ROCKE 3D Seminar, 2024-06-10
Speaker: Kaushal Gianchandani (MIT)
Title: “Revisiting the hard vs soft snowball debate”
Abstract: Geochemical and sedimentary evidence indicate that Earth's climate exhibited extreme glaciations - the snowball Earth events, at least twice during the Neoproterozoic era (1000 - 541 million years ago). Though, it is still debated whether the oceans were completely covered in hundreds of meters of ice ('hard' snowball) or whether the tropical ocean was ice-free ('soft' snowball). Reprise of layered, iron-rich sedimentary rocks called banded iron formations (BIFs) is considered evidence of a hard snowball state in which ferrous iron, Fe(II), accumulated in the anoxic ocean interior. However, such an extreme climate poses a challenge to the continuation of life through these glaciations. Alternatively, the soft snowball state does not pose a similar challenge to the marine biosphere, but air-sea oxygen fluxes may have prevented the mobility of Fe(II) required for the widespread deposition of BIFs. I use a state-of-the-art ocean model that includes representation of thick sea glaciers and Neoproterozoic biogeochemistry to demonstrate that BIFs can be produced in a soft snowball state.
9 июн 2024
