scholarly journals Assessment of Empirical and Semi-Analytical Algorithms Using MODIS-Aqua for Representing In-Situ Chromophoric Dissolved Organic Matter (CDOM) in the Bering, Chukchi, and Western Beaufort Seas of the Pacific Arctic Region

2021 ◽  
Vol 13 (18) ◽  
pp. 3673
Author(s):  
Melishia I. Santiago ◽  
Karen E. Frey

We analyzed a variety of satellite-based ocean color products derived using MODIS-Aqua to investigate the most accurate empirical and semi-analytical algorithms for representing in-situ chromophoric dissolved organic matter (CDOM) across a large latitudinal transect in the Bering, Chukchi, and western Beaufort Seas of the Pacific Arctic region. In particular, we compared the performance of empirical (CDOM index) and several semi-analytical algorithms (quasi-analytical algorithm (QAA), Carder, Garver-Siegel-Maritorena (GSM), and GSM-A) with field measurements of CDOM absorption (aCDOM) at 412 nanometers (nm) and 443 nm. These algorithms were compared with in-situ CDOM measurements collected on cruises during July 2011, 2013, 2014, 2015, 2016, and 2017. Our findings show that the QAA a443 and GSM-A a443 algorithms are the most accurate and robust representation of in-situ conditions, and that the GSM-A a443 algorithm is the most accurate algorithm when considering all statistical metrics utilized here. Our further assessments indicate that geographic variables (distance to coast, latitude, and sampling transects) did not obviously relate to algorithm accuracy. In general, none of the algorithms investigated showed a statistically significant agreement with field measurements beyond an approximately ± 60 h offset, likely owing to the highly variable environmental conditions found across the Pacific Arctic region. As such, we suggest that satellite observations of CDOM in these Arctic regions should not be used to represent in-situ conditions beyond a ± 60 h timeframe.

1986 ◽  
Vol 26 (1) ◽  
pp. 100-120 ◽  
Author(s):  
Fiorenzo C. Ugolini

Pedogenic zonation in the soils of the polar regions is a result of gradients in environmental factors and attendant chemical processes. Along a latitudinal transect, it is best manifested at well-drained sites and by soils developed on predominantly silicate rocks. Selected sites in arctic Alaska, in the Canadian arctic, Greenland, and Svalbard adequately fulfill these prerequisites. The processes of podzolization, decarbonization-carbonization, pervection, and salinization as models of arctic pedogenesis demonstrate that processes occurring in the temperate region also operate in the Far North. Brunification, melanization, and oxidation are recognized for the first time as current geochemical and pedogenic mechanisms of the Arctic region. Traditional genetic soil names have been retained because they represent a closer relationship to pedogenic processes than the more modern nomenclature. The identification, the chemical behavior, the strength, abundance, and mobility of the proton donors and conjugate bases are keys to the genesis of soils and the distinction of contrasting soil processes. This new approach to the understanding of arctic pedogenesis can be better fulfilled by collecting, analyzing, and interpreting soil solution obtained in situ.


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