utilizing the aspect sea ice thickness data set to evaluate a global coupled sea ice ocean model 1 simulated sea ice thickness in the orca2 lim coupled sea ice ocean model is compared with thicknesses from the antarctic sea ice processes and climate aspect database we find a qualitative agreement of the large scale patterns of ice thickness distribution regional averages for the various sectors of the southern ocean yield a very good correspondence between observations and model data exceptions are the eastern bellingshausen and northwestern weddell seas a poor representation of the antarctic peninsula in the atmospheric forcing data and the related overestimation of westerly winds in this region lead to a spurious accumulation of sea ice on the western side of the peninsula and to an underestimation of sea ice coverage on the eastern side since the spatial scale of observations is not comparable to the size of a model grid cell there is little agreement between individual observations and the corresponding model ice thicknesses a model analysis of the seasonal and interannual variability indicates that the aspect data underestimate the climatological ice thickness in the central and southern weddell sea and the eastern ross sea by up to 1 m because of a winter bias in the observations an overestimation of similar magnitude is expected in the bellingshausen sea ice thickness data in most of the indo pacific sector appear to be representative for the long term climatology a model estimate of the bias is used to compute a revised distribution of climatological sea ice thickness

residual mean solutions for the antarctic circumpolar current and its associated overturning circulation abstract residual mean theory is applied to the streamwise averaged antarctic circumpolar current to arrive at a concise description of the processes that set up its stratification and meridional overturning circulation on an f plane simple solutions are found in which transfer by geostrophic eddies colludes with applied winds and buoyancy fluxes to determine the depth and stratification of the thermocline and the pattern of associated residual meridional overturning circulation

evolution of el nino precipitation relationships from satellites and gauges 1 this study uses a 23 year 1979 2001 satellite gauge merged community data set to further describe the relationship between el nino southern oscillation enso and precipitation the globally complete precipitation fields reveal coherent bands of anomalies that extend from the tropics to the polar regions el nino precipitation relationships were analyzed during the six strongest events from 1979 to 2001 el ninos were defined based on the zonal contrast in rainfall in the equatorial pacific and seasons of precipitation evolution pre onset onset peak decay and postdecay were identified areas with a consistent el nino precipitation relationship were determined based on this unique definition of el nino and season of year the latter analysis confirms previous studies and suggests other areas of significant signal over the oceans gulf of alaska the former analysis reveals subtle shifts in tropical rainfall from onset to decay namely negative anomalies moving from the maritime continent and south pacific to the north tropical pacific and positive anomalies from the central equatorial pacific southeastward these distributions of tropical convection appear to be connected to extratropical precipitation anomalies through meridional atmospheric circulations concentrated in the eastern indian ocean sector during onset and in the pacific sector during decay the yangtze river basin which is known to flood during el nino is affected during the entire evolution

oxygen isotopes of phosphate and soil phosphorus cycling across a 6500 year chronosequence under lowland temperate rainforest abstract phosphorus p availability declines during ecosystem development due in part to chemical transformations of p in the soil here we report changes in soil p pools and the oxygen isotopic signature of inorganic phosphate 18op in these pools over a 6500 year soil coastal dune chronosequence in a temperate humid environment total p declined from 384 to 129 mg p kg 1 during the first few hundred years of pedogenesis due mainly to the depletion of primary mineral p in the hcl extractable pool the 18op of hcl extractable inorganic p initially reflected the signature of the parent material but shifted over time towards but not reaching isotopic equilibrium in contrast 18op signatures of inorganic p extracted in water and nahco3 approximately 9 and 39 mg p kg 1 respectively were variable but consistent with isotopic equilibrium with soil water in the naoh extractable p pool which doubled from 63 to 128 mg p kg 1 in the early stages of pedogenesis and then gradually declined the 18op of the extracted inorganic p changed from equilibrium values early in the chronosequence to more depleted signatures in older soils indicating greater rates of hydrolysis of labile organic p compounds such as dna and increase involvement in p cycling as overall p availability declines through the sequence in summary this application of 18op to a long term soil chronosequence provides novel insight into p dynamics indicating the importance of efficient recycling through tight uptake and mineralization in maintaining a stable bioavailable p pool during long term ecosystem development

temporal variability of transformation formation and subduction rates of upper southern ocean waters 1 kinematic and thermodynamic approaches are employed to diagnose the time dependent transformation formation and subduction rates of upper southern ocean waters in a multidecadal simulation within an eddy permitting coupled climate model in the subantarctic mode water samw density class a convergence of diapycnal volume fluxes leads to the formation and inflation of mixed layer waters during winter a portion of this water is detrained into the pycnocline during early spring when surface heating restratifies the deep winter mixed layer the annually averaged subduction rate of samw shows pronounced interannual variability partly controlled by the temporal tendency of the winter mixed layer depth from one year to the next no significant correlation between the southern annular mode sam and the isopycnally integrated samw subduction rate is apparent however ekman downwelling upwelling intensities modulated by the sam influence interannual variations in the subduction rates of water masses lighter and heavier than samw with an opposing sign during positive phases of the sam more pycnocline waters are entrained into the mixed layer and transformed into lighter densities within the antarctic intermediate water density class whereas more mixed layer waters are subducted into the pycnocline within the subtropical mode water density class such distinct responses of upper southern ocean water masses to the sam are qualitatively consistent with observational constraints based on a comparison between offline kinematic and thermodynamic diagnostics we infer that diapycnal mixing within the mixed layer may contribute up to 50 of the formation rate of samw on interannual timescales

on land ice loss and glacial isostatic adjustment at the drake passage 2003 2009 1 land glacier extent and volume at the northern and southern margins of the drake passage have been in a state of dramatic demise since the early 1990s here time varying space gravity observations from the gravity recovery and climate experiment grace are combined with global positioning system gps bedrock uplift data to simultaneously solve for ice loss and for solid earth glacial isostatic adjustment gia to little ice age lia cryospheric loading the present day ice loss rates are determined to be 26 6 gt yr and 41 5 9 gt yr in the southern and northern patagonia ice fields npi spi and antarctic peninsula ap respectively these are consistent with estimates based upon thickness and flux changes bounds are recovered for elastic lithosphere thicknesses of 35 h 70 km and 20 h 45 km and for upper mantle viscosities of 4 8 1018 pa s and 3 10 1019 pa s using a half space approximation for npi spi and ap respectively using an iterative forward model strategy antarctic peninsula ice models with a prolonged lia extending to a d 1930 are favored in all 2 fits to the gps uplift data this result is largely decoupled from earth structure assumptions the gia corrections account for roughly 20 60 of the space determined secular gravity change collectively the on land ice losses correspond to volume increases of the oceans equivalent to 0 19 0 045 mm yr of sea level rise for the last 15 years

antarctic intermediate water circulation and variability in a coupled climate model the variability of antarctic intermediate water aaiw in a long term natural integration of a coupled climate model is examined the mean state of the climate model includes a realistic representation of aaiw which appears centered on the su 5 27 2 kg m23 density surface hereinafter s 27 2 both in observations and the model an assessment of ventilation rates on the s 27 2 surface suggests that this particular climate model forms aaiw in a mostly circumpolar fashion with a significant contribution from antarctic surface water this motivates the assessment of oceanic variability along this core aaiw isopycnal surface complex empirical orthogonal function analyses decompose the variability into three dominant modes showing circumpolar patterns of zonal wavenumber 1 2 and 3 on the s 27 2 density surface the modes contain eastward propagating signals at interannual to centennial time scales mechanisms forcing this variability are investigated using heat and salt budget analyses at the wintertime outcrop of the s 27 2 surface such an approach ignores the mechanism of aaiw variability sourced by subantarctic mode water variations which has been examined previously and is for the most part beyond the present study variability in meltwater rates and atmospheric heat and freshwater fluxes are found to dominate the intermediate water variability at the outcrop region in contrast northward ekman transport of heat and salt plays a significant but localized role in aaiw temperature salinity variability there is also an important contribution from the antarctic circumpolar current to the variability at the outcrop region via zonal transport of heat and salt while the magnitude of aaiw natural variability can be large near the outcrop of the salinity minimum layer recent observations of cooling and freshening at depth are suggested to be beyond that of the unperturbed system

