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Late Pleistocene And Holocene Glacier And Climate Change
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Book Synopsis Late Pleistocene and Holocene Glacier and Climate Change by : Shaun Andrew Marcott
Download or read book Late Pleistocene and Holocene Glacier and Climate Change written by Shaun Andrew Marcott and published by . This book was released on 2011 with total page 259 pages. Available in PDF, EPUB and Kindle. Book excerpt: This dissertation presents results from three studies that address major scientific questions in glacial geology and paleoclimatology for the late Pleistocene and Holocene using relatively new geochemical and statistical techniques. Each of the studies attempts to answer a longstanding question in the respective field using geochemical or statistical methods that have not been applied to the problem thus far. A longstanding question in glaciology is the nature and mechanism of the so- called "Heinrich events" of the last ~60 ka. These massive iceberg discharge events into the North Atlantic from the partial breakup of the Laurentide Ice Sheet are identified from distinct ice rafted debris and detrital carbonate layers in marine sediment cores. The mechanism associated with the initiation of these events is commonly thought to be related to internal ice sheet instabilities. However, Heinrich events consistently occur following a long cooling trend that culminates in an extreme cold event, thus suggesting a possible triggering mechanism by climate. Recent modeling work has proposed an oceanic mechanism associated with ocean warming, but no physical evidence has been made available to date. To test this ocean-warming hypothesis, we measured temperature sensitive trace metals and stable isotopes in benthic foraminifera from a sediment core collected in the western North Atlantic that spans the last six Heinrich events and compared our results to climate model simulations using CCSM3. Our results show subsurface warming occurred prior to or coeval with nearly all of the Heinrich events of the last ~60 ka, thus implicating subsurface ocean warming as the main trigger of these rapid breakups of the Laurentide Ice Sheet. In the field of glacial geology a longstanding question has been the timing of alpine glacial advances during the Holocene. A number of studies have interpreted several Holocene glacial advances in western North America, but age control is based largely on relative dating techniques, which have been shown to be in error by up to 10,000 yrs in some cases. Based on 124 10Be surface exposure ages from twenty cirque moraines in ten mountain ranges across western North America, glacier were retreating from moraine positions during the latest Pleistocene or earliest Holocene and not throughout the Holocene epoch as previously assumed, thus requiring a refined interpretation of Holocene glacial activity in western North America and the associated climate forcing. In the field of paleoclimatology a question regarding how global temperature varied over the entirety of the Holocene epoch has remained to be answered for some time. While many temperature reconstructions exist for the last 2000 years, a full Holocene temperature stack does not exist, despite its potential utility of putting modern climate change into a full interglacial perspective. Based on a global composite of 73 proxy based temperature record, a Holocene temperature stack was constructed and used to demonstrate that a general cooling of ~1°C has occurred from the early to mid Holocene and that centennial and millennial scale variability is modest. We account for both temperature calibration and chronologic uncertainties using a Monte Carlo based approach. Our results are consistent with prior reconstructions of the last 2000 years and now allow for a full Holocene temperature perspective for evaluation with present and future climate change.
Book Synopsis Late Pleistocene and Holocene Environmental Change on the Olympic Peninsula, Washington by : Daniel G. Gavin
Download or read book Late Pleistocene and Holocene Environmental Change on the Olympic Peninsula, Washington written by Daniel G. Gavin and published by Springer. This book was released on 2014-11-25 with total page 148 pages. Available in PDF, EPUB and Kindle. Book excerpt: This study brings together decades of research on the modern natural environment of Washington's Olympic Peninsula, reviews past research on paleoenvironmental change since the Late Pleistocene, and finally presents paleoecological records of changing forest composition and fire over the last 14,000 years. The focus of this study is on the authors’ studies of five pollen records from the Olympic Peninsula. Maps and other data graphics are used extensively. Paleoecology can effectively address some of these challenges we face in understanding the biotic response to climate change and other agents of change in ecosystems. First, species responses to climate change are mediated by changing disturbance regimes. Second, biotic hotspots today suggest a long-term maintenance of diversity in an area, and researchers approach the maintenance of diversity from a wide range and angles (CITE). Mountain regions may maintain biodiversity through significant climate change in ‘refugia’: locations where components of diversity retreat to and expand from during periods of unfavorable climate (Keppel et al., 2012). Paleoecological studies can describe the context for which biodiversity persisted through time climate refugia. Third, the paleoecological approach is especially suited for long-lived organisms. For example, a tree species that may typically reach reproductive sizes only after 50 years and remain fertile for 300 years, will experience only 30 to 200 generations since colonizing a location after Holocene warming about 11,000 years ago. Thus, by summarizing community change through multiple generations and natural disturbance events, paleoecological studies can examine the resilience of ecosystems to disturbances in the past, showing how many ecosystems recover quickly while others may not (Willis et al., 2010).
