Ice Sheets

Recently discovered outcrops of post-glacial Early Palaeozoic mudstones in northern Ethiopia have yielded a well-preserved assemblage of cryptospores (e.g., Rugosphaera rugosa, Segestrespora laevigata, Tetrahedraletes medinensis, Velatitetras laevigata and V. retimembrana). These palynomorphs represent the first biostratigraphic evidence of Early Palaeozoic sediments in NE Africa and have the potential to shed light on the postHirnantian plant colonization of Gondwana.

First clear data of land-living plants in form of cryptospores in Gondwanan sediments dates well back into the Middle Ordovician. However, the earliest macroplant remains do not appear before the Mid Silurian. In the time between, plant evolution on terrestrial environments in Gondwana was severely hampered by the Hirnantian glaciation event. The nature of the plants remains mysterious. How did they survive the glaciation and how did they recolonise once glaciated areas? First answers to these questions are expected from fine-grained early postglacial continental or marginal marine sediments because of their promising potential for macroflora preservation. However, such deposits are rare in Gondwana with the fossil record highly biased towards marine sediments.

Broadcast have frequency, pattern, impedance, power capacities are imposed by regulatory agencies like federal Communication commission (FCC).FM radio frequencies are limited to the band between 88 to 108 MHz. we have developed a V-Multi-Crossed Dipole and its basic structure .For applications that require a circularly polarized antenna such as TV and FM broadcasts and space communications, at least two dipoles, each of which has a linear polarization, must be combined in an array, often referred to as crossed dipoles.

The mid-Pleistocene climate transition (MPT) is defined by the emergence of high amplitude, quasi-100 ka glacial-interglacial cycles from a prior regime of more subtle 41 ka cycles. This change in periodicity and amplitude cannot be explained by a change in 'external' astronomical forcing. Here, we review and integrate published records of sea-surface temperatures (SSTs) to assess whether a common global expression of the MPT in the surface ocean can be recognized, and examine our findings in light of mechanisms proposed to explain climate system reorganization across the MPT. We show that glacial-interglacial variability in SSTs is superimposed upon a longer-term cooling trend in oceanographic systems spanning the low-to high-latitudes. Regional variability exists in the timing of the onset and magnitude of cooling but, in most cases, a long-term cooling trend begins or intensifies from ~1.2 Ma (Marine Isotope Stage, MIS, 35-34). The SST cooling accompanies a long-term trend towards higher global ice volume as recorded in benthic foraminifera  18 O, but pre-dates a step-like increase in  18 O at ~0.9 Ma (MIS 24-22) that is argued to reflect expansion of continental icesheets. The strongest expression of Pleistocene cooling is found during glacial stages, whereas minor or negligible trends in interglacial temperatures are identified. However, pronounced cooling during both glacial and interglacial maxima is evident at 0.9 Ma. Alongside the long-term SST cooling trends, quasi-100 ka cycles begin to emerge in both the SST and  18 O records at 1.2 Ma, and become dominant with the expansion of the ice-sheets at 0.9 Ma. We show that the intensified glacial-stage cooling is accompanied by evolving pCO 2 , abyssal ocean ventilation, atmospheric circulation and/or dust inputs to the Southern Ocean. These changes in diverse environmental parameters suggest that glacial climate boundary conditions evolved across the MPT. In

Paired benthic foraminiferal trace metal and stable isotope records have been constructed from equatorial Pacific Ocean Drilling Program Site 1218. The records include the two largest abrupt (<1 Myr) increases in the Cenozoic benthic oxygen isotope record: Oi-1 in the earliest Oligocene ($34 Ma) and Mi-1 in the earliest Miocene ($23 Ma). The paired Mg/Ca and oxygen isotope records are used to calculate seawater d 18 O (dw). Calculated dw suggests that a large Antarctic ice sheet formed during Oi-1 and subsequently fluctuated throughout the Oligocene on both short (<0.5 Myr) and long (2-3 Myr) timescales, between about 50 and 100% of its maximum earliest Oligocene size. The magnitudes of these fluctuations are consistent with estimates of sea level derived from sequence stratigraphy. The transient expansion of the Antarctic ice sheet at Mi-1 is marked in the benthic d 18 O record by two positive excursions between 23.7 and 22.9 Ma, each with a duration of 200-300 kyr. Bottom water temperatures decreased by $2°C over the 150 kyr immediately prior to both rapid d 18 O excursions. However, the onset of each of these phases of ice growth is synchronous, within the resolution of the records, with the onset of a 2°C warming over $150 kyr. We suggest that the warming during these glacial expansions reflect increased greenhouse forcing prompted by a sudden decrease in global chemical weathering rates as Antarctic basement silicate rocks became blanketed by an ice sheet. This represents a negative feedback process that might have operated during major abrupt growth phases of the Antarctic ice sheet.

The sensitivities of benthic foraminiferal Mg/Ca and Li/Ca to bottom water temperature and carbonate saturation state have recently been assessed. Here we present a new approach that uses paired Mg/Ca and Li/Ca records to calculate simultaneous changes in temperature and saturation state. Using previously published records, we first use this approach to document a cooling of deep ocean waters associated with the establishment of the Antarctic ice sheet at the Eocene-Oligocene climate transition. We then apply this approach to new records of the Middle Miocene Climate Transition from ODP Site 761 to estimate variations in bottom water temperature and the oxygen isotopic composition of seawater. We estimate that the oxygen isotopic composition of seawater varied by ∼1‰ between the deglacial extreme of the Miocene Climatic Optimum and the glacial maximum following the Middle Miocene Climate Transition, indicating large amplitude variations in ice volume. However, the longer-term change between 15.3 and 12.5 Ma is marked by a ∼1°C cooling of deep waters, and an increase in the oxygen isotopic composition of seawater of ∼0.6‰. We find that bottom water saturation state increased in the lead up to the Middle Miocene Climate Transition and decreased shortly after. This supports decreasing pCO 2 as a driver for global cooling and ice sheet expansion, in agreement with existing boron isotope and leaf stomatal index CO 2 records but in contrast to the published alkenone CO 2 records.

