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 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

spatial variation in the influence of the north atlantic oscillation on precipitation across greenland 1 ice core derived accumulation records from greenland have been proposed as proxies for north atlantic oscillation nao reconstruction in a series of single site analyses accumulation records from ice cores drilled in western greenland were found to exhibit the strongest linear association with nao in this paper we expand on these findings by proposing a spatiotemporal statistical model to explore further the relationship between nao and the accumulation records from 35 firn and ice cores drilled in western and southern greenland in particular we propose a temporal extension of the bayesian spatially varying coefficient regression model which is fit using a markov chain monte carlo algorithm this model readily accommodates the irregular features of the data i e variation in record lengths and irregular spacing among ice core locations and the serial dependence within individual records using our statistical model we are able to exploit the spatial dependence structure of the derived accumulation nao relationship to explore the regional patterns in the strength of this relationship our findings support previous work that identified a region in western greenland where derived accumulation is most correlated with nao however we also identify a region further inland to the east and south where the estimated strength of the linear accumulation nao relationship is weaker but more certain than in the previously identified region thus our findings can be used to guide decisions regarding where to locate future drilling efforts in greenland by weighing the trade off between the potential strength of the accumulation nao relationship and its uncertainty

paleoseismic investigations in the santa cruz mountains california implications for recurrence of large magnitude earthquakes on the san andreas fault trenching microgeomorphic mapping and tree ring analysis provide information on timing of paleoearthquakes and behavior of the san andreas fault in the santa cruz mountains at the grizzly flat site alluvial units dated at 1640 1659 a d 1679 1894 a d 1668 1893 a d and the present ground surface are displaced by a single event this was the 1906 surface rupture combined trench dates and tree ring analysis suggest that the penultimate event occurred in the mid 1600 s possibly in an interval as narrow as 1632 1659 a d there is no direct evidence in the trenches for the 1838 or 1865 earthquakes which have been proposed as occurring on this part of the fault zone in a minimum time of about 340 years only one large surface faulting event 1906 occurred at grizzly flat in contrast to previous recurrence estimates of 95 110 years for the santa cruz mountains segment comparison with dates of the penultimate san andreas earthquake at sites north of san francisco suggests that the san andreas fault between point arena and the santa cruz mountains may have failed either as a sequence of closely timed earthquakes on adjacent segments or as a single long rupture similar in length to the 1906 rupture around the mid 1600 s the 1906 coseismic geodetic slip and the late holocene geologic slip rate on the san francisco peninsula and southward are about 50 70 and 70 of their values north of san francisco respectively the slip gradient along the 1906 rupture section of the san andreas reflects partitioning of plate boundary slip onto the san gregorio sargent and other faults south of the golden gate if a mid 1600 s event ruptured the same section of the fault that failed in 1906 it supports the concept that long strike slip faults can contain master rupture segments that repeat in both length and slip distribution recognition of a persistent slip rate gradient along the northern san andreas fault and the concept of a master segment remove the requirement that lower slip sections of large events such as 1906 must fill in on a periodic basis with smaller and more frequent earthquakes

norwegian fjord sediments reveal nao related winter temperature and precipitation changes of the past 2800 years abstract the north atlantic oscillation nao is the leading mode of atmospheric circulation variability in the north atlantic region associated shifts of storm tracks precipitation and temperature patterns affect energy supply and demand fisheries and agricultural as well as marine and terrestrial ecological dynamics long term nao records are crucial to better understand its response to climate forcing factors and assess predictability and shifts associated with ongoing climate change a recent study of instrumental time series revealed nao as main factor for a strong relation between winter temperature precipitation and river discharge in central norway over the past 50 years here we compare geochemical measurements with instrumental data and show that primary productivity recorded in central norwegian fjord sediments is sensitive to nao variability this observation is used to calibrate paleoproductivity changes to a 500 year reconstruction of winter nao luterbacher et al 2001 conditioned on a stationary relation between our climate proxy and the nao we establish a first high resolution nao proxy record nao tfj from marine sediments covering the past 2800 years the nao tfj shows distinct co variability with climate changes over greenland solar activity and northern hemisphere glacier dynamics as well as climatically associated paleo demographic trends the here presented climate record shows that fjord sediments provide crucial information for an improved understanding of the linkages between atmospheric circulation solar and oceanic forcing factors

