flow variability at the continental shelf break of the mackenzie shelf in the beaufort sea observations from four yearlong current meter deployments made in 1987 1988 near the shelf break in the canadian beaufort sea are analyzed by statistical and spectral methods to characterize the structure and variability vertical and horizontal of the velocity field and to compare measurements obtained during summer ice free and winter ice covered conditions three main frequency bands are defined low frequencies 0 01 0 07 cpd intermediate or synoptic scale frequencies 0 07 0 7 cpd and high frequencies 0 7 cpd including tides and inertial currents within this division about 65 of the kinetic energy is in the low frequency band 15 in the intermediate band and 20 is in the high frequency band the latter is dominated by tidal motions low frequency variability is well correlated both vertically and horizontally along the shelf for separation distances exceeding 200 km variability in this band appears to be related to wind forcing and topographic wave propagation over large horizontal scales low frequency variability is highest during october and november in association with the occurrence of intense autumn storms and lowest during periods of ice cover due to wind shielding and increased frictional damping by ice cover intermediate scale motions have significant correlation in the vertical but poor correlation in the horizontal motions in this frequency band appear to be associated with mesoscale eddies advected by the mean flow there is also evidence of local generation of intermediate frequency current fluctuations by storms in late autumn and again an apparent damping during winter periods of ice cover finally high frequency motions show significant peaks in diurnal and semidiurnal tidal bands which are well correlated horizontally and vertically however other high frequency motions in this band show no significant correlation in either the vertical or horizontal direction there is no clear evidence in the current meter records of coupling between high frequency motions and direct atmospheric forcing

upwelling of atlantic water along the canadian beaufort sea continental slope favorable atmospheric conditions and seasonal and interannual variations abstractthe role of wind forcing on the vertical displacement of the 1 c isotherm and 33 8 isohaline depths was examined based on snapshots of historical 1950 2013 temperature and salinity profiles along the mackenzie continental slope beaufort sea it is found that upwelling is correlated with along slope northeast t59 winds during both ice free and ice covered conditions although the wind impact is more efficient during the ice free season one of the most important factors responsible for vertical displacements of isopycnals is sustained wind forcing that can last for several weeks and even longer it accounts for 14 55 of total variance in isotherm isohaline depths although these numbers might be underestimated the upwelling and downwelling events are discussed in the context of the interplay between two regional centers of action the beaufort high and aleutian low that control the wind pattern over the southern beaufort sea the probability of upwelling favorable wind occurrence is close

upwelling in the alaskan beaufort sea atmospheric forcing and local versus non local response abstract the spin up and relaxation of an autumn upwelling event on the beaufort slope is investigated using a combination of oceanic and atmospheric data and numerical models the event occurred in november 2002 and was driven by an aleutian low storm the wind field was strongly influenced by the pack ice distribution resulting in enhanced winds over the open water of the chukchi sea flow distortion due to the brooks mountain range was also evident mooring observations east of barrow canyon show that the beaufort shelfbreak jet reversed to the west under strong easterly winds followed by upwelling of atlantic water onto the shelf after the winds subsided a deep eastward jet of atlantic water developed centered at 250 m depth an idealized numerical model reproduces these results and suggests that the oceanic response to the local winds is modulated by a propagating signal from the western edge of the storm the disparity in wave speeds between the sea surface height signal traveling at the fast barotropic shelf wave speed versus the interior density signal traveling at the slow baroclinic wave speed leads to the deep eastward jet the broad scale response to the storm over the chukchi sea is investigated using a regional numerical model the strong gradient in windspeed at the ice edge results in convergence of the offshore ekman transport leading to the establishment of an anti cyclonic gyre in the northern chukchi sea accordingly the chukchi shelfbreak jet accelerates to the east into the wind during the storm and no upwelling occurs west of barrow canyon hence the storm response is fundamentally different on the beaufort slope upwelling versus the chukchi slope no upwelling the regional numerical model results are supported by additional mooring data in the chukchi sea

