the dynamics of australian monsoon bursts abstractthe wet season of the australian monsoon is characterized by subseasonal periods of excessively wet or dry conditions commonly known as monsoon bursts and breaks this study is concerned with the synoptic evolution prior to monsoon bursts which are defined here by abrupt transitions of the area averaged rainfall over the tropical parts of the australian continent there is large variability in the number of monsoon bursts from year to year and in the time interval between consecutive monsoon bursts reanalysis data are used to construct a lag composite of the sequence of events prior to a monsoon burst it is determined that a burst in the australian monsoon is preceded by the development of a well defined extratropical wave packet in the indian ocean which propagates toward the australian continent in the few days leading up to the onset of heavy rainfall in the tropics as in previous studies on the monsoon onset the extratropical disturbances propagate equatorward over the australian contine

a global climatology of atmospheric fronts 1 atmospheric fronts in the lower troposphere often mark regions of significant weather and serve as an important conceptual tool that is frequently used and well understood by the public this study uses an objective method to identify fronts in the era 40 reanalysis and to compile a quantitative global climatology of their occurrence the climatology confirms the mid latitude storm tracks as the regions of highest front frequency and identifies slow moving frontal boundaries in the subtropics corresponding to major climate features such as the mei yu front the climatology also shows fronts to be common features of the south pacific convergence zone in the northern hemisphere fronts shift poleward in summer in the southern hemisphere this and other aspects of seasonal behavior are rather different

the onset of the australian monsoon during winter monex synoptic aspects abstract a case study is presented of the onset of the southern hemisphere summer monsoon at longitudes near australia during december 1978 the numerical analyses comprising this case study are used in conjunction with station data and operational manually derived analyses for other years to investigate the following 1 the case or definition of monsoon onset 2 the three dimensional structure of the troposphere during an active monsoon situation and 3 the flow changes preceding and during the transition from a period of suppressed to a period of enhanced cumulonimbus activity over tropical australia a well defined onset occurs in six of the seven years considered onset defined as a satellite observed large scale increase in tropical convection is consistent with that determined by the wind criterion of troup 1961 in 1978 onset occurs in two stages an increase in convergence followed by an increase in convection the monsoon cloudiness exists entirely in the region of low level westerly win

a midlatitude influence on australian monsoon bursts abstractthe initiation of northern australian monsoon rainfall bursts is accompanied by an increase in cyclonic circulation in the monsoon region this study shows that the change in circulation at the start of the composite rainfall burst is predominantly influenced by midlatitude frontlike features by exploiting the relationship between circulation tendency and the convergence of absolute vorticity flux the circulation changes accompanying the initiation of australian monsoon bursts is investigated moisture flux convergence is found to be proportional to the circulation changes in the monsoon region using a composite analysis it is shown that absolute vorticity fluxes through the southern boundary are by far the most important influence on monsoon burst circulation changes with only one third of events more closely related to other influences including the madden julian oscillation this is shown to be true throughout the wet season

a composite study of onset of the australian summer monsoon abstract onset of the australian summer monsoon is identified each year 1957 87 using the wind and rainfall record at darwin onset is defined as the first occurrence of wet 850 mb westerly winds composites of atmospheric fields at stations in and about the australian tropics are constructed relative to the onset date at darwin the composite onset is accompanied by the development of a convectively driven baroclinic circulation over northern australia upper tropospheric easterlies expand about the equator and the subtropical jet shifts poleward at onset this behavior is interpreted as a transient southerly shift of the local hadley circulation concurrent with the development of an upper level anticyclone over northern australia the composite onset coincides with the arrival of an eastward propagating convective anomaly the anomaly originates in the southern indian ocean propagates eastward at 5 m s 1 and is detectable as far east as the date line an eastward propagating zonal wind anomaly also