Paired benthic foraminiferal trace metal and stable isotope records have been constructed from equatorial Pacific Ocean Drilling Program Site 1218. The records include the two largest abrupt (&lt;1 Myr) increases in the Cenozoic benthic oxygen isotope record: Oi‐1 in the earliest Oligocene (∼34 Ma) and Mi‐1 in the earliest Miocene (∼23 Ma). The paired Mg/Ca and oxygen isotope records are used to calculate seawater δ18O (δw). Calculated δw suggests that a large Antarctic ice sheet formed during Oi‐1 and subsequently fluctuated throughout the Oligocene on both short (&lt;0.5 Myr) and long (2–3 Myr) timescales, between about 50 and 100% of its maximum earliest Oligocene size. The magnitudes of these fluctuations are consistent with estimates of sea level derived from sequence stratigraphy. The transient expansion of the Antarctic ice sheet at Mi‐1 is marked in the benthic δ18O record by two positive excursions between 23.7 and 22.9 Ma, each with a duration of 200–300 kyr. Bottom water ...

In the largest global cooling event of the Cenozoic Era, between 33.8 and 33.5 Myr ago, warm, high-CO 2 conditions gave way to the variable 'icehouse' climates that prevail today. Despite intense study, the history of cooling versus ice-sheet growth and sea-level fall reconstructed from oxygen isotope values in marine sediments at the transition has not been resolved. Here, we analyse oxygen isotopes and Mg/Ca ratios of benthic foraminifera, and integrate the results with the stratigraphic record of sea-level change across the Eocene-Oligocene transition from a continental-shelf site at Saint Stephens Quarry, Alabama. Comparisons with deep-sea (Sites 522 (South Atlantic) and 1218 (Pacific)) δ 18 O and Mg/Ca records enable us to reconstruct temperature, ice-volume and sea-level changes across the climate transition. Our records show that the transition occurred in at least three distinct steps, with an increasing influence of ice volume on the oxygen isotope record as the transition progressed. By the early Oligocene, ice sheets were ∼25% larger than present. This growth was associated with a relative sea-level decrease of approximately 105 m, which equates to a 67 m eustatic fall.

The mid-Pleistocene climate transition (MPT) is defined by the emergence of high amplitude, quasi-100 ka glacial-interglacial cycles from a prior regime of more subtle 41 ka cycles. This change in periodicity and amplitude cannot be explained by a change in 'external' astronomical forcing. Here, we review and integrate published records of sea-surface temperatures (SSTs) to assess whether a common global expression of the MPT in the surface ocean can be recognized, and examine our findings in light of mechanisms proposed to explain climate system reorganization across the MPT. We show that glacial-interglacial variability in SSTs is superimposed upon a longer-term cooling trend in oceanographic systems spanning the low-to high-latitudes. Regional variability exists in the timing of the onset and magnitude of cooling but, in most cases, a long-term cooling trend begins or intensifies from ~1.2 Ma (Marine Isotope Stage, MIS, 35-34). The SST cooling accompanies a long-term trend towards higher global ice volume as recorded in benthic foraminifera  18 O, but pre-dates a step-like increase in  18 O at ~0.9 Ma (MIS 24-22) that is argued to reflect expansion of continental icesheets. The strongest expression of Pleistocene cooling is found during glacial stages, whereas minor or negligible trends in interglacial temperatures are identified. However, pronounced cooling during both glacial and interglacial maxima is evident at 0.9 Ma. Alongside the long-term SST cooling trends, quasi-100 ka cycles begin to emerge in both the SST and  18 O records at 1.2 Ma, and become dominant with the expansion of the ice-sheets at 0.9 Ma. We show that the intensified glacial-stage cooling is accompanied by evolving pCO 2 , abyssal ocean ventilation, atmospheric circulation and/or dust inputs to the Southern Ocean. These changes in diverse environmental parameters suggest that glacial climate boundary conditions evolved across the MPT. In

We analysed a nearly 133-km-long portion of the Sudetic Marginal Fault (SMF) in Poland (99.7 km) and the Czech Republic (33.8 km), comprised between Złotoryja in the NW and Jesenik in the SE. The fault trace has been subdivided into fifteen segments showing different orientation (N29°W to N56°W, and even N111°W SE of Złoty Stok), geological setting, length (8.8-22.9 km in Poland and 1.4-7.5 km in the Czech Republic), and height of the fault-and fault-line scarps (5-75 m to 200-360 m). Orientation of the entire fault trace approaches N41°W, and the mountain front sinuosity amounts to 1.051. Individual fault segments bear a flight of two to five tiers of triangular facets, showing differentiated state of preservation and degree of erosional remodelling. The highest triangular facets are confined to Rychlebské (Złote) and Sowie Mts. This tiering points to at least five episodes of uplift of the SMF footwall, starting shortly after 31 Ma, i.e. after basalts of the Sichów Hills area were displaced by the fault, and most probably postdating 7-5 Ma time interval, during which rapid cooling and exhumation of the Sowie Góry Mts. massif took place. Morphometric parameters of 244 small catchment areas of streams that dissect the fault scarp include, i.a. elongation, relief, and average slope of individual catchment areas, together with values of the valley floor width to valley height ratios. These figures point to moderate tectonic activity of the SMF and allow us to conclude about Quaternary uplift, particularly important in the Sowie and Rychlebské (Złote) segments.

This comprehensive analysis presents complete mathematical derivations demonstrating that the confirmed 24-hour polar sun phenomenon violates energy conservation by infinite factors. Through exhaustive calculations incorporating every known correction factor-maximum albedo (95%), Beer-Lambert atmospheric absorption, elevation effects at 2,835m, minimum sun angles, spectral dependencies, angular variations, cloud cover, wind effects, ocean circulation, and 47 additional examined mechanisms-we prove that even the most conservative calculations predict 0.59-27.54 meters of Antarctic ice melting annually versus essentially zero observed. Temperature predictions yield +64°C expected versus-57°C observed, a 121°C error. We provide complete step-by-step derivations for every calculation, examine and mathematically refute all proposed explanations, and demonstrate that no combination of physical mechanisms can resolve these infinite-factor violations of thermodynamic laws. The December 2024 Final Experiment's confirmation of 24-hour sun paradoxically strengthens these impossibilities.

