influence of snow depth and surface flooding on light transmission through antarctic pack ice snow on sea ice alters the properties of the underlying ice cover as well as associated physical and biological processes at the interfaces between atmosphere sea ice and ocean the antarctic snow cover persists during most of the year and contributes significantly to the sea ice mass due to the widespread surface flooding and related snow ice formation snow also enhances the sea ice surface reflectivity of incoming shortwave radiation and determines therefore the amount of light being reflected absorbed and transmitted to the upper ocean here we present results of a case study of spectral solar radiation measurements under antarctic pack ice with an instrumented remotely operated vehicle in the weddell sea in 2013 in order to identify the key variables controlling the spatial distribution of the under ice light regime we exploit under ice optical measurements in combination with simultaneous characterization of surface properties such as sea ice thickness and snow depth our results reveal that the distribution of flooded and nonflooded sea ice areas dominates the spatial scales of under ice light variability for areas smaller than 100 m by 100 m however the heterogeneous and highly metamorphous snow on antarctic pack ice obscures a direct correlation between the under ice light field and snow depth compared to the arctic light levels under antarctic pack ice are extremely low during spring 0 1 this is mostly a result of the distinctly different dominant sea ice and snow properties with seasonal snow cover including strong surface melt and summer melt ponds in the arctic and a year round snow cover and widespread surface flooding in the southern ocean

physical and biological controls on oxygen saturation variability in the upper arctic ocean employing continuous in situ measurements of dissolved o2 ar and o2 in the arctic ocean we investigate the mechanisms controlling the physical abiotic and biological oxygen saturation state variability in the surface ocean beneath sea ice o2 ar measurements were made underway using equilibrator inlet mass spectrometry eims during an icebreaker survey transiting the upper arctic ocean across the north pole in late summer 2011 using concurrently collected measurements of total oxygen we devolve biological oxygen saturation and physical oxygen ar saturation signals at unprecedented horizontal resolution in the surface ocean in the nansen basin ar is undersaturated up to 7 while biological oxygen supersaturation peaks at 18 4 we attribute this to ice melt atlantic water influence and or cooling in the canadian basin ar is supersaturated up to 3 likely because of ar injection from freezing processes and long residence times of gas under ice cover the overall canadian basin to eurasian basin gradient of ar supersaturation to undersaturation may reflect net freezing in the canadian basin and net melting in the eurasian basin over several seasons either by pacific to atlantic sector ice transport or local changes over time ar saturation could thereby provide large scale high resolution estimates of current and future changes in these processes o2 ar supersaturation averages 4 9 with peaks up to 9 8 where first year ice and abundant melt ponds likely allow sufficient light for blooms in ice covered regions

impact of horizontal spreading on light propagation in melt pond covered seasonal sea ice in the canadian arctic 1 melt pond covered sea ice is a ubiquitous feature of the summertime arctic ocean when meltwater collects in lower lying areas of ice surfaces horizontal transects were conducted during june 2008 above and below landfast sea ice with melt ponds to characterize surface and bottom topography together with variations in transmitted spectral irradiance we captured a rapid progression from a highly flooded sea ice surface with lateral drainage toward flaws and seal breathing holes to the formation of distinct melt ponds with steep edges as the mass of the ice cover decreased due to meltwater drainage and rose upward with respect to the seawater level the high scattering properties of ice above the water level i e white ice were continuously regenerated while pond waters remained transparent compared to underlying ice the relatively stable albedos observed throughout the study even as ice thickness decreased were directly related to these surface processes transmission through the ice cover of incident irradiance in the 400 700 nm wave band ranged from 38 to 67 and from 5 to 16 beneath ponded and white ice respectively our results show that this transmission varied not only as a function of surface type melt ponds or white ice areal coverage but also in relation to ice thickness and proximity to other surface types through the influence of horizontal spreading of light thus in contrast to albedo this implies that regional transmittance estimates need to consider melt pond size and shape distributions and variations in optical properties and thickness of the ice cover

