ALBERT

Description: A realistic representation of the North Atlantic tropical cyclone tracks is crucial as it allows, for example, explaining potential changes in U.S. landfalling systems. Here, the authors present a tentative study that examines the ability of recent climate models to represent North Atlantic tropical cyclone tracks. Tracks from two types of climate models are evaluated: explicit tracks are obtained from tropical cyclones simulated in regional or global climate models with moderate to high horizontal resolution (1°–0.25°), and downscaled tracks are obtained using a downscaling technique with large-scale environmental fields from a subset of these models. For both configurations, tracks are objectively separated into four groups using a cluster technique, leading to a zonal and a meridional separation of the tracks. The meridional separation largely captures the separation between deep tropical and subtropical, hybrid or baroclinic cyclones, while the zonal separation segregates Gulf of Mexico and Cape Verde storms. The properties of the tracks’ seasonality, intensity, and power dissipation index in each cluster are documented for both configurations. The authors’ results show that, except for the seasonality, the downscaled tracks better capture the observed characteristics of the clusters. The authors also use three different idealized scenarios to examine the possible future changes of tropical cyclone tracks under 1) warming sea surface temperature, 2) increasing carbon dioxide, and 3) a combination of the two. The response to each scenario is highly variable depending on the simulation considered. Finally, the authors examine the role of each cluster in these future changes and find no preponderant contribution of any single cluster over the others.

Description: Published

Description: 1333–1361

Description: 4A. Clima e Oceani

Description: JCR Journal

Description: restricted

Description: This work explores the impact of orbital parameters and greenhouse gas concentrations on the climate of marine isotope stage (MIS) 7 glacial inception and compares it to that of MIS 5. The authors use a coupled atmosphere-ocean general circulation model to simulate the mean climate state of six time slices at 115, 122, 125, 229, 236, and 239 kyr, representative of a climate evolution from interglacial to glacial inception conditions. The simulations are designed to separate the effects of orbital parameters from those of greenhouse gas (GHG). Their results show that, in all the time slices considered, MIS 7 boreal lands mean annual climate is colder than the MIS 5 one. This difference is explained at 70% by the impact of the MIS 7 GHG. While the impact of GHG over Northern Hemisphere is homogeneous, the difference in temperature between MIS 7 and MIS 5 due to orbital parameters differs regionally and is linked with the Arctic Oscillation. The perennial snow cover is larger in all the MIS 7 experiments compared to MIS 5, as a result of MIS 7 orbital parameters, strengthened by GHG. At regional scale, Eurasia exhibits the strongest response to MIS 7 cold climate with a perennial snow area 3 times larger than in MIS 5 experiments. This suggests that MIS 7 glacial inception is more favorable over this area than over North America. Furthermore, at 239 kyr, the perennial snow covers an area equivalent to that of MIS 5 glacial inception (115 kyr). The authors suggest that MIS 7 glacial inception is more extensive than MIS 5 glacial inception over the high latitudes.

Description: Italian Ministry of Education, University and Research Ministry for Environment, Land and Sea through the project GEMINA

Description: Published

Description: 8918-8933

Description: 4A. Clima e Oceani

Description: JCR Journal

Description: open

Description: We present early Cretaceous to present paleobathymetric reconstructions and quantitative uncertainty estimates for the South Atlantic, offering a strong basis for studies of paleocirculation, paleoclimate and paleobiogeography. Circulation in an initially salty and anoxic ocean, restricted by the topography of the Falkland Plateau, Rio Grande Ridge and Walvis Rise, favoured deposition of thick evaporites in shallow water of the Brazilian-Angolan margins. This ceased as sea oor spreading propagated northwards, opening an equatorial gateway to shallow and intermediate circulation. This gateway, together with subsiding volcano-tectonic barriers would have played a key role in Late Cretaceous climate changes. Later deepening and widening of the South Atlantic, together with gateway opening at Drake Passage would lead, by mid-Miocene (∼15 Ma) to the establishment of modern-style thermohaline circulation.

Description: Currently there is a scarcity of paleo-records related to the North Atlantic Oscillation (NAO), particularly in East-Central Europe (ECE). Here we report δ15N analysis of guano from a cave in NW Romania with the intent of reconstructing past variation in ECE hydroclimate and examine NAO impacts on winter precipitation. We argue that the δ15N values of guano indicate that the nitrogen cycle is hydrologically controlled and the δ15N values likely reflect winter precipitation related to nitrogen mineralization prior to the growing season. Drier conditions indicated by δ15N values at AD 1848–1852 and AD 1880–1930 correspond to the positive phase of the NAO. The increased frequency of negative phases of the NAO between AD 1940–1975 is contemporaneous with higher δ15N values (wetter conditions). A 4‰ decrease in δ15N values at the end of the 1970’s corresponds to a strong reduction in precipitation associated with a shift from negative to positive phase of the NAO. Using the relationship between NAO index and δ15N values in guano for the instrumental period, we reconstructed NAO-like phases back to AD 1650. Our results advocate that δ15N values of guano offer a proxy of the NAO conditions in the more distant past, helping assess its predictability.

