the upper end of the uk 37 temperature calibration revisited 1 being able to decipher paleo sea surface temperatures for warm oceanic waters is of the utmost importance to further evaluate the role of the tropics in global climate change the uk 37 index is one of such paleothermometers although the warm range of temperatures often poses serious analytical challenges this paper discusses and reviews several important aspects of the uk 37 index calibration for waters warmer than 26 27 c amongst them insights into the possible existence of a limit above which the uk 37 index is not able to accurately record temperature variations are presented some warnings are also given on the misleading practice and expected consequences of reporting uk 37 index values of unity in the cases when abundances of the minor triunsaturated alkenone below detection limit are encountered future directions toward an improved knowledge of the behaviour of the uk 37 calibration for warm waters are suggested

reevaluation of the oxygen isotopic composition of planktonic foraminifera experimental results and revised paleotemperature equations cultured planktonic foraminifera orbulina universa symbiotic and globigerina bulloides nonsymbiotic are used to reexamine temperature 18o relationships at 15 25 c relationships for both species can be described by linear equations equations for o universa grown under low light ll and high light hl share a slope of 4 80 0 21 c 1 with a hl ll offset of 0 33 due to symbiont photosynthetic activity the effect of co32 on o universa is 0 002 mol 1 kg 1 and is insensitive to temperature for g bulloides ontogenetic effects produce size related trends in temperature 18o whereby larger shells are enriched in 18o relative to smaller specimens the o universa temperature 18o relationships are more accurate than previously published equations for describing plankton tow data our equations do not explain planktonic core top data with the same precision but provide a good fit to benthic cibicidoides data below 10 c temperature 18o relationships for g bulloides provide good agreement with field data for this species from the northeast pacific

a novel proxy for terrestrial organic matter in sediments based on branched and isoprenoid tetraether lipids we propose a novel tracer for terrestrial organic carbon in sediments based on the analysis of tetraether lipids using high performance liquid chromatography mass spectrometry hplc ms analysis of terrestrial soil and peats shows that branched tetraether lipids are predominant in terrestrial environments in contrast to crenarchaeol the characteristic membrane lipid of non thermophilic crenarchaeota which is especially abundant in the marine and lacustrine environment based on these findings an index was developed the so called branched and isoprenoid tetraether bit index based on the relative abundance of terrestrially derived tetraether lipids versus crenarchaeol this bit index was applied to surface sediments from the angola basin where it was shown to trace the outflow of the congo river furthermore analyses of particulate organic matter from the north sea showed relatively higher bit indices in water column particulate organic matter near large river inputs a survey of globally distributed marine and lacustrine surface sediments shows that the bit index in these environments correlates with the relative fluvial input of terrestrial organic material making this index generally applicable the new proxy allows the rapid assessment of the fluvial input of terrestrial organic material in immature sediments up to 100 ma old

perennial spring occurrence in the expedition fiord area of western axel heiberg island canadian high arctic this paper documents perennial spring activity at expedition fiord on western axel heiberg island in the canadian high arctic two groups of mineralized springs occur near the mcgill university axe

an investigation into the mechanisms controlling seasonal speedup events at a high arctic glacier bingham r g hubbard a l nienow p w sharp m j 2008 an investigation into the mechanisms controlling seasonal speedup events at a high arctic glacier journal of geophysical research earth surface 113 f2 f02006 sponsorship nerc nserc the university of alberta circumpolar institute and northern science training programme the geological society of america

