Boreas最新文献

{"title":"Palaeoclimatic and regional implications of Older Dryas and Younger Dryas local glacier activity in the low-Arctic valley Finnkongdalen, Andøya, northern Norway","authors":"Henrik Løseth Jansen,&nbsp;Svein Olaf Dahl,&nbsp;Henriette Linge,&nbsp;Jostein Bakke,&nbsp;Pål Ringkjøb Nielsen,&nbsp;Bjørn Christian Kvisvik","doi":"10.1111/bor.12609","DOIUrl":"10.1111/bor.12609","url":null,"abstract":"<p>Continuous glacier margin and equilibrium-line altitude fluctuations of a former glacier on central Andøya, northern Norway, are reconstructed during the Lateglacial based on moraines and AMS ¹⁴C-dated sediments from the distal glacier-fed lake Ner-Finnkongdalsvatnet. The results indicate that a valley glacier occupied the entire valley during the Last Glacial Maximum (before 21 970±620 cal. a BP). The glacier remained large throughout the early Lateglacial until a significant glacier retreat took place about 14 300±330 cal. a BP. Major advances occurred during the Older Dryas (OD) and during the Younger Dryas (YD), while minor advances are suggested to have taken place during the Intra Allerød Cold Period and the Late Allerød Cooling. Additionally, three smaller glacier retreats/re-advances within the YD are suggested to have taken place, the latter being the largest. The glacier re-formations/advances during the Lateglacial are consistent with increases in temperature, and they are thus suggested to be the result of increased winter precipitation. Comparing the results with relevant glacier and sea-surface temperature records, a south–north migration of storm tracks may have occurred between 12 100–11 810±220 cal. a BP. The high temporal resolution of local glacier activity in Finnkongdalen improves our understanding of the climate forcing of the regional glacier fluctuations of the northwestern sector of the Scandinavian Ice Sheet during the Skarpnes- (OD) and Tromsø-Lyngen (YD) re-advances.</p>","PeriodicalId":9184,"journal":{"name":"Boreas","volume":"52 2","pages":"168-193"},"PeriodicalIF":2.2,"publicationDate":"2023-01-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1111/bor.12609","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"49502101","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":"Central Mediterranean tephrochronology between 313 and 366 ka: New insights from the Fucino palaeolake sediment succession","authors":"Niklas Leicher,&nbsp;Biagio Giaccio,&nbsp;Alison Pereira,&nbsp;Sebastien Nomade,&nbsp;Lorenzo Monaco,&nbsp;Giorgio Mannella,&nbsp;Paolo Galli,&nbsp;Edoardo Peronance,&nbsp;Danilo Mauro Palladino,&nbsp;Gianluca Sottili,&nbsp;Giovanni Zanchetta,&nbsp;Bernd Wagner","doi":"10.1111/bor.12610","DOIUrl":"10.1111/bor.12610","url":null,"abstract":"<p>Thirty-two tephra layers were identified in the time-interval 313–366 ka (Marine Isotope Stages 9–10) of the Quaternary lacustrine succession of the Fucino Basin, central Italy. Twenty-seven of these tephra layers yielded suitable geochemical material to explore their volcanic origins. Investigations also included the acquisition of geochemical data of some relevant, chronologically compatible proximal units from Italian volcanoes. The record contains tephra from some well-known eruptions and eruptive sequences of Roman and Roccamonfina volcanoes, such as the Magliano Romano Plinian Fall, the Orvieto–Bagnoregio Ignimbrite, the Lower White Trachytic Tuff and the Brown Leucitic Tuff. In addition, the record documents eruptions currently undescribed in proximal (i.e. near-vent) sections, suggesting a more complex history of the major eruptions of the Colli Albani, Sabatini, Vulsini and Roccamonfina volcanoes between 313 and 366 ka. Six of the investigated tephra layers were directly dated by single-crystal-fusion ⁴⁰Ar/³⁹Ar dating, providing the basis for a Bayesian age–depth model and a reassessment of the chronologies for both already known and dated eruptive units and for so far undated eruptions. The results provide a significant contribution for improving knowledge on the peri-Tyrrhenian explosive activity as well as for extending the Mediterranean tephrostratigraphical framework, which was previously based on limited proximal and distal archives for that time interval.