quartz backed tools as arrowheads and hand cast spearheads hunting experiments and macro fracture analysis the invention of the bow and arrow was a milestone in late pleistocene technological evolution preservation biases and methodological problems imped our ability to detect its presence in the archaeological record currently south africa has the earliest suggested evidence for arrowheads amongst others small quartz backed tools dating 65 60 ka these artefacts inferred function is based on their small size micro and macro wear traces and micro residues recorded on quartz segments from sibudu cave experimental support for these inferences or to show that similar artefacts are associated with bow hunting are however lacking here we describe breakage patterns on 150 quartz backed tools hafted as transverse arrowheads and hand cast spearheads in simulated hunting experiments these experiments controlled for hafting variability to test the effects of propulsion velocity on the types patterns and area of diagnostic impact fractures difs our results show step terminating bending fracture spin off fracture and impactburination frequencies dif locations and ventrally situated dif frequencies to be robust means of distinguishing arrowheads from spearheads our experiments verify previous observations that overall dif frequencies differentiate between these weapon types importantly we confirm that dif size is linked to weapon propulsion velocity but that fracture area is affected by tool area these findings provide methods for future testing of the hypothesis that bow and arrow technology was in use at least 65 ka in southern africa and in other regions where quartz was used to tip weapons

the intraseasonal 30 50 day oscillation of the australian summer monsoon abstract the tropical intraseasonal 30 50 day oscillation manifests itself in the australian summer monsoon by a pronounced modulation of the monsoonal westerlies these 30 50 day fluctuations of the monsoonal westerlies are coherent with rainfall and olr across northern australia the olr fluctuation originates in the indian ocean and systematically propagates eastward at 5 m s 1 consistent with previous studies of the intraseasonal oscillation the detailed evolution of the intraseasonal oscillation of the monsoon is studied via composites of upper air data in and about the australian tropics during the summer periods 1957 87 91 events were identified at darwin australia the composite oscillation at darwin has a very deep baroclinic structure with westerlies extending up to 300 mb the westerly phase lasts about ten days and lags a similar duration rainfall event by about four days during the westerly phase the upper troposphere is warm and the extreme lower troposphere is cool this structure

vegetation and environmental changes at the middle stone age site of wonderkrater limpopo south africa wonderkrater a middle stone age site in the interior of south africa is a spring and peat mound featuring both paleoclimatic and archaeological records the site preserves three small msa lithic assemblages with age estimates of 30 ka 45 ka and 138 01 7 7 ka here we present results of the pollen analysis of a core retrieved from the middle of the peat mound which covers with hiatuses the timespan between ca 70 10 ka and 30 ka pollen percentages of terrestrial local aquatic and semi aquatic plants reveal changes in the regional climate and in the water table of the spring results identify regional wet conditions at ca 70 10 ka followed by a dry and a wet period between 60 ka and 30 ka superimposed on these three phases recurring changes in the size and depth of the water table are observed between 45 ka and 30 ka wet conditions at 70 ka and 30 ka are tentatively correlated here with marine isotope stage 4 and heinrich stadial 3 respectively a warm and dry savanna landscape was present during human occupation older than 45 ka and a wet phase was contemporaneous with the final occupation dated at 30 ka

variability of the australian summer monsoon at darwin 1957 1992 abstract the variability of the australian summer monsoon is reexamined using data covering 35 monsoon seasons a new easily applied objective definition of active and break phases of the monsoon based solely on the zonal wind at darwin is proposed attempts to define wet westerly onsets are shown to be misleading since no clear relationship is found between westerly winds and rainfall on the timescales associated with the transition between active and break phases the resulting dates of monsoon onset at darwin differ from those reported in some recent studies resulting in significantly different relationships with the southern oscillation in particular the date of monsoon onset is shown to be significantly related to and hence predicted from prior values of the southern oscillation index also in contrast to a number of recent studies that have highlighted the so called 40 50 day oscillation in the australian summer monsoon no dominant timescales are found in the length of the active period

