On the Links between Microwave and Solar Wavelength Interactions with Snow-Covered First-Year Sea Ice

Electromagnetic (EM) energy at solar and microwavelengths will interact with a snow-covered sea ice volume as a function of its geophysical properties. The seasonal metamorphosis of the snow cover modulates the relative distribution of the three main interaction mechanisms of EM energy: reflection, transmission, and absorption. We use a combination of modeling and observational data to illustrate how the total relative scattering cross section (Sigma 0) at microwavelengths can be used to estimate the surface climatological shortwave albedo and the transmitted Photosynthetically Active Radiation (PAR) for a snow-covered, first-year sea ice volume typical of the Canadian Arctic. Modeling results indicate that both 5.3 and 9.25 GHz frequencies, at HH polarization and incidence angles of 20 degrees, 30 degrees, and 40 degrees can be used to estimate the daily averaged integrated climatological albedo (Alpha). The models at 5.3 GHz, HH polarization, at 20 degree, 30 degree, and 40 degree incidence angles were equally precise in predications of Alpha. The models at 9.25 GHz were slightly less precise, particularly at the 40 degree incidence angle. The reduction in precision at the 40 degree incidence angle was attributed to the increased sensitivity at both 5.3 and 9.25 GHz to the snow surface scattering term (Sigma 0 ss) used in computation of the total relative scattering cross section (Sigma 0). Prediction of subsnow PAR was also possible using the same combination of microwave sensor variables utilized in prediction of Alpha, but because subice algal communities have evolved to be low light sensitive, the majority of the growth cycle occurs prior to significant changes in Sigma 0. A method of remote estimation of snow thickness is required to be scientifically useful. Observational data from the European ERS-1 SAR were used to confirm the appropriateness of the modeled relationships between Sigma 0, Alpha, and PAR. Over a time series spanning all conditions used in the modeled relationships, the same general patterns were observed between Sigma, Alpha, and PAR.Key words: microwave scattering models, snow, sea ice, climatological shortwave radiation, photosynthetically active radiation, microwave remote sensingL'énergie électromagnétique à des ondes ultra-courtes et solaires va interagir avec un volume de glace de mer couverte de neige, en fonction de ses propriétés géophysiques. La métamorphose saisonnière du couvert nival module la distribution relative des trois grands mécanismes d'interaction de l'énergie électromagnétique: réflexion, transmission et absorption. On utilise une combinaison de résultats de modélisation et de données d'observation pour illustrer la façon dont la coupe transversale totale de diffusion relative (sigma-zero) à des longueurs d'onde ultra-courtes peut être utilisée pour estimer l'albédo climatologique en ondes courtes de la surface et le rayonnement photosynthétiquement utilisable (RPU) pour un volume de glace de mer nouvelle couverte de neige, typique de l'Arctique canadien. Les résultats de modélisation indiquent qu'on peut utiliser les deux fréquences de 5,3 et 9,25 GHz, ayant une polarisation HH et des angles d'incidence de 20, 30 et 40° pour estimer la moyenne quotidienne de l'albédo climatologique intégré (alpha). Les modèles à 5,3 GHz, ayant une polarisation HH et des angles d'incidence de 20, 30 et 40° prédisaient alpha avec le même degré de précision. Les modèles à 9,25 GHz étaient légèrement moins précis, surtout en ce qui concerne l'angle d'incidence de 40°. La réduction de précision à l'angle d'incidence de 40° était attribuée à une augmentation de sensibilité, aux deux fréquences de 5,3 et 9,25 GHz, au terme de diffusion de la surface nivale (sigma-zero-ss) utilisé dans le calcul de la coupe transversale totale de diffusion relative (sigma-zero). Pour prédire le RPU sous la couche nivale, on a également pu utiliser la même combinaison de variables de capteurs d'ondes ultra-courtes que celle utilisée pour prédire alpha. Mais parce que les communautés d'algues vivant sous la glace ont développé un niveau de photosensibilité élevé, la plupart du cycle de croissance se produit avant que des changements importants n'aient lieu dans sigma-zero. Il faut développer une méthode d'estimation de l'épaisseur nivale par la télédétection pour que cette méthode soit utilisable du point de vue scientifique. On a utilisé des données d'observation prises au RALS dans le cadre du ERS-1 européen pour confirmer la pertinence des rapports de modélisation entre sigma-zero, alpha et le RPU. Dans une série chronologique couvrant toutes les conditions utilisées dans les rapports de modélisation, on a observé les mêmes grandes tendances entre sigma-zero, alpha et le RPU.Mots clés: modèles de diffusion d’hyperfréquences, neige, glace de mer, rayonnement climatologique de courtes longueurs d’onde, rayonnement photosynthétiquement utilisable, télédétection des ondes ultra-courte

The SIMMS Program: A Study of Change and Variability within the Marine Cryosphere

