dryline on 19 june 2002 during ihop part i airborne doppler and leandre ii analyses of the thin line structure and convection initiation the evolution and finescale structure of a dryline that initiated a line of thunderstorms is presented both the along line variability and mean vertical structure were examined using data collected by an airborne doppler radar and a water vapor differential absorption lidar dial the initiation of convection appeared to result from the diurnally induced easterly flow in the maritime air east of the dryline that typically develops late in the day this flow increased the low level convergence and allowed rising parcels of air to reach the level of free convection the along line variability was largely attributed to numerous misocyclones distorting the thin line of radar reflectivity by advecting dry moist air across the dryline south north of the misocyclone the misocyclones also influenced the location of the updrafts with most of the peak values positioned north of the circulations as a result these updrafts were fortuitously positioned in regions of high mixing ratio where the first convective cells initiated

large scale patterns associated with tropical cyclogenesis in the western pacific abstract five characteristic low level large scale dynamical patterns associated with tropical cyclogenesis in the western north pacific basin are examined along with their capacity to generate the type of mesoscale convective systems that precede genesis an 8 yr analysis set for the region is used to identify and create composites for the five characteristic patterns of monsoon shear line monsoon confluence region monsoon gyre easterly waves and rossby energy dispersion this brings out the common processes that contribute to tropical cyclogenesis within that pattern which are described in detail a 3 yr set of satellite data is then used to analyze the mesoscale convective system activity for all cases of genesis in that period and to stratify based on the above large scale patterns it is found that mesoscale convective systems develop in all cases of genesis except one seventy percent of cases developed mesoscale convective systems at more than one time during the genesis period and 44 of

boundary layer control on convective available potential energy implications for cumulus parameterization 1 convective available potential energy cape frequently regarded as an indicator of the potential intensity of deep convection is strongly controlled by the properties of the planetary boundary layer bl variations in cape observed during field experiments in midcontinent north america the tropical east atlantic and the tropical west pacific can be accounted for mostly by changes in the temperature and humidity in the bl the coupling between cape and the bl holds for both convective and nonconvective conditions the coupling under conditions of deep convection implies a constraint on the intensity of deep convection which can be used as a closure for cumulus parameterization this constraint requires equilibrium in the environment of the parcel used as a basis for calculating cape over many cases parcel environment equilibrium is observed to hold more robustly than equilibrium of cape itself when observational uncertainties are considered it is uncertain whether quasi equilibrium in which the rate of change of cape is substantially less than the rate at which mean advection and bl fluxes change cape holds at subdiurnal timescales in the eastern atlantic and the western pacific quasi equilibrium is a poor approximation at subdiurnal timescales in midcontinent north america at timescales approaching diurnal quasi equilibrium holds in all cases cumulus parameterizations based on quasi equilibrium may be limited in their ability to model diurnal cycles as a result cape fluctuations related to large subdiurnal variations in surface fluxes are much sharper than cape fluctuations related to changes in mean advection above the bl especially over land the strong bl control on cape indicates that deep convection does not equilibrate rapid high amplitude variations in cape originating there less

vertical velocity characteristics of deep convection over darwin australia abstract continuous vertical velocity measurements using a 50 mhz wind profiler located at darwin in northern australia during periods of active convection have been analyzed this dataset is dominated by continental type convection numerous examples of shallow deep and decaying convection were seen and it is shown that only the deep systems have substantial tilts to the draft structure the most intense updrafts occur above the freezing level but shallow convection also produces large amplitude vertical motions the strength of these updrafts in this dataset is very similar to other tropical oceanic data that observation is consistent with the idea that the magnitude of the updrafts is much less in the tropics than for intense midlatitude convection because the convective available potential energy is distributed over a much deeper layer in the tropics although more intense updrafts may be present at other tropical locations such as the tiwi islands north of darwin the size of the cores however

biogeochemistry of arsenic and antimony in the north pacific ocean the biogeochemical cycles of the metalloid elements arsenic and antimony were examined along a 15 000 km surface water transect and at 9 vertical profile stations in the western north pacific ocean as part of the 2002 ioc contaminant baseline survey results show that the speciation of dissolved arsenic as iii as v and methylated as was subtly controlled by the arsenate asv phosphate ratio an additional fraction of presumed organic arsenic previously reported in coastal waters was also present 15 of the total as in oceanic surface waters dissolved inorganic antimony displayed mildly scavenged behavior that was confirmed by correlations with aluminum but atmospheric inputs that may be anthropogenic in origin also affected its concentrations monomethyl antimony the predominant organic form of the element behaved almost conservatively throughout the water column radically changing the known biogeochemical cycle of antimony

the biogeochemistry of aluminum in the pacific ocean abstract vertical distributions and horizontal surface transects of dissolved and particulate al at several locations in the pacific ocean are presented here concentrations of dissolved al in the pacific range from 0 3 to 5 nmol kg in the surface waters from 0 1 to 1 nmol kg in mid depths and from 0 5 to 2 nmol kg in the deep waters from these data and published data from other regions it is evident that al has a unique oceanic chemistry relative to that of other metals external sources and rapid particle scavenging throughout the water column are the major controls on dissolved al distributions in the oceans vertical profiles generally exhibit a surface maximum a mid depth minimum and increasing concentrations toward the sediment water interface this suggests two sources of dissolved al one to the surface waters and one to the deep waters concentrations of dissolved al in surface waters are lowest within the eutrophic low salinity california current 0 3 1 nmol kg and increase westwardly into the subtropical gyre of the north pacific 5 nmol kg values in the south pacific gyre are fivefold lower these horizontal trends indicate that the primary source of dissolved al to the surface waters of the central pacific is from eolian input dissolved al supplied by rivers to the eastern north pacific appears to be rapidly scavenged in estuaries and or the highly productive coastal region the source of dissolved al to the deep waters is not known but could be due to a flux out of the sediments or a remineralization process suspended particulate al concentrations increase with depth at all stations and decrease with distance from the ocean boundary surface values range from 1 5 nmol kg near shore to 0 3 nmol kg in the central gyres of the pacific deep water concentrations range from 22 nmol kg near shore to 4 nmol kg in the north pacific central gyre and decrease to 1 3 nmol kg in the south pacific central gyre observed distributions indicate that suspended particulate al varies with the intensity of bottom sediment resuspension and the horizontal mixing of the resulting nepheloid layer out from ocean boundary regions particle residence times estimated are consistent with other reported values

dissolved iron in the southern ocean atlantic sector abstract we report a comprehensive dataset of dissolved iron fe comprising 482 values at 22 complete vertical profiles along a 1 latitudinal section at the zero meridian in addition a shorter high resolution 00 09 surface section of the southernmost part of the transect 66 00 69 35 s is presented within the upper surface mixed layer the concentrations of dissolved fe vary between 0 1 and 0 3 nm an inverse trend versus fluorescence suggests significant fe removal by plankton blooms vertical mixing and upwelling are the most important supply mechanisms of iron from deep waters to the upper surface mixed layer at lower latitude 42 s there is a distinct maximum of 0 6 0 7 nm in the 2000 3000 m depth range due to inflow of north atlantic deep water in one region 55 s elevated dissolved fe found in the surface mixed layer is ascribed to the recent deposition of aeolian dust originating from south america close to the antarctic continent there is an indication of fe supply in surface waters from icebergs in the deep waters there is a strong indication of a hydrothermal plume of dissolved fe and mn over the ridge in the bouvet region 52 56 s in the weddell gyre basin the dissolved fe in the deep water is 0 47 0 16 nm in the eastward flow at 56 62 s and is lower with a value of 0 34 0 14 nm in the westward flow at high 62 69 s latitude at the edge of the continental ice sheet on the prime meridian the continental margin of the antarctic continent appears to be lesser source of dissolved fe than in any other place in the world this is likely because it is unique in being overlain by the extending continental ice sheet that largely prevents biogeochemical cycling

formation and spreading of subtropical mode water in the north pacific a time averaged description of the formation and spreading of north pacific subtropical mode water npstmw is presented the formation of npstmw is studied using transpac expendable bathythermograph data the data are transformed into a stream coordinate system and averaged the coordinate system uses the position of the kuroshio front as its origin maps are presented of the temperature structure and mixed layer distribution in winter relative to the kuroshio front the formation of npstmw occurs in two separate stages cooling and thickening as water flows at the surface in the kuroshio in winter the water is cooled by the intense ocean atmosphere heat flux taking place in the area when water leaves the kuroshio to the south the thermocline underneath becomes deeper convection is able to penetrate deep into the water column and the heat flux acts more to thicken the surface mixed layer rather than reduce the temperature the area south of the kuroshio where relatively homogeneous waters are found is the source region for npstmw at the end of the winter the thick mixed layers are assumed to be covered over by a seasonal thermocline and become npstmw the levitus 1982 data are used to study the way in which npstmw is spread away from its source region by the subtropical circulation the distribution of potential vorticity pv on four npstmw isopycnals is studied with low pv used as a tracer for npstmw the pv reveals a pattern of differential spreading whereby npstmw formed in the western part of the source region is advected to the west after its formation npstmw formed farther east is advected more to the south or east after formation differential spreading allows npstmw to be found in a large part of the northwestern subtropical gyre well away from its source region the distribution of npstmw described by masuzawa 1969 with npstmw getting colder from west to east is explained as a combination of the distribution of npstmw at its source and the way it is spread after it is formed

