ALBERT

Beschreibung: The Central and South Atlantic represents a vast ocean area and is home to a diverse range of ecosystems and species. Nevertheless, and similar to the rest of the global south, the area is comparatively understudied yet exposed to increasing levels of multisectoral pressures. To counteract this, the level of scientific exploration in the Central and South Atlantic has increased in recent years and will likely continue to do so within the context of the United Nations (UN) Decade of Ocean Science for Sustainable Development. Here, we compile the literature to investigate the distribution of previous scientific exploration of offshore (30 m+) ecosystems in the Central and South Atlantic, both within and beyond national jurisdiction, allowing us to synthesise overall patterns of biodiversity. Furthermore, through the lens of sustainable management, we have reviewed the existing anthropogenic activities and associated management measures relevant to the region. Through this exercise, we have identified key knowledge gaps and undersampled regions that represent priority areas for future research and commented on how these may be best incorporated into, or enhanced through, future management measures such as those in discussion at the UN Biodiversity Beyond National Jurisdiction negotiations. This review represents a comprehensive summary for scientists and managers alike looking to understand the key topographical, biological, and legislative features of the Central and South Atlantic.

Beschreibung: Changes in the background climate are known to affect El Niño–Southern Oscillation (ENSO) by altering feedbacks that control ENSO’s characteristics. Here, the sensitivity of ENSO variability to the background climate is investigated by utilizing two Community Earth System Model, version 1 (CESM1), simulations in which the solar constant is altered by ±25 W m−2. The resulting stable warm and cold climate mean state simulations differ in terms of ENSO amplitude, frequency, diversity, asymmetry, and seasonality. In the warm run, ENSO reveals a larger amplitude and occurs at higher frequencies relative to the cold and control runs as well as observations. The warm run also features more eastern Pacific El Niños, an increased asymmetry, and a stronger seasonal phase locking. These changes are linked to changes in the mean state via the amplifying and damping feedbacks. In the warm run, a shallower mean thermocline results in a stronger subsurface–surface coupling, whereas the cold run reveals reduced ENSO variability due to a reduced Bjerknes feedback in accordance with a deeper mean thermocline and enhanced surface wind stress. A strong zonal advective and upwelling feedback further contribute to the large ENSO amplitude in the run with a warmer mean state. In the cold run, ENSO events are partly forced by anomalous shortwave radiation. However, in light of the large temperature contrast between the simulations of up to 6 K in the tropical Pacific, the relatively small changes in ENSO variability highlight the robustness of ENSO dynamics under vastly different climate mean states.

Beschreibung: Long-term changes in the life history and behaviour of seabirds during the non-breeding season can reflect shifts in environmental conditions. However, long-term marine studies are scarce, particularly on southern hemisphere seabirds. Here, we used moult scores from 86 Brown Skuas (Stercorarius antarcticus lonnbergi), a large predatory seabird breeding on the Chatham Islands, Aotearoa/New Zealand to model both the timing and duration of primary feather moult. In addition, we analysed stable isotope values (δ13C and δ15N) from 62 modern (2014–16) and ten museum tail feathers. These data provide insights into the non-breeding behaviour of Brown Skua. Interestingly, our results show that the primary feather moult occurred prior to birds departing the colony, starting on average on 2 January ± 5 days (SE). The average start of primary feather moult occurred five days prior to the end of breeding (7 January ± 10 days (SD)) and 42 days before the birds departed the colony (13 February ± 11 days (SD)). The average duration of primary feather moult was 189 ± 14 days (SE). Importantly, low δ13C values in four females suggested that tail feather moult might also occur while skuas are at the colony. There was no difference in tail feather δ13C and δ15N values between any pairwise comparison of modern and museum years. However, values of δ15N from tail feathers sampled in 2014 were different from those sampled in 2015 and 2016. This large annual variation in δ15N values from tail feathers over such a short period makes long-term comparisons difficult to interpret, particularly between years with low sample sizes. While the stable isotope analyses of tail feathers are informative, we recommend future studies of skuas sample the primary coverts rather than tail feathers.

Beschreibung: Coarse woody habitat (CWH) is an important structural habitat in freshwater ecosystems. In natural lakes, CWH accumulates over centuries alongside the succession of littoral tree communities. Newly created gravel pit lakes have difficulties in accumulating CWH due to their young age. Additionally, CWH presence might be negatively affected by shoreline development, where wood is removed to facilitate recreational activities such as angling. We studied 26 gravel pit lakes with an age ≤ 55 yrs in Lower Saxony, Germany, to quantify CWH density and to understand the impact of environmental factors, including lake morphology, lake age, wind direction, abundance of riparian trees, and the presence or absence of fisheries management, on CWH density. We sampled small and large CWH in the littoral zone of the study lakes using a transect-based approach. Density of CWH was lower in German gravel pit lakes than in North American natural lakes. In gravel pit lakes, we detected increasing densities of small CWH with increasing numbers of large trees on the shore and with increasing littoral slopes in lakes managed for recreational fisheries. Large CWH density was positively affected by lake age, by the density of large trees on the shore and with wind from land, and again by steep littoral slopes in lakes managed for recreational fisheries. We recommend that recreational fisheries managers and individual anglers maintain CWH in shallow littoral zones to promote fish habitats in generally low-structured gravel pit lakes.

Beschreibung: Two decades of high-resolution satellite observations and climate modeling studies have indicated strong ocean–atmosphere coupled feedback mediated by ocean mesoscale processes, including semipermanent and meandrous SST fronts, mesoscale eddies, and filaments. The air–sea exchanges in latent heat, sensible heat, momentum, and carbon dioxide associated with this so-called mesoscale air–sea interaction are robust near the major western boundary currents, Southern Ocean fronts, and equatorial and coastal upwelling zones, but they are also ubiquitous over the global oceans wherever ocean mesoscale processes are active. Current theories, informed by rapidly advancing observational and modeling capabilities, have established the importance of mesoscale and frontal-scale air–sea interaction processes for understanding large-scale ocean circulation, biogeochemistry, and weather and climate variability. However, numerous challenges remain to accurately diagnose, observe, and simulate mesoscale air–sea interaction to quantify its impacts on large-scale processes. This article provides a comprehensive review of key aspects pertinent to mesoscale air–sea interaction, synthesizes current understanding with remaining gaps and uncertainties, and provides recommendations on theoretical, observational, and modeling strategies for future air–sea interaction research.

Beschreibung: Cambrian igneous rocks in the Takaka Terrane of New Zealand provide important constraints for geodynamic reconstructions of the Cambrian SE Gondwana margin. We provide field data and a comprehensive trace element and isotope dataset for such rocks from the upper Baton River area in northwest Nelson, New Zealand, including the first combined Hf-Nd isotope data for Takaka Terrane rocks. These submarine volcanic rocks, known as Mataki and Benson volcanics of the Devil River Volcanics Group, are both interbedded with Haupiri Group sediments, providing a previously not observed direct stratigraphic link between the two volcanic units. Incompatible element abundances of Mataki Volcanics display a full spectrum from subduction-modified back-arc-tholeiites to E-MORB type tholeiites. Initial Hf-Nd isotope compositions are coupled, spanning a range from MORB-like to OIB-like compositions. The MORB-like endmember (initial ϵNd +7 and ϵHf +13), taps moderately depleted asthenospheric mantle. If extrapolated to present-day composition, this depleted mantle endmember does not resemble modern Pacific-type mantle, suggesting formation in a back-arc basin separated from Pacific mantle by a continent-ward, intra-oceanic subduction zone. The enriched asthenospheric mantle endmember in the Mataki Volcanics may be an equivalent to the sources of Neoproterozic or middle Cambrian intra-continental flood basalts in central and SE-Australia.

Beschreibung: Several years of moored turbulence measurements from xpods at three sites in the equatorial cold tongues of Atlantic and Pacific Oceans yield new insights into proxy estimates of turbulence that specifically target the cold tongues. They also reveal previously unknown wind dependencies of diurnally varying turbulence in the near-critical stratified shear layers beneath the mixed layer and above the core of the Equatorial Undercurrent that we have come to understand as deep cycle (DC) turbulence. Isolated by the mixed layer above, the DC layer is only indirectly linked to surface forcing. Yet, it varies diurnally in concert with daily changes in heating/cooling. Diurnal composites computed from 10-min averaged data at fixed xpod depths show that transitions from daytime to nighttime mixing regimes are increasingly delayed with weakening wind stress t. These transitions are also delayed with respect to depth such that they follow a descent rate of roughly 6 m h-1, independent of t. We hypothesize that this wind-dependent delay is a direct result of wind-dependent diurnal warm layer deepening, which acts as the trigger to DC layer instability by bringing shear from the surface down-ward but at rates much slower than 6 m h-1. This delay in initiation of DC layer instability contributes to a reduction in daily averaged values of turbulence dissipation. Both the absence of descending turbulence in the sheared DC layer prior to arrival of the diurnal warm layer shear and the magnitude of the subsequent descent rate after arrival are roughly predicted by laboratory experiments on entrainment in stratified shear flows.

Beschreibung: Numerical weather prediction models operate on grid spacings of a few kilometers, where deep convection begins to become resolvable. Around this scale, the emergence of coherent structures in the planetary boundary layer, often hypothesized to be caused by cold pools, forces the transition from shallow to deep convection. Yet, the kilometer-scale range is typically not resolved by standard surface operational measurement networks. The measurement campaign FESSTVaL aimed at addressing this gap by observing atmospheric variability at the hectometer to kilometer scale, with a particular emphasis on cold pools, wind gusts and coherent patterns in the planetary boundary layer during summer. A unique feature was the distribution of 150 self-developed and low-cost instruments. More specifically, FESSTVaL included dense networks of 80 autonomous cold pool loggers, 19 weather stations and 83 soil sensor systems, all installed in a rural region of 15-km radius in eastern Germany, as well as self-developed weather stations handed out to citizens. Boundary layer and upper air observations were provided by 8 Doppler lidars and 4 microwave radiometers distributed at 3 supersites; water vapor and temperature were also measured by advanced lidar systems and an infrared spectrometer; and rain was observed by a X-band radar. An uncrewed aircraft, multicopters and a small radiometer network carried out additional measurements during a four-week period. In this paper, we present FESSTVaL’s measurement strategy and show first observational results including unprecedented highly-resolved spatio-temporal cold-pool structures, both in the horizontal as well as in the vertical dimension, associated with overpassing convective systems.

Beschreibung: We investigate the origin of the equatorial Pacific cold sea surface temperature (SST) bias and its link to wind biases, local and remote, in the Kiel Climate Model (KCM). The cold bias is common in climate models participating in the 5 th and 6 th phases of the Coupled Model Intercomparison Project. In the coupled experiments with the KCM, the interannually varying NCEP/CFSR wind stress is prescribed over four spatial domains: globally, over the equatorial Pacific (EP), the northern Pacific (NP) and southern Pacific (SP). The corresponding EP SST bias is reduced by 100%, 52%, 12% and 23%, respectively. Thus, the EP SST bias is mainly attributed to the local wind bias, with small but not negligible contributions from the extratropical regions. Erroneous ocean circulation driven by overly strong winds cause the cold SST bias, while the surface-heat flux counteracts it. Extratropical Pacific SST biases contribute to the EP cold bias via the oceanic subtropical gyres, which is further enhanced by dynamical coupling in the equatorial region. The origin of the wind biases is examined by forcing the atmospheric component of the KCM in a stand-alone mode with observed SSTs and simulated SSTs from the coupled experiments. Wind biases over the EP, NP and SP regions originate in the atmosphere model. The cold EP SST bias substantially enhances the wind biases over all three regions, while the NP and SP SST biases support local amplification of the wind bias. This study suggests that improving surface-wind stress, at and off the equator, is a key to improve mean-state equatorial Pacific SST in climate models.

Beschreibung: As an important external forcing, the effect of the 11-yr solar cycle on the tropical Pacific decadal variability is an interesting question. Here, we systematically investigate the phase-locking of the atmosphere and ocean covariations to the solar cycle in the tropical Pacific and propose a new mechanism to explain these decadal covariations. In both observation/reanalysis datasets and a solar cycle forced sensitivity experiment (named the SOL experiment), the ocean heat content anomalies (OHCa; 300 m) resemble a La Niña–like pattern in the solar cycle ascending phase, and the Walker circulation shifts westward. In the declining phase, the opposite is true. The accumulative solar irradiation directly contributes to this coherent decadal variability via changing the warm water volume and the solar-related heat is redistributed by the ocean dynamic processes. During the 11-yr solar cycle, the Pacific Walker circulation anomalies maintain the OHCa in the western equatorial Pacific and work as negative feedback for the eastern Pacific to help the OHCa phase transition. In addition, oceanic meridional heat transport via the subtropical cells and the propagation of off-equatorial Rossby waves also provide a lagged negative feedback to the OHCa phase transition according to the 11-yr solar cycle. The decadal coupled responses of the tropical Pacific climate system are 2 years more lag in the SOL experiment than in the observation/reanalysis. Significance Statement Here, we propose a new mechanism that the heating effect of the accumulative solar irradiation during the 11-yr solar cycle can be “integrated” into the tropical Pacific OHC and then provide a bottom-up effect on the atmosphere at decadal time scales. The strongly coupled processes in this region amplify the decadal phase-locking of the covariations to the 11-yr solar cycle. Our study demonstrates the role of the 11-yr solar cycle in the tropical Pacific decadal variability and provides a new explanation for the “bottom-up” mechanism of the solar cycle forcing. Our results update the understanding of the tropical Pacific decadal variability and may help to improve climate predictions at decadal time scales.