streamflow changes in alaska between the cool phase 1947 1976 and the warm phase 1977 2006 of the pacific decadal oscillation the influence of glaciers 1 streamflow data from 35 stations in and near alaska were analyzed for changes between the cool phase 1947 1976 and the warm phase 1977 2006 of the pacific decadal oscillation winter spring and summer flow changes and maximum annual flow changes were different for glaciated basins more than 10 glacier covered area than for nonglaciated basins showing the influence of glaciers on historical streamflow changes mean february flows for example increased for the median of available stations by 45 for glaciated basins and by 17 for nonglaciated ones

a segment is not a monolith evidence from the howiesons poort of sibudu south africa segments from the howiesons poort of sibudu south africa can be separated into at least three populations based on quartz hornfels and dolerite rocks used for their production length breadth thickness and tip cross sectional areas are significantly different between segments made on the three rock types segments are not monoliths and they were not intended as a single tool type they were flexible enough to be mounted to shafts in a variety of ways several hafting strategies are evident including the use of different adhesive recipes most segments were probably parts of hunting weapons based on use trace analysis but weapon types varied quartz segments have standardized shapes short and deep perhaps because they were hafted as transverse arrowheads while hornfels and dolerite segments may on occasion also have been parts of projectiles the large dolerite segments could sometimes have served as parts of spearheads with two segments hafted back to back howiesons poort segment technology is sophisticated its makers appreciated distinct properties of rocks their flaking wear and impact possibilities further they recognized the best sizes and shapes for use with each kind of weapon they understood the qualities and applications of various adhesive recipes and they knew how to make a variety of hafts from materials that included bone and wood

a techno functional perspective on quartz micro notches in sibudu s howiesons poort indicates the use of barbs in hunting technology abstract in this paper we present the results of a use wear study of quartz micro notches identified during a technological analysis of lithics from the howiesons poort layers of sibudu cave building on the technological analysis and preliminary functional screening of the archaeological material a series of experiments was designed to evaluate different hypotheses for notch formation blank production intentional notching hafting projectile use and trampling the experimental reference collection was compared with archaeological micro notches and a large sample of other archaeological quartz pieces including bladelets bipolar blanks flakes and retouched pieces this allowed us to evaluate the causes of micro notch formation in the studied assemblage results indicate two novelties in the howiesons poort hunting technology at sibudu the use of quartz barbs and non retouched quartz blanks it seems that in addition to backed pieces segments obliquely backed points etc unretouched pieces were mounted as elements in hunting weapons during the howiesons poort techno tradition seven probable and 29 tentative barbs were identified we thus present one of the strongest and oldest bodies of evidence for the use of barbs as projectile elements

middle stone age bone tools from the howiesons poort layers sibudu cave south africa abstract recently discovered bone implements from middle stone age msa deposits at sibudu cave south africa confirm the existence of a bone tool industry for the howiesons poort hp technocomplex previously an isolated bone point from klasies river provided inconclusive evidence this paper describes three bone tools two points and the end of a polished spatula shaped piece from unequivocal hp layers at sibudu cave with ages greater than 61 ka comparative microscopic and morphometric analysis of the sibudu specimens together with bone tools from southern african middle and later stone age lsa deposits an iron age occupation nineteenth century bushman hunter gatherer toolkits and bone tools used experimentally in a variety of tasks reveals that the sibudu polished piece has use wear reminiscent of that on bones experimentally used to work animal hides a slender point is consistent with a pin or needle like implement while a larger point reminiscent of the single specimen from peers cave parallels large un poisoned bone arrow points from lsa iron age and historical bushman sites additional support for the sibudu point having served as an arrow tip comes from backed lithics in the hp compatible with this use and the recovery of older larger bone and lithic points from blombos cave interpreted as spear heads if the bone point from the hp layers at sibudu cave is substantiated by future discoveries this will push back the origin of bow and bone arrow technology by at least 20 000 years and corroborate arguments in favour of the hypothesis that crucial technological innovations took place during the msa in africa

