agulhas current influence on the shelf dynamics of the kwazulu natal bight abstractthe agulhas current is a fast western boundary current flowing along the south african east coast strongly influencing oceanographic variability on the adjacent kwazulu natal shelf hydrographic observations in january 2010 july 2010 and july 1989 have been used to describe variations in geostrophic currents and water masses and to elucidate mechanisms of change in circulation and thermohaline structure differences in wind forcing precipitation and solar insolation caused modifications in stratification and mixing that resulted in seasonal changes in surface temperature salinity and mixed layer depth zmld between the austral summer and winter surveys during january 2010 surface temperatures were elevated and there was a large range in salinity as the upper 10 m was influenced by river outflow and rainfall in july 2010 and 1989 surface temperatures were lower and the salinity range was significantly less the zmld in january 2010 was much shallower varying between 5 and 40 m while dee

preservation potential for late quaternary river alluvium valley sequences of late quaternary alluvial units reflect alluvial preservation as well as alluvial production factors effects of lateral channel migration incision aggradation and channel stability on preservation potential are explored and then considered in the light of 14 available data sets cartographically dated and model data based on lateral channel migration well mapped and dated late quaternary valley unit surveys and composite age frequency plots for dated alluvial units and flood sediments despite much expectable variation between sites and the complex effects of river activity combinations a common characteristic of the data sets examined is the significance of preservation factors lateral migration tends to eliminate older units as it creates new alluvial deposits whereas incision may lead to the preferential preservation of older units beyond the incision slot aggradational environments are likely to preserve more complete records although simultaneous lateral migration may eliminate possibly repeatedly the upper parts of alluvial units the common pattern of inset and incised streams within pleistocene and early holocene fills or bedrock gives finite extent to later units within narrowing valleys so that development of new valley floor units is necessarily at the expense of reprocessing earlier ones floods associated with both slack water deposits and berms are also responsible for the removal of accessible earlier materials thus limiting the preserved record of earlier events in light of these censoring effects of river activities the sequence of preserved late quaternary units within uk sequences is reconsidered it is concluded that preservation potential factors have led to spatial and temporal bias in the alluvial record and that both here and elsewhere preservation potential needs to be considered systematically alongside variable sedimentation resulting from allogenic environmental factors when interpreting the alluvial archive copyright 2003 john wiley sons ltd journal of quaternary science

sedimentary record and luminescence chronology of palaeoflood events along the gold gorge of the upper hanjiang river middle yangtze river basin china abstract palaeoflood slackwater deposits swds along the river banks have important implications for the reconstruction of the past hydro climatic events two palaeoflood swd beds were identified in the holocene loess soil sequences on the cliff river banks along the gold gorge of the upper hanjiang river by field investigation and laboratory analysis they have recorded two palaeoflood events which were dated by optically stimulated luminescence to 3 2 2 8 ka and 2 1 1 8 ka respectively the reliability of the ages obtained for the two events are further confirmed by the presence of archaeological remains and good regional pedostratigraphic correlation the peak discharges of two palaeoflood events at the studied sites were estimated to be 16 560 17 930 m3 s a correlation with the palaeoflood events identified in the other reaches shows that great floods occurred frequently during the episodes of 3200 2800 and 2000 1700 a bp along the upper hanjiang river valley during the last 4000 years these phases of palaeoflood events in central china are well correlated with the climatic variability identified by 18o record in the stalagmites from the middle yangtze river basin and show apparent global linkages palaeoflood studies in a watershed scale also imply that strengthened human activities during the shang dynasty bce 1600 1100 and han dynasty bce206 ce265 may have caused accelerated soil erosion along the upper hanjiang river valley

generation of submesoscale frontal eddies in the agulhas current copyright 2019 brill due to copyright restrictions the attached pdf file contains the abstract of the full text item for access to the full text item please consult the publisher s website https agupubs onlinelibrary wiley com doi full 10 1029 2019jc015229

spatio temporally variable response of fluvial systems to late pleistocene climate change a case study from central germany abstract the change of the earth s climate and anthropogenic forcing challenge catchment management as the deliberate use of the fluvial system s natural resources depends to some extent on the predictability of the system s variable sensitivity to external impacts the alluvial history of the wetter valley in central germany provides an example of the occurrence of a spatio temporally variable catchment sensitivity to the late pleistocene climate change empirical models that are based on sediment flux controls such as sediment supply transport capacity and gradient serve to explain differential floodplain construction during the early younger dryas the large scale basin upland morphology caused localised divergent cooling impacts and vegetation changes which generated reach scale variable sediment transport system states in the wetter valley the spatial arrangement of reach scale variable response is ascribed to the tectonically driven morphological configuration of the wetter catchment the crucial amplification of differential floodplain construction can be assigned to the spatially variable availability of a surplus of laacher see tephra particles in manner of a pulsed sediment input the ubiquitous tephra cover was previously deposited by the laacher see volcano event in the upper allerod thus the reach scale variable response during the early younger dryas can be deemed to have been climatically triggered but superimposed by an internally driven specific upstream catchment response the documented processes of late quaternary alluviation in the wetter valley imply the need for whole catchment approaches the latter are a prerequisite to reveal the occurrence and causalities of variable fluvial response in relation to external impacts that interact with internal morphological controls this is seen to be crucial to achieve an improved predictability of future environmental change in fluvial landscapes

high resolution fluvial record of late holocene geomorphic change in northern tunisia climatic or human impact abstract in northern tunisia the late holocene alluvial record of medjerda floodplain sediments indicates geomorphic changes due to fluctuations of past climate superimposed by the effects of human activity geomorphic activity occurred several times interrupting stable conditions enhanced fluvial dynamics occurred around 4 7 3 0 1 7 1 0 and 0 7 ka cal bp a peak of activity took place about 0 4 ka cal bp some periods of fluvial activity show event like phenomena in particular when an anthropogenic impact intensifies climatic aridification this has been the case around 1 7 1 0 0 7 and 0 4 ka cal bp with severe floods in the medjerda valley during antiquity as well as around 1 3 0 8 and 0 5 ka cal bp immature alluvial soils have developed the first one being the most distinct late holocene medjerda alluvial history shows that fluvial dynamics in northern tunisia were predominantly climate driven anthropogenic impact only intensified or weakened these processes

the natal pulse an extreme transient on the agulhas current an analysis of satellite data collected over a period of 9 years as well as historic hydrographic data show that the northern agulhas current is subject to large intermittent and solitary meanders these transient events collectively named the natal pulse progress downstream at consistent rates of 21 cm s upon reaching the area where the shelf broadens their rate of progression slackens to 5 cm s they are present in some stages of development at least 17 of the time extend offshore by about 170 km on average and show a continuous lateral growth on moving downstream with few exceptions the pulses are spawned as cold core cyclonic trapped lee eddies in the natal bight they are held responsible for the intermittent coastal counter currents observed inshore of the agulhas current along the southern african coast and may play a crucial role in sediment distribution on the shelf

changes in sediment flux and storage within a fluvial system some examples from the rhine catchment the rhine river system can look back on a long history of human impact whereas significant anthropogenic changes to the river channel started only 200 years ago the impacts of land use have been felt for more than 7500 years here we review results from several case studies and show how land use change and climate impacts have transformed the fluvial system we focus on changes in sediment delivery pathways and slope channel coupling and show that these vary in time and depend on the magnitude of a rainfall event these changes must be accounted for when trying to use sediments as archives of land use change and climatic impacts on fluvial systems for example human impact is recorded in slope deposits only as long as rainfall intensity and runoff generation do not exceed the threshold for gullying similarly climatic impacts are only recorded in alluvium when both the landscape is rendered sensitive by human activities e g deforestation and rainfall thresholds for gullying are exceeded copyright 2003 john wiley sons ltd

late glacial to mid holocene palaeoclimate development of southern greece inferred from the sediment sequence of lake stymphalia ne peloponnese abstract the sedimentary sequence of lake stymphalia ne peloponnese for the first time sheds light on the palaeoclimate development of southern greece from 15 to 5 ka bp new geochemical data based on high resolution x ray fluorescence scanning provide in situ and continuous analysis of predefined element suites on split core surfaces variations of elements over time were assessed constructing correlation matrices based on the calculation of pearson correlation coefficients the element suite includes al si k ca ti mn fe zn rb sr and zr a major result includes that changes in element behaviour are related to hydrological changes in the catchment precipitation lake level status and evaporation insolation solar activity and are ultimately driven by climate major trends shifts in elemental ratios correspond to the climate development in the eastern mediterranean region based on correlation of rb sr reflecting wet dry climates with foraminiferal proxies of marine core lc21 from the southern aegean sea and the stable oxygen isotope record of soreq cave israel the bolling allerod the younger dryas and the 8 2 ka cold event were identified