Beschreibung: Carbon Dioxide Removal (CDR) will be necessary to fulfil the hundreds of pledges to reach net-zero by 2050. As with any industry, standard methodologies and certification are crucial to guarantee successful and reliable activities. However, buyers and policymakers currently face challenges in evaluating the ecosystem of CDR certification. The issue is not with CDR, nor with individual certifications – some of which may be very robust – but with the lack of transparency in the overall ecosystem. To bring some clarity, we present a snapshot of the CDR certification and standards ecosystem for the year 2021–2022. We find a complex ecosystem with at least 30 standard developing organizations proposing at least 125 standard methodologies for carbon removal from 23 different CDR activities and selling 27 different versions of certification instruments in voluntary and compliance markets. This exercise reveals many more existing standards for nature-based than for engineering-based activities and more diversity from standards serving the voluntary rather than the compliance market. It also highlights a proliferation of standards for the same activity, and a plethora of activities without standards. The process revealed ambiguity on what constitutes carbon removal, with many standards certifying activities that remove CO2 already in the environment as well as activities that avoid or reduce new emissions by sequestering the carbon into reservoirs. This mapping highlights key gaps and potential starting points for reforms to strengthen the CDR certification industry; it also underscores the need for independent oversight.

Beschreibung: Numerical simulations allow us to gain a comprehensive understanding of the underlying mechanisms of past, present and future climate changes. The mid-Holocene and the last interglacial were the two most recent warm episodes of Earth’s climate history and are the focus of paleoclimate research. Here, we present results of MH and LIG simulations with two versions of the state-of-the-art earth system model AWI-ESM. Most of the climate changes in MH and LIG compared to the pre-industrial era are agreed upon by the two model versions, including: (1) enhanced seasonality in surface temperature which is driven by the redistribution of seasonal insolation; (2) northward shift of the Intertropical Convergence Zone (ITCZ) and tropical rain belt; (3) a reduction in annual mean Arctic sea ice concentration; (4) weakening and northward displacement of the Northern Hemisphere Hadley Circulation, which is related to the decrease and poleward shift of the temperature gradient from the subtropical to the equator in the Northern Hemisphere; (5) westward shift of the Indo-PacificWalker Circulation due to anomalous warming over the Eurasia and North Africa during boreal summer; and (6) expansion and intensification of Northern Hemisphere summer monsoon rainfall, with the latter being dominated by the dynamic component of moisture budget, i.e., the strengthening of wind circulation. However, the simulated responses of the Atlantic Meridional Overturning Circulation (AMOC) in the two models yield different results for both the LIG and the MH. AMOC anomalies between the warm interglacial and pre-industrial periods are associated with changes in North Atlantic westerly winds and stratification of the water column at the North Atlantic due to changes in ocean temperature, salinity and density.

Beschreibung: The prediction of a spatial variable is of particular importance when analyzing spatial data. The main objective of this study is to evaluate and compare the performance of several prediction-based methods in spatial prediction through a simulation study. The studied methods include ordinary Kriging (OK), along with several neural network methods including Multi-Layer Perceptron network (MLP), Ensemble Neural Networks (ENN), and Radial Basis Function (RBF) network. We simulated several spatial datasets with three different scenarios due to changes in data stationarity and isotropy. The performance of methods was evaluated using the Root Mean Square Error (RMSE), Mean Absolute Error (MAE) and Concordance Correlation Coefficient (CCC) indexes. Although the results of the simulation study revealed that the performance of the neural network in spatial prediction is weaker than the Kriging method, but it can still be a good competitor for Kriging.

Beschreibung: Algae are the oldest representatives of the plant world with reserves exceeding hundreds of millions of tons in the world's oceans. Currently, a growing interest is placed toward the use of algae as feedstocks for obtaining numerous natural products. Algae are a rich source of polyphenols that possess intriguing structural diversity. Among the algal polyphenols, phlorotannins, which are unique to brown seaweeds, and have immense value as potent modulators of biochemical processes linked to chronic diseases. In algae, flavonoids remain under-explored compared to other categories of polyphenols. Both phlorotannins and flavonoids are inclusive of compounds indicating a wide structural diversity. The present paper reviews the literature on the ecological significance, biosynthesis, structural diversity, and bioactivity of seaweed phlorotannins and flavonoids. The potential implementation of these chemical entities in functional foods, cosmeceuticals, medicaments, and as templates in drug design are described in detail, and perspectives are provided to tackle what are perceived to be the most momentous challenges related to the utilization of phlorotannins and flavonoids. Moving beyond: industrial biotechnology applications, metabolic engineering, total synthesis, biomimetic synthesis, and chemical derivatization of phlorotannins and flavonoids could broaden the research perspectives contributing to the health and economic up-gradation.

Beschreibung: This study utilizes observations and a series of idealized experiments to explore whether eastern Pacific (EP)- and central Pacific (CP)-type El Niño–Southern Oscillation (ENSO) events produce surface wind stress responses with distinct spatial structures. We find that the meridionally broader sea surface temperatures (SSTs) during CP events lead to zonal wind stresses that are also meridionally broader than those found during EP-type events, leading to differences in the near-equatorial wind stress curl. These wind spatial structure differences create differences in the associated pre- and post-ENSO event WWV response. For instance, the meridionally narrow winds found during EP events have (i) weaker wind stresses along 58N and 58S, leading to weaker Ekman-induced pre-event WWV changes; and (ii) stronger near-equatorial wind stress curls that lead to a much larger post-ENSO event WWV changes than during CP events. The latter suggests that, in the framework of the recharge oscillator model, the EP events have stronger coupling between sea surface temperatures (SST) and thermocline (WWV), supporting more clearly the phase transition of ENSO events, and therefore, the oscillating nature of ENSO than CP events. The results suggest that the spatial structure of the SST pattern and the related differences in the wind stress curl, are required along with equatorial wind stress to accurately model the WWV changes during EP- and CP-type ENSO events.

Beschreibung: Equatorial deep jets (EDJ) are zonal currents along the equator in all three ocean basins that alternate in direction with depth and time. In the Atlantic below the thermocline, they are the dominant variability on interannual timescales. Observations of equatorial deep jets are available but scarce, given the EDJs’ location at depth, their small vertical scale and their long periodicity of several years. In the last few years, Argo floats have added a significant amount of measurements at intermediate depth. In this study we therefore revise estimates of the EDJ scales based on Argo float data. Mostly, we use velocity data at 1000 m depth calculated from float displacement, which yield robust estimates of the Atlantic EDJ period (4.6 years), amplitude distribution, phase distribution, zonal wavelength (146.7°), and meridional structure. We also show that the equatorial amplitude of the EDJs’ first meridional mode Rossby wave component (9.8 cm s −1 ) is larger than that of their Kelvin wave component (2.8 cm s −1 ). Additionally, we present a new estimation of the EDJs’ vertical structure throughout the Atlantic basin, based on an equatorial geostrophic velocity reconstruction from hydrographic Argo float measurements from depths between 400 and 2000 m. Our new estimates from Argo float data provide the first basin-wide assessment of the Atlantic EDJ scales, as well as having smaller uncertainties than estimates from earlier studies.

Beschreibung: The physical processes driving the genesis of surface- and subsurface-intensified cyclonic and anticyclonic eddies originating from the coastal current system of the Mauritanian Upwelling Region are investigated using a high-resolution (~1.5 km) configuration of GFDL’s Modular Ocean Model. Estimating an energy budget for the boundary current reveals a baroclinically unstable state during its intensification phase in boreal summer and which is driving eddy generation within the near-coastal region. The mean poleward coastal flow’s interaction with the sloping topography induces enhanced anticyclonic vorticity, with potential vorticity close to zero generated in the bottom boundary layer. Flow separation at sharp topographic bends intensifies the anticyclonic vorticity, and submesoscale structures of low PV coalesce to form anticyclonic vortices. A combination of offshore Ekman transport and horizontal advection determined the amount of SACW in an anticyclonic eddy. A vortex with a relatively dense and low PV core will form an anticyclonic mode-water eddy, which will subduct along isopycnals while propagating offshore and hence be shielded from surface buoyancy forcing. Less contribution of dense SACW promotes the generation of surface anticyclonic eddies as the core is composed of a lighter water mass, which causes the eddy to stay closer to the surface and hence be exposed to surface buoyancy forcing. Simulated cyclonic eddies are formed between the rotational flow of an offshore anticyclonic vortex and a poleward flowing boundary current, with eddy potential energy being the dominant source of eddy kinetic energy. All three types of eddies play a key role in the exchange between the Mauritanian Coastal currents system and the adjacent eastern boundary shadow zone region.

Beschreibung: The Earth system is accumulating energy due to human-induced activities. More than 90% of this energy has been stored in the ocean as heat since 1970, with similar to 60% of that in the upper 700 m. Differences in upper-ocean heat content anomaly (OHCA) estimates, however, exist. Here, we use a dataset protocol for 1970-2008-with six instrumental bias adjustments applied to expendable bathythermograph (XBT) data, and mapped by six research groups-to evaluate the spatiotemporal spread in upper OHCA estimates arising from two choices: 1) those arising from instrumental bias adjustments and 2) those arising from mathematical (i.e., mapping) techniques to interpolate and extrapolate data in space and time. We also examined the effect of a common ocean mask, which reveals that exclusion of shallow seas can reduce global OHCA estimates up to 13%. Spread due to mapping method is largest in the Indian Ocean and in the eddy-rich and frontal regions of all basins. Spread due to XBT bias adjustment is largest in the Pacific Ocean within 30 degrees N-30 degrees S. In both mapping and XBT cases, spread is higher for 1990-2004. Statistically different trends among mapping methods are found not only in the poorly observed Southern Ocean but also in the well-observed northwest Atlantic. Our results cannot determine the best mapping or bias adjustment schemes, but they identify where important sensitivities exist, and thus where further understanding will help to refine OHCA estimates. These results highlight the need for further coordinated OHCA studies to evaluate the performance of existing mapping methods along with comprehensive assessment of uncertainty estimates.

Beschreibung: Modular Observation Solutions of Earth Systems (MOSES) is a novel observation system that is specifically designed to unravel the impact of distinct, dynamic events on the long-term development of environmental systems. Hydrometeorological extremes such as the recent European droughts or the floods of 2013 caused severe and lasting environmental damage. Modeling studies suggest that abrupt permafrost thaw events accelerate Arctic greenhouse gas emissions. Short-lived ocean eddies seem to comprise a significant share of the marine carbon uptake or release. Although there is increasing evidence that such dynamic events bear the potential for major environmental impacts, our knowledge on the processes they trigger is still very limited. MOSES aims at capturing such events, from their formation to their end, with high spatial and temporal resolution. As such, the observation system extends and complements existing national and international observation networks, which are mostly designed for long-term monitoring. Several German Helmholtz Association centers have developed this research facility as a mobile and modular “system of systems” to record energy, water, greenhouse gas, and nutrient cycles on the land surface, in coastal regions, in the ocean, in polar regions, and in the atmosphere—but especially the interactions between the Earth compartments. During the implementation period (2017–21), the measuring systems were put into operation and test campaigns were performed to establish event-driven campaign routines. With MOSES’s regular operation starting in 2022, the observation system will then be ready for cross-compartment and cross-discipline research on the environmental impacts of dynamic events.

Beschreibung: Wetlands physical and biological processes are fundamental to the distribution and structuring of organic matter in sediments. This study investigated spatial and temporal changes in organic matter sources in sediments within the Nylsvley Wetland, South Africa across two seasons, five sites and three wetland zones and identified pertinent contributors to sediment organic matter. Results showed distributions were uneven throughout the wetlands, with the seasonal zone having slightly high sediment organic matter in the cool-dry season and the permanent zone had high sediment organic matter in the hot-wet season, whereas the temporary zone had low SOM concentrations. Significant differences in nutrient concentrations were observed across wetland zones and seasons for Phosphorous, Potassium, Calcium and Magnesium, with the seasonal zone tending to be the most nutrient-rich in the cool-dry season, and with permanent zone nutrient levels rising substantially in the hot-wet season. Sediment δ13C differed significantly among wetland zones, whereas δ15N was statistically similar. Autochthonous plants were the main sources of organic matter in sediments overall across sites and zones. This study’s findings help to better understand the distribution of organic matter in wetland ecosystems and the role wetland zones play in the seasonal provisioning of allochthonous inputs.

Beschreibung: Since 1750, land use change and fossil fuel combustion has led to a 46 % increase in the atmospheric carbon dioxide (CO2) concentrations, causing global warming with substantial societal consequences. The Paris Agreement aims to limiting global temperature increases to well below 2°C above pre-industrial levels. Increasing levels of CO2 and other greenhouse gases (GHGs), such as methane (CH4) and nitrous oxide (N2O), in the atmosphere are the primary cause of climate change. Approximately half of the carbon emissions to the atmosphere is sequestered by ocean and land sinks, leading to ocean acidification but also slowing the rate of global warming. However, there are significant uncertainties in the future global warming scenarios due to uncertainties in the size, nature and stability of these sinks. Quantifying and monitoring the size and timing of natural sinks and the impact of climate change on ecosystems are important information to guide policy-makers’ decisions and strategies on reductions in emissions. Continuous, long-term observations are required to quantify GHG emissions, sinks, and their impacts on Earth systems. The Integrated Carbon Observation System (ICOS) was designed as the European in situ observation and information system to support science and society in their efforts to mitigate climate change. It provides standardized and open data currently from over 140 measurement stations across 12 European countries. The stations observe GHG concentrations in the atmosphere and carbon and GHG fluxes between the atmosphere, land surface and the oceans. This article describes how ICOS fulfills its mission to harmonize these observations, ensure the related long-term financial commitments, provide easy access to well-documented and reproducible high-quality data and related protocols and tools for scientific studies, and deliver information and GHG-related products to stakeholders in society and policy.

