61 research outputs found
Experiential Learning on an Urban Farm: Hands-on pedagogy for deep learning, sustainability, food security, and social justice
No full textJoin CSU Dominguez Hills faculty Alfredo Carlos (Labor Studies) and Jenney Hall (Interdisciplinary Studies) for a couple of minutes with the university’s urban farm and current students. Here the learning is literally hands-on: students leave with a firsthand understanding of the basic principles of agriculture, soil, and sustainability, while better able to address the environmental degradation and food insecurity that beset city dwellers, all without leaving home
(Table 2) Ba content and stable isotope composition of Neogloboquadrina pachyderma sinistral of sediment core 94B17
No full text(Table 2) Ba content and stable isotope composition of Neogloboquadrina pachyderma sinistral of sediment core 94B1
(Table 1) Replicate Analyses of Ba/Ca in Neogloboquadrina pachyderma sinistra of sediment core 94B17
No full textData from Intensity Ratios (IR) are from Rosenthal et al. (1999)
Barium and lithium in foraminifera: glacial-interglacial changes in the North Atlantic
No full textThe trace element content of calcareous foraminifera provides a powerful tool to the study of glacial-interglacial changes in the physical and chemical properties of the ocean. Foraminifera incorporate barium in direct proportion to its concentration in seawater. Using barium as a nutrient proxy, Ba/Ca in benthic Planulina wuellerstorfi is used to reconstruct changes in thermocline ventilation and mid-depth circulation in the North Atlantic during the last glacial and deglacial time. Rivers are concentrated in barium compared to surface seawater. Therefore, barium in planktonic Neogloboquadrina pachyderma is used to identify deglacial meltwater in the Arctic Ocean. Foraminiferal Li/Ca was analyzed to elucidate factors influencing incorporation behavior, including interspecies differences, temperature, pressure, dissolution, and shell mass. To investigate the use of lithium isotopes as a proxy for paleo-seawater chemistry, d6Li was determined in planktonic Orbulina universa. During the last glacial maximum, nutrients in the thermocline and the intermediate water of the North Atlantic was lower than today due to increased ventilation and the presence of nutrient-depleted Glacial North Atlantic Intermediate Water (GNAIW). During deglacial time, GNAIW was replaced by southern component water, resulting in an enrichment of nutrients in the mid-depth Atlantic water. Increased Ba/Ca in the surface Arctic Ocean indicates an increase in meltwater discharge between 12.4 and 11.3 14C ka BP. This may have triggered an increase in the export of freshwater to the North Atlantic, contributing to a shutdown in GNAIW production, and leading to the onset of the Younger Dryas. A second meltwater event at 9.4 14C ka BP may be the result of glacial Lake Agassiz draining through the Clearwater spillway to the Mackenzie River. Foraminiferal Li/Ca shows systematic glacial-interglacial variation coincident with d18O. The incorporation behavior of lithium in foraminifera does not appear to be dominated by changes in temperature, pressure, dissolution, or shell mass, but is potentially controlled by changes in growth conditions, including calcification rate. Preliminary work indicates that d6Li remained constant throughout the Holocene and the last glacial maximum at 30.5 ± 1.1‰. Further developmental studies are necessary to fully engage lithium isotopes as a tracer of seawater composition
The influence of tropical Pacific weather on U.S. heat waves
No full textLong-range predictions of heat waves offer little improvement over climatology despite the continuing improvements of weather forecast models. Tropical variability in weather at sub-seasonal timescales is well-understood to influence weather in the Extratropics, particularly in the winter. For this reason, it is considered a potential source of sub-seasonal predictability of weather. However, much less is understood about the tropical-extratropical connection in the summer. we show that a major climate oscillation in the tropical west pacific is significantly correlated to U.S. heat waves with long lead times, suggesting potential for use in seasonal prediction of these events.Great Minds in Research - Honorable Mention
Ba/Ca ratios in Neogloboquadrina pachyderma of sedimet core 94B17
No full textDown-core samples of the planktonic foraminifer Neogloboquadrina pachyderma sinistral from the Mendeleyev Ridge in the western Arctic Ocean have been analyzed for Ba/Ca and d18O. The apparent distribution coefficient for N. pachyderma sin. is estimated at DBa = 0.22 ± 0.02. A meltwater event is identified at around 11.8 14C kyr BP and is coincident with elevated Ba/Ca ratios. The barium enrichment is believed to be the result of enhanced weathering and erosion following glaciation. Additionally, barium may have desorbed from shelf sediments as sea level rose. Changes in Ba/Ca correlate with the retreat of the Laurentide Ice Sheet and the evolution of the Mackenzie River drainage basin. Therefore maximum Ba/Ca in Arctic surface waters at 11.8 ka may be indicative of an increase in the export of freshwater from the Arctic to the North Atlantic, potentially contributing to the onset of the Younger Dryas. This work suggests that Ba/Ca in planktonic foraminifera may be a useful indicator of the timing and processes associated with deglaciation
(Table 2) Ba/Ca ratios of Cibicides wuellerstorfi and Orbulina universa from Bahaman sediment cores
No full textThis geochemical investigation utilizes Ba/Ca in the benthic foraminifer Cibicides wuellerstorfi from cores taken from the Bahama Banks and the Caribbean Sea to reconstruct changes in basal thermocline ventilation (800–1000 m) and middepth thermohaline circulation (1000–2000 m) in the western North Atlantic during the last glacial period, focusing on the deglacial transition. Previous studies show that an increase in ventilation of the North Atlantic subtropical gyre during the Last Glacial Maximum (LGM) caused a 30–60% decrease in labile nutrients within the thermocline layer. Using foraminiferal Ba/Ca as a proxy of refractory nutrients, increased ventilation during the LGM produced a depletion of less than 20% compared to Holocene values. Following glaciation, the production of Glacial North Atlantic Intermediate Water (GNAIW) shut down owing to the presence of meltwater in the surface ocean, which resulted in a decrease in ventilation, as seen by an enrichment of barium in the basal thermocline. GNAIW was subsequently replaced by barium-rich southern component water in the middepth western North Atlantic. Foraminiferal Ba/Ca data suggest a 38% contribution from southern component water to a depth as shallow as 1475 m and a 14% contribution at 1123 m during deglaciation
Ba/Ca in benthic foraminifera: Thermocline and middepth circulation in the North Atlantic during the last glaciation
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