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Abstract. Predictions of future sea-level change and ice-sheet stability rely on accurate reconstructions of sea levels for past warm intervals, such as the mid-Pliocene Warm Period (MPWP; 3.264–3.025 Ma). The magnitude of MPWP glacial cycles and the relative contribution of meltwater sources remain uncertain. We explore this issue by modeling processes of glacial isostatic adjustment for a wide range of possible MPWP ice-sheet melt zones, including North America, Greenland, Eurasia, and West Antarctica, as well as the Wilkes Basin, the Aurora Basin, and the embayment of Prydz Bay in East Antarctica. As a case study, we use a series of ice histories together with a suite of viscoelastic Earth models to predict global changes in sea level from the Marine Isotope Stage (MIS) M2 glacial to the MIS KM3 interglacial. At the Whanganui Basin (New Zealand), a location with stratigraphic constraints on Pliocene glacial–interglacial sea-level amplitude, the calculated local-sea-level (LSL) rise is on average ∼ 15 % lower than the associated change in the global mean sea level (GMSL) in the ice-sheet scenarios explored here. In contrast, the calculated LSL rise over the deglaciation from MIS M2 to MIS KM3 at Enewetak Atoll is systematically larger than the GMSL change by 10 %. While no single LSL observation (field site) can provide a unique constraint on the sources of ice melt observed during this period, combinations of observations have the potential to yield a stronger constraint on GMSL change and to narrow the list of possible sources.
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The influence of glacial isostatic adjustment on continental shelf stratigraphic correlation
Glacial isostatic adjustment (GIA) imparts geographic variability in the amplitude and timing of local sea-level (LSL) change arising from glacial-interglacial oscillations relative to a global mean signal (eustasy). We modeled how GIA manifests in the stratigraphic record across four shelf-perpendicular transects moving progressively more distal to the Quaternary North American ice complex, subject to varying amounts of GIA during glacial-interglacial cycles. Along each transect, we obtained LSL histories for nine sites between 1 m and 250 m water depth from the output of a gravitationally self-consistent GIA model run from marine oxygen isotope stage (MIS) 11 to the present. We paired each site’s unique LSL history with 50 identical annual sedimentation models to create a library of 400-k.y.-duration synthetic stratigraphic columns (each assuming no tectonics). Comparison of the suite of synthetic stratigraphic columns between transects for a given bathymetric depth reveals latitudinal differences in the stratigraphically determined number, magnitude, and age of glacial-interglacial cycles, as inferred from stratigraphic sequence count, apparent water-depth change, and age of preserved deglacial transgression. We conclude that, for many field locales, extraction of primary information about the number, scale, and duration of pre-Cenozoic glacial-interglacial cycles from continental shelf stratigraphic records near ice sheets demands a deconvolution of the GIA signal.
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- Award ID(s):
- 2046244
- PAR ID:
- 10334345
- Date Published:
- Journal Name:
- Geology
- ISSN:
- 0091-7613
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
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Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.1130/G49841.1
