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In this paper we provide an overview of new knowledge on oxygen depletion (hypoxia) and related phenomena in aquatic systems resulting from the EU-FP7 project HYPOX (\"In situ monitoring of oxygen depletion in hypoxic ecosystems of coastal and open seas, and landlocked water bodies\", http://www.hypox.net). In view of the anticipated oxygen loss in aquatic systems due to eutrophication and climate change, HYPOX was set up to improve capacities to monitor hypoxia as well as to understand its causes and consequences. Temporal dynamics and spatial patterns of hypoxia were analyzed in field studies in various aquatic environments, including the Baltic Sea, the Black Sea, Scottish and Scandinavian fjords, Ionian Sea lagoons and embayments, and Swiss lakes. Examples of episodic and rapid (hours) occurrences of hypoxia, as well as seasonal changes in bottom-water oxygenation in stratified systems, are discussed. Geologically driven hypoxia caused by gas seepage is demonstrated. Using novel technologies, temporal and spatial patterns of water-column oxygenation, from basin-scale seasonal patterns to meter-scale sub-micromolar oxygen distributions, were resolved. Existing multidecadal monitoring data were used to demonstrate the imprint of climate change and eutrophication on long-term oxygen distributions. Organic and inorganic proxies were used to extend investigations on past oxygen conditions to centennial and even longer timescales that cannot be resolved by monitoring. The effects of hypoxia on faunal communities and biogeochemical processes were also addressed in the project. An investigation of benthic fauna is presented as an example of hypoxia-devastated benthic communities that slowly recover upon a reduction in eutrophication in a system where naturally occurring hypoxia overlaps with anthropogenic hypoxia. Biogeochemical investigations reveal that oxygen intrusions have a strong effect on the microbially mediated redox cycling of elements. Observations and modeling studies of the sediments demonstrate the effect of seasonally changing oxygen conditions on benthic mineralization pathways and fluxes. Data quality and access are crucial in hypoxia research. Technical issues are therefore also addressed, including the availability of suitable sensor technology to resolve the gradual changes in bottom-water oxygen in marine systems that can be expected as a result of climate change. Using cabled observatories as examples, we show how the benefit of continuous oxygen monitoring can be maximized by adopting proper quality control. Finally, we discuss strategies for state-of-the-art data archiving and dissemination in compliance with global standards, and how ocean observations can contribute to global earth observation attempts.

The evolution of environmental changes during the last decades and the impact on the living biomass in the western part of Amvrakikos Gulf was investigated using abundances and species distributions of benthic foraminifera and lipid biomarker concentrations. These proxies indicated that the gulf has markedly changed due to eutrophication. Eutrophication has led to a higher productivity, a higher bacterial biomass, shifts towards opportunistic and tolerant benthic foraminifera species (e.g. Bulimina elongata, Nonionella turgida, Textularia agglutinans, Ammonia tepida) and a lower benthic species density. Close to the Preveza Strait (connection between the gulf and the Ionian Sea), the benthic assemblages were more diversified under more oxygenated conditions. Sea grass meadows largely contributed to the organic matter at this sampling site. The occurrence of isorenieratane, chlorobactane and lycopane supported by oxygen monitoring data indicated that anoxic (and partly euxinic) conditions prevailed seasonally throughout the western part of the gulf with more severe oxygen depletion towards the east. Increased surface water temperatures have led to a higher stratification, which reduced oxygen resupply to bottom waters. Altogether, these developments led to mass mortality events and ecosystem decline in Amvrakikos Gulf.

This article is composed of three independent commentaries about the state of Integrated, Coordinated, Open, Networked (ICON) principles (Goldman et al., 2021, https://doi.org/10.1002/essoar.10508554.1) in the AGU section paleoclimatology and paleoceanography (P&P), and a discussion on the opportunities and challenges of adopting them. Each commentary focuses on a different topic: (Section 2) Global collaboration, technology transfer and application, reproducibility, and data sharing and infrastructure; (Section 3) Local knowledge, global gain: improving interactions within the scientific community and with locals, indigenous communities, stakeholders, and the public; (Section 4) Field, experimental, remote sensing, and real‐time data research and application. P&P projects can better include ICON principles by directly incorporating them into research proposals. A promising way to overcome the challenges of interdisciplinarity and integration is to foster networking, which will advance our research discipline through the application of ICON. Plain Language Summary Paleoceanography and Paleoclimatology seeks to reveal past changes in the oceans and the climate, to help us better understand how Earth systems work. Traditionally, it has a strong focus on international networks and cooperation and we have accomplished many international projects. However, we are still facing some major challenges to achieve equity among researchers and science questions. In this article we discuss the current state, issues and solutions from three different perspectives: (a) data structure problems and data sharing issues, (b) relationships between research groups with different levels of knowledge, cultural aspects and their interaction with local communities in fieldwork, and (c) utilization of data, instrument sharing, promotion of networking, and effective communication with the public to make our research as inclusive and visible as possible. Actions aimed at ICON could be further promoted by research programs, governments, and scientists via integration of cooperation strategies into research projects. Key Points Open science and global collaboration increase networking opportunities, data availability, and quality of scientific outcomes ICON principles support inclusivity and diversity, and ultimately resulting in increased and quicker uptake of scientific outcomes ICON practices are well established in large‐scale international collaborations, but coordinated data and sampling standards are needed