Beschreibung: Glacio-eustatic cycles lead to changes in sedimentation on all types of continental margins. There is, however, a paucity of sedimentation rate data over eustatic sea-level cycles in active subduction zones. During International Ocean Discovery Program Expedition 375, coring of the upper ∼110 m of the northern Hikurangi Trough Site U1520 recovered a turbidite-dominated succession deposited during the last ∼45 kyrs (Marine Isotope Stages (MIS) 1–3). We present an age model integrating radiocarbon dates, tephrochronology, and δ18O stratigraphy, to evaluate the bed recurrence interval (RI) and sediment accumulation rate (SAR). Our analyses indicate mean bed RI varies from ∼322 yrs in MIS1, ∼49 yrs in MIS2, and ∼231 yrs in MIS3. Large (6-fold) and abrupt variations in SAR are recorded across MIS transitions, with rates of up to ∼10 m/kyr occurring during the Last Glacial Maximum (LGM), and 〈1 m/kyr during MIS1 and 3. The pronounced variability in SAR, with extremely high rates during the LGM, even for a subduction zone, are the result of changes in regional sediment supply associated with climate-driven changes in terrestrial catchment erosion, and critical thresholds of eustatic sea-level change altering the degree of sediment bypassing the continental shelf and slope via submarine canyon systems.

Beschreibung: In the equatorial Atlantic Ocean, meridional velocity variability exhibits a pronounced peak on intraseasonal timescales whereas zonal velocity dominantly varies on seasonal to interannual timescales. We focus on the intraseasonal meridional velocity variability away from the near-surface layer, its source regions and its pathways into the deep ocean. This deep intraseasonal velocity variability plays a key role in equatorial dynamics as it is an important energy source for the deep equatorial circulation. The results are based on the output of a high-resolution ocean model revealing intraseasonal energy levels along the equator at all depths that are in good agreement with shipboard and moored velocity data. Spectral analyses reveal a pronounced signal of intraseasonal Yanai waves with westward phase velocities and zonal wavelengths longer than 450 km. Different sources and characteristics of these Yanai waves are identified: near the surface between 40°W and 10°W low-baroclinic-mode Yanai waves with periods of around 30 days are exited. These waves have a strong seasonal cycle with a maximum in August. High-frequency Yanai waves (10–20-day period) are excited at the surface east of 10°W. In the region between the North Brazil Current and the Equatorial Undercurrent high-baroclinic-mode Yanai waves with periods between 30 and 40 days are generated. Yanai waves with longer periods (40-80 days) are shed from the Deep Western Boundary Current. The Yanai wave energy is carried along beams east- and downward thus explaining differences in strength, structure and periodicity of the meridional intraseasonal variability in the equatorial Atlantic Ocean.

Beschreibung: The extent of our duties to mitigate climate change is commonly conceptualized in terms of temperature goals like the 1.5°C and the 2°C target and corresponding emissions budgets. While I do acknowledge the political advantages of any framework that is relatively easy to understand, I argue that this particular framework does not capture the true extent of our mitigation duties. Instead I argue for a more differentiated approach that is based on the well-known distinction between subsistence and luxury emissions. At the heart of this approach lies the argument that we have no budget of substantial, net-positive luxury emissions left. In a world in which dangerous climate change has begun, we must expect all further substantial, net-positive luxury emissions to cause harm. Since they lack the kind of justification needed for them to be nevertheless permissible, I conclude that we must stop emitting them with immediate effect. I also briefly discuss the difficult case of subsistence emissions and offer some first thoughts on the morality of a third category of emissions, what I call ‘transition emissions’.

Beschreibung: Traceability and reliable results are the two pillars of analytical methods; certified reference materials (CRMs) meet this requirement. ISO 17034:2016 credentials provide brief information on general requirements for the competence of Reference Material Producers (RMPs). The different types of CRMs have been produced in recent years for chemical analysis in food, water, soil, and sediment matrices in recent years. This review provides a detailed overview of the development of CRMs in the field of marine environment, as matrix CRMs play an important role in the field of environmental monitoring. COMAR database, EVISA database: materials, LGC standards, and JRC catalogs are very helpful online resources to find various types of CRMs according to the application requirements. Highlights - The classification of certified reference materials (CRMs) in the field of marine environment is presented; - General information about the production and characteristics of CRMs is discussed; - Examples of use of existing marine CRMs are described in detail; - Importance of CRMs for QA/QC and CRMs development for chemical analysis is presented; - The parameters that characterize the CRMs: representativeness, homogeneity, stability, and certified value are provided.

Beschreibung: Sea ice conditions and navigability along four typical routes of the Northeast Passage (NEP) are analysed using remote-sensing data from 1979 to 2019. The influence of air temperature (Tair) and surface wind on the sea ice concentration (SIC) and the navigability of routes is determined. It is found that the annually averaged SICs of the different routes have decreased over the past 41 years. The fastest rate of decrease occurred in the Kara Sea (∼−1% per year), while the slowest rates of decrease occurred in the Laptev/East Siberian Sea (∼−0.42% per year). The number of navigable days for the Kara Sea has become ∼1–2 months longer than the Laptev/East Siberian Sea route as a result. The effect of Tair on SIC, quantified by ΔSIC/ΔTair in the routes through the eastern Kara Sea and Laptev/East Siberian Sea in 2010s was ∼−0.04/°C, two to three times that seen during the 1980s. Air temperature is becoming a significant driving force of melting ice in these routes. Surface winds are also a crucial factor for the navigability of the Vilkitsky Strait and Long Strait, as they drive ice drift, and affect the navigability of the Kara Strait by introducing warm air.

Beschreibung: Negative emissions technologies (NETs) are an essential part of most scenarios for achieving the Paris Agreement goal of limiting warming to below 2°C and for all scenarios that limit warming to 1.5 °C. The deployment of these technologies requires carbon accounting methods for a range of different purposes, such as determining the effectiveness of specific technologies or incentivising NETs. Although the need for carbon accounting methods is discussed within the literature on NETs, there does not appear to be a clear understanding of the range of different accounting challenges. Based on a systematic literature review this study identifies five distinct accounting issues related to NETs: 1. estimating total system-wide change in emissions/removals; 2. non-permanence; 3. non-equivalence of ‘no overshoot’ and ‘overshoot and removal’; 4. accounting for incentives for NETs; and 5. the temporal distribution of emissions/removals. Solutions to these accounting challenges are proposed, or alternatively, areas for further research and the development of solutions are highlighted. One key recommendation is that carbon accounting methods should follow a ‘reality principle’ to report emissions and removals when and where they actually occur, and an important overall conclusion is that it is essential to use the correct accounting method for its appropriate purpose. For example, consequential methods that take account of total system-wide changes in emissions/removals should be used if the purpose is to inform decisions on the deployment or incentivisation of NETs. Attributional methods, however, should be used if the purpose is to construct static descriptions of possible net zero worlds.

Beschreibung: Touch interaction has established a dominating role in the realisation of Human–Machine Interfaces. However, to be able to use touch effectively and efficiently, users have to comply with particular prerequisites. Due to age-related changes, such as the decline of tactile accuracy and speed, especially elderly users often struggle with the touch modality. Interfaces that adapt to specific user characteristics could be a promising solution to overcome this problem. Notwithstanding the advantages of adaptive systems, perceived changes in the user interface can reduce the system's predictability and transparency. The present study compares three approaches concerning the adaptation of touch button sizes: no adaptation and adaptation with visible and invisible feedback. Results show that especially elderly users substantially benefit from an adaptive approach. Furthermore, data shows that the type of adaptation supports different usage goals. While adaption with visual feedback enables a higher interaction speed, invisible adaptation leads to a higher degree of accuracy.

Beschreibung: Pyroxene crystals from recent Central Plateau tephras are used to deduce their formation conditions through two-pyroxene thermobarometry. Crystals return pseudo-pressures and pseudo-temperatures that are artefacts of uptake of antecrysts formed at a range of crustal levels by isobaric cooling of previously intruded magmas. MELTS modelling of tephra glass compositions shows that pseudo-PT conditions are reproduced at oxygen fugacities above the nickel-nickel oxide buffer (NNO+1, NNO+2), mid- to upper crustal pressures (100–400 MPa), and temperatures between c. 900°C and 〉1100°C. Modelled crystals from the deep crust (800 MPa) are restricted to clinopyroxenes. However, these display chemical equilibrium with shallow orthopyroxenes at higher pseudo-PT conditions than observed in Central Plateau pyroxenes. The data indicate uptake of high-temperature pyroxenes at mid- to shallow crustal levels into ascending andesitic melts and thus preclude the presence of long-lived crustal mush zones (〈1000°C) as a source for the crystal cargo of the Central Plateau tephras studied here. Further, the apparent absence of deep crustal pyroxene antecrysts does not preclude models of arc andesite genesis without a ‘deep crustal hot zone’ beneath the Central Plateau. Generation and ascent of primary andesites from a heterogeneous mantle wedge is therefore a possible scenario at the southern Hikurangi margin.

Beschreibung: Whakaari/White Island is a partially submerged, offshore andesite island volcano, located at the northern end of the Taupō Volcanic Zone. Since the late 1960s, volcanic activity has alternated between quiescence, unrest, and eruption on short timescales. For this review we compiled extensive observational records, examined the rich scientific literature, and use newly acquired data, to understand the broad volcanic history and system dynamics. Based on recent bathymetry data, we propose a distinction exists between the Whakaari edifice and Te Paepae o Aotea/Volkner Rocks, which were previously considered to be part of the same edifice. Geochemical analyses of scoria samples from the island have been used to build a magma system model where dominantly andesitic-dacitic magma is periodically intruded by basalt. More dynamic processes are recorded in the hydrothermal system, where the location and activity of fumarolic features have been ephemeral and the crater lake has varied in scale over short time intervals. Eruptions of the dominantly andesitic magma have historically been small and range from phreatomagmatic through to magmatic, largely depositing ash and scoria to a restricted distance that is confined to the main crater floor. Phreatic eruptions are the most common eruption style, based on recently observed and monitored activity.

Beschreibung: Recently, the aeromagnetic survey with Unmanned Aerial Vehicle (UAV) for mineral exploration has become ubiquitous. They can fly at a lower speed, lower altitude, need fewer crew members, and are cost-effective compared to traditional manned aeromagnetic. With the development of drones, magnetometers were also developed, which reduced the cost, weight, size, and energy consumption of these sensors. One of these sensors is the magneto-inductive magnetometer. This study investigates the integration of the UAV with a magneto-inductive sensor. We have performed an aeromagnetic survey along with six profiles and compared them with the terrestrial magnetic survey using a proton precision magnetometer. We show that the magneto-inductive sensor can sense Earth’s magnetic field’s change up to less than 60 nT. These results show the promising potential of using the UAV equipped with the magneto-inductive sensor to prospect the magnetic ore deposits.

Beschreibung: Tephra deposits in Aotearoa New Zealand (ANZ) have been studied for 〉180 years. The now-global discipline of tephrochronology, which has some developmental roots in ANZ, forms the basis of a powerful chronostratigraphic correlational tool and age-equivalent dating method for geological, volcanological, palaeoenvironmental, and archaeological research in ANZ. Its utility is founded on the key principle that tephras or cryptotephras provide widespread isochrons in many different environments. In the first part of this article, we summarise the history of tephra studies in ANZ and then describe how tephras have been mapped, characterised, and correlated using field and laboratory-based methods. We document advances in geochemical fingerprinting of glass; tephra/cryptotephra detection and correlation by sediment-core scanning methods (e.g. X-radiography, CT imaging, XRF elemental analysis, magnetic susceptibility); statistical correlation methods; and dating of tephras/cryptotephras. We discuss the advent of ANZ cryptotephra studies (from mid-1970s) and their more-recent growth. The second part comprises examples of applications of tephrochronology in ANZ: climate-event stratigraphy (NZ-INTIMATE project); eruptive-event stratigraphy in the Auckland Volcanic Field; developments in the marine tephra record; advances in identifying, correlating, and dating old (pre-50 ka) tephras and weathered-tephra deposits; forming soils/paleosols on tephras; tephras and archaeology; Kopouatai bog tephrostratigraphy and palaeoenvironments; and volcanic-hazard assessments.

Beschreibung: There is a significant interest in the usage of algae in everyday diet because of their positive influence on the gastrointestinal system due to the presence of high amounts of dietary fibres, while the presence of ω-3 fatty acids contributes to the protection of cardiovascular system. Algal derived polysaccharides are found in the food products as stabilisers, thickening agents and emulsifiers. In the cosmetic industry, algae are used in sunscreen, anti-age, anti-cellulite, moisturising and skin whitening products. These products can be used for the development of cosmeceuticals which contain algal derived bioactive compounds and they can exert a pharmaceutical therapeutic benefit. However, these compounds also have potential for being isolated and used for development of novel drugs against diseases, such as cancer, neurodegenerative disorders, and diabetes. Present review provides information about algal compounds incorporated into various food, cosmetic or medicinal products, as well as their potential for health improvement was evaluated.

Beschreibung: During World War I, an enormous amount of chemical and conventional munitions was fired. Many of these munitions did not explode and are still recovered in the soil of the regions where the war raged for several years. After the war, many of the remaining munitions were dumped in the sea as an easy way of removal. These unexploded and dumped munitions are still present so many years after the end of the war. The explosive material inside the munitions is more than 100 years old now. Samples were collected from some of these old munitions. These samples have been analyzed to determine their composition. The explosives typically used in World War I (TNT, DNT, DNB and picric acid) have been identified. It has been shown that the aged samples still contain their energy. They have not become more sensitive to friction or impact. For one the samples, it has been shown that it is still cap-sensitive and detonates normally. These results are important for any risk assessment involving old munitions.

