holocene glacier activity at the southwestern part of hardangerjokulen central southern norway evidence from lacustrine sediments lacustrine sediments from lake isdalsvatn downstream from the southwestern margin of the plateau glacier hardangerjokulen central southern norway show that the lake received glacial meltwater until 7890 95 bp a thin bluish grey minerogenic silt layer probably reflects a short glacial re advance between 7005 90 and 6835 150bp after the latter date inflow of glacial meltwater ceased indicating that small or more probably no glaciers existed on the southwestern hard angerjokulen plateau a drop in organic content and a slight increase in detrital content inferred from magnetic susceptibility at 120cm depth in the core may indicate some glacier activity in the catchment from about 3400 bp textural changes at 50cm depth indicate increased neoglacial activity in the upper catchment area from 2265 80 bp differences in glacier chronologies between the southern and northern sectors of hardangerjokulen may be explained partly by different glacier responses to the precipitation and wind distribu

nonuniform response of the major surface currents in the nordic seas to insolation forcing implications for the holocene climate variability 1 high resolution sediment cores from the voring plateau the north iceland shelf and the east greenland shelf have been studied to investigate the stability of major surface currents in the nordic seas during the holocene results from diatom assemblages and reconstructed sea surface temperatures ssts indicate a division of the holocene into three periods the holocene climate optimum 9500 6500 calendar cal years bp the holocene transition period 6500 3000 cal years bp and the cool late holocene period 3000 0 cal years bp the overall climate development is in step with the decreasing insolation on the northern hemisphere but regional differences occur regarding both timing and magnitude of sst changes sites under the direct influence of the norwegian atlantic current and the irminger current indicate sst cooling of 4 5 c from early holocene to present compared to 2 c recorded under the east greenland current superimposed on the general holocene cooling trend there is a high frequency sst variability which is in the order of 1 1 5 c for the voring plateau and the east greenland shelf and 2 5 3 c on the north iceland shelf

late quaternary lithofacies provenance and depositional environments 12 30 cal ka north and south of the denmark strait this paper describes the lithofacies and chronology of cores from north and south of the denmark strait for a period when ice sheets flanked both sides of the strait a wide range of sediments have been recovered indicating a complex of depositional processes jm96 1229ggc1 1047 m water depth is from the base of the nw iceland slope at the southern edge of the blosseville basin whereas jm96 1226ggc4 retrieved sediments south of the sill in 1519 m of water additional information is based on jm96 1220ggc2 and 1221ggc2 which were recovered from the upper w iceland slope at 500 m water depth below the latra moraine of possible last glacial maximum age and upslope of jm96 1226 ams 14c dates indicate that jm96 1226 and 1229 span the last 10 to 27 32 ka bp whereas jm96 1220 and 1221 recovered sediments dated between ca 8 and 18 ka bp closely spaced radiocarbon dates on jm96 1229 indicate an erosional hiatus of 7 ky between 12 and 19 cal ka lithofacies descriptions are based on visual descriptions and x radiographs jm96 1229 consists of fine grained sediments sometimes graded with scattered ice rafted debris whereas jm96 1226 consists largely of beds of matrix supported diamicton provenance indicators mass magnetic susceptibility and geochemistry for jm96 1229 support the delivery of sediments from nw iceland but there is a substantial difference in these properties between sediments from the w iceland upper slope and the sediments in jm96 1226 south of the denmark strait this indicates that the diamictons on the floor of the strait did not derive entirely from the iceland ice sheet and adjacent upper slope the general absence of sediments 12 cal ka on the slopes and floor of the denmark strait indicates that denmark strait overflow waters inhibited sediment accumulation during the holocene between ca 12 and 30 cal ka however a combination of more proximal sediment sources ice sheets and reduced thermohaline activity resulted in the accumulation of sediments on the slopes and basin floors

briksdalsbreen western norway climatic effects on the terminal response of a temperate glacier between ad 1901 and 1994 annual measurements of the frontal variations of briksdalsbreen are compared with twentieth century records of summer temperature winter precipitation and mass budget to evaluate the effects of climatic change on the glacier fluctuations frontal variations are shown to be determined by both summer temperature and winter precipitation between ad 1901 and 1931 the glacier front was in a more or less stable position warm summers in the 1930s and 1940s caused a significant retreat of the glacier reaching a maximum rate of annual retreat of 84 m in 1948 cooler summers in the late 1940s led to a stabilization of the glacier front from 1952 between 1987 88 and 1993 94 the terminus advanced 231 m 155 m of which has occurred after 1992 the increased glacier net mass balance in western norway after the 1988 89 season resulted in the largest annual glacier advances measured this century at briksdalsbreen 75 and 80 m in 1992 93 and 1993 94 respectively present knowledge about glacier history in western n

