air sea interactions during an arctic storm 1 the impacts of increased open water in the beaufort sea were investigated for a summer arctic storm in 2008 using a coupled atmosphere ice ocean model the storm originated in northern siberia and slowly moved into the beaufort sea along the ice edge in late july the maximum wind associated with the storm occurred when it was located over the open water near the beaufort sea coast after it had moved over the chukchi and beaufort seas the coupled model system is shown to simulate the storm track intensity maximum wind speed and the ice cover well the model simulations suggest that the lack of ice cover in the beaufort sea during the 2008 storm results in increased local surface wind and surface air temperature compared to enhanced ice cover extents such as occurred in past decades in addition due to this increase of open water the surface latent and sensible heat fluxes into the atmosphere are significantly increased however there were no significant impacts on the storm track the expanded open water and the loss of the sea ice results in increases in the surface air temperature by as much as 8 c although the atmospheric warming mostly occurs in the boundary layer there is increased atmospheric boundary turbulence and downward kinetic energy transport that reach to mid levels of the troposphere and beyond these changes result in enhanced surface winds by as much as 4 m s during the 2008 storm compared to higher ice concentration conditions typical of past decades the dominant sea surface temperature response to the storm occurs over open water storm generated mixing in the upper ocean results in sea surface cooling of up to 2 c along the southern beaufort sea coastal waters the ekman divergence associated with the storm caused a decrease in the fresh water content in the central beaufort sea by about 11 cm

experimental insights into pyroclast ice heat transfer in water drained low pressure cavities during subglacial explosive eruptions subglacial explosive volcanism generates hazards that result from magma ice interaction including large flow rate meltwater flooding and fine grained volcanic ash we consider eruptions where subglacial cavities produced by ice melt during eruption establish a connection to the atmosphere along the base of the ice sheet that allows accumulated meltwater to drain the resulting reduction of pressure initiates or enhances explosive phreatomagmatic volcanism within a steam filled cavity with pyroclast impingement on the cavity roof heat transfer rates to melt ice in such a system have not to our knowledge been assessed previously to study this system we take an experimental approach to gain insight into the heat transfer processes and to quantify ice melt rates we present the results of a series of analogue laboratory experiments in which a jet of steam air and sand at approximately 300 c impinged on the underside of an ice block a key finding was that as the steam to sand ratio was increased behavior ranged from predominantly horizontal ice melting to predominantly vertical melting by a mobile slurry of sand and water for the steam to sand ratio that matches typical steam to pyroclast ratios during subglacial phreatomagmatic eruptions at 300 c we observed predominantly vertical melting with upward ice melt rates of 1 5 mm s 1 which we argue is similar to that within the volcanic system this makes pyroclast ice heat transfer an important contributing ice melt mechanism under drained low pressure conditions that may precede subaerial explosive volcanism on sloping flanks of glaciated volcanoes

barents sea seasonal ice zone features and processes from ers 1 synthetic aperture radar seasonal ice zone experiment 1992 sea ice features and processes in the barents sea were studied during the seasonal ice zone experiment 1992 sizex92 a dedicated ers 1 satellite synthetic aperture radar sar field campaign carried out in march 1992 sizex92 was based around the research vessels polarsyssel and hakon mosby in situ oceanographic meteorological and ice measurements were made coordinated with low altitude aerial observations and ers 1 sar data acquired in near real time fifty eight low and full resolution sar scenes were obtained during sizex92 which provided a validation data set for ers 1 sar backscatter under winter conditions in the barents sea analysis of sizex92 data has provided geophysical insights including a better understanding of barents sea ice edge freezing processes and ice edge development in response to atmospheric forcings in particular areas of new ice formation were found to be related to bathymetric features through their influence on the circulation of arctic and atlantic water masses ers 1 sar image sequences revealed rapid mesoscale variations in new ice areas and the ice edge in response to wind conditions in addition to geophysical insight sizex92 demonstrated some of the technical capabilities and limitations of ers 1 sar to identify new ice areas the ice edge ice floes and ice types mapping new ice areas using satellite sar data may be considered the most promising new application the limitations of ers 1 sar derived ice classification and ice motion estimates in the marginal ice zone are identified

shallow magma transport for the 2002 3 mt etna eruption inferred from thermal infrared surveys abstract the 26 october 2002 28 january 2003 eruption of mt etna volcano was characterised by lava effusion and by an uncommon explosivity along a 1 km long eruptive fissure on the southern upper flank of the volcano the intense activity promoted rapid growth of cinder cones and several effusive vents analysis of thermal images recorded throughout the eruption allowed investigation of the distribution of vents along the eruptive fissure and of the nature of explosive activity the spatial and temporal distribution of active vents revealed phases of dike intrusion expansion geometric stabilization and drainage these phases were characterised by different styles of explosive activity with a gradual transition from fire fountaining through transitional phases to mild strombolian activity and ending with non explosive lava effusion here we interpret the mechanisms of the dike emplacement and the eruptive dynamics according to changes in the eruptive style vent morphology and apparent temperature variations at vents detected through thermal imaging this is the first time that dike emplacement and eruptive activity have been tracked using a handheld thermal camera and we believe that its use was crucial to gain a detailed understanding of the eruptive event

measuring the sea ice floe size distribution sea ice is broken into floes whose diameters range from meters to a hundred kilometers this fragmentation affects the resistance of the ice cover to deformation and the melting at floe sidewalls in summer floes are broken by waves and swell near the ice edge and throughout the pack by isostatic imbalances thermal cracking winds and currents in winter they are welded together by freezing floe size can be measured by several properties p for instance area or mean caliper diameter two definitions of floe size distribution seem useful f p the fraction of area covered by floes no smaller than p and n p the number of floes per unit area no smaller than p f p can be measured by sets other than areas such as the fraction of a line or of a point set covered by floes no smaller than p if n behaves like for small where is mean caliper diameter must be greater than 2 so that the small floes occupy finite area if 2 1 the perimeter of small floes is infinite several summertime distributions have been measured on a log log graph their slopes local values of range from 1 7 to 2 5 one distribution follows a power law the others have steeper slopes for larger floes and more gradual slopes for smaller floes another sampling strategy is to measure the lengths of line segments on floes the distribution of these chord lengths is equivalent to the distribution of floe diameters the variance of an estimate of the fraction g of area covered by floes in any size range is g 1 g k 1 where k is the equivalent number of independent samples k can be found from the autocovariance of the indicator function for the chosen size range for line sampling of a narrow range of floe diameters k is the ratio of the sample length to the floe diameter

