climate instability during the last interglacial period recorded in the grip ice core isotope and chemical analyses of the grip ice core from summit central greenland reveal that climate in greenland during the last interglacial period was characterized by a series of severe cold periods which began extremely rapidly and lasted from decades to centuries as the last interglacial seems to have been slightly warmer than the present one its unstable climate raises questions about the effects of future global warming

palaeo moisture evolution in monsoonal central asia during the last 50 000 years abstract the late quaternary climate history of monsoonal central asia was inferred from 75 palaeoclimatic records which provide information about moisture conditions in the last 50 ka or part of this period wet conditions occurred during middle and late marine isotope stage 3 while the last glacial maximum lgm was characterized by dry climate conditions in the region a stepwise climate amelioration is suggested by the climate records following the lgm several climate signals of this period which were reported from high latitude ice core records are preserved in archives from monsoonal central asia as well during the early holocene high effective moisture was inferred from most records from the area dominated by the indian monsoon e g the tibetan plateau suggesting that holocene optimal climate conditions occurred there during this period in contrast areas which are dominated by the south east asian monsoon se monsoon and the westerlies in north western and north central china mongolia do not uniformly show an early holocene climate optimum for this area optimal conditions prevailed during the mid holocene these apparent contradictions can possibly be explained by the regional uplift and descent of air masses in the holocene during the early holocene strengthened insolation possibly caused an enhanced low level convergence over the tibetan plateau which led to the intensification of the summer monsoon the strong air uplift caused intensified precipitation and air divergence in the upper troposphere over the tibetan plateau the areas adjacent to the north therefore experienced an intensified descent of air masses and consequently increased aridity the majority of the palaeoclimatic records suggest reduced effective moisture since the late holocene in the region

observed degree day factors and their spatial variation on glaciers in western china the degree day factor ddf is an important parameter for the degree day model which is a widely used method for ice and snowmelt computation spatial variations of the ddf greatly affect the accuracy of snow and ice melt modelling this study analyzes the spatial variability of ddfs obtained from observed glaciers in different regions of western china the results clearly show that the ddf for a single glacier is subject to significant small scale variations and the factor for maritime glaciers is higher than that for subcontinental and extremely continental glaciers in western china the factors increase gradually from northwest to southeast in general the regional patterns of ddfs are detectable on the glaciers due to the unique climatic environment and heat budget of the tibetan plateau and surrounding regions low ddfs can be expected for cold dry areas whereas high ddfs can be expected for warm wet areas in western china depending on spatial variation of the characteristics of ddfs and the meteorological data we can provide gridded degree day models for non monitored glaciers to reconstruct gridded historical glacier mass balance series in western china

high resolution records of climate change in arid eastern central asia during mis 3 51 600 25 300 cal a bp from wulungu lake north western china detailed records of climate change during the last glaciation in arid central asia are scarce here we present a sedimentological and geochemical record from wulungu lake in north western china providing the first high resolution continuous sedimentary records in this region covering marine isotope stage mis 3 51 600 25 300 cal a bp high lake power end member 2 values and bioproductivity concurrent with low terrigenous clastic input unanimously indicate high lake water levels during 46 180 39 770 31 680 30 080 and 27 780 26 540 cal a bp and moderately wet conditions during 51 600 46 180 and 39 770 31 680 cal a bp the lake attained its lowest water levels after 30 080 cal a bp few dry events characterized by high pool power end member 3 values and terrigenous input are documented for the studied interval and three of them are correlative with heinrich events 5 3 our study supports the hypothesis for a positive northern hemisphere july insolation anomaly which increased the temperature gradient between low and high latitudes increasing the strength of westerlies and increasing sea surface temperatures in the north atlantic resulting in more moisture transported to arid central asian by westerlies

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

growth of greenland ice sheet measurement measurements of ice sheet elevation change by satellite altimetry show that the greenland surface elevation south of 72 degrees north latitude is increasing the vertical velocity of the surface is 0 20 0 06 meters per year from measured changes in surface elevations at 5906 intersections between geosat paths in 1985 and seasat in 1978 and 0 28 0 02 meters per year from 256 694 intersections of geosat paths during a 548 day period of 1985 to 1986

application of a distributed degree day model of glaciers in the upper reaches of the beida river basin based on in situ data of qiyi glacier from 2010 to 2012 a daily distributed degree day model on a 90 90 m grid was developed to simulate the spatial and temporal variations of the glacier mass balance ela and meltwater run off depth in the beida river basin from 1957 to 2012 in the model different vertical lapse rates of temperature and precipitation gradients were used in different months and height belts and the influence of temperature jump was also considered the results indicated that the average annual mass balance and meltwater run off depth of the glaciers in the beida river basin were 93 3 mm w e and 443 mm respectively assuming a continuous linear trend the ela had risen by 505 m over 55 years the mass balance linearly increased with the altitude in the cold season oct apr and exponentially in the warm season may sep the most possible abrupt change points of the mass balance ela and meltwater run off depth time series were all in 1992 93 as determined through the m k test the mass balance turned increasingly negative since then but the ela and meltwater run off increased rapidly the climate sensitivity test showed that the air temperature was a dominant factor that affected the mass balance of the continental glaciers on the basin scale which was different from the response mechanism of maritime glaciers when the air temperature 1 c and precipitation 10 increased simultaneously the glacier mass loss and meltwater run off reached 1 66 108 m3 and 2 45 108 m3 respectively

atmospheric radiocarbon calibration to 45 000 yr b p late glacial fluctuations and cosmogenic isotope production more than 250 carbon 14 accelerator mass spectrometry dates of terrestrial macrofossils from annually laminated sediments from lake suigetsu japan provide a first atmospheric calibration for almost the total range of the radiocarbon method 45 000 years before the present the results confirm the recently revised floating german pine chronology and are consistent with data from european and marine varved sediments and combined uranium thorium and carbon 14 dating of corals up to the last glacial maximum the data during the glacial show large fluctuations in the atmospheric carbon 14 content related to changes in global environment and in cosmogenic isotope production

