Download or read book Reconstruction of a High resolution Late Holocene Arctic Paleoclimate Record from Colville River Delta Sediments written by and published by . This book was released on 2013 with total page 20 pages. Available in PDF, EPUB and Kindle. Book excerpt: This work was partially supported by the Sandia National Laboratories, 'Laboratory Directed Research and Development' (LDRD) fellowship program in conjunction with Texas A & M University (TAMU). The research described herein is the work of Kathryn M. Schreiner ('Katie') and her advisor, Thomas S. Bianchi and represents a concise description of Katie's dissertation that was submitted to the TAMU Office of Graduate Studies in May 2013 in partial fulfillment of her doctorate of philosophy degree. High Arctic permafrost soils contain a massive amount of organic carbon, accounting for twice as much carbon as what is currently stored as carbon dioxide in the atmosphere. However, with current warming trends this sink is in danger of thawing and potentially releasing large amounts of carbon as both carbon dioxide and methane into the atmosphere. It is difficult to make predictions about the future of this sink without knowing how it has reacted to past temperature and climate changes. This project investigated long term, fine scale particulate organic carbon (POC) delivery by the high-Arctic Colville River into Simpson's Lagoon in the near-shore Beaufort Sea. Modern POC was determined to be a mixture of three sources (riverine soils, coastal erosion, and marine). Downcore POC measurements were performed in a core close to the Colville River output and a core close to intense coastal erosion. Inputs of the three major sources were found to vary throughout the last two millennia, and in the Colville River core covary significantly with Alaskan temperature reconstructions.

Download or read book Reconstructing Late Holocene Artctic Climate Change Using High Resolution Sediment Records from Simpson Lagoon Alaska and the Colville River Alluvial Valley written by Andrea Jo Miller Hanna and published by . This book was released on 2015 with total page 604 pages. Available in PDF, EPUB and Kindle. Book excerpt: Arctic nearshore environments proximal to large rivers, like Simpson Lagoon, Alaska, potentially contain high-resolution sediment archives that can be utilized to reconstruct paleoclimate variability over the late Holocene. The ongoing, rapid environmental changes recently observed in the Arctic highlight the need for high-resolution records of pre-industrial climate change in this climatically sensitive region; such records are fundamental for understanding recent anthropogenic changes in the context of natural variability. This dissertation utilizes a suite of geochemical and sedimentological proxies in combination with age-constrained, shallow acoustic reflection data to demonstrate that these underutilized coastal sediment archives are capable of generating high-resolution paleoclimate records on par with other terrestrial climate archives (i.e. lake sediments, ice cores, tree rings) and provides the first ~1650-year long record of climate variability from the inner shelf of the Alaskan Beaufort Sea. An analysis of sedimentation patterns within Simpson Lagoon using CHIRP seismic data and radioisotope geochronology reveals that sediment infilling in Simpson Lagoon began ~3500 y BP, creating a primary depocenter with mm y−1 sediment accumulation in western Simpson Lagoon. The interbedded sediments suggest that major sediment reworking from ice processes, a common occurrence in Arctic shelf environments, does not disrupt the sediment archive contained within the lagoon. Quantitative reconstructions of surface air temperature are obtained using the brGDGT-derived MBT'/CBT paleothermometer. A comprehensive study of lagoon and river sediments and catchment soils demonstrate that brGDGTs are primarily soil-derived, and yield reconstructed temperatures consistent with instrumental summer temperature observations from Alaska's North Slope. Temperature reconstructions from Simpson Lagoon also show similarities with regional and pan-Arctic climate records over the last few millennia, with evidence of temperature departures correlative with noted climate events (i.e., Little Ice Age, Medieval Climate Anomaly). In addition, temporal variability in sediment sourcing to the lagoon, determined using a multi-proxy approach (i.e., granulometry, elemental analysis, clay mineralogy), broadly corresponds with temperature fluctuations, indicating relative increases in fluvial sediment discharge during colder intervals and decreased river discharge/increased coastal erosion during warmer periods. This paleoclimate variability may be driven by variations in solar output and/or shifts in the regional ocean-atmosphere circulation patterns (e.g., the Aleutian Low).