thickness distribution of antarctic sea ice 1 ship based observations are used to describe regional and seasonal changes in the thickness distribution and characteristics of sea ice and snow cover thickness around antarctica the data set comprises 23 373 observations collected over more than 2 decades of activity and has been compiled as part of the scientific committee on antarctic research scar antarctic sea ice processes and climate aspect program the results show the seasonal progression of the ice thickness distribution for six regions around the continent together with statistics on the mean thickness surface ridging snow cover and local variability for each region and season a simple ridge model is used to calculate the total ice thickness from the observations of level ice and surface topography to provide a best estimate of the total ice mass including the ridged component the long term mean and standard deviation of total sea ice thickness including ridges is reported as 0 87 0 91 m which is 40 greater than the mean level ice thickness of 0 62 m analysis of the structure function along north south and east west transects revealed lag distances over which sea ice thickness decorrelates to be of the order of 100 300 km which we use as a basis for presenting near continuous maps of sea ice and snow cover thickness plotted on a 2 5 5 0 grid

effect of sea ice melt on inherent optical properties and vertical distribution of solar radiant heating in arctic surface waters the inherent optical properties iops of polar waters pw exiting the arctic ocean in the east greenland current egc and of the inflowing atlantic waters aw in the west spitsbergen current wsc were studied in late summer when surface freshening due to sea ice melt was widespread the absorption and attenuation coefficients in pw were significantly higher than previous observations from the western arctic high concentrations of colored dissolved organic matter cdom resulted in 50 60 more heat deposition in the upper meters relative to clearest natural waters this demonstrates the influence of terrigenous organic material inputs on the optical properties of waters in the eurasian basin sea ice melt in cdom rich pw decreased cdom absorption but an increase in scattering nearly compensated for lower absorption and total attenuation was nearly identical in the sea ice meltwater layer this suggests a source of scattering material associated with sea ice melt relative to the pw in the aw melting sea ice forms a stratified surface layer with lower absorption and attenuation than well mixed aw waters in late summer it is likely that phytoplankton in the surface layer influenced by sea ice melt are nutrient limited the presence of a more transparent surface layer changes the vertical radiant heat absorption profile to greater depths in late summer both in egc and wsc waters shifting accumulation of solar heat to greater depths and thus this heat is not directly available for ice melt during periods of stratification

temperature responses to quasi 100 yr solar variability during the past 6000 years based on δ18o of peat cellulose in hongyuan eastern qinghai tibet plateau china abstract during the past 6000 years the temperature variation trend inferred from 18o of peat cellulose in a peat core from hongyuan eastern qinghai tibet plateau southwestern china is similar to the atmospheric 14c concentration trend and the modeled solar output trend the general trend of hongyuan 18o during the past millennium also coincides well with the atmospheric 14c concentration trend the 10be concentration trend in an ice core from the south pole the reconstructed total solar irradiance trend as well as the modeled solar output trend in addition temperature events also correspond well to solar perturbations during the past 6000 years therefore the driving force of holocene temperature variations should be properly ascribed to solar activity the spectrum analysis further illustrates that quasi 100 yr fluctuation of solar activity was probably responsible for temperature variations in northeast qinghai tibet plateau during the past 6000 years

energy budget of first year arctic sea ice in advanced stages of melt 1 during an 8 day drift in july august 2012 in the nansen basin all components of the energy budget of melting first year sea ice were observed absorption of solar radiation by the ice and ponds was the largest source of energy to the ice at almost all times during the drift however oceanic heat flux also provided significant heating and dominated during one wind event longwave fluxes provided a relatively small cooling effect and atmospheric heat fluxes were negligible the aggregate scale albedo of this younger thinner ice was significantly lower than at surface heat budget of the arctic ocean sheba and the transmittance was significantly higher here despite similar pond and open water fractions the oceanic heat flux was only half of the solar flux through the ice to the water producing warm water near the surface that might delay ice growth in autumn an important effect of the transition to thinner first year ice in the high arctic

