Search results for "Ice sheet"
showing 10 items of 36 documents
South Pole glacial climate reconstruction from multi-borehole laser particulate stratigraphy
2013
AbstractThe IceCube Neutrino Observatory and its prototype, AMANDA, were built in South Pole ice, using powerful hot-water drills to cleanly bore>100 holes to depths up to 2500 m. The construction of these particle physics detectors provided a unique opportunity to examine the deep ice sheet using a variety of novel techniques. We made high-resolution particulate profiles with a laser dust logger in eight of the boreholes during detector commissioning between 2004 and 2010. The South Pole laser logs are among the most clearly resolved measurements of Antarctic dust strata during the last glacial period and can be used to reconstruct paleoclimate records in exceptional detail. Here we use…
Size variations in the genus Gephyrocapsa during the Early Plaeistocene in the eastern Mediterranean
2014
The genus Gephyrocapsa, belonging to coccolithophores, hasoften been used in biostratigraphic and paleoceanographic studies ofthe late Cenozoic. This taxon exhibits a gradual increase in sizeduring the Early Pleistocene which has been ascribed to evolutiveand/or environmental processes and has been used for biostratigraphicpurposes.Here we show both biometric and relative abundance data ofspecimens of this genus between about 2.0 and 0.9 Ma, from sedimentsof the Ionian Sea (eastern Mediterranean). Measurements onthe long axis of placoliths highlight a gradual size increase betweenthe upper part of MNN 19a and the top of MNN 19d biozones. Onthe basis of the comparison with paleoenvironmental…
Mise en évidence d’une dynamique de fleuves de glace durant la glaciation ordovicienne par l’enregistrement géomorphologique
2007
On Contemporary Ice streams the most important factor controlling polar ice-sheet sheet stability and ice flowing occurs in ice streams. On Pleistocene Ice Sheet, Ice stream can be located using several geomorphologic criteria predict from known characteristic of contemporary ice streams, these criteria defining the conceptual Ice Stream land system model. But nowadays, during fossil glaciations, ice streams characterization is still poorly documented and only few studies illustrate fast ice velocity. In this work, we characterize geomorphological markers of ice stream activity in order to define the Ordovician ice stream glacial landsystem. The study area is located in Sahara from Niger to…
Seasonal changes in glacial polynya activity inferred from Weddell Sea varves
2013
Abstract. The Weddell Sea and the associated Filchner–Rønne Ice Shelf constitute key regions for global bottom-water production today. However, little is known about bottom-water production under different climate and ice-sheet conditions. Therefore, we studied core PS1795, which consists primarily of fine-grained siliciclastic varves that were deposited on contourite ridges in the southeastern Weddell Sea during the Last Glacial Maximum (LGM). We conducted high-resolution X-ray fluorescence (XRF) analysis and grain-size measurements with the RADIUS tool (Seelos and Sirocko, 2005) using thin sections to characterize the two seasonal components of the varves at sub-mm resolution to distingui…
Subglacial bedforms of the Zemgale Ice Lobe, south-eastern Baltic
2015
Abstract Presented in this paper are the results of the mapping of ∼6600 subglacial bedforms of the Zemgale Ice Lobe (ZIL), their composition and internal structure in the south-eastern Baltic region. Topographic maps at scale 1:10,000 were mainly used to map bedforms in Latvia, while a digital elevation model with cell size of 5 m was used for North Central Lithuania. The ZIL operated during the deglaciation of the Late Weichselian Scandinavian Ice Sheet (SIS), at least in the Middle Lithuanian and North Lithuanian glacial phases, and created a subglacial landform assemblage consisting of glacial lineations such as drumlins, mega-flutings, Mega Scale Glacial Lineations (MSGLs) and transver…
New Evidence of MIS 3 Relative Sea Level Changes from the Messina Strait, Calabria (Italy)
2021
Investigation of sea-level positions during the highly-dynamic Marine Isotope Stage 3 (MIS 3: 29–61 kyrs BP) proves difficult because: (i) in stable and subsiding areas, coeval coastal sediments are currently submerged at depths of few to several tens of meters below the present sea level
21. Abrupt change of El Niño activity off Peru during stage MIS 5e-d
2007
Abstract High-resolution proxy data for El Nino variability during the last glacial cycle were derived from a laminated marine sediment core from a region whose climatology and oceanography is strongly affected by ENSO variability. The proxies used are the seasurface temperature and the lithic flux from the continent onto the continental shelf that is largely controlled by the river flood discharge after strong El Nino rainfall in northern and northern central Peru. The focus of this paper is on an abrupt, possibly orbitally driven change of El Nino activity within marine isotope stage 5e. A similar sharp decline of El Nino activity is also observed during the middle of the Holocene intergl…
Surviving the Holocene: Human Ecological Responses to the Current Interglacial in Southern Valencia, Spain
2009
For hunter-gatherer groups, the dramatic changes in climate at the end of the last glacial cycle necessitated rearrangement of land use, including shifts in mobility strategies, settlement location, and resource use. We examine these behavioral changes using lithic attribute data as well as spatial distributions of artifacts and features. Using data from intensive survey and excavation, we trace human ecological response through the onset of the current interglacial in central Mediterranean Spain, comparatively far from the margins of the north-temperate ice sheets.
The low-latitude monsoon climate during Dansgaard–Oeschger cycles and Heinrich Events
2000
During the last 100,000 years Dansgaard–Oeschger cycles (D/O cycles) and Heinrich Events have been the dominant signal of past climate variability over Greenland and the North Atlantic. The succession of stadials (cold) and interstadials (warm) associated with these cycles has been documented in records from the entire northern hemisphere, South America, New Zealand, Antarctica, the South Atlantic and the Southern Ocean. Evidently, climate forcing in the D/O band affects both hemispheres. The origin and cause of these teleconnected patterns is still unknown, even if a large proportion of the cooling in Europe and northern Asia during Heinrich Events is a meteorological response to cold surf…
The origin and glaciodynamic significance of sandstone ridge networks from the Hirnantian glaciation of the Djado Basin (Niger)
2007
The Djado Basin (Niger) was located beneath the inner part of the Late Ordovician ice sheet. The Felar-Felar Formation consists mainly of glaciomarine deposits, associated with the major ice sheet recession within the glaciation, and is bounded by two glacial unconformities. Structures corresponding to sandstone ridges are found within the Felar-Felar Formation. Sandstone ridges are several metres high, about 10 m wide and hundreds of metres long. These structures are organized in extensive anastomosed to subpolygonal networks. The association of sandstone ridge networks with the later glacial unconformity and with other glacial evidence suggests sub-glacial conditions for their origin. San…