Book Synopsis Holocene Climate Change and Environment by : Navnith Kumaran
Download or read book Holocene Climate Change and Environment written by Navnith Kumaran and published by Elsevier. This book was released on 2021-09-24 with total page 693 pages. Available in PDF, EPUB and Kindle. Book excerpt: Holocene Climate Change and Environment presents detailed, diverse case studies from a range of environmental and geological regions on the Indian subcontinent which occupies the central part of the monsoon domain. This book examines Holocene events at different time intervals based on a new, high-resolution, multi-proxy records (pollen, spores, NPP, diatoms, grain size characteristics, total organic carbon, carbon/nitrogen ratio, stable isotopes) and other physical tools from all regions of India. It also covers new facilities in chronological study and luminescence dating, which have added a new dimension toward understanding the Holocene glacial retreats evolution of coastal landforms, landscape dynamics and human evolution. Each chapter is presented with a unified structure for ease of access and application, including an introduction, geographic details, field work and sampling techniques, methods, results and discussion. This detailed examination of such an important region provides key insights in climate modeling and global prediction systems. - Provides data and research from environmentally and geologically diverse regions across the Indian subcontinent - Presents an integrated and interdisciplinary approach, including considerations of human impacts - Features detailed case studies that include methods and data, allowing for applications related to research and global modeling
Book Synopsis Reconstructing Late Pleistocene and Holocene Glacier Fluctuations Using Cosmogenic 10Be Exposure Dating and Lacustrine Sediment, Brooks Range, Arctic Alaska by : Elizabeth Grayce Ceperley
Download or read book Reconstructing Late Pleistocene and Holocene Glacier Fluctuations Using Cosmogenic 10Be Exposure Dating and Lacustrine Sediment, Brooks Range, Arctic Alaska written by Elizabeth Grayce Ceperley and published by . This book was released on 2014 with total page 102 pages. Available in PDF, EPUB and Kindle. Book excerpt: Due to cryosphere-albedo feedbacks mechanisms, climate change is amplified in the Arctic, making it sensitive to changes in temperature. Alpine glaciers grow and retreat depending on climate, and are excellent recorders of past climate fluctuations. By analyzing the landforms and sediment deposited by glaciers, high-resolution climate chronologies can be constructed and past glacier fluctuations can be inferred. 10Be ages and physical properties of lake sediment are used here to reconstruct Late Pleistocene and Holocene glacier activity from Alapah River valley and Shainin Lake in the north-central Brooks Range. 10Be ages from moraine boulders in Alapah River valley in the north-central Brooks Range were used to reconstruct the maximum glacier extent during the LGM. After eliminating outliers, the 10Be ages from a terminal moraine deposit in the Alapah River valley indicate that the local LGM culminated at 21. 0 ℗ł 0. 8 ka. This new 10Be chronology is the first to firmly constrain the timing of the local LGM in the Brooks Range, and is in agreement with LGM moraine records from other sites in Alaska and the globe. Two 10Be ages from boulders located on bedrock 14 km upvalley from the Itkillik II terminal moraine give an age of deglaciation in Alapah River valley of 18. 2 ℗ł 0. 8 ka. This indicates rapid retreat after the LGM and shows that deglaciation is synchronous with sites in Alaska but was initiated earlier than the age of 17 ka previously proposed for onset of LGM deglaciation in the western US. Physical and geochemical properties of lake sediment from a proglacial lake in Alapah River valley, Shainin Lake, were analyzed to investigate any glacial signals recorded in the lake sediment. Age-depth models for each core were established using 14C ages and analytical methods included magnetic susceptibility, wet bulk density (WBD), scanning X-Ray fluorescence (ITRAX) and visible scanning reflectance spectroscopy. The WBD record from Shainin Lake may serve as a proxy for glacial history of Alapah and Kayak Creek valleys. If interpreted correctly, glacial activity increased from 12,700 to ~10,000 cal yr, decreased from ~10,000 to ~5700 cal yr BP, then increased from ~5700 cal yr BP to the present. This indicates that there is evidence for early Holocene glacial activity, the retreating or stagnating glaciers in the middle Holocene until ~5700 cal yr BP, followed by expanding ice.