volcanic risk and tourism in southern iceland implications for hazard risk and emergency response education and training abstract this paper examines the relationship between volcanic risk and the tourism sector in southern iceland and the complex challenge emergency management officials face in developing effective volcanic risk mitigation strategies an early warning system and emergency response procedures were developed for communities surrounding katla the volcano underlying the m rdalsjokull ice cap however prior to and during the 2007 tourist season these mitigation efforts were not effectively communicated to stakeholders located in the tourist destination of orsmork despite its location within the hazard zone of katla the hazard zone represents the potential extent of a catastrophic jokulhlaup glacial outburst flood furthermore volcanic risk mitigation efforts in orsmork were based solely on information derived from physical investigations of volcanic hazards they did not consider the human dimension of risk in order to address this gap and provide support to current risk mitigation efforts questionnaire surveys were used to investigate tourists and tourism employees hazard knowledge risk perception adoption of personal preparedness measures predicted behaviour if faced with a katla eruption and views on education results indicate that tourists lack hazard knowledge and they do not adopt preparedness measures to deal with the consequences of an eruption despite a high level of risk perception tourism employees lack knowledge about the early warning system and emergency response procedures results show that tourists are positive about receiving information concerning katla and its hazards and therefore the reticence of tourism employees with respect to disseminating hazard information is unjustified in order to improve the tourism sector s collective capacity to positively respond during a future eruption recommendations are made to ensure adequate dissemination of hazard risk and emergency response information most importantly education campaigns should focus on a increasing tourists knowledge of katla jokulhlaup and other volcanic hazards and b increasing tourist and employee awareness of the early warning and information system and appropriate behavioural response if a warning is issued further tourism employees should be required to participate in emergency training and evacuation exercises annually these efforts are timely given that katla is expected to erupt in the near future and international tourism is an expanding industry in orsmork

the formation of helgafell southwest iceland a monogenetic subglacial hyaloclastite ridge sedimentology hydrology and volcano ice interaction abstract helgafell a little eroded basaltic hyaloclastite ridge in southwest iceland formed in a single eruption under a pleistocene ice sheet the ice thickness at the eruption site was at least 500 m and it was probably located some 15 km from the glacier s snout the eruption created a 2 km long 0 8 km wide and initially 300 m high ridge gravity modelling indicates that helgafell has a bulk density of 1800 kg m 3 and that holocene lavas around it are 40 80 m thick this confirms that helgafell is predominantly made of hyaloclastite with pillow lavas and intrusions only making up a few percent of the total volume the southeast side is made of unsorted eruption fed hyaloclastites considered to have been piled up against an ice wall while moderately to well sorted water transported material is found on the northwest side glacier flow and meltwater drainage was towards the northwest the absence of basal pillow lavas suggests that magma fragmentation occurred from the onset of the eruption until its end the lithofacies preserved indicate a fully subglacial eruption although a final subaerial eruptive phase may have taken place through an ice chimney the volatile contents h 2 o 0 26 0 37 wt of several glass samples from the southeast side of the mountain indicate water pressures of 1 mpa throughout the eruption efficient syn eruptive drainage of meltwater coupled with rapid ice subsidence probably led to partial dynamic support of the ice causing water pressure in the vault to be much lower than the static load of the overlying ice observed lack of correlation between elevation and volatile content may be a consequence of gradual reduction in dynamic support as the eruption rate declined and the edifice grew higher helgafell demonstrates that explosive activity may occur under 500 m thick ice and it may be an analogue to the ridge formed in the gjalp eruption in 1996

wind and wave influences on sea ice floe size and leads in the beaufort and chukchi seas during the summer fall transition 2014 sea ice floe size distribution and lead properties in the beaufort and chukchi seas are studied in the summer fall transition 2014 to examine the impact on the sea ice cover from storms and surface waves floe size distributions are analyzed from medea landsat8 and radarsat 2 imagery with a resolution span of 1 100 m landsat8 imagery is also used to identify the orientation and spacing of leads the study period centers around three large wave events during august september 2014 identified by swift buoys and wavewatch iii model data the range of floe sizes from different resolutions provides the overall distribution across a wide range of ice properties and estimated thickness all cumulative floe size distribution curves show a gradual bending toward shallower slopes for smaller floe sizes the overall slopes in the cumulative floe size distribution curves from landsat8 images are lower than while those from radarsat 2 are similar to previously reported results in the same region and seasonal period the medea floe size distributions appeared to be sensitive to the passage of storms lead orientations regardless of length correlate slightly better with the peak wave direction than with the mean wave direction their correlation with the geostrophic wind is stronger than with the surface wind the spacing between shorter leads correlates well with the local incoming surface wavelengths obtained from the model peak wave frequency the information derived shows promise for a coordinated multisensor study of storm effects in the arctic marginal ice zone

major effusive eruptions and recent lava fountains balance between expected and erupted magma volumes at etna volcano 1 over the last four decades etna has shown a high output rate through numerous eruptions the volcano has displayed two eruptive behaviors the first is characterized by effusive eruptions that efficiently drained the storage system and emitted large volumes of magma the second behavior is related to lava fountains erupting small magma batches which are normally with high frequency and have been considered as precursors of major effusive eruptions in this paper we present an updated estimation of emitted volumes from etna eruptions which include the 38 lava fountain episodes that occurred from january 2011 to april 2013 these recent explosive episodes have been frequent discharging significant magma volumes observing the steady trend of magma output over time we present insights on expected erupted volumes we highlight that the january 2011 to april 2013 lava fountains efficiently drained the intermediate shallow storage system and favored a balance between the incoming and outgoing magma

ice floe distribution in the sea of okhotsk in the period when sea ice extent is advancing 1 ice floe distribution in the sea of okhotsk during a cold air outbreak was investigated by analyzing several thousand of sea ice images obtained by the aircraft observation on 18 february in 2000 the effective floe size became small from 10 m to 2 m within the marginal ice zone miz the scaling properties of floe distribution are demonstrated by a cumulative number frequency which follows a power law scaling with an exponent the value of increased from 1 5 within the internal ice zone to 2 1 within the miz which means that relatively small ice floes dominate in the miz the effective width of the miz estimated by a wave attenuation theory agreed with the observed width suggesting that the flexural stress of waves penetrating into the ice is one of the possible mechanisms which cause the difference in the scaling property

measurements of total carbon dioxide and alkalinity by potentiometric titration in the geosecs program abstract approximately 6000 determinations of the alkalinity and total carbon dioxide content of seawater have now been made in the atlantic pacific and indian oceans as part of the geosecs program by a computer controlled potentiometric titration technique the equations used to locate the equivalence points of the carbonic acid system on this titration curve were developed in 1971 but have not previously been published these functions may be represented by f 1 v 2 v v 0 n h k 1 c v 0 v v 0 h h s o 4 h f b o h 4 1 h k 1 c f 2 v 0 v v 0 h h s o 4 h f h c o 3 upon inspection these functions are analogous to the modified gran functions of hansson and jagner 25 with the omission of the contributions of oh and co 3 2 and with the contribution of b oh 4 being assessed at a chlorinity of 19 for all samples reprocessing the original titration e m f volume data with appropriate corrections and modified gran functions reveals an error of about 12 mol kg in the geosecs total carbon dioxide data in addition the protonation of dissolved phosphate species during the titration results in a contribution to measured total carbon dioxide equal to the total phosphate concentration differences in the application of the geosecs functions between the atlantic and the pacific indian oceans expeditions are also to be found so that the error deriving from this source for the atlantic expedition was only 5 mol kg the application of the correct functions increases precision enabling smaller differences such as those attributable to fossil fuel carbon dioxide potentially to be observed and increases accuracy so that the error in titrator total carbon dioxide previously diagnosed by takahashi 14 can be logically accounted for

