an inverse modeling study in fram strait part i dynamics and circulation abstract in order to reconstruct the circulation in the northern greenland sea between 77 n and 81 n and the exchanges with the arctic ocean through fram strait a variational inverse model is applied to the density field observed in summer 1984 during the mizex 84 experiment an estimate of the three dimensional large scale pressure field is obtained in which the solution is decomposed into a limited number of vertical modes and the mode amplitudes are described by piece wise polynomials on a finite element grid the solution should be consistent with a frictional depth integrated vorticity balance and with the density data the global model parameters are tuned to ensure agreement between the retrieved geostrophic velocity and independent currentmeter data in a companion paper schlichtholz and houssais 1999b the same method but without dynamical constraint is applied to the same hydrographic dataset to perform a detailed water mass analysis and to estimate individual water mass transports a comprehensive picture of the summer geostrophic circulation in fram strait is obtained in which northward recirculations in the east greenland current egc and various recirculations from the west spitsbergen current wsc to the egc are identified it is suggested that the branch of the wsc following the upper western slope of the yermak plateau turns westward beyond 81 n and recirculates southward along the lower slope then merging with a westward recirculating branch south of 79 n at 79 n a southward net transport of 6 5 sv is found in the egc which combined with a northward net transport of only 1 5 sv in the wsc results in a fairly large outflow of 5 sv from the arctic ocean to the greenland sea the inverse solutions show that in summer the local induction of vorticity by the wind stress curl or by meridional advection of planetary vorticity should be small so that in the egc and in the wsc the vorticity balance is mainly achieved between the bottom pressure torque and dissipation of vorticity through bottom friction a substantial barotropic flow associated with along slope potential energy gradients is indeed identified on both sides of the strait

introduction summer marginal ice zone experiments during 1983 and 1984 in fram strait and the greenland sea sphere is complicated by numerous land masses which largely confine it during the winter to the sea of okhotsk and to the bering labrador and greenland norwegian seas during the spring and summer the miz retreats from the peripheral seas generally the total extent of the northern miz is less than one half that of the southern numerous studies have demonstrated the sensitivity of weather and climate to the state of the polar ice cover and it is of fundamental importance to understand how annual and interannual variations in ice extent are related to large scale and mesoscale circulations in the atmosphere and ocean successful modeling and parameterization of processes which govern the location and state of the miz are important not only for predicting the impact of sea ice on global climate but also for furthering man s activities in the miz regions e g offshore oil exploration seaborne transport of arctic resources development of the rich fisheries close to the ice margin and naval operations in recent years realization of the scientific and economic significance of the miz has focused attention on the need for coordinated multidisciplinary studies of conditions and processes near ice open ocean boundaries and has led to the development of the marginal ice zone experiment mizex although of substantial interest the remoteness of the vast antarctic miz poses serious logistic difficulties and mizex efforts to date have concentrated on the more accessible northern miz considerable work has been carried out in the

seasonal variations in the west spitsbergen current estimated from bottom pressure measurements from 1982 to 1985 two pressure gauges were deployed across the continental shelf northwest of spitsbergen to determine the seasonal variations in the barotropic component of the west spitsbergen current the variation in current velocity was calculated after analysis and removal of the tidal signals and correction of the pressure difference across the 47 km section for bottom buoyancy effects the pressure derived velocity fluctuates about 10 cm s 1 peak to peak with the maximum northward flow occurring in the winter the maximum appears to the correlated with the seasonal cycle of wind stress curl in the northern greenland sea in fact the magnitude of the velocity variation corresponds to the sverdrup transport due to the fluctuation in wind stress curl at 79 n 7 5 e the idea that the observed variation might also be due to the spin up of the basin by wind stress curl is explored with two simple analytical models basin spin up does appear to be a possible cause however east greenland current velocity data from muench et al 1986 indicate that the fluctuation about the mean in the deep currents on the western side of the basin is northward in winter while basin spin up would produce a southward fluctuation this supports the idea that sverdrup transport dominates basin spin up at least at the margins of the basin the fluctuations in transport and heat flux though the pressure gauge section are estimated to be 2 sv and 30 to 60 tw peak to peak these values are major fractions of historical estimates of the mean transport and heat flux values in the west spitsbergen current and they are significant fractions of the total oceanic fluxes into the arctic ocean this suggests that long time series are required to make meaningful estimates of the heat budget of the arctic

origin of methane in high arsenic groundwater of taiwan evidence from stable isotope analyses and radiocarbon dating abstract groundwaters in the confined aquifers of the chianan and ilan coastal plains of taiwan are rich in dissolved methane ch4 serious endemic blackfoot disease which occurred in the chianan plain especially during ad1950 1970 has been demonstrated to have arisen from drinking highly reducing groundwater with abnormal arsenic and humic substance levels in order to explore the origin of ch4 and its hydrological implications stable carbon isotope ratios 13c and radiocarbon 14c ages of exsolved ch4 dissolved inorganic carbon dic and sedimentary biogenic sediments from a total of 34 newly completed water wells at 16 sites were determined the main results obtained are as follows 1 the 13 c ch 4 65 to 75 values indicate that except for one thermogenic sample 13 c ch 4 38 2 from the ilan plain all ch4 samples analyzed were produced via microbially mediated co2 reduction many 13cdic values are considerably greater than 10 and even up to 10 due to rayleigh enrichment during co2 reduction 2 almost all the 14c ages of ch4 samples from the shallow aquifer i

