representation of the carbon cycle in box models and gcms 1 solubility pump 1 bacastow 1996 broecker et al 1999 and archer et al 2000 have called attention recently to the fact that box models and general circulation models gcms represent the thermal partitioning of co2 between the warm surface ocean and cold deep ocean in different ways they attribute these differences to mixing and circulation effects in gcms that are not resolved in box models the message that emerges from these studies is that box models have overstated the importance of the ocean s polar regions in the carbon cycle a reduced role for the polar regions has major implications for the mechanisms put forth to explain glacial interglacial changes in atmospheric co2 in parts 1 and 2 of this paper a new analysis of the ocean s carbon pumps is carried out to examine these findings this paper part 1 shows that unresolved mixing and circulation effects in box models are not the main reason for box model gcm differences the main factor is very different kinds of restrictions on gas exchange in polar areas polar outcrops in gcms are much smaller than in box models and they are assumed to be ice covered in an unrealistic way this finding does not support a reduced role for the ocean s polar regions in the cycling of organic carbon the subject taken up in part 2

circulation mixing and production of antarctic bottom water abstract the antarctic source of bottom water to the abyssal layer of the world ocean is examined as well as its large scale flow pattern and ultimate entrainment rate into the deep water above we make use of the available high quality station data in the southern ocean to construct bottom maps of neutral density and mean property maps including chlorofluorocarbon cfc for the abyssal layer underneath a selected neutral density surface the maximum density at the sill depth of drake passage is used to distinguish between the voluminous deep water mass that is a continuous component of the antarctic circumpolar current from the relatively denser bottom water originated along the antarctic continental margins based on water density antarctic bottom water aabw is defined here generically to include all volumes of non circumpolar water of antarctic origin over the shelf regime multiple localized sources of specific aabw types contribute to the abyssal layer of the adjacent antarctic basins characteristics of these dense bottom waters reflect closely those observed on the parent shelf water mass spreading paths of newly formed deep and bottom waters over the slope regime and their subsequent oceanic circulation patterns are analyzed on the basis of global property maps for the aabw layer interior mixing and interbasin exchanges of aabw are deduced from mean characteristic curves following the southern streamline of the antarctic circumpolar current outflow and mixing of aabw from the weddell sea to the argentine basin is depicted using density and cfc distributions of two zonal hydrographic lines recirculation and mixing of deep and bottom waters within the weddell gyre are also detailed using a meridional section along the greenwich meridian the strength of all localized sources of aabw combined is estimated by two independent approaches an estimate of the total production rate of aabw is calculated based on the oceanic cfc budget for the aabw layer offshore of the 2500 m isobath the sum of all downslope inputs of well ventilated bottom water types underneath the top isopycnal must account for the measured cfc content in the bottom layer the resulting total aabw production rate is about 8 sv which is a conservative figure that neglects the loss of cfc bearing waters across the top isopycnal in recent years whereas about 9 5 sv is calculated assuming a well mixed bottom layer making use of their transient nature cfc distributions at the top of the aabw layer indicate that more direct and rapid entrainment of cfc rich bottom waters below occurs over localized areas with relatively strong upwelling rates and enhanced vertical mixing a second more ad hoc but independent oceanic mass budget of the bottom layer is also constructed a typical basin wide rate of deep upwelling of 3 10 7 m s 1 requires 10 sv 1 sv 106 m3 s 1 of newly formed aabw to sink down the slope around antarctica we have also formulated a spatial distribution of deep upwelling on the isopycnal at the top of the aabw it is expressed as a combination of wind topographic and turbulent components which in turn are functions of the isopycnal depth bottom depth and bottom layer thickness this non uniform upwelling field yields about 12 sv of aabw exported across the top isopycnal fortuitously the overall average of upward speed at the top isopycnal 3 7 10 7 m s 1 compares well with previous estimates of deep upwelling in the northern basins a series of likely sites for strong vertical entrainment of aabw are clearly identified in the modeled distribution of deep upwelling consonant with the observed cfc distributions on the top isopycnal altogether regions with relatively high upwelling rates 5 10 7 m s 1 occupy only a quarter of the total areal extent of the top isopycnal but they account for as much as 45 of the total vertical transport

on the linkage between antarctic surface water stratification and global deep water temperature the suggestion is advanced that the remarkably low static stability of antarctic surface waters may arise from a feedback loop involving global deep water temperatures if deep water temperatures are too warm this promotes antarctic convection thereby strengthening the inflow of antarctic bottom water into the ocean interior and cooling the deep ocean if deep waters are too cold this promotes antarctic stratification allowing the deep ocean to warm because of the input of north atlantic deep water a steady state deep water temperature is achieved such that the antarctic surface can barely undergo convection a two box model is used to illustrate this feedback loop in its simplest expression and to develop basic concepts such as the bounds on the operation of this loop the model illustrates the possible dominating influence of antarctic upwelling rate and antarctic freshwater balance on global deep water temperatures

