solar radiation maintained glacier recession on kilimanjaro drawn from combined ice radiation geometry modeling 1 in the context of investigating modern glacier recession on kilimanjaro which began around 1880 this study addresses the glacier regime of the vertical ice walls that typically form the margins of kilimanjaro s summit glaciers these walls have suffered a continuous lateral retreat during the twentieth century to evaluate the role of solar radiation in maintaining glacier recession on kilimanjaro a radiation model is applied to an idealized representation of the 1880 ice cap the combined process based model calculates the spatial extent and geometry of the ice cap for various points in time after 1880 support for input data and fundamental assumptions are provided by an automatic weather station that has operated on the summit s northern icefield since february 2000 even in a simple climatic scenario only forced with an annual cycle of clouds the basic evolution in spatial distribution of ice bodies on the summit is modeled well the northern and southern icefields form in characteristic east west orientation which verifies the basic idea behind the model forcing the model with further climate related phenomena improves the results it then additionally reproduces the eastern icefield the third big ice entity on the summit this study qualitatively demonstrates that solar radiation is the main climatic parameter maintaining modern glacier recession on kilimanjaro summit but also suggests that retreat on the inner ice cap margin might have been supported by a secondary energy source the need for additional field measurements is emphasized in order to better understand the complex processes of glacier climate interaction on kilimanjaro index terms 1620 global change climate dynamics 3309 1827 hydrology glaciology 1863 3309 meteorology and atmospheric dynamics climatology 1620 3359 meteorology and atmospheric dynamics radiative processes 9305 information related to geographic region africa keywords tropical glaciers kilimanjaro climate change glacier retreat solar radiation modeling

characterization of the last deglacial transition in tropical east africa insights from lake albert abstract new biomarker analyses from lake albert east africa spanning 15 9 ka show the most extreme abrupt multi stage climate and environmental shifts during the last deglacial transition of anywhere in africa records of hydroclimate expressed in compound specific d values from terrestrial leaf waxes and a tex86 paleotemperature record support multiple stages of pronounced drying and cooling from 13 8 to 11 5 ka and demonstrate the dynamic behavior of the low latitude tropics during the deglaciation the vegetation response illustrated by compound specific 13c values and fossil pollen records was an expansion of c4 grassland when the region was cool and arid these results advance our understanding of a spatially and temporally complex regional response to global climate forcing suggesting weakening of the indian ocean monsoon at the end of the pleistocene that coincides with a minor decrease in the rate of the atlantic meridional overturning circulation amoc and during a time of stepwise cooling in the northern high latitudes

cosmic ray labeling of erosion surfaces in situ nuclide production rates and erosion models a number of in situ cosmogenic radionuclides and stable nuclides have been measured in natural exposed rock surfaces with a view to study their in situ production and rock erosion rates 1 the in situ radionuclides can be used for a high resolution tomography of the erosional history of an exposed surface two stable nuclides 3he 21ne and five radionuclides 10be 26al 36cl 14c 39ar having half lives in the range of 300 1 5 106 yr half life are measurable in many rock types a prerequisite for the application of the in situ nuclides for the study of erosional histories of surfaces is a knowledge of their production rates under different irradiation conditions altitude latitude irradiation geometry and shielding relative nuclide production rates can be determined fairly accurately using the extensive available data on cosmic ray neutrons 2 absolute nuclide production rates cannot generally be predicted with any accuracy because of lack of data on excitation functions of nuclides unless some normalization is possible as was done in the case of several cosmic ray produced isotopes in the atmosphere 3 based on a recent natural calibration experiment in which erosion free surfaces exposed to cosmic radiation for 11 000 yrs were sampled the absolute production rates of 10be and 26al in quartz have been accurately estimated for mountain altitudes in sierra nevada 4 the absolute production rates of 10be and 26al in quartz can therefore be estimated fairly accurately for any given latitude and altitude some measurements of 14c in rocks of low erosion rate 5 similarly allow an estimate of its production rate attempts made to measure the in situ production rates of 3he in rocks have not yet led to a convergent production rate in view of the importance of knowing the production rates of isotopes of he ne and ar i present here theoretical estimates of their production rates based on available cross section data i discuss the information that can be extracted from the study of the in situ nuclides in rocks useful parameters characterizing the exposure history of a rock surface are 1 the effective surface exposure age and 2 the time averaged erosion rate the implications of these parameters for single and multiple nuclide studies are discussed in terms of the erosion models considered

insolation values for the climate of the last 10 million years new values for the astronomical parameters of the earth s orbit and rotation eccentricity obliquity and precession are proposed for paleoclimatic research related to the late miocene the pliocene and the quaternary they have been obtained from a numerical solution of the lagrangian system of the planetary point masses and from an analytical solution of the poisson equations of the earth moon system the analytical expansion allows the direct determination of the main frequencies with their phase and amplitude numerical and analytical comparisons with the former astronomical solution ber78 are performed so that the accuracy and the interval of time over which the new solution is valid can be estimated the corresponding insolation values have also been computed this analysis leads to the conclusion that the new values are expected to be reliable over the last 5 ma in the time domain and at least over the last 10 ma in the frequency domain

putting the younger dryas cold event into context abstract the younger dryas event is by far the best studied of the millennial scale cold snaps of glacial time yet its origin remains a subject of debate the long held scenario that the younger dryas was a one time outlier triggered by a flood of water stored in proglacial lake agassiz has fallen from favor due to lack of a clear geomorphic signature at the correct time and place on the landscape the recent suggestion that the younger dryas was triggered by the impact of a comet has not gained traction instead evidence from chinese stalagmites suggests that rather than being a freak occurrence the younger dryas is an integral part of the deglacial sequence of events that produced the last termination on a global scale

