interannual variability of summer biochemical enhancement in relation to mesoscale eddies at the shelf break in the vicinity of the pribilof islands bering sea abstract this study examined variability of the eddy field and primary production over the bering sea s eastern shelf break area during summer using a satellite multi sensor data set the eddy field and on shelf nutrient flux below 50 m water depth were also investigated using a numerical model the satellite altimeter data analysis and numerical experiments indicated that the eddy field was induced by perturbations of the bering slope current system and or instabilities in the bering sea basin via flow through the aleutian passes the distribution of high primary production roughly coincided with the high variability area of the eddy field numerical experiments showed a 70 increase in net on shelf flux and 54 increase in net on shelf transport by the generation propagation of eddies along the shelf break at pribilof canyon towed ctd fluorometer measurements during the summer of 2003 revealed a stable water column and high fluorescence 10 g l 1 in the area between the 200 and 1000 m isobaths at a time when there was a low level of on shelf flux regardless of the eddy field conversely the eddy induced on shelf flux and stable water column can enhance primary production from spring to summer at the shelf break moreover the eddy induced on shelf nutrient flux probably contributes to the primary productivity at the western shelf of the pribilof islands where the bering sea ecosystem is very dynamic this eddy related shelf break process can be applied to not only the bering sea shelf break but also all shelf break areas in which propagating eddies are found

an inverse modeling study of circulation in the eastern bering sea during 2007 2010 a two way nested 4d variational data assimilation system is implemented in the eastern bering sea ebs to investigate changes in circulation and thermodynamic state for a 3 8 year period assimilated observations include data from 19 moorings deployed on the shelf and in the bering strait 1705 hydrographic stations occupied during eight surveys and remotely sensed sea surface temperature and sea surface height ssh data validation of the presented 4dvar reanalysis against the output of two sequential data assimilative systems the bering ecosystem study ice ocean modeling and assimilation system bestmas and the arctic cap nowcast forecast system acnfs has shown that the product is more consistent with the observed transports in the bering strait and in the ebs interior both in terms of their magnitude and time variability analysis of the data optimized solution quantifies a sequence of wind forced events that resulted in the anomalous heat and freshwater transports through the bering strait including a 28 day long flow reversal that occurred in november of 2009 and carried siberian coastal current water down to the gulf of anadyr lagrangian study of the arctic bound pacific waters indicates the extreme importance of the cross shelf exchange along the path of the bering slope current and quantifies the spectrum of residence times for the waters entering ebs through unimak pass and through aleutian passages residence times in the ebs cold pool are diagnosed to be 2 3 times longer than those in the surrounding waters this article is protected by copyright all rights reserved

a simplified ice ocean coupled model for the antarctic ice melt season abstract in the antarctic ocean sea ice melts mostly by warming of the ocean mixed layer through heat input mainly solar radiation in open water areas a simplified ice upper ocean coupled model is proposed in which sea ice melts only by the ocean heat supplied from the air the model shows that the relationship between ice concentration i e fraction c and mixed layer temperature t converges asymptotically with time c t relationship which agrees with observed c t plots during summer in the sector 25 45 e this relationship can be used for estimating the bulk heat transfer coefficient between ice and ocean by fitting to observations and a value of 1 2 10 4 m s 1 is obtained the model shows that the ratio of the heat used for melting to the heat input through open water is inclined to be determined as a function of ice concentration for typical conditions in the antarctic ice melt season the ratio ranges mostly between 0 7 and 0 9 when the model is extended to two dimensions in the meri

modeling effects of tidal and wave mixing on circulation and thermohaline structures in the bering sea process studies 1 ocean circulation and the tidal current in the bering sea are simulated simultaneously using a coupled ice ocean model ciom with tidal and parameterized wave mixing to investigate several important physical processes the simulated circulation pattern in the deep basin is relatively stable cyclonic and has little seasonal change the bering slope current is estimated at 5 sv and the kamchatka current at 20 sv the modeled volume transports through the aleutian passes compared reasonably well with observations it is confirmed that subtidal clockwise circulation around st george and st paul islands are driven by tidal rectification the simulation results show that wind wave mixing and tidal stirring are the main factors controlling the formation of the upper and the bottom mixed layers respectively the mechanism of thermocline and the cold pool summer minimum temperature water formation in the middle shelf are investigated in depth the ciom reproduces the cold winter convective water in the middle shelf that forms the bottom cold pool which persists throughout the summer until sea surface cooling and strong wind mixing in fall leading to an unstable vertical water column and eventually to vertically well mixed water in the winter sensitivity experiments show that tidal and wind wave mixing are two important factors in accurately estimating the volume of the cold pool which is the ideal marine habitat for cold water species

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

seismic mountain building landslides associated with the 2008 wenchuan earthquake in the context of a generalized model for earthquake volume balance here we assess earthquake volume balance and the growth of mountains in the context of a new landslide inventory for the mw 7 9 wenchuan earthquake in central china coseismic landslides were mapped from high resolution remote imagery using an automated algorithm and manual delineation which allow us to distinguish clustered landslides that can bias landslide volume calculations employing a power law landslide area volume relation we find that the volume of landslide associated mass wasting 2 8 0 9 0 7 km3 is lower than previously estimated 5 7 15 2 km3 and comparable to the volume of rock uplift 2 6 1 2 km3 during the wenchuan earthquake if fluvial evacuation removes landslide debris within the earthquake cycle then the volume addition from coseismic uplift will be effectively offset by landslide erosion if all earthquakes in the region followed this volume budget pattern the efficient counteraction of coseismic rock uplift raises a fundamental question about how earthquakes build mountainous topography to provide a framework for addressing this question we explore a group of scaling relations to assess earthquake volume balance we predict coseismic uplift volumes for thrust fault earthquakes based on geophysical models for coseismic surface deformation and relations between fault rupture parameters and moment magnitude mw by coupling this scaling relation with landslide volume mw scaling we obtain an earthquake volume balance relation in terms of moment magnitude mw which is consistent with the revised wenchuan landslide volumes and observations from the 1999 chi chi earthquake in taiwan incorporating the gutenburg richter frequency mw relation we use this volume balance to derive an analytical expression for crustal thickening from coseismic deformation based on an index of seismic intensity over a defined area this model yields reasonable rates of crustal thickening from coseismic deformation e g 0 1 0 5 km ma 1 in tectonically active convergent settings and implies that moderate magnitude earthquakes mw 6 7 are likely responsible for most of the coseismic contribution to rock uplift because of their smaller landslide associated volume reduction our first order model does not consider a range of factors e g lithology climate conditions epicentral depth and tectonic setting nor does it account for viscoelastic effects or isostatic responses to erosion and there are important large uncertainties on the scaling relationships used to quantify coseismic deformation nevertheless our study provides a conceptual framework and invites more rigorous modeling of seismic mountain building

geomorphometric assessment of spatial sediment connectivity in small alpine catchments abstract complex and rugged topography induces large variations in erosion and sediment delivery in the headwaters of alpine catchments an effective connection of hillslopes with the channel network results in highly efficient sediment transfer processes such as debris flows in contrast morphological conditions producing decoupling of hillslopes from channels e g glacial cirques may exclude large areas of the catchment from sediment delivery to its lower parts moreover an efficient connection between hillslopes and channel network does not always ensure an effective downstream transfer of sediment low slope channel reaches e g in hanging valleys cause sediment deposition which often results in changes of the sediment transport processes typically from debris flow to streamflow with low bedload and suspended load rates the availability of high resolution digital terrain models such as those derived from aerial lidar improves our capability to quantify the topographic controls on sediment connectivity a geomorphometric index based on the approach by borselli et al 2008 was developed and applied to assess spatial sediment connectivity in two small catchments of the italian alps featuring contrasting morphological characteristics the results of the geomorphometric analysis were checked against field evidences showing good performance and thus potential usefulness of the index

an ice ocean coupled model an ice model an ocean model and a method of coupling the models are described the ice model is a synthesis with variations and extensions of previous modeling ideas ice thickness concentration velocity and internal energy are prognostic variables the ice thermodynamics are represented by temperatures at the snow surface ice surface the interior and the bottom surface melting and freezing rates are calculated at the ice atmosphere ice ocean and atmosphere ocean interfaces a prescribed portion of summer meltwater can be stored on the surface and refrozen in the fall the ocean model includes a second moment turbulence closure submodel and enables one to solve for oceanic heat flux the interfacial stress and subsurface properties in this paper the model is applied to one dimensional simulations but the equations are cited in a form for implementation by two and three dimensional models in a companion paper kantha and mellor this issue the model is used for two dimensional vertical plane simulations in the bering sea several one dimensional sensitivity studies are performed in the case where the ice model is decoupled from the ocean here the oceanic heat flux and sea surface temperature are prescribed constants the studies reveal the role and sensitivity of surface trapped meltwater ice concentration and ice divergence with the coupled ice ocean model the seasonally varying oceanic heat flux and mixed layer properties are determined by the model some comparisons with observations in the central arctic ocean are possible the role of the molecular sublayer immediately adjacent to the ice is examined frazi ice production is related to the large disparity in the molecular diffusivities for temperature and salinity the mixed layer model contains empirical constants which are known from turbulence data the molecular sublayer parameterization requires one empirical parameter b which is uncertain but from this study is assuredly greater than zero the value implicit in previous models the ice model requires the empirical parameters ci f and ci u to quantitatively account for freezing or melting processes in open leads their values are also uncertain but we present reasoning and sensitivity studies to suggest specific values finally an empirical parameter g is introduced it is the ratio of the value of the ice thickness used to represent average ice volume in the dynamic and thermodynamic equations to the value of the thickness needed in the heat conduction equation estimates of g are made from observed thickness distribution functions sensitivity studies show it to be an important parameter

why so few landslides triggered by the 2002 denali earthquake alaska abstract the 2002 m w 7 9 denali fault earthquake alaska provides an unparalleled opportunity to investigate in quantitative detail the regional hillslope mass wasting response to strong seismic shaking in glacierized terrain we present the first detailed inventory of 1580 coseismic slope failures out of which some 20 occurred above large valley glaciers based on mapping from multi temporal remote sensing data we find that the denali earthquake produced at least one order of magnitude fewer landslides in a much narrower corridor along the fault ruptures than empirical predictions for an m 8 earthquake would suggest despite the availability of sufficiently steep and dissected mountainous topography prone to frequent slope failure in order to explore potential controls on the reduced extent of regional coseismic landsliding we compare our data with inventories that we compiled for two recent earthquakes in periglacial and formerly glaciated terrain i e at yushu tibet m w 6 9 2010 and aysen fjord chile 2007 m w 6 2 fault movement during these events was similarly to that of the denali earthquake dominated by strike slip offsets along near vertical faults our comparison returns very similar coseismic landslide patterns that are consistent with the idea that fault type geometry and dynamic rupture process rather than widespread glacier cover were among the first order controls on regional hillslope erosional response in these earthquakes we conclude that estimating the amount of coseismic hillslope sediment input to the sediment cascade from earthquake magnitude alone remains highly problematic particularly if glacierized terrain is involved