This article is composed of three independent commentaries about the state of Integrated, Coordinated, Open, Networked (ICON) principles in the American Geophysical Union Biogeosciences section, and discussion on the opportunities and challenges of adopting them. Each commentary focuses on a different topic: (a) Global collaboration, technology transfer, and application (Section 2), (b) Community engagement, community science, education, and stakeholder involvement (Section 3), and (c) Field, experimental, remote sensing, and real‐time data research and application (Section 4). We discuss needs and strategies for implementing ICON and outline short‐ and long‐term goals. The inclusion of global data and international community engagement are key to tackling grand challenges in biogeosciences. Although recent technological advances and growing open‐access information across the world have enabled global collaborations to some extent, several barriers, ranging from technical to organizational to cultural, have remained in advancing interoperability and tangible scientific progress in biogeosciences. Overcoming these hurdles is necessary to address pressing large‐scale research questions and applications in the biogeosciences, where ICON principles are essential. Here, we list several opportunities for ICON, including coordinated experimentation and field observations across global sites, that are ripe for implementation in biogeosciences as a means to scientific advancements and social progress. Plain Language Summary Biogeosciences is an interdisciplinary field that requires multiscale global data and concerted international community efforts to tackle grand challenges. However, several technical, institutional, and cultural hurdles have remained as major roadblocks toward scientific progress, hindering seamless global data acquisition and international community engagement. To bring a paradigm shift in biogeosciences, there is a need to implement integrated, coordinated, open, and networked efforts, collectively known as the Integrated, Coordinated, Open, Networked (ICON) principles. In this article, we present three related commentaries about the state of ICON, discuss needs to reduce geographical bias in data for enhancing scientific progress, and identify action items. Action items are primarily people‐centric and include but are not limited to: longer‐term funding priorities to institutionalize capacity and reduce entry costs, engagement of local stakeholders across the globe, incentivization of collaborations, and development of training and workshops for capacity building. Key Points Biogeosciences needs Integrated, Coordinated, Open, Networked (ICON) principles to address multiscale global problems and reduce geographical bias in scientific progress Much potential exists for emphasizing people‐centric capacity building, involving relevant stakeholders within an ICON framework Globally coordinated experimental and field data provide challenges and opportunities for scientific advancement in biogeosciences

The Antarctic environment is amongst the coldest and driest environments on Earth. The ultraxerous soils in the McMurdo Dry Valleys support exclusively microbial communities, however, 15 million years ago, a tundra ecosystem analogous to present-day southern Greenland occupied this region. The occurrence of ancient soil organic carbon combined with low accumulation of contemporary material makes it challenging to differentiate between ancient and modern organic processes. Here, we explore the additions of modern organic carbon, and the preservation and degradation of organics and lipid biomarkers, in a 1.4 m mid-Miocene age (∼14.5–14.3 Ma) permafrost soil column from Friis Hills. The total organic carbon is low throughout the soils (<1 wt %). The near-surface (upper 35 cm) dry permafrost has lower C:N ratios, higher δ13Corg values, higher proportion of branched fatty acids with an iso and anteiso configuration relative to n-fatty acids, lower phytol abundance and higher contributions of low-molecular weight homologues of n-alkanes, than the underlying icy permafrost, indicating higher contributions from bacteria-derived organic matter. Conversely, the icy permafrost contains higher molecular weight n-alkanes, n-fatty acids and n-alkanols, along with phytosterols (e.g. sitosterol and stigmasterol) and phytol (and its derivatives pristane and phytane) that are indicative of the contributions and preservation of higher-level plants. This implies that legacy mid-Miocene age carbon in the near-surface soils (ca. 35 cm) has been prone to microbial organic matter degradation during times when the permafrost thawed, likely during relatively warm intervals through the late Neogene (∼6.0 Ma) and sporadically during the Holocene (<1 %), when ground summer temperatures were ≥+2 °C (based on branched glycerol dialkyl glycerol tetraether (brGDGT) temperature reconstructions). Conversely, lipid biomarkers found deeper in the permafrost have been preserved for millions of years. These results suggest that ancient organics preserved in permafrost could underpin significant ecological changes in the McMurdo Dry Valleys under the current warming climate.

Marine glycerol dialkyl glycerol tetraethers (GDGTs) are used in various proxies (such as TEX86) to reconstruct past ocean temperatures. Over 20 years of improvements in GDGT sample processing, analytical techniques, data interpretation and our understanding of proxy functioning have led to the collective development of a set of best practices in all these areas. Further, the importance of Open Science in research has increased the emphasis on the systematic documentation of data generation, reporting and archiving processes for optimal reusability of data. In this paper, we provide protocols and best practices for obtaining, interpreting and presenting GDGT data (with a focus on marine GDGTs), from sampling to data archiving. The purpose of this paper is to optimize inter-laboratory comparability of GDGT data, and to ensure published data follows modern open access principles.

