extension of global creepex definition ms mb to local studies md ml the case of the italian region creepex defined as the systematic deviation of the magnitude of a single earthquake from the linear orthogonal regression between local magnitude ml and coda duration magnitude md calculated for the whole region is used as a measure of the frequency content of the seismic sources in the italian region predominantly high frequency events are found in the two areas of quaternary tectonic shortening in north central italy and in the calabrian arc this result confirmed by two independent statistical tests is in agreement with the global pattern obtained from the study of the regression between body wave magnitude mb and surface wave magnitude ms systematic shift to high frequencies in the energy release of seismic sources located in subduction zones and to low frequencies in zones of spreading the analysis of the correlation between the patterns of heat flow and of seismic source spectral properties indicates that these source properties in general do not reflect thermal conditions in the lithosphere but rather represent the result of tectonic processes

temporal and spatial changes of laika glacier canadian arctic since 1959 inferred from satellite remote sensing and mass balance modelling the retreat of laika glacier 4 4 km 2 part of a small ice cap situated on coburg island canadian arctic archipelago is analyzed using field data satellite remote sensing and mass balance modelling we present a methodology for merging various data types and numerical models and investigate the temporal and spatial changes of a remote glacier during the past five decades a glacier mass balance and surface evolution model is run for the period 1959 2006 forced with in situ weather observations and climate re analysis data era 40 narr the model is calibrated using the ice volume change observed between 1959 and 1971 and measured seasonal mass balances calculated glacier surface elevation is validated against icesat glas altimeter data and aster derived elevation landsat derived glacier outlines are used to validate calculated ice extent the piedmont tongue of laika glacier has retreated considerably and is in a state of disintegration the modelled glacier mass balance between 1959 and 2006 was 0 41 m w e a 1 on average model results indicate a significant trend towards higher mass balance gradients a complete wastage of laika glacier by 2100 is predicted by model runs based on climate scenarios

springtime north pacific oscillation and summer sea ice in the beaufort sea we investigate the linkage between the spring april june north pacific oscillation npo and the following summer sea ice in the beaufort sea a positive npo is characterized by an intensified and northeastward extended aleutian low a strong beaufort high and enhanced easterly winds in the beaufort sea concomitantly while the deepening east asian trough steers more cyclones from siberia to the sub polar pacific and thus fewer cyclones into the western arctic ocean a weak polar vortex and weak baroclinicity in the beaufort sea does not favor cyclone activity in addition the east asian trough enhances warm air advection from the pacific to the northwestern america the spring npo accounts for 29 of interannual variability of the following september sea ice cover in the beaufort sea and can be used as a potential predictor for ice melting in the beaufort sea during a positive npo the strong easterly winds over the beaufort sea enhance ice advection and reduce ice thickness on the synoptic scale there are more occurrences of the pack ice becoming detached from the coast due to the strong easterly winds moreover increases in shortwave radiation and longwave radiations accelerate the ice melting

the mass balance of circum arctic glaciers and recent climate change the sum of winter accumulation and summer losses of mass from glaciers and ice sheets net surface mass balance varies with changing climate in the arctic glaciers and ice caps excluding the greenland ice sheet cover about 275 000 km2of both the widely glacierized archipelagos of the canadian norwegian and russian high arctic and the area north of about 60 n in alaska iceland and scandinavia since the 1940s surface mass balance time series of varying length have been acquired from more than 40 arctic ice caps and glaciers most arctic glaciers have experienced predominantly negative net surface mass balance over the past few decades there is no uniform recent trend in mass balance for the entire arctic although some regional trends occur examples are the increasingly negative mass balances for northern alaska due to higher summer temperatures and increasingly positive mass balances for maritime scandinavia and iceland due to increased winter precipitation the negative mass balance of most arctic glaciers may be a response to a step like warming in the early twentieth century at the termination of the cold little ice age arctic ice masses outside greenland are at present contributing about 0 13 mm yr 1to global sea level rise

modeling global sea ice with a thickness and enthalpy distribution model in generalized curvilinear coordinates abstract a parallel ocean and ice model poim in generalized orthogonal curvilinear coordinates has been developed for global climate studies the poim couples the parallel ocean program pop with a 12 category thickness and enthalpy distribution ted sea ice model although the poim aims at modeling the global ocean and sea ice system the focus of this study is on the presentation implementation and evaluation of the ted sea ice model in a generalized coordinate system the ted sea ice model is a dynamic thermodynamic model that also explicitly simulates sea ice ridging using a viscous plastic rheology the ted model is formulated such that all the metric terms in generalized curvilinear coordinates are retained following the pop s structure for parallel computation the ted model is designed to be run on a variety of computer architectures parallel serial or vector when run on a computer cluster with 10 parallel processors the parallel performance of the poim is close to that of a correspon

processes of buildup and retreat of the greenland ice sheet sensitivity experiments were conducted to study the influence of several physical processes on the evolution of the greenland ice sheet over the last 250 000 years the experiments were carried out by means of a three dimensional thermodynamical model the mass balance is modeled by a surface energy balance model this means that variations in orbital parameters following from the astronomical milankovitch theory can be incorporated in the ablation calculations it is shown that with regard to the greenland ice sheet variations in shortwave radiation are only of minor importance for the changes in volume over time calculations of the various components of the energy balance under glacial and interglacial conditions show that the changes in absorbed shortwave radiation resulting from changes in orbital parameters are considerably smaller than the variations in the sensible heat flux caused by temperature variations thermodynamics are only of importance for the volume changes of the ice sheet if the climate is on average stable over a long period in between 110 kyr b p and 20 kyr b p the ice volume increased slowly due to the cooling of the ice which resulted in a higher effective viscosity and thus a thicker ice sheet the long response time of the thermodynamics means that the thermodynamics cannot play a crucial role during transition from a glacial to a deglacial period which occur typically within several thousands of years the mass balance height feedback has an important function in the buildup of the ice sheet after a warm period like the eemian without isostatic bedrock compensation the ablation will remain very high in some marginal parts yielding a considerably smaller ice sheet volume for the last glacial period

sea ice response to an extreme negative phase of the arctic oscillation during winter 2009 2010 3 the long term annual mean arctic slp field features an anticyclone centered over the northern beaufort sea known as the beaufort sea high bsh and a trough of low pressure extending from the icelandic low northeastward into the kara sea associated surface winds drive the clockwise beaufort gyre ice motion and the transpolar drift stream tds representing ice motion from the siberian coast across the arctic and then into the north atlantic through fram strait when the winter ao is in its positive mode slp over the icelandic low region and extending into the arctic is anomalously low and the bsh is weak promoting a cyclonic counter clockwise sea ice circulation anomaly this is expressed as decreased ice transport from the beaufort sea westward across the dateline into the chukchi sea increased ice transport out of the arctic ocean through fram strait and increased transport of ice away from the siberian coast leaving open water areas that foster new iceformation rigoretal 2002 bypromotingmorethinice in spring the positive ao sets the stage for negative summer ice extent anomalies conversely during a negative ao phase slp is above normal over the arctic most prominent in the vicinity of the icelandic low ice motion tends to have an anticyclonic clockwise anomaly ice flow through fram strait is reduced and the beaufort gyre is stronger leading to enhanced ice transport from the western to the eastern arctic where ice thickens by ridging and rafting against the siberian coast the stronger beaufort gyre also sequesters and thickens ice in the canada basin collectively these processes favor survival of sea ice through summer