Even if greenhouse gas emissions were stopped today sea level would continue to rise for centuries with the long-term sea-level commitment of a two-degree-warmer world significantly exceeding 2 m. In view of the potential implications for coastal populations and ecosystems worldwide we investigate, from an ice-dynamic perspective, the possibility to delay sea-level rise by pumping ocean water onto the surface of the Antarctic Ice Sheet. We find that due to wave propagation ice is discharged much faster back into the ocean than would be expected from a pure advection with surface velocities. The delay time depends strongly on the distance from the coastline at which the additional mass is placed and less strongly on the rate of sea-level rise that is mitigated. A millennium-scale storage of at least 80 % of the additional ice requires placing it at a distance of at least 700 km from the coast line. The pumping energy required to elevate the potential energy of ocean water to mitigate...

The post-Caledonian development in the western Bergen Are System and the nearby offshore area is characterized by a gradual transition from ductile through semi-ductile to brittle deformation. Interpretation of offshore seismic data shows a dominance of pre-late Jurassic faulting, with relatively minor late or post-Jurassic reactivation. This history is also seen in the Bj orøy tunnel in the Hjeltefjord fa ult zone, where most, but not all of the (semi)brittle faulting history is pre-Oxfordian (pre-late Jurassic). Pre-Oxfordian fa ults are typically cohesive fault rocks with striations on slip surfaces, whereas post-Oxfordian faults are identified as non-cohesive gouge zones without clear kinematic indicators. Slip analysis of the fault population with cohesive fault rocks in the Øygarden, Sotra, Løvstakken and Hjeltefjord area gives a relatively consistent NW -SE extension direction. Detailed investigation of Permian dikes in western Sotra and Permo-Jurassic dikes in Sunnhordland indicate a very precise E-W extension direction at about 260 Ma. These dikes intruded along pre-existing fa ults and fr actures, and are mostly undeformed or weakly jointed. M uch of the brittle or semi-brittle deformation in the region is therefore thought to be older than the Permian dikes. This suggests that a change in the orientation of the minimum principal stress axis happened at some time between the fo rmation of the fault systems and intrusion of the Permian dikes. Since the NW extension direction is similar to the early to mid-Devonian stretching direction detected in the Caledonian nappe region, it is suggested that the main population of fa ults with well-developed slip indicators west of Bergen reflects the (late) Devonian stress field.

A new, high-resolution record of sea surface temperature from the subtropical western North Atlantic documents a series of abrupt coolings within marine isotope stage 5 which can be objectively correlated with marine-core evidence for increased ice-sheet discharge at subpolar latitudes and reduced North Atlantic deep water formation. These results indicate that ice-sheet forcing of deep ocean circulation influenced surface temperatures over much of the North Atlantic. A proposed correlation to the pollen record of Grande Pile, France, indicates that each cold event seen in the pollen sequence has a unique counterpart in the record of subtropical ocean temperature. If this correlation is correct, it suggests that the warmest part of the European Eemian ended suddenly in response to oceanographic changes, and that the subsequent post-temperate phase of the Eemian extended well into the interval of ice sheet growth corresponding to marine isotope substage 5d.

Recent analysis of 38 globally distributed paleoclimatic records covering Marine Isotope Stage 3 (MIS 3) 60-26 ka demonstrated that the two leading empirical orthogonal functions (EOFs) explaining the data are the Greenland ice-core signal (''northern'' signal) and the Antarctic ice-core signal (''southern'' signal). Here singular spectral analysis (SSA) is used to show that millennial-scale variability of each of these two leading EOFs is characterized by two independent modes. The two modes of each EOF share similar relative distributions of variance, identical spectra, and, where each mode has spectral power, coherency spectra, which are significantly above the null hypothesis level at 95% confidence. The only difference between the modes of the northern and southern signals is that they are phase shifted. The phasing and long response time of the low-frequency mode, combined with its relationship to atmospheric CO 2 and sea level, are consistent with coupled changes in the ocean, ice sheets, atmosphere, and carbon cycle, whereas the phasing and short response time of the high-frequency mode are consistent with an atmospheric transmission likely induced by changes in hemispheric sea ice distributions and attendant feedbacks.

A strong basis of observational data is crucial for improving the understanding of the physical processes driving these changes, and for improving models used to predict the state of the cryosphere in the future. mm /yr rise in sea level (unpublished data from IES and IMO; Björnsson et al., submitted). The DEMs are being used in several glaciological and geomorphological research projects of subglacial eruptions, jökulhlaups and hazard assessments for settlements near the glaciers and they will be useful in research of glacier dynamics such as studies of surges, calving, subglacial water flow and ice flow over bedrock topography. The very high resolution and good relative accuracy also make LiDAR maps useful for mapping crevasses and the creation of various special purpose maps of the glaciers, including maps to improve the safety of travel and search and rescue operations on the glaciers.

The expansion of ice masses across southern Africa during the Late Palaeozoic Ice Age has been known for 150 years, including the distribution of upland areas in controlling the configuration of glaciation. In Namibia, increasing attention has focussed on long and deep palaeovalley networks in the Kaokoland region in the north, but comparatively little work has been attempted in the topographically subdued plains of the south, in the Aranos and Karasburg basins. The desert terrain of the Aranos area exposes diamictites of the Dwyka Group discontinuously over about 300 km, extending further south to the Karasburg area at the Namibian‐South African border along the Orange River. Whilst examined at a stratigraphic level, the nature of the contact between the Dwyka glacial rocks and underlying lithologies has not been systematically investigated. This paper presents the results from fieldwork in austral winter 2019, in which a highly varying basal contact is described that records the p...

