Alfred Wegener Institute for Polar and Marine Research
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Snow on permafrost: the effect of spatial snow variability on soil temperature in Trail Valley Creek, NWT, Canada
Get PDFSnow is a potent insulator, influencing the temperature of the active layer and the permafrost in the Arctic region. However, our understanding of spatial patterns of snow properties and their interplay with vegetation remains limited due to scarcity of local and regional snow data. Furthermore, the duration, depth, and physical properties of the Arctic snow cover are changing with rising air temperature and new precipitation patterns. We study the spatial snow distribution and its drivers and consequences around the Trail Valley Creek research catchment in the Northwest Territories, Canada. Our dataset includes a 143 km&#178; snow depth raster captured on April 2, 2023, at a 1-meter spatial resolution, as well as data from 13 spatially distributed loggers measuring air/snow temperature, soil surface temperature, and soil temperature at 8 cm depth from August 27, 2022, to August 9, 2023. Detailed information on vegetation types, structure, and soil properties at all locations is included. Our analysis covers the timing of soil freeze and thaw, snow and soil temperatures, and their correlation with vegetation characteristics, particularly focusing on April snow depth. Our findings underscore the pivotal role of snow in regulating soil temperature, making it a key driver for permafrost protection or thaw. The results reveal significant variability in April snow depth across the 13 study locations, ranging from no snow to 1.7 meters, resulting in winter minimum soil temperatures between -31&#176;C and -4&#176;C. The study confirms that thicker snow cover contributes to warmer soil temperatures. While the soil at 8 cm freezes uniformly in mid-October across all sites, snow patterns lead to high variability in soil thawing dates, which span one month between May 10 and June 08, 2023. Understanding the spatial patterns of snow depth, thermal properties, and timing is crucial for assessing the snow effect on soil temperature. The large range of winter soil temperatures, which we observed, may lead to differences in thaw depth development in the following summer and potentially to talik formation affecting permafrost stability.</jats:p
Quantitative description of six fish species’ gut contents and prey abundances in the Baltic Sea (1968–1978)
Get PDFThe dataset presents a compilation of stomach contents from six demersal fish species from two functional groups inhabiting the Baltic Sea. It includes detailed information on prey identities, body masses, and biomasses recovered from both the fish’s digestive systems and their surrounding environment. Environmental parameters, such as salinity and temperature levels, have been integrated to enrich this dataset. The juxtaposition of information on prey found in stomachs and in the environment provides an opportunity to quantify trophic interactions across different environmental contexts and investigate how fish foraging behaviour adapts to changes in their environment, such as an increase in temperature. The compilation of body mass and taxonomic information for all species allows approaching these new questions using either a taxonomic (based on species identity) or functional trait (based on body mass) approach
Local hydroclimate alters interpretation of speleothem δ18O records
No full textOxygen isotopes (δ18O) are the most commonly utilized speleothem proxy and have provided many foundational records of paleoclimate. Thus, understanding processes affecting speleothem δ18O is crucial. Yet, prior calcite precipitation (PCP), a process driven by local hydrology, is a widely ignored control of speleothem δ18O. Here we investigate the effects of PCP on a stalagmite δ18O record from central Vietnam, spanning 45 – 4 ka. We employ a geochemical model that utilizes speleothem Mg/Ca and cave monitoring data to correct the δ18O record for PCP effects. The resulting record exhibits improved agreement with regional speleothem δ18O records and climate model simulations, suggesting that the corrected record more accurately reflects precipitation δ18O (δ18Op). Without considering PCP, our interpretations of the δ18O record would have been misleading. To avoid misinterpretations of speleothem δ18O, our results emphasize the necessity of considering PCP as a significant driver of speleothem δ18O
Quantifying the influence of snow over sea ice morphology on L-band passive microwave satellite observations in the Southern Ocean
