dense water formation beneath a time dependent coastal polynya abstract recent modeling studies of dense water formation beneath an idealized steady coastal polynya have provided simple analytical expressions for the maximum density anomaly achievable as a function of the polynya geometry and the imposed surface buoyancy flux these studies have assumed that the buoyancy flux and polynya geometry are both constant and independent parameters to relax these assumptions dense water formation is examined beneath a coastal polynya whose size and surface buoyancy flux are computed from atmospheric temperature and wind velocity according to a polynya model developed by pease though highly idealized the pease model produces polynyas that open and close on reasonably realistic timescales and it thermodynamically couples the polynya size and buoyancy flux results reveal several interesting and potentially useful features of the ocean response to time dependent polynya forcing first under reasonable atmospheric conditions both the maximum density anomaly achievable and

seismo ionospheric coupling appearing as equatorial electron density enhancements observed via demeter electron density measurements we report the processes and results of statistical analysis on the ionospheric electron density data measured by the detection of electro magnetic emissions transmitted from earthquake regions demeter satellite over a period of 6 years 2005 2010 in order to investigate the correlation between seismic activity and equatorial plasma density variations to simplify the analysis three equatorial regions with frequent earthquakes were selected and then one dimensional time series analysis between the daily seismic activity indices and the equatorial ionization anomaly eia intensity indices which represent relative equatorial electron density increase were performed for each region the statistically significant values of the lagged cross correlation function particularly in the region with minimal effects of longitudinal asymmetry indicate that some of the very large earthquakes with m 5 0 in the low latitude region can accompany observable precursory and concurrent eia enhancements even though the seismic activity is not the most significant driver of the equatorial ionospheric evolution the physical mechanisms of the seismo ionospheric coupling is consistent with our observation and the possibility of earthquake prediction using the eia intensity variation is discussed

effects of regional fast ice and iceberg distributions on the behaviour of the mertz glacier polynya east antarctica an observational account of research carried out in july august 1999 shows that grounded iceberg and related fast ice distributions and periodic break outs of fast ice in winter as well as at other times have an important impact on the size and behaviour of the mertz glacier polynya east antarctica and a smaller polynya to the east analysis of satellite and in situ data shows that a semi constant stream of thick broken out fast ice and other large floes from the east extends westwards from north of the glacier terminus to form a compact barrier to the net west northwesterly export of ice formed in the polynya an annual fast ice promontory to the west further narrows the outlet path as a result of this and high ice production rates the polynya periodically back fills significantly reducing the open water area present intervening flush outs by synoptic storm events clear the polynya region to some extent before it back fills again this cycle continued from mid march until early october in 1999 when a significant change in the regional ice drift occurred a preliminary comparison with data from 1998 indicates that the timing and magnitude of the processes may vary interannually similar morphological features were also observed in 1963 on a declassified photoreconnaissance satellite image

water column euxinia and wildfire evidence during deposition of the upper famennian hangenberg event horizon from the holy cross mountains central poland a palynological study of the uppermost famennian section from kowala quarry holy cross mountains central poland allowed recognition of two miospore zones lv retispora lepidophyta apiculiretusispora verrucosa and ln retispora lepidophyta verrucosisporites nitidus based on palynology and sedimentology the black shale within the upper part of the section is identified as equivalent to the hangenberg black shale which is known globally this black shale contains compounds characteristic of photic zone euxinia including isorenieratane and its derivatives such compounds are absent in the organic poor marls and shales occurring below the ln zone and are present only as traces in the layers just above the black shale indicating fluctuations in the oxygen minimum zone during uppermost famennian sedimentation palynofacies show high amounts of amorphous organic matter and prasinophyte concentrations in the black shale and a subsequent significant decrease of amorphous organic matter concomitant with a rapid increase of terrestrial input mainly miospores with common tetrads in the layers above the black shale this supports the relatively rapid change in the taxonomic composition of phytoplankton caused by fluctuations of the chemocline the whole succession corresponds to one sea level rise and fall the presence of high concentrations of peri condensed polycyclic aromatic hydrocarbons and large amounts of small charcoal particles at the hangenberg event horizon indicate the occurrence of wildfires such observations suggest that atmospheric o2 levels had exceeded the critical threshold of 13 above which wildfires may occur by latest famennian time

polynya flux model solutions incorporating a parameterization for the collection thickness of consolidated new ice previous polynya flux models have specified a constant value for the collection thickness of frazil ice h at the polynya edge in certain circumstances this approach can cause the frazil ice depth h within the polynya to exceed h a result which violates assumptions made in the formulation of the ice flux balance equations at the polynya edge to overcome this problem a parameterization for h is derived in terms of the depth of frazil ice arriving at the polynya edge and the component normal to the polynya edge of the frazil ice velocity relative to the velocity of the consolidated ice pack thus h is coupled to the unknown polynya edge using the new parameterization for h an analysis of the unsteady one dimensional opening of a coastal polynya is presented analytical solutions are also derived using the new parameterization for h for steady state two dimensional polynyas adjacent to a semi infinite and finite length coastal barrier the latter case representing a prototype island in all cases the solutions show close qualitative and quantitative agreement with those derived using a constant value for h however the steady state two dimensional polynya edge can in certain circumstances exhibit a corner at the point where the offshore equilibrium width is reached precise conditions for the existence of a corner are derived in terms of the orientation of the frazil ice velocity u and the consolidated ice velocity u upper and lower bounds are also obtained for the area of the steady state island polynya and it is shown that over a large range of orientations of u and u the area exceeds that associated with the island polynya with constant h finally two simulations of the st lawrence island polynya are presented using the new parameterization for h and the results are compared with the h constant theory

formation mechanism of huge coastal polynyas and its application to okhotsk northwestern polynya abstract this paper investigates the formation mechanism of broad coastal polynyas beyond 100 km in offshore width it is known that two regimes for wind driven polynya opening exist one is a convergent regime at the polynya edge in which inner frazil ice catches up with outer consolidated ice whereas the other is a divergent regime in which the consolidated ice drifts offshore faster than the frazil ice at the edge in this study the authors focus on the latter divergent polynya edge regime because in the divergent regime the polynya possibly evolves without bound they consider a thermal growth for inner frazil ice to find a finite solution of offshore width then the authors investigate responses of the polynya opening for various wind angles from the offshore direction from the viewpoint of the polynya edge regimes at first the authors estimate the deviation angle and wind factor for the frazil and consolidated ice based on each momentum balance because sea ice motion driven by wind varies

growth of megaspherulites in a rhyolitic vitrophyre megaspherulites occur in a rhyolitic vitrophyre near the base of a thick rhyolitic vitrophyre that occupies a late eocene to early oligocene volcanic tectonic basin near silver cliff colorado diameters of the megaspherulites range from 0 3 to over 3 66 m including an alteration layer the megaspherulites are compound spherulites they are holocrystalline very fine to fine grained composed of sanidine and quartz and surrounded by a thin sanidine quartz rind and an alteration layer containing mordenite and 15 a montmorillonite megaspherulite crystallization began soon after the vitrophyre was emplaced as the result of sparse heterogeneous nucleation under highly nonequilibrium conditions spherulite growth proceeded in a diffusion controlled manner under lowered viscosity as a result of a high water content 5 to 7 wt which also contributed to sparse nucleation when nucleation did occur it was at a large t 245 350 c on near critical sized nuclei once the spherulites began to grow continued nucleation was on existing growth cones and new independent spherulites did not form sanidine crystals grew with a fibrous habit which is favored by a large t restricting fibril lengths and diameters between 10 30 and 3 7 m respectively during crystallization these growth cones impinged upon each other resulting in fibril cone free areas these cone free interconal areas consist of coarser fine grained phases dominated by quartz which crystallized from the melt as it accumulated between the crystallizing sanidine fibrils of the cones the anhydrous nature of the sanidine and quartz suggests that their crystallization concentrated a water rich residual fluid enriched in ca mg and fe and depleted in si k and na at the megaspherulite vitrophyre interface this fluid phase enclosed the megaspherulites resulting in the hydrothermal alteration of the vitrophyre forming a hydrothermal alteration layer as indicated by the presence of the minerals mordenite and montmorillonite