Beschreibung: Marine heatwaves along the coast ofWestern Australia, referred to as Ningaloo Niño, have had dramatic impacts on the ecosystem in the recent decade. A number of local and remote forcing mechanisms have been put forward, however little is known about the depth structure of such temperature extremes. Utilizing an eddy-active global Ocean General Circulation Model, Ningaloo Niño and the corresponding cold Ningaloo Niña events are investigated between 1958-2016, with focus on their depth structure. The relative roles of buoyancy and wind forcing are inferred from sensitivity experiments. Composites reveal a strong symmetry between cold and warm events in their vertical structure and associated large-scale spatial patterns. Temperature anomalies are largest at the surface, where buoyancy forcing is dominant and extend down to 300m depth (or deeper), with wind forcing being the main driver. Large-scale subsurface anomalies arise from a vertical modulation of the thermocline, extending from the western Pacific into the tropical eastern Indian Ocean. The strongest Ningaloo Niños in 2000 and 2011 are unprecedented compound events, where long-lasting high temperatures are accompanied by extreme freshening, which emerges in association with La Niñas, more common and persistent during the negative phase of the Interdecadal Pacific Oscillation. It is shown that Ningaloo Niños during La Nina phases have a distinctively deeper reach and are associated with a strengthening of the Leeuwin Current, while events during El Niño are limited to the surface layer temperatures, likely driven by local atmosphere-ocean feedbacks, without a clear imprint on salinity and velocity.

Beschreibung: The Antarctic Slope Front (ASF) is a fundamental feature of the subpolar Southern Ocean that is still poorly observed. In this study we build a statistical climatology of the temperature and salinity fields of the upper 380 m of the Antarctic margin. We use a comprehensive compilation of observational datasets including the profiles gathered by instrumented marine mammals. The mapping method consists first of a decomposition in vertical modes of the combined temperature and salinity profiles. Then the resulting principal components are optimally interpolated on a regular grid and the monthly climatological profiles are reconstructed, providing a physically plausible representation of the ocean. The ASF is located with a contour method and a gradient method applied on the temperature field, two complementary approaches that provide a complete view of the ASF structure. The front extends from the Amundsen Sea to the eastern Weddell Sea and closely tracks the continental shelf break. It is associated with a sharp temperature gradient that is stronger in winter and weaker in summer. The emergence of the front in the Amundsen and Bellingshausen sectors appears to be seasonally variable (slightly more westward in winter than in summer). Investigation of the density gradients across the shelf break indicates a winter slowdown of the baroclinic component of the Antarctic Slope Current at the near surface, in contrast with the seasonal variability of the temperature gradient.

Beschreibung: There is a controversy about the nature of multidecadal climate variability in the North Atlantic (NA) region, concerning the roles of ocean circulation and atmosphere–ocean coupling. Here we describe NA multidecadal variability from a version of the Kiel Climate Model, in which both subpolar gyre (SPG)–Atlantic meridional overturning circulation (AMOC) coupling and atmosphere–ocean coupling are essential. The oceanic barotropic and meridional overturning streamfunctions and the sea level pressure are jointly analyzed to derive the leading mode of Atlantic sector variability. This mode accounting for 23.7% of the total combined variance is oscillatory with an irregular periodicity of 25–50 years and an e-folding time of about a decade. SPG and AMOC mutually influence each other and together provide the delayed negative feedback necessary for maintaining the oscillation. An anomalously strong SPG, for example, drives higher surface salinity and density in the NA’s sinking region. In response, oceanic deep convection and AMOC intensify, which, with a time delay of about a decade, reduces SPG strength by enhancing upper-ocean heat content. The weaker gyre leads to lower surface salinity and density in the sinking region, which reduces deep convection and eventually AMOC strength. There is a positive ocean–atmosphere feedback between the sea surface temperature and low-level atmospheric circulation over the southern Greenland area, with related wind stress changes reinforcing SPG changes, thereby maintaining the (damped) multidecadal oscillation against dissipation. Stochastic surface heat flux forcing associated with the North Atlantic Oscillation drives the eigenmode.

Beschreibung: The Agulhas Current (AC) creates a sharp temperature gradient with the surrounding ocean, leading to a large turbulent flux of moisture from ocean to atmosphere. We use two simulations of the Weather Research and Forecasting (WRF) model to show the seasonal impact of the warm core of the AC on southern Africa precipitation. In one simulation the sea surface temperature (SST) of the AC is similar to satellite observations, while the second uses satellite SST observations spatially smoothed to reduce the temperature of the core of the AC by ~1.5°C. We show that decreasing the SST of the AC reduces the precipitation of the wettest seasons (austral summer and autumn) inland. Over the ocean, reducing the SST reduces precipitation, low-level wind convergence, SST and SLP Laplacian above the AC in all seasons, consistent with the pressure adjustment mechanism. Moreover, winter precipitation above the Current may be also related to increased latent flux. In summer and autumn, the AC SST reduction is also associated with decreased precipitation further inland (more than 1.5 mm/day), caused by an atmospheric circulation that decreases the horizontal moisture flux from the AC to South Africa. The reduction is also associated with higher geopotential height extending from the surface east and over the AC to the mid-troposphere over southeastern Africa. The westward tilted geopotential height is consistent with the linear response to shallow diabatic heating in midlatitudes. An identical mechanism occurs in spring but is weaker. Winter rainfall response is confined above the AC.

Beschreibung: Spatial and temporal variations of nutrient-rich upwelled water across the major eastern boundary upwelling systems are primarily controlled by the surface wind with different, and sometimes contrasting, impacts on coastal upwelling systems driven by alongshore wind and offshore upwelling systems driven by the local wind-stress-curl. Here, concurrently measured wind-fields, satellite-derived Chlorophyll-a concentration along with a state-of-the-art ocean model simulation spanning 2008-2018 are used to investigate the connection between coastal and offshore physical drivers of the Benguela Upwelling System (BUS). Our results indicate that the spatial structure of long-term mean upwelling derived from Ekman theory and the numerical model are fairly consistent across the entire BUS and closely followed by the Chlorophyll-a pattern. The variability of the upwelling from the Ekman theory is proportionally diminished with offshore distance, whereas different and sometimes opposite structures are revealed in the model-derived upwelling. Our result suggests the presence of sub-mesoscale activity (i.e., filaments and eddies) across the entire BUS with a large modulating effect on the wind-stress-curl-driven upwelling off Lüderitz and Walvis Bay. In Kunene and Cape Frio upwelling cells, located in the northern sector of the BUS, the coastal upwelling and open-ocean upwelling frequently alternate each other, whereas they are modulated by the annual cycle and mostly in phase off Walvis Bay. Such a phase relationship appears to be strongly seasonally dependent off Lüderitz and across the southern BUS. Thus, our findings suggest this relationship is far more complex than currently thought and seems to be sensitive to climate changes with short- and far-reaching consequences for this vulnerable marine ecosystem.

Beschreibung: Enhanced Southern Ocean ventilation in recent decades has been suggested to be a relevant modulator of the observed changes in ocean heat and carbon uptake. This study focuses on the Southern Ocean midlatitude ventilation changes from the 1960s to the 2010s. A global 1/4° configuration of the NEMO–Louvain-la-Neuve sea ice model, version 2 (LIM2), including the inert tracer CFC-12 (a proxy of ocean ventilation) is forced with the CORE, phase II (CORE-II), and JRA-55 driving ocean (JRA55-do) atmospheric reanalyses. Sensitivity experiments, where the variability of wind stress and/or the buoyancy forcing is suppressed on interannual time scales, are used to unravel the mechanisms driving ventilation changes. Ventilation changes are estimated by comparing CFC-12 interior inventories among the different experiments. All simulations suggest a multidecadal fluctuation of Southern Ocean ventilation, with a decrease until the 1980s–90s and a subsequent increase. This evolution is related to the atmospheric forcing and is caused by the (often counteracting) effects of wind stress and buoyancy forcing. Until the 1980s, increased buoyancy gains caused the ventilation decrease, whereas the subsequent ventilation increase was driven by strengthened wind stress causing deeper mixed layers and a stronger meridional overturning circulation. Wind stress emerges as the main driver of ventilation changes, even though buoyancy forcing modulates its trend and decadal variability. The three Southern Ocean basins take up CFC-12 in distinct density intervals but overall respond similarly to the atmospheric forcing. This study suggests that Southern Ocean ventilation is expected to increase as long as the effect of increasing Southern Hemisphere wind stress overwhelms that of increased stratification.

Beschreibung: Geological archives record multiple reversals of Earth’s magnetic poles, but the global impacts of these events, if any, remain unclear. Uncertain radiocarbon calibration has limited investigation of the potential effects of the last major magnetic inversion, known as the Laschamps Excursion [41 to 42 thousand years ago (ka)]. We use ancient New Zealand kauri trees (Agathis australis) to develop a detailed record of atmospheric radiocarbon levels across the Laschamps Excursion. We precisely characterize the geomagnetic reversal and perform global chemistry-climate modeling and detailed radiocarbon dating of paleoenvironmental records to investigate impacts. We find that geomagnetic field minima ~42 ka, in combination with Grand Solar Minima, caused substantial changes in atmospheric ozone concentration and circulation, driving synchronous global climate shifts that caused major environmental changes, extinction events, and transformations in the archaeological record.

Beschreibung: This article presents the results of a marine geophysical and sedimentological study carried out around Lesvos Island (NE Aegean) to investigate the potential of exploitable marine aggregate (MA) deposits that could be used for beach replenishment purposes. Sub-bottom profiler data showed a good prospect for potential coarse-grained deposits in two of the three surveyed areas around Lesvos. Grain size and mineralogical analysis of the surficial sediments revealed sands that could properly feed nourishment schemes for eroded beaches or artificial beach development. Observed MA volumes are considered adequate for renourishment operations, when the threat of projected sea-level rise is introduced. Environmental constraints, as well as human activities, are considered for the suggestion and prioritization of specific areas for detailed surveying before future exploitation.

Beschreibung: Modelling the drift of marine debris in quasi-real time can be of societal relevance. One pertinent example is Malaysia Airlines flight MH370. The aircraft is assumed to have crashed in the Indian Ocean, leaving floating wreckage to drift on the surface. Some of these items were recovered around the western Indian Ocean. We use ocean currents simulated by an operational ocean model in conjunction with surface Stokes drift to determine the possible paths taken by the debris. We consider: (1) How important is the influence of surface waves on the drift? (2) What are the relative benefits of forward- and backward-tracking in time? (3) Does including information from more items refine the most probable crash-site region? Our results highlight a critical contribution of Stokes drift and emphasise the need to know precisely the buoyancy characteristics of the items. The differences between the tracking approaches provide a measure of uncertainty which can be minimised by simulating a sufficiently large number of virtual debris. Given the uncertainties associated with the timings of the debris sightings, we show that at least 5 items are required to achieve an optimal most probable crash-site region. The results have implications for other drift simulation applications.

Beschreibung: Chirp sub-bottom profilers (SBP) provide centi-to-decimetre resolution, seismic data with applications for various geophysical and geological purposes. To verify the field application of imaging of a buried target with a cost-effective and easy-to-apply pseudo-3D Chirp SBP survey, we explored the buried site of an ancient wooden shipwreck off the west coast of Korea before underwater excavations. The survey was conducted using a commercial 2D Chirp SBP system with a newly devised recording system that preserved the true polarity of the chirp signal. To produce high-resolution 3D Chirp SBP data from 2D Chirp SBP datasets recorded by the novel system, an optimal data processing sequence, consisting of a first phase of 2D data processing and a second phase of 3D data processing was designed. The first, 2D phase, included the estimation of a source sweep signature, cross-correlation, and deconvolution using an inverse filter. The resulting resolution of the 2D Chirp SBP data was better than that of the enveloped data provided by the commercial acquisition system. The second phase of 3D data processing included gathering 3D datasets, redistributing of ping positions, and static correction. To improve the consistency of the seismic events and reduce the repetitive corrections (swell, tidal, tie, and residual corrections), a static correction was based on multi-beam echo sounder data. The amplitude variation near the shipwreck was clearly apparent in the time slice from the final pseudo-3D Chirp SBP dataset with a bin size of 2.0 m (crossline) × 0.6 m (inline). Through 3D rendering, the buried ancient shipwreck with dimensions of 5 m (width) × 12 m (length) × 2 m (depth) was imaged successfully.

Beschreibung: Riparian zones are important for the maintenance of aquatic ecosystem functional integrity, yet are considered to be particularly vulnerable to plant invasions. The role of terrestrial riparian plant invasions in compromising aquatic ecosystem processes is, however, still poorly understood. This issue is particularly relevant for temporary rivers, which are understudied compared to permanent river systems, despite their ubiquity and largescale contributions to biogeochemical processes. Here we experimentally assessed leaf litter breakdown dynamics in situ in a temporary river in arid southeastern Botswana, Southern Africa. We contrasted aquatic leaching and microbial and invertebrate litter breakdown contributions to the native leadwood Combretum imberbe and invasive river red gum Eucalyptus camaldulensis in the Lotsane River. Fine-mesh (detritivore exclusion) and coarse-mesh (detritivore inclusion) bags were separately filled with leaf litter from each species and deployed in the river during a hydroperiod (wet phase), with decomposition measured over a 6-week period. E. camaldulensis shed significantly more leachate than the native C. imberbe. Significantly more microbial and detritivore breakdown was, however, observed in native than in invasive leaf litter. Overall, invertebrates contributed little to biological leaf litter breakdown processes compared to microbial breakdown contributions. Although significantly higher in native leaves, low invertebrate numbers were found in leaf litter in the study. This study highlights the role of microbial contributions to detrital decay in temporary arid zone rivers, whereas invertebrate contributions were relatively minor. The study further contributes to our understanding of how invasive riparian plant species alter aquatic detrital pool dynamics in invaded temporary wetland ecosystems.

