how does arctic summer wind modulate sea ice ocean heat balance in the canada basin 1 the impacts of arctic summer wind on ice ocean heat processes in the sea ice reduction zone were investigated using a pan arctic ice ocean model the interannual simulation demonstrated event like sea ice melting because of enhanced solar radiation input and upward ocean heat transfer in the canada basin area both factors were derived from mechanical ice divergence under cyclonic wind stress atmospheric heat penetration into the newly formed open leads was estimated to be a primary contributor to sea ice lateral bottom melting the vertical ocean heat flux associated with wind driven upwelling mixing was the secondary factor on a monthly time scale the modeled interannual variability indicated that the relative role of internal ocean dynamics in sea ice variability was greater under cyclonic wind patterns compared with anticyclonic wind conditions

variations in the age of arctic sea ice and summer sea ice extent 1 three of the past six summers have exhibited record low sea ice extent on the arctic ocean these minima may have been dynamically induced by changes in the surface winds based on results of a simple model that keeps track of the age of ice as it moves about on the arctic ocean we show that the areal coverage of thick multi year ice decreased precipitously during 1989 1990 when the arctic oscillation was in an extreme high index state and has remained low since that time under these conditions younger thinner ice anomalies recirculate back to the alaskan coast more quickly decreasing the time that new ice has to ridge and thicken before returning for another melt season during the 2002 and 2003 summers this anomalously younger thinner ice was advected into alaskan coastal waters where extensive melting was observed even though temperatures were locally colder than normal the age of sea ice explains more than half of the variance in summer sea ice extent

downwelling longwave flux over summit greenland 2010 2012 analysis of surface based observations and evaluation of era interim using wavelets this study analyzes the downwelling longwave radiation dlw over the greenland ice sheet gris using surface based observations from summit station 72 n 38 w 3210 m and the european centre for medium range weather forecasts interim reanalysis era interim dlw fields since surface based observations are sparse in the arctic the accuracy of including reanalyses for spatial context is assessed first the dlw at summit is reported including the significant time scales of variability using time frequency decomposition wavelet analysis a new method for evaluating reanalyses is then introduced that also uses wavelet analysis era interim dlw performs reasonably well at summit but because it includes too many thin clouds and too few thick clouds it is biased low overall the correlation between the observations and era interim drops from r2 0 8 to near 0 for time series reconstructed from time scales less than 4 days these low correlations and additional analyses suggest that the spatial resolution of the data sets is a factor in representing variability on short time scales the bias is low across all time scales and is thus likely tied to cloud generation processes in the model rather than the spatial representation of the atmosphere across the gris the exception is autumn when era interim overestimates the influence of clouds at time scales of 1 and 4 weeks the spatial distribution of cloud influence on the dlw across the gris indicates that summit is located in a transition zone with respect to cloud properties the gradient across this transition zone is steepest near summit in autumn so the spatial characteristics of the atmosphere near summit may contribute to the era interim bias during this time

a modeling study of coastal circulation and landfast ice in the nearshore beaufort and chukchi seas using ciom this study investigates sea ice and ocean circulation using a 3 d 3 8 km ciom coupled ice ocean model under daily atmospheric forcing for the period 1990 2008 the ciom was validated using both in situ observations and satellite measurements the ciom successfully reproduces some observed dynamical processes in the region including the bering inflow originated coastal current that splits into three branches alaska coastal water acw central channel branch and herald valley branch in addition the beaufort slope current bsc the beaufort gyre the east siberian current esc mesoscale eddies and seasonal landfast ice are well simulated the ciom also reproduces reasonable interannual variability in sea ice such as landfast ice and anomalous open water less sea ice during the positive dipole anomaly da years vice versa during the negative da years sensitivity experiments were conducted with regard to the impacts of the bering strait inflow heat transport onshore wind stress and sea ice advection on sea ice change in particular on the landfast ice it is found that coastal landfast ice is controlled by the following processes wind forcing bering strait inflow and sea ice dynamics