modern changes of the high mountain landscapes and glaciation in southern siberia russia by the example of the eastern sayan mountains the period of observations of glaciation of the munku sardyk mountain massif in siberia is one of the longest i e 155 years however the data obtained are scattered and not systematic the paper presents an integrated analysis of the materials collected since the first description by the explorer of siberian mountains g i radde istoriy 1896 and extended by peretolchin 1908 and komarov 1953 as well as by glaciologists maksimov 1965 arefiev and mukhametov 1996 the authors considered the current state of the glaciers and interaction of natural geosystems of the massif taking into account the nival glacial processes since the beginning of the current millennium regular observations have been conducted on the munku sardyk massif by the v b sochava institute of geography sb ras limnological institute sb ras and east siberian state academy of education the studies revealed the leading landscape forming factors and examined the landscape structure of the surroundings of the contemporary nival glacial geosystems with due regard for the manifestations of altitudinal zonation a medium scale landscape typological mapping was carried out presented are the quantitative parameters of the dynamics of the nival glacial geosystems obtained on the basis of modern remote sensing instruments gps measurements and surface laser scanning using gis analysis the stump and stem of larch detected in the valley of the bugovek river 300 m above the contemporary upper forest limit and 1330 m up the valley show that most likely there was no glaciation during the atlantic period 7000 7300 years ago the modern glacier complex has formed only during the last 4000 5000 years the trend of shrinkage of glaciers since the end of the little ice age can be traced especially in recent years the length and area of the open part of the glaciers have decreased by half from 0 68 to 0 34 km2 the presence of small forms of glaciation on the southernmost limit of the siberian glaciation 1500 m below the theoretical climate boundary suggests that this area can be considered a unique key site to identify trends in development of the mountain and nival glacial geosystems and provides an opportunity to built reconstructive and predictive models of development of mountain landscapes under the conditions of ever increasing anthropogenic influence

north atlantic forcing of amazonian precipitation during the last ice age the last glacial period was marked by rapid reorganizations of oceanic and atmospheric circulation speleothem records from the amazon basin suggest that precipitation variability was linked to these events the last glacial period was marked by multiple abrupt reorganizations of ocean and atmosphere circulation1 on thousand year timescales slowing of the atlantic meridional overturning circulation was associated with cooling in the high northern latitudes whereas strengthened circulation was linked to northern warming1 2 in the tropics these millennial scale events were primarily reflected in altered patterns of precipitation3 these hydrologic fluctuations induced ecological changes in the atlantic seaboard and the high andes2 but less is known about the amazon basin here we reconstruct precipitation over amazonian ecuador over the past 94 000 years using a 18o record from speleothems collected in santiago cave in western amazonia we interpret the variability of the 18o record as changes in the source and amount of precipitation with the exception of the period between 40 000 and 17 000 years ago abrupt high frequency changes coincide with shifts in north atlantic circulation indicating a high latitude influence on amazonian precipitation over millennial timescales on longer timescales the record shows a relationship to precessional changes in the earth s orbit in light of the lack of extreme aridity in our records we conclude that ecosystems in western amazonia have not experienced prolonged drying over the past 94 000 years

abrupt onset and termination of the african humid period rapid climate responses to gradual insolation forcing a detailed ca 100 yr resolution and well dated 18 ams 14 c dates to 23 cal ka bp record of latest pleistocene holocene variations in terrigenous eolian sediment deposition at odp site 658c off cap blanc mauritania documents very abrupt large scale changes in subtropical north african climate the terrigenous record exhibits a well defined period of low influx between 14 8 and 5 5 cal ka bp associated with the african humid period when the sahara was nearly completely vegetated and supported numerous perennial lakes an arid interval corresponding to the younger dryas chronozone punctuates this humid period the african humid period has been attributed to a strengthening of the african monsoon due to gradual orbital increases in summer season insolation however the onset and termination of this humid period were very abrupt occurring within decades to centuries both transitions occurred when summer season insolation crossed a nearly identical threshold value which was 4 2 greater than present these abrupt climate responses to gradual insolation forcing require strongly non linear feedback processes and current coupled climate model studies invoke vegetation and ocean temperature feedbacks as candidate mechanisms for the non linear climate sensitivity the african monsoon climate system is thus a low latitude corollary to the bi stable behavior of high latitude deep ocean thermohaline circulation which is similarly capable of rapid and large amplitude climate transitions

coupled thermal and hydrological evolution of tropical africa over the last deglaciation we analyzed the distribution of branched tetraether membrane lipids derived from soil bacteria in a marine sediment record that was recovered close to the congo river outflow and the results enabled us to reconstruct large scale continental temperature changes in tropical africa that span the past 25 000 years tropical african temperatures gradually increased from 21 to 25 c over the last deglaciation which is a larger warming than estimated for the tropical atlantic ocean a direct comparison with sea surface temperature estimates from the same core revealed that the land sea temperature difference was through the thermal pressure gradient an important control on central african precipitation patterns

glacier fluctuation in northern and high asia historical and methods perspective glaciers in asia occupy nowadays much smaller extents than those of the pleistocene but they still play an important role in alpine ecosystems e g shahgedanova 2002 glaciers also pose hazards to society and infrastructure with avalanches and glacial lake outburst floods being the most destructive of glacier related natural events richardson and reynolds 2000 jansk et al 2010 nie et al 2013 wang and zhang 2014 since the end of the little ice age lia glaciers have been retreating almost everywhere around the world and this process has dramatically accelerated during the recent decades fig 1 wgms 2013 however individual glaciers are behaving differently and some have advanced while most have been in retreat ipcc 2013 yao et al 2012 mountain glaciers are sensitive indicators of climate change e g dyurgerov and meier 2000 haeberli et al 2004 and to fully understand the connection between changing climate and glacier fluctuations all the variables of the glacier mass balance need to be assessed at the local and regional scale dowdeswell et al 1997 oerlemans 2005 one of the regions where information about glacier changes is still scarce is northern and high asia fig 1 largely because glaciers of the region are located relatively far from human settlements and some have only been found after the 1940s for example ivanov et al 2015 have provided the first inventory of glaciers in the barguzinsky ridge east of lake baikal russia in this issue at the same time continental glaciers of northern and high asia are located far from the main sources of moisture and are thus sensitive to climate change fujita 2008 kaser et al 2010 in this issue we have collected information about glaciers situated along a southwestnortheast transect from 77 e 32 n the western himalaya india to 128 e 65 n the orulgan range russia fig 2 and fed from different sources of moisture the north atlantic the arctic and the indo pacific air masses because glaciers in our focus area belong to different climate systems their systematic study across the whole region has the potential not only to assess the climate change at local and regional scales but also to reveal climate change patterns at a larger continental scale the papers of this issue cover a variety of glacier related topics methods studies glacier inventories current glacier dynamics and paleo reconstructions and are based on a range of data such as satellite imagery synoptic maps biogeochemical proxies from proglacial lake bottom sediments and meltwater streams pollen and oxygen isotope records from snow ice cores and high resolution seismic reflection data