Beschreibung: The cold-water coral Lophelia pertusa builds up bioherms that sustain high biodiversity in the deep ocean worldwide. Photographic monitoring of the polyp activity represents a helpful tool to characterize the health status of the corals and to assess anthropogenic impacts on the microhabitat. Discriminating active polyps from skeletons of white Lophelia pertusa is usually time-consuming and error-prone due to their similarity in color in common RGB camera footage. Acquisition of finer resolved spectral information might increase the contrast between the segments of polyps and skeletons, and therefore could support automated classification and accurate activity estimation of polyps. For recording the needed footage, underwater multispectral imaging systems can be used, but they are often expensive and bulky. Here we present results of a new, light-weight, compact and low-cost deep-sea tunable LED-based underwater multispectral imaging system (TuLUMIS) with eight spectral channels. A brunch of healthy white Lophelia pertusa was observed under controlled conditions in a laboratory tank. Spectral reflectance signatures were extracted from pixels of polyps and skeletons of the observed coral. Results showed that the polyps can be better distinguished from the skeleton by analysis of the eight-dimensional spectral reflectance signatures compared to three-channel RGB data. During a 72-hour monitoring of the coral with a half-hour temporal resolution in the lab, the polyp activity was estimated based on the results of the multispectral pixel classification using a support vector machine (SVM) approach. The computational estimated polyp activity was consistent with that of the manual annotation, which yielded a correlation coefficient of 0.957.

Beschreibung: The El Niño-Southern Oscillation (ENSO) is the dominant mode of interannual climate variability on the planet, with far-reaching global impacts. It is therefore key to evaluate ENSO simulations in state-of-the-art numerical models used to study past, present and future climate. Recently, the Pacific Region Panel of the International Climate and Ocean - Variability, Predictability, and Change (CLIVAR) Project, as a part of the World Climate Research Programme (WCRP), led a community-wide effort to evaluate the simulation of ENSO variability, teleconnections and processes in climate models. The new CLIVAR 2020 ENSO metrics package enables model diagnosis, comparison, and evaluation to (1) highlight aspects that need improvement; (2) monitor progress across model generations; (3) help in selecting models that are well suited for particular analyses; (4) reveal links between various model biases, illuminating the impacts of those biases on ENSO and its sensitivity to climate change; and to (5) advance ENSO literacy. By interfacing with existing model evaluation tools, the ENSO metrics package enables rapid analysis of multi-petabyte databases of simulations, such as those generated by the Coupled Model Intercomparison Project phases 5 (CMIP5) and 6 (CMIP6). The CMIP6 models are found to significantly outperform those from CMIP5 for 8 out of 24 ENSO-relevant metrics, with most CMIP6 models showing improved tropical Pacific seasonality and ENSO teleconnections. Only one ENSO metric is significantly degraded in CMIP6, namely the coupling between the ocean surface and subsurface temperature anomalies, while the majority of metrics remain unchanged.

Beschreibung: Accurate and repeatable population estimates are key to establishing population trends and conservation status. Rako, or Buller’s Shearwater (Ardenna bulleri) is a seabird endemic to New Zealand that breeds only on the Poor Knights Islands, but forages throughout wider areas of the Pacific Ocean during the non-breeding season. The lack of threats on the breeding grounds and the wide foraging range of Buller’s Shearwaters makes them ideal sentinels of ocean health. Although they are commonly seen at sea and the population in the 1980s was thought to be around 2.5 million birds, other rapid land-based surveys suggested a much lower figure (~100,000 pairs on Aorangi), and no thorough population estimate has been undertaken to date. We calculated a population estimate for Buller’s Shearwater based on burrow counts and state of occupancy conducted at the Poor Knights during either the 2016–2017 or the 2017–2018 breeding seasons. We incorporated information on habitat availability and preference in population models. Our estimate of 78,645 (95% confidence interval 67,176–89,178) active burrows, broadly representing breeding pairs, is lower than some previously published assessments. This is a repeatable quantitative study of the Buller’s Shearwater breeding population, including breeding activity, and provides critical baseline data to determine population trends for this potentially important marine indicator species. © 2021 BirdLife Australia.

Beschreibung: Anthropogenic pressures on standing waterbody systems potentially result in changes to sediment and water qualities, and thus ecological community characteristics. We tested effects of drawdown on physical, water and sediment variables, as well as their effects on littoral macroinvertebrate community composition in two subtropical reservoirs. Water levels differed significantly between reservoirs and over time, with significant effects on several water chemistry parameters (e.g., pH, conductivity, Mg, Fe), whilst sediment properties were less affected. Significant effects of water level, site and macrophyte cover on macroinvertebrate community structures were not detected, however macroinvertebrate community structuring differed significantly over time. Redundancy analysis (RDA) highlighted that the first and second axes accounted for 45.6% of the total macroinvertebrate community and environmental variables relationship variance. Most of the sediment variables, such as Cu, Mg, Na and Pb and water chemistry (i.e., HCO3-), were positively associated with the first axis, while water temperature and pH were negatively associated with the first axis. The RDA variation partitioning showed that water and sediment chemistry variables accounted for 40.3% and 30.3%, respectively, of the total macroinvertebrate variation. The present study contributes to understandings of the interplays between water level, physico-chemical properties and community compositions in human-altered aquatic ecosystems.

Beschreibung: Despite the diversity and oftentimes large biomass of jellyfish in marine systems, their ecological role remains poorly understood. We here provide the first systematic review of studies on jellyfish trophic ecology in the Baltic Sea (a regional marine system under strong multiple global and regional anthropogenic pressures). In total, we identified 57 peer-reviewed publications, with notable taxonomic bias towards two species (Aurelia aurita; non-indigenous Mnemiopsis leidyi) and spatial bias towards five areas (Bornholm Basin, Kiel Bight, Kertinge Nor, Lim- and Gullmarsfjord). The studies provide evidence for diverse trophic roles of jellyfish as predators and as competitors of other jellyfish, zooplankton and fish species. In combination, the studies also highlight potentially large impacts via top-down (grazing) and bottom-up (nutrient excretion) effects, but also, strong spatio-temporal variability in the magnitude of these effects, depending on the occurrence of jellyfish blooms. Studies on the role of jellyfish as prey for fish, seabirds or marine mammals, and for benthic systems via food-falls, were limited or lacking for the Baltic Sea, despite increasing focus on these topics globally. Improved understanding of the temporal (seasonal, inter-annual, long-term) and spatial variability of blooms and corresponding trophic effects, would provide more systematic understanding of the ecological role of jellyfish in the spatio-temporally variable Baltic Sea. A broader spatial coverage, inclusion of more jellyfish taxa and under-studied early life history stages, as well as the implementation and continuation of long-term data series would represent important steps towards this goal.

Beschreibung: This study demonstrates that the generalization that strong anomalous equatorial Pacific westerly (easterly) winds during El Niño (La Niña) events displays strong adjusted warm water volume (WWV) discharges (recharges) is often incorrect. Using ocean model simulations, we categorize the oceanic adjusted responses to strong anomalous equatorial winds into two categories: (i) transitioning (consistent with the above generalization); and (ii) neutral adjusted responses (with negligible WWV re- and discharge) During the 1980-2016 period only 47% of strong anomalous equatorial winds are followed by transitioning adjusted responses, while the remaining are followed by neutral adjusted responses. Moreover, 55% (only 30%) of the strongest winds lead to transitioning adjusted responses during the pre-2000 (post-2000) period in agreement with the previously reported post-2000 decline of WWV lead time to El Niño-Southern Oscillation (ENSO) events. The prominent neutral adjusted WWV response is shown to be largely excited by anomalous wind stress forcing with a weaker curl (on average consistent with a higher ratio of off-equatorial to equatorial wind events) and weaker Rossby wave projection than the transitioning adjusted response. We also identify a prominent ENSO phase asymmetry where strong anomalous equatorial westerly winds (i.e., El Niño events) are roughly 1.6 times more likely to strongly discharge WWV than strong anomalous equatorial easterly winds (i.e., La Niña events) are to strongly recharge WWV. This ENSO phase asymmetry may be added to the list of mechanisms proposed to explain why El Niño events have a stronger tendency to be followed by La Niña events than vice versa.

Beschreibung: Gonatus fabricii (Lichtenstein, 1818) is an ecologically important squid that spends its entire life cycle within the Arctic where it is the most abundant cephalopod. Due to the rarity of mature and reproducing females, it is unknown how many eggs females spawn (actual fecundity). Among 47,000 specimens studied between 2005 and 2019 one spent, degenerated and gelatinous female with a mantle length of 230 mm was caught in West Greenland in 2019. Examination allowed the first detailed description of fecundity and spawning pattern in the species. Oocyte development shows that the most considerable maturation of mid-vitellogenic oocytes to late vitellogenic and then to ripe stages occurs immediately after the first ripe oocytes appear in the ovary. There were no ripe oocytes in the ovary or oviducts. The ovary contained an estimated 6561 oocytes and 2551 post-ovulatory follicles and hence the total fecundity was 9112. This specimen of G. fabricii realised 28.0% of its potential fecundity which is comparable to Berryteuthis magister, which also belongs to Gonatidae, and lower than in the majority of studied deep-sea squids (including other gonatids). Spent females may provide clues as to where the major spawning areas of this abundant but poorly known squid are located.

Beschreibung: The extratropical effect of the quasi-biennial oscillation (QBO), known as the Holton-Tan effect, is manifest as a weaker, warmer winter Arctic polar vortex during the east QBO phase. While previous studies have shown that the extratropical QBO signal is caused by the modified propagation of planetary waves in the stratosphere, the mechanism dominating the onset and seasonal development of the Holton-Tan effects remains unclear. Here, the governing wave-mean flow dynamics of the early winter extratropical QBO signal onset and its reversibility is investigated on a synoptic time scale with a finite-amplitude diagnostic using reanalysis and a chemistry-climate model. The extratropical QBO signal onset in October is found to primarily result from modulated stratospheric life cycles of wave pulses entering the stratosphere from the troposphere, rather than from a modulation of their tropospheric wave source. A comprehensive analysis of the wave activity budget during fall, when the stratospheric winter polar vortex starts forming and waves start propagating up into the stratosphere, shows significant differences. During the east QBO phase, the deceleration of the mid-high-latitude stratospheric zonal-mean jet by the upward-propagating wave pulses is less reversible, due to stronger dissipation processes, while during the west phase, a more reversible deceleration of the main polar vortex is found owing to the waves being dissipated at lower latitudes, accompanied by a weak but different response of the tropospheric subtropical jet. From this synoptic wave-event viewpoint, the early season onset of the Holton-Tan effect results from the cumulative effect of the QBO dependent wave-induced deceleration during the life cycle of individual upward wave pulses.

Beschreibung: A recent analysis of observed oxygen changes shows a 2% decline in marine oxygen during the 50 years since 1960. However, these oxygen changes vary on time scales related to climate modes and by regions, including areas of increasing oxygen. Hence, any local oxygen change is related to various subsets of these drivers for the different regions and time scales. Here we provide an overview of drivers presently known for the different regions in the upper and deep ocean and the regional influence of climate modes, focussing on decadal and longer time scales for open ocean regions. We identify and compile regions where changes in solubility, stratification, decadal to multidecadal variability, source waters (either increases or decreases), overturning circulation or circulation-driven changes, and biological or nutrient stimulation have been shown to play a role in oxygen changes. The superposition and interaction of drivers and processes makes the decomposition of the impact on oxygen distribution difficult. Nevertheless, the description of the different drivers identified will help in better understanding the oxygen changes observed and lead to better verification of numerical models of future ocean oxygen levels.

Beschreibung: The marine environment encompasses a huge biological diversity and can be considered as an underexplored location for prospecting bioactive molecules. In this review, the current state of art about antimicrobial molecules from marine bacteria has been summarized considering the main phylum and sources evolved in a marine environment. Considering the last two decades, we have found as most studied group of bacteria producers of substances with antimicrobial activity is the Firmicutes phylum, in particular strains of the Bacillus genus. The reason for that can be attributed to the difficult cultivation of typical Actinobacteria from a marine sediment, whose members are the major producers of antimicrobial substances in land environments. However, a reversed trend has been observed in recent years with an increasing number of reports settling on Actinobacteria. Great diversity of chemical structures have been identified, such as fijimicyns and lynamicyns from Actinomycetes and macrolactins produced by Bacillus.

Beschreibung: Introduction: The marine environment is a very promising resource for natural product research, with many of these reaching the market as new drugs, especially in the field of cancer therapy as well as the drug discovery pipeline for new antimicrobials. Exploitation for bioactive marine compounds with unique structures and novel bioactivity such as the isoquinoline alkaloid; trabectedin, the polyether macrolide; halichondrin B, and the peptide; dolastatin 10, requires the use of analytical techniques, which can generate unbiased, quantitative, and qualitative data to benefit the biodiscovery process. Metabolomics has shown to bridge this understanding and facilitate the development of new potential drugs from marine sources and particularly their microbial symbionts. Areas covered: In this review, articles on applied secondary metabolomics ranging from 1990–2018 as well as to the last quarter of 2019 were probed to investigate the impact of metabolomics on drug discovery for new antibiotics and cancer treatment. Expert opinion: The current literature review highlighted the effectiveness of metabolomics in the study of targeting biologically active secondary metabolites from marine sources for optimized discovery of potential new natural products to be made accessible to a R&D pipeline.

Beschreibung: Freshwater sponges can be considered a promising new source of bioactive compounds for the pharmaceutical industry; however, the research on their chemical composition is still in the incipient stage. We evaluated the most endemic Amazonian freshwater sponge species from the Drulia and Metania genera by untargeted metabolomic approaches, based on UHPCL-HRMS, in order to identify chemical markers and explore the diversity of specialized metabolites. The use of untargeted approaches allowed us to observe subsets of metabolites that enabled the characterization of, not only each genus, but also, of each species. Freshwater sponge species presented themselves as rich sources of fatty acids and sterols, which were putatively identified. These metabolites were suggested as chemical markers for further targeted metabolomic studies.