a corollary to the silicic acid leakage hypothesis 1 the silicic acid leakage hypothesis salh attempts to explain part of the large and regular atmospheric co2 changes over the last glacial interglacial cycles it calls for a reduction in the carbonate pump through a growth in diatoms at the expense of coccolithophorids in low latitude surface waters driven by a leakage of high si n waters from the southern ocean recent studies that present low opal accumulation rates from the glacial eastern equatorial pacific have challenged salh in a corollary to salh we argue that the key to salh is the dominance of diatoms over coccolithophorids and this does not depend on the magnitude of diatom production per se in support of our claim we show in a numerical model that atmospheric co2 can be lowered with even a reduced absolute flux of silicic acid leakage provided that si n in the leakage is elevated and that the excess si can be used by diatoms to shift the floral composition in their favor

the interaction of acid mine drainage with a carbonate terrane evidence from the obey river north central tennessee abstract the production of acidic drainage from active or abandoned coal mines is controlled by a complex series of reactions triggered by the oxidation of sulphide minerals limestone is frequently used as a neutralizing agent neutralization occurs both through dissolution of the limestone and exsolution of carbon dioxide from the water demonstration of these processes in a natural system is provided by the east fork of the obey river where acidic mine waters travel through conduits in limestone bedrock for several kilometers application of discharge concentration relationships allows tracking of the evolution of these waters within the karst aquifer several trends are evident virtually all of the iron in the acid mine drainage is precipitated along the flow path within the limestone the h released during this reaction together with the h generated by pyrite oxidation is largely neutralized by both exsolution of co 2 and dissolution of calcite dolomite in the carbonate bedrock releasing calcium and magnesium nevertheless the ph is still sufficiently low that all bicarbonate is converted to carbonic acid leaching of clay minerals by the acid waters releases small amounts of al and si the species cl f and no 3 are more or less inert the sulphate concentration substantially increases during evolution of the acid drainage this seems to be related to an input of sulphate enriched waters that have dissolved gypsum anhydrite as they follow deep flow paths within the limestone calculations of the relative proportions of h removed by reaction with calcite dolomite and co 2 degassing show that the latter is important in acidic waters that have reacted significantly with limestone and can readily lose co 2 to the atmosphere these results indicate that acid neutralization through carbonic acid dissociation in addition to neutralization through dissolution of carbonates is a useful method for the commercial a batement of acid mine drainage

diatom bound 15n 14n new support for enhanced nutrient consumption in the ice age subantarctic 1 diatom bound 15n 14n was used to reconstruct the glacial nutrient status of the subantarctic zone in the southern ocean down core records from both the pacific and indian sectors show 15n of 5 to 6 during the last glacial maximum and a decrease coincident with the glacial termination to values as low as 2 the effect of either diatom assemblage or physiological change on the diatom bound 15n 14n is unknown and cannot yet be ruled out as a possible explanation for the observed change however the consistency between indian and pacific sector records and with other paleoceanographic data suggests that the glacial interglacial difference in diatom bound 15n 14n was driven by higher consumption of nitrate in the subantarctic surface during the last ice age such a change in nutrient consumption may have resulted from atmospheric iron fertilization and or decreased glacial mixed layer depths associated with sea ice melting enhanced nutrient consumption in the glacial subantarctic would have worked to lower the concentration of co2 in the ice age atmosphere it also would have reduced the preformed nutrient content of the low latitude thermocline leading to decreases in low latitude productivity suboxia and denitrification

north atlantic ventilation of southern sourced deep water in the glacial ocean one potential mechanism for lowering atmospheric co2 during glacial times is an increase in the fraction of the global ocean ventilated by the north atlantic which produces deep water with a low concentration of unused nutrients and thus drives the ocean s biological pump to a high efficiency however the data indicate that during glacial times a water mass low in 13c 12c and 14c c occupied the deep atlantic apparently at the expense of north atlantic deep water nadw this water is commonly referred to as southern sourced because of its apparent entry into the atlantic basin from the south prompting the inference that it was ventilated at the southern ocean surface here we propose that this deep atlantic water mass actually included a large fraction of north atlantic ventilated water the chemical characteristics of which were altered by recirculation in the deep southern and indo pacific oceans in an ocean model sensitivity experiment that reduces antarctic bottom water formation and weakens its overturning circulation we find that a much greater fraction of nadw is transported into the southern ocean without contacting the surface and is entrained and mixed into the southern sourced deep water that spreads into the global abyssal ocean thus north atlantic ventilation takes over more of the ocean interior lowering atmospheric co2 and yet the abyssal atlantic is filled from the south with old water low in 13c 12c and 14c c consistent with glacial data