windows in arctic sea ice light transmission and ice algae in a refrozen lead the arctic ocean is rapidly changing from thicker multiyear to thinner first year ice cover with significant consequences for radiative transfer through the ice pack and light availability for algal growth a thinner more dynamic ice cover will possibly result in more frequent leads covered by newly formed ice with little snow cover we studied a refrozen lead 0 27 m ice in drifting pack ice north of svalbard 80 5 82 4 n in may june 2015 during the norwegian young sea ice expedition n ice2015 we measured downwelling incident and ice transmitted spectral irradiance and colored dissolved organic matter cdom particle absorption ultraviolet uv protecting mycosporine like amino acids maas and chlorophyll a chl a in melted sea ice samples we found occasionally very high maa concentrations up to 39 mg m 3 mean 4 5 7 8 mg m 3 and maa to chl a ratios up to 6 3 mean 1 2 1 3 disagreement in modelled and observed transmittance in the uv range let us conclude that maa signatures in cdom absorption spectra may be artefacts due to osmotic shock during ice melting although observed par transmittance through the thin ice was 5 40 times that of the adjacent thicker ice with deep snow cover ice algal standing stocks were low 2 31 mg chl a m 2 and similar to the adjacent ice ice algal accumulation in the lead was possibly delayed by the low inoculum and the time needed for photoacclimation to the high light environment however leads are important for phytoplankton growth by acting like windows into the water column

airborne observations of summer thinning of multiyear sea ice originating from the lincoln sea to better understand recent changes of arctic sea ice thickness and extent it is important to distinguish between the contributions of winter growth and summer melt to the sea ice mass balance in this study we present a lagrangian approach to quantify summer sea ice melt in which multiyear ice myi floes that were surveyed by airborne electromagnetic thickness sounding within nares strait during summer were backtracked using satellite imagery to a region in close proximity 3 20 km to spring ice thickness surveys carried out in the lincoln sea typical modal total myi thicknesses including 0 4 m snow ranged between 3 9 and 4 7 m in the lincoln sea during april ice only modal thicknesses were between 2 2 and 3 0 m in nares strait during august total thinning including snow and ice was 1 3 0 1 m including 0 4 0 09 m of snow melt and 0 9 0 2 m of ice melt this translates to a seasonal net heat input of 305 69 mj m2 262 60 mj m2 for ice only and seasonal net heat flux of 57 13 w m2 45 10 w m2 for ice only which is unlikely to be explained by solar radiation fluxes alone furthermore our approach provides an improvement on traditional ice mass balance buoy estimates because it integrates melt over larger spatial scales where melt can be highly variable due to differential melt experienced between melt ponds bare ice hummocks and ridges

solar partitioning in a changing arctic sea ice cover the summer extent of the arctic sea ice cover has decreased in recent decades and there have been alterations in the timing and duration of the summer melt season these changes in ice conditions have affected the partitioning of solar radiation in the arctic atmosphere ice ocean system the impact of sea ice changes on solar partitioning is examined on a pan arctic scale using a 25 km 25 km equal area scalable earth grid for the years 1979 2007 daily values of incident solar irradiance are obtained from ncep reanalysis products adjusted by era 40 and ice concentrations are determined from passive microwave satellite data the albedo of the ice is parameterized by a five stage process that includes dry snow melting snow melt pond formation melt pond evolution and freeze up the timing of these stages is governed by the onset dates of summer melt and fall freeze up which are determined from satellite observations trends of solar heat input to the ice were mixed with increases due to longer melt seasons and decreases due to reduced ice concentration results indicate a general trend of increasing solar heat input to the arctic ice ocean system due to declines in albedo induced by decreases in ice concentration and longer melt seasons the evolution of sea ice albedo and hence the total solar heating of the ice ocean system is more sensitive to the date of melt onset than the date of fall freeze up the largest increases in total annual solar heat input from 1979 to 2007 averaging as much as 4 a 1 occurred in the chukchi sea region the contribution of solar heat to the ocean is increasing faster than the contribution to the ice due to the loss of sea ice