The degree to which Permo-Carboniferous cyclothemic successions archive evidence for longterm variations in ice volume during the Late Paleozoic Ice Age is insufficiently resolved. Here we develop the sequence stratigraphy and onlap-offlap history for a 33-my interval of the Carboniferous using the U-Pb calibrated succession of the Donets Basin, Ukraine, in order to assess the relationship between sea-level, high-latitude changes in glacial extent, and climate. Integrated subsurface and outcrop data permit meter-scale correlation of 242 biostratigraphically constrained limestones and coals, and in turn individual cyclothems, across ~250 km of the Donets Basin. Rapid uniform subsidence and basinwide continuity of marker beds indicate Pennsylvanian deposition under relatively stable tectonic conditions. Three scales of sequences (avg. durations of ~140 ky, ~480 ky and 1.6 my) are recognized on the basis of stratigraphic stacking patterns and basinwide architecture of marine to terrestrial facies assemblages. The hierarchy of sequences and the geographic and stratigraphic positions of shifts in base-level sensitive facies across the Donets ramp permit the construction of an onlap-offlap history at a sub-400 ky scale. Major sea-level lowstands occur across the mid-Carboniferous boundary and during the early Moscovian. These lowstands coincide with glacial maxima inferred from highlatitude glacigenic deposits. The middle to late Pennsylvanian is characterized by a stepwise onlap, culminating in an earliest Gzhelian highstand, suggesting contraction of Carboniferous ice sheets prior to the initiation of Early Permian glaciation. The stratigraphic position of climate sensitive facies within individual Donets cyclothems indicates a turnover from seasonal sub-humid or semi-arid climate to everwet conditions during the late lowstand and maximum ice sheet accumulation. Comparison of the stratigraphic and aerial distribution of coals and evaporites in the Donets Basin with the onlap-offlap history further indicates everwet conditions during lowstands and inferred glacial maxima and drier climate during onlap and inferred ice sheet contraction at the intermediate (~0.8 to 1.6 my) and long (10 6 yr) time-scales. Taken together, the relationship between inferred climate and glacioeustasy suggests a likely teleconnection between high-latitude ice sheet behavior and low-latitude atmospheric dynamics.

Comment: “The wording &quot;non-linear system response&quot;. Due to the Northern Hemisphere summer forcing (Berger, 1978), the system receives already a strong nonlinearity. Please clarify this somewhere” Answer: We concede that the phrasing was unfortunate. When we say “This non-linear system response has a dramatic effect on ice-age dynamics”, we mean that the system responds to a millennial-period sinusoid by a shift of the time-mean ice-sheet area and temperature, and that this shift depends non-linearly on the amplitude of the forcing.

There is an increasing body of aeromagnetic, radar ice-sounding, heat flow, subglacial volcanic earthquakes, several exposed active and subglacial volcanoes and other lines of evidence for volcanic activity associated with the West Antarctic Rift System (WR) since the origin (~25 Ma) of the West Antarctic Ice Sheet (WAIS), which flows through it. Exposed late Cenozoic, alkaline volcanic rocks, 34 Ma to present concentrated in Marie Byrd Land (LeMasurier and Thomson, 1990), but also exposed along the rift shoulder on the Transantarctic Mountains flank of the WR, and >1 million cubic kilometers, of mostly subglacially erupted "volcanic centers" beneath the WAIS inferred from aeromagnetic data, have been interpreted as evidence of a magmatic plume. About 18 high relief, (~600-2000 m) "volcanic centers" presently beneath the WAIS surface, probably were erupted subaerially when the WAIS was absent, based on the 5-km orthogonally line spaced Central West Antarctica aerogeophysical survey. All would be above sea level after ice removal and isostatic adjustment. Nine of these high relief peaks are in the general area beneath the divide of the WAIS. This high bed relief topography was first interpreted in the 1980s as the volcanic "Sinuous Ridge " based on a widely spaced aeromagnetic -radar ice sounding survey (Jankowski et al,. 1983). A 70-km wide, circular ring of interpreted subglacial volcanic rocks was cited as evidence of a volcanic caldera underlying the ice sheet divide based on the CWA survey (Behrendt et al., 1998). A broad magnetic "low" surrounding the caldera area possibly is evidence of a shallow Curie isotherm. High heat flow reported from temperature logging (Clow et al., 2012) in the WAISCORE and a thick volcanic ash layer in the core (Dunbar et al., 2012) are consistent with this interpretation. A 2 km-high subaerially erupted volcano (subglacial Mt Thiel, ~78.5 degrees S, 111 degrees W) ~ 100 km north from the WAISCORE could be the source of the ash layer if it has been recently active. Models by Tulaczyk and Hossainzadeh (2011) indicate >4mm/yr Basal melting in the general area of the WAIS, again supportive of high heat flow and the presence of subglacial lakes in West Antarctica. These various lines of evidence lead to the general interpretation that the ice divide area of the WAIS overlies present to recent subglacial volcanic activity that may have an influence on the past and future behavior of the WAIS.

This paper describes a validation study performed by comparing the Climate-SAF Surface Albedo Product (SAL) to ground truth observations over Greenland and the ice-covered Arctic Ocean. We compare Advanced Very High Resolution Radiometer (AVHRR)-based albedo retrievals to data from the Greenland Climate Network (GCN) weather stations and the floating ice station Tara for polar summer 2007. The AVHRR dataset consists of 2755 overpasses. The overpasses are matched to in situ observations spatially and temporally. The SAL algorithm presented here derives the surface broadband albedo from AVHRR channels 1 and 2 using an atmospheric correction, temporal sampling of an empirical Bidirectional Reflectance Distribution Function (BRDF), and a narrow-tobroadband conversion algorithm. The satellite product contains algorithms for snow, sea ice, vegetation, bare soil, and water albedo. At the Summit and DYE-2 stations on the Greenland ice sheet, instantaneous SAL RMSE is 0.073. The heterogeneous surface conditions at satellite pixel scale over the stations near the Greenland west coast increase RMSE to N 0.12. Over Tara, the instantaneous SAL RMSE is 0.069. The BRDF sampling approach reduces RMSE over the ice sheet to 0.053, and to 0.045 over Tara. Taking into account various sources of uncertainty for both satellite retrievals and in situ observations, we conclude that SAL agrees with in situ observations within their limits of accuracy and spatial representativeness.

