Past Global Changes

<strong class="journal-contentHeaderColor">Abstract.</strong> The Beaufort Sea region in the Canadian Arctic has undergone substantial sea ice loss in recent decades, primarily driven by anthropogenic climate warming. To place these changes within the context of natural climate variability, Holocene sea ice evolution and environmental conditions (sea surface temperature, salinity, terrestrial input) were reconstructed using lipid biomarkers (IP₂₅, and other HBIs, OH-GDGT, brGDGT, C_16:0 fatty acid, phytosterols) from two marine sediment cores collected from the Beaufort Shelf and slope, spanning the past 9.1 ka and 13.3 cal kyr BP, respectively. The Early Holocene (12&ndash;8.5 ka) is characterized by relatively higher sea surface temperature, lower salinity and no spring/summer sea ice until 8.5 ka on the Beaufort Sea slope. Around 8.5 ka, a peak in organic matter content is linked to both increased terrestrial input and primary production and may indicate increased riverine input from the Mackenzie River and terrestrial matter input from coastal erosion. Following this period, terrestrial inputs decreased throughout the Middle Holocene in both cores. A gradual increase in IP₂₅ and HBI-II concentrations aligns with relatively higher salinity, lower sea surface temperature and rising sea levels, and indicate the establishment of seasonal (spring) sea ice on the outer shelf around 7 ka and on the shelf around 5 ka. These patterns suggest an expansion of the sea ice cover beginning in the Middle Holocene, influenced by decreasing summer insolation. During the Late Holocene (4&ndash;1 ka), permanent sea ice conditions are inferred on the slope with a peak during the Little Ice Age. After 1 ka, seasonal sea ice conditions on the slope are observed again, alongside an increase in salinity and terrestrial input, and variable primary productivity. Similar patterns of Holocene sea ice variability have been observed across other Arctic marginal seas, highlighting a consistent response to external climate forcing. Continued warming may drive the Beaufort Sea toward predominantly ice-free conditions, resembling those inferred for the Early Holocene.

Radiolaria and Phaeodaria are single-celled eukaryotic zooplankton that inhabit diverse marine environments. While the sedimentary fossil record reveals their ancient origins and morphological diversity, recent advancements in metagenomics and sedimentary ancient DNA ( seda DNA) techniques have highlighted the significant contributions of rarely preserved taxa (e.g., those that are only lightly silicified or soft-bodied) to marine biodiversity and the carbon cycle. Using a paleo-genomic approach, we produced a sed aDNA-based time series of the Radiolarian and Phaeodarian community from the Scotia Sea covering the last 500 kyr. We compared the use of two reference databases, one Radiolarian- and Phaeodarian-specific (RPD) and one more comprehensive eukaryote database (PR 2 ), to assess the validity of a small, taxa-specific database. We determined that the two databases produced comparable results, showing that the overall assemblage changes at the glacial-interglacial scale were similar. At the Class level, Radiolarian and Phaeodarian assemblages appear to have experienced compositional changes during termination events and warm Interglacial periods. This study produced the first Radiolarian- and Phaeodarian-specific reference database. We showed that the Class-level changes that occurred over the last 500 kyr were associated with glacial-interglacial (G-I) cycles, and no permanent shifts away from the natural variation associated with the G-I cycles were found. • Analysis results of the Radiolarian and Phaeodarian database (RPD) and PR 2 datasets were in relative agreement. • Changepoint and cluster analyses revealed that Radiolarian and Phaeodarian assemblage shifts at the Class level were related to glacial-interglacial cycles. • Scotia Sea Radiolaria and Phaeodaria responded predominantly to rapid warming during Interglacial periods, but have remained within the variability of the glacial-interglacial assemblages at the Class level over the last ~450 kyr.

Abstract. The Beaufort Sea region in the Canadian Arctic has undergone substantial sea ice loss in recent decades, primarily driven by anthropogenic climate warming. To place these changes within the context of natural climate variability, Holocene sea ice evolution and environmental conditions (sea surface temperature, salinity, terrestrial input) were reconstructed using lipid biomarkers (IP25, and other HBIs, OH-GDGT, brGDGT, C16:0 fatty acid, phytosterols) from two marine sediment cores collected from the Beaufort Shelf and slope, spanning the past 9.1 ka and 13.3 cal kyr BP, respectively. The Early Holocene (12–8.5 ka) is characterized by relatively higher sea surface temperature, lower salinity and no spring/summer sea ice until 8.5 ka on the Beaufort Sea slope. Around 8.5 ka, a peak in organic matter content is linked to both increased terrestrial input and primary production and may indicate increased riverine input from the Mackenzie River and terrestrial matter input from coastal erosion. Following this period, terrestrial inputs decreased throughout the Middle Holocene in both cores. A gradual increase in IP25 and HBI-II concentrations aligns with relatively higher salinity, lower sea surface temperature and rising sea levels, and indicate the establishment of seasonal (spring) sea ice on the outer shelf around 7 ka and on the shelf around 5 ka. These patterns suggest an expansion of the sea ice cover beginning in the Middle Holocene, influenced by decreasing summer insolation. During the Late Holocene (4–1 ka), permanent sea ice conditions are inferred on the slope with a peak during the Little Ice Age. After 1 ka, seasonal sea ice conditions on the slope are observed again, alongside an increase in salinity and terrestrial input, and variable primary productivity. Similar patterns of Holocene sea ice variability have been observed across other Arctic marginal seas, highlighting a consistent response to external climate forcing. Continued warming may drive the Beaufort Sea toward predominantly ice-free conditions, resembling those inferred for the Early Holocene.

