factors affecting the magnetic susceptibility of baked rocks above a burned coal seam abstract magnetic susceptibility was determined for ninety nine mixed sandstone siltstone and shale samples collected above a burned coal seam near kemmerer wyoming magnetite is the predominant ferrimagnetic mineral present magnetic susceptibility of unbaked sedimentary rocks from this location is quite low o 2 10 5 atm in contrast the massive siltstones with low permeabilities have larger magnetic susceptibilities because the oxidizing gases do not penetrate the rocks large magnetic susceptibilities were also recorded along the edges of the burns and in vents used by escaping volatiles and were probably caused by reduction of hematite during the final stages of combustion in response to a decrease in the oxygen fugacity

responses of ocean circulation and carbon cycle to changes in the position of the southern hemisphere westerlies at last glacial maximum 1 we explore the impact of a latitudinal shift in the westerly wind belt over the southern ocean on the atlantic meridional overturning circulation amoc and on the carbon cycle for last glacial maximum background conditions using a state of the art ocean general circulation model we find that a southward northward shift in the westerly winds leads to an intensification weakening of no more than 10 of the amoc this response of the ocean physics to shifting winds agrees with other studies starting from preindustrial background climate but the responsible processes are different in our setup changes in amoc seemed to be more pulled by upwelling in the south than pushed by downwelling in the north opposite to what previous studies with different background climate are suggesting the net effects of the changes in ocean circulation lead to a rise in atmospheric pco2 of less than 10 atm for both northward and southward shift in the winds for northward shifted winds the zone of upwelling of carbon and nutrient rich waters in the southern ocean is expanded leading to more co2outgassing to the atmosphere but also to an enhanced biological pump in the subpolar region for southward shifted winds the upwelling region contracts around antarctica leading to less nutrient export northward and thus a weakening of the biological pump these model results do not support the idea that shifts in the westerly wind belt play a dominant role in coupling atmospheric co2 rise and antarctic temperature during deglaciation suggested by the ice core data

a model data comparison of δ13c in the glacial atlantic ocean 1 we compare a compilation of 220 sediment core 13c data from the glacial atlantic ocean with three dimensional ocean circulation simulations including a marine carbon cycle model the carbon cycle model employs circulation fields which were derived from previous climate simulations all sediment data have been thoroughly quality controlled focusing on epibenthic foraminiferal species such as cibicidoides wuellerstorfi or planulina ariminensis to improve the comparability of model and sediment core carbon isotopes the model captures the general 13c pattern indicated by present day water column data and late holocene sediment cores but underestimates intermediate and deep water values in the south atlantic the best agreement with glacial reconstructions is obtained for a model scenario with an altered freshwater balance in the southern ocean that mimics enhanced northward sea ice export and melting away from the zone of sea ice production this results in a shoaled and weakened north atlantic deep water flow and intensified antarctic bottom water export hence confirming previous reconstructions from paleoproxy records moreover the modeled abyssal ocean is very cold and very saline which is in line with other proxy data evidence

application of an inverse method to interpret 231pa 230th observations from marine sediments constraints then sediment 231 pa 230 th data for each time interval are combined with an advection scavenging model in order to determine their in consistency with the modern circulation estimate we find that the majority of sediment 231 pa 230 th data for the holocene lgm or h1 can be brought into consistency with the modern circulation if plausible assumptions are made about the large scale distribution of 231 pa and about model uncertainties moreover the adjustments in the data needed to reach compatibility with a hypothetical state of no flow no advection are positively biased for each time interval suggesting that the 231 pa 230 th data including that for h1 are more consistent with a persistence of some circulation than with no circulation our study does not imply that earlier claims of a circulation change during the lgm or h1 are inaccurate but that these claims cannot be given a rigorous basis given the current uncertainties involved in the analysis of the 231 pa 230 th data

the southern westerlies during the last glacial maximum in pmip2 simulations the southern hemisphere westerly winds are an important component of the climate system at hemispheric and global scales variations in their intensity and latitudinal position through an ice age cycle have been proposed as important drivers of global climate change due to their influence on deep ocean circulation and changes in atmospheric co2 the position intensity and associated climatology of the southern westerlies during the last glacial maximum lgm however is still poorly understood from empirical and modelling standpoints here we analyse the behaviour of the southern westerlies during the lgm using four coupled ocean atmosphere simulations carried out by the palaeoclimate modelling intercomparison project phase 2 pmip2 we analysed the atmospheric circulation by direct inspection of the winds and by using a cyclone tracking software to indicate storm tracks the models suggest that changes were most significant during winter and over the pacific ocean for this season and region three out four models indicate decreased wind intensities at the near surface as well as in the upper troposphere although the lgm atmosphere is colder and the equator to pole surface temperature gradient generally increases the tropospheric temperature gradients actually decrease explaining the weaker circulation we evaluated the atmospheric influence on the southern ocean by examining the effect of wind stress on the ekman pumping again three of the models indicate decreased upwelling in a latitudinal band over the southern ocean all models indicate a drier lgm than at present with a clear decrease in precipitation south of 40 s over the oceans we identify important differences in precipitation anomalies over the land masses at regional scale including a drier climate over new zealand and wetter over nw patagonia

atlantic meridional overturning circulation during the last glacial maximum the circulation of the deep atlantic ocean during the height of the last ice age appears to have been quite different from today we review observations implying that atlantic meridional overturning circulation during the last glacial maximum was neither extremely sluggish nor an enhanced version of present day circulation the distribution of the decay products of uranium in sediments is consistent with a residence time for deep waters in the atlantic only slightly greater than today however evidence from multiple water mass tracers supports a different distribution of deep water properties including density which is dynamically linked to circulation