sea ice response to atmospheric and oceanic forcing in the bering sea abstract a coupled sea ice ocean model is developed to quantify the sea ice response to changes in atmospheric and oceanic forcing in the bering sea over the period 1970 2008 the model captures much of the observed spatiotemporal variability of sea ice and sea surface temperature sst and the basic features of the upper ocean circulation in the bering sea model results suggest that tides affect the spatial redistribution of ice mass by up to 0 1 m or 15 in the central eastern bering sea by modifying ice motion and deformation and ocean flows the considerable interannual variability in the pattern and strength of winter northeasterly winds leads to southwestward ice mass advection during january may ranging from 0 9 1012 m3 in 1996 to 1 8 1012 m3 in 1976 and averaging 1 4 1012 m3 which is almost twice the january may mean total ice volume in the bering sea the large scale southward ice mass advection is constrained by warm surface waters in the south that melt 1 5 1012 m3 of ice in mainly t

late miocene high and rapid surface uplift and its erosional response in the andes of central chile 33 35 s 1 we address the question of the late cenozoic geomorphological evolution of the central chile andes 33 35 s using uplift markers river incision previous and new ages of volcanic bodies and new fission track ages the uplift markers consist of relicts of high elevated peneplains that evidence 2 km of regional surface uplift lasting 2 ma with variable amount along an e w transect the eastern coastal cordillera was uplifted 1 5 2 1 km at 33 34 s and 2 5 at 33 45 s and 1 5 km at 34 30 s erosional response to uplift was characterized by the retreat of a sharp knickpoint with celerities between 10 and 40 mm a 1 extrapolation using a stream power law shows that uplift began shortly before 4 ma or at 10 5 4 6 ma 7 6 ma central age depending on the morphostructural units involved the first alternative implies simultaneous uplift of the continental margin the second model the most reliable one implies that the uplift affected together the eastern coastal cordillera and the principal cordillera while the rest of the western fore arc subsided this regional uplift can be mostly balanced by crustal thickening resulting from coeval shortening related to the out of sequence thrusting event in the principal cordillera and the uplift of the frontal cordillera simultaneously emplacement of the southern edge of the flat slab subduction zone might have partially contributed to this uplift event

stratification in the northern bering sea in early summer of 2017 and 2018 abstract we investigated spatial and interannual variation in the physical environment in the northern bering sea focusing on stratification which is one factor affecting biological production in arctic subarctic regions in particular we analyzed in situ data obtained onboard the training ship oshoro maru in early summer in 2017 and 2018 we found that stratification in the areas just north of st lawrence island around 64 5 n and west of 168 5 w and south southwest of st lawrence island was significantly weaker in 2018 than in 2017 these results are consistent with the extremely low sea ice extent present in the winter of 2017 2018 which would have resulted in less freshwater being supplied to the surface layers and a warmer and less saline bottom water conversely stratification was as strong in 2018 as in 2017 in the area close to the alaska mainland including the bering strait area suggesting that the alaskan coastal water dominates stratification in this area in early summer moreover we found that the weakly stratified water column in the bering strait area stratified quickly shortly after the occurrence of strong northerly winds likely because of the ekman transport of warm and low salinity alaskan coastal water from the east

lake sediments record cycles of sediment flux driven by large earthquakes on the alpine fault new zealand large earthquakes in mountain regions commonly trigger extensive landsliding and are important drivers of erosion but the contribution of this landsliding to long term erosion rates and seismic hazard remains poorly understood here we show that lake sediments record postseismic landscape response as a sequence of turbidites that can be used to quantify erosion related to large moment magnitude m w 7 6 earthquakes on the alpine fault new zealand alpine fault earthquakes caused a threefold increase in sediment flux over the 50 yr duration of each postseismic landscape response this represents considerable delayed hazard following earthquake induced strong ground motion earthquakes were responsible for 27 of the sediment flux from the lake catchment over the past 1100 yr leading us to conclude that alpine fault earthquakes are one of the most important drivers of erosion in the range front of the southern alps

the importance of earthquake induced landslides to long term slope erosion and slope failure hazards in seismically active regions abstract this paper describes a general method for determining the amount of earthquake induced landsliding that occurs in a seismically active region over time this determination can be used as a quantitative measure of the long term hazard from seismically triggered landslides as well as a measure of the importance of this process to regional slope erosion rates and landscape evolution the method uses data from historical earthquakes to relate total volume of landslide material dislodged by an earthquake to the magnitude m and seismic moment m0 of the earthquake from worldwide data a linear regression relation between landslide volume v and m0 is determined as v m0 1018 9 0 13 where v is measured in m3 and m0 is in dyn cm to determine the amount of earthquake generated landsliding over time this relation is combined with data on seismic moment release for a particular region which may be derived from either earthquake history or fault slip data the form of the m0 v relation allows the rate of production of earthquake induced landslides over time to be determined from total rate of seismic moment release without regard to the distribution of individual events thus simplifying and generalizing the determination application of the method to twelve seismically active regions with areas ranging from 13 275 to 2 308 000 km2 shows that erosion rates from earthquake induced landslides vary significantly from region to region of the regions studied the highest rates were determined for the island of hawaii new zealand western new guinea and the san francisco bay region of california significantly lower rates were determined for iran tibet the sierra nevada great basin region of california and central japan for the time period from 715 ad to the present intermediate rates were determined for peru southern california onshore california turkey and central japan for the time period from 1586 ad to the present to determine the relative long term importance of seismically triggered landslides these erosion rates are compared to erosion rates calculated for other slope processes and to rates calculated from fluvial sediment discharge comparisons with other slope processes indicate that earthquake induced landslides are the predominant agents of slope erosion on the island of hawaii in the san francisco bay region and in western new guinea for hawaii the san francisco bay region and sierra nevada great basin region of california the erosion rates calculated for earthquake induced landslides also exceed the regional erosion rates calculated from fluvial sediment discharge

teleconnections in the geopotential height field during the northern hemisphere winter abstract contemporaneous correlations between geopotential heights on a given pressure surface at widely separated points on earth referred to as teleconnections in this paper are studied in an attempt to identify and document recurrent spatial patterns which might be indicative of standing oscillations in the planetary waves during the northern hemisphere winter with time scales on the order of a month or longer a review of existing literature on the subject reveals the existence of at least four such patterns the north atlantic and north pacific oscillations identified by walker and bliss 1932 a zonally symmetric seesaw between sea level pressures in polar and temperature latitudes first noted by lorenz 1951 and what we will refer to as the pacific north american pattern which has been known to operational long range forecasters in this country since the 1950 s a data set consisting of nmc monthly mean sea level pressure and 500 mb height analyses for a 15 year period is used as a basis fo

altered regional sediment transport regime after a large typhoon southern taiwan analyses of river suspended sediment response to record breaking regional rainfall in southern taiwan during typhoon morakot 7 9 august 2009 reveal systematic changes in the regional sediment transport regime as characterized by rating curve parameters with decreasing b typically considered to be a constant for a given gauging station and increasing intercept k values in concentration discharge c q relations c kq b these changes result in much greater sediment concentration and thus sediment transport in subsequent low flow events after the typhoon an effect that amplifies and extends the influence of such extreme events through increased low flow sediment transport our finding that the exponent b is not constant contrasts with the conventional assumption that large events influence sediment yields through increased intercept k values thereby supporting the interpretation that basin sediment delivery influences both rating parameters and increases post event low flow sediment transport surveys of landslide density and riverbed grain sizes before and after typhoon morakot support the interpretation that the observed decrease in b values and the synchronous shift from an inverse correlation between k and mean catchment slope before the typhoon to a positive correlation afterward reflect an altered sediment transport regime and a change from channel migration and bank erosion to reworking of landslide debris and enhanced bed mobility as the dominant processes supplying fluvial sediment

seasonal variations of sea ice and ocean circulation in the bering sea a model data fusion study 1 a 9 km coupled ice ocean model ciom was implemented in the entire bering sea to investigate seasonal cycles of sea ice and ocean circulation under atmospheric forcing sea ice cover with a maximum of 0 6 106 km2 in february to late march was reasonably reproduced by the bering ciom and validated by special sensor microwave imager ssm i measurements the model also captures some important spatial variability and downscaling processes such as polynyas and ridging which the ssm i measurements cannot reproduce because of their coarse 25 km resolution there are two distinct surface ocean circulation patterns in winter and summer on the bering shelves because of the dominant winds which are northeasterly in winter and southwesterly in summer summer low temperature high salinity water mass 3 c on the bering shelf is formed locally during winter because of strong vertical convection caused by salt injection when ice forms wind and wind wave mixing on the shelf the northward volume transport across the 62 5 n line with an annual mean of 0 8 0 33 sv 1 sv 106 m3 s 1 that is consistent with the measurements in the bering strait has barotropic structure which transports heat flux with an annual mean of 7 74 tw 1 tw 1012 w northward the anadyr current advects warmer saltier water northward during summer nevertheless it reverses its direction to southward during winter because of predominant northeasterly and northerly wind forcing therefore the anadyr current advects cold salty water southward the volume transport on the broad midshelf is northward year round advecting heat 3 3 2 4 tw and freshwater 8 10 104 practical salinity unit psu m3 s 1 northward one important finding is that the anadyr current and the midshelf current are out of phase in volume and heat transports the alaskan coastal current also transports heat and freshwater northward on an annual basis the bering ciom also captures the winter dense water formation along the siberian coast which is promoted by the downwelling favorable northeasterly wind and the summer upwelling due to the basin scale upwelling favorable southwesterly wind which brings up the cold salty and nutrient rich water from the subsurface to the surface within a narrow strip along the west coast this upwelling found in the model was also confirmed by satellite measurements in this study

