regionally differentiated contribution of mountain glaciers and ice caps to future sea level rise the contribution to sea level rise from mountain glaciers and ice caps has grown over the past decades a projection of their melting during the twenty first century based on temperature and precipitation projections from ten climate models suggests that by 2100 these glaciers will lose about 21 of their total global volume

paleomagnetism of coastal california and baja california alternatives to large scale northward transport paleomagnetic data from the santa lucia orocopia sloa and baja borderland bba allochthons of coastal california and baja california have been interpreted to indicate up to 2500 km of post mid cretaceous northward transport of these regions with respect to interior north america however with neogene strike slip offsets taken into account geological interpretations correlate basement rocks of the coastal allochthons with continental basement rocks directly across the san andreas and related fault systems we have examined paleomagnetic data from sloa and bba and conclude that apparent discordances can be explained without large scale pre neogene tectonic transport three major observations are fundamental to this analysis 1 paleolatitudes derived from volcanic rocks of the jurassic eugenia formation of bba and coast range ophiolite of sloa are concordant when compared to revised jurassic reference paleomagnetic poles from interior north america 2 isotopic and paleobarometric data from the peninsula ranges batholith in southern california indicate that the batholith has been tilted northeast side up by an amount that can account for discordant paleomagnetic directions observed in plutonic rocks of the batholith without large scale northward transport 3 literal interpretation of the paleolatitudes determined from paleomagnetic directions in upper cretaceous and paleogene marine sedimentary rocks of sloa and bba requires north then south then north transport and a complex motion history between the two allochthons however concordant paleolatitudes are indicated by some sedimentary rocks while coeval or younger sedimentary rocks of the same allochthon have discordant paleolatitudes coupled with recent documentations of compaction shallowing of paleomagnetic inclination in other marine sedimentary rocks these inconsistencies suggest that paleolatitudes derived from most of the marine sedimentary rocks of sloa and bba are biased towards low paleolatitudes by compaction shallowing

elevation changes of ice caps in the canadian arctic archipelago 1 precise repeat airborne laser surveys were conducted over the major ice caps in the canadian arctic archipelago in the spring of 1995 and 2000 in order to measure elevation changes in the region our measurements reveal thinning at lower elevations below 1600 m on most of the ice caps and glaciers but either very little change or thickening at higher elevations in the ice cap accumulation zones recent increases in precipitation in the area can account for the slight thickening where it was observed but not for the thinning at lower elevations for the northern ice caps on the queen elizabeth islands thinning was generally 0 5 m yr 1 which is consistent with what would be expected from the warm temperature anomalies in the region for the 5 year period between surveys and appears to be a continuation of a trend that began in the mid 1980s farther south however on the barnes and penny ice caps on baffin island this thinning was much more pronounced at over 1 m yr 1 in the lower elevations here temperature anomalies were very small and the thinning at low elevations far exceeds any associated enhanced ablation the observations on barnes and perhaps penny are consistent with the idea that the observed thinning is part of a much longer term deglaciation as has been previously suggested for barnes ice cap on the basis of the regional relationships between elevation and elevation change in our data the 1995 2000 mass balance for the archipelago is estimated to be 25 km3 yr 1 of ice which corresponds to a sea level increase of 0 064 mm yr 1 this places it among the more significant sources of eustatic sea level rise though not as substantial as the greenland ice sheet alaskan glaciers or the patagonian ice fields

calibration of an ice core glaciochemical sea salt record with sea ice variability in the canadian arctic correlation between glaciochemical time series from an ice core collected on devon ice cap nunavut canada and gridded time series of sea ice concentrations reveals statistically significant inverse relationships between sea salt concentrations mainly na m g 2 and cl in the ice core and sea ice cover in baffin bay over the period 1980 97 an empirical orthogonal function eof analysis performed on all major ions shows that the dominant mode of glaciochemical variability eof1 represents a sea salt signal which correlates best with sea ice concentration in baffin bay on a seasonal basis the strongest and most spatially extensive anticorrelations are found in baffin bay during the fall followed by spring summer and winter these results support the notion that increased open water conditions in baffin bay during the stormy seasons fall and spring promote increased production transport and deposition of sea salt aerosols on devon ice cap comparison of ice core time series of eof1 d 18 o and melt percentage with air temperatures recorded in upernavik greenland suggests that ice cover variations in baffin bay over the past 145 years were dynamically rather than thermodynamically controlled with periods of strengthened cyclonic circulation leading to increased open water conditions and a greater sea salt flux on devon ice cap

greenland ice sheet surface melt extent and trends 1960 2010 observed meteorological data and a high resolution 5 km model were used to simulate greenland ice sheet surface melt extent and trends before the satellite era 1960 79 and during the satellite era through 2010 the model output was compared with passive microwave satellite observations of melt extent for 1960 2010 the average simulated melt extent was 15 5 for the period 1960 72 simulated melt extent decreased by an average of 6 whereas 1973 2010 had an average increase of 13 with record melt extent in 2010 the trend in simulated melt extent since 1972 indicated that the melt extent in 2010 averaged twice that in the early 1970s the maximum and mean melt extents for 2010 were 52 9 5 10 5 km 2 and 28 5 2 10 5 km 2 respectively due to higher than average winter and summer temperatures and lower than average winter precipitation for 2010 the southwest greenland melt duration was 41 60 days longer than the 1960 2010 average while the northeast greenland melt duration was up to 20 days shorter from 1960 to 1972 the melting period with a 10 melt extent decreased by an average of 3 days a 1 after 1972 the period increased by an average of 2 days a 1 indicating an extended melting period for the ice sheet of about 70 days 40 and 30 days in spring and autumn respectively