formation of winter water on the canadian beaufort shelf new insight from observations during 2009 2011 the arctic halocline forms a cold stratified barrier between the seasonally modified near surface layers and deeper atlantic derived waters its low temperature is maintained by intrusions of cold water formed over arctic shelves in winter surprisingly cold salty 33 water capable of halocline ventilation beaufort sea winter water bsww has been observed in the beaufort sea during some winters despite the low salinity 20 25 of shelf waters there in summer this study uses year round data from moored instruments on the beaufort shelf and slope during 2009 2011 to investigate the mechanisms involved our analysis reveals that four air sea interaction processes contribute to the formation of bsww flushing of the low salinity surface water from the shelf via ekman transport in late summer and early fall compensatory upwelling of more saline halocline water onto the shelf net seaward ice drift that promotes ice production by maintaining a flaw lead and entrainment of dense upwelled water into the freezing surface layer on the inner shelf this work moves beyond earlier studies in revealing that while weather conditions were more favorable to bsww formation in the winter of 2010 2011 than in 2009 2010 the difference was more strongly influenced by ekman transport offshore at the surface onshore at the seabed than by differences in cumulative brine injection from ice growth the strength of the ekman circulation over the canadian beaufort shelf in winter and its interannual variation have significance for surface nutrient renewal and for the cross shelf transport of pollutants at the surface and the seabed

an annual study of inorganic and organic nitrogen and phosphorus and silicic acid in the southeastern beaufort sea 1 water column samples from the mackenzie shelf the beaufort sea and the amundsen gulf were obtained during 2003 2004 to investigate nutrient dynamics in an arctic ecosystem influenced by a large river and flaw lead polynya nutrient inventories in the upper water column showed a significant seasonal drawdown of nitrate no3 and silicic acid si oh 4 1 1 75 mol mol and subsequent accumulation of nitrite no2 and ammonium nh4 dissolved organic nitrogen and phosphorus concentrations don and dop were elevated in surface waters during the time of peak phytoplankton growth bloom and postbloom phases and covaried in a 17 1 molar ratio vertical profiles showed the typical middepth maxima in no3 po43 and si oh 4 at salinity 32 33 1 the concentration of dop 0 76 0 27 mol p l 1 was also 2 times higher in this layer compared to the surface average and inversely correlated with the water mass tracer n n no3 16 po43 2 9 0 87 suggesting that pacific derived waters were a source of the enrichment below the mixed layer don was generally constant with depth although averaged profiles like those of urea suggested the presence of subsurface maxima at 50 m and between 250 and 300 m regeneration ratios varied with depth and were approximately 9 0 mol o2 mol no3 and 122 5 mol o2 mol po43 in shallow pacific derived waters halocline layer and 17 4 and 193 5 in deep atlantic waters atlantic layer respectively deep waters of the amundsen gulf contained an excess of 1 7 mol no3 l 1 0 12 mol po43 l 1 and 6 2 mol si oh 4 l 1 and a deficit in o2 relative to waters of similar density in the beaufort sea in proportions consistent with the remineralization ratios derived from oxygen nutrient regressions enhanced export of particulate matter from the overlying polynya and subsequent remineralization at depth are hypothesized to create this nutrient enrichment

seasonal variation of upwelling in the alaskan beaufort sea impact of sea ice cover 1 data from a mooring array deployed from august 2002 to september 2004 are used to characterize differences in upwelling near the shelf break in the alaskan beaufort sea due to varying sea ice conditions the record is divided into three ice seasons open water partial ice and full ice the basic response is the same in each of the seasons roughly 8 h after the onset of easterly winds the shelf break jet reverses followed approximately 10 h later by upwelling of saltier water which is cold near the shelf break pacific winter water and warm at depth atlantic water the secondary circulation at the outer shelf is to first order consistent with a two dimensional ekman balance of offshore flow in the upper layer and onshore flow at depth there are however important seasonal differences in the upwelling overall the response is strongest in the partial ice season and weakest in the full ice season it is believed that these differences are dictated by the degree to which wind stress is transmitted through the pack ice as the strength of the wind forcing was comparable over the three seasons an eof based upwelling index is constructed using information about the primary flow secondary flow and hydrography the ability to predict upwelling using the wind record alone is explored which demonstrates that 90 of easterly wind events exceeding 9 5 m s 1 drive significant upwelling during certain periods the ice cover on the shelf became landfast which altered the upwelling and circulation patterns near the shelf break