high frequency holocene glacier fluctuations in new zealand differ from the northern signature understanding the timings of interhemispheric climate changes during the holocene along with their causes remains a major problem of climate science here we present a high resolution 10be chronology of glacier fluctuations in new zealand s southern alps over the past 7000 years including at least five events during the last millennium the extents of glacier advances decreased from the middle to the late holocene in contrast with the northern hemisphere pattern several glacier advances occurred in new zealand during classic northern warm periods these findings point to the importance of regional driving and or amplifying mechanisms we suggest that atmospheric circulation changes in the southwest pacific were one important factor in forcing high frequency holocene glacier fluctuations in new zealand

high resolution sedimentary record of the last deglaciation from a high altitude lake in ethiopia sedimentological and geochemical studies conducted on a 15 82 m long core collected from lake garba guracha ethiopia associated with a precise ams 14c time scale document a unique record of the sedimentary processes linked to the progressive retreat of a high altitude glacier in the bale mountains since 17 000 yr cal bp lake sedimentation is interpreted as the result of discharges of meltwater and glaciogenic sediment which progressively filled the accommodation space generated by glacier retreat within the basin monogenic sediment originated from glacial erosion of the trachytic tuff forming the cirque floor ice melting ended progressively between 12 600 and 11 800 cal bp as suggested by the decrease in sedimentation energy followed by a sharp change in sedimentary facies from 11 800 cal bp the lake reached its maximum development and clastic input was replaced by organic rich sedimentation this relates to a major increase of lake productivity which lasted up to 4500 cal bp from this period a lowering in productivity reflects the widespread dryness which occurred throughout the east african tropics

interhemispheric atlantic seesaw response during the last deglaciation the asynchronous relationship between millennial scale temperature changes over greenland and antarctica during the last glacial period has led to the notion of a bipolar seesaw which acts to redistribute heat depending on the state of meridional overturning circulation within the atlantic ocean here we present new records from the south atlantic that show rapid changes during the last deglaciation that were instantaneous within dating uncertainty and of opposite sign to those observed in the north atlantic our results demonstrate a direct link between the abrupt changes associated with variations in the atlantic meridional overturning circulation and the more gradual adjustments characteristic of the southern ocean these results emphasize the importance of the southern ocean for the development and transmission of millennial scale climate variability and highlight its role in deglacial climate change and the associated rise in atmospheric carbon dioxide

glacial fluctuations in tropical africa during the last glacial termination and implications for tropical climate following the last glacial maximum abstract the tropics are a dynamic component of the global climate system and exert a profound influence on modern climate variability yet the role of the tropics in past climate changes for example during the last glacial termination is uncertain this uncertainty is due in part to the relative paucity of terrestrial temperature records from the tropics which hinders efforts to understand the mechanisms that influenced deglacial warming and abrupt climate events tropical glaciers are sensitive to changes in climate and mapping and dating past tropical glacial fluctuations provides a valuable record of terrestrial climate changes in the low latitudes we report a chronology of past glacial extents in the rwenzori mountains of uganda 0 3 n 29 9 e based on 51 beryllium 10 10be surface exposure ages from three separate glacial catchments results indicate that rwenzori glaciers retreated considerably during heinrich stadial 1 the rate of net glacial recession slowed between 15 and 11 ka although glaciers continued to retreat during this period rwenzori glaciers then retreated more rapidly during the early holocene the rwenzori glacial chronology is broadly similar to glacial chronologies reconstructed elsewhere in east africa and in tropical south america we suggest that this similarity may reflect coherent tropics wide temperature fluctuations during the last deglaciation the rwenzori glacial chronology provides crucial information on the global footprint of deglacial warming and abrupt climate events and thus the potential mechanisms that influenced tropical climate during the last glacial termination

cosmogenic dating of late pleistocene glaciation southern tropical andes peru we present 30 10be dates on three moraines formed by small glaciers in the southern tropical andes of peru to determine the timing of the local last glacial maximum lgm and subsequent deglaciation two terminal moraines indicate that the local lgm ended at 23 5 0 5 and 21 2 0 8 ka or well before the end of the global lgm 20 19 ka a recessional moraine perched at the base of a steep valley wall has a 10be age of 19 8 0 3 ka suggesting that glaciers had largely retreated from the area during the earliest stages of the last termination and before the onset of the deglacial co2 rise and increase in tropical sea surface temperatures these ages generally agree with other tropical glacial chronologies and reflect a broad synchroneity between low and high latitude deglaciation at the lgm but the trigger for early deglaciation of the tropics remains unclear

a cosmogenic 10be chronology for the local last glacial maximum and termination in the cordillera oriental southern peruvian andes implications for the tropical role in global climate abstract resolving patterns of tropical climate variability during and since the last glacial maximum lgm is fundamental to assessing the role of the tropics in global change both on ice age and sub millennial timescales here we present a10be moraine chronology from the cordillera carabaya 14 3 s a sub range of the cordillera oriental in southern peru covering the lgm and the first half of the last glacial termination additionally we recalculate existing 10be ages using a new tropical high altitude production rate in order to put our record into broader spatial context our results indicate that glaciers deposited a series of moraines during marine isotope stage 2 broadly synchronous with global glacier maxima but that maximum glacier extent may have occurred prior to stage 2 thereafter atmospheric warming drove widespread deglaciation of the cordillera carabaya a subsequent glacier resurgence culminated at 16 100 yrs followed by a second period of glacier recession together the observed deglaciation corresponds to heinrich stadial 1 hs1 18 000 14 600 yrs during which pluvial lakes on the adjacent peruvian bolivian altiplano rose to their highest levels of the late pleistocene as a consequence of southward displacement of the inter tropical convergence zone and intensification of the south american summer monsoon deglaciation in the cordillera carabaya also coincided with the retreat of higher latitude mountain glaciers in the southern hemisphere our findings suggest that hs1 was characterised by atmospheric warming and indicate that deglaciation of the southern peruvian andes was driven by rising temperatures despite increased precipitation recalculated 10be data from other tropical andean sites support this model finally we suggest that the broadly uniform response during the lgm and termination of the glaciers examined here involved equatorial pacific sea surface temperature anomalies and propose a framework for testing the viability of this conceptual model

