internal characteristics of ice marginal sediments deduced from georadar profiling and sediment properties brogger peninsula svalbard abstract georadar and sedimentological data were acquired in the ny alesund area on brogger peninsula in order to study diamicton in frontal areas of vestre broggerbreen and midre lovenbreen parallel common offset georadar lines were acquired for information on thickness and layering and multioffset measurements served to deduce the subground velocity short permafrost cores

ultra long range hydroacoustic observations of submarine volcanic activity at monowai kermadec arc monowai is an active submarine volcanic center in the kermadec arc southwest pacific ocean during may 2011 it erupted over a period of 5 days with explosive activity directly linked to the generation of seismoacoustic t phases we show using cross correlation and time difference of arrival techniques that the eruption is detected as far as ascension island equatorial south atlantic ocean where a bottom moored hydrophone array is operated as part of the international monitoring system of the comprehensive nuclear test ban treaty organization hydroacoustic phases from the volcanic center must therefore have propagated through the sound fixing and ranging channel in the south pacific and south atlantic oceans a source receiver distance of 15 800 km we believe this to be the furthest documented range of a naturally occurring underwater signal above 1 hz our findings which are consistent with observations at regional broadband stations and long range acoustic parabolic equation modeling have implications for submarine volcano monitoring

glacial geomorphic features in the northern barents sea direct evidence for grounded ice and implications for the pattern of deglaciation and late glacial sedimentation

a glacio isostatic facies model and amino acid stratigraphy for late quaternary events in spitsbergen and the arctic strong early holocene crustal uplift over the spitsbergen archipelago reflects disappearance of an ice mass centred just north east of the archipelago and which decayed rapidly just after 10 000 bp after a maximum extension between 12 600 and 10 000 bp from the lithofacies distributions associated with these events a glacio isostatic facies model can be defined which combined with analyses of amino acid racemization provides a valuable stratigraphic method for correlating pre holocene glacio isostatic events these are correlated with events in greenland and both are contrasted with weichselian glacial events at the southern margins of the two great northern hemisphere ice sheets and with contemporary water mass changes in the north atlantic and norwegian sea the geographical variation in glacier response through time is explained by three principal climatic circulation patterns

the late weichselian glacial maximum on western spitsbergen inferred from offshore sediment cores abstract the late weichselian glacial history of the continental shelf off western spitsbergen is discussed based on acoustic sub bottom records and sediment cores the outer part of isfjorden and the inner shelf to the west of this fjord are characterized by a thin veneer 10 20 m of glacigenic sediments and absence of ice marginal features towards the outer shelf the sediment thickness increases significantly and exceeds 500 m at the shelf edge possible moraine complexes were identified in this outer part sediment cores from the inner shelf sampled a firm diamicton interpreted as till beneath soft glaciomarine sediments radiocarbon dates on shells from the clay resting directly on the till suggest an age of around 12 500 yrs b p for the base of the marine sequence we argue that grounded ice covered the sites shortly before in contrast to suggestions that the fjords and coast were partly ice free during the late weischselian we conclude that the ice must have reached out onto the continental shelf

tracking submarine volcanic activity at monowai constraints from long range hydroacoustic measurements monowai is a submarine volcanic center in the kermadec arc southwest pacific ocean in the past activity at the volcano had been intermittently observed in the form of fallout at the sea surface discolored water changes in seafloor topography and t phase seismicity but there is no continuous record for more recent years in this study we investigated 3 5 years of recordings at a hydrophone array of the international monitoring system ims located near juan fernandez islands for long range underwater sound waves from monowai results from direction of arrival calculations and density based spatial clustering indicate that 82 discrete episodes of activity occurred between july 2003 and march 2004 and from april 2014 to january 2017 volcanic episodes are typically spaced days to weeks apart range from hours to days in length and amount to a cumulative sum of 137 days of arrivals in total making monowai one of the most active submarine arc volcanoes on earth the resolution of the hydrophone recordings surpasses broadband network data by at least one order of magnitude identifying seismic events as low as 2 2 mb in the kermadec arc region further observations suggest volcanic activity at a location approximately 400 km north of monowai in the tonga arc and at healy or brothers volcano in the southern kermadec arc our findings are consistent with previous studies and highlight the exceptional capabilities of the ims network for the scientific study of active volcanism in the global ocean supporting information

late weichselian glacier retreat in kongsfjorden west spitsbergen svalbard the chronology of late weichselian to holocene deglaciation of kongsfjorden west spitsbergen has been reconstructed based on the geomorphic and stratigraphic record of ice retreat relative sea level relationships and 14c dating of associated marine organic materials the seaward extent of glacial drift and fjord bathymetry constrain a secure reconstruction for the ice sheet near the mouth of the fjord at ca 13 000 yr b p but do not rule out the possibility that more extensive glaciation was achieved earlier during the late weichselian regional shoreline relations rates of emergence and radiocarbon dating of foraminifera deposited just above till indicate that deglaciation occurred in two steps one beginning during or just prior to the late weichselian marine limit phase at 13 000 12 000 yr b p and another beginning at 10 000 9500 yr b p the fjord was completely deglaciated by 9440 130 yr b p a period of stable relative sea level began 10 700 yr b p and ended between 10 000 and 9500 yr b p which we take to indicate renewed glacial loading during the younger dryas glacier readvance within kongsfjorden at this time was diminutive suggesting that most of the younger dryas ice sheet growth was confined to the eastern part of the archipelago and or to the barents shelf the two step deglaciation of kongsfjorden occurred during intervals of accelerated global ice sheet melting and rapid oceanic and atmospheric warming in more temperate latitudes of the circum atlantic region this coincidence most likely resulted from contemporaneous increases in the poleward transport of oceanic heat

bioclastic carbonate sediments on the southwestern svalbard shelf the poleward continuation of one of the largest known arctic carbonate factories the western spitsbergenbank of the barents sea has been surveyed along the narrow sw svalbard shelf on this shelf formation of cold water carbonate sediments occurs under glaciomarine environmental conditions mya truncata and hiatella arctica colonized a soft glacio marine diamicton 3000 6000 years after the final retreat of the icedome from the sw svalbard shelf since 2600 yr b p an increase of along shelf bottom currents washed out the fine terrigenous deposits leaving behind a shelly lag deposit and winnowed boulders on a morainic shelf topography the most favourable depth interval promoting the establishment of an amalgamated bioclastic blanket is located in 50 80 m water depth in this interval strong bottom currents prevent sedimentation thus facilitating colonisation of filter feeding benthic communities dominated by balanus balanus and chlamys islandica additional skeletal components are supplied by echinoderms bryozoans serpulids brachiopods and gastropods in shallower water depths carbonate production is hampered by intense iceberg scouring and release of ice rafted debris from the still glaciated hinterland of svalbard in deeper water 80 m olive grey muds with dispersed pebbles rich in benthic foraminiferans clinocardium ciliatum and taxodont bivalves are present on all surveyed shelf banks the deepest unit is a blue mud in water depths 120 m with benthic foraminiferans taxodont bivalves and sipunculids compared to spitsbergenbank carbonate production is much more restricted and impoverished on the sw svalbard shelf but is still an instructive modern example for the formation of skeletal carbonates resting on tillites in the geological record