numerical simulation of cyclone sidr using a cloud resolving model characteristics and formation process of an outer rainband abstractcyclone sidr one of the most devastating tropical cyclones that resulted in several thousand deaths and substantial damages developed in the north indian ocean and made landfall over the bangladesh coast on 15 november 2007 observation and simulation results show that sidr was embedded in a nonuniform environment and contained an intense outer rainband to the east of its center and a significant frontal band to the northwest a detailed study of the outer rainband is performed by numerical simulation the eastern band was a long quasi straight shape in the meridional direction that remained stationary relative to the cyclone center this band was composed of convective cells that developed southeast of the center within a synoptic scale convergence zone and propagated along the band toward the northeast quadrant the speed of the downwind propagating cells was greater than that of the cyclone which resulted in a convective cluster northeast of the center only the downwind portion of the band

mapping climatological seasonal variations of surface currents in the tropical atlantic using ship drifts the seasonal variability of current velocities in the tropical atlantic was studied by grouping ship drift velocity observations into 2 5 boxes and calculating monthly mean velocity values these values were used to calculate and map the annual mean velocity the seasonal variation about the mean the annual and semiannual harmonics and the first two empirical orthogonal functions eofs the seasonal variation is primarily zonal in the equatorial band and in the north equatorial countercurrent necc and primarily alongshore near the coast of south america maxima of seasonal variation of 23 cm s are centered in the necc near 6 n 42 5 w and in the gulf of guinea near 2 n 7 5 w most 80 of the variance in the necc and along the western boundary of the area studied has an annual period most of the variance along the equator in the mid atlantic has a semiannual period over the whole region 49 of the seasonal variance is explained by the annual harmonic and 69 is explained by a combination of the annual and semiannual harmonics the second eof contains 29 of the variance of the data set and shows a simultaneous speeding slowing of the major equatorial currents the south equatorial current sec the north brazil current the necc and the guinea current along their principal axes of variation with a concurrent slowing speeding of the guyana current and the brazil current the pattern of variation resembles a large equatorial gyre centered along 4 n that flows clockwise from may to september and counterclockwise most of the rest of the year the first eof accounts for 35 of the variance and shows a simultaneous speeding slowing of eastward velocity from 5 s to 10 n except in the western sec the western end of the north brazil current and the guinea current the out of phase fluctuations apparent in the western sec near the equator are explained by the slowing and reversal of the south equatorial current near 2 n 40 w between april and june this slowing of the sec is associated with the start up of the necc which accelerates eastward in may june and july and flows eastward across the atlantic from july through december the sec divides seasonally near the eastern tip of brazil where residual alongshore velocities are northward for half the year peaking during may and june and southward for the other half of the year a second division can be seen north of the amazon where the north brazil current continues up the coast into the guyana current during the first half of the year but partially retroflects into the necc during the last half of the year a fast eastward flow in the necc coincides with below average velocities in the guyana current and above average velocities in the western sections of the north brazil current and the sec north of the equator

silicon isotope fractionation during nutrient utilization in the north pacific the distribution of silicon in the north pacific is controlled by the utilization of silicic acid by diatoms a process that fractionates silicon si isotopic compositions silicon isotope variations are presented for six water column profiles from the surface mixed layer down to the deep waters of the north pacific ocean although the observed si isotopic variations display an apparently simple inverse relationship with dissolved nutrient concentrations in fact they reflect mixing of surface waters undergoing active si isotope fractionation and deep waters with more uniform concentrations and isotope compositions samples from the surface of the subtropical gyre have the lowest dissolved si concentrations and heaviest si isotope compositions of marine waters measured thus far fractionation in the surface waters follows a typical rayleigh type distillation curve for a closed surface water reservoir resulting from stratification of the surface layer in the subarctic region in contrast an open system prevails within the subtropical gyre where there is significant recycling of silicic acid in the upper water column and lateral transport of silicon within surface currents for deep waters the si isotope composition distinguishes between the northern north pacific deep water npdw and the southerly derived bottom water the relatively light si isotope compositions measured from waters within the subarctic gyre provides evidence for isolation of the nutrient pool in the north pacific

ventilation of the subtropical north pacific the shallow salinity minimum abstract the shallow salinity minimum of the subtropical north pacific is shown to be a feature of the ventilated wind driven circulation subduction of low salinity surface water in the northeastern subtropical gyre beneath higher salinity water to the south causes the salinity minimum variation of salinity along surface isopycnals causes variations in density and salinity at the minimum a model of ventilated flow is used to demonstrate how the shallow salinity minimum can arise the model is modified to account for nonzonal realistic winds it is also extended to examine the three dimensional structure of the western shadow zone the boundary between the subtropical and subpolar gyres is given by the zero of the zonal integral of ekman pumping the western shadow zone fills the subtropical gyre at the base of the ventilated layers and decreases in extent with decreasing density for parameters appropriate to the north pacific the eastern shadow zone is of very limited extent observations of salini

an overview of dissolved fe and mn distributions during the 2010 2011 u s geotraces north atlantic cruises geotraces ga03 abstract high resolution dissolved fe dfe and dissolved mn dmn distributions were obtained using a trace metal clean rosette during the geotraces ga03 zonal transect cruises usgt10 and usgt11 across the north atlantic ocean this manuscript provides a general overview of the dfe as well as dmn and dissolved al dal distributions that reveal several fe inputs at varying depths across the study region elevated dfe concentrations correlate with elevated dal concentrations in the surface waters of the subtropical gyre indicating a significant atmospheric source of fe in contrast there is no apparent significant dust source for mn in the subsurface waters dfe maxima are a result of the remineralization process as revealed by their correspondence with dissolved oxygen minima within the oxygen minimum the ratio of dfe to apparent oxygen utilization aou is lower than would be expected from the measured fe content of surface water phytoplankton suggesting that a significant amount of dfe that is remineralized at depth 63 90 is subsequently scavenged from the water column the rate of remineralization which is based on the slope of dfe aou plot is similar across a wide area of the north atlantic in addition to the remineralization process sedimentary inputs are apparent from elevated dmn signals in the eastern basin particularly near the african coast in the western basin sedimentary input is also occurring along the advective flow path of the upper labrador sea water ulsw as ulsw transits along the north american continental shelf region the largest dfe anomaly 68 nm which also corresponds to a dmn anomaly up to 33 nm is seen in the neutrally buoyant hydrothermal plume sampled over the mid atlantic ridge and that signal is visible for 500 km to the west of the ridge

aluminium as a tracer of the deep outflow from the mediterranean dissolved aluminium has been determined in sea water samples from the southwestern alboran sea and the gulf of cadiz partial dissolution of eolian dust is responsible for the elevated levels of dissolved al that were found in both the western mediterranean deep water wmdw 111 5 nm and levantine intermediate water liw 86 2 nm masses in the alboran sea the al concentration in the outflowing plume of mediterranean water sampled in the gulf of cadiz is also elevated 72 nm these enhanced signals and the differences between them are used in a three water mass system to calculate a maximum 10 contribution of western mediterranean deep water to the outflow plume considerably less than has been previously supposed while the synoptic nature of this study and the possibility of involvement of other water masses in the outflow plume leave scope to increase the participation of wmdw in the outflow plume these measurements indicate the potential of a nontransient tracer in elucidating the component parts of complex flow systems copyright american geophysical union 1988

dissolved and particulate aluminum in the columbia river and coastal waters of oregon and washington behavior in near field and far field plumes the distribution of dissolved soluble and total and particulate leachable and total aluminum was examined in the columbia river and estuary in near field and far field river plumes and in adjacent coastal waters of washington and oregon during the river influence on shelf ecosystems rise cruise of may june 2006 dissolved and particulate aluminum al concentrations were significantly greater in the river than in the coastal waters that mixed to form the plume dissolved al concentrations in the columbia river w80 nm were low relative to other major rivers leachable and total particulate al concentrations within the river reached concentrations greater than 1000 nm and 18 000 nm respectively dissolved al within the columbia river estuary showed a significant removal w60 at salinities between 0 and 10 with salt induced flocculation of colloidal al complexes and enhanced particle scavenging being probable explanations for aluminum removal dissolved and particulate al concentrations were significantly greater in near field plumes relative to surrounding coastal waters as the plume advected from near field to far field away from the river mouth dilution of the plume with lower dissolved al surface waters as well as particle scavenging along the flow path appeared to be controlling dissolved al distributions particle settling as well as dilution with lower particle load waters led to observed decreases in particulate al as the plume moved from near field to far field however the percent leachable particulate aluminum in both near field and far field plumes was remarkably constant at w7 dissolved and particulate al in a far field plume over 100 km southwest of the columbia river mouth were over an order of magnitude greater than surrounding waters illustrating the importance of the columbia river plume as a mechanism for transporting al offshore aluminum could be used to trace the input of biologically required elements such as iron into waters off the shelf

fluxes and distribution of dissolved iron in the eastern sub tropical north atlantic ocean aeolian dust transport from the saharan sahel desert regions is considered the dominant external input of iron fe to the surface waters of the eastern sub tropical north atlantic ocean to test this hypothesis we investigated the sources of dissolved fe dfe and quantified dfe fluxes to the surface ocean in this region in winter 2008 surface water dfe concentrations varied between 1 5 nm correlated positively with apparent oxygen utilization aou and showed the importance of organic matter remineralization as an dfe source as a consequence vertical diffusive mixing formed an important fe flux to the surface ocean in this region even surpassing that of a major dust event

