cross season relation of the south china sea precipitation variability between winter and summer the present study reveals cross season connections of rainfall variability in the south china sea scs region between winter and summer rainfall anomalies over northern south china sea in boreal summer tend to be preceded by the same sign rainfall anomalies over southern south china sea in boreal winter denoted as in phase relation and succeeded by opposite sign rainfall anomalies over southern south china sea in the following winter denoted as out of phase relation analysis shows that the in phase relation from winter to summer occurs more often in el nino la nina decaying years and the out of phase relation from summer to winter appears more frequently in el nino la nina developing years in the summer during the el nino la nina decaying years cold warm and warm cold sea surface temperature sst anomalies develop in tropical central north pacific and the north indian ocean respectively forming an east west contrast pattern the in phase relation is associated with the influence of anomalous heating cooling over the equatorial central pacific during the mature phase of el nino la nina events that suppresses enhances precipitation over southern south china sea and the impact of the above east west sst anomaly pattern that reduces increases precipitation over northern south china sea during the following summer the impact of the east west contrast sst anomaly pattern is confirmed by numerical experiments with specified sst anomalies in the el nino la nina developing years regional air sea interactions induce cold warm sst anomalies in the equatorial western north pacific the out of phase relation is associated with a rossby wave type response to anomalous heating cooling over the equatorial central pacific during summer and the combined effect of warm cold sst anomalies in the equatorial central pacific and cold warm sst anomalies in the western north pacific during the mature phase of el nino la nina events

rapid circulation of warm subtropical waters in a major glacial fjord in east greenland the recent rapid increase in mass loss from the greenland ice sheet is primarily attributed to an acceleration of outlet glaciers oceanographic data obtained in summer 2008 show that subtropical waters that reside year round in the shelf ocean off greenland continuously enter a large glacial fjord in east greenland and contribute to melting at the glacier terminus the recent rapid increase in mass loss from the greenland ice sheet1 2 is primarily attributed to an acceleration of outlet glaciers3 4 5 one possible cause of this acceleration is increased melting at the ice ocean interface6 7 driven by the synchronous warming8 9 10 of subtropical waters offshore of greenland however because of the lack of observations from greenland s glacial fjords and our limited understanding of their dynamics this hypothesis is largely untested here we present oceanographic data collected in sermilik fjord east greenland by ship in summer 2008 and from moorings our data reveal the presence of subtropical waters throughout the fjord these waters are continuously replenished through a wind driven exchange with the shelf where they are present all year the temperature and renewal of these waters indicate that they currently cause enhanced submarine melting at the glacier terminus key controls on the melting rate are the volume and properties of the subtropical waters on the shelf and the patterns of along shore winds suggesting that the glaciers acceleration has been triggered by a combination of atmospheric and oceanic changes our measurements provide evidence for a rapid advective pathway for the transmission of oceanic variability to the ice sheet margins

two distinctive processes for abnormal spring to summer transition over the south china sea abstractthe period from april to june signifies the transition from spring to summer over the south china sea scs the present study documents two distinct processes for abnormal spring to summer transition over the scs one process is related to large scale sea surface temperature sst anomalies in the tropical indo pacific region during spring of la nina decaying years negative sst anomalies in the equatorial central pacific ecp and the southwestern tropical indian ocean tio coexist with positive sst anomalies in the tropical western north pacific negative ecp sst anomalies force an anomalous walker circulation negative southwestern tio sst anomalies induce anomalous cross equatorial flows from there and positive tropical western north pacific sst anomalies produce a rossby wave type response to the west together they contribute to enhanced convection and an anomalous lower level cyclone over the scs leading to an advanced transition to summer there the other process is related to region

relation of the south china sea precipitation variability to tropical indo pacific sst anomalies during spring to summer transition abstractthe present study investigates the relationship of south china sea scs precipitation to tropical indo pacific sea surface temperature sst during april june amj which is the transition season from spring to summer it is revealed that scs rainfall anomalies in amj are influenced by sst anomalies in the equatorial pacific ep tropical indian ocean tio and western north pacific wnp three types of sst influenced cases are obtained based on different combinations of sst anomalies in the above three regions when same sign ep and tio sst anomalies are accompanied by opposite wnp sst anomalies both anomalous cross equatorial flows from the southwestern tio induced by negative sst anomalies there and an anomalous walker circulation forced by negative ep sst anomalies contribute to enhanced convection over the scs and the surrounding regions with additional contribution from positive wnp sst anomalies via a rossby wave type response in the cases of combined effects of ep and wnp sst anomal

dynamics of a turbulent buoyant plume in a stratified fluid an idealized model of subglacial discharge in greenland fjords abstractthis study reports the results of large eddy simulations of an axisymmetric turbulent buoyant plume in a stratified fluid the configuration used is an idealised model of the plume generated by a subglacial discharge at the base of a tidewater glacier with an ambient stratification typical of greenland fjords the plume is discharged from a round source of various diameters and characteristic stratifications for summer and winter are considered the classical theory for the integral parameters of a turbulent plume in a homogeneous fluid gives accurate predictions in the weakly stratified lower layer up to the pycnocline and the plume dynamics are not sensitive to changes in the source diameter in winter when the stratification is similar to an idealised two layers case turbulent entrainment and generation of internal waves by the plume top are in agreement with the theoretical and numerical results obtained for turbulent jets in a two layer stratification in summer instead the stratification

submarine melting at the terminus of a temperate tidewater glacier leconte glacier alaska u s a heat fresh and sea water balances indicate that the late summer rate of submarine melting at the terminus of tidewater leconte glacier alaska u s a in 2000 was about 12md 1 w e averaged over the submerged face this is 57 of the estimated total ice loss at the terminus calving plus melting at this time submarine melting may thusprovidea significantcontributiontotheoverallablationofatidewaterglacier oceano graphic measurements conductivity temperature depth made 200 500m from the ter minus identified an isohaline 27ppt and isothermal 7 2 c layer extending from 130m depthto the fjord floor capping this is a 40mthick overflow plume distinguishedby high outflow rates low salinity 22 25ppt and lower temperatures 5 6 c mixing models indicate that fresh water comprised about11 of this plume it originates mostly as sub glacial discharge whose buoyancy drives convection at the terminus deep warm saline watersareincorporatedintotheplumeasitascends causingsubstantialmeltingoficealong the submarine face the calving terminus undergoes seasonal changes that coincide with changes in subglacial discharge and fjord water temperatures and we suggest that these fluctuations interminuspositionare directly relatedto changes in submarine melting