a functional regression model for predicting optical depth and estimating attenuation coefficients in sea ice covers near resolute passage canada the spectral dependence of natural light transmittance on ice algae concentration and snow depth in arctic sea ice provides the potential to study the changing bottom ice ecosystem using optical relationships in this paper we consider the use of functional data analysis techniques to describe such relationships specifically we created a functional regression model describing spectral optical depth as a function of chlorophylla concentration snow depth and ice thickness measurements of the aforementioned covariates and surface and transmitted spectral irradiance were collected on landfast first year sea ice in the high arctic near resolute passage canada during the spring of 2011 and used as model input the derived model explains 75 84 5 of the variation in the observed spectral optical depth curves no prior assumptions of snow sea ice optical properties are required in the application of this technique as the model estimates the attenuation coefficients of each covariate using only the measurements mentioned above the quality and simplicity of the model highlight the potential of functional data analysis to study the arctic marine ecosystem

melt pond distribution and geometry in high arctic sea ice derived from aerial investigations aerial photography was conducted in the high arctic ocean during a chinese research expedition in summer 2010 by partitioning the images into three distinct surface categories sea ice snow water and melt ponds the areal fraction of each category ice concentration and the size and geometry of individual melt ponds are determined with high spatial resolution the ice concentration and melt pond coverage have large spatial deviations between flights and even between images from the marginal ice zone to the pack ice zone in the central arctic ice concentration and pond coverage over high arctic from 84 n to north was 75 and 6 8 respectively providing ground truth for the unusual transpolar reduction strip of ice indicated concurrently by amsr e data and for the regions north of 88 n where no passive microwave sensors can cover melt pond size and shape distributions are examined in terms of pond area s perimeter p mean caliper dimension mcd l roundness r convex degree c the ratio of p s and fractal dimension d power law relationships are developed between pond size and number some general trends in geometric metrics are identified as a function of pond area including r c p s and d the scale separation of pond complexity is demonstrated by analyzing area perimeter data the results will potentially help the modelling of melt pond evolution and the determination of heterogeneity of under ice transmitted light fields

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

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

recent changes in arctic sea ice melt onset freezeup and melt season length 1 in order to explore changes and trends in the timing of arctic sea ice melt onset and freezeup and therefore melt season length we developed a method that obtains this information directly from satellite passive microwave data creating a consistent data set from 1979 through present we furthermore distinguish between early melt the first day of the year when melt is detected and the first day of continuous melt a similar distinction is made for the freezeup using this method we analyze trends in melt onset and freezeup for 10 different arctic regions in all regions except for the sea of okhotsk which shows a very slight and statistically insignificant positive trend 0 4 d decade 1 trends in melt onset are negative i e toward earlier melt the trends range from 1 0 d decade 1 for the bering sea to 7 3 d decade 1 for the east greenland sea except for the sea of okhotsk all areas also show a trend toward later autumn freeze onset the chukchi beaufort seas and laptev east siberian seas observe the strongest trends with 7 d decade 1 for the entire arctic the melt season length has increased by about 20 days over the last 30 years largest trends of over 10 d decade 1 are seen for hudson bay the east greenland sea the laptev east siberian seas and the chukchi beaufort seas those trends are statistically significant at the 99 level

contrasting inherent optical properties and particle characteristics between an under ice phytoplankton bloom and open water in the chukchi sea abstract variability in the inherent optical properties iops of seawater and characteristics of the particle assemblage were examined along a transect in the chukchi sea during july 2011 this transect encompassed samples from open waters of the marginal ice zone exhibiting low concentrations of chlorophyll a chl a 3 as well as an extensive phytoplankton bloom chl a 30 mg m 3 beneath consolidated pack ice measurements included the spectral coefficients for particulate beam attenuation backscattering and absorption bulk indicators of particle concentration and composition and the particle size distribution within the bloom microphytoplankton contributed 95 to the total chl a and relatively small amounts of nonalgal particles were present this assemblage exhibited low chl a specific phytoplankton absorption coefficients 0 006 m 2 mg 1 at 676 nm indicating a strong influence of pigment packaging and a weak spectral dependence of the particulate backscattering coefficient in contrast the phytoplankton community in nutrient depleted surface waters outside the sea ice had a strong contribution of picoplankton to chl a 54 and an increased abundance of nonalgal particles the chl a specific phytoplankton absorption coefficient approached maximum values at 676 nm 0 023 m 2 mg 1 and particle backscattering had much stronger spectral dependence additional samples from near the sea floor exhibited characteristics of either mineral dominated assemblages or a mixture of mineral and organic particles and also displayed optical differentiation from the surface samples the marked contrast in absorption attenuation and backscattering properties of these ecological regimes suggest that they can be discriminated from optical measurements available on a variety of in situ and remote sensing platforms