connecting source and transport suspended sediments in the nepal himalayas understanding the dynamics of sediment fluxes is a key issue to constrain modern erosion rates in mountain belts and determine the still debated level of control exerted by precipitation topography and tectonics the well defined monsoon seasonality in the himalayas together with active tectonics and strong relief provide an ideal environment to assess these possible interactions for this purpose we present a new compilation of daily suspended sediment data for 12 stations of the major rivers of the nepal himalayas we analyze the relationships of sediment transport with daily river discharge and precipitation data as well as with morphometric parameters we show that suspended sediment concentrations vary systematically through the seasons and asynchronously to river discharge displaying a hysteresis effect this clockwise hysteresis effect disappears when suspended sediment fluxes are directly compared with direct storm discharge therefore we attribute the hysteresis effect to groundwater dilution rather than a sediment supply limitation we infer a rating model to calculate erosion rates directly from long river discharge chronicles we show that when normalized by drainage area and mean sediment flux all rivers exhibit the same trend this similarity implies that all river basins have the same erosion behavior independent of location size and catchment characteristics erosion rates calculated from suspended sediment fluxes range between 0 1 and 2 8 mm yr the erosion rates of the three main basins of nepal are in the range 0 9 1 5 mm yr erosion rates in the higher himalayas are relatively low 0 5 mm yr except for kali gandaki while in the lesser himalayas they range from 0 2 to 2 mm yr we propose that material transport in the rivers depends on hillslope sediment supply which is in turn controlled by those rainfalls producing direct runoff in other words the rivers in the nepal himalayas are supply limited and the hillsopes as a contributing source are transport limited we also show that erosion processes are not as much controlled by infrequently occurring extreme precipitation events than by moderate ones with a high recurrence interval

arctic dipole anomaly and its contribution to sea ice export from the arctic ocean in the 20th century 1 the winter dipole anomaly da in the arctic atmosphere and its contribution to sea ice export are investigated by using a high resolution coupled global general circulation model the spatial distributions of the first two leading eof modes of winter mean sea level pressure slp and geopotential height at 500 hpa north of 70n obtained by the long term simulation 1900 2010 are highly similar to those derived from the national center for environmental prediction and the national center for the atmospheric research ncep ncar reanalysis datasets 1948 2004 the first leading mode corresponds to the arctic oscillation ao the da is defined as the second leading mode the ao and da account for 59 and 19 of the total variance respectively composite spatial patterns of slp sea ice thickness and velocity in the extreme years when both the absolute values of principal component pc1 and pc2 exceed 1 0 standard deviation indicate that the da plays a great important role in sea ice export from the arctic ocean to the greenland sea due to its strong meridionality sea ice export is highly promoted restricted in the positive negative da phase the dependence of sea ice export on the da is comparable to or rather larger than that on the ao citation watanabe e j wang a sumi and h hasumi 2006 arctic dipole anomaly and its contribution to sea ice export from the arctic ocean in the 20th century geophys res lett 33 l23703 doi 10 1029 2006gl028112

a seismologically consistent expression for the total area and volume of earthquake triggered landsliding we present a new seismologically consistent expression for the total area and volume of populations of earthquake triggered landslides this model builds on a set of scaling relationships between key parameters such as landslide spatial density seismic ground acceleration fault length earthquake source depth and seismic moment to assess the model we have assembled and normalized a catalog of landslide inventories for 40 shallow continental earthquakes low landscape steepness causes systematic overprediction of the total area and volume of landslides when this effect is accounted for the model predicts the total landslide volume of 63 of 40 cases to within a factor 2 of the volume estimated from observations r2 0 76 the prediction of total landslide area is also sensitive to the landscape steepness but less so than the total volume and it appears to be sensitive to controls on the landslide size frequency distribution and possibly the shaking duration some outliers are likely associated with exceptionally strong rock mass in the epicentral area while others may be related to seismic source complexities ignored by the model however the close match between prediction and estimate for about two thirds of cases in our database suggests that rock mass strength is similar in many cases and that our simple seismic model is often adequate despite the variety of lithologies and tectonic settings covered this makes our expression suitable for integration into landscape evolution models and application to the anticipation or rapid assessment of secondary hazards associated with earthquakes

extraordinary sediment delivery and rapid geomorphic response following the 2008 2009 eruption of chaiten volcano chile u s geological survey volcano science center sernageomin s programa de riesgos volcanicos conicyt fondecyt grants 1110609 1141064 11130671 conicyt fondap 15090013 vamos research centre

toward understanding tectonic control on the mw 8 8 2010 maule chile earthquake the maule earthquake of 27th february 2010 m w 8 8 affected similar to 500 km of the nazca south america plate boundary in south central chile producing spectacular crustal deformation here we present a detailed estimate of static coseismic surface offsets as measured by survey and continuous gps both in near and far field regions earthquake slip along the megathrust has been inferred from a joint inversion of our new data together with published gps insar and land level changes data using green s functions generated by a spherical finite element model with realistic subduction zone geometry the combination of the data sets provided a good resolution indicating that most of the slip was well resolved coseismic slip was concentrated north of the epicenter with up to 16 m of slip whereas to the south it reached over 10 m within two minor patches a comparison of coseismic slip with the slip deficit accumulated since the last great earthquake in 1835 suggests that the 2010 event closed a mature seismic gap slip deficit distribution shows an apparent local overshoot that highlight cycle to cycle variability which has to be taken into account when anticipating future events from interseismic observations rupture propagation was obviously not affected by bathymetric features of the incoming plate instead splay faults in the upper plate seem to have limited rupture propagation in the updip and along strike directions additionally we found that along strike gradients in slip are spatially correlated with geometrical inflections of the megathrust our study suggests that persistent tectonic features may control strain accumulation and release along subduction megathrusts c 2012 elsevier b v all rights reserved

the size distribution and mobility of landslides caused by the 2015 mw7 8 gorkha earthquake nepal abstract coseismic landslides pose immediate and prolonged hazards to mountainous communities and provide a rare opportunity to study the effect of large earthquakes on erosion and sediment budgets by mapping landslides using high resolution satellite imagery we find that the 25 april 2015 m w 7 8 gorkha earthquake and aftershock sequence produced at least 25 000 landslides throughout the steep himalayan mountains in central nepal despite early reports claiming lower than expected landslide activity our results show that the total number area and volume of landslides associated with the gorkha event are consistent with expectations when compared to prior landslide triggering earthquakes around the world the extent of landsliding mimics the extent of fault rupture along the east west trace of the main himalayan thrust and increases eastward following the progression of rupture in this event maximum modeled peak ground acceleration pga and the steepest topographic slopes of the high himalaya are not spatially coincident so it is not surprising that landslide density correlates neither with pga nor steepest slopes on their own instead we find that the highest landslide density is located at the confluence of steep slopes high mean annual precipitation and proximity to the deepest part of the fault rupture from which 0 5 2 hz seismic energy originated we suggest that landslide density was determined by a combination of earthquake source characteristics slope distributions and the influence of precipitation on rock strength via weathering and changes in vegetation cover determining the relative contribution of each factor will require further modeling and better constrained seismic parameters both of which are likely to be developed in the coming few years as post event studies evolve landslide mobility in terms of the ratio of runout distance to fall height is comparable to small volume landslides in other settings and landslide volume runout scaling is consistent with compilations of data on larger slope failures in general the size ratios of landslide source area to full landslide area are smaller than global averages and hillslope length seems to largely control runout distance which we propose reflects a topographic control on landslide mobility in this setting we find that landslide size dictates runout distance and that more than half of the landslide debris was deposited in direct connection with stream channels connectivity which is defined as the spatial proximity of landslides to fluvial channels is greatest for larger landslides in the high relief part of the high himalaya although these failures are less abundant than those at lower elevations they may have a disproportionate impact on sediment dynamics and cascading hazards such as landslide reactivation by monsoon rainfall and landslide dams that lead to outburst floods the overall high fluvial connectivity of coseismic landsliding in the gorkha event suggests coupling between the earthquake cycle and sediment geochemical budgets of fluvial systems in the himalaya

evaluation of factors controlling earthquake induced landslides caused by chi chi earthquake and comparison with the northridge and loma prieta events over 10 000 landslides were triggered by the september 21 1999 chi chi earthquake a large number of these landslides have been mapped from spot images and a smaller number were described in a detailed field investigation geographic information systems gis was used to conduct a spatial characterization of the slope failures including distribution of type size slope angle bedrock geology ground motion and distance from earthquake source the most abundant landslides were shallow disaggregated rock and soil slides landslides occurred primarily in tertiary sedimentary rocks which are well known for their susceptibility to landsliding in many parts of the world landslide concentration values diminish beyond epicentral distances of 40 and 70 km from the epicenter and the surface projection of the fault plane respectively ground motion was found to be the most significant factor in triggering the shallow landslides in the chi chi earthquake overall 74 of all slope failures occurred in regions with vertical ground motions greater than 0 2g and 81 of all slope failures occurred in the region with mean horizontal peak ground accelerations pga greater than 0 15g these factors were used to compare landslides generated by the chi chi earthquake to the landslides triggered by the 1989 loma prieta earthquake and the 1994 northridge earthquake the major difference in distribution of landslides between the chi chi earthquake and the two california earthquakes was the distribution of slope angles in the chi chi earthquake 90 of the failures occurred on slopes steeper than 45 while more than 80 of failures occurred on slopes less than 50 in california apparently reflecting much steeper and tectonically more active geologic setting in taiwan

seasonality of the enso related rainfall variability in central chile and associated circulation anomalies the seasonality of the enso rainfall relationship in central chile 308 418s and associated circulation anomalies are studied using correlation and compositing techniques during el nino episodes there is a tendency for the occurrence of above average precipitation between 308 and 358s in winter june july august jja and from 358 to 388s in late spring october november on while rainfall deficit is typically observed from around 388 to 418s during the following summer january february march jfm when el nino reaches its maximum development opposite rainfall anomalies are characteristic during la nina events this study confirms results from previous investigations indicating that enhanced blocking activity over the amundsen bellings hausen seas area in the southeastern se pacific during el nino is a key feature explaining the wet conditions in winter it is also shown that the same circulation anomaly explains the relatively wet conditions in late spring in the 358 388s region during el nino episodes furthermore the southward displacement from winter to late spring of the area with significant enso related rainfall anomalies seems associated with the seasonal migration of the boundary separating the region under the influence of the subtropical domain from the extratropical domain where the westerly regime and associated disturbances prevail blocking episodes in the se pacific during el nino seem to be part of a wave structure particularly intense during spring characterized by a sequence of positive and negative quasi barotropic height anomalies stretching southeastward from the equator toward the se pacific and back to the southwestern atlantic on the other hand anomalously dry conditions in winter and late spring during la nina are favored by long lasting and intense ridges at subtropical latitudes over the se pacific and south america resulting in a southward migration of the midlatitude storm tracks in summer a higher frequency of ridges in the southern tip of the south america during el nino episodes presumably contributes to reinforcement of the southern edge of the subtropical anticyclone in the se pacific which at this time of the year reaches its southernmost position resulting in the annual rainfall minimum on the other hand an increased frequency of cyclonic circulation anomalies crossing the southern tip of the continent is associated with relatively wet conditions in southern central chile particularly during la nina events