mixing in the west spitsbergen current abstract twenty eight profiles of temperature and salinity down to 1 km depth have been measured in the area north from the coast of svalbard to latitude 84 40 n between 0 and 32 e longitude they show atlantic waters of the west spitsbergen current entering the arctic ocean in a bifilimentary mode one filament following the coastline and the other 300 km farther north apparently following the continental shelf break the profiles show these filaments mixing into the ambient water in a series of intrusive layers which are remarkably uniform over distances of hundreds of kilometers a triple peak structure at the atlantic water maximum is the dominant oceanographic characteristic of the area with salt fingering occurring on the upper surface of the cold intrusions and indications of double diffusive exchanges through the lower surface a system or eddies or meanders is postulated as the mechanism for the production of multiple fronts allowing the intrusive layers to extend to distances much greater t

formation and pathways of north atlantic deep water in a coupled ice ocean model of the arctic north atlantic oceans we investigate the formation process and pathways of deep water masses in a coupled ice ocean model of the arctic and north atlantic oceans the intent is to determine the relative roles of these water masses from the different source regions arctic ocean nordic seas and subpolar atlantic in the meridional overturning circulation the model exhibits significant decadal variability in the deep western boundary current and the overturning circulation we use detailed diagnostics to understand the process of water mass formation in the model and the resulting effects on the north atlantic overturning circulation particular emphasis is given to the multiple sources of north atlantic deep water the dominant deep water masses of the world ocean the correct balance of labrador sea greenland sea and norwegian sea sources is difficult to achieve in climate models owing to small scale sinking and convection processes the global overturning circulation is described as a function of potential temperature and salinity which more clearly signifies dynamical processes and clarifies resolution problems inherent to the high latitude oceans we find that fluxes of deep water masses through various passages in the model are higher than observed estimates despite the excessive volume flux the nordic seas overflow waters are diluted by strong mixing and enter the labrador sea at a lighter density through strong subpolar convection these waters along with other north atlantic water masses are converted into the densest waters similar density to antarctic bottom water aabw in the north atlantic we describe the diminished role of salinity in the labrador sea where a shortage of buoyant surface water or excess of high salinity water leads to overly strong convection the result is that the atlantic overturning circulation in the model is very sensitive to the surface heat flux in the labrador sea and hence is correlated with the north atlantic oscillation as strong subpolar convection is found in other models we discuss broader implications

submarine landforms and ice sheet flow in the kvitoya trough northwestern barents sea high resolution geophysical and sediment core data are used to investigate the pattern and dynamics of former ice flow in kvitoya trough northwestern barents sea a new swath bathymetric dataset identifies three types of submarine landform in the study area streamlined landforms meltwater channels and cavities iceberg scours subglacially produced streamlined landforms provide a record of ice flow through kvitoya trough during the last glaciation flow directions are inferred from the orientations of streamlined landforms drumlins crag and tail features ice flowed northward for at least 135 km from an ice divide at the southern end of kvitoya trough a large channel cavity system incised into bedrock in the southern trough indicates that subglacial meltwater was present at the former ice sheet base modest landform elongation ratios and a lack of mega scale glacial lineations suggest that although ice in kvitoya trough was melting at the bed and flowed faster than the likely thin and cold based ice on adjacent banks a major ice stream probably did not occupy the trough retreat was relatively rapid after 14 13 5 14c kyr b p and probably progressed via ice sheet bed decoupling in response to rising sea level there is little evidence for still stands during ice retreat or of ice proximal deglacial sediments relict iceberg scours in present day water depths of more than 350 m in the northern trough indicate that calving was an important mass loss mechanism during retreat

a numerical investigation of the circulation in the greenland and norwegian seas abstract an ocean general circulation model is used to investigate the circulation in the greenland and norwegian seas the primitive equations are solved on 12 levels with a horizontal grid point distance of 20 km this resolution is sufficient to take into account mesoscale topographic structures which according to observations and the model results presented here have a large influence on the distribution of hydrographic variables however the model is not eddy resolving the baroclinic deformation radius in this region is about 5 km only at first a 2 year experiment is run with the forcing functions and the initial stratification derived from climatological annual mean data compared with quasi synoptic data the calculated temperature and salinity distributions show a much better adjustment to the topography than does the climatology the velocities and transports lie within the range of observed long term mean values the model fields obtained by this experiment are used to initialize another e

triggering of the hinlopen yermak megaslide in relation to paleoceanography and climate history of the continental margin north of spitsbergen 1 on the basis of the detailed sedimentological record of the key core ps66 309 1 and a review of open literature we present an assessment of the paleoenvironmental conditions as well as trigger mechanism of the hinlopen yermak megaslide north of spitsbergen the svalbard archipelago is characterized by strong inflow of atlantic water accompanied by rapidly falling sea level rapidly growing svalbard barents sea ice sheet and associated increasing glaciotectonic activity during the time window around 30 calendar kyr b p of this catastrophic failure event thus the potential trigger mechanisms include sediment buoyancy and excess pore pressure hydrate stability and tectonic glaciotectonic processes while the common scenarios seem to fail to explain this unique submarine megaslide we focus on glacial processes and their consequences for the regional tectonic framework we conclude that the hinlopen yermak megaslide has been the consequence of the rapid onset of late weichselian glaciation resulting in a drastic sea level drop asymmetrical ice loading and a forebulge development leading to enhanced tectonic movements along the hinlopen fault zone as the final trigger we assume a strong earthquake positioned below or close to the se sophia basin