physical and biological regulation of the soft tissue carbon pump 1 we examine the relationship between aeolian iron deposition ocean circulation and atmospheric co2 in the context of a global ocean circulation and biogeochemistry model with a coupled atmospheric reservoir of co2 in common with previous models we find only a small reduction of atmospheric pco2 in response to an enhanced aeolian iron source consistent with last glacial maximum conditions we show this to be due to a combination of limiting factors including control of deep ocean iron concentrations by complexation to an organic ligand regional compensation in changes to export production and the maintenance of high preformed nutrient concentrations in deep water formation regions we also demonstrate a significant sensitivity of atmospheric pco2 to changes in the residual mean overturning circulation of the southern ocean dominated by its regulation of the accumulation of biogenic carbon in the deep ocean although it is not enough to explain the full drawdown of pco2 to glacial levels a reduction in overturning can lead to significant reduction in atmospheric pco2 providing mechanistic basis for the control by vertical mixing inferred from box models

climate and marine carbon cycle response to changes in the strength of the southern hemispheric westerlies 1 it has been previously suggested that changes in the strength and position of the southern hemisphere westerlies could be a key contributor to glacial interglacial atmospheric co2 variations to test this hypothesis we perform a series of sensitivity experiments using an earth system model of intermediate complexity a strengthening of the climatological mean surface winds over the southern ocean induces stronger upwelling and increases the formation of antarctic bottom water enhanced ekman pumping brings more dissolved inorganic carbon dic rich waters to the surface however the stronger upwelling also supplies more nutrients to the surface thereby enhancing marine export production in the southern hemisphere and decreasing the dic content in the euphotic zone the net response is a small atmospheric co2 increase 5 ppmv compared to the full glacial interglacial co2 amplitude of 90 ppmv roughly the opposite results are obtained for a weakening of the southern hemisphere westerly winds

the cooling rate effect on microwave archeointensity estimates 1 new microwave mw paleointensity data on historical bricks from northeast brazil presented a bias toward higher fields when compared to previous cooling rate corrected double heating paleointensity estimates the same relates to the previously reported values for pottery from southwestern pacific islands a simple theoretical approach suggests that the mw bias in both collections is due to a cooling rate effect on mw estimates we then experimentally corrected the mw cooling rate effect on brazilian fragments increasing the degree of consistency between the previous and new results reducing discrepancies from 25 to 8 results indicate similar experimental behavior between microwave and thermal procedures despite the different ways in which the energy is transferred into the spin system finally they allow cooling times of less than 90 s to be empirically estimated in most of these mw experiments highlighting the need for systematic cooling rate corrections to be applied in similar mw paleointensity studies in the future

the dependence of southern ocean meridional overturning on wind stress an eddy resolving numerical model of a zonal flow meant to resemble the antarctic circumpolar current is described andanalyzedusing the framework of j marshallandt radko in additionto windand buoyancy forcing at the surface the model contains a sponge layer at the northern boundary that permits a residual meridional overturning circulation moc to exist at depth the strength of the residual moc is diagnosed for different strengths of surface wind stress it is found that the eddy circulation largely compensates for the changes in ekman circulation the extent of the compensation and thus the sensitivity of the moc to the winds depend on the surface boundary condition a fixed heat flux surface boundary severely limits the ability of the moc to change an interactive heat flux leads to greater sensitivity to explain the moc sensitivity to the wind strength under the interactive heat flux transformed eulerian mean theory is applied in which the eddy diffusivity plays a central role in determining the eddy response a scaling theory for the eddy diffusivity based on the mechanical energy balance is developed and tested the average magnitude of the diffusivity is found to be proportional to the square root of the wind stress the moc sensitivity to the winds based on this scaling is compared with the true sensitivity diagnosed from the experiments

eddy saturation of equilibrated circumpolar currents abstractthis study uses a sector configuration of an ocean general circulation model to examine the sensitivity of circumpolar transport and meridional overturning to changes in southern ocean wind stress and global diapycnal mixing at eddy permitting and finer resolution the sensitivity of circumpolar transport to forcing magnitude is drastically reduced at sufficiently high resolution there is little or no sensitivity of circumpolar transport to wind stress even in the limit of no wind in contrast the meridional overturning circulation continues to vary with southern ocean wind stress but with reduced sensitivity in the limit of high wind stress both the circumpolar transport and meridional overturning continue to vary with diapycnal diffusivity at all model resolutions the circumpolar transport becomes less sensitive to changes in diapycnal diffusivity at higher resolution although sensitivity always remains in contrast the overturning circulation is more sensitive to change in diapycnal

connecting antarctic sea ice to deep ocean circulation in modern and glacial climate simulations antarctic sea ice formation plays a key role in shaping the abyssal overturning circulation and stratification in all ocean basins by driving surface buoyancy loss through the associated brine rejection changes in antarctic sea ice have therefore been suggested as drivers of major glacial interglacial ocean circulation rearrangements here the relationship between antarctic sea ice buoyancy loss deep ocean stratification and overturning circulation is investigated in last glacial maximum and preindustrial simulations from the paleoclimate modelling intercomparison project pmip the simulations show substantial inter model differences in their representation of the glacial deep ocean state and circulation which is often at odds with the geological evidence we argue that these apparent inconsistencies can largely be attributed to differing and likely insufficient antarctic sea ice formation discrepancies can be further amplified by short integration times deep ocean equilibration and sea ice representation should therefore be carefully evaluated in the forthcoming pmip4 simulations

