Elementa-Science of the Anthropocene最新文献

{"title":"HELiPOD—Revolution and evolution of a helicopter-borne measurement system for multidisciplinary research in demanding environments","authors":"Falk Pätzold, Lutz Bretschneider, Stefan Nowak, Björn Brandt, Andreas Schlerf, Magnus Ole Asmussen, Sven Bollmann, Konrad Bärfuss, Barbara Harm-Altstädter, Peter Hecker, Birgit Wehner, Berend G. van der Wall, Torsten Sachs, Heidi Huntrieser, Anke Roiger, Astrid Lampert","doi":"10.1525/elementa.2023.00031","DOIUrl":"https://doi.org/10.1525/elementa.2023.00031","url":null,"abstract":"The helicopter-borne measurement system HELiPOD is a platform for atmospheric and other environmental measurements to investigate local and regional phenomena. It can be operated in remote areas, as from a research vessel with a helicopter, without the need for a runway. This article presents the current design concept, technical details, and sensor package of HELiPOD, which was completely renewed for the deployment during the MOSAiC (Multidisciplinary drifting Observatory for the Study of Arctic Climate) expedition across the North Polar Ocean in 2019/2020. It was updated for the deployment in the methane campaigns METHANE-To-Go-Poland to study methane emissions from coal mines in South Poland, and METHANE-To-Go-Nordstream, a follow-up campaign to study methane emissions from the Baltic Sea after the NordStream pipeline leaks in 2022. The HELiPOD has the dimensions of 5.2 m × 2.1 m × 1.2 m and a weight of around 325 kg. It provides the possibility for flight patterns on a horizontal scale of typically 100 m–100 km and at altitudes from 10 m up to 3 km. HELiPOD employs distributed data acquisition and central data synchronization, equipped with sensors relevant to five fields of research: atmospheric dynamics, trace gases, aerosols, radiation, and surface properties. The focus of this article is the technical realization, in particular the data acquisition system for about 60 sensors, as well as concepts for energy supply and thermal management. It describes the complementary use of different measurement principles and redundant sensors for improved data quality. Operational procedures are also discussed.","PeriodicalId":54279,"journal":{"name":"Elementa-Science of the Anthropocene","volume":"99 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135058593","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"环境科学与生态学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Snowmelt contribution to Arctic first-year ice ridge mass balance and rapid consolidation during summer melt","authors":"Benjamin A. Lange, Evgenii Salganik, Amy Macfarlane, Martin Schneebeli, Knut Høyland, Jessie Gardner, Oliver Müller, Dmitry V. Divine, Doreen Kohlbach, Christian Katlein, Mats A. Granskog","doi":"10.1525/elementa.2022.00037","DOIUrl":"https://doi.org/10.1525/elementa.2022.00037","url":null,"abstract":"Sea ice ridges are one of the most under-sampled and poorly understood components of the Arctic sea ice system. Yet, ridges play a crucial role in the sea ice mass balance and have been identified as ecological hotspots for ice-associated flora and fauna in the Arctic. To better understand the mass balance of sea ice ridges, we drilled and sampled two different first-year ice (FYI) ridges in June–July 2020 during the Multidisciplinary drifting Observatory for the Study of Arctic Climate (MOSAiC). Ice cores were cut into 5 cm sections, melted, then analyzed for salinity and oxygen (δ18O) isotope composition. Combined with isotope data of snow samples, we used a mixing model to quantify the contribution of snow to the consolidated sea ice ridge mass. Our results demonstrate that snow meltwater is important for summer consolidation and overall ice mass balance of FYI ridges during the melt season, representing 6%–11% of total ridged ice mass or an ice thickness equivalent of 0.37–0.53 m. These findings demonstrate that snowmelt contributes to consolidation of FYI ridges and is a mechanism resulting in a relative increase of sea ice volume in summer. This mechanism can also affect the mechanical strength and survivability of ridges, but also contribute to reduction of the habitable space and light levels within FYI ridges. We proposed a combination of two pathways for the transport of snow meltwater and incorporation into ridge keels: percolation downward through the ridge and/or lateral transport from the under-ice meltwater layer. Whether only one pathway or a combination of both pathways is most likely remains unclear based on our observations, warranting further research on ridge morphology.","PeriodicalId":54279,"journal":{"name":"Elementa-Science of the Anthropocene","volume":"21 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135182922","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"环境科学与生态学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Structures of coexisting marine snow and zooplankton in coastal waters of Svalbard (European Arctic)","authors":"Emilia