230th normalization an essential tool for interpreting sedimentary fluxes during the late quaternary there is increasing evidence indicating that syndepositional redistribution of sediment on the seafloor by bottom currents is common and can significantly affect sediment mass accumulation rates notwithstanding its common incidence this process generally referred to as sediment focusing is often difficult to recognize if redistribution is near synchronous to deposition the stratigraphy of the sediment is not disturbed and sediment focusing can easily be overlooked ignoring it however can lead to serious misinterpretations of sedimentary fluxes particularly when past changes in export flux from the overlying water are inferred in many instances this problem can be resolved at least for sediments deposited during the late quaternary by normalizing to the flux of 230th scavenged from seawater which is nearly constant and equivalent to the known rate of production of 230th from the decay of dissolved 234u we review the principle advantages and limitations of this method notwithstanding its limitations it is clear that 230th normalization does provide a means of achieving more accurate interpretations of sedimentary fluxes and eliminates the risk of serious misinterpretations of sediment mass accumulation rates

evidence for indonesian throughflow slowdown during heinrich events 3 5 we present sea surface and upper thermocline temperature records 60 100 year temporal resolution spanning marine isotope stage 3 similar to 24 62 ka b p from international marine global change study core md01 2378 121 degrees 47 27 e and 13 degrees 04 95 s 1783 m water depth located in the outflow area of the indonesian throughflow within the timor sea stable isotopes and mg ca of the near surface dwelling planktonic foraminifer globigerinoides ruber white and the upper thermocline dwelling pulleniatina obliquiloculata reveal rapid changes in the thermal structure of the upper ocean during heinrich events thermocline warming and increased delta o 18 seawater p obliquiloculata record during heinrich events 3 4 and 5 reflect weakening of the relatively cool and fresh thermocline flow and reduced export of less saline water from the north pacific and indonesian seas to the tropical indian ocean three main factors influenced indonesian throughflow variability during marine isotope stage 3 1 global slowdown in thermohaline circulation during heinrich events triggered by northern hemisphere cooling 2 increased freshwater export from the java sea into the indonesian throughflow controlled by rising sea level from similar to 60 to 47 ka and 3 insolation related changes in the australasian monsoon with associated migration of hydrological fronts between indian ocean and indonesian throughflow derived water masses at similar to 46 40 ka

deep crustal deformation textures along megathrusts from newfoundland and ontario implications for microstructural preservation strain rates and strength of the lithosphere lithospheric scale thrusts from the west newfoundland ophiolite belt white hills peridotite shear zone and the south western grenville province parry sound shear zone involve rocks of lower crustal and or upper mantle origin that exhibit intense crystal plastic deformation of plagioclase k feldspar orthopyroxene and clinopyroxene minerals that are commonly viewed as representative of low ductility phases the occurrence of this extreme deformation in shear zones that exhibit similar lower crustal syntectonic p t conditions suggests a phenomenological link between the megathrust environment and both the generation and subsequent preservation of the observed deformation microstructures an empirical homologous parameter is constructed in an attempt to characterize conditions for similar behaviour among different minerals and to explore the feasibility of refining a threshold recovery preservation condition within the megathrusts studied this parameter predicts at the estimated syntectonic temper

high resolution record of northern hemisphere climate extending into the last interglacial period high resolution record of northern hemisphere climate extending into the last interglacial period

glacier velocities and dynamic discharge from the ice masses of baffin island and bylot island nunavut canada speckle tracking of alos palsar fine beam data from 2007 2011 are used to determine the surface motion of major ice masses on baffin island and bylot island in the southern canadian arctic archipelago glacier velocities are low overall with peaks of 100 m a 1 and means of 20 60 m a 1 common along the main trunk of many outlet glaciers peak velocities on penny and bylot island ice caps tend to occur near the mid sections of their primary outlet glaciers while the fastest velocities on all other glaciers usually occur near their termini due to relatively large accumulation areas draining through narrow outlets estimates of ice thickness at the fronts of tidewater terminating glaciers are combined with the velocity measurements to determine a regional dynamic discharge rate of between 17 mt a 1 and 108 mt a 1 with a mid point estimate of 55 mt a 1 revising downward previous approximations these velocities can be used as inputs for glacier flow models and provide a baseline dataset against which

