mainly by surface wind curl on baroclinic rossby waves annual baroclinic rossby waves cross the basin in less than a few months leaving the upper ocean in a quasi steady sverdrup balance an anomalous cyclonic anticyclonic gyre is generated in winter summer by the anomalous cyclonic anticyclonic wind curl that is associated with the northeasterly southwesterly monsoon in addition surface heat flux acts to enhance the wind generated variability the winter surface cooling warming cools warms the mixed layer especially in the central scs reducing

heavy metal and anionic contamination in the water and sediments in al mujib reservoir central jordan sixty five sediment samples and 25 water samples were collected from al mujib reservoir central jordan in order to investigate the heavy metal and ionic contamination assessment therefore to achieve this aim water and sediment samples were collected during winter and summer seasons 2007 from al mujib reservoir and the areas surrounding it the study shows that there are elevated levels of so4 2 cl and na in reservoir water which might originate from anthropogenic activities in the reservoir catchment area in addition the reservoir water has higher total hardness th values together with high ca and mg contents this might be attributed to ph of reservoir water and the nature of the rocks exposed in the catchment area the average levels of heavy metals in reservoir sediments are fe 14 888 1 cu 17 8 zn 88 6 ni 38 7 cd 4 4 mn 337 9 and pb 6 1 mg kg which are lower than that observed in wadi al arab reservoir northern jordan the values of enrichment factor are cd 35 5 ni 3 02 zn 2 54 cu 1 26 mn 1 2 and pb 0 57 these values indicate that heavy metals in sediments of al mujeb reservoir have a different anthropogenic incrimination inputs the study showed that the sediments are polluted with cd relatively contaminated with ni and zn and uncontaminated with respect to mn pb and cu

subannual seasonal and interannual variability of the north atlantic meridional overturning circulation abstract an eddy permitting numerical ocean model is used to investigate the variability of the meridional overturning circulation moc both wind stress and fluctuations of the seawater density contribute to moc changes on subannual and seasonal time scales whereas the interannual variability mainly reflects changes in the density field even on subannual and seasonal time scales a significant fraction of the total moc variability is due to changes of the density field in the upper 1000 m of the ocean these changes reflect perturbations of the isopycnal structure that travel westward as rossby waves because of a temporally changing phase difference between the eastern and western boundaries the rossby waves affect the moc by modifying the basinwide east west density gradient both the numerical model used in this study and calculations based on rossby wave theory suggest that this effect can account for an moc variability of several sverdrups sv 106 m3 s 1 these results have implications for t

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

a simple model of the decadal response of the ocean to stochastic wind forcing abstract a simple linear model is used to estimate the decadal response of the extratropical ocean to wind stress forcing assuming a flat bottom a mean state at rest and no dissipation the barotropic fields are governed by a time dependent sverdrup balance the baroclinic ones by the long rossby wave equation the ocean is bounded by a coast in the east and a radiation condition is used in the west at each frequency the baroclinic response consists of a forced response plus a rossby wave generated at the eastern boundary for zonally independent forcing the response propagates westward at twice the rossby phase speed the wind stress is assumed to be stochastic with a white frequency spectrum so the model represents the continuous excitation of the ocean interior by the weather fluctuations the model predicts the shape and level of the frequency spectra of the oceanic pressure field and their variation with longitude and latitude the baroclinic response is spread over a continuum of frequencies

coherent sea level variability on the north atlantic western boundary interannual to decadal sea level variability on the north atlantic western boundary is surprisingly coherent over substantial distances stretching from the caribbean to nova scotia the physical mechanisms responsible for this basin scale low frequency coherence are explored in a diagnosis of simulated ocean fields from gecco which reproduces the observations to good approximation coastal sea level variability on the western boundary is known to be influenced by meridional divergence in the boundary current resulting in a geostrophic tilting of the sea surface this mechanism is found to be of leading order along some stretches of the boundary but it does not account for the coherence spanning the western north atlantic instead the coherence along the entire boundary is accounted for by vertical divergence resulting in the uniform rise and fall of the sea surface west of the 295 e meridian the vertical divergence is found to be due to net vertically integrated zonal transport across this meridian resulting from meridional variation in the sverdrup transport over the basin interior

