Alfred Wegener Institute for Polar and Marine Research
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Hygroscopic aerosols amplify longwave downward radiation in the Arctic
Full text linkThis study investigates the impact of hygroscopic aerosols, such as sea salt and sulfate, on longwave downward radiation in the Arctic. These aerosols absorb atmospheric water vapor, leading to wet growth, increased size, and enhanced longwave downward radiation emission, defined as the aerosol infrared radiation effect. Observations of aerosols, especially their composition, are challenging during the Arctic winter. We use an emission Fourier transform spectrometer to measure aerosol composition. Observations show that the aerosol infrared radiation effect of dry aerosols is limited to about 1.45±2.00 W m−2. Wet growth significantly increases this effect. During winter, at relative humidity levels between 60 % and 80 %, wet aerosols exhibit effects approximately 7 times greater than dry aerosols. When relative humidity exceeds 80 %, the effect can be up to 20 times higher. Sea salt aerosols in Ny-Ålesund demonstrate high effect values, while non-hygroscopic aerosols like black carbon and dust show consistently low values. Reanalysis data indicate increased water vapor and sea salt aerosol optical depth in Ny-Ålesund after 2000, correlating with significant positive temperature anomalies in this area. Moreover, wet aerosols can remain activated even in dry environments, continuously contributing high effects, thereby expanding the area affected by aerosol-induced warming. This warming effect may exacerbate Arctic warming, acting as a positive feedback mechanism
Morpho-phylogenetic and toxicological characterisation of Pseudo-nitzschia multiseries from the Sea of Marmara (Türkiye)
No full textPseudo-nitzschia multiseries is a diatom known for producing domoic acid (DA), a neurotoxin that can cause Amnesic Shellfish Poisoning (ASP), which poses risks to both marine life and human health. This study reports the first detailed investigation of P. multiseries in the Sea of Marmara, focusing on its morphology, phylogeny, and toxin production. Morphological analysis using light and electron microscopy confirmed key diagnostic features consistent with P. multiseries. Phylogenetic analysis, focusing on ITS and LSU gene sequences, showed a close genetic relationship between the Turkish strain and other strains of P. multiseries. Domoic acid levels, quantified using LC-MS/MS during exponential and stationary growth phases, ranged between 2.46 and 3.24 pg cell−1, with minor amounts of isoDA (A, D and E) also detected. These findings highlight the importance of monitoring P. multiseries in Turkish coastal waters due to its significant potential for DA production. This study provides valuable insights into the morphology, phylogeny, and toxin production of P. multiseries, as well as its potential implications for management of marine resources and public health protection. It offers a comprehensive examination of this potentially toxic diatom species in Turkish coastal waters
Vibrio are a potential source of novel colistin-resistance genes in European coastal environments
Full text linkColistin is a widespread last resort antibiotic for treatment of multidrug-resistant bacteria. The recent worldwide emergence of colistin resistance (Col-R) conferred by mcr-1 in human pathogens has raised concern, but the putative sources and reservoirs of novel mcr genes in the marine environment remain underexplored. We observed a high prevalence of Col-R, particularly in Vibrio isolated from European coastal waters by using the same cohorts of oysters as bioaccumulators in three sites across Europe. The high sequence diversity found in the mcr/eptA gene family was geographically structured, particularly for three novel eptA gene variants, which were restricted to the Mediterranean (France, Spain) and occurred as a dgkA-eptA operon. The RstA/RstB two component system was shown to control both the dgkA-eptA operon and the Col-R phenotype. The analysis of 29 427 Vibrionaceae genomes revealed that this mechanism of intrinsic resistance is prevalent and specific to the Harveyi clade, which includes the human pathogens Vibrio parahaemolyticus and Vibrio alginolyticus. The operon conferred colistin-resistance when transferred to sensitive non-Vibrio strains. In general, eptA gene variants are widespread and evolved with the Vibrio lineage. They occur in clade-specific genomic environments, suggesting that eptA expression responds to distinct environmental signals across the Vibrio phylogeny. However, we also identified mobile eptA paralogues that have been recently transferred between and within Vibrio clades. This highlights Vibrio as a potential source of Col-R mechanisms, emphasizing the need for enhanced surveillance to prevent colistin-resistant infections in coastal areas
Impact of wildfire smoke on Arctic cirrus formation – Part 1: Analysis of MOSAiC 2019–2020 observations
Full text linkThe potential impact of wildfire smoke on Arctic cirrus formation is discussed based on lidar and radar observations during the winter half year of the 1-year MOSAiC (Multidisciplinary drifting Observatory for the Study of Arctic Climate) expedition. Aerosol and ice cloud observations were performed aboard the icebreaker Polarstern at latitudes > 85° N. Aged Siberian wildfire smoke polluted the tropopause region over the central Arctic during the entire winter half year of 2019-2020. The smoke particle surface area concentration at the tropopause was of the order of 5-15 μm2cm-3 and indicated considerably enhanced levels of aerosol pollution for more than 6 months. Numerous cirrus systems with cloud-top temperatures between -60 and -75 °C developed in the polluted upper troposphere. We analyzed all MOSAiC winter cirrus layers with respect to their geometrical and optical properties and a subgroup of 20 cirrus