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

combined oceanic and atmospheric influences on net accumulation on devon ice cap nunavut canada an annual net accumulation history of the high elevation region of devon ice cap nunavut canada was reconstructed for the period 1963 2003 using five shallow firn cores annual net accumulation decreased significantly after 1989 to explain variability in the reconstructed annual net accumulation record monthly and seasonal moisture source probabilities were calculated for gridcells throughout the arctic during 1979 2003 seasonally moisture source probabilities reach a maximum in northern baffin bay in late summer early fall and approach zero throughout the arctic in winter late summer early fall moisture source probabilities were significantly higher around the north open water now polynya during the 4 year period of highest annual net accumulation during the 1979 2003 period 1984 87 than during the 4 year period with the lowest annual net accumulation 1994 97 this is due to both a significant decrease in the sea ice fraction and a significant increase in low elevation atmospheric transport over the now area during the high net accumulation period anomalously low net accumulation and anomalously high firnification rates during the 1989 2003 period suggest that a change in ice dynamics rather than a change in surface mass balance may explain recent ice cap thickening observed by laser altimetry

glacier velocities and dynamic ice discharge from the queen elizabeth islands nunavut canada recent studies indicate an increase in glacier mass loss from the canadian arctic archipelago as a result of warmer summer air temperatures however no complete assessment of dynamic ice discharge from this region exists we present the first complete surface velocity mapping of all ice masses in the queen elizabeth islands and show that these ice masses discharged 2 6 0 8 gt a 1 of ice to the oceans in winter 2012 approximately 50 of the dynamic discharge was channeled through non surge type trinity and wykeham glaciers alone dynamic discharge of the surge type mittie glacier varied from 0 90 0 09 gt a 1 during its 2003 surge to 0 02 0 02 gt a 1 during quiescence in 2012 highlighting the importance of surge type glaciers for interannual variability in regional mass loss queen elizabeth islands glaciers currently account for 7 5 of reported dynamic discharge from arctic ice masses outside greenland

a record of holocene summer climate from a canadian high arctic ice core melt layers in ice cores are formed by melting on the snow pack surface which produces water that percolates down and refreezes in the colder snow layers below melt layers are distinguished by their bubble texture because more ice forms in the snow pack in warm summers than in cool summers the changing concentration with depth of melt layers in snow pits1 2 and ice cores3 5 is an indicator of past summer climate here we report on studies of melt layers in two canadian high arctic surface to bedrock ice cores although changes in elevation of the drill site owing to isostatic depression and uplift may contribute up to 40 of the total climatic signal recorded in the melt layers we interpret their varying concentrations in terms of changing summer temperatures over the past 10 000 years the warmest summers occurred 8 10 kyr ago and the coldest only 150 years ago the summers over the past 100 years have been the warmest for more than 1 000 years but are still not as warm as those of the early holocene the melt layer record is in broad agreement with geological records of glacier retreat during the holocene6 8 indicating that these data also contain information of regional significance

integrated pan arctic melt onset detection from satellite active and passive microwave measurements 2000 2009 1 an integrated pan arctic melt onset data set is generated for the first time by combining estimates derived from active and passive microwave satellite data using algorithms developed for the northern high latitude land surface ice caps large lakes and sea ice the data set yields new insights into the spatial and temporal patterns of mean melt onset date mmod and the associated geographic and topographic controls for example in the terrestrial arctic tree fraction and latitude explain more than 60 of the variance in mmod with the former exerting a stronger influence on mmod than the latter elevation is also found to be an important factor controlling mmod with most of the arctic exhibiting significant positive relationships between mmod and elevation with a mean value of 24 5 m d 1 melt onset progresses fastest over land areas of uniform cover or elevation 40 80 km d 1 or both and slows down in mountainous areas on ice caps and in the forest tundra ecotones over sea ice melt onset advances very slowly in the marginal seas while in the central arctic the rate of advance can exceed 100 km d 1 comparison of the observed mmod with simulated values from the third version of the canadian coupled global climate model showed good agreement over land areas but weaker agreement over sea ice particularly in the central arctic where simulated mmod is about 2 3 weeks later than observed because of a cold bias in simulated surface air temperatures over sea ice