analysis of tec data from the topex poseidon mission 1 topex poseidon mission has provided an extensive database of vertical tec over the ocean since august 1992 data from nearly 10 years of topex tec observations were analyzed to study the tec climatology first tec data were binned by season geomagnetic activity and solar activity to create longitudinally averaged tec maps in magnetic latitude and local time these maps show the annual and semiannual anomalies well known from climatological studies of nmf2 but lack the seasonal anomaly because of the longitudinally averaged binning the equatorial anomaly is the most prominent feature in the maps and they show strong tec variations with solar activity but relatively weak variations with geomagnetic activity in our three kp bins compared with the low solar activity conditions f10 7 120 the tec values for f10 7 120 are much larger and the equatorial anomaly lasts longer into the night up to midnight during geomagnetically active periods the tec maps generally show a noticeable increase at low latitudes for f10 7 120 but this effect is barely detectable for f10 7 120 finally three longitudinal bins indian pacific and atlantic were added in order to see how the tec morphology varies with longitude the tec measurements display strong longitudinal variations that closely follow the longitudinal variation of the magnetic declination in the southern pacific where the declination is positive and large the diurnal tec variations significantly differ from those in the other longitude sectors where the magnetic declination is negative in the southern hemisphere also at noon the phase of the longitudinal tec variation is typically opposite to that at midnight

polynya dynamics a review of observations and modeling 1 polynyas are nonlinear shaped openings within the ice cover ranging in size from 10 to 105 km2 polynyas play an important climatic role first winter polynyas tend to warm the atmosphere thus affecting atmospheric mesoscale motions second ocean surface cooling and brine rejection during sea ice growth in polynyas lead to vertical mixing and convection contributing to the transformation of intermediate and deep waters in the global ocean and the maintenance of the oceanic overturning circulation since 1990 there has been an upsurge in polynya observations and theoretical models for polynya formation and their impact on the biogeochemistry of the polar seas this article reviews polynya research carried out in the last 2 decades focusing on presenting a state of the art picture of the physical interactions between polynyas and the atmosphere sea ice ocean system observational and modeling studies the surface heat budget and water mass transformation within these features are addressed

the production of ice and dense shelf water in the okhotsk sea polynyas this paper examines the ice and dense water production in the okhotsk sea coastal polynyas for the 1990 1995 winters the dominant polynyas occur on the northwest and northern shelves and in shelikhov bay we use an algorithm developed for the special sensor microwave imager ssm i to derive for each polynya the area and composition of thin ice and open water and a heat flux algorithm to derive the ice and brine production historic oceanographic observations show that the northwest shelf is the only north pacific region where the 26 8 potential density surface outcrops to the surface and is also that part of the okhotsk shelf where the densest water is observed to occur in support of these observations we find that the northwest shelf polynya is the dominant ice and brine producer contributing on average about 55 of the total production shelikhov bay is the second largest producer with about 25 of the total this region has been previously neglected by both oceanographic and remote sensing studies using a combination of two dense water production models we find that the 6 year average dense water production lies between 0 2 0 4 sv the ice and brine production for the dominant northwest shelf vary interannually by a factor of 3 while the production from all the northern polynyas varies by factor of 2 the source of the variability for the northwest shelf comes from the fact that the southwest to northeast trend of the coastline and the mean winter geostrophic wind velocities are roughly parallel which means that small variations in the wind direction yield large changes in the ice production

numerical study of winter water formation in the chukchi sea roles and impacts of coastal polynyas winter water formation is examined in the chukchi sea for the winters of 1992 2006 using a primitive equation ocean model forced by ncep wind and surface salinity flux derived from ssm i thin ice thickness estimates the model is also forced by an external inflow of 0 8 sv through the bering strait the model successfully reproduces the oceanic circulation on the chukchi shelf thus providing numerous insights into behaviors of salt enriched water produced on the shelf the experiments show that under northeasterly winds northward throughflow across barrow canyon is reduced this results in salinity buildup under freezing conditions and ultimately in greater enhancement of salinity of the waters carried into the arctic basin the flow and salinity enhancement of the flow through herald canyon is less extreme but more steady than through barrow canyon together with moored salinity in the bering strait the model results estimate the actual salinity to be 32 9 0 8 psu and 32 7 0 3 psu respectively for waters moving through the barrow and herald canyons both estimates are less than 33 1 psu that is typically observed for the cold halostad layer in the canada basin suggesting the importance of diapycnal mixing with saltier atlantic origin water

the weathering of sedimentary organic matter as a control on atmospheric o2 i analysis of a black shale to investigate the weathering of sedimentary organic matter and its role in regulating atmospheric oxygen a drill core of black shale from the new albany formation upper devonian clay city ky has been analyzed for total and organic carbon nitrogen phosphorus and sulfur and for porosity permeability and specific surface area the distribution of organic matter and pyrite in the shale has also been examined by means of electron photomicrography and element mapping element mapping indicates that shale organic matter is present mainly as 0 5 to 50 m discoidal clots and discontinuous laminae stringers and not as monomolecular coatings on clay grains loss of organic matter by oxidative weathering takes place across a reaction front where organic carbon content decreases sharply toward the land surface along with organic nitrogen and sulfur but not organic phosphorus which remains relatively constant over the same depth range accompanying the decrease in organic matter is an increase in porosity these results agree with earlier work on a single stratigraphic layer that found also that the oxygen content of the organic matter increases sharply toward the land surface across a similar carbon oxidation front pyrite in both the core and the layer was found to decrease toward the surface more continuously than organic matter and at intermediate depths is essentially absent in the presence of high levels of organic matter these results suggest that organic matter weathering in shales can be treated in terms of the reaction of organic matter with gaseous o2 and o2 dissolved in groundwater once a weathering profile is developed the inward or downward migrating o2 reacts first with modern soil organic matter and subsequently with low concentrations of remaining pyrite and ancient organic matter before reaching the front pyrite apparently reacts faster with o2 than does organic matter for a given local concentration of oxygen as evidenced by reduced pyrite concentrations accompanying high organic matter concentrations at the front upon further inward migration lower levels of o2 react with higher concentrations of pyrite and organic matter these data provide an important basis for the theoretical modeling of organic matter oxidation during weathering

seismoionospheric gps total electron content anomalies observed before the 12 may 2008 mw7 9 wenchuan earthquake 1 the global ionospheric map gim is used to observe variations in the total electron content tec of the global positioning system gps associated with 35 m 6 0 earthquakes that occurred in china during the 10 year period of 1 may 1998 to 30 april 2008 the statistical result indicates that the gps tec above the epicenter often pronouncedly decreases on day 3 5 before 17 m 6 3 earthquakes the gps tec of the gim and electron density profiles probed by six microsatellites of formosat3 cosmic f3 c are further employed to simultaneously observe seismoionospheric anomalies during an mw7 9 earthquake near wenchuan china on 12 may 2008 it is found that gps tec above the forthcoming epicenter anomalously decreases in the afternoon period of day 6 4 and in the late evening period of day 3 before the earthquake but enhances in the afternoon of day 3 before the earthquake the spatial distributions of the anomalous and extreme reductions and enhancements indicate that the earthquake preparation area is about 1650 km and 2850 km from the epicenter in the latitudinal and longitudinal directions respectively the f3 c results further show that the ionospheric f2 peak electron density nmf2 and height hmf2 significantly decreases approximately 40 and descends about 50 80 km respectively when the gps tec anomalously reduces

a statistical analysis of ionospheric anomalies before 736 m6 0 earthquakes during 2002 2010 1 this paper presents a statistical study of the pre earthquake ionospheric anomaly by using the total electron content tec data from the global ionosphere map a total of 736 m 6 0 earthquakes in the global area during 2002 2010 are selected the anomaly day is first defined then the occurrence rates of abnormal days for both the days within 1 21 days prior to the earthquakes pe and the background days pn are calculated the results show that the values of pe depend on the earthquake magnitude the earthquake source depth and the number of days prior to the earthquake the pe is larger for earthquakes with greater magnitude and lower depth and for days closer to the earthquakes the results also show that the occurrence rate of anomaly within several days before the earthquakes is overall larger than that during the background days especially for the large magnitude and low depth earthquakes these results indicate that the anomalous behavior of tec within just a few days before the earthquakes is related with the forthcoming earthquakes with high probability

