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Butanetriol and pentanetriol dialkyl glycerol tetraethers (BDGTs and PDGTs) are membrane lipids, recently discovered in sedimentary environments and in the methanogenic archaeon Methanomassiliicoccus luminyensis. They possess an unusual structure, which challenges fundamental assumptions in lipid biochemistry. Indeed, they bear a butanetriol or a pentanetriol backbone instead of a glycerol at one end of their core structure. In this study, we unambiguously located the additional methyl group of the BDGT compound on the C3 carbon of the lipid backbone via high-field nuclear magnetic resonance (NMR) experiments. We further systematically explored the abundance, distribution and isotopic composition of BDGTs and PDGTs as both intact polar and core lipid forms in marine sediments collected in contrasting environments of the Mediterranean Sea and Black Sea. High proportions of intact polar BDGTs and PDGTs in the deeper methane-laden sedimentary layers and relatively 13C-depleted BDGTs, especially in the Rhone Delta and in the Black Sea, are in agreement with a probable methanogenic source for these lipids. However, contributions from heterotrophic Archaea to BDGTs (and PDGTs) cannot be excluded, particularly in the eastern Mediterranean Sea, and contrasting BDGT and PDGT headgroup distribution patterns were observed between the different sites studied. This points to additional, non-methanogenic, archaeal sources for these lipids.

Gordon & Betty Moore FoundationGordon and Betty Moore Foundation [5596]; Canada Research Chairs FoundationCanada Research Chairs; European Union's Horizon 2020 research and innovation programme under Marie Sklodowska-Curie grant [747946]; Fundacao para a Ciencia e Tecnologia I.P. Portugal (FCT); Direcao-Geral de Politica do Mar (DGPM) [2/2017/001-MiningImpact 2]; FCTPortuguese Foundation for Science and TechnologyEuropean Commission [CEECIND005262017, UID/MAR/00350/2013, IF/01194/2013, IF/00029/2014/CP1230/CT0002, Mining2/0005/2017]; RF State Assignment [0149-2019-0009]; Horizon 2020 Agricultural Interoperability and Analysis System (ATLAS) projects [678760]; JM Kaplan Fund; National Science FoundationNational Science Foundation (NSF) [OCE 1634172]; JPI Oceans project Mining Impact -Environmental Impacts and Risks of Deep-Sea Mining Aug 2018-Feb 2022 (NWO-ALW) [856.18.001] info:eu-repo/semantics/publishedVersion

Ice sheet numerical modeling is an important tool to estimate the dynamic contribution of the Antarctic ice sheet to sea level rise over the coming centuries. The influence of initial conditions on ice sheet model simulations, however, is still unclear. To better understand this influence, an initial state intercomparison exercise (initMIP) has been developed to compare, evaluate, and improve initialization procedures and estimate their impact on century-scale simulations. initMIP is the first set of experiments of the Ice Sheet Model Intercomparison Project for CMIP6 (ISMIP6), which is the primary Coupled Model Intercomparison Project Phase 6 (CMIP6) activity focusing on the Greenland and Antarctic ice sheets. Following initMIP-Greenland, initMIP-Antarctica has been designed to explore uncertainties associated with model initialization and spin-up and to evaluate the impact of changes in external forcings. Starting from the state of the Antarctic ice sheet at the end of the initialization procedure, three forward experiments are each run for 100 years: a control run, a run with a surface mass balance anomaly, and a run with a basal melting anomaly beneath floating ice. This study presents the results of initMIP-Antarctica from 25 simulations performed by 16 international modeling groups. The submitted results use different initial conditions and initialization methods, as well as ice flow model parameters and reference external forcings. We find a good agreement among model responses to the surface mass balance anomaly but large variations in responses to the basal melting anomaly. These variations can be attributed to differences in the extent of ice shelves and their upstream tributaries, the numerical treatment of grounding line, and the initial ocean conditions applied, suggesting that ongoing efforts to better represent ice shelves in continental-scale models should continue.

The uptake of anthropogenic CO2 by the oceans has led to a rise in the oceanic partial pressure of CO2, and to a decrease in pH and carbonate ion concentration. This modification of the marine carbonate system is referred to as ocean acidification. Numerous papers report the effects of ocean acidification on marine organisms and communities but few have provided details concerning full carbonate chemistry and complementary observations. Additionally, carbonate system variables are often reported in different units, calculated using different sets of dissociation constants and on different pH scales. Hence the direct comparison of experimental results has been problematic and often misleading. The need was identified to (1) gather data on carbonate chemistry, biological and biogeochemical properties, and other ancillary data from published experimental data, (2) transform the information into common framework, and (3) make data freely available. The present paper is the outcome of an effort to integrate ocean carbonate chemistry data from the literature which has been supported by the European Network of Excellence for Ocean Ecosystems Analysis (EUR-OCEANS) and the European Project on Ocean Acidification (EPOCA). A total of 185 papers were identified, 100 contained enough information to readily compute carbonate chemistry variables, and 81 data sets were archived at PANGAEA – The Publishing Network for Geoscientific & Environmental Data. This data compilation is regularly updated as an ongoing mission of EPOCA. Data access: http://doi.pangaea.de/10.1594/PANGAEA.735138