hydrographic biases in global coupled climate models and their relation to the meridional overturning circulation comparison of the volumetric s distribution of models participating in the climate model intercomparison project 3 cmip3 indicates that these models differ widely in their ability to represent the thermohaline properties of water masses relationships between features of the quasi equilibrium hydrographic mean state of these models and aspects of their overturning circulations are investigated this is achieved quantitatively with the help of seven diagnostic hydrographic stations these few stations were specifically selected to provide a minimalist schematic of the global water mass system relationships between hydrographic conditions in the north atlantic measured with a subset of these stations suggest that hydrographic properties in the subpolar north atlantic are set by the circulation field of each model pointing towards deficiencies in the models ability to resolve the gulf stream north atlantic current system as a major limitation since diapycnal mixing and viscosity parameterizations differ across cmip3 models and exert a strong control on the overturning it is likely that these architectural differences ultimately explain the main across model differences in overturning circulation temperature and salinity in the north atlantic the analysis of properties across the quasi equilibrium states of the cmip3 models agrees with previously reported relationships between meridional steric height gradients or horizontal density contrasts at depth and the strength of the deep water cell robust relationships are also found in the southern ocean linking measures of vertical stratification with the strength of the abyssal circulations across the cmip3 models consistent correlations between aspects of the quasi equilibrium hydrography in the southern ocean and the sensitivity of the abyssal cell to increasing radiative forcing by 2100 were found using these relations in conjunction with modern hydrographic observations to interpolate the fate of the abyssal cell suggests that the southern abyssal cell may decrease by roughly 20 by the end of the century similar systematic relationships between the quasi equilibrium hydrographic states of the models and the sensitivity of their atlantic deep water cell could not be found

the southern ocean as a source region for tropical atlantic variability abstract a coupled model of intermediate complexity is used to examine the effect of the southern ocean on tropical atlantic variability model experiments with positive surface temperature freshwater and wind forcings in the southern ocean show an increased advection of polar water into the atlantic basin resulting in anomalously cold freshwater in the eastern atlantic ocean at 25 s with time these anomalies spread northward and away from the coast into the tropical thermocline the magnitude of the response increases linearly with the strength of the forcing the results of these experiments show that southeastern atlantic ocean temperature and salinity are particularly sensitive to changes in the southern ocean these findings suggest that this link could be the oceanic branch of a mode of variability linking the southern and tropical atlantic oceans a possible mechanism for the as yet unexplained decadal mode of tropical atlantic variability

importance of wind driven sea ice motion for the formation of antarctic intermediate water in a global climate model an ocean atmosphere sea ice model is used to show the importance of wind driven sea ice motion in the formation of antarctic intermediate water aaiw the model is able to reasonably simulate a tongue of low salinity aaiw even when the direct momentum transfer from wind to the ocean is neglected provided that the wind stress is applied to sea ice in contrast when the wind stress exclusively drives the ocean the model fails to capture the properties of aaiw the growth and subsequent offshore transport of sea ice acts as a freshwater conduit from near shore regions where aabw is formed to subpolar regions where aaiw is formed sea ice dynamics are also shown to be important in the simulation of a local salinity minimum at intermediate depths in the southern indian ocean and a local salinity maximum in the western weddell sea

interior water mass variability in the southern hemisphere oceans during the last decade abstractusing an argo dataset and the eccov4 reanalysis a volume budget was performed to address the main mechanisms driving the volume change of the interior water masses in the southern hemisphe

compensation and alignment of thermohaline gradients in the ocean mixed layer the surface mixed layer of the ocean is often characterized by thermohaline compensation and alignment that is temperature and salinity gradients tend to be parallel and to cancel in their contribution to density in this paper a combination of theoretical arguments and numerical simulations is presented to investigate how compensation and alignment emerge as a result of processes at work within the mixed layer the dynamics of the mixed layer is investigated through a simple model that couples a nonlinear diffusive parameterization for the horizontal transports of temperature and salinity with stirring by mesoscale eddies it is found that stirring quickly aligns the temperature and salinity gradients and that nonlinear diffusion creates compensation neither process by itself is sufficient to reproduce the observations

a doubling in snow accumulation in the western antarctic peninsula since 1850 1 we present results from a new medium depth 136 metres ice core drilled in a high accumulation site 73 59 s 70 36 w on the south western antarctic peninsula during 2007 the gomez record reveals a doubling of accumulation since the 1850s from a decadal average of 0 49 mweq y 1 in 1855 1864 to 1 10 mweq y 1 in 1997 2006 with acceleration in recent decades comparison with published accumulation records indicates that this rapid increase is the largest observed across the region evaluation of the relationships between gomez accumulation and the primary modes of atmospheric circulation variability reveals a strong temporally stable and positive relationship with the southern annular mode sam furthermore the sam is demonstrated to be a primary factor in governing decadal variability of accumulation at the core site r 0 66 the association between gomez accumulation and enso is complex while sometimes statistically significant the relationship is not temporally stable thus at decadal scales we can utilise the gomez accumulation as a suitable proxy for sam variability but not for enso

distribution of oxygen isotopes in the water masses of drake passage and the south atlantic measurements of the ratio of stable isotopes of oxygen 18o and 16o from samples collected on world ocean circulation experiment sections sr1b eastern drake passage and a11 punta arenas to cape town are used together with hydrographic data to deduce information about the formation and variability of south atlantic and southern ocean water masses the drake passage surface waters south of the polar front pf are isotopically light 18o around 0 4 owing to the influence of meteoric waters the salinity and 18o of the a11 surface waters yield an apparent freshwater end member which is much isotopically lighter than the local precipitation thus advection of these waters from farther south dominates over local effects in determining the surface water properties the drake passage section shows unusual proximity of the two main fronts of the antarctic circumpolar current the pf and subantarctic front saf and we observe cold fresh and isotopically light water derived from the temperature minimum winter water at the saf this water is of the correct density to freshen the intermediate water north of the saf and thus play a role in the formation of the comparatively fresh antarctic intermediate water aaiw of the south atlantic this confirms the role of antarctic water in forming the south atlantic variety of aaiw across the a11 section the oxygen isotope and salinity data at the aaiw core show very similar traces with waters in the malvinas current loop showing lowest values of both at the eastern boundary of the south atlantic the input of red sea water from east of south africa is observed via the presence of anomalously isotopically heavy aaiw we deduce potentially significant temporal variability in the isotopic composition of weddell sea deep water wsdw by comparing the drake passage data to earlier data covering the outflow of the weddell sea the a11 data show wsdw consistent with such variability indicating that its effects could persist in the waters as they flow north into the western south atlantic we speculate that such variability could be due to small changes in the amount of glacial ice melt in wsdw

the microbial cycling of phosphorus on long term fertilized soil insights from phosphate oxygen isotope ratios abstract microorganisms mobilize phosphorus p from soil and make it available for plants however the role of microbial activity in soil p dynamics especially among different p pools is poorly understood largely due to methodological limitations in this study we analyzed the oxygen isotope ratios in phosphate 18op of sequentially extracted inorganic p pi pools h2o pi nahco3 pi naoh pi and hcl pi in a long term agricultural research field in henan china with different fertilization histories and coupled with soil enzyme activity and p cycling bacteria gene abundance studies results showed the dominant enzymes were alkaline phosphatase apase and phosphodiesterase pde and the functional genes for p cycling were bpp cphy phox and pqqc after long term p fertilization the 18op values of h2o pi nahco3 pi and naoh pi pools approached to or achieved equilibrium suggesting that the externally applied p was actively mobilized and cycled by soil microorganisms and speciated into different p pools based on the extent of isotope excursion among different pi pools the equilibrium fractionation oriented the source signature in the nahco3 pi and naoh pi pools and hcl pi pool could be derived from p fertilizer but through multistep reactions and mixed with the hcl pi from rock weathering product which constituted hcl pi pool in the non p treatments overall the long term p fertilization especially the balanced fertilization with nitrogen n p and potassium k was found to be beneficial for extensive utilization of soil p with abundant biological uptake and cell internal pi cycling variation partitioning analysis vpa indicated that the expression of functional genes may be stimulated to mobilize soil p under specific p pools distribution in this alkaline environment overall our findings provide new insights to understand the roles of microbial activities in soil p biogeochemistry that are useful for agricultural p sustainability

on the variability of antarctic circumpolar current fronts inferred from 1992 2011 altimetry abstractantarctic circumpolar current acc fronts defined as water mass boundaries have been known to respond to large scale atmospheric variabilities especially the southern hemisphere annular mode sam and el nino southern oscillation enso distinct patterns of localized variability in meridional front displacements during 1992 2011 are derived from the analysis of satellite sea surface height data major basin scale differences are found between the southeast pacific 150 90 w and the southeast indian 75 150 e sectors of the acc frontal positions in the southeast pacific show large year to year meridional fluctuations attributed mostly to enso and in part sam and no apparent seasonal cycles or long term trends in contrast summer winter frontal locations in the southeast indian extend farther to the south north of their long term mean distribution a southward drift of acc fronts is indicated over the indian sector during the past two decades this long term shift is not directly re

atmospheric circulation impacts on winter maximum sea ice extent in the west antarctic peninsula region 1979 2001 increasing evidence exists that the strong warming of the west antarctic peninsula wap region since the 1950s is related to reduced sea ice that is likely to be due to changes in the atmospheric circulation over twenty years of sea ice extent ice motion and reanalysed near surface wind data are used to establish that winter ice extent in the west antarctic peninsula wap region is largely determined by the meridional north south atmospheric circulation a remarkably strong ice extent wind relationship is found in the wap no other antarctic or comparable sub arctic sea ice region shows this ice motion data confirm wind induced drift is crucial for extensive winter ice to occur reasons for winter ice extent and winds being more strongly correlated in the wap than in other parts of the antarctic are discussed along with implications for understanding the observed warming

relative influences of the interdecadal pacific oscillation and enso on the south pacific convergence zone 1 the south pacific convergence zone spcz one of the most extensive features of the global atmospheric circulation is shown to vary its location according to both the polarity of the el nino southern oscillation enso and of the interdecadal pacific oscillation ipo we first demonstrate that the ipo can be regarded as the quasi symmetric pacific wide manifestation of the pacific decadal oscillation that has been described for the north pacific shifts in the position of the spcz related to enso on interannual time scales and to the ipo on decadal time scales appear to be of similar magnitude and are largely linearly independent a station pressure based index of variations in spcz latitude is shown to be significantly related to the polarity of the ipo when enso influences are accounted for movements of this sensitive section of the spcz have occurred in phase with those of the ipo since the 1890s

