the use of remote sensing and linear wave theory to model local wave energy around alphonse atoll seychelles abstract this paper demonstrates a practical step wise method for modelling wave energy at the landscape scale using gis and remote sensing techniques at alphonse atoll seychelles inputs are a map of the benthic surface seabed cover a detailed bathymetric model derived from remotely sensed compact airborne spectrographic imager casi data and information on regional wave heights incident energy at the reef crest around the atoll perimeter is calculated as a function of its deepwater value with wave parameters significant wave height and period hindcast in the offshore zone using the wavewatch iii application developed by the national oceanographic and atmospheric administration energy modifications are calculated at constant intervals as waves transform over the forereef platform along a series of reef profile transects running into the atoll centre factors for shoaling refraction and frictional attenuation are calculated at each interval for given changes in bathymetry and benthic coverage type and a nominal reduction in absolute energy is incorporated at the reef crest to account for wave breaking overall energy estimates are derived for a period of 5 years and related to spatial patterning of reef flat surface cover sand and seagrass patches

spectrally based remote sensing of river bathymetry this paper evaluates the potential for remote mapping of river bathymetry by 1 examining the theoretical basis of a simple ratio based technique for retrieving depth information from passive optical image data 2 performing radiative transfer simulations to quantify the effects of suspended sediment concentration bottom reflectance and water surface state 3 assessing the accuracy of spectrally based depth retrieval under field conditions via ground based reflectance measurements and 4 producing bathymetric maps for a pair of gravel bed rivers from hyperspectral image data consideration of the relative magnitudes of various radiance components allowed us to define the range of conditions under which spectrally based depth retrieval is appropriate the remotely sensed signal must be dominated by bottom reflected radiance we developed a simple algorithm called optimal band ratio analysis obra for identifying pairs of wavelengths for which this critical assumption is valid and which yield strong linear relationships between an image derived quantity x and flow depth d obra of simulated spectra indicated that water column optical properties were accounted for by a shorter wavelength numerator band sensitive to scattering by suspended sediment while depth information was provided by a longer wavelength denominator band subject to strong absorption by pure water field spectra suggested that bottom reflectance was fairly homogeneous isolating the effect of depth and that radiance measured above the water surface was primarily reflected from the bottom not the water column obra of these data 28 of which were collected during a period of high turbidity yielded strong x versus d relations r2 from 0 792 to 0 976 demonstrating that accurate depth retrieval is feasible under field conditions moreover application of obra to hyperspectral image data resulted in spatially coherent hydraulically reasonable bathymetric maps though negative depth estimates occurred along channel margins where pixels were mixed this study indicates that passive optical remote sensing could become a viable tool for measuring river bathymetry copyright 2009 john wiley sons ltd

vegetation change at the southern boreal forest margin in northeast china over the last millennium the role of permafrost dynamics abstract to better understand the nature and causes of boreal forest change and in particular the role of permafrost dynamics we reconstruct the recent vegetation history of the greater hingan mountains of northeast china based on a lake sediment core this core is located in an area of boreal forest underlain by permafrost and spans a 1000 year warming to cooling cycle palynological assemblages indicate that throughout most of its history vegetation was characterized by changes in the relative proportions of taxa including the cold resistant boreal conifer species larix and pinus and warmth adapted temperate broadleaf shrub species corylus and rhododendron corresponding to variations in temperature however after 1950 ce rapid warming led to the breakdown of this relationship between vegetation and climate and the proportion of conifers increased in the short term most likely due to permafrost thawing this effect was most pronounced in lowland areas whose frost table depth was initially 20 cm closer to the surface than the corresponding frost table on mountain slopes the increase in frost table depth due to warmer temperatures provided greater root space for shallow rooted conifers in lowlands as well as meltwater from thawing permafrost we speculate that the coupled system of vegetation climate and permafrost was stable before 1950 ce however most recently there has been a transition due to warming induced permafrost thawing as the southern boundary of permafrost moves poleward it is suspected that lowland rather than slope sites will witness the sharpest vegetation shifts

a bathymetry mapping approach combining log ratio and semianalytical models using four band multispectral imagery without ground data four band multispectral remote sensing imagery is widely used for a variety of purposes and has a long historical data record however most of the existing bathymetry inversion methods are either unable to determine the optimal solution through theoretical or semianalytical models due to the limited number of bands or their application is limited by the difficulty in obtaining in situ data in this article a log ratio model and a semianalytical model are combined to develop a new shallow water depth inversion method l s model using four band multispectral remote sensing images without the need for supporting truth data a case study was conducted for ganquan island in the south china sea using four band multispectral imagery from the geoeye 1 worldview 2 four bands selected sentinel 2 four bands selected and gaofen 1 satellites a sound range of 30 m was achieved when compared to lidar measured water depth data geoeye 1 worldview 2 sentinel 2 and gaofen 1 data have root mean square errors rmses of 1 33 1 97 m in addition compared with the results of the log ratio model trained using 200 lidar based depth readings the l s model results obtained for the four satellite types are similar in the rmse these results show that the l s model can achieve results that are close to those of the log ratio model without the need for external inputs this provides a feasible new method for bathymetry inversion in areas without truth data using only four band imagery

tracing the mobility of individuals using stable isotope signatures in biological tissues locals and non locals in an ancient case of violent death from central california abstract stable isotope analyses of biological tissues that grow during different phases of life can be used to trace the geographic location of individuals during different windows of time we apply this principle and reexamine three prehistoric skeletons excavated in 1964 from archaeological site ca yol 117 in central california field evidence suggests they were killed as part of a single violent event we report new radiocarbon dates and strontium oxygen carbon and nitrogen isotopic data from first molars third molars and bone to examine circumstances surrounding their death data suggest two of the three individuals were born and all three lived their teenage years near the site they were buried in however as adults they lived elsewhere likely to the north along the sacramento river around ad 1450 upon returning to the territory of their childhood years they were killed and placed in a mass grave the data invite a more nuanced interpretation of how we view local and non local individuals archaeologically overall the analysis provides an interesting glimpse into the nature of warfare and violence among pre contact hunter gatherers of northern california

holocene paleoceanography of the northwest passage canadian arctic archipelago abstract a series of cores box and piston were collected at 2 key locations in lancaster sound cores 2004 804 009 bc and pc and barrow strait cores 2005 804 004 bc and pc in the canadian arctic archipelago to document the evolution of sea surface conditions in the main axis of the northwest passage during the holocene time period reconstruction of sea surface parameters summer temperature and salinity duration of sea ice cover were estimated based on transfer functions using dinoflagellate cyst assemblages as proxy indicators the chronology of these cores is based on calibrated ams 14c dates 210pb analyses and correlations between paleomagnetic secular variations of the geomagnetic field and a predicted spherical harmonic model of the geomagnetic field cals7 k 2 our age models for both cores indicate that 009 pc spans the last 11 100 cal bp while 004 pc encompasses the last 10 800 cal bp calculated sedimentation rates are in the range of 43 140 cm kyr for core 009 pc and 15 118 cm kyr for core 004 pc allowing for a millennial time scale resolution in each core our results indicate relatively harsh conditions in lancaster sound between 10 800 and 9000 cal bp summer temperatures 2 c cooler than at present which we associate with the presence of active ice streams in northernmost baffin bay and a weak west greenland current this is followed by a warming trend up to 3 c higher than present that took place between 8500 and 5500 cal bp which we associate with the holocene thermal maximum and to a large scale atmospheric pattern such as the arctic oscillation operating at the millennial time scale this is concomitant with an increase in the relative abundance of phototrophic dinoflagellate cyst taxa a gradual cooling of sea surface temperature and increased sea ice follow this from 5500 cal bp until the modern period in barrow strait harsh sea surface conditions prevailed from 11 100 to 5500 cal bp with summer temperatures as low as 4 c cooler than at present the warming trend occurred later in this region between 5500 and 1000 cal bp after which a gradual cooling is observed until the modern period the apparent shift or opposite warming trends between lancaster sound and barrow strait after 5500 cal bp could be the result of a change in atmospheric circulation patterns related to a possible shift in the ao mode from ao to ao comparison of ice core 18o record from devon island ice cap and the reconstructed sea surface temperature from core 009 pc suggests a strong atmospheric oceanic coupling throughout the holocene in this area

geochemical tracers of sediment sources to san francisco bay river inflow and suspended sediment flux to san francisco bay are dominated by the sacramento and san joaquin river systems suspended sediments collected from rivers within the sacramento and san joaquin drainage basinsshow distinct chemical and sr isotope signatures reflecting their distinct bedrock lithologies concentrations of sm nd k and rb and 8 7 sr 8 6 sr ratios in suspended sediments increase from north to south in sierra nevada rivers and are significantly higher in the san joaquin drainage than in the sacramento drainage we show that variations in the geochemistry of fine grained detrital sediments cored beneath the bay can be used to assess the relative contributions of suspended sediment and inflow from these two major drainages in california for the sampled intervals over the past 1850 yr the proportion of suspended sediment from the sacramento drainage relative to the san joaquin drainage ranged between 5 and 85 average value of 55 compared with a modern value of 91 the current predominance of sediment entering san francisco bay from the sacramento drainage may be the result of greater trapping of sediments by reservoirs within the san joaquin drainage basin changes in the relative proportion of sediment from the sacramento and san joaquin drainages may reflect changes in the position of the storm track over california

paleoecology of a 90 000 year lacustrine sequence from fog lake baffin island arctic canada a 137 cm sediment core from fog lake a small upland basin that was not glaciated during the late wisconsinan reveals the following stratigraphic succession i basal diamicton ii laminated silts iii compacted dewatered gyttja iv stratified minerogenic sediments and v overlying gyttja units i iii and most of unit iv were deposited prior to the holocene unit v represents approximately the last 8000 14c years alternate luminescence dating techniques tl and irsl place unit iii in latter oxygen isotope stage ois 5 74 000 years bp a suite of 20 ams 14c dates suggests that much of the post ois 5 paleoenvironmental record is characterized by either extremely low continuous sediment accumulation or by one or more episodes of more rapid sedimentation diverse pollen and spore assemblages have concentrations that are unexpectedly high throughout the pre holocene sediments 10 000 grains cm 3 by comparison to the holocene 5000 grains cm 3 exceedingly low sediment accumulation rates appear to have resulted in the concentration of atmospherically derived pollen and spores diatom assemblages record the evolution of the lake s chemistry and past algal production several abrupt changes occurred synchronously in both the terrestrial and aquatic components of the system and these appear to represent ecological responses to pre holocene climatic variability the sediments of fog lake provide the first integrated paleoecological record older than holocene for a vast region of the canadian arctic thereby refining our understanding of long term arctic ecosystem ontogeny 2000 elsevier science ltd all rights reserved