a case study of ionospheric storm effects during long lasting southward imf bz driven geomagnetic storm multiple instrumental observations including gps total electron content tec fof2 and hmf2 from ionosondes vertical ion drift measurements from communication navigation outage forecasting system magnetometer data and far ultraviolet airglow measured by thermosphere ionosphere mesosphere energetics and dynamics global ultraviolet imager timed guvi are used to investigate the profound ionospheric disturbances at midlatitude and low latitude during the 14 17 july 2012 geomagnetic storm event which was featured by prolonged southward interplanetary geomagnetic field component for about 30 h below 10 nt in the east asian australian sector latitudinal profile of tec variations in the main phase were characterized by three bands of increments and separated by weak depressions in the equatorial ionospheric anomaly eia crest regions which were caused by the combined effects of disturbance dynamo electric fields ddef and equatorward neutral winds in the recovery phase strong inhibition of eia occurred and the summer crest of eia disappeared on 16 july due to the combined effects of intrusion of neutral composition disturbance zone as shown by the timed guvi o n2 measurements and long lasting daytime westward ddef inferred from the equatorial electrojet observations the transit time of ddef over the dip equator from westward to eastward is around 2200 lt in the american longitude the salient ionospheric disturbances in the summer hemisphere were characterized by daytime periodical intrusion of negative phase for three consecutive days in the recovery phase preceded by storm enhanced density plume in the initial phase in addition multiple short lived prompt penetration electric fields appeared during stable southward interplanetary magnetic field imf bz in the recovery phase and were responsible for enhanced the eia and equatorial ionospheric uplift around sunset

a two dimensional time dependent model of a wind driven coastal polynya application to the st lawrence island polynya a two dimensional time dependent model of a wind driven coastal polynya is presented the model combines and extends previous one dimensional time dependent and two dimensional steady state flux formulations given the coastline geometry and the time varying surface winds and heat fluxes as free parameters the model calculates the growth rate distribution and motion of frazil ice within the polynya and the mass fluxes of frazil ice and consolidated new ice at the polynya edge the difference between these two mass fluxes determines the velocity of the polynya edge at all times and hence its evolution analytical solutions are found for the special case when the coastline is a straight line segment of finite length d an idealization of an island and the forcing fields are spatially uniform and constant in time two timescales and two spatial scales are shown to be important in characterizing the shape size and evolution of the polynya the consolidated new ice and frazil ice timescales tce and tfe respectively and the offshore and alongshore adjustment length scales roe and rae respectively the timescale tce is the time required for the polynya to grow ice of thickness equal to the collection thickness of frazil at the polynya edge the timescale tfe is the time it takes frazil to cross the equilibrium width of the polynya which is in turn determined by the length scale roe in combination tce and tfe control the timescale for the polynya to respond to variations in the forcing the length scale rae is the distance that the angle between the consolidated new ice and frazil ice drifts spans along the equilibrium polynya edge this length scale measures the sensitivity of the polynya edge to alongshore variations in the coastline geometry and in particular to its total extent it is shown that if rae is comparable to d then the offshore dimension of the polynya and the timescale for the polynya to reach equilibrium can be very different from those obtained from a one dimensional formulation the model is applied to the study of seasonal and short term variability of the st lawrence island polynya in the bering sea

ionosphere disturbances observed throughout southeast asia of the superstorm of 20 22 november 2003 1 ionospheric disturbances in the southeast asian region during the super magnetic storm of 20 22 november 2003 were investigated through an ionosonde chain and a gps network assisted by the space borne instruments at early stage of the storm in the postsunset sector large enhancements in the critical frequency of f2 layer and total electron content were observed at northern crest region of the equatorial ionization anomaly eia which might be produced by both the storm meridional wind superimposed with traveling atmospheric disturbances and prompt penetration electric field ppe during the main phase of the storm when interplanetary magnetic field started a 12 h southward turning equatorial ionosphere was elevated to a very high level which should be most probably caused by a long duration ppe event meanwhile at mid low latitudes ionosphere witnessed an initial simultaneous decrease then followed by drastic increases which is very different from the past observations in this region reddy and nishida 1992 combined analysis of the data from the ionosonde and other space based measurement shows that for the present case the penetration efficiency of the interplanetary electric field ief to the equatorial ionosphere was larger at night than in the daytime which agrees with the results of fejer et al 2007 showing the ratios of ppe and ief changes were highly variable with the local time during the recovery phase eia was severely inhibited owing to a wind convergence and possibly because of the westward disturbance dynamo electric field

estimation of the thin ice thickness and heat flux for the chukchi sea alaskan coast polynya from special sensor microwave imager data 1990 2001 1 one of the largest arctic polynyas occurs along the alaskan coast of the chukchi sea between cape lisburne and point barrow for this polynya a new thin ice thickness algorithm is described that uses the ratio of the vertically and horizontally polarized special sensor microwave imager ssm i 37 ghz channels to retrieve the distribution of thicknesses and heat fluxes at a 25 km resolution comparison with clear sky advanced very high resolution radiometer data shows that the ssm i thicknesses and heat fluxes are valid for ice thicknesses less than 10 20 cm and comparison with several synthetic aperture radar sar images shows that the 10 cm ice ssm i ice thickness contour approximately follows the sar polynya edge for the twelve winters of 1990 2001 the ice thicknesses and heat fluxes within the polynya are estimated from daily ssm i data then compared with field data and with estimates from other investigations the results show the following first our calculated heat losses are consistent with 2 years of over winter salinity and temperature field data second comparison with other numerical and satellite estimates of the ice production shows that although our ice production per unit area is smaller our polynya areas are larger so that our ice production estimates are of the same order because our salinity forcing occurs over a larger area than in the other models the oceanic response associated with our forcing will be modified index terms 4540 oceanography physical ice mechanics and air sea ice exchange processes 3360 meteorology and atmospheric dynamics remote sensing 4504 oceanography physical air sea interactions 0312 4572 oceanography physical upper ocean processes 4207 oceanography general arctic and antarctic oceanography keywords chukchi sea coastal polynya remote sensing

a nonlinear steady state model of the north water polynya baffin bay abstract a nonlinear steady state model of the north water now the arctic s largest polynya is presented the model follows in the spirit of the recently developed latent and sensible heat polynya model of mysak and huang but extends it in several important ways finite amplitude displacements of the upper layer thickness are allowed the channel walls diverge to the south the sensible heat flux from the lower layer is physically well defined in terms of a vertical entrainment velocity and the free drifting frazil ice to the north of the now ice edge is allowed to move to the right of the northerly winds an important result found here is that with the exception of late spring the asymptotic southern ice edge position of the now can be simulated in terms of a latent heat model alone in this case the observed equatorward curvature of the ice edge in the region adjacent to the west greenland coast can be produced by a combination of a channel that widens in the equatorward direction together wit

deciphering the upper famennian hangenberg black shale depositional environments based on multi proxy record abstract presented for the first time in this paper are the results of a detailed multi proxy investigation conducted on the hangenberg black shale hbs from the polish part of the laurussian shelf which provide details about the environmental conditions in existence during deposition of the shale and the role played by anoxic conditions in the mass extinction events that occurred at the end of the devonian times inorganic and organic redox indicators indicate that bottom water redox conditions changed periodically from being mainly anoxic euxinic to oxic or being partially depleted in oxygen u th values above 1 25 ni co values above 7 and v v ni values above 0 8 recorded from the lower part of the hbs all point to anoxic euxinic conditions being present as do high total organic carbon contents toc above 10 and degree of pyritisation dop values around 0 75 however the presence of benthic fauna over the lower part of the hbs attests to opportunistic colonisation of the seafloor during oxic episodes evidence for similar episodes has also been recognised over the middle part of the hbs e g u th values below 1 25 ni co values below 4 v v ni values below 0 8 toc values of 3 to 5 5 and dop values of 0 4 to 0 75 plus the common occurrence of benthic fauna anoxic conditions returned during the deposition of the upper part of the hsb though they were not as well developed as when the lower part of the shale was laid down of interest is the presence of small pyrite framboids and isorenieratene biomarkers in all the analysed samples which suggest that euxinic conditions persisted in the photic zone of the water column a twenty centimetre thick layer of volcanogenic deposits tuffites is present in the middle part of the hbs the geochemical characteristics of which are typical of ocean floor basalts the occurrence of volcanogenic material below and within the hbs together with an absence of calcium carbonate over its upper part the presence of abundant tetrads just above the black shale and a drastic decrease in faunal frequency in the upper part of the hbs imply that volcanism may have caused oceanic acidification or hypercapnia that in turn potentially may have influenced the hangenberg mass extinction event

