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

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

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

topographic control of thermohaline frontal structure in the barents sea polar front on the south flank of spitsbergen bank a combination of observations and process oriented numerical modeling is used to investigate the thermohaline structure of the barents sea polar front on the south flank of spitsbergen bank the polar front is the boundary between warm saline north atlantic water and cool fresh arctic water located over the outer edge of the bank observations from the barents sea polar front experiment in august 1992 show that north atlantic water was present in waters of 250 m or deeper with little vertical structure beneath the upper 50 m of the water column the mean velocity field over the south flank of the bank shows a westward flow of roughly 0 1 m s 1 in the north atlantic water and weak mean velocities over the outer edge of the bank a primitive equation model is used with idealized bathymetry to show that the inflow of north atlantic water into the barents sea via the bear island trough bifurcates at the sill between nordkapp bank and sentral bank at the eastern edge of the bear island trough one branch of the north atlantic water recirculates westward out of the barents sea and back into the norwegian sea the flow of north atlantic water is barotropic and linear following the bathymetry the recirculating branch is sheared off at the sill such that the core of recirculating flow is concentrated between the isobath coincident with the sill depth 260 m and the center of the trough 500 m both the cross bank structure of the model thermohaline fields as well as the along bank velocity are very similar to the observations at a depth of 80 m thus the frontal structure is controlled by the interaction of the barotropic inflow with the sill at the eastern edge of the bear island trough and is not controlled by processes occurring over the bank

effects of mackenzie river discharge and bathymetry on sea ice in the beaufort sea mackenzie river discharge and bathymetry effects on sea ice in the beaufort sea are examined in 2012 when arctic sea ice extent hit a record low satellite derived sea surface temperature revealed warmer waters closer to river mouths by 5 july 2012 mackenzie warm waters occupied most of an open water area about 316 000 km2 surface temperature in a common open water area increased by 6 5 c between 14 june and 5 july 2012 before and after the river waters broke through a recurrent landfast ice barrier formed over the shallow seafloor offshore the mackenzie delta in 2012 melting by warm river waters was especially effective when the strong beaufort gyre fragmented sea ice into unconsolidated floes the mackenzie and other large rivers can transport an enormous amount of heat across immense continental watersheds into the arctic ocean constituting a stark contrast to the antarctic that has no such rivers to affect sea ice

annual cycles of pco2sw in the southeastern beaufort sea new understandings of air sea co2 exchange in arctic polynya regions 1 from 23 october 2007 to 1 august 2008 we made continuous measurements of sea surface partial pressure of co2 pco2sw in three regions of the southeastern beaufort sea canada the amundsen gulf the banks island shelf and the mackenzie shelf all three regions are seasonally ice covered with mobile winter ice and an early spring opening that defines them as polynya regions amundsen gulf was characterized by undersaturated pco2sw with respect to the atmosphere in the late fall followed by an under ice increase to near saturation in winter a return to undersaturation during the spring and an increase to near saturation in summer the banks island shelf acted similarly while the mackenzie shelf experienced high supersaturation in the fall followed by a spring undersaturation and a complex spatially heterogeneous summer season none of these patterns are similar to the annual cycle described or proposed for other arctic polynya regions we hypothesize that the discrepancy reflects the influence of several previously unconsidered processes including fall phytoplankton blooms upwelling winter air sea gas exchange the continental shelf pump spring nutrient limitation summer surface warming horizontal advection and riverine input in order to properly predict current and future rates of air sea co2 exchange in such regions these processes must be considered on a location by location basis

joint up down decomposition and reconstruction using three component streamers with or without ghost model the sampling theory this paper addresses two artefacts inherent to marine towed streamer surveys 1 ghost reflections and 2 too sparse a sampling in the crossline direction a ghost reflection is generated when an upcoming reflection bounces off the sea surface back into the sensors and can in principle be removed by decomposing the measured wavefield into its up and downgoing constituents this process requires a dense sampling of the wavefield in both directions along and perpendicular to the streamers a dense sampling in the latter direction is however often impossible due to economical and operational constraints recent multi component streamers have been designed to record the spatial gradients on top of the pressure which not only benefits the wavefield decomposition but also facilitates a lower than nyquist sampling rate of the pressure in this paper wavefield reconstruction and deghosting are posed as a joint inverse problem we present two approaches to establish a system matrix that embeds both a deghosting and an interpolation operator the first approach is derived with a ghost model whereas the second approach is derived without a ghost model the embodiment of a ghost model leads to an even lower sampling rate but relies on a more restrictive assumption on the sea surface

palaeobiogeography and the ordovician and mesozoic cenozoic biotic radiations curves of taxonomic diversity through geological time consistently show major evolutionary radiations during the ordovician period and from the mid mesozoic to the present day both intervals were characterized by marked biotic provincialism reflecting episodes of major continental break up and global tectonism and their later histories featured steep global climatic gradients the ordovician radiation can be recognized at a wide spectrum of taxonomic levels from species to class and the biogeographical patterns associated with the radiation of individual clades reflect a complex combination of plate distribution tectonic activity sedimentary environment sea level rise and ultimately glaciation the true scale of the mid mesozoic cenozoic biotic radiation is currently a topic of intense debate but there is no doubt that it affected plants and animals in both the marine and terrestrial realms the role of land bridges and ocean gateways in controlling the for mation of biodiversity patterns has been a persistent theme in mesozoic cenozoic bio geography and a complex set of neogene tectonic events probably aided the development of both latitudinal and longitudinal provinces during the cenozoic the present volume highlights some of the successes across a spectrum of approaches to unravelling the ordovician and mesozoic cenozoic radiations within the context of palaeobiogeography