strontium isotopes as tracers of ecosystem processes theory and methods abstract the strontium sr isotope method can be a powerful tool in studies of chemical weathering and soil genesis cation provenance and mobility and the chronostratigraphic correlation of marine sediments it is a sensitive geochemical tracer applicable to large scale ecosystem studies as well as to centimeter scaled examination of cation mobility within a soil profile the 87sr 86sr ratios of natural materials reflect the sources of strontium available during their formation isotopically distinct inputs from precipitation dryfall soil parent material and surface or groundwater allow determination of the relative proportions of those materials entering or leaving an ecosystem the isotopic compositions of labile soil exchange complex and soil solution strontium and sr in vegetation reflect the sources of cations available to plants strontium isotopes can be used to track the biogeochemical cycling of nutrient cations such as calcium the extent of cation contributions from in situ weathering and external additions to soil from dust and rain can also be resolved with this method in this paper we review the geochemistry and isotopic systematics of strontium and discuss the use of this method as a tracer of earth surface processes

multispectral bathymetry using a simple physically based algorithm a simple method for estimating water depths from multispectral imagery is described and is applied to several ikonos data sets for which independent measurements of the water depth are available the methodology is based on a physical model for the shallow water reflectance and is capable of correcting for at least some range of water quality and bottom reflectance variations corrections for sun glint effects are applied prior to the application of the bathymetry algorithm the accuracy of the depth algorithm is determined by comparison with ground truth measurements and comparisons between the observed and calculated radiances are presented for one case to illustrate how the algorithm corrects for water attenuation and or bottom reflectance variations

archaeological perspectives on the effects of medieval drought in prehistoric california abstract inspired by stine s 1994 extreme and persistent drought in california and patagonia during mediaeval time nature 369 546 549 findings from mono lake and graumlich s 1993 a 1000 year record of temperature and precipitation in the sierra nevada quaternary research 39 249 255 tree ring study from the southern sierra nevada california archaeologists have for over a decade been investigating the possibility that prehistoric societies were noticeably impacted by severe droughts during the medieval climatic anomaly mca cal a d 800 1350 decreased production at obsidian sources dramatic increases in bead production trade and sociopolitical complexity in the channel islands and subsistence changes on the central coast were among the trends attributed to drought related demographic stress by researchers in the 1990s review of more recent archaeological research shows that as the search for signs of unusual cultural changes during the mca has broadened some of these early patterns e g violence and health problems have been found to be more complicated and regionally varied than previously thought while others e g settlement disruption deterioration of long distance trade and population movements have been further corroborated

multiproxy paleoecological evidence of holocene climatic changes on the boothia peninsula canadian arctic a study of chironomid remains in the sediments of lake jr01 on the boothia peninsula in the central canadian arctic provides a high resolution record of mean july air temperatures for the last 6 9 ka diatom and pollen studies have previously been published from this core peak holocene temperatures occurred prior to 5 0 ka a time when overall aquatic and terrestrial biological production was high chironomid inferred summer air temperatures reached up to 7 5 c during this period the region of lake jr01 cooled over the mid to late holocene with high biological production between 6 1 and 5 4 ka biological production decreased again at 2 ka and the rate of cooling increased in the past 2 ka with coolest temperatures occurring between 0 46 and 0 36 ka coinciding with the little ice age although biological production increased in the last 150 yr the reconstructed temperatures do not indicate a warming during this time during transitions either warming or cooling chironomid production increases suggesting an ecosystem level response to climate variability seen at a number of lakes across the arctic

brackish water foraging isotopic landscapes and dietary reconstruction in suisun marsh central california while bone stable isotope signatures of humans foraging in open coastal and fully terrestrial environments have been relatively well documented the signature of foraging near brackish water estuaries is less well known this study examines the central california isotopic landscape or isoscape showing how foods in different ecosystems have distinctive isotopic compositions we present new bone collagen and apatite stable isotope data from two late holocene sites ca sol 11 and ca sol 69 near suisun marsh a low salinity brackish water estuary upstream from san francisco bay faunal remains at the sites include significant numbers of aquatic resources including fish and shellfish in addition to terrestrial mammals while paleobotanical remains suggest mainly terrestrial nuts and seeds stable isotope data at the population level corroborate this finding and show consumption of significant levels of brackish water nutrients including both dietary protein and dietary carbohydrates and fats paired with terrestrial foods this dietary focus generates a unique brackish water isotopic signature that is distinct from others in central california the documentation of an isoscape with strong regional gradients can be of tremendous help in reconstructing ancient patterns in subsistence migration and trade

mid to late holocene hydroclimatic and geochemical records from the varved sediments of east lake cape bounty canadian high arctic abstract a long sedimentary sequence from east lake cape bounty melville island 74 55 n 109 30 w contains a 4200 year long clastic varved record of paleohydrologic variations at high resolution sedimentary elemental geochemistry from micro x ray fluorescence xrf and sediment fabric variability reflect changes in sediment sources and lacustrine conditions through time the sedimentary environment progressed from marine in the mid holocene to estuarian from 2195 bc to 243 ad to fully lacustrine source after 244 ad correlation with local meteorological data indicates that varve thickness vt is positively correlated with snow depth on may 1st and negatively correlated with mean sept may temperatures our paleoclimatic reconstruction from vt series revealed high snow accumulation and warm sept may months before 1350 bc and a period of low snow accumulation and cold sept may between 1600 1900 ad that may correspond to the little ice age the general trends of vt series from cape bounty are in phase with the 18o series in agassiz ice cap and in anti phase with the vt series from lower murray lake in the northeastern of queen s elizabeth islands qei low mean arctic temperatures coincide with clusters of high sediment yield events at east nicolay and south sawtooth lakes especially during 1600 1750 ad and 1810 1910 ad the east lake record also exhibits the signature of the atlantic multidecadal oscillation amo for periods 600 850 ad 1400 1550 ad and 1750 1850 ad

salmon origin in california s sacramento san joaquin river system as determined by otolith strontium isotopic composition geochemical methods for distinguishing salmon of different runs would improve management practices designed to mitigate for declines in salmon populations in california9s sacramento san joaquin river system strontium isotopic measurements show a strong relationship between the 87 sr 86 sr ratio in hatchery water and the 87 sr 86 sr ratio in the otoliths aragonitic ear bones of juvenile chinook salmon oncorhynchus tshawytscha raised in those waters as a result of differences in basin geology from north to south along the western slope of the sierra nevada important salmon spawning rivers within the sacramento san joaquin river system have distinct 87 sr 86 sr ratios of the 10 rivers in this study those in the sacramento river drainage have lower 87 sr 86 sr ratios 0 7039 0 7063 than those in the san joaquin river basin 0 7068 0 7092 with the exception of the american river which has the highest 87 sr 86 sr ratios in this study average 0 7100 the combination of distinct river 87 sr 86 sr ratios and the relationship between water and otolith sr isotope ratios indicates that this geochemical method can be used to identify the origin and potentially the migration history of juvenile out migrating salmon in the sacramento san joaquin system

field measurements of intertidal bar evolution on a high energy beach system nearshore bars play a pivotal role in coastal behaviour helping to protect and restore beach systems particularly in post storm conditions examination of bar behaviour under various forcing conditions is important to help understand the short to medium term evolution of sandy beach systems this study carried out over a nine week period examines the behaviour of three intertidal bars along a high energy sandy beach system in northwest ireland using high frequency topographic surveys and detailed nearshore hydrodynamic modelling results show that in general there was onshore migration for all the bars during the study period despite the variability observed between bars which was driven mostly by wave dominated processes under the prevailing conditions migration rates of up to 1 83 m day 1 and as low as 0 07 m day 1 were observed during higher wave energy events the migration rates of the bars decelerated in their onshore route however under lower wave energy conditions they quickly accelerated maintaining their shoreward migration direction tidal influence appears to be subordinate in these conditions being restricted to moderating the localized wave energy at low tides and in maintaining runnel configurations providing accommodation space for advancing slip faces the study highlights the intricate behavioural patterns of intertidal bar behaviour along a high energy sandy coastline and provides new insights into the relative importance of wave and tidal forcing on bar behaviour over a relatively short time period copyright 2016 john wiley sons ltd

modelling storm impacts on beaches dunes and barrier islands a new nearshore numerical model approach to assess the natural coastal response during time varying storm and hurricane conditions including dune erosion overwash and breaching is validated with a series of analytical laboratory and field test cases innovations include a non stationary wave driver with directional spreading to account for wave group generated surf and swash motions and an avalanching mechanism providing a smooth and robust solution for slumping of sand during dune erosion the model performs well in different situations including dune erosion overwash and breaching with specific emphasis on swash dynamics avalanching and 2dh effects these situations are all modelled using a standard set of parameter settings the results show the importance of infragravity waves in extending the reach of the resolved processes to the dune front the simple approach to account for slumping of the dune face by avalanching makes the model easily applicable in two dimensions and applying the same settings good results are obtained both for dune erosion and breaching

post glacial climatic change on boothia peninsula nunavut canada abstract a high temporal resolution pollen diagram from a lake in the mid arctic region of the boothia peninsula nunavut canada documents the history of the regional vegetation and climate for the past 7200 yr major tundra pollen taxa in the core include cyperaceae and salix with cyperaceae comprising over 50 of the pollen in the early and late holocene tree pollen transported from far to the south comprised a large percentage of the pollen sum with pinus accounting for 30 of the pollen in some levels of the core pollen percentages and concentrations of taxa typical of the mid arctic were highest in the mid holocene corresponding to warm conditions decreasing pollen concentrations indicate cooling temperatures with more rapid decreases occurring around 4200 3800 3400 and 2500 cal yr bp pollen percentages of salix cyperaceae and artemisia increased in the past 35 yr in response to global warming reconstructions of july temperature using the modern analog technique showed that the mid holocene 5800 2800 cal yr bp was approximately 1 c higher than during the past 1000 yr

