The Best of Both Worlds: Connecting Remote Sensing and Arctic Communities for Safe Sea Ice Travel

  Northern communities are increasingly interested in technology that provides information about the sea ice environment for travel purposes. Synthetic aperture radar (SAR) remote sensing is widely used to observe sea ice independently of sunlight and cloud cover, however, access to SAR in northern communities has been limited. This study 1) defines the sea ice features that influence travel for two communities in the Western Canadian Arctic, 2) identifies the utility of SAR for enhancing mobility and safety while traversing environments with these features, and 3) describes methods for sharing SAR-based maps. Three field seasons (spring and fall 2017 and spring 2018) were used to engage residents in locally guided research, where applied outputs were evaluated by community members. We found that SAR image data inform and improve sea ice safety, trafficability, and education. Information from technology is desired to complement Inuit knowledge-based understanding of sea ice features, including surface roughness, thin sea ice, early and late season conditions, slush and water on sea ice, sea ice encountered by boats, and ice discontinuities. Floe edge information was not a priority. Sea ice surface roughness was identified as the main condition where benefits to trafficability from SAR-based mapping were regarded as substantial. Classified roughness maps are designed using thresholds representing domains of sea ice surface roughness (smooth ice/maniqtuk hiku, moderately rough ice/maniilrulik hiku, rough ice/maniittuq hiku; dialect is Inuinnaqtun). These maps show excellent agreement with local observations. Overall, SAR-based maps tailored for on-ice use are beneficial for and desired by northern community residents, and we recommend that high-resolution products be routinely made available in communities.  Les collectivités du Nord s’intéressent de plus en plus aux technologies qui leur fournissent de l’information au sujet de l’environnement de glace de mer à des fins de déplacements. La télédétection par radar à synthèse d’ouverture (SAR) est couramment utilisée pour observer la glace de mer, indépendamment de la lumière du soleil et de la nébulosité. Cependant, dans les collectivités du Nord, l’accès au SAR est restreint. Cette étude 1) définit les caractéristiques de la glace de mer qui exercent une influence sur les déplacements de deux collectivités dans l’ouest de l’Arctique canadien; 2) détermine l’utilité du SAR pour améliorer la mobilité et la sécurité quand vient le temps de traverser des environnements comportant ces caractéristiques; et 3) décrit les méthodes de partage de cartes établies à l’aide du SAR. Trois saisons sur le terrain (le printemps et l’automne de 2017, et le printemps de 2018) ont permis d’inciter les résidents à participer à une recherche locale guidée, là où les extrants appliqués ont été évalués par les membres de la collectivité. Nous avons trouvé que les données émanant des images du SAR éclairent et améliorent la sécurité de la glace de mer, l’aptitude à la circulation et l’éducation. L’information découlant de la technologie s’avère un complément désirable aux connaissances inuites en vue de la compréhension des caractéristiques de la glace de mer, dont la rugosité de la surface, la glace de mer mince, les conditions en début et en fin de saison, la bouillie de glace et la glace mouillée, la glace de mer rencontrée par les bateaux, et la discontinuité de la glace. Les données sur la glace de banc ne constituaient pas une priorité. La rugosité de la surface de la glace de mer était considérée comme la principale condition pour laquelle les avantages de la praticabilité déterminés au moyen des cartes établies à l’aide du SAR étaient substantiels. Les cartes indiquant la rugosité sont conçues en fonction de seuils représentant les caractéristiques de rugosité de la surface des glaces de mer (glace lisse/maniqtuk hiku, glace modérément rugueuse/maniilrulik hiku, glace rugueuse/maniittuq hiku; en dialecte inuinnaqtun). Ces cartes sont largement en accord avec les observations locales. Dans l’ensemble, les cartes établies à l’aide du SAR préparées en fonction des utilisations de la glace sont bénéfiques et désirées par les résidents des collectivités du Nord. Nous recommandons que des produits de haute résolution soient régulièrement mis à la disposition des collectivités

Advances in understanding and parameterization of small-scalephysical processes in the marine Arctic climate system: a review