lacustrine turbidites produced by surficial slope sediment remobilization a mechanism for continuous and sensitive turbidite paleoseismic records turbidite records along ocean margins and in lake basins are increasingly used as paleoseismic proxies however the slope remobilization processes that formed the earthquake related turbidity currents are poorly understood and therefore it is difficult to assess the consistency of turbidite paleoseismic records we analyzed the sedimentary imprint of the giant ad 1960 mw 9 5 chile earthquake in four south central chilean lakes mass transport deposits and turbidites were compared by interpreting reflection seismic profiles sedimentary facies volume balances and proxies for turbidite composition i e grain size radionuclides sediment color organic matter sediment lightness was used as a proxy for organic matter content comparison of lightness of turbidites and the underlying sediments shows that earthquake triggered turbidites in the four lakes result from remobilization of a thin veneer on average about 5 cm of slope sediments and do not result from disintegration of subaquatic landslides statistical analysis of 34 turbidites in a new 5200 year sedimentary record does not show any correlation between inter event time and turbidite thickness and thus volume this means that inter event slope recharging is not a dominant factor governing turbidite recurrence and that initiation of turbidity currents by remobilization of surficial sediments is different to slope failure related to subaquatic landslides we conclude that surficial slope sediment remobilization forms a valid mechanism that explains why turbidite paleoseismic records can be of excellent continuity and high sensitivity moreover based on correlations between seismic intensity turbidite volume and stratigraphic remobilization depth we propose that surficial slope sediment remobilization allows for turbidite records containing information about paleo earthquake intensity

slope and climate variability control of erosion in the andes of central chile climate and topography control millennial scale mountain erosion but their relative impacts remain matters of debate confl icting results may be explained by the infl uence of the erosion threshold and daily variability of runoff on long term erosion however there is a lack of data documenting these erosion factors here we report suspended load measurements derived decennial erosion rates and 10 be derived millennial erosion rates along an exceptional climatic gradient in the andes of central chile both erosion rates decennial and millenial follow the same latitudinal trend and peak where the climate is temperate mean runoff 500 mm yr 1 both decennial and millennial erosion rates increase nonlinearly with slope toward a threshold of 0 55 m m the comparison of these erosion rates shows that the contribution of rare and strong erosive events to millennial erosion increases from 0 in the humid zone to more than 90 in the arid zone our data confi rm the primary role of slope as erosion control even under contrasting climates and support the view that the infl uence of runoff variability on millennial erosion rates increases with aridity

bering sea cyclonic and anticyclonic eddies observed during summer 2000 and 2001 abstract using satellite altimeter and ship data bering sea cyclonic and anticyclonic eddies were observed in summer 2000 and 2001 to examine their biological chemical and physical structures results from the ship transect revealed the interactions between the physical and biological conditions of bering sea eddies at the center of a cyclonic anticlockwise eddy upwelling was transporting nutrient no3 no2 rich water 25 m to the surface which resulted in relatively high chlorophyll a concentrations 1 0 mg m 3 developing under the pycnocline in contrast in the center of an anticyclonic clockwise eddy there was downwelling this downwelling of surface warm water was destroying a cold layer at about 150 m depth caused by winter convection however around the periphery of the anticyclonic eddy the isopycnals were tilted up and nutrient rich water was being transported along with them up into the euphotic zone so that high chlorophyll a concentrations were being developed above the pycnocline inside the anticyclonic eddy

modeling the seasonal variation of sea ice in the labrador sea with a coupled multicategory ice model and the princeton ocean model we use a multicategory sea ice model coupled to the princeton ocean model which is driven by monthly climatological atmospheric forcing to study the seasonal variation of ice cover in the labrador sea initial ocean conditions are derived from a gridded objectively analyzed temperature salinity data set that provides improved resolution of gradients in the vicinity of the shelf break the model produces a realistic seasonal variation of sea ice there is ice growth over the inner shelf and ice melt over the outer shelf and slope over the inner shelf advection and diffusion decrease the ice mass over the outer shelf advection and diffusion increase the ice mass which maintains the location of the ice edge near the offshore ice edge the melt rate exceed s1mp er month and the heat to melt ice together with the heat lost to the atmosphere exceeds 500 wm 22 the heat lost at the ocean surface is compensated for by advection of heat from an offshore convective region the dominant heat source for the spring retreat of ice in the south is shortwave radiation over the open water fraction marginal ice zones are regions of dynamic interaction be tween atmosphere ice and ocean in the labrador marginal ice zone the ice edge is located near the labrador current and its associated shelf break front wintertime convection in the western labrador sea is thought to form labrador intermedi ate water clarke and gascard 1983 since the ice edge bor ders the convective region it is important to clarify the pro cesses that limit the ice extent and to examine the heat and salt fluxes in the vicinity of the ice edge in this study we investigate the seasonal evolution of sea ice over the labrador shelf with a coupled ice ocean model our objective is to assess the capability of the model in simulating the evolution of the ice cover and to identify model deficien cies we examine the processes that limit the ice extent labrador sea ice has been the subject of a number of studies with numerical models most recently ikeda et al 1996 cou pled a two category ice model hibler 1979 with the geo physical fluid dynamics laboratory gfdl ocean model bryan 1969 cox 1984 there was overall agreement with the seasonal cycle as well as with interannual variations the re sults showed that shoreward advection of relatively warm off shore water is an important source of heat to melt ice how ever the model ice decayed too rapidly partly because the two category ice model underestimates ice concentration there are a number of differences between the present model and the model of ikeda et al 1996 we have imple mented a multicategory ice model and used the sigma coordi nate princeton ocean model blumberg and mellor 1987 mel lor 1996 with its embedded turbulence closure submodel we use a climatology from the national centers for environmen tal prediction ncep national center for atmospheric re

crustal extensional faulting triggered by the 2010 chilean earthquake the pichilemu seismic sequence 1 we report a sequence of crustal quakes that began after the mw 8 8 thrust subduction maule earthquake that affected the central chile margin on 27 february 2010 this activity lasted by several months having the most important events on 11 march 2010 mw 6 9 and mw 7 0 with normal focal mechanisms seismicity shows a rupture oriented along a nw striking and sw dipping normal fault from the surface down to the interplate contact seismicity can be correlated with neotectonics extensional structures similarly oriented in the region which have coexisted with nne ssw reverse faults since the late pliocene even though both have older periods of activity since the paleozoic this crustal rupture would have been triggered by the high coulomb stress change produced by the maule earthquake enhanced by likely fluid presence along weakened zones of the forearc crust as evidenced by high vp vs ratio the occurrence of relevant neotectonic activity in coincidence with short term deformation suggests a relationship with long term tectonic features of this region which would have been acting as a barrier during the interseismic period increasing the strain accumulation and triggering contractional faulting in the crust as well as producing high slip patches during great subduction ruptures favoring triggering of crustal extensional faulting crustal faulting in pichilemu suggests that this kind of events should be considered in seismic hazard analysis despite the absence of historical crustal seismic activity before the maule earthquake

the contribution of alaskan siberian and canadian coastal polynyas to the cold halocline layer of the arctic ocean numerous arctic ocean circulation and geochemical studies suggest that ice growth in polynyas over the alaskan siberian and canadian continental shelves is a source of cold saline water which contributes to the maintenance of the arctic ocean halocline the purpose of this study is to estimate for the 1978 1987 winters the contributions of arctic coastal polynyas to the cold halocline layer of the arctic ocean the study uses a combination of satellite oceanographic and weather data to calculate the brine fluxes from the polynyas then an oceanic box model is used to calculate their contributions to the cold halocline layer of the arctic ocean this study complements and corrects a previous study of dense water production by coastal polynyas in the barents kara and laptev seas recurrent polynyas form on the canadian and alaskan coasts from banks island to the bering strait and on the siberian coast from the bering strait to the new siberian islands in the bering sea polynyas form in norton sound south and west of st lawrence island and in the gulf of anadyr two regions that account for almost 50 of the total dense water production are the siberian coastal polynyas in the adjacent regions of the gulf of anadyr and anadyr strait and the alaskan coastal polynyas which occur along the coast from cape lisburne to point barrow for all of the western arctic coastal regions examined the mean annual total brine flux is 0 5 0 2 sv combination of this flux with the contribution from the barents kara and laptev seas which is recalculated from data in the earlier study shows that over the entire arctic coastal polynyas generate about 0 7 1 2 sv of dense water this compares well with the theoretical estimates of 1 1 5 sv because an unknown fraction of the barents kara and laptev brine flux must go to the eurasian basin deep water the coastal polynyas alone cannot renew the halocline layer other potential brine generation mechanisms include overall freezing on the shelves and the response of the ice to infrequent violent storms for example during february 1982 an intense storm generated a large region of low ice concentration in the eastern chukchi sea over barrow canyon the refreezing of the region was followed by the flow of a dense plume down barrow canyon although the ocean dynamical response to this refreezing needs to be established the possible response of a barrow canyon flow to this refreezing event suggests that the overall refreezing in response to infrequent violent storms may be a potential source of the additional brine needed to maintain the arctic ocean halocline

delineating hydrological response units by geographical information system analyses for regional hydrological modelling using prms mms in the drainage basin of the river brol germany a modified concept of hydrological response units hrus for regional modelling of river basins using the prms mms model is presented the hrus are delineated by geographical information system gis analysis from physiographic basin properties such as topography soils geology rainfall and land use using a thorough hydrological systems analysis the hrus once classified by gis analysis preserve the three dimensional heterogeneity of the drainage basin the river brol basin a 216km 2 rheinisches schiefergebirge germany was selected to apply the concept in total 23 hrus were delineated and tested with the prms mms model using a 20 year hydrometeorological daily database the hydrological systems analysis revealed that interflow is the dominant flow process through the basin s slopes and the major contribution to groundwater recharge and river runoff this was accounted for by parameterizing the hrus in the model control file to drain their surplus water not used for satisfying the demand of evapotranspiration to a common conceptual subsurface storage this storage was simulated by interflow drainage to the groundwater aquifer in the valley floor which in turn drained to the channel network the prms mms model simulated the observed daily discharge very well and the fit was described by a daily correlation coefficient of r 0 91 the nasim and hspf models using different means to represent the basin s physiographic heterogeneity were applied to the brol basin as well but did not achieve this correlation the hru concept was found to be a reliable method for regional hydrological basin modelling and allows spatial up and downscaling future research on this concept will focus on incorporating the variable precipitation distribution into the classification of hrus and on the hydrodynamic routing of the modelled discharge additionally satellite imagery must be used for classifying land use in macroscale drainage basins