retrieval of nearshore bathymetry from landsat 8 images a tool for coastal monitoring in shallow waters abstract nearshore bathymetry is likely to be the coastal variable that most limits the investigation of coastal processes and the accuracy of numerical models in coastal areas as acquiring medium spatial resolution data in the nearshore is highly demanding and costly as such the ability to derive bathymetry using remote sensing techniques is a topic of increasing interest in coastal monitoring and research this contribution focuses on the application of the linear transform algorithm to obtain satellite derived bathymetry sdb maps of the nearshore at medium resolution 30 m from freely available and easily accessible landsat 8 imagery the algorithm was tuned with available bathymetric light detection and ranging lidar data for a 60 km long nearshore stretch of a highly complex coastal system that includes barrier islands exposed sandy beaches and tidal inlets ria formosa portugal a comparison of the retrieved depths is presented enabling the configuration of nearshore profiles and extracted isobaths to be explored and compared with traditional topographic bathymetric techniques e g high and medium resolution lidar data and survey grade echo sounding combined with high precision positioning systems the results demonstrate that the linear algorithm is efficient for retrieving bathymetry from multi spectral satellite data for shallow water depths 0 to 12 m showing a mean bias of 0 2 m a median difference of 0 1 m and a root mean square error of 0 89 m accuracy is shown to be depth dependent an inherent limitation of passive optical detection systems accuracy further decreases in areas where turbidity is likely to be higher such as locations adjacent to tidal inlets the sdb maps provide reliable estimations of the shoreline position and of nearshore isobaths for different cases along the complex coastline analysed the use of freely available satellite imagery proved to be a quick and reliable method for acquiring updated medium resolution high frequency days and weeks low cost bathymetric information for large areas and depths of up to 12 m in clear waters without wave breaking allowing almost constant monitoring of the submerged beach and the shoreface

holocene climate history of geographical society o east greenland evidence from lake sediments abstract sediment cores from two lakes in the outer coastal region of east greenland were investigated for chronology lithology palynology and biogeochemistry a 10 m long sequence recovered in basaltso comprises the entire lake history following the last glaciation of the area probably during the preboreal oscillation this is indicated by a succession from glacial via glaciolimnic to limnic sediments deglaciation of the area was associated with a high sedimentation rate mirrored also in the basal part of a 2 6 m long core from a smaller lake b1 about 1 km south of basaltso limnic sedimentation without glacial influence commenced about 10 000 cal yr bp according to radiocarbon dated terrestrial plant remains biogeochemical and palynological data indicate an early holocene climatic optimum from 9000 to 6500 cal yr bp a climatic deterioration began at 6500 cal yr bp with an increase in snow accumulation documented by a change in the pollen assemblage and a coinciding change in the grain size distribution at least since 5000 cal yr bp a decrease in the biogeochemical parameters in both lake sediment successions indicates a temperature decline this deterioration culminated at about 3000 1000 cal yr bp when the climate was cold and dry a slight warming is indicated in the pollen assemblage between ca 1000 and 800 cal yr bp following a subsequent rise in precipitation cooling during the little ice age is mirrored in lowest dwarf shrub pollen percentages and in low contents of organic components

watershed scale reconstruction of middle and late holocene paleoenvironmental changes on melville peninsula nunavut canada abstract arctic regions have heightened sensitivity to climatic changes however regional scale differences exist in the magnitude and timing of biotic responses melville peninsula in the east central canadian arctic is a transitional area with respect to modern climate with a continental climate to the west and more maritime influences to the east this and the presence of thule archaeological sites make the peninsula an area of high importance for paleoclimate reconstructions lake sediment cores from two adjacent ultra oligotrophic and very dilute lakes sp02 and sp04 from interior melville peninsula 68 33 n and 83 17 w 220 m a s l were analyzed for diatom assemblages microscopic algae to track paleoclimatic changes high magnetic susceptibility coarse grained sediments low organic matter and lack of diatoms in sediments older than 6000 years bp confirm earlier suggestions of a persistent ice cap on the peninsula peak diatom concentration and biogenic silica and maximum values for sediment organic matter between 4400 and 2900 years bp may indicate the holocene thermal maximum htm the timing of the htm is similar to that of the baffin region to the east decreases in these proxies as well as small shifts in diatom assemblages following 2900 years bp indicate the advancement of neoglacial cooling the changes of the pre industrial portion of the last millennium were of smaller magnitude than those of the htm but subtle changes in diatom assemblages after 750 years bp may be indicative of the little ice age the timing of which agrees well with that of boothia peninsula to the west the anthropocene is well marked in these records with increases in diatom species richness from a pre industrial maximum of 28 51 diatom species in the modern assemblage at lake sp02 planktonic diatoms appear in the 20th century signalling profound ecological changes associated with longer ice free seasons

holocene climate change in arctic canada and greenland abstract this synthesis paper summarizes published proxy climate evidence showing the spatial and temporal pattern of climate change through the holocene in arctic canada and greenland our synthesis includes 47 records from a recently published database of highly resolved holocene paleoclimate time series from the arctic sundqvist et al 2014 we analyze the temperature histories represented by the database and compare them with paleoclimate and environmental information from 54 additional published records mostly from datasets that did not fit the selection criteria for the arctic holocene database combined we review evidence from a variety of proxy archives including glaciers ice cores and glacial geomorphology lake sediments peat sequences and coastal and deep marine sediments the temperature sensitive records indicate more consistent and earlier holocene warmth in the north and east and a more diffuse and later holocene thermal maximum in the south and west principal components analysis reveals two dominant holocene trends one with early holocene warmth followed by cooling in the middle holocene the other with a broader period of warmth in the middle holocene followed by cooling in the late holocene the temperature decrease from the warmest to the coolest portions of the holocene is 3 0 1 0 c on average n 11 sites the greenland ice sheet retracted to its minimum extent between 5 and 3 ka consistent with many sites from around greenland depicting a switch from warm to cool conditions around that time the spatial pattern of temperature change through the holocene was likely driven by the decrease in northern latitude summer insolation through the holocene the varied influence of waning ice sheets in the early holocene and the variable influx of atlantic water into the study region

late holocene δ13c and pollen records of paleosalinity from tidal marshes in the san francisco bay estuary california abstract records of stable carbon isotopes 13c are presented from cores collected from four san francisco bay marshes and used as a proxy for changes in estuary salinity the 13c value of organic marsh sediments are a reflection of the relative proportion of c3 vs c4 plants occupying the surface and can thus be used as a proxy for vegetation change on the marsh surface the four marshes included in this study are located along a natural salinity gradient that exists in the san francisco bay and records of vegetation change at all four sites can be used to infer changes in overall estuary paleosalinity the 13c values complement pollen data from the same marsh sites producing a paleoclimate record for the late holocene period in the san francisco bay estuary the data indicate that there have been periods of higher than average salinity in the bay estuary reduced fresh water inflow including 1600 1300 cal yr b p 1000 800 cal yr b p 300 200 cal yr b p and ca a d 1950 to the present periods of lower than average salinity increased fresh water inflow occurred before 2000 cal yr b p from 1300 to 1200 cal yr b p and ca 150 cal yr b p to a d 1950 a comparison of the timing of these events with records from the california coast watershed and beyond the larger drainage of the bay reveals that the paleosalinity variations reflected regional precipitation

carbon isotope diatom and pollen evidence for late holocene salinity change in a brackish marsh in the san francisco estuary analysis of diatoms pollen and the carbon isotopic composition of a sediment core from a brackish marsh in the northern part of the san francisco estuary has provided a paleosalinity record that covers the past 3000 yr changes in marsh composition and diatom frequencies are assumed to represent variations in freshwater inflow to the estuary three periods of relatively high salinity low freshwater inflow are indicated 3000 to 2500 cal yr b p 1700 to 730 cal yr b p and ca a d 1930 to the present the most recent period of high salinity is primarily due to upstream storage and water diversion within the sacramento san joaquin watershed although drought may also have been a factor the two earlier high salinity periods are likely the result of reduced precipitation low salinity high freshwater flow is indicated for the period 750 cal yr b p to a d 1930 c 2001 university of washington

diatom community response to multiple scales of holocene climate variability in a small lake on victoria island nwt canada abstract a lake sediment core spanning 9900 years collected from a small lake on western victoria island nwt canada provides a high resolution record of diatom community dynamics over the holocene ten radiocarbon dates and 210 pb dating provided the core chronology loss on ignition loi magnetic susceptibility biogenic silica content and diatom concentrations provided information on changes in the sedimentary environment loi gradually increased over the holocene whereas magnetic susceptibility showed an inverse trend biogenic silica content showed three distinct peaks spaced approximately 3000 years apart major shifts in diatom assemblages occurred at 8100 8000 5800 5700 and 3800 3500 cal yr bp there is evidence of diatom community response to centennial scale variations such as the medieval warm period 1000 700 cal yr bp little ice age 800 150 cal yr bp and recent warming although recent changes in diatom community composition productivity and species richness are apparent they were surpassed at other periods throughout the holocene variations of the taxa within the genera staurosira pseudostaurosira fragilaria and staurosirella usually combined into one genus in arctic lake sediment studies suggest these taxa provide useful insight into paleonvironmental questions

late holocene environmental conditions in coronation gulf southwestern canadian arctic archipelago evidence from dinoflagellate cysts other non pollen palynomorphs and pollen boxcore 99lssl 001 68 0958 n 114 1868 w 211 m water depth from coronation gulf represents the first decadal scale marine palynology and late holocene sediment record for the southwestern part of the northwest passage the record was studied for organic walled microfossils dinoflagellate cysts non pollen palynomorphs pollen terrestrial spores and sediment characteristics 210 pb 137 cs and three accelerator mass spectrometry 14 c dates constrain the chronology three prominent palaeoenvironmental zones were identified during the interval ad 1470 1680 zone i the climate was warmer and wetter than at present and environmental conditions were more favourable to biological activity and northward boreal forest migration with reduced sea ice and a longer open water growing season the interval ad 1680 1940 zone ii records sea ice increase and generally cool polar conditions during the little ice age during ad 1940 2000 zone iii organic microfossils indicate an extended open water season and decreased sea ice with suggested amelioration surpassing that of zone i although more marine studies are needed to place this record into an appropriate context the succession from ameliorated zone i to cooler sea ice influenced conditions zone ii and finally to 20th century warming zone iii corresponds well with several terrestrial climatic records from the neighbouring mainland and victoria island and with lower resolution marine records to the west copyright 2011 john wiley sons ltd

simulation based investigation of the generality of lyzenga s multispectral bathymetry formula in case 1 coral reef water abstract lyzenga s multispectral bathymetry formula has attracted considerable interest due to its simplicity however there has been little discussion of the effect that variation in optical conditions and bottom types which commonly appears in coral reef environments has on this formula s results the present paper evaluates lyzenga s multispectral bathymetry formula for a variety of optical conditions and bottom types a noiseless dataset of above water remote sensing reflectance from worldview 2 images over case 1 shallow coral reef water is simulated using a radiative transfer model the simulation based assessment shows that lyzenga s formula performs robustly with adequate generality and good accuracy under a range of conditions as expected the influence of bottom type on depth estimation accuracy is far greater than the influence of other optical parameters i e chlorophyll a concentration and solar zenith angle further based on the simulation dataset lyzenga s formula estimates depth when the bottom type is unknown almost as accurately as when the bottom type is known this study provides a better understanding of lyzenga s multispectral bathymetry formula under various optical conditions and bottom types