a local magnitude scale for new zealand earthquakes abstract new procedures have been used since 1977 for assigning local earthquake magnitudes in new zealand based on a slightly modified form of richter9s definition and derived from amplitude distance relations determined from new zealand earthquakes the magnitudes for all crustal earthquakes and for subcrustal earthquakes in or north of the main seismic region are determined using a formula for geometric spreading which is appropriate to head wave propagation for subcrustal earthquakes south of the main seismic region they are determined assuming body wave propagation inelastic attenuation needs to be taken into account for subcrustal earthquakes south of the main seismic region and when paths from crustal earthquakes pass through a region which includes the zone of recent volcanism in the center of the north island

vertical structure and energetics of the western pacific teleconnection pattern abstractthe western pacific wp pattern characterized by north south dipolar anomalies in pressure over the far east and western north pacific is known as one of the dominant teleconnection patterns in the wintertime northern hemisphere composite analysis reveals that monthly height anomalies exhibit baroclinic structure with their phase lines tilting southwestward with height in the lower troposphere the anomalies can thus yield not only a poleward heat flux across the climatological thermal gradient across the strong pacific jet but also a westward heat flux across the climatological thermal gradient between the north pacific and the cooler asian continent the resultant baroclinic conversion of available potential energy ape from the climatological mean flow contributes most efficiently to the ape maintenance of the monthly wp pattern acting against strong thermal damping effects by anomalous heat exchanges with the underlying ocean and anomalous precipitation in the subtropics and by the effec

coupled wind forced controls of the bering chukchi shelf circulation and the bering strait throughflow ekman transport continental shelf waves and variations of the pacific arctic sea surface height gradient abstract we develop a conceptual model of the closely co dependent bering shelf bering strait and chukchi shelf circulation fields by evaluating the effects of wind stress over the north pacific and western arctic using atmospheric reanalyses current meter observations satellite based sea surface height ssh measurements hydrographic profiles and numerical model integrations this conceptual model suggests bering strait transport anomalies are primarily set by the longitudinal location of the aleutian low which drives oppositely signed anomalies at synoptic and annual time scales synoptic time scale variations in shelf currents result from local wind forcing and remotely generated continental shelf waves whereas annual variations are driven by basin scale adjustments to wind stress that alter the magnitude of the along strait meridional pressure gradient in particular we show that storms centered over the bering sea excite continental shelf waves on the eastern bering shelf that carry northward velocity anomalies northward through bering strait and along the chukchi coast the integrated effect of these storms tends to decrease the northward bering strait transport at annual to decadal time scales by imposing cyclonic wind stress curl over the aleutian basin and the western subarctic gyre ekman suction then increases the water column density through isopycnal uplift thereby decreasing the dynamic height sea surface height and along strait pressure gradient storms displaced eastward over the gulf of alaska generate an opposite set of bering shelf and aleutian basin responses while ekman pumping controls canada basin dynamic heights proshutinsky et al 2002 we do not find evidence for a strong relation between beaufort gyre sea surface height variations and the annually averaged bering strait throughflow over the western chukchi and east siberian seas easterly winds promote coastal divergence which also increases the along strait pressure head as well as generates shelf waves that impinge upon bering strait from the northwest

two circulation regimes of the wind driven arctic ocean the major goal of this paper is to demonstrate the existence in the arctic ocean of two regimes of wind forced circulation we simulated the vertically averaged currents sea level heights and ice drift in the arctic ocean from 1946 to 1993 using a two dimensional wind forced barotropic model that includes frictional coupling between the ocean and ice the model has a spatial resolution of 55 5 km and is driven by winds river runoff and an imposed but realistic sea level slope between the pacific and the atlantic oceans there is a good agreement between velocities from observed buoy motions and velocities of modeled ice drift even though the model lacks ocean baroclinicity and ice thermodynamics the results indicate that wind driven motion in the central arctic alternates between anticyclonic and cyclonic circulation with each regime persisting for 5 7 years based upon our analysis of the modeled sea level and ice motion anticyclonic wind driven motion in the central arctic appeared during 1946 1952 1958 1963 1972 1979 and 1984 1988 and cyclonic motion appeared during 1953 1957 1964 1971 1980 1983 and 1989 1993 shifts from one regime to another are forced by changes in the location and intensity of the icelandic low and the siberian high the two regimes may help explain the significant basin scale changes in the arctic s temperature and salinity structure observed recently the great salinity anomaly and the variability of ice conditions in the arctic ocean

teleconnections in the geopotential height field during the northern hemisphere winter abstract contemporaneous correlations between geopotential heights on a given pressure surface at widely separated points on earth referred to as teleconnections in this paper are studied in an attempt to identify and document recurrent spatial patterns which might be indicative of standing oscillations in the planetary waves during the northern hemisphere winter with time scales on the order of a month or longer a review of existing literature on the subject reveals the existence of at least four such patterns the north atlantic and north pacific oscillations identified by walker and bliss 1932 a zonally symmetric seesaw between sea level pressures in polar and temperature latitudes first noted by lorenz 1951 and what we will refer to as the pacific north american pattern which has been known to operational long range forecasters in this country since the 1950 s a data set consisting of nmc monthly mean sea level pressure and 500 mb height analyses for a 15 year period is used as a basis fo

relating glacier mass balance to meteorological data using a seasonal sensitivity characteristic we propose to quantify the climate sensitivity of the mean specific balance b of a glacier by a seasonal sensitivity characteristic ssc the ssc gives the dependence of b on monthly anomalies in temperature and precipitation it is calculated from a mass balance model we show and discuss examples for franz josef glacier new zealand nigardsbreen norway hintereisferner austria peyto glacier canadian rockies abramov glacier kirghizstan and white glacier canadian arctic with regard to the climate sensitivity of b the sscs clearly show that summer temperature is the most important factor for glaciers in a dry climate for glaciers in a wetter climate spring and fall temperatures also make a significant contribution to the overall sensitivity the ssc is a 2 12 matrix multiplying it with monthly perturbations of temperature and precipitation for a particular year yields an estimate of the balance for that year we show that with this technique mass balance series can be re constructed from long meteorological records or from output of atmospheric models