western pacific coastal sources of iron manganese and aluminum to the equatorial undercurrent 1 we present results from the first zonal transect of iron aluminum and manganese conducted from the western source region of the equatorial undercurrent euc to the central equatorial pacific trace metals were elevated along the slope of papua new guinea and within the new guinea coastal undercurrent ngcu which is the primary southern hemisphere entry path of water to the euc subsurface maxima in total acid soluble iron aluminum and manganese were evident in the euc these maxima were generally greatest in the western equatorial pacific and decreased in magnitude eastward maxima in iron and aluminum persisted to 140 w maxima in manganese extended to 175 w iron and manganese maxima were deeper 25 75 m than aluminum maxima and located in the lower euc which undergoes less interior ocean mixing than shallower waters the depth of the aluminum subsurface maxima correlated strongly r 0 88 with the depth of the euc velocity maximum surface waters were enriched in aluminum and manganese offshore of papua new guinea surface metal concentrations decreased eastward throughout the western warm pool up to the longitude 180 w of the salinity front detrital sediment input from either direct riverine input or sediment resuspension appeared to be the primary mechanism of supplying metals to the ngcu we estimated eastward fluxes of metals in the euc and found greatest fluxes in the western equatorial pacific between 160 e and 165 e except for aluminum fluxes of aluminum and to a lesser extent manganese increased concurrently with water volume transport in the central equatorial pacific iron transport in the euc remained constant east of the dateline apparently due to the combined effects of dilution by meridional entrainment and scavenging iron was mobilized in a highly active western boundary current region and transported eastward in the lower euc

glacial interglacial co2 change the iron hypothesis several explanations for the 200 to 280 ppm glacial interglacial change in atmospheric co2 concentrations deal with variations in southern ocean phytoplankton productivity and the related use or nonuse of major plant nutrients an hypothesis is presented herein in which arguments are made that new productivity in today s southern ocean 7 4 1013g yr 1 is limited by iron deficiency and hence the phytoplankton are unable to take advantage of the excess surface nitrate phosphate that if used could result in total southern ocean new production of 2 3 1015 g c yr 1 as a consequence of fe limited new productivity holocene interglacial co2 levels preindustrial are as high as they were during the last interglacial 280 ppm in contrast atmospheric dust fe supplies were 50 times higher during the last glacial maximum lgm because of this fe enrichment phytoplankton growth may have been greatly enhanced larger amounts of upwelled nutrients may have been used and the resulting stimulation of new productivity may have contributed to the lgm drawdown of atmospheric co2 to levels of less than 200 ppm background information and arguments in support of this hypothesis are presented

thermocline ventilation of anthropogenic lead in the western north atlantic massive industrial aerosol emissions from north america have over the past century overwhelmed the natural distribution of lead in the western north atlantic thermocline the resultant features to 2000 m depth have been mapped near bermuda for the year 1984 since earlier reported measurements have largely been rejected on grounds of sample contamination the twentieth century evolution of anthropogenic pb in the oceanic water column is unknown coupling of the 1984 water column pb distribution to historical records in reef building corals and tracer derived thermocline ventilation rates jenkins 1980 has permitted a model reconstruction of pb penetration into the sargasso sea the model is constrained by three distinct pb distributions pb concentration stable pb isotopes and 210pb with adjustable scavenging and regeneration parameters to account for nonconservative behavior the results of the model substantiate the importance of lateral isopycnal ventilation while pointing out the necessity of dissolved particulate exchange i e scavenging of the order of 70 years in the deep thermocline minimum regeneration of 10 particulate pb between surface and 1700 m residual discrepancies between model isotopic predictions and observations below 800 m are likely due to a combination of the following factors 1 presence of nonradiogenic background pb in intermediate depth waters 2 geographic variability in north american industrial source signatures 3 mediterranean pb inputs of european origin and 4 along isopycnal mixing effects

iron deficiency limits phytoplankton growth in antarctic waters enrichment experiments were performed in the ross sea to test the hypothesis that iron deficiency is responsible for the phytoplankton s failure to use up the luxuriant major nutrient supplies found in these and all other offshore antarctic ocean waters nitrate uptake rates in the controls without added trace elements ranged from 0 58 to 1 22 mol kg 1 d 1 the addition of 1 to 5 nmol of unchelated fe per liter resulted in rates that were 2 to 10 times higher 2 54 to 6 00 mol no3 kg 1 d 1 rates in bottles with 2 nmol mn added were identical to those in the controls 0 57 to 1 04 mol no3 kg 1 d 1 total decreases in no3 were balanced by increases in particulate organic n these results suggest that fe deficiency is the primary reason that the present day southern ocean biological pump is shut off in contrast iron was 50 times more abundant during the last glacial maximum greater fe availability may have stimulated the biological pump and contributed to the ice age drawdown of atmospheric c02 these results also imply that large scale southern ocean fe fertilization is feasible at least in terms of the total amounts of fe required i e 100 000 to 500 000 tons yr 1

an integrated view of the 1987 australian monsoon and its mesoscale convective systems i horizontal structure this observational study is organized around three issues the forcing of the monsoon flow by embedded deep convection the thermodynamic conditions that support the convection and the structures of the mesoscale convective systems mcss that constitute much of the deep convection the monsoon convective cloudiness occurred predominantly offshore over the earth s warmest waters week long periods of widespread deep convection caused cycles of monsoon spin up culminating in tropical cyclone formation momentum transports by the convection also created smaller scale vortex pairs in the upper troposphere sounding data suggest that the convection was modulated by low level processes not by large scale deep forced ascent triggering by mesoscale boundary layer cold pool boundaries and coastlines determined specifically where convection occurred while several positive feedbacks acted to keep regional thermodynamic conditions favourable hence monsoon convection once initiated persisted as self exciting superclusters composed at any instant of many distinct mcss the observed mcss all contained areas of deep convection and stratiform precipitation areas stratiform precipitation usually evolved in place from convective cells although precipitation also occasionally fell from overhanging anvils created by upper level shear the mcss within similar synoptic wind environments tended to have similar mesoscale structures this fact reflects the effects illustrated herein of environmental winds upon the relative motions of cold pools which trigger new convective cells and stratiform precipitation areas which evolve from old convective cells

spring warming of the eastern arabian sea and bay of bengal from buoy data observations from moored buoys during spring of 1998 2000 suggest that the warming of the mixed layer similar to20 m deep of the north indian ocean warm pool is a response to net surface heat flux q net similar to100 w m 2 minus penetrative solar radiation q pen similar to45 w m 2 a residual cooling due to vertical mixing and advection is indirectly estimated to be about 25 w m 2 the rate of warming due to typical values of q net minus q pen is not very sensitive to the depth of the mixed layer if it lies between 10 m and 30 m

impact of atmospheric deposition on the contrasting iron biogeochemistry of the north and south atlantic ocean dissolved iron dfe distributions and atmospheric and vertical subduction fluxes of dfe were determined in the upper water column for two meridional transects of the atlantic ocean the data demonstrate the disparity between the iron biogeochemistry of the north and south atlantic ocean and show well defined gradients of size fractionated iron species in surface waters between geographic provinces the highest dfe and lowest mixed layer residence times 0 4 2 5 years were found in the northern tropical and subtropical regions in contrast the south atlantic gyre had lower dfe concentrations 5 years presumably due to lower atmospheric inputs and more efficient biological recycling of iron in this region vertical input fluxes of dfe to surface waters ranged from 20 to 170 nmol m 2 d 1 in the north atlantic and tropical provinces whereas average fluxes of 6 13 nmol m 2 d 1 were estimated for the south atlantic our estimates showed that the variable dfe distribution over the surface atlantic 50 of total vertical fe flux to surface waters rather than upwelling or vertical mixing this demonstrates the strength of the connection between land derived atmospheric fe fluxes and the biological cycling of carbon and nitrogen in the atlantic ocean

role of synoptic scale forcing in cyclogenesis over the bay of bengal the cyclone frequency distribution over the bay of bengal during 1990 2009 was distinctly bimodal with a primary post monsoon peak and a secondary pre monsoon peak despite the very high convective available potential energy cape during the pre monsoon the location of the monsoon trough over the bay is a primary factor in tropical cyclogenesis because the trough was in the northernmost bay during the pre monsoon season cyclogenesis was inactive in the southern bay where a strong southwesterly wind shear was found in this season moreover a hot dry air mass extending vertically from 950 to 600 hpa was advected from northwestern india toward the bay moist warm southwesterly winds penetrating below the deep dry air mass caused a prominent dryline to form aloft on the northwestern side of the bay the synoptic scale hot dry air forcing to the bay suppressed the active convection necessary for cyclogenesis the strength of the stable environmental layer represented by convective inhibition cin was extremely large and acted as a cap over the northern and northwestern bay conversely during the post monsoon there were no horizontal temperature or moisture gradients and cape and cin were fairly modest the entire bay was covered by a very deep moist layer from the surface to 700 hpa transported from the east the monsoon trough position and the environmental cin in combination can explain the lower frequency of cyclogenesis during the pre monsoon compared with the post monsoon season

eolian dust input to the subarctic north pacific eolian dust is a significant source of iron and other nutrients that are essential for the health of marine ecosystems and potentially a controlling factor of the high nutrient low chlorophyll status of the subarctic north pacific we map the spatial distribution of dust input using three different geochemical tracers of eolian dust 4he 232th and rare earth elements in combination with grain size distribution data from a set of core top sediments covering the entire subarctic north pacific using the suite of geochemical proxies to fingerprint different lithogenic components we deconvolve eolian dust input from other lithogenic inputs such as volcanic ash ice rafted debris riverine and hemipelagic input while the open ocean sites far away from the volcanic arcs are dominantly composed of pure eolian dust lithogenic components other than eolian dust play a more crucial role along the arcs in sites dominated by dust eolian dust input appears to be characterized by a nearly uniform grain size mode at 4 m applying the 230th normalization technique our proxies yield a consistent pattern of uniform dust fluxes of 1 2 g m2 yr across the subarctic north pacific elevated eolian dust fluxes of 2 4 g m2 yr characterize the westernmost region off japan and the southern kurile islands south of 45 n and west of 165 e along the main pathway of the westerly winds the core top based dust flux reconstruction is consistent with recent estimates based on dissolved thorium isotope concentrations in seawater from the subarctic north pacific the dust flux pattern compares well with state of the art dust model predictions in the western and central subarctic north pacific but we find that dust fluxes are higher than modeled fluxes by 0 5 1 g m2 yr in the northwest northeast and eastern subarctic north pacific our results provide an important benchmark for biogeochemical models and a robust approach for downcore studies testing dust induced iron fertilization of past changes in biological productivity in the subarctic north pacific