the howiesons poort and msa iii at klasies river main site cave 1a we present the results of a technological analysis of the howiesons poort and msa iii lithic artifacts from cave 1a at klasies river we studied most of the debitage and retouched pieces from deacon s excavations about 3000 pieces and all the cores and retouched pieces from three layers of singer and wymer excavations 640 pieces our analysis shows 1 that hp blade production was based on the use of marginal percussion by soft stone hammer as at rose cottage 2 that impact scars at klasies rose cottage and sibudu indicate that the backed pieces were hafted in two differentways and 3 that the hp backed pieces were an innovativeway of hafting spear tips but are not clear evidence of the invention of bows and arrows we document the gradual evolution of debitage techniques within the hp sequence with progressive abandonment of the hp technological style very similar trends occur in the upper part of the hp sequence at rose cottage the similarity in temporal trends between sites separated by more than 600 km has significant implications for the disappearance of the hp industry we suggest that the disappearance of the hp was not due to a phenomenon of population contraction and isolation that caused the collapse of social networks the internal evolution and parallel process of change documented at klasies and rose cottage speak against a collapse of social systems and are associated with evidence of environmental and subsistence changes at the transition mis 4 3

klipdrift shelter southern cape south africa preliminary report on the howiesons poort layers abstract surveys for archaeological sites in the de hoop nature reserve southern cape south africa resulted in the discovery of a cave complex comprising two locations klipdrift cave and klipdrift shelter excavations commenced in 2010 with later stone age deposits initially being recovered at the former site and middle stone age deposits at the latter the lithic component at klipdrift shelter is consistent with the howiesons poort a technological complex recorded at a number of archaeological sites in southern africa the age for these deposits at klipdrift shelter obtained by single grain optically stimulated luminescence spans the period 65 5 4 8 ka to 59 4 4 6 ka controlled and accurate excavations of the discrete layers have resulted in the recovery of a hominin molar marine shells terrestrial fauna floral remains organic materials hearths lithics ochre and ostrich eggshell more than 95 pieces of the latter distributed across the layers are engraved with diverse abstract patterns the preliminary results from klipdrift shelter presented in this report provide new insights into the howiesons poort in this sub region and contribute further to ongoing knowledge about the complex behaviours of early homo sapiens in southern africa excavations at the klipdrift complex will continue in the future

finding resolution for the howiesons poort through the microscope micro residue analysis of segments from sibudu cave south africa in this paper i present the results of a micro residue analysis of stone segments the type fossils of the howiesons poort technocomplex in south africa with an age of more than 60 ka at sibudu cave kwazulu natal fifty three segments were systematically analysed and 1826 organic micro residue occurrences were documented on the sample the distribution patterns of micro residues and other use traces are interpreted in terms of hafting and function it is shown that most of the tools were indeed hafted and most were probably used as inserts for hunting weapons there is evidence for differences and changes over time in haft materials and hafting configurations of the segments the study demonstrates how functional studies could improve our understanding of change and variability in human behaviour during the middle stone age a period that used to be portrayed as static or slow changing

new knapping methods in the howiesons poort at sibudu kwazulu natal south africa abstract the lithic technology study of layer grey sand at sibudu reveals a large number of cores on flakes varying knapping methods of core reduction are presented here most of the core reduction techniques can be attributed to bladelet or small flake production also we point to a new type of blade production from prismatic cores revealed by the study of debitage these innovative knapping methods demonstrate the technological variability associated with howiesons poort lithic assemblages

