The Remote Sensing and Measurement of Melting Processes on Greenland and Antarctica
Item
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Title
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The Remote Sensing and Measurement of Melting Processes on Greenland and Antarctica
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Identifier
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d_2009_2013:3ae871e38687:11485
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identifier
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11925
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Creator
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Steiner, Nicholas,
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Contributor
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Marco Tedesco
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Date
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2012
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Language
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English
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Publisher
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City University of New York.
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Subject
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Remote sensing | Climate change | Environmental science | Antarctica | Greenland | Melt Detection | QuikSCAT | Wavelet
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Abstract
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We report measurements of melt-related processes for Antarctic and Greenland made using novel remote sensing algorithms and in-situ measurement techniques. First, persistent melting is mapped over Antarctica at high resolution using a novel melt-detection algorithm, based on wavelet-theory and multiscale analysis for the duration of the QuikSCAT satellite record (1999 through 2009). This novel approach is compared with threshold based methods, where melting is detected at 3dB below the winter mean backscatter, indicating an agreement to within 7 percent accuracy in yearly melt index [days-km2] and within 10 percent accuracy based automated weather station (AWS) comparisons due to the omission of short-duration melting events. In further comparison with Special Sensor Microwave/Image (SSMI) melting records, a higher degree of agreement (9 percent relative difference) is obtained by employing the wavelet-based approach than threshold-based (11 percent relative difference) methods. Secondly, we assess the validity of remote sensing based multispectral bathymetry from the analysis of concurrent in-situ multi-spectral and depth measurements collected over a supraglacial lake during early July 2010 in West Greenland (Lake Olivia, 69º36'35"N, 49º29'40"W). In particular, we evaluate lake bottom albedo and the water attenuation coefficient. Analysis of in-situ data (using a remotely controlled boat equipped with a GPS, sonar and a spectrometer) illustrates the exponential trend of the water-leaving reflectance with lake depth. The attenuation factors obtained are compared with those proposed in the literature. Finally, measured ablation rates at the bottom of the two lakes, collected during the summers of 2010 and 2011, are on the order of ∼ 6 cm/day, versus a rate of ∼ 2.5 - 3 cm/day in the case of bare ice of surrounding areas. These measurements are compared with a thermodynamic model forced with the outputs of a regional climate model. In general, the model is able to satisfactorily reproduce the measured quantities with RMSE of the order of 3 -- 4 cm for the ablation and ∼ 1.5 ºC in the case of water temperature. Results confirm that the ablation at the bottom of supraglacial lakes can account for close to ten percent of the total lake depth.
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Type
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dissertation
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Source
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2009_2013.csv
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degree
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Ph.D.
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Program
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Earth & Environmental Sciences
