Relative sea-level change in Greenland during the last 700 yrs and ice sheet response to the Little Ice Age

Abstract

This paper presents new evidence regarding relative sea-level (RSL) changes and vertical land motions at three sites in Greenland since 1300A.D., a time interval that spans the later part of the Medieval Climate Anomaly (MCA) and the Little Ice Age (LIA). We observe RSL rise at two sites in central west Greenland from c. −0.80±0.20m at c. 1300A.D. to c. −0.20m±0.25m at c. 1600A.D., after which RSL slowed and then stabilised. At a third site in south Greenland, we observe RSL rise from c. −1.40±0.20m at c. 1400A.D. until c. 1750A.D., after which RSL slowed and was stable during at least the latter part of the 20th century. The c. 1600A.D. RSL slow-down seen at the two former sites is surprising because it occurs during the LIA when one might expect the ice sheet to be gaining mass and causing RSL to rise. We interpret this RSL slowdown to indicate a period of enhanced regional mass loss from central west Greenland since c. 1600A.D. and propose two hypotheses for this loss: first, a reduction in precipitation during cold and dry conditions and second, higher air temperatures and increased peripheral surface melt of the ice sheet from this date onwards. The latter hypothesis is compatible with a well-established temperature seesaw between western Greenland and northern Europe and, potentially, a previously identified shift from a positive to generally more negative NAO conditions around 1400 to 1600A.D. Our study shows how RSL data from Greenland can provide constraints on the timing of ice sheet fluctuations in the last millennium and challenges the notion that during cold periods in northern Europe the ice sheet in west Greenland gained mass.