Book Synopsis North Pacific Environment and Paleoclimate from the Late Pleistocene to Present by : Miriam Jones
Download or read book North Pacific Environment and Paleoclimate from the Late Pleistocene to Present written by Miriam Jones and published by Frontiers Media SA. This book was released on 2020-01-13 with total page 208 pages. Available in PDF, EPUB and Kindle. Book excerpt: The vast area of the North Pacific, spanning ~55˚ longitude, represents a challenge for documenting and understanding the geologic history of ocean, atmosphere, and terrestrial environmental change. Nevertheless, its importance for many issues, including our fundamental understanding of ocean and atmospheric circulation patterns and teleconnections with natural modes of climate variability through time, has led to a steady rise in the numbers of study sites and proxy types. By bringing together a wide range of proxies and timescales that examine the impacts of paleoclimate on ecosystems, water, carbon, and humans, and interactions between marine and terrestrial processes, this Research Topic contributes to an improved understanding of the region’s significance at global, hemispheric, and regional scales.
Book Synopsis Late Pleistocene and Holocene Aged Glacial and Climate Reconstructions in the Goat Rocks Wilderness, Washington, United States by : Joshua Andrews Heard
Download or read book Late Pleistocene and Holocene Aged Glacial and Climate Reconstructions in the Goat Rocks Wilderness, Washington, United States written by Joshua Andrews Heard and published by . This book was released on 2012 with total page 142 pages. Available in PDF, EPUB and Kindle. Book excerpt: Eight glaciers, covering an area of 1.63 km2, reside on the northern and northeastern slopes of the Goat Rocks tallest peaks in the Cascades of central Washington. At least three glacial stands occurred downstream from these glaciers. Closest to modern glacier termini are Little Ice Age (LIA) moraines that were deposited between 1870 and 1899 AD, according to the lichenometric analysis. They are characterized by sharp, minimally eroded crests, little to no soil cover, and minimal vegetation cover. Glacier reconstructions indicate that LIA glaciers covered 8.29 km2, 76% more area than modern ice coverage. The average LIA equilibrium line altitude (ELA) of 1995 ± 70 m is ~150 m below the average modern ELA of 2149 ± 76 m. To satisfy climate conditions at the LIA ELA, the winter snow accumulation must have been 8 to 43 cm greater and mean summer temperatures 0.2 to 1.3 oC cooler than they are now. Late Pleistocene to early Holocene (LPEH) aged moraines are located between 100 and 400 m below the LIA deposits. They have degraded moraine crests, few surface boulders, and considerable vegetation and soil cover. Volcanic ashes indicate LPEH moraines were deposited before 1480 AD while morphometric data suggest deposition during the late Pleistocene or early Holocene. The average LPEH ELA of 1904 ± 110 m is ~ 240 m and ~90 m below the modern and LIA ELAs, respectively. The climate change necessary to maintain a glacier with an ELA at that elevation for LPEH conditions requires the winter accumulation to increase by 47 to 48 cm weq and the mean summer temperature to cool by 1.4 to 1.5 oC. Last glacial maximum (LGM) moraines are located more than 30 km downstream from modern glacial termini. They are characterized by hummocky topography, rounded moraine crests, complete vegetation cover, and well developed soil cover. Moraine morphometry, soil characteristics, and distance from modern glacial termini indicate that deposition occurred at least 15 ka BP during an expansive cooling event, the last being the LGM. The LGM ELA of 1230 m is ~920 m below the modern ELA. The climate change necessary to maintain a glacier with an ELA at that elevation for LGM conditions requires the mean summer temperature to cool by 5.6 oC with no change in precipitation.