multi proxy records showing significant holocene environmental variability the inner n iceland shelf hunafloi abstract over the last 50 yr the n iceland margin has seen dramatic changes in temperature and salinity associated with the relative dominance of warm atlantic water versus cold arctic or polar waters we report a study of holocene environmental changes to assess the sensitivity of this area on a longer timescale we present sedimentologic isotopic and biotic coccolith proxies from a 5 5 m piston core b997 330pc that was retrieved from a small basin on the inner n iceland shelf seven ams dates indicate a relatively constant rate of sediment accumulation which averaged 55 cm kyr sampling resolution of our proxies varied between 16 and 90 yr sample our data indicate substantial variability in environmental conditions over the last 10 000 cal yr total carbonate content and coccolith concentrations track each other and indicate that the early holocene was a time of low net carbonate accumulation net accumulation of carbonate reached maximum values in the mid to late holocene 4 2 cal ka but there has since been a substantial decrease with a minima during the little ice age north atlantic drift coccolith species show peaks in accumulation rates at 2 and 8 cal ka and low influx between 3 5 and 6 cal ka reworked neogene coccoliths occur also 8 ka and coincide with light 18 o values in the epifaunal foraminifera cibicides lobatulus principal component analysis indicates considerable covariance between biotic isotopic and sedimentological parameters three axes explain 84 of the variance in the data set and define three groups of interrelated variables a major change occurs ca 5 cal ka after which conditions become more variable with a 1 5 kyr cyclicity

scandinavian glacial and climatic fluctuations during the holocene abstract historical documents and lichenometric studies give a detailed picture of the little ice age in scandinavia there was a large advance in norway which has been dated at a few places to 1750 small readvances during the retreat occurred around a d 1780 1810 1840 1850 1850 1870 1890 1910 and 1930 in sweden most of these advances have been recognized and in addition extensive advances are dated by lichenometry to around a d 1600 1650 and 1700 1720 soils buried beneath moraines often yield radiocarbon dates that are much too old methods dependent on these must therefore be used with care evidence for pre little ice age advances are often considered equivocal the most reliable information is probably provided by studies of lacustrine sediments combining information from all sources the most significant pre little ice age glacier advances most likely occurred in 7 5 5 1 4 5 3 2 2 8 2 2 1 9 and 1 5 1 1 radiocarbon ka bp advances that were less extensive or for which there is less evidence occurred around 6300 5600 2500 940 600 560 and 380 bp

the sant agata feltria landslide marche region central italy a case of recurrent earthflow evolving from a deep seated gravitational slope deformation abstract this paper examines the evolution of a large scale earthflow located in the northern sector of the marche region central italy in this area mass movements of different typology are particularly frequent since geological and geomorphological conditions often favour slope instability among these many mass movements the one affecting the historical village of sant agata feltria has been chosen also because its evolution has been recorded in chronicles starting from ancient times in fact reactivations of the 5 4 km long earthflow crossing the village have been quoted at least 12 times starting from the 16th century even though more ancient activations have been inferred historic researches and geomorphologic analyses allowed the detailed reconstruction of the evolution and the mechanism of the phenomenon outlining its causes and delineating risk zonation in particular a deep seated gravitational movement lateral spreading marked by trenches and ponds has been recognised at the top of the landslide the earthflow has been interpreted as a more surficial side effect of the deep seated phenomenon which constitutes its source area it has also been highlighted that reactivations coincided with long lasting and intense rainfalls whilst no direct connection seems to exist with earthquakes even though the area is seismically rather active and seismic shocks could have been among the major triggering factors for the deep seated deformation the oldest and probably most catastrophic recorded event itself 1561 a d took place during the first stages of a period of severe climate that involved the whole of europe

superlakes megafloods and abrupt climate change about 8200 years ago the climate of much of the northern hemisphere cooled abruptly for a period of about 200 years in their perspective clarke et al examine the most likely culprit for this cooling an outburst of fresh water from a vast ice dammed glacial lake in north america the superlake had formed when the kilometers thick ice sheet covering much of north america disintegrated when the ice dam became unstable fresh water flooded from the lake into the north atlantic it remains unclear how this fresh water affected ocean circulation or whether the outburst occurred in more than one stage but the timing points strongly to the outburst flood as the trigger of the 8200 year climate event

lake sediment studies of holocene glacial activity in the karsa valley northern sweden contrasts in interpretation a multidisciplinary study of lake sediments deposited in lake basins in the karsa valley northern sweden suggests the complete disappearance of the karsa glacier during the early and mid holocene glacier reformation indicated by the deposition of sediment with a fine particle size distribution and low organic content in the three lakes took place at c 3000 14 c years bp this interpretation contrasts with a study based on the weight loss on ignition of the same sediments which suggests several glacier advances throughout the entire holocene the contrasting interpretation is due to different methodological approaches single core site studies should be avoided in the future and only features that are consistently reproducible and can be dated in spatially distributed cores should be interpreted in terms of variations in glacial activity environmental conditions and ultimately climate