synchronism of holocene east asian monsoon variations and north atlantic drift ice tracers eighteen radiocarbon dated eolian and paleosol profiles within a 1500 km long belt along the arid to semi arid transition zone of north central china record variations in the extent and strength of the east asian summer monsoon during the holocene dated paleosols and peat layers represent intervals when the zone was dominated by a mild moist summer monsoon climate that favored pedogenesis and peat accumulation brief intervals of enhanced eolian activity that resulted in the deposition of loess and eolian sand were times when strengthened winter monsoon conditions produced a colder drier climate the monsoon variations correlate closely with variations in north atlantic drift ice tracers that represent episodic advection of drift ice and cold polar surface water southward and eastward into warmer subpolar water the correspondence of these records over the full span of holocene time implies a close relationship between north atlantic climate and the monsoon climate of central china

carbonate isotopes from high altitude tso moriri lake nw himalayas provide clues to late glacial and holocene moisture source and atmospheric circulation changes abstract high resolution isotopic 18 o and 13 c investigations on endogenic carbonates calcite aragonite from tso moriri lake nw himalaya show dramatic fluctuations during the late glacial and the early holocene and a persistent enrichment trend during the late holocene changes in this lake are largely governed by the input meltwater monsoon precipitation evaporation i e ratio also reflected in changes in the carbonate mineralogy with aragonite being formed during periods of lowest i e using new isotopic data on endogenic carbonates in combination with the available data on geochemistry mineralogy and reconstructed mean annual precipitation we demonstrate that the late glacial and early holocene carbonate 18 o variability resulted from fluctuating indian summer monsoon ism precipitation in nw himalaya this region experienced increasing ism precipitation between ca 13 1 and 11 7 cal ka and highest ism precipitation during the early holocene 11 2 8 5 cal ka however during the late holocene evaporation was the dominant control on the carbonate 18 o regional comparison of reconstructed hydrological changes from tso moriri lake with other archives from the asian summer monsoon and westerlies domain shows that the intensified westerly influence that resulted in higher lake levels after 8 cal ka in central asia was not strongly felt in nw himalaya

holocene environment changes around the sara us river northern china revealed by optical dating of lacustrine aeolian sediments abstract the sara us river is located along the boundary of the mu us desert and the chinese loess plateau in northern china the river has cut down through quaternary sediments creating 70 80 m deep valleys with thick lacustrine aeolian sequences exposed we applied optical stimulated luminescence on sediments from a holocene section of aeolian sand lacustrine deposits in the top of the river valley the dating results show that a humid period existed from 7 1 to 2 0 ka ago as evidenced by two layers of peat and lacustrine sediments however compared to other published holocene sections in the sara us river valleys close to the section under studying the local environment experienced very complicated changes during the holocene all of the sections recorded a period with drought and or cold before the holocene at around 13 ka and an episode of aridity after about 2 ka ago as evidenced by the layers of aeolian sand however the ages of the lacustrine and peat layers in these sections are substantially different geomorphological analysis by digital elevation models does not support the existence of a mega lake covering the study area at 2 ka the intricate environmental changes may have been caused by the meandering of the sara us river environmental changes also strongly affected human migration in this area which is documented by chinese historical records

positive degree day factors for ablation on the greenland ice sheet studied by energy balance modelling ice ablation is related to air temperature by the positive degree day factor variations of the positive degree day factor in west greenland are studied using an energy balance model to simulate ablation under different conditions degree day factors for simulated and measured ice ablation at nordbogletscher and qaman rssup sermia agree well with values around 8 mm d 1 c 1 degree day factors for snow are less than half those for ice energy balance modelling shows that degree day factors vary with summer mean temperature surface albedo and turbulence but there is only evidence of large positive degree day factors at lower temperatures and with low albedo 0 3 the greatest effect of albedo variations 0 3 0 7 is at lower temperatures while variations in turbulence have greater effect at higher temperatures current models may underestimate runoff from the greenland ice sheet by several tenths because they use a degree day factor for melting ice that is too small for the colder parts of the ice sheet i e the upper ablation area and the northerly margin

teleconnections between the subtropical monsoons and high latitude climates during the last deglaciation the major deglacial intensification of the southwest monsoon occurred at 11 450 150 calendar years before present synchronous with a major climate transition as recorded in greenland ice an earlier event of monsoon intensification at 16 000 150 calendar years before present occurred at the end of heinrich layer 1 in the atlantic and parallels the initial rise in global atmospheric methane concentrations and the first abrupt climate changes in the antarctic thus the evolution of the monsoonal and high latitude climates show teleconnections but hemispheric asymmetries superimposed on abrupt events the monsoonal climate shows high frequency variability of 1785 1450 and 1150 year oscillations and abrupt climate change seems to occur when at least two of these oscillations are in phase

changes in fire regimes on the chinese loess plateau since the last glacial maximum and implications for linkages to paleoclimate and past human activity abstract a high resolution black carbon bc record from 27 5 kyr bp to present was reconstructed using a chemical oxidation method on loess and paleosol samples from the lijiayuan section of the chinese loess plateau the black carbon mass sedimentation rates bcmsr and carbon isotopic record reveal a paleofire history and its relationship with climate and vegetation changes at the study site the bcmsr record was decomposed into two components background bcmsr and the bcmsr peaks the background bcmsr represents regional fires and shows high fire activities occurred contemporaneous with the younger dryas older dryas heinrich events and greenland stadials as registered in the loess grain size record this suggests a rapid response of regional fires on the loess plateau to abrupt climate changes spectral analysis of background bcmsr showed two meaningful periodicities of 1620 and 1040 years close to the cyclicity of the east asian monsoon as recorded in the stalagmite 18o record in central china this indicates a tight control of millennial scale wet dry changes in the monsoonal climate on regional fires on the loess plateau by contrast the bcmsr peaks are considered to reflect local fire episodes the occurrences of local fires were more frequent during the last glacial period with a maximum frequency of 6 episodes 1000 years during the last glacial maximum lgm 22 3 to 14 6 kyr bp when the climate was drier and more continuous grassy fuels existed on the landscape during the last glacial interglacial transition lgit period 14 6 to 11 0 kyr bp fire frequency was largely reduced due to an increase in precipitation and more woody vegetation if the lgit period is taken as an analog for the projected near future then future global warming alone may not produce large wildfires in northwestern china wildfires remained infrequent during the early to middle holocene biomass burning increased after 4 0 kyr bp when the climate became drier and land use was more intensive bc carbon isotope ratios may well reflect changes in the vegetation being burnt i e grasses versus trees yielding results consistent with the associated pollen data in the region

