Download or read book Developing a Little Ice Age Glacial Chronology in the Southern Peruvian Andes Using Lichenometry and Cosmogenic 10BE Surface Exposure Dating written by Jean R. Taggart and published by . This book was released on 2009 with total page 220 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Increasing the Resolution of the Last Glacial Maximum Record in the Tropical Andes Using 10Be Cosmogenic Surface Exposure Dating in the Cordillera Carabaya Peru written by Zachary E. Mason and published by . This book was released on 2016 with total page 74 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Ice Age Southern Andes written by C.J. Heusser and published by Elsevier. This book was released on 2003-11-12 with total page 257 pages. Available in PDF, EPUB and Kindle. Book excerpt: The Southern Andes, stretching from the subtropics to the subantarctic, are ideally located for palaeoenvironmental research. Over the broad and continuous latitudinal extent of the cordillera (-24˚), vegetation is adjusted to climatic gradients and atmospheric circulation patterns. Opposed to the prevailing Southern Westerlies, the Southern Andes are positioned to receive the brunt of the winds, while biota are set to record the shifting of incoming storm systems over time. Sequential, latitudinally-placed, sedimentary deposits containing microfossils and macroremains, as archives of past vegetation and climate, make possible the detection of equatorward and poleward displacement of plant communities and, as a consequence, changes in climatic controls. No terrestrial setting in the Southern Hemisphere is so unique for palaeoenvironmental reconstruction during and since the last ice age. Twenty radiocarbon-dated fossil pollen and spore records chosen to place emphasis on the last ice age include high-resolution, submillennial data sets that also cover the Holocene, thus providing contrast between present interglacial and past glacial ages. From a refined data base, the records constitute the foundation for interpreting factors responsible for vegetation change over >50,000 14C years, glacial-interglacial migration and refugial patterns for a diversity of taxa, and the extent of intrahemispheric and polar hemispheric synchroneity versus asynchroneity.
Download or read book Glacial History and Climate Change in the Peruvian Bolivian Andes written by Geoffrey Owen Seltzer and published by . This book was released on 1991 with total page 416 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Little Ice Age Chronology for Classen and Godley Glaciers Mount Cook National Park New Zealand written by and published by . This book was released on 2001 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: As part of ongoing research investigating whether or not glacial systems in the Northern and Southern Hemispheres have responded synchronously to climate change, a Little Ice Age (LIA) glacial chronology was established for the Classen and Godley Glaciers, Mount Cook National Park, New Zealand. Additionally, a population-based method of lichenometry was developed and relative retreat pattern established for the Classen and Godley Foreplains, which was then verified against historical records from the Mount Cook National Park area to test the effectiveness of the method. Radiocarbon dates indicate initiation of the most recent LIA advance no later than 1790 AD. Maximum extent occurred by 1862 AD. Ages of ice margin position at and subsequent to the recent LIA maximum position were determined from historical records. Retreat patterns suggest three phases of retreat. Phase one, the slowest phase, lasted from the 1860's to the 1890's. Total marginal retreat for both glaciers was 100 m. Phase two, with slightly higher retreat rates, lasted until the 1950's, during which the Godley separated from two of its tributaries, the Grey and Maud. Total marginal retreat by the end of the second phase was 1 km for the Classen, 3 km for the Grey and Maud, and 5 km for the Godley. Phase three, with the highest retreat rates, began with the formation of a pro-glacial lake at each of the three ice margins, included the separation of the Grey and Maud in 1990, and continues today. Total marginal retreat has been 3.5 km for the Classen, 4 km for the Grey and Maud, and 7.0 for the Godley. Preliminary comparison of Northern and Southern Hemisphere LIA chronologies suggests that Northern Alaska and Scandinavian LIA maximums correspond to the initiation of the recent New Zealand LIA advance. The New Zealand maximum ice extent in 1862 matches LIA maximums from Iceland, Switzerland, Southern Alaska, and British Columbia. During the retreat phase no evidence of major readvance is observed in New Zealand, but is observed in many Northern Hemisphere retreat patterns during the 1930-40's.
