Paleolimnology of Lake Tanganyika, East Africa, over the past 100 kyr

New sediment core data from a unique slow-sedimentation rate site in Lake Tanganyika contain a much longer and continuous record of limnological response to climate change than have been previously observed in equatorial regions of central Africa. The new core site was first located through an extensive seismic reflection survey over the Kavala Island Ridge (KIR), a sedimented basement high that separates the Kigoma and Kalemie Basins in Lake Tanganyika.Proxy analyses of paleoclimate response carried out on core T97-52V include paleomagnetic and index properties, TOC and isotopic analyses of organic carbon, and diatom and biogenic silica analyses. A robust age model based on 11 radiocarbon (AMS) dates indicates a linear, continuous sedimentation rate nearly an order of magnitude slower here compared to other core sites around the lake. This age model indicates continuous sedimentation over the past 79 k yr, and a basal age in excess of 100 k yr.The results of the proxy analyses for the past 20 k yr are comparable to previous studies focused on that interval in Lake Tanganyika, and show that the lake was about 350 m lower than present at the Last Glacial Maximum (LGM). Repetitive peaks in TOC and corresponding drops in ¹³C over the past 79 k yr indicate periods of high productivity and mixing above the T97-52V core site, probably due to cooler and perhaps windier conditions. From 80 through 58 k yr the ¹³C values are relatively negative (–26 to –28 l) suggesting predominance of algal contributions to bottom sediments at this site during this time. Following this interval there is a shift to higher values of ¹³C, indicating a possible shift to C-4 pathway-dominated grassland-type vegetation in the catchment, and indicating cooler, dryer conditions from 55 k yr through the LGM. Two seismic sequence boundaries are observed at shallow stratigraphic levels in the seismic reflection data, and the upper boundary correlates to a major discontinuity near the base of T97-52V. We interpret these discontinuities to reflect major, prolonged drops in lake level below the core site (393 m), with the lower boundary correlating to marine oxygen isotope Stage 6. This suggests that the previous glacial period was considerably cooler and more arid in the equatorial tropics than was the last glacial period.     

Geoarchaeology of the Nehalem spit: Redistribution of beeswax galleon wreck debris by Cascadia earthquake and tsunami (∼A.D. 1700), Oregon,USA

A coincidence of the Beeswax galleon shipwreck (ca. A.D. 1650–1700) and the last Cascadia earthquake tsunami and coastal subsidence at ∼A.D. 1700 redistributed and buried wreck artifacts on the Nehalem Bay spit, Oregon, USA. Ground‐penetrating radar profiles (∼7 km total distance), sand auger probes, trenches, cutbank exposures (29 in number), and surface cobble counts (49 sites) were collected from the Nehalem spit (∼5 km² area). The field data demonstrate (1) the latest prehistoric integrity of the spit, (2) tsunami spit overtopping, and (3) coseismic beach retreat since the A.D. 1700 great earthquake in the Cascadia subduction zone. Wreck debris was (1) initially scattered along the spit ocean beaches, (2) washed over the spit by nearfield tsunami (6–8 m elevation), and (3) remobilized in beach strandlines by catastrophic beach retreat. Historic recovery of the spit (150 m beach progradation) and modern foredune accretion (>5 m depth) have buried both the retreat scarp strandlines and associated wreck artifacts. The recent onshore sand transport might re‐expose heavy ship remains in the offshore area if the wreck grounded in shallow water (<20 m water depth of closure). © 2011 Wiley Periodicals, Inc.     

Identification and geochemical significance of some aromatic components of coal

The aromatic fraction of a Homestead, Kentucky, coal extract was analyzed by combined gas chromatography-mass spectrometry using glass capillary columns. The aromatic fraction was further analyzed by gas chromatography using sulfur specific flame photometric detection. Seventy-eight compounds were identified, some of which have been traced to their possible biological origins. Sulfur-containing aromatic compounds are thought to originate from reaction of elemental sulfur or pyrite with hydrocarbons.     