diagnostic study of the fram strait marginal ice zone during summer from 1983 and 1984 marginal ice zone experiment lagrangian observations from 1984 marginal ice zone experiment observations in fram strait three main results concerning large scale mesoscale and summer marginal ice zone miz features are presented and discussed in this paper regarding the large scale the main conclusion is that the east greenland current egc is a narrow stable current in contradiction with past results presenting the egc as a broad and unstable current in the mesoscale the west spitsbergen current wsc and the norwegian current are the main generators for eddies in fram strait these eddies propagate northwestward preferentially following topographic features like fracture zones which are quite abundant in this region in our opinion these wsc eddies represent an important part of the atlantic water recirculation in fram strait when approaching the east greenland continental slope they interact with the egc and they form well developed eddies these ice edge eddies associated with ice edge tongues are quite recognizable with remote sensing techniques the summer marginal ice zone in fram strait is clearly characterized by sea ice concentrations from 1 10 to 3 10 and floe sizes limited to 1 km or less there is a well defined limit which separates the pack ice from the miz where no big ice floes are ever recorded the breaking action of waves and swell propagating into the ice are likely to be the only mechanisms explaining such a drastic filtering effect according to their amplitudes and directions winds and eddies act in the miz in shrinking or stretching this zone

on a modified arrested topographic wave in fram strait 1 the bottom geostrophic flow in fram strait is explained in terms of a modified arrested topographic wave model the model is based on a combination of the vorticity balance between the topographic vortex stretching and the bottom ekman pumping due to liner friction with a relation between the bottom flow and the bottom pressure gradient over a sloping bottom such a combination emphasizes a dynamical relevance of along isobath density variations at the bottom using an inverse solution based on the hydrographic data from the mizex 84 experiment it is shown that the along isobath bottom density variations should be dynamically important for example in the east greenland current a relatively high correlation between an along isobath distribution of the bottom geostrophic flow and the bottom density is reported for that current the density variations identified in the data should be able to drive a bottom geostrophic flow with a magnitude consistent with the inverse solution and observations

observations of a potential mars analog at the microscale using rover inspired methods a 10 sol observation of fort rock tuff ring 1 the terrestrial geologist s hand lens is a fundamental tool for identifying and correlating rocks and minerals we used rover inspired methods of remote hand lens scale data acquisition to conduct reconnaissance of a well characterized martian analog field site the objective was to determine if the current methodologies associated with the use of remote hand lens scale imagers maximizes science return field geologists provided with hand lens scale images of targets in geologic context could correctly identify many important characteristics of those targets however they could not fully confirm or rule out any formation hypothesis using the data provided solely through rover driven observational strategies this was due to 1 a lack of intermediate scale or millimeter to centimeter scale images providing important contextual information for the targets studied and 2 the limited number of hand lens scale images that were taken using rover driven methodology we conclude that the benefits of the hand lens as an effective triage tool and discriminator of microtexture are limited using current rover driven methodology because the hand lens type imager is not deployed frequently and resulting data cannot be used to fully support geochemical observations we recommend pursuing ways to increase the number of images that can reasonably be acquired at the hand lens scale in order for hand lens scale imaging to be fully effective textural characteristics diagnostic of the nature of a geologic site need to be identifiable at a number of different resolutions rover microscale observational strategies must include more contextual imaging

circulation and water masses of the east greenland shelf the water masses and circulation over the northern greenland continental shelf are described based on two cruises to the region during the summers of 1979 and 1984 the cold polar water over the shelf was found to increase notably in salinity toward the shelf break and the east greenland polar front a colder more saline and relatively isolated fraction of the polar water was identified just above the atlantic intermediate water of the front a middepth layer stable in time indicates little vertical heat exchange warm atlantic intermediate water was found to intrude close to the coast via a newly defined system of troughs in the shelf the polar water was found to circulate over the shelf in a clockwise gyre baroclinic transports northward near the coast with 0 58 sv mean flow and southward elsewhere with 1 47 sv mean flow yielded a net southward transport in the east greenland current of 0 89 sv

branching of atlantic water within the greenland spitsbergen passage an estimate of recirculation atlantic water aw supplies the largest source of heat mass and salt to the arctic ocean via fram strait greenland spitsbergen passage yet it represents only a fraction of the atlantic water that resides in the greenland iceland norwegian and barents seas this is a result of both the branching of the central core of aw along its northward flow and the modification of its t s signature through air sea ice interactions and internal mixing this paper addresses the quantitative analysis of the three dominant atlantic water cores within fram strait and north of 76 n using an 11 year 1977 to 1987 hydrographic database spatial variations of heat volume and salt along its flow path of some 600 km showed that the major core of atlantic water that directly enters the arctic ocean svalbard branch did not extend past 20 e of the 9719 km3 of atlantic water existing within the region one third resided within the svalbard branch the remainder 22 and 45 were held within the return atlantic current and the yermak branches respectively restricting the analysis to a southern limit of 79 n effectively removed the return atlantic current and showed a nearly equal split between the two remaining branches work completed by bourke et al 1988 indicated that the yermak branch is largely recirculated to the south if true this analysis supports rudels 1987 model estimate of a 50 recirculation of aw within this region