preservation of glaciochemical time series in snow and ice from the penny ice cap baffin island a detailed investigation of major ion concentrations of snow and ice in the summit region of penny ice cap pic was performed to determine the effects of summer melt on the glaciochemical time series while ion migration due to meltwater percolation makes it difficult to confidently count annual layers in the glaciochemical profiles time series of these parameters do show good structure and a strong one year spectral component suggesting that annual to biannual signals are preserved in pic glaciochemical records

an ice marginal δ18o record from barnes ice cap baffin island canada barnes ice cap baffin island canada is a remnant of the laurentide ice sheet that separated from it about 8500 years ago owing to recession of the ice cap during the holocene pleistocene age i

spatial and temporal variability in the snowpack of a high arctic ice cap implications for mass change measurements interpretation of ice mass elevation changes observed by satellite altimetry demands quantification of the proportion of elevation change which is attributable to variations in firn densification detailed stratigraphic logging of snowpack structure and density was carried out at 1k m intervals along a 47 km transect on devon ice cap canada in spring pre melt and autumn during after melt 2004 and 2006 to characterize seasonal snowpack variability across the full range of snow facies simultaneous meteorological measurements were gathered spring pre melt snowpacks show low variability over large spatial scales with low magnitude changes in density the end of summer autumn density profiles show high variability in both 2004 and 2006 with vastly different melt regimes generating dissimilar patterns of ice layer formation over the two melt seasons dye tracing experiments from spring to autumn 2006 reveal that vertical and horizontal distribution of meltwater flow within and below the annual snowpack is strongly affected by the pre existing often subtle stratigraphic interfaces in the snowpack rather than its bulk properties strong interannual variability suggests that using a simple relationship between air temperature elevation and snowpack densification to derive mass change from measurements of elevation change across high arctic ice caps may be misguided melt timing and duration are important extrinsic factors governing snowpack densification and ice layer formation in summer rather than averaged air temperatures

accumulation storage and release of atmospheric mercury in a glaciated arctic catchment baffin island canada abstract part of the mercury hg entering arctic ecosystems is believed to be delivered from the atmosphere in snow but this source is difficult to quantify due to limited spatial coverage of hg data in snow here we evaluate the atmospheric deposition storage and release of total hg thg and monomethyl mercury mehg on penny ice cap baffin island this is the first such study in the baffin region thg levels in snow and firn mean 0 61 ng l 1 are comparable to those on high arctic glaciers but mehg levels are noticeably higher mean 0 11 ng l 1 we find little evidence of springtime enhancement of hg deposition in snow attributable to atmospheric mercury depletion events estimated accumulation rates of thg and mehg in firn are 0 33 and 0 03 g m 2 a 1 higher than on high arctic glaciers possibly due to higher precipitation on southern baffin island the estimated net annual release of thg by glacial snow and ice melt is small thg 1 86 kg mehg 0 18 kg in the study area geogenic hg contributions from sediment loaded glacial meltwater could be as large or larger than those from melting ice mehg levels are very low in meltwater fed streams and lakes 0 01 ng l 1 suggesting that mehg is released early in the snowmelt season and or quickly removed from meltwater by various processes summer melt and percolation on penny ice cap remobilise hg in firn after deposition and this imposes resolution limits of at least 3 years on depositional trends inferred from ice cores

holocene glaciation and climate evolution of baffin island arctic canada abstract lake sediment cores and cosmogenic exposure ce dates constrain the pattern of deglaciation and evolution of climate across baffin island since the last glacial maximum lgm ce dating of erratics demonstrates that the northeastern coastal lowlands became ice free ca 14 ka as the laurentide ice sheet lis receded from its lgm margin on the continental shelf coastal lakes in southeastern baffin island started to accumulate sediment at this time whereas initial lacustrine sedimentation was delayed by two millennia in the north reduced organic matter in lake sediment deposited during the younger dryas chron and the lack of a glacial readvance at that time suggest cold summers and reduced snowfall ice retreated rapidly after 11 ka but was interrupted by a widespread readvance of both the lis and local mountain glaciers 9 6 ka cockburn substage a second readvance occurred just before 8 ka during a period of unusually cold summers corresponding to the 8 2 ka cold event in the greenland ice sheet most local glaciers were behind their present margins before 7 ka and in some instances much earlier although the foxe dome of the lis continued to slowly retract toward the present day barnes ice cap throughout the holocene pollen in lake sediments is rare and dominated by exotic sources prior to 12 ka subsequently grass tundra became established followed by modern tundra vegetation ca 8 ka with subtle changes in pollen assemblages in the late holocene lake primary productivity peaked in the early holocene before terrestrial vegetation or marine surface waters reached their apparent thermal maxima lacustrine marine and glacial proxies all reflect significant late holocene cooling the onset of neoglaciation is well dated in lacustrine records at ca 6 ka with intensification after 2 5 ka the expansion of local glaciers during the little ice age represents the most extensive advance since 7 ka we suggest that the replacement of atlantic surface waters by cold low salinity arctic ocean water coupled with the steady reduction of summer insolation resulted in a significant positive sea ice feedback that produced a larger late holocene summer temperature depression over the baffin region than in the pacific sector of the arctic