The Arctic climate system includes numerous highly interactive small-scale physical processes in the atmosphere, sea ice, and ocean. During and since the International Polar Year 2007–2009, significant advances have been made in understanding these processes. Here, these recent advances are reviewed, synthesized, and discussed. In atmospheric physics, the primary advances have been in cloud physics, radiative transfer, mesoscale cyclones, coastal, and fjordic processes as well as in boundary layer processes and surface fluxes. In sea ice and its snow cover, advances have been made in understanding of the surface albedo and its relationships with snow properties, the internal structure of sea ice, the heat and salt transfer in ice, the formation of superimposed ice and snow ice, and the small-scale dynamics of sea ice. For the ocean, significant advances have been related to exchange processes at the ice–ocean interface, diapycnal mixing, double-diffusive convection, tidal currents and diurnal resonance. Despite this recent progress, some of these small-scale physical processes are still not sufficiently understood: these include wave–turbulence interactions in the atmosphere and ocean, the exchange of heat and salt at the ice–ocean interface, and the mechanical weakening of sea ice. Many other processes are reasonably well understood as stand-alone processes but the challenge is to understand their interactions with and impacts and feedbacks on other processes. Uncertainty in the parameterization of small-scale processes continues to be among the greatest challenges facing climate modelling, particularly in high latitudes. Further improvements in parameterization require new year-round field campaigns on the Arctic sea ice, closely combined with satellite remote sensing studies and numerical model experiments.publishedVersio

Arctic sea ice trafficability: new strategies for a changing icescape

Thesis (Ph.D.) University of Alaska Fairbanks, 2017Sea ice is an important part of the Arctic social-environmental system, in part because it provides a platform for human transportation and for marine flora and fauna that use the ice as a habitat. Sea ice loss projected for coming decades is expected to change ice conditions throughout the Arctic, but little is known about the nature and extent of anticipated changes and in particular potential implications for over-ice travel and ice use as a platform. This question has been addressed here through an extensive effort to link sea ice use and key geophysical properties of sea ice, drawing upon extensive field surveys around on-ice operations and local and Indigenous knowledge for the widely different ice uses and ice regimes of Utqiaġvik, Kotzebue, and Nome, Alaska. A set of nine parameters that constrain landfast sea ice use has been derived, including spatial extent, stability, and timing and persistence of landfast ice. This work lays the foundation for a framework to assess and monitor key ice-parameters relevant in the context of ice-use feasibility, safety, and efficiency, drawing on different remote-sensing techniques. The framework outlines the steps necessary to further evaluate relevant parameters in the context of user objectives and key stakeholder needs for a given ice regime and ice use scenario. I have utilized this framework in case studies for three different ice regimes, where I find uses to be constrained by ice thickness, roughness, and fracture potential and develop assessment strategies with accuracy at the relevant spatial scales. In response to the widely reported importance of high-confidence ice thickness measurements, I have developed a new strategy to estimate appropriate thickness compensation factors. Compensation factors have the potential to reduce risk of misrepresenting areas of thin ice when using point-based in-situ assessment methods along a particular route. This approach was tested on an ice road near Kotzebue, Alaska, where substantial thickness variability results in the need to raise thickness thresholds by 50%. If sea ice is thick enough for safe travel, then the efficiency of travel is relevant and is influenced by the roughness of the ice surface. Here, I develop a technique to derive trafficability measures from ice roughness using polarimetric and interferometric synthetic aperture radar (SAR). Validated using Structure-from-Motion analysis of imagery obtained from an unmanned aerial system near Utqiaġvik, Alaska, I demonstrate the ability of these SAR techniques to map both topography and roughness with potential to guide trail construction efforts towards more trafficable ice. Even when the ice is sufficiently thick to ensure safe travel, potential for fracturing can be a serious hazard through the ability of cracks to compromise load-bearing capacity. Therefore, I have created a state-of-the-art technique using interferometric SAR to assess ice stability with capability of assessing internal ice stress and potential for failure. In an analysis of ice deformation and potential hazards for the Northstar Island ice road near Prudhoe Bay on Alaska's North Slope I have identified a zone of high relative fracture intensity potential that conformed with road inspections and hazard assessments by the operator. Through this work I have investigated the intersection between ice use and geophysics, demonstrating that quantitative evaluation of a given region in the ice use assessment framework developed here can aid in tactical routing of ice trails and roads as well as help inform long-term strategic decision-making regarding the future of Arctic operations on or near sea ice

Tenuous Correlation between Snow Depth or Sea Ice Thickness and C- or X-Band Backscattering in Nunavik Fjords of the Hudson Strait

Radar penetration in brine-wetted snow-covered sea ice is almost nil, yet reports exist of a correlation between snow depth or ice thickness and SAR parameters. This article presents a description of snow depth and first-year sea ice thickness distributions in three fjords of the Hudson Strait and of their tenuous correlation with SAR backscattering in the C- and X-band. Snow depth and ice thickness were directly measured in three fjords of the Hudson Strait from 2015 to 2018 in April or May. Bayesian linear regression analysis was used to investigate their relationship with RADARSAT-2 (C-band) or TerraSAR-X (X-band). Polarimetric ratios and the Cloude–Pottier decomposition parameters were explored along with the HH, HV and VV bands. Linear correlations were generally no higher than 0.3 except for a special case in May 2018. The co-polarization ratio did not perform better than the backscattering coefficients