circulation near submarine canyons a modeling study circulation near a submarine canyon is analyzed with a numerical model previous theoretical work indicated that stratification controlled the interaction of coastal flow with canyons specifically the ratio of canyon width to the internal radius of deformation a wide canyon was thought to merely steer the flow while a narrow canyon would create substantial cross shelf exchange four cases are analyzed considering two directions of alongshore flow and two choices of initial stratification the weakly stratified case has an internal radius about equal to the canyon width while the strongly stratified case has one about 3 times the canyon width the direction of the alongshore flow is shown in this study to be the more important of the two factors in particular right bounded flow flow with the coast on the right looking downstream in the northern hemisphere leads to shallow downwelling in the canyon and weak exchange across the shelf break while left bounded flow creates upwelling at the head of the canyon and strong exchange between the ocean and shelf in left bounded flow upwelling dense water is pumped onto the shelf even for strong stratification however the stratification limits the vertical extent of the topographic influence so that the alongshore flow above the canyon is only weakly affected in the strongly stratified case with any level of stratification the surface temperature density is not modified at all by the flow interaction with the submarine canyon the important dynamics involve pressure gradients and coriolis acceleration and how they interact with the bathymetric gradients but not advection of momentum advection of density is clearly important in the upwelling cases finally continued upwelling onto the shelf acts as a drag mechanism and retards the alongshore coastal flow

the freshwater budget and under ice spreading of mackenzie river water in the canadian beaufort sea based on salinity and 18o 16o measurements in water and ice observations of salinity and oxygen isotope composition 18o were made for the beaufort shelf mackenzie estuary waters in september 1990 just prior to ice formation and for both the water column and ice in april may 1991 at the end of winter these measurements are used to determine the apportioning of fresh water in the estuary between its two main sources runoff and sea ice melt changes in disposition of water between seasons and amounts frozen into the growing ice sheet are also derived two domains are considered in order to construct a freshwater budget for the mackenzie shelf the nearshore within which landfast ice grows in winter and the outer shelf most of the winter inflow from the mackenzie river appears to remain impounded as liquid under the ice within the landfast zone at the end of winter and about 15 of it is incorporated into the landfast ice oxygen isotopes 18o in ice cores collected from across the shelf record the progress beneath the ice of new mackenzie inflow as it invades the nearshore throughout winter rates of spreading are about 0 2 cm s 1 away from the coast and 1 3 cm s 1 along the coast as this inflow spreads across the shelf it progressively shuts off convection driven by brine production at locations within the landfast ice salinity and 18o in the offshore water column suggest that about 3 m of sea ice was formed in the outer shelf domain since both brine and newly formed sea ice can be advected off the shelf a complete budget for brine or sea ice production cannot be established without first measuring the advection of one of these two components

regional differences in pb isotopic compositions of feldspars in plutonic rocks of the northern appalachian mountains u s a and canada a geochemical method of terrane correlation feldspar pb isotopic compositions from paleozoic tonalitic to leucogranitic caledonian plutons from the northern appalachian mountains of the u s a and canada range from nonradiogenic to radiogenic relative to the evolution curve of stacey and kramers 1975 pb isotopic values in the feldspars are generally independent of modal and major and trace element contents of the plutons plutons with the least radiogenic pb isotopic signatures northern group have intruded allochthonous rocks closest to the north american craton and plutons with the most radiogenic pb southern group have intruded avalonian basement feldspars from plutons in the central group have intermediate pb isotopic compositions between the northern and southern groups and do not define an isotopically unique group the predominant source of the felsic magmas was the continental lithosphere as indicated by the general pb isotopic similarity of the plutonic feldspars with either grenville or chain lakes basement in the case of the northern group and with avalonian basement rocks in the case of the southern group the source region for plutons in the central group may have contained a mixture of grenvillian and avalonian components plutons in the northern appalachians are as a group more evolved in their pb isotopic compositions relative to caledonian plutons in the british isles

