Author:
Publisher:
ISBN:
Category : Algorithms
Languages : en
Pages :

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Author: Steven A. Ackerman
Publisher:
ISBN:
Category : Algorithms
Languages : en
Pages : 9

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Author: Jeffrey Key
Publisher:
ISBN:
Category : Microwave devices
Languages : en
Pages : 13

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Author: Hauke Flores
Publisher: Frontiers Media SA
ISBN: 2889638057
Category :
Languages : en
Pages : 155

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This eBook is a collection of articles from a Frontiers Research Topic. Frontiers Research Topics are very popular trademarks of the Frontiers Journals Series: they are collections of at least ten articles, all centered on a particular subject. With their unique mix of varied contributions from Original Research to Review Articles, Frontiers Research Topics unify the most influential researchers, the latest key findings and historical advances in a hot research area! Find out more on how to host your own Frontiers Research Topic or contribute to one as an author by contacting the Frontiers Editorial Office: frontiersin.org/about/contact.

Author: Josefino C. Comiso
Publisher:
ISBN:
Category : Algorithms
Languages : en
Pages : 64

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Author: Bohai Zhang
Publisher:
ISBN:
Category :
Languages : en
Pages : 0

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Arctic sea ice extent has been of considerable interest to scientists in recent years, mainly due to its decreasing temporal trend over the past 20 years. In this article, we propose a hierarchical spatio-temporal generalized linear model for binary Arctic sea-ice-extent data, where statistical dependencies in the data are modeled through a latent spatio-temporal linear mixed effects model. By using a fixed number of spatial basis functions, the resulting model achieves both dimension reduction and non-stationarity for spatial fields at different time points. An EM algorithm is proposed to estimate model parameters, and an empirical-hierarchical-modeling approach is applied to obtain the predictive distribution of the latent spatio-temporal process. We illustrate the accuracy of the parameter estimation through a simulation study. The hierarchical model is applied to spatial Arctic sea-ice-extent data in the month of September for 20 years in the recent past, where several posterior summaries are obtained to detect the changes of Arctic sea ice cover. In particular, we consider a time series of latent 2)×)2 tables to infer the spatial changes of Arctic sea ice over time.

Author: Benjamin Lundquist Saenz
Publisher: Stanford University
ISBN:
Category :
Languages : en
Pages : 242

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Sea ice is an important driver of climate patterns and polar marine ecosystem dynamics. In particular, primary production by microalgae in sea ice has been postulated as a sink for anthropogenic CO2, and as a critical resource in the life cycle of Antarctic krill Euphausia superba, a keystone species. Study of the sea ice ecosystem is difficult at regional and global scales, however, because of the expense and logistical difficulties in accessing such a remote and hostile environment. Consequently, models remain valuable tools for investigations of the spatial and temporal dynamics of sea ice and associated ecology and biogeochemistry. Recent advances in model representations of sea ice have called into question the accuracy of previous studies, and allow the creation of new tools to perform mechanistic simulations of sea ice physics and biogeochemistry. To address spatial and temporal variability in Antarctic sea ice algal production, and to establish the bounds and sensitivities of the sea ice ecosystem, a new, coupled sea ice ecosystem model was developed. In the vertical dimension, the model resolves incorporated saline brine, macronutrients concentrations, spectral shortwave radiation, and the sea ice algae community at high resolution. A novel method for thermodynamics, desalination, and fluid transfer in slushy, high-brine fraction sea ice was developed to simulate regions of high algal productivity. The processes of desalination, fluid transfer, snow-ice creation, and superimposed ice formation allowed the evolution of realistic vertical profiles of sea ice salinity and algal growth. The model replicated time series observations of ice temperature, salinity, algal biomass, and estimated fluid flux from the Ice Station Weddell experiment. In the horizontal dimension, sub-grid scale parameterizations of snow and ice thickness allow more realistic simulation of the ice thickness distribution, and consequently, sea ice algal habitat. The model is forced from above by atmospheric reanalysis climatologies, and from below by climatological ocean heat flux and deep-water ocean characteristics. Areal sea ice concentration and motion are specified according to SSM/I passive microwave satellite estimates of these parameters. Sensitivity testing of different snow and ice parameterizations showed that without a sub-grid scale ice thickness distribution, mean ice and snow thickness is lower and bottom sea ice algal production is elevated. Atmospheric forcing from different reanalysis data sets cause mean and regional shifts in sea ice production and associated ecology, even when sea ice extent and motion is controlled. Snow cover represents a first-order control over ice algal production by limiting the light available to bottom ice algal communities, and changes to the regional, rather than mean, snow thickness due to the use of different ice and snow representations are responsible for large differences in the magnitude and distribution of sea ice algal production. Improved convective nutrient exchange in high-brine fraction (slush) sea ice is responsible for up to 18% of total sea ice algal production. A continuous 10-year model run using climatological years 1996-2005 produced a time series of sea ice algal primary production that varied between 15.5 and 18.0 Tg C yr-1. This study represents the first interannual estimate of Antarctic sea ice algal production that dynamically considers the light, temperature, salinity, and nutrient conditions that control algal growth. On average, 64% of algal production occurred in the bottom 0.2 m of the ice pack. Production was spatially heterogeneous, with little consistency between years when examined at regional scales; however, at basin or hemispheric scales, annual production was fairly consistent in magnitude. At a mean of 0.9 g C m-2 yr-1, the magnitude of carbon uptake by sea ice algae will not significantly affect the Southern Ocean carbon cycle. Light availability was the dominant control on sea ice algae growth over the majority of the year; however, severe nutrient limitation that occurred annually during late spring and summer proved to be the largest control over sea ice algal productivity.

