wind driven circulation for the eastern north atlantic subtropical gyre from argo data 1 a trans oceanic section at 24 5 n in the north atlantic has been sampled at a decadal frequency this work demonstrates that the wind driven component of the meridional overturning circulation moc may be monitored using autonomous profiling floats deployed in the eastern north atlantic subtropical gyre more than 500 ctd vertical profiles from the surface to 2000 m depth spanning one year from april 2002 to march 2003 are used to compute the geostrophic transport stream function at 24 5 n the baroclinic transport obtained from the autonomous profiling floats is not statistically different than that from three hydrographic cruises carried out in 1957 1981 and 1992 a good agreement is found between the geostrophic transport stream function and the transport derived from the wind field through the sverdrup relation

a model of the western laurentide ice sheet using observations of glacial isostatic adjustment we present the results of a new numerical model of the late glacial western laurentide ice sheet constrained by observations of glacial isostatic adjustment gia including relative sea level ind

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

formation of large beaches in an area of rapid differential isostatic rebound the three outlet control of lake agassiz abstract shorelines in basins undergoing differential isostatic rebound do not remain geographically fixed for long periods and are either transgressive or regressive during regression a relatively uniform blanket of shoreface sediment may be deposited but unless regression is slow or punctuated by periods of lake level equilibrium large beaches do not form in contrast along transgressive shorelines which migrate upslope large morphostratigraphic features commonly are maintained along the lake s margin these may subsequently be stranded when lake level declines beaches around isostatically rebounding proglacial lakes are commonly considered to have formed during a period of lake regression punctuated by abrupt drops in lake level however in basins that are differentially rebounding large beaches cannot form this way and only periods of transgressing waters allow enough time for large beaches to form and define a continuous shoreline around the basin with this in mind some of the largest and most extensive beaches in the glacial lake agassiz basin the norcross tintah and upper campbell constructed between 10 4 and 9 4 ka 14 c yr bp are reinterpreted as strandlines that were formed by transgression each of these three transgressions followed lower lake phases and resulted from in sequence differential isostatic rebound of the eastern outlet rebound and ice damming of the northwestern outlet and rebound of the northwestern outlet each of these transgressions ended when lake level reached the southern outlet stranding the norcross tintah and upper campbell beaches about 10 2 9 9 and 9 4 ka 14 c yr bp respectively

origin of the herman norcross tintah sequence of lake agassiz beaches in manitoba canada abstract the giant glacial lake agassiz basin is fringed by many strandlines which have long been used to trace the paleogeography of the former lake over its 5000 year history the oldest and highest of these strandlines were placed into three groups by warren upham in the 1890 s the herman norcross and tintah and form a staircase of small landforms the formation of these old strandlines began as early as 13 9 cal 12 0 14 c kyr bp and ended 12 8 cal 10 8 14 c kyr bp based on osl dates and the history of lake level in the agassiz basin new mapping and augering of beach ridges in southern manitoba canada associated with the earliest phase of the lake indicate that there are a series of up to 28 small discontinuous beach ridges that are generally only a few metres high and a few tens of metres wide these beaches mainly consist of weakly defined beds of poorly sorted sediments in many cases a central sandy diamicton unit lies stratigraphically between overlying beach sediments and clay diamicton till below spatially ridges are separated by silty or sandy units or gravel lags inter beach lagoonal organics were not found we discuss the possible origin of these lake agassiz beaches concluding that they were deposited over a few centuries by episodic storm events as lake level slowly declined we base this conclusion on the nature of the sediments in the beach ridges and the regional geomorphology as well theoretical considerations about sedimentation along a regressing shoreline of a large lake other origins are rejected although some other factors may have contributed to formation of some of the beaches such as temporary increases in sediment supply variable rate of outlet erosion and short increases in lake level that reworked sediment upslope into ridges using the time frame of 13 9 to 12 8 cal kyr bp for the formation of the beaches the average interval between formation of each beach is 39 years

an analysis of the late glacial lake levels within the western lake superior basin based on digital elevation models abstract this study establishes a detailed lake level history for the lake superior basin by mapping strandlines from 10 m and 3 m digital elevation models there are 24 levels above the mid holocene nipissing level and elevations increase along a direction of 23 1 due to post glacial rebound the highest level the epi duluth is steeper than subsequent levels and may pre date the lake view ice advance into the western lake superior basin at the end of the younger dryas stade the most prominent level is the duluth ca 10 800 cal yr bp ice retreat exposed successively lower outlets routing overflow to the lake michigan and huron basins by 10 600 cal yr bp lake levels in the western superior basin had dropped almost 200 m this transformative period is complicated by multiple basin wide events the influx of glacial lake agassiz overflow the creation of three sub aqueous moraines and a red to gray color transition in basin sediments a later drawdown event has been hypothesized to have initiated the 9300 cal yr bp cooling event but this flood was much smaller than estimated previously if freshwater triggered the 9300 cal yr bp event the source of the water must have been lake agassiz not lake superior

on the possible influence of extraterrestrial volatiles on earth s climate and the origin of the oceans abstract a consideration of observational and circumstantial evidence suggests that earth may be subject to high influx rates 1011 1012 kg yr of extraterrestrial sourced volatile elements carbon hydrogen oxygen nitrogen derived from comets or other primitive solar system material the total extraterrestrial influx rate may be four to five orders of magnitude greater than previously thought large enough to account for today s total near surface inventories of water and carbon the possibility of high rates of extraterrestrial volatile accretion suggests a new climatic paradigm wherein earth s surface temperature is influenced by conflicting internal and external processes a variable influx of volatile elements tends to warm the earth while terrestrial processes cool the planet by absorbing these gasses at a more uniform rate variations in extraterrestrial influx rates may explain the variation of sea level and mean global temperature over geologic time as well as some types of climate change the occurrence of the pleistocene ice ages and the asymmetry of the phanerozoic climate record sudden warmings slow coolings the extraterrestrial influx rate may also act as the pacemaker of terrestrial evolution at times leading to mass extinctions through climatic shifts induced by changes in accretion rates with concomitant disruptions of the carbon and nitrogen cycles life on earth may be balanced precariously between cosmic processes which deliver an intermittent stream of life sustaining volatiles from the outer solar system or beyond and biological and tectonic processes which remove these same volatiles from the atmosphere by sequestering water and carbon in the crust and mantle

