Boreas最新文献

{"title":"Hydroclimatic development from the Early Holocene to anthropogenic times: a comparative study of diatom oxygen isotope records and multiproxy data from Lake Khamra, eastern Siberia","authors":"Amelie Stieg,&nbsp;Boris K. Biskaborn,&nbsp;Ulrike Herzschuh,&nbsp;Jens Strauss,&nbsp;Svetlana S. Kostrova,&nbsp;Luidmila A. Pestryakova,&nbsp;Hanno Meyer","doi":"10.1111/bor.70022","DOIUrl":"https://doi.org/10.1111/bor.70022","url":null,"abstract":"<p>Northern Eurasia underwent major hydroclimatic changes since the beginning of the Holocene interglacial. A rapid warming period reaching the Holocene Thermal Maximum (HTM), followed by a general cooling trend until recent times, was observed in Eurasian lacustrine diatom oxygen isotope (δ¹⁸O_diatom) records. In this study, we present a new Holocene δ¹⁸O_diatom record from Lake Khamra (59.99°N, 112.98°E, Siberia). Our record aligns with Holocene δ¹⁸O_diatom records across the Northern Hemisphere, showing a general millennial-scale cooling trend following an initial maximum at 11.2 cal. ka BP and a second maximum at 6.7 cal. ka BP. These maxima correspond to the summer insolation maximum and elevated Northern Hemisphere air temperatures, as well as increased bioproductivity. Variability on centennial scales is likely driven by precipitation changes, which coincide with higher sedimentation rates and overlay the general decreasing trend throughout the Holocene. In addition, we compared two multiproxy datasets with decadal resolution from Lake Khamra, including δ¹⁸O_diatom data and biogeochemical proxies such as total organic carbon (TOC), total nitrogen (TN), stable carbon (δ¹³C) and nitrogen (δ¹⁵N) isotopes, and total mercury (THg). The datasets cover a ~210-year period (<i>c</i>. 6.140–6.350 cal. ka BP) at the end of the HTM and a recently published ~220-year record (<i>c</i>. 1790–2015 CE) that embraces the anthropogenic times. The comparison of these two warm phases reveals distinct differences in both the absolute values and the variability of the records. Regarding the δ¹⁸O_diatom data, the recent period shows a nearly threefold increase in range and double the standard deviation, suggesting greater hydroclimatic variability compared to the end of the HTM. Notably, THg levels indicate a sharp increase in recent decades, while δ¹³C declined, contrasting with the observations at the end of the HTM. We attribute these observations partially to far-reaching anthropogenic effects on remote lake systems.</p>","PeriodicalId":9184,"journal":{"name":"Boreas","volume":"54 3","pages":"447-467"},"PeriodicalIF":2.4,"publicationDate":"2025-06-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1111/bor.70022","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144647742","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Processes and Palaeo-Environmental Changes in the Arctic from Past to Present (PalaeoArc) – introduction","authors":"Astrid Lyså,&nbsp;Ívar Ö. Benediktsson,&nbsp;Nicolaj K. Larsen,&nbsp;Juliane Müller,&nbsp;Matt O'Regan","doi":"10.1111/bor.70021","DOIUrl":"https://doi.org/10.1111/bor.70021","url":null,"abstract":"&lt;p&gt;PalaeoArc (Processes and Palaeo-Environmental Changes in the Arctic: from Past to Present) is an international research network dedicated to understanding and explaining climate-driven environmental changes in the Arctic from the Early Pleistocene to the present day. This initiative builds upon a strong foundation of previous palaeo-Arctic research programmes dating back to the 1980s.&lt;/p&gt;&lt;p&gt;The legacy began with the Polar North Atlantic Margins – Late Cenozoic Evolution project (PONAM: 1990–1994; Hjort &amp; Persson &lt;span&gt;1994&lt;/span&gt;; Landvik &amp; Salvigsen &lt;span&gt;1995&lt;/span&gt;; Elverhøi &lt;i&gt;et al&lt;/i&gt;. &lt;span&gt;1998&lt;/span&gt;), followed by the Quaternary Environment of the Eurasian North project (QUEEN: 1996–2002) (Larsen &lt;i&gt;et al&lt;/i&gt;. &lt;span&gt;1999&lt;/span&gt;; Thiede &lt;i&gt;et al&lt;/i&gt;. &lt;span&gt;2001&lt;/span&gt;, &lt;span&gt;2004&lt;/span&gt;; Kjær &lt;i&gt;et al&lt;/i&gt;. &lt;span&gt;2006&lt;/span&gt;). These efforts were succeeded by the Arctic Palaeoclimate and its Extremes programme (APEX: 2004–2012) (Jakobsson &lt;i&gt;et al&lt;/i&gt;. &lt;span&gt;2008&lt;/span&gt;, &lt;span&gt;2010&lt;/span&gt;, &lt;span&gt;2014&lt;/span&gt;) and the Palaeo-Arctic Spatial and Temporal Gateways programme (PAST Gateways: 2012–2018) (Ó Cofaigh &lt;i&gt;et al&lt;/i&gt;. &lt;span&gt;2016&lt;/span&gt;, &lt;span&gt;2018&lt;/span&gt;).