the response of ice shelf basal melting to variations in ocean temperature abstract a three dimensional ocean general circulation model is used to study the response of idealized ice shelves to a series of ocean warming scenarios the model predicts that the total ice shelf basal melt increases quadratically as the ocean offshore of the ice front warms this occurs because the melt rate is proportional to the product of ocean flow speed and temperature in the mixed layer directly beneath the ice shelf both of which are found to increase linearly with ocean warming the behavior of this complex primitive equation model can be described surprisingly well with recourse to an idealized reduced system of equations and it is shown that this system supports a melt rate response to warming that is generally quadratic in nature this study confirms and unifies several previous examinations of the relation between melt rate and ocean temperature but disagrees with other results particularly the claim that a single melt rate sensitivity to warming is universally valid the hypothesized

the effect of meltwater plumes on the melting of a vertical glacier face abstractfreshwater produced by the surface melting of ice sheets is commonly discharged into ocean fjords from the bottom of deep fjord terminating glaciers the discharge of the freshwater forms upwelling plumes in front of the glacier calving face this study simulates the meltwater plumes emanated into an unstratified environment using a nonhydrostatic ocean model with an unstructured mesh and subgrid scale mixing calibrated by comparison to established plume theory the presence of an ice face reduces the entrainment of seawater into the meltwater plumes so the plumes remain attached to the ice front in contrast to previous simple models ice melting increases with height above the discharge also in contrast to some simple models and the authors speculate that this overcutting may contribute to the tendency of icebergs to topple inwards toward the ice face upon calving the overall melt rate is found to increase with discharge flux only up to a critical value which depends on the channel size

rapid submarine melting of the calving faces of west greenland glaciers widespread glacier acceleration has been observed in greenland in the past few years oceanographic observations taken in summer 2008 show that ocean waters melted a substantial fraction of ice along the calving fronts of three west greenland glaciers indicating that submarine melting has a profound influence on grounding line stability widespread glacier acceleration has been observed in greenland in the past few years1 2 3 4 associated with the thinning of the lower reaches of the glaciers as they terminate in the ocean5 6 7 these glaciers thin both at the surface from warm air temperatures and along their submerged faces in contact with warm ocean waters8 little is known about the rates of submarine melting9 10 11 and how they may affect glacier dynamics here we present measurements of ocean currents temperature and salinity near the calving fronts of the eqip sermia kangilerngata sermia sermeq kujatdleq and sermeq avangnardleq glaciers in central west greenland as well as ice front bathymetry and geographical positions we calculate water mass and heat budgets that reveal summer submarine melt rates ranging from 0 7 0 2 to 3 9 0 8 m d 1 these rates of submarine melting are two orders of magnitude larger than surface melt rates but comparable to rates of iceberg discharge we conclude that ocean waters melt a considerable but highly variable fraction of the calving fronts of glaciers before they disintegrate into icebergs and suggest that submarine melting must have a profound influence on grounding line stability and ice flow dynamics

indian ocean capacitor effect on indo western pacific climate during the summer following el nino significant climate anomalies persist through the summer june august after el nino dissipates in spring over the equatorial pacific they include the tropical indian ocean tio sea surface temperature sst warming increased tropical tropospheric temperature an anomalous anticyclone over the subtropical northwest pacific and increased mei yu baiu rainfall over east asia the cause of these lingering el nino effects during summer is investigated using observations and an atmospheric general circulation model gcm the results herein indicate that the tio warming acts like a capacitor anchoring atmospheric anomalies over the indo western pacific oceans it causes tropospheric temperature to increase by a moist adiabatic adjustment in deep convection emanating a baroclinic kelvin wave into the pacific in the northwest pacific this equatorial kelvin wave induces northeasterly surface wind anomalies and the resultant divergence in the subtropics triggers suppressed convection and the anomalous anticyclone the gcm results support this kelvin wave induced ekman divergence mechanism in response to a prescribed sst increase over the tio the model simulates the kelvin wave with low pressure on the equator as well as suppressed convection and the anomalous anticyclone over the subtropical northwest pacific an additional experiment further indicates that the north indian ocean warming is most important for the kelvin wave and northwest pacific anticyclone a result corroborated by observations these results have important implications for the predictability of indo western pacific summer climate the spatial distribution and magnitude of the tio warming rather than simply whether there is an el nino in the preceding winter affect summer climate anomalies over the indo western pacific and east asia

the effect of the marginal ice zone on the directional wave spectrum of the ocean abstract during the mizex 84 experiment in the greenland sea in june july 1984 a cooperative program was carried out between the scott polar research institute spri and the institute of oceanographic sciences ios to measure the change in the directional character of the ocean wave spectrum in the immediate vicinity of the ice edge the aim was to extend one dimensional spectral measurements made hitherto so as to study in full the processes of reflection and refraction directional spectrum analysis of these records shows that i significant reflection of wave energy occurs at the ice edge detected using long hasselmann analysis ii within the ice the directional spectrum at high frequencies where attenuation is rapid broadens to become almost isotropic whereas iii the directional spectrum at swell frequencies where the attenuation is slower becomes initially narrower before broadening more slowly than the high frequency energy an explanation of these effects is offered in terms of scatte

convection driven melting near the grounding lines of ice shelves and tidewater glaciers subglacial meltwater draining along the bed of fast flowing marine terminating glaciers emerges at the groundingline wheretheiceeithergoesafloattoformaniceshelforterminates inacalvingface theinputof freshwater to the ocean provides a source of buoyancy and drives convective motion alongside the ice ocean interface this process is modeled using the theory of buoyant plumes that has previously been applied to the study of the larger scale circulation beneath ice shelves the plume grows through entrainment of ocean waters and the heat brought into the plume as a result drives melting at the ice ocean interface the equations are nondimensionalized by using scales appropriate for the region where the subglacial drainage rather than the subsequent addition of meltwater supplies the majority of the buoyancy forcing it is found that the melt rate within this region can be approximated reasonably well by a function that is linear in ocean temperature has a cube root dependence on the flux of subglacial meltwater and has a complex dependency on the slope of the ice ocean interface the model is used to investigate variability in melting induced by changes in both ocean temperature and subglacial discharge for a number of realistic examples of ice shelves and tidewater glaciers the results show how warming ocean waters and increasing subglacial drainage both generate increases in melting near the grounding line

