reconstructing mid late holocene cyclone variability in the central pacific using sedimentary records from tahaa french polynesia abstract we lack an understanding of the geographic and temporal controls on south pacific cyclone activity overwash records from backbarrier salt marshes and coastal ponds have been used to reconstruct tropical cyclone strikes in the north atlantic basin however these specific backbarrier environments are scarce in the south pacific with cyclone records limited primarily to the period of modern observation this instrumental record suggests a correlation with the el nino southern oscillation enso but longer records are necessary to test this relationship over geologic timescales and explore other potential climate drivers of tropical cyclone variability deep lagoons behind coral reefs are widespread in the pacific and provide an alternative setting for developing long term sedimentary reconstructions of tropical cyclone occurrence coarse grained event deposits within the sediments of a back reef lagoon surrounding tahaa reveal a 5000 year record of cyclone occurrences timing of recent high energy deposits matches well with observed tropical cyclone strikes and indicates coarse deposits are storm derived longer records show tropical cyclone activity was higher from 5000 to 3800 and 2900 to 500 yrs bp comparison to records from the north pacific out of phase and north atlantic in phase suggests a coordinated pattern of storm activity across tropical cyclone basins over the mid late holocene the changes in tropical cyclone activity we observe in the south pacific and across other basins may be related to enso as well as precession driven changes in ocean atmosphere thermal gradients

greenland flow variability from ice sheet wide velocity mapping using radarsat synthetic aperture radar data we have mapped the flow velocity over much of the greenland ice sheet for the winters of 2000 01 and 2005 06 these maps provide a detailed view of the ice sheet flow including that of the hundreds of glaciers draining the interior the focused patterns of flow at the coast suggest a strong influence of bedrock topography differences between our two maps confirm numerous early observations of accelerated outlet glacier flow as well as revealing previously unrecognized changes the overall pattern is one of speed up accompanied by terminus retreat but there are also several instances of surge behavior and a few cases of glacier slowdown comprehensive mappings such as these at regular intervals provide an important new observational capability for understanding ice sheet variability

recent changes in the pacific subtropical cells inferred from an eddy resolving ocean circulation model abstract in this study the subtropical cells stc in the pacific ocean are analyzed using an eddy resolving ocean general circulation model driven by atmospheric forcing for the years 1992 2003 in particular the authors seek to identify decadal changes in the stcs in the model and to compare them with observations in order to understand the consequences of such changes for the equatorial ocean heat and mass budgets the simulation shows a trend toward increasing pycnocline volume transport at 9 n and 9 s across the basin from 1992 to 2003 this increase 4 9 1 0 sv sv 106 m3 s 1 is in qualitative agreement with observations and is attributed primarily to changes in the interior ocean transport which are partially compensated by opposing western boundary transports the subtropical meridional volume transport convergence anomalies in the model pycnocline are found to be consistent with anomalous volume transports in both the observed and modeled equatorial undercurrent as well as with the magni

tropical cyclone genesis factors in simulations of the last glacial maximum abstractlarge scale environmental factors that favor tropical cyclogenesis are calculated and examined in simulations of the last glacial maximum lgm from the paleoclimate modelling intercomparison project phase 2 pmip2 despite universally colder conditions at the lgm values of tropical cyclone potential intensity which both serves as an upper bound on thermodynamically achievable intensity and indicates regions supportive of the deep convection required are broadly similar in magnitude to those in preindustrial era control simulation some regions including large areas of the central and western north pacific feature higher potential intensities at the lgm than they do in the control runs while other regions including much of the atlantic and indian oceans are lower changes in potential intensity are strongly correlated with the degree of surface cooling during the lgm additionally two thermodynamic parameters one that measures midtropospheric entropy deficits relevant for tropical cyclogen

global distribution of koppen geiger climate types during the last glacial maximum mid holocene and present abstract this research presents koppen geiger k g climate type maps of the last glacial maximum lgm of 21 000 years ago 21 ka the mid holocene mh of 6 ka and the present 1976 2005 data used to calculate and map the k g climate type are year monthly mean 2 m air temperature and precipitation from the national center for atmospheric research ncar community climate system model version 4 ccsm4 community atmosphere model version 4 cam4 as part of the coupled model intercomparison project phase 5 cmip5 results suggest that the model depicts similar modern climate distributions as in data based research excepting a larger distribution of tropical wet dry and humid subtropical types and a smaller distribution of hot arid and hot semi arid types the modeled modern k g climate types cover similar percentages of earth s terrestrial and marine surface as during the mh with slight enlargement of the tropical wet dry and decreased area of mesothermal monsoonal hot summer type in the modern period at the lgm the k g polar e climate was far more extensive than in modern times with concurrent decreases in area of the tropical a climates because koppen type classifications are intended to mimic the biome distributions these results may be helpful in identifying biotic realms from the geologic past and the potential vegetative response to future climate changes

multi decadal retreat of greenland s marine terminating glaciers many marine terminating glaciers draining the greenland ice sheet have retreated over the past decade yet the extent and magnitude of retreat relative to past variability is unknown we measure changes in front positions of 210 marine terminating glaciers using landsat imagery spanning nearly four decades and compare decadal scale rates of change with earlier observations we find that 90 of the observed glaciers retreated between 2000 and 2010 approaching 100 in the northwest with rapid retreat observed in all sectors of the ice sheet the current retreat is accelerating and likely began between 1992 and 2000 coincident with the onset of warming following glacier stability and minor advance during a mid century cooling period while it is clear an extensive retreat occurred in the early 20th century a period of increasing air temperatures a comparison of our results with historical observations provides evidence that the current retreat is more widespread the onset of rapid retreat with warming relative to the slow and lagged advance with cooling suggests an asymmetry in the response of marine fronts to external forcing

how deep argo will improve the deep ocean in an ocean reanalysis abstractglobal ocean sampling with autonomous floats going to 4000 6000 m known as the deep argo array constitutes one of the next challenges for tracking climate change the question here is how

