Lateral transport of sediment and organic matter, derived from coastal erosion, into the nearshore zone of the southern Beaufort Sea, Canada

Herschel Basin is a natural depression on the southern Beaufort Shelf, which is located in the western Canadian Arctic between the Mackenzie Delta and the Alaskan border. The submarine basin of late Wisconsin age is a natural sediment trap for material eroded along the Yukon coast and through its unique position within the area also a valuable paleoenvironmental archive. During a field campaign in spring 2016, a thirteen meter long sediment core was obtained from the Herschel Basin. The aim of this Master’s thesis was to quantify the amount of carbon, nitrogen and sediment with terrestrial origin throughout the sediment column from the Herschel Basin. The increasing research effort to understand the dynamics of Arctic coasts is justified by their contribution to the global carbon budget and their vulnerability. The results showed that the majority of sediment found in the sediment column of the Herschel Basin could be assigned to a mix of riverine and terrestrial/coastal inputs. However, the individual percentage of each input (marine, fluvial and terrestrial) could not be distinguished, due to lack of data. In conclusion, this thesis showed that in the Arctic nearshore zone coastal erosion affected by climate change will definitely have a negative impact on “[…] climate feedbacks, on nearshore food webs, and on local communities, whose survival still relies on marine biological resources”(M. Fritz et al., 2017)

Effect of temperature on carbon accumulation in northern lake systems over the past 21,000 years

Introduction: Rising industrial emissions of carbon dioxide and methane highlight the important role of carbon sinks and sources in fast-changing northern landscapes. Northern lake systems play a key role in regulating organic carbon input by accumulating carbon in their sediment. Here we look at the lake history of 28 lakes (between 50°N and 80°N) over the past 21,000 years to explore the relationship between carbon accumulation in lakes and temperature changes. Method: For this study, we calculated organic carbon accumulation rates (OCAR) using measured and newly generated organic carbon and dry bulk density data. To estimate new data, we used and evaluated seven different regression techniques in addition to a log-linear model as our base model. We also used combined age-depth modeling to derive sedimentation rates and the TraCE-21ka climate reanalysis dataset to understand temperature development since the Last Glacial Maximum. We determined correlation between temperature and OCAR by using four different correlation coefficients. Results: In our data collection, we found a slightly positive association between OCAR and temperature. OCAR values peaked during warm periods Bølling Allerød (38.07 g·m−2·yr−1) and the Early Holocene (40.68 g·m−2·yr−1), while lowest values occurred during the cold phases of Last Glacial Maximum (9.47 g·m−2·yr−1) and Last Deglaciation (10.53 g·m−2·yr−1). However, high temperatures did not directly lead to high OCAR values. Discussion: We assume that rapid warming events lead to high carbon accumulation in lakes, but as warming progresses, this effect appears to change as increased microbial activity triggers greater outgassing. Despite the complexity of environmental forcing mechanisms affecting individual lake systems, our study showed statistical significance between measured OCAR and modelled paleotemperature for 11 out of 28 lakes. We concluded that air temperature alone appears to drive the carbon accumulation in lakes. We expected that other factors (catchment vegetation, permafrost, and lake characteristics) would influence accumulation rates, but could not discover a conclusive factor that had a statistical significant impact. More data available on long-term records from northern lake systems could lead to more confidence and accuracy on the matter.Peer Reviewe

Diatom responses and geochemical feedbacks to environmental changes at Lake Rauchuagytgyn (Far East Russian Arctic)

This study is based on multiproxy data gained from a 14C-dated 6.5 m long sediment core and a 210Pb-dated 23 cm short core retrieved from Lake Rauchuagytgyn in Chukotka, Arctic Russia. Our main objectives are to reconstruct the environmental history and ecological development of the lake during the last 29 kyr and to investigate the main drivers behind bioproduction shifts. The methods comprise age-modeling, accumulation rate estimation, and light microscope diatom species analysis of 74 samples, as well as organic carbon, nitrogen, and mercury analysis. Diatoms have appeared in the lake since 21.8 ka cal BP and are dominated by planktonic Lindavia ocellata and L. cyclopuncta. Around the Pleistocene–Holocene boundary, other taxa including planktonic Aulacoseira, benthic fragilarioid (Staurosira), and achnanthoid species increase in their abundance. There is strong correlation between variations of diatom valve accumulation rates (DARs; mean 176.1×109 valves m2 a1), organic carbon accumulation rates (OCARs; mean 4.6 g m−2 a−1), and mercury accumulation rates (HgARs; mean 63.4 µg m−2 a−1). We discuss the environmental forcings behind shifts in diatom species and find moderate responses of key taxa to the cold glacial period, postglacial warming, the Younger Dryas, and the Holocene Thermal Maximum. The short-core data likely suggest recent change of the diatom community at the beginning of the 20th century related to human-induced warming but only little evidence of atmospheric deposition of contaminants. Significant correlation between DAR and OCAR in the Holocene interglacial indicates within-lake bioproduction represents bulk organic carbon deposited in the lake sediment. During both glacial and interglacial episodes HgAR is mainly bound to organic matter in the lake associated with biochemical substrate conditions. There were only ambiguous signs of increased HgAR during the industrialization period. We conclude that if increased short-term emissions are neglected, pristine Arctic lake systems can potentially serve as long-term CO2 and Hg sinks during warm climate episodes driven by insolation-enhanced within-lake primary productivity. Maintaining intact natural lake ecosystems should therefore be of interest to future environmental policy

