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

a modeling study of coastal circulation and landfast ice in the nearshore beaufort and chukchi seas using ciom this study investigates sea ice and ocean circulation using a 3 d 3 8 km ciom coupled ice ocean model under daily atmospheric forcing for the period 1990 2008 the ciom was validated using both in situ observations and satellite measurements the ciom successfully reproduces some observed dynamical processes in the region including the bering inflow originated coastal current that splits into three branches alaska coastal water acw central channel branch and herald valley branch in addition the beaufort slope current bsc the beaufort gyre the east siberian current esc mesoscale eddies and seasonal landfast ice are well simulated the ciom also reproduces reasonable interannual variability in sea ice such as landfast ice and anomalous open water less sea ice during the positive dipole anomaly da years vice versa during the negative da years sensitivity experiments were conducted with regard to the impacts of the bering strait inflow heat transport onshore wind stress and sea ice advection on sea ice change in particular on the landfast ice it is found that coastal landfast ice is controlled by the following processes wind forcing bering strait inflow and sea ice dynamics

flow of winter transformed pacific water into the western arctic abstract the dynamics of the flow of dense water through barrow canyon is investigated using data from a hydrographic survey in summer 2002 the focus is on the winter transformed bering water the highest volumetric mode of winter water in the chukchi sea which drains northward through the canyon in spring and summer the transport of this water mass during the time of the survey was 0 2 0 3 sv as the layer flowed from the head of the canyon to the mouth it sank decelerated and stretched strong cyclonic relative vorticity was generated on the seaward side of the jet which compensated for the stretching this adjustment was incomplete however in that it did not extend across the entire current possibly because of internal mixing due to shear instabilities the resulting vorticity structure of the flow at the canyon mouth was conducive for baroclinic instability and eddy formation multiple eddies of winter transformed bering water were observed along the chukchi beaufort shelfbreak those to the west of barrow canyon were in the process of being spawned by the eastward flowing shelfbreak current emanating from herald canyon while the single eddy observed to the east originated from the barrow canyon outflow it is argued that such an eddy formation is a major source of the ubiquitous cold core anti cyclones observed historically throughout the canada basin implications for the ventilation of the upper halocline of the western arctic are discussed

non transform offsets along the mid atlantic ridge south of the azores 38 n 34 n ultramafic exposures and hosting of hydrothermal vents ten contiguous non transform offsets ntos along the mid atlantic ridge mar south of the azores between 38 n and 35 40 n have been studied in detail using swath bathymetric acoustic backscatter and deep tow high resolution sidescan sonar tobi data in contrast with discontinuities studied elsewhere at slow spreading ridges these left lateral ntos are consistently broader and larger with complex structural fabrics accommodating the offset they are characterized by a range of elevated and faulted massifs detached from their segment flanks with an irregular acoustic backscatter pattern some of these massifs have been explored and sampled recently during dive cruises revealing that they are composed of upper mantle peridotites and lower crustal rocks and sometimes associated with high temperature hydrothermal venting water column surveys adjacent to these massifs show high ch4 and low tdm total dissolvable manganese concentrations possibly resulting from the process of serpentinization of ultramafic rocks the correlation between the shallow dome like shaped massifs and the high concentrations of ch4 associated with low levels of mn is of particular interest to predict the outcrop of ultramafic rocks within the ntos where no geological data are available the exposure of the ultramafic massifs within the ntos is favored by low magmatic supply and low angle detachment faulting occurring at segment ends the pervasive fracturing and faulting at these discontinuities favor circulation of hydrothermal fluids and occurrence of high temperature vent sites

microstructure observations of turbulent heat fluxes in a warm core canada basin eddy abstractan intrahalocline eddy was observed on the chukchi slope in september of 2015 using both towed ctd and microstructure temperature and shear sections the core of the eddy was 6 c significa

response of total and eddy kinetic energy to the recent spinup of the beaufort gyre abstractthe beaufort gyre in the arctic ocean has spun up over the past two decades in response to changes of the wind forcing and sea ice conditions accumulating a significant amount of freshwate