&lt;/p&gt;&lt;p&gt;The current network of PalaeoArc was launched in 2019, where a new international steering committee was formed to lead activities, annual conferences and field trips from 2019 to 2025. The first meeting took place in Poznań, Poland (2019) (Lyså &lt;i&gt;et al&lt;/i&gt;. &lt;span&gt;2019&lt;/span&gt;). A second conference, originally planned for 2020 in Pisa, was postponed due to the COVID-19 pandemic and held online in 2021. A PalaeoArc paper collection in &lt;i&gt;Arctic Antarctic and Alpine Research&lt;/i&gt; (Lyså &lt;i&gt;et al&lt;/i&gt;. &lt;span&gt;2022&lt;/span&gt;) originates from that conference and reflects the network's broad scientific scope, fostering interdisciplinary discussions on Arctic environmental change across a range of timescales. The third PalaeoArc conference was held in Rovaniemi, Finland, in 2022, and some papers from the conference were published in Bulletin of The Geological Society of Finland (Sarala &lt;span&gt;2023&lt;/span&gt;). Thereafter, conferences were held in Akureyri, Iceland (2023) and Stockholm, Sweden (2024), from which the articles in this special issue originate. The final PalaeoArc conference is scheduled to take place in Tromsø, Norway, in 2025.&lt;/p&gt;&lt;p&gt;The Arctic is experiencing some of the fastest and most dramatic impacts of global warming, with surface air temperatures rising nearly four times faster than the global average between 1979 and 2021 (Rantanen &lt;i&gt;et al&lt;/i&gt;. &lt;span&gt;2022&lt;/span&gt;). Even if global temperature increases are kept below 2 °C, the region is expected to undergo profound and lasting changes such as loss of sea- and glacial ice, permafrost thaw and shifts in precipitation patterns (AMAP &lt;span&gt;2017&lt;/span&gt;; Fox-Kemper &lt;span&gt;2021&lt;/span&gt;).&lt;/p&gt;&lt;p&gt;To understand these changes and their complex feedback mechanisms, long-term palaeorecords are essential. They offer critical context for","PeriodicalId":9184,"journal":{"name":"Boreas","volume":"54 3","pages":"284-287"},"PeriodicalIF":2.4,"publicationDate":"2025-06-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1111/bor.70021","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144647554","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Complex past ice flow from Norway to the North Sea Plateau during the Quaternary: evidence from Marstein Trough and earlier reconstructions using 3D seismic data sets","authors":"Dag Ottesen,&nbsp;James D. Kirkham,&nbsp;Julian A. Dowdeswell,&nbsp;Harald Brunstad,&nbsp;Morten Halvorsen","doi":"10.1111/bor.70007","DOIUrl":"https://doi.org/10.1111/bor.70007","url":null,"abstract":"<p>Based on a regional 3D seismic data set and a small high-resolution 3D seismic data set (~40 km²) we have mapped a buried glacially eroded trough on the North Sea Plateau, west of the Norwegian Channel (latitude 59°N, longitude 3°E). The trough, which we informally name Marstein Trough, is 60 km long, 30 km wide, 120 m deep, and trends NE–SW. Marstein Trough contains an extensive pattern of glacial lineations at its base, which follow the trough axis, and is infilled by two seismic units interpreted as tills. From its stratigraphical position, we infer that the trough was eroded by an ice stream that flowed from western Norway and crossed the Norwegian Channel in a southwesterly direction, probably during the penultimate, Saalian glaciation. Marstein Trough, and its diagnostic landforms, provide detailed evidence of complex, switching ice flow across the North Sea during the Quaternary. Westward ice flow from Norway took place during early Scandinavian Ice-Sheet build-up prior to the activation of the Norwegian Channel Ice Stream. In contrast, ice-flow patterns during full-glacial conditions caused ice flow to reorientate to a S–N direction when the Norwegian Channel Ice Stream with a huge catchment that included the Baltic was established. Our results highlight the complex patterns of ice flow experienced over this region of the North Sea, with implications for reconstructions of Quaternary history, modern renewable energy infrastructure installation, and glacial processes during the build-up phase of ice sheets.