Download or read book The Ice Age in North America and Its Bearings Upon the Antiquity of Man written by George Frederick Wright and published by . This book was released on 1889 with total page 704 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Glaciations in North and South America from the Miocene to the Last Glacial Maximum written by Nat Rutter and published by Springer Science & Business Media. This book was released on 2012-06-30 with total page 75 pages. Available in PDF, EPUB and Kindle. Book excerpt: Improved dating methods have increased our ability to more precisely determine the timing and durations of glaciations. Utilizing glacial and loess deposits, we have compared glaciations that occurred in North and South America in order to determine if events are synchronous or not, to explore forcing mechanisms, and to compare glaciations with cold periods of the Marine Oxygen Isotope stages and the loess/paleosol records of China. Stratigraphic sections containing a variety of glacial deposits, some with interbedded volcanics, as well as loess deposits, were used in reconstructing the glacial history. The Late Pleistocene (Brunhes Chron) Last Glacial Maximum is recognized in mountain and continental areas of North America but only in the mountains of South America. Commonly our comparisons indicate roughly synchronous glaciations on the two continents, whereas other glaciations are more elusive and difficult to compare. Although our comparisons are at low resolutions, the results suggest that Milankovitch forcing is most likely the dominant trigger for hemispheric glaciation modified by local factors.
Download or read book Timing and Extent of the Little Ice Age Glacial Advances in the Eastern Tian Shan China written by Yanan Li and published by . This book was released on 2015 with total page 156 pages. Available in PDF, EPUB and Kindle. Book excerpt: Located in Central Asia, one of the most continental regions on Earth, the Tian Shan’s glaciers contribute critical fresh water to populated areas in the lowland. These glaciers are sensitive to climate change, and knowledge of contemporary glaciers and their changes in the past is of critical importance for sustainable development in this region. Constraining glacial fluctuations in recent centuries will fill a gap in numerical constraints on glacial history and paleoclimate information, and provide important evidence on the spatio-temporal changes of the climate systems in the Tian Shan. This doctoral dissertation investigates the timing and extent of Little Ice Age (LIA) glacial advances in the eastern Tian Shan. In particular, I conducted: 1) the mapping of glacial extents during the LIA and around 2010 using Google Earth high-resolution imagery and ArcGIS; 2) statistical analyses to examine relationships between local topographic/geometric factors and glacier change parameters; and 3) cosmogenic 10Be [beryllium 10] surface exposure dating of presumed LIA moraines. The major contributions of this dissertation include: 1) a total of 1173 contemporary glaciers with their corresponding presumed LIA extents were delineated in the eastern Tian Shan; 2) glacier area and mean elevation are the two major local factors that affect glacier area changes, but topographic/geometric factors cannot well explain changes in equilibrium line altitudes; 3) three major LIA advances occurred at 730±300 yr BP, 370±100 yr BP, and 210±50 yr BP were constrained based on 10Be surface exposure ages, and the maximum LIA extent (about 700–900 m beyond glacier termini) was reached asynchronously in different sub-regions; 4) presumed LIA moraines in front of small, thin glaciers yielded widely scattered and much older ages than LIA ages. The glacial deposits in front of such glaciers might have formed prior to the LIA and have been reworked during non-erosive glacial transport in LIA. This suggests that inheritance could be a more significant problem than degradation in the exposure age scatter of young glacial event. More dating work is needed to extend our knowledge on LIA glacial advances, and to better understand the influence of climate systems on glacier changes.