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

mesoscale subduction at the antarctic polar front driven by baroclinic instability abstract a study of mesoscale subduction at the antarctic polar front pf is conducted by use of hydrographic data from a high resolution quasi synoptic survey of the front the geostrophic velocity and isopycnal potential vorticity pv fields are computed and the ageostrophic flow diagnosed from the semigeostrophic omega equation it is found that the ageostrophic circulation induced by baroclinic instability counteracts the frontogenesis and frontolysis effected by the confluence and difluence respectively of the geostrophic velocity field though the sense of the ageostrophic circulation is reversed repeatedly along the front the existence of pv gradients along isopycnals leads to a net cross front bolus transport in response to a reversal of this gradient with depth a necessary condition for the onset of baroclinic instability the bolus transport is northward at the protruding temperature minimum layer that characterizes the pf and southward above this net cross front overturning circul

heat distribution in the southeast pacific is only weakly sensitive to high latitude heat flux and wind stress the southern ocean features regionally varying ventilation pathways that transport heat and carbon from the surface ocean to the interior thermocline on timescales of decades to centuries but the factors that control the distribution of heat along these pathways are not well understood in this study we use a global ocean state estimate eccov4 to 1 define the recently ventilated interior pacific rvp using numerical passive tracer experiments over a 10 year period and 2 use an adjoint approach to calculate the sensitivities of the rvp heat content rvph to changes in net heat flux and wind stress we find that rvph is most sensitive to local heat flux and wind stress anomalies north of the sea surface height contours that delineate the antarctic circumpolar current with especially high sensitivities over the south pacific gyre surprisingly rvph is not especially sensitive to changes at higher latitudes we perform a set of step response experiments over the south pacific gyre the subduction region and the high latitude so in consistency with the adjoint sensitivity fields rvph is most sensitive to wind stress curl over the subtropical gyre which alter isopycnal heave and it is only weakly sensitive to changes at higher latitudes our results suggest that despite the localized nature of mode water subduction hotspots changes in basin scale pressure gradients are an important controlling factor on rvph because basin scale wind stress is expected to change in the coming decades to centuries our results may have implications for climate via the atmosphere ocean partitioning of heat

circulation and water mass modification in the brazil malvinas confluence abstract the confluence between the brazil current and the malvinas current the brazil malvinas confluence bmc in the argentine basin is characterized by a complicated thermohaline structure favoring the exchanges of mass heat and salt between the subtropical gyre and the antarctic circumpolar current acc analysis of thermohaline properties of hydrographic sections in the bmc reveals strong interactions between the acc and subtropical fronts in the subantarctic front subantarctic mode water samw antarctic intermediate water aaiw and circumpolar deep water cdw warm become saltier by 0 4 0 08 0 3 0 02 and 0 6 c 0 1 respectively in the subtropical gyre aaiw and north atlantic deep water have cooled freshened by 0 4 0 07 and 0 7 c 0 11 respectively to quantify those acc subtropical gyre interactions a box inverse model surrounding the confluence is built the model diagnoses a subduction of 16 4 sv 1 sv 106 m3 s 1 of newly formed samw and aaiw under the subtro

variability of subantarctic mode water and antarctic intermediate water in the drake passage during the late twentieth and early twenty first centuries a time series of the physical and biogeochemical properties of subantarctic mode water samw and antarctic intermediate water aaiw in the drake passage between 1969 and 2005 is constructed using 24 transects of measurements across the passage both water masses have experienced substantial variability on interannual to interdecadal time scales samw is formed by winter overturning on the equatorward flank of the antarctic circumpolar current acc in and to the west of the drake passage its interannual variability is primarily driven by variations in wintertime air sea turbulent heat fluxes and net evaporation modulated by the el nino southern oscillation enso despite their spatial proximity the aaiw in the drake passage has a very different source than that of the samw because it is ventilated by the northward subduction of winter water originating in the bellingshausen sea changes in aaiw are mainly forced by variability in winter water properties resulting from fluctuations in wintertime air sea turbulent heat fluxes and spring sea ice melting both of which are linked to predominantly enso driven variations in the intensity of meridional winds to the west of the antarctic peninsula a prominent exception to the prevalent modes of samw and aaiw formation occurred in 1998 when strong wind forcing associated with constructive interference between enso and the southern annular mode sam triggered a transitory shift to an ekman dominated mode of samw ventilation and a 1 2 yr shutdown of aaiw production the interdecadal evolutions of samw and aaiw in the drake passage are distinct and driven by different processes samw warmed by 0 3 c and salinified by 0 04 during the 1970s and experienced the reverse trends between 1990 and 2005 when the coldest and freshest samw on record was observed in contrast aaiw underwent a net freshening by 0 05 between the 1970s and the twenty first century although the reversing changes in samw were chiefly forced by a 30 yr oscillation in regional air sea turbulent heat fluxes and precipitation associated with the interdecadal pacific oscillation with a sam driven intensification of the ekman supply of antarctic surface waters from the south contributing significantly too the freshening of aaiw was linked to the extreme climate change that occurred to the west of the antarctic peninsula in recent decades there a freshening of the winter water ventilating aaiw was brought about by increased precipitation and a retreat of the winter sea ice edge which were seemingly forced by an interdecadal trend in the sam and regional positive feedbacks in the air sea ice coupled climate system all in all these findings highlight the role of the major modes of southern hemisphere climate variability in driving the evolution of samw and aaiw in the drake passage region and the wider south atlantic and suggest that these modes may have contributed significantly to the hemispheric scale changes undergone by those waters in recent decades

precipitation variability over northwest himalaya from 4 0 to 1 9 ka bp with likely impact on civilization in the foreland areas abstract we present a stalagmite based high resolution climatic record between 4 0 and 1 9 ka bp from dharamjali cave in pithoragarh kumaun himalaya an area which is influenced primarily by the indian summer monsoon ism and supplemented by the indian winter monsoon iwm the chronology of the 41 5 cm long dh 1 stalagmite was constructed using a stalage model on six 230th u dates however some samples have higher 232th concentrations leading to an increase in the final age uncertainties hence the chronology supports only the possible climatic boundaries however the significance of this work lies in its being one of the rare studies of speleothems to reconstruct high resolution climatic changes in the nw india for the upper holocene the 18o values ranging between 5 3 and 10 show a large variation compared to the areas dominated by a single monsoon and this can be ascribed to the two sources of moisture e g ism and iwm in the study area during the upper holocene the sample consists of aragonite except for two sections of calcite growth from 0 7 3 cm and 8 5 13 5 cm from the top the climatic reconstruction within the age uncertainties indicates strengthened precipitation from 4 0 ka bp with a sharp drop 2 in 18o values peaking at 3 7 ka bp a gradual decline in precipitation is observed from 3 7 to 3 0 ka bp with possible droughts centered at 3 4 3 2 and 3 0 ka bp subsequently climatic amelioration took place between 3 0 and 2 9 ka bp showing fluctuating trend in 18o values with comparatively more rainfall possibly generated by the iwm in the form of thunderstorms and hailstorms from 2 9 to 2 7 ka bp precipitation declined from 2 7 to 2 4 ka bp with a decadal scale major drought event strongest in the present data set at 2 5 2 4 ka bp whereas an abrupt drop in stalagmite 18o values from 2 4 to 2 3 ka bp points to increased precipitation intensity thereafter the precipitation gradually decreased until ca 2 1 ka bp with one of the driest events at 2 1 ka bp a century scale increasing trend in the precipitation intensity is observed from 2 1 to 2 0 ka bp following which the precipitation again declined accordingly five sudden drought events are documented centering at 3 4 3 2 3 0 2 5 2 4 and 2 1 ka bp a gradual reduction in precipitation from 3 7 to 3 0 ka bp coincides with reduction and deurbanisation and step wise disintegration of the harappan civilization along the indus ghaggar sarasvati valleys in the foreland areas of northwestern india