recent cooling in coastal southern greenland and relation with the north atlantic oscillation 1 analysis of new data for eight stations in coastal southern greenland 1958 2001 shows a significant cooling trend line change 1 29 c for the 44 years as do sea surface temperatures in the adjacent part of the labrador sea in contrast to global warming 0 53 c over the same period the land and sea temperature series follow similar patterns and are strongly correlated but with no obvious lead lag either way this cooling is significantly inversely correlated with an increased phase of the north atlantic oscillation nao over the past few decades r 0 76 and will probably have significantly affected the mass balance of the greenland ice sheet

centennial scale asian monsoon variability during the mid younger dryas from qingtian cave central china the regional climate correlation within the northern hemisphere in the cold dry mid younger dryas event yd remains elusive a key to unraveling this issue is sufficient knowledge of the detailed climate variability at the low latitudes here we present a high resolution 3 yr 18o record of an annually laminated stalagmite from central china that reveals a detailed asian monsoon am history from 13 36 to 10 99 ka the yd in this record is expressed as three phases characterized by gradual onsets but rapid ends during the mid yd the am variability exhibited an increasing trend superimposed by three centennial oscillations well correlated to changes in greenland temperatures these warming wetting fluctuations show a periodicity of 200 yr generally in agreement with centennial changes in cosmogenic nuclides indicated by the 10be flux from the greenland ice this relationship implies that centennial scale climate changes during the mid yd are probably caused by solar output and rapidly transported over broad regions through atmosphere reorganization

palynological evidence of climatic and oceanographic changes in the north sea during the last deglaciation abstract palynological analyses performed on cores from the norwegian channel troll 8903 led to reconstruction of the late glacial variations in sea surface conditions using dinoflagellate cyst data and permitted direct correlation with the vegetation history of northwestern europe derived from pollen assemblages by 15 000 yr b p ice rapidly receded from the norwegian shelf and relatively warm summer conditions prevailed in surface waters a first late glacial cooling marked by extensive seasonal sea ice cover is dated at ca 13 600 13 00014c yr b p which coincides with the oldest dryas interval during the bolling allerod interval a rise in sea surface temperature both in february up to 3 c and august up to 15 c led to the establishment of ice free conditions in the northern north sea while pollen data reveal a densification of the vegetation cover the beginning of the younger dryas interval is marked by an increase in nonarboreal pollen input indicative of the opening of the forest vegetation cover concomitant with a cooling of surface waters during winter and development of sea ice cover however sea surface conditions remained relatively warm in summer until about 10 300 yr b p when extremely cold conditions and extensive sea ice cover developed up to 7 months yr improving conditions are recorded in surface waters by 10 100 yr b p a few hundred years before the development of forest cover onshore as shown by the pollen record such a discrepancy between marine and terrestrial indicators at the end of younger dryas time suggests a delayed response of the vegetation to regional climate warming

calibration and evaluation of a high resolution surface mass balance model for paakitsoq west greenland modelling the hydrology of the greenland ice sheet including the filling and drainage of supraglacial lakes requires melt inputs generated at high spatial and temporal resolution here we apply a high spatial 100 m and temporal 1 hour mass balance model to a 450 km 2 subset of the paakitsoq region west greenland the model is calibrated by adjusting the values for parameters of fresh snow density threshold temperature for solid liquid precipitation and elevation dependent precipitation gradient to minimize the error between modelled output and surface height and albedo measurements from three greenland climate network stations for the mass balance years 2000 01 and 2004 05 best fit parameter values are consistent between the two years at 400 kg m 3 28c and 14 100 m 1 respectively model performance is evaluated first by comparing modelled snow and ice distribution with that derived from landsat 7 etm satellite imagery using normalized difference snow index classification and supervised image thresholding and second by comparing modelled albedo with that retrieved from the modis sensor mod10a1 product calculation of mass balance components indicates that 6 of surface meltwater and rainwater refreezes in the snowpack and does not become runoff such that refreezing accounts for 31 of the net accumulation

the flickering switch of late pleistocene climate change polar ice contains a unique record of past climate variations previous greenland ice cores have documented relatively warm interstadial periods during the last glaciation and short centuryscale returns to colder conditions during the glacial to interglacial warming see for example ref 1 these climate features have also been observed to varying degrees in ocean sediment cores2 4 and terrestrial pollen and insect records5 7 here we report electrical conductivity measurements from a new greenland ice core which confirm these previous observations and also reveal a hitherto unrecognized mode of rapid climate variation fluctuations in ice conductivity on the scales of 5 20 years reflect rapid oscillations in the dust content of the atmosphere this flickering between two preferred states would seem to require extremely rapid reorganizations in atmospheric circulation

greenland ice sheet surface temperature melt and mass loss 2000 06 author posting international glaciological society 2008 this article is posted here by permission of international glaciological society for personal use not for redistribution the definitive version was published in journal of glaciology 54 2008 81 93 doi 10 3189 002214308784409170

palaeoenvironmental implications of a holocene sequence of lacustrine peat sediments from the desert loess transitional zone in northern china abstract a high resolution lacustrine peat record from the desert loess transitional zone in northern china was obtained to reconstruct holocene environmental change in the region ams 14c dates are used to provide a chronology the results indicate that the site was a desert environment before 12 2 cal kyr bp and was then occupied by a paleolake which started to shrink with a wetland occurring from 6 2 to 3 0 cal kyr bp subsequently the site became a seasonally water filled depression based on the lithology and measurements of grain size and total organic carbon content the climate changed from arid to humid at 12 2 cal kyr bp and became more humid after 8 3 cal kyr bp from 6 2 to 3 0 cal kyr bp precipitation decreased but the climate remained at an optimum after 3 0 cal kyr bp the climate was dry overall but with several humid intervals a comparison of paleoclimatic records from lacustrine and aeolian deposits from the region reveals a discrepancy about the nature of the early holocene climate and we conclude that this is because lacustrine sediments responded more sensitively to precipitation than aeolian deposits when the temperature was low the environmental evolution of the region was synchronous with changes in the asian summer monsoon asm but temperature also played a key role in the early holocene

a δ 13 c record of late quaternary climate change from tropical peats in southern india stable isotope ratios of carbon in soils or lake sediments1 3 and of oxygen and hydrogen in peats4 5 have been found to reflect past moisture variations and hence to provide valuable palaeoclimate records previous applications of the technique to peat have been restricted to temperate regions largely because tropical climate variations are less pronounced making them harder to resolve here we present a 13c record spanning the past 20 kyr from peats in the nilgiri hills southern india because the site is at high altitude 2 000 m above sea level it is possible to resolve a clear climate signal we observe the key climate shifts that are already known to have occurred during the last glacial maximum 18 kyr ago and the subsequent deglaciation in addition we observe an arid phase from 6 to 3 5 kyr ago and a short wet phase about 600 years ago the latter appears to correspond to the mediaeval warm period which previously was believed to be confined to europe and north america6 7 our results therefore suggest that this event may have extended over the entire northern hemisphere

