recent wind driven variability in atlantic water mass distribution and meridional overturning circulation abstractinterannual variability in the volumetric water mass distribution within the north atlantic subtropical gyre is described in relation to variability in the atlantic meridional overturning circulation the relative roles of diabatic and adiabatic processes in the volume and heat budgets of the subtropical gyre are investigated by projecting data into temperature coordinates as volumes of water using an argo based climatology and an ocean state estimate ecco version 4 this highlights that variations in the subtropical gyre volume budget are predominantly set by transport divergence in the gyre a strong correlation between the volume anomaly due to transport divergence and the variability of both thermocline depth and ekman pumping over the gyre suggests that wind driven heave drives transport anomalies at the gyre boundaries this wind driven heaving contributes significantly to variations in the heat content of the gyre as do anomalies in the air sea fluxes the analysis presented suggests tha

eddy impacts on the florida current the gulf stream in the atlantic carries warm water northwards and forms both the return closure of the subtropical gyre as well as the upper limb of the meridional overturning circulation recent time series recorded east of the bahamas at 26 n indicate that from may 2009 to april 2011 in contrast with past observations the northward flowing antilles current covaried with the gulf stream in the florida straits the florida current even though the florida and antilles currents are separated by banks and islands spanning 150 km the peak to trough amplitude of transport variations during this period was 15 106 m3 s 1 for the florida current and 12 106 m3 s 1 for the antilles current at time scales of 50 days to a year from satellite observations we show that the fluctuations in both the florida and antilles currents between may 2009 and april 2011 are driven by eddy activity east of the bahamas since the florida current time series is a critical time series for the state of the oceans and often compared to climate models this newly identified source of variability needs careful consideration when attributing the variability of the florida current to changes in the larger scale circulations e g gyre and overturning or wind forcing

the accuracy of estimates of the overturning circulation from basin wide mooring arrays previous modeling and observational studies have established that it is possible to accurately monitor the atlantic meridional overturning circulation amoc at 26 5 n using a coast to coast array of instrumented moorings supplemented by direct transport measurements in key boundary regions the rapid mocha wbts array the main sources of observational and structural errors have been identified in a variety of individual studies here a unified framework for identifying and quantifying structural errors associated with the rapid array based amoc estimates is established using a high resolution eddy resolving at low mid latitudes eddy permitting elsewhere ocean general circulation model which simulates the ocean state between 1978 2010 we define a virtual rapid array in the model in close analogy to the real rapid array and compare the amoc estimate from the virtual array with the true model amoc the model analysis suggests that the rapid method underestimates the mean amoc by 1 5 sv 1 sv 106 m3 s 1 at 900m depth however it captures the variability to high accuracy we examine three major contributions to the streamfunction bias i due to the assumption of a single fixed reference level for calculation of geostrophic transports ii due to regions not sampled by the array and iii due to ageostrophic transport a key element in i and iii is use of the model sea surface height to establish the true or absolute geostrophic transport in the upper 2000m we find that the reference level bias is strongest and most variable in time whereas the bias due to unsampled regions is largest below 3000m the ageostrophic transport is significant in the upper 1000m but shows very little variability the results establish for the first time the uncertainty of the amoc estimate due to the combined structural errors in the measurement design and suggest ways in which the error could be reduced our work has applications to basin wide circulation measurement arrays at other latitudes and in other basins as well as quantifying systematic errors in ocean model estimates of the amoc at 26 5 n

recent slowing of atlantic overturning circulation as a recovery from earlier strengthening the atlantic meridional overturning circulation has weakened over the past decade examination of a global reanalysis that matches independent observations shows that the decline is consistent with recovery from an earlier invigoration

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

fingerprints for early detection of changes in the amoc abstractdifferent strategies have been proposed in previous studies for monitoring the atlantic meridional overturning circulation amoc as well as arrays to directly monitor the amoc strength v