topographically generated subinertial flows within a finite length canyon abstract the presence of a canyon cutting the continental shelf has been observed to enhance wind driven upwelling in particular in the vicinity of juan de fuca canyon at the mouth of the juan de fuca strait an eddy containing deep water from a depth of approximately 450 m has been documented strong upcanyon flows have been observed within numerous canyons including astoria canyon which cuts the shelf offshore of the mouth of the columbia river the author develop a linear theory for wind driven flow over an infinitesimally thin but finite length canyon to illustrate the basic mechanism two regimes are considered the initial growing velocity field and a later steady velocity field the flow toward the shore is enhanced by o 10 by the presence of the canyon in a homogeneous fluid the presence of stratification introduces smaller horizontal length scales the baroclinic rossby radius and allows further enhancement of the upcanyon flow numerical simulations show that the linear theory is a reaso

co2 fluxes across the air sea interface in the southeastern beaufort sea ice free period 1 surface mixed layer co2 fugacities fco2 sw calculated from carbonate system parameters in the southeastern beaufort sea during the ice free period ranged from 240 to 350 atm in fall 2003 and from 175 to 515 atm in summer 2004 the surface mixed layer remains mostly undersaturated with respect to atmospheric co2 378 atm and therefore acts as a potential co2 sink throughout this period air sea co2 fluxes fco2 were first computed assuming ice free conditions and ranged from 32 4 to 8 6 mmol m 2 d 1 in fall 2003 and summer 2004 respectively then we included a reduction factor to account for ice cover ic and we computed the resulting fluxes fco2 ic in fall 2003 fco2 ic ranged from 4 7 mmol m 2 d 1 in the relatively open water of the cape bathurst polynya to 0 1 mmol m 2 d 1 in the southeastern beaufort sea limited by the presence of the multiyear sea ice in summer 2004 fco2 ic ranged from 13 1 mmol m 2 d 1 on the western mackenzie shelf to 8 6 mmol m 2 d 1 at cape bathurst the variability being ascribed to competing effects of vertical mixing temperature variations and possibly biological production on average a net sink of 2 3 3 5 mmol m 2 d 1 was estimated for the ice free period over the study area nevertheless the fco2 displays strong variability due to ice coverage freshwater input and upwelling events the potential responses direction and intensity of potential feedbacks of the carbon cycle in the study area to a changing arctic climate are discussed

barotropic and baroclinic tidal currents on the mackenzie shelf break in the southeastern beaufort sea 1 tidal currents near the outer shelf break of the mackenzie shelf in the southern beaufort sea were examined using year long 1987 1988 current measurements from the upper 35 m and lower 150 m layers at four sites along the southeast ss1 northeast ss2 north central ss3 and northwest ss4 perimeter of the shelf at all stations semidiurnal currents were dominant and upper layer currents were approximately double those observed in the lower layer maximum m2 currents were observed above the sharp northeastern corner of the mackenzie shelf 6 0 7 5 cm s 1 while in the mackenzie canyon they were negligible diurnal currents were weaker and depth uniform maximum k1 currents 1 5 3 0 cm s 1 were found in the eastern part of the shelf diurnal and lower layer semidiurnal currents were in good agreement with those computed numerically by kowalik and proshutinsky 1994 indicating that these currents are essentially barotropic in contrast upper layer semidiurnal currents were mainly baroclinic about 74 of the total energy of semidiurnal currents was associated with baroclinic coherent phase locked tidal currents while barotropic 12 baroclinic incoherent 7 and inertial 7 components are the remaining semidiurnal currents in this area high baroclinic generation coefficients the ratio of locally generated baroclinic waves to barotropic waves for stations ss2 and ss3 about 7 0 8 0 in comparison with 0 3 for ss1 and ss4 located near the northeastern mackenzie shelf identify this region as a probable generation source of intensive internal tidal waves which become then locally resonantly trapped between the shelf and the critical latitudes

upwelling on the continental slope of the alaskan beaufort sea storms ice and oceanographic response 1 the characteristics of pacific born storms that cause upwelling along the beaufort sea continental slope the oceanographic response and the modulation of the response due to sea ice are investigated in fall 2002 a mooring array located near 152w measured 11 significant upwelling events that brought warm and salty atlantic water to shallow depths when comparing the storms that caused these events to other aleutian lows that did not induce upwelling interesting trends emerged upwelling occurred most frequently when storms were located in a region near the eastern end of the aleutian island arc and alaskan peninsula not only were these storms deep but they generally had northward tending trajectories while the steering flow aloft aided this northward progression the occurrence of lee cyclogenesis due to the orography of alaska seems to play a role as well in expanding the meridional influence of the storms in late fall and early winter both the intensity and frequency of the upwelling diminished significantly at the array site it is argued that the reduction in amplitude was due to the onset of heavy pack ice while the decreased frequency was due to two different upper level atmospheric blocking patterns inhibiting the far field influence of the storms