distribution of aluminium in waters of the north east atlantic 25 n to 35 n abstract dissolved al concentrations from the ne atlantic between 25 n and 35 n off the coast of nw africa range from 16 nm to 32 nm in a well mixed surface layer extending to 150 m depth increasing towards the maximum of the saharan dust plume mediterranean outflow water is detected as a high al anomaly corresponding to the salinity signal of the mediterranean water other than in surface and mediterranean waters al concentrations are invariant with depth but increase from 6 nm to 11 nm towards the continental margin the magnitude of the dissolved al signal in the surface layer is compatible with dissolution of al from the highest of present estimates of dust input to this area comparison with data from other areas indicates that al cannot be cycled through the oceans in parallel to silica as has been previously suggested

high resolution al and fe data from the atlantic ocean clivar co2 repeat hydrography a16n transect extensive linkages between atmospheric dust and upper ocean geochemistry 1 trace element sampling and shipboard flow injection analysis during the june august 2003 climate variability and predictability clivar co2 repeat hydrography a16n transect has produced a high resolution section of dissolved fe and al in the upper 1000 m of the atlantic ocean between 62 n and 5 s using the surface water dissolved al and the model of aluminum for dust calculation in oceanic waters madcow model we have calculated the deposition of mineral dust to the surface ocean along this transect and compare that to dissolved fe concentrations the lowest mean mineral dust depositions of 0 2 g m 2 a 1 are found to the north of 51 n a region which also exhibits characteristics of biological fe limitation through its low dissolved surface water fe 0 1 nm and residual macronutrients e g nitrate 2 m to the south of this region mean dust deposition increases by an order of magnitude reaching 3 g m 2 a 1 at 10 n underneath the saharan dust outflow surface water fe values also increase along this section to 1 nm distinct minima in fe concentrations at the depth of the chlorophyll maximum in the vertical profiles between 18 and 4 n illuminate the role that active biological uptake plays in fe cycling an extensive subsurface zone of enhanced dissolved fe concentrations 1 5 nm underlying this region is a result of the biological vertical transport and remineralization of the surface water fe and is coincident with the intermediate nutrient maximum and oxygen minimum of this region elevated concentrations of dissolved al in subsurface waters seen between 30 and 20 n coincide with the domain of the subtropical mode waters stmw which result from the sinking of surface waters in late winter in regions imprinted by dust deposition the magnitude of the al enrichment observed in this water mass implies that the predominant source to the stmw is from the more dust impacted western atlantic with only limited contributions from the stmw formation region near madeira a deeper subsurface al enrichment 30 45 n is associated with the outflow from the mediterranean another heavily dust impacted basin these two regions of al enrichment show the widespread geochemical connection between atmospheric transport processes and the north atlantic and underscore its susceptibility to imprinting by atmospherically borne materials natural as well as anthropogenic

combined oxygen and silicon isotope analysis of diatom silica from a deglacial subarctic pacific record we present an sif4 separation line coupled to a laser fluorination system which allows for an efficient combined silica d18o and d30si analysis 50 min per sample the required sample weight of 1 5 2 0mg allows for high resolution isotope studies on biogenic opal besides analytical tests the new instrumentation set up was used to analyse two marine diatom fractions 63 mm 10 20mm with different diatom species compositions extracted from a bolling allerod holocene core section md01 2416 north west nw pacific to evaluate the palaeoceanographic significance of the diatom isotopic signals and to address isotopic effects related to contamination and species related isotope effects vital and environmental effects while d30si offsets between the two fractions were not discernible supporting the absence of species related silicon isotope effects systematic offsets occur between the d18o records although small these offsets point to species related isotope effects as bias by contamination can be discarded the new records strengthen the palaeoceanographic history during the last deglaciation in the nw pacific characterized by a sequence of events with varying surface water structure and biological productivity with such palaeoceanographic evolution it becomes unlikely that the observed systematic d18o offsets signal seasonal temperature variability this calls for reconsideration of vital effects generally excluded to affect d18o measurements

aluminium in the northwest atlantic abstract a series of profiles between woods hole and bermuda has been measured on board ship for al the extrema in the upper waters can be explained by the accumulation of aeolian inputs in the thin summer mixed layer the depletion of the underlying winter water by scavenging during the spring bloom and the enrichment of the subtropical mode 18 c water by aeolian accumulation during winter and local convection before the spring bloom the pronounced minimum at mid depth is associated with the antarctic intermediate water and the underlying labrador sea med water complex presumably the aaiw and the med water are depleted by the ageing effect on this short residence time element during their transit to the area the lsw is formed from surface waters containing a large component of arctic waters extremely depleted in al advected south in the east greenland current the linear increase to the bottom is caused by mixing of enriched lower north atlantic deep water with the depleted bottom water and lsw cores the enrichment in the deep water appears to be produced by the entrainment of high al waters from the north european shelf by the gyre in the norwegian greenland sea and its injection into the denmark straits overflow waters in a manner recently described for the radiocaesium releases from the windscale reprocessing plant on the irish sea an additional contribution probably comes from the shelf north of iceland

dissolved fe and al in the upper 1000 m of the eastern indian ocean a high resolution transect along 95 e from the antarctic margin to the bay of bengal a high resolution section of dissolved iron dfe and aluminum dal was obtained along 95 e in the upper 1000 m of the eastern indian ocean from the antarctic margin 66 s to the bay of bengal 18 n during the u s climate variability and predictability clivar co2 repeat hydrography i08s and i09n sections february april 2007 in the southern ocean low concentrations of dal

dust deposition to the surface waters of the western and central north pacific inferred from surface water dissolved aluminum concentrations 1 dissolved al was determined on similar to 3500 surface water samples collected in the nw pacific during the 2002 intergovernmental oceanographic commission ioc contaminant baseline survey in addition dissolved al was determined on samples collected at 9 vertical stations occupied along the cruise track surface water al distributions when converted to annual mineral dust deposition measures and brown 1996 imply extremely low depositions mean values 0 3 g m 2 yr 1 to surface waters of the subarctic gyre despite the atmospheric transport of large amounts of mineral dust across this region from the desert regions of china the calculated deposition values are also much lower than the 1 10 g m 2 yr 1 predicted for this region by the gesamp model duce et al 1991 the lowest mineral dust depositions correspond to the high nutrient low chlorophyll hnlc region of the nw pacific which implies that the biogeochemical status of this region is the result of low atmospheric micronutrient input similar to other hnlc regions in the subtropical gyre the al derived dust deposition mean values 0 1 0 6 g m 2 yr 1 agrees well with the 1 g m 2 yr 1 predictions of the gesamp model enriched concentrations of dissolved al in the coastal waters near kauai from fluvial sources indicate the potential role of remote high islands in adding reactive trace elements to the nearby surface waters in the vertical profiles elevated dissolved al concentrations 4 8 nm were found to correspond to the potential density of the western pacific subtropical mode waters which form in the recirculation zone of the kuroshio

mesoscale convection and bimodal cyclogenesis over the bay of bengal abstractmesoscale convective systems mcss are an essential component of cyclogenesis and their structure and characteristics determine the intensity and severity of associated cyclones case studies were performed by simulating tropical cyclones that formed during the pre and postmonsoon periods in 2007 and 2010 over the bay of bengal bob the pre post monsoon environment was characterized by the coupling of northwesterly southwesterly wind to the early advance southwesterly northeasterly monsoonal wind in the bob the surges of low level warm southwesterlies with clockwise rotating vertical shear in the premonsoon period and moderately cool northeasterlies with anticlockwise rotating vertical shear in the postmonsoon period transported moisture and triggered mcss within preexisting disturbances near the monsoon trough over the bob mature mcss associated with bimodal cyclone formations were quasi linear and they featured leading edge deep convection and a trailing stratiform precipitation r

temporal variability of lead in the western north atlantic consumption of alkyl leaded gasoline has decreased considerably in the united states over the last 15 years in order to evaluate the chemical response of the ocean to decreased atmospheric deposition of anthropogenic lead new 210pb and stable pb data have been obtained near bermuda june 1983 to december 1984 concentrations of these tracers in the mixed layer are highly variable during the period of observations 25 from june through september soluble eolian deposits accumulate in the shallow mixed layer because mixing and productivity are inhibited by the seasonal thermocline in the fall these enriched surface waters mix with upper thermocline waters and surface pb concentrations decrease in the winter storms from the east coast of north america cause local episodes of high pb and 210pb input into the ocean surface the resulting areally limited high pb concentrations are dispersed within less than 2 weeks by vertical and horizontal mixing pb 210pb ratios in surface waters are almost invariant over this period averaging 669 pmol dpm ranging from 564 to 718 pmol dpm surface pb 210pb appears to have declined by a factor of 2 since 1979 similar to the 2 6 fold decrease in u s leaded gasoline consumption during this period a substantial fraction on the order of 10 of gasoline pb is transported into the ocean pb concentrations in the upper thermocline may have declined by about 15 from 1979 to 1984 the helium tritium thermocline ventilation model of jenkins 1980 coupled with boundary conditions appropriate for pb and 210pb shows that the supply of pb and 210pb to the thermocline is dominated by lateral isopycnal ventilation the shape of the vertical profile is dominated by this physical ventilation near surface biological removal processes in situ scavenging and for stable lead time dependent input vertical transport by particles is responsible for minimal transport of dissolved lead into the upper ocean similar processes are likely to account for the plutonium maximum in the thermocline of the north pacific observations of pb and other reactive species in winter surface outcrops of thermocline isopycnals would provide valuable constraints on chemical processes within the thermocline