Beschreibung: The representation of tropical precipitation is evaluated across three generations of models participating in phases 3, 5, and 6 of the Coupled Model Intercomparison Project (CMIP). Compared to state-of-the-art observations, improvements in tropical precipitation in the CMIP6 models are identified for some metrics, but we find no general improvement in tropical precipitation on different temporal and spatial scales. Our results indicate overall little changes across the CMIP phases for the summer monsoons, the double-ITCZ bias, and the diurnal cycle of tropical precipitation. We find a reduced amount of drizzle events in CMIP6, but tropical precipitation occurs still too frequently. Continuous improvements across the CMIP phases are identified for the number of consecutive dry days, for the representation of modes of variability, namely, the Madden–Julian oscillation and El Niño–Southern Oscillation, and for the trends in dry months in the twentieth century. The observed positive trend in extreme wet months is, however, not captured by any of the CMIP phases, which simulate negative trends for extremely wet months in the twentieth century. The regional biases are larger than a climate change signal one hopes to use the models to identify. Given the pace of climate change as compared to the pace of model improvements to simulate tropical precipitation, we question the past strategy of the development of the present class of global climate models as the mainstay of the scientific response to climate change. We suggest the exploration of alternative approaches such as high-resolution storm-resolving models that can offer better prospects to inform us about how tropical precipitation might change with anthropogenic warming.

Beschreibung: Understanding the physical and biogeochemical interactions and feedbacks between the ocean and atmosphere is a vital component of environmental and Earth system research. The ability to predict and respond to future environmental change relies on a detailed understanding of these processes. The Surface Ocean-Lower Atmosphere Study (SOLAS) is an international research platform that focuses on the study of ocean-atmosphere interactions, for which Future Earth is a sponsor. SOLAS instigated a collaborative initiative process to connect efforts in the natural and social sciences related to these processes, as a contribution to the emerging Future Earth Ocean Knowledge-Action Network (Ocean KAN). This is imperative because many of the recent changes in the Earth system are anthropogenic. An understanding of adaptation and counteracting measures requires an alliance of scientists from both domains to bridge the gap between science and policy. To this end, three SOLAS research areas were targeted for a case study to determine a more effective method of interdisciplinary research: valuing carbon and the ocean’s role; air-sea interactions, policy and stewardship; and, air-sea interactions and the shipping industry.

Beschreibung: Weather and climate variations on subseasonal to decadal time scales can have enormous social, economic, and environmental impacts, making skillful predictions on these time scales a valuable tool for decision-makers. As such, there is a growing interest in the scientific, operational, and applications communities in developing forecasts to improve our foreknowledge of extreme events. On subseasonal to seasonal (S2S) time scales, these include high-impact meteorological events such as tropical cyclones, extratropical storms, floods, droughts, and heat and cold waves. On seasonal to decadal (S2D) time scales, while the focus broadly remains similar (e.g., on precipitation, surface and upper-ocean temperatures, and their effects on the probabilities of high-impact meteorological events), understanding the roles of internal variability and externally forced variability such as anthropogenic warming in forecasts also becomes important. The S2S and S2D communities share common scientific and technical challenges. These include forecast initialization and ensemble generation; initialization shock and drift; understanding the onset of model systematic errors; bias correction, calibration, and forecast quality assessment; model resolution; atmosphere-ocean coupling; sources and expectations for predictability; and linking research, operational forecasting, and end-user needs. In September 2018 a coordinated pair of international conferences, framed by the above challenges, was organized jointly by the World Climate Research Programme (WCRP) and the World Weather Research Programme (WWRP). These conferences surveyed the state of S2S and S2D prediction, ongoing research, and future needs, providing an ideal basis for synthesizing current and emerging developments in these areas that promise to enhance future operational services. This article provides such a synthesis.

Beschreibung: Monowai is an active submarine volcanic centre in the Kermadec Arc, Southwest Pacific Ocean. Multi-beam data acquired during expedition SO225 aboard R/V SONNE in December 2012 indicates that the topography of the main stratocone has evolved significantly since the last survey in June 2011. Bathymetric measurements of the edifice reveal differences of up to 42 m in seafloor depth and indicate a net volume increase of ∼0.037 km3 across the summit area. Explosive volcanism observed onsite during the SO225 mapping campaign could be linked to a 20h-long swarm of unusually coherent T phase arrivals, suggesting that Monowai is a prime source of broadband seismic noise in the Southwest Pacific region during times of activity. Our findings further document the dynamic nature of volcanic processes at Monowai and have implications for future expedition planning.

Beschreibung: There is a zonally oriented teleconnection pattern over the high-latitude Eurasian continent, which is maintained through baroclinic energy conversion. In this study, we investigate the unique features of the maintenance mechanism of this teleconnection. It is found that the baroclinic energy conversion is most efficient in both the mid-troposphere and the lower troposphere, and that the baroclinic energy conversion in the lower troposphere is comparable to that in the mid-troposphere. Further results indicate that the basic state plays a crucial role in the baroclinic energy conversion. For both the mid and lower troposphere, the atmospheric stability is low and the Coriolis parameter is large over high-latitude Eurasia, favoring strong baroclinic energy conversion. Particularly, in the lower troposphere, the atmospheric stability exhibits a clear land-sea contrast, favoring baroclinic energy conversion over the continents rather than the oceans. Furthermore, in the lower troposphere, the in-phase configuration of the meridional wind and temperature anomalies, which results from the strong meridional gradient of mean temperature around the north edge of the Eurasian continent, also significantly contributes to baroclinic energy conversion. This study highlights the role of the basic state of temperature rather than zonal wind in maintaining the high-latitude teleconnection through baroclinic energy conversion.

Beschreibung: Subtropical dry zones, located in the Hadley cells' subsidence regions, strongly influence regional climate as well as outgoing longwave radiation. Changes in these dry zones could have significant impact on surface climate as well as on the atmospheric energy budget. This study investigates the behavior of upper-tropospheric dry zones in a changing climate, using the variable upper-tropospheric humidity (UTH), calculated from climate model experiment output as well as from radiances measured with satellite-based sensors. The global UTH distribution shows that dry zones form a belt in the subtropical winter hemisphere. In the summer hemisphere they concentrate over the eastern ocean basins, where the descent regions of the subtropical anticyclones are located. Recent studies with model and satellite data have found tendencies of increasing dryness at the poleward edges of the subtropical subsidence zones. However, UTH calculated from climate simulations with 25 models from phase 5 of the Coupled Model Intercomparison Project (CMIP5) shows these tendencies only for parts of the winter-hemispheric dry belts. In the summer hemisphere, even though differences exist between the simulations, UTH is increasing in most dry zones, particularly in the South and North Pacific Ocean. None of the summer dry zones is expanding in these simulations. Upper-tropospheric dry zones estimated from observational data do not show any robust signs of change since 1979. Apart from a weak drying tendency at the poleward edge of the southern winter-hemispheric dry belt in infrared measurements, nothing indicates that the subtropical dry belts have expanded poleward.

Beschreibung: It might be impossible to truly fathom the magnitude of the threat that global-mean sea level rise poses. However, conceptualizing the scale of the solutions required to protect ourselves against global-mean sea level rise, aids in our ability to acknowledge and understand the threat that sea level rise poses. On these grounds, we here discuss a means to protect over 25 million people and important economical regions in northern Europe against sea level rise. We propose the construction of a Northern European Enclosure Dam (NEED) that stretches between France, the United Kingdom and Norway. NEED may seem an overwhelming and unrealistic solution at first. However, our preliminary study suggests that NEED is potentially favorable financially, but also in scale, impacts and challenges compared to that of alternative solutions, such as (managed) migrations and that of country-by-country protection efforts. The mere realization that a solution as considerable as NEED might be a viable and cost-effective protection measure is illustrative of the extraordinary global threat of global-mean sea level rise that we are facing. As such, the concept of constructing NEED showcases the extent of protection efforts that are required if mitigation efforts fail to limit sea level rise.

Beschreibung: The comparison of equivalent neutral winds obtained from (a) four WHOI buoys in the subtropics and (b) scatterometer estimates at those locations reveals a root-mean-square (RMS) difference of 0.56-0.76 m/s. To investigate this RMS difference, different buoy wind error sources were examined. These buoys are particularly well suited to examine two important sources of buoy wind errors because: (1) redundant anemometers and a comparison with numerical flow simulations allow us to quantitatively assess flow distortion errors, and (2) one-minute sampling at the buoys allows us to examine the sensitivity of buoy temporal sampling/averaging in the buoy-scatterometer comparisons. The inter-anemometer difference varies as a function of wind direction relative to the buoy wind vane and is consistent with the effects of flow distortion expected based on numerical flow simulations. Comparison between the anemometers and scatterometer winds supports the interpretation that the inter-anemometer disagreement, which can be up to 5% of the wind speed, is due to flow distortion. These insights motivate an empirical correction to the individual anemometer records and subsequent comparison with scatterometer estimates show good agreement.

Beschreibung: The North Atlantic (NA) basin-averaged sea surface temperature (NASST) is often used as an index to study climate variability in the NA sector. However, there is still some debate on what drives it. Based on observations and climate models, an analysis of the different influences on the NASST index and its low-pass filtered version, the Atlantic multidecadal oscillation (AMO) index, is provided. In particular, the relationships of the two indices with some of its mechanistic drivers including the Atlantic meridional overturning circulation (AMOC) are investigated. In observations, the NASST index accounts for significant SST variability over the tropical and subpolar NA. The NASST index is shown to lump together SST variability originating from different mechanisms operating on different time scales. The AMO index emphasizes the subpolar SST variability. In the climate models, the SST-anomaly pattern associated with the NASST index is similar. The AMO index, however, only represents pronounced SST variability over the extratropical NA, and this variability is significantly linked to the AMOC. There is a sensitivity of this linkage to the cold NA SST bias observed in many climate models. Models suffering from a large cold bias exhibit a relatively weak linkage between the AMOC and AMO and vice versa. Finally, the basin-averaged SST in its unfiltered form, which has been used to question a strong influence of ocean dynamics on NA SST variability, mixes together multiple types of variability occurring on different time scales and therefore underemphasizes the role of ocean dynamics in the multidecadal variability of NA SSTs.

Beschreibung: This study examined the residential perceptions of industrial activities in Ilupeju, Lagos, Nigeria. The relevance of distance decay theory, which postulates that the magnitude of effects of the outputs from an industrial establishment would decrease with increasing distance from the point of origin, was tested in the study. Global Positioning System was used to capture the coordinates of the identified firms in Ilupeju. Additionally, two different sets of structured questionnaire were designed; the first set, which was distributed among the industrialists, sought information on the types of waste generated among others while the second set was randomly distributed among the residents and was used to elicit information on the types of pollution emanating from the industries, socioeconomic benefits, among others. The result shows that there is a significant variation in the perceived effects as people living within 0.5 km to the industrial sites claimed to suffer more pollution than those living 1.5 km away from the industrial sites, which is consistent with the distance decay theory. On the other hand, the distance decay theory cannot explain socioeconomic impacts such as increase in living costs, among others as they are felt around the study area irrespective of distance away from the industrial sites.

Beschreibung: Dissimilatory iron reduction and sulfate reduction are the most important processes for anaerobic mineralization of organic carbon in marine sediments. The thermodynamics and kinetics of microbial Fe(III) reduction depend on the characteristics of the Fe(III) minerals, which influence the potential of Fe(III)-reducers to compete with sulfate-reducers for common organic substrates. In the present study, we tested different methods to quantify and characterize microbially reducible Fe(III) in sediments from a transect in Kongsfjorden, Svalbard, using different standard sequential endpoint extractions and time-course extractions with either ascorbate or a Fe(III)-reducing microbial culture. Similar trends of increasing ‘reactive Fe’ content of the sediment along the fjord transect were found using the different extraction methods. However, the total amount of ‘reactive Fe’ extracted differed between the methods, due to different Fe dissolution mechanisms and different targeted Fe fractions. Time-course extractions additionally provided information on the reactivity and heterogeneity of the extracted Fe(III) minerals, which also impact the favorability for microbial reduction. Our results show which fractions of the existing Fe extraction protocols should be considered ‘reactive’ in the sense of being favorable for microbial Fe(III) reduction, which is important in studies on early diagenesis in marine sediments.

Beschreibung: Microbial metabolisms in sediments play a pivotal role in marine element cycling. In hydrothermal sediments chemosynthetic microorganisms likely prevail, while in non-hydrothermally impacted sediment regimes microorganisms associated with organic matter decomposition are primarily recognized. To test how these microorganisms are distributed along the hitherto neglected transition zone influenced to different degrees by hydrothermal input we sampled four sediment sites: these were (i) near an active vent, (ii) the outer rim, and (iii) the inactive area of the Kairei hydrothermal field as well as (iv) sediments roughly 200 km south-east of the Kairei field. Chemistry and microbial community compositions were different at all sampling sites. Against expectations, the sediments near the active vent did not host typical chemosynthetic microorganisms and chemistry did not indicate current, extensive hydrothermal venting. Data from the outer rim area of the active Kairei field suggested microbially mediated saponite production and diffuse hydrothermal flow from below accompanied by increased metal concentrations. A steep redox gradient in the inactive Kairei field points towards significant redox driven processes resulting in dissolution of hydrothermal precipitates and intense metal mobilization. Local microorganisms were primarily Chloroflexi, Bacillales, Thermoplasmata, and Thaumarchaeota.

