Physical Sciences and Mathematics Commons^™

Environmental History Of A Closed-Basin Lake In The Us Great Plains: Diatom Response To Variations In Groundwater Flow Regimes Over The Last 8500 Cal. Yr Bp, William O. Hobbs, Sherilyn C. Fritz, Jeffery R. Stone, Joseph J. Donovan, Eric C. Grimm, James E. Almendinger

Department of Earth and Atmospheric Sciences: Faculty Publications

Sediment records from closed-basin lakes in the Northern Great Plains (NGP) of North America have contributed significantly to our understanding of regional paleoclimatology. A high-resolution (near decadal) fossil diatom record from Kettle Lake, ND, USA that spans the last 8500 cal. yr BP is interpreted in concert with percent abundance of aragonite in the sediment as an independent proxy of groundwater flow to the lake (and thus lake water level). Kettle Lake has been relatively fresh for the majority of the Holocene, likely because of the coarse substrata and a strong connection to the underlying aquifer. Interpretation of diatom assemblages …

Late Pleistocene Climate And Proboscidean Paleoecology In North America: Insights From Stable Isotope Compositions Of Skeletal Remains, Jessica Z. Metcalfe

Electronic Thesis and Dissertation Repository

This thesis uses the carbon, nitrogen, and oxygen isotope compositions of mammoth (Mammuthus) and mastodon (Mammut) skeletal remains to reconstruct paleoclimate and paleoecology in Late Pleistocene North America. Analytical methods, sampling strategies, environmental adaptations and seasonal behaviors of proboscideans were investigated.

Reliable and reproducible results are crucial for a study of this nature. A persistent methodological problem in the isotope analysis of structural carbonate in bioapatite was solved by reacting bioapatite under “sealed vessel” conditions.

Growth rate determinations are critical for designing sampling strategies and interpreting results. Histological and isotopic measurements demonstrated variations in enamel growth …

Late Pleistocene Paleohydrography And Diatom Paleoecology Of The Central Basin Of Lake Malawi, Africa, Jeffery R. Stone, Karlyn S. Westover, Andrew S. Cohen

Department of Earth and Atmospheric Sciences: Faculty Publications

Analysis of sedimentary diatom assemblages (10 to 144 ka) form the basis for a detailed reconstruction of the paleohy­drography and diatom paleoecology of Lake Malawi. Lake-level fluctuations on the order of hundreds of meters were in­ferred from dramatic changes in the fossil and sedimentary archives. Many of the fossil diatom assemblages we observed have no analog in modern Lake Malawi. Cyclotelloid diatom species are a major component of fossil assemblages prior to 35 ka, but are not found in significant abundances in the modern diatom communities in Lake Malawi. Salinity- and alkalin­ity-tolerant plankton has not been reported in the modern …

Natural Archives, Changing Climates, Raymond S. Bradley

Raymond S Bradley

Climatic changes have occurred throughout human history, but instrumental measurements do not provide us with a very long perspective on climate variations. In many regions, instrumental records only extend back a century or two. To understand the longer-term variability of the climate system, we rely on natural archives— sediments, ice caps, peat bogs, cave deposits, banded corals and tree rings—in which a record of past changes in climate has been preserved. They are a treasure trove of the climatic and environmental history of the planet and provide information about factors that may have caused the climate to change, such as …

High-Resolution Paleoclimatology, Raymond S. Bradley

Raymond S Bradley

High resolution paleoclimatology involves studies of natural archives as proxies for past climate variations at a temporal scale that is comparable to that of instrumental data. In practice, this generally means annually resolved records, from tree rings, ice cores, banded corals, laminated speleothems and varved sediments. New analytical techniques offer many unexplored avenues of research in high resolution paleoclimatology. However, critical issues involving accuracy of the chronology, reproducibility of the record, frequency response to forcing and other factors, and calibration of the proxies remain. Studies of proxies at high resolution provide opportunities to examine the frequency and magnitude of extreme …

A Synthesis Of The Long-Term Paleoclimatic Evolution Of The Arctic, Matthew O'Regan, Christopher J. Williams, Karen E. Frey, Martin Jakobsson

Geography

Since the Arctic Ocean began forming in the Early Cretaceous 112-140 million years ago, the Arctic region has undergone profound oceanographic and paleoclimatic changes. It has evolved from a warm epicontinental sea to its modern state as a cold isolated ocean with extensive perennial sea ice cover. Our understanding of the long-term paleoclimate evolution of the Arctic remains fragmentary but has advanced dramatically in the past decade through analysis of new marine and terrestrial records, supplemented by important insights from paleoclimate models. Improved understanding of how these observations fit into the long-term evolution of the global climate system requires additional …

Paleoclimate From Corals, Helen V. Mcgregor

Faculty of Science - Papers (Archive)

Ocean- atmosphere interactions in the tropics have farreaching conscqucnccs for climate variabi lity across the globe. The tropics drive heat transfer to the poles, and tropical inter-annual oscillations such as the El Nino-Southern Oscillation (ENSO) and Indian Ocean dipole (IOD), via atmospheric tcleconncctions, affcct rain rail patterns and climate conditions in arcas far bcyond the tropics (Ropelewski and Halpert, 1987), causing major socioeconomic impacts. Monitoring eIT0l1s have focused on improving obscrvations and undcrstanding of tropical climate variability, with the view to refining modeling or the tropical oceans and atmosphere. Despite these efforts, most instrumcntal records span only the past few …

Declining Atmospheric Co2 During The Late Middle Eocene Climate Transition, Gabriela Doria, Dana Royer, Alexander Wolfe, Andrew Fox, J. Westgate, David Beerling

Gabriela Doria

No abstract provided.