turbulent heat flux in the upper ocean under sea ice turbulence data from three arctic drift station experiments demonstrate features of turbulent heat transfer in the oceanic boundary layer time series analysis of several w t records shows that heat and momentum flux occur at nearly the same scales typically by turbulent eddies of the order of 10 20 m in horizontal extent and a few meters in vertical extent probability distribution functions of w t have large skewness and kurtosis where the latter confirms that most of the flux occurs in intermittent events with positive and negative excursions an order of magnitude larger than the mean value an estimate of the eddy heat diffusivity in the outer ekman part of the boundary layer based on measured heat flux and temperature gradient during a diurnal tidal cycle over the yermak plateau slope north of fram strait agrees reasonably well with the eddy viscosity with values as high as 0 15 m2 s 1 an analysis of measurements made near the ice ocean interface at the three stations shows that heat flux increases with both temperature elevation above freezing and with friction velocity at the interface it also reveals a surprising uniformity in parameters describing the heat and mass transfer e g the thickness of the transition sublayer from a modified version of the yaglom kader theory is about 10 cm at all three sites despite nearly a fivefold difference in the under ice roughness z0 which ranges from approximately 2 to 9 cm a much simplified model for heat and mass transfer at the ice ocean interface suggested by the relative uniformity of the heat transfer coefficients at the three sites is outlined

physical structural and isotopic characteristics and growth processes of fast sea ice in lutzow holm bay antarctica a sea ice ocean study was conducted off queen maud land and enderby land antarctica from 1990 to 1991 by the japanese antarctic research expedition observations of multiyear land fast sea ice were made in lutzow holm bay over a period of 2 years to determine the snow and ice characteristics and ice growth processes the snow depth in the bay reached large values of 1 0 to 1 5 m during the winter season at offshore locations from the analysis of ice thickness measurements it is confirmed that the fast ice with deep snow cover grew little in winter but substantially thickened during the summer months on the basis of ice core structure salinity and stable isotopic composition we conclude that the summer growth was caused by upward growth at the top of the ice to which snow ice and superimposed ice formation contribute these processes were the primary contributors to sea ice growth and characteristics only where the snow accumulation was large in areas of low snow accumulation there was no surface growth superimposed ice formation on sea ice in antarctica has not been reported previously evidence for snow cover melting which is a prerequisite for superimposed ice formation was also found

in situ measurements of the evolution of young sea ice 1 we present data from in situ measurements of the salinity evolution of young sea ice in the arctic the measurements were carried out with very high vertical and temporal resolution over the course of a few days until the ice had reached a thickness of around 20 cm the measured bulk salinity profiles show that during ice growth sea ice salinity is continuous across the ice ocean interface and that there is no instantaneous loss of salt at the advancing front measured salt fluxes emanating from the ice are as high as 90 g m 2 h 1 during the first few hours of new ice formation and are roughly half as large during later stages of the experiments the bulk salinity within the ice decreases continuously with time from the ocean water salinity to a near steady state value of around 4 parts per thousand ppt these results are interpreted with ideas from mushy layer theory using a rayleigh number to analyze gravity drainage as the driving mechanism for the observed salt loss in our experiments gravity drainage occurs for a critical rayleigh number of around 10 in close agreement with earlier theoretical and experimental studies

the percolation phase transition in sea ice sea ice exhibits a marked transition in its fluid transport properties at a critical brine volume fraction p c of about 5 percent or temperature t c of about 5 c for salinity of 5 parts per thousand for temperatures warmer than t c brine carrying heat and nutrients can move through the ice whereas for colder temperatures the ice is impermeable this transition plays a key role in the geophysics biology and remote sensing of sea ice percolation theory can be used to understand this critical behavior of transport in sea ice the similarity of sea ice microstructure to compressed powders is used to theoretically predict p c of about 5 percent