north atlantic oscillation dynamics recorded in greenland ice cores carefully selected ice core data from greenland can be used to reconstruct an annual proxy north atlantic oscillation nao index this index for the past 350 years indicates that the nao is an intermittent climate oscillation with temporally active coherent and passive incoherent phases no indication for a single persistent multiannual nao frequency is found in active phases most of the energy is located in the frequency band with periods less than about 15 years in addition variability on time scales of 80 to 90 years has been observed since the mid 19th century

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

annual accumulation over recent centuries at four sites in central greenland 1 accurate accumulation records are fundamental to understanding mass balance of the greenland ice sheet ice cores can provide multicentury high resolution ground based point estimates of water accumulation in 2003 and 2004 four new ice cores were collected in the central western d4 and d5 and summit sandy and katie regions of greenland annual layer counting based on multiple glaciochemical parameters primarily hydrogen peroxide sea salt and dust proxies was used to date the ice cores resulting in annual dating the bottom depth ages for d4 d5 sandy and katie were estimated at 1738 1673 1844 and 1934 a d with mean annual accumulation rates of 41 4 35 2 22 4 and 22 4 cmweq yr 1 respectively these new records were in good agreement with previous accumulation maps and four previously published records from nearby multicentury ice cores spatial variability was quantified through an analysis of variance thereby allowing for more meaningful comparisons to atmospheric processes more regionally representative accumulation records were constructed for the central western and summit regions spanning recent centuries using a principle component analysis of both the new and previously reported ice core measurements these regional records exhibited 6 7 interannual variability 1 standard deviation of the mean and had lower spatial variability uncertainties than individual accumulation records correlations indicate that 20 of the variance in the central western region was explained by the north atlantic oscillation nao and suggests that an array of more northern ice cores may correlate more closely with nao

palaeohydrology of kangerlussuaq sondre stromfjord west greenland during the last 8000 years major fluctuations of hydroclimate in west greenland are recorded in paleoshoreline terraces that encircle several lakes near kangerlussuaq greenland 67 01 n 50 40 w geomorphic and stratigraphic analyses were used to construct a lake level curve for hunde so a large closed basin lake in this region changes in lake volume associated with lake level fluctuations were cal culated and a water balance model was used to determine the primary factors influencing lake volume and the changes in those factors necessary to affect reconstructed lake level change sensitivity tests suggest that mean annual precipitation and the relative proportion of summer versus winter precipitation are the primary climate drivers of lake level change temperature effects are less important unless coupled with changes in one of the other variables two pluvial periods occurred centered around 4600 and 2000 cal yr bp with mean annual precipitation estimated at 130 mm and 70 mm higher than modern respectively in contrast a low stand prior to 6070 cal yr bp with water levels as much as 18 m below modern was a result of summer temperatures 2 3 above modern coupled with a 14 day increase in the length of the iceoff period and a reduction in mean annual precipitation of 80 mm relative to modern

modeled variations of precipitation over the greenland ice sheet abstract a parameterization of the synoptic activity at 500 hpa and a simple orographic scheme are used to model the spatial and temporal variations of precipitation over the greenland ice sheet for 1963 88 from analyzed geopotential height fields produced by the national meteorological center nmc model coefficients are fitted to observed accumulation data primarily from the summit area of the ice sheet all major spatial characteristics of the observed accumulation distribution are reproduced apart from the orographic accumulation maximum over the northwestern coastal slopes the modeled time averaged total precipitation amount over greenland is within the range of values determined by other investigators from surface based observations a realistic degree of interannual variability in precipitation is also simulated a downward trend in simulated ice sheet precipitation over the 26 years is found this is supported by a number of lines of evidence it matches the accumulation trends during this peri

