Search

To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.earscirev.2008.12.002 Byline: Charles Harris (a), Lukas U. Arenson (b), Hanne H. Christiansen (c), Bernd Etzelmuller (d), Regula Frauenfelder (d), Stephan Gruber (e), Wilfried Haeberli (e), Christian Hauck (f), Martin Holzle (e), Ole Humlum (d), Ketil Isaksen (g), Andreas Kaab (d), Martina A. Kern-Lutschg (a), Michael Lehning (h), Norikazu Matsuoka (i), Julian B. Murton (j), Jeanette Notzli (e), Marcia Phillips (h), Neil Ross (k), Matti Seppala (l), Sarah M. Springman (m), Daniel Vonder Muhll (n) Keywords: European permafrost; climate change; geothermal monitoring; geothermal modelling; geophysics; slope stability; permafost hazards; permafrost engineering Abstract: We present a review of the changing state of European permafrost within a spatial zone that includes the continuous high latitude arctic permafrost of Svalbard and the discontinuous high altitude mountain permafrost of Iceland, Fennoscandia and the Alps. The paper focuses on methodological developments and data collection over the last decade or so, including research associated with the continent-scale network of instrumented permafrost boreholes established between 1998 and 2001 under the European Union PACE project. Data indicate recent warming trends, with greatest warming at higher latitudes. Equally important are the impacts of shorter-term extreme climatic events, most immediately reflected in changes in active layer thickness. A large number of complex variables, including altitude, topography, insolation and snow distribution, determine permafrost temperatures. The development of regionally calibrated empirical-statistical models, and physically based process-oriented models, is described, and it is shown that, though more complex and data dependent, process-oriented approaches are better suited to estimating transient effects of climate change in complex mountain topography. Mapping and characterisation of permafrost depth and distribution requires integrated multiple geophysical approaches and recent advances are discussed. We report on recent research into ground ice formation, including ice segregation within bedrock and vein ice formation within ice wedge systems. The potential impacts of climate change on rock weathering, permafrost creep, landslides, rock falls, debris flows and slow mass movements are also discussed. Recent engineering responses to the potentially damaging effects of climate warming are outlined, and risk assessment strategies to minimise geological hazards are described. We conclude that forecasting changes in hazard occurrence, magnitude and frequency is likely to depend on process-based modelling, demanding improved understanding of geomorphological process-response systems and their impacts on human activity. Author Affiliation: (a) School of Earth and Ocean Sciences, Cardiff University, CF10 3YE, UK (b) Department of Civil and Environmental Engineering, University of Alberta, Edmonton, Alberta, Canada T6G 2W2 (c) Department of Geology, The University Centre in Svalbard, 9171 Longyearbyen, Norway (d) Department of Geosciences, University of Oslo, Blindern, NO-0316 Oslo, Norway (e) Department of Geography, University of Zurich, CH-8057 Zurich, Switzerland (f) Institute for Meteorology and Climate Reasearch, Karlsruhe Institute of Technology, 76131 Karlsruhe, Germany (g) The Norwegian Meteorological Institute, Blindern, 0313 Oslo, Norway (h) WSL,Swiss Federal Institute for Snow and Avalanche Research, SLF Davos, CH-7260 Davos Dorf, Switzerland (i) Graduate School of Life and Environmental Sciences, University of Tsukuba, Ibaraki 305-8572, Japan (j) Department of Geography, University of Sussex, Brighton, BN1 9SJ, UK (k) School of Geosciences, University of Edinburgh, West Mains Road, Edinburgh EH9 3JW, UK (l) Department of Geography, University of Helsinki, Helsinki, FIN-00014, Finland (m) Geotechnical Institute, ETH Zurich, CH-8093 Zurich, Switzerland (n) The Swiss Initiative in Systems Biology, ETH-Zurich, CH-8092 Zurich, Switzerland Article History: Received 13 July 2007; Accepted 5 December 2008

Author(s): David J. Stevenson [1] Earth is an engine, tending to obliterate some of the evidence of events that are distant in time, but a memory is retained in its [...]

1 Introduction Scientific advances in geosciences increasingly depend on large scale computing (e.g. NRC 2001; NSF 2003). Appropriately, much attention has been given to the computational resources, sometimes called cyberinfrastructure, […], An accurate cost model that accounts for dataset size and structure can help optimize geoscience data analysis. We develop and apply a computational model to estimate data analysis costs for arithmetic operations on gridded datasets typical of satelliteor climate model-origin. For these dataset geometries our model predicts data reduction scalings that agree with measurements of widely used geoscience data processing software, the netCDF Operators (NCO). I/O performance and library design dominate throughput for simple analysis (e.g. dataset differencing). Dataset structure can reduce analysis throughput ten-fold relative to same-sized unstructured datasets. We demonstrate algorithmic optimizations which substantially increase throughput for more complex, arithmetic-dominated analysis such as weighted-averaging of multi-dimensional data. These scaling properties can help to estimate costs of distribution strategies for data reduction in cluster and grid environments. Key words: computational model, geoscience, scaling, data analysis, netCDF

