quantification of sediment transport by rockfall and rockslide processes on a proglacial rock slope kaunertal austria abstract rockfalls and rockslides are significant geomorphic processes on high alpine proglacial rock slopes in this study we quantitatively evaluate sediment transport on a recently deglaciated rock slope that is directly connected to the shrinking gepatschferner glacier by multi temporal terrestrial and airborne lidar observations according to the lidar measurements sediment transport by gravitational mass movements on this single proglacial rock slope 0 2 km 2 yielded 159 gj a geomorphic work the most significant part 141 gj a was released by rockfall while 18 gj a were performed by the sliding activity of a 1 250 000 m 3 large unstable rock mass the results indicate that slope development and talus formation in proglacial environments may be a rapid process despite of being caused by continuous rockfall activity over several millennia

diatom response to the holocene climatic optimum on the north icelandic shelf abstract a diatom record from core md992275 on the north icelandic shelf reveals palaeoclimatic and palaeoceanographic changes during the time interval 9000 to 5600 cal year bp the study period includes the holocene climate optimum hco as widely known in the north atlantic region a comparison with data for the last 2000 years and with the present day surface sediment diatom assemblages shows that there was considerably stronger influence of atlantic water masses in the area during the hco than in the late holocene and today the results of cluster analysis and principal component analysis divide the studied period into three intervals each characterised by a specific diatom assemblage the assemblages indicate changes in the interaction of the relatively warm irminger current ic and the cold east greenland current egc and east icelandic current eic the north icelandic shelf was strongly affected by the ic during the interval 8000 6800 cal year bp which may be the warmest period of the holocene during the intervals 9000 8000 and 6800 5600 cal year bp the influence of the ic was relatively weak and that of the egc and eic increased correspondingly the well known 8200 cal year bp cooling event shown in many records from the north atlantic is reflected by a relatively strong influence of the egc and eic between about 8300 and 8100 cal year bp in our record however the diatom assemblages show that the inferred circulation change did not bring the strength of the ic down to the levels seen at present and during the last two millennia

coarse sediment dynamics in a proglacial fluvial system fagge river tyrol abstract alpine regions are strongly affected by the global climate change alpine glaciers have had a negative net balance since the end of the little ice age lia proglacial areas with freshly exposed subglacial sediments are expanding due to the retreat of glaciers these sediments moraines tills glaciofluvial deposits etc are unconsolidated nearly unvegetated and therefore unstable and highly vulnerable to surface changes triggered by geomorphological processes particularly during heavy rainfall events glacial and glaciofluvial deposits are remobilized and transported within the fluvial system this study is focused on rapidly changing surfaces in the proglacial fluvial system of the fagge river which drains the gepatschferner one of the biggest glaciers in austria and is located in the kaunertal austria the field site covers an area from the snout of the glacier 2206 m a s l to the outlet of the fagge river into the gepatsch reservoir at 1750 m a s l the main goal of this study is to measure surface changes and quantify mass balances of important sediment sources alluvial plains bars in the proglacial area which are directly connected to the fluvial system for this purpose multiple terrestrial laser scans are performed with an optech ilris 36d laser scanner during the field season in 2011 and 2012 several sediment sources were scanned at least twice significant surface changes occurred during the investigation period mainly caused by an extreme flood event after heavy rain on august 26 2012 large amounts of sediment 70 000 m3 were remobilized especially in the upper parts of the proglacial area and were accumulated further downstream during this event

application of tephrochronology to the timing and correlation of palaeoceanographic events recorded in holocene and late glacial shelf sediments off north iceland abstract the north icelandic shelf is partly distinguished by the tjornes fracture zone featuring numerous active basins in a mud dominated shelf environment late glacial and holocene high resolution sedimentary records from this area have been studied with tephrochronology as the main tool for correlation and for exact timing of palaeoceanographic events in the area data from three new piston cores from the shelf demonstrate the importance of tephra markers for the first chronological evaluation and correlation of the cores the correlation is extended with lithological logs and with magnetic susceptibility records a detailed multidisciplinary study including biostratigraphy and tephrochronology of a late holocene record of predominantly muddy sediments at the same location demonstrates that marked variations in the distribution of water masses occurred repeatedly through the last 4500 cal yr of special interest is the exact timing of a marked drop in sea surface temperature in the area indicated by ice rafting debris concentration to about 50 years before the hekla 3 eruption which occurred at 2980 cal yr bp this appears to predate most records of a general cooling event in nw europe by a couple of centuries two different possible age models one based on 14c dates combined with tephra markers and one based on tephra markers alone are discussed in context with the problem of different marine reservoir ages of the water masses in the area

determination of the bedload transport rate in a small proglacial high arctic stream using direct semi continuous measurement abstract the article presents the results of a 34 day series of direct semi continuous measurements of the bedload transport performed during the melt season 2013 in the scott river catchment nw part of the wedel jarlsberg land spitsbergen the daily variability of the bedload transport rates and its relation to the dissolved and suspended load were analysed in two cross sections located in the lower course of a proglacial gravel bed river the bedload flux was measured by means of two 4 module sets of river bedload traps rbt in the research period a total of 34 day long samples of bedload and 34 water samples for the determination of the dissolved and suspended load were collected in each of the two cross sections 200 m apart the measurements showed longitudinal and temporal variability of bedload flux and the remaining components solutions suspensions corresponding with changes in water discharge the mean daily bedload flux qb in consecutive measurement cross sections xs amounted to 124 kg d 1 xs i and 59 kg d 1 xs ii respectively and showed high variability and an evident relationship with temperature the unequal bedload flux of the two measuring stations xs i and xs ii suggests aggradation within the alluvial fan that separates the two reaches the volume and rate of bedload flux were determined by the frequency of the occurrence of flood flows during which approximately from 59 xs i to 77 xs ii of total bedload was discharged the highest recorded daily values constituted 12 of total bedload flux through the cross section below the alluvial fan the river discharged approximately 6 million cubic meters m m3 of water 3 t of bedload lb 2238 t of suspended load ls and 613 t of dissolved load ld the relationships between the three components of the load suggest a 500 fold excess of suspended load and a 100 fold excess of dissolved load in relation to bedload flux high temporal and latitudinal variability of the bedload transport rate resulted in changes in the channel morphology and during floods also the floodplain

sigmoidal inclusion trails punctuated fabric development and interactions between metamorphism and deformation porphyroblast inclusion fabrics are consistent in style and geometry across three proterozoic metamorphic field gradients comprising two pluton related gradients in central arizona and one regional gradient in northern new mexico garnet crystals contain curved sigmoidal inclusion trails in low grade chlorite schists these trails can be correlated directly with matrix crenulations of an older schistosity s1 the garnet crystals preferentially grew in crenulation hinges but some late crenulations nucleated on existing garnet porphyroblasts at higher grade biotite staurolite and andalusite porphyroblasts occur in a homogeneous s2 foliation primarily defined by matrix biotite and ilmenite biotite porphyroblasts have straight to sigmoidal inclusion trails that also represent the weakly folded s1 schistosity staurolite and andalusite contain distinctive inclusion rich and inclusion poor domains that represent a relict s2 differentiated crenulation cleavage together the inclusion relationships document the progressive development of the s2 fabric through six stages garnet and biotite porphyroblasts contain stage 2 or 3 crenulations staurolite and andalusite generally contain stage 4 crenulations and the matrix typically contains a homogeneous stage 6 cleavage the similarity of inclusion relationships across spatially and temporally distinct metamorphic field gradients of widely differing scales suggests a fundamental link between metamorphism and deformation three end member relationships may be involved 1 tectonic linkages where similar p t time histories and similar bulk compositions combine to produce similar metamorphic and structural signatures 2 deformation controlled linkages where certain microstructures particularly crenulation hinges are favourable environments for the nucleation and or growth of porphyroblasts and 3 reaction controlled linkages where metamorphic reactions particularly dehydration reactions are associated with an increase in the rate of fabric development a general model is proposed in which 1 garnet and biotite porphyroblasts preferentially grow in stage 2 or 3 crenulation hinges and 2 chlorite consuming metamorphic reactions lead to pulses in the rate of fabric evolution the data suggest that fabric development and porphyroblast growth may have been quite rapid of the order of several hundreds of thousands of years in these rocks these microstructures and processes may be characteristic of low pressure first cycle metamorphic belts

geomorphic effectiveness a linear concept in a non linear world geomorphic effectiveness has been an influential concept in geomorphology since its introduction by reds wolman and john miller in 1960 it provided a much needed framework to assess the significance of an event by comparing event magnitude to the resultant geomorphic effects initially this concept was applied primarily in river channels under the linear assumption that geomorphic responses to similarly sized flood events will be consistent numerous authors have since attempted to quantify a direct proportional relationship between event magnitude and different forms of geomorphic response in a variety of geomorphic settings in doing so these investigations applied an array of metrics that were difficult to compare across different spatiotemporal scales and physiographic and geomorphic environments critically the emergence of other geomorphic concepts such as sensitivity connectivity thresholds and recovery has shown that relationships between causes events and geomorphic effects responses are often complex and non linear this paper disentangles the complex historical development of the geomorphic effectiveness concept and reviews the utility of various metrics for quantifying effectiveness we propose that total energy joules is the most appropriate metric to use for quantifying the magnitude of disturbance events cause and volumetric sediment flux associated with landform modification is the most appropriate metric for quantifying geomorphic effects while both metrics are difficult to quantify they are the only ones which facilitate comparison across a range of spatiotemporal scales comparability in a variety of geomorphic environments flexibility the geomorphic effectiveness concept can continue to be useful provided that geomorphologists use flexible and comparable metrics today geomorphologists are better prepared to consider the influence of non linear processes on determinations of geomorphic effectiveness allowing investigators to not only determine if a disturbance event was effective but also to explain why or why not copyright