mass fluxes in the canary basin abstract ocean studies in the 1970s provided an improved knowledge of the coastal upwelling region off nw africa while in the 1980s and 1990s they led to a good description of the open ocean flow patterns in the canary basin it was not until the late 1990s that major research addressed the open coastal ocean coupled response here we examine the mean and seasonal circulation patterns in the canary basin with data from four hydrographic cruises carried out in the region between cape ghir madeira island and the canary islands we apply an inverse box model to an ocean divided into 14 layers with several layers representing each water mass or stratum to obtain mass fluxes consistent with the thermal wind equation an optimum flow description is obtained using conservation of mass salt and heat anomaly biologically corrected oxygen and silicate and allowing for ekman transport in the surface layer and dianeutral mixing between adjacent layers the deep waters show no predominant flow direction while the intermediate waters display localized southward flowing mediterranean water far from shore and northward flowing antarctic intermediate water near the continental slope specially in the passage between the eastern canary islands and the african slope the mean upper thermocline canary current composed of north atlantic central water flows south with an open ocean branch transporting about 3 1 sv 1 sv 10 6 m 3 s 1 10 9 kg s 1 and an upwelling related branch near the continental slope carrying 1 0 3 sv the seasonal transport by the open ocean branch intensifies and moves offshore from spring to fall 2 8 1 2 sv in spring 2 9 1 1 sv in summer and 4 5 1 2 sv in fall while it carries its lowest southward mass flux in winter 1 7 1 0 sv possibly as a result of a migration offshore the sampled region upwelling related southward flow is present in spring and summer 1 9 0 1 sv and 2 4 0 1 sv respectively while in fall and winter it merges with the offshore southward branch this westward migration allows a northward mass flux between the canary islands and the african coast 1 8 0 1 sv that by winter reaches cape ghir 0 5 0 2 sv seasonal air sea heat fluxes fit well with the climatological values the net phosphate transport in the surface layer indicates that primary production was negligible in this region during january 1997 and april 1998 though in this last month production was probably starting as a result of significant nutrient supply

questioning the age of the moorhead phase in the glacial lake agassiz basin abstract the stratigraphy of sites within the lake agassiz basin that constrain the timing of the onset of the moorhead low water phase is reexamined stratigraphic interpretation of the oldest date 10 960 14 c yr bp from cross bedded sand of the ojata beach is questioned particularly in light of demonstrated long distance transport and reworking of older organic material from elsewhere in the basin a maximum onset age for the moorhead phase is suggested from a 10 675 60 14 c yr bp age from wood in gravel from the base of the southern outlet whereas radiocarbon dates from in situ peat indicate a later minimum onset age of 10 340 100 14 c bp

mapping and measuring lake agassiz strandlines in north dakota and manitoba using lidar dem data comparing techniques revising correlations and interpreting anomalous isostatic rebound gradients based on light detection and ranging lidar digital elevation model dem data at 1 m spatial resolution lake agassiz strandlines were mapped and their elevations determined in northeastern north dakota and southern manitoba two different techniques for determining strandline elevations from lidar imagery are compared one based on measuring the crests of constructional beaches and the other using the elevation of slope breaks along the shorelines defined by shadows on the lidar hillshade map our measurements on lake agassiz strandlines show that previous correlations of younger strandlines around the pembina delta accepted for more than a century are incorrect the gladstone ojata and emerado strandlines south of the delta are offset by 10 m from their namesakes to the north and so are equivalent to the ojata emerado and hillsboro strandlines respectively furthermore anomalously low gradients for the ojata and emerado strandlines around the pembina delta are interpreted as resulting from postdepositional compaction of underlying fine sediment elevations on the isostatically rebounded strandlines confirm that older higher ones have steeper northward rising elevations and that gradients on those strandlines can be used as proxies for relative age

abandonment chronology of glacial lake agassiz s northwestern outlet abstract spillway scour lakes and basins in northwestern saskatchewan were cored to determine when the spillways were abandoned the cores contained the target contact of organic muck gyttja overlying inorganic sand or silty clay rhythmites new ams radiocarbon dates on terrestrial macrofossils in conjunction with previously published and unpublished data from the area indicate that the spillways were abandoned between 9 07 and 9 59 14c kyr bp 10 220 10 810 cal yr bp of great interest is whether the channels are associated with northwestern drainage from glacial lake agassiz the radiocarbon ages recording spillway abandonment are consistent with previous work which claims that overflow through the northwestern outlet ended 9 5 14c kyr bp 10 700 cal yr bp this is consistent with shifting drainage to the southern outlet at this time the scarcity of dates from the northwestern outlets and other outlets of lake agassiz underscores the need to establish a tighter chronological control on outlet switching before outburst flooding from lake agassiz can be assumed to be the trigger for abrupt climate change