observations and modelling of first year ice growth and simultaneous second year ice ablation in the prydz bay east antarctica the seasonal cycle of fast ice thickness in prydz bay east antarctica was observed between march and december 2012 in march we observed a 0 16 m thickness gain of 0 22 m thick first year ice fyi while 1 16 m thick second year ice syi nearby simultaneously ablated by 0 59 m a 1 d thermodynamic sea ice model was applied to identify the factors that led to the simultaneous growth of fyi and melt of syi the different evolutions were explained by the difference in the conductive heat flux between the fyi and syi as the fyi was thin there was a large temperature gradient between the ice base and the colder ice surface this generated an upward conductive heat flux which was larger than the heat flux from the ocean to the ice base yielding basal growth of ice in the case of the thicker syi the temperature gradient and hence the conductive heat flux were smaller and not sufficient to balance the oceanic heat flux at the ice base yielding basal ablation penetration of solar radiation affected the conductive heat flux in both cases and the model results were sensitive to the initial ice temperature profile and the uncertainty of the oceanic heat flux

joint inversion for vp vs and vp vs at safod parkfield california we refined the three dimensional 3 d vp vs and vp vs models around the san andreas fault observatory at depth safod site using a new double difference dd seismic tomography code tomoddps that simultaneously solves for earthquake locations and all three velocity models using both absolute and differential p s and s p times this new method is able to provide a more robust vp vs model than that from the original dd tomography code tomodd obtained simply by dividing vp by vs for the new inversion waveform cross correlation times for earthquakes from 2001 to 2002 were also used in addition to arrival times from earthquakes and explosions in the region the vp values extracted from the model along the safod trajectory match well with the borehole log data providing in situ confirmation of our results similar to previous tomographic studies the 3 d structure around parkfield is dominated by the velocity contrast across the san andreas fault saf in both the vp and vs models there is a clear low velocity zone as deep as 7 km along the saf trace compatible with the findings from fault zone guided waves there is a high vp vs anomaly zone on the southwest side of the saf trace that is about 1 2 km wide and extends as deep as 4 km which is interpreted to be due to fluids and fractures in the package of sedimentary rocks abutting the salinian basement rock to the southwest the relocated earthquakes align beneath the northeast edge of this high vp vs zone we carried out a 2 d correlation analysis for an existing resistivity model and the corresponding profiles through our model yielding a classification that distinguishes several major lithologies

wintertime heat flux to the underside of east antarctic pack ice in the sea ice zone there is a delicate balance between the heat loss from the surface of the snow covered sea ice and the heat supplied to the underside of the ice by the deep ocean the difference between these two heat fluxes determines the amount of ice growth or melt in global atmospheric models the ocean heat flux is often prescribed and has been shown to be an important parameter in determining how thick sea ice will grow thermodynamically although this ocean heat flux is a critical component in climate models there are relatively few direct measurements in the antarctic sea ice region in this study we use measurements of the temperature gradient through the sea ice and of ice growth during a field experiment to estimate the ocean heat flux in the east antarctic region around 140 e 65 s during august 1995 we find an average ocean heat flux of 13 0 14 5 w m 2 this is more than twice the winter values reported in the western weddell sea under multiyear sea ice but similar to the 19 w m 2 that has been estimated for the entire weddell gyre during august 1995 the air temperature showed large variations ranging from near freezing to 30 c this resulted in the thicker ice floes 50 60 cm alternating between a no growth or melting condition and an active ice growth at the base however it is likely that the thicker 60 cm ridged portions of the floes were continually melting

ocean heat flux under antarctic sea ice in the bellingshausen and amundsen seas two case studies we examine the role of ocean heat flux ohf in antarctic sea ice growth and melt using data from autonomous ice mass balance buoys deployed on pack ice in the bellingshausen sea and on fast ice in the amundsen sea during the spring summer october december 2007 and summer autumn february march 2009 transitions respectively ohfs are derived using two methods that examine changes in 1 sub ice ocean water properties ohf1 and 2 ice thickness ohf2 the latter only applying to thick snow covered ice i e a near zero temperature gradient near the ice bottom good agreement is found between the time averaged estimates of ohf1 and ohf2 average ohf measured was 8 2wm 2 under the pack ice and 17 2wm 2 under the landfast ice some short term ohf values ohf1 in both seas exceeded 55wm 2 the spring ohf variations in the bellingshausen sea were periodic and controlled by semi diurnal ice velocity fluctuations larger temperature fluctuations in the summer amundsen sea originating from incursions of warm deep water masses contributed to the ohf being twice as high as in the bellingshausen sea and also accounted for the irregular ohf variability there

