middle to late holocene moisture changes in the desert of northwest namibia derived from fossil hyrax dung pollen new pollen results and radiocarbon dating from fossil hyrax middens derived from the edge of the northern namib desert address the shortage of continental palaeobotanical evidence in arid namibia by providing evidence for the environmental conditions during the mid to late holocene in the region the results obtained reflect long term stability in the area throughout most of the sequence higher than modern moisture availability is suggested between c 6 and 1 ka bp by the increased abundance of poaceae cyperaceae or chenopodiaceae which respond rapidly by flowering after modest quantities of rainfall around 1 ka and recently arid conditions seem to have prevailed with a decrease in poaceae and an increase in acanthaceae other palaeoecological evidence from the local and regional surroundings that focused on fluvial deposits marine palynology and mineralogy confirms this mid holocene increase in more effective rainfall

a high resolution 15 600 year pollen and microcharcoal record from the cederberg mountains south africa abstract the cederberg mountains western cape province south africa are located within the fynbos biome which exhibits some of the highest levels of species richness and endemism in the world the region s post glacial vegetation history however remains largely unknown presented here are high resolution pollen and microcharcoal records spanning the last 15 600 years obtained from the de rif rock hyrax midden from the driehoek valley of the central cederberg in this region previous pollen studies have shown muted variability in vegetation community composition during periods of globally marked climatic variability e g the last glacial interglacial transition in our record however significant changes in vegetation composition are apparent most notably they indicate a shift from ericaceous restioid fynbos present from 15 600 to 13 300 cal yr bp to a brief but prominent development of proteoid fynbos at the beginning of the holocene around 11 200 cal yr bp this vegetation shift is associated with increased moisture at the site and coincides with reduced fire frequency as indicated by the microcharcoal record at 10 400 cal yr bp there is a marked reduction in protea type pollen which is replaced by thicket characterised by dodonaea which became the dominant arboreal pollen type this shift was likely the result of a long relatively fire free period coupled with warmer and wetter climates spanning much of the early holocene a brief but marked decrease in water availability around 8500 8000 cal yr bp resulted in the strong decrease of dodonaea pollen the vegetation of the mid to late holocene is characterised by the increased occurrence of asteraceae and succulent taxa suggesting substantially drier conditions these data give unprecedented insight into the vegetation dynamics across a period of substantial rapid climate change and while they confirm the presence of fynbos elements throughout the last 15 600 years the results highlight significant fluctuations in the vegetation that were triggered by changes in both climate and fire regimes

palynology of hyrax middens 2000 years of palaeoenvironmental history in namibia abstract well preserved and dateable faunal middens in rock shelters of dry areas in southern africa occur as desiccated urine rich masses under local conditions which exclude microbial decomposition and oxidation urine cements together faecal pellets and other inclusions nine radiocarbon dated hyrax procavia capensis dung middens from the kuiseb river basin of the namib desert were sub sampled and analysed for fossil pollen some contain small proportions of rat droppings but not many macro fossils comparative modern pollen in faecal samples were also studied most plant macro fossils are severely digested but seeds are well preserved some insect inclusions were identified small scale changes in vegetation over the last two millennia were observed representing environmental fluctuations in cycles of ca 100 200 years the fluctuations partly agree with other palynological data from southern africa and with geomorphologic evidence for environmental changes in the desert region

impacts of recent paraglacial dynamics on plant colonization a case study on midtre lovenbreen foreland spitsbergen 79 n climatic changes since the end of the little ice age have considerably disturbed environmental balances of plant colonization in high latitudes within one century on spitsbergen valley glaciers have retreated up to one kilometre from their original terminus as of 1918 affecting several hundred hectares of two types of landscape processes plant colonization and paraglacial morphogenesis since these processes are limited to the chronological position of the old ice front it is possible to know the rate of plant colonization by both qualitative and quantitative means as well as speculate on the processes involved such as the effects of runoff the present study is limited to the midtre lovenbreen forefield latitude 79 n longitude 12 e where geomorphologic and floristic samples were collected in 2003 on stable deposits in this area the settlement and the evolution of floristic groups have been documented during this time period of colonization the plain areas are reworked by runoff at a kilometric scale and are characterized as similar to their surrounding biogeographic landscapes thus a relationship can be observed between the paraglacial process occurring in the proglacial forelands and surrounding stable surfaces on till deposits these features that occur as spatial discontinuities across the landscape are perceptible through either plant colonization or disturbance to vegetation caused by hydrological processes ultimately however runoff dynamics maintain pioneer vegetation groups which are superimposed on plant colonization that are driven by temporal periods of deglaciation differences in the rates and the nature of plant colonization are biomarkers of paraglacial dynamics

the mass balance of circum arctic glaciers and recent climate change the sum of winter accumulation and summer losses of mass from glaciers and ice sheets net surface mass balance varies with changing climate in the arctic glaciers and ice caps excluding the greenland ice sheet cover about 275 000 km2of both the widely glacierized archipelagos of the canadian norwegian and russian high arctic and the area north of about 60 n in alaska iceland and scandinavia since the 1940s surface mass balance time series of varying length have been acquired from more than 40 arctic ice caps and glaciers most arctic glaciers have experienced predominantly negative net surface mass balance over the past few decades there is no uniform recent trend in mass balance for the entire arctic although some regional trends occur examples are the increasingly negative mass balances for northern alaska due to higher summer temperatures and increasingly positive mass balances for maritime scandinavia and iceland due to increased winter precipitation the negative mass balance of most arctic glaciers may be a response to a step like warming in the early twentieth century at the termination of the cold little ice age arctic ice masses outside greenland are at present contributing about 0 13 mm yr 1to global sea level rise

mass balance of white glacier axel heiberg island n w t canada 1960 91 white glacier is a valley glacier at 79 5 n with an area of 38 7 km 2 its mass balance has been measured over 32 years with a 3 year gap by standard techniques using the stratigraphic system with a stake density of the order of one stake per km 2 errors in stake mass balance are about 200 250 mm due largely to the local unrepresentativeness of measurements errors in the whole glacier mass balance b are of the same order as single slake errors however the lag 1 autocorrelation in the time series of b is effectively zero so it consists of independent random samples and the error in the long term balance normal b is noticeably less b is 100 48 mm the equilibrium line altitude ela averages 970 m with a range of 470 1400 m mass balance is well correlated with ela but detailed modelling shows that the equilibrium line is undetectable on visible band satellite images a reduced network of a few stakes could give acceptable but less accurate estimates of the mass balance as could estimates based on data from a weather station 120 km away there is no evidence of a trend in the mass balance of white glacier to detect a climatologically plausible trend will require a ten fold reduction of measurement error a conclusion which may well apply to most estimates of mass balance based on similar stake densities

little ice age glacier extent and subsequent retreat in svalbard archipelago the influence of the little ice age lia on the glaciers of svalbard has been well documented for a long time this paper presents new data on the lia maximum glacier extent and retreat by aeria

paraglacial gullying of sediment mantled slopes a case study of colletthogda kongsfjorden area west spitsbergen svalbard this paper evaluates the paraglacial evolution of a sediment mantled slope in a polar maritime environment the intensity of paraglacial processes is estimated through quantifi cation of erosion and dating of fi eld sectors with the help of photographic archives gully erosion has been estimated using morphometric parameters and by surveys of vegetation cover the rapid melting of dead ice cores controls gully formation this leads to slope form modifi cation gully profi le gradients are reduced from a mean of 35 to a mean ranging between 10 and 15 profi le evolution results from the collapse of glacier lateral moraine all data mean slope angle of individual gullies frequency distribution of slope angles fractional distance to the apex gullying index volume of debris mobilized vertical erosion rate tend to increase with increasing deglaciation age and the duration of paraglacial activity vegetation colonization is a response to stabilization of the ground surface and the drying up of the ground surface due to dead ice melting the full sequence of paraglacial slope adjustment gully incision stabilization may occur rapidly at the study site i e within two decades finally a lateral morphogenic sequence is proposed showing the importance of paraglacial processes at the onset of the deglaciation