</p>","PeriodicalId":9184,"journal":{"name":"Boreas","volume":"54 3","pages":"351-369"},"PeriodicalIF":2.4,"publicationDate":"2025-04-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1111/bor.70007","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144647643","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Relative sea-level trends in southern Norway during the last millennium","authors":"Max Holthuis,&nbsp;F. Chantel Nixon,&nbsp;Malin E. Kylander,&nbsp;Willem G. M. van der Bilt,&nbsp;Isabel Hong,&nbsp;Kristen M. Joyse,&nbsp;Thomas R. Lakeman,&nbsp;Jake Martin,&nbsp;Maria Peter,&nbsp;Simon Solheim Holme,&nbsp;Benjamin P. Horton","doi":"10.1111/bor.70006","DOIUrl":"https://doi.org/10.1111/bor.70006","url":null,"abstract":"<p>Geological reconstructions of relative sea level (RSL) from southern Norway show falling RSL during the last 7000 cal. a BP, but tide gauge measurements document a slow RSL rise since at least 1960 CE. With an age gap of <i>c.</i> 1400 years between the youngest geologically reconstructed sea-level index point (SLIP) and the installation of the Tregde tide gauge in southernmost Norway, the exact nature and timing of the onset of RSL rise in southern Norway remain unknown. To fill this gap, we collected peat cores from a salt marsh to reconstruct RSL trends over the past 1000 years using a multiproxy approach, including ²¹⁰Pb and ¹⁴C dating, grain-size analysis, loss-on-ignition (LOI), geochemistry (stable carbon isotopes, carbon to nitrogen ratios and XRF) and diatoms. Our data suggest decreasing tidal current strength and salinity over most of the last millennium, suggesting falling RSL. Sediment geochemistry also appears to vary with wetter and drier climatic periods. An increase in marine-brackish diatoms in combination with an acceleration in sedimentation rates after 1930 CE (1899–1954 CE) suggest that the onset of RSL rise began around this time in southernmost Norway. While most of the proxy data appear to have delayed sensitivity to RSL changes and may be linked to other causal processes, they, nonetheless, provide valuable insight into the environmental response of high-latitude temperate salt marshes to slow rates of RSL change.</p>","PeriodicalId":9184,"journal":{"name":"Boreas","volume":"54 3","pages":"414-430"},"PeriodicalIF":2.4,"publicationDate":"2025-03-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1111/bor.70006","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144647852","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Response to Comment on ‘Automatic identification of streamlined subglacial bedforms using machine learning: an open-source Python approach’","authors":"Marion McKenzie,&nbsp;Ellianna Abrahams,&nbsp;Fernando Pérez,&nbsp;Ryan Venturelli","doi":"10.1111/bor.70004","DOIUrl":"https://doi.org/10.1111/bor.70004","url":null,"abstract":"&lt;p&gt;Li &lt;i&gt;et al&lt;/i&gt;. (&lt;span&gt;2025&lt;/span&gt; this issue) state that they identify areas for improvement to our development of bedfinder through including more data sets at training, evaluating our filtering methods, and exploring modular approaches of the tool. Here we respond to these Comments by highlighting where we have already addressed each of these areas within our work and notably, our supporting information (Abrahams &lt;i&gt;et al&lt;/i&gt;. &lt;span&gt;2024&lt;/span&gt;). In our paper, we describe that bedfinder is an inherently modular tool, allowing a user to choose which components of the pipeline might be useful to them. Furthermore, bedfinder already allows a user to customize the choice to over- or under-predict a glacially derived bedform assignment. In Abrahams &lt;i&gt;et al&lt;/i&gt;. (&lt;span&gt;2024&lt;/span&gt;) we previously justified why we made the choice to over-predict, emphasizing the need for manual post-processing, which we reiterate here. Finally, we reshare statements from the ‘Model limitations’ section of Abrahams &lt;i&gt;et al&lt;/i&gt;. (&lt;span&gt;2024&lt;/span&gt;) where we also recommend incorporating additional data in future tool creation to strengthen our approach.