near surface hydraulic conductivity of northern hemisphere glaciers the hydrology of near surface glacier ice remains a neglected aspect of glacier hydrology despite its role in modulating meltwater delivery to downstream environments to elucidate the hydrological characteristics of this near surface glacial weathering crust we describe the design and operation of a capacitance based piezometer that enables rapid economical deployment across multiple sites and provides an accurate high resolution record of near surface water level fluctuations piezometers were employed at 10 northern hemisphere glaciers and through the application of standard bail recharge techniques we derive hydraulic conductivity k values from 0 003 to 3 519 m day 1 with a mean of 0 185 0 019 m day 1 these results are comparable to those obtained in other discrete studies of glacier near surface ice and for firn and indicate that the weathering crust represents a hydrologically inefficient aquifer hydraulic conductivity correlated positively with water table height but negatively with altitude and cumulative short wave radiation since the last synoptic period of either negative air temperatures or turbulent energy flux dominance the large range of k observed suggests complex interactions between meteorological influences and differences arising from variability in ice structure and crystallography our data demonstrate a greater complexity of near surface ice hydrology than hitherto appreciated and support the notion that the weathering crust can regulate the supraglacial discharge response to melt production the conductivities reported here coupled with typical supraglacial channel spacing suggest that meltwater can be retained within the weathering crust for at least several days not only does this have implications for the accuracy of predictive meltwater run off models but we also argue for biogeochemical processes and transfers that are strongly conditioned by water residence time and the efficacy of the cascade of sediments impurities microbes and nutrients to downstream ecosystems because continued atmospheric warming will incur rising snowline elevations and glacier thinning the supraglacial hydrological system may assume greater importance in many mountainous regions and consequently detailing weathering crust hydraulics represents a research priority because the flow path it represents remains poorly constrained

the development of a pulsating supraglacial stream supraglacial streams are a significant part of the glacial hydrological system and important for understanding the connection between glacial hydrology and glacier dynamics here we determine the factors that influence the development of step pool formation and pulsating flow in a supraglacial stream on bylot island nunavut results show that during the second week of a 2 week study multiple successive rainfall events occurred stream temperature increased and ablation decreased which also caused stream discharge to decrease in addition the stream which flowed over a 13 m high waterfall off the front of fountain glacier rapidly formed 21 step pools and began to pulsate the pulsating phenomenon involved the complete stoppage of flow over the waterfall and the subsequent restart between 8 and 20 s later pulsating flow resulted from rapid changes in the streambed morphology in particular the formation of the step pool sequence was caused by helical flow around meander bends and hydrologically induced slippage along transverse shear planes evidenced by observations of high pressure artesian flow from transverse fractures contrary to previous literature this study shows that high discharge is not necessarily the cause of step pool formation and pulsating flow within supraglacial streams

glacial conditions that contribute to the regeneration of fountain glacier proglacial icing bylot island canada proglacial icings are one of the most common forms of extrusive ice found in the canadian arctic however the icing adjacent to fountain glacier bylot island is unique due to its annual cycle of growth and decay and perennial existence without involving freezing point depression of water due to chemical characteristics its regeneration depends on the availability of subglacial water and on the balance between ice accretion and hydro thermal erosion the storage and conduction of the glacial meltwater involved in the accretion of the icing were analyzed by conducting topographic and ground penetrating radar surveys in addition to the modelling of the subglacial drainage network and the thermal characteristics of the glacier base the reflection power analysis of the geophysical data shows that some areas of the lower ablation zone have a high accumulation of liquid water particularly beneath the centre part of the glacier along the main supraglacial stream a dielectric permittivity model of the glacier sediment interface suggests that a considerable portion of the glacier is warm based allowing water to flow through unfrozen subglacial sediments towards the proglacial outwash plain all these glacier related characteristics contribute to the annual regeneration of the proglacial icing and allow for portions of the icing to be perennial copyright 2013 john wiley sons ltd