Get PDFAntarctic snow on sea ice can contain slush, snow ice, and stratified layers, complicating satellite retrieval processes for snow depth, ice thickness, and sea ice concentration. The presence of moist and brine-wetted snow alters microwave snow emissions and modifies the energy and mass balance of sea ice. This study assesses the impact of brine-wetted snow and slush layers on L-band surface brightness temperatures (TBs) by synergizing a snow stratigraphy model (SNOWPACK) driven by atmospheric reanalysis data and the RAdiative transfer model Developed for Ice and Snow in the L-band (RADIS-L) v1.0 The updated RADIS-L v1.1 further introduces parameterizations for brine-wetted snow and slush layers over Antarctic sea ice. Our findings highlight the importance of including both brine-wetted snow and slush layers in order to accurately simulate L-band brightness temperatures, laying the groundwork for improved satellite retrievals of snow depth and ice thickness using satellite sensors such as Soil Moisture and Ocean Salinity (SMOS) and Soil Moisture Active Passive (SMAP). However, biases in modelled and observed L-band brightness temperatures persist, which we attribute to small-scale sea ice heterogeneity and snow stratigraphy. Given the scarcity of comprehensive in situ snow and ice data in the Southern Ocean, ramping up observational initiatives is imperative to not only provide satellite validation datasets but also improve process-level understanding that can scale up to improving the precision of satellite snow and ice thickness retrievals
Diversity of eukaryote plankton and phycotoxins along the West Kalaallit Nunaat (Greenland) coast
Get PDFThe West Kallaallit Nunaat (Greenland) coast, characterized by a variety of fjords, bays, and channels influenced by glacier melting and Atlantic and Arctic waters, is one of the most affected ecosystems by climate change. Here, we combine oceanography, optics, microscopy, high throughput sequencing, microalgal strain establishments, and state-of-the-art analytical methods to fully characterize the diversity, community composition, and toxin repertoire of the eukaryotic plankton members of the coast of the West Kalaallit Nunaat (Greenland). Results indicate that the West Kalaallit Nunaat (Greenland) coast is a complex and oceanographically challenging system, where the superimposition of water masses of different origins, the penetration of light and its repercussions, generate mainly vertical, rather than horizontal heterogeneity in nutrient concentration and plankton biomass. Nevertheless, our molecular data reveal a strong homogeneity and a high diversity in the plankton community along the Greenland coast. We confirmed the presence of five phycotoxin groups: domoic acid and paralytic shellfish toxins were most abundant along the transect from Qeqertarsuup Tunua (Disko Bay) to the northern Baffin Bay, while spirolides, yessotoxins and pectenotoxins were predominant in Nuup Kangerlua (GodthaabFjord) and Qeqertarsuup Tunua (Disko Bay). Concentrations of these phycotoxins correlate differently to temperature, salinity and nutrients, reflecting the ecological differences of their producers. Patterns of paralytic shellfish and spirolide toxins suggest the presence of genetically distinct populations of Alexandrium along the Western Kalaallit Nunaat (Greenland). Phytoplankton strains isolated during this oceanographic campaign resemble, in most cases, the toxin profiles of the respective field stations. Overall, this work shows the diversity and community composition of the plankton at the Western Kalaallit Nunaat coast and reveals a distinct spatial distribution of phycotoxins, with certain toxin groups restricted to specific areas.</jats:p
Modeling coupled small scale Multi-X anisotropic processes in sea ice - a physical-biological coupled bi-scale approach
Get PDFModerate and extreme warming under a varied resource supply alter the microzooplankton–phytoplankton coupling in North Sea coastal communities
Get PDFRising temperature is one of the most visible effects of global change on Earth; however, it is barely known how moderate or extreme warming events impact the trophic interactions and the energy transfer in food webs. Combining a mesocosm approach and two-point dilution incubations, we quantified how natural plankton assemblages respond to moderate and extreme warming (+6°C vs. +12°C above ambient temperature), covering a nitrogen-to-phosphorus gradient from nutrient-saturated to limited conditions. We addressed how both drivers altered the community structure and mediated the phytoplankton growth (μ) and microzooplankton grazing (m) rates. Moderate and extreme warming effects on the microzooplankton–phytoplankton relationship differed and were mediated by time. This trophic interaction was weakened due to μ outpacing m regardless of the warming treatment at the middle of the experiment. By contrast, after the acclimation period, the trophic interaction was strengthened by increased grazing under extreme warming. The variable grazing pressure found at different temporal scales only under extreme warming could be due to a decreased microzooplankton grazing pressure with increasing temperature when prey biomass is low, and vice versa. Also, it could be a consequence of a switch toward mixotrophy or that the temperatures experienced by grazers were suboptimal compared to their prey. Finally, we found that temperature was the main driver whereas resource availability played a minor role in this trophic interaction. As climate change will intensify in the future, food webs could be less productive but more efficient, and thus, potentially support a higher secondary production
Effect of particles from wind turbine blades erosion on blue mussels Mytilus edulis.
