Oscillatory dynamics do not mask linear trends in the timing of ice breakup for Northern Hemisphere lakes from 1855 to 2004

Our analyses partition the relative influence of progressive climate change and large-scale climate drivers that can be associated with the Quasi-Biennial Oscillation (QBO), El Niño Southern Oscillation (ENSO), North Atlantic Oscillation (NAO), solar sunspot cycle, and multi-decadal oscillations on lake ice breakup dates for thirteen Northern Hemisphere lakes. Oscillatory dynamics explain 26 % of the total variance in the time series compared with 15 % for linear trends, leaving 60 % unexplained and likely attributable, in part, to local weather. Significant oscillatory dynamics include frequencies in 2–3 year periods (9.4 % of the total variance), 3–6 year periods (8.2 %), 10–12 year periods (1.6 %) and various multidecadal periods (0.4–1.3 %). All 13 study lakes, although widely scattered in the Northern Hemisphere, had similar oscillatory dynamics and linear trends, emphasizing that global processes influence lake ice breakup locally. We illustrate that while quasi-periodic dynamics associated with large-scale climate drivers are important, they do not mask the clear evidence for progressive climate change.     

Nomograms for determining the gravity attraction of a right rectangular prism

Summary A rectangular prism is one of the versatile models which is often used to approximate many geological features and also for calculation of topographic and isostatic effects. The analytical formula for the gravity attraction of a right rectangular prism contains 24 lengthy expressions which though compatible for use on an electronic computer, are rather prohibitive for hand computations.Some need has, therefore, been felt for designing a simple graphical device to enable a fairly quick estimate of the gravity effect of a rectangular block model, especially for small-scale jobs involving only a few computation points. In so far as is known to the author, no such graphical device has been made available to the geophysicists.The set of nomograms presented in this communication should fulfill this long felt need. With this aid now it is possible to compute in only a few minutes the gravity attraction of a finite rectangular prism at a point lying outside or on the prism surface.

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Zusammenfassung Das Quader ist eines der Modelle, das häufig als Annäherung vieler geologischer Körper und bei der Berechnung topographischer und isostatischer Effekte angewandt wird. Die analytische Formel für die Schweresanziehung eines aufrechten Quaders enthält 24 lange Formeln, diezwar für elektronische Rechenautomat aber nicht für Berechnungen von Hand geeignet sind.Es bestand deshalb ein Bedarf für ein einfaches graphisches Mittel, welch eine rasche Abschätzung des Schwereseffektes eines Block-models ermöglichen kann, insbesondere für kleinere Aufgaben mit nur wenigen Berechnungspunkten. Dem Verfasser sind noch keine solche Diagramme bis jetzt bekannt.Die Nomogramme dieser Abhandlung sollten diesen Bedarf erfüllen; an Hand dieses Hilfsmittels sollte es möglich sein in wenigen Minuten die Schweresanziehung für jeden Punkt ausserhalb oder auf der Oberfläche eines begrenzten Quaders zu berechnen.

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Paper presented at the 32nd E.A.E.G. Meeting in Edinburgh (May 1970).     

Assessment of Impact on Seafloor Features in INDEX Area

Abstract

Observations on seafloor features from subbottom profiling and seabed photography data show that the undisturbed and natural conditions before the benthic disturbance undergo a substantial change after operation of the disturber. The effects can be seen in the form of deep trenches and grooves, formed by the action of the sleds and the pumping of the sediment along its path, as well as sediment piles on either side of the track. Biological traces such as fecal coils, casts, tubes, burrows, and trails get obliterated in the areas of disturbance and resedimentation. The smooth, uniform nature of the seafloor observed in pre-disturbance phase shows microtopographic changes in and around the disturbed area as a result of sediment excavation and resettlement. Vertical mixing as well as lateral transport of sediment alter the geological, biological, physical, and chemical conditions on the seafloor, which need to be monitored over time to assess the process and the time taken for restoration of environmental conditions.     

Real Time Analysis and Display of Scanning Lidar Scattering Data

We describe software for an IBM compatible personal computer (PC) that we have developed and used to collect and analyze backscatter data from a multi-wavelength Mie-Rayleigh scanning lidar system. Both one and two-dimensional distributions of optical scattering coefficients are calculated from the lidar return signals and displayed in real time. Although we are using the software for analyzing marine aerosols, the modular nature of the software and data acquisition drivers make it straightforward to adapt the software to different systems, such as differential absorption lidar (DIAL) and oceanic lidars. We show examples of both horizontal and vertical Mie-Rayleigh lidar scans collected at the Makai Pier and Bellows Beach on the northeast side of the island of Oahu.     

Force-directed layout of origin-destination flow maps

This paper introduces a force-directed layout method for creating origin-destination flow maps. Design principles derived from manual cartography and automated graph drawing to increase readability of flow maps and graph layouts are taken into account. The origin-destination flow maps produced with our algorithm show flows with quadratic Bézier curves that reduce flow-on-flow and flow-on-node overlaps, and avoid sharp or irregular bends in flow lines. A survey of expert cartographers found that flow maps created with our automated method are similar in quality to manually produced flow maps.