evidence for ice flow prior to trough formation in the martian north polar layered deposits the relative importance of surface mass fluxes and ice flow in shaping the north polar layered deposits npld now or in the past remains a fundamental and open question motivated by observation of an apparent ice divide on gemina lingula also known as titania lobe we propose a two stage evolution leading to the present day topography on that lobe of the npld ice flow approximately balances surface mass fluxes in the first stage but in the second stage ice flow has minimal influence and topography is modified predominantly by the formation of troughs we focus here on evidence for the first stage by testing the fit of topography between troughs to an ice flow model we find that independent model fits on distinct flow paths closely match inter trough topography uniformly over a broad region on gemina lingula with mutually consistent and physically reasonable fitting parameters however our model requires ice to occupy and flow in spaces where troughs currently incise the ice we therefore infer that the troughs and the distribution of mass balance that caused them post date deposition of the inter trough material and its modification by flow because trough formation has apparently altered inter trough topography very little we infer that trough formation must have been rapid in comparison to the still unknown time scale of flow since troughs began to form we view the evidence for past flow as strong but we do not think that topographic evidence alone can be conclusive observations of englacial stratigraphy using orbital sounding radars will yield conclusive tests of our inferred mechanism for the formation of inter trough topography

changes in melt season characteristics on devon ice cap canada and their association with the arctic atmospheric circulation using june august surface meteorological measurements for 2004 10 we found that the duration of the summer melt season at elevations of 1800 1300 and 1000 m a s l on devon ice cap canada increased at a rate of 3 4 p p p 1 respectively the calculated surface melt rate at 1300m a s l increased from 74 to 133 cm w e a 1 between 2007 and 2010 these changes are linked to two types of change in the arctic atmospheric circulation strengthening of the 500 hpa ridge over the arctic in june july resulted in increases in both the advection of warm air into the region and the occurrence of cloud free conditions over the ice cap causing the available melt energy to increase by 4 24 relative to june july 2007 10 mean conditions more frequent southwesterly low pressure systems in august after 2004 accounted for a 12 38 increase in available melt energy relative to the august 2007 10 daily mean due to advection of warm air into the arctic reduced incoming shortwave radiation and increased net longwave radiation this delayed the timing of freeze up by an average of 5 5 days a 1 p

area change of glaciers across northern ellesmere island nunavut between 1999 and 2015 using a variety of optical satellite scenes this study quantifies the change in the areal extent of 1773 glaciers across northern ellesmere island between 1999 and 2015 our results show that the regional ice coverage decreased by 1705 3 km 2 over the 16 year period a loss of 5 9 ice shelves had the greatest losses relative to their size of 42 4 glaciers feeding into ice shelves reduced in area by 4 7 while tidewater glaciers reduced in area by 3 3 marine terminating glaciers with floating ice tongues reduced in area by 4 9 and 19 of these 27 ice tongues disintegrated causing these glaciers to retreat to their grounding lines land terminating glaciers lost 4 9 of their 1999 area including the complete loss of three small ice caps 2 our study highlights the high sensitivity of the ice cover of northern ellesmere island to recent climate warming and the continued losses that are likely to occur in the future in particular the ice masses most susceptible to further losses are marine terminating glaciers with floating termini and small land terminating ice caps at low elevations

a numerical study on hurricane induced storm surge and inundation in charleston harbor south carolina 1 a storm surge and inundation model is configured in charleston harbor and its adjacent coastal region to study the harbor s response to hurricanes the hydrodynamic component of the modeling system is based on the princeton ocean model and a scheme with multiple inundation speed options is imbedded in the model for the inundation calculation historic observations hurricane hugo and its related storm surge and inundation in the charleston harbor region indicate that among three possible inundation speeds in the model taking ct gd 1 2 ct is a terrain related parameter as the inundation speed is the best choice choosing a different inundation speed in the model has effects not only on inundation area but also on storm surge height a nesting technique is necessary for the model system to capture the mesoscale feature of a hurricane and meanwhile to maintain a higher horizontal resolution in the harbor region where details of the storm surge and inundation are required hurricane induced storm surge and inundation are very sensitive to storm tracks twelve hurricanes with different tracks are simulated to investigate how charleston harbor might respond to tracks that are parallel or perpendicular to the coastline or landfall at charleston at different angles experiments show that large differences of storm surge and inundation may have occurred if hurricane hugo had approached charleston harbor with a slightly different angle a hurricane s central pressure radius of maximum wind and translation speed have their own complicated effects on surge and inundation when the hurricane approaches the coast on different tracks systematic experiments are performed in order to illustrate how each of such factors or a combination of them may affect the storm surge height and inundation area in the charleston harbor region finally suggestions are given on how this numerical model system may be used for hurricane induced storm surge and inundation forecasting