comparison of oxygen isotope records from the gisp2 and grip greenland ice cores recent results1 2 from the greenland ice core project grip summit ice core suggest that the climate in greenland has been remarkably stable during the holocene but was extremely unstable for the time period represented by the rest of the core spanning the last two glaciations and the intervening eemian inter glacial here we present the complete oxygen isotope record for the greenland ice sheet project 2 gisp2 core drilled 28 km west of the grip core we observe large rapid climate fluctuations throughout the last glacial period which closely match those reported for the grip core however in the bottom 10 of the cores spanning the eemian interglacial and the previous glacia tion there are significant differences between the two records it is possible that ice flow may have altered the chronological sequences of the stratigraphy for the bottom part of one or both of the cores considerable further work will be necessary to evaluate the likelihood of this and the extent to which it will still be possible to extract meaningful climate information from the lowest sections of the cores

a 20 000 year high resolution pollen record from huguangyan maar lake in tropical subtropical south china abstract a high resolution pollen record from huguangyan maar lake near the south china sea spanning the past 20 400 yr bp has been presented aimed to provide an improved understanding of the response of the regional vegetation in tropical subtropical south china to climatic variations since the late last glacial maximum the results reveal the strong control of the asian summer monsoon asm strength on vegetation via orbitally induced variations in northern hemisphere summer solar insolation the trend of climatic evolution of the region consists of change from a warm temperate northern subtropical climate 20 400 18 700 cal yr bp to a southern subtropical climate 16 500 11 500 cal yr bp during the last deglaciation followed by a stepwise environmental shift from a tropical climate 11 500 8200 cal yr bp to a southern subtropical climate 8200 6600 cal yr bp and finally to a middle northern subtropical climate the bolling allerod warming is characterized by the highest percentages of evergreen quercus but the lowest percentages of xerophytic gramineae throughout the record suggesting intensified warm wet conditions during 15 000 13 000 cal yr bp by contrast the younger dryas is characterized by a marked decrease in subtropical evergreen broad leaved plants but a significant increase in herbaceous taxa representing a brief cold reversal during 13 000 12 000 cal yr bp the occurrence of two major cooling events at 8 2 and 6 6 kyr bp both of which are characterized by dramatic decreases in tropical evergreen broad leaved plants is supposed to be linked to a distinct weakening of the asm and southward migration of the intertropical convergence zone associated with marked declines in atlantic meridional overturning circulation the subsequent brief intervals of high herbaceous pollen percentages but low percentages of tropical taxa correspond to high el nino southern oscillation enso activity supporting a link between the weakening of solar isolation driven asm strength and a gradual intensification of enso

environmental variability within the chinese desert loess transition zone over the last 20000 years the desert loess transition zone in northern china is sensitive to climate variability which is con trolled mainly by the relative strengths of the east asian summer and winter monsoons sandy loess layers found in the loess plateau and palaeosol sequences found in the sandy desert demonstrate latitudinal shifts of the southern desert margin over the last 20000 years stratigraphic investigations together with radiocarbon and some thermoluminescence dating show that during the last glacial maximum the desert margin was at its most southerly position 38 n during the early holocene it moved northward about three degrees in latitude 41 n at present the desert margin is again close to its most southerly position 38 219 n yet the northern boundary position of modern summer monsoon activity is placed at 41 459 n which is close to the estimated holocene optimum desert margin 41 n this situation cannot be explained from natural climate models hence an external driving mechanism needs to be considered and the most obvious one is that caused by human activity on the natural environment over the last 3000 years historical evidence tends to reinforce this consideration

a simple energy balance model to calculate ice ablation at the margin of the greenland ice sheet apres avoir etabli les relations donnees climatiques taux d enlevement de la glace dans 2 glaciers du groenland un modele simple de bilan energetique est effectue pour calculer le taux d enlevement de la glace aux bordures du glacier

classification of glacier zones in western greenland using albedo and surface roughness from the multi angle imaging spectroradiometer misr the greenland ice sheet has been the subject of mass balance and melt measurements over the past two decades and its margins have shown significant thinning in recent years surface characteristics of the ice sheet margins are strongly modified by the annual process of snow accumulation and melt in this work we explore spatial and temporal relationships between near infrared albedo and surface roughness from the multi angle imaging spectroradiometer misr aboard nasa s terra satellite our study area is a region in western greenland in the vicinity of jakobshavn glacier and its upland drainage basin we compute near infrared albedo from misr data using imagery over the april to september period for 2000 through 2005 near infrared albedo is inversely related to both snow age and melt intensity we map surface roughness using the normalized difference angular index ndai applied to misr atmospherically corrected surface hemispherical directional reflectance in previous work the ndai has been correlated with surface roughness on the scale of about 70 m we have further substantiated that relationship here the ndai and albedo images for each of the six years are used in an isodata unsupervised classification classification results for the individual years show year to year differences which appear to depend on the number and temporal distribution of images with minimal cloud cover as well as interannual differences in ice sheet surface properties the year 2003 which had the greatest number of images with minimal cloud cover shows good correspondence with previously mapped glacier zones however we do not have an isodata class that corresponds to the dry snow zone and we see greater differentiation between zones at lower elevations within each isodata class distinct relationships between near infrared albedo and surface roughness emerge and in all cases but one there is an inverse temporal relationship between albedo and roughness the one class that shows a direct relationship between albedo and surface roughness is hypothesized to be the superimposed ice zone while still somewhat preliminary these results suggest that concurrent measurements of near infrared albedo and surface roughness have significant potential for ice sheet surface characterization as well as for ongoing monitoring

response of the energy balance on the margin of the greenland ice sheet to temperature changes daily ice ablation on two outlet glaciers from the greenland ice sheet nordbogletscher 1979 83 and qaman rssup sermia 1980 86 is related to air temperature by a linear regression equation analysis of this ablation temperature equation with the help of a simple energy balance model shows that sensible heat flux has the greatest temperature response and accounts for about one half of the temperature response of ablation net radiation accounts for about one quarter of the temperature response of ablation and latent heat flux and errors account for the remainder the temperature response of sensible heat flux at qqaman rssup sermia is greater than at nordbogletscher mainly due to higher average wind speeds the association of high winds with high temperatures during fohn events further increases sensible heat flux the energy balance model shows that ablation from a snow surface is only about half that from an ice surface at the same air temperature

