Title: Time scales of climate change and environmental stress across the tropical oceans

Authors: Thomas Felis¹, Jessica A. Hargreaves¹, Hana Camelia¹, Oliver Knebel¹, Andrew M. Dolman², Alyssa R. Atwood³

Affiliations: 
¹ MARUM-Center for Marine Environmental Sciences, University of Bremen, Germany

²Alfred‐Wegener‐Institut Helmholtz‐Zentrum für Polar‐ und Meeresforschung, Germany

³Department of Earth, Ocean, & Atmospheric Science, Florida State University, USA

Abstract: The last two years were characterized by record global temperatures and regional weather extremes, further amplified by an El Niño event in the tropical Pacific. Surface temperatures of the world's oceans reached unprecedented levels, leading to marine heatwaves that severely stressed vulnerable ecosystems such as tropical coral reefs. On the continents, heatwaves, droughts, extreme rainfall and floods led to the destruction of lives and infrastructure. The interaction between the tropical ocean basins plays a key role in modulating climate variability on interannual to decadal timescales. These timescales are of strong relevance to societies and ecosystems, because they control the time interval for recovery between extreme events. The PAGES 2k Network provides critical context for our understanding of anthropogenic forcing of climate, as well as information about Earth’s natural climate variability over the past 2000 years. Building on key findings around the response of the global water cycle to temperature changes by the Iso2k project, the focus of ongoing 2k research is the reconstruction of hydroclimate over the past two millennia. Hydroclimatic changes are a key parameter in projections of the regional impacts in a warming climate. Throughout the tropical oceans, a key archive for reconstructions of temperature and hydrology are massive shallow-water corals. Annually to monthly resolved coral records, archived in the CoralHydro2k database, are critical for our understanding of tropical ocean-atmosphere interactions. Discrepancies between proxy reconstructions, instrumental observations, and model simulations on longer timescales highlight the need for ongoing research in this area. The new CoralHydro2k seawater oxygen isotope database will be essential in calibrating reconstructions of surface ocean hydrology, providing additional avenues to resolve discrepancies. Finally, tropical corals not only provide information about the thermal and hydrologic history experienced during their lifetime, but also insights into the response of ecosystems to past and ongoing environmental stress.

Biography: Thomas Felis is the head of the Coral Paleoclimatology Group at MARUM-Center for Marine Environmental Sciences, University of Bremen. In 2017, Thomas co-initiated the PAGES CoralHydro2k Project, which aims to reconstruct tropical ocean hydroclimate and temperature from coral archives. Within this project, together with many early-career researchers, the CoralHydro2k Database was compiled, a global, actively-curated compilation of coral oxygen isotope and Sr/Ca records covering the Common Era. Thomas has been involved in three IODP expeditions to Tahiti, the Great Barrier Reef and Hawai’i to recover fossil corals from the last deglacial, glacial and beyond. Currently, Thomas coordinates the Priority Programme "Tropical Climate Variability & Coral Reefs" of the German Research Foundation (DFG), which aims to improve our understanding of tropical marine climate variability and its impacts on coral reef ecosystems in a warming world, and which involves more than 40 interdisciplinary researchers from 15 institutions across Germany.