Description: The Antarctic silverfish (Pleuragramma antarctica) is a critically important forage species with a circumpolar distribution and is unique among other notothenioid species for its wholly pelagic life cycle. Previous studies have provided mixed evidence of population structure over regional and circumpolar scales. The aim of the present study was to test the recent population hypothesis for Antarctic silverfish, which emphasizes the interplay between life history and hydrography in shaping connectivity. A total of 1067 individuals were collected over 25 years from different locations on a circumpolar scale. Samples were genotyped at fifteen microsatellites to assess population differentiation and genetic structuring using clustering methods, F-statistics, and hierarchical analysis of variance. A lack of differentiation was found between locations connected by the Antarctic Slope Front Current (ASF), indicative of high levels of gene flow. However, gene flow was significantly reduced at the South Orkney Islands and the western Antarctic Peninsula where the ASF is absent. This pattern of gene flow emphasized the relevance of large-scale circulation as a mechanism for circumpolar connectivity. Chaotic genetic patchiness characterized population structure over time, with varying patterns of differentiation observed between years, accompanied by heterogeneous standard length distributions. The present study supports a more nuanced version of the genetic panmixia hypothesis that reflects physical-biological interactions over the life history.

Description: Whilst the AtlantOS project is directed towards bringing together the existing, but currently disparate observing programmes in the Atlantic Ocean, there are still some gaps in terms of requirements for addressing the collection and curation of data around the Essential Ocean Variables. This deliverable will identify gaps and emerging observing networks. Here we use the term emerging network to classify science areas that are starting to gain importance with respect to EOV’s and their measurement and curation, or are existing small scale programmes or communities that might become more important in the future if we can find means of enhancing the collaboration among investigators/groups, increasing resources to the area or using new technological developments. In the AtlantOS project we have identified a number of areas in which there are gaps in our knowledge and where opportunities exist to enhance current small-scale networks. The scope of this document is to assess these networks, based on where we are now and where the networks could be in three and ten years’ time, respectively. An assessment of the state of the existing networks is useful to identify the level of international organisation and potential for further development in the future. We identify opportunities where synergies are possible with more established global projects, and where small levels of investment in resource and time for governance and coordination can productively and realistically develop the networks. We also identify if there are ways to develop coordinated approaches to metrology technology development. For this analysis, the networks have been allocated to one of the three groups outlined below.

Description: The need to cover established and emerging Essential Ocean Variables (EOVs) as defined by the Global Ocean Observing System (GOOS) calls for the development and refinement of the available sensors and samplers, specifically for biogeochemical and biology/ecosystem observations. For several of these EOVs as well as for microplastics as a relatively novel variable of particular societal concern, technological progress has been made as part of AtlantOS. This involves the samplers and sensors and the platforms to use them from as such as well as the required methodologies for obtaining relevant and well-validated results and disseminate data according to the FAIR principles. For biological observations, a main focus was on automated sampling of particles and water samples. While active, pump-based samplers for particles in the water column have been available for many years, it turned out that they were not yet fully mature for operational sampling of zooplankton, microorganisms (e.g., bacteria, archaea, phytoplankton and other eukaryotic unicellular organisms), and microplastics. AtlantOS partners joined forces with manufacturers to overcome limitations with respect to quantitative filtering without leakage, avoidance of plastic contamination and the option for preservation with appropriate agents. Technical solutions were identified and partly tested but could not in all cases be fully implemented in the time frame of the project. Technologies for automated water sampling proved to be more mature and samplers could already be successfully included in observation programs. For both water and particle samples only very few manufacturers offer off-the-shelf solutions which slows down innovation and adaption to user’s needs and may impede successful implementation of appropriate instruments on a larger scale. Particle traps are well-established and operational passive samplers of sinking particles that are widely used for phytoplankton and particulate matter observations based on microscopic sorting and chemical analyses. Using legacy samples collected in the Arctic it could be demonstrated that the same samples can also be used for omics-based observations allowing to address the emerging EOV ‘Microbe biomass and diversity’ and also contributing to the ‘Phytoplankton biomass and diversity’ EOV. Applied to legacy samples also from other sites, this holds the potential to assess past microbial communities of the Atlantic that could serve as a baseline for comparisons to recent communities that are subject to global change. Significant progress was achieved in building capacities for the implementation of omics-based observations of marine organisms into recent and future observation programs. The feasibility of samplers and different preservation agents was tested and a comparison of different methods for omics-based investigations of microbial communities was conducted. The Global Omics Observatory Network (GLOMICON) was established to better connect the institutes and initiatives that are active in the field. As part of GLOMICON, solutions were implemented that allow for a registration of omics observatories and for the sharing of protocols and bioinformatics code. Irrespective of these achievements, major steps still need to be taken to consolidate and standardize approaches in this rapidly evolving field and to establish operational and well-integrated omics-observations as part of an Atlantic Ocean Observation System. For biogeochemical observations, the focus was placed on sensors for oxygen and marine CO2 system parameters (pCO2, total alkalinity) and their readiness for integration into classical as well as emerging biogeochemical observation platforms. For oxygen, the situation is very favourable as the oxygen optode technology and the best practices routines developed around it can be considered fully operational. There are no obstacles for the D3.17 „OceanSITES Innovation Report“ 5 integration of oxygen optodes into the full range of autonomous ocean observation platforms (mooring, drifter, glider, wave gliders, floats, voluntary observing ship etc.). For marine CO2 system parameters, work carried out in AtlantOS focussed the CO2 partial pressure (pCO2) and total alkalinity (TA). With respect to pCO2 it can be stated, that the membraneequilibration sensors with NDIR detection have clearly matured to a level that they can be used routinely on a range of platforms (mooring, wave glider, voluntary observing ship) with an accuracy of ~1% under well-constrained operation conditions and with rigorous data processing routines. Major limitations still exist, however, for this sensor technology on moving platforms (long sensor response time) and platforms with stringent payload and energy limitations (float, glider etc.). In contrast, the pCO2 (as well as pH) optode technology, in which significant hopes lie, has not been forthcoming and existing products still do not meet the quality requirements for open ocean applications. For TA, our intensive testing both in the laboratory and in the field has led to significant improvement of the commercially available system, which now can be considered operational. It allows high-quality autonomous bench-top measurements (e.g., on voluntary observing ships). Ideas for a submersible version of the system are in early stages and would need significant design and testing efforts. With respect to the possibilities of oxygen and carbon measurements from novel autonomous observation platforms, our work in AltantOS has shown very promising applications on profiling Argo floats, submersible winch systems with upper ocean profilers as well as wave gliders. On all these platforms, we were able to successfully implement oxygen and carbon measurements for high-quality observations.