a continuous marine record 8000 1600 cal yr bp from the malangenfjord north norway foraminiferal and isotopic evidence holocene oceanography and climate were studied in the continuous marine sediment sequence in a piston core from the high latitude malangenfjord north norway using benthic foraminifera and stable isotopes radiocarbon dates indicate that the investigated sequence covers the period from c 8000 to 1600 cal bp and has a sedimentation rate of 0 3 12 7 m 1000 years bottom water temperatures reconstructed from benthic foraminiferal stable isotopes in the malangenfjord show a cooling of c 3 c ranging from 10 c and reaching c 7 c at 1600 cal yr bp which is similar to present bottom water temperature at the core location a planktic foraminiferal 18o record was established from c 6400 to 1600 cal yr bp generally following the same pattem as the benthic record this long term cooling correlates to the decreasing insolation at 70 n following the orbital forcing the long term cooling also corresponds well with atmospheric proxy records implying a close ocean atmosphere coupling it is also indicated both b

holocene climatic instability a prominent widespread event 8200 yr ago the most prominent holocene climatic event in greenland ice core proxies with approximately half the amplitude of the younger dryas occurred 8000 to 8400 yr ago this holocene event affected regions well beyond the north atlantic basin as shown by synchronous increases in windblown chemical indicators together with a significant decrease in methane widespread proxy records from the tropics to the north polar regions show a short lived cool dry or windy event of similar age the spatial pattern of terrestrial and marine changes is similar to that of the younger dryas event suggesting a role for north atlantic thermohaline circulation possible forcings identified thus far for this holocene event are small consistent with recent model results indicating high sensitivity and strong linkages in the climatic system

direct dating of the oxygen isotope record of the last deglaciation by 14c accelerator mass spectrometry major trends of quaternary global climate are reflected in the continental ice volume changes which have been reconstructed by oxygen isotope analysis1 2 18o records from deep sea sediments show that the net glacial build up occurs relatively slowly3 but that the end of an ice age occurs quickly in less than 10 000 yr implying a nonlinear response4 5 to simple milankovitch theory6 the latter observation suggests that the cause of the most recent deglaciation was the maximum in summer calorific radiation at the upper latitudes of the northern hemisphere centred around 11 000 yr ago a view supported by early studies7 later work has produced conflicting dates the main source of confusion being problems with obtaining accurate and reliable dates here by using accelerator mass spectrometry we have measured 14c for various species of foraminifera to produce a reliable timescale for the oxygen isotope record our results show that at the end of the last ice age continental ice sheets began to melt more than 4 000 yr before the northern hemisphere maximum of summer calorific radiation

two terrestrial records of rapid climatic change during the glacial holocene transition 14 000 9 000 calendar years b p from europe two independent multidisciplinary studies of climatic change during the glacial holocene transition ca 14 000 9 000 calendar yr b p from norway and switzerland have assessed organism responses to the rapid climatic changes and made quantitative temperature reconstructions with modern calibration data sets transfer functions chronology at krakenes western norway was derived from calibration of a high resolution series of 14c dates chronologies at gerzensee and leysin switzerland were derived by comparison of 18o in lake carbonates with the 18o record from the greenland ice core project both studies demonstrate the sensitivity of terrestrial and aquatic organisms to rapid temperature changes and their value for quantitative reconstruction of the magnitudes and rates of the climatic changes the rates in these two terrestrial records are comparable to those in greenland ice cores but the actual temperatures inferred apply to the terrestrial environments of the two regions

oxygen isotope and palaeotemperature records from six greenland ice core stations camp century dye 3 grip gisp2 renland and northgrip oxygen isotope variations spanning the last glacial cycle and the holocene derived from ice core records for six sites in greenland camp century dye 3 grip gisp2 renland and northgrip show strong similarities this suggests that the dominant influence on oxygen isotope variations reflected in the ice sheet records was regional climatic change differences in detail between the records probably reflect the effects of basal deformation in the ice as well as geographical gradients in atmospheric isotope ratios palaeotemperature estimates have been obtained from the records using three approaches i inferences based on the measured relationship between mean annual 18o of snow and of mean annual surface temperature over greenland ii modelled inversion of the borehole temperature profile constrained either by the dated isotopic profile or iii by using monte carlo simulation techniques the third of these approaches was adopted to reconstruct holocene temperature variations for the dye 3 and grip temperature profiles which yields remarkably compatible results a new record of holocene isotope variations obtained from the northgrip ice core matches the grip short term isotope record and also shows similar long term trends to the dye 3 and grip inverted temperature data the northgrip isotope record reflects i a generally stronger isotopic signal than is found in the grip record ii several short lived temperature fluctuations during the first 1500 yr of the holocene iii a marked cold event at ca 8 2 ka the 8 2 ka event iv optimum temperatures for the holocene between ca 8 6 and 4 3 ka a signal that is 0 6 stronger than for the grip profile v a clear signal for the little ice age and vi a clear signal of climate warming during the last century these data suggest that the northgrip stable isotope record responded in a sensitive manner to temperature fluctuations during the holocene copyright 2001 john wiley sons ltd

