trace metal distribution in sediments of northern continental shelf of crete island eastern mediterranean the present study investigates the distribution of trace metals zn hg cd cu and pb as indicators of pollution in the surficial offshore shelf sediments along the northern coast of heraklion prefecture crete mediterranean sea the concentrations and the spatial distribution of the different trace metals in relation to the sedimentological characteristics and the water circulation pattern of the entire continental shelf are associated with human inshore sources of pollutants located along the coastline of the study area although the trace metal concentrations measured are higher than the background values they are not considered to be dangerous to human health as they are lower than the standard values given by the world health organisation with only a few localised exceptions furthermore results reveal the important role of local hydrodynamism that moves fine grained material and associated trace metals offshore seawards to wave breaking zone and then transports them eastwards by entrapping them in the prevailing offshore shelf water circulation

comparison of ice water classification in fram strait from c and l band sar imagery in this paper an algorithm for ice water classification of c a nd l band dual polarization synthetic aperture radar data is presented a comparison of the two different frequencies is made in order to investigate the potential to improve classification results with multi frequency data the algorithm is based on backscatter intensities in co a nd cross polarization and autocorrelation as a texture feature the mapping between image features and ice water classification is made with a neural network accurate ice water maps for both frequencies are produced by the algorithm and the results of two frequencies generally agree very well differences are found in the marginal ice zone where the time difference between acquisitions causes motion of the ice pack c band reliably reproduces the outline of the ice edge while l band has its strengths for thin ice calm water areas within the icepack the classification shows good agreement with ice water maps derived from met no ice charts and radiometer data from amsr 2 variations are found in the marginal ice zone where the generalization of the ice charts and lower accuracy of ice concentration from radiometer data introduce deviations usage of high resolution dual frequency data could be beneficial for improving ice cover information for navigation and modelling

sea ice monitoring by l band sar an assessment based on literature and comparisons of jers 1 and ers 1 imagery spaceborne single polarization c band synthetic aperture radar sar imagery is widely used to gather information about the state of the sea ice cover in the polar regions c band is regarded as a reasonable choice for all season monitoring capabilities for specific mapping tasks however other frequency bands can be more suitable in the first part of this paper the summary of a literature study dealing with the utilization of l band sar imagery for sea ice monitoring is presented investigations reveal that if deformation features such as ice ridges rubble fields and brash ice are to be mapped l band radar is superior in a number of cases the second part of this paper addresses the comparison of jers 1 and ers 1 sar images that were acquired over sea ice east of svalbard and along the east coast of greenland the effects of the different frequencies polarizations and incidence angles of the two sar systems are discussed it is demonstrated that the images of both sensors complement one another in the analysis of ice conditions resulting in a more detailed view of the sea ice cover state

sea surface circulation variability in the ionian adriatic seas abstract the surface circulation of the ionian and adriatic seas is explored by the re analysis of available datasets that estimate the mean monthly ocean state for the 60 years long time period 1955 2015 emphasis is given to the major recurrent and transitional events in the area two circulation indices are utilized for the quantification of the cyclonic or anticyclonic circulation modes and intensity one based on the vorticity flux of the reconstructed mean monthly surface velocity field and another based on an appropriately modified version of the velocity field such quantification consequently allows for a detailed analysis of the surface circulation variability for the entire ionian and adriatic basins as well as for sub regions of particular interest discontinuities associated with possible regime shifts of the examined flow field were identified by time series analysis of the circulation indices and compared to well documented events in the hydrography of the studied area subsequently the statistically significant components of the surface circulation variability were resolved out of a red noise background in the time frequency domain and their evolution was studied the results highlight the presence of various circulation modes and reversals in different temporal scales mainly seasonal and decadal to inter decadal which are discussed in reference to the dynamics of both the sub regional western northern eastern and southern ionian as well as northern and southern adriatic and of the basin wide ionian or adriatic spatial scales the relationships of the surface circulation variability between the ionian and the adriatic basins are also assessed through wavelet coherence

meiofaunal distribution in the levantine basin eastern mediterranean spatial variability at different scales depths and distance to coast abstract deep sea ecosystems have been characterised in many ways such as deserts stable monotonous poor remote building on knowledge over the years we now know that these extreme environments are highly variable and diverse hosting rich benthic communities that are largely affected and structured by food availability and quality in the land locked oligotrophic mediterranean sea food supply to the deep sea is expected to be dependent on pelagic production but also to be affected by inputs from the surrounding landmasses having this in mind we used samples collected during the levar expedition on board r v meteor m71 2 winter 2006 2007 from two distinct deep sea areas in the levantine sea for describing meiobenthic communities in relation to factors that may drive their spatial distribution variability and patchiness at several scales area 1 within the pliny trench is located close to the island of crete at ca 4000 m depth whereas area 2 within herodotus abyssal plain is more distant from the island but shallower ca 2700 m independent multiple corer deployments performed at three stations within each area the use of several sediment cores from each deployment and the vertical sectioning of one sediment sample per deployment allowed to explore meiobenthic patterns at multiple scales a set of permutational analyses indicated differences between the two areas in terms of sedimentary food proxies that were coupled with corresponding differences in meiofauna richness composition and in abundances of the two most dominant meiobenthic metazoans i e nematodes and copepods though to a lesser extent variability in meiobenthic characteristics was also detected within and among stations a similar trend was not clearly evident within deployments changes in meiofauna distribution occurred in relation to sediment depth layer as well with evidence that the meiofauna vertical profile may differ between the two areas overall our study shows that higher meiobenthic variability in the eastern mediterranean deep sea is accounted for at the scale of area habitat inferences of our results in light of previous findings in the same area imply that the relationship between food and meiobenthic composition could not be attributed to bathymetry or distance from the land but is more probably explained by the high complexity and dynamics of trench habitats and their role as depositional environments acting as physical traps of organic material

melt ponds on sea ice in the canadian archipelago 2 on the use of radarsat 1 synthetic aperture radar for geophysical inversion microwave scattering from a first year sea ice fyi melt ponded surface is examined using radarsat 1 synthetic aperture radar sar data collected during the 1997 collaborative interdisciplinary cryospheric experiment c ice 97 near resolute bay nunavut this paper 1 investigates the utility of time series of microwave scattering to detect melt pond formation and 2 investigates approaches toward geophysically inverting information on the physical and radiative properties of this surface we found melt pond formation to coincide with a sharp rise in the temporal evolution of the microwave scattering coefficient over fyi radarsat 1 incidence angle and surface wind speed explained 90 of the variation in radarsat 1 was sensitive r2 0 80 to the fractional coverage of melt ponds during windy conditions 5 3 m s 1 spatial and temporal coincident measurements of radarsat 1 and the integrated shortwave albedo revealed a strong negative statistical correlation r2 0 91 during windy conditions 5 3 m s 1 a weaker but strong negative relationship r2 0 78 was observed for less windy conditions 3 2 m s 1 and a very weak positive relationship r2 0 19 was found for low wind speed conditions 1 5 m s 1 all relationships were observed for melt pond fractions between 13 and 34

mapping of different sea ice regimes using images from sentinel 1 and alos synthetic aperture radar airborne c and l band synthetic aperture radar sar images were acquired for three test sites over different sea ice regimes around svalbard in march 2007 complemented by optical imagery environmental data and ice observations one objective was to use the high resolution low noise radar data for investigations on the technical performance of european space agency s sentinel 1 mission for sea ice mapping the other to assess the potential gain of additional use of l band sar data currently available from advanced land observing satellite alos the airborne sar images were employed to simulate data products resembling the interferometric wide swath mode iwsm of sentinel 1 and alos palsar fine resolution mode frm in order to quantify the information loss due to the higher noise level and coarser spatial resolution at the iwsm noise level zones of deformation level ice and new ice can be well separated at like polarization at cross polarization the noise level is too high for a robust automated classification including thin ice but deformed and level ice can be discriminated palsar frm is on average better suited to distinguish deformed and level ice over all ice regimes it was worse for separating new from thicker level ice at two test sites for the third test site with very few patches of new ice the palsar frm showed larger intensity contrasts between new and level ice than sentinel 1 iwsm the spatial resolution provided by the iwsm and frm is sufficient to identify most ice features and types without ambiguities typical characteristics of the imaged ice regimes are described

the mechanisms of sea ice melt pond formation and evolution 1 a series of observations were made on melting first year landfast arctic sea ice near barrow alaska to explore the seasonal evolution of melt pond coverage observations of pond coverage albedo and ice properties are combined with terrestrial lidar measurements of surface topography and meltwater balance to quantitatively identify the timing and role of mechanisms driving pond coverage the formation of interposed fresh ice is found to eliminate meltwater percolation through early pond formation and allow widespread ponding well above sea level pond drainage to sea level occurs principally by horizontal meltwater transport over the ice surface to macroscopic flaws freeboard loss caused by buoyancy decline as the ice thins controls pond growth late in the melt season after percolation begins the majority of the macroscopic flaws that drain melt ponds to sea level are observed to develop from brine drainage channels within the ice a simple thermodynamic model of meltwater percolation illustrates that fresh meltwater inflow causes pores in the ice to either shrink and freeze shut or enlarge based on initial size and ice temperature this threshold behavior of pore diameter controls both the blockage of smaller pores with interposed ice and the enlargement of larger brine drainage channels to allow meltwater drainage the results identify links between the temporal evolution of pond coverage and ice temperature salinity and thickness providing new opportunities to realistically parameterize ponds and summer ice albedo within sea ice models

carboniferous floras in siliciclastic rocks of kashmir himalaya india and the evolutionary history of the tethyan basin the fenestella shale formation of jammu and kashmir himalaya comprises latest visean or serpukhovian siliciclastic deposits formed along the southern margins of the palaeotethys ocean a sequence of shallowing upward and deepening upward units indicates changes from shoreface to offshore and deeper shelf conditions probably controlled by eustatic changes in an otherwise passive depositional system some of the finer grained shallow marine deposits have yielded fossil floras dominated by sub arborescent lycopsids sublepidodendron lepidodendropsis sphenophytes archaeocalamites and pteridophylls nothorhacopteris triphyllopteris the assemblage compares with other gondwanan floras of this age that have been assigned to the paraca floral realm and are taken to indicate relatively warm climatic conditions that existed just prior to the onset of the carboniferous permian ice age

an imprint of the mediterranean middle miocene circulation pattern in a satellite sea during the langhian a case study from the carpathian foredeep central paratethys abstract the langhian central paratethys sea represents a unique marine environment with a complicated circulation pattern influenced by the mediterranean sea here we present a review study based on previously published stable isotopic foraminiferal and calcareous nannoplankton data from various locations in the central paratethys supplemented by new datasets from the interval of 14 6 13 9 ma we compared the paratethyan data with data reported from the mediterranean area together with the results of computer models and with the latest paleogeographical studies as a tool for comparison of particular water masses we chose 18o data from various benthic and planktonic foraminiferal species globigerinoides trilobus globigerina bulloides cibicidoides spp to obtain information for both surficial and bottom waters hydrography moreover we chose 13c data as an indicator of the relationship between the surficial and bottom waters at particular localities the composition of foraminiferal and calcareous nannoplankton assemblages was used to verify the paleoecological situation at the studied localities it was discovered that an anti estuarine circulation regime was the basic circulation pattern during the studied interval this is supported by a similarity in hydrography of surficial waters surface mixed layer between the paratethys and the mediterranean sea which is shown by the isotopic data nevertheless the isotopic data comparison revealed differences regarding the bottom waters pointing to an existence of the paratethyan bottom waters and a subsequent change in the bottom waters isotopic composition between 14 4 13 9 ma this change could be linked with the shallowing of the basin that is indicated by various paleobiological data furthermore we tried to summarize possible regional consequences of the suggested paleocirculation patterns

