historical trends in the surface temperature over the oceans based on the coads based on a new and unique compilation of surface ship data over the world ocean the comprehensive ocean atmosphere data set coads the temperature records since 1870 were thoroughly analyzed results for the air and sea surface temperature are presented for the two hemispheres and for individual 10 latitude wide belts the results support most earlier results of a relatively warm period over the oceans in the late 19th century a cool period between about 1905 and 1930 and a warm period from the 1940 s onward of considerable interest and perhaps unique in the historical record are the diverging trends in the midlatitude sea and air temperatures of the two hemispheres during the 1960 s and early 1970 s with relative cooling in the northern hemisphere and relative heating in the southern hemisphere

rare earth element concentrations and nd isotopes in the southeast pacific ocean 1 three vertical profiles of rare earth element concentrations and nd isotopic compositions have been measured in the remote southeast pacific ocean the three stations represent contrasting environments the oligotrophic center of the gyre station gyr the transition zone east of the south tropical front station egy and the peru chile upwelling marked by a pronounced oxygen minimum station upx rare earth concentrations display nutrient like vertical profiles except at upx where surface waters are enriched at this station nd isotopic compositions are clearly more radiogenic than in the open ocean suggesting that boundary exchange process is releasing lithogenic rare earth element from the volcanic andes unexpected radiogenic values end reaching 3 7 are also observed at 2000 m at station gyr in the upper circumpolar deep water that commonly have end values around 6 exchange processes related to hydrothermal activity are suspected to produce this increase in end in the vicinity of the east pacific rise these results provide some guidance for higher resolution studies planned in this region by the international geotraces program

ice record of a large eruption of deception island volcano antarctica in the xviith century a well marked volcanic ash layer was found at 145 9 m depth in a 154 3 m ice core recovered in 1981 on james ross island antarctic peninsula ash composition analysis indicates that we are dealing with an eruption of the deception island volcano located some 200 km northwestward from james ross island regional lake sediments seem also to have recorded the eruption its date some 350 years ago has been determined precisely by comparison with a well dated south pole station ice core the strength and regional to global impact of the event are discussed it is concluded it was most probably the largest eruption of this volcano over the studied time period this exceptional layer was used to adjust the dating of the core

sedimentary trace element constraints on the role of north atlantic igneous province volcanism in late paleocene early eocene environmental change abstract a growing body of geologic evidence suggests that emplacement of the north atlantic igneous province naip played a major role in global warming during the early paleogene as well as in the transient paleocene eocene thermal maximum petm event a 5 million year record of major and trace element abundances spanning 56 to 51 ma at deep sea drilling project sites 401 and 549 confirms that the majority of naip volcanism occurred as subaerial flows thus the trace element records provide constraints on the nature and scope of the environmental impact of the naip during the late paleocene early eocene interval subaerial volcanism would have injected mantle co2 directly into the atmosphere resulting in a more immediate increase in atmospheric greenhouse gas abundances than co2 input through submarine volcanism the lack of significant hydrothermalism contradicts recently proposed mechanisms for thermally destabilizing methane hydrate reservoirs during the petm any connection between naip volcanism and petm warming had to occur through the atmosphere

environmental signals in a highly resolved ice core from james ross island antarctica 1 the accumulation isotopic and chemical signals of an ice core from james ross island antarctica are investigated for the interval from 1967 to 2008 over this interval comparison with station satellite and reanalysis data allows for a detailed assessment of the environmental information preserved in the ice accumulation at james ross island is enhanced during years when the circumpolar westerlies are weak allowing more precipitation events to reach the northeastern antarctic peninsula the stable water isotope composition of the ice core has an interannual temperature dependence consistent with the spatial isotope temperature gradient across antarctica and preserves information about both summer and winter temperature variability in the region sea salts in the ice core are derived from open water sources in the marginal sea ice zone to the north of james ross island and transported to the site by strengthened northerly and westerly winds in the winter a strong covariance with temperature means that the sea salt record may be able to be utilized in conjunction with the isotope signal as an indicator of winter temperature marine biogenic compounds in the ice core are derived from summer productivity within the sea ice zone to the south of james ross island this source region may have become significant only in recent decades when the collapse of nearby ice shelves established new sites of open water with high summer productivity these findings provide a foundation for interpreting the environmental signals in the james ross island ice core which extends though the whole holocene and represents the oldest ice core that has been recovered from the antarctic peninsula region

hydrothermal manganese plumes in the mid atlantic ridge rift valley the concentration of dissolved manganese in sea water can be used as a chemical tracer of hydrothermal activity on the underlying sea floor here we present vertical profiles of seawater manganese concentrations above the rift valley of the mid atlantic ridge mar the values obtained indicate the presence of plumes that are presently active generated by hydrothermal vents in the rift valley these plumes are confined to the rift valley and do not spill over into the adjacent deep ocean basins differences between them suggest that there are at least five hydrothermal sources along this 1 700 km long section of mid ocean ridge

spatial covariance of water isotope records in a global network of ice cores spanning twentieth century climate change 1 estimating the spatial extent of past climate changes has been an ongoing challenge for paleoclimatology for such estimates to be made with confidence it is important to establish an understanding of the spatial coherence of proxy records during an interval of known climate change we use water stable isotopes from high resolution ice cores and twentieth century observations of sea level pressures and sea surface temperatures to assess the covariance among isotopic records and its link to organized patterns of climate variability covarying signals in the cores are identified using empirical orthogonal function analysis results from regression analysis show that the leading signals are consistent with key climate patterns including the northern atlantic oscillation and southern annular mode and variability in tropical pacific sea surface temperatures associated with the el nino southern oscillation patterns that have recently been identified in instrumental data such as positive tropical pacific sst anomalies associated with the negative phase of the sam are evident in the ice cores these explanations for the variance of stable isotopes are consistent with recent studies using isotope enabled general circulation models and provide a physical basis for interpreting the observed isotopic signals while there is also a global change signal that is evident when analyzing the records collectively there are some limitations in reconstructing global temperatures due to the geographic coverage of the available records and the current lack of modeling studies to explain the observed global scale changes still water stable isotope ratios preserved in ice cores provide a sufficiently rich sampling of large scale climate variability that they can be more widely used in physically based paleoclimate reconstructions covering the last millennium and other periods

recent climate and ice sheet changes in west antarctica compared with the past 2 000 years west antarctic temperature and pressure observations begin onlyin 1957 and reliable satellite observations of antarctic sea icedate to 1979 comprehensive observations of glacier dynamicsin the most rapidly changing areas were initiated in the 1990s borehole temperature data from the wais although confirmingthe recent rapid rise in temperature do not resolve decadal scalevariability in the past

stable isotope air temperature relationships in ice cores from dolleman island and the palmer land plateau antarctic peninsula whilst stable isotope analysis of ice cores yields the best quantitative evidence for past climate there remains considerable uncertainty about the detailed relationship between the isotopic composition and air temperature analysis of two ice cores from the antarctic peninsula a 47 2 m core from the palmer land plateau 74 oi s 70 38 w and a 32 m core from dolleman island 70035 2 s 60055 5 w has shown that an oxygen isotope temperature relationship exists at a resolution of inter annual variations during the period 1938 86 all the major regional temperature anomalies known from climatic records at several stations are visible in the isotope profiles including the overall temperature increase between 1960 and 1980 an isotope temperature gradient of 0 5 o 6 c is indicated for the climatic interpretation of isotopic fluctu

the east pacific rise near 21 n 13 n and 20 s inferences for along strike variability of axial processes of the mid ocean ridge abstract data obtained along various segments of the mid ocean ridge mor are used to construct an idealized model for crustal accretion the model seeks to predict the topographic volcanic tectonic and hydrothermal characteristics of any given spreading segment of the mor as a function of distance away from the bounding transform faults this model is based on a series of detailed mapping efforts carried out on segments of the mor having a broad range of spreading rates between 2 and 16 cm yr this paper includes the results of the french searise program carried out during the summer of 1980 aboard the n o jean charcot and two american cruises conducted in 1981 aboard the r v melville

high resolution multiproxy climatic records from ice cores tree rings corals and documentary sources using eigenvector techniques and maps assessment of recovered signal and errors palaeotemperature sensitive series from tree rings ice cores corals and documentary sources are combined to producepalaeo summer temperaturereconstructions ad 1970 1761 and geographical eigenvector eof maps in both hemispheres they are compared favourably to those of existing summer temperature average series there are 51 palaeoseries in the northern hemisphere mostly north of 40 n and 16 series in the southern hemisphere the statistics and significance of the palaeoreconstructions are examined by 1 finding the correlation coefficient palaeo to measured as a function of the number and geographical distribution of the palaeo series 2 developing and running a multiproxy model that generates pseudo series containing a signal and the same types and amounts of noise found in the various real palaeo series the model reproduces the measured correlation coefficients and the eigenvector s eof explained variances as functions of the number of sites about 77 of the signal variance can be reco

ice shelf history from petrographic and foraminiferal evidence northeast antarctic peninsula a detailed record of late pleistocene deglaciation followed by mid holocene ice shelf breakup and late holocene re growth is contained in continental shelf sediments in the northern larsen area northeast antarctic peninsula the zero age of core tops is confirmed by new and published 210pb profiles and 70 accelerator mass spectrometer ams 14c dates on bulk organic carbon define sedimentation rates of 7 6 92 cm ka the varied geology in the local ice drainage basins facilitates the use of ice rafted debris ird provenance in determining the presence or absence of ice shelves all inshore cores contain an interval of non local ird in the post glacial section demonstrating widespread ice shelf breakup in the mid holocene both breakup and re growth may have taken centuries and there are no widespread debris layers associated with breakup cores beyond and up to 30 km inside the historical ice shelf limit exhibit a varied ird provenance throughout the holocene suggesting the maximum ice shelf limit may date only from the little ice age benthic foraminiferal assemblages are related to water masses and position on the continental shelf and have been modified by taphonomic processes nevertheless we discern a deglaciation signal in prince gustav channel of a calcareous spike in predominantly agglutinated assemblages and this is repeated at the time of mid holocene ice shelf breakup the inferred mid holocene warm period occurred later in the northern larsen area than on the west coast of the antarctic peninsula

the james ross island and the fletcher promontory ice core drilling projects following on from the successful project to recover an ice core to bedrock on berkner island similar drilling equipment and logistics were used on two further projects to recover ice cores to bedrock in the antarctic peninsula at james ross island a ship and helicopter supported project drilled to bedrock at 363m depth in a single season while a twin otter supported project drilled to bedrock at 654m depth again in a single season from fletcher promontory in both new projects drilling was from the surface with the infrastructure enclosed in a tent using an uncased partially fluid filled borehole

characteristics of the heat balance of the greenland ice sheet for modelling les donnees du bilan thermique recoltees au cours de l egig de 1959 a 1967 sont appliquees au calcul du deplacement de la ligne d equilibre du au changement climatique

micro meteorological conditions for snow melt conditions meteorologiques des periodes de debut et de fin des fontes des neiges et glaces de glaciers alpins on utlise la temperature de l air l humidite les rayonnements total global reflechi le coefficient d echange turbulent utilise est 18 5 wm 2 k 1 il apparait que la neige peut fondre a 10 c et rester solide a 10 c

the geochemistry of inorganic germanium in natural waters we present the initial results from a survey of the distribution of dissolved inorganic germanium in rivers in the oceans and in hydrothermal vents and plumes in the ocean germanium cycling mimics that of silica since siliceous organisms incorporate ge as a trace constituent in biogenic opal the vertical and horizontal distributions of ge concentrations in seawater are thus identical to those of silica ge si 0 7 10 6 and reflect uptake into and dissolution from the frustules of siliceous organisms germanium enters the ocean via dissolution of continental and seafloor silicates the naturally weathered flux from continents to oceans carries a dissolved ge si atom ratio in rivers of about 0 7 10 6 which reflects the ratio in average continental granites rivers draining industrial regions with significant coal combustion are contaminated with ge leached from fly ash particles resulting in ge si ratios up to tenfold above the naturally weathered background the flux to the oceans via high temperature alteration of seafloor basalts hot springs produces a ge anomaly in hydrothermal plumes over the east pacific rise crest 20 s combining the observed ge and 3he anomalies in plumes with 3he si observations in hot springs suggests that the ge si hydrothermal flux to the oceans is about 4 10 6 near the ratio for average oceanic basalts 2 6 10 6 vent effluents from the galapagos hot springs measured directly display ge si ratios of 16 10 6 suggesting that the ratio is variable between vent fields metalliferous sediments accumulating on the epr crest 17 s are enriched in germanium suggesting that a fraction of the hydrothermal germanium source on the rise crest is scavenged into these rapidly accumulating iron and manganese hydroxyoxide phases

retention of greenland runoff by refreezing implications for projected future sea level change melting produced at the surface of subfreezing permeable firn does not freely percolate but instead refreezes near its point of origin raising the firn temperature and decreasing the pore space if sufficient meltwater is introduced the firn will warm to 0 c and subsequent water will fill the remaining pore space without freezing only after the residual water content of the firn is exceeded will water flow through the firn and possibly escape as runoff this process prevents summer melt on high arctic glaciers and ice caps from escaping in its entirety and it must be accounted for in modeling glacier runoff on the basis of surface energy balance a model is presented here which describes in a simple way the transient process of infiltration refreezing and runoff in a future warming climate the model is applied to greenland for which predictions of runoff induced sea level rise that do not consider the refreezing process could be as much as 5 0 cm too high over 150 years

bransfield basin fine grained sediments late holocene sedimentary processes and antarctic oceanographic conditions the antarctic peninsula is sensitive to climatic change due to its northerly position and to the relatively reduced volume and character of its ice cover high resolution palaeoclimatic records from the ant arctic peninsula ice cores extend back only 500 years a climatic record of 2850 years in the bransfield basin is investigated through the analysis of sediment gravity cores from the floor of the central subbasin core gebra 1 and the slope of the eastern subbasin core gebra 2 sedimentological mineralogical and geo chemical properties have been systematically measured together with accelerator mass spectrometry ams radiocarbon dating the fine grained sediments result from two main processes hemipelagic settling from resuspensions and primary productivity and turbidity currents hemipelagic sediments were selected to investi gate the oceanographic and climatic conditions of the northern antarctic peninsula region during the last three millennia cold climatic periods are characterized by millimetric laminations and or black layers with higher organic carbon nitrogen and opal contents warm periods are recorded as massive to diffuse laminated facies with lower biogenic contents the results include the little ice age lia cold pulse as well as several 200 300 year long fluctuations within the lia and before this major climatic event of the holocene

decadal timescale links between antarctic peninsula ice core oxygen 18 deuterium and temperature the antarctic peninsula region has exprienced a long term warming trend over the twentieth century with the 1971 90 mean at faraday being 1 9 c warmer than the mean over 1903 41 based on expedition reports for the period prior to 1900 there is conflicting evidence from different data sources an initial interpretation of isotopic data from ice cores suggests that the nineteenth century was warmer than the twentieth century in contrast snow accumulation rate data for the nineteenth century from the same ice cores suggest lower temperatures here we investigate these facts by studying the links between atmospheric temperature over the antarctic peninsula circulation parameters and isotopic data over the period of instrumental records we show that the relationships between these variables are complex and highly spatially variable in particular the correlations between temperature and 18o and d are generally of the order r 0 5 or less on timescales of one to five years conflicts between evidenc

co diagenesis of iron and phosphorus in hydrothermal sediments from the southern east pacific rise implications for the evaluation of paleoseawater phosphate concentrations abstract we present a detailed study of the co diagenesis of fe and p in hydrothermal plume fallout sediments from 19 s on the southern east pacific rise three distal sediment cores from 340 1130 km from the ridge crest collected during dsdp leg 92 were analysed for solid phase fe and p associations using sequential chemical extraction techniques the sediments at all sites are enriched in hydrothermal fe oxyhydr oxides but during diagenesis a large proportion of the primary ferrihydrite precipitates are transformed to the more stable mineral form of goethite and to a lesser extent to clay minerals resulting in the release to solution of scavenged p however a significant proportion of this p is retained within the sediment by incorporation into secondary goethite by precipitation as authigenic apatite and by readsorption to fe oxyhydr oxides molar p fe ratios for these sediments are significantly lower than those measured in plume particles from more northern localities along the southern east pacific rise and show a distinct downcore decrease to a depth of 12 m molar p fe ratios are then relatively constant to a depth of 35 m the fe and p speciation data indicate that diagenetic modification of the sediments is largely complete by a depth of 2 5 m and thus depth trends in molar p fe ratios can not solely be explained by losses of p from the sediment by diffusion to the overlying water column during early diagenesis instead these sediments are likely recording changes in dissolved p concentrations off the sepr possibly as a result of redistribution of nutrients in response to changes in oceanic circulation over the last 10 million years furthermore the relatively low molar p fe ratios observed throughout these sediments are not necessarily solely due to losses of scavenged p by diffusion to the overlying water column during diagenesis but may also reflect post depositional oxidation of pyrite originating from the volatile rich vents of the southern east pacific rise this study suggests that the molar p fe ratio of oxic fe rich sediments may serve as a proxy of relative changes in paleoseawater phosphate concentrations particularly if fe sulfide minerals are not an important component during transport and deposition

the little ice age as recorded in the stratigraphy of the tropical quelccaya ice cap the analyses of two ice cores from a southern tropical ice cap provide a record of climatic conditions over 1000 years for a region where other proxy records are nearly absent annual variations in visible dust layers oxygen isotopes microparticle concentrations conductivity and identification of the historical a d 1600 huaynaputina ash permit accurate dating and time scale verification the fact that the little ice age about a d 1500 to 1900 stands out as a significant climatic event in the oxygen isotope and electrical conductivity records confirms the worldwide character of this event

plume dispersed hydrothermal particles a time series record of settling flux from the endeavour ridge using moored sensors abstract settling particles collected with moored sediment traps near an area of active hydrothermal venting in the northeast pacific ocean provide information about the deep sea distribution of hydrothermal material results of an 8 day near field single trap experiment and a 340 day multi instrument 5 trap deployment two kilometers from the endeavour ridge vent field show variability in the quantity and composition of the plume to sediment particle flux over time with depth and with distance from the vent field hydrothermal elemental fluxes vary by a factor of two among the four sampling intervals of the longer experiment a factor of three variation in fe s among these periods reflects temporal changes in phase composition changes in flux with depth for example a 200 fold increase in cu and zn between above and below plume traps are evidence of hydrothermal input comparison of fluxes determined in the near and far field experiments reveals the spatial influence of vent effluent near field particle flux exceeds that measured two kilometers away by a factor of 10 to 20 and is relatively enriched in fe cu and organic carbon but depleted in mn calculations of the residence time of the plume with respect to settling indicate that more than 90 percent of the particulate material is transported farther than two kilometers from the vent field interpretation of elemental mineralogical and grain size analyses suggest that chemical precipitation kinetics other physical and biological particle forming processes changes in vent output and lateral transport of hydrothermal material by abyssal currents are tenable explanations for our observations our findings suggest that these rate interdependent processes be included in realistic models of hydrothermal particle flux

determination of timing and location of water movement and ice layer formation by temperature measurements in sub freezing snow measurements of temperature in snow along a vertical profile during the onset of spring melting are used to calculate spatial and temporal temperature gradients and terms of the conduction equation with an internal energy production term are calculated heat transfer information is combined with stratigraphic observations made during melting and allow detailed determination of the timing and location of heterogeneous water movement and of refreezing internal energy production is interpreted as latent heat of refreezing of percolated meltwater times and locations of flow and refreezing of meltwater are calculated and compared to stratigraphic observations of layering and changes in density and liquid water content sequences of melt piping layering and refreezing seen in calculations and in stratigraphy demonstrate retarded flow at fine to coarse transitions flow along such transitions and refreezing at the transitions to form ice layers downslope flow is also observed in the absence of an impermeable horizon to redirect flow from the vertical

mineralogy bulk and rare earth element geochemistry of massive sulphide associated hydrothermal sediments of the brunswick horizon bathurst mining camp new brunswick massive sulphides are spatially and temporally associated with iron formation if and other hydrothermal sedimentary rocks in the vicinity of the brunswick no 12 brunswick no 6 and austin brook deposits bathurst mining camp sulphide carbonate oxide and silicate predominant if is present carbonate predominant if is best developed in and around the brunswick no 12 deposit whereas hematite bearing if is absent here but prominent in the austin brook brunswick no 6 area the if is composed dominantly of si co2 fe mn and ca minor constituents include mg p ti al and s statistically significant interelement correlations between eu fe mn pb zn cd au ca sr ba p co2 and s indicate that these elements were precipitated from hydrothermal fluids vented onto the seafloor positive interelement correlations between si ti al mg k zr rare earth elements ree s except eu se v y yb co ni and cr reflect the presence of detrital clastic mafic and aluminosilicate minerals and

a 400 years isotope record of the antarctic peninsula climate a 400 year deuterium record has been obtained from a 154 3 m ice core drilled on dalinger dome james ross island antarctic peninsula based on a comparison between the isotope profile and the temperature data over the recent period aristarain et al 1986 an interpretation is proposed in terms of temperature changes the warmest part of this proxy record occurs around 1850 with as a salient feature a temperature decline of 2 c from that time up until present conditions this feature at odds with the long timescale warming trend recorded for both hemispheres over the same period likely reflects a regional characteristic related to the lack of a high latitude low latitude link in southern hemisphere circulation patterns

dispersal patterns for hydrothermal plumes in the south pacific using manganese as a tracer abstract manganese profiles over the spreading axis of the east pacific rise epr between 22 15 s and 19 25 s disclose a series of plumes which are formed by buoyant emanations of hot hydrothermal vent fluids the plume ceilings or anomaly maxima can occur several hundred meters above the sea floor these plumes are dispersed laterally and are detectable as mid depth manganese anomalies 2000 km from the spreading axis along this section the plumes are dispersed mainly westward but at 30 s the plumes are advected eastward the asymmetrical dispersal pattern inferred from these data is coincident with the asymmetrical distribution of metalliferous sediments about the epr which suggests that plumes generated by high temperature venting play a dominant role in the formation of these sediments

hydrothermal methane and manganese variation in the plume over the superfast spreading southern east pacific rise abstract onboard analyses of dissolved ch4 and mn were conducted on the water column along the southern east pacific rise between 13 50 and 18 40 s during the 1993 ridge flux cruise many hydrothermal plumes were identified by chemical anomalies which overlie more than half of the surveyed ridge crest the ch 4 mn ratio in the plumes shows wide variability ranges from about 0 05 to 3 9 due to wide range of ch 4 concentration the ch 4 rich plumes were detected in the region of 16 00 18 40 s where vigorous magmatic budget was confirmed by previous studies moreover the ch 4 mn ratio of the plumes is highly correlated with other volatile metal parameters such as the s fe ratio in plume particulate these results strongly suggest that volatile input caused by magmatic perturbation to hydrothermal systems is responsible for the ch 4 mn variability in the southern epr plumes based on analogy of the case at the epr 9 50 n site the detection of several volatile rich plumes and the extensive hydrothermal flux of volatile species are attributed to frequent magmatic events in the superfast spreading southern epr

variability in the teleconnection between the el nino southern oscillation and west antarctic climate deduced from west antarctic ice core isotope records 1 the u s contribution to the international trans antarctic scientific expedition itase program obtained several ice cores from the west antarctic ice sheet because of proximity to the pacific ocean the west antarctic ice cores are expected to have an el nino southern oscillation enso signature the itase 2001 5 core 18o isotope was selected for detailed analysis here because its location high annual accumulation and record length make it an ideal candidate for capturing the effects of regional circulation anomalies in the isotopic composition the 2001 5 core is compared to two other cores the 2001 2 and 2001 3 cores which are further west and therefore capture some spatial variability of the regional circulation on various time scales analysis shows that several phenomena including enso leave a signature in the ice cores evidence suggests that enso signals in the ice cores are significantly modulated by low frequency variability correlation with the southern annular mode sam global temperature pacific decadal oscillation and enso shows that temperature and enso generally appear to have the strongest influence on the 2001 5 isotope signal while there is no clearly dominant single influence in the other cores results suggest that the teleconnection between enso and the 2001 5 core is quite dependent on the state of the sam specifically when the southern oscillation index soi and sam are in phase there is an enso related pressure anomaly west of the antarctic peninsula in the vicinity of the ice cores studied this extends previous findings to span the entire 20th century

quaternary of tierra del fuego southernmost south america an updated review abstract the quaternary of tierra del fuego is represented by glacial glaciofluvial glaciolacustrine marine and aeolian deposits six drift units have been described the oldest dating from the late pliocene these are starting from the oldest the rio grande sierra de los frailes cabo virgenes punta delgada primera angostura and segunda angostura drifts neoglacial and little ice age events are represented in cirques and higher mountain valleys marine deposits and raised beaches were formed during middle pleistocene late pleistocene and holocene interglacial stages after the definitive ice retreat 10 ka ago vegetation changed from tundra and cold steppe to subantarctic forest environments marine deposits reflect also colder conditions than the present ones aeolian processes prevailed in northern tierra del fuego where semiarid conditions and the frequent westerlies favoured the retransportation of finer materials coming from pre existing deposits before the opening of the magellan straits earliest human colonization occurred in northern tierra del fuego ca 11 ka bp in tundra like environmental conditions pedestrian hunters of camelids and foxes co existed with pleistocene fauna that became extinct during late glacial earliest holocene times the steppe area inland and atlantic coast was successively occupied since then until recent times on the other hand the beagle channel coasts were occupied since 6 ka bp by hunter gatherer groups adapted to maritime littoral conditions finally the easternmost area of the island was inhabited at least since 1 5 ka bp the human settlements in these latter areas occurred under environmental conditions similar to the present ones when the fuegian forest was definitively established

iron and copper enrichment of suspended particles in dispersed hydrothermal plumes along the mid atlantic ridge particulate fe and cu concentrations are used in conjunction with dissolved mn values to identify hydrothermal venting at several sites along the mid atlantic ridge mar in dispersed hydrothermal plumes as defined by dissolved mn anomalies suspended matter fe and cu values were as high as 15 8 and 1100 g g respectively relative to al at 1 7 suspended matter fe and cu values correlate well with dissolved mn concentrations tracing the intensity of dispersed plumes in contrast with fe and cu particulate mn values in vent plumes were low at 700 1200 g g calculated al fe mn al ratios for mar particles increase with increasing dissolved mn concentrations this ratio is used to estimate the percent hydrothermal component of the suspended matter these sensitive tracers identify a 2 20 hydrothermal contribution to the 10 2 g of total suspended matter 1 found along the rift valley

effects of climatic perturbations on the equilibrium line altitude west greenland perturbation analysis is applied to the heat balance at the egig line west greenland with respect to climatic changes the shift of the equilibrium line altitude is obtained for perturbations of temperature absolute humidity cloudiness and annual accumulation the total net ice ablation at the egig line increases by 45 with a perturbation of 1 k

a major helium 3 source at 15 s on the east pacific rise an extensive plume of water enriched with helium 3 has been discovered in the deep pacific ocean at latitude 15 s on the east pacific rise in the core of the plume at a depth of 2500 meters over the ridge crest the helium 3 helium 4 ratio is 50 percent higher than the ratio in atmospheric helium indicating a strong injection of mantle or primordial helium at the spreading center axis through local hydrothermal systems the helium 3 plume is completely absent east of the rise but it can be traced over 2000 kilometers to the west above a newly observed physical feature a density discontinuity here caled the ridge crest front the injected plume provides a unique deep sea tracer with an asymmetric distribution which shows that the deep circulation across the rise is from east to west the striking intensity and lateral extent of this helium 3 anomaly compared to observations at known oceanic hydrohrmal sites suggest that the largest hydrothermal fields in the ocean are yet to be discovered and that they will be found near 15 s on the east pacific rise