the last 18 kyr fluctuations in norwegian sea surface conditions and implications for the magnitude of climatic change evidence from the north sea a combined record of three cores spanning the last 18 kyr from the northern north sea is investigated for content of benthic and planktonic foraminifera and stable oxygen isotopes the paleoenvironmental development through this time period shows an early deglaciation 18 14 4 ka and the younger dryas 12 7 11 5 ka characterized by arctic polar conditions and increased ice rafting in the norwegian channel during the bolling allerod period warm sea surface temperature 9 c conditions similar to present conditions are inferred while bottom waters stayed cold 0 1 c with normal salinity the bolling allerod period is interrupted twice at 13 9 13 6 ka older dryas and at 13 0 12 8 ka inter allerod cooling period by reductions in sea surface temperatures and increased sea ice cover the beginning of the holocene period is marked by increases in surface and bottom water temperature superimposed on the broad climatic changes through the holocene a series of short lived oscillations in the ocean circulation are recorded the amplitude of these holocene events appears larger in the early holocene prior to 8 ka than compared with the remaining part of the holocene this amplification can possibly be attributed to a general increased freshwater budget in the north atlantic at this time during the final stages of the deglaciation of the laurentide and scandinavian ice sheets

temporal changes in holocene δ18o records from the northwest and central north iceland shelf the region of north iceland is highly sensitive climatically owing to its location with respect to atmospheric and oceanographic fronts in this study we present total carbonate and 18o records of benthic and planktic foraminifera from nine sediment cores from the north iceland shelf the results of this work indicate that the deglaciation of the vestfirdir peninsula was completed by 10 200 cal yr bp the 8200 cal yr bp cold event is present only as a minor isotopic event and seems not to have had much of a cooling effect on the bottom waters of the northwest iceland shelf the holocene maximum warmth attributed to a stronger north icelandic irminger current occurred between ca 7800 and 6200 cal yr bp over the past 4500 cal yr bp a general cooling trend has occurred on the north iceland shelf and superimposed on this overall cooling trend are a number of oscillations between periods when relatively warmer and cooler waters occupied the shelf relatively cooler waters were present at 4200 4000 cal yr bp 3200 2900 cal yr bp 2500 2350 cal yr bp and 600 200 cal yr bp whereas relatively warmer waters were present on the shelf at 3750 3450 cal yr bp 2800 2600 cal yr bp and 1700 1000 cal yr bp copyright 2004 john wiley sons ltd

latest pleistocene and holocene alpine glacier fluctuations in scandinavia abstract during the early holocene abrupt decadal to centennial scale climate variations caused significant glacier variations in norway increased freshwater inflow to the north atlantic and arctic oceans has been suggested as one of the most likely mechanisms to explain the abrupt and significant lateglacial and early holocene climatic events in nw europe the largest early holocene glacier readvances occurred 11 200 10 500 10 100 9700 9200 and 8400 8000 cal yr bp the studied norwegian glaciers apparently melted away at least once during the early mid holocene the period with the most contracted glaciers in scandinavia was between 6600 and 6000 cal yr bp subsequent to 6000 cal yr bp the glaciers started to advance and the most extensive glaciers existed at about 5600 4400 3300 2300 1600 cal yr bp and during the little ice age times with overall less glacier activity were apparently around 5000 4000 3000 2000 and 1200 cal yr bp it has been proposed that several glacier advances occurred in scandinavia including northern sweden at 8500 7900 7400 7200 6300 6100 5900 5800 5600 5300 5100 4800 4600 4200 3400 3200 3000 2800 2700 2000 1900 1600 1200 1000 and 700 200 cal yr bp glaciers in northern sweden probably reached their greatest little ice age extent between the 17th and the beginning of the 18th centuries evidence for early holocene glacier advances in northern scandinavia however has been questioned by more recent multi disciplinary studies the early to mid holocene glacier episodes in northern sweden may therefore be questioned most norwegian glaciers attained their maximum little ice age extent during the mid 18th century cumulative glacier length variations in southern norway based on marginal moraines dated by lichenometry and historic evidence show an overall retreat from the mid 18th century until the 1930s 40s subsequently most norwegian glaciers retreated significantly maritime outlet glaciers with short frontal time lags 15 20 years continued their retreat to the 1970s and 1980s however maritime glaciers started to advance as a response to higher winter accumulation during the first part of the 1990s after 2000 several of the observed glaciers have retreated remarkably fast annual frontal retreat 100 m mainly due to high summer temperatures the general glacier retreat during the early holocene and the neoglacial advances after 6000 cal yr bp are in line with orbital forcing due to the decrease of northern hemisphere summer solar insolation and the increase in winter insolation in addition regional weather modes such as the north atlantic oscillation nao and the arctic oscillation ao play a significant role with respect to decadal and multi decadal climate variability