floristic migration in south america during the carboniferous phytogeographic and biostratigraphic implications abstract new data on the carboniferous flora of northern south america are combined with existing data for gondwanaland to re examine the floristic evolution of south america during the carboniferous the integration of paleobotanical palynological paleomagnetic paleogeographic and paleoclimatologic data makes it possible to reconstruct the floristic evolution of south america during the carboniferous as a dynamic process that was mainly controlled by the northward movement of the south american plate towards the equator during the carboniferous three carboniferous floras the cold archaeosigillaria lepidodendropsis frenguellia flora the temperate nothorhacopteris flora and the tropical euramerican flora characterize south america intra south american floristic migration is documented by the different age and composition of the nothorhacopteris flora it is of late early carboniferous age in northern south america bolivia northeastern brazil and peru whereas it is of late carboniferous age in southern south america argentina and southern brazil the flora was adapted to warm temperate climatic conditions indicating that southern south america moved into this climatic zone during the late carboniferous this migration explains the different ages recorded for the same taxa e g nothorhacopteris in northern and southern south america taxonomic differences between the northern and southern nothorhacopteris flora reflect visean westphalian evolution

long lived mesoscale eddies in the eastern mediterranean sea analysis of 20 years of aviso geostrophic velocities we analyzed 20 years of aviso data set to detect and characterize long lived eddies which stay coherent more than 6 months in the eastern mediterranean sea in order to process the coarse gridded 1 8 aviso geostrophic velocity fields we optimized a geometrical eddy detection algorithm our main contribution was to implement a new procedure based on the computation of the local and normalized angular momentum lnam to identify the positions of the eddy centers and to follow their lagrangian tra jectories we verify on two mesoscale anticyclones sampled during the egypt campaign in 2006 that our methodology provides a correct estimation of the eddy centers and their characteristic radius corresponding to the maximal tangential velocity our analysis reveals the dominance of anticyclones among the long lived eddies this cyclone anticyclone asymmetry appears to be much more pronounced in eastern mediter ranean sea than in the global ocean then we focus our study on the formation areas of long lived eddies we confirm that the generations of the ierapetra and the pelops anticyclones are recurrent and correlated to the etesian wind forcing we also provide some evidence that the smaller cyclonic eddies formed at the southwest of crete may also be induced by the same wind forcing on the other hand the generation of long lived eddies along the libyo egyptian coast are not correlated to the local wind stress curl but surprisingly their initial formation points follow the herodotus trough bathymetry moreover we identify a new formation area not discussed before along the curved shelf off benghazi

cyclothem digital correlation and biostratigraphy across the global moscovian kasimovian gzhelian stage boundary interval middle upper pennsylvanian in north america and eastern europe the long standing difficulty of correlating pennsylvanian strata among provincial faunal regions is resolved by effecting digital correlation of major glacial eustatic cyclothems that represent high stands when certain species achieved more global distribution than usual in the late moscovian early gzhelian late desmoinesian early virgilian succession in the midcontinent united states several major cyclothems are correlated by both conodont species in common and cyclothem scale with cyclothems in russia moscow basin and ukraine donets basin and the remaining cyclothems fit into the framework by position and scale in this way the suggested event marker for the global kasimovian gzhelian stage boundary first appearance of idiognathodus simulator is supported while possible event markers for the moscovian kasimovian boundary await further evaluation

suspended particulate matter and nepheloid layers over the southern margin of the cretan sea n e mediterranean seasonal distribution and dynamics seawater along the southern margin of the cretan sea may 1994 september 1995 has been found to have light transmission values ranging from 79 to 94 corresponding to spm values ranging from 1 5 mg l 1 to 0 2 mg l 1 the highest spm concentrations mostly of terrigenous origin were found close to the sea bed over the shelf break and upper slope the origins of spm in the surface waters 150 m is principally biogenic the occurrence of nepheloid layers at intermediate depths within the upper water column is mostly a result of density stratification the dynamics of spm distributions are governed by the 2 gyre system which induces a general onslope flow and so inhibits the seaward dispersion of the relatively more turbid coastal shelf waters this is in agreement with the virtual absence of suspensates of terrigenous origin offshore of the shelf break near bottom nepheloid layers bnl and detached intermediate nepheloid layers occur in the vicinity of the shelf break and over upper slope region these may be explained by resuspension induced by near bed current activity and breaking of internal waves high concentrations of spm near the seabed may be caused by anthropogenic trawling activity occasionally the formation of bnl may result from local seismic activity resulting in gravity driven mass movements

a synthesis of the levantine basin circulation and hydrography 1985 1990 abstract the levantine basin circulation derived from recent data consists of a series of sub basin scale to mesoscale eddies interconnected by jets the basin scale circulation is masked by eddy variability that modulates and modifies it on seasonal and interannual time scales long term qualitative changes in the circulation are reflected in the bifurcation pattterns of ther mid basin jets relative strengths of eddies and the hydrographic properties at the core of these eddies confinement within the basin geometry strongly influences the co evolution of the circulation features surface measurements satellite images and the mass field indicate an entire range of scales of dynamical features in the region the complexity of the circulation is consistent with the basin wide and mesoscale heterogeneity of the hydrographic properties the interannual variability of liw levantine intermediate water formation in the region appears correlated with the changes in the circulation wintertime convective overturning of water masses reach intermediate depths and constitute a dominant mechanism of liw formation especially in anticyclonic eddies and along the coasts of the northern levantine basin

separability of sea ice types from wide swath c and l band synthetic aperture radar imagery acquired during the melt season abstract differentiating between first year ice fyi and multi year ice myi in c band synthetic aperture radar sar imagery during spring summer melt when wet snow and melt ponds mask the underlying ice is difficult it has been suggested that the use of l band sar may alleviate this concern given increased penetration depths at longer wavelengths however this has not been thoroughly assessed here the separability of fyi and myi is compared using horizontally polarized hh c band radarsat 2 and l band alos palsar scansar images acquired over landfast sea ice in the canadian arctic archipelago in the spring and summer of 2009 l band provided enhanced contrast between fyi and myi during early melt onset and during the drainage phase of advanced melt while c band was found to provide enhanced contrast when the wet snowpack was transitioning from the pendular regime to the funicular regime at the time of the pendular funicular transition the backscatter signatures of fyi and myi reversed at both c and l band this behavior is well established at c band but has not been reported previously at l band the l band imagery also provided improved definition of floe boundaries and ridges throughout the melt season finally the l band data had reduced speckle equivalent number of looks 12 relative to the c band data 9 equivalent looks these results indicate that l band sar data acquired during the melt season could be used to enhance operational and scientific sea ice information products that have traditionally been derived from single frequency c band sar data

water masses and hydrography during april and june 2016 in the cretan sea and cretan passage eastern mediterranean sea abstract two successive cruises in the cretan sea and cretan passage west levantine basin during april and june 2016 surveyed the physical characteristics of the water masses in these large eastern mediterranean basins data confirm that the hydrographical status is far different from that of the eastern mediterranean transient emt period however the basins have not yet returned to the pre emt status in the cretan sea intermediate water masses of both cretan and levantine origins are detected the stagnating bottom waters of this basin still hold high salinity density and dissolved oxygen values remnant of the emt deep water formation episodes characterised by low salinity and oxygen values transitional waters of mediterranean origin are present between intermediate and bottom layers throughout the cretan sea intermittent weak outflow of warm and saline masses of cretan origin towards the eastern mediterranean is observed at the bottom of both east and west cretan straits in the cretan passage there is no sign of the ierapetra anticyclonic gyre possibly related to the seasonality of the gyre or linked to larger scale eastern mediterranean circulation variability the observed surface circulation in this area is comprised of a series of smaller gyres between the cretan cyclone and the rhodes gyre the bottom waters of the cretan passage present a west to east gradient of increasing salinity and decreasing oxygen related to the propagation of new adriatic deep water from the ionian sea towards the levantine basin

comparing l and c band synthetic aperture radar estimates of sea ice motion over different ice regimes abstract estimating sea ice motion from synthetic aperture radar sar imagery at c band is the most reliable approach because of its high spatial resolution and ever increasing temporal resolution given the multiple current and upcoming sar platforms however there is still uncertainty in sar derived sea ice motion depending on the ice type and its thermodynamic state there have been suggestions mostly theoretical that use of l band sar and its inherent longer wavelength 15 30 cm and subsequent increased penetration capability could be beneficial for estimating sea ice motion especially during the melt season here we estimate and analyze sea ice motion for 9 pairs of c and l band sar imagery from radarsat 2 palsar 1 and palsar 2 located in the canadian arctic over a variety of sea ice types at different thermodynamic states results show that the increased signal penetration of l band sar into multi year ice myi during the melt season facilitates the detection of more motion vectors with stronger cross correlation coefficients compared to c band sar over newly formed ice and dry first year ice the reduced sensitivity to surface scattering and richer texture from l band sar imagery facilitates the detection of more motion vectors with stronger cross correlation coefficients compared to c band sar over dry myi l band provided stronger cross correlation coefficients but c band detected more motion vectors with a more representative spatial distribution with arctic sea ice continuing shift from a multi year to first year dominated icescape coupled with an increasing melt season length l band sar s ability to provide improved sea ice motion estimates during both the melt and freeze up time periods could prove even more useful in the coming decades

current structures and topographic rossby waves in the levantine basin south of crete revealed by snapshot and time series current measurements abstract the 1 5 lat x 3 5 lon levantine area south of crete was surveyed for the first time in april 2016 with a combination of direct current measurements comprised by ctd ladcp lowered acoustic doppler current profiler grid casts and ship track adcp measurements in the upper 500 m while a mooring was launched at the end of the continental slope and provided yearly current records at 700 m and 30 m off the bottom depth of 4300 m horizontal flow structures are mapped in the upper 1000 m via objective analysis of the direct current measurements depicting the cretan cyclone at the west the rhodes gyre at the east and anticyclonic circulation in the middle due to modified atlantic water in the upper 80 m and a thick saline warm mass extending from 100 m to 1500 m possibly of cretan origin the bottom kinetic energy spectra have higher density values than those at 700 m in the two month energetic period of end jan to end mar 2017 topographic rossby waves trw with wavelength of 42 km exist in the window of 34 19 days with significant coherence between the near bottom and the 700 m records at the trw spectral window the motions are transverse and the direction of maximum velocity variance veers from nearly along isobaths 20 north northeast to 45 northeast with decreasing period the presence of trws in the specific time period within 2017 appears to be related to the lateral shifts of the ierapetra anticyclone over the sloping bottom of the continental margin

a new serpukhovian mississippian fossil flora from western argentina paleoclimatic paleobiogeographic and stratigraphic implications an uppermost mississippian serpukhovian fossil flora from western argentina is described for the first time its particular composition includes both warm climate plants typical from the pennsylvanian of gondwana namely pteridosperms sphenophytes as well as arboreous lycopsids and small lycopsids characteristic of cooler climates of pre serpukhovian times a warm temperate climate is inferred for this association which fills a time gap between those pennsylvanian and mississippian classic floras previously known the presence of tomiodendron nothorhacopteris kellaybelenensis and paracalamites allow the recognition of the paraca floral realm in argentina supporting the existence of a nonglacial paleoclimate period developed just before of the bashkirian moscovian gondwanan glaciation and after a latest visean glaciation it likewise would indicate the paleogeographic position of south west gondwana which would have acceded to a warm temperature latitudinal belt during serpukhovian times the recognition of this floral assemblage has relevant biostratigraphic and lithostratigraphic implications for the western margin of gondwana it defines a new zone for western argentina herein named frenguellia eximia nothorhacopteris kellaybelenensis cordaicarpus cesarii fnc zone which is recorded in the oldest known lithostratigraphic unit from the paganzo basin the loma de los piojos formation nom nov

