CO<sub>2</sub> and summer insolation as drivers for the Mid-Pleistocene Transition
<p>During the Mid-Pleistocene Transition (MPT; <span class="inline-formula">∼</span> 1.2–0.8 Myr ago) the dominant periodicity of glacial cycles increased from 41 kyr to an average of 100 kyr, without any appreciable change in the orbital pacing. As the MPT is not a linea...
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Copernicus Publications
2025-06-01
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| Series: | Climate of the Past |
| Online Access: | https://cp.copernicus.org/articles/21/1061/2025/cp-21-1061-2025.pdf |
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| author | M. D. W. Scherrenberg M. D. W. Scherrenberg C. J. Berends R. S. W. van de Wal R. S. W. van de Wal |
| author_facet | M. D. W. Scherrenberg M. D. W. Scherrenberg C. J. Berends R. S. W. van de Wal R. S. W. van de Wal |
| author_sort | M. D. W. Scherrenberg |
| collection | DOAJ |
| description | <p>During the Mid-Pleistocene Transition (MPT; <span class="inline-formula">∼</span> 1.2–0.8 Myr ago) the dominant periodicity of glacial cycles increased from 41 kyr to an average of 100 kyr, without any appreciable change in the orbital pacing. As the MPT is not a linear response to orbital forcing, it must have resulted from feedback processes in the Earth system. However, the precise mechanisms underlying the transition are still under debate.</p>
<p>In this study, we investigate the MPT by simulating the Northern Hemisphere ice-sheet evolution over the past 1.5 Myr. The transient climate forcing of the ice-sheet model was obtained using a matrix method, by interpolating between two snapshots of global climate model simulations. Changes in climate forcing are caused by variations in CO<span class="inline-formula"><sub>2</sub></span> and insolation, as well as implicit climate–ice-sheet feedbacks.</p>
<p>Using this method, we were able to capture glacial–interglacial periodicity during the past 1.5 Myr and thereby reproduce the shift from 41 to 100 kyr cycles without any additional drivers. Instead, the modelled frequency change results from the prescribed CO<span class="inline-formula"><sub>2</sub></span> combined with orbital forcing and ice-sheet feedbacks. Early Pleistocene terminations are initiated by insolation maxima. After the MPT, low interstadial CO<span class="inline-formula"><sub>2</sub></span> levels may compensate insolation maxima which would otherwise favour deglaciation, leading to a longer duration of the glacial cycle. Terminations are also affected by ice volume. If the North American ice sheet is small or very large, it becomes sensitive to small temperature increases. A medium-sized ice sheet is less sensitive through its location and the merger of the Laurentide and Cordilleran ice sheets. Therefore, Late Pleistocene terminations are also facilitated by the large ice-sheet volume, where small changes in temperature lead to self-sustained melt.</p>
<p>Additionally, we carried out experiments with constant CO<span class="inline-formula"><sub>2</sub></span>, where we can capture the 41 kyr cycles and some Late Pleistocene cycles. However, no persistent 100 kyr periodicity is established. Experiments with constant (or evolving) CO<span class="inline-formula"><sub>2</sub></span> concentrations did not generate a substantial precession signal in the ice volume. Instead, the frequency is dominated by successful terminations, which are initiated by strong (generally obliquity) insolation maxima. Our results therefore indicate that the glacial cycle periodicity of the past 1.5 Myr can be described by changes in insolation, CO<span class="inline-formula"><sub>2</sub></span>, and ice-sheet feedback processes and that maintaining low CO<span class="inline-formula"><sub>2</sub></span> throughout insolation maxima may prolong glacial cycles.</p> |
| format | Article |
| id | doaj-art-a725bcdbb9b54bb5972b82897b79e5f7 |
| institution | DOAJ |
| issn | 1814-9324 1814-9332 |
| language | English |
| publishDate | 2025-06-01 |
| publisher | Copernicus Publications |
| record_format | Article |
| series | Climate of the Past |