sea ice switch mechanism and glacial interglacial co2 variations 1 a physical mechanism is proposed for the glacial interglacial variations in the rate of vertical mixing and in sea ice cover in the southern ocean such variations were postulated without an explanation by toggweiler 1999 and stephens and keeling 2000 who used them to explain the glacial interglacial co2 variations in the physical mechanism explored here initially given by gildor and tziperman 2001b changes in the stratification of the southern ocean due to the cooling of north atlantic deep water nadw during glacial maxima reduce the rate of vertical mixing of the surface water with the deep water the changed temperature of the nadw arriving to the southern ocean and the reduced vertical mixing there also increase the southern ocean sea ice cover during glacial maxima these vertical mixing and sea ice cover changes are shown to be a natural result of the sea ice switch mechanism of the glacial cycles a box model of the climate system is used to demonstrate the above physical mechanism and its effect on the atmospheric co2 because of the uncertainties in the exact dependence of the vertical mixing on vertical stratification it is impossible to quantify the exact separate contribution of reduced vertical mixing and larger sea ice cover to the glacial co2 variations the co2 variations are not essential to the existence of the glacial cycles in the sea ice switch mechanism yet they are shown to amplify the glacial interglacial variability consistent with the view of the role of co2 deduced from proxy observations

geochemistry of rare earth elements in a neutral mine drainage environment anjir tangeh northern iran abstract this study investigates the geochemical characteristics of rare earth elements and yttrium ree y in the neutral mine drainage nmd and river water in the vicinity of the anjir tangeh coal washing plant mazandaran province northern iran the nmd water had a neutral ph along with high sulphate and bicarbonate concentrations the total concentrations of ree in the nmd water were lower than in the river water according to the north american shale composite nasc normalised concentrations the patterns of nmd showed heavy ree hree enrichment while the river water represented middle ree mree enhancement both negative europium eu and positive gadolinium gd anomalies were observed in the drainage and river water within the study area the sum of ree concentration increased gradually downstream of the discharging point of the plant reject water in contrast to decreasing of al fe mn and cu pb zn concentrations the river sediment with high fe concentrations was enriched with lanthanum la and cerium ce the overall ree pattern of the nmd approximates those of coal except for the depletion in light ree lree and the enrichment of eu dominant inorganic ree species in the river water included ln co3 2 and lnco3 while lnco3 ln co3 2 and ln so4 were the main complexes in the nmd the saturation index indicated that al and fe were both oversaturated in the drainage and river water which can control the fractionation of ree by the sorption process according to both hierarchical cluster analysis hca and principal component analysis pca ph al and p were the significant parameters in the ree distribution

quantitative interpretation of atmospheric carbon records over the last glacial termination 1 the glacial interglacial rise in atmospheric pco2 is one of the best known changes in paleoclimate research yet the cause for it is still unknown forcing the coupled ocean atmosphere biosphere box model of the global carbon cycle bicycle with proxy data over the last glacial termination we are able to quantitatively reproduce transient variations in pco2 and its isotopic signatures 13c 14c observed in natural climate archives the sensitivity of the box model of the isotopic carbon cycle bicycle to high or low latitudinal changes is comparable to other multibox models or more complex ocean carbon cycle models respectively the processes considered here ranked by their contribution to the glacial interglacial rise in pco2 in decreasing order are the rise in southern ocean vertical mixing rates 30 ppmv decreases in alkalinity and carbon inventories 30 ppmv the reduction of the biological pump 20 ppmv the rise in ocean temperatures 15 20 ppmv the resumption of ocean circulation 15 20 ppmv and coral reef growth 5 ppmv the regrowth of the terrestrial biosphere sea level rise and the increase in gas exchange through reduced sea ice cover operate in the opposite direction decreasing pco2 during termination i by 30 ppmv according to our model the sequence of events during termination i might have been the following a reduction of aeolian iron fertilization in the southern ocean together with a breakdown in southern ocean stratification the latter caused by rapid sea ice retreat trigger the onset of the pco2 increase after these events the reduced north atlantic deep water nadw formation during the heinrich 1 event and the subsequent resumption of ocean circulation at the beginning of the bolling allerod warm interval are the main processes determining the atmospheric carbon records in the subsequent time period of termination i we further deduce that a complete shutdown of the nadw formation during the younger dryas was very unlikely changes in ocean temperature and the terrestrial carbon storage are the dominant processes explaining atmospheric 13c after the bolling allerod warm interval

representation of the carbon cycle in box models and gcms 2 organic pump 1 box models of the ocean atmosphere co 2 system rely on mechanisms at polar outcrops to alter the strength of the ocean s organic carbon pump gcm based carbon system models are reportedly less sensitive to the same processes here we separate the carbon pumps in a three box model and the gcm based princeton ocean biogeochemistry model to show how the organic pumps operate in the two kinds of models the organic pumps are found to be quite different in two respects deep water in the three box model is relatively well equilibrated with respect to the pco 2 of the atmosphere while deep water in the gcm tends to be poorly equilibrated this makes the organic pump inherently stronger in the gcm than in the three box model the second difference has to do with the role of polar nutrient utilization the organic pump in the gcm is shown to have natural upper and lower limits that are set by the initial po 4 concentrations in the deep water formed in the north atlantic and southern ocean the strength of the organic pump can swing between these limits in response to changes in deep water formation that alter the mix of northern and southern deep water thus unlike the situation in the three box model the organic pump in the gcm can become weaker or stronger without changes in polar nutrient utilization