thermodynamic sea ice growth in the central weddell sea observed in upward looking sonar data upward looking sonar uls data were used to analyze thermodynamic sea ice growth the study was carried out for an ocean region in the central weddell sea for which data of sea ice thickness variability and of the oceanic heat flux through the ice are rare in the study area the contribution of sea ice deformation to vertical ice growth is relatively small in some years this provides the opportunity to simulate thermodynamic sea ice growth considering the influence of a snow cover and of the oceanic heat flux to this end a modified version of stefan s law was used the resulting ice thickness variations were then compared with the uls measurements for the investigated cases the best consistency between data and model results was obtained assuming a snow layer of less than 5 cm thickness and average oceanic heat fluxes between 6 and 14 w m 2 it is demonstrated that in conjunction with ice drift data and analytical models for thermal sea ice growth uls ice thickness measurements are useful for studying the seasonal cycle of growth and decay and for inferring the magnitude of the average oceanic heat flux under sea ice

seismotectonics of northeastern sicily and southern calabria italy new constraints on the tectonic structures featuring in a crucial sector for the central mediterranean geodynamics

potential glacial evidence for the younger dryas event in the cordillera of north and south america there is debate as to whether or not the younger dryas yd climatic event affected areas outside of the north atlantic region the potential of alpine glacial deposits to record the yd is of interest because alpine glaciers would be likely to leave a morainal record even during minor short lived advances caused by a period of deteriorating climate in the cordilleran ranges of north and south america there are several candidate moraines many bracketed between radiocarbon ages of ca 12 and 10 ka which may be yd in age the best examples are in the canadian and american rockies the ecuadorian peruvian and bolivian andes and around the patagonian ice cap in most cases temporal brackets are not narrow enough and some radiocarbon ages may not be accurate enough to allow correlation at the present time there are two cases of lateglacial readvance whose ages are interpreted to match or fall within the yd interval an advance of the crowfoot glacier in canada is interpreted to have occurred within the period ca 11 3 and 10 14c ka bp and an advance of the reschreiter glacier in ecuador is interpreted to have culminated in the period ca 11 to 10 6 14c ka bp the latter interpretation depends on an assumption that lake level variations were caused by glacier advances and retreats

thermal conductivity and heat transfer through the snow on the ice of the beaufort sea 1 eighty nine point measurements of the thermal conductivity ks of the snow on the sea ice of the beaufort sea were made using a heated needle probe average values ranged from 0 078 w m 1 k 1 for new snow to 0 290 w m 1 k 1 for an ubiquitous wind slab ks increased with increasing density consistent with published equations but could also be reliably estimated from the metamorphic state of the snow using measured values of ks and snow stratigraphy the average bulk value for the full snowpack was 0 14 w m 1 k 1 in contrast ks inferred from ice growth and temperature gradients in the snow was 0 33 w m 1 k 1 the mismatch arises in part because the second estimate is based on measurements from an aggregate scale that includes enhanced heat flow due to two and three dimensional snow and ice geometry a finite element model suggests that the complex geometry produces areas of concentrated heat loss at the snow surface these hot spots however increase the apparent conductivity only by a factor of 1 4 not enough to fully explain the mismatch nonconductive heat transfer mechanisms like natural and forced air convection may also be operating in the snowpack though the ubiquitous presence of low permeability wind slabs potentially limits their effectiveness the relative contributions of effects due to snow and ice geometric and nonconductive processes within the snowpack remain uncertain

multiyear sea ice thermal regimes and oceanic heat flux derived from an ice mass balance buoy in the arctic ocean the conductive and oceanic heat fluxes and the mass balance of sea ice were investigated utilizing an ice mass balance buoy imb deployed in the arctic ocean after imb deployment the ice thinned from 1 95 m in late august to 1 46 m by mid october 2008 from then on ice growth until mid june 2009 increased the ice thickness to 3 12 m the ice temperature and consequently the conductive heat flux at the ice surface exhibited persistent high frequency variations due to diurnal and synoptic scale atmospheric forcing these signals propagated downward with damped magnitude and temporal lag the competition of oceanic and conductive heat flux dominated the low frequency variations of ice growth however high frequency variations in ice growth were controlled largely by the oceanic heat flux from mid november 2008 to mid june 2009 the average oceanic heat flux along a track from 86 2 n 115 2 w to 84 6 n 33 9 w was 7 1 w m2 this was in agreement with that derived from an imb deployed in 2005 about 1 5 to the north of our buoy we attributed the relatively high oceanic heat flux 10 15 w m2 observed during autumn and early winter to summer warming of the surface ocean upward mixing of warm deep water as observed when our buoy drifted over the shallow region of the lomonosov ridge 85 4 85 9 n 52 2 66 4 w demonstrated the impact of bathymetry on the oceanic heat flux under ice cover and consequently on the basal ice mass balance 2013 american geophysical union all rights reserved