Book Synopsis Late Pleistocene Glacial and Environmental Change, Eastern Glacier National Park, Montana by : Nathan Schachtman
Download or read book Late Pleistocene Glacial and Environmental Change, Eastern Glacier National Park, Montana written by Nathan Schachtman and published by . This book was released on 2014 with total page 108 pages. Available in PDF, EPUB and Kindle. Book excerpt: Few records in the alpine landscape of western North America document the geomorphic and glaciologic response to climate change during the Pleistocene-Holocene transition. While glacial moraines can provide snapshots of glacier extent in the northern U.S. Rocky Mountains, high-resolution records of environmental change spanning glacial retreat at the end of the Last Glacial Maximum, the Younger Dryas (YD) cooling, and subsequent warming into the stable Holocene are rare. We describe the transition from the late Pleistocene to the early Holocene using a ~17 ka sediment core from Swiftcurrent Lake in eastern Glacier National Park, MT, with a focus on ~17-11 ka. Total organic carbon (%TOC), total inorganic carbon (%TIC), grain size, and carbon/nitrogen (C/N) values provide evidence for warming climate from the late Pleistocene into the Holocene, with the exception of a well-constrained interval of rapid cooling during the YD between 12.5 and 11.5 ka. The variable concentration of detrital dolomite, derived from glacial erosion of bedrock near the valley headwall and cirque basin, provides a high-resolution record of Grinnell Glacier advance and retreat. Dolomite concentrations decrease during glacial retreat and increase during periods of advancing ice, corroborated by sedimentological and geochemical data. We interpret increased dolomite concentration in Swiftcurrent Lake as reflecting enhanced glacial erosion and sediment transport, likely a result of more proximal ice terminus position, possibly increased hydrologic energy, and a reduction in the number of alpine lakes acting as sediment sinks in the valley.
Book Synopsis Second Assessment of Climate Change for the Baltic Sea Basin by : The BACC II Author Team
Download or read book Second Assessment of Climate Change for the Baltic Sea Basin written by The BACC II Author Team and published by Springer. This book was released on 2015-04-03 with total page 515 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book is an update of the first BACC assessment, published in 2008. It offers new and updated scientific findings in regional climate research for the Baltic Sea basin. These include climate changes since the last glaciation (approx. 12,000 years ago), changes in the recent past (the last 200 years), climate projections up until 2100 using state-of-the-art regional climate models and an assessment of climate-change impacts on terrestrial, freshwater and marine ecosystems. There are dedicated new chapters on sea-level rise, coastal erosion and impacts on urban areas. A new set of chapters deals with possible causes of regional climate change along with the global effects of increased greenhouse gas concentrations, namely atmospheric aerosols and land-cover change. The evidence collected and presented in this book shows that the regional climate has already started to change and this is expected to continue. Projections of potential future climates show that the region will probably become considerably warmer and wetter in some parts, but dryer in others. Terrestrial and aquatic ecosystems have already shown adjustments to increased temperatures and are expected to undergo further changes in the near future. The BACC II Author Team consists of 141 scientists from 12 countries, covering various disciplines related to climate research and related impacts. BACC II is a project of the Baltic Earth research network and contributes to the World Climate Research Programme.
Book Synopsis Reconstructing Late Pleistocene Deglaciation and Holocene Glacial Advance Using Lacustrine Sediments and 10Be Exposure Dating, Brooks Range, Arctic Alaska℗ by : Michael E. Badding
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.
Book Synopsis 10Be Chronology of Late Pleistocene and Holocene Glaciation of the Alapah Mountain and Arrigetch Peaks Areas, Central Brooks Range, Alaska by : Simon L. Pendleton
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.
Book Synopsis Global Climates since the Last Glacial Maximum by : H. E. Wright
Download or read book Global Climates since the Last Glacial Maximum written by H. E. Wright and published by U of Minnesota Press. This book was released on 1993 with total page 646 pages. Available in PDF, EPUB and Kindle. Book excerpt: Traces the evolution of the global climate since the last period of glacial maximum approximately 18,000 years ago. Examines how changes in climate have transformed Earth's biomes in this period and how this change has influenced the evolution of life.
Book Synopsis European Glacial Landscapes by : David Palacios
Download or read book European Glacial Landscapes written by David Palacios and published by Elsevier. This book was released on 2023-10-21 with total page 637 pages. Available in PDF, EPUB and Kindle. Book excerpt: European Glacial Landscapes: The Holocene presents the current state of knowledge on glacial landscapes of Europe and nearby areas over the Holocene to deduce the influence of atmospheric and oceanic currents and the insolation forcing variability and volcanic activity on Holocene paleoclimates, the existence of asynchronies in the timing of occurrence of glacier expansion and shrinkage during the Holocene, time lags between the identification of oceanic and atmospheric changes and those occurring in glacial extension during the Holocene, the role of Holocene glaciers on the climate of Europe, and on sea level variability, and the delimitation of landscapes that need special protection. Students, academics and researchers in Geography, Geology, Environmental Sciences, Physics and Earth Science departments will find this book provides novel findings of all the major European Regions in a single publication, with updated information about Holocene glacial geomorphology and paleo-climatology and clear figures that model the landscapes covered. Provides a synthesis and summary of glacial processes in Europe over the Holocene period Features research from experts in palaeo-climatology, palaeo-oceanography and palaeo-glaciology Includes access to a companion website with an interactive map, photos of glacial features, and geospatial data related to European Glacial Landscapes
Download or read book The Great Ice Age written by J.A. Chapman and published by Routledge. This book was released on 2005-06-21 with total page 381 pages. Available in PDF, EPUB and Kindle. Book excerpt: Documents and explains the natural climatic and ecological changes that have occurred during the past 2.6 million years. It also outlines the emergence and global impact of humans during this period.