on the abyssal circulation in the glacial atlantic an inverse method is used to evaluate the information contained in sediment data for the atlantic basin during the last glacial maximum defined here as the time interval 18 21 kyr before present the data being considered are an updated compilation of the isotopic ratios 18 o 16 o 18 o and 13 c 12 c 13 c of fossil shells of benthic foraminifera bottom dwelling organisms first an estimate of the abyssal circulation in the modern atlantic is obtained which is consistent with i climatologies of temperature and salinity of the world ocean circulation experiment ii observational estimates of volume transport at specific locations and iii the statements of a finite difference geostrophic model second estimates of water properties 18 o of equilibrium calcite or 18 oc and 13 c of dissolved inorganic carbon or 13 cdic derived from sediment data are combined with this circulation estimate to test their consistency with the modern flow it is found that more than approximately 80 of water property estimates 18 oc or 13 cdic are compatible with the modern flow given their uncertainties the consistency of glacial 13 cdic estimates with the modern flow could be rejected after two assumptions are made i the uncertainty in these estimates is 0 1 this uncertainty includes errors in sediment core chronology and oceanic representativity of benthic 13 c which alone appears better than this value on average and ii 13 cdic in the glacial deep atlantic was dominated by a balance between water advection and organic c remineralization measurements of 13 c on benthic foraminifera are clearly useful but the current uncertainties in the distribution and budget of 13 cdic in the glacial atlantic must be reduced to increase the power of the test

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

comparison of methods to estimate the rate of co2 emissions and coal consumption from a coal fire near durango co abstract subsurface fires in coal beds consume coal resources and contribute to the global emissions of co2 and air pollutants many of these fires are found in china india indonesia and the united states combustion product gases at these coal fires exit through surface fissures that form over fires these fissures are created when subsurface subsidence causes preexisting fractures in the area to widen fissures act as both inlets for air and exhaust for combustion gases while remote sensing approaches have been used to quantify the rate of coal consumption and co2 emissions at large scale fires that extend over large distances methods for estimating the coal consumption and co2 emissions values based on surface observations are less well established in this paper a coal fire near durango co is described a combination of fissure mapping thermocouple temperatures and a cesium vapor magnetometer survey was used to delineate the aerial extent of the current combustion zone and previously burned zones three methods were then used to estimate combustion rates at an active region at the site in the first method time lapse high resolution topographic surveys were used to relate surface volumetric losses over the active region to coal consumption and rates of co2 emission in the second method measured temperatures gas compositions and dimensions of an exhaust fissure were used in a simple natural convection chimney model to estimate rate values the third method estimated coal consumption and co2 emission rates by measuring the velocity of exhaust gases gas compositions and exhaust fissure dimensions for the second and third methods 13c isotope signatures were used to determine the fractions of co2 that were emitted from coal and ch4 combustion or from co2 in the native gas in the coal seam a flux accumulation chamber was also used to quantify co2 leakage rates from non fissured regions over an active fire region the three methods produced roughly consistent estimates of coal combustion and co2 emission rates

estimated strength of the atlantic overturning circulation during the last deglaciation the atlantic meridional overturning circulation affects the latitudinal distribution of heat and is a key component of the climate system proxy reconstructions based on sedimentary 231 pa 230 th ratios and the difference between surface and deep water radiocarbon ages indicate that during the last glacial period the overturning circulation was reduced during millennial scale periods of cooling 1 5 however much debate exists over the robustness of these proxies 6 8 here we combine proxy reconstructions of sea surface and air temperatures and a global climate model to quantitatively estimate changes in the strength of the atlantic meridional overturning circulation during the last glacial period we find that relative to the last glacial maximum the overturning circulation was reduced by approximately 14 sv during the cold heinrich event 1 during the younger dryas cold event the overturning circulation was reduced by approximately 12 sv relative to the preceding warm interval these changes are consistent with qualitative estimates of the overturning circulation from sedimentary 231 pa 230 th ratios in addition we find that the strength of the overturning circulation during the last glacial maximum and the holocene epoch are indistinguishable within the uncertainty of the reconstruction the atlantic meridional overturning circulation amoc is an important feature of the earth s climate system it is characterized by northward flowing water masses at the surface ocean deepwater formation in the north atlantic and southward flowing water masses in the intermediate to deep ocean this overturning cell is complemented by an underlying generally weaker reversed overturning cell that originates in the southern ocean in the following we use amoc to refer only to the upper overturning cell owing to the large heat capacity of water the northwardflowing near surface waters contribute effectively to the heat transport from the tropics to the mid and high latitudes and therefore affect the regional climate around the north atlantic 9 10 hence changes of the amoc strength can substantially influence climate in the north especially in europe the depth of the southward flowing waters and the strength of the circulation have changed in the past during the last glacial period abrupt warming events of several degrees within a few decades followed by slower cooling were detected in greenland ice cores 11 as effects of the so called dansgaardoeschger events were found far beyond the greenland ice sheet 1214 with patterns reminiscent of varying inter hemispheric heat distribution 15 16 they are believed to be the result of rapid changes of the amoc strength 17 other examples of a reduction or even a complete shutdown of the