tectonic setting of the bela ophiolites southern pakistan abstract the bela ophiolites consist of a 3 5 km thick sequence of basaltic pillow lava inter flow sedimentary rocks chert argillite limestone and diabase gabbro sills debris of serpentinite up to kilometer sized blocks serpentinite carbonate breccia and less commonly of basalt gabbro peridotite pelagic limestone and their metamorphic equivalents occur throughout the ophiolite sequence and may form extensive horizons the age of the ophiolites as indicated by pelagic microfauna is aptian early maestrichtian the lava flows belong to a spilite keratophyre basaltic andesite suite of tholeiites enriched in fe tio 2 and other trace elements the lava flows although similar to the e type morb differ in details such as la ta ratio ranges 9 62 18 04 for the bela lavas versus 10 15 for the morb the diabase gabbro sills are similar to the associated lava flows however due to their relative enrichment in certain elements e g fe ti hf th and ta etc they may represent more fractionated late melts a comparison of the stratigraphic and structural features of the bela ophiolites with modern oceanic environments reveals that these ophiolites probably originated in a large oceanic fracture zone leaky transform this is based on lithotectonic features such as the common occurrence of debris of foliated serpentinite and serpentinite carbonate breccia bearing rocks in the ophiolite sequence and on geodynamic considerations the fracture zone ancestral to the bela ophiolites probably acted as a boundary between the indian and the neo tethys plates during the cretaceous analogous to the present day owen fracture zone which separates the indian and the arabian plates this ancestral fracture zone was destroyed when transform movement gave way to oblique convergence culminating in the ophiolite obduction in paleocene early eocene time the ophiolite obduction on the west indian continental margin was preceded by alkaline wpb type volcanism which is represented by the porali basalts the bibai lavas and the deccan basalts

air sea disequilibrium of carbon dioxide enhances the biological carbon sequestration in the southern ocean 1 sinking and subduction of organic material removes carbon from the surface ocean and stores it in inorganic form after remineralization the wind driven upwelling of deep waters notably in the southern ocean counteracts the biological carbon sequestration by returning excess carbon from the abyss potentially releasing it back to the atmosphere numerical models have shown that significant fraction of the excess carbon in the antarctic surface water is not degassed to the atmosphere but reenters into the deep ocean due to the incomplete air sea equilibration effectively increasing the efficiency of biological carbon storage in the deep ocean we develop a simple theory to consider the controls on this effect the theory predicts a strong coupling between biological carbon sequestration and air sea disequilibrium expressed as a linear relationship between the biological carbon pump and the degree of supersaturation in the deep ocean sensitivity experiments with a three dimensional ocean biogeochemistry model support this prediction and demonstrate that the disequilibrium pump almost doubles the efficiency of biological carbon sequestration relative to the effect of nutrient utilization

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

constraining ventilation during deepwater formation using deep ocean measurements of the dissolved gas ratios 40ar 36ar n2 ar and kr ar equilibrium saturation and for d 40 ar a value of 1 188 0 055 relative to air these data are used to constrain high latitude ventilation processes in the framework of three box and seven box ocean models for the three box model tracer data we constrain the appropriate surface area of the high latitude region in both models to be 3 6 2 5 1 7 of ocean surface area and the bubble air injection rate to be 22 7 8 8 7 3 mol air m 2 yr 1 results for the seven box model were similar with a high latitude area of 3 3 2 2 1 3 our results provide geochemical support for suggestions that the effective area of high latitude ventilation is much smaller than the region of elevated preformed nutrients and demonstrate that noble gases strongly constrain the ocean solubility pump reducinghigh latitude surfaceareaweakens theco2solubility pumpintheboxmodels and limits communication between the atmosphere and deep ocean these tracers should be usefulconstraintsonhigh latitudeventilationandthestrengthofthesolubilitypumpinmore complex ocean general circulation models

deep pacific ventilation ages during the last deglaciation evaluating the influence of diffusive mixing and source region reservoir age enhanced ventilation of the deep ocean during the last deglaciation may have caused the rise in atmospheric carbon dioxide that drove earth s climate from a glacial to interglacial state recent results based on the projection age method however suggest the ventilation rate of the deep pacific slowed during the deglaciation opposite the expected pattern lund et al 2011 because the projection age method does not account for tracer diffusion adkins and boyle 1997 it can yield spurious results and therefore requires validation with alternative techniques here ventilation ages are determined using the transit time equilibration time distribution ttd etd method which explicitly accounts for diffusive mixing in the ocean interior devries and primeau 2010 the overall time history of deep pacific ttd etd and projection ages is very similar both show a 1000 yr increase in ventilation age during heinrich stadial 1 hs1 14 5 17 5 kyr bp and a 500 yr increase during the younger dryas yd the similarity is due in part to the use of projection age error estimates that take into account uncertainty in both calendar age and benthic 14c age centennial scale offsets between the ttd etd and projection ages are due primarily to the different approaches used to estimate surface ocean radiocarbon content both the ttd etd and projection age results imply that the ventilation rate of the deep pacific decreased during the deglaciation opposite the pattern expected if southern ocean upwelling and enhanced meridional overturning drove outgassing of co2 from the abyss variations in surface water reservoir age could cause an apparent shift in deep pacific ventilation age but existing proxy records from the southern ocean appear to be inconsistent with such a driver