southeast greenland winter precipitation strongly linked to the icelandic low position abstractgreenland s largest precipitation flux occurs in its southeast se region during the winter controlled primarily by easterly winds and frequent cyclogenesis in the north atlantic several

the impact of cloud cover on the net radiation budget of the greenland ice sheet energy balancemodelsdrivenbyradiationandturbulentheatfluxeshave beenwidelyappliedto predictingtheresponse ofthegreenland ice sheetto climatechange however a lackof knowledge of the temporal and spatial distribution of cloudamount and type has necessitated the use of parameterizations or statistical models of cloud cover this deficiency results in large uncertainties in both shortwave and longwave radiation fluxes stereo matching of nadir and forward viewalongtrack scanning radiometer 2 atsr 2 image pairs has been shown to be a reliable method of retrieving cloud top height and further cloud properties can be derived from thermal imagery allowing classification into cloud type a1year cloud record for a transect across southern greenland derived from stereo matching is presented here and comparisons are made with climate re analysis data and ground observations the cloud cover data were used in a simple radiative transfer model and the impact of clouds on the net radiation fluxes was found to be considerable different cloud scenarios produced up to 40wm 2 difference in net radiation balance in theablationzone wherethealbedoislowerandmost variable thesensitivity to cloud cover fraction was less marked but the higher spatial resolution of the atsr 2 cloud record was reflected by a much more varied trend in radiation balance whether the net radiation balance increases or decreases with increased cloud cover was foundto be a function of the cloud amount andtype and also the surface albedo the sensitivity of the model to a 5 change in cloud amount was found to be comparable to a1k change in temperature this clearlydemonstratestheimportanceofreliable quantitativeclouddatainmass balanceand otherglaciological studies

modeled precipitation variability over the greenland ice sheet on the basis of the evaluation of recent greenland precipitation studies some of the deficiencies in the modeled precipitation are probably related to the topographic data employed in modeling in this paper the modern digital elevation data of ekholm 1996 is used if the horizontal pressure gradient force in coordinates is separated into its irrotational and rotational parts which are expressed by the equivalent geopotential and geo stream function respectively the topographic effect on the precipitation can be accurately modeled the equivalent geopotential and geo stream function are implemented in a fully consistent manner in the generalized equation in this paper a simplified large scale condensation without evaporation of condensate is also used these improvements are combined to yield an improved dynamic method two aspects of the precipitation distribution are refined by the improved dynamic method one is the 10 cm yr 1 contour near summit greenland and the other is a relative large precipitation area centered near the point 70 n 49 w extensive comparisons are made between the retrieved precipitation and the observed annual accumulation time series from 11 ice core sites on the ice sheet the modeled precipitation from the original method must use sealers to have a high degree of interannual correspondence between the measured accumulation and the retrieved precipitation but the retrieved precipitation from the improved method increases at all ice core sites and a good correspondence is obtained without any sealer being required the spatial average of multiyear mean error e j is 11 5 cm yr 1 for the modeled precipitation from the improved method while that for p from era 15 is 14 5 cm yr 1 the total mean error em is 3 0 cm yr 1 for the improved method while em for the p from era 15 is 4 0 cm yr 1 these two errors show that the precipitation modeled by the improved method is better than the p from era 15 thus the distribution of precipitation over the 11 sites retrieved by the improved dynamic method is considerably refined large downward trends in annual amounts are present in the precipitation retrieved by the improved dynamic method for all of greenland and its southern and central west coastal regions the modeled precipitation from the improved dynamic method and observed accumulation from ice cores are all in agreement with the thomas et al 1999 result that the southern greenland ice sheet above 2000 m is approximately in balance it also shows that local thickening and thinning areas of the ice sheet derived by airborne laser altimetry from 1993 to 1999 over the entire greenland above 2000 m krabill et al 2000 are approximately consistent with precipitation change retrieved by the improved dynamic method