a new interpretation of the date of the little ice age glacier maximum at svartisen and okstindan northern norway new results concerning the dating of little ice age glacier variations at svartisen and okstindan northern norway are presented measurements of lichens of the rhizocarpon subgenus on gravestones are used to construct several local sets of lichenometric dating curves these are partly adjusted in relation to well established lichenometric dating curves from southern norway the little ice age maximum at svartisen and okstindan is thereby dated to the mid eighteenth century i e in agreement with southern norway pre viously suggested earlier little ice age advances are demonstrated to have resulted from an underestimation of the growth rates of the rhizocarpon subgenus synchroneity of little ice age maxima in southern norway and at svartisen and okstindan suggest that a north south migration of latitudinal depressional tracks can be excluded as the main forcing factor as an alternative an increased se nw trend of moist air ow in winter parallel to the coast of norway is suggested as the

cretaceous 100 ma high silica granites in the gajin area central tibet petrogenesis and implications for collision between the lhasa and qiangtang terranes abstract high silica granites that occur as isolated plutons are widely distributed in collisional orogenic belts and are considered a hallmark of continental collision processes the late mesozoic collision between the lhasa and qiangtang terranes along the bangong nujiang suture zone was key event in the evolution of the tibetan plateau however the timing of this collision remains debated here we report the ages and geochemical characteristics of granites from the gajin area in the north central lhasa terrane central tibet zircon u pb dating reveals that the gajin granites formed at 100 ma these granites exhibit uniformly high sio2 contents 74 9 78 4 wt are weakly peraluminous compositions and have high k2o moderate na2o and al2o3 and low fe2o3t mgo and cao contents they are characterized by enrichments in rb cs and u and by depletions in zr hf nb and ti these characteristics in combination with high rb sr ratios and pronounced negative eu anomalies indicate that the gajin granites are highly fractionated rocks the granites have enriched whole rock nd end t 4 3 to 2 9 and relatively depleted and slightly variable zircon hf ehf t 1 0 to 5 5 isotope compositions the gajin granites were probably generated by high degrees of crystal fractionations of magma produced by partial melting of mature crustal sources the cretaceous magmatic rocks in the north central lhasa terrane record a magmatic lull between 100 and 85 ma which corresponds to a transition in both geochemical composition e g hf nd isotopes and rock association at 100 ma combining the above characteristics with the development of a regional angular unconformity around the time of the formation of the granites we suggest that the initial continental collision between the lhasa and qiangtang terranes probably occurred between 110 and 90 ma therefore the 100 ma high silica granites in the gajin area were formed during the continuing continental convergence that followed the initial collision between the lhasa and qiangtang terranes the generation of discrete and monotonous high silica granites may constitute evidence for a significant tectonothermal transition in evolution of the continental crust

holocene periodicity in north atlantic climate and deep ocean flow south of iceland climate fluctuations during the past millennium are relatively well documented1 on a longer timescale there is growing evidence of millennial scale variability of holocene climate at periodicities of 2 500 and 950 years possibly caused by changes in solar flux 2 3 and 1 500 years maybe related to an internal oscillation of the climate system 4 5 6 but the involvement of deep water masses in these holocene climate changes has yet to be established here we use sediment grain size data from the iceland basin to reconstruct past changes in the speed of deep water flow the study site is under the influence of iceland scotland overflow water isow the flow of which is an important component of the thermohaline circulation that modulates european climate flow changes coincide with some known climate events the little ice age and the mediaeval warm period and extend over the entire holocene epoch with aquasi periodicity of 1 500 years the grain size data indicate afaster isow flow when the climate of northern europe is warmer however a second mode of operation is observed in the early holocene when warm climate intervals are associated with slower isow flow at that time the melting remnant of land based glacial age ice may have provided a sufficient source of fresh water to the ocean to reduce isow flow south of iceland

a new approach to calculating holocene winter precipitation by combining glacier equilibrium line altitudes and pine tree limits a case stud from hardangerjokulen central southern norway at hardangerjokulen central southern norway detailed knowledge of the number age and magnitude of holocene glacier fluctuations is used to reconstruct variations in equilibrium line altitude ela for the last 10 000 years present and past elas are based on an accumulation area ratio aar of 0 7 and are adjusted for land uplift a synchronous relationship between advanced glacier positions and the highest pine tree limits pinus sylvestris l is demonstrated for the early to mid holocene in southern scandinavia which indicates that warm summers were compensated for by high winter precipitation based on pine tree limit fluctuations as a measure of mean ablation season temperature holocene variations in winter precipitation at hardangerjokulen have been calculated by substitution in the close exponential relationship between mean ablation season temperature and winter precipitation at the ela of norwegian glaciers setting the winter precipitation during the period ad 1961 1990 at 100 mean values

irregular glacial interstadials recorded in a new greenland ice core the greenland ice sheet offers the most favourable conditions in the northern hemisphere for obtaining high resolution continuous time series of climate related parameters profiles of 18o 16o ratio along three previous deep greenland ice cores1 3 seemed to reveal irregular but well defined episodes of relatively mild climate conditions interstadials during the mid and late parts of the last glaciation but there has been some doubt as to whether the shifts in oxygen isotope ratio were genuine representations of changes in climate rather than artefacts due to disturbed stratification here we present results from a new deep ice core drilled at the summit of the greenland ice sheet where the depositional environ ment and the flow pattern of the ice are close to ideal for core recovery and analysis the results reproduce the previous findings to such a degree that the existence of the interstadial episodes can no longer be in doubt according to a preliminary timescale based on stratigraphic studies the interstadials lasted from 500 to 2 000 years and their irregular occurrence suggests complexity in the behaviour of the north atlantic ocean circulation