gas exchange and co2 flux in the tropical atlantic ocean determined from 222rn and pco2 measurements measurements of sup 222 rn vertical profiles and pco sub 2 in the surface water and the atmosphere were made simultaneously in the tropical atlantic ocean as part of the tto tas program the gas exchange rate or piston velocity was determined from the sup 222 rn profiles and the delta pco sub 2 between the surface ocean and the atmosphere was determined from the pco sub 2 measurements the net flux of co sub 2 across the sea air interface was calculated from these two data sets the piston velocity ranged from 1 4 to 6 9 m d and was correlated with wind speed the slope of piston velocity versus wind speed was estimated to be between 0 3 and 1 1 m d m s the delta pco sub 2 ranged from minus 35 mu atm at 15 degree n 55 degree w to 64 mu atm at 5 degree s 28 degree w with the zero delta pco sub 2 isopleth located at about 10 degree n the high delta pco sub 2 values can be explained by lateral advection of surface water from the east with heating and biological consumption of co sub 2 and alkalinity during transit the net flux of co sub 2 was into the ocean north of 10 degree n latitude with values reaching a maximum of 1 4 mol m sup minus 2 yr sup minus 1 at 15 degree n 50 degree w south of 10 degree n more the net flux was out of the ocean reaching a maximum value of 2 7 mol m sup minus 2 yr sup minus 1 at 8 degree s 28 degree w the average net flux from 10 degree n to 10 degree s was 1 3 mol m sup minus 2 yr sup minus 1 out of the ocean which is equivalent to 0 15 gigatons of carbon per year if the flux determined applied throughout the year 56 refs 16 figs 4 tabs ss less

observed changes in sea ice floe size distribution during early summer in the western weddell sea abstract digital aerial photographs are used to measure the change in floe size distribution over an area of the western weddell sea during the ice station polarstern ispol program the results show a significant increase in the number of small floes and brash ice over a 23 day period from 9 december 2004 to 1 january 2005 this is attributed to a net divergence of the pack ice coupled with ice melt that caused ridges to relax and break into their component parts the net effect is a significant increase in total floe perimeter that is important for lateral melt and primary production near floe edges

size distribution and shape properties of relatively small sea ice floes in the antarctic marginal ice zone in late winter in the marginal sea ice zone miz where relatively small ice floes are dominant the floe size distribution is an important parameter affecting melt processes given the larger cumulative perimeter of multiple small floes compared with a single ice floe of the same area smaller ice floes are therefore subject to increased lateral melt however the available data have been very limited so far analysis of sea ice in the sea of okhotsk revealed that while floe size distribution is basically scale invariant a regime shift occurs at a size of about 40 m in order to extend this preliminary result to the antarctic miz and further examine the controlling factors the first concurrent ice floe size and ice thickness measurements were conducted in the northwestern weddell sea and off wilkes land around 64 s 117 e with a heli borne digital video camera in the late winter of 2006 and 2007 respectively the floe sizes ranged from 2 to 100 m our analysis shows 1 the scale invariance and regime shift are confirmed in both regions 2 the floe size at which regime shift occurs slightly increases from 20 to 40 m with ice thickness consistent with the theory of the flexural failure of sea ice and 3 the aspect ratio is 1 6 1 9 on average close to the previous results based on these results the processes affecting the floe size distribution and the subsequent implications on melt processes are discussed by applying a renormalization group method to interpret the scale invariance in floe size distribution the fractal dimension is related to the fragility of sea ice these results indicate the importance of wave ice interaction in determining the floe size distribution

sea ice melting and floe geometry in a simple ice ocean model a coupled sea ice ocean numerical model has been developed that addresses the role of floe geometry during summertime melting the model contains a diagnostic equation for average floe diameter in addition to the usual prognostic equations for ice volume per unit area and ice concentration the partition between melting on the top bottom and lateral side surfaces of floes is examined using time dependent simulations with differing initial average floe diameters the different parameterizations for bottom and lateral melting in the literature are also compared and found to vary significantly the results show that lateral melting is important only for floes with diameters less than o 30 m given atmospheric thermal forcing typical of the central arctic in summer this means that the decrease in ice concentration over the summer is a strong function of floe diameter in keeping with simple geometrical arguments in all cases about 80 of the net thermal energy that enters the ocean through leads goes toward melting ice while the rest warms the ocean

glacial conditions in the red sea in this paper results from previous studies on planktonic foraminifera 6 o and global sea level are combined to discuss climatic conditions in the red sea during the last glacial maximum 18 000 b p first the influence of 120 m sea level lowering on the exchange transport through the strait of bab el mandab is considered this strait is the only natural connection of the red sea to the open ocean next glacial red sea outflow salinity is estimated about 48 parts per thousand from the foraminiferal record combined these results yield an estimate of the glacial net water deficit which appears to have been quite similar to the present about 2 rn yf finally budget calculation of 6 o fluxes suggests that the glacial 6 o value of evaporation was about 50 of the present value this is considered to have resulted from substantially increased mean wind speeds over the glacial red sea which would have caused a rapid drop in the kinematic fractionation factor foro the sensitivity of the calculated values for water deficit and isotopic fractionation to the various assumptions and estimates is evaluated in the discussion improvents are to be expected especially through research on the glacial salinity contrast between the red sea and gulf of aden it is argued however that such future improvement will likely result in a worsening of the isotopic discrepancy thus increasing the need for an additional mechanism that influenced fractionation such as mean wind speed this study demonstrates the need for caution when calculating pal osaliniti s from 5 so records under the assumption that the modem s 5 so relation has remained constant through time previously overlooked factors such as mean wind speed may have significantly altered that relation in the past

power scaling and seasonal changes of floe areas in the arctic east siberian sea the cumulative number versus floe area distribution of seasonal sea floes from six satellite images of the arctic ocean during the summer breakup and melting is fit by two scale invariant power law scaling regimes for floe areas ranging from 30 to 28 400 000 m2 scaling exponents for larger floe areas range from 0 6 to 1 0 with an average of 0 8 scaling exponents for smaller floe areas range from 0 3 to 0 6 with an average of 0 5 the inflection point between the two scaling regimes ranges from 283 102 to 4850 102 m2 and generally moves from larger to smaller floe areas through the summer melting season the stability of the power scaling results is demonstrated for two of the images by dividing each in half and analyzing each half separately with the result that the scaling exponents and the size of the inflection points are nearly the same for each half as for the whole image we propose that the two scaling regimes and the inflection between them are established during the initial breakup of sea ice solely by the process of fracture the distributions of floe size regimes retain their scaling exponents as the floe pack evolves from larger to smaller floe areas from the initial breakup through the summer season due to grinding crushing fracture and melting the scaling exponents for floe area distribution are in the same range as those reported in previous studies of arctic floes and for the single scaling exponents found for crushed and ground geologic materials including streambed gravel lunar debris and artificially crushed quartz the single scaling exponent found for fault gouge falls below the range for floes possibly because the fracturing and grinding process in fault gouge takes place under high confining pressure a probabilistic model of fragmentation is proposed that generates a single power law scaling distribution of fragment size

