A new approach for simulating the paleo-evolution of the Northern Hemisphere ice sheets

• Published in: Geoscientific Model Development
• Main Authors: Alvarez Solas, Jorge, Banderas, Rubén, Robinson, Alexander, Montoya, Marisa
• Format: Article in Journal/Newspaper
• Language: English
• Published: Copernicus Gesellschaft MBH 2018
• Subjects: Astrofísica; Astronomía; Greenland; Greenland ice core; ice core; Ice Sheet
• Online Access: https://eprints.ucm.es/id/eprint/49241/; https://eprints.ucm.es/id/eprint/49241/1/alvarezsolas11libre%2BCC.pdf; https://doi.org/10.5194/gmd-11-2299-2018

Offline forcing methods for ice-sheet models often make use of an index approach in which temperature anomalies relative to the present are calculated by combining a simulated glacial-interglacial climatic anomaly field, interpolated through an index derived from the Greenland ice-core temperature reconstruction, with present-day climatologies. An important drawback of this approach is that it clearly misrepresents climate variability at millennial timescales. The reason for this is that the spatial glacial-interglacial anomaly field used is associated with orbital climatic variations, while it is scaled following the characteristic time evolution of the index, which includes orbital and millennial-scale climate variability. The spatial patterns of orbital and millennial variability are clearly not the same, as indicated by a wealth of models and data. As a result, this method can be expected to lead to a misrepresentation of climate variability and thus of the past evolution of Northern Hemisphere (NH) ice sheets. Here we illustrate the problems derived from this approach and propose a new offline climate forcing method that attempts to better represent the characteristic pattern of millennial-scale climate variability by including an additional spatial anomaly field associated with this timescale. To this end, three different synthetic transient forcing climatologies are developed for the past 120 kyr following a perturbative approach and are applied to an ice-sheet model. The impact of the climatologies on the paleo-evolution of the NH ice sheets is evaluated. The first method follows the usual index approach in which temperature anomalies relative to the present are calculated by combining a simulated glacial-interglacial climatic anomaly field, interpolated through an index derived from ice-core data, with present-day climatologies. In the second approach the representation of millennial-scale climate variability is improved by incorporating a simulated stadial-interstadial anomaly field. The third is a ...