A global perspective on the timing and nature of sub-orbital sea level oscillations during MIS 5e

Abstract:

Although multiple, sub-orbital peaks in sea level during Marine Isotope Stage (MIS) 5e have a long history in the literature, there is still debate regarding the number, timing, and magnitude of sea–level peaks. A wide range of competing scenarios have been proposed based on observations from individual field sites including: (i) a stable sea level, (ii) a stable sea level punctuated by an ephemeral drop in sea level (2 peaks), (iii) a stable sea level followed by a rapid rise (2 peaks), or (iv) several (3-4) peaks in sea level that define an oscillating trend during the highstand. While some field sites appear to have conflicting evidence regarding the timing and nature of relative sea-level changes that cannot be reconciled through glacial isostatic processes alone, clearly there must be one global mean sea level (GMSL) reconstruction that gave rise to the evidence that is presently observed in the geologic record.

We take a holistic approach to understanding the evolution of sea level during the MIS 5e highstand by integrating sedimentary, floral, faunal, and geochemical evidence from coral reef sites around the globe. Our aim is to develop a scenario for sea-level change during the MIS 5e highstand that satisfies the global observational dataset. Several conclusions emerge from this analysis: (1) there are many sites that preserve clear sedimentary evidence for two distinct sub-orbital peaks in sea level, and fewer that have possible evidence for more than two peaks; (2) there is conflicting evidence as to whether these two peaks are separated by an ephemeral sea-level fall, or whether they are defined by a stable sea level followed by a rapid rise; (3) multiple sites demonstrate significantly different geochemical signatures associated with distinct generations of reef growth as defined by their U-series geochemistry, indicating different post-depositional histories that may be related to differences in post-depositional marine submergence and exposure. Finally, while many studies agree that there was a significant Antarctic contribution to the MIS 5e sea level budget, the timing of this contribution remains debated. This presentation will focus on evaluating and reconciling competing hypotheses about the timing of rapid mass loss from the Antarctic ice sheet.