the duration of the active phase on surge type glaciers contrasts between svalbard and other regions many glaciers in svalbard and in other glacierized areas of the world are known to surge however the time series of observations required to assess the duration of fast motion is very restricted data on active phase duration in svalbard come from aerial photographs satellite imagery field surveys and airborne reconnaissance evidence on surge duration is available for eight svalbard ice masses varying from 3 to 1250 km 2 worldwide active phase duration is recorded for less than 50 glaciers few observations are available on high polar ice masses the duration of the active phase is significantly longer for svalbard glaciers than for surge type glaciers in other areas from which data are available in svalbard the active phase may last from 3 to 10 years by contrast a surge duration of 1 2 years is more typical of ice masses in northwest north america iceland and the pamirs ice velocities during the protracted active phase on svalbard glaciers are considerably lower than those for many surge type glaciers in these other regions mass is transferred down glacier more slowly but over a considerably longer period svalbard surge type glaciers do not exhibit the very abrupt termination of the active phase over periods of a few days observed for several alaskan glaciers the duration of the active phase in svalbard is not dependent on parameters related to glacier size the quiescent phase is also relatively long 50 500 years for svalbard ice masses detailed field monitoring of changing basal conditions through the surge cycle is required from surge type glaciers in svalbard in order to explain the significantly longer length of the active phase for glaciers in the archipelago which may also typify other high polar ice masses the finding that surge behaviour in the form of active phase duration shows systematic differences between different regions and their environments has important implications for understanding the processes responsible for glacier surges

simulating climatic mass balance seasonal snow development and associated freshwater runoff in the kongsfjord basin svalbard 1980 2016 the kongsfjord basin in northwest svalbard is the site of a number of interdisciplinary studies concerned with the effect of fresh water from seasonal snow and glacier melt on the physical and biol

a late quaternary pollen record from the transvaal bushveld south africa pollen spectra from cores of organic spring deposits from the transvaal provide evidence for the climatic evolution of the province during the last 35 000 yr b p or more the past climatic phases are derived from palynological reconstructions of past vegetation types by comparison of fossil pollen data with modern surface pollen spectra from various localities evidence is provided for an early moist cool phase with relatively mesic bushveld and expanded montane forest in the central transvaal followed by a drier period with drier bushveld which probably lasted until approximately 25 000 yr b p during the next phase which at the latest ended about 11 000 yr b p the temperatures were probably 5 6 c cooler than at present at that time bushveld vegetation in the central transvaal was replaced by open grassland with macchia elements climatic amelioration came and semiarid savanna returned to the plains at first gradually and then developing into a warm kalahari thornveld type vegetation after 6000 yr b p it apparently became slightly wetter and a more broad leafed bushveld developed about 4000 yr b p it again became cooler and slightly wetter and the bushveld vegetation on the central and northern plains was comparable to present open upland types after 2000 yr b p conditions gradually became warner until about 1000 yr b p when the modern climate of the central transvaal bushveld originated

pollen analysis of hyena coprolites and sediments from equus cave taung southern kalahari south africa equus cave in quaternary tufa near taung in the semiarid woodland of the southern kalahari yielded 2 5 m of sediment in which a rich assemblage of bones and coprolites was preserved the fossils were accumulated mainly by hyenas during the late pleistocene and holocene pollen from coprolites reflects diet as well as vegetation over relatively large areas visited by hyenas while pollen from sediments represents more local sources the pollen sequence derived from coprolites and sediments demonstrates how the vegetation evolved from open grassland with small shrubs and occasional trees during the late pleistocene to open savanna with more small shurbs then during the last 7500 yr to modern savanna temperatures were not more than 4 c cooler and it was slightly moister than today during the late pleistocene phase it became gradually warmer but relatively dry before optimal temperature and moisture conditions developed around 7500 yr b p climatic conditions slightly less favorable for woodland occurred during part of the late holocene

late holocene environmental change in the northwestern namib desert margin new fossil pollen evidence from hyrax middens abstract the lack of anoxic environments in arid lands makes well preserved fossil pollen difficult to find the scarcity of continental palaeobotanical data in tropical arid zones restricts the understanding of aridification processes in these endangered ecosystems it is essential to improve the knowledge about their environmental histories during the holocene and therefore we attempt to investigate the causes and describe the patterns of vegetation change in northern namibia with that aim we analyzed pollen from fossil hyrax dung that accumulated over long periods of time by sampling stratigraphically coherent sequences in five radiocarbon dated middens the fossil hyrax middens were found in rock shelters on the eastern desert edge in the northwestern kaokoveld within the so called nama karoo biome this is an ecotonal area between the namib desert and the savanna biomes which reflects features from both systems and its life form composition largely depends on an erratic rainfall pattern thirty three samples were analyzed for pollen and the pollen record reflects a non continuous vegetation history over the last 5200 yr with a hiatus between ca 4200 and 1690 yr bp the pollen spectra reflect arid savanna vegetation with a marked increase in the tree grass ratio from ca 1300 cal yr bp the most likely cause for this change is a decline in moisture that we relate to intrinsic savanna dynamics with early pastoralism megahervibore migration and changes in the hyrax diet playing a minor role

mega lake in the kalahari a late pleistocene record of the palaeolake makgadikgadi system abstract a distinct series of beach ridges marking the former shorelines of large inter connected lacustrine basins in the kalahari can be clearly identified from landsat imagery and shuttle radar topography mission srtm data these basins which form the terminal sump of the okavango system in northern botswana are now almost completely dry during the quaternary they were intermittently occupied by large stable lake bodies and are thought to have periodically filled to a point of coalescence inundating an area that at its largest extent encompassed 66 000 km 2 poor chronological control has previously limited the utility of this important palaeo archive as part of a region wide lake palaeo shoreline research programme a systematic optically stimulated luminescence osl dating programme has utilised a lightweight hydraulic auger to take samples at depth from relict shoreline features twenty drill sites have generated 140 samples for dating establishing a firm chronology for multiple lake full phases in all three component basins ngami mababe and makgadikgadi of this mega lake this paper presents the final set of ages in the programme derived from four cores from the western and north eastern shorelines of makgadikgadi and uses these ages to establish a chronology of mega lake high stands during the last 300 ka providing a rare directly dated long terrestrial record of positive hydrological excursions within the southern hemisphere

surge type glaciers in the russian high arctic identified from digital satellite imagery landsat digital imagery was used to search the island archipelagos of franz josef land severnaya zemlya and novaya zemlya russian high arctic for the presence of looped moraines characteristic of past glacier surges the imagery provides almost complete summer time coverage of the 60000 km 2 of ice in these islands very few surge type glaciers are identified none in franz josef land three in novaya zemlya and two on severnaya zemlya this contrasts greatly with svalbard ice covered area 36 600 km 2 to the west where 36 of glaciers and ice cap drainage basins are inferred to surge the strong climatic gradient across the eurasian high arctic with decreasing temperature and moisture eastward may provide a gross control on this pattern through colder glacier thermal structure limiting basal drainage on the thinner ice masses in particular