on the spatiotemporal behavior of sea ice concentration anomalies in the northern hemisphere 1 reduction in the aerial extent and thickness of sea ice in the northern hemisphere is an important element in understanding how the arctic responds to global scale climate variability and change previous studies have demonstrated a significant reduction in minimum sea ice extent serreze et al 2003 with record reduction in 2005 observational studies attribute this phenomenon to variations in sea level pressure and large scale atmospheric teleconnection patterns such as the northern annular mode nam deser et al 2000 serreze et al 2003 in this study we examine variations in sea ice in the context of spatiotemporal variability of sea ice concentration sic anomalies in the northern hemisphere during the onset of ice formation examined in particular are timescales associated with coherent regions of persistence in an e folding time spatial distribution efsd annual variations of weekly sic anomalies are studied and spatial relations between positive and negative sic anomalies are explored on a hemispheric scale the results from this investigation demonstrate coherent sic persistence patterns throughout the northern hemisphere with timescales ranging from 3 to 7 weeks spatial correspondence between negative trends in sic anomalies and the efsd suggests that the same mechanism may be responsible for both increased ice reduction and persistence in this region examination of spatial coherence in sic anomalies indicates that maximum sic anomalies prevail near the kara sea beaufort sea and chukchi sea regions during late summer early fall from 1979 to 2004 a latitudinal assessment at 80 70 and 60 n indicates a poleward shift and retreat in sic anomalies while also underlining the decadal shift in variability often attributed to the nam

depletion of perennial sea ice in the east arctic ocean 1 the extent of perennial sea ice in the east arctic ocean 0 180 e decreased by nearly one half with an abrupt reduction of 0 95 106 km2 while the west arctic ocean 0 180 w had a slight gain of 0 23 106 km2 between 2004 and 2005 as observed by satellite scatterometer data during november december the net decrease in the total perennial ice extent is 0 72 106 km2 about the size of texas perennial ice in the east arctic ocean continued to be depleted with an areal reduction of 70 from october 2005 to april 2006 with the east arctic ocean dominated by seasonal sea ice a strong summer melt may open a vast ice free region with a possible record minimum ice extent largely confined to the west arctic ocean simultaneous scatterometer measurements of sea ice and winds will be crucial for sea ice monitoring and forecasts

reconstruction and analysis of the chukchi sea circulation in 1990 1991 1 the chukchi sea cs circulation reconstructed for september 1990 to october 1991 from sea ice and ocean data is presented and analyzed the core of the observational data used in this study comprises the records from 12 moorings deployed in 1990 and 1991 in u s and russian waters and two hydrographic surveys conducted in the region in the fall of 1990 and 1991 the observations are processed by a two step data assimilation procedure involving the pan arctic ice ocean modeling and assimilation system employing a nudging algorithm for sea ice data assimilation and the semi implicit ocean model utilizing a conventional four dimensional variational 4d var assimilation technique the reconstructed cs circulation is studied to identify pathways and assess residence times of pacific water in the region quantify the balances of volume freshwater and heat content and determine the leading dynamical factors configuring the cs circulation it is found that in 1990 1991 high ao index and a cyclonic circulation regime pacific water transiting the cs toward the canada basin followed two major pathways namely via herald canyon herald branch of circulation 0 23 sv and between herald shoal and cape lisburne central branch of circulation and alaskan coastal current 0 32 sv the annual mean flow through long strait was negligible 0 01 sv typical residence time of pacific water in the region varied between 150 days for waters entering the cs in september and 270 days for waters entering in february march momentum balance analysis reveals that geostrophic balance between barotropic pressure gradient and coriolis force dominated for most of the year baroclinic effects were important for circulation only in the regions with large horizontal salinity gradients associated with the fresh alaskan and siberian coastal currents and the cape lisburne and great siberian polynyas in the polynyas the baroclinic effects were due to strong salinification and convection processes associated with sea ice formation

sea ice thickness from field measurements in the northwestern barents sea the barents sea is one of the fastest changing regions of the arctic and has experienced the strongest decline in winter time sea ice area in the arctic at 23 4 per decade sea ice thickness in the barents sea is not well studied we present two previously unpublished helicopter borne electromagnetic hem ice thickness measurements from the northwestern barents sea acquired in march 2003 and 2014 the hem data are compared to ice thickness calculated from ice draft measured by uls deployed between 1994 and 1996 these data show that ice thickness varies greatly from year to year influenced by the thermodynamic and dynamic processes that govern local formation vs long range advection in a year with a large inflow of sea ice from the arctic basin the barents sea ice cover is dominated by thick multiyear ice as was the case in 2003 and 1995 in a year with an ice cover that was mainly grown in situ the ice will be thin and mechanically unstable as was the case in 2014 the hem data allow us to explore the spatial and temporal variability in ice thickness in 2003 the dominant ice class was more than 2 years old and modal sea ice thickness varied regionally from 0 6 to 1 4 m with the thinner ice being either first year ice or multiyear ice which had come into contact with warm atlantic water in 2014 the ice cover was predominantly locally grown ice less than 1 month old regional modes of 0 5 0 8 m these two situations represent two extremes of a range of possible ice thickness distributions that can present very different conditions for shipping traffic or have a different impact on heat transport from ocean to atmosphere

geobiology and paleobiogeography tracking the coevolution of the earth and its biota abstract paleobiogeographic research is an important area of geobiology that involves the study of the coevolution of the earth and its biota by considering how tectonic and climatic changes have affected the evolution and distribution of organisms the intellectual heritage of the discipline stretches back well before darwin phylogenetic approaches to paleobiogeography have played an important part in the expansion of the field and recent analyses have incorporated geographic information systems gis each of these approaches by enhancing the precision of paleobiogeography helps make the discipline more relevant to geobiology the interaction occurring between the geological and biological sciences in paleobiogeography is apparent in several areas first there is the emergence of new techniques such as the ability to analyze ancient dna sequences also paleobiogeographers and biogeographers have realized that geo dispersal a biogeographic process first identified through studies of the fossil record can powerfully influence the evolution and distribution of biotas finally biogeographers have recognized that paleontological incompleteness and extinction constrain our ability to reconstruct biogeographic patterns in the fossil record and the extant biota respectively each of these developments suggests that further growth in paleobiogeography will involve important interactions between studies involving the fossil record and the extant biota and this along with the discipline s commitment to studying how tectonic and climatic changes have influenced evolution reaffirms the validity of the synthetic field that is geobiology