the mode and timing of windward reef island accretion in relation with holocene sea level change a case study from takapoto atoll french polynesia abstract takapoto atoll northern tuamotu islands french polynesia central pacific was selected as a test area to clarify the conditions of atoll island accretion in relation to mid to late holocene sea level changes surveys were conducted along two distinct cross island profiles on the windward coast of the atoll in addition the stratigraphy of an ocean facing islet was described from an excavation in order to reconstruct the successive island accretionary stages at both sites the basement of the atoll rims consists of conglomerate pavements on which lie shingle ridges reaching 4 m in elevation stratigraphic analysis of the excavated ridge reveals alternation of gravelly sand supported to gravel dominated sediments the chronology of island accretion is based on dating of 41 u th surface and excavated coral specimens ridge initiation occurred from about 1000 yr bp when sea level was close to its present position shingle deposits progressively prograded from the lagoon margins oceanwards and were partially cemented at their bases cementation may have increased the resistance of the islets to erosion as a result some island lands accumulated and have persisted over the last millennium the modern gross island morphology was acquired during the last 500 years this model can be considered to be of regional value for the northern tuamotu islands adjusted for local thermal subsidence hydroisostasy and or lithospheric flexure compared to some other indo pacific reef islands island initiation at takapoto appears to be have been delayed by 2 to 4 millennia probably in response to retardation in the reef catching up with mid holocene sea level dating of individual coarse grained coral clasts allowed the major wave surge events that have hit takapoto to be identified for the last millennium the use of gravels results in the identification of a greater number of medium energy surge impacts when compared with megaclast based records the frequency of storm events identified is consistent with that derived from historical observations severe storms have a very low frequency of occurrence one to two events per century on average

assessing sedimentary records of paleohurricane activity using modeled hurricane climatology patterns of overwash deposition observed within back barrier sediment archives can indicate past changes in tropical cyclone activity however it is necessary to evaluate the significance of observed trends in the context of the full range of variability under modern climate conditions here we present a method for assessing the statistical significance of patterns observed within a sedimentary hurricane overwash reconstruction to alleviate restrictions associated with the limited number of historical hurricanes affecting a specific site we apply a recently published technique for generating a large number of synthetic storms using a coupled ocean atmosphere hurricane model set to simulate modern climatology thousands of overwash records are generated for a site using a random draw of these synthetic hurricanes a prescribed threshold for overwash and a specified temporal resolution based on sedimentation rates observed at a particular site as a test case we apply this monte carlo technique to a hurricane induced overwash reconstruction developed from laguna playa grande lpg a coastal lagoon located on the island of vieques puerto rico in the northeastern caribbean apparent overwash rates in the lpg overwash record are observed to be four times lower between 2500 and 1000 years b p when compared to apparent overwash rates during the last 300 years however probability distributions based on monte carlo simulations indicate that as much as 65 of this drop can be explained by a reduction in the temporal resolution for older sediments due to a decrease in sedimentation rates periods of no apparent overwash activity at lpg between 2500 and 3600 years b p and 500 1000 years b p are exceptionally long and are unlikely to occur above 99 confidence under the current climate conditions in addition breaks in activity are difficult to produce even when the hurricane model is forced to a constant el nino state results from this study continue to support the interpretation that the western north atlantic has exhibited significant changes in hurricane climatology over the last 5500 years

ice front variation and tidewater behavior on helheim and kangerdlugssuaq glaciers greenland we used satellite images to examine the calving behavior of helheim and kangerdlugssuaq glaciers greenland from 2001 to 2006 a period in which they retreated and sped up these data show that many large iceberg calving episodes coincided with teleseismically detected glacial earthquakes suggesting that calving related processes are the source of the seismicity for each of several events for which we have observations the ice front calved back to a large pre existing rift these rifts form where the ice has thinned to near flotation as the ice front retreats down the back side of a bathymetric high which agrees well with earlier theoretical predictions in addition to the recent retreat in a period of higher temperatures analysis of several images shows that helheim retreated in the 20th century during a warmer period and then re advanced during a subsequent cooler period this apparent sensitivity to warming suggests that higher temperatures may promote an initial retreat off a bathymetric high that is then sustained by tidewater dynamics as the ice front retreats into deeper water the cycle of frontal advance and retreat in less than a century indicates that tidewater glaciers in greenland can advance rapidly greenland s larger reservoir of inland ice and conditions that favor the formation of ice shelves likely contribute to the rapid rates of advance

the southwest pacific ocean circulation and climate experiment spice the southwest pacific ocean circulation and climate experiment spice is an international research program under the auspices of clivar the key objectives are to understand the southwest pacific ocean circulation and the south pacific convergence zone spcz dynamics as well as their influence on regional and basin scale climate patterns south pacific thermocline waters are transported in the westward flowing south equatorial current sec toward australia and papua new guinea on its way the sec encounters the numerous islands and straits of the southwest pacific and forms boundary currents and jets that eventually redistribute water to the equator and high latitudes the transit in the coral solomon and tasman seas is of great importance to the climate system because changes in either the temperature or the amount of water arriving at the equator have the capability to modulate the el nino southern oscillation while the southward transports influence the climate and biodiversity in the tasman sea after 7 years of substantial in situ oceanic observational and modeling efforts our understanding of the region has much improved we have a refined description of the spcz behavior boundary currents pathways and water mass transformation including the previously undocumented solomon sea the transports are large and vary substantially in a counter intuitive way with asymmetries and gating effects that depend on time scales this paper provides a review of recent advancements and discusses our current knowledge gaps and important emerging research directions

exploring typhoon variability over the mid to late holocene evidence of extreme coastal flooding from kamikoshiki japan sediment cores from two coastal lakes located on the island of kamikoshiki in southwestern japan lake namakoike and lake kaiike provide evidence for the response of a backbarrier beach system to episodic coastal inundation over the last 6400 years sub bottom seismic surveys exhibit acoustically laminated parallel to subparallel seismic reflectors intermittently truncated by erosional unconformities sediment cores collected from targeted depocenters in both lakes contain finely laminated organic mud interbedded with coarse grained units with depths of coarse deposits concurrent with prominent seismic reflectors the timing of the youngest deposit at kamikoshiki correlates to the most recently documented breach in the barrier during a typhoon in 1951 ad assuming that this modern deposit provides an analog for identifying past events paleo typhoons may be reconstructed from layers exhibiting an increase in grain size a break in fine scale stratigraphy and elevated sr concentrations

force perturbation analysis of recent thinning and acceleration of jakobshavn isbrae greenland observations between 1997 and 2001 of a 30 velocity increase and up to 60 m thinning of downstream parts of jakobshavn isbrae greenland immediately following calving of about 4 km of its 15 km floating ice tongue suggest that acceleration may have been initiated by the calving assuming that the force perturbation associated with such weakening is swiftly transmitted far up glacier i develop equations to estimate the perturbation initially the observed changes are consistent with the comparatively small perturbation associated with the calving thereafter it was probably sustained by thinning of the remaining ice tongue at rates of about 80 m a 1 otherwise the force perturbation would soon have been balanced by reduction in the hydrostatic driving force for longitudinal creep as the glacier thinned with velocities dropping to their former values the calculated force perturbation increases to a maximum about 10 km inland of the grounding line consistent with decreasing weight forces as the glacier thins over bedrock that slopes uphill seawards further inland it progressively decreases probably because marginal drag increased as the glacier accelerated both here and on the floating tongue marginal ice appears to have been softened by the influence of locally intense shear on ice temperature and or fabric more recent observations show continued acceleration and thinning and most of the remaining ice tongue calved away in april 2003 so thinning is likely to continue