a study of temperature changes in the upper north atlantic 1950 94 in this paper decadal evolution of warm and cold anomalies in the subtropical and subpolar gyres of the north atlantic in the 300 500 m and 100 250 m depth ranges is described a series of pentadally averaged objective maps of upper ocean thermal anomalies from bathythermograph data are presented warm and cold anomalies in the western subtropical gyre are succeeded by similar anomalies in the subpolar gyre and the east atlantic and subtropical return flow major warm and cold anomalies in the 1950s and 1970s respectively are similar to those described previously in ssts although there is more temporal continuity in the subsurface anomalies two very strong events in the subtropical gyre are identified a cold anomaly in 1966 72 and an intense warm anomaly in 1988 94 that show the greatest temperature anomalies in the north atlantic during the period of the study interisotherm thickness anomalies are shown for the subtropical gyre during these periods in the warm period mode waters are both warmer 188 198c and of greater volume than on average and lie in a narrow band south of the gulf stream above a depressed thermocline with warm temperature anomalies to at least 800 m depth in the cold period the predominant mode water temperature is closer to 178c but there is reduced water formation overall with a raised thermocline and cold temperature anomalies down to 600 m depth the bowl of the gyre is flat during the cold period and the implied recirculation may be weaker and extend farther to the south the changes appear to be consistent with the intensification of the subtropical gyre in the warm period and a spindown in the cold period although the relative roles of wind stress and air sea heat fluxes in these changes need to be determined

annual variation of the kuroshio transport in a two layer numerical model with a ridge abstract a two layer numerical model driven by the wind stress is used to explain the observed annual variation of the kuroshio transport south of japan special attention is given to the effect of a ridge representing the izu ogasawara ridge on the generation of the baroclinic activity through the coupling of the barotropic and baroclinic modes of motion for annual variation lower layer motion is found in areas surrounding the ridge because isostasy a state of no motion in the lower layer is not achieved within such a short timescale thus the lower layer flow impinges on the bottom slope this impinging process generates anomalies of the upper layer thickness especially on the eastern side of the ridge thereafter anomalies move westward with characteristic velocities composed of the vertically averaged flow and westward propagation of the long baroclinic rossby wave forced above the ridge as anomalies of the upper layer thickness move westward above the ridge isostasy is accomplished with res

a simple model of the response of the atlantic to the north atlantic oscillation the response of an idealized atlantic ocean to wind and thermohaline forcing associated with the north atlantic oscillation nao is investigated both analytically and numerically in the framework of a reducedgravity model the nao related wind forcing is found to drive a time dependent leaky gyre circulation that integrates basinwide stochastic wind ekman pumping and initiates low frequency variability along the western boundary thisissubsequentlycommunicated togetherwith the stochasticvariability induced bythermohaline forcing at high latitudes to the remainder of the atlantic via boundary and rossby waves at low frequencies the basinwide ocean heat content changes owing to nao wind forcing and thermohaline forcing are found to oppose each other the model further suggests that the recently reported opposing changes of the meridional overturning circulation in the atlantic subtropical and subpolar gyres between 1950 70 and 1980 2000 may be a generic feature caused by interplay between the nao wind and thermohaline forcing

modelling hydrographic changes in the labrador sea over the past five decades abstract inter annual to inter decadal changes of hydrographic structure and circulation in the subpolar north atlantic are studied using a coarse resolution ocean circulation model the study covers 1949 through 2001 inclusive a time mean state nudging method is applied to assimilate the observed hydrographic climatology into the model the method significantly reduces model biases in the long term mean distribution of temperature and salinity which commonly exist in coarse resolution ocean models by reducing the time mean biases we also significantly improve the model s representation of inter annual to inter decadal variations in the central labrador sea the model broadly reproduces the heat and salt variations of the labrador sea water lsw as revealed by hydrographic observations model sensitivity experiments confirm that the low frequency hydrographic changes in the central labrador sea are closely related to changes in the intensity and depth of deep convection changes in surface heat flux associated with the winter north atlantic oscillation nao index play a major role in driving the changes in t s and sea surface height ssh changes in wind stress play a secondary role in driving these changes but are important in driving the changes in the depth integrated circulation the total changes in both ssh and depth integrated circulation are almost a linear combination of the separate influences of variable buoyancy and momentum fluxes

