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Abstract

Glacial inception is commonly interpreted as a response to declining summer insolation, which reduces ablation and allows perennial snow to accumulate. How the controls on ice-sheet growth evolve after this initial phase, however, is less well understood. Here, we analyze a transient simulation of the last glacial inception from 127 to 65 ka using the AWI Earth System Model (AWI-ESM) coupled to the Parallel Ice Sheet Model (PISM) for the Northern Hemisphere domain. Our results show two stages of Laurentide Ice Sheet (LIS) growth. During the early phase (127–115 ka), glaciation is mainly associated with reduced summer melt and follows the southward migration of the summer 0 °C isotherm. After approximately 115 ka, this relationship changes and the ice sheet margin continues to advance into regions with negative surface mass balance. A decomposition of changes in local ice thickness indicates that dynamic mass redistribution from the interior to the margin supports this advance. Changes in LIS surface elevation are associated with changes in regional moisture transport and an increasing fraction of precipitation falling as snow over parts of the ice sheet help maintain a positive surface mass balance in the interior. Our simulation indicates a transition from early, climate-limited glaciation to dynamically supported growth, in which local climate conditions no longer determine ice-sheet advance. Although the timing and magnitude of this transition depend on the experimental setup, our results show how an evolving ice sheet can shift the relative roles of melt, accumulation, and ice dynamics during glacial inception.

Speaker information

Lars Ackermann is a postdoctoral researcher in the Paleoclimate Dynamics section at the Alfred Wegener Institute (AWI). He received his PhD from the University of Bremen in 2023 and has been part of the PalMod project (Paleo Modelling) since 2020. His research focuses on long-term climate–ice sheet interactions, particularly the role of the Greenland Ice Sheet and icebergs in past and future climate change. Using coupled climate–ice sheet modelling, he investigates ice sheet evolution and its impacts on ocean circulation and the wider climate system over centennial to millennial timescales.

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Jarle Børve Sleire disputerer 20.11.2026 for ph.d.-graden ved Universitetet i Bergen med avhandlingen «Crossing the threshold: lake sediments record glacier-climate change and floods».

Les mer her: Disputas: Jarle Børve Sleire | UiB

Dear All,

We are pleased to announce the 1st BCCR AMOC forum, that will take place on December 10th 2026 in the Bjerknes meeting room 4020. 

We plan to provide some light snack or meal for lunch/coffee break during this event, within limits of budget and number of participants. Hence, we kindly ask participants to register by Friday December 4th using the link below, so we can plan for this.

 Link to registration form and tentative program:

https://docs.google.com/forms/d/e/1FAIpQLSdlIqpgCVQNbE1D66BiwY2TLB-HTbn2WvBf8g1zEkhXZhMM1Q/viewform?usp=dialog

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