evaluating southern ocean sea ice for the last glacial maximum and pre industrial climates pmip 2 models and data evidence sea ice is recognized as an important factor controlling climate conditions at high latitudes it has a major impact in controlling the ocean to atmosphere exchanges e g for co2 as well as surface oceanic conditions and deep water formation in the high latitude oceans being at the interface of two major components of the climate system sea ice is useful to evaluate and intercompare different climate models we here analyze the results of eight coupled climate models from which seven are from the pmip 2 database against available reconstructions for winter and summer sea ice extent around antarctica to evaluate the ability of models in representing different climate states we compare their results for both the pre industrial and the last glacial maximum lgm we find that models generally have identical seasonal ranges for the two climate states analyzed which is not supported by data inferences indeed data indicate that the lgm seasonality was enhanced compared to the pre industrial the shape of the sea ice distribution is also different in models circular around the antarctic continent and in reconstructions oval shaped distribution similar to modern sea ice distribution we show that models underestimating the sea ice extent for the pre industrial are also underestimating the last glacial maximum extent our results thus point to difficulties for climate models in representing the sea ice dynamics in the southern ocean

carbon isotope constraints on the deglacial co2 rise from ice cores the stable carbon isotope ratio of atmospheric co2 13catm is a key parameter in deciphering past carbon cycle changes here we present 13catm data for the past 24 000 years derived from three independent records from two antarctic ice cores we conclude that a pronounced 0 3 per mil decrease in 13catm during the early deglaciation can be best explained by upwelling of old carbon enriched waters in the southern ocean later in the deglaciation regrowth of the terrestrial biosphere changes in sea surface temperature and ocean circulation governed the 13catm evolution during the last glacial maximum 13catm and atmospheric co2 concentration were essentially constant which suggests that the carbon cycle was in dynamic equilibrium and that the net transfer of carbon to the deep ocean had occurred before then

strength and geometry of the glacial atlantic meridional overturning circulation during the last glacial maximum the pattern of atlantic meridional overturning circulation was different from today a combination of sediment chemistry and a scavenging model suggests that the glacial circulation was shallower and at least as vigorous as today

last glacial maximum and holocene climate in ccsm3 abstract the climate sensitivity of the community climate system model version 3 ccsm3 is studied for two past climate forcings the last glacial maximum lgm and the mid holocene the lgm approximately 21 000 yr ago is a glacial period with large changes in the greenhouse gases sea level and ice sheets the mid holocene approximately 6000 yr ago occurred during the current interglacial with primary changes in the seasonal solar irradiance the lgm ccsm3 simulation has a global cooling of 4 5 c compared to preindustrial pi conditions with amplification of this cooling at high latitudes and over the continental ice sheets present at lgm tropical sea surface temperature sst cools by 1 7 c and tropical land temperature cools by 2 6 c on average simulations with the ccsm3 slab ocean model suggest that about half of the global cooling is explained by the reduced lgm concentration of atmospheric co2 50 of present day concentrations there is an increase in the antarctic circumpolar current an

can paleoceanographic tracers constrain meridional circulation rates abstract the ability of paleoceanographic tracers to constrain rates of transport is examined using an inverse method to combine idealized observations with a geostrophic model considered are the spatial distribution accuracy and types of tracers required to constrain changes in meridional transport within an idealized single hemisphere basin measurements of density and radioactive tracers each act to constrain rates of transport conservative tracers while not of themselves able to inform regarding rates of transport improve constraints when coupled with density or radioactive observations it is found that the tracer data would require an accuracy one order of magnitude better than is presently available for paleo observations to conclusively rule out factor of 2 changes in meridional transport even when assumed available over the entire model domain when data are available only at the margins and bottom of the model radiocarbon is unable to constrain transport while density remains effective o

southern hemisphere westerly wind changes during the last glacial maximum model data comparison the southern hemisphere sh westerly winds are thought to be critical to global ocean circulation productivity and carbon storage for example an equatorward shift in the winds though its affect on the southern ocean circulation has been suggested as the leading cause for the reduction in atmospheric co2 during the last glacial period despite the importance of the winds it is currently not clear from observations or model results how they behave during the last glacial here an atmospheric modelling study is performed to help determine likely changes in the sh westerly winds during the last glacial maximum lgm using lgm boundary conditions the maximum in sh westerlies is strengthened by 1 m s 1 and moved southward by 2 at the 850 hpa pressure level boundary layer stabilisation effects over equatorward extended lgm sea ice can lead to a small apparent equatorward shift in the wind band at the surface further sensitivity analysis with individual boundary condition changes indicate that changes in sea surface temperatures are the strongest factor behind the wind change the hadam3 atmospheric simulations along with published pmip2 coupled climate model simulations are then assessed against the newly synthesised database of moisture observations for the lgm although the moisture data is the most commonly cited evidence in support of a large equatorward shift in the sh winds during the lgm none of the models that produce realistic lgm precipitation changes show such a large equatorward shift in fact the model which best simulates the moisture proxy data is the hadam3 lgm simulation which shows a small poleward wind shift while we cannot prove here that a large equatorward shift would not be able to reproduce the moisture data as well we show that the moisture proxies do not provide an observational evidence base for it