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

can we extend local sea ice measurements to satellite scale an example from the n ice2015 expedition knowledge of arctic sea ice conditions is of great interest for arctic residents as well as for commercial usage and to study the effects of climate change information gained from analysis of satellite data contributes to this understanding in the course of using in situ data in combination with remotely sensed data the question of how representative local scale measurements are of a wider region may arise we compare in situ total sea ice thickness measurements from the norwegian young sea ice expedition in the area north of svalbard with airborne derived total sea ice thickness from electromagnetic soundings a segmented and classified synthetic aperture radar sar quad pol alos 2 palsar 2 satellite scene was grouped into three simplified ice classes the area fractions of the three classes are 11 2 thin 74 4 level and 14 4 deformed the area fractions of the simplified classes from ground and helicopter based measurements are comparable with those achieved from the sar data thus this study shows that there is potential for a stepwise upscaling from in situ to airborne to satellite data which allow us to assess whether in situ data collected are representative of a wider region as observed by satellites

evolution of dynamics in the eastern mediterranean affecting water mass structures and properties in the ionian and adriatic seas 1 basin wide hydrographic observations performed in the eastern mediterranean during the past 2 decades attest changes in the thermohaline circulation as well as new aspects concerning the onset and the follow up of the major transient event that occurred at the beginning of the 1990s i e the change of the dense water formation site from the adriatic to the aegean sea since 1999 the upper thermohaline circulation has indicated the restoring of the opposite flows of the atlantic water and the levantine intermediate water which were greatly reduced in the period 1987 1995 in the deep layer the comparison between water mass structures observed in 1995 during the mature status of the transient and those observed in 1999 shows a damping of the event and a regained role of the adriatic sea as a primary source of dense waters separate calculations of the salt content in the ionian and in the levantine seas show an overall salt redistribution during 1987 1995 a salt loss of about 25 1012 kg was computed for the upper 800 m constituting only 27 of the salt gain in the deep layer over most of the eastern mediterranean on the contrary during 1995 1999 the restored upper thermohaline circulation caused a salt redistribution between the two basins of about the same amount but in the opposite sense while an extra quantity of 12 1012 kg was deposited in the deep layer in addition calculations of the salt concentration in the convection region of the southern adriatic reveal a remarkable amount of the salt not yet totally transferred into the deep layers by its interior dynamics because of mild winters

the response of the aegean sea eastern mediterranean to the extreme 2016 2017 winter the exceptionally cold december 2016 over the aegean sea one of the most important dense water formation areas of the eastern mediterranean sea resulted in winter heat loss comparable to the peak eastern mediterranean transient winters 1992 1993 hydrological data sampled in march april 2017 showed that newly produced dense waters ventilated the north aegean deep basins up to density horizons of 29 35 kg m3 the water column ventilation was unable to reach the bottom as the present upper thermohaline circulation of the eastern mediterranean does not favor the salinity preconditioning of the aegean sea in the southwest aegean the myrtoan basin was ventilated by dense waters traceable further south to the west cretan straits export of these masses from the aegean sea can potentially have a broader impact on the thermohaline circulation of the eastern mediterranean

cretan deep water outflow into the eastern mediterranean abstract a simple hydraulic model is used to estimate the deep water fluxes of cretan deep water cdw through the cretan arc straits and into the eastern mediterranean basins the input to the model consists of the height of the deep water reservoir above sill depth and its density difference from the overlying water masses data from four hydrographic cruises which took place in 1995 1991 and 1987 are used to estimate the depth of the reservoir above the sill and the density difference the results show a significant cdw outflow of 0 75 106 m3 s 1 in early 1995 the outflow of cdw through kassos strait in the east is 0 53 106 m3 s 1 while 0 22 106 m3 s 1 outflows through the antikithira strait in the west the model results agree with fluxes estimated from current meter observations the cdw outflow has been neither steady nor uniform during the period 1987 95 in the kassos strait the outflow commenced in 1987 and increased rapidly until 1991 since then it appears to have stabilised in the antikithira strait in contrast the outflow has increased steadily since 1987 such modifications in the cdw outflow are associated with changes in its hydrographic characteristics the salinity of cdw increased constantly by approximately 0 1 between 1987 and 1995 while its temperature warmed between 1987 and 1991 and then cooled

changes in arctic melt season and implications for sea ice loss the arctic wide melt season has lengthened at a rate of 5 days decade 1 from 1979 to 2013 dominated by later autumn freezeup within the kara laptev east siberian chukchi and beaufort seas between 6 and 11 days decade 1 while melt onset trends are generally smaller the timing of melt onset has a large influence on the total amount of solar energy absorbed during summer the additional heat stored in the upper ocean of approximately 752 mj m 2 during the last decade increases sea surface temperatures by 0 5 to 1 5 c and largely explains the observed delays in autumn freezeup within the arctic ocean s adjacent seas cumulative anomalies in total absorbed solar radiation from may through september for the most recent pentad locally exceed 300 400 mj m 2 in the beaufort chukchi and east siberian seas this extra solar energy is equivalent to melting 0 97 to 1 3 m of ice during the summer

tropical marine climate during the late paleozoic ice age using trace element analyses of brachiopods abstract the late paleozoic ice age can be considered an important analogue to the modern ice age but comparisons between the two time intervals have been hampered by the difficulty of resolving climatic changes that occur over short e g seasonal time scales in the paleozoic record as a first step toward overcoming these limitations this study employed mg ca trace element ratios sampled across the growth bands of six specimens of the brachiopod composita to assess differences in tropical marine mean temperature and seasonality in visean and moscovian time these time intervals bracket the onset of the late paleozoic ice age which occurred in mid serpukhovian time and thus provide a snapshot of climate changes from a greenhouse to an icehouse world shells were screened for diagenetic alteration by cathode luminescence and by comparing the values of mn sr na and b to those reported for modern brachiopods in addition a 87sr 86sr value measured for one specimen agreed with a published strontium isotope curve for the late paleozoic era both the mean and range of mg ca values were larger in visean than moscovian time suggesting colder and less seasonal temperatures during the late paleozoic ice age the decline in seasonality was due to a greater proportional reduction of maximum values which presumably represent summer temperatures than minimum values these relative differences between the pre ice age and ice age tropical climate provide a first step toward understanding the broad patterns of seasonal scale changes in temperature during a critical time in earth s history

an upper paleozoic bio chronostratigraphic scheme for the western margin of gondwana abstract the carboniferous and permian fossiliferous sequences of the central western argentina contain abundant plant remains palynomorphs and invertebrates they include a continuous record of large distribution in the paganzo rio blanco calingasta uspallata and san rafael basins the most recent biostratigraphic schemes recognize a floristic succession represented by the biozones archaeosigillaria frenguellia af biozone frenguellia eximia nothorhacopteris kellaybelenensis cordaicarpus cesarii fnc biozone nothorhacopteris botrychiopsis ginkgophyllum nbg biozone interval biozone and gangamopteris biozone the associated palynological record is represented by the biozones reticulatisporites magnidictyus verrucosisporites quasigobbetti mq biozone raistrickia densa convolutispora muriornata dm biozone pakhapites fusus vittatina subsaccata fs biozone and lueckisporites weylandites lw biozone the precise age of the upper paleozoic western gondwanan biozones has been under discussion and remains controversial to date in some regions the main issue hampering an integrated comparison of the gondwanan biozones was its imprecise chronostratigraphic framework however new studies in some argentinian stratigraphic sections bearing floras and faunas have yielded several radiometric ages from these 206 pb 238 u zircon datings it is possible to determine the chronostratigraphic range of many fossiliferous assemblages in this sector of gondwana in this way the af and mq biozones are restricted to the late mississippian and they would be not younger than 335 ma according to radiometric ages 206 pb 238 u ages suggest that the nbg dma and dmb biozones characterize the late serpukhovian glacial deposits and persisted up to the late bashkirian beds containing the interval and dmc biozones have yielded 206 pb 238 u ages of 312 82 0 11 ma and 310 71 0 1 ma which would indicate that both zones characterize the moscovian the remains of gangamopteris biozone found in the paganzo basin overlie basalt levels ranging between 308 6 and 293 6 ma therefore the incoming of the first glossopterids was closely associated to the carboniferous permian boundary in this part of gondwana the data presented in this paper are used for establishing comparisons with other gondwanan biozones constrained by absolute ages

a greenhouse interval between icehouse times climate change long distance plant dispersal and plate motion in the mississippian late visean earliest serpukhovian of gondwana abstract the late paleozoic ice age lpia is the closest example that can be compared with current climate conditions near the beginning of the lpia fossil plants of mississippian late visean to earliest serpukhovian age indicate a widespread frost free climate in a wide belt on gondwana indicating an interval of greenhouse conditions between the earlier visean and later serpukhovian icehouse times this warm temperate floral belt has been named the paraca floral belt after the locality on the peruvian coast where it was first recognized the origin of this particular zono biome was due to the interplay of 1 climate oscillations 2 several kinds of long distance plant dispersal within between or through zono biomes and 3 plate motion the carboniferous age strata on the paracas peninsula in peru serve as an example for an analysis of these large scale patterns through the analysis of local geology paleobotany and paleoecology the processes observed during this time interval can serve as a model for long distance plant dispersal at other times

evolution of microwave sea ice signatures during early summer and midsummer in the marginal ice zone emissivities at frequencies from 5 to 94 ghz and backscatter at frequencies from 1 to 17 ghz were measured from sea ice in fram strait during the marginal ice zone experiment in june and july of 1983 and 1984 the ice observed was primarily multiyear the remainder first year ice was often deformed results from this active and passive microwave study include the description of the evolution of the sea ice during early summer and midsummer the absorption properties of summer snow the interrelationship between ice thickness and the state and thickness of snow and the modulation of the microwave signature especially at the highest frequencies by the freezing of the upper few centimeters of the ice

