Title:	Imprint of global climate transitions on Swedish climate
DNr:	SNIC 2015/1-324
Project Type:	SNIC Medium Compute
Principal Investigator:	Barbara Wohlfarth <barbara.wohlfarth@geo.su.se>
Affiliation:	Stockholms universitet
Duration:	2015-11-01 – 2017-03-01
Classification:	10501 10508 10504
Homepage:	http://people.geo.su.se/frederik/
Keywords:

Abstract

The transition (deglaciation) from the last glacial maximum (around 21.000 years BP) into the Holocene (around 11.700 BP) is characterized by rapid climate shifts to warmer (interstadial) and colder (stadials) episodes within decades to centuries. These episodes are understood as highly non-linear responses of the climate system to gradual changes in astronomical forcing. The regional imprint of these dramatic climate shifts and their dynamics and mechanisms are however not well known. The aim of this project is therefore to enhance knowledge on the Euro-Atlantic and specifically Scandinavian climate evolution, spatial teleconnections and variability during the global climate transition from glacial to inter-glacial climate. We focus here on the most prominent rapid climate shift from the warm interstadial of the late Alleröd (13.100 BP) into the cold stadial of the Younger Dryas (12.170 BP). Prescribing monthly mean sea-surface temperatures from an older quasi-transient but coarser (approx. 375 km) Atmosphere-Ocean General Circulation Model (AOGCM) simulation of the last 21.000 years (Liu et al. 2009, Nature), we run high resolution time slice experiments at around 100 km horizontal resolution with the NCAR Community Earth System Model version 1 (CESM 1.0.5). At this resolution, regional details such as the continental ice sheets and lower sea-levels / exposed land masses relevant for local to regional climate will be resolved. The project has run since summer 2012, initiated and funded by the Swedish nuclear fuel and waste management company (SKB) with the goal of improved quantitative climate data for south-central Sweden. Purpose of this dynamical downscaling with CESM1 of the coarser Liu et al.'s simulation is to resolve the climate variability at a regional scale and to facilitate comparison to proxy data which generally represent a local or regional spatial scale. To estimate the influence of uncertain continental ice sheet height and extent on climate, sensitivity runs using different ice sheets and topographies for the same time slices are run.