anomalous recent growth of part of a large arctic ice cap austfonna svalbard 1 observations from repeat pass airborne laser altimetry acquired in 1996 and 2002 indicate an anomalous positive ice surface elevation change for the central accumulation area of the largest ice cap in the eurasian arctic austfonna eastern svalbard the increase is equivalent to 35 of the long term annual accumulation rate and coincides with the loss of perennial sea ice in the adjacent barents sea which we conclude is the most likely explanation for the increase extrapolation of the observed trends in sea ice decline over the next 50 years suggests large perturbations in the mass balance of other arctic ice masses may be expected

glacier surface temperatures in the canadian high arctic 2000 15 canada s queen elizabeth islands qei contain 14 of the world s glacier and ice cap area sparse in situ measurements indicate that interannual variability in glacier surface mass balance in this region is driven primarily by variations in summer melt and that the annual surface mass balance of four index glaciers has become increasingly negative since 2007 here we use a 16 a record of satellite derived mean summer june august land surface temperatures lst from nasa s moderate resolution imaging spectroradiometer to investigate large scale spatial and temporal variability in the duration and intensity of summer melt across glaciated surfaces in the qei from 2000 to 2015 during this period qei mean summer glacier surface temperatures increased at an average rate of 0 06 0 04 c a 1 for a total of nearly 1 c most of this increase occurred between 2005 and 2012 when mean summer near surface 2 m and upper air 700 hpa temperatures were 1 0 1 2 c higher than the 1948 2015 mean there is a strong correlation between the glacier lst and 700 hpa air temperature records r 0 8 the period 2005 12 when mean summer lsts were anomalously high was likely the warmest period in the region since at least 1948

out of the woods driftwood insights into holocene pan arctic sea ice dynamics the collation of 913 driftwood samples from across the western arctic with spatiotemporal distribution and available provenance data enabled the production of a high resolution proxy based reconstruction of holocene arctic ocean surface current and sea ice dynamics regionally bounded driftwood based sea ice reconstructions studies suggest spatiotemporally complex past arctic sea ice extent and movement however a large scale compilation of holocene arctic driftwood has not previously been developed sparse driftwood in the early holocene 8 2 cal ka b p deglacial period was followed by increased driftwood deposition in the warmer mid holocene 8 2 4 2 cal ka b p characterized by an enhanced transpolar drift tpd 7 cal ka b p leading to sea ice loss through the fram strait driftwood incursion peaks show spatial e w progression from the eurasian archipelagos to greenland and the canadian arctic archipelago suggesting a progressive shift in the orientation of the tpd on centennial millennial time scales and intermediate phases in the arctic oscillation late holocene cooling 4 2 cal ka b p is indicated by increased influx of probably north american picea via a strengthened beaufort gyre bg which enhanced sea ice recirculation starting in the western arctic and progressing eastward in recent millennia 2 cal ka b p a more variable driftwood record alternates between bg and tpd dominance on centennial time scales to further constrain a spatiotemporal reconstruction of variations in holocene ocean current and sea ice dynamics a more definitive determination of driftwood provenance is recommended to build upon the current framework such as through radiogenic isotope tracing and adna analysis

is the high elevation region of devon ice cap thickening devon ice cap nunavut canada has been losing mass since at least 1960 laser altimetry surveys however suggest that the high elevation region 1200m of the ice cap thickened between 1995 and 2000 perhaps because of anomalously high accumulation rates during this period we derive an independent estimate of thickness change in this region by comparing 40 year mean annual net accumulation rates to mean specific outflow rates for 11 drainage basins the area averaged rate of thickness change across the whole region is within error of zero 0 01 0 12m w e a 1 but two drainage basins in the northwest are thickening significantly and two basins in the south are thinning significantly the laser altimetry observations are biased towards the drainage basins where we find thickening recent changes in the rate of accumulation or the rate of firnification cannot explain the observed thickening but decreased ice outflow due to the penetration of neoglacial cooling to and subsequent stiffening of the basal ice may provide an explanation thinning in the south may result from increased ice outflow from basins in which fast flow and basal sliding extend above 1200 m