circulation and hydrography of the levantine basin results of poem coordinated experiments 1985 1986 abstract a brief review of the meteorological setting hydrography and the circulation in the levantine basin of the eastern mediterranean is given the recent high resolution data obtained in poem coordinated experiments of 1985 1986 are then used to optimally estimate the circulation in the basin in two different seasons and to describe the water mass distributions some of the features observed during the experiments support the historical knowledge on the locations of sub basin scale gyres and the general circulation in addition to which some new features are established details of the circulation such as the intensity the multiple scales and the three dimensional structure of the various vortices and the central levantine basin current are displayed extensively a variety of sub basin meso and sub mesoscale vortices occur with highly assymmetric baroclinic vertical structures some eddies split into multiple centres with depth interpreted as indicating possible coalescences a number of long lived eddies were persistent in both surveys the sub surface atlantic water aw is advected by and entrapped within the eddy field the levantine intermediate water liw at intermediate depths is shown to be maintained throughout the year in the northeastern sector of the levantine basin and along the periphery of the rhodes gyre the levantine intermediate water also has a patchy distribution owing to the advection and trapping by the eddy field which it helps to generate through adjustment processes

x c and l band sar signatures of newly formed sea ice in arctic leads during winter and spring abstract we examine an extensive synthetic aperture radar sar data set from the arctic ocean spanning a time period from january to june 2015 with the aim of identifying multi polarization parameters that can be used to accurately separate newly formed sea ice from the surroundings newly formed sea ice areas both provide favourable routing for ship traffic and are key to arctic climate science because they enable heat exchange between the ocean and the atmosphere our data set encompasses three different frequencies x c and l band at a range of incidence angles and were acquired under different environmental conditions our results suggest that by combining the scattering entropy and the co polarization ratio we can successfully separate the newly formed sea ice from open water and thicker sea ice within all three frequencies throughout the winter and spring season we observe a high correlation between scattering entropy values calculated using quad polarization c and l band data and scattering entropy values calculated using the same scenes reduced to the co polarization channels hh and vv we therefore conclude that dual polarization hh and vv x band scenes can be directly used to complement quad polarimetric c and l band scenes for studies of newly formed sea ice to confine the quad polarimetric data sets to their co polarization channels one can ensure a higher signal to noise ratio incidence angles below 35 are needed to keep the signal to noise ratios sufficiently high for the scattering entropy and co polarization ratio due to its lack of incidence angle dependency the polarization difference can provide additional support in newly formed sea ice studies the regular coverage of the arctic ocean with c band sar means that such scenes should to be included in any automatic monitoring however x and l band sar can based on their difference in penetration depth provide additional information about newly formed sea ice types and surface structure

dense intermediate water outflow from the cretan sea a salinity driven recurrent phenomenon connected to thermohaline circulation changes data collected from different platforms in the cretan sea during the 2000s decade present evidence of gradually increasing salinity in the intermediate and deep intermediate layers after the middle of the decade the observed gradual salt transport toward the deeper layers indicates contributions of dense water masses formed in various aegean sea subbasins the accumulation of these saline and dense water masses in the cretan sea finally led to outflow from both cretan straits with density greater than typical levantine cretan intermediate water but not dense enough to penetrate into the deep layers of the eastern mediterranean we name this outflowing water mass as dense cretan intermediate water dciw a retrospective analysis of in situ data and literature references during the last four decades shows that similar events have occurred in the past in two occasions a in the 1970s and b during the eastern mediterranean transient emt onset 1987 1991 we argue that these salinity driven aegean outflows are mostly attributed to recurrent changes of the eastern mediterranean upper thermohaline circulation that create favorable dense water formation conditions in the aegean sea through salinity preconditioning we identify these phenomena as emt like events and argue that in these cases internal thermohaline mechanisms dominate over atmospheric forcing in dense water production however intense atmospheric forcing over an already salinity preconditioned basin is indispensable for creating massive deep water outflow from the cretan sea such as the emt event

internal wave measurements on the cycladic plateau of the aegean sea 1 the internal wave climate in the southern aegean sea is examined with an array of two bottom mounted acoustic doppler current profilers and three profiling moorings deployed on the northern continental slope of the cretan sea for 3 months frequency spectra indicate an extremely weak internal wave continuum about 4 10 times weaker than the garrett munk and levine reference levels spectra are instead dominated by semidiurnal internal tides and near inertial waves which are examined in detail by bandpass filtering in the semidiurnal band a barotropic tidal flow of 2 cm s 1 is observed with a pronounced spring neap modulation in phase with the lunar fortnightly cycle one to two days following several of these spring tide periods a distinct internal tide featuring 10 20 m vertical displacements and 15 20 cm s 1baroclinic velocities is detectable propagating upward and to the southeast time mean energy increases a factor of 2 5 within about 100 m from the bottom implying generation and or scattering from the bottom whose slope is nearly critical to semidiurnal internal waves over much of the array several strong downward propagating near inertial events are also seen each of which occurs following a period of work done by the wind on the mixed layer as estimated from a nearby surface mooring the high frequency internal wave continuum is more temporally constant but increases substantially toward the end of the deployment significant but unexplained differences in kinetic energy occur between successive spring tide periods in the case of the internal tides and between successive wind events in the case of the near inertial signals substantial variability is observed in the low frequency flows which likely contributes to the time variability of the internal wave signals

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 1987 aegean dense water formation a streamtube investigation by comparing theoretical model results satellite field and numerical data with contourite distribution abstract we here discuss a detailed investigation of the dense water formation evolution and spreading in the aegean sea during the year 1987 immediately prior to the onset of the eastern mediterranean transient emt we use hydrologic data collected during the lia cruise satellite images for sst sea surface temperature and protheus data a coupled ocean atmosphere numeric model along with theoretical streamtube models these hydrological analyses are related to late quaternary sedimentary drifts in the cyclades plateau and in the myrtoon basin our analysis shows that streamtube dynamics provide a novel model of dense water evolution and spreading in the aegean basin applying this model to dense water masses observed in winter and spring 1987 near samothrace and over the limnos lesbos plateau results in a geostrophic flow of this dense cold water towards the limnos sporades channel in the north aegean sea there it mixes with dense water from the limnos lesbos plateau and finally both move geostrophically towards the cyclades plateau these results indicate that most of the dense water observed near the cyclades formed initially about 3 months earlier at samothrace and limnos shelves during its long pathway it partially mixed with adjacent water masses although our analysis concerns only one year of dense water analyses these results are thought to reflect a more general and recurrent phenomenon in the aegean basin indeed high resolution airgun 10 in seismic reflection data from the cyclades plateau reveal the presence of late quaternary sediment drifts these observations are concordant with results from our theoretical model this suggests a direct link between such a dense water cascading and contourite dynamics the continuation of sediment drifts into the deep basin floor 900 m deep of the myrtoon basin moreover indicates a cascading character of such bottom currents at the flanks of the basin a feature that set further investigations

the role of the north aegean in triggering the recent eastern mediterranean climatic changes drastic changes have occurred in the vertical structure of the deep waters of the eastern mediterranean in the early 1990s as dense water of aegean origin has displaced lighter waters of adriatic origin at the bottom of the deep basins this work suggests that the initiation of this process took place in the north aegean in the winter of 1986 1987 and was intensified by another formation event in 1992 1993 the available observations from the north aegean support such a scenario furthermore we propose that the outflow of black sea waters into the aegean through the dardanelles could act as an insulator of the deeper layer from the atmosphere thus absorbing a large part of the heat and salt exchange despite this fact the existence of the densest bottom water of the mediterranean in the north aegean and the continuation of density increase for a large period of time suggests that it is a region of formation thus that the insulation layer may at times be penetrated we suggest that reduced black sea outflow into the north aegean could facilitate dense water formation during the passage of cold atmospheric fronts in the winter

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

late quaternary bottom current activity in the south aegean sea reflecting climate driven dense water production abstract the eastern mediterranean transient emt represents a recent early 1990s to today water circulation phenomenon during which more arid climatic conditions in the mediterranean lead to the production of very dense surface water masses in the north aegean sea the produced north aegean dense water nadw sinks to seafloor flows to the south aegean sea and then spills into the eastern mediterranean sea through the cretan straits contributing to the rejuvenation of the bottom water a large dataset of vintage high resolution seismic reflection profiles indicates that the floors of the basins in the southwest aegean sea are characterised by late quaternary erosional gullies abraded surfaces and channel related sediment drifts such structures provide evidence for the presence of strong bottom currents which originate from the southward propagation of nadw masses the basins have depths of 300 m to 1000 m and are connected to each other by narrow a few km straits and sills the dominance of abraded surfaces and erosional gullies on the northern flank of the basins and in the narrow straits sills between them provides evidence that the southward propagation of the nadw occurs by the filling and flooding of each basin by dense water which then spills and cascades into the next basin southward seismic stratigraphy suggests that the formation of the drifts started at marine isotope stage mis 11 420 ka bp the coincidence of at least three erosional surfaces within the sediment drifts with interglacial mis 11 5 and 1 respectively suggests that bottom currents were mostly active during high sea level stands and sluggish during glacial low sea level stands a 90 100 m drop of the sea level below the current level would have resulted in the emergence of the eastern cyclades plateau and thus in the disconnection of the southwest aegean sea from the north aegean sea several 0 05 0 5 m thick beds of gravelly sand with algal and mollusc debris laminated to mottled sand and mottled mud are observed in the sediment cores analysed in this paper these beds can be confidently correlated from core to core and are interpreted as bottom current deposits the separation of these beds by hemipelagic sediments indicates that bottom current activity in the southwest aegean is not permanently established but episodic six episodes of intense bottom current activity are recorded in the mis 2 4 10 80 ka sediments and they appear to correlate well with the cold and dry younger dryas and heinrich 3 4 5 6 and 7 events in contrast at least three episodes of intense bottom current activity are recorded in the cores during the holocene the higher frequency of strong bottom current episodes in the southwest aegean sea during the holocene is attributed to the higher sea level stand that makes the circulation of water masses in the aegean sea more sensitive to climatic changes

abrupt shoaling of the nutricline in response to massive freshwater flooding at the onset of the last interglacial sapropel event a detailed assessment of the respective roles of production export and subsequent preservation of organic carbon corg in the eastern mediterranean emed sediments during the formation of sapropels remains elusive here we present new micropaleontological results for both surface samples taken at several locations in the emed and last interglacial sapropel s5 from core lc21 in the southeastern aegean sea a strong exponential anticorrelation between relative abundances of the lower photic zone coccolithophore florisphaera profunda in the surface sediments and modern concentrations of chlorophyll a chl a at the sea surface suggests that f profunda percentages can be used to track past productivity changes in the emed prior to s5 deposition an abrupt and large increase of f profunda percentages in lc21 coincided within the multidecadal resolution of the records with the marked freshening of emed surface waters this suggests a strong coupling between freshwater bound surface to intermediate water density stratification and enhanced upward advection of nutrients to the base of the photic zone fuelling a productive deep chlorophyll maximum dcm underneath a nutrient starved surface layer our findings imply that at least at the onset of sapropel formation physical and biogeochemical processes likely operated in tandem enabling high corg accumulation at the seafloor