melt features in ice cores from site j southern greenland some implications for summer climate since ad 1550 horizontal and vertical distributions of melt features ice layers were examined using two ice cores 206 6 and 101 5 m deep 1 m apart from site j 66 51 9 n 46 15 9 w 2030 m a s l the temperature at 10 m was 16 3 c we observed 2804 melt features with a total thickness of 30 32 m in the 206 6 m core corresponding to 16 4 by volume of the ice equivalent core length horizontal distribution of melt features was examined by correlating melt feature thicknesses in the two cores the correlation coefficient was 0 71 n 514 for each melt feature in the two cores it was maximum for data passed through 5 and 40 year low pass filters a significant relationship p 0 005 n 36 was obtained for the vertical distribution of melt features and the june temperature on the west coast of greenland jakobshavn using this june temperatures at jakobshavn since 1550 were estimated there are three periods 1685 1705 1835 70 and 1933 45 during which mean june temperatures clearly decreased when they were estimated to he 0 1 0 4 and 0 2 c lower than the average for the whole period 1550 1989 the first two cold periods have been identified in melt features of the dye 3 and devon island ice cores and in a tree ring profile from yukon territory canada melt feature percentages in the site j ice core have increased since about 1945 probably reflecting summer temperature warming on the ice sheet

six decades of glacial mass loss in the canadian arctic archipelago the canadian arctic archipelago comprises multiple small glaciers and ice caps mostly concentrated on ellesmere and baffin islands in the northern ncaa northern canadian arctic archipelago and southern parts scaa southern canadian arctic archipelago of the archipelago respectively because these glaciers are small and show complex geometries current regional climate models using 5 to 20 km horizontal resolution do not properly resolve surface mass balance patterns here we present a 58 year 1958 2015 reconstruction of daily surface mass balance of the canadian arctic archipelago statistically downscaled to 1 km from the output of the regional climate model racmo2 3 at 11 km by correcting for biases in elevation and ice albedo the downscaling method significantly improves runoff estimates over narrow outlet glaciers and isolated ice fields since the last two decades ncaa and scaa glaciers have experienced warmer conditions 1 1 c resulting in continued mass loss of 28 2 11 5 and 22 0 4 5 gt year respectively more than doubling 11 9 gt year and doubling 11 9 gt year the pre 1996 average while the interior of ncaa ice caps can still buffer most of the additional melt the lack of a perennial firn area over low lying scaa glaciers has caused uninterrupted mass loss since the 1980s in the absence of significant refreezing capacity this indicates inevitable disappearance of these highly sensitive glaciers

inorganic carbon in a high latitude estuary fjord system in canada s eastern arctic abstract rapidly changing conditions in the arctic can have a significant impact on biogeochemical cycles and can be particularly important in high latitude estuary fjord systems with abundant and diverse freshwater sources this study provides a first look into the inorganic carbon system and its relation to freshwater sources in cumberland sound in the east coast of baffin island nunavut canada these data contribute to the very limited set of inorganic carbon measurements in high latitude estuary fjord systems during the ice free conditions in august 2011 the meteoric freshwater fractions mw in the upper 40 m ranged from 11 to 21 and no sea ice melt sim was present in the sound surface waters were undersaturated with pco 2 260 and 300 atm and dic and ta ranged between 1779 and 1966 mol dic kg 1 and 1922 and 2140 mol ta kg 1 respectively aragonite saturation ar state ranged from 1 9 in the surface to 1 4 in the subsurface waters data show decreasing ta and ar with increasing mw fraction and suggest that cumberland sound waters would become aragonite undersaturated ar 18 o 19 2 and ta 174 mol ta kg 1 end members indicate mw was most likely a mixture of river water and glacial melt in august 2012 mw fractions at the surface were between 8 and 11 5 and sim between 7 and 23 significant interannual variability of summertime sim could potentially result in ar undersaturation

stable carbon isotope ratios from archaeological charcoal as palaeoenvironmental indicators abstract the potential to provide environmental proxies using stable carbon isotopes from modern and archaeological charcoal is explored experiments on modern podocarpus yellowwoods show that 13 c values of stems branches and charcoal preserve proxy environmental conditions including rainfall humidity and temperature an additional experiment showed that combustion temperature affects the carbon isotope signature of charcoal burning at 450 c to 500 c depletes 13 c values with respect to the original wood but the charcoal retains the seasonal and inter annual isotopic trends recorded during the growth of the tree the 13 c of podocarpus charcoal from three levels from the middle stone age site of sibudu cave kwazulu natal south africa was compared with modern analogues from two different environments seaton park kwazulu natal and the baviaans kloof eastern cape other environmental proxies from levels dated from 70 ka and 48 ka show that environmental conditions changed from warmer and wetter to colder and drier and finally becoming warmer and drier the isotope data is consistent with this reconstruction the results from this series of experiments indicate that it is possible to obtain meaningful palaeoenvironmental information from 13 c values of archaeological charcoal

extent and duration of antarctic surface melting the extent and duration of surface melting on the antarctic ice shelves and margins of the antarctic ice sheet are derived from satellite passive microwave data for 1978 87 the occurrence of surface melting in daily maps of t b is indicated by a marked increase in microwave brightness temperature t b which is caused by moisture in the near surface firn t b increases of more than 30 deg above the annual mean t b are chosen to indicate melting most antarctic surface melting occurs during december and january the observed melting is correlated with regional air temperatures but some melt patterns also appear to be related to katabatic wind effects the correlations suggest that the surface melting in antarctica increases about 3 5 10 6 d km 2 per degree of summer temperature increase the surface melt index duration times area of melting calculated for antarctica is 24 10 6 d km 2 averaged over nine summers the observed inter annual and regional variability is large surface melting was most extensive during the 1982 83 summer 36 10 6 d km 2 and least extensive during the 1985 86 summer 15 10 6 d km 2 the data indicate a decline in surface melting over the 9 years but meaningful inferences regarding trends in surface melting are precluded by the large inter annual variability