seasonal dynamics in the azores gibraltar strait region a climatologically based study abstract annual and seasonal mean circulations in the azores gibraltar strait region north eastern atlantic are described based on climatological data an inverse box model is applied to obtain absolute water mass transports consistent with the conservation of volume salt and heat and the equations of the thermal wind the large scale gyre circulation azores current azores counter current canary current and portugal current is well represented in climatological data the azores current annual mean transport was estimated to be 6 5 0 8 sv 1 sv 106 m3 s eastward exhibiting a seasonal signal with minimum transport in the spring 5 3 0 8 sv and maximum transport in autumn 7 3 0 8 sv the azores current transport is twice that of the azores counter current in spring and autumn and is four times higher in summer and winter the southward portugal and canary currents show similar seasonal cycles with maximum transports in spring 3 5 0 6 and 6 6 0 4 sv respectively the overturning circulation within the area has an annual mean magnitude of 2 2 0 1 sv and two seasonal extremes the highest in summer 2 6 0 1 sv and the lowest in winter 1 7 0 1 sv of the annual mean about two thirds 1 4 sv of the overturning circulation results from water mass transformation west of the strait of gibraltar the downwelling and recirculation of upper central water 0 6 sv in the intermediate layer the entrainment of central water 0 6 sv into the mediterranean outflow and the contribution of antarctic intermediate water 0 2 sv to the mediterranean outflow the remaining 0 8 sv relates to the overturning in the mediterranean sea through the two layer exchange at the gibraltar strait accordingly the density level dividing the upper inflowing and lower outflowing limbs of the overturning circulation was found to be 1 31 65 kg m 3 1 potential density referred to 1000 db which is above the isopycnal that typically separates central and mediterranean water 1 31 8 kg m 3 in terms of water masses we describe quantitatively the water mass composition of the main currents focusing on the spread of mediterranean water we found that when the northward mediterranean water branch weakens in spring and autumn the westward mediterranean water vein strengthens and vice versa the maximum net transports of mediterranean water across the northern and western sections of the box were estimated at 1 9 0 6 sv summer and 0 8 0 2 sv spring respectively within the error bar 0 2 sv we found no significant net volume transport of mediterranean water across the southern section

three dimensional circulation in the nw africa coastal transition zone abstract high resolution data collected southeast of the canary islands during late winter 2006 are analyzed to describe the hydrography and three dimensional circulation in the coastal transition zone off nw africa the data are optimally interpolated over a regular grid the geostrophic velocity field is calculated and the q vector formulation of the omega equation is used to compute the quasi geostrophic qg mesoscale vertical velocity the coastal transition zone is divided into upwelling frontal and offshore regions with distinct physical and dynamic characteristics the upwelling region is characterized by cold and weakly stratified waters flowing towards the equator with a poleward undercurrent of approximately 0 05 m s 1 over the continental slope the frontal region exhibits a southwestward baroclinic jet associated with cross shore raising isopycnals the jet transport is close to 1 sv with maximum velocities of 0 18 m s 1 at surface decreasing to 0 05 m s 1 at 300 db vertical sections across the frontal region show the presence of deep eddies probably generated by the topographic blocking of the islands to the southward current as well as much shallower eddies that likely have arisen as instabilities of the baroclinic upwelling jet the qg mesoscale vertical velocity field is patchy estimated to range from 18 to 12 m day 1 with the largest absolute values corresponding to an anticyclonic eddy located south of fuerteventura island these values are significantly larger than estimates for other vertical velocities diapycnal vertical velocities associated with mixing in the frontal region a few meters per day and wind induced vertical velocities non linear ekman pumping arising from the interaction between the wind stress and the background vorticity maximum values of a few meters per day linear ekman pumping due to the divergence of ekman transport a fraction of a meter per day or the coastal constraint in the upwelling region about 0 7 m day 1 however the patchiness in both the qg mesoscale vertical velocity and the non linear ekman pumping velocity cause their integrated vertical transports to be one order of magnitude smaller than either coastal ekman transport 0 08 sv integrated linear ekman pumping 0 05 sv or diapycnal transfer about 0 1 0 2 sv the pattern of the near surface fluorescence field is a good indicator of these different contributions with large homogeneous values in the coastal upwelling region and a patchy structure associated with the offshore mesoscale structures

canary current and north equatorial current from an inverse box model 1 the large scale canary basin circulation is estimated from a box inverse model applied to hydrographic data from a quasi synoptic survey carried out in september 2003 the cruise consisted of 76 full depth ctd and oxygen stations circulation is required to nearly conserve mass and anomalies of salinity and heat within layers bounded by neutral surfaces it permits advective and diffusive exchange between layers and an adjustment of the ekman transport and the freshwater flux divergences the canary current at the thermocline layer transports a net mass of 4 7 0 8 sv southward north of the canary islands from the african coast to 19 w it is divided into a northward circulation at a rate of 1 1 0 5 sv between the african coast and lanzarote island and a southward transport of 5 8 0 6 sv it transports north atlantic central water and organic matters advected offshore by the filaments protruding from the upwelling system off northwest africa at 24 n the canary current feeds the north equatorial current that transports a mixture of north and south atlantic central waters westward in the intermediate layer a southwestward flow of 1 2 1 1 sv transports mediterranean water to the subtropical gyre though the highest salt flux is transported by a meddy oxygen distribution and mass transport suggest a northeastward deep flow of a water mass colder than 2 2 c consisting of diluted antarctic bottom water the heat and freshwater divergences and the average dianeutral velocity and diffusion between the sections and the african coast are negligible

seasonal flow reversals of intermediate waters in the canary current system east of the canary islands two 9 yr current meter and salinity records together with climatological data reveal marked seasonal variability of the intermediate flow at a key location in the canary basin the region is characterized by a summer july september and early fall october northward progression of antarctic intermediate water followed by a fall november december intense flow reversal of mediterranean water a sverdrup type model confirms that these movements are associated with stretching or shrinking of the intermediate water strata

