monsoon reconstruction from radiocarbon dated tropical indian speleothems the potential of tropical speleothems as a climate proxy has been investigated amplitudes of 180 and 813c variations are found to be large and are likely to be primarily controlled by past rainfall contribution from past temperature variations seems to be relatively small the amount effect in rainfall has been observed and quantified by analysing rainwater samples collected during a monsoon season a tentative chronology to these speleothems is asssigned by the 14c radiometric dating method assuming that the variations in the 180 of cave carbonates are solely due to the past variations in rainfall a history of the latter has been reconstructed a high resolution rainfall reconstruction up to the last 3400 years is now available from gupteswar cave orissa subject to validation of dates by the u th method it is observed that in a tropical speleothem 513c is dominantly controlled by rainfall the study has shown that tropical indian speleothems faithfully record the annual monsoon rainfall in the

the quaternary glacial history of the lahul himalaya northern india this paper presents the first glacial chronology for the lahul himalaya northern india the oldest glaciation the chandra glacial stage is represented by glacially eroded benches at altitudes greater than 4300 m above sea level this glaciation was probably of a broad valley type the second glaciation the batal glacial stage is represented by highly weathered and dissected lateral moraines which are present along the chandra valley and some of its tributaries this was an extensive valley glaciation the third major glaciation the kulti glacial stage is represented by well preserved moraines in the main tributary valleys of the chandra valley this represents a less extensive valley glaciation two minor glacial advances the sonapani i and ii are represented by small sharp crested moraines which are within a few hundred metres or few kilometres of the present day glaciers the change in style and extent of glaciation is attributed to an increase in aridity throughout the quaternary due either to global climatic change or uplift of the pir panjal mountains to the south of lahul which restricted the northward penetration of the south asian summer monsoon 1996 john wiley sons ltd

precambrian permafrost horizons as indicators of palaeoclimate abstract periglacial phenomena such as polygonal wedge structures and microrelief features commonly preserved in fossil permafrost horizons can provide valuable information on palaeoclimate including indications of mean annual air temperature seasonal temperature range relative precipitation and evidence for long term 104 years oscillations of climate such features are known from early and late proterozoic rocks and indicate mean annual air temperatures as low as 12 to 20 c or lower and strongly seasonal periglacial climates these palaeoclimatic data together with information on palaeolatitude and proximity to palaeo sea level may impose strong constraints on palaeoclimate models for proterozoic glaciation

speleothem evidence for changes in indian summer monsoon precipitation over the last 2300 years speleothems from a well ventilated dolomitic cave in the pokhara valley central nepal preserve a mineralogic record of indian summer monsoon variability over the past 2300 yr annually deposited aragonite layers formed between 2300 and 1500 yr b p indicating reduced monsoon precipitation and increased cave aridity whereas alternating calcite aragonite laminae deposited after 1500 yr b p record elevated summer monsoon precipitation and increased cave humidity dense optically clear calcite layers deposited from 450 5 to 360 20 yr b p 1550 to 1640 a d indicate a less evaporative cave environment and suggest moister and or cooler conditions possibly related to climatic change associated with the onset of the little ice age

interaction of mediterranean water eddies with sedlo and seine seamounts subtropical northeast atlantic abstract during years 2003 and 2004 both sedlo and seine seamounts lying in the area of influence of the mediterranean water outflow in the northeast atlantic were investigated in the framework of the eu funded project oasis analysis of ctd data shows that the levels of major variability in temperature and salinity were confined to the upper ocean layer which is subject to seasonal air sea heat exchange and to the mediterranean water mw level in this paper we concentrate on the latter case and show that the variability observed resulted from mediterranean water eddies meddies colliding with the seamounts combined data from ctd surveys current meter moorings ship mounted adcp and satellite altimetry suggest that during the period of observations there was only one meddy interacting with each of the seamounts on sedlo seamount intensive interaction resulted in the loss by the meddy of about 25 of the salt around the seamount whereas on seine the meddy or portion of it escaped the seamount after performing several rotations around the summit without any significant interaction

