distribution of pleuroncodes monodon larvae over the continental shelf of south central chile field and modeling evidence for partial local retention and transport abstract in situ and modeled spatial distribution of squat lobster pleuroncodes monodon larvae over the continental shelf off south central chile 35 37 s was analyzed along with currents and hydrography we aimed to identify the main larval transport retention characteristics in the study area which constitutes the southernmost p monodon fishing grounds embedded in the humboldt current system we hypothesized that the main contribution to population renewal originates in the two persistent adult aggregations close to the nursery ground that occurs over a continental shelf terrace limited by two submarine canyons two extensive bio physical field campaigns were carried out during the main 2001 2002 upwelling season field data indicated that larvae were released from late austral winter to spring from spots to the north and south of the nursery zoea i were found mainly below 50 m depth in southward flowing waters whereas older zoea dominated in northward flowing layers above 50 m larvae were circumscribed between the coast and the shelf break front and pelagic retention areas were identified over the widest shelf area megalopa and juveniles during march were only found over the nursery area individual based simulations coupled to the output of a hydrodynamic model climatological configuration for the studied area showed that the release sites close to the nursery made the largest contribution to recruitment sites further north could also contribute to recruitment if hatching occurred later in the upwelling season the contribution of vertical behavior to larval success was also important as was the former s interaction with the site and time of larval release our results support the relevance of coastal circulation affected by topography on the persistence of p monodon populations off southern chile and the modulation of temporal variability these results might apply to other abundant species in the area

iceberg calving flux and mass balance of the austfonna ice cap on nordaustlandet svalbard 1 satellite radar interferometry 60 mhz airborne ice penetrating radar data and visible band satellite imagery were used to calculate the velocity structure ice thickness and the changing ice marginal extent of austfonna 8000 km2 and 2500 km3 the largest ice cap in the eurasian arctic ice cap motion is generally less than about 10 m a 1 except where faster flowing curvilinear features with velocities of several tens to over 200 m a 1 are present most drainage basins of austfonna have undergone ice marginal retreat over the past few decades at an average of a few tens of meters per year integrating margin change around the whole ice cap gives a total area loss of about 10 km2 a 1 iceberg flux from the marine margins of austfonna is about 2 5 0 5 km3 a 1 water equivalent about 45 of the total calving flux from the whole svalbard archipelago when mass loss by iceberg production is taken into account the total mass balance of austfonna is negative by between about 2 5 and 4 5 km3 a 1 this iceberg flux represents about 33 5 of total annual mass loss from austfonna with the remainder lost through surface ablation iceberg flux should be included in calculations of the total mass balance of the many large arctic ice caps including those located in the russian and canadian arctic that end in tidewater the neglect of this term has led to underestimates of mass loss from these ice caps and thus to underestimates of the contribution of arctic ice caps to global sea level rise

recent mass changes of glaciers in the russian high arctic 1 glaciers and ice caps are known to contribute significantly to present day sea level rise but there are still glaciated regions where little is known about modern changes in glacier mass one of these regions is the russian high arctic archipelagos which has a total glaciated area of 51 500 km2 we have assessed the glacier mass budget of this region for a 6 year period between october 2003 and october 2009 using independent icesat laser altimetry and grace gravimetry over this period we found that the archipelagos have lost ice at a rate of 9 1 2 0 gt a 1 which corresponds to a sea level contribution of 0 025 mm a 1 approximately 80 of the ice loss came from novaya zemlya with the remaining 20 coming from franz josef land and severnaya zemlya meteorological records of temperature and precipitation for the period 1980 2009 suggest that the recent climatic mass budget is not substantially different from the longer term trend

altimeter observations of the peru chile countercurrent data from geosat and topex altimeters are used to infer the structure of the peru chile countercurrent a jet that flows from at least as far north as 10 s historical data suggests 7 s to 35 40 s maintaining its position between approximately 100 300 km offshore although the annual mean current cannot be determined from altimeter observations the nearly antisymmetric patterns in spring and fall combined with historical observations suggest that the countercurrent is poleward at most times and is maximum in spring and minimum in fall previous studies have linked the offshore countercurrent at 7 s to the equatorial undercurrent west of the galapagos islands suggesting that the countercurrent is part of a continuous flow that extends from the western equatorial pacific to the region off chile between 35 40 s

1997 1998 el nino off peru a numerical study an eddy resolving numerical simulation for the peru chile system between 1993 and 2000 is analyzed mainly for the 1997 1998 el nino atmospheric and lateral oceanic forcings are realistic and contain a wide range of scales from days to interannual the solution is validated against altimetric observations and the few in situ observations available the simulated 1997 1998 el nino closely resembles the real 1997 1998 el nino in its time sequence of events the two well marked sea level peaks in may june and november december 1997 are reproduced with amplitudes close to those observed other sub periods of the el nino seem to be captured adequately simple dynamical analyses are performed to explain the 1997 1998 evolution of the upwelling in the model the intensity of the upwelling appears to be determined by an interplay between alongshore poleward advection related to coastal trapped waves and wind intensity but also by the cross shore geostrophic flow and distribution of the water masses on a scale of 1000 km or more involving rossby waves westward propagation and advection from equatorial currents in particular the delay of upwelling recovery until fall 1998 i e well after the second el nino peak is partly due to the persistent advection of offshore stratified water toward the coast of peru altimetry data suggest that these interpretations of the numerical solution also apply to the real ocean

circulation and low frequency variability near the chilean coast remotely forced fluctuations during the 1991 92 el nino results are reported from the first long recording current meter observations over the slope off chile these observations at 308s during the 1991 92 el nino event are analyzed together with observations of currents at a local deep sea site local wind and sea level sea level from the peru and chile coasts and wind temperature and currents from the equatorial pacific mean poleward flow of 12 cm s21 was observed within the peru chile undercurrent over the slope mean flow in the depth range of antarctic intermediate water was not distinguishable from zero in the presence of strong low frequency lf variability which dominated slope currents at all depths the strongest lf fluctuations had periods of about 50 days but periods of 10 and about 5 days were also observed significant local wind forcing of slope currents was only found in the period band 6 10 days and may be related to coastal trapped waves in the atmosphere our analysis shows that free coastal trapped waves in the ocean arriving from the north dominated the lf variability over the shelf and slope off northern and central chile during the 1991 92 el nino event strong 50 day period fluctuations there started their journey about two months earlier and 15 000 km farther up the coastal equatorial waveguide near the date line in the equatorial pacific as equatorial kelvin waves forced by westerly wind events of similar period upon reaching the south american coast these waves forced coastal trapped waves which propagated along the peru coast into the study region likewise a scenario of equatorial trapped waves forcing coastal trapped waves may explain 10 day as well as 6 day and 4 5 day period coastal trapped waves off chile stemming from mixed rossby gravity and inertia gravity waves trapped at the equator since the large 50 day period coastal trapped waves may strongly modify coastal upwelling source water such remotely forced waves may have a significant influence on the pelagic ecosystem off chile at least during el nino events

biogeochemistry of surface sediments off concepcion 36 s chile el nino vs non el nino conditions abstract we compared the signals of several water column properties upwelling intensity sea level anomaly temperature nutrients dissolved oxygen chlorophyll a and surface sediments of the continental shelf off concepcion 36 s during the 1997 1998 el nino with those of a normal year 2002 2003 we found that the primary hydrographic effect of el nino 1997 1998 was a reduction in the input of nutrient rich oxygen poor equatorial subsurface water over the shelf this affected the biology of the water column as evidenced by the reduced phytoplankton biomass surface sediment properties biogenic opal organic carbon bulk 15n observed during el nino 1997 1998 reflected a reduced export production and the sediments failed to show the water column seasonality that occurs under normal conditions in addition weakened denitrification and or upper water column fertilization could be inferred from the sedimentary 15n although diminished export production was preserved in the surface sediments revealing less degraded organic matter in the upwelling period of the el nino year than in the normal year we suggest that the fresher organic material on the seafloor was probably associated with a severe reduction in the polychaete parapronospio pinnata which is considered to be the most important metazoan remineralizer of organic carbon at the sediment water interface in the study area

structure of palaeogene sediments in east ellesmere island constraints on eurekan tectonic evolution and implications for the nares strait problem abstract the nares strait problem represents a debate about the existence and magnitude of left lateral movements along the proposed wegener fault within this seaway study of palaeogene eurekan tectonics at its shorelines could shed light on the kinematics of this fault palaeogene late paleocene to early eocene sediments are exposed at the northeastern coast of ellesmere island in the judge daly promontory they are preserved as elongate sw ne striking fault bounded basins cutting folded early paleozoic strata the structures of the palaeogene exposures are characterized by broad open synclines cut and displaced by steeply dipping strike slip faults their fold axes strike ne sw at an acute angle to the border faults indicating left lateral transpression weak deformation in the interior of the outliers contrasts with intense shearing and fracturing adjacent to border faults the degree of deformation of the palaeogene strata varies markedly between the northwestern and southeastern border faults with the first being more intense structural geometry orientation of subordinate folds and faults the kinematics of faults and fault slip data suggest a multiple stage structural evolution during the palaeogene eurekan deformation 1 the fault pattern on judge daly promontory is result of left lateral strike slip faulting starting in mid to late paleocene times the palaeogene judge daly basin formed in transtensional segments by pull apart mechanism transpression during progressive strike slip shearing gave rise to open folding of the palaeogene deposits 2 the faults were reactivated during se directed thrust tectonics in mid eocene times chron 21 a strike slip component during thrusting on the reactivated faults depends on the steepness of the fault segments and on their obliquity to the regional stress axes strike slip displacement was partitioned to a number of sub parallel faults on shore and off shore hence large scale lateral movements in the sum of 80 100 km or more could have been accommodated by a set of faults each with displacements in the order of 10 30 km the wegener fault as discrete plate boundary in nares strait is replaced by a bundle of faults located mainly onshore on the judge daly promontory

surface elevation change and mass balance of icelandic ice caps derived from swath mode cryosat 2 altimetry we apply swath processing to cryosat 2 interferometric mode data acquired over the icelandic ice caps to generate maps of rates of surface elevation change at 0 5 km postings this high resolution mapping reveals complex surface elevation changes in the region related to climate ice dynamics and subglacial geothermal and magmatic processes we estimate rates of volume and mass change independently for the six major icelandic ice caps 90 of iceland s permanent ice cover for five glaciological years between october 2010 and september 2015 annual mass balance is highly variable during the 2014 2015 glaciological year the vatnajokull ice cap 70 of the glaciated area experienced positive mass balance for the first time since 1992 1993 our results indicate that between glaciological years 2010 2011and 2014 2015 icelandic ice caps have lost 5 8 0 7 gt a 1 on average 40 less than the preceding 15 years contributing 0 016 0 002 mm a 1 to sea level rise