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

beaufort shelf break eddies and shelf basin exchange of pacific summer water in the western arctic ocean detected by satellite and modeling analyses 1 mesoscale eddies and shelf basin exchange of pacific summer water in the western arctic ocean are examined using satellite data sets and an eddy resolving coupled sea ice ocean model several surface eddy like features along the beaufort shelf break are detected by the moderate resolution imaging spectroradiometer modis sea surface temperature and the global imager gli radiance image the quikscat sea wind vectors indicate that summertime shelf wide wind is an important factor for interannual variations in the eddy properties a realistic numerical experiment reveals that the origin of shelf break warm eddies and timing of their generation can be classified into three types type i eddies are frequently produced in the vicinity of the barrow canyon throughout the summer season by a combination of outflow of pacific summer water with a low potential vorticity from the barrow canyon and lateral velocity shear of the canyon jet surface wind variability modulates the timing of generation type ii and type iii eddies originate from an eastward current along the beaufort shelf break although origin depth and background hydrographic structure differ between them type ii eddies are spawned from the shelf slope at middepth during early summer type iii eddies are generated from the surface isopycnal front over the shelf break during late summer the shift from type ii eddies to type iii eddies is caused by surface buoyancy input in the upstream region a sensitivity experiment using different atmospheric forcing data suggest that the mechanism controlling pacific water transport from the chukchi shelf to the canada basin differs depending on surface wind fields in the shelf region the mesoscale eddies primarily induce the shelf to basin transport under weak or westerly wind conditions during summer while wind driven ekman transport is a major driver in the easterly wind regime year 2003 2007 corresponds to the former latter case

local and regional controls on holocene sea ice dynamics and oceanography in nares strait northwest greenland abstract nares strait is one of three channels that connect the arctic ocean to baffin bay unique sea ice conditions in the strait lead to the formation of landfast ice arches at its northern and southern ends these ice arches regulate arctic sea ice and freshwater export through the strait and promote the opening of the north water polynya the present study addresses the paucity of pre satellite records of environmental conditions in the nares strait area and aims at reconstructing holocene sea ice conditions and ocean circulation in the strait the investigation is based on a marine sediment core strategically retrieved from under the current ice arch in kane basin to the south of nares strait and provides a continuous record spanning the past ca 9 kyrs we use benthic foraminiferal assemblages and sea ice biomarkers to infer changes in holocene ocean circulation and sea ice conditions in kane basin the establishment of the modern ocean circulation in kane basin is related to ice sheet retreat and postglacial rebound while changes in sea ice cover concur with major shifts in the arctic oscillation ao our results suggest that sea ice cover in kane basin was highly variable between ca 9 0 and 8 3 cal ka bp before increasing probably in link with the 8 2 cold event and the opening of nares strait a short period of minimum sea ice cover and maximum atlantic bottom water influence occurred between ca 8 1 and 7 5 cal ka bp when kane basin was deeper than for the remaining of the holocene as atmospheric temperatures dropped sea ice cover intensified in kane basin between ca 7 5 and 5 5 cal ka bp but strong winds under prevailing positive like ao conditions likely prevented the formation of ice arches in nares strait during this time our micropaleontological data show that atlantic water was progressively excluded from kane basin by the postglacial isostatic rebound increasingly cooler atmospheric temperatures and a shift towards more negative phases of the ao may have promoted the establishment of ice arches in nares strait between ca 5 5 and 3 0 cal ka bp instabilities in the kane basin ice arch ca 3 0 cal ka bp coincide with a shift towards prevailing positive phases of the ao while a brief recovery of the ice arch occurred during more negative like ao conditions between ca 1 2 and 0 2 cal ka bp

propagating atmospheric patterns associated with sea ice motion through the fram strait abstracta novel analysis method involving phase shifted complex hilbert empirical orthogonal functions heofs was used to examine how variations in predominant propagating patterns of arctic surface wind influence daily fram strait sea ice export f during extended winter october april a primary control on arctic sea ice volume northwesterly winds favorable to f were provided by poleward moving anticyclones upstream over the canadian arctic associated with the leading heof of wind and also by eastward moving cyclones downstream over the barents sea associated with the second heof of wind a suite of spatial and statistical analyses indicated that the aggregate of the two propagating patterns largely explains a sea level pressure pattern analyzed in several prior studies as a standing wave oriented east west across the strait

climate links and recent extremes in antarctic sea ice high latitude cyclones southern annular mode and enso in this article we study the climate link between the southern annular mode sam and the southern sea ice extent sie and discuss the possible role of stationary waves and synoptic eddies in establishing this link in doing so we have used a combination of techniques involving spatial correlations of sie eddy streamfunction and wind anomalies and statistics of high latitude cyclone strength it is suggested that stationary waves may be amplified by eddy anomalies associated with high latitude cyclones resulting in more sea ice when the sam is in its positive phase for most but not all longitudes a similar association is observed during enso la nina years although this synergy in the sam enso response may partially reflect preferential areas for wave amplification around antarctica the short extent of the climate records does not allow for a definite causality connection to be established with sie stronger polar cyclones are observed over the areas where the stationary waves are amplified these deeper cyclones will break up and export ice equatorward more efficiently but the near coastal regions are cold enough to allow for a rapid re freeze of the resulting ice break up we speculate that if global warming continues this same effect could help reverse the current positive antarctic sie trends once the ice gets thinner similarly to what has been observed in the northern hemisphere