the impact of horizontal resolution of density field on the calculation of the atlantic meridional overturning circulation at 34 s the atlantic meridional overturning circulation and meridional heat transport hereafter the amoc and mht at 34 s as simulated by global 1 16 eddy rich henceforth glob16 and eddy permitting glob4 models are compared with observational estimates three different methods are used for calculating the modeled amoc the first method mocmod is based on simulated velocity fields while the second mocob relies on the same assumptions as available observed derived estimates the third method mocob2 is also based on hydrostatic and geostrophic relationships but relative to a barotropic circulation instead of the definition of velocity at a specific reference depth all methods correctly reproduce the time mean glob16 amoc strength but the value of the non ekman component of the glob16 amoc is only about 75 of the observed derived estimate the glob16 mht is also significantly less than observation value slightly more than 60 of the observed however the mean amoc and mht values at 34 s obtained with coarser resolution glob4 model are comparable with the observed derived estimates possible causes for the differences between the eddy rich model and observational data are studied it is shown that the density field from the eddy rich model has high temporal variability along 34 s with spatial scale of about two hundred km that can be due to mesoscale variations caused by agulhas leakage this results in the decrease of the mean meridional geostrophic velocity which leads to smaller values of the amoc and mht in glob16 subsampling glob16 density on or longitude grid along 34 s for mocob calculation significantly increases the amoc values the findings in this paper provide guidance in understanding amoc and mht dissimilarities between observation based estimates and eddy rich ocean models at 34 s

sea level changes an integrated approach sea level changes an integrated approach in october 1985 sepm sponsored a four day conference entitled sea level changes an integrated approach the purpose of the conference was to provide a forum for an interdisciplinary exchange of ideas on sea level changes and to provide an opportunity for integrating various types of evidence in approaching unresolved issues the conference was successful in bringing together scientists from industry academia and government representing all of the major geosciences disciplines presentations of many new papers plus significant releases of data that were previously held proprietary provided fertile ground for discussion this much cited volume represents the best of the material presented at the conference includes the early vail chart

topographic coupling of the atlantic overturning and gyre circulations abstractthe vorticity dynamics associated with the mean and time varying gyre and overturning circulations of the atlantic ocean are examined in a realistic ocean model hindcast simulation of the late twentieth century abyssal flow interaction with sloping bottom bathymetry gives rise to the bottom pressure torque bpt term of the vertically integrated vorticity equation the dominance of this term in the closure of the barotropic gyre circulation noted in previous studies is corroborated here for both non eddy resolving and eddy resolving versions of the parallel ocean program pop model this study shows that bpt is also a dominant term in the vorticity balance of the atlantic meridional overturning circulation amoc and therefore represents a key dynamical link between the overturning and gyre streamfunctions the interannual variability of the atlantic circulation over the last several decades viewed in terms of time varying integral vorticity balances demonstrates the fundamental role played by

the isotopic composition of strontium and sulfur in seawater of late permian zechstein age abstract the paleozoic minima of 87 sr 86 sr ratios and 34 s values in seawater are observed in anhydrite layers of the stassfurt a 2 and aller a 4 cycles of evaporation of late permian age in germany these minima were probably caused by extremely low rates of continental runoff and bacterial sulfate reduction thereafter conditions changed suddenly with a steeply increasing supply of radiogenic sr and of nutrients into seawater the latter induced a large growth in the production of organic material in bacterial activity in sediments and in the flow of isotopically heavy sulfur back into the oceans this large change in the cycles of s and sr as well as of c and o within the relatively short zechstein period 2 5 ma reflects a considerable modification of the plate tectonic and environmental conditions shortly before the beginning of the mesozoic era the ochoan deposition in the usa is probably of the same age as the stassfurt leine evaporation in w europe

atlantic meridional heat transports in two ocean reanalyses evaluated against the rapid array 1 the atlantic meridional overturning circulation in two versions of the nemo 14 global ocean model has been compared with the rapid transport array at 26 n both model versions reproduce the mean moc strength well although the florida straits flows differ because the pathway of the gulf stream is not strongly constrained at this resolution both models however have a mean meridional heat transport of 1 07pw much lower than the 1 35pw from rapid observations in april 2004 october 2007 much of the heat transport discrepancy is due to lower transports in summer across the midocean bahamas africa section due to stronger southward geostrophic flows in the top 100 m where the water is warmest seasonal thermocline changes increase temperature differences across the basin driving stronger geostrophic shear but this effect is much weaker in the top 100 m of the rapid velocity data the effect accounts for a reduction of 1 1sv in moc and 0 1pw in heat transports the rest of the discrepancy comes from lower ekman transports from using erainterim winds instead of quikscat a smaller zonally varying eddy heat transport component estimated from repeat xbt sections in the observations and the southward throughflow in the model other differences in depth structure of the model moc and rapid observations are described but have much less impact on heat transports