the effect of a storm on the 1992 summer sea ice cover of the beaufort chukchi and east siberian seas for the summer beaufort chukchi and east siberian seas a variety of active and passive microwave satellite data are used to determine the response of the ice edge and interior to a storm specifically the study concentrates on a low pressure system that passed over the region between august 14 and 20 1992 with peak geostrophic winds of about 18 m s 1 through the use of the ers 1 imaging radar and the special sensor microwave imager the ice response is examined at two locations at the ice edge for a nearly stationary location in the chukchi sea and in the ice interior along three swaths in the beaufort chukchi and east siberian seas the ice edge observations show that the storm fractures the large floes into small floes some of which are advected into the adjacent warm water the ice interior observations show that the storm caused an increase in the open water amount and a shift in the floe size distribution toward smaller floes in the ice interior application of the cumulative number distribution n d where n is the number of floes per unit area that are no smaller than some floe diameter d shows that for d 1 km n behaves like d where lies in the range 1 8 2 9 our analysis also shows that this slope is not affected by the storm and is slightly larger near the ice edge

a review of modern coral δ18o and δ14c proxy records abstract this paper is a review of published modern coral 18 o and 14 c isotopic records that are at least 30 and 20 years long respectively the data are presented to show basin scale trends in both of these proxy records on decadal to centennial timescales the goal was to qualitatively integrate the general inter annual to centennial timescale variability revealed in these data as well as the statistical and modeling output results that have been produced using these coral records while many review papers typically include a representative subset of the data available this review aims to include as much of the available data as possible in general coral 18 o records show a long term warming and or freshening throughout the tropical oceans and agree with the noaa extended reconstruction sea surface temperature 2 ersst on decadal timescales in the western pacific it is most likely a freshening of the seawater 18 o that dominates the signal el nino southern oscillation enso variability dominates most 18 o records either by varying local seawater temperature or salinity depending on the regional oceanography climatology outside of the pacific enso affects seawater temperature and salinity via atmospheric or oceanic teleconnections post bomb coral 14 c records collectively show that the uptake of 14 c has been greatest in gyre water fed sites followed in descending order by western boundary current areas equatorial upwelling regions and eastern tropical pacific upwelling sites these surface water 14 c values indicate the proportion of surface water and or the residence time of water at the surface at a given location and can be used to model water mass mixing rates such models have only begun to be run and show that the amount of eastern pacific water entering the central south pacific increases during el ninos and that the indonesian throughflow is supplied year round by the north pacific comparing ocean circulation models with coral 14 c modelled circulation enables researchers to explore the mechanisms that drive seawater 14 c variability and fine tune their models in addition our comparison between the rate of coral 14 c increase between 1960 and 1970 and total anthropogenic co 2 uptake rates show general agreement demonstrating the value of coral records in understanding past carbon fluxes overall coral 18 o and 14 c proxy records represent natural archives of seawater conditions and are critical for studying the natural variability in local and regional patterns within and teleconnection patterns between the tropics extra tropics temperate and polar regions on intra annual to centennial timescales

photogrammetric observations of the lateral melt of sea ice floes melting of the sidewalls of ice floes affects the ice concentration and subsequently the heat and mass balance of the ice cover lateral melt was measured photogrammetrically during marginal ice zone experiments in the greenland sea in june and july 1983 and 1984 a medium format metric camera was used in the second year geometric control was established by surveying a set of targets on each measured floe floe perimeters were measured from sequential photographs and mean lateral melt was estimated to an accuracy of about 6 cm in 1984 melt rates increased from 3 cm d 1 on day 179 to 10 cm d 1 on day 193 the increase precedes the increase of water temperature noted by others on day 191

on the sources formation and circulation of red sea deep water red sea deep water is renewed from sources in the far north of the red sea upwelling of deep water throughout the basin maintains the sharp pycnocline with its base near the depth of the sill at bab el mandeb before now deep water renewal was thought to occur mainly by means of convective deep water formation in the north which renews the bottom water and gives rise to a southward flowing bottom current carbon 14 and 3he data from the geosecs indian ocean expedition lead to the identification of an additional volumetrically larger mode of northern deep water formation in which new deep water is injected immediately beneath the pycnocline this mode of deep water formation to be called the isopycnal mode also gives rise to a southward flowing current in this case at the top of the deep water mass geosecs data also demonstrate the existence at intermediate depths in the deep water of a return flow to the north the surface history in the nuclear era of the 14c in the deep water source region was reconstructed by direct radiocarbon measurements on annual growth bands of corals calculation then shows that new deep water forms in the convective mode at a rate of 0 05 0 01 sverdrup sv expressed as if the flow were continuous and is due principally to processes occurring in the mouth of the gulf of suez the injection beneath the pycnocline of new deep water formed in the isopycnal mode is 0 11 0 02 sv this new deep water appears to originate mainly in the extreme open northern red sea the gulf of aqaba makes a modest but significant contribution to both modes the total deep water renewal rate is about 0 16 sv yielding a bulk deep water residence time of about 36 years oxygen consumption in the deep water shows approximately exponential decrease of consumption rate with depth as expected on geological and geophysical grounds hydrographically significant fluxes of heat and salt from the sea floor into the red sea deep water are discernible in the hydrography helium 3 flux from the sea floor into the deep water is about 69 1 stp year

ice melt rates by steam condensation during explosive subglacial eruptions subglacial volcanism melts cavities in the overlying ice these cavities may be flooded with meltwater or they may be fully or partially drained we quantify for the first time heat transfer rates by condensation of steam on the walls and roof of a fully or partially drained subglacial eruption cavity our calculations indicate that heat fluxes of up to 1 mw m 2 may be obtained when the bulk vapor in the cavity is in free convection this is considerably smaller than heat fluxes inferred from ice penetration rates in recent subglacial eruptions forcing of the convection by momentum transfer from an eruption jet may allow heat fluxes of up to 2 mw m 2 consistent with values inferred for the gjalp 1996 subglacial eruption vapor dominated cavities in which vapor liquid equilibrium is maintained have thermal dynamic responses that are an order of magnitude faster than the equivalent flooded cavities

characteristics of sea ice floe size distribution in the seasonal ice zone 1 the size distribution of sea ice floes was observed by coordinated landsat imagery and video monitoring conducted from an icebreaker and a helicopter for an area 38 km 26 km in seasonal sea ice in the southern sea of okhotsk in february 2003 the combination of imagery on several scales allowed measurements of ice floes over three orders of magnitude from 1 m to 1 5 km two different regimes were observed floes larger than about 40 m have a power law number density with an exponent of 1 87 in the lower range of earlier results below 40 m the power law exponent is 1 15 the cause of these two different regimes is hypothesized to lie in the effects of swell on floes of different sizes and thicknesses the importance of the floe size distribution for lateral melting is elucidated