</p>","PeriodicalId":9184,"journal":{"name":"Boreas","volume":"52 2","pages":"240-271"},"PeriodicalIF":2.2,"publicationDate":"2022-12-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1111/bor.12610","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"42936247","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":"Revised marine reservoir offset (ΔR) values for molluscs and marine mammals from Arctic North America","authors":"Anna J. Pieńkowski,&nbsp;Roy D. Coulthard,&nbsp;Mark F. A. Furze","doi":"10.1111/bor.12606","DOIUrl":"10.1111/bor.12606","url":null,"abstract":"<p>Appropriate marine–terrestrial reservoir offset (ΔR) values are essential for accurate calibration of marine radiocarbon dates. However, ΔR values are only valid for the specific calibration curve that their calculation is based on. Here, we present revised ΔR values for the Marine20 calibration curve from Arctic North America, based on previously published ¹⁴C dates on pre-bomb live-collected marine molluscs (<i>n</i> = 124) and cetaceans (beluga whales; tooth dentine; <i>n</i> = 12), and bowhead whale–driftwood age comparisons from the same glacio-isostatically uplifted shorelines (<i>n</i> = 18). Molluscan-based ΔR are: Chukchi/Beaufort sea coasts, 265±116 ¹⁴C years; NW Canadian Arctic Archipelago, 188±91 ¹⁴C years; NE Baffin Island, 81±18 ¹⁴C years; SE Baffin Island, 14±58 ¹⁴C years; Hudson Strait, −73±64 ¹⁴C years; Ungava Bay, 0±86 ¹⁴C years; Foxe Basin, 175±89 ¹⁴C years; Hudson Bay, −21±72 ¹⁴C years; James Bay, 209±114 ¹⁴C years; West Greenland, −93±111 ¹⁴C years. Species-specific marine mammal ΔR terms are 107±59 ¹⁴C years for beluga and 24±58 ¹⁴C years for bowheads. Our revised ΔR values are applicable for as long as the same broad oceanographic conditions (circulation, ventilation) have persisted, i.e. through the Holocene. While molluscan values are applicable to other marine carbonate (e.g. foraminifera), cetacean ΔR are valid only for the species they were calculated for and should not be applied to other marine mammals. Importantly, the ΔR terms calculated here are only valid for Marine20 and should not be used with earlier or later calibration curves.</p>","PeriodicalId":9184,"journal":{"name":"Boreas","volume":"52 2","pages":"145-167"},"PeriodicalIF":2.2,"publicationDate":"2022-11-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1111/bor.12606","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"48023633","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":"Stratigraphy and age of a Neoglacial sedimentary succession of proglacial outwash and an alluvial fan in Langedalen, Veitastrond, western Norway","authors":"Atle Nesje,&nbsp;Denise C. Rüther,&nbsp;Jacob C. Yde","doi":"10.1111/bor.12608","DOIUrl":"10.1111/bor.12608","url":null,"abstract":"<p>This study presents the sedimentary succession of an outwash plain and an alluvial fan located along the valley Langedalen at the south-eastern side of the Jostedalsbreen ice cap in inner Sogn, western Norway. A newly exposed ~2.8-m-high section along the southern riverbank of Langedøla river shows alternating layers of minerogenic sediments and peat layers with tree logs, identified as <i>Salix</i> sp. The section is situated in the distal part of an alluvial fan built out from the southern slope of Langedalen. Six AMS radiocarbon dates of tree fragments indicate that the accumulation of the fine-grained sediments in the lower part of the section was initiated earlier than the basal radiocarbon date of 914–976 calibrated years CE (1<i>σ</i> age range). These basal, fine-grained sediments are interpreted as proglacial outwash deposited in a floodplain depression or abandoned river channel in a low-energy glaciofluvial environment. Periods of low glacier cover, low river discharge or low-water stands over the floodplain allowed