a decadal prediction case study late twentieth century north atlantic ocean heat content an ensemble of initialized decadal prediction dp experiments using the community climate system model version 4 ccsm4 shows considerable skill at forecasting changes in north atlantic upper ocean heat content and surface temperature up to a decade in advance coupled model ensembles were integrated forward from each of 10 different start dates spanning from 1961 to 2006 with ocean and sea ice initial conditions obtained from a forced historical experiment a coordinated ocean ice reference experiment with interannual forcing core ia which exhibits good correspondence with late twentieth century ocean observations from the north atlantic subpolar gyre spg region north atlantic heat content anomalies from the dp ensemble correlate highly with those from the core ia simulation after correcting for a drift bias in particular theobservedlarge rapid rise in spgheatcontentin themid 1990sis successfullypredicted in the ensemble initialized in january of 1991 a budget of spg heat content from the core ia experiment sheds light on the origins of the 1990s regime shift and it demonstrates the extent to which low frequency changes in ocean heat advection related to the atlantic meridional overturning circulation dominate temperature tendencies in this region similar budgets from the dp ensembles reveal varying degrees of predictive skill in the individual heat budget terms with large advective heat flux anomalies from the south exhibiting the highest correlation with core ia the skill of the dp in this region is thus tied to correct initialization of ocean circulation anomalies while external forcing is found to contribute negligibly and for incorrect reasons to predictive skill in this region over this time period

evidence linking satellite derived sea surface temperature signals to changes in the atlantic meridional overturning circulation abstract this study explores an application of satellite derived sea surface temperature sst to climate studies by focusing on a connection with the atlantic meridional overturning circulation amoc here we focus on ssts from the advanced very high resolution radiometer and report a 99 significant correlation between the changes of in situ measured amoc transport and the variation of 1 month leading sst anomalies in the subpolar north atlantic region 45 n 70 n based on analyses of an 85 month period the leading mode of the singular value decomposition analysis of sst and sea level pressure slp for 31 years 1981 12 2012 12 shows an apparent north atlantic oscillation nao forcing on the sst fields specifically the sst and slp one month phase lag covariance is notable at temporal scales of 4 to 11 months after removing the first order component of the nao the residual sst resst provides better estimates of the amoc on a shorter time scale than the sst this is because that resst is less likely to be affected by the local slp on these time scales the high correlation is primarily between the resst and variations of the geostrophic upper mid ocean transport component of the amoc the 31 year resst time series in the north atlantic subpolar region is also significantly correlated with the gulf stream path sst anomalies with a one month lead implying a fast signal transport from the subpolar north atlantic to the gulf stream a similar fast adjustment signal is also found in 500 year control simulations of the gfdl model cm2 1 these results indicate a prospective capability of satellite derived ssts to predict amoc variability

monitoring the atlantic meridional overturning circulation the rapid climate change programme rapid has established a prototype system to continuously observe the strength and structure of the atlantic meridional overturning circulation moc at 26 5 n here we provide a detailed description of the rapid moc monitoring array and how it has evolved during the first four deployment years as well as an overview of the main findings so far the rapid moc monitoring array measures 1 gulf stream transport through florida strait by cable and repeat direct velocity measurements 2 ekman transports by satellite scatterometer measurements 3 deep western boundary currents by direct velocity measurements 4 the basin wide interior baroclinic circulation from moorings measuring vertical profiles of density at the boundaries and on either side of the mid atlantic ridge and 5 barotropic fluctuations using bottom pressure recorders the array became operational in late march 2004 and is expected to continue until at least 2014 the first 4 years of observations april 2004 april 2008 have provided an unprecedented insight into the moc structure and variability we show that the zonally integrated meridional flow tends to conserve mass with the fluctuations of the different transport components largely compensating at periods longer than 10 days we take this as experimental confirmation of the monitoring strategy which was initially tested in numerical models the moc at 26 5 n is characterised by a large variability even on timescales as short as weeks to months the mean maximum moc transport for the first 4 years of observations is 18 7 sv with a standard deviation of 4 8 sv the mechanisms causing the moc variability are not yet fully understood part of the observed moc variability consists of a seasonal cycle which can be linked to the seasonal variability of the wind stress curl close to the african coast close to the western boundary fluctuations in the gulf stream and in the north atlantic deep water nadw coincide with bottom pressure variations at the western margin thus suggesting a barotropic compensation ongoing and future research will put these local transport variations into a wider spatial and climatic context

