holocene climatic changes and vegetation development in the kuril islands abstract the response of kuril island vegetation to climatic changes during the holocene is reconstructed from data obtained from key sections that included various depositional environments these climatic fluctuations were not as marked in the kuril archipelago as they were in nearby continental margins and large islands during the early holocene dwarf stone pine coniferous and birch forest prevailed in the south kurils and tundra landscapes in the north kurils the greatest northward movement of kuril vegetation zones occurred during the holocene optimum 6600 5000 14c bp mean annual temperatures in the kuril islands were 2 3 c higher than modern shifts in the location of warm and cold marine currents which strengthened or dampened insolation driven climatic changes played an important role in vegetation development cool temperate broadleaf forests and mixed coniferous broadleaf forests were widespread on south kurils rising holocene sea levels flooded land bridge connections to hokkaido island and the mainland resulting in the formation of several small islands in the south kurils meadows and boggy landscapes prevailed this flooding had a great effect on repopulation of island biota as did the deep straits that separate southern islands from the central and north kurils all paleovegetation associations can be found on the current landscape although their geographic distribution has changed during the holocene no introduction of plants from adjacent land occurred in the holocene forb and graminoid meadows characterized the middle holocene vegetation of central kurils on north kurils forb meadows were widespread tundra area decreased climatic changes did not occur synchronously throughout the kurils at times not even on the closest islands local volcanism played a special role in kuril vegetation history the considerable microclimatic variability within the islands also has been important in determining the development and preservation of vegetation communities and their reaction to more regional climatic changes

aspects of climate variability in the north atlantic sector discussion and relation to the greenland ice sheet project 2 high resolution isotopic signal this paper reviews aspects of climate variability in the north atlantic sector that may influence the seasonal to decadal scale isotopic signal in the greenland ice sheet project 2 gisp2 ice core interpretation of the isotopic signal and its spatial applicability at the seasonal level requires investigation into synoptic scale climatology we discuss possible climatic influences of 1 likely source regions of precipitation reaching the gisp2 site 2 the characteristics of cyclone activity over the north atlantic sector and 3 changes in major atmospheric features such as the mean sea level icelandic low and azores high pressure systems the north atlantic oscillation and the baffin trough next we evaluate correlations between the gisp2 deuterium isotopic signal and coastal temperatures with atmospheric pressure patterns thereby deriving climatic interpretations of the high resolution isotopic record the gisp2 site is influenced by both the icelandic low to the southeast and davis strait baffin bay storms to the southwest and west the north atlantic oscillation influences the gisp2 isotopic signal through the seesaw in winter temperatures between west greenland and northern europe agreement in excursion directions of gisp2 isotopes and east greenland and iceland temperature records is associated with different positions of the baffin trough in winter and also with anomalous 500 mbar net geostrophic flow linkages between isotopic excursion direction and atmospheric variability need to be explored further by comparison with additional seasonal data sets from other greenland ice cores

the younger dryas termination and north atlantic deep water formation insights from climate model simulations and greenland ice cores results from the gisp2 and grip ice cores show that the termination of the younger dryas yd climate event in greenland was a large and extremely fast climate change a reinitiation of north atlantic deep water formation following a shutdown and its associated winter release of heat to the atmosphere has been suggested as the most likely cause of this climate transition to test this idea two general circulation model experiments using genesis have been completed for yd time 12 000 calendar years ago one with low heat flux in the nordic seas 10 w m deep water shutdown and one with high nordic sea heat flux 300 w m active deep water formation comparison of greenland climate differences between these experiments with the ice core records shows that when deep water is turned on much of the yd termination warming is achieved the increase in precipitation is underestimated because of a model tendency to overestimate summertime precipitation which obscures the dominantly wintertime response to the specified forcing the winter storm track shift toward greenland contributes much of the climate change at the yd termination

early holocene climate oscillations recorded in three greenland ice cores a new ice core chronology for the greenland dye 3 grip and ngrip ice cores has been constructed making it possible to compare the 18 o and accumulation signals recorded in the three cores on an almost annual scale throughout the holocene we here introduce the new time scale and investigate 18 o and accumulation anoma lies that are common to the three cores in the early holocene 7 9 11 7 ka before present three time periods with significant and synchronous anomalies in the 18 o and accumulation signals stand out the well known 8 2 ka event an event of shorter duration but of almost similar amplitude around 9 3 ka before present and the preboreal oscillation during the first centuries of the holocene for each of these sections we present a 18 o anomaly curve and a common accumulation signal that represents regional changes in the accumulation rate over the greenland ice cap

variations in melt layer frequency in the gisp2 ice core implications for holocene summer temperatures in central greenland the rare melt features in the gisp2 central greenland deep ice core have decreased in frequency over the most recent 7000 years calibration of this change in melt frequency against modern spatial variation of melt frequency and temperature in central greenland and against modern temporal variability of temperatures in central greenland indicates that mean mid summer temperatures have cooled over the most recent 7000 years probably by slightly more than l c if variability of summer temperatures has not changed comparison to grip isotopic records from central greenland and to the melt record from the agassiz ice cap arctic canada suggests some seasonal and regional coherence for this cooling signal as well as for a cold event about 8000 8500 bp