ocean acidification and biologically induced seasonality of carbonate mineral saturation states in the western arctic ocean calcium carbonate caco3 mineral saturation states for aragonite aragonite and calcite calcite are calculated for waters of the chukchi sea shelf and canada basin of the western arctic ocean during the shelf basin interactions project from 2002 to 2004 on the chukchi sea shelf a strong seasonality and vertical differentiation of aragonite and calcite saturation states was observed during the summertime sea ice retreat period high rates of phytoplankton primary production and net community production act to increase the aragonite and calcite of surface waters while subsurface waters become undersaturated with respect to aragonite due primarily to remineralization of organic matter to co2 this seasonal phytoplankton carbonate saturation state interaction induces strong undersaturation of aragonite aragonite 10 the seasonal aragonite undersaturation of waters observed on the chukchi sea shelf is likely a recent phenomenon that results from the uptake of anthropogenic co2 and subsequent ocean acidification with seasonality of saturation states superimposed by biological processes these undersaturated waters are potentially highly corrosive to calcifying benthic fauna e g bivalves and echinoderms found on the shelf with implications for the food sources of large benthic feeding mammals e g walrus gray whales and bearded seals the benthic ecosystem of the chukchi sea and other arctic ocean shelves is thus potentially vulnerable to future ocean acidification and suppression of caco3 saturation states

pleistocene and holocene interglacial molluscan assemblages from patagonian and bonaerensian littoral argentina sw atlantic palaeobiodiversity and palaeobiogeography abstract our analysis of palaeobiodiversity and palaeobiogeography of quaternary molluscan assemblages provide information on the last coastal scenarios in the sw atlantic we present patterns of species richness areas of endemism and between areas relationships based on records 721 taxa from argentina and northwards in south america surinam brazil uruguay including pleistocene holocene and modern sites 48 localities in argentina our data since the mid late pleistocene mis11 1 ca 400 ka b p to present suggest environmental changes linked to sea level and climatic fluctuations large enough to alter benthic associations compositional geographical variations including a few extinctions the southwards decreasing diversity trend for modern bivalves mostly infaunal taxa and gastropods mostly epifaunal taxa from surinam to tierra del fuego responds mainly to latitudinal sst salinity barriers hydrodynamic forces rivers and shallow currents minima peaks fit with local estuarine and marginal marine sites influenced by the rio de la plata plume highest peaks with fully marine warmer waters influenced by the brazilian current bonaerensian sector a similar trend applies for the holocene pleistocene maxima peaks in patagonia belong to mis11 and mis5 highstands warmer than today multivariate cluster analysis ca minimum spanning trees superimposed to principal coordinates analysis pco and cladistic parsimony analysis of endemicity pae methods showed congruent relationships between localities discriminating marginal from open marine environments but pco combined with pae was most advantageous for our area and dataset 382 gastropods 339 bivalves 29 pleistocene 28 holocene and 35 modern sites allowing objective quick comparisons shifts of areas of endemism during the holocene and pleistocene relate with sst and salinity changes a more homogeneous mid holocene ca 7 5 ka b p scenario of regionally increased salinity and higher ca 2 c sst defined the bonaerensian and northern patagonian sectors facilitating southwards shifts of bivalve and gastropod taxa for patagonia a colder pleistocene scenario south of sao is documented by tegula atra exclusive pleistocene cold water species extinct in the swa probably a signal of post lgm palaeoceanographical changes in the mar argentino

modeling ice dynamics of coastal seas a coupled sea ice barotropic ocean model with a 1 km resolution and a seaward domain of 200 km quantifies three coastal processes coupling of ice motion to wind driven coastal currents ice thickness redistribution under compaction at the coast and formation of coastal shear zones the model consists of an ice momentum balance mass concentration and two parameter ice thickness distribution and equations for horizontal water motion and continuity using vertical structure functions an appropriate constitutive law appears to be a hardening plastic based on qualitative observations from alaskan continental shelves for first year sea ice strength is taken to be proportional to the square of ice thickness a north wind example of 10 m s with the coastline to the west shows the depth dependence of rotational shear in the sea ice ocean boundary layer and sea surface tilt which contributes an alongshore slope current there is slight convergence of sea ice over the shelf a coastal shear zone of 4 km and an alongshore ice speed seaward of the shear zone of 6 of the wind speed caused by the combination of an under ice shear layer and an alongshore slope current for an onshore wind ice is near free drift at 3 of the wind seaward of a ridging front which propagates seaward a square dependence of ice strength on thickness is required for the rubble field to approach a limiting thickness consistent with observations the hardening plastic interpretation of the rubble field has the stress state at the yield limit in contrast with a rigid plastic of high constant strength that yields only at the coast we conclude that 1 ice thickness motion feedback is important on scales less than 10 km 2 the observational base to discriminate between mesoscale constitutive laws is not yet available and 3 the relation of ice velocity to wind stress is variable because the ocean slope current responds only to the alongshore component of the wind

the great ordovician biodiversification event gobe the palaeoecological dimension abstract the great ordovician biodiversification event gobe saw a spectacular increase in marine biodiversity at all taxonomic levels largely within the phyla established much earlier during the so called cambrian explosion the diversification was probably the result of a combination of several geological and biological processes and the positive feedbacks resulting from them the present paper reviews the palaeoecological dimension of the gobe it involved major increases in s and biodiversity largely associated with the rise of the paleozoic evolutionary fauna dominated by suspension feeders and involving a greater occupation of ecospace and more complex ecological structures in the ecological evolutionary units p1 and p2 in the benthos these include more complex food webs than those of the cambrian greater tiering especially above the sediment water interface and the development of guild structures indicating increased competition between taxa for particular resources the ordovician is characterized by a profound change in reef composition with a switch from microbial dominated reefs in the early and middle ordovician to metazoan dominated reefs in the late ordovician increases in complexity of deep water trace fossil assemblages began in the early ordovician and mark the increasing exploitation in that environment and the development of hardgrounds permitted bioerosion and encrusting strategies together with the appearance of cryptic communities within the water column the gobe involved a significant increase in the diversity of the phytoplankton and the development of a diverse zooplankton including planktotrophic larvae from a range of invertebrate clades this revolution in the plankton enabled the establishment of a diverse fauna of pelagic vertebrates molluscs and arthropods and promoted the rise of suspension feeders in the benthos an escalation amongst predators and thus community evolution may also have been a major driver of biodiversification