Get PDFOffshore wind farms (OWFs) pose new anthropogenic pressures on the marine environment as the erosion of turbine blades release organic and inorganic substances with potential consequences for marine life. In the present study, possible effects of the released particles and their chemical constituents on the metabolic profile of the blue mussel, Mytilus edulis, were investigated, utilizing 1H NMR spectroscopy. In the lab, mussels were exposed for 7 and 14 days to different concentrations (10 and 40 mg/L) of microplastic (MP) particles which were derived from cryo-milled rotor blade coatings and core materials (glass fiber polymer, GFP). Raman imaging techniques revealed that 30-40 % of the coating and GFP particles had MP sizes below 5 μm, with the majority (~98 %) being ≤50 μm. Despite the identified enrichment factors (EF) for metals and metalloids from the rotor blade materials, especially Ba, Cu, Cd, Cr and Ni with EFs between 0.93 and 6.1, untargeted metabolic profiling of the entire soft body tissues of M. edulis showed no significant metabolic disruption, regardless of the particle concentration. Observed trends in elevated concentrations of metabolites may indicate a possible short-term effect on mussels' neuroendocrine system and a possible long-term effect on energy metabolism. Experimental worst-case scenario of massive abrasion and the minimal response observed in M. edulis under the conditions tested suggest that erosion caused by wind turbine blades may pose little to no risk to bivalves at this stage. However, it is important to note that this study is only a preliminary step and further studies are needed to obtain a comprehensive overview of the issue before reaching a definite firm conclusion regarding the potential threat of OWFs abrasion to the marine environment, particularly considering the planned future extension of windpark construction in connection with the ongoing EU-wide energy transition
The effects of biomass depth distribution on phytoplankton spring bloom dynamics and composition in an Arctic fjord
Get PDFFjord systems are among the most productive and best described of Arctic marine habitats. Contributing substantially to that overall productivity, spring phytoplankton blooms are one of the most important features of fjord systems and of mid- and high-latitude oceans in general. Understanding specific mechanisms that control the timing, magnitude, and composition of these blooms is among the most central, and yet unresolved, questions within biological oceanography. To elucidate how the distribution of phytoplankton with depth affects bloom dynamics, we analyzed a comprehensive dataset on spring blooms in an Arctic fjord from three consecutive years, covering environmental drivers as well as ecological and biogeochemical dynamics. Our data show that the build-up of biomass correlated positively with the chlorophyll layer depth (CLD, defined as the depth at the bottom of the layer containing a threshold concentration of chlorophyll a), with highest rates of biomass accumulation occurring in more depth-extended distributions despite lower light availability at greater depths. Based on our results, we hypothesize that this relationship is caused by reduced grazing pressure under conditions of deepening mixing layers. Further, we postulate that changes in the depth to which phytoplankton biomass is distributed have the potential to control the species composition of the Arctic phytoplankton spring bloom, with diatoms dominating in situations with shallow CLDs and Phaeocystis pouchetii with deepening CLDs, which may impact the biogeochemistry of the studied fjord system differently