synchronizing ice cores from the renland and agassiz ice caps to the greenland ice core chronology 1 four ice cores from the agassiz ice cap in the canadian high arctic and one ice core from the renland ice cap in eastern greenland have been synchronized to the greenland ice core chronology 2005 gicc05 which is based on annual layer counts in the dye 3 grip and ngrip ice cores volcanic reference horizons seen in electrical conductivity measurements ecm have been used to carry out the synchronization throughout the holocene the agassiz ice cores have been matched to the ngrip ice core ecm signal while the renland core has been matched to the grip ice core ecm signal thus tying the cores to gicc05 furthermore it has been possible to synchronize the renland ice core to ngrip gicc05 in the glacial period back to 60 000 years b2k years before a d 2000 on the basis of a matching of transitions between stadials and interstadials this work brings the total number of ice core records that have been rigorously tied to the gicc05 timescale up to nine renland annual layer thicknesses are increasing with depth during the period from 7 to 8 5 ka b2k a highly unusual observation only matched by a similar thickness increase in the glacial section of the renland core some 60 ka ago annual layer thicknesses in the agassiz ice cores point to a well developed raymond bump in the agassiz ice cap

the north atlantic oscillation signature in deuterium and deuterium excess signals in the greenland ice sheet project 2 ice core 1840 1970 the greenland ice sheet project 2 gisp2 core can enhance our understanding of the relationship between parameters measured in the ice in central greenland and variability in the ocean atmosphere and cryosphere of the north atlantic ocean and adjacent land masses seasonal summer winter to annual responses of d and deuterium excess isotopic signals in the gisp2 core to the seesaw in winter temperatures between west greenland and northern europe from a d 1840 to 1970 are investigated this seesaw represents extreme modes of the north atlantic oscillation which also influences sea surface temperatures ssts atmospheric pressures geostrophic wind strength and sea ice extents beyond the winter season temperature excursions inferred from the d record during seesaw extreme nao mode years move in the same direction as the west greenland side of the seesaw symmetry with the west greenland side of the seesaw suggests a possible mechanism for damping in the ice core record of the lowest decadal temperatures experienced in europe from a d 1500 to 1700 seasonal and annual deuterium excess excursions during seesaw years show negative correlation with d this suggests an isotopic response to a sst land temperature seesaw the isotopic record from gisp2 may therefore give information on both ice sheet and sea surface temperature variability cross plots of d and d show a tendency for data to be grouped according to the prevailing mode of the seesaw but do not provide unambiguous identification of individual seesaw years a combination of ice core and tree ring data sets may allow more confident identification of ga and gb extreme nao mode years prior to 1840

climatic signals in multiple highly resolved stable isotope records from greenland abstract twenty ice cores drilled in medium to high accumulation areas of the greenland ice sheet have been used to extract seasonally resolved stable isotope records relationships between the seasonal stable isotope data and greenland and icelandic temperatures as well as atmospheric flow are investigated for the past 150 200 years the winter season stable isotope data are found to be influenced by the north atlantic oscillation nao and very closely related to sw greenland temperatures the linear correlation between the first principal component of the winter season stable isotope data and greenland winter temperatures is 0 71 for seasonally resolved data and 0 83 for decadally filtered data the summer season stable isotope data display higher correlations with stykkisholmur summer temperatures and north atlantic sst conditions than with sw greenland temperatures the linear correlation between stykkisholmur summer temperatures and the first principal component of the summer season stable isotope data is 0 56 increasing to 0 66 for decadally filtered data winter season stable isotope data from ice core records that reach more than 1400 years back in time suggest that the warm period that began in the 1920s raised southern greenland temperatures to the same level as those that prevailed during the warmest intervals of the medieval warm period some 900 1300 years ago this observation is supported by a southern greenland ice core borehole temperature inversion as greenland borehole temperature inversions are found to correspond better with winter stable isotope data than with summer or annual average stable isotope data it is suggested that a strong local greenland temperature signal can be extracted from the winter stable isotope data even on centennial to millennial time scales

late holocene history of tokotan lake kuril archipelago russian far east the use of lacustrine records for paleoclimatic reconstructions from geologically dynamic settings abstract a high resolution multiproxy analysis of a core from tokotan lake urup island illustrates the complex paleoenvironmental signals that can be preserved in sedimentary deposits from geologically active areas such as the kuril archipelago diatom and geochemical analyses of the tokotan core suggest a shallowing and lessening of the lake area over the last 3450 cal bp without other proxies the record could be interpreted as showing a general decrease in precipitation over the late holocene however palynological data indicate no change in vegetation thereby implying no significant climatic variation neither of these paleoclimatic interpretations agrees with late holocene reconstructions from the kuril archipelago or the russian mainland paleomagnetic data imply variable sediment sources during the lake s history indicating alterations within the tokotan catchment e g shifts in gradients or sediment loads in the inflowing streams such changes would be particularly important in the shabalina river which today has formed a partial dam across the lake s outlet the results of the tokotan study indicate that other factors e g volcanism seismic activity sea level changes rather than climate were more probable determinants of the late holocene lake record given the geologic dynamism of the region it is perhaps not surprising that paleo records from the kuril islands display an inconsistency in the numbers and or duration of proposed holocene climatic oscillations underscoring the importance of multiproxy investigations in areas that are or have been geologically dynamic

holocene environments of central iturup island southern kuril archipelago russian far east two lake records document holocene changes in sea level vegetation and climate on the okhotsk and pacific sides of central iturup island southern kuril islands the sediment cores originated within tidal flats that subsequently developed into a marine strait which crosscut the island as sea levels rose during the early holocene brackish lagoons and eventually freshwater lakes formed by 7100 cal yr bp associated with warmer than present conditions past vegetation changes indicate a clear holocene thermal maximum recorded on the pacific coast but a less distinct optimum on the western shores 7200 6100 cal yr bp a gradual cooling toward modern levels occurred 6100 3500 cal yr bp four prominent layers of coarse sediment found in mid to late holocene lake deposits may correspond to intervals of climate cooling dune formation previously documented in coastal sections although chronological limitations question the synchronicity of these events across the south russian far east it seems probable that they have a regional signature however the mechanisms responsible for holocene climatic changes are likely the result of complex interactions of hemispheric scale atmospheric patterns marine characteristics and regional feedbacks rather than simply fluctuations in sea levels as suggested in the current interpretative model