Trudnowska, Katarzyna Błachowiak-Samołyk, Lars Stemmann","doi":"10.1525/elementa.2023.00010","DOIUrl":"https://doi.org/10.1525/elementa.2023.00010","url":null,"abstract":"How plankton and particles are arranged spatially and the configurations of their co-occurrence shape the rates of organic matter production, utilization, and export within marine systems. The aim of this study was to examine whether the composition of marine snow (particles and aggregates >500 µm) and its coexistence with zooplankton change with depth layer, level of zooplankton dominance, chlorophyll fluorescence, and turbidity across the coastal–offshore gradients of hydrographically different Arctic fjords. The distribution and concentrations of zooplankton and marine snow were assessed in situ using an underwater vision profiler (UVP) in Svalbard waters during summer 2019. UVP counts of marine snow drastically outnumbered zooplankton at glacial stations, whereas zooplankton dominated offshore and in upper water layers, even in coastal waters. The most common compositional structure was dominance by an elongated morphotype of marine snow, often co-occurring with small dark (opaque) particles below 40 m depth, implying that these were the typical forms exported directly from surface layers. The other widespread type of structuring was dominance of UVP counts by copepods. They often coexisted with a flake morphotype of marine snow associated with high chlorophyll fluorescence. Structuring dominated by dark morphotypes was observed mainly near glaciers and in deep fjord basins. The highest amount of marine snow, represented by a high degree of dark morphotype, was observed in Hornsund, the most Arctic-type fjord. A Phaeocystis-associated agglomerated morphotype of marine snow occurred scarcely and only in more Atlantic-influenced fjords. A bimodal distribution pattern, with one abundance peak at the surface and another in deeper layers (>80 m) was observed offshore and in Kongsfjorden. This study emphasizes the high potential of UVPs for tracking links between plankton and detritus directly in their natural environment, and that variation in their co-occurrence may provide a proxy for the state of a pelagic ecosystem.","PeriodicalId":54279,"journal":{"name":"Elementa-Science of the Anthropocene","volume":"165 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135214215","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"环境科学与生态学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Thin and transient meltwater layers and false bottoms in the Arctic sea ice pack—Recent insights on these historically overlooked features","authors":"Madison M. Smith, Hélène Angot, Emelia J. Chamberlain, Elise S. Droste, Salar Karam, Morven Muilwijk, Alison L. Webb, Stephen D. Archer, Ivo Beck, Byron W. Blomquist, Jeff Bowman, Matthew Boyer, Deborah Bozzato, Melissa Chierici, Jessie Creamean, Alessandra D’Angelo, Bruno Delille, Ilker Fer, Allison A. Fong, Agneta Fransson, Niels Fuchs, Jessie Gardner, Mats A. Granskog, Clara J. M. Hoppe, Mario Hoppema, Mario Hoppmann, Thomas Mock, Sofia Muller, Oliver Müller, Marcel Nicolaus, Daiki Nomura, Tuukka Petäjä, Evgenii Salganik, Julia Schmale, Katrin Schmidt, Kirstin M. Schulz, Matthew D. Shupe, Jacqueline Stefels, Linda Thielke, Sandra Tippenhauer, Adam Ulfsbo, Maria van Leeuwe, Melinda Webster, Masaki Yoshimura, Liyang Zhan","doi":"10.1525/elementa.2023.00025","DOIUrl":"https://doi.org/10.1525/elementa.2023.00025","url":null,"abstract":"The rapid melt of snow and sea ice during the Arctic summer provides a significant source of low-salinity meltwater to the surface ocean on the local scale. The accumulation of this meltwater on, under, and around sea ice floes can result in relatively thin meltwater layers in the upper ocean. Due to the small-scale nature of these upper-ocean features, typically on the order of 1 m thick or less, they are rarely detected by standard methods, but are nevertheless pervasive and critically important in Arctic summer. Observations during the Multidisciplinary drifting Observatory for the Study of Arctic Climate (MOSAiC) expedition in summer 2020 focused on the evolution of such layers and made significant advancements in understanding their role in the coupled Arctic system. Here we provide a review of thin meltwater layers in the Arctic, with emphasis on the new findings from MOSAiC. Both prior and recent observational datasets indicate an intermittent yet long-lasting (weeks to months) meltwater layer in the upper ocean on the order of 0.1 m to 1.0 m in thickness, with a large spatial range. The presence of meltwater layers impacts the physical system by reducing bottom ice melt and allowing new ice formation via false bottom growth. Collectively, the meltwater layer and false bottoms reduce atmosphere-ocean exchanges of momentum, energy, and material. The impacts on the coupled Arctic system are far-reaching, including acting as a barrier for nutrient and gas exchange and impacting ecosystem