diatoms from the surface sediments of the south china sea and their relationships to modern hydrography abstract a principal components analysis of diatoms in surface sediment samples from the south china sea scs shows a clear relationship between the spatial distributions of diatoms and the current pattern of the region six diatom assemblages are distinguished representing environments with different hydrological characteristics the neritic planktonic species thalassionema nitzschioides is the dominant component in the surface sediment diatoms with relatively small changes throughout the scs suggesting that the water mass exchanges between the scs and the pacific and indian oceans are relatively small the strongest impact of the warm oceanic water occurs in the northeasternmost part of the scs where assemblage v is located with nitzschia marina azpeitia nodulifera azpeitia neocrenulata rhizosolenia bergonii and thalassionema frauenfeldii as main taxa warm oceanic planktonic species n marina r bergonii and a neocrenulata can be used as indicators of warm oceanic waters flowing into the scs in paleoceanographic reconstructions of the area in particular in tracking the water from the western pacific including the kuroshio current it may however be problematic to use another tropical oceanic planktonic species a nodulifera as an environmental indicator because of its strong resistance to dissolution thus possibly further transport

multi proxy records showing significant holocene environmental variability the inner n iceland shelf hunafloi abstract over the last 50 yr the n iceland margin has seen dramatic changes in temperature and salinity associated with the relative dominance of warm atlantic water versus cold arctic or polar waters we report a study of holocene environmental changes to assess the sensitivity of this area on a longer timescale we present sedimentologic isotopic and biotic coccolith proxies from a 5 5 m piston core b997 330pc that was retrieved from a small basin on the inner n iceland shelf seven ams dates indicate a relatively constant rate of sediment accumulation which averaged 55 cm kyr sampling resolution of our proxies varied between 16 and 90 yr sample our data indicate substantial variability in environmental conditions over the last 10 000 cal yr total carbonate content and coccolith concentrations track each other and indicate that the early holocene was a time of low net carbonate accumulation net accumulation of carbonate reached maximum values in the mid to late holocene 4 2 cal ka but there has since been a substantial decrease with a minima during the little ice age north atlantic drift coccolith species show peaks in accumulation rates at 2 and 8 cal ka and low influx between 3 5 and 6 cal ka reworked neogene coccoliths occur also 8 ka and coincide with light 18 o values in the epifaunal foraminifera cibicides lobatulus principal component analysis indicates considerable covariance between biotic isotopic and sedimentological parameters three axes explain 84 of the variance in the data set and define three groups of interrelated variables a major change occurs ca 5 cal ka after which conditions become more variable with a 1 5 kyr cyclicity

alpine glaciers to disappear within decades 1 past present and potential future glacier cover in the entire european alps has been assessed from an integrated approach combining in situ measurements remote sensing techniques and numerical modeling for equilibrium line altitudes alpine glaciers lost 35 of their total area from 1850 until the 1970s and almost 50 by 2000 total glacier volume around 1850 is estimated at some 200 km3 and is now close to one third of this value from the model experiment we show that a 3 c warming of summer air temperature would reduce the currently existing alpine glacier cover by some 80 or up to 10 of the glacier extent of 1850 in the event of a 5 c temperature increase the alps would become almost completely ice free annual precipitation changes of 20 would modify such estimated percentages of remaining ice by a factor of less than two

nonuniform response of the major surface currents in the nordic seas to insolation forcing implications for the holocene climate variability 1 high resolution sediment cores from the voring plateau the north iceland shelf and the east greenland shelf have been studied to investigate the stability of major surface currents in the nordic seas during the holocene results from diatom assemblages and reconstructed sea surface temperatures ssts indicate a division of the holocene into three periods the holocene climate optimum 9500 6500 calendar cal years bp the holocene transition period 6500 3000 cal years bp and the cool late holocene period 3000 0 cal years bp the overall climate development is in step with the decreasing insolation on the northern hemisphere but regional differences occur regarding both timing and magnitude of sst changes sites under the direct influence of the norwegian atlantic current and the irminger current indicate sst cooling of 4 5 c from early holocene to present compared to 2 c recorded under the east greenland current superimposed on the general holocene cooling trend there is a high frequency sst variability which is in the order of 1 1 5 c for the voring plateau and the east greenland shelf and 2 5 3 c on the north iceland shelf

persistent solar influence on north atlantic climate during the holocene surface winds and surface ocean hydrography in the subpolar north atlantic appear to have been influenced by variations in solar output through the entire holocene the evidence comes from a close correlation between inferred changes in production rates of the cosmogenic nuclides carbon 14 and beryllium 10 and centennial to millennial time scale changes in proxies of drift ice measured in deep sea sediment cores a solar forcing mechanism therefore may underlie at least the holocene segment of the north atlantic9s 1500 year cycle the surface hydrographic changes may have affected production of north atlantic deep water potentially providing an additional mechanism for amplifying the solar signals and transmitting them globally

gisp2 oxygen isotope ratios the gisp2 oxygen isotope record with its high resolution detail yields crucial information on past climate change the glacial 18o oscillations of the gisp2 core with their very fast onsets are templates of a prototype oscillation of variable duration with an amplitude of 3 9 the halfway mark of the cold warm transition is reached in 2 years the top is reached in 50 years the 18o time gradient of the leading front is about 7 8 per 100 yr after reaching the top 18o slowly declines by 0 14 per 100 yr the duration of 18o decline varies from a couple of centuries for fast oscillations to about 4000 yr for slower ones the subsequent 18o downturn during the warm cold transition has a 18o time gradient of 3 2 per 100 yr and lasts about 80 yr

is there evidence for solar forcing of climate in the gisp2 oxygen isotope record abstract changes in solar constant over an 11 yr cycle suggest a certain but limited degree of solar forcing of climate the high resolution climate oxygen isotope record of the greenland gisp2 greenland ice sheet project 2 ice core has been analyzed for solar and volcanic influences the atmospheric14c record is used as a proxy of solar change and compared to the oxygen isotope profile in the gisp2 ice core an annual oxygen isotope profile is derived from centimeter scale isotope measurements available for the post a d 818 interval associated extreme summer and winter isotope ratios were found to yield similar climate information over the last millennium the detailed record of volcanic aerosols converted to optical depth and volcanic explosivity change was also compared to the isotope record and the oxygen isotope response calibrated to short term volcanic influences on climate this calibration shows that century scale volcanic modulation of the gisp2 oxygen isotope record can be neglected in our analysis of solar forcing the timing estimated order of temperature change and phase lag of several maxima in14c and minima in18o are suggestive of a solar component to the forcing of greenland climate over the current millennium the fractional climate response of the cold interval associated with the maunder sunspot minimum and14c maximum as well as the medieval warm period and little ice age temperature trend of the past millennium are compatible with solar climate forcing with an order of magnitude of solar constant change of 0 3 even though solar forcing of climate for the current millennium is a reasonable hypothesis for the rest of the holocene the century scale events are more frequent in the oxygen isotope record than in the14c record and a significant correlation is absent for this interval oceanic atmospheric circulation forcing of climate may dominate solar forcing during the surprisingly strong 1470 yr climate cycle of the 11 000 75 000 yr b p interval is rather hypothetical

diatom surface sediment assemblages around iceland and their relationships to oceanic environmental variables canonical correspondence analysis of diatoms from surface sediment samples and oceanographic environmental variables shows that summer and winter sea surface temperatures water depth and winter sea surface salinity are the main environmental factors affecting diatom distribution around iceland of these summer sea surface temperature is the most important five diatom assemblages are distinguished and the distribution of these assemblages is clearly correlated with oceanic current patterns in the region the sea ice diatom assemblage is limited to the area where the east greenland current polar water has its strongest influence and the cold diatom assemblage is basically controlled by the less cold east icelandic current modified polar water the mixing diatom assemblage results from the interaction between the cold east greenland and east icelandic currents and the warm irminger current the warm diatom assemblage is located in the area dominated by the irminger current and may be used as an indicator of warm water masses atlantic water the coastal diatom assemblage is the only one strongly influenced by both water depth and summer water temperatures

short term geomorphological evolution of proglacial systems proglacial systems are amongst the most rapidly changing landscapes on earth as glacier mass loss permafrost degradation and more episodes of intense rainfall progress with climate change this review addresses the urgent need to quantitatively define proglacial systems not only in terms of spatial extent but also in terms of functional processes it firstly provides a critical appraisal of prevailing conceptual models of proglacial systems and uses this to justify compiling data on rates of landform change in terms of planform horizontal motion elevation changes and sediment budgets these data permit us to produce novel summary conceptual diagrams that consider proglacial landscape evolution in terms of a balance of longitudinal and lateral water and sediment fluxes throughout we give examples of newly emerging datasets and data processing methods because these have the potential to assist with the issues of i a lack of knowledge of proglacial systems within high mountain arctic and polar regions ii considerable inter and intra catchment variability in the geomorphology and functioning of proglacial systems iii problems with the magnitude of short term geomorphological changes being at the threshold of detection iv separating short term variability from longer term trends and v of the representativeness of plot scale field measurements for regionalisation and for upscaling we consider that understanding of future climate change effects on proglacial systems requires holistic process based modelling to explicitly consider feedbacks and linkages especially between hillslope and valley floor components such modelling must be informed by a new generation of repeated distributed topographic surveys to detect and quantify short term geomorphological changes

