Alfred Wegener Institute for Polar and Marine Research
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Validation of Multisource Altimeter SWH Measurements for Climate Data Analysis in China’s Offshore Waters
Get PDFClimate data derived from long-term, multisource altimeter significant wave height (SWH) measurements are more valuable than those obtained from a single altimeter source. Such data facilitate exploration of long-term air–sea momentum transfer and more comprehensive investigation of weather system dynamics processes over the ocean. Despite the deployment of the first satellite in the Chinese Haiyang-2 (HY-2) series more than 12 years ago, validation and integration of SWH data from China’s offshore waters, derived using Chinese altimeters, have been limited. This study constructed a high-resolution, long-term, multisource gridded SWH climate dataset using along-track data from the HY-2 series, CFOSAT, Jason-2, Jason-3, and Cryosat-2 altimeters. Validation against observations from 31 buoys covering China’s offshore waters indicated that the SWH variances from HY-2A, HY-2B, HY-2C, CFOSAT, and Jason-3 altimeters correlated well with observations, with a temporal correlation coefficient of approximately 0.95 (except HY-2A, correlation: 0.89). These SWH measurements generally showed a robust linear relationship with the buoy data. Additionally, cross-calibration between Jason-3 and the HY-2A, HY-2B, HY-2C, and CFOSAT altimeters also demonstrated a typically linear relationship for SWH > 6.0 m. Using this relationship, the SWH data were linearly corrected and integrated into a 10 d mean, long-term, multisource altimeter gridded SWH dataset. Compared with in situ observations, the merged 10 d mean SWHs are more accurate and closely match the observations, with temporal correlation coefficients improving from 0.87 to 0.90 and bias decreasing from 0.28 to 0.03 m. The merged gridded SWHs effectively represent the local spatial distribution of SWH. This study revealed the importance of observational data in the process of merging and recalibrating long-term multisource altimeter SWH datasets, particularly before their application in specific ocean regions
AI-SUPPORTED DEVELOPMENT OF DIATOM-INSPIRED LATTICE STRUCTURES TO IMPROVE CONSTRUCTION OF ENDOPROSTHESES
No full textOpen-pored lattice structures can be designed and adapted in a variety of ways to be used in many fields of application and contribute to the optimisation of existing components. However, the large number of different shapes and customization options also makes it difficult to select the optimum lattice structure.
For this reason, the "KIKI" project is working on the development of an AI-supported design workflow for the generation of bio-inspired lattice structures that can be used to structure mechanical test specimens and, in the long term, to improve additively manufactured endoprostheses made of Ti-6Al-4V. AI-supported lattice development is used to select the optimum lattice configuration for a given load case and enables a stress-optimized design. In this way, the customizability of endoprostheses, the most natural possible load distribution between bone and prosthesis, and the ingrowth of bone can be improved.
To train the AI, the first step is to create a data base. For this purpose, a wide variety of diatom-based lattice structures are developed. Once suitable structures of the diatoms have been identified, parametric unit cells are derived from them, which are developed and optimized in algorithm-based design software. Subsequently, regular, uniform, open-pore lattices are generated from the unit cells. The choice of unit cell, a customizable uniform material thickness, and a possible rotation of the unit cell can be used to adapt the generated lattice. These design principles are developed in such a way that they can be used in a highly variable manner, taking design properties relevant to endoprosthesis into account and enable optimization in terms of weight, porosity, strength, and producibility.
Further, a suitable AI model is developed to obtain optimal parameters for lattice structure generation. Through sophisticated algorithms and neural networks, it analyzes the data base of over 40,000 examples to determine the most suitable lattice configurations for user inputs. This tool supports the selection of suitable lattice structures in the design process of the bio-inspired mechanical samples and thus improves the generation of an optimized structure. The AI tool's ability to adapt and learn from big data base ensures precise outcomes tailored to specific requirements, marking a significant advancement in the use of optimized lattice structures in engineering and health care sector.