To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.chb.2006.02.014 Byline: Chun-Yen Chang (a), James P. Barufaldi (b), Ming-Chao Lin (a), Yi-Chun Chen (a) Keywords: Problem solving; Secondary school; Science education; Assessment Abstract: This study examined tenth-grade students' (n =263) problem solving ability (PSA) online through assessing students' domain-specific knowledge (DSK) and reasoning skills (RS) in Earth sciences as well as their attitudes toward (AT) Earth sciences related topics in a secondary school of Taiwan. The students' PSA was evaluated based on a previous model (Chang, C. Y. (2004, November 26-27). Trends in assessing student earth science problem solving ability: the importance of domain-specific knowledge and reasoning skills in earth sciences. Paper presented at the Seoul Conference for International Earth Science Olympiad (IESO), Seoul, Korea; Chang, C. Y., & Barufaldi, J. P. (submitted). Does problem solving=prior knowledge+reasoning skills in science? An exploratory study. Journal of Experimental Education; Chang, C. Y., & Weng, Y. H. (2002). An exploratory study on students' problem-solving ability in earth science. International Journal of Science Education, 24(5), 441-452) which empirically established that students' PSA is a composite of DSK, RS and AT subscales. Major findings are as follows: (a) The correlation coefficient among students' DSK, RS and AT was relatively small, indicating that these subscales might have successfully represented different constructs of students' PSA; (b) a significantly positive correlation existed between students' PSA total scores and each subscale. It is, therefore, suggested that students' PSA may be potentially assessed online by measuring their essential components in the area of Earth sciences. Author Affiliation: (a) Department of Earth Sciences, National Taiwan Normal University, 88, Section 4, Ting-Chou Road, Taipei 11677, Taiwan, ROC (b) Center for Science and Mathematics Education, The University of Texas at Austin, USA

To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.dsr.2004.12.001 Byline: Fredrick G. Prahl (a), Brian N. Popp (b), David M. Karl (c), Margaret A. Sparrow (a) Keywords: Haptophytes; Alkenones; Euphotic zone; Sea-surface temperature; Export production; Sedimentation; Subtropical North Pacific Abstract: In our study of Station ALOHA, a site representative of the oligotrophic North Pacific subtropical gyre (NPSG), alkenone content and composition were examined in (1) sinking particulate materials collected in sediment traps moored at 2800m during 2 year-long deployments (1992-1993 and 2000-2001) and (2) suspended particulate materials collected throughout the euphotic zone in two contrasting seasons (winter and summer). Each year, sediment trap records documented pronounced alkenone export events in both seasons. The winter event appears triggered by eddy diffusive mixing of nutrients into the upper water column and the release of light limitation on alkenone-producing photoautotrophs growing in the deep chlorophyll maximum layer (DCML). The summer event originates apparently from a stratified euphotic depth well above the DCML where others have now documented the occurrence of N.sub.2 fixation-based 'new production'. Although our time series record is yet limited, it is likely that the absolute magnitude of alkenone export and its quantitative importance in winter relative to summer is an ecological feature of the NPSG which can oscillate significantly on decadal time scales in response to climatic forcing. Despite the significant seasonal and interannual differences in alkenone export noted in our study, findings suggest that paleotemperature assessments based on analysis of the alkenone unsaturation index U.sub.37.sup.K' measured in underlying sediments would likely be unimpaired by the higher frequency temporal variability in the surface water ecology of alkenone-producers. When translated using a widely accepted calibration equation (U.sub.37.sup.K'=0.034T+0.039), U.sub.37.sup.K' values in average sediment trap particles are consistent with the mean annual sea-surface temperature at Station ALOHA. Author Affiliation: (a) College of Oceanic and Atmospheric Sciences, Oregon State University, Corvallis, OR 97331,-5503, USA (b) Department of Geology and Geophysics, University of Hawaii, Honolulu, HI, USA (c) Department of Oceanography, University of Hawaii, Honolulu, HI, USA Article History: Received 8 July 2004; Accepted 8 December 2004

The observation of the Earth reveals the study of its global climatic changes and the interaction between the planet's ocean, air and land systems. The first observation named Summit, began on 31 July 2003, at Washington, D.C., with the political meeting that included a mission statement and the 10-year implementation plans.

The reasons for low minority participation in the geosciences are discussed. Various methods like recruitment, collecting and analyzing data, introducing a watershed and field trips and mentoring for increasing minority participation in the geosciences are described.