observed runoff jokulhlaups and suspended sediment load from the greenland ice sheet at kangerlussuaq west greenland 2007 and 2008 this study fills the gap in hydrologic measurements of runoff exiting a part of the greenland ice sheet gris the kangerlussuaq drainage area west greenland the observations are of value for obtaining knowledge about the terrestrial freshwater and sediment output from part of the gris and the strip of land between the gris and the ocean in the context of varying ice sheet surface melt and influx entering the ocean high resolution stage discharge and suspended sediment load show a decrease in runoff of approx 25 and in sediment load of approx 40 from 2007 to 2008 in response to a decrease in the summer accumulated number of positive degree days during the 2007 and 2008 runoff season joekulhlaups are observed at kangerlussuaq drained from an ice dammed lake at the margin of the gris

interannual and interdecadal variations of the east asian summer monsoon and tropical pacific ssts part i roles of the subtropical ridge the interannual relationship between the east asian summer monsoon and the tropical pacific ssts is studied using rainfall data in the yangtze river valley and the ncep reanalysis for 1951 96 the datasets are also partitioned into two periods 1951 77 and 1978 96 to study the interdecadal variations of this relationship a wet summer monsoon is preceded by a warm equatorial eastern pacific in the previous winter and followed by a cold equatorial eastern pacific in the following fall this relationship involves primarily the rainfall during the pre mei yu mei yu season may june but not the post mei yu season july august in a wet monsoon year the western north pacific subtropical ridge is stronger as a result of positive feedback that involves the anomalous hadley and walker circulations an atmospheric rossby wave response to the western pacific complementary cooling and the evaporation wind feedback this ridge extends farther to the west from the previous winter to the following fall resulting in an 850 hpa anomalous anticyclone near the southeast coast of china this anticyclone 1 blocks the pre mei yu and mei yu fronts from moving southward thereby extending the time that the fronts produce stationary rainfall 2 enhances the pressure gradient to its northwest resulting in a more intense front and 3 induces anomalous warming of the south china sea surface through increased downwelling which leads to a higher moisture supply to the rain area a positive feedback from the strong monsoon rainfall also appears to occur leading to an intensified anomalous anticyclone near the monsoon region this sst subtropical ridge monsoon rainfall relationship is observed in both the interannual timescale within each interdecadal period and in the interdecadal scale the sst anomalies sstas change sign in northern spring and resemble a tropospheric biennial oscillation tbo pattern during the first interdecadal period 1951 77 in the second interdecadal period 1978 96 the sign change occurs in northern fall and the tbo pattern in the equatorial eastern pacific sst is replaced by longer timescales this interdecadal variation of the monsoon sst relationship results from the interdecadal change of the background state of the coupled ocean atmosphere system this difference gives rise to the different degrees of importance of the feedback from the anomalous circulations near the monsoon region to the equatorial eastern pacific in a wet monsoon year the anomalous easterly winds south of the monsoon enhanced anomalous anticyclone start to propagate slowly eastward toward the eastern pacific in may and june apparently as a result of an atmosphere ocean coupled wave motion these anomalous easterlies carry with them a cooling effect on the ocean surface in 1951 77 this effect is insignificant as the equatorial eastern pacific sstas already change from warm to cold in northern spring probably as a result of negative feedback processes discussed in enso mechanisms in 1978 96 the equatorial eastern pacific has a warmer mean sst a stronger positive feedback between ssta and the walker circulation during a warm phase tends to keep the ssta warm until northern fall when the eastward propagating anomalous easterly winds reach the eastern pacific and reverse the ssta

increasing rates of ice mass loss from the greenland and antarctic ice sheets revealed by grace 1 we use monthly measurements of time variable gravity from the grace gravity recovery and climate experiment satellite gravity mission to determine the ice mass loss for the greenland and antarctic ice sheets during the period between april 2002 and february 2009 we find that during this time period the mass loss of the ice sheets is not a constant but accelerating with time i e that the grace observations are better represented by a quadratic trend than by a linear one implying that the ice sheets contribution to sea level becomes larger with time in greenland the mass loss increased from 137 gt yr in 2002 2003 to 286 gt yr in 2007 2009 i e an acceleration of 30 11 gt yr2 in 2002 2009 in antarctica the mass loss increased from 104 gt yr in 2002 2006 to 246 gt yr in 2006 2009 i e an acceleration of 26 14 gt yr2 in 2002 2009 the observed acceleration in ice sheet mass loss helps reconcile grace ice mass estimates obtained for different time periods

interruption of two decades of jakobshavn isbrae acceleration and thinning as regional ocean cools jakobshavn isbrae has been the single largest source of mass loss from the greenland ice sheet over the last 20 years during that time it has been retreating accelerating and thinning here we use airborne altimetry and satellite imagery to show that since 2016 jakobshavn has been re advancing slowing and thickening we link these changes to concurrent cooling of ocean waters in disko bay that spill over into ilulissat icefjord ocean temperatures in the bay s upper 250 m have cooled to levels not seen since the mid 1980s observations and modelling trace the origins of this cooling to anomalous wintertime heat loss in the boundary current that circulates around the southern half of greenland longer time series of ocean temperature subglacial discharge and glacier variability strongly suggest that ocean induced melting at the front has continued to influence glacier dynamics after the disintegration of its floating tongue in 2003 we conclude that projections of jakobshavn s future contribution to sea level rise that are based on glacier geometry are insufficient and that accounting for external forcing is indispensable

