Centennial-scale variations in the carbon cycle enhanced by high obliquity

Centennial-scale increases of atmospheric carbon dioxide, known
as carbon dioxide jumps, are identified during deglacial, glacial and
interglacial periods and linked to the Northern Hemisphere abrupt climate
variations. However, the limited number of identified carbon dioxide
jumps prevents investigating the role of orbital background conditions
on the different components of the global carbon cycle that may lead
to such rapid atmospheric carbon dioxide releases. Here we present a
high-resolution carbon dioxide record measured on an Antarctic ice core
between 260,000 and 190,000 years ago, which reveals seven additional
carbon dioxide Jumps. Eighteen of the 22 jumps identified over the past
500,000 years occurred under a context of high obliquity. Simulations
performed with an Earth system model of intermediate complexity point
towards both the Southern Ocean and the continental biosphere as the two
main carbon sources during carbon dioxide jumps connected to Heinrich
ice rafting events. Notably, the continental biosphere appears as the
obliquity-dependent carbon dioxide source for these abrupt events.
We demonstrate that the orbital-scale external forcing