expanded late wisconsinan ice cap and ice sheet margins in the western queen elizabeth islands arctic canada abstract recent mapping of surficial geology and geomorphology in the western canadian high arctic melville and eglinton islands together with new radiocarbon dates acquired from ice contact raised marine sediments document expanded late wisconsinan ice limits for the northwest laurentide ice sheet and the western innuitian ice sheet an extension of the northwestern margin of the laurentide ice sheet onto eglinton island is proposed based on evidence from till containing erratics derived from the canadian shield and a pattern of meltwater channels indicating ice retreat offshore into m clure strait expansion of the western melville island ice cap part of the western lowland sector of the innuitian ice sheet to its offshore late wisconsinan limit was facilitated by coalescence with the laurentide ice sheet whose buttressing allowed thickening to occur estimates of ice extent and thickness 500 m of the western melville island ice cap are in agreement with high marine limits 70 m asl lateral and proglacial meltwater channels moraines and glaciomarine glaciolacustrine and glaciofluvial deposits indicate radial retreat of the western melville island ice cap onto central highlands after 13 0 cal ka bp older marine limit shorelines on southern eglinton island 13 6 cal ka bp are broadly synchronous with the early and rapid deglaciation of other areas formerly glaciated by the northwestern laurentide ice sheet to the southeast and southwest 14 2 13 6 cal ka bp the collapse of the northwest laurentide ice sheet in m clure strait beginning at 14 2 cal ka bp in addition to prior inferred thinning opens the possibility that it made a significant contribution to meltwater pulse 1a

sensitivity of net mass balance estimates to near surface temperature lapse rates when employing the degree day method to estimate glacier melt glacier mass balance models that employ the degree day method of melt modeling are most commonly driven by surface air temperatures that have been downscaled over the area of interest using digital elevation models and assuming a constant free air lapse rate that is often taken to be the moist adiabatic lapse rate malr 6 58 ck m 1 air temperature lapse rates measured over melting glacier surface are however consistently less steep than free air values and have been shown to vary systematically with lower tropospheric temperatures in this study the implications of including a variable near surface lapse rate in a 26 year 1980 2006 degree day model simulation of the surface mass balance of devon ice cap nunavut canada are examined and compared with estimates derived from surface air temperatures downscaled using a constant near surface lapse rate equal to the measured summer mean 4 98 ck m 1 and the malr our results show that degree day models are highly sensitive to the choice of lapse rate when compared with 23 years of surface mass balance measurements from the northwest sector of the ice cap model estimates are significantly better when surface air temperatures are downscaled using a modeled daily lapse rate rather than a constant lapse equal to either the summer mean or the malr

mass balance of the prince of wales icefield ellesmere island nunavut canada 1 this paper estimates the mass balance of the prince of wales icefield ellesmere island canada averaged over four decades from measurements of surface mass balance smb and iceberg calving shallow ice core net accumulation measurements and annual mass balance stake measurements are used in conjunction with a digital elevation model and knowledge of the location of the dominant moisture source for precipitation over the ice cap to interpolate and extrapolate spatial patterns of smb across the prince of wales icefield the contribution of iceberg calving to the mass balance is calculated from estimates of 1 the annual volume of ice discharged at the major tidewater glacier termini and 2 the annual volume loss or gain due to terminus fluctuations two different approaches to determining the smb conclude that the smb of the ice field is approximately in balance average equals 0 1 0 4 km3 w e a 1 where w e means water equivalent largely because of its proximity to the main year round moisture source that is the smith sound portion of the north open water polynya iceberg calving is a highly significant component of mass loss 1 9 0 2 km3 w e a 1 and is sufficient to make the overall mass balance of the ice field averaged over the period 1963 2003 clearly negative 2 0 45 km3 w e a 1 equivalent to a mean specific mass balance across the ice field of 0 1 m w e a 1 the prince of wales icefield contributes 0 005 mm a 1 to global eustatic sea level rise

glacier extent during the younger dryas and 8 2 ka event on baffin island arctic canada greenland ice cores reveal that mean annual temperatures during the younger dryas yd cold interval about 12 9 to 11 7 thousand years ago ka and the 150 year long cold reversal that occurred 8 2 thousand years ago were 15 and 3 to 4 c colder than today respectively reconstructing ice sheet response to these climate perturbations can help evaluate ice sheet sensitivity to climate change here we report the widespread advance of laurentide ice sheet outlet glaciers and independent mountain glaciers on baffin island arctic canada in response to the 8 2 ka event and show that mountain glaciers during the 8 2 ka event were larger than their yd predecessors in contrast to the wintertime bias of yd cooling we suggest that cooling during the 8 2 ka event was more evenly distributed across the seasons