Beschreibung: MILAN was a multidisciplinary, international study examining how the diel variability of sea-surface microlayer biogeochemical properties potentially impacts ocean-atmosphere interaction, in order to improve our understanding of this globally important process. The sea-surface microlayer (SML) at the air-sea interface is 〈 1 mm deep but it is physically, chemically and biologically distinct from the underlying water and the atmosphere above. Wind-driven turbulence and solar radiation are important drivers of SML physical and biogeochemical properties. Given that the SML is involved in all ocean-atmosphere exchanges of mass and energy, its response to solar radiation, especially in relation to how it regulates the air-sea exchange of climate-relevant gases and aerosols, is surprisingly poorly characterised. MILAN (sea-surface MIcroLAyer at Night) was an international, multidisciplinary campaign designed to specifically address this issue. In spring 2017, we deployed diverse sampling platforms (research vessels, radio-controlled catamaran, free-drifting buoy) to study full diel cycles in the coastal North Sea SML and in underlying water, and installed a land-based aerosol sampler. We also carried out concurrent ex situ experiments using several microsensors, a laboratory gas exchange tank, a solar simulator, and a sea spray simulation chamber. In this paper we outline the diversity of approaches employed and some initial results obtained during MILAN. Our observations of diel SML variability, e.g. the influence of changing solar radiation on the quantity and quality of organic material, and diel changes in wind intensity primarily forcing air-sea CO2 exchange, underline the value and the need of multidisciplinary campaigns for integrating SML complexity into the context of air-sea interaction.

Beschreibung: Mesoscale eddies can be strengthened by the absorption of submesoscale eddies resulting from mixed-layer baroclinic instabilities. This is shown for mesoscale eddies in the Agulhas Current system by investigating the kinetic energy cascade with a spectral and a coarse-graining approach in two model simulations of the Agulhas region. One simulation resolves mixed-layer baroclinic instabilities and one does not. When mixed-layer baroclinic instabilities are included, the largest submesoscale near-surface fluxes occur in winter-time in regions of strong mesoscale activity for upscale as well as downscale directions. The forward cascade at the smallest resolved scales occurs mainly in frontogenetic regions in the upper 30 m of the water column. In the Agulhas ring path, the forward cascade changes to an inverse cascade at a typical scale of mixed-layer eddies (15 km). At the same scale, the largest sources of the upscale flux occur. After the winter, the maximum of the upscale flux shifts to larger scales. Depending on the region, the kinetic energy reaches the mesoscales in spring or early summer aligned with the maximum of mesoscale kinetic energy. This indicates the importance of submesoscale flows for the mesoscale seasonal cycle. A case study shows that the underlying process is the mesoscale absorption of mixed-layer eddies. When mixed-layer baroclinic instabilities are not included in the simulation, the open-ocean upscale cascade in the Agulhas ring path is almost absent. This contributes to a 20 %-reduction of surface kinetic energy at mesoscales larger than 100 km when submesoscale dynamics are not resolved by the model.

Beschreibung: The structure, transport, and seasonal variability of the West Greenland boundary current system near Cape Farewell are investigated using a high-resolution mooring array deployed from 2014 to 2018. The boundary current system is comprised of three components: the West Greenland Coastal Current, which advects cold and fresh Upper Polar Water (UPW); the West Greenland Current, which transports warm and salty Irminger Water (IW) along the upper slope and UPW at the surface; and the Deep Western Boundary Current, which advects dense overflow waters. Labrador Sea Water (LSW) is prevalent at the seaward side of the array within an offshore recirculation gyre and at the base of the West Greenland Current. The 4-yr mean transport of the full boundary current system is 31.1 ± 7.4 Sv (1 Sv ≡ 106 m3 s-1), with no clear seasonal signal. However, the individual water mass components exhibit seasonal cycles in hydrographic properties and transport. LSW penetrates the boundary current locally, through entrainment/mixing from the adjacent re-circulation gyre, and also enters the current upstream in the Irminger Sea. IW is modified through air–sea interaction during winter along the length of its trajectory around the Irminger Sea, which converts some of the water to LSW. This, together with the seasonal increase in LSW entering the current, results in an anticorrelation in transport between these two water masses. The seasonality in UPW transport can be explained by remote wind forcing and subsequent adjustment via coastal trapped waves. Our results provide the first quantitatively robust observational description of the boundary current in the eastern Labrador Sea.

Beschreibung: Versatile peroxidase, a new family of ligninolytic peroxidases have catalytic properties of both lignin peroxidase and manganese peroxidase and has been isolated from citrus sinensis leaf extract which contains manganese peroxidase activity of 2.2 IU/ml and lignin peroxidase activity of 0.44 IU/ml. The overall recovery yield was 11 % with specific activity 1.0 IU/mg. Its molecular wt was found to be 24.60KDa. Km and Kcat value using veratryl alcohol and manganese sulphate as a substrate is 20 μM, 7.87sec and 12.5 μM, 13.84sec-1. The calculated pH optimum was 2.4 ± 0.1 for lignin peroxidase activity and 4.5 ± 0.1 for manganese peroxidase activity. The temperature optimum of the enzyme was 18°C for LiP and 25°C for MnP. Degradation of polyaromatic hydrocarbons like α-naphthol, β-naphthol, and 1,10-phenanthroline has been studied using UV/VIS spectrophotometer and cyclovoltameter at room temperature. Enzyme activity was inhibited by sodium azide and EDTA effectively.

Beschreibung: State of the climate in 2019

Beschreibung: Geoengineering is regarded by advocates as a creative and responsible technological option in the face of a climate emergency. Critics often see it as a hubristic attempt to play God, with disastrous consequences for the planet and humanity. These antipodal perspectives are represented by the ideal types of Prometheans and Gaians. Prometheans and Gaians typically talk past each other. The geoengineering debate can be made more fruitful by well articulating their respective positions and subsequently situating them in the discourse of sustainability. A sustainability orientation does not answer the troubling question whether geoengineering should be developed and deployed. But it can foster a ‘fusion of horizons’ between Prometheans and Gaians, providing common ground in an otherwise polarized debate and making a more productive dialogue possible.

Beschreibung: Hydroacoustic and optical remote sensing have been commonly used to map shallow nearshore benthic features. However, the number, type, scale, and accuracy of the mapping products that can be obtained from the two sensors differ; as such, there can be limited agreement between their mapping products. These differences can be further accentuated if the hydroacoustic data are interpolated to produce a map. Interpolation introduces spatial uncertainty and reduces map accuracy. Consequently, maps generated from the two sensors may provide dissimilar spatial and temporal representations of the same benthic features. We therefore compared the performance of a random forest regression (RFr) and a universal kriging (UK) interpolation method and a post-classification enhancement that can be used to increase the accuracy and complementarity of benthic habitat maps derived from hydroacoustic data. First, we used single beam echosounder (SBES) survey bathymetry data from the Bluefields Bay marine protected area (MPA) in western Jamaica (13.82 km2 in size), to create a bathymetric surface model (BSM), from which rugosity and bathymetric position index (BPI) maps were generated. Next, the RFr was used to create submerged aquatic vegetation (SAV) percentage cover maps from the SBES SAV cover data by predicting cover at un-sampled locations. Predictors included auxiliary data such as depth, BPI, survey points coordinates and radiometrically corrected, deglinted and water column corrected image reflectance index values from each of the following: WorldView-2, Geoeye-1 and Landsat 8. Additionally, a SAV map was created using the UK. The most accurate SAV cover thresholds were identified and were used to create binary maps from the RFr and UK maps. A rugosity derived coral reef map was then added to the binary maps. The resulting benthic habitat maps had comparable accuracies and class coverage to benthic maps classified from GeoEye-1 and WorldView-2 images using pixel and object-based classifiers. However, map accuracies were calculated using a suboptimal number of reference points (〈50) for two of the benthic map classes (SAV absent and coral reef). This was not considered to be problematic as the addition of the coral reef class to the binary maps resulted in a significant decrease in uncertainty (standard error and confidence interval width of the overall accuracy) and a significant increase in the user’s accuracy of the SAV absent map class. Also, the difference in uncertainty and accuracy between the map classes did not change. The methods used in this study can therefore be used to increase the accuracy (and to decrease the uncertainty) and the complementarity of maps derived from hydroacoustic data.

Beschreibung: A series of triaxial compression tests of frozen sandy soil are carried out under five confining pressures (1 MPa, 4 MPa, 6 MPa, 8 MPa and 10 MPa) at –6 °C. By comparing the grain size distribution curves of frozen sandy soil before and after shearing, it is found that significant particle breakage can occur during triaxial shearing. Particle breakage changes internal structure of geomaterials and has a significant effect on their stress–strain relationships. In order to accurately describe the effect of particle breakage of frozen sandy soil on the stress–strain relationships, an elastoplastic constitutive model for frozen sandy soil considering particle breakage is proposed. Based on the energy balance equation established by Indraratna and Salim, the constant critical state stress ratio (Mcr) in the energy balance equation is modified to the stress ratio (M) which changed with shear strain during the shearing process. A yield function, considering particle breakage, is proposed using the modified energy balance equation. The hardening law is determined based on the rebound test results of frozen sandy soil, and the associated flow rule is adopted in the model. Compared with experimental data, the model can well simulate the stress–strain relationships under different confining pressures for frozen sandy soil. • Highlights • The particle breakage characteristics of frozen sandy soil are studied. • The energy balance equation considering particle breakage is modified to calculate the energy dissipation of frozen sandy soil. • An elastoplastic constitutive model for frozen sandy soil considering particle breakage is proposed.

Beschreibung: A simple analytical model of the atmospheric boundary layer (ABL) coupled to sea ice is presented. It describes clear-sky cooling over sea ice during polar night in the presence of leads. The model solutions show that the sea ice concentration and wind speed have a strong impact on the thermal regime over sea ice. Leads cause both a warming of the ABL and an increase of stability over sea ice. The model describes a sharp ABL transition from a weakly stable coupled state to a strongly stable decoupled state when wind speed is decreasing. The threshold value of the transition wind speed is a function of sea ice concentration. The decoupled state is characterized by a large air–surface temperature difference over sea ice, which is further increased by leads. In the coupled regime, air and surface temperatures increase almost linearly with wind speed due to warming by leads and also slower cooling of the ABL. The cooling time scale shows a nonmonotonic dependency on wind speed, being lowest for the threshold value of wind speed and increasing for weak and strong winds. Theoretical solutions agree well with results of a more realistic single-column model and with observations performed at the three Russian “North Pole” drifting stations (NP-35, -37, and -39) and at the Surface Heat Budget of the Arctic Ocean ice camp. Both modeling results and observations show a strong implicit dependency of the net longwave radiative flux at the surface on wind speed.

Beschreibung: The last extended time period when climate may have been warmer than today was during the Last Interglacial (LIG; ca. 129 to 120 thousand years ago). However, a global view of LIG precipitation is lacking. Here, seven new LIG climate models are compared to the first global database of proxies for LIG precipitation. In this way, models are assessed in their ability to capture important hydroclimatic processes during a different climate. The models can reproduce the proxy-based positive precipitation anomalies from the preindustrial period over much of the boreal continents. Over the Southern Hemisphere, proxy-model agreement is partial. In models, LIG boreal monsoons have 42% wider area than in the preindustrial and produce 55% more precipitation and 50% more extreme precipitation. Austral monsoons are weaker. The mechanisms behind these changes are consistent with stronger summer radiative forcing over boreal high latitudes and with the associated higher temperatures during the LIG.

Beschreibung: Surfactant-mediated extraction (SME), pressurized liquid extraction (PLE), and enzyme-assisted extraction (EAE) have been compared to improve the isolation of phlorotannins from the brown algae Lobophora variegata. Enzymatic treatment with Alcalase 2.4 L FG, Carezyme 4500 L, protease from Streptomyces griseus, pectinase from Aspergillus niger, Celluclast 1.5 L, protease from Bacillus licheniformis; surfactant extraction with triacetin and guaiacol and PLE with ethanol:water as extracting solvent, have been studied in terms of total phenolic content by the Folin–Ciocalteu method and total phlorotannin content using the DMBA assay. The results showed that SME yields the highest amount of phenols and phlorotannins by using food grade guaiacol as the surfactant. An extraction protocol was developed to maximize the amount of extract obtained from L. variegata. The effects of various parameters such as the type of surfactant, efficacy of surfactant, and optimum pH, on the extraction efficiency of polyphenols were examined. The simultaneous use of the enzyme and surfactant was also investigated. However, a synergistic effect between the enzymes and the surfactant for the extraction of polyphenols has not been observed. Considering total phenols and total phlorotannins in the extract, the extraction yield were obtained for total phenols as SME 〉 EAE 〉 PLE and for total phlorotannins as SME 〉 PLE 〉 EAE.

Beschreibung: The Ponto-Caspian round goby (Neogobius melanostomus Pallas, 1814) is a prominent invasive species in many European waters. Eggs of the Western Baltic Spring Spawning Atlantic herring might be attractive prey for the invasive round goby during the spawning season. However, investigations of the small fish fauna in an important spawning area of herring, which was characterized by high densities of macrophytes, indicated a spatio-temporal mismatch of round goby and herring spawn in spring, at least on some of the known important spawning beds situated on vegetated sandy bottoms. In contrast, a spatio-temporal overlap between round gobies and herring spawn was observed in a more structured area, characterized with stones, where round gobies’ stomachs were sampled. Further field study results suggest that large round gobies (〉 10 cm) do not feed on herring eggs, while smaller round gobies (〈 10 cm) do so. To support these results, we conducted laboratory feeding experiments with round gobies. When C. crangon, M. edulis and herring eggs were offered simultaneously, round gobies preferred C. crangon. M. edulis was preferred over herring eggs when C. crangon was absent. The predatory impact of the round goby on herring eggs seems to be of minor importance compared to other species, such as three-spined stickleback or perch. Applying the same data, different food ‘preference indices’ revealed a discrepancy in preference between indices. Therefore, we propose a modified food preference index (mE), taking into account four important parameters and combining benefits of two commonly applied indices.