dinocyst based reconstructions of sea ice cover concentration during the holocene in the arctic ocean the northern north atlantic ocean and its adjacent seas abstract sea ice cover extent expressed in terms of mean annual concentration was reconstructed from the application of the modern analogue technique to dinocyst assemblages the use of an updated database which includes 1492 sites and 66 taxa yields sea ice concentration estimates with an accuracy of 1 1 10 holocene reconstructions of sea ice cover were made from dinocyst counts in 35 cores of the northern north atlantic and arctic seas in the canadian arctic the results show high sea ice concentration 7 10 with little variations throughout the interval in contrast in arctic areas such as the chukchi sea and the barents sea the reconstructions show large amplitude variations of sea ice cover suggesting millennial type oscillations with a pacing almost opposite in western vs eastern arctic other records show tenuous changes with some regionalism either in trends or sea ice cover variability during the mid holocene and notably at 6 0 5 ka minimum sea ice concentration is recorded in the eastern fram strait northern baffin bay and labrador sea however this minimum cannot be extrapolated at the scale of the arctic and circum arctic the comparison of recent observations and reconstructions suggests larger variations in the arctic sea ice cover during the last decades than throughout the holocene

implications of fractured arctic perennial ice cover on thermodynamic and dynamic sea ice processes decline of the arctic summer minimum sea ice extent is characterized by large expanses of open water in the siberian laptev chukchi and beaufort seas and introduces large fetch distances in the arctic ocean long waves can propagate deep into the pack ice thereby causing flexural swell and failure of the sea ice this process shifts the floe size diameter distribution smaller increases floe surface area and thereby affects sea ice dynamic and thermodynamic processes the results of radarsat 2 imagery analysis show that a flexural fracture event which occurred in the beaufort sea region on 6 september 2009 affected 40 000 km2 open water fractional area in the area affected initially decreased from 3 7 to 2 7 but later increased to 20 following wind forced divergence of the ice pack energy available for lateral melting was assessed by estimating the change in energy entrainment from longwave and shortwave radiation in the mixed layer of the ocean following flexural fracture 11 54 mj m 2 of additional energy for lateral melting of ice floes was identified in affected areas the impact of this process in future arctic sea ice melt seasons was assessed using estimations of earlier occurrences of fracture during the melt season and is discussed in context with ocean heat fluxes atmospheric mixing of the ocean mixed layer and declining sea ice cover we conclude that this process is an important positive feedback to arctic sea ice loss and timing of initiation is critical in how it affects sea ice thermodynamic and dynamic processes

three dimensional model of the feeder conduit of the 1983 eruption of mt etna volcano from ground deformation measurements a levelling network and a horizontal distance measuring network down mt etna s south flank were measured before during and after the 1983 eruption we analyse the large movements recorded using theoretical models of surface displacement to determine the shape and position of the feeder conduit that supplied magma to the eruption the results indicate that a dyke the top surface extending nearly horizontally connects the eruption site to a point near the southeast crater the top of the dyke lies at an altitude of 2400 m to 2500 m and dips between 75 and 90 to the west more tentative evidence indicates that the top of the active dyke dropped by about 150 m between the 25th and the 95th day of the eruption and that a small branching dyke 1 km long was emplaced to the east of the main dyke but did not attain the surface the implications of these observation are discussed

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

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

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

autumn atmospheric response to the 2007 low arctic sea ice extent in coupled ocean atmosphere hindcasts the autumn and early winter atmospheric response to the record low arctic sea ice extent at the end of summer 2007 is examined in ensemble hindcasts with prescribed sea ice extent made with the european centre for medium range weather forecasts state of the art coupled ocean atmosphere seasonal forecast model robust warm anomalies over the pacific and siberian sectors of the arctic as high as 10 c at the surface are found in october and november a regime change occurs by december characterized by weaker temperatures anomalies extending through the troposphere geopotential anomalies extend from the surface up to the stratosphere associated to deeper aleutian and icelandic lows while the upper level jet is weakened and shifted southward over the continents it is intensified over both oceanic sectors especially over the pacific ocean on the american and eurasian continents intensified surface highs are associated with anomalous advection of cold warm polar air on their eastern western sides bringing cooler temperatures along the pacific coast of asia and northeastern north america transient eddy activity is reduced over eurasia intensified over the entrance and exit regions of the pacific and atlantic storm tracks in broad qualitative agreement with the upper level wind anomalies potential predictability calculations indicate a strong influence of sea ice upon surface temperatures over the arctic in autumn but also along the pacific coast of asia in december when the observed sea ice extent from 2007 is prescribed throughout the autumn a higher correlation of surface temperatures with meteorological re analyses is found at high latitudes from october until mid november this further emphasises the relevance of sea ice for seasonal forecasting in the arctic region in the autumn