Download or read book A Multi proxy Record of Holocene Paleoenvironmental and Paleoclimate Change at Lake Tokun South central Alaska written by Jonathan Gilbert Griffith and published by . This book was released on 2014 with total page 105 pages. Available in PDF, EPUB and Kindle. Book excerpt: Sediment cores from Lake Tokun were used to reconstruct paleoenvironmental and paleoclimate changes in the Copper River delta area, Alaska. A 4.2-m-long sediment sequence was analyzed for organic matter, chlorophyll-a, magnetic susceptibility, and bulk density. The chronology was based on radiocarbon ages and short-lived isotopes. Distinct changes in the sedimentary succession record major paleoenvironmental changes during the Holocene. Prior to 8.8 ka, Lake Tokun received meltwater from the Martin River Glacier at a time when sea level had transgressed at least 6 km inland of the present shoreline likely due to isostatic depression upon deglaciation. From 8.8 to 0.7 ka, Lake Tokun was a shallow lake receiving sporadic pulses of rock flour when Martin River overtopped its channels. At 735-1215 AD, rock flour deposited in Lake Tokun represents an aggrading outwash plain as the Martin River Glacier expanded and then deposited its terminal moraine. The proximal end of the associated outwash plain dammed Lake Tokun, deepening the lake and enhancing sediment deposition. The lake attained its present depth about 1215 AD and rock flour has not reentered the lake since then. The uppermost sedimentary unit (150 cm thick) was analyzed at 0.5 cm resolution (average of 3 year per sample) using VNIR reflectance spectroscopy to infer the concentration of chlorophyll-a (chl-a). Instrumental weather data from Cordova (1917 to 2009) show a strong inverse correlation (r2 = 0.49; p = 0.03) between August precipitation and sedimentary chl-a content in Lake Tokun. Storms beginning in the late summer and persisting through the fall are important in controlling peak discharges and the subsequent transport of allochthonous material into Lake Tokun. Winter (DJF) temperature is also inversely correlated with chl-a content (r2 = 0.33; p = 0.04), indicating that warm winters, which tend to be wet, also lead to enhanced runoff, which carries mineral matter that dilutes the chl-a content of the lake sediment. Decreased chl-a values suggest increased runoff during the early to middle Little Ice Age (LIA; 1215-1650 AD). Increased chl-a values during the late LIA (1650-1850 AD) are suggestive of decreased runoff. This study demonstrates that multi-proxy analysis of lake sediments is an effective method for inferring past paleoenvironmental and paleoclimate change.

Download or read book Late Holocene Environmental Change Across the Canadian Arctic written by Camille Tamo and published by . This book was released on 2019 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Lake sediment cores spanning the last 2000 years from four sites across the Canadian Arctic Archipelago (CAA) document the responses of terrestrial and freshwater ecosystems to regional climate variability. Biogenic silica (BSi) records in cores from Banks Island, NWT (Lake B503; 72.3245, -123.4036, 84 masl), Bathurst Island, Nunavut (PR01; 75.6497, -99.1144, 30 masl), Prince of Wales Island, Nunavut (SW08; 72.3177, -97.2678, 104 masl), and Ellesmere Island, Nunavut (CV03; 79.9211, -82.9348, 363 masl) were used to examine the relationship between diatom production and climate. A pollen record from Prince of Wales Island provided the first high-resolution July temperature reconstruction for the last 1000 years for the central CAA. Dissolution was evident in three out of the four lakes; core SW08 contained no BSi above detection and cores CV03 and PR01 only contained values above detection in the uppermost sediments, suggesting that the preservation of biogenic silica (BSi) in the sediment is likely influenced by sedimentary carbonates. A BSi sequence from core B503 showed that diatom production was affected by climate changes such as the Medieval Climate Anomaly and the Little Ice Age. The vegetation on southern Prince of Wales Island underwent marked transitions during the Little Ice Age and Medieval Climate Anomaly, which was mainly observed in the proportion of Cyperaceae and Poaceae. The mean July temperature reconstruction showed a long-term cooling from 1080-1915 CE with a sustained cold period from 1800-1915 CE prior to 20th-century warming. A synthesis of paleoclimate records from across the Arctic demonstrated that pollen-based reconstructions record both high and low frequency climate variability, when sampling resolution is sufficient, and can improve regional climate reconstructions.