La centrale hydroélectrique de Kapichira, d’une puissance de 130 MW, est située près des chutes de Kapichira sur la rivière Shire au Malawi, en Afrique australe. Elle est exploitée par EGENCO (la société nationale de production). Une prise d'eau menant à un nouveau canal d'irrigation était en cours de construction pour le compte du Shire Valley Transformation Project (SVTP) en janvier 2022 lors du passage du cyclone Ana sur le Malawi. De fortes pluies associées aux difficultés rencontrées avec le contrôle des vannes du barrage de Kapichira ont entraîné la surverse du barrage avec affouillement et rupture du remblai en rive droite. Un batardeau en sol cimenté (CSD) élaboré à partir du sol d’un gisement voisin a été construit pour permettre d'élever le niveau d'eau dans le barrage afin de rétablir la production d'électricité et de protéger la partie endommagée du remblai du Barrage de Kapichira. Ce rapport présente le développement de la conception du batardeau, en abordant les défis liés aux études de sol et à la formulation du sol cimenté, ainsi que les contraintes sur les activités de conception et de construction dans un temps très limité. Il illustre un exemple de coopération internationale dans le domaine de la 1100technologie CSD réunissant des ingénieurs de Nouvelle Zélande, de France, de Corée, du Portugal, d'Afrique du Sud, et du Malawi pour assurer la reconstruction en toute sécurité du Barrage de Kapichira. Les conditions d'extraction du sol, de fabrication et de mise en œuvre du sol cimenté à l'intérieur et autour du bassin du barrage sont présentées en abordant les difficultés propres au site. Le rapport traite aussi des interactions complexes entre la formulation du sol cimenté et l’atelier de construction, des contraintes d'approvisionnement en ciment et en carburant et de la manière dont la réalisation rapide dans un site écologiquement sensible d'une réserve nationale d’animaux a conduit au développement de conceptions et de mode de construction spécifiques. À la lumière des enseignements tirés de cette application dans un contexte particulier, le rapport illustre comment la technologie des barrages en sol cimenté peut être utilisée pour relever les défis des barrages à l'avenir.

The climate of the past two thousand years (2k) provides context for current and future changes, and as such is vital for developing our understanding of the modern climate system. Building on previous phases of the PAGES 2k network, Phase 4 of the PAGES 2k Network paves the way for a new level of understanding of the global water cycle, including enhanced science-policy integration.&amp;#160;Previous PAGES 2k network phases emphasised temperature reconstructions, fundamentally improving our understanding of global climate changes over the Common Era. These reconstructions received widespread recognition and were featured in the Summary for Policymakers of the IPCC&amp;#8217;s Sixth Assessment Report. Integration of this data with state-of-the-art Earth systems models, proxy system models and data assimilation yielded a more comprehensive understanding of the associated physical drivers and climate dynamics. &amp;#160;Phase 4 challenges our community to turn its focus towards hydroclimate. Our aim is to reconstruct hydroclimatic variability over the Common Era, from local to global spatial scales, at sub-annual to multi-centennial time scales, developing a process-level understanding of past hydroclimate events and variability. Our multi-faceted approach includes (1) developing new hydroclimate syntheses that are well-suited for data-model comparisons, (2) improving the interoperability and scope of existing data and model products, and (3) facilitating the translation of our science into evidence-based policy outcomes. In this presentation, we report on our activities and progress to date, particularly highlighting the early stages of our data synthesis efforts.

