Last Interglacial Hydroclimate Seasonality Reconstructed From Tropical Atlantic Corals

Abstract

Abstract The seasonality of hydroclimate during past periods of warmer than modern global temperatures is a critical component for understanding future climate change scenarios. Although only partially analogous to these scenarios, the last interglacial (LIG, Marine Isotope Stage 5e, ~127–117 ka) is a popular test bed. We present coral δ 18 O monthly resolved records from multiple Bonaire (southern Caribbean) fossil corals ( Diploria strigosa ) that date to between 130 and 118 ka. These records represent up to 37 years and cover a total of 105 years, offering insights into the seasonality and characteristics of LIG tropical Atlantic hydroclimate. Our coral δ 18 O records and available coral Sr/Ca‐sea surface temperature (SST) records reveal new insights into the variable relationship between the seasonality of tropical Atlantic seawater δ 18 O (δ 18 O seawater ) and SST. Coral δ 18 O seasonality is found to covary with SST and insolation seasonality throughout the LIG, culminating in significantly higher than modern values at 124 and 126 ka. At 124 ka, we reconstruct a 2 month lead of the coral δ 18 O versus the Sr/Ca‐SST annual cycle and increased δ 18 O seawater seasonality. A fully coupled climate model simulates a concomitant increase of southern Caribbean Sea summer precipitation and depletion of summer δ 18 O seawater . LIG hydroclimate at Bonaire differed from today's semiarid climate with a minor rainy season during winter. Cumulatively, our coral δ 18 O, δ 18 O seawater , and model findings indicate a mid‐LIG northward expansion of the South American Intertropical Convergence Zone into the southern Caribbean Sea, highlighting the importance of regional aspects within model and proxy reconstructions of LIG hydroclimate seasonality.