the relationship between climate change and quaternary glacial cycles on the qinghai tibetan plateau review and speculation the quaternary climatic history of the qinghai tibetan plateau is reconstructed using quaternary glacial geologic data four major glaciations are recognized the xixiabangma naynayxungla guxiang the penultimate and baiyu the last glaciation these are dated at about 800 1170 500 720 130 300 and 10 70ka respectively these correspond to marine oxygen isotopic stages mis 20 similar to 36 14 similar to 18 6 similar to 8 and 2 similar to 4 the most extensive glaciation occurred during the naynayxungla glaciation when there were many large ice caps glacier complexes and great valley glaciers covering a total area greater than or equal to500 000 km 2 the guxiang glaciation stage 6 was characterized by valley glaciers while during the baiyu glaciation stages 2 4 the glaciers were more restricted in extent and covered a total area of similar to350 000 km 2 these data show that glaciation become less extensive throughout the quaternary and may have been the result of variations in climate in response to changing patterns of insolation related to changes in the earth s orbit c 2002 elsevier science ltd and inqua all rights reserved

widespread aggradation in the mountainous catchment of the alaknanda ganga river system timescales and implications to hinterland foreland relationships abstract cut and fill type fluvial terraces are ubiquitous in the lesser himalayan zone of the alaknanda ganga ganges rivers system which flows perpendicular to himalayan lithotectonic units and traverses a steep climatic gradient lithofacies analysis of the sedimentary sequences of cut and fill terraces indicated that the valley aggradation took place via 1 channel bar development and excess sediment supply 2 debris flows composed of mixed rounded to sub rounded lithoclasts resulting from episodic high intensity rainfalls in the upper catchment or 3 debris flows or rockfalls generated by local landslides the luminescence chronology indicates that valley aggradation took place in two phases 49 25 ka and 18 11 ka the incision of the fill started soon after 11 ka paleoclimatic records from marine sediments indicate that the aggradation and incision in the alaknanda ganga river has oscillated in phase with global climatic variations glaciation deglaciation processes in the upper catchment produced huge amounts of sediment between 63 and 11 ka which was fluvially transferred to the lower valley via several cycles of erosion and deposition leading to extensive aggradation the climatic amelioration at 11 ka and the completion of deglaciation processes led to increased fluvial discharge and decreased sediment supply conditions conducive for incision of the alluvial fills records from the indo gangetic plain and the ganga delta demonstrate that the phase of aggradation was regional but that incision in the foreland started at least 2 3 ka later after 7 ka bedrock incision rates as calculated from dated alluvial covers of terraces that are separated by bedrock steps are spatially variable and fall within the range of rates reported from across the himalaya these estimated rates however are higher than the basin average erosion rates calculated using isotopic mass balance in riverbed sediments this study suggests that during the last 50 ka river dynamics in the himalayas were dominated by monsoon variability and the role of tectonic activity was limited to bedrock incision in few reaches only

timing and extent of late quaternary glaciation in the western himalaya constrained by 10be moraine dating in garhwal india glacial chronologies from the himalayan region indicate various degrees of asynchronous glacial behavior part of this has been related to different sensitivities of glaciers situated in contrasting climatic compartments of the orogen but so far field data in support for this hypothesis is lacking here we present a new 10 be derived glacial chronology for the upper tons valley in western garhwal india and initial results for the pin and thangi valleys in eastern himachal pradesh these areas cover a steep gradient in orographic precipitation and allow testing for different climatic sensitivities our data provide a record of five glacial episodes at w16 ka w11 12 ka w8 9 ka w5 ka and 1 ka in the thangi valley our results indicate a glacial episode at w19 ka but no data are available for younger glacial deposits in this valley at their largest mapped extent w16 ka the two main glaciers in the upper tons valley joined and descended down to w2500 m asl which represents a drop of w1400 m compared to the present day glacial extent during the holocene the two largest glaciers produced distinct glacial landforms that allowed us to reconstruct changes in the equilibrium line altitude ela over w20 km north south distance that is presently associated with a steep gradient in rainfall we observe that ela changes have been consistently w2 times higher for the glacier located in a presently wetter climate pointing at different climate sensitivities related to the amount of precipitation that they receive at regional scale our data is in reasonable agreement with other published glacial chronologies from the western himalaya and suggest that glacial advances during the holocene have been largely synchronous in this region comparison of glacial chronologies from the western himalaya with other palaeoclimatic proxy data suggests that long term changes in glacial extents are controlled by glacial interglacial temperature oscillations related to the waxing and waning of the large northern hemisphere ice sheets while the timing of millennial scale advance and retreat cycles are more directly related to monsoon strength