mesoscale eddies of the arctic ocean subsurface baroclinic eddies in the arctic ocean have a diameter of 10 20 km and are confined in depth between 50 and 300m during the arctic ice dynamics joint experiment aidjex in the central beaufort sea between march 1975 and may 1976 extensive information on eddy characteristics statistics and behavior was collected from four manned drifting ice camps during this 14 month period 146 eddies were encountered of which 19 were found to be repeated crossings making a total of 127 separate eddies observed during this period on the basis of the 1975 1976 aidjex data set it is concluded that eddies are 1 prevalent in the amerasia basin of the arctic ocean and in particular the beaufort sea where they may occupy up to a quarter of the available surface area 2 located in the depth range of 50 300 m although a few deeper eddies are also present 3 the second largest producers 32 of kinetic energy found within the upper 200 m of the beaufort sea and 4 predominantly anticyclonic in rotational tendency these eddies apparently originate north of point barrow alaska as a result of instability in the eastward flowing alaskan coastal current and transfer seasonally varying water properties from the chukchi sea and alaskan shelf into the arctic ocean they appear to translate in response to barotropic forcing over short time scales and over longer time periods move with the mean geostrophic field the season of formation for an eddy may be identified by the anomalous thermal properties still residing in its core

evaluation of shelf basin interaction in the western arctic by use of short lived radium isotopes the importance of mesoscale processes shelf basin exchange in the western arctic was evaluated by use of water column analyses of 228 ra 226 ra ratios and the first measurements of the short lived 224 ra t1 2 3 64 d in the arctic during the 2002 shelf basin interaction sbi program excess 224 ra was detected over the shelf but was not found seaward of the shelf break similarly the 228 ra 226 ra ratio dropped rapidly from the shelf across the shelf break consequently the model age gradient elapsed time since shelf residence northward across the chukchi shelf increased from 1 5 years nearshore to approximately 14 years in surface waters sampled off shelf at the southern margin of the beaufort gyre this steep gradient is consistent with very slow exchange between the chukchi shelf and the beaufort gyre whereby bering strait inflow is constrained by the earth s rotation to follow local isobaths and does not easily move into deeper water the strong dynamic control inhibiting water that enters the system through bering strait from flowing north across isobaths also would lead to a long recirculation time of river water emptied into the beaufort gyre possible mechanisms that can generate cross shelf currents that break the topographic constraint to follow isobaths and thereby transport water and associated properties off the shelves include wind induced upwelling downwelling meandering jets and eddies evidence of such a process was found during the icex project in the beaufort sea in april 2003 when excess 224 ra was measured over 200 km from any shelf source this required an ne offshore flow of 40 cm s 1 assuming that the source water derives from the mouth of barrow canyon a weak northeastward flow was measured using an ladcp within the upper 300 m of the ocean but was of lower speed than required by the 224 raxs at the time of the icex occupation

a large eddy in the central arctic ocean 1 long term moored measurements of temperature salinity and velocity over the abyssal plain near the north pole show a rich array of eddy like structures over a wide range of depths here we demonstrate an anticyclone that extends from the surface to at least 1700 m is about 60 km across and has a likely origin along the eurasian continental margin

upwelling of arctic pycnocline associated with shear motion of sea ice 1 high resolution radar imagery shows that the dynamic response of winter sea ice to gradients in large scale surface wind stress is often localized along quasi linear fractures hundreds of kilometers long relative shearing motion across these narrow fractures can exceed 10 cm s 1 in one event recorded during the drift of the sheba ice camp we observed an intense zone of pycnocline upwelling 14 m associated with significant shear motion near the camp while upward turbulent heat flux in the ocean boundary layer reached nearly 400 w m 2 an order of magnitude greater than at any other time during the year long drift we attribute the upwelling to ekman pumping associated with concentrated ice shear over the entire arctic ocean sea ice cover this process could be responsible for significant heat exchange between the cold surface layer and warmer subsurface water at the ubiquitous fractures resulting from large scale atmosphere ice interactions

characterizing the eddy field in the arctic ocean halocline ice tethered profilers itp deployed in the arctic ocean between 2004 and 2013 have provided detailed temperature and salinity measurements of an assortment of halocline eddies a total of 127 mesoscale eddies have been detected 95 of which were anticyclones the majority of which had anomalously cold cores these cold core anticyclonic eddies were observed in the beaufort gyre region canadian water eddies and the vicinity of the transpolar drift stream eurasian water eddies an arctic wide calculation of the first baroclinic rossby deformation radius rd has been made using itp data coupled with climatology rd 13 km in the canadian water and 8 km in the eurasian water the observed eddies are found to have scales comparable to rd halocline eddies are in cyclogeostrophic balance and can be described by a rankine vortex with maximum azimuthal speeds between 0 05 and 0 4 m s the relationship between radius and thickness for the eddies is consistent with adjustment to the ambient stratification eddies may be divided into four groups each characterized by distinct core depths and core temperature and salinity properties suggesting multiple source regions and enabling speculation of varying formation mechanisms

