Assessment of Red Sea temperatures in CMIP5 models for present and future climate

RESEARCH ARTICLE Assessment of Red Sea temperatures in CMIP5 models for present and future climate Miguel AgullesID1*, Gabriel JordàID1, Ibrahim Hoteit2, Susana Agustı´2, Carlos M. Duarte2 1 Centre Oceanogràfic de Balears, Instituto Español de Oceanografı´a, Palma, Spain, 2 King Abdullah University of Science and Technology (KAUST), Red Sea Research Center (RSRC), Thuwal, Saudi Arabia * miguel.agulles@ieo.es Abstract The increase of the temperature in the Red Sea basin due to global warming could have a large negative effect on its marine ecosystem. Consequently, there is a growing interest, from the scientific community and public organizations, in obtaining reliable projections of the Red Sea temperatures throughout the 21st century. However, the main tool used to do climate projections, the global climate models (GCM), may not be well suited for that rela- tively small region. In this work we assess the skills of the CMIP5 ensemble of GCMs in reproducing different aspects of the Red Sea 3D temperature variability. The results suggest that some of the GCMs are able to reproduce the present variability at large spatial scales with accuracy comparable to medium and high-resolution hindcasts. In general, the skills of the GCMs are better inside the Red Sea than outside, in the Gulf of Aden. Based on their performance, 8 of the original ensemble of 43 GCMs have been selected to project the tem- perature evolution of the basin. Bearing in mind the GCM limitations, this can be an useful benchmark once the high resolution projections are available. Those models project an

averaged warming at the end of the century (2080–2100) of 3.3 ±> 0.6˚C and 1.6 ±> 0.4˚C at the surface under the scenarios RCP8.5 and RCP4.5, respectively. In the deeper layers the warming is projected to be smaller, reaching 2.2 ±> 0.5˚C and 1.5 ±> 0.3˚C at 300 m. The projected warming will largely overcome the natural multidecadal variability, which could induce temporary and moderate decrease of the temperatures but not enough to fully counteract it. We have also estimated how the rise of the mean temperature could modify the characteristics of the marine heatwaves in the region. The results show that the average length of the heatwaves would increase ~15 times and the intensity of the heatwaves ~4 times with respect to the present conditions under the scenario RCP8.5 (10 time and 3.6 times, respectively, under scenario RCP4.5). Introduction The Red Sea holds one of the most diverse marine ecosystems in the world, but fragile and vul- nerable to oceanic warming [1], as reflected in massive coral bleaching across the southern Red Sea during the 2015 global bleaching event [2–4]. Water temperature plays a key role in PLOS ONE PLOS ONE | https://doi.org/10.1371/journal.pone.0255505 July 30, 2021 1 / 26 a1111111111 a1111111111 a1111111111 a1111111111 a1111111111 OPEN ACCESS Citation: Agulles M, Jordà G, Hoteit I, Agustı´ S, Duarte CM (2021) Assessment of Red Sea temperatures in CMIP5 models for present and future climate. PLoS ONE 16(7): e0255505. https:// doi.org/10.1371/journal.pone.0255505 Editor: João Miguel Dias, Universidade de Aveiro, PORTUGAL

Received: April 19, 2021 Accepted: July 18, 2021 Published: July 30, 2021 Peer Review History: PLOS recognizes the benefits of transparency in the peer review process; therefore, we enable the publication of all of the content of peer review and author responses alongside final, published articles. The editorial history of this article is available here: https://doi.org/10.1371/journal.pone.0255505 Copyright: © 2021 Agulles et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. Data Availability Statement: All relevant data are within the manuscript and its Supporting Information files. Funding: This research was funded by King Abdullah University of Science and Technology