ipcc climate models do not capture arctic sea ice drift acceleration consequences in terms of projected sea ice thinning and decline 1 ipcc climate models underestimate the decrease of the arctic sea ice extent the recent arctic sea ice decline is also characterized by a rapid thinning and by an increase of sea ice kinematics velocities and deformation rates with both processes being coupled through positive feedbacks in this study we show that ipcc climate models underestimate the observed thinning trend by a factor of almost 4 on average and fail to capture the associated accelerated motion the coupling between the ice state thickness and concentration and ice velocity is unexpectedly weak in most models in particular sea ice drifts faster during the months when it is thick and packed than when it is thin contrary to what is observed also models with larger long term thinning trends do not show higher drift acceleration this weak coupling behavior 1 suggests that the positive feedbacks mentioned above are underestimated and 2 can partly explain the models underestimation of the recent sea ice area thickness and velocity trends due partly to this weak coupling ice export does not play an important role in the simulated negative balance of arctic sea ice mass between 1950 and 2050 if we assume a positive trend on ice speeds at straits equivalent to the one observed since 1979 within the arctic basin first order estimations give shrinking and thinning trends that become significantly closer to the observations

persistence of late carboniferous tropical vegetation during glacially driven climatic and sea level fluctuations abstract the late carboniferous glaciation reached its peak during the latter part of the westphalian late desmoinesian in the tropical illinois basin this was the time of deposition of the carbondale and lower modesto formations characterized by the cyclic repetition of major coal deposits black shales limestones gray shales and sandstones these lithological changes evidence repeated major fluctuations in climate and sealevel fossil floras from the tropical ever wet to seasonally wet terrestrial lithofacies coals and shales above coals remain compositionally similar throughout the 1 1 5 m y time interval floras from coals known from coal balls and palynology characteristically were composed of three major plant communities the wettest sites were dominated by monocarpic lycopsids intermediate sites were dominated by polycarpic lycopsids and areas subject to fires and intermittent flooding were dominated by medullosans and the small lycopsid paralycopodites clastic substrate environments were dominated by ferns and pteridosperms and conform to a single biozone indicating their compositional unity and distinctness from earlier and later assemblages the composition of lowland floras is poorly known from times between the deposition of coals and associated terrestrial rocks intervals during which most of the lowlands were flooded and marine rocks were being deposited consequently the temporally intermittent recurrence of lowland floras despite repeated widespread environmental disruption may be explained either by vegetational persistence and migration of floras or repeated disruption and reassembly several lines of evidence suggest persistence as a likely explanation

co2 forced climate and vegetation instability during late paleozoic deglaciation the late paleozoic deglaciation is the vegetated earth9s only recorded icehouse to greenhouse transition yet the climate dynamics remain enigmatic by using the stable isotopic compositions of soil formed minerals fossil plant matter and shallow water brachiopods we estimated atmospheric partial pressure of carbon dioxide pco2 and tropical marine surface temperatures during this climate transition comparison to southern gondwanan glacial records documents covariance between inferred shifts in pco2 temperature and ice volume consistent with greenhouse gas forcing of climate major restructuring of paleotropical flora in western euramerica occurred in step with climate and pco2 shifts illustrating the biotic impact associated with past co2 forced turnover to a permanent ice free world

incidence angle dependence of hh polarized c and l band wintertime backscatter over arctic sea ice synthetic aperture radar sar incidence angle has a significant effect on the microwave backscatter from sea ice this paper investigates the incidence angle dependence of c and l band hh polarized microwave backscatter coefficient over arctic first year sea ice fyi and multiyear sea ice myi in winter advanced land observation satellite phased array type l band sar l band and radarsat 2 c band images are used to derive ice type specific incidence angle dependencies calculated using linear regression models for l band mean ice type specific incidence angle dependencies for fyi and myi are 0 21 and 0 30 db 1 respectively and for c band they are 0 22 and 0 16 db 1 respectively to validate our results we calculated root mean square deviation rmsd by comparing the ice type specific dependence from 2010 with individual dependencies from 2009 based on ice types and frequencies the rmsd is found to be smaller than the standard deviation of ice type specific dependencies for both frequencies the rmsd values for the l band incidence angle dependencies are 0 03 and 0 04 db 1 for fyi and myi respectively for c band the rmsd values for the fyi and myi dependencies are 0 03 and 0 01 db 1 respectively subsequently we demonstrate that after applying incidence angle normalization the variability of c and l band sar backscatter reduces and separability of ice types increase substantially

backscatter characteristics of the winter ice cover in the beaufort sea the microwave backscatter statistics of the sea ice cover in the winter beaufort sea are characterized using c band synthetic aperture radar sar data collected by the european earth resources satellite 1 sea ice backscatter signatures were sampled from sar image data collected during the winter of 1991 1992 and winter of 1992 1993 the spatial and temporal variabilities of the backscatter signatures of different ice types are discussed the results show considerable seasonal stability of the backscatter signature of multiyear ice as well as of first year ice small amplitude regional variations of the multiyear ice backscatter can be observed consistent contrast between multiyear ice and first year ice is maintained throughout the season the highest radiometric variability is observed in sea ice in leads on the basis of these observations the backscatter from the principal ice types multiyear and first year are consistent with scatterometer observations and can be easily identified under winter conditions correlations of the regional variations of multiyear ice signatures to physical processes are suggested

ice thickness in the northwest passage recently the feasibility of commercial shipping in the ice prone northwest passage nwp has attracted a lot of attention however very little ice thickness information actually exists we present results of the first ever airborne electromagnetic ice thickness surveys over the nwp carried out in april and may 2011 and 2015 over first year and multiyear ice these show modal thicknesses between 1 8 and 2 0 m in all regions mean thicknesses over 3 m and thick deformed ice were observed over some multiyear ice regimes shown to originate from the arctic ocean thick ice features more than 100 m wide and thicker than 4 m occurred frequently results indicate that even in today s climate ice conditions must still be considered severe these results have important implications for the prediction of ice breakup and summer ice conditions and the assessment of sea ice hazards during the summer shipping season

the early quaternary palaeobiogeography of the eastern ionian deep sea teleost fauna a novel palaeocirculation approach abstract the early quaternary stratigraphic and geographic distribution of teleostean fishes in the ionian sea eastern mediterranean is examined based on the fossil otolith record through comparison between the western and the eastern ionian early middle pleistocene deep sea ichthyofauna the stratigraphic distributions of nineteen taxa are revised a new method of assemblage analysis is attempted in order to discern the palaeoceanographic conditions prevailing at this time the relative contributions of tropical subtropical temperate and subpolar taxa to the surface intermediate and deepwater fish palaeofauna are calculated using fossil material from akrotiri kephallonia island greece gerakas zakynthos island greece and montalbano jonico italy sections which span the gelasian ionian time interval eleven distinct phases in the ionian sea palaeoceanographic evolution are distinguished from prior 1 95 ma to 0 61 ma furthermore a case study is conducted to test the hypothesis that palaeoichthyofauna can be used to draw conclusions regarding the palaeocirculation patterns and their variability in the ionian sea the local production and or atlantic origin of the deep cold waters is registered already during the gelasian the presence of oceanic fish in the eastern ionian can be explained by the existence of a strong anticyclonic gyre in the area during the early quaternary further indicating that the basin s geometry exhibited sufficient bathymetric variation to allow for the activation of the gyre

object based landfast sea ice detection over west antarctica using time series alos palsar data abstract landfast sea ice fast ice is an important feature prevalent around the antarctic coast which is affected by climate change and energy exchanges with the atmosphere and ocean this study proposed a method for detection of the west antarctic fast ice using the advanced land observing satellite phased array l band sar alos palsar images the algorithm has combined image segmentation image correlation analysis and machine learning techniques i e random forest rf extremely randomized trees ert and logistic regression lr we used sar images with a baseline of 5 days that are not in the same orbit but overlap each other as overlaps between swaths in adjacent orbits are often available in the polar regions the underlying assumption for the proposed fast ice detection algorithm is that fast ice regions in sar images with a time interval of 5 days are highly correlated the object based approach proposed in this study was well suited to high resolution sar images in deriving spatially homogeneous fast ice regions the image segmentation results using the optimized parameters showed a distinct difference in the backscatter temporal evolution between fast ice and pack ice regions correlation and std of backscattering coefficients were found to be the most significant variables for the object based fast ice detection from two temporally separated images in overall the quantitative and qualitative evaluation demonstrated that the algorithm was an effective approach to detect fast ice with high accuracies the models well detected various fast ice regions in the west antarctica but misclassified some objects the misclassifications occurred toward the edge of fast ice regions with relatively rapid changes in backscattering between both data acquisitions on the other hand few fast ice objects were misclassified as uniform backscattering over time occurred by chance on very small objects far from the coast very old multi year fast ice regions with high backscattered signals were also a source for some misclassifications this may be due to the sensitivity of l band to snow structure to some extent and a thinner ice over the region with either ice growth no deformation or closing slight deformation between both images heavy snow load on the ice could be another error source for some misclassification as well the approach allowed for the reliable detection of fast ice regions by using l band sar images with a small local incidence angle difference

comments on cascades of dense water around the world ocean abstract evidences of temperature controlled dense water cascading off the gulf of lion shelf in the northwestern mediterranean and several aegean shelves in the northeastern mediterranean are reported together with the adiatic shelf already listed by ivanov shapiro huthnance aleynik golovin 2004 these zones represent the major coastal areas of the mediterranean sea where dense water is produced

a synthesis of the ionian sea hydrography circulation and water mass pathways during poem phase i abstract in this paper we revisit with a thorough in depth analysis the dataset collected in the hydrographic surveys of the international collaborative programme poem physical oceanography of the eastern mediterranean in the period 1986 1987 the work has two major objectives the first is to refine the dynamic picture of the ionian upper thermocline sub basin scale circulation rather less definitive than the dynamic picture of the levantine sea circulation the second is to identify the pathways of the major water masses of the basin not only in the near surface but also in the intermediate and deep layers to our knowledge this is the first work defining the pathways of the levantine intermediate water liw and of the adriatic deep water adw eastern mediterranean deep water emdw that characterize the intermediate and deep circulations the major novel results can be summarized as follows in the upper thermocline 1 the atlantic ionian stream ais jet entering the sicily straits bifurcates into two main branches at 37 n 17 e it advects the modified atlantic water maw into the ionian sea interior the first branch turning directly southward encloses an overall anticyclonic area comprising multiple centers around which the maw is advected 2 the second ais branch extends further into the northeastern ionian where it too turns southward before crossing the entire ionian sea meridionally advecting maw on its left side and ionian surface water isw on its right this branch of the jet is confined to the ionian margin and does not pass around the pelops gyre 3 a new water mass the lsw is formed in the levantine basin and enters the cretan passage then is first veered cyclonically south of crete by the cretan gyre and successively is entrained anticyclonically around the pelops gyre and then enters the aegean sea 4 a permanent cyclone located in the northeastern ionian determines the pathway of mixed adriatic surface water ionian surface water asw isw 5 a permanent cyclone is found in all the surveys near the tip of the italian boot this novel analysis of the liw pathways shows that 1 the major source of intermediate liw during the period 1986 1987 was actually in the levantine sea liw formed there entered the cretan passage was veered cyclonically by the cretan gyre south of crete and then entered the southern ionian sea the major liw pathway was westward directly to the sicilian straits 2 secondary important liw pathways were determined by the interior structures the strong pelops anticyclone was entraining liw around its periphery and was determining the liw northward pathway that closely followed the eastern greek coastline it was along this pathway that liw entered the otranto strait a further branch of liw was entrained and recirculated around the multiple ionian anticyclones ia of the western ionian sea 3 the cretan cyclone is a feature confined to the upper thermocline intermediate layer it disappears at 400 dbar while the pelops anticyclone is strongly barotropic below the upper 100 dbar and penetrates quite intense down to 800 dbar 4 a further completely novel result concerns the new water mass found in the deep layer that spreads on the 29 15 kg m3 isopycnal surface this water mass characterized by high salinity and high oxygen content is formed inside the aegean sea and is observed to spread out all around the cretan arc straits the final fully novel result is the demonstration of a second pathway for the adw exiting from the otranto strait that is transformed into emdw and occupies the abyssal layers of the ionian sea interior the traditional pathway for emdw is along the isobaths along the western side of italy but adw was observed to be exiting from the otranto strait in the eastern hellenic trench at 39 5 n both during poem on86 and poem as87 this second pathway for emdw follows isobath contours along the western side of greece the two emdw routes converge and merge between 36 n and 35 n so producing a deep layer of emdw that occupies uniformly the abyssal plain of the interior of the ionian sea