the source of the canary current in fall 2009 1 the source of the canary current has been inferred from an inverse box model applied to the hydrographic data of a survey carried out in 2009 in the northeast subtropical gyre 29 37 n 9 24 w the portugal current is observed between 13 5 and 14 8 w at 37 n carrying 1 8 0 4 sv southward this current presumably merges with the eastward transport of the azores current system and partly contributes to the mediterranean inflow and partly to the northward recirculation of the azores current through the gulf of cadiz the azores current system is located in the meridional range 33 50 36 25 n at 24 50 w this system transports eastward 7 2 0 5 sv in the thermocline layers and 1 1 0 8 sv at intermediate layers the azores current intermediate water mass has the highest portion of sub arctic intermediate water saiw in the region while the azores countercurrent intermediate waters mass is mainly mediterranean water the canary current extends from 22 25 to 18 50 w at 29 n the westernmost position ever observed this current transports southward 6 2 0 6 sv in the thermocline layers and 2 0 0 8 sv in the intermediate layers this intermediate flow shows a relative maximum of oxygen and a relative minimum in nutrient concentration indicating the presence of saiw the study concludes that at least in fall 2009 the canary current extends to the intermediate waters n 27 9220 approximately 1600 dbar and that azores current feeds the canary current at surface and intermediate layers

megaflooding associated with glacial lake agassiz abstract significant baseline and episodic megaflooding from glacial lake agassiz was routed to the south east and north coasts of north america over the lake s nearly 6000 year history the five phases of lake level change were controlled by which outlet was active which in turn was controlled by ice margin position and glacioisostatic adjustment the southern outlet is the oldest and best understood outlet while successively younger outlets are progressively less understood eastern drainage synchronous with the younger dryas chronozone had been assumed by most studies but a spillway to accommodate the 90 m drop in lake level is yet to be described with the south and east outlets unable to accommodate the necessary lake level drawdown the northwest outlet has become the default outlet with arctic ocean core data supporting it however extant terrestrial data from the continent only provides data for a large flood from the fort mcmurray area closer to the end of the younger dryas coinciding with the timing of the preboreal oscillation the challenge remains to find agreement between the marine and terrestrial records uncontroversial is the geomorphic and sedimentologic evidence for flooding into and out of the lake consisting of large spillways large boulders and in places giant current ripples composed of boulders flood discharge estimates into and out of the lake range from 0 04 to 1 sv with final subglacial drainage into the tyrell sea estimated at 5 sv sufficient to raise global sea level by 0 18 m and initiate the 8 2 ka stadial

the eastern boundary current system between the canary islands and the african coast to study the easternboundarycurrentsystem off northwest africa in detail several ctd adcp sections and long term mooring work were carried out in the channel between lanzarote and africa the observations are compared with a fine resolution model which was developed in the framework of the canigo project the water masses which are observed in this area are characterised and classified in density ranges the current field shows a high spatial and temporal variability with maximum velocities of about 35 cm s seasonal means as well as currents averaged across the channel are only a few cm s in the surface water a steady southward flow in the middle of the channel indicates the canarycurrent in this area during fall a strong northward current is observed close to the african shelf though the canarycurrent strengthens during summer and fall due to an increase of the trade winds the transport in the channel decreases or turns northward during that time due to the enhanced poleward current at the eastern side a northward undercurrent with a mean velocity of 2 3 cm s is observed at the african slope in 950 m depth the poleward transport of aaiw increases during fall and a strong influence of relatively fresh aaiw is observed during that time most of the observations fit well to the results of the canigo model but the occurrence of mw at the bottom of the channel and the corresponding southward flow cannot be resolved by the model

routing of meltwater from the laurentide ice sheet during the younger dryas cold episode rooth1 proposed that the younger dryas cold episode which chilled the north atlantic region from 11 000 to 10 000 yr bp was initiated by a diversion of meltwater from the mississippi drainage to the st lawrence drainage system the link between these events is postulated to be a turnoff during the younger dryas cold episode of the north atlantic s conveyor belt circulation system which currently supplies an enormous amount of heat to the atmosphere over the north atlantic region2 this turnoff is attributed to a reduction in surface water salinity and hence also in density of the waters in the region where north atlantic deep water nadw now forms here we present oxygen isotope and accelerator radiocarbon measurements on planktonic foraminifera from orca basin core en32 pc4 which reveal a significant reduction in meltwater flow through the mississippi river to the gulf of mexico from about 11 200 to 10 000 radiocarbon years ago this finding is consistent with the record for lake agassiz which indicates that the meltwater from the southwestern margin of the laurentide ice sheet was diverted to the northern atlantic ocean through the st lawrence valley during the interval from 11 000 to 10 000 years before present yr bp

ages for the big stone moraine and the oldest beaches of glacial lake agassiz implications for deglaciation chronology glacial lake agassiz has been implicated as the trigger for numerous episodes of abrupt climate change at the close of the last ice age yet the beginning age of the lake has never been determined here we report the fi rst numerical age data on the big stone moraine and the oldest beaches of glacial lake agassiz organic remains from lakes bogs and channels distal to and inset to the big stone moraine require that glacial activity at this moraine ceased prior to 12 000 14 c yr b p 13 950 cal calendar yr a site near new effi ng ton south dakota united states implies full glacial recession north of the topographic divide prior to 11 810 14 c yr b p 13 670 cal yr synchronous with the beginning of glacial lake agassiz lake agassiz shorelines inset to the moraine yield optically stimulated luminescence osl ages from 14 200 12 600 yr cal lower strandlines are younger but the similarity of ages suggests that initial lake lowering was faster than osl ages can currently resolve nevertheless the osl ages represent the fi rst numerical age assignments for the herman norcross and upham beach ridges setting the stage for future numerical age assignments within the lake agassiz basin these two dating methods yield strongly consistent results within stated uncertainties the age of the big stone moraine implies an interval of rapid retreat for the des moines lobe of the laurentide ice sheet during the bolling allerod warm interval the overlapping ages for the uppermost beach levels and abandonment of the highest lake agassiz spillway indicate a rapidly evolving lake until at least 13 500 yr cal