Download or read book A Correlation of Western Arctic Ocean Sedimentation During the Late Holocene with an Atmospheric Temperature Proxy Record from a Glacial Lake in the Brooks Range Alaska written by Jeffrey Michael Harrison and published by . This book was released on 2013 with total page 112 pages. Available in PDF, EPUB and Kindle. Book excerpt: The delivery of sediment to the Alaskan continental shelf is largely associated with sea-ice drift and wind driven Arctic Ocean circulation patterns that have varied during the Holocene. This study presents a comparison of two high-resolution proxy records from the western Arctic over the past 2,000 years. To provide variations of sedimentation patterns in the Arctic Ocean (e.g., sea-ice transport, density flows, ocean currents), the grain size distributions were measured in a piston core (HLY02-04 JPC16) from the eastern Chukchi Sea at a higher resolution than previously reported. A revised JPC16 age-depth model was used in this analysis (Darby et al., 2012). The sediment core, collected on the east flank of Barrow Canyon (72.1555°N, 153.50817°W, ~1300 mwd), preserves a record of local variations in sedimentation mechanisms in the Chukchi-Beaufort Seas. A Varimax-rotated Principle Component Analysis (VPCA) was conducted on the grain-size data from JPC16. We inferred three principal components (PCs) of sediment deposition at the core site related to anchor ice, nepheloid flows, and suspension freezing based on variations in grain-size distributions from a Malvern Mastersizer sediment analysis. This interpretation is consistent with previous downcore analysis by Darby et al. (2009) on multiple western Arctic Ocean cores. A fourth, much less significant mode, is related to resuspension and deposition connected to intermittent suspension and ocean currents. While all VPCA modes showed increased variability since 200 yr BP, components related to sea-ice showed the highest positive loadings between 2000-1300 cal yr BP. The most likely cause of positive anomalies observed in these two components is associated with increased ice melt and settling of sediment, or a greater influx of sea-ice into Alaskan waters. It can therefore be argued that oscillations in these modes are closely related to changes in atmospheric temperature or oscillations in the atmosphere-ocean circulation patterns, primarily the Arctic Oscillation. The high-resolution record of sediment deposition in the Arctic Ocean allowed for direct correlation with an atmospheric climate proxy as recorded by varve thickness measurements retrieved from a glacial lake located in the Brooks Range (Bird et al., 2009). The time interval investigated here shows a significant relationship between marine sea-ice sedimentation and atmospheric temperature (r = 0.7). This analysis suggests that warmer atmospheric intervals are likely related to greater sea-ice melt and sedimentation of entrained sediments.

Download or read book Holocene Paleo Environmental Reconstruction in Central Tibetan Plateau Inferred from a Lacustrine Sediment Record written by Man-Ching Cheung and published by Open Dissertation Press. This book was released on 2017-01-27 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: This dissertation, "Holocene Paleo-environmental Reconstruction in Central Tibetan Plateau Inferred From a Lacustrine Sediment Record" by Man-ching, Cheung, 張敏青, was obtained from The University of Hong Kong (Pokfulam, Hong Kong) and is being sold pursuant to Creative Commons: Attribution 3.0 Hong Kong License. The content of this dissertation has not been altered in any way. We have altered the formatting in order to facilitate the ease of printing and reading of the dissertation. All rights not granted by the above license are retained by the author. Abstract: Previous studies on reconstructing the paleoclimate on the Tibetan Plateauare commonly based on a single proxy, and have thus limited the usage of their results. Therefore this study was designed firstly to evaluate the applicability of organic carbon isotopes from modern plants in the Tibetan Plateau as a paleo-environmental proxy, and secondly to apply palynology, organic geochemistry and biomarkers to the reconstructions ofpaleo-environmental history of central Tibet. The new, comprehensive records reveal the history of regional precipitation, temperature and vegetation change in responding to Holocene climatic changesin the region. Organic carbon isotope (δ13C) and lipid n-alkanes were measured from plant samples collected