glacial history of the kuznetsky alatay mountains field investigations showed that the leeward slopes across the kuznetsky alatay mountains also the windward slopes in the tigertysh ridge are intensively eroded by glaciers and represent the classical type of alpine type landscape accumulative glacial landforms are developed in all types of glacial valleys study of five valleys the karatas the lower and the upper tayzhasu perekhodnya the right source of the small kazyr rivers showed that four stadial moraine complexes can be identified these moraines are very different by their morphology they indicate the change of glaciation from large ancient valley glaciers to modern small cirque and slope glaciers in this article the first data are assessed about evolution of glaciers and climate in the kuznetsky alatay mountains from the last glacial maximum of late pleistocene between 26 500 and 19 000 20 000 years bp to nowadays on the basis of studies of glacial landforms sedimentology and biostratigraphy in the glacier inventory complied in 1970s early 1980s 91 glaciers were recorded in the kuznetsky alatay however some were erroneously identified as glaciers the review of the current changes of modern glaciation of the kuznetsky alatay is made on the basis of repeated photographs and direct field measurements of 30 glaciers 18 out of the 30 studied glaciers melted away completely their area decreased from 1 4 to 0 5 0 3 km2 not all glaciers strongly degraded large cirque glaciers have not changed significantly over the past 110 years the area of perennial snowfields in the kuznetsky alatay mountains had reduced by 90 over the century the timberline has risen by about 50 m and is currently located at 1220 1200 m a s l

modeling tropical precipitation in a single column abstract a modified formulation of the traditional single column model for representing a limited area near the equator is proposed this formulation can also be considered a two column model in the limit as the area represented by one of the columns becomes very large compared to the other only a single column is explicitly modeled but its free tropospheric temperature rather than its mean vertical velocity is prescribed this allows the precipitation and vertical velocity to be true prognostic variables as in prior analytical theories of tropical precipitation two models developed by other authors are modified according to the proposed formulation the first is the intermediate atmospheric model of j d neelin and n zeng but with the horizontal connections between columns broken rendering it a set of disconnected column models the second is the column model of n o renno k a emanuel and p h stone in the first model the set of disconnected column models is run with a fixed temperature

a revised 30 000 year paleoclimatic and paleohydrologic history of lake albert east africa abstract new geochemical and palynological data and a sedimentological reinterpretation of two cores from lake albert allow a revision of the paleoclimatic and paleohydrologic history of northwest uganda over the last 30 000 14 c yr bp our findings document one and possibly three periods of significantly reduced inflow to the nile river system from the white nile based on sediment fabric and mineralogy shifts in percentages of total organic carbon toc and total organic nitrogen ton hydrogen index hi and 13 c and 15 n as well as poor preservation of sporopollenin and siliceous microfossils we recognize two mature paleosols that formed between 18 000 and 12 500 14 c yr bp at the surface of exposed lacustrine muds a thin fossiliferous zone between the two soils documents a brief period of flooding lake albert was below the level of the coring site and thus a closed basin for several thousand years during the late pleistocene around 12 500 14 c yr bp the younger vertisol was flooded by a major rise in lake level relatively deep water conditions were established soon after this transgression but an apparent change in sedimentation rate sometime between 8 000 and 3 400 14 c yr bp may reflect another briefer period of low water which resulted in interruption of sedimentation at the coring site palynological data document a rapid and abrupt shift to drier conditions around lake albert from 11 400 to 9 900 14 c yr bp coincident with the cool younger dryas event of the northern hemisphere geochemical evidence suggests that throughout the terminal pleistocene and early holocene and again in the late holocene the water column was relatively well mixed with little tendency to persistent anoxia

high resolution record of northern hemisphere climate extending into the last interglacial period high resolution record of northern hemisphere climate extending into the last interglacial period

cosmogenic 10be production rate calibrated against 3he in the high tropical andes 3800 4900 m 20 22 s abstract many geomorphologic applications notably glacier chronologies require improvements in both the precision and the accuracy of the cosmogenic dating tool of particular importance is the need to better constrain the spatial variability of the cosmogenic nuclides production rates at high elevation and low latitudes one strategy that can be adopted for this is to couple absolute calibrations from independently dated surfaces with cross calibration studies performed by measuring several cosmogenic nuclides in the same rock in the present study we report the highest elevation 4800 m cross calibration published to date comprising measurements of cosmogenic 3 he and 10 be in cogenetic pyroxene and quartz the samples were collected from six dacitic moraine boulders exposed from 32 to 65 ka at 4820 m on the flanks of the uturuncu volcano 22 s 67 w southern lipez bolivia the samples yield a remarkably tight cluster of 3 he 10 be production ratios with a weighted mean of 33 3 0 9 1 this production ratio is undistinguishable within uncertainties from the 3 he 10 be production ratio of 32 3 0 9 determined in the same mineral pair at low elevation 1333 m by amidon et al 2009 these results agree at the 1 level and suggest that any hypothetical increase of the 3 he 10 be production ratio in pyroxene and quartz is likely to be lower than 5 over this elevation range 1000 5000 m moreover the production ratio is almost insensitive to the li content of the pyroxene 20 to 50 ppm li suggesting that the cosmogenic thermal neutron production of 3 he is very low in this setting the high elevation 3 he 10 be production ratio is used in combination with a local determination of the 3 he production rate in the high central altiplano 3800 m blard et al 2013 to establish a local 10 be production rate of 30 0 1 4 at g 1 yr 1 at 3800 m and 20 s after scaling to sea level high latitude with the time dependent lal stone model this yields a 10 be production rate in quartz of 3 63 0 17 at g 1 yr 1 importantly this rate can be used for high precision geomorphologic dating for example for determining glacial chronologies 1 4 through 10 be dating of moraines in the high tropical andes any inaccuracy attached to the scaling model is canceled out when the calibration site is located close to the dated object the same experiment was also undertaken in pyroxene and plagioclase from two andesitic boulders from the tunupa volcano moraines exposed at 3800 m and 4200 m a 3 he 10 be production ratio of 35 9 1 3 1 is obtained for this mineral pair indicating that the 10 be production rate in plagioclase is about 8 lower than in quartz