influence of the st lawrence island polynya upon the bering sea benthos the influence of a polynya a persistent ice free region on water column production and subsequent transport to the shallow continental shelf benthos of the bering sea was evaluated by studying spatial patterns of organic material deposition benthic biomass community sediment metabolism benthic population structure and other potential indicators of enhanced organic carbon transport to benthic communities underlying the st lawrence island polynya despite suggestions that polynyas may be important localized centers of primary production in polar waters we found that the st lawrence island polynya does not obviously enhance the biomass of benthic communities directly below the polynya however southward flowing baroclinic currents generated as a result of brine injection at the polynya edge do appear to have an influence on the biomass and ecological structure of bering sea benthic communities south of st lawrence island these currents appear to affect mean sediment oxygen consumption surface organic carbon nitrogen ratios total organic content and bottom water ammonia by sweeping phytodetrital matter south and to the west of the island a particle reactive short lived natural radioisotope 7be used as an indicator of rapid days to weeks deposition of particulate material from the water column was detected only in surface sediments to the southwest of the island indicating enhancement of particle deposition to the southwest of the island finally the 18o content of tunicate cellulose was highest in the polynya region consistent with increased filter feeding in the late winter when the polynya is present and presumably promoting primary production in the open water the anadyr current consisting of nutrient rich deeper bering sea water that is upwelled onto the shelf in the gulf of anadyr flows west to east in the region south of st lawrence island throughout the year and is the major forcing function for high production in the region the interaction of anadyr water with the winter spring ephemeral polynya and associated baroclinic currents combine to positively influence benthic communities

the super interseismic phase of the megathrust earthquake cycle in chile along a subduction zone great megathrust earthquakes recur either after long seismic gaps lasting several decades to centuries or over much shorter periods lasting hours to a few years when cascading successions of earthquakes rupture nearby segments of the fault we analyze a decade of continuous global positioning system observations along the south american continent to estimate changes in deformation rates between the 2010 maule m8 8 and 2015 illapel m8 3 chilean earthquakes we find that surface velocities increased after the 2010 earthquake in response to continental scale viscoelastic mantle relaxation and to regional scale increased degree of interplate locking we propose that increased locking occurs transiently during a super interseismic phase in segments adjacent to a megathrust rupture responding to bending of both plates caused by coseismic slip and subsequent afterslip enhanced strain rates during a super interseismic phase may therefore bring a megathrust segment closer to failure and possibly triggered the 2015 event

linking the northern hemisphere sea ice reduction trend and the quasi decadal arctic sea ice oscillation the nature of the reduction trend and quasi decadal oscillation in northern hemisphere sea ice extent is investigated the trend and oscillation that seem to be two separate phenomena have been found in data this study examines a hypothesis that the arctic sea ice reduction trend in the last three decades amplified the quasi decadal arctic sea ice oscillation asio due to a positive ice ocean albedo feedback based on data analysis and a conceptual model proposed by ikeda et al the theoretical conceptual model predicts that the quasi decadal oscillation is amplified by the thinning sea ice leading to the asio which is driven by the strong positive feedback between the atmosphere and ice ocean systems such oscillation is predicted to be out of phase between the arctic basin and the nordic seas with a phase difference of 3 4 with the nordic seas leading the arctic the wavelet analysis of the sea ice data reveals that the quasi decadal asio occurred actively since the 1970s following the trend starting in the 1960s i e as sea ice became thinner and thinner as the atmosphere experienced quasi decadal oscillations during the last century the wavelet analysis also confirms the prediction of such out of phase feature between these two basins which varied from 0 62 in 1960 to 0 25 in 1995 furthermore a coupled ice ocean general circulation model gcm was used to simulate two scenarios one without the greenhouse gas warming and the other having realistic atmospheric forcing along with the warming that leads to sea ice reduction trend the quasi decadal asio is excited in the latter case compared to the no warming case the wavelet analyses of the simulated ice volume were also conducted to derive decadal asio and similar phase relationship between the arctic ocean and the nordic seas an independent data source was used to confirm such decadal oscillation in the upper layer or freshwater thickness which is consistent with the model simulation a modified feedback loop for the sea ice trend and asio was proposed based on the previous one by mysak and venegas and the ice albedo and cloud albedo feedabcks which are responsible for the sea ice reduction trend

late stage volatile saturation as a potential trigger for explosive volcanic eruptions magma reservoirs typically accumulate over hundreds to thousands of years yet geochemical analyses of volcanic rocks from campi flegrei suggest activity there was triggered by injections of volatile rich magma only days before the eruption

large rockslides in the southern central andes of chile 32 34 5 s tectonic control and significance for quaternary landscape evolution abstract the distribution and age of large 0 1 km2 pliocene to recent rockslides in the chilean cordillera principal 32 34 5 s the southern central andes has been analyzed to determine the rockslide triggering mechanisms and impact on regional landscape evolution most of the rockslides appear in the western cordillera principal and cluster along major geological structures variographic analyses show spatial correlation between rockslides geological structures and shallow seismicity a relative chronosequence was calibrated with existing 14c and 40ar 39ar dates and new cosmogenic nuclide exposure ages for selected rockslides rockslide induced sediment yield was estimated with empirical relations for rockslide area distributions throughout the quaternary rockslides have delivered sediment to streams at rates equivalent to denudation rates of 0 10 0 06 mm a 1 while estimates using short term 20 a seismicity records are 0 3 0 2 0 6 mm a 1 the estimates of sediment transfer and the spatial distribution of rockslides reflect a landscape in which tectonic and geological controls on denudation are more significant than climate

sedimentary records of bulk organic matter and lipid biomarkers in the bering sea a centennial perspective of sea ice variability and phytoplankton community abstract in this study organic geochemical analyses of two sediment cores bl16 and lv63 23 recovered from the western bering sea were carried out to examine the sea ice variability and its relationship to phytoplankton community evolution over the past century bulk stable organic carbon isotopic composition 13ctoc showed pronounced depletion on the northern shelf since the late 1970s indicating greater terrigenous organic matter om under warming during recent decades variation in sedimentary om in the southward core was closely associated with marine primary productivity and regional deposition processes arctic sea ice proxy ip25 throughout the two cores with different temporal profile patterns demonstrated sea ice presence with the spatio temporal variability across the study area over the past century the phytoplankton marker ip25 index pip25 a proxy for estimating semi quantitatively sea ice concentrations reflected a decreased sea ice cover with more distinct interannual fluctuations between 0 7 and 0 2 especially in core bl16 after the late 1970s coinciding with the recent warming scenario increased concentrations of phytoplankton biomarkers brassicasterol and dinosterol and their ratios as well as the pip25 record in core bl16 indicated a synchronous variability of reduced sea ice cover with the enhancement of phytoplankton productivity since the late 1970s these results suggested a coupled interaction of the sea ice condition and planktonic ecosystem in the north bering shelf our results also revealed recent since the 2000s spatial heterogeneity in sea ice coverage between the northern and southern parts of the bering sea

forecasting bering sea ice edge behavior a coupled ice ocean dynamics model is developed to provide arctic offshore operators with 5 to 7 day forecasts of ice motions ice conditions and ice edge motions an adaptive grid is introduced to follow the ice edge and the grid may move independently of the ice motion the grid can be lagrangian or eulerian at different locations away from the ice edge ice stress is described using an elastic plastic model with strength determined by the ice conditions the ocean dynamics model describes time dependent three dimensional behavior including wind driven currents and barotropic and baroclinic flows the thermal energy budget of the ice cover is coupled to the ocean with mass and salt interchange accompanying freezing or melting near the marginal ice zone miz surface winds determined by reducing and turning the geostrophic winds are enhanced to reflect observed behavior the model was tested by simulating ice edge motions observed during the 1983 marginal ice zone experiment west and during drilling of the 1983 north aleutian shelf continental offshore stratigraphic test well simulations of ice edge movement in the bering sea compare with observed data to within about 5 km d the model correctly describes mixed layer evolution in the marginal ice zone as fresh meltwater ismore mixed downward by turbulence along edge baroclinic flows due to density gradients across the ice edge are simulated by the model in agreement with observations increased ice drift speeds generate higher melt rates due to increased turbulence levels with the result that ice edge advance is moderated in spite of higher ice drift speeds less

a comparison of the sedimentary records of the 1960 and 2010 great chilean earthquakes in 17 lakes implications for quantitative lacustrine palaeoseismology seismically induced event deposits embedded in the sedimentary infill of lacustrine basins are highly useful for palaeoseismic reconstructions recent well documented great megathrust earthquakes provide an ideal opportunity to calibrate seismically induced event deposits for lakes with different characteristics and located in different settings this study used 107 short sediment cores to investigate the sedimentary impact of the 1960 mw 9 5 valdivia and the 2010 mw 8 8 maule earthquakes in 17 lakes in south central chile i e lakes negra lo encanado aculeo vichuquen laja villarrica calafquen pullinque pellaifa panguipulli neltume rinihue ranco maihue puyehue rupanco and llanquihue a combination of image analysis magnetic susceptibility and grain size analysis allows identification of five types of seismically induced event deposits i mass transport deposits ii in situ deformations iii lacustrine turbidites with a composition similar to the hemipelagic background sediments lacustrine turbidites type 1 iv lacustrine turbidites with a composition different from the background sediments lacustrine turbidites type 2 and v megaturbidites these seismically induced event deposits were compared to local seismic intensities of the causative earthquakes eyewitness reports post earthquake observations and vegetation and geomorphology of the catchment and the lake megaturbidites occur where lake seiches took place lacustrine turbidites type 2 can be the result of i local near shore mass wasting ii delta collapse iii onshore landslides iv debris flows or mudflows or v fluvial reworking of landslide debris on the contrary lacustrine turbidites type 1 are the result of shallow mass wasting on sublacustrine slopes covered by hemipelagic sediments due to their more constrained origin lacustrine turbidites type 1 are the most reliable type of seismically induced event deposits in quantitative palaeoseismology because they are almost exclusively triggered by earthquake shaking moreover they most sensitively record varying seismic shaking intensities the number of lacustrine turbidites type 1 linearly increases with increasing seismic intensity starting with no lacustrine turbidites type 1 at intensities between v and vi and reaching 100 when intensities are higher than vii combining different types of seismically induced event deposits allows the reconstruction of the complete impact of an earthquake