from various altitudes and environments across the study area. The δ13C results indicate the importance of availability of water to C3/C4 herbs distribution in this alpine region. The molecular distributions of trees, shrubs, herbs and submergent macrophytes show distinctive features in a number of indices. These indices are considered to be useful for paleo-environmental reconstructions. A 5.8m-long peat core, which were dated back to 95,000 yr BP was obtained from a river valley at an altitude of 4300 m above sea level. The pollen data from the core reveals a sparse herbaceous vegetation in the catchment area during early Holocene, suggesting non-favourable conditions for vegetation growth. The environment became wetter during the early mid-Holocene around 8100-7000 cal. yr BP, and since then a sedge-dominated wetland habitat was developed. This vegetation changed little until about 1100 cal. yr BP; from which an increase of drought-tolerant herbs was indicated by the pollen data, implying a slightly drier condition of the latter part of late Holocene. The pollen record suggests that the optimum precipitation in central Tibet occurred later and lasted longer than that in the East Asian Monsoon region. Finally, bulk sample carbon geochemistry(TOC, δ13C) as well as the biomarkers analysis on n-alkanes and GDGTs as paleo-limnology and paleo-temperature indicators respectively were applied to the core. Before 1500 cal. yr BP, the wetland was dominated by both vascular herbs as suggested by the δ13Cdata and aquatic floating/submerged macrophytes as indicated by mid-chain n-alkanes. The relative proportion of the two sources of organic matter input varied slightly, and vascular herbs increased in two episodes(5400 -4700 and 2800 -2300 cal. yr BP) indicated by the increase of long-chain n-alkanes (>n-C25). Considering of the soil water content variation by the ratios of iGDGTs to bGDGTs, the change between the two plant communities could to be caused by different lake status. GDGTs paleo-temperature reconstruction indicates a warm period from 6700 to 6000 cal. yr BP, which is believed to be the warmest and highly humid in central Tibetan region. Then the temperature decreased towards the late Holocene, consistent with other paleo climate records across the Plateau region, i.e. largely controlled by change of solar insolation. Along the decreasing trend, a warm episode at about 1200 yr BP that inferred from MAAT was suggested corresponding with the North Hemisphere Medieval Warming. DOI: 10.5353/th_b5270537 Subjects: Paleoecology - Tibet, Plateau of Paleoecology - Holocene

Download or read book High Resolution Geochemical XRF Data from Elk Lake Minnesota written by Robert Allen Rush and published by . This book was released on 2010 with total page 138 pages. Available in PDF, EPUB and Kindle. Book excerpt:

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 Late Holocene Climate Variability as Preserved in High resolution Estuarine and Lacustrine Sediment Archives written by Jeremiah Bradford Hubeny and published by . This book was released on 2006 with total page 478 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Reconstruction of a High Resolution Holocene and Late Glacial Record of Atmospheric CO2 Concentration from Stable Carbon Isotopes in Peat written by Regina Ann Figge and published by . This book was released on 1996 with total page 364 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Holocene Proxy climate Data from the Canadian Arctic written by Lynn Ovenden and published by Energy Mines and Resources Canada. This book was released on 1988 with total page 20 pages. Available in PDF, EPUB and Kindle. Book excerpt: Quaternary studies by the Geological Survey of Canada (GSC) have produced data on the biological, geomorphological, and glacial history of Canada. Some of the climatically significant discoveries have not become general knowledge, as indicated by their omission from literature reviews and bibliographies. This review of GSC reports and publications is an attempt to make some of its proxy-climate data more accessible. In this review, only data of Holocene age from the Northwest Territories and Yukon Territory are considered, using such phenomena indicative of climate change as vascular plant range extensions, eolian deposition, peat accumulation, and thermokarst and thaw. The report includes a compilation of these data types, comments on their relationship to climate, and concludes with some general thoughts on the nature of proxy-climate data.