global climate instability reflected by eastern mediterranean marine records during the late holocene abstract extremely high sediment accumulation rates in the southeastern se mediterranean off israel make this region ideal for high resolution paleoceanographic reconstructions two cores were examined and foraminiferal oxygen and carbon isotope composition as well as physical and geochemical properties of the sediments were used to reconstruct the climatic and environmental changes of the se mediterranean basin during the late holocene 3 6 ka the 18o values of globigerinoides ruber suggest that the freshwater balance changed several times during this time interval humid phases took place between 3 5 3 0 ka bp and 1 7 1 0 ka bp the later was accompanied by enhanced preservation of terrestrial organic matter within the sediment ors event relatively more arid conditions prevailed in this area between 3 0 and 1 7 ka bp during the last millennia at ca 0 8 and 0 27 ka two climatic events occurred which are probably correlative to both the medieval warm period and the cooling global event known as the little ice age respectively a long term slight increase in planktonic foraminiferal 18o values occurs together with a gradual decrease in the 13c values of both g ruber and the benthic foraminifera uvigerina mediterranea this trend is associated with an increase in sedimentation rates ti al ratio magnetic susceptibility and color index of the sediments we suggest that this trend shown by various independent proxies seems to be related to the aridification process that started ca 7 0 ka in the mid low latitude desert belt and the se mediterranean region and continuous until the present the long term 13c decrease shown by surface and bottom water foraminifera reflects a gradual change in the 13c of the dissolved co2 of the entire se mediterranean water column this follows the global co2 rise in the late holocene as a result of the terrestrial biomass destruction during the aridification process moreover the gradual reduction of the vegetation cover in east africa led to an increased erratic flood related sediment flux via the nile river up to the present this is reflected by the general change in the local sediment composition at 3 6 ka the saharan eolian input reached 65 whereas at about 0 3 ka 70 of the se mediterranean sediment was composed of nile particulate matter

understanding geomorphic responses to environmental change a 19 000 year case study from semi arid central texas usa understanding the impact of past climatic changes on landscape stability is crucial in order to predict and mitigate the effects of future changes however in arid and semi arid environments reconstructions are often hampered by a poor understanding of the relationship between sediment deposition and climate we present here data from central texas a region that is sensitive to environmental change but has received relatively little attention the study integrates a chronology of 29 optically stimulated luminescence osl ages from six sedimentary sites in a range of depositional contexts with a 19 000 a climate record derived from pollen extracted from the adjacent boriack bog by comparing the two records we aimed to assess the relationship between climate change and geomorphic activity data show that extensive aeolian and colluvial deposition occurred during the mid to late holocene with sedimentation generally increasing during more arid phases however a number of depositional events on slopes were associated with moister episodes and sediment was also deposited in a summit setting immediately after phases of increased precipitation linkages between climate change and geomorphic response were therefore complex being controlled by both sediment supply and transport energy the climatic fluctuations identified in the boriack bog record highlight the sensitivity of central texas to environmental change while disparities in conditions recorded between it and other palaeoenvironmental sites in the southern usa emphasise the need for further work in order to enhance understanding of landscape sedimentary response to climate copyright c 2010 john wiley sons ltd

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

holocene environmental change and its impact on sediment dynamics in the eastern mediterranean abstract investigators have studied past environmental change in the eastern mediterranean region from a number of perspectives while climate reconstructions and palynological research have focused on forces that drive the geomorphologic system many researchers have attempted to use sediment archive studies to identify periods of change in sediment dynamics due to the large variability in environmental parameters and the variety of landscapes present in the eastern mediterranean region research has focused on sediment archives ranging from small colluvial sites to deltas of large rivers on the mediterranean coast as the cultural record for the region is extremely rich the main goal of palaeo environmental research in the eastern mediterranean has been to identify the relative importance of human impact on the landscape nevertheless sediment archives have significant limitations chronological control for many palaeo environmental records is highly uncertain and rates of landscape change are oftentimes difficult to assess most palaeo environmental research has been conducted on or near archeological sites where direct human impact may obscure the indirect impact on sediment dynamics through land use changes quantification and modeling of sediment dynamics in the eastern mediterranean environment offer one solution when erosion and sediment transport rate analyses are incorporated periods of relatively important change can be identified using multiple approaches the relative importance of the main driving forces climate and land use become distinguishable since field based data from the actual sediment archives remain vital an overview of numerous studies in the eastern mediterranean is provided in order to draw a general picture for different time periods and the relative scale of regional landscape development during the holocene a comparison of sediment dynamics with the record of driving forces indicates that while climate was the main driver of the geomorphic system during the early holocene at some point human impact became widespread and began to dictate sediment dynamics to a large extent from the byzantine period onward soil properties seem to play an increasingly important role as the hillslope soil reservoir in the eastern mediterranean was progressively depleted during the late holocene

holocene valley incision in the southern bukk foreland climate human environment interferences in northern hungary abstract prehistoric human settlement activities in northern hungary have been well studied for several decades recent studies from the great hungarian plain provide evidence of human impact starting as early as in the neolithic c 8200 cal bp archaeological records suggest that with establishment of the baden culture c 5500 cal bp settlements were moved from tisza river towards the northern mountainous area although quaternary landscape development of the bukk mountains is well studied holocene human environment interactions in particular have not been focused on so far here we present holocene landscape history around bogacs in the southern bukk mountain foreland sediment records were sampled from fans of secondary tributaries in the middle course of the hor valley morphology of the tributary valleys suggests different incision phases with older forms and less human impact in the northern part of the studied valley section type 1 and younger forms and stronger human impact in the southern part type 2 however 14c dates from the fan of a type 2 valley in the southern part suggest initial incision between 9000 and 8000 cal bp whereas human activity is not reflected in the sediments in the fan sediments of a type 1 tributary in the northern part of the studied valley section daub was found in the context of deposits dated to 3000 cal bp here thickness of holocene sediments suggest significant soil erosion it can be summarised that post pleistocene valley incision was restricted to short periods of extreme climate conditions during the early to mid holocene human activities did not contribute to initial valley incision nevertheless human activities seem to have enhanced soil erosion in the catchments of type 1 tributaries

variability of shallow and deep western boundary currents off the bahamas during 2004 05 results from the 26 n rapid moc array data from an array of six moorings deployed east of abaco bahamas along 26 5 n during march 2004 may 2005 are analyzed these moorings formed the western boundary array of a transbasin observing system designed to continuously monitor the meridional overturning circulation and meridional heat flux in the subtropical north atlantic under the framework of the joint u k u s rapid climate change rapid meridional overturning circulation moc program important features of the western boundary circulation include the southward flowing deep western boundary current dwbc below 1000 m and the northward flowing antilles current in the upper 1000 m transports in the western boundary layer are estimated from direct current meter observations and from dynamic height moorings that measure the spatially integrated geostrophic flow between moorings the results of these methods are combined to estimate the time varying transports in the upper and deep ocean over the width of the western boundary layer to a distance of 500 km offshore of the bahamas escarpment the net southward transport of the dwbc across this region inclusive of northward deep recirculation is 26 5 sv sv 10 6 m 3 s 1 which is divided nearly equally between upper 13 9 sv and lower 12 6 sv north atlantic deep water nadw in the top 1000 m 6 0 sv flows northward in a thermocline intensified jet near the western boundary these transports are found to agree well with historical current meter data in the region collected between 1986 and 1997 variability in both shallow and deep components of the circulation is large with transports above 1000 m varying between 15 and 25 sv and deep transports varying between 60 and 3 sv much of this transport variability associated with barotropic fluctuations occurs on relatively short time scales of several days to a few weeks upon removal of the barotropic fluctuations slower baroclinic transport variations are revealed including a temporary stoppage of the lower nadw transport in the dwbc during november 2004

characteristics energetics and origins of agulhas current meanders and their limited influence on ring shedding abstractthe agulhas current intermittently undergoes dramatic offshore excursions from its mean path because of the downstream passage of mesoscale solitary meanders or natal pulses new observations and analyses are presented of the variability of the current and its meanders using mooring observations from the agulhas current time series experiment act near 34 s using a new rotary eof method mesoscale meanders and smaller scale meanders are differentiated and each captured in a single mode of variance during mesoscale meanders an onshore cyclonic circulation and an offshore anticyclonic circulation act together to displace the jet offshore leading to sudden and strong positive conversion of kinetic energy from the mean flow to the meander via nonlinear interactions smaller meanders are principally represented by a single cyclonic circulation spanning the entire jet that acts to displace the jet without extracting kinetic energy from the mean flow synthesizing in situ observations with altimeter