Impacts of collapsing permafrost coasts: the fate of carbon, nutrients and sediments in the Arctic nearshore zone

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Second Data Science Symposium at AWI

The second Data Science Symposium at AWI gathered several data science related talks from AWI, GEOMAR and HZG

Nitrogen from sediment core EN18218, Lake Rauchuagytgyn, expedition to Chukotka 2018, Russian Arctic

These dataset contains multi proxy data from sediment core EN18218 obtained from Arctic glacial lake Rauchuagytgyn (67.7922°N, 168.7312°E) by piston coring during the Chukotka 2018 expedition (Siberia). We provide original count data of diatom species from 53 samples along a ca. 5.5 m interval in the sediment core, next to nitrogen and mercury concentrations. The data are complementary to the sedimentological and radiocarbon data published in an earlier data set by Vyse et al. 2021. The data sets provides, calculated from the original data, estimated accumulation rates based on a revised age model explained in the manuscript for diatom valves (diatom accumulation rate, DAR), organic carbon (organic carbon accumulation rates, OCAR), and mercury (Hg accumulation rates, HgAR)

Mercury from sediment core EN18218, Lake Rauchuagytgyn, expedition to Chukotka 2018, Russian Arctic

These dataset contains multi proxy data from sediment core EN18218 obtained from Arctic glacial lake Rauchuagytgyn (67.7922°N, 168.7312°E) by piston coring during the Chukotka 2018 expedition (Siberia). We provide original count data of diatom species from 53 samples along a ca. 5.5 m interval in the sediment core, next to nitrogen and mercury concentrations. The data are complementary to the sedimentological and radiocarbon data published in an earlier data set by Vyse et al. 2021. The data sets provides, calculated from the original data, estimated accumulation rates based on a revised age model explained in the manuscript for diatom valves (diatom accumulation rate, DAR), organic carbon (organic carbon accumulation rates, OCAR), and mercury (Hg accumulation rates, HgAR)

Diatom species from sediment core EN18218, Lake Rauchuagytgyn, expedition to Chukotka 2018, Russian Arctic

These dataset contains multi proxy data from sediment core EN18218 obtained from Arctic glacial lake Rauchuagytgyn (67.7922°N, 168.7312°E) by piston coring during the Chukotka 2018 expedition (Siberia). We provide original count data of diatom species from 53 samples along a ca. 5.5 m interval in the sediment core, next to nitrogen and mercury concentrations. The data are complementary to the sedimentological and radiocarbon data published in an earlier data set by Vyse et al. 2021. The data sets provides, calculated from the original data, estimated accumulation rates based on a revised age model explained in the manuscript for diatom valves (diatom accumulation rate, DAR), organic carbon (organic carbon accumulation rates, OCAR), and mercury (Hg accumulation rates, HgAR)

Accumulation rates from sediment core EN18218, Lake Rauchuagytgyn, expedition to Chukotka 2018, Russian Arctic

These dataset contains multi proxy data from sediment core EN18218 obtained from Arctic glacial lake Rauchuagytgyn (67.7922°N, 168.7312°E) by piston coring during the Chukotka 2018 expedition (Siberia). We provide original count data of diatom species from 53 samples along a ca. 5.5 m interval in the sediment core, next to nitrogen and mercury concentrations. The data are complementary to the sedimentological and radiocarbon data published in an earlier data set by Vyse et al. 2021. The data sets provides, calculated from the original data, estimated accumulation rates based on a revised age model explained in the manuscript for diatom valves (diatom accumulation rate, DAR), organic carbon (organic carbon accumulation rates, OCAR), and mercury (Hg accumulation rates, HgAR)

Harmonizing heterogeneous multi-proxy data from lake systems

When performing spatial-temporal investigations of multiple lake systems, geoscientists face the challenge of dealing with complex and heterogeneous data of different types, structure, and format. To support comparability, it is necessary to transform such data into a uniform format that ensures syntactic and semantic comparability. This paper presents a data science approach for transforming research data from different lake sediment cores into a coherent framework. For this purpose, we collected published and unpublished data from paleolimnological investigations of Arctic lake systems. Our approach adapted methods from the database field, such as developing entity-relationship (ER) diagrams, to understand the conceptual structure of the data independently of the source. We demonstrated the feasibility of our approach by transforming our ER diagram into a database schema for PostgreSQL, a popular database management system (DBMS). We validated our approach by conducting a comparative analysis on a set of acquired data, hereby focusing on the comparison of total organic carbon and bromine content in eight selected sediment cores. Still, we encountered serious obstacles in the development of the ER model. Heterogeneous structures within collected data made an automatic data integration impossible. Additionally, we realized that missing error information hampers the development of a conceptual model. Despite the strong initial heterogeneity of the original data, our harmonized dataset leads to comparable datasets, enabling numerical inter-proxy and inter-lake comparison