La lumière disponible pour les microalgues dans l'océan Arctique : une perspective satellitaire

Les écosystèmes marins arctiques sont alimentés à la base de la chaîne trophique par la production de biomasse algale. Alors que l’on croyait la croissance du phytoplancton (algues unicellulaires en suspension dans l’eau de mer) largement limitée à la saison durant laquelle l’océan Arctique est le plus dépourvu de glace de mer, on a découvert que des développements massifs de phytoplancton se produisaient sous la banquise arctique dès le printemps. Il n’est actuellement pas possible de déterminer l’étendue du phénomène et sa contribution, peut-être majeure, à la production primaire marine annuelle, car on connaît peu les mécanismes qui contrôlent la dynamique des floraisons de phytoplancton sous la banquise. Les observations in situ suggèrent que les floraisons sous banquise sont largement conditionnées par l’accès à la lumière visible dans la colonne d’eau. Que savons nous de cette lumière? Nous savons qu’elle est contrainte par les éléments qui se trouvent à la surface de l’océan Arctique (la présence et l’état de la glace de mer), ainsi que par l’atmosphère (en particulier, par les nuages). Mais comment analyser à la fois l’influence de la surface de l’océan et de l’atmosphère qui varient énormément avec le temps et l’espace, sur la lumière disponible pour la production primaire? La télédétection par satellite est un outil puissant pour suivre et étudier les propriétés du système Arctique à différentes échelles spatio-temporelles. Cet outil, combiné dans différents modèles, est utilisé pour déterminer le rôle que jouent les composantes de l’environnement dans les fluctuations de la lumière sous-marine. Ainsi, le premier chapitre de cette thèse porte sur la transmittance de la lumière par l’atmosphère à l’échelle pan-Arctique et on y évalue la tendance multiannuelle entre 2000 et 2016. On trouve que l’atmosphère devient moins transparente d’environ 2% par décennie. Ensuite, au deuxième chapitre, on développe une méthode satellitaire pour quantifier la perte de photons par réflexion dans la glace de mer. La méthode est évaluée par les données de terrain collectées en marge de la baie de Baffin aux printemps 2015 et 2016 pendant la campagne Green Edge. Finalement, au troisième chapitre, on utilise un modèle de propagation de la lumière dans l’atmosphère, qui, combiné au modèle développé au chapitre deux, permet d’évaluer la lumière potentiellement disponible pour la production primaire, à haute résolution temporelle tout au long de la saison de croissance. Ce modèle est appliqué localement, toujours en marge de la baie de Baffin, mais la méthode est développée pour investiguer le régime lumineux sous la banquise n’importe où en Arctique. Cette thèse contribue à l’avancement des connaissances sur la lumière servant à la production primaire et à sa propagation dans le système atmosphère-glace-océan.Arctic marine ecosystems are fueled by the production of algal biomass. While the growth of phytoplankton (single-cell algae suspended in seawater) was believed to be largely limited to the season during which the Arctic Ocean is mostly free of ice, massive phytoplankton blooms have recently been discovered under Arctic sea ice during spring. It is currently not possible to determine the extent of this phenomenon and its contribution, perhaps major, to annual primary production, because little is known about the mechanisms that control the dynamics of phytoplankton blooms under sea ice. Recent in situ observations conducted to understand this phenomenon suggest that the under-ice phytoplankton blooms are largely conditioned by access to visible sunlight in the water column. This light is constrained by the elements which are on the surface of the Arctic Ocean, in particular the presence and the state of the sea ice which vary enormously with time and space. Likewise, in the atmosphere, the omnipresence of clouds in the Arctic strongly constrains light. How can we analyze both the influence of the surface and the atmosphere on the light available for phytoplankton under sea ice? Satellite remote sensing is a powerful tool for monitoring and studying the properties of the Arctic system at different space-time scales. This tool, combined with different models, is used to determine the role that these different components of the environment play in the fluctuations of underwater light. The first chapter of the thesis deals with the transmittance of light by the atmosphere for which we assess the multi-annual trend between 2000 and 2016 at the pan-Arctic scale. We find that the atmosphere becomes less transparent at a rate of 2% per decade. Then, in chapter two, we develop a satellite remote sensing method to quantify the loss of reflected light in sea ice. This method is validated by field data collected during the Green Edge campaign on the West coast of Baffin Bay during the springs of 2015 and 2016. Finally, in chapter three, we use a model to propagate light in the atmosphere, and, combining it with the model developed in the previous chapter, we assess the potential light for phytoplankton at high temporal resolution throughout the growing season. This model is applied locally, still at a coastal Baffin Bay location (Green Edge campaign), but the method was developed to investigate the light regime under the pack ice anywhere in the Arctic. This thesis contributes to our knowledge on the propagation of light available for photosynthesis in the atmosphere-ice-ocean system and thus helps to better understand the impact of climate change on the Arctic marine ecosystem

