Evolution of the East Greenland Current between 1150 and 1740 AD, revealed by diatom-based sea surface temperature and sea-ice concentration reconstructions

Abstract

Sediment core MD99-2322 from the East Greenland shelf has been studied to assess the variability of the East Greenland Current between 1150 and 1740 AD. Only the top 100 cm of the high-resolution core—with a 4-year resolution through the upper 20 cm, and a 10-year resolution through the remaining section—was studied. Diatoms were utilized to reconstruct both the August sea-surface temperature (SST) and the May sea-ice concentration, using the weighted averages–partial least squares and maximum likelihood transfer function methods, respectively. The record can be divided into three periods: two periods of relatively stable August SSTs and May sea-ice concentrations, separated by a period of higher August SSTs and decreasing May sea-ice concentrations between 1500 and 1670 AD, and between 1450 and 1610 AD, respectively. Both trends are statistically significant, based on the SIZER (significant zero crossing of the derivatives) analysis of the records. These changes are explained by a decrease in the strength of the East Greenland Current between 1450 and 1670 AD, which was responsible for bringing cold polar water and sea ice to the core site. Simultaneous changes observed in both these parameters points to a strong coupling between them. Because of the high resolution of the record, the natural variability of the system over the period of almost 700 years can be assessed. This variability is about 1°C (_0.9°C) for August SSTs and 12% (_7.4%) for May sea-ice concentrations.