india eurasia collision chronology has implications for crustal shortening and driving mechanism of plates the motion of the indian plate is determined in an absolute frame of reference and compared with the position of the southern margin of eurasia deduced from palaeomagnetic data in tibet the 2 600 900 km of continental crust shortening observed is shown to have occurred in three different episodes subduction of continental crust intracontinental thrusting and internal deformation and lateral extrusion the detailed chronology of the collision and plate reorganizations in the indian and pacific oceans supports the hypothesis that slab pull is a dominant driving mechanism of plate tectonics

climate evolution at the last deglaciation the role of the southern ocean abstract two sediment sequences recovered close to and south of the present polar front 50 53 s in the atlantic sector of the southern ocean were analysed in order to evaluate the environmental evolution of the southern ocean surface over the last deglaciation and the holocene our reconstruction is based on radiocarbon dated records of diatom based sea surface temperature and sea ice proxies and planktic foraminiferal stable isotopes the onset of the deglacial warming and gradual southward retreat of the winter sea ice field between 18 and 17 cal kyr bp occurrence of a thermal reversal centered at ca 13 cal kyr bp antarctic cold reversal or acr and early holocene occurrence of the climatic optimum well correlate with climatic reconstructions available from the indian southern ocean and from antarctic ice cores time correspondence of southern ocean warming and heinrich event 1 in the north atlantic is compatible with the transmission of the climate signal from the northern to the southern hemisphere through the bipolar seesaw our data support modeling results suggesting that the northern hemisphere bolling warming and turn on of the north atlantic deep water formation are triggered by gradual warming and sea ice retreat in the southern ocean meltwater shedding into the southern ocean associated with the acr may maintain northern hemisphere warming during the allerod the development of sea surface warming and sea ice retreat is compatible with a southern ocean control on the atmospheric co2 increase during the deglaciation during the early holocene 9 7 cal kyr bp our southern core records renewed surface ocean cooling and northward readvance of the winter sea ice field such early holocene cooling is common to cores from the high latitude atlantic sector and might be brought about by expansion of the weddell gyre circulation at that time

the wind driven subtropical gyres and the solubility pump of co2 1 using a suite of abiotic ocean atmosphere carbon cycle models we demonstrate that the representation of the ventilated thermocline leads to a significant enhancement of the sensitivity of atmospheric pco2 to subtropical surface ocean properties in particular we study an idealized sector ocean circulation and abiotic carbon cycle model with a coupled atmospheric reservoir and examine the solubility pump of co2 in the subtropical oceans we compare solutions for atmospheric pco2 when driven only by buoyancy forces to those with both buoyancy and wind stress forcing introducing the wind stress leads to the formation of a subtropical gyre and the warm lens of the ventilated thermocline this lens is depleted in carbon relative to the surrounding waters since its properties are inherited from the warm subtropical surface ocean it is undersaturated in carbon since subduction quickly follows the strong cooling in the western boundary current before equilibration with the overlying atmosphere can occur plausible wind stress patterns increase atmospheric pco2 relative to the case without wind forcing and double the sensitivity of atmospheric pco2 to perturbations of the low latitude surface carbon system properties we suggest that it is the resolution of the ventilated thermocline in global three dimensional ocean circulation models that enhances their sensitivity of atmospheric pco2 to warm surface water properties relative to highly idealized box models

the sequence of events surrounding termination ii and their implications for the cause of glacial interglacial co2 changes events surrounding termination ii as preserved in the vostok ice core provide a number of clues about the mechanisms controlling glacial to interglacial climate change antarctic temperature and the atmosphere s co2 content increased together over a period of 8000 years this increase is bounded by a drop in dust flux at its onset and by a drop in the 18o of trapped air at its finish a similar lag between dust flux and foraminiferal 18o is seen in a southern ocean marine record suggesting that the 18o in air trapped in vostok ice is a valid proxy for ice volume the synchronous change of atmospheric co2 and southern hemisphere temperature thus preceded the melting of the northern hemisphere ice sheets this observation coupled with the fact that nutrient reorganization in the north atlantic occurs with or after the sea level rise eliminates many scenarios proposed to explain the co2 rise including those which rely on sea level change conveyor related nutrient redistribution or north atlantic cooling southern ocean scenarios become the front runners but the most popular mechanism iron fertilization has two problems in explaining the co2 rise before termination ii first much of the dust demise occurs prior to the change in co2 so if iron is the villain a threshold value of its supply must be called upon above which productivity does not continue to increase second the co2 rise continues for some 4 5 kyr after the dust flux has fallen to close to zero these problems may be solved if the increased iron supply in dust caused higher rates of nitrogen fixation during the glacial periods in this case the residence time of oceanic nitrate of a few thousand years would enable decreasing productivity to be a global rather than a local phenomenon and would explain the slow rampup of atmospheric co2