a numerical study of the upwelling circulation off central chile effects of remote oceanic forcing 1 a numerical ocean model is used to study the upwelling circulation off central chile in response to local winds and remote forcing in an idealized study of equatorial forced intraseasonal variability period of 50 days a first mode coastal trapped wave ctw paddle is applied to the northern boundary with coastal sea level amplitude of 12 cm without this ctw forcing the steady seasonal winds upwell undercurrent water from depths of 250 320 m to depths of 180 250 m the subsequent formation of mesoscale and headland eddies drive this water into the gulf of arauco and to depths of 50 120 m with the ctw paddle the circulation is strongly modified the mesoscale and headland eddies reform during the ctw upwelling phase during the ctw upwelling phase the upwelling over winds and eddies is enhanced by up to 40 m on the shelf model simulations are undertaken using realistic winds and a ctw paddle modulated by observed sea level without ctw forcing included in the model the agreement with data is poor in the gulf of arauco area the variability of alongshore currents below 130 m is dominated by ctw activity above 130 m wind driven current variability dominates in agreement with the idealized ctw analysis water is found to be upwelled from depths of 320 m to 100 m or less and 10 c undercurrent water is found at the surface and within the gulf

altimeter derived variability of surface velocities in the california current system 2 seasonal circulation and eddy statistics abstract satellite surface height and temperature fields are used to examine the seasonal surface circulation in the california current system in spring and summer an equatorward jet develops next to the coast with an initial latitudinal structure that responds to the latitudinal distribution of equatorward alongshore winds this jet moves offshore from spring to fall and develops meanders and closed eddies that contribute eddy kinetic energy and water mass properties to the nearby deep ocean higher eke appears first in spring near the coast and moves offshore with the seasonal jet along altimeter tracks parallel to the coastline 200 and 400 km offshore the greatest eke is found in summer and fall respectively with wavelengths of approximately 300 km these are the wavelengths of the largest meanders and the distance between the largest eddies visible in altimeter snapshots of the jet at 600 800 km offshore the wavelengths are generally smaller 100 150 km similar to eddy sizes reported by others for the quiescent northeast pacific some energy with longer wavelengths arrives at the track 600 km offshore in winter and 800 km offshore in spring which we interpret as the most offshore extension of the eke generated by the jet and eddy system closer to the coast in the previous spring and summer a sequence of snapshots from october 1992 to october 1993 shows details of the evolution of the jet and eddy system over one complete annual cycle

grace gravity observations constrain weichselian ice thickness in the barents sea the barents sea is subject to ongoing postglacial uplift since the melting of the weichselian ice sheet that covered it the regional ice sheet thickness history is not well known because there is only data at the periphery due to the locations of franz joseph land svalbard and novaya zemlya surrounding this paleo ice sheet we show that the linear trend in the gravity rate derived from a decade of observations from the gravity recovery and climate experiment grace satellite mission can constrain the volume of the ice sheet after correcting for current ice melt hydrology and far field gravitational effects regional ice loading models based on new geologically inferred ice margin chronologies show a significantly better fit to the grace data than that of ice 5g the regional ice models contain less ice in the barents sea than present in ice 5g 5 6 3 m equivalent sea level versus 8 5 m which increases the ongoing difficulty in closing the global sea level budget at the last glacial maximum

ellesmere greenland fold belt structural evidence for left lateral shearing abstract regardless of whether they were passive or active markers of the eurekan deformation fold axial traces in the ellesmere greenland fold belt define a regional pattern typical of left lateral ductile shear zones it is therefore postulated that a left lateral mega shear zone spanned the entire east west width of ellesmere island plus adjacent northern greenland and that the shear direction was subparallel to nares strait a left lateral motion along nares strait is required by the plate tectonic models of j t wilson and e c bullard to explain the opening of the labrador sea and baffin bay by sea floor spreading these models involve a left lateral displacement between greenland and north america of 200 400 km because of the lack of lithological and structural offsets across nares strait the models have been controversial the mega shear zone proposed herein reconciles all the conflicting evidence accordingly the ductile behaviour of the sedimentary strata on ellesmere island permitted a large left lateral displacement of greenland relative to north america without a large offset of geological features across nares strait

satellite altimetry data reveal jet like dynamics of the humboldt current 1 satellite derived mean sea level anomalies were blended with mean dynamic topography to obtain seasonal climatologies of the eastern south pacific ocean s surface circulation with an emphasis on the humboldt current the humboldt current is confined to a narrow northward flowing jet like stream of about 350 km associated with maximum geostrophic velocities of more than 15 cm s 1 from 35 to 23 s the current streams closer to the coast in the south within 500 km but is found 500 km offshore in its northern section a bifurcation takes place at 23 s with a more coastal branch heading toward the coast of southern peru 15 s and an oceanic branch continuing in a north northwesterly direction the humboldt current intensifies by 3 cm s 1 in austral summer as compared to winter in contrast the humboldt current s coastal branch is stronger in austral winter by the same order of magnitude we attribute these distinct seasonal flow fields to the meridional movement of the south pacific anticyclone which includes a seasonal relocation of a strong wind stress curl nucleus from offshore central southern austral summer to central northern chile austral winter thus driving the humboldt current by means of seasonal sverdrup dynamics the geostrophic flow field in the eastern south pacific communicates colder and fresher sub antarctic surface water toward the tropics along the eastern rim of the subtropical gyre

a view of the 1993 1994 california current based on surface drifters floats and remotely sensed data near surface drifters were deployed in the california current system during the period 1993 1994 in order to study mean and eddy currents the deployment scheme allowed a 2 year period where data density was high enough to make meaningful estimates of eddy statistics and of seasonal mean currents and variances on a 5 grid eddy variability which tended to be isotropic was higher near the coast standard deviations around 0 2 m s 1 and decreased offshore down to 0 1 m s 1 seasonal mean surface flow west of california was southward during all seasons if a davidson current existed during 1993 1995 it was probably either short lived or only found closer to the coast than our study area i e within 100 150 km of shore in some cases drifter populations within a discrete feature were high enough to allow some detailed resolution of its behavior we note a tendency for individual eddies which can last for up to 3 5 months to drift westward at rates of o 5 km day 1 not all eddies in the region are surface intensified there is clear evidence for at least the occasional presence of a thin meandering southward jet in the region that can be 1000 km or more long this jet can be identified with that found in the coastal transition zone program in association with cool filaments the jet appears to become broader and slower south of point conception we hypothesize on the basis of others results as well as ours that the eddies that are strongest at the surface result primarily from instabilities on a southward alongshore mean current and that eddies that are maximal at depth are spawned by the northward undercurrent

on the pressure gradient force over steep topography in sigma coordinate ocean models abstract the error in computing the pressure gradient force near steep topography using terms following coordinates is investigated in an ocean model using the family of vertical differencing schemes proposed by arakawa and suarez the truncation error is estimated by substituting known buoyancy profiles into the finite difference hydrostatic and pressure gradient terms the error due to hydrostatic inconsistency which is not simply a space truncation error is also documented the results show that the pressure gradient error is spread throughout the water column and it is sensitive to the vertical resolution and to the placement of the grid points relative to the vertical structure of the buoyancy field being modeled removing a reference state as suggested for the atmosphere by gary reduces the truncation error associated with the two lowest vertical modes by a factor of 2 to 3 as an example the error in computing the pressure gradient using a standard 10 level primitive equation model appl

continental rifting and the implications for plate tectonic reconstructions previous plate tectonic reconstructions have tried to recreate the pre rifting pangea configuration of the continents by matching contours or lineaments that are thought to represent the continental boundaries such reconstructions have the inherent assumptions that no extension occurs within the continent during rifting that the continental boundaries are isochrons and that the continents rift without distortion this paper proposes a model for continental breakup with distortion where ocean basins are formed by propagating rifts this model challenges the assumptions made by previous reconstructions and presents a new method for representing the prerift geometry of the continents as rifts propagate through a continent the region in front of the rift extends by continental faulting and crustal thinning while the region behind the rift expands by seafloor spreading the propagating rift model implies that large amounts of continental extension up to 150 km occur and that the continental boundaries are not isochrons this extension due to rifting results in apparent overlap when the continents are returned to their original configuration because of the gradational nature of this extension the best representation of the pre rift configuration is obtained by matching the initial rifting point and having overlap increase in the direction of rift propagation the overlap is equivalent to the amount of extension that has taken place on both continental edges reconstructions based on this model are presented for the gulf of california the gulf of aden the norwegian greenland sea and the south atlantic ocean they are able to resolve the discrepancies that occur when rigid plate tectonics are applied this model has implications that can be used to predict the age and structure of the continental shelves and the location and orientation of the oldest magnetic isochrons

surge type glaciers in the russian high arctic identified from digital satellite imagery landsat digital imagery was used to search the island archipelagos of franz josef land severnaya zemlya and novaya zemlya russian high arctic for the presence of looped moraines characteristic of past glacier surges the imagery provides almost complete summer time coverage of the 60000 km 2 of ice in these islands very few surge type glaciers are identified none in franz josef land three in novaya zemlya and two on severnaya zemlya this contrasts greatly with svalbard ice covered area 36 600 km 2 to the west where 36 of glaciers and ice cap drainage basins are inferred to surge the strong climatic gradient across the eurasian high arctic with decreasing temperature and moisture eastward may provide a gross control on this pattern through colder glacier thermal structure limiting basal drainage on the thinner ice masses in particular

estimating the long term calving flux of kronebreen svalbard from geodetic elevation changes and mass balance modelling this study independently quantifies geodetic elevation change and models surface mass balance to solve the continuity equation the approach is tested on two dynamically different glaciers kongsvegen and kronebreen in northwest svalbard through two time epochs 1966 1990 95 i and 1990 95 2007 ii on kongsvegen a dynamically inactive glacier the residual term represents an error associated with determining elevation changes and surface mass balance it is apparent that centerline mass balance estimates are not representative of the entire glacier which we relate to center line accumulation being larger than the elevation bin average on kronebreen a fast flowing and actively calving glacier a significant part of the residual is identified with the long term calving flux for both glaciers the cumulative surface mass balance remained close to zero during the first epoch but became increasingly negative in the second epoch the long term calving flux of kronebreen is estimated to be 0 14 0 03 km3 w e a 1 during epoch i and 0 20 0 05 km3 w e a 1 in epoch ii