Download or read book Late Holocene Climate Variability from Northern Gulf of Mexico Sediments written by Julie N. Richey and published by . This book was released on 2010 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: ABSTRACT: Accurate reconstruction of natural climate variability over the past millennium is critical for predicting responses to future climate change. In order to improve on current understanding of climate variability in the sub-tropical North Atlantic region over the past millennium, a rigorous study of Gulf of Mexico (GOM) sea surface temperature (SST) variability was conducted using both inorganic (foraminiferal Mg/Ca) and molecular organic (TEX6) geochemical proxies. In addition to generating multiple high-resolution climate records, the uncertainties of the SST proxies are rigorously assessed. There are 3 major research questions addressed: (1) What was the magnitude of GOM SST variability during the past 1,000 years, particularly during large-scale climate events such as the Little Ice Age (LIA) and the Medieval Warm Period (MWP). (2) Is the SST signal reproducible within the same sediment core, among different northern GOM basins, and using different geochemical SST proxies? (3) What are the ecological controls on the paleothermometers used to reconstruct SST variability in the GOM? Can differences in the ecology (i.e. seasonal distribution, depth habitat, etc.) of distinct paleothermometers be exploited to gain insight into changes in upper water column structure or seasonality in the GOM during the LIA and MWP? The major findings include: (1) The magnitude of temperature variability in the GOM over the past millennium is much larger than that estimated from Northern Hemisphere temperature reconstructions. The MWP (1400-900 yrs BP) was characterized by SSTs in the GOM that were similar to the modern SST, while the LIA (400-150 yrs BP) was marked by a series of multidecadal intervals that were 2-2.5°C cooler than modern. (2) This LIA cooling was replicated in the Mg/Ca-SST records from three different well-dated northern GOM basins (Pigmy, Garrison and Fisk Basins), as well as in two different geochemical proxies. (3) It is determined that foraminiferal test size has a significant effect on shell geochemistry. Using core-top calibration, discrepancies in the seasonal/depth habitats between different planktonic Foraminifera, and between Foraminifera and Crenarchaeota are inferred. Downcore differences are used to make inferences about changes in GOM mixed layer depth and seasonality over the past millennium.

Download or read book Late Holocene Oxygen Isotope Record of Hydroclimate Variability in Nicaragua from Lake Asososca written by Stephen Perdziola and published by . This book was released on 2018 with total page 115 pages. Available in PDF, EPUB and Kindle. Book excerpt: Investigation of hydroclimate requires a higher level of spatial and temporal detail than what currently exists for Central America. High resolution lake sediment archives are critical to gaining a more complete understanding of late Holocene climate variability in the region. The climate of Central America is influenced by both tropical Atlantic and Pacific Ocean-atmosphere processes. A better understanding of how these processes have impacted regional hydroclimate is important as it will enable more accurate predictions of future climate changes associated with shifting conditions in a drought sensitive region. Here a 1,000-year carbonate oxygen isotope record is presented from Lake Asososca, located in western Nicaragua. In this record, high delta 18O values indicate drier conditions, while lower ?18O values indicate drier conditions. My data indicate wet conditions at the start of the Medieval Climate Anomaly (MCA) and a trend towards drier conditions until A.D. 1200. The transitional period between the MCA and the Little Ice Age (LIA) from A.D. 1200 - 1400 experienced a shift towards wetter conditions. The LIA from A.D. 1400 -- 1850 was a period of variable conditions. My record indicates a shift from wet to dry conditions from A.D. 1400 - 1600. A pronounced period of wetter conditions occurred from A.D. 1650-1700 during the Maunder Minimum solar event. From A.D 1700 -- 1800 the record indicates variable conditions that alternated between shifts towards dry and wet. After the LIA, the record indicates a trend towards drier conditions. The El Nino Southern Oscillation (ENSO), the North American Oscillation (NAO), and the Atlantic Multidecadal Oscillation (AMO), were often temporally correlated with the Lake Asososca record and suggest that these modes have impacted regional hydroclimate over the late Holocene. Correspondence between the Lake Asososca record and solar variability highlight a potential linkage. Climate models indicate that the Atlantic Meridional Overturning Circulation responds to changes in solar variability and can have impacts on Atlantic SSTs, and therefore may be provide a mechanism to amplify changes in solar variability to Central American hydroclimate. Comparison of the Lake Asososca delta18O record to regional hydroclimate proxies across show little correspondence over the past millennium. While some similarities exist between the Lake Asososca record and other regional proxies, the lack of a coherent hydroclimate signal over the late Holocene suggests temporally and spatially variability hydroclimate shifts. More hydroclimate reconstructions and modelling studies need to be performed in order to fully resolve hydroclimate variability in Central America over the past millennium. This record adds to the network of regional paleoclimate reconstructions in Central America and indicates that modes of variability in both the Atlantic and Pacific Ocean basins have impacted regional hydroclimate over the past millennium.