the influence of canyons on shelf currents a theoretical study the influence of submarine canyons on shelf currents is studied using the rossby adjustment method for a homogeneous inviscid fluid on an f plane the canyon in the model is assumed to have vertical edges and constant width the geostrophic flow around a canyon is found to be dependent upon two geometric parameters the ratio of the depth of the canyon to the depth of the shelf and the ratio of the width of the canyon to the rossby radius over the canyon moreover a single parameter determines most of the properties of the geostrophic state this parameter is called the canyon number and is a combination of the two basic geometric parameters in the geostrophic state an infinitely long flat bottom canyon will act as a complete barrier to an approaching shelf flow the approaching flow is asymmetrically diverted along the canyon and a net flux is generated to the left of the flow in the northern hemisphere if the canyon cuts a shelf between the shelf break and the coast and connects to a strait the geometry of juan de fuca canyon an in canyon out canyon current will be generated when the shelf break current flows keeping the shelf at its left right in the northern hemisphere if the canyon has a stepped or sloped bottom the geostrophic flow has a singularity where the step or slope meets the left canyon edge looking upcanyon in the northern hemisphere flow can cross the canyon edge through the singularity so the canyon is no longer a complete barrier to the approaching shelf flow in this case as above a net flux is generated to the left of the approaching shelf flow

current response to wind in the chukchi sea a regional coastal upwelling event a cruise was conducted on the noaa ship oceanographer in august and september 1986 in the chukchi sea four short term moorings were instrumented with sediment traps and aanderaa rcm4 current meters the currents at the three moorings near the alaskan coast indicate a reversal of the normal northeastward flow to southwestward this reversal was produced by wind which had begun to blow from the east northeast at up to 4 2 m s 1 the temperature time series indicated that upwelling colder water was moving upward near the coast the nearshore mooring had the largest amplitude variation of currents and the largest temperature variation the amplitude of the reversal decreased offshore the station farthest from the coast was near the ice edge and on the other side of barrow canyon and a subsea bank the flow there was consistently toward the east and is only poorly related to the wind water mass analysis was conducted using two techniques the first was a traditional ts diagram method and the second was a cluster analysis on ts pairs for the surface and near bottom waters based on the shapes of the ts curves and their positions on the ts diagrams a map of the water masses was constructed a cluster analysis was performed on the surface ts pairs from each station and separately for the bottom ts pairs for both of these techniques the line separating the groupings follows the temperature contours 5 at the surface and 4 at the bottom and the bottom salinity contours 32 5 psu

the distribution of nutrients in the southeastern beaufort sea implications for water circulation and primary production hydrographic data collected above the shelf and slope in the southeastern beaufort sea show marked contrast in surface properties of nutrients temperature salinity and oxygen between august 1974 a year when ice remained close to shore and august 1975 a year with much open water the near surface properties are dominated by river inputs biological activity and the ice regime below the winter mixed zone 40 50 m properties are similar to those observed elsewhere in the arctic ocean bering sea water is detected at 50 60 m as a very weak signal in temperature nutrients and oxygen upwelling in both years was observed at the eastern side of mackenzie canyon this upwelling likely results from the interaction of coastal circulation with topography estimates of new productivity based on nutrient budgets are low 20 g c m 2 yr 1 compared to temperate coastal waters but fall in the range expected for the arctic in 1974 the heavy ice year turbid water and ice cover appear to have reduced new production by about 30 calculations show that this production over the shelf could potentially supply a significant portion of the nutrients found in the upper halocline over a wide region of the arctic ocean by regeneration at the shelf bottom and transport off the shelf in brine drainage

