Oceanic islands as stepping stones under climate change : temperature trends, extreme events and species shifts
Globally, climate change can affect biodiversity and the environment in many ways. One of the most pressing challenges for the marine environment is the change in seawater temperature. Such changes can be observed in long-term averages as well as sporadic, distinct extreme events like marine heatwav...
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| Format: | Thesis |
| Language: | English |
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2022
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| Online Access: | https://oceanrep.geomar.de/id/eprint/59673/ https://oceanrep.geomar.de/id/eprint/59673/1/Diss_Schaefer_S_2022.pdf |
| Summary: | Globally, climate change can affect biodiversity and the environment in many ways. One of the most pressing challenges for the marine environment is the change in seawater temperature. Such changes can be observed in long-term averages as well as sporadic, distinct extreme events like marine heatwaves and cold spells. Both processes profoundly impact species' physiology and distribution in the marine realm. Furthermore, due to their isolation, oceanic islands represent peculiar habitats that are expected to be more vulnerable to disturbances like species introductions or changes in climatic conditions. In this context, Macaronesia constitutes a group of highly isolated archipelagos in the Northeast Atlantic formed by the Azores, Madeira, Canary Islands, and Cape Verde island systems. This thesis focused on analyzing the different aspects of changes in sea surface temperatures at Madeira Island and their impact on local species. Furthermore, it represents the first comprehensive regional study of marine heatwaves and cold spells performed on an oceanic island and a pioneering effort for the Macaronesia region. Ongoing changes in sea surface temperatures can be separated into two different elements: changes in long-term average temperatures and distinct extreme events. To this end, both aspects of ocean warming were analyzed for the Madeira Archipelago. Satellite data analysis showed an increase of 0.8°C in the average temperatures over the last four decades at Madeira. The comparison of different time periods showed that current warming trends are accelerating. The analysis of temperature extreme events showed that temporal trends in heatwave and cold spell frequencies were both driven by the underlying warming trends. After removing the long-term trend, both marine heatwaves and cold spells at Madeira occurred at a rate of an average of about two events per year, reaching maximum intensities of ~3.5°C and lasting on average ~11 days. This thesis is structured in two sections: The first section includes two ... |
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