greenland ice sheet high elevation balance and peripheral thinning aircraft laser altimeter surveys over northern greenland in 1994 and 1999 have been coupled with previously reported data from southern greenland to analyze the recent mass balance of the greenland ice sheet above 2000 meters elevation the ice sheet is in balance on average but has some regions of local thickening or thinning thinning predominates at lower elevations with rates exceeding 1 meter per year close to the coast interpolation of our results between flight lines indicates a net loss of about 51 cubic kilometers of ice per year from the entire ice sheet sufficient to raise sea level by 0 13 millimeter per year approximately 7 of the observed rise

the north atlantic oscillation and its imprint on precipitation and ice accumulation in greenland interannual to decadal fluctuations in net precipitation and ice accumulation are examined over greenland it is shown that in western greenland these fluctuations are correlated with the north atlantic oscillation the analysis is based on two complementary data sources a highly resolved net precipitation and accumulation history over 15 years derived form the reanalysis data of the european centre for medium range weather forecasts and a composite ice accumulation record representative for the western part of central greenland it is suggested that western greenland snow accumulation is a good proxy for the nao index with the potential for the reconstruction of a long time series

a freshwater jet on the east greenland shelf in august 1997 rrs discovery cruise 230 world ocean circulation experiment woce section a25 ran a hydrographic section into cape farewell on the southern tip of greenland the closest approach to the shore was 2 nm in a water depth of 160 m over the east greenland shelf analysis of the hydrographic data conductivity temperature depth ctd vessel mounted acoustic doppler current profiler and thermosalinograph has revealed a current flowing southwestward 15 km wide 100 m deep and centered 10 km offshore we believe it to be driven by meltwater runoff from greenland this feature which we call the east greenland coastal current egcc carries a little less than 1 sv 106 m3 s 1 with peak current speeds of 1 m s 1 at the surface the center of the egcc lies on a salinity front with maximum salinity contrast 4 practical salinity units psu between coast and shelf break and between surface and bottom a spot value of freshwater transport is 0 06 sv 1800 km3 yr 1 which is equivalent to 30 of the arctic freshwater gain the presence of the egcc and its continuity up the east greenland coast as far as denmark strait is confirmed in satellite sea surface temperature images and surface drifter tracks we estimate the sensitivity of its freshwater flux to changes in melt season mean surface air temperature to be 25 per 1 c

interannual variations of snow accumulation on the greenland ice sheet 1985 1996 new observations versus model predictions newly measured time series of net water equivalent accumulation from ice cores are reported for 11 sites located near the 2000 m contour of the greenland ice sheet many of these sites are located in regions where accumulation has not been previously measured we compared these new time series of annual accumulation with previously reported modeled precipitation covering the same time range because ice core accumulation records include both regional and local accumulation components we used adjacent ice core records at six multiple core sites to estimate the local component and extrapolated these results to the five single core sites we investigated the impact of this short scale spatial variability in accumulation on statistical comparisons between the observed accumulation and model precipitation although sealers were required to match the 12 year mean modeled precipitation to the mean observed accumulation a high degree of correspondence between observed interannual accumulation and scaled modeled precipitation was found at 7 of 11 locations the need for scaling and the low correspondence between model simulations and observations at some sites clearly indicate that model improvements are needed although very encouraging a more spatially distributed array of ice core accumulation measurements spanning the same time period as the precipitation modeling is necessary for continued model improvement and validation in agreement with earlier studies the large temporal variability in snow accumulation predicted by modeling and confirmed by ice cores indicates that the ice sheet elevation varies by tens of centimeters from year to year simply because of changing accumulation