the arctic sea ice biomarker ip25 a review of current understanding recommendations for future research and applications in palaeo sea ice reconstructions in recent years a novel proxy for the past occurrence of arctic sea ice has been proposed that is based on the variable marine sedimentary abundance of an organic geochemical lipid derived from sea ice diatoms in the spring this lipid termed ip25 ice proxy with 25 carbon atoms is a highly branched isoprenoid mono unsaturated alkene that appears to be sufficiently stable in sediments to permit meaningful palaeo sea ice reconstructions to be carried out over short to long term timescales since the first proposed use of ip25 as a proxy for palaeo sea ice by belt et al 2007 a number of laboratories have measured this biomarker in arctic sediments and it is anticipated that research activity in this area will increase further in the future the content of this review is divided into a number of sections firstly we describe the scientific basis for the ip25 proxy and its initial discovery in arctic sea ice sedimenting particles and sediments secondly we summarise the relatively few studies that have to date concentrated on examining the factors that influence the production and fate of ip25 and we identify some areas of future research that need to be addressed in order to improve our understanding of ip25 data obtained from sedimentary analyses what is clear at this stage however it that the presence of ip25 in arctic marine sediments appears to represent a proxy measure of past seasonal sea ice rather than permanent or multi year ice conditions thirdly we highlight the importance of rigorous analytical identification and quantification of ip25 especially if measurements of this biomarker are going to be used for quantitative sea ice reconstructions rather than qualitative analyses alone presence absence fourthly we review some recent attempts to make the interpretations of ip25 biomarker data more detailed and quantitative by combining sedimentary abundances with those of phytoplankton and other sea ice derived biomarkers thus the bases for the so called pip25 and dip25 indices are described together with an overview of potential limitations concluding that investigations into the use of these indices needs further research before their full potential can be realised in the final section we provide a summary of ip25 based palaeo sea ice reconstruction case studies performed to date these case studies cover different arctic regions and timescales spanning decades to tens of thousands of years

coral reef habitat mapping a combination of object based image analysis and ecological modelling despite being one of the most important and well studied coral reefs in the world the full extent of coral habitat of the great barrier reef gbr is not well mapped and there is no current and comprehensive map of the gbr s geomorphic zonation or benthic composition this paper demonstrates an approach that integrates ecological coral habitat mapping with empirical modelling to map the geomorphic zonation and benthic composition of the shallow offshore reefs of the gbr using the capricorn bunker group cbg as a case study the approach combined environmental data sets and geo ecological rule sets to identify geomorphic zones the benthic composition of individual geomorphic zones was mapped for shallow reef flat zones using object based image analysis with context driven rules based on coral reef ecology and reef slope zones using levels of wave exposure to predict the distribution of coral types the environmental data sets used were field based benthic composition data landsat 8 oli satellite image derived bottom reflectance water depth and slope 15 m 15 m pixel size data reef impact data and modelled wave exposure the study showed that the combination of geomorphic ecological rules and models with remote sensing imagery provided robust mapping results over a large 2500 km2 reef system of which 245 km2 was mapped as shallow coral reefs and 88 km2 of that was mapped as areas containing coral most importantly the method produced defined the geomorphic zones and benthic composition of a study area that is significantly larger than the majority of coral reef remote sensing mapping projects previously published with some modifications the methods presented have the potential to be applied to the full extent of the shallow offshore reefs of the gbr or any large reef globally monitoring and management of coral reefs for conservation and other purposes at regional to global scales will benefit from the ability to produce and use this type of essential information on a regular basis

coastal engineering applications of high resolution lidar bathymetry abstract in 1994 the us army corps of engineers completed development of the scanning hydrographic operational airborne lidar survey shoals system a state of the art hydrographic survey instrument using lidar light detection and ranging technology and operating from a bell 212 helicopter shoals remotely collects accurate high resolution bathymetry at a rate of 8 km2 h a nominal depth and position measurement spacing of 4 m yields high density bottom coverage of coastal projects producing soundings from the above water beach or coastal structure to depths of 40 m since becoming fully operational shoals surveyed over 2000 km2 along the atlantic ocean pacific ocean gulf of mexico great lakes and caribbean sea survey projects varied from tidal inlets and navigation channels to beach nourishment and monitoring these projects quantify current coastal structure condition navigation channel alignments and morphologic changes over time in addition to monitoring coastal projects sediment transport can be estimated with accurate high resolution bathymetry bathymetry can be translated into sediment transport through a combination of the sediment continuity equation a surf zone energetics based longshore transport formula and bathymetric data this paper presents the shoals system describing both lidar technology and the survey system several shoals data sets are presented to show today s benefits of high resolution lidar bathymetry to the coastal engineering community finally ongoing research using these unique data sets is presented to show the future benefits of lidar bathymetry to the coastal field

post glacial vegetation reconstruction and a possible 8200 cal yr bp event from the low arctic of continental nunavut canada climate models suggest that the global warming during the early to mid holocene may have partly resulted from the northward advance of the northern treeline and subsequent reduction of the planetary albedo we investigated the holocene vegetation history of low arctic continental nunavut canada from a radiocarbon dated sediment core from tk 2 lake a small lake ca 200 km north of the limit of the forest tundra the pollen and loss on ignition data indicate the presence of dwarf shrub tundra in the region since the beginning of organic sedimentation at ca 9000 cal yr bp with dominance of betula especially since 8700 cal yr bp at 8100 7900 cal yr bp the dominance of the shrub tundra was punctuated by a transient decline of betula and coincident increases of ericaceae undiff vaccinium type and gramineae this suggests an abrupt disturbance of the betula glandulosa population approximately simultaneously with the sudden 8200 cal yr bp event in the north atlantic however in the absence of other sites studied in the area linkage to the 8200 cal yr bp event remains tentative the lack of any evidence of forest tundra in the region constrains the northern limit of the mid holocene advance of the forest tundra boundary in central northern canada consequently our results show that the climate models imposing a mid holocene advance of the limit of the forest tundra to the arctic coast of canada may have overestimated the positive climatic feedback effects that can result from the replacement of tundra by the boreal forest copyright 2003 john wiley sons ltd

diffuse reflectance of oceanic shallow waters influence of water depth and bottom albedo we used simplifying assumptions to derive analytical formulae expressing the reflectance of shallow waters as a function of observation depth and of bottom depth and albedo these formulae also involve two apparent optical properties of the water body a mean diffise attenuation coefficient and a hypothetical reflectance which would be observed if the bottom was infinitely deep the validity of these approximate formulae was tested by comparing their outputs with accurate solutions of the radiative transfer obtained under the same boundary conditions by monte carlo simulations these approximations were also checked by comparing the reflectance spectra for varying bottom depths and compositions determined in coastal lagoons with those predicted by the formulae these predictions were based on separate determinations of the spectral albedos of typical materials covering the floor such as coral sand and various green or brown algae the simple analytical expressions are accurate enough for most practical applications and also allow quantitative discussion of the limitations of remote sensing techniques for bottom recognition and bathymetry as early as 1944 duntley used a spectrograph mounted in a glass bottomed boat or flown in an airplane to analyze radiances emerging from the ocean and shallow waters he evidenced the influence of the water depth on the spectral composition of the upward flux duntley 1963 using a monte carlo technique plass and kattawar 1972 calculated the radiative field in the atmosphere cean system and in particular examined the dependence of the upward flux on the albedo of the ocean floor gordon and brown 1974 studied the diffuse reflectance of a shallow ocean using monte carlo simulations and a probabilistic approach gordon and brown provided an analysis based on photon history of the light field as modified by the presence of a reflecting bottom in addition ackleson and klemas 1986 developed a two flow model that simulated the light field within a canopy of bottom adhering plants a single scattering approximation for irradiance reflectance was also

determination of water depth with high resolution satellite imagery over variable bottom types a standard algorithm for determining depth in clear water from passive sensors exists but it requires tuning of five parameters and does not retrieve depths where the bottom has an extremely low albedo to address these issues we developed an empirical solution using a ratio of reflectances that has only two tunable parameters and can be applied to low albedo features the two algorithms the standard linear transform and the new ratio transform were compared through analysis of ikonos satellite imagery against lidar bathymetry the coefficients for the ratio algorithm were tuned manually to a few depths from a nautical chart yet performed as well as the linear algorithm tuned using multiple linear regression against the lidar both algorithms compensate for variable bottom type and albedo sand pavement algae coral and retrieve bathymetry in water depths of less than 10 15 m however the linear transform does not distinguish depths 15 m and is more subject to variability across the studied atolls the ratio transform can in clear water retrieve depths in 25 m of water and shows greater stability between different areas it also performs slightly better in scattering turbidity than the linear transform the ratio algorithm is somewhat noisier and cannot always adequately resolve fine morphology structures smaller than 4 5 pixels in water depths 15 20 m in general the ratio transform is more robust than the linear transform

spectral signatures of coral reefs features from space the spectral signatures of coral reefs and related scenes as they would be measured above the earth s atmosphere are calculated using a coupled atmosphere ocean discrete ordinates radiative transfer model actual measured reflectance spectra from field work are used as input data four coral species are considered to survey the natural range of coral reflectance montastrea cavernosa acropora palmata dichocoenia stokesii and siderastrea siderea four noncoral objects associated with reefs are also considered sand coralline algae green macroalgae and algal turf the reflectance spectra as would be measured at the top of the atmosphere are substantially different from the in situ spectra due to differential attenuation by the water column and most importantly by atmospheric rayleigh scattering the result is that many of the spectral features that can be used to distinguish coral species from their surroundings or from one another which have been used successfully with surface or aircraft data would be obscured in spectral measurements from a spacecraft however above the atmosphere the radiance contrasts between most coral species and most brighter noncoral objects remain noticeable for water column depths up to 20 m over many spectral intervals the reflectance from dark coral under shallow water is smaller than that of deep water the maximum top of atmosphere radiances and maximum contrasts between scene types occur between 400 nm and 600 nm this study supports the conclusions of recent satellite reef mapping exercises suggesting that coral reef identification should be feasible using satellite remote sensing but that detailed reef mapping e g species identification may be more difficult