late holocene summer sea surface temperatures based on a diatom record from the north icelandic shelf diatom assemblages from a high resolution core on the north icelandic shelf reveal a general late holocene cooling trend which is interrupted by three relatively warm periods diatom data from sur

geomorphic coupling and sediment connectivity in an alpine catchment exploring sediment cascades using graph theory through their relevance for sediment budgets and the sensitivity of geomorphic systems geomorphic coupling and sediment connectivity represent important topics in geomorphology since the introduction of the systems perspective to physical geography by chorley and kennedy 1971 a catchment has been perceived as consisting of landscape elements e g landforms subcatchments that are coupled by geomorphic processes through sediment transport in this study we present a novel application of mathematical graph theory to explore the network structure of coarse sediment pathways in a central alpine catchment numerical simulation models for rockfall debris flows and hillslope and channel fluvial processes are used to establish a spatially explicit graph model of sediment sources pathways and sinks the raster cells of a digital elevation model form the nodes of this graph and simulated sediment trajectories represent the corresponding edges model results are validated by visual comparison with the field situation and aerial photos the interaction of sediment pathways i e where the deposits of a geomorphic process form the sources of another process forms sediment cascades represented by paths a succession of edges in the graph model we show how this graph can be used to explore upslope contributing area and downslope source to sink functional connectivity by analysing its nodes edges and paths the analysis of the spatial distribution composition and frequency of sediment cascades yields information on the relative importance of geomorphic processes and their interaction however regardless of their transport capacity in the study area the analysis stresses the importance of mass movements and their interaction e g the linkage of large rockfall source areas to debris flows that potentially enter the channel network moreover it is shown that only a small percentage of the study area is coupled to the channel network which itself is longitudinally disconnected by natural and anthropogenic barriers besides the case study we discuss the methodological framework and alternatives for node and edge representations of graph models in geomorphology we conclude that graph theory provides an excellent methodological framework for the analysis of geomorphic systems especially for the exploration of quantitative approaches towards sediment connectivity

holocene climatic instability a prominent widespread event 8200 yr ago the most prominent holocene climatic event in greenland ice core proxies with approximately half the amplitude of the younger dryas occurred 8000 to 8400 yr ago this holocene event affected regions well beyond the north atlantic basin as shown by synchronous increases in windblown chemical indicators together with a significant decrease in methane widespread proxy records from the tropics to the north polar regions show a short lived cool dry or windy event of similar age the spatial pattern of terrestrial and marine changes is similar to that of the younger dryas event suggesting a role for north atlantic thermohaline circulation possible forcings identified thus far for this holocene event are small consistent with recent model results indicating high sensitivity and strong linkages in the climatic system

late glacial and holocene palaeoceanography of the north icelandic shelf high resolution gravity cores and box cores from the north icelandic shelf have been studied for palaeoceanographic history based on lithological and biostratigraphical foramin iferal data results from two outer shelf cores covering the last 13 6 k 14 c yr bp are presented in this paper the sediments accumulated in north south trending basins on each side of the kolbeinsey ridge at water depths of ca 400 m sedimentation rates up to 1 5 m kyr 1 are observed during the late glacial and holocene the vedde and saksunarvatn tephras are present in the cores as well as the hekla 1104 a new tephra kol gs 2 has been identified and dated to 13 4 k 14 c yr bp and another tephra geochemically identical to the borrobol tephra has been found at the same level at present the oceanographic polar front is located on the north icelandic shelf which experiences sharp oceanographic surface boundaries between the cold east icelandic current and the warmer irminger current past changes in sedimentological and biological processes in the study area are assumed to be related to fluctuations of the polar front the area was deglaciated before ca 14 kyr bp but there is evidence of ice rafting up to the end of the gs 1 greenland stadial 1 younger dryas period increasing again towards the end of the holocene foraminiferal studies show a relatively strong gs 2 pre 13 kyr bp palaeo irminger current followed by severe cooling and then by unstable conditions during the remainder of the gi 1 greenland interstadial 1 bolling allerod and gs 1 younger dryas another cooling event occurred during the preboreal before the holocene current system was established at about 9 kyr bp after a climatic optimum between 9 and 6 kyr bp the climate began to deteriorate and fluctuate copyright 2000 john wiley sons ltd

the gisp2 δ18o climate record of the past 16 500 years and the role of the sun ocean and volcanoes measured 18o 16o ratios from the greenland ice sheet project 2 gisp2 ice core extending back to 16 500 cal yr b p provide a continuous record of climate change since the last glaciation high resolution annual 18o 16o results were obtained for most of the current millennium a d 818 1985 and record the medieval warm period the little ice age and a distinct 11 yr 18o 16o cycle volcanic aerosols depress central greenland annual temperature 1 5 c maximally and annual 18o 16o for about 4 yr after each major eruptive event on a bidecadal to millennial time scale the contribution of solar variability to holocene greenlandic temperature change is 0 4 c the role of thermohaline circulation change on climate problematic during the holocene is more distinct for the 16 500 10 000 cal yr b p interval analogous to 14c age calibration terminology we express time in calibrated cal yr b p a d 1950 0 cal yr b p the oldest dryas bolling older dryas allerod younger dryas sequence appears in great detail bidecadal variance in 18o 16o but not necessarily in temperature is enhanced during the last phase of lateglacial time and the younger dryas interval suggesting switches of air mass transport between jet stream branches the branched system is nearly instantaneously replaced at the beginning of the bolling and holocene at 14 670 and 11 650 cal yr b p respectively by an atmospheric circulation system in which 18o 16o and annual accumulation initially track each other closely thermodynamic considerations of the accumulation rate temperature relationship can be used to evaluate the 18 o 16o temperature relationship the gisp2 ice layer count years of major gisp2 climate transitions also support the use of coral 14c ages for age calibration

evidence for solar forcing of sea surface temperature on the north icelandic shelf during the late holocene diatom proxies from the modern position of the oceanographic polar front north of iceland record variability in sea surface temperatures ssts during the past 2 k y the sedimentary record is dated with tephrochronology alleviating marine 14c reservoir age uncertainties comparison of changes in ssts on the north icelandic shelf with variations in the atmospheric circulation above greenland north american atlantic coastal ssts and mean temperature anomalies for the northern hemisphere suggests synchronous north atlantic wide fluctuations which would seem to imply a common forcing factor a positive and significant correlation between our sst record from the north icelandic shelf and reconstructed solar irradiance together with modeling results supports the hypothesis that solar forcing is an important constituent of natural climate variability in the northern north atlantic region

the last 18 kyr fluctuations in norwegian sea surface conditions and implications for the magnitude of climatic change evidence from the north sea a combined record of three cores spanning the last 18 kyr from the northern north sea is investigated for content of benthic and planktonic foraminifera and stable oxygen isotopes the paleoenvironmental development through this time period shows an early deglaciation 18 14 4 ka and the younger dryas 12 7 11 5 ka characterized by arctic polar conditions and increased ice rafting in the norwegian channel during the bolling allerod period warm sea surface temperature 9 c conditions similar to present conditions are inferred while bottom waters stayed cold 0 1 c with normal salinity the bolling allerod period is interrupted twice at 13 9 13 6 ka older dryas and at 13 0 12 8 ka inter allerod cooling period by reductions in sea surface temperatures and increased sea ice cover the beginning of the holocene period is marked by increases in surface and bottom water temperature superimposed on the broad climatic changes through the holocene a series of short lived oscillations in the ocean circulation are recorded the amplitude of these holocene events appears larger in the early holocene prior to 8 ka than compared with the remaining part of the holocene this amplification can possibly be attributed to a general increased freshwater budget in the north atlantic at this time during the final stages of the deglaciation of the laurentide and scandinavian ice sheets

regional scale controls on the spatial activity of rockfalls turtmann valley swiss alps a multivariate modeling approach abstract in mountain geosystems rockfalls are among the most effective sediment transfer processes reflected in the regional scale distribution of talus slopes however the understanding of the key controlling factors seems to decrease with increasing spatial scale due to emergent and complex system behavior and not least to recent methodological shortcomings in rockfall modeling research in this study we aim i to develop a new approach to identify major regional scale rockfall controls and ii to quantify the relative importance of these controls using a talus slope inventory in the turtmann valley swiss alps we applied for the first time the decision tree based random forest algorithm rf in combination with a principal component logistic regression pclr to evaluate the spatial distribution of rockfall activity this study presents new insights into the discussion on whether periglacial rockfall events are controlled more by topo climatic cryospheric paraglacial or and rock mechanical properties i both models explain the spatial rockfall pattern very well given the high areas under the receiver operating characteristic roc curves of 0 83 highest accuracy was obtained by the rf correctly predicting 88 of the rockfall source areas the rf appears to have a great potential in geomorphic research involving multicollinear data ii the regional permafrost distribution coupled to the bedrock curvature and valley topography was detected to be the primary rockfall control rockfall source areas cluster within a low radiation elevation belt 2900 3300 m a s l consistent with a permafrost probability of 90 the second most important factor is the time since deglaciation reflected by the high abundance of rockfalls along recently deglaciated the study demonstrates the benefit of combined statistical approaches for predicting rockfall activity in deglaciated permafrost affected mountain valleys and highlights the complex interplay between rock mechanical paraglacial and topo climatic controls at the regional scale