seasonal dynamics of the near surface alongshore flow off central chile 1 the seasonal cycle of the near surface circulation off central chile was analyzed using satellite altimetry and an oceanic model to evaluate the role of the wind stress curl on the circulation we performed two identical simulations except for the wind forcing the control run used long term monthly mean wind stress and the no curl run used a similar wind stress field but without curl the observed and modeled control run surface currents showed a strong seasonal cycle and a well defined equatorward flow with a jet like structure this jet develops during spring and summer consistent with the presence of a low level wind jet south of punta lavapie cape 37 s the equatorward surface current remains close to the coast after the flow passes this cape however it separates to become an offshore jet in contrast in the no curl simulation the separation at punta lavapie is not observed and the offshore jet farther north is not present demonstrating the importance of the wind stress curl on the dynamics of this flow although the offshore integrated sverdrup transport was similar to the model transport the offshore jet was not located where the wind stress curl was maximum instead the position of the jet followed approximately the zero wind stress curl which corresponds to the climatological location of the low level wind jet axis these results illustrate the importance of the offshore upwelling downwelling associated with curl driven ekman pumping which tilts isopycnals upward downward toward the east west of the wind jet forcing a northward flow through thermal wind balance

warming glacier melt and surface energy budget from weather station observations in the melville bay region of northwest greenland the glaciers in the melville bay region of northwest greenland have shown a mean retreat since the earliest observations at the beginning of the 20th century the largest steenstrup gletscher has retreated 20 km partly during the period of atmospheric cooling 1940 80 melville bay air temperature observations starting in 1981 indicate a regional change of 0 208 ca 1 this exceeds the warming on the east coast of greenland confirming the west coast to be a region of relatively large change also in a global perspective the largest temperature increase is observed in the winter months 0 3 0 48 ca 1 results from a 4 year 2004 08 net ablation record obtained by an automatic weather station aws near the calving front of steenstrup gletscher show an ablation rate that is relatively low for a low elevation position on the greenland ice sheet 2 4 m ice equivalent per year a first order estimate from positive degree day totals suggests that net ablation has roughly doubled since the 1980s a surface energy and mass balance model is applied to the steenstrup aws data to quantify the energy flux contributions to surface melt solar radiation is the main source for melt energy but due to shortwave radiation penetration into the ice only one third of the melt takes place at the glacier surface nearly two thirds occurs within the upper ice layers

a mechanism for enhanced upwelling off central chile eddy advection 1 a regional numerical model is developed for the mid chile shelf and ocean circulation 30 s to 43 s the model is forced with mean summertime wind stress and transports from a global model over the first 10 days deep 250 300 m peru undercurrent puc water is upwelled to depths of 170 270 m after this time upwelling by the steady winds is largely shut down and a 55 km diameter cyclonic eddy is found to grow in deep water off punta lavapie the mechanism for eddy growth is identified to be baroclinic instability of an initial offshore meander of the equatorward chile coastal current ccc over a period of more than 100 days the onshore arm of the deep water eddy upwells puc water to depths of 150 m toward the shelf a shallow headland eddy then sweeps this puc water to depths of less than 50 m and into the gulf of arauco the net upwelling of 200 m is the largest found for the region observational evidence is cited for the existence of the deep water cyclonic eddy over a period of 4 months a spatially intermittent puc is also found to lie below the ccc in agreement with observational studies the model also predicts the existence of an offshore branch of the ccc that is directed to the northwest

on vertical motion divergence and the thermal wind balance in cold dome meanders a diagnostic study wavelike meanders are observed along the length of the florida current from the florida keys to cape hatteras these propagating meanders are three dimensional each has a cold dome and the meandering flow that overtakes the dome in a cyclonic turn is characteristically stronger when flowing offshore than when flowing onshore we focus on vertical motion as a key to understanding the interdependence of the downstream propagation the upwelling in the cold dome and the skewness in the strength of the meandering flow inferred from a composite of drogue and temperature observations the pattern of vertical motion is one of upwelling that extends throughout the water column formed by the forepart of the translating dome and its overlying on shore flow and a downwelling that similarly extends vertically through the rear part of the dome and its overlying offshore flow it is shown that the vertical motion and the translation of the meander are interrelated and both enter importantly in the acceleration of the water columns and hence in the skewness in the strength of the meandering flow component as the thermal wind changes with the divergence accompanying the vertical motion it also provides a twisting mechanism to help restore the thermal wind balance

intra and inter annual variability in dynamic discharge from the academy of sciences ice cap severnaya zemlya russian arctic and its role in modulating mass balance

how biophysical interactions associated with sub and mesoscale structures and migration behavior affect planktonic larvae of the spiny lobster in the juan fernandez ridge a modeling approach abstract the juan fernandez ridge jfr is a chain of topographical elevations in the eastern south pacific 33 35 s 76 81 5 w rich in endemic marine species this ridge is frequently affected by the arrival of mesoscale eddies originating in the coastal upwelling zone off central southern chile the impacts of these interactions on the structure and dynamics of the jfr pelagic system have however not been addressed yet the present model based study is focused on the coupled influence of mesoscale submesoscale processes and biological behavior i e diel vertical migration on the horizontal distribution of planktonic larvae of the spiny lobster jasus frontalis around the jfr waters two case studies were selected from a hydrodynamic regional ocean modeling system to characterize mesoscale and submesoscale structures and an individual based model ibm to simulate diel vertical migration dvm and its impact on the horizontal distribution and the patchiness level dvm behavior of these larvae has not been clearly characterized therefore three types of vertical mechanisms were assessed on the ibm 1 no migration lg 2 a short migration 0 50 m depth dvm1 and 3 a long migration 10 200 m depth dvm2 the influence of physical properties eddy kinetic energy stretching deformation and divergence on larval aggregation within meso and submesoscale features was quantified the patchiness index assessed for mesoscale and submesoscale structures showed higher values in the mesoscale than in the submesoscale however submesoscale structures revealed a higher accumulation of particles by unit of area both vertical migration mechanisms produced larger patchiness indices compared to the no migration experiment dvm2 was the one that showed by far the largest aggregation of almost all the aggregation zones larval concentrations were highest in the submesoscale structures these zones were characterized by low eddy kinetic energy negative stretching deformation and slight convergence stretching deformation flow appeared to be triggered by the eddy eddy interactions and the robinson island barrier effect and it likely promotes the aggregation of the spiny lobster larvae in the juan fernandez system these results highlighted the importance of the coupled effect of physical mesoscale and submesoscale oceanographic features and biological processes dvm in the generation of larval patchiness and concentration of spiny lobster larvae around the jfr which could be key for their survival and retention in those waters

eurekan transpressive deformation in the wandel hav mobile belt northeast greenland 1 besides the w e trending kap cannon thrust zone and harder fjord fault zone the 300 km long and nw se striking wandel hav mobile belt represents the third major fault zone in north greenland structural analyses in several areas of this belt suggest that compressive deformation is characterized by transpressive dextral strike slip kinematics this is demonstrated by a combination of folding around w e axes approximately north and south directed reverse faulting and dextral strike slip displacements along nw se trending fault lines the initial formation of the long linear faults is interpreted to be related to deformational events in late paleozoic triassic jurassic and late cretaceous times due to the lack of structural evidence we assume that deformations led to the generation of extension faults which probably were reactivated during dextral strike slip tectonism it is suggested that dextral transpressive deformation was coeval with n s compression at the harder fjord fault zone and cap cannon thrust zone and took place during eocene eurekan times dextral strike slip tectonism in the wandel hav mobile belt was the result of n s compression due to a general northward movement of the greenland plate as a zone of crustal weakness the belt can be interpreted as the onshore equivalent of the main transcurrent fault zone de geer fault which caused the intracontinental dextral slip of svalbard barents shelf relative to north greenland during early tertiary eurekan times and prior to their separation in this configuration it represents one part of the belt of eurekan deformation which extends from the canadian arctic islands over north greenland to the barents shelf where compressive deformation is recorded in the west spitsbergen fold and thrust belt

water column cooling and sea surface salinity increase in the upwelling region off central south chile driven by a poleward displacement of the south pacific high abstract here we present results of direct observations of seawater temperature and salinity over the continental shelf off central south chile that shows an unprecedented cooling of the entire water column and an increase in upper layer salinity during 2002 to 2013 we provide evidence that this phenomenon is related to the intensification but mostly to a recent southward displacement of the south pacific high over the same period from 2007 on this in turn has accelerated alongshore equatorward subtropical coastal upwelling favorable winds particularly during winter injecting colder water from below into the upper water column consequently the environmental conditions on the shelf off central south chile shifted from a warmer fresher to a cooler saltier phase water column temperature dropped from 11 7 c 2003 2006 to 11 3 c 2007 2012 and upper layer salinity rose by 0 25 water column stratification gradually decreased the biological impacts of such abrupt cooling are apparently already happening in this coastal ecosystem as recent evidence shows substantial changes in the plankton community and negative trends in zooplankton biomass over the same period

nares strait a suture zone geophysical and geological implications abstract the motion of greenland relative to ellesmere island along nares strait is determined from poles of rotation which provide control for the motion independent of local geology and geophysics the plate kinematics around the north atlantic ocean the norwegian and greenland seas and the eurasian basin of the arctic ocean constrain motion along nares strait these motions are checked by examining the stability characteristics of the triple junctions these junctions are found to be stable the motion along nares strait between anomalies 34 and 13 is a combination of strike slip and compression the regional geology is found to support the plate reconstructions the local geology of the nares strait area is reviewed and found not to refute the predicted motions the geophysical and geological data are interpreted in terms of the wilson cycle the opening and closing of an ocean the nares strait area has the characteristics of a cryptic suture a join between regions of collided continental crust