peat formation and the growth of trees and shrubs in the valley. The radiocarbon dates further indicate relatively rapid sediment accretion (~2.7–3 cm a⁻¹) between 190 and 125 cm below the sediment surface, equivalent to approximately 1220 to 1250 cal. a CE (1<i>σ</i> age range). At ~60 cm depth below the surface, dated to approximately 1590 to 1620 cal. a CE (1<i>σ</i> age range), a transition to more coarse-grained, sandy and gravelly sediments indicates increased sediment supply and distal expansion of the alluvial fan. This occurred most likely as a consequence of increased sediment yield from expanding glaciers along the southern valley side of Langedalen as a response to the initial Little Ice Age glacier growth. Based on these results, the accretion and progradation of glacier-fed alluvial fans mainly occur during periods of glacier advance rather than during glacier recession.</p>","PeriodicalId":9184,"journal":{"name":"Boreas","volume":"52 2","pages":"194-205"},"PeriodicalIF":2.2,"publicationDate":"2022-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1111/bor.12608","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"43527774","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 geodynamic and limnological evolution of Balkan Lake Ohrid, possibly the oldest extant lake in Europe","authors":"Bernd Wagner,&nbsp;Paul Tauber,&nbsp;Alexander Francke,&nbsp;Niklas Leicher,&nbsp;Steven A. Binnie,&nbsp;Aleksandra Cvetkoska,&nbsp;Elena Jovanovska,&nbsp;Janna Just,&nbsp;Jack H. Lacey,&nbsp;Zlatko Levkov,&nbsp;Katja Lindhorst,&nbsp;Katerina Kouli,&nbsp;Sebastian Krastel,&nbsp;Konstantinos Panagiotopoulos,&nbsp;Arne Ulfers,&nbsp;Dušica Zaova,&nbsp;Timme H. Donders,&nbsp;Andon Grazhdani,&nbsp;Andreas Koutsodendris,&nbsp;Melanie J. Leng,&nbsp;Laura Sadori,&nbsp;Mirko Scheinert,&nbsp;Hendrik Vogel,&nbsp;Thomas Wonik,&nbsp;Giovanni Zanchetta,&nbsp;Thomas Wilke","doi":"10.1111/bor.12601","DOIUrl":"10.1111/bor.12601","url":null,"abstract":"<p>Studies of the upper 447 m of the DEEP site sediment succession from central Lake Ohrid, Balkan Peninsula, North Macedonia and Albania provided important insights into the regional climate history and evolutionary dynamics since permanent lacustrine conditions established at 1.36 million years ago (Ma). This paper focuses on the entire 584-m-long DEEP sediment succession and a comparison to a 197-m-long sediment succession from the Pestani site ~5 km to the east in the lake, where drilling ended close to the bedrock, to unravel the earliest history of Lake Ohrid and its basin development. ²⁶Al/¹⁰Be dating of clasts from the base of the DEEP sediment succession implies that the sedimentation in the modern basin started at <i>c</i>. 2 Ma. Geophysical, sedimentological and micropalaeontological data allow for chronological information to be transposed from the DEEP to the Pestani succession. Fluvial conditions, slack water conditions, peat formation and/or complete desiccation prevailed at the DEEP and Pestani sites until 1.36 and 1.21 Ma, respectively, before a larger lake extended over both sites. Activation of karst aquifers to the east probably by tectonic activity and a potential existence of neighbouring Lake Prespa supported filling of Lake Ohrid. The lake deepened gradually, with a relatively constant vertical displacement rate of ~0.2 mm a⁻¹ between the central and the eastern lateral basin and with greater water depth presumably during interglacial periods. Although the dynamic environment characterized by local processes and the fragmentary chronology of the basal sediment successions from both sites hamper palaeoclimatic significance prior to the existence of a larger lake, the new data provide an unprecedented and detailed picture of the geodynamic evolution of the basin and lake that is Europe’s presumed oldest extant freshwater lake.