comparison of three velocity sections of the agulhas current and agulhas undercurrent lowered acoustic doppler current profiles ladcp from an early march 1995 cruise across the agulhas current show a swift narrow undercurrent flowing northeast along the continental slope neither this agulhas undercurrent nor the adjacent deep extension of the agulhas current are evident from measurements of water properties alone and their absence from the conventional referencing of geostrophic current estimates biases net southward transport estimates high by several sverdrups here we refine the original transport calculation by removing barotropic tides and by estimating instrumental and sampling errors two additional ladcp sections from cruises in late march and june 1995 also show the undercurrent and the deep extension of the agulhas differences in the current structure are evident the agulhas current extends throughout the water column in march but extends only to 2300 m depth in june additionally the current extends further offshore in march of the three available ladcp sections only those from early march and june have sufficient sampling to calculate the net southward transport of the agulhas current and undercurrent the two estimates 78 3 and 76 2 sv are nearly identical consideration of water properties on density surfaces shows that although the undercurrent carries intermediate water with red sea water influence northward the bulk of this water mass is flowing southward away from its source in the agulhas current

sea land oxygen isotopic relationships from planktonic foraminifera and speleothems in the eastern mediterranean region and their implication for paleorainfall during interglacial intervals the oxygen and carbon stable isotope compositions of cave speleothems provide a powerful method for understanding continental climate change here we examine the question of the regionality of this isotopic record and its linkage with the marine isotopic record in the eastern mediterranean em region the study presents a new accurately dated 250 kyr 18o and 13c record determined from speleothems of the peqiin cave northern israel its comparison with the continuous 185 kyr isotopic record of the soreq cave speleothems from central israel reveals striking similarities thus a strong regional climatic signal brought about by variations in temperature and rainfall amount is reflected in both cave records low 18o minima in the peqiin profile for the last 250 to 185 kyr period interglacial marine isotopic stage 7 match the timing of sapropels 9 to 7 and are indicative of high rainfall in the em region at these times the combined soreq and peqiin 18o record for the last 250 kyr excellently matches the published globigerinoides ruber g ruber marine 18o record for the em sea with the isotopic compositional difference g ruber speleothems remaining relatively constant at 5 6 0 7 thus establishing for the first time a robust exploitable link between the land and the marine isotopic records the correspondence of low 18o speleothem values and high cave water stands with low g ruber 18o values during interglacial sapropel events indicates that these periods were characterized by enhanced rainfall in the em land and sea regions by use of sea surface temperatures derived from alkenone data as a proxy for land temperatures at the soreq cave we calculate the paleorainfall 18o values and its amounts maximum rainfall and lowest temperature conditions occurred at the beginning of the sapropel events and were followed by decrease in rainfall and increase in temperatures leading to arid conditions the record for the last 7000 yr shows a trend toward increasing aridity and agrees well with climatic and archeological data from north africa and the middle east

paleolithic caves and hillslope processes in south western samaria israel environmental and archaeological implications abstract south western samaria is emerging as a major province of paleolithic cave sites most recently discovered caves have been naturally filled with terra rossa type colluvial deposits when the hillslopes above the caves were stripped from vegetation during late quaternary times site formation processes differ significantly between caves with pit like openings such as qesem emanuel and rantis caves vs those with cliff side entrances such as shukbah tinshemet and deir kaddis caves the former favored accumulation of colluvial debris while the latter were relatively protected from these deposits caves discovered in the 20th century were mainly of the latter cliff face type while in the 21st century new discoveries commonly occur where construction works intersect previously unnoticed filled caves

late quaternary alluviation and soil formation in the southern argolid its history causes and archaeological implications in the context of an archaeological survey of the southern argolid greece studies have been carried out to elucidate the evolution of the landscape since its earliest known human occupation about 50 000 years ago one of these studies was a detailed geological mapping of the late quaternary alluvium and soils in the area dated by means of thorium uranium disequilibria archaeological finds and historical information seven periods of alluviation were identified each of short duration relative to long intervening periods of stability and soil formation the three earliest alluvial phases falling before and during the last glacial interval range from about 330 000 to 32 000 years in age no alluviation accompanied the last glacial maximum around 20 000 years ago in fact a stable landscape persisted until about 4500 years ago when debris flows and widespread aggradation in the valleys resulted from major slope destabilization and soil erosion probably as a result of extensive land clearance in the early bronze age a subsequent stable period lasted through the many upheavals of the later bronze age the dark ages and the early historical period it came to an end with a brief phase of alluviation between about 300 and 50 bc stability returned through the late roman period notwithstanding considerable expansion of the settled area another period of destabilization this one marked by debris flows and hence major soil erosion is poorly fixed in time but probably coincides with expanded maquis clearance accompanying the resettlement of the area around ad 1000 subsequent events of soil erosion and aggradation vary in nature and timing from one drainage to the next and in some areas continue today nature and chronology of the soil forming and alluviation events show that simple correlations with climatic events do not suffice to explain them for the latter ones past about 2500 bc human activity seems to be the dominant cause but once again the relation between cause and effect is not straightforward land clearing or neglect of soil conservation efforts during economic downturns appear to have a more devastating effect upon the landscape than do intensive land use or total land abandonment

palaeo earthquake and palaeo mudflow events at the machangyuan ruins in the huangshui river valley northeastern margin of the tibetan plateau palaeo earthquake event recorded by loess rapture fissures n30 40 w and n40 50 e trending and palaeo mudflow event recorded by red clay deposits were identified at the machangyuan ruins in the huangshui river valley at the foot of the northeastern tibetan plateau comparative analysis of grain size distributions and geochemical elements of local outcrops indicates that the red mudflows were sourced from the gullies on the valley side where unconsolidated neogene red clay formation was exposed the palaeo earthquake was associated with regional tectonic structures including a nnw trending left lateral strike slip fault lajishan fault and a ne trending local fault bazhougou fault analysis combining optically stimulated luminescence ages and radiocarbon ages of archaeological record dates the palaeo earthquake and palaeo mudflow events to ca 4 80 ka bp during that stage many neolithic settlements distributed around the machangyuan ruins enhanced human activities of the majiayao culture disturbed

holocene environmental variability in the central ebro basin ne spain from geoarchaeological and pedological records abstract environmental fluctuations during the holocene caused important landscape changes in the central ebro basin which is a very sensitive region due to its semiarid climate lithology and continuous human presence severe erosion processes hinder palaeoenvironmental and archaeological record preservation infills of ephemeral stream valleys in semiarid environments are some of the best contexts for geoarchaeological studies in this paper we analyse the geomorphological processes pedological features and charcoal and pollen content and composition of the sedimentary sequence of la poza valley catchment area with the support of additional information from la bajada valley 14 c dates for 13 charcoal fragments provide the necessary chronological control we describe 5 sedimentary units and a polycyclic sequence of six soils that covers most of the holocene beginning ca 9 5 ky cal bp buried soils help to identify stability periods in the sedimentary sequence while incision stages are detected through erosive contacts and terraced organisation of the sedimentary units charcoal and pollen content and composition as well as the soil development reveal an open forest of junipers and pines for the early holocene in the lower part of the sequence mainly in unit 1 very different from the current deforested landscape also represented in the sequence unit 4 thus la poza record shows the environment was favourable for hunter gatherers from the late mesolithic and for the first neolithic farmers from then on progressive degradation due to a combination of climate changes and increasing human pressure led to the current deforested landscape

climate and anthropogenic factors affecting alluvial fan development during the late holocene in the central ebro valley northeast spain the late holocene in the central ebro depression is characterized by a number of morphodynamic stages that affected hillslopes and channels climate fluctuations and human activities together caused severe erosion and floods resulting in alternating stages of accumulation and incision in the valley floors seven accumulation levels n6 n0 correlated with ebro river fluvial terraces have been identified in the secondary fluvial network of the central ebro depression the main accumulation level n3 corresponds to a long period of increased hillslope erosion and sedimentation in the valleys from the neolithic to the late roman periods the accumulation levels are evident throughout the valleys and extend to the valley mouths where many connect with alluvial fans the study of several sedimentological profiles 14c ams dating and many archaeological remnants have enabled detailed assessment of sedimentation characteristics in the alluvial fans and the relationship thereof to the presence of human sett