peralkaline volcanicity on the eurasia basin margin the kap washington group of post palaeozoic explosive volcanic rocks was discovered in 1969 on the north coast of greenland although there have been uncertainties regarding their age and chemical character they have featured prominently in geotectonic reconstructions of the arctic regions in recent interpretations as products of the yermak hot spot generated on the nansen spreading axis during the opening of the eurasia basin we present here new evidence which confirms the volcanicity as end cretaceous in age and of peralkaline type we show that a direct connection with the yermak hot spot is improbable and infer that the volcanic rocks were generated in a continental extensional rift environment before the break up of the laurasian plate in the arctic their age helps to constrain the timing of this poorly understood event

the distribution of chlorophyll a and dominant planktonic components in the coastal transition zone off concepcion central chile during different oceanographic conditions abstract the oceanographic setting and the planktonic distribution in the coastal transition zone off concepcion 35 38 s 73 77 w an area characterized by its high biological production were assessed during two different seasons austral spring with equatorward upwelling favorable winds and austral winter with predominately northerly winds oceanographic and biological data total chlorophyll a particulate organic carbon microplankton large mesozooplankton 500 m as potential consumers of microplankton were obtained during two cruises october 1998 july 1999 together with satellite imagery for wind stress geostrophic flow surface temperature and chlorophyll a data the physical environment during the spring sampling was typical of the upwelling period in this region with a well defined density front in the shelf break area and high concentrations of surface chlorophyll a 5 mg m 3 on the shelf over the itata terrace during the winter sampling highly variable though weakly upwelling favorable winds were observed along with lower surface chlorophyll a values 100 km from the coast cyclonic and anti cyclonic eddies were evident in the flow field during both periods the former coinciding with higher chlorophyll a contents 1 mg m 3 than in the surrounding waters also a cold chlorophyll a rich filament was well defined during the spring sampling extending from the shelf out to 350 400 km offshore along a cross shelf transect the micro and meso planktonic assemblages displayed higher coastal abundances during the spring cruise but secondary peaks appeared in the oceanic area during the winter cruise coinciding with the distribution of the eddies these results suggest that the mesoscale features in this region in combination with upwelling play a role in potentially increasing the biological productivity of the coastal transition zone off concepcion

decadal variabilities of the upper layers of the subtropical north atlantic an ocean model study numerical simulations of the atlantic ocean during the period 1950 to 1989 using a sigma coordinate free surface numerical model show long term variabilities in the upper ocean subtropical gyre similar to those obtained from observations the simulations show how westward propagating planetary waves originated in the eastern north atlantic affect interdecadal variabilities of ocean properties such as the bermuda sea level the gulf stream position and strength and subsurface temperature anomalies in the western north atlantic special attention is given to the dramatic sea level drop at bermuda in the early 1970s which is accompanied by cooling of subsurface layers in the western north atlantic and a northward shift and weakening of the gulf stream following these events between 1970 and 1980 the cold temperature anomalies in the upper layers of the western north atlantic slowly propagated eastward and downward the strongest propagating signal in the model is found at 200 m depth suggesting that advection of anomalies downstream by the gulf stream current and changes in winter mixing are involved significant correlations were found between the sea level anomalies at bermuda and sea level anomalies in the eastern north atlantic up to eight years earlier sensitivity experiments with different atmospheric forcing fields are used to study the ocean response to observed sea surface temperature and wind stress anomalies it is shown that on decadal timescales the ocean model responds in a linear fashion to the combined effect of sst and wind stress anomalies a fact that might be exploited in future climate prediction studies

a review of postglacial emergence on svalbard franz josef land and novaya zemlya northern eurasia the pattern of postglacial emergence in the barents sea is pivotal to constraining the timing of deglaciation and extent and thickness of the last ice sheet in northern eurasia this review unites records of holocene relative sea level from svalbard franz josef land and novaya zemlya to better understand the geometries of past ice sheet loads emergence data from northern eurasia confine the maximum area of glacier loading to the northwestern barents sea where 100 m of emergence is measured on kongs ya deglacial unloading commenced on western and northern spitsbergen c 13 12 14 c ka ago and by c 10 5 14 ck a on eastern svalbard and more distal sites on franz josef land and novaya zemlya the marine limit phase c 13 12 14 c ka on western and northern spitsbergen is characterized by the construction of spits indicating a dominance of long shore drift over stormgenerated fetch reflecting extensive sea ice coverage of coastal areas at sites in proximity to the ice sheet margin on western and northern spitsbergen there is evidence for a transgressive regressive cycle c 6 4 14 c ka possibly reflecting back migration of displaced mantle material a modern transgression is inferred from the marine erosion of 17th century cultural features and 14 c ages of whalebone and terrestrial peat buried by modern storm gravels that place sea level at its present position by c 2 to 1 ka ago the greatest observed emergence on franz josef land occurs on bell island with a marine limit at 49 m aht formed c 10 14 c ka available emergence data since 9 ka show rising strandlines toward the southwest at b0 3 m km the northern limit of emergence on franz josef land is poorly constrained because relative sea level data is sparse north of 80 30 0 n in contrast to svalbard and franz josef land the marine limit on northern novaya zemlya is only 10 15 m above high tide and formed between 6 5 and 5 0 14 c ka when global sea level was stabilizing all sites show little apparent emergence during the past 2 ka with the youngest raised landforms at identical heights to storm beaches this minimal glacio isostatic signature on novaya zemlya and on vaygach island where deglaciation commenced 10 ka ago indicates ice sheet thicknesses of o1 5 km the spatial variation in emergence for the barents sea indicates that western and northern spitsbergen and novaya zemlya were near the reactive margin of the ice sheet and these areas sustained the briefest ice coverage 2 6 ka and were probably not in isostatic equilibrium in contrast central and eastern svalbard and southern franz josef land were beneath a substantial ice load and probably sustained this load for c 10 14 c ka and achieved isostatic equilibrium isostasy residual from an ice sheet model portrays well the general pattern of uplift and load response at the centre of ice sheets but deviates substantial at the ice sheet margin or areas covered by thin ice like novaya zemlya

a reconciled estimate of glacier contributions to sea level rise 2003 to 2009 glaciers distinct from the greenland and antarctic ice sheets are losing large amounts of water to the world s oceans however estimates of their contribution to sea level rise disagree we provide a consensus estimate by standardizing existing and creating new mass budget estimates from satellite gravimetry and altimetry and from local glaciological records in many regions local measurements are more negative than satellite based estimates all regions lost mass during 2003 2009 with the largest losses from arctic canada alaska coastal greenland the southern andes and high mountain asia but there was little loss from glaciers in antarctica over this period the global mass budget was 259 28 gigatons per year equivalent to the combined loss from both ice sheets and accounting for 29 13 of the observed sea level rise

observations of buried lake drainage on the antarctic ice sheet between 1992 and 2017 the antarctic ice sheet ais lost ice equivalent to 7 6 3 9 mm of sea level rise ais mass loss is mitigated by ice shelves that provide a buttress by regulating ice flow from tributary glaciers however ice shelf stability is threatened by meltwater ponding which may initiate or reactivate preexisting fractures currently poorly understood processes here through ground penetrating radar gpr analysis over a buried lake in the grounding zone of an east antarctic ice shelf we present the first field observations of a lake drainage event in antarctica via vertical fractures concurrent with the lake drainage event we observe a decrease in surface elevation and an increase in sentinel 1 backscatter finally we suggest that fractures that are initiated or reactivated by lake drainage events in a grounding zone will propagate with ice flow onto the ice shelf itself where they may have implications for its stability

mean surface circulation and mesoscale turbulent flow characteristics in the eastern south pacific from satellite tracked drifters 1 circulation of the eastern south pacific region 10 34 s 70 100 w was studied using drifting buoy trajectories from 1979 to 2003 three different current regimes were highlighted the south equatorial current flowing westward north of 26 s with surface velocities of 7 8 cm s 1 the south pacific current an eastward current of 2 cm s 1 south of 25 30 s and the chile peru current a northwestward flow of 6 cm s 1 found to the east of 82 w and south of 22 s the velocity variance distribution showed the regional flow to be anisotropic in nature maps of eddy kinetic energy obtained from drifter measurements and satellite altimetry data showed similar patterns with higher energy levels near the south american coast the lagrangian time and length scales of the turbulent flow revealed typical values of 5 9 0 6 days and 40 7 5 4 km in the zonal direction and of 3 5 0 4 days and 29 3 4 km in the meridional direction the estimated diffusivities were 4 9 0 5 107 cm2 s 1 and 2 6 0 3 107 cm2 s 1 in the eastward and northward directions respectively finally we estimated the respective role of horizontal advection and lateral diffusion on the mixed layer heat and salt budgets near the coast the lateral turbulent fluxes in the surface layer were two times larger than the horizontal transports associated with the large scale circulation mean horizontal heat and salt diffusive fluxes were around 25 w m 2 and 50 g m 2 d 1

geological evidence against major displacement in the nares strait early continental drift1 3 and later plate tectonic reconstructions4 14 indicate left lateral sinistrai movement along nares strait of between 150 and 400 km during the cretaceous tertiary a basic concept in such reconstructions is the substantial part played by seafloor spreading in the origin of labrador sea baffin bay until recently geological knowledge of the area adjacent to nares strait was insufficient to put tight constraints on displacement along nares strait fig 1 of seven independent lines of evidence from bedrock geology termed markers all are consistent with sinistrai net displacement of greenland along nares strait of 0 25 km the three most imprecise markers can be reconciled with maximum movement of 100 km this refutes conventional plate tectonic reconstructions which suggest movement of 150 km or more new mechanisms should now be considered to explain the broad area of oceanic crust in baffin bay

eddy activity in the four major upwelling systems from satellite altimetry 1992 2007 eddy activity in the four major eastern boundary upwelling systems ebus is investigated using 15 years of satellite altimetry data based on the analysis of more than 4000 long lived eddy trajectories in every ebus we show that mesoscale structures are mainly generated along the continental coasts and south of the main archipelagos and propagate westward with velocities increasing toward the equator these mesoscale eddies having radii of 70 160 km are then frequently observed along the coastal transition zones and frontal regions and some large oceanic areas are preferentially populated by cyclonic or anticyclonic eddies temporal variations of the number of newly formed eddies and the associated eddy activity index defined as the mean eddy energy density are finally examined at seasonal and interannual scales the strongest seasonal interannual respectively variations are observed in the california benguela upwelling systems the proposed indices also exhibit contrasted long term trends in each ebus which suggests that eddy activity might be sensitive to a warming climate