interdecadal water mass changes in the southern ocean between 30 e and 160 e interdecadal water mass changes in the indian western pacific sectors of the southern ocean were investigated using the japanese antarctic research expeditions and historical hydrographic observations from the 1950s to 1990s freshening and cooling occurred on the neutral density surfaces of 27 0 kgm3 equatorward of sub antarctic front results for the area south of the polar front show warm and saline anomalies and oxygen decreases on the surfaces around 27 9 kgm3 which correspond to the upper circumpolar deep water these latter anomalies are most simply explained by the mixing of these shallow waters with warmer and fresher surface waters steric sea level has also increased with an average change of 1mmyr1 from the 1970s to 1990s the changes are larger north of the sub antarctic front implying a strengthening of the antarctic circumpolar current it appears that the observed changes are consistent with the results from coupled climate model results for a similar period

the open ocean side of the malvinas current in argo floats and 24 years of mercator ocean high resolution 1 12 physical reanalysis downstream of drake passage the northern branches of the antarctic circumpolar current the polar front and the subantarctic front veer northward and the latter forms the malvinas current mc the mc flows along the continental slope up to 38 s where it loops southward as the malvinas return flow using 24 years of mercator ocean physical reanalysis outputs and argo float data we explore the open ocean side of the mc we observe the occurrence of blocking events at 49 s a region where the mc is exposed to the warm and salty anticyclonic anomalies propagating westward along the steep slope of the malvinas escarpment during these events the mc is cut off from its source and the mc transport is considerably reduced at 49 s the open ocean side of the mc is regularly supplied with cold polar waters from the polar front the polar waters accumulate and recirculate between the mc and the malvinas return flow the water characteristics of the recirculation region change over time the recirculation region hosts significantly lighter and fresher waters during the period 1997 2003 compared with prior and later years the 1997 2003 salinity minimum in the recirculation region corresponds to a period with reduced feeding events at 49 s

mixing and remineralization in waters detrained from the surface into subantarctic mode water and antarctic intermediate water in the southeastern pacific a hydrographic data set collected in the region and season of subantarctic mode water and antarctic intermediate water samw and aaiw formation in the southeastern pacific allows us to estimate the preformed properties of surface water detrained into these water masses from deep mixed layers north of the subantarctic front and antarctic surface water south of the front using 10 measured seawater properties we estimate the fractions of samw aaiw that originate as surface source waters as well as fractions that mix into these water masses from subtropical thermocline water above and upper circumpolar deep water below the subducted samw aaiw ages associated with the detrained surface water and remineralization and dissolution rates and ratios the mixing patterns imply that cabbeling can account for 0 005 0 03 kg m 3 of additional density in aaiw and 0 0 02 kg m 3 in samw we estimate a shallow depth 300 700 m above the aragonite saturation horizon calcium carbonate dissolution rate of 0 4 0 2 mol caco3 kg 1 yr 1 a phosphate remineralization rate of 0 031 0 009 mol p kg 1 yr 1 and remineralization ratios of p n o2 corg of 1 15 5 0 6 143 10 104 22 for samw aaiw our shallow depth calcium carbonate dissolution rate is comparable to previous estimates for our region our o2 p ratio is smaller than many global averages our model suggests neglecting diapycnal mixing of preformed phosphate has likely biased previous estimates of o2 p and corg p high but that the corg p ratio bias may have been counteracted by a second bias in previous studies from neglecting anthropogenic carbon gradients

a region of enhanced northward antarctic intermediate water transport in a coupled climate model abstract a global coupled model is used to examine pathways of freshwater transport in the southern ocean on the background of a strong zonal freshwater transport along the pathway of the antarctic circumpolar current acc there are meridional freshwater flows distributed nonuniformly around the globe including in the upper ocean the analysis does not support a simple two dimensional scheme of antarctic intermediate water aaiw formation according to which the fresh aaiw forms uniformly around the circumpolar ocean rather a more complex three dimensional picture of the freshwater transport in the southern ocean is revealed with enhanced aaiw formation in the southeast pacific ocean both north and south of the drake passage latitudes freshened by intense precipitation and surface waters from around antarctica the acc transports freshwater from the northwest to the southeast toward drake passage there a fraction of this freshwater is transported southward across 60 s with the subsurface acc an

snowfall in coastal west antarctica much greater than previously assumed 1 a new antarctic accumulation distribution based on regional model output calibrated with 1900 in situ observations is used to re assess accumulation in 24 antarctic ice drainage basins when compared to the previous compilation good agreement is found for 19 of the 24 basins representing 93 of the ice sheet that is reasonably well covered with observations in contrast the amundsen sea sector of west antarctica and the western antarctic peninsula both data sparse regions are found to receive 80 96 more accumulation than previously assumed for the pine island and thwaites glaciers west antarctica which have recently undergone rapid acceleration and thinning this means a downward adjustment of their contribution to global sea level rise from 0 24 to 0 14 mm per year model time series do not show a significant change in antarctic accumulation over the period 1980 2004

relation between phosphorus fractions and development of soils from galicia nw spain abstract the relationship between soil development and the distribution of p among its fractions in the surface horizons of native soils in galicia nw spain was studied p forms were determined by sequential fractionations and the fractions were regrouped as slow turnover and rapid turnover organic and inorganic forms in soils developed on siliceous rock an accumulation of slow turnover organic p sonic naoh extractable organic p is accompanied by an increase in rapid turnover inorganic p resin extractable p bicarbonate extractable inorganic p and a decrease in slow turnover inorganic p naoh sonic naoh hcl extractable inorganic p that could be due to destruction of inorganic p adsorbing complex in soils developed on carbonate bearing rock slow turnover organic p declined and rapid turnover organic p bicarbonate naoh extractable organic p increased these trends are explained in terms of soil processes

wind driven export of weddell sea slope water the export of waters from the weddell gyre to lower latitudes is an integral component of the southern subpolar contribution to the three dimensional oceanic circulation here we use more than 20 years of repeat hydrographic data on the continental slope on the northern tip of the antarctic peninsula and 5 years of bottom lander data on the slope at 1000 m to show the intermittent presence of a relatively cold fresh westward flowing current this is often bottom intensified between 600 and 2000 dbar with velocities of over 20 cm s 1 transporting an average of 1 5 1 5 sv by comparison with hydrography on the continental slope within the weddell sea and modeled tracer release experiments we show that this slope current is an extension of the antarctic slope current that has crossed the south scotia ridge west of orkney plateau on monthly to interannual time scales the density of the slope current is negatively correlated r 0 6 with a significance of over 95 with eastward wind stress over the northern weddell sea but lagging it by 6 13 months this relationship holds in both the high temporal resolution bottom lander time series and the 20 year annual hydrographic occupations and agrees with weddell sea export variability observed further east we compare several alternative hypotheses for this wind stress export relationship and find that it is most consistent with wind driven acceleration of the gyre boundary current possibly modulated by eddy dynamics and represents a mechanism by which climatic perturbations can be rapidly transmitted as fluctuations in the supply of intermediate level waters to lower latitudes

control of mode and intermediate water mass properties in drake passage by the amundsen sea low the evolutionof the physical properties of subantarctic mode water samw and antarctic intermediate water aaiw in the drake passage region is examined on time scales down to intraseasonal within the 1969 2009 period both samw and aaiw experience substantial interannual to interdecadal variability significantly linked to the action of the amundsen sea low asl in their formation areas observations suggest that the interdecadal freshening tendency evident in samw over the past three decades has recently abated while aaiw has warmed significantly since the early 2000s the two water masses have also experienced a substantial lightening since the start of the record examination of the mechanisms underpinning water mass property variability shows that samw characteristics are controlled predominantly by a combination of air sea turbulent heat fluxes cross frontal ekman transport of antarctic surface waters and the evaporation precipitation balance in the subantarctic zone of the southeast pacific and drake passage while aaiw properties reflect air sea turbulent heat fluxes and sea ice formation in the bellingshausen sea the recent interdecadal evolution of the asl is consistent with both the dominance of the processes described here and the response of samw and aaiw on that time scale

destruction of potential vorticity by winds the destruction of potential vorticity pv at ocean fronts by wind stress driven frictional forces is examined using pv flux formalism and numerical simulations when a front is forced by downfront winds that is winds blowing in the direction of the frontal jet a nonadvective frictional pv flux that is upward at the sea surface is induced the flux extracts pv out of the ocean leading to the formation of a boundary layer thicker than the ekman layer with nearly zero pv and nonzero stratification the pv reduction is not only active in the ekman layer but is transmitted through the boundary layer via secondary circulations that exchange low pv from the ekman layer with high pv from the pycnocline extraction of pv from the pycnocline by the secondary circulations results in an upward advective pv flux at the base of the boundary layer that scales with the surface nonadvective frictional pv flux and that leads to the deepening of the layer at fronts forced by both downfront winds and a destabilizing atmospheric buoyancy flux f b the critical parameter that determines whether the wind or the buoyancy flux is the dominant cause for pv