</p>","PeriodicalId":9184,"journal":{"name":"Boreas","volume":"52 1","pages":"1-26"},"PeriodicalIF":2.2,"publicationDate":"2022-10-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1111/bor.12601","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"46749233","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":"Holocene relative sea level changes in the Västervik-Gamlebyviken region on the southeast coast of Sweden, southern Baltic Sea","authors":"Christos Katrantsiotis,&nbsp;Martin Dahl,&nbsp;Veronica Palm,&nbsp;Johan Rönnby,&nbsp;Thomas Andrén,&nbsp;Elinor Andrén","doi":"10.1111/bor.12605","DOIUrl":"10.1111/bor.12605","url":null,"abstract":"<p>We reconstruct the Holocene shore displacement of the Västervik-Gamlebyviken area on the southeast coast of Sweden, characterised by a maritime cultural landscape and archaeological significance since the Mesolithic. Sediment cores were retrieved from four lake basins that have been raised above sea level due to the postglacial land uplift and eustatic sea level changes after the melting of the Fennoscandian Ice Sheet. The cores were radiocarbon dated and analysed for loss on ignition and diatoms. The isolation thresholds of the basins were determined using LiDAR data. The results provide evidence for the initiation of the first Littorina Sea transgression in this area at 8.5 thousand calibrated years before present (cal. ka BP). A relative sea level rise by ∼7 m a.s.l. is recorded between 8.0 and 7.5 cal. ka BP with a highstand at ∼22 m a.s.l. between 7.5 and 6.2 cal. ka BP. These phases coincide with the second and third Littorina Sea transgressions, respectively, in the Blekinge area, southern Sweden and are consistent with the final deglaciation of North America. After 6.2 cal. ka BP, the relative sea level dropped below 22 m a.s.l., and remained at ∼20 m a.s.l. until 4.6 cal. ka BP coinciding with the fourth Littorina Sea transgression in Blekinge. From 4.6 to 4.2 cal. ka BP, the shore displacement shows a regression rate of 10 mm a⁻¹ followed by a slowdown with a mean value of 4.6 mm a⁻¹ until 1.6 cal. ka BP, when the relative sea level dropped below 3.3 m a.s.l. The Middle to Late Holocene highstand and other periods of minor sea level transgressions and/or higher salinity between 6.2 and 1.7 cal. ka BP are attributed to a combination of warmer climate and higher inflow of saline waters in the southern Baltic Sea due to stronger westerlies, caused by variations in the North Atlantic atmospheric patterns.</p>","PeriodicalId":9184,"journal":{"name":"Boreas","volume":"52 2","pages":"206-222"},"PeriodicalIF":2.2,"publicationDate":"2022-10-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1111/bor.12605","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"45080395","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":"Multi-proxy climate and environmental records from a Holocene eutrophic mire, southern taiga subzone, West Siberia","authors":"Irina V. Kurina,&nbsp;Elena E. Veretennikova,&nbsp;Anna A. Il’ina,&nbsp;Marina L. Egorova,&nbsp;Lyudmila V. Salisch,&nbsp;Vladimir N. Dolgin,&nbsp;Albert V. Udaloi,&nbsp;Evgeniya A. Golovatskaya,&nbsp;Egor A. Dyukarev,&nbsp;Sergei V. Smirnov","doi":"10.1111/bor.12604","DOIUrl":"10.1111/bor.12604","url":null,"abstract":"<p>Palaeoenvironmental reconstructions from peat are strongly focused on ombrotrophic mires, but this study demonstrates that eutrophic mires can also be used. A multi-proxy approach was applied to a eutrophic mire on a floodplain terrace in the southern taiga of West Siberia. The results of the reconstruction were considered in the wide geographic context of the surrounding regions, including Siberia and Central Asia. Different palaeoecological proxies (analysis of plant macrofossils, testate amoebae, oribatid mites, molluscs, peat humification, ash content and spectral characteristics of humic acids) were used in this study. The results of different proxies showed a high level of consistency among themselves, which allowed for a robust interpretation of Holocene mire development. Throughout the ~7800 years history of the mire, there was a high level of surface wetness. The presence of mineral matter in the peat between 