correlations between glacier properties finding appropriate parameters for global glacier monitoring to develop new strategies for global mass balance monitoring data for the period 1961 90 have been compiled for 80 glaciers with a variety of mass balance and morphological parameters this dataset is significantly larger than that used in previous studies this allows us to check the mass balance data for both strong and weak correlations with different glacier parameters in many cases the strong correlations suggest new approaches to monitoring glaciers on a global scale for example the mass balance at the terminus is strongly correlated with the difference in clevation between the terminus and the glacier s mean clevation these casily measured parameters could be particularly useful in assessing maximum ablation and meltwater potential based on altitudes derived from maps and photographs good correlations also exist between differences in mass balance parameters e g net balance minus terminus balance and several other morphological properties e g clevation range and length equally important the weak correlations demonstrate that some relationships commonly used on individual glaciers are not appropriate whe considering global monitoring strategies for example the correlation between net mass balance and terminus balance is very poor likewise the correlation between the net mass balance and equilibrium line altitude is weak and the correlation between the net mass balance and activity index is almost non existent this suggests that although these elimatically sensitive parameters may be closely related on individual glaciers these same relationships are not reliable as tools for monitoring glaciers on a global scale

seven decades of uninterrupted advance of good friday glacier axel heiberg island arctic canada previous studies reported that good friday glacier had been actively surging in the 1950 60s 1990s and again in 2000 15 based on observations of terminus position change from air photos and satellite imagery we fill the gaps between previous studies and conclude that the glacier has been advancing continuously since 1959 ice surface velocities extracted from optical and synthetic aperture radar satellite images show higher flow rates than on most other marine terminating glaciers in the region this behaviour contrasts with the regional trend of glacier retreat over this period possible explanations involve a delayed response to positive mass balance conditions of the little ice age or a dynamic instability there is however insufficient evidence to attribute this behaviour to classical glacier surging as suggested in previous studies based on present day ice velocity and glacier geometry patterns in the terminus region we reconstruct the evolution of ice motion throughout the advance and suggest that what has previously been interpreted as a surge may instead have been a localised response to small scale perturbations in bedrock topography

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

a five year record of summer melt on eurasian arctic ice caps abstract climatologies and annual anomaly patterns 2000 04 of melt season duration and dates of melt onset freeze up on eurasian arctic ice masses were derived from quick scatterometer quikscat backscatter data severnaya zemlya russia has later melt onset earlier freeze up and shorter melt seasons than svalbard norway novaya zemlya russia in all three archipelagos 2001 was the longest melt season and 2000 was the shortest anomalously long short melt seasons on svalbard were associated with negative positive sea ice concentration anomalies along the north coast in june and august annual mean melt duration was strongly correlated with the mean june august ncep ncar reanalysis 850 hpa air temperature allowing reconstruction of melt durations for the period of 1948 2005 the 2000 04 pentad had the second or third longest mean melt duration of all pentads in the 1950 2004 epoch while the 1950 54 pentad probably had the longest integration of these results with previous results from gre

last interglacial arctic warmth confirms polar amplification of climate change the warmest millennia of at least the past 250 000 years occurred during the last interglaciation when global ice volumes were similar to or smaller than today and systematic variations in earth s orbital parameters aligned to produce a strong positive summer insolation anomaly throughout the northern hemisphere the average insolation during the key summer months m j j was ca 11 above present across the northern hemisphere between 130 000 and 127 000 years ago with a slightly greater anomaly 13 over the arctic greater summer insolation early penultimate deglaciation and intensification of the north atlantic drift combined to reduce arctic ocean sea ice allow expansion of boreal forest to the arctic ocean shore across vast regions reduce permafrost and melt almost all glaciers in the northern hemisphere insolation amplified by key boundary condition feedbacks collectively produced last interglacial summer temperature anomalies 4 5 c above present over most arctic lands significantly above the average northern hemisphere anomaly the last interglaciation demonstrates the strength of positive feedbacks on arctic warming and provides a potentially conservative analogue for anticipated future greenhouse warming