himalayan tectonics weathering processes and the strontium isotope record in marine limestones the time evolution of the isotopic composition of seawater strontium the ratio of strontium 87 to strontium 86 over the last 500 million years has the form of an asymmetric trough the values are highest in the cambrian and recent 0 7091 and lowest in the jurassic 0 7067 superimposed on this trend are a number of smaller oscillations consideration of the geochemical cycle of strontium and the dynamics of weathering shows that only himalayan style continental collisions can influence the isotope ratio on the scale observed the contemporary himalayan orogeny is by far the largest since the late precambrian pan african event that produced the high in the cambrian

late holocene climatic variability south of the alps as recorded by lake level fluctuations at lake ledro trentino italy a lake level record for the late holocene at lake ledro trentino northeastern italy is presented it is based on the sediment and pollen analysis of a 1 75 m high stratigraphic section observed on the southern shore site ledro i and a 3 2 m long sediment core taken from a littoral mire on the southeastern shore site ledro ii the chronology is derived from 15 radiocarbon dates and pollen stratigraphy the late holocene composite record established from these two sediment sequences gives evidence of centennial scale fluctuations with highstands at c 3400 2600 1700 1200 and 400 cal bp in agreement with various palaeohydro logical records established in central and northern italy as well as north of the alps in addition high lake level conditions at c 2000 cal bp may be the equivalent of stronger river discharge observed at the same time in central italy s rivers in agreement with the lake level record of accesa tuscany the ledro record also suggests a relatively complex palaeohydrological pattern for the period around 4000 cal bp on a millennial scale sediment hiatuses observed in the lower part of the ledro i sediment sequence indicate that except for a high stand occurring just after 7500 cal bp lower lake levels generally prevailed rather before c 4000 cal bp than afterwards finally the lake level data obtained at lake ledro indicate that the relative continuity of settlements in humid areas of northern italy during the bronze age in contrast to their general abandonment north of the alps between c 3450 and 3150 cal bp does not reflect different regional patterns of climatic and palaeohy drological conditions in contrast the rise in lake level dated to c 3400 cal bp at ledro appears to coincide with a worldwide climate reversal observed in both the hemispheres while palaeoenvironmental and archaeological data collected at lake ledro may suggest as a working hypothesis a relative emancipation of proto historic societies from climatic conditions

multi band spectral matching inversion algorithm to derive water column properties in optically shallow waters an optimization of parameterization abstract deriving inherent optical properties iops and other water quality parameters from satellite remote sensing data covering optically shallow environments has historically been problematic due to difficulties in separating the benthic signal from that of the water column while recent advances have improved such retrievals most methods have high uncertainties for very shallow

the origin of the juch uypampa cave mummies strontium isotope analysis of archaeological human remains from bolivia previous analyses of strontium isotopes from human bone and teeth have identified diverse patterns of residential mobility in the south central andes during the middle horizon ad 500e1100 during this time the large polity of tiwanaku exerted great influence over what are now southern peru northern chile northwestern argentina and bolivia recently five naturallymummified individuals were discovered in the cave of juch uypampa in the pulacayo region of southern bolivia although these individuals were buried with a number of fine tiwanaku style grave goods as well as non tiwanaku items the burial site is isolated and does not conform to the pattern of large tiwanaku affiliated cemeteries and residential sites outside of the lake titicaca basin strontium isotope analysis was performed on enamel from two adult men and bone from a third adult male in order to test the hypotheses that one or more of the males was from either the tiwanaku heartland in the lake titicaca basin the chilean oasis of san pedro de atacama which contains a series of cemeteries with tiwanaku style grave goods or the local area in which they were buried results show that two individuals likely spent their childhood in the local area where they were interred while the third man probably spent at least the last twenty years of his life in that region before being buried there this raises interesting questions regarding the nature of tiwanaku influence in southern bolivia and the relationship between the juch uypampa mummies and the tiwanaku polity 2005 elsevier ltd all rights reserved

a diatom based holocene palaeoenvironmental record from a mid arctic lake on boothia peninsula nunavut canada a 485 cm sediment core from a lake unoffcially called jr01 boothia peninsula nunavut canada yielded a high resolution diatom record documenting environmental change in the mid arctic five radi

late holocene paleoceanography and climate variability over the mackenzie slope beaufort sea canadian arctic abstract late holocene paleoceanography and climate variability of the southeastern beaufort sea canadian arctic have been investigated on the basis of sedimentary cores collected over the mackenzie slope piston trigger and box cores were sampled at station 803 in 2004 aboard the ccgs amundsen at 218 m water depth the chronology of the piston core is constrained by 4 ams 14 c dates as the sedimentation rate in the box core is assessed from 210 pb data we obtain a continuous composite sequence covering the last 4600 years with a sedimentation rate of 140 cm kyr 1 transfer functions modern analogue technique based on dinoflagellate cyst dinocyst assemblages were used to reconstruct the evolution of sea surface conditions over the time period covered by the cores palynological data reveal that dinocyst assemblages are dominated by operculodinium centrocarpum sensu lato mean of 43 3 throughout the core with the accompanying taxa brigantedinium spp 19 6 islandinium minutum 15 6 and cysts of pentapharsodinium dalei 13 7 four zones have been established on the basis of dinocyst relative abundances dinocyst assemblage zone 1 d1 from 4600 to 2700 cal years bp is dominated by o centrocarpum mean of 49 0 in zone d2 2700 1500 cal years bp the relative abundances of o centrocarpum decrease 34 4 in favour of the opportunistic heterotrophic taxa brigantedinium spp 28 8 and cysts of polykrikos sp var arctic quadratus 2 8 dinocyst zone d3 1500 30 cal years bp or 450 1920 ad is characterised by the high relative abundance of the peridinioid taxa i minutum 19 9 the last zone d4 spanning from 1920 to 2004 ad is again dominated by o centrocarpum 44 5 and shows low relative abundances of brigantedinium spp and cf echinidinium karaense quantitative reconstructions of past sea surface parameters august sea surface temperature sst august sea surface salinity sss and duration of sea ice cover indicate relatively stable conditions over the last 4 6 kyr with episodic cooling events sst of 1 5 c below the modern value of 6 c that took place between 700 and 1820 ad we associate the last and the longest of these cooling events 1560 1820 ad with the little ice age reconstructed sss shows decadal oscillations since 1920 ad that we tentatively associate with the accumulation of freshwater by the beaufort gyre and the subsequent great salinity anomalies our data suggest that similar salinity anomalies could have occurred ca 1860 and 1790 ad stable isotopic data show a slight increase in 13 c values from 27 1 at the base to 25 8 at the top over the last 4 6 kyr that we associate with the gradual increase in atmospheric co 2 concentration as recorded by antarctic ice cores variations in the 15 n profile suggest variations in pacific water influence from 4600 to 1300 cal years bp associated with centennial scale shifts of the arctic oscillation phases

satellite derived bathymetry in optically complex waters using a model inversion approach and sentinel 2 data abstract this study presents an assessment of a model inversion approach to derive shallow water bathymetry in optically complex waters with the aim of both understanding localised capability and contributing to the global evaluation of sentinel 2 for coastal monitoring a dataset of 12 sentinel 2 msi images in three different study areas along the irish coast has been analysed before the application of the bathymetric model two atmospheric correction procedures were tested deep water correction dwc and case 2 regional coastal color c2rcc processor dwc outperformed c2rcc in the majority of the satellite images showing more consistent results using dwc for atmospheric correction before the application of the bathymetric model the lowest average rmse was found in dublin bay rmse 1 60 bias 0 51 followed by mulroy bay rmse 1 66 bias 1 30 while brandon bay showed the highest average error rmse 2 43 bias 1 86 however when the optimal imagery selection was considered depth estimations with a bias less than 0 1 m and a spread of 1 40 m were achieved up to 10 m these results were comparable to those achieved by empirical tuning methods despite not relying on any in situ depth data this conclusion is of particular relevance as model inversion approaches might allow future modifications in crucial parts of the processing chain leading to improved results atmospheric correction the selection of optimal images e g low turbidity the definition of suitably limited ranges for the per pixel occurrence of optical constituents phytoplankton cdom backscatter and seabed reflectances in combination with the understanding of the specifics characteristics at each particular site were critical steps in the derivation of satellite bathymetry

modeling wave effects on storm surge and coastal inundation abstract we present a parametric study of surface wave effects on storm surge and coastal inundation hurricane wind forcing terms atmosphere pressure gradient terms and radiation open boundary conditions are implemented into an existing quasi 3d nearshore model nearcom tvd which uses a shock capturing tvd scheme and can better simulate the wetting drying process during inundation than a conventional finite difference model systematic numerical experiments are carried out in an idealized continental shelf beach land system to identify the role of waves in modeling storm surge and inundation under different storm characteristics four storm parameters including storm intensity storm size translation speed and incident angle are investigated modeling results reveal that the presence of waves can increase the maximum storm surge heights significantly through wave setup and the contribution of waves varies considerably depending on the storm characteristics in addition to direct wave forcing the wave enhanced bottom stress in the surfzone also promotes higher wave setup and hence higher surge heights waves also have a major influence on the maximum inland inundation distance however we find that waves do not always favor more inundation as expected for storms traveling at very slow translation speeds or nearly parallel to the coast waves surprisingly exert a negative effect on the maximum inundation distance we argue that wave enhanced bottom stress combined with longer forcing duration in such storms counteract the positive effect of wave setup and thus less inundation is predicted in wave current coupled simulations our results highlight the necessity of fully incorporating wave effects in storm surge and inundation modeling

stromatolite provinces of hamelin pool physiographic controls on stromatolites and associated lithofacies recent studies recognized distinct stromatolite provinces in hamelin pool western australia each with morphologically distinct stromatolite structures paired with characteristic shelf physiography in the present paper we couple detailed lithofacies mapping with hamelin pool bathymetry and consider physiography as a control of sedimentation processes including stromatolite development bathymetric transects derived from a high resolution bathymetry map with depths from 0 to 11 meters allow calculation of slope gradients in the provinces as in other settings bathymetry is linked to energy regimes which in turn appear to be coupled with variations in stromatolite morphologies and associated lithofacies as follows 1 low gradient ramps with low energy settings are associated with sheet mats and elongate clustered stromatolites that exhibit regular spatial patterns possibly indicative of self organization 2 low gradients coupled with high energy settings resulting from strong winds result in seif stromatolites with pronounced directional bands 3 medium to steep gradients coupled with medium to high energy are associated with individual and merged stromatolites often with thin basal necks 4 headlands and promontories where the topography deflects currents are associated with elongate nested stromatolites and 5 medium to high energy slopes typically found at promontory edges and shelf margins are dominated by blocky pavement observations linking stromatolite morphology to physiography in a modern microbial system provide insight into the long lived debate about biology versus environment in controlling stromatolite morphology when physiography leads to a high energy regime environmental controls are the main factor determining stromatolite morphology in contrast when physiography promotes a low energy environment the response of biological communities becomes the main driver of macroscale stromatolite morphology