subsidence at southern andes volcanoes induced by the 2010 maule chile earthquake large earthquakes in subduction zones can affect nearby volcanoes analysis of ground deformation following the 2010 earthquake in maule chile shows that some volcanoes subsided by up to 15 cm probably because of quake triggered release of hydrothermal fluids

estimation of sea ice production in the bering sea from amsr e and amsr2 data with special emphasis on the anadyr polynya

northern bering sea tip jets 1 low level regions of high wind speed known as tip jets have been identified near cape farewell greenland s southernmost point these wind systems contribute to this area being the windiest location on the ocean s surface and play an important role in the regional weather and climate here we present the first analysis of the wind systems that make the siberian coast of the northern bering sea the windiest location in the north pacific ocean during the boreal winter in particular we show that tips jets characterized by enhanced northeasterly winds occur in the vicinity of the two prominent headlands along the coast cape navarin and cape olyutorsky the advance of sea ice in the region is shown to impact the frequency and location of the high speed winds in the vicinity of these two capes furthermore we show that these jets are associated with the interaction of extra tropical cyclones with the high topography of the koryak mountain range situated just inland of the capes the windstress imparted to the ocean via the tip jets is argued to help drive the formation of dense water in winter in the northern bering sea thus playing an important role in the regional oceanic circulation

the 2010 mw 8 8 maule megathrust earthquake of central chile monitored by gps large earthquakes produce crustal deformation that can be quantified by geodetic measurements allowing for the determination of the slip distribution on the fault we used data from global positioning system gps networks in central chile to infer the static deformation and the kinematics of the 2010 moment magnitude m w 8 8 maule megathrust earthquake from elastic modeling we found a total rupture length of 500 kilometers where slip up to 15 meters concentrated on two main asperities situated on both sides of the epicenter we found that rupture reached shallow depths probably extending up to the trench resolvable afterslip occurred in regions of low coseismic slip the low frequency hypocenter is relocated 40 kilometers southwest of initial estimates rupture propagated bilaterally at about 3 1 kilometers per second with possible but not fully resolved velocity variations

large landslides and their effect on sediment flux in south westland new zealand landslides and runoff are dominant erosional agents in the tectonically active alpine south westland area of new zealand characterized by high uplift rates and extreme orographic precipitation despite a high density of shallow debris slides and flows the geomorphic imprints of deep seated bedrock failures are dominant and persistent over 50 large 1k m 2 landslides comprising rock slide avalanches complex rotational and rock block slides wedge failures and deep seated gravitational slope deformation were detected on air photos and shaded relief images major long term impacts on alpine rivers include 1 forced alluviation upstream of landslide dams 2 occlusion of gorges and triggering of secondary riparian landslides and 3 diversion of channels around deposits to form incised meandering gorges remnants of large prehistoric i e pre 1840 landslide deposits possibly represent the low frequency in terms of total area affected yet dominant end of the spectrum of mass wasting in the western southern alps this is at odds with high erosion rates in an active erosional landscape large landslides appear to have dual roles of supplying and retaining sediment the implications of these roles are that 1 previous models of shallow landslide derived sediment flux need to be recalibrated and 2 geomorphic effects of earthquake induced landsliding may persist for at least 10 2 years copyright 2005 john

drag measurements for first year sea ice over a shallow sea for a free drift case a method is developed for simultaneously determining air ca and water cw drag coefficients by solving the vertically integrated stress balance equation for sea ice the method allows the algebraic determination of ca and cw from measurements of relative wind and relative current at single reference levels from estimates of the densities of all three fluids and ice thickness and from estimates of the accelerations caused by the nonsurface stress terms derived from position measurements the method treats the ice as a natural drag plate and therefore includes contributions from both skin and form drag one shortcoming of the technique is that if the relative wind and current are colinear then only the ratio of ca and cw can be determined another is that the accelerations caused by other forces need to be independently determined an experiment was conducted on a single floe in the eastern bering sea over the continental shelf during march 1981 the site was about 80 km from the ice edge and was occupied for approximately 3 days following the passage of a storm which had broken the pack into 10 20 m diameter floes both profile and slab inversion estimates of drag were made from the current meter and anemometer measurements at the site ca at 3 m was 4 55 10 3 by the profile method compared to 3 63 4 39 10 3 for slab depending on assumptions cw at 1 1 m by profile was 24 2 10 3 compared to 18 3 22 0 10 3 for slab the two methods gave results which were not statistically separable and which were among the highest drags observed for sea ice the instantaneous stress balance on the floe included contributions from material acceleration coriolis force the two surface stresses and sea surface tilt relative to mean current and tide

post fire bedload sediment delivery across spatial scales in the interior western united states post fire sediment yields can be up to three orders of magnitude greater than sediment yields in unburned forests much of the research on post fire erosion rates has been at small scales 100 m2 or less and post fire sediment delivery rates across spatial scales have not been quantified in detail we developed relationships for post fire bedload sediment delivery rates for spatial scales up to 117 ha using sediment yield data from six published studies and two recently established study sites sediment yields and sediment delivery ratios sdrs sediment delivered at the catchment scale divided by the sediment delivered from a plot nested within the catchment were related to site factors including rainfall characteristics area length and ground cover unit area sediment yields significantly decreased with increasing area in five of the six sites the annual sdrs ranged from 0 0089 to 1 15 and these were more closely related to the ratio of the plot lengths than the ratio of plot areas the developed statistical relationships will help quantify post fire sediment delivery rates across spatial scales in the interior western united states and develop process based scaling relationships published in 2013 this article is a u s government work and is in the public domain in the usa

seesaw structure of subsurface temperature anomalies between the barents sea and the labrador sea 1 using a coupled ocean sea ice model of the pan arctic and north atlantic ocean we investigate the response of the arctic and subarctic thermohaline structure to seasonal extreme atmospheric forcing associated with the winter arctic oscillation ao during the positive phase of ao significant surface cooling occurs in the labrador sea but there is no substantial surface warming in the barents sea i e no seesaw pattern in sea surface temperature sst anomaly between the barents sea and labrador sea a possible explanation is that arctic sea ice export into the barents sea melts locally and lowers the sst however a seesaw structure in subsurface below the mixed layer 40 100 m water temperature anomaly between the two regions is found exceeding the 95 significance level corresponding to the positive phase of the winter ao a significant warming of the subsurface water in the barents sea and a concurrent cooling in the northwestern labrador sea are seen in the model results which is analogous to the seesaw structure in both surface air temperature sat and sea ice extent anomalies the mechanism leading to the anomalous subsurface temperature seesaw is consistent with the northward advection of the warm atlantic water into the barents sea and the southward advection of the cold arctic and sub arctic water into the labrador sea from the david strait and baffin bay hydrographic data are analyzed and the resulting temperature distribution supports this new finding

prolonged seismically induced erosion and the mass balance of a large earthquake large earthquakes deform the earth s surface and drive topographic growth in the frontal zones of mountain belts they also induce widespread mass wasting reducing relief the sum of these two opposing effects is unknown using a time series of landslide maps and suspended sediment transport data we show that the mw7 6 chi chi earthquake in taiwan was followed by a period of enhanced mass wasting and fluvial sediment evacuation peaking at more than five times the background rate and returning progressively to pre earthquake levels in about six years therefore it is now possible to calculate the mass balance and topographic effect of the earthquake the choshui river has removed sediment representing more than 30 of the added rock mass from the epicentral area this has resulted in a reduction of surface uplift by up to 0 25 m or 35 of local elevation change and a reduction of the area where the chi chi earthquake has built topography for other large earthquakes erosion may evolve in similar predictable ways reducing the efficiency of mountain building in fold and thrust belts and the topographic expression of seismogenic faults prolonging the risk of triggered processes and impeding economic regeneration of epicentral areas

landslides earthquakes and erosion this paper relates landslide inventories to erosion rates and provides quantitative estimates of the landslide hazard associated with earthquakes we do this by utilizing a three parameter inverse gamma distribution which fits the frequency area statistics of three substantially dcompletet landslide event inventories a consequence of this general distribution is that a landslide event magnitude ml lognlt can be introduced where nlt is the total number of landslides associated with the landslide event using this general distribution landslide event magnitudes ml can be obtained from incomplete landslide inventories and the total area and volume of associated landslides as well as the area and volume of the maximum landslides can be directly related to the landslide event magnitude using estimated recurrence intervals for three landslide events and the time span for two historical inventories we estimate regional erosion rates associated with landslides as typically 0 1 2 5 mm year 1 we next give an empirical correlation between the earthquake magnitude associated landslideevent magnitude and the total volume of associated landslides using these correlations we estimate that the minimum earthquake magnitudes that will generate landslides is m 4 3f0 4 finally using gutenberg richter frequency magnitude statistics for regional seismicity we relate the intensity of seismicity in an area and the magnitude of the largest regional earthquakes to erosion rates we find that typical seismically induced erosion rates in active subduction zones are 0 2 7 mm year 1 and adjacent to plate boundary strike slip fault zones are 0 01 0 7 mm year 1

circulation in the bering sea basin observed by satellite tracked drifters 1986 1993 abstract from 1986 through april 1993 86 satellite tracked buoys were deployed in the north pacific and bering sea most of the buoys were drogued at 40 m a composite current pattern is derived using these data the two principal currents the alaskan stream and kamchatka current are clearly evident eddy kinetic mean kinetic energy ratios are low in the stream and along the western bering sea basin an eastward flowing current occurred along the north flank of the aleutian islands this flow was modified by inflow at the passes westward flow occurred north of 56 n its source was the bering slope current the kamchatka current originated near 175 e along the russian coast numerous eddies and meanders were observed in the kamchatka current eddies were also present on the eastern side of the basin

a seismological study of the 1835 seismic gap in south central chile we study the possible seismic gap in the concepcion constitucion region of south central chile and the nature of the m 7 8 earthquake of january 1939 from 1 march to 31 may 1996 a seismic network of 26 short period digital instruments was deployed in this area we located 379 hypocenters with rms travel time residuals of less than 0 50 s using an approximate velocity distribution using the velest program we improved the velocity model and located 240 high precision hypocenters with residuals less than 0 2 s the large majority of earthquakes occurred along the wadati benioff zone along the upper part of the downgoing slab under central chile a few shallow events were recorded near the chain of active volcanos on the andes these events are similar to those of las melozas near santiago a few events took place at the boundary between the coastal ranges and the central valley well constrained fault plane solutions could be computed for 32 of the 240 well located events most of the earthquakes located on the wadati benioff zone had slab pull fault mechanism due to tensional stresses sub parallel to the downgoing slab this slab pull mechanism is the same as that of eight earthquakes of magnitude around 6 that are listed in the cmt catalog of harvard university for the period 1980 1998 this is also the mechanism inferred for the large 1939 chilean earthquake a very small number of events in the benioff zone had slab push mechanisms that is events whose pressureaxis is aligned with the slab these events are found in double layered wadati benioff zones such as in northern chile or japan our spatial resolution is not good enough to detect the presence of a double layer but we suspect there may be one 2002 elsevier science b v all rights reserved