&lt;/p&gt;&lt;p&gt;The objective of Abrahams &lt;i&gt;et al&lt;/i&gt;. (&lt;span&gt;2024&lt;/span&gt;) was to build an open-source tool that would allow for the automatic detection of glacially derived streamlined subglacial bedforms, based on the previous successes of manual approaches (e.g. Clark &lt;span&gt;1993&lt;/span&gt;; Greenwood &amp; Clark &lt;span&gt;2008&lt;/span&gt;; Spagnolo &lt;i&gt;et al&lt;/i&gt;. &lt;span&gt;2014&lt;/span&gt;; Ely &lt;i&gt;et al&lt;/i&gt;. &lt;span&gt;2016&lt;/span&gt;; Principato &lt;i&gt;et al&lt;/i&gt;. &lt;span&gt;2016&lt;/span&gt;; Clark &lt;i&gt;et al&lt;/i&gt;. &lt;span&gt;2018&lt;/span&gt;). To develop this tool, we used Random Forest (Breiman &lt;span&gt;2001&lt;/span&gt;), XGBoost (Chen &amp; Guestrin &lt;span&gt;2016&lt;/span&gt;), and an ensemble average of these two model fits on a publicly available training data set of nearly 600 000 data points across the deglaciated Northern Hemisphere (McKenzie &lt;i&gt;et al&lt;/i&gt;. &lt;span&gt;2022&lt;/span&gt;). Li &lt;i&gt;et al&lt;/i&gt;. (&lt;span&gt;2025&lt;/span&gt;) suggest a constructive critique to our approach stating our work should include more data sets at training, further evaluate our filtering methods, and explore better modularizing bedfinder. However, these suggestions have either already been implemented as existing features of bedfinder (i.e. modularity of pipeline components and tunability of bedform predictions to the needs of the user) or we have already named them in our study as known limitations of the tool that will require wider community participation (the creation of larger, more nuanced machine learning data sets for model training).&lt;/p&gt;&lt;p&gt;Abrahams &lt;i&gt;et al&lt;/i&gt;. (&lt;span&gt;2024&lt;/span&gt;) outlined the limitations of the presented approach in the section ‘Model limitations’. There, we state that the ‘TPI tool used to compile our training set performs most poorly in regions with highly elongate bedforms with low surface relief (McKenzie &lt;i&gt;et al&lt;/i&gt;. &lt;span&gt;2022&lt;/span&gt;)’ (i.e. bedforms across crystalline bedrock surfaces) (Abrah","PeriodicalId":9184,"journal":{"name":"Boreas","volume":"54 2","pages":"277-280"},"PeriodicalIF":2.4,"publicationDate":"2025-03-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1111/bor.70004","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143809968","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Reassessing the predictive power of bedfinder: insights into machine learning for subglacial bedform detection – Comments on ‘Automatic identification of streamlined subglacial bedforms using machine learning: an open-source Python approach’","authors":"Ming Li,&nbsp;Huanyu Zhao,&nbsp;Tianfei Yu","doi":"10.1111/bor.70005","DOIUrl":"https://doi.org/10.1111/bor.70005","url":null,"abstract":"&lt;p&gt;The integration of machine learning (ML) into geomorphological research presents significant opportunities for automating the identification of streamlined subglacial bedforms. In their study, Abrahams &lt;i&gt;et al&lt;/i&gt;. (&lt;span&gt;2024&lt;/span&gt;) introduce bedfinder, an open-source Python tool designed to detect subglacial features with high efficiency. While the tool demonstrates promise, this discussion highlights critical challenges and areas for refinement. The representativeness of the training data set, dominated by sedimentary bed conditions, limits the model's generalizability to regions with diverse bedrock compositions. Additionally, the reliance on binary classifications oversimplifies complex geomorphic settings, reducing the model's adaptability. Performance metrics such as F1 scores, though favourable, warrant cautious interpretation