varieties of shallow temperature maximum waters in the western canadian basin of the arctic ocean the properties and spreading pathways of shallow temperature maximum waters stms in the western canadian basin are investigated using ctd and mooring data obtained in 1997 98 as part of the sheba surface heat budget of the arctic ocean drift experiment and available historical data three distinct varieties of stm are recognized on the basis of salinity range 1 surface mixed layer water smlw with s 32 psu these stms carry sufficient heat within the upper layers of the ocean to significantly affect the rates of ice cover and decay for example during the winter of 1997 98 anomalously warm stm 0 c originating from ecsw was observed to spread northwards along the northwind ridge and chukchi plateau where the maximum reduction of the ice covers was subsequently observed in late summer 1998 maslanik et al 1999 regional climate variability and ice cover in the western canadian basin are thus affected not only by anomalous atmospheric circulation patterns but also by the circulation of upper ocean water masses

dense water formation in the laptev sea flaw lead 1 two primitive equation based models are used to estimate the formation of total volumes either of arctic cold halocline water chw intermediate water imw or deep water dw through freeze related salt rejection in the siberian laptev sea flaw lead system model a assumes that the rejected salt remixes with surface mixed water smw beyond the leads until salinities allow for contribution to the midlayers of either the chw the imw or the dw model b simulates direct salt rejection to the upper layer of the cold halocline and after remixing here further contribution to the midlayers of chw imw or dw averaging both model estimates laptev leads contribute either 0 161 sv of chw 0 075 sv of imw or 0 065 sv of dw which represents as much as 23 16 or 30 of arctic wide lead derived dense water contribution to the appropriate layer respectively northwestern laptev leads produce the greatest amount of dense water these lead sections show very short buoyancy equilibrium timescales 6 to 13 days and local dense water production may potentially be amplified by lateral brine injection into the cold halocline through bottom eddies central southern and southeastern leads generally produce little salt due to low surface water salinities as definite separation mechanisms and proportion distributions of rejected lead brines into chw iwm and dw are still unidentified in nature a combination of lead salt rejection and remixing model a and direct downward expulsion of brine packages model b is assumed to steer laptev lead dense water production

nutrient supply and biological response to wind induced mixing inertial motion internal waves and currents in the northern chukchi sea a fixed point observation station was set up in the northern chukchi sea during autumn 2013 and for about 2 weeks conductivity temperature depth ctd water samplings 6 h and microstructure turbulence measurements 2 to 3 times a day were performed this enabled us to estimate vertical nutrient fluxes and the impact of different types of turbulent mixing on biological activity there have been no such fixed point observations in this region where incoming low salinity water from the pacific ocean river water and sea ice meltwater promote a strong pycnocline halocline that stabilizes the water column previous studies have suggested that because of the strong pycnocline wind induced ocean mixing could not change the stratification to impact biological activity however the present study indicates that a combined effect of an uplifted pycnocline accompanied by wind induced inertial motion and turbulent mixing caused by intense gale force winds 10 m s 1 did result in increases in upward nutrient fluxes primary productivity and phytoplankton biomass particularly large phytoplankton such as diatoms convective mixing associated with internal waves around the pycnocline also increased the upward nutrient fluxes and might have an impact on biological activity there for diatom production at the fixed point observation station it was essential that silicate was supplied from a subsurface silicate maximum a new feature that we identified during autumn in the northern chukchi sea water mass distributions obtained from wide area observations suggest that the subsurface silicate maximum water was possibly derived from the ventilated halocline in the canada basin

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

tectonic processes in papua new guinea and past productivity in the eastern equatorial pacific ocean phytoplankton growth in the eastern equatorial pacific ocean today accounts for about half of the new production the fraction of primary production fuelled by externally supplied nutrients in the global ocean the recent demonstration that an inadequate supply of iron limits primary production in this region1 supports earlier speculation that in the past fluctuations in the atmospheric deposition of iron bearing dust may have driven large changes in productivity2 but we argue here that only small 2 nm increases in the iron concentration in source waters of the upwelling equatorial undercurrent are needed to fuel intense diatom production across the entire eastern equatorial pacific ocean episodic increases in iron concentrations of this magnitude or larger were probably frequent in the past because a large component of the undercurrent originates in the convergent island arc region of papua new guinea which has experienced intensive volcanic erosional and seismic activity over the past 16 million years cycles of plankton productivity recorded in eastern equatorial pacific sediments may therefore reflect the influence of tectonic processes in the papua new guinea region superimposed on the effects of global climate forcing

impact of the arctic ocean atlantic water layer on siberian shelf hydrography this paper examines the role of the arctic ocean atlantic water aw in modifying the laptev sea shelf bottom hydrography on the basis of historical records from 1932 to 2008 field observations carried out in april may 2008 and 2002 2009 cross slope measurements a climatology of bottom hydrography demonstrates warming that extends offshore from the 30 50 m depth contour bottom layer temperature time series constructed from historical records links the laptev sea outer shelf to the aw boundary current transporting warm and saline water from the north atlantic the aw warming of the mid 1990s and the mid 2000s is consistent with outer shelf bottom temperature variability for april may 2008 we observed on shelf near bottom warm and saline water intrusions up to the 20 m isobath these intrusions are typically about 0 2 c warmer and 1 1 5 practical salinity units saltier than ambient water the 2002 2009 cross slope observations are suggestive for the continental slope upward heat flux from the aw to the overlying low halocline water lhw the lateral on shelf wind driven transport of the lhw then results in the bottom layer thermohaline anomalies recorded over the laptev sea shelf we also found that polynya induced vertical mixing may act as a drainage of the bottom layer permitting a relatively small portion of the aw heat to be directly released to the atmosphere finally we see no significant warming up until now over the laptev sea shelf deeper than 10 15 m in the historical record future climate change however may bring more intrusions of atlantic modified waters with potentially warmer temperature onto the shelf which could have a critical impact on the stability of offshore submarine permafrost

