A diatom-based sea-ice concentration (SIC) transfer function was developed by using 72 surface samples from west of Greenland and around Iceland, and validated against associated modern SIC. Canonical correspondence analysis on surface sediment diatoms and monthly average of SIC indicated that April SIC is the most important environmental factor controlling the distribution of diatoms in the area, justifying the development of a diatom-based SIC transfer function. The agreement between reconstructed SIC based on diatoms from West Greenland and the satellite and modelled sea-ice data during the last ~. 75. yr suggests that the diatom-based SIC reconstruction is reliable for studying the palaeoceanography off West Greenland.Relatively warm conditions with a strong influence of the Irminger Current (IC) were indicated for the early part of the record (~. 5000-3860. cal. yr BP), corresponding in time to the latest part of the Holocene Thermal Maximum. Between 3860 and 1510. cal. yr BP, April SIC oscillated around the mean value (55%) and during the time interval 1510-1120. cal. yr BP and after 650. cal. yr BP was above the mean, indicating more extensive sea-ice cover in Disko Bugt.Agreement between reconstructed April SIC and changes in the diatom species suggests that the sea-ice condition in Disko Bugt was strongly influenced by variations in the relative strength of two components of the West Greenland Current, i.e. the cold East Greenland Current and the relatively warm IC. Further analysis of the reconstructed SIC record suggests that solar radiation may be an important forcing mechanism behind the historic sea-ice changes.
- Programområde 5: Natur og klima