The origin of large, long-term sea-level oscillations during non-glacial times remains uncertain. Here, the authors develop geological evidence that reveals astronomically forced land–ocean water exchange as a potential missing link for reconciling geological records and models of sea-level change. (Li et al., Nat. Commun. 2018)
Coastal landscape in an ancient world
An artist’s rendering of a coastal ocean landscape in the early Triassic world 250 million years ago 
(Credit: Hewei Duan)
Article | OPEN

Sedimentary noise and sea levels linked to land–ocean water exchange and obliquity forcing

Mingsong Li, Linda A. Hinnov, Chunju Huang & James G. Ogg

Abstract
In ancient hothouses lacking ice sheets, the origins of large, million-year (myr)-scale sea-level oscillations remain a mystery, challenging current models of sea-level change. To address this mystery, we develop a sedimentary noise model for sea-level changes that simultaneously estimates geologic time and sea level from astronomically forced marginal marine stratigraphy. The noise model involves two complementary approaches: dynamic noise after orbital tuning (DYNOT) and lag-1 autocorrelation coefficient (ρ1). Noise modeling of Lower Triassic marine slope stratigraphy in South China reveal evidence for global sea-level variations in the Early Triassic hothouse that are anti-phased with continental water storage variations in the Germanic Basin. This supports the hypothesis that long-period (1-2 myr) astronomically forced water mass exchange between land and ocean reservoirs is a missing link for reconciling geological records and models for sea-level change during non-glacial periods.
Figure 7. Water exchange between continental water storage and the ocean forced by astronomically forced climate change leads to major sea-level variations. a More moisture transferred to the continent leads to recharging of groundwater and lakes, and a flourishing terrestrial ecosystem. This results in a lowering of sea-level and wave base and more environmental noise (e.g., increased sediment mixing) at the location of observer (red flag). b Less moisture transferred to the continent leads to depleted groundwater and lakes, and a rise in sea-level and wave base with less environmental noise at the location of the observer.
Illustrations © Hewei Duan

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