extratropical tropical interaction during onset of the australian monsoon reanalysis diagnostics and idealized dry simulations abstract the onset of the australian monsoon is examined using i reanalysis data for seasons when enhanced observational networks were available and ii a 15 yr onset composite similar to previous findings onset is characterized by a sudden strengthening and deepening in tropical westerly winds which are overlain with upper tropospheric easterlies all onsets are preceded by up to a 7 day preconditioning period of enhanced vertical motion and moistening during the transition season the 6 weeks prior to onset a number of moist westerly events occur generally they are only sustained for short periods and overlain by upper level westerly winds suggesting an association with midlatitude troughs which protrude into the deep tropics for individual years and for a 15 yr composite monsoon onset is associated with major cyclogenesis events over the southwest indian ocean in the presence of a subtropical jet over the eastern indian ocean the proposed mechanism for extratropical tropical interaction i

middle stone age reduction strategies at the desert s edge a multi site comparison across the gebel akhdar of northeast libya abstract haua fteah cave situated between the mediterranean coast and the gebel akhdar of northeast libya preserves rich middle stone age msa and late stone age lsa cultural horizons excavated in the 1950s and more recently the richness and time depth of the cave s archaeological record are unsurpassed by any other site in northern cyrenaica as a result the haua fteah sequence has long been used to represent the culture history of the region as a whole recent geoarchaeological surveys of the gebel akhdar as well as pre desert and desert biomes further to the south have resulted in the discovery of numerous msa and lsa sites the vast majority of these sites consist of surface lithics that cannot be dated currently in contrast parts of the haua fteah sequence have been dated using various chronometric methods using data collected through lithic attribute analysis coupled with various statistical approaches including discriminant function analysis or dfa this paper explores variation in core reduction strategies within haua fteah from the early msa to early lsa collections of cores from various sites located throughout the landscape are contrasted against those from haua fteah by comparing undated cores from the landscape with those from different occupation phases at haua fteah dfa classification is tested as a method for imparting an approximate chronology to the former the results indicate notable variation in reduction strategies within the msa at haua fteah and notable similarities between early msa pre aurignacian and early lsa early dabban core morphologies and technologies because of the latter in particular together with several other factors that may be underpinning spatio temporal variability in core reduction strategies caution is recommended in loosely assigning approximate chronologies to surface lithic sites

increased groundwater to stream discharge from permafrost thawing in the yukon river basin potential impacts on lateral export of carbon and nitrogen 1 arctic and subarctic watersheds are undergoing climate warming permafrost thawing and thermokarst formation resulting in quantitative shifts in surface water groundwater interaction at the basin scale groundwater currently comprises almost one fourth of yukon river water discharged to the bering sea and contributes 5 10 of the dissolved organic carbon doc and nitrogen don and 35 45 of the dissolved inorganic carbon dic and nitrogen din loads long term streamflow records 30 yrs of the yukon river basin indicate a general upward trend in groundwater contribution to streamflow of 0 7 0 9 yr and no pervasive change in annual flow we propose that the increases in groundwater contributions were caused predominately by climate warming and permafrost thawing that enhances infiltration and supports deeper flowpaths the increased groundwater fraction may result in decreased doc and don and increased dic and din export when annual flow remains unchanged

variability and trends in runoff in the rivers of british columbia s coast and insular mountains this study examines the 1914 2015 runoff trends and variability for 136 rivers draining british columbia s bc s coast and insular mountains rivers are partitioned into eastward and westward flowing rivers based on flow direction from the coast mountains thus eastward and westward runoff trends and influence of topography on runoff are explored our findings indicate that rivers flowing eastward to the nechako and chilcotin plateaus contribute the lowest annual runoff compared to westward rivers where runoff is high low interannual runoff variability is evident in westward rivers and their alpine watersheds whereas eastward rivers exhibit high interannual runoff variability on vancouver island some of the rivers with the highest annual runoff exhibit high interannual variability a significant p 1 trends in annual and seasonal runoff from the middle to the late period across the study domain most positive detectable seasonal runoff trends in the middle period occur in spring in glacierized westward rivers located 1200 m whereas in the late period they all occur in fall and are regionally coherent around vancouver island and south coastal bc rivers draining eastward exhibit more positive trends over 1986 2015 compared to westward rivers this study provides crucial information on the hydrology of mountain watersheds across bc s coast in response to pacific decadal oscillation phase changes the elevational amplification of regional climate change and their influences on precipitation and glacier retreat