due to class imbalances that may skew predictions. Furthermore, the integration of filtering techniques, while enhancing precision, raises concerns about potential biases from manual data curation. To enhance scientific rigour, future efforts should incorporate diverse data sets, conduct comprehensive evaluations of filtering methods, and explore modular approaches for greater applicability. Addressing these challenges will not only strengthen bedfinder but also contribute to the evolving role of ML in advancing glacial and geomorphological research. This contribution provides a constructive critique to guide future improvements and interdisciplinary applications of this innovative tool.&lt;/p&gt;&lt;p&gt;Abrahams &lt;i&gt;et al&lt;/i&gt;. (&lt;span&gt;2024&lt;/span&gt;) present a cutting-edge approach to the identification of streamlined subglacial bedforms, which are crucial in understanding past glacial dynamics and their impact on geomorphology. The authors have developed an open-source Python tool, bedfinder, that employs supervised ML algorithms – Random Forest and XGBoost – to automate the identification of these features across deglaciated landscapes. This tool is an ambitious attempt to enhance efficiency and accuracy in a domain traditionally burdened by labour-intensive, subjective, and time-consuming manual processes. The authors also provide a thorough validation of the model using an extensive data set of known subglacial bedforms from various regions in the Northern Hemisphere.&lt;/p&gt;&lt;p&gt;While the study contributes valuable insights into how ML can automate the mapping of complex glacial features, several critical issues arise from the selection of data, the application of ML methods, and the interpretation of results. Here, we will highlight some of these issues and offer suggestions to enhance the scientific robustness of the study and its potential applications. The concerns outlined here include the representativeness of the training data, the challenges in interpreting the performance metrics, and the potential over-simplifications in model design and validation.&lt;/p&gt;&lt;p&gt;A central issue in Abrahams &lt;i&gt;et al&lt;/i&gt;. (&lt;span&gt;2024&lt;/span&gt;) ","PeriodicalId":9184,"journal":{"name":"Boreas","volume":"54 2","pages":"273-276"},"PeriodicalIF":2.4,"publicationDate":"2025-03-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1111/bor.70005","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143809833","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Cladocera assemblages indicate environmental gradients of lake productivity and morphometry in central Europe","authors":"Izabela Zawiska,&nbsp;Alex Correa-Metrio,&nbsp;Monika Rzodkiewicz,&nbsp;Jacek Wolski","doi":"10.1111/bor.70001","DOIUrl":"https://doi.org/10.1111/bor.70001","url":null,"abstract":"<p>Lakes play a vital role in numerous human activities, yet extensive economic development has led to significant pollution and nutrient enrichment, resulting in widespread eutrophication and ecological disruption. To accurately assess the current state of lakes, it is essential to understand their historical, pre-impact conditions. Palaeolimnological methods, including the analysis of subfossil Cladocera, offer a valuable tool for studying lake ecosystems over extended timeframes that go beyond modern instrumental records. Our research aims to identify the primary environmental factors that influence the distribution of individual Cladocera species and evaluate the systematic patterns within species assemblages to enhance their use as ecological indicators. This study presents an analysis of Cladocera assemblages based on environmental surveys conducted in 64 lakes across northeastern Poland. Principal component analysis revealed that the two dominant factors driving variability in the dataset are lake trophic state, indicated by total phosphorus (TP) levels, and lake depth. Species distributions across these gradients showed a turnover, reflecting distinct environmental preferences. Further, end member (EM) analysis identified five distinct assemblages of Cladocera, each associated with specific combinations of trophic status and lake size. EM1 is associated with higher trophic states, while EM2, EM3 and EM4 are indicative of medium to low trophic states. EM5 is independent of trophic status, associated with large and deep-water bodies.