Abstract:

Arctic coastal areas can experience higher erosion rates than temperate regions due to the combined influence of seasonal permafrost melt and extreme temperatures. In addition to these ordinary dynamics, high latitude coastal areas are even more affected by climate-induced changes such as increased weather hazards, rising temperatures or changes in river discharges and sediment supply.

The Svalbard region consists of an archipelago of Arctic islands and a rocky and sandy coastline chiseled by numerous fjords connected to glaciers and a complex hydrographic network. Highly sensitive and exposed to the impacts of climate change, this coastal area is a perfect witness to the environmental changes of our century.

The Svalbard Archipelago has recently become a key hotspot with an increasing number of studies, mainly focusing on glacier melt, temperature change or soil destabilization. The environmental, geographical, and geomorphological conditions of Svalbard make it extremely difficult to monitor coastal change on a large-scale. However, several studies, including Lim et al. (2020), Jaskolski et al. (2018), and Sisneros-Kidd et al. (2019), have highlighted the strong pressure of climate change, population, and human activities on the Svalbard coastal area.

This littoral is fully in line with our approach to apprehend the past, present, and expected consequences of climate change on the environment and populations.

In close collaboration with local researcher Maria Jensen from the University of Svalbard (UNIS) and other experts in France (Agnès Baltzer and Franck Garestier), we have explored the potential of the Copernicus Programme satellite images to produce key information on the past and recent dynamics of nearly 300 km of coastline on the archipelago. This is a major challenge, given the complexity of the environment and the meteorological and climatic conditions of the region, which limit the volume of usable spatial data (cloud cover and seasonal ice on the monitored sediments).

After a first phase of adapting the algorithms to our developments, we extracted the coastline over 25 years, as well as the evolution of the banks and the extent of the hydrographic network along several major fjords in Svalbard. Particular attention was given to Advenfjorden to improve our effort, due to the greater availability of data to validate our results. We experienced the bathymetric monitoring into the fjord. This information was one of the most complex challenge in terms of methodology and algorithm development regarding the environmental context, but it is also a crucial insight to consider the full climate change impact on coastal sediment dynamics. Finally, we extracted another coastal indicator to focus on changes in the deltaic areas, namely the pioneer vegetation coverage, which reveals the impact of warming on these highly dynamic regions.

For the first time, we present our new results issued from these investigations.

Abstract: The 15 January 2022 climactic eruption of Hunga volcano, Tonga, produced an explosion in the atmosphere of a size that has not been documented in the modern geophysical record. The event generated a broad range of atmospheric waves observed globally by various ground-based and spaceborne instrumentation networks. Most prominent was the surface-guided Lamb wave (?0.01 hertz), which we observed propagating for four (plus three antipodal) passages around Earth over 6 days. As measured by the Lamb wave amplitudes, the climactic Hunga explosion was comparable in size to that of the 1883 Krakatau eruption. The Hunga eruption produced remarkable globally detected infrasound (0.01 to 20 hertz), long-range (~10,000 kilometers) audible sound, and ionospheric perturbations. Seismometers worldwide recorded pure seismic and air-to-ground coupled waves. Air-to-sea coupling likely contributed to fast-arriving tsunamis. Here, we highlight exceptional observations of the atmospheric waves.

Abstract: Many animals form long-term monogamous pair bonds, and the disruption of a pair bond (through either divorce or widowhood) can have significant consequences for individual vital rates (survival, breeding, and breeding success probabilities) and life-history outcomes (lifetime reproductive success [LRS], life expectancy). Here, we investigated the causes and consequences of pair-bond disruption in wandering albatross (Diomedea exulans). State-of-the-art statistical and mathematical approaches were developed to estimate divorce and widowhood rates and their impacts on vital rates and life-history outcomes. In this population, females incur a higher mortality rate due to incidental fishery bycatch, so the population is male-skewed. Therefore, we first posited that males would show higher widowhood rates negatively correlated with fishing effort and females would have higher divorce rates because they have more mating opportunities. Furthermore, we expected that divorce could be an adaptive strategy, whereby individuals improved breeding success by breeding with a new partner of better quality. Finally, we posited that pair-bond disruptions could reduce survival and breeding probabilities owing to the cost of remating processes, with important consequences for life-history outcomes. As expected, we showed that males had higher widowhood rates than females and females had higher divorce rates in this male-skewed population. However, no correlation was found between fishing effort and male widowhood. Secondly, contrary to our expectation, we found that divorce was likely nonadaptive in this population. We propose that divorce in this population is caused by an intruder who outcompetes the original partner in line with the so-called forced divorce hypothesis. Furthermore, we found a 16.7% and 18.0% reduction in LRS only for divorced and widowed males, respectively, owing to missing breeding seasons after a pair-bond disruption. Finally, we found that divorced individuals were more likely to divorce again, but whether this is related to specific individual characteristics remains an important area of investigation.

Abstract: Multiple initiatives have called for large-scale representative networks of marine protected areas (MPAs). MPAs should be ecologically representative to be effective, but in large, remote regions this can be difficult to quantify and assess. We present a novel bioregionalization for the Southern Ocean, which uses the modelled circumpolar habitat importance of 17 marine bird and mammal species. The habitat-use of these predators indicates biodiversity patterns that require representation in Southern Ocean conservation and management planning. In the predator habitat importance predictions, we identified 17 statistical clusters, falling into four larger groups. We characterized and contrasted these clusters based on their predator, prey and oceanographic characteristics. Under the existing Southern Ocean MPA network, some clusters fall short of 10 % representation, yet others meet or exceed these targets. Implementation of currently proposed MPAs can in some cases contribute to meeting even 30 % spatial coverage conservation targets. However, the effectiveness of mixed-use versus no-take MPAs should be taken into consideration, since some clusters are not adequately represented by no-take MPAs. These results, combined with previous studies in the Southern Ocean, can help inform the continued design, implementation, and evaluation of a representative system of MPAs for Southern Ocean conservation and management.