large scale flow and the long lasting blocking high over russia summer 2010 abstractseveral studies show that the anomalous long lasting russian heat wave during the summer of 2010 linked to a long persistent blocking high appears mainly as a result of natural atmospheric variability this study analyzes the large scale flow structure based on the ecmwf re analysis interim era interim data 1989 2010 the anomalous long lasting blocking high over western russia including the heat wave occurs as an overlay of a set of anticyclonic contributions on different time scales i a regime change in enso toward la nina modulates the quasi stationary wave structure in the boreal summer hemisphere supporting the eastern european blocking the polar arctic dipole mode is enhanced and shows a projection on the mean blocking high ii together with the quasi stationary wave anomaly the transient eddies maintain the long lasting blocking iii three different pathways of wave action are identified on the intermediate time scale 10 60 days one pathway commences over the eastern nort

arctic dipole anomaly and its contribution to sea ice export from the arctic ocean in the 20th century 1 the winter dipole anomaly da in the arctic atmosphere and its contribution to sea ice export are investigated by using a high resolution coupled global general circulation model the spatial distributions of the first two leading eof modes of winter mean sea level pressure slp and geopotential height at 500 hpa north of 70n obtained by the long term simulation 1900 2010 are highly similar to those derived from the national center for environmental prediction and the national center for the atmospheric research ncep ncar reanalysis datasets 1948 2004 the first leading mode corresponds to the arctic oscillation ao the da is defined as the second leading mode the ao and da account for 59 and 19 of the total variance respectively composite spatial patterns of slp sea ice thickness and velocity in the extreme years when both the absolute values of principal component pc1 and pc2 exceed 1 0 standard deviation indicate that the da plays a great important role in sea ice export from the arctic ocean to the greenland sea due to its strong meridionality sea ice export is highly promoted restricted in the positive negative da phase the dependence of sea ice export on the da is comparable to or rather larger than that on the ao citation watanabe e j wang a sumi and h hasumi 2006 arctic dipole anomaly and its contribution to sea ice export from the arctic ocean in the 20th century geophys res lett 33 l23703 doi 10 1029 2006gl028112

changes in the thickness distribution of arctic sea ice between 1958 1970 and 1993 1997 1 submarine sonar data collected in the central arctic basin during middle and late summer were used to examine differences in the sea ice thickness distribution function g h between the periods 1958 1970 and 1993 1997 cruises during the former period were made in july and august whereas the 1993 1997 cruises were made in september and october seasonal correction was applied to adjust for the differences in thickness while ice drafts were from only seven submarine cruises and somewhat spatially limited results indicate that the fractional area covered by open water and first year ice increased from 0 19 to 0 30 during the time interval this was balanced by an 11 reduction of level multiyear and ridged ice substantial losses occurred in ice thicker than 2 m with an increase in the amount of 1 2 m ice the volume of ice less than 4 m thick remained nearly the same and the total volume decreased about 32 losses in the volume of thicker ice increased with increasing thickness part of the change in g h is likely caused by increased ice area export through fram strait in the late 1980s and early 1990s because decadal variations in the north atlantic oscillation and arctic oscillation indices correlate with ice export anomalies export induced changes in g h probably tend to be cyclical in nature however a substantial shift in the peak of g h suggests that changes in thermal forcing were also a major factor in the observed thinning

a vorticity based analysis of the spatial and temporal characteristics of the beaufort anticyclone 1 the beaufort anticyclone is the dominant pressure feature over the arctic ocean in all seasons and has a large influence on the surface wind regime and sea ice motion sea level pressure slp from the national center for atmospheric research national centers for environmental prediction reanalysis is used to create a vorticity metric to investigate the spatial and temporal characteristics of the beaufort anticyclone from 1948 to 2008 correlations between vorticity averaged over the beaufort anticyclone region and northern hemisphere slp are strongest south of alaska and north of siberia these two areas are also present in slp composite maps based on extremes of the vorticity metric temporal characteristics are investigated using running means and spectral analysis in which the only predominant peak is the annual cycle if 30 year time periods are compared little to no trend in the vorticity metric is found except in october december where the more recent time period has slightly larger vorticity magnitudes the beaufort anticyclone vorticity metric is correlated with teleconnection index values the pacific ocean patterns show a larger influence than the atlantic patterns including the arctic oscillation which has been shown in recent studies to have little correspondence to changes in sea ice in the early 21st century a significant correlation is found with the pacific north american pattern in all seasons except summer the el nino southern oscillation shows a significant correlation with the vorticity metric in winter and the pacific decadal oscillation shows a significant correlation in winter and spring