the forcing of the pacific decadal oscillation the pacific decadal oscillation pdo defined as the leading empirical orthogonal function of north pacific sea surface temperature anomalies is a widely used index for decadal variability it is shown that the pdo can be recovered from a reconstruction of north pacific sea surface temperature anomalies based on a first order autoregressive model and forcing by variability of the aleutian low el nino southern oscillation enso and oceanic zonal advection anomalies in the kuroshio oyashio extension the latter results from oceanic rossby waves that are forced by north pacific ekman pumping the sst response patterns to these processes are not orthogonal and they determine the spatial characteristics of the pdo the importance of the different forcing processes is frequency dependent at interannual time scales forcing from enso and the aleutian low determines the response in equal parts at decadal time scales zonal advection in the kuroshio oyashio extension enso and anomalies of the aleutian low each account for similar amounts of the pdo variance these results support the hypothesis that the pdo is not a dynamical mode but arises from the superposition of sea surface temperature fluctuations with different dynamical origins

seasonal variability of the canary current a numerical study 1 a high resolution numerical model study of the canary basin in the northeast subtropical atlantic ocean is presented a long term climatological solution from the regional oceanic modeling system roms reveals mesoscale variability associated with the azores and canary current systems the northwest african coastal upwelling and the canary island archipelago the primary result concerns the canary current canc which in the solution transports 3 sv southward in line with observations the simulated canc has a well defined path with pronounced seasonal variability this variability is shown to be mediated by the westward passage of two large annually excited counterrotating anomalous structures that originate at the african coast the anomalies have a sea surface expression permitting their validation using altimetry and travel at the phase speed of baroclinic planetary rossby waves the role of nearshore wind stress curl variability as a generating mechanism for the anomalies is confirmed through a sensitivity experiment forced by low resolution winds the resulting circulation is weak in comparison to the base run but the propagating anomalies are still discernible so we cannot discount a further role in their generation being played by annual reversals of the large scale boundary flow that are known to occur along the african margin an additional sensitivity experiment where the azores current is removed by closing the strait of gibraltar presents the same anomalies and canc behavior as the base run suggesting that the canc is rather insensitive to upstream variability from the azores current

the canary basin contribution to the seasonal cycle of the atlantic meridional overturning circulation at 26 n this study examines the seasonal cycle of the atlantic meridional overturning circulation amoc and its eastern boundary contributions the cycle has a magnitude of 6 sv as measured by the rapid mocha wbts project array at 26 n which is driven largely by the eastern boundary the eastern boundary variations are explored in the context of the regional circulation around the canary islands there is a 3 month lag between maximum wind forcing and the largest eastern boundary transports which is explained in terms of a model for rossby wave generated at the eastern boundary two dynamic processes take place through the lanzarote passage lp in fall the recirculation of the canary current and the northward flow of the intermediate poleward undercurrent in contrast during the remaining seasons the transport through the lp is southward due to the canary upwelling current these processes are linked to the seasonal cycle of the amoc

on the propagation of baroclinic waves in the general circulation the propagation of long first mode baroclinic planetary waves in eddy resolving quasigeostrophic general circulation models is studied recent topex poseidon observations argue oceanic first mode planetary waves move with speeds other than those predicted by simple theory these data have prompted theoretical analyses of wave propagation in a mean flow with the results suggesting mean shear can have a controlling effect on the planetary wave guide some of the predicted effects appear to be relevant to the observations while others are less obvious this coupled with other explanations for the observations motivates the calculations based on these experiments the authors suggest that the predicted effects of mean shear on wave propagation are consistent with those computed in a fully geostrophically turbulent ocean these are that a two layer model misses the dominant component of long wave interaction with a mean flow a three layer model captures this interaction qualitatively and the correction to wave propagation is in the direction opposite to the mean flow quantitative comparisons between the theory and the numerical experiments are good in the northern latitudes and questionable in the southern latitudes reasons for the southern discrepancy are offered

the response of the north pacific ocean to decadal variability in atmospheric forcing wind versus buoyancy forcing abstract both wind and buoyancy forcing result in variability in the north pacific ocean thermocline a vertical modal analysis of the density deviations in a 30 yr run of an ocean general circulation model of the north pacific forced by atmospheric variability is used to identify the spatial and temporal patterns of the different baroclinic modes the different dynamic vertical modes show distinct propagation characteristics with the first baroclinic mode exhibiting consistent westward propagation at all latitudes the higher baroclinic modes show westward phase propagation at low latitudes but propagate eastward at higher latitudes the propagation characteristics of each mode can be understood by the inclusion of the zonal mean flow in the vertical structure equation evaluation of the ekman pumping and diapycnal fluxes in the quasigeostrophic potential vorticity equation for each dynamic vertical mode distinguishes their effects on the thermocline variability wind variability dominantly forces the f