penny ice cap cores baffin island canada and the wisconsinan foxe dome connection two states of hudson bay ice cover ice cores from penny ice cap baffin island canada provide continuous holocene records of oxygen isotopic composition 18 o proxy for temperature and atmospheric impurities a time scale was established with the use of altered seasonal variations some volcanic horizons and the age for the end of the wisconsin ice age determined from the grip and gisp2 ice cores there is pre holocene ice near the bed the change in 18 o since the last glacial maximum lgm is at least 12 5 per mil compared with an expected value of 7 per mil suggesting that lgm ice originated at the much higher elevations of the then existing foxe dome and foxe ridge of the laurentide ice sheet the lgm 18 o values suggest thick ice frozen to the bed of hudson bay

early holocene delevelling and deglaciation of the cumberland sound region baffin island arctic canada radiocarbon cosmogenic surface exposure and relative sea level data are used to examine deglaciation and glacioisostatic adjustment of cumberland sound and cumberland peninsula and southeastern baffin island in the context of a new model for the glacial history of the eastern canadian arctic over the last decade a multidisciplinary effort on easternmost baffin island has documented far greater ice expansion during the last glacial maximum than previously believed including low gradient glaciation in marine embayments coexisting with ice free or thin cold based ice on adjacent upland crystalline terrain this study documents that the cumberland sound region underwent about twice as much glacioisostatic movement during the last glacial maximum as shown in previous reconstructions however the loading impact of the laurentide ice sheet and local glaciation on adjacent cumberland peninsula was limited the mapped zero isoline on emergence shows that postglacial eustatic rise exceeded glacial isostatic uplift for much of the eastern peninsula a finding that is consistent with that of prior studies the center of loading and the major source of glacial ice for the entire cumberland sound region were foxe basin and western baffin island strandlines dated 10 500 and 8500 1 4 c yr b p show that slow deglaciation of cumberland sound was punctuated by at least two periods of faster grounding line retreat coastal southeastern cumberland peninsula was deglaciated before 9400 1 4 c yr b p and other areas surrounding cumberland sound were deglaciated after ca 9000 1 4 c yr b p these land areas experienced relatively slow glacial retreat and restrained rebound cosmogenic surface exposure ages on glacially scoured bedrock support the 1 4 c based inferred timing for deglaciation of the sound although inheritance of nuclides from prior exposure is evident in samples indicating limited bedrock erosion in many areas for central cumberland sound a rapid rise of relative sea level of 4 5 m 100 1 4 c yr 4 6 m 100 yr and a half life for crustal response of 720 1 4 c yr 1400 yr are consistent with those values obtained in other studies of isostatic adjustment around the edges of the former northern hemisphere ice sheets where lithospheric influences were relatively dominant

visual stratigraphic dating of the gisp2 ice core basis reproducibility and application annual layers are visible in the greenland ice sheet project 2 ice core from central greenland allowing rapid dating of the core changes in bubble and grain structure caused by near surface primarily summertime formation of hoar complexes provide the main visible annual marker in the holocene and changes in cloudiness of the ice correlated with dustiness mark wisconsinan annual cycles both markers are evident and have been intercalibrated in early holocene ice layer counts are reproducible between different workers and for one worker at different times with 1 error over century length times in the holocene reproducibility is typically 5 in wisconsinan ice age ice and decreases with increasing age and depth cumulative ages from visible stratigraphy are not significantly different from independent ages of prominent events for ice older than the historical record and younger than approximately 50 000 years visible observations are not greatly degraded by brittle ice or many other core quality problems allowing construction of long consistently sampled time series high accuracy requires careful study of the core by dedicated observers

signal and noise in four ice core records from the agassiz ice cap ellesmere island canada details of the last millennium for stable isotopes melt and solid conductivity four ice cores and two deep pit auger sequences from the top of the agassiz ice cap have been variously analysed for o18 ecm solid conductivity and ice melt layer stratigraphy the high resolution data are presented on time scales covering about the last 1000 years the 8 time series are compared and the noise examined in terms of snow drifting and wind scouring of winter snow from the higher exposed parts of flow lines the highly scoured 8 records reflect a mixture of summer biased conditions and the amount of winter scoured snow sites away from the ridges and domes are not scoured the signal part of the scoured and unscoured sites is obtained by stacking averaging normalized series the stacked unscoured series of 8 and accumulation are compared to similar stacked series from central greenland for the last century of annual averages the comparison is surprisingly good suggesting that at these resolutions low noise 8 series have some coherence over fairly large distances the percentage melt

postglacial environmental succession of nettilling lake baffin island canadian arctic inferred from biogeochemical and microfossil proxies abstract nettilling lake baffin island nunavut is currently the largest lake in the canadian arctic archipelago despite its enormous size this freshwater system remains little studied until the present day existing records from southern baffin island indicate that in the early postglacial period the region was submerged by the postglacial tyrell sea due to isostatic depression previously exerted by the laurentide ice sheet however these records are temporally and spatially discontinuous relying on qualitative extrapolation this paper presents the first quantitative reconstruction of the postglacial environmental succession of the nettilling lake basin based on a 8300 yr long high resolution sedimentary record our multi proxy investigation of the glacio isostatic uplift and subsequent changes in paleosalinity and sediment sources is based on analyses of sediment fabric elemental geochemistry xrf diatom assemblage composition as well as on the first diatom based oxygen isotope record from the eastern canadian arctic results indicate that the nettilling lake basin experienced a relatively rapid and uniform marine invasion in the early holocene followed by progressive freshening until about 6000 yr bp when limnological conditions similar to those of today were established our findings present evidence for deglacial processes in the foxe basin that were initiated at least 400yrs earlier than previously thought

