Quantitative reconstruction of Holocene sea ice and sea surface temperature off West Greenland from the first regional diatom dataset (transfer function)

Holocene oceanographic conditions in Disko Bay, West Greenland were reconstructed from high-resolution diatom records derived from two marine sediment cores. A modern dataset composed of 35 dated surface sediment samples collected along the entire West Greenland coast accompanied by remote sensing data were used to develop a diatom transfer function to reconstruct April Sea Ice Concentration (SIC) supported by July Sea Surface Temperature (SST) in the area. Our quantitative reconstruction shows that oceanographic changes recorded throughout the last c. 11000 years reflect seasonal interplay between spring (April SIC) and summer (July SST) conditions. Our records show clear correlation with climate patterns identified from ice core data from GISP2 and Agassiz-Renland for the early to mid Holocene. The early Holocene deglaciation of western Greenland Ice Sheet was characterised in Disko Bay by initial strong centennial-scale fluctuations in April SIC with amplitude of over 40%, followed by high April SIC and July SST. These conditions correspond to a general warming of the climate in the Northern Hemisphere. A decrease in April SIC and July SST was recorded during the Holocene Thermal Optimum reflecting more stable spring-summer conditions in Disko Bay. During the late Holocene, high April SIC characterised the Medieval Climate Anomaly, while high July SST prevailed during the Little Ice Age, supporting previously identified anti-phase relationship between surface waters in West Greenland and climate in NW Europe. This anti-phase pattern might reflect seasonal variations in regional oceanographic conditions and large-scale fluctuations within the North Atlantic Oscillation and Atlantic Meridional Overturning Circulation.