an analysis of mixing in the frontal zone of south and north atlantic central water off north west africa abstract multi parameter mixing analysis is applied to 26 stations of auftrieb 75 a joint expedition of r r s discovery and fs meteor north atlantic central water nacw and south atlantic central water sacw are represented by two water types each and phosphate silicate and nitrate are all used as an additional parameter with temperature and salinity yielding three sets of independent solutions solutions from different parameters show similar vertical distributions but can differ considerably in absolute terms this is believed to be caused by insufficient knowledge of nutrient values of pure nacw and sacw and by low range precision ratios of nutrient determination it is shown that isopycnal mixing analysis correctly describes the water mass distribution to lowest order i e there is agreement between results from isopycnal and multi parameter analysis at most stations within the error bounds which are inherent in the method and which are presently very high significant non isopycnal mixing could be confirmed for only one station situated on the continental slope in the area of the undercurrent of the canary current upwelling regime and may be caused by active upwelling increased lateral and vertical shear in the under current or internal waves interacting with the bottom five stations do not yield oceanographically acceptable solutions and an attempt is made to include a coastal water mass in the analysis in order to improve the result for these stations i e three parameter analysis for nacw and sacw is replaced by four parameter analysis for nacw sacw and coastal water by combining temperature and salinity with phosphate and silicate or with nitrate and silicate simultaneously the combination phosphate and nitrate is degenerate because both nutrients are linearly correlated this indeed improves the results indicating the presence of coastal water at those stations but accumulation of errors inhibits quantitative conclusions

nine years of mass transport data in the eastern boundary of the north atlantic subtropical gyre 1 one of the longest current meter time series in the lanzarote passage in the eastern boundary of the north atlantic subtropical gyre has been used to determine and quantify the 9 year mean transport the inter annual and seasonal mass transport variability for the three water masses present in the area results show north atlantic central water nacw flowing southward in the upper levels with a mean mass transport of 0 81 1 48 sv antarctic intermediate water aaiw flowing northward at intermediate levels with a mean transport of 0 09 0 57 sv and mediterranean water mw flowing southward in the deep part of the passage with a mean transport of 0 05 0 17 sv harmonic and wavelet analysis show the presence of a seasonal pattern in the passage for the three water masses a maximum southward transport in winter and spring has been observed for the nacw followed by a minimum in summer and fall near zero values during winter and spring are found for aaiw with a maximum northward value in summer and a negative value in fall when this water mass reverses its flow mw has a similar seasonal pattern to nacw the vertical structure in the lanzarote passage can be approximated by four significant oscillatory modes which cumulatively explain 86 4 of the variance the strong transport fluctuation found at the seasonal and inter annual timescales demonstrates that the eastern boundary current transport has a strong impact on meridional overturning estimates thus indicating that to understand meridional overturning circulation variability these transport estimates at the eastern atlantic margin are necessary

the climatology of the north atlantic abstract data from approximately 144 000 hydrographic stations in the north atlantic have been retrieved from the national oceanic data centre and analysed to produce maps of mean pressure temperature salinity and oxygen on selected potential density surfaces for the domain bounded by 0 85 w and 0 65 n the data span the period from 1904 to 1990 with the majority of the data from the last four decades the data set for this region is 60 larger than that used in the production of levitus climatological world atlas this increase in stations coupled with smoothing scales specific to the north atlantic rather than the global ocean considerably improves the resolution of the basin s features the mean property fields and their associated standard deviations are resolved on a one degree grid with little smoothing contrasting with the levitus atlas where properties although presented on a one degree grid have been smoothed on the order of 1000km another important feature of this database is the process by which irregularly spaced data are averaged onto a regular grid in a significant departure from the levitus analysis which averaged on depth surfaces these data were averaged on potential density surfaces thus eliminating an artificial mixing of water mass properties the database is used to describe the baroclinicity of well known features such as the gulf stream the north atlantic current and the deep western boundary current and to elucidate the recirculations associated with these currents it additionally resolves several new features in the intermediate and deep north atlantic these features include the signature of a large scale deep recirculation that extends southwestward from the eastward extension of the north atlantic current to the separation point of the gulf stream near cape hatteras this recirculation which spans approximately 2000m of the water column encompasses more local recirculations and potentially mixes subpolar and subtropical waters furthermore in the upper thermocline this database reveals a coherent azores current that stretches from the gulf stream system south of the tail of the grand banks to madeira this flow is marked by divergences to the south and convergences from the north such that its downstream transport is not much changed

age determinations for glacial lake agassiz shorelines west of fargo north dakota usa understanding the evolution of lake agassiz is vital to developing a comprehensive late quaternary history of central north america although many of the geomorphic features of the lake are well known current reconstructions pri marily depend upon relative ages of landforms here we report new optically stimulated luminescence osl ages on a flight of strandlines located 140 km north of the southern outlet strandline ages at this location range from 14 3 0 2 to 10 0 0 2 ka cal spanning 4000 years of lake history using geomorphic relationships and osl age control it is pro posed that the herman through tintah strandlines developed over a period of 1000 years followed by a hiatus of strandline development until the campbell strandline developed at 10 3 0 2 ka cal there is agreement between our new osl dates and osl and radiocarbon ages from geomorphically correlative landforms elsewhere in the lake basin the use of high reso lution lidar imagery greatly aids localized mapping of shoreline features additional site specific field work and osl ages are necessary to further evaluate strandline tracing across the basin resume il est essentiel de comprendre l evolution du lac agassiz pour avoir un historique complet du quaternaire tardif du centre de l amerique du nord bien que plusieurs des caracteristiques geomorphologiques du lac soient bien connues les reconstructions actuelles sont surtout determinees par l ge relatif des formes de terrain dans cet article nous donnons de nouveaux ges determines par luminescence stimulee optiquement osl a d anciennes lignes de plage situees a 140 km au nord de l exutoire sud les ges des anciennes lignes de plage a cet endroit varient entre 14 3 0 2 et 10 0 0 2 ka cal soit 4000 ans d histoire du lac base sur des relations geomorphologiques et le controle de l ge par osl il est propose que les anciennes lignes de plage herman a tintah se soient developpees durant une periode de moins de 1000 ans une periode sans developpement de lignes de plage aurait suivi jusqu au developpement de la ligne de plage campbell vers 10 3 0 2 ka cal il y a concordance entre nos nouvelles dates osl et les ges determines par osl et par radiocar bone sur des formes de terrain correlees par geomorphologie ailleurs dans le bassin du lac l utilisation d imagerie lidar a haute resolution a grandement aide la cartographie locale des caracteristiques des lignes de rivage d autres travaux speci fiques au site et d autres ges osl sont necessaires pour continuer a tracer les anciennes lignes de plage a travers le bassin traduit par la redaction