radiocarbon in the northern indian ocean two decades after geosecs 1 the 14c measurements in the arabian sea and the bay of bengal during the late 1990s offer a way to assess the temporal changes in the inventories of bomb 14c and its penetration into the ocean in two decades since geosecs expeditions 1977 1978 the mean penetration depth of bomb radiocarbon during geosecs 1977 1978 was 270 m which increased by 40 to 381 m in 1994 1998 the small changes in bomb 14c inventories significant increase in the mean penetration depths and lowering of the surface 14c values in the northern indian ocean indicate the temporal variation of bomb 14c in two decades is mainly through downward transfer through mixing with deeper waters the observed bomb 14c inventory in the northern indian ocean agrees with numerical model simulated values except at the equatorial indian ocean the high bomb 14c inventory at the equator can be attributed to lateral advection of 14c enriched waters from the pacific ocean through the indonesian archipelago the air sea co2exchange rates in the northern indian ocean calculated from the bomb 14c inventories range from 7 mol m 2 yr 1 in the northern bay of bengal to 20 mol m 2 yr 1 in the equatorial indian ocean net sea air flux of co2 estimated for the northern indian ocean between 0 and 25 n is 104 30 tgc yr 1 the bay of bengal is a net sink of atmospheric co2 1 0 4 tgc yr 1 while the arabian sea is a source of co2 69 21 tgc yr 1

declassified high resolution visible imagery for arctic sea ice investigations an overview abstract since 2009 subsets of declassified satellite images of arctic sea ice have been released as literal image derived products lidps with one meter resolution for scientific use the collections include imagery acquired over six fixed locations in the arctic basin since 1999 targeted acquisitions over drifting ice parcels from 2009 on provide an added dimension to the lidp archive this mode of acquisition is especially useful for capturing time varying processes during the melt season in this paper we describe the characteristics of lidps the extent of the current archive and highlight their uses for arctic sea ice science at this writing the archive of lidps is still quite limited and thus this paper illustrates the potential utility of the imagery we provide an overview of the retrieval of five sea ice parameters that would benefit significantly from the surface details afforded by the higher resolution lidps they include melt pond coverage open water fraction ridge height floe size and openings and closings two other uses are suggested measurement of lateral melt and the interpretation of radar backscatter the intent is to motivate geophysical uses of the lidp and future acquisitions results here suggest that the effective observations of sea ice parameters and especially their changes require more focused sampling strategies to address specific spatial and temporal sampling needs presently acquisitions of this type of imagery at fixed locations and drifting sites are being continued and lidps are added to the archive as they are released

interaction between volcanic plumes and wind during the 2010 eyjafjallajokull eruption iceland 1 estimates of volcanic source mass flux currently deduced from observations of plume height are crucial for ash dispersion models for aviation and population hazard this study addresses the role of the atmospheric wind in determining the height at which volcanic plumes spread in the atmosphere and the relationship between source mass flux and plume height in a wind field we present a predictive model of volcanic plumes that describes the bending over of the plume trajectory in a crosswind and show that model predictions are in accord with a dataset of historic eruptions if the profile of atmospheric wind shear is described the wind restricts the rise height of volcanic plumes such that obtaining equivalent rise heights for a plume in a windy environment would require an order of magnitude increase in the source mass flux over a plume in a quiescent environment our model calculations are used to calibrate a semi empirical relationship between the plume height and the source mass flux that explicitly includes the atmospheric wind speed we demonstrate that the model can account for the variations in plume height observed during the first explosive phase of the 2010 eyjafjallajokull eruption using independently measured wind speeds and show that changes in the observed plume height are better explained by changing meteorology than abrupt changes in the source mass flux this study shows that unless the wind is properly accounted for estimates of the source mass flux during an explosive eruption are likely to be very significant underpredictions of the volcanic source conditions

observations of the summer breakup of an arctic sea ice cover the arctic sea ice cover evolves dramatically through the summer melt season floe size distribution fsd is a critical parameter used to examine this change as the ice cover transitions from large rectilinear plates in spring to an ensemble of discrete rounded floes by midsummer the fsd at a given time impacts the dynamic and thermodynamic behavior of the ice cover focusing on the seasonal marginal ice zone in the beaufort and chukchi seas from may to september 2014 we present qualitative and quantitative results derived from national technical means high resolution imagery and supported by ice mass balance buoy data results indicate that as melt accelerates floe breaking pattern and therefore fsd is heavily influenced by the distribution of melt ponds discrete element model results using morphological conditions derived from analyzed satellite imagery confirmed that breaking occurs along ponds and perpendicular to applied stress

isotopic versus micrometeorologic ocean co2 fluxes a serious conflict eddy correlation measurements over the ocean give co2 fluxes an order of magnitude or more larger than expected from mass balance measurements using radiocarbon and radon 222 in particular smith and jones 1985 reported large upward and downward fluxes in a surf zone at supersaturations of 15 and attributed them to the equilibration of bubbles at elevated pressures they argue that even on the open ocean such bubble injection may create steady state co2 supersaturations and that inferences of fluxes based on air sea pco2 differences and radon exchange velocities must be made with caution we defend the global average co2 exchange rate determined by three independent radioisotopic means prebomb radiocarbon inventories global surveys of mixed layer radon deficits and oceanic uptake of bomb produced radiocarbon we argue that laboratory and lake data do not lead one to expect fluxes as large as reported from the eddy correlation technique that the radon method of determining exchange velocities is indeed useful for estimating co2 fluxes that supersaturations of co2 due to bubble injection on the open ocean are negligible that the hypothesis that smith and jones advance cannot account for the fluxes that they report and that the pco2 values reported by smith and jones are likely to be systematically much too high the co2 fluxes for the ocean measured to date by the micrometeorological method can be reconciled with neither the observed concentrations of radioisotopes of radon and carbon in the oceans nor the tracer experiments carried out in lakes and in wind wave tunnels

ice melt rates during volcanic eruptions within water drained low pressure subglacial cavities subglacial volcanism generates proximal and distal hazards including large scale flooding and increased levels of explosivity direct observation of subglacial volcanic processes is infeasible therefore we model heat transfer mechanisms during subglacial eruptions under conditions where cavities have become depressurized by connection to the atmosphere we consider basaltic eruptions in a water drained low pressure subglacial cavity including the case when an eruption jet develops such drained cavities may develop on sloping terrain where ice may be relatively shallow and where gravity drainage of meltwater will be promoted we quantify for the first time the heat fluxes to the ice cavity surface that result from steam condensation during free convection at atmospheric pressure and from direct and indirect radiative heat transfer from an eruption jet our calculations indicate that the direct radiative heat flux from a lava fountain a dry end member eruption jet to ice is c 25 kw m 2 and is a minor component the dominant heat transfer mechanism involves free convection of steam within the cavity we estimate the resulting condensation heat flux to be c 250 kw m 2 absorption of radiation from a lava fountain by steam enhances convection but the increase in condensing heat flux is modest at c 25 kw m 2 overall heat fluxes to the ice cavity surface are likely to be no greater than c 300 kw m 2 these are comparable with heat fluxes obtained by single phase convection of water in a subglacial cavity but much less than those obtained by two phase convection