light stable isotope systematics of granitic pegmatites from north america and norway abstract oxygen hydrogen and carbon isotope analysis of minerals whole rocks and fluid inclusions were performed on pegmatites and associated wall rocks from ten pegmatite districts and individual occurrences of precambrian late cretaceous age the pegmatites and pegmatite districts include the evje iveland area norway harding pegmatite new mexico u s a tanco pegmatite manitoba canada kiawa pegmatite new mexico u s a and the crestmore pegmatite california u s a the results of more than 350 isotopic analyses indicate no principal isotopic differences among pegmatites of widely different age the 18 o of quartz for analyzed pegmatites varies from 18 o 8 6 to 11 8 the 18 o of quartz from a sanidine bearing pegmatite in a sub volcanic environment is 7 10 late stage lower temperature quartz is typically the heaviest in any pegmatite the whole rock isotopic compositions of the pegmatites analyzed appear to largely reflect composition of the melt although some isotopic exchange with the wall rocks may have occurred oxygen isotope fractionations can be used to indicate a magmatic temperature range for crystallization 540 750 c compatible with experimental data on li bearing and simple granitic bulk compositions lower solidus temperatures for the li bearing pegmatites are reflected by larger isotopic fractionations continued subsolidus crystallization and replacement of many pegmatite minerals is compatible with both isotopic mineralogie and textural evidence the hydrogen isotope composition of muscovite and biotite varies for most samples from 45 to 70 depending to a large degree on the temperature of crystallization d of water from primary fluid inclusions from the same samples are enriched in d relative to the hydrous minerals the hydrogen isotope fractionations between inclusion fluid and muscovite or biotite indicate in most cases a range in crystallization temperature compatible with that suggested on the basis of oxygen isotope fractionations and experimental data interaction with meteoric water is not typical of pegmatite emplacement and crystallization the carbon isotope composition of c0 2 in most fluid inclusions is typically 6 1 to 7 1 several 13 c values heavier than 6 1 to 2 2 may record either contamination or isotopic effects due to separation of c02 from the melt

episode of strengthened summer monsoon climate of younger dryas age on the loess plateau of central china abstract the baxie loess section just east of the tibetan plateau contains evidence showing that the asian monsoon climate experienced an abrupt reversal near the end of the last glacial age rapid deposition of dust under cool dry full glacial conditions gave way to an interval of soil development and reduced dust influx attributed to a strengthening of the warm moist summer monsoon a subsequent abrupt increase in dust deposition a response to a weakening of the summer monsoon was later followed by renewed soil formation as summer monsoon circulation again intensified during the early holocene by one interpretation the thin upper loess is a manifestation of the european younger dryas oscillation however in this case the available 14c ages require either that 1 onset of loess deposition lagged the beginning of the younger dryas event in europe by as much as 2000 calibrated 14c years or 2 all the 14c ages are too young possibly due to contamination alternatively the late glacial paleosol the top of which is synchronous with the abrupt end of the late glacial 18o anomaly in the dye 3 greenland ice core records the younger dryas event such an interpretation is consistent with general circulation model simulations of younger dryas climate that show strong seasonality and a strengthened summer monsoon and with marine cores from the western pacific ocean that contain evidence of pronounced cooling of surface waters during younger dryas time

variability of monsoon climate in east asia at the end of the last glaciation abstract high resolution paleomonsoon proxy records from peat and eolian sand paleosol sequences at the desert loess transition zone in china denote a rapid oscillation from cold dry conditions 11 200 10 60014c yr b p to cool humid conditions 10 600 10 20014c yr b p followed by a return to cold dry climate 10 200 10 00014c yr b p variations in precipitation proxies suggest that significant climatic variability occurred in monsoonal eastern asia during the younger dryas interval late glacial climate in the chinese desert loess belt that lies downwind from europe was strongly influenced by cold air from high latitudes and from the north atlantic via the westerlies the inferred precipitation variations were likely caused by variations in the strength of the siberian high which influenced the pressure gradient between land and ocean and therefore influenced the position of the east asian monsoon front

seasonally specific responses of the east asian monsoon to deglacial climate changes the deglacial meltwater pulse in the north atlantic that induced the younger dryas event also prompted climate cooling in east asian monsoon regions such as japan and coastal mid latitude china however very little is understood about the mechanism that can transmit changes in the north atlantic to the far east here we show that the shutdown of the north atlantic thermohaline circulation brought about significantly lower temperatures and higher precipitation in the japanese winter whereas the change in the japanese summer climate was considerably smaller the cooling of the siberian air mass seems to have caused an increased pressure gradient between siberia and the west pacific in winter intensifying the winter monsoon the mongolian high pressure system and the westerly jet stream played an important role in the teleconnection in contrast the warming at the onset of the late glacial interstadial gi 1 bolling allerod in the west pacific did not have season specific features implying that the principal driving mechanism of this warming event may lie in a pan hemispheric or global factor such as insolation changes

comparison of avhrr derived and in situ surface albedo over the greenland ice sheet abstract this paper discusses a methodology for computing the clear sky surface albedo over the greenland ice sheet by using advanced very high resolution radiometer avhrr global area coverage visible and near infrared reflectances this approach is then used to map the monthly changes in albedo over the entire greenland ice sheet during the spring and summer months the methodology includes corrections for the intervening atmosphere by using the 6s radiative transfer model additional corrections for the anisotropic nature o f snow reflectance and the conversion from a marrow into a broadband albedo are made based on in site measurements from the swiss federal institute of technology university of colorado camp at 69 34 n 49 18 w comparison with surface albedo field ineasureinents indicates that before the onset of snoic melt agreement is good between the satellite derived and measured surface albedo after melt begins it is difficult to compare the satellite values with the field data owing to melt water ponding on the ice sheet surface with appropriate modifications the 6s radiative transfer model is suitable for atmospherically correcting avhrr visible and near infrared radiances atmospherically polar regions

