Past ocean-atmosphere variability from tropical corals

The interaction of warm tropical ocean surface waters with the overlying atmosphere on seasonal, interannual, and decadal timescales is the source of climate extremes throughout the tropics and beyond. Tropical cyclones, heatwaves, flash floods, droughts, and El Niño have severe effects on ecosystems and societies globally. Projecting their amplitude and frequency changes in a warming climate requires knowledge of how the tropical ocean-atmosphere system operated in the past. Tropical shallow-water corals are a powerful paleoclimatic archive for extending the short and rather sparse instrumental record of sea surface observations at monthly resolution. Coral records deliver quantitative information about the fluctuations of sea surface temperature and hydrology on seasonal, interannual, and decadal timescales, with precise chronology. They provide a paleo-observational constraint on climate model simulations of past and future tropical ocean-atmosphere variability. The given course will introduce to scientific methods and findings from coral-based reconstructions of surface ocean conditions. It will focus on the expression of modes of seasonal, interannual and decadal climate variability in isotopic and geochemical proxies incorporated in coral carbonate skeletons. During the course, samples and cores from modern and fossil corals will be investigated. Students will obtain a broad perspective on climate variability on these timescales, with insights into coral-based examples from the last millennium, the Holocene, the last deglaciation, and the last interglacial period

- acquire insights into techniques for constructing coral proxy records
- acquire knowledge in coral drilling field campaigns, coordinated coral reef drilling expeditions (IODP), and community-driven data synthesis efforts
- provide an overview of interannual to decadal modes of climate variability
- discover the mechanisms that control climate variability on seasonal to decadal timescales
- study selected extreme interannual climate events during the recent past in detail
- advanced skills in literature review, scientific writing and presentation by supplementing findings from coral proxy records to gain a comprehensive understanding of tropical climate variability on these timescales

15 minutes conference-style talks and a scientific article style report (in groups of 2-3)

Projektarbeitsbericht

Abram, N.J., Wright, N.M., Ellis, B. et al. (2020) Coupling of Indo-Pacific climate variability over the last millennium. Nature, 579, 385–392. https://doi.org/10.1038/s41586-020-2084-4
Felis, T (2020) Extending the instrumental record of ocean-atmosphere variability into the last interglacial using tropical corals. Oceanography, 33, 68-79. https://doi.org/10.5670/oceanog.2020.209
Thompson, D. M. (2022) Environmental records from coral skeletons: A decade of novel insights and innovation. Wiley Interdisciplinary Reviews: Climate Change, 13, e745. https://doi.org/10.1002/wcc.745
Ummenhofer, C.C., Murty, S.A., Sprintall, J. et al. (2021) Heat and freshwater changes in the Indian Ocean region. Nature Reviews Earth & Environment, 2, 525–541. https://doi.org/10.1038/s43017-021-00192-6

1st Day: Coral proxy records and instrumental observations of climate
2nd Day: Coral drilling expeditions and community-driven data synthesis efforts
3rd Day: Modes of interannual to decadal climate variability in coral proxy records
4th Day: Seasonality and interannual extreme events in coral proxy records
5th Day: “Scientific Conference” with presentations of the participants
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