ash from the eyjafjallajokull eruption iceland fragmentation processes and aerodynamic behavior 1 the fragmentation process and aerodynamic behavior of ash from the eyjafjallajokull eruption of 2010 are investigated by combining grain size scanning electron microscopy sem and quantitative particle morphology ash samples were collected on land in iceland at 3 55 km distance from the volcanic vent and represent various phases of the pulsating eruption the grain size is fine even for deposits close to the vent suggesting that the parent particle population at fragmentation consisted of a substantial amount of fine ash sem investigation reveals that ash produced during the first phase of the eruption consists of juvenile glass particles showing key features of magma water interaction suggesting that phreatomagmatism played a major role in the fragmentation of a vesicle poor magma in the last phase of the eruption fragmentation was purely magmatic and resulted from stress induced reaction of a microvesicular fragile melt the shape of ash as determined by quantitative morphology analysis is highly irregular rendering the settling velocity quite low this makes transportation by wind much easier than for other more regularly shaped particles of sedimentary origin we conclude that the combination of magma s fine brittle fragmentation and irregular particle shape was the main factor in the extensive atmospheric circulation of ash from the mildly energetic eyjafjallajokull eruption

gas exchange on mono lake and crowley lake california gas exchange coefficients have been determined for freshwater crowley lake and for saline mono lake through the use of a man made purposefully injected gas sulfur hexafluoride sf6 the concentration decreased from an initial value of 40 10 12 mol l to 4 10 12 mol l for mono lake and from 20 10 12 mol l to 1 10 12 mol l for crowley lake over a period of 6 weeks wind speed records from anemometers on the shore of each lake enabled us to determine the relationship between the gas exchange coefficient k and wind speed u the average wind speed and average exchange coefficient for the experiment were identical for the two lakes uav 2 9 m s kav 2 5 cm h despite a large difference in size and chemical composition from laboratory experiments and theoretical calculations it is estimated that for wind speeds observed over mono lake from july until december 1984 the exchange of co2 occurred 2 times faster than without chemical enhancement this is a factor of 4 lower than needed to explain the high invasion rate of 14c produced by nuclear bomb tests

observation of autumn freeze up in the beaufort and chukchi seas using the ers 1 synthetic aperture radar we present observations of the transition in sea ice backscattering signatures from late summer into early winter in the beaufort and chukchi seas during 1991 and 1992 using data from the ers 1 synthetic aperture radar sar we employ both analyzed surface temperature fields and direct observations of near surface temperature from drifting buoys consistent with previous surface based observations backscattering from sea ice surviving at the end of summer increases strongly and rapidly when temperatures fall below freezing for the final time in the autumn apparently because of increased volume scattering from bubbles in the upper part of the ice areally averaged backscattering sometimes overshoots typical winter multiyear ice values by 1 2 db before settling back over a period of approximately a week the backscattering temperature link forms a sufficient basis for an algorithm to estimate retrospectively from time series of sar images the date of freeze up defined here to be the date on which all liquid water in the bubbly upper layer of surviving sea ice freezes and remains frozen for the duration of the ensuing autumn and winter we present a prototype algorithm and use it to estimate freeze up dates in nine lagrangian cells in the beaufort sea during the autumn of 1992 we observe a 12 day spread in freeze up dates between latitudes of approximately 73 n and 82 n with dates in the northernmost cells of august 29 30 and those in the southernmost cells of september 7 two cells at latitudes of 75 n 77 n appear to freeze up earlier than cells further north but present uncertainties limit the significance of this observation

explosive rhyolite tuya formation classic examples from kerlingarfjoll iceland rhyolite eruptions in iceland mostly take place at long lived central volcanoes examples of which are found associated with each of the present day rift zone ice caps subglacial eruptions at kerlingarfjoll central volcano produced rhyolite tuyas that are notable for their exposures of early erupted pyroclastic material observations from a number of these edifices are synthesised into a general model for explosive rhyolite tuya formation eruptions begin with violent phreatomagmatic explosions that generate massive tuff mt but the influence of water quickly declines leading to the formation of massive lapilli tuffs mlt containing magmatically fragmented vesicular pumice and ash these are deposited rapidly near the vent probably by moist pyroclastic density currents confined by ice but not within a meltwater lake the explosive effusive transition is controlled by the ascent rate and gas content of the magma an unusual obsidian rich massive lapilli tuff lithofacies omlt is identified and interpreted as pyroclastic material that was intruded into gas fluidised deposits at the explosive effusive transition the effusive phase of eruption involves the emplacement of intrusions and lava caps intrusions of lava into the early erupted phreatomagmatic deposits are characterised by peperitic margins and the formation of hyaloclastite intrusions into stratigraphically higher levels of the pyroclastic material show more limited interaction with the host tephra and have microcrystalline cores large lava bodies with columnar jointed margins cap the tuyas and have intrusive basal contacts with the tephras the main influence of the ice is to confine the rhyolite eruptive products to immediately above the vent region this is in contrast to subglacial basaltic tuya forming eruptions which are characterised by the formation of meltwater lakes phreatomagmatic fragmentation and subaqueous deposition the lack of meltwater storage may reduce the potential for large jokulhlaups

the 1996 eruption at gjalp vatnajokull ice cap iceland efficiency of heat transfer ice deformation and subglacial water pressure the 13 day long gjlp eruption within the vatnajkull ice cap in october 1996 provided important data on ice volcano interaction in a thick temperate glacier the eruption produced 0 8 km 3 of mainly volcanic glass with a basaltic icelandite composition equivalent to 0 45 km 3 of magma ice thickness above the 6 km long volcanic fissure was initially 550 750 m the eruption was mainly subglacial forming a 150 500 m high ridge only 2 4 of the volcanic material was erupted subaerially monitoring of the formation of ice cauldrons above the vents provided data on ice melting heat flux and indirectly on eruption rate the heat flux was 5 6 10 5 wm 2 in the first 4 days this high heat flux can only be explained by fragmentation of magma into volcanic glass the pattern of ice melting during and after the eruption indicates that the efficiency of instantaneous heat exchange between magma and ice at the eruption site was 50 60 if this is characteristic for magma frag mentation in subglacial eruptions volcanic material and meltwater will in most cases take up more space than the ice melted in the eruption water accumulation would therefore cause buildup of basal water pressure and lead to rapid release of the meltwater continuous drainage of meltwater is therefore the most likely scenario in subglacial eruptions under temperate glaciers deforma tion and fracturing of ice played a significant role in the eruption and modified the subglacial water pressure it is found that water pressure at a vent under a subsiding cauldron is substantially less than it would be during static loading by the overlying ice since the load is partly compensated for by shear forces in the rapidly deforming ice in addition to intensive crevassing due to subsidence at gjlp a long and straight crevasse formed over the southernmost part of the volcanic fissure on the first day of the eruption it is suggested that the feeder dyke may have overshot the bedrock ice interface caused high deformation rates and fractured the ice up to the surface the crevasse later modified the flow of meltwater explaining surface flow of water past the highest part of the edifice the dominance of magma fragmentation in the gjlp eruption suggests that initial ice thickness greater than 600 700 m is required if effusive eruption of pillow lava is to be the main style of activity at least in similar eruptions of high initial magma discharge