dissolved iron in the tropical and subtropical atlantic ocean 1 detailed depth profiles and surface transects of dissolved iron dfe defined by 0 4 m filtration were investigated on three cruises in the subtropical and tropical atlantic ocean where dust deposition varied by 3 orders of magnitude surface dfe and dissolved mn concentrations reflected dust deposition trends but are not proportional to the estimated inputs using estimates of the atmospheric flux of dfe surface dfe residence times were calculated to be on the order of 1 to 5 months deepwater dfe concentrations varied with water masses depending on their source age and transit pathways at a site located on the edge of the equatorial system 10 n 45 w high dfe 1 nmol kg was associated with an oxygen minimum zone at depths of 130 to 1100 m dfe concentrations in north atlantic deep water nadw decreased by 30 from sites in the north atlantic to a site in the south atlantic 24 5 s 37 w and dfe was lower in the antarctic derived water masses 0 4 nmol kg than in nadw at the south atlantic site an estimate of deepwater scavenging residence time for dfe was 270 140 years based on decreasing dfe along the nadw flow path

distribution of be al se and bi in the surface waters of the western north atlantic and caribbean abstract the mixed layer distributions of several trace elements have been determined along a detailed transect from rhode island to the panama canal when taken together with a new and existing profile data from the north atlantic and north pacific some general inferences emerge as to the processes controlling their concentrations in the surface waters the large enrichments in be observed in the upper waters of the north atlantic relative to the north pacific appear to be sustained mainly by fluvial inputs those of se are derived from atmospheric transport aluminium and bi also appear to have an aeolian source in the sargasso sea however in the tropical eastern pacific the al input may be fluvial on this cruise be al and the se species were analyzed on board ship within a few hours of collection the demonstration that this is feasible opens up the prospect of the application of large scale chemical hydrography to the study of the processes controlling the distribution and water column variability of trace elements in the oceans

aluminium in the south atlantic steady state distribution of a short residence time element the aluminium concentrations of water samples from 18 hydrographic profiles and 35 surface samples in the south atlantic were determined on board ship during leg iii of the south atlantic ventilation experiment save the observed surface water distributions range 0 5 to 57 nm are though to arise from the partial dissolution of eolian transported continental dusts coupled with limited lateral transport by prevailing surface currents in the deep water the greatest enrichments are observed coincident with the depth of the lower north atlantic deep water the similarity between the al si ratios in this water mass in both the south and north atlantic is taken as evidence that no significant al additions are being made to this water during its transit the lower al concentrations observed in the water masses of antarctic origin approximately 3 nm are consistent with their formation in areas of limited dust input the somewhat higher values observed in the antarctic bottom water suggest that the shelf component of this water mass may have elevated al concentrations

response of lead cycling in the surface sargasso sea to changes in tropospheric input lead and its stable isotopes have been analyzed in surface water samples 0 600 m and trapped particles collected at the bermuda atlantic time series station u s joint global ocean flux study in april and november 1989 these results are compared with wet atmospheric lead deposition as determined from precipitation continuously collected in bermuda since august 1988 as pan of the atmosphere ocean chemistry experiment program despite an expected seasonal variability lead concentrations in surface waters have clearly decreased by 30 to 40 since 1979 in response to a corresponding decline by a factor of 5 to 8 of the tropospheric deposition this result is corroborated by stable lead isotope measurements with 206pb 207pb ratios which are significantly less radiogenic 1 18 1 20 in the first 500 m of the 1989 profile than those measured in 1984 1 20 1 21 this isotopic shift reflects changes of lead ore supply in the united states as well as a relative increase of the eurafrican contribution to lead input in the northwest atlantic that is likely due to the reduction of lead emissions from gasoline consumption in north america this fast response of lead to interannual variations of the tropospheric input into surface waters is related to its efficient bioreactivity as demonstrated with a sediment trap deployed at 150 m in april 1989 sediment trap results show the rapid penetration of lead into the first 200 m associated with large particles during a period of high plankton activity retrospective isentropic air mass trajectories in three dimensions coupled with the precipitation events collected in bermuda in 1988 1989 show that 30 to 40 of the annual lead deposition originates from the trade easterly meteorological regime this input is clearly evidenced with lead isotopic signals observed in surface waters 0 100 m in april and november 1989 we show that lead accumulated in the seasonal mixed layer 0 50 m reflects this atmospheric input taking into account the isotopic signal measured in this mixed layer 1 178 0 001 as well as the respective contribution of the temperate westerlies and trade easterlies to atmospheric lead deposition to the sargasso sea we calculate that the isotopic signature from the eurafrican regions is 1 155 0 004 based on these results we calculate that the actual 206pb 207pb average ratio in surface waters of the sargasso sea is 1 188 0 004

neodymium isotopic composition and concentration in the western north atlantic ocean results from the geotraces ga02 section the neodymium nd isotopic composition of seawater is commonly used as a proxy to study past changes in the thermohaline circulation the modern database for such reconstructions is however poor and the understanding of the underlying processes is incomplete here we present new observational data for nd isotopes and concentrations from twelve seawater depth profiles which follow the flow path of north atlantic deep water nadw from its formation region in the north atlantic to the northern equatorial atlantic samples were collected during two cruises constituting the northern part of the dutch geotraces transect ga02 in 2010 the results show that the different water masses in the subpolar north atlantic ocean which ultimately constitute nadw have the following nd isotope characteristics upper labrador sea water ulsw end 14 2 0 3 labrador sea water lsw end 13 7 0 9 northeast atlantic deep water neadw end 12 5 0 6 northwest atlantic bottom water nwabw end 11 8 1 4 in the subtropics where these source water masses have mixed to form nadw which is exported to the global ocean upper nadw is characterised by end values of 13 2 1 0 2sd and lower nadw exhibits values of end 12 4 0 4 2sd while both signatures overlap within error the signature for lower nadw is significantly more radiogenic than the traditionally used value for nadw end 13 5 due to the dominance of source waters from the nordic seas nwabw and neadw comparison between the concentration profiles and the corresponding nd isotope profiles with other water mass properties such as salinity silicate concentrations neutral densities and chlorofluorocarbon cfc concentration provides novel insights into the geochemical cycle of nd and reveals that different processes are necessary to account for the observed nd characteristics in the subpolar and subtropical gyres and throughout the vertical water column while our data set provides additional insights into the contribution of boundary exchange in areas of sediment resuspension the results for open ocean seawater demonstrate at an unprecedented level the suitability of nd isotopes to trace modern water masses in the strongly advecting western atlantic ocean

iron from melting glaciers fuels the phytoplankton blooms in amundsen sea southern ocean iron biogeochemistry dissolved iron dfe and total dissolvable fe tdfe were measured in january february 2009 in pine island bay as well as in the pine island and amundsen polynyas amundsen sea southern ocean iron fe has been shown to be a limiting nutrient for phytoplankton growth even in the productive continental shelves surrounding the antarctic continent however the polynyas of the amundsen sea harbor the highest concentrations of phytoplankton anywhere in antarctica here we present data showing the likely sources of fe that enable such a productive and long lasting phytoplankton bloom circumpolar deep water cdw flows over the bottom of the shelf into the pine island bay where dfe and tdfe were observed to increase from 0 2 to 0 4 nm dfe and from 0 3 4 0 to 7 14 nm tdfe respectively at the southern end of pine island bay the cdw upwelled under the pine island glacier bringing nutrients including fe to the surface and melting the base of the glacier concentrations of dfe in waters near the pine island glacier and the more westward lying crosson dotson and getz ice shelves varied between 0 40 and 1 31 nm depending on the relative magnitude of upwelling turbulent mixing and melting these values represent maximum concentrations since associated ligands which

double seismic zone beneath the mariana island arc a double zone of seismicity has been found beneath the northern marianas in the depth range 80 120 km the benioff zone undergoes a pronounced bend with radius of curvature about 200 km before straightening and descending nearly vertically to a depth of more than 600 km thus this is an ideal area in which to search for evidence of stresses associated with unbending of the subducted oceanic plate we relocated all teleseismic events from 1963 through 1975 by using a regional composite master event technique which significantly decreased the scatter of the hypocenters the three events of the lower seismic zone are separated from the upper zone by about 30 35 km the true thickness of the upper seismic zone is probably 20 km or less the limited focal mechanism data indicate that there is downdip tension in the lower zone and downdip compression in the upper zone the seismicity patterns could be generated either by thermal stresses or by unbending a plate which was originally deformed anelastically we show that an elastic perfectly plastic model of the rheology of the plate can account for the separation of the two seismic zones the focal mechanisms and the greater activity of the upper seismic zone