the last glacial termination a major puzzle of paleoclimatology is why after a long interval of cooling climate each late quaternary ice age ended with a relatively short warming leg called a termination we here offer a comprehensive hypothesis of how earth emerged from the last global ice age a prerequisite was the growth of very large northern hemisphere ice sheets whose subsequent collapse created stadial conditions that disrupted global patterns of ocean and atmospheric circulation the southern hemisphere westerlies shifted poleward during each northern stadial producing pulses of ocean upwelling and warming that together accounted for much of the termination in the southern ocean and antarctica rising atmospheric co2 during southern upwelling pulses augmented warming during the last termination in both polar hemispheres

a new greenland ice core chronology for the last glacial termination 1 we present a new common stratigraphic timescale for the north greenland ice core project ngrip and grip ice cores the timescale covers the period 7 9 14 8 kyr before present and includes the bolling allerod younger dryas and early holocene periods we use a combination of new and previously published data the most prominent being new high resolution continuous flow analysis cfa impurity records from the ngrip ice core several investigators have identified and counted annual layers using a multiparameter approach and the maximum counting error is estimated to be up to 2 in the holocene part and about 3 for the older parts these counting error estimates reflect the number of annual layers that were hard to interpret but not a possible bias in the set of rules used for annual layer identification as the grip and ngrip ice cores are not optimal for annual layer counting in the middle and late holocene the timescale is tied to a prominent volcanic event inside the 8 2 kyr cold event recently dated in the dye 3 ice core to 8236 years before a d 2000 b2k with a maximum counting error of 47 years the new timescale dates the younger dryas preboreal transition to 11 703 b2k which is 100 150 years older than according to the present grip and ngrip timescales the age of the transition matches the gisp2 timescale within a few years but viewed over the entire 7 9 14 8 kyr section there are significant differences between the new timescale and the gisp2 timescale the transition from the glacial into the bolling interstadial is dated to 14 692 b2k the presented timescale is a part of a new greenland ice core chronology common to the dye 3 grip and ngrip ice cores named the greenland ice core chronology 2005 gicc05 the annual layer thicknesses are observed to be log normally distributed with good approximation and compared to the early holocene the mean accumulation rates in the younger dryas and bolling periods are found to be 47 2 and 88 2 respectively

calibration and application of the branched gdgt temperature proxy on east african lake sediments branched glycerol dialkyl glycerol tetraethers brgdgts are a novel proxy for mean annual air temperature maat and have the potential to be broadly applicable to climate reconstruction using lacustrine sediments several calibrations have been put forth relating brgdgt distributions to maat using a variety of linear regressions including the methylation mbt and cyclization cbt indices of brgdgts the relative abundances of the major non cyclized brgdgts mbrgdgts and best subsets regression bsr of the fractional abundances of the nine most common brgdgts however these calibrations have rarely been applied to lake sediment cores to reconstruct temperatures and test the applicability of this proxy as a paleothermometer we present an expanded east african lakes surface sediment brgdgt dataset based upon 111 lakes and examine three methods of calibrating brgdgts to maat these methods include recalculations of the east african lake mbt cbt calibration and mbrgdgts calibrations as well as a new stepwise forward selection sfs calibration that uses the four combined brgdgts that explain the most variance in temperature in our calibration set we apply these new calibrations as well as five previously published lacustrine brgdgt calibrations to the brgdgt distributions of our surface sediment dataset and a 48 kyr sediment core from sacred lake mt kenya producing the first brgdgt temperature reconstruction available from a small tropical lake we compare the reconstructed temperatures to previously published paleotemperature records from east africa to help us assess the performance of the brgdgt calibrations we find that the sfs calibration has a consistently low root mean squared error of prediction rmsep over the entire range of maat while the mbt cbt and mbrgdgt calibrations have relatively large rmseps particularly between lakes with similar temperatures but variable ph this suggests that these techniques do not properly deconvolve the temperature and ph signals recorded in the distributions of the brgdgts we further find that only the sfs calibration produces a credible reconstructed temperature history from sacred lake when compared to other last glacial maximum paleotemperature estimates from east africa thus we advocate for the use of the sfs calibration when reconstructing paleotemperatures from brgdgts in east africa

structure and origin of holocene cold events abstract the present interglacial the holocene spans the period of the last 11 700 years it has sustained the growth and development of modern society the millennial scale decreasing solar insolation in the northern hemisphere summer lead to northern hemisphere cooling a southern shift of the intertropical convergence zone itcz and a weakening of the northern hemisphere summer monsoon systems on the multidecadal to multicentury scale periods of more stable and warmer climate were interrupted by several cold relapses at least in the northern hemisphere extra tropical area based on carefully selected 10 000 year long time series of temperature and humidity precipitation as well as reconstructions of glacier advances the spatiotemporal pattern of six cold relapses during the last 10 000 years was analysed and presented in form of a holocene climate atlas hoclat see http www oeschger unibe ch research projects holocene atlas a clear cyclicity was not found and the spatiotemporal variability of temperature and humidity precipitation during the six specific cold events 8200 6300 4700 2700 1550 and 550 years bp was very high different dynamical processes such as meltwater flux into the north atlantic low solar activity explosive volcanic eruptions and fluctuations of the thermohaline circulation likely played a major role in addition internal dynamics in the north atlantic and pacific area including their complex interaction were likely involved

recent glacial recession in the rwenzori mountains of east africa due to rising air temperature based on field surveys and analyses of optical spaceborne images landsat5 landsat7 we report recent decline in the areal extent of glaciers in the rwenzori mountains of east africa from 2 01 0 56 km 2 in 1987 to 0 96 0 34 km 2 in 2003 the spatially uniform loss of glacial cover at lower elevations together with meteorological trends derived from both station and reanalysis data indicate that increased air temperature is the main driver clear trends toward increased air temperatures over the last four decades of similar to 0 5 degrees c per decade exist without significant changes in annual precipitation extrapolation of trends in glacial recession since 1906 suggests that glaciers in the rwenzori mountains will disappear within the next two decades

earthquake premonitory processes evolution of stresses and electric current generation the principles and assumptions of the earthquake premonitory and rebound theory are reviewed the theory based on a continuum model of fracturing processes the stress evolution equations describe the dynamic processes governing a continuous distribution of dislocations special attention is paid to the problem of electric current generation in a seismic source zone electric current is considered as reflecting the rate of polarization which is influenced by motion of the charge bearing dislocations the relationship between the current density and stress accumulation rate is derived