the gin sea a synthesis of its physical oceanography and literature review 1972 1985 abstract a synthesis and review of the physical oceanography of the gin sea greenland iceland and norwegian seas is presented an accompanying bibliography is included from 1972 through 1985 some 1986 works are also noted emphasis is placed on describing the gin sea as a major semi enclosed basin that plays a role unique among the world s oceans by providing a strong two way advective exchange between the ice covered polar sea and the north atlantic ocean and at the same time acting as the primary site for northern hemisphere bottom water formation the water masses for the gin sea are defined in a manner as consistent as possible with the literature the large scale oceanographic and meteorological factors influencing the water mass formation and circulation are described a sample calculation of the various horizontal and vertical thermohaline driven exchanges is given

late quaternary contourites and glaciomarine sedimentation in the fram strait two sites in the eastern fram strait the vestnesa ridge and the yermak plateau have been surveyed and sampled providing a depositional record over the last glacial interglacial cycle the fram strait is the only deep water connection from the arctic ocean to the north atlantic and contains a marine sediment record of both high latitude thermohaline flow and ice sheet interaction on the vestnesa ridge the western svalbard margin a sediment drift was identified in 1226 m of water gravity and multicores from the crest of the drift recovered turbidites and contourites 14c dating indicates an age range of 8287 to 26 900 years bp early holocene to late weichselian the yermak plateau is characterized by slope sediments in 961 m of water gravity and multicores recovered contourites and hemipelagites 14c ages were between 8615 and 46 437 years bp early holocene to mid weichselian downcore dinoflagellate cyst analyses from both sites provide a record of changing surface water conditions since the mid weichselian suggesting variable sea ice extent productivity and polynyas present even during the last glacial maximum four layers of ice rafted debris were also identified and correlated within the cores these events occurred ca at 9 24 to 25 26 to 27 and 43 ka asynchronous with heinrich layers in the wider north east atlantic and here interpreted as reflecting instability in the svalbard barents ice sheet and the northward advection of warm atlantic water during the late weichselian the activity of the ancestral west spitsbergen current is interpreted using mean sortable silt records from the cores on the vestnesa ridge drift the modern mass accumulation rate calculated using excess 210pb is 0 076 g cm 2 year 1 on the yermak plateau slope the modern mass accumulation rate is 0 053 g cm 2 year 1

laboratory simulation of exchange through fram strait laboratory experiments and theory were conducted to observe the flow patterns and transport in both buoyancy driven and wind driven rotating fluids in lock exchange experiments water with one density flows into a second basin after a sliding gate is removed water of a second density flows back into the first basin the size and location of the currents for various values of density difference rotation rate and assorted sidewall geometries was recorded volume flux of the fluid was also measured and compared with a theory for lock exchange flow of a rotating fluid in a separate group of experiments with a passive upper layer easterly winds like those in the arctic ocean drive the upper level water into the arctic ocean and therefore oppose the buoyant exchange westerly winds would drive the water out of the arctic ocean this indicates that the exchange between the arctic ocean and the greenland norwegian sea is likely to be driven by buoyancy rather than by driven by wind crude estimates of the volumetric and fresh water exchange rate from the lock exchange formulas are compared with observed ocean fluxes and approximate agreement is found

a model based study of ice and freshwater transport variability along both sides of greenland we investigate some aspects of the variability of the arctic freshwater content during the 1965 2002 period using the drakkar eddy admitting global ocean sea ice model 12 km resolution in the arctic a comparison with recent mooring sections shows that the model realistically represents the major advective exchanges with the arctic basin through bering fram and davis straits and the barents sea this allows the separate contributions of the inflows and outflows across each section to be quantified in the model the arctic freshwater content variability is explained by the sea ice flux at fram and the combined variations of ocean freshwater inflow at bering and outflow at fram and davis at all routes except trough fram strait the freshwater transport variability is mainly accounted for by the liquid component with small contributions from the sea ice flux the ocean freshwater transport variability through both davis and fram is controlled by the variability of the export branch baffin island current and east greenland current respectively the variability of the inflow branches playing a minor role we examine the respective role of velocity and salinity fluctuations in the variability of the ocean freshwater transport fram and davis straits offer a striking contrast in this regard freshwater transport variations across davis strait are completely determined by the variations of the total volume flux 0 91 correlation on the other hand the freshwater transport through fram strait depends both on variations of volume transport and salinity as a result there is no significant correlation between the variability of freshwater flux at fram and davis although the volume transports on each side of greenland are strongly anti correlated 0 84 contrary to davis strait the salinity of water carried by the east greenland current through fram strait varies strongly due to the ice ocean flux north of greenland

transports of nordic seas water masses and excess sf6 through fram strait to the arctic ocean to determine the exchanges between the nordic seas and the arctic ocean through fram strait is one of the most important aspects and one of the major challenges in describing the circulation in the arctic mediterranean sea especially the northward transport of arctic intermediate water aiw from the nordic seas into the arctic ocean is little known in the two ship study of the circulation in the nordic seas arctic ocean 2002 the swedish icebreaker oden operated in the ice covered areas in and north of fram strait and in the western margins of greenland and iceland seas while rv knorr of woods hole worked in the ice free part of the nordic seas here two hydrographic sections obtained by oden augmented by tracer and velocity measurements with lowered acoustic doppler current profiler ladcp are examined the first section reaching from the svalbard shelf across the yermak plateau covers the region north of svalbard where inflow to the arctic ocean takes place the second western section spans the outflow area extending from west of the yermak plateau onto the greenland shelf geostrophic and ladcp derived velocities are both used to estimate the exchanges of water masses between the nordic seas and the arctic ocean the geostrophic computations indicate a total flow of 3 6 sv entering the arctic on the eastern section the southward flow on the western section is found to be 5 1 sv the total inflow to the arctic ocean obtained using the ladcp derived velocities is much larger 13 6 sv and the southward transport on the western section is 13 7 sv equal to the northward transport north of svalbard sulphur hexafluoride sf6 originating from a tracer release experiment in the greenland sea in 1996 has become a marker for the circulation of aiw from the geostrophic velocities we obtain 0 5 sv and from the ladcp derived velocities 2 8 sv of aiw flowing into the arctic the annual transport of sf6 into the arctic ocean derived from geostrophy is 5 kg year which is of the same magnitude as the observed total annual transport into the north atlantic while the ladcp measurements 19 kg year imply that it is substantially larger little sf6 was found on the western section confirming the dominance of the arctic ocean water masses and indicating that the major recirculation in fram strait takes place farther to the south