decadal changes in the relationship between the tropical pacific and the north pacific 1 it has been recognized that the tropical pacific sea surface temperature sst anomaly associated with the el nino southern oscillation enso is closely tied to large scale atmospheric anomalies in the extra tropical region based on observational data this connection appears to have changed significantly since 1999 this study examines the characteristics of this connection during two sub periods 1980 1998 and 1999 2010 using cyclostationary empirical orthogonal function cseof analysis we found that the atmospheric anomalies induced by the enso alter the sst over the north pacific through surface heat flux change during the earlier period of 1980 1998 during the later period in contrast enso related atmospheric anomalies feature the north pacific oscillation npo pattern during winter which is characterized by a southward shift of the atmospheric center of action from its climatological position the npo related atmospheric anomalies extend to the subtropical pacific this extension potentially links midlatitude and tropical pacific variability through air sea interactions the physical change appears to alter the el nino characteristics into that of the central pacific el nino through the wind sst coupling mechanism this process may be related to the recent change in which the central pacific el nino occurs more frequently than the conventional eastern pacific el nino detailed descriptions of the physical changes between the tropical pacific and the north pacific are presented in this study along with the possible implications of this change

changes in the velocity structure of the greenland ice sheet using satellite radar interferometry observations of greenland we detected widespread glacier acceleration below 66 north between 1996 and 2000 which rapidly expanded to 70 north in 2005 accelerated ice discharge in the west and particularly in the east doubled the ice sheet mass deficit in the last decade from 90 to 220 cubic kilometers per year as more glaciers accelerate farther north the contribution of greenland to sea level rise will continue to increase

the dynamics of a subglacial salt wedge marine terminating glaciers such as those along the coastline of greenland often release meltwater into the ocean in the form of subglacial discharge plumes though these plumes can dramatically alter the mass loss along the front of a glacier the conditions surrounding their genesis remain poorly constrained in particular little is known about the geometry of subglacial outlets and the extent to which seawater may intrude into them here the latter is addressed by exploring the dynamics of an arrested salt wedge a steady state two layer flow system where salty water partially intrudes a channel carrying fresh water building on existing theory we formulate a model that predicts the length of a non entraining salt wedge as a function of the froude number the slope of the channel and coefficients for interfacial and wall drag in conjunction a series of laboratory experiments were conducted to observe a salt wedge within a rectangular channel for experiments conducted with laminar flow reynolds number re 800 good agreement with theoretical predictions are obtained when the drag coefficients are modelled as being inversely proportional to re however for fully turbulent flows on geophysical scales these drag coefficients are expected to asymptote toward finite values adopting reasonable drag coefficient estimates for this flow regime our theoretical model suggests that typical subglacial channels may permit seawater intrusions of the order of several kilometres while crude these results indicate that the ocean has a strong tendency to penetrate subglacial channels and potentially undercut the face of marine terminating glaciers

impact of fjord dynamics and glacial runoff on the circulation near helheim glacier greenland to show that the melting circulation is affected by seasonal runoff from the glacier and by the fjord s externally forced currents and stratification the presence of light arctic and dense atlantic waters in the fjord in particular causes meltwater to be exported at depth and influences the vertical distribution of heat along the ice margin our results indicate that the melting circulation is more complex than hypothesized and influenced by multiple external parameters we conclude that the shape and stability of greenland s glaciers may be strongly influenced by the layering of the arctic and atlantic waters in the fjord as well as their variability

large scale changes in greenland outlet glacier dynamics triggered at the terminus the recent dramatic retreat of many outlet glaciers of the greenland ice sheet has raised concerns over greenland s contribution to future sea level rise simulations with a numerical ice flow model indicate that the recent rates of mass loss in greenland s outlet glaciers are transient and should not be extrapolated into the future

subglacial hydrology at rink isbrae west greenland inferred from sediment plume appearance marine terminating outlet glaciers discharge most of the greenland ice sheet s mass through frontal ablation and meltwater runoff while calving can be estimated by in situ and remote sensing observations submarine melting and subglacial meltwater transport are more challenging to quantify here we investigate the subglacial hydrology of rink isbrae a fast flowing west greenland tidewater glacier using time lapse photography modeled runoff estimates and daily satellite imagery from 2007 to 2011 we find that sediment plumes appear episodically at four distinct locations across the terminus and last between 2 h and 17 d this suggests short term variability in discharge and the existence of persistent pathways the seasonal onset of sediment plumes occurs before supraglacial lake drainages shortly after the onset of runoff and only after the wintertime ice melange has begun disintegrating plumes were also visible after the cessation of runoff 23 5 d which is indicative of subglacial storage the lack of either a seasonal velocity change or a correspondence between meltwater availability and plume occurrence suggests that the subglacial system persists in a state of inefficient drainage subglacial hydrology at tidewater glaciers is of critical importance in understanding dynamics at the ice front

katabatic wind driven exchange in fjords the general issue of katabatic wind driven exchange in fjords is considered using an idealized numerical model theory and observations two regimes are identified for fjords narrower than a viscous boundary layer width the exchange is limited by a balance between wind and friction in lateral boundary layers for the nonlinear viscous parameterization used here this boundary layer thickness depends on the properties of the fjord such as stratification and length as well as on the wind stress and numerical parameters such as grid spacing and an empirical constant for wider fjords typical of east greenland the balance is primarily between wind the along fjord pressure gradient and acceleration in general agreement with previous two layer nonrotating theories it is expected that o 10 of the surface layer will be flushed out of the fjord by a single wind event application of the idealized model to a typical katabatic wind event produces outflowing velocities that are in general agreement with observations in sermilik fjord the presence of a sill has only a minor influence on the exchange until the sill penetrates over most of the lower layer thickness in which cases the exchange is reduced it is concluded that the multiple katabatic wind events per winter that are experienced by the fjords along east greenland represent an important mechanism of exchange between the fjord and shelf with implications for the renewal of warm salty waters at depth and for the export of glacial freshwater in the upper layer

turbulent heat and momentum transfer in the oceanic boundary layer under melting pack ice a theory for momentum flux in the planetary boundary layer pbl stabilized by continuous surface buoyancy is extended to include turbulent flux of an arbitrary scalar contaminant and then used to estimate how wind driven sea ice melts as it encounters temperatures in the oceanic boundary layer that are above the melting point given wind stress and temperature difference across the oceanic pbl the theory predicts melt rate and ice drift velocity results indicate that the effect of buoyancy on pbl turbulence is significant even with small values of 0 5 k curves of melt rate and ice speed as functions of u the interfacial friction velocity show that melting is strongly dependent on stress at the interface and that the effective drag on the ice undersurface is significantly reduced at oceanic temperatures commonly observed in the marginal ice zone the latter suggests that divergence will occur at the ice margin when off ice winds advect the pack over water above the melting temperature the structure of mean currents beneath the ice is also investigated results indicate that advection will play an important if not dominant role in determining water column properties near an ice edge front