events with respect to their ice water content (IWC) and ice crystal number concentration (ICNC). In individual ice fallstreaks that are connected to individual ice nucleation events, ICNCs typically ranged from 1 to 10 crystals L-1 but were frequently also as high as 20-50 L-1; however, observations > 100 L-1 were rare. Three observational facts corroborate our hypothesis that smoke significantly influenced Arctic cirrus formation: (1) the occurrence of a long-lasting, persistent smoke pollution layer in the upper troposphere so that favorable conditions for heterogeneous ice nucleation on smoke particles were always given and, at the same time, homogeneous freezing of background aerosol was probably widely suppressed; (2) the high smoke particle surface area concentrations, which were high enough to significantly trigger ice nucleation on smoke particles (as shown in Part 2, the companion paper to this article; ); and (3) the frequently found maximum cirrus ice saturation ratios of 1.3-1.5, which point to the dominance of heterogeneous ice nucleation processes, initiated by inefficient ice-nucleating particles (INPs), as expected when aged smoke particles (i.e., organic aerosol particles) serve as INPs. The studies are continued in the simulation portion of this work (Part 2; Ansmann et al., 2025)
Calm ocean, stormy sea: atmospheric and oceanographic observations of the Atlantic during the Atlantic References and Convection (ARC) ship campaign
Full text linkDuring the Atlantic References and Convection (ARC) ship campaign with the reference MSM114/2, which took place in early 2023, the German research vessel Maria S. Merian travelled from Mindelo, Cape Verde, to Punta Arenas, Chile. One of the main objectives of ARC was to obtain vertically resolved cross sections of the Intertropical Convergence Zone (ITCZ). To this end, we crossed the ITCZ three times in the meridional direction. We present the atmospheric and oceanographic measurements collected during ARC in a standardised way to facilitate working with data from different instruments and to make the data easily accessible. This approach is not limited to ARC but could serve as a prototype for future (and past) ship campaigns. We present data from the integrated ship sensors (DSHIP); a humidity and temperature profiler (HATPRO); a ceilometer; aerosol instruments (DustTrak, Microtops, and Calitoo); radiosondes; uncrewed aircraft vehicles (UAVs); and conductivity, temperature, and depth (CTD) profiles of the upper ocean. We distinguish between temporal continuous data (DSHIP, HATPRO, Ceilometer, and DustTrak) from point measurements (radiosondes, UAVs, CTDs, Calitoo, and Microtops). To illustrate the data sets provided, we present examples of measurements taken during the three crossings of the ITCZ and during a storm in the Roaring Forties in the South Atlantic at the end of the campaign. An overview of all available data sets, including DOIs and download links, can be found in with the DOI 10.1594/PANGAEA.966616. For references to the individual data sets, please refer to the "Data availability"section
Falkland/Malvinas Trough: Indications for Cenozoic tectonic and oceanographic evolution in the southwestern South Atlantic
No full textThe Falkland/Malvinas Trough (F/MT) bounds the southern extremity of the Falkland/Malvinas Plateau. This
Cenozoic bathymetric depression developed as the orogenic foreland basin of the North Scotia Ridge. The
sedimentary infill of the F/MT carries a history of development in a transpressional setting along the South
American-Scotian Plate boundary, in association with the evolution of the Drake Passage-Scotia Sea zone. Since
the F/MT is located on the pathway of the Antarctic Circumpolar Current, the current-controlled depositional
and erosional features within its sedimentary infill provide valuable information on the palaeoceanographic
modifications in the southwestern South Atlantic. Via a set of 2D high-resolution seismic reflection data, the
structural and morphological features of these strata are investigated and discussed with respect to the tectonic
evolution of the Drake Passage-Scotia Sea zone. Evidence of fold structures and normal faulting during Oligocene
to mid-Miocene times in the study area argue for a transpressional regime linked with the development of the
Drake Passage-Scotia Sea zone. The current-related depositional and erosional processes in the F/MT started
between Oligocene to early Miocene times. With the full opening of the Drake Passage, the evolution of the Scotia
Sea and the demise of the Ancestral South Sandwich Arc by the mid-Miocene, an oceanographic setting analogous
to the present would have established. Evidences suggests that since then, with the enhancement of the
abyssal circulation subsequent to the perennial Antarctic glaciation, a precursor of the Weddell Sea Deep Water
has been circulating the F/MT, shaping a confined sediment drift deposit
A Review of Abrupt Permafrost Thaw: Definitions, Usage, and a Proposed Conceptual Framework
Full text linkPurpose of Review: We review how ‘abrupt thaw’ has been used in published studies, compare these definitions to abrupt processes in other Earth science disciplines, and provide a definitive framework for how abrupt thaw should be used in the context of permafrost science
Recent Findings: We address several aspects of permafrost systems necessary for abrupt thaw to occur and propose a framework for classifying permafrost processes as abrupt thaw in the future. Based on a literature review and our collective expertise, we propose that abrupt thaw refers to thaw processes that lead to a substantial persistent environmental change within a few decades. Abrupt thaw typically occurs in ice-rich permafrost but may be initiated in ice-poor permafrost by external factors such as hydrologic change (i.e., increased streamflow, soil moisture fluctuations, altered groundwater recharge) or wildfire.