multiple origins of methane in the earth methane occurrences in the earth s crust are predominantly of biogenic origin i e their ultimate source is biologically formed organic matter methane can also form through inorganic reactions and is consequently termed abiogenic biogenic methanes can either form through bacterial or thermogenic processes bacterial processes follow a co2 reduction and or fermentation pathway the fermentation processes are quantitatively more important in recent fresh sediments and swamps methane formed by co2 reduction however is most common in older sediments and commercial gasfields temperature organic substrate and age may be the major factors controlling the relative importance of the two pathways stable isotope concentrations in thermogenic methanes seem to be controlled by the extent of conversion of organic matter the timing of gas expulsion and trapping the different character of methane in individual sedimentary basins may be a result of the geologic history geothermal methanes are most likely derived from pyrolysis of organic matter abiogenic methane occurs in hydrothermal vents and ophiolite complexes inorganic reactions either surficial or deep seated are the likely source of such methanes a uniform mantle origin of methane is not supported by the observed isotope variations in naturally occurring methanes

environmental variability off ne greenland western fram strait during the past 10 600 years to reconstruct the climatic and paleoceanographic variability offshore northeast greenland during the last 10 ka with multidecadal resolution sediment core ps93 025 from the outermost north east

changes in current patterns in the fram strait at the pliocene pleistocene boundary seismic reflection profiles from the northwestern and central part of the fram strait show thick packages of drift type sediments mainly along the western yermak plateau flank but also in the central flat part of the fram strait north of 80 5 n a large scale field of sediment waves along the yermak plateau rise separates a western lower from an eastern upper drift body these drift bodies were deposited by bottom currents most likely the northbound yermak branch of the west spitsbergen current but we cannot rule out that the western drift body may also have been influenced by southbound bottom currents a stratigraphic boundary is clearly visible within the drift bodies and even more pronounced within the sediment waves separating a lower package of waves migrating upslope at low angle 5 from an upper package with significantly increased wave crest migration 16 5 this stratigraphic boundary could be tracked along the seismic network and corresponds to the lithostratigraphic boundary between units ia and ib at odp leg 151 site 911 that was dated to 2 7 ma the increase in wave crest migration angle indicates a shift towards higher sedimentation rates at 2 7 ma which corresponds to the intensification of the northern hemisphere glaciation with a major expansion of the greenland scandinavian northern barents sea and north american ice sheets the subaerially exposed barents shelf and the expansion of the northern barents sea ice sheet as well as svalbard are likely sources for enhanced erosion and enhanced fluvial input along the pathway of the west spitsbergen current resulting in higher sedimentation rates in the fram strait

an inverse modeling study in fram strait part ii water mass distribution and transports abstract a water mass analysis is carried out in fram strait between 77 15 and 81 15 n based on three dimensional large scale potential temperature and salinity distributions reconstructed from the mizex 84 hydrographic data collected in summer 1984 combining these distributions with the geostrophic flow field derived from the same data in a companion paper schlichtholz and houssais 1999 the heat fresh water and volume transports are estimated for each of the water masses identified in the strait twelve water masses are selected based on their different origins among them the polar water pw enters fram strait from the arctic ocean both over the greenland slope and over the western slope of the yermak plateau in the atlantic water aw range four modes with distinct geographical distributions are indentified in the deep water range the eurasian basin deep water ebdw is confined to the lena trough and to the molloy deep area where it is involved in a cyclonic circulation the warm and shallower mode of the norwegian sea deep water nsdw concentrated to the west is mainly seen as an outflow from the arctic ocean while the cold and deeper mode essentially observed to the east enters the strait from the greenland sea apart from the ebdw there is a tendency for all water masses of polar origin to flow along the greenland slope the two most abundant water masses the aw and the nsdw occupy as much as 67 of the total water volume the southward net transport of pw through fram strait is about 1 sv at 78 9 n at the same latitude the net transport of aw is southward and equal to about 1 7 sv only the transport of the warm mode aww is northward amounting to 0 2 sv the overall net outflow of the deep waters to the greenland sea is about 2 6 sv two upper water masses the fresh aw f and the cold awc mode of the aw and one deep water mass the nsdw appear to be produced in the strait with production rates between 77 6 and 79 9 n of about 0 2 1 0 and 1 7 sv respectively a southward net fresh water transport through the strait of about 2000 km 3 yr 1 relative to a salinity of 34 93 is mainly due to the pw the net heat transport relative to 0 1 c is northward but undergoes a rapid northward decrease suggesting an area averaged surface heat loss of 50 100 w m 2 in the strait