&amp;lt;p&amp;gt;&amp;lt;img src=&amp;quot;https://contentmanager.copernicus.org/fileStorageProxy.php?f=gnp.d17138223ed164871591461/sdaolpUECMynit/22UGE&amp;amp;app=m&amp;amp;a=0&amp;amp;c=811fe277410d9ff3699ef0224ece3bef&amp;amp;ct=x&amp;amp;pn=gnp.elif&amp;amp;d=1&amp;quot; alt=&amp;quot;&amp;quot; width=&amp;quot;353&amp;quot; height=&amp;quot;140&amp;quot;&amp;gt;&amp;lt;/p&amp;gt;&amp;lt;p&amp;gt;Understanding the climate of the past two millennia (2k) remains vital for developing our wider comprehension of the climate system, including the nature and scale of recent and future anthropogenic change. Phase 4 of the PAGES 2k network will build on previous phases and take us to a new level of understanding and science-policy integration.&amp;lt;/p&amp;gt;&amp;lt;p&amp;gt;During previous phases, PAGES 2k members compiled global networks of proxy measurements, extending records beyond the instrumental period by more than an order of magnitude, reconstructing past climate and developing new knowledge of past variability and processes. Through data-model integration with state-of-the-art Earth systems models, proxy system modelling and data assimilation, we took key steps towards a more comprehensive understanding of climate dynamics.&amp;lt;/p&amp;gt;&amp;lt;p&amp;gt;Phase 4 will take us even further, challenging our community to turn its focus primarily towards the hydroclimate of the Common Era: performing new reconstructions and improving the interoperability, extent and scope of our data and model products. In doing so, we also seek to facilitate the translation of our science into evidence-based policy outcomes. Our overarching aim is to reconstruct hydroclimate variability over the Common Era from local to global spatial scales, at sub-annual to multi-centennial time scales. We propose to achieve this through new community-led data curation efforts and the development of new data-driven tools and practices to maximise the interoperability of convenient, efficient and widespread model/data products. We will aim for a process-level understanding of past hydroclimate events and variability by evaluating and constraining Earth system models and through data assimilation.&amp;lt;/p&amp;gt;&amp;lt;p&amp;gt;Our coordination team places a strong emphasis on respect and inclusion, aiming to foster a diverse and equitable community. Through a &amp;amp;#8216;hub and spoke&amp;amp;#8217; structure, our team will provide a facilitation, coordination and support role (the hub) for Pages 2k working groups (the spokes). We are actively seeking participation of those engaging in climate policy and climate services. Welcome to Phase 4!&amp;amp;#160; We warmly invite your collaborations and contributions!&amp;amp;#160;&amp;lt;/p&amp;gt;

&amp;lt;p&amp;gt;South America hydrological cycle is highly dependent on the water vapor transport advected from tropical-equatorial Atlantic, Southern Pacific as well as the polar advections. While the Pacific contribution in the continental water budget is basically restricted to the western Andes region, the Atlantic Ocean and others mechanism &amp;amp;#8211; as advection in Amazonas basin &amp;amp;#8211; play a great role in modulating precipitation over the continent. Besides, modes of climatic variability, such as ENSO, have an important role in pluviosity distribution patterns and respectively intensity, influencing the availability of water resources from mountainous regions, vital to ecosystems and to economy and human wellbeing. Intense droughts and floods observed continentally during the modern epoch have pointed to the need of better understanding the regional climate related issue. Recent paleoclimate advances, especially the creation of high-standard regional proxy record databases, allow describing the South American climate from a new perspective. Here we present an effort of the South American PAGES 2k paleo-community LOTRED-SA to build a South America hydrology robust and unique multiproxy database. We present a spatial and temporal approach of the South American hydro-climate reconstruction based on more than 360 available databases in an attempt to unravel their changes and impacts. Following a multi-proxy approach, we expect to better describe duration and location of wet and dryer climate regimes at most important climate spatial domains, and modes patterns on South America, during each period; as well as their predominant variability base on high resolution records (tree rings, speleothems, lake, marine and ice cores). we combine here the use of different proxy records and spatial-temporal approach, owing to consolidate interpretations of the hydrological cycles in South America.&amp;lt;/p&amp;gt;

Abstract. This PAGES (Past Global Changes) 2k (climate of the past 2000 years working group) special issue of Climate of the Past brings together the latest understanding of regional change and impacts from PAGES 2k groups across a range of proxies and regions. The special issue has emerged from a need to determine the magnitude and rate of change of regional and global climate beyond the timescales accessible within the observational record. This knowledge also plays an important role in attribution studies and is fundamental to understanding the mechanisms and environmental and societal impacts of recent climate change. The scientific studies in the special issue reflect the urgent need to better understand regional differences from a truly global view around the PAGES themes of “Climate Variability, Modes and Mechanisms”, “Methods and Uncertainties”, and “Proxy and Model Understanding”.

In the version of this Review Article originally published, ref. 10 was mistakenly cited instead of ref. 107 at the end of the sentence: “This complexity of residual ice cover makes it likely that HTM warming was regional, rather than global, and its peak warmth thus had different timing in different locations.” In addition, for ref. 108, Scientific Reports was incorrectly given as the publication name; it should have been Scientific Data. These errors have now been corrected in the online versions.

VOLUME 291 (2016) PAGES 22703–22713 PAGES 22705, 22706, and 22708: There were several errors in this article. Figs. 1C and 2A did not indicate the borders between different sections of the same gel. In Fig. 4, one of the figure panel labels was missing. These errors have now been corrected and do not affect the results or conclusions of this work.Fig. 2AView Large Image Figure ViewerDownload Hi-res image Download (PPT)Fig. 4View Large Image Figure ViewerDownload Hi-res image Download (PPT)