Alfred Wegener Institute for Polar and Marine Research
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Multi-year simulations at kilometre scale with the Integrated Forecasting System coupled to FESOM2.5 and NEMOv3.4
Get PDFWe report on the first multi-year kilometre-scale global coupled simulations using ECMWF's Integrated Forecasting System (IFS) coupled to both the NEMO and FESOM ocean-sea ice models, as part of the H2020 Next Generation Earth Modelling Systems (nextGEMS) project. We focus mainly on an unprecedented IFS-FESOM coupled setup, with an atmospheric resolution of 4.4 km and a spatially varying ocean resolution that reaches locally below 5 km grid spacing. A shorter coupled IFS-FESOM simulation with an atmospheric resolution of 2.8 km has also been performed. A number of shortcomings in the original numerical weather prediction (NWP)-focused model configurations were identified and mitigated over several cycles collaboratively by the modelling centres, academia, and the wider nextGEMS community. The main improvements are (i) better conservation properties of the coupled model system in terms of water and energy budgets, which also benefit ECMWF's operational 9 km IFS-NEMO model; (ii) a realistic top-of-the-atmosphere (TOA) radiation balance throughout the year; (iii) improved intense precipitation characteristics; and (iv) eddy-resolving features in large parts of the mid- and high-latitude oceans (finer than 5 km grid spacing) to resolve mesoscale eddies and sea ice leads. New developments at ECMWF for a better representation of snow and land use, including a dedicated scheme for urban areas, were also tested on multi-year timescales. We provide first examples of significant advances in the realism and thus opportunities of these kilometre-scale simulations, such as a clear imprint of resolved Arctic sea ice leads on atmospheric temperature, impacts of kilometre-scale urban areas on the diurnal temperature cycle in cities, and better propagation and symmetry characteristics of the Madden-Julian Oscillation
Prey dynamics as a buffer: Enhancing copepod resilience to Ocean Alkalinity Enhancement
Get PDFOcean alkalinity enhancement (OAE) aims to counteract climate change by increasing the ocean’s carbon storage capacity through the addition of alkaline substances into seawater. However, this process alters seawater chemistry, increasing total alkalinity and pH, which can directly influence marine organisms’ metabolic activities or indirectly impact them through changes in prey availability and quality. This study disentangled the OAE-driven factors that might influence zooplankton physiology. We assessed the direct effects of altered chemistry on the copepod, Temora longicornis, and the indirect effects through changes in the phytoplankton prey, Rhodomonas salina. We cultured the prey under OAE conditions and used it to feed copepods to investigate the indirect effects. We found that OAE negatively impacted prey growth but improved its nutritional quality, thereby offsetting the direct negative impact of OAE on the copepod. These findings regarding OAE’s impact on prey-predator dynamics contribute to a deeper understanding of how OAE may influence zooplankton communities
Phylogenetic and Autecology Characteristics of Five Potentially Harmful Dinoflagellate Alexandrium Species (Dinophyceae, Gonyaulacales, Pyrocystaceae) in Tropical Waters: A. affine, A. fraterculus, A. leei, A. pseudogonyaulax, and A. tamiyavanichii
Get PDFFive species of Alexandrium (A. affine, A. fraterculus, A. leei, A. pseudogonyaulax, and A. tamiyavanichii) are commonly found in Vietnamese waters. They were distinguished based on their apical pore complex (A.P.C), precingular first plate (1′), ventral pore (Vp), and sulcal platelets. A genetic analysis was conducted using nuclear rDNA sequences of ITS and LSU (D1–D3, D8–D10). The growth rates of A. fraterculus, A. leei, A. tamiyavanichii, and A. pseudogonyaulax were quite similar. Specifically, these four species had the highest growth rates at two temperature levels of 24 ◦C and 27 ◦C, at salinities ranging from 25 psu to 35 psu. Furthermore, these species were able to adapt to a low salinity of 20 psu at temperatures from 18 ◦C to 27 ◦C. No Paralytic Shellfish Toxins (PSTs) were found in the two Alexandrium affine strains, VINVN01-1 and VINVN01-2. The detection limit for PSTs ranged from 0.45 to 15.5 fg cell−1, depending on the molecular response and available biomass
Nearshore Hydrodynamics and Sediment Dispersal Along Eroding Permafrost Coasts—Insights From Acoustic Doppler Current Profiler Measurements Around Herschel Island–Qikiqtaruk (Yukon, Canada)
Get PDFPermafrost coasts are eroding at an accelerating pace, delivering vast amounts of sediments, organic matter, nutrients, and pollutants into the Arctic Ocean. These fluxes play a crucial role in the coastal biogeochemical cycle, yet their magnitude, as well as the trajectory and fate of the eroded material, is largely unknown. Direct observations of hydrodynamics in the Arctic nearshore zone are needed to overcome this issue, but these are challenging and scarce. Here, we report on direct current measurements performed in the nearshore zone. We deployed two Acoustic Doppler Current Profilers (ADCP) in 7- and 12-m water depth close to Herschel Island–Qikiqtaruk Yukon, Canada, to measure current velocities and directions throughout the water column. The data show that the currents change on a synoptic scale based on meteo-oceanographic forcing. During storms, these currents exceed the threshold of bottom sediment remobilization. The mobilization potential in the nearshore zone is therefore primarily related to wind forcing but can be strongly diminished by the presence of sea ice. These observations have implications for the future state of the Arctic nearshore zone, because larger fetches and a longer open water season could enhance sediment mobilization and dispersal