climate driven fluctuations in freshwater flux to sermilik fjord east greenland during the last 4000 years the freshwater runoff from the glaciated and snow covered sermilik fjord catchment se greenland was estimated at annual resolution for the period 1900 2008 and at decadal resolution for the past four millennia our simulations were forced with available meteorological station data 1900 2008 and greenland ice core estimated temperature data 1899 bc ad 1980 from dye3 and gisp2 time series of estimated ice discharge 2000 2009 for the three major outlet glaciers helheim fenris and midgard indicate that 53 74 of the ice discharge variations could be explained by variations in areally averaged glacier terminus surface supraglacial runoff based on these data and together with calculated subglacial geothermal and frictional melting as well as net precipitation for the fjord area the sermilik fjord freshwater flux was deduced for the period 1900 2008 our simulations indicated that during the last century surface freshwater runoff has equaled 13 of the sermilik fjord average freshwater flux of 33

assessment of greenland albedo variability from the advanced very high resolution radiometer polar pathfinder data set the advanced very high resolution radiometer polar pathfinder app data set is used to examine the variability of the surface albedo over greenland analysis of the app albedo record from 1981 to 1998 show anomalously low albedo during 1995 and 1998 over most of the ice sheet as compared with the other years the low albedo encountered during these years suggests that the ice sheet experienced considerable melt in 1995 and 1998 particularly near the western margin of the ice sheet conversely anomalously high albedos were found in 1992 as a result of colder temperatures and hence less melt following the eruption of mount pinatubo the relationship between the annual north atlantic oscillation nao index and the mean summer albedo from all the stations reveals a positive correlation of 0 44 and a positive correlation of 0 55 for the southern part of the ice sheet therefore variations in the mean summer albedo over greenland can in part be explained by variations in the nao such that during periods of intensification of the normal mode of the nao the mean summer albedo is above normal trend analysis reveals an overall downward trend in surface albedo from 1981 to 1998 which agrees with recent trends in melt and precipitation however the trend was found not to be statistically significant but rather influenced by the low albedo in recent years

a comparison of quasigeostrophic and nonquasigeostrophic vertical motions for a model simulated rapidly intensifying marine extratropical cyclone abstract large scale departures from quasigeostrophic vertical motions are diagnosed for a model simulation of the qe ii storm 9 11 september 1978 the simulation was performed by the limited area mesoscale prediction system lamps initialized at 1200 utc 9 september 1978 the model cyclone intensified from a central pressure of 1003 mb to 976 mb in 24 h considerably short of the 59 mb 24 h 1 observed deepening but reasonable in comparison to other model simulations of this storm this diagnosis centers on a hydrostatic generalized omega equation which scales to the quasigeostiophic omega equation for small rossby number vertical motions were computed both from this generalized omega equation and the quasigeostrophic omega equation in order to examine the importance of nonquasigeostrophic effects the high correlation of vertical motions from a control experiment using most of the terms in the generalized omega equation with the vertical motions predicted by the model establishes the validity o

evaluation of recent precipitation studies for greenland ice sheet the retrieval of an accurate spatial and temporal record of contemporary greenland precipitation is a uniquely challenging task because of the extreme variability in both atmospheric processes and the resulting precipitation distribution over relatively small spatial scales a comparison of precipitation data sets composed of monthly mean values from recent studies shows a convergence on the general features of the long term spatial patterns but substantial disagreement on the temporal variability both regionally and for all of greenland there is general agreement on a long term greenland average of about 35 cm yr 1 and on long term values for regional scales although differences for outlying data sets exceed 50 of the observed glaciological estimate for particular regions a fundamental problem is the inadequate topographic representation of greenland in the numerical analyses nearly all of the data sets are overly dry for high elevation areas as seen from comparisons with glaciological observations from summit the east central region of greenland is found to be particularly susceptible to the temporal discontinuities in data sets which employ operational analyses in contrast there is strong agreement among all methods on the temporal variability for the west central region over a 15 year period from the comparison it is concluded that none of the data sets is able to capture all of the regional scale features in general however the deficiencies of each data set are readily identifiable from comparison and evaluation in the context of circulation features agreement among the methods on particular regions and timescales gives increased confidence in drawing conclusions related to aspects of greenland s precipitation climatology in particular an enhanced precipitation retrieval method is found to be less susceptible to data artifacts than other methods using operational analyses in the north anomalously high precipitation is associated with cyclonic development near the fram strait for west central greenland the close agreement among methods is related to the dominant contribution of the mean circulation