on the influence of coastline orientation on the steady state width of a latent heat polynya this paper investigates under what conditions the steady state shape of a coastal latent heat polynya is influenced by 1 the direction of flow of free drifting frazil ice and the consolidated offshore ice sheet and 2 coastline orientation analytical solutions are obtained for coastal polynyas when the coastline is straight and when a coastline has a single step from the solutions it is shown that the asymptotic polynya width is given by the generalized pease 1987 width l cos where l is the classical pease width and is the angle between the consolidated ice sheet velocity and the normal to the coastline an expression is also obtained for the alongshore length scale l c over which the polynya adjusts toward its asymptotic width and it is shown that l c depends upon the directions of travel of the frazil ice and the consolidated ice sheet when the frazil ice and the consolidated ice sheet both drift offshore normal to the coast l c 0 in agreement with the classical pease theory variations in the coastline which occur on a length scale much smaller than l c are not reproduced in the polynya shape two numerical simulations are presented for terra nova bay antarctica and the st lawrence island polynya in the bering sea both examples employ realistic coastline geometry and information about the direction of drift of the consolidated ice sheet in each example a realistic polynya shape is obtained the examples highlight the versatility of the model because in the former case the ice sheet drifts almost parallel to the coast while in the latter it drifts offshore

variability and ice production budget in the ross ice shelf polynya based on a simplified polynya model and satellite observations we examined to what degree a simplified polynya model can explain a real polynya based on satellite derived sea ice data in the model the polynya area defined as the frazil ice production region is determined by a balance between the offshore consolidated ice drift and frazil ice production we used daily polynya area ice production and ice drift data derived from amsr e the study area is the ross ice shelf polynya risp which has the highest sea ice production in the southern ocean as a modification of the original model to apply the available satellite data set we introduced the lag time by which produced frazil ice is transported and accumulated at the polynya edge the model represents a half 48 60 of the polynya variability when using a lag time of 1 5 days the frazil ice collection depth at the polynya edge a key parameter in the model is estimated to be 16 cm the expansion of the risp is achieved by ice divergence and the contraction is achieved mostly by ice production both the wind and the remaining components mainly regarded as the ocean current component in the ice divergence are larger in the western part of the risp which explains the larger extent there in the one dimensional frame assuming that the frazil ice produced within the risp transforms into consolidated ice with a thickness of 16 cm the frazil ice production 1 7 103 m2 d 1 within the risp approximately balances the export 1 6 103 m2 d 1 of consolidated thin ice from the risp edge

statistical evidences of seismo ionospheric precursors applying receiver operating characteristic roc curve on the gps total electron content in china abstract evidence of the seismo ionospheric precursor sip is reported by statistically investigating the relationship between the total electron content tec in global ionosphere map gim and 56 m 6 0 earthquakes during 1998 2013 in china a median based method together with the z test is employed to examine the tec variations 30 days before and after the earthquake it is found that the tec significantly decreases 0600 1000 lt 1 6 days before the earthquake and anomalously increases in 3 time periods of 1300 1700 lt 12 15 days 0000 0500 lt 15 17 days and 0500 0900 lt 22 28 days before the earthquake the receiver operating characteristic roc curve is then used to evaluate the efficiency of tec for predicting m 6 0 earthquakes in china during a specified time period statistical results suggest that the sip is the significant tec reduction in the morning period of 0600 1000 lt the sip is further confirmed since the area under the roc curve is positively associated with the earthquake magnitude

the ionospheric anomalies prior to the m9 0 tohoku oki earthquake the gps total electron content tec data were used to investigate the ionospheric abnormal behaviors prior to the 2011 tohoku oki earthquake the observations show a significant enhancement in tec on march 8 2011 and during the same period the solar activity also has a large increase both an empirical model and a theoretical model were used to check whether the tec anomalies were entirely contributed by the increase in solar radiation the comparison between the observations and the simulation results shows that only the solar radiation enhancement was not enough to produce the observed significant tec enhancement it means that some additional mechanisms such as the per earthquake ionospheric disturbance or the geomagnetic activities may play a significant role in the significant tec enhancement on march 8 the temporal spatial distribution of the extreme tec enhancement within 30 days before the earthquake was particularly pursued it is found that the extreme enhancement was persistently located in the region adjacent to the epicenter and the magnetic conjugate point for a long time of 16 h in addition a geomagnetic disturbance with kp 4 occurred on march 7 therefore the significant tec enhancement on march 8 might be related to the m9 0 tohoku oki earthquake and the geomagnetic disturbance

total electron content behavior over japan during geomagnetic storms 1 the total electron content tec obtained from gps signals is used to study ionospheric dynamics over japan during geomagnetically disturbed conditions the numerous tec measurements are averaged in cells with a size 1 5 1 5 geographic scale and formatted as time series within the years 2000 2002 to extract the storm time changes of tec the diurnal and 27 day periodicities are subsequently removed diurnal variations are removed by replacing absolute tec values in each cell with their relative deviations rtec from medians the hourly rtec values from all cells within the central 4 wide band over japan area are then approximated by a plane surface this surface is represented by two parameters its value at the center rt and the slope b along the main axis taken as constants of the linear regression the 27 day periodicity was approximated by fourier waves with main period of 640 hours and two harmonics separately for rt and b and subtracted from them the analysis of rt and b behavior during a number of geomagnetic storms allowed us to reveal several repeatable features of average tec behavior it was found that tec behavior during the storms is similar to that of fof2 at the f region and was local time dependent a marked poleward expansion of the equatorial ionosphere crest region at the end of recovery phase is persistently observed feature produced probably by intensified eastward zonal winds such an expansion of equatorial ionosphere is observed also during isolated substorms outside main geomagnetic storms an oscillation like change of positive and negative disturbances with period of 24 hours is observed during a 4 day period following a moderate storm in the absence of geomagnetic activity driver that effect is probably caused by the alternative expansion and contraction of equatorial ionosphere

a model for the influence of wind and oceanic currents on the size of a steady state latent heat coastal polynya abstract this paper presents a model for determining the size and shape of a steady state latent heat coastal polynya in terms of the following free parameters 1 the frazil ice production rate f 2 the wind stress 3 the surface ocean velocity field u 4 the offshore consolidated thin ice transport t 5 the coastline shape and 6 the intersection of the polynya ice edge with the coastline all of which must be prescribed frazil ice trajectories are determined via the free drift ice momentum balance analytical solutions for the polynya shape are derived for a straight coastline in the special case when u t and are uniform in the alongshore direction and the rotation of the earth is neglected when the latter constraint is relaxed an expression for the asymptotic uniform polynya width is obtained an expression for the alongshore adjustment length scale of the polynya associated with alongshore variations in the coastline shape u t and is derived with rotation of the earth incl

temporal and spatial precursors in ionospheric total electron content of the 16 october 1999 mw7 1 hector mine earthquake 1 in this paper temporal and spatial analyses are employed to detect seismo ionospheric precursors sips in the ionospheric total electron content tec during the 16 october 1999 mw7 1 hector mine earthquake to discriminate anomalies caused by global effects such as solar radiations magnetic storms etc and local effects such as earthquake we cross examine the gps tecs and their gradients in the eastward and northward directions at epicenter centers of the hector mine area and the other two reference areas at similar magnetic latitudes in europe and japan temporal variations of the northward tec gradient suggest sips most likely appearing on days 6 5 before the earthquake a global search by using the tec of the global ionosphere map shows that the tec increase and decrease anomalies continuously and specifically appear around the epicenter on day 5 before the earthquake

observations and simulations of seismoionospheric gps total electron content anomalies before the 12 january 2010 m7 haiti earthquake 1 in this paper the total electron content tec of the global ionosphere map gim is used to detect seismoionospheric anomalies associated with the 12 january 2010 m7 haiti earthquake and an ionospheric model is applied to simulate the detected anomalies the gim temporal variation shows that the tec over the epicenter significantly enhances on 11 january 2010 1 day before the earthquake the latitude time tec ltt plots reveal three anomalies 1 the northern crest of equatorial ionization anomaly eia moves poleward 2 the tecs at the epicenter and its conjugate increase and 3 the tecs at two dense bands in the midlatitude ionosphere of 35 n and 60 s further enhance the spatial analysis demonstrates that the tec enhancement anomaly appears specifically and persistently in a small region of the northern epicenter area the simulation well reproduces the three gim tec anomalies which indicate that the dynamoelectric field of the ionospheric plasma fountain might have been perturbed by seismoelectric signals generated around the epicenter during the earthquake preparation period

a study of the ionospheric disturbances associated with strong earthquakes using the empirical orthogonal function analysis abstract in this study an ionospheric logtec model has been constructed using an empirical orthogonal function eof decomposition method the main orders 1 9 orders of this eof model represent the ionospheric background while the rest high orders represent ionospheric tec perturbations based on this model logtec data during 16 ms 8 0 earthquakes from 2000 to 2012 have been analyzed we found that ionospheric disturbances occurred in 10 earthquakes ionospheric abnormities were clearly observed 5 days before the earthquakes but ionospheric disturbances can also be seen 1 day before and 1 day and 2 days after the earthquakes for the tec data the possibility of positive enhanced tec and negative decreased tec abnormities is almost the same furthermore by using the simulation results of ionospheric electric field and sami2 model we show that an abnormal westward electric field can lead to electron density enhancements equatorward and decrease polarward of the epicenters and vice versa for an eastward abnormal electric field

