Comparison between Greenland ice-margin and ice-core oxygen-18 records

Abstract

AbstractOld ice for palaeoenvironmental studies retrieved by deep core drilling in the central regions of the large ice sheets can also be retrieved from the ice-sheet margins. the δ18O content of the surface ice was studied at 15 different Greenland ice-margin locations. At some locations, two or more records were obtained along closely spaced parallel sampling profiles, showing good reproducibility of the records. We present ice-margin δ18O records reaching back to the Pleistocene. Many of the characteristic δ18O variations known from Greenland deep ice cores can be recognized, allowing an approximate time-scale to be established along the ice-margin records. A flowline model is used to determine the location on the ice sheet where the margin ice was originally deposited as snow. the Pleistocene–Holocene δ18O change at the deposition sites is determined by comparing the δ18O values in the ice-margin record to the present δ18O values of the surface snow at the deposition sites. on the northern slope of the Greenland ice sheet, the Pleistocene–Holocene δ18O change is about 10‰ in contrast to a change of 6–7‰ at locations near the central ice divide. This is in accordance with deep ice-core results. We conclude that δ18O records measured on ice from the Greenland ice-sheet margin provide useful information about past climate and dynamics of the ice sheet, and thus are important (and cheap) supplements to deep ice-core records.