advection in polar and sub polar environments impacts on high latitude marine ecosystems we compare and contrast the ecological impacts of atmospheric and oceanic circulation patterns on polar and sub polar marine ecosystems circulation patterns differ strikingly between the north and south meridional circulation in the north provides connections between the sub arctic and arctic despite the presence of encircling continental landmasses whereas annular circulation patterns in the south tend to isolate antarctic surface waters from those in the north these differences influence fundamental aspects of the polar ecosystems from the amount thickness and duration of sea ice to the types of organisms and the ecology of zooplankton fish seabirds and marine mammals meridional flows in both the north pacific and the north atlantic oceans transport heat nutrients and plankton northward into the chukchi sea the barents sea and the seas off the west coast of greenland in the north atlantic the advected heat warms the waters of the southern barents sea and with advected nutrients and plankton supports immense biomasses of fish seabirds and marine mammals on the pacific side of the arctic cold waters flowing northward across the northern bering and chukchi seas during winter and spring limit the ability of boreal fish species to take advantage of high seasonal production there southward flow of cold arctic waters into sub arctic regions of the north atlantic occurs mainly through fram strait with less through the barents sea and the canadian archipelago in the pacific the transport of arctic waters and plankton southward through bering strait is minimal in the southern ocean the antarctic circumpolar current and its associated fronts are barriers to the southward dispersal of plankton and pelagic fishes from sub antarctic waters with the consequent evolution of antarctic zooplankton and fish species largely occurring in isolation from those to the north the antarctic circumpolar current also disperses biota throughout the southern ocean and as a result the biota tends to be similar within a given broad latitudinal band south of the southern boundary of the acc there is a large scale divergence that brings nutrient rich water to the surface this divergence along with more localized upwelling regions and deep vertical convection in winter generates elevated nutrient levels throughout the antarctic at the end of austral winter however such elevated nutrient levels do not support elevated phytoplankton productivity through the entire southern ocean as iron concentrations are rapidly removed to limiting levels by spring blooms in deep waters however coastal regions with the upward mixing of iron maintain greatly enhanced rates of production especially in coastal polynyas in these coastal areas elevated primary production supports large biomasses of zooplankton fish seabirds and mammals as climate warming affects these advective processes and their heat content there will likely be major changes in the distribution and abundance of polar biota in particular the biota dependent on sea ice

variability of the antarctic coastal current in the amundsen sea abstract the nature of the antarctic coastal current aacc and its seasonal and non seasonal several day variability were investigated using long term mooring data obtained near the dotson ice shelf in the amundsen sea the moored instruments were operated from february 2012 to january 2014 in the dotson trough which is one of the deep troughs on the amundsen sea shelf the hydrographic structure of sigma density distribution at the ice shelf 27 25 kg m 3 at the surface was found to be higher than at the continental shelf 27 00 kg m 3 whereas in the middle layer 27 45 kg m 3 isopycnal extended to 300 m depth near the ice shelf but below 200 m depth in the offshore the surface mixed layer thickened from the shelf break toward the ice shelf this thickening was caused partially by coastal downwelling resulting from onshore ekman transport and by ekman pumping in the coastal area the baroclinic component of the aacc near the dotson ice shelf increased from july to october and decreased from january to june in 2013 in comparison with other potential driving forces the seasonal and non seasonal short term variation of the aacc correlated well with density variability determined principally by salinity variation therefore it is suggested that the variability of the isopycnocline by ekman pumping in the coastal area is one of the important factors controlling the seasonality and non seasonal variability of the aacc

the impact of freshening on phytoplankton production in the pacific arctic ocean since the 1990s drastic melting of sea ice and continental ice in the arctic region triggered by global warming has caused substantial freshening of the arctic ocean while several studies attempted to quantify the magnitude of this freshening its consequences on primary producers remain poorly documented in this study we evaluate the impact of the freshwater content fwc of the upper arctic ocean on phytoplankton across the pacific sector from the bering strait 65 n to the north pole 86 n during summer 2008 we performed statistical analyses on the physical biogeochemical and biological data acquired during the chinare 2008 cruise to investigate the effect of sea ice melting on the arctic phytoplankton we found that the strong freshening observed in the canada basin had a negative impact on primary producers as a result of the deepening of the nitracline and the establishment of a subsurface chlorophyll maximum scm in contrast regions with lower freshening such as the chukchi shelf and the marginal ice zone miz over the chukchi borderland exhibited a shallower nitracline sustaining relatively high primary production and biomass our results imply that the predicted increase freshening in future years will likely cause the arctic deep basin to become more oligotrophic because of weaker surface nutrient renewal from the subsurface ocean despite higher light penetration

halocline water formation in the barents sea hydrographic data from the first phase of the coordinated eastern arctic experiment cearex are analyzed the data consist of temperature and salinity measurements made by a ship based conductivity temperature depth ctd instrument and by a drifting salargos buoy these data were collected in the autumn and early winter of 1988 1989 in the northern barents sea mostly in ice covered conditions and then across the marginal ice zone miz the data show that relatively warm salty water of atlantic origin is modified by air cooling and ice melting to produce lighter water that has properties identical to lower halocline water found in the arctic ocean this occurs mostly at the miz and to a lesser degree within the ice pack itself at the miz the halocline water subducts underneath the lighter meltwater that resides directly under the ice pack geostrophic velocity calculations indicate that it then turns eastward and flows toward the kara sea in keeping with previous chemical tracer analyses a rough calculation reveals that the amount of halocline water formed in this way in the barents sea and fram strait is 30 50 of that formed by ice growth in eastern arctic polynyas

water mass distribution and polar front structure in the western barents sea the water mass distribution in the western barents sea the thermohaline structure of the western barents sea polar front and the local formation of a dense water mass are described on the basis of an analysis of historical hydrographic data this study concentrated on the frontal region between bjornoya and hopen island where arctic water is found on the spitsbergen bank and atlantic water in the bear island trough and hopen trench the distributions of atlantic and arctic waters in relation to topography were consistent with the hypothesis that the location of the polar front is fixed at about the 250 m isobath by the barotropic circulation of atlantic water within the bear island trough and hopen trench in winter vertical gradients of temperature and salinity were weak throughout the frontal region consistent with a barotropic topographically controlled front in summer vertical gradients remained weak below 100 m depth but increased in the upper layer as a result of the presence of fresh warm surface water produced by melting ice the topographic control of thermohaline properties at the surface was disrupted by the meltwater pool and the meltwater contributed to water mass modification in the frontal region the following seasonal cycle of water mass formation was hypothesized summer heating melts the sea ice on the spitsbergen bank and produces the surface meltwater pool this meltwater not only increases vertical thermohaline gradients on the bank but also crosses the front and freshens the surface layer throughout the western barents sea subsequent winter cooling which creates ice over the bank also forms dense water in the bear island trough and hopen trench by convective mixing of atlantic water and the overlying meltwater

the early devonian palaeobiogeography of eastern australasia abstract biogeographical analyses of devonian australasia australia and new zealand have previously presented a narrative approach to the interrelationships of continental faunal provinces useful for the creation of biotic hypotheses similarities and differences between biotic provinces remains untested this study seeks to propose the first regional faunal provinces allowing a test of geological and biotic hypotheses using parsimony analysis of endemicity the relationships of eastern australasian terranes were tested through the hierarchical analysis of faunal composition biochorologic sub provinces were proposed using geo spatial computer software and analysed through phylogenetic software that resulted in the formalisation of 20 biochorologic sub provinces the relationships between these units show a significant holdover of silurian species the interactions between convergent terranes and the continental margin the distinct history of the lachlan fold belt terranes and offers biotic support for the existence of the tasmanian microcontinent vandieland