the origin of the pacific equatorial 13 c water abstract examination of the vertical distributions of temperature salinity oxygen and nutrient salts in the thermostad of the equatorial 13 c water in the eastern pacific ocean indicates that local vertical mixing is unimportant in creating the thermostad and the characteristics of the 13 c water maps are presented that show the oceanwide distributions of depth geostrophic flow salinity oxygen phosphate silica and nitrate on the 160 cl t 1 isanosteric surface which nearly coincides with the core of the 13 c water the maps suggest that the original characteristics of the 13 c water are acquired in the surface and thermocline layers to the northeast of new zealand and in the tasman sea by winter convection and vertical mixing the acquired characteristics are advected to the thermostad in the eastern pacific via a long route starting from the source region the flow is first eastward in high latitudes and then returns westward in low latitudes around the anticyclonic subtropical gyre of the sout

seasonal speedup along the western flank of the greenland ice sheet it has been widely hypothesized that a warmer climate in greenland would increase the volume of lubricating surface meltwater reaching the ice bedrock interface accelerating ice flow and increasing mass loss we have assembled a data set that provides a synoptic scale view spanning ice sheet to outlet glacier flow with which to evaluate this hypothesis on the ice sheet these data reveal summer speedups 50 to 100 consistent with but somewhat larger than earlier observations the relative speedup of outlet glaciers however is far smaller 15 furthermore the dominant seasonal influence on jakobshavn isbrae s flow is the calving front s annual advance and retreat with other effects producing outlet glacier speedups an order of magnitude larger seasonal melt s influence on ice flow is likely confined to those regions dominated by ice sheet flow

meridional volume transport in the south pacific mean and sam related variability the large increase in upper ocean sampling during the past decade enables improved estimation of the mean meridional volume transport in the midlatitude south pacific and hence of the climatically important meridional overturning circulation transport is computed using argo float profile data for geostrophic shear and trajectory data for reference velocities at 1000 m for the period 2004 2012 the mean geostrophic transport across 32s is 20 6 6 0 sv in the top 2000 m of the ocean from west to east this includes the southward east australian current 23 3 2 9 sv its northward recirculation 16 3 3 6 sv the broad interior northward flow 18 4 4 1 sv and the net northward flow 9 2 2 2 sv in opposing currents in the eastern pacific the basin integrated geostrophic transport includes 7 3 0 9 sv of surface and thermocline waters 4 9 1 0 sv of subantarctic mode water and 4 9 1 4 sv of antarctic intermediate water interannual variability in volume transport across 32s in the south pacific shows a southern annual mode signature characterized by an increase during the positive phase of the southern annular mode and a decrease during the negative phase maximum amplitudes in geostrophic transport anomalies seen in the east australian current and east australian current recirculation are consistent with wind stress curl anomalies near the western boundary key points improved meridional volume transport in the south pacific using argo eac transport variability tied to the sam published 2014 this article is a u s government work and is in the public domain in the usa

the effect of vertical shear on tropical cyclone intensity change abstract the effect of vertical shear on tropical cyclone intensity change is usually explained in terms of ventilation where heat and moisture at upper levels are advected away from the low level circulation which inhibits development a simple two layer diagnostic balance model is used to provide an alternate explanation of the effect of shear when the upper layer wind in the vortex environment differs from that in the lower layer the potential vorticity pv pattern associated with the vortex circulation becomes tilted in the vertical the balanced mass field associated with the tilted pv pattern requires an increased midlevel temperature perturbation near the vortex center it is hypothesized that this midlevel warming reduces the convective activity and inhibits the storm development previous studies have shown that diabatic heating near the storm center acts to reduce the vertical tilt of the vortex circulation these studies have also shown that there is an adiabatic process that acts to redu

last millennium climate and its variability in ccsm4 abstractan overview of a simulation referred to as the last millennium lm simulation of the community climate system model version 4 ccsm4 is presented the ccsm4 lm simulation reproduces many large scale climate patterns suggested by historical and proxy data records with northern hemisphere nh and southern hemisphere sh surface temperatures cooling to the early 1800s common era by 0 5 c nh and 0 3 c sh followed by warming to the present high latitudes of both hemispheres show polar amplification of the cooling from the medieval climate anomaly mca to the little ice age lia associated with sea ice increases the lm simulation does not reproduce la nina like cooling in the eastern pacific ocean during the mca relative to the lia as has been suggested by proxy reconstructions still dry medieval conditions over the southwestern and central united states are simulated in agreement with proxy indicators for these regions strong global cooling is associated with large volcanic erup

lake sediment record of late holocene hurricane activities from coastal alabama coastal lake sediments contain a stratigraphically and chronologically distinct record of major hurricane strikes during late holocene time frederic a category 3 hurricane that struck the alabama coast on the gulf of mexico in 1979 left a distinct sand layer in the nearshore sediments of lake shelby as a result of storm tide overwash of beaches and dunes sediment cores taken from the center of lake shelby contain multiple sand layers suggesting that major hurricanes of category 4 or 5 intensity directly struck the alabama coast at ca 3 2 3 0 2 6 2 2 1 4 and 0 8 ka 14 c yr with an average recurrence interval of 600 yr the alabama coast is likely to be struck by a category 4 or 5 hurricane within the next century