a late holocene record of environmental changes from kotihi lagoon elis northwest peloponnesus greece the late holocene instability of the coastline of elis was investigated using two boreholes three evolutionary stages are distinguished a from earlier than 7000 to 3810 cal bp there was a static coastline and predominantly lagoon floor sediments accumulated b from 3810 to 1400 cal bp the rate of sedimentation was higher than the rate of relative sea level change possibly because of the proximity of the mouth of the peneus river and predominantly fluvial sediments accumulated c from 1400 cal bp to present time landward migration of the coast and the re establishment of lagoonal facies was probably the result of the avulsion of the peneus river from 150 cal bp until present the rate of sedimentation in lagoon area was high about 5 2 mm a

anthropogenic and climatic impact on holocene sediment dynamics in se spain a review the climatic and anthropogenic control on holocene sediment dynamics was not well constrained for the western mediterranean basin the paucity of high resolution palaeoenvironmental records long hampered a detailed understanding of the human impact on erosion rates this paper analyses holocene sediment dynamics in the context of regional climatic conditions land cover and human occupation based on an extended compilation of recently published high resolution paleoenvironmental proxy data from both terrestrial and marine environments the palaeoenvironmental reconstruction identified four main aridification episodes a at 5600 4700 a4 4100 3400 a3 2800 2500 a2 and 1900 1300 1200 a1 cal bp most of the severe aridification phases were climatically induced not human driven and well correlated with a large dataset of paleoenvironmental records from the western mediterranean basin and north atlantic ocean the phases of enhanced aridity are generally associated with enhanced sediment dynamics independent of the intensity and type of human occupation in contrast wet climatic conditions are found to be associated with both high and low sediment dynamics dependent on the human impact on the environment the mid late phoenician phoenician ii republican rome civilizations and the christian reconquest are all associated with high human impact on the environment and high erosion rates are reported for the vera basin and ne spain despite the improved hydrological conditions human occupation is not necessarily associated with geomorphic instability as shown by the post argaric omeya and nazarene periods that are characterized by low erosion rates and geomorphic stability

the evolution of saharan dust input on lanzarote canary islands influenced by human activity in the northwest sahara during the early holocene an overall holocene increase of saharan dust input to the canary islands and to the north canary basin is accompanied by a strong coarsening of saharan dust in loess like sediments deposited on lanzarote from 7 8 ka no similar coarsening events are indicated in investigations of the sedimentological record for the last 180 ka a period showing several dramatic climate changes therefore a mobilisation of holocene dust by anthropogenic activity in the northwest sahara east of the canary islands is assumed although scarce archaeological data from the coastal area of that region does not point to strong anthropogenic activity during the early holocene a high density of unexplored archaeological remains is reported from the coastal hinterlands in the western sahara thus the hypothesis of early anthropogenic activity cannot be excluded

the tempo of holocene climatic change in the eastern mediterranean region new high resolution crater lake sediment data from central turkey this study presents results from a multi proxy analysis of cores taken in a crater lake sequence from eski acigol in central turkey which cover the period from pre c 16000 cal yr bp to the present the sediments comprise an upper unit of generally non laminated banded to massive silts and peats of mid to late holocene age overlying a laminated unit of late pleistocene to early mid holocene age the laminae comprising mainly aragonite amorphous silica diatom frustules and organic matter were formed in a relatively deep dilute meromictic lake pollen data indicate an abrupt replacement of artemisia chenopod steppe by grass oak terebinth parkland during the period of laminae deposition marking the start of the holocene a gradual increase in tree pollen during the early holocene came to an end c 6500 cal yr bp u series and adjusted c 14 timescale when mesic deciduous taxa declined at the same time as lake levels fell human impact on regional vegetation is inferred from a sharp decline in oak around 4500 4000 cal yr bp diatom isotopic and mineralogical data indicate that during the second half of the holocene the lake became relatively shallow and oscillated between fresh and brackish evaporated water conditions the contrast between wetter early and drier late holocene climatic conditions is matched by other eastern and central mediterranean proxy climate data while the eski acigol sequence resembles holocene hydroclimatic changes in the saharo arabian zone and was also apparently linked to orbital forcing it is unlikely to have had the same direct cause i e an expansion and subsequent retreat of monsoon rainfall

controls on denudation rates in tectonically stable mediterranean carbonate terrain using cosmogenic isotopes and solute load analysis we quantify chemical weathering solutional erosion and denudation rates over variable time scales in a tectonically stable moderate relief carbonate terrain soreq drainage judea hills israel located in a semihumid mediterranean climate long term 10 4 yr denudation rates were calculated from 36 cl concentrations in 51 bedrock and sediment samples bedrock samples range in elevation 340 850 m hillslope gradient 0 30 and mean annual precipitation map 500 630 mm and vary in soil cover thickness 0 75 cm mg ca ratio 0 0 1 0 mol clay mineral contents 0 6 wt and mechanical strength 41 58 schmidt hammer rebound units soil pco2 values at a single location during the course of 1 yr range between 0 4 and 9 0 mmol mol 1 average long term denudation rate of exposed bedrock samples is 21 7 mm k y 1 field observations and 36 cl measurements indicate that soil pockets undergo cycles in the rate of deepening and that over 10 5 yr time scale average denudation rates beneath soil pockets are similar to those of exposed bedrock sediment samples yield even higher denudation rates which are probably anthropogenically induced but could also indicate that the sediment source is soil pockets long term denudation rates are decoupled from hillslope gradient elevation and rock strength denudation rates show a positive correlation with present day map values exhibit a complex relation with rock mg content and show a weak correlation with clay content annual chemical weathering rates were calculated from modern day solute load measured in waters of perched springs and the regional carbonate aquifer our results indicate that on annual decadal and 10 4 yr time scales chemical weathering and denudation are controlled by carbonate dissolution while mechanical processes are far less signifi cant overlap between the distributions of hco3 concentrations measured in runoff springs and the regional aquifer water suggests that chemical weathering focuses at the bedrock surface and therefore is comparable with solutional denudation this result is in contrast to the features of ancient fl uvial and colluvial activity steep nonconcave hillslopes and stream profi les and knickzones in the streams preserved in the present landscape such features were formed in response to mid pleistocene uplift and could have been preserved due to a decrease in stream power following the formation of subsurface drainage and the lowering in abrasive clast supply that followed the stabilization of hillslopes in the drainage long term denudation rates calculated from exposed bedrock samples are higher by factor of 1 4 relative to annual contemporary chemical weathering rates increased precipitation by a similar factor averaged over the last glacial and present interglacial can explain this difference

sensitivity of the eastern mediterranean geomorphic system towards environmental change during the late holocene a chronological perspective alluvial and colluvial sediment deposition provide a vital record of environmental change during the holocene firm chronological control on these archives is necessary to enable us to relate sediment dynamics to human activity and climate variability in the eastern mediterranean such relationships are hard to establish due to the lack of spatially well distributed sediment archives with good chronological control this scarcity is problematic with respect to regional scale reconstructions of the temporal variation of sediment dynamics here we present a radiocarbon database n 178 of geomorphological activity collected from multiple distinct sediment archives within the territory of sagalassos in south western turkey the data were grouped according to their sedimentary facies for analysis using cumulative probability distributions cpds and sedimentation rate sr modelling two small scale colluvial valleys where chronological information was abundant were investigated in more detail results show that sedimentation chronology differs between individual nearby cores as it depends strongly on the local geomorphic situation a generalizing approach combining multiple core results yields more widely valid conclusions high sedimentation rates coincided with the initial major anthropogenic disturbance of the landscape and decreased afterwards probably due to hillslope soil depletion cpd and sr analysis indicates that in general colluvial sedimentation rates did not change much from 2000 bc onwards river floodplain sedimentation in contrast increased markedly during the first millennium bc and during recent times and a significant time lag in enhanced sediment deposition between the upper and lower reaches of the river valleys was observed copyright 2012 john wiley sons ltd