water mass properties and dynamic conditions of the eastern mediterranean in june 2007 abstract five locations in the eastern mediterranean situated in the ionian sea cretan passage and levantine basin were characterized for their physical and biogeochemical properties on the basis of the data collected during an oceanographic cruise in june 2007 basinwide subbasin and mesoscale surface dynamic features are described in terms of absolute dynamic topography of the sea surface sea surface temperature and chlorophyll a distribution additional information along the ship s track was acquired via the vessel mounted thermosalinograph and the acoustic doppler current profiler providing data on temperature salinity and marine current the latter helped identify the depth penetration

sedimentological processes in the southern margin of the cretan sea ne mediterranean abstract the cretan basin can be characterized as a back arc basin of the hellenic trench system that is related to the subduction zone of the african plate under the eurasia plate the study area includes the narrow and relatively steep gradient 1 5 continental shelf of the island of crete followed by the steep slope 2 4 and the rather flat deeper part of the cretan basin water depths 1700 m surficial sediments of the coastal zone are coarser and of terrigenous origin while in deeper waters finer sediments of biogenic origin are more abundant sand sized calcareous sediment accumulations identified in middle lower slope may be attributed to the aggregation of seabed biogenic material related to the near bed current activity high resolution profiles 3 5 khz taken from the inner shelf shows a typical sigmoid oblique progradational configuration implying prodelta sediment accumulation during the holocene in the upper middle slope sub bottom reflectors indicate continuous sedimentation of alternating fine and or coarse grained material small scale gravity induced synsedimentary faults appeared locally in contrast a series of gravity induced faults identified in the lower slope are associated with sediment instabilities due to seismotectonic activity sediment cores taken from the shelf break consists of calcareous muddy sand with small amounts of terrigenous silt and fine sand while the cores recovered from the middle slope has revealed a more homogeneous fine sediment texture of hemipelagic deposition the prevailing accumulation processes in the southern margin of the cretan basin are i prodelta deposition in the inner middle shelf ii settling from bottom nepheloid layers in the shelf and upper slope iii calcareous sediment formation due to settling from suspension and post accumulation aggregation middle lower slope iv long term episodic sediment gravity processes in the lower slope and v to a lesser extent redeposition from resuspension due to gravity processes and bottom currents

transient eastern mediterranean deep waters in response to the massive dense water output of the aegean sea in the 1990s abstract we present a detailed account of the changing hydrography and the large scale circulation of the deep waters of the eastern mediterranean emed that resulted from the unique high volume influx of dense waters from the aegean sea during the 1990s and of the changes within the aegean that initiated the event the so called eastern mediterranean transient emt the analysis uses repeated hydrographic and transient tracer surveys of the emed in 1987 1991 1995 1999 and 2001 2002 hydrographic time series in the southern aegean and southern adriatic seas and further scattered data aegean outflow averaged nearly 3 10 6 m 3 s 1 between mid 1992 and late 1994 and was largest during 1993 when south and west of crete aegean influenced deep waters extended upwards to 400 m depth emt related aegean outflow prior to 1992 confined to the region around crete and to 1800 m depth wise amounted to about 3 of the total outflow outflow after 1994 up to 2001 2002 derived from the increasing inventory of the tracer cfc 12 contributed 20 to the total of 2 8 10 14 m 3 densities in the southern aegean sea deep waters rose by 0 2 kg m 3 between 1987 and 1993 and decreased more slowly thereafter the aegean waters delivered via the principal exit pathway in kasos strait east of crete propagated westward along the cretan slope such that in 1995 the highest densities were observed in the hellenic trench west of crete aegean influenced waters also crossed the east mediterranean ridge south of crete and from there expanded eastward into the southeastern levantine sea transfer into the ionian mostly followed the hellenic trench largely up to the trench s northern end at about 37 n from there the waters spread further west while mixing with the resident waters additional transfer occurred through the herodotus trough in the south levantine waters after 1994 consistently showed temperature salinity t s inversions in roughly 1000 1700 m depth with amplitudes decreasing in time the t s distributions in the ionian sea were more diverse one cause being added aegean outflow of relatively lower density through the antikithira strait west of crete spreading of the aegean influenced waters was quite swift such that by early 1995 the entire emed was affected and strong mixing is indicated by near linear t s relationships observed in various places referenced to 2000 and 3000 dbar the highest aegean generated densities observed during the event equaled those generated by adriatic sea outflow in the northern ionian sea prior to the emt a precarious balance between the two dense water source areas is thus indicated a feedback is proposed which helped triggering the change from a dominating adriatic source to the aegean source but at the same time supported the previous long year dominance of the adriatic the emed deep waters will remain transient for decades to come

deposition of a saline giant in the mississippian windsor group nova scotia and the nascent late paleozoic ice age abstract saline giants are vast marine evaporite deposits that currently have no modern analogues and remain one of the most enigmatic of chemical sedimentary rocks the mississippian windsor group ca 345 ma maritimes basin atlantic canada is a saline giant that consists of two evaporite rich sedimentary sequences that are subdivided into five subzones sequence 1 is composed almost entirely of thick halite belonging to subzone a osagean sequence 2 is in unconformable contact and comprised of stacked carbonate evaporite peritidal cycles of subzones b through e meramecian subzone b the focus of research herein documents the transition from wholly evaporitic to open marine conditions and thus preserves an exceptional window into the processes forming saline giants lithofacies stacking patterns in subzone b reveal that higher order fluctuations in relative sea level produced nine stacked parasequences interpreted to reflect high frequency glacioeustatic oscillations during the onset of the late paleozoic ice age each parasequence reflects progradation of intertidal and sabkha sediments over subtidal carbonate and evaporite deposits dissimilarities in cycle composition between sub basins imply the development of contrasting brine chemistries from differing recharge rates with the open ocean what the windsor group shows is that evaporite type is ostensibly linked to the amplitude and frequency of sea level rise and fall during deposition true saline giants like the basinwide evaporites of sequence 1 apparently require low amplitude long frequency changes in sea level to promote the development of stable brine pools that are only periodically recharged with seawater by contrast the high amplitude short frequency glacioeustatic variability in sea level that controlled the accumulation of peritidal evaporites in subzone b produce smaller subeconomic deposits with more complex facies relationships

geophysical controls on c band polarimetric backscatter from melt pond covered arctic first year sea ice assessment using high resolution scatterometry 1 geophysical controls on c band polarimetric backscatter from the discrete surface cover types which comprise advanced melt first year sea ice fyi snow covered ice bare ice and melt pond are assessed using polarimetric radar scatterometry from test sites representing high arctic and marginal ice zones in the canadian arctic surface characterization data is used to evaluate the interaction of polarized radiation with each feature and dominant scattering mechanisms are assessed in a regional context high resolution time series diurnal scatterometry and coincident atmospheric boundary layer profile data are used to explain linkages between ice atmosphere interactions and polarimetric backscatter in a marginal ice zone the co polarization ratio for fyi melt ponds is shown to be distinct from snow covered ice or bare ice during early and peak phases of advanced melt making it a candidate parameter for the unambiguous detection of pond formation and the inversion of melt pond fraction the ratio displays an increasing trend with radar incidence angle in a manner consistent with bragg surface scattering theory though it is not predictable by a bragg model cross polarization backscatter intensity shows potential for discriminating the onset and duration of freeze events in a marginal ice zone due to dominant backscatter from the snow cover adjacent to melt ponds preliminary results here outline the potential of covariance matrix derived polarimetric measurements for the inversion of advanced melt sea ice geophysical parameters and provide a basis for the investigation of distributed targets in late season spaceborne polarimetric sar scenes

temporal evolution of the water mass properties during the eastern mediterranean transient emt in the aegean sea 1 we present time series of temperature and salinity of the aegean sea using the data sets for the period from 1991 to 1996 from 15 oceanographic cruises to depict the temporal variability of the water masses of the aegean sea this period covers an interesting large scale change in the thermohaline circulation in the eastern mediterranean and the aegean sea this change is known as the eastern mediterranean transient emt and was first described during early 1990s our analysis reveals that very dense water formation in the central aegean sea is partially due to the anomalous decrease in winter atmospheric temperature although this alone cannot completely account for the formation of the dense water a synchronous increase in surface salinity accompanied by low temperature values in the winter months is also necessary for the emt event to occur

recurrent intrusions of transitional waters of eastern mediterranean origin in the cretan sea as a tracer of aegean sea dense water formation events abstract available temperature and salinity data in the cretan sea from 1955 up to 2014 as well as literature sources were revisited in order to trace the appearance of low salinity temperature oxygen and nutrient rich waters inside the basin at depths below the intermediate layer first appearing as far back as 1961 in literature these waters were found originating in the layers that separate intermediate and deep waters of the eastern mediterranean sea emed and were named transitional mediterranean water tmw in the 1990s data analysis showed that the appearance of tmw in the cretan sea is a recurrent phenomenon connected to water mass exchanges between the aegean sea and the emed in particular the inflow of tmw in the cretan basin acts as compensation for the outflow of equally dense or denser masses from the aegean this export is a result of dense water formation dwf events taking place inside the aegean sea triggering tmw compensatory inflow into the cretan sea through the cretan straits in this context tmw intrusions in the cretan basin can be used as a tracer of dwf in the aegean sea while the depth of the intrusion can provide valuable information about the intensity of the dwf event the importance of tmw intrusions is not solely restricted to the tracing and evaluation of dwf events but could additionally expand to the impact on local ecological processes as tmw is a nutrient carrier for the oligotrophic cretan sea

sea ice deformation state from synthetic aperture radar imagery part i comparison of c and l band and different polarization in this paper we present a quantitative comparison of l and c band airborne synthetic aperture radar imagery acquired at like and cross polarizations over deformed sea ice under winter conditions the parameters characterizing the deformation state of the ice are determined at both radar bands and at different polarizations the separation of deformed and level ice is based on a target detection technique the threshold is set such that image pixels with intensities equal to or larger than the highest 2 of the level ice intensity distribution are classified as deformed ice independent of the radar configuration and ice conditions optical imagery of sufficient quality for comparison is available only in a very few cases to characterize the deformation state the areal fraction of deformation features and the average distance between these features are evaluated the values obtained for both parameters are very sensitive to the radar frequency aeral fractions are larger and average distances are smaller at l band than at c band because of the much higher intensity contrast between the deformed and level ice at l band the differences between polarizations at one radar band are smaller but not always negligible in comparison to optical images it was observed that deformed ice areas can be distinguished from level ice over their whole length and extension at l band whereas at c band often only prominent parts are visible