reconstruction of the historical temperature trend from measurements in a medium length borehole on the lomonosovfonna plateau svalbard a medium length ice core was drilled at the ice divide on the lomonosovfonna plateau 1230 m a s l svalbard in may1997 as part of this project temperature measurements were performed in the 120 m deep borehole at this site the ice thickness based on radar measurements is 126 5 m and the mean annual accumulation rate is 380 kg m 3 the measurements over the 15 120 m depth interval show a nearly isothermal profile with a mean value of 2 8 c and a standard deviation of 0 2 c the measurements reveal a temperature minimum at approximately 70 m depth and a temperature gradient of 0 011 0 004 c m 1 near the bottom the temperature minimum and relatively low temperature gradient cannot be explained in terms of a steady state climate numerical calculations with a simple onedimensional diffusion advection model show that the temperature increased at a maximum rate of 0 02 0 025 k a 1 over the last 100 years the total temperature increase amounting to 2 0 3 0 k forcing the model with the observed record at svalbard airport revealed that in the 19th century the surface temperature was at most 2 5 k lower and that the instrumental observations started during a period with temperatures comparable to the end of the 19th century the data are of particular interest for historical simulations since often no other temperature data are available in polar areas

glacier velocities and dynamic discharge from the ice masses of baffin island and bylot island nunavut canada speckle tracking of alos palsar fine beam data from 2007 2011 are used to determine the surface motion of major ice masses on baffin island and bylot island in the southern canadian arctic archipelago glacier velocities are low overall with peaks of 100 m a 1 and means of 20 60 m a 1 common along the main trunk of many outlet glaciers peak velocities on penny and bylot island ice caps tend to occur near the mid sections of their primary outlet glaciers while the fastest velocities on all other glaciers usually occur near their termini due to relatively large accumulation areas draining through narrow outlets estimates of ice thickness at the fronts of tidewater terminating glaciers are combined with the velocity measurements to determine a regional dynamic discharge rate of between 17 mt a 1 and 108 mt a 1 with a mid point estimate of 55 mt a 1 revising downward previous approximations these velocities can be used as inputs for glacier flow models and provide a baseline dataset against which

surface melt induced acceleration of greenland ice sheet flow ice flow at a location in the equilibrium zone of the west central greenland ice sheet accelerates above the midwinter average rate during periods of summer melting the near coincidence of the ice acceleration with the duration of surface melting followed by deceleration after the melting ceases indicates that glacial sliding is enhanced by rapid migration of surface meltwater to the ice bedrock interface interannual variations in the ice acceleration are correlated with variations in the intensity of the surface melting with larger increases accompanying higher amounts of summer melting the indicated coupling between surface melting and ice sheet flow provides a mechanism for rapid large scale dynamic responses of ice sheets to climate warming

recent air temperature changes in the arctic a detailed analysis of the spatial and temporal changes in mean seasonal and annual surface air temperature sat in the arctic is presented mainly for the period 1951 2005 mean seasonal and annual homogenized and complete series of sat from up to 35 arctic stations were used in the analysis the focus in this paper is on the 11 years 1995 2005 a period which saw dramatic warming in the arctic 1 c for annual values in relation to the 1951 90 mean an abrupt rise in sat occurred in the mid 1990s and was most pronounced in autumn and winter 2 c the greatest warming in the period 1995 2005 occurred in the pacific and canadian regions 1 c while the lowest was in the siberian region 0 82 c this period has been the warmest since at least the 17th century in particular 2005 was an exceptionally warm year 2 c in relation to the 1951 90 mean and was warmer than 1938 the warmest year in the 20th century the seasonal and annual trends of the areally averaged arctic sat for the periods 1936 2005 1951 2005 and 1976 2005 are positive with the exception of winter and autumn for the first period the majority of trends calculated for the last two periods are statistically significant while there are varying opinions about the forces driving the present warming it seems likely that the marked rise in sat in the mid 1990s mainly from 1994 to 1995 was caused by i a set of natural factors ii non linear effects of greenhouse gas loading or iii the combined effect of these two groups of factors

modeling the microwave emission of bubbly ice applications to blue ice and superimposed ice in the antarctic and arctic passive microwave remote sensing is extensively used in polar regions to study the cryosphere to better understand the measured signal above continental ice covered areas our objective is to estimate the microwave emission of bubbly ice surfaces using a physically based multilayer electromagnetic model i e the dense media radiative transfer multilayer model dmrt ml this model accounts for ice layers with variable amounts of bubbles each layer is fully described by its temperature density thickness and air bubble radius simulations are performed using in situ data from two distinct sites one in antarctica on a coastal blue ice area near the cap prud homme cph station in adelie land and the other on the barnes ice cap bic located on baffin island in the arctic on this ice cap superimposed ice with seasonal snow cover about 1 m thick was observed in both cases several ice parameters were measured or estimated and the others were optimized results of the dmrt ml simulations are compared with in situ surface based radiometer sbr measurements at 11 19 and 37 ghz at both horizontal and vertical polarizations results show that dmrt ml is able to reproduce the microwave emission of different ice types with good accuracy when accounting for ice bubbles final hbox rmse 7 37 hbox k and 8 42 k for cph and bic respectively compared with rmse ranging from 15 k to 40 k without bubbles comparisons between sbr measurements and satellite data for the bic also show good agreement hbox rmse 4 1 hbox k for 19 and 37 ghz both polarizations