The evolution of the obliquity of the ecliptic (epsilon), the Earth's axial tilt of 23.5 degrees, may have greatly influenced the Earth's dynamical, climatic and biotic development. For epsilon > 54 degrees, climatic zonation and zonal surface winds would be reversed, low to equatorial latitudes would be glaciated in preference to high latitudes, and the global seasonal cycle would be greatly amplified. Phanerozoic palaeoclimates were essentially uniformitarian in regard to obliquity, with normal climatic zonation and zonal surface winds, circum-polar glaciation and little seasonal change in low latitudes. Milankovitch-band periodicity in early Palaeozoic evaporites implies (Mathematical Expression Omitted) at approximately 430 Ma, suggesting that the obliquity during most of Phanerozoic time was comparable to the present value. By contrast, the paradoxical Late Proterozoic (is approximately 800-600 Ma) glacial environment - frigid, strongly seasonal climates, with permafrost and grounded ice-sheets near sea level preferentially in low to equatorial palaeolatitudes - implies glaciation with epsilon > 54 degrees (assuming a geocentric axial dipolar magnetic field). Palaeotidal data accord with a large obliquity in Late Proterozoic time. Indeed, Proterozoic palaeoclimates in general appear non-uniformitarian with respect to climatic zonation, consistent with epsilon > 54 degrees. The primordial Earth's obliquity is unconstrained by the widely-accepted single-giant-impact hypothesis for the origin of the Moon; an impact-induced obliquity greater than or similar to 70 degrees is possible, depending on the impact parameters. Subsequent evolution of epsilon depends on the relative magnitudes of the rate of obliquity-increase (Mathematical Expression Omitted) caused by tidal friction, and the rate of decrease (Mathematical Expression Omitted) due to dissipative core-mantle torques during precession (epsilon < 90 degrees is required for precessional torques to move epsilon toward 0 degree). Proterozoic palaeotidal data indicate (Mathematical Expression Omitted) (seconds of arc per century) during most of Earth history, only half the rate estimated using the modern, large value for tidal dissipation. The value of (Mathematical Expression Omitted) resulting from the combined effects of viscous, electromagnetic and topographic core-mantle torques cannot be accurately determined because of uncertainties in estimating, at present and for the geological past, the effective viscosity of the outer core, the nature of magnetic fields at the core-mantle boundary (CMB) and within the lower mantle, and the topography of the CMB. However, several estimates of (Mathematical Expression Omitted) approximate, or exceed by several orders of magnitude, the indicated value of (Mathematical Expression Omitted). If (Mathematical Expression Omitted) did indeed exceed (Mathematical Expression Omitted) in the past, then the obliquity would have decreased during Earth history. It is postulated here that the primordial Earth acquired an obliquity of approximately 70 degrees (54 degrees < epsilon < 90 degrees) from the Moon-producing single giant impact at approximately 4500 Ma (approach velocity approximately equal to 5-20 km/s, impactor/Earth mass-ratio approximately equal to 0.08-0.14). Secular decrease in ??? subsequently occurred under the dominant influence of dissipative core-mantle torques. From 4500-650 Ma, ??? slowly decreased to (Mathematical Expression Omitted). ??? then decreased relatively rapidly from approximately 60 degrees to approximately 26 degrees between 650 and 430 Ma (Mathematical Expression Omitted); climatic zonation changed from reverse to normal when (Mathematical Expression Omitted) at approximately 610 Ma, and ??? and the rate of amelioration of global seasonality were maxima for (Mathematical Expression Omitted) at approximately 550 Ma (the precessional rate omega is maximum when epsilon = 45 degrees, and (Mathematical Expression Omitted) varies as omega squared. Since 430 Ma, ??? has been less than or similar to -0.0025 inches/cy and ??? has remained near its Quaternary range. The postulated relatively rapid decrease in ??? between 650 and 430 Ma may partly reflect special conditions at the CMB which caused significant increase in dissipative core-mantle torques at that time. This inflection in the curve of ??? versus time centred at (Mathematical Expression Omitted) also may be partly explained by the function (Mathematical Expression Omitted) where omega is the Earth's rate of rotation, and other dynamical effects on (Mathematical Expression Omitted). The Proterozoic-Phanerozoic transition may record profound change in global state caused by reduction in through the critical values of 54 degrees and 45 degrees. The postulated flip-over of climatic zonation at approximately 610 Ma (Mathematical Expression Omitted) coincides with the widespread appearance of the Ediacaran metazoans at approximately 620-590 Ma, and the interval of most rapid reduction of obliquity and seasonality at approximately 550 Ma (Mathematical Expression Omitted) with the 'Cambrian explosion' of biota at 550 plus or minus 20 Ma. These two most spectacular radiations in the history of life thus may mark the passage from an inhospitable global state of reverse climatic zonation and extreme seasonality (the Earth's Precambrian 'Uranian' obliquity state) to a relatively benign state of normal climatic zonation and moderate seasonality. Further geological, palaeomagnetic and geochronological studies of Precambrian glaciogenic and aeolian deposits can test the predictions of a large obliquity (epsilon > 54 degrees) and reverse climatic zonation and zonal surface winds during the pre-Ediacaran Precambrian.