Download or read book Reconstructing Late Pleistocene Deglaciation and Holocene Glacial Advance Using Lacustrine Sediments and 10Be Exposure Dating Brooks Range Arctic Alaska written by Michael E. Badding and published by . This book was released on 2012 with total page 112 pages. Available in PDF, EPUB and Kindle. Book excerpt: The Arctic is among the most sensitive locations to climate change, where feedback mechanisms involving the cryosphere result in climate amplification. Because of their sensitivity to summer temperature and winter precipitation, glaciers can be used as proxies for climate change and reconstructions of past glacier fluctuations provide details about paleoclimate. Here, a chronology of late Pleistocene deglaciation and Neoglacial growth is constructed for two valleys in the north-central Brooks Range, Arctic Alaska. Cosmogenic 10Be exposure dating was used on ice-sculpted valley-bottom bedrock outcrops and boulders from Holocene moraine crests. Both valleys show evidence of retreat from the range front ~16-15 ka, and retreat into individual cirques by ~14 ka. There is no evidence for a standstill or re-advance during Late Glacial (14-11 ka) time. Neoglaciation was underway during the middle Holocene, constrained by a moraine dated to 4. 6±0. 5 ka.^Using this moraine age, and another moraine dated at 2. 7±0. 2 ka, this project confirms the accuracy of the previously established lichen growth curve to estimate moraine ages. This project also confirms that glaciers during early Neoglaciation had equal or larger extents than during the Little Ice Age (1200-1900 AD). Sediments collected from a proglacial lake downvalley of modern cirque glaciers reveal episodic sediment deposition from which it is difficult to isolate a signal of glacier advance. Comparing the lake sediment data to the moraine chronology suggests that Upper Kurupa Lake, based on the measured proxies, does not record glacial advances. Several conditions within the lake's catchment likely obscures any glacial signal. Further, more detailed measurements on the lake sediment might reveal additional clues on glacier activity.^Despite the apparent lack of recording changes in glacial length, sediment characteristics suggest a period of stable deposition since 1300 AD, possibly attributed to cooling during the Little Ice Age.
Download or read book 10Be Chronology of Late Pleistocene and Holocene Glaciation of the Alapah Mountain and Arrigetch Peaks Areas Central Brooks Range Alaska written by Simon L. Pendleton and published by . This book was released on 2013 with total page 112 pages. Available in PDF, EPUB and Kindle. Book excerpt: The amplification of climate change in the Arctic is due to several cyrosphere related feedback mechanisms, making it one of the most climate sensitive environments in the world. Due to this sensitivity, glaciers in this region are excellent recorders of past climate fluctuations. This high-resolution chronology left on the land by these glaciers is an important link in deciphering the dynamic relationship between glaciers and climate, leading to a better understanding of the extent and magnitude of past Arctic climate variability. Here we present new 10Be based glacier chronologies from the late Pleistocene through the Little Ice Age (LIA) for two valleys located in the north- and south-central Brooks range, Alaska. Moraine boulders from the Alapah Mountain moraines on the northern flank of the range indicate that the Itkillik III glaciation culminated by ~17 ka. This age is much older than previous estimates (~15-13 ka) and suggests a revision of the original late Pleistocene glacial chronology. This new Itkillik chronology requires substantial glacial retreat between ~27-23 ka, at the height of the northern hemisphere last glacial maximum (LGM). Due to their moisture sensitivity, expanded Arctic sea ice may have starved glaciers of precipitation during this time. Erratic boulders and scoured bedrock from several valleys in both the northern and southern Brooks Range show that deglaciation was underway by ~16 ka and glaciers retreated rapidly up valley to their Neoglacial limits, in some case by 14. 9 ℗ł 0. 8 ka. Sampled boulders from two Neoglacial moraines show that glaciers reached their maximum Holocene extent by 3. 2 ℗ł 0. 3 ka. In conjunction, these ages show that glaciers remained at or behind their Holocene maximum from ~14-3 ka. This means that Late Glacial (14-11 ka) or early to middle Holocene advances were either absent or less extensive than their Holocene maximum.