on the mechanism of conversion of seismic waves to and from t waves in the vicinity of island shores high frequency seismic records from the polynesian seismic network are used to investigate in detail the processes of conversion of acoustic t wave energy from and to seismic waves at island shores on the source side we study the seismic to acoustic conversion based on t phases from hawaiian events recorded at polynesian stations located on the coral platter on the receiver side we study the acoustic to seismic conversion based on t phases from marine sources recorded across the polynesian islands in both instances our results underline the importance of steep slopes typically 50 in allowing an efficient conversion between p waves in the island structure and t waves in the water column these slopes can be coral reefs or the heads of young presumably unconsolidated basalt flows under this geometry modeling based on raytracing indicates that the seismic record of the t phase consists of a p wave at distances from the conversion point greater than 9 km at shorter distances s waves and surface waves are generated in the absence of a steep slope only surface waves are present these models can be used to compute precise and predictable travel time station corrections allowing the use of seismometers located inland to exploit the superb detection and location capabilities of t waves

pre holocene raised beaches at cape ross southern victoria land antarctica raised marine beach deposits along the coast of the ross embayment are important for relative sea level reconstructions and for determining the timing of deglaciation following the last glacial maximum lgm flights of beaches from mcmurdo sound to terra nova bay long have been thought to be of holocene age however new data from cape ross indicate that pre holocene beach material is common and may be predominant at elevations greater than 23 m above mean sea level this discovery leads to unanswered questions regarding the full spatial extent of pre holocene beaches in the antarctic and other formerly glaciated areas more important it indicates that undated raised beaches cannot be assumed to result from isostatic uplift following the lgm and should not be used for relative sea level reconstructions

localization of t wave energy on land revealed by a dense seismic network in japan summary we have investigated the wave propagation characteristics of a seismic t wave on land in northeastern japan using the seismograms recorded by a dense seismic network the analysed t wave is a unique one that was generated by a large intermediate depth earthquake beneath the network that backpropagated from the emperor seamount chain in the northern pacific the t wave has a predominant frequency of 1 5 hz which is lower than the previously reported values spatiotemporal variation of an rms envelope bandpass filtered with a passband of 1 2 hz demonstrates multiple arrivals of the t wave and inhomogeneous distribution of amplitude judging from the spatial pattern of first arrival times and the polarization characteristics such as the relatively large dip angle and high planarity we regard the seismic t wave as a rayleigh wave a possible conversion area estimated by a method similar to the source scanning algorithm is located to the northeast of honshu island and may have a dimension of 100 km the most prominent feature of the spatiotemporal variation of the rms amplitude is the localization of t wave energy in the northeastern part of honshu island this localization can be attributed either to the close proximity of the conversion area to land or to the large extent of the area however these factors are only supplementary because they cannot explain a sharp contrast in amplitude between the two areas with comparable distance but different azimuth from the conversion point an additional and essential factor in explaining the observation is the non isotropic radiation from the conversion points since the conversion occurred on the continental slope the maximum amplitude of converted energy is expected to appear either in the propagation direction of incoming acoustic waves or in the steepest direction of the local topography these factors in particular a convex shape of bathymetry probably caused the focusing of converted energy into the northeastern part of honshu island

late weichselian and holocene sedimentary environments and ice rafting in isfjorden spitsbergen abstract multi proxy analyses of two sediment cores from central isfjorden were used to reconstruct the glacial history in central spitsbergen during the late weichselian and the holocene and to relate iceberg rafting and sea ice rafting to climatic and oceanographic changes in the north atlantic region a basal till was deposited beneath an ice stream prior to 12 700 cal years bp calendar years before the present several tidewater glaciers influenced the sedimentary environment during the younger dryas and probably already during the allerod the younger dryas cooling might be reflected by enhanced sea ice formation and suspension settling as well as reduced iceberg rafting the final deglaciation was dominated by intense iceberg rafting it terminated around 11 200 cal years bp optimum holocene climatic and oceanographic conditions with significantly reduced ice rafting occurred between c 11 200 and 9000 cal years bp ice rafting occurred almost exclusively from icebergs after 10 200 cal years bp the icebergs most probably originated from tidewater glaciers on east spitsbergen indicating the presence of a strong east west temperature gradient at this time an increase of iceberg rafting around 9000 cal years bp followed by enhanced sea ice rafting reflects the onset of a general cooling in the western barents sea svalbard region comparatively intense rafting from icebergs and sea ice between 9000 and 4000 cal years bp is related to this cooling a general reduction in ice rafting after 4000 cal years bp is most probably the result of the enhanced formation of shore fast and or more permanent sea ice cover reducing the drift of icebergs and sea ice in the fjord the results indicate that the palaeoenvironmental conditions on central spitsbergen to a large degree depended on the oceanographic conditions in the western barents sea and west off spitsbergen however climatic trends affecting greenland and the entire north atlantic region can also be identified

t waves with long inland paths synthetic seismograms in order to provide more insight into land propagation of t phases signal analysis of these phases recorded inland has been carried out we found that the wave train is composed mainly of pg and sg waves which reach the seismic station from different azimuths with the hypothesis that the signal is the sum of discrete arrivals due to different rays crossing the continental slope at different locations synthetic seismograms of t waves are computed taking into account the variation of the conversion point along the slope the transmission of energy from the ocean to the continental crust is mainly due to diffraction effects the duration arid the amplitude of the t phase which are two criteria used to evaluate tsunami risk are greatly influenced by the shape of the continental slope

late weichselian and holocene relative sea level history of broggerhalvoya spitsbergen abstract radiocarbon dated whalebones from raised beaches record a relative sea level history for broggerhalvoya western spitsbergen that suggest a two step deglaciation on svalbard at the end of the late weichselian glaciation the late weichselian marine limit was reached at about 13 000 yr b p and was followed by relatively slow emergence until about 10 000 yr b p either in response to ice unloading in the barents sea initial retreat of local fjord glaciers or some combination of the two rare whale skeletons dating between 13 000 and 10 000 yr b p indicate that the norwegian sea was at least seasonally ice free during that interval deglaciation of spitsbergen is recorded by the rapid emergence of broggerhalvoya after 10 000 yr b p this was followed by a transgression during the mid holocene here named the talavera transgression and another in modern times raised beach morphologies suggest striking differences in nearshore depositional processes before and after 10 000 yr b p that are probably related to changes in the rate of uplift and in sea ice conditions