icesat antarctic elevation data preliminary precision and accuracy assessment 1 since first light on february 20th 2003 nasa s ice cloud and land elevation satellite icesat has derived surface elevations from 86 n to 86 s latitude these unique altimetry data have been acquired in a series of observation periods in repeated track patterns using all three geoscience laser altimeter system glas lasers here we focus on antarctic ice sheet elevation data that were obtained in 2003 2004 we present preliminary precision and accuracy assessments of selected elevation data and discuss factors impacting elevation change detection we show that for low slope and clear sky conditions the precision of gla12 laser 2a release 21 data is 2 1 cm and the relative accuracy of icesat elevations is 14 cm based on crossover differences

rapid large area mapping of ice flow using landsat 8 abstract we report on the maturation of optical satellite image based ice velocity mapping over the ice sheets and large glacierized areas enabled by the high radiometric resolution and internal geometric accuracy of landsat 8 s operational land imager oli detailed large area single season mosaics and time series maps of ice flow were created using data spanning june 2013 to june 2015 the 12 bit radiometric quantization and 15 m pixel scale resolution of oli band 8 enable displacement tracking of subtle snow drift patterns on ice sheet surfaces at 1 m precision ice sheet and snowfield snow drift features persist for typically 16 to 64 days and up to 432 days depending primarily on snow accumulation rates this results in spatially continuous mapping of ice flow extending the mapping capability beyond crevassed areas our method uses image chip cross correlation and sub pixel peak fitting in matching landsat path row pairs high pass filtering is applied to the imagery to enhance local surface texture the current high image acquisition rates of landsat 8 725 scenes per day globally reduces the impact of high cloudiness in polar and mountain terrain and allows rapid compilation of large areas or dense temporal coverage of seasonal ice flow variations the results rival the coverage and accuracy of interferometric synthetic aperture radar insar mapping

threefold increase in marine terminating outlet glacier retreat rates across the atlantic arctic 1992 2010 accelerated discharge through marine terminating outlet glaciers has been a key component of the rapid mass loss from arctic glaciers since the 1990s however glacier retreat and its climatic controls have not been assessed at the pan arctic scale consequently the spatial and temporal variability in the magnitude of retreat and the possible drivers are uncertain here we use remotely sensed data acquired over 273 outlet glaciers located across the entire atlantic arctic i e areas potentially influenced by north atlantic climate and or ocean conditions specifically greenland novaya zemlya franz josef land and svalbard to demonstrate high magnitude accelerating and near ubiquitous retreat between 1992 and 2010 overall mean retreat rates increased by a factor of 3 5 between 1992 and 2000 30 5 m a 1 and 2000 10 105 8 m a 1 with 97 of the study glaciers retreating during the latter period the retreat was greatest in northern western and south eastern greenland and also increased substantially on the barents sea coast of novaya zemlya glacier retreat showed no significant or consistent relationship with summer air temperatures at decadal timescales the rate of frontal position change showed a significant but weak correlation with changes in sea ice concentrations we highlight large variations in retreat rates within regions and suggest that fjord topography plays an important role we conclude that marine terminating arctic outlet glaciers show a common response of rapid and accelerating retreat at decadal timescales

structure and surface properties of eddies in the southeast pacific ocean 1 a number of studies have posited that coastally generated eddies could cool the southeast pacific ocean sep by advecting cool upwelled waters offshore we examine this mechanism by characterizing the upper ocean properties of mesoscale eddies in the sep with a variety of observations and by estimating the surface layer eddy heat flux divergence with satellite data cyclonic and anticyclonic eddies observed during two cruises featured deep positive salinity anomalies along the 26 5 kg m 3isopycnal indicating that the eddies had likely trapped and transported coastal waters offshore the cyclonic eddies observed during the cruises were characterized by shoaling isopycnals in the upper 200 m and cool near surface temperature anomalies whereas the upper ocean structure of anticyclonic eddies was more variable using a variety of large scale observations including argo float profiles drifter records and satellite sea surface temperature fields we show that relative to mean conditions cyclonic eddies are associated with cooler surface temperatures and that anticyclonic eddies are associated with warmer surface temperatures within each data set the mean eddy surface temperature anomalies are small and of approximately equal magnitude but opposite sign eddy statistics drawn from satellite altimetry data reveal that cyclonic and anticyclonic eddies occur with similar frequency and have similar average radii in the sep a satellite based estimate of the surface layer eddy heat flux divergence while large in coastal regions is small when averaged over the sep suggesting that eddies do not substantially contribute to cooling the surface layer of the sep

paleomagnetism of the esayoo formation permian of northern ellesmere island possible clue to the solution of the nares strait dilemma abstract the esayoo formation lower permian of northern ellesmere island 81 n 82 w has been sampled at two localities twelve sites 88 cores studied in the early tertiary eurekan orogeny fold and thrust belt of the northern sverdrup basin northern ellesmere island the directions of remanent magnetization at the two localities are in excellent agreement after correction for geological tilt their mean is 126 2 61 8 b sites 12 k 105 95 4 3 and the corresponding paleopole is 48 1 n 159 2 e k 52 a 95 6 1 comparison with early permian reference paleopoles for north america shows that the formation of overthrust sheets has produced no paleomagnetically detectable displacement in a paleolatitudinal sense as would be inferred from the geology but there is a significant anticlockwise rotation of 36 8 this rotation is the first to be observed in the canadian arctic islands geological evidence allows no more than about 50 km of lateral motion along nares strait between ellesmere island and greenland this falls far short of the 300 km of relative motion required by the marine geophysical evidence for the opening of the labrador sea and baffin bay this discrepancy between the geological and geophysical evidence is the nares strait paradox evidently relative motion between greenland and ellesmere island is not restricted to nares strait itself and must be more generally distributed across ellesmere island we suggest that the 36 rotation observed is a manifestation of this distributed strain and therefore provides a clue to the solution of the nares strait paradox

a modeling study of the coastal eastern boundary current system off iberia and morocco to investigate the northern canary current system nccs results from four numerical experiments of increasing complexity are examined experiment 1 which uses seasonal wind forcing only shows that as expected wind forcing is the key generative mechanism for the current upwelling meander eddy and filament structures experiments 2 and 3 which have the additional effects of irregular coastline geometry show the following capes are areas for enhanced upwelling extensive filaments maximum current velocities and enhanced growth of cyclonic meanders and eddies an embayment like the gulf of cadiz is a primary region for anticyclonic meander and eddy development the results from the complex flow regime of experiment 4 which has the additional effects of thermohaline gradients and mediterranean outflow highlights the major characteristics and unique features such as the generation of meddies of the nccs with relatively close similarities to field observations

new evidence on the structure of the labrador sea greenland continental margin a 275 km section of a regional seismic reflection profile from the greenland side of the labrador sea has been reprocessed and interpreted three zones of different structural style have been identified the innermost of which is block faulted magnetic modelling based on the seismic line shows that sea floor spreading anomalies are confined to the outermost zone and the oldest identified anomaly is 27n all attempts to model the area landward of anomaly 27n as a series of remanent magnetizations of alternating polarity failed however a model in which the innermost zone is interpreted as extended and block faulted continental crust and the intermediate zone as continental crust intruded and overlain by reversely magnetized igneous material fits the magnetic and seismic data it is concluded that at least in the northern labrador sea sea floor spreading started in palaeocene times chron 27 and large areas formerly thought to be underlain by oceanic crust should now be considered to be continental one plate kinematic consequence may be a reduced need to postulate large strike slip movements along nares strait

outlet glacier response to the 2012 collapse of the matusevich ice shelf severnaya zemlya russian arctic the matusevich ice shelf mis located within the severnaya zemlya archipelago in the russian arctic rapidly broke apart between 10 august and 7 september 2012 we examine the response of the outlet glaciers that fed the mis from local ice caps to the removal of the ice shelf we use spaceborne laser altimetry and multiple optically derived digital elevation models to track ice surface elevation change rates dh dt between 1984 and 2014 glacier speeds are measured by pixel tracking from optical and radar imagery between 2010 and 2014 and interferometric synthetic aperture radar in 1995 to compare precollapse and postcollapse velocities we find that the three main outlet glaciers that fed the mis are thinning an order of magnitude more rapidly than most of the rest of severnaya zemyla based upon icesat data from 2003 to 2009 recent 2012 to 2014 thinning rates are three to four times faster than the 30 year average thinning rate calculated between 1984 and 2014 the springtime speeds of the largest outlet glacier issledovateley have increased more than 200 at the terminus between april 2010 and april 2014 to date changes in surface elevation dh dt and velocity at the outlet glaciers near mis are smaller than glacier responses to ice shelf collapse in antarctica it is possible that the mis was already very weak prior to the 2012 collapse and unable to support back stress further observations are required to assess whether the thinning and nonmelt season glacier speeds are continuing to accelerate

channelized melting drives thinning under a rapidly melting antarctic ice shelf ice shelves play a vital role in regulating loss of grounded ice and in supplying freshwater to coastal seas however melt variability within ice shelves is poorly constrained and may be instrumental in driving ice shelf imbalance and collapse high resolution altimetry measurements from 2010 to 2016 show that dotson ice shelf dis west antarctica thins in response to basal melting focused along a single 5 km wide and 60 km long channel extending from the ice shelf s grounding zone to its calving front if focused thinning continues at present rates the channel will melt through and the ice shelf collapse within 40 50 years almost two centuries before collapse is projected from the average thinning rate our findings provide evidence of basal melt driven sub ice shelf channel formation and its potential for accelerating the weakening of ice shelves

recent changes in glacier velocities and thinning at novaya zemlya abstract ice loss from the glaciers of novaya zemlya nvz is the dominant contributor to sea level for the russian arctic here we present maps of glacier elevation change rates dh dt and velocities at novaya zemlya that reveal evidence of the impact of both calving flux and surface melt on ice mass loss dh dt are calculated by applying a weighted linear regression to stacked digital elevation models dems from a 1952 map and dems created from stereo pairs of worldview images acquired between 2012 and 2014 the 60 year average mass change rate is 0 23 0 04 m w e yr 1 the recent short term 2012 2013 2014 average mass change rate is 0 40 0 09 m w e yr 1 we apply the same weighted linear regression to stacked worldview dems and icesat elevations from 2003 to 2009 as well as stacked worldview dems and aster dems from 2000 to 2013 the dh dt from both datasets confirm that thinning has been more rapid than the 60 year average since 2000 average mass loss has accelerated at the lower elevations of land terminating glaciers suggesting that recent near surface warming and increased melt have led to greater thinning marine terminating glaciers along the barents sea coast have substantially higher thinning rates near their termini in recent years than adjacent land terminating glaciers suggesting that calving flux is an important contributor to overall ice mass loss in the region flow velocities are generated by feature tracking on optical and radar image pairs marine terminating glaciers along the barents sea coast have the highest frontal velocities of any glaciers on nvz our surface velocity measurements constrain the calving flux at the two fastest retreating glaciers inostrantseva ino and vil kitskogo vis which are both on the barents sea coast we find that the calving flux is high enough to drive frontal thinning and retreat at those two glaciers summer terminus speeds at inostrantseva glacier have accelerated from a 2006 maximum of 3 m day 1 to a 2012 maximum of 9 to 10 m day 1 and the front has retreated by more than 3 km between 2006 06 27 and 2013 08 17