radiocarbon in corals from the cocos keeling islands and implications for indian ocean circulation annual bands of a porites coral from the cocos keeling islands eastern indian ocean were analysed by radiocarbon for 1955 1985 ad a rapid oceanic response of the site to bomb c is found with a maximum c value of 132 in 1975 this value is considerably higher than those for the northwestern indian ocean suggesting that surface waters reaching cocos are not derived from the arabian sea instead c values for cocos and those for watamu kenya agree well over most of the study interval suggesting that the south equatorial current carries c elevated water rather than c depleted water westward across the indian ocean this implies that oceanic upwelling in the northwestern indian ocean is spatially confined with little contribution to the upper limb of the global thermohaline circulation copyright 2005 by the american geophysical union

ice volcano interactions during the 2010 eyjafjallajokull eruption as revealed by airborne imaging radar 1 during the eruption of the ice covered eyjafjallajokull volcano a series of images from an airborne synthetic aperture radar sar were obtained by the icelandic coast guard cloud obscured the summit from view during the first three days of the eruption making the weather independent sar a valuable monitoring resource radar images revealed the development of ice cauldrons in a 200 m thick ice cover within the summit caldera as well as the formation of cauldrons to the immediate south of the caldera additionally radar images were used to document the subglacial and supraglacial passage of floodwater to the north and south of the eruption site the eruption breached the ice surface about four hours after its onset at about 01 30 utc on 14 april 2010 the first sar images obtained between 08 55 and 10 42 utc show signs of limited supraglacial drainage from the eruption site floodwater began to drain from the ice cap almost 5 5 h after the beginning of the eruption implying storage of meltwater at the eruption site due to initially constricted subglacial drainage from the caldera heat transfer rates from magma to ice during early stages of cauldron formation were about 1 mw m 2 in the radial direction and about 4 mw m 2 vertically meltwater release was characterized by accumulation and drainage with most of the volcanic material in the ice cauldrons being drained in hyperconcentrated floods after the third day of the eruption meltwater generation at the eruption site diminished due to an insulating lag of tephra

late holocene radiocarbon variability in northwest atlantic slope waters abstract deep sea gorgonian corals secrete a 2 part skeleton of calcite derived from dissolved inorganic carbon at depth and gorgonin derived from recently fixed and exported particulate organic matter radiocarbon contents of the calcite and gorgonin provide direct measures of seawater radiocarbon at depth and in the overlying surface waters respectively using specimens collected from northwest atlantic slope waters we generated radiocarbon records for surface and upper intermediate water layers spanning the pre and post bomb 14 c eras in labrador slope water lsw convective mixing homogenizes the pre bomb 14 c signature 67 4 to at least 1000 m depth surface water bomb 14 c signals were lagged and damped peaking at 45 in the early 1980s relative to other regions of the northwest atlantic and intermediate water signals were damped further off southwest nova scotia the vertical gradient in 14 c is much stronger in surface water pre bomb 14 c averaged 75 5 at 250 475 m depth pre bomb 14 c oscillated quasi decadally between 80 and 100 likely reflecting interannual variability in the presence of labrador slope water vs warm slope water wsw finally subfossil corals reveal no systematic changes in vertical 14 c gradients over the last 1200 yr

the role of shortwave radiation in the summer decay of a sea ice cover heat balance models of ice leads and the underlying water column were used to investigate the role of shortwave radiation in the summer decay of a sea ice cover because of the potential importance of positive feedback between decreasing ice concentration and increasing solar input to the ocean particular emphasis was given to the treatment of heat transfer and lateral melting in leads the rate of heat loss to floe edges was calculated from lead temperatures using an empirical boundary layer parameterization coefficients for this parameterization were obtained from field measurements in the dynamically active ice cover of the greenland sea during the 1984 marginal ice zone experiment and in the static ice of mould bay northwest territories field coefficients were found to be considerably larger than those previously obtained in the laboratory suggesting that heat transfer rates near floe edges were controlled more by winds and currents than by local density differences model studies of individual leads indicate that heat losses to the atmosphere cause lateral melt rates to asymptotically approach a constant value as lead size increases thus although very wide leads transmit considerable energy to the underlying ocean they have relatively little effect on lateral melting other results provide information on the relative importance of horizontal heat transfer rates ice thickness floe perimeter atmospheric forcing and oceanic heat flux in general the calculations indicate that much of the shortwave radiation entering the ocean is absorbed below the ice where it contributes to bottom ablation rather than lateral melting this suggests that previous work has seriously overestimated the magnitude of the feedback between ice concentration and incident shortwave radiation

the distribution of bomb radiocarbon in the ocean water column inventories are calculated for bomb radiocarbon at all the stations occupied during the geosecs and norpax expeditions and for the available tto stations the pattern of global inventories obtained in this way suggests that a sizable portion of the bomb radiocarbon that entered the antarctic the northern pacific and the tropical ocean has been transported to the adjacent temperate zones a strategy for utilizing these inventory anomalies as constraints on global ocean circulation models is presented essential to this strategy are the improvement of our knowledge of the pattern of wind speed over the ocean the establishment of the wind speed dependence of the rate of gas exchange between the atmosphere and sea and the continued mapping of the distribution of bomb produced radiocarbon in the sea

ice melt rates in liquid filled cavities during explosive subglacial eruptions subglacial eruptions are often associated with rapid penetration of overlying ice and release of large flow rates of water as jokulhlaups observations of recent subglacial eruptions indicate rapid syn eruptive ice melting within liquid filled subglacial cavities but quantitative descriptions of possible heat transfer processes need to be developed calculations of heat flux from the ice cavity fluid to the melting ice surface indicate that up to 0 6 mw m 2 may be obtained for fluids undergoing single phase free convection similar to minimum estimates of heat flux inferred from observations of recent eruptions our model of boiling two phase free convection in subglacial cavities indicates that much greater heat fluxes in the range 3 5 mw m 2 can be obtained in the vent region of the cavity and may be increased further by momentum transfer from the eruption jet rapid magma water heat transfer from fragmented magma is needed to sustain these heat fluxes similar heat fluxes are anticipated for forced convection of subcooled cavity water induced by momentum transfer from an eruption jet these heat fluxes approach those required to explain jokulhlaup flow rates and rapid ice penetration rates by melting in some but not all recent eruptions