river runoff sea ice meltwater and pacific water distribution and mean residence times in the arctic ocean hydrographic and tracer data collected during ark iv 3 fs polarstern in 1987 arctic91 ib oden and aos94 ccgs louis s st laurent expeditions reveal the evolution of the near surface waters in the arctic ocean during the late 1980s and early 1990s salinity nutrients dissolved oxygen and 18 o data are used to quantify the components of arctic freshwater river runoff sea ice meltwater and pacific water the calculated river runoff fractions suggest that in 1994 a large portion of water from the pechora ob yenisey kotuy and lena rivers did not flow off the shelf closest to their river deltas but remained on the shelf and traveled via cyclonic circulation into the laptev and east siberian seas river runoff flowed off the shelf at the lomonosov ridge and most left the shelf at the mendeleyev ridge arctic91 and aos94 pacific water fraction estimates of upper halocline water the traditionally defined core of the pacific water mass document a decrease in extent compared to historical data the front between atlantic water and pacific water shifted from the lomonosov ridge location in 1991 to the mendeleyev ridge in 1994 the relative age structure of the upper waters is described by using the 3 h 3 he age the mean 3 h 3 he age measured in the halocline within the salinity surface of 33 1 0 3 is 4 3 1 7 years and that for the 34 2 0 2 salinity surface is 9 6 4 6 years lateral variations in the relative age structure within the halocline and atlantic water support the well known cyclonic boundary current circulation

a numerical study of dense water formation and transport on a shallow sloping continental shelf the circulation and transport of dense water generated by an idealized coastal polynya is studied using a three dimensional primitive equation model starting with a homogeneous quiescent ocean a constant negative buoyancy flux is imposed at the surface over a half elliptical region adjacent to the coastal boundary on a gently sloping continental shelf the flow response can be divided into the following three phases geostrophic adjustment instability and offshore eddy transport during geostrophic adjustment the fluid within the forcing region becomes denser and the flow at the edge of the forcing region accelerates in response to the strong density gradient there eventually the flow at the leading edge of the forcing region relative to kelvin wave propagation becomes unstable and a train of counterrotating eddies develops these eddies then form a complex three dimensional flow field and rapidly transport dense water offshore across isobaths the density within the forcing region reaches a maximum which remains fairly constant after the eddies begin to transport the dense fluid offshore the results are qualitatively insensitive to weakening of the negative buoyancy forcing and to changing the bottom slope eddy scales and velocities are consistent with observations in the arctic the results suggest that instability processes and eddy fluxes are important in transporting dense water off continental shelves and into marginal seas

eddy kinetic energy in the arctic ocean from a global simulation with a 1 km arctic simulating arctic ocean mesoscale eddies in ocean circulation models presents a great challenge because of their small size this study employs an unstructured mesh ocean sea ice model to conduct a decadal scale global simulation with a 1 km arctic it provides a basinwide overview of arctic eddy energetics increasing model resolution from 4 to 1 km increases arctic eddy kinetic energy eke and total kinetic energy tke by about 40 and 15 respectively eke is the highest along main currents over topography slopes where strong conversion from available potential energy to eke takes place it is high in halocline with a maximum typically centered in the depth range of 70 110 m and in the atlantic water layer of the eurasian basin as well the seasonal variability of eke along the continental slopes of southern canada and eastern eurasian basins is similar stronger in fall and weaker in spring

brine driven eddies under sea ice leads and their impact on the arctic ocean mixed layer abstract eddy generation induced by a line shaped salt flux under a sea ice lead and associated salt transport are investigated using a three dimensional numerical model the model is designed to represent a typical condition for the wintertime arctic ocean mixed layer where new ice formation within leads is known to be one of the primary sources of dense water the result shows that along lead baroclinic jets generate anticyclonic eddies at the base of the mixed layer and almost all the lead originated salt is contained inside these eddies these eddies survive for over a month after closing of the lead and transport the lead originated salt laterally consequently the lead origin salt settles only on the top of the halocline and is not used for increasing salinity of the mixed layer sensitivity experiments suggest that the horizontal scale of generated eddies depends only on the surface forcing and is proportional to the cube root of the total amount of salt input this scaling of eddy size is consi

enhanced diapycnal mixing due to near inertial internal waves propagating through an anticyclonic eddy in the ice free chukchi plateau abstractthe arctic ocean is known to be quiescent in terms of turbulent kinetic energy tke associated with internal waves to investigate the current state of tke in the seasonally ice free chukchi plateau arctic ocean this study performed a 3 week fixed point observation fpo using repeated microstructure hydrographic and current measurements in september 2014 during the fpo program the microstructure observation detected noticeable peaks of tke dissipation rate e during the transect of an anticyclonic eddy moving across the fpo station particularly e had a significant elevation in the lower halocline layer near the critical level reaching the order of 10 8 w kg 1 the adcp measured current displayed energetic near inertial internal waves niws propagating via the stratification at the top and bottom of the anticyclone according to spectral analyses of horizontal velocity the waves had almost downward energy propagation and its current amplitude reached 10 cm s 1 the wkb scaling inco