earth science time of reversal at intervals the polarity of the earth s magnetic field reverses the timescale for this reversal is unclear in fact it seems to depend on the latitude of the site from which the geological data are extracted

from mountain top to the deep sea deglaciation in 4d of the northwestern barents sea ice sheet abstract the timing of the deglaciation of the northern barents sea ice sheet bsis documented in terrestrial and offshore records from the svalbard archipelago is reviewed we present new cosmogenic nuclide cn ages from formerly unexplored inland areas of northern svalbard to investigate the timing of thinning of past local ice domes cn data are compared with radiocarbon ages from marine and terrestrial deposits 10be isotope cn dates on erratic boulders from interior svalbard suggest that glacier surfaces in northern and western svalbard thinned 950 650 m from 26 4 ka and continued over an extended period until 16 ka initial ice retreat from the western outer to the inner shelf began at 20 5 ka and in storfjordrenna southwest of svalbard around 19 18 ka retreat of grounded ice from the northern outer to the inner shelf did not begin before 15 9 ka we therefore suggest increasing summer insolation and aridification due to atmospheric circulation changes and perennial sea ice cover as the main mechanisms for the ice thinning and grounded ice retreat from the outer shelves before and during the heinrich 1 event the frontal position of the grounded ice sheet however did not change during several millennia despite further thinning in interior northern svalbard the inner shelf areas rapidly deglaciated towards the fjord mouths along the western coasts between 15 and 14 ka and became ice free before and during meltwater pulse 1a mwp 1a the collapse of the ice shelves from the inner shelf towards the fjord mouths and inner fjords occurred on a decadal to centennial time scale based on overlapping radiocarbon ages from marine sediment cores in addition to cn data from erratic boulders in lowlands we suggest that additional mechanisms must have caused this rapid collapse together with reduced moisture supply in the accumulation areas we assume that subsurface warm atlantic water masses that reached the western shelf after 17 5 ka may have accelerated debuttressing of the ice shelves in addition to the bolling warming that kicked in around 15 1 ka due to increased insolation and the global sea level rise called mwp 1a conservative calculations estimate the contribution of only the northwestern part of the bsis to sea level rise with 0 0004 cm yr 1 between 26 and 16 ka and 0 02 cm yr 1 in assumed 300 years between 15 and 14 ka

the island of amsterdamoya a key site for studying past climate in the arctic archipelago of svalbard abstract this paper introduces a series of articles assembled in a special issue that explore holocene climate evolution as recorded in lakes on the island of amsterdamoya on the westernmost fringe of the arctic svalbard archipelago due to its location near the interface of oceanic and atmospheric systems sourced from arctic and atlantic regions amsterdamoya is a key site for recording the terrestrial response to marine and atmospheric changes we employed multi proxy approaches on lake sediments integrating physical biogeochemical and isotopic analyses to infer past changes in temperature precipitation and glacier activity the results comprise a series of quantitative holocene length paleoclimate reconstructions that reveal different aspects of past climate change each of the four papers addresses various facets of the holocene climate history of north western svalbard including a reconstruction of the annabreen glacier based on the sedimentology of the distal glacier fed lake gjoavatnet a reconstruction of changing hydrologic conditions based on sedimentology and stratigraphy in lake hakluytvatnet reconstruction of summer temperature based on alkenone paleothermometry from lakes hakluytvatnet and hajeren and a hydrogen isotope based hydrological reconstruction from lake hakluytvatnet we also present high resolution paleomagnetic secular variation data from the same lake which document important regional magnetic field variations and demonstrate the potential for use in synchronizing holocene sedimentary records in the arctic the paleoclimate picture that emerges is one of early holocene warmth from ca 10 5 ka bp interrupted by transient cooling ca 10 8ka bp and followed by cooling that mostly manifested as two stepwise events ca 7 and 4 ka bp the past 4ka were characterized by dynamic glaciers and summer temperature fluctuations decoupled from the declining summer insolation

micromorphological criteria for discriminating subglacial and glacimarine sediments evidence from a contemporary tidewater glacier spitsbergen abstract sedimentological and micromorphological evidence is presented from four sites within st jonsfjorden western spitsbergen sedimentological and geomorphological evidence is used to distinguish sites comprising undisturbed glacimarine sediments from glacially over ridden glacimarine sediments and subglacial diamicts impregnated thin sections are used to define associations of micromorphological characteristics that allow diamicts formed under these different conditions to be discriminated in situ glacimarine deposits display winnowed textures dropstone structures and distinct vertical orientations of sand grains whilst subglacial conditions result in structures indicative of deformation under moderate to high stress regimes these criteria may help to determine the origin of ancient and quaternary diamicts of questionable subglacial or glacimarine origin

marine 14c reservoir ages for 19th century whales and molluscs from the north atlantic abstract in order to compare radiocarbon dates on marine and terrestrial samples the former have to be corrected for a reservoir age we present reservoir ages from dating 21 whales collected 1860 1901 and recalculating dates of 23 molluscs collected 1857 1926 most of the whales were caught along the coast of norway but one is from france and one from iceland we assume the former mainly lived in the north and equatorial atlantic and in the norwegian sea whales feed only on pelagic organisms and will provide the reservoir age for the open ocean surface water however they travel long distances and will integrate the reservoir ages of the different water masses along their way molluscs dated from norway spitsbergen and arctic canada are stationary and monitor the sea water passing their dwelling site but some also take up carbon from particulate food or sediment pore water coastal water also often contains some continental carbon we present two different views on how to analyze and interpret the data mangerud recommends to use reservoir ages based on a combination of the whale and mollusc dates i e 380 30 and 360 30 yr relative to intcal04 and british oak respectively and a r value of 20 30 for the surface water in the n atlantic and norwegian sea bondevik and gulliksen maintain that the reservoir age and r along the norwegian coast is latitude dependant with r values increasing from 3 22 in the south to 105 24 at spitsbergen whales reflecting north atlantic open ocean surface water have lower r 7 11 than most molluscs