paleodepositional setting of the late cretaceous pautut flora from west greenland as determined by sedimentological and plant taphonomical data abstract preservation of the santonian campanian pautut flora in west greenland is mainly the result of a high energy river system that flowed across a well vegetated delta plain to carry and deposit plant parts and terrestrial clastic sediments into a low energy marine setting a diverse flora is represented mainly in three depositional settings 1 a dominant angiosperm vegetation preserved with fern and a few conifer species is found within backswamp lakes possibly near rivers 2 conifer organs and a sparse angiosperm leaf association occur in nearshore marine deltaic deposits dominated by fluvial sedimentation and 3 a unique pautut angiosperm vegetational assemblage with a few conifer and cycad species preserved in a brackish to fully marine bay setting fossil plant material preserved in the backswamp lakes and fluvial settings probably were deribed mostly from local sources indicating that angiosperms were able to a degree to invade into the backswamp arctic habitats considered to have been dominated by conifers however these backswamp habitats probably were short lived oxbow lakes with a successional angiosperm vegetation plant material in the fully marine setting is allochthonous very diverse and probably derived mostly from the upper delta palin the observed differences within the fossil plant assemblages deposited in the marine setting those containing mostly conifer parts occur in nearshore marine environments as compared to assemblages with mostly angiosperm leaves in more distal marine environments are used to interpret sorting of different plant parts due to individual taphonomical characters this means that the heavier conifer cones in the nearshore marine setting sank sooner than the lighter leaves which were dispersed further out to sea strengthening the argument for sorting is that both types of plant parts had a final resting position due to subaqueous transport the unique angiosperm leaf assemblage found in the fully marine setting is used to support the interpretation that the upper delta plain levees or extrabasinal sites were inhabited by a vegetational community distinct from that near the backswamp areas of the lower delta plain there are a few angiosperm species in common between the distal and nearshore marine and the backswamp lake settings these species are found througout the pautut area and exemplify a riparian element which was more prone to enter a depositional regime nearshore habitats were inhabited by non woody plants

intrathermocline eddies in the coastal transition zone off central chile 31 41 s 1 the three dimensional structure and the origin of mesoscale anticyclonic intrathermocline eddies ites in the coastal transition zone ctz off central chile 31 41 s were analyzed through the combination of data from oceanographic cruises and satellite altimetry and the application of an eddy resolving primitive equation ocean model coupled with a numerical experiment using a passive tracer in this region ites are represented by subsurface lenses 100 km diameter 500 m thickness or vertical extension of nearly homogeneous salinity 34 5 and oxygen deficient 1 0 ml l 1 waters properties which are linked to the equatorial subsurface water mass essw transported poleward by the peru chile undercurrent pcuc in the coastal band at least five to seven ites were observed simultaneously in the area between 31 and 38 s during winter cruises in 1997 and 2009 satellite data indicated that the ites identified from in situ data moved westward each at a mean speed of 2 km d 1 and transported a total volume of 1 106 m3 s 1 1 sv the lifespan of each ite ranged from a few months to 1 year model results indicate that ites become detached from the pcuc under summer upwelling conditions in the coastal zone

modeling vertical and horizontal diffusivities with the sigma coordinate system abstract the use of diffusive terms in numerical ocean models is examined relative to different coordinate systems the conventional model for horizontal diffusion is found to be incorrect when bottom topographical slopes are large a new formulation is suggested which is simpler than the conventional formulation when transformed to a sigma coordinate system and makes it possible to model realistically both surface ekman and bottom boundary layers

vertical velocities and dynamical balances in gulf stream meanders a triangular array of current meter moorings was deployed within the cyclonic flank of the gulf stream in the south atlantic bight from september 1981 to april 1982 using velocity and temperature data and the nondiffusive heat equation a time series of vertical velocity was derived a mean vertical velocity of 0 013 cm s 1 and standard deviation of 0 078 cm s 1 were obtained to better understand the subsurface structure of gulf stream meanders the time series of horizontal and vertical velocities and temperature were examined at times when events were passing through the array the flow along the trailing edge of a gulf stream meander and within the leading portion of a cold core frontal eddy was found to have an upward component positive w while that within the trailing portion of the frontal eddy and along the leading edge of a meander had a downward component negative w using the horizontal and vertical velocity time series cross stream and along stream momentum balances were calculated the downstream flow was found to be in geostrophic balance in contrast the coriolis and nonlinear terms were found to contribute equally to the determination of the cross stream flow

north atlantic spreading axes terminate in the continental cul de sacs of baffin bay and the laptev sea in conventional plate tectonic models an independent greenland plate is supposed to have drifted in the paleogene along a transform fault through nares strait that links the two branches of the north atlantic spreading system however this postulated structure widely known as the wegener fault cannot be detected by any means in the southern part of the strait the mapped geology flanking this part of the strait is identical with no evidence whatsoever of any strike slip displacement or compressional deformation and geophysical data provide no support for the existence of such tectonism offshore we analyse the serious drawback of having a major transform located within a precambrian crustal block stable since the paleozoic and emphasize that the extinct labrador baffin bay spreading axis is but a mirror image of the active north atlantic gakkel ridge that terminates in a continental cul de sac in the laptev sea we conclude that in the baffin bay nares strait region there is only one plate

coastal transition zone off chile 1 seven years of subsurface current observations at deep sea and continental slope moorings off chile 30 s satellite sea surface anomaly and satellite wind stress are used to examine space time and propagation characteristics of the mesoscale eddy activity in the coastal transition zone off chile this zone off chile extends from the coast to 600 800 km offshore and can be separated into two latitudinal regions the first region between 29 and 39 s off central chile is characterized by high eddy kinetic energy and strong but variable equatorward wind stress the second region between 19 and 29 s off northern chile is characterized by low eddy kinetic energy and weak but persistent equatorward wind stress low frequency mesoscale variability off central chile is mainly associated with baroclinic instability of coastal currents and westward propagation of rossby waves from the eastern boundary and is strongly modulated over el nino la nina cycles application of a new rotary wavelet spectrum method to the recording current meter data and the use of current estimates from satellite altimeter data show that mesoscale eddies and meanders in the coastal transition zone fluctuate with periods centered on 120 days and with length scales centered on 200 km cross rotary wavelet analyses of currents and wind stress indicate that fluctuations of coastal currents with periods longer than 220 days propagated westward as free rossby waves during 1995 1996 and as forced rossby waves during 1999 2001

identification and characteristics of surge type glaciers on novaya zemlya russian arctic we present a comprehensive new inventory of surge type glaciers on the novaya zemlya archipelago using high resolution up to 4 m satellite imagery from 1976 77 hexagon 1989 landsat tm 2001 landsat etm and 2006 aster a total of 692 glaciers and their forelands were observed for glaciological and geomorphological criteria indicative of glacier surging e g looped moraines heavy surface crevassing surface potholes thrust block moraines concertina eskers this enabled the identification of 32 potential surge type glaciers compared with four previously identified representing 4 6 of the total but 18 by glacier area we assess the characteristics of surge type glaciers surge type glaciers are statistically different from non surge type glaciers in terms of their area length surface slope minimum elevation mid range elevation and terminus type they are typically long median length 18 5 km large median area 106 8 km 2 outlet glaciers with relatively low overall surface slopes median slope 1 7 and tend to terminate in water marine or lacustrine they are predominantly directed towards and located in the more maritime western region of the russian arctic and we suggest that surge occurrence might be related to large and complex catchment areas that receive increased delivery of precipitation from the barents sea

seasonal variability of coastal upwelling and the upwelling front off central chile 1 we analyze sea surface temperature sst and chlorophyll a chl a satellite data to study the seasonal variability of the upwelling off central chile data from an oceanographic cruise are used to illustrate the vertical characteristics of the upwelling front and the geostrophic flow the mean offshore extension of the sst front in summer is 110 km there sst changes from 13 5 c near the coast to 14 5 15 c offshore hydrographic data show that the thermocline becomes progressively shallower toward the coast but that at a certain distance it abruptly bends to form a horizontal front that extends until 50 m depth satellite data show that the chl a decays exponentially offshore and a concentration of 1 mg m 3 indicates the offshore limit of the frontal region the sst front observed most of the year is absent in winter when the coastal water is only slightly colder than the oceanic one however relatively higher chl a values remain present near the coast during winter northwest of punta lavapie 37 15 s the frontal region is located progressively farther offshore suggesting that a branch of an equatorward surface jet separates from the coast to form a meander which is associated with a filament of cold water and an anticyclonic eddy observed frequently in this zone during summer hydrographic data show that isotherm and current disturbances related to mesoscale eddies can extend several hundreds of meters below the surface in contrast the coastal jet is quite shallow extending until 150 m depth

short paper nares strait was not a cenozoic plate boundary nares strait the linear seaway between greenland and arctic canada has long been regarded as a palaeogene plate boundary along which major transform movement accommodated opening of the labrador sea fieldwork however revealed several stratigraphic markers which cross the strait and precle substantial displacement current plate reconstructions based on geophysical data continue to invoke major convergence and strike slip along the strait the manner in which palaeozoic structural trends curve into parallelism with the strait as they cross it has been used to support this idea restoration of the trends gives an apparent 200 km offset along the strait the curvature is an original tectonic feature and cannot be restored stratigraphic data preclude substantial cenozoic displacement along or across nares strait reconstructions based on indirect geophysical evidence which violate the geology must be wrong