an assessment of human versus climatic impacts on holocene soil erosion in ne peloponnese greece soil erosion is a natural geomorphological process which can be triggered by both natural climate tectonics or both and anthropogenic e g agriculture perturbation of the ecosystem evidence has accrued that the holocene climate experienced large fluctuations in amplitude and suggestions of human impact on the ecosystem provided by the neolithic revolution dating back to the early holocene have been made the question of whether man or climate was the dominant factor responsible for holocene soil erosion remains unresolved to resolve the reasons for holocene sediment redistribution high resolution chronometric data on sediments derived from colluvial and alluvial archives from southern greece were obtained and combined with available archaeological and paleoclimatic data from the eastern mediterranean these data show a significant correlation between sedimentation rates and settlement history climatic fluctuations are only weakly correlated with sedimentation history the results show high sedimentation rates during the early neolithic 7th millennium bc in southern greece suggesting that holocene soil erosion was triggered by human activity and then amplified by enhanced precipitation this would explain the high sedimentation rates during the early neolithic in connection with enhanced precipitation in the eastern mediterranean which continued until the mid holocene

the velocity and vorticity structure of the agulhas current at 32 s the full depth velocity field of the agulhas current the western boundary current of the southwest indian ocean has been directly measured using a lowered acoustic doppler current profiler ladcp fifteen combined conductivity temperature depth ctd and ladcp stations were occupied across the current at 32 s off the east coast of south africa in february march 1995 as part of the world ocean circulation experiment indian ocean program the deep velocity structure of the agulhas current was found to be very different than previously described using geostrophic estimates in particular ladcp results reveal a v shaped pattern for the level of no motion across the agulhas current and an agulhas undercurrent is observed flowing equatorward below 800 m depth directly beneath the surface core of the poleward flowing agulhas current comparisons of direct and geostrophic velocities suggest that the velocity structure of the agulhas current is essentially geostrophic below about 200 m depth where differences are generally less than estimated errors above these depths the ladcp measured shears and geostrophic shears exhibit differences and velocities can diverge shipboard adcp data support ladcp results near the surface indicating that both instruments are measuring real signals the geostrophic and ladcp measured shears are well matched away from the surface and a depth averaged fit below 200 m between them exhibits small standard deviations the geostrophic volume transport of the agulhas current as referenced to ladcp is 73 sv and is just 3 different from the direct ladcp transport estimate the most recent full depth estimate of agulhas current transport in the literature is given by toole and warren 1993 who estimate a geostrophic volume transport of 85 sv the baroclinic velocity structures from their section and from this work are similar indicating that the difference in the transport estimates is due to the choice of geostrophic reference level and ultimately to the presence of the previously unobserved agulhas undercurrent combined ctd ladcp data are very useful for potential vorticity analysis since velocity and density measurements are simultaneous and coincident the vorticity structure of the agulhas current suggests the presence of a mixing boundary at middepths similar to features observed in the gulf stream the feature appears to be associated with a sharp upturn in isopycnals coincident with the foot of the continental slope the boundary inhibits cross stream mixing of intermediate water masses and may help explain the appearance of a discrete filament of red sea water inshore of antarctic intermediate waters in the same density layer despite intense cross stream shears

palaeoclimatic interpretation of high resolution oxygen isotope profiles derived from annually laminated speleothems from southern oman high resolution stable isotope profiles of three contemporaneously deposited stalagmites from a shallow cave in southern oman provide an annually resolved record of indian ocean monsoon rainfall variability for the past 780 years uranium series age dating and counts of annual growth bands enable an excellent age calibration although modern speleothems do not grow in perfect isotopic equilibrium oxygen isotope ratios 18o are a proxy for the amount of monsoon rainfall this is supported by the statistically significant correlation between 18o and the thickness of annual bands whereas 18o is inversely correlated with annual band thickness additionally overlapping 18o profiles are very similar in pattern and range indicating that sample specific noise did not blur the climatic signal the longest oxygen isotope profile derived from stalagmite s3 clearly shows the transition at 1320 ad from a generally wetter medieval warm period to a drier little ice age that lasted from approximately ad 1320 1660 in southern oman the decrease in monsoon rainfall since the 1960s is also obvious in meteorological records from northern africa and india indicating that our speleothem based rainfall records do not only reflect local monsoon rainfall variability

geomorphological dynamic changes during the holocene through ephemeral stream analyses from northwest argentina abstract this paper studies the changes in the geomorphological dynamics recorded in 18 ephemeral streams located on the east side of loma pelada tafi valley a part of the sierras subandinas northwest argentina the applied methodology is based on photointerpretation field survey and descriptions of the holocene alluvial fillings dated by tephras archaeological artefacts and absolute datings the records show a coupled system of slope terrace alluvial fans resulting from the environmental changes of four alternating aggradation degradation stages the oldest stage 1 was generated by climatic causes and covers early to mid holocene ca 13 000 10 000 bp to ca 4200 bp after the incision of these accumulations a new aggradation stage 2 was triggered by anthropogenic activity occurring from right before 2500 bp to the 15th century during that time human occupations of the tafi valley were intense two wetter events occurred around 4200 and 2800 bp in the area related to global cooling phases lastly two more recent phases 3 and 4 are associated with the climatic variability of the lia and the present warm period the results highlight the sensitivity of headwater catchments of dry subtropical mountainous areas to climate changes anthropogenic impact and their relationship with global climatic data

application of geoarchaeological evolutionary models for the interpretation of complex archaeological structures in the central ebro basin spain in landscapes that are extremely sensitive to small environmental changes like some mediterranean areas archaeological contexts could present some problems to their interpretation and evolutionary reconstruction this is the case of los pedregales archaeological site located in the hoya de huesca ne of spain where several stone mounds of unknown age and function were found in an extensive badland the geomorphological edaphological and archaeological study together with radiocarbon and osl datings and contextualization into the geomorphological regional framework made it possible to interpret these structures and to establish an evolutionary model it was determined that they were silos excavated in pleistocene sands and silts unit 1 during the visigothic and early muslim epochs 6th 7th centuries and that they were later filled with limestone blocks successive aggradational and degradational stages units 2 3 and 4 during mca medieval climatic anomaly and lia little ice age periods covered and incised the area leaving the shape of positive structures included in the badland

a time series of agulhas undercurrent transport abstract a 550 day record of agulhas undercurrent transport between march 2003 and august 2004 is constructed from five deep moorings placed on the continental shelf off south africa at nominally 32 s the vertical and lateral scales of the undercurrent are estimated to be 2000 m and 40 km respectively using the average of seven direct velocity sections predominantly taken in austral autumn over a 10 yr period from 1995 to 2005 peak speeds in the undercurrent are some of the greatest ever seen at depth over 90 cm s 1 at 1400 m the undercurrent has a transport of 4 2 5 2 sv 1 sv 1 106 m3 s 1 in close agreement with a previous estimate from a single current meter record during 1995 of 4 2 2 9 sv records below 1800 m within the north atlantic deep water nadw layer of the undercurrent show a higher level of coherence and less variance than those at intermediate depths on average 2 3 3 0 sv of nadw is carried northeastward within the undercurrent an amount similar to that estimated p

karst depressions as geoarchaeological archives the palaeoenvironmental reconstruction of zominthos central crete based on geophysical prospection sedimentological investigations and gis abstract sediment filled karst depressions e g dolines have rarely been used as geoarchives in greece due to an uncertainty about the thickness of accumulations and their vague suitability for palaeoenvironmental research however such terrestrial proxy data sources can yield important records for the analysis of the holocene landscape history a multi method approach was applied in order to evaluate the potential of colluvial fillings for reconstructing the geoarchaeological landscape in mount ida central crete subsequent to an area wide survey of appropriate karst hollows through remote sensing and gis analyses geophysical prospection refraction seismics earth resistivity tomography was conducted at the most promising archive locations selective percussion drilling within the sinkholes provided vibra cores for mineralogical and sedimentological investigations grain size distribution heavy and light minerals x ray diffraction thin sections as well as ams 14 c dates as demonstrated by the results the dolines are partially filled by loose material up to 20 m b s and thus offer valuable information about the environmental history the diversified sediment constitution indicates several geomorphodynamic oscillations and a polygenetic nature of the colluvial fills xrd spectra of clay minerals and quartz grain morphology both indicate a significant aeolian dust contribution to soil formation and pedo sediments glass shards and substantially heterogeneous heavy mineral compositions point to supra regional origin and external volcanogenic deposits minoan eruption of santorini 3 6 ka regarding the hitherto discussed distribution of z2 tephra in the mediterranean the spatial fallout must be revised as great amounts have also been deposited in the high mountains of crete moreover the redeposition of the sedimentary fills proves to be comparatively young since most materials were accumulated within the dolines post eruptively huge and previously unknown subsurface archaeological remains strongly suggest that year around settlement in the mid holocene might have been possible under better climatic conditions the results imply that karst depressions serve as suitable geoarchives particularly when investigated within a multi method approach