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

sea level on the u s east coast decadal variability caused by open ocean wind curl forcing one of the puzzling features of sea level on the east coast of the united states is the decedal scale variability the fluctuations are 10 15 cm peak to peak at periods longer than a few years the authors find that this variability in the frequency band treated with the model is largely caused by a deep sea signal generated by the wind stress curl over the north atlantic a simple forced long rossby wave model of the response of the thermocline to wind forcing is used computing long wave speeds from observed hydrographic data the authors model the response of the ocean at periods longer than 3 years for the full width of the atlantic and for the north south extent of the main anticyclonic gyre 188 388n the model output in deep water shows remarkably good agreement with tide gauges both at bermuda 328n and puerto rico 188n as well as with dynamic height fluctuations of 20 cm peak to peak once these fluctuations reach the western side of the ocean the authors estimate coastal sea level by constructing a complementary coastal model the coastal model is geostrophic and conserves mass within a nearshore region that encompasses the gulf stream by extending this nearshore region as far south as 148 188n and using only the oceanic fluctuations to force the variability in the stream between 80 and 90 of the variance of sea level at coastal tide gauges can be explained sea level along the coast is used to test the model assumptions the basic results however seem important because they are constrained only by open ocean wind forcing and not by input boundary conditions

an idealized model study of the mass and heat transports between the subpolar and subtropical gyres abstract the response of an ocean model of the subtropical and subpolar gyres to idealized surface forcing anomalies that mimic the thermal and mechanical forcing associated with the north atlantic oscillation nao is analyzed emphasis is given on the subpolar gyre and the mechanisms that drive the mass and heat exchanges between the two gyres first steady anomalies are applied surface heat flux anomalies induce density gradient anomalies at depth which drive current anomalies reinforcing the north eastward mean current separating the two gyres the northward heat transport of these anomalous currents is 10 times stronger than that associated with the transport of temperature anomalies by the mean current the heat transport anomalies between the two gyres balances the prescribed surface heat flux after 6 7 yr a similar mechanism is at work when a decadal harmonic forcing is considered but the lag is shortened to 3 4 yr the model response to a wind stress curl anomaly shows a similar behavior to

gyre scale atmospheric pressure variations and their relation to 19th and 20th century sea level rise 1 most of the long tide gauge records in the north atlantic and north pacific commonly used to estimate global sea level rise and acceleration display a marked difference in behavior in the late 1800 s early 1900 s compared to the latter half of the 20th century the rates of sea level rise tend to be lower in the 19th compared to 20th century we show this behavior may be related to long term gyre scale surface pressure variations similar to those associated with the northern annular mode as sea level pressure increases decreases at decadal and longer timescales at the centers of the subtropical atmospheric gyres sea level trends along the eastern margins in each ocean basin decrease increase this is not an isostatic response the scaling between local surface pressure and sea level at interannual and longer timescales is 3 to 6 times greater than expected by that mechanism rather it appears to be the result of large possibly gyre scale changes in ocean circulation some evidence is also presented indicating slow 2 cm sec westward propagation of sea level changes in the atlantic from the west coast of europe to the east coast of the u s which produce the decadal variability seen there