pacific east asian teleconnection how does enso affect east asian climate observational evidence is presented to show a teleconnection between the central pacific and east asia during the extreme phases of enso cycles this pacific east asian teleconnection is confined to the lower troposphere the key system that bridges the warm cold events in the eastern pacific and the weak strong east asian winter monsoons is an anomalous lower tropospheric anticyclone cyclone located in the western north pacific the western north pacific wind anomalies develop rapidly in late fall of the year when a strong warm or cold event matures the anomalies persist until the following spring or early summer causing anomalously wet dry conditions along the east asian polar front stretching from southern china northeastward to the east of japan kuroshio extension using atmospheric general circulation and intermediate models the authors show that the anomalous philippine sea anticyclone results from a rossby wave response to suppressed convective heating which is induced by both the in situ ocean surface cooling and the subsidence forced remotely by the central pacific warming the development of the anticyclone is nearly concurrent with the enhancement of the local sea surface cooling both the anticyclone and the cooling region propagate slowly eastward the development and persistence of the teleconnection is primarily attributed to a positive thermodynamic feedback between the anticyclone and the sea surface cooling in the presence of mean northeasterly trades the rapid establishment of the philippine sea wind and sst anomalies implies the occurrence of extratropical tropical interactions through cold surge induced exchanges of surface buoyancy flux the central pacific warming plays an essential role in the development of the western pacific cooling and the wind anomalies by setting up a favorable environment for the anticyclone sst interaction and midlatitude tropical interaction in the western north pacific

oceanic boundary conditions for jakobshavn glacier part i variability and renewal of ilulissat icefjord waters 2001 14 jakobshavnglacier west greenland has respondedtotemperaturechangesinilulissaticefjord intowhich it terminates thisstudycollectedhydrographicobservationsinsideilulissaticefjordandfromadjacentdiskobay between2001and2014 thewarmestdeepdiskobaywaterswereblockedbytheentrancesillanddidnotreach jakobshavn glacier in the fjord basin the summer mean temperature was 2 88c from 2009 to 2013 excluding 2010 whenitwas 18c cooler despitethisvariability summerpotential densities in the basinwereinthe narrow range of 27 20 su 27 31kgm 23 and basin water properties matched those of disko bay in this layer each summer this relation has likely held since at least 1980 basin waters from 2009 and 2011 13 were therefore similar tothosein1998 99 whenjakobshavn glacier began toretreat whilebasin watersin2010wereascoolas in the 1980s the 2010 basin temperature anomaly was advected into disko bay not produced by local atmospheric variability this anomaly also shows that ilulissat icefjord basin waters were renewed annually or faster time series fragments inside the fjord did not capture the 2010 anomaly but show that the basin temperatures varied little subannually outside of summer fjord velocity profiles from summer 2013 implied a basin renewal time scale of about 1 month in model simulations of the fjord circulation subglacial discharge from jakobshavn glacier could drive renewal of the fjord basin over a single summer while baroclinic forcing from outside the fjord could not because of the sill at the mouth

observation and parameterization of ablation at the base of ronne ice shelf antarctica parameterizations of turbulent transfer through the oceanic boundary layer beneath an ice shelf are tested using direct measurements of basal ablation observations were made in the southwestern part of ronne ice shelf about 500 km from open water the mean basal ablation rate was measured over a month long and a year long period using phase sensitive radar to record the thinning of the ice shelf ocean temperatures were observed within about 25 m of the ice shelf base over the period of the radar observations while the tidally dominated ocean currents were estimated from tidal analysis of collocated current observations from an earlier period ablation rates derived using these ocean data and a number of bulk parameterizations of turbulent transfer within the boundary layer are compared with the direct measurements the ablation rates derived using a parameterization that explicitly includes the impact of ocean currents on the turbulent transfer of heat and salt match the observations to within 40 with suitable tuning of the drag coefficient the mismatch can be reduced below the level of the observational errors equally good agreement can be obtained with two slightly simpler current dependent parameterizations that use constant turbulent transfer coefficients andtheoptimalvaluesforthecoefficientsatthis particularlocationon ronneice shelfaregiven

air sea relationship associated with precipitation anomaly changes and mean precipitation anomaly over the south china sea and the arabian sea during the spring to summer transition abstractthe period from april to june is the time of transition from spring to summer over the north indian ocean and the south china sea analysis shows that precipitation anomaly changes from april to june may indicate summer june august mean precipitation anomalies over the south china sea and the arabian sea this study documents and compares the evolution of precipitation surface wind and sea surface temperature sst anomalies during the spring to summer transition corresponding to april june precipitation anomaly changes and april june mean precipitation anomalies over the south china sea and the arabian sea over the south china sea a clear signal of local air sea interaction is identified corresponding to the precipitation anomaly change as indicated by a sequence of less precipitation higher sst more precipitation and lower sst in contrast the mean precipitation anomaly features a response to remote sst forcing and a local forcing of atmosphere on the ocean the evolution of surface h

on the role of sea surface temperature gradients in forcing low level winds and convergence in the tropics abstract we examine the importance of pressure gradients due to surface temperature gradients to low level p 700 mb flow and convergence in the tropics over time scales 1 month the latter plays a crucial role in determining the distribution of cumulonimbus convection and rainfall our approach is to consider a simple one layer model of the trade cumulus boundary layer wherein surface temperature gradients are mixed vertically consistent with ecmwf analyzed data the top of the layer is taken at 700 mb the influence from higher levels is intentionally suppressed by setting horizontal pressure gradients and frictional stresses to zero at the top of the layer horizontal convergence within the layer is taken up by cumulonimbus mass flux however the development of the cumulonimbus mass flux is associated with a short relaxation time o hr roughly the development time for such convection during this short time horizontal convergence acts to redistribute mass so as to reduce horizontal pressur

