Relative Sea-Level Changes and Ice Sheet History in Finderup Land, North Greenland

Abstract

Rising global sea level caused by melting ice sheets poses a major challenge in a persistently warming climate. The Greenland Ice Sheet (GrIS) is among the main contributors, and in order to make accurate predictions of future ice retreat and sea level rise, it is imperative to understand how the ice sheet responded to global warming in the past. Reconstructions of relative sea level (RSL) are a key constraint in models of past ice sheet fluctuations, however, high-precision data has until now been sparse in North Greenland. In this study, we present a RSL reconstruction for Finderup Land, North Greenland based on five isolation lakes located between 19.6 and 81.2 m a.s.l. The transition between marine and lacustrine sediments has been identified using XRF, lithological interpretation, and foraminiferal analysis. Age constraints are based on 14 C dating of foraminifera and paleomagnetic age correlation. Our results show that Finderup Land was ice free by 10.8 ± 0.2 cal ka BP with a subsequent rapid RSL fall occurring from 9.5 ± 0.2 to 8.0 cal ka BP, at which point the RSL started to approach present level. Furthermore, we establish the marine limit to be minimum at 81.2 m a.s.l. We compare our data to modeled RSL predictions for the area and our results indicate a faster RSL fall, which in turn reflects that the ice retreat was more rapid than estimated and possibly, that the ice sheet in North and Northeast Greenland was larger than previous estimates suggest.

Evidence of early deglaciation (18 000 cal a bp) and a postglacial relative sea‐level curve from southern Karmøy, south‐west Norway

“…Knowing that Grødheimsvatnet must have been isolated before Kringlemyr (due to the higher outlet altitude), we find that unit III is the most likely candidate for a marine–lacustrine transitional phase in Grødheimsvatnet based on lithostratigraphic criteria and geochemical variations. Decreasing Ca/Fe ratios in the upper part of unit II indicate a gradually smaller influx of marine‐sourced Ca as we approach the lower boundary of unit III (Strunk et al , ), whereas the distinct dark laminations and increased sulphur values within the unit itself (Fig. ) are typical features of a marine–lacustrine transitional phase (Kaland, ; Kjemperud, ; Svendsen and Mangerud, ; Lohne et al , ; Balascio et al , ; Long et al , ; Romundset et al , ).…”

Local ice caps in Finderup Land, North Greenland, survived the Holocene Thermal Maximum

“…The sediment cores were dated using a combination of radiocarbon dating and palaeomagnetic intensity measurements (Strunk et al . ). All of the sediment cores were checked for organic remains that could be used for radiocarbon dating.…”

“…We did not proceed with bulk radiocarbon dating as a previous attempt at bulk dating of sediments from T2 yielded ‘too old’ ages probably due to the incorporation of reworked carbon (Strunk et al . ). It was only possible to find sufficient foraminifera for radiocarbon dating in some intervals within the marine units and combined with palaeomagnetic intensity measurements this made the basis of the sediment‐core chronologies for T2 and T8.…”

“…(Strunk et al . ). Recent ice recession has left pronounced trimlines in the terrain and large LIA moraines in front of outlet glaciers.…”

“…Two of the lake records have previously been used to reconstruct the relative sea‐level (RSL) change (Strunk et al . ). In addition, we date reworked marine shells from LIA moraines adjacent to Flade Isblink to further constrain periods when the ice cap was smaller than present.…”