morpho sedimentary records at the brahmaputra river exit ne himalaya climate tectonic interplay during the late pleistocene holocene morphological and sedimentary records at the exit of brahmaputra river at pasighat in the ne himalaya inform about the climate tectonic interplay during the past ca 15 ka the geomorphology of the area comprises 1 fan terrace t3 2 a high angle fan 3 terrace t2 4 terrace t1 and 5 a low angle fan geomorphic consideration suggests that the fan terrace t3 and high angle fans are the oldest units and were coeval the low angle fan is the youngest geomorphic unit sedimentological studies and optically stimulated luminescence chronology suggest that i fan terrace t3 formed between 13 and 10 5 ka and comprised multiple events of debris flows separated by the aggradation as channel bars in a braided river environment ii the high angle fan formed during 15 10 ka and comprises channel bar aggradation in braided river conditions iii terrace t2 formed during 10 8 ka due to aggradation in a braided channel environment with lesser events of debris flows iv terrace t1 formed during 7 and 3 ka took place as bars of the braided river sudden coarsening of the sediment indicated a tectonic rejuvenation in the provenance region between 7 and 3 ka and v the low angle fans dated to 3 ka formed due to aggradation in a small tributary joining the brahmaputra river this implies a phase when the main channel of the brahmaputra did not flood regularly and the tributaries were actively aggrading the sedimentation style and incision of these geomorphic units responded to contemporary climatic changes and uplift in the siwalik range along the himalayan frontal fault copyright 2008 john wiley sons ltd

periglacial paleosols and cryogenian paleoclimate near adelaide south australia abstract late cryogenian deformation of the reynella siltstone near hallett cove south australia has been interpreted as shallow marine methane seeps which were furthermore proposed to have played a role in deglaciation from snowball earth re examination and new analyses of these same outcrops confirms an earlier interpretation of this intrastratal deformation as periglacial paleosols which are evidence that even at maximum extent late cryogenian glaciers did not cover all continental lowlands let alone the world ocean known miocene and pliocene methane seeps of california examined for this study are very different in their gray color rounded nodules and clayey host rock compared with red highly deformed and silty to pebbly reynella siltstone of hallett cove stable isotopic composition of nodular carbonate in the reynella siltstone fails to show extreme carbon isotopic depletion or the meteoric oxygen lines characteristic of known methane seeps and sphaerosideritic waterlogged paleosols but instead shows covariance of carbon and oxygen isotopic composition comparable with that in pedogenic and subaerial carbonate of well drained soils mass balance geochemical analyses show modest weathering compatible with sand wedge structures and evaporitic pseudomorphs indicative of arid and frigid paleoclimate outcrops of reynella siltstone near hallett cove represent frigid low latitude floodplains not submarine methane seeps nor global glaciation

late quaternary holocene landscape evolution of a monsoon influenced high himalayan valley gori ganga nanda devi ne garhwal the garhwal himalaya provides an excellent natural laboratory in which to examine landscape evolution in a monsoon influenced high mountain environment geomorphic and sedimentological analysis and 10be cosmogenic radionuclide crn surface exposure dating of moraines fans and river and strath terraces in the gori ganga valley of nanda devi ne garhwal indicate that fans and river terraces developed rapidly by debris flow and flood processes during periods of deglaciation these phases of high sediment transfer occurred at 1 2 4 5 and 7 8 ka fan incision rates subsequent to major times of resedimentation after each glacial advance are between 19 and 57 mm year this contrasts with bedrock incision rates based on mid holocene strath terraces of 5 mm year these rates indicate that despite episodes of rapid denudation and resedimentation linked to glacial activity in this region the background rates of denudation are similar to those for other regions of the himalaya averaging several millimeters per year furthermore these data show the importance of climatic controls on landscape evolution and suggest a strong monsoonal control on the dynamics of earth surface processes in this region