distribution of polar membrane lipids in permafrost soils and sediments of a small high arctic catchment the distribution of bacteriohopanepolyols bhps and intact polar membrane lipids ipls was studied in different soil profiles and in fluvial and marine sediments along the pathway of transport in a small catchment in the high arctic at ny alesund svalbard 79 n 12 e both groups of cellular membrane lipids have been used as biomarkers for determining major microbial groups and biogeochemical processes in natural environments little is known about their distribution and usefulness as environmental markers in the arctic in this study we show that both membrane lipid groups are variably distributed in the drainage area of the broggerbreen glacier with highest abundance and diversity in the organic mat overlying the mineral soils as well as in mossy surface soil the bhp and ipl composition and abundance both indicate a larger community of phototrophic bacteria in the organic mats and fluvial sediments the greater diversity and abundance of bhps relative to ipls in sub soils including probable markers for cyanobacteria suggest a greater resistance to degradation in contrast ipl concentration decreased strongly with soil depth pointing to their rapid degradation bacterial ipls are thus thought to reflect more reliably the biomass of viable phototrophic bacteria the high concentrations of proposed soil marker bhps adenosylhopane and related structures vs published results and their relative increase with soil depth suggest better preservation and more effective accumulation of the compounds at low temperature

marine molluscs and late quaternary environmental studies with particular reference to the late glacial period in northwest europe a review abstract although it is now commonly thought that temperature is a minor factor in limiting the distribution of marine invertebrates particularly on a local scale there is evidence to suggest that some boreal molluscs particularly those which occur in similar environments on both sides of the north atlantic are valuable as oceanic temperature indicators this applies particularly to planktotrophic species whose northern limits of distribution are apparently controlled by summer surface temperature the oceanography of the eastern north atlantic is briefly considered in relation to zoogeographic subdivisions based on temperature and it is concluded that the latter are fairly crude and apply only to shelf seas most glaciomarine molluscan faunas are not specific to that environment an exception being that dominated by the bivalve portlandia arctica the role of marine molluscs in palaeoenvironmental research at the local level for the 13 11 ka bp period is illustrated by a site at inchinnan scotland it is concluded that a shell bed at this locality consists partly of a little modified life assemblage and partly of shells which have been gently reworked under conditions of generally rapid deposition during the same time interval the changing composition of molluscan faunas on the nw european seaboard suggests that a weak drift of north atlantic water replaced polar water at or a little later than 13 ka bp off scotland and a few hundred years later off northern norway evidence for relatively warm intervals early and late in the 13 11 ka bp period has been found particulary on the scottish coast and to a lesser extent more generally the later warm interval may be related to the southward movement of the polar front at the beginning of the younger dryas the value of the bivalve shell itself in the determination of temperature seasonality and calendar years is briefly discussed

identification of t waves in the alboran sea analyses of seismograms from 1 100 north moroccan earthquakes recorded at stations of the red sismica de andalucia southern spain reveal the systematic presence of late phases embedded in the earthquake codas these phases have distinctive frequency contents similar to the p and s spectra and quite different to the frequency contents of the earthquake codas they are best detected at near shore stations their amplitudes decay significantly with distance to the shoreline the delays with respect to the p wave onsets of the preceding earthquakes are consistently around 85 s late phases are only detected for earthquakes located in a small region of about 100 60 km centered at 35 4 n 4 0 w near the northern coast of morocco several hypotheses could in principle explain the presence of these late phases in the seismograms for example the occurrence of low energy aftershocks efficient wave reflections or rayleigh waves generated along the source station paths however we conclude that the most likely origin of these phases corresponds to the incidence of t waves generated by conversion from elastic to acoustic energy in the north moroccan coast in the southern coast of the iberian peninsula t waves are thought to be generated by energy trapping in low velocity channels along long oceanic paths in this case we demonstrate that they can be produced in much shorter paths as well although t waves have been already documented in other areas of the mediterranean sea this is the first time that they have been identified in the alboran sea

coarse clastic barrier beaches a discussion of the distinctive dynamic and morphosedimentary characteristics abstract coarse clastic barriers are common on mid and high latitude coasts they possess a morphosedimentary and dynamic distinctiveness which sets them apart from sandy fineclastic barrier forms the reflective nature of the seaward barrier favors the development of zero mode sub harmonic edge waves particularly during long period swells 10 20 s manifest in the formation of high level cusps in some circumstances the pattern of recent overwashing of the barrier is related to cusps lack of distinct tidal passes due partly to the high seepage potential of coarse barriers means that very little sediment is transported seaward thus the barriers roll steadily onshore and sections show a variety of washover facies related to the volume of overwash surges

t phase observations in global seismogram stacks the t phase conversion of acoustic to seismic energy is typically observed as a high frequency wave train at hydrophones or coastal seismic stations here we show that the t phase can be observed in broadband waveform stacks of 5200 earthquakes recorded by the global seismic network to enhance the phase arrivals in stacks we apply short time window average over long time window average filtering to individual traces before stacking although the t phase arrival is visible in stacks from seismograms filtered at 0 5 5 hz it appears much stronger at higher frequencies 2 8 hz and is further enhanced by only stacking seismograms from oceanic paths stacking only subsets of the data depending on continental path lengths on the receiver side shows that the t phase can be observed at stations up to 4 inland from the coast and changes in the t phase arrival time correspond to reasonable crustal velocities

a review of postglacial emergence on svalbard franz josef land and novaya zemlya northern eurasia the pattern of postglacial emergence in the barents sea is pivotal to constraining the timing of deglaciation and extent and thickness of the last ice sheet in northern eurasia this review unites records of holocene relative sea level from svalbard franz josef land and novaya zemlya to better understand the geometries of past ice sheet loads emergence data from northern eurasia confine the maximum area of glacier loading to the northwestern barents sea where 100 m of emergence is measured on kongs ya deglacial unloading commenced on western and northern spitsbergen c 13 12 14 c ka ago and by c 10 5 14 ck a on eastern svalbard and more distal sites on franz josef land and novaya zemlya the marine limit phase c 13 12 14 c ka on western and northern spitsbergen is characterized by the construction of spits indicating a dominance of long shore drift over stormgenerated fetch reflecting extensive sea ice coverage of coastal areas at sites in proximity to the ice sheet margin on western and northern spitsbergen there is evidence for a transgressive regressive cycle c 6 4 14 c ka possibly reflecting back migration of displaced mantle material a modern transgression is inferred from the marine erosion of 17th century cultural features and 14 c ages of whalebone and terrestrial peat buried by modern storm gravels that place sea level at its present position by c 2 to 1 ka ago the greatest observed emergence on franz josef land occurs on bell island with a marine limit at 49 m aht formed c 10 14 c ka available emergence data since 9 ka show rising strandlines toward the southwest at b0 3 m km the northern limit of emergence on franz josef land is poorly constrained because relative sea level data is sparse north of 80 30 0 n in contrast to svalbard and franz josef land the marine limit on northern novaya zemlya is only 10 15 m above high tide and formed between 6 5 and 5 0 14 c ka when global sea level was stabilizing all sites show little apparent emergence during the past 2 ka with the youngest raised landforms at identical heights to storm beaches this minimal glacio isostatic signature on novaya zemlya and on vaygach island where deglaciation commenced 10 ka ago indicates ice sheet thicknesses of o1 5 km the spatial variation in emergence for the barents sea indicates that western and northern spitsbergen and novaya zemlya were near the reactive margin of the ice sheet and these areas sustained the briefest ice coverage 2 6 ka and were probably not in isostatic equilibrium in contrast central and eastern svalbard and southern franz josef land were beneath a substantial ice load and probably sustained this load for c 10 14 c ka and achieved isostatic equilibrium isostasy residual from an ice sheet model portrays well the general pattern of uplift and load response at the centre of ice sheets but deviates substantial at the ice sheet margin or areas covered by thin ice like novaya zemlya