coupling between hillslopes and channels in upland fluvial systems implications for landscape sensitivity illustrated from the howgill fells northwest england abstract the sensitivity of upland fluvial systems depends on the magnitude and frequency of sediment and flood producing events modified by the internal coupling characteristics of the system this paper assesses the role of hillslope channel coupling for the sensitivity of upland geomorphic systems using evidence from a 30 year monitoring programme of geomorphic change in the carlingill valley howgill fells northwest england in the hillslope zone there is little sediment supply to the stream system locally slope failures occur in response to extreme events six such events in 30 years within the ca 6 km 2 carlingill valley in the footslope coupling zone basally induced gullies are major sediment sources to the stream sediment production events occur ca 30 times per year feeding sediment to basal debris cones stream floods which can entrain these sediments occur once every ca 2 5 years stream channel morphology is adjusted to this regime downstream of gullies channels are wide and braided elsewhere they are narrow and single thread as the gullies develop however this coupling weakens and the eroding slopes eventually stabilise by revegetation over the 30 year monitoring period there has been a progressive trend towards gully stabilisation and an associated reduction in channel instability massive destabilisation may occur in response to rare extreme flood events such an event return period 100 years occurred in neighbouring langdale and bowderdale valleys in june 1982 that event destabilised the system causing slope failures fan deposition and in some places a switch in channel style to wide braided channels since 1982 there has been a progressive recovery by slope stabilisation and single thread sinuous channels have become reestablished a different style of extreme event occurred in carlingill in october 1998 in response to the wettest week in the 30 year period a slope failure fed debris flows 400 m downslope almost coupling with the channel system future climatic change could render the system prone to destabilisation through either extreme flood events or through major slope failures

luminescence dating applications in geomorphological research abstract chronological control remains critical to the interpretation of environmental change and to establishing long term rates of geomorphological processes radiocarbon dating will continue to be the central technique for age assessment of carbon bearing sediments deposited in the last ca 40 ka but alternative absolute dating strategies are required for older or non carbon bearing sediments they include uranium series dating of precipitated sediments k ar and ar ar dating of primary volcanic materials and cosmogenic isotopic dating of surface exposure ages an additional family of methods collectively termed luminescence techniques is increasingly providing a basis for the age assessment of detrital sedimentary deposits these methods directly date the deposition of detrital mineral grains typically quartz and feldspar and have been demonstrated to provide accurate deposition chronologies for up to 800 ka although 150 ka is more typical in the past decade a subset of luminescence techniques which employ optical sample stimulation methods called optical dating has made it possible to date samples from a much wider range of depositional systems given that the methods directly date sedimentation they allow direct assessment of depositional dynamism in numerous terrestrial and subaqueous including marine sedimentary systems and have demonstrated particular potential in the elucidation of chronologies from aeolian dune and loess fluvial colluvial coastal and volcaniclastic environments this paper provides a summary of the principles of the luminescence especially optical dating methods and shows how recent developments specifically single aliquot dating procedures have dramatically enhanced the scope and potential of the method the luminescence techniques are increasingly being incorporated into a wide range of geomorphological studies which seek to establish the nature of landscape changes over the past interglacial glacial cycle and beyond

geomorphic responses to long term land use changes in eastern macedonia greece distinct phases of stream aggradation soil erosion and landscape stability in the basin of drama eastern macedonia greece over the past 7000 years can be tied directly to long term land use changes during the middle and late holocene 1 4 m of alluvial fill accumulated in the centre of the basin and along the angithis valley low levels of alluvial aggradation were recorded during the late neolithic and the early bronze age 7400 4000 cal bp in the centre of the basin along the lower course of the river xeropotamos the rate of aggradation has doubled since the late bronze age 0 5 0 6 mm year 1 compared to the holocene as a whole 0 25 mm year 1 moderate rates of alluvial fill were experienced during the late bronze age 3600 3000 cal bp but the most significant destabilisation of the soils occurred later than in many regions of greece two historical phases of alluvial aggradation and soil erosion are identified in the antique and the early byzantine era 3rd century bc 7th century ad and more significantly in the ottoman period beginning of the 15th to the 20th century ad in the latter period the rate of accumulation was three to five times greater than in the late holocene almost three millennia intervened between the arrival of the first farmers and the onset of erosion this is mainly explained by the settlement pattern during the neolithic and the early bronze age it seems that the early farmers preferred to cultivate the more stable soils on the gentle slopes at the centre of the basin during the late bronze age the land use pattern changed the soils then under cultivation on the foothills were less stable and the steeper slopes were more susceptible to erosion this limited the potential for forest restoration after the first noticeable land clearance and probably explains the extent of alluvial aggradation since the antique era the intensity of land use has increased the two phases of accelerated alluviation in historical times are clearly linked to land use changes particularly with the upstream progression of cropping and grazing onto more sensitive lands in foothills and mountainous areas though this was also influenced by climatic fluctuations the major period of aggradation in the ottoman period is clearly associated with both climatic and anthropogenic factors it seems that the early historic deforestation and agricultural activities rendered river systems more sensitive to relatively modest changes in climate

variability and coherence of the agulhas undercurrent in a high resolution ocean general circulation model abstract the agulhas current system has been analyzed in a nested high resolution ocean model and compared to observations the model shows good performance in the western boundary current structure and the transports off the south african coast this includes the simulation of the northward flowing agulhas undercurrent it is demonstrated that fluctuations of the agulhas current and undercurrent around 50 70 days are due to natal pulses and mozambique eddies propagating downstream a sensitivity experiment that excludes those upstream perturbations significantly reduces the variability as well as the mean transport of the undercurrent although the model simulates undercurrents in the mozambique channel and east of madagascar there is no direct connection between those and the agulhas undercurrent virtual float releases demonstrate that topography is effectively blocking the flow toward the north

weathering limited hillslope evolution in carbonate landscapes understanding topographic evolution requires integrating elementary processes acting at the hillslope scale into the long wavelength framework of landscape dynamics recent progress has been made in the quantification of denudation of eroding landscapes and its links with topography despite these advances data is still sparse in car bonate terrain which covers a significant part of the earth s surface in this study we measured both long term denudation rates using in situ produced 36 cl concentrations in bedrock and regolith clasts and surface convexity at 12 sites along ridges of the luberon carbonate range in provence southeastern france starting from 30 mm ka for the lowering of the summit plateau surface denudation linearly increases with increasing hilltop convexity up to 70 mm ka as predicted by diffusive mass transport theory beyond this point denuda tion rates appear to be insensitive to the increase in hilltop convexity we interpret this constant denudation as indicating a transition from a regime where hillslope evolution is primarily controlled by diffusive downslope regolith transport toward a situation in which denuda tion is limited by the rate at which physical and chemical weathering processes can produce clasts and lower the hilltop such an abrupt transition into a weathering limited dynamics may prevent hillslope 1 denudation from balancing the rate of base level fall imposed by the river network and could potentially explain the development of high local relief in many mediterranean carbonate landscapes

sea surface slope as a proxy for agulhas current strength the linear relation between the strength of the agulhas current at nominal latitude 34 s and the gradient in sea level height anomaly across the current is investigated in a 1 10 resolution regional numerical ocean model our results show that the strength of the current can be estimated with reasonable accuracy using altimeter data once it has been calibrated using in situ transport measurements three years of transport measurements provide a calibration with worst case correlation r 0 78 in that case the errors in proxy transport have a standard deviation of 9 8 sv compared to a 20 2 sv standard deviation of the transport time series itself from these results we conclude that the design of the agulhas current timeseries act experiment a three year deployment of moorings across the agulhas current and along a topex jason altimeter ground track will likely produce a good quality multi decadal time series of agulhas current strength