Relaxation‐Based Point Feature Matching for Vector Map Conflation

With the rapid advance of geospatial technologies, the availability of geospatial data from a wide variety of sources has increased dramatically. It is beneficial to integrate / conflate these multi‐source geospatial datasets, since the integration of multi‐source geospatial data can provide insights and capabilities not possible with individual datasets. However, multi‐source datasets over the same geographical area are often disparate. Accurately integrating geospatial data from different sources is a challenging task. Among the subtasks of integration/conflation, the most crucial one is feature matching, which identifies the features from different datasets as presentations of the same real‐world geographic entity. In this article we present a new relaxation‐based point feature matching approach to match the road intersections from two GIS vector road datasets. The relaxation labeling algorithm utilizes iterated local context updates to achieve a globally consistent result. The contextual constraints (relative distances between points) are incorporated into the compatibility function employed in each iteration's updates. The point‐to‐point matching confidence matrix is initialized using the road connectivity information at each point. Both the traditional proximity‐based approach and our relaxation‐based point matching approach are implemented and experiments are conducted over 18 test sites in rural and suburban areas of Columbia, MO. The test results show that our relaxation labeling approach has much better performance than the proximity matching approach in both simple and complex situations.     

Paleoclimate data constraints on climate sensitivity: The paleocalibration method

The relationship between paleoclimates and the future climate, while not as simple as implied in the paleoanalog studies of Budyko and others, nevertheless provides sufficient constraints to broadly confirm the climate sensitivity range of theoretical models and perhaps eventually narrow the model-derived uncertainties. We use a new technique called paleocalibration to calculate the ratio of temperature response to forcing on a global mean scale for three key intervals of Earth history. By examining surface conditions reconstructed from geologic data for the Last Glacial Maximum, the middle Cretaceous and the early Eocene, we can estimate the equilibrium climate sensitivity to radiative forcing changes for different extreme climates. We find that the ratios for these three periods, within error bounds, all lie in the range obtained from general circulation models: 2–5 K global warming for doubled atmospheric carbon dioxide. Paleocalibration thus provides a data-based confirmation of theoretically calculated climate sensitivity. However, when compared with paleodata on regional scales, the models show less agreeement with data. For example, our GCM simulation of the early Eocene fails to obtain the temperature contrasts between the Equator and the Poles (and between land and ocean areas) indicated by the data, even though it agrees with the temperature data in the global average. Similar results have been reported by others for the Cretaceous and for the Last Glacial Maximum.The U.S. Government right to retain a non-exclusive royalty-free license in and to any copyright is acknowledged.     

Geometric Localization of CMEs in 3D Space Using STEREO Beacon Data: First Results

The geometric localization technique (Pizzo and Biesecker, Geophys. Res. Lett. 31, 21802, 2004) can readily be used with Solar Terrestrial Relations Observatory (STEREO) Space Weather Beacon data to observe coronal mass ejection (CME) propagation within three-dimensional space in near-real time. This technique is based upon simple triangulation concepts and utilizes a series of lines of sight from two space-based observatories to determine gross characteristics of CMEs, such as location and velocity. Since this work is aimed at space weather applications, the emphasis is on use of COR2 coronagraph data, which has a field of view from 2.5R _⊙ to 15R _⊙; this spatial coverage allows us to observe the early temporal development of a CME, and hence to calculate its velocity, even for very fast CMEs. We apply this technique to highly-compressed COR2 beacon images for several CMEs at various spacecraft separation angles: 21 August 2007, when the separation angle between the two spacecraft was 26°; 31 December 2007 and 2 January 2008, when the separation angle was 44°; and 17 October 2008, when the spacecraft separation was 79°. We present results on the speed and direction of propagation for these events and discuss the error associated with this technique. We also compare our results to the two-dimensional plane-of-sky speeds calculated from STEREO and SOHO.