snowball earth termination by destabilization of equatorial permafrost methane clathrate the recovery from the marinoan snowball ice age of about 635 million years ago is one of the most severe climate change events known to have occurred on earth hypotheses accounting for the abruptness of deglaciation include ice albedo feedback deep ocean out gassing during post glacial oceanic overturn or methane hydrate destabilization martin kennedy and colleagues now report the broadest range of oxygen isotope values yet measured in marine sediments in methane seeps in marinoan deglacial sediments underlying a thin interval of carbonate these deposits are thought to record widespread oceanic carbonate precipitation during postglacial sea level rise the range of values is likely the result of mixing between ice sheet derived meteoric waters and clathrate derived fluids during the flushing and destabilization of a clathrate field by glacial meltwater their findings suggest that methane released from low latitude permafrost clathrates acted as a trigger and or strong positive feedback for deglaciation and warming this paper reports the broadest range of oxygen isotope values yet measured in marine sediments in methane seeps in marinoan deglacial sediments underlying a thin interval of carbonate these deposits are thought to record widespread oceanic carbonate precipitation during postglacial sea level rise the range of values is likely the result of mixing between ice sheet derived meteoric waters and clathrate derived fluids during the flushing and destabilization of a clathrate field by glacial meltwater the start of the ediacaran period is defined by one of the most severe climate change events recorded in earth history the recovery from the marinoan snowball ice age 635 myr ago ref 1 marinoan glacial marine deposits occur at equatorial palaeolatitudes2 and are sharply overlain by a thin interval of carbonate that preserves marine carbon and sulphur isotopic excursions of about 5 and 15 parts per thousand respectively3 4 5 these deposits are thought to record widespread oceanic carbonate precipitation during postglacial sea level rise1 3 4 this abrupt transition records a climate system in profound disequilibrium3 6 and contrasts sharply with the cyclical stratigraphic signal imparted by the balanced feedbacks modulating phanerozoic deglaciation hypotheses accounting for the abruptness of deglaciation include ice albedo feedback3 deep ocean out gassing during post glacial oceanic overturn7 or methane hydrate destabilization8 9 10 here we report the broadest range of oxygen isotope values yet measured in marine sediments 25 to 12 in methane seeps in marinoan deglacial sediments underlying the cap carbonate this range of values is likely to be the result of mixing between ice sheet derived meteoric waters and clathrate derived fluids during the flushing and destabilization of a clathrate field by glacial meltwater the equatorial palaeolatitude implies a highly volatile shelf permafrost pool that is an order of magnitude larger than that of the present day a pool of this size could have provided a massive biogeochemical feedback capable of triggering deglaciation and accounting for the global postglacial marine carbon and sulphur isotopic excursions abrupt unidirectional warming cap carbonate deposition and a marine oxygen crisis our findings suggest that methane released from low latitude permafrost clathrates therefore acted as a trigger and or strong positive feedback for deglaciation and warming methane hydrate destabilization is increasingly suspected as an important positive feedback to climate change11 12 13 that coincides with critical boundaries in the geological record14 15 and may represent one particularly important mechanism active during conditions of strong climate forcing

panigarh cave stalagmite evidence of climate change in the indian central himalaya since ad 1256 monsoon breaks and winter southern jet depressions abstract variations in petrography stable isotopes reflectance and luminescence along the central growth axis of a 14 5 cm stalagmite from panigarh cave indicate cooler and slightly wetter conditions in the himalayan foothills of northern india during the little ice age lia which lasted from ad 1489 1889 based on deposition of calcite and ad 1450 1820 based on rapid changes in 18o values conditions were warmer and drier during the preceding medieval climate anomaly mca and also in the post lia periods as evidenced by deposition of aragonite a review of currently existing stalagmite and other proxy data from south and east asia reveals a broad spatial pattern in precipitation over south and east asia during the lia with northern areas showing generally increased precipitation and southern areas reduced precipitation during the mca and after the lia the records suggest this pattern was reversed weaker ism during the lia brought drought conditions to the core ism area but triggered more monsoon breaks that brought higher precipitation to the himalayas at the same time the weaker ism may also have pushed more depressions along the path of the southern winter jet which brought more winter precipitation to the himalayas and therefore a lia wetter in our study area