the dry holocene megathermal in inner mongolia the paleoclimate since 14 kyr bp 14c age was reconstructed based on a 16 22 m long sediment core collected from lake yanhaizi a saline lake located near the northern limit of the east asian summer monsoon in inner mongolia coarse sediments were deposited there during a shrinkage phase of the lake when sand dunes reactivated these sediments have low organic carbon contents but high maturity indices indicating that they were deposited in an arid environment by contrast based on high organic contents and low maturity indices fine sediments were deposited during periods of high lake stand in a humid environment it was in general dry between 8 0 and 4 3 kyr bp the above dry and wet phases are consistent with those recovered from the arid semiarid transition zone elsewhere but are unlike the widely perceived humid holocene megathermal reported in east china and the newly reconstructed record in the alpine retreat lake in taiwan the discrepancy may be due to a relative insensitivity to humidity changes in these two areas since they have both been under the total influence of the summer monsoon on the other hand much enhanced evaporation over higher monsoon precipitation at lake yanhaizi reduces the effective humidity in the warm climate near the northern boundary of the summer monsoon this also accounts for the fact the high temperature holocene megathermal as revealed in the okinawa trough and the northern south china sea is correlated to the dry phases at lake yanhaizi conversely the 4 2 kyr bp coldest period in the holocene corresponds to a wet phase at lake yanhaizi

degree day glacier mass balance modelling with applications to glaciers in iceland norway and greenland a degree day glacier mass balance model is applied to three glaciers in iceland norway and greenland for which detailed mass balance measurements are available over a period of several years model results are in good agreement with measured variations in the mass balance with elevation over the time periods considered for each glacier in addition the model explains 60 80 of the year to year variance in the elevation averaged summer season mass balance measurements on the glaciers using a single parameter set for each glacier the increase in ablation on the glaciers due to a warming of 2 c is predicted to range from about 1 m w e year 1 at the highest elevations to about 2 5 m w e year 1 at the lowest elevations predicted changes in the winter balance measured between fixed date are relatively small except at the lowest elevations on the icelandic and norwegian glaciers where the winter balance is significantly reduced equilibrium line altitudes are raised by 200 300 m on the icelandic and norwegian glaciers except at the highest elevations the winter balance of the icelandic and norwegian glaciers is predicted to decrease even if the warming is accompanied by a 10 increase in the precipitation no firm evidence of a climate related variation in the degree day factors or in the temperature lapse rate on the same glacier could be found the model furthermore reproduces large variations in the mass balance with elevation and from year to year on each glacier using the same parameter set we assume therefore that these parameters will not change significantly for the climate scenarios considered here

new evidence on deglacial climatic variability from an alpine lacustrine record in northwestern yunnan province southwestern china abstract new deglacial pollen and conifer stoma records from tiancai lake northwestern yunnan province southwestern china an alpine lake in the southwest monsoon region are presented in this study based on these records the lithology of core tcyl1 and pca analysis of pollen data between 21 and 11 5 ka bp calibrated 14 c years the deglacial vegetation and climate changes are discussed in detail the results show that tiancai lake was above the upper limit of picea abies forest a treeline in the study area between 21 and 11 5 ka bp and the climate was colder and drier than that of the holocene during this period eight significant vegetation changes are recorded that are considered to be responses to changing temperatures and variations in the southwest monsoon in southwestern china the heinrich event 1 h1 the bolling allerod warm period ba and the younger dryas cold event yd are all clearly detected in this record in addition this study finds that the initial late glacial warming in northwestern yunnan province was at 18 7 ka bp which is coincident with the climate records in monsoonal central asia the indian ocean the tropical and subtropical pacific ocean and antarctica and is a response to solar insolation changes a noted temperature increase between 15 8 and 14 4 ka bp occurred at the end of the h1 and before the ba which indicates a strong pre bolling warming based on the study we consider that the hypothesis about a slowdown of the ocean s thermohaline circulation is sufficient to explain these late glacial abrupt events

seasonal variation of ice ablation at the margin of the greenland ice sheet and its sensitivity to climate change qamanârssup sermia west greenland monthly ice ablation was measured at the margin of the greenland ice sheet for june july and august over 7 years 1980 86 the total winter ablation september may has also been measured and a simple ablation temperature model used to assign ablation values to individual months under the present climate the most ablation occurred in june august on average 81 of annual ablation moderate ablation took place in may and september 17 and very little ablation occurred in october april 2 the effect of climate change on ice ablation is simulated using the ablation model to recalculate ablation for higher temperatures summer ice ablation increases with temperature in the model but there is proportionally greater increase for may and september whereas the period from october to april is presently so cold that even a temperature rise of 5 c will hardly increase ablation the difference in annual ice ablation caused by future climate change will therefore depend upon the seasonal distribution of the temperature change changes in precipitation and accumulation will further modify the seasonal variation of ablation

holocene environmental and climatic changes inferred from wulungu lake in northern xinjiang china abstract sedimentological geochemical and palynological data from wulungu lake in northern xinjiang china are used to reconstruct environmental and climate changes since 9550 cal yr bp high abundance of sparganium and poaceae low md median diameter and 13 c organic values indicate aridity between 9550 and 6730 cal yr bp high md and 13 c organic values and the prevalence of desert steppe and steppe vegetation between 4200 and 560 cal yr bp indicate that effective moisture increased after 6730 cal yr bp peaking at 4200 and 560 cal yr bp low md values a negative excursion of 13 c org and the transition from steppe to desert vegetation since 560 cal yr bp reflect a decrease in effective moisture during the latest holocene late holocene human activities were indicated by sharp increase in the abundance of pediastrum then variations in carbonate contents indicate that temperature was generally high between 9550 and 7740 cal yr bp low between 7740 and 6730 cal yr bp intermediate between 6730 and 560 cal yr bp and low during the last 560 yr regional comparison indicates that the asian monsoon did not extend to wulungu lake and westerlies were the main factor in determining the moisture availability during the holocene

