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Articles 1 - 5 of 5
Full-Text Articles in Physical Sciences and Mathematics
Transition In The Fractal Geometry Of Arctic Melt Ponds, C. Hohenegger, B. Alali, K. R. Steffen, D. K. Perovich, K. M. Golden
Transition In The Fractal Geometry Of Arctic Melt Ponds, C. Hohenegger, B. Alali, K. R. Steffen, D. K. Perovich, K. M. Golden
Dartmouth Scholarship
During the Arctic melt season, the sea ice surface undergoes a remarkable transformation from vast expanses of snow covered ice to complex mosaics of ice and melt ponds. Sea ice albedo, a key parameter in climate modeling, is determined by the complex evolution of melt pond configurations. In fact, ice–albedo feedback has played a major role in the recent declines of the summer Arctic sea ice pack. However, understanding melt pond evolution remains a significant challenge to improving climate projections. By analyzing area–perimeter data from hundreds of thousands of melt ponds, we find here an unexpected separation of scales, where …
Joint Diagonalization Applied To The Detection And Discrimination Of Unexploded Ordnance, Fridon Shubitidze, Juan Pablo Fernández, Irma Shamatava, Benjamin Barrowes, Kevin O’Neill
Joint Diagonalization Applied To The Detection And Discrimination Of Unexploded Ordnance, Fridon Shubitidze, Juan Pablo Fernández, Irma Shamatava, Benjamin Barrowes, Kevin O’Neill
Dartmouth Scholarship
Efforts to discriminate buried unexploded ordnance from harmless surrounding clutter are often hampered by the uncertainty in the number of buried targets that produce a given detected signal. We present a technique that helps determine that number with no need for data inversion. The procedure is based on the joint diagonalization of a set of multistatic response (MSR) matrices measured at different time gates by a time-domain electromagnetic induction sensor. In particular, we consider the Naval Research Laboratory’s Time-Domain Electromagnetic Multisensor Towed Array Detection System (TEMTADS), which consists of a 5×5 square grid of concentric transmitter/receiver pairs. The diagonalization process …
New Shortwave Infrared Albedo Measurements For Snow Specific Surface Area Retrieval, B. Montpetit, A. Royer, A. Langlois, P. Cliche, A. Roy, N. Champollion, G. Picard, F. Domine, R. Obbard
New Shortwave Infrared Albedo Measurements For Snow Specific Surface Area Retrieval, B. Montpetit, A. Royer, A. Langlois, P. Cliche, A. Roy, N. Champollion, G. Picard, F. Domine, R. Obbard
Dartmouth Scholarship
Snow grain-size characterization, its vertical and temporal evolution is a key parameter for the improvement and validation of snow and radiative transfer models (optical and microwave) as well as for remote-sensing retrieval methods. We describe two optical methods, one active and one passive shortwave infrared, for field determination of the specific surface area (SSA) of snow grains. We present a new shortwave infrared (SWIR) camera approach. This new method is compared with a SWIR laser- based system measuring snow albedo with an integrating sphere (InfraRed Integrating Sphere (IRIS)). Good accuracy (10%) and reproducibility in SSA measurements are obtained using the …
Surficial Redistribution Of Fallout 131iodine In A Small Temperate Catchment, Joshua D. Landis, Nathan T. Hamm, Carl E. Renshaw, W. Brian Dade, Francis J. Magilligan, John D. Gartner
Surficial Redistribution Of Fallout 131iodine In A Small Temperate Catchment, Joshua D. Landis, Nathan T. Hamm, Carl E. Renshaw, W. Brian Dade, Francis J. Magilligan, John D. Gartner
Dartmouth Scholarship
Isotopes of iodine play significant environmental roles, including a limiting micronutrient (127I), an acute radiotoxin (131I), and a geochemical tracer (129I). But the cycling of iodine through terrestrial ecosystems is poorly understood, due to its complex environmental chemistry and low natural abundance. To better understand iodine transport and fate in a terrestrial ecosystem, we traced fallout 131iodine throughout a small temperate catchment following contamination by the 11 March 2011 failure of the Fukushima Daiichi nuclear power facility. We find that radioiodine fallout is actively and efficiently scavenged by the soil system, where it …
The Ecology Of Pulse Events: Insights From An Extreme Climatic Event In A Polar Desert Ecosystem, U. N. Nielsen, D. H. Wall, B. J. Adams, R. A. Virginia
The Ecology Of Pulse Events: Insights From An Extreme Climatic Event In A Polar Desert Ecosystem, U. N. Nielsen, D. H. Wall, B. J. Adams, R. A. Virginia
Dartmouth Scholarship
Climate change is occurring globally, with wide ranging impacts on organisms and ecosystems alike. While most studies focus on increases in mean temperatures and changes in precipitation, there is growing evidence that an increase in extreme events may be particularly important to altering ecosystem structure and function. During extreme events organisms encounter environmental conditions well beyond the range normally experienced. Such conditions may cause rapid changes in community composition and ecosystem states. We present the impact of an extreme pulse event (a flood) on soil communities in an Antarctic polar desert. Taylor Valley, McMurdo Dry Valleys, is dominated by large …