Keywords: Deep Learning, Optimization, Health Infrastructur
Relations between cyclones and ozone changes in the Arctic using data from satellite instruments and the MOSAiC ship campaign
Get PDFLarge-scale meteorological events (e.g. cyclones), referred to as synoptic events, strongly influence weather predictability but still cannot be fully characterised in the Arctic region because of the sparse coverage of measurements. Due to the fact that atmospheric dynamics in the lower stratosphere and troposphere influence the ozone field, one approach to analyse these events further is the use of space-borne measurements of ozone vertical distributions and total columns in addition to conventional parameters such as pressure or wind speed. In this study we investigate the link between cyclones and changes in stratospheric ozone by using a combination of unique measurements during the Multidisciplinary drifting Observatory for the Study of Arctic Climate (MOSAiC) ship expedition, ozone profile and total column observations by satellite instruments (OMPS-LP, TROPOMI), and ERA5 reanalysis data. The final goal of the study is to assess whether the satellite ozone data can be used to obtain information about cyclones and provide herewith an additional value in the assimilation by numerical weather prediction models. Three special cases during the MOSAiC expedition were selected and classified for the analysis. They are one “normal” cyclone, where a low surface pressure coincides with a minimum in tropopause height, and two “untypical” cyclones, where this is not observed. The influence of cyclone events on ozone in the upper-troposphere lower-stratosphere (UTLS) region was investigated, using the fact that both are correlated with tropopause height changes. The negative correlation between tropopause height from ERA5 and ozone columns was investigated in the Arctic region for the 3-month period from June to August 2020. This was done using total ozone columns and sub-columns from TROPOMI, OMPS-LP, and MOSAiC ozonesonde data. The greatest influence of tropopause height changes on ozone contour levels occurs at an altitude between 10 and 20 km. Moreover, the lowering of the 250 ppb ozonopause (at about 11 km altitude) below 9 km was used to detect cyclones using OMPS-LP ozone observations. The potential of this approach was demonstrated in two case studies where the boundaries of cyclones could be determined using ozone observations. The results of this study can help improve our understanding of the relationship between cyclones, tropopause height, and ozone in the Arctic and demonstrate the usability of satellite ozone data in addition to the conventional parameters for investigating cyclones in the Arctic
Tectonic structures of the Dome Fuji region, East Antarctica, based on new magnetic data
Get PDFThe Oldest Ice Reconnaissance (OIR) airborne geophysical survey in East Antarctica was flown over approximately 170,000 km2 of the Dome Fuji region in 2016/17. The survey’s results support new insights into the subglacial geology and its meaning for the tectonic histories of the supercontinents Rodinia and Gondwana. The new magnetic and radar-derived bed topography data are integrated with previously acquired magnetic and gravity data, allowing the mapping of crustal domains within and beyond the survey’s limits. The magnetic data reveal three distinct domains within the survey region, delineated by N–S oriented boundaries, partly aligned with gravity domains following upward continuation transformations for both datasets. Additionally, four primary sets of magnetic lineaments were identified, exhibiting correlations with topographic and gravity patterns. These correlations indicate the continuation of the Tonian Oceanic Arc Super Terrane (TOAST) southward of its previously known southern limit. Moreover, an E–W-trending magnetic anomaly, the Elbert magnetic anomaly, suggests the suture between the recently-proposed subglacial Valkyrie craton and the TOAST. Furthermore, the analysis reveals a broad scale shear zone, named here the OIR shear zone, which formed as a result of oblique collision of the Ruker and Valkyrie cratons during the amalgamation of Gondwana
The Role Of Bottom Meso-Scale Dynamics In Contourite Formation In The Argentine Basin
Get PDFThe Argentine Basin is a deep-sea basin located in the South Atlantic Ocean that contains sedimentary deposits derived from different provenances. It is characterized by complex ocean dynamics encompassing diverse spatial and temporal dimensions. The northward subantarctic Malvinas Current and southward subtropical Brazil Current converge at the western margin of the Argentine Basin, resulting in the formation of the Brazil–Malvinas Confluence region. Bottom currents, particularly currents flowing alongslope and horizontal eddies, are crucial in shaping the seafloor and in the formation of sedimentary features (e.g., contourites). The poorly understood strength and variability of bottom currents leave the processes that control sedimentation in deep environments unclear. High-resolution (1/12°) reanalysis was used to analyze near-bottom flows and bottom dynamics were compared with seafloor sedimentary characteristics obtained from geophysical datasets and sediment cores. High speeds, up to 3.5 m/s at the surface and up to 1.4 m/s at the bottom, reveal the presence of intense flows in this area. The Zapiola Drift, an ∼ 1,200 m high sedimentary deposit located in the central part of the Argentine Basin, is bounded by a zone of high bottom eddy kinetic energy (EKE) that resulted in the erosion of the seafloor and in the accumulation of sandy mud. The Malvinas Current is distinguished by strong and constant currents flowing northwards along the continental slope and by minimal EKE at the bottom. The area of the continental slope along which the Malvinas Current flows corresponds to a contourite terrace, a relatively flat surface composed almost entirely of sandy sediments and with abundant erosional features. The regions of highest EKE activity in the bottom layer is the overshoot of the Brazil Current and the abyssal plain. Our study highlights the impact of bottom-current dynamics on contouritic sedimentation. In certain regions, the process of sedimentation is subject to the influence of sporadic events that occur between periods of intense and weak flow. These events are regarded as intermittent processes. While sedimentation in other areas is controlled by constant flows. A better understanding of the strength and variability of bottom currents will improve paleoceanographic reconstructions based on the sedimentary record