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

dipole anomaly in the winter arctic atmosphere and its association with sea ice motion abstract this paper identified an atmospheric circulation anomaly dipole structure anomaly in the arctic atmosphere and its relationship with winter sea ice motion based on the international arctic buoy program iabp dataset 1979 98 and datasets from the national centers for environmental prediction ncep and the national center for atmospheric research ncar for the period 1960 2002 the dipole anomaly corresponds to the second leading mode of eof of monthly mean sea level pressure slp north of 70 n during the winter season october march and accounts for 13 of the variance one of its two anomalous centers is stably occupied between the kara sea and laptev sea the other is situated from the canadian archipelago through greenland extending southeastward to the nordic seas the dipole anomaly differs from one described in other papers that can be attributed to an eastward shift of the center of action of the north atlantic oscillation the finding shows that the dipole anomaly also differs from

seasonal ice loss in the beaufort sea toward synchrony and prediction the seasonal evolution of sea ice loss in the beaufort sea during 1979 2012 is examined focusing on differences between eastern and western sectors two stages in ice loss are identified the day of opening doo is defined as the spring decrease in ice concentration from its winter maximum below a value of 0 8 areal concentration the day of retreat dor is the summer decrease below 0 15 concentration we consider three aspects of the subject i e i the long term mean ii long term linear trends and iii interannual variability we find that in the mean doo occurs earliest in the eastern beaufort sea ebs owing to easterly winds which act to thin the ice there relative to the western beaufort sea wbs where ice has been generally thicker there is no significant long term trend in ebs doo although wbs doo is in fact trending toward earlier dates this means that spatial differences in doo across the beaufort sea have been shrinking over the past 33 years i e these dates are becoming more synchronous a situation which may impact human and marine mammal activity in the area retreat dates are also becoming more synchronous although with no statistical significance over the studied time period finally we find that in any given year an increase in monthly mean easterly winds of 1 m s during spring is associated with earlier summer dor of 6 15 days offering predictive capability with 2 4 months lead time

what drove the dramatic retreat of arctic sea ice during summer 2007 1 a model study has been conducted of the unprecedented retreat of arctic sea ice in the summer of 2007 it is found that preconditioning anomalous winds and ice albedo feedback are mainly responsible for the retreat arctic sea ice in 2007 was preconditioned to radical changes after years of shrinking and thinning in a warm climate during summer 2007 atmospheric changes strengthened the transpolar drift of sea ice causing more ice to move out of the pacific sector and the central arctic ocean where the reduction in ice thickness due to ice advection is up to 1 5 m more than usual some of the ice exited fram strait and some piled up in part of the canada basin and along the coast of northern greenland leaving behind an unusually large area of thin ice and open water thin ice and open water allow more surface solar heating because of a much reduced surface albedo leading to amplified ice melting the arctic ocean lost additional 10 of its total ice mass in which 70 is due directly to the amplified melting and 30 to the unusual ice advection causing the unprecedented ice retreat arctic sea ice has entered a state of being particularly vulnerable to anomalous atmospheric forcing

is the dipole anomaly a major driver to record lows in arctic summer sea ice extent recent record lows of arctic summer sea ice extentare found to be triggered by the arctic atmospheric dipoleanomaly da pattern this local second leading mode ofsea level pressure slp anomaly in the arctic produced astrong meridional wind anomaly that drove more sea ice outof the arctic ocean from the western to the eastern arcticinto the northern atlantic during the summers of 1995 1999 2002 2005 and 2007 in the 2007 summer the daalso enhanced anomalous oceanic heat flux into the arcticoceanviaberingstrait whichacceleratedbottomandlateralmelting of sea ice and amplified the ice albedo feedback acoupled ice ocean model was used to confirm the historicalrecord lows of summer sea ice extent

climate sensitivity of storglaciaren sweden an intercomparison of mass balance models using era 40 re analysis and regional climate model data estimates of glacier contributions to future sea level rise are often computed from mass balance sensitivities derived for a set of representative glaciers our purpose is to investigate how mass b

static mass balance sensitivity of arctic glaciers and ice caps using a degree day approach the purpose of this study is to enhance our understanding of the response of glaciers to climate change global sea level is affected by changes in glacier ice volume and melt water from glaciers is a principal water source in many regions this study applies glacier mass balance modelling with varying complexity and spatial resolution ranging from individual glaciers to regional and global assessments of glacier mass losses glaciers located in maritime environments generally show considerably higher mass balance sensitivities than those in continental settings on average an assumed increase in annual precipitation of 10 tends to offset the effect of an annual temperature change of 1 k by roughly 20 two case studies at storglaciaren sweden and hofsjokull iceland involve model results of future mass balance change and glacier melt induced changes in runoff applying a temperature and precipitation scenario for iceland in 2050 results in increased total runoff from hofsjokull by roughly one third and results emphasize the role of the firn layer in delaying water flow through glaciers yielding a redistribution of discharge within the year based on a global gridded data set of glacierized area the sea level equivalent from all mountain glaciers and ice caps outside the ice sheets in greenland and antarctica during 1961 2004 caused by changes in temperature and precipitation is estimated to be 0 58 0 34 mm a 1 the mountain glaciers and ice caps around antarctica alone contribute almost 40 of the global estimate and hence their contribution is considerably larger than previously assumed

comparing and contrasting the behaviour of arctic and antarctic sea ice over the 35 year period 1979 2013 we examine the evolution of sea ice extent sie over both polar regions for 35 years from november 1978 to december 2013 as well as for the global total ice arctic plus antarctic our examination confirms the ongoing loss of arctic sea ice and we find significant p 0 001 negative trends in all months seasons and in the annual mean the greatest rate of decrease occurs in september and corresponds to a loss of 3 x 10 6 km 2 over 35 years the antarctic shows positive trends in all seasons and for the annual mean p 0 01 with summer attaining a reduced significance p 0 10 based on our longer record which includes the remarkable year 2013 the positive antarctic ice trends can no longer be considered small and the positive trend in the annual mean of 15 29 3 85 x 10 3 km 2 a 1 is almost one third of the magnitude of the arctic annual mean decrease the global annual mean sie series exhibits a trend of 35 29 5 75 x 10 3 km 2 a 1 p

greater role for atlantic inflows on sea ice loss in the eurasian basin of the arctic ocean arctic sea ice loss is a leading indicator of climate change and can be attributed in large part to atmospheric forcing here we show that recent ice reductions weakening of the halocline and shoaling of the intermediate depth atlantic water layer in the eastern eurasian basin have increased winter ventilation in the ocean interior making this region structurally similar to that of the western eurasian basin the associated enhanced release of oceanic heat has reduced winter sea ice formation at a rate now comparable to losses from atmospheric thermodynamic forcing thus explaining the recent reduction in sea ice cover in the eastern eurasian basin this encroaching atlantification of the eurasian basin represents an essential step toward a new arctic climate state with a substantially greater role for atlantic inflows

local earthquake quantification abstract the diversity of noise conditions and consequently the diversity of types of seismographs that are found in different environments make it unlikely that a single method of determining magnitudes for local earthquakes will be developed in each area local studies must be carried out to determine the appropriate attenuation distance function taking into account known structural features each locally determined magnitude scale should be related to either a standard teleseismic scale or preferably to richter s original local magnitude scale ml

contribution of glacier melt to sea level rise since ad 1865 a regionally differentiated calculation the contribution of glacier melt including the greenland ice sheet to sea level change since ad 1865 is estimated on the basis of modelled sensitivity of glacier mass balance to climate change and historical temperature data calculations are done in a regionally differentiated manner to overcome the inhomogeneity of the global distribution of glaciers a distinction is made between changes in summer temperature and in temperature over the rest of the year our best estimate of the ice melt in the period 1865 1990 in terms of sea level change equivalent is 5 7 cm 2 7 cm for glaciers and 3 0 cm for the greenland ice sheet additional calculations show that simpler methods like using annual or even global mean temperature anomaly give estimates that differ by up to 55 consequently a regionally differentiating approach is advised for making projections of glacier melt with gcm output