thin and thinner sea ice mass balance measurements during sheba 1 as part of a large interdisciplinary study of the surface heat budget of the arctic ocean sheba we installed more than 135 ice thickness gauges to determine the sea ice mass balance while installing these gauges during the fall of 1997 we found that much of the multiyear ice cover was only 1 m thick considerably thinner than expected over the course of the yearlong field experiment we monitored the mass balance for a wide variety of ice types including first year ice ponded ice unponded ice multiyear ice hummocks new ridges and old ridges initial ice thicknesses for these sites ranged from 0 3 to 8 m and snow depths varied from a few centimeters to more than a meter however for all of their differences and variety these thickness gauges sites shared a common trait at every site there was a net thinning of the ice during the sheba year the thin ice found in october 1997 was even thinner in october 1998 the annual cycle of ice thickness was also similar at all sites there was a steady increase in thickness through the winter that gradually tapered off in the spring this was followed by a steep drop off in thickness during summer melt and another tapering in late summer and early fall as freeze up began maximum surface melting was in july while bottom ablation peaked in august combining results from the sites we found an average winter growth of 0 51 m and a summer melt of 1 26 m which consisted of 0 64 m of surface melt and 0 62 m of bottom melt there was a weak trend for thicker ice to have less winter growth and greater net loss for the year however ice growth was also impacted by the snow depth considerable variability was observed between sites in both accretion and ablation the total accretion during the 9 month growth season ranged from zero for thick ridged ice to more than a meter for young ice ponds tended to have a large amount of surface melting while ridges had considerable bottom ablation

the phase evolution of young sea ice sea ice forms as a porous matrix consisting of pure ice crystals in equilibrium with brine we present an experimental and theoretical study that reveals that the brine expelled by growing sea ice initially remains trapped within the crystalline interstices but that drainage into the underlying water is ultimately triggered abruptly due to the onset of buoyancy driven convection the onset is quantified by a critical porous medium rayleigh number and we present an empirical marginal stability diagram that defines the transition

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

the spatio temporal patterns of landfast ice in antarctica during 2006 2011 and 2016 2017 using high resolution sar imagery abstract landfast ice is an important component of the antarctic sea ice regime it affects the antarctic climate and ecological system in this study the first high resolution long time series of the landfast ice edge from 2006 to 2011 and 2016 to 2017 is presented the dataset was produced based on the improved net gradient difference algorithm using 2470 sar scenes from envisat and sentinel 1a b as well as manual analysis of modis imagery to fill in sar data gaps the study results show that the landfast ice area in november for all studied years was approximately 49 49 3 25 104 km2 accounting for about 3 4 of the total antarctic sea ice area the maximum area was 55 70 104 km2 in november 2007 compared to the minimum area 44 01 104 km2 in 2011 the area in west antarctica was about 40 of that in east antarctica the distribution of landfast ice in antarctica has significant regional differences the extent in the indian ocean sector is the maximum with a mean value of 16 49 1 1 104 km2 however the ratio of the landfast ice area to the sea ice area in the pacific ocean sector is the highest twenty four landfast ice zones with groups of small grounded icebergs were identified most of which were located in east antarctica particularly along the wilkes land and oates land two cases are presented to illustrate how giant grounded icebergs affected landfast ice results from this study are well suited to underpin the antarctic climate or ecological system studies