climatic fluctuations during the lia and post lia in the kumaun lesser himalaya india evidence from a 400 y old stalagmite record this paper presents the first stable isotope delta o 18 and delta c 13 data of a similar to 400 years 1590 2006 ad long annual to decadal resolution speleothem record collected from the indian lesser himalaya the data show a variation from 2 7 to 5 9 parts per thousand in delta o 18 and 5 3 to 8 8 parts per thousand in delta c 13 the isotopic analyses indicate that the climate during this period can be divided into two stages a wet phase during the little ice age lia 1590 1850 ad and comparatively dry phase during the post lia after 1850 ad however the record also documents the minor dry events during the lia and a wet episode after the lia within the age uncertainty the dry spells during the lia are linked with the historical drought events in the indian subcontinent and similar latitudes the isotopic record is consistent with a number of previous studies in the areas influenced by the westerlies but appears to be conflicting to the regions dominated by the indian summer monsoon ism this may be due to the possible changes in the strength of westerlies in the study area and added by negative anomaly of north atlantic oscillation nao during the lia c 2012 elsevier ltd and inqua all rights reserved

late holocene climate response and glacial fluctuations revealed by the sediment record of the monsoon dominated chorabari lake central himalaya we studied a periglacial lake situated in the monsoon dominated central himalaya where an interplay of monsoonal precipitation and glacial fluctuations during the late holocene is well preserved a

style and timing of glacial and paraglacial sedimentation in a monsoon influenced high himalayan environment the upper bhagirathi valley garhwal himalaya abstract the gangotri glacier at the source of the ganges river has fluctuated greatly throughout the late quaternary in response to climatic oscillations this has resulted in impressive moraines paraglacial debris flow fans and terraces along the upper stretches of the bhagirathi valley cosmogenic radionuclide crn dating of glacial and paraglacial landforms shows that fans terraces and associated moraines formed approximately synchronously as the landscape readjusted to changing environmental conditions this synchronicity suggests that fan and terrace formation is intimately related to glaciation and that fluctuations in glacial and associated environments during times of climatic instability cause rapid sediment transfer and resedimentation of glacial landforms the crn dates show that all existing glacial and paraglacial landforms in the upper bhagirathi valley formed during the late pleistocene and holocene this demonstrates that in this high mountain environment paraglacial and glacial landforms are eroded and resedimented within about 20 000 years furthermore this testifies to the dynamic nature of glacial environments in monsoon influenced high mountain regions

palaeoclimate marinoan meltdown the termination of the marinoan glaciation 635 million years ago is one of the most spectacular climate change events ever recorded methane release from equatorial permafrost might have triggered this global meltdown

sharp decrease in summer monsoon strength 4000 3500 cal yr b p in the central higher himalaya of india based on pollen evidence from alpine peat age constrained pollen data and magnetic susceptibility of an alpine peat profile from the garhwal higher himalaya display a continuous record of climate and monsoon trends for the past 7800 yr about 7800 cal yr b p dominance of evergreen oak quercus semecarpifolia alder alnus and grasses in the pollen record reflect a cold wet climate with moderate monsoon precipitation from 7800 to 5000 cal yr b p vegetation was progressively dominated by conifers indicating ameliorated climate with a stronger monsoon a warm humid climate with highest monsoon intensity from 6000 4500 cal yr b p represents the mid holocene climatic optimum between 4000 and 3500 cal yr b p the abundance of conifers sharply decreased with the greatest increase in evergreen oak this trend suggests progressive cooling with a decrease in the monsoon to its minimum about 3500 cal yr b p two relatively minor cold dry events at ca 3000 and 2000 cal yr b p marked step wise strengthening of the monsoon until ca 1000 cal yr b p after a cold dry episode that culminated ca 800 cal yr b p the monsoon again strengthened and continued until today a sharp decrease in temperature and rainfall at 4000 3500 cal yr b p represents the weakest monsoon event of the holocene record this cold dry event correlates with proxy data from other localities of the indian subcontinent arabian sea and western tibet

holocene late pleistocene climatic ice core records from qinghai tibetan plateau three ice cores to bedrock from the dunde ice cap on the north central qinghai tibetan plateau of china provide a detailed record of holocene and wisconsin wurm late glacial stage lgs climate changes in the subtropics the records reveal that lgs conditions were apparently colder wetter and dustier than holocene conditions the lgs part of the cores is characterized by more negative 18 o ratios increased dust content decreased soluble aerosol concentrations and reduced ice crystal sizes than the holocene part these changes occurred rapidly 10 000 years ago in addition the last 60 years were apparently one of the warmest periods in the entire record equalling levels of the holocene maximum between 6000 and 8000 years ago