thermohaline circulation in the arctic mediterranean seas the renewal of the deep north atlantic by the various overflows of the greenland scotland ridges is only one manifestation of the convective and mixing processes which occur in the various basins and shelf areas to the north the arctic ocean and the greenland iceland and norwegian seas collectively called the arctic mediterranean the traditional site of deep ventilation for these basins is the greenland sea but a growing body of evidence also points to the arctic ocean as a major source of deep water this deep water is relatively warm and saline and it appears to be a mixture of dense brine enriched shelf water with intermediate strata in the arctic ocean the deep water exits the arctic ocean along the greenland slope to mix with the greenland sea deep water conversely very cold low salinity deep water from the greenland sea enters the arctic ocean west of spitsbergen within the arctic ocean the lomonosov ridge excludes the greenland sea deep water from the canadian basin leaving the latter warm saline and rich in silica in general the entire deep water sphere of the arctic mediterranean is constrained by the greenland scotland ridges to circulate internally therefore it is certain of the intermediate waters formed in the greenland and iceland seas which ventilate the north atlantic these waters have a very short residence time in their formation areas and are therefore able to rapidly transmit surface induced signals into the deep north atlantic

winter oceanographic conditions in the fram strait yermak plateau region temperature salinity and currents were measured in the yermak plateau and northern fram strait region during march april 1989 an isothermal upper layer was near the freezing point everywhere except seaward of the ice edge near western svalbard temperatures in the underlying atlantic water layer decreased in general toward the northwest from maximum values in the west spitsbergen current west of svalbard mesoscale features were superimposed on this trend and the most apparent of these was a middepth 200 300 m warm filament overlying the northwestern flank of the plateau currents in the warm filament were northward at 2 4 cm s for a 10 day period in april providing a possible advective explanation for presence of the filament the mechanism for these currents may involve topographic control over a western extension of the north flowing west spitsbergen current or alternately rectification of diurnal currents which are enhanced by the bottom topography of the plateau our data favor the tidal rectification mechanism a warm core anticyclonic eddy associated with the filament contained atlantic water which was virtually unmodified from that occurring more than 200 km farther south characteristics of this eddy were consistent with an origin in the west spitsbergen current in the upper layer a generally cyclonic baroclinic circulation was present about the plateau measured upper layer current speeds were greatest 8 cm s in the southward flowing east greenland current where they exceeded the baroclinic currents by approximately 1 cm s which may represent a southward barotropic component farther to the northeast both measured and baroclinic upper layer currents were weak and variable

changes in the properties and distribution of the intermediate and deep waters in the fram strait abstract the fram strait is the only deep connection between the arctic ocean and the nordic seas greenland iceland and norwegian seas with a sill depth of approximately 2600 m consequently observations from this area reflect changes in the deep waters of the arctic mediterranean possible changes in the properties and distribution of the intermediate and deep water masses passing through the fram strait have been studied for the period from 1982 to 2008 at a zonal section at 79 n with special emphasis on the period from 1997 to 2008 the temperature of the arctic intermediate water shows large interannual variability where the period from 2002 to 2004 was especially cold indicating a strong winter convection in the nordic seas prior to those years the deep water originating from the norwegian sea has become warmer by about 0 10 c during the study period the changes in the properties of the norwegian sea deep water are caused by changes in its composition i e an increasing fraction of the eurasian basin deep water and a decreasing fraction of the greenland sea deep water each year if this trend continues the norwegian sea deep water will have similar characteristics as the eurasian basin deep water in about 15 years a prominent feature seen in the s diagrams from the deep fram strait is the disappearance of water with the characteristics of greenland sea deep water this very cold water temperature below 1 1 c was not observed after 1997 and the minimum temperature in the strait increased by 0 24 c between 1982 and 2008 in the fram strait the fraction of intermediate waters has increased while the fraction of deep waters from the nordic seas has decreased the fraction of deep waters originating from the arctic ocean shows no trend

the westward turning branch of the west spitsbergen current a salinity temperature survey of fram strait in september 1985 extending to north of 81 n demonstrated the western branch of the west spitsbergen current flowing northwest and then west mainly south of 81 n there also was a southwestward recirculation from the eastern branch of the west spitsbergen current baroclinic flow of warm water northward through 81 n was negligible or zero some doubt is cast on past flow diagrams based on core analysis which show the western branch of the west spitsbergen current coursing northward to 83 n one of a probable line of mesoscale eddies is described in some detail

current regimes across the east greenland polar front at 78 40 north latitude during summer 1984 four weeks of concurrent temperature and current observations from three moorings across the east greenland polar front at approximately 78 40 n showed pronounced differences between the current regimes on either side of the front east of the front vertical shear was minimal mean flow was not statistically significant and fluctuations showed evidence of wind influence west of the front vertical shear and southward mean flow were significant however observed fluctuations were not strongly influenced by local winds the mean current and density structure of the front was similar to that of a two layer boundary current model with constant potential vorticity current fluctuations west of the front were in part related to mesoscale features generated farther north and subsequently advected downstream by the east greenland current or to eddylike features apparently generated through potential vorticity conservation local instabilities of the front most likely account for the remainder of the mesoscale variability seen in the records