biotic and geochemical evidence for a global latitudinal shift in ocean biogeochemistry and export productivity during the late pliocene during the late pliocene 3 to 2 5 ma oceanic records of opal and c37 alkenone accumulation from around the world show a secular shift towards lower values in the high latitudes and higher values in the low and mid latitudes these shifts are broadly coincident with the intensification of northern hemisphere glaciation and are suggestive of changes in export productivity with potential implications for pliocene atmospheric carbon dioxide concentrations the interpretation of a global latitudinal shift in productivity however requires testing because of the potential uncertainties associated with site to site comparisons of records that can be influenced by highly nonlinear processes associated with production export and preservation here we assess the inferred pliocene latitudinal productivity shift interpretation by presenting new records of c37 alkenone accumulation from ocean drilling program odp site 982 in the north atlantic and biotic assemblages calcareous nannoplankton from this site and odp site 846 in the eastern tropical pacific our results corroborate the interpretation of c37 alkenone accumulation as a proxy for gross export productivity at these sites indicating that large scale productivity decreases at high latitudes and increases at tropical sites are recorded robustly we conclude that the intensification of northern hemisphere glaciation during the late pliocene was associated with a profound reorganisation of ocean biogeochemistry

origin of the 100 000 year timescale in antarctic temperatures and atmospheric co2 1 a new mechanism is proposed to explain the 100 000 year timescale for variations in antarctic temperatures and atmospheric co2 over the last 650 000 years it starts with fluctuations in the oceanic overturning around antarctica that release co2 up to the atmosphere or trap it in the deep ocean every 50 000 years one of these fluctuations coincides with a changeover in the burial of caco3 in the deep ocean the changeover alters the atmospheric pco2 in a way that augments the tendency of the overturning the augmented overturning then enhances the tendency of the caco3 burial which augments the overturning etc in this way an individual random fluctuation becomes one of the big transitions seen in the antarctic ice cores alternating transitions toward the warm and cold states every 50 000 years produce the 100 000 year timescale the 50 000 year time interval is set by the turnover time for co3 ions in the ocean with respect to the co2 induced weathering of silicate rocks and the burial of caco3 on the seafloor

awesome ocim a simple flexible and powerful tool for modeling elemental cycling in the oceans abstract here we present a new flexible modeling tool for simulating the distribution of tracers in the modern ocean a working environment for simulating ocean movement and elemental cycling within an ocean circulation inverse model the awesome ocim is a transport matrix model tmm which is specifically designed to be easy accessible and intuitive even for scientists without prior modeling experience the awesome ocim comes with a variety of selectable biogeochemical functions including sources atmospheric dust hydrothermal vents and seafloor nepheloid layers internal cycling processes biological uptake remineralization and scavenging and sinks radioactive decay and burial of particles in the sediments a wide variety of elements can be simulated through different combinations of this suite of processes we anticipate that the awesome ocim will be a valuable tool for interpreting transect data from ocean surveys particularly the trace elements and isotopes distributions mapped by the ongoing geotraces program this manuscript provides an introduction to the philosophical mathematical and functional basis of the awesome ocim

a review of indian phanerozoic palaeomagnetism implications for the india asia collision abstract an overview is presented of the indian apparent polar wander path apwp for the phanerozoic and in particular for post late palaeozoic times this apwp is compiled on basis of data available at october 1981 from peninsular and extrapeninsular indo pakistan and from dsdp cores from the indian plate one of the more important and newly recognized features of this apwp is a large scale triassic jurassic loop this loop indicates a changeover from a late palaeozoic early mesozoic northwards and counter clockwise rotational movement with greater india reaching moderately low southern latitudes into a southwards and clockwise rotational movement during the early to middle jurassic recognizable likewise in apwp s from other gondwana continents this loop reflects the opening of the neotethys studies of extrapeninsular regions up to and north of the indus tsangpo suture zone have shown wide spread presence of magnetic overprints which delineate two regionally confined age groups younger overprints 20 40 m y predominate in the more external thrust zones older overprints 50 60 m y in contrast are found in the more internal zones both north and south of the indus tsangpo suture zone the latter are interpreted to reflect a late phase of relaxation in the early tertiary collision of greater india with south central asia or off shore island arcs which occurred at equatorial to low northern palaeolatitudes 0 10 n subsequent northwards movement over 2500 3000 km or more and impingement of greater india into southern asia resulted into large scale underthrusting of greater india along the main central thrust beneath southern tibet and to clockwise rotation of thrust units in the western himalaya a discrepancy between indian palaeomagnetic data and results available todate from southern tibet is discussed