50 000 years of vegetation and climate change in the southern namib desert pella south africa abstract this paper presents the first continuous pollen record from the southern namib desert spanning the last 50 000 years obtained from rock hyrax middens found near the town of pella south africa these data are used to reconstruct vegetation change and quantitative estimates of temperature and aridity results indicate that the last glacial period was characterised by increased water availability at the site relative to the holocene changes in temperature and potential evapotranspiration appear to have played a significant role in determining the hydrologic balance the record can be considered in two sections 1 the last glacial period when low temperatures favoured the development of more mesic nama karoo vegetation at the site with periods of increased humidity concurrent with increased coastal upwelling both responding to lower global regional temperatures and 2 the holocene during which time high temperatures and potential evapotranspiration resulted in increased aridity and an expansion of the desert biome during this latter period increases in upwelling intensity created drier conditions at the site considered in the context of discussions of forcing mechanisms of regional climate change and environmental dynamics the results from pella stand in clear contrast with many inferences of terrestrial environmental change derived from regional marine records observations of a strong precessional signal and interpretations of increased humidity during phases of high local summer insolation in the marine records are not consistent with the data from pella similarly while high percentages of restionaceae pollen has been observed in marine sediments during the last glacial period they do not exceed 1 of the assemblage from pella indicating that no significant expansion of the fynbos biome has occurred during the last 50 000 years these findings pose interesting questions regarding the nature of environmental change in southwestern africa and the significance of the diverse records that have been obtained from the region

estimating the long term calving flux of kronebreen svalbard from geodetic elevation changes and mass balance modelling this study independently quantifies geodetic elevation change and models surface mass balance to solve the continuity equation the approach is tested on two dynamically different glaciers kongsvegen and kronebreen in northwest svalbard through two time epochs 1966 1990 95 i and 1990 95 2007 ii on kongsvegen a dynamically inactive glacier the residual term represents an error associated with determining elevation changes and surface mass balance it is apparent that centerline mass balance estimates are not representative of the entire glacier which we relate to center line accumulation being larger than the elevation bin average on kronebreen a fast flowing and actively calving glacier a significant part of the residual is identified with the long term calving flux for both glaciers the cumulative surface mass balance remained close to zero during the first epoch but became increasingly negative in the second epoch the long term calving flux of kronebreen is estimated to be 0 14 0 03 km3 w e a 1 during epoch i and 0 20 0 05 km3 w e a 1 in epoch ii

fossil hyrax dung and evidence of late pleistocene and holocene vegetation types in the namib desert abstract pollen was derived from fossil dung of herbivorous hyraxes deposited in a rock shelteron the highest mountain in namibia da ures or brandberg situated on the namib desert margin radiocarbon dating ranging in age between modern times and 30000yrbp showed it representsthe rst empirical pollen evidence of continental palaeovegetation during the late pleistocene alongthe western escarpment of southern africa the initial results indicate last glacial maximum vegeta tion differed totally from the current pattern as vegetation types were dominated by small asteraceaeshrubs in contrast to those of the holocene and modern times which show more succulents grassandwoody elements arboreal pollen the resultssuggest that cape oral communities didnot reachinto thetropics along thewestern escarpment ofafrica despite such pollentypes occurring inmarinecores copyright 2004 john wiley sons ltd keywords palynology namibia restionaceae late pleistocene last glacial maximum

glacier bed characteristics of midtre lovenbreen svalbard from high resolution seismic and radar surveying we conducted a seismic and radar survey of the central part of midtre lovenbreen a small polythermal valley glacier in svalbard we determined the physical properties of the material beneath the glacier by measuring the reflection coefficient of the bed by comparing the energy of the primary and multiple reflections and deriving the acoustic impedance by making reasonable assumptions about the properties of the basal ice we determined the acoustic impedance of the bed material as 6 78 1 53 x 10 6 kg m 2 s 1 we interpret the material beneath the glacier to be permafrost with up to 50 ice and we speculate that the material may be frozen talus similar to a deposit observed directly by others beneath another svalbard glacier the implication for midtre lovenbreen is that the basal material beneath the present glacier is not able to support fast flow we conclude that midtre lovenbreen has most likely had limited capability for faster flow in the past with motion dominated by internal deformation midtre lovenbreen is used as a study glacier for the scientific community in svalbard and a large number of studies have been based there our results show that it cannot be used as an analogue for larger glaciers in svalbard having distinct basal boundary conditions

glacier hydrology in svalbard norwegian high arctic abstract progress in glacier hydrology has focused on temperate glaciers although partly or wholly non temperate glaciers are found in many parts of the world and significant areas of former ice sheets were probably non temperate it has usually been assumed that drainage from non temperate glaciers consists of relatively dilute and invariable supraglacial runoff in this paper the hydrology of glaciers in the high arctic archipelago of svalbard is examined variations in the thermal regimes of glaciers and their implications for drainage are first addressed results from svalbard concerning meltwater discharge and storage and solute and suspended sediment dynamics are then reviewed in general meltwater penetration of non temperate ice is limited and drainage from non temperate glaciers in svalbard has many of the characteristics of sub aerial drainage however it would be erroneous to view this drainage simply as dilute supraglacial runoff as significant material transport occurs in suspension and solution furthermore twentieth century climate change has probably led to changes in the thermal regimes of some svalbard glaciers such that relict drainage structures are sometimes observed while meltwater yields are augmented by runoff which can be attributed to the loss of mass from glaciers at large spatial scales turbid plumes observed at the marine margins of polythermal ice caps indicate that meltwater can be routed subglacially through non temperate ice

a record of the last 460 thousand years of upper ocean stratification from the central walvis ridge south atlantic the upper branch of the atlantic meridional overturning circulation predominantly enters the atlantic ocean through the southeast where the subtropical gyre is exposed to the influence of the agulhas leakage al to understand how the transfer of indian ocean waters via the al affected the upper water column of this region we have generated new proxy records of planktic foraminifera from a core on the central walvis ridge on the eastern flank of the south atlantic gyre sag we analyzed the isotopic composition of subsurface dweller globigerinoides ruber sensu lato and thermocline globorotalia truncatulinoides sinistral spanning the last five pleistocene glacial interglacial g ig cycles the former displays a response to obliquity suggesting connection with high latitude forcing and a warming tendency during each glacial termination in response to the interhemispheric seesaw the 18o difference between the two species interpreted as a proxy for upper ocean stratification reveals a remarkably regular sawtooth pattern bound to g ig cyclicity it rises from interglacials until glacial terminations with fast subsequent decrease appearing to promptly respond to deglacial peaks of al stratification however bears a different structure during the last cycle being minimal at last glacial maximum and peaking at termination i we suggest this to be the result of the intensified glacial wind field over the sag and or of the invasion of the south atlantic thermocline by glacial north atlantic intermediate waters the 13c time series of the two species have similar g ig pattern whereas their difference is higher during interglacials we propose that this may be the result of the alternation of intermediate water masses in different circulation modes and of a regionally more efficient biological pump at times of high pco2

rock hyrax middens a palaeoenvironmental archive for southern african drylands abstract like many of the world s subtropical regions southern africa is highly sensitive to changes in the earth s climate system but a dearth of reliable palaeoenvironmental records means that relatively little is known about how regional environments have been affected over centennial to multi millennial timescales to a large extent this sensitivity is a function of the position of these regions at the interface between temperate and tropical circulation systems the resulting seasonality and irregularity of rainfall have limited the development of suitable archives such as lakes and wetlands for the preservation of palaeoenvironmental proxies this paper reviews and evaluates the value of rock hyrax middens as novel palaeoenvironmental archives in southern africa considered are 1 the contemporary taxonomy distribution and ecology of hyraxes 2 the mechanisms of hyrax midden development their physical and chemical structure rates of accumulation and age and 3 the palaeoenvironmental proxies preserved within hyrax middens including fossil pollen stable isotopes and biomarkers the interpretive constraints and opportunities offered by these various midden characteristics are assessed with a view to demonstrating the potential of these deposits widespread as they are through arid and semi arid southern africa in providing a more detailed and chronologically resolved view of late quaternary palaeoenvironments across the subcontinent

palaeoenvironmental conditions in south africa at the pleistocene holocene transition abstract palaeoenvironmental records which include the interval between 11 000 and 10 000 bp have been investigated for 15 sites in south africa less than half of them are well dated and have a resolution adequate for elucidating climatic conditions during the time of the younger dryas a sea surface temperature record from a marine mollusc sequence provides the only unequivocal evidence of cooling during this time none of the palynological sequences from the interior of the subcontinent suggest consistent deviations in temperature or moisture attributable to a younger dryas equivalent based on the available evidence therefore it seems that if global younger dryas conditions influenced the climate of south africa the effect was too small to register a spatially consistent pattern in the pollen sequences of the interior of the country