nao signal recorded in the stable isotopes of greenland ice cores 1 the winter 18o signal is extracted from 7 greenland ice cores covering the past 700 years to filter out noise and local variations in the 7 isotope records a principal component analysis is carried out on the ice core data a comparison between the time series of the first principal component pc1 with 67 years of winter december to march temperature measurements from 3 southern greenland synoptic stations shows highly significant correlations southern greenland winter temperatures are known to be greatly influenced by the north atlantic oscillation nao a good proxy for southern greenland temperatures is therefore expected to reveal at least parts of the nao signal it is shown that the pc1 time series indeed is significantly correlated to the nao during the winter months the inclusion of ice core winter season 18o time series in future multiproxy nao reconstructions is therefore recommended

boundary layer growth over snow and soil patches field observations much of the snowmelt season is characterized by a patchy surface differential heating of the snow and snow free surfaces results in a significant horizontal transport of energy that affects and contributes to the snowmelt the calculation of the rate of energy advection requires some knowledge of the behaviour of the thermal boundary layer over the patches of snow and snow free surfaces we present the results from a series of field observations of the rate of growth of the thermal boundary layer over snow and snow free patches the results confirm that the boundary layer growth can be described by a power function of the distance from the leading edge of the patch for the case of the thermal boundary layer over a snow patch within a bare field the boundary layer growth is affected by the upwind surface roughness the thermal boundary layer over a snow patch within a rough field grows much more quickly than that in a smooth field relationships are derived and presented for the parameterization of the boundary layer growth as a function of distance and upwind surface roughness copyright 2006 crown in the right of canada published by john wiley sons ltd

abrupt increase in greenland snow accumulation at the end of the younger dryas event the warming at the end of the last glaciation was characterized by a series of abrupt returns to glacial climate the best known of which is the younger dryas event1 despite much study of the causes of this event and the mechanisms by which it ended many questions remain unresolved1 oxygen isotope data from greenland ice cores2 4 suggest that the younger dryas ended abruptly over a period of about 50 years dust concentrations2 4 in these cores show an even more rapid transition 20 years this extremely short timescale places severe constraints on the mechanisms underlying the transition but dust concentrations can reflect subtle changes in atmospheric circulation which need not be associated with a large change in climate here we present results from a new greenland ice core gisp2 showing that snow accumulation doubled rapidly from the younger dryas event to the subsequent preboreal interval possibly in one to three years we also find that the accumulation rate change from the oldest dryas to the bo11ing allerod warm period was large and abrupt the extreme rapidity of these changes in a variable that directly represents regional climate implies that the events at the end of the last glaciation may have been responses to some kind of threshold or trigger in the north atlantic climate system

classification seasonality and persistence of low frequency atmospheric circulation patterns abstract orthogonally rotated principle component analysis rpca of northern hemisphere 1 month mean 700 mb heights is used to identify and describe the seasonality and persistence of the major modes of interannual variability the analysis is detailed and comprehensive in that 1 a high resolution approximately equal area 358 point grid is used for the virtually maximum possible 35 year period of record 2 a positive bias in the nmc data base in the early 1950s in the subtropics is largely eliminated for the first time and 3 homogeneous separate analyses of each month of the year are carried out detailing the mouth to month changes in the dominant circulation patterns winter results are similar to those of other recent rpca and teleconnection studies except that some less obvious patterns are identified and further detail of the better known patterns is provided two north south dipole patterns are found over the pacific ocean west pacific oscillation and east pacific pattern and over the atla

precipitation over greenland retrieved by a dynamic method and its relation to cyclonic activity abstract in order to calculate the vertical motion over some high mountain regions such as greenland an equation without the quasigeostrophic approximation in coordinates has been developed a dynamic method for retrieving precipitation over greenland is based on this equation the retrieved annual mean precipitation distribution for 1987 and 1988 is in very good agreement with the observed annual accumulation pattern over the greenland ice sheet the major weather system producing precipitation over greenland is the frontal cyclone based on the precipitation characteristics greenland can be divided into five subregions precipitation over the north coastal and central interior regions primarily occurs in summer for the three other subregions if the composite monthly mean sea level pressure charts for high and low monthly precipitation amounts are constructed a clear relationship between precipitation and cyclonic activity emerges if a mean cyclone exists in the labrador sea heavy precipita

middle and late holocene environments and vegetation history of kunashir island kurile islands northwestern pacific natural middle and late holocene environmental development of kunashiri island reflects global climatic changes and the migration of warm and cold currents dry and cool climate changed to warm and moist about 7000 6500 bp later than on hokkaido island at this time kuroshio current system became more active on kunashir island birch assemblages were replaced by cool temperate broadleaf forests in the south and mixed coniferous broadleaf forests in the north the highest sea level position reached 2 5 3 m above psl about 6500 6300 bp cooling about 4700 4500 bp island vegetation weakly changed that connected with warm current influence major regression at this period led to formation of extensive coastal dunefields the warming at the beginning of the late holocene was almost similar to the holocene optimum two minor transgressions are recorded about 4010 3400 and 2950 2620 bp active entrance of detrital material to the coastal zone resulted in growth of accumulative landforms vegetation changes and