wind forced upwelling and internal kelvin wave generation in mackenzie canyon beaufort sea low frequency current temperature and salinity variations over the shelf break in the southeastern beaufort sea mackenzie shelf are examined to determine the response of seasonally ice free waters to wind forcing and the role of submarine canyons in upwelling events and shelf circulation upwelling events were found to be statistically correlated to northeasterly winds which transport surface waters offshore and draw up water from deeper layers the response to alongshore wind stress is significantly amplified in mackenzie canyon where isopycnal displacements of over 400 m are observed such displacements are then observed to propagate eastward at a phase velocity near 0 6 m s 1 the canyon is thus a site of intense upwelling while the collapse of displaced isopycnals subsequent to cessation of wind forcing creates a disturbance propagating northeast along shelf as a free internal kelvin wave

water mass structure and boundaries in the mackenzie shelf estuary the mackenzie shelf is a broad estuarine region bordering the southeastern beaufort sea in the arctic ocean its fields of temperature and salinity result from the modification of offshore water masses by river inflow ice melting and freezing solar insolation and air sea exchange we here relate water masses resident on the mackenzie shelf to the large scale oceanography of the arctic mediterranean the summertime exchange between the shelf and open ocean is largely confined to waters lying above the main halocline s 34 2 psu cross shelf property distributions show that individual water masses maintain their structural identity i e core properties and buoyancy frequency as they move across the shelf and participate in the estuarine circulation shelf waters are strongly influenced by river inflow however the concept of a single plume issuing from the incoming river and forming a strictly two layered structure over uniform shelf water is misleading since a variety of temperature salinity and turbidity fronts co exist on the shelf at any given time

wind driven shelf basin exchange on an arctic shelf the joint roles of ice cover extent and shelf break bathymetry 1 the efficiency of shelf basin exchange sbe in polar regions during summer is strongly moderated by the location of the ice edge relative to underlying topography numerical model calculations suggest that upwelling favorable winds generate very little sbe so long as the ice edge remains shoreward of the shelf break but an abrupt onset of shelf break upwelling takes place when the ice edge retreats beyond the shelf break a climatology 1968 2000 of ice conditions from the canadian shelf of the beaufort sea shows large interannual variability in ice edge extent and duration of ice free conditions in summer similarly available hydrographic data reflect a corresponding variability in water mass properties under scenarios of climate warming associated with greenhouse gas build up both the extent and duration of summer melt back are predicted to increase and this may have dramatic impacts on sbe and biological productivity

composition and modification of water masses in the mackenzie shelf estuary the distributions of 18o salinity temperature and nutrients have been used to quantify water sources to the mackenzie shelf in the beaufort sea comparison of water mass analyses with satellite imagery confirms that the meteoric runoff water is associated with the mackenzie plume the seasonally variable surface layer for the shelf is viewed as cycling between a reverse estuary in winter when the polar mixed layer pml is formed and a positive estuary in summer when the shelf waters respond to freshwater inputs runoff and ice melt we infer a standing stock of 3 7 m fresh water at the end of summer 1986 of which 30 owes its origin to the melting of sea ice our data coupled with river flow imply a freshwater flushing time for the mackenzie shelf at about 150 days to re form the pml during winter requires the removal of this seasonal fresh water through the combined processes of flushing and ice formation once this fresh water has been removed continued ice growth can produce new brine which would be observed as a deeper and saltier pml from the previous year a simple geochemical model shows that autumn conditions freshwater accumulation and the rate of flushing are important controls on the potential of the shelf to produce new brine and that winter runoff were it to distribute evenly across the shelf is sufficient to inhibit brine production

the interior shelves of the arctic ocean physical oceanographic setting climatology and effects of sea ice retreat on cross shelf exchange abstract the interior shelves of the arctic mediterranean are the shelves of the kara sea laptev sea east siberian sea and beaufort sea they comprise approximately 40 of the total arctic shelf area 2 5 10 6 km 2 and are distinguished from inflow and outflow shelves by their principal forcing dynamics along their southern continental boundary the interior shelves are dominated by the major arctic rivers receiving over 80 of the total freshwater input to the arctic ocean in the mid shelf region wind and ice motion surface stresses dominate mixing and circulation resulting in high variability along their northern seaward boundary they are forced by upwelling and downwelling favourable surface stresses which drive shelf basin exchanges with atlantic and pacific origin cyclonic boundary currents over the upper slope shelf basin exchange is further modified by shelf break morphometry e g canyons valleys headlands and bottom slope here we review the physical oceanographic settings and forcing of the interior shelves and then focus on shelfbreak exchange and supply of nutrients for new primary production due to upwelling across the shelfbreak as a proxy for this nutrient supply we show seasonal and annual time series of along shelfbreak surface stress due to wind and ice motion from 1979 to 2011 we apply this analysis to the shallow shelves from the kara sea to the beaufort sea and comment on recent increases due to atmospheric changes and sea ice retreat