</p>","PeriodicalId":9184,"journal":{"name":"Boreas","volume":"54 2","pages":"258-272"},"PeriodicalIF":2.4,"publicationDate":"2025-03-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1111/bor.70001","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143809761","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"The role of inland ice dynamics in controlling the variable maximum extent of the Laurentide Ice Sheet off southeastern Baffin Island","authors":"Alexis P. Belko,&nbsp;Patrick Lajeunesse,&nbsp;Alexandre Normandeau,&nbsp;Pierre-Olivier Couette,&nbsp;Etienne Brouard","doi":"10.1111/bor.70000","DOIUrl":"https://doi.org/10.1111/bor.70000","url":null,"abstract":"<p>Reconstructions of the maximum extent and dynamics of the Laurentide Ice Sheet (LIS) during the Last Glacial Maximum (LGM) are needed for understanding how marine-based ice sheets will respond to modern climate change. The partitioning of ice masses and the location of dominant ice flows within the LIS are broadly known at regional scales, but their influence on the marine-based maximum extent of the ice sheet remains poorly constrained. Here, we provide evidence for the maximal extent of the LIS margin during the LGM in the Broughton and Merchants cross-shelf troughs off southeastern Baffin Island based on newly acquired sea floor geomorphology data. Grounding-zone wedges (GZWs), moraines and ice-stream bedforms within the Merchants cross-shelf trough delimit the maximum extent of the LIS in this sector to near the mouth of the modern fjords. Two lateral moraines, mega-scale glacial lineations (MSGLs), and iceberg scours also indicate the presence of an ice shelf extending beyond the former grounding line. In Broughton Trough, the maximum extent of the LIS is interpreted from the distribution of MSGLs and iceberg scours. The presence of sticky spots near the shelf edge may have played a role in subglacial flow and thus glacier behaviour. The difference in ice extent between the two nearby troughs is attributed to partitioning of the LIS between ice flowing from the Penny Ice Cap into Broughton Trough and ice from local alpine glaciers flowing into Merchants Trough. In addition, the presence of a dominant ice flow south of the Cumberland Peninsula may have drained ice masses of Cumberland Peninsula towards the south and caused minimal expansion in Merchants Trough to the north. These results provide a clearer understanding of the relationship between ice-sheet extent along continental margins and inland ice dynamics.</p>","PeriodicalId":9184,"journal":{"name":"Boreas","volume":"54 3","pages":"468-479"},"PeriodicalIF":2.4,"publicationDate":"2025-02-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1111/bor.70000","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144647769","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Lateglacial and Holocene glacier variations in an active volcanic area, northern Jan Mayen (Nord-Jan), Norway","authors":"Astrid Lyså,&nbsp;Eiliv A. Larsen,&nbsp;Johanna Anjar,&nbsp;Naki Akçar,&nbsp;Asbjørn Hiksdal,&nbsp;Georgios Tassis","doi":"10.1111/bor.12697","DOIUrl":"https://doi.org/10.1111/bor.12697","url":null,"abstract":"<p>Jan Mayen is a volcanic island situated 550 km NE of Iceland. It has been shown previously that the island and probably also shallow shelf areas around it were covered by a contiguous ice cap during the last glaciation. Today, active glaciers exist only in the northern part of the island around the Beerenberg volcano. Until now, information on Lateglacial and Holocene glacier and environmental variations has been sparse. We focus on the northern part (Nord-Jan), discussing glacier evolution and environmental changes from the Lateglacial to the Holocene. Widespread volcanic activity during the postglacial era resulted in lava flows and volcanic craters amidst glaciogenic