numerical treatment of cross shelf open boundaries in a barotropic coastal ocean model abstract using a barotropic coastal ocean model with a straight coastline and uniform cross shelf bottom slope seven different cross shelf open boundary conditions four of which are applied in either implicit or explicit form are compared in three numerical experiments 1 a mound of water is allowed to collapse and radiate waves toward the open boundaries 2 a uniform alongshelf wind stress is applied at zero time over the entire shelf and held constant for the duration of the experiment 3 a uniform cross shelf wind stress is applied at zero time over the entire shelf and held constant for the duration of the experiment the boundary condition which is most transparent to waves consists of a sponge at the outer edge of the model domain with an orlanski radiation condition at the outer edge of the sponge several open boundary conditions perform adequately in the wind stress experiments but the orlanski radiation condition alone without a sponge appears to give the best total performance of thes

seasonal and interannual variability of currents and temperature off central chile results are reported for continuous 6 year records of current and temperature from a continental slope station at 308s off chile these observations for november 1991 to november 1997 span the moderate weak and strong el nino events of 1991 1992 1994 and 1997 and the la nina event of 1995 1996 results for current and temperature are analyzed together with observations of wind along the south american coast from the ers 1 and 2 satellite scatterometers wind from a local coastal site sea level from northern and central chile sea surface temperature anomalies from the south pacific region and traditional el nino indices mean poleward flow of 12 8 cm s 21 was observed for the 6 year period in the core of the peru chile undercurrent 220 m mean flow in the depth range of antarctic intermediate water 750 m was equatorward at 1 1 cm s 21 intraseasonal scale variability associated with coastal trapped waves was weaker during the austral winter greatest during el nino events and weakest during the la nina event winds adjacent to the coast showed a strong annual cycle with a southward progression of maximum equatorward upwelling favorable winds alongshore flow over the slope exhibited strong semiannual and weaker annual variations poleward flow in the undercurrent was strongest in the austral spring and fall and weakest in the winter near the bottom 750 m seasonal scale variability was less intense but led that higher up in the water column 220 m by 1 month strong interannual variability of alongshore current and temperature was found at all depths over the slope whereby changes at depth led changes higher up a rapid warming event was observed at the end of 1996 beginning of 1997 over the slope this event also seen in sea level and sea surface temperature off chile led el nino indices by several months and may be best explained by local wind anomalies coupled to atmospheric teleconnections from the western tropical pacific at the onset of el nino some aspects of our current and temperature observations are consistent with results from eastern boundary current models our results indicate that both ocean and atmosphere pathways from the equatorial pacific contribute significantly to interannual scale variability of alongshore flow and thermocline depth off chile

form and flow of the academy of sciences ice cap severnaya zemlya russian high arctic 1 the 5 575 km2 academy of sciences ice cap is the largest in the russian arctic a 100 mhz airborne radar digital landsat imagery and satellite synthetic aperture radar sar interferometry are used to investigate its form and flow including the proportion of mass lost through iceberg calving the ice cap was covered by a 10 km spaced grid of radar flight paths and the central portion was covered by a grid at 5 km intervals a total of 1 657 km of radar data digital elevation models dems of ice surface elevation ice thickness and bed elevation data sets were produced cell size 500 m the dems were used in the selection of a deep ice core drill site total ice cap volume is 2 184 km3 5 5 mm sea level equivalent the ice cap has a single dome reaching 749 m maximum ice thickness is 819 m about 200 km or 42 of the ice margin is marine about 50 of the ice cap bed is below sea level the central divide of the ice cap and several major drainage basins in the south and east of the ice cap and of up to 975 km2 are delimited from satellite imagery there is no evidence of past surge activity on the ice cap sar interferometric fringes and phase unwrapped velocities for the whole ice cap indicate slow flow in the interior and much of the margin punctuated by four fast flowing features with lateral shear zones and maximum velocity of 140 m yr 1 these ice streams extend back into the slower moving ice to within 5 10 km of the ice cap crest they have lengths of 17 37 km and widths of 4 8 km mass flux from these ice streams is 0 54 km3 yr 1 tabular icebergs up to 1 7 km long are produced total iceberg flux from the ice cap is 0 65 km3 yr 1 and probably represents 40 of the overall mass loss with the remainder coming from surface melting driving stresses are generally lowest 40 kpa close to the ice cap divides and in several of the ice streams ice stream motion is likely to include a significant basal component and may involve deformable marine sediments

the randolph glacier inventory a globally complete inventory of glaciers the randolph glacier inventory rgi is a globally complete collection of digital outlines of glaciers excluding the ice sheets developed to meet the needs of the fifth assessment of the intergovernmental panel on climate change for estimates of past and future mass balance the rgi was created with limited resources in a short period priority was given to completeness of coverage but a limited uniform set of attributes is attached to each of the 198 000 glaciers in its latest version 3 2 satellite imagery from 1999 2010 provided most of the outlines their total extent is estimated as 726 800 34 000 km 2 the uncertainty about 5 is derived from careful single glacier and basin scale uncertainty estimates and comparisons with inventories that were not sources for the rgi the main contributors to uncertainty are probably misinterpretation of seasonal snow cover and debris cover these errors appear not to be normally distributed and quantifying them reliably is an unsolved problem combined with digital elevation models the rgi glacier outlines yield hypsometries that can be com bined with atmospheric data or model outputs for analysis of the impacts of climatic change on glaciers the rgi has already proved its value in the generation of significantly improved aggregate estimates of glacier mass changes and total volume and thus actual and potential contributions to sea level rise

the southern cape conductive belt south africa its composition origin and tectonic significance abstract magnetometer array studies have led to the discovery and mapping of the southern cape conductive belt sccb crossing the southern tip of africa from west to southeast coasts the sccb lies just south of the namaqua natal belt of cratonic rocks remobilized about 1000 m y b p it is shown that it coincides with a zone of weakness which has been exploited by three major geosynclinal accumulations over some 600 m y relationships between the sccb and the basement geochronology geology and tectonics are considered in detail these relationships support the view that the conductive belt was formed by an accumulation of marine sediments and oceanic lithosphere at the top of a proterozoic subduction which stopped about 1000 to 800 m y b p associated with this subduction we propose a proterozoic range of andean mountains whose roots are now exposed in the namaqua natal belt later subduction further south near the present south coast is proposed to account for the intrusion between the south coast and the sccb of the cape granites in the time interval 600 500 m y b p there is some evidence for a third yet more distant subduction episode off permian gondwanaland after outlining this tectonic history the paper turns to a closer examination of the hypothesis that the southern cape conductive belt consists of partly serpentinized basalt accumulated at the top of a proterozoic subduction a large static magnetic anomaly which correlates with the sccb over most of its length is well fitted by a model which strongly supports this hypothesis bouguer gravity anomalies along western and central profiles likewise support the hypothesis a discussion follows of the process of formation of the proposed block of serpentinized marine rocks beginning with serpentinization of the crust near oceanic ridges by reaction of warm porous newly extruded basalt with seawater convecting through it the serpentinized basalt is stable at crustal temperatures and pressures and so is transported in the seafloor until it reaches a subduction where it accumulates because of its low density examples of such accumulations are cited finally it is shown that any iron in the olivine and pyroxene in the original basalt precipitates when these silicates are hydrated to serpentine as magnetite which is the dominant mineral conferring high electrical conductivity and high magnetic susceptibility on serpentinites in particular the beattie static magnetic anomaly requires in our model calculation a very high susceptibility readily attainable in basalt at 15 20 serpentinization the authors know of no other rock able to provide this high susceptibility a similar percentage of serpentinization provides the density required to model the gravity anomalies

a numerical study of the seasonal variability in the circulation off central chile the princeton ocean model is used to study the coastal ocean circulation off central chile between 30 and 45 s and its seasonal transitions in response to monthly mean climatological wind stress and surface heat flux the model reproduces many of the dominant circulation features including an equatorward coastal current coastal upwelling and a poleward undercurrent to get the correct seasonal variability in the undercurrent it was necessary to prescribe the inflow of the undercurrent on the northern model boundary meanders and eddies form throughout the simulation period seaward of the coastal current in response to baroclinic instability of the flow the flow associated with the meanders shows upwelling in the shoreward flow and downwelling in the seaward flow this upwelling downwelling pattern is explained by conservation of relative vorticity in the flow the upwelling velocity associated with the meanders corresponds to a vertical migration of 15 30 m over a typical timescale of the meanders of 1 2 months it is argued that this upwelling may be important for maintaining observed high phytoplankton biomass and primary production seaward of the coastal zone directly affected by wind driven upwelling

ice loss rates at the northern patagonian icefield derived using a decade of satellite remote sensing abstract we use a satellite based survey of glacier surface elevation changes speeds and surface melt conditions between 2000 and 2011 to quantify mass loss from the northern patagonian icefield npi chile a history of ice elevation change is found by differencing aster digital elevation models dems relative to a void filled version of the dem collected by the shuttle radar topography mission srtm in february 2000 thinning rates have accelerated at lower elevations while above the equilibrium line altitude ela recent thinning rates are not significantly different from those observed in previous studies a volumetric change of 4 06 0 11 km 3 yr is found by summing surface elevation changes over all glaciers in the npi this is regarded as a lower bound because volume loss due to frontal retreat and sub aqueous melting is not included this volume change is converted to a mass loss of 3 40 0 07 gt yr taking into account density differences above and below the equilibrium line we find that the npi is providing at least 0 009 0 0002 mm yr to ongoing sea level change in agreement with previous estimates sub pixel offset tracking of aster image pairs is used to produce glacier displacements over intervals typically ranging from 6 days to 18 months the first whole icefield composite velocity map is presented the terminus of the san rafael glacier on the western side of the npi sustained a peak calving front speed of 19 7 1 2 m day for 7 days in the austral fall of 2007 passive microwave observations indicate that the surface of the accumulation basin of the glacier was wet during this period of rapid motion suggesting that the fast speed may be a consequence of a rise in sub glacial water pressure sourced from melt or rainwater making its way to the glacier bed and reducing basal friction several other outlet glaciers including the benito and hpn1 glaciers on the isolated western side of the icefield accelerated while thinning between 2007 and 2011 marked acceleration also occurred after 2007 at the front of the san quintin glacier the largest outlet glacier of the npi the paucity of thickness measurements at the outlet glaciers means it is impossible to accurately gauge the mass flux of the icefield and thus give a full estimate of the mass balance

