Boreas最新文献

{"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}

{"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,&nbsp;Francisco J. Jimenez-Espejo,&nbsp;Robert B. Dunbar,&nbsp;David Mucciarone,&nbsp;Antonio García-Alix,&nbsp;Ina Neugebauer,&nbsp;Daniel Ariztegui","doi":"10.1111/bor.12600","DOIUrl":"https://doi.org/10.1111/bor.12600","url":null,"abstract":"<p>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.</p>","PeriodicalId":9184,"journal":{"name":"Boreas","volume":"52 1","pages":"124-138"},"PeriodicalIF":2.2,"publicationDate":"2022-09-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1111/bor.12600","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"50137526","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 history of the eastern side of Novaya Zemlya from glaciomarine sediment records in the Tsivol’ki Fjord’: Comments","authors":"Ekaterina Taldenkova","doi":"10.1111/bor.12603","DOIUrl":"10.1111/bor.12603","url":null,"abstract":"<p>Rusakov <i>et al</i>. (<span>2022</span>) present a multiproxy-based reconstruction of the Holocene history of Tsivol’ki Fjord located on the Kara Sea coast of the northern Novaya Zemlya. A considerable portion of the palaeoreconstructions is derived from the data on macro- and microfossils. As an author of these data (although not acknowledged in the paper), I point to several mistakes in the data presentation, argue for a different palaeoenvironmental interpretation of certain fossil assemblages and add new data for the topmost part of the sediment core. Additionally, information on ice- and iceberg-rafted debris (IRD) counts is presented that provides evidence for past variations in the glacier front position and iceberg calving. Altogether, this considerably changes the palaeoenvironmental reconstructions of the Holocene history of Tsivol’ki Fjord as drawn by Rusakov <i>et al</i>. (<span>2022</span>). The revised environmental interpretation is as follows: microfossil data give evidence for a distal position of the glacier front from the studied core site in the outer fjord and a persistent exchange with open sea waters throughout the whole time period since 10.6 cal. ka BP. After the relatively warm Early–Middle Holocene, cooling started that resulted in the offshore glacier advance manifested by the rise in sedimentation rates and strong meltwater influence that were the reason for the drop in the total abundance of microfossils and IRD during 3.6 to 4.6 cal. ka BP. Between 3.6 and 0.9 cal. ka BP, the highest relative abundance of the glacier-distal benthic foraminiferal species <i>Islandiella norcrossi/helenae</i>, the growing total abundance and diversity of microfossils, the decrease in sedimentation rates and the rising IRD content imply the gradual retreat of the glacier front after the short progradation event. The last millennium is characterized by the highest total abundance and diversity of microfossils, low sedimentation rates and benthic foraminiferal assemblages gradually becoming similar to the Early–Middle Holocene ones.</p><p>The lead author of Rusakov <i>et al</i>. (<span>2022</span>) article was invited by <i>Boreas</i> to reply to these comments but we received no response.</p>","PeriodicalId":9184,"journal":{"name":"Boreas","volume":"52 1","pages":"139-144"},"PeriodicalIF":2.2,"publicationDate":"2022-09-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1111/bor.12603","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"47454707","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":"Growth and retreat of the last British–Irish Ice Sheet, 31 000 to 15 000 years ago: the BRITICE-CHRONO reconstruction","authors":"Chris D. Clark,&nbsp;Jeremy C. Ely,&nbsp;Richard C. A. Hindmarsh,&nbsp;Sarah Bradley,&nbsp;Adam Ignéczi,&nbsp;Derek Fabel,&nbsp;Colm Ó Cofaigh,&nbsp;Richard C. Chiverrell,&nbsp;James Scourse,&nbsp;Sara Benetti,&nbsp;Tom Bradwell,&nbsp;David J. A. Evans,&nbsp;David H. Roberts,&nbsp;Matt Burke,&nbsp;S. Louise Callard,&nbsp;Alicia Medialdea,&nbsp;Margot Saher,&nbsp;David Small,&nbsp;Rachel K. Smedley,&nbsp;Edward Gasson,&nbsp;Lauren Gregoire,&nbsp;Niall Gandy,&nbsp;Anna L. C. Hughes,&nbsp;Colin Ballantyne,&nbsp;Mark D. Bateman,&nbsp;Grant R. Bigg,&nbsp;Jenny Doole,&nbsp;Dayton Dove,&nbsp;Geoff A. T. Duller,&nbsp;Geraint T. H. Jenkins,&nbsp;Stephen L. Livingstone,&nbsp;Stephen McCarron,&nbsp;Steve Moreton,&nbsp;David Pollard,&nbsp;Daniel Praeg,&nbsp;Hans Petter Sejrup,&nbsp;Katrien J. J. Van Landeghem,&nbsp;Peter Wilson","doi":"10.1111/bor.12594","DOIUrl":"10.1111/bor.12594","url":null,"abstract":"<p>The BRITICE-CHRONO consortium of researchers undertook a dating programme