from proxy data to paleoclimate interpretation the mid holocene paradox of the atacama desert northern chile abstract the question whether the mid holocene climate between ca 9 and 4 cal kyr b p in the atacama desert and the central andes in general was humid or dry has wide implications with regard to the understanding of long term climate variability in south america paleosols regional groundwater tables abiotic proxy data and pollen of aquatic plants in lake sediments show a marked and rapid shift from very humid late glacial early holocene climatic conditions between ca 14 and 9 5 kyr b p to extremely dry mid holocene conditions more arid than today between ca 9 and 4 kyr b p an exception during this hyperarid period is a century scale more humid interval around ca 5 5 6 kyr b p that appears systematically in lake sediment archives in contrast pollen for most terrestrial plants preserved in lake sediments do not show major changes during the holocene whereas more humid mid holocene conditions compared with late holocene conditions were inferred from plant macrofossils in rodent middens is the reason for this disagreement to be attributed to misinterpretation of the paleoenvironments or of the proxy records themselves or to incomplete paleoclimatic interpretation of the paleoenvironments we argue that these different paleoclimate archives record different aspects and facets of climate while paleosols and groundwater in the atacama desert record low frequency climate variability at century to millennium scales lake sediments on the altiplano record decade to century scale variability terrestrial vegetation responds to shorter high frequency climate variability at seasonal to inter annual scales and preferably to humid years vegetation remains in hibernation or does not germinate during arid years thus information from these three types of archives is not a priori comparable and requires careful site specific archive specific and time scale specific evaluation what is natural in modern climatology is also true for paleoclimatology a comprehensive assessment must account for the complex daily and seasonal cycles for the range of climate variability and trends at different scales in space and time for impacts of short term extreme events and for specific often non linear responses of individual bio geo physical archives to any of the numerous aspects of climate

the east madagascar current volume transport and variability based on long term observations abstractthis study provides a long term description of the poleward east madagascar current emc in terms of its observed velocities estimated volume transport and variability based on both 2 5 yr of continuous in situ measurements and 21 yr of satellite altimeter data an array of five moorings was deployed at 23 s off eastern madagascar as part of the indian atlantic exchange in present and past climate inatex observational program on average the emc has a horizontal scale of about 60 100 km and is found from the surface to about 1000 m depth its time averaged core is positioned at the surface at approximately 20 km from the coast with velocity of 79 21 cm s 1 the emc mean volume transport is estimated to be 18 3 8 4 sverdrups sv 1 sv 106 m3 s 1 during the strongest events maximum velocities and transport reach up to 170 cm s 1 and 50 sv respectively a good agreement is found between the in situ transport estimated over the first 8 m of water column 0 32 0 13 sv with the

effective timescales of coupling within fluvial systems this paper presents a review of the coupling concept in fluvial geomorphology based mainly on previously published work coupling mechanisms link the components of the fluvial system controlling sediment transport down the system and the propagation of the effects of base level change up the system they can be viewed at several scales at the local scale involving within hillslope coupling hillslope to channel coupling and within channels tributary junction and reach to reach coupling at larger scales coupling can be considered as zonal coupling between major zones of the system or as regional coupling relating to complete drainage basins these trends are illustrated particularly by the examples of hillslope to channel coupling in the howgill fells northwest england badland systems in southeast spain alluvial fans in spain usa and uae and base level induced dissection of neogene sedimentary basins in southeast spain as the spatial scales increase so do the timescales involved effective temporal scales relate to magnitude and frequency characteristics recovery time and propagation time the relative importance changing with the spatial scale for downsystem coupling at the local scale the first two are important with propagation time increasing in importance in larger systems especially in those involving upsystem coupling related to base level change the effective timescales range from the individual event with a return period of decades through decadal to century timescales for downsystem coupling to tens to hundreds of thousands of years for the basinwide response to base level change the effective timescales influence the relative importance of factors controlling landform development

western boundary current structure and variability east of abaco bahamas at 26 5 n abstract during april 1987 to june 1988 a four mooring transport resolving current meter array was deployed in a section extending 70 km eastward from abaco bahamas at 26 5 n mean currents in the upper layer 800 m showed a clockwise rotation that appears to be associated with a small scale quasi permanent anticyclonic gyre centered just northeast or the bahamas deep mean currents were persistenly southward and indicated a strong deep jet the deep western boundary current dwbc reaching core speeds of 20 cm s 1at 2500 m depth about 25 km seaward of the western boundary vertically integrated meridional volume transport over the section showed a surprisingly large variability ranging from approximately 20 sv northward to 70 sv southward 1 sv 106m3s 1 the mean meridional volume transport was 30 sv to the south with about 3 sv flowing northward above 800 m which could be produced by a weak antilles current and 33 sv flowing southward below 800 m the deep southward transport of 33 sv i

the history of holocene soil erosion in the phlious basin ne peloponnese greece based on optical dating anthropogenic induced soil erosion has occurred in the mediterranean during historic and pre historic times but precise timeframes for periods of past soil erosion are largely missing due to the lack of datable material and suitable dating methods in this study optical dating of colluvial sediments from the phlious basin ne peloponnese greece was applied the results show that soil erosion derived colluvium formed under a mediterranean type climate can be successfully dated by optical stimulated luminescence osl and a high resolution chronology of holocene soil erosion could be established colluvial formation occurred in the early holocene but increased distinctly in the seventh millennium parallel with the onset of the neolithic the start of farming activities other periods of strong colluviation are the middle and late bronze age second millennium the roman period first century to sixth century and the period since the sixteenth century rates of reduced colluviation occurred during

natural and human induced environmental changes preserved in a holocene sediment sequence from the etoliko lagoon greece new evidence from geochemical proxies abstract a key feature of greece is the large amount of historical and archaeological records the sedimentary record of the etoliko lagoon aetolia western greece offers an ideal opportunity to study human environment interaction and to disentangle natural and anthropogenic imprints in the sedimentary record by applying an interdisciplinary approach of combining geoscientific methods xrf loi grain size analysis with archaeological and historical records the 8 8 m long sedimentary sequence eto1c reveals the palaeoenvironmental history of the lagoon and its catchment since 11 670 cal bp with a thorough chronology based on 14 c age depth modelling including varve counting different evolutionary stages were put in a chronological context these stages include a lake period 11 670 8310 cal bp followed by a period of sporadic saltwater intrusion 8310 1350 cal bp as a result of continuing transgression phases of limnic predominance associated with freshwater inflow of episodically activated distributaries around 5230 cal bp still occurred by 1350 cal bp ongoing sea level rise had connected the lagoons of etoliko and messolonghi and freshwater influence had ceased with the onset of settlement activity in the late helladic 1700 1100 cal bc humans took advantage of the prevailing environmental landscape a sudden increase in coarse sedimentation correlates with the history of human occupation with its peak of prosperity from the late helladic until the end of the hellenistic period 30 cal bc

palaeoenvironment and anthropogenic activity in the southeastern mediterranean since the mid holocene the case of tell es safi gath israel abstract the younger fill phenomenon defined by vita finzi related to sediments that were deposited in many mediterranean valleys has been a topic of discussion for several decades the main challenge regarding this issue is deciphering the origin of the fill geomorphic processes induced by natural climatic or by anthropogenic activity the current research is an attempt to deal with this issue by using a concept in which the environmental records i e climate hydrology and sedimentology were examined in conjunction with human history in the area of the bronze and iron age archaeological site of tell es safi gath in central israel the study investigated geomorphic structures of various scales a single slope 1st and 2nd order valleys and larger drainage basins of a few tens to hundreds km 2 high resolution dating of the sediments by osl and 14 c allowed the identification of different sedimentary phases the sedimentary history of the tell es safi gath environs shows that a during the chalcolithic period and early bronze age 4200 3050 bce stable conditions prevailed in the small valleys represented by soil formation b during the iron age ii and up to the early arab period 800 bce 800ce aggradation took place in the small and the large valleys c during the post byzantine early arab periods after 800 ce major incision occurred in the large valleys whereas minor aggradation occurred in the small valleys climatic and natural geomorphic processes are the major factors shaping the landscape in the current research area anthropogenic activity was expressed at localized sites and for a limited time in two locations only one location is the siege trench that surrounds tell es safi gath where sedimentation occurred shortly after the destruction of the site by hazael king of aram damascus ca late 9th century bce and in the same locality during the byzantine period the other location is the 2nd order valley close to the archaeological site where enhanced sedimentation rates occurred shortly after site destruction in addition these results suggest that the small basin valleys underwent aggradation that continuously recorded the local environmental history whereas the large drainage basins underwent cut and fill processes related to the regional environmental history in a less continuous record