paleosalinity and δ18o a critical assessment in paleoceanography a traditional application of oxygen isotope ratios in fossil carbonate from deep sea cores concerns the reconstruction of paleotemperatures recently isotopic data have been increasingly employed in the reconstruction of paleosalinities as well this application involves a number of basic assumptions a critical review of which is presented here as the calculation of paleosalinity from 18o residuals assumes constant and linear surface water salinity s 18o relationships we investigate this basic assumption for areas with important and variable freshwater budget and or sea ice influences we show that it is particularly unwarranted to assume such temporally invariant linearity in temperate and subpolar seas because of the effects of freezing and melting more critically we argue that the determinant of many regions s 18o is advection not the local water balance so that the basic 18o of seawater in many regions of the world ocean would likely have changed in a manner somewhat different from that expected from the ice volume record although the differences may not be significant for the gross reconstruction of such features as past sea level we believe they do potentially bias paleosalinity reconstructions mostly toward high salinities to fully exploit the potential of oxygen isotope records as quantitative paleosalinity indicators both the spatial and temporal variabilities need to be constrained hence we recommend that 1 for any time slice of specific interest to paleoceanographic and paleoclimatological studies a coupled ocean atmosphere isotope model or at least an ocean isotope model driven by a paleoclimate isotope model should be used to define the distribution of the base mixing end member 18o of sea water 2 much further regional scale research is needed on flux rates and isotopic compositions of the various terms in the freshwater budget as well as on the variability in the various advective terms the latter variability may be assessed from reconstructions of past seaice distributions and of volume fluxes isotopic compositions of outflow from marginal seas and through sea straits passages

climatological evaporation seasonality in the northern red sea 1 the dynamic and thermodynamic processes that underlie the exceptionally high evaporation over the northern red sea are examined through a combination of data analysis and a simple numerical model we show that the key boundary layer dehumidifier is ageostrophic cross channel sea breezes this circulation develops semidiurnally in response to thermal gradients across the red sea s coasts because of disparate land ocean heat capacities during the summer day the thermally induced high pressure center over the red sea axis results in near surface flows from the red sea toward the neighboring deserts the strong divergence associated with these flows is maximized along the red sea axis and is accompanied by strong subsidence that suppresses boundary layer relative humidity by both reducing specific humidity and increasing temperatures because the summer nighttime reversed thermal gradients are smaller in magnitude the daytime circulation dominates over the nighttime in summer and thus dominates over the daily and seasonal means following similar reasoning we also devise a winter dehumidifier we conclude by advancing a simple means of estimating red sea evaporation under diverse paleoinsolation regimes and we show small but clear evaporation changes during the course of the holocene our estimates represent lower bounds and we plan to refine them in follow up work

bomb radiocarbon in the red sea a medium scale gas exchange experiment the history of bomb produced radiocarbon in the surface waters of the red sea and the western gulf of aden was reconstructed from annual growth bands of corals gulf of aden surface water entering the red sea and flowing to the north at the surface of the red sea becomes progressively enriched in bomb sup 14 c by air sea exchange of carbon dioxide with physical oceanographic observations and analysis as the basis of a simple model this progressive northward enrichment can be used to calculate a mean invasionn flux for co sub 2 across the red sea surface the co sub 2 invasion flux so calculated is 8 mol m sup 2 yr with an uncertainty of approximately 2 mol m sup 2 yr when combined with the extensive historical observations of wind speeds in the red sea the calculated co sub 2 invasion flux supports the empirical relationship between co sub 2 invasion and wind speed proposed by other workers sea surface pco sub 2 was measured at seven stations along the length of the red sea in january 1985 these pco sub 2 data show that in midwinter the net flux of co sub 2 across the red sea surface i e the difference between the invasion and evasion fluxes is approximately zero formore the red sea as a whole copyright american geophysical union 1989 less

the effect of possible taylor columns on the summer ice retreat in the chukchi sea the chukchi sea topography consists of a broad flat 50 m deep plain with two prominent shoals herald and hanna which have horizontal dimensions of about 100 km and rise to depths of about 30 m herald shoal in particular is a prominent isolated seamount which because of the warm water flux in summer through bering strait has a warm 0 1 m s 1 flow incident upon it examination of active and passive microwave imagery of the region for 1992 1994 shows that as the general ice cover recedes the ice remains preferentially over herald shoal for 3 4 weeks after the surrounding ice has melted a scale analysis suggests that the cause of the ice persistence is the formation of a taylor column over the shoal which traps cold water and ice above it a similar trapping of ice occurs over hanna shoal and on its eastern slope but the response is complicated by a very different topography and the northward flow down barrow canyon

the seasonal evolution of sea ice floe size distribution the arctic sea ice cover undergoes large changes over an annual cycle in winter and spring the ice cover consists of large snow covered plate like ice floes with very little open water by the end of summer the snow cover is gone and the large floes have broken into a complex mosaic of smaller rounded floes surrounded by a lace of open water this evolution strongly affects the distribution and fate of the solar radiation deposited in the ice ocean system and consequently the heat budget of the ice cover in particular increased floe perimeter can result in enhanced lateral melting we attempt to quantify the floe evolution process through the concept of a floe size distribution that is modified by lateral melting and floe breaking a time series of aerial photographic surveys made during the sheba field experiment is analyzed to determine evolution of the floe size distribution from spring through summer based on earlier studies we assume the floe size cumulative distribution could be represented by a power law d where d is the floe diameter the exponent as well as the number density of floes ntot are estimated from measurements of total ice area and perimeter as summer progressed there was an increase in as the size distribution shifted toward smaller floes and the number of floes increased lateral melting causes the distribution to deviate from a power law for small floe sizes

thermodynamics and fluid dynamics of effusive subglacial eruptions we consider the thermodynamic and fluid dynamic processes that occur during subglacial effusive eruptions subglacial eruptions typically generate catastrophic floods jokulhlaups due to melting of ice by lava and generation of a large water cavity we consider the heat transfer from basaltic and rhyolitic lava eruptions to the ice for typical ranges of magma discharge and geometry of subglacial lavas in iceland our analysis shows that the heat flux out of cooling lava is large enough to sustain vigorous natural convection in the surrounding meltwater in subglacial eruptions the temperature difference driving convection is in the range 10 100 c average temperature of the meltwater must exceed 4 c and is usually substantially greater we calculate melting rates of the walls of the ice cavity in the range 1 40 m day indicating that large subglacial lakes can form rapidly as observed in the 1918 eruption of katla and the 1996 eruption of gjalp fissure in vatnajokull the volume changes associated with subglacial eruptions can cause large pressure changes in the developing ice cavity these pressure changes can be much larger than those associated with variation of bedrock and glacier surface topography previous models of water cavity stability based on hydrostatic and equilibrium conditions may not be applicable to water cavities produced rapidly in volcanic eruptions energy released by cooling of basaltic lava at the temperature of 1200 c results in a volume deficiency due to volume difference between ice and water provided that heat exchange efficiency is greater than approximately 80 a negative pressure change inhibits escape of water allowing large cavities to build up rhyolitic eruptions and basaltic eruptions with less than approximately 80 heat exchange efficiency cause positive pressure changes promoting continual escape of meltwater the pressure changes in the water cavity can cause surface deformation of the ice laboratory experiments were carried out to investigate the development of a water cavity by melting ice from a finite source area at its base the results confirm that the water cavity develops by convective heat transfer