Coral Oxygen Isotopic Records Capture the 2015/2016 El Niño Event in the Central Equatorial Pacific

Abstract

The El Niño-Southern Oscillation (ENSO) is the dominant mode of interannual climate variability, but its response to greenhouse warming remains highly uncertain (Bellenger et al., 2014;Ng et al., 2021;Stevenson, 2012). Although projections of ENSO-related sea surface temperature (SST) variability differ across climate models, simulations forced with projected anthropogenic greenhouse gas emissions generally agree on an increase in the hydrological extremes associated with ENSO (

Central Equatorial Pacific Warming and Freshening in the Twentieth Century: Insights From a Coral Ensemble Approach

“…It is worth noting that the contribution of SST and SSS to the twentieth century Kiritimati coral δ 18 O trend is markedly different than the ∼70% SST and ∼30% δ 18 O sw contributions to coral δ 18 O anomalies documented across recent strong El Niño events at the site (O’Connor et al., 2021). Frequency‐dependent relationships between SST and SSS have been inferred from other studies (Liu and Di Lorenzo, 2018; Xie et al., 2010), including coral studies (Russon et al., 2013), and our study further supports the notion that different physical processes likely dominate regional climate across interannual, multi‐decadal and centennial timescales…”

“…We present three twentieth century Kiritimati coral δ 18 O composites: (a) fossil coral δ 18 O composite records spanning 1952-1972 and 1978-2006 constructed by splicing together new and existing fossil coral δ 18 O data; (b) a modern coral δ 18 O composite constructed from previously published records (Evans et al, 1999;Cobb et al, 2013;Grothe et al, 2019;Nurhati et al, 2011;O'Connor et al, 2021); and (3) a composite of all modern and fossil coral records spanning 1891-2016 (Figures 1 and 2a). Coral δ 18 O composites were constructed from centered δ 18 O records, where mean offsets in coral δ 18 O were removed by subtracting the mean δ 18 O value of each record from the mean δ 18 O value of all overlapping records (Sayani et al, 2019).…”

“…Figure 1. (a) Twentieth century Kiritimati modern (gray;Cobb et al, 2013;Grothe et al, 2019;Nurhati et al, 2009;O'Connor et al, 2021) and fossil coral (various colors) δ 18 O sequences. U/Th dates (triangles) for the fossil coral sequences are shown with 2σ error bars in corresponding colors (TableS2in Supporting Information S1).…”

“…Figure 2. (a) Composite Kiritimati coral δ 18 O record, built using published modern(Cobb et al, 2013;Grothe et al, 2019;Nurhati et al, 2009;O'Connor et al, 2021) and new fossil coral δ 18 O sequences, with corresponding ±2σ uncertainties (light blue shading). Uncertainties are not visible on the scale shown from 1938 to 2016 CE.…”

Contrasting Central Equatorial Pacific Oxygen Isotopic Signatures of the 2014/2015 and 2015/2016 El Niño Events

“…However, nearby Christmas Island (1.9°N, 202.1°E) is only a few hundred miles away but experienced much stronger El Niño responses owing to its proximity to the equator (Cobb et al., 2013; Grothe et al., 2020; O’Connor et al., 2021). At Christmas, temperature accounted for roughly 70%–80% of the δ 18 O excursion during the 2015–2016 El Niño (O’Connor et al., 2021). While consistent with previous work (Nurhati et al., 2009, 2011), this study thus illustrates the power of local observations to quantify temperature and hydrological impacts on δ 18 O.…”