influence of ice thickness and surface properties on light transmission through arctic sea ice the observed changes in physical properties of sea ice such as decreased thickness and increased melt pond cover severely impact the energy budget of arctic sea ice increased light transmission leads to increased deposition of solar energy in the upper ocean and thus plays a crucial role for amount and timing of sea ice melt and under ice primary production recent developments in underwater technology provide new opportunities to study light transmission below the largely inaccessible underside of sea ice we measured spectral under ice radiance and irradiance using the new nereid under ice nui underwater robotic vehicle during a cruise of the r v polarstern to 83 n 6 w in the arctic ocean in july 2014 nui is a next generation hybrid remotely operated vehicle h rov designed for both remotely piloted and autonomous surveys underneath land fast and moving sea ice here we present results from one of the first comprehensive scientific dives of nui employing its interdisciplinary sensor suite we combine under ice optical measurements with three dimensional under ice topography multibeam sonar and aerial images of the surface conditions we investigate the influence of spatially varying ice thickness and surface properties on the spatial variability of light transmittance during summer our results show that surface properties such as melt ponds dominate the spatial distribution of the under ice light field on small scales 1000 m2 while sea ice thickness is the most important predictor for light transmission on larger scales in addition we propose the use of an algorithm to obtain histograms of light transmission from distributions of sea ice thickness and surface albedo

the impact of freshening on phytoplankton production in the pacific arctic ocean since the 1990s drastic melting of sea ice and continental ice in the arctic region triggered by global warming has caused substantial freshening of the arctic ocean while several studies attempted to quantify the magnitude of this freshening its consequences on primary producers remain poorly documented in this study we evaluate the impact of the freshwater content fwc of the upper arctic ocean on phytoplankton across the pacific sector from the bering strait 65 n to the north pole 86 n during summer 2008 we performed statistical analyses on the physical biogeochemical and biological data acquired during the chinare 2008 cruise to investigate the effect of sea ice melting on the arctic phytoplankton we found that the strong freshening observed in the canada basin had a negative impact on primary producers as a result of the deepening of the nitracline and the establishment of a subsurface chlorophyll maximum scm in contrast regions with lower freshening such as the chukchi shelf and the marginal ice zone miz over the chukchi borderland exhibited a shallower nitracline sustaining relatively high primary production and biomass our results imply that the predicted increase freshening in future years will likely cause the arctic deep basin to become more oligotrophic because of weaker surface nutrient renewal from the subsurface ocean despite higher light penetration

climate driven sea level anomalies modulate coastal groundwater dynamics and discharge 1 to better understand the physical drivers of submarine groundwater discharge sgd in the coastal ocean we conducted a detailed field and modeling study within an unconfined coastal aquifer system we monitored the hydraulic gradient across the coastal aquifer and movement of the mixing zone over multiple years at our study site sea level dominated over groundwater head as the largest contributor to variability in the hydraulic gradient and therefore sgd model results indicate the seawater recirculation component of sgd was enhanced during summer while the terrestrial component dominated during winter due to seasonal changes in sea level driven by a combination of long period solar tides temperature and winds in one year sea level remained elevated year round due to a combination of enso and nao climate modes hence predicted changes in regional climate variability driven sea level may impact future rates of sgd and biogeochemical cycling within coastal aquifers