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

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

on data independent multicomponent interpolators and the use of priors for optimal reconstruction and 3d up down separation of pressure wavefields in marine acquisition the interference between the upgoing and downgoing wavefields introduces a receiver ghost which reduces the effective bandwidth of the seismic wavefield a two component streamer provides means for removing the receiver ghost by measuring pressure and vertical particle velocity however due to nonuniform and relatively sparse sampling in the crossline direction the seismic data are usually severely aliased in the crossline direction and the deghosting may not be feasible in a true 3d sense a true multicomponent streamer measures all components of the particle motion wavefield in addition to the pressure wavefield this enables solving the 3d deghosting and crossline reconstruction problems simultaneously without making assumptions on the wavefield or the subsurface we havedeveloped two data independent algorithms suited for multicomponent acquisition the first algorithm reconstructs the total pressure wavefield in the crossline direction by using the pressure and the crossline

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

response of sea ice drift to wind forcing on the northeastern newfoundland shelf observations of sea ice drift obtained with satellite tracked ice beacons in march april of 1988 and 1989 have been used to examine the response of sea ice drift to wind forcing over the northern newfoundland continental shelf the short term 5 20 days response of sea ice drift ranges from 2 6 to 5 4 of the local wind over much of the inner continental shelf which is comparable to that in the bering sea and the antarctic but larger than that in arctic sea ice drifts to the right of the local wind at angles ranging from 10 to 63 the response to wind forcing is largest near the ice edge both over the middle portions of the shelf and along the southern margins of the seasonal ice zone and during strong and steady wind of several days duration the large wind driven response of ice drift observed in this study in comparison with the arctic may result from 1 reduced levels of internal ice stress associated with the generally thin ice cover and lower areal concentration of sea ice 2 large atmospheric drag coefficients associated with the small ice floes in areas of comparatively higher ice concentration and 3 smooth ice bottom caused by melting in nearshore areas the ice to wind coupling is reduced owing to larger internal ice stresses experienced locally due to ice pileup

interannual variability of arctic landfast ice between 1976 and 2007 abstractanalysis of weekly sea ice charts produced by the u s national ice center from 1976 to 2007 indicates large interannual variations in the averaged winter landfast ice extent around the arctic basin during the 32 yr period of the record landfast ice cover was relatively extensive from the early to mid 1980s but since then has declined in many coastal regions of the arctic particularly after the early 1990s while the barents baltic and bering seas show increases in landfast ice area the overall change for the northern hemisphere is negative about 12 27 2 8 103 km2 yr 1 or 7 1 5 decade 1 relative to the long term mean except in a few coastal regions the seasonal duration of landfast ice is shorter overall particularly in the laptev east siberian and chukchi seas the decreased winter landfast ice extent is associated with some notable changes in ice growth and melt patterns in particular the slowed landfast ice expansion during fall and early winter since 1990 the observed

seafloor control on sea ice abstract the seafloor has a profound role in arctic sea ice formation and seasonal evolution ocean bathymetry controls the distribution and mixing of warm and cold waters which may originate from different sources thereby dictating the pattern of sea ice on the ocean surface sea ice dynamics forced by surface winds are also guided by seafloor features in preferential directions here satellite mapping of sea ice together with buoy measurements are used to reveal the bathymetric control on sea ice growth and dynamics bathymetric effects on sea ice formation are clearly observed in the conformity between sea ice patterns and bathymetric characteristics in the peripheral seas beyond local features bathymetric control appears over extensive regions of the sea ice cover across the arctic ocean the large scale conformity between bathymetry and patterns of different synoptic sea ice classes including seasonal and perennial sea ice is identified an implication of the bathymetric influence is that the maximum extent of the total sea ice cover is relatively stable as observed by scatterometer data in the decade of the 2000s while the minimum ice extent has decreased drastically because of the geologic control the sea ice cover can expand only as far as it reaches the seashore the continental shelf break or other pronounced bathymetric features in the peripheral seas since the seafloor does not change significantly for decades or centuries sea ice patterns can be recurrent around certain bathymetric features which once identified may help improve short term forecast seasonal outlook and decadal prediction of the sea ice cover moreover the seafloor can indirectly influence the cloud cover by its control on sea ice distribution which differentially modulates the latent heat flux through ice covered and open water areas

seasonal variability of sea surface height in the coastal waters and deep basins of the nordic seas sea surface height measured by the envisat radar altimeter over open ocean and from leads in sea ice are combined to generate a complete view of variability in the nordic seas geographically and seasonally the observed seasonal variability is decomposed using empirical orthogonal functions and is consistent with seasonal variations in steric and dynamic forcing wintertime increase in sea surface height on the east greenland shelf is hypothesised to be caused by wind forced downwelling which provides direct evidence for the regional play of coastal dynamics high levels of eddy kinetic energy around the sea ice edge in fram strait and off east greenland and svalbard are consistent with the interaction of the wind with the ice edge