linking the northern hemisphere sea ice reduction trend and the quasi decadal arctic sea ice oscillation the nature of the reduction trend and quasi decadal oscillation in northern hemisphere sea ice extent is investigated the trend and oscillation that seem to be two separate phenomena have been found in data this study examines a hypothesis that the arctic sea ice reduction trend in the last three decades amplified the quasi decadal arctic sea ice oscillation asio due to a positive ice ocean albedo feedback based on data analysis and a conceptual model proposed by ikeda et al the theoretical conceptual model predicts that the quasi decadal oscillation is amplified by the thinning sea ice leading to the asio which is driven by the strong positive feedback between the atmosphere and ice ocean systems such oscillation is predicted to be out of phase between the arctic basin and the nordic seas with a phase difference of 3 4 with the nordic seas leading the arctic the wavelet analysis of the sea ice data reveals that the quasi decadal asio occurred actively since the 1970s following the trend starting in the 1960s i e as sea ice became thinner and thinner as the atmosphere experienced quasi decadal oscillations during the last century the wavelet analysis also confirms the prediction of such out of phase feature between these two basins which varied from 0 62 in 1960 to 0 25 in 1995 furthermore a coupled ice ocean general circulation model gcm was used to simulate two scenarios one without the greenhouse gas warming and the other having realistic atmospheric forcing along with the warming that leads to sea ice reduction trend the quasi decadal asio is excited in the latter case compared to the no warming case the wavelet analyses of the simulated ice volume were also conducted to derive decadal asio and similar phase relationship between the arctic ocean and the nordic seas an independent data source was used to confirm such decadal oscillation in the upper layer or freshwater thickness which is consistent with the model simulation a modified feedback loop for the sea ice trend and asio was proposed based on the previous one by mysak and venegas and the ice albedo and cloud albedo feedabcks which are responsible for the sea ice reduction trend

meteorological conditions in a thinner arctic sea ice regime from winter to summer during the norwegian young sea ice expedition n ice2015 atmospheric measurements were made over arctic sea ice north of svalbard from winter to early summer january june 2015 during the norwegian young sea ice n ice2015 expedition these measurements which are available publicly represent a comprehensive meteorological data set covering the seasonal transition in the arctic basin over the new thinner sea ice regime winter was characterized by a succession of storms that produced short lived less than 48 h temperature increases of 20 to 30 k at the surface these storms were driven by the hemispheric scale circulation pattern with a large meridional component of the polar jet stream steering north atlantic storms into the high arctic nonstorm periods during winter were characterized by strong surface temperature inversions due to strong radiative cooling radiatively clear state the strength and depth of these inversions were similar to those during the surface heat budget of the arctic ocean sheba campaign in contrast atmospheric profiles during the opaquely cloudy state were different to those from sheba due to differences in the synoptic conditions and location within the ice pack storm events observed during spring summer were the result of synoptic systems located in the barents sea and the arctic basin rather than passing directly over n ice2015 these synoptic systems were driven by a large scale circulation pattern typical of recent years with an arctic dipole pattern developing during june surface temperatures became near constant 0 c on 1 june marking the beginning of summer atmospheric profiles during the spring and early summer show persistent lifted temperature and moisture inversions that are indicative of clouds and cloud processes

marine aerosol source regions to prince of wales icefield ellesmere island and influence from the tropical pacific 1979 2001 using a coastal ice core collected from prince of wales pow icefield on ellesmere island we investigate source regions of sea ice modulated chemical species methanesulfonic acid msa and chloride cl to pow icefield and the influence of large scale atmospheric variability on the transport of these marine aerosols 1979 2001 our key findings are 1 msa in the pow icefield core is derived primarily from productivity in the sea ice zone of baffin bay and the labrador sea with influence from waters within the north water now polynya 2 sea ice formation processes within the now polynya may be a significant source of sea salt aerosols to the pow core site in addition to offshore open water source regions primarily in hudson bay and 3 the tropical pacific influences the source and transport of marine aerosols to pow icefield through its remote control on regional winds and sea ice variability regression analyses during times of msa deposition reveal sea level pressure slp anomalies favorable for opening of the now polynya and subsequent oceanic dimethyl sulfide production regression analyses during times of cl deposition reveal slp anomalies that indicate a broader oceanic region of sea salt sources to the core site these results are supported by scanning multichannel microwave radiometer and special sensor microwave imager based sea ice reconstructions and air mass transport density analyses and suggest that the marine biogenic record may capture local polynya variability while sea salt transport to the site from larger offshore source regions in baffin bay is likely regression analyses show a link to tropical dynamics via an atmospheric rossby wave