the imprint of southern ocean overturning on seasonal water mass variability in drake passage seasonal changes in water mass properties are discussed in thermohaline coordinates from a seasonal climatology and repeat hydrographic sections the sr1b ctd transects along drake passage are used as a case study the amount of water within temperature and salinity classes and changes therein are used to estimate dia thermal and dia haline transformations these transformations are considered in combination with climatologies of surface buoyancy flux to determine the relative contributions of surface buoyancy fluxes and subsurface mixing to changes in the distribution of water in thermohaline coordinates the framework developed provides unique insights into the thermohaline circulation of the water masses that are present within drake passage including the erosion of antarctic winter water aaww during the summer months and the interaction between the circumpolar deep waters cdw and antarctic intermediate water aaiw the results presented are consistent with summertime wind driven inflation of the cdw layer and deflation of the aaiw layer and with new aaiw produced in the winter as a mixture of cdw remnant aaww and surface waters this analysis therefore highlights the role of surface buoyancy fluxes in the southern ocean overturning

changes in antarctic temperature wind and precipitation in response to the antarctic oscillation output of a 14 year integration with a high resolution 55 km 55 km regional atmospheric climate model is used to study the response of antarctic near surface climate to the antarctic oscillation aao the periodical strengthening and weakening of the circumpolar vortex in the southern hemisphere in spite of the relatively short record wind temperature and precipitation show widespread and significant aao related signals when the vortex is strong high aao index northwesterly flow anomalies cause warming over the antarctic peninsula ap and adjacent regions in west antarctica and the weddell sea in contrast cooling occurs in east antarctica the eastern ross ice shelf and parts of marie byrd land most of the annual temperature signal stems from the months march august the spatial distribution of the precipitation response to changes in the aao does not mirror temperature changes but is in first order determined by the direction of flow anomalies with respect to the antarctic topography when the vortex is strong high aao index the western ap becomes wetter while the ross ice shelf parts of west antarctica and the lambert glacier basin east antarctica become drier

links between eastern equatorial pacific stratification and atmospheric co2 rise during the last deglaciation it is difficult to untangle the mixed influences of high and low latitude climate forcing in the eastern equatorial pacific eep here we test the hypothesis that the southern ocean drove change in the eep via subsurface intermediate waters during the last deglaciation we use the 18o signature of benthic foraminifera to reconstruct water density changes during the last 25 kyr at three intermediate water depths 370 m 600 m and 1000 m in the eep carbonate 18o records a combined signature of temperature and salinity and is therefore more closely related to density than temperature or salinity alone we find that benthic foraminiferal 18o values decreased first in the subsurface simultaneously with rising temperatures over antarctica and propagated up to the surface within 3 kyr the early subsurface response initiated a rapid decrease in density stratification over the upper water column as indicated by reduced 18o gradients between surface and intermediate depths stratification of the upper water column remained low through the termination with stratification minima reached during heinrich stadial 1 and the younger dryas yd synchronous with the two part deglacial rise in atmospheric co2 centennial scale shifts toward heavier 18o signatures at 370 and 600 m during the yd indicate short lived shifts in the subantarctic mode water antarctic intermediate water boundary to shallower intermediate depths we suggest that decreased density gradients during the deglaciation accelerated vertical mixing across the eep and potentially the entire south pacific subtropical gyre which enhanced co2 delivery from depth to the surface ocean and atmosphere

water mass conversion fluxes and mixing in the scotia sea diagnosed by an inverse model abstract an inverse box model of the scotia sea is constructed using hydrographic tracer and velocity data collected along the rim of the basin during the antarctic large scale box analysis and the role of the scotia sea albatross cruise the model provides an estimate of the time mean three dimensional circulation as the antarctic circumpolar current acc crosses the region it concurrently solves for geostrophic and wind driven ekman transports across the boundaries of the basin air sea driven diapycnal fluxes and interior diapycnal fluxes below the ocean surface an increase is diagnosed in the acc volume transport from 143 13 sv sv 106 m3 s 1 at drake passage to 149 16 sv on leaving the scotia sea supplied by the import of 5 9 1 7 sv of weddell sea deep water wsdw over the south scotia ridge there is a lateral redistribution of the transport primarily in response to a topographically induced branching of the 70 80 sv polar front pf jet and an increase in the transport associa

decadal freshening of the antarctic bottom water exported from the weddell sea recent decadal changes in southern hemisphere climate have driven strong responses from the cryosphere concurrently there has been a marked freshening of the shelf and bottom waters across a wide sector of the southern ocean hypothesised to be caused by accelerated glacial melt in response to a greater flux of warm waters from the antarctic circumpolar current onto the shelves of west antarctica however the circumpolar pattern of changes has been incomplete no decadal freshening in the deep layers of the atlantic sector had been observed in this study we document a significant freshening of the antarctic bottom water exported from the weddell sea which is the source for the abyssal layer of the atlantic overturning circulation and we trace its possible origin to atmospheric forced changes in the ice shelves and sea ice on the eastern flank of the antarctic peninsula that include an anthropogenic component these findings suggest that the expansive and relatively cool weddell gyre does not insulate the bottom water formation regions in the atlantic sector from the ongoing changes in climatic forcing over the antarctic region

variability of the lower circumpolar deep water in drake passage 1926 2004 lower circumpolar deep water lcdw is an important component of the global overturning circulation as it upwells south of the antarctic circumpolar current acc renewing the ocean interior the lcdw also aids the transport of water properties between the major ocean basins the property variability of the lcdw salinity maximum layer was examined using 37 meridional sections across drake passage between 1926 2004 within the limits of experimental error and high frequency variability the core properties of this layer have remained constant between 1926 2004 a comparison of modern sections and the 1932 discovery ii cruise indicates that this observation may be true for lcdw throughout the southern ocean the significance of this result in terms of the observations of decadal changes in the southern ocean intermediate and mode waters is that these changes are most likely due to contemporary atmospheric forcing and not due to variations in the source water properties

impact of coral spawning on the biogeochemistry of a hawaiian reef abstract we examined the impact of montipora capitata coral spawning on local biogeochemistry in kane ohe bay hawai i this event supplied labile spawn derived organic matter sdom to the water column triggering a cascading series of related effects on the biogeochemistry of the reef specifically we measured the isotopic composition and nutrient ratios of spawning material and coral tissues and utilized these signatures to track pathways of sdom incorporation into this coral dominated ecosystem we observed 1 shifts in the isotopic signatures of coral tissues after the spawning event 2 rapid turnover of sdom within the water column and enhanced deposition of pom to the sediment surface 3 enhanced sediment efflux of nh 4 after the spawning event that triggered a phytoplankton bloom in the overlying water and 4 drawdown of dissolved nutrients in the water column after spawning that coincided with the occurrence of a water column phytoplankton bloom our results show that single species spawning events can serve as a source of substantial nutrient input to the water column contributing in similar ways to storm driven river nutrient input and with measurable impact on the biogeochemistry of the reef

holocene changes in antarctic intermediate water flow strength in the southwest atlantic abstract antarctic intermediate water aaiw is an essential component of the atlantic meridional overturning circulation amoc contributing to balance the southward flow of north atlantic deep water nadw however the role of aaiw in holocene abrupt climate changes remains poorly understood here we reconstruct changes in the flow strength of aaiw based on a high temporal resolution paleocurrent record from the southwest atlantic superimposed on a slight increase in aaiw strength at 7 ka bp a succession of millennial scale aaiw variations is recognized in our paleocurrent records indicating a highly variable intermediate water circulation throughout the holocene although variations in the strength and position of the southern westerlies winds sww are proposed to greatly influence the formation and circulation of aaiw we cannot confirm such a potential sww aaiw linkage since our records of aaiw flow strength do not correlate to holocene shifts of the sww across the atlantic however our data shows a good correspondence with abrupt variations in the amoc with enhanced reduced northward advection of aaiw during periods of reduced enhanced nadw circulation these results provide evidence for a holocene aaiw nadw see saw thus although the exact forcing mechanism remains unresolved we suggest that holocene perturbations in aaiw exerted a significant impact on the amoc

the three dimensional overturning circulation of the southern ocean during the woce era a box inverse model of the southern ocean during the world ocean circulation experiment is constructed to investigate the three dimensional structure of the regional overturning circulation in that era the model has many features in common with various preceding inverse studies but also contains several novel elements that make it well suited for addressing many of the significant uncertainties that surround the circulation at present the net overturning circulation of the southern ocean is found to consist of two well defined cells of similar strength the upper cell consists of a northward transport of 18 8 5 5 sv of surface mode and intermediate waters lighter than the 27 5 kg m 3 isoneutral and an equivalent southward flow in the approximate 27 5 27 9 kg m 3 neutral density range encompassing the bulk of the upper circumpolar deep water the lower cell involves the northward export of 18 6 0 9 sv of antarctic bottom water and lower circumpolar deep water denser than 28 08 kg m 3 and an opposing transport in the lighter classes of that water mass substantial structural differences between the overturning circulations of the atlantic indian and pacific basins are indicated by the model s solution overall the diagnosed southern ocean circulation shares many qualitative and some quantitative features with previous inverse estimates particularly as regards the large scale depth integrated lateral circulation and associated energy fluxes in the subtropics and in the antarctic circumpolar current and the strength of the upper overturning cell however it also suggests several significant adjustments to current views of the regional circulation most notable amongst these are the subpolar circulation of the southern ocean is more vigorous and zonally interconnected than generally thought the associated lower overturning cell is more intense than indicated by most preceding estimates contrary to common perception sub surface mixing processes play a role of comparable importance to air sea ice exchanges of buoyancy in underpinning the dianeutral closure of the southern ocean overturning even at shallow mode and intermediate water levels and the connection between north atlantic deep water formation and southern ocean upwelling is fundamentally three dimensional such that deep waters from the north atlantic must upwell dianeutrally before being returned to the permanent pycnocline of the northern oceans