large inert carbon pool in the terrestrial biosphere during the last glacial maximum during each of the late pleistocene glacial interglacial transitions atmospheric carbon dioxide concentrations rose by almost 100 ppm the sources of this carbon are unclear and efforts to identify them are hampered by uncertainties in the magnitude of carbon reservoirs and fluxes under glacial conditions here we use oxygen isotope measurements from air trapped in ice cores and ocean carbon cycle modelling to estimate terrestrial and oceanic gross primary productivity during the last glacial maximum we find that the rate of gross terrestrial primary production during the last glacial maximum was about 40 10 pg c yr 1 half that of the pre industrial holocene despite the low levels of photosynthesis we estimate that the late glacial terrestrial biosphere contained only 330 pg less carbon than pre industrial levels we infer that the area covered by carbon rich but unproductive biomes such as tundra and cold steppes was significantly larger during the last glacial maximum consistent with palaeoecological data our data also indicate the presence of an inert carbon pool of 2 300 pg c about 700 pg larger than the inert carbon locked in permafrost today we suggest that the disappearance of this carbon pool at the end of the last glacial maximum may have contributed to the deglacial rise in atmospheric carbon dioxide concentrations

how important are southern hemisphere wind changes for low glacial carbon dioxide a model study 1 the response of atmospheric co2 to modifications in the strength and position of southern hemisphere westerlies is examined with the bern3d ocean model the model responds more sensitively to changes in the wind amplitude than to variations in latitudinal position depending on the model setup a 50 reduction in wind strength leads to a co2 drawdown of 3 34 ppm while a 50 increase results in a rise of 10 24 ppm a poleward shift of 5 lowers co2 by 2 16 ppm whereas an equatorward shift of 5 induces a co2 increase of 2 14 ppm physical and biological mechanisms equally contribute to the modeled changes in atmospheric co2 our results are in conflict with the hypothesis that southern hemisphere wind changes are responsible for the low atmospheric co2 concentrations during glacial periods

distinct modes of internal variability in the global meridional overturning circulation associated with the southern hemisphere westerly winds the internal variability of the global meridional overturning circulation gmoc in long term integration of the earth system model community earth system models cosmos is examined in this study two distinct modes of the gmoc which are closely linked to the southern hemisphere westerly winds sww anomalies are found to vary on multidecadaland centennial time scales the dominantmode is characterized by southern ocean dynamics strengthening and poleward shift of the sww associated with a positive phase of the southern annular mode yield ekman induced northward mass transport including a zonally asymmetric response in the southern ocean sea surface temperature and a cooling in the tropical pacific ocean due to large scale upwelling the second mode projects mainly onto the atlantic meridional overturning circulation amoc it is driven by a combination of sww variation and buoyancy forcing based on the relationship between the two modes together with the wind perturbation experiments the authors emphasize that the full amoc response to the sww change takes several centuries in their model the sea surface temperature in northern hemisphere high latitudes is significantly affected in this mode showing a largescale warming their results from a mid holocene experiment imply that both modes are independent from the climate background conditions in the holocene finally the authors argue that the natural modes of gmoc are important to understand trends in ocean circulation with consequences for heat and carbon budgets for past present and future climate

oxidatively and thermally altered high volatile bituminous coals in high temperature coal fire zone no 8 of the wuda coalfield north china abstract coal fires have received increasing attention due to their environmental economic and social impacts their significant influence on coal properties is widely documented by geophysical and geochemical methods the present paper demonstrates by means of coal petrological methods significant changes of microstructure optical appearance and optical properties of medium rank bituminous coals affected by an underground coal fire the studied changes are suggested to result from distinct oxidative and thermal alterations induced by a high temperature regime temperatures over 800 c encountered in the coal fire zone no 8 wuda coalfield the investigated coal seam no 9 represents a high volatile a bituminous coal and is dominated by vitrinite followed by inertinite with minor amounts of liptinite the microstructure of the coal fire affected coals facilitate a broad spectrum of characteristic features the microscopic analyses revealed development of 1 non tectonic fissures and non tectonic fractures 2 distinct micropores 3 dark oxidations rims and 4 bright spots interpreted as incipient mesophases optical properties were characterised for megasporinite and vitrinite in the examined megasporinite a noticeable anisotropy and distinct granular appearance was observed in the investigated coals both a dominant increase as well as a minor decrease in both random and maximum vitrinite reflectances were documented for 1 coal grains and 2 dark rimmed vitrinite at non tectonic fissures and non tectonic fractures in addition also a characteristic bimodal vitrinite population was measured the increase in bireflectance was clearly documented for two sub zones within the coal fire zone no 8 the applied kilby s cross plots suggested a large overlapping of the data sets of r max and r min indicating marked changes in vitrinite structure the applied coal petrological approach revealed distinct changes to the coal s microstructure appearance as well as to optical properties induced by the underground coal fire the presented coal petrographic approach may help determine the extent of coal fires in coal mines and the direction of propagation of coal fire front

particle swarm optimization inversion of self potential data for depth estimation of coal fires over east basuria colliery jharia coalfield india coal fires pose a serious threat to the environment and it is important to detect them at an early stage for their control and hazard mitigation the present study addresses an innovative approach for depth estimation of coal fires using self potential sp method and its inversion through particle swarm optimization pso technique the suitability of pso inversion technique for self potential data has been established using synthetic models of spherical and cylindrical objects and inclined sheet with large horizontal extent as causative sources present study reveals that the geometry of subsurface coal combustion is possibly similar to inclined sheet with relatively large horizontal extension the depth of coal fires has been estimated using pso inversion of sp anomaly data over the east basuria colliery jharia coal field jharkhand india with good accuracy the results of the analysis are compared with borehole lithologic log data which proves efficacy of the pso inversion technique