mass balance of glaciers other than the ice sheets small glaciers appear to have been at equilibrium or shrinking very slightly during 1961 90 according to analysis of an essentially compl ete set of published measurements simple calculations give an average annual mass balance of 195 59 mm a 1 water equivalent but this is too low because of systema tic errors eglect of internal accumulation is respon sible for some tens of millime ters of under esti mate uneven spatial coverage with fewer measurements where mass balances are less negative accounts for about 50 mm a 1 of underestimate this figure derives from spatial interpolati on based on global data on ice extent and on an analysis of correlations between balance time series the eorrelogram shows exponential decay the scale length being about 600 km the largest bias is due to a newly detec ted dependence of mass balance on glacier size among the 231 measured glaciers many arc small and belong to a restricted size range in which balance is negativ e but much of the small glacier extent is accounted for by larger glac iers in a size range where balance is indisti ngui shable from zero correct ing for this size bias increases the average balance to 35 89 mm a i inspection of time series for 1940 95 251 glaciers shows that mass balance was least negative during the 1960s and has varied in broad agreementvith northern hemisphere temperature anomalies smaller small glaciers a 16 km2 appear to be more sensitive than larger small glaciers to changes in thermal forci ng the small glaci er contribution to sea level rise implied by this asse ssment is only 0 06 0 32 mm a i consistent with glaciers in general mak i ng little or no contri bution to sea level change during 1961 90

meltwater percolation impermeable layer formation and runoff buffering on devon ice cap canada the retention of meltwater in the accumulation area of the greenland ice sheet and other arctic ice masses buffers their contribution to sea level change however sustained warming also results in impermeable ice layers or ice slabs that seal the underlying pore space here we use a 1 d physically based high resolution model to simulate the surface mass balance smb percolation refreezing ice layer formation and runoff from across the high elevation area of devon ice cap canada from 2001 to 2016 we vary the thickness of the impermeable ice layer at which underlying firn becomes inaccessible to meltwater thick near surface ice layers are established by an initial deep percolation the formation of decimetre ice layers and the infilling of interleaving pore space the cumulative smb increases by 48 by varying impermeable layer thickness between 0 01 and 5 m within this range we identify narrower range 0 25 1 m that can simulate both the temporal variability in smb and the observed near surface density structure across this range cumulative smb variation is limited to 6 and 45 49 of mass retention takes place within the annually replenished snowpack our results indicate cooler summers after intense mid 2000s warming have led to a partial replenishment of pore space

changes in accumulation area firn stratigraphy and meltwater flow during a period of climate warming devon ice cap nunavut canada 1 to document climate driven changes in firn stratigraphy and their implications for meltwater flow patterns within firn on the devon ice cap nunavut during the 21st century summer warming 500 mhz ground penetrating radar gpr surveys were conducted along a 40 km transect in each spring from 2007 to 2012 these linear gpr surveys were supplemented by four 190 m by 100 m gpr grid surveys and 36 firn cores increased meltwater percolation and infiltration ice formation associated with high surface melt rates since 2005 modified the firn stratigraphy substantially over a horizontal distance of nearly 30 km the most dramatic change involved the growth of a thick ice layer within the firn body this layer grew primarily by upward accretion over an initial widespread ice layer formed during summer 2005 it thickened by between 0 5 and 4 5 m over the study period and filled much of the pore volume in the upper part of the firn reducing vertical percolation of meltwater into deeper sections of the firn and thus the water storage potential of much of the firn reservoir heterogeneous percolation of surface meltwater promoted by rolling topography played an important role in meltwater infiltration and drainage encouraging lateral flow at the tops of small hills and ponding and refreezing of meltwater beneath surface depressions

baffin island snow extent sensitivity insights from a regional climate model 1 recent modeling efforts suggest that the little ice age lia onset could be explained by a series of four large decadally spaced volcanic eruptions at that time glaciers on baffin island advanced and did not retreat until the past century perhaps due to arctic and north atlantic ocean sea ice feedbacks to try to determine what parameters sustain snow cover we investigate the relative impacts of changes in radiation and advection on minimum summer snow extent over baffin island we used the weather research and forecasting wrf model to run eight 6 month long april september 10 km resolution simulations in which we varied boundary condition temperatures solar radiation and sea ice cover although the control run underestimated cloud cover and thus produced an exaggerated diurnal 2 m temperature cycle the relative changes of snow extent show that wrf accurately simulates snow expansion into the same regions as during the lia with an average temperature decrease from current temperatures by 3 9 1 1 k it only requires one season for the model to lower the snowline by comparable elevation changes seen during the descent into the lia wrf s maximum snow line sensitivity is 7 k km within the range of the typically assumed lapse rate of 5 7 k km in the canadian arctic thus if a shift in the arctic climate greatly expanded sea ice coverage following large volcanic eruptions this would have been enough to perpetuate an ice sheet on baffin island throughout the lia

