The Holocene thermal maximum in the Nordic Seas: the impact of Greenland Ice Sheet melt and other forcings in a coupled atmosphere–sea-ice–ocean model

摘要

The relatively warm early Holocene climate in the Nordic Seas, known as theHolocene thermal maximum (HTM), is often associated with an orbitally forcedsummer insolation maximum at 10 ka BP. The spatial and temporal responserecorded in proxy data in the North Atlantic and the Nordic Seas revealsa complex interaction of mechanisms active in the HTM. Previous studies haveinvestigated the impact of the Laurentide Ice Sheet (LIS), as a remnant fromthe previous glacial period, altering climate conditions with a continuoussupply of melt water to the Labrador Sea and adjacent seas and witha downwind cooling effect from the remnant LIS. In our present work we extendthis approach by investigating the impact of the Greenland Ice Sheet (GIS) onthe early Holocene climate and the HTM. Reconstructions suggest melt rates of13 mSv for 9 ka BP, which result in our model in an ocean surface coolingof up to 2 K near Greenland. Reconstructed summer SST gradients agree bestwith our simulation including GIS melt, confirming that the impact of theearly Holocene GIS is crucial for understanding the HTM characteristics inthe Nordic Seas area. This implies that modern and near-future GIS melt canbe expected to play an active role in the climate system in the centuries tocome.