postglacial history and paleoecology of wampum manitoba a former lagoon in the lake agassiz basin a small paleolagoon along the margin of the glacial lake agassiz basin near wampum manitoba 130 km southeast of winnipeg contains an unusually thick and continuous sequence of late glacial and holocene organic sediment cores at 17 sites through this sequence provide insight into the fluctuations of the level of lake agassiz the timing of the construction of the lake9s most extensive strandline the upper campbell beach and the paleoecology of this area during the past 10 000 14 c yr the history of this area is established from 26 new ams radiocarbon dates siliceous microfossils plant macrofossils mineralogy sediment characteristics and stratigraphic relationships following deglaciation at wampum about 11 14 c ka deposition of largely unfossiliferous silty clay with occasional ice rafted clasts represents relatively deep water conditions in lake agassiz overlying this is a spatially and temporally variable mixture of silt sand peat gyttja and marl containing an allochthonous assemblage of siliceous microfossils and plant macrofossils with a wide range of radiocarbon dates these sediments were deposited in an embayment of lake agassiz mainly in shallow quiet waters as the lake transgressed about 10 ka over the moorhead low water phase surface between about 9 7 and 9 3 ka the wampum embayment was progressively isolated from lake agassiz by growth of the upper campbell spit resulting in the formation of a lagoon organic rich deposits on the lakeward side of the lagoon were buried 9 3 9 4 ka by sand and gravel of the spit and a thin overwash of sand marks this event throughout the lagoon at about this time lake agassiz fell below the upper campbell beach level subsequent accumulation at wampum consists mainly of algal gyttja during the early holocene and marl during the middle holocene only minor fluctuations in hydrological conditions occurred except for slightly warmer and drier conditions between 6 2 and 4 0 14 c ka these stable shallow water conditions may be due partly to persistent groundwater contributions to the site progressive encroachment of rooted aquatics led to present day fen conditions peat accumulation across the basin began by about 4 0 ka

using lidar digital elevation model data to map lake agassiz beaches measure their isostatically induced gradients and estimate their ages abstract high resolution lidar digital elevation model dem data were used to create dem mosaics and hillshade maps of a large region in north dakota for better defining and measuring the strandlines of glacial lake agassiz although many of the strandlines in this region had been identified and named more than a century ago by warren upham lidar images clearly reveal their complexity and identify additional small and low relief ridges not previously mapped the elevations of the crests of six well developed strandlines the campbell mccauleyville lower blanchard emerado upper ojata and lower ojata beaches were measured for each of these strandlines north south gradients were calculated which were produced by differential isostatic rebound the steepest gradient is on the uppermost campbell beach in the sequence and the gradient on each beach below is progressively lower confirming that these beaches were deposited in sequence from oldest to youngest as the level of lake agassiz declined because there were no anomalous beach gradients in this sequence the ojata beach formed after 9400 14 c 10 630 cal bp which is when the higher elevation campbell beach was deposited rather than at 10 000 14 c 11 480 cal years ago as some have suggested because of the age of organics below the ojata beach those organics and the subaerial surface on which they lie survived the moorhead transgression to the campbell beach and the ojata beach must have been deposited over the older organic unit later as lake level regressed a simple extrapolation model was used to estimate the ages of beaches in the sequence

optically stimulated luminescence ages from the lake agassiz basin in manitoba geomorphic analysis and optically stimulated luminescence osl ages from undated lake agassiz beaches and adjacent fluvial sediments on riding mountain in manitoba provide insight into their early history new osl ages of 14 5 2 4 and 13 4 0 7 ka on the oldest herman to norcross beaches of lake agassiz near the canada u s border indicate that the laurentide ice sheet lis retreated from that part of the agassiz basin by 14 5 ka to the north along riding mountain the herman strandlines are absent and osl ages on the oldest beach there average 12 9 ka which links it to the younger norcross tintah strandlines in adjacent riding mountain osl ages and geomorphological relationships of a large abandoned glacial spillway 200 m above the oldest beaches of lake agassiz indicate that this channel predates retreat of the lis and formation of beaches in this part of the agassiz basin with ice remaining in this area until after 14 5 ka osl ages on the gimli beach 170 km to the east are 3000 yr older than conventional assignments suggesting that it formed during the moorhead low water phase 12 8 10 6 ka luminescence ages support the conclusion that the campbell beach formed 10 9 ka near the end of the moorhead low water phase