zooplankton inside an arctic ocean cold core eddy probable origin and fate abstract in september 2004 an extensive survey of a cold core eddy in the canada basin western arctic was carried out with high horizontal resolution physical and chemical sampling and lower horizontal resolution biological sampling the eddy was located over the continental slope north of the chukchi shelf and had a radius of 8 km its core was centered at a depth of 160 m water mass characteristics and the presence of copepods from the north pacific ocean neocalanus flemingeri and metridia pacifica demonstrated that the core contained water of pacific origin vertical distributions of zooplankton were associated with the physical structure of the water column for most taxa concentrations in the eddy core were elevated compared with those in similar density water in the surrounding basin based on tracer age estimates and previous observations of eddy formation the eddy is believed to have been formed during the previous spring summer from the chukchi shelfbreak jet surprisingly the eddy also contained elevated abundances of arctic origin copepods metridia longa and calanus glacialis analysis of a shelf basin transect occupied in the region in august 2004 showed that these species were present in high abundances in relatively shallow water 50 m inshore of the shelfbreak due to upwelling of deeper basin water and copepods onto the shelf in response to easterly winds if the formation of the observed eddy occurred during or shortly after a period of such winds upwelled arctic origin copepods on the shelf might have been entrained into the feature our observations suggest that formation and subsequent migration of such eddies may provide a mechanism for transporting zooplankton from the chukchi shelf into the interior canada basin the periodic input of high abundances of zooplankton from productive shelf areas could affect food webs in the less productive basin

kugmallit valley as a conduit for cross shelf exchange on the mackenzie shelf in the beaufort sea 1 kugmallit valley spans the midsection of a transect across the mackenzie shelf of the beaufort sea its greatest relief is 20 m and its width is 20 km using a yearlong record of ice drift ocean current temperature and salinity acquired near the center of the valley we describe a pattern of flow that is correlated with wind stress and ice motion and discuss its similarity to flow within larger submarine canyons that cut through the shelf break as in such canyons there is enhanced cross shelf transport within kugmallit valley during upwelling favorable surface stress the data also document the down valley flow of dense water from a flaw lead

shelfbreak current over the canadian beaufort sea continental slope wind driven events in january 2005 the shelfbreak current over the beaufort sea continental slope is known to be one of the most energetic features of the beaufort sea hydrography in january 2005 three oceanographic moorings deployed over the canadian eastern beaufort sea continental slope simultaneously recorded two consecutive shelfbreak current events with along slope eastward bottom intensified flow up to 120 cm s 1 both events were generated by the local wind forcing associated with two pacific born cyclones passing north of the beaufort sea continental slope toward the canadian archipelago over the mooring array the associated westerly wind exceeded 15 m s 1 these two cyclones generated storm surges along the beaufort sea coast with sea surface height ssh rising up to 1 4 m following the two westerly wind maxima we suggest that the westerly along slope wind generated a surface ekman onshore transport the associated ssh increase over the shelf produced a cross slope pressure gradient that drove an along slope eastward geostrophic current in the same direction as the wind this wind driven barotropic flow was superimposed on the background baroclinic bottom intensified shelfbreak current that consequently amplified summer fall satellite altimetry data for 1992 2013 show that the ssh gradient in the southeastern beaufort sea is enhanced over the upper continental slope in response to frequent storm surge events because the local wind forcing and or sea ice drift could not explain the reduction of sea ice concentration over the beaufort sea continental slope in january 2005 we speculate that wind driven sea level fluctuations may impact the sea ice cover in winter

warm water interactions in the barrow canyon in winter an extensive set of salinity temperature measurements was taken in the ice covered barrow canyon in early april 1976 an intrusion of relatively warm water into the mid depth of the canyon is believed due to a surge driven mixing of the atlantic layer with arctic ocean surface water on the upper continental slope