last glacial maximum ocean thermohaline circulation pmip2 model intercomparisons and data constraints the ocean thermohaline circulation is important for transports of heat and the carbon cycle we present results from pmip2 coupled atmosphere ocean simulations with four climate models that are also being used for future assessments these models give very different glacial thermohaline circulations even with comparable circulations for present an integrated approach using results from these simulations for last glacial maximum lgm with proxies of the state of the glacial surface and deep atlantic supports the interpretation from nutrient tracers that the boundary between north atlantic deep water and antarctic bottom water was much shallower during this period there is less constraint from this integrated reconstruction regarding the strength of the lgm north atlantic overturning circulation although together they suggest that it was neither appreciably stronger nor weaker than modern two model simulations identify a role for sea ice in both hemispheres in driving the ocean response to glacial forcing

what sets the mean transport through drake passage twelve experiments with two coarse resolutions of a global ocean model using a variety of surface forcings are analyzed to address the question of what sets the mean transport through drake passage seven of the experiments do not have an active sea ice model but the remaining five do previous theories have suggested that the drake passage transport is governed by the cape horn sverdrup transport or alternatively is proportional to the square root of the meridional ekman transport at the latitude of drake passage the results presented here do not support either of these theories the drake passage transport depends quite strongly on the isopycnal diffusivity parameter in the model and less strongly on the background vertical diffusivity and horizontal viscosity parameters however when the magnitudes of these parameters are fixed the results show a very strong correlation between drake passage transport and both the strength of the meridional ekman transport at the latitude of drake passage and the thermohaline circulation off the antarctic shelf the relationships are monotonic but not linear the best estimate is that the meridional ekman transport drives 100 sv of drake passage transport while the remaining 30 sv are driven by the global thermohaline circulation

competition between ocean carbon pumps in simulations with varying southern hemisphere westerly wind forcing we analyse the impact of migration and strength of southern hemisphere westerly winds on the ocean carbon cycle in a systematic sensitivity study with the university of victoria earth system climate model we find that changes in the biological pump are mainly driven by changes in ocean residence times while changes in export production are negligible changes in the biological and physical pumps are always of opposite sign with the physical pump being dominant for southward shifts and the biological pump being dominant for northward shifts furthermore changes in the pacific ocean carbon budget dictate the overall changes in global marine and atmospheric carbon overall atmospheric hbox co 2 increases and delta 14 hbox c decreases for northward shifts or a strengthening in wind forcing the opposite is true for a southward shift or a weakening in wind forcing combining forcings shift and intensity change results in a combination of their impacts with the direction of the shift being the first order forcing the terrestrial carbon reservoir absorbs releases 50 70 of the net oceanic carbon loss increase counterbalancing the effect on atmospheric hbox co 2

lowering of glacial atmospheric co2 in response to changes in oceanic circulation and marine biogeochemistry 1 we use an earth system model of intermediate complexity climber 2 to investigate what recent improvements in the representation of the physics and biology of the glacial ocean imply for the atmospheric concentration the coupled atmosphere ocean model under the glacial boundary conditions is able to reproduce the deep salty stagnant water mass inferred from antarctic deep pore water data and the changing temperature of the entire deep ocean when carbonate compensation is included in the model we find a co2 drawdown of 43 ppmv associated mainly with the shoaling of the atlantic thermohaline circulation and an increased fraction of water masses of southern origin in the deep atlantic fertilizing the atlantic and indian sectors of the southern ocean north of the polar front leads to a further drawdown of 37 ppmv other changes to the glacial carbon cycle include a decrease in the amount of carbon stored in the terrestrial biosphere 540 pg c which increases atmospheric co2 by 15 ppmv and a change in ocean salinity resulting from a drop in sea level which elevates co2 by another 12 ppmv a decrease in shallow water caco3 deposition draws down co2 by 12 ppmv in total the model is able to explain more than two thirds 65 ppmv of the glacial to interglacial co2 change based only on mechanisms that are clearly documented in the proxy data a good match between simulated and reconstructed distribution of 13c changes in the deep atlantic suggests that the model captures the mechanisms of reorganization of biogeochemistry in the atlantic ocean reasonably well additional poorly constrained mechanisms to explain the rest of the observed drawdown include changes in the organic carbon caco3 ratio of sediment rain reaching the seafloor iron fertilization in the subantarctic pacific ocean and changes in terrestrial weathering

magnetometer measurements to characterize a subsurface coal fire underground coal fires pose a threat to the environment and the health of those living in their proximity and can result in economic losses if these fires occur at mining areas design of methods to extinguish these fires requires that the extent of the subsurface fire be delineated a conceptual picture of the workings of a subsurface coal fire near durango co is presented first which shows how the overburden above the burning coal seam can become heated in high temperature and low o2 conditions the heating of the overburden leads to the formation of magnetite and its presence and the alignment of magnetic moments can be detected by a magnetometer magnetometer surveys allow high resolution areal mapping that differentiates among previously burned currently burning and unburned coal seam areas the current and previous locations of the subsurface fire regions that are delineated by the magnetometer survey conducted at a fire on the southern ute indian reservation are consistent with various supporting data such as gas composition temperature and snowmelt data