By comparing modelled and averaged satellite altimeter return, it is demonstrated that time profiles of altimeter return can be used to provide important information on the surface properties of the ice sheets. Altimeter ice-sheet radar echoes from low altitudes and/or relatively low latitudes are, in general, dominated by surface scattering and, in Greenland, the area of surface-dominated return broadly coincides with the zone of summer melting. Seasonal variations in the echo wave-form shapes are negligible in all regions studied, with the possible exception of an area near the margin of the Greenland dry-snow zone. In general, the model explains well the observed variations in mean wave-form shape, but small discrepances between the model wave forms and the recorded wave forms indicate that sub-surface layers may be influencing the shape of the return. The possibility of deriving quantitative estimates of surface properties is explored by fitting model returns to averaged altimet...

ue to time and distance problems of the authors, a road log for this field trip is being issued separately. For similar reasons and because exposures of glacial deposits in this area are so ephemeral, specific field trip stops are not identified in this article. Detailed descriptions and interpretations are included, however, for the most likely stops. We intend to visit at least one glacial lake spillway, an exposure of collapsed lake sediments overlain by noncollapsed stream-terrace deposits, and exposures of deltaic deposits that pertain to the problems of lake damming, lacustrine and bog sedimentation, and postglacial uplift. Other appropriate stops can be made as time permits. * U. S. Geological Survey,

Monitoring of terrestrial vegetation from satellites at global and regional scales requires accurate and frequent measurements of surface reflectance. In this context, the POLDER instrument leads a key improvement providing, at high temporal resolution, measurements of the Bi-directional Reflectance Distribution Function corrected for atmospheric effects. In the frame of the ADEOS-2/POLDER-2 project, advanced Land Surface Level 3 algorithms have been developed to retrieve the spectral Directional-Hemispherical Reflectances (DHR), the Normalized Difference Vegetation Index (NDVI) corrected for directional effects, the Leaf Area Index (LAI) and the Fraction of Vegetation Cover (FVC). The retrieved parameters are validated following a procedure based upon the analyze of the spatial and temporal variability, the comparison with available equivalent products derived from other sensors by similar or different approaches, and finally the comparison with up-scaled in-situ measurements collected over selected areas. Le suivi de la végétation continentale à l'échelle global et régionale demande des mesures fréquentes et précises de la réflectance de surface. Dans ce contexte, l'instrument POLDER apporte une information inédite en fournissant des mesures journalières de la Fonction de Distribution de la Réflectance Bi-directionnelle (FDRB) corrigées des effets atmosphériques. Dans le cadre du projet ADEOS-2/POLDER-2, des algorithmes améliorés de restitution des paramètres biophysiques des surfaces continentales ont été développés. Ils estiment les réflectances hémisphériques-directionnelles, l'indice de végétation NDVI corrigé des effets directionnels, l'indice foliaire LAI et la fraction de couverture végétale FVC. Les paramètres ainsi restitués sont ensuite validés selon une procédure qui repose sur l'analyse de leur variabilité spatiale et temporelle, la comparaison à des produits équivalents issus d'autres capteurs par des méthodes similaires ou différentes, et enfin la comparaison à des mesures terrains spatialisées acquises sur des sites sélectionnés.

Recent trends and climate models suggest that the Arctic summer sea ice cover is likely to be lost before climate interventions can stabilize it. There are environmental, socioeconomic, and sociocultural arguments for, but also against, restoring and sustaining current conditions. Even if global warming can be reversed, some people will experience ice-free summers before perennial sea ice begins to return. We ask: How will future generations feel about bringing sea ice back where they have not experienced it before? How will conflicted interests in ice-covered vs. ice-free conditions be resolved? What role will science play in these debates? COMMENTARY 10.1002/2016EF000356 Key Points: • The Arctic is likely to experience ice-free summers for decades before warming can be reversed through mitigation or engineering solutions • Diverse, often conflicting interests will emerge as ecological conditions, economies, and societies adapt to the new climate • Development of options for adaptation or a return to perennial sea ice must account for these stakeholder conflicts

Discrete boulder fields attributed to the last glacial maximum (LGM) are suggested here to have had a catastrophic origin similar to that of the 500,000 Carolina bays distributed along the Atlantic seaboard and Gulf Coasts of the continental United States. Carolina bays are suggested by others to be secondary impact basins from the ejecta curtain of Laurentide ice-sheet fragments from a primary bolide impact on or airburst above the Laurentide ice sheet in the Great Lakes region, 12,800 B.P. Ballistic trajectories that fell short of the coastal regions and landed on thin soil may have fractured the underlying bedrock, in some cases creating discrete boulder fields that are still devoid of vegetative cover almost 13 thousand years later.

A hydrostratigraphical approach to support environmentally safe siting of a mining waste facility at Rautuvaara, Finland Based on the construction of a detailed sedimentological model, hydrostratigraphy and local groundwater/surface water flows, this paper analyses the Niesajoki river valley as a suitable area for the expansion of a tailings facility, associated with the nearby Hannukainen (Cu, Au, Fe) mine, Finnish Lapland. Three different glacial/interglacial cycles were identified from the sedimentary observations and, optical stimulated luminescence (OSL) datings showed them to be of Early to Late Weichselian in age. Two groups of hydro-stratigraphical units were identified from hydraulic conductivities. The first, fluvial deposits, lie in the centre of the valley along the valley axis, and are the main aquifers. The second, till group, with lower conductivities, are located on the flanks of the valley. The thickness and complexity of sediments varied across the study area. To the E/SE of the valley, sediments are thick (~40 m), and more complex., In contrast the S/W/NW of the area, sediments are thinner (~10 m) and more simple. Groundwater is found to flow towards the centre of the valley and along its axis, where a bedrock controlled divide forms two groundwater basins. Based on the results of this research, it is suggested that any future expansion of the tailings facility should be restricted to the western and southern side of the valley, where waters are more manageable.