holocene climate variability and periodicities in south central sweden as interpreted from peat humification analysis analysis of the decomposition of peat has been used to identify climatic shifts over the last 10 000 years in two raised bogs stomyren and kortlandamossen south central sweden age depth curves have been constructed using radiocarbon dates and tephra layers peat humification data have been subjected to spectral analyses using the lomb scargle fourier method and reveal a periodicity of c 250 years in both records cycles of c 200 yr and c 400 yr were found at stomyren and at kortlandamossen respectively these periodicities could correspond to changes in solar activity levels a test estimating the possible level of noise has been applied to the spectral analyses the humification indices indicate prominent shifts to wetter conditions at c 7500 4300 4200 3700 3500 and 2800 2400 cal yr bp the most distinct drier phases start at c 4500 and 3250 cal yr bp

complexity of holocene climate as reconstructed from a greenland ice core glaciochemical time series developed from summit greenland indicate that the chemical composition of the atmosphere was dynamic during the holocene epoch concentrations of sea salt and terrestrial dusts increased in summit snow during the periods 0 to 600 2400 to 3100 5000 to 6100 7800 to 8800 and more than 11 300 years ago the most recent increase and also the most abrupt coincides with the little ice age these changes imply that either the north polar vortex expanded or the meridional air flow intensified during these periods and that temperatures in the mid to high northern latitudes were potentially the coldest since the younger dryas event

holocene glacier history of bjornbreen and climatic reconstruction in central jotunheimen norway based on proximal glaciofluvial stream bank mires abstract holocene variations of bjornbreen smorstabbtinden massif west central jotunheimen are reconstructed from the lithostratigraphy of two alpine stream bank mires flooded episodically by meltwater the approach uses multiple sedimentological indicators weight loss on ignition mean grain size grain size fractions bulk density moisture content and magnetic susceptibility an a priori model of overbank deposition of suspended glaciofluvial sediments a detailed chronology based on 56 radiocarbon dates and a little ice age sedimentological analogue rapid late preboreal deglaciation was indicated by immigration of betula pubescens by 9700 cal bp an interval of at least 3000 years in the early holocene when glaciers were absent was interrupted by two abrupt episodes of glacier expansion around the time of the finse event the first at ca 8270 7900 cal bp bjornbreen i event and the second at ca 7770 7540 cal bp bjornbreen ii event neoglaciation began shortly before ca 5730 cal bp with gradual build up to the maximum of the bjornbreen iii event at ca 4420 cal bp later maxima occurred at ca 2750 cal bp bjornbreen iv event and at 1300 1260 1060 and 790 cal bp all within the bjornbreen v event glaciers were smaller than today and possibly melted away on several occasions in the late holocene ca 3950 1410 and 750 cal bp minor maxima also occurred at ca 660 and 540 cal bp within the late mediaeval warm period and the early little ice age respectively the little ice age maximum was dated to 213 25 bp ca 205 cal bp the relative magnitudes of the main glacier maxima were determined erdalen event little ice age event bjornbreen vi bjornbreen i finse event bjornbreen ii bjornbreen v bjornbreen iv bjornbreen iii these episodic events of varying magnitude and abruptness were used in conjunction with an independent summer temperature proxy to reconstruct variations in equilibrium line altitude ela and a holocene record of winter precipitation since the preboreal ela varied within a range of about 390 m and winter precipitation ranged between 40 and 160 of modern values winter precipitation variations appear to have been the main cause of these century to millennial scale holocene glacier variations

sudden changes in north atlantic circulation during the last deglaciation sudden changes in the flow of warm atlantic surface waters into the norwegian sea occurred frequently during the last deglaciation typically involving shifts in sea surface temperature of 5 c in fewer than 40 years these led to equally large and rapid changes in atmospheric temperatures and to shifts in atlantic deep thermo haline circulation and ice sheet melting rates

north atlantic thermohaline circulation during the past 20 000 years linked to high latitude surface temperature during a surface cooling event 10 000 to 12 000 years ago higher cd ca and lower 13c 12c ratios are observed in benthic foraminifera shells from rapidly accumulating western north atlantic sediments data from sediment cores show that marked nutrient depletion of intermediate waters occurs in association with reduced glacial north atlantic deep water flux it is proposed that cold high latitude sea surface temperatures enhance intermediate water formation at the expense of deep water formation