Book Synopsis Ice Age Earth by : Alastair G. Dawson
Download or read book Ice Age Earth written by Alastair G. Dawson and published by Routledge. This book was released on 2013-06-17 with total page 312 pages. Available in PDF, EPUB and Kindle. Book excerpt: Ice Age Earth provides the first detailed review of global environmental change in the Late Quaternary. Significant geological and climatic events are analysed within a review of glacial and periglacial history. The melting history of the last ice sheets reveals that complex, dynamic and catastrophic change occurred, change which affected the circulation of the atmosphere and oceans and the stability of the Earth's crust.
Book Synopsis Quaternary Glaciation in the Mediterranean Mountains by : P.D. Hughes
Download or read book Quaternary Glaciation in the Mediterranean Mountains written by P.D. Hughes and published by Geological Society of London. This book was released on 2017-01-30 with total page 320 pages. Available in PDF, EPUB and Kindle. Book excerpt: The mountains of the Mediterranean world are now largely ice free, but many were repeatedly glaciated during the Quaternary ice age. This created spectacular glaciated landscapes with a rich array of glacial deposits and landforms. The glacial and glacio-fluvial records are often very well preserved and our understanding of the timing of Quaternary glaciation has very recently been transformed through the application of dating methods utilizing uranium-series and cosmogenic isotopes. Glacial records from the Mediterranean now boast some of the most robust chronologies for mountain glaciation anywhere in the world – they represent a unique archive of Quaternary environmental change of global significance. The southerly latitude and relatively small size of Mediterranean glaciers rendered them especially sensitive to Pleistocene and Holocene climate changes. This volume brings together the leading researchers and the latest research on Mediterranean glaciation. Several papers also explore glacier behaviour in the Holocene – including those glaciers of southernmost Europe at risk of disappearing this century.
Book Synopsis Late Pleistocene and Holocene Climate Change in Southern Nevada by : Peter E. Wigand
Download or read book Late Pleistocene and Holocene Climate Change in Southern Nevada written by Peter E. Wigand and published by . This book was released on 1987 with total page 54 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Deglaciation and Latest Pleistocene and Early Holocene Glacier Readvances on the Alaska Peninsula: Records of Rapid Climate Change Due to Transient Changes, in Solar Intensity and Atmospheric CO2 Content? by : De Anne S. Pinney Stevens
Download or read book Deglaciation and Latest Pleistocene and Early Holocene Glacier Readvances on the Alaska Peninsula: Records of Rapid Climate Change Due to Transient Changes, in Solar Intensity and Atmospheric CO2 Content? written by De Anne S. Pinney Stevens and published by . This book was released on 1992 with total page 7 pages. Available in PDF, EPUB and Kindle. Book excerpt: Geologic mapping near Windy Creek, Katmai National Park, identified two sets of glacial deposits postdating late-Wisconsin Iliuk moraines and separated from them by volcaniclastic deposits laid down under ice-free conditions. Radiocarbon dating of organic material incorporated in the younger Katolinat till and in adjacent peat and lake sediments suggests that alpine glaciers on the northern Alaska Peninsula briefly expanded between ca. 8500 and 10,000 years B.P. Stratigraphic relationships and radiocarbon dates suggest an age for the older Ukak drift near the Pleistocene-Holocene boundary between ca. 10,000 and 12,000 years B.P. We suggest that rapid deglaciation following deposition of the Iliuk drift occurred ca. 13,000-12,000 years B.P. in response to large increases in global atmospheric greenhouse gas content, including C02. Short-term decreases in these concentrations, as recorded in polar ice cores, may be linked with brief periods of glacier expansion during the latest Pleistocene and early Holocene. A transient episode of low solar intensity may also have occurred during parts of the early Holocene. Rapid environmental changes and glacial fluctuations on the Alaska Peninsula may have been in response to transient changes in the concentration of atmospheric greenhouse gases and solar intensity.