Download or read book The Ice Age in North America written by George Frederick Wright and published by . This book was released on 1911 with total page 840 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Antarctic Glacial Chronology New Constraints from Surface Exposure Dating written by and published by . This book was released on 2000 with total page 215 pages. Available in PDF, EPUB and Kindle. Book excerpt: Surface exposure dating using 3He, Ne-21 and Cl-36 combined with mapping of moraines, provide new constraints on West Antarctic Ice Sheet (WAIS) chronology. New He-3 production rates are determined from a 125 ka lava flow. Measurements of inherited He-3/He-4 in two common Antarctic lithologies allow measurement of exposure ages 6000 years. At Mt. Waesche, a moraine band records interior WAIS elevations higher than present. Surface exposure ages indicate that the last ice highstand occurred 10 +/- 1 ka. The data constrain past WAIS behavior and ice volume. Surface exposure ages place age constraints on six Beardmore Glacier drifts. Two drifts record damming of the glacier during the last glacial maximum (10-20 ka) by an expanded WAIS. The four older drifts record similar damming by the WAIS approx. 600 ka, approx. 1 Ma, and approx. 2 Ma. Moraines of Koettlitz Glacier also record damming by the WAIS prior to the LGM. The oldest moraines are 400 ka. Independent stratigraphic control allows evaluation of prior exposure, cover and determination of erosion rates. Taken together, the results are consistent with sea level control of WAIS extent; the WAIS probably has fluctuated synchronously with the Northern Hemisphere ice sheets for at least the last 1 million years.
Download or read book Glacier and Climate Reconstruction in the Central Andes Based on 10Be Surface Exposure Dating written by Roland Zech and published by . This book was released on 2006 with total page 202 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Antarctic Glacial Chronology written by Robert P. Ackert and published by . This book was released on 2000 with total page 213 pages. Available in PDF, EPUB and Kindle. Book excerpt: Surface exposure dating, using the concentration of cosmogenic nuclides (3He, 21Ne, and 36Cl) in moraine boulders, combined with mapping of glacial moraines from three key locations, is used to provide new constraints to Antarctic glacial chronology. The results are used to reconstruct past West Antarctic Ice Sheet (WAIS) geometry and test models of WAIS behavior. Mount Waesche is a volcanic nunatak near the dome of the WAIS in Marie Byrd Land. The Dominion Range is at the head of the Beardmore Glacier, an outlet glacier of the East Antarctic Ice Sheet in the Transantarctic Mountains. Dromedary Platform is a bench along the Koettlitz Glacier which flows into southern McMurdo Sound. In addition, a new 3He production rate calibration, and determination of initial 3He/4He in Ferrar Dolerite and Beacon Sandstone, substantially reduce uncertainties in Antarctic exposure ages. 3He production rates of 129 ± 4 atoms/g/yr (olivine) and 124 ± 4 atoms/g/yr (clinopyroxene) at sea level, high latitude, are determined from an independently dated 125 ka lava flow in Patagonia (46°S). Paired 3He and 36Cl measurements are consistent with negligible surface erosion which is inferred from flow morphology. These mid-latitude, long term, 3He production rates reduce uncertainties previously introduced when scaling production rates calibrated at lower latitudes to Antarctica. The results also confirm the compositional dependence of 3He production rates predicted by theoretical calculations and are used to scale the production rates to quartz. Determinations of initial 3He/4He in pyroxene from shielded dolerite and by incremental heating of quartz show that inherited (nucleogenic) 3He concentrations are very low (3He/4He
Download or read book Glacial Chronology Soil Development and Paleoclimate Reconstructions for Mid latitude South America 1 MA to Recent written by Daniel Corbin Douglass and published by . This book was released on 2005 with total page 228 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Late Holocene Glacier Fluctuations in Southernmost Patagonia written by Malyssa Kay Maurer and published by . This book was released on 2015 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Documenting past climate dynamics aids in our understanding of the climate system. In order to assess future climate change it is valuable to examine the connectivity of climatic phenomena between hemispheres. Although studies that estimate past climate fluctuations are common in the Northern Hemisphere, fewer well-constrained glacier chronologies exist in the Southern Hemisphere. The assessment of past glacier activity remains the most direct method of creating a climatic record for a region, and the comparison of these glacial chronologies tests the synchronicity of climatic change between regions. This study investigates inter-hemispheric synchronicity by developing a detailed glacier history in southern Patagonia for comparison to robust glacier chronologies from the northwestern North America. Five Neoglacial advances of Stoppani Glacier in the Cordillera Darwin of southern Patagonia broadly correspond to the Neoglacial activity documented in northwestern North America. This Stoppani Glacier chronology is based on radiocarbon-dated detrital and in situ plant material contained within the northeastern lateral moraine stratigraphy. The age range from dated plant material records the first Neoglacial expansion of Stoppani Glacier which, overlaps with the end of the 4.2 ka Advance' reported throughout northwestern North America. Stoppani Glacier advanced multiple times between 3500-1900 cal yr BP which overlaps with the 'Peyto-Tiedemann Advance' documented in northwestern North America. The lacustrine record from nearby Lago Roca also suggests that local sea level lowered during the 3500-1900 cal yr BP period, resulting in the isolation of the lake from the Beagle Channel ca. 2300 cal yr BP. Plant material from within till at Stoppani Glacier and lacustrine sediments from Lago Roca yield an age range for the last advance of glaciers in the Cordillera Darwin the range coincides with the end of the wide-spread Little Ice Age Advance' documented throughout northwestern North.