onset of deglacial warming in west antarctica driven by local orbital forcing an annually resolved ice core record from west antarctica indicates that warming driven by local insolation resulting from sea ice decline began in that region about 2 000 years before warming in east antarctica reconciling two alternative explanations for deglacial warming in the southern hemisphere

holocene glacier fluctuations and climate changes in the southeastern part of the russian altai south siberia based on a radiocarbon chronology abstract this study investigates glacier dynamic and climatic variations in the southeastern part of the russian altai se altai during the last 7000 years recent glacier retreats and ice melting in moraines has led to exhumation of organic material allowing the possibility of radiocarbon dating we report here 57 new radiocarbon dates from wood remains buried by moraines and from proglacial forefields from peat layers and lacustrine sediments that cover moraines from dead trees at the upper tree limit and from rock glaciers on trough slopes from six glacial valleys in the north chuya range se altai such a numerous dataset for the vast but unified in neotectonic and climatic conditions area is presented for the first time the history of research in the altai together with 62 previously published radiocarbon ages mainly of fossil soils and peat layers in the foot of the ranges in se altai they form the basis for understanding the relative magnitudes and timing of the most important glacial and climatic events of se altai new data refute the traditional concept of the russian altai holocene glaciations as a consecutive retreat of the late wurm glaciers and argue their complete degradation at the head of trough valleys at least 7000 cal years bp moraine complexes of three holocene glacial stages are morphologically expressed in trough valleys of the north chuya range they correlate with three identified periods of glacial advances from 4900 to 4200 cal years bp akkem stage from 2300 to 1700 cal years bp historical stage and in the 13th 19th centuries little ice age lia or aktru stage the coincident extremes of lowering temperature and increasing precipitation during the akkem stage led to abrupt glacier advances and forming of the most remote moraine complexes downstream in the valleys following glacier advances had distinctly smaller magnitudes in addition to the radiocarbon data the time limits of the historical stage were defined more precisely using dendrochronological and archaeological data from scythian burials of pazyryk culture in se altai repeated forest regrowth in the presently glaciatiated area indicates significant retreat or even complete glacier degradation during interstage warming the decreases of glacier length in the following stages argues for intensification of aridity in the se altai during the second half of the holocene the thermal minimum in the middle of 19th century the greatest in the last millennium did not positively influence the mass balance of glaciers which also supports this conclusion

expanded glaciers during a dry and cold last glacial maximum in equatorial east africa glaciers on the world s highest tropical mountains are among the most sensitive components of the cryosphere yet the climatic controls that infl uence their fl uctuations are not fully under stood here we present the fi rst 10 be ages of glacial moraines in africa and use these to assess the climatic conditions that infl uenced past tropical glacial extents we applied 10 be surface exposure dating to determine the ages of quartz rich boulders atop moraines in the rwenzori mountains 1 n 30 e located on the border of uganda and the democratic republic of congo the 10 be ages document expanded glaciers ca 23 4 and 20 1 ka indicating that glaciers in equatorial east africa advanced during the global last glacial maximum ca 26 19 5 ka a comparison of these moraine ages with regional paleoclimate records indicates that rwen zori glaciers expanded contemporaneously with dry and cold conditions recession from the moraines occurred after ca 20 1 ka similar in timing to a rise in air temperature documented in east african lake records our results suggest that on millennial time scales past fl uctua tions of rwenzori glaciers were strongly infl uenced by air temperature

northern hemisphere controls on tropical southeast african climate during the past 60 000 years the processes that control climate in the tropics are poorly understood we applied compound specific hydrogen isotopes d and the tex86 tetraether index of 86 carbon atoms temperature proxy to sediment cores from lake tanganyika to independently reconstruct precipitation and temperature variations during the past 60 000 years tanganyika temperatures follow northern hemisphere insolation and indicate that warming in tropical southeast africa during the last glacial termination began to increase 3000 years before atmospheric carbon dioxide concentrations d data show that this region experienced abrupt changes in hydrology coeval with orbital and millennial scale events recorded in northern hemisphere monsoonal climate records this implies that precipitation in tropical southeast africa is more strongly controlled by changes in indian ocean sea surface temperatures and the winter indian monsoon than by migration of the intertropical convergence zone

pollen based reconstructions of vegetation and climate changes during the late holocene in the southern altai mountains we here preset a result of high resolution pollen data of a lacustrine peat sediment core from yushenkule yskl peat southern altai mountains northwestern china we aim to reconstruct the palaeo

inventory of nival glacial geosystems in lake baikal area east siberia russia glaciers in lake baikal area were plotted on topographic and tourist maps but often big perennial snow patches were designated as glaciers a special study of these entities to classify them in one group or another was necessary recently published data of remote sensing satellite images of high resolution allow distinguishing a variety of snow and ice objects accurate to 0 5 m in identifying sustainable nival glacial formations it was necessary to measure the characteristic parameters of these objects and their boundaries using topographic maps satellite images and gps devices the gis project and the database of nival glacial formations for the quantitative analysis of the accumulated information have been created the glaciers of mountain ridges of east siberia significantly reduced in thickness for the last decades and their abrupt degradation is manifested in the last 5 10 years the main glaciers of the barguzinskiy ridge decreases with 0 002 km2 year 1 that is comparable with the reduction rate of the glaciers of the eastern sayan ridge but is less than of the representative of the kodar ridge the azarovoy glacier

interhemispheric dynamics of the african rainbelt during the late quaternary abstract the spatial pattern of precipitation variability in tropical and subtropical africa over the late quaternary has long been debated prevailing hypotheses variously infer 1 insolation controlled asymmetry of wet phases between hemispheres 2 symmetric contraction and expansion of the tropical rainbelt and 3 independent control on moisture available in southern africa via sea surface temperatures in the indian ocean in this study we use climate model simulations covering the last glacial cycle 120 kyr with hadcm3 and the multi model ensembles from pmip3 the palaeoclimate model intercomparison project to investigate the long term behaviour of the african rainbelt and test these simulations against existing empirical palaeohydrological records through regional model data comparisons we find evidence for the validity of several hypotheses with various proposed processes occurring concurrently but with different regional emphasis e g asymmetric shifts at the seasonal extremes and symmetric expansions contractions towards west equatorial regions crucially variations in rainfall are associated with multiple forcing mechanisms that vary in their dominance both spatially and temporally over the glacial cycle an important consideration when interpreting and extrapolating from often relatively short palaeoenvironmental records