the role of southern ocean processes in orbital and millennial co2 variations a synthesis abstract recent progress in the reconstruction of atmospheric co 2 records from antarctic ice cores has allowed for the documentation of natural co 2 variations on orbital time scales over the last up to 800 000 years and for the resolution of millennial co 2 variations during the last glacial cycle in unprecedented detail this has shown that atmospheric co 2 varied within natural bounds of approximately 170 300 ppmv but never reached recent co 2 concentrations caused by anthropogenic co 2 emissions in addition the natural atmospheric co 2 concentrations show an extraordinary correlation with southern ocean climate changes pointing to a significant direct or indirect influence of climatic and environmental changes in the southern ocean region on atmospheric co 2 concentrations here we compile recent ice core and marine sediment records of atmospheric co 2 temperature and environmental changes in the southern ocean region as well as carbon cycle model experiments in order to quantify the effect of potential southern ocean processes on atmospheric co 2 related to these orbital and millennial changes this shows that physical and biological changes in the so are able to explain substantial parts of the glacial interglacial co 2 change but that none of the single processes is able to explain this change by itself in particular changes in the southern ocean related to changes in the surface buoyancy flux which in return is controlled by the waxing and waning of sea ice may favorably explain the high correlation of co 2 and antarctic temperature on orbital and millennial time scales in contrast the changes of the position and strength of the westerly wind field were most likely too small to explain the observed changes in atmospheric co 2 or may even have increased atmospheric co 2 in the glacial also iron fertilization of the marine biota in the southern ocean contributes to a glacial drawdown of co 2 but turns out to be limited by other factors than the total dust input such as bioavailability of iron or macronutrient supply

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 effect of a northward shift in the southern hemisphere westerlies on the global ocean we examine the effect of a northward shift in the position of the southern hemisphere subpolar westerly winds swws on the vertical and horizontal distribution of temperature and salinity in the world ocean a northward shift of the swws causes a latitudinal contraction of the subpolar gyres in the southern hemisphere sh in the indian and pacific this leads to subsurface warming in the subtropical thermocline as the southern margins of the gyres move into latitudes characterised by warmer surface air temperature sat the layers at mid depth below 400 m depth become ventilated by warmer water we characterize the approximation of the ventilated thermocline in our coarse resolution model using a set of passive tracer experiments and illustrate how the northward shift in the swws causes an equatorward shift in the latitude of origin of water ventilating layers deeper than 400 m in the indian and pacific leaving the total surface ventilation of the upper 1200 m unchanged in contrast the latitudinal constraint on the antarctic circumpolar current posed by the drake passage causes a cooling and freshening throughout the atlantic thermocline here subsurface thermocline water originates from higher latitudes under the wind shift on longer timescales atlantic cooling and freshening is reinforced by a reduction in north atlantic deep water nadw formation and surface salinification of the indian and pacific oceans in effect the latitude of zero wind stress curl in the swws regulates the relative importance of the cold water route via the drake passage and the warm water route associated with thermocline water exchange via the indian ocean thus a more northward location of the swws corresponds with a reduced salinity contrast between the indian pacific oceans and the atlantic this results in reduced nadw formation also a more northward location of the swws facilitates the injection of cool fresh antarctic intermediate water into the south atlantic subtropical gyre beyond these changes on a millennial timescale the deep ocean warms throughout the water column in response to the wind shift global salinity stratification also becomes less stable as more saline water remains at the surface and accumulates in the indian and pacific thermocline the freshening of the deep ocean reflects a reduced stirring of the global ocean due to reduced net circulation arising from a misalignment between the westerlies and the topographically constrained acc our results lend support to the idea that a more equatorward location of the sww maximum during glacial climates contributed to cooler and fresher conditions in the atlantic inhibiting nadw

synchronous volcanic eruptions and abrupt climate change 17 7 ka plausibly linked by stratospheric ozone depletion glacial state greenhouse gas concentrations and southern hemisphere climate conditions persisted until 17 7 ka when a nearly synchronous acceleration in deglaciation was recorded in paleoclimate proxies in large parts of the southern hemisphere with many changes ascribed to a sudden poleward shift in the southern hemisphere westerlies and subsequent climate impacts we used high resolution chemical measurements in the west antarctic ice sheet divide byrd and other ice cores to document a unique 192 y series of halogen rich volcanic eruptions exactly at the start of accelerated deglaciation with tephra identifying the nearby mount takahe volcano as the source extensive fallout from these massive eruptions has been found 2 800 km from mount takahe sulfur isotope anomalies and marked decreases in ice core bromine consistent with increased surface uv radiation indicate that the eruptions led to stratospheric ozone depletion rather than a highly improbable coincidence circulation and climate changes extending from the antarctic peninsula to the subtropics similar to those associated with modern stratospheric ozone depletion over antarctica plausibly link the mount takahe eruptions to the onset of accelerated southern hemisphere deglaciation 17 7 ka

southern hemisphere westerly wind changes during the last glacial maximum paleo data synthesis changes in the strength and position of southern hemisphere westerly winds during the last glacial cycle have been invoked to explain both millennial and glacial interglacial climate fluctuations however neither paleo models nor paleodata agree on the magnitude or even the sign of the change in wind strength and latitude during the most studied glacial period the last glacial maximum lgm compared to the recent past this paper synthesizes paleo environmental data that have been used to infer changes in lgm winds data compilations are provided for changes in terrestrial moisture dust deposition sea surface temperatures and ocean fronts and ocean productivity and existing data on southern hemisphere ocean circulation changes during the lgm are summarized we find that any hypothesis of lgm wind and climate change needs to provide a plausible explanation for increased moisture on the west coast of continents cooler temperatures and higher productivity in the subantarctic zone and reductions in agulhas leakage around southern africa our comparison suggests that an overall strengthening an equatorward displacement or no change at all in winds could all be interpreted as consistent with observations if a single cause related to the southern westerlies is sought for all the evidence presented then an equatorward displacement or strengthening of the winds would be consistent with the largest proportion of the observations however other processes such as weakening or poleward shifts in winds a weakened hydrological cycle extended sea ice cover and changed buoyancy fluxes cannot be ruled out as potential explanations of observed changes in moisture surface temperature and productivity we contend that resolving the position and strength of westerly winds during the lgm remains elusive based on data reconstructions alone however we believe that these data reconstructions of environmental conditions can be used in conjunction with model simulations to identify which processes best represent westerly wind conditions during the lgm