fine aeolian quartz records in cheju island korea during the last 6500 years and pathway change of the westerlies over east asia 1 we investigated the fine component of aeolian dust deposited on a maar of cheju island korea during the last 6500 years to specify the variability of fine aeolian dust transported by the westerlies and its main controlling factor from the viewpoint of global atmospheric circulation as a proxy for the fine aeolian dust we used the fine component of chemically isolated aeolian quartz from bulk sediments the fine quartz flux fqf varies from 0 1 to 1 4 mg cm2 a with periodicities of 1620 810 400 325 and 210 years mainly providing information on the aridity change in the dust source region the taklimakan desert the median grain size of the fine quartz mfq representing the pathway of the dust transporting westerlies fluctuates between 2 and 6 m with significant cycles of 1030 390 280 220 and 195 years and shows similar variation pattern to the fqf on the basis of visual and spectral analyses the high low fqf and the large small mfq correspond to the warm cold atmospheric temperature record from greenland ice cores with significant coherent cycles indicating that the aridity in the dust source areas and the pathway of the westerlies in east asia were linked to climatic and atmospheric conditions in greenland through the pathway change of the westerlies during the middle to late holocene the pathway change of the westerlies mainly responsible for the variability of the fine aeolian dust in east asia was probably controlled by a climatic response to initial solar activity and resulting atmospheric reorganization in polar and high latitude regions

modelling snow melt and snowcover depletion in a small alpine cirque canadian rocky mountains spatial and temporal patterns of areal snowcover depletion scd were studied over a small 0 6 km 2 alpine cirque within the canadian rocky mountains using a combined approach of daily acquisition of remotely sensed imagery together with meteorological observations and snowmelt modelling digital terrestrial photographs were georeferenced using a novel software tool together with a high resolution digital elevation model and used to derive measurements of fractional snowcovered area sca over the cirque manual snow surveys carried out in the pre melt period were used to describe the initial frequency distribution of snow water equivalent swe values over the cirque and indicated a lognormal distribution of swe when surveys were stratified by terrain features rates of snowmelt were simulated using a physically based snowmelt energy balance model snobal driven by observed meteorological conditions at a nearby station which were adjusted for slope orientation and exposure by making corrections to observed incoming shortwave and longwave radiation components in the cold regions hydrological model platform simulated melt rates were then applied to the approximated swe distributions to model the decline in sca over the spring the model was found to perform well for the simulation of snowmelt based on point observations of swe at the meteorological station and produced a close correspondence between simulated and observed scd curves representing two opposing slopes within the cirque the results show that both the pre melt distributions of swe and the spring melt rates exhibit considerable spatial variability between distinct slope units within the cirque and that this variability has a significant impact on simulated scd assuming a unimodal pre melt frequency distribution and conditions of spatially uniform snowmelt over complex terrain such as this can lead to large errors in the simulation results it is suggested that modelling applications intended to represent snowmelt dynamics and areal scd in similar alpine environments consider the effects of spatial variation in swe distribution and melt energetics between slopes

precipitation over greenland and its relation to the north atlantic oscillation the equation method based on an equivalent isobaric geopotential height in coordinates has been used to retrieve the precipitation over greenland this approach is designed to accurately represent the topographic effects of the greenland ice sheet on atmospheric motion and precipitation the 11 year mean precipitation from 1985 to 1996 over all of greenland is 376 mm yr 1 which is close to the long term mean precipitation of 346 mm yr 1 estimated from glaciological data the precipitation over all of greenland shows that the largest value in 1986 is 472 mm yr 1 and the smallest value in 1995 is 309 mm yr 1 the major interannual variability of the atmospheric circulation in the north atlantic can be represented by the variation of the north atlantic oscillation nao index which is most pronounced during winter it is found that if the nao index increases the total precipitation over greenland decreases and vice versa the correlation coefficient between these two series for 1985 1995 is 0 75 the mean precipitation over southern greenland where the majority of precipitation falls is more closely related to the nao index in winter and their correlation coefficient is 0 80 this relationship can be understood from the composite maps of sea level pressure and greenland precipitation for the high and low index months during months of high nao index values the icelandic low is strong during months of low nao index values the monthly mean low is located to the southwest of greenland over the labrador sea precipitation amounts over the southeast coast of greenland are about 100 mm larger during the low nao index months than the high nao index months precipitation over all of greenland during the low nao index months is higher there are significant downward trends in annual precipitation from 1985 1995 for all of greenland and its southern and central west coastal regions amounting to about 3 per year

paleoenvironments of kuril islands in late pleistocene holocene climatic changes and volcanic eruption effects the kuril islands are noted for a variety of landscapes from nemoral broadleaf forests to forest tundra and tundra some large islands display a distinct altitudinal zonality environments of the islands bear evidence of various catastrophic events that controlled the landscape evolution to a considerable extent changes of climate during the pleistocene were of particular importance in evolution of the environments dramatic rapid fluctuations of climate at the late pleistocene holocene boundary resulted in repeated restructuring of landscapes at the land bridge connecting the south kuriles and hokkaido in the southern part of the small kuril ridge open forests might persist until the land mass was broken into small islands dominated by meadow marsh vegetation since the middle holocene on the central and northern kuril islands environmental changes during the middle and late holocene resulted both from climatic fluctuations and from repeated fallout of volcanic ash deposition of organic matter began about 6 5 ka bp it resulted from the onset of more favorable conditions namely warming increase of moisture supply and reduction of volcanic activity the evolution of island landscapes consisted mainly in changes of relative area occupied by various plant communities most of which are present in modern vegetation the holocene climatic optimum was not particularly pronounced in this part of the great kuril ridge some consideration is given to issues of changes in zonal boundaries at different time intervals within late pleistocene and holocene