diversity and productivity.","PeriodicalId":54279,"journal":{"name":"Elementa-Science of the Anthropocene","volume":"233 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135403116","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"环境科学与生态学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Fossil fuel divestment in U.S. higher education: Endowment dependence and temporal dynamics","authors":"Alexander R. Barron, Rachel C. Venator, Ella V. H. Carlson, Jane K. Andrews, Junwen Ding, David DeSwert","doi":"10.1525/elementa.2023.00059","DOIUrl":"https://doi.org/10.1525/elementa.2023.00059","url":null,"abstract":"Since 2011, students and others have pushed U.S. higher education institutions (HEIs) to divest their endowments from fossil fuel producing industries. In the past decade, fossil fuel divestment (FFD) has become the fastest growing divestment movement in history, with over 140 U.S. HEIs announcing divestment commitments. We conduct a quantitative analysis of the phases of U.S. 4-year HEI divestment announcements (as well as rejections of divestment) to better understand the dynamics. Announcements began (2012–2017) with a number of schools divesting, followed by a second phase, where new divestment announcements slowed. The third phase, which began around 2019, showed a renewed increase in divestments. Formal rejections of divestment followed a similar pattern in the early years, where rejections were slightly more common and represented more endowment value but have declined as some schools reversed public positions. Schools that have divested from fossil fuels now represent roughly 3% of 4-year U.S. HEIs and 39% of HEI endowment value in our data. Roughly 133% more endowment value is now associated with U.S. schools that have publicly divested from fossil fuels than with those that have explicitly rejected it. Early divestments from all fossil fuels came nearly exclusively from schools with a relatively low endowment dependence (the share of operating expenses derived from the endowment) although qualitative factors were also likely important. We discuss the implications of these findings in the context of different theories of change for the divestment movement. In particular, we note that 99% of 4-year HEIs representing roughly 95% of endowment value in our dataset are less dependent upon their endowment than at least one recently divested HEI, suggesting that large endowment or high dependence on endowment are no longer strict barriers to FFD for most schools.","PeriodicalId":54279,"journal":{"name":"Elementa-Science of the Anthropocene","volume":"7 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135507486","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"环境科学与生态学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Pan-Arctic plankton community structure and its global connectivity","authors":"F. Ibarbalz, N. Henry, F. Mahé, M. Ardyna, A. Zingone, Eleonora Scalco, C. Lovejoy, F. Lombard, O. Jaillon, D. Iudicone, S. Malviya, Matthew B. Sullivan, Samuel Chaffron, E. Karsenti, M. Babin, E. Boss, P. Wincker, Lucie Zinger, C. de Vargas, C. Bowler, L. Karp‐Boss","doi":"10.1525/elementa.2022.00060","DOIUrl":"https://doi.org/10.1525/elementa.2022.00060","url":null,"abstract":"The Arctic Ocean (AO) is being rapidly transformed by global warming, but its biodiversity remains understudied for many planktonic organisms, in particular for unicellular eukaryotes that play pivotal roles in marine food webs and biogeochemical cycles. The aim of this study was to characterize the biogeographic ranges of species that comprise the contemporary pool of unicellular eukaryotes in the AO as a first step toward understanding mechanisms that structure these communities and identifying potential target species for monitoring. Leveraging the Tara Oceans DNA metabarcoding data, we mapped the global distributions of operational taxonomic units (OTUs) found on Arctic shelves into five biogeographic categories, identified biogeographic indicators, and inferred the degree to which AO communities of unicellular eukaryotes share members with assemblages from lower latitudes. Arctic/Polar indicator OTUs, as well as some globally ubiquitous OTUs, dominated the detection and abundance of DNA reads in the Arctic samples. OTUs detected only in Arctic samples (Arctic-exclusives) showed restricted distribution with relatively low abundances, accounting for 10–16% of the total Arctic OTU pool. OTUs with high abundances in tropical and/or temperate latitudes (non-Polar indicators) were also found in the AO but mainly at its periphery. We observed a large change in community taxonomic composition across the Atlantic-Arctic continuum, supporting the idea that advection and environmental filtering are important processes that shape plankton assemblages in the AO. Altogether, this study highlights the connectivity between the AO and other oceans, and provides a framework for monitoring and assessing future changes in this vulnerable