deep and bottom water of the weddell sea s western rim oceanographic observations from the ice station weddell 1 show that the western rim of the weddell gyre contributes to weddell sea bottom water a thin 300 meters highly oxygenated benthic layer is composed of a low salinity type of bottom water overlying a high salinity component this complex layering disappears near 66 s because of vertical mixing and further inflow from the continental margin the bottom water flowing out of the western rim is a blend of the two types additionally the data show that a narrow band of warmer weddell deep water hugged the continental margin as it flowed into the western rim providing the continental margin with the salt required for bottom water production

subarctic pacific evidence for a glacial deepening of the oceanic respired carbon pool abstract measurements of benthic foraminiferal cadmium calcium cd ca have indicated that the glacial interglacial change in deep north pacific phosphate po4 concentration was minimal which has been taken by some workers as a sign that the biological pump did not store more carbon in the deep glacial ocean here we present sedimentary redox sensitive trace metal records from ocean drilling program odp site 882 nw subarctic pacific water depth 3244 m to make inferences about changes in deep north pacific oxygenation and thus respired carbon storage over the past 150 000 yr these observations are complemented with biogenic barium and opal measurements as indicators for past organic carbon export to separate the influences of deep water oxygen concentration and sedimentary organic carbon respiration on the redox state of the sediment our results suggest that the deep subarctic pacific water mass was depleted in oxygen during glacial maxima though it was not anoxic we reconcile our results with the existing benthic foraminiferal cd ca by invoking a decrease in the fraction of the deep ocean nutrient inventory that was preformed rather than remineralized this change would have corresponded to an increase in the deep pacific storage of respired carbon which would have lowered atmospheric carbon dioxide co2 by sequestering co2 away from the atmosphere and by increasing ocean alkalinity through a transient dissolution event in the deep sea the magnitude of change in preformed nutrients suggested by the north pacific data would have accounted for a majority of the observed decrease in glacial atmospheric pco2

observational constraints on the causes of holocene co2 change the mechanisms that controlled past atmospheric co2 levels are not directly measurable hence many proxy data sources are combined when reconstructing past carbon cycling the accuracy of holocene modeling reconstructions is checked by seeking consistency between data based observables and their numerically simulated counterparts a new framework is presented to evaluate which combinations of observables can best constrain carbon cycle mechanisms with the minimum of uncertainty we show that when previous studies have combined ocean temperatures ocean co32 and the 13c of atmospheric co2 as observables uncertainties in the data sources are amplified by over 2 orders of magnitude when reconstructing the mechanisms responsible for co2 increase however incorporating mean 13c of ocean dic since 8000 years ago as an additional data source reduces the uncertainties by more than a factor of 5 making this observable a priority for future research our analysis indicates that the 20 ppm increase in co2 between 8000 years bp and preindustrial was caused by significant caco3 precipitation and a reduction in the ocean soft tissue pump meanwhile an increase in terrestrial carbon storage opposed the co2 increase the methods presented here are useful for investigating a range of paleoclimate events

response of air sea carbon fluxes and climate to orbital forcing changes in the community climate system model 1 a global general circulation model coupled to an ocean ecosystem model is used to quantify the response of carbon fluxes and climate to changes in orbital forcing compared to the present day simulation the simulation with the earth s orbital parameters from 115 000 years ago features significantly cooler northern high latitudes but only moderately cooler southern high latitudes this asymmetry is explained by a 30 reduction of the strength of the atlantic meridional overturning circulation that is caused by an increased arctic sea ice export and a resulting freshening of the north atlantic the strong northern high latitude cooling and the direct insolation induced tropical warming lead to global shifts in precipitation and winds to the order of 10 20 these climate shifts lead to regional differences in air sea carbon fluxes of the same order however the differences in global net air sea carbon fluxes are small which is due to several effects two of which stand out first colder sea surface temperature leads to a more effective solubility pump but also to increased sea ice concentration which blocks air sea exchange and second the weakening of southern ocean winds that is predicted by some idealized studies occurs only in part of the basin and is compensated by stronger winds in other parts