a non destructive method for measuring the salinity and solid fraction of growing sea ice in situ we describe an instrument developed to make in situ measurements of salinity and solid fraction profiles in growing sea ice the vertical resolution of the measurements is up to a few millimeters with a temporal resolution of up to fractions of a second the technique is based on impedance measurements between platinum wires around which sea ice grows data obtained using this instrument in laboratory experiments are in good agreement with theoretical predictions in a field test in the arctic the bulk salinity of growing sea ice has been measured in situ throughout the whole depth of the ice layer the data are compared with bulk salinities obtained from ice cores and confirm the general understanding that the bulk salinity in ice core studies is significantly underestimated in the lower parts of the cores the approach can also be used in other glaciological applications and for general studies of two phase two component porous media

sea ice salinity and structure a winter time series of salinity and its distribution 1 we present a winter time series of antarctic sea ice salinity from eastern mcmurdo sound an area close to an ice shelf where a subice platelet layer forms below the sea ice late in winter this dramatically changes the sea ice structure as the sea ice grows into the subice platelet layer every 2 weeks during the 5 months of sea ice formation salinity profiles were measured along with detailed measurements of ice structure and growth rates once the influence of growth rate on sea ice bulk salinity is removed the data from 69 cores and the results of a basic parameterization demonstrate that bulk salinity for platelet ice is higher than that for columnar sea ice we also present measurements of the salinity profile close to the ice water interface and use these to investigate the expected regime of fluid flow within the permeable portions of the sea ice with particular reference to mushy layer and percolation theory finally we provide a new distribution of sea ice salinity from 740 measurements which can be interpreted as the sum of two spatial fields that we attribute to sea ice samples with and without brine channels and which should be reproduced by any realistic sea ice models this distribution suggests that two measurements of quantities linearly linked to sea ice salinity must differ by 29 if they are to be considered different with 90 confidence

the thermal conductivity of seasonal snow twenty seven studies on the thermal conductivity of snow k eff have been published since 1886 combined they comprise 354 values of k eff and have been used to derive over 13 regression equation and predicting k eff vs density due to large and largely undocumented differences in measurement methods and accuracy sample temperature and snow type it is not possible to know what part of the variability in this data set is the result of snow microstructure we present a new data set containing 488 measurements for which the temperature type and measurement accuracy are known a quadratic equation where is in g cm 3 and k eff is in w m 1 k 1 can be fit to the new data r 2 0 79 a logarithmic expression can also be used the first regression is better when estimating values beyond the limits of the data the second when estimating values for low density snow within the data set snow types resulting from kinetic growth show density independent behavior rounded grain and wind blown snow show strong density dependence the new data set has a higher mean value of density but a lower mean value of thermal conductivity than the old set this shift is attributed to differences in snow types and sample temperatures in the sets using both data sets we show that there are well defined limits to the geometric configurations that natural seasonal snow can take

desalination processes of sea ice revisited 1 we reexamine five processes that have been suggested to be important for the loss of salt from sea ice these processes are the initial fractionation of salt at the ice ocean interface brine diffusion brine expulsion gravity drainage and flushing with surface meltwater we present results from analytical and numerical studies as well as from laboratory and field experiments that show that among these processes only gravity drainage and flushing contribute to any measurable net loss of salt we show that during ice growth the salinity field is continuous across the ice ocean interface hence there is no immediate segregation of salt at the advancing front

topography of the calabria subduction zone southern italy clues for the origin of mt etna 1 calabria represents an ideal site to analyze the topography of a subduction zone as it is located on top of a narrow active wadati benioff zone and shows evidence of rapid uplift we analyzed a pattern of surface deformation using elevation data with different filters and showed the existence of a long wavelength 100 km relatively positive topographic signal at the slab edges the elevation of mis 5 5 stage marine terraces supports this pattern although the record is incomplete and partly masked by the variable denudation rate we performed structural analyses along the major active or recently reactivated normal faults showing that the extensional direction varies along the calabrian arc and laterally switches from arc normal within the active portion of the slab to arc oblique or even arc parallel along the northern and southern slab edges this surface deformation pattern was compared with a recent high resolution p wave tomographic model showing that the high seismic velocity anomaly is continuous only within the active wadati benioff zone whereas the northern and southwestern sides are marked by low velocity anomalies suggesting that large scale topographic bulges volcanism and uplift could have been produced by mantle upwelling we present numerical simulations to visualize the three dimensional mantle circulation around a narrow retreating slab ideally similar to the one presently subducting beneath calabria we emphasize that mantle upwelling and surface deformation are expected at the edges of the slab where return flows may eventually drive decompression melting and the mount etna volcanism