impact of ural blocking on winter warm arctic cold eurasian anomalies part ii the link to the north atlantic oscillation abstractin part i of this study the ural blocking ub induced amplification role of winter warm arctic cold eurasian wace anomalies has been examined it was found that the long lived ub together with the positive north atlantic oscillation nao significantly contributes to the amplification of the wace pattern the present study examines how the ub variability affects quasi biweekly wace qb wace anomalies and depends on the nao and north atlantic conditions by classifying the ub based on a case study of a cold event that occurred over southern china in january 2008 a composite analysis during 1979 2013 shows that the qb wace anomalies associated with the ub that often occur with the nao are strong and influenced by the north atlantic jet naj and zonal wind strengths over eurasia for nao related ub the qb wace anomaly depends strongly on the location of ub and the ub anomalies lag the nao by approximately 4 7 days the strength of the naj determines whether the combined nao and ub anomal

arctic sea ice circulation and drift speed decadal trends and ocean currents 1 we examine the basinwide trends in sea ice circulation and drift speed and highlight the changes between 1982 and 2009 in connection to regional winds multiyear sea ice coverage ice export and the thinning of the ice cover the polarity of the arctic oscillation ao is used as a backdrop for summarizing the variance and shifts in decadal drift patterns the 28 year circulation fields show a net strengthening of the beaufort gyre and the transpolar drift especially during the last decade the imprint of the arctic dipole anomaly on the mean summer circulation is evident 2001 2009 and enhances summer ice area export at the fram strait between 2001 and 2009 the large spatially averaged trends in drift speeds winter 23 6 decade summer 17 7 decade are not explained by the much smaller trends in wind speeds winter 1 46 decade summer 3 42 decade notably positive trends in drift speed are found in regions with reduced multiyear sea ice coverage over 90 of the arctic ocean has positive trends in drift speed and negative trends in multiyear sea ice coverage the increased responsiveness of ice drift to geostrophic wind is consistent with a thinner and weaker seasonal ice cover and suggests large scale changes in the air ice ocean momentum balance the retrieved mean ocean current field from decadal scale average ice motion captures a steady drift from siberia to the fram strait an inflow north of the bering strait and a westward drift along coastal alaska this mean current is comparable to geostrophic currents from satellite derived dynamic topography

decline in arctic sea ice thickness from submarine and icesat records 1958 2008 1 the decline of sea ice thickness in the arctic ocean from icesat 2003 2008 is placed in the context of estimates from 42 years of submarine records 1958 2000 described by rothrock et al 1999 2008 while the earlier 1999 work provides a longer historical record of the regional changes the latter offers a more refined analysis over a sizable portion of the arctic ocean supported by a much stronger and richer data set within the data release area dra of declassified submarine sonar measurements covering 38 of the arctic ocean the overall mean winter thickness of 3 64 m in 1980 can be compared to a 1 89 m mean during the last winter of the icesat record an astonishing decrease of 1 75 m in thickness between 1975 and 2000 the steepest rate of decrease is 0 08 m yr in 1990 compared to a slightly higher winter summer rate of 0 10 0 20 m yr in the five year icesat record 2003 2008 prior to 1997 ice extent in the dra was 90 during the summer minimum this can be contrasted to the gradual decrease in the early 2000s followed by an abrupt drop to 55 during the record setting minimum in 2007 this combined analysis shows a long term trend of sea ice thinning over submarine and icesat records that span five decades

sensitivity of a greenland ice sheet model to ice flow and ablation parameters consequences for the evolution through the last climatic cycle sensitivity experiments are conducted to test the influence of poorly known model parameters on the simulation of the greenland ice sheet by means of a three dimensional numerical model including the mechanical and thermal processes within the ice two types of experiments are performed steady state climatic conditions and simulations over the last climatic cycle with a climatic forcing derived from the grip record the experiments show that the maximum altitude of the ice sheet depends on the ice flow parameters deformation and sliding law coefficients geothermal flux and that it is low when the ice flow is fast on the other hand the maximum altitude is not sensitive to the ablation strength and consequently during the climatic cycle it is driven by changes in accumulation rate the ice sheet extension shows the opposite sensitivity it is barely affected by ice flow velocity and the ice covered area is smaller for large ablation coefficients for colder climates when there is no ablation the ice sheet extension depends on the sea level an interesting result is that the variations with time of the altitude at the ice divide summit do not depend on the parameters we tested the present modelled ice sheets resulting from the climatic cycle experiments are compared with the present measured ice sheet in order to find the set of parameters that gives the best fit between modelled and measured geometry it seems that compared to the parameter set most commonly used higher ablation rate coefficents must be used

the spatial distribution of solar radiation under a melting arctic sea ice cover 1 the sea ice cover of the chukchi and beaufort seas is currently undergoing a fundamental shift from multiyear ice to first year ice field observations of sea ice physical and optical properties were collected in this region during june july 2010 revealing unexpectedly complex spatial distributions of solar radiation under the melt season ice cover based on our optical measurements of first year ice we found the under ice light field in the upper ocean to be spatially heterogeneous and dependent on wavelength ice thickness and the areal and geometric distribution of melt ponded and bare ice surfaces much of the observed complexity in radiation fields arose because the transmission of light through ponded ice was generally an order of magnitude greater than through bare unponded ice furthermore while many sites exhibited a consistent exponential decay in light transmission through both ponded and bare ice surfaces light transmission under bare ice was also observed to increase with depth reaching maximum values 5 10 m below the bottom of the ice a simple geometric model shows these transmission peaks are a result of scattering in the ice and the interspersion of bare and ponded sea ice surfaces these new observations of complex radiation fields beneath melt season first year sea ice have significant implications for biological production biogeochemical processes and the heat balance of sea ice and under ice ocean waters and should be carefully considered when modeling these sea ice related phenomena

influence of the meridional shifts of the kuroshio and the oyashio extensions on the atmospheric circulation abstract the meridional shifts of the oyashio extension oe and of the kuroshio extension ke as derived from high resolution monthly sea surface temperature sst anomalies in 1982 2008 and historical temperature profiles in 1979 2007 respectively are shown based on lagged regression analysis to significantly influence the large scale atmospheric circulation the signals are independent from the enso teleconnections which were removed by seasonally varying asymmetric regression onto the first three principal components of the tropical pacific sst anomalies the response to the meridional shifts of the oe front is equivalent barotropic and broadly resembles the north pacific oscillation western pacific pattern in a positive phase for a northward frontal displacement the response may reach 35 m at 250 hpa for a typical oe shift a strong sensitivity since the associated sst anomaly is 0 5 k however the amplitude but not the pattern or statistical significance strongly depends on the lag and an

when will the summer arctic be nearly sea ice free 1 the observed rapid loss of thick multiyear sea ice over the last 7 years and the september 2012 arctic sea ice extent reduction of 49 relative to the 1979 2000 climatology are inconsistent with projections of a nearly sea ice free summer arctic from model estimates of 2070 and beyond made just a few years ago three recent approaches to predictions in the scientific literature are as follows 1 extrapolation of sea ice volume data 2 assuming several more rapid loss events such as 2007 and 2012 and 3 climate model projections time horizons for a nearly sea ice free summer for these three approaches are roughly 2020 or earlier 2030 10 years and 2040 or later loss estimates from models are based on a subset of the most rapid ensemble members it is not possible to clearly choose one approach over another as this depends on the relative weights given to data versus models observations and citations support the conclusion that most global climate model results in the cmip5 archive are too conservative in their sea ice projections recent data and expert opinion should be considered in addition to model results to advance the very likely timing for future sea ice loss to the first half of the 21st century with a possibility of major loss within a decade or two