to constrain the timing of advance, maximum extent and retreat of the British–Irish Ice Sheet between 31 000 and 15 000 years before present. The dating campaign across Ireland and Britain and their continental shelves, and across the North Sea included 1500 days of field investigation yielding 18 000 km of marine geophysical data, 377 cores of sea floor sediments, and geomorphological and stratigraphical information at 121 sites on land; generating 690 new geochronometric ages. These findings are reported in 28 publications including synthesis into eight transect reconstructions. Here we build ice sheet-wide reconstructions consistent with these findings and using retreat patterns and dates for the inter-transect areas. Two reconstructions are presented, a wholly empirical version and a version that combines modelling with the new empirical evidence. Palaeoglaciological maps of ice extent, thickness, velocity, and flow geometry at thousand-year timesteps are presented. The maximum ice volume of 1.8 m sea level equivalent occurred at 23 ka. A larger extent than previously defined is found and widespread advance of ice to the continental shelf break is confirmed during the last glacial. Asynchrony occurred in the timing of maximum extent and onset of retreat, ranging from 30 to 22 ka. The tipping point of deglaciation at 22 ka was triggered by ice stream retreat and saddle collapses. Analysis of retreat rates leads us to accept our hypothesis that the marine-influenced sectors collapsed rapidly. First order controls on ice-sheet demise were glacio-isostatic loading triggering retreat of marine sectors, aided by glaciological instabilities and then climate warming finished off the smaller, terrestrial ice sheet. Overprinted on this signal were second order controls arising from variations in trough topographies and with sector-scale ice geometric readjustments arising from dispositions in the geography of the landscape. These second order controls produced a stepped deglaciation. The retreat of the British–Irish Ice Sheet is now the world’s most well-constrained and a valuable data-rich environment for improving ice-sheet modelling.</p>","PeriodicalId":9184,"journal":{"name":"Boreas","volume":"51 4","pages":"699-758"},"PeriodicalIF":2.2,"publicationDate":"2022-09-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1111/bor.12594","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"41454026","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":"An Early Pleistocene interglacial deposit at Pingorsuit, North-West Greenland","authors":"Ole Bennike,&nbsp;William Colgan,&nbsp;Lars Hedenäs,&nbsp;Oliver Heiri,&nbsp;Geoffrey Lemdahl,&nbsp;Peter Wiberg-Larsen,&nbsp;Sofia Ribeiro,&nbsp;Roberto Pronzato,&nbsp;Renata Manconi,&nbsp;Anders A. Bjørk","doi":"10.1111/bor.12596","DOIUrl":"10.1111/bor.12596","url":null,"abstract":"<p>At the Pingorsuit Glacier in North-West Greenland, an organic-rich deposit that had recently emerged from the retreating ice cap was discovered at an elevation of 480 m above sea level. This paper reports on macrofossil analyses of a coarse detritus gyttja and peaty soil, which occurred beneath a thin cover of till and glacifluvial deposits. The sediments contained remains of vascular plants, mosses, beetles, caddisflies, midges, bryozoans, sponges and other invertebrates. The flora includes black spruce, tree birch, boreal shrubs and wetland and aquatic taxa, which shows that mires, lakes and ponds were present in the area. We describe a new extinct waterwort species <i>Elatine odgaardii</i>. The fossils were deposited in a boreal environment with a mean July air temperature that was at least 9 °C higher than at present. The fossil assemblages show strong similarities with others from Greenland that have been assigned an Early Pleistocene age, and we suggest a similar age for the sediments found at the margin of the Pingorsuit Glacier.</p><p>At the Pingorsuit Glacier in North-West Greenland, an organic-rich deposit was discovered at an elevation of 480 m above sea level. The sediments contained remains of vascular plants, mosses, beetles, caddisflies, midges, bryozoans, sponges and other invertebrates. The fossils were deposited in a boreal environment with a mean July air temperature that was at least 9 °C higher than at present.</p>","PeriodicalId":9184,"journal":{"name":"Boreas","volume":"52 1","pages":"27-41"},"PeriodicalIF":2.2,"publicationDate":"2022-08-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1111/bor.12596","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"42292564","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}