volcanic forcing of climate over the past 1500 years an improved ice core based index for climate models 1 understanding natural causes of climate change is vital to evaluate the relative impacts of human pollution and land surface modification on climate we have investigated one of the most important natural causes of climate change volcanic eruptions by using 54 ice core records from both the arctic and antarctica our recently collected suite of ice core data more than double the number of cores ever used before reduces errors inherent in reconstructions based on a single or small number of cores which enables us to obtain much higher accuracy in both detection of events and quantification of the radiative effects we extracted volcanic deposition signals from each ice core record by applying a high pass loess filter to the time series and examining peaks that exceed twice the 31 year running median absolute deviation we then studied the spatial pattern of volcanic sulfate deposition on greenland and antarctica and combined this knowledge with a new understanding of stratospheric transport of volcanic aerosols to produce a forcing data set as a function of month latitude and altitude for the past 1500 years we estimated the uncertainties associated with the choice of volcanic signal extraction criteria ice core sulfate deposition to stratospheric loading calibration factor and the season for the eruptions without a recorded month we forced an energy balance climate model with this new volcanic forcing data set together with solar and anthropogenic forcing to simulate the large scale temperature response the results agree well with instrumental observations for the past 150 years and with proxy records for the entire period through better characterization of the natural causes of climate change this new data set will lead to improved prediction of anthropogenic impacts on climate the new data set of stratospheric sulfate injections from volcanic eruptions for the past 1500 years as a function of latitude altitude and month is available for download in a format suitable for forcing general circulation models of the climate system

reconstructing 7000 years of north atlantic hurricane variability using deep sea sediment cores from the western great bahama bank q1 enso show abrupt changes around 6000 yrs b p but most coastal sedimentary records do not span this time period establishing longer records is essential for understanding mid holocene patterns of storminess and their climatic drivers which will lead to better forecasting of how climate change over the next century may affect tropical cyclone frequency and intensity storms are thought to be an important mechanism for transporting coarse sediment from shallow carbonate platforms to the deep sea and bank edge sediments may offer an unexplored archive of long term hurricane activity here we develop this new approach reconstructing more than 7000 years of north atlantic hurricane variability using coarse grained deposits in sediment cores from the leeward margin of the great bahama bank high energy event layers within the resulting archive are 1 broadly correlated throughout an offbank transect of multi cores 2 closely matched with historic hurricane events and 3 synchronous with previous intervals of heightened north atlantic hurricane activity in overwash reconstructions from puerto rico and elsewhere in the bahamas lower storm frequency prior to 4400 yrs b p in our records suggests that precession and increased nh summer insolation may have greatly limited hurricane potential intensity outweighing weakened enso and a stronger west african monsoon factors thought to be favorable for hurricane development

last glacial maximum and holocene climate in ccsm3 abstract the climate sensitivity of the community climate system model version 3 ccsm3 is studied for two past climate forcings the last glacial maximum lgm and the mid holocene the lgm approximately 21 000 yr ago is a glacial period with large changes in the greenhouse gases sea level and ice sheets the mid holocene approximately 6000 yr ago occurred during the current interglacial with primary changes in the seasonal solar irradiance the lgm ccsm3 simulation has a global cooling of 4 5 c compared to preindustrial pi conditions with amplification of this cooling at high latitudes and over the continental ice sheets present at lgm tropical sea surface temperature sst cools by 1 7 c and tropical land temperature cools by 2 6 c on average simulations with the ccsm3 slab ocean model suggest that about half of the global cooling is explained by the reduced lgm concentration of atmospheric co2 50 of present day concentrations there is an increase in the antarctic circumpolar current an

interannual to decadal variations of tropical subtropical exchange in the pacific ocean boundary versus interior pycnocline transports abstract interannual to decadal variations of tropical subtropical mass exchange in the pacific ocean are investigated using a near global ocean general circulation model along with satellite observations of sea level and wind and a data assimilation product the analysis focuses on the variability of pycnocline transports through the western boundary and interior near 10 n and 10 s in contrast to time mean exchange where boundary and interior pycnocline transports are both equatorward the variations of boundary and interior pycnocline transports are found to be generally anticorrelated to each other moreover the variation of the boundary pycnocline transport is smaller than that of the interior again different from time mean exchange where the boundary transport at 10 n is substantially larger than that through the interior interannual variations of the boundary and interior transports are consistent with near surface geostrophic flow inferred from sea level data interior pycnocline flow into th

ice sheet grounding line dynamics steady states stability and hysteresis 1 the ice sheet ice shelf transition zone plays an important role in controlling marine ice sheet dynamics as it determines the rate at which ice flows out of the grounded part of the ice sheet together with accumulation this outflow is the main control on the mass balance of the grounded sheet in this paper we verify the results of a boundary layer theory for ice flux in the transition zone against numerical solutions that are able to resolve the transition zone very close agreement is obtained and grid refinement in the transition zone is identified as a critical component in obtaining reliable numerical results the boundary layer theory confirms that ice flux through the grounding line in a two dimensional sheet shelf system increases sharply with ice thickness at the grounding line this result is then applied to the large scale dynamics of a marine ice sheet our principal results are that 1 marine ice sheets do not exhibit neutral equilibrium but have well defined discrete equilibrium profiles 2 steady grounding lines cannot be stable on reverse bed slopes and 3 marine ice sheets with overdeepened beds can undergo hysteresis under variations in sea level accumulation rate basal slipperiness and ice viscosity this hysteretic behavior can in principle explain the retreat of the west antarctic ice sheet following the last glacial maximum and may play a role in the dynamics of heinrich events

palaeohurricane reconstructions from sedimentary archives along the gulf of mexico caribbean sea and western north atlantic ocean margins hurricanes annually threaten the atlantic ocean margins historical hurricane records are relatively short and palaeohurricane sedimentary archives provide a geological and climatic context that sheds light on future hurricane activity here we review palaeo trends in hurricane activity elucidated from sedimentary archives we discuss dating methods site selection and stat istics associated with previously published records these archives have been useful for under standing the long term evolution of coastal systems and the response of intense hurricane activity to climatic changes regional shifts in hurricane overwash on centennial to millennial timescales have been linked to various climatic modes of variability including el nino southern oscillation and the north atlantic oscillation but could also reflect regional scale controls on hurricane activity

jakobshavn glacier west greenland 30 years of spaceborne observations early 1960 s reconnaissance satellite images are compared to more recent image and map data in an inter annual and seasonal study of west central greenland margin fluctuations from 1962 to 1992 ice sheet margins to the north and south of jakobshavn glacier retreated despite a decline in average summer temperatures the retreat may be reversing along the southern flank of the ice stream where regional mass balance estimates are positive from 1950 to fluctuated 2 5 km around its annual mean position the total calving flux during the summer is more than six times that during winter we identified that summer melting and the break up of sea ice and icebergs in the fjord are important in controlling the rate of iceberg production if correct calving rates may be expected to increase should climate become warmer in the near future