holocene fluctuations of a polythermal glacier in high alpine eastern jotunheimen central southern norway abstract bukkehammarbreen is a polythermal cirque glacier lying in the permafrost zone of eastern jotunheimen central southern norway in the proglacial lake bukkehammartjorna sediment analyses of loss on ignition loi magnetic susceptibility and analyses of grain size distribution have been used to reconstruct holocene variations in glacier activity and other catchment processes the glacier has low sediment production hence a low signal to noise ratio of minerogenic sediment flux is found grain size analyses are used to enhance the glacigenic signal and to detect glacier variations and other changes in sediment input the sedimentological record from bukkehammartjorn is compared with three other lake records from the same region in order to separate the glacial signal from variations in organic production and episodes of enhanced non glacial minerogenic sedimentation subsequent to the deglaciation after the younger dryas a preboreal glacial advance culminated before 10 100 cal bp this was followed by a prolonged period with no glaciers in the catchment until 7500 cal bp after which there is evidence of limited glacier activity lasting until 6800 cal bp between 6700 and 6000 cal bp the catchment was deglaciated after 6000 cal bp bukkehammarbreen reformed increasing in size towards 3800 cal bp with evidence for reduced glacier activity around 5200 cal bp a glacier with approximately similar size as at present has existed after 3800 cal bp the investigation has demonstrated the usefulness of multi site and multi parameter lacustrine investigations in reconstructing glacier fluctuations and for testing and validating the results the investigations have shown that grain size variations in sediment cores located at increasing distance from the meltwater inlet of a lake may provide an indicator of paraglacial activity in the catchment during the holocene the results also suggest that the lower altitudinal limit of permafrost in eastern jotunheimen remained below about 1800 m during the holocene

holocene glacier variations in central jotunheimen southern norway based on distal glaciolacustrine sediment cores abstract sediment cores from two glacier fed lakes are used to reconstruct a continuous record of glacier variations since about 10 000 cal bp in the smorstabbtinden massif of central jotunheimen southern norway particular attention is paid to the century to millennial scale pre little ice age glacial signal based on an estimated temporal resolution of 55 and 25 yr cm 1 for bovertunsvatnet and dalsvatnet respectively visible lithostratigraphic variations organic content loss on ignition calcium carbonate content magnetic susceptibility and grain size fractions especially the fine silt are used as proxy indicators of glacier presence and extent in the lake catchments following deglaciation the early holocene was characterized by generally small glaciers until a major advance the finse event peaking at approximately 8200 cal bp from 7900 to at least 5300 cal bp glaciers appear to have been absent from central jotunheimen there is evidence of glacier expansion between about 2400 and 1600 cal bp the bovertun i event and between about 1400 and 800 cal bp the bovertun ii event before reduced glacier extent during the mediaeval warm period finally the most extensive neoglacial maximum occurred during the little ice age after 500 cal bp in addition to providing a record of the broad pattern of climatically forced holocene glacier variations periodicities at 110 140 200 285 and about 500 yr have been identified uncertainties remain concerning the precise timing of events glacierization and deglacierization detection thresholds a possible mid to late holocene 5300 2500 cal bp neoglacial build up of small glaciers and shorter term decadal to century scale variations in glacier size for which more proximal sites are required

a high resolution study of holocene paleoclimatic and paleoceanographic changes in the nordic seas 1 high resolution records from images core md95 2011 in the eastern norwegian sea provide evidence for relatively large and small scale high latitude climate variability throughout the holocene during the early and mid holocene a situation possibly driven by consistent stronger westerlies increased the eastward influence of arctic intermediate and near surface waters for the late holocene a relaxation of the atmospheric forcing resulted in increased influence of atlantic water the main changes in holocene climate show no obvious connection to changing solar irradiance and spectral analysis reveals no consistent signature for any periodic behavior of holocene climate at millennial or centennial timescales there are however indications of consistent multidecadal variability

sea surface temperatures and ice rafting in the holocene north atlantic climate influences on northern europe and greenland abstract the oceanographic conditions in the high latitude north atlantic ocean during the holocene were reconstructed through analyses of sea surface temperature sst alkenone unsaturation ratios and ice rafting mineralogy and grain size from two sediment sequences one recovered from the reykjanes ridge at 59 n and the other from the norwegian sea at 68 n comparison of our records to published ice core and terrestrial proxy climate data sets suggests that atmospheric temperature changes over northern europe and greenland were coupled to sst variability and ice rafting the records outline four major climatic phases i an early holocene thermal maximum that lasted until approximately 6 7 kyr bp ii a distinctly cooler phase associated with increased ice rafting between 6 5 and 3 7 kyr bp iii a transition to generally warmer but relatively unstable climate conditions between 3 7 and 2 kyr bp and iv a second distinct sst decline that took place between 2 and 0 5 kyr bp in contrast to the dominant control of northern hemisphere summer insolation on early holocene climate development via strong seasonality the trigger for the onset of relatively unstable climatic conditions in the north atlantic at 3 7 kyr bp is not straightforward however it is possible that this change was triggered by late holocene winter insolation increase at high northern latitude and or by inter hemispheric changes in orbital forcing the late holocene neoglaciation trend which is characteristic of numerous terrestrial archives in northern europe may not only be attributed to a gradual decrease in orbitally forced summer temperature but also to increase snow precipitation at high northern latitudes during generally milder winters