formation of ice layers by infiltration and refreezing of meltwater melt layer frequency and magnitude in polar and sub polar ice cores have been interpreted as measures of past summer temperature and calibrations have been proposed relating frequency of occurrence of ice layers in ice cores to past summer temperatures but observations in the percolation facies in greenland and an analysis of the combined processes of meltwater infiltration and refreezing of water in snow indicate that in addition to unusually high rates of meltwater input formation of ice layers will also be facilitated by unusually cold initial conditions or early onset of melt uniform warming of both summer and winter conditions has the opposite effect and suppresses ice layer formation in favor of uniform wetting and refreezing of the snowpack numerical modeling of infiltration and refreezing at a stratigraphic fine to coarse transition allows quantification of the effects of significant parameters initial temperature grain size and density contrast across the stratigraphic transition water input rate and minimum impermeable layer thickness calculations are made to distinguish threshold values of parameters at which infiltration progresses faster than refreezing resulting in a break through of water across the stratigraphic transition from values leading to the formation of an ice layer when refreezing progresses faster than infiltration

a new greenland ice core chronology for the last glacial termination 1 we present a new common stratigraphic timescale for the north greenland ice core project ngrip and grip ice cores the timescale covers the period 7 9 14 8 kyr before present and includes the bolling allerod younger dryas and early holocene periods we use a combination of new and previously published data the most prominent being new high resolution continuous flow analysis cfa impurity records from the ngrip ice core several investigators have identified and counted annual layers using a multiparameter approach and the maximum counting error is estimated to be up to 2 in the holocene part and about 3 for the older parts these counting error estimates reflect the number of annual layers that were hard to interpret but not a possible bias in the set of rules used for annual layer identification as the grip and ngrip ice cores are not optimal for annual layer counting in the middle and late holocene the timescale is tied to a prominent volcanic event inside the 8 2 kyr cold event recently dated in the dye 3 ice core to 8236 years before a d 2000 b2k with a maximum counting error of 47 years the new timescale dates the younger dryas preboreal transition to 11 703 b2k which is 100 150 years older than according to the present grip and ngrip timescales the age of the transition matches the gisp2 timescale within a few years but viewed over the entire 7 9 14 8 kyr section there are significant differences between the new timescale and the gisp2 timescale the transition from the glacial into the bolling interstadial is dated to 14 692 b2k the presented timescale is a part of a new greenland ice core chronology common to the dye 3 grip and ngrip ice cores named the greenland ice core chronology 2005 gicc05 the annual layer thicknesses are observed to be log normally distributed with good approximation and compared to the early holocene the mean accumulation rates in the younger dryas and bolling periods are found to be 47 2 and 88 2 respectively

a glacial isostatic adjustment model for the central and northern laurentide ice sheet based on relative sea level and gps measurements the thickness and equivalent global sea level contribution of an improved model of the central and northern laurentide ice sheet is constrained by 24 relative sea level histories and 18 present day gps measured vertical land motion rates the final model termed laur16 is derived from the ice 5g model by holding the timing history constant and iteratively adjusting the thickness history in four regions of northern canada in the final model the last glacial maximum lgm thickness of the laurentide ice sheet west of hudson bay was 3 4 3 6 km conversely east of hudson bay peak ice thicknesses reached 4 km the ice model thicknesses inferred for these two regions represent respectively a 30 per cent decrease and an average 20 25 per cent increase to the load thickness relative to the ice 5g reconstruction which is generally consistent with other recent studies that have focussed on laurentide ice sheet history the final model also features peak ice thicknesses of 1 2 1 3 km in the baffin island region a modest reduction relative to ice 5g and unchanged thicknesses for a region in the central canadian arctic archipelago west of baffin island vertical land motion predictions of the final model fit observed crustal uplift rates well after an adjustment is made for the elastic crustal response to present day ice mass changes of regional ice cover the new laur16 model provides more than a factor of two improvement of the fit to the rsl data 2 measure of misfit and a factor of nine improvement to the fit of the gps data mean squared error measure of fit compared to the ice 5g starting model laur16 also fits the regional rsl data better by a factor of two and gives a slightly better fit to gps uplift rates than the recent ice 6g model the volume history of the laur16 reconstruction corresponds to an up to 8 m reduction in global sea level equivalent compared to ice 5g at lgm

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

palaeoenvironmental history of the last six centuries in the nettilling lake area baffin island canada a multi proxy analysis the baffin island region in the eastern canadian arctic has recently experienced a rapid warming possibly unprecedented in millennia to investigate theresponse of freshwater environments to this warming and place it in a secular perspective we analyzed a 90 cm long sediment core from nettilling lake the largest lake of the canadian arctic archipelago the core was taken from a part of the lake basin that receives meltwater and sediment inputs from thenearby penny ice cap the core time scale established using 137cs and palaeomagnetic techniques spans an estimated 600 years a multi proxy approachwas used to document changes in the physical chemical and biological properties of the sediments we found evidence for a relatively warm period mid late 15th century to mid late 16th century during the early part of the little ice age lia characterized by high sedimentation rates and laminations this was followed by colder drier and windier conditions corresponding to the coldest phase of lia and coinciding with the latest and most extensiveperiod of regional ice cap expansion early 16th to late 19th centuries a rapid warming occurred at the beginning of the 20th century variations intitanium ti content in the core a proxy for detrital sediment inputs showed good agreement with reconstructed secular variations in summer meltrates on penny ice cap between the mid 14th century and the present day providing supporting evidence for a climatic hydrological connection betweenthe ice cap and nettilling lake