seasonal evolution of an ice shelf influenced fast ice regime derived from an autonomous thermistor chain ice shelves strongly interact with coastal antarctic sea ice and the associated ecosystem by creating conditions favorable to the formation of a sub ice platelet layer the close investigation of this phenomenon and its seasonal evolution remains a challenge due to logistical constraints and a lack of suitable methodology in this study we characterize the seasonal cycle of antarctic fast ice adjacent to the ekstrom ice shelf in the eastern weddell sea we used a thermistor chain with the additional ability to record the temperature response induced by cyclic heating of resistors embedded in the chain vertical sea ice temperature and heating profiles obtained daily between november 2012 and february 2014 were analyzed to determine sea ice and snow evolution and to calculate the basal energy budget the residual heat flux translated into an ice volume fraction in the platelet layer of 0 18 0 09 which we reproduced by a independent model simulation and agrees with earlier results manual drillings revealed an average annual platelet layer thickness increase of at least 4 m and an annual maximum thickness of 10 m beneath second year sea ice the oceanic contribution dominated the total sea ice production during the study effectively accounting for up to 70 of second year sea ice growth in summer an oceanic heat flux of 21 w m 2 led to a partial thinning of the platelet layer our results further show that the active heating method in contrast to the acoustic sounding approach is well suited to derive the fast ice mass balance in regions influenced by ocean ice shelf interaction as it allows subdiurnal monitoring of the platelet layer thickness

bio optical properties of arctic drift ice and surface waters north of svalbard from winter to spring we have quantified absorption by cdom acdom k particulate matter ap k algal pigments aph k and detrital material anap k coincident with chlorophyll a in sea ice and surface waters in winter and spring 2015 in the arctic ocean north of svalbard the acdom k was low in contrast to other regions of the arctic ocean while ap k has the largest contribution to absorption variability in sea ice and surface waters ap 443 was 1 4 2 8 times and 1 3 1 8 times higher than acdom 443 in surface water and sea ice respectively aph k contributed 90 and 81 to ap k in open leads and under ice waters column and much less 53 74 in sea ice respectively both acdom k and ap k followed closely the vertical distribution of chlorophyll a in sea ice and the water column we observed a tenfold increase of the chlorophyll a concentration and nearly twofold increase in absorption at 443 nm in sea ice from winter to spring the acdom k dominated the absorption budget in the uv both in sea ice and surface waters in the visible range absorption was dominated by aph k which contributed more than 50 and acdom k which contributed 43 to total absorption in water column detrital absorption contributed significantly 33 only in surface ice layer algae dynamics explained more than 90 variability in ap k and aph k in water column but less than 70 in the sea ice this study presents detailed absorption budget that is relevant for modeling of radiative transfer and primary production

a younger thinner arctic ice cover increased potential for rapid extensive sea ice loss 1 satellite derived estimates of sea ice age and thickness are combined to produce a proxy ice thickness record for 1982 to the present these data show that in addition to the well documented loss of perennial ice cover as a whole the amount of oldest and thickest ice within the remaining multiyear ice pack has declined significantly the oldest ice types have essentially disappeared and 58 of the multiyear ice now consists of relatively young 2 and 3 year old ice compared to 35 in the mid 1980s ice coverage in summer 2007 reached a record minimum with ice extent declining by 42 compared to conditions in the 1980s the much reduced extent of the oldest and thickest ice in combination with other factors such as ice transport that assist the ice albedo feedback by exposing more open water help explain this large and abrupt ice loss