lateglacial and early holocene palaeoclimatic reconstruction based on glacier fluctuations and equilibrium line altitudes at northern folgefonna hardanger western norway northern folgefonna c 23 km 2 is a nearly circular maritime ice cap located on the folgefonna peninsula in hardanger western norway by combining the position of marginal mor aines with ams radiocarbon dated glacier meltwater induced sediments in proglacial lakes draining northern folgefonna a continuous high resolution record of variations in glacier size and equili brium line altitudes elas during the lateglacial and early holocene has been obtained after the termination of the younger dryas c 11 500 cal yr bp a short lived 100 150 years climatically induced glacier readvance termed the jondal event 1 occurred within the preboreal oscillation pbo c 11 100 cal yr bp bracketed to 10 550 10 450 cal yr bp a second glacier readvance is named the jondal event 2 a third readvance occurred about 10 000 cal yr bp and corresponds with the erdalen event 1 recorded at jostedalsbreen an exponential relationship between mean solid winter precipitation and ablation season temperature at the ela of norwegian glaciers is used to reconstruct former variations in winter precipitation based on the corresponding ela and an indepen dent proxy for summer temperature compared to the present the younger dryas was much colder and drier the jondal event 1 pbo was colder and somewhat drier and the jondal event 2 was much wetter the erdalen event 1 started as rather dry and terminated as somewhat wetter varia tions in glacier magnitude elas and corresponding palaeoclimatic reconstructions at northern folge fonna suggest that low altitude cirque glaciers lowest altitude of marginal moraines 290 m in the area existed for the last time during the younger dryas these low altitude cirque glaciers of sug gested younger dryas age do not fit into the previous reconstructions of the younger dryas ice sheet in hardanger copyright 2005 john wiley sons ltd

holocene sediment properties of the east greenland and iceland continental shelves bordering denmark strait 64 68 n north atlantic the oceanographic polar front separates the east greenland and iceland margins surface water temperatures across denmark strait vary by 8 12 c and represent one of the steepest oceanographic gradients on earth the eastgreenland margin is a polar environment with extensive sea ice cover and calving glacier margins in contrast the iceland shelf is much more temperate and freshwater run off is a key component in land ocean sediment transfers average sediment properties from these two contrasting climate and oceanographic continental shelf environments are compared in the spatial domain at 13 sites the data represent the last 10 000 radiocarbon years of normal marine sedimentation for the two regions the two regions have similar average rates of sediment accumulation around 43 5 cm kyr 1 so that this key variable is factored out in explaining any differences in sediment properties dry sediment density moisture content hygroscopic moisture total organic carbon and carbonate contents mass magnetic susceptibility and the percentages of sand and silt are compared focusing on 1 median values for sediment properties and 2 downcore variability measured by the coefficient of variation cv there are significant differences in all but one hygroscopic moisture of the sediment properties between iceland and east greenland in four cases the sense of the differences was not as predicted in terms of downcore variation cv no difference was found between the two regions nor between the 13 sites whereas there are some significant differences between the variables carbonate and mass magnetic susceptibility have the largest spreads and moisture content and dry sediment density are the least variable protocols are developed to identify the type core in a regional series of sites the results indicate a need to develop a regional perspective on sediment properties both as inputs to models of sedimentary processes in different polar arctic environments and as an indication of which sediment properties might be best suited for palaeoenvironmental downcore time series

glacier variations in breheimen southern norway dating little ice age moraine sequences at seven low altitude glaciers moraine sequences in front of seven relatively low altitude glaciers in the breheimen region of central southern norway are described and dated using a multi proxy approach to moraine stratigraphy lichenometric dating based on the rhizocarpon subgenus is used to construct a composite moraine chronology which indicates eight phases of synchronous moraine formation ad 1793 1799 1807 1813 1845 1852 1859 1862 1879 1885 1897 1898 1906 1908 and 1931 1933 although the existence of a few cases of older moraines possibly dating from earlier in the eighteenth or late in the seventeenth centuries cannot be ruled out by lichenometry schmidt hammer r values from boulders on outermost moraine ridges suggest an absence of holocene moraines older than the little ice age twenty three radiocarbon dates from buried soils and peat associated with outermost moraines at three glaciers tverreggibreen storegrovbreen and greinbreen also indicate that the little ice age glacier maximum was the neoglacial maximum at most if not all glaciers several maximum age estimates for the little ice age glacier maximum range between the fifteenth and seventeenth centuries with the youngest from a buried soil being ad 1693 a pre little ice age maximum cannot be ruled out at greinbreen however where the age of buried peat suggests the outermost moraine dates from ad 981 1399 at variance with the lichenometric evidence glaciofluvial stratigraphy at tverreggibreen provides evidence for minor glacier advances about ad 655 963 and ad 1277 1396 respectively copyright 2003 john wiley sons ltd