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

a sea ice free summer arctic within 30 years an update from cmip5 models interpreted as sea ice extent less than 1 0 million km 2 w e consider this estimate to be still valid based on projections of updated climate models cmip5 and observational data similar to previous models cmip3 cmip5 still shows a wide spread in hindcast and projected sea ice loss among different models further there is no consensus in the scientific literature for the cause of such a spread in results for cmip3 and cmip5 while cmip5 model mean sea ice extents are closer to observations than cmip3 the rates of sea ice reduction in most model runs are slow relative to recent observations all cmip5 models do show loss of sea ice due to increased anthropogenic forcing relative to preindustrial control runs applying the same technique of model selection and extrapolation approach to cmip5 as we used in our previous paper the interval range for a nearly sea ice free arctic is 14 to 36 years with a median value of 28 years relative to a 2007 baseline this suggests a nearly sea ice free arctic in the 2030s citation wang m and j e overland 2012 a sea ice free summer arctic within 30 years an update from cmip5 models geophys res lett 39 l18501

response of sea ice to the arctic oscillation abstract data collected by the international arctic buoy programme from 1979 to 1998 are analyzed to obtain statistics of sea level pressure slp and sea ice motion sim the annual and seasonal mean fields agree with those obtained in previous studies of arctic climatology the data show a 3 hpa decrease in decadal mean slp over the central arctic ocean between 1979 88 and 1989 98 this decrease in slp drives a cyclonic trend in sim which resembles the structure of the arctic oscillation ao regression maps of sim during the wintertime january march ao index show 1 an increase in ice advection away from the coast of the east siberian and laptev seas which should have the effect of producing more new thin ice in the coastal flaw leads 2 a decrease in ice advection from the western arctic into the eastern arctic and 3 a slight increase in ice advection out of the arctic through fram strait taken together these changes suggest that at least part of the thinning of sea ice recently observed ov

recent arctic sea ice variability connections to the arctic oscillation and the enso 1 trends in the satellite derived arctic sea ice concentrations 1978 2002 show pronounced decreases in the barents kara seas between the chukchi and beaufort seas the central sea of okhotsk and a portion of the hudson baffin bay by 2 8 per decade exceeding the 95 confidence level qualitatively speaking positive phases of the arctic oscillation ao and el nino southern oscillation enso produce similar ice changes in the western arctic but opposite ice changes in the eastern arctic the manner in which the ice changes are related to the ao and enso are demonstrated over the last 24 years the magnitude of the ice changes associated with the positive ao trend and the negative enso trend is much smaller than the regional ice trends thus more local or less understood large scale processes should be investigated for explanations

heat flow in vapor dominated areas of the yellowstone plateau volcanic field implications for the thermal budget of the yellowstone caldera the yellowstone caldera the 0 11 km 2 obsidian pool thermal area opta and the 0 25 km 2 solfatara plateau thermal area spta conductive heat flux through a low permeability layer capping large vapor reservoirs is calculated from soil temperature measurements at 600 locations and from laboratory measurements of soil properties the conductive heat output is 3 6 0 4 mw and 7 5 0 4 mw from the opta and the spta respectively the advective heat output from soils is 1 3 0 3 mw and 1 2 0 3 mw from the opta and the spta respectively and the heat output from thermal pools in the opta is 6 8 1 4 mw these estimates result in a total heat output of 11 8 1 4 mw and 8 8 0 4 mw from opta and spta respectively focused zones of high heat flux in both thermal areas are roughly aligned with regional faults suggesting that faults in both areas serve as conduits for the rising acid vapor

elevation changes measured on svalbard glaciers and ice caps from airborne laser data precise airborne laser surveys were conducted during spring in 1996 and 2002 on 17 ice caps and glaciers in the svalbard archipelago covering the islands of spitsbergen and nordaustlandet we present the derived elevation changes lower elevation glaciers in south spitsbergen show the largest thinning rates of 0 5 m a 1 while some of the higher more northerly ice caps appear to be close to balance the pattern of elevation change is complex however due to several factors including glacier aspect microclimatological influences and the high natural annual variability in local accumulation and ablation rates anomalous changes were observed on fridtjovbreen which started surging in 1996 at the start of the measurement period on this glacier thinning of 0 6 m a 1 w as observed in the accumulation area coincident with thickening at lower elevations asymmetric thinning was found on two ice caps on nordaustlandet with the largest values on the eastern side of vestfonna but the western slopes of vegafonna the mean elevation change for all ice masses was 0 19 m a 1 w e which is 1 6 times the net mass balance value determined for the last 30 years using mass balance sensitivity estimates for svalbard suggests that the implied increase in negative balance is linked to warmer air temperatures in the late 1990s multiple linear regression suggests that mass balance is most closely correlated with latitude rather than mean altitude or longitude

phytoplankton blooms beneath the sea ice in the chukchi sea in the arctic ocean phytoplankton blooms on continental shelves are often limited by light availability and are therefore thought to be restricted to waters free of sea ice during july 2011 in the chukchi sea a large phytoplankton bloom was observed beneath fully consolidated pack ice and extended from the ice edge to 4100 km into the pack the bloom was composed primarily of diatoms with biomass reaching 1291 mg chlorophyll a m 2 and rates of carbon fixation as high as 3 7 g c m 2 d 1 although the sea ice where the bloom was observed was near 100 concentration and 0 8 1 2 m thick 30 40 of its surface was covered by melt ponds that transmitted 4 fold more light than adjacent areas of bare ice providing sufficient light for phytoplankton to bloom phytoplankton growth rates associated with the under ice bloom averaged 0 9 d 1

the influence of drainage boundaries on specific mass balance results a case study of engabreen norway mass balance measurements were initiated on engabreen an outlet glacier from the svartisen ice cap norway in 1970 the glacier boundary was defined based on where meltwater drained as the interest in engabreen was mainly hydrological however the apparent discrepancy between the calculated cumulative glacier mass balance since 1970 and changes in glacier geometry prompted a re examination of the glacier boundary the glaciological drainage boundary is defined by studying whether ice flow physically contributes to engabreen tongue and corresponds to a glacier with an area of 27 2 km 2 significantly smaller than that defined by the hydrological drainage boundary at 39 6 km 2 this glaciological drainage boundary is here named the ice flow perimeter the area difference between this and the hydrological drainage boundary is largest for the altitudinal range 1300 1400 m a s l generally the glaciological glacier is lower in mean altitude than the hydrological glacier and this affects the calculated specific mass balance using the glaciological boundary leads to reductions in mean annual winter and summer balance when spatial differences are ignored of 0 12 m w e from 2 92 to 2 80 m w e and 0 15 m w e from 2 32 to 2 47 m w e respectively the reduction in mean net balance for the period 1970 2006 is 0 27 m w e from 0 59 to 0 32 m w e which is about 50 of the calculated mass surplus in this period this illustrates that the choice of glacier outline can significantly influence the long term cumulative mass balance and that results from outlet glaciers must be interpreted with care when used for regional estimates of glacier change