dissolved iron in the cretan sea eastern mediterranean dissolved iron fe distributions in the water column of the cretan sea show consistent patterns of elevated surface mixed layer concentrations mean values of 1 44 and 1 95 nmol l 21 in march and september respectively that rapidly decrease with depth to low and relatively uniform concentrations in deep waters circa 0 5 nmol l 21 these features are consistent with inputs of dissolved fe to surface waters and with rapid scavenging to low values in deep waters the main source of surface dissolved fe is probably saharan atmospheric dust the supply of which is variable depending on sporadic dust storm events and transport to the cretan sea the short residence times estimated for dissolved fe in the mixed layer 0 7 2 yr emphasize the rapid removal of this element from surface waters and are consistent with recent mass balance calculations for fe in the western mediterranean sea in which rapid removal of fe to sediments is needed to provide a balance in the budget the deep water concentrations are strikingly constant and similar to or slightly lower than those reported for the open ocean the high surface concentrations we observed would be ample to support substantial primary production and it is likely that the macronutrients and phosphorus in particular limit production in this region iron fe is an essential nutrient for phytoplankton bacteria and other marine microorganisms and the role of this metal as a potentially limiting factor for phytoplankton has come under increasing scrutiny since the initial iron hypothesis was put forward by martin et al 1988 to explain limited productivity in high nutrient low chlorophyll hnlc oceanic systems experiments such as ironex and soiree have now clearly demonstrated that fe additions can stimulate phytoplankton growth in hnlc zones watson 2001 although many questions still remain about the forms of fe present uptake mechanisms and the impact of fe on export carbon production the distributions sources and sinks of fe in seawater have recently been reviewed de baar and de jong 2001 there is a coherent trend in reported data for all regions with increasing concentrations approaching the continental margins up to circa 100 nmol l 21 while in the open ocean dissolved fe has typically low concentrations in surface waters 0 02 1 nmol l 21 and higher 0 4 2 0 nmol l 21 concentrations in deep waters the rapid removal of dissolved fe through association with biotic and abiotic particles and its loss from the water column results in fe having a short residence time de baar and de jong 2001 and upper ocean concentrations should largely reflect local inputs e g aeolian and shallow benthic sourc1

physical dielectric and c band microwave scattering properties of first year sea ice during advanced melt 1 this paper investigates the influence of solar heating and intermittent cloud cover on the physical and dielectric properties of naturally snow free warm 2 first year sea ice fyi in the southeastern margin of the beaufort sea during advanced melt a simple three layer physical model describing the surface is introduced and copolarized c band microwave signatures are simulated using a multilayer scattering model forced with four sets of measured surface parameters modeled backscatter signatures are compared to coincident surface based c band scatterometer signatures in order to elucidate the signature controlling properties of the ice results show that 50 mhz impedance probe dielectric measurements of desalinated upper ice layers exhibit statistically significant diurnal variations due to the link between solar forcing and the availability of free water in brine free upper ice layers enhanced downwelling longwave radiation to the surface from low level stratus clouds is positively linearly associated r 0 709 with volumetric moisture mv detected in upper ice layers model results show that desalinated upper ice layers contribute volume scattering from smooth snow free fyi under the observed surface mv range sustained cloud free periods result in the formation of a 0 5 2 5 cm granular surface layer composed of 5 2 mm ice grains which enhances backscatter under relatively dry conditions sensitivity analyses show that layer thickness plays a significant role in scattering due to the increased number density of inclusions which act as discrete scatterers and sufficient energy may penetrate to and scatter from the saline columnar ice layer under relatively dry conditions only mv 2

hydrology and circulation in the southern cretan sea during the cincs experiment may 1994 september 1995 this work is a description of the water masses and circulation in the site of the cincs pelagic benthic coupling in the oligotrophic cretan sea experiment in the southern boundary of the cretan sea a region of recently renewed interest with respect to the hydrology of the eastern mediterranean basin analysis of hydrological data from the study area reveals the presence of five water masses local surface water and remotely advected modified atlantic water maw share the surface layers below them are cretan intermediate water ciw between 50 and 150 dbar transition mediterranean waters tmw with its core located between 300 400 dbar and the cretan deep waters cdw occupying the depths below 800 dbar the circulation over the coastal shelf and slope is dictated by the offshore semi permanent mesoscale features that dominated the cretan sea in 1994 1995 forcing locally a shoreward flow the hydrographic observations are verified by current meter measurements from a mooring in the sampling area the recorded velocity is generally towards the se direction seasonally modulated reaching maximum speeds of 27 cm s 1 analysis of the new data set has revealed a previously unobserved feature of the oceanographic characteristics of the region over the base of the cretan slope there occur lenses of water that are warmer and more saline than their surroundings these lenses probably form on the shelf seasonally their waters are rich in oxygen and have a density that is higher than historical cretan deep water values

a synthesis of the circulation and hydrography of the south aegean sea and the straits of the cretan arc march 1994 january 1995 abstract four seasonal oceanographic cruises were carried out in the eastern mediterranean sea within the framework of the cec mast mtp project pelagos during 1994 1995 the surveys covered the south aegean sea and the adjacent open sea regions southeastern ionian northwestern levantine analysis of ctd data revealed that a multiscaled circulation pattern prevails in the area it differs from the circulations detected during the 1986 87 thus indicating interannual variability cyclonic and anticyclonic gyres and eddies are interconnected by currents and jets variable in space and time most of the features are persistent others seem transitional or recurrent the hydrological structure is also complex and apart from the upper layer does not present basinwide any significant seasonality dynamical and hydrological regimes are variable in the upper and intermediate layers at the straits of the cretan arc while the deep regime seems rather constant topographic control is evident on the flows through the straits the new very dense deep water mass namely the cretan deep water cdw and a well defined intermediate layer of minimum temperature and salinity the so called transition mediterranean water tmw consists the new important structural elements of the south aegean sea the cdw outflows towards the deep and bottom layers of the eastern mediterranean thus considerably contributing to the formation of the new denser deep and bottom water of the eastern mediterranean which sinks and displaces the eastern mediterranean deep water of adriatic origin in the adjacent sea regions outside the aegean sea

vertical distribution and temporal trends of 137cs at lemnos and cretan deep basins of the aegean sea greece abstract caesium 137 activity concentrations 137cs were measured between 2003 and 2014 in the water column of lemnos and cretan deep basins of the aegean sea the purpose was to assess water mass dynamics and mixing processes by combining typical oceanographic data with the activity concentrations of 137cs the radiological data combined with dissolved oxygen profiles provided substantially more information than solely temperature and salinity regarding processes such as water mass identification formation and mixing in each basin it was possible to determine stagnant periods where turbulent mixing was dominant as well as periods where replenishment of the deep basins had been taken place at lemnos basin the data profile in 2013 proved evidence of water column ventilation down to 800 m and replenishment of the deep basin by less saline water mass the 137cs information provided evidence for contribution of water from the black sea to the intermediate and deep layers of the south aegean cretan basin the profiles of 2013 and 2014 were characterized by the return of 137cs inventories to pre chernobyl levels

dynamics of the terra nova bay polynya the potential of multi sensor satellite observations research on processes leading to formation maintenance and disappearance of polynyas in the polar regions benefits significantly from the use of different types of remote sensing data the sentinels of the european space agency esa together with other satellite missions provide a variety of data from different parts of the electromagnetic spectrum at different spatial scales and with different temporal resolutions in a case study we demonstrate the advantage of merging data from different spaceborne instruments for analysing ice conditions and ice dynamics in and around the frequently occurring terra nova bay polynya tnbp in the ross sea in the antarctic starting with a list of polynya parameters that are typically retrieved from satellite images we assess the usefulness of different sensor types on regional scales several 100 km passive microwave radiometers provide a view on the mutual influence of the three ross sea polynyas on sea ice drift and deformation patterns optical sensors with meter scale resolution on the other hand allow very localized analyses of different polynya zones the combination of different ranges of the electromagnetic spectrum is essential for recognition and classification of ice types and structures radar images together with data from thermal infrared sensors operated at tens to hundreds of meters resolution improve the separation of the outlet zone of the polynya from the adjacent pack ice the direct comparison of radar and passive microwave images reveals the visibility of deformed ice zone in the latter a sequence of radar images was employed to retrieve ice drift around the tnb which allows analysing the temporal changes of the polynya area and the extension and structure of the outlet zone as well as ice movements and deformation that are influenced by the katabatic winds

distribution of the thermohaline characteristics in the aegean sea related to water mass formation processes 2005 2006 winter surveys 1 aiming at portraying the aegean s water mass structure and identifying dense water formation processes two winter cruises were conducted in 2005 2006 across the plateaus and depressions of the aegean sea the most prominent feature of the water mass distribution in the basin is a distinct x shape of the s characteristics suggesting a complicated coupling of the major aegean sub basins the surface and deep waters are relatively decoupled with diverse origin characteristics while the intermediate layers act as connectors of the main thermohaline cells the central aegean seems to play a key role due to formation processes of water masses with densities equal and or higher than 29 2 kg m3 that take place in the sub basin and disperses in the north aegean on the other hand the south aegean appears greatly influenced by the eastern mediterranean circulation and water mass distribution especially under the eastern mediterranean transient status the transitional mediterranean water monitored in the post emt period and characterized by low temperature at 14 2 c low salinity at 38 92 and low dissolved oxygen at 3 97 ml l with its core around 750 m and above the saline 39 06 cretan deep water altered significantly the south aegean structure the pre emt thermohaline pattern of the central and south aegean deep layers were similar while the bottom density of the central basin was higher than that in the south aegean thus it is possible that the deep waters of the central aegean acted as a dense water reserve supply for the deeper part of the southern basin

low frequency current variability at the straits of crete eastern mediterranean current meter data from six moorings are analyzed to study current variability at the straits of the cretan arc which connect the south aegean sea with the eastern mediterranean the three layers in which the current meters were deployed show different current characteristics the upper layer shows evidence of the asia minor current in the rhodes strait and a clockwise eddy in the karpathos strait water in the middle layer moves slowly into the south aegean the bottom current meters in kassos and antikithira straits recorded currents steady in amplitude and direction with speeds equal to or higher than those observed in the upper layer the observations suggest a significant outflow 0 5 sv of cretan dense water cdw to the levantine and ionian seas rotary empirical orthogonal functions are used to extract and describe the coherent part of the variability forty four percent of the total variability is described by the first three empirical orthogonal functions less than 20 of the current variability of the western strait is coherent with variability of the eastern straits the coherent part of the variability refers mainly to periods longer than 20 days the current meter data are compared with atmospheric pressure showing good correlation during the first period of the measurements when a major atmospheric pressure low passed over the aegean

