Fossil coral reconstructions of El Niño-Southern Oscillation variability during Heinrich Stadial 1 and the Younger Dryas

Abstract:

The El Niño-Southern Oscillation (ENSO) is the leading mode of interannual climate variability and has widespread socioeconomic impacts on human activities. Current climate model projections for the future disagree on how ENSO will respond to anthropogenic warming. Reconstructions of past ENSO variability provide an opportunity to investigate the response of ENSO to changes in external forcings. Obtaining coral paleo-records from the last deglaciation 11-19 thousand years ago (ka) will address a missing gap in our understanding of ENSO’s response to abrupt climate changes associated with large scale changes in ocean circulation patterns. However, coral paleo-records concurrent with abrupt climate events are increasingly sparse farther back in time, as it is difficult to recover fossil coral specimens from this time period when sea level was lower. Here we present sub-annually resolved records of paleo-ENSO variability (~50-200 years in length) over the interval from 10-15 ka. The selected corals provide “snapshots” of paleo-ENSO variability during Heinrich Stadial 1, the Bølling-Allerød, the Younger Dryas, and the early Holocene, which allows us to investigate the range of ENSO variability during times concurrent with abrupt changes in Atlantic Meridional Overturning Circulation strength. Our work provides insights about ENSO’s response during periods of abrupt climate change and provides important independent validation for climate model simulations run under past climate conditions.