| spelling | doaj-art-a725bcdbb9b54bb5972b82897b79e5f72025-08-20T03:23:11ZengCopernicus PublicationsClimate of the Past1814-93241814-93322025-06-01211061107710.5194/cp-21-1061-2025CO<sub>2</sub> and summer insolation as drivers for the Mid-Pleistocene TransitionM. D. W. Scherrenberg0M. D. W. Scherrenberg1C. J. Berends2R. S. W. van de Wal3R. S. W. van de Wal4Institute for Marine and Atmospheric research Utrecht, Utrecht University, Utrecht, the NetherlandsInvited contribution by Meike D. W. Scherrenberg, recipient of the EGU Climate: Past, Present & Future Outstanding Student and PhD candidate Presentation Award 2024.Institute for Marine and Atmospheric research Utrecht, Utrecht University, Utrecht, the NetherlandsInstitute for Marine and Atmospheric research Utrecht, Utrecht University, Utrecht, the NetherlandsFaculty of Geosciences, Department of Physical Geography, Utrecht University, Utrecht, the Netherlands<p>During the Mid-Pleistocene Transition (MPT; <span class="inline-formula">∼</span> 1.2–0.8 Myr ago) the dominant periodicity of glacial cycles increased from 41 kyr to an average of 100 kyr, without any appreciable change in the orbital pacing. As the MPT is not a linear response to orbital forcing, it must have resulted from feedback processes in the Earth system. However, the precise mechanisms underlying the transition are still under debate.</p> <p>In this study, we investigate the MPT by simulating the Northern Hemisphere ice-sheet evolution over the past 1.5 Myr. The transient climate forcing of the ice-sheet model was obtained using a matrix method, by interpolating between two snapshots of global climate model simulations. Changes in climate forcing are caused by variations in CO<span class="inline-formula"><sub>2</sub></span> and insolation, as well as implicit climate–ice-sheet feedbacks.</p> <p>Using this method, we were able to capture glacial–interglacial periodicity during the past 1.5 Myr and thereby reproduce the shift from 41 to 100 kyr cycles without any additional drivers. Instead, the modelled frequency change results from the prescribed CO<span class="inline-formula"><sub>2</sub></span> combined with orbital forcing and ice-sheet feedbacks. Early Pleistocene terminations are initiated by insolation maxima. After the MPT, low interstadial CO<span class="inline-formula"><sub>2</sub></span> levels may compensate insolation maxima which would otherwise favour deglaciation, leading to a longer duration of the glacial cycle. Terminations are also affected by ice volume. If the North American ice sheet is small or very large, it becomes sensitive to small temperature increases. A medium-sized ice sheet is less sensitive through its location and the merger of the Laurentide and Cordilleran ice sheets. Therefore, Late Pleistocene terminations are also facilitated by the large ice-sheet volume, where small changes in temperature lead to self-sustained melt.</p> <p>Additionally, we carried out experiments with constant CO<span class="inline-formula"><sub>2</sub></span>, where we can capture the 41 kyr cycles and some Late Pleistocene cycles. However, no persistent 100 kyr periodicity is established. Experiments with constant (or evolving) CO<span class="inline-formula"><sub>2</sub></span> concentrations did not generate a substantial precession signal in the ice volume. Instead, the frequency is dominated by successful terminations, which are initiated by strong (generally obliquity) insolation maxima. Our results therefore indicate that the glacial cycle periodicity of the past 1.5 Myr can be described by changes in insolation, CO<span class="inline-formula"><sub>2</sub></span>, and ice-sheet feedback processes and that maintaining low CO<span class="inline-formula"><sub>2</sub></span> throughout insolation maxima may prolong glacial cycles.</p>https://cp.copernicus.org/articles/21/1061/2025/cp-21-1061-2025.pdf |
| spellingShingle | M. D. W. Scherrenberg M. D. W. Scherrenberg C. J. Berends R. S. W. van de Wal R. S. W. van de Wal CO<sub>2</sub> and summer insolation as drivers for the Mid-Pleistocene Transition Climate of the Past |
| title | CO<sub>2</sub> and summer insolation as drivers for the Mid-Pleistocene Transition |
| title_full | CO<sub>2</sub> and summer insolation as drivers for the Mid-Pleistocene Transition |
| title_fullStr | CO<sub>2</sub> and summer insolation as drivers for the Mid-Pleistocene Transition |
| title_full_unstemmed | CO<sub>2</sub> and summer insolation as drivers for the Mid-Pleistocene Transition |
| title_short | CO<sub>2</sub> and summer insolation as drivers for the Mid-Pleistocene Transition |
| title_sort | co sub 2 sub and summer insolation as drivers for the mid pleistocene transition |
| url | https://cp.copernicus.org/articles/21/1061/2025/cp-21-1061-2025.pdf |
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