the fate of terrigenous dissolved organic carbon on the eurasian shelves and export to the north atlantic dissolved lignin phenols chromophoric dissolved organic matter cdom absorption and fluorescence were analyzed along cross slope mooring locations in the barents laptev and east siberian seas to gain a better understanding of terrigenous dissolved organic carbon tdoc dynamics in arctic shelf seas and the arctic ocean a gradient of river water and tdoc was observed along the continental shelf eastward into the east siberian sea correlations of carbon normalized yields of lignin derived phenols supplied by siberian rivers with river water fractions and known water residence times yielded in situ decay constants of 0 18 0 58 yr 1 calculations showed 50 of annual tdoc discharged by siberian rivers was mineralized in estuaries and on eurasian shelves per year indicating extensive removal of tdoc bioassay experiments and in situ decay constants indicated a reactivity continuum for tdoc cdom parameters and acid aldehyde ratios of vanillyl v and syringyl s lignin phenols showed biomineralization was the dominant mechanism for the removal of tdoc characteristic ratios of p hydroxy p s and v phenols p v s v also identified shelf regions in the kara sea and regions along the western laptev sea shelf where formation of low salinity halocline waters lshw and lower halocline water lhw occurred the efficient removal of tdoc demonstrates the importance of eurasian margins as sinks of tdoc derived from the large siberian rivers and confirms tdoc mineralization has a major impact on nutrients budgets air sea co2 exchange and acidification in the siberian shelf seas

interannual variability of arctic landfast ice between 1976 and 2007 abstractanalysis of weekly sea ice charts produced by the u s national ice center from 1976 to 2007 indicates large interannual variations in the averaged winter landfast ice extent around the arctic basin during the 32 yr period of the record landfast ice cover was relatively extensive from the early to mid 1980s but since then has declined in many coastal regions of the arctic particularly after the early 1990s while the barents baltic and bering seas show increases in landfast ice area the overall change for the northern hemisphere is negative about 12 27 2 8 103 km2 yr 1 or 7 1 5 decade 1 relative to the long term mean except in a few coastal regions the seasonal duration of landfast ice is shorter overall particularly in the laptev east siberian and chukchi seas the decreased winter landfast ice extent is associated with some notable changes in ice growth and melt patterns in particular the slowed landfast ice expansion during fall and early winter since 1990 the observed

tropical cyclone effects on arctic sea ice variability 1 in recent years increasing interest has been put on the role that intense tropical cyclones can play in the climate system the following study is aimed at highlighting the effects of strong tropical cyclones over the tropical atlantic on the mean climate their composite effect on the surface winds is made apparent by a wide cyclonic perturbation that affects a large portion of the atlantic tropical ocean teleconnection patterns which are visible in the sea level pressure anomalies associated with this tropical composite cyclone appear to link the activity of the hurricanes to the arctic ocean a significant negative correlation between the energy dissipated by hurricanes in the tropical atmosphere and the sea ice cover along the transpolar drift stream path has also been found

arctic sea ice reemergence the role of large scale oceanic and atmospheric variability abstractarctic sea ice reemergence is a phenomenon in which spring sea ice anomalies are positively correlated with fall anomalies despite a loss of correlation over the intervening summer months this work employs a novel data analysis algorithm for high dimensional multivariate datasets coupled nonlinear laplacian spectral analysis nlsa to investigate the regional and temporal aspects of this reemergence phenomenon coupled nlsa modes of variability of sea ice concentration sic sea surface temperature sst and sea level pressure slp are studied in the arctic sector of a comprehensive climate model and in observations it is found that low dimensional families of nlsa modes are able to efficiently reproduce the prominent lagged correlation features of the raw sea ice data in both the model and observations these families provide an sst sea ice reemergence mechanism in which melt season spring sea ice anomalies are imprinted as sst anomalies and stored over the summer months allowing for

assimilating summer sea ice concentration into a coupled ice ocean model using a lseik filter the decrease in summer sea ice extent in the arctic ocean opens shipping routes and creates potential for many marine operations for these activities accurate predictions of sea ice conditions are required to maintain marine safety in an attempt at arctic sea ice prediction the summer of 2010 is selected to implement an arctic sea ice data assimilation da study the da system is based on a regional arctic configuration of the massachusetts institute of technology general circulation model mitgcm and a local singular evolutive interpolated kalman lseik filter to assimilate special sensor microwave imager sounder ssmis sea ice concentration operational products from the us national snow and ice data center nsidc based on comparisons with both the assimilated nsidc ssmis concentration and concentration data from the ocean and sea ice satellite application facility the forecasted sea ice edge and concentration improve upon simulations without data assimilation by the nature of the assimilation algorithm with multivariate covariance between ice concentration and thickness sea ice thickness fields are also updated and the evaluation with in situ observation shows some improvement compared to the forecast without data assimilation