pacific east asian teleconnection part ii how the philippine sea anomalous anticyclone is established during el nino development the anomalous philippine sea anticyclone psac conveys impacts of el nino to east asian climate during the mature and decay of an el nino from the winter to ensuing summer it is shown that the anomalous psac forms in fall about one season prior to the peak el nino its strength increases with the el nino intensity and its sign reverses during a la nina the psac formation concurs with abnormal deepening of the east asian trough and with increasing number of northward recurvature of tropical storms in the western pacific the psac establishment is abrupt coupling with a swing from a wet to dry phase of an intraseasonal oscillation iso and often concurrent with early retreat of the east asian summer monsoon the iso becomes inactive after psac establishment the development of the psac is attributed to combined effects of the remote el nino forcing tropical extratropical interaction and monsoon ocean interaction the developing el nino induces off equatorial as cending rossby wave responses and land surface cooling in northeast asia both deepen the east asian trough in fall and induces vigorous tropical extratropical exchange of air mass and heat which enhances the cold air outbreak and initiation of the psac through exciting descending rossby waves the el nino induced indonesian subsidence generates low level anticyclonic vorticity over south asia which is advected by mean monsoon westerly instigating the anomalous psac the iso interacting with the underlying ocean plays a critical role in the abrupt establishment of psac the wind evaporation entrainment feedback tends to amplify suppress iso before after winter northeasterly monsoon commences suggesting the roles of atmosphere ocean inter action and the seasonal march of background winds in changing the philippine sea iso intensity and maintaining psac

columbia bay alaska an upside down estuary abstract circulation and water properties within columbia bay alaska are dominated by the effects of columbia glacier at the head of the bay the basin between the glacier terminus and the terminal moraine sill depth of about 22 m responds as an upside down estuary with the subglacial discharge of freshwater entering at the bottom of the basin the intense vertical mixing caused by the bouyant plume of freshwater creates a homogeneous water mass that exchanges with the far field water through either a two or a three layer flow in general the glacier acts as a large heat sink and creates a water mass which is cooler than that in fjords without tidewater glaciers the predicted retreat of columbia glacier would create a 40 km long fjord that has characteristics in common with other fjords in prince william sound

where glaciers meet water subaqueous melt and its relevance to glaciers in various settings glacier change is ubiquitous but the fastest and largest magnitude changes occur in glaciers that terminate in water this includes the most rapidly retreating glaciers and also several advancing ones often in similar regional climate settings furthermore water terminating glaciers show a large range in morphology particularly when ice flow into ocean water is compared to that into freshwater lakes all water terminating glaciers share the ability to lose significant volume of ice at the front either through mechanical calving or direct melt from the water in contact here we present a review of the subaqueous melt process we discuss the relevant physics and show how different physical settings can lead to different glacial responses we find that subaqueous melt can be an important trigger for glacier change it can explain many of the morphological differences such as the existence or absence of floating tongues subaqueous melting is influenced by glacial runoff which is largely a function of atmospheric conditions this shows a tight connection between atmosphere oceans and lakes and glaciers subaqueous melt rates even if shown to be large should always be discussed in the context of ice supply to the glacier front to assess its overall relevance we find that melt is often relevant to explain seasonal evolution can be instrumental in shifting a glacier into a different dynamical regime and often forms a large part of a glacier s mass loss on the other hand in some cases melt is a small component of mass loss and does not significantly affect glacier response

an investigation of a polynya in the canadian archipelago 1 introduction and oceanography in certain parts of the canadian archipelago small localized areas of water remain ice free throughout the winter despite the extreme temperature differences between the atmosphere and the ocean surface one such area close to dundas island has been studied in detail both from the point of view of the atmospheric oceanic heat exchange over the open water and its local geographic and oceanographic context this paper describes the oceanography of the area and local weather and tidal flow conditions a significant feature of the oceanographic records is a strong modulation of near surface ocean temperature at tidal frequencies involving temperature differences as great as 0 2 c within a single tidal cycle for the most part the surface waters are 0 1 to 0 2 c above freezing the presence of this relatively warm surface water is thought to be due to upward mixing occasioned by fast tidal flows across the shallow sill connecting dundas and devon islands historical records of water properties in the sverdrup basin lying to the north of the polynya area show temperatures substantially above freezing point at depths of 50 m and below this readily accessible body of warm water is thought to be the source of the sensible heat required for the existence of the polynya this is supported by existing current measurements which suggest a mean southerly transport in the channels leading into and out of the region of the polynya site a tentative application of the atmospheric heat flux measurements to the whole dundas island bailey hamilton island area suggests that sufficient heat may be lost to affect significantly the water column further south in crozier strait and wellington channel the limited information available shows the more southerly waters of these passages to be relatively well mixed and cooled relative to the water of the sverdrup basin just to the north of the dundas polynya area

subglacial water storage and drainage beneath the fennoscandian and barents sea ice sheets abstract subglacial hydrology modulates how ice sheets flow respond to climate and deliver meltwater sediment and nutrients to proglacial and marine environments here we investigate the development of subglacial lakes and drainage networks beneath the fennoscandian and barents sea ice sheets over the late weichselian utilizing an established coupled climate ice flow model we calculate high resolution spatio temporal changes in subglacial hydraulic potential from ice sheet build up 37 ka bp to complete deglaciation 10 ka bp our analysis predicts up to 3500 potential subglacial lakes the largest of which was 658 km2 and over 70 of which had surface areas

decadal shift in el nino influences on indo western pacific and east asian climate in the 1970s abstract el nino s influence on the subtropical northwest nw pacific climate increased after the climate regime shift of the 1970s this is manifested in well organized atmospheric anomalies of suppressed convection and a surface anticyclone during the summer june august of the el nino decay year jja 1 a season when equatorial pacific sea surface temperature sst anomalies have dissipated in situ observations and ocean atmospheric reanalyses are used to investigate mechanisms for the interdecadal change during jja 1 the influence of the el nino southern oscillation enso on the nw pacific is indirect being mediated by sst conditions over the tropical indian ocean tio the results here show that interdecadal change in this influence is due to changes in the tio response to enso during the postregime shift epoch the el nino teleconnection excites downwelling rossby waves in the south tio by anticyclonic wind curls these rossby waves propagate slowly westward causing persistent sst warmi

