Geochemical and mineralogical evidence for Sahara and Sahel dust additions to Quaternary soils on Lanzarote,eastern Canary Islands,Spain   总被引：1，自引：0，他引：1  

Daniel R. Muhs  James Budahn  Gary Skipp  Joseph M. Prospero  DeAnna Patterson  E. Arthur Bettis III 《地学学报》2010,22(6):399-410

Africa is the most important source of dust in the world today, and dust storms are frequent on the nearby Canary Islands. Previous workers have inferred that the Sahara is the most important source of dust to Canary Islands soils, with little contribution from the Sahel region. Soils overlying a late Quaternary basalt flow on Lanzarote, Canary Islands, contain, in addition to volcanic minerals, quartz and mica, exotic to the island’s bedrock. Kaolinite in the soils also likely has an exotic origin. Trace‐element geochemistry shows that the soils are derived from varying proportions of locally derived basalt and African dust. Major‐element geochemistry, clay mineralogy and interpretation of satellite imagery suggest that dust additions to the Canary Islands come not only from the Sahara Desert, but also from the Sahel region.  相似文献   

A portable extruder for accurate and precise high-resolution subsampling of unconsolidated sediment cores     

Patterson  R. Timothy  Nasser  Nawaf A.  Tremblay  Steven  Galloway  Jennifer M. 《Journal of Paleolimnology》2022,67(2):183-189

Journal of Paleolimnology - We developed a portable extruder for precise and accurate high-resolution subsampling of unconsolidated sediment cores. This extruder is capable of producing subsamples...  相似文献   

The non-radially pulsating primary of the cataclysmic variable GW Librae     

L. van Zyl  B. Warner  D. O'Donoghue  C. Hellier  P. Woudt  D. Sullivan  J. Pritchard  J. Kemp  J. Patterson  W. Welsh  J. Casares  T. Shahbaz  F. van der Hooft  S. Vennes 《Monthly notices of the Royal Astronomical Society》2004,350(1):307-316

  相似文献   

Spectroscopic far ultraviolet observations of transition zone instabilities and their possible role in a pre-flare energy build-up     

G. E. Brueckner  N. P. Patterson  V. E. Scherrer 《Solar physics》1976,47(1):127-146

(1) Highly flare-productive new emerging active regions are characterized by numerous small low-lying loops which frequently show a chaotic pattern. (2) Flare activity in such a region subsides as the chaotic loop structures relax and expand into a bipolar configuration. (3) The transition zone in such an active region is highly unstable as shown by broadened and shifted non-thermal line profiles of medium ionized elements like Si iii, Si iv, C iv, etc. (4) These transition zone instabilities which occur as isolated events in active regions of low flare productivity are often observed prior to flares. (5) Transition zone instabilities can be traced to the footpoints of active loops, and seem to be accompanied by heating of the loop. (6) The loops vary in size and show differing degrees of activity, with the brightest and most compact ones seemingly being in a pre-flare state which results in the catastrophic energy release along the loop during a flare.  相似文献   

Late Holocene lake level dynamics inferred from magnetic susceptibility and stable oxygen isotope data: Lake Elsinore, southern California (USA)     

Matthew E. Kirby  Christopher J. Poulsen  Steve P. Lund  William P. Patterson  Liam Reidy  Douglas E. Hammond 《Journal of Paleolimnology》2004,31(3):275-293

Southern California faces an imminent freshwater shortage. To better assess the future impact of this water crisis, it is essential that we develop continental archives of past hydrological variability. Using four sediment cores from Lake Elsinore in Southern California, we reconstruct late Holocene (3800 calendar years B.P.) hydrological change using a twentieth-century calibrated, proxy methodology. We compared magnetic susceptibility from Lake Elsinore deep basin sediments, lake level from Lake Elsinore, and regional winter precipitation data over the twentieth century to calibrate the late Holocene lake sediment record. The comparison revealed a strong positive, first-order relationship between the three variables. As a working hypothesis, we suggest that periods of greater precipitation produce higher lake levels. Greater precipitation also increases the supply of detritus (i.e., magnetic-rich minerals) from the lake's surrounding drainage basin into the lake environment. As a result, magnetic susceptibility values increase during periods of high lake level. We apply this modern calibration to late Holocene sediments from the lake's littoral zone. As an independent verification of this hypothesis, we analyzed ¹⁸O_(calcite), interpreted as a proxy for variations in the precipitation:evaporation ratio, which reflect first order hydrological variability. The results of this verification support our hypothesis that magnetic susceptibility records regional hydrological change as related to precipitation and lake level. Using both proxy data, we analyzed the past 3800 calendar years of hydrological variability. Our analyses indicate a long period of dry, less variable climate between 3800 and 2000 calendar years B.P. followed by a wet, more variable climate to the present. These results suggest that droughts of greater magnitude and duration than those observed in the modern record have occurred in the recent geological past. This conclusion presents insight to the potential impact of future droughts on the over-populated, water-poor region of Southern California.  相似文献   

Climate simulations of major estuarine watersheds in the Mid-Atlantic region of the US     