distribution of glaciofluvial sediment within and on the surface of a high arctic valley glacier marthabreen svalbard marthabreen is a 7 8km long valley glacier in sw spitsbergen the glacier is partially covered by a layer of angular debris derived from rockfall in its accumulation area pierced in places by pinnacles and ridges of glaciofluvial sediment these concentrations of glaciofluvial sediment fall into three categories 1 debris pinnacles 2 longitudinal sediment dykes 3 longitudinal ridge accumulations debris pinnacles are slabs of sediment predominantly sands gravels and cobbles elevated to the glacier surface along thrusts longitudinal sediment dykes are low 1m high ridges of sorted sand and gravels which are not associated with penetrative ice structures their occurrence downglacier of sediment dykes and debris pinnacles suggests that they originate as supraglacial or englacial channels or tunnels filled by sediment derived from the dykes or thrusts the presence of large quantities of glaciofluvial sediment on the surface of marthabreen does not imply englacial water flow at high levels within the glacier but is related to ice deformational processes such as thrusting and folding of debris rich stratification copyright 1999 john wiley sons ltd

elastic parabolic equation solutions for oceanic t wave generation and propagation from deep seismic sources oceanic t waves are earthquake signals that originate when elastic waves interact with the fluid elastic interface at the ocean bottom and are converted to acoustic waves in the ocean these waves propagate long distances in the sound fixing and ranging sofar channel and tend to be the largest observed arrivals from seismic events thus an understanding of their generation is important for event detection localization and source type discrimination recently benchmarked seismic self starting fields are used to generate elastic parabolic equation solutions that demonstrate generation and propagation of oceanic t waves in range dependent underwater acoustic environments both downward sloping and abyssal ocean range dependent environments are considered and results demonstrate conversion of elastic waves into water borne oceanic t waves examples demonstrating long range broadband t wave propagation in range dependent environments are shown these results confirm that elastic parabolic equation solutions are valuable for characterization of the relationships between t wave propagation and variations in range dependent bathymetry or elastic material parameters as well as for modeling t wave receptions at hydrophone arrays or coastal receiving stations

holocene glacial history of svalbard status perspectives and challenges abstract we synthesize the current understanding of glacier activity on svalbard from the end of the late pleistocene 12 000 yrs before present to the end of the little ice age c 1920 ad our glacier history is derived from the svalhola database the first compilation of holocene geochronology for svalbard and the surrounding waters including over 1 800 radiocarbon terrestrial cosmogenic nuclide and optically stimulated luminescence ages data have been categorized by geological setting uniformly re calibrated quality assessed and ultimately used to constrain glacier fluctuations deglaciation ice free conditions glacier re advances and ice marginal positions we advance existing knowledge by mapping the extent and distribution of ice cover during the holocene glacial maximum and the glacial minimum as well as present retreat rates and percentages within early holocene fjord systems throughout the holocene svalbard glaciers have responded to a varying combination of climatic environmental and dynamic driving factors which influence both the extent and behavior of ice margins we discuss the complexities of glacier systems and their dynamics in response to changes in climate this review provides a holistic state of the art of holocene glaciers on svalbard suitable for orienting future works which address gaps in our current knowledge

the last glacial maximum on spitsbergen svalbard most scientists have concluded previously that the west coast of spitsbergen svalbard remained ice free during the late weichselian between 25 000 and 10 000 yr b p we conclude that the glaciation was more extensive terraces that were postulated to have been ice free are covered by a thin late weichselian till sudden drop in the marine limit and basal radiocarbon dates of raised glaciomarine sediments demonstrates that the glaciers in the main fjords isfjorden and van mijenfjorden terminated west outside of the fjord mouths basal radiocarbon dates from glaciomarine clay above till in cores from the continental shelf west of spitsbergen yielded ages of about 12 500 yr b p from which we conclude that the ice extended to the shelf edge based on the extent of amino acid diagenesis in radiocarbon dated molluscs the duration of the maximum extension of the late weichselian glaciation was short certainly less than 10 000 years during the ice free period preceding that glaciation at least back to 40 000 yr b p the glaciers on svalbard were not significantly larger than at present as shown by marine deposits close to the glacier snouts many radiocarbon dates place deglaciation of the outer coast at about 12 500 yr b p at about 10 000 yr b p the rest of the archipelago rapidly became ice free

holocene relative sea level fluctuations in the st lawrence estuary quebec canada abstract between 7000 and 6000 yr b p relative sea level was as much as 5 m lower than today in the st lawrence estuary quebec a small transgression laurentian transgression occurred between 5800 and 4400 yr b p which resulted in the construction of an 8 to 10 m terrace about 3000 yr b p relative sea level was similar to present and then a stillstand or a slight rise occurred during which a cliff micmac cliff was cut into the emerged terrace during a subsequent lowering of relative sea level coastal emergence a low aggradational terrace mitis terrace was built between 2300 and 1500 yr b p at the base of the micmac cliff a new emergence curve for the south shore of the st lawrence estuary showing a mid holocene high stand of relative sea level is therefore proposed

paleoclimatic inferences from glacial fluctuations on svalbard during the last 20 000 years the climate history of western spitsbergen svalbard is deduced from variations of glaciers during the last 20 000 years a major depression of the regional equilibrium line altitude ela occurred during the late weichselian glacial maximum 18000 13000y ago when low summer temperatures may have caused year round snow accumulation on the ground this rapid expansion of the glaciers also indicates nearby moisture sources suggesting partly open conditions in the norwegian sea during the summers a rapid glacial retreat around 13 000 12 500 y bp was caused by a sudden warming during the younger dryas the ela along the extreme western coast of spitsbergen was not significantly lower than at present in contrast to fennoscandia the british isles and the alps there is no evidence for readvance of local glaciers during younger dryas on western spitsbergen this difference is attributed to a much dryer climate on spitsbergen and probably only slight changes in sea surface temperatures in addition summer melting in this high arctic area is more sensitive to orbitally increased insolation around 10 000 y bp another rapid warming occurred and during early and mid holocene the summer temperatures were significantly higher than at present a temperature decline during the late holocene caused regrowth of the glaciers which reached their maximum holocene position during the last century

surface waves from underground explosions with spall analysis of elastic and nonlinear source models anomalous surface wave observations from underground explosions have been widely attributed to the phenomenon of spall i e the detachment and subsequent slapdown of near surface layers in response to explosion induced tensile stresses we argue on the basis of a simple equivalent force model that while spall can enhance explosion surface waves at very short periods it cannot contribute significantly to the teleseismic surface waves radiated by underground explosions at periods exceeding about 10 sec previous theoretical results to the contrary are in error having been based on source models which do not conserve momentum a nonlinear two dimensional axisymmetric finite difference simulation of a buried explosion in granite further supports the conclusion that spall cannot contribute to long period surface waves the simulation exhibits extensive spall nonetheless predicted fundamental mode rayleigh wave spectra are nearly identical to those obtained from a spherically symmetric simulation which does not include spall at periods exceeding about 10 sec at shorter periods the two dimensional simulation predicts some rayleigh wave enhancement compared to the one dimensional simulation the maximum enhancement about a factor of 2 occurs at a period of approximately 2 5 sec synthetic long period rayleigh wave seismograms at 3000 km range show no perceptible phase or amplitude anomalies due to spall these results are in excellent agreement with the predictions of our equivalent force model

empirical and numerical modeling of t phase propagation from ocean to land t phase propagation from ocean onto land is investigated by comparing data from hydrophones in the water column with data from the same events recorded on island and coastal seismometers several events located on hawaii and the emerging seamount loihi generated very large amplitude t phases that were recorded at both the preliminary ims hydrophone station at point sur and land based stations along the northern california coast we use data from seismic stations operated by u c berkeley along the coast of california and from the pg e coastal california seismic network to estimate the t phase transfer functions the transfer function and predicted signal from the loihi events are modeled with a composite technique using normal mode based numerical propagation codes to calculate the hydroacoustic pressure field and an elastic finite difference code to calculate the seismic propagation to land based stations the modal code is used to calculate the acoustic pressure and particle velocity fields in the ocean off the california coast which is used as input to the finite difference code tres to model propagation onto land we find both empirically and in the calculations that t phases observed near the conversion point consist primarily of surface waves although the t phases propagate as p waves after the surface waves attenuate surface wave conversion occurs farther offshore and over a longer region than body wave conversion which has the effect that surface waves may arrive at coastal stations before body waves we also look at the nature of t phases after conversion from ocean to land by examining far inland t phases we find that t phases propagate primarily as p waves once they are well inland from the coast and can be observed in some cases hundreds of kilometers inland t phase conversion attenuates higher frequencies however we find that high frequency energy from underwater explosion sources can still be observed at t phase stations

limitations of thermoluminescence to date waterlain sediments from glaciated fiord environments of western spitsbergen svalbard abstract a fundamental problem in the tl dating of waterlain sediments particularly in the arctic is the accurate determination of the level of solar resetting prior to deposition this study determined the effect of wavelength on the solar resetting of the tl signal and concomitant effects on the accuracy of tl age estimates for late glacial and modern glacial and nearshore marine sediments from fiords on spitsbergen the reduction in tl level decreases with filtering of wavelengths above 400 nm modern and late weichselian tills have tl levels at saturation probably received no light exposure prior to deposition and thus cannot be dated by tl glacial marine sediments deposited within 0 5 km of a glacier terminus yielded tl age estimates 10 times the known age presumably because these sediments received limited light exposure prior to deposition modern sublittoral sediments and fiord muds yielded tl apparent ages between

estimating the horizontal and vertical direction of arrival of water borne seismic signals in the northern philippine sea conventional and adaptive plane wave beamforming with simultaneous recordings by large aperture horizontal and vertical line arrays during the 2009 philippine sea engineering test philsea09 reveal the rate of occurrence and the two dimensional arrival structure of seismic phases that couple into the deep ocean a ship deployed controlled acoustic source was used to evaluate performance of the horizontal array for a range of beamformer adaptiveness levels ninety t phases from unique azimuths were recorded between yeardays 107 to 119 t phase azimuth and s minus p phase time of arrival range estimates were validated using united states geological survey seismic monitoring network data analysis of phases from a seismic event that occurred on yearday 112 near the east coast of taiwan approximately 450 km from the arrays revealed a 22 clockwise evolution of t phase azimuth over 90 s two hypotheses to explain such evolution body wave excitation of multiple sources or in water scattering are presented bas

ice 3g a new global model of late pleistocene deglaciation based upon geophysical predictions of post glacial relative sea level change a new high resolution global model of late pleistocene deglaciation is inferred on the basis of geophysical predictions of postglacial relative sea level variations in which the ice ocean solid earth interaction is treated in a gravitationally self consistent fashion for the purpose of these analyses the radial viscoelastic structure of the planet is assumed known on the basis of previously published sensitivity tests on solutions of the forward problem only radiocarbon controlled relative sea level histories from sites that were actually ice covered with one or two additions are employed to constrain the model leaving relative sea level rsl data from sites that were not ice covered to be employed to confirm its consistency results for these confirmatory analyses are reported elsewhere here the new deglaciation model referred to as ice 3g is compared to previous models derived by several independent means and tested against a number of additional observations other than sea level histories including geologically controlled retreat isochrones oxygen isotope data from deep sea sedimentary cores and coral terrace elevations the latter two observations strongly constrain the net sea level rise that has occurred since the onset of deglaciation and therefore the mass of ice that melted during the last glacial interglacial transition

glaciers on svalbard survived the holocene thermal optimum abstract about 60 of svalbard is covered by glaciers today but many of these glaciers were much reduced in size or gone in the early holocene high resolution modeling of the glacial isostatic rebound reveals that the largest glaciers in nordaustlandet and eastern spitsbergen survived the early holocene warming while the smaller more peripheral glaciers especially in the northwest started to form about 5 500 years ago and reached 3 4 of their current size about 600 years ago relative sea level has been rising during the last few millennia in the north and western parts of spitsbergen while land still emerges in the remaining part of svalbard here we show that this sea level rise in the northwest is caused by the regrowth of glaciers in the mid to late holocene that slowed down and even reversed the post glacial isostatic uplift and caused the crust to subside over large areas of spitsbergen

hybrid numerical modelling of t wave propagation application to the midplate experiment summary a hybrid method coupling a ray tracing method and a nite diierence approach is proposed for modelling t wave propagation from an underwater source to an on land seismic station the long range hydroacoustic wave eld estimated in the sofar channel by the maslov approach shows many triplications of propagation with an increasing number of caustics as the range increases ray tracing approaches lead to a straightforward analysis of the sofar propagation we nd that the duration and the amplitude of the hydroacoustic t waves generated by a source close to the sofar axis may be respectively eight times longer and almost seven times higher than the duration and the amplitude of hydroacoustic t waves generated by a source close to the sofar limits the nite diierence modelling handles the complex hydroacoustic seismic t wave conversion on atoll shores with an illustration of seismic t waves recorded during the midplate experiment in 1989 two diierent seismic stations fga on the fangataufa atoll and din on the mururoa atoll both in french polynesia have recorded the seismic t waves due to an underwater chemical blast at a distance greater than 900 km synthetic seismograms computed by our proposed hybrid method are close enough to the real data for quantitative interpretation we believe that the input model structure is accurate enough to allow such analysis of the seismic t waves the numerical simulation shows that the seismic t waves recorded at both stations are mainly composed of p phases and rayleigh phases the simulation shows that the seismic t wave duration is often linked to the source depth although other factors the continental slope or the distance between the top of the continental slope and the seismic station may also aiect the signal duration

deglacial land emergence and lateral upper mantle heterogeneity in the svalbard archipelago ii extended results for high resolution load models summary in paper i breuer wolf 1995 a preliminary interpretation of the postglacial land emergence observed at a restricted set of six locations in the svalbard archipelago was given the study was based on a simple model of the barents sea ice sheet and suggested increases in lithosphere thickness and asthenosphere viscosity with increasing distance from the continental margin in the present paper the newly developed high resolution load model barents 2 and land uplift observations from an extended set of 25 locations are used to study further the possibility of resolving lateral heterogeneity in the upper mantle below the northern barents sea a comparison of the calculated and observed uplift values shows that the lithosphere thickness is not well resolved by the observations although values above 110 km are most common for this parameter in contrast to this there are indications of a lateral variation of asthenosphere viscosity whereas values in the range 10 8 1020 pa s are inferred for locations close to the continental margin 1020 102 pa s are suggested further away from the margin a study of the sensitivity of the values found for lithosphere thickness and asthenosphere viscosity to modifications of load model barents 2 shows that such modifications can be largely accommodated by appropriate changes in lithosphere thickness whereas the suggested lateral variation of asthenosphere viscosity is essentially unaffected an estimate of the influence of the fennoscandian ice sheet leads to the conclusion that its neglect results in an underestimation of the thickness of the barents sea ice sheet by about 10 per cent

constraints on the late weichselian ice sheet over the barents sea from observations of raised shorelines abstract direct evidence for late weichselian grounded glacier ice over extensive areas of the barents sea is based largely on indirect observations including elevations of old shorelines on svalbard and arguments of isostatic rebound such isostatic models are discussed here for two cases representing maximum and minimum ice sheet reconstructions in the former model the ice extends over the kara sea whereas in the latter the ice is limited to the barents sea and island archipelagos comparisons of predictions with observations from a number of areas including spitsbergen nordaustlandet edgeoya kong karls land franz josef land novaya zemlya and finnmark support arguments for the existence of a large ice sheet over the region at the time of the last glacial maximum this ice sheet is likely to have had the following characteristics conclusions that are independent of assumptions made about the earth s rheological parameters i the maximum thickness of this ice was about 1500 2000 m with the centre of the load occurring to the south and east of kong karls land ii the ice sheet extended out to the western edge of the continental shelf and its maximum thickness over western spitsbergen was about 800 m iii to the north of svalberg and frans josef land the ice sheet extended out to the northern shelf edge iv retreat of the grounded ice across the southern barents sea occurred relatively early such that this region was largely ice free by about 15 000 bp v by 12 000 bp the grounded ice had retreated to the northern archipelagos and was largely gone by 10 000 bp vi the ice sheet may have extended to the kara sea but ice thicknesses were only a fraction of those proposed in those reconstructions where the maximum ice thickness is centered on novaya zemlya models for the palaeobathymetry for the barents sea at the time of the last glacial maximum indicate that large parts of the barents sea were either very shallow or above sea level providing the opportunity for ice growth on the emerged plateaux as well as on the islands but only towards the end of the period of fennoscandian ice sheet build up

dynamics and retreat of the late weichselian kongsfjorden ice stream nw svalbard terrestrial cosmogenic nuclide dating in combination with detailed landform mapping in the kongsf jordhallet area nw svalbard have provided new insight on configuration dynamics and deglaciation of the late weichselian kongsfjorden ice stream the minimum late weichselian ice surface elevation in kongsfjorden was 449 m a s l indicating considerably thicker ice and a steeper surface gradient than earlier suggested for the adjacent inter ice stream area an even steeper surface slope is reconstructed the glacial landforms as well as the surface exposure ages of erratic boulders at different elevations suggest a gradual lowering of the ice surface deglaciation of the higher elevations was probably underway by 20 0 ka at ca 16 6 ka a large moraine complex the kongsfjorden moraine was deposited close to the fjord mouth the shape of the moraines the steep ice surface gradient as well as the correlation to fine laminated clay lacking ice rafted debris deposited in the trough beyond the moraine suggest that ice dynamics switched from ice stream behaviour to a slower flowing outlet tidewater glacier a younger dryas or early holocene advance of local valley glaciers is shown by moraine lobes cross cutting the late weichselian lateral moraines c 2013 elsevier ltd all rights reserved less

unusual rates and patterns of holocene emergence ellesmere island arctic canada substantial postglacial emergence up to 150 m characterizes the canadian high arctic following the last glacial maximum across northern ellesmere island rapid emergence is not observed during the early stages of deglaciation as it is in other parts of arctic canada rather the curves show an interval of slow emergence c 1 m per century during initial ice retreat this is attributed to a slow rate of glacial rebound that was countered by a similar rate of eustatic sea level rise normally isobases drawn on postglacial shorelines define broad cells of uplift that mimic centres of former maximum ice thickness however isobases on the 8 ka bp shoreline surveyed throughout northern ellesmere island indicate more complex patterns of crustal uplift that seem in congruent with reported ice thicknesses on west central ellesmere island the isobases 110 150 m asl trace a plunging ridge aligned with geological structure across an area considered to have had minimal ice cover during the last glacial maximum the ridge may record an important structural influence associated with the geologically youthful sverdrup basin collectively this evidence cautions against the view that postglacial emergence has a universally predictable signature solely portraying former ice loads

normal mode composition of earthquake t phases understanding the nature of the coupling between the underwater acoustic field and the land seismic field is important for evaluating the performance of the t phase stations in the international monitoring system for the comprehensive nuclear test ban treaty for upslope propagation in an ocean environment the places where underwater acoustic field energy couples into the land seismic field are determined to first approximation by the local water depth and the normal mode composition of the acoustic energy therefore the use of earthquake generated t phases as natural probes of water to land coupling characteristics is aided by knowledge of their modal composition data collected by a 200 element 3000 m aperture vertical hydrophone array during a 1989 experiment in the deep northeast pacific ocean are used to determine the mode composition of t phase arrivals from two mb 4 1 earthquakes near the w est coast of the u s one occurring offshore and the other on land results from an eigenanalysis approach and conventional mode decomposition for the two events are consistent and show that at 5 hz the offshore event s arrivals have higher order mode content compared to those from the event on land single hydrophone recordings at pt sur of two mb 4 4 hawaiian events in 1996 and 1997 one occurring offshore and the second on land display time frequency arrival structures that are explainable by the dispersion characteristics over the oceanic path although other effects due to complex source time functions and shear wave and dispersive propagation effects along the initial land path cannot be separated with these single element data differences in these two events arrival structures suggest differences in normal mode content consistent with those seen in the pair of 1989 events ocean path dispersion also appears to play a significant role in determining the i n water arrival structure from a 1995 french nuclear test at mururoa recordings of two hawaiian events in 1997 by the t phase station vib and the seismic station at berkeley illustrate that the water land coupling confuses the relative timing between normal modes resulting in apparent loss of information about the source

nonlinear model of tectonic release from underground explosions reversal of teleseismic rayleigh wave polarity has been observed for some underground explosions in eastern kazakh furthermore the reversed polarity rayleigh waves are observed to be time delayed by several seconds we analyze two dimensional nonlinear numerical simulations of underground explosions to examine the hypothesis that these phase reversals and apparent time delays result from the action of tectonic prestress on the explosion created nonlinear volume the shatter zone model of tectonic release we conclude that tectonic shear stress exceeding about 10 mpa 100 bars is sufficient to reverse the rayleigh wave polarity and cause an apparent time delay of several seconds even in the absence of triggered strain release on faults shear stresses of this magnitude are plausible at several hundred meters depth in that they do not exceed strength bounds for a fractured rock mass as estimated from byerlee s law the nonlinear model predictions imply that if tectonic release is modeled elastically as the relaxation of the deviatoric part of the prestress into a spherical cavity the appropriate cavity radius is approximately 80 per cent of the explosion elastic radius the apparent time delays result from interference between the explosion and tectonic source functions and can be quantitatively related to the presence of overshoot in the isotropic part of the explosion moment rate tensor it is therefore conceivable that careful observations of rayleigh wave phase for the anomalous events relative to nearby unreversed events could help constrain the amount of overshoot in the explosion source function even though the overshoot occurs on a time scale of a few tenths of a second and has a negligible effect on rayleigh wave spectral amplitudes

late weichselian environmental change in norway including svalbard a synthesis of the principal environmental changes that are inferred to have occurred in norway and svalbard fig 1 during the late glacial period 14 9 ka bp is presented the paper has three sections dealing separately with i western norway ii northern norway and iii spitsbergen svalbard the main conditions described include glacial events sea level changes vegetation history and climatic variations a summary chart of environmental reconstructions is presented for each of the three areas each including a curve of temperature reconstructions for the late glacial period these indicate some significant regional variations in contemporaneous thermal conditions during the late glacial

isostatic adjustments in a full glacial sea during the last glaciation an ice free corridor existed between the northeast ellesmere island and northwest greenland ice sheets this corridor constituted a peripheral depression in which the marine limit marks the uppermost extent of a full glacial sea the full glacial sea is characterized by 1 14c dates on in situ marine shells that predate initial emergence unloading followed by 2 synchronous emergence from the marine limit throughout the peripheral depression relative sea level curves from the full glacial sea confirm previous morphostratigraphic and glacioisostatic evidence for limited ice extent during the last glaciation these curves also document the history of glacial unloading and the form of the relative sea level curve that one would theoretically expect in the peripheral depression the form of the curves presented here is unlike any other published emergence curves from arctic canada or from fennoscandia the relative sea level curves for northeast ellesmere island show three segme

evidence from fram strait 78 n for early deglaciation recent syntheses of the history of the last northern hemisphere glaciation and deglaciation illustrate that understanding of the mechanisms and timing of deglaciation before approximately 12 000 years bp1 5 is limited after 12 000 yr bp however there is sufficient evidence from radiocarbon dated moraines raised beaches varved lake sediments and pollen records to provide a reasonable temporal and geographic picture of the decay of the ice sheets here we report on the first oxygen isotope record from the norwegian greenland sea that is radiocarbon dated directly by accelerator mass spectrometry a significant light oxygen isotope event is recorded at approximately 15 000 years bp which suggests that the marine based barents shelf ice sheet disintegrated rapidly at this time recent studies6 7 have estimated that the decay of this ice sheet could have contributed as much as 15 metres to eustatic sea level rise the decay of the barents shelf ice sheet is the earliest major deglacial event yet dated and may have triggered subsequent deglacial events through eustatic sea level effects

seismicity and velocity structure of loihi seamount from the 1996 earthquake swarm the largest earthquake swarm yet recorded on loihi submarine volcano took place in july and august of 1996 the swarm consisted of two phases of seismic activity and was associated with the formation of a pit crater and additional faulting of loihi s summit platform the first phase of activity was comprised of predomi nantly high frequency events scattered over the southern flanks of the volcano fol lowing a day of seismic quiescence the second phase of activity began consisting of lower frequency earthquakes with strong t phases the phase 2 events took place beneath loihi s summit presumably marking the formation of the pit crater pele s pit data obtained by an ocean bottom seismometer obs on loihi during the swarm help constrain a new velocity model for loihi the relocated earthquakes combined with other characteristics of the swarm enabled us to develop a model for the events leading up to the formation of pele s pit that includes 1 a prolonged eruption 2 a tectonic event beneath loihi s south flank and 3 the drainage of a shallow magma chamber