ecosystem.","PeriodicalId":54279,"journal":{"name":"Elementa-Science of the Anthropocene","volume":"1 1","pages":""},"PeriodicalIF":3.9,"publicationDate":"2023-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"66944632","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"环境科学与生态学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Trends in agroforestry research over 4 decades","authors":"Zoe Hastings Silao, Xorla S. Ocloo, Melissa Chapman, Lauren Hunt, Katelyn Stenger","doi":"10.1525/elementa.2022.00151","DOIUrl":"https://doi.org/10.1525/elementa.2022.00151","url":null,"abstract":"Agroforestry has a high potential to contribute to climate change mitigation and adaptation as a nature-based climate solution and is increasingly included as a climate strategy in international agreements and national plans. Yet, how to equitably increase and sustain agroforestry on the scale needed to meet these targets remains unclear. Examining broad trends in the existing 4 decades of agroforestry literature can highlight gaps and opportunities for future research that enables agroforestry transitions. Using text analytics and a full-text, corpus-based approach, we analyzed changes in word use in 9,664 agroforestry research articles and reports published between 1980 and 2020 with regard to 4 key themes of the social dimensions of agroforestry transitions: (1) agreements and policies; (2) scales and decision-making agents; (3) knowledge, culture, and equity; and (4) frameworks and methods. We then compared the frequency of these themes in research articles and reports. Despite the most frequently used terms across all 4 decades being primarily ecological (e.g., forest, species, soil), the lexicon of agroforestry literature has expanded to incorporate more social, economic, and political elements (e.g., livelihood, knowledge, community) over time, and as agroforestry has become more central to climate change adaptation and mitigation targets. Trends in the frequency of several terms (e.g., biodiversity, development, climate) corresponded with the signing of intergovernmental agreements, illustrating the responsiveness of the field to global priorities. Reports had a higher frequency of terms related to social themes than research articles. We discuss the implications of these emergent trends and opportunities for future research in support of sustainable and just agroforestry transitions.","PeriodicalId":54279,"journal":{"name":"Elementa-Science of the Anthropocene","volume":"22 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135561482","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"环境科学与生态学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Spatiotemporal changes in Iranian rivers’ discharge","authors":"Mohsen Maghrebi, R. Noori, A. D. Mehr, R. Lak, Farzaneh Darougheh, Rahman Razmgir, Hossein Farnoush, Hamid Taherpour, Seyed Mohammad Reza Alavai Moghaddam, Alireza Araghi, B. Kløve","doi":"10.1525/elementa.2022.00002","DOIUrl":"https://doi.org/10.1525/elementa.2022.00002","url":null,"abstract":"Trends in river flow at national scale in Iran remain largely unclear, despite good coverage of river flow at multiple monitoring stations. To address this gap, this study explores the changes in Iranian rivers’ discharge using regression and analysis of variance methods to historically rich data measured at hydrometric stations. Our assessment is performed for 139 selected hydrometric stations located in Iranian data-rich basins that cover around 97% of the country’s rivers with more than 30 years of observations. Our findings show that most of the studied Iran’s rivers (>56%) have undergone a downward trend (P value < 0.1) in mean annual flow that is 2.5 times bigger than that obtained for the large world’s rivers, resulting in a change from permanent to intermittent for around 20% of rivers in Iran’s subbasins. Given no significant change observed in the main natural drivers of Iranian rivers’ discharge, these findings reveal the country’s surface fresh-water shortage was caused dominantly by anthropogenic disturbances rather than variability in climate parameters. It may even indicate the development of new river regimes with deep implications for future surface fresh-water storage in the country. This research’s findings improve our understanding of changes in Iranian rivers’ discharge and provide beneficial insights for sustainable management of water resources in the country.","PeriodicalId":54279,"journal":{"name":"Elementa-Science of the Anthropocene","volume":"1 1","pages":""},"PeriodicalIF":3.9,"publicationDate":"2023-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"66943147","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"环境科学与生态学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Plume dispersion from the Nelson and Hayes rivers into Hudson Bay using satellite remote sensing of CDOM and suspended