Description: During the course of AtlantOS, our ability to provide biogeochemical (BGC) time series and Eulerian data which is of sufficient quality and quantity to approach basin-scale capacity has improved in a major way in some areas but has declined or not progressed in others. Indeed, the increased coordination achieved through AtlantOS has both increased our capacity to collectively further a basin-scale operation, and revealed new challenges in implementation. These outcomes are synthesised in this report to improve future planning for Eulerian capacities in BGC observation. Areas of significant progress 1. Development of capacity for emerging BGC variables 2. Establishment of a system for developing “Best practice” recording. 3. Transatlantic MOU with Canada 4. Data management and dissemination The ways to address the areas in which progress has not been made are conceptually simple but practically demanding. In all cases this needs to be carried out at the global scale and therefore under the auspices of OceanSITES. A coherent system which can provide data of sufficient quality and quantity to address societal needs cannot be achieved in isolation by any one Nation state or by Europe and must not be restricted by discipline. It will become self-evident that such an integrated approach will lead to a system which performs at a much higher level than the sum of its component parts. With continuous pressure from the European Commission, further and additional support from member states, continuing political and scientific dialogue with South Atlantic countries and strong management encouragement at all levels, the establishment of an effective eulerian observatory network is anticipated within the coming decade.

Description: Slope failure like in the Hinlopen/Yermak Megaslide is one of the major geohazards in a changing Arctic environment. We analysed hydroacoustic and 2D high-resolution seismic data from the apparently intact continental slope immediately north of the Hinlopen/Yermak Megaslide for signs of past and future instabilities. Our new bathymetry and seismic data show clear evidence for incipient slope instability. Minor slide deposits and an internally-deformed sedimentary layer near the base of the gas hydrate stability zone imply an incomplete failure event, most probably about 30000 years ago, contemporaneous to or shortly after the Hinlopen/Yermak Megaslide. An active gas reservoir at the base of the gas hydrate stability zone demonstrate that over-pressured fluids might have played a key role in the initiation of slope failure at the studied slope, but more importantly also for the giant HYM slope failure. To date, it is not clear, if the studied slope is fully preconditioned to fail completely in future or if it might be slowly deforming and creeping at present. We detected widespread methane seepage on the adjacent shallow shelf areas not sealed by gas hydrates.

Description: Little is known about the production of fluorescent dissolved organic matter (FDOM) in the anoxic oceanic sediments. In this study, sediment pore waters were sampled from four different sites in the Chukchi-East Siberian Seas area to examine the bulk dissolved organic carbon (DOC) and their optical properties. The production of FDOM, coupled with the increase of nutrients, was observed above the sulfate-methane-transition-zone (SMTZ). The presence of FDOM was concurrent with sulfate reduction and increased alkalinity (R2 〉 0.96, p 〈 0.0001), suggesting a link to organic matter degradation. This inference was supported by the positive correlation (R2 〉 0.95, p 〈 0.0001) between the net production of FDOM and the modeled degradation rates of particulate organic carbon sulfate reduction. The production of FDOM was more pronounced in a shallow shelf site S1 with a total net production ranging from 17.9 to 62.3 RU for different FDOM components above the SMTZ depth of ca. 4.1 mbsf, which presumably underwent more accumulation of particulate organic matter than the other three deeper sites. The sediments were generally found to be the sources of CDOM and FDOM to the overlying water column, unearthing a channel of generally bio-refractory and pre-aged DOM to the oceans.