age source and distribution of holocene tephra in the southern kurile islands evaluation of holocene eruptive activities in the southern kurile arc abstract we identified 32 distinct layers of holocene tephra in the southern kurile islands on the basis of petrological features and 14c ages of soils beneath or above the tephra layers three layers were derived from the volcanoes of kunashir island one from mendeleev volcano ca 2 6 cal ka and two from tyatya volcano 1420 cal bp and ad 1973 fourteen widely distributed silicic tephra layers were derived from four volcanoes in hokkaido mashu rausudake tarumai and hokkaido komagatake a widespread tephra was derived from baitoushan volcano between china and north korea fourteen tephra layers have unknown source volcanoes 1 silicic medium k ash 2 silicic low k ash and 11 scoria pumice ash layers except for the medium k ash these tephra are presumed to be derived from the volcanoes in the kurile islands it has been known that caldera forming eruptions occurred at mashu hokkaido and lvinaya past iturup volcanoes in the early holocene ca 12 8 ka however we did not find any tephra from lvinaya past volcano our results provide evidence of the temporal and spatial evolution of eruptive activity in the southern kurile arc we conclude that the level of the eruptive activity in the southern kurile islands especially kunashir island has been lower than that in eastern hokkaido since 8 ka the islands produced mainly vulcanian and strombolian eruptions of mafic magma whereas eastern hokkaido produced plinian eruptions of silicic magma repeated at intervals of 1000 2000 years

isotopic diffusion in cold snow and firn molecular mixing in cold snow and firn is ordinarily controlled by vapor diffusion diffusion through or along the ice matrix is slow whereas diffusion from the air to within separate grains is comparatively rapid thus mixing occurs in the vapor phase and exchange with the local ice involves all the water molecules a quantification of these concepts is applied to the diffusion of oxygen isotopic depth profiles in southern greenland and at dome c antarctica it successfully describes the smoothing of measured profiles the smoothing rate is strongly dependent on temperature and density of the firn

quaternary forest and climate history of hokkaido japan from marine sediments abstract pollen data from quaternary marine sediments deposited in central hokkaido northern japan provide insight into northeast asian vegetation and climatic changes over the last few million years during the early pleistocene coniferous forest dominated by picea and cryptomeria japonica and taiga composed of larix and picea developed under cool wet and cold dry climates respectively strong climatic contrasts are inferred from late pleistocene interglacial and glacial pollen assemblages which precede the last glacial cycle in the former cool temperate broad leaf forest mainly composed of fagus reflects a warmer and wetter climate than now in the latter taiga similar to that now found in northern sakhalin apparently flourished in hokkaido the composition of pollen assemblages correlated with oxygen isotope stage 5 changed from cool temperate forest of quercus ulmus and juglans substage 5e to picea larix taiga substage 5d cool temperate forest of quercus and ulmus substage 5c and picea abies forest substage 5b compared with present conditions climate during stage 5 in northern japan apparently fluctuated from warmer wetter to colder drier taiga composed of picea pinus and larix indicating colder dry conditions during stage 4 was replaced by picea abies forest and picea larix taiga in stage 3 suggesting relatively cool and cold dry environments taiga and mixed forest with taiga and cool temperate components characterize stage 2 holocene forests with juglans betula and quercus juglans were succeeded by picea and abies during the early holocene warm interval 7000 bp subsequently quercus ulmus and abies alnus assemblages reflect climatic deterioration pan mixed forest has been developed in hokkaido since 2000 bp

the role of global and local factors in determining the middle to late holocene environmental history of the south kurile and komandar islands northwestern pacific abstract the study of holocene deposits from northwestern pacific islands is very important for understanding the natural development of the area in the context of oceanic climate strong microclimate variability and the influence of contrasting marine currents holocene sections from bering island record the following events cooling at about 4600 4500 yr bp warming at about 3500 3400 yr bp cooling at about 3000 yr bp sea level rise up to 1 5 m at about 2700 bp cooling at about 1800 1400 yr bp and sea level rise at about 1000 yr bp on the south kuriles a dry and cool climate changed to warm and moist about 7000 6500 yr bp later than on hokkaido island at this time the kuroshio current system became more active and birch assemblages were replaced by cool temperate broadleaf forests and mixed coniferous broadleaf forests at the holocene optimum about 6000 yr bp temperate broadleaf forest occupied almost all of kunashir and the okhotsk side of iturup and the climate was warmer than present the highest sea level position reached was 2 5 3 m above present level about 6500 6300 yr bp during the cooling about 4700 4500 yr bp island vegetation changed slightly due to the influence of warm currents major sea level regression during this period led to the formation of extensive coastal dune fields the warming at the beginning of the late holocene was almost as great as that of the holocene optimum two minor transgressions are recorded the vegetation changes and climatic deterioration that took place in the second half of the late holocene resulted in either a disappearance of thermophylous taxa or in a southward shift of their natural habitats during the cooling from 1700 to 1300 yr bp the isthmus area increased coastal wetlands with lakes and coastal dunes with paleosols were formed and grassland and swamp landscapes developed late holocene warming was not intensive volcanic impact on environments led to changes in vegetation assemblage swamping of the area and thick soil profile formation

boundary layer growth and advection of heat over snow and soil patches modelling and parameterization essery rlh rj granger and jw pomeroy 2006 boundary layer growth and advection of heat over snow and soil patches modelling and parametrization hydrological processes 20 953 967

a 700 year record of atmospheric circulation developed from the law dome ice core east antarctica 1 a 700 year high resolution multivariate ice core record from dome summit south dss 66 46 s 112 48 e 1370 m law dome is used to investigate sea level pressure slp variability in the region of east antarctica empirical orthogonal function eof analysis reveals that the first eof ldeof1 of the combined glaciochemical oxygen isotope ratio and accumulation rate record from dss represents most of the variability in sea salt seen in the record ldeof1 is positively correlated at least 95 confidence level to instrumental june mean slp across most of east antarctica over the last 700 years ldeof1 levels at law dome were the highest during the nineteenth century suggesting an increase in intensification of winter circulation during this period the law dome dss oxygen isotope ratio series also indicates that the nineteenth century had the coldest winters of any century in the record in contrast ldeof1 levels were the lowest at law dome during the eighteenth century suggesting a significant shift in the patterns and or intensity of east antarctic atmospheric circulation between the eighteenth and the nineteenth centuries the ldeof1 sea salt record is characterized by significant decadal scale variability with a strong 25 year periodic structure