dust deposition in the eastern indian ocean the ocean perspective from antarctica to the bay of bengal atmospheric deposition is an important but still poorly constrained source of trace micronutrients to the open ocean because of the dearth of in situ measurements of total deposition i e wet dry deposition in remote regions in this work we discuss the upper ocean distribution of dissolved fe and al in the eastern indian ocean along a 95 e meridional transect spanning the antarctic margin to the bay of bengal we use the mixed layer concentration of dissolved al in conjunction with empirical data in a simple steady state model to produce 75 estimates of total dust deposition that we compare with historical observations and atmospheric model estimates except in the northern bay of bengal where the ganges brahmaputra river plume contributes to the inventory of dissolved al the surface distribution of dissolved al along 95 e is remarkably consistent with the large scale gradients in mineral dust deposition and multiple source regions impacting the eastern indian ocean the lowest total dust deposition fluxes are calculated for the southern ocean 66 60 mg m 2 yr 1 and the highest for the northern end of the south indian subtropical gyre up to 940 mg m 2 yr 1 at 18 s and in the southern bay of bengal 2500 570 mg m 2 yr 1 our total deposition fluxes which have an uncertainty on the order of a factor of 3 5 are comparable with the composite atmospheric model data of mahowald et al 2005 except in the south indian subtropical gyre where models may underestimate total deposition using available measurements of the solubility of fe in aerosols we confirm that dust deposition is a minor source of dissolved fe to the southern ocean and show that aeolian deposition of dissolved fe in the southern bay of bengal may be comparable to that observed underneath the saharan dust plume in the atlantic ocean

the f ratio on 20 w during the north atlantic bloom experiment abstract we have used data gathered during the north atlantic bloom experiment to model new and total production and the f ratio on 20 w the results imply that as much as half the spring bloom total production occurs well in advance of stratification however although new production potentially equals export production into the interior of the ocean observations during nabe and the model suggest that this export may not be fully realized during the bloom and may be trapped and recycled in the upper water column during the year

evaluation of environmental conditions for the formation of severe local storms across the indian subcontinent 1 the spatial and temporal distributions of thermal instability and vertical wind shear in the indian subcontinent are evaluated as the important factors for occurrence and development of severe local storms and compared with the climatology of severe local storms across the indian subcontinent high thermal instability and vertical wind shear occur in bangladesh and northeastern india during the pre monsoon season from march to may peaking in april there is great potential for severe local storms during the pre monsoon season in bangladesh and northeastern india

surface water dissolved aluminum and titanium tracers for specific time scales of dust deposition to the atlantic surface water distributions of dissolved al dal and dissolved ti dti were investigated along a meridional atlantic transect and related to dust deposition estimates in the zone of saharan dust deposition highest dal concentrations occurred in the tropical salinity minimum and suggest increasing al dissolution from saharan aerosols with wet deposition by contrast the dti distribution is not related to precipitation but agrees with the pattern of annual dust deposition in the zone of patagonian dust deposition elevated dti concentrations contrasted with decreased dal concentrations indicating excess dal scavenging onto biogenic particles in surface waters estimated residence times range from months to years for dal and are 10 times higher for dti this suggests that dal reflects seasonal changes in dust deposition while dti is related to longer temporal scales however spatial variations in input and removal processes complicate the quantification of dust deposition from surface water concentrations

the pace of east african monsoon evolution during the holocene african monsoon precipitation experienced a dramatic change in the course of the holocene the pace with which the african monsoon shifted from a strong early to middle to a weak late holocene is critical for our understanding of climate dynamics hydroclimate vegetation interaction and shifts of prehistoric human settlements yet it is controversially debated on the basis of planktonic foraminiferal ba ca time series from the eastern mediterranean sea here we present a proxy record of nile river runoff that provides a spatially integrated measure of changes in east african monsoon eam precipitation the runoff record indicates a markedly gradual middle to late holocene eam transition that lasted over 3500 years the timing and pace of runoff change parallels those of insolation and vegetation changes over the nile basin indicating orbitally forced variation of insolation as the main eam forcing and the absence of a nonlinear precipitation vegetation feedback a tight correspondence between a threshold level of nile river runoff and the timing of occupation abandonment of settlements suggests that along with climate changes in the eastern sahara the level of nile river and intensity of summer floods were likely critical for the habitability of the nile valley egypt

the potential source of dissolved aluminum from resuspended sediments to the north atlantic deep water abstract laboratory and field studies were conducted to investigate the significance of resuspended sediments as a source of dissolved al to the deep northwest atlantic sediment resuspension experiments demonstrate the effect on dissolved al concentration initially 11 nm of adding natural suspended sediments ca 0 1 10 mg l to seawater the concentration of dissolved al increased by the resuspension of sediments for example addition of 0 15 mg l sediments caused dissolved al to increase by 10 nm distributions of dissolved and leachable particulate al off the tail of the grand banks near the highenergy western boundary current show elevated levels in the near bottom waters we suggest that resuspended sediments associated with nepheloid layers along the western boundary of the north atlantic are a source of dissolved al strong western boundary currents provide the energy to resuspend and maintain intense nepheloid layers of sediments continued resuspension and deposition of sediments within the nepheloid layer promotes the release of al from sediments to the overlying water the al rich terrigenous sediments that predominate along the deep boundary of the denmark strait labrador sea newfoundland and off nova scotia constitute a potentially significant source of dissolved al release of al from resuspended sediments associated with nepheloid layers at a more northern location e g denmark strait may contribute to the near linear increase in dissolved al with depth observed in the deep northwest atlantic

investigating the use of 232th 230th as a dust proxy using co located seawater and sediment samples from the low latitude north atlantic abstract the thorium isotope ratio 232 th 230 th can be measured in seawater and sediment samples and has been used as a proxy to reconstruct lithogenic fluxes to the oceans for the modern day and the pleistocene there has not yet been a systematic study testing the proxy using the 232 th 230 th ratio in seawater and the ratio recorded in the underlying sediment in this study we use co located core top sediments and seawater samples from five seamount sites spanning the tropical north atlantic to investigate the link between seawater and sediment 232 th 230 th ratios across a range of water depths our results indicate that a broad correlation exists between seawater and sedimentary 232 th 230 th ratios both seawater and sedimentary 232 th 230 th ratios record a signal consistent with decreasing lithogenic input east to west from africa to south america however calculated 232 th fluxes for the core top sediment samples indicate a strong dependence on depth with up to a factor of 4 difference from shallow 2900 m this depth dependence is likely caused by either a deficit of 230 th burial at depth compared to the production in the overlying water column through addition of 232 th or by a combination of the two by comparing seawater and sedimentary 232 th 230 th ratios we derive an apparent fractional solubility of 232 th of 29 3 in reasonable agreement with the upper end of existing estimates

variability in oceanic dissolved iron is dominated by the colloidal fraction abstract oceanic surface and deep iron distribution and size fractionation were investigated on three cruises in the sub tropical and tropical atlantic ocean detailed profiles and transects were collected and analyzed for dissolved fe dfe 0 4 m filtered and soluble fe sfe 0 02 m filtered the difference between dfe and sfe is inferred to be the colloidal fraction of fe cfe sfe concentration distributions and profiles showed little variability in the atlantic ocean with slightly lower concentrations of sfe in the upper ocean than the relatively uniform concentrations observed in deep water 0 3 to 0 4 nmol kg in contrast variability in the atlantic dfe was dominated by variability in cfe dfe and cfe followed dust deposition trends and observed surface maxima in dfe profiles were always due to maxima in the cfe fraction where dust deposition and surface dfe were low i e the south atlantic the cfe fraction of dfe was low and frequently negligible in surface waters below the surface maxima in cfe and dfe cfe always decreased to negligible levels at 30 80 m remained low or negligible throughout the pycnocline and increased with depth below the pycnocline at a site located on the edge of the equatorial system 10 n high dfe and cfe concentrations were associated with an oxygen minimum zone omz at depths of 130 to 1100 m deep water dfe and cfe concentrations varied between water masses depending on the source age and path of the water masses dfe in nadw decreased by 30 from the north atlantic to the south atlantic site with most of the decrease due to loss of cfe at the south atlantic site nadw had higher dfe and a higher fraction of cfe than the antarctic water masses

surface ocean lower atmosphere interactions in the northeast pacific ocean gyre aerosols iron and the ecosystem response 1 here we report measurements of iron and aluminum in surface and subsurface waters during late march and late may of 2001 on transects between central california and hawaii a large cloud of asian dust was detected during april 2001 and there was a clear signal in surface water iron due to aerosol deposition on the may transect iron and aluminum concentrations increased synchronously by 0 5 and 2 nm along the southern portion of the transect which includes the hawaii ocean time series hot station from background values in march 0 1 to 0 2 nm fe these changes occurred in a ratio that is close to the crustal abundance ratio of the metals which indicates a soil aerosol source a vertical profile of dissolved iron was also measured at the hot station in late april and this profile also shows a large increase near the surface direct observations of aerosol iron concentration at mauna loa observatory on hawaii indicate that aerosol concentrations were significantly lower than climatological values during this period soil aerosol concentrations along the transect were estimated using the real time navy aerosol analysis and prediction system naaps the naaps results show a large meridional gradient with maximum concentrations in the boundary layer north of 30 n however the deposition of iron and aluminum to surface waters was highest south of 25 n near hawaii there were only weak signals in the ecosystem response to the aerosol deposition

possible linkage between the monsoon trough variability and the tropical cyclone activity over the western north pacific abstractthe present study investigates the influence of the monsoon trough mt on the interannual variability of tropical cyclone tc activity over the western north pacific during july november for the period 1979 2007 it is shown that the tc activity is closely related to the mt location during the years when the mt extends eastward retreats westward more less tcs form within the southeastern quadrant of the western north pacific such a relationship can be explained by the changes in large scale environmental factors associated with the movement of the mt an eastward extension of the mt coincides with warmed ocean surface enhanced convection increased relative humidity in the lower and midtroposphere reduced vertical shear of zonal wind intensified upper level divergence and low level anomalous cyclonic vorticity over the southeast quadrant of the western north pacific these conditions associated with the eastern extension of the mt are favorable for tc genesis while those associated w