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

glacier fluctuations during the past 2000 years abstract a global compilation of glacier advances and retreats for the past two millennia grouped by 17 regions excluding antarctica highlights the nature of glacier fluctuations during the late holocene the dataset includes 275 time series of glacier fluctuations based on historical tree ring lake sediment radiocarbon and terrestrial cosmogenic nuclide data the most detailed and reliable series for individual glaciers and regional compilations are compared with summer temperature and when available winter precipitation reconstructions the most important parameters for glacier mass balance in many cases major glacier advances correlate with multi decadal periods of decreased summer temperature in a few cases such as in arctic alaska and western canada some glacier advances occurred during relatively warm wet times the timing and scale of glacier fluctuations over the past two millennia varies greatly from region to region however the number of glacier advances shows a clear pattern for the high mid and low latitudes and hence points to common forcing factors acting at the global scale globally during the first millennium ce glaciers were smaller than between the advances in 13th to early 20th centuries ce the precise extent of glacier retreat in the first millennium is not well defined however the most conservative estimates indicate that during the 1st and 2nd centuries in some regions glaciers were smaller than at the end of 20th early 21st centuries other periods of glacier retreat are identified regionally during the 5th and 8th centuries in the european alps in the 3rd 6th and 9th centuries in norway during the 10th 13th centuries in southern alaska and in the 18th century in spitsbergen however no single period of common global glacier retreat of centennial duration except for the past century has yet been identified in contrast the view that the little ice age was a period of global glacier expansion beginning in the 13th century or earlier and reaching a maximum in 17th 19th centuries is supported by our data the pattern of glacier variations in the past two millennia corresponds with cooling in reconstructed temperature records at the continental and hemispheric scales the number of glacier advances also broadly matches periods showing high volcanic activity and low solar irradiance over the past two millennia although the resolution of most glacier chronologies is not enough for robust statistical correlations glacier retreat in the past 100 150 years corresponds to the anthropogenic global temperature increase many questions concerning the relative strength of forcing factors that drove glacier variations in the past 2 ka still remain

a comparison of recent elevation change estimates of the devon ice cap as measured by the icesat and envisat satellite altimeters we have used surface elevation measurements acquired by the ice cloud and land elevation satellite geoscience laser altimeter system glas and envisat radar altimeter 2 ra 2 satellite altimeters to assess the elevation change of the 13 700 km2 devon ice cap dic in arctic canada between 2002 and 2008 we present algorithms for the retrieval of elevation change rates over ice caps using data acquired from these satellites a comparison of glas elevation data to those acquired by the ra 2 shows reasonable agreement between the two instruments the root mean square elevation change difference was 56 cm and the correlation coefficient between the two data sets was 0 68 using only ra 2 elevation measurements which are spatially and temporally more continuous we determined the elevation change rate of the areas of the dic where the surface geometry allows the ra 2 retracker to maintain lock this includes most of the dic excluding large parts of the eastern half of the ice cap the elevation change rate was found to be insignificant given a statistical estimate of the measurement error 0 09 0 29 m a we also present an assessment of the regional variations of the dic elevation change including a significant 0 71 0 49 m a elevation change rate of the 1980 km2 western arm furthermore we present evidence of a localized 2 m drop in the surface elevation of the south croker bay glacier during summer 2007 this drop is apparent within both satellite data sets and we interpret this signal to reflect a sudden speedup of the glacier

abrupt onset of the little ice age triggered by volcanism and sustained by sea ice ocean feedbacks 1 northern hemisphere summer temperatures over the past 8000 years have been paced by the slow decrease in summer insolation resulting from the precession of the equinoxes however the causes of superposed century scale cold summer anomalies of which the little ice age lia is the most extreme remain debated largely because the natural forcings are either weak or in the case of volcanism short lived here we present precisely dated records of ice cap growth from arctic canada and iceland showing that lia summer cold and ice growth began abruptly between 1275 and 1300 ad followed by a substantial intensification 1430 1455 ad intervals of sudden ice growth coincide with two of the most volcanically perturbed half centuries of the past millennium a transient climate model simulation shows that explosive volcanism produces abrupt summer cooling at these times and that cold summers can be maintained by sea ice ocean feedbacks long after volcanic aerosols are removed our results suggest that the onset of the lia can be linked to an unusual 50 year long episode with four large sulfur rich explosive eruptions each with global sulfate loading 60 tg the persistence of cold summers is best explained by consequent sea ice ocean feedbacks during a hemispheric summer insolation minimum large changes in solar irradiance are not required