Summary: Permafrost thaw alters greenhouse gas emissions, soil and vegetation properties, and hydrologic flow, threatening infrastructure and the cultures and livelihoods of northern communities. The term ‘abrupt thaw’ has emerged in scientific discourse over the past two decades to differentiate processes that rapidly impact large depths of permafrost, such as thermokarst, from more gradual, top-down thaw processes that impact centimeters of near-surface permafrost over years to decades. However, there has been no formal definition for abrupt thaw and its use in the scientific literature has varied considerably. Our standardized definition of abrupt thaw offers a path forward to better understand drivers and patterns of abrupt thaw and its consequences for global greenhouse gas budgets, impacts to infrastructure and land-use, and Arctic policy- and decision-making
Phase and gain stability for adaptive dynamical networks
Full text linkIn adaptive dynamical networks, the dynamics of the nodes and the edges influence each other. We show that we can treat such systems as a closed feedback loop between edge and node dynamics. Using recent advances on the stability of feedback systems from control theory, we derive local, sufficient conditions for steady states of such systems to be linearly stable. These conditions are local in the sense that they are written entirely in terms of the (linearized) behavior of the edges and nodes. We apply these conditions to the Kuramoto model with inertia written in an adaptive form and the adaptive Kuramoto model. For the former, we recover a classic result, and for the latter, we show that our sufficient conditions match necessary conditions where the latter are available, thus completely settling the question of linear stability in this setting. The method we introduce can be readily applied to a vast class of systems. It enables straightforward evaluation of stability in highly heterogeneous systems
Investigating the influence of tourism on the Wadden Sea using a multi-layer social-ecological network
Full text linkCoastal zones are the epicentre of significant social, cultural, and economic development worldwide. A human activity with increasing importance for coastal ecosystems is the expanding tourism sector, a core economic activity, one of the fastest-growing sectors worldwide and included in the list of cultural ecosystem services. The World Heritage Site of the Wadden Sea, located in the south-eastern North Sea, belongs to the coastal ecosystems of outstanding value and is a highly attractive area for tourism. Given the complexity of potential ecological, social, and socio-economic relationships involved in tourism, single-discipline studies fall short in capturing the full range of interactions between tourism's economic value and its ecological influences. To bridge the gap between these social and ecological aspects, a comprehensive approach utilising Social-Ecological Systems (SES) has been suggested by different authors and employed to study human-nature linkages. Social-ecological networks (SENs) provide a suitable tool to study SES, utilising language, methods, and models common in both natural and social sciences. Hence, we used a SEN approach to study tourism's ecological, and socio-economic relations in the Wadden Sea with the aim to provide a holistic picture of the relationships between tourism and ecological nodes, socio-economic nodes, other ecosystem services, and threats that might influence the area's natural value. We constructed a multi-layer social-ecological network with 30 nodes and 147 edges representing to our knowledge the first SEN approach in the Wadden Sea. With a total degree of 37, tourism was the most connected node in the SEN, with numerous direct and indirect relationships to nodes from the same and other layers indicating a huge potential for cascade effects. Furthermore, we identified 12 loops in the network related to tourism that could result in positive or negative feedbacks. Furthermore, critical data and knowledge gaps were revealed to fully capture the complexity of tourism interaction in the Wadden Sea. By highlighting the interconnectedness of tourism, ecosystem services, and anthropogenic threats, this study provides guidance for sustainable management practices that can preserve the Wadden Sea for future generations