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

rapid formation of a sea ice barrier east of svalbard 1 daily seawinds scatterometer images acquired by the quikscat satellite show an elongated sea ice feature that formed very rapidly 1 2 days in november 2001 east of svalbard over the barents sea this sea ice structure called the svalbard sea ice barrier spanning approximately 10 in longitude and 2 in latitude restricts the sea route and poses a significant navigation hazard the secret of its formation appears to lie in the bottom of the sea a comparison between bathymetry from the international bathymetric chart of the arctic ocean data and the pattern of sea ice formation from scatterometer data reveals that the sea ice barrier conforms well with and stretches above a deep elongated channel connecting the franz josef victoria trough to the hinlopen basin between svalbard and franz josef land historic hydrographic data from this area indicate that this sea channel contains cold arctic water less than 50 m below the surface strong and persistent cold northerly winds force strong heat loss from this shallow surface layer leading to the rapid formation of the sea ice barrier heat transfer rates estimated from european centre for medium range weather forecasts temperature and wind data over this region suggest that the surface water along the deep channel can be rapidly cooled to the freezing point scatterometer results in 1999 2003 show that sea ice forms in this area between october and december understanding the ice formation mechanisms helps to select appropriate locations for deployment of buoys measuring wind and air sea temperature profile and to facilitate ice monitoring modeling and forecasting

wavefield decomposition based on acoustic reciprocity theory and applications to marine acquisition in marine seismic acquisition the free surface generates seismic events in our recorded data that are often categorized as noise because these events do not contain independent information about the subsurface geology ghost events are considered as such noise because these events are generated when the energy generated by the seismic source as well as any upgoing wavefield propagating upward from the subsurface is reflected downward by the free surface as a result complex interference patterns between up and downgoing wavefields are present in the recorded data affecting the spectral bandwidth of the recorded data negatively the interpretability of the data is then compromised and hence it is desirable to remove the ghost events from the data rayleigh s reciprocity theorem is used to derive the relevant equations for wavefield decomposition for multisensor and single sensor data for depth varying and depth independent recordings from marine seismic experiments using a single source or dual source configuration a comparison is made between the results obtained for a 2d synthetic example designed to highlight the strengths and weaknesses of the various acquisition configurations it is demonstrated that using the proposed wavefield decomposition method multisensor data measurements of pressure and particle velocity components or multidepth pressure measurements allow for optimal wavefield decomposition as independent measurements are used to eliminate the interference patterns caused by the free surface single sensor data using constant depth recordings are found to be incapable of producing satisfactory results in the presence of noise single sensor data using a configuration with depth varying measurements are able to deliver better results than when constant depth recordings are used but the results obtained are not of the same quality when multisensor data are used

early middle devonian brachiopod provincialism and bioregionalization at high latitudes a case study from southwestern gondwana the paleobiogeography of early middle devonian pragian eifelian brachiopods from west gondwana was assessed to determine any potential controls regional climatic differences or global eustasy that may have driven bioregionalization the pragian eifelian interval of west gondwana was examined because work by previous authors suggested that this was a period when regionally extensive areas of provincialism among marine invertebrates were present and most pronounced factors of particular interest in this study were the controls over brachiopod bioregionalization at high 60 90 southern latitudes which the malvinokaffric realm is thought to have entirely occupied a large presence absence data matrix was compiled consisting of the occurrences of 206 genera from 17 localities across west gondwana and an array of multivariate methods cluster analysis nonmetric multidimensional scaling and network analysis was employed to assess regional bioregionalization trends the results of our study suggest that regional climatic differences brought on by latitudinal effects were the determining driver for bioregionalism of brachiopods during the pragian eifelian and these trends were coincident with a global cooling period during the early middle devonian our study further suggests that of the three regional paleobiogeographic realms thought to be present in west gondwana during the early middle devonian eastern americas old world and malvinokaffric only the malvinokaffric realm is valid as a single biogeographic area its area however is reduced it is interpreted to have been a second order biogeographic area and not a first order area as suggested by previous authors given these factors we suggest a new demonym for this area the malvinoxhosan given the racially charged connotations of malvinokaffric we present a new biogeographic framework for west gondwana that is free of preconceived biogeographic area and rank biases with the understanding that a more globally expansive study should be undertaken to elucidate these areas and their rank within the correct hierarchy two first order paleobiogeographic areas are recognized in west gondwana and are named according to their latitudinal extent namely the high latitude 60 s 90 s and temperate latitude 30 s 60 s bioregions the temperate latitude bioregion consists of a single second order paleobiogeographic area the colombian west african bioregion two second order bioregions are present in the high latitude bioregion namely the amazonian and malvinoxhosan bioregions here the amazonian 50 s 70 s compositionally was an intermediate region between the colombian west african 30 s 50 s and malvinoxhosan 70 s 90 s end members latitudinal effects may also have been responsible for dividing the malvinoxhosan bioregion into two tentative third order paleobiogeographic areas namely the andeo south african 70 s 80 s and the parana 80 s 90 s bioregions

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

sources of dissolved inorganic carbon to the canada basin halocline a multitracer study we examine the dissolved inorganic carbon maximum in the canada basin halocline using a suite of geochemical tracers to gain insight into the factors that contribute to the persistence of this feature hydrographic and geochemical samples were collected in the upper 500 m of the southwestern canada basin water column in the summer of 2008 and fall of 2009 these observations were used to identify conservative and nonconservative processes that contribute dissolved inorganic carbon to halocline source waters including shelf sediment organic matter remineralization air sea gas exchange and sea ice brine export our results indicate that the remineralization of organic matter that occurs along the bering and chukchi sea shelves is the overwhelming contributor of dissolved inorganic carbon to pacific winter water that occupies the middle halocline in the southwestern canada basin nonconservative contributions from air sea exchange and sea ice brine are not significant the broad salinity range associated with the dic maximum compared to the narrow salinity range of the nutrient maximum is due to mixing between pacific and atlantic water and not abiotic addition of dic

