Search

The darkening effects of biological impurities on ice and snow have been recognised as a control on the surface energy balance of terrestrial snow, sea ice, glaciers and ice sheets. With a heightened interest in understanding the impacts of a changing climate on snow and ice processes, quantifying the impact of biological impurities on ice and snow albedo (bioalbedo) and its evolution through time is a rapidly growing field of research. However, rigorous quantification of bioalbedo has remained elusive because of difficulties in isolating the biological contribution to ice albedo from that of inorganic impurities and the variable optical properties of the ice itself. For this reason, isolation of the biological signature in reflectance data obtained from aerial/orbital platforms has not been achieved, even when ground-based biological measurements have been available. This paper provides the cell-specific optical properties that are required to model the spectral signatures and broadband darkening of ice. Applying radiative transfer theory, these properties provide the physical basis needed to link biological and glaciological ground measurements with remotely sensed reflectance data. Using these new capabilities we confirm that biological impurities can influence ice albedo, then we identify 10 challenges to the measurement of bioalbedo in the field with the aim of improving future experimental designs to better quantify bioalbedo feedbacks. These challenges are (1) ambiguity in terminology, (2) characterising snow or ice optical properties, (3) characterising solar irradiance, (4) determining optical properties of cells, (5) measuring biomass, (6) characterising vertical distribution of cells, (7) characterising abiotic impurities, (8) surface anisotropy, (9) measuring indirect albedo feedbacks, and (10) measurement and instrument configurations. This paper aims to provide a broad audience of glaciologists and biologists with an overview of radiative transfer and albedo that could support future experimental design.

In the Norwegian archipelago of Svalbard, 90%-100% of exposed land is underlain by continuous permafrost. Permafrost is estimated to store over 1600 gigatons of carbon worldwide. Pingos, features that only exist in permafrost, ventilate methane in much the same manner as pockmarks can ventilate methane clathrates on the ocean floor. In winter 2019, pingos identified on satellite imagery were studied in the field via water samples. This was done to better understand these uncommon periglacial features and of the methane they release. A database was created using elevation datasets, GIS analysis, winter satellite photography, and geological data to identify pingos in Svalbard as well as the factors that influence their formation and behaviour. The spatial distribution of pingos and fault lines suggests a relationship between fault zones and the formation of pingos, possibly due to the discontinuity caused by the faults allowing for easier flow of groundwater. In addition, carbon dioxide and methane had a correlation which is probably associated to the microbial processes leading to the formation of methane. Deuterium was another important compound, likely due to the marine sediments within the Holocene marine limit. A predictive model was then established to show the relationship of carbon dioxide and deuterium with methane. This model estimates the amount of methane ventilated based on other compounds measured in pingos. By combining these scientific approaches, this data provides a step forward in understanding methane reservoirs within permafrost environments, particularly relevant in an unstable and changing climate. No arquipélago norueguês de Svalbard, 90% a 100% da terra exposta assenta em permafrost. Estima-se que o permafrost armazene mais de 1600 gigatoneladas de carbono, em todo o mundo. Pingos são morfologias que só existem no permafrost e que ventilam metano da mesma maneira que as pockmarks podem ventilar clatratos de metano no fundo do oceano. No inverno de 2019, os pingos identificados por imagens de satélite foram estudados no campo, através de amostras de água. Tal foi feito para melhor se entender as características destas incomuns estruturas periglaciais e o metano que elas libertam. Foi criada uma base de dados que congrega um conjunto de dados de elevação, análise de SIG, fotografia de satélite de inverno e dados geológicos que permitem identificar os pingos. A distribuição espacial dos pingos em relação às linhas de falhas parece indicar uma relação entre as zonas de falha e a formação de pingos, possivelmente devido às descontinuidades causadas pelas falhas, permitindo um fluxo mais fácil das águas subterrâneas. Além disso, verificou-se que o dióxido de carbono e o metano estão correlacionados, o que é provavelmente devido aos processos microbianos que levam à formação de metano. O deutério foi outro composto importante, provavelmente devido aos sedimentos marinhos dentro do limite marinho do Holocénico. Um modelo preditivo foi então estabelecido para mostrar a relação do metano com dióxido de carbono e deutério. Este modelo estima a quantidade de metano ventilada com base em outros compostos medidos em pingos. Ao combinar várias abordagens científicas, estes dados são um passo em frente na compreensão dos reservatórios de metano em ambientes de permafrost, particularmente relevantes numa situação climática instável e em mudança.