coccolithophore export in three deep sea sites of the aegean and ionian seas eastern mediterranean biogeographical patterns and biogenic carbonate fluxes abstract coccolithophore export fluxes were investigated via the analysis of sinking matter obtained from eastern mediterranean time series sediment traps moored in three open sites of the north eastern mediterranean sea located in the athos basin of north aegean m2 site cretan sea of south aegean m3 site and at ionian sea nestor site the aim of our study was to determine the spatial temporal and seasonal variability in coccolithophore fluxes as well as to estimate coccolith biogenic carbonate contribution to the sedimentation process data from an additional time series sediment trap located in the southwestern black sea were also considered for the comparison of the oligotrophic eastern mediterranean setting with the eutrophic black sea coccolithophore fluxes revealed a highly seasonal pattern during february march in the north aegean peak in late february 2015 85 6 x 105 coccospheres m 2 day 1 27 9 x 108 coccoliths m 2 day 1 during march may in the cretan sea peak in late march 2015 33 7 x 105 coccospheres m 2 day 1 19 5 x 108 coccoliths m 2 day 1 and during february march and may june in the ionian sea peak in late may 2012 14 3 x 105 coccospheres m 2 day 1 1 53 x 108 coccoliths m 2 day 1 the recorded maxima coincide with low sea surface temperatures increased precipitation and high pic fluxes coccosphere fluxes were dominated by emiliania huxleyi comprising 70 of the total abundance in the north aegean and 50 in the cretan and ionian seas syracosphaera pulchra was also prominent in the study sites where its abundance reached 14 in the north aegean and 10 in the cretan and ionian seas respectively florisphaera profunda represented one of the major taxa in the coccolith fluxes of all three eastern mediterranean sites 25 in north aegean 20 in cretan and ionian seas while algirosphaera robusta and umbilicosphaera sibogae were the most abundant among the minor taxa the north aegean sea exhibited a considerably higher coccolith flux when compared to other sediment traps due to the prominent seasonal peak of e huxleyi during winter february march 95 of the total abundance in contrast to the eastern mediterranean sediment traps the time series data from the black sea showed presence of monospecific e huxleyi assemblage increasing its abundance during late september november max 320 x 105 coccospheres m 2 day 1 at least 7 79 x 108 coccoliths m 2 day 1 coccolith flux derived only from coccospheres converted to coccoliths in the eastern mediterranean biogenic carbonate fluxes followed the general pattern of the total mass flux in all investigated areas with the black sea coccolithophore caco3 flux being the lowest due to low the e huxleyi coccolith mass overall in the north aegean sea coccolithophore fluxes are strongly dependent on surface waters nutrients enrichment due to winter vertical water column mixing riverine inputs and black sea water inflows while the fertilization and or formation of fast sinking aggregates due to episodic dust input event are affecting the coccolithophore fluxes in the cretan and ionian seas the intercomparison of the coccolith export fluxes in the studied ne sw mooring transects implies a north south and east west decreasing pattern depending on the variable oceanographic regimes and the associated environmental factors controlling the investigated areas

late quaternary paleoenvironmental reconstruction and paleoclimatic implications of the aegean sea eastern mediterranean based on paleoceanographic indexes and stable isotopes the late quaternary palaeoenvironmental evolution and the main palaeoceanographic changes of the aegean sea was reconstructed using planktonic foraminifera obtained from the sediments of a northern sk 1 and a southern ns 14 core site multivariate statistical approach including q mode cluster and principal component pca analyses gives an insight into the relationships between sea surface environmental changes between the north and south aegean and furthermore serves as a baseline data set for palaeoclimatic and palaeoceanographic reconstructions of the eastern mediterranean sea stable isotope analyses coupled with additional paleoceanographic sea surface temperature sst productivity ssp stratification s index upwelling u index seasonality sn index proxies provide insights into the sedimentological hydrographic and trophic evolution and ecosystem dynamics of the aegean sea and furthermore serve as a baseline data set for palaeoclimatic and palaeoceanographic reconstructions of the eastern mediterranean sea concentrating on the last 19 ka faunal and isotopic data concur suggesting a series of climatic zones corresponding to well known climatic phases of the last glacial cycle cold and arid conditions during the late glacial period were followed by a warmer and wetter climate trend during deglacial time a marked seasonality characterized by homogenous water column favored by efficient upwelling during the winter and by warm stratified water column during the summer has also been recognized during this period bolling allerod b a in both basins an abrupt switch to cool arid climatic event younger dryas yd suggests a strengthening of winter convection around 12 9 ka which seems to be more evident in the north aegean core however the more pronounced environmental changes between the north and south aegean sea were identified during the holocene and they coincide with the deposition of sapropel s1 and sapropel mid holocene smh the comparison between sk 1 and ns 14 records indicated significant changes in both the productivity and stratification patterns with the former the main factor in north aegean and the latter in south aegean for s1 deposition regarding the localized deposition of smh in the semi enclosed shallow south aegean site the fully oxygenated and less productive water column conditions prevailing during that time 5 4 4 3 ka in the north aegean were the limiting factor for its deposition

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

water masses and circulation in the central region of the eastern mediterranean eastern ionian south aegean and northwest levantine 1986 1987 in the framework of the major multinational coordinated poem ii 86 march april 1986 and poem v 87 september october 1987 cruises in the eastern mediterranean high resolution hydrographic ctd data were collected by r v aegaio in the eastern ionian sea south aegean sea and northwest levantine basin the intercalibrated data sets were analyzed objectively for an optimal estimation of the basin s circulation in two different seasons the analysis reveals a rather complex general circulation pattern consisting of basin sub basin and mesoscale features during both study periods the major results concern the advection of the modified atlantic water maw along its eastward route the spreading of the levantine intermediate water liw and its trapping by the eddy fields the interaction between the south aegean sea and the eastern mediterranean and the reverse circulation in the cretan sea during winter and summer from the hydrography and the dynamic height maps synthetic schemes show the main circulation features in the two seasons

the role of snow on the thermal dependence of microwave backscatter over sea ice our understanding of snow distribution in the polar regions is severely restricted owing to the heterogeneity both in space and time of this solid precipitate processes such as vapor and mass fluxes across the interface are to a large extent controlled by the presence and geophysical state of the snow cover on sea ice numerous studies have shown the importance of snow cover in ecosystem processes and particularly in photosynthetically active radiation extinction researchers are currently exploiting developments in electromagnetic interaction theory in an attempt to measure snow thickness distributions remotely in this paper we investigate the dependence of radar backscatter on snow thickness over smooth first year ice we use data from the seasonal sea ice monitoring and modeling site located in the canadian archipelago results show that the thermodynamics of the snow cover affect wave propagation attenuation and scattering through the control that brine volume exerts on interfacial characteristics of the snow and ice layers the effect is subtle and specific to certain ranges of salinity surface roughness and thickness of sea ice we describe the phenomenon responsible for this effect using a microwave model consistently for both complex effective permittivities and backscatter coefficients coupled to a one dimensional model we validate the physical principles using in situ field data we then discuss the potential of synthetic aperture radar in estimating snow thickness distributions under these specific conditions using both observed and modeled microwave scattering

aegean sea water masses during the early stages of the eastern mediterranean climatic transient 1988 90 abstract the aegean water masses and circulation structure are studied via two large scale surveys performed during the late winters of 1988 and 1990 by the r v yakov gakkel of the former soviet union the analysis of these data sheds light on the mechanisms of water mass formation in the aegean sea that triggered the outflow of cretan deep water cdw from the cretan sea into the abyssal basins of the eastern mediterranean sea the so called eastern mediterranean transient it is found that the central aegean basin is the site of the formation of aegean intermediate water which slides southward and depending on their density renews either the intermediate or the deep water of the cretan sea during the winter of 1988 the cretan sea waters were renewed mainly at intermediate levels while during the winter of 1990 it was mainly the volume of cdw that increased this aegean water mass redistribution and formation process in 1990 differed from that in 1988 in two major aspects i during the winter of

impact of the spatial distribution of the atmospheric forcing on water mass formation in the mediterranean sea the impact of the atmospheric forcing on the winter ocean convection in the mediterranean sea was studied with a high resolution ocean general circulation model the major areas of focus are the levantine basin the aegean cretan sea the adriatic sea and the gulf of lion two companion simulations differing by the horizontal resolution of the atmospheric forcing were compared the first simulation med16 era40 was forced by air sea fields from era40 which is the ecmwf reanalysis the second simulation med16 ecmwf was forced by the ecmwf analyzed surface fields that have a horizontal resolution twice as high as those of era40 the analysis of the standard deviations of the atmospheric fields shows that increasing the resolution of the atmospheric forcing leads in all regions to a better channeling of the winds by mountains and to the generation of atmospheric mesoscale patterns comparing the companion ocean simulation results with available observations in the adriatic sea and in the gulf of lion shows that med16 ecmwf is more realistic than med16 era40 in the eastern mediterranean although deep water formation occurs in the two experiments the depth reached by the convection is deeper in med16 ecmwf in the gulf of lion deep water formation occurs only in med16 ecmwf this larger sensitivity of the western mediterranean convection to the forcing resolution is investigated by running a set of sensitivity experiments to analyze the impact of different time space resolutions of the forcing on the intense winter convection event in winter 1998 1999 the sensitivity to the forcing appears to be mainly related to the effect of wind channeling by the land orography which can only be reproduced in atmospheric models of sufficient resolution thus well positioned patterns of enhanced wind stress and ocean surface heat loss are able to maintain a vigorous gyre circulation favoring efficient preconditioning of the area at the beginning of winter and to drive realistic buoyancy loss and mixing responsible for strong convection at the end of winter

continuing influence of the changed thermohaline circulation in the eastern mediterranean on the distribution of dissolved oxygen and nutrients physical and chemical characterization of the water masses 1 changes in the vertical distribution of the physical and chemical parameters observed during this study point to the continuing spatial and temporal evolution of the eastern mediterranean deep water emdw these changes influenced primarily the water column below 800 m and confined the old emdw of adriatic origin to the 1000 2000 m in the levantine uplifting the minimum oxygen maximum nutrient minox maxnut from 2500 m in 1995 to 1500 m in 1999 the denser and younger emdw of aegean origin emdwaeg appeared at the bottom layer more evident at the central eastern mediterranean and moving prevalently into the levantine basin younger water still intruded the central area at intermediate depths in the levantine intermediate waters liw oxygen decreased and nutrients increased westward in agreement with its pathway across the basin however a temporal decrease in oxygen and concurrent increase in nutrient was found in the liw because of its confinement in the levantine by anticyclonic features temporal changes were also found in the emdw at the western ionian and eastern cretan passage the differences in the vertical placement of the minox maxnut layer among the different areas were explained by the physical processes but the relative displacement of the extreme points within the same area were probably a result of oxidation of particulate matter poorer in nitrogen and phosphorus in the levantine than in the ionian maximal concentrations of silicic acid were located deeper than the other nutrients because of the slower chemical dissolution of silicious tests the n p molar ratios at the emdw were high 26 2 30 7 highest in the younger emdwaeg these differences could not be explained by different dissolved inorganic nutrients concentration at the sources nor by the composition of particulate matter in the euphotic zone it was suggested that dom may have a significant role in determining those differences however data on dom concentration and composition across the basin is lacking in order to test this hypothesis