temperature and precipitation history of the arctic as the planet cooled from peak warmth in the early cenozoic extensive northern hemisphere ice sheets developed by 2 6 ma ago leading to changes in the circulation of both the atmosphere and oceans from not vert similar2 6 to not vert similar1 0 ma ago ice sheets came and went about every 41 ka in pace with cycles in the tilt of earth s axis but for the past 700 ka glacial cycles have been longer lasting not vert similar100 ka separated by brief warm interglaciations when sea level and ice volumes were close to present the cause of the shift from 41 ka to 100 ka glacial cycles is still debated during the penultimate interglaciation not vert similar130 to not vert similar120 ka ago solar energy in summer in the arctic was greater than at any time subsequently as a consequence arctic summers were not vert similar5 c warmer than at present and almost all glaciers melted completely except for the greenland ice sheet and even it was reduced in size substantially from its present extent with the loss of land ice sea level was about 5 m higher than present with the extra melt coming from both greenland and antarctica as well as small glaciers the last glacial maximum lgm peaked not vert similar21 ka ago when mean annual temperatures over parts of the arctic were as much as 20 c lower than at present ice recession was well underway 16 ka ago and most of the northern hemisphere ice sheets had melted by 6 ka ago solar energy reached a summer maximum 9 higher than at present not vert similar11 ka ago and has been decreasing since then primarily in response to the precession of the equinoxes the extra energy elevated early holocene summer temperatures throughout the arctic 1 3 c above 20th century averages enough to completely melt many small glaciers throughout the arctic although the greenland ice sheet was only slightly smaller than at present early holocene summer sea ice limits were substantially smaller than their 20th century average and the flow of atlantic water into the arctic ocean was substantially greater as summer solar energy decreased in the second half of the holocene glaciers re established or advanced sea ice expanded and the flow of warm atlantic water into the arctic ocean diminished late holocene cooling reached its nadir during the little ice age about 1250 1850 ad when sun blocking volcanic eruptions and perhaps other causes added to the orbital cooling allowing most arctic glaciers to reach their maximum holocene extent during the warming of the past century glaciers have receded throughout the arctic terrestrial ecosystems have advanced northward and perennial arctic ocean sea ice has diminished here we review the proxies that allow reconstruction of quaternary climates and the feedbacks that amplify climate change across the arctic we provide an overview of the evolution of climate from the hot house of the early cenozoic through its transition to the ice house of the quaternary with special emphasis on the anomalous warmth of the middle pliocene early quaternary warm times the mid pleistocene transition warm interglaciations of marine isotope stages 11 5e and 1 the stage 3 interstadial and the peak cold of the last glacial maximum

ice velocity changes on penny ice cap baffin island since the 1950s predicting the velocity response of glaciers to increased surface melt is a major topic of ongoing research with significant implications for accurate sea level rise forecasting in this study we u

sharply increased mass loss from glaciers and ice caps in the canadian arctic archipelago the canadian arctic archipelago contains one third of the global volume of land ice outside the ice sheets but its contribution to sea level change is largely unknown gardner et al use three independent techniques to reveal that mass loss from the archipelago was 92 12 gigatonnes per year in 2007 09 about three times greater than in 2004 06 and coincident with warmer summer temperatures the record is too short to allow a firm conclusion on longer term trends but it is clear that the canadian arctic archipelago is a significant contributor to sea level rise mountain glaciers and ice caps are contributing significantly to present rates of sea level rise and will continue to do so over the next century and beyond1 2 3 4 5 the canadian arctic archipelago located off the northwestern shore of greenland contains one third of the global volume of land ice outside the ice sheets6 but its contribution to sea level change remains largely unknown here we show that the canadian arctic archipelago has recently lost 61 7 gigatonnes per year gt yr 1 of ice contributing 0 17 0 02 mm yr 1 to sea level rise our estimates are of regional mass changes for the ice caps and glaciers of the canadian arctic archipelago referring to the years 2004 to 2009 and are based on three independent approaches surface mass budget modelling plus an estimate of ice discharge smb d repeat satellite laser altimetry icesat and repeat satellite gravimetry grace all three approaches show consistent and large mass loss estimates between the periods 2004 2006 and 2007 2009 the rate of mass loss sharply increased from 31 8 gt yr 1 to 92 12 gt yr 1 in direct response to warmer summer temperatures to which rates of ice loss are highly sensitive 64 14 gt yr 1 per 1 k increase the duration of the study is too short to establish a long term trend but for 2007 2009 the increase in the rate of mass loss makes the canadian arctic archipelago the single largest contributor to eustatic sea level rise outside greenland and antarctica

climatic analysis of sea ice variability in the canadian arctic from operational charts 1980 2004 we present a complete climatic analysis of sea ice conditions in the canadian arctic based on digitized operational charts from the canadian ice service for the period 1980 2004 the seasonal climatology spatial variance and linear trends in total ice concentrations ct were calculated the maximum reduction rate in ct was found in the beaufort sea 24 decade 1 and in the davis strait labrador sea region 18 decade 1 during spring and summer empirical orthogonal function eof analysis performed on monthly ct deviations yielded four significant eof modes explaining 32 of the total variance the spatial pattern temporal behaviour and seasonality of these four eof modes are discussed and correlated with fields of sea level pressure surface winds surface air temperature and sea surface temperature monthly anomalies these results point to the dominant influence of the north atlantic oscillation on ct decadal anomalies during the cold season while climate variability in the pacific influences ct variations in the beaufort sea region during spring summer