glacial hydrological system characterization using ground penetrating radar hydrological systems near the terminus of a high arctic glacier and a proglacial icing on bylot island canada were investigated using ground penetrating radar gpr the ice thickness and the location and depth of tunnels within the glacier and icing were imaged modelling of the gpr response was utilized to predict the data quality and to assist in its interpretation the unique properties of the ice enabled velocity determinations from the diffraction patterns generated by point source reflectors as well as traditional velocity surveys the propagation velocity of the radar pulses through the ice depended on the air and water content in the ice the identification of drainage tunnels was attained through pulse polarity analysis and interpolation between the profiles in gridded surveys it was found that reflectivity analysis may enable gpr to be used for acquiring three dimensional information on the thermal structure of glaciers the much more complicated structure of the icing was imaged with higher frequency antennae and it was found that general ice types could be mapped using radar stratigraphical analysis both buried slush mounds and subsurface channel fills were identified within the icing a portion of the icing near the centre of the valley floor that has persisted perennially for over 50 years was found to be sitting on a slightly higher area of the valley bottom and thus was not subjected to the same hydrothermal erosional forces as the edges of the icing setting up a feed back loop encouraging the preservation of the central core of ice and promoting the destruction and rebuilding of the edges every year

climate impact of late quaternary equatorial pacific sea surface temperature variations magnesium calcium data from planktonic foraminifera in equatorial pacific sediment cores demonstrate that tropical pacific sea surface temperatures ssts were 2 8 0 7 c colder than the present at the last glacial maximum glacial interglacial temperature differences as great as 5 c are observed over the last 450 thousand years changes in sst coincide with changes in antarctic air temperature and precede changes in continental ice volume by about 3 thousand years suggesting that tropical cooling played a major role in driving ice age climate comparison of sst estimates from eastern and western sites indicates that the equatorial pacific zonal sst gradient was similar or somewhat larger during glacial episodes extraction of a salinity proxy from the magnesium calcium and oxygen isotope data indicates that transport of water vapor into the western pacific was enhanced during glacial episodes

seasonal changes in ground penetrating radar signature observed at a polythermal glacier bylot island canada in recent years ground penetrating radar gpr has been increasingly used for characterization of subglacial and englacial environments at polythermal glaciers the geophysical method is able to exploit the dielectric difference between water air sediment and ice allowing delineation of subsurface hydrological thermal and structural conditions more recent gpr research has endeavoured to examine temporal change in glaciers in particular the distribution of the cold ice zone at polythermal glaciers however the exact nature of temporal change that can be identified using gpr has not been fully examined this research presents the results of three gpr surveys conducted over the course of a summer ablation season at a polythermal glacier in the canadian arctic a total of approximately 30 km of gpr profiles were collected in 2002 repeatedly covering the lower 2 km of stagnation glacier bylot island 72 58 n 78 22 w comparison between profiles indicated changes in the radar signature including increased noise appearance and disappearance of englacial reflections and signal attenuation in the latter survey further an area of chaotic returns in up glacier locations which was interpreted to be a wet temperate ice zone showed marked recession over the course of the ablation season combining all the temporal changes that were detected by gpr results indicate that a polythermal glacier may exhibit strongly seasonal changes in hydrological and thermal characteristics throughout the ice body including the drainage of 17 000 m 3 of temporarily stored intra glacial meltwater it is also proposed that the liquid water content in the temperate ice zone of polythermal glaciers can be described as a fraction of a specific retention capacity copyright 2006 john wiley sons ltd

warm pool hydrological and terrestrial variability near southern papua new guinea over the past 50k here we presenta 50k archiveof u37 seasurface temperature sst planktic foraminifera oxygen isotopes and terrestrial input indicators including branched and isoprenoid tetraether bit biomarkers 232 th activity and non biogenic sediment components recorded in core md052928 from the wpwp near southern papua new guinea png the planktic foraminifer oxygen isotopes in the core show millennial scale changes indicating fresher seawater during the nh cold periods i e heinrich events hes and suggesting hydrological changes that are most likely linked to the strength of the boreal winter asian australian monsoon aam our observations are corroborated by evidence from the same core that indicates increased terrestrial input caused by higher precipitation on land and more river runoff from southern png during the cold periods consistent with other nearby hydrological records from land our study indicates persistent millennial scale hydrological changes within the past 50k in the western tropical pacific and southeast asia the timing of the millennial scale changes appears to have been determined by the latitudinal displacement of the intertropical convergencezone itcz thatreflectsahistoryofheattrans