short term variations of deep water masses in drake passage revealed by a multiparametric analysis of the ant xxiii 3 bottle data short term variations of deep water masses in drake passage revealed by a multiparametric analysis of the ant xxiii 3 bottle data j sudre v garcon c provost n sennechael o huhn and m lacombe doi 10 1016 j dsr2 2011 01 005 a multiparametric analysis is applied on the ant xxiii 3 bottle data to determine the spreading and mixing of water masses across drake passage during january february 2006 focusing our interest on the flow of the deep water masses mixing proportions are quantified along both the southward and northward journeys between the tip of south america and the antarctic peninsula the method is sensitive enough to detect a marked variability in the flow pathways of the circumpolar deep water the southeast pacific deep water spdw and the weddell sea deep water at the intersection of the shackleton fracture zone sfz and the west scotia ridge wsr between the southward and northward journeys indeed the presence of a sharp meander of the southern branch of the polar front pfs together with the displacement of the northern branch of the southern antarctic circumpolar current front saccfn above the complex bathymetric structure of the wsr induced a strong perturbation in the deep flow field during the southward journey the height of the sfz crests clearly sets the lower limit of the spdw in the ona basin an enhanced 3 he signature is confined to the north of the polar front between 55 5 s and 56 5 s in the 1500 2200 m depth range it clearly indicates the signature of the core of the southeast pacific deep slope water the entry pathway in the acc of the spdsw during ant xxiii 3 was farther to the south off the continental slope of south america than it was during the woce a21 expedition in 1990 probably due to the sharp changes in the slope orientation at the extreme tip of the south america

processes controlling upper ocean heat content in drake passage 1 a 16 year record of expendable bathythermograph transects across drake passage is used to examine variability in upper ocean heat content that is not associated with the annual cycle links between upper ocean heat content and anomalous heat fluxes winds two large scale climate indices and mesoscale eddies and meanders are examined results suggest that interannual variations in surface heat fluxes explain 5 to 10 of the variance in upper ocean heat content anomalous surface heat fluxes are linked to meridional wind anomalies upstream of drake passage which in turn are linked to forcing by el nino southern oscillation enso and the southern annular mode sam enso and sam are correlated with upper ocean heat content at near zero lags and statistically significant correlations occur at longer time lags as well the impact of mesoscale eddies and meanders on upper ocean heat content is explored with the use of a tracked eddy database an empirical relationship is constructed relating upper ocean heat content anomalies to eddy length scales and amplitudes eddies and meanders are estimated to account for more than one third of the nonannual cycle variance in drake passage upper ocean heat content

reestablishing the circumpolar wave in sea ice around antarctica from one winter to the next remarkable correlation exists between warm water poleward winds over the ocean and low sea ice concentrations and extents over the winter sea ice pack around antarctica even to the point of continuing paterns across the ice sea boundary since the wind stress associated with poleward wind is expected to compact the ice during sea ice edge retraction we conclude that the memory of the antarctic circumpolar wave in the sea ice pack is carried from one austral winter to the next by the neighboring water temperatures since the sea ice pack retracts nearly to antarctica in austral summer

southwest pacific ocean water mass changes between 1968 69 and 1990 91 abstract water mass changes are estimated in the southwest pacific ocean by comparing a meridional hydrographic section along 170 w between 60 s and the equator occupied in 1968 69 during the southern cross cruise and again in 1990 during a noaa climate and global change cruise another comparison is made using a hydrographic section along 35 s between the date line and 169 w occupied in 1969 during usns eltanin cruise 40 and again in 1991 during a mapkiwi cruise the most robust change consists of cooling and freshening on isopycnals with peak differences exceeding 1 0 c 0 25 pss at the base of the subtropical thermocline the cooling and freshening starts above the stratification minimum of the subantarctic mode water and persists to below the salinity minimum of the antarctic intermediate water amplitudes are largest at 48 s near where these water masses subduct and decay toward 20 s near the axis of the subtropical gyre this change is likely the result of surface warming and or freshening

abrupt changes in high latitude nutrient supply to the atlantic during the last glacial cycle the supply of nutrients to the low latitude thermocline is largely controlled by intermediate depth waters formed at the surface in the high southern latitudes silicic acid is an essential macronutrient for diatoms which are responsible for a significant portion of marine carbon export production changes in ocean circulation such as those observed during the last deglaciation would influence the nutrient composition of the thermocline and therefore the relative abundance of diatoms in the low latitudes here we present the first record of the silicic acid content of the atlantic over the last glacial cycle our results show that at intermediate depths of the south atlantic the silicic acid concentration was the same at the lgm as it is today overprinted by high silicic acid pulses that coincided with abrupt changes in ocean and atmospheric circulation during heinrich stadials and the younger dryas we suggest these pulses were caused by changes in intermediate water formation resulting from shifts in the subpolar hydrological cycle with fundamental implications for the nutrient supply to the atlantic

thermohaline effects of the seasonal sea ice cover in the sea of okhotsk 1 by using a coupled ice ocean model the seasonal extent of the sea ice cover in the sea of okhotsk was examined the model results show that the sea ice at the ice edge is advected southward along sakhalin island with a mean velocity of 0 31m s into ocean water with temperatures above freezing as a result even in mid winter a large amount of ice melting occurs around the edge it results in temperature decrease in the surface mixed water during the 1993 1994 winter the total volume ratio of ice melting to ice production is estimated at 0 76 the negative latent heat flux from the ice melting is nearly comparable to the total atmospheric heat flux around the ice edge furthermore the meltwater supply to the surface layer is estimated to be approximately 3 5 times the annual amur river inflow thus it is concluded that the ice melting around the extending ice edge is a significant factor for the heat and salt balance between the sea ice and the surface mixed layer and plays an important role in the maintenance of the large seasonal sea ice extent in the sea of okhotsk

cadmium isotope variations in the southern ocean abstract cadmium concentrations and isotope compositions were determined for 47 seawater samples from the high nutrient low chlorophyll hnlc zone of the atlantic sector of the southern ocean the samples include 13 surface waters from a transect of the weddell gyre and 3 depth profiles from the weddell sea and drake passage the southern ocean mixed layer samples from this study and abouchami et al 2011 define a clear but broad hnlc trend in a plot of e cd 114 110 versus cd which is primarily a consequence of isotopic fractionation associated with biological uptake e cd 114 110 is the deviation of the 114cd 110cd ratio of a sample from nist srm 3108 cd in parts per 10 000 the trend is especially apparent in comparison to the large range of values shown by a global set of seawater cd data for shallow depths the southern ocean samples are also distinguished by their relatively high cd concentrations typically 0 2 to 0 6 nmol kg and moderately fractionated e cd 114 110 generally between 4 and 8 that reflect the limited biological productivity of this region detailed assessment reveals fine structure within the hnlc trend which may record differences in the biological fractionation factor different scenarios of closed and open system isotope fractionation and or distinct source water compositions southern ocean seawater from depths 1000 m has an average e cd 114 110 of 2 5 0 2 2se n 16 and together with previous results this establishes a relatively constant e cd 114 110 value of 3 0 0 3 2se n 27 for global deep waters significant isotopic variability was observed at intermediate depths in the southern ocean seawater from 200 m to 400 m in weddell sea has high cd concentrations and e cd 114 110 as low as 1 presumably due to remineralization of cd from biomass that records incomplete nutrient utilization antarctic intermediate water which was sampled at 150 to 750 m depth in the drake passage features a distinct cd isotope signature of e cd 114 110 4 which reflects biological isotope fractionation at the surface and subsequent mixing into the ocean interior taken together our results demonstrate that coupled cd isotope and concentration data provide valuable insights into the distribution and biological cycling of cd in the water column the highly systematic nature of cd isotope signatures may furthermore prove to be of utility for future research in marine geochemistry and paleoceanography

