Ice cores from Greenland and Antarctica are ideal archives for retrieving long time series of deuterium-excess (d = δ D - 8 *δ18 O), a parameter influenced by conditions prevailing in the oceanic regions which provide moisture for polar snow. The central Greenland GRIP deuterium-excess record has recently been interpreted in terms of oceanic source temperatures both for the Holocene and for the last glacial period, this approach being less straightforward for the latter period because of changes in the precipitation seasonality between glacial and interglacial periods. This article examines why a conventional, or sea surface temperature, interpretation of the GRIP excess record seems inconsistent with inferred site and source temperature changes. In addition, the GRIP excess record is extended back into the penultimate glacial period and we assess its geographic significance through a comparison with existing Dye 3 and North GRIP data. We examine why low δD/δ18O slopes observed during glacial times are associated with low deuterium-excess values. Similarities between the Greenland GRIP and Antarctic Vostok excess records are discussed in terms of potential links with insolation and insolation gradient changes. Finally, the isotope records in specific DO events are examined in light of intruiging differences between the isotope ratios (δD or δ18O) and the excess records that may result from a feedback mechanism linked with freshwater oceanic input.