Alfred Wegener Institute for Polar and Marine Research
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Lessons From Transient Simulations of the Last Deglaciation With CLIMBER-X: GLAC1D Versus PaleoMist
Get PDFKönnen die Klimaänderungen in der Arktis Wetter- und Klimaextreme über Mitteleuropa beeinflussen?
Get PDFSeit etwa 1990 wird das Phänomen der „Arktischen Verstärkung“ beobachtet, das die 3- bis 4-fach stärkere Erwärmung der Arktis im Vergleich zur globalen Erwärmung beschreibt. Diese Zeit fällt mit einer Periode zusammen, in der die Zahl der extremen Wetter- und Klimaereignisse in den mittleren Breiten der nördlichen Hemisphäre zunahm. Diese Zunahme kann teilweise direkt durch die globale Erwärmung und die damit verbundenen thermodynamischen Effekte erklärt werden, aber auch Veränderungen der atmosphärischen Zirkulation tragen zu dem häufigeren Auftreten von Extremen wie Hitzewellen oder extremen Niederschlägen bei. Nach kontroversen wissenschaftlichen Studien in den letzten Jahren, besteht mittlerweile Konsens darüber, dass die arktische Verstärkung die Eigenschaften der atmosphärischen Zirkulation auf komplexe und nichtlineare Weise beeinflussen kann.
Der Einfluss des arktischen Klimawandels auf zukünftige Veränderungen von Extremereignissen über Mitteleuropa wird in dieser Studie hauptsächlich auf der Basis von Klimamodellsimulation mit dem globalen atmosphärischen Modell ECHAM6 untersucht, die durch das Projekt PAMIP (Polar Amplification Model Intercomparison Project), zur Verfügung gestellt wurden. Zur Identifizierung von dynamischen Treibern für Extremereignisse wird ein Storyline-Ansatz angewendet, da die Anwendung des konventionellen probabilistischen Ansatzes zur Attribution von Extremereignissen im Fall von dynamisch getriebenen Extremen begrenzt ist.
Zum einen wird analysiert, wie sich die Häufigkeit des Auftretens von Zirkulationsregimen unter zukünftigen Bedingungen des Meereises und der Meeresoberflächentemperaturen in den verschiedenen ECHAM6 PAMIP-Sensitivitätsexperimenten verändert. Unter Verwendung eines Ansatzes für die bedingte Attribution von Extremereignissen werden die meereisbedingten Häufigkeitsänderungen der winterlichen europäischen kalten und warmen Temperaturextreme analysiert. Es wird gezeigt, wie die Änderungen in der Häufigkeit des Auftretens von Zirkulationsregimen unter zukünftiger Meereisabnahme dem thermodynamischen Erwärmungseffekt entgegenwirken. Um die Bedeutung der zukünftigen arktischen Meereisabnahme im Vergleich zu globalen Aspekten der zukünftigen Erwärmung zu bewerten, werden auch die PAMIP-Experimente analysiert, die mit zukünftigen Meeresoberflächentemperaturen angetrieben wurden.
Da die sommerlichen Zirkulationsregime als Storylines f&#252;r das Auftreten sommerlicher Hitzeextreme nicht geeignet sind, wird au&#223;erdem ein Ansatz vorgestellt, der auf dem Konzept von Zirkulationsanalogien basiert. Dies erm&#246;glicht auch eine Absch&#228;tzung, wie die zuk&#252;nftige arktische Meereisabnahme die H&#228;ufigkeit des Auftretens von blockierenden Wetterlagen beeinflusst, die in der Regel mit sommerlichen Hitzewellen &#252;ber verschiedenen europ&#228;ischen Regionen verbunden sind.</jats:p
Weakening of the Atlantic Meridional Overturning Circulation abyssal limb in the North Atlantic
Get PDFThe abyssal limb of the global Meridional Overturning Circulation redistributes heat and carbon as it carries Antarctic Bottom Water from the Southern Ocean towards the Northern Hemisphere. Using mooring observations and hydrographic data from multiple sources in the North Atlantic, we show that northward-flowing Antarctic Bottom Water is constrained below 4,500 m with a mean volume transport of 2.40 ± 0.25 Sv at 16° N. We find that during 2000–2020, the Antarctic Bottom Water northward transport weakened by approximately 0.35 ± 0.13 Sv, corresponding to a 12 ± 5% decrease. The weakening of the Atlantic Meridional Overturning Circulation abyssal cell is a probable response to reduced Antarctic Bottom Water formation rates over the past several decades and is associated with abyssal warming observed throughout the western Atlantic Ocean. We estimate that the warming of the Antarctic Bottom Water layer in the subtropical North Atlantic is, on average, 1 m°C per year in the last two decades due to the downward heaving of abyssal isopycnals, contributing to the increase of abyssal heat content and, hence, sea-level rise in the region (1 m°C = 0.001 °C). This warming trend is approximately half of the Antarctic Bottom Water warming trend observed in the South Atlantic and parts of the Southern Ocean, indicating a dilution of the signal as the Antarctic Bottom Water crosses the Equator
Oceans sing, are you listening? Sounding out potentials for artistic audio engagements with science through the Polar Sounds project
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Impact of persistently high sea surface temperatures on the rhizobiomes of Zostera marina in a Baltic Sea benthocosms
Get PDFPersistently high marine temperatures are escalating and threating marine biodiversity. The Baltic Sea, warming faster than other seas, is a good model to study the impact of increasing sea surface temperatures. Zostera marina, a key player in the Baltic ecosystem, faces susceptibility to disturbances, especially under chronic high temperatures. Despite the increasing number of studies on the impact of global warming on seagrasses, little attention has been paid to the role of the holobiont. Using an outdoor benthocosm to replicate near-natural conditions, this study explores the repercussions of persistent warming on the microbiome of Z. marina and its implications for holobiont function. Results show that both seasonal warming and chronic warming, impact Z. marina roots and sediment microbiome. Compared with roots, sediments demonstrate higher diversity and stability throughout the study, but temperature effects manifest earlier in both compartments, possibly linked to premature Z. marina die-offs under chronic warming. Shifts in microbial composition, such as an increase in organic matter-degrading and sulfur-related bacteria, accompany chronic warming. A higher ratio of sulfate-reducing bacteria compared to sulfide oxidizers was found in the warming treatment which may result in the collapse of the seagrasses, due to toxic levels of sulfide. Differentiating predicted pathways for warmest temperatures were related to sulfur and nitrogen cycles, suggest an increase of the microbial metabolism, and possible seagrass protection strategies through the production of isoprene. These structural and compositional variations in the associated microbiome offer early insights into the ecological status of seagrasses. Certain taxa/genes/pathways may serve as markers for specific stresses. Monitoring programs should integrate this aspect to identify early indicators of seagrass health. Understanding microbiome changes under stress is crucial for the use of potential probiotic taxa to mitigate climate change effects. Broader-scale examination of seagrass–microorganism interactions is needed to leverage knowledge on host–microbe interactions in seagrasses
Holocene lake response to glacier and catchment changes on the eastern Tibetan Plateau from quantitative conductivity reconstructions based on sedaDNA-derived macrophyte records
Get PDFUnderstanding the response of long-term aquatic environmental changes in lakes to ongoing climate change and human activities is key to forecasting future lake conditions. In this study, we infer the Holocene limnological changes in Emu Co, a proglacial lake in Nianbaoyuze on the eastern Tibetan Plateau, from sedimentary ancient DNA (sedaDNA) data, and palynomorph, element, lithological, and grain-size analyses. We developed a transfer function based on Siberia and Tibet/China surface sedimentary DNA and applied it to Emu Co sedaDNA to trace lake conductivity changes. The results show that the conductivity of Emu Co was high during 12.6−9.7 cal ka BP, often surpassing 1000 μs cm−1, driven by elevated summer solar radiation. The freshwater influx from glacial meltwater and precipitation, however, reduced the lake's conductivity as the climate warmed and humidified. This led to a decrease in the abundance of taxa characterised by high conductivity. Freshwater pulses, triggered by climatic fluctuations, likely led to significant variations in conductivity within the overarching downward trend. By 8 cal. ka BP, lake recharge conditions stabilised and conductivity reached a lower level of ∼70 μs cm−1. The warm and humid mid-Holocene (8−5 cal. ka BP) provided suitable habitat conditions for many submerged freshwater taxa. After 5 cal. ka BP, the growth of submerged taxa was restricted, as indicated by a shift from asexual to sexual reproduction in macrophytes, likely in response to suboptimal conditions of a colder and drier climate. Since 1 cal. ka BP, human activities might have increased lake nutrient levels, with an enhanced richness of macrophytes. Our results indicate how millennial-scale hydrological changes in a lake are related to glacial retreat and catchment changes in the alpine region of the Tibetan Plateau, which is today facing climate change much greater than the global average
Responses of the mesozooplankton community to marine heatwaves: Challenges and solutions based on a long‐term time series
Get PDFMarine heatwaves (MHWs) are extreme weather events that have major impacts on the structure and functioning of marine ecosystems worldwide. Due to anthropogenic climate change, the occurrence of MHWs is predicted to increase in future. There is already evidence linking MHWs with reductions in biodiversity and incidence of mass mortality events in coastal ecosystems. However, because MHWs are unpredictable, the quantification of their effects on communities is challenging. Here, we use the Helgoland Roads long-term time series (German Bight, North Sea), one of the richest marine time series in the world, and implement a modified before-after control-impact (BACI) design to evaluate MHW effect on mesozooplankton communities. Mesozooplankton play an essential role in connecting primary producers to higher trophic levels, and any changes in their community structure could have far-reaching impacts on the entire ecosystem. The responses of mesozooplankton community to MHWs in terms of community structure and densities occurred mainly in spring and autumn. Abundances of seven taxa, including some of the most abundant groups (e.g. copepods), were affected either positively or negatively in response to MHWs. In contrast, we observed no clear evidence of an impact of summer and winter MHWs; instead, the density of the most common taxa remained unchanged. Our results highlight the seasonally dependent impacts of MHWs on mesozooplankton communities and the challenges in evaluating those impacts. Long-term monitoring is an important contributor to the quantification of effects of MHWs on natural populations
FAIR-EuMon: a FAIR-enabling resource for biodiversity monitoring schemes
Get PDFWithin the scope of the Helmholtz Metadata Collaboration (HMC), the ADVANCE project – Advanced metadata standards for biodiversity survey and monitoring data: supporting of research and conservation – aimed at supporting rich metadata generation with interoperable metadata standards and semantic artefacts that facilitate data access, integration and reuse across terrestrial, freshwater and marine realms. HMC's mission is to facilitate the discovery, access, machine-readability, and reuse of research data across and beyond the Helmholtz Association.
We revised, adapted and expanded existing metadata schemas, vocabularies and thesauri to build a FAIR metadata schema and a metadata entry form built on it for users to provide their metadata instances focused on biodiversity monitoring data. The schema is FAIR because it is both machine-interpretable and follows domain-relevant community standards. This report provides a general overview of the project results and instructions on how to access, re-use and complete the metadata form.</jats:p