a 1400 year high resolution record of atmospheric circulation over the north atlantic and asia major ion series developed from new subannual scale sampling of an ice core from central greenland are calibrated with instrumental series of atmospheric sea level pressure recording major marine icelandic low and terrestrial siberian high atmospheric circulation systems to provide proxy records of atmospheric circulation over the past 1400 years examination of the proxy records reveals major changes in behaviour of these systems c ad 1400 multidecadal and centennial scale periodic components characterization of mean sea level pressure anomaly fields during the little ice age and the mediaeval warm period the potential role of solar forcing coupled ocean atmosphere associations and a perspective within which the characteristics of instrumental era climate can be assessed

paleoenvironments and landscape history of the minor kuril islands since the late glacial abstract the problems of vegetation development of the minor kuriles since the last glacial maximum are discussed the size of island land and relief features influenced landscape development under post glacial holocene climatic changes and sea level oscillations the results suggest that isolation had a great role on development of the landscapes low flat relief active wetlands and the cooling influence of the ocean were the main factors in the development of grassland and wetland landscapes on small islands in the late holocene forest vegetation was preserved only on shikotan island which has upland relief the appearance of broad leaved genera and the disappearance of some taxa are discussed

retrieving a common accumulation record from greenland ice cores for the past 1800 years 1 in the accumulation zone of the greenland ice sheet the annual accumulation rate may be determined through identification of the annual cycle in the isotopic climate signal and other parameters that exhibit seasonal variations on an annual basis the accumulation rate in different greenland ice cores is highly variable and the degree of correlation between accumulation series from different ice cores is low however when using multiyear averages of the different accumulation records the correlation increases significantly a statistical model has been developed to estimate the common climate signal in the different accumulation records through optimization of the ratio between the variance of the common signal and of the residual using this model a common greenland accumulation record for the past 1800 years has been extracted the record shows significant 11 9 years periodicity a sharp transition to very dry conditions is found just before a d 1200 and very dry conditions during the 13th century together with dry and cold spells during the 14th century may have put extra strain on the norse population in greenland and may have contributed to their extinction accumulation rates gradually decrease from a distinct maximum in a d 1394 to very dry conditions in the late 17th century and thus reflect the little ice age

atmospheric circulation and cyclone frequency variations linked to the primary modes of greenland snow accumulation 1 data from 34 greenland firn cores extending from 1982 to 1996 are used to identify spatial accumulation variability patterns and their associated atmospheric circulation and cyclone frequencies the first principal component representing west central greenland accumulation is correlated to nao variability having increased southwesterly northeasterly flow over that area during high low accumulation winters the flow is linked to a relative increase in cyclone activity on the west central region of the ice sheet during high accumulation periods the second principal component represents accumulation over southeastern greenland where strong westerly flow leads to high accumulation and an increase in lee cyclones on the east and southeast coast the study provides evidence that increased cyclone activity occurs over or immediately adjacent to areas experiencing anomalously high accumulation and it is important to distinguish lee cyclones from icelandic cyclones as they produce opposite precipitation effects over the ice sheet

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

sensible heat flux and local advection over a heterogeneous landscape at an arctic tundra site during snowmelt during snowmelt over a continuous snow cover the vertical turbulen t exchanges of sensible and latent energy arc influenced by reo ional ai r mass chara cteris tics which exert a strong conlrol on air temperature in hig b h iatitude sites the melting surface rapidly becomes heterogeneous with patches of snow and snow free areas local advection occurs when near surface air layers are warmed due to sensible heat flux from the snow free areas with the resulting heat transferred horizontally to adjacent snow patches this advection greatly increases the rate of snow melt along the leading edges of the snowpat ches in order to estimate correctly the average melt rates of the snowpatches and the bulk energy balancc of the entire landscape it is necessary to estimate the local advection component to date few studies have dealt with this problem this paper reports results from an arctic tundra site located approximately 55 km northeast of inuvik northwest 1erritories canada the importance of local ad cction is estimated by comparing the sensible heat flux of the snowpatches to estimates of sensible heat with out local advection this latter term is derived from a relationship between upper air temp erature and sensible heat flux over a continuous snow cover this work has imponalll lmpllcalions for de eloplng models that correctly represent the cryosphere of tundra regions and in developing appropriate scaling techniques for heterogeneous landscapes

a synchronized dating of three greenland ice cores throughout the holocene as part of the effort to create the new greenland ice core chronology 2005 gicc05 a synchronized stratigraphical timescale for the holocene parts of the dye 3 grip and ngrip ice cores is made by using volcanic reference horizons in electri cal conductivity measurements to match the cores the main annual layer counting is carried out on the most suited records only exploit ing that the three ice cores have been drilled at locations with different climatic con ditions and differences in ice flow however supplemental counting on data from all cores has been performed between each set of reference horizons in order to verify the valid ity of the match after the verification the main dating is transferred to all records us ing the volcanic reference horizons as tie points an assessment of the mean annual layer thickness in each core section confirms that the new synchronized dating is consistent for all three cores the data used for the main annual layer counting of the past 7900 years are the dye 3 grip and ngrip stable isotope records as the high accumulation rate at the dye 3 drill site makes the seasonal cycle in the dye 3 stable isotopes very resistant to firn diffusion an effort has been made to extend the dye 3 holocene record the new syn chronized dating relies heavily on this record of 75 000 stable isotope samples the dat ing of the early holocene consists of an already established part of gicc05 for grip and ngrip which has now been transferred to the dye 3 core gicc05 dates the younger dryas termination as defined from deuterium excess to 11 703 b2k 130 years earlier than the previous grip dating