the δ13c in benthic foraminiferal tests of fontbotia wuellerstorfi schwager relative to the δ13c of dissolved inorganic carbon in southern ocean deep water implications for glacial ocean circulation models on a transect between 20 and 70 s in the eastern atlantic ocean and weddell sea water samples from 19 hydrographic stations and bottom water from 55 surface sediment samples taken with a multiple corer were investigated for the stable carbon isotopic composition of the total dissolved inorganic carbon 13c co2 these measurements were compared to 13c values determined on live specimens of the benthic foraminifer fontbotia wuellerstorfi and closely related genera from the same stations in addition at 16 stations the stable carbon isotope composition of sedimentary organic carbon was measured general deepwater and bottom water mass circulation patterns as inferred from the 13c co2 are in close agreement with those known from other nonconservative tracers very low 13c values of upper circumpolar deep water 0 3 pee dee belemnite pdb in the polar front region and the eastern limb of the weddell gyre coincide with nutrient maxima however a significant decoupling of the dissolved phosphate signal from the 13c co2 signal is indicated in the abyssal weddell sea we attribute this to temperature dependent fractionation processes during gas exchange of surface waters with the atmosphere at sites of bottom water formation multiple corer water from the sediment water interface is slightly 13c depleted relative to deepwater and bottom water 13 co2 the surface sediment organic carbon 13c is 3 to 4 lower south of the polar front than north of it and the 13corg in freshly accumulated phytodetritus is 3 to 4 lower than surface sediment organic carbon 13c comparison of live f wuellerstorfi 13c and related genera with bottom water 13c co2 exhibits at most stations between the subtropical front 41 s and the southern boundary of the antarctic circumpolar current 55 s a significant lowering of foraminiferal 13c values compilation of a mean last glacial interglacial 13c amplitude 13c from six published southern ocean cores results in a shift of 0 99 0 13 pdb this shift is greater than that in all other regions however all of these cores are from positions close to recent oceanic fronts thus for these peripheral areas of the southern ocean we suggest about half of the glacial interglacial shift can be explained by varying frontal zone positions and widths accompanied by a change in mode and height of export production

age of initiation of collision between india and asia a review of stratigraphic data abstract the collision of india with asia is perhaps the most profound tectonic event to have occurred in past 100 ma it is responsible for the uplift of the himalayas and tibetan plateau and has been argued to have been responsible for geological geochemical and climatological consequences of global extent yet the age of initiation of this collision remains poorly constrained the literature is replete with estimates that range from the late cretaceous 65 ma to latest eocene

decoupling of δ13cσco 2 and phosphate in recent weddell sea deep and bottom water implications for glacial southern ocean paleoceanography

performance of a second order moments advection scheme in an ocean general circulation model 1 the reliability of ocean general circulation models ogcms strongly depends on the quality of their tracer advection schemes for the sake of simplicity and computing time tracer advection schemes most commonly used in large scale ogcms tend to be low order schemes which suffer from spurious numerical diffusion and dispersion that result in distorted solutions the application of high order schemes would reduce numerical errors but at a considerable cost in terms of computing time an alternative to the use of high order methods is the implementation of algorithms that take into account the sub grid distribution of tracers one such method is the second order moments som scheme of prather 1986 which is more accurate than a fourth order scheme but at the time consumption of a second order algorithm this article presents results from coarse resolution global ocean simulations with very low explicit diapycnal mixing in which active and passive tracers were advected with the som method we compare the performance of the method with that of more traditional schemes namely the fct flux corrected transport and quicker quadratic upstream interpolation for convective kinematics schemes in general the use of the som method significantly improves tracer distributions and transports compared to fct and quicker thus leading to a better representation of ocean currents notably boundary currents and frontal systems while model simulations employing the fct and quicker schemes recreate a global overturning circulation with strong upwelling occurring in low latitudes the som simulations admit a circulation pattern closer to that known as the reconfigured conveyor belt toggweiler and samuels 1993 in which the bulk of the global ocean upwelling occurs in the southern ocean

environmental impact of the abandoned coal mines on the surface water and the groundwater quality in the south of bochum germany surface water and groundwater samples were collected from 20 locations situated in the vicinity of the abandoned coal mine fields south of bochum the main objective of this research is to assess the environmental impacts of these mines on the surface water and groundwater quality as well as to determine the factors controlling these impacts the water samples were collected from stream sources groundwater surface water and engineered channels during april 2011 physicochemical parameters were measured during fieldwork water samples were analysed for major ions and aluminium iron manganese ferrous iron zinc and hydrogen sulphide the hydrochemistry of the surface water and the groundwater of this area is characterized by near neutral to alkaline conditions represented by predominance of calcium bicarbonate and sometimes calcium sulphate water types hence the surface water and the groundwater quality in this region is significantly affected by abandoned coal mines these effects resulted from oxidation of iron disulphide minerals that release iron sulphate and hydrogen the presence of carbonate rich materials which contained within the landfilling materials has led the releasing of calcium magnesium and bicarbonate these materials could be the main source responsible for raising the alkalinity of the affected water the environmental hazard of the abandoned coal mines in this area is related to the high concentration of fe especially in the groundwater that possess the highest fe concentration compared to other water sources the fe is 18 times larger than the allowed value in drinking water significant spatial variations of the water pollution were noted in this study for this reason the environmental hazards of the abandoned coal mines in germany should be considered at closure of coal mines in the near future otherwise these mines will be sources of environmental threats unless all necessary measures are taken to reduce their impact