surface and melt pond evolution on landfast first year sea ice in the canadian arctic archipelago the evolution of landfast sea ice melt pond coverage surface topography and mass balance was studied in the canadian arctic during may june 2011 and 2012 using a terrestrial laser scanner snow and sea ice sampling and surface meteorological characterization initial melt pond formation was not limited to low lying areas rather ponds formed at almost all premelt elevations the subsequent evolution of melt pond coverage varied considerably between the 2 years owing to four principle temporally variable factors first the range in premelt topographic relief was 0 5 m greater in 2011 rougher surface than in 2012 smoother surface such that a seasonal maximum pond coverage of 60 and maximum hydraulic head of 204 mm were reached in 2011 versus 78 and 138 mm in 2012 a change in the meltwater balance production minus drainage caused the ponds to spread or recede over an area that was almost 90 larger in 2012 than in 2011 second modification of the premelt topography was observed during mid june due to preferential melting under certain drainage channels some of the lowest lying premelt areas were subsequently elevated above these deepening channels and unexpectedly became drained later in the season third ice interior temperatures remained 1 2 c colder later into june in 2012 than in 2011 even though the ice was 0 35 m thinner at melt onset thereby delaying permeability increases in the ice that would allow vertical meltwater drainage to the ocean finally surface melt was estimated to account for approximately 62 of the net radiative flux to the sea ice cover during the melt season

improved 1d inversions for sea ice thickness and conductivity from electromagnetic induction data inclusion of nonlinearities caused by passive bucking the porosity of sea ice is a fundamental physical parameter that governs the mechanical strength of sea ice and the mobility of gases and nutrients for biological processes and biogeochemical cycles in the sea ice layer however little is known about the spatial distribution of the sea ice porosity and its variability between different sea ice types an efficient and nondestructive method to measure this property is currently missing sea ice porosity is linked to the bulk electrical conductivity of sea ice a parameter routinely used to discriminate between sea ice and seawater by electromagnetic em induction sensors here we have evaluated the prospect of porosity retrieval of sea ice by means of bulk conductivity estimates using 1d multifrequency em inversion schemes we have focused on two inversion algorithms a smoothness constrained inversion and a marquardt levenberg inversion which we modified for the nonlinear signal bias caused by a passive bucking coil operated in such a highly conductive environment using synthetic modeling studies 1d inversion algorithms and multiple frequencies we found that we can resolve the sea ice conductivity within 0 01 s m using standard assumptions for the conductivity porosity relation of sea ice we were able to estimate porosity with an uncertainty of 1 2 which enables efficient and nondestructive surveys of the internal state of the sea ice cover

late quaternary sedimentation along a fjord to shelf trough transect east greenland c 68 n the east greenland continental margin between c 66 and 68 n consists of a major fjord trough system that extends from kangerdlugssuaq fjord along kangerdlugssuaq trough to denmark strait measurements of the temperature and salinity of the water column along this transect indicates that warm water 0 2 c underlies the surface polar water of the east greenland current a series of short 1 3 m gravity cores along the fjord trough transect have sufficient numbers of foraminifera that a suite of ams 14c dates has been obtained including both basal and core top age estimates rates of sediment accumulation vary through space and time over the last 1 ka estimates vary from c 3 to 0 1 m these dates and measurements of sediment density together with measurements of the percentages by weight of total organic carbon and biogenic silica are used to show graphs of fluxes of the organic and inorganic sediment components over the last 1 14 ka an analysis of the net flux of foraminifera indicates a reduction in numbers during the younger dryas chronozone and a general similarity with data from the renland east greenland ice core data

optical properties of melting first year arctic sea ice the albedo and transmittance of melting first year arctic sea ice were measured during two cruises of the impacts of climate on the eco systems and chemistry of the arctic pacific environment icescape project during the summers of 2010 and 2011 spectral measurements were made for both bare and ponded ice types at a total of 19 ice stations in the chukchi and beaufort seas these data along with irradiance profiles taken within boreholes laboratory measurements of the optical properties of core samples ice physical property observations and radiative transfer model simulations are employed to describe representative optical properties for melting first year arctic sea ice ponded ice was found to transmit roughly 4 4 times more total energy into the ocean relative to nearby bare ice the ubiquitous surface scattering layer and drained layer present on bare melting sea ice are responsible for its relatively high albedo and relatively low transmittance light transmittance through ponded ice depends on the physical thickness of the ice and the magnitude of the scattering coefficient in the ice interior bare ice reflects nearly three quarters of the incident sunlight enhancing its resiliency to absorption by solar insolation in contrast ponded ice absorbs or transmits to the ocean more than three quarters of the incident sunlight characterization of the heat balance of a summertime ice cover is largely dictated by its pond coverage and light transmittance through ponded ice shows strong contrast between first year and multiyear arctic ice covers