high resolution paleoproductivity fluctuations during the past 24 kyr as indicated by benthic foraminifera in the marginal arctic ocean abstract analyses of benthic foraminifera in sediment cores taken at about 1000 m water depth at the yermak plateau and the barents sea slope adjacent to the position of the ice sheet edge during the last glacial maximum show that paleoproductivity was reduced to about a third of its present level during peak glacial stadials these reduced values are still higher than values for modern permanently ice covered regions suggesting that the core locations were at least partially ice free even during stadials paleoproductivity at the core locations was higher than or equal to that of today during initial deglaciations and warm substages peak paleoproductivity occurred in samples with low salinity surface waters as indicated by oxygen isotope values of planktonic foraminifera and slightly after increased abundance of atlantic species suggesting that enhanced advection of warmer waters from the atlantic supported the initial ice sheet retreat during the holocene climatic optimum productivity was much less than at present on the yermak plateau high at the barents sea site perhaps because of increased advection of atlantic water to the latter site and heavier ice coverage at the former after this optimum paleoproductivity at both sites was similar with slightly lower values during cold periods such as the little ice age

large scale oceanography in fram strait during the 1984 marginal ice zone experiment the pattern of large scale circulation in fram strait during summer 1984 is inferred from hydrographic data and water mass analysis and direct current observations by use of surface and subsurface floats the west spitsbergen current carrying warm and salty atlantic water splits into several branches two flowing northward into the arctic ocean and two turning westward causing a recirculation across the main axis of fram strait the individual flow paths are topographically controlled suggesting a strong barotropic component of the circulation

interpretations of the jebar term abstract in diagnostic calculations of the ocean s circulation the so called jebar joint effect of baroclinicity and relief term may induce a significant depth average current field as has been noted in the oceanographic literature here we present two consistent interpretations of this term in the equation governing the vorticity of the depth averaged current a topographic vortex stretching term proportional to the dot product of depth averaged velocity and the depth gradient arises we show that jebar corrects this term by removing the contribution of the geostrophic flow referenced to the bottom which cannot generate topographic vortex stretching in the evolution equation for the vorticity of the depth integrated flow a bottom torque term is present we show that the jfbar term discussed above enters here as a contribution to the bottom torque emphasizing the role of jebar as a forcing term we also show that when a diagnostic calculation is formulated completely in terms of the transport str

an investigation of the dynamics of the east greenland current in fram strait based on a simple analytical model abstract the east greenland current egc in fram strait is examined in summer based on the hydrographic data from the mizex 84 experiment and its dynamics is further analyzed using a simple analytical model from the observed density field the southward geostrophic transport relative to the bottom in the egc is estimated to be about 4 sv sv 106 m3 s 1 at 78 4 n which assuming a ratio 1 1 between the bottom and the relative transports as suggested in the literature allows one to postulate a 4 sv bottom transport the hydrographic data also reveal a northward gradient of potential energy along the east greenland slope between 77 5 n and 80 5 n such a gradient is the prerequisite for the existence of the joint effect of baroclinicity and relief jebar which is here proposed as a driving mechanism for the bottom transport in the egc a model with idealized topography and a density distribution prescribed from the above data is constructed based on a steady state vorticity equation in which the

pleistocene iceberg dynamics on the west svalbard margin evidence from bathymetric and sub bottom profiler data large icebergs leave evidence of their drift via ploughing of the seabed thereby providing a geological record of episodes of calving from thick ice sheets we interpret large scale curvilinear depressions on the western svalbard margin as ploughmarks produced by the keels of icebergs that grounded on the seafloor as they drifted through this area iceberg ploughmarks were identified at modern water depths between 300 m and 1000 m and in two distinct stratigraphic units combining data from sediment cores with seismic stratigraphy from sub bottom profiler data suggests that the ploughmarks developed in two phases 1 during marine isotope stage mis 6 and 2 during mis 2 indicating the presence of large drifting icebergs on the western svalbard margin during both the late saalian and late weichselian glaciations sediment core data along the western svalbard margin indicate a sharp increase in mass transported sediments dated at 23 7 0 2 ka consistent with the mis 2 age of the younger iceberg ploughed surface the ploughmarks are oriented in two main directions sw ne and s n s n oriented ploughmarks which shallow to the north indicate iceberg drift from the south with a sw ne component marking the zone of splitting of the west spitsbergen current wsc into the yermak slope current ysc and north spitsbergen current nsc large mis 6 and mis 2 icebergs most likely had an arctic ocean source we suggest that these icebergs probably left the arctic ocean southward through fram strait and circulated within the norwegian greenland sea before being transported northwards along the svalbard margin by the wsc an additional likely source of icebergs to the western svalbard margin during mis 2 was the ice sheet terminating in the western barents sea from which icebergs drifted northward

the west spitsbergen current disposition and water mass transformation recent work suggests that the west spitsbergen current which provides the principal contribution to the arctic ocean of salt and sensible heat as well as of a variety of anthropogenic tracers is a rather complex circulation feature north of 79 n where the isobaths diverge markedly the current contains two separate warm cores that follow different isobaths the western core carried by the offshore branch of the current follows the western flank of the yermak plateau and north of 80 n at least part of this flow detaches from the plateau probably to contribute to the recirculation in fram strait in contrast the inshore branch follows the shelf break into the arctic ocean it is this inshore branch that provides the primary focus in this paper during the transit of the inshore waters past northwestern spitsbergen the core properties change primarily through vertical heat flux which during ice free conditions in winter is estimated to be of the order of 200 w m 2 from the core layer alone together with some freshening within the arctic ocean this process is responsible for fully transforming the original atlantic water into arctic intermediate water within about 600 km of fram strait