the interior shelves of the arctic ocean physical oceanographic setting climatology and effects of sea ice retreat on cross shelf exchange abstract the interior shelves of the arctic mediterranean are the shelves of the kara sea laptev sea east siberian sea and beaufort sea they comprise approximately 40 of the total arctic shelf area 2 5 10 6 km 2 and are distinguished from inflow and outflow shelves by their principal forcing dynamics along their southern continental boundary the interior shelves are dominated by the major arctic rivers receiving over 80 of the total freshwater input to the arctic ocean in the mid shelf region wind and ice motion surface stresses dominate mixing and circulation resulting in high variability along their northern seaward boundary they are forced by upwelling and downwelling favourable surface stresses which drive shelf basin exchanges with atlantic and pacific origin cyclonic boundary currents over the upper slope shelf basin exchange is further modified by shelf break morphometry e g canyons valleys headlands and bottom slope here we review the physical oceanographic settings and forcing of the interior shelves and then focus on shelfbreak exchange and supply of nutrients for new primary production due to upwelling across the shelfbreak as a proxy for this nutrient supply we show seasonal and annual time series of along shelfbreak surface stress due to wind and ice motion from 1979 to 2011 we apply this analysis to the shallow shelves from the kara sea to the beaufort sea and comment on recent increases due to atmospheric changes and sea ice retreat

arctic sea ice seasonal prediction by a linear markov model abstracta linear markov model has been developed to predict sea ice concentration sic in the pan arctic region at intraseasonal to seasonal time scales which represents an original effort to use a reduced dimension statistical model in forecasting arctic sea ice year round the model was built to capture covariabilities in the atmosphere ocean sea ice system defined by sic sea surface temperature and surface air temperature multivariate empirical orthogonal functions of these variables served as building blocks of the model a series of model experiments were carried out to determine the model s dimension the predictive skill of the model was evaluated by anomaly correlation and root mean square errors in a cross validated fashion on average the model is superior to the predictions by anomaly persistence damped anomaly persistence and climatology the model shows good skill in predicting sic anomalies within the arctic basin during summer and fall long term trends partially contribute to the

circulation of summer pacific halocline water in the arctic ocean 1 we present an analysis of arctic ocean hydrographic and sea ice observations from the 1990s with a focus on the circulation of water that originates in the north pacific ocean previous studies have shown the presence of two varieties of relatively warm summer halocline water in the vicinity of the chukchi sea i e the relatively fresh alaskan coastal water acw and the relatively saltier summer bering sea water sbsw here we extend these studies by tracing the circulation of these waters downstream into the arctic ocean we find that acw is generally most evident in the southern beaufort gyre while sbsw is strongest in the northern portion of the beaufort gyre and along the transpolar drift stream we find that this separation is most extreme during the early mid 1990s when the arctic oscillation was at historically high index values this leads us to speculate that the outflow to the north atlantic ocean through the canadian archipelago and fram strait may be similarly separated as arctic oscillation index values fell during the later 1990s acw and sbsw began to overlap in their regions of influence these changes are evident in the area north of ellesmere island where the influence of sbsw is highly correlated with a 3 year lag with the arctic oscillation index we also note the presence of winter bering sea water wbsw which underlies the summer varieties all together this brings the number of distinct pacific water types in our arctic ocean inventory to three acw sbsw and wbsw

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

natural fluorinated organics in fluorite and rocks results of measurements of fluorinated compounds in gasses extracted from igneous and metamorphic rocks are reported a new extraction method analogous to a pepper mill for geological samples is described it permits extraction at low temperatures and ensures a rapid transfer of extracted gases from active surfaces to cryogenic pre concentration loop values for cf4 cf3cl cf2cl2 cfcl3 chf3 sf6 and nf3 in fluorites granites basalts and other igneous and metamorphic rocks are reported it is proposed that trifluoroacetic acid tfa that was recently discovered in various environmental archives could also origin from similar geogenic sources