deposits, complicating glacial and environmental reconstructions. We suggest that the ice cap covering Jan Mayen separated into two (northern and southern) approximately 20 ka ago, based on observations from glacial striae and terrestrial cosmogenic nuclide exposure dating. Deglaciation of the southern flank of the Beerenberg ice cap was accelerated by initial subglacial volcanic activity, which probably rapidly evolved to protrude above the glacier surface. Subsequently, around 18.9 ka, vertical melting and ice-marginal recession intensified in Nord-Jan. A relatively warm period followed thereafter, evidenced by organic material giving a calibrated age of 17 to 16 cal. ka BP. The extent of deglaciation during this period is unknown as the dated material was found redeposited in lake sediments. Several cosmogenic exposure ages from bedrock and glacial erratics correspond to the Lateglacial period. The interpretation of these ages is not obvious, but we favour a hypothesis involving a Lateglacial readvance of the glaciers when lateral moraines were also deposited. Mild conditions, characterized by plant growth and soil formation, prevailed during the Early Holocene. During this period, the lateral moraines formed during the Lateglacial probably disintegrated, leaving only the remnants visible today.</p>","PeriodicalId":9184,"journal":{"name":"Boreas","volume":"54 3","pages":"305-327"},"PeriodicalIF":2.4,"publicationDate":"2025-02-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1111/bor.12697","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144646909","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Drivers of glacially induced fault reactivation in the Baltic Sea sector of the Tornquist Fan","authors":"Elisabeth Seidel,&nbsp;Holger Steffen,&nbsp;Rebekka Steffen,&nbsp;Niklas Ahlrichs,&nbsp;Christian Hübscher","doi":"10.1111/bor.12689","DOIUrl":"https://doi.org/10.1111/bor.12689","url":null,"abstract":"<p>We analyse the effect of Quaternary glaciations on the complex tectonic pattern within the southwestern Baltic Sea, a sector of the transition zone from the East European Craton to the West European Platform. This area comprises the Caledonian Trans–European Suture Zone in the south and the Tornquist Zone in the north. Multiple fault zones in between, with different strike and dip angles, and characters (normal, thrust/reverse, strike-slip), document like scars the alternately transpressional and transtensional stress activities since the Palaeozoic. We determine the strike directions and dip angles of more than 40 potential glacially reactivated faults identified in 2D marine reflection seismic data. Finite element simulations of different glacial isostatic adjustment models provide glacially induced Coulomb failure stress changes (ΔCFS) at the faults over time, starting 200 000 years ago (200 ka, Saalian phase) up to 1000 years into the future. Assuming strike-slip or thrust/reverse background stresses, a potential reactivation of each fault is analysed. The detected reactivation phases are related to the waxing and waning ice masses (Late Saalian ice advances: <i>c.</i> 170–135 ka ago; Weichselian ice advances: 70–60, 45–38, 26–14 ka ago) and point to an activation in front of the ice margin. Comparing the ΔCFS results of the individual faults laterally and over time, we found that the location of the fault, depending on its position during a glacial maximum, has an important effect on its reactivation potential. The closer a fault was located to the former ice margin, the higher was the glacially induced stress during the ice retreat. Based on earlier findings in Germany and Denmark, glacially triggered faults are a typical consequence of the Fennoscandian glaciation throughout northern central Europe, and this also applies to future glaciation phases.</p>","PeriodicalId":9184,"journal":{"name":"Boreas","volume":"54 2","pages":"220-245"},"PeriodicalIF":2.4,"publicationDate":"2025-01-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1111/bor.12689","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143809956","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}