Alfred Wegener Institute for Polar and Marine Research
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The MOSES Sternfahrt Expeditions of the Research Vessels ALBIS, LITTORINA, LUDWIG PRANDTL and MYA II to the Elbe River, Elbe Estuary and German Bight in 2023
Get PDFPresenting land surface changes through the web-based Arctic Landscape EXplorer (ALEX) to permafrost communities – A permafrost service
Get PDFThe EU-funded Arctic PASSION research project focuses on refining, improving and extending pan-Arctic scientific and community-based monitoring systems. The aim is to create a coherent and integrated Arctic observing system, tailored to the needs of the users or stakeholders. Within the project’s Permafrost Service, we are developing a web-based portal, the ‘Arctic Landscape EXplorer’ (ALEX). In this online tool we present data on permafrost region land surface changes derived from remote sensing analysis. Using tailored visualizations and story maps as a means of more effectively communicating scientific observations of change, we specifically address non-scientific user communities, stakeholders, and rights holders in the Arctic
Microbial Communities Degrade Ancient Permafrost-Derived Organic Matter in Arctic Seawater
No full textThe Arctic is experiencing rapid warming, which among other processes results in increasing erosion of coastal permafrost and the release of ancient organic carbon (OC) into the Arctic Ocean, which in turn might result in greenhouse gas emissions following its decomposition. Supply of terrigenous organic matter to the ocean affects near‐shore nutrient concentrations and the composition of microbial communities—highlighting the need to understand the fate of permafrost‐derived carbon in this fragile ecosystem. We incubated material from coastal Yedoma permafrost for 85 days in seawater collected during the Arctic Century expedition. During this experiment, 2.8 ± 1.4% of OC from coastal Yedoma was respired to CO2. Radiocarbon analysis revealed that 88 ± 15% of the released CO2 originated from ancient material (∼40,000 years), indicating that degradation of permafrost OC reintroduces old carbon into the short‐term carbon cycle. Hence, the permafrost climate feedback may be enhanced in the coming decades when coastal erosion accelerates. Additionally, 0.9 ± 0.3% of Yedoma OC was leached as dissolved OC. The observed net production of inorganic nitrogen during the incubation could potentially provide a negative feedback by stimulating primary production. Bacterial community analysis showed a succession of primary responders to biolabile substrates (e.g., Psychrobacter and Colwellia) followed by secondary consumers of less biolabile substrates (e.g., Maribacter and Pseudohongiella), plus a potential establishment of permafrost associated‐bacteria on particles. Overall, our data show that OC input from thawing permafrost stimulates bacterial dynamics, with likely implications for regional biogeochemical cycles and the Earth's climate
Total alkalinity change: The perspective of phytoplankton stoichiometry
Get PDFMany biogeochemical processes change total alkalinity: this has been reported for carbonate precipitation and dissolution, uptake and release of various nitrogen-containing compounds, uptake of phosphate, sulfate reduction combined with methane oxidation. However, the list is not exhaustive. Here we discuss additional processes, namely the uptake of Mg, K, Ca by phytoplankton, and calculate their contribution based on the explicit conservative expression for TA and an extended (compared to Redfield's C : N : P) stoichiometry of phytoplankton. These additional contributions are of the same order of magnitude as that of phosphate uptake and thus much smaller than the contribution from nitrate uptake and of opposite sign to the contribution by nitrate and phosphate uptake
Changing greenhouse gas production within a thermokarst lagoon system, Reindeer Island, Mackenzie Delta, Canada
Get PDFThe permafrost carbon pool is an important storage of the terrestrial carbon cycle that is at risk as the Arctic rapidly warms. Accordingly, in 2019, the United Nations Environmental Program identified permafrost thaw as one of the top five emerging environmental issues of global concern (UNEP, 2019).
In addition to increasing microbial decomposition of organic material and greenhouse gas release, permafrost thaw also leads to surface changes. Thermokarst lakes and basins are the result of the decrease in soil volume by melting ice in the subsurface. Rising sea levels and coastal erosion lead to the flooding of thermokarst lakes or drained lake basins along the ice-rich permafrost coasts of Siberia, Alaska and Canada, leading to the formation of thermokarst lagoons. These Arctic lagoons form a transition zone between the terrestrial and marine permafrost regime and represent an ideal research object for how permafrost carbon is affected by increasingly marine conditions. Due to current and future climate change in the Arctic, it is expected that the formation and development of thermokarst lagoons will accelerate (Jenrich et al. 2021). So far, thermokarst lagoons and their role in climate change have hardly been explored. To investigate the greenhouse gas production under varying degrees of seawater influence, and thus to assess whether the organic material in thermokarst lagoons is degraded on different temporal scales, we incubated the surface sediment below the lagoons with artificial sea water at two concentrations (brackish 13 g/L and marine 36 g/L) anaerobic at 4°C for 1 year. Here brackish conditions are considered as near natural conditions and represent the greenhouse gas production in the current state, while marine conditions represent the greenhouse gas production after the transition into a subsea state.