characteristics and dynamics of wind driven upwelling in the alaskan beaufort sea based on six years of mooring data abstract six years of mooring data from the alaskan beaufort sea slope together with meteorological observations and reanalysis fields are used to quantify the occurrence of wind driven upwelling and the associated atmospheric forcing the canonical upwelling event composited from 115 individual events reveals that when the easterly wind is strongest the entire shelfbreak jet is reversed to the west at the end of the event a bottom intensified eastward flowing rebound jet spins up that is stronger than the normal shelfbreak jet the cross isobath flow has a three layer structure with onshore flow in the surface layer offshore flow in the middle of the water column and onshore flow near the bottom this is because the reversed shelfbreak jet is oriented slightly onshore which overwhelms the cross isobath surface ekman transport the vertically integrated along isobath momentum balance supports this interpretation and indicates that the rebound jet is driven by the zonal gradient in sea surface height during over two thirds of the events atlantic water aw is upwelled to the shelfbreak while for the remaining events only pacific water pw is upwelled the primary driving factor behind this is the seasonal variation in the pw aw interface depth offshore of the shelfbreak which is controlled by the local wind stress curl during summer when pw type events dominate ekman pumping associated with negative wind stress curl deepens the interface depth limiting access to the atlantic layer over the remainder of the year when aw events dominate ekman suction associated with positive wind stress curl raises the interface these variations are due to the influence of the two regional atmospheric centers of action the aleutian low and the beaufort high

frontal structures associated with coastal upwelling and ice edge subduction events in southern beaufort sea during the canadian arctic shelf exchange study the near surface temperature structure in the southeastern beaufort sea is shown to have been largely dependent on frontal dynamics in spring 2004 which may be typical for the region easterly wind events generated coastal upwelling along the cap bathurst peninsula a recurring event in that area further west a large mesoscale anticyclone simultaneously developed and subsequently controlled the sea surface circulation in the central amundsen gulf sharp temperature and density fronts were created at the surface at both eastern and western ends of the domain sampling north of cape bathurst and cape parry showed evidence of frontal intensification frontal features were detected near the 50 200 m isobaths at the mouth of the gulf where density compensated near surface intrusions driven by agesotrophic vertical circulation were identified these warm water tongues intruded into the outcropping isopycnal layers which dipped down between 5 and 25 m over the mackenzie shelf they then crossed the density surfaces with an inverse slope consistent with n f as predicted for quasi geostrophic flows the front event ended prior to the breakup of the landfast ice bridge in late june with sea surface temperature undergoing quick and widespread changes throughout the amundsen gulf

on sea ice concentration anomaly coherence in the southern beaufort sea 1 the circumpolar flaw lead polynya system is a region of enhanced biological productivity and for significant portions of the annual cycle dominates the exchange of energy and mass across the ocean sea ice atmosphere osa interface we investigate the nature of sea ice concentration sic anomalies for spatial and temporal statistical persistence within a portion of this flaw lead system we find such a structure in the shelf break zone between amundsen gulf and the canada basin ncep ncar reanalysis data is used to determine the potential roles of oceanic and atmospheric forcing in creating and maintaining this observed coherence in the sic anomalies results suggest that the coherence pattern is consistent over the instrumental record 1979 to 2000 although it changes in shape and extent between years the forcing mechanisms creating this coherence in sic anomalies appear to be tied to surface wind driven upwelling in the shelf break areas of the southern beaufort sea sbs

coastal trapped waves on the east australian continental shelf part i propagation of modes abstract the currents observed over the shelf and slope during the australian coastal experiment ace are used to determine the amplitudes as functions of time of the first three coastal trapped wave ctw modes at three locations along the southeast coast of australia a statistical eddy mode is included to minimize contamination of the coastal trapped wave currents from east australian current eddies the first three ctw modes account for about 65 of the observed variance in the alongshelf currents on the shelf and slope at cape howe about 40 at stanwell park but only about 24 at newcastle currents associated with the east australian current dominate the observations offshore from newcastle ctws account for all but 10 37 and 27 of the currents observed at the most nearshore locations on the shelf at cape howe stanwell park and newcastle the first two coastal trapped wave modes propagate at close to the appropriate theoretical phse speeds but the third coastal trapped wave mode and the