acceleration of jakobshavn isbrae triggered by warm subsurface ocean waters observations over past decades show a sudden switch of jakobshavn isbrae a large outlet glacier feeding a deep ocean fjord on greenland s west coast from slow thickening to rapid thinning in 1997 this switch is associated with a doubling in glacier velocity hydrographic data show a concurrent sudden increase in subsurface ocean temperatures along the entire west coast of greenland suggesting that the changes in jakobshavn isbrae were triggered by the arrival of relatively warm water originating from the irminger sea observations over the past decades show a rapid acceleration of several outlet glaciers in greenland and antarctica1 one of the largest changes is a sudden switch of jakobshavn isbrae a large outlet glacier feeding a deep ocean fjord on greenland s west coast from slow thickening to rapid thinning2 in 1997 associated with a doubling in glacier velocity3 suggested explanations for the speed up of jakobshavn isbrae include increased lubrication of the ice bedrock interface as more meltwater has drained to the glacier bed during recent warmer summers4 and weakening and break up of the floating ice tongue that buttressed the glacier5 here we present hydrographic data that show a sudden increase in subsurface ocean temperature in 1997 along the entire west coast of greenland suggesting that the changes in jakobshavn isbrae were instead triggered by the arrival of relatively warm water originating from the irminger sea near iceland we trace these oceanic changes back to changes in the atmospheric circulation in the north atlantic region we conclude that the prediction of future rapid dynamic responses of other outlet glaciers to climate change will require an improved understanding of the effect of changes in regional ocean and atmosphere circulation on the delivery of warm subsurface waters to the periphery of the ice sheets

modeling ice shelf cavities in a z coordinate ocean general circulation model 1 processes at the ice shelf ocean interface and in particular in ice shelf cavities around antarctica have an observable effect on the solutions of basin scale to global coupled ice ocean models despite this these processes are not routinely represented in global ocean and climate models it is shown that a new ice shelf cavity model for z coordinate models can reproduce results from an intercomparison project of earlier approaches with vertical or isopycnic coordinates as a proof of concept ice shelves are incorporated in a 100 year global integration of a z coordinate model in this simulation glacial meltwater can be traced as far as north as 15 s the observed effects of processes in the ice shelf cavities agree with previous results from a coordinate model notably the increase in sea ice thickness however melt rates are overestimated probably because the parameterization of basal melting does not suit the low resolution of this configuration

signals of the south china sea summer rainfall variability in the indian ocean the present study investigates signals of the south china sea scs summer rainfall variability in the indian ocean it is found that the scs summer rainfall has a negative relationship with december january february djf western equatorial indian ocean wio sea surface temperature sst a positive relationship with an asymmetric mode of precipitation anomalies in the tropical indian ocean during march april may mam and a positive relationship with june july august jja south indian ocean sio sst the wio sst anomalies induce same sign southeast indian ocean sst anomalies through an anomalous zonal vertical circulation the southeast indian ocean sst anomalies last from late winter to early summer and induce opposite sign scs summer rainfall anomalies via an anomalous meridional vertical circulation the asymmetric mode influences the scs summer rainfall variation via the north indian ocean nio sst anomalies with significant cloud radiation and wind evaporation effect positive negative sio sst anomalies drive an anomalous direct circulation between the sio and the nio and an anomalous indirect circulation between the nio and the scs which facilitates the occurrence of cyclonic anti cyclonic wind anomalies over the scs western north pacific and results in positive negative scs summer rainfall anomalies partial correlation analysis indicates that the influence of djf wio sst anomalies and jja sio sst anomalies on the scs summer rainfall is partly enso independent while the mam asymmetric mode is mostly related to the preceding djf eastern pacific sst anomalies

on the spacing and draft distributions for pressure ridge keels the negative exponential distribution is reconsidered as a description of pressure ridge spacings and drafts it is found to give an excellent fit for drafts but not for spacings the spacing distribution is found to be fitted much better by a three parameter lognormal distribution of which the third parameter the threshold is dependent on the beam width of the instrument used to collect the ice bottom profile

change in coherence of interannual variability of summer rainfall over the western pacific around the early 2000s role of indo pacific ocean forcing abstractthe observations show that the covariability between the western north pacific wnp and the south china sea scs summer rainfall has experienced an obvious weakening since the early 2000s during the period 1982 2003 the combined north indian ocean nio central north pacific cnp and central equatorial pacific cep sea surface temperature sst forcing results in a high coherence between the wnp and scs summer rainfall variations via a zonally elongated anomalous lower level cyclone over the western pacific during the period 2004 16 the indian ocean sst contribution is largely weakened and the wnp rainfall variability is dominated by the enhanced pacific sst forcing with an eastward retreated lower level wind and rainfall anomalies whereas the scs rainfall variability is mainly associated with local air sea interaction processes the results obtained from observational analysis are supported by numerical experiments with atmospheric and coupled general circulation models the change in

spectral albedos of sea ice and incident solar irradiance in the southern beaufort sea spectral albedos and incident spectral irradiances have been measured over the wavelength range 400 to 2400 nm on the sea ice near the naval arctic research laboratory narl at pt barrow alaska the observation interval extended from mid may when the ice was still relatively cold until mid june when summer melting was fully established the temporal dependence of albedo for the available surface types was obtained over this time interval showing a general decrease from snow and snow covered ice to blue ice and melt ponds data were also obtained for glacier ice on the athabasca glacier for melting lake ice and for certain other nonice surfaces in the vicinity of narl snow and ice albedos are characteristically highest at visible wavelengths decreasing strongly in the infrared because of the increase in absorption by ice and water local maxima in the spectra correspond to minima in the ice and water absorption variations in albedo are due primarily to differences in the vapor bubble density crystal structure and free water content of the upper layers of the ice incident spectral shortwave radiation was measured as a function of cloudiness and the optical thickness of arctic clouds is significantly less than the thickest clouds at lower latitudes the decrease of the infrared component relatiave to the visible portion of the irradiance with increasing cloud cover is determined this can give rise to an increase in wavelength integrated albedos of as much as 15 using the present data a graphical method is outlined by which visible near infrared satellite imagery can be used to distinguish among melt ponds open leads and other spring and summer sea ice surface types