Download or read book Glacier Sensitivity Along the Andes written by Esteban A. Sagredo and published by . This book was released on 2012 with total page 119 pages. Available in PDF, EPUB and Kindle. Book excerpt: Accompanying the drastic increase of global temperatures observed since the end of the nineteenth century, and particularly during the last decades, glaciers worldwide have experienced rapid retreating trend. Considering the magnitude of the climate change projected for the next decades, and the potential impacts of glacier retreat on human livelihood, a thorough comprehension of climate-glacier interaction is critical in order to i) predict the response of glaciers to the different scenarios of climate change and ii) reconstruct the climatic conditions associated with former glacial fluctuations, which in turn could provide important background information for the study of both natural cycles and human impacts on climate change. This study explores the magnitude of response of the equilibrium line altitude (ELA) to different scenarios of climate change, along the climatically diverse Andes range, and its applicability to reconstruct paleoclimates. A statistical analysis of the climatic conditions at 234 glacier sites permits to classify the climate that host present-day Andean glaciers into seven groups. These groups have a distinctive geographical distribution. It has been suggested that glaciers located in different climates could respond with different magnitude to similar climatic perturbations. Here, a full-surface energy and mass balance (SEMB) model was applied to quantify the ELA sensitivity to climate across glaciated Andean regions. The results suggest that there is spatial variability in the magnitude of response of the ELA to uniform changes in temperature and precipitation, and that the spatial pattern of this variability has a general correspondence with the climatic groups identified along the Andes. The most sensitive areas to changes in temperature are the inner tropics, whereas precipitation sensitivities are relatively greater in the subtropics and northernmost mid-latitudes. It is suggested that the variability in the ELA sensitivity has implications for the reconstruction of paleoclimates across large areas. Based on an approach that combine the geomorphic reconstruction of ELA of Andean glaciers and the application of the SEMB model, different scenarios of climatic conditions for the maximum glacial advance occurred during the Little Ice Age (LIA, sensu lato AD 1300-1850) are suggested. To conduct this experiment, three glacial sites (located in different climatic regimes) were selected: Cordillera Vilcanota (13°S), Cipreses glacier (34°S) and Tranquilo glacier (47°S). The results consist of a set of combination of temperature and precipitation anomalies that can account for ELA changes from the maximum glacial advance that occurred during the LIA to the present for each site. Assuming no changes in precipitation, the ELA fluctuation since the LIA could be explained by a cooling of at least: -0.7°C at Vilcanota, -0.5°C at Cipreses and -1.3°C at Tranquilo glacier. Assuming no changes in temperature, on the other hand, the ELA changes could be explained by an increase in the precipitation greater than 63% at Vilcanota, 21% at Cipreses and 62% at Tranquilo glacier. Finally, it is expected that the integration of these analysis provides a framework to understand former episodes of glacial fluctuation, as well as to predict the response of glacier to different scenarios of climate change.
