Preprints
https://doi.org/10.5194/egusphere-2023-1462
https://doi.org/10.5194/egusphere-2023-1462
04 Jul 2023
 | 04 Jul 2023
Status: this preprint is open for discussion and under review for Climate of the Past (CP).

Glacial inception through rapid ice area increase driven by albedo and vegetation feedbacks

Matteo Willeit, Reinhard Calov, Stefanie Talento, Ralf Greve, Jorjo Bernales, Volker Klemann, Meike Bagge, and Andrey Ganopolski

Abstract. We present transient simulations of the last glacial inception using the Earth system model CLIMBER-X with dynamic vegetation, interactive ice sheets and visco-elastic solid-Earth response. The simulations are initialized at the middle of the Eemian interglacial (125 kiloyears before present, ka) and run until 100 ka, driven by prescribed changes in Earth’s orbital parameters and greenhouse gas concentrations from ice core data.

CLIMBER-X simulates a rapid increase in Northern Hemisphere ice sheet area through MIS5d, with ice sheets expanding over northern North America and Scandinavia, in broad agreement with proxy reconstructions. While most of the increase in ice sheet area occurs over a relatively short period between 119 ka and 117 ka, the larger part of the increase in ice volume occurs afterwards with an almost constant ice sheet extent.

We show that the vegetation feedback plays a fundamental role in controlling the ice sheet expansion during the last glacial inception. In particular, with prescribed present-day vegetation the model simulates a global sea level drop of only ∼20 m, compared with the ∼35 m decrease in sea level with dynamic vegetation response. The ice sheet and carbon-cycle feedbacks play only a minor role during the ice sheet expansion phase prior to ∼115 ka, but are important in limiting the deglaciation during the following phase characterized by increasing summer insolation.

The model results are sensitive to climate model biases and to the parameterisation of snow albedo, while they show only a weak dependence on changes in the ice sheet model resolution and the acceleration factor used to speed up the climate component.

Overall, our simulations confirm and refine previous results showing that climate-vegetation-cryosphere-carbon cycle feedbacks play a fundamental role in the transition from interglacial to glacial states characterising Quaternary glacial cycles.

Matteo Willeit et al.

Status: open (until 13 Oct 2023)

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Matteo Willeit et al.

Matteo Willeit et al.

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Short summary
We present transient simulations of the last glacial inception with the coupled climate-ice sheet model CLIMBER-X showing a rapid increase in Northern Hemisphere ice sheet area and a sea level drop by ~35 m, with the vegetation feedback playing a key role. Overall, our simulations confirm and refine previous results showing that climate-vegetation-cryosphere-carbon cycle feedbacks play a fundamental role in the transition from interglacial to glacial states.