This paper describes the scientific context of an experimental program for an eight year study of change and variability within the marine cryosphere in the Canadian Arctic and summarizes the field program since its inception in 1990. The focus is on understanding the process linkages between the atmosphere, cryosphere and ocean at the sea ice interface and in establishing a method by which these processes can be modeled numerically. Remote sensing plays a significant role as a major source of temporally and spatially consistent data in this relatively inaccessible region. In this program, we combine in situ measurement of geophysical characteristics of the sea ice interface, electromagnetic radiation interactions with the interface, and numerical modeling of marine cryosphere processes operating across this interface. Our primary objective is to observe and simulate the mechanisms that may contribute to change and variability. We conclude by proposing a conceptual spatial signature of an icescape as the basis for integration of these processes and illustrate how remote sensing data can be used to identify these functional signatures.Key words: Canadian Arctic, marine cryosphere, remote sensing, atmosphere-cryosphere interactions, snow and sea iceCet article décrit le contexte scientifique d'un programme expérimental consistant en une étude portant sur une période de huit ans des changements et de la variabilité au sein de la cryosphère marine dans l'Arctique canadien, et il résume le programme de terrain depuis sa création en 1990. On se concentre sur la compréhension des liens entre les processus à l'oeuvre, à l'interface de la glace de mer, qui impliquent l'atmosphère, la cryosphère et l'océan, ainsi que sur l'élaboration d'une méthode permettant de faire une modélisation numérique de ces processus. La télédétection joue un rôle important comme source principale de données cohérentes sur les plans temporel et spatial provenant de cette région relativement inaccessible. Dans ce programme on combine les mesures in situ des caractéristiques géophysiques de l'interface de la glace de mer, les interactions du rayonnement électromagnétique avec l'interface et la modélisation numérique des processus de la cryosphère agissant à cette interface. Notre objectif premier est d'observer et de simuler les mécanismes qui peuvent contribuer au changement et à la variabilité. On conclut en proposant sur le plan conceptuel une signature spatiale d'un panorama glaciaire comme base d'intégration de ces processus, et on illustre la façon dont les données obtenues par la télédétection peuvent servir à identifier ces signatures fonctionnelles.Mots clés: Arctique canadien, cryosphère marine, télédétection, interactions atmosphère-cryosphère, neige et glace de me

Modeling synthetic aperture radar (SAR) scattering from a seasonally varying snow-covered sea ice volume at 5.3 and 9.25 GHz

A series of sensitivity analyses using dielectric, mixture and microwave scattering models is presented. Data from the Seasonal Sea Ice Monitoring and Modeling Site (SIMMS) in 1990 and 1991 are used to initialize the models. The objective of the research is to investigate the role of various geophysical and electrical properties in specifying the total relative scattering cross section (???) of snow covered first-year sea ice during the spring period. The seasonal transition period from the Winter SAR scattering season to Early Melt was shown to signal a transition in dielectric properties which caused the snow volume to become a factor in the microwave scattering process. The effect of the thermal insulation of a snow cover on sea ice was shown to be significant for both ?? and ???. Higher atmospheric temperatures caused proportionally greater changes in the dielectric properties of the sea ice at the base of the snow cover. Model ?0 was computed for a range of sensor, sensor-earth geometry, and geophysical properties. In the Winter season the surface roughness terms (ohand L) were shown to have a significant impact on ?0 when the ice surface was the primary scattering mechanism. Once the snow cover began to warm and water was available in a liquid phase, the ice surface became masked because of the decrease in microwave penetration depths. During this period the water volume variable dominated ?0, both from its impact on ?v0, and due to its control over the dielectric mismatch created at the air/snow interface

The Northern Voice: Listening to Indigenous and Northern Perspectives on Management of Data in Canada

The Canadian Cryospheric Information Network and Polar Data Catalogue (CCIN/PDC) provide: (1) a trusted archive to store data from Canadian cryospheric research and (2) a public access portal to this information. The CCIN/PDC has since expanded its collection to include data from health, ecological, social, and other sciences. Since its inception, CCIN/PDC has engaged Indigenous and northern Canadians to understand and meet their information needs. This paper describes three instances of such engagement and next steps for enhanced interaction and support. First, feedback from northern and Indigenous communities led to the development of PDC Lite. Compared to the full-featured online PDC Search application, PDC Lite accommodates slower Internet speeds and allows one to search by particular northern communities. PDC Lite continues to be improved by input from the people that it serves. Next, to facilitate discussion and strengthen collaborative relationships within the polar data community, CCIN/PDC co-hosted two major meetings in 2015. Emerging from both these events was a need to prioritize what has been termed 'human interoperability' and the need to have Indigenous and northern community involvement at all levels of data management. Future plans for CCIN/PDC include more effective partnerships in which we work with and listen to northern and Indigenous Canadians to better understand their requirements for data management services and expertise. Our ultimate goal is to provide, through collaboration with partners, data, information, and expertise that facilitate northern and Indigenous Canadians’ access to publicly-archived data and enable and support management of their own data and resources

Remote sensing of coral reefs and their physical environment

There has been a vast improvement in access to remotely sensed data in just a few recent years. This revolution of information is the result of heavy investment in new technology by governments and industry, rapid developments in computing power and storage, and easy dissemination of data over the internet. Today, remotely sensed data are available to virtually anyone with a desktop computer. Here, we review the status of one of the most popular areas of marine remote sensing research: coral reefs. Previous reviews have focused on the ability of remote sensing to map the structure and habitat composition of coral reefs, but have neglected to consider the physical environment in which reefs occur. We provide a holistic review of what can, might, and cannot be mapped using remote sensing at this time. We cover aspects of reef structure and health but also discuss the diversity of physical environmental data such as temperature, winds, solar radiation and water quality. There have been numerous recent advances in the remote sensing of reefs and we hope that this paper enhances awareness of the diverse data sources available, and helps practitioners identify realistic objectives for remote sensing in coral reef areas