sensitivity to long term climate change of subpermafrost groundwater systems in svalbard deep subpermafrost aquifers are highly climate dependent with the permafrost as an aquitard preventing groundwater recharge and discharge a study from the high arctic island of spitsbergen svalbard shows that during a glacial to interglacial phase both the permafrost and the glacier regime will respond to climatic changes and a glacier fed groundwater flow system will vary accordingly a full glaciation results in the melting of permafrost and groundwater can flow through pores and fracture systems in the rocks and sediments below the temperate zones of glaciers these groundwater flow systems will mainly be localized to fjords and valleys and form low lying terrestrial springs when the relative sea level drops during deglaciation due to glacio isostatic rise during an interglaciation permafrost develops and thickens and the groundwater recharge and discharge areas will thereby be gradually reduced to a minimum reached at the warmest part of an interglaciation an already frozen spring system cannot reopen before the permafrost melts only groundwater springs related to permanently warm based glacial ice will persist into the next glaciation during a new glaciation flow systems that terminated during the previous interglaciation may become revitalized if overridden by warm based ice causing permafrost thawing

late quaternary dynamics of southern africa s winter rainfall zone abstract variations in the nature and extent of southern africa s winter rainfall zone wrz have the potential to provide important information concerning the nature of long term climate change at both regional and hemispheric scales positioned at the interface between tropical and temperate systems southern africa s climate is influenced by shifts in the intertropical convergence zone the westerlies and the development and position of continental and oceanic anticyclones over the last glacial interglacial cycle substantial changes in the amount and seasonality of precipitation across the subcontinent have been linked to the relative dominance of these systems central to this discussion has been the extent to which the region s glacial climates would have been affected by expansions of antarctic sea ice equatorward migrations of the westerlies more frequent intense winter storms and an expanded wrz this paper reviews the developing body of evidence pertaining to shifts in the wrz and the evolution of ideas that have been presented to explain the patterns observed dividing the region into three separate axes along the western and southern margins of the continent and across the interior into the karoo and the kalahari a range of evidence from both terrestrial sites and marine cores is considered and potential expansions of the wrz expansions are explored despite the limitations of many of the region s proxy records a coherent pattern has begun to develop of a significantly expanded wrz during phases of the last glacial period with the best documented being between 32 17 ka while more detailed inferences will require the recovery and analysis of longer and better dated records this synthesis provides a new baseline for further research in this key region

late quaternary highstands at lake chilwa malawi frequency timing and possible forcing mechanisms in the last 44 ka the extensive shoreline deposits of lake chilwa southern malawi a shallow water body today covering 600 km2 of a basin of 7500 km2 are investigated for their record of late quaternary highstands osl dating applied to 36 samples from five sediment cores from the northern and western marginal sand ridges reveal a highstand record spanning 44 ka using two different grouping methods highstand phases are identified at 43 7 33 3 ka 26 2 21 0 ka and 17 9 12 0 ka total error method or 38 4 35 5 ka 24 3 22 3 ka 16 2 15 1 ka and 13 5 12 7 ka finite mixture model age components with two further discrete events recorded at 11 01 0 76 ka and 8 52 0 56 ka highstands are comparable to the timing of wet phases from other basins in east and southern africa demonstrating wet conditions in the region before the lgm which was dry and a wet lateglacial which commenced earlier in the southern compared to northern hemisphere in east africa we find no evidence that wet phases are insolation driven but analysis of the dataset and gcm modelling experiments suggest that heinrich events may be associated with enhanced monsoon activity in east africa in both timing and as a possible causal mechanism

mid latitude southern indian ocean response to northern hemisphere heinrich events abstract the lack of temporal resolution and accurate chronology of southern ocean marine cores has hampered comparison of glacial millennial scale oscillations between the southern ocean antarctic ice and other records from both hemispheres in this study glacial climate variability is investigated over the last 50 ka using a multi proxy approach a precise chrono stratigraphy was developed on the high sedimentation rate core md94 103 indian southern ocean 45 35 s 86 31 e 3560 m water depth by geomagnetic synchronization between the later core and napis75 and 14c dates high resolution time series of 18o in planktonic foraminifera globigerina bulloides and neogloboquadrina pachyderma and sea surface temperatures ssts estimated from the alkenone uk 37 index and foraminifera assemblages have been generated temporal evolution of the two temperature proxy records is notably different during the last glacial period while foraminifera data indicate a consistent cooling towards the last glacial maximum anomalous warm glacial alkenone temperatures suggest a strong advection of warm detrital alkenones by surface waters of the agulhas current superimposed to this general trend during heinrich events foraminiferal ssts point to warmer surface waters while concurrent alkenone ssts exhibit apparent coolings probably caused by enhanced local alkenone production by analogy to modern observations possible influence of enso like conditions on the subantarctic southern ocean ssts is discussed

pollen distribution in the marine surface sediments of the mudbelt along the west coast of south africa abstract the distribution of pollen in marine surface sediments offshore of the west coast of south africa has been investigated to aid in the interpretation of marine pollen records of onshore vegetation changes a transect of sediment surface pollen samples retrieved from the namaqualand mudbelt from just south of the orange river mouth 29 s to st helena bay 33 s indicates distinctive pollen spectra reflecting vegetation communities on the adjacent continent pollen concentration increases southwards partly in relation to greater pollen productivity due to higher biomass and density of fynbos vegetation and of sedimentary processes and low pollen concentrations consequent to dilution with silt and clay from the orange river the distribution of specific pollen taxa suggests that the orange river is a major contributor of pollen to the northern mudbelt declining southwards while the pollen distribution in the central mudbelt is largely attributable to seasonal inputs of pollen from offshore berg winds and local ephemeral namaqualand rivers the typical fynbos elements dominate in the southern mudbelt indicating a pollen source mainly in the fynbos vegetation types these conclusions support a companion analysis of fossil pollen records of two marine sediment cores from the northern and southern mudbelt respectively this study demonstrates that pollen records from marine sediment cores in the namaqualand mudbelt have the potential to be a tool to reconstruct palaeovegetation on the adjacent continent however to better reconstruct the palaeoclimate of south africa and fully understand the relations between terrestrial and marine deposits more marine surface sediments along the western coast of south africa as well as more terrestrial surface sediments need to be studied

superimposed ice regime of a high arctic glacier inferred using ground penetrating radar flow modeling and ice cores 1 a 900 mhz ground penetrating radar gpr profile collected along 1 7 km of the centerline of a high arctic glacier in svalbard is interpreted using shallow ice core data and thermomechanical flow modeling four distinct zones are visible in the image and correspond to areas of firn recent and older superimposed ice and ablation zone glacier ice on the ground the areas of firn and superimposed ice are characterized by relatively steeply and gently dipping internal reflecting horizons irh respectively in the radar image the irhs arise from permittivity contrasts due to density variations produced in firn by alternating firn and ice layers and in superimposed ice by varying air bubble content recently formed and older superimposed ice can be distinguished in the gpr image a three dimensional flow model is used to indicate the long term mass balance and flow history responsible for the spatial distribution and orientation of superimposed ice irhs in the radar image results indicate that the irh distribution can only be explained by invoking a down glacier shift in mean 30 year equilibrium line altitude ela by 20 30 m compared with measured mean 30 year ela they also suggest that many of the superimposed irhs are relict features produced 100 years b p when the ela was 100 150 lower than at present this work advocates combined gpr and flow modeling as a unique tool for validating mass balance measurements and or inferring the mass balance dynamic history of a glacier beyond a recent measurement period