First sighting of Streptosyllis nunezi (Polychaeta: Syllidae) in the German Bight, SE North Sea
Get PDFLong-term marine monitoring programmes have provided numerous quantitative data on the composition of North Sea benthic communities and their changes over time, including species introductions. Particularly in the German Bight, the rapid environmental and hydrographical changes are promoting the spreading (usually anthropogenically mediated) of neobiota, with more than 150 species being registered to date. During routine seafloor monitoring, grab samples taken on the subtidal sandbank of the Borkum Reef Ground revealed the presence of the polychaete Streptosyllis nunezi in different years, a species previously unreported in the southern North Sea. In this paper, these individuals are described morphologically and the population status is discussed. Our finding demonstrates the importance of intensive and regular environmental monitoring programmes for the assessment of regional biodiversity and its potential changes
Holocene rangeland characteristics on the northeastern Tibetan Plateau in relation to climate and pastoralism from sedimentary ancient DNA
Get PDFThe northeast Tibetan Plateau, functioning as an alpine pasture, has been influenced by prehistoric settlements for millennia. However, the extent to which climate and anthropogenic activities have shaped this rangeland remains contentious. Here, we present sedimentary ancient DNA evidence from Lake Donggi Cona sediment core, focusing on the trnL p6-loop region of vascular plants and the internal transcribed spacer (ITS1) region of nuclear ribosomal DNA for Poaceae and Cyperaceae. Our findings indicate that before 7.4 cal ka BP, the rangeland was characterized by alpine steppe with low richness, influenced by dry environmental conditions. By 7.4 cal ka BP, more taxa migrated to the study region, with a relatively high richness supported by a humid environment. The climate conditions, coupled with low grazing pressure, sustained a relatively high pastoral quality. Intensified nomadic activities after 4 cal ka BP contributed to a severe decline in pasture quality, characterized by a high abundance of poisonous taxa. This study highlights that both human activity and moisture availability contribute to the rangeland characteristic, with human activity as the predominant factor since 4 cal ka BP
Individuals departing non-breeding areas early achieve earlier breeding and higher breeding success
Get PDFConditions experienced by an individual during migration have the potential to shape migratory tactic and in turn fitness. For large birds, environmental conditions encountered during migration have been linked with survival and subsequent reproductive output, but this is less known for smaller birds, hindering our understanding of mechanisms driving population change. By combining breeding and tracking data from 62 pied flycatchers (Ficedula hypoleuca) representing two breeding populations collected over 2016-2020, we determine how variation in migration phenology and tactic among individuals affects subsequent breeding. Departure date from West African non-breeding areas to European breeding grounds was highly variable among individuals and had a strong influence on migration tactic. Early departing individuals had longer spring migrations which included longer staging duration yet arrived at breeding sites and initiated breeding earlier than later departing individuals. Individuals with longer duration spring migrations and early arrival at breeding sites had larger clutches, and for males higher fledging success. We suggest that for pied flycatchers, individual carry-over effects may act through departure phenology from West Africa, and the associated spring migration duration, to influence reproduction. While our results confirm that departure date from non-breeding areas can be associated with breeding success in migratory passerines, we identify spring staging duration as a key component of this process
Predicting resilience of migratory birds to environmental change.
Get PDFThe pace and scale of environmental change represent major challenges to many organisms. Animals that move long distances, such as migratory birds, are especially vulnerable to change since they need chains of intact habitat along their migratory routes. Estimating the resilience of such species to environmental changes assists in targeting conservation efforts. We developed a migration modeling framework to predict past (1960s), present (2010s), and future (2060s) optimal migration strategies across five shorebird species (Scolopacidae) within the East Asian-Australasian Flyway, which has seen major habitat deterioration and loss over the last century, and compared these predictions to empirical tracks from the present. Our model captured the migration strategies of the five species and identified the changes in migrations needed to respond to habitat deterioration and climate change. Notably, the larger species, with single or few major stopover sites, need to establish new migration routes and strategies, while smaller species can buffer habitat loss by redistributing their stopover areas to novel or less-used sites. Comparing model predictions with empirical tracks also indicates that larger species with the stronger need for adaptations continue to migrate closer to the optimal routes of the past, before habitat deterioration accelerated. Our study not only quantifies the vulnerability of species in the face of global change but also explicitly reveals the extent of adaptations required to sustain their migrations. This modeling framework provides a tool for conservation planning that can accommodate the future needs of migratory species