multiproxy record of late holocene climatic changes and natural hazards from paleolake deposits of urup island kuril islands north western pacific abstract the evolution of the late holocene environments has been reconstructed on the basis of multiproxy studies of peat sequences the vegetation response to short period climate fluctuations has been traced early in the late holocene there were birch forests with oak and other broadleaf trees vast areas were occupied by forb meadows under cooling 3250 yr bp the shrub pine pinus pumila became the landscape forming species and since 2490 yr bp selaginella selaginoides appeared in abundance the little ice age was marked by the disappearance of broadleaf trees and widely spread heath land communities the higher stands of the lake level were related to warmings 3660 3590 3450 3180 2960 2840 2410 2260 cal yr bp shallowing coincided with short term coolings 3590 3450 3180 2960 2840 2410 2260 2150 cal yr bp marked by reduced precipitations the dune ridge formation began during the longest cooling accompanied by a minor regression the dunes were stabilized and a paleosol developed 2340 2260 yr bp a younger generation of eolian sands developed during the little ice age an ecological effect of volcanic ashfalls has been estimated the local biotic components seem to have been most afflicted by the eruption in the north of iturup in 2100 2300 cal yr bp when ckr tephra up to 30 cm thick was deposited the ages of 4 strongest tsunamis that occurred over the last 3660 years were determined they appeared to be related to the earthquakes with focuses close to urup island or south of it the lake microflora shows ecological effect of the marine water invasions

new pollen records of late pleistocene and holocene changes of environment and climate in the lower amur river basin ne eurasia abstract the late pleistocene holocene paleoclimate and paleoenvironmental changes of the lower amur basin are presented based on pollen records from radiocarbon dated peat sections the gur section represents the most complete terrestrial record of the russian far east and probably for all of northeast asia landscape changes are reconstructed for warm events corresponding to the bolling and allerod and cold episodes as middle dryas and younger dryas in europe there were three warm periods in the lower amur basin 8900 8300 5000 5700 and 3200 4200 bp a major expansion of diverse species in the forest formations in the entire lower amur river basin occurred at 5000 5700 bp changes and developments of paleoclimate events and paleoenvironmental changes of late pleistocene and holocene in lower amur basin were correlative with european climate events

patterns of low frequency monthly sea level pressure variability 1899 1986 and associated wave cyclone frequencies abstract spatial patterns of low frequency sea level pressure slp variability are identified by performing rotated principal component analysis rpca on a long term 1899 1986 northern hemisphere gridded dataset the analysis is limited to the region 160 e eastward to 40 e due to missing data early in the century the objective is to identify a comprehensive set of highly recurrent slp teleconnection patterns to examine some aspects of their seasonality and to identify the associated mean winter pressure fields and cyclone frequencies occurring at times of opposite eigenvector polarity the results are further described in the context of the southern oscillation and known midtropospheric teleconnection patterns four low frequency variability patterns are identified over the atlantic european sector including i the north atlantic 0scillation nao and spatial patterns with slp variability centers over ii the eastern atlantic eatl iii southern europe and the northern mediterranean basin s

large arctic temperature change at the wisconsin holocene glacial transition analysis of borehole temperature and greenland ice sheet project ii ice core isotopic composition reveals that the warming from average glacial conditions to the holocene in central greenland was large approximately 15 c this is at least three times the coincident temperature change in the tropics and mid latitudes the coldest periods of the last glacial were probably 21 c colder than at present over the greenland ice sheet

seasonal precipitation timing and ice core records this is a commentary on global circulation model experiments of moisture source changes in greenland urging caution in how they are applied because they have important implications for paleoclimate reconstruction from ice cores the work comes from preliminary find is of a ice core gisp2 of the authors the authors conclude that at present anomalies in greenland ice core records should not be interpreted solely in terms of source region variations the combined use of oxygen 18 d and ionic species in the new summit greenland cores should make it possible to answer empirically some of the questions raised by the gcm experiments as to the interpretation of oxygen 18 records in terms of temperature 4 refs 1 fig

holocene climatic changes and environmental history of iturup island kurile islands northwestern pacific the study of holocene deposits on iturup island is very important for understanding palaeolandscape changes on the island it is separated by deep straits from the neighbouring islands and was isolated during the last glacial maximum landscape changes over the last 40000 years and the role of refugia on vegetation development are discussed changes in natural processes in this region were controlled both by global climatic changes and by regional factors birch forests developed at the warming about 36 37 ka ago whereas tundrapark landscape developed with the cooling of the last glacial maximum holocene environments reflect climatic changes and sea level oscillations the fluctuation of warm and cold currents influenced the landscape development at the holocene optimum about 6 ka broadleaved forests with quercus phellodendron carpinus juglans fagus fraxinus and syinga occupied the okhotsk side of central iturup climate was warmer than present and the sum of active tempe ratures 10 c was n

atmospheric circulation and variations in scandinavian glacier mass balance abstract mountain glaciers in scandinavia are currently advancing while most of the monitored mountain glaciers of the world are retreating we examine atmospheric circulation variability and compare changes in air pressure indices to changes in the mass balance of glaciers in the northeastern part of the atlantic ocean the glacier mass balance correlates well with the strength of maritime flow in both winter and summer the presence of high pressure over the barents sea being a critical factor in summer the advance of scandinavian glaciers is due partly to persistently strong westerlies over the northeastern atlantic during post 1980 winters and partly to cold summertime flow which together have helped maintain positive glacier net balance by decreasing ablation since 1980