carbonate mounds in the santaren channel bahamas a current dominated periplatform depositional regime abstract new hydroacoustic data high resolution multichannel seismic reflection data ctd casts and sampling document the dominance of bottom currents and the occurrence of carbonate mounds in the santaren channel off great bahama bank and cay sal bank based on these data sets three types of carbonate mounds have been identified in water depths between 285 and 685 m their distribution is strongly related to the present current regime bank driven sediments are caught up by the currents and redeposited mainly in the channel center resulting in the accumulation of giant confined drifts flanked by moats the moats at the banks toe of slope are formed by a southward and northward flowing water mass respectively mainly antarctic intermediate water and subtropical underwater the observed carbonate mounds are concentrated in these moats mound type 1 has an elongated shape parallel to the prevailing bottom current direction a gently inclined flank facing the water flow and a steep flank in its current shadow its upstream flank is covered by a thin sediment wedge whereas the lee side is marked by a parabolic scour type 1 occurs at both bank margins but mainly off great bahama bank consisting of cold water coral rubble floating in a sediment matrix and is thus interpreted as cold water coral mound by contrast type 2 mounds are restricted to the cay sal margin and have a predominately conical outline bottom samples including living sessile crinoids show that its surface must be lithified and colonized by macroepibenthos except corals the mounds are situated in pockmark like depressions that are underlain by fluid escape structures like pipes and chimneys these fluid pathways are generated by a network of fractures mound type 2 is probably formed by abiotic carbonate precipitation however a chemoherm nature cannot be ruled out mound type 3 has a conical to polygonal shape and occurs off cay sal bank and great bahama bank it is surrounded by a scour which is elongated in downcurrent and crescent in upcurrent direction a sediment bulge formed at its front this type is consistent with blocks and boulders colonized by macroepibenthos and related to gravity controlled mass movements at the steep bank slopes principally two habitats can be distinguished the great bahama bank periplatform deep water province dominated by mound type 1 and the cay sal bank slope to basin province occupied by mound type 2 that is associated with pockmark like structures mound type 3 occurs in both habitats physical water mass properties for the existence of cold water corals are limited to a depth range of ca 430 to 685 m with seawater densities of 26 93 to 27 29 kg m and temperatures below 13 c their dominance off great bahama bank might be addressed to a more effective food supply induced by local downwelling

on the relationship between decadal buoyancy anomalies and variability of the atlantic meridional overturning circulation abstractowing to the role of the atlantic meridional overturning circulation amoc in ocean heat transport amoc variability is thought to play a role in climate variability on a wide range of time scales this paper focuses on the potential role of the amoc in climate variability on decadal time scales coupled and ocean only general circulation models run in idealized geometries are utilized to study the relationships between decadal amoc and buoyancy variability and determine whether the amoc plays an active role in setting sea surface temperature on decadal time scales decadal amoc variability is related to changes in the buoyancy field along the western boundary according to the thermal wind relation buoyancy anomalies originate in the upper ocean of the subpolar gyre and travel westward as baroclinic rossby waves when the buoyancy anomalies strike the western boundary they are advected southward by the deep western boundary current leading to latitudinally coherent amoc variability the amoc i

spectrum of wind driven baroclinic fluctuations of the ocean in the midlatitudes in the midlatitudes the thermocline depth variations are largely due to rossby waves of first baroclinic mode forced by stochastic wind stress the frequency spectrum of this oceanic response is investigated with a simple model with emphasis on the impact of i the horizontal mixing ii the zonal variations of the forcing and iii the nonlinearity due to variations of the rossby wave celerity in function of the thermocline depth horizontal mixing which acts here as a frequency dependent newtonian damping smoothes the singularities of the spectrum computed in a linear nondissipative case and slightly increases the slope of the spectrum at periods shorter than 10 yr considering a wind stress with a continuous spectrum also smoothes the response spectrum and modifies the power at decadal and interdecadal frequency it alters its dependence on the distance from the eastern boundary a spectral peak appears when the forcing has a dominant zonal scale but this peak disappears in more realistic cases the nonlinearity included in rossby wave celerity induces energy transfers from decadal frequency to annual frequency thereby whitening the frequency spectrum at periods ranging from 0 5 to 5 yr these features lead to a better agreement with gcm simulations and observations

remote forcing of tasman sea marine heatwaves recent marine heatwave mhw events in the tasman sea have had dramatic impacts on the ecosystems fisheries and aquaculture off tasmania s east coast however our understanding of the large scale drivers forcing and potential predictability of mhw events in this region off southeast australia is still in its infancy here we investigate the role of oceanic rossby waves forced in the interior south pacific on observed mhw occurrences off southeast australia from 1994 to 2016 including the extreme 2015 16 mhw event first we used an upper ocean heat budget analysis to show that 51 of these historical tasman sea mhws were primarily due to increased east australian current eac extension poleward transports through the region second we used lagged correlation analysis to empirically connect the eac extension intensification to incoming westward propagating sea surface height ssh anomalies from the interior south pacific third we dynamically analyzed these ssh anomalies using simple process based baroclinic and barotropic rossby wave models forced by wind stress curl changes across the south pacific finally we show that associated monthly ssh changes around new zealand may be a useful index of western tasman sea mhw predictability with a lead time of 2 3 years in conclusion our findings demonstrate that there is potential predictability of advection dominated mhw event likelihoods in the eac extension region up to several years in advance due to the deterministic contribution from baroclinic and barotropic rossby waves in modulating the eac extension transports