First results of the incubation experiment show that the greenhouse gas production is depending more on the location, thus microbial community and/or carbon degradability, than the salinity treatment. Highest methane and carbon dioxide production was measured at location 13, which is the youngest lagoon, least connected to the sea.
In conclusion, we expect that coastal permafrost erosion is leading to higher sediment and organic carbon input and newly formed thermokarst lagoons produce more greenhouse gases than older, more connected lagoons
Separating Common Signal From Proxy Noise in Tree Rings
Get PDFTree rings are the most widely-used proxy records for reconstructing Common Era temperatures. Tree-ring records correlate strongly with temperature on an interannual basis, but studies have found discrepancies between tree rings and climate models on longer timescales, indicating that low-frequency noise could be prevalent in these archives. Using a large network of temperature-sensitive tree-ring records, we partition timeseries variance into a common (i.e., “signal”) and non-climatic (i.e., “noise”) component using a frequency-resolved signal-to-noise ratio (SNR) analysis. We find that the availability of stored resources from prior years (i.e., biological “memory”) dampens the climate signal at high-frequencies, and that independent noise reduces the SNR on long timescales. We also find that well-replicated, millennial-length records had the strongest common signal across centuries. Our work suggests that low-frequency noise models are appropriate for use in pseudoproxy experiments, and speaks to the continued value of high-quality data development as a top priority in dendroclimatology
Tracking gonadal development in fish: An in vivo MRI study on polar cod, Boreogadus saida (Lepechin, 1774)
Get PDFAbstractMagnetic resonance imaging (MRI) was applied to determine the sex of polar cod (Boreogadus saida Lepechin, 1774) (Actinopterygii: Gadidae) and to follow the gonadal development in individual animals over time. Individual unanaesthetised fish were transferred to a measurement chamber inside a preclinical 9.4 T MRI scanner and continuously perfused with aerated seawater. A screening procedure at an average of 3.5 h, consisting of a set of MRI scans of different orientations, was repeated every 4 weeks on the same set of reproducing B. saida (n = 10) with a body length of about 20 cm. Adapted multi‐slice flow‐compensated fast low‐angle shot (FcFLASH) and rapid acquisition with relaxation enhancement (RARE) protocols with an in‐plane resolution of 313 μm and an acquisition time of 2.5 min were used to visualise the morphology of various organs, including the gonads within the field of view (FOV). The MR images provided high resolution, enabling specific sex determination, calculation of gonad volumes, and determination of oocyte sizes. Gonad maturation was followed over 4 months from November 2021 until shortly before spawning in February 2022. The gonad volume increased by 2.3–25.5% for males and by 11.5–760.7% for females during the observation period. From October to February, the oocyte diameter increased from 427 μm (n = 1) to 1346 ± 27 μm (n = 4). Interestingly, individual oocytes showed changes in MR contrast over time that can be attributed to the morphological development of the oocytes. The results fit well with previous literature data from classical invasive studies. The presented approach has great potential for various ecophysiological applications such as monitoring natural or delayed development of internal organs or sex determination under different environmental conditions.</jats:p
Spatial Scales of Kinetic Energy in the Arctic Ocean
Get PDFDespite the importance of the Arctic Ocean for the large-scale circulation and climate, there is still a knowledge gap in our understanding of the spatial characteristics of the Arctic Ocean circulation, especially for the mesoscale. This paper investigates the spatial characteristics of the Arctic Ocean circulation using a simulation with 1 km horizontal resolution. We revealed that there are two peaks in the kinetic energy (KE) spectral density at the 400 m depth, one at the gyre scale of the Arctic Circumpolar Boundary Current (centered at 1,700–2,000 km), and the other associated with the mesoscale (at about 60 km). However, at the 70 m depth, the boundary currents tend to mask the spectrum peak associated with the mesoscale. The KE spectrum exhibits a power-law scaling typical for ocean eddies. We found that about 80% (50%) of the KE is on scales smaller than 100 km (30 km). The maximum KE content is in the 10–20 km scale band in most of the eddy-rich regions of the abyssal ocean. The seasonality of the KE spectrum and KE content inside the Arctic Ocean follow the seasonality of eddy activity and baroclinicity, with low values in spring and maxima in late summer to autumn, and the seasonal variation is stronger at the 70 m depth than the 400 m depth. The strong concentration of KE on the very small spatial scales warrants future studies on energy transfer between scales in the Arctic Ocean