on thermal expansion over the last hundred years estimates of sea level rise during the period 1856 1991 due to thermal expansion are presented the estimates are based on an ocean model that consists of three zonally averaged ocean basins representing the atlantic pacific and indian oceans these basins are connected by a circumpolar basin that represents the southern ocean the ocean circulation in the model was prescribed surface ocean forcing was calculated from observed sea surface temperatures global mean forcing and regionally varying forcing were distinguished different parameterizations of ocean heat mixing were incorporated according to the model presented global mean sea level rise caused by thermal expansion over the last hundred years ranged from 2 2 to 5 1 cm a best estimate being 3 5 cm 34 refs 5 figs

arctic oscillation or north atlantic oscillation abstract the definition and interpretation of the arctic oscillation ao are examined and compared with those of the north atlantic oscillation nao it is shown that the nao reflects the correlations between the surface pressure variability at its centers of action whereas this is not the case for the ao the nao pattern can be identified in a physically consistent way in principal component analysis applied to various fields in the euro atlantic region a similar identification is found in the pacific region for the pacific north american pna pattern but no such identification is found here for the ao the ao does reflect the tendency for the zonal winds at 35 and 55 n to anticorrelate in both the atlantic and pacific regions associated with the nao and pna because climatological features in the two ocean basins are at different latitudes the zonally symmetric nature of the ao does not mean that it represents a simple modulation of the circumpolar flow an increase in the ao or nao implies stro

climate sensitivity of glaciers in southern norway application of an energy balance model to nigardsbreen hellstugubreen and alfotbreen three glaciers in southern norway with very different massbalance characteristics are studied with an energy balance model of the ice snow surface the model simulates the observed mass balance profiles in a satisfactory way and can thus be used with some confidence in a study of climate sensitivity calculated changes in equilibrium line altitude for a 1 k temperature increase are 110 108 and 135 in for nigardsbreen hellstugubreen and alfotbreen respectively the corresponding changes in mass balance averaged over the entire glacier area are 0 88 0 715 and 1 11 in year water equivalent runs with an ice flow model for nigardsbreen to which calculated mass balance profiles are imposed predict that the front will advance by 3 km for a 1 k cooling and will retreat by as much as 6 5 km for a 1 k warming the response to a 10 increase in precipitation would be a 2 km advance of the snout whereas a 4 km retreat is predicted for a 10 decrease this large sensitivity as compared to many other glaciers is to a large extent due to the geometry of nigardsbreen

the impact of an intense summer cyclone on 2012 arctic sea ice retreat 1 this model study examines the impact of an intense early august cyclone on the 2012 record low arctic sea ice extent the cyclone passed when arctic sea ice was thin and the simulated arctic ice volume had already declined 40 from the 2007 2011 mean the thin sea ice pack and the presence of ocean heat in the near surface temperature maximum layer created conditions that made the ice particularly vulnerable to storms during the storm ice volume decreased about twice as fast as usual owing largely to a quadrupling in bottom melt caused by increased upward ocean heat transport this increased ocean heat flux was due to enhanced mixing in the oceanic boundary layer driven by strong winds and rapid ice movement a comparison with a sensitivity simulation driven by reduced wind speeds during the cyclone indicates that cyclone enhanced bottom melt strongly reduces ice extent for about 2 weeks with a declining effect afterward the simulated arctic sea ice extent minimum in 2012 is reduced by the cyclone but only by 0 15 106 km2 4 4 thus without the storm 2012 would still have produced a record minimum

the dynamic response of the greenland and antarctic ice sheets to multiple century climatic warming new calculations were performed to investigate the combined response of the greenland and antarctic ice sheets to a range of climatic warming scenarios over the next millennium use was made of fully dynamic 3d thermomechanic ice sheet models which were coupled to a two dimensional climate model the experiments were initialized with simulations over the last two glacial cycles to estimate the present evolution and were subsequently forced with temperature scenarios resulting from greenhouse emission scenarios which assume equivalent co2 increases of two four and eight times the present 1990 a d value by the year 2130 a d and a stabilization after that the calculations brought to light that during the next century short term effect the background evolution trend would dominate the response of the antarctic ice sheet but would be negligible for the greenland ice sheet on that timescale the greenland and antarctic ice sheets would roughly balance one another for the middle scenario similar to the ipcc96 is92a scenario with respective contributions to the worldwide sea level stand on the order of about 610 cm on the longer term however both ice sheets would contribute positively to the worldwide sea level stand and the most important effect would come from melting on the greenland ice sheet sensitivity experiments highlighted the role of ice dynamics and the height massbalance feedback on the results it was found that ice dynamics cannot be neglected for the greenland ice sheet not even on a century timescale but becomes only important for antarctica on the longer term the latter is related to an increased outflow of ice into the ice shelves and to the grounding line retreat of the west antarctic ice sheet which are both found to be sensitive to basal melting below ice shelves and the effective viscosity of the ice shelves stretching parameters to their limits yielded a combined maximum rate of sea level rise of 85 cm century21 of which 60 cm would originate from the greenland ice sheet alone

the recent shift in early summer arctic atmospheric circulation 1 the last six years 2007 2012 show a persistent change in early summer arctic wind patterns relative to previous decades the persistent pattern which has been previously recognized as the arctic dipole ad is characterized by relatively low sea level pressure over the siberian arctic with high pressure over the beaufort sea extending across northern north america and over greenland pressure differences peak in june in a search for a proximate cause for the newly persistent ad pattern we note that the composite 700 hpa geopotential height field during june 2007 2012 exhibits a positive anomaly only on the north american side of the arctic thus creating the enhanced mean meridional flow across the arctic coupled impacts of the new persistent pattern are increased sea ice loss in summer long lived positive temperature anomalies and ice sheet loss in west greenland and a possible increase in arctic subarctic weather linkages through higheramplitude upper level flow the north american location of increased 700 hpa positive anomalies suggests that a regional atmospheric blocking mechanism is responsible for the presence of the ad pattern consistent with observations of unprecedented high pressure anomalies over greenland since 2007 2012 american geophysical union all rights reserved

the north pacific oscillation west pacific teleconnection pattern mature phase structure and winter impacts abstract the north pacific oscillation npo in sea level pressure and its upper air geopotential height signature the west pacific wp teleconnection pattern constitute a prominent mode of winter midlatitude variability the npo wp its mature phase expression is identified from principal component analysis of monthly sea level pressure variability as the second leading mode just behind the pacific north american variability pattern npo wp variability primarily on subseasonal time scales is characterized by a large scale meridional dipole in slp and geopotential height over the pacific and is linked to meridional movements of the asian pacific jet and pacific storm track modulation the hemispheric height anomalies at upper levels resemble the climatological stationary wave pattern attributed to transient eddy forcing the npo wp divergent circulation is thermal wind restoring pointing to independent forcing of jet fluctuations intercomparison of sea level pressure geopotential height and zonal

