Rapid Climate Shifts during last Deglaciation over Central to Northern Europe

Abstract:

Abrupt climate shifts during the last deglaciation provide test cases for analyzing the transient response of our climate system to changes in external forcings and internal feedbacks. The regional imprints of rapid climate shifts, their timing and hence connection to local vs. large-scale mechanisms are however still poorly understood owing to a limited number of records with usually large age uncertainties and low sampling rates.

In this study we examine the spatiotemporal evolution of rapid climate shifts over central Europe and Scandinavia during Bølling-Allerød (14.7-12.7kyr BP) and Younger Dryas (~12kyr BP) by means of pollen data and climate simulations. For a better understanding of physical mechanisms behind regional imprints of climate shifts, time slice experiments with the Community Earth System Model (CCSM1.0.5) are set up at high resolution (1°x1°) using different topographies and ice sheets (ICE-5G and a new version of GLAC). Matching these time slice experiments with the spatial temperature pattern derived from pollen records, we estimate the extent to which environmental conditions (pollen) represent the direct large-scale influence of climate over the Euro-Atlantic sector vs. regional-scale climate effects e.g. caused by shrinking ice sheets and coastal transgression due to sea-level rise.