mapping thermal and hydrological conditions beneath a polythermal glacier with radio echo sounding spatial patterns in residual bed reflection power brp r derived from ground based radio echo sounding were mapped and interpreted in terms of the thermal and hydrological conditions at the base of a high arctic polythermal glacier john evans glacier ellesmere island canada brp r is the residual from a statistical relationship between measured bed reflection power and ice thickness that describes the rate of dielectric loss with depth in the glacier we identified three types of thermal structure a positive brp r and an internal reflecting horizon occur over the glacier terminus the reflecting horizon is interpreted as the boundary between warm and cold ice and suggests the presence of a warm basal layer b positive brp r occurs without an internal reflector in the upper part of the ablation zone this suggests that ice is at the pressure melting point only at the bed c negative brp r without an internal reflector occurs in all other regions suggesting cold ice at the bed where brp r is positive its pattern is similar to the pattern of subglacial water flow predicted from the form of the subglacial hydraulic equipotential surface this suggests that hydrological conditions at the glacier bed are a major control on brp r probably because the dielectric contrast between ice and water is higher than that between ice and other subglacial materials

factors influencing the basal temperatures of a high arctic polythermal glacier a number of glaciers in the canadian high arctic are composed primarily of cold ice but the ice at or near their beds reaches the pressure melting point pmp in the ablation zone past modelling studies have suggested that the basal temperatures of some of these glaciers reach the pmp where they should not indicating that they are not in thermal equilibrium with present day surface air temperatures to investigate the possible reasons for thermal disequilibria in such glaciers a two dimensional ice temperature model was used to simulate the inferred thermal characteristics of john evans glacier ellesmere island results indicate that while surface refreezing and historical ice thickness changes have had a warming effect upon basal ice temperatures supraglacial meltwater reaching the glacier bed provides the single most critical heat source for explaining the apparent thermal disequilibrium between present day inferred ice bed temperatures and those modelled under present day boundary conditions

polythermal glacier hydrology a review 1 the manner by which meltwater drains through a glacier is critical to ice dynamics runoff characteristics and water quality however much of the contemporary knowledge relating to glacier hydrology has been based upon and conditioned by understanding gleaned from temperate valley glaciers globally a significant proportion of glaciers and ice sheets exhibit nontemperate thermal regimes the recent growing concern over the future response of polar glaciers and ice sheets to forecasts of a warming climate and lengthening summer melt season necessitates recognition of the hydrological processes in these nontemperate ice masses it is therefore timely to present an accessible review of the scientific progress in glacial hydrology where nontemperate conditions are dominant this review provides an appraisal of the glaciological literature from nontemperate glaciers examining supraglacial englacial and subglacial environments in sequence and their role in hydrological processes within glacierized catchments in particular the variability and complexity in glacier thermal regimes are discussed illustrating how a unified model of drainage architecture is likely to remain elusive due to structural controls on the presence of water cold ice near glacier surfaces may reduce meltwater flux into the glacier interior but observations suggest that the transient thermal layer of near surface ice holds a hydrological role as a depth limited aquifer englacial flowpaths may arise from the deep incision of supraglacial streams or the propagation of hydrofractures forms which are readily able to handle varied meltwater discharge or act as locations for water storage and result in spatially discrete delivery of water to the subglacial environment the influence of such drainage routes on seasonal meltwater release is explored with reference to summer season upwellings and winter icing formation moreover clear analogies emerge between nontemperate valley glacier and ice sheet hydrology the discussion of which indicates how persistent reassessment of our conceptualization of glacier drainage systems is required there is a clear emphasis that continued integrated endeavors focused on process glaciology at nontemperate glaciers are a scientific imperative to augmenting the existing body of research centered on ice mass hydrology