spatio temporal variability in elevation changes of two high arctic valley glaciers uncertainties in estimates of glacier and ice cap contribution to sea level rise exist in part due to poor quantification of mass balance errors particularly those resulting from extrapolation of sparse measurements centre line data are often assumed to be representative of the glacier as a whole with little attention paid to extrapolation errors or their effect on mass balance estimates here we present detailed digital elevation model dem measurements of glacier wide elevation changes over the last 40 years at two glaciers on svalbard norwegian arctic austre broggerbreen and midtre lovenbreen are shown to have lost 27 54 0 98 and 9 65 0 76 10 7 m 3 of ice respectively between 1966 and 2005 findings that we relate to trends in average summer air temperatures and winter accumulation these volume losses correspond to geodetic balances of 0 58 0 03 and 0 41 0 03 m w e a 1 respectively our analysis revealed high spatial complexity in patterns of elevation change varying between glaciers between measurement intervals and within and between elevation bins balances from extrapolated centre line geodetic data were the same within errors as those from full coverage dem differencing in the majority of comparisons yet significantly underestimated balance in three instances additionally field mass balance from centre line ablation stake data underestimated balances from full coverage geodetic measurements during three of six measurement periods these findings may support the hypothesis that field measurements under estimate svalbard glacier mass loss at least partly as a result of the failure of centre line measurements to account for glacier wide variations in ablation our results demonstrate the importance of deriving accurate interpolation functions and constraining extrapolation errors from sparse measurements

styles of sedimentation beneath svalbard valley glaciers under changing dynamic and thermal regimes glacier beds provide crucial information concerning past and present ice dynamics and thermal regime in this paper we present structural and sedimentological data from four valley glaciers austre lovenbreen midtre lovenbreen vestre lovenbreen and austre broggerbreen on broggerhalvoya nw spitsbergen the main focus of this paper is midtre and austre lovenbreen two typical high arctic land based polythermal valley glaciers the former has a long record of documentation regarding its response to twentieth century climatic warming structural mapping on the glacier surface and analysis of sediments in the proglacial area of midtre lovenbreen indicate that the dynamic regime and thermal structure of the glacier have changed through time dynamically midtre lovenbreen was once heavily crevassed and relatively fast moving but now is virtually crevasse free and slow moving the sedimentary record indicates that extensive areas of this glacier were wet based when it was in a more advanced state probably at its neoglacial maximum late nineteenth early twentieth centuries during this advance a thin deforming layer of diamicton commonly fluted was draped over the existing morphology in the presently exposed proglacial area this morphology consisted of large streamlined ridges aligned parallel to ice flow erosion of the underlying bedrock appears to have been limited radio echo soundings of the glacier show that at present it is characterized by a polythermal basal thermal regime with wet based subglacial conditions only beneath its thicker parts modification of the bed is limited under this thermal regime and as a result the supraglacial environment dominates modern sedimentation comparative studies on austre lovenbreen which also is probably polythermal indicate similar sedimentary characteristics and facies associations although here there are much more extensive areas of striated bedrock indicative of former basal sliding in contrast both austre broggerbreen and by analogy vestre lovenbreen are known to be predominantly cold based collectively these four glaciers suggest a trend of glacier recession and thinning accompanied by a change in thermal regime from predominantly wet based through partly frozen to completely frozen this study suggests that svalbard valley glaciers have several dynamic modes and that glaciers switch between these modes largely as a reaction to changes in mass balance

geometry change between 1990 and 2003 at finsterwalderbreen a svalbard surge type glacier from gps profiling surface mass balance and geometry data are key to quantifying the climate response of glaciers and confidence in data synthesis and model interpretations and forecasts requires data from as wide a range of locations and glacier types as possible this paper presents measurements of surface elevation change at the svalbard surge type glacier finsterwalderbreen by comparing a 1990 digital elevation model dem with a surface gps profile from 2003 the pattern of elevation change is consistent with that previously noted between 1970 and 1990 and reflects the continued quiescent phase evolution of the glacier with mass loss in the down glacier receiving area of up to 1 25 m w e a 1 and mass gain in the up glacier reservoir area of up to 0 60 m w e a 1 the area weighted mean change for the whole glacier is 0 19 m w e a 1 the spatial pattern of elevation increase and decrease is complex and the boundary between thickening and thinning determined by combining gps and dem data does not appear to correspond with the equilibrium line altitude determined from surface mass balance measurements there is no evidence yet of a decrease in the rate of reservoir area build up driven by mass balance change resulting from the warmer winter air temperatures and decreased proportion of snowfall in total precipitation noted at meteorological stations in svalbard

interhemispheric comparison of deglacial sea surface temperature patterns in atlantic eastern boundary currents abstract sediment core geob 1023 5 from the eastern south atlantic was investigated at high temporal resolution for variations of sea surface temperature sst during the past 22 kyr using the alkenone u k 37 method ssts increased by 3 5 c from about 18 c during the last ice age 21 2 cal kyr bp to about 21 5 c at 14 5 cal kyr bp this warming trend associated with the deglaciation phase was followed by a cooling event with lowest ssts near 20 c persisting for about 1000 years between 13 and 12 cal kyr bp the ssts then continued to increase to about 22 5 c at the holocene climatic optimum at 7 cal kyr bp and decreased again during the late holocene to a core top value of 19 8 c that is comparable to modern annual mean sst values when compared with alkenone sst records from the eastern north atlantic our sst record indicates continuous warming throughout the deglaciation phase in the benguela current while its northern counterpart the canary current experienced prominent cooling during heinrich event 1 h1 on the other hand for the time period corresponding to the younger dryas yd cooling event the benguela sst record exhibits a cold temperature interval that corresponds to that observed in the eastern north atlantic sst records this observation suggests that interhemispheric climate response in atlantic eastern boundary current systems was different with respect to the two abrupt climate events associated with termination i for the h1 the eastern south atlantic sst record strongly supports the hypothesis that an anti phase thermal behavior in south atlantic surface waters was forced by the slowdown of the north atlantic deep water formation during cold spells in the north atlantic in contrast the abrupt cooling in the eastern south atlantic coincident with the yd period was probably induced by more vigorous global atmospheric circulation enhancing the upwelling intensity in both eastern boundary current systems this atmospheric control may have overridden any effect caused by changes in thermohaline circulation on the south atlantic ssts during the yd which leads to the assumption that the thermohaline circulation was already much closer to its interglacial mode during the yd than during the h1

pollen in fossil hyrax dung from marine isotope stages 2 and 3 reveals past environments in namibia abstract in view of a scarcity of terrestrial quaternary pollen records relating to climate change in desert areas we present new terrestrial sequences from hyrax middens in namibia while the few previously available pollen records are mainly holocene we present climate time series for marine isotope stages 2 and 3 mis 2 and mis 3 the data are from two sites in central namibia that are surrounded by desert plains and close to the namibian escarpment viz the d ures massif brandberg and 200 km further south the mirabib shelter located in a small inselberg in the studied material grass rich pollen assemblages were more common at mirabib where the vegetation is desert grassland than at brandberg with its mountain vegetation hyrax radiocarbon ages range from 21 ka to 50 ka with inconsistencies in ages near the limit of effective radiocarbon dating however correlation of overlapping sequences supports the chronology we present despite chronological gaps in the available deposits pollen assemblages from different middens indicate marked climate cycles starting with moderately cool dry conditions with grassy karroid vegetation at mirabib c 50 ka after a gap in the record warmer conditions with savanna woodland are indicated at both mirabib and brandberg around 40 ka eventually cool conditions supporting shrubby grassland with wild olives developed at brandberg during mis 2 c 21 ka comparison with marine pollen data confirms earlier findings that terrestrial pollen assemblages differ markedly from south atlantic ocean marine pollen assemblages of the same age presumably due to mixing of pollen from wide source areas at the marine localities versus the more locally restricted terrestrial pollen sources trapped in hyrax dung the results therefore add information for the interpretation of local vegetation shifts on land during the interval between 50 ka and 21 ka in namibia