Effects of subgrid-scale snow thickness variability on radiative transfer in sea ice

Snow is a principal factor in controlling heat and light fluxes through sea ice. With the goal of improving radiative and heat flux estimates through sea ice in regional and global models without the need of detailed snow property descriptions, a new parameterization including subgrid-scale snow thickness variability is presented. One-parameter snow thickness distributions depending only on the gridbox-mean snow thickness are introduced resulting in analytical solutions for the fluxes of heat and light through the snow layer. As the snowpack melts, these snow thickness distributions ensure a smooth seasonal transition of the light field under sea ice. Spatially homogenous melting applied to an inhomogeneous distribution of snow thicknesses allows the appearance of bare sea ice areas and melt ponds before all snow has melted. In comparison to uniform-thickness snow used in previous models, the bias in the under sea-ice light field is halved with this parameterization. Model results from a one-dimensional ocean turbulence model coupled with a thermodynamic sea ice model are compared to observations near Resolute in the Canadian High Arctic. The simulations show substantial improvements not only to the light field at the sea ice base which will affect ice algal growth but also to the sea ice and seasonal snowpack evolution. During melting periods, the snowpack can survive longer while sea ice thickness starts to reduce earlier. © 2015. American Geophysical Union. All Rights Reserved

Mapping Arctic Sea-Ice Surface Roughness with Multi-Angle Imaging SpectroRadiometer

Sea-ice surface roughness (SIR) is a crucial parameter in climate and oceanographic studies, constraining momentum transfer between the atmosphere and ocean, providing preconditioning for summer-melt pond extent, and being related to ice age and thickness. High-resolution roughness estimates from airborne laser measurements are limited in spatial and temporal coverage while pan-Arctic satellite roughness does not extend over multi-decadal timescales. Launched on the Terra satellite in 1999, the NASA Multi-angle Imaging SpectroRadiometer (MISR) instrument acquires optical imagery from nine near-simultaneous camera view zenith angles. Extending on previous work to model surface roughness from specular anisotropy, a training dataset of cloud-free angular reflectance signatures and surface roughness, defined as the standard deviation of the within-pixel lidar elevations, from near-coincident operation IceBridge (OIB) airborne laser data is generated and is modelled using support vector regression (SVR) with a radial basis function (RBF) kernel selected. Blocked k-fold cross-validation is implemented to tune hyperparameters using grid optimisation and to assess model performance, with an R2 (coefficient of determination) of 0.43 and MAE (mean absolute error) of 0.041 m. Product performance is assessed through independent validation by comparison with unseen similarly generated surface-roughness characterisations from pre-IceBridge missions (Pearson’s r averaged over six scenes, r = 0.58, p < 0.005), and with AWI CS2-SMOS sea-ice thickness (Spearman’s rank, rs = 0.66, p < 0.001), a known roughness proxy. We present a derived sea-ice roughness product at 1.1 km resolution (2000–2020) over the seasonal period of OIB operation and a corresponding time-series analysis. Both our instantaneous swaths and pan-Arctic monthly mosaics show considerable potential in detecting surface-ice characteristics such as deformed rough ice, thin refrozen leads, and polynyas

Examining Melt Pond Dynamics and Light Availability in the Arctic Ocean via High Resolution Satellite Imagery