observed winter salinity fields in the surface layer of the arctic ocean and statistical approaches to predicting large scale anomalies and patterns significant salinity anomalies have been observed in the arctic ocean surface layer during the last decade our study is based on an extensive gridded dataset of winter salinity in the upper 50 m layer of the arctic ocean for the periods 1950 1993 and 2007 2012 obtained from 20 000 profiles we investigate the interannual variability of the salinity fields identify predominant patterns of anomalous behavior and leading modes of variability and develop a statistical model for the prediction of surface layer salinity the statistical model is based on linear regression equations linking the principal components of surface layer salinity obtained through empirical orthogonal function decomposition with environmental factors such as atmospheric circulation river runoff ice processes and water exchange with neighboring oceans using this model we obtain prognostic fields of the surface layer salinity for the winter period 2013 2014 the prognostic fields generated by the model show tendencies of surface layer salinification which were also observed in previous years although the used data are proprietary and have gaps they provide the most spatiotemporally detailed observational resource for studying multidecadal variations in basin wide arctic salinity thus there is community value in the identification dissemination and modeling of the principal modes of variability in this salinity record

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

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

changes in summer sea ice albedo and portioning of surface solar radiation in the pacific sector of arctic ocean during 1982 2009 ssm i sea ice concentration and clara black sky composite albedo were used to estimate sea ice albedo in the region 70 82 n 130 180 w the long term trends and seasonal evolutions of ice concentration composite albedo and ice albedo were then obtained in july august 1982 2009 the linear trend of the composite albedo and the ice albedo was 0 069 and 0 046 units per decade respectively during 1 june to 19 august melting of sea ice resulted in an increase of solar heat input to the ice ocean system by 282 mj m 2 from 1982 to 2009 however because of the counter balancing effects of the loss of sea ice area and the enhanced ice surface melting the trend of solar heat input to the ice was insignificant the summer evolution of ice albedo matched the ice surface melting and ponding well at basin scale the ice albedo showed a large difference between the multiyear and first year ice because the latter melted completely by the end of a melt season at the sheba geolocations a distinct change in the ice albedo has occurred since 2007 because most of the multiyear ice has been replaced by first year ice a positive polarity in the arctic dipole anomaly could be partly responsible for the rapid loss of summer ice within the study region in the recent years by bringing warmer air masses from the south and advecting more ice toward the north both these effects would enhance ice albedo feedback this article is protected by copyright all rights reserved

the arctic oscillation signature in the wintertime geopotential height and temperature fields the leading empirical orthogonal function of the wintertime sea level pressure field is more strongly coupled to surface air temperature fluctuations over the eurasian continent than the north atlantic oscillation nao it resembles the nao in many respects but its primary center of action covers more of the arctic giving it a more zonally symmetric appearance coupled to strong fluctuations at the 50 hpa level on the intraseasonal interannual and interdecadal time scales this arctic oscillation ao can be interpreted as the surface signature of modulations in the strength of the polar vortex aloft it is proposed that the zonally asymmetric surface air temperature and mid tropospheric circulation anomalies observed in association with the ao may be secondary baroclinic features induced by the land sea contrasts the same modal structure is mirrored in the pronounced trends in winter and springtime surface air temperature sea level pressure and 50 hpa height over the past 30 years parts of eurasia have warmed by as much as several k sea level pressure over parts of the arctic has fallen by 4 hpa and the core of the lower stratospheric polar vortex has cooled by several k these trends can be interpreted as the development of a systematic bias in one of the atmosphere s dominant naturally occurring modes of variability

patterns of sea ice retreat in the transition to a seasonally ice free arctic abstractthe patterns of sea ice retreat in the arctic ocean are investigated using two global climate models gcms that have profound differences in their large scale mean winter atmospheric circulation and sea ice drift patterns the community earth system model large ensemble cesm le presents a mean sea level pressure pattern that is in general agreement with observations for the late twentieth century the community climate system model version 4 ccsm4 exhibits a low bias in its mean sea level pressure over the arctic region with a deeper icelandic low a dynamical mechanism is presented in which large scale mean winter atmospheric circulation has significant effect on the following september sea ice extent anomaly by influencing ice divergence in specific areas a lagrangian model is used to backtrack the 80 n line from the approximate time of the melt onset to its prior positions throughout the previous winter and quantify the divergence across the pacific and eurasian sectors of the arctic i

summer retreat of arctic sea ice role of summer winds 1 the unprecedented retreat of first year ice during summer 2007 was enhanced by strong poleward drift over the western arctic induced by anomalously high sea level pressure slp over the beaufort sea that persisted throughout much of the summer comparison of the tracks of drifting buoys with monthly mean slp charts shows a substantial ekman drift by means of linear regression analysis it is shown that ekman drift during summer has played an important role in regulating annual minimum arctic sea ice extent in prior years as well in combination the preconditioning by events in prior years as represented by an index of may multi year ice and current atmospheric conditions as represented by an index of july august september slp anomalies over the arctic basin account for 60 of the year to year variance of september sea ice extent since 1979