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

influence on marine ecosystem structure and function [22–24]. They lead to discrete climatic events that can drive step-wise changes in species distributions and ecosystem structure and functioning [25]. Thus, MHWs have profound ecological impacts that included widespread mortality of benthic invertebrates [26] and loss of seagrass meadows [27]. The future evolution of MHWs depends on changes in the mean temperature and on changes in the intra-seasonal variability. The first factor is usually the dominant one, accounting for a large part of the pro- jected changes in MHWs [18,22,23]. Unfortunately, high frequency outputs from the selected GCMs were not available, so here we analyse how changes in the mean temperature would affect the characteristics of MHWs in the Red Sea. The paper is structured as follows. The observational datasets, the numerical simulations and the indicators used to assess model skills are presented in Section 2. The model skill assess- ment and model selection are presented in Section 3 while the results for temperature projec- tions are described in Section 4. Then the results are discussed in Section 5 and the main conclusions are drawn in Section 6. Data and methods Observational datasets In-situ data. We used the TEMPERSEA gridded product [17] as the reference observa- tional dataset for model performance assessment. TEMPERSEA is based on a large dataset of in-situ temperature observations which are homogenized and mapped into a 3D field using optimal interpolation. The database covers the Red Sea and the Outer Region with a spatial

resolution of 0.25˚x 0.25˚ and 23 vertical levels, (Fig 1 for the limits of both regions), providing Fig 1. Domain and bathymetry of the region of interest. The two zones used in the presentation of the results (Red Sea and the Outer Region) are identified by blue and red dashed contours, respectively. Eastern boundary limit of the KAUST model (vertical grey line). Northern and Southern zones, as considered for the computations, are separated at latitude 20˚ (horizontal green line). https://doi.org/10.1371/journal.pone.0255505.g001 PLOS ONE Assessment of Red Sea temperatures in CMIP5 models for present and future climate PLOS ONE | https://doi.org/10.1371/journal.pone.0255505 July 30, 2021 3 / 26