Recent Constraints on MIS 3 Sea Level Support Role of Continental Shelf Exposure as a Control on Indo-Pacific Hydroclimate

Abstract

The mechanisms controlling changes in atmospheric circulation and rainfall over the Indo‐Pacific Warm Pool (IPWP) on glacial‐interglacial timescales remain a subject of considerable debate. Continental shelf exposure, through sea‐level drawdown during glacial periods, has been proposed as an important and possibly dominant control on rainfall intensity over the IPWP and Indian Ocean. However, longer records of hydroclimate change undermine this shelf exposure hypothesis. In particular, trends in some proxy records of rainfall do not track the extent of continental shelf exposure inferred from global benthic oxygen isotope records during Marine Isotope Stage 3 (MIS 3). We revisit the hypothesis that continental shelf exposure controls IPWP precipitation using the latest constraints on ice‐age sea level. Recent studies on the timing and magnitude of global mean sea level during mid‐MIS 3 (~45) suggest significantly higher peak sea level relative to previous work. Our gravitationally self‐consistent glacial isostatic adjustment sea‐level reconstructions, which adopt recent constraints on MIS 3 sea level, predict a transition from widely inundated to exposed shelves in the Indo‐Pacific region from mid‐MIS 3 to the beginning of the Last Glacial Maximum (LGM, ~19–26 ka). Over this same time period, proxy records of vegetation and hydrology from central Indonesia suggest a transition from wetter conditions during mid‐MIS 3 to drier conditions during the LGM. Our new calculations thus negate prior criticisms related to the timing and extent of shelf exposure, indicating that shelf exposure may remain an important driver for hydroclimate variability in the IPWP region on glacial‐interglacial timescales.

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