recent greenland accumulation estimated from regional climate model simulations and ice core analysis the accumulation defined as precipitation minus evaporation over greenland has been simulated with the high resolution limited area regional climate model hirham4 applied over an arctic integration domain this simulation is compared with a revised estimate of annual accumulation rate distribution over greenland taking into account information from a new set of ice core analyses based on surface sample collections from the north greenland traverse the region with accumulation rates below 150 mm yr21 in central northwest greenland is much larger than previously assumed and extends about 500 km farther to the south it is demonstrated that good agreement between modeled and observed regional precipitation and accumulation patterns exists particularly concerning the location and the values of very low accumulation in the middle of greenland the accumulation rates in the northern part of greenland are reduced in comparison to previous estimates these minima are connected with a prevailing blocking high over the greenland ice sheet and katabatic wind systems preventing humidity transports to central greenland the model reasonably represents the synoptic situations that lead to precipitation maxima of precipitation and accumulation occur at the southwestern and southeastern coasts of greenland and are connected with cyclonic activity and the main storm tracks around greenland the central region of the greenland ice sheet acts as a blocking barrier on moving weather systems and prohibits cyclones moving from west to east across this region and thus prevents moisture transports

the 1958 2009 greenland ice sheet surface melt and the mid tropospheric atmospheric circulation in order to assess the impact of the mid tropospheric circulation over the greenland ice sheet gris on surface melt as simulated by the regional climate model mar an automatic circulation type classification ctc based on 500 hpa geopotential height from reanalyses is developed general circulation correlates significantly with the surface melt anomalies for the summers in the period 1958 2009 the record surface melt events observed during the summers of 2007 2009 are linked to the exceptional persistence of atmospheric circulations favouring warm air advection the ctc emphasizes that summer 500 hpa circulation patterns have changed since the beginning of the 2000s this process is partly responsible for the recent warming observed over the gris

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

new precipitation and accumulation maps for greenland annual total precipitation and the annual accumulation on the greenland ice sheet are evaluated and presented in two maps the maps are based on accumulation measurements of 25 1 pits and cores obtained from the upper accumulation zone and precipitation measurements made at 35 meteorological stations in the coastal region to construct the accumulation map the annual precipitation was split into solid and liquid precipitation components annual total precipitation exceeding 2500 mm w e occurs on the southeastern tip of greenland while the minimum precipitation is estimated to occur on the northeastern slope of the ice sheet the mean annual precipitation for all of greenland is 340 mm w e the largest annual accumulation of about 1500 mm w e is found on the glaciers in the southeastern corner of greenland while the smallest accumulation is found on the northeastern slope of the ice sheet west of danmarkshavn the mean accumulation on the greenland ice sheet is estimated at 310 mm w e the regional difference in accumulation is examined with respect to the 850 hpa m bar level circulation the present surface topography is found to play an important role in determining regional accumulation on the ice sheet

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

early proterozoic granulites in central korea tectonic correlation with chinese cratons abstract a coherent granulite complex has been discovered in the central part of the korean peninsula formerly regarded as the eastern imjingang belt this granulite complex hwacheon granulite complex hgc experienced two cycles of tectonometamorphic events the first event corresponded to crustal thickening followed by peak granulite facies metamorphism and associated partial melting the quasi isobaric cooling path suggested by the occurrences of secondary garnet mantling orthopyroxene and secondary kyanite in mafic and pelitic granulites respectively indicates substantial residence time at midcrustal levels prior to exhumation of the hgc the timing of peak metamorphism was dated from the unzoned overgrowth rims on zircons in a migmatitic granulite at documentclass aastex usepackage amsbsy usepackage amsfonts usepackage amssymb usepackage bm usepackage mathrsfs usepackage pifont usepackage stmaryrd usepackage textcomp usepackage portland xspace usepackage amsmath amsxtra