eddy maintenance and attrition in a vertically sheared current under arctic ice abstract steady drift of an ice cover produces a vertically sheared current in the upper ocean of the arctic under the ice cover mesoscale shallow brine and freshening sources generate submerged anticyclones and cyclones respectively a submerged eddy extending deep into the water column experiences differential advections by the vertically sheared current interaction between subsurface eddies and the sheared current is examined using a three dimensional numerical model in a coordinate system moving with the ice the initial salinity field is in geostrophic balance with the sheared current and a pulse of brine or freshening forcing produces an anticyclone or a cyclone in a coordinate system moving with the ice eddies are in a vertically sheared backward ambient current to an observer looking into the direction of the backward ambient current eddies move with the current and deflect to the right left for counterclockwise clockwise rotating eddies in both hemispheres the lower half of the eddy

an ultra refractory inclusion from the ornans carbonaceous chondrite a small refractory inclusion 1 g was found in the ornans carbonaceous chondrite the inclusion is extremely enriched in the most refractory ree lu er ho the more volatile light ree having more than two orders of magnitude lower concentrations refractory metals are fractionated in a similar way high abundances of the most refractory metals os re low content of more volatile metals such as ru and pt gas solid equilibrium at high temperatures can easily account for the observed relative abundances of refractory elements independent temperature estimates from ree abundances and refractory metal contents suggest an equilibrium temperature of about 1670 k at 10 3 atm the trace element pattern of the inclusion is complementary to the pattern of fine grained allende inclusions the inclusion may either represent a first condensate from a cooling gas of approximately solar composition or the very last residue from an evaporation process only the low contents of w and mo do not fit the pattern of refractory elements predicted from condensation calculations both elements however readily form volatile oxides therefore this depletion could be taken as indication of an evaporative origin of the inclusion the metal phase consists of small os rich grains in a comparatively os poor matrix grains and matrix appear to be a mechanical mixture this textural evidence cannot be easily reconciled with an evaporative origin a condensation origin of the inclusion would require that w and mo were lost at a later time in a more oxidising environment without affecting the metallic ta found in some of the metal grains

wave effects on ocean ice interaction in the marginal ice zone the effects of wave train on ice ocean interaction in the marginal ice zone are studied through numerical modeling a coupled two dimensional ice ocean model has been developed to include wave effects and wind stress for the predictions of ice edge dynamics the sea ice model is coupled to the reduced gravity ocean model through interfacial stresses the main dynamic balance in the ice momentum is between water ice stress wind stress and wave radiation stresses by considering the exchange of momentum between waves and ice pack through radiation stress for decaying waves a parametric study of the effects of wave stress and wind stress on ice edge dynamics has been performed the numerical results show significant effects from wave action the ice edge is sharper and ice edge meanders form in the marginal ice zone owing to forcing by wave action and refraction of swell system after a couple of days upwelling at the ice edge and eddy formation can be enhanced by the nonlinear effects of wave action wave action sharpens the ice edge and can produce ice meandering which enhances local ekman pumping and pycnocline anomalies the resulting ice concentration pycnocline changes and flow velocity field are shown to be consistent with previous observations

generation of submesoscale vortices a new mechanism small scale intense vortices composed of water with anomalous values of quasi conservative tracers have been observed in many oceans they are particularly numerous in the beaufort gyre of the arctic ocean possible mechanisms responsible for the generation of these features are examined conservation of temperature salinity and nutrients requires that beaufort sea vortices be created from water that flows into the arctic ocean from the pacific ocean across the broad shallow chukchi sea much of this water passes through barrow canyon near point barrow alaska observations in the canyon show the generation of vortices of approximately the same size as those observed in the beaufort sea barrow canyon is therefore a likely site for the generation of beaufort sea vortices most observed beaufort sea vortices have a central potential vorticity near zero because of a relative vorticity close to their chukchi sea source water is typically stratified with little relative vorticity so that its potential vorticity is nonzero a key step in the generation of the vortices is therefore the reduction of the potential vorticity of chukchi sea water to nearly zero it is proposed that this occurs through the action of frictional torques occurring as the chukchi sea water flows through barrow canyon rather than througji the action of vertical mixing because this flow is driven by a downstream pressure gradient it is concentrated on the right hand wall of the canyon by the coriolis force the frictional torques thus preferentially reduce the potential vorticity of the fluid anticyclonic vortices are therefore preferentially generated it is suggested that a similar scenario may play a role in the generation of submesoscale vortices containing water from the mediterranean and labrador seas