mo total organic carbon covariation in modern anoxic marine environments implications for analysis of paleoredox and paleohydrographic conditions 1 sedimentary molybdenum mo s has been widely used as a proxy for benthic redox potential owing to its generally strong enrichment in organic rich marine facies deposited under oxygen depleted conditions a detailed analysis of mo s total organic carbon toc covariation in modern anoxic marine environments and its relationship to ambient water chemistry suggests that 1 mo s while useful in distinguishing oxic from anoxic facies is not related in a simple manner to dissolved sulfide concentrations within euxinic environments and 2 patterns of mo s toc covariation can provide information about paleohydrographic conditions especially the degree of restriction of the subchemoclinal water mass and temporal changes thereof related to deepwater renewal these inferences are based on data from four anoxic silled basins the black sea framvaren fjord cariaco basin and saanich inlet and one upwelling zone the namibian shelf representing a spectrum of aqueous chemical conditions related to water mass restriction in the silled basin environments increasing restriction is correlated with a systematic decrease in mo s toc ratios from 45 5 for saanich inlet to 4 5 1 for the black sea this variation reflects control of mo s by mo aq which becomes depleted in stagnant basins through removal to the sediment without adequate resupply by deepwater renewal the basin reservoir effect the temporal dynamics of this process are revealed by high resolution chemostratigraphic data from framvaren fjord and cariaco basin sediment cores which exhibit long term trends toward lower mo s toc ratios following development of water column stratification and deepwater anoxia mo burial fluxes peak in weakly sulfidic environments such as saanich inlet owing to a combination of greater mo aq availability and enhanced mo transport to the sediment water interface via fe mn redox cycling and are lower in strongly sulfidic environments such as the black sea and framvaren fjord these observations demonstrate that at timescales associated with deepwater renewal in anoxic silled basins decreased sedimentary mo concentrations and burial fluxes are associated with lower benthic redox potentials i e more sulfidic conditions these conclusions apply only to anoxic marine environments exhibiting some degree of water mass restriction e g silled basins and are not valid for low oxygen facies in open marine settings such as continent margin upwelling systems

recent progress in ionospheric earthquake precursor study in china a brief review abstract the study of ionospheric anomaly variation before large earthquakes has attracted the attention of geophysicists for many years this is primarily because ionospheric anomaly variation has been considered to constitute one possible method to identify earthquake precursors since china covers several major earthquake zones it is critical for chinese scientists to study possible ionospheric earthquake precursors in this report we provide a brief summary of recent progress in the study of ionospheric earthquake precursors mainly from chinese mainland researchers as well as some other scientists this report focuses on 1 some case studies of ionospheric abnormal behaviors before some great earthquakes around the world e g m7 9 wenchuan earthquake m9 0 tohoku oki earthquake m7 0 haiti earthquake and 2 some statistical characteristics of ionospheric anomalies before earthquakes including their temporal and spatial distributions and the relationship with the forthcoming earthquake the above mentioned studies may provide some new and beneficial insights for the future study of ionospheric earthquake precursors

modeling the f layer during specific geomagnetic storms important progress has been made recently in developing an understanding of the effects of geomagnetic storms in the thermosphere and ionosphere numerical simulations of theoretical storms with the coupled thermosphere ionosphere model ctim have provided a better understanding of the dynamics of the upper atmosphere and have also permitted the identification of the processes responsible for global storm effects at highlatitude and midlatitude the theory developed based on the model simulations can explain most of the apparent coherence of local time and seasonal dependencies and the apparent randomness in the longitudinal response of the global ionosphere uncovered through statistical analysis of storm observations a true test of the model and the theory is their ability to predict the large scale distribution of storm effects for specific storms in this paper ctim simulation results for the december 7 9 1982 period are presented we compare model results with de 2 temperature and plasma density data we also compare modeled electron densities with ionosonde data from several sectors in both hemispheres the global characteristics of the response are reproduced by the model and we are able to explain the pronounced longitude differences in the summer hemisphere the australian sector passes through midnight during the main driven phase of the storm and experiences the largest energy input and the largest neutral composition changes the deepest ionospheric negative phase seen in ionosonde data is over australia and is consistent with this interpretation given the large uncertainties in our knowledge of the magnitude and spatial distribution of energy input during a particular storm predicting local changes is still a challenge

variations of ionospheric total electron content during the chi chi earthquake on 20 september1999 ut 21 septemberin local time lt a large earthquake mw 7 7 struck central taiwan nearthe small town of chi chi the greatest plasma frequency in the ionosphere fof2 observed by the chung li ionosonde 25 0 n 121 2 e reveals three clear precur sors at 1 3 and 4 days prior to the earthquake this paper examines the ionospheric total electron content tec ob served by a network of the global positioning system gps receivers in taiwan area it is found that variations in fof2 and overhead tec recorded at chung li have a similar ten dency combining the data of the network of 13 gps re ceivers time and spatial variations of tec prior to the chi chi earthquake are examined results show that the equa torial anomaly crest moves equatorward and its tec value significantly decreases 1 3 and 4 days before the earth quake a comparison between the disturbed and reference previous 15 day median days confirms that tec decreases significantly around the epicenter in the afternoons of these days finally possible mechanisms are proposed and dis cussed

time resolved study of charge generation and propagation in igneous rocks electrical resistivity changes ground potentials electromagnetic em and luminous signals preceding or accompanying earthquakes have been reported many times in addition to ground uplift and tilt and other parameters however no concept exists that would tie these diverse phenomena together into a physically coherent model using low to medium velocity impacts to measure electrical signals with microsecond time resolution it is observed that when gabbro and diorite cores are impacted at relatively low velocities 100 m s highly mobile charge carriers are generated in a small volume near the impact point they spread through the rocks causing electric potentials exceeding 400 mv em and light emission as the charge cloud spreads the rock becomes momentarily conductive when a granite block is impacted at higher velocity 1 5 km s the propagation of the p and s waves is registered through the transient piezoelectric response of quartz after the sound waves have passed the surface of the granite block becomes positively charged suggesting the same charge carriers as observed during the low velocity impact experiments expanding from within the bulk during the next 2 3 ms the surface potential oscillates indicating pulses of electrons injected from ground and contact electrodes the observations are consistent with positive holes e g defect electrons in the o2 sublattice traveling via the o 2p dominated valence band of the silicate minerals the positive holes propagate as charge clouds rather than as classical em waves before activation they lay dormant in form of electrically inactive positive hole pairs php chemically equivalent to peroxy links o3x oo xo3 with x si4 al3 etc phps are introduced into the minerals by way of hydroxyl o3x oh which all nominally anhydrous minerals incorporate when crystallizing in h2o laden environments the fact that positive holes can be activated by low energy impacts and their attendant sound waves suggests that they can also be activated in the crust by microfractures during the dilatancy phase depending on where in the stressed rock volume the charge carriers are activated they will form rapidly moving or fluctuating charge clouds that can account for earthquake related electrical signals and em emission wherever such charge clouds intersect the surface high fields are expected causing electric discharges and earthquake lights

storm time dependence of equatorial disturbance dynamo zonal electric fields we use jicamarca radar observations of f region vertical plasma drifts and auroral electrojet indices during 1968 1988 to study the characteristics and temporal evolution of equatorial disturbance dynamo zonal electric fields these electric fields result from the dynamo action of storm time winds and or thermospheric composition changes driven by enhanced energy deposition into the high latitude ionosphere during geomagnetically active conditions the equatorial vertical drift perturbations last for periods of up to 30 hours after large increases in the high latitude currents on the average this process can be described by two basic components with time delays of about 1 12 hours and 22 28 hours between the high latitude current enhancements and the equatorial velocity perturbations our data indicate strong coupling between dynamo processes with different timescales the short term disturbance dynamo drives upward equatorial drifts eastward electric fields at night with largest amplitudes near sunrise and small downward drifts during the day these perturbation drifts are in good agreement with results from the blanc richmond disturbance dynamo theory the dynamo process with time delays of about a day drives upward drift velocities at night with largest values near midnight and downward drifts in the sunrise noon sector in this case the amplitudes of the disturbance drifts maximize during geomagnetically quiet times preceded by strongly disturbed conditions we also present results of a new equatorial storm time dependent empirical model which illustrate the characteristics of the vertical disturbance dynamo drifts