coherent changes of southeastern equatorial and northern african rainfall during the last deglaciation during the last deglaciation wetter conditions developed abruptly 14 700 years ago in southeastern equatorial and northern africa and continued into the holocene explaining the abrupt onset and hemispheric coherence of this early african humid period is challenging due to opposing seasonal insolation patterns in this work we use a transient simulation with a climate model that provides a mechanistic understanding of deglacial tropical african precipitation changes our results show that meltwater induced reduction in the atlantic meridional overturning circulation amoc during the early deglaciation suppressed precipitation in both regions once the amoc reestablished wetter conditions developed north of the equator in response to high summer insolation and increasing greenhouse gas ghg concentrations whereas wetter conditions south of the equator were a response primarily to the ghg increase

analysis of the electromagnetic field recorded in the friuli seismic zone northeast italy abstract some examples of unusual telluric activity were found during the italian polish magnetotelluric measurement campaign in the friuli seismic zone 1987 1988 the standard procedure for the elimination of the induction component from the telluric recordings and the calculation of the transfer functions were first applied however due to a high noise level in the observed telluric fields in the northern alpine region it appeared indispensable to develop new methods for the detection of any tectonically related component of the telluric field the common function defined as the average curve derived from two telluric stations and multiplied by the correlation coefficients moving window procedure allowed an increase in the telluric activity time changes of variances to be traced before and during seismic events in september 1987 and february 1988 another approach was based on the time frequency isoline calculations of the poynting vector of electromagnetic field positive isoline values opposite to the usual downward direction of this flux were discovered and correlated with a course of seismic activity some good results were found for the time intervals studied some considerations on a mechanism for the generation of an electric current in a zone of seismic preparation are discussed an accumulation of stress leads to an oriented motion of the charged charge bearing dislocations the mechanism consists of the formation of a kind of polarization current induced by the motion of these dislocations

tropical climate changes at millennial and orbital timescales on the bolivian altiplano tropical south america is one of the three main centres of the global zonal overturning circulation of the equatorial atmosphere generally termed the walker circulation1 although this area plays a key role in global climate cycles little is known about south american climate history here we describe sediment cores and down hole logging results of deep drilling in the salar de uyuni on the bolivian altiplano located in the tropical andes we demonstrate that during the past 50 000 years the altiplano underwent important changes in effective moisture at both orbital 20 000 year and millennial timescales long duration wet periods such as the last glacial maximum marked in the drill core by continuous deposition of lacustrine sediments appear to have occurred in phase with summer insolation maxima produced by the earth s precessional cycle short duration millennial events correlate well with north atlantic cold events including heinrich events 1 and 2 as well as the younger dryas episode at both millennial and orbital timescales cold sea surface temperatures in the high latitude north atlantic were coeval with wet conditions in tropical south america suggesting a common forcing

consistent dating for antarctic and greenland ice cores we are hereby presenting a new dating method based on inverse techniques which aims at calculating consistent gas and ice chronologies for several ice cores the proposed method yields new dating scenarios simultaneously for several cores by making a compromise between the chronological information brought by glaciological modeling i e ice flow model firn densification model accumulation rate model and by gas and ice stratigraphic constraints this method enables us to gather widespread chronological information and to use regional or global markers i e methane volcanic sulfate beryllium 10 tephra layers etc to link the core chronologies stratigraphically confidence intervals of the new dating scenarios can be calculated thanks to the probabilistic formulation of the new method which takes into account both modeling and data uncertainties we apply this method simultaneously to one greenland ngrip and three antarctic epica dome c epica dronning maud land and vostok ices cores and refine existent chronologies our results show that consistent ice and gas chronologies can be derived for depth intervals that are well constrained by relevant glaciological data in particular we propose new and consistent dating of the last deglaciation for greenland and antarctic ice and gas records

chronology of quaternary glaciations in east africa abstract a new glacial chronology for equatorial east africa is developed using in situ cosmogenic 36 cl measured in 122 boulders from moraines on mount kenya and kilimanjaro the oldest deposits sampled on kilimanjaro yield a limiting 36 cl age of 360 calendar kyr all 36 cl ages are in calendar years cal kyr or cal yr on mount kenya the oldest moraines give ages of 355 420 kyr liki i and 255 285 kyr teleki given the uncertainty in our 36 cl ages the liki i moraine may correspond to either marine isotope stage 10 or 12 whereas the teleki moraine correlates with stage 8 there is no evidence for stage 6 on either mountain the liki ii moraines on mt kenya and moraines of the fourth glaciation on kilimanjaro give ages of 28 3 kyr and 20 1 kyr respectively they represent the last glacial maximum lgm and correlate with stage 2 of the marine isotope record a series of smaller moraines above the lgm deposits record several readvances that occurred during the late glacial on mt kenya these deposits date to 14 6 1 2 kyr liki iia 10 2 0 5 kyr liki iii 8 6 0 2 kyr liki iiia and 200 yr lewis the corresponding deposits on kilimanjaro have mean ages of 17 3 2 9 kyr fourth glaciation saddle 15 8 2 5 kyr little glaciation saddle and 13 8 2 3 kyr fourth glaciation kibo these data indicate that the climate of the tropics was extremely variable at the end of the last glacial cycle

interpretation of long period magnetotelluric soundings in friuli north east italy and the electrical characteristic of the lithosphere summary one year long records of two magnetotelluric mt stations located in the seismic friuli region north east italy were analysed in the 60 28 800s period range the aim was the investigation of the deep lithospheric electric structure the computation of the impedances was made by an iterative signal to noise enhancing method impedances were analysed with complex singular value decomposition svd some tests were made trying to consider the distortion due to the shallow in homogeneities 1 d inversion of the apparent resistivity curves was carried out the models obtained indicate that the lithosphere thickens from 90 to 120 km westward in agreement with surface wave inversion the westernmost sounding located in an area of thickened crust indicates the presence of a 10 km thick intracrustal conductor which may be associated with incipient melting of lower crustal rocks