long term trends and interannual variability of temperature in drake passage abstract temperature data collected over the last 36 years 1969 2004 in drake passage are used to examine interannual temperature variation and long term trends in the upper ocean to reduce the effect of variation from different sampling locations and temporal variability introduced by meridional shifts in the polar front pf the data were divided into two sub regions north 3800 temperature profiles and south 3400 of the pf temperature anomalies were formed by removing a temporal mean field for each profile in each sub region at 100 m depth intervals from the surface to 700 m north of the pf statistically significant warming trends of 0 02 c yr 1 were observed that were largely depth independent between 100 and 700 m a statistically significant cooling trend of 0 07 c yr 1 was observed at the surface south of the pf which was smaller 0 04 c yr 1 but still statistically significant when possible seasonal sampling biases were accounted for the observed cooling at the surface and warming at depth is largely consistent with a poleward shift of the pf due to enhancement of westerly winds in the southern ocean as recently suggested by models and observations the observed annual temperature anomalies in the upper 400 m north of the pf and in the upper 100 m south of the pf are highly correlated to variability in sea ice and also to climate indices of the antarctic oscillation and the el nino southern oscillation variability in sea ice and temperature anomalies lag el nino variability in the pacific with a phasing consistent with the observed cyclical patterns of sea ice and sea surface temperature associated with the antarctic circumpolar wave or antarctic dipole mode in the southern ocean in contrast the sea ice variability and temperature anomalies at all depths north of the pf and at 0 100 m depth south of the pf were primarily coincident with or led the antarctic oscillation index no significant correlations were found with the large scale climate variability indices in southern drake passage below 100 m depth which is occupied by upper circumpolar deep water ucdw this water mass is not formed locally is largely isolated from the surface and exhibits vertical and lateral homogeneity hence changes may be difficult to detect in the available measurements and climate variation in the source water regions of ucdw may take a long time to reach drake passage

pedogenesis soil mass balance phosphorus dynamics and vegetation communities across a holocene soil chronosequence in a super humid climate south westland new zealand abstract this study quantifies progressive pedogenesis under a super humid climate on the west coast of south island new zealand it focuses on soil morphology pedogenic oxides soil mass balance phosphorus transformation and linking pedogenesis trajectories to vegetation communities the study comprises a set of dune ridges of a coastal sand dune complex covered by unmodified conifer podocarp angiosperm forest the surface ages of the chronosequence range from 370 y to 6500 y rapid podzolisation is characteristic for the study area within 1000 y soils reach the spodosol stage with typical eluvial illuvial horizons and mobilisation of fe and al this period is also characterised by the most rapid losses of total phosphorus at a rate of 110 g m 2 ky 1 a relative loss of 41 beyond 3000 y changes in soil chemistry and losses for all nutrients markedly slow soil mass balance shows that the 6500 y soil has lost 75 total p 62 k 52 ca and 54 na soil p fractions substantially change across the gradient high leaching losses of apatite and non occluded p in the first hundreds of years coincide with accumulation of organic and occluded inorganic forms in the topsoil and subsoil which mitigate total p loss beyond 1000 y of pedogenesis all p fractions decline at similar rates to low more persistent levels with apatite non occluded p being the dominant p form after 6500 y of pedogenesis this incipient steady state is assumed to be sustained by the advection of parent material derived p through surface lowering and reduced biological cycling vegetation communities change from more diverse communities on young and less impoverished soils in the first 1000 y to less diverse and less variable communities beyond 1000 y of ecosystem development the soil evolution correlated vegetation changes documented in this study are consistent with general schemes of vegetation succession for the west coast of south island

some highly weathered soils of puerto rico 3 chemical properties some chemical properties of 11 soils developed in highly weathered regoliths in puerto rico have been recorded particular attention has been given to properties which reflect the extent to which weathering has progressed and to properties which may be most useful for developing valid soil management practices if the pina soil were excluded the saturation extracts of oxisols generally contained less si than the ultisols the saturation extract of pina soil which was 89 quartz sand contained 10 ppm si a value out of keeping with highly weathered soils phosphate solubility was greatest in the pina soil also phosphate adsorption by the puerto rico soils when corrected for dilution by sand was approximately that of highly weathered soils of hawaii north carolina or colombia most of the soils contained more than 4000 kg s ha in the 120 cm profiles the most striking difference between the oxisol and ultisol groups was in extractable aluminum in general these oxisols have been weathered beyond the point where aluminum is readily extracted with a neutral salt the ph at which net charge of the soils was zero was lower than the soil ph usually encountered in the field the soils were poorly buffered at low ph as a group the oxisols contained less exchangeable k than the ultisols in 6 of the 11 soils both calcium and magnesium were 1 meq 100 g in some horizon in most soil samples the balance among exchangeable cations was appropriate for reasonable potassium nutrition even so the quantity of exchangeable nutrient cations was low in most cases mineralization of organic nitrogen tended to stop with nh4 in the acid soils

formation regions of subantarctic mode water detected by ofes and argo profiling floats 1 we investigated the distribution of the deep mixed layer in the southern ocean where subantarctic mode water samw forms by using argo profiling floats and the ocean general circulation model for the earth simulator ofes the mixed layer depth mld generally increased eastward from 50 180 e and from 180 80 w with distinct local maxima near major bathymetric features a sudden transition from deep to shallow mixed layer was found along the equatorward limit of the deep mixed layer this diagnosed mld front coincides with the line of ug s 0 indicating the distributions of the general deepening and local maxima of mld were affected by near surface geostrophic flow the flow is steered by the major bottom topographies and the local mld maxima occurred where the flow direction was deflected southward this implies a link between the bathymetric features and formation of thick samw

parallel decadal variability of inferred water temperatures for northern and southern hemisphere intermediate water masses we use a novel proxy growth rates of long lived deep water fish orange roughy to reconstruct inferred water temperatures of intermediate water masses in both northern and southern hemispheres since the mid 1800s the data are consistent with instrumental records showing long term warming in the northern hemisphere but also indicate decadal variability of intermediate depth temperatures that is coherent across the two hemispheres this variability correlates with the dominant subpolar annular mode in each hemisphere and implies a bihemispheric oceanic response to external forcing that influences the properties of intermediate depth water masses

observed property changes in eastern south pacific antarctic intermediate water 1 we compared potential temperature and salinity of antarctic intermediate water along 32 30 s from the coast of chile to the central south pacific ocean between 2003 and 1992 based on two vertically and horizontally high resolution repeat sections each being 6795 km long the temperature of antarctic intermediate water considering the entire body of the water mass along the section increased by 0 048 c and salinity by 0 002 the increase in salinity could be explained by a slight shift in the evaporation precipitation balance of the south pacific ocean

subantarctic mode water variability influenced by mesoscale eddies south of tasmania 1 subantarctic mode water samw is formed by deep mixing on the equatorward side of the antarctic circumpolar current the subduction and export of samw from the southern ocean play an important role in global heat freshwater carbon and nutrient budgets however the formation process and variability of samw remain poorly understood largely because of a lack of observations to determine the temporal variability of samw in the australian sector of the southern ocean we used a 15 year time series of repeat expendable bathythermograph sections from 1993 to 2007 seven repeat conductivity temperature depth sections from 1991 to 2001 and sea surface height maps the mean temperature of the samw lies between 8 5 c and 9 5 c mean of 8 8 c standard deviation of 0 3 c and there is no evidence of a trend over the 18 year record however the temperature salinity and pycnostad strength of the samw can change abruptly from section to section in addition the samw pool on a single section often consists of two or more modes with distinct temperature salinity and vertical homogeneity characteristics but similar density we show that the multiple types of mode water can be explained by the advection of anomalous water from eddies and meanders of the fronts bounding the subantarctic zone and by recirculation of samw of different ages our results suggest that infrequently repeated sections can potentially produce misleading results because of aliasing of high interannual variability

influence of the southern annular mode on the sea ice ocean system 1 the global sea ice ocean model orca2 lim driven by the ncep ncar national centers for environmental prediction national center for atmospheric research reanalysis daily 2 m air temperatures and 10 m winds and by monthly climatologies for precipitation cloud cover and relative humidity is used to investigate the impact of the southern annular mode sam on the antarctic sea ice ocean system our results suggest that the response of the circumpolar southern ocean consists of an annular and a nonannular component for the sea ice cover the non annular component seems to be the most important the annular component strongly affects the overall patterns of the upper ocean circulation when the sam is in its positive phase a northward surface ekman drift a downwelling at about 45 degreess and an upwelling in the vicinity of the antarctic continent are simulated the non annular component has a significant impact at the regional scale especially in the weddell ross amundsen and bellingshausen seas in those regions the pressure pattern associated with the sam induces meridional winds which advect warmer air in the weddell sea and around the antarctic peninsula and colder air in the amundsen and ross seas this implies a dipole response of sea ice to the sam with on average a decrease in ice area in the weddell sea and around the antarctic peninsula and an increase in the ross and amundsen seas during years with a high sam index the long term trend in the observed sea ice area does not appear to be related to the trend in the sam index