Based on Nationally Determined Contributions concurrent with Shared Socioeconomic Pathways (SSPs) 2-4.5, the IPCC predicts global warming of 2.1–3.5 ∘C (very likely range 10–90th percentile) by 2100 CE. However, global average temperature is a poor indicator of regional warming and global climate models (GCMs) require validation with instrumental or proxy data from geological archives to assess their ability to simulate regional ocean and atmospheric circulation, and thus, to evaluate their performance for regional climate projections. The south-west Pacific is a region that performs poorly when GCMs are evaluated against instrumental observations. The New Zealand Earth System Model (NZESM) was developed from the United Kingdom Earth System Model (UKESM) to better understand south-west Pacific response to global change, by including a nested ocean grid in the south-west Pacific with 80 % greater horizontal resolution than the global-scale host. Here, we reconstruct regional south-west Pacific sea-surface temperatures (SSTs) for the mid-Pliocene warm period (mPWP; 3.3–3.0 Ma), which has been widely considered a past analogue with an equilibrium surface temperature response of +3 ∘C to an atmospheric CO2 concentration of ∼350–400 ppm, in order to assess the warming distribution in the south-west Pacific. This study presents proxy SSTs from seven deep sea sediment cores distributed across the south-west Pacific. Our reconstructed SSTs are derived from molecular biomarkers preserved in the sediment – alkenones (i.e. U37K′ index) and isoprenoid glycerol dialkyl glycerol tetraethers (i.e. TEX86 index) – and are compared with SSTs reconstructed from the Last Interglacial (125 ka), Pliocene Model Intercomparison Project (PlioMIP) outputs and transient climate model projections (NZESM and UKESM) of low- to high-range SSPs for 2090–2099 CE. Mean interglacial equilibrium SSTs during the mPWP for the south-west Pacific sites were on average 4.2 ∘C (1.8–6.1 ∘C likely range) above pre-industrial temperatures and show good agreement with model outputs from NZESM and UKESM under mid-range SSP 2–4.6 conditions. These results highlight that not only is the mPWP an appropriate analogue when considering future temperature change in the centuries to come, but they also demonstrate that the south-west Pacific region will experience warming that exceeds that of the global mean if atmospheric CO2 remains above 350 ppm.

​​​​​​​Late Paleocene deposition of an organic-rich sedimentary facies on the continental shelf and slope of New Zealand and eastern Australia has been linked to short-lived climatic cooling and terrestrial denudation following sea level fall. Recent studies confirm that the organic matter in this facies, termed “Waipawa organofacies”, is primarily of terrestrial origin, with a minor marine component. It is also unusually enriched in 13C. In this study we address the cause of this enrichment. For Waipawa organofacies and its bounding facies in the Taylor White section, Hawke's Bay, paired palynofacies and carbon isotope analysis of heavy liquid-separated density fractions indicate that the heaviest δ13C values are associated with degraded phytoclasts (woody plant matter) and that the 13C enrichment may be partly due to lignin degradation. Compound-specific stable carbon isotope analyses of samples from the Taylor White and mid-Waipara (Canterbury) sections display similar trends and further reveal a residual 13C enrichment of ∼ 2.5 ‰ in higher plant biomarkers (long chain n-alkanes and fatty acids) and a ∼ 2 ‰–5 ‰ change in subordinate marine biomarkers. Using the relationship between atmospheric CO2 and C3 plant tissue δ13C values, we determine that the 3 ‰ increase in terrestrial δ13C may represent a ∼ 35 % decrease in atmospheric CO2.Refined age control for Waipawa organofacies indicates that deposition occurred between 59.2 and 58.5 Ma, which coincides with an interval of carbonate dissolution in the deep sea that is associated with a Paleocene oxygen isotope maximum (POIM, 59.7–58.1 Ma) and the onset of the Paleocene carbon isotope maximum (PCIM, 59.3–57.4 Ma). This association suggests that Waipawa deposition occurred during a time of cool climatic conditions and increased carbon burial. This relationship is further supported by published TEX86-based sea surface temperatures that indicate a pronounced regional cooling during deposition. We suggest that reduced greenhouse gas emissions from volcanism and accelerated carbon burial, due to tectonic factors, resulted in short-lived global cooling, growth of ephemeral ice sheets and a global fall in sea level. Accompanying erosion and carbonate dissolution in deep-sea sediment archives may have hidden the evidence of this “hypothermal” event until now.

A game on trees that is related to the dictionary problem is considered. There are two players, $A$ and $B$, which take turns. Player $A$ models the user of the dictionary and player $B$ models the implementation of it. At his turn, player $A$ modifies the tree by adding new leaves and player $B$ modifies the tree by replacing subtrees. The cost of an insertion is the depth of the new leaf, and the cost of an update is the size of the subtree replaced. The goal of player $A$ is to maximize cost and the goal of $B$ is to minimize it. It is shown that there is a strategy for player $A$, which forces a cost of $\\Omega (n \\log \\log n)$ for an $n$-game, i.e., a game in which each player takes $n$ turns, and that there is a strategy for player $B$, which keeps the cost within $O(n \\log \\log n)$.