Internal ice - sheet variability as source for the multi-century and millennial-scale iceberg events during the Holocene? A model study

M. Bügelmayer, D.M.V.A.P. Roche, H. Renssen, J.T. Andrews

Research output: Contribution to JournalArticleAcademicpeer-review

Abstract

The climate of the Holocene, the current interglacial covering the past 11,700 years, has been relatively stable compared to previous periods. Nevertheless, repeating occurrence of rapid natural climate changes that challenged human society are seen in proxy reconstructions. Ocean sediment cores for example display prominent peaks of enhanced ice rafted debris (IRD) during the Holocene with a multi-decadal to millennial scale periodicity. Different mechanisms were proposed that caused these enhanced IRD events, for example variations in the incoming total solar irradiance (TSI), volcanic eruptions and the combination of internal climate variability and external forcings. We investigate the probable mechanisms causing the occurrence of IRD-events over the past 6000 years using a fully coupled climate - ice-sheet - iceberg model (iLOVECLIM). We performed 19 experiments that differ in the applied forcings (TSI, volcanic) and the initial atmospheric conditions. To explore internal ice sheet variability one further experiment was done with fixed climate conditions. All the model runs displayed prominent peaks of enhanced iceberg melt flux (IMF), independent of the chosen experimental set-up. The spectral analysis of the experiments with the ice-sheet - climate model coupled displays significant peaks at 2000, 1000 years in all the experiments and at 500 years in most runs. The experiment with fixed climate conditions displays one significant peak of about 1500 years related to internal ice sheet variability. This frequency is modulated to 2000 and 1000 years in all the experiments with a coupled climate - ice sheet due to interactions between the climate components. We further investigate the impact of minimum TSI events on the timing and occurrence of enhanced IMF. In the experimental set-up that was forced with idealized sinusoidal TSI variations (±4 Wm
Original languageEnglish
Pages (from-to)119-130
JournalQuaternary Science Reviews
Issue number138
DOIs
Publication statusPublished - 2016

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