on the interannual variability of ocean temperatures around south georgia southern ocean forcing by el nino southern oscillation and the southern annular mode abstract the ocean around south georgia in the southwest atlantic sector of the southern ocean is highly productive with large stocks of antarctic krill supporting extensive colonies of marine and land based predators the operation of this ecosystem is strongly influenced by physical forcings and the role of the el nino southern oscillation enso phenomenon has been highlighted previously here we examine in detail the transmission of enso signals to south georgia and investigate other sources of interannual variability enso variability generates anomalies in sea surface temperature sst across the south pacific via atmospheric teleconnections these anomalies are advected toward south georgia within the antarctic circumpolar current acc and previous studies have focussed on long period advection order of 2 3 years from the southwest pacific we observe here however that the region close to the antarctic peninsula in the southeast pacific is especially susceptible to enso forcing via anomalous meridional winds this induces sst anomalies that are advected to south georgia on a much more rapid timescale order 5 6 months the phasing of these teleconnections is such that anomalies that reach the southeast pacific from farther west tend to be reinforced here by air sea ice interaction we also find an important role for the southern annular mode sam in determining sst variability at south georgia this is a circumpolar mode of climate variability and thus can readily influence local sst at south georgia directly the sam is however not perfectly zonally symmetric and like enso has a particular impact on meridional winds in the southeast pacific the average timescale for sam influence on south georgia sst is shorter than that of enso since it includes a stronger component of direct local forcing the south georgia ecosystem is not self sustaining with import of krill from breeding and nursery grounds upstream in the acc being important we speculate here that these varying meridional winds close to the antarctic peninsula play a direct role in promoting restricting the injection of shelf waters and the krill therein into the acc following which anomalies in krill density would be advected toward south georgia this offers a dynamical mechanism that might contribute to interannual changes in biological communities at south georgia in addition to existing theories both sam and enso have shown long period changes in recent decades with enso exhibiting a higher preponderance of el nino events compared with la nina events and the sam showing a marked trend toward a higher index state such long period behaviour is likely to induce changes in the south georgia ecosystem via their impacts on advection and sst for which an understanding of the physical mechanisms elucidated here will be key to unravelling

standing and transient eddies in the response of the southern ocean meridional overturning to the southern annular mode abstractto refine the understanding of how the southern ocean responds to recent intensification of the southern annular mode sam a regional ocean model at two eddy permitting resolutions was forced with two synthetic interannual forcings the first forcing corresponds to homogeneously intensified winds while the second concerns their poleward intensification consistent with positive phases of the sam resulting wind driven responses differ greatly between the nearly insensitive antarctic circumpolar current acc and the more sensitive meridional overturning circulation moc as expected eddies mitigate the response of the acc and moc to poleward intensified winds however transient eddies do not necessarily play an increasing role in meridional transport with increasing resolution as winds and resolution increase meridional transport from standing eddies becomes more efficient at balancing wind enhanced overturning these results question the current paradigms on the role of eddies and present

circumpolar response of southern ocean eddy activity to a change in the southern annular mode 1 analysis of satellite altimeter data reveals anomalously high eddy kinetic energy eke in the antarctic circumpolar current acc during the period 2000 2002 around 2 3 years earlier 1998 the circumpolar eastward wind stress as quantified by the southern annular mode sam showed a significant positive peak and we have shown previously that the acc peaked around 1998 in response an eddy resolving ocean model is used to investigate the delay between wind forcing and the eddy response and demonstrates that the lag is due to the time taken to influence the deep circulation of the acc winds over the southern ocean have shown a strong climatic increase over the past few decades if this increase in winds is also reflected as an increase in eddy activity as our analysis suggests it might then the increased poleward heat flux may have played a significant role in the observed warming of the southern ocean citation meredith m p and a m hogg 2006 circumpolar response of southern ocean eddy activity to a change in the southern annular mode geophys res lett 33 l16608 doi 10 1029 2006gl026499

the spatiotemporal structure of diabatic processes governing the evolution of subantarctic mode water in the southern ocean abstracta coupled ice ocean eddy permitting southern ocean state estimate sose for 2008 10 is used to describe and quantify the processes forming and destroying water in the subantarctic mode water samw density range 26 7 27 2 kg m 3 all the terms in the temperature and salinity equations have been diagnosed to obtain a three dimensional and time varying volume budget for individual isopycnal layers this study finds that air sea buoyancy fluxes diapycnal mixing advection and storage are all important to the samw volume budget the formation and destruction of water in the samw density range occurs over a large latitude range because of the seasonal migration of the outcrop window the strongest formation is by wintertime surface ocean heat loss occurring equatorward of the subantarctic front spring and summertime formation occur in the polar gyres through the freshening of water with 27 2 kg m 3 with an important contribution from sea ice melt further buoyancy gain by heating is ac

comparison of subantarctic mode water and antarctic intermediate water formation rates in the south pacific between ncar ccsm4 and observations average formation rates for subantarctic mode water samw and antarctic intermediate water aaiw in the south pacific are calculated from the national center for atmospheric research community climate system model version 4 ncar ccsm4 using chlorofluorocarbon inventories cfc 12 when compared to observations ccsm4 accurately simulates the southeast pacific as the main formation region for samw and aaiw formation rates for samw in ccsm4 are 3 4 sverdrup sv about half of the observational rate due in part to shallow mixed layers a thinner samw layer and insufficient meridional transport a formation rate of 8 1 sv for aaiw in ccsm4 is higher than observations due to higher inventories in the southwest and central pacific and surface concentrations within ccsm4 also a lack of data in the southwest pacific may bias the observational rate low this model observation comparison is useful for understanding the uptake and transport of other gases e g co2 by the model

two repeat crossings of drake passage in austral summer 2006 short term variations and evidence for considerable ventilation of intermediate and deep waters abstract a high resolution full depth hydrographic section across drake passage with tracers and horizontal velocity measurements was repeated within three weeks in austral summer 2006 in situ data temperature salinity dissolved oxygen and horizontal current velocities are used to determine the location of the fronts and eddies of the antarctic circumpolar current acc inferred by barre et al 2011 from 7 day composite dynamic topography maps along the transect frontal displacements are about 40 km 2 stations along the section considerable differences in properties between the two sections are observed throughout the whole water column with values as high as 0 2 c in temperature 0 01 in salinity 0 03 kg m 3 in neutral density and 10 mol kg 1 in dissolved oxygen concentration found below a depth of 3000 m only part of the differences is attributable to frontal or eddy displacements along the section the other part results from the spatial heterogeneity of water properties upstream the section and the funnelling of the flow due to the topographic constraints of the shackleton fracture zone sfz the considerable short term differences in water properties in rather large scale structures that cannot be accounted for by frontal motions along the section call for caution when interpreting differences in hydrographical properties obtained by oceanographic cruises that are years apart in terms of climatic signals the two sections show efficient ventilation of antarctic intermediate water aaiw by winter water ww in the yaghan basin with an estimated eddy enhanced subduction rate of over 170 m year 1 the sfz constitutes a barrier causing the two southern acc fronts saccf branches to separate by about 400 km and creating sheltered conditions in partial isolation from the acc while promoting an active recirculation region in the ona basin this active recirculation marked by cyclonic eddies carrying cold fresh and oxygenated water from south of the southern boundary of the acc causes effective ventilation of the whole circumpolar deep water cdw density range the differences in small scale structures between the two sections deserve further analyses

a station based southern annular mode index from 1884 to 2005 atmospheric pressure observations from the southern hemisphere are used to estimate monthly and annually averaged indexes of the southern annular mode sam back to 1884 this analysis groups all relevant observations in the following four regions one for antarctica and three in the subtropical zone continuous surface pressure observations are available at a number of locations in the subtropical regions since the end of the nineteenth century however year round observations in the subpolar region near the antarctic continent began only during the 1940 60 period the shorter antarctic records seriously compromise the length of a traditionally estimated sam index to improve the situation proxy estimates of antarctic sea level pressure anomalies are provided based on the concept of atmospheric mass conservation poleward of 208s this allows deriving a longer sam index back to 1884 several aspects of the new record its statistical properties seasonal trends and the regional pressure anomaly correlations are presented

soil nutrient dynamics during podzol development under lowland temperate rain forest in new zealand abstract the haast chronosequence on the west coast of the south island of new zealand consists of a series of coastal dune ridges formed by periodic earthquake disturbance over the last 6500 years it approximates an ideal chronosequence because soils are under the same climate and vegetation have similar topography and are developed in the same parent material we assessed soil development and the changes in nutrients at eleven sites along the sequence to determine rates of nutrient transformations and the potential for limitation of biological activity by nitrogen and phosphorus availability soils develop rapidly to podzols spodosols under the super humid climate involving acidification and depletion of base cations in the first few hundred years development of a bleached eluvial horizon under a thick organic horizon within 2000 years and formation of a continuous cemented iron pan within 4000 years soil phosphorus concentrations decline markedly in the first few hundred years in both the organic and upper mineral soil horizons with rapid depletion of primary mineral phosphate and the accumulation of organic phosphorus to 80 of the total phosphorus in the upper mineral soil these changes lead to an increasing degree of phosphorus limitation along the sequence as indicated by an increase in c p and n p ratios and a decline in available phosphate the rates of soil development and phosphorus depletion are more rapid than at the nearby franz josef post glacial chronosequence where glacial moraine derived from graywacke contains a relatively high phosphorus concentration and weathers into fine textured soils the haast chronosequence therefore provides an important additional example of soil development linked to long term depletion of soil phosphorus under a perudic moisture regime