is the tropical atmosphere conditionally unstable abstract we examine the mean and standard deviation of the bouyancy of lifted boundary layer parcels from a large sample of soundings from the western equatorial pacific the inclusion of condensate loading in the definition of buoyancy is emphasized as is the precise originating level of parcels in the subcloud layer we confirm the observation of betts that those parts of the tropical atmosphere experiencing deep convection are nearly neutral to adiabatic parcel ascent from the subcloud layer when adiabatic condensate loading is included in the definition of buoyancy parcels lifted from the top of the subcloud layer are more nearly neutral than those originating near the surface and atmospheres with higher levels of free convection lfcs are closer to neutral than those with low lfcs we explore possible reasons for these observations and discuss their implications for tropical meteorology

greenland ice sheet high elevation balance and peripheral thinning aircraft laser altimeter surveys over northern greenland in 1994 and 1999 have been coupled with previously reported data from southern greenland to analyze the recent mass balance of the greenland ice sheet above 2000 meters elevation the ice sheet is in balance on average but has some regions of local thickening or thinning thinning predominates at lower elevations with rates exceeding 1 meter per year close to the coast interpolation of our results between flight lines indicates a net loss of about 51 cubic kilometers of ice per year from the entire ice sheet sufficient to raise sea level by 0 13 millimeter per year approximately 7 of the observed rise

variations in tropical cyclone genesis factors in simulations of the holocene epoch the thermodynamic factors related to tropical cyclone genesis are examined in several simulations of the middle part of the holocene epoch when the precession of earth s orbit altered the seasonal distribution of solar radiation and in one transient simulation of the millennium preceding the industrial era the thermodynamicpropertiesmostcrucialforgenesisdisplayabroadstabilityacrossbothperiods althoughbothorbital variations during the mid holocene mh 6000 years ago 6ka and volcanic eruptions in the transient simulation have detectable effects it is shown that the distribution of top of the atmosphere radiation 6ka altered the northern hemisphere seasonal cycle of the potential intensity of tropical cyclones in addition to slightly increasing the difference between middle tropospheric and boundary layer entropy a parameter that has been related to the incubation period required for genesis the southern hemisphere which receives more solar radiation during its storm season today than it did 6ka displays slightly more favorable thermodynamic properties during the mh than in the preindustrial era control surface temperatures over the ocean in both hemispheres respond to radiation anomalies more slowly than those in upper levels altering the thermal stability volcanism produces a sharp but transient temperature response in the last millennium simulation that stronglyreducespotentialintensityduringthe seasonsimmediatelyfollowingamajor eruption here too the differential vertical temperature response is key temperatures in the lower and middle troposphere cool while those near the tropopause rise aside from these deviations there is no substantial variation in thermodynamic properties over the 1000 yr simulation

enso and short term variability of the south equatorial current entering the coral sea abstracthistorical section data extending to 1985 are used to estimate the interannual variability of transport entering the coral sea between new caledonia and the solomon islands typical magnitudes of this variability are 5 8 sv sv 106 m3 s 1 in the 0 400 m layer relative to 400 m and 8 12 sv in the 0 2000 m layer relative to 2000 m on a mean of close to 30 sv relative to 2000 m transport increases a few months after an el nino event and decreases following a la nina interannual transport variability is well simulated by a reduced gravity long rossby wave model vigorous westward propagating mesoscale eddies can yield substantial aliasing on individual ship or glider surveys since transport variability is surface intensified and well correlated with satellite derived surface geostrophic currents a simple index of south equatorial current transport based on satellite altimetry is developed

the global ocean imprint of enso 1 the enso related spatial patterns and global averages of ocean temperature salinity and steric height are estimated from over 7 years of argo data 2004 2011 substantial extratropical variability is seen in all variables in addition to familiar tropical enso signals surface layer 0 100 dbar and subsurface 100 500 dbar temperature variations are both important in determining steric height and sea surface height patterns for the two years prior to the 2009 el nino the upper 100 dbar of the ocean gained 3 3 1022 j yr 1 of heat while the 100 500 dbar layer lost a similar amount the enso related vertical redistribution of globally averaged heat content between surface and subsurface layers occurring throughout the record is due primarily to changes in the east west tilting of the equatorial pacific thermocline the large temperature changes in the individual layers mask the smaller vertically averaged temperature change in which the ocean loses heat when the surface layer is anomalously warm and gains heat when the surface layer is cool

a decadally resolved paleohurricane record archived in the late holocene sediments of a florida sinkhole article i nfo a 4500 year record of hurricane induced storm surges is developed from sediment cores collected from a coastal sinkhole near apalachee bay florida recent deposition of sand layers in the upper sediments of the pond was found to be contemporaneous with significant historic storm surges at the site modeled using slosh and the best track post 1851 a d dataset using the historic portion of the record for calibration paleohurricane deposits were identified by sand content and dated using radiocarbon based age models marine indicative foraminifera some originating at least 5 km offshore were present in several modern and ancient storm deposits the presence and long term preservation of offshore foraminifera suggest that this site and others like it may yield promising microfossil based paleohurricane reconstructions in the future due to the sub decadal 7 years resolution of the record and the site s high susceptibility to hurricane generated storm surges the average local frequency of recorded events approximately 3 9 storms per century is greater than that of previously published paleohurricane records from the region the high incidence of recorded events permitted a time series of local hurricane frequency during the last five millennia to be constructed variability in the frequency of the largest storm layers was found to be greater than what would likely occur by chance alone with intervals of both anomalously high and low storm frequency identified however the rate at which smaller layers were deposited was relatively constant over the last five millennia this may suggest that significant variability in hurricane frequency has occurred only in the highest magnitude events the frequency of high magnitude events peaked near 6 storms per century between 2800 and 2300 years ago high magnitude events were relatively rare with about 0 3 storms per century occurring between 1900 and 1600 years ago and between 400 and 150 years ago a marked decline in the number of large storm deposits which began around 600 years ago has persisted through present with below average frequency over the last 150 years when compared to the preceding five millennia

large fluctuations in speed on greenland s jakobshavn isbrae glacier it is important to understand recent changes in the velocity of greenland glaciers because the mass balance of the greenland ice sheet is partly determined by the flow rates of these outlets jakobshavn isbrae is greenland s largest outlet glacier draining about 6 5 per cent of the ice sheet area and it has been surveyed repeatedly since 1991 ref 2 here we use remote sensing data to measure the velocity of jakobshavn isbrae between 1992 and 2003 we detect large variability of the velocity over time including a slowing down from 6 700 m yr 1 in 1985 to 5 700 m yr 1 in 1992 and a subsequent speeding up to 9 400 m yr 1 by 2000 and 12 600 m yr 1 in 2003 these changes are consistent with earlier evidence for thickening of the glacier in the early 1990s and rapid thinning thereafter our observations indicate that fast flowing glaciers can significantly alter ice discharge at sub decadal timescales with at least a potential to respond rapidly to a changing climate