7800 and 5100 cal. a BP indicates regular flooding caused by the intensive fluvial activity, apparently resulting from increased precipitation. This was followed by a trend towards a gradual decrease in surface wetness from conditions of high surface moisture (stagnant water) between 5100 and 3000 cal. a BP to present day conditions of moderate surface moisture with a water table slightly below the mire surface. This pattern is consistent with the well-documented long-term trend from palaeoecological records throughout the taiga and arctic zones in West Siberia and central arid Asia. Our data further support the idea that the westerlies were the dominant driver of climate for the southern taiga of West Siberia during the Middle to Late Holocene.</p>","PeriodicalId":9184,"journal":{"name":"Boreas","volume":"52 2","pages":"223-239"},"PeriodicalIF":2.2,"publicationDate":"2022-10-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1111/bor.12604","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"49305415","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":"Millennial-scale oscillations and an environmental regime shift around the Middle to Late Holocene transition in the North Atlantic region based on a multiproxy record from Isfjorden, West Spitsbergen","authors":"Camille Brice,&nbsp;Anne de Vernal,&nbsp;Pierre Francus,&nbsp;Matthias Forwick,&nbsp;Seung-Il Nam","doi":"10.1111/bor.12602","DOIUrl":"10.1111/bor.12602","url":null,"abstract":"<p>Palynological and sedimentological analyses were performed on the sediment core HH16-1205-GC retrieved from the central Isfjorden, West Spitsbergen. The sequence, which spans the last 7000 years, revealed an overall cooling trend with an important climate shift between 4.4 and 3.8 cal. ka BP, in addition to millennial-scale oscillations. Sea-surface reconstruction from dinocyst assemblages indicates a decrease in summer sea-surface temperature, from 2.5 to 1.5 °C, and primary productivity, from 750 to 650 gC m⁻² a⁻¹ over the last 7000 years. From around 6.8 to 5.8 cal. ka BP, the sedimentological and palynological data suggest a predominant sediment supply from the inner part of the fjord, ice rafting, dense sea ice cover, strongly stratified water masses and high primary productivity. The interval from 4.4 to 3.8 cal. ka BP is marked by a layer of coarser material and a significant decrease in the grain-size mode. Our geochemical data show large-amplitude fluctuations after 2.0 cal. ka BP, while an increase in the dinocysts <i>Impagidinium pallidum</i> and <i>Spiniferites elongatus</i> from 2.0 to 1.2 cal. ka BP suggests enhanced Atlantic Water inflow. The dinocyst-based reconstructions also reveal large-amplitude millennial fluctuations in sea ice cover, summer sea-surface temperature and salinity. Wavelet analysis and cross-wavelet analysis on K/Ti ratio coupled with sea-ice estimates confirm a strong signal with a periodicity of 1200–1500 years.</p>","PeriodicalId":9184,"journal":{"name":"Boreas","volume":"52 1","pages":"42-59"},"PeriodicalIF":2.2,"publicationDate":"2022-10-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1111/bor.12602","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"42017143","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":"Reconstruction of cropland change in European countries using integrated multisource data since AD 1800","authors":"Yu Ye,&nbsp;Jun Li,&nbsp;Xiuqi Fang,&nbsp;Diyang Zhang,&nbsp;Zhilong Zhao,&nbsp;Zhilei Wu,&nbsp;Yujie Lu,&nbsp;Beibei Li","doi":"10.1111/bor.12598","DOIUrl":"10.1111/bor.12598","url":null,"abstract":"<p>Credible historical land use/cover data are very important for past global change research. This study generates a set of integrated reconstruction methods based on multisource data and produces a new set of improved historical cropland data sets in Europe over the past 200 years. For AD 2000, FAO data, existing research results and statistical data are integrated. For AD 1900, a method of integrating two sets of independent historical agricultural