The number concentration of cloud particles is a key quantity for understanding aerosol–cloud interactions and describing clouds in climate and numerical weather prediction models. In contrast with recent advances for liquid clouds, few observational constraints exist regarding the ice crystal number concentration (Ni). This study investigates how combined lidar–radar measurements can be used to provide satellite estimates of Ni, using a methodology that constrains moments of a parameterized particle size distribution (PSD). The operational liDAR–raDAR (DARDAR) product serves as an existing base for this method, which focuses on ice clouds with temperatures Tc<-30 ∘C. Theoretical considerations demonstrate the capability for accurate retrievals of Ni, apart from a possible bias in the concentration in small crystals when Tc≳−50 ∘C, due to the assumption of a monomodal PSD shape in the current method. This is verified via a comparison of satellite estimates to coincident in situ measurements, which additionally demonstrates the sufficient sensitivity of lidar–radar observations to Ni. Following these results, satellite estimates of Ni are evaluated in the context of a case study and a preliminary climatological analysis based on 10 years of global data. Despite a lack of other large-scale references, this evaluation shows a reasonable physical consistency in Ni spatial distribution patterns. Notably, increases in Ni are found towards cold temperatures and, more significantly, in the presence of strong updrafts, such as those related to convective or orographic uplifts. Further evaluation and improvement of this method are necessary, although these results already constitute a first encouraging step towards large-scale observational constraints for Ni. Part 2 of this series uses this new dataset to examine the controls on Ni.

This deliverable is a report to provide information and recommendations on the monitoring strategy of Argo in transitional areas between the coastal shelf seas and the open ocean zone taking into account the collaboration framework of Euro-Argo ERIC with other Marine RIs and research communities.

Version of the 'Finite Volume Sea ice - Ocean Model' (FESOM2) that was used in the coupled model IFS-FESOM for nextGEMS Cycle 3 simulations. It includes all changes from FESOM2.5 plus modifications for better stability on DKRZ Levante. This is the source code used in the study Rackow, Pedruzo-Bagazgoitia, Becker, Milinski, Sandu et al. : Multi-year simulations at kilometre scale with the Integrated Forecasting System coupled to FESOM2.5/NEMOV3.4 This work was supported by the European Union's Horizon 2020 collaborative project NextGEMS (grant number 101003470). For more infos about the nextGEMS project, see https://nextgems-h2020.eu (last access: 30.11.2023) 

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 NOC lead cruise, JC077 represents the main cruise activity as part of the UK’s input to the EC funded ECO2 project. The project aims to develop a “Best environmental practice” for the carbon capture and storage (CCS) industry. CCS has been proposed as a means of mitigating climate change by storing CO2 in geological reservoirs. The UK has identified sub-seabed storage as the most likely CCS process to be used. Other countries such as the US and Germany are pursuing land based CCS geological storage. Two types of reservoirs have been identified, saline aquifers such as Slepiner or depleted hydrocarbon reservoirs (oil and gas fields). The storage process require a monitoring strategy to ensure that any storage site is effectively monitored to ensure no leakage, or if there is leakage, to detect and monitor the effect of that leakage on the marine environment. The Sleipner site in the Norwegian sector of the North Sea is one of the longest operated CCS sites in Europe. It uses CO2 that has been separated from the natural gas from the Sleipner West Field and injects it into a saline aquifer in a permeable sand body called the Utsira sand. The aquifer is capped by a seal of shale and is thought to be impermeable. The depth of the aquifer is 900 m below the seafloor with 80m of water. This storage site has been in operation since 1996 and contains more than 14 million m3 of CO2 with more being continually added. The site has been monitored mainly though the use of seismic on regular intervals to produce “4D” maps of the distribution of the CO2 though the reservoir. These models show a migration of the plume of CO2 to the north west. JC077 takes a multidisciplinary approach to assess the Sleipner area for signs of leakage from the existing CCS reservoir. We will use a combination of AUV technology with a suite of sensors to determine if leakage is already occurring from the Sleipner field and if so to examine the effects of such leakage. The use of the AUV Autosub allows us to survey areas of the seabed at a resolution that is simply not possible by other means over a comparable time frame. The newly developed pH, pCO2 and Eh sensors attached to Autosub allow us to detect sites of leakage if it is occurring. Chirp and sidescan sonar mounted on Autosub would also allow the identification of sub-seabed and seabed features of interest. In conjunction with this we will use ship based multibeam and EK60 to look for leakage sites, and use water and sediment sampling systems to examine the state of the environment at present, and examine any areas of leakage detected.

This newsletter is part of the OCEAN:ICE Dissemination activities, OCEAN:ICE News. Newsletters are released every month on the OCEAN:ICE LinkedIn page and uploaded to the project's website and Zenodo.