a fission track transect across nares strait canada greenland further evidence that the wegener fault is a myth many workers continue to model nares strait between greenland and ellesmere island canada as a plate boundary and locus of major cenozoic compression and strike slip marked by the postulated wegener transform fault this despite continuity of precambrian paleozoic provinces across the seaway including an undeformed neoproterozoic mafic dyke swarm that crosses at a high angle as a test of the speculative plate kinematic modelling apatite fission track aft dating was undertaken along a transect across the paleoproterozoic shield of smith sound at the south end of nares strait running from sea level to ca 600 m elevation and as much as 70 km inland on both sides the shield is overlain by three sedimentary basins separated by major hiatuses the aft ages fall into two groups 282 34 and 650 51 ma they indicate maximum depth was 4 km in the lower paleozoic from both coasts to 50 km inland and at 50 km inland temperatures were below the annealing interval throughout phanerozoic time durin

recent elevation changes of svalbard glaciers derived from icesat laser altimetry abstract we have tested three methods for estimating 2003 2008 elevation changes of svalbard glaciers from multi temporal icesat laser altimetry a linear interpolation of crossover points between ascending and descending tracks b projection of near repeat tracks onto common locations using digital elevation models dems and c least squares fitting of rigid planes to segments of repeat track data assuming a constant elevation change rate the two repeat track methods yield similar results and compare well to the more accurate but sparsely sampled crossover points most glacier regions in svalbard have experienced low elevation thinning combined with high elevation balance or thickening during 2003 2008 the geodetic mass balance excluding calving front retreat or advance of svalbard s 34 600 km2 glaciers is estimated to be 4 3 1 4 gt y 1 corresponding to an area averaged water equivalent w e balance of 0 12 0 04 m w e y 1 the largest ice losses have occurred in the west and south while northeastern spitsbergen and the austfonna ice cap have gained mass winter and summer elevation changes derived from the same methods indicate that the spatial gradient in mass balance is mainly due to a larger summer season thinning in the west and the south than in the northeast our findings are consistent with in situ mass balance measurements from the same period confirming that repeat track satellite altimetry can be a valuable tool for monitoring short term elevation changes of arctic glaciers

some limitations in using leaf physiognomic data as a precise method for determining paleoclimates with an example from the late cretaceous pautut flora of west greenland abstract plant parts of the late cretaceous west greenland pautut flora are derived from vegetation growing in lower delta plain delta upland and levee habitats a large river system drained the uplands and deposited leaves from species there and levee areas into a shallow bay setting the large drainage area of the rivers caused a great diversity of species to be preserved in the bay when these upland and levee species are combined with those that grew and were deposited in the lower delta plain areas 12 fern six cycad cycadeoid 1 ginkgoalean 35 conifer and over 85 angiosperm species represent the pautut flora when the paleotemperature derived from the angiosperm leaf margin ratio of the complete pautut flora 8 c is compared to other paleobotanical data and oxygen isotope values warm temperate to subtropical there is a serious discrepancy that puts the leaf physiognomic approach for precisely determining paleoclimate in the cretaceous in serious doubt also paleoclimatic interpretations based on the angiosperm leaf margin data of leaves from the lower delta plain species would indicate slightly cooler conditions than that suggested by the upper delta plain species leaf size would indicate wetter conditions in the lower delta plain even though other leaf features e g drip tips suggest moist conditions did occur in the upper delta plain these preservation enough that regional paleoclimate scenarios drawn from only one depositional setting or loclity can be erroneous a sampling size of less than 30 angiosperm species for a fossil flora also is suspect for reliably indicating climatic conditions unless the flora was originally impoverished of angiosperm species taphonomic factors play a significant role in fossil leaf preservation so collected fossil assemblages must closely represent the original vegetation before paleoclimatic interpretations based on leaf physiognomy can have a degree of credibility a limit to plausibility is especially significant in cretaceous floras because they have a limited diversity due to evolutionary constraints and appear to have consisted of more successional species than younger floras thus displaying intermediate climatic conditions moisture and arctic light levels further restrict determination of paleoclimatic conditions derived from leaf margin ratios and leaf size

on the recent elevation changes at the flade isblink ice cap northern greenland 1 we have used radar altimeter 2 ra 2 onboard esa s envisat and geosciences laser altimeter system glas onboard nasa s icesat to map the elevation change of the flade isblink ice cap fiic in northern greenland based on ra 2 data we show that the mean surface elevation change of the fiic has been near zero 0 03 0 03 m a between fall 2002 and fall 2009 we present the elevation change rate maps and assess the elevation change rates of areas above the late summer snow line 0 09 0 04 m a and below it 0 16 0 05 m a the glas elevation change rate maps show that some outlet glaciers previously reported to have been in a surge state are thickening rapidly using the ra 2 measured average elevation change rates for different parts of the ice cap we present a mass change rate estimate of 0 0 0 5 gt a for the fiic we compare the annual elevation changes with surface mass balance smb estimates from a regional atmospheric climate model racmo2 we find a strong correlation between the two r 0 94 and p 0 002 suggesting that the surface elevation changes of the fiic are mainly driven by net smb the correlation of modeled net smb and measured elevation change is strong in the southern areas of the fiic r 0 97 and p 0 0005 but insignificant in the northern areas r 0 38 and p 0 40 this is likely due to higher variability of glacier flow in the north relative to the south

accelerating glacier mass loss on franz josef land russian arctic abstract the glaciers of the franz josef land fjl archipelago in the russian arctic are subjected to rapidly warming temperatures but are small contributors to sea level we analyze ice surface elevation data derived from satellite stereo imagery worldview and spot radar altimetry cryosat 2 and a digitized 1953 cartographic map to calculate elevation change rates d h d t mass loss from fjl doubled between 2011 and 2015 compared to 1953 2011 2015 increasing from a rate of 2 18 0 72 gt yr 1 to 4 43 0 78 gt yr 1 this 2011 2015 rate indicates an acceleration in ice loss from that observed in 2003 2009 by multiple studies using icesat and grace glacier thinning rates are spatially highly variable we observe glacier thinning rates of up to 10 m per year and in general we see a trend of increased thinning from the ne towards the sw glacier retreat is widespread and has led to the creation of at least one new island historically ice wastage from fjl is thought to have been relatively small but accelerating ice loss may be the new normal for this archipelago in a warming arctic

the possible transition from glacial surge to ice stream on vavilov ice cap an edited version of this paper was published by agu copyright 2019 american geophysical union

on subsurface cooling associated with the biobio river canyon chile submarine canyons cutting across the continental shelf can modulate the cross shelf circulation being effective pathways to bring water from the deep ocean onto the shelf here we use 69 days of moored array observations of temperature and ocean currents collected during the spring of 2013 and winter spring 2014 as well as shipboard hydrographic surveys and sea level observations to characterize cold oxygen poor and nutrient rich upwelling events along the biobio submarine canyon bbc the bbc is located within the gulf of arauco at 36 50 s in the central chilean coast the majority of subtidal temperature at 150 m depth is explained by subtidal variability in alongshore currents on the canyon with a lag of less than a day r2 0 65 using the vertical displacement of the 10 and 10 5 c isotherms we identified nine upwelling events lasting between 20 h to 4 5 days that resulted in vertical isothermal displacements ranging from 29 to 137 m the upwelled water likely originated below 200 m majority of the cooling events were related with strong northward opposite kelvin wave propagation flow and low pressure at the coast most of these low pressure events occur during relatively weak local wind forcing conditions and were instead related with coastal trapped waves ctws propagating southwards from lower latitudes these cold high nutrient low oxygen waters may be further upwelled and advected into the gulf of arauco by wind forcing thus canyon upwelling may be a key driver of biological productivity and oxygen conditions in this gulf

icesat validation of srtm c band digital elevation models 1 the geoscience laser altimeter system glas on the ice cloud and land elevation satellite icesat provides a globally distributed data set well suited for evaluating the vertical accuracy of shuttle radar topography mission srtm digital elevation models dems the horizontal error 2 4 7 3 m and vertical error 0 04 0 13 m per degree of incidence angle for the icesat data used are small compared to those for srtm using glas echo waveforms we document differences between the srtm c band phase center and the highest centroid and lowest elevations within icesat laser footprints in the western united states in areas of low relief and sparse tree cover the mean and standard deviation of elevation differences between the icesat centroid and srtm are 0 60 3 46 m the differences are 5 61 15 68 m in high relief sparse tree cover areas and 3 53 8 04 m in flat areas with dense tree cover the largest differences occur in rugged densely vegetated regions

recent contributions of glaciers and ice caps to sea level rise satellite measurements of earth s gravity field show that the mass loss of glaciers and ice caps contributed to sea level rise by approximately 0 4 millimetres per year between 2003 and 2010 the extent to which mass loss from ice covered land areas contributes to sea level rise is not known accurately in part because previous global estimates use different techniques for glaciers ice caps and ice sheets the gravity recovery and climate experiment grace satellite has provided monthly measurements of the global gravity field since 2002 using grace data jacob et al assess regional mass loss between 2003 and 2010 and conclude that mass loss from ice covered land areas contributed almost 1 5 mm per year to the sea level rise estimated mass loss from the high mountains of asia was negligible in contrast to some other reports glaciers and ice caps gics are important contributors to present day global mean sea level rise1 2 3 4 most previous global mass balance estimates for gics rely on extrapolation of sparse mass balance measurements1 2 4 representing only a small fraction of the gic area leaving their overall contribution to sea level rise unclear here we show that gics excluding the greenland and antarctic peripheral gics lost mass at a rate of 148 30 gt yr 1 from january 2003 to december 2010 contributing 0 41 0 08 mm yr 1 to sea level rise our results are based on a global simultaneous inversion of monthly grace derived satellite gravity fields from which we calculate the mass change over all ice covered regions greater in area than 100 km2 the gic rate for 2003 2010 is about 30 per cent smaller than the previous mass balance estimate that most closely matches our study period2 the high mountains of asia in particular show a mass loss of only 4 20 gt yr 1 for 2003 2010 compared with 47 55 gt yr 1 in previously published estimates2 5 for completeness we also estimate that the greenland and antarctic ice sheets including their peripheral gics contributed 1 06 0 19 mm yr 1 to sea level rise over the same time period the total contribution to sea level rise from all ice covered regions is thus 1 48 0 26 mm 1 which agrees well with independent estimates of sea level rise originating from land ice loss and other terrestrial sources6