stable isotope systematics in mesozoic granites of central and northern california and southwestern oregon 18o d and h2o contents were measured for whole rock specimens of granitoid rocks from 131 localitics in california and southwestern oregon with 41 new determinations in the klamath mountains and sierra nevada initial strontium isotope ratios are known for 104 of these samples large variations in 18o 5 5 to 12 4 d 130 to 31 water contents 0 14 to 2 23 weight percent and initial strontium isotope ratios 0 7028 to 0 7095 suggest a variety of source materials and identify rocks modified by secondary processes regular patterns of variation in each isotopic ratio exist over large geographical regions but correlations between the ratios are generally absent except in restricted areas for example the regular decrease in d values from west to east in the sierra nevada batholith is not correlative with a quite complex pattern of 18o values implying that different processes were responsible for the isotopic variations in these two elements in marked contrast to a good correlation between 87sr 86sr o and 18o observed in the peninsular ranges batholith to the south such correlations are lacking except in a few areas d values on the other hand correlate well with rock types chemistry and 87sr 86sr o except in the coast ranges where few of the isotopic signatures are primary the uniformly low d values of samples from the mojave desert indicate that meteoric water contributed much of the hydrogen to the rocks in that area even so the 18o values and 18o fractionations between quartz and feldspar are normal in these same rocks

nearshore sandbars crest position dynamics analysed based on earth observation data abstract understanding long term underwater sandbars dynamics is a key element for optimal coastal zone management but this endeavour is often held back by data availability in order to increase the spatial and temporal resolution availability and quality of sandbars observations this study proposes and evaluates a new approach for automatic extraction of sandbars positions from freely available satellite imagery using a case study of complex waters located on the danube delta coast black sea validation of the satellite extracted sandbars locations against 4 in situ measurements between 2016 and 2018 shows a very good correlation between the two datasets demonstrating the high accuracy of satellite derived data in revealing the underwater morphology of the upper shoreface along large areas and with high temporal resolution the obtained sandbars positions were then integrated into an automatic workflow able to accurately represent the seasonal and multi annual sandbars dynamics and also to give an insight about the sandbars alongshore behavioural changes the results are similar to the ones previously suggested by other studies which empowered different methods these prove the high potential of the newly proposed algorithm to be used for the automatic extraction of the positions of underwater features in the surf zone on other sites worldwide after proper tuning of parameters in accordance with local conditions the main constraints of the proposed approach are represented by the omission of sandbars position that imprint a low signal on the satellite image due to increased water depth especially for the outer bar high turbidity mostly for the inner bar or any other noise generation situation sun glint small wind waves the main advantages of the described algorithm are related to the simplicity of implementation and adaptability to other areas of interest and other types of satellite data

climate change and arctic ecosystems 1 vegetation changes north of 55 n between the last glacial maximum mid holocene and present a unified scheme to assign pollen samples to vegetation types was used to reconstruct vegetation patterns north of 55 n at the last glacial maximum lgm and mid holocene 6000 years b p the pollen data set assembled for this purpose represents a comprehensive compilation based on the work of many projects and research groups five tundra types cushion forb tundra graminoid and forb tundra prostrate dwarf shrub tundra erect dwarf shrub tundra and low and high shrub tundra were distinguished and mapped on the basis of modern pollen surface samples the tundra forest boundary and the distributions of boreal and temperate forest types today were realistically reconstructed during the mid holocene the tundra forest boundary was north of its present position in some regions but the pattern of this shift was strongly asymmetrical around the pole with the largest northward shift in central siberia 200 km little change in beringia and a southward shift in keewatin and labrador 200 km low and high shrub tundra extended farther north than today at the lgm forests were absent from high latitudes graminoid and forb tundra abutted on temperate steppe in northwestern eurasia while prostrate dwarf shrub erect dwarf shrub and graminoid and forb tundra formed a mosaic in beringia graminoid and forb tundra is restricted today and does not form a large continuous biome but the pollen data show that it was far more extensive at the lgm while low and high shrub tundra were greatly reduced illustrating the potential for climate change to dramatically alter the relative areas occupied by different vegetation types

multiple optimal depth predictors analysis modpa for river bathymetry findings from spectroradiometry simulations and satellite imagery abstract remote mapping of bathymetry can play a key role in gaining spatial and temporal insight into fluvial processes ranging from hydraulics and morphodynamics to habitat conditions this research introduces multiple optimal depth predictors analysis modpa which combines previously developed depth predictors along with additional predictors derived from the intensity component of the hsi color space transformation modpa empirically selects a set of optimal predictors among all candidates utilizing partial least squares pls stepwise or principal component pc regression models the primary focus of this study was on shallow

applications of lead and strontium isotopic relationships to the petrogenesis of granitoid rocks central sierra nevada batholith california pb isotope data are given on 80 whole rock and or feldspar samples from 51 dated samples covering a traverse across the central sierra nevada batholith largely between latitudes 36 and 37 n in addition sr isotope data were measured on 30 whole rock samples no correlation is observed between age and isotope ratios in agreement with previously published data 87 sr 86 sr ratios are low 0 704 along the western margin and increase to high values 0 707 at the eastern margin 206 pb 204 pb ratios increase from 18 6 at the western margin to 19 5 in the middle of the batholith then decrease regularly to 18 5 toward the eastern margin 2o8 pb 204 pb ratios mirror the 206 pb 204 pb data but do not exhibit the decrease in values toward the eastern margin pb and sr isotopic data from the western margin plutons plot within or close to the field of primitive island arc magmas indicating predominantly mantle sources the high 206 pb 204 pb ratios in the central batholith suggest assimilation of sediments derived from precambrian basement rocks the decrease in 206 pb 204 pb ratios in the eastern segment of the batholith without corresponding reduction in 208 pb 204 pb ratios is attributed to assimilation of lower crustal granulitic amphibolitic rocks by mafic magmas initial pb ratios for samples with 87 sr 86 sr 0 706 from the central and eastern segments of the batholith indicate components from recycled crustal rocks with a mean 207 pb 206 pb age of ca 1 8 ga nd and o isotopic data from the literature are consistent with the pb sr model obtained in this study very similar isotope patterns to the present model are reported across the salinian block

adaptive bathymetry estimation for shallow coastal waters using planet dove satellites abstract accurate bathymetric mapping of shallow waters above 15 m is essential for a wide range of scientific research government transport and industry globally satellite based bathymetry estimation approaches offer an alternative to traditional shipborne measurements especially given advancements in their spatial and temporal resolution of satellite imagery including the new planet dove constellation of 150 satellites providing daily coastal coverage dove satellites provide abundant cloud free images even over cloudy tropical coastal environment offering an opportunity to generate frequent bathymetry maps at high spatial resolution 4 m we developed a new adaptive bathymetry estimation algorithm for planet dove and similar satellites the algorithm adaptively tunes a depth estimator according to water column attenuation conditions the algorithm was tested at five diverse reef sites globally lighthouse reef belize saona island dominican republic st croix u s virgin islands heron island australia hawaii island u s using 31 satellite images from six dove satellites derived water depth was validated rmse 1 22 to 1 86 m with field measured sampling points 61 025 ranging in depth from 1 to 15 m algorithm performance was best at depths of 4 10 m this new adaptive algorithm can be effectively applied to derive high spatial resolution bathymetric maps from planet dove satellite imagery across a wide range of conditions

holocene thermal maximum in the western arctic 0 180 w the spatio temporal pattern of peak holocene warmth holocene thermal maximum htm is traced over 140 sites across the western hemisphere of the arctic 0 180 w north of 60 n paleoclimate inferences based on a wide variety of proxy indicators provide clear evidence for warmer than present conditions at 120 of these sites at the 16 terrestrial sites where quantitative estimates have been obtained local htm temperatures primarily summer estimates were on average 1 6 0 8 c higher than present approximate average of the 20th century but the warming was time transgressive across the western arctic as the precession driven summer insolation anomaly peaked 12 10 ka thousands of calendar years ago warming was concentrated in northwest north america while cool conditions lingered in the northeast alaska and northwest canada experienced the htm between ca 11 and 9 ka about 4000 yr prior to the htm in northeast canada the delayed warming in quebec and labrador was linked to the residual laurentide ice sheet which chilled the region through its impact on surface energy balance and ocean circulation the lingering ice also attests to the inherent asymmetry of atmospheric and oceanic circulation that predisposes the region to glaciation and modulates the pattern of climatic change the spatial asymmetry of warming during the htm resembles the pattern of warming observed in the arctic over the last several decades although the two warmings are described at different temporal scales and the htm was additionally affected by the residual laurentide ice the similarities suggest there might be a preferred mode of variability in the atmospheric circulation that generates a recurrent pattern of warming under positive radiative forcing unlike the htm however future warming will not be counterbalanced by the cooling effect of a residual north american ice sheet

pollen based summer temperature reconstructions for the eastern canadian boreal forest subarctic and arctic pollen based paleoclimate reconstructions using response surface and modern analog methods reveal an 8000 year record of july temperature fluctuations for 25 eastern canadian lake sites located from the forest tundra to the high canadian arctic postglacial conditions characterized by warmer than present summer temperatures prevailed in baffin island and ne labrador beginning about 7500 and 7000 14c yr bp respectively resulting in warmer than present conditions throughout the region by 6000 14c yr bp 0 5 c to 1 c further south in quebec and w labrador july temperatures were 1 2 c colder than present until after 6000 14c yr bp and only reached modern values after all residual laurentide ice had melted increased summertime insolation and the final disappearance of laurentide ice during the middle holocene probably caused july temperatures throughout eastern canada to peak between approximately 5000 and 3500 14c yr bp mid holocene warming relative to today was more pronounced in baffin island and ne labrador 1 c to 2 c compared to the boreal and subarctic regions of quebec and w labrador 1 c over the past 4000 years decreasing summertime insolation and colder sea surface temperatures in the davis strait and labrador sea contributed to a decline in july temperatures of 1 2 c throughout baffin island and the tundra regions of n quebec and labrador the absence of similar cooling in the records from the boreal forest may support the notion that the mean position of the summertime polar front blocked the colder arctic air during the late holocene