nonlinear principal component analysis in the detection of ionospheric electron content anomalies related to a deep earthquake 300 km m 7 0 on 1 january 2012 izu islands japan 1 nonlinear principal component analysis nlpca and image processing are used to detect an ionospheric total electron content tec anomaly above japan s izu islands relating to an earthquake on 1 january 2012 ut mw 7 0 this earthquake was 348 km deep the earthquake occurred at 05 27 54 ut nlpca is applied to the time period 06 40 to 12 00 ut nlpca shows that the tec anomaly is highly localized and decreases in intensity with time pca was unable to detect the anomaly this work discusses potential reasons for the tec anomaly over the izu islands after this earthquake and possible reasons including acoustic gravity waves radon gas release and p type semiconductor effects

thickness and production of sea ice in the okhotsk sea coastal polynyas from amsr e 1 from comparisons with thickness of sea ice from advanced very high resolution radiometer avhrr and ice profiling sonar data we have developed an advanced microwave scanning radiometer eos amsr e thin ice thickness algorithm for the sea of okhotsk this algorithm can estimate ice thickness of 0 2 m without snow using the polarization ratio of amsr e brightness temperature at a 36 5 ghz channel from a linear relationship with avhrr ice thickness when a snow cover exists on the thin ice surface as occurred a few times in each winter it is shown that the algorithm cannot detect the thin ice sea ice and dense shelf water dsw production in coastal polynya are estimated on the basis of heat flux calculation with the daily amsr e ice thickness for three winters december march of 2002 2003 to 2004 2005 the ice production is largest in the northwest shelf nws polynya which accounts for 45 of the sum of ice production in major coastal polynyas the ice production in major coastal polynyas would cover the maximum ice area of the okhotsk sea if the average ice thickness is assumed to be 1 m variability of the ice production is mainly modulated by air temperature in the nws polynya which is the main dsw production area the annual dsw formation rate is estimated to be 0 36 sv

multiple controls on the preservation of organic matter in devonian mississippian marine black shales geochemical and petrographic evidence geochemical and petrographic analysis of an interval of black shales between the huron shale member of the new albany shale upper devonian famennian and the sunbury shale lower mississippian tournaisian suggests that multiple controls influenced the accumulation of organic matter stratigraphic trends were determined following detailed analysis of a core from the central appalachian basin d6 montgomery county ky specifically c s fe relationships mo v v ni ni co and v cr were used to assess paleo redox conditions during sediment accumulation the role of clastic input was evaluated using ti al k al and si al and c p was used as a proxy for paleoproductivity the terrestrial to marine maceral ratio t m vitrinite plus inertinite alginite plus bituminite was used to evaluate changes in om source c s fe relationships and trace element ratios suggest anoxic conditions prevailed during deposition of much of the upper part of this interval however bottom water conditions were intermittently dysoxic during accumulation of the huron shale member and possibly dysoxic to marginally oxic during accumulation of the lowermost huron shale member productivity appears to have been an important factor in the accumulation of corg and high c p ratios are consistent with a productivity anoxia feedback mechanism in addition nutrients from increased terrestrial weathering may have contributed to enhanced productivity variations in sediment influx may also have influenced corg concentrations through sediment starvation one of the more significant observations in this work is an increase in terrestrial om inertinite and vitrinite up section which may reflect vegetative changes occurring on land during this time interval most of this increase is due to inertinite much of which appears to be fusinitic in origin and hence may be fossil charcoal this latter observation has implications for the expansion of land plants into drier niches and for late devonian atmospheric oxygen levels introduction of more resistant terrestrial om to anoxic basins may have been an important factor in the preservation of high carbon 10 intervals especially in the cleveland member of the new albany shale upper devonian famennian and the sunbury shale lower mississippian tournaisian

ionosphere plasma bubbles and density variations induced by pre earthquake rock currents and associated surface charges 1 recent ionospheric observations indicate that the total electron content tec may anomalously decrease or increase up to 5 20 before the occurrence of big earthquakes the ionospheric density variations can be caused by earth surface charges currents produced from electric currents associated with the stressed rock we formulate a coupling model for the stressed rock earth surface charges atmosphere ionosphere system the stressed rock acts as the dynamo to provide the currents for the coupling system the electric fields and currents in the atmosphere and the lower boundary of ionosphere are obtained by solving the current continuity equation j 0 where j is the current density a three dimensional ionosphere simulation code is then used to study the ionospheric dynamics based on the obtained electric fields and currents the simulation results show that a current density jrock 0 2 10 a m2 in an earthquake fault zone is required to cause daytime tec variations of 2 25 the simulation results also show that a current density jrock 0 01 1 a m2 can lead to nighttime tec variations of 1 30 as well as the formation of a nighttime plasma bubble equatorial spread f extending over the whole magnetic flux tube containing the earthquake epicenter we suggest that observations of daytime and nighttime tec variations and a nighttime plasma bubble within the affected region can be used as precursors for earthquake prediction

ionospheric and geomagnetic disturbances caused by the 2008 wenchuan earthquake a revisit previous works have shown that coseismic ionospheric disturbances cids after the tsunamigenic 2011 tohoku earthquake tohoku eq mw9 1 covered a vast area and were observed thousands of kilometers away from the epicenter for the purpose of making a comprehensive comparison between powerful oceanic and inland eqs we conduct a retrospective investigation of cids and geomagnetic responses to the 2008 wenchuan eq mw7 9 using a combination of techniques total electron content hf doppler and ground magnetometer it is the very first study to present cids recorded by different techniques at co located sites and profiled with regard to changes of both ionospheric plasma and current geomagnetic field simultaneously the integrated observation also shows that 1 in the wenchuan case most of the ionospheric and geomagnetic disturbances were observed within 1000 km distance which is far less than the tohoku case 2 two groups of cids were found with maximum amplitudes in the direction of azimuth 150 and 135 respectively and 3 the geomagnetic changes were only registered by three magnetometers located to the east and southeast of the epicenter all the facts indicate that the main directional lobe of wenchuan eq energy propagation is to southeast and perpendicular to the direction of the fault rupture but this kind of directivity is not that distinct in the tohoku case we suggest that the different fault slip inland or submarine affecting the way of couplings of lithosphere with atmosphere may contribute to the discrepancies between the two events

effects of along shore wind on dsw formation beneath coastal polynyas application to the sea of okhotsk 1 it is known that salinity anomaly under a polynya reaches and remains an equilibrium value s after termination of its initial increase associated with brine rejection at the surface in this paper we investigate effect of along shore downwelling favorable wind on the equilibrium salinity anomaly by idealized numerical calculations and scale based estimates numerical calculations showed that high saline water beneath polynya is advected downstream by wind driven circulations over the shelf besides baroclinically developed eddies which consequently induces a decrease in s beneath polynya the downwelling favorable wind generates an offshore overturning flow through lower layers referred to as ekman compensation flow ecf which causes a great offshore salinity flux as well as an along shore current we also constructed an equation for estimation of s from the viewpoint of salinity budget over the polynya region in which lateral salinity fluxes caused by ecf along shore wind driven current and baroclinic eddies are scaled the solution s was also verified by a series of numerical calculations furthermore we investigated the effects of along shore wind on dense water generation beneath the okhotsk coastal polynyas we conducted simplified numerical experiments assuming the okhotsk situation in which fs and offshore width b of polynya are predicted by a thermodynamic polynya model with ecmwf meteorological variables the simulated salinity shows a good agreement with the direct measurements the theoretical estimates for s was also applied to two okhotsk polynyas northwestern polynya nwp and northern polynya np in conclusion we found that the along shore wind causes greater salinity decrease in np than in nwp whose variations substantially depend on the aleutian low activity

no evidence for fungal infection of upper jurassic horseshoe crabs a comment on blazejowski et al 2019 abstract blazejowski et al 2019 intended to provide evidence for fungal infection of upper jurassic horseshoe crabs from poland based on the presence of boring traces preserved on their carapaces and assigned to the ichnogenus mycelites however the borings are in fact burrows which can be assigned to the ichnogenus arachnostega thus their hypothesis about the fungal infection is rejected on the basis of erroneous identification of the ichnofossils preserved there is also no compelling evidence for environmental deterioration causing the infection rather the bottom waters were oxygenated and thus hospitable for benthic organisms

