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

• Published in: Geophysical research letters 2022-01, Vol.49 (1), p.n/a
• Main Authors: Hitt, Nicholas T., Sayani, Hussein R., Atwood, Alyssa R., Grothe, Pamela R., Maupin, Christopher, O’Connor, Gemma K., Walter, Rachel M., Gebregiorgis, Daniel, Hardt, Madeleine E., Lu, Yanbin, Cheng, Hai, Edwards, R. Lawrence, Cobb, Kim M.
• Format: Article
• Language: English
• Subjects: 20th century; Anthropogenic factors; Atolls; Climate; Climate trends; Climate variability; Climate variations; Corals; Fossils; Global temperatures; Human influences; Natural variability; Oxygen; Oxygen isotopes; Rain; Rainfall; Rainfall patterns; Reconstruction; Records; Sea surface; Sea surface temperature; Surface temperature; Trends; Tropical climate; Tropical climates; Tropical environments; Variability
• ISSN: 0094-8276; 1944-8007
• DOI: 10.1029/2021GL094051

The tropical Pacific influences climate patterns across the globe, yet robust constraints on decadal to centennial‐scale climate variations are difficult to extract from sparse instrumental observations in this region. Oxygen isotope (δ18O) records from long‐lived corals enable the quantitative reconstruction of tropical Pacific climate variability and trends over the twentieth century and beyond, but such corals are exceedingly rare. Here, we use multiple short coral δ18O records to create a coral ‘ensemble’ reconstruction of twentieth century climate in the central tropical Pacific. Ten U/Th‐dated fossil coral δ18O records from Kiritimati Island (2°N, 157°W) span 1891 CE to 2006 CE, with the younger samples enabling quantitative comparison to a large ensemble of modern coral records and instrumental sea surface temperature. A composite record constructed of modern and fossil Kiritimati coral δ18O records shows a shift toward warmer and fresher conditions from 1970 CE onward, consistent with previously published records in this region. Plain Language Summary The tropical Pacific plays a major role in shaping global temperature and rainfall patterns, but sparse instrumental observations prior to ∼1950 CE hamper the detection of potential anthropogenic climate signals against the rich background of natural variability in this region. This study demonstrates the utility of reconstructing twentieth century climate trends using an ensemble of multiple, short coral records in data‐sparse regions of the tropics. When applied to the central equatorial Pacific, coral data from Kiritimati Atoll resolve a twentieth century shift toward warmer and wetter conditions in this region, in line with evidence from continuous, century‐long coral records previously published from this region. Key Points Ensembles of short fossil coral δ18O records yield robust estimates of nineteenth‐twentieth century climate variability and trends Seawater δ18O contributions to Kiritimati coral δ18O are larger on multi‐decadal timescales than on interannual timescales Coral δ18O records reveal a trend toward warmer and wetter conditions in the central equatorial Pacific over the twentieth century