linking pattern to process in reef sediment dynamics at lady musgrave island southern great barrier reef linking surficial sediment patterns in reef environments to the processes that underlie their depositional dynamics enables predictions to be made of how environmental changes will influence reef associated sedimentary landforms such as islands and beaches geomorphic linkages between sediment deposition patterns and the biophysical processes that drive them are often poorly resolved particularly at broad landscape scales where tangible statements can be made about structural changes to landforms the present study applies geospatial techniques to link patterns in reef sediment dynamics at lady musgrave island to the underlying processes driving them in situ calcification is characterized by developing a high resolution map of the surficial calcium carbonate producing communities inhabiting the reef platform and associated sediments across the reef flat are analysed for grain size kurtosis sorting and threshold bed shear stress to explore transport pathways across the reef flat and lagoon wave energy is modelled across the entire reef platform as a potential driver of sediment dynamics and morphometric linkages are empirically defined between wave energy and grain size findings indicate that carbonate sediments are primarily sourced from calcifying communities colonizing the outer periphery of the reef platform and that sediment grain size can be reliably linked to wave energy by virtue of a linear model

lateglacial and holocene paleoenvironmental changes recorded in lake sediments brock plateau melville hills northwest territories canada sediments from south lake brock plateau melville hills northwest territories provide one of the longest postglacial records from the mainland western canadian arctic outside of eastern beringia sedimentation commenced at least 13 900 cal yr bp and possibly as early as 16 000 cal yr bp in response to early deglaciation of the site pollen is present throughout the record with an initial artemisia salix assemblage indicative of very cold conditions consistent with a locally severe younger dryas stade or simply continued proximity of the laurentide ice sheet margin c 12 700 to 11 500 cal yr bp at c 11 000 cal yr bp abiotic proxies signal a transition to warmer conditions corroborated by a pollen assemblage dominated by betula and cyperaceae although south lake was biologically productive during the early holocene c 11 000 to 7000 cal yr bp diatoms and other siliceous organisms are notably absent from the record suggesting severe silica limitation rises in alnus crispa and picea mariana pollen at c 7000 cal yr bp suggest cooling and or an increase in effective moisture wetter conditions and increased hydrological inputs and silica supply likely led to the establishment of a pioneering diatom community at c 6500 cal yr bp decreased organic sedimentation after c 2000 cal yr bp suggests cooler conditions additionally changing niveo eolian deposition of sand on lake ice varied with a c 3000 year periodicity through the entire record the south lake multiproxy record supports the hypothesis that the brock plateau was one of the earliest deglaciated regions during the late wisconsinan

influence of bathymetric fluctuations on coastal storm surge abstract natural events constantly alter nearshore bathymetric properties hurricanes particularly affect bathymetry as they pass over a body of water to compute an accurate forecast or recreate a hurricane s effects through hindcasting techniques an operational bathymetry data set must be known in advance however obtaining and maintaining current and accurate bathymetric data can be costly and difficult to manage in this paper we examine the extent to which variations in nearshore bathymetry affect the storm surge at the coast a common question for wave and surge modeling is how good is the bathymetric data if we can allow for a range of fluctuations in the bathymetry without significantly adjusting the results of the surge predictions we can potentially save months of field work and millions of dollars a one dimensional 1d analytical solution for waves and water level is developed for initial testing in the 1d case we find that as long as the amplitudes of the bathymetric fluctuations are less than 60 of the original depth the surge at the coast is within 10 of the surge generated on the initial bottom slope if the fluctuation produces a hole a deepening of the local bathymetry within 80 of the local water depth the coastal storm surge calculated is still within 10 of the unperturbed value computed for bottom slopes shallower than 1 20 in addition we find there is an optimum distance offshore for each sloped profile that corresponds to a depth between 25 and 40 m beyond which the effects of bathymetric fluctuations begin to decrease a coupled 2d modeling system is implemented to test our hypothesis along a realistic coastline after selecting three study sites we vary the bathymetry at the selected locations by 20 consistent with the 1d tests the storm surge at the shoreline varies by less than 5

influence of elevation modelling on hydrodynamic simulations of a tidally dominated estuary summary hydrodynamic simulation of estuaries requires a single digital elevation model dem resulting from merging of both topographic and bathymetric data these two datasets are usually produced using different technologies co ordinate systems and datums intertidal data in particular are often lacking due to the difficulty of data acquisition using conventional survey techniques this paper presents a fast accurate and low cost methodology to fill this gap and highlights the effect of the digital elevation model characteristics such as the interpolation method and spatial resolution on modelled water levels and flooded areas the lima river estuary located in north western portugal is used as a case study validation tests for commonly available spatial interpolators showed ordinary kriging to be the most adequate interpolator digital elevation models with regular grids of 5 m and 50 m resolution were used together with the original not interpolated elevation dataset as input to a finite element hydrodynamic model for astronomic tide simulation results indicate that the larger differences between using different elevation models occur at low tide during spring tide marginally impacting the flood modelling the effect of a vertical offset of the chart datum with respect to a part of the digital elevation model was finally investigated showing a limited influence in the determination of the water levels

multi proxy record of postglacial environmental change south central melville island northwest territories canada abstract a sediment core from lake bc01 75 10 945 n 111 55 181 w 225 m asl on south central melville island nwt canada provides the first continuous postglacial environmental record for the region fossil pollen results indicate that the postglacial landscape was dominated by poaceae and salix typical of a high arctic plant community whereas the arctic herb oxyria underwent a gradual increase during the late holocene pollen based climate reconstructions suggests the presence of a cold and dry period 12 000 cal yr bp possibly representing the younger dryas followed by warmer and wetter conditions from 11 000 to 5000 cal yr bp likely reflective of the holocene thermal maximum the climate then underwent a gradual cooling and drying from 5000 cal yr bp to the present suggesting a late holocene neoglacial cooling diatom preservation was poor prior to 5000 cal yr bp when conditions were warmest suggesting that diatom dissolution may in part be climatically controlled diatom concentrations were highest 4500 cal yr bp but then decreased substantially by 3500 cal yr bp and remained low before recovering slightly in the 20th century an abrupt warming occurred during the past 70 yr at the site although the magnitude of this warming did not exceed that of the early holocene

micro sampling of human bones for mobility studies diagenetic impacts and potentials for elemental and isotopic research abstract the nature of long bone formation and the pathways of interaction between bone samples and the burial environment suggest that portions of the bones disconnected from the arterial system are resistant to diagenetic alteration preliminary work on femurs from early bronze age hunter gatherers in cis baikal siberia shows that the nature and progression of chemical changes in the bone matrix due to microbial attack can be analyzed using laser ablation inductively coupled plasma mass spectrometry intra osteon variability in elemental concentrations and strontium isotope ratios 87 sr 86 sr indicate the presence of unaltered portions of bone within diagenetically modified bone and suggest that useful data remain accessible these biogenic signals can potentially be useful for mobility research in broad terms and the smaller timescales within an individual s lifetime months years accessible therein laser ablation micro sampling of femur specimens showed that intra osteon elemental composition of ba re and cs varied within and was correlated between multiple osteons of a single bone portions of chemically unaffected bone were identified within and effectively discriminated from diagenetically altered bone tissue areas showing visual alterations and erratic or uncorrelated ca and sr elemental results also had anomalous sr isotope ratios suggesting diagenetic alteration in those places compositional and isotopic analysis of intact portions of bone supports the hypothesis that hunter gatherer groups in cis baikal made numerous major movements during their lives microscopic analysis of long bones clarifies aspects of biodeterioration and correlations between trace elemental results and diagenetic alteration micro sampling of intact portions of bone expands the scope of available materials for research on mobility and other aspects of human past behavior

differential diagenesis of strontium in archaeological human dental tissues the investigation of prehistoric human migration from the measurement of sr isotope ratios within preserved tissue is critically dependent on the preservation of biogenic sr a number of recent studies have involved isotope ratio measurements on samples of archaeological tooth and bone but doubt remains as to the extent of diagenesis in various skeletal tissues and the effectiveness of procedures designed to decontaminate them the authors have compared sr abundance and isotope ratios in enamel and dentine from archaeological teeth in order to assess the integrity of the biogenic sr signal preserved within the respective tissues it is concluded that enamel appears in most cases to be a reliable reservoir of biogenic sr but that dentine and by implication bone is not the diagenesis of dentine is highly variable even between burials within a single site for the majority of teeth dentine diagenesis was not simply by addition of soil derived sr but involved substantial sometimes complete turnover of the original biogenic material it is suggested that for most of the samples investigated current decontamination techniques may not have been effective in isolating biogenic sr from dentine similar considerations are likely to apply to archaeological and fossil bone but the possibility arises to use dentine and enamel measurements to assess the effectiveness of decontamination procedures which may then be used for bone

paleodietary analysis of a san francisco bay area shellmound stable carbon and nitrogen isotope analysis of late holocene humans from the ellis landing site ca cco 295 abstract the late holocene archaeofaunal record of the san francisco bay area demonstrates temporal declines in the abundance of low cost high ranked marine and terrestrial resources during later periods of occupation faunal assemblages are often dominated by lower ranked higher cost resources suggesting an increase in diet breadth through time archaeological resource intensification models argue that this marks a late holocene decline in foraging efficiency in the bay area driven by human induced harvest pressure this study examines dietary change in the region using stable carbon and nitrogen isotope data from 65 human burials spanning two temporal components cal ad 55 890 and cal ad 762 1550 at the ellis landing site ca cco 295 the strong linear relationship between collagen carbon and nitrogen isotope values reflects both marine and terrestrial food consumption with individuals showing a high level of dietary variability at the site no temporal trend or meaningful sex differences were found in isotope values the widening of diet breadth predicted by the archaeofaunal record occurred prior to the occupation of the ellis landing shellmound site the trend in exploiting a greater amount of terrestrial resources during the middle and late period in central california was supported by isotopic evidence