summer precipitation events over the western slope of the subtropical andes abstractsummertime december february djf precipitation over the western slopes of the subtropical andes 32 36 s accounts for less than 10 of the annual accumulation but it mostly occurs as rain and may trigger landslides leading to serious damages based on 13 year of reanalysis in situ observations and satellite imagery a synoptic climatology and physical diagnosis reveal two main weather types lead to distinct precipitation systems the most frequent type 80 of the cases occurs when a short wave midlevel trough with weak winds and thermally driven mountain winds favor the development of convective precipitation during the daytime the trough progresses northwest of a long lasting warm ridge which produces low level easterly airflow that enhances its buoyancy as it moves over the arid land of western argentina toward the andes the weak winds aloft facilitate the penetration of the moist easterly flow into the andes midlevel flow coming from the west side of the andes is decoupled from

tectonic response of the central chilean margin 35 38 s to the collision and subduction of heterogeneous oceanic crust a thermochronological study along strike geological segmentation in the andean chain has been recognized at various scales and is usually attributed to changes in plate motion vectors as well as the upper plate expression of differing subducted slab age strength and composition we present new multi phase 40ar 39ar apatite fission track and zircon and apatite u th he data from a north south oriented traverse between 35 and 38 s along the principal andean cordillera of chile that reveal 1 rapid cooling at 18 and 15 ma which can be attributed to both thermal relaxation following magmatic intrusion and regional scale exhumation and 2 along strike differences in the extent of exhumation since 7 5 ma that may be a consequence of the subduction of the juan fernandez ridge above the flat slab segment at 32 since 10 ma a comparison of the response of the south american plate to the collision of the carnegie nazca and juan fernandez ridges suggests that slab flattening is not the dominant driving force that exhumes the upper plate in these settings rather the extent of exhumation is controlled by pre existing structural weaknesses the time duration of the dynamically supported topography and climate

ocean circulation and exchanges through the northern bering sea 1979 2001 model results abstract we have developed and run a model with sufficiently high resolution 9 km and 45 levels and a large enough spatial domain to allow for realistic representation of flow through the narrow and shallow straits in the northern bering sea this is potentially important for quantification of long term mean and time dependent ocean circulation and water mass and property exchanges between the pacific and arctic oceans over a 23 year interval 1979 2001 mean transport through bering strait is estimated to be 0 65 sv comparison of our model results with published observations indicates that ocean circulation is not only variable at seasonal to interdecadal scales but it is also responsive to short term atmospheric forcing one of such events occurred during the winter of 2000 2001 with reversed oceanic flow in some areas and much reduced sea ice cover analyses of eddy kinetic energy fields identify some high biological productivity regions of the chirikov basin coincident with persistent high energy up to 2700 cm 2 s 2 in the surface layer and up to 2600 cm 2 s 2 at mid depth throughout the annual cycle model output in the bering strait region is validated against several time series of moored observations of water mass properties comparison with shipboard observations of near bottom salinity from late winter through autumn indicates that the model reasonably represents the major water mass properties in the region the modeled vertical water column structure in the northern bering sea allows increased understanding of the mechanisms of water transformation and transport northward through bering strait into the chukchi and beaufort seas we conclude that the long term model results for the northern bering sea provide important insights into the ocean circulation and fluxes and they are a useful frame of reference for limited observations that are short term and or cover only a small geographic region

arctic oscillation and arctic sea ice oscillation the variability of the sea ice cover in the arctic and subpolar regions associated with the arctic oscillation ao was investigated using historical data from 1901 to 1997 unrotating principal component analyses or empirical orthogonal functions eofs were applied to demeaned normalized sea level pressure slp surface air temperature sat and sea ice area sia for the periods 1901 97 and 1953 97 the leading slp eof mode is the ao the leading sia eof mode is named the arctic sea ice oscillation asio which accounts for 41 of the total variance for the period of 1901 1995 this dominant asio is ao related its spatial and temporal patterns are consistent with the leading modes of slp and sat and with the total arctic sea ice anomalies the second sia mode is north atlantic oscillation nao related because sea ice anomalies in the labrador sea region and the greenland sea region are out of phase during the last three decades the arctic sea ice has significantly decreased which may be the decreasing phase of long term variations

adcp referenced geostrophic circulation in the bering sea basin abstract a month long circumnavigation of the bering sea basin in august 1991 was designed to study the basin scale circulation for the first time in this region vessel mounted acoustic doppler current profiler adcp measurements provided an absolute reference for geostrophic currents transport in the alaskan stream 01 1500 db was 24 sv sv 106 m3 s 1 westward considerably higher than the 10 15 sv usually inferred from geostrophic calculations referred to 1500 db but in good agreement with previous work relative to moored current meters as previously reported the stream separated from the aleutian ridge forming an anticyclonic eddy that restricted inflow to the bering sea flow through the aleutians varied substantially across the passes the kamchatka current was traceable for 800 km until it left the bering sea carrying 14 sv 0 3000 db eddies were detected from the clustering of centers of curvature of sequential adcp vectors incompletely spanned eddies can bias transports counterrotat

eddy induced cross slope exchange maintaining summer high productivity of the bering sea shelf break 1 eddy related cross slope exchange along the bering sea shelf break was investigated using a hydrographic observations data set and a numerical model results of observations in summer of 2001 showed a shelf break front that formed at a shelf break near an anticyclonic eddy high nitrate nitrite concentrations in the subsurface layer and high chlorophyll a chl a concentrations 6 mg m 3 in the surface layer a hydrographic observation in summer of 2002 exhibited relatively high chl a concentrations at the surface around the anticyclonic eddy tracer experiments revealed two types of cross slope exchange under isopycnals nutrient rich water in the basin is transported to the shelf and there is about a 64 53 increase in integrated nitrate nitrite on shelf flux 50 m depth bottom when mesoscale eddies are formed and propagated along the shelf break at the surface high chl a waters in the shelf are advected to the deep basin area by eddy transport and propagation these indicate that 1 mesoscale eddies supply nutrients and sustain primary productivity at the shelf break and 2 eddies expand the high chl a area to the basin then to the highly productive area so that the green belt is maintained

earthquake triggered increase in sediment delivery from an active mountain belt in tectonically active mountain belts earthquake triggered landslides deliver large amounts of sediment to rivers we quantify the geomorphic impact of the 1999 mw 7 6 chi chi earthquake in taiwan which triggered 20 000 landslides coseismic weakening of substrate material caused increased landsliding during subsequent typhoons most coseismic landslides remained confined to hillslopes downslope transport of sediment into the channel network occurred during later storms the sequential processes have led to a factor of four increase in unit sediment concentration in rivers draining the epicentral area and increased the magnitude and frequency of hyperpycnal sediment delivery to the ocean four years after the earthquake rates of hillslope mass wasting remain elevated in the epicentral area

a model data study of the 1999 st lawrence island polynya in the bering sea 1 a coupled ice ocean model ciom and in situ measurements were used to investigate sea ice and the st lawrence island polynya slip in the bering sea in 1999 the modeled 1999 seasonal cycle of ice cover compared well with satellite measurements the simulated maximum sea ice coverage was 0 8 106 km2 and the simulated maximum sea ice volume was 344 km3 the polynya south of st lawrence island was captured by the ciom and investigated in depth against the measurements it was found that an offshore wind was necessary but not sufficient on its own for the development of the slip it was found that a strong offshore wind offshore surface water velocity and the angle 60 between wind and water current are the three major factors for the development of the slip multiple variable linear regression models were developed to confirm these three mechanisms yearly potential sea ice production in the slip area was estimated to be about 95 7 km3 which accounts for 2 8 of the total potential production of 3393 km3 in the whole bering sea sea ice contributes to approximately 63 of winter salinity changes in the bering shelf 200 m while the slip can contribute more than twice the local salinity changes the relationships among wind sea ice and surface ocean current were examined the classic ekman drift theory that surface water velocity drifts 45 to the right of the wind direction is modified to be 50 4 on the ice covered bering shelf due to the year round existence of a background northward ocean transport

controls on fluvial evacuation of sediment from earthquake triggered landslides large earthquakes in active mountain belts can trigger landslides which mobilize large volumes of clastic sediment delivery of this material to river channels may result in aggradation and flooding while sediment residing on hillslopes may increase the likelihood of subsequent landslides and debris flows despite recognition of these processes the controls on the residence time of coseismic landslide sediment in river catchments remain poorly understood here we assess the residence time of fine grained 5 mm day 1 together with previous observations from the c e 1999 chi chi earthquake in taiwan our results demonstrate the importance of landslide density and runoff intensity in setting the duration of earthquake triggered landslide impacts on river systems

landslide erosion controlled by hillslope material landslide erosion is a primary control of landscape relief a wide ranging analysis of landslide geometry shows that soil based landslides are generally less voluminous than landslides that involve the failure of bedrock and provides refined metrics for estimating the volume of a landslide from the area of the failure

biotic controls on shallow translational landslides in undisturbed tropical montane rainforests massive organic layers accommodate the majority of roots and only a small fraction of roots penetrate the mineral soil we investigated the contribution of vegetation to slope stability in such environments by modifying a standard model for slope stability to include an organic layer with distinct mechanical properties the importance of individual model parameters was evaluated using detailed measurements of soil and vegetation properties to reproduce the observed depth of 11 shallow landslides in the andes of southern ecuador by distinguishing mineral soil organic layer and above ground biomass it is shown that in this environment vegetation provides a destabilizing effect mainly due to its contribution to the mass of the organic layer up to 973 t ha 1 under wet conditions sensitivity analysis shows that the destabilizing effect of the mass of soil and vegetation can only be effective on slopes steeper than 37 9 this situation applies to 36 of the study area thus on the steep slopes of this megadiverse ecosystem the mass of the growing forest promotes landsliding which in turn promotes a new cycle of succession this feedback mechanism is worth consideration in further investigations of the impact of landslides on plant diversity in similar environments copyright 2012 john wiley sons ltd