Download or read book High resolution Reconstruction of Glacial to Holocene Climate Variability from Sediments of the Cariaco Basin and Arabian Sea written by Gaudenz Deplazes and published by . This book was released on 2012 with total page 205 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Reconstructing High resolution Paleoclimate for Portions of the Last 250 000 Years from Cave of the Mounds Speleothems written by Cameron Jean Batchelor and published by . This book was released on 2022 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: The Pleistocene period was a time of Earth's History marked by 100-kyr paced glacial-interglacial cycles and dominated by the influence of polar glaciation that stimulated Earth system feedbacks. Climate archives that grew during the Pleistocene thus provide the opportunity to explore past climate variability during a time of known global forcings and when distinct climate transitions occurred. Other than ice cores - one of the most robust terrestrial climate archives used by the paleoclimate community - speleothem-based paleoclimate reconstructions provide some of the highest-resolution continental climate records. This is due to their ability to be precisely dated, relatively continuous growth potential that is uninterrupted by surficial erosional processes, and because they form within carbonate (karst) rocks which are located in a variety of locations from the low- to high-latitudes, and thus not restricted to one geographic location. For this dissertation, I use a collection of speleothem samples from a southwestern Wisconsin cave, Cave of the Mounds, to reconstruct paleoclimate for portions of the last 250,000 years. This dissertation seeks to (1) resolve high-resolution oxygen isotope (Îþ18O) records representative of mid-continental North America during former glacial and interglacial periods through the use of specialized imaging and mass spectrometry techniques, and (2) provide data that will characterize climate variability and regional climate response to distinct global forcings in a relatively data-sparse region of the world. Except for Chapter 1, which focuses on U-Th dating methods of speleothems, all chapters of this dissertation use specialized imaging (confocal laser fluorescent microscopy, CLFM) and mass spectrometry (secondary ion mass spectrometer, SIMS) techniques to produce high-resolution Îþ18O records during different time periods of the last 250,000 years. Each chapter focuses on a different time period of the last 250,000 years, specifically the Last Glacial Period (70-50 ka, respectively; Chapter 2), the Late Holocene (3-2 ka; Chapter 3), the Last Interglacial Period (122-118 ka, respectively; Chapter 4), and the Penultimate Interglacial Period (230-218 ka, respectively; Chapter 5).