sverdrup and nonlinear dynamics of the pacific equatorial currents abstract the sverdrup circulation in the tropical pacific is constructed from satellite scatterometer winds compared with measured ocean currents and diagnosed in an ocean gcm previous depictions of the sverdrup circulation near the equator have shown only weak vertically integrated flows here it is shown that the actual transports are not weak this discrepancy could be due either to inaccuracies in the wind forcing or to sverdrup dynamics being too simple in this region scatterometer winds show a strip of positive curl along the sst front north of the equator in the eastern pacific that is due to wind speed changes induced by the front including that additional element of curl forcing greatly improves the realism of the sverdrup representation but the magnitudes of the equatorial transport are still too small by a factor of about 2 although the nonlinear advective and friction terms are small in the model momentum balance they are o 1 in the vorticity balance especially because their meridi

sand beach ridges record 6000 year history of extreme tropical cyclone activity in northeastern australia sand beach ridges are considered to be derived either from aeolian processes and or waves but their deposition by individual or multiple storms has not been investigated in any detail we use numerical meteorological and oceanographic models to determine the origin of a sequence of 29 shore parallel sand beach ridges in northeastern australia the results suggest that the ridges were constructed by waves and that the final form or height of the ridges is a function of high energy tropical cyclone generated waves plus storm tides hence these landforms archive a nearly 6000 year long history of intense tropical cyclones the record implies that these extreme tempests occur considerably more frequently than that suggested by the short historical record for this region the genesis of this sand beach ridge plain has implications for the interpretation of similar sequences elsewhere along the northeast coast of australia and in comparable environments globally if other similar sand beach ridge plains have also been deposited by like processes it stands to reason that these long term records of high intensity tropical cyclones can be used to ascertain a regional scale risk assessment from this hazard

mapping tide water glacier dynamics in east greenland using landsat data landsat multispectral scanner and thematic mapper images were co registered for the kangerdlugssuaq fjord region in east greenland and were used to map glacier drainage basin areas changes in the positions of tide water glacier termini and to estimate surface velocities of the larger tide water glaciers statistics were compiled to document distance and area changes to glacier termini the methodologies developed in this study are broadly applicable to the investigation of tide water glaciers in other areas the number of images available for consecutive years and the accuracy with which images are co registered are key factors that influence the degree to which regional glacier dynamics can be characterized using remotely sensed data three domains of glacier state were interpreted net increase in terminus area in the southern part of the study area net loss of terminus area for glaciers in upper kangerdlugssuaq fjord and a slight loss of glacier terminus area northward from ryberg fjord local increases in the concentrations of drifting icebergs in the fjords coincide with the observed extension of glacier termini positions ice surface velocity estimates were derived for several glaciers using automated image cross correlation techniques the velocity determined for kangerdlugssuaq gletscher is approximately 5 0 km a 1 and that for kong christian iv gletscher is 0 9 km a 1 the continuous presence of icebergs and brash ice in front of these glaciers indicates sustained rates of ice front calving

pacific ocean circulation rebounds 1 recent observations indicate that the shallow meridional overturning circulation in the tropical pacific ocean has rebounded since 1998 following 25 years of significantly weaker flow convergence of cold interior ocean pycnocline water towards the equator increased to 24 1 1 8 106 m3 s 1 during 1998 2003 from a low of 13 4 1 6 106 m3 s 1 during 1992 98 intensified circulation led to the development of anomalously cool tropical pacific sea surface temperatures which may have affected pacific marine ecosystems and global climate the abruptness of the rebound also obscures presumed anthropogenic warming trends in the instrumental temperature record of the tropical pacific

changes in ice front position on greenland s outlet glaciers from 1992 to 2007 1 previous studies in greenland show that retreat of tidewater glaciers may be linked to recent increases in ice loss raising greenland s contribution to sea level rise we examined ice front changes of 203 tidewater glaciers land terminating glaciers and glaciers terminating with ice shelves to understand greenland glacier behavior over three periods 1992 2000 2000 2006 and 2006 2007 we observed synchronous ice sheet wide increases in tidewater retreat during 2000 2006 relative to 1992 2000 coinciding with a 1 1 c increase in mean summer temperature at coastal weather stations rates of retreat for the southeast and east slowed during 2006 2007 when temperatures were slightly cooler than the 2000 2006 average our work suggests that regional greenland tidewater retreat responds strongly to climate change with higher temperatures corresponding to increasing retreat and helps confirm a link between ice thickness velocity and ice front position

rapid retreat and acceleration of helheim glacier east greenland 1 a significant amount of the measured coastal thinning of the greenland ice sheet may be due to recent acceleration of outlet glaciers using remote sensing we measured two major periods of speedup on helheim glacier between 2000 and 2005 that increased peak speeds from approximately 8 to 11 km yr these speedups coincided with rapid retreats of the calving front totaling over 7 5 km the glacier also thinned by over 40 m from 2001 to 2003 retreat of the ice front appears to decrease resistance to flow and concentrates the gravitational driving force over a smaller area farther up glacier acceleration may be a delayed response to surface draw down and steepening of the glacier s main trunk if the 2005 speedup also produces strong thinning then much of the glacier s main trunk may un ground leading to further retreat citation howat i m i joughin s tulaczyk and s gogineni 2005 rapid retreat and acceleration of helheim glacier east greenland geophys res lett 32 l22502 doi 10 1029 2005gl024737

holocene changes in eastern tropical pacific climate inferred from a galapagos lake sediment record abstract paleoclimate records from the tropical pacific suggest the early to mid holocene was a period of reduced el nino southern oscillation enso variability with a transition to modern increased enso frequency occurring some time in the last few thousand years however the nature and timing of this shift remains uncertain due to the discontinuous nature and or coarse resolution of many enso proxies as well as a lack of agreement between previously published records a new continuous climate record from el junco crater lake in the galapagos islands reveals several abrupt changes in lake level and precipitation through the holocene hydroclimatic model simulations suggest that el junco lake level responds sensitively to increases in precipitation associated with el nino events rising during wet el nino events and falling during the intervening dry periods grain size data from el junco sediment cores indicate past lake level variability likely associated with changing seasonal precipitation and enso frequency the grain size data suggest increased precipitation intensity prior to 9000 120 cal years bp and after 4200 130 cal years bp as well as a two step increase in precipitation at 3200 160 and 2000 100 cal years bp maximum holocene precipitation and inferred enso variability occurred between 2000 100 and 1500 70 cal years bp during the same period that six other independent proxy records suggest higher enso frequency and longer stronger el nino events decreasing sediment carbon nitrogen c n ratios in el junco sediments indicate rising lake levels from the early holocene to present corroborating the grain size data the inferred increase in precipitation at 4200 130 cal years bp and at 2000 100 cal years bp coincides with decreasing southwest asian and east asian monsoon intensity suggesting tropical pacific climate and the asian monsoon were interconnected systems at centennial to millennial timescales during the holocene a weakening trend in the asian monsoon and the trend toward wetter conditions at el junco also coincide with a trend toward cooler and drier conditions inferred from cariaco basin sediment proxies from the mid holocene to present suggesting the migration of the intertropical convergence zone itcz likely influenced hydrological changes in both the eastern tropical pacific and the asian monsoon region during the holocene

continued evolution of jakobshavn isbrae following its rapid speedup 1 several new data sets reveal that thinning and speedup of jakobshavn isbrae continue following its recent rapid increase in speed as its floating ice tongue disintegrated the present speedup rate of 5 a 1 over much of the fast moving region appears to be a diffusive response to the initial much larger speedup near the front there is strong seasonality in speed over much of the fast flowing main trunk that shows a good inverse correlation with the seasonally varying length of a short typically 6 km floating ice tongue this modulation of speed with ice front position supports the hypothesis that the major speedup was caused by loss of the larger floating ice tongue from 1998 to 2003 analysis of image time series suggests that the transient winter ice tongue is formed when sea ice bonds glacier ice in the fjord to produce a nearly rigid mass that almost entirely suppresses calving major calving only resumes in late winter when much of this ice clears from the fjord the collapse of the ice tongue in the late 1990s followed almost immediately after a sharp decline in winter sea ice concentration in disko bay this decline may have extended the length of the calving season for several consecutive years leading to the ice tongue s collapse

gliders measure western boundary current transport from the south pacific to the equator abstract spray gliders most launched from small boats near shore have established a sustainable time series of equatorward transport through the solomon sea the first 3 5 years mid 2007 through 2010 are analyzed coast to coast equatorward transport through the solomon sea fluctuates around a value of 15 sv 1 sv 106 m3 s 1 with variations approaching 15 sv transport variability is well correlated with el nino indices like nino 3 4 with strong equatorward flow during one el nino and weak flow during two la ninas mean transport is centered in an undercurrent focused in the western boundary current variability has a two layer structure with layers separated near 250 m near the core of the undercurrent that fluctuate independently the largest variations are in midbasin confined to the upper layer and are well correlated with enso analysis of velocity and salinity on isopycnals shows that the western boundary current within the solomon sea consists of a deep core coming from the coral sea

tropical pacific decadal variability and the subtropical tropical cells abstract the decadal scale variability in the tropical pacific has been analyzed herein by means of observations and numerical model simulations the two leading modes of the sea surface temperature sst variability in the central western pacific are a decadal mode with a period of about 10 yr and the enso mode with a dominant period of about 4 yr the sst anomaly pattern of the decadal mode is enso like the decadal mode however explains most variance in the western equatorial pacific and off the equator a simulation with an ocean general circulation model ogcm forced by reanalysis data is used to explore the origin of the decadal mode it is found that the variability of the shallow subtropical tropical overturning cells is an important factor in driving the decadal mode this is supported by results from a multicentury integration with a coupled ocean atmosphere general circulation model cgcm that realistically simulates tropical pacific decadal variability finally the sensitivity of the shal

suppression of el nino during the mid holocene by changes in the earth s orbit a number of recent reports have interpreted paleoproxy data to describe the state of the tropical pacific especially changes in the behavior of the el nino southern oscillation enso over the holocene these interpretations are often contradictory especially for the eastern tropical pacific and adjacent areas of south america here we suggest a picture of the mid holocene tropical pacific region which reconciles the data enso variability was present throughout the holocene but underwent a steady increase from the mid holocene to the present in the mid holocene extreme warm el nino events were smaller in amplitude and occurred less frequently about a mean climate state with a cold eastern equatorial pacific and largely arid coastal regions as in the present climate this picture emerges from an experiment in which a simple numerical model of the coupled ocean atmosphere system in the tropical pacific was driven by orbital forcing we suggest that the observed behavior of the tropical pacific climate over the mid to late holocene is largely the response to orbitally driven changes in the seasonal cycle of solar radiation in the tropics which dominates extratropical influences

consistent decrease in north atlantic tropical cyclone frequency following major volcanic eruptions in the last three centuries injection of sulphate aerosols into the stratosphere following major volcanic eruptions alters global climate through the absorption and scattering of solar radiation one proposed consequence is a decrease in north atlantic tropical cyclone tc activity as was observed following the el chichon 1982 and mount pinatubo 1991 eruptions we test this relationship using documentary and proxy reconstructions of major volcanic eruptions and tc frequency in the north atlantic basin over the last three centuries we find a consistent reduction in the number of tcs formed during the 3 years following major eruptions compared to the preceding 3 years including after eruptions located at northern high latitudes our findings suggest that low latitude eruptions reduce atlantic tc frequency by decreasing local sea surface temperatures whereas the mechanisms for the decrease in tc frequency following high latitude eruptions are less clear and attribution is hampered by poor identification of these events

tropical cyclone genesis factors in a simulation of the last two millennia results from the community earth system model abstractusing a coupled global climate model community earth system model cesm the authors investigate the response of tropical cyclone tc genesis factors i e potential intensity vertical wind shear midtropospheric moisture content and absolute vorticity to external forcings in the last two millennia l2m they then examine how the large scale conditions that favor tc activity varied using a genesis potential index gpi these large scale genesis factors generally exhibit no long term trend in the simulation of the l2m prior to the industrial revolution and the spread in the interannual variability lies within a small window the estimated tc activity is highly variable from region to region on multidecadal time scales conditions appear to be more favorable for tc genesis in the twentieth century in the northern hemisphere relative to earlier centuries of the l2m additionally conditions in this simulation are not more favorable for tc formation during the medieval climate anomaly ad 10