subglacial drainage by groundwater channel coupling and the origin of esker systems part 1 glaciological observations this work is presented in two parts part i presents observations on the coupling between subglacial channel flow and groundwater flow in determining subglacial hydraulic regime and creating eskers from an icelandic glacier that is suggested as an analogue for many parts of pleistocene ice sheets part ii develops a theory of perennial subglacial stream flow and the origin of esker systems and models the evolution of the subglacial stream system and associated groundwater flow in a glacier of the type described in part i it is suggested that groundwater flow may be the predominant mechanism whereby meltwater at the glacier bed finds its way to the major subglacial streams that discharge water to glacier margins

hydrology and dynamics of a polythermal mostly cold high arctic glacier to improve our understanding of the interactions between hydrology and dynamics in mostly cold glaciers in which water flow is limited by thermal regime we analyse short term every two days variations in glacier flow in the ablation zone of polythermal john evans glacier high arctic canada we monitor the spatial and temporal propagation of high velocity events and examine their impacts upon supraglacial drainage processes and evolving subglacial drainage system structure each year in response to the rapid establishment of supraglacial subglacial drainage connections in the mid ablation zone a spring event of high horizontal surface velocities and high residual vertical motion propagates downglacier over two to four days from the mid ablation zone to the terminus subsequently horizontal velocities fall relative to the spring event but remain higher than over winter reflecting channelization of subglacial drainage but continued supraglacial meltwater forcing further transient high velocity events occur later in each melt season in response to melt induced rising supraglacial meltwater inputs to the glacier bed but the dynamic response of the glacier contrasts with that recorded during the spring event with the degree of spatial propagation a function of the degree to which the subglacial drainage system has become channelized copyright 2006 john wiley sons ltd

short pulse radar wavelet recovery and resolution of dielectric contrasts within englacial and basal ice of matanuska glacier alaska u s a wavelets transmitted by short pulse radar are recovered from continuous profiles and used to determine interfacial dielectric contrasts within the englacial and basal ice at the terminus area of matanuska glacier alaska u s a the field studies were in the ablation region where radar horizons could at some point be identified with interfaces between clear ice and air water or basal ice and were performed in early spring before drainage fully developed the profiles usedclosely spaced antennas with bandwidths centered near 50 and 400 mhz transmitted wavelets reflected from interfaces of known dielectric contrasts are used to establish a phase reference for other events from interfaces between unknown contrasts migration and fourier transform filtering are then applied to the profiles and shown to recover these wavelets from diffractions and reflections interfacial dielectric contrasts are determined from the relative phase of the wavelets near the terminus lake some basal ice events above 8 m depth are interpreted as voids further up glacier most englacial events are interpreted as voids but deeper localized reflectors and horizons to 90 m depth and within the basal zone are interpreted as voids water or debris phase cannot be determined for the basal substrate transition reflections recommendations are made for improving the wavelet recovery process and the quality of gpr migration

correlation between climate events in the north atlantic and china during the last glaciation episodes of massive iceberg release heinrich events 1 3 into the north atlantic ocean during the last glaciation were associated with recurring episodes of unusually cold north atlantic surface water bond cycles 4 and cold air temperatures over greenland dansgaard oeschger events 5 6 four of the youngest of these cold events have also been reported in climate records from sites outside the north atlantic region7 but until now the entire suite has been identified only in north atlantic marine sediments greenland ice core records and tentatively in french lake sediments8 here we examine grain size data from chinese loess and intercalated accretionary palaeosols of last glacial age for evidence of similar climate signals remote from the north atlantic region we see grain size maxima with ages that match those of the last six heinrich events which we interpret as an indication of the changing strength of the east asian winter monsoon which largely controls the transport and deposition of central asian aeolian dust thus it seems that these heinrich events have left their signature in the chinese loess record this is consistent with simulations of the glacial climate9 which imply that the climates of the north atlantic and china were linked by the effect of westerly winds