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

glacial lake agassiz a 5000 yr history of change and its relationship to the δ18o record of greenland lake agassiz was the largest lake in north america during the last period of deglaciation the lake extended over a total of 1 5 10 6 km 2 before it drained at ca 7 7 14 c ka 8 4 cal calendar ka new computer reconstructions controlled by beaches isostatic rebound data the margin of the laurentide ice sheet outlet elevations and a digital elevation model dem of modern topographic data show how variable the size and depth of this lake were during its 4000 14 c yr 5000 cal yr history abrupt reductions in lake level ranging from 8 to 110 m occurred on at least 18 occasions when new outlets were opened reducing the extent of the lake and sending large outbursts of water to the oceans three of the largest outbursts correlate closely in time with the start of large 18 o excursions in the isotopic records of the greenland ice cap suggesting that those freshwaters may have had an impact on thermohaline circulation and in turn on climate

strandline analysis in the southern basin of glacial lake agassiz minnesota and north and south dakota usa glacial lake agassiz a large pleistocene lake left behind strandlines at multiple elevations within its basin prior researchers have used these strandlines to identify four relatively stable water level stages but tracing them over long distances is often problematic in this study the elevation of the tintah strandline is returned to its original designation and a newly interpreted stable lake level at 1020 1030 ft 311 314 m is referred to as the upham level based on a concentration of ridges and a spit at that elevation cores from strandline and lagoon complexes from the milnor to tintah beaches reveal a decreasing thickness of strandline sediment associated with shorter aggregate length strandlines this relationship is most likely controlled by sediment starvation greater water level fluctuations and shallower water beaches near the head of the southern outlet spillway indicate that shoreline occupation at the lower campbell level was either very short lived or strandline development was hampered by shallow water the modern day sill elevation between the southern outlet spillway and the lake basin is found to be 3 km south of white rock minnesota at an elevation of 974 ft 297 m all but the campbell strandlines at the southern outlet are interpreted as the result of a regression driven by incision of the southern outlet spillway

the chronology climate and confusion of the moorhead phase of glacial lake agassiz new results from the ojata beach north dakota usa rapid drainage of glacial lake agassiz to the north atlantic ocean has been implicated as a triggering mechanism for the younger dryas yd cold event 13 11 6 ka cal a key component to this hypothesis is the interpretation that the ojata beach of lake agassiz in north dakota usa formed during a regression of the lake at the beginning of the yd this paper reviews the chronological data for the lowwater moorhead phase presents new radiocarbon and optically stimulated luminescence osl ages for the ojata beach and utilizes plant and insect macrofossils to reconstruct the paleoenvironmental conditions during the moorhead phase in eastern north dakota the integrated analysis of the geochronologic data emphasizes the need to distinguish between in situ and reworked plant macrofossils new ages obtained stratigraphically below the ojata beach sediments and reinterpreted chronologic data for the moorhead phase suggest that contrary to previous interpretations the ojata beach is a record of transgression of the lake in the later part of the yd and the oldest in situ minimum age for the moorhead phase is 10 47775 ka 14 c bp paleoenvironmental analysis indicates that a

a chronology for glacial lake agassiz shorelines along upham s namesake transect abstract four traditionally recognized strandline complexes in the southern basin of glacial lake agassiz are the herman norcross tintah and campbell whose names correspond to towns in west central minnesota that lie on a linear transect defined by the great northern railroad grade the active corridor for commerce at the time when warren upham was mapping and naming the shorelines of lake agassiz ca 1880 1895 because shorelines represent static water planes their extension around the lake margin establishes time synchronous lake levels transitions between shoreline positions represent significant water level fluctuations however geologic ages have never been obtained from sites near the namesake towns in the vicinity of the southern outlet here we report the first geologic ages for lake agassiz shorelines obtained at field sites along the namesake transect and evaluate the emerging chronology in light of other paleoclimate records our current work from 11 sampling sites has yielded 16 independent ages these results combined with a growing osl age data set for lake agassiz s southern basin provide robust age constraints for the herman norcross and campbell strandlines with averages and standard deviations of 14 1 0 3 ka 13 6 0 2 ka and 10 5 0 3 ka respectively

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

northward penetration of antarctic intermediate water off northwest africa abstract in this article historical and climatological datasets are used to investigate the seasonal northward propagation of antarctic intermediate waters aaiw along the eastern margin of the north atlantic subtropical gyre a cluster analysis for data north of 26 n shows the presence of a substantial number of hydrographic stations with aaiw characteristics that stretch northeast along the african slope this water mass extends north during fall as shown both through the comparison of actual and climatological data and by applying a mixing analysis to normal to shore seasonal sections at both 28 5 and 32 n the mixing analysis is further used with several fall cruises between 32 and 36 n and shows that at these latitudes the core of aaiw propagates along the 27 5 isoneutral with contributions that reach as much as 50 at 32 5 n an idealized sverdrup type model is used in combination with climatological hydrographic and wind data to examine what forces this eastern boundary propagation it is fo

isostatic rebound in the northwestern part of the lake agassiz basin isobase changes and overflow abstract based on new gps elevation data on the upper and lower campbell strandlines in the northwestern part of the glacial lake agassiz basin the trend of isobases representing differential glacio isostatic rebound in that region is shown to bend and assume a nearly west east orientation this differs from the northwest southeast orientation to the southeast of the study area which others had projected into the northwestern corner of the lake agassiz basin this means that there was more isostatic depression than previously thought north of 53 n the difference in slopes on reconstructed water planes of the upper and lower campbell beaches is less with these isobases which better reflects the short period of time between their formation it is likely that the change in orientation of isobases reflects the presence of a thick keewatin ice center to the north our revised west east isobase reconstruction indicates that when the lake was at the campbell beach levels 9900 9400 14c b p lake agassiz overflowed across the paleo divide at wycherley lake saskatchewan which controlled flow through the northwestern outlet of lake agassiz during part of its history overflow would not have occurred through the wycherley lake channels at this time using the old isobase projections