rare earth elements of sinking particulate matter in the japan trench abstract settling particles were collected with time series sediment traps at four depths 1174 m 3680 m 5687 m and 8688 m moored at the deepest site water depth 9200 m of the japan trench for the period from march 5 1991 to march 2 1992 the composition of rare earth elements rees in the sinking particles selected for four seasons were measured to investigate the ree fractionation during scavenging and settling transport through the water column the ree particle associations were also investigated by sequential digestion with three chemical treatments acetic acid mild hcl hno3 and hf hno3 hclo4 the measured vertical particulate flux increased with depth suggesting that there is a significant addition of particles at least to the deeper traps from horizontal sources no systematic variation was observed in the ree concentration in the particles with respect to depth and season the shale normalized ree data show either flat or slightly heavy ree enriched patterns with a middle ree enrichment in which the maximum is usually centred at gd but sometimes at eu and a significantly positive ce anomaly the chemical digestion experiments indicated characteristic patterns for shale normalized rees the acetic acid leach showed a marked middle ree enriched pattern with a maximum at eu and distinctively negative ce anomaly the mild hcl hno3 leach had a middle ree enriched pattern with a maximum at gd but roughly no ce anomaly the residue showed a rather flat ree pattern with a marked positive ce and often middle ree enrichment with a maximum at gd these results are compared with those reported previously for sinking and suspended particles in other parts of the oceans it is suggested that rees adsorbed on the suspended particles are altered into some refractory phases prior to or during transport by settling the possibility exists that authigenic barite formed in the microenvironment around aggregates may effectively coprecipitate the rees attracted to the particle surfaces

increase and decrease of sea ice area in the sea of okhotsk ice production in coastal polynyas and dynamic thickening in convergence zones 1 this paper examines the production and reduction of sea ice area in the sea of okhotsk analyses were carried out for 10 winters december april from 1991 1992 to 2000 2001 using daily data of sea ice velocity and concentration derived from images of the defense meteorological satellite program dmsp special sensor microwave imager ssm i first we mapped sea ice divergence which was calculated from the daily ice velocity field in the case of offshore winds high divergence was observed along the coastline while there existed a broad convergence area with inshore winds next we examined local changes in an area of sea ice as in the case of ice divergence ice production and reduction are strongly controlled by wind direction we found that a large amount of sea ice was produced in coastal areas under offshore wind conditions the geographical distribution of the ice production area agrees well with that of the well known coastal polynya areas our estimation shows that 8 7 105 km2 yr 1 of sea ice is produced in the northern coastal area and 3 7 105 km2 yr 1 in the sakhalin coastal area in contrast 7 4 105 km2 yr 1 of the ice area disappeared in shantarskiy bay this reduction of ice area is mainly caused by dynamic deformation of existing ice forming rafted ice or pressure ridges this dynamic deformation plays an important role not only in the reduction of okhotsk sea ice area but also in the thickening of ice

is an unusual large enhancement of ionospheric electron density linked with the 2008 great wenchuan earthquake 1 on 12 may 2008 at 0628 ut a major earthquake ms 8 0 struck wenchuan county 31 0 n 103 4 e in southwest china the maximum ionospheric electron density at f2 peak nmf2 recorded an unusual large enhancement during the afternoon sunset sector by the chinese ionosondes over wuhan 30 5 n 114 4 e and xiamen 24 4 n 123 9 e which are close to the earthquake epicenter an averaged increase at these two stations is about 2 times on a geomagnetic quiet day 9 may kp 2 3 days prior to the earthquake relative to the median value of 1 12 may whereas the increase was much less significant over yamagawa 31 2 n 130 6 e and okinawa 26 7 n 128 2 e in japan combining the data from the network of 58 global positioning system receivers around china and the global ionospheric map the variations of the total electron content reveal the region where enhancement persisted for a long period to be within longitudes 90 130 e our results suggest that this abnormal enhancement is most possibly a seismo ionospheric signature

causes of the multidecadal scale warming of the intermediate water in the okhotsk sea and western subarctic north pacific abstractcauses of the multidecadal scale warming of the intermediate water in the okhotsk sea and the western subarctic north pacific during 1980 2008 are investigated using an ice ocean coupled model with interannually varying atmospheric forcing a hindcast experiment qualitatively reproduces the warming and decadal fluctuations of the intermediate water that are similar to those of observations the warming is significant along the western part of the okhotsk sea and subarctic frontal region the effects of the thermohaline and wind driven ocean circulation on the warming are evaluated from perturbation experiments on thermohaline turbulent heat and freshwater fluxes and wind causes respectively the thermohaline causes are shown to contribute positively to warming in the okhotsk sea intermediate water osiw the heat budget analysis for the osiw indicates that the warming is related to a decrease in cold and dense shelf water dsw flux which is caused by a decrease in sea ice and surface water

gradual reduction in ionospheric f 2 region before the 2013 lushan earthquake contributed to the forthcoming earthquake or solar activity ionospheric anomalies before earthquakes during geomagnetic quiet conditions have been extensively discussed due to the importance of earthquake prediction however because of the high variability of ionosphere a real caution should be adopted before attributing the observations to seismo ionospheric precursors sips in an investigation of contradictory results in ionospheric variation before 2013 lushan earthquake we examine the ionospheric variation versus solar activity in order to assess the influence of solar activity of 27 day periodicity on ionospheric variation a quadratic regression model is developed by using the data of f2 layer critical frequency fof2 in april of 2008 2014 using the model ionospheric variation before the 2013 lushan earthquake is analyzed the results show that fof2 was strongly correlated with solar activity index f10 7 and had a low correlation with the remaining by eliminating the contribution of solar radiation which indicates that the gradual reduction in fof2 before the earthquake was contributed to the variation of solar radiation rather than the forthcoming earthquake

seismo ionospheric signatures prior to m 6 0 taiwan earthquakes this paper examines variations of the greatest plasma frequency in the ionosphere fof2 recorded by the chung li ionosonde 25 0 n 121 1 e before m 6 0 earthquakes during 1994 1999 the 15 day running median and the associated inter quartile range are utilized as the reference and the upper or lower bounds to monitor the ionospheric fof2 variations for finding seismo ionospheric signatures precursors of the earthquakes it is found that precursors in the form of the recorded fof2 falling below its associated lower bound around 1200 1700 lt appear 1 6 days prior to these earthquakes on september 20 1999 ut september 21 taiwan local time a large mw 7 7 earthquake struck central taiwan near the small town of chi chi we analyzed the fof2 and found three clear precursors 1 3 and 4 days prior to the chi chi earthquake

variations of ionospheric plasma at different altitudes before the 2005 sumatra indonesia ms 7 2 earthquake resent years many researchers pay more attention to abnormities before earthquake and in this study seismo ionospheric synchronous disturbances at different altitudes by gps and satellite observations were firstly studied around one sumatra indonesia ms 7 2 earthquake occurred on july 5 2005 by using the same temporal and spatial methods data of gps tec from jpl electron density ne from demeter and ion density ni from dmsp were deeply analyzed the ionospheric plasma disturbances in gps tec and increasement of ne at 710 km were found on july 4 and plasma density at the three altitudes has all increased on july 7 after the earthquake all the disturbances were not just above the epicenter tec perturbations have happened at the east of the epicenter for the two days and electron density enhancement at 710 km has moved to west of the tec perturbations at the same time on july 4 which may be caused by e b drift the moving direction of up going plasma was simulated using sami2 model the results have shown that the plasma will move to higher altitude along the geomagnetic force line which could exactly account for the plasma density enhancement in the northern direction of the geomagnetic south latitude earthquake

cerium a chemical tracer for paleo oceanic redox conditions abstract the ce anomalies found in marine carbonates provide a sensitive indicator for the study of paleo oceanic redox conditions the dependency of cce the observed ce concentration and cepo04 the activity of the cepo4 complex to the po2 ph and pco2 of seawater can be used for deciphering some aspects of the paleo ocean chemistry and is log c ce log cepo 0 4 13 2 0 25 log p o 2 3 0 ph 1 95 0 25 log p o 2 1 50 log p co 2 1 50 log ca the ph which is related to pco2 and po2 are major factors for controlling the ce concentration in seawater therefore ce anomalies ceas ce observed ce interpolated between la and pr or nd serve as indicators for ph or pco2 or po2 changes nearly uniform ce abundances found in pacific 5000 m water columns piepgras and jacobsen 1988 and the ceas in ichthyoliths can be explained using this model a general cea shift in sediments from d s d p holes 525a 530a b 516 516f suggest that the entire south atlantic water redox condition changed from reducing to oxidizing at 56 my in the north atlantic the galicia margin samples show a redox change between 132 148 my indicating active surface currents between the atlantic ocean and the shallow sea off the iberian peninsula the carbonate samples from d s d p hole 316 in the central pacific yielded an average cea of 0 15 0 01 which is 2 3 the ceas observed in deep pacific seawater by piepgras and jacobsen 1988 the relative enrichment of ce in these samples is ascribed to coprecipitation of ce oh 4 onto fe mn o coatings the striking similarities in the trace element profiles of ree sc hf th and ceas and the low u abundances 0 08 ppm in many marine carbonates indicate insignificant ce redox and trace elemental concentration changes for the pacific ocean over the past 95 my no significant ce redox change occurred in the pacific ocean within k t boundary one 240 my china limestone deposited under oxic sedimentary conditions yielded a cea of 0 53 calculations indicate a pco2 of 1 9 present value prevailed over the 240 my tethyan ocean u th ratios and low u concentrations are diagnostic indicators for obtaining reliable ceas in marine carbonates and perhaps for biogenic apatites and conodonts as well