atmosphere drives recent interannual variability of the atlantic meridional overturning circulation at 26 5 n the atlantic meridional overturning circulation amoc has been observed at 26 5 n since 2004 during 2009 2010 there was a transient 30 weakening of the amoc driven by anomalies in geostrophic and ekman transports here we use simulations based on the met office forecast ocean assimilation model foam to diagnose the relative importance of atmospheric forcings and internal ocean dynamics in driving the anomalous geostrophic circulation of 2009 2010 data assimilating experiments with foam accurately reproduce the mean strength and depth of the amoc at 26 5 n in addition agreement between simulated and observed stream functions in the deep ocean is improved when we calculate the amoc using a method that approximates the observing array at 26 5 n the main features of the geostrophic circulation anomaly are captured by an ensemble of simulations without data assimilation these model results suggest that the atmosphere played a dominant role in driving recent interannual variability of the amoc

antarctic bottom water flux in the equatorial western atlantic a moored array at the equator in the western basin of the atlantic provides a 604 day time series of abyssal currents and temperatures spanning the full breadth of the antarctic bottom water aabw flowing from the brazil basin to the guiana basin mean aabw transport is estimated to be 2 0 sv sv 106 m3 s21 comprising organized westward flow of 2 24 sv and return flow of 0 24 sv the low frequency variability is dominated by a quasi annual transport cycle of amplitude 0 9 sv and a 120 day period of amplitude 0 6 sv maximum transports occur in september october while minimum transports occur in february march allowing for this quasiannual cycle and extrapolating the 604 day record to a full two years adds about 7 to the estimated mean aabw transport the array also provides limited sampling in the overlying lower north atlantic deep water lnadw where a southern boundary intensified flow of lnadw gives the strongest recorded mean speed through the array 9 9 cm s21 into the brazil basin the lnadw records also have a quasi annual cycle with strong lnadw flow episodes occurring in april may time series of temperature indicate that the lnadw aabw transition layer rises and falls in synchrony with the quasi annual aabw transport cycle uplifted transition layer during strong aabw transport periods an observed overall warming trend appears to be accompanied by a decline in aabw transport

locally and remotely forced subtropical amoc variability a matter of time scales mechanisms driving the north atlantic meridional overturning circulation amoc variability at low frequency are of central interest for accurate climate predictions although the subpolar gyre region has been identified as a preferred place for generating climate timescale signals their southward propagation remains under consideration complicating the interpretation of the observed time series provided by the rapid climate change meridional overturning circulation and heatflux array western boundary time series rapid mocha wbts program in this study we aim at disentangling the respective contribution of the local atmospheric forcing from signals of remote origin for the subtropical low frequency amoc variability we analyze for this a set of four ensembles of a regional 208s 558n eddy resolving 1 128 north atlantic oceanic configuration where surface forcing and open boundary conditions are alternatively permuted from fully varying realistic to yearly repeating signals their analysis reveals the predominance of local atmospherically forced signal at interannual time scales 2 10 years whereas signals imposed by the boundaries are responsible for the decadal 10 30 years part of the spectrum due to this marked timescale separation we show that although the intergyre region exhibits peculiarities most of the subtropical amoc variability can be understood as a linear superposition of these two signals finally we find that the decadal scale boundary forced amoc variability has both northern and southern origins although the former dominates over the latter including at the site of the rapid array 26 58n

stratigraphic architecture of upper jurassic oxfordian reefs in the northeastern gulf coast u s and the eastern paris basin france abstract the late jurassic was a major period of reef expansion many jurassic reefs are potential hydrocarbon reservoirs but their stratigraphic distribution has been difficult to predict examination of the stratigraphic architecture of oxfordian reefs in the northeast u s gulf coast and the eastern paris basin france affords a comparison of mixed coral algal sponge reefs versus microbial dominated reefs the smackover formation in the northeastern gulf coast contains microbial dominated reefs the smackover represents deposition during a major transgression and reefs occur within late transgressive system tract tst deposits reefs of mixed coral algae and sponges characterize the oxfordian of the eastern paris basin in the ardennes lorraine reefs appear after the maximum flooding event of a stratigraphic sequence and are maintained through the highstand systems tract hst deposition and into the overlying stratigraphic sequence in burgundy reefs occur in association with the maximum flooding event of the upper stratigraphic sequence dominated by platy microsolenids reef growth begins in the tst this interval is traditionally called the lower reef complex more diverse reef growth the upper reef complex continues above the maximum flooding event through the early hst reef growth ceases by deposition of the late hst with the introduction of grainstones and other high energy lithologies all reefs in this examination regardless of biota are associated with maximum flooding events the sequence stratigraphy of the oxfordian reefs in france and the gulf coast provides a framework for studying jurassic reefs of both mixed and microbial dominated assemblages