holocene changes in sea ice cover and polynya formation along the eastern north greenland shelf new insights from biomarker records abstract understanding the processes controlling the natural variability of sea ice in the arctic one of the most dynamic components of the climate system can help to constrain the effects of future climate change in this highly sensitive area for the first time a high resolution biomarker study was carried out to reconstruct past sea ice variability off eastern north greenland this area is strongly influenced by cold surface waters and drift ice transported via the east greenland current meltwater pulses from the outlet glaciers of the northeast greenland ice stream and the build up of landfast ice the well dated holocene sedimentary section of core ps93 025 provides insights into variations of the sea ice conditions regional and local sea ice signal oceanic and atmospheric circulation and the biotic response to these changes these biomarker records show a reduced to variable sea ice cover during the early holocene between 10 2 and 9 3 ka followed by a steady increase in sea ice conditions during the mid holocene during the last 5 6 ka sea ice conditions remained more stable representing a seasonal to marginal sea ice situation based on our biomarker records stable sea ice edge conditions with a fully developed polynya situation occurred since the last 1 ka

climatological baroclinic forcing of the barotropic flow in the east greenland current in fram strait 1 baroclinic forcing of the barotropic flow in the east greenland current in fram strait egcfs is studied using theoretical analysis and climatological data first the validity of the arrested topographic wave atw vorticity balance is reexamined then a distribution of the net depth averaged relative geostrophic flow and the associated along isobath variations of the bottom density are estimated from the polar science center hydrographic climatology seattle washington united states the effect of the along isobath bottom density variations is referred to as jebarb in order to distinguish it from the famous jebar joint effect of baroclinicity and relief which involves depth integrated density variations it is shown that the jebarb is able to maintain a significant bottom geostrophic flow in the climatological egcfs estimates of the jebarb at 79 n correspond to an increase of the magnitude of the flow by 3 cm s 1 over a distance of 200 km along the continental slope an analytical solution for the flow that is driven by a constant jebarb term and satisfies the atw vorticity balance is then obtained in a domain bounded by two parallel isobaths finally the jebarb is related to the jebar it is shown that while the jebarb maintains the curl of the coriolis force associated with the bottom geostrophic flow the jebar maintains the curl of the net coriolis force associated with the absolute geostrophic flow in the climatological egcfs over the continental slope the jebar is nearly equal to the jebarb

arctic salinity anomalies and their link to the north atlantic during a positive phase of the arctic oscillation abstract many of the changes observed during the last two decades in the arctic ocean and adjacent seas have been linked to the concomitant abrupt decrease of the sea level pressure in the central arctic at the end of the 1980s the decrease was associated with a shift of the arctic oscillation ao to a positive phase which persisted throughout the mid 1990s the arctic salinity distribution is expected to respond to these dramatic changes via modifications in the ocean circulation and in the fresh water storage and transport by sea ice the present study investigates these different contributions in the context of idealized ice ocean experiments forced by atmospheric surface wind stress or temperature anomalies representative of a positive ao index wind stress anomalies representative of a positive ao index generate a decrease of the fresh water content of the upper arctic ocean which is mainly concentrated in the eastern arctic with almost no compensation from the western arctic sea ice contributes to about two third of this salinification another third being provided by an increased supply of salt by the atlantic inflow and increased fresh water export through the canadian archipelago and fram strait the signature of a saltier atlantic current in the norwegian sea is not found further north in both the barents sea and the fram strait branches of the atlantic inflow where instead a widespread freshening is observed the latter is the result of import of fresh anomalies from the subpolar north atlantic through the iceland scotland passage and enhanced advection of low salinity waters via the east icelandic current the volume of ice exported through fram strait increases by 20 primarily due to thicker ice advected into the strait from the northern greenland sector the increase of ice drift velocities having comparatively less influence the export anomaly is comparable to those observed during events of great salinity anomalies and induces substantial freshening in the greenland sea which in turn contributes to increasing the fresh water export to the north atlantic via denmark strait with a fresh water export anomaly of 7 msv the latter is the main fresh water supplier to the subpolar north atlantic the canadian archipelago contributing to 4 4 msv the removal of fresh water by sea ice under a positive winter ao index mainly occurs through enhanced thin ice growth in the eastern arctic winter sat anomalies have little impact on the thermodynamic sea ice response which is rather dictated by wind driven ice deformation changes the global sea ice mass balance of the western arctic indicates almost no net sea ice melt due to competing seasonal thermodynamic processes the surface freshening and likely enhanced sea ice melt observed in the western arctic during the 1990s should therefore be attributed to extra winter atmospheric effects such as the noticeable recent spring summer warming in the canada alaska sector or to other modes of atmospheric circulations than the ao especially in relation to the north pacific variability

distribution and isotopic characterization of methane in a confined aquifer in southern ontario canada abstract methane is one of the major carbon pools in the groundwater of the confined alliston aquifer geochemical geological and hydrological tools were used to evaluate the origin and distribution of this hydrocarbon the potential sources for methane were migration of thermocatalytic methane from bedrock units and in situ production by bacteria mediated reactions the distribution of methane in the aquifer excludes the possibility that methane occurrences were controlled by the nature of the underlying bedrock limestone vs shale 13 c and 2 h data in ch 4 from aquifer and bedrock wells indicate that these gases are microbial in origin and they are formed in situ mainly by co 2 reduction chemical and 14 c data in ch 4 and doc support the hypothesis of the existence of carbon sources for in situ microbial production of ch 4 in the aquifer