ReefTEMPS: the Pacific Islands coastal temperature network

Abstract. While the rise in global ocean temperature continues its course, reaching 1.45±0.12 °C above pre-industrial level according to the World Meteorological Organization in 2023, marine heatwave frequencies and intensities increase. Consequently, coral reef ecosystems, which are among the most vulnerable environments, are strongly impacted by dystrophic events and corals experiencing increasing frequencies of bleaching events. That has devastating consequences for the Pacific Island countries and territories (PICTs) that strongly rely on these ecosystems. In situ observation remains the best alternative for providing accurate characterization of long-term trends and extremes in these shallow environments. This paper presents the coastal temperature dataset of the ReefTEMPS monitoring network (Varillon et al., 2025, https://doi.org/10.17882/55128; Liao et al., 2025, https://doi.org/10.17882/82291) in which moored stations are implemented over a number of PICTs over a wide region in the western and central South Pacific from New Caledonia to French Polynesia. These in situ temperature time series are unique in several ways: in the length of some historical stations dating back to 1958 for the oldest, thus providing more than 65 years of daily data; in the number of countries sampled (16 PICTs); and in the variety of coral ecosystems monitored (from atolls to high islands and from barrier reefs' external slopes to shallow and narrow lagoons). Measurement devices have evolved over the years to provide increasingly precise and frequent observations, so the ReefTEMPS network was endorsed as a French National Observation Service in 2020, a label ensuring quality-controlled and open-access data of long-term observations. All stations are publicly available in ASCII or formatted NetCDF files either in the ReefTEMPS dedicated information system, which also allows for a quick visualization of time series, or on the SEANOE marine data platform. All links and accesses to these temperature time series are provided herein. The longevity of these temperature time series allows for diagnosing long-term trends, highlighting the influence of multiple processes on temperature dynamics (e.g. internal waves, cyclones, seasonal, and climate modes) and documenting the time evolution of extreme events. All files are made publicly available on dedicated SEANOE repositories.