a means of estimating the intrinsic and atmospherically forced contributions to sea surface height variability applied to altimetric observations drawing on a 50 member ocean ensemble hindcast the magnitude and characteristic temporal and spatial scales of intrinsic and forced sea surface height ssh variability are evaluated over a 37 year period the intrinsic and forced contributions derived from the ensemble are found to have similar temporal spectra but different characteristic spatial scales these results suggest that with an appropriate choice of cutoff scales simple spatial filtering can be used to estimate the forced and intrinsic contributions given either a single model run or an observational data set the method is tested using a single member drawn from the ensemble before being applied to the observed altimetric record two sample applications with relevance to large scale climate are used to illustrate the method s potential utility firstly the long term trends calculated from the total and recreated forced components using the altimetric record are compared and local differences highlighted second the recreated forced ssh is shown to covary with the north atlantic oscillation at seasonal time scales in regions where no such influence can be found using the original ssh signal some limitations and uses for which the method may prove unsuitable are also briefly considered

observed interannual variability of the atlantic meridional overturning circulation at 26 5 n the atlantic meridional overturning circulation moc plays a critical role in the climate system and is responsible for much of the heat transported by the ocean a mooring array nomianally at 26 circ n between the bahamas and the canary islands deployed in apr 2004 provides continuous measurements of the strength and variability of this circulation with seven full years of measurements we now examine the interannual variability of the moc while earlier results highlighted substantial seasonal and shorter timescale variability there had not been significant interannual variability the mean moc from 1 apr 2004 to the 31 march 2009 was 18 5 sv with the annual means having a standard deviation of only 1 0 sv from 1 april 2009 to 31 march 2010 the annually averaged moc strength was just 12 8 sv representing a 30 decline this downturn persisted from early 2009 to mid 2010 we show that the cause of the decline was not only an anomalous wind driven event from dec 2009 mar 2010 but also a strengthening of the geostrophic flow in particular the southward flow in the top 1100 m intensified while the deep southward return transport particularly in the deepest layer from 3000 5000 m weakened this rebalancing of the transport from the deep overturning to the upper gyre has implications for the heat transported by the atlantic

temporal variability of the atlantic meridional overturning circulation at 26 5 n the vigor of atlantic meridional overturning circulation moc is thought to be vulnerable to global warming but its short term temporal variability is unknown so changes inferred from sparse observations on the decadal time scale of recent climate change are uncertain we combine continuous measurements of the moc beginning in 2004 using the purposefully designed transatlantic rapid climate change array of moored instruments deployed along 26 5 n with time series of gulf stream transport and surface layer ekman transport to quantify its intra annual variability the year long average overturning is 18 7 5 6 sverdrups sv range 4 0 to 34 9 sv where 1 sv a flow of ocean water of 106 cubic meters per second interannual changes in the overturning can be monitored with a resolution of 1 5 sv

seasonal to interannual variability in density around the canary islands and their influence on the atlantic meridional overturning circulation at 26 n the meridional interior flow obtained from the rapid array is determined by horizontal density fluctuations at the eastern and western boundary of 26 n the physical causes of these density variations are responsible for fluctuations in the atlantic meridional overturning circulation amoc and through it the meridional heat transport of the atlantic in this modelling study a high resolution ocean model is used to investigate the source and origin of the amoc variability associated with the density fluctuations at the eastern boundary the amoc in the model is in good agreement with the rapid observations and appears to adequately represent the smaller scale features of variability around the canary islands in this paper we identify a robust relationship between the density structure south of the canary islands the local wind stress curl wsc around these islands and the amoc using an empirical orthogonal functions analysis wavelet transform and wavelet coherence we find that the deep density fluctuations at the eastern boundary of 26 n arise from the pumping effect of the spatial pattern of wsc south of the islands these deep density fluctuations drive the amoc both on seasonal and interannual timescales through their influence on the basinwide tilt of the thermocline at seasonal timescales the density fluctuations south of the islands are driven by the wsc and directly influence the amoc at interannual timescales a significant coherence is found between the density fluctuation and the southward umo transport although the origin of these density fluctuations is not explained by the the direct pumping caused by the wsc