As the Arctic experiences consequences of climate change, a shift from thicker, multi-year ice to thinner, first-year ice has been observed. First-year ice is prone to extensive pools of meltwater (“melt ponds”) forming on its surface, which enhance light transmission to the ocean. Changes in the timing and distribution of melt pond formation and associated increases in under-ice light availability are the primary drivers for seasonal progression of water column primary production and warming. Observations of melt pond development and distribution require meter scale resolution and have traditionally been limited to airborne images. However, recent advances in high spatial resolution satellites now allow for observations of individual melt ponds from space. Images of pack ice in the Chukchi Sea during 2018 obtained from WorldView satellite systems showed minimal melt pond coverage in June, with a rapid increase in late June, leading to saturated and flooded ice floes by mid-July. Cumulative hours above freezing (air temperature) was a stronger predictor for pond development than daily average values of temperature and irradiance and was well represented by a logistic growth curve. Size distributions (normalized to total pond area) of melt pond area was dominated by small (≤10 m2) ponds at the onset of ponding, shifting towards medium sized ponds (mode of 100 to 1,000 m2) as surface melt progressed. Late in the summer when ice flows were saturated with ponds, the distribution was skewed towards a handful of very large ponds nearing 1,000,000 m2, connected by channels which created a myriad of complex shapes. A primary production model driven by under-ice light intensity estimated from our classified images revealed that initial small increases in melt pond fraction have a large impact on potential under-ice chlorophyll growth and carbon uptake, eventually trending towards a saturating upper limit as ponds continued to spread. Results shown here offer novel insights into melt pond growth and distribution, along with estimates of how ponding impacts primary production. These conclusions showcase physical, observable consequences of an Arctic Ocean dominated by thin, first-year ice, and can be employed to advise future efforts in Arctic modeling

Alaska Shorefast Ice: Interfacing Geophysics With Local Sea Ice Knowledge And Use

Thesis (Ph.D.) University of Alaska Fairbanks, 2011This thesis interfaces geophysical techniques with local and traditional knowledge (LTK) of indigenous ice experts to track and evaluate coastal sea ice conditions over annual and inter-annual timescales. A novel approach is presented for consulting LTK alongside a systematic study of where, when, and how the community of Barrow, Alaska uses the ice cover. The goal of this research is to improve our understanding of and abilities to monitor the processes that govern the state and dynamics of shorefast sea ice in the Chukchi Sea and use of ice by the community. Shorefast ice stability and community strategies for safe hunting provide a framework for data collection and knowledge sharing that reveals how nuanced observations by Inupiat ice experts relate to identifying hazards. In particular, shorefast ice break-out events represent a significant threat to the lives of hunters. Fault tree analysis (FTA) is used to combine local and time-specific observations of ice conditions by both geophysical instruments and local experts, and to evaluate how ice features, atmospheric and oceanic forces, and local to regional processes interact to cause break-out events. Each year, the Barrow community builds trails across shorefast ice for use during the spring whaling season. In collaboration with hunters, a systematic multi-year survey (2007--2011) was performed to map these trails and measure ice thickness along them. Relationships between ice conditions and hunter strategies that guide trail placement and risk assessment are explored. In addition, trail surveys provide a meaningful and consistent approach to monitoring the thickness distribution of shorefast ice, while establishing a baseline for assessing future environmental change and potential impacts to the community. Coastal communities in the region have proven highly adaptive in their ability to safely and successfully hunt from sea ice over the last 30 years as significant changes have been observed in the ice zone north of Alaska. This research further illustrates how Barrow's whaling community copes with year-to-year variability and significant intra-seasonal changes in ice conditions. Hence, arctic communities that have coped with such short-term variability may be more adaptive to future environmental change than communities located in less dynamic environments

Toward quantifying the increasing role oceanic heat in sea ice loss in the new Arctic

Author Posting. © American Meteorological Society, 2015. This article is posted here by permission of American Meteorological Society for personal use, not for redistribution. The definitive version was published in Bulletin of the American Meteorological Society 96 (2015): 2079–2105, doi:10.1175/BAMS-D-13-00177.1.The loss of Arctic sea ice has emerged as a leading signal of global warming. This, together with acknowledged impacts on other components of the Earth system, has led to the term “the new Arctic.” Global coupled climate models predict that ice loss will continue through the twenty-first century, with implications for governance, economics, security, and global weather. A wide range in model projections reflects the complex, highly coupled interactions between the polar atmosphere, ocean, and cryosphere, including teleconnections to lower latitudes. This paper summarizes our present understanding of how heat reaches the ice base from the original sources—inflows of Atlantic and Pacific Water, river discharge, and summer sensible heat and shortwave radiative fluxes at the ocean/ice surface—and speculates on how such processes may change in the new Arctic. The complexity of the coupled Arctic system, and the logistic and technological challenges of working in the Arctic Ocean, require a coordinated interdisciplinary and international program that will not only improve understanding of this critical component of global climate but will also provide opportunities to develop human resources with the skills required to tackle related problems in complex climate systems. We propose a research strategy with components that include 1) improved mapping of the upper- and middepth Arctic Ocean, 2) enhanced quantification of important process, 3) expanded long-term monitoring at key heat-flux locations, and 4) development of numerical capabilities that focus on parameterization of heat-flux mechanisms and their interactions.2016-06-0