depositional frequency of german subfossil oaks climatically and non climatically induced fluctuations in the holocene a highly resolved record of the depositional frequency of subfossil trees since 8263 bc in the valley of the river main is presented different aspects of forest dynamics are explored including depositional anomal ies phases of low or zero departures changes in forest density based on tree growth trend classes gtcs and regeneration using mean lifespan ml data this reveals a number of climatically induced environmental changes that are synchronous with events in the north atlantic region and therefore may reflect a facet of the north atlantic climate system three periods are recognized 1 pre 3500 bc when depositional frequency was dominated by climatic events with notable anomalies at 6200 and 4100 bc 2 between 3500 and 1200 bc when climatically triggered events were enhanced by forest clearances especially marked anomalies occurring around 2700 2300 and 1700 bc and 3 post 1200 bc when the climatic information is obscured by human activities

climate reconstruction using data assimilation of water isotope ratios from ice cores water isotope data from ice cores particularly 18o have long been used in paleoclimatology although 18o has been primarily interpreted as a proxy for local air temperature isotope enabled climate models have established that there are many nonlocal and nontemperature related climatic influences on isotopic signals at coring locations moreover recent observational studies have linked ice core isotopes to nonlocal patterns of climate variability particularly to midlatitude atmospheric circulation patterns and to variations in tropical climate therefore paleoclimate reconstructions may better utilize ice core isotope proxies by combining them with isotope enabled climate models here we employ a data assimilation based technique that fuses isotopic proxy information with the dynamical constraints of climate models through several idealized and real proxy experiments we assess the spatial and temporal extent to which isotope records can reconstruct surface temperature 500 hpa geopotential height and precipitation we find local reconstruction skill to be most robust across the reconstructions particularly for temperature and geopotential height as well as limited nonlocal skill in the tropics these results are in agreement with long held views that isotopes in ice cores have clear value as local climate proxies particularly for temperature and atmospheric circulation these results also show that in principle nonlocal climate information may also be inferred from ice cores however the spatial range of this information is nonuniform and depends on skillful modeling of the proxy data within the reconstruction process

holocene and deglacial ocean temperature variability in the benguela upwelling region implications for low latitude atmospheric circulation 1 mg ca analyses of g bulloides and abundances of n pachyderma left coiling from ocean drilling program odp leg 175 hole 1084b in the benguela coastal upwelling system document lower sea surface temperatures during the last glacial maximum lgm younger dryas mid holocene and little ice age in the southeastern atlantic taking into consideration the possible effects of differential carbonate dissolution the mg ca data indicate younger dryas temperatures 2 3 c cooler than those of the early holocene and lgm temperatures 4 5 c cooler than those of the early holocene the cool interval during the deglacial period at hole 1084b matches the timing of younger dryas shifts in cariaco basin and greenland ice sheet records and that of a nearby alkenone record comparison of mid holocene cooling at hole odp1084b with other high resolution records of holocene and last deglacial sea surface temperatures from the tropical atlantic implies consistent basin wide changes in atmospheric circulation a brief period of 1 5 2 c cooling between 17 8 and 17 2 ka if related to heinrich event 1 is consistent with a previously hypothesized tropical origin of all heinrich climate change events

reconstruction of the undiffused seasonal oxygen isotope signal in central greenland ice cores the climatologically important seasonal signal in ice core oxygen isotope records is altered by diffusion with time here we use the diffusion model of whillans and grootes 1985 to calculate the effects of isotopic diffusion in nine shallow ice cores recovered over a 150 150 km grid centered on summit greenland two different computational methods give similar results for the back diffused 18o seasonal extrema although back diffusing the ice core 18o records improves the correlations between the individual ice core oxygen isotope and greenland coastal temperature records the correlations remain poor particularly for the low accumulation sites stacking the back diffused isotopic records from several cores results in much higher correlations with a strong winter linkage between west coast stations and central greenland these correlations are also significantly greater than the correlations between the stacked measured diffused isotopic profiles and coastal temperatures our results indicate that the use of ice core isotopic records to identify anomalous seasons requires that diffusion effects be accounted for

atmospheric circulation variability associated with shallow core seasonal isotopic extremes near summit greenland seasonal back diffused 18o time series reconstructed for nine shallow firn cores from the greenland summit for 1959 1987 are evaluated in terms of 1 their spatial and temporal variability and 2 their association to the atmospheric circulation rotated principal component analysis evaluates spatial and temporal patterns of organization in the back diffused 18o ice core time series mean sea level pressure and 500 hpa height fields are obtained for winter and summer seasons that fall in the isotopically warmest and coldest thirds of the seasonal data the winter back diffused 18o data indicate that some degree of longitudinal separation takes place between isotopic records from western and eastern greenland in agreement with coastal station climatic data temporal variability is linked with statistical significance to the variability of the atmospheric circulation over the denmark strait as well as over the norwegian and barents seas the north atlantic oscillation nao and the mean icelandic low in the denmark strait affect isotopic variability over the cores west of the ice divide just as they have been shown to prominently affect west coast air temperature records isotopic variability at some ice cores east of the divide is influenced by pressure variability over the norwegian and barents seas although statistical significance is lower the nao appears insignificant in summer isotopic variability as the circulation in that season is very much localized and dominated by either ridging warm cases or troughs cold cases over eastern greenland and the arctic ocean results suggest that long term winter 18o variability can potentially be linked to climate variation over europe especially from the mediterranean basin northward to about 55 n and as far east as central siberia