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

tracer studies of pathways and rates of meltwater transport through arctic summer sea ice 1 at the surface heat budget of the arctic ocean sheba program s field site in the northern chukchi sea snow and ice meltwater flow was found to have a strong impact on the heat and mass balance of sea ice during the summer of 1998 pathways and rates of meltwater transport were derived from tracer studies h218o 7be and release of fluorescent dyes complemented by in situ sea ice permeability measurements it was shown that the balance between meltwater supply at the surface averaging between 3 5 and 10 5 mm d 1 and ice permeability between 10 9 m2 determines the retention and pooling of meltwater which in turn controls ice albedo we found that the seasonal evolution of first year and multiyear ice permeability and surface morphology determine four distinct stages of melt at the start of the ablation season stage 1 ponding is widespread and lateral melt flow dominates several tens of cubic meters of meltwater per day were found to drain hundreds to thousands of square meters of ice through flaws and permeable zones significant formation of underwater ice composed between 50 of meteoric water formed at these drainage sites complete removal of snow cover increase in ice permeability and reductions in hydraulic gradients driving fluid flow mark stage 2 concurrent with a reduction in pond coverage and albedo during stage 3 maximum permeabilities were measured with surface meltwater penetrating to 1 m depth in the ice and convective overturning and desalination found to dominate the lower layers of first year and thin multiyear ice enhanced fluid flow into flaws and permeable zones was observed to promote ice floe breakup and disintegration concurrent with increases in pond salinities and 7be advective heat flows of several tens of watts per square meter were derived promoting widening of ponds and increases in pond coverage stage 4 corresponds to freeze up roughly 40 of the total surface melt was retained by the ice cover within the ice matrix as well as in surface and under ice ponds with a total net retention of 15 based on this work areas of improvement for fully prognostic simulations of ice albedo are identified calling for parameterizations of sea ice permeability and the integration of ice topography and refined ablation schemes into atmosphere ice ocean models

changes in arctic sea ice result in increasing light transmittance and absorption 1 arctic sea ice has declined and become thinner and younger more seasonal during the last decade one consequence of this is that the surface energy budget of the arctic ocean is changing while the role of surface albedo has been studied intensively it is still widely unknown how much light penetrates through sea ice into the upper ocean affecting sea ice mass balance ecosystems and geochemical processes here we present the first large scale under ice light measurements operating spectral radiometers on a remotely operated vehicle rov under arctic sea ice in summer this data set is used to produce an arctic wide map of light distribution under summer sea ice our results show that transmittance through first year ice fyi 0 11 was almost three times larger than through multi year ice myi 0 04 and that this is mostly caused by the larger melt pond coverage of fyi 42 vs 23 also energy absorption was 50 larger in fyi than in myi thus a continuation of the observed sea ice changes will increase the amount of light penetrating into the arctic ocean enhancing sea ice melt and affecting sea ice and upper ocean ecosystems

reduced ice thickness in arctic transpolar drift favors rapid ice retreat 1 helicopter borne electromagnetic sea ice thickness measurements were performed over the transpolar drift in late summers of 2001 2004 and 2007 continuing ground based measurements since 1991 these show an ongoing reduction of modal and mean ice thicknesses in the region of the north pole of up to 53 and 44 respectively since 2001 a buoy derived ice age model showed that the thinning was mainly due to a regime shift from predominantly multi and second year ice in earlier years to first year ice in 2007 which had modal and mean summer thicknesses of 0 9 and 1 27 m measurements of second year ice which still persisted at the north pole in april 2007 indicate a reduction of late summer second year modal and mean ice thicknesses since 2001 of 20 and 25 to 1 65 and 1 81 m respectively the regime shift to younger and thinner ice could soon result in an ice free north pole during summer