quantification of historical landscape change on the foreland of a receding polythermal glacier horbyebreen svalbard the assessment of multidecadal scale change in a polythermal glacial landsystem in the high arctic is facilitated by a quantitative approach that utilises time series of aerial photographs satellite images digital elevation models and field geomorphological mapping the resulting spatiotemporal analysis illustrates a transition from glacial to proglacial paraglacial conditions indicating that 1 the areal coverage of ice between the maximum lia extent and 2013 decreased from 29 35 to 16 07 km2 which is a reduction in the glacierized area in the catchment from 62 to 34 2 the ice volume loss in the proglacial area amounted to 214 9 3 million m3 which was attributed mostly to ablation of the glacier snout but to a lesser extent the degradation of ice cored landforms 3 the transition from areas formerly covered by glacier ice to ice cored moraines glacifluvial deposits and other landforms was the most intense in the period 1990 2013 4 two end member scenarios polythermal glacial landsystem domains evolve during glacier recession each one dictated by the volume of debris in englacial and supraglacial positions and include a subglacial surfaces limited englacial and supraglacial debris related to temperate basal ice and b ice cored lateral moraines and moraine mound complexes significant supraglacial debris accumulations related to marginal cold based ice an additional assemblage of geometric ridge networks discrete or linear englacial and supraglacial debris concentrations relates to crevasse and hydrofracture infill branching out from an esker complex and is indicative of either surging or later rapid release of pressurised meltwater from temperate to cold based parts of the former glacier snout

a 19 5 kyr vegetation history from the central cederberg mountains south africa palynological evidence from rock hyrax middens abstract in arid and semi arid areas such as southern africa rock hyrax procavia capensis middens represent an exceptionally valuable source of late quaternary palaeoenvironmental information pollen and stable isotope data derived from two rock hyrax middens extracted from de rif in the cederberg mountains of the southwestern cape casts new light on climatic changes that occurred across the last glacial interglacial transition lgit and the holocene 19 5 0 7 cal kbp and how the region s vegetation responded to these changes significant changes in vegetation community composition would be expected in response to environmental changes characteristic of the contrast between glacial and interglacial climates however the pollen assemblages in general indicate that mountain fynbos remained dominant throughout the record and that most of the pollen taxa exhibited only muted frequency variations this finding could be considered to be inconsistent with indications of marked climatic variations recorded in the stable isotope records for the same midden an analysis of the geological setting and the bioclimatic affinities of the taxa suggest that the explanation for this inconsistency may lie in the dominating influence of sandstone substrates and the relative resilience of mountain fynbos vegetation to climate change

the thermal regime of sub polar glaciers mapped by multi frequency radio echo sounding radio echo soundings provide an effective tool for mapping the thermal regimes of polythermal glaciers on a regional scale radar signals of 320 370 mhz penetrate ice at sub freezing temperatures but are reflected from the top of layers of ice which are at the melting point and contain water radar signals of 5 20 mhz on the other hand see through both the cold and the temperate ice down to the glacier bed radio echo soundings at these frequencies have been used to investigate the thermal regimes of four polythermal glaciers in svalbard kongsvegen uversbreen midre lovenbreen and austre broggerbreen in the ablation area of kongsvegen a cold surface layer 50 160m thick was underlain by a warm basal layer which is advected from the temperate accumulation area the surface ablation of this cold layer may be compensated by freezing at its lower cold temperate interface this requires that the free water content in the ice at the freezing interface is about 1 of the volume the cold surface layer is thicker beneath medial moraines and where cold based hanging glaciers enter the main ice stream on uversbreen the thermal regime was similar to that of kongsvegen a temperate hole was found in the otherwise cold surface layer of the ablation area in a surface depression between kongsvegen and uversbreen where meltwater accumulates during the summer near the subglacial lake setevatnet 250 m a s l lovenbreen was frozen to the bed at the snout and along all the mountain slopes but beneath the central part of the glacier a warm basal layer up to 50m thick was fed by temperate ice from two cirques on austre broggerbreen a temperate basal layer was not detected by radio echo soundings but the basal ice was observed to be at the melting point in two boreholes

a record of rapid holocene climate change preserved in hyrax middens from southwestern africa the discovery of sensitive paleoenvironmental proxies contained within fossilized rock hyrax middens from the margin of the central namib desert africa is providing unprecedented insight into the region s environmental history high resolution stable carbon and nitrogen isotope records spanning 0 11 700 cal calibrated yr b p indicate phases of relatively humid conditions from 8700 7500 6900 6700 5600 4900 and 4200 3500 cal yr b p with a period of marked aridity occurring from 3500 until ca 300 cal yr b p transitions between these phases appear to have occurred very rapidly often within 200 years of particular importance are 1 the observed relationship between regional aridifi cation and the decline in northern hemisphere insolation across the holocene and 2 the signifi cance of suborbital scale variations in climate that covary strongly with fl uctuations in solar forcing together these elements call for a fundamental reexamination of the role of orbital forcing on tropical african systems and a reconsideration of what factors drive climate change in the region the quality and resolution of these data far surpass any other evidence available from the region and the continued development of this unique archive promises to revolutionize paleoenvironmental studies in southern africa

sediment accumulation rates in subpolar fjords impact of post little ice age glaciers retreat billefjorden svalbard abstract the little ice age 1600 1900 ad and 20th century sediment accumulation rates in billefjorden a subpolar fjord on svalbard were reconstructed by applying 210 pb 137 cs and ams 14 c datings the modern sediment accumulation rate decreases from more than 0 39 cm y 1 at the fjord head to 0 08 cm y 1 close to the fjord mouth however during the little ice age the sediments accumulated at a much lower rate of 0 02 cm y 1 in the central fjord basin this difference is most likely related to the rapid retreat of glaciers during the 20th century when most of them withdrew up to 2 km the post little ice age increases in temperature and a negative glacier mass balance resulted in a larger meltwater discharge transferring substantial amounts of sediments released from the glaciers as well as those eroded from previously stored unconsolidated glacial sediments a comparison of data from the subpolar fjords of svalbard suggests that the increase in the sediment accumulation rate is a common trend and further increases might be expected if climate warming continues the properties of the fjord sediments grain size ird coarse fraction composition clay mineralogy from the little ice age and the 20th century showed no distinct differences the change in the accumulation rate may be the most evident sedimentary record of this climatic change

holocene environmental changes in namibia inferred from pollen analysis of swamp and lake deposits spring deposits exposed during building operations in downtown windhoek and lake sediments retrieved from underneath 50 m of water in a sinkhole lake otjikoto contain pollen profiles which reflect environmental changes in namibia during the holocene at windhoek moist local conditions are reflected by pollen in the spring deposits which were radiocarbon dated to between ca 7000 and 6000 bp they remained relatively favourable until 5630 bp despite signs of drying weedy compositae lactucoideae or liguliflorae increased until the end of this record ca 2410 bp indicating local disturbance deposits from lake otjikoto were dated to the late holocene although an accurate chronology could not be estabiished for the sequence due to unexpected results with radiocarbon measurements pollen accumulation values and composition indicate relatively dry conditions after 3500 bp which were followed temporarily by a wetter climate during more recent times

statistical modelling of the surface mass balance variability of the morteratsch glacier switzerland strong control of early melting season meteorological conditions in this study we analyse a 15 year long time series of surface mass balance smb measurements performed between 2001 and 2016 in the ablation zone of the morteratsch glacier complex engadine switzerland for a better understanding of the smb variability and its causes multiple linear regressions analyses are performed with temperature and precipitation series from nearby meteorological stations up to 85 of the observed smb variance can be explained by the mean may june july temperature and the total precipitation from october to march a new method is presented where the contribution of each month s individual temperature and precipitation to the smb can be examined in a total sample of 2 24 16 8 million combinations more than 90 of the observed smb can be explained with particular combinations in which the may june july temperature is the most recurrent followed by october temperature the role of precipitation is less pronounced but autumn winter and spring precipitation are always more important than summer precipitation our results indicate that the length of the ice ablation season is of larger importance than its intensity to explain year to year variations the widely used june july august temperature index may not always be the best option to describe smb variability through statistical correlation