Beschreibung: Gas hydrates continue to attract enormous attention throughout the energy industry, as both a hindrance in conventional production and a substantial unconventional resource. Scientists continue to be fascinated by the hydrates’ ability of sequestering large amounts of hydrophobic gases, unusual thermal transport properties and unique molecular structures. Technologically, clathrate hydrates promise advantages in applications as diverse as carbon sequestration and water desalination. The communities interested in hydrates span traditional academic disciplines, including earth science, physical chemistry and petroleum engineering. The studies on this field are equally diverse, including field expeditions to attempt the production of natural gas from hydrate deposits accumulated naturally on the seafloor, to lab-scale studies to exchange CO2 for CH4 in hydrates; from theoretical studies to understand the stability of hydrates depending on the guest molecules, to molecular simulations probing nucleation mechanisms. This review highlights a few fundamental questions, with focus on knowledge gaps representing some of the barriers that must be addressed to enable growth in the practical applications of hydrate technology, including natural gas storage, water desalination, CO2 – CH4 exchange in hydrate deposits and prevention of hydrate plugs in conventional energy transportation.

Beschreibung: Variations in Earth’s orbit pace the glacial-interglacial cycles of the Quaternary, but the mechanisms that transform regional and seasonal variations in solar insolation into glacial-interglacial cycles are still elusive. Here, we present transient simulations of coevolution of climate, ice sheets, and carbon cycle over the past 3 million years. We show that a gradual lowering of atmospheric CO2 and regolith removal are essential to reproduce the evolution of climate variability over the Quaternary. The long-term CO2 decrease leads to the initiation of Northern Hemisphere glaciation and an increase in the amplitude of glacial-interglacial variations, while the combined effect of CO2 decline and regolith removal controls the timing of the transition from a 41,000- to 100,000-year world. Our results suggest that the current CO2 concentration is unprecedented over the past 3 million years and that global temperature never exceeded the preindustrial value by more than 2°C during the Quaternary.

Beschreibung: Fermentation plays a fundamental role in organic carbon degradation on a global scale. However, little is known about how environmental variables influence this process. In a step towards quantifying how temperature and composition influence fermentation, we have calculated the Gibbs energies of 47 fermentation reaction, ΔGr, from 0–150 °C for a broad range of compositions representing microbial habitats as variable as sediments, estuaries, soils, and crustal rocks. The organic compounds in these reactions include amino acids, nucleic acid bases, monosaccharides, carboxylates, methanogenic compounds and more. The amount of energy available varies considerably, from +54 kJ (mol C)−1 for palmitate fermentation, to −184 kJ (mol C)−1 for methylamine disproportionation. For some reactions, there is little difference in ΔGr between low and high energy systems (e.g., the monosaccharide reactions) while others span a much broader range (e.g., the nucleic acid bases). There is no clear-cut trend between exergonicity and temperature, and the values of standard state Gibbs energies of reactions, ΔG0r, for nearly half of the reactions lie outside the range of ΔGr values. To carry out some of these calculations, the thermodynamic properties for six organic compounds were estimated: dimethylamine, trimethylamine, resorcinol, phloroglucinol and cyclohexane carboxylate and its conjugate acid.

Beschreibung: As an emerging technology, hyperspectral imaging (HSI), which combines both advanced spectroscopy and imaging techniques, provides sufficient information for spectral and spatial analysis and is thus suitable for distribution and property investigation of nanoscale materials. Considering the applications of HSI have spread from remote sensing to quality control of macro products such as food and milk, this article reviews recent research of HSI in a new field of nanoscale materials. On the basis of fundamental parts of a HSI system, new techniques fitting specifically for nanoscale materials imaging such as dark field and Raman spectroscopy are introduced. Nanoscale materials, including metal nanoparticles, carbon nanotubes and graphene, biological components in cells and tissues, as well as multi-layer nanoscale materials, are the research hotspots utilizing HSI technology. Related research reports of the above materials are reviewed based on the physical distinction of these nanoscale materials. It is believed that HSI technology is a strongly potential technique for property investigation and manipulation of nanomaterial for various applications.

Beschreibung: Proxy data and observations suggest that large tropical volcanic eruptions induce a poleward shift of the North Atlantic jet stream in boreal winter. However, there is far from universal agreement in models on this effect and its mechanism, and the possibilities of a corresponding jet shift in the Southern Hemisphere or the summer season have received little attention. Using a hierarchy of simplified atmospheric models, this study examines the impact of stratospheric aerosol on the extratropical circulation over the annual cycle. In particular, the models allow the separation of the dominant shortwave (surface cooling) and longwave (stratospheric warming) impacts of volcanic aerosol. It is found that stratospheric warming shifts the jet poleward in both summer and winter hemispheres. The experiments cannot definitively rule out the role of surface cooling, but provide no evidence that it shifts the jet poleward. Further study with simplified models demonstrates that the response to stratospheric warming is remarkably generic and does not depend critically on the boundary conditions (e.g., the planetary wave forcing) or the atmospheric physics (e.g., the treatment of radiative transfer and moist processes). It does, however, fundamentally involve both zonal-mean and eddy circulation feedbacks. The timescales, seasonality, and structure of the response provide further insight into the mechanism, as well as its connection to modes of intrinsic natural variability. These findings have implications for the interpretation of comprehensive model studies and for post-volcanic prediction

Beschreibung: To provide an observational basis for the Intergovernmental Panel on Climate Change projections of a slowing Atlantic meridional overturning circulation (MOC) in the 21st century, the Overturning in the Subpolar North Atlantic Program (OSNAP) observing system was launched in the summer of 2014. The first 21-month record reveals a highly variable overturning circulation responsible for the majority of the heat and freshwater transport across the OSNAP line. In a departure from the prevailing view that changes in deep water formation in the Labrador Sea dominate MOC variability, these results suggest that the conversion of warm, salty, shallow Atlantic waters into colder, fresher, deep waters that move southward in the Irminger and Iceland basins is largely responsible for overturning and its variability in the subpolar basin.

Beschreibung: DNA barcoding analysis, using tufA, revealed considerable differences between the expected and observed species inventory of Ulva sensu lato in the Baltic and North Sea areas of the German state of Schleswig-Holstein. Of 20 observed genetic entities, at least four (U. australis, U. californica, U. gigantea and Umbraulva dangeardii) had been introduced recently, whereas three others (one Ulva sp. and two Blidingia spp.) could not be identified at the species level and could also represent recently introduced species. In addition, the observed distributions of Kornmannia leptoderma and U. rigida were much more extensive than indicated by historical records, whereas Blidingia minima and Gayralia oxysperma were absent or much less common than expected. Barcoding analysis also revealed that both U. tenera (type material) and U. pseudocurvata (historical vouchers) from Helgoland, an off-shore island in the North Sea, actually belong to U. lactuca, a species that appears to be restricted to this island. Furthermore, past morphological descriptions of U. intestinalis and U. compressa have apparently been too restrictive and have been responsible for numerous misidentifications. The same is true for U. linza, which, in northern Germany, clusters into two genetically closely related but morphologically indistinguishable entities. One of these entities is present on Helgoland, while the second is present on North Sea and Baltic Sea mainland coasts.

Beschreibung: To resolve historical misinterpretations of species descriptions and to comprehend the morphological diversity together with the distribution of Ulva compressa Linnaeus in northern Germany, a morphological and molecular study was undertaken of recently collected specimens and herbarium vouchers. Phylogenetic analyses from sequences of the plastid encoded tufA gene confirmed that U. compressa is abundant along the German Baltic Sea and North Sea coasts. We were able to genetically confirm the presence of U. compressa in the Baltic Sea below salinities of 15 PSU. However, we detected morphologies agreeing with the attached and branched tubular type material only in the North Sea, while U. compressa on Baltic Sea coasts indiscriminately exhibited a very distinct morphology of sheet-like thalli that were always unattached, with the exception of one collection site. Drifting forms were also frequently detected in the Wadden Sea, but not on the island of Helgoland. The tufA sequences of attached and tubular forms of U. compressa from the German Wadden Sea were identical to the drifting sheets found in the Wadden and Baltic Seas and the sequence divergence was extremely small at ≤0.9%. The proliferating, blade-like thalli of U. compressa appear as a nuisance ecotype that is able to form massive accumulations associated with oxygen depletion. Mass accumulations were observed to cause severe damage and increased mortality of habitat forming Zostera and Ruppia populations.

Beschreibung: To model tracer spreading in the ocean, Lagrangian simulations in an offline framework are a practical and efficient alternative to solving the advective–diffusive tracer equations online. Differences in both approaches raise the question of whether both methods are comparable. Lagrangian simulations usually use model output averaged in time, and trajectories are not subject to parameterized subgrid diffusion, which is included in the advection–diffusion equations of ocean models. Previous studies focused on diffusivity estimates in idealized models but could show that both methods yield similar results as long as the deformations-scale dynamics are resolved and a sufficient amount of Lagrangian particles is used. This study compares spreading of an Eulerian tracer simulated online and a cloud of Lagrangian particles simulated offline with velocities from the same ocean model. We use a global, eddy-resolving ocean model featuring 1/20° horizontal resolution in the Agulhas region around South Africa. Tracer and particles were released at one time step in the Cape Basin and below the mixed layer and integrated for 3 years. Large-scale diagnostics, like mean pathways of floats and tracer, are almost identical and 1D horizontal distributions show no significant differences. Differences in vertical distributions, seen in a reduced vertical spreading and downward displacement of particles, are due to the combined effect of unresolved subdaily variability of the vertical velocities and the spatial variation of vertical diffusivity. This, in turn, has a small impact on the horizontal spreading behavior. The estimates of eddy diffusivity from particles and tracer yield comparable results of about 4000 m2 s−1 in the Cape Basin.

Beschreibung: We quantify the oceanic sink for anthropogenic carbon dioxide (CO 2 ) over the period 1994 to 2007 by using observations from the global repeat hydrography program and contrasting them to observations from the 1990s. Using a linear regression–based method, we find a global increase in the anthropogenic CO 2 inventory of 34 ± 4 petagrams of carbon (Pg C) between 1994 and 2007. This is equivalent to an average uptake rate of 2.6 ± 0.3 Pg C year −1 and represents 31 ± 4% of the global anthropogenic CO 2 emissions over this period. Although this global ocean sink estimate is consistent with the expectation of the ocean uptake having increased in proportion to the rise in atmospheric CO 2 , substantial regional differences in storage rate are found, likely owing to climate variability–driven changes in ocean circulation.

Beschreibung: Satellite observations and output from a high-resolution ocean model are used to investigate how the Loop Current in the Gulf of Mexico affects the Gulf Stream transport through the Florida Straits. We find that the expansion (contraction) of the Loop Current leads to lower (higher) transports through the Straits of Florida. The associated surface velocity anomalies are coherent from the southwestern tip of Florida to Cape Hatteras. A simple continuity-based argument can be used to explain the link between the Loop Current and the downstream Gulf Stream transport: as the Loop Current lengthens (shortens) its path in the Gulf of Mexico, the flow out of the Gulf decreases (increases). Anomalies in the surface velocity field are first seen to the southwest of Florida and within 4 weeks propagate through the Florida Straits up to Cape Hatteras and into the Gulf Stream Extension. In both the observations and the model this propagation can be seen as pulses in the surface velocities. We estimate that the Loop Current variability can be linked to a variability of several Sverdrups (1Sv = 10(6) m(3) s(-1)) through the Florida Straits. The exact timing of the Loop Current variability is largely unpredictable beyond a few weeks and its variability is therefore likely a major contributor to the chaotic/intrinsic variability of the Gulf Stream. However, the time lag between the Loop Current and the flow downstream of the Gulf of Mexico means that if a lengthening/shortening of the Loop Current is observed this introduces some predictability in the downstream flow for a few weeks.

Beschreibung: Cytospora is a genus including important phytopathogens causing severe dieback and canker diseases distributed worldwide with a wide host range. However, identification of Cytospora species is difficult since the currently available DNA sequence data are insufficient. Aside the limited availability of ex-type sequence data, most of the genetic work is only based on the ITS region DNA marker which lacks the resolution to delineate to the species level in Cytospora. In this study, three fresh strains were isolated from the symptomatic branches of Elaeagnus angustifolia in Xinjiang Uygur Autonomous Region, China. Morphological observation and multi-locus phylogenetic analyses (ITS, LSU, ACT and RPB2) support these specimens are best accommodated as a distinct novel species of Cytospora. Cytospora elaeagnicola sp. nov. is introduced, having discoid, nearly flat, pycnidial conidiomata with hyaline, allantoid conidia, and differs from its relatives genetically and by host association.

Beschreibung: The long-term trend of diurnal temperature range (DTR) over Nigeria was examined using daily station-based datasets for the period 1971–2013. The results show that the regionally averaged DTR has decreased significantly (−0.34°C per decade) over the Nigerian Sahel (north of 10°N), but there has been a slight increasing trend (0.01°C per decade) over the Nigerian Guinea Coast. The annual decreasing trend of DTR in the Nigerian Sahel is mainly attributable to the significant increasing trend in daily minimum temperature (Tmin, 0.51°C per decade), which far outstrips the rate of increase in the daily maximum (Tmax, 0.17°C per decade). In contrast, the comparable trends in Tmin (0.19°C per decade) and Tmax (0.20°C per decade) may explain the non-significant trend of the DTR averaged over the Guinea Coast region. It is observed that the DTR has decreased more in boreal summer (June–July–August) than in boreal winter (December–January–February) for the regions. Furthermore, it is found that the significant DTR declining trend over the Nigerian Sahel is closely associated with an increasing trend of annual and summer precipitation in the region, but the increasing DTR trend in the Nigerian Guinea Coast region can be attributed to the decreasing trend of cloud cover over the region.