regions of rapid sea ice change an inter hemispheric seasonal comparison this bi polar analysis resolves ice edge changes on space time scales relevant for investigating seasonal iceocean feedbacks and focuses on spatio temporal changes in the timing of annual sea ice retreat and advance over 1979 80 to 2010 11 where arctic sea ice decrease is fastest the sea ice retreat is now nearly 2 months earlier and subsequent advance more than 1 month later compared to 1979 80 resulting in a 3 month longer summer ice free season in the antarctic peninsula and bellingshausen sea region sea ice retreat is more than 1 month earlier and advance 2 months later resulting in a more than 3 month longer summer icefree season in contrast in the western ross sea antarctica region sea ice retreat and advance are more than 1 month later and earlier respectively resulting in a more than 2 month shorter summer ice free season regardless of trend magnitude or direction and at latitudes mostly poleward of 70 n s there is strong correspondence between anomalies in the timings of sea ice retreat and subsequent advance but little correspondence between advance and subsequent retreat these results support a strong ocean thermal feedback in autumn in response to changes in spring sea ice retreat further model calculations suggest different net ocean heat changes in the arctic versus antarctic where autumn sea ice advance is 1 versus 2 months later ocean atmosphere changes particularly in boreal spring and austral autumn i e during march may are discussed and compared as well as possible inter hemispheric climate connections

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

dramatic interannual changes of perennial arctic sea ice linked to abnormal summer storm activity 1 the perennial september arctic sea ice cover exhibits large interannual variability with changes of over a million square kilometers from one year to the next here we explore the role of changes in arctic cyclone activity and related factors in driving these pronounced year to year changes in perennial sea ice cover strong relationships are revealed between the september sea ice changes and the number of cyclones in the preceding late spring and early summer in particular fewer cyclones over the central arctic ocean during the months of may june and july appear to favor a low sea ice area at the end of the melt season years with large losses of sea ice are characterized by abnormal cyclone distributions and tracks they lack the normal maximum in cyclone activity over the central arctic ocean and cyclones that track from eurasia into the central arctic are largely absent fewer storms are associated with above average mean sea level pressure strengthened anticyclonic winds an intensification of the transpolar drift stream and reduced cloud cover all of which favor ice melt it is also shown that a strengthening of the central arctic cyclone maximum helps preserve the ice cover although the association is weaker than that between low cyclone activity and reduced sea ice the results suggest that changes in cyclone occurrence during late spring and early summer have preconditioning effects on the sea ice cover and exert a strong influence on the amount of sea ice that survives the melt season

form and flow of the academy of sciences ice cap severnaya zemlya russian high arctic 1 the 5 575 km2 academy of sciences ice cap is the largest in the russian arctic a 100 mhz airborne radar digital landsat imagery and satellite synthetic aperture radar sar interferometry are used to investigate its form and flow including the proportion of mass lost through iceberg calving the ice cap was covered by a 10 km spaced grid of radar flight paths and the central portion was covered by a grid at 5 km intervals a total of 1 657 km of radar data digital elevation models dems of ice surface elevation ice thickness and bed elevation data sets were produced cell size 500 m the dems were used in the selection of a deep ice core drill site total ice cap volume is 2 184 km3 5 5 mm sea level equivalent the ice cap has a single dome reaching 749 m maximum ice thickness is 819 m about 200 km or 42 of the ice margin is marine about 50 of the ice cap bed is below sea level the central divide of the ice cap and several major drainage basins in the south and east of the ice cap and of up to 975 km2 are delimited from satellite imagery there is no evidence of past surge activity on the ice cap sar interferometric fringes and phase unwrapped velocities for the whole ice cap indicate slow flow in the interior and much of the margin punctuated by four fast flowing features with lateral shear zones and maximum velocity of 140 m yr 1 these ice streams extend back into the slower moving ice to within 5 10 km of the ice cap crest they have lengths of 17 37 km and widths of 4 8 km mass flux from these ice streams is 0 54 km3 yr 1 tabular icebergs up to 1 7 km long are produced total iceberg flux from the ice cap is 0 65 km3 yr 1 and probably represents 40 of the overall mass loss with the remainder coming from surface melting driving stresses are generally lowest 40 kpa close to the ice cap divides and in several of the ice streams ice stream motion is likely to include a significant basal component and may involve deformable marine sediments

spatial and temporal transferability of a distributed energy balance glacier melt model abstract modeling melt from glaciers is crucial to assessing regional hydrology and eustatic sea level rise the transferability of such models in space and time has been widely assumed but rarely tested to investigate melt model transferability a distributed energy balance melt model debm is applied to two small glaciers of opposing aspects that are 10 km apart in the donjek range of the st elias mountains yukon territory canada an analysis is conducted in four stages to assess the transferability of the debm in space and time 1 locally derived model parameter values and meteorological forcing variables are used to assess model skill 2 model parameter values are transferred between glacier sites and between years of study 3 measured meteorological forcing variables are transferred between glaciers using locally derived parameter values 4 both model parameter values and measured meteorological forcing variables are transferred from one glacier site to the other treating the second glacier

divergent patterns of recent sea ice cover across the bering chukchi and beaufort seas of the pacific arctic region abstract over the past three decades of the observed satellite record there have been significant changes in sea ice cover across the bering chukchi and beaufort seas of the pacific arctic region par satellite data reveal that patterns in sea ice cover have been spatially heterogeneous with significant declines in the chukchi and beaufort seas yet more complex multi year variability in the bering sea south of st lawrence island these patterns in the chukchi and beaufort seas have intensified since 2000 indicating a regime shift in sea ice cover across the northern portion of the par in particular satellite data over 1979 2012 reveal localized decreases in sea ice presence of up to 1 64 days year canada basin and 1 24 days year beaufort sea which accelerated to up to 6 57 days year canada basin and 12 84 days year beaufort sea over the 2000 2012 time period in contrast sea ice in the bering sea shows more complex multi year variability with localized increases in sea ice presence of up to 8 41 days year since 2000 the observed increases in sea ice cover since 2000 in the southern bering sea shelf region are observed in wintertime whereas sea ice losses in the canada basin and beaufort sea have occurred during summer we further compare sea ice variability across the region with the national centers for environmental prediction ncep north american regional reanalysis narr wind and air temperature fields to determine the extent to which this recent variability is driven by thermal vs wind driven processes results suggest that for these localized areas that are experiencing the most rapid shifts in sea ice cover those in the beaufort sea are primarily wind driven those offshore in the canada basin are primarily thermally driven and those in the bering sea are influenced by elements of both sea ice variability and its drivers across the par provides critical insight into the forcing effects of recent shifts in climate and its likely ultimate profound impacts on ecosystem productivity across all trophic levels