fast ice distribution in east antarctica during 1997 and 1999 determined using radarsat data 1 we present the first detailed maps of fast ice around east antarctica 75 e 170 e using an image correlation technique applied to radarsat scansar images from november in 1997 and 1999 this method is based upon searching for and distinguishing correlated regions of the ice covered ocean which remain stationary in contrast to adjacent moving pack ice within the overlapping longitudinal range of 86 e 150 6 e the total fast ice area is 141 450 km2 in 1997 and 152 216 km2 in 1999 calibrated radar backscatter data are also used to determine the distribution of two fast ice classes based on their surface roughness characteristics these are smooth fast ice 25 4 db to 13 5 db and rough fast ice 13 5 db to 2 5 db the former comprises 67 of the total area with rough fast ice making up the remaining 33 an estimate is made of fast ice volume on the basis of fast ice type as a proxy measure of ice thickness and area results suggest that although fast ice forms 2 16 of the total november sea ice area for this sector of east antarctica in 1997 and 1999 average 8 3 across maps it may comprise 6 57 of the total ice volume average 28 across maps grounded icebergs play a key role in fast ice distribution in all regions apart from 150 e 170 e these are snapshot estimates only and more work is required to determine longer term spatiotemporal variability

using sea ice to measure vertical heat flux in the ocean results of an experiment performed at drifting ice station fram i in the arctic ocean northwest of spitzbergen during march may 1979 indicate that sensible heat flux from the ocean to the ice cover was less than 2 w m 2 the estimate is based on measurements of temperature gradient growth rate and salinity of young sea ice uncertainty in the magnitude of the heat flux results more from evidence of horizontal inhomogeneity in the growing ice sheet than from measurement errors

linkages between salinity and brine channel distribution in young sea ice a high resolution study of bulk salinity was undertaken on laboratory grown sea ice to determine the extent of spatial variability of salinity and whether this was associated with brine channel structures ice samples at two different stages of development were compared with respect to physical state brine distribution and brine channel structures cold growing sea ice is shown to have steep bulk salinity gradients and a highly variable brine distribution that is closely linked to the location and morphology of brine channels areas of high bulk salinity are found to correspond directly to the positions of the brine channels and these areas are surrounded by ice that shows significant brine depletion it is observed that redistribution of the brine occurs as the ice cover goes through warming and melting phases the redistribution is attributed to an increase in porosity and pore connectivity permitting migration of brine through the ice the distribution of brine in warm ice is shown to be more homogeneous and independent of brine channel structures a number of mechanisms exploiting the enhanced mobility of brine in warm sea ice are used to explain the changes in the salinity profiles and brine distribution

signatures of supercooling mcmurdo sound platelet ice near ice shelves around antarctica the ocean becomes supercooled and has been observed to carry small suspended ice crystals our measurements demonstrate that these small crystals are persistently present in the water column beneath the winter fast ice and when incorporated in sea ice they reduce the mean grain size of the sea ice cover by midwinter larger ice crystals below the ice water interface are observed to form a porous sub ice platelet layer with an ice volume fraction of 0 25 0 06 the magnitude and direction of the oceanic heat flux varied between 5 6 wm 2 upwards and 15 10 wm 2 downwards in may but by september it settled between 6 2 and 11 2 w m 2 the negative values imply that the ocean acts as a heat sink which is responsible for the growth of 12 of the ice thickness between june and september this oceanic contribution should not be ignored in models of antarctic sea ice thickness close to an ice shelf