land data by correction and validation and supplemented by other historical cropland data are developed. For AD 1850 and 1800, a methodological scheme of diversified proxy integrative technology and methods based on multisource data is constructed. In this new data set, quantitative reconstructions for AD 1900, 1850 and 1800 are improved to account for 100, 78 and 57% of all European countries, respectively. The reconstruction results show that each region in Europe has been in different stage of historical agricultural development. More than 86% of the countries’ cropland area and its proportion peaked in AD 1900 or did not exceed the data for AD 2000. Specifically, a high reclamation zone gradually formed from France to Ukraine, in which every country’s cropland fraction was ≥40% during AD 1800–1900. From AD 1900–2000, the highly cultivated region contracted, and the centre of higher cropland proportions shifted to eastern Europe and Poland, Czechia and Hungary. The cropland area was systematically underestimated by HYDE3.2, with a relative difference ratio of −20 to −30% between HYDE3.2 and this study. Historical empirical data were used for only 32% of countries in HYDE3.2. This method of multiproxy integrated reconstruction is applicable to other regions of the world and it would be worth attempting to apply it to earlier historical European cropland data sets in the future.</p>","PeriodicalId":9184,"journal":{"name":"Boreas","volume":"52 1","pages":"60-77"},"PeriodicalIF":2.2,"publicationDate":"2022-09-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1111/bor.12598","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"44950245","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":"Southern Hemisphere Westerly Winds have modulated the formation of laminations in sediments in Lago Fagnano (Tierra del Fuego, Argentina) over the past 6.3 ka","authors":"Alexis Vizcaino, F. Jiménez‐Espejo, R. Dunbar, D. Mucciarone, A. García‐Alix, I. Neugebauer, D. Arizteguí","doi":"10.1111/bor.12600","DOIUrl":"https://doi.org/10.1111/bor.12600","url":null,"abstract":"Tierra del Fuego in Argentina is a unique location to examine past Holocene wind variability since it intersects the core of the Southern Hemisphere Westerly Winds (SHWW). The SHWW are the most powerful prevailing winds on Earth. Their variation plays a role in regulating atmospheric CO2 levels and rainfall amounts and distribution, both today and in the past. We obtained a piston core (LF06‐PC8) from Bahía Grande, a protected sub‐basin at the southern margin of Lago Fagnano, the largest lake in Tierra del Fuego. This article focuses on the uppermost 185 cm of this core, corresponding to laminated sediment from the last ~6.3 ka. Laminations consist of millimetre‐scale paired dark and light layers. Previous studies and new geochemical analysis show that the dark and light layers are characterized by differing concentrations of Mn and Fe. We attribute the distribution of Mn and Fe to episodic hypolimnic oxic–anoxic variations. The age model suggests an approximately bidecadal timescale for the formation of each layer pair. We propose a new model of these redox changes with the SHWW variations. The most likely phenomenon to produce complete water‐column mixing is thermobaric instability, which occurs in colder winters with low‐intensity SHWW (El Niño‐like conditions). In contrast, windier winters are characterized by higher temperatures and reduced mixing in the water column, facilitating a decline in oxygen concentration. Laminations, and the inferred presence of periodic hypolimnion redox changes, are common features of the past ~6.3 ka. Geochemical proxy variability is compatible with an intensification of El Niño/Southern Oscillation activity during the past ~2 ka.","PeriodicalId":9184,"journal":{"name":"Boreas","volume":"52 1","pages":""},"PeriodicalIF":2.2,"publicationDate":"2022-09-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"63530773","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}