uncertainty in modeled arctic sea ice volume 1 uncertainty in the pan arctic ice ocean modeling and assimilation system piomas arctic sea ice volume record is characterized a range of observations and approaches including in situ ice thickness measurements icesat retrieved ice thickness and model sensitivity studies yields a conservative estimate for october arctic ice volume uncertainty of 1 35 103 km3 and an uncertainty of the ice volume trend over the 1979 2010 period of 1 0 103 km3 decade 1 a conservative estimate of the trend over this period is 2 8 103 km3 decade 1 piomas ice thickness estimates agree well with icesat ice thickness retrievals 0 1 m mean difference for the area for which submarine data are available while difference outside this area are larger piomas spatial thickness patterns agree well with icesat thickness estimates with pattern correlations of above 0 8 piomas appears to overestimate thin ice thickness and underestimate thick ice yielding a smaller downward trend than apparent in reconstructions from observations piomas ice volume uncertainties and trends are examined in the context of climate change attribution and the declaration of record minima the distribution of 32 year trends in a preindustrial coupled model simulation shows no trends comparable to those seen in the piomas retrospective even when the trend uncertainty is accounted for attempts to label september minima as new record lows are sensitive to modeling error however the september 2010 ice volume anomaly did in fact exceed the previous 2007 minimum by a large enough margin to establish a statistically significant new record

an estimate of glacier mass balance for the chandra basin western himalaya for the period 1984 2012 an improved understanding of fresh water stored in the himalaya is crucial for water resource management in south asia and can be inferred from glacier mass balance estimates however field investigations in the rugged himalaya are limited to a few individual glaciers and short duration therefore we have recently developed an approach that combines satellite derived snowlines a temperature index melt model and the accumulation area ratio method to estimate annual mass balance of glaciers at basin scale and for a long period in this investigation the mass balance of 146 glaciers in the chandra basin western himalaya is estimated from 1984 to 2012 we estimate the trend in equilibrium line altitude of the basin as 113 m decade 1 and the mean mass balance as 0 61 0 46 m w e a 1 our basin wide mass balance estimates are in agreement with the geodetic method during 1999 2012 sensitivity analysis suggests that a 20 increase in precipitation can offset changes in mass balance for a 1 degrees c temperature rise a water loss of 18 of the total basin volume is estimated and 67 for small and low altitude glaciers during 1984 2012 indicating a looming water scarcity crisis for villages in this valley

on the existence of storm tracks abstract given that middle latitude weather systems transport heat in a manner such as to weaken the baroclinicity that is thought to be crucial to their growth it is perhaps surprising that concentrated regions of such eddy activity i e storm tracks are found in the northern hemisphere winter the existence and possible self maintenance of storm tracks is investigated using a linear stationary wave model with storm track region forcings taken from data averaged over a number of winters it is found that the direct thermal effect of the eddies does indeed act against the existence of the storm track their vorticity fluxes lead to some reduction of this effect it is argued that the mean diabatic heating in the storm track region is an indirect eddy effect this heating is found to maintain the mean maximum in baroclinicity in the region further the mean low level flow induced by the eddy effects is such as to enhance the warm western oceanic boundary currents that are crucial to the existence of t

rapid wastage of alaska glaciers and their contribution to rising sea level we have used airborne laser altimetry to estimate volume changes of 67 glaciers in alaska from the mid 1950s to the mid 1990s the average rate of thickness change of these glaciers was 0 52 m year extrapolation to all glaciers in alaska yields an estimated total annual volume change of 52 15 km 3 year water equivalent equivalent to a rise in sea level sle of 0 14 0 04 mm year repeat measurements of 28 glaciers from the mid 1990s to 2000 2001 suggest an increased average rate of thinning 1 8 m year this leads to an extrapolated annual volume loss from alaska glaciers equal to 96 35 km 3 year or 0 27 0 10 mm year sle during the past decade these recent losses are nearly double the estimated annual loss from the entire greenland ice sheet during the same time period and are much higher than previously published loss estimates for alaska glaciers they form the largest glaciological contribution to rising sea level yet measured

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

recent changes in the dynamic properties of declining arctic sea ice a model study 1 results from a numerical model simulation show significant changes in the dynamic properties of arctic sea ice during 2007 2011 compared to the 1979 2006 mean these changes are linked to a 33 reduction in sea ice volume with decreasing ice concentration mostly in the marginal seas and decreasing ice thickness over the entire arctic particularly in the western arctic the decline in ice volume results in a 37 decrease in ice mechanical strength and 31 in internal ice interaction force which in turn leads to an increase in ice speed 13 and deformation rates 17 the increasing ice speed has the tendency to drive more ice out of the arctic however ice volume export is reduced because the rate of decrease in ice thickness is greater than the rate of increase in ice speed thus retarding the decline of arctic sea ice volume ice deformation increases the most in fall and least in summer thus the effect of changes in ice deformation on the ice cover is likely strong in fall and weak in summer the increase in ice deformation boosts ridged ice production in parts of the central arctic near the canadian archipelago and greenland in winter and early spring but the average ridged ice production is reduced because less ice is available for ridging in most of the marginal seas in fall the overall decrease in ridged ice production contributes to the demise of thicker older ice as the ice cover becomes thinner and weaker ice motion approaches a state of free drift in summer and beyond and is therefore more susceptible to changes in wind forcing this is likely to make seasonal or shorter term forecasts of sea ice edge locations more challenging

arctic sea ice retreat in 2007 follows thinning trend the minimum of arctic sea ice extent in the summer of 2007 was unprecedented in the historical record a coupled ice ocean model is used to determine the state of the ice and ocean over the past 29 yr to investigate the causes of this ice extent minimum within a historical perspective it is found that even though the 2007 ice extent was strongly anomalous the loss in total ice mass was not rather the 2007 ice mass loss is largely consistent with a steady decrease in ice thickness that began in 1987 since then the simulated mean september ice thickness within the arctic ocean has declined from 3 7 to 2 6 m at a rate of 0 57 m decade 1 both the area coverage of thin ice at the beginning of the melt season and the total volume of ice lost in the summer have been steadily increasing the combined impact of these two trends caused a large reduction in the september mean ice concentration in the arctic ocean this created conditions during the summer of 2007 that allowed persistent winds to push the remaining ice from the pacific side to the atlantic side of the basin and more than usual into the greenland sea this exposed large areas of open water resulting in the record ice extent anomaly

estimating the contribution of arctic glaciers to sea level change in the next 100 years in this paper we report on an approach to estimate the contribution of arctic glaciers to sea level change in our calculation we assume that a static approach is feasible we only calculate changes in the surface balance from modelled sensitivities these sensitivities summarized in the seasonal sensitivity characteristic can be used to calculate the change in the surface mass budget for given anomalies of monthly temperature and precipitation we have based our calculations on a subdivision of all arctic ice into 13 regions four sectors of the greenland ice sheet the canadian arctic 74 n the canadian arctic 60 n as forcing for the calculations we have used the output from five climate models for the period 2000 2100 these models were forced by the same greenhouse gas scenario ipcc b2 the calculated contributions to sea level rise in the year 2100 vary from almost zero to about 6 cm the differences among the models stem first of all from differences in the precipitation the largest contribution to sea level change comes from the greenland ice sheet the glaciers in alaska also make a large contribution not because of the area they cover but because they are more sensitive than other glaciers in the arctic the climate models do not agree on regional patterns the runoff from svalbard glaciers for instance increases for two models and decreases for the three other models we conclude that the uncertainty due to a simple representation of the glaciological processes is probably smaller than the uncertainty induced by the differences in the climate change scenarios produced by the models