sediment","authors":"A. Basu, G. McCullough, S. Bélanger, A. Mukhopadhyay, D. Doxaran, K. Sydor, D. Barber, J. Ehn","doi":"10.1525/elementa.2022.00076","DOIUrl":"https://doi.org/10.1525/elementa.2022.00076","url":null,"abstract":"Change in the dispersion pattern of Arctic river plumes due to climate change and hydroelectric regulation is challenging to monitor, calling for synoptic and continuous observation using satellite remote sensing. Algorithms for colored dissolved organic matter (CDOM) and total suspended solids (TSS) were applied to moderate resolution imaging spectroradiometer (MODIS) imagery to study Nelson and Hayes river plume dispersion into southwestern Hudson Bay, employing quantile regressions to capture dispersion variability along a freshwater–marine gradient. MODIS-derived CDOM and TSS quantile concentrations (Q0.05–Q0.95) decreased exponentially with distance from the Nelson River mouth. The Q0.95 asymptote marked the offshore extent of the river plume and was used to determine the marine and river water fractions of surface water in southwestern Hudson Bay. At about 125 km from the Nelson River mouth, CDOM was reduced by 75% of its river mouth values. Owing to the significant co-variability between CDOM dilution and river discharge, a 0.25 river water fraction was estimated at this distance, which varied by ±35 km during flood and ebb flows. Anti-cyclonic winds transported the river plume along the 54° azimuth towards central Hudson Bay, while cyclonic winds propagated the plume eastward along the south shore. Particle settling in the coastal waters and resuspension events from mudflats and/or bank erosion caused non-significant relationships between TSS and river discharge. This non-conservative behavior renders TSS a less useful optical tracer of Nelson and Hayes river water in southwestern Hudson Bay. The novel quantile regression approach for defining boundaries of river water dilution in transitional waters may provide helpful information for coastal management on a spatial scale of tens to hundreds of kilometers, ranging from near real-time monitoring to seasonal and multi-year studies.","PeriodicalId":54279,"journal":{"name":"Elementa-Science of the Anthropocene","volume":"1 1","pages":""},"PeriodicalIF":3.9,"publicationDate":"2023-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"66944314","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"环境科学与生态学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Evolution of the microstructure and reflectance of the surface scattering layer on melting, level Arctic sea ice","authors":"Amy R. Macfarlane, R. Dadić, M. Smith, B. Light, M. Nicolaus, Hannula Henna-Reetta, M. Webster, F. Linhardt, S. Hämmerle, M. Schneebeli","doi":"10.1525/elementa.2022.00103","DOIUrl":"https://doi.org/10.1525/elementa.2022.00103","url":null,"abstract":"The microstructure of the uppermost portions of a melting Arctic sea ice cover has a disproportionately large influence on how incident sunlight is reflected and absorbed in the ice/ocean system. The surface scattering layer (SSL) effectively backscatters solar radiation and keeps the surface albedo of melting ice relatively high compared to ice with the SSL manually removed. Measurements of albedo provide information on how incoming shortwave radiation is partitioned by the SSL and have been pivotal to improving climate model parameterizations. However, the relationship between the physical and optical properties of the SSL is still poorly constrained. Until now, radiative transfer models have been the only way to infer the microstructure of the SSL. During the MOSAiC expedition of 2019–2020, we took samples and, for the first time, directly measured the microstructure of the SSL on bare sea ice using X-ray micro-computed tomography. We show that the SSL has a highly anisotropic, coarse, and porous structure, with a small optical diameter and density at the surface, increasing with depth. As the melting surface ablates, the SSL regenerates, maintaining some aspects of its microstructure throughout the melt season. We used the microstructure measurements with a radiative transfer model to improve our understanding of the relationship between physical properties and optical properties at 850 nm wavelength. When the microstructure is used as model input, we see a 10–15% overestimation of the reflectance at 850 nm. This comparison suggests that either a) spatial variability at the meter scale is important for the two in situ optical measurements and therefore a larger sample size is needed to represent the microstructure or b) future work should investigate either i) using a ray-tracing approach instead of explicitly solving the radiative transfer equation or ii) using a more appropriate radiative transfer model.","PeriodicalId":54279,"journal":{"name":"Elementa-Science of the Anthropocene","volume":"67 1","pages":""},"PeriodicalIF":3.9,"publicationDate":"2023-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"66945151","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"环境科学与生态学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}