Author: Gunnar Spreen
Publisher: GRIN Verlag
ISBN: 3640129288
Category : Science
Languages : en
Pages : 209

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Doctoral Thesis / Dissertation from the year 2008 in the subject Geography / Earth Science - Physical Geography, Geomorphology, Environmental Studies, grade: 1,0, University of Hamburg (Institut für Meereskunde), 170 entries in the bibliography, language: English, abstract: The sea ice export out of the Arctic Ocean through Fram Strait into the Greenland Sea is the single largest source of freshwater in the Nordic Seas and therefore of spezial importance for the hydrological cycle of the North Atlantic. On its way south, the exported sea ice melts and thereby modifies the stratification of the ocean surface mixed layer, which in turn influences oceanic deep convection and water mass transformation processes in the Nordic Seas and thus impact global ocean thermohaline circulation. The lack of spatial sea ice thickness information has been one of the weaknesses for previous existing methods to determine the sea ice export. In this study a new method to obtain the sea ice volume flux exclusively from satellite measurements is presented. Previous estimates of the sea ice volume flux relayed on ice draft measurements of a single Upward Looking Sonar (ULS) in the Greenland Sea. The GLAS laser altimeter onboard the ICESat satellite launched in 2003 offers for the first time the opportunity to obtain the spatial sea ice thickness distribution up to 86°N latitude. In this study a method to determine the sea ice freeboard from ICESat altimeter data is developed and applied to nine ICESat measurement periods between 2003 and 2007. Assuming hydrostatic balance and by utilization of further satellite, in situ and climatological data these sea ice freeboard measurements are converted to sea ice thickness maps of the Fram Strait region. The satellite-based ice thickness estimates are combined with sea ice area and sea ice drift, as retrieved from AMSR-E microwave radiometer measurements at 89GHz, to obtain the sea ice volume flux. The errors of the input quantities and the final sea ice volume flux are assessed. Using this method the spatial sea ice volume flux distribution is obtained from satellite observations for the first time. The Fram Strait sea ice volume flux is further investigated by calculating a monthly sea ice volume flux time series between January 2003 and April 2007. Summer months have to be disregarded due to missing sea ice drift data. The sea ice volume flux shows large interannual and -seasonal variability. A mean monthly Fram Strait sea ice volume flux of (248±90) km3/month with respective minimum and maximum values of 112 km3/month (May 2003) and 484 km3/month (December 2004) was found...

Author: SeungHyun Son
Publisher: MDPI
ISBN: 3039436457
Category : Science
Languages : en
Pages : 279

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Ocean satellite remote sensing plays important roles in the observations of physical, biological and biogeochemical features in inland, coastal, and global ocean waters, with high temporal and spatial resolution. The satellite-measured ocean products are used for near-real-time ocean monitoring and climate data records to understand short-/long-term variabilities in marine environments and ecosystems as well as for decision making tools to manage social, economic, and environmental benefits. Validation/evaluation including a combination of field measurements and inter-satellite comparison is an essential step in providing more accurate satellite-derived ocean products. In this Special Issue, 14 papers have been published and include research on validation/evaluation, retrieval algorithms of ocean geophysical and biogeochemical parameters, and application of the satellite ocean products in the regional and global ocean. Subjects treated include: Sea Surface Temperature; Sea Ice Surface Temperature from VIIRS thermal infrared sensor; Sea Ice Detection from Spectroradiometer; Sea Surface Winds from HY-2A Scatterometer and GNSS—Reflectometry; Wave Height from Sentinel-3A SAR; Retrievals of Sea Surface Salinity, Chlorophyll-a, Particulate Organic Carbon, Particulate Backscattering, Marine Fishery resource, and Submesoscale Eddies from multiple Ocean Colour sensors.

Author: Tom Carrieres
Publisher: Cambridge University Press
ISBN: 1108417426
Category : Science
Languages : en
Pages : 263

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A comprehensive overview of the science involved in automated prediction of sea ice, for sea ice analysts, researchers, and professionals.