evidence for progressive holocene aridification in southern africa recorded in namibian hyrax middens implications for african monsoon dynamics and the african humid period abstract presented here are stable nitrogen isotope data from a rock hyrax procavia capensis middens from northwestern namibia that record a series of rapid aridification events beginning at ca 3800 cal yr bp and which mark a progressive decrease in regional humidity across the holocene strong correlations exist between this record and other terrestrial and marine archives from southern africa indicating that the observed pattern of climate change is regionally coherent combined these data indicate hemispheric synchrony in tropical african climate change during the holocene with similar trends characterising the termination of the african humid period ahp in both the northern and southern tropics these findings run counter to the widely accepted model of direct low latitude insolation forcing which requires an anti phase relationship to exist between the hemispheres the combined dataset highlights 1 the importance of forcing mechanisms influencing the high northern latitudes in effecting low latitude climate change in africa and 2 the potential importance of solar forcing and variations in the earth s geomagnetic shield in determining both long term and rapid centennial scale climate changes identifying a possible mechanism for the variations marking the ahp termination in both the southern and northern tropics

insolation and glacial interglacial control on southwestern african hydroclimate over the past 140 000 years available online xxxx editor g m henderson keywords leaf wax n alkane hydrogen and carbon isotopes african palaeoclimate monsoonal precipitation namibia the past climate evolution of southwestern africa is poorly understood and interpretations of past hydrological changes are sometimes contradictory here we present a record of leaf wax d and 13 c taken from a marine sediment core at 23 s off the coast of namibia to reconstruct the hydrology and c 3 versus c 4 vegetation of southwestern africa over the last 140 000 years 140 ka we find lower leaf wax d and higher 13 c more c 4 grasses which we interpret to indicate wetter southern hemisphere sh summer conditions and increased seasonality during sh insolation maxima relative to minima and during the last glacial period relative to the holocene and the last interglacial period nonetheless the dominance of c 4 grasses throughout the record indicates that the wet season remained brief and that this region has remained semi arid our data suggest that past precipitation increases were derived from the tropics rather than from the winter westerlies comparison with a record from the congo basin indicates that hydroclimate in southwestern africa has evolved in antiphase with that of central africa over the last 140 ka

laboratory study on the evolution of gravel bed surfaces in bed armoring processes abstract cluster microforms in bed armoring have important implications for bedload transport in this study two sets of flume experiments were carried out to study the evolution of the cluster microforms in the bed armoring and their influences on the bedload transport dynamically stable armor layers were formed by applying a staged hydrograph on a mobile sediment bed consisted of poorly sorted sand and gravel thus enabling the investigation of the cluster microforms associated with different flow characteristics simulated in these experiments the size and the planimetric positions of the large particles on the bed surface were extracted using photogrammetric technique allowing analysis of surface grain size distribution and particle clustering pattern of the bed the results showed a tendency towards a coarsened and clustered bed surface which is likely responsible for the declining bedload transport rate the cluster microforms evolved with increasing bed shear stress in the following sequence flat bed pebble cluster line cluster heap cluster reticulate structure we found a bed armoring statistics that can partially explain the declining bedload transport rate under constant discharge nonetheless additional parameters are needed to simulate the fluctuation in the bedload transport rate under changing flow conditions

the hydrochemistry of bayelva a high arctic proglacial stream in svalbard major ion silica and ph data from a high arctic proglacial stream network are examined factor analysis shows that the major controls upon hydrochemistry in the basin include snowpack solute elution rapid alteration of minerals via surface reactions and slow incongruent silicate dissolution the importance of chemical weathering is found to increase downstream at the expense of solute acquisition from the transient snowpack data from a series of snow pits show that snowpack solute elution is characterised by the preferential elution of so42 evidence for the preferential elution of no3 is equivocal however no3 levels in proglacial runoff may be enhanced by the leaching of cryotic soils later in the ablation season chemical weathering is dominated by calcite dissolution at high elevations and a combination of calcite and dolomite dissolution in the downstream proglacial environment silicate weathering at high elevations is characterised by the enrichment of k relative to si concentrated active layer soil waters show less enrichment of k and constitute a potentially important source of dissolved silica to the river system na is also produced by silicate weathering but its mobility is believed to be largely governed by ion exchange with ca2 early in the ablation season all chemical weathering environments are characterised by high p co2 due to either respiration within the soil or at higher elevations within the catchment h provision from acid aerosol and sulphide oxidation however rates of sulphide oxidation are limited because the cold based thermal regime of the glaciers effectively prevents access of meltwaters to freshly comminuted sub glacial sulphide minerals the restricted sub glacial weathering therefore means that ice marginal and proglacial environments are the most important zones of solute acquisition by meltwaters causing significant enrichment of major ions silica and dissolved co2 within only a short distance of the contemporary ice margin

mass balance change as a control on the frequency and occurrence of glacier surges in svalbard norwegian high arctic the end of the little ice age lia in svalbard 76 81 n a climate sensitive region at the northern extreme of strong poleward heat transfer was marked by an abrupt increase in mean annual air temperature of up to 5 c around 1920 glacier mass balance has been consistently negative since this time and large cumulative net losses of mass have occurred at most glaciers energy balance modelling confirms the sensitivity of svalbard glaciers to climate change predicting a negative shift in net mass balance of up to 0 8 m a 1 water equivalent per degree temperature rise this climate related shift in glacier mass balance has reduced the intensity of glacier surge activity in svalbard one glacier known to have surged since the end of the lia has since failed to accumulate the mass required to re initiate the surge cycle and is also now cold at its base and incapable of rapid flow by basal sliding three overviews of the total number of actively surging glaciers in svalbard between 1936 90 show a decrease from 18 to 5 this is significant compared with the expected numbers of surges based on lia conditions post lia climate change in svalbard has therefore affected not only glacier extent but also ice dynamics this is trend will probably continue given co2 induced climate warming

fluctuations of vegetation and climate over the last 75 000 years in the savanna biome south africa tswaing crater and wonderkrater pollen sequences reviewed abstract quaternary palynological information from the savanna biome of south africa is limited due to the scarcity of suitable pollen traps and new extensive pollen records of palaeoenvironments in the region are unlikely to be obtained easily those that are available including the tswaing crater and the wonderkrater spring sequences can however be reassessed and their data optimised these two pollen records are relevant to palaeo environmental research in the area although they have chronologies beyond the radiocarbon dating range that complicate interpretations the tswaing sequence in this study focuses on the upper 34 m of pollen rich layers out of a total of 90 m of lake deposits a new chronology is experimented with for this upper part of the sequence it differs slightly from the previous one in that it does not rely on adjustments of the ages according to the precession cycle accordingly the age at 34 m is estimated to be c 75 ka based on interpolation of the radiocarbon sequence and a basal fission track date of c 200 ka at 90 m in the case of the second site wonderkrater recently published excavation and dating of the deposits and comparisons with the tswaing pollen sequence provide new clues for the age of the lowermost deposit of the original borehole sequence of peats sands and clay which is estimated at c 60 000 years the new results better situate the two pollen sequences in a wider regional and global palaeoenvironmental framework

measurement and simulation of snow and superimposed ice at the kongsvegen glacier svalbard spitzbergen 1 multiyear glaciometeorological data have been collected at about the equilibrium line of kongsvegen glacier in svalbard during the first summer of the investigation period about 0 6 m of superimposed ice si was built up because of effective meltwater refreeze upon the former glacier surface thus winter accumulation is completely retained from runoff and latent heat is released equivalent to 27 of july net radiation this ice layer as well as part of the former year s ice disappeared during the subsequent summer using a physically based snow model the evolution of the snow pack properties as well as the observed amount of si is successfully reproduced however the latter is only possible by modifying the model s water transport routine to also treat effects of ponding water which have been observed two distinct phases of si formation can be distinguished a first one 15 cm is initiated as soon as meltwater has penetrated to the underlying cold glacier ice toward the end of the melt period however the remaining body of si is rapidly formed because of intense atmospheric cooling the availability of ponding water plays an essential role in this context during the following summer the initial refreezing phase was terminated by exposure of the newly built si at the surface the whole amount of the actual year and the major part of the former year s si was melted then a positive ice albedo feedback process plays an additional role there sensitivity studies prove that the model results and their interpretation do not critically depend on possible uncertainties of input data and model parameters despite their local nature these studies are valuable steps toward understanding the regional distribution of si on arctic glaciers as well as their climate sensitivity remote sensing studies indicate that si presently covers 35 of kongsvegen s surface area

