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Gdgt Distribution In A Stratified Lake And Implications For The Application Of Tex86 In Paleoenvironmental Reconstructions, Zhaohui Zhang, Rienk Smittenberg, Raymond S. Bradley
Gdgt Distribution In A Stratified Lake And Implications For The Application Of Tex86 In Paleoenvironmental Reconstructions, Zhaohui Zhang, Rienk Smittenberg, Raymond S. Bradley
Geosciences Department Faculty Publication Series
We investigated the relationship between distributions of GDGTs, GDGT-based proxies and environmental factors in a stratified lake in northwestern Norway. More than 90% of isoGDGTs were produced at the bottom of the oxycline, indicating a predominance of ammonia-oxidizing Group I.1a of Thaumarchaeota, supported by high crenarchaeol/caldarchaeol ratios. Dissolved oxygen content, rather than temperature, exercised a primary control on TEX86 values. In spite of low BIT value in surface sediment, the reconstructed lake surface temperature was “cold” biased. MBT values in streams and lake surface water were significantly smaller than those in the catchment soil, suggesting in situ production of …
Windblown Pliocene Diatoms And East Antarctic Ice Sheet Retreat, Reed P. Scherer, Robert M. Deconto, David Pollard, Richard B. Alley
Windblown Pliocene Diatoms And East Antarctic Ice Sheet Retreat, Reed P. Scherer, Robert M. Deconto, David Pollard, Richard B. Alley
Geosciences Department Faculty Publication Series
Marine diatoms in tillites along the Transantarctic Mountains (TAMs) have been used to suggest a diminished East Antarctic Ice Sheet (EAIS) during Pliocene warm periods. Updated ice-sheet modelling shows significant Pliocene EAIS retreat, creating marine embayments into the Wilkes and Aurora basins that were conducive to high diatom productivity and rapid accumulation of diatomaceous sediments. Here we show that subsequent isostatic uplift exposed accumulated unconsolidated marine deposits to wind erosion. We report new atmospheric modelling utilizing Pliocene climate and derived Antarctic landscapes indicating that prevailing mid-altitude winds transported diatoms towards the TAMs, dominantly from extensive emerged coastal deposits of the …
Use Of Distributed Temperature Sensing Technology To Characterize Fire Behavior, Douglas Cram, Christine E. Hatch, Scott Tyler, Carlos Ochoa
Use Of Distributed Temperature Sensing Technology To Characterize Fire Behavior, Douglas Cram, Christine E. Hatch, Scott Tyler, Carlos Ochoa
Geosciences Department Faculty Publication Series
We evaluated the potential of a fiber optic cable connected to distributed temperature sensing (DTS) technology to withstand wildland fire conditions and quantify fire behavior parameters. We used a custom-made ‘fire cable’ consisting of three optical fibers coated with three different materials—acrylate, copper and polyimide. The 150-m cable was deployed in grasslands and burned in three prescribed fires. The DTS system recorded fire cable output every three seconds and integrated temperatures every 50.6 cm. Results indicated the fire cable was physically capable of withstanding repeated rugged use. Fiber coating materials withstood temperatures up to 422 °C. Changes in fiber attenuation …
Bering Sea Surface Water Conditions During Marine Isotope Stages 12 To 10 At Navarin Canyon (Iodp Site U1345), Beth E. Caissie, Julie Brigham-Grette, Mea S. Cook, Elena Colmenero-Hidalgo
Bering Sea Surface Water Conditions During Marine Isotope Stages 12 To 10 At Navarin Canyon (Iodp Site U1345), Beth E. Caissie, Julie Brigham-Grette, Mea S. Cook, Elena Colmenero-Hidalgo
Geosciences Department Faculty Publication Series
Records of past warm periods are essential for understanding interglacial climate system dynamics. Marine Isotope Stage 11 occurred from 425 to 394 ka, when global ice volume was the lowest, sea level was the highest, and terrestrial temperatures were the warmest of the last 500 kyr. Because of its extreme character, this interval has been considered an analog for the next century of climate change. The Bering Sea is ideally situated to record how opening or closing of the Pacific–Arctic Ocean gateway (Bering Strait) impacted primary productivity, sea ice, and sediment transport in the past; however, little is known about …
Large Ensemble Modeling Of The Last Deglacial Retreat Of The West Antarctic Ice Sheet: Comparison Of Simple And Advanced Statistical Techniques, David Pollard, Won Chang, Murali Haran, Patrick Applegate, Robert Deconto
Large Ensemble Modeling Of The Last Deglacial Retreat Of The West Antarctic Ice Sheet: Comparison Of Simple And Advanced Statistical Techniques, David Pollard, Won Chang, Murali Haran, Patrick Applegate, Robert Deconto
Geosciences Department Faculty Publication Series
A 3-D hybrid ice-sheet model is applied to the last deglacial retreat of the West Antarctic Ice Sheet over the last ∼ 20 000 yr. A large ensemble of 625 model runs is used to calibrate the model to modern and geologic data, including reconstructed grounding lines, relative sea-level records, elevation–age data and uplift rates, with an aggregate score computed for each run that measures overall model–data misfit. Two types of statistical methods are used to analyze the large-ensemble results: simple averaging weighted by the aggregate score, and more advanced Bayesian techniques involving Gaussian process-based emulation and calibration, and Markov …