The 15 N/ 14 N and 18 O/ 16 O ratios of nitrate in the Greenland Ice Sheet Project 2 (GISP2) (Summit, Greenland) ice core are much higher in ice from the last glacial period than in the pre-industrial Holocene, despite the lack of a significant glacial/interglacial change in nitrate concentration. While both the 15 N/ 14 N and 18 O/ 16 O records are anticorrelated with snow accumulation rate, neither is satisfactorily explained by accumulation changes or post-depositional processes. The similarity in the glacial/ interglacial change in 15 N/ 14 N from several different Greenland ice cores and the large amplitude of this change relative to observed seasonal variation raise the possibility that the isotopes of nitrate in ice cores indicate a large-scale glacial/interglacial change in the isotopic composition of atmospheric NO x . The glacial/interglacial change in 18 O/ 16 O is best explained by a greater contribution of HNO 3 production from hydrolysis of N 2 O 5 , which has implications for reconstruction of past atmospheric oxidant levels. Although isotope effects associated with NO x photochemistry and nitrate scavenging have not been fully characterized, the 15 N/ 14 N data may indicate glacial/interglacial changes in the relative contributions from different natural sources of NO x on a hemispheric or global scale.

Speleothems from a well-ventilated dolomitic cave in the Pokhara Valley, central Nepal, preserve a mineralogic record of Indian summer monsoon variability over the past 2300 yr. Annually deposited aragonite layers formed between 2300 and 1500 yr B.P., indicating reduced monsoon precipitation and increased cave aridity, whereas alternating calcite/aragonite laminae deposited after 1500 yr B.P. record elevated summer monsoon precipitation and increased cave humidity. Dense, optically clear calcite layers deposited from 450 ± 5 to 360 ± 20 yr B.P. (1550 to 1640 A.D.) indicate a less-evaporative cave environment and suggest moister and/or cooler conditions, possibly related to climatic change associated with the onset of the Little Ice Age.

The stop (24°50'2"E, 57°10'15"N, for location see Fig. .1) at the Krimulda Castle ruins in Sigulda introduces the geological structure, morphology and formation of the River Gauja valley and slope processes between the towns of Valmiera and Vangaži. This stretch of the river valley, also known as the Lower Gauja spillway valley, is about 110 km long. The spillway is confined to an ancient buried valley incised into Middle and Upper Devonian sedimentary rock (Pērkons 1947). The oversized river valley is 1-2.5 km wide and reaches a depth of 25 m near Valmiera, 35-40 m in the vicinity of Cēsis and 85 m at Sigulda. The floor of the bedrock within the valley lies at 17-18 m a.s.l. near Valmiera, 12 m b.s.l. in the vicinity of Cēsis and more than 50 m b.s.l. at Sigulda (Fig. 1.2). It is significant that downstream of Cēsis the ancient valley is carved into weakly-cemented and/or soft Devonian terrigenous rock that runs along the lithological boundary with carbonate rock.

New op ti cally stim u lated lu mi nes cence (OSL) ages show that sandy de pos its over lain by Late Weichselian subglacial till in cen tral Lat via are of Early to Mid dle Weichselian age. The finer chro no log i cal res o lu tion of un con sol i dated sed i ment de po sition in the Cen tral Lat vian Low land (CLL) re mains rel a tively un stud ied, and here we pro vide a first char ac teri sa tion of the depos its with re spect to their age. Three OSL ages rang ing be tween 84 ± 9 ka and 112 ± 11 ka sug gest that the de pos its stud ied in the CLL are of Early Weichselian age (MIS 5). We found no Mid dle Weichselian de pos its in the CLL, and as sume that any such youn ger sed i ments might have been eroded dur ing the ad vance of the Zemgale Lobe in the Late Weichselian. One site, in the ice-mar ginal zone ad ja cent to the interlobate area, has nev er the less de pos its dated to 44 ± 10 ka cor re spond ing to the Mid dle Weichselian (MIS 3). Our re sults are com pat i ble with ex ist ing ESR ages on three sets of Portlandia arctica shells from the cen tral part of the low land; the shells had been in cor po rated into gla cial de pos its dur ing later gla cial ad vances. Fi nally, our find ings largely sup port ice-free con di tions dur ing the Early and Mid dle Weichselian in the mid dle and south ern part of cen tral Lat via.

It has been hypothesised that during interglacials, thinning of the Ross Ice Shelf allowed a more open water environment with increased local precipitation. This resulted in outlet glaciers, which drain the Transantarctic Mountains and fed by the East Antarctic Ice Sheet, advancing during moist warmer periods, apparently out of phase with colder arid dry periods. Significantly the ice core record during these warm periods also shows increased accumulation continent wide

The Yulong Mountain massif is tectonically active during Quaternary and contains the southernmost glacierized mountains in China, and all of Eurasia. Past glacial remnants remain preserved on the east and west sides of the Yulong Mountains. A ridge of moraine protruded into the Jinsha River at the Daju Basin, damming the river, and forming a lake at the head of the Jinsha River. Cosmogenic 10 Be and 26 Al provide exposure age dates for the moraine-based fluvial terraces left behind after the dam breached, and for moraine boulders on both the eastern and western sides of the Yulong Mountains. Our results yield exposure ages for the terraces that range from 29 ka to 8 ka, and a downcutting rate of 7.6 m/ka. The preservation of the remaining dam for over 10,000 years suggests stability of the moraine dam and gradual erosion of the dam during drainage of the dammed lake. From the relationship between exposure ages and elevations of the fluvial terraces located in different walls of the Daju fault, we obtain a late Quaternary dip-slip rate of about 5.6 m/ka for the Daju fault. The exposure ages of 10.2 ka and 47 ka for moraine boulders located in the east and west sides of the Yulong Mountains, respectively, coincide with warm periods in the late Quaternary. This implies that precipitation provides the major control for glaciations on the Yulong Mountains, a domain of the southwest Asian monsoon.