A transdisciplinary, comparative analysis reveals key risks from Arctic permafrost thaw
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Permafrost thaw poses diverse risks to Arctic environments and livelihoods. Understanding the effects of permafrost thaw is vital for informed policymaking and adaptation efforts. Here, we present the consolidated findings of a risk analysis spanning four study regions: Longyearbyen (Svalbard, Norway), the Avannaata municipality (Greenland), the Beaufort Sea region and the Mackenzie River Delta (Canada) and the Bulunskiy District of the Sakha Republic (Russia). Local stakeholders’ and scientists’ perceptions shaped our understanding of the risks as dynamic, socionatural phenomena involving physical processes, key hazards, and societal consequences. Through an inter- and transdisciplinary risk analysis based on multidirectional knowledge exchanges and thematic network analysis, we identified five key hazards of permafrost thaw. These include infrastructure failure, disruption of mobility and supplies, decreased water quality, challenges for food security, and exposure to diseases and contaminants. The study’s novelty resides in the comparative approach spanning different disciplines, environmental and societal contexts, and the transdisciplinary synthesis considering various risk perceptions.</jats:p
Biodiversity monitoring in the southeastern North Sea: identification and characterization of threatened benthic biotopes
No full textKnowledge of the structure and distribution of benthic biotopes is essential for marine conservation. It is a prerequisite for the assessment of the environmental status of marine ecosystems, the designation of protected areas, and the design of monitoring programmes to evaluate the effectiveness of conservation measures. Building on extensive datasets with high spatial coverage from ongoing national monitoring programmes, targeted environmental impact assessments, and basic research studies, we analysed benthic communities of the North Sea to characterize sublittoral biotopes and evaluate their ecological value within the network of seafloor habitats in this region. The application of advanced geo-statistical methods revealed the complex spatial structuring of the seafloor with a considerable diversity of benthic biotopes. Specific infauna associations were identified and characterized by their species inventories and composition of characteristic species. Supposedly isolated biotopes shared common features, highlighting connectivity which may crucially enhance their resilience against disturbance. Further, the distribution of key species demonstrated substantial contribution of some biotopes to ecosystem functioning. Our extensive monitoring of the biodiversity of benthic species communities and habitats essentially improved our understanding of the structure and functioning of the North Sea ecosystem, supporting the development and implementation of management tools and conservation measures in the face ongoing environmental change and anthropogenic disturbances.</jats:p
Biological effects of munition left on sunken war ships in the North Sea: a multi-biomarker study using caged blue mussels and fish caught at WWII wreck sites at the Belgian coast
Get PDFThe environmental risks associated with dumped munitions, unexploded ordnance (UXO) and sunken war ships is gaining more and more attention nowadays, since these warfare materials may start leaking, posing a threat to marine wildlife. This study aims to assess the effects of pollution by explosives for marine fauna associated with sunken war ships still loaded with munitions at the time of sinking. For this purpose, transplanted blue mussels (Mytilus edulis) and passive samplers were exposed for several weeks on two WWII warship wrecks (HMS Basilisk and V1302, formerly named John Mahn) to detect leakage of explosives and to characterize the effects of those substances on mussel health. In addition, fish (Trisopterus luscus) dwelling at V1302 were caught and investigated following the same approach as used with the mussels. The hazardous potential of dissolved explosives was assessed using multi-biomarker analysis, which includes the enzyme activity of catalase (CAT), glutathione S-transferase (GST) and acetylcholinesterase (AChE), as well as histochemical biomarkers like lysosomal membrane stability (LMS), lipofuscin (LIPF), neutral lipids (NL) and glycogen (GLY) as an indicator of mussel’s energy reserve. Chemical analysis of passive samplers as well as mussel and fish tissue indicated leakage of explosives at both wrecks and a subsequent uptake by exposed organisms. The leakage of explosives was correlated with membrane impairments and signs of oxidative stress measured in exposed mussels and fish.</jats:p