technological successions in the middle stone age sequence of diepkloof rock shelter western cape south africa the southern african msa comprises a series of phases of unique technological innovations that fuel current models on the evolutionary processes of anatomically modern humans however the nature and variability of these technological phases remain poorly documented this study reports on the previously unpublished sequence of diepkloof rock shelter south africa and investigates the main technological changes therein particularly emphasizing the emergence succession and disappearance of the still bay sb and the howiesons poort hp we argue for technological change that occurred at different rates and under the influence of variable driving factors our model implies that the sb and the hp are not related to the influx of new populations but have regionally specific origins unlike the other techno complexes the hp at diepkloof is subdivided into different phases early intermediate and late but only the upper phases resemble the so called classic hp finally the technological sequence of diepkloof questions the homogeneous picture which has been so far assumed for the southern african msa and places emphasis on the importance of exploring long regional sequences

osl and tl dating of the middle stone age sequence at diepkloof rock shelter south africa a clarification diepkloof rock shelter offers an exceptional opportunity to study the onset and evolution of both still bay sb and howiesons poort hp techno complexes however previous age estimates based on luminescence dating of burnt quartzites tribolo et al 2009 and of sediments jacobs et al 2008 were not in agreement here we present new luminescence ages for 17 rock samples equivalent dose estimated with a sar itl protocol instead of classical maad tl as well as for 5 sediment samples equivalent dose estimated with sar single grain osl protocol and an update of the 22 previous age estimates for burnt lithics modified calibration and beta dose estimates while a good agreement between the rock and sediment ages is obtained these estimates are still significantly older than those reported by jacobs et al 2008 after our own analyses of the sediment from diepkloof it is suspected that these authors did not correctly chose the parameters for the equivalent dose determination leading to an underestimate of the equivalent doses and thus of the ages from bottom to top the mean ages are 100 10 ka for stratigraphic unit su noel and 107 11 ka for su mark uncharacterized lower msa 100 10 ka for su lynn leo pre sb type lynn 109 10 ka for sus kim larry sb 105 10 ka for sus kerry kate and 109 10 ka for su jess early hp 89 8 ka for su jude msa type jack 77 8 ka for su john 85 9 ka for su fox 83 8 ka for su fred and 65 8 ka for su ob5 intermediate hp 52 5 ka for sus ob2 4 late hp this chronology together with the technological analyses greatly modifies the current chrono cultural model regarding the sb and the hp and has important archaeological implications indeed sb and hp no longer appear as short lived techno complexes with synchronous appearances for each and restricted to oxygen isotopic stage ois 4 across south africa as suggested by jacobs et al 2008 2012 rather the sequence of diepkloof supports a long chronology model with an early appearance of both sb and hp in the first half of ois 5 and a long duration of the hp into ois 3 these new dates imply that different technological traditions coexisted during ois 5 and 4 in southern africa and that sb and hp can no longer be considered as horizon markers

rapid wastage of alaska glaciers and their contribution to rising sea level we have used airborne laser altimetry to estimate volume changes of 67 glaciers in alaska from the mid 1950s to the mid 1990s the average rate of thickness change of these glaciers was 0 52 m year extrapolation to all glaciers in alaska yields an estimated total annual volume change of 52 15 km 3 year water equivalent equivalent to a rise in sea level sle of 0 14 0 04 mm year repeat measurements of 28 glaciers from the mid 1990s to 2000 2001 suggest an increased average rate of thinning 1 8 m year this leads to an extrapolated annual volume loss from alaska glaciers equal to 96 35 km 3 year or 0 27 0 10 mm year sle during the past decade these recent losses are nearly double the estimated annual loss from the entire greenland ice sheet during the same time period and are much higher than previously published loss estimates for alaska glaciers they form the largest glaciological contribution to rising sea level yet measured