damping of large scale traveling ionospheric disturbances detected with gps networks during the geomagnetic storm 1 large scale traveling ionospheric disturbances lstids during the geomagnetic storm on 22 september 1999 were studied using total electron content tec data from the gps earth observation network geonet in japan international gps service igs and continuously operating reference stations cors in the united states the damping rates of the lstids were precisely derived in several local time sectors and were found to depend on values of the background tec this indicates that the dominant physical mechanism of the lstids damping is the ion drag effect by the background ionosphere the high resolution tec data from geonet revealed that two successive lstids were damped significantly as they traveled equatorward in the dawn sector the ratio of the perturbation component of tec to the background component i i0 decreased exponentially with the damping rate of 0 89 1000 km and 0 77 1000 km we studied also the amplitude of i i0 at high latitudes using igs data and found that the damping rates of lstids at high latitudes tended to be smaller than those at midlatitudes global tec observations during this geomagnetic storm by the igs and cors networks detected that several lstids propagated also equatorward in the afternoon sector and in the night sector the lstids in the afternoon sector were most damped with the damping rate of 1 04 1000 km which corresponds to the e folding length of 961 km the damping rate of lstids in the night sector was found to be small the lstids had a tendency to be damped rapidly in the regions where background tec was large this dependence of the damping rate on latitude and local time indicates that this intense damping of lstids was caused mainly by the ion drag effect that is proportional to the ion collision frequency the relation between the damping rates and the background tec derived from the observation are consistent with those estimated with a theoretical calculation of the gravity wave damping by the ion drag effect the worldwide distribution of gps receivers enabled us to estimate the longitudinal extent of these lstids the zonal width of lstids in the dawn sector was narrower than 45 in longitude 2 900 km around 55 n and wider than 20 in longitude 1 800 km around 40 n these widths were narrower than those reported in previous studies

spatial variation in sediment fluxes redox conditions and productivity in the permian triassic panthalassic ocean abstract two permian triassic boundary sections in central japan provide a rare window into environmental conditions within the panthalassic ocean which encompassed more than half the earth s surface at 252 ma integration of petrographic geochemical and time series data provides new insights regarding the fluxes of major and trace components to the sediment as well as environmental conditions in both the deep and intermediate water masses at each study site the ubara section was located in a high productivity peri equatorial location whereas the gujo hachiman section was located in a moderate productivity location at some distance from the paleoequator an upward transition from gray organic poor cherts to black siliceous mudstones at both sites occurred in conjunction with increased primary productivity intensified euxinia within the oxygen minimum zone omz and decimation of the radiolarian zooplankton community euxinia in the omz of the equatorial panthalassic ocean developed episodically for a 200 250 kyr interval during the late permian followed by an abrupt intensification and lateral expansion of the omz around the permian triassic boundary throughout the study interval bottom waters at both sites remained mostly suboxic a finding that counters hypotheses of development of a superanoxic permo triassic deep ocean as a consequence of stagnation of oceanic overturning circulation

environment deterioration and related fungal infection of upper jurassic horseshoe crabs with remarks on their exceptional preservation abstract approximately 10 of late jurassic tithonian horseshoe crabs collected from the kcynia formation in the owadow brzezinki quarry central poland display microborings covering the entire carapace of specimens detailed examination of the surrounding sediment indicates the occurrence of short term fluctuations in the oxygenation level of bottom waters and their salinities the identified palynomorph assemblage from the sediment suggests pathogenic algal blooms as the probable cause for mass mortality anoxic conditions resulting from algal blooms in restricted environments facilitated fungal infection evidenced by the damage microborings caused by the hyphae on the surface of the exoskeletons associated biochemical factors contributed to the excellent preservation of diversified fauna with soft tissues

latitudinal distribution of anomalous ion density as a precursor of a large earthquake 1 data obtained by the u s satellite de 2 are used to investigate possible precursor features in the ionosphere associated with a large earthquake latitude 33 13 longitude 73 07 m 7 5 which occurred during a moderate geomagnetic disturbance atomic oxygen ion and molecular ion distributions show characteristic latitudinal features similar to the well known equatorial ionization anomaly eia feature but centered around the earthquake epicenter we name this the precursor ionization anomaly pia the density minima of both the atomic oxygen and molecular ions are in two latitude zones depending on the distance from the epicenter one of the pia minima aligns with the geomagnetic latitude crossing the epicenter another minimum is found along the geographic latitude of the epicenter these minima are located in an area spanning about 40 in latitude and about 140 in longitude it is noted that the molecular ion minimum is more clearly defined even when the atomic ion density minimum is not indicated clearly the ion density reduction seems to be caused by a superposition of natural quiet time ionospheric eastward electric field and an electric field associated with the earthquake although we studied one single event our careful examination of results suggests that the location and day of occurrence of the pia can be predicted for some large earthquakes even during moderate geomagnetic disturbance if the satellite orbit is properly chosen

reply to the comment on no evidence for fungal infection of upper jurassic horseshoe crabs a comment on blazejowski et al 2019 by zaton 2020 palaeo3 xxx xxx abstract in the comment on our paper this issue zaton 2020 questions the conclusions reported in blazejowski et al 2019 we present further arguments defending our theses late jurassic horseshoe crabs preserved in sediments of the kcynia formation owadow brzezinki quarry lived in a restricted lagoon repeatedly subjected to dysoxia anoxia which promoted their excellent state of preservation the palaeobiological interpretation of the traces visible on horseshoe crab exoskeletons is consistent with the occurrence of temporal oxygen deficiency

ionospheric anomalies possibly associated with m 6 0 earthquakes in the japan area during 1998 2010 case studies and statistical study abstract in this paper we examine pre earthquake ionospheric anomalies in time series and perform a statistical test by using total electron content tec derived from global ionosphere maps gim around the japan area for the first time the normalized gim tec gim tec which is computed based on 15 days backward running mean of gim tec have been investigated for minimizing possible confounding effects of consecutive earthquakes and identify the abnormal signals meanwhile to reduce the effect of strong geomagnetic activities such as geomagnetic storms the criterion for removing the gim tec data have been adapted that is when dst index exceeds 60 nt temporal variations of gim tec for large and destructive earthquakes in japan have been studied which are the 2004 mid niigata prefecture earthquake m6 8 its aftershock m6 1 the 2007 offshore mid niigata earthquake m6 8 and the 2008 iwate miyagi nairiku earthquake m7 2 although there are some positive and negative tec anomalies before and after the four earthquakes there is a tendency that positive tec anomalies appear 1 5 days before all the above earthquakes even during the quiet geomagnetic condition superposed epoch analyses have been performed for the statistical analysis of tec anomalies associated with m 6 0 earthquakes during the 12 year period of may 1998 may 2010 the statistical result indicates the significance of the positive tec anomalies 1 5 days before earthquakes within 1000 km from the epicenter around japan

suspected seismo ionospheric coupling observed by satellite measurements and gps tec related to the m7 9 wenchuan earthquake of 12 may 2008 anomalous changes in the ionospheric conditions related to the wenchuan earthquake of 12 may 2008 are investigated using electron density ne from detection of electro magnetic emissions transmitted from earthquake regions demeter and champ satellites electric field from demeter and gps total electron content tec maps the normalized ne from the demeter satellite reveal that the previously reported tec increments before the earthquake can be considered as fragments of the gradual equatorial ionization anomaly eia enhancements near the epicenter longitude that began approximately 1 month before the earthquake and reached its maximum with an exceptionally large strength index 8 days prior to the main shock this feature is indirectly confirmed through the champ ne and gps tec data following the eia intensity peak disturbances in the ne and o density were observed in the nightside based on the concurrent electric field and ne changes it is suggested that eia intensification could be triggered by the e field disturbances over the epicenter