spatial patterns of mixing in the solomon sea the solomon sea is a marginal sea in the southwest pacific that connects subtropical and equatorial circulation constricting transport of south pacific subtropical mode water and antarctic intermediate water through its deep narrow channels marginal sea topography inhibits internal waves from propagating out and into the open ocean making these regions hot spots for energy dissipation and mixing data from two hydrographic cruises and from argo profiles are employed to indirectly infer mixing from observations for the first time in the solomon sea thorpe and finescale methods indirectly estimate the rate of dissipation of kinetic energy and indicate that it is maximum in the surface and thermocline layers and decreases by 2 3 orders of magnitude by 2000 m depth estimates of diapycnal diffusivity from the observations and a simple diffusive model agree in magnitude but have different depth structures likely reflecting the combined influence of both diapycnal mixing and isopycnal stirring spatial variability of is large spanning at least 2 orders of magnitude within isopycnal layers seasonal variability of reflects regional monsoonal changes in large scale oceanic and atmospheric conditions with increased in july and decreased in march finally tide power input and topographic roughness are well correlated with mean spatial patterns of mixing within intermediate and deep isopycnals but are not clearly correlated with thermocline mixing patterns

the mean and the time variability of the shallow meridional overturning circulation in the tropical south pacific ocean the meridional transport in the pacific ocean subtropical cell is studied for the period from 2004 to 2011 using gridded argo temperature and salinity profiles and atmospheric reanalysis surface winds the poleward ekman and equatorward geostrophic branches of the subtropical cell exhibit an el ni no southern oscillation signature with strong meridional transport occurring during la ni and weak meridional transport during el ni no at 7 58s mean basinwide geostrophictransportabove 1000 dbar is 48 56 2 5 sv sv 10 6 m 3 s 21 of which 30 3 38 4 sv return to the subtropics in the surface ekman layer whereas 10 2 18 3 sv flow northward feeding the indonesian throughflow geostrophic transport within the subtropical cell is stronger in the ocean interiorandweakerinthewesternboundaryduringlani theinteriordominatingbasinwide transport using atmospheric reanalyses only half of the mean heat gain by the pacific north of 7 58 si s compensated by oceanicheat transport outof theregion thenationaloceanography centreat southampton air sea flux climatology is more consistent for closing the oceanic heat budget in summary the use of argo data for studying the pacific subtropical cell provides an improved estimate of basinwide mean geostrophic transport includes both interior and western boundary contributions quantifies el ni ni transport variability and illustrates how the meridional overturning cell dominates ocean heat transport at 7 58s

on the pathways of the equatorial subsurface currents in the eastern equatorial pacific and their contributions to the peru chile undercurrent 1 theconnections between theequatorial currentsystem andtheperu currentsystem in the eastern tropical pacific etp are examined with a primitive equations eddy resolving regional model the quasi equilibrium solutions reproduce three eastward equatorial subsurface currents of interest the equatorial undercurrent euc located between 1 n and 1 s the primary southern subsurface countercurrent psscc between 3 and 4 s and farther south the secondary southern subsurface countercurrent ssscc between 7 and 8 s using a lagrangian tracking procedure the fate of these currents in the etp and their contribution to the peru chile undercurrent pcuc are studied lagrangian diagnostics show that for the most part the euc water contributes to westward flows including the south equatorial current and deeper flows below it and strikingly only a very little fraction feeds the pcuc while a significant part of both ssccs contribute substantially mesoscale eddies are shown to exert an effect on these connections in addition about 30 of the pcuc is fed by the three subsurface equatorial flows euc psscc ssscc the remaining part of the pcuc comes from an alongshore recirculation associated with flows below it and from the southern part of the domain south of 9 s

atlantic hurricane activity following two major volcanic eruptions 1 in 1982 and 1991 two major volcanic eruptions loaded the stratosphere with long lived sulfate aerosols altering the global climate by redistributing longwave and shortwave radiation at the surface and throughout the atmosphere cooling the surface and subsurface waters of the tropical oceans theory and observations demonstrate through direct and indirect mechanisms a causal relationship between tropical north atlantic sea surface temperatures and seasonal atlantic hurricane frequency duration and intensity therefore it is plausible that hurricane activity in the seasons immediately following these eruptions is diminished however to date such a theory remains untested here i use observations reanalysis data and output from a numerical model to suggest that the number duration and intensity of hurricanes in the years following the eruptions of el chichon 1982 and mount pinatubo 1991 decreased via the aerosol direct effect determining the effects of each eruption on seasonal cyclone activity is complicated by simultaneous positive enso events thus further study of the relationship between atlantic tropical cyclones and major volcanic eruptions is warranted

changes in tropical pacific thermocline depth and their relationship to enso after 1999 abstractthe characteristics of el nino southern oscillation enso variability have experienced notable changes since the late 1990s including a breakdown of the zonal mean upper ocean heat content as a precursor for enso these changes also initiated a debate on the role of thermocline variations on the development of enso events since the beginning of the twenty first century in this study the connection between thermocline variations and el nino and la nina events is examined separately for the 1980 98 and 1999 2012 periods the analysis highlights the important role of thermocline variations in modulating enso evolutions in both periods it is found that thermocline variation averaged in the central tropical pacific including both equatorial and off equatorial regions is a good precursor for enso evolutions before and after 1999 while the traditional basinwide mean of equatorial thermocline variation is a good precursor only before 1999 the new precursor including both high frequency variabili

2500 year paleotempestological record of intense storms for the northern gulf of mexico united states abstract the northern gulf of mexico has been devastated by recent intense storms camille 1969 and katrina 2005 are two notable hurricanes that made landfall in nearly the same location in mississippi fully understanding the risks and processes associated with hurricane impacts are impeded by a short and fragmented instrumental record however paleotempestology has the potential to employ modern analogues from intense storms in this region to extend the hurricane record beyond pre observational time existing empirically based models can back calculate surge heights over coastal systems as a function of transport distance particle settling velocity and gravitational acceleration we collected sediment cores in a pond 3 and adjacent beach 1 in hancock county mississippi grain size loss on ignition and microfossil analyses were conducted on cores in the context of a bayesian statistical age model using 137cs and 14c dating using hurricane camille to calibrate the archive similar coarse grained deposits were identified and inverse sediment transport models calculated paleosurge intensities similar in magnitude to camille over the 2500 yr record our multi millennial annual average landfall probability 0 48 closely matches previously published studies from the gulf of mexico indicating that intense hurricanes have not varied over these timescales over centennial timescales active intervals occurred between 900 to 600 and 2200 to 1900 yr bp with relative quiescence between 1900 to 900 yr bp comparisons with other published sites support the notion that southerly shifts in the loop current may be responsible for the decline in activity around 600 yr bp