a high resolution record of vegetation and environmental variation through the last 25 000 years in the western part of the chinese loess plateau abstract we present a high resolution reconstruction of vegetation and environmental changes from a 40 m thick section in the western part of the chinese loess plateau in attempt to reveal the details of the mis 2 and mis 1 climate variations our data show that a desert steppe occupied the landscape between 24 500 and 13 600 14 c yr bp two episodes of further vegetation deteriorations occurred between 20 000 and 17 100 14 c yr bp and between 15 100 and 13 600 14 c yr bp corresponding to the heinrich events 2 and 1 the late glacial stage between 13 600 and 9880 14 c yr bp included four sub stages that correspond chronologically and climatologically to the european deglacial sub stages the first sub stage 13 600 to 12 400 14 c yr bp corresponds to the bolling warm period the second sub stage 12 400 to 11 500 14 c yr bp to the older dryas cold period the third sub stage 11 500 to 10 700 14 c yr bp to the allerod warm period and the fourth sub stage 10 700 to 9880 14 c yr bp to the younger dryas cold period the early mid holocene 9880 to 4370 14 c yr bp was a period when a forest steppe dominated the landscape under a warm and wet climate during this period eight cool and dry spells occurred at 9720 14 c yr bp e1 9380 14 c yr bp e2 8870 14 c yr bp e3 8660 14 c yr bp e4 8440 14 c yr bp e5 8240 to 8060 14 c yr bp e6 7120 to 6550 14 c yr bp e7 and 5640 to 5120 14 c yr bp e8 after a major deterioration in vegetation between 4370 to 3270 14 c yr bp the study area experienced improved moisture conditions between 3270 to 1450 14 c yr bp followed by a persistent deterioration of vegetation under a drying climate during the past 1500 years

teleconnection of climatic events between east asia and polar high latitude areas during the last deglaciation abstract from observations of continuous aeolian and swamp sediment sequences augmented by a detailed 14 c chronology 13 c and organic c analyses we can demonstrate century to millennium scale fluctuations in east asian monsoon palaeoclimatic events we also infer significant precipitation variability within the last deglaciation the major climatic zones that have been recognised in europe and find counterparts in east asia are the bolling allerod 14 750 12 800 cal yr b p and the younger dryas 12 800 11 600 cal yr b p the last deglaciation sediment sequences are characterised by frequent facies changes reflecting climate instability these frequent abrupt climatic events correlate well with fluctuations recorded in high latitude and polar areas as represented by the greenland ice core gisp 2 and a core from the north sea this indicates a palaeoclimate teleconnection between the high latitude and polar areas and the east asian monsoon areas through cold air mass activity and the related atmospheric pressure system

temperature gradients in northern europe during the last glacial holocene transition 14 914c kyr bp interpreted from coleopteran assemblages late glacial and early holocene climatic conditions have been reconstructed for northern europe using the mutual climatic range mcr palaeoclimate method based on fossil coleopteran assemblages altogether beetle faunas from 77 sites have been analysed ranging from ireland in the west to poland and finland in the east and mcr estimates calculated the results are plotted on 16 maps each representative of a selected time slice covering the period from 14 5 14c kyr bp to 9 0 14c kyr bp eight of the maps show the mcr estimates of tmax mean temperature of the warmest month derived from each site for which data are available while the remainder show estimated tmax isotherms interpolated from these values it can be demonstrated that at times the thermal climate was fairly uniform throughout the study area whereas at others temperature gradients were much steeper than they are in the region today there also appears to be a distinct contrast between cold periods when contours trended nw se and warmer periods when contours trend w e or even ne sw the pattern of climatic changes that emerges is shown to be very different from the traditional view that has been used up to now as a template for classifying late glacial climatic events on a wide even global scale the suddenness and intensity of changes in the thermal climate may have been partially responsible for an apparent lack of equilibrium between the flora and fauna of the time and the physical environment in which they lived 1998 john wiley sons ltd

increased ablation at the margin of the greenland ice sheet under a greenhouse effect climate increased ablation under a greenhouse effec t climate is calculated by an energy balance model for two sites at the margin of the greenland ice sheet nordbogletscher south greenland and qaman lrssop sermia west greenland the change in summer ablation is nearly linear with change in summer temperature with gradients of 0 43 and 0 57 m water a i deg i for nordbogletscher and qamanarssup sermia respectively however the increase in ablation rate must be less in the higher parts of the ice sheet a future climatic warming will therefore cause a rapid retreat of the ice sheet margin and a steeper ice sheet profile

climate changes in northern china since the late pleistocene and its response to global change abstract nine representative high resolution profiles with reliable 14c chronologies have been chosen from the monsoon sensitive areas in china winter monsoon from the north west and summer monsoon from the east to provide a comparative picture of climate change within these areas comprehensive analyses of stratigraphic sequences and climatic proxy data have been used to reconstruct a history of fluctuating dry and wet environmental conditions in these monsoon sensitive areas since the last deglaciation these records have also been compared with greenland ice core and guliya ice core data four major events representing these climate fluctuations e1 e4 are recognised among them e3 indicates an abrupt cooling event after the younger dryas interval this event has so far only been recognised in china and high latitude areas in the northern hemisphere it is proposed that century to millenial scale global temperature changes affect the intensity of monsoon circulation through ocean atmosphere interactions hence producing dry and wet climate fluctuations in monsoon sensitive areas in an era of global warming the overall picture presented by the sequences of wet dry periods recorded in chinese monsoon affected areas during the last deglaciation can be used as an historical analogue for future predictions of medium to long term climate change within these areas

east asian monsoon variation and climate changes in jeju island korea during the latest pleistocene to early holocene a 4 96 m long sediment core from the hanon paleo maar in jeju island korea was studied to investigate the paleoclimatic change and east asian monsoon variations during the latest pleistocene to early holocene 23 000 9000 cal yr bp high resolution toc content magnetic susceptibility and major element composition data indicate that jeju island experienced the coldest climate around 18 000 cal yr bp which corresponds to the last glacial maximum lgm further these multi proxy data show an abrupt shift in climatic regime from cold and arid to warm and humid conditions at around 14 000 cal yr bp which represents the commencement of the last major deglaciation after the last major deglaciation the toc content decreased from 13 300 to 12 000 cal yr bp and from 11 500 to 9800 cal yr bp thereby reflecting the weakening of the summer monsoon the lgm in jeju island occurred later in comparison with the chinese loess plateau such a disparity in climatic change events between central china and jeju island appears to be caused by the asynchrony between the coldest temperature event and the minimum precipitation event in central china and by the buffering effect of the pacific ocean