soil magnetic susceptibility and its relationship with naturally occurring processes and soil attributes in pedosphere in a tropical environment abstract soil magnetic susceptibility has potential to be used as a pedoenvironmental indicator from which mineralogy pedogeochemical pedogeomorphological and pedogenic processes can be inferred it can be used in pedosphere studies as an auxiliary information for appropriate and sustainable soil use and management this research aimed to analyze how pedogenesis and geochemical processes affect the and some of its attributes as well as its potential use in discriminating soil great groups following the digital soil mapping approach the study area is located in sao paulo state brazil soil samples were collected for physical chemical analysis from 79 locations 0 20 cm depth at these sites magnetic susceptibility was measured with a portable field instrument and analyzed in terms of geology relief and soil class the results showed that geology strongly affects mainly in diabase derived soils followed by metamorphosed siltstone and siltstone in fluvial sediments the exhibits different behaviors due to different sediments deposited by the capivari river in less evolved soils such as cambisols lithology is a more important contributor to than pedogenesis in more evolved soils pedogenesis increases whereas argilluviation ferralitization reduces it the values did not decrease significantly or even increase downslope due to the presence of diabase on the lower parts differences in where observed between diabase bedrock located in different parts of the study area indicating more of an influence by geomorphic processes rather than lithology with respect to soil attributes positive correlations between and base saturation cation exchange capacity organic matter and iron and clay content were found whereas a negative correlation was found between and sand content the correlates with changes in lithology and soil class demonstrating its application as a potential tool for the discrimination of soil great groups and digital soil mapping

simulated impact of altered southern hemisphere winds on the atlantic meridional overturning circulation 1 previous work has suggested that the strength and latitudinal position of the southern hemisphere sh mid latitude westerly winds has an important impact on climate and the atlantic meridional overturning circulation amoc we probe this hypothesis by conducting ensembles of experiments using the gfdl cm2 1 coupled ocean atmosphere model with altered sh wind stress we find consistent with previous work that enhanced reduced and poleward equatorward displaced sh westerly winds lead to an amoc intensification weakening while the amoc takes more than a century to respond fully to the altered sh winds initial effects in the north atlantic can occur within a few decades the amoc changes generate sst and surface air temperature responses in the north atlantic and adjacent continental regions in the southern hemisphere the atmosphere responds to the altered ocean circulation with a further strengthening and poleward movement of the sh winds thereby constituting a modest positive feedback

last glacial maximum co2 and δ13c successfully reconciled 1 during the last glacial maximum lgm 21 000 years ago the cold climate was strongly tied to low atmospheric co2 concentration 190 ppm although it is generally assumed that this low co2 was due to an expansion of the oceanic carbon reservoir simulating the glacial level has remained a challenge especially with the additional 13c constraint indeed the lgm carbon cycle was also characterized by a modern like 13c in the atmosphere and a higher surface to deep atlantic 13c gradient indicating probable changes in the thermohaline circulation here we show with a model of intermediate complexity that adding three oceanic mechanisms brine induced stratification stratification dependant diffusion and iron fertilization to the standard glacial simulation which includes sea level drop temperature change carbonate compensation and terrestrial carbon release decreases co2 down to the glacial value of 190 ppm and simultaneously matches glacial atmospheric and oceanic 13c inferred from proxy data lgm co2 and 13c can at last be successfully reconciled

southern ocean wind response to north atlantic cooling and the rise in atmospheric co2 modeling perspective and paleoceanographic implications 1 a recent study found enhanced upwelling rates in the southern ocean during the last glacial termination that coincided with the deglacial warming in antarctica and the rise in atmospheric co2 they hypothesized that the intensification of southern hemisphere midlatitude westerlies the presumed cause of the increased wind driven upwelling was triggered by an initial cooling within the glacial north atlantic whose influence was then communicated to the southern midlatitudes through an atmospheric teleconnection in this study we explore the viability of the above hypothesis using a modeling strategy focusing on the atmospheric teleconnection in simulations where north atlantic cooling was applied the model intertropical convergence zone shifted southward and westerlies and wind stress over southern ocean increased by as much as 25 while the perennial westerly anomalies occur over the entire southern ocean they are strongest over the south pacific during the austral winter when the wind stress anomalies were applied to an earth system model incorporating interactive marine biogeochemistry atmospheric co2 rises between 20 and 60 ppm depending on the biological response we thus confirm the viability of the proposed atmospheric teleconnection hypothesis the teleconnection appears to involves two distinct steps first the north atlantic cooling shifts the intertropical convergence zone southward weakening the southern branch of the hadley circulation and second how the altered hadley circulation in turn modifies the structure of midlatitude westerlies in the south pacific via the former s influence on the southern hemisphere subtropical jet this study underscores the control of the northern hemisphere has on southern midlatitude westerlies mediating by tropical circulation in contrast to past paleoclimate hypotheses that the magnitude and position of the southern midlatitude westerlies was controlled by global mean temperature our results do not preclude other potential mechanisms for affecting southern ocean ventilation in particular through oceanic pathways