influence of offshore shoals on spatial variability of storm surge abstract idealized bathymetries were subjected to idealized cyclones in order to measure the storm surge response to a range of shoals under various storm conditions for the purpose of informing the development of bathymetry thinning algorithms nine bathymetries were considered including eight large offshore shoals and a featureless reference domain six storm realizations two different sizes intensities and three different landfall directions were used as meteorological forcing shoal influence on surge was examined over the entire continental shelf throughout the surge event quantification of shoal impact on surge was performed prior to landfall near the time of peak surge and during surge recession three elevation difference contours 1 0 0 5 and 0 5 m were used to quantify the spatial variation in surge caused by the shoals at the three times examined positive contours 1 0 and 0 5 m were used to show that a shoal increased surge locally and the negative contour 0 5 m to show that a shoal decreased surge locally the influences of three shoal parameters depth below mean sea level msl cross shore width and distance from shore were isolated and examined to see which characteristics caused the shoals to alter surge in many cases the shoals did not have much effect on the surge response only 13 of the samples used to quantify shoal impact on surge indicated any shoal influence whatsoever and the shoals did not alter maximum elevation within the threshold considered 0 5 m anywhere in the domain however analysis of the elevation difference contours revealed multiple types of shoal influence the shoals increased surge when they reduced setdown in storms with offshore winds prior to landfall and when they delayed surge recession after all storms the shoals decreased surge when they impeded shoreward flow delaying the arrival of surge in cases when the shoals altered surge 95 of the impact was caused by shallow features 0 5 m below msl also there appears to be a maximum area over which a shoal can influence surge all changes in surge greater than the threshold of 0 5 m occurred over the shoal or approximately between the shoal and the shore the implications of our results for bathymetry thinning follow in general offshore shoals do not need to be resolved in bathymetry data sets used in surge modeling especially if their impact on maximum elevation is the primary concern since a shoal s depth below msl was an excellent indicator of whether it would impact storm surge we recommend that feature depth below msl be used as a bathymetry thinning criterion finally a feature s maximum area of influence could be a useful property for determining whether it should be retained in a bathymetry dataset if one s area of interest is outside of a feature s area of influence the feature could be omitted regardless of its impact on surge

late holocene sea temperatures along the central california coast mussel shells from central california coastal archaeological sites record changes in sea surface temperatures in the past 2000 years water temperatures inferred from oxygen isotopes in the shells were about 1 c cooler than present and stable between 2000 and 700 yr ago between about 700 and 500 yr ago seasonal variation was greater than present with extremes above and below historic levels water temperatures were 2 3 c cooler than today 500 300 yr ago the interval of variable sea temperatures 700 500 yr ago partially coincided with an interval of drought throughout central california a coincident disruption in human settlement along the coast suggests movements of people related to declining water sources quantities of fish bone in central coast middens dating to this same period are high relative to other periods and the remains of northern anchovies a species sensitive to changing oceanographic conditions are also abundant the continued use of local fisheries suggests that changes in settlement and diet were influenced more by drought than by a decrease in marine productivity as fish provided a staple during an interval of low terrestrial productivity

modern and late quaternary pollen spectra of fiord sediments eastern baffin island arctic canada abstract pollen spectra of thirty surface samples from baffin island fiords are dominated by abetula filicales cyperaceae gramineae association that is somewhat representative of local or regional vegetation however betula and filicales are over represented andsalix cyperaceae and ericales are under represented compared to their importance in the present vegetation two possible causes for this disparity related to the fluvial processes that furnish most pollen to fiords are 1 fluvial reworking of older sediment that contains abundantbetula and filicales and 2 greater resistance of these taxa to corrosion and degradation during fluvial transport the pollen stratigraphy of five piston cores from fiords contains two types of pollen assemblages in the lower portions of the cores exotic pollen types and pre quaternary palynomorphs are abundant the upper portions of the cores contain an assemblage roughly representative of the present vegetation in which cyperaceae and gramineae are abundant and exotic and pre quaternary types are reduced or absent the lower assemblage was deposited during the late glacial deglacial transition and deglaciation ca 12 000 to 6000 b p when eastern baffin island had little vegetation cover and long distance transport and reworking were virtually the only pollen sources a feature of several cores is a major peak in dinoflagellates about 5000 b p this event may be related to the postglacial marine climatic optimum in the eastern canadian arctic between 5000 and 3000 b p

paleoenvironments of the canadian high arctic derived from pollen and plant macrofossils problems and potentials abstract analyses of peat sections lake sediments and ice cores provide information about late quaternary arctic environments palynomorphs and plant macrofossils from each of these three types of sediments record different aspects of the environment with particular spatial and temporal scales of resolution in the arctic the limits to the interpretation of past environments are particularly significant problems of low pollen concentrations long distance transport stratigraphic inversions and contamination by fossils from older deposits are more serious in this region due to the biogeographic context that characterizes these high latitudes and influences the particular ecological and geomorphological processes however recent work has shown that past environments can be reconstructed from evidence preserved in high arctic sediments and ice cores if these problems are taken into account before their interpretation

postglacial environmental history of western victoria island canadian arctic abstract changes in chironomid species assemblages and community dynamics at lake kr02 western victoria island were analysed to produce a record of environmental change over the holocene for the western arctic past air temperatures were inferred from the chironomid record using transfer function and modern analogue techniques and past lake water ph was reconstructed using sediment carbonate and biogenic silica content the early holocene 10 2 6 5 ka was a warm period of high aquatic and terrestrial production a further change in environmental conditions occurred at 4 ka and lasted for the next two millennia conditions warmed abruptly at 1 6 ka and rapidly cooled at 1 0 ka a warming then started at 0 14 ka and continued through to recent times although temperatures still remained cooler than those experienced prior to 6 5 ka the climatic changes over the holocene as recorded at lake kr02 are consistent with those inferred from independent records from other sites on victoria island and across the arctic

striking similarities in temporal changes to spring sea ice occurrence across the central canadian arctic archipelago over the last 7000 years abstract a 7000 year spring sea ice record for victoria strait arc 4 and dease strait arc 5 in the canadian arctic archipelago caa has been determined by quantification of the sea ice diatom derived biomarker ip 25 in two marine sediment piston cores obtained in 2005 the chronologies of the arc 4 and arc 5 cores were determined using a combination of 14 c ams dates obtained from macrobenthic fossils and magnetic susceptibility measurements the ages of the tops of the piston cores were estimated by matching chemical and physical parameters with those obtained from corresponding box cores these analyses revealed that while the top of the arc 4 piston core was estimated to be essentially modern ca 60 cal yr bp a few hundred years of sediment appeared to be absent from the arc 5 piston core downcore changes to ip 25 fluxes for both cores were interpreted in terms of variations in spring sea ice occurrence and correlations between the individual ip 25 flux profiles for victoria strait dease strait and barrow strait reported previously were shown to be statistically significant at both 50 and 100 year resolutions the ip 25 data indicate lower spring sea ice occurrences during the early part of the record ca 7 0 3 0 cal kyr bp and for parts of the late holocene ca 1 5 0 8 cal kyr bp especially for the two lower latitude study locations in contrast higher spring sea ice occurrences existed during ca 3 0 1 5 cal kyr bp and after ca 800 cal yr bp the observation of consecutively lower and higher spring sea ice occurrence during two periods of the late holocene coincides broadly with the medieval warm period and little ice age epochs respectively the ip 25 data are complemented by particle size and mineralogical data although these may alternatively reflect changes in sea level at the study sites the ip 25 data are also compared to previous proxy based determinations of palaeo sea ice and palaeoclimate for the caa including those based on bowhead whale remains and dinocyst assemblages the spatial consistency in the proxy data which most notably indicates an increase in spring sea ice occurrence around 3 cal kyr bp provides a potentially useful benchmark for the termination of the holocene thermal maximum for the central caa

modern and holocene pollen assemblages from some small arctic lakes on somerset island nwt canada abstract modern pollen samples from 15 lakes along a north south transect on western somerset island nwt canada show a decrease in pollen concentrations from the high arctic to the mid arctic zone but there are few differences in the pollen percentages between these sites long distance transport accounts for up to 50 of the pollen in these lake sediments cores from two lakes show few changes in the percentages of important pollen types except for an initial period before 6000 yr b p of increased salix the pollen concentration of lake rs36 from the mid arctic is twice that of lake rs29 from the high arctic and at both sites the concentrations decreased during the past 6000 yr b p this suggests a climatic deterioration during the past 6000 yr which has caused a decrease in the abundance of plants on the landscape

palynological evidence of holocene climate change in the eastern arctic a possible shift in the arctic oscillation at the millennial time scalethis article is one of a series of papers published in this special issue on the theme polar climate stability network dinocyst assemblages and the physical properties of two sediment cores collected in the easternmost part of the main axis of the northwest passage canadian arctic ocean cores 2004 804 009 bc and 2004 804 009 pc 74 11 2 n 81 11 7 w were used to reconstruct changes in sea surface conditions and to characterize changes in the depositional environment core 2004 804 009 pc spans the last 12 180 calibrated cal years bp with sedimentation rates ranging from 45 to 122 cm ka quantitative estimates of sea surface parameters reveal relatively large hydrographic variability at millennial time scale before 11 000 cal years bp our records suggest terrigenous inputs related to the last deglaciation between 11 000 and 9600 cal years bp harsh conditions prevailed with august sea surface temperatures 2 c and the dominance of heterotrophic taxa this episode was followed by a gradual increase in the relative abundance of phototrophic taxa and the establishment of milder condition with sea surface temperature

immigrants at the mississippian polity of cahokia strontium isotope evidence for population movement abstract archaeologists have long debated the role of regional interaction in the 11th to 14th centuries at the mississippian polity of cahokia architectural styles exotic materials and cultural objects provide indirect evidence for cultural interaction and ethnic and social diversity however identifying the movement of individuals rather than materials is key to our growing understanding of the population history that enabled the formation of this unique polity this study is the first to use strontium isotope analysis 87sr 86sr of human tooth enamel to identify immigrants at cahokia modern and archaeological fauna were used to establish a baseline local range of strontium isotope ratios for the american bottom region surrounding cahokia teeth from individuals interred in diverse mortuary locations including mounds within this region were analyzed and compared to the local strontium isotope range to identify individuals of non local origin one third of all individuals analyzed were identified as non local and the range and variability of their strontium ratios suggests multiple places of origin the correlation of isotopic data with available biological and mortuary evidence allows us to examine the role of migration in the history of this mississippian polity

holocene climate and vegetation change on victoria island western canadian arctic abstract a detailed pollen record from victoria island provides the first quantitative holocene climate reconstruction from the western canadian arctic the pollen percentage data indicate that arctic herbs increased over the holocene in response to long term cooling the influx of locally and regionally derived pollen grains varies throughout the core and tracks several major changes observed in the biogenic silica record from arolik lake alaska and the gisp2 ice core suggesting that climate change closely controlled arctic plant productivity using modern analogue and transfer function techniques we generated quantitative reconstructions of mean july temperature and total annual precipitation for the past 10 000 years to place recent climate changes within the context of holocene climate variability the quantitative reconstructions indicate that july temperature cooled by 1 1 5 c during the holocene the pollen based reconstructions record an increase in temperature of 0 5 c over the last 100 years and the pollen percentage and influx data indicate impacts of recent warming on the regional vegetation

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