refining the glacial lake coverage of the southern laurentide ice margin using lidar dem based reconstructions the case of lake obedjiwan in south central quebec canada abstract the existence of former glacial lakes remains poorly documented in the remote regions of the canadian shield where the dense forest cover and poor access complicate classical mapping methods here we use a high resolution digital elevation model dem 1 m pixel based on lidar data to map quaternary deposits and landforms in the vicinity of the gouin reservoir in the laurentian highlands of quebec canada a total of 598 raised shorelines were identified providing new evidence for the presence of a large proglacial lake lake obedjiwan that formed in front of the northward retreating laurentide ice sheet margin during the last deglaciation a few kilometers east of the larger lake ojibway that covered extensive areas in northern ontario and quebec the elevation of shorelines outlines a tilted water plane that depicts the influence of the glacio isostatic adjustment across the basin with shorelines ranging from 409 m in the south to 439 m in the north the calculated uplift gradient of 0 78 m km indicates that the lake developed during the early stages of the deglaciation our reconstruction constrains the full areal extent and maximum elevation of the lake which covered an area of 1800 km2 and reached an elevation of 450 m it also indicates that lake obedjiwan developed independently from lake ojibway the lake surface elevation was controlled by an outlet located in the southeastern part of the basin where a topographic depression lying at an elevation of 390 m routed meltwater overflow southward through the saint maurice river and into the st lawrence river another important outlet is located in the northernmost part of the basin and ice retreat beyond this topographic depression 427 m caused the drawdown of the lake obedjiwan which drained westward into lake ojibway this discharge added around 19 km3 of meltwater an event that likely impacted the hydrological budget and sedimentology of lake ojibway the results suggest that other glacial lakes probably developed along the southern lis ice margin and that the approach developed in this study may contribute to the refinement of their areal coverage and improve paleogeographic reconstructions

quasi synoptic transport budgets and water mass transformation in the azores gibraltar strait region during summer 2009 abstract we describe the circulation patterns in the azores gibraltar strait region north eastern atlantic during the 2009 caibox cruise on the basis of hydrographic and direct current velocity measurements this study offers new data for a region where importation of central waters subpolar and subtropical modes of eastern north atlantic central water and exports of mediterranean water are strongly related to large scale dynamics in the north atlantic ocean azores current mediterranean water system the description is backed up quantitatively by the results of a box inverse model which was used to obtain absolute water mass transport values consistent with thermal wind equations and with conservation of volume salt and heat the contributions of water masses were determined in an extended optimum multiparameter analysis from a quasi synoptic point of view providing detail in addition to volume salt and heat transport the surface subsurface large scale current system in the region consists of the azores current 13 1 2 5 sverdrup sv 1 sv 10 6 m 3 s 1 the azores counter current 5 2 2 1 sv the portugal current 4 5 1 4 sv and the canary current 7 1 1 1 sv broadly speaking central waters are imported into the caibox region at a rate of 1 6 0 9 sv and mediterranean water is exported at a rate of 1 5 0 4 sv the downwelling of central waters west of gibraltar strait was quantified at 1 1 sv not all this volume participates in mw formation but 0 8 sv of entrained central waters of which 0 5 sv are from central waters of subpolar origin and 0 3 sv from subtropical central waters of the 4 9 sv of subtropical central waters advected by the azores current about 0 7 sv would reach the gulf of cadiz region either to take part in central water entrainment or to flow across the gibraltar strait as part of the atlantic inflow to the mediterranean sea

temporal variability of mass transport in the canary current abstract the variability of the canary current is investigated using bimonthly expandable bathythermograph sections from gran canaria island to the african coast between november 1996 and september 1998 the geostrophic transport of the easternmost branch of the canary current is estimated by integrating the thermal wind equation using the layer of neutral density 27 3 roughly 600 m depth as the layer of no motion the yearly average geostrophic transport of this branch of the canary current is 1 8 1 4 10 9 kg s 1 southward approximately half of the transport flows through the channel between the islands of gran canaria and fuerteventura and the other half through the channel between fuerteventura and the african coast the total southward geostrophic transport shows significant seasonal variability ranging from 1 2 0 3 10 9 kg s 1 in may to 2 6 0 1 10 9 kg s 1 in january although november is the only month with considerable differences in geostrophic transport between 1996 and 1997 there is seasonal northward transport in both channels during may in the gran canaria fuerteventura channel and during november in the fuerteventura african coast channel this seasonal pattern is probably linked to autumn weakening of upwelling in the canary islands area and the offshore diversion of this flow at cape ghir

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

meridional overturning transports at 7 5n and 24 5n in the atlantic ocean during 1992 93 and 2010 11 abstract transatlantic hydrographic sections along latitudes 7 5n and 24 5n have been repeated with about 20 years difference at the beginning of the 1990s and 2010s for each period an inverse model is applied to the closed box bound by both sections the model imposes mass conservation for individual layers defined by isoneutral surfaces and the whole water column using surface ekman transport and several transport constraints for specific ranges of longitudes and depths as a result the velocities at the reference layer for each station pair and the dianeutral velocities between layers are estimated and the horizontal velocity fields and the water heat and freshwater transports are calculated in particular we find that mass transport per stratum at 24 5n in 2011 is in good agreement with the transport estimates from the rapid watch array during both realizations the dianeutral velocities downwell from the upper north atlantic deep water unadw to the lower north atlantic deep water lnadw strata resulting in the merging of the two southward flowing strata at 24 5n into one deep southward moving stratum at 7 5n at 24 5n there is an increase in southward unadw transport between 1992 and 2011 compensated by a decrease of southward lnadw transport a descent in the upper limit of the antarctic bottom water aabw from 1992 to 2011 is also inferred the atlantic meridional overturning circulation amoc is larger in 1992 93 than in 2010 11 decreasing from 24 7 1 7 to 20 1 1 4 sv at 24 5n and from 29 2 1 7 to 16 9 1 5 sv at 7 5n much of this decrease arises because of the northward flow of antarctic intermediate water aaiw which was much more intense in 1992 93 than in 2010 11 as a consequence heat transport at 24 5n is not significantly different in 1992 1 4 0 1 pw and 2011 1 2 0 1 pw the estimation of heat transport at 7 5n strongly depends on the magnitude of the north brazil current over the american continental platform the freshwater flux into the box bounded by the two transoceanic sections decreases significantly from 1992 93 0 45 0 05 sv to 2010 11 0 36 0 3 sv meaning a decrease in net evaporation over this same area

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