the effect of ocean heat flux on seasonal ice growth in young sound northeast greenland the seasonal ice cover plays an important role in the climate system limiting the exchange of heat and momentum across the air water interface among other factors sea ice is sensitive to the ocean heat flux in this study we use in situ oceanographic sea ice and meteorological data collected during winter 2013 2014 in young sound ys fjord in northeast greenland to estimate the ocean heat flux to the landfast ice cover during the preceding ice free summer incident solar radiation caused sea surface temperatures of up to 5 6 c subsequently this heat was transferred down to the intermediate depths but returned to the surface and retarded ice growth throughout winter two different approaches were used to estimate the ocean heat fluxes i a residual method based on a 1 d thermodynamic ice growth model and ii a bulk parameterization using friction velocities and available heat content of water beneath the ice the average heat flux in the inner ys varied from 13 w m 2 in october december to less than 2 w m 2 in january may an average heat flux of 9 w m 2 was calculated for the outer ys moreover we show that the upward heat flux in the outer fjord is strongly modulated by surface outflow which produced two maxima in heat flux up to 18 24 w m 2 during 26 december to 27 january and from 11 february to 14 march by may 2014 the upward ocean heat flux reduced the landfast ice thickness by 18 and 24 in the inner and outer ys respectively

interannual variability of monthly southern ocean sea ice distributions the region of the southern ocean exhibiting interannual variability in monthly averaged sea ice distributions has been mapped and analyzed using data from the nimbus 5 electrically scanning microwave radiometer esmr and the nimbus 7 scanning multichannel microwave radiometer smmr over the 13 year record from the two instruments 1973 1976 and late 1978 through mid 1987 interannual variability is particularly high for the early summer month of december when 10 106 km2 of the ocean had ice covered conditions in some years and ice free conditions in other years this area of december variability is almost three times the ocean area consistently having ice covered conditions in the 13 esmr smmr decembers in contrast in mid winter the area of consistent ice coverage far exceeds the area of variability which in spite of the much greater ice coverage overall is not as large as the area of variability in december the mid winter variability is confined to 1 a ring of variable width around the edge of the ice pack and 2 the location of the 1974 1976 weddell polynya separation of the results to the esmr and smmr time periods shows that ice in the west indian ocean and the ross sea tended to be more expansive in the earlier esmr years than in the later smmr years but that ice in the weddell sea tended to be less expansive in the esmr years in the bellingshausen and amundsen seas the esmr years tended to have less summer ice than the smmr years but not less winter ice the images and plots provide a succinct summary of the range of spatial distributions of southern ocean sea ice during the esmr and smmr time periods they can hence be used as a convenient base for comparisons with future sea ice distributions in the effort to identify occurrences of climate change

annual cycle of landfast sea ice in prydz bay east antarctica 1 under the chinese national antarctic research expedition program in 2006 the annual thermal mass balance of landfast ice in the vicinity of zhongshan station prydz bay east antarctica was investigated sea ice formed from mid february onward and maximum ice thickness occurred in late november snow cover remained thin and blowing snow caused frequent redistribution of the snow the vertical ice salinity showed a question mark shaped profile for most of the ice growth season which only turned into an i shaped profile after the onset of ice melt the oceanic heat flux as estimated from a flux balance at ice ocean interface using internal ice temperatures decreased from 11 8 3 5 w m 2 in april to an annual minimum of 1 9 2 4 w m 2 in september it remained low through late november in mid december it increased sharply to about 20 0 w m 2 simulations applying the modified versions of stefan s law taking account the oceanic heat flux and ice atmosphere coupling compare well with observed ice growth there was no obvious seasonal cycle for the thermal conductivity of snow cover which was also derived from internal ice temperatures its annual mean was 0 20 0 04 w m 1 c 1

tectonics and seismicity of the tindari fault system southern italy crustal deformations at the transition between ongoing contractional and extensional domains located above the edge of a subducting slab 1 the tindari fault system southern tyrrhenian sea italy is a regional zone of brittle deformation located at the transition between ongoing contractional and extensional crustal compartments and lying above the western edge of a narrow subducting slab onshore structural data an offshore seismic reflection profile and earthquake data are analyzed to constrain the present geometry of the tindari fault system and its tectonic evolution since neogene including the present seismicity results show that this zone of deformation consists of a broad nnw trending system of faults including sets of right lateral left lateral and extensional faults as well as early strike slip faults reworked under late extension earthquakes and other neotectonic data provide evidence that the tindari fault system is still active in the central and northern sectors and mostly accommodates extensional or right lateral transtensional displacements on a diffuse array of faults from these data a multiphase tectonic history is inferred including an early phase as a right lateral strike slip fault and a late extensional reworking under the influence of the subduction related processes which have led to the formation of the tyrrhenian back arc basin within the present regional geodynamic context the tindari fault system is interpreted as an ongoing accommodation zone between the adjacent contractional and extensional crustal compartments these tectonic compartments relating to the complex processes of plate convergence occurring in the region the tindari fault system might also be included in an incipient oblique extensional transfer zone linking the ongoing contractional belts in the calabrian ionian and southern tyrrhenian compartments

