In:
Proceedings of the National Academy of Sciences, Proceedings of the National Academy of Sciences, Vol. 114, No. 50 ( 2017-12-12), p. 13114-13119
Abstract:
During the Mid-Pleistocene Transition (MPT; 1,200–800 kya), Earth’s orbitally paced ice age cycles intensified, lengthened from ∼40,000 (∼40 ky) to ∼100 ky, and became distinctly asymmetrical. Testing hypotheses that implicate changing atmospheric CO 2 levels as a driver of the MPT has proven difficult with available observations. Here, we use orbitally resolved, boron isotope CO 2 data to show that the glacial to interglacial CO 2 difference increased from ∼43 to ∼75 μatm across the MPT, mainly because of lower glacial CO 2 levels. Through carbon cycle modeling, we attribute this decline primarily to the initiation of substantive dust-borne iron fertilization of the Southern Ocean during peak glacial stages. We also observe a twofold steepening of the relationship between sea level and CO 2 -related climate forcing that is suggestive of a change in the dynamics that govern ice sheet stability, such as that expected from the removal of subglacial regolith or interhemispheric ice sheet phase-locking. We argue that neither ice sheet dynamics nor CO 2 change in isolation can explain the MPT. Instead, we infer that the MPT was initiated by a change in ice sheet dynamics and that longer and deeper post-MPT ice ages were sustained by carbon cycle feedbacks related to dust fertilization of the Southern Ocean as a consequence of larger ice sheets.
Type of Medium:
Online Resource
ISSN:
0027-8424
,
1091-6490
DOI:
10.1073/pnas.1702143114
Language:
English
Publisher:
Proceedings of the National Academy of Sciences
Publication Date:
2017
detail.hit.zdb_id:
209104-5
detail.hit.zdb_id:
1461794-8
SSG:
11
SSG:
12
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