Download or read book Holocene Ice Sheet Dynamics and Detrital Provenance Shifts Along the West Greenland Margin written by Lina Madaj and published by . This book was released on 2021 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Due to the effect of Arctic Amplification the Arctic is currently warming at least twice as fast as the rest of the planet. Seasonal sea-ice extent has been alarmingly declining in the past decade. Glaciers and ice caps along the Greenland coast and in the Canadian Arctic have been losing mass on an accelerated rate during the past century. As the global climate system is a complex system connecting different regions via atmospheric transport, changes in Arctic climate patterns are affecting the climate and weather conditions in the lower latitudes. The Greenland Ice Sheet as well as glaciers and ice caps in the Canadian Arctic are the largest freshwater storages on the northern hemisphere and expected to be among the highest contributors to global sea level rise. Freshwater input through meltwater discharge is not only affecting sea level rise but further influencing deep water formation in the Labrador Sea and the subpolar North Atlantic and hence global ocean circulation and climate patterns. To be able to sufficiently predict future developments of the Greenland Ice Sheet with respect to mass loss and resulting impacts on the global climate, data from past climate and Greenland Ice Sheet extents are crucially important. The Holocene spanning the last period of the deglaciation after the Last Glacial Maximum culminating in the Holocene Thermal Maximum when atmospheric temperatures were warmer and glacier and ice-sheet extent smaller than today represents the closest analogue to current atmospheric warming and Greenland Ice Sheet mass loss. The wide west Greenland shelf of Baffin Bay and Labrador Sea hosts thick marine sediments archiving around ten thousand years of this past climate and ice-sheet history. Siliciclastic detrital material discharged into Baffin Bay and the Labrador Sea via meltwater and erosion can be separated from those sedimentary archives and traced back to its source region. Radiogenic isotopes (Sr, Nd, Pb) label the source regions of those sediments by fingerprinting the isotopic composition of the prevailing bedrock. Hence, they can be used as reliable provenance tracers. Retreating land-ice masses expose bedrock that before was not subject to erosion, influencing the isotopic signatures delivered into the surrounding ocean. Based on this theory, radiogenic isotopes can record changes in siliciclastic detrital sediment provenance and hence, indirectly trace ice-sheet dynamics. The overall aim of this thesis work is to reconstruct changes in detrital sediment provenance along the west Greenland shelf to gain new insights into Holocene Greenland Ice Sheet dynamics and ocean current-induced sediment transport. Sedimentary archives from three main research areas (eastern Labrador Sea, northeastern Baffin Bay, and Kane Basin, central Nares Strait) record obvious shifts in sediment provenance throughout the Holocene. Those shifts coincide with major regional climatic changes in the research area. Generally, all records reveal the local bedrock as the main source region of detrital material and distal-sourced material transported along the coast via the West Greenland Current as a secondary source. Although the proportion of distal sourced material appears to be small, changes in West Greenland Current strength have been recorded in the isotopic composition. In southwestern Greenland and the Labrador Sea radiogenic isotope records reveal a shift towards a higher proportion of the local Archean Block in the late Holocene caused by Neoglacial ice advance and a reduction in West Greenland Current speed delivering less material from southern most Greenland. Farther north in the Upernavik region, midwest Greenland coast, the isotopic composition marks a change with the transition from early to mid Holocene caused by increased West Greenland Current strength and the opening of Vaigat Strait which enabled erosion and transport of freshly exposed basalts from the Disko Bay area due to ice-sheet retreat. This basalt input is, however, not transported all the way to northernmost Melville Bay (northern Baffin Bay) where the detrital sediment composition is clearly dominated by contribution of the local Committee-Melville Belt without any significant provenance changes throughout the Holocene. Farthest north, the sedimentary record from Kane Basin records provenance shifts that confirm the opening of Nares Strait around 8.3 ka BP. This event is followed by an increased delivery of carbonate-rich detrital sediments from northern Ellesmere Island due to the newly established gateway of Arctic Ocean water transporting sediments from further north to the core location. Additionally determined mineralogical composition of the sedimentary records along the west Greenland coast supports the interpretation drawn from the radiogenic isotopic composition. Furthermore, it points out the additional value of radiogenic isotopes through variations only visible in isotopic composition but not in the mineralogical composition. Further comparison to other studies from the region based on different tracers confirms the reliability and sufficient application of radiogenic isotopes in provenance studies as well as the advantage of multi-proxy approaches in paleoclimatological studies. Overall, this study highlights the advantages and reliability of radiogenic isotopes in provenance studies with regards to reconstructions of ice-sheet dynamics. The combination of the three isotopic systems (Sr, Nd, Pb) enables source region determination with a higher probability compensating for overlapping signatures within individual isotopic systems. The transect of sedimentary records along the west Greenland coast identifies clearly distinguishable isotopic ranges for the different Greenland bedrock terrains, qualifying this approach for further high-resolution investigation in past Greenland Ice Sheet development.

Download or read book A Late Holocene Earthquake and Paleoclimate Record from Ozette Lake Washington written by Lillian Sarah Slajus and published by . This book was released on 2020 with total page 58 pages. Available in PDF, EPUB and Kindle. Book excerpt: