Alfred Wegener Institute for Polar and Marine Research
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Smoother sea ice with fewer pressure ridges in a more dynamic Arctic
Get PDFPressure ridges, formed by sea ice deformation, affect momentum transfer in the Arctic Ocean and support a larger biomass than the surrounding-level ice. Although trends in Arctic sea ice thickness and concentration are well documented, changes in ridge morphology remain unclear. This study provides airborne-based evidence of a shift towards a smoother ice surface, with fewer pressure ridges and reduced surface drag, attributed to the loss of old ice. Furthermore, an increase in seasonal ice cover enhances overall deformation in the Arctic and acts as a negative feedback mechanism on pan-Arctic ridge morphology: the greater the proportion of seasonal ice, the higher the pan-Arctic mean ridge rate, dampening an overall decline in ridges with age. While thinner and less frequent ridges benefit industries such as shipping, these changes are likely to have profound impacts on the energy and mass balance and the ecosystem of the Arctic Ocean
Do you remember? Within generation and transgenerational heat stress memory of recurring marine heatwaves in threespine stickleback
Get PDFMarine heatwaves can have major and lasting effects on organism physiology and species persistence. Such temperature extremes are increasing in frequency, with consecutive heatwave events already occurring within the lifetime of many organisms. Heat stress memory (thermal priming) by individuals is a potential within-generation response to cope with recurring marine heatwaves. However, whether this form of biological memory can be inherited across generations is not well known. We used a three-generation experiment to investigate individual and transgenerational effects of single and recurring marine heatwaves on fitness-related traits using stickleback (Gasterosteus aculeatus) as a model species. We exposed adults (both sexes) to heatwaves, and assessed female reproductive output in both the parent and offspring generation, and offspring (both sexes) survival, growth, and behaviour to establish a holistic picture of potential heatwave effects on ectothermic fish. Exposure to single, extreme heatwaves lowered reproductive output, and decreased offspring exploratory behaviour, impeded capacity to respond to further thermal stress, and reduced long-term survival. However, prior experience of heatwaves (heat stress memory) mitigated some of these effects at both an individual (growth) and transgenerational (fecundity) level, indicating that species experiencing increasing heatwave frequency as part of ongoing climate change may cope better than previously thought
The Solar System's passage through the Radcliffe wave during the middle Miocene
Get PDFAs the Solar System orbits the Milky Way, it encounters various Galactic environments, including dense regions of the interstellar medium (ISM). These encounters can compress the heliosphere, exposing parts of the Solar System to the ISM while also increasing the influx of interstellar dust into the Solar System and Earth's atmosphere. The discovery of new Galactic structures, such as the Radcliffe wave, raises the question of whether the Sun has encountered any of them. The present study investigates the potential passage of the Solar System through the Radcliffe wave gas structure over the past 30 million years (Myr). We used a sample of 56 high-quality, young (≤30 Myr ) open clusters associated with a region of interest of the Radcliffe wave to trace its motion back and investigate a potential crossing with the Solar System’s past orbit. We find that the Solar System’s trajectory intersected the Radcliffe wave in the Orion region. We have constrained the timing of this event to between 18.2 and 11.5 Myr ago, with the closest approach occurring between 14.8 and 12.4 Myr ago. Notably, this period coincides with the Middle Miocene climate transition on Earth providing an interdisciplinary link with paleoclimatology. The potential impact of the crossing of the Radcliffe wave on the climate on Earth is estimated. This crossing could also lead to anomalies in radionuclide abundances, which is an important research topic in the field of geology and nuclear astrophysics.</jats:p
Interplay of anthropogenic and natural drivers of observed coupled sea surface temperature - Arctic sea ice variability
Get PDFArctic sea ice plays a pivotal role in shaping the climate system at high latitudes, acting as both an indicator and driver of climate change processes in this sensitive region. Its seasonal variability and long-term decline have far-reaching implications for global climate dynamics, regional ecosystems, and human activities. While climate models indicate clear evidence of human-induced sea ice decline, quantification of the relative contributions of forcing factors in relation to climate-system internal processes remains uncertain. Here, we tackle this uncertainty by employing a combination of statistical analyses on observational data, highlighting the distinct fingerprints of increased atmospheric CO2 concentration as external forcing, the Atlantic Multidecadal Oscillation (AMO) as well as the North Atlantic Oscillation (NAO), as modes of internal variability, on global sea surface temperature (SST) and Arctic sea ice concentration (SIC) since 1950. Our analyses reveal that rising atmospheric CO2 concentrations are by far the dominant causal factor for SIC variability, while AMO and NAO also play a significant role in either exacerbating or mitigating sea ice loss. Since mid-1980s, the positive trend of the AMO has amplified the declining trend in Arctic sea ice, with its effects being roughly half as large as the effect of rising CO2 concentrations. Linear regression analyses shed light on the physical processes linking the drivers of Arctic sea ice decline both during phases of sea-ice accumulation and melting. Causal links between increasing atmospheric CO2 concentrations, the AMO, the NAO, on the one hand, and observed global SST—Arctic SIC patterns on the other are also established. Observation-based coupled SST-SIC interactions underline the past evolution of Arctic sea ice and emphasize the important roles of these drivers in shaping its current and future evolution
Ocean carbon sink assessment via temperature and salinity data assimilation into a global ocean biogeochemistry model
Get PDFGlobal ocean biogeochemistry models are frequently used to derive a comprehensive estimate of the global ocean carbon uptake. These models are designed to represent the most important processes of the ocean carbon cycle, but the idealized process representation and uncertainties in the initialization of model variables lead to errors in their predictions. Here, observations of ocean physics (temperature and salinity) are assimilated into the ocean biogeochemistry model FESOM2.1-REcoM3 over the period 2010–2020 to study the effect on the air–sea carbon dioxide (CO₂) flux and other biogeochemical (BGC) variables. The assimilation nearly halves the model–observation differences in sea surface temperature and salinity, with modest effects on the modeled ecosystem and CO₂ fluxes. The main effects of the assimilation on the air–sea CO₂ flux occur on small scales in highly dynamic regions, which pose challenges to ocean models. Its largest imprint is in the Southern Ocean during winter. South of 50° S, winter CO₂ outgassing is reduced; thus the regional CO₂ uptake increases by 0.18 Pg C yr⁻¹ through the assimilation. Other particularly strong regional effects on the air–sea CO₂ flux are located in the area of the North Atlantic Current (NAC). However, the effect on the global ocean carbon uptake is a comparatively small increase by 0.05 Pg C y⁻¹ induced by the assimilation, yielding a global mean uptake of 2.78 Pg C yr⁻¹ for the period 2010–2020
Bedmap3 updated ice bed, surface and thickness gridded datasets for Antarctica
Get PDFAbstract
We present Bedmap3, the latest suite of gridded products describing surface elevation, ice-thickness and the seafloor and subglacial bed elevation of the Antarctic south of 60 °S. Bedmap3 incorporates and adds to all post-1950s datasets previously used for Bedmap2, including 84 new aero-geophysical surveys by 15 data providers, an additional 52 million data points and 1.9 million line-kilometres of measurement. These efforts have filled notable gaps including in major mountain ranges and the deep interior of East Antarctica, along West Antarctic coastlines and on the Antarctic Peninsula. Our new Bedmap3/RINGS grounding line similarly consolidates multiple recent mappings into a single, spatially coherent feature. Combined with updated maps of surface topography, ice shelf thickness, rock outcrops and bathymetry, Bedmap3 reveals in much greater detail the subglacial landscape and distribution of Antarctica’s ice, providing new opportunities to interpret continental-scale landscape evolution and to model the past and future evolution of the Antarctic ice sheets.</jats:p
Climate Signals from NEUMAYER, Coastal Dronning Maud Land, Antarctica: A 33-Year Statistical Analysis of Snow Accumulation in a Stake Farm
Get PDFChanges in snow accumulation on the Antarctic Ice Sheet are of significant relevance
to global mean sea level. Measurements taken over a 33-year period near the Neumayer
Stations, Dronning Maud Land (DML), Antarctica, were used to statistically
analyse both interannual and intraannual trends and variability of snow accumulation.
While a significant increases in snow accumulation have been observed at
Kohnen Station on the DML plateau in the interior of the continent, the question
arises as to whether the coastal measurements near Neumayer show similar trends.
This study reveals that two unprecedented accumulation years, 2021 and 2023, were
recorded near Neumayer; however, no statistically significant long-term trend could
be identified in the time series, which shows several periods of increasing and decreasing
mulit-annual means in snow accumulation. Despite this, shifts in certain
accumulation characteristics during the study period suggest the possible onset of
a positive trend. Specifically, positive annual accumulation anomalies have become
more frequent and more intense, the rate of interannual accumulation increase has
accelerated, and the current period reflects a prolonged state of above-average accumulation.
High interannual variability, however, prevents the identification of a
significant trend within the available data period.
Periodicities observed in the time series suggest possible links to larger atmospheric
patterns, such as the Antarctic Circumpolar Wave. Further research is required to
also investigate the role of the major climate modes such as the Southern Annular
Mode (SAM) and El Ni˜no-Southern Oscillation (ENSO) and how these might influence
local accumulation trends. This climatological analysis offers valuable data
that could be used for future ground-truthing of satellite observations and benchmarking
of climate models, especially given the higher temporal resolution of these
measurements compared to firn and ice core records
Ecological reef restoration: consumptive and nonconsumptive interactions among common North Sea predators and European oysters
Get PDFOyster reefs are biodiversity hotspots with multiple ecosystem functions and services that are declining worldwide. Historic populations of European oysters (Ostrea edulis) have been decimated by overfishing and are nowadays considered functionally extinct in European waters. To halt and reverse the associated biodiversity loss, oyster reef restoration was implemented into marine conservation measures and several reef restoration projects started across Europe. Following ecological restoration standards, it is crucial to identify reef-associated predators and predator-prey interactions influencing reef recovery as predators can control prey populations. Therefore, this study examined consumptive and nonconsumptive interactions among common North Sea predators, brown crabs (Cancer pagurus) and European lobsters (Homarus gammarus), and European oysters on Helgoland island (German Bight, North Sea) for the first time. Field surveys and monitorings in offshore pilot oyster reefs and experimental seafloor areas showed (i) that brown crabs, lobsters and oysters co-occur in these subtidal environments and (ii) interact with each other. Manipulative experiments indicated (iii, iv) that both predators consume oysters, (v) that medium-sized to large oysters are safe from brown crabs, and (vi) that large oysters are relatively safe from lobsters. They also found (vii) that the presence of common mussels (Mytilus spp.), as an alternative and more profitable prey, and (viii) the formation of larger and heavier oyster clumps, that are more difficult to handle, can reduce predation on oysters. Furthermore, they showed (ix) that the presence of brown crab conspecifics and (x) lobsters in natural abundances can nonconsumptively limit oyster consumption of brown crabs through intimidation mediated by (xi) brown crab- and (xii) lobster-released waterborne predator cues detected by brown crabs which indicates naturally underlying mechanisms regulating and limiting predation on oysters. Thereby, this study provides fundamental knowledge that is essential to understand predator-prey interactions in offshore oyster reefs and to facilitate ecological reef restoration
Stopover regions, phenology, and spatiotemporal group dynamics of adult and juvenile common terns Sterna hirundo from inland lakes in North America
Get PDFUnderstanding the behavior of migratory birds can help determine levels of connectivity and inform conservation actions for species of conservation concern. The common tern Sterna hirundo is a long-distance migratory seabird that is considered a species of conservation concern in the North American Great Lakes region and that has experienced significant declines in breeding numbers across large lakes in Manitoba. To better understand the movement ecology of common terns, we used data from multiple tracking technologies (solar geolocation, GPS tracking, and Motus radio tracking) obtained from individuals (n = 83) across five breeding colonies on four inland lakes in North America. We identified key stopover regions used during southward migration and explored how demographics and social interactions influence connectivity. We identified three key stopover regions (Lake Erie, the southern Atlantic Coast, and Florida) and documented, for the first time, differences in post-natal and post-breeding migration for inland nesting terns. Juveniles arrived, on average, three weeks later than unrelated adults to their first major staging area. Although adult female arrival to and departure from Lake Erie was similar to adult males, female schedules became significantly earlier than males as southward migration progressed. Using a graph network to describe the spatiotemporal associations among adults from the same inland lake, individuals appeared to be highly connected, meeting up in different regions throughout the non-breeding season, suggesting that social interactions may play an important role in maintaining spatial connectivity. Despite differences in migration schedules by sex and arrival to the first major staging area by age class, birds appeared to rely on the same key stopover regions during southward migration. The stopover regions identified in this study can help identify potential bottlenecks and guide future research aimed at assessing the impacts of climate change and human disturbance on common terns breeding in North America