eolian environmental changes in the northern mongolian plateau during the past 35 000 yr abstract this study focuses on an eolian section shaamar section in the northern mongolian plateau and compares the eolian sequences in the northern mongolian plateau with those along the southern boundary of the gobi deserts to better understand the dynamics of the gobi deserts during the past 35 000 14c yr bp only a weak entisol like paleosol was formed around 29 000 14c yr bp in the exposed mis 3 portion at the shaamar section whereas an eolian colluvium paleosol sequence at nearby bureghkanga section exhibits three paleosols formed around 29 000 14c yr bp 31 000 14c yr bp 34 000 14c yr bp loess paleosol sequences in the western siberian lowland exhibit four paleosols formed from 40 000 to 25 000 14c yr bp i e mis 3 during mis 2 two mollisol like paleosols were formed from 25 000 to 21 000 14c yr bp and from 16 000 to 13 000 14c yr bp and one entisol like paleosol was formed around 9500 14c yr bp at the shaamar section the mis 2 was characterized primarily by silt deposition except for the interval between 21 000 and 16 000 14c yr bp that was dominated by sand deposition the holocene began with the mollisol like paleosol formation from 8600 to 7000 14c yr bp the mid holocene 7000 to 3000 14c yr bp was marked by a relatively poor vegetation cover and the late holocene since 3000 14c yr bp by the densest vegetation cover of the entire holocene in summary the maximal extent of hyperarid and arid areas gobi deserts and gobi like occurred twice 1 from 21 000 to 16 000 14c yr bp and from 13 000 to 8600 14c yr bp when the dominant eolian deposition conditions extended from 56 n to 33 n or even larger the extent of hyperarid and arid areas retreated to the area between 38 n and 48 n or even much smaller several times during mis 3 and during the early holocene considering the uncertainties of dates it seems that the holocene bioclimatic conditions might have changed more or less synchronously between the north and the south and that the bioclimatic conditions varied more frequently in the north than in the south during mis 3 two mollisol like paleosols iic 13 000 to 16 000 14c yr bp and iiia 21 000 to 25 000 14c yr bp were well developed during mis 2 in the north but no corresponding major paleosols were discovered in the south suggesting that the climate did not change synchronously during mis 2 the climates during the stadial interstadial mis 3 2 transition 25 000 to 21 000 14c yr bp and during the last glacial maximum deglacial transition 16 000 to 13 000 14c yr bp were much more humid in the north than in the south

responses of various sized alpine glaciers and runoff to climatic change this paper presents a glacier ice flow model that simulates changes to alpine glaciers of various sizes and their runoff response to climate change in the yili river basin in the tien shall mountains northwestern china it is suggested that the sensitivity of glaciers to climatic change is determined by glacier size the change in glacial runoff does not keep pace with climactic change as climate warms and glaciers retreat the glacier runoff tends to increase and then decrease the runoff peak and its timing depend not only on glacier size but also on the rate of air temperature rise

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

reconstructed late quaternary hydrological changes from lake tso moriri nw himalaya abstract we present the results of our investigations on the radiocarbon dated core sediments from the lake tso moriri nw himalaya aimed at reconstructing palaeohydrological changes in this climatically sensitive region based on the detailed geochemical mineralogical and sedimentological analysis we recognise several short term fluctuations superimposed upon seven major palaeohydrological stages identified in this lake since 26 cal ka stage i 20 2 cal ka shallow lake characterised by input of coarse grained detrital sediments stage ii 20 2 16 4 cal ka lake deepening and intensification of this trend ca 18 cal ka stage iii 16 4 11 2 cal ka rising lake levels with a short term wet phase 13 1 11 7 cal ka stage iv 11 2 8 5 cal ka early holocene hydrological maxima and highest lake levels inferred to have resulted from early holocene indian monsoon intensification as records from central asia indicate weaker westerlies during this interval stage v 8 5 5 5 cal ka mid holocene climate deterioration stage vi 5 5 2 7 cal ka progressive lowering of lake level stage vii 2 7 0 cal ka onset of modern conditions the reconstructed hydrological variability in lake tso moriri is governed by temperature changes meltwater inflow and monsoon precipitation increased runoff a regional comparison shows considerable differences with other palaeorecords from peninsular india during late holocene

the chronology of the last deglaciation implications to the cause of the younger dryas event it has long been recognized that the transition from the last glacial to the present interglacial was punctuated by a brief and intense return to cold conditions this extraordinary event referred to by european palynologists as the younger dryas was centered in the northern atlantic basin evidence is accumulating that it may have been initiated and terminated by changes in the mode of operation of the northern atlantic ocean further it appears that these mode changes may have been triggered by diversions of glacial meltwater between the mississippi river and the st lawrence river drainage systems we report here accelerator mass spectrometry ams radiocarbon results on two strategically located deep sea cores one provides a chronology for surface water temperatures in the northern atlantic and the other for the meltwater discharge from the mississippi river our objective in obtaining these results was to strengthen our ability to correlate the air temperature history for the northern atlantic basin with the meltwater history for the laurentian ice sheet

evaluation of the relative contribution of meteorological and oceanic forces to the drift of ice islands offshore newfoundland on 29 april 2015 four beacons were deployed onto an ice island in the strait of belle isle to record positional data the ice island later broke up into many fragments four of which were tracked by the beacons the relative influences of wind drag current drag coriolis force sea surface height gradient and sea ice force on the drift of the tracked ice island fragments were analyzed using atmospheric and oceanic model outputs the sea ice force was calculated as the residual of the fragments net forces and the sum of all other forces this was compared against the force obtained through ice concentration dependent relationships when sea ice was present the sea ice forces calculated from the residual approach and concentration dependent relationships were significant only when sea ice was present at medium high concentrations in the vicinity of the ice island fragments the forces from ocean currents and sea surface tilt contributed the most to the drift of the ice island fragments wind however played a minimal role in the total force governing the drift of the four ice island fragments and coriolis force was significant when the fragments were drifting at higher speeds

correlation between climate events in the north atlantic and china during the last glaciation episodes of massive iceberg release heinrich events 1 3 into the north atlantic ocean during the last glaciation were associated with recurring episodes of unusually cold north atlantic surface water bond cycles 4 and cold air temperatures over greenland dansgaard oeschger events 5 6 four of the youngest of these cold events have also been reported in climate records from sites outside the north atlantic region7 but until now the entire suite has been identified only in north atlantic marine sediments greenland ice core records and tentatively in french lake sediments8 here we examine grain size data from chinese loess and intercalated accretionary palaeosols of last glacial age for evidence of similar climate signals remote from the north atlantic region we see grain size maxima with ages that match those of the last six heinrich events which we interpret as an indication of the changing strength of the east asian winter monsoon which largely controls the transport and deposition of central asian aeolian dust thus it seems that these heinrich events have left their signature in the chinese loess record this is consistent with simulations of the glacial climate9 which imply that the climates of the north atlantic and china were linked by the effect of westerly winds