summer melt rates on penny ice cap baffin island past and recent trends and implications for regional climate 1 at latitude 67 n penny ice cap on baffin island is the southernmost large ice cap in the canadian arctic yet its past and recent evolution is poorly documented here we present a synthesis of climatological observations mass balance measurements and proxy climate data from cores drilled on the ice cap over the past six decades 1953 to 2011 we find that starting in the 1980s penny ice cap entered a phase of enhanced melt rates related to rising summer and winter air temperatures across the eastern arctic presently 70 to 100 volume of the annual accumulation at the ice cap summit is in the form of refrozen meltwater recent surface melt rates are found to be comparable to those last experienced more than 3000 years ago enhanced surface melt water percolation and refreezing have led to a downward transfer of latent heat that raised the subsurface firn temperature by 10 c at 10 m depth since the mid 1990s this process may accelerate further mass loss of the ice cap by pre conditioning the firn for the ensuing melt season recent warming in the baffin region has been larger in winter but more regular in summer and observations on penny ice cap suggest that it was relatively uniform over the 2000 m altitude range of the ice cap our findings are consistent with trends in glacier mass loss in the canadian high arctic and regional sea ice cover reduction reinforcing the view that the arctic appears to be reverting back to a thermal state not seen in millennia

physical properties of the p96 ice core from penny ice cap baffin island canada and derived climatic records 1 ice cores from nonpolar environments are being developed as valuable paleoclimatic resources however the recognition of a climatic signal and the development of timescales in those ice cores are both difficult due to heavy summer melting a 177 91 m long ice core p96 was drilled in such a high melt area from penny ice cap baffin island canada in 1996 the core covers the holocene period and has pre holocene ice near the bed the purpose of this work is to investigate the physical properties of the ice and to show how these properties can be interpreted in terms of climatic signals visual stratigraphic observations and measurements of crystal size and c axis orientation were performed using conventional techniques melt features provided a clear picture of holocene summer climatic changes a warmer period prior to 2 ka the little ice age and the modern warming trend the crystalline structure displayed normal grain growth down to 50 m and recrystallization below this in the 0 50 m depth interval periodical variations in crystal size were observed and are attributed to the difference of time for which the ice was soaked in meltwater every season these variations made it possible to develop an annual record the c axis fabric evolution displayed a change in the ice flow pattern from divergent above 140 m depth to shear dominated flow below that the initial fabric of superimposed ice shows a preferred c axis distribution normal to the surface the fabric is shown to be important for reconstructing mass balance chronologies from ice cores drilled in areas of superimposed ice formation these physical properties provide information on climatic change

thinning of the south dome of barnes ice cap arctic canada over the past two decades between 1970 and 1984 ground surveys were carried out along a flowline extending from the top of the south dome of barnes ice cap to the margin over this time span the ice cap thinned an average of 1 7 m or 0 12 m yr 1 by comparing the 1984 survey with elevations derived from satellite imagery in 2006 we find that it has now thinned an additional 16 8 7 7 m or an average of 0 76 0 35 m yr 1 laser altimeter profiles show that between 2004 and 2006 the thinning rate was 1 0 0 14 m yr 1 a correlation between mass balance and mean summer temperature at nearby weather stations developed over the period of the ground surveys permits independent estimates of the thinning rate these estimates are in excellent agreement with those based on satellite imagery the acceleration in thinning is consistent with meteorological records documenting an increase in the number of positive degree days atmospheric warming in the region

glaciological reconnaissance of an ice core drilling site penny ice cap baffin island analyse climatique sur 10 4 ans d une carotte de glace de 20 m prelevee dans l ile de baffin on a etudie les teneurs en oxygene en tritium le ph la conductivite electrolytique la concentration en ions majeurs et en particules une carotte proche a ete analysee de son contenu en pollen l epaisseur et la morphologie de la couche ont ete mesurees par echo radar

recent contributions of glaciers and ice caps to sea level rise satellite measurements of earth s gravity field show that the mass loss of glaciers and ice caps contributed to sea level rise by approximately 0 4 millimetres per year between 2003 and 2010 the extent to which mass loss from ice covered land areas contributes to sea level rise is not known accurately in part because previous global estimates use different techniques for glaciers ice caps and ice sheets the gravity recovery and climate experiment grace satellite has provided monthly measurements of the global gravity field since 2002 using grace data jacob et al assess regional mass loss between 2003 and 2010 and conclude that mass loss from ice covered land areas contributed almost 1 5 mm per year to the sea level rise estimated mass loss from the high mountains of asia was negligible in contrast to some other reports glaciers and ice caps gics are important contributors to present day global mean sea level rise1 2 3 4 most previous global mass balance estimates for gics rely on extrapolation of sparse mass balance measurements1 2 4 representing only a small fraction of the gic area leaving their overall contribution to sea level rise unclear here we show that gics excluding the greenland and antarctic peripheral gics lost mass at a rate of 148 30 gt yr 1 from january 2003 to december 2010 contributing 0 41 0 08 mm yr 1 to sea level rise our results are based on a global simultaneous inversion of monthly grace derived satellite gravity fields from which we calculate the mass change over all ice covered regions greater in area than 100 km2 the gic rate for 2003 2010 is about 30 per cent smaller than the previous mass balance estimate that most closely matches our study period2 the high mountains of asia in particular show a mass loss of only 4 20 gt yr 1 for 2003 2010 compared with 47 55 gt yr 1 in previously published estimates2 5 for completeness we also estimate that the greenland and antarctic ice sheets including their peripheral gics contributed 1 06 0 19 mm yr 1 to sea level rise over the same time period the total contribution to sea level rise from all ice covered regions is thus 1 48 0 26 mm 1 which agrees well with independent estimates of sea level rise originating from land ice loss and other terrestrial sources6

revised estimates of recent mass loss rates for penny ice cap baffin island based on 2005 2014 elevation changes modified for firn densification repeat airborne or satellite measurements of surface elevation over ice caps are often used tocalculate glacier wide surface mass changes over time however these measurements typically do notacco