cryosphere response resolves conflicting evidence for the timing of peak holocene warmth on baffin island arctic canada abstract holocene paleotemperature reconstructions across the western arctic suggest strong spatial variations in air temperature despite zonally uniform northern hemisphere insolation forcing although most paleotemperature reconstructions across the eastern canadian arctic place the holocene thermal maximum 3 kyr after peak summer insolation other records indicate maximum summer warmth was coincident with peak summer insolation to address this discrepancy we use radiocarbon inventories in plants and rocks recently exposed by receding ice caps to reconstruct early holocene changes in glacier dimensions a reliable proxy for summer air temperature fourteen radiocarbon ages from newly exposed plants in growth position collected at the margins of eight retreating ice caps on baffin island indicate ice caps expanded 9 3 0 3 ka and remained over these sites until recent summer warming indicating peak early holocene summer warmth occurred prior to 9 3 ka we test this conclusion using in situ cosmogenic 14c in situ 14c inventories in rocks at four sites with dated plants in situ 14c production simulations using realistic holocene ice cover histories constrained by plant 14c ages show that measured in situ 14c concentrations are consistent with centuries to millennia of pre 9 3 ka exposure followed by continuous ice burial the combination of plant and in situ 14c data provide firm evidence that the eastern canadian arctic experienced peak holocene summer warmth prior to 9 3 ka consistent with peak summer insolation followed by continuously colder summers until modern warming

source area and rupture parameters of the 31 december 1881 mw 7 9 car nicobar earthquake estimated from tsunamis recorded in the bay of bengal 1 on the morning of 31 december 1881 a submarine earthquake beneath the andaman islands generated a tsunami with a maximum crest height of 0 8 m that was recorded by eight tide gauges surrounding the bay of bengal since the earthquake occurred 8 years before the construction of the world s first teleseismic recording seismometer little has been known about its rupture parameters or location waveform and amplitude modeling of the tsunami indicate that it was generated by a mw 7 9 0 1 rupture on the india andaman plate boundary resulting in 10 60 cm of uplift of the island of car nicobar the rupture consisted of two segments the northern 40 km long segment is separated from the southern 150 km long segment by a 100 km region corresponding to the westward projection of the west andaman spreading center the main rupture occurred between 8 5 n and 10 n with a total area of 150 km 60 km dipping 20 e with a mean slip of 2 7 m the recurrence time for 1881 type events is estimated to be 114 200 years on the basis of inferred gps convergence rates and inferred plate closure vectors although slip partitioning in the region may extend this estimate by as much as 30

glacier specific ablation rate derived by remote sensing measurements 1 the specific ablation rate in a transect of storstrommen a large outlet glacier from the northeast greenland ice sheet is derived by combining airborne laser altimetry measurements with emergence submergence velocities derived from satellite synthetic aperture radar interferometry insar and airborne ice sounding radar measurement of ice thickness the results are compared with in situ point observations of ablation measured at poles drilled into the glacier considering the different measurement periods for the different data sets the agreement between derived and observed ablation rates is satisfactory the new method of deriving specific mass balance particularly ablation rate by remote sensing measurements alone has the potential to substantially increase the density of observational based ablation rates on ice sheet and ice cap margins

iceberg calving rates from northern ellesmere island ice caps canadian arctic 1999 2003 optical satellite imagery was used to estimate glacier surface velocities and iceberg calving rates from agassiz and western grant ice caps nunavut canada between 1999 and 2003 the largest mean annual surface velocities ranged from 400 to 700 m a 1 but velocities in the 100 200 m a 1 range were common summer velocities were up to an order of magnitude larger than annually averaged velocities the highest velocity 1530 m a 1 was measured on the floating tongue of lake tuborg glacier between 19 july and 19 august 2001 calving rates from individual glaciers varied by up to a factor of two between successive years summer calving rates were 2 8 times larger than annual average rates the average ratio of the calving flux due to terminus volume change to that due to ice flow through the glacier terminus was 0 81 for the annual rates and 1 71 for summer rates the estimated mean annual calving rate from agassiz ice cap in the period 1999 2002 was 0 67 0 15 km 3 a 1 o f which 54 emanated from eugenie glacier alone this total rate is similar to a previously estimated calving rate from devon ice cap