estimating the benthic efflux of dissolved iron on the ross sea continental shelf continental margin sediments provide a potentially large but poorly constrained source of dissolved iron dfe to the upper ocean the ross sea continental shelf is one region where this benthic supply is thought to play a key role in regulating the magnitude of seasonal primary production here we present data collected during austral summer 2012 that reveal contrasting low surface 0 08 0 07 nm and elevated near seafloor 0 74 0 47 nm dfe concentrations combining these observations with results from a high resolution physical circulation model we estimate dfe efflux of 5 8 107 mol yr 1 from the deeper portions 400 m of the ross sea continental shelf more than sufficient to account for the inferred winter reserve dfe inventory at the onset of the growing season in addition elevated dfe concentrations observed over shallower bathymetry suggest that such features provide additional inputs of dfe to the euphotic zone throughout the year

dissolved al in the zonal n atlantic section of the us geotraces 2010 2011 cruises and the importance of hydrothermal inputs abstract the distribution of dissolved aluminium determined during ga03 the us geotraces north atlantic transects us gt nazt shows large inputs to the basin from three main sources atmospheric deposition outflow from the mediterranean and inputs from hydrothermal sources along the mid atlantic ridge mar the partial dissolution of atmospheric aerosols emanating from the sahara yield high concentrations of dissolved al in the surface waters of the basin and are used to estimate the geographical pattern of dust deposition the mediterranean outflow delivers a large source of dissolved al to the intermediate waters of the eastern basin and its subsequent distribution within the basin can be explained by simple isopycnal mixing with surrounding water masses hydrothermal venting at the trans atlantic geotraverse tag hydrothermal field in the mar produces a neutrally buoyant plume that introduces copious quantities of dissolved al with concentrations of up to 40 nm to the deeper waters of the north atlantic that can be seen advecting to the west of the mar the concentration of dissolved al in the deep waters of the eastern basin of the atlantic can be accounted for by admixing the mar al enriched plume water and antarctic bottom water aabw as they pass through the vema fracture zone the data sets show no evidence for biological remineralisation of dissolved al from si carrier phases in deep waters

dissolved iron anomaly in the deep tropical subtropical pacific evidence for long range transport of hydrothermal iron abstract dissolved iron profiles along a north south transect along 158 w in the tropical pacific show evidence of two deepwater anomalies the first extends from station aloha 22 78 n to the equator at 1000 1500 m and lies below the maximum apparent oxygen utilization and nutrient n p concentrations the feature is not supported by vertical export processes but instead corresponds with the lateral dilution field of 3 he derived from the loihi seamount hawaii though a sediment source associated with the hawaiian island chain cannot be entirely ruled out the second deeper 2000 3000 m anomaly occurs in tropical south pacific waters 7 s and also does not correlate with the depths of maximum nutrient concentrations or apparent oxygen utilization but it does coincide closely with 3 he emanating from the east pacific rise more than 5000 km to the east we hypothesize that these anomalies represent the long range 2000 km transport of hydrothermal iron residuals stabilized against scavenging by complexation with excess organic ligands in the plume source regions such trace leakage of hydrothermal iron to distal plume regions would have been difficult to identify in most hydrothermal vent mapping studies because low analytical detection limits were not needed for the proximal plume regions these findings suggest that hydrothermal activity may represent a major source of dissolved iron throughout the south pacific deep basin today as well as other regions having high mid ocean spreading rates in the geologic past in particular we hypothesize that high spreading rates along the south atlantic and southern ocean mid oceanic ridges combined with the upwelling ventilation of these distal hydrothermal plumes may have increased ocean productivity and carbon export in the southern ocean assessing the magnitude and persistence of dissolved hydrothermal iron in basin scale deep waters will be important for understanding the marine biogeochemistry of iron and potentially on ocean productivity and climate change during the geologic past

reactive trace metals in the stratified central north pacific abstract vertical concentration profiles of the dissolved and suspended particulate phases were determined for a suite of reactive trace metals al fe mn zn and cd during summertime at a station in the center of the north pacific gyre during summer the euphotic zone becomes stratified forming a shallow 0 25 m oligotrophic mixed layer overlying a subsurface 25 140 m strongly stratified region the physical biological and chemical structure within the euphotic zone during this period enhanced the effect of atmospheric inputs of al fe and mn on mixed layer concentrations for example the concentration of dissolved fe in the surface mixed layer was eighteen times that observed at a depth of 100 m the observed aeolian signature of these metals matched that predicted from estimates of atmospheric input during the period between the onset of stratification and sampling the distributions of suspended particulate al fe and mn all exhibited minima in the euphotic zone and increased with depth into the main thermocline particulate al and fe were then uniform with depth below 1000 m before increasing in the near bottom nepheloid layer average particulate phase concentrations in intermediate and deep waters of the central north pacific were 1 0 0 31 and 0 055 nmol kg 1 for al fe and mn respectively the distribution of particulate cd exhibited a maximum within the subsurface euphotic zone particulate zinc also exhibited a surface maximum albeit a smaller one concentrations of particulate zn and cd in intermediate and deep waters were 17 and 0 2 pmol kg 1 substantial interbasin differences in particulate trace metals occur concentrations of suspended particulate al fe and mn were three to four times lower in the central north pacific than recently reported for the central north atlantic gyre consistent with differences in atmospheric input to these two regions concentrations of suspended particulate cd and zn were enriched in the north pacific relative to the north atlantic an observation consistent with their assimilation by plankton reactive trace metals exhibit a range of biogeochemical behaviors that can be characterized by two endmembers nutrient type and scavenged type nutrient type metals best exemplified by zn and cd are primarily removed from surface waters by biogenic particles and then remineralized at depth internal biogeochemical cycles together with physical mixing and circulation patterns control the distributions of nutrient type metals scavenged type metals best exemplified by al continue to be removed onto particles in intermediate and deep waters as well as at the surface external inputs such as the deposition of aeolian dust control the concentrations and distributions of scavenged type metals other metals such as fe exhibit a mixture of the characteristic behaviors of these two endmembers

a case study of severe storm development along a dryline within a synoptically active environment part ii multiple boundaries and convective initiation abstract a dryline that occurred on 16 may 1991 within a synoptically active environment is examined in detail using research aircraft radar surface satellite and upper air observations the work focuses on multiple boundaries in the dryline environment and initiation of tornadic storms in two along line areas aircraft measurements in the boundary layer reveal that both the east west extent of moisture gradients and the number of regions containing large moisture gradients vary in the along dryline direction aircraft penetrations of thinlines observed in clear air return from radar reveal that all thinlines are associated with convergence and a moisture gradient and that more distinct thinlines are associated with stronger convergence however significant moisture gradients are not always associated with either thinlines or convergent signatures convective clouds on this day formed at the dryline rather than significantly east of the dryline the three thunderstorm cells that occurred in east cen

dissolved particulate and acid leachable trace metal concentrations in north atlantic precipitation collected on the global change expedition rainwater samples from six precipitation events were collected on board ship during legs 3 and 4 of the global change expedition over the north atlantic ocean and analyzed for dissolved particulate al and pb and acid leachable trace metals al fe mn cd cu pb zn acid leachable concentrations of the elements in 0 4 v v hno3 were similar to reported values from the north atlantic and pacific oceans which were measured using comparable acidification procedures concentrations of dissolved and particulate al and pb were determined in rain events concurrently sampled comparisons between acid leachable and total dissolved plus particulate trace metal concentrations suggest that the acid leachable fraction of metals can significantly underestimate total concentrations of crustal elements e g al in rain the solubilities of al and pb in precipitation were variable and mean solubilities of the elements were 13 and 45 respectively recycled sea salt components were less than 14 for al fe mn pb cd cu and zn indicating that the net trace metal flux is from the atmosphere to the oceans deep sea particle fluxes for these metals through the western tropical north atlantic exceed atmospheric deposition fluxes by a factor of 18 41

the role of atmospheric deposition in the biogeochemistry of the mediterranean sea abstract estimates of atmospheric inputs to the mediterranean and some coastal areas are reviewed and uncertainities in these estimates considered both the magnitude and the mineralogical composition of atmospheric dust inputs indicate that eolian deposition is an important 50 or even dominant 80 contribution to sediments in the offshore waters of the entire mediterranean basin model data for trace metals and nutrients indicate that the atmosphere delivers more than half the lead and nitrogen one third of total phosphorus and 10 of the zinc entering the entire basin measured data in sub basins such as the north western mediterranean and northern adriatic indicate an even greater proportions of atmospheric versus riverine inputs when dissolved fluxes are compared the form most likely to impinge on surface water biogeochemical cycles the atmosphere is found to be 5 to 50 times more important than rivers for dissolved zinc and 15 to 30 times more important for lead fluxes neglecting co limitation by other nutrients new production supported by atmospheric nitrogen deposition ranges from 2 4 g c m 2 yr 1 whereas atmospheric phosphorus deposition appears to support less than 1 g c m 2 yr 1 in spite of the apparently small contribution of atmospheric deposition to overall production in the basin it has been suggested that certain episodic phytoplankton blooms are triggered by atmospheric deposition of n p or fe future studies are needed to clarify the extent and causal links between these episodic blooms and atmospheric oceanographic forcing functions a scientific program aimed at elucidating the possible biogeochemical effects of saharan outbreaks in the mediterranean through direct sampling of the ocean and atmosphere before and after such events is therefore highly recommended

the madeira mode water quasi homogeneous layers in vertical profiles of temperature and salinity in the eastern north atlantic near madeira indicate the existence of a subtropical mode water in the eastern basin temperature sections show a maximum horizontal extent of at least 500 km the frequency distribution analysis of homogeneous layers in a historical xbt dataset shows a mode water formation region near and to the north of madeira this mode water is found at increasing depths and displaced to the west and southwest during the course of the year after its formation by wintertime convection it disappears almost completely due to mixing before the next winter volume estimates suggest that this madeira mode water in the eastern atlantic accounts for 15 20 of the total central water formation in the corresponding density range as obtained from tracer studies in the north atlantic gyre

