A Neoproterozoic Transition in the Marine Nitrogen Cycle

Glacial flow of floating marine ice in ‘‘Snowball Earth’’

[1] Simulations of frigid Neoproterozoic climates have not considered the tendency of thick layers of floating marine ice to deform and spread laterally. We have constructed a simple model of the production and flow of marine ice on a planetary scale, and determined ice thickness and flow in two situations: when the ocean is globally icecovered (‘‘hard snowball’’) and when the tropical waters r...

Dynamics of the Neoproterozoic carbon cycle.

The existence of unusually large fluctuations in the Neoproterozoic (1,000-543 million years ago) carbon-isotopic record implies strong perturbations to the Earth's carbon cycle. To analyze these fluctuations, we examine records of both the isotopic content of carbonate carbon and the fractionation between carbonate and marine organic carbon. Together, these are inconsistent with conventional, ...

Late Proterozoic Transitions in Climate, Oxygen, and Tectonics, and the Rise of Complex Life

—The transition to the diverse and complex biosphere of the Ediacaran and early Paleozoic is the culmination of a complex history of tectonic, climate, and geochemical development. Although much of this rise occurred in the middle and late intervals of the Neoproterozoic Era (1000–541 million years ago [Ma]), the foundation for many of these developments was laid much earlier, during the latest...

Biogeochemical cycling through the Neoproterozoic-Cambrian transition in China: an integrated study of redox-sensitive elements

Limited impact of atmospheric nitrogen deposition on marine productivity due to biogeochemical feedbacks in a global ocean model

The impact of increasing anthropogenic atmospheric nitrogen deposition on marine biogeochemistry is uncertain. We performed simulations to quantify its effect on nitrogen cycling and marine productivity in a global 3-D ocean biogeochemistry model. Nitrogen fixation provides an efficient feedback by decreasing immediately to deposition, whereas water column denitrification increases more gradual...