luminescence dating of hillslope deposits a review abstract luminescence dating determines the last exposure to light of quartz and feldspar mineral grains and thus the time a sediment was laid down prerequisite is that the sediment grains were sufficiently exposed to light prior to deposition for eolian deposits this seems a fair assumption although exceptions may well exist for other depositional environments light exposure prior to burial is often restricted in duration intensity and spectral composition and may result in an age overestimation recent developments now allow dating of sediments that were exposed to only little light prior to deposition the main developments are single aliquot techniques and statistical tests that allow extraction of valid age estimates even from deposits in which bleached and unbleached grains are mixed these developments in combination with the fact that the great majority of sediments near the earth s surface are not of eolian origin have resulted in the large interest in the luminescence dating of non eolian deposits here we review possibilities and challenges of luminescence dating of colluvial deposits we summarize techniques for the detection and handling of insufficiently bleached sediments a common condition in colluvial deposits we give an overview how luminescence dating has been applied on hillslope sediments for reconstructing landscape response to climate change to analyze past fault activity and unravel human induced soil erosion we discuss sampling strategies and give guidelines as to which techniques are best suited to establish luminescence chronologies for colluvium

the sources and mixing characteristics of the agulhas current recent observations taken at four principal latitudes in the agulhas current show that the watermass properties on either side of its dynamical core are significantly different inshore of its velocity core are found waters of predominantly arabian sea red sea and equatorial indian ocean origin while offshore waters are generally from the atlantic ocean the southern ocean and the southeast indian ocean for the most part the inshore waters approach the agulhas current through the mozambique channel while those offshore are circulated within the southern indian ocean subtropical gyre before joining the current these disparate water masses remain distinct during their 1000 km journeys along the south african continental slope despite the convergence extreme velocity shears and high eddy kinetic energies found within the agulhas current both potential vorticity conservation and kinematic arguments are discussed as potential inhibitors of along isopycnal mixing it is concluded that a high cross stream gradient of potential vorticity is the dominant mechanism for watermass separation near the surface while the kinematic steering of water particles by the current is dominant at intermediate depths where cross stream potential vorticity is homogeneous hence three lateral mixing regimes for the agulhas current are suggested the surface and thermocline waters are always inhibited from mixing by the presence of both a strong cross frontal potential vorticity gradient and kinematic steering at intermediate depths mixing is inhibited by steering alone and thus in this regime periodic mixing is expected during meander events such as natal pulses when the steering level will rise and allow cross frontal exchange below the steering level in the deep waters there is a regime of free lateral mixing the deep waters of the agulhas current are homogeneous in the cross stream sense being from the same north atlantic source and their salinity steadily and rather rapidly decreases to the north here it is suggested that mixing must be dominated by vertical processes and a large vertical mixing coefficient of order 10 cm 2 s 1 is estimated

palaeoclimate and the formation of sapropel s1 inferences from late quaternary lacustrine and marine sequences in the central mediterranean region abstract synchronous responses to climatic changes during the late pleistocene holocene transition are inferred from marine and lacustrine stratigraphic records in the central mediterranean region new stratigraphic data are presented from well dated sequences in the meso adriatic depression mad two crater lakes in the lazio region and in the tyrrhenian sea the sequences all span the last termination and the holocene but we focus here on the evidence in each record for the time period during which sapropel s1 formed in the mediterranean ca 9 0 to 6 8 cal kyr b p the new records provide evidence of palaeoenvironmental changes on land and sea that can be reconstructed at a high temporal resolution and which throw some light on the processes which led to the formation of s1 the collective evidence indicates that i organic rich sediments occurred in both the marine and the crater lake sites during the time of formation of the s1 sapropel ii there is evidence of increased stratification and anoxia in the sea water column during the period of s1 formation iii the s1 period in the study area is divisible into two sub phases s1a and s1b which reflect short term variations in oceanographic conditions stratification and anoxia iv changes in stratification in the marine column were contemporaneous with regional climate variations that are inferred from the terrestrial records we conclude that the key factor that initiated the formation of s1 was increased discharge of freshwater into the mediterranean following a change post 9 0 cal kyr b p to a warmer and wetter climate furthermore the period of s1 formation was interrupted by a short lived episode ca 500 years of comparatively cooler and drier conditions during the early middle holocene transition emht

the socio environmental history of the peloponnese during the holocene towards an integrated understanding of the past published archaeological palaeoenvironmental and palaeoclimatic data from the peloponnese in greece are compiled discussed and evaluated in order to analyse the interactions between humans and the environment over the last 9000 years our study indicates that the number of human settlements found scattered over the peninsula have quadrupled from the prehistoric to historical periods and that this evolution occurred over periods of climate change and seismo tectonic activity we show that societal development occurs both during periods of harsh as well as favourable climatic conditions at some times some settlements develop while others decline well known climate events such as the 4 2 ka and 3 2 ka events are recognizable in some of the palaeoclimatic records and a regional decline in the number and sizes of settlements occurs roughly at the same time but their precise chronological fit with the archaeological record remains uncertain local socio political processes were probably always the key drivers behind the diverse strategies that human societies took in times of changing climate the study thus reveals considerable chronological parallels between societal development and palaeoenvironmental records but also demonstrates the ambiguities in these correspondences and in doing so highlights some of the challenges that will face future interdisciplinary projects we suggest that there can be no general association made between societal expansion phases and periods of advantageous climate we also propose that the relevance of climatic and environmental regionality as well as any potential impacts of seismo tectonics on societal development need to be part of the interpretative frameworks

influence of climate change and human activities on the organic and inorganic composition of peat during the little ice age el payo mire w spain the study of environmental change during the little ice age lia offers a great potential to improve our current understanding of the climate system and human environment interactions here a

climate change and the collapse of the akkadian empire evidence from the deep sea the akkadian empire ruled mesopotamia from the headwaters of the tigris euphrates rivers to the persian gulf during the late third millennium b c archeological evidence has shown that this highly developed civilization collapsed abruptly near 4170 150 calendar yr b p perhaps related to a shift to more arid conditions detailed paleoclimate records to test this assertion from mesopotamia are rare but changes in regional aridity are preserved in adjacent ocean basins we document holocene changes in regional aridity using mineralogic and geochemical analyses of a marine sediment core from the gulf of oman which is directly downwind of mesopotamian dust source areas and archeological sites our results document a very abrupt increase in eolian dust and mesopotamian aridity accelerator mass spectrometer radiocarbon dated to 4025 125 calendar yr b p which persisted for 300 yr radiogenic nd and sr isotope analyses confirm that the observed increase in mineral dust was derived from mesopotamian source areas geochemical correlation of volcanic ash shards between the archeological site and marine sediment record establishes a direct temporal link between mesopotamian aridification and social collapse implicating a sudden shift to more arid conditions as a key factor contributing to the collapse of the akkadian empire

mediterranean pluvial periods and sapropel formation over the last 200 000 years abstract three mediterranean deep sea cores have been studied to reconstruct the hydrological conditions at the time of deposition of interglacial and glacial sapropels during the time interval 200 60 kyr bp the isotopic and sea surface temperature records of planktonic foraminifera were used to estimate the oxygen isotopic composition of surface water w in the tyrrhenian sea and levantine basin our results show a strong w salinity decrease in both basins associated with each sapropel these w decreases reflect a drastic change in the local freshwater budget and were comparable to that observed during the last sapropel s 1 centred at ca 8 kyr bp a strong precipitation increase transformed the whole mediterranean sea into a non concentration basin the low surface salinity was responsible for the water column stratification while nutrients brought in by the runoff enhanced productivity it resulted in a significant reduction in the rate of deep water oxygenation and sapropel formation in the eastern basin in addition the mediterranean sea 18 o record is very similar to that of the bay of bengal as the latter is very sensitive to the summer monsoon rain this similarity suggests that both glacial and interglacial sapropels result from enhanced monsoon like precipitation due to an increase in summer insolation driven by precession variations

holocene river and slope activity in the visoko basin bosnia herzegovina climate and land use effects alluvial and colluvial deposits were investigated at prehistoric tells close to the bosna river the chronology is based on ten radiocarbon ages five optically stimulated luminescence ages and on the archaeological record fluvial activity of the bosna river is indicated by overbank fines ca 5000 1000 bc 500 bc until today and a phase of lateral displacement of the river bed with subsequent channel fills ca 2000 500 bc early holocene fluvial activity was probably triggered by climatic variability but might have promoted the expansion of neolithic societies into the visoko basin mid to late holocene river activity occurred under increased climatic aridity but coincided with the expansion of prehistoric settlements to a wider area of the river basin on hard rocks in the adjacent mountainous areas the destruction of the thin soil cover in the mountains is discussed as a probable trigger for enduring subsequent river activity this is also indicated by a change in the geochemical signature of the alluvial sediments the proposed mechanism might explain the mid to late holocene river history in other regions the potential of geochemical analyses and diachronous high resolution archaeological records to make inferences regarding sediment sources and geomorphological processes is demonstrated copyright 2013 john wiley sons ltd