a major advance of tropical andean glaciers during the antarctic cold reversal a moraine chronology determined by surface exposure dating shows that glaciers in the northern tropical andes expanded to a larger extent during the antarctic cold reversal 14 500 to 12 900 years ago than during the younger dryas stadial 12 800 to 11 500 years ago contrary to previous studies as a result previous chronologies and climate interpretations from tropical glaciers may need to be revisited the younger dryas was a cold period immediately prior to the present warm interglacial period there is clear evidence that it occurred throughout much of the northern hemisphere but its global extent remains debatable prior work in the tropical andes suggested extensive glacial advances during the younger dryas vincent favier and colleagues present new cosmogenic dating of glacial deposits and a reassessment of existing datasets from other glaciated andean landscapes to show that instead maximal glacial advances took place in the preceding antarctic cold reversal rather than a major advance the younger dryas now appears to have been associated with modest glacial retreat the younger dryas stadial a cold event spanning 12 800 to 11 500 years ago during the last deglaciation is thought to coincide with the last major glacial re advance in the tropical andes1 this interpretation relies mainly on cosmic ray exposure dating of glacial deposits recent studies however have established new production rates2 3 4 for cosmogenic 10be and 3he which make it necessary to update all chronologies in this region1 5 6 7 8 9 10 11 12 13 14 15 and revise our understanding of cryospheric responses to climate variability here we present a new 10be moraine chronology in colombia showing that glaciers in the northern tropical andes expanded to a larger extent during the antarctic cold reversal 14 500 to 12 900 years ago than during the younger dryas on the basis of a homogenized chronology of all 10be and 3he moraine ages across the tropical andes we show that this behaviour was common to the northern and southern tropical andes transient simulations with a coupled global climate model suggest that the common glacier behaviour was the result of atlantic meridional overturning circulation variability superimposed on a deglacial increase in the atmospheric carbon dioxide concentration during the antarctic cold reversal glaciers advanced primarily in response to cold sea surface temperatures over much of the southern hemisphere during the younger dryas however northern tropical andes glaciers retreated owing to abrupt regional warming in response to reduced precipitation and land surface feedbacks triggered by a weakened atlantic meridional overturning circulation conversely glacier retreat during the younger dryas in the southern tropical andes occurred as a result of progressive warming probably influenced by an increase in atmospheric carbon dioxide considered with evidence from mid latitude andean glaciers16 our results argue for a common glacier response to cold conditions in the antarctic cold reversal exceeding that of the younger dryas

links between tropical rainfall and north atlantic climate during the last glacial period the last glacial period was marked by dramatic climate fluctuations sediment records from the cariaco basin and the arabian sea suggest that cooling in the north atlantic region was tightly coupled with a southward displacement of the intertropical convergence zone and a weakening of the indian summer monsoon

magneto telluric recordings from the friuli seismic zone northeast italy abstract magneto telluric measurements were undertaken in the friuli seismic area of north east italy the purpose was to find possible correlations between magneto telluric signals and seismic activity two stations were operational between july 1987 and june 1988 apparent resistivity curves were found for september 1987 and january 1988 data and a magneto telluric inversion problem was solved artificial noise and natural disturbances of the electromagnetic field especially those related to tectonic processes are discussed

large temperature variability in the southern african tropics since the last glacial maximum 1 the role of the tropics in global climate change is actively debated particularly in regard to the timing and magnitude of thermal and hydrological response continuous high resolution temperature records through the last glacial maximum lgm from tropical oceans have provided much insight but surface temperature reconstructions do not exist from tropical continental environments here we used the tex86 paleotemperature proxy to reconstruct mean annual lake surface temperatures through the last glacial maximum lgm in lake malawi east africa 9 14 s we find a 3 5 c overall warming since the lgm with temperature reversals of 2 c during the younger dryas 12 5 ka bp and at 8 2 ka bp maximum holocene temperatures of 29 c were found at 5 ka bp a period preceding severe drought in africa these results suggest a substantial thermal response of southeastern tropical africa to deglaciation and to varying conditions during the holocene

timing of millennial scale climate change in antarctica and greenland during the last glacial period a precise relative chronology for greenland and west antarctic paleotemperature is extended to 90 000 years ago based on correlation of atmospheric methane records from the greenland ice sheet project 2 and byrd ice cores over this period the onset of seven major millennial scale warmings in antarctica preceded the onset of greenland warmings by 1500 to 3000 years in general antarctic temperatures increased gradually while greenland temperatures were decreasing or constant and the termination of antarctic warming was apparently coincident with the onset of rapid warming in greenland this pattern provides further evidence for the operation of a bipolar see saw in air temperatures and an oceanic teleconnection between the hemispheres on millennial time scales

tropical ocean atmospheric forcing of late glacial and holocene glacier fluctuations in the cordillera blanca peru evaluating the timing and style of past glacier fluctuations in the tropical andes is important for our scientific understanding of global environmental change terrestrial cosmogenic nuclide ages on moraine boulders combined with 14c dated clastic sediment records from alpine lakes document glacial variability in the cordillera blanca of peru during the last 16 ka late glacial ice extents culminated at the start of the antarctic cold reversal and began retracting prior to the younger dryas multiple moraine crests dating to the early holocene mark brief readvances or stillstands that punctuated overall retreat of the queshque valley glacier terminus during this interval glaciers were less extensive during the middle holocene before readvancing during the latest holocene these records suggest that tropical atlantic and pacific ocean atmospheric processes exerted temporally variable forcing of late glacial and holocene glacial changes in the peruvian andes

sensitivities of the equilibrium line altitude to temperature and precipitation changes along the andes abstract equilibrium line altitudes elas of alpine glaciers are sensitive indicators of climate change and have been commonly used to reconstruct paleoclimates at different temporal and spatial scales however accurate interpretations of ela fluctuations rely on a quantitative understanding of the sensitivity of elas to changes in climate we applied a full surface energy and mass balance model to quantify ela sensitivity to temperature and precipitation changes across the range of climate conditions found in the andes model results show that ela response has a strong spatial variability across the glaciated regions of south america this spatial variability correlates with the distribution of the present day mean climate conditions observed along the andes we find that elas respond linearly to changes in temperature with the magnitude of the response being prescribed by the local lapse rates ela sensitivities to precipitation changes are nearly linear and are inversely correlated with the emissivity of the atmosphere temperature sensitivities are greatest in the inner tropics precipitation becomes more important in the subtropics and northernmost mid latitudes these results can be considered an important step towards developing a framework for understanding past episodes of glacial fluctuations and ultimately for predicting glacier response to future climate changes