analyzing niche stability and biogeography of late ordovician brachiopod species using ecological niche modeling abstract gauging the potential impacts of environmental change on the geographic distributions of species is a central area of modern biogeographic analysis often involving complex models of species environment interactions the geographic distribution of fossil species can also provide a framework to test the impact of environmental change on biogeography and ecological niches of species yet few paleontological analyses have attacked this question in deep time herein we present a quantitative biogeographic analysis to examine the stability of ecological niches and geographic ranges of rhynchonelliform brachiopods during an interval of sea level change preserved in upper ordovician strata of the cincinnati arch the intensive sampling excellent preservation and numerous prior paleoecological and sedimentological analyses within the tri state region of kentucky indiana and ohio provide a robust framework for detailed paleobiogeographic study quantitative biogeographic modeling methods incorporating gis geographic information systems are utilized in order to spatially analyze the geographic ranges of brachiopod species of the corryville and mt auburn formations of the c3 uppermost maysvillian depositional sequence this study employs the ecological niche modeling program garp genetic algorithm using rule set prediction to predict the geographic distribution of eight brachiopod species during three time slices within the c3 sequence this method estimates a species geographic range by modeling the ecological niche of the species based on a set of known species occurrence data coupled with environmental data inferred from sedimentologic proxies once environmental tolerances for a species are modeled the species is predicted to occur wherever its preferred set of environmental conditions occurs within the study region distributional patterns were reconstructed for three time slices during the c3 sequence recovered range predictions were quantitatively analyzed for evidence of temporal range changes results indicate that average species range within the study area decreased and species tracked their preferred niche with high fidelity during the transition from the early to middle portions of the c3 depositional sequence an interval of rapid relative sea level change however during the transition from the middle to late portions of the sequence gradual shallowing within the basin and development of discontinuous habitat patches correlates with niche evolution of five of the eight species modeled the average area a species occupied within the basin increased during this interval but there is a mixed response including both increases and decreases in range size within the study group in general the species that exhibit niche evolution increased their geographic range size while those that continue to track their niche with high fidelity experience a decrease in geographic range size during the latter half of the c3 sequence previously continuous habitats become fragmented thereby isolating individual populations and providing a mechanism for niche evolution the rate of sea level change and the corresponding fragmentation of previously continuous habitats into isolated patches appear to be the primary controls on both mean geographic range size and relative degree of niche evolution

early and mid jurassic molluscan biogeography and the establishment of the central atlantic seaway abstract a new analysis of lower and middle jurassic bivalve faunas of western north america and the southern andes in comparison to europe supported by evidence from other molluscs throws further light on the establishment of a central atlantic epicontinental seaway prior to the formation of a true oceanic strait between eastern north america and africa south america some restriction to free communication persisted until the early callovian but there was an episode of relatively free intermigration in the toarcian to early bajocian time interval which is associated with major rise of sea level one of the most significant consequences of this event was a spread into northwest europe of taxa which were previously confined to the pacific margins to occupy niches vacated as a result of an early toarcian extinction event

using gis to unlock the interactions between biogeography environment and evolution in middle and late devonian brachiopods and bivalves abstract the late devonian was a time of profound evolutionary and environmental change associated with the frasnian famennian biodiversity crisis one way to unravel the faunal dynamics of this complex crisis is to document the spatial and temporal patterns associated with biodiversity decline this analysis investigates the relationship between biogeography relative sea level and environmental changes in laurentian brachiopod and bivalve species during the givetian through famennian stages upper middle to terminal devonian representatives from all major brachiopod and bivalve clades and paleocommunities were examined to provide a cross faunal comparison species ranges were reconstructed both spatially and temporally at the level of conodont zones using gis to understand the timing and extent of species invasions and the importance of geographic range during the crisis interval species geographic ranges were linked closely with both relative sea level change and depositional environment and expanded as relative sea level rose in addition times of interbasinal species invasions corresponded closely with sea level rises that breached tectonic barriers species with larger geographic ranges were more resistant to extinction during the late devonian this relationship is reflected partly in a general trend towards increased extinction resistance in taxa that are found farther offshore in environments that potentially included more area for example there is an increased survival advantage for species that inhabited the middle and outer platform environments though not for species inhabiting the open shelf additionally species whose givetian to frasnian history includes at least one interbasinal invasion event were more likely to survive the late devonian biodiversity crisis than noninvasive species this may have relevance for our understanding of the current biodiversity crisis given the role that invasive species are playing in mediating modern extinctions

association of orogenic activity with the ordovician radiation of marine life the ordovician radiation of marine life was among the most substantial pulses of diversification in earth history and coincided in time with a major increase in the global level of orogenic activity to investigate a possible causal link between these two patterns the geographic distributions of 6576 individual appearances of ordovician vician genera around the world were evaluated with respect to their proximity to probable centers of orogeny foreland basins results indicate that these genera which belonged to an array of higher taxa that diversified in the middle and late ordovician trilobites brachiopods bivalves gastropods monoplacophorans were far more diverse in and adjacent to foreland basins than they were in areas farther removed from orogenic activity carbonate platforms this suggests an association of orogeny with diversification at that time

extraction of the normal component of the particle velocity from marine pressure data the authors present a general wave theoretical method for extracting the normal component of the particle velocity from marine pressure data a possible use of the normal component of the particle velocity and the pressure is the separation of upgoing and downgoing waves at the receivers for one special acquisition geometry the source wavelet can also be estimated the method in principle is exact no information about the properties of the elastic earth is required when the pressure data are recorded on a single surface it is necessary to known the source signatures if the source array location is above the receiver surface if the sources are located below the signatures need not be known the locations of the individual receivers must be specified and the reflecting properties of the sea surface must be known when the receiver surface is plane and horizontal the extraction process can be performed in the frequency horizontal wavenumber domain the normal component of the particle velocity can furthermore be extracted from pressure data recorded at two surfaces at different depths in this case the reflectivity of the sea surface does not come into play it is only the medium properties between the two receiver surfacesmore that enter the problem the actual depths of the receivers need not be known only their relative distances if the sources are located above the uppermost receiver surface the source signatures can also be estimated a simple synthetic data example demonstrates the extraction of the normal component of the pressure from the pressure field recorded along a dipping receiver line below a free surface less

ocean acidification in the three oceans surrounding northern north america 1 the uptake of anthropogenic co2 drives ocean acidification with attendant effects on the saturation state of calcium carbonate and marine ecosystems here we examine ocean acidification within the context of large scale water mass exchange and local physical and biogeochemical processes along a section around northern north america waters in the north pacific are preconditioned by the global scale circulation to be low source waters and as they move northward across the bering and chukchi seas they are modified by biological activity these waters then enter the canada basin and canadian arctic archipelago where cooling river discharge sea ice formation and biological activities modify water mass characteristics further continuing eastward into baffin bay relatively low waters extend from the surface to depth due to remineralization changes in are large along this pathway and the response of local marine ecosystems will likewise be shaped by the biogeography of species occupying a given region

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