calcium carbonate dissolution in the upper 1000 m of the eastern north atlantic recent analyses suggest that considerable caco3 dissolution may occur in the upper water column of the ocean 1500 m this study uses the distribution of particulate calcium from high resolution suspended matter sampling along the climate variability and predictability co2 repeat hydrography a16n transect in 2003 to estimate caco3 dissolution in the top 1000 m of the north atlantic dissolution rates were also approximated using changes in total alkalinity measurements along isopycnal surfaces water masses were found to be undersaturated with respect to aragonite at intermediate depths 400 1000 m in the eastern tropical north atlantic the caco3 dissolution rate in this region is estimated to be 0 9 mmol caco3 m 2 d 1 indicating this region is a hotspot for upper water column caco3 dissolution compared to the atlantic basin as a whole dissolution rates calculated from particulate calcium distributions outside of this region were significantly lower 0 2 mmol caco3 m 2 d 1 and are comparable to previous estimates of caco3 dissolution flux for the atlantic ocean the magnitude of upper water column dissolution rates compared to measured surface ocean caco3 standing stocks suggests that biologically mediated caco3 dissolution may be occurring in the top 1000 m of the atlantic

lead and aluminum in atlantic surface waters 50 n to 50 s reflecting anthropogenic and natural sources in the eolian transport lead and aluminum were measured with a 40 100 km resolution in surface water on two transects across the atlantic ocean one in may 1990 from cape town to the north sea the other in november 1990 from the north sea to the strait of magellan samples were drawn 14 m below surface at normal speed from a 2 m long snorkel system mounted on the bottom of the ship directly into a clean room area in the tropics both pb and al show maximum concentrations in the intertropical convergence zone itcz correlated with each other and with minimum salinities indicating wet deposition as their common source even in this area characterized by large inputs of mineral aerosols the pb al ratio shows that the major source of soluble lead 95 is anthropogenic at higher latitudes al is low throughout 10 20 nmol kg whereas enhanced pb values show the anthropogenic inputs off south africa northern argentina and especially western europe very low pb and especially al concentrations in the upwelling areas associated with the canary and benguela currents show that the enhanced biogenic particle fluxes cause an efficient scavenging of both lithogenic particles known to arrive here by dry deposition and of the adhering reactive trace metals

the role of dust deposition in determining surface water distributions of al and fe in the south west atlantic abstract underway dissolved al and fe determinations were made on surface water samples collected between 34 s and 8 n in the southern and tropical atlantic ocean using a towed surface water sampler the general distribution of dissolved al which ranged from 8 nm in the sub tropical gyre to 61 nm under the intertropical convergence zone itcz north of the equator corresponds clearly with atmospheric dust deposition patterns a striking correlation between al and surface water salinities between 28 s and 8 n further indicates that wet deposition is the predominant mechanism of delivery of this atmospheric source iron concentrations in contrast were more uniform varying between 0 6 and 0 8 nm south of the equator highest fe values up to 1 4 nm also were found associated with the maximum dust inputs at the itcz indicating an atmospheric source for this element whose input appears to be limited by the solubility of fe in sea water the lowest fe values 0 4 nm also were observed in the equatorial region and are assumed to result from the biological removal of fe from nutrient rich water masses originating in the nearby equatorial and coastal upwelling regions the high frequency data acquisition of the towed sampler revealed significant variations up to 50 in both al and fe concentrations over short distances most notably along the interface between the south equatorial and canary currents the high variability of a biologically important trace element such as fe in these dynamic regions is indicative of the interplay between chemical and biological patchiness in surface waters

dissolved and particulate fe in the western and central north pacific results from the 2002 ioc cruise 1 the goals of the 2002 intergovernmental oceanographic commission ioc cruise were to examine the variability in dissolved and particulate fe over the cruise track relate this variability to atmospheric aerosol fe input and examine the relationships between fe nitrate and dust deposition with regards to fe limitation particularly in the subarctic north pacific dissolved fe in the surface waters was quite variable ranging from 0 10 nm to 0 30 nm dissolved fe in the vertical profiles showed significant variability the most prominent feature being an fe maximum 1 5 nm fe associated with a broad nitrate maximum at 400 1000 m in the western subarctic gyre deep water fe values in the subarctic region ranged from 0 8 nm to 1 1 nm subtropical gyre surface water dissolved fe values were also quite variable ranging from 0 15 nm to 0 4 nm intermediate and deep water fe values were on the order of 0 6 0 9 nm significant differences were observed between total dissolvable fe and dissolved fe tdfe dfe in surface waters over the course of the cruise track and these differences are discussed in terms of particulate fe and possible sources of fe to surface waters finally nitrate fe ratios in the western subarctic gyre atmospheric dust flux estimates based on surface water aluminum concentrations and aerosol fe fluxes from ship based aerosol collections are used to evaluate the relative importance of atmospheric and or continental fe input versus upwelling fluxes of fe to the surface waters of the subarctic gyre

three dimensional structure of the wind driven circulation in the subtropical north pacific abstract the subduction rate is calculated for the north pacific based on levitus climatology data and hellerman and rosenstein wind stress data because the period of effective subduction is rather short subduction rates calculated in eulerian and lagrangian coordinates are very close the subduction rate defined in the lagrangian sense consists of two parts the first part is due to the vertical pumping along the one year trajectory and the second part is due to the difference in the winter mixed layer depth over the one year trajectory since the mixed layer is relatively shallow in the north pacific the vertical pumping term is very close to the ekman pumping while the sloping mixed layer base enhances subduction especially near the kuroshio extension for most of the subtropical north pacific the subduction rate is no more than 75 m yr 1 slightly larger than the ekman pumping the water mass volume and total amount of ventilation integrated for each interval of 0 2 unit is computed the corre

partitioning of dissolved iron and iron isotopes into soluble and colloidal phases along the ga03 geotraces north atlantic transect abstract the size partitioning of dissolved fe dfe 56 fe of 1 3 to 1 5 relative to dfe 56 fe 0 5 in the surface ocean where sfe and cfe cycle independently and identical sfe and dfe isotope ratios below 250 m where sfe and cfe are constantly partitioned and exchanged

combining seawater 232th and 230th concentrations to determine dust fluxes to the surface ocean abstract aeolian dust is a significant source of iron and other nutrients to the surface ocean but constraining the size of this flux is difficult chemical tracers such as al are useful but are limited by lack of information about their rate of removal from surface seawater in this study we test the use of th isotopes as an improved tracer of dust input by measuring 232 th and 230 th concentrations of upper ocean seawater at six stations along a meridional atlantic section that spans the saharan dust plume open ocean 232 th like al is dominantly derived from dust dissolution while 230 th is produced in seawater by u decay and provides an assessment of th removal rates the highest 232 th concentrations and 232 th 230 th ratios particularly in the surface waters are observed at stations expected to be influenced by input of saharan dust the pattern of 232 th concentration is in agreement with dissolved al distributions and seawifs aerosol imagery supporting the use of 232 th as a proxy for short term dust addition deeper in the water column 232 th concentration may also reflect longer term dust inputs in addition lateral input of 232 th from mediterranean outflow water is detected at 1000 m in the north atlantic surface water residence times are calculated separately from 230 th and 234 th using a simple scavenging model and values from the two isotopes are generally consistent with one another th 230 residence times appear to reflect the longer term value however rather than exhibiting the strong seasonal influence seen for 234 th these th residence times allow dust flux to the surface ocean to be calculated using the known concentration of th in dust and assumed values for the solubility of dust th in seawater resulting dust fluxes show good agreements with models of dust deposition if th solubility is 1 to 5 in the north atlantic yielding fluxes of 0 4 19 2 g m 2 yr 1 and 5 to 10 in the south atlantic fluxes of 0 2 0 7 g m 2 yr 1 despite the need for better constraints on the fractional solubility of dust th this study demonstrates the power of combining th isotope measurements to constrain dust fluxes to the surface ocean

the role of tropical waves in tropical cyclogenesis abstract this paper analyzes relationships between tropical wave activity and tropical cyclogenesis in all of the earth s major tropical cyclone basins twenty nine years of outgoing longwave radiation data and global reanalysis winds are filtered and analyzed to determine statistical relationships between wave activity in each basin and the corresponding cyclogenesis composite analyses relative to the storm genesis locations show the structures of the waves and their preferred phase relationships with genesis five wave types are examined in this study including mixed rossby gravity waves tropical depression type or easterly waves equatorial rossby waves kelvin waves and the madden julian oscillation the latter is not one of the classical tropical wave types but is a wavelike phenomenon known to have a strong impact on tropical cyclogenesis tropical cyclone formation is strongly related to enhanced activity in all of the wave filter bands except for the kelvin band in each basin the structure o

shallow salinity minima in the north pacific abstract ctd std data from 24 cruises in the north pacific are studied for their vertical salinity structure and compared to bottle observations a triple salinity minimum is found in two separated regions in the eastern north pacific in the first region bounded by the northern edge of the subarctic frontal zone and the 34 n front between 160 and 150 w a middle salinity minimum is found below the permanent pycnocline in the density range of 26 0 and 26 5 this middle minimum underlies reid s shallow salinity minimum and overlies the north pacific intermediate water npiw in the second region southeast of the first a seasonal salinity minimum appears above the shallow salinity minimum at densities lower than 25 1 the shallow salinity minimum and the npiw can be found throughout year while the seasonal minimum only appears in summer and fall the middle and shallow salinity minima as well as the seasonal minimum originate at the sea surface in the northeast pacific the properties at the m