aerial observations of floe size distribution in the marginal ice zone of summer prydz bay 1 on the basis of aerial photographs of sea ice floes in the marginal ice zone miz of prydz bay acquired from december 2004 to february 2005 during the 21st chinese national antarctic research expedition image processing techniques are employed to extract some geometric parameters of floes from two merged transects covering the whole miz variations of these parameters with the distance into the miz are then obtained different parameters of floe size namely area perimeter and mean caliper diameter mcd follow three similar stages of increasing flat and increasing again with distance from the open ocean floe shape parameters roundness and the ratio of perimeter to mcd however have less significant variations than that of floe size then to modify the deviation of the cumulative floe size distribution from the ideal power law an upper truncated power law function and a weibull function are used and four calculated parameters of the above functions are found to be important descriptors of the evolution of floe size distribution in the miz among them lr of the upper truncated power law function indicates the upper limit of floe size and roughly equals the maximum floe size in each square sample area l0 in the weibull distribution shows an increasing proportion of larger floes in squares farther from the open ocean and roughly equals the mean floe size d in the upper truncated power law function is closely associated with the degree of confinement during ice breakup its decrease with the distance into miz indicates the weakening of confinement conditions on floes owing to wave attenuation the of the weibull distribution characterizes the degree of homogeneity in a data set it also decreases with distance into miz implying that floe size distributes increase in range finally a statistical test on floe size is performed to divide the whole miz into three distinct zones made up of floes of quite different characteristics this zonal structure of floe size also agrees well with the trends of floe shape and floe size distribution and is believed to be a straightforward result of wave ice interaction in the miz

insights into brine dynamics and sea ice desalination from a 1 d model study of gravity drainage 1 we study gravity drainage using a new 1 d multiphase sea ice model a parametrization of gravity drainage based on the convective nature of gravity drainage is introduced whose free parameters are determined by optimizing model output against laboratory measurements of sea ice salinity evolution optimal estimates of the free parameters as well as the parametrization performance remain stable for vertical grid resolutions from 1 to 30 mm we find a strong link between sea ice growth rate and bulk salinity for constant boundary conditions but only a weak link for more realistic boundary conditions we also demonstrate that surface warming can trigger brine convection over the whole ice layer over a growth season replacing the convective parametrization with constant initial salinities leads to an overall 3 discrepancy of stored energy thermal resistance and salt release we also derive from our convective parametrization a simplified numerically cheap and stable gravity drainage parametrization this parametrization results in an approximately 1 discrepancy of stored energy thermal resistance and salt release compared to the convective parametrization a similarly low discrepancy to our complex parametrization can be reached by simply prescribing a depth dependent salinity profile

salinity profiles of antarctic sea ice field data and model results in order to describe and compare sea ice salinity distributions which are of interest in the study of physical and biological ice characteristics as well as ice ocean interaction we have computed composite profiles and fitted third degree polynomials to salinity data of 129 cores from the weddell sea four characteristic profile shapes have been recognized and described through the polynomial coefficients c s i and type profiles the field data have been compared with ideal salinity profiles generated by a simulation scheme based on thermodynamic growth under climatological conditions representative of the weddell sea composite salinity profiles agree well with simulations irrespective of the growth mechanism i e frazil or congelation suggesting that ice properties which depend on salinity or porosity may evolve independent of ice growth conditions analysis of salinity and 18o data in conjunction with the simulations demonstrates that apart from meteorological conditions controlling growth velocity and temperature distribution within the ice flooding and upward brine expulsion are important in raising top salinities as frequently observed low top salinities are typical of ice that has undergone retexturing and differential desalination salinity decreases towards the bottom of a floe are a result of high oceanic heat fluxes and snow cover effects as a consequence of these processes the bulk salinity of weddell sea ice cannot be described by a simple linear age thickness relationship as characteristic of arctic first year ice