the arctic oscillation signature in the wintertime geopotential height and temperature fields the leading empirical orthogonal function of the wintertime sea level pressure field is more strongly coupled to surface air temperature fluctuations over the eurasian continent than the north atlantic oscillation nao it resembles the nao in many respects but its primary center of action covers more of the arctic giving it a more zonally symmetric appearance coupled to strong fluctuations at the 50 hpa level on the intraseasonal interannual and interdecadal time scales this arctic oscillation ao can be interpreted as the surface signature of modulations in the strength of the polar vortex aloft it is proposed that the zonally asymmetric surface air temperature and mid tropospheric circulation anomalies observed in association with the ao may be secondary baroclinic features induced by the land sea contrasts the same modal structure is mirrored in the pronounced trends in winter and springtime surface air temperature sea level pressure and 50 hpa height over the past 30 years parts of eurasia have warmed by as much as several k sea level pressure over parts of the arctic has fallen by 4 hpa and the core of the lower stratospheric polar vortex has cooled by several k these trends can be interpreted as the development of a systematic bias in one of the atmosphere s dominant naturally occurring modes of variability

linkages between sea ice coverage pelagic benthic coupling and the distribution of spectacled eiders observations in march 2008 2009 and 2010 northern bering sea icebreaker based sampling in the northern bering sea south of st lawrence island in march of 2008 2009 and 2010 has provided new data on overall ecosystem function early in the annual productive cycle while water column chlorophyll concentrations 5 m these data together with other physical biological and nutrient data are presented here in conjunction with observed sea ice dynamics and the distribution of an apex predator the spectacled eider somateria fischeri sea ice dynamics in addition to benthic food availability as determined by sedimentation processes play a role in the distribution of spectacled eiders which cannot always access the greatest biomass of their preferred bivalve prey overall the data and observations indicate that the northern bering sea is biologically active in late winter but with strong atmospheric and hydrographic controls these controls pre determine nutrient and chlorophyll distributions water column mixing as well as pelagic benthic coupling

landslides in eastern honshu induced by the 2011 tohoku earthquake in this article we discuss the character and spatial pattern of coseismic landslides from the eastern honshu region of japan which was strongly shaken in the 2011 tohoku earthquake we developed a detailed geospatial database of 3477 landslides based on postearthquake field surveys and examination of high resolution satellite imagery across a 28 380 km2 landslide study area analysis of the database shows that a substantial majority 80 of landslides occurred in quaternary soil and neogene rock units despite their abundance in the study area relatively few landslides occurred in pre neogene rocks i e older than 23 ma further examination of the data showed that the most common types of landslides were 1 disrupted landslides in neogene sedimentary rocks and 2 lateral spreading in quaternary sediments however we found that coseismic landslide erosion i e debris mobilization was almost fully dominated by lateral spreading within quaternary sediments when comparing the landslide inventory with ground motions recorded by dense regional seismic arrays we found no statistically significant correlation between landslide intensity and ground motion within the study area online material derivation of empirical parameters used in the area to volume transformations for lateral spreads

a numerical simulation of sea ice cover in hudson bay abstract hibler s dynamic thermodynamic sea ice model with viscous plastic rheology is used to simulate the seasonal cycle of sea ice motion thickness compactness and growth rate in hudson bay under monthly climatological atmospheric forcing and a prescribed ocean surface current field the sea ice motion over most of the domain is driven mainly by the wind stress wintertime sea ice velocities are only of the order of 1 5 10 4 m s 1 due to the nearly solid ice cover and the closed boundary constraint of hudson bay however the velocities rise to 0 10 0 20 m s 1 during the melting and freezing seasons when there is partial ice cover the simulated thickness distribution in mid april the time of heaviest ice cover ranges from 1 3 m in james bay to 1 7 m in the northern part of hudson bay which compares favorably with observations the area averaged growth rate computed from the model is 1 5 0 5 cm day 1 from december to march is negative in may indicative of melting and reaches its minimum v

a theoretical two layer reduced gravity model for descending dense water flow on continental shelves slopes 1 a theoretical two layer reduced gravity model for descending dense water flow on continental shelves slopes has been developed to investigate the dynamics of bottom dense water plumes the model is nonsteady state and includes vertical viscosity the coriolis force and bottom friction an integral solution rather than a perfect analytical expression is derived and thus the simpson s 1 3 rule to approximate the integral is applied at the very bottom the dense water plume moves about 45 to the right left in the northern southern hemisphere looking downslope from the bottom the velocity vector rotates anticyclonically upward indicating a bottom ekman spiral that mimics the atmospheric ekman boundary layer the dense water within the bottom ekman layer obeys a three force balance while the dense water above the bottom ekman layer is governed by a two force balance which is a geostrophic flow with superimposed cycloidal inertial oscillations oriented from about 25 to 140 to the right left of the downslope direction in the northern southern hemisphere the transport within the bottom ekman layer is directed about 60 70 to the right left of the downslope direction in the northern southern hemisphere forming an offshore cross isobath transport in the absence of eddy flux and wind forcing the ratio of offshore transport to alongshore transport within the bottom ekman layer is about 0 19 19 while the ratio above the bottom ekman layer i e geostrophic layer of the dense water is only 3 negligible compared to its alongshore transport which however is equivalent in magnitude to its counterpart in the bottom ekman layer if o de h 0 1 where de is the bottom ekman layer thickness and h is the dense water layer thickness in other words the bottom ekman layer and the geostrophic dense layer contribute equivalent dense water offshore each contributes 50 the magnitude of the descending dense water velocity depends linearly on reduced gravity and sin slope angle

land level changes produced by the mw 8 8 2010 chilean earthquake we observed vertically displaced coastal and river markers after the 27 february 2010 chilean earthquake moment magnitude mw 8 8 land level changes range between 2 5 and 1 meters evident along an approximately 500 kilometers long segment identified here as the maximum length of coseismic rupture a hinge line located 120 kilometers from the trench separates uplifted areas to the west from subsided regions a simple elastic dislocation model fits these observations well model parameters give a similar seismic moment to seismological estimates and suggest that most of the plate convergence since the 1835 great earthquake was elastically stored and then released during this event

contrasting mountain and piedmont dynamics of sediment discharge associated with groundwater storage variation in the biobio river supply and transport of sediment in catchments involve processes with fundamental consequences for river management land use and the prediction of climate driven sediment fluxes in the present study we addressed spatial variability in the water routes through the surface and subsurface of a catchment and the suspended sediment discharge qs over a mountain piedmont system we analyzed daily suspended sediment concentration cs and water discharge q measurements at stations located in different topographic settings mountain and piedmont in the biobio river basin southern central andes 37 39 s in steep catchments the q versus qs relationship has a marked seasonal hysteresis in the piedmont qs is proportional to q with no seasonal hysteresis the contrast in the hysteresis pattern between catchments with different topographies is explained by differences in the routing of rainfall derived water in the piedmont most of the rainfall is converted into surface runoff because the water table is near the surface in the mountains groundwater storage results in large seasonal variations in the proportion of q that flows at the surface and transports sediment from the hillslopes producing hysteresis by separating the total q into two components direct discharge qd and base flow qb we observed the response of qs to the fraction of water that quickly leaves the catchment after a rainfall event qd similar results between the mountain and piedmont and the absence of hysteresis simplify the behavior of qs into a linear relationship with qd over the entire catchment and lead us to propose that sediment mobilization to the river along the biobio catchment is primarily controlled by overland flow our findings highlight the importance of an adequate hydrological model for understanding the erosion and transport processes of a catchment and which can be applied to other natural and modeled mountain piedmont systems

mooring observations of the thermal structure salinity and currents in the se bering sea basin utilizing recently developed deep sea mooring technology we present the first interannual time series measurements of the ocean temperature salinity and velocity fields in the bering sea basin these were made during spring and summer of 1992 and 1993 and late winter to summer of 1994 in 2195 m of water results show a weak background flow of 5 cm s with semidiurnal tides superimposed anticyclonic clockwise eddies pass by sporadically inducing currents up to 80 cm s and depressing the isopycnals and isotherms up to 200 m the thermal structure in the upper 400 m shows a deep temperature maximum from warm alaskan stream inflows and a minimum above due to winter cooling a sea surface cooling event was observed in the late winter of 1994 with cold water penetrating to 120 m depth spring warming begins in late april to early may of each year marked by the arrival of the 3 75 c isotherm the local wind plays little role in forcing ocean currents at the site except at the inertial frequency

on the functioning of the southern oscillation in the south american sector part i surface climate abstract the functioning of the southern oscillation so over south america and the surrounding tropical atlantic and eastern pacific oceans is studied through analyses of bimonthly patterns of correlation between an so index and the fields of pressure wind temperature and rainfall hydrometeorological anomalies being further ascertained from river discharge and lake level records and measurements of outgoing longwave radiation most pronounced is the anomalously low pressure over the eastern pacific during the negative so phase defined by anomalously low high pressure at tahiti darwin consistently positive so pressure correlations over the eastern tropical pacific extend eastward into the north atlantic region and southern south america during the respective winter semester during the austral winter the tendency for anomalously abundant rainfall in central chile during the negative so phase appears related to an anomalously weak and northward displaced south pacific subtropical high while relativ

the relationship between sea ice break up water mass variation chlorophyll biomass and sedimentation in the northern bering sea the northern bering sea shelf is dominated by soft bottom infauna and ecologically significant epifauna that are matched by few other marine ecosystems in biomass the likely basis for this high benthic biomass is the intense spring bloom but few studies have followed the direct sedimentation of organic material during the bloom peak in may satellite imagery water column chlorophyll concentrations and surface sediment chlorophyll inventories were used to document the dynamics of sedimentation to the sea floor in both 2006 and 2007 as well as to compare to existing data from the spring bloom in 1994 an atmospherically derived radionuclide 7be that is deposited in surface sediments as ice cover retreats was used to supplement these observations as were studies of light penetration and nutrient depletion in the water column as the bloom progressed chlorophyll biomass as sea ice melted differed significantly among the three years studied 1994 2006 2007 the lowest chlorophyll biomass was observed in 2006 after strong northerly and easterly winds had distributed relatively low nutrient water from near the alaskan coast westward across the shelf prior to ice retreat by contrast in 1994 and 2007 northerly winds had less northeasterly vectors prior to sea ice retreat which reduced the westward extent of low nutrient waters across the shelf additional possible impacts on chlorophyll biomass include the timing of sea ice retreat in 1994 and 2007 which occurred several weeks earlier than in 2006 in waters with the highest nutrient content late winter brine formation and associated water column mixing may also have impacts on productivity that have not been previously recognized these observations suggest that interconnected complexities will prevent straightforward predictions of the influence of earlier ice retreat in the northern bering sea upon water column productivity and any resulting benthic ecosystem re structuring as seasonal sea ice retreats in the northern bering sea