R. Najjar  L. Patterson  S. Graham 《Climatic change》2009,95(1-2):139-168

To better understand the implications of anthropogenic climate change for three major Mid-Atlantic estuaries (the Chesapeake Bay, the Delaware Bay, and the Hudson River Estuary), we analyzed the regional output of seven global climate models. The simulation given by the average of the models was generally superior to individual models, which differed dramatically in their ability to simulate twentieth-century climate. The model average had little bias in its mean temperature and precipitation and, except in the Lower Chesapeake Watershed, was able to capture the twentieth-century temperature trend. Weaknesses in the model average were too much seasonality in temperature and precipitation, a shift in precipitation’s summer maximum to spring and winter minimum to fall, interannual variability that was too high in temperature and too low in precipitation, and inability to capture the twentieth-century precipitation increase. There is some evidence that model deficiencies are related to land surface parameterizations. All models warmed over the twenty-first century under the six greenhouse gas scenarios considered, with an increase of 4.7 ± 2.0°C (model mean ± 1 standard deviation) for the A2 scenario (a medium-high emission scenario) over the Chesapeake Bay Watershed by 2070–2099. Precipitation projections had much weaker consensus, with a corresponding increase of 3 ± 12% for the A2 scenario, but in winter there was a more consistent increase of 8 ± 7%. The projected climate averaged over the four best-performing models was significantly cooler and wetter than the projected seven-model-average climate. Precipitation projections were within the range of interannual variability but temperature projections were not. The implied research needs are for improvements in precipitation projections and a better understanding of the impacts of warming on streamflow and estuarine ecology and biogeochemistry.  相似文献   

Late Holocene paleoceanographic evidence of the influence of the Aleutian Low and North Pacific High on circulation in the Seymour-Belize Inlet Complex, British Columbia, Canada     

Natalia Vzquez Riveiros  R. Timothy Patterson 《Quaternary Science Reviews》2009,28(25-26):2833-2850

Foraminiferal and thecamoebian faunas from the Seymour-Belize Inlet Complex (SBIC), a fjord network situated on the mainland coast of British Columbia, were studied to assess climatic cycles and trends impacting the area through the AD 850–AD 2002 interval. Ocean circulation patterns prevalent in the SBIC are strongly linked to precipitation, which is closely linked to the relative strength and position (center of action; COA) of the seasonally developed Aleutian Low (AL) and North Pacific High (NPH) atmospheric circulation gyres.Through interpretation of cluster analysis and ordination methods, a period of weak estuarine circulation was recognized to have impacted the SBIC area between AD 850 and AD 1500. During this time waters in the SBIC were dysoxic to anoxic and the sediment–water interface was comprised of a depauperate foraminiferal fauna consisting of low diversity agglutinated forms. These reduced oxygen conditions came about as a result of diminished precipitation in the SBIC catchment as the COA of the AL progressively migrated westward over time, resulting in greatly reduced estuarine circulation and only infrequent and feeble incursions of well oxygenated open ocean water into the SBIC basin. By AD 1575, following a gradual transition period of 75 years when circulation patterns in the inlet were unstable, very strong estuarine circulation developed in the SBIC, concomitant with the onset of the Little Ice Age (LIA) in western Canada. In the SBIC this interval was characterized by higher levels of precipitation, which greatly enhanced estuarine circulation resulting in frequent incursions of cold, well oxygenated ocean currents into the bottom waters of the SBIC and the development of a diverse calcareous foraminiferal fauna. This circulation pattern began to break down in the late 19th century AD and by AD 1940 conditions similar to those that existed in the inlet prior to AD 1500 had redeveloped, a process that continues at present.  相似文献   

Hydrogen atoms and ions in the thermosphere and exosphere     

D. R. Bates  T. N. L. Patterson 《Planetary and Space Science》1961,5(4):257-273

The distribution of atomic hydrogen in the thermosphere and exosphere is computed taking into account the upward flow which balances the escape flux. Because of the upward flow the number-density gradient is much steeper than it would be in a static atmosphere. Attention is drawn to the fact that the ratio of the amount of hydrogen above the 100 or 110km levels to the amount of hydrogen above the 200 or 300 km levels is a sensitive measure of the temperature of the exosphere. The evidence on the absolute abundance of atomic hydrogen is examined. It is concluded that the number density at the 120km level is probably about 5 × 10⁵/cm³. The Ly. absorption line at this level is beyond the linear part of the curve of growth.

Consideration is also given to the steady-state distributions of O⁺ and H⁺ ions. In the lower part of the exosphere the number density of O⁺ ions falls with increase in altitude (the associated scale height being twice that of the O atoms) and the number density of H⁺ ions rises at the same rate (as was first pointed out by Dungey). The altitude at which the number densities of O⁺ and H⁺ ions become equal is calculated on various assumptions regarding the temperature and hydrogen content of the exosphere. It is found to be about 1200 km when the temperature is 1250° K and the hydrogen content corresponds to the number density cited near the end of the preceding paragraph. The gradient of the predicted electrondensity distribution at several Earth radii is much less than that deduced from whistler studies.

The passage from charge transfer to diffusive equilibrium is discussed in an Appendix.  相似文献   

Climate change and the long-term viability of the World’s busiest heavy haul ice road     

Mullan  Donal  Swindles  Graeme  Patterson  Tim  Galloway  Jennifer  Macumber  Andrew  Falck  Hendrik  Crossley  Laura  Chen  Jie  Pisaric  Michael 《Theoretical and Applied Climatology》2017,129(3-4):1089-1108

Theoretical and Applied Climatology - Climate models project that the northern high latitudes will warm at a rate in excess of the global mean. This will pose severe problems for Arctic and...  相似文献   

Late Holocene hydroclimatic variability linked to Pacific forcing: evidence from Abbott Lake,coastal central California     

Christine A. Hiner  Matthew E. Kirby  Nicole Bonuso  William P. Patterson  Jennifer Palermo  Emily Silveira 《Journal of Paleolimnology》2016,56(4):299-313

  相似文献