Cosmogenic 10Be and 26Al measurements from bedrock exposures in East Antarctica provide indications of how long the rock surface has been free from glacial cover. Samples from the crests of Zakharoff Ridge and Mount Harding, two typical nunataks in the Grove Mountains, show minimum 10Be ages of 2.00 ± 0.22 and 2.30 ± 0.26 Ma, respectively. These ages suggest that the crests were above the ice sheet at least since the Plio–Pleistocene boundary. Adopting a ‘reasonable’ erosion rate of 5–10 cm Ma-1 increases the exposure ages of these two samples to extend into the mid-Pliocene. The bedrock exposure ages steadily decrease with decreasing elevation on the two nunataks, which indicates ~200 m decrease of the ice sheet in the Grove Mountains since mid-Pliocene time. Seven higher elevation samples exhibit a simple exposure history, which indicates that the ice sheet in the Grove Mountains decreased only ~100 m over a period as long as 1–2 Ma. This suggests that the East Antarctic Ice Sheet...

When structures such as oil drilling rigs are constructed on or through the ice plate in coastal and offshore regions, the shear strength of sea ice must be estimated to determine the loading on these structures. Testing methods for shear strength must be established so that shear strength of sea ice in various conditions can be determined.The authors have been conducting, for five years, direct shear strength experiments using sea ice samples from the Okhotsk Sea coast. Physical characteristics of sea ice, including shear strength, depend to a great extent on such properties as salinity, porosity, grain size, etc; thus, there is variation in the test results of five years experimentation since the samples obtained varied from year to year.The following conclusions were drawn from this experiment: i)Under certain conditions the relation between shear strength and vertical stress can be represented by Coulomb’s equation of soil; ie, where Ts: shear strength, C* : apparent cohesion (s...

Based on benthic foraminiferal N 18 O from ODP Site 1143, a 5-Myr astronomical timescale for the West Pacific Plio^Pleistocene was established using an automatic orbital tuning method. The tuned Brunhes/Matuyama paleomagnetic polarity reversal age agrees well with the previously published age of 0.78 Ma. The tuned ages for several planktonic foraminifer bio-events also agree well with published dates, and new ages for some other bio-events in the South China Sea were also estimated. The benthic N 18 O from Site 1143 is highly coherent with the Earth's orbit (ETP) both at the obliquity and precession bands for the last 5 Myr, and at the eccentricity band for the last 2 Myr. In general, the 41-kyr cycle was dominant through the Plio^Pleistocene although the 23-kyr cycle was also very strong. The 100-kyr cycle became dominant only during the last 1 Myr. A comparison of the benthic N 18 O between the Atlantic (ODP 659) and the East and West Pacific (846 and 1143) reveals that the Atlantic^Pacific benthic oxygen isotope difference ratio (vN 18 O AtlÀPac ) displays an increasing trend in three time intervals: 3.6^2.7 Ma, 2.7^2.1 Ma and 1.5^0.25 Ma. Each of the intervals begins with a rapid negative shift in vN 18 O AtlÀPac , followed by a long period with an increasing trend, corresponding to the growth of the Northern Hemisphere ice sheet. This means that all three intervals of ice sheet growth in the Northern Hemisphere were accompanied at the beginning by a rapid relative warming of deep water in the Atlantic as compared to that of the Pacific, followed by its gradual relative cooling. This general trend, superimposed on the frequent fluctuations with glacial cycles, should yield insights into the processes leading to the boreal glaciation. Cross-spectral analyses of the vN 18 O AtlÀPac with the Earth's orbit suggests that after the initiation of Northern Hemisphere glaciation at about 2.5 Ma, obliquity rather than precession had become the dominant force controlling the vertical structure or thermohaline circulation in the paleo-ocean.

This paper presents a 40000-year-long high-resolution mangrove record from sediments of Core 18300, 18302 and 18323 on the continental shelf of the southern South China Sea and reconstructs the coastline changes on Sunda Shelf since the last 40000 years. In the period Marine Isotope 3, the old Sunda Shelf had low sea level, and it was partly exposed. Flourishing vegetations grew on the exposed old land. Mangroves developed along the coastline. On the Last Glacial Maximum, the sea level dropped greatly, coastline moved from inner shelf to outer shelf, the Old Sunda Land exposed further, and the lowering sea level induced the gradual disappearing of mangroves from the inner Sunda Shelf to the outer Sunda Shelf. And pioneer vegetation ferns covered the broadly exposed old land immediately. At the time of the last Deglaciation, sea level rose greatly，the coastline moved to the sea and the Sunda Shelf was drown again. Mangroves were emergent again from outer shelf to inner shelf and developed quickly.

In the spring of 1999 the Ocean Drilling Program (ODP) Leg 184 Shipboard Party cored 17 holes at 6 deep water sites in the northern and southern parts of the South China Sea (SCS). Chinese scientists actively participated in the entire process of this first deep-sea drilling leg off China, from proposal to post-cruise studies. More than 30 categories of analyses have been conducted post-cruise in various Chinese laboratories on a large number of core samples, and the total number of analyses exceeded 60 thousand. The major scientific achievements of the Leg 184 studies are briefly reported in three successive papers, with the first one presented here dealing with deep-sea stratigraphy and evolution of climate cycles. This ODP leg has established the best deep-sea stratigraphic sequences in the Western Pacific: the 23-Ma isotope sequence from the Dong-Sha area is unique worldwide because of its continuity; the last 5-Ma sequence from the Nansha area represents one of the best 4 ODP sites worldwide with the highest time-resolution for that time interval, and the sequences of physical properties enable a decadal-scale time resolution. All these together have provided for the first time high-quality marine records for paleoenvironmental studies in the Asian-Pacific region. This new set of stratigraphic records has revealed changes in climate cyclicity over the last 20 Ma with the fluctuating power of the 100 ka, 400 ka, 2000 ka eccentricity cycles, indicating the evolving response of the climate system to orbital forcing along with the growth of the Antarctic and Northern Hemisphere ice sheets.

Introduction: From the earliest missions to Mars a clear view of the current Mars climate has persisted: Mars is a cold, dry environment incapable of supporting liquid water at the surface for sustained periods of time [1,2]. But the same missions have also provided a related view: Mars once had sufficient water to create the catastrophic outflow channels, meandering channels, and deltas clearly evident in the geomorphology of the surface [1,2]. This paradox remains a major challenge in our understanding of the early Martian climate. Newly developed global and mesoscale atmospheric models allow us to investigate not just radiative models of early Mars, as has been done previously [3], but also the atmospheric dynamics of early Mars. We use one such model, Caltech&#39;s MarsWRF, to investigate the atmospheric dynamics of early Mars for a range of possible atmospheres [4]. Previous Climate Studies: The evidence of extensive surface water in the Martian past led scientists to hypothesi...

Till geochemistry has been widely used as a mineral exploration method in glaciated terrain. Applying this exploration method in regions affected by multi-phase glacial ice flows requires a good understanding of dispersal processes involved with each ice flow trajectory. The West Iznogoudh (WIZ) showing occurs in a region of thin to moderate glacial cover with a wide array of ice flow trajectories.The landforms and surface materials of the Point Lake map sheet (86H) are the result of glaciation that flowed in a general westward direction from the Keewatin Sector of the Laurentide Ice Sheet. Recent fieldwork confirmed the earliest ice flow direction to be 220-230, with a short-lived intermediate flow in the northwest direction (approximately 340) and a strong, sustained flow to be in the 287 direction. Rock samples were collected from outcrop at the WIZ showing to define the source trace element geochemical signature. Preliminary petrographic analysis indicates pyrite, chalcopyrit...

Following the densification of GPS permanent and episodic trackers in Antarctica, geodetic observations are playing an increasing role in geodynamics research and the study of the glacial isostatic adjustment (GIA). The improvement in geodetic measurements accuracy suggests their use in constraining GIA models. It is essential to have a deeper knowledge on the sensitivity of GPS data to motions related to long-term ice mass changes and the present-day mass imbalance of the ice sheets. In order to investigate the geodynamic phenomena in Northern Victoria Land (NVL), GPS geodetic observations were made during the last decade within the VLNDEF (Victoria Land Network for Deformation control) project. The processed data provided a picture of the motions occurring in NVL with a high level of accuracy and depicts, for the whole period, a well defined pattern of vertical motion. The comparison between GPSderived vertical displacements and GIA is addressed, showing a good degree of agreement and highlighting the future use of geodetic GPS measurements as constraints in GIA models. In spite of this agreement, the sensitivity of GPS vertical rates to non-GIA vertical motions has to be carefully evaluated.

 Geodynamic activity in the Victoria Land is evidenced from VLNDEF network measurements;  By a preliminary comparison, the ICE-6G_C-VM5 and W12A_v1 GIA models overestimate uplift rates with respect to GPS-derived ones;  The up component confirms the presence of active extensional/transtensional faulting along the SE segment of the Tucker Fault and the central segment of the Leap Year Fault.

The main objective of this work is to locate and identify the outcrops considered iconic and valuable as references, not only from the point of view of Cultural or Didactic Tourism, but also in paleoenvironmental reconstruction studies, based on the lithologies that comprise the Itararé Group, in the State of São Paulo, Brazil. This work also intends to relate these sites to outcrops of sedimentary facies, in an area located at south of Itu and Porto Feliz, and north of Sorocaba. The Itararé Group lies within the Paraná Basin (Paleozoic), and is composed by sedimentary sequences associated with the record of the Permo-Carboniferous glaciation event that occurred in the Gondwana supercontinent. This work is based on observations of outcrops in a macro-and mesoscopic scale, considering the characterization of external and internal aspects of the layer, the stratigraphic sequence in the outcrop, and the continuity of the layers within the mapped area. The study area has outcrops where the evidences of glaciomarine deposits predominate. Sedimentary sequences deposited in a subaquatic low-energy environment, as well as episodic deposits, in which relatively more energetic phases alternated with low hydrodynamic conditions are well-developed in the study area. There are also fluvio-deltaic environmental occurrences related to sea level oscillations linked with glacier advances and receding.

RESUMO: Os deslizamentos de encostas são muito frequentes no Rio de Janeiro, principalmente no verão, onde as condições meteorológicas são influenciadas pelo calor e alta umidade do ar, contribuindo para formação de áreas de instabilidade ocasionando chuva forte. O Maciço da Tijuca ocupa a posição central do município e devido à morfologia, características geológicas, urbanização e a alta densidade populacional ocorrem muitos movimentos de massa que são agravados principalmente em dias de chuva intensa. Então é necessário ter o conhecimento prévio de onde são as áreas mais afetadas, para que medidas mitigadoras sejam empregadas, e muitas tragédias não voltem a acontecer. Neste trabalho, é apresentado o mapa de susceptibilidade ao risco geotécnico utilizando o modelo de atualização bayesiana de probabilidades, a partir da análise de laudos de ocorrências geotécnicas no ano de 2010 e aplicando a metodologia proposta por Lima (2017), onde todas as ocorrências são classificadas de acordo com a gravidade do movimento de massa associados ao correspondente risco de susceptibilidade. Definidos os valores das probabilidades em cada grupo de pontos, torna-se possível a modelagem do mapa de com a utilização de ferramenta de interpolação geoestatística do software ArcGIS.

In situ cosmogenic 10 Be exposure dating, radiocarbon determinations, salt and sediment geochemistry, and rock weathering observations indicate that parts of Larsemann Hills, East Antarctica have been subaerially exposed throughout much of the last glacial cycle, with the last glaciation occurring prior to 100 ka BP. Salt-enhanced subaerial weathering, coupled with a paucity of glacial erratics, made exposure age dating challenging. Rapid subaerial surface lowering in some places means that some exposure ages may underestimate the true age of deglaciation. Despite this uncertainty, the data are consistent with the absence of overriding by a thick ice sheet during the Last Glacial Maximum ,20-18 ka BP.