numerical experiments on subaqueous melting of greenland tidewater glaciers in response to ocean warming and enhanced subglacial discharge the largest dischargers of ice in greenland are glaciers that terminate in the ocean and melt in contact with sea water studies of ice sheet ocean interactions have mostly focused on melting beneath near horizontal floating ice shelves for tidewater glaciers melting instead takes place along the vertical face of the calving front here we modify the massachusetts institute of technology general circulation model mitgcm to include ice melting from a calving face with the freshwater outflow at the glacier grounding line we use the model to predict melt rates and their sensitivity to ocean thermal forcing and to subglacial discharge we find that melt rates increase with approximately the one third power of the subglacial water flux and increase linearly with ocean thermal forcing our simulations indicate that consistent with limited field data melting ceases when subglacial discharge is shut off and reaches several meters per day when subglacial discharge is high in the summer these results are a first step toward a more realistic representation of subglacial discharge and of ocean thermal forcing on the subaqueous melting of tidewater glaciers in a numerical ocean model our results illustrate that the ice front melting process is both complex and strongly time dependent

effect of acceleration on sea ice growth field studies1 and laboratory experiments2 3 have shown that sea currents align the crystallographic c axes in sea ice illustrating the profound effect of fluid motion on the freezing of brine the role of buoyancy forces in the melt is further investigated here by solidifying nacl solution in a centrifuge when the ice is grown under negative accelerations choosing the solidification direction as positive the salt concentration in the ice decreases monotonically with depth whilst with positive acceleration it has the characteristic c shaped profile found in natural sea ice in addition the concentration decreases as the acceleration increases at any given depth this behaviour has been found to be due to variations in the initial trapping of brine rather than to subsequent buoyancy driven drainage accelerations up to 250 ms 2 25 5g reduce the scale of features within the solid while maintaining the essential characteristics of a sea ice cover

atmospheric boundary layer structure and drag coefficients over sea ice this paper estimates the air sea drag coefficient for first year ice from recent aircraft measurements and reconciles the range of observed drag coefficients 103cd 1 2 3 7 referenced to 10 m for all sea ice types based on ice roughness and seasonal meteorology for the purpose of sea ice modeling it is necessary to define an effective drag coefficient which relates regional stress to regional wind because sea ice is heterogeneous on scales less than 20 km regional stress is influenced by the distribution of surface roughness the buoyancy flux from quasi periodic leads and external atmospheric conditions principally the inversion height 103cd is 1 3 1 5 for smooth ice but is much greater for nonflat surfaces for wind speeds greater than 5 m s and air temperatures below freezing the effective 103cd is 2 5 3 0 for nearly continuous pack ice such as first year ice in seasonal ice zones and central arctic basin the range of values of 103cd is 3 0 3 7 for unstable boundary layers typical of off ice winds in the marginal ice zone miz or even greater if the ice has been broken by a recent storm cd values at the lower end of these ranges are associated with low inversion heights these coefficients are confirmed by 103cd of 2 9 2 5 and 3 1 for first year sea ice calculated from gust probe data collected by the noaa p 3 aircraft interior to the inner miz in the bering sea during the marginal ice zone experiment mizex west in february 1983 and 103cd of 2 6 for the arctic calculated from arctic ice dynamics joint experiment aidjex aircraft data for february 1976 the effective drag coefficient with the presence of even a small concentration of sea ice is greater than the oceanic value as shown by a 103cd of 2 2 calculated from noaa p 3 gust probe data over a 40 km track of 0 4 ice concentration in the outer miz of the greenland sea in june 1984 during mizex 84 the relation of surface wind and stress to the geostrophic wind for shallow inversion heights typical of high latitudes is reviewed with a turbulent closure atmospheric boundary layer model the winter arctic is typified by low inversions 100 m low geostrophic drag coefficients and large geostrophic surface wind turning angles with low functional dependence on surface roughness seasonal ice zones are typified by a more modest influence of the inversion on boundary layer characteristics

externally forced fluctuations in ocean temperature at greenland glaciers in non summer months the factors that control the submarine melt rate at greenland s glaciers are uncertain and largely inferred from brief summer surveys in the fjords where glaciers terminate continuous records of water properties and velocity for the months september to may from two large greenland fjords reveal strong variability on 3 to 10 day timescales as a result of pulses of water that are propagated from the shelf ocean

an asymmetric mode of tropical indian ocean rainfall variability in boreal spring 1 an analysis of observational estimates has revealed an asymmetric mode of boreal spring rainfall and wind variability over the tropical indian ocean the asymmetric mode is characterized by opposite rainfall and surface wind anomalies north and south of the equator this mode is associated with a cross equatorial gradient in sea surface temperature anomalies the evolution of this mode is related to air sea interactions in the tropical indian ocean in particular surface heat fluxes play an important role in the initiation development and decay of this mode the occurrence of this mode in observations is closely linked to both el nino southern oscillation enso and the indian ocean dipole mode coupled general circulation model experiments indicate that this mode can occur in the absence of enso the variability associated with this mode enhances enso s teleconnection to the indian ocean and affects the seasonal transition in the tropical indian ocean

greenland ice sheet mass balance reconstruction part iii marine ice loss and total mass balance 1840 2010 abstractgreenland ice sheet mass loss to the marine environment occurs by some combination of iceberg calving and underwater melting referred to here as marine ice loss lm this study quantifies the relation between lm and meltwater runoff r at the ice sheet scale a theoretical basis is presented explaining how variability in r can be expected to govern much of the lm variability over annual to decadal time scales it is found that r enhances lm through three processes 1 increased glacier discharge by ice warming softening and basal lubrication sliding 2 increased calving susceptibility through undercutting glacier front geometry and reducing ice integrity and 3 increased underwater melting from forcing marine convection applying a semiempirical lm f r parameterization to a surface mass balance reconstruction enables total ice sheet mass budget closure over the 1840 2010 period the estimated cumulative 171 yr net ice sheet sea level contribution is 25 10 mm the rise punctuated by periods