late glacial interhemispheric climate dynamics revealed in south african hyrax middens our ability to identify the timing and extent of past major climate fluctuations is central to understanding changes in the global climate system of the events that have occurred in recent geological time the younger dryas yd 13 11 5 ka an abrupt return to near glacial conditions during the last glacial interglacial transition ca 18 11 5 ka is one of the most widely reported while this event is apparent throughout the northern hemisphere peteet 1995 1 evidence for its occurrence in the southern hemisphere remains equivocal due to a lack of well dated terrestrial records here we report high resolution stable carbon and nitrogen isotope records obtained from a rock hyrax midden revealing the first unequivocal terrestrial manifestation of the yd from the southern african subtropics these results provide key evidence for the relative influence of the yd and suggest that a subtropical temperate transition zone existed along the oceanic subtropical front 41 s across the southern hemisphere with the northern hemisphere exerting a strong influence on all but the higher latitudes of the southern hemisphere after the heinrich stadial 1 15 ka 1 ref 22

the influence of drifting snow on the location of glaciers on western spitsbergen svalbard on western spitsbergen svalbard the amount of winter precipitation is insufficient to maintain the present day mass balance of the local glaciers additional snow mass must be added to the precipitation to reach the observed accumulation rates of the glaciers it was assumed in previous work that this additional mass is transported onto the glaciers by drifting snow and snow avalanches this study is a first attempt to quantify the amount of snow mass added to the glacier mass balance by wind transported snow the wind field over an area of 60 50 km2 on western spitsbergen was simulated for 24 idealized weather types by a mesoscale meteorological model on a 750 m grid the resulting wind velocities and directions were coupled to a two level snowdrift model the model output clearly shows erosion and accumulation areas in the terrain comparison with the present glacier locations suggests that the glacier accumulation areas coincide with low wind speeds moreover exposed areas with high wind speeds are mostly glacier free in reality thus the wind field and corresponding snowdrift gives an indication of the location of the present glaciers on western spitsbergen

vegetation history inferred from pollen in late quaternary faecal deposits hyraceum in the cape winter rain region and its bearing on past climates in south africa abstract pollen analysis shed light on vegetation community structure over the last 23 000 year in the western cape the pollen from dated hyrax faecal accumulations hyraceum relates to the evolution of climate and contributes to proxy records in southern africa principal components analyses of the pollen data and 13c values of the hyrax dung samples show millennial and shorter scale temperature moisture and seasonality variations in the winter rain region the moisture availability at times do not parallel that in previously studied proxy records in the summer rain region showing an asynchronous moist event in the early holocene and drier conditions in the middle holocene anomalies in climate between the two regions may depend on the degree of northward or southward shifting of winter and summer rain circulation systems scenarios with winter rain or cool growing seasons mostly typify the dung sequence but do not exclude the possibility of southward displacement of the westerly belt under precessional strength with slight summer rain increases during the last glacial maximum limited southward displacement is also possible during the mid holocene

arctic holocene glacier fluctuations reconstructed from lake sediments at mitrahalvoya spitsbergen the arctic region has experienced a significantly larger warming during the last decades compared to the rest of the world and model simulations indicate a continued amplification of future global warming in the polar regions a better understanding of natural climate variability in the arctic is much needed to provide a better context for the observed warming trend by utilising proxy data it is possible to obtain palaeoclimatic records beyond the range of instrumental observations which increase our understanding of long term arctic climate change here a continuous record of past changes in equilibriumline altitude ela has been reconstructed for the alpine glacier karlbreen located on the northwest coast of spitsbergen 79 n based on sediment analyses from a distal glacier fed lake a multivariate statistical analysis suggests that the concentration of geochemical elements ti si and k in the lake sediments together with the physical parameter dry bulk density dbd reflect changes in the amount of inorganic detrital input to klosa which is closely linked to the size and ela of the upstream glacier karlbreen a linear regression model based on historically documented glacier extents was used to calculate continuous ela changes back to 3500 cal yr bp from about 9200 to 3500 cal yr bp the sedimentary record indicates that karlbreen was very small or had completely melted away karlbreen was probably close to its maximum holocene extent several times during the neoglacial first around 1700 cal yr bp then later at 225 and 135 cal yr bp an ice cored moraine system in front of karlbreen extends well into the main basin of klosa and it is difficult to explain how this moraine could have formed without disturbing the sedimentary record in the lake e g through slumping events the sedimentary record in klosa is continuous and undisturbed over the past 6700 years suggesting that the outermost moraine formed prior to this time and that it most likely survived the holocene thermal maximum on svalbard

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

a 300 kyr record of aridity and wind strength in southwestern africa inferences from grain size distributions of sediments on walvis ridge se atlantic abstract the terrigenous fraction of sediments recovered from walvis ridge se atlantic ocean reveals a history of southwestern african climate of the last 300 kyr end member modelling of a data set of grain size distributions n 428 results in three end members the two coarsest end members are interpreted as eolian dust the third end member as hemipelagic mud the ratio of the two eolian end members reflects the eolian grain size and is attributed to the intensity of the se trade winds trade winds were intensified during glacials compared to interglacials changes in the ratio of the two eolian end members over the hemipelagic one are interpreted as variations in southwestern african aridity late quaternary southwestern african climate was relatively arid during the interglacial stages and relatively humid during the glacial stages owing to meridional shifts in the atmospheric circulation system during glacials the polar front shifted equatorward resulting in a northward displacement of the zone of westerlies causing increased rainfall in southwestern africa the equatorward shift of the polar front is coupled with an increase of the meridional pressure gradient leading to enhanced atmospheric circulation and increased trade wind intensity

holocene and deglacial ocean temperature variability in the benguela upwelling region implications for low latitude atmospheric circulation 1 mg ca analyses of g bulloides and abundances of n pachyderma left coiling from ocean drilling program odp leg 175 hole 1084b in the benguela coastal upwelling system document lower sea surface temperatures during the last glacial maximum lgm younger dryas mid holocene and little ice age in the southeastern atlantic taking into consideration the possible effects of differential carbonate dissolution the mg ca data indicate younger dryas temperatures 2 3 c cooler than those of the early holocene and lgm temperatures 4 5 c cooler than those of the early holocene the cool interval during the deglacial period at hole 1084b matches the timing of younger dryas shifts in cariaco basin and greenland ice sheet records and that of a nearby alkenone record comparison of mid holocene cooling at hole odp1084b with other high resolution records of holocene and last deglacial sea surface temperatures from the tropical atlantic implies consistent basin wide changes in atmospheric circulation a brief period of 1 5 2 c cooling between 17 8 and 17 2 ka if related to heinrich event 1 is consistent with a previously hypothesized tropical origin of all heinrich climate change events

heinrich events massive late pleistocene detritus layers of the north atlantic and their global climate imprint 1 millennial climate oscillations of the glacial interval are interrupted by extreme events the so called heinrich events of the north atlantic their near global footprint is a testament to coherent interactions among earth s atmosphere oceans and cryosphere on millennial timescales heinrich detritus appears to have been derived from the region around hudson strait it was deposited over approximately 500 250 years several mechanisms have been proposed for the origin of the layers binge purge cycle of the laurentide ice sheet jokulhlaup activity from a hudson bay lake and an ice shelf buildup collapse fed by hudson strait to determine the origin of the heinrich events i recommend 1 further studies of the timing and duration of the events 2 further sedimentology study near the hudson strait and 3 greater spatial and temporal resolution studies of the layers as well as their precursory intervals studies of previous glacial intervals may also provide important constraints

structure and changing dynamics of a polythermal valley glacier on a centennial timescale midre lovenbreen svalbard hambrey michael murray t glasser n f hubbard a 2005 structure and changing dynamics of a polythermal valley glacier on a centennial timescale midre lovenbreen svalbard journal of geophysical research 110 pp 1 19 rae2008