Under-ice environment observations from a remotely operated vehicle during the MOSAiC expedition
Get PDFChanges in the Arctic sea-ice cover affect the planet’s energy budget, atmospheric and oceanic circulation patterns as well as the ecosystem associated with this unique habitat. Interdisciplinary observations at the interfaces between sea ice and ocean are crucial to better understand the driving processes and bio-physical linkages in this coupled system. During the MOSAiC expedition 2019/2020 to the Arctic Ocean, we used a remotely operated vehicle (ROV) underneath drifting sea ice throughout an entire year. The main objective was to measure physical, chemical, and biological parameters across different surface and sea-ice types while the dive missions were optimized to retrieve optical properties and sea-ice bottom topography. All parameters were measured synchronously, enabling the quantification of their relationships and spatial and temporal variability. In addition, visual documentation of the under-ice environment and the permanently on-ice deployed instrumentation was performed. Overall, we completed more than 80 surveys covering all seasons and various sea-ice and surface conditions. Here, we present all available data, allowing for a year-round comprehensive picture of the under-ice environment
Formation and fate of freshwater on an ice floe in the Central Arctic
Get PDFThe melt of snow and sea ice during the Arctic summer is a significant source of relatively fresh meltwater. The fate of this freshwater, whether in surface melt ponds or thin layers underneath the ice and in leads, impacts atmosphere–ice–ocean interactions and their subsequent coupled evolution. Here, we combine analyses of datasets from the Multidisciplinary drifting Observatory for the Study of Arctic Climate (MOSAiC) expedition (June–July 2020) for a process study on the formation and fate of sea ice freshwater on ice floes in the Central Arctic. Our freshwater budget analyses suggest that a relatively high fraction (58 %) is derived from surface melt. Additionally, the contribution from stored precipitation (snowmelt) outweighs by 5 times the input from in situ summer precipitation (rain). The magnitude and rate of local meltwater production are remarkably similar to those observed on the prior Surface Heat Budget of the Arctic Ocean (SHEBA) campaign, where the cumulative summer freshwater production totaled around 1 m during both. A relatively small fraction (10 %) of freshwater from melt remains in ponds, which is higher on more deformed second-year ice (SYI) compared to first-year ice (FYI) later in the summer. Most meltwater drains laterally and vertically, with vertical drainage enabling storage of freshwater internally in the ice by freshening brine channels. In the upper ocean, freshwater can accumulate in transient meltwater layers on the order of 0.1 to 1 m thick in leads and under the ice. The presence of such layers substantially impacts the coupled system by reducing bottom melt and allowing false bottom growth; reducing heat, nutrient, and gas exchange; and influencing ecosystem productivity. Regardless, the majority fraction of freshwater from melt is inferred to be ultimately incorporated into the upper ocean (75 %) or stored internally in the ice (14 %). Terms such as the annual sea ice freshwater production and meltwater storage in ponds could be used in future work as diagnostics for global climate and process models. For example, the range of values from the CESM2 climate model roughly encapsulate the observed total freshwater production, while storage in melt ponds is underestimated by about 50 %, suggesting pond drainage terms as a key process for investigation
Extensive Variation in Thermal Responses and Toxin Content Among 40 Strains of the Cold-Water Diatom Pseudo-nitzschia seriata—In a Global Warming Context
Get PDFPhytoplankton are single-celled microorganisms with short generation times that may comprise high diversity in genetic and phenotypic traits, allowing them to acclimate to changes rapidly. High intraspecific genetic variation is well known in phytoplankton, but less is known about variation in physiological traits. To investigate variability and plasticity in genetic, morphological, and physiological traits of the toxigenic diatom genus Pseudo-nitzschia in a global warming scenario, we exposed 40 strains of the cold-water P. seriata to different temperatures (2 °C, 6 °C and 10 °C). The maximum growth rate and cellular toxin content showed extensive intraspecific variation, whereas morphological and genetic variation was minor. Thermal reaction norms showed a general increase in growth rate with increasing temperature; however, three distinct types of thermal responses were found among the 40 strains. All 40 strains contained toxins (domoic acid) in both exponential and stationary growth phase, and toxin content increased significantly with temperature. Most strains (>87%) contained measurable levels of domoic acid at all three temperatures. In conclusion, P. seriata shows extensive intraspecific variation in measured physiological traits like growth and toxin content, a variation exceeding the response of each strain to increases in temperature. Intraspecific variation in harmful species thus needs attention for the future understanding of food web dynamics, as well as the management and forecasting of harmful blooms