25 research outputs found
Surface salinity fields in the Arctic Ocean and statistical approaches to predicting anomalies and patterns
Significant salinity anomalies have been observed in the Arctic Ocean surface
layer during the last decade. Using gridded data of winter salinity in the
upper 50 m layer of the Arctic Ocean for the period 1950-1993 and 2007-2012, we
investigated the inter-annual variability of the salinity fields, attempted to
identify patterns and anomalies, and developed a statistical model for the
prediction of surface layer salinity. The statistical model is based on linear
regression equations linking the principal components with environmental
factors, such as atmospheric circulation, river runoff, ice processes, and
water exchange with neighboring oceans. Using this model, we obtained
prognostic fields of the surface layer salinity for the winter period
2013-2014. The prognostic fields demonstrated the same tendencies of surface
layer freshening that were observed previously. A phase portrait analysis
involving the first two principal components exhibits a dramatic shift in
behavior of the 2007-2012 data in comparison to earlier observations
Infographics and Mathematics: A Mechanism for Effective Learning in the Classroom
This work discusses the creation and use of infographies in an undergraduate mathematics course. Infographies are a visualization of information combining data, formulas, and images. This article discusses how to form an infographic and uses infographics on topics within mathematics and climate as examples. It concludes with survey data from undergraduate students on both the general use of infographics and on the specific infographics designed by the authors
The geometry of large Arctic tundra lakes observed in historical maps and satellite images
The climate of the Arctic is warming rapidly and this is causing major changes to the cycling of carbon and the distribution of permafrost in this region. Tundra lakes are key components of the Arctic climate system because they represent a source of methane to the atmosphere. In this paper, we aim to analyze the geometry of the patterns formed by large (> 0.8 km2) tundra lakes in the Russian High Arctic. We have studied images of tundra lakes in historical maps from the State Hydrological Institute, Russia (date 1977; scale 0.21166 km/pixel) and in Landsat satellite images derived from the Google Earth Engine (G.E.E.; date 2016; scale 0.1503 km/pixel). The G.E.E. is a cloud-based platform for planetary-scale geospatial analysis on over four decades of Landsat data. We developed an image-processing algorithm to segment these maps and images, measure the area and perimeter of each lake, and compute the fractal dimension of the lakes in the images we have studied. Our results indicate that as lake size increases, their fractal dimension bifurcates. For lakes observed in historical maps, this bifurcation occurs among lakes larger than 100 km2 (fractal dimension 1.43 to 1.87). For lakes observed in satellite images this bifurcation occurs among lakes larger than ∼100 km2 (fractal dimension 1.31 to 1.95). Tundra lakes with a fractal dimension close to 2 have a tendency to be self-similar with respect to their area–perimeter relationships. Area–perimeter measurements indicate that lakes with a length scale greater than 70 km2 are power-law distributed. Preliminary analysis of changes in lake size over time in paired lakes (lakes that were visually matched in both the historical map and the satellite imagery) indicate that some lakes in our study region have increased in size over time, whereas others have decreased in size over time. Lake size change during this 39-year time interval can be up to half the size of the lake as recorded in the historical map
Initial State Parton Broadening and Energy Loss Probed in d+Au at RHIC
The impact parameter and rapidity dependence of the Cronin effect for
massless pions in reactions at GeV at RHIC is
computed in the framework of pQCD multiple elastic scattering on a nuclear
target. We introduce a formalism to incorporate initial state energy loss in
perturbative calculations and take into account the elastic energy loss in
addition to the transverse momentum broadening of partons.We argue that the
centrality dependence of the Cronin effect can distinguish between different
hadron production scenarios at RHIC. Its magnitude and rapidity dependence are
shown to carry important experimental information about the properties of cold
nuclear matter up to the moderate- and large- antishadowing/EMC regions.Comment: 15 pages, 4 eps figures. Final version to appear in Phys.Lett.