temporal changes in holocene δ18o records from the northwest and central north iceland shelf the region of north iceland is highly sensitive climatically owing to its location with respect to atmospheric and oceanographic fronts in this study we present total carbonate and 18o records of benthic and planktic foraminifera from nine sediment cores from the north iceland shelf the results of this work indicate that the deglaciation of the vestfirdir peninsula was completed by 10 200 cal yr bp the 8200 cal yr bp cold event is present only as a minor isotopic event and seems not to have had much of a cooling effect on the bottom waters of the northwest iceland shelf the holocene maximum warmth attributed to a stronger north icelandic irminger current occurred between ca 7800 and 6200 cal yr bp over the past 4500 cal yr bp a general cooling trend has occurred on the north iceland shelf and superimposed on this overall cooling trend are a number of oscillations between periods when relatively warmer and cooler waters occupied the shelf relatively cooler waters were present at 4200 4000 cal yr bp 3200 2900 cal yr bp 2500 2350 cal yr bp and 600 200 cal yr bp whereas relatively warmer waters were present on the shelf at 3750 3450 cal yr bp 2800 2600 cal yr bp and 1700 1000 cal yr bp copyright 2004 john wiley sons ltd

temperature reconstructions for sw and n iceland waters over the last 10 cal ka based on δ18o records from planktic and benthic foraminifera abstract we have obtained 18 o carb data from planktic n pachyderma s and benthic foraminifera c lobatulu s m barleeanu s from eight cores between 40 and 500 m water depth along the sw core b997 347 and n iceland margins cores b997 321 324 327 328 329 330 and 332 that span the last 10 cal ka sampling resolution varies between centuries to millennial scales over this time range changes in 18 o carb in foraminifera are the product of changes in the global ice volume and the temperature and salinity of the water at the level in which the foraminifera live in order to evaluate the relative roles of these variables we investigate 1 the salinity s and 18 o water values for present day waters off iceland and 2 the present day relationships between 18 o carb or calcite values of foraminifera and water column temperature and salinity data we estimate the average error in the temperature estimate to be 0 3 c based on a monto carlo simulation of the various error terms we argue that around iceland the variations in 18 o carb of both benthic and planktic species over the last 10 cal ka are principally controlled by temperature variations while salinity changes prove less important spatial and temporal changes are examined for both bottom water and 50 m water temperature reconstructions based on six and four cores respectively reconstructed temperatures for sites around sw n iceland indicate that surface and seafloor water temperatures were warmest in the early holocene 10 6 cal ka beginning at 6 cal ka surface and seafloor temperatures began to cool in n iceland and to become less stratified in sw iceland over the last 5000 yrs sea surface temperature variations have been 1 c for 50 of the observations with a maximum range of 2 5 c a profound decrease in temperature of 1 5 c is recorded in our fjord site b997 328 during the little ice age an abrupt earlier cold event is well expressed in at least three n iceland cores around 5 cal ka

a high resolution holocene sediment record from hunafloaall n iceland margin centuryto millennial scale varability since the vedde tephra md99 2269 is a 25 m long core from hunafloaall a deep trough which runs northward towards the shelf break from the narrow neck of land which joins the northwest peninsula of iceland with the main land the core was recovered from the thickest part of an elongate shelf sediment body underlain by glacial diainictons with ages 26 ka bp 3 5 khz profiles indicate the presence of a reflector ri which can be traced over long distances twelve ams radiocarbon dates and the presence of the saksunarvatn tephra which is the origin for the ri reflector at 21 m core depth define a linear depth age relation with an accumulation rate of 200 cm ky the date on the core top is modern x radiographs indicate that the sediments are principally massive bioturbated muds the data were measured at resolutions of between 5 and 40 yr sample our primary data represent aspects of a multisensor track measurements b colour c grain size d sediment properties and e sediment magnetic properties principal component analysis pca was used to simplify the analysis of these five data sets and resulted in nine significant axes compared to over 70 original variables the explained variance on the first axes varied between 47 and 96 these time series were reduced to a common 50 yr sample interval which were then also subject to pca using the resulting pc scores we present three primary axes of environmental variability in hunafloaall that have century scale quasi periodicities and demonstrate that these are highly correlated with specific raw variables we focus on variables linked to changes in grain size and productivity and show regional coherence cores b997 321 and 330 in the coercivity grain size measure armj 20 armj 0 which have a close similarity to the detrended 14 c series this provides a potential link to the vigour of the thermohaline circulation to the north of the iceland shelf in the iceland and greenland seas our data indicate increas

surface sediment diatom distribution and holocene paleotemperature variations in the greenland iceland and norwegian sea one hundred and four surface sediment samples and two piston cores from the greenland iceland and the norwegian gin sea hopkins 1988 were analyzed diatoms were common to abundant in most surface sediment samples and throughout the holocene q mode factor analysis allowed the definition of six significantly different floral assemblages which explained 91 7 of the total variance mapping of the six factors showed their close affinity to hydrographic regimes these are the norwegian atlantic current assemblage thalassionema nitzschioides paralia sulcata proboscia alata arctic water assemblage thalassiosira gravidaspores sea ice assemblage nitzschia grunowii nitzschia cylindra thalassiosira hyalina arctic norwegian waters mixing assemblage rhizosolenia hebetata f semispina rhizosolenia borealis atlantic assemblage thalassiosira oestrupii and norwegian arctic waters mixing assemblage thalassiosira gravida vegetative cells transfer functions gint2 relating factor distributions to winter february and summer august surface water temperatures were generated the transfer functions have a standard error of estimate of 1 5 c august and 1 0 c february downcore studies of core 52 43 from the norwegian basin and core 57 5 from the iceland plateau revealed diatom abundance and sea surface paleotemperature trends in the area during the holocene the first appearance of diatoms in cores 52 43 and 57 5 occurs within the vedde ash layer 10 600 years b p and the saksunarvatn ash layer 9100 years b p respectively diatom abundances increase steadily throughout the pre boreal atlantic time to 25 and 35 million valves per gram dry sediment in the norwegian basin and iceland plateau cores respectively application of the temperature transfer functions gint2 to the two holocene records revealed higher than present sea surface temperatures during the boreal atlantic chronozones for the iceland plateau and during the middle younger dryas sub boreal chronozones for the norwegian basin core temperatures decreased steadily since then with a slight increase to the present values both the iceland and the norwegian seas experienced a strong influx of temperate atlantic surface waters in the beginning of the holocene sea surface temperatures dropped steadily in the latter part of the holocene as the influx of the atlantic surface waters diminished

a highly unstable holocene climate in the subpolar north atlantic evidence from diatoms a composite record lo09 14 of three sediment cores from the subpolar north atlantic reykjanes ridge was investigated in order to assess surface ocean variability during the last 11 kyr the core site is today partly under the influence of the irminger current ic a branch of the north atlantic drift continuing northwestward around iceland however it is also proximal to the sub arctic front saf that may cause extra dynamic hydrographic conditions we used statistical methods applied to the fossil assemblages of diatoms to reconstruct quantitative sea surface temperatures ssts our investigations give evidence for different regional signatures of holocene surface oceanographic changes in the north atlantic core lo09 14 reveal relatively low and highly variable ssts during the early holocene indicating a weak ic and increased advection of subpolar water over the site a mid holocene thermal optimum with a strong ic occurs from 7 5 to 5 kyr and is followed by cooler and more stable late holocene surface conditions several intervals throughout the holocene are dominated by the diatom species rhizosolenia borealis which we suggest indicates proximity to a strongly defined convergence front most likely the saf several coolings reflecting southeastward advection of cold and ice bearing waters occur at 10 4 9 8 8 3 7 9 6 4 4 7 4 3 and 2 8 kyr the cooling events recorded in the lo09 14 ssts correlate well with both other surface records from the area and the nadw reductions observed at odp site 980 indicating a surface deepwater linkage through the holocene

environmental changes off north iceland during the deglaciation and the holocene foraminifera diatoms and stable isotopes abstract a combined study of foraminifera diatoms and stable isotopes in marine sediments off north iceland records major changes in sea surface conditions since about 15 800 cal years yr bp results are presented from two gravity cores obtained at about 400 m water depth from two separate sedimentary basins on each side of the submarine kolbeinsey ridge the chronology of the sedimentary record is based partly on ams 14c dates partly on the vedde and the saksunarvatn tephra markers as well as the historical hekla ad 1104 tephra during the regional deglaciation the planktonic foraminiferal assemblages are characterised by consistently high percentages of sinistrally coiled neogloboquadrina pachyderma however major environmental variability is reflected by changes in stable isotope values and diatom assemblages low 18o values indicate a strong freshwater peak as well as possible brine formation by sea ice freezing during a pre bolling interval greenland stadial 2 corresponding to the heinrich 1 event the foraminifera suggest a strong concurrent influence of relatively warm and saline atlantic water and both the foraminifera and the diatoms suggest mixing of cold and warm water masses similar but weaker environmental signals are observed during the younger dryas greenland stadial 1 around the level of the vedde ash each freshwater peak is succeeded by an interval of severe cooling both at the beginning of the bolling allerod interstadial complex greenland interstadial 1 and during the preboreal presumably associated with the onset of intense deep water formatiom in the nordic seas the holocene thermal optimum between 10 200 and about 7000 cal years yr bp is interrupted by a marked cooling of the surface waters around 8200 cal yr bp this cold event is clearly expressed by a pronounced increase in the percentages of sinistrally coiled n pachyderma corresponding to a temperature decrease of about 3 c a general cooling in the area is indicated after 7000 6000 cal yr bp both by the diatom data and by the planktonic foraminiferal data after a severe cooling around 6000 cal yr bp the planktonic foraminiferal assemblages suggest a warmer interval between 5500 and 4500 cal yr bp minor temperature fluctuations are reflected both in the foraminiferal and in the diatom data in the upper part of the record but the time resolution of the present data is not high enough to pick up details in environmental changes through the late holocene

the 8k event cause and consequences of a major holocene abrupt climate change abstract a prominent abrupt climate event about 8200 years ago brought generally cold and dry conditions to broad northern hemisphere regions especially in wintertime in response to a very large outburst flood that freshened the north atlantic changes were much larger than typical climate variability before and after the event with anomalies up to many degrees contributing to major displacement of vegetative patterns this 8k event provides a clear case of cause and effect in the paleoclimatic realm and so offers an excellent opportunity for model testing the response to north atlantic freshening has the same general anomaly pattern as observed for older events associated with abrupt climate changes following north atlantic freshening and so greatly strengthens the case that those older events also reflect north atlantic changes the north atlantic involvement in the 8k event helps in estimating limits on climate anomalies that might result in the future if warming caused ice melt and hydrologic cycle intensification at high latitudes lead to major changes in north atlantic circulation few model experiments have directly addressed the 8k event and most studies of proxy records across this event lack the time resolution to fully characterize the anomalies so much work remains to be done

field testing of three bedload samplers efficiency in a gravel bed river spitsbergen abstract a comparative study of the three bedload traps was accomplished to determine the effectiveness differences between the devices the research was carried out in two transverse sections of the proglacial gravel bedded scott river sw svalbard using three devices to perform direct measurements of bedload transport in the river channels several samplers are used for field measurements but none of them has gained widespread acceptance as a standard so far the paper compares transport rates collected in three bedload samplers that differ in structure and functionality i a portable helley smith pressure difference bedload sampler h s ii an anchored river bedload trap rbt and iii the portable sampler used by the polish hydrological services pihm type c all three samplers are constructed using the same components a frame made of thin stainless steel sheet and a nylon bag with the same 2 mm mesh size except pihm measurements were conducted within three consecutive days in two cross sections in the same vertical profiles and at the same time at intervals of 30 and 60 min measurements of bedload transport and water velocity were performed simultaneously in order to determine the effectiveness and representativeness of short term measurements using particular devices the masses of the samples were converted into a specific rate of bedload transport and compared to the results of long term continuous measurement 24 h measurement cycle the results confirm that both specific transport indicators and the mass of the samples collected by the tested devices show a significant variation generally the highest mass and specific transport indicators were obtained using the h s sampler the rbt produced moderate transport rates while the pihm sampler gave the lowest rates the bedload transport rate in a profile estimated on the short term measurements was compared to results of the continuous measurements conducted in the same cross sections in the 7 cases we obtained underestimation to max 10 times and in the next 7 cases overestimation to max 114 times only in four cases were the results of short term measurements similar to the continuous ones the results obtained from the rbt sampler show the smallest variability among all tested devices

high resolution record of late glacial and deglacial sea ice changes in fram strait corroborates ice ocean interactions during abrupt climate shifts the transition from last glacial to deglacial and subsequently to modern interglacial climate conditions was accompanied by abrupt shifts in the palaeoceanographic setting in the subpolar north atlantic knowledge about the role that sea ice coverage played during these rapid climate reversals is limited since most marine sediment cores from the higher latitudes provide only a coarse temporal resolution and often poorly preserved microfossils here we present a highly resolved reconstruction of sea ice conditions that characterised the eastern fram strait a key area for water mass exchange between the arctic ocean and the north atlantic for the past 30 ka bp this reconstruction is based on the distribution of the sea ice biomarker ip25 and phytoplankton derived biomarkers in a sediment core from the continental slope of western svalbard during the late glacial 30 ka to 19 ka bp recurrent advances and retreats of sea ice characterised the study area and point to a hitherto less considered oceanic and or atmospheric variability a long lasting perennial sea ice coverage in eastern fram strait persisted only at the very end of the last glacial maximum i e from 19 2 to 17 6 ka bp and was abruptly reduced at the onset of heinrich event 1 coincident with or possibly even inducing the collapse of the atlantic meridional overturning circulation amoc further maximum sea ice conditions prevailed during the younger dryas cooling event and support the assumption of an amoc reduction due to increased formation and export of arctic sea ice through fram strait a significant retreat of sea ice and sea surface warming are observed for the early holocene

significance of rockfall magnitude and carbonate dissolution for rock slope erosion and geomorphic work on alpine limestone cliffs reintal german alps abstract the proportional contribution of low mid and high magnitude rock slope failure orchestrates rock slope erosion and rockfall hazard in alpine and arctic environments in this study we compare sediment yield geomorphic work and rock wall retreat of carbonate dissolution and five different magnitudes of rock slope failure in the steep alpine reintal trough valley we combine a four year rockfall collector measurement of 140 mg of fragmental rockfall a 20th century scientific record of mid magnitude rockfall as well as carbon dating and a historical record of 15th to 19th century rock avalanche activity the total rockfall sediment yield of 8 6 3 4 10 3 m 3 year 1 is dominated by high magnitude rock avalanches 10 6 m 3 62 and low magnitude debris falls 3 18 while mid magnitude boulder block and cliff falls are less important the magnitude signal contradicts studies on siliceous rocks where mid magnitude rockfall dominates rock slope erosion the geomorphic work released in the 17 3 km 2 large catchment by rockfalls 123 47 w km 2 i e 0 38 0 15 mm year 1 and solute transport 34 18 w km 2 i e 0 05 0 03 mm year 1 exceeds previously published alpine values by one to multiple orders of magnitude we hypothesise that the magnitude signal of enhanced small and high magnitude rockfall is characteristic for carbonate cliffs the elevated porosity related susceptibility to fragmentation and persistent carbonate dissolution along potential sliding planes are likely to favour both low and high magnitude rock slope failures here we show how the magnitude signal of rock slope failure influences rock wall retreat geomorphic work rockfall deposition and sediment connectivity

millennial climate oscillations over the course of the ice ages the climate oscillated with a period of about 20 000 to 100 000 years superimposed on these variations were millennial oscillations of 1000 to 2000 years these oscillations also occurred in the holocene which began 11 000 years ago and has been thought to be a time of a relatively stable climate as shown on p 1257 of this issue by bond et al the perspective by oppo discusses these results obtained from marine sediments and the possible mechanisms underlying these relatively rapid changes in climate

holocene periodicity in north atlantic climate and deep ocean flow south of iceland climate fluctuations during the past millennium are relatively well documented1 on a longer timescale there is growing evidence of millennial scale variability of holocene climate at periodicities of 2 500 and 950 years possibly caused by changes in solar flux 2 3 and 1 500 years maybe related to an internal oscillation of the climate system 4 5 6 but the involvement of deep water masses in these holocene climate changes has yet to be established here we use sediment grain size data from the iceland basin to reconstruct past changes in the speed of deep water flow the study site is under the influence of iceland scotland overflow water isow the flow of which is an important component of the thermohaline circulation that modulates european climate flow changes coincide with some known climate events the little ice age and the mediaeval warm period and extend over the entire holocene epoch with aquasi periodicity of 1 500 years the grain size data indicate afaster isow flow when the climate of northern europe is warmer however a second mode of operation is observed in the early holocene when warm climate intervals are associated with slower isow flow at that time the melting remnant of land based glacial age ice may have provided a sufficient source of fresh water to the ocean to reduce isow flow south of iceland

holocene north atlantic surface circulation and climatic variability evidence from diatom records diatom analyses have been performed on a 425cm long holocene marine sediment sequence from the north atlantic south of iceland and a 920cm sediment core spanning the last c 7500 years from skalafjord faeroe islands additional core data include stable isotopes and results from magnetic susceptibility measurements while chronostratigraphic control has been provided by ams 14c measurements the diatom records reveal distinct changes in north atlantic surface circulation and climate that have been correlated with published terrestrial and marine records initial holocene warming is dated at 9900 14c years bp and after a preboreal cold spell enhanced north atlantic current activity and warming prevailed from 9600 to 8800 14c years bp from 8800 to 8000 4c years bp the advection of warm atlantic water masses weakened presumably under atmospheric circulation conditions characterized by a dominating negative nao prior to the holocene climatic optimum 6000 5000 14c years bp distinct hydrographic gradient

sea surface conditions in the southern nordic seas during the holocene based on dinoflagellate cyst assemblages dinoflagellate cyst dinocyst records from the southern nordic seas were compiled in order to evaluate the evolution of upper ocean conditions on a millennial timescale and supported by a highly resolved record from the voring plateau after the transitional phase from the last deglaciation three main phases define the holocene the early holocene 7 5 ka bp features important numbers of cool temperate species dominated by nematosphaeropsis labyrinthus and impagidinium pallidum in the west the assemblage composition changes drastically at the transition from the early to the mid holocene from when on operculodinium centrocarpum dominates the changeover is dated between 6 1 and 7 5 ka bp perhaps earlier closer to the iceland scotland ridge and appears to be linked to the onset of a modern type of surface circulation warmest assemblages occur at the voring plateau shortly after the transition when atlantic waters also appear to have spread farthest westward the recurrence of colder elements can be linked to cooling from 2 4 ka bp at the voring plateau and presumably earlier in the west but is difficult to date there because of the low sedimentation rates this is a general issue in many areas of the nordic seas and appears to have an important effect on cyst concentrations and assemblage composition with the possible loss of oxygenation sensitive cysts in the older parts of the cores comparing dinocyst based quantitative reconstructions with those retrieved from other plankton reveals a significantly different trend between proxies linked to a differing autecological response to seasonal changes at their respective depth habitats

retreating ice research in pro glacial areas matters glacier forefields are landscapes in transition from glacial to non glacial conditions this implies intense geomorphic hydrological and ecological dynamics with important on and off site effects this special issue collects 13 papers covering recent research in both sub polar and alpine proglacial environments that focus on i proglacial sediment sources ii proglacial rivers iii proglacial lakes iv ground water and ice and v the development of soil and vegetation in its interplay with morphodynamics advances in mapping surveying and geophysical techniques form the basis for research perspectives related to the historical evolution of proglacial areas the understanding of complex interactions of multiple processes and the effects of continued glacier recession

work persistence and formative events the geomorphic impact of landslides abstract understanding the scale and frequency of physical processes that act upon and form the surface of the earth is a fundamental goal of earth science here we determine the magnitudes of landslides that impact the landscape in terms of work persistence and formative events a systematic analysis of rapid landsliding the analysis did not consider creep and other slow semi continuous processes indicates that moderate sized landslides do the most work transporting material on hillslopes the work peak defines the moderate magnitude and that magnitude varies based on local physiography and climate landslides that form the work peak are distinct from catastrophic landslides that are themselves formative and system resetting the persistence time for debris slides debris flows p ds and rock slides rock avalanches p rs is calculated over six orders of magnitude we consider an event catastrophic when it persists in the landscape as described by a persistence ratio p f an order of magnitude longer than the population of landslides that form the work peak

sediment export transient landscape response and catchment scale connectivity following rapid climate warming and alpine glacier recession abstract in the face of rapid climate warming rapid glacier recession should lead to a marked increase in the spatial extent of the paraglacial zone in glaciated drainage basins the extent of the paraglacial zone has been well established to be transient but there are very few studies of this transient response and what it means for sediment export there is good reason to expect that glacier recession could increase basin scale sediment connectivity as sediment becomes less dependent on glacier surface transport proglacial streams are more able to migrate laterally than subglacial streams and so access sediment for transport and glacier debuttressing may aid the development of gullies that can dissect moraines and so aid hillslope to proglacial zone connectivity by using records of the flushing of hydroelectric power installations we were able to develop a record of coarse sediment sand and gravel export from a basin with a rapidly retreating valley glacier the haut glacier d arolla from 1977 to 2014 modelling suggested that these data could only be partially controlled by transport capacity implying an important role for sediment supply and potentially for the influence of changing sediment connectivity indeed there was evidence of the effects of glacial debuttressing upon gullying processes and hence a possible increase in the ease of connection of upstream basins to the proglacial area more recently we were able to show possible temperature control on sediment export which may only have become apparent because of the progressive development of better sediment connectivity however whilst rapid glacier recession should result in theory in a progressive increase in connectivity of sediment sources to the basin outlet the supply to capacity ratio does not increase continually with glacier recession until maximum capacity is reached we identified two possible examples of why first gullying was also accompanied by the sediment accumulation at the base of moraines that was too coarse to be transported by the proglacial stream maintaining disconnection of the upper basins second the sediment capacity ratio appeared to be elevated during periods of more rapid retreat and we attribute this to the importance of a continued supply of unworked glacial till before fluvial reworking and sorting of freshly exposed sediment increased the resistance of sediment to entrainment and hence export rates thus the transient geomorphic response of glaciated basins to glacier recession may involve negative feedbacks that can reduce the extent to which increases in connectivity elsewhere in the basin lead to increased sediment export

irregular glacial interstadials recorded in a new greenland ice core the greenland ice sheet offers the most favourable conditions in the northern hemisphere for obtaining high resolution continuous time series of climate related parameters profiles of 18o 16o ratio along three previous deep greenland ice cores1 3 seemed to reveal irregular but well defined episodes of relatively mild climate conditions interstadials during the mid and late parts of the last glaciation but there has been some doubt as to whether the shifts in oxygen isotope ratio were genuine representations of changes in climate rather than artefacts due to disturbed stratification here we present results from a new deep ice core drilled at the summit of the greenland ice sheet where the depositional environ ment and the flow pattern of the ice are close to ideal for core recovery and analysis the results reproduce the previous findings to such a degree that the existence of the interstadial episodes can no longer be in doubt according to a preliminary timescale based on stratigraphic studies the interstadials lasted from 500 to 2 000 years and their irregular occurrence suggests complexity in the behaviour of the north atlantic ocean circulation

holocene climate variability although the dramatic climate disruptions of the last glacial period have received considerable attention relatively little has been directed toward climate variability in the holocene 11 500 cal yr b p to the present examination of similar to50 globally distributed paleoclimate records reveals as many as six periods of significant rapid climate change during the time periods 9000 8000 6000 5000 4200 3800 3500 2500 1200 1000 and 600 150 cal yr b p most of the climate change events in these globally distributed records are characterized by polar cooling tropical aridity and major atmospheric circulation changes although in the most recent interval 600 150 cal yr b p polar cooling was accompanied by increased moisture in some parts of the tropics several intervals coincide with major disruptions of civilization illustrating the human significance of holocene climate variability c 2004 university of washington all rights reserved

complexity of holocene climate as reconstructed from a greenland ice core glaciochemical time series developed from summit greenland indicate that the chemical composition of the atmosphere was dynamic during the holocene epoch concentrations of sea salt and terrestrial dusts increased in summit snow during the periods 0 to 600 2400 to 3100 5000 to 6100 7800 to 8800 and more than 11 300 years ago the most recent increase and also the most abrupt coincides with the little ice age these changes imply that either the north polar vortex expanded or the meridional air flow intensified during these periods and that temperatures in the mid to high northern latitudes were potentially the coldest since the younger dryas event

contemporary suspended sediment dynamics within two partly glacierized mountain drainage basins in western norway erdalen and bodalen inner nordfjord abstract this paper focuses on environmental controls spatiotemporal variability and rates of contemporary fluvial suspended sediment transport in the neighboring partly glacierized and steep erdalen 79 5 km 2 and bodalen 60 1 km 2 drainage basins in the fjord landscape of the inner nordfjord in western norway field work including extended samplings and measurements was conducted since 2004 in erdalen and since 2008 in bodalen the distinct intra and inter annual temporal variability of suspended sediment transport found is mostly controlled by meteorological events with most suspended sediment transport occurring during pluvial events in autumn september november followed by mostly thermally determined glacier melt in summer july august and by mostly thermally determined snowmelt in spring april june extreme rainfall events 70 mm d 1 in autumn can trigger significant debris flow activity that can cause significant transfers of suspended sediments from ice free surface areas with sedimentary covers into main stream channels and is particularly important for fluvial suspended sediment transport in years with occurring relevant debris flow activity the total annual drainage basin wide suspended sediment yields are strongly determined by these single extreme events the proportion of glacier coverage followed by steepness of slopes and degree of vegetation cover in ice free surface areas with sedimentary covers are the main controls for the detected spatial variability of suspended sediment yields the contemporary sediment supply from glacierized surface areas and the jostedalsbreen ice cap through different defined outlet glaciers shows a high spatial variability the fact that the mean annual suspended sediment yield of bodalen is with 31 3 t km 2 yr 1 almost twice as high as the mean annual suspended sediment yield of erdalen 16 4 t km 2 yr 1 is to a large extent explained by the higher proportion of glacier coverage in bodalen 38 of the drainage basin surface area as compared to erdalen 18 of the drainage basin surface area and by a significantly higher sediment yield from the glacierized area of the bodalen drainage basin compared to the glacierized surface area in erdalen when looking at the total annual mass of suspended sediments being fluvially exported from both entire drainage basin systems the total amount of suspended sediments coming from the ice free drainage basin surface areas altogether dominates over the total amount of suspended sediments coming from the glacierized surface area of both drainage basins drainage basin wide annual suspended sediment yields are rather low when compared with yields of other partly glacierized drainage basin systems in norway and in other cold climate environments worldwide which is mainly due to the high resistance of the predominant gneisses towards glacial erosion and weathering the altogether only small amounts of sediments being available within the entire drainage basin systems the stable and nearly closed vegetation cover in the ice free surface areas with sedimentary covers and the efficiency of proglacial lakes in trapping sediments supplied by defined outlet glaciers both contemporary and long term suspended sediment yields are altogether supply limited contemporary suspended sediment transport accounts for nearly two thirds of the total fluvial transport and accordingly plays an important role within the sedimentary budgets of the entire erdalen and bodalen drainage basins

transfer function between surface sediment diatom assemblages and sea surface temperature and salinity of the labrador sea abstract q mode factor analysis cabfac of 38 diatom species in 66 surface sediment samples from the labrador sea allowed the definition of six assemblages explaining 95 69 of the total variance the first assemblage 40 12 of the total variance is represented by thalassiothrix longissima a species characteristic of the irminger current and associated with the west greenland current the second assemblage 34 52 of the total variance is represented by thalassiosira gravida resting spores a cold water species associated with the labrador current a third assemblage 11 43 of the variance represented by chaetoceros spp is concentrated in the northeastern section of the labrador sea and associated with upwelling and high productivity the fourth the fifth and the sixth assemblages represented respectively by coscinodiscus marginatus coscinodiscus oculus iridis and coscinodiscus divisus and nitzschia frigida are less significant and account respectively for 4 95 2 62 and 2 04 of the total variance transfer functions derived by relating factor assemblages to surface water temperature and salinity august and february give standard errors of estimate of 0 93 c august and 0 64 c february for temperature and of 0 58 august and 0 45 february for salinity high correlations between the measured and estimated parameters confirm the validity of the paleoecological equations for the reconstruction of the labrador sea paleoclimate

funnel shaped surface depressions indicator or accelerant of rapid glacier disintegration a case study in the tyrolean alps abstract alpine glaciers have been retreating at extreme and historically unprecedented rates while the general course of regional retreat rates reflects long term climatic change individual extreme events are closely related to the geomorphological settings and processes of the specific glacier nevertheless these extreme events also influence the regional means and might be an important feedback mechanism accelerating the response of glaciers to climate change in 2009 during the recent disintegration of the terminus of gepatschferner 46 52 30 n 10 45 25 e a shallow circular depression appeared at the glacier tongue with a decrease of surface ice flow velocity to almost nil in 2015 the area was ice free during a heavy precipitation event in august 2012 a subglacial sediment layer of 10 m was flushed out which accelerated the subsidence of the ice surface the development of this 15 to 30 m deep depression was monitored with a combination of methods in high detail including direct ablation measurements and a time series of seven high resolution airborne laser dems plus recordings of ice flow velocity and surface elevation with dgps the thickness of ice and sediment layers was measured with vibroseismic soundings in 2012 and 2013 similar developments were observed at three other glaciers with extreme retreat rates our investigation suggests that this mechanism has a major impact on and can be read as an indicator of a nonlinear increased response of glaciers to climate change

assessment of sediment sources throughout the proglacial area of a small arctic catchment based on high resolution digital elevation models abstract the article presents calculations of quantitative modifications of the morphology of selected subsystems of a glacial valley through i identification of the spatial distribution of important sources of sediment ii assessment of the spatiotemporal variety of sediment volume and landform morphology and iii assessment of the role of particular subsystems in sediment distribution the study involved a comparison of the results of field measurements from 2010 to 2013 performed in the scott glacier catchment 10 1 km2 in nw wedel jarlsberg land spitsbergen the assessment of the landform surface changes was performed by means of a precise terrestrial laser scanning tls survey the applied field and post processing techniques for oblique laser scanning permitted the acquisition of digital elevation data at a resolution 0 01 m and density 500 pt m 2 this allowed the development of a detailed terrain model and balancing spatial quantitative changes in six research test areas 10 000 m2 located within two subsystems of the catchment in a cascade arrangement in the alluvial valley floor subsystem the survey covered 1 the glacier terminus 2 the intramarginal outwash plain 3 the extramarginal braid plain and 4 the alluvial fan and in the slope subsystem 5 the erosional depositional slope in the gorge through terminal moraines and 6 the solifluction slope three zones differing in terms of the spatiotemporal dynamics of geomorphic processes were distinguished within the two analysed valley subsystems in the valley floor subsystem these are i the zone of basic supply distribution throughout the melting season and ii the redeposition zone distribution particularly during floods and in the slope subsystem iii zone of periodical supply distributed mainly in periods of increased precipitation and rapid increases in temperature in summer and during snow avalanches in winter the glacier and the landforms of the channel and valley floor as well as slope sediments transported as a result of mass wasting processes and activity of the active permafrost layer constitute important sources of sediment supply over a short 3 year timescale evidence of major changes of the surface morphology slopes floodplain and channel platform resulted in varied sediment budgets the subtraction of consecutive dems of the test areas located in the alluvial valley subsystem revealed downstream spatial and volumetric differentiation from the predominance of erosion 79 of volume 43 of area to the dominance of deposition 90 91 respectively in upper part of the valley floor to erosion predominance in the central 88 95 and lower 87 82 part of valley floor the test areas located on the slope subsystem showed the opposite relationship deposition dominance 88 of volume 80 of area in the upper gorge and erosion dominance 99 99 respectively in the lower part solifluction slopes the analysis of short time repeated surveys 3 week survey where volumes were calculated following dem subtraction showed increased deposition 82 of volume 79 of area for the alluvial fan and for solifluction slopes 70 57 respectively

temporal dynamics of suspended sediment transport in a glacierized andean basin abstract suspended sediment transport can affect water quality and aquatic ecosystems and its quantification is of the highest importance for river and watershed management suspended sediment concentration ssc and discharge were measured at two locations in the estero morales a chilean andean stream draining a small basin 27 km2 hosting glacierized areas of about 1 8 km2 approximately half of the suspended sediment yield 470 t year 1 km 2 was transported during the snowmelt period and half during glacier melting the hysteresis patterns between discharge and ssc were calculated for each daily hydrograph and were analysed to shed light on the location and activity of different sediment sources at the basin scale during snowmelt an unlimited supply of fine sediments is provided in the lower and middle part of the basin and hysteresis patterns tend to be clockwise as the peaks in ssc precede the peak of discharge in daily hydrographs instead during glacier melting the source of fine sediments is the proglacial area producing counterclockwise hysteresis it is suggested that the analysis of hysteretic patterns over time provides a simple concept for interpreting variability of location and activity of sediment sources at the basin scale

a high resolution study of holocene paleoclimatic and paleoceanographic changes in the nordic seas 1 high resolution records from images core md95 2011 in the eastern norwegian sea provide evidence for relatively large and small scale high latitude climate variability throughout the holocene during the early and mid holocene a situation possibly driven by consistent stronger westerlies increased the eastward influence of arctic intermediate and near surface waters for the late holocene a relaxation of the atmospheric forcing resulted in increased influence of atlantic water the main changes in holocene climate show no obvious connection to changing solar irradiance and spectral analysis reveals no consistent signature for any periodic behavior of holocene climate at millennial or centennial timescales there are however indications of consistent multidecadal variability

effective timescales of coupling within fluvial systems this paper presents a review of the coupling concept in fluvial geomorphology based mainly on previously published work coupling mechanisms link the components of the fluvial system controlling sediment transport down the system and the propagation of the effects of base level change up the system they can be viewed at several scales at the local scale involving within hillslope coupling hillslope to channel coupling and within channels tributary junction and reach to reach coupling at larger scales coupling can be considered as zonal coupling between major zones of the system or as regional coupling relating to complete drainage basins these trends are illustrated particularly by the examples of hillslope to channel coupling in the howgill fells northwest england badland systems in southeast spain alluvial fans in spain usa and uae and base level induced dissection of neogene sedimentary basins in southeast spain as the spatial scales increase so do the timescales involved effective temporal scales relate to magnitude and frequency characteristics recovery time and propagation time the relative importance changing with the spatial scale for downsystem coupling at the local scale the first two are important with propagation time increasing in importance in larger systems especially in those involving upsystem coupling related to base level change the effective timescales range from the individual event with a return period of decades through decadal to century timescales for downsystem coupling to tens to hundreds of thousands of years for the basinwide response to base level change the effective timescales influence the relative importance of factors controlling landform development

diatom evidence of hydrographic changes and ice conditions in igaliku fjord south greenland during the past 1500 years biostratigraphic diatom analyses were carried out on two sediment cores from igaliku fjord south greenland in order to reconstruct hydrographic and climatic fluctuations during the late holocene ad 550 to present pronounced differences in hydrographic setting of the coring sites provide palaeoenvironmental information of both local and more regional character five diatom zones were identified from the subfossil diatom records each describing a hydrographic setting two major climate periods the mediaeval warm period ad 800 1250 and the little ice age ad 1580 1850 that were separated by a variable transitional period were recognized prior to these periods a cold and presumably moist climate regime prevailed between ad 500 and 700 cooling events were identified during the mediaeval warm period in the period ad 960 to 1140 the diatom data demonstrate that marked hydrographic changes occurred in the course of a relatively short timespan beginning at about ad 1300 and culminating around

distribution patterns of diatom surface sediment assemblages in the laptev sea arctic ocean abstract the modern diatom distribution in the laptev sea arctic ocean was investigated in 89 surface sediment samples diatom concentrations are relatively low showing values between 0 01 10 6 and 6 7 10 6 valves per gram dry sediment based on a factor analysis using seventeen taxa or taxa groups five diatom surface sediment assemblages can be defined the ice diatom assemblage of the central region of the laptev sea the chaetoceros assemblage of the eastern and southeastern shelf the thalassiosira antarctica assemblage of the continental slope and deep sea the freshwater diatom assemblage in the vicinity of river mouths and deltas and the thalassiosira nordenskioeldii assemblage which shows a patchy occurrence on the central laptev sea shelf the distribution pattern of diatom assemblages in surface sediment is significantly related to oceanographic conditions of surface water masses the main factors controlling the distribution of diatoms in the laptev sea are the riverine freshwater input during the summer which strongly affects the salinity conditions and the sea ice extent furthermore the composition of the thalassiosira antarctica assemblage of the continental slope is largely influenced by dissolution and lateral transport processes

evidence for enhanced debris flow activity in the northern calcareous alps since the 1980s plansee austria abstract debris flows are among the most important natural hazards the northern calcareous alps with their susceptible lithology are especially affected by a double digit number of major hazard events per year it is hypothesised that debris flow intensity has increased significantly in the last decades in the northern calcareous alps coincident to increased rainstorm frequencies but yet there is only limited evidence the plansee catchment exposes extreme debris flow activity due to the intensely jointed upper triassic hauptdolomit lithology being responsible for most of the debris flow activity in the northern calcareous alps the debris flows feed into a closed sediment system the plansee lake where holocene lateglacial sedimentation rates rates since the late 1940s and recent rates can be inferred accurately using aerial photos and field mapping the temporal and spatial development of eight active debris flow fans is reconstructed in six time intervals from 1947 1952 1971 1979 1987 2000 and 2010 and mean annual debris flow volumes are calculated these are compared with mean holocene lateglacial debris flow volumes derived from the most prominent cone whose contact with the underlying till is revealed by electrical resistivity tomography ert debris flow activity there increased by a factor of 10 from 1947 1952 0 23 0 07 103 m3 yr to 1987 2000 2 41 0 66 103 m3 yr mean post 1980 rates from all eight fans exceed pre 1980 rates by a factor of more than three coinciding with enhanced rainstorm activity recorded at meteorological stations in the northern calcareous alps the frequency of rain storms def 35 mm d has increased in the study area on average by 10 per decade and has nearly doubled since 1921 recent debris flow activity is also 2 3 times higher than mean holocene lateglacial rates the strong correlation between the non vegetated catchment area and the annual debris flow volume might indicate a decadal positive feedback between enhanced rainstorm activity and debris flows here we investigate the temporal and spatial development of debris flow fans to better understand the sensitivity of alpine catchments to heavy rainfall events in the context of climate change

marine reservoir age variability and water mass distribution in the iceland sea abstract lateglacial and holocene tephra markers from icelandic source volcanoes have been identified in five sediment cores from the north icelandic shelf and correlated with tephra layers in reference soil sections in north iceland and the grip ice core land sea correlation of tephra markers that have been radiocarbon dated with terrestrial material or dated by documentary evidence provides a tool for monitoring reservoir age variability in the region age models developed for the shelf sediments north of iceland based on offshore tephrochronology on one hand and on calibrated ams 14c datings of marine molluscs on the other display major deviations during the last 4500 years the inferred temporal variability in the reservoir age of the regional water masses exceeds by far the variability expected from the marine model calculations the observed reservoir ages are generally considerably higher by up to 450 years than the standard model ocean it is postulated that the intervals with increased and variable marine reservoir age reflect incursions of arctic water masses derived from the east greenland current to the iceland sea and the north icelandic shelf

paleoceanographic implications of a 90 000 year long diatom record in piston core kh94 3 lm 8 off ne japan abstract q mode principal component analysis pca of a fossil diatom assemblage reveals the late quaternary paleoceanography of the nw pacific margin based on submarine core kh94 3 lm 8 recovered off the sanriku coast of ne japan 38 53 46 n 143 22 19 e overall diatoms were abundant during interglacials but low in abundance and poor in preservation during the last glacial with each oxygen isotope stage having its own characteristic assemblage the results of pca are principal component 1 pc1 is composed mainly of thalassionema nitzschioides which predominated during the coldest oxygen isotopic stages 4 75 58 ka and 2 25 11 ka and by allochthonous taxa the diatom tests are poorly preserved and the diatom mass accumulation rate dmar is the lowest in these stages pc2 is characterized by ice related diatoms that predominate in stage 3 the interstadial whereas pc3 which is characterized by neodenticula seminae and odontella aurita shows high values in stage 1 diatom assemblages exhibit drastic changes between oxygen isotopic stages 3 and 1 11 0 ka distinct increases of dmar occurred during both periods we infer an intensified advection of sea ice from the sea of okhotsk toward the area off sanriku during stage 3 this interpretation explains the high dmar in stage 3 owing to high productivity at the sea ice edge our study can contribute to marine environmental reconstruction since the last glaciation because fewer micropaleontological data exist in the nw pacific margin for these time intervals compared with other oceans

holocene centennial to millennial scale climatic variability evidence from high resolution magnetic analyses of the last 10 cal kyr off north iceland core md99 2275 abstract high resolution magnetic analysis has been performed on the top 25 m of core md99 2275 66 33 06 n 17 41 59 w 440 m water depth from the mid outer shelf off north iceland this is a key boundary region for climate changes related to atmospheric and oceanographic variations influenced by the moving limit between the cold and warm water masses at the polar front and the low depression track with its associated westerlies situated across iceland an age model based on tephrochronology was previously reported for this core and has allowed precise timing of significant variations in the magnetic mineral concentration and grain size over the last 10 cal kyr the holocene climatic optimum identified in north iceland between 10 and 6 cal kyr bp is characterized by minor variations in the magnetic record while there is a clear increase in oceanographic instability from 6 cal kyr bp to the present at large scale a decreasing trend in the magnetic mineral content toward the present is presumably associated with a change in the circulation pattern and coincides in time with decreasing north atlantic deep water formation short term intervals of decreased magnetic mineral content are also identified at 5 2 4 9 3 77 3 41 3 01 2 7 and 0 93 0 62 cal kyr bp the youngest one ad 1020 to 1330 corresponding in time to the medieval warm period these events are interpreted to reflect periods of increased activity of the relatively warm high salinity surface irminger current related to stronger input of north atlantic waters into the nordic seas in addition spectral analysis of selected magnetic parameters demonstrates centennial scale periodicities of 715 240 170 and 100 yr which are more clearly expressed in the last 6 cal kyr bp than in the previous period these periodicities might be attributed to intervals of persistence in the north atlantic oscillation nao mode at centennial timescales this record therefore indicates that the holocene climate was more unstable than is often assumed and it demonstrates the importance of high resolution climatic studies for this recent time period to improve climate model predictions

ice sheet and ocean interactions margin of the east greenland ice sheet 14 ka to present diatom evidence seven marine sediment cores were collected from the kangerdlugssuaq trough off the southeast coast of greenland the trough cuts across the continental shelf from the fjord mouth to the upper slope in denmark strait and provides a sedimentary environment sheltered from the east greenland current flowing along the shelf the cores have been 14c dated accelerator mass spectroscopy dates and analyzed for diatom accumulation rates and changes in floral composition it was found that the shelf probably was not glaciated by grounded ice but occupied by an ice shelf and or permanent sea ice between 14 000 years b p and the present average retreat rates of glacial permanent sea ice were circa 60 m yr between circa 13 500 and 11 000 years b p the retreat rates increased to about 150 m yr between 11 000 to 10 000 years b p the increase is unexpected because this correlates with fairbanks 1989 projected low glacial meltwater discharge for the same time which is coeval with the younger dryas several events of sea surface warming cooling took place on the outer shelf from 12 000 to 9000 years b p followed by cooling to the present with a possible warming between 3000 4000 years bp on the inner shelf pulses of warm cool surface water occurred from 9000 to 6000 years b p which was succeeded by surface water cooling until present

millennial lag times in the himalayan sediment routing system abstract any understanding of sediment routing from mountain belts to their forelands and offshore sinks remains incomplete without estimates of intermediate storage that decisively buffers sediment yields from erosion rates attenuates water and sediment fluxes and protects underlying bedrock from incision we quantify for the first time the sediment stored in 38 000 mainly postglacial himalayan valley fills based on an empirical volume area scaling of valley fill outlines automatically extracted from digital topographic data the estimated total volume of 690 242 452 km 3 is mostly contained in few large valley fills 1 km 3 while catastrophic mass wasting adds another 177 31 km 3 sediment storage volumes are highly disparate along the strike of the orogen much of the himalaya s stock of sediment is sequestered in glacially scoured valleys that provide accommodation space for 44 of the total volume upstream of the rapidly exhuming and incising syntaxes conversely the step like long wave topography of the central himalayas limits glacier extent and thus any significant glacier derived storage of sediment away from tectonic basins we show that exclusive removal of himalayan valley fills could nourish contemporary sediment flux from the indus and brahmaputra basins for 1 kyr though individual fills may attain